Electronic devices such as handy phones and micro computers have been rapidly expanding their market recent years due to their enhanced performance, down sizing and cost down. This has been realized by the innovation in the precision micro- fabrication technology of semiconductors and printed wiring circuit boards (PWB) where laser technologies such as lithography, drilling, trimming, welding and soldering play an important role. In phot lithography, for instance, KrF excimer lasers having a resolution of 0.18 micrometers has been used in production instead of mercury lamp. Laser drilling of PWB has been increased up to over 1000 holes per second, and approximately 800 laser drilling systems of PWB are expected to be delivered in the world market this year, and most of these laser processing systems are manufactured in Japan. Trend of laser micro-fabrication in Japanese industry is described along with recent topics of R&D, government supported project and future tasks of industrial laser precision micro-fabrication on the basis of the survey conducted by Japan laser Processing Society.

Today the laser technologies are widely used in the processing of materials, including also the precise micro shaping. Deep UV lasers have very good prospects in the lithography, used for fabrication of chips, while the femtosecond pused lasers open the new horizons for the micro- and submicroprofiling. But these are the field of the future prospects. As for today state-of-the-art, contribution to the application of lasers for these purposes are the numerous advantages of the laser techniques over the traditional methods, such as: - wide variety of materials to be treated, - possibility of achieving narrow cuts and practically waste-fee separation, - small heat-affected zone, - minimal mechanical effect and minimum thermal deformations, - possibility of micro shaping along a complex profile in two, or even three, dimensions, - possibility of fast and precise process switch-on and off and to include in the processing feedback on the treated parameters.

Ultrashort pulsed laser ablation of dielectrics has been investigated using ex-situ morphological examinations in combination with in-situ time-of-flight mass spectrometry of the ablated species. Analysis of the energy spectrum of the ablation products provides a wealth of information on the processes occurring during femtosecond laser ablation of materials. The presentation will focus on the case of sapphire (Al₂O₃) and discuss the fundamental processes in ultrashort pulsed laser sputtering. Two different ablation phases have been identified, a gentle phase with low ablation rates and a strong etch phase with higher ablation rates, but with limitation in structure quality. A comparison of the energy and momentum distributions of ejected ions, neutrals and electrons allows one to distinguish between non-thermal and thermal processes that lead to the macroscopic material removal. Fast positive ions with equal momenta are resulting from Coulomb explosion of the upper layers at low fluence and low number of irradiating laser pulses (gentle etch phase). Pump-probe studies with fs laser pulses reveal the dynamics of excitation and electron mediated energy transfer to the lattice. At higher laser fluences or after longer incubation, evidence for phase explosion can be derived from both the morphology of the surface and the results of the in-situ experiments.

We used 395-nm and 790-nm femtosecond laser pulses to deposit aluminum-doped zinc oxide films by pulsed laser deposition. Electrical resistivity of the films was lowered (5.6 x 10₄(Omega) cm) at 200 degree(s)C for the 395-nm laser pulses, while maintaining the optical transparency. In addition, the deposition rate increased six times. Optical emission was measured to compare the plumes generated by 395-nm and 790-nm laser pulses. We found that the emission from ions was suppressed relative to neutral atoms. Also the kinetic energy of ejected species was nearly doubled for the 395-nm laser pulses.

We report a novel photo-polymerization technique of well- defined three-dimensional layer-by-layer structures by two- photon absorption (TPA in resins. By changing the structural parameters such as the rod diameter, pitch )intra-rod distance in plane) and angular orientation between neighbor planes different lattice types can be accomplished. This enables a systematic investigation of optical properties of photonic crystals (PhCs) made by TPA photo-polymerization. The solidified skeleton of PhC can be utilized as a mold to infiltrate solidifiable dye. Selective removal of the solidified resin can yield in a reverse PhC structures. When the defect-layer(s) are introduced into PhC during fabrication the PhC may act as a high-quality microcavity. A defect mode has been observed for the first time in thus-fabricated structures. Laser- microexplosion fabrication is another promising technique for the PhC and optical memory applications. TO achieve an opening of a full-bandgap the media of high dielectric constant is of request (a high dielectric contrast is necessary).

The various microscopic modifications in glasses by ultra- short pulses were examined. It was confirmed that permanent refractive index changes, and creation of microcrystals with second-order nonlinear optical functions could be produced with a femtosecond pulse laser only in selective internal areas in glasses. By using a femtosecond laser with a high repetition rater, permanent optical waveguides can be successfully written in various glasses, where refractive index changes are continuously induced along a path traversed by focal point. We also confirmed that single crystals are created from the core region in the waveguides by the laser irradiation, which is used for various kinds of optical devices.

The time-resolved dynamics of plasma self-channeling and refractive index bulk modification in the silica glasses are first observed using a high-intensity femtosecond (110 fs) Ti: sapphire laser ((Lambda) _pequals790 nm) We propose the new pump-probe measurement to observe the lifetime of both plasma self-channeling and induced refractive index bulk modification. The energy variation of transmitted probe beam, which propagates transversely through the plasma self- channeling is measured. At the pre-breakdown domain, the lifetime of induced plasma self-channeling is 20 ps and structural transition time for reforming the refractive index change is 10 ps. At the breakdown domain, however, the lifetime of induced plasma formation is 30 ps and structural transition time for forming the optical damage is 40 ps. We find that the process of refractive index bulk modification is significantly different from those of optical damage. We also measure a wavelength shift (blueshift) of reflected probe beam from the surface of the plasma self-channeling induced by the pump beam. A maximum value of blue wavelength shift is 3 nm when the time delay of probe beam is 2 ps. The expanding velocity of the plasma ionization is calculated from the wavelength shirt (blueshift) using the Doppler formula. A maximum velocity of the plasma ionization is calculated to be approximately 6x10⁵ m/s at the delay time of 2 ps.

Many researchers have investigated the interaction of femtosecond laser pulses with a wide variety of materials. The structural modifications both on the surface and inside the bulk of transparent materials have been demonstrated. When femtosecond laser pulses are focused into glasses with a high numerical-aperture objective, voids are formed. We demonstrate that one can seize and move voids formed by femtosecond laser pulses inside silica glass and also merge two voids into one. We also present clear evidence that a void is a cavity by showing a scanning-electron-microscope image of cleft voids: we clove through the glass along a plane that includes the laser-ablated thin line on the surface and the voids formed inside. The optical seizing and merging of voids are important basic techniques for fabricate micro-optical dynamic devices, such as the rewritable 3-D optical storage.

Ultrashort duration laser sources are considered as a promising tool for new micromachining applications: precise microdrilling and microcutting on various materials. As an illustration of the non thermal micromachining, we also paid attention to precious wood. Cutting is achieved without burning, and the cut surface remains undamaged. However, until now, only low-average-power sources are available. An average power level of 10 W appears to be the lowest limit for this type of laser to really become industrial. We are presently developing such a source based on the use of a 15kHz, 100W copper HyBrID laser as a pump laser. Thus, we intend to reach in a near future a typical drilling rate of one mm per second, for instance, in stainless steel compared with a 50 microns per second drilling rate obtained with presently available kHz and low-average-power sources. Micromachining obtained with out a 1 kHz source will be presented and discussed.

The laser has become an increasingly important tool, which helps to overcome the limitations of conventional microfabrication technologies, delivering devices capable of performing new and increased numbers of operations within an ever shrinking volume. In addition to classical applications of lasers such as via hold drilling, trimming or pulsed laser deposition of thin films, there have been new developments in laser-based technologies for the fabrication of advanced micro- and nano-devices. Of particular interest for optoelectronic and photonic applications is the potential for commercial processing of semiconductors and the fabrication of integrated and monolithically integrated photonic devices and circuits.

For the past several years, our group has focused on the development of polysilicon thin film transistor (TFT) processes having maximum allowable substrate temperatures between 100 degree(s) to 350 degree(s)C. These processes are based on excimer laser crystallization of low temperature deposited a-Si thin films combined with low temperature deposited dielectrics and self-aligned gate TFT structures. We have also developed a laser-based, source-drain-gate doping/annealing process. Typical n-channel TFT mobilities found are (mu) _napproximately 150 cm²/V-s for the 100 degree(s)C process and approximately 400 cm²/V-s for the 350 degree(s)C process. In this paper we describe the basic processes and process physics. We then show results for TFTs fabricated at a variety of maximum substrate temperatures and a-Si deposition techniques.

F₂ laser ablation etching of GaN has been demonstrated. The etching geometry, etching rate and microroughness were investigated, and compared to the case of KrF excimer laser ablation etching. The etching process is consisted of the ablation and hydrochloric acid treatment. Very sharp edge was found along the etched area. The microroughness of etched surface is reduced as the laser intensity increases. The f₂ laser ablation of GaN is thought to be initiated by direct photoionization by single-7.9 eV photon absorption.

Ultra-Short pulsed lasers are highly useful tools in the field of microfabrication. In microfabrication, the laser pulse usually is very short in the pico-second or subpico- second range: therefore, it is very difficult to observe the transient material processing phenomena experimentally. Over the years, the authors have conducted molecular dynamics (MD) simulation to study the ablation process with ultra-short pulsed laser irradiation. The MD method has been modified to simulate the laser ablation of metals by updating heat conduction effect by free electrons at each calculation time step. In this paper, a review of the modified MD simulations on ablation and shock phenomena for metal with pico-second laser irradiation is presented.

Precision microfabrication of diamond has many applications in the fields of microelectronics and cutting tools. In this work, and ultra-short pulsed Ti: Sapphire laser was used to perform patterning, hold drilling, and scribing of synthetic and CVD diamonds. Scanning electron microscopy, atomic force microscopy, profilometry, and Raman spectroscopy were employed to characterize the microstructures. A tight-binding molecular dynamics (TBMD) model was used to investigate atomic movements during ablation and predict thresholds for ablation. The ultra- short pulsed laser generated holes and grooves that were nearly perfect with smooth edges, little collateral thermal damage and recast layer. The most exciting observation was the absence of graphite residue that always occurs in the longer-pulsed laser machining. The ablation threshold for ultra-short pulsed laser was two orders of magnitude lower than that of longer-pulsed laser. Finite-difference thermal modeling showed that ultra-short pulses raised the electron temperatures of diamond in excess of 100,ooo K due to multiphoton absorption, absence of hydrodynamic motion, and lack of time for energy transfer from electrons to the lattice during the pulse duration. TBMD simulations, carried out on (111) and (100) diamond surfaces, revealed that ultra-short pulses peel carbon atoms layer-by -layer from the surface, leaving a smooth surface after ablation. However, longer pulses cause thermal melting resulting in graphite residue that anchors to the diamond surface following ablation.

Effects of irradiating number of pulses of Nd:YAG laser in laser ablation of metals in air have been studied by both photoacoustic and fast-imaging techniques. Photacoustic detection technique using piezoelectric polymer film revealed the change of coupling among laser radiation, ablated matter, plasma and the target as a function of the laser fluence. Nanosecond imaging technique, where the second harmonic radiation from the same laser was used as illuminating light pulse, showed surface phenomena during and immediately after the ablating laser pulse. Photacoustic signal intensity as a function of laser fluence was measured at constant pulse energy. It was constant at low fluence, started to increase with fluence at certain threshold, reached a peak and then decreased gradually with increasing fluence. Shapes of the functions were similar but the threshold fluence and the fluence at the peak increased with irradiating pulse number. Imaging observation revealed that a surface layer and/or absorbed contaminants was ablated by initial few pulses and that material ablation occurred at higher fluence than the surface layer. Ablation of the surface layer caused shock wave and terminated less than 10 pulses while aluminum ablation was accompanied with bright plume and shock wave and affected only slightly by preceding pulses.

Hybrid laser processing for precision microfabrication of hard materials, in which interaction of a conventional pulsed laser beam and another medium on the material surface leads to effective ablation, is reviewed. The main role of the medium is to produce strong absorption of the ns-laser beam tot the materials. Simultaneous irradiation of the UV laser beam with the VUV laser beam possessing extremely small laser fluence performs accurate ablation of the hard materials such as fused silica, crystal quartz, sapphire, GaN, SiC, etc. (VUV-UV multiwavelength excitation process). Metal plasma generated by the laser beam effectively assists high-quality ablation of transparent materials, leading to submicron grating fabrication and high-speed hole drilling of glass materials (laser-induced plasma-assisted ablation (LIPAA)). The detailed discussion includes ablation mechanism of hybrid laser processing and comparison of advantages and disadvantages with F₂ laser ablation.

Over the last decades laser technology has found the way into various industries. For microfabrication specifically excimer lasers have developed to powerful manufacturing tools because of their short UV wavelengths as well as the progress in excimer laser technology. More recently the development of pulsed medium-power diode-pumped solid-state lasers has opened the way to new micromachining applications related to the available superior beam quality. Here we review technological achievements in boh industrialized excimer lasers and diode-pumped Nd:YAG lasers for microfabrication. Data are presented for industrial 308 nm excimer lasers with energy stability better than 1 % (sigma) at 300 W average power. Using the latest technology in 157 nm excimer lasers applications of processing of difficult materials are presented. Finally we review results on studies of microdrilling of metals and ceramics using a newly developed 10 kHz diode-pumped solid-state laser at wavelengths 1064 nm, 532 nm and 355 nm.

Reports in 1982 of polymers ablated and etched by excimer laser radiation mark the founding of laser microfabrication and micromachining as technologies that in the intervening period has matured into a manufacturing process used by a diverse range of industries. This paper describes some of these industrial applications.

Drilling rate of thin silicon wafer of 50(mu) thickness was determined as a function of beam diameter and laser fluence of KrF excimer laser with a pulse width of approximately 30ns FMHW. Analysis of drilling process indicated that decreasing beam diameter and laser fluence enhanced the drilling rate with improved quality of the drilled hole. The extent of debris and molten particles ejected from the hole was also reduced as the laser fluence was decreased. The drilling rate, approximately 0.6(mu) per pulse at beam diameters larger than 100(mu) , increased significantly as the beam diameter decreased especially below 20(mu) , reaching approximately as large as 4(mu) per pulse at 10(mu) in diameter under constant laser fluence. On the other hand, only very small increase in drilling rate was observed as the laser fluence was increased. A simple formula was derived where the drilling rate is proportional to the fourth root of the laser fluence and inversely proportional to the square root of the beam diameter, assuming that the silicon is removed in a liquid state out of the hole.

Femtosecond laser systems have been proved to be effective tools for high precision micro-machining. Almost all solid materials can be processed with high precision. The dependence on material properties like thermal conductivity, transparency, heat- or shock sensitivity is strongly reduced and no significant influence on the remaining bulk material is observed after ablation using femtosecond laser pulses. In contrast to conventional laser processing, where the achievable precision is reduced due to a formed liquid phase causing burr formation, the achievable precision using femtosecond pulses is only limited by the diffraction of the used optics. Potential applications of this technique, a\including the structuring of biodegradable polymers for cardiovascular implants, so-called stents, as well as high precision machining of transparent materials are presented.

Conventional laser machining is based on continuous-wave or long-pulse lasers. With these lasers, thermal diffusion limits the accuracy and the reproducibility of the machining process. Laser-matter interaction is fundamentally different in the ultrafast (femtosecond) regime. This discovery has opened the way for generalized fine laser micromachining.

In these few years, telecommunication appliances, for example cellular mobile telephone and mobile computer, have been becoming smaller and lighter. In addition they have been equipped with higher performances. Stepping with that progress, the technologies about integrated circuits, electrical components, battery and display devices that are used in those equipment mentioned before have been developing successfully. In the field of multi-layer printed wiring board, many efforts have been made to drill smaller size via holes in order to minimize the size of wiring pattern. Especially laser micro drilling technology that has been expected to be able to overcome the conventional mechanical drilling technology has been spread rapidly into the factory mainly in Japanese market since 1996. As a result, the typical size of the via hole diameter has become 100 to 200 micrometer from 300-400 micrometer and the structure of multi-layer has been changed from through-hole structure to inner via hold structure. Laser micro hole drilling technology nowadays including the ALIVH, which is the name of the printed wiring board that Matsushita has developed, and the survey of the next generation laser drilling technology will be presented.

One of the most important technical driving forces for IC manufacturing is lithography. IC manufacturing equipment is required to work in sever full-time operation, such as 24 hours a day and 7 days a week. KrF laser, however, has established its status, and has proven the applicability of excimer laser itself. The transition from super high pressure mercury lamp (i-line:365nm) to KrF laser was a natural trend, because the resolution is improved proportionally with shorter wavelength. Practical resolution is now said to attain half the wavelength, using high NA optics and imaging tricks, such as phase shifting masks, oblique illumination, etc. At present, 130nm resolution is pursued using a KrF laser and a projection lens whose NA is nearly 0.7. ArF laser lithography is also under extensive development. In the initial stage, it has proven 120nm resolution with an NA 0.6 projection lens, and now aims at 100nm resolution of 4G-bit DRAM as the next generation. The light source development always comes first in lithography, and F2 laser technology is now paid much attention.

A complete set-up for local annealing of Shape Memory Alloys (SMA) is proposed. Such alloys, when plastically deformed at a given low temperature, have the ability to recover a previously memorized shape simply by heating up to a higher temperature. They find more and more applications in the fields of robotics and micro engineering. There is a tremendous advantage in using local annealing because this process can produce monolithic parts, which have different mechanical behavior at different location of the same body. Using this approach, it is possible to integrate all the functionality of a device within one piece of material. The set-up is based on a 2W-laser diode emitting at 805nm and a scanner head. The laser beam is coupled into an optical fiber of 60(mu) in diameter. The fiber output is focused on the SMA work-piece using a relay lens system with a 1:1 magnification, resulting in a spot diameter of 60(mu) . An imaging system is used to control the position of the laser spot on the sample. In order to displace the spot on the surface a tip/tilt laser scanner is used. The scanner is positioned in a pre-objective configuration and allows a scan field size of more than 10 x 10 mm². A graphical user interface of the scan field allows the user to quickly set up marks and alter their placement and power density. This is achieved by computer controlling X and Y positions of the scanner as well as the laser diode power. A SMA micro-gripper with a surface area less than 1 mm² and an opening of the jaws of 200(mu) has been realized using this set-up. It is electrically actuated and a controlled force of 16mN can be applied to hold and release small objects such as graded index micro-lenses at a cycle time of typically 1s.

Laser adjustment allows a new process chain for fast, cost- efficient and highly precise assembly. It can be done without the usually very elaborate exact positioning of the jointing parts since after joining the components are adjusted into the desired position by laser forming. In order to make this new process chain possible an actuator can be joined between the bearer and the relevant functional element. This actuator enable the functional element to be moved into the desired position by conversion of laser energy. After the adjustment it remains in the assembly. For simple adjustment tasks an intuitively controlled design process can lead to solutions to an actuator design. As far as more complex tasks are concerned, like e.g. adjusting the 7 relevant degrees of freedom of all optics in electro- optical transducers, new design principles are necessary. After elucidating the process principle this paper presents the demands imposed on such actuators. Founded on the basic actuators, the integral approach to the actuator design is presented with its complete mathematical description being the basis of the computer-aided procession of all actuator- specific data. Thus it becomes possible to solve the inverse problem of the requirements made on geometry.

Frequency doubled Nd:YAG lasers represent an attractive alternative to other laser tools for many material processing applications, but frequency doubling with pulsed Nd:YAG lasers has been performed until now only with pulses of tens of nanoseconds. In material processing with longer pulses (10-1000 microsecond(s) ), such as encountered in typical 1.06 micrometers industrial Nd:YAG applications, the laser-material interaction is different and, in particular, higher material ablation rates are performed. Furthermore, the green light material processing permits a better focusability and a higher absorption in most materials. However, frequency doubling with long pulse lasers is much more difficult and less efficient up to now. The main problems are the generation of a fundamental 1.064 micrometers beam of high quality necessary for the non-linear process, and the low damage threshold of the non linear materials in the long pulse regime. Therefore, a zigzag slab laser, which has a high beam quality and an inherently linear polarization of the beam, is an ideal candidate for non-linear processes. The optical damage threshold in the non-linear materials is the main limiting parameter. The 140 W instantaneous power obtained for a 200 microsecond(s) pulse duration in extra-cavity configuration allows us to finely process sheets up to 200 micrometers thick.

The development of ultrashort pulse laser technology will have a strong impact on the advancement of laser machining. Ultrashort laser pulses can reduce the heat-affected zone and the shock-affected zone, resulting in much cleaner cuts, and therefore higher precision. However, acceptance of ultrafast technology is hindered by the cost and complexity of ultrafast lasers. In this paper, we describe recent progress in fiber-based ultrafast laser technology which promises to be sufficiently rugged and low-cost to enter the industrial arena. We also discuss results of micromachining using a sub-nanosecond laser pulses from a new Yb:fiber- based laser system.

A new scheme for phase control of optical components using laser ablation shaping (LAS) has been developed. The surface shape of optical plastic material coated on a glass plate is ablated using 193 nm laser light to control the transmission wave front. The surface shape is monitored in situ and corrected to attain the desired aberration level. The irradiation fluence is about 40 mJ/cm², and the ablation depth per pulse is about 0.01 micrometers per pulse for UV-cured resin. A wave front aberration of 3.0(lambda) is reduced to 0.17(lambda) in the case of flat surface shaping. In the case of spherical surface generation, an aberration of 2.5(lambda) is reduced to 0.2(lambda) . Increase in surface roughness is kept within the acceptable levels. This scheme has been applied to the fabrication of micro-optical elements for the collimation of laser diode (LD) or single mode optical fiber (SMF). In the case of LD lens, micro- collimate lens was placed at the output surface of LD, and the wave-front error was measured with Shack Hrtmass wave- front sensor. In the case of SMF, small lens was formed directly at the output surface with UV-cured resin. The laser beam was focused to 250 micrometers in radius for micro- fabrication. The wave-front distortion was decreased from about 15(lambda) to less than 2(lambda) in mm size lens.

A non-lithographic coherent array of ultrafine tungsten particles (150-500 nm diameter) is self-assembly arranged around a laser-irradiated mark on a tungsten substrate. Single and poly-crystal tungsten substrates were irradiated by a Q-switched Nd:YAG laser under low pressure in an inert gas atmosphere. We studied the effect of the laser fluence on the morphology of the coherent arrays. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used for these observations. The spacing of the coherent array increases with increasing laser fluence. For a 10.5 J/cm² irradiation, many droplets and peeling of the surfaces induced by rapid thermal expansion of the tungsten surface were observed. The recrystallizatoin texture on the surface was also confirmed by TEM observations. This suggests that the irradiated surface layer was partially recrystallized during laser irradiation. We concluded that coherent arrays are related to the laser fluence, the crystal surface structure, and the crystal growth. The recrystallization of the slightly melted tungsten on the top surface induced by the repeated laser irradiation plays a vital role in the formation of the array. If we can produce a coherent array of ultrafine tungsten particles with a higher aspect ratio, it may have potential applications for the emission cathodes of field emission displays (FED) and microelectronic devices.

The needs to quantity and quality of cold-rolled steel sheets demanded its fine surface quality. Some efficient methods of surface measurement are introduced to construct a surface quality controlling system. Through theoretical analysis and large amount of experiments, the basic relationship between surface topography and process parameters can be established and the optimal parameters can be got to instruct to obtain more ideal surface of roller and steel sheet.

Laser ablation with a Q-switched diode-pumped Nd:YAG laser was used to produce grooves in H-13 tool steel and 6061 aluminum specimens. The relationships between laser wavelength, power and travel speed and the material removal rate, groove depth and quality were studied. Nondimensional relationships between the process and material variables and groove area and depth were found. The material removal rate was found to be significantly higher for the aluminum material. However, no significant increase in material removal or groove quality was found for the shorter wavelength laser energy. Significant recast was observed in grooves having a depth/width ratio larger than approximately 1 and all grooves had some amount of recast material remaining as a burr at the top edges.

This contribution will present results for high-precision cutting of technical ceramics with short-pulsed solid-state lasers in fundamental and frequency-doubled wavelength. On the basis of ample experiments, a surprising absorption behavior of some ceramics in the case of irradiation with high intensity will be discussed. Furthermore, the influence of wavelength and process gas on cutting speed and quality is demonstrated. The investigations resulted in a process strategy with multiple passing over of the kerf suited for remarkably improving process velocity and quality. Finally, structures applicable for nozzles and spinnerets are shown.

In this contribution a technique will be presented using a cw solid-state laser for high precision micro-machining of steel which avoids recast layers and burr formation. This processing technique gets rid of the detrimental melt production by using oxidizing for material removal. The produced oxide chips can be removed from the structure completely by compressed air. No processing chemicals are necessary like in etching techniques. Other advantages of this method are sharp edges without any burrs, smooth bottoms in the structure ground and a small heat affected zone compared to material removal by melting.

The production of microsystems and miniaturized devices often requires joining technologies, which meet the demands of ultra clean manufacturing. Especially for optical and medical products low pollution and distortion joining processes are necessary to guarantee the quality and the function of the device. For this applications laser welding with fiber lasers at laser powers of up to P = 10 W and focus dimensions < 30 micrometers have been used for welding micro mechanical devices. At intensities I > 10⁶W/cm² welding depths of 100 micrometers can be achieved with minimized pollution of the parts and smooth and clean appearance of the surface of the welds. For joining polymers and dissimilar materials high power diode lasers have been used providing even better conditions regarding pollution of the joining partners. By using material adapted laser wavelengths the heating of the material can be concentrated to the inner joining area of an overlap material joint. With this technique, thermoplastic polymer compounds and silicon glass compounds have been joined with low temperature and no influence on the quality of the parts with joining widths of less that 100 micrometers .

Three different prototypes of ear implants have been successfully produced using Nd-YAG laser welding. The prototypes differ in use and dimensions. This presentation will deal with the latest developed ear implant, i.e. a box containing special electronics inside. The implant has to be He leak tight, the weld penetration should be between 50 and 65% of the cover in order to be sure to avoid damage of the electronics in the box and the temperature should not exceed 100 degree(s)C during welding. Furthermore no sharp edges and no surface contamination or oxidation is allowed. Pulsed Nd-YAG welding proved to be a fabrication technique who allowed satisfying those conditions. Through an appropriate choice of pulse energy, pulse time, pulse frequency, overlap and an external cooling device we succeeded to fulfil all those requirements. Special devices have been developed and are used to position the boxes adequately in front of the laser beam. During the welding a copper heat sink was used to eliminate the developed heat, and at the same time this was used to keep a good contact between the cover and the rest of the box. In the development phase the internal temperature during the welding cycle has been measured. With an appropriate choice of pulse frequency, pulse time, the internal temperature could be limited to about 80 degree(s)C. XPS measurements have also been performed on dummies in order to control the eventual formation of a titanium deposit during welding. Finally 30 implants have been welded successfully, and they will now be used for further medical tests, first on animals and later on human beings.

In order to improve the reliability of micro-spot welding of metal parts in production such as e.g. in electron guns for TV picture tubes, real-time information about the evolution of the welding process should be available to allow on-line modification of the laser parameters. Such information can be derived from a set of sensors that are mounted on a laser-scanning head. Different sensors are used to monitor the optical fiber output power to determine the evolution of temperature during the spot welding process, to measure plasma emission and back-reflected laser light. A vision channel and a CCD camera are used to control the position of the laser spot on the parts to be processed. The compact scanning head is composed of a tip/tilt laser scanner, a collimating lens and a focusing lens. The scanner is fast steering, with a bandwidth of 700Hz, and can tilt by +/- 3.5 degree(s) with a repeatability better than 50(mu) rad. The settling time for maximum deflection is less that 10ms. The scanning lens is a newly developed focusing lens designed to replace commercial cumbersome scanning lenses such as F-(theta) lenses, which have large volume, weight and price. This lens is based on the well-known Cooke triplet design and guarantees a constant shape of the spot all over the scan surface and is specially well suited for high power beam delivery. The scan field achieved by the system is limited to 25mm x 25mm. The laser used for this application is a pulsed Nd:YAG laser delivered by an optical fiber to the optical head. However, the system can be adapted to different types of lasers. Laser micro-spot welding on copper substrate has been performed in the frame of the Brite-Euram project MAIL. Smaller tolerances (a factor of 2 less) on the spot diameters were obtained in the case of a sensor controlled operation compared to the case where sensor control is not used.

We have investigated the formation process of nanoparticles in the laser ablation plume by different laser imaging spectroscopy techniques, such as Two-Dimensional laser induced fluorescence (2D-LIF), UV Rayleigh scattering (UV- RS), and Re-Decomposition LIF (ReD-LIF). Clusters, which are hardly observed by the UV-RS method due to their small size, are observed by the ReD-LIF method. The dynamics and formation processes of the nanoparticles, which are synthesized in the Si or ZnO ablation plume, is presented.

Carbon nitride films were deposited by pulsed Nd:YAG laser ablation of graphite with assistance of nitrogen ion beam bombardment. The nitrogen to carbon (N/C) atomic ratio, surface morphology and bonding state of the deposited carbon nitride films were characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy and atomic force microscopy (AFM). The influence of laser fluence on the synthesis of carbon nitride films was investigated. The N/C atomic ratio of the carbon nitride films can reach the maximum at the highest laser fluence. XPS and FTIR analyses indicated that the bonding state between the carbon and nitrogen in the deposited films was influenced by the laser fluence during deposition. The carbon-nitrogen bonding of C-N, C=N together with very few CequalsVN were found in the films. Results indicated that the laser fluence also had critical effect on the surface morphologies of the carbon nitride films.

The preparation of metal oxide thin films have been developed using the metalorganic (MO) compounds coating photolysis process with ArF excimer laser irradiation at room temperature. The effect of the starting materials and irradiation method on the product films was investigated by FT-IR, UV, XRD and SEM. It was found that metal acetylacetonates or metal 2-ethylhexanoate was effective as the starting materials. When using metal acetylacetonates as the starting materials, crystallized TiO₂, In₂O₃ and ZrO₂ were obtained with ArF laser irradiation at 50 mJ/cm² at a repetition rate of 5 Hz for 5 min. When using An-acac, Fe, Sn, or In 2-ethylhexanoate as the starting material, a two-step process consisting of both preliminary weak (10mJ/cm²) and sufficiently strong irradiation (50mJ/cm²) was found to be effective for obtaining crystallized ZnO, Fe₂O₃, SnO₂ and In₂O₃ films. In addition, crystallized complex oxide thin films such as ITO, PbTo₃ and PbZrO₃ were successfully obtained from the metal acetylacetonates or metal 2-ethylhexanoate using MO coating photolysis process. Patterned metal oxide thin films were also obtained by the ArF laser irradiation through the photomask, followed by leaching with solvents. The crystallization mechanism was discussed from the point of view of the photochemical reaction and photothermal reaction.

UV Laser-Assisted Deposition (UV-LAD) of three kinds of thiophene related compounds, 2,5-dibromothiophene (DBT), 5,5'-dibromo-2, 2'-bithiophene (DBBT) and 5,5'''-dibromo- 2,2':5',5''-terthiophene (DBTT) with 248 (KrF), 308 (XeCl) and 351nm (XeF) beams enabled us to obtain polythiophene thin films with highly oriented fibrous structure called laser induced periodic structure (LIPS). The conductivities of the films from DBBT with a 308nm beam and from DBTT with a 351nm beam have reached to the order of 10^-3 and 10^-1 Scm^-1, respectively, by doping with iodine after the UV-LAD process. FT-IR, XPS and UV-vis. Spectra show that, although sulfur atoms are eliminated to some extent, polymerization basically occurs at (alpha) positions of the thiophene related compounds by elimination of halogen atoms.

By definition Nanosatellites are space systems that can weigh 1010 kg and can perform unique missions (e.g. global cloud cover monitoring, store-and-forward communications) acting either in constellation of distributed sensor-nodes or in a many-satellite platoon that flies in formation. The Aerospace Corporation has been exploring the application of microelectronics fabrication and advanced packaging technology to the development of a mass-producible nanosatellite. Particular attention is being directed at M³ (Micromachining/MEMS/Microsystems) technology which appears to be important in the integration and manufacturing of these satellites. Laser direct-write processing techniques are being applied for rapid prototyping and to specific 3D fabrication steps where conventional microelectronics fabrication techniques fall short. In particular, a laser based technique has been developed that combines the rapid prototyping aspects of direct-write and the low cost/process uniformity aspects of batch processing. This technique has been used to develop various fluidic components and a microthruster subsystem in a photostructurable glass/ceramic material.

Currently, an ever increasing need for bandwidth, compactness and efficiency characterizes the world of interconnect and data communication. This tendency has already led to serial links being gradually replaced by parallel optical interconnect solutions. However, as the maximum capacity for the latter will be reached in the near future, new approaches are required to meet demand. One possible option is to switch to 2D parallel implementations of fiber arrays. In this paper we present the fabrication of a 2D connector for coupling a 4x8 array of plastic optical fibers to RCLED or VCSEL arrays. The connector consists primarily of dedicated PMMA plates in which arrays of 8 precisely dimensioned grooves at a pitch of 250 micrometers are introduced. The trenches are each 127 micrometers deep and their width is optimized to allow fixation of plastic optical fibers. We used excimer laser ablation for prototype fabrication of these alignment microstructures. In a later stage, the plates can be replicated using standard molding techniques. The laser ablation technique is extremely well suited for rapid prototyping and proves to be a versatile process yielding high accuracy dimensioning and repeatability of features in a wide diversity of materials. The dependency of the performance in terms of quality of the trenches (bottom roughness) and wall angle on various parameters (wavelength, energy density, pulse frequency and substrate material) is discussed. The fabricated polymer sheets with grooves are used to hold optical fibers by means of a UV-curable adhesive. In a final phase, the plates are stacked and glued in order to realize the 2D-connector of plastic optical fibers for short distance optical interconnects.

Ce-doped yttrium iron garnet (Ce:YIG) thin films were deposited for the first time by pulsed-laser deposition (PLD) on gadolinium gallium garnet (GGG(111)) substrates. Well crystallized film was obtained at high substrate temperature (approximately 900 degree(s)C) and in low Ar gas pressure (approximately 50 mtorr). A Faraday rotation angle was wavelength dependent, and the largest value was 4.2 x 10⁴ deg/cm at 420 nm. The control of the charge state of Ce ion is necessary for crystallization. The deposited Ce:YIG films were transferred by laser-induced forward transfer (LIFT) process to obtain a thick film.

Excimer laser ablation of a scanned substrate can be used for prototyping of lab-on-a-chip microfluidic channels [1]. Here, the relationship between the wetting properties of the channels and the irradiation conditions is described. The wetting properties are quantified by electro-osmotic flow measurements in channels, produced with different conditions of scanning ablation. The observed variations can be explained in terms of a competition between a direct and an indirect redeposition pathway for the debris.

The powerful transition from electronic to photonic systems in today's Internet-driven communication industry is driving the development of processes to miniaturize and integrate optical components. New processing and packaging technologies are now required that can precisely shape and assemble transparent optical components to sub-wavelength accuracy. Laser microfabrication technology is beginning to play a role here. Our groups are exploring two extremes in laser technology- ultrafast lasers and very short wavelength F₂ lasers- to microstructure optical surfaces and to profile refractive-index structures inside transparent glasses. In this paper, we compare photosensitivity responses, spatial resolution, and processing windows for the deep-ultraviolet and ultrafast laser approaches, and discuss prospects for laser printing and trimming of optical waveguide components and circuits.

Micron-scale convex deformations can be produced in two kinds of chalcogenide glasses only by exposures to focused cw laser beams. In covalent compounds such as As₂S₃ the deformation is formed through the so-called giant photoexpansion phenomenon, and in Ag-containing chalcogenide glasses it is made through photinduced accumulation of Ag⁺ ions. These phenomena are promising for fabrication of micro optical components.

An investigation on the laser ablative shaping (LAS) of the quartz glass has been made experimentally. F2 laser was used as the laser light source for efficient ablation of quartz material. The output beam of F2 laser was focused on to the surface of quartz plate. The ablation rate was about 10 micron m/pulse at the irradiation fluence of 2 J/cm². A uniform ablation of quartz plate has been demonstrated using F2 laser. The waveform of incident and transmitted laser light was measured by high speed photo-tubes to observe the time dependence of the absorption. The measured waveform indicates that the absorption was small at the leading edge of the laser pulse, and a strong absorption was induced at the end of laser pulse due to the excited state absorption. These phenomena are quite similar to both in F2 and ArF laser light. We have developed a simple model in which the instantaneous absorption is proportional to the absorbed energy prior to the moment. The calculated absorption was in good agreement with the measured wave- form. The change of transmittance in UV and VUV region was measured after the irradiation of F2 laser for samples of different concentrations of impurities.

Laser cleaning as a new cleaning technique has emerged in order to effectively remove contaminants from solid surfaces. Two types of laser cleaning techniques have been developed recently, relying on pulsed laser heating of the surface without or with the presence of a thin liquid coating. Laser cleaning was demonstrated both theoretically and experimentally to be an effective cleaning technique for removing contaminants from solid surfaces without damage. For dry laser cleaning, two cleaning models were established for removal of particles from substrate surfaces from the viewpoint of energy and force. For steam laser cleaning, a cleaning model was established for removal of particles from substrate surfaces with a thin liquid layer by taking Van der Waals force, capillary force, cleaning force, and chemical bonding into account. The models not only explain the influence of incident direction, wavelength, fluence on cleaning efficiency, but also predict the cleaning thresholds. The experimental results show that the laser cleaning efficiency increases with increasing fluence and pulse number, but does not depend on the repetition rate. The surface cleanliness can be monitored in real time by acoustic, electric and optical means. Applications of laser cleaning to clean magnetic slider surface, magnetic media surface, silicon wafer and IC mold surface will also be addressed. Engineering efforts and technical barriers of laser cleaning will be discussed in detail.

The technique of laser micro-processing has recently found several important and widespread applications in the manufacturing of disk-drive components. Examples provided here include the cleaning of surface contaminants, the formation of nano-bumps on disk surfaces for controlled surface texturing or for making glide height standards, and the micro-bending of magnetic head sliders for flight-height controls. Short-pulsed laser irradiation at suitable wavelength, fluence, and incidence direction can be used to clean off particulate and organic-film contaminants from surfaces of critical components, for example, the slider and the disk. Controlled disk texturing is needed to alleviate the problem of stiction which occurs when the disk stop spinning and the super smooth slider comes into stationary contact with the super smooth disk. A compact laser operating at high pulse repetition rate can be used to produce a low-stiction racetrack composed of typically a million nano-bumps. This can be done both for NiP/aluminum disks, or for glass disks. Single isolated bump with a specified height for providing height-standard can also be tailor-made. Very recently, we have developed a 'laser curvature adjust technique' and implemented it into production of magnetic head sliders. Here, microscopic adjustments of the curvature of air bearing surface of sliders can be produced by suitable laser scribing at the back side of the ceramic slider.

This paper presents a new micro-machining using optical radiation pressure induced by incident laser light, which is based on laser trapping technology. In order to verify the feasibility of our proposed new micro-machining, we construct the experimental system and carry out the fundamental experiments. As a result, we found that the proposed micro-machining will make it possible to remove effectively the surface up to the depth of several nm using the particles trapped by the optical radiation pressure, even if the pressure force is as small as 0.1nN.

Small dot matrix marking on a silicon wafer has been performed using an second-harmonic generation (SHG) laser of yttrium aluminum garnet (YAG), liquid-crystal-display (LCD) mask, and projection optics. A marked image was obtained after laser irradiation through the pattern on the LCD mask. The each dot is a square with sides of 3.6micrometers , the pitch of each dot is 4.5micrometers and the height (not the depth) of each dot is approximately 0.5micrometers . The topography of each dot is unique, and features a central peak and peripheral depression. We have named this topography micropeak and have proposed a hypothesis for the micropeak formation mechanism, based on the density of liquid silicon and the congelation of molten silicon. In this report, micropeaks were formed in the scribe line on a wafer covered with oxide layers. Without being torn, these oxide layers were pushed up by micropeak generation and rose. Silicon particle scattering around the laser irradiation area was prevented completely. Clear dot images were observed through the transparent oxide layers. The conditions forc lean marking by laser irradiation greatly depend on the thickness of the oxide layers.

A novel laser-based direct-write technique, called Matrix Assisted Pulsed Laser Evaporation Direct Write (MAPLE-DW), has been developed for the rapid prototyping of electronic devices. MAPLE-DW is a maskless deposition process operating under ambient conditions which allows for the rapid fabrication of complex patterns of electronic materials. The technique utilizes a laser transparent substrate with one side coated with a matrix of the materials of interest mixed with an organic vehicle. The laser is focused through the transparent substrate onto the matrix coating which aids in transferring the materials of interest to an acceptor substrate placed parallel to the matrix surface. With MAPLE-DW, diverse materials including metals, dielectrics, ferroelectrics, ferrites and polymers have been transferred onto various acceptor substrates. The capability for laser-modifying the surface of the acceptor substance and laser-post-processing the transferred material has been demonstrated as well. This simple yet powerful technique has been used to fabricate passive thin film electronic components such as resistors, capacitors and metal lines with good functional properties. An overview of these key results along with a discussion of their materials and properties characterization will be presented.

We report the observation of high light-induced change in refractive index (recognizable by observation in conventional microscope) in PMMA film doped with an optically non-linear dye 2-nitroaniline (NO₂(C₆H₄)NH₂ abbreviated as 2NA). The optically altered micrometer-sized regions were fabricated by single-shot radiation of 120 fs laser pulses into doped PMMA film using high numerical aperture 1.3 and high magnification x100 objective lens. The doping of films can be achieved in a wide range of 2NA concentrations (up to 40 wt%) without precipitation. This allows to control a storage time of an optically altered region up to one month by the adjusting the energy of the femtosecond (fs) recording pulse at 800 nm. Typical recording energy was 10-80 nJ/pulse at the point of irradiation. Total recovery of transmission of the PMMA2NA film was confirmed by optical transmission measurements in a microscope. The light induced damage threshold (LIDT) (for permanent damage) was increased more than by four times (up to 40 nJ/pulse) when 2NA doping were ca.1e wt%. While the LIDT for transient damage was decreased by 1.5-2 times. Total optical recovery was observed single exponential with decay time of ca. 0.5-1 minute for moderate irradiation intensities (0.1xLIDT of permanent damage). The damage induced with at the higher intensities lasts up to a month, but the recovery was not total (residual transmission changes were observable). The phenomenon can be applied for the optical memory, photonic crystal, and micro-mechanical applications. The underlying mechanism of the phenomenon is discussed in terms of anelastic (alpha) and (beta) -relaxation (polymer backbone and side chain relaxation, respectively).

Nitridation of semiconductor surfaces is attractive for passivation as well as fabrication of new materials. Nitridation of the III-V semiconductors has been mainly reported for GaAs. In this paper, we demonstrate the surface nitridation of InP by KrF excimer laser irradiation in an NH₃ ambient. The laser fluence was fixed at 80 mJ/cm² and number of pulses was changed from 500 to 10,000. S-ray photoelectron spectroscopy (XPS) analysis of the nitrided samples reveals that the InP surface contains both InN_x and PN_y compounds. Nitrogen content increases with the increase of number of pulses. Near- stoichiometric InN and P₃N₅ are formed by the 2500- pulse irradiation. Aging test reveals that the nitrided samples show anti-oxidation property, which is improved as the number of pulses increases.

We have developed a nanosecond imaging technique, where fundamental radiation of a Nd:YAG laser was used as ablating beam while the second harmonic radiation from the same laser was used as illuminating light pulse, to study surface phenomena during and immediately after the ablating laser pulse. Using this system, we observed the ablation phenomena of metals in air and found that, at fluence higher than about 10 J/cm², there appeared jet-like plasma growing towards incident laser beam at velocities of as high as 10⁵ ms₁ in addition to the laser induced plume. The jet grew during the laser pulse and when the pulse terminated, its rapid growth stopped. In this paper, we investigated the effects of laser pulse shape on this jet- like plasma. We found that appearance of the jet became later and its grown continued longer as pulse width increased. Growth speed of the jet depended on the pulse shape, even though the jet grew up to similar height at the end of the pulse. Our results showed that, even though a laser parameter in laser ablation was usually represented as the fluence, the controlling parameter for the jet growth was temporal change of laser power.

Recently, ultra-short pulsed lasers with high peak power have been developed, and their application to the materials processing is expected for a tool of precision microfabrication. During surface generation process with laser ablation, lattice defects such as dislocations, vacancies, grain boundaries, are also generated beneath the surface. Lattice defects influence the quality or accuracy of materials processing, therefore it is important for laser precision microfabrication to elucidate the generation mechanism of them. In this paper, laser ablation phenomena of metal were analyzed using the modified molecular dynamics method, which has been developed by Ohmura and Fukumoto. Main results obtained are summarized as follows: (1) The shock wave induced by the Gaussian beam irradiation propagates radially from the surface to the interior. (2) A lot of dislocations are generated near the surface by the propagation of shock wave. (3) Many grains are generated in the resolidification process after the end of laser pulse. They are metastable and some crystal-orientations of them change to one of the base metal and the grain boundaries disappear in the cooling process.

This paper reports a novel methodology of microfabrication particularly suitable for machining sub-millimeter wave components. The proposed technique entails the use of a positive photoresist (known as EPON SU-8 ^tm) in realization of E-plane components, in addition to other 3-D polymer structures such as rectangular waveguides. Because the micro-structure fabricated with the said photoresist can be less than ten microns thick, a high-Q E-plane circuitry of negligible substrate thickness can be lithographically processed to attain minimal dielectric loss. On the other hand, a planar whisker can be glued onto the E-plane circuits, enabling electrical contact of the small-diameter devices to be formed. But realizing non-planar structures with parametric variation in thickness is not lithographically trivial, adding the fact that the waveguide flanges can only be machined mechanically at the time of this writing. As suck, the authors suggest that an oversized waveguide channel and standard flange interfaces be first mechanically milled onto a metal block. The components to be processed with the said photoresist are then directly fabricated onto the oversized waveguide channel, in such a way that their interfaces to other standard waveguides can be maintained without loss of geometrical accuracy. In this paper, the basic fabrication procedures are first described, with formulae given on some design criteria. Laser Direct Imaging as applied to processing of SU-8 based submillimeter wave components are discussed, with particular reference given to the technical considerations as found from our recent experimental evidence. Measurements will be given to further substantiate this presentation.

High-resolution contact lithography was conducted by both 248-nm KrF and 193-nm ArF excimer lasers on PMMA resist. The resist thickness is about 0.5 (mu) . Resolution of 0.5- (mu) lines and spaces was obtained on PMMA resist after KrF excimer laser exposure and subsequent wet development. No self-developing photoetching was observed. However, with ArF excimer laser as the exposure light source, resolution of 0.3-(mu) lines and spaces was obtained on the same resist by direct photoetching under high exposure dose combined with subsequent conventional wet developing process.

Tetraethoxyorthosilicate and methacryloxypropyl trimethoxy silane are used to form inorganic and organic networks, respectively. Photosensitive agent is added to initiate free-radical cross-linking polymerization of unsaturated carbon bonds and thus makes the material act as a negative tone photoresist. Developed in dilute base solution, micro- optical element, such as lenses and gratings, were fabricated by contact with UV-exposure. Shrinkage effect is investigated after optical elements obtained. Compared with the mask, the spacing of the exposed areas in sol-gel film shrinks, and the shrinkage rate is about 20%.

The paste dried and hardened on glass substrate for fabrication of the PDP (Plasma Display Panel) barrier rib was selectively etched using focused Ar⁺ laser ((lambda) =532 nm), the threshold laser fluence was about 6.5 mJ/cm² for the barrier rib samples softened at 120 degree(s)C. The thickness of 180 (mu) of the sample was completely removed without any damages on the glass substrate by laser fluence of 19.5 J/cm². In order to increase the etch rate of the barrier rib materials, samples were heated on a hot plate during the laser irradiation. The etch rate at the hot plate temperature of 200 degree(s)C was roughly 4.2 times faster than that of room temperature.

The physical mechanisms of dry and steam laser cleaning of the surface are investigated theoretically. At dry laser cleaning particles are removed from the surface due to inertial force that caused by particles and/or substrate thermal expansion by light absorption and thermal conduction. The condition of complete particle removal, when it does not return to the substrate, is defined. The considered physical mechanism of dry laser cleaning is propagated to multipulse regime. The physical mechanisms of steam laser cleaning are proposed to be caused by liquid layer vaporization near the particle surface due to substrate and/or particle light absorption and non-uniform action of vapor pressure to the particles. The evaluated thresholds of dry and steam laser cleaning are in a good agreement with known experimental data.

A number of pulsed and/or continuous wave lasers are applied in stereo-lithography. In particular, the He-Cd laser and Ar ion laser with a wavelength of 325nm and 351/364nm respectively are used as ultraviolet (UV) light source. Disadvantages of these lasers include inefficient output energy, which is less that 0.1%, large machine size, insufficient output power, and they are very expensive. In the near future, these lasers are expected to increasingly lack the requested performance for higher speed stereo- lithography systems. Moreover, there will be growing demands for lower cost apparatus. For the laser stereo- lithography, the N2 laser with cylindrical tube has been adopted to achieve a lower cost type UV light source. Because of its excellent output efficiency, it is expected to downsize the power supply and laser head, and allows air- cooling. Moreover we adopt an optical fiber system for its optics, because the N2 laser output beam divergence has an excessive. In view of this, attempts were made to develop a special design cylindrical tube as the UV light source. This paper reports the fundamental characteristics of this laser.

Using 30-1000 (mu) s pulses and 9.3 (mu) m wavelength from a CO₂ slab waveguide laser, focused to a spot size of 130 (mu) m, we have produced holes in synthetic quartz, soda-lime glass, and Pyrex glass substrates. In the three types of substrates, the mass removal per pulse increases almost linearly with the pulse energy used to vary the pulse interval. The removal rates of the three substrates are almost the same. We examine the effect of the pulse interval on the hole structure and the pile-up around the hole in single- and multiple-pulse hole drilling. The deformation on the pile-up region can be accounted by the melting walls of the hole. Moreover, we examine the effect of pulse energy on the inclination of the hole walls. A multiple-pulse hole shaping technique is effective in decreasing the height coefficient of the pile-up region and the angle of inclination.

The F₂ Laser (wavelength 157nm) is becoming the most promising candidate of light source for next generation optical micro-lithography below the 100nm-technology node. We have developed VUV optics evaluation system, which is able to measure the transmittance between DUV and VUV region right after laser irradiation and the temporal transmittance during 157nm-laser irradiation. This system structured by Ni-plated Aluminum and stainless steel. The inside of chamber is purged of any laser light absorption gas away with high purity nitrogen gas during the irradiation. Using this system, we can measure the characteristics of the irradiated sample without exposing to the air of other contamination sources. So this system has +/- 0.5% accuracy result in repeated measurement. In the in-situ transmittance measure system, the transmittance can be monitored during F₂ laser irradiation. And we evaluated characteristics of VUV optical materials in the early period of F₂ laser irradiation by this in-situ transmittance measure system.

ArF excimer lasers are the light source of choice for the next generation of micro-lithographic tools enabling structures below the 130nm technology node. For these lithographic mass production lines Komatsu successfully developed an ArF excimer laser, named G20A, which has a 2kHz pulse repetition rate, 10W average power and 0.5pm (FWHM) spectral bandwidth. G20A has three significantly improved important items: (1) the high resolution line narrowing module, (2) the high power and high repetition rate solid state pulse power module, and (3) the Xe added laser gas yielding an improved overall laser performance. ArF laser spectra were determined with out newly developed high-resolution spectrometer. The instrument function of the spectrometer was measured with a 193nm coherent light source jointly developed with the University of Tokyo. The laser gas composition is one key parameter of excimer laser performance. The deteriorating effect of impurities on ArF performance is e.g. ten times larger than on KrF performance. We observed that added Xe gas, however, has a beneficial effect on the pulse energy and the energy stability at high repetition rates. Experimental results of a currently developed 4 kHz ArF laser are also reported.

50-mJ green and 12-mJ UV pulse beam were generated at 1-kHz repetition rate. Intracavity-frequency-doubling of a quasi- cw laser-diode-pumped Nd:YAG laser was used as a green beam source. CLBO(CsLiB₆O₁₀) crystal was used for 4th harmonic generation.

Laser texturing on a hard disk for a computer has been already used practically, but the mechanism of bump formation has not been elucidated yet. The purpose of this study is to elucidate the mechanism of bump formation in laser texturing by thermohydrodynamics analysis. Latent heat of evaporation, movement of gas and liquid interface, evaporation recoil pressure, Marangoni force that depends on temperature gradient and the surface tension are considered. The VOF (Volume of Fluid) method is used for the analysis of behavior of the free surface. Obtained results are as follows : (1) The downward flow is generated in the molten pool by the evaporation recoil pressure, and then it induces the outward flow in the radial direction. (2) After laser irradiation is stopped, the downward flow at the center of the molten pool and the outward flow in the radial direction are kept. Therefore, the center of the molten pool is lowered and the surface rises around the hole, that is, a bump is formed. (3) When the temperature coefficient of surface tension is negative, Marangoni force is most effective to the surface rise when the resolidification starts outside of the bump.

Recently, scanning probe microscope (SPM) has become a promising technique for nano-fabrication. In this paper, we present a novel method of nano-fabrication, namely, nano- fabrication by atomic force microscope (AFM) tips under laser irradiation. The SPM was operated as an AFM. During imaging and nano-fabrication, the AFM is in constant force mode. The tip is fixed with the sample moving via a tube scanner. Nano-lithography software controls the scanner motion in x and y directions. The SPM has an open architecture allowing an external laser beam incident on the tip at an incident angle between 0 to 45 degree(s). A vertical polarized Nd:YAG pulsed laser with a pulse duration of 7 ns was focused on the tip. An electrical shutter was introduced to switch the laser irradiation. Alignment between the laser beam and the tip was performed under a high-power charge coupled device (CCD) microscope. Nano- fabrication was carried out on gold films deposited on n- type Si substrates using the physical deposition method. The kinetics of the nanostructure fabrication has been studied. Craters were created in air ambient under different laser pulse numbers, pulse energies and tip force. The feature size of the craters, which are in the nanometer scale, increases with the pulse number, pulse energy and the tip force. This technique has potential applications in the high-density data storage.

In the present work, laser surface annealing has been applied to an age-hardened Ni base supper alloy Inconel 718 using a 2.5kW CO₂ laser to improve its performance in hydrogen environment. Laser surface annealing can produce a locally solutionized zone at the surface of Inconel 718. In the solutionized zone the age precipitates of (gamma) ^' and (gamma) ^'' are dissolved in the matrix, and thereby the hardness of the solutionized zones is reduced to below 250Hv from approximately 450Hv of the aged base metal hardness. The surface softened zones having several hundred micro meters in depth can be obtained without melting the treated zone by controlling the laser parameters, i.e. thee defocus distance and traverse speed. Having much greater ductility than the aged base metal in hydrogen environment, the surface softened zones can effectively prevent hydrogen induced cracking, which tends to occur at the surface of a stress concentrated region. In the present case, the ductility of the surface annealed specimen is almost twice that of the base metal in a tensile test under a 29.3MPa hydrogen atmosphere at room temperature with hydrogen pre- charging. Since a controlled laser irradiation can precisely and locally anneal the surface of a stress concentrated region where hydrogen induced cracking is liable to occur, a sacrifice of strength of the structure caused by the surface softening is negligible.

PulsESPI, combined with an innovative beam deliver device, may enable obtaining a very accurate control sensor to determine with improved accuracy some of the laser material processing parameters like the geometry of the keyhole and cutting kerf in real time.

Behaviors of the plasma, the emission intensity, distribution, source and species were evaluated using a high-speed video camera, a color CCD camera, and a spectrum multi-channel analyzer. It was found that a strong blue radiation from iron atoms of workpiece, nitrogen molecules or ions of a gas jet, when the cut surface quality was not acceptable. As cutting speed increased, plasma formation region where a laser beam was focused was more extended. It was found that flow speeds of molten material at bottom in which the plasma was induced became slower than those of top and middle points. Also, scattering angles of molten material droplets at a bottom exit of a kerf became larger and, at the same time, reattachment of molten material at the bottom was observed. Moreover, it was found that additional branches of the flows of molten material with smaller and darker droplets were formed intermittently, and that parts of the branches of the flowing droplets were being attached as dross to the bottom edges. From these results, it was confirmed that the plasma formation (region) and sizes and angles of striations (cut surface quality) were strongly correlated. Possibilities of the in-process evaluation of the cut surface quality by monitoring the plasma sizes and/or brightness in laser beam cutting were discussed.

Solderability of conventional Sn-37Pb solder pastes and Pb- free alloys (Sn-43Bi and Sn-2Ag-5Bi-0.5Cu) were examined on micro soldering using a YAG laser. Experiments were performed in order to determine the range of soldering parameters of a laser power density and an irradiation time for obtaining an appropriate wettability based on a visual inspection by a Japanese Industrial Standard. And the laser soldering processes were monitored by measuring temperature change inside solder joint (solder and Cu pad) and on a surface of a chip component. Next joining strength of chip components for surface mounting soldered on printed circuit board (glass epoxy) was tested on application thickness of solder paste (0.2, 0.3, and 0.4 mm). In addition, joining strength characteristics at different power density and materials were examined around thermal shock test by the gas phase method. As a result, characteristics of Sn-Ag-Bi-Cu (Pb-free) solder paste are equivalent to that of Sn-Pb solder paste.

This study, the action of molten metal in the kerf using oxygen and an assist gas was observed with the high speed digital CCD camera. The ejection of molten metal is changed direction in every 2ms. Case of the optimum condition speed cutting (1800mm/min), the molten metal moves straight down to bottom of the kerf. Case of the high speed cutting (2800mm/min), case of the mass molten metal stays in the kerf, dross appeared underneath the workpiece. And case of ejection angle is over the 45 degree, dross appeared underneath the workpiece. Mass molten metal and small molten metal is every pulsed.

Titanium aluminide intermetallic compound is attracting attentions as heat-resistant and high-specific strength material in the next generation, especially, it is promising material in the field of aerospace components. Conventional machining process including welding, however, can be hardly applied due to its very low ductility. The objective of this study, as a first stage, is to find out paying attention to crack and hardness the fundamental good conditions of the bead-on-plate welding of TiAl intermetallic compound using CO₂ laser irradiation. In the experiment, we used the casting gamma titanium aluminide contained iron, vanadium and boron with a thickness of 2mm. We carried out bead-on-plate laser welding in the titanium aluminide material in inert gas environment filled with argon. We measured fused depth, Vickers hardness, transverse crack numbers and so on as major parameters of welding speed from 1000 to 4600 mm/min and initial temperature of specimen from R.T. to 873 K with a beam spot size of 0.5 mm and an output power of 1.5 kW. In addition, the specimens were analyzed by Electron Probe X-ray Micro Analyzer, Energy Dispersive X-ray Spectroscopy and X-ray Diffractometry. As a result of experiments, transverse crack-free welding was achieved, when initial temperature was at 873 K. In every condition, the value of Vickers hardness of fused zone increased compared with base. We think the reason of it is an increase of (alpha) ₂(Ti₃Al) phase, which is caused by rapid cooling, taking in Oxygen, fine structure and so on.

YAG laser has widely been used for precision micro machining in many fields. However, adhesions of dross and spatter to the base material due to high energy beam machining lead to the deterioration of the surface integrity. It is important to understand the assist gas flow from the tip of a convergent nozzle in order to improve the surface integrity, since material is mostly removed away by the gas flow spouted in the same direction of the laser beam. In this paper, effects of the nozzle shape on assist gas flow and the machined results were experimentally analyzed using the Schlieren method. There exists an unstable region in which the pressure on the workpiece changes periodically, and the region becomes wider with the reduction of the exit diameter. The pressure on the workpiece increases with an increase of the exit diameter, which makes the dross height smaller. However, it is necessary to select the nozzle shape according to the demand of the surface integrity, because the consumption of the assist gas increases and the kerf width becomes wider with an increase of the exit diameter. Moreover, it was pointed out that a kind of nozzle with a convex curve on inner wall of nozzle led to better surface integrity.

A system consisting of 11 photodiode sensors from 0 to 90 degrees with respect to the workpiece surface has been developed to detect the angular distribution of the reflected laser intensity. Spot welding process in thin copper sheet using pulsed Nd:YAG laser was experimentally analyzed by detecting angular distribution of reflected laser beam with time resolution. Spot welding was performed with pulse duration of 1 ms on a phosphorus copper thin sheet with thickness 250 (mu) m in atmospheric condition. The change in the contour of the molten pool was investigated by time-resolved angular distribution of the reflected laser beam and penetrating time at a sampling frequency of 40 kHz. The laser beam passing through the thin sheet was also detected; the penetration time through the thin sheet was approximately 0.6 ms at an incident power density of 2.7x10⁶W/cm². The reflectance determined by integrating angular distribution of the reflected laser intensity was approximately 85% at the beginning of the pulse and then decreased with time. It is also shown that this system can be used for monitoring the quality of the lap welding of thin sheet metals.

The optical emission spectra of the plasma produced by infrared and ultraviolet laser ablation of graphite in a vacuum were observed. The fundamental output of an Nd: YAG laser was used as the infrared laser. The fourth harmonic output of an Nd: YAG laser and a KrF excimer laser were used as the ultraviolet lasers. The emission intensity of the ionic carbon as well as C₂ and C₃ from the plasma produced by the infrared laser were stronger than that produced by the UV lasers at the same fluences. The C₂ and C₃ emission intensities decreased rapidly with increasing the distance from the target. The emission intensity of atomic carbon at 247.8 nm from the plasma produced by the KrF excimer laser was much stronger than that produced by the other lasers at the same laser fluence, due to the wavelenght of the KrF laser being so close to that of atomic carbon's emission line as to raise its electrical state.

A new manipulation technique using Q-Switched laser beam was developed in this research. By using which, we could trap a fine particle in the air with relatively lower laser output. In order to clarify the possibility of the application of this method in micro-machining, the assembly experiments were conducted and the experimental results showed that the three dimensional microstructure from fine particles can be realized by this technique.

A wideband and ultrafast phototube is applied to diagnose laser-induced plasma-assisted ablation of fused quartz. It is found that signal waveform is closely related to laser fluence and target-to-substrate distance. For the distance less than a threshold, below which quartz ablation takes place even by single pulse irradiation, there are three peaks detected. Signal analyses show that the first peak is attributed to laser scattering, the second and third ones to Ag target and quartz substrate ablation. It confirms that there is a direct influence of target plasma on substrate ablation. The third peak moves forward and overlaps with other peaks as the distance decreases and laser fluence increases. Peak amplitude and its arrival time of the quartz plasma are used to characterize the ablation dynamics. Signal variation with pulse number shows that at a higher distance, there are only two optical peaks attributed to laser scattering and target ablation in the first pulse. While by further pulse irradiation, the peak for quartz ablation is recorded. It is due to Ag thin film deposited on quartz rear side surface after the first pulse irradiation. As the distance increases further, the peak for quartz ablation moves to the right and finally disappears because of no thin film deposited.

Recently, the structural modifications of glass by focusing femtosecond laser pulses have been demonstrated. We present photo-induced structural changes in silica glass with femtosecond laser pulses. We investigated the relationship between the formation of filaments and local refractive index changes in silica glass. In situ observation revealed the coincidence between the location of filament and that of refractive index change. The observation also showed that the region of refractive index change elongates toward the upstream direction of laser pulses with the exposure time. The region of refractive index change was several hundred- micron long and the diameter was smaller than two microns. The length of the region was dependent on the numerical aperture of focusing lenses. The refractive index change was confirmed to be as large as 0.01 by three different methods. We fabricated a 2-mm waveguide by translating the sample along the optical axis.

We introduce some preliminary results of measurement on a simulated corneal surface. The possibility to devise a reliable mathematical model to simulate the corneal behavior in order to obtain target refraction (TR) is also discussed during and after Photo Therapeutic Keratectomy (PKT).

In laser rear patterning, a thin film deposited on the supporting substrate is irradiated by a laser beam from the rear side of the thin film through the substrate to remove the irradiated area of the film. In this study, a KrF excimer laser with a pulse width of 30 ns and different values of fluences was focused onto metal such as a gold and a copper thin films, which were deposited on a fused silica substrate using the ion sputter deposition method. The intensities of the incident and the transmitted laser beams were measured simultaneously using photodiodes during the laser rear patterning. The results show that the film removal started after approximately 10 ns of laser irradiation under optimized deposition condition. During the laser rear patterning, it was found that the recoil force of the evaporation generated between the film and the substrate pressed the film. As a result, the molten part at the edge of the unirradiated part was peeled and ejected away by the momentum from the recoil force.

A method that uses a Nd:YAG laser was developed to mark bar codes on glass substrates. In this method, bar codes are created by a combination of laser deposition and laser trimming; a film for the black bars of the bar code is deposited on the glass substrate, and part of the deposited film is trimmed to expose the white bars of the code. The resulting bar code has high contrast and high resolution. The measured transmission coefficient of the black bars was 2%. When the transmission coefficient was less than 70%, the bar codes were identified at an acceptable level, i.e. the code identification rate was at least 70%, with an average of 91%. The bar code was impossible to identify when the transmission coefficient was 78%. The laser power tolerance of the film deposition for code identification was about (formula available in paper)at optimum laser power.

Two laser processing systems for micro drilling of printed circuit boards and/or LSI packages are presented. One is a pulsed CO2 laser system and the other is a LD-pumped THG-YAG laser system, both are now commercially available.

The performance of the concurrent in-line inspection system in CO₂ laser drilling process has improved by the defect pattern estimation algorithm. The optical detection principle of the system is based on the relationship between the reflected laser intensity from the bottom copper foil in via-hole and the area size of the exposed copper surface. The principle and the advantage of the enhance concurrent inspection system was described. Using the improved concurrent inspection system, the etched hole diameter and defect of PWB can be examined. This function has a capability to substitute AOI function. As a result, reliability and throughput in PWB drilling process has been improved.

In this paper, we propose a new method of fabricating 3-D models of the high-temperature structural materials such as ceramics by selective laser sintering (SLS). To save the laser energy, we adopted the combustion synthesis which is the exothermic reaction between the raw materials. By adding chemical reaction heat to laser heat, the particles of the products of the reaction were bonded together by relatively low laser energy. The combinations of the raw materials and the laser scanning conditions for solidifying the products and laminating the solidified layers were investigated experimentally. Since burning in the furnace is unnecessary in the proposed method, it is possible to fabricate the models in a short time.

This is the report for compact laser micro processing unit excimer laser employed featuring a very fine process with high accuracy. This unit consists of objective lens, of which magnification is 10 to 80, used for both processing and observation. It makes possible high energy density resulting 0.5micrometers resolution at 248nm, accurate positioning and compact size. Applications 1) Removing upper metal layer of LSI in order to inspect pattern of the bottom layer. 2) Creating fine geometrical pattern on PET fiber cloth in order to apply new function such as better dyeing and adhesiveness. 3) Creating 100micrometers dia. Hole to artificial blood vessel made of polyurethane tube with 2mm inner dia. In order to have similar mechanical property to real blood vessel.

High power diode lasers gain considerable interest for materials processing applications, since they are very efficient, easy to use, reliable and almost service free. In contrast to conventional lasers, state-of-the-art high power diode lasers consist of a high number incoherently coupled individual semiconductor lasers, which are combined to one unit by use of semiconductor technology, micro- mechanics and micro-optics. A power range from 10 W until up to 8 kW can be covered. This paper describes the technology of diode lasers in the range between 30 and 150 W. The diode lasers have already successfully entered the industrial manufacturing area. As applications of lasers in this power range soldering and polymer welding are described in more detail.

Transparent materials such as fused silica, quartz, calcium fluoride, and fluorocarbon polymer were etched upon irradiation of organic solution containing pyrene with a conventional KrF excimer laser. Threshold fluence for etching was 240 mJ/cm² for fused silica. Etch rate remarkably depended on a concentration of pyrene: higher etch rate with the increase of pyrene concentration. It means that pyrene molecules play an important role in this process. The etch rate can be easily controlled through changing a laser pulse number, a laser fluence and a concentration of solution. The mechanism for this process is discussed by cyclic multiphotonic absorption of pyrene in the excited states, thermal relaxation, and formation of super-heated solution. As the results, it is suggested that the process is based on the combination of two processes in the interface between the transparent materials and the liquid: one is a heating process by a super-heated liquid and the other is an attacking process by a high temperature and pressure vapor.