We present laser results of OPS structures based on highly strained InGaAs quantum wells emitting at 1178nm and
frequency doubled to produce high power, high beam quality laser radiation at 589nm. The laser architecture is the same
as in our commercial offerings, allowing us to achieve the desired results with a system significantly simpler than
Optically-pumped semiconductor (OPS) lasers are power-scalable, wavelength-flexible, infrared brightness converters.
Adding intra-cavity frequency doubling turns them into efficient, low noise, high power visible laser sources. We report
on a laser combining an InGaAs gain medium with an LBO nonlinear crystal to produce more than 20 Watt CW in
single transverse mode at 532 nm. Efficient cooling of the single gain chip using advanced mounting techniques is the
key to making the laser reliable at high CW powers. A rugged and compact package withstands significant
environmental excursions. The laser's low noise makes it suitable for demanding Ti:Sapphire pumping applications.
We discuss a compact RGB source with ouput power of several watts per color consisting of a red (638 nm) diode and OPS lasers with blue (460 nm) and green (530) nm output. Suitability for display applications is shown by replacing the lamp of a standard Rear Projection TV.
We report performance parameters of a robust, 50 W, high repetition rate amplified ArF excimer laser system with FWHM bandwidth of less than 0.25 pm, 95% energy content bandwidth of less than 0.55 pm, and ultra-low ASE level. Proprietary design solutions enable stable operation with a substantial reliability margin at this high power level. We report on characterization of all the key parameters of importance for the next generation microlithography tools, such as spectrum and dose control stability, in various operating modes.
Today the molecular fluorine (F2) laser emitting at a wavelength of 157 nm represents the strongest commercially available coherent light source in the vacuum-ultraviolet spectral range. Lambda Physik produces a broad variety of F2-Lasers which cover a wide range of output power (from less than 1 W to more than 20 W), repetition rate (from less than 100 Hz to more than 4 kHz) and single pulse energy (from less than 1 mJ to more than 30 mJ). The parameters of each of these kinds of F2-lasers are designed and suitable for specific fields of application. In the paper we will review the main parameters of these different types of F2-lasers, compare their special features and discuss the principle applications they are used for. The low energy, medium repetition rate is basically used for metrology and calibration tasks, the high energy or high repetition rate and high power F2-laser systems are mainly used for material investigations and in a growing extent for 157 nm-micromachining. Lithography tools use the high repetition rate, high power single-line F2-laser systems. All of these scientific or industrial applications take advantage of the unique properties of the 157 nm radiation, i.e. the ultra-short wavelength of emission and the very high photon energy of nearly 8 eV. Thus, very precise and fine microstructuring in the micrometer range is possible and the 157 nm optical lithography is on target for critical dimensions of integrated circuits below 70 nm. The short pulse duration and high photon energy also enables efficient and exactly located icroscopic ablation of most critical materials without thermal impact on the surrounding area. In the last part of the paper some recent results on F2-laser development and an outlook on future products will be given.
According to the ITRS-Roadmap, the 157 nm wavelength of the F2-laser is the most likely solution to extend the optical lithography for production of ICs with critical dimensions below 70 nm down to the 50 nm node. This requires high power, high repetition rate F2-lasers with highest reliability, operating in the power range of more than 40 W at repetition rates of at least 4 kHz. In the recent three years strong efforts have been done in order to investigate and develop all kind of materials, technologies and devices which are necessary to introduce the 157 nm lithography for high volume mass production in the year 2004/5. Towards this road Lambda Physik has developed a 4 kHz line selected F2-laser with an output power of 20 W meeting the spectral performance requirements and therefore suitable for pilot 157 nm scanner. In order to reach an output power of 40 W under retention of the required spectral performance, we are now concentrating on the output power increase which comprises a new tube design, a modified discharge and charging circuit. In this paper the laser performance data which has been verified and measured by existing and improved 157 nm metrology as well as new findings on general F2-laser properties at high repetition rate, high power operation will be discussed. The prototype 4 kHz line selected F2-laser gains benefit from the outstanding long term reliability of the resonator optics. The field proven NovaLine F2020 optics modules are only slightly modified for 4 kHz operation. Lambda Physik will present appropriate reliability data which had been confirmed from field application showing laser tube and optical modules life times passing 5 Bio shots at 2 kHz repetition rate operation.
