Results on laser-assisted deposition and surface modification of II-VI semiconductors and real-time optical diagnostics of laser-assisted reactions are reported. Excimer laser-assisted metal-organic vapor phase epitaxy has been used to deposit epitaxial layers of CdTe on GaAs(100) and HgTe and [HgCd]Te layers on CdTe/GaAs(100) at 165°C. KrF excimer laser radiation (248 nm) was used to photodissociate divinylmercury, dimethylcadmium and diethyltellurium source materials in the gas phase in a substrate-parallel irradiation geometry. Laser-induced fluorescence and multi-photon ionization spectroscopy was used to probe Te alkyl photodissociation dynamics. Single photon excitation at 248 nm results in the formation of ground state (5p3P2) Te atoms and alkyl photofragments. These results are consistent with a mechanism in which 248 nm excitation results in destabilization and cleavage of both Te-C bonds in the metal alkyl. Controllable surface layer removal and reproducible fluence-dependent composition changes were produced in CdTe thin films by KrF excimer laser irradiation. Time-of-flight mass spectrometric measurements of the velocity distribution of photoejected species are consistent with a thermal mechanism for the laser ablation process.

First experiments of the epitaxial growth of diamond structured a-Sn films by synchrotron radiation assisted photodissociation are reported. Surface sensitive core and valence band photoemission spectroscopy is used to study the adsorption behavior and photodissociation of tetramethyltin on clean and highly ordered CdTe(100) surfaces. A quantitative analysis including the work function change and the evolution of substrate and adsorbate intensities during the overlayer deposition suggests that individual monolayers can be grown by the technique of synchrotron radiation assisted metalorganic layer epitaxy (SRMOLE).

The growth mechanism in photo-assisted metal organic vapor phase epitaxy of ZnSe on GAAs substrate using dimethylzinc and dimethylselenide has been investi-gated using Ar ion laser as an irradiation source. It has been found that following three parameters greatly affect the film growth: (1)hydrogen gas partial pressure, (2)Ar ion laser irradiation, and (3)thickness of the growing ZnSe layer itself. From the results obtained, it has been found that the absorption of photons by ZnSe layer and following formation of excess-holes near the surface are essential for the growth-rate enhancement in the photo-assisted MOVPE of ZnSe. A plausible growth mechanism utilizing a band diagram of ZnSe/GaAs junction in which excess-holes play an important role at the ZnSe surface has been proposed.

Studies of the thermal and photon-induced surface chemistry of dimethyl cadmium (DMCd) and dimethyl tellurium (DMTe) on GaAs(100) substrates under ultrahigh vacuum conditions have been performed for substrate temperatures in the range of 123 K to 473 K. Results indicate that extremely efficient conversion of admixtures of DMTe and DMCd to CdTe can be obtained using low power (5 - 10 mJ cm-2) 193 nm laser pulses at substrate temperatures of 123 K. Subsequent annealing at 473 K produces an epitaxial film.

Selective epitaxy by direct writing of thin films GaAs using laser chemical vapor deposition on GaAs substrates has been achieved. Careful control of the deposition parameters for the epitaxial growth is is necessary. The deposited materials are comparable to those grown with conventional metalorganic vapor deposition techniques. We report a model on the growth conditions that can be used without the occurrence of plastic deformation in the epitaxial films. The model considers the thermal stresses that induce lattice distortion in GaAs substrates. This lattice distortion is caused by heating with laser beam which has a Gaussian power density distribution. Experimental results are compared with the model.

Resistless microfabrication of Cu thin films on n-type GaAs by projection patterned laser doping using a KrF excimer laser and a SiH4 gas is described. Copper thin films with a linewidth as narrow as 2.35gm are deposited selectively on the doped region by electroplating in a CuSO4 aqueou solution. The resistivity of the deposited Cu films is evaluated to be 2.45x 10° S2cm, which is compared to that of bulk Cu. Using this technique, nonallpyed ohmic contacts can be formed with a specific contact resistance of 2.32x 10a S2 cm 4, which is one-thirtieth of that of the conventional alloyed contacts. The mechanism of Cu film deposition by electroplating is discussed.

In this paper, we report on the carrier activation and deep level crystal defects in pulsed excimer laser (A = 308 nm) anealed samples of GaAs implanted with Si and Se to a dose ranging from 2.2 x 1012 to 6.0 x 10" cm'. The residual defects in the pulsed-laser annealed GaAs have been investigated by means of photo-induced current transient spectroscopy (PITS). The electron concentration and carrier mobility were studied by Hall effect and Van der Pauw measurements. Although the implanted layer recrystallization was good and the sheet carrier concentration was high, the electron mobility was low. The correlation between deep traps, the carrier concentration, the electron mobility, and laser light intensity is presented.

Critical current density measurements have been made on in-situ processed and patterned, laser deposited thin films.These films were deposited on LaA103 and KTa03 with substrate temperatures ranging at from 500-650°C. Epitaxial growth was achieved as targets of Y (123) and Y (123) Ag3 were ablated by an excimer laser in an oxygen ambient atmosphere. A steel mask was placed near the substrate to pattern the films. Transport critical current density was measured as a function of temperature in order to ascertain any role flux pinning may play in determining critical current density.

Reported here is the use of a unique laser plasma source able to deposit thin films of amorphic diamond at practical rates of growth. The beam from a pulsed Nd:Yag Laser is focused at very high power densities of 1012 W/cm2 onto graphite feedstock in an ultrahigh vacuum environment. The resulting plasma ejects carbon ions able to migrate to the plane of deposition. In this way diamond-like coatings have been applied to silicon, gold, germanium, glass, copper, InAs, and plastic. On these substrates electrical resistivity is high and the materials seem to fall into the same class of "dehydrogenated" materials as are traditionally produced by the ion beam methods. However, growth rates are much higher with this laser plasma source, routinely reaching 0.5 μm/hr. No seeding or heating of the substrate is needed and substrate temperatures seem to remain at ambient room values during processing.

Thin films of epitaxial germanium were deposited on (100) silicon substrates which were atomically cleaned using a pulsed excimer laser ( wavelength 308 nm, pulse duration 45 nanosecond, and energy density (0.75 - 1 J cm-2 ) in high vacuum ( 3.0 x 10-7 torr ). Thin films of germanium were then deposited in similar vacuum using the excimer laser at a higher energy density (3.5-6 J cm-2) to ablate germanium from a single crystal target. The substrate temperature during cleaning and deposition ranged from 300 to 500°C showing this to be a low temperature process. The films were analyzed using cross-section and plan-view transmission electron microscopy and high-resolution transmission electron microscopy. These films show the initial stages of epitaxial growth and Ge/Si interface with absence of an intermediate oxide layer. The significant reduction in substrate temperature for the formation of high quality epitaxial films opens up many new areas of applications requiring reduced thermal-budget processing.

The chemical structures of polyimide(PI) and polyethylene terephthalate) (PET) surfaces after ablation with a single laser pulse from a KrF excimer laser are studied by x-ray photoelectron spectroscopy(XPS). For both polymers, carbon-rich surfaces with a modified bonding environment are found to be produced. The formation mechanisms of these surfaces are discussed in terms of the etching processes based on the preferential bond breaking between the aromatic rings and imide groups in PI and between the aromatic ring and carbonyl groups in PET, followed by rearrangement and recombination reactions. Furthermore, as a result of angular-dependent XPS studies/ the changes in atomic concentration and bonding environment along a 4~º100Å depth of the surfaces remaining after ablation are observed. The possibility of surface oxidation after ablation is discussed.

We investigated silicon photochemical vapor deposition using a disilane, diborane, and hydrogen gas system under a deuterium and a mercury lamps. Vacuum ultraviolet light reduces seriously the boron doping. We found that this is mainly due to gas phase reaction of vacuum ultraviolet excited radicals. Ultraviolet light does not affect these gas phase reaction. It irradiates the wafer surface and make it active. The enhancement of the electric activation rate of boron in silicon layer observed under UV irradiation is due to the surface activation.

The deposition of hydrogen free as well as hydrogenated hard, amorphous, diamondlike carbon films by a novel laser ablation and plasma hybrid technique (20nsec(FWHM), XeC1 laser output focussed by a lens onto the target at a power density of 2.5*10.8 W/cm.2) are described. In the novel laser ablation and plasma hybrid technique, the energy stored in a capacitor is fed synchronously with the ablating laser pulse into the laser ablated region of the target. The hydrogenated films are deposited by ablating the carbon films deliberately in hydrogen ambient using the capacitor discharge technique. The hydrogen content may be varied by controlling the energy stored in the capacitor. Hydrogen free, DLC films deposited by this new technique by ablating carbon targets in high vacuum have been characterized by spectroscopic ellipsometry, FT-IR, TEM, and Microhardness maeasurements. To date, we have seen reduced extinction coefficient in the 2 to 2.5 eV range, enhanced hardness and a high value of band gap of 1.27 eV for films deposited by this technique.

We have investigated the formation of polycrystalline TiN films on (100) Si substrates and epitaxial (100)-oriented TiN films on (100) MgO substrates by laser physical vapor deposition. The films were deposited by excimer laser (wavelength 308 nm, pulse duration 45 nanosecond, and energy density 4-6 J cm-2 ) ablation of a TiN target pellet in high vacuum (~ 3.0 x 10-7 torn) with the substrate temperature ranging from 25 to 750°C. The epitaxial films on Mg° were obtained at relatively low substrate temperatures ( 450°C ) and polycrystalline films on Si were obtained at substrate temperatures ranging from 25 to 550°C. The deposited films were analyzed using cross-section and plan-view transmission electron microscopy, X-Ray diffraction, Rutherford backscattering / channeling patterns, Auger electron spectroscopy, and electron channeling patterns. Results for epitaxial film growth indicate <100> TiN parallel to <100> MgO with the minimum channeling yield( xmin ) < 10% and room temperature resistivity of 501.112-cm. Typical resistivity values of the polycrystalline films were 150 I. -cm and microhardness values were found to be as high as 17 GPa. The polycrystalline films are very dense with an average grain size of 100 A which remained approximately constant with substrate temperature up to 550°C. The polycrystalline films were of equiaxed nature with no preferred growth orientation. These microstructural features couple with low temperature deposition and dense nature make these films suitable for many advanced applications.

Crystalline diamond was deposited on on silicon (100) substrates at750° C by hot filament (2000° C) decomposition of methane and hydrogen (0.5 to 5 % CH4 in Hydrogen) mixtures between 20 to 60 ton. The crystalline diamond film deposited by the hot filament technique is rich in morphology and show considerable diversity in carbon-carbon bonding primarily due to the inhomogenuities in the deposition process. The morphology of diamond crystals show cubic or octahedral structures at low substrate temperatures T<800° C. These structures can be controlled by the temperature gradient surrounding the substrate material. The deposited films are characterized by TEM and Raman techniques. Amorphous carbon surrounds the intergranular regions of the diamond crystals. Preliminary results of irradiation of the CVD diamond film with a XeC1 UV-eximer laser selectively removes the sp2 bonded carbon component, improving the quality of the film.

Resistless photo etching of the SiC was performed by using KrF excimer laser beams. In the present method, C1F3 was used for etchant gas. The C1F3 gas has the absorption band in the range between 200 and 400 nm. Therefore, C.1F3 gas is effectively decomposed by the XeF,KrF and ArF excimer lasers irradiation. It is found that absorption factor of SiC is about 50% in, the range of between 200 and 400 nm, and that the bonding energy of Si-C is lower than the photon energy of KrF laser beam. The above results indicate the direct decomposition of Si-C bond. On the other hand, KrF laser beams were simultaneously irradiated parallel and perpendicular to the substrate. The parallel beam induced decomposition of CIF: near the surface of a substrate to produce radicals and the perpendicular beam induced on the surface of the SiC substrate. Fluence of parallel beam was 50 mJ/cm2 , perpendicular beam on the substrate was 200 mJ/cm2 and a total flow rates through the cell were 0.05 1/min. The etched feature of reticle pattern can be fabricated by reductive projection. Line and space was 5 μm.

Silicon doping by high fluence pulsed laser irradiation in BC13 and PC13 atmospheres has been performed giving rise to shallow heavily doped junctions. The doped layers are free from extended defects, nevertheless a reduction of carrier mobility has been evidenced. Point defects originated by the fast solidification of the molten surface are responsible for the degradation of the transpOrt properties in the doped layer. The strain profile, originated from the point defect distribution, have been measured for different irradiation conditions. It was evidenced that the defective region is mostly limited inside the doped layer. A remarkable reduction of point defects is obseved when the laser irradiation takes place on samples kept at 400°C. At this temperature the speed of the solidification front is reduced of about 40%, thus limiting the number of quenched point defects.

Systematic investigations of thin Cr, Mo and W films deposited from the hexacarbonyls with low power, cw UV light have been carried out in order to learn about sources of contamination by C and 0 (luring film growth. Dissociative chemisorption of CO from the precursor, reactions with oxygen-containing background gases during deposition and air alter deposition all affect film compositions. Laser heating can also he important. General aspects of film contamination are discussed for other precursors such as the alkyls and acetylacetonates, and compared to the present data.

The use of pulsed lasers operating in the ultra-violet for the formation and modification of metal alloys opens a range of processing techniques which offer the precision of ion beam mixing techniques but at much higher processing rates. In addition, excimer laser surface processing offers the possibility of new surface modification technologies. Most metals have low reflectivities in the UV, so laser light is coupled strongly to the surface. The short pulse length of these lasers, along with a shallow absorption depth, results in a heated zone which is also quite shallow, of the order of 1 micrometer. Modest fluences, of the order of 1 J-cm-2 are sufficient to melt this surface zone. Typical quench rates from the melt are of the order of 1010 K-sec-1; high enough to produce amorphous phases in some materials. Mixing by liquid phase diffusion between layers of vacuum evaporated materials and zone refinement can result from multiple melt resolidification events. These techniques make available a large range of alloy compositions on engineering materials. The surface morphology of the processed layers is quite smooth with a surface finish less than 100 nm. Further processing prior to use is therefore not required for most applications. We have studied laser mixing of metals into engineering materials, both metal alloys and ceramics, the formation of ceramic structures on metals, the modification of alloys by surface zone refinement, and the mixing of binary and ternary multilayer structures.

Rapid isothermal processing (RIP) based on incoherent sources of light has emerged as a major semiconductor processing technique. In this paper, new results on the use of in-situ RIP for the solid phase epitaxial growth of II A fluorides, annealing of phosphosilicate glass on Si substrates, RIP assisted MOCVD of Y-Ba-Cu-O as well as unexplored areas and directions for future research are presented.

The laser chemical vapor deposition (LCVD) of aluminum and gold has been achieved via pyrolytic decomposition of trimethylamine aluminum hydride and dimethylgold (p-diketonates