Laser micromachining has become a key enabling technology in the ever-continuing trend of miniaturization in microelectronics, micro-optics, and micromechanics. New applications have become commercially viable due to the emergence of innovative laser sources, such as diode pumped solid-state lasers (DPSSL), and the progress in processing technology. Examples of industrial applications are laser-drilled micro-injection nozzles for highly efficient automobile engines, or manufacturing of complex spinnerets for production of synthetic fibers. The unique advantages of laser-based techniques stem from their ability to produce high aspect ratio holes, while yielding low heat affected zones with exceptional surface quality, roundness and taper tolerances. Additionally, the ability to drill blind holes and slots in very hard materials such as diamond, silicon, sapphire, ceramics and steel is of great interest for many applications in microelectronics, semiconductor and automotive industry. This kind of high quality, high aspect ratio micromachining requires high peak power and short pulse durations.
During the last decade the development of fiber Bragg gratings (FBG) was forced by the ever growing demand on data transmission capacity. Fiber Bragg gratings support as filters, amplifiers, and stabilizers the entire optical network philosophy avoiding optical to electrical signal conversion. Whereas in the early 1990s the most gratings were manufactured by researchers with continuous wave (cw) laser sources, the excimer laser became a common tool for high throughput writing of Bragg gratings in the mid 1990s. The excimer laser is nowadays still the most efficient UV laser source which leads to low cost of operations compared to other UV sources. This paper presents the possibilities and advantages of excimer lasers in regards to writing of fiber Bragg gratings.
According to the ITRS-Roadmap, the 157nm wavelength of the F2-laser is the most likely solution to extend the optical lithography for production of ICs with critical dimensions below 70nm down to the 50nm node. The introduction of the 157nm lithography for high volume mass production requires high power, high repetition rate F2-lasers operating in the power range of more than 40W or at repetition rates of more than 4kHz. To meet the narrow time gap for an introduction of the full-field 157nm-scanner systems for real production in the year 2004/5 the community have to solve several challenging issues even in the laser section. F2-laser systems are needed which completely fulfill all specifications of a lithography light source, either for a refractive or a catadioptic projection optics. Verification and precise measurement of the key laser parameters in the VUV usually requires a specific development of the metrology, necessary for this task. In this report we present the progress which had been achieved in the development of high repetition rate high power single-line F2 lasers for catadioptic lithography application. The key features of a F2-laser > 4kHz will be demonstrated. We will also review the main parameters and the performance data from the field of the standard lithography-grade F2020 a 2kHz system which is already applied for pilot scanner tool design. Some improvements of these systems with regard to single line power, dose stability, polarization and gas life will be shown and reliability data from the field will be reviewed. Critical dependence of the spectral properties of the F2-laser emission at 2 kHz and 4 kHz will be discussed. Some new investigations on the coherence properties of the Fluorine laser are also implemented.
The material processing of an industrial, short-pulse duration DPPS YAG laser producing peak powers greater than 0.2MW is discussed in this paper. This peak power provides sufficient materials processing capability to meet the micro machining needs in the automotive, semiconductor, micro- electronic, medical and telecommunication industries. All hard and soft materials including: plastics, metals, ceramics, diamond and other crystalline materials are suitable candidates for the processing capability of this laser. Micro level features can be machined in these materials to a depth in excess of 1mm with high quality results. In most applications feature sizes can be achieved that are not possible or economical with existing technologies. The optical beam delivery system requirements, and overall micro-machining set-up are also described. The drilling and cutting versatility down to feature sizes of less than 7 micrometers , as well as, complex shapes are shown. The wavelength, pulse length, and peakpower are described and relate to their effect on recast, micro-cracking and material removal rates. Material removal effects related to progressive penetration into the material will be reviewed. The requirements of this DPSS laser technology to meet the operational requirements for high duty cycle operation in industrial environments is covered along with processing flexibility and lower operating cost.
According to the SIA-Roadmap, the 157 nm wavelength of the F2 laser is the most likely solution to extend the optical lithography for chip production from the critical dimensions of 100 nm down to the 50 nm node. The introduction of the 157 nm lithography for high volume mass production requires high power, high repetition rate F2 lasers operating in the power range of more than 40 W or at repetition rates of more than 4 kHz. These leading specifications are combined with other challenging laser specifications on dose stability and bandwidth which must be realized within a very aggressive time line for the introduction of the full-field scanner systems in the year 2003. According to this roadmap of the tool suppliers Lambda Physik has now introduced a 2 kHz lithography-grade F2 laser F2020 for further pilot scanner systems. In this report we present basic performance data of this single line 2 kHz F2 laser and some typical results on key laser parameters which had been measured with new and improved metrology equipment. We demonstrate for the first time precise measurements on the correlation of the natural bandwidth versus pressure which had been performed with an ultrahigh resolution VUV spectrometer. In addition a new compact and transportable high resolution VUV spectrometer was used for analyses of spectral purity and line suppression ratio of the laser emission. The experimental setup and result of an absolute calibration of a power meter, for the first time directly performed at the true 157 nm wavelength, are presented.
We develop several new optical techniques for microscopic semiconductor diagnostics and use them for inspection of semiconductor surfaces. Short-pulse lasers (femtosecond Ti:sapphire and Cr4+:forsterite) are used for nonlinear optical studies.
The 157 nm F2 laser is becoming the workhorse for lithography tools for the 70 nm technology node. In this paper we review our recent advances in technology and reliability of 157 nm lasers. We discuss the improved lifetimes of main laser components and their impact on Cost of Ownership (CoO) of the F2 laser. The typical lifetime of Lambda Physik Novaline laser discharge tube, coated CaF2 optics, and energy monitors exceeds 3 billion, 2 billion, and 2.5 billion respectively. The CoO of the F2 lasers reaches that of ArF lasers. We also report the results of our very thorough studies on the various line-narrowing arrangements, and feasibility of amplification at 157 nm, in the context of our recent studies of the fundamental spectral properties of F2 lasers.
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.
Performance limits of 10 kHz, 15 nsec-pulse diode-pumped solid- state laser in microdrilling of metals and ceramics were studied. Average drilling rates approaching 1 cm/sec with micrometer-range accuracy of micro-holes are achievable in steel and ceramic samples up to 1 mm thick. We found that shielding effects of plasma plume can be minimized by proper selection of laser intensity. In samples 1 mm and thicker, using third harmonic output allows drilling of high aspect ratio holes at almost an order of magnitude higher ablation rates as compared to IR laser output.
According to the SIA-Roadmap, the 157 nm wavelength of the F2 laser emission will be used for chip production with critical dimensions of 100 nm down tot eh 70 nm node. Currently al basic technologies for 157 nm lithography are under investigation and development at material suppliers, coating manufacturers, laser suppliers, lens and tool manufacturers, mask houses, pellicle manufacturers, and resist suppliers.
We investigated wavelength- and intensity-dependence of ablation rate achievable with a diode-pumped Q-switched Nd:YAG laser with frequency doubling and tripling. The laser produced 15 ns-long pulses at a repetition rate of 10 kHz and output power of 28 W in the fundamental beam, and 15 W and 10 W in the second and third harmonics, respectively. We found that in thin stainless and carbon steel foils, fast ablation starts at the laser fluence level of 10 J/cm2. The ablation rate remains close to 1 micrometers per pulse with very little change as the laser fluence increases by more than order of magnitude above this threshold exit of the hole. This attenuation is strongly dependent on the laser wavelength. Particularly, using third harmonic output, we were able to sustain average drilling speed of more than 1 micrometers per pulse in samples up to 1 mm thick. At the same time, removal rate at fundamental wavelength decreased by almost an order of magnitude.
This paper reports the development of high power excimer lasers with enhanced spatial and temporal coherence. These excimer lasers are applicable to writing fiber Bragg gratings by interferometric or phase-mask techniques. An excimer laser with a novel unstable resonator will be analyzed with respect to its suitability to the production of passive fiber optic components and in terms of production flexibility, efficiency, and reliability. A survey of applicability of this tool to short and long period fiber Bragg gratings will be presented.
Optical deep UV (DUV) lithography is aiming to reach feature sizes of below 100 nm. The likely choice of the exposure wavelength will be 157 nm, which is emitted by the F2 excimer laser. Experience with this laser type in a variety of applications has been gained at Lambda Physik for the past 20 years. A major breakthrough in performance, in particular laser efficiency and durability, was achieved with the introduction of our metal ceramic laser tube in 1996. In this paper, we report on the progress in the development of the F2 laser light source. A major advance in narrowing the bandwidth of a 10W laser is the achievement of output spectral width of about 1 pm. With a newly developed NovaTube based F2 discharge chamber we show more than 19 million pulses gas lifetime without any additional gas actions. The laser achieves up to 1 kHz repetition rate. Energy stability sigma is 1 percent, dose energy stability 0.5 percent. The performance characteristics as temporal and spatial beam profile and the suitability the laser for microlithography are discussed. Typical lifetimes of the key components and a projection of the present and future cost of operation are presented.
High power laser sources of deep UV radiation play an important role in numerous applications such as microlithography, micromachining and material modification. Usefulness of deep UV lasers for each specific application arises from their unique characteristics, most importantly wavelength, temporal and spatial coherence and intensity distribution of the beam. Recent progress in the areas of DUV optical materials, laser resonators and electronics made possible dramatic improvements in power levels, brightness and intensity uniformity at these extremely short wavelengths, combined with long term stability and reliability. We report on recent advances in development of high power excimer lasers at the wavelengths of 248 nm, 1 93 nm and 1 57 nm for applications requiring high spectral brightness, such as microlithography, and high spatial and temporal coherence, such as writing of fiber Bragg gratings. We also present new data on high power all-solid-state laser sources of 266 nm, 213 nm and tunable UV radiation which are becoming a real alternative to excimer lasers in some DUV applications. We discuss impact of the long-term degradation of optical elements on the performance, reliability and running costs of recently developed DUV lasers
We report on the generation and potential applications of an UV light source tunable from 280 nm to 315 nm with an average power of more than 0.5 W and high absolute conversion efficiency. Overall conversion from the diode pumped Nd:YAG laser fundamental (1064 micrometers ) wavelength to the tunable output exceeded 6%, and an absolute efficiency of Ce:LiCaF laser to the 266 nm pump was in excess of 27%. The diode pumped Nd:YAG laser used in the experiments delivered 1.9 W of average power at 266 nm by successive doubling and quadrupling of 8 W output at 1064 mum. The advantage of using 1 kHz pulsed-diode pumped Nd:YAG laser source lies in relatively high energy per pulse, as compared to the systems with continuous diode pumping, thus allowing high conversion efficiency into fourth harmonic. The fourth harmonic output beam was slightly focused into a 5 mm long Ce(2at.%):LiCaF crystal with AR coated faces. The relatively large energy of the pump pulses resulted in a large beam cross-section in the crystal, thus allowing efficient quasicollinear longitudinal pumping. The laser was tunable from 280 nm to 315 nm. The output linewidth varied from 0.3 to 0.6 nm, depending on spectral position and the pump power. Applications in microelectronic and optoelectronic manufacturing will be discussed.
We report here the experimental results on the SHG and linear reflectivity studies of the dynamics of laser-induced melting of a GaAs surface layer under subpicosecond pulsed laser excitation. We find that the SH intensity drops in a time less than 100 fs after excitation, while the linear reflectivity reaches a value characteristic of molten GaAs on a time scale of about 1 ps. Thus, the experimental results unambiguously indicate that ultra-fast phase
transition to a new solid phase with structural properties different both from that of initial material and that of molten GaAs takes place in the surface layer under strong femtosecond laser excitation. This transition occurs on a time scale of 100 fs which is about an order of magnitude less than the time required for the electron relaxation to the bottom of the conduction band.
Nonlinear absorption of 176-fs laser pulses in GaP was measured using both time-domain and intensity-domain techniques. The nonlinear response turned out to have a very short relaxation time. The absolute value of the two-photon absorption coefficient was measured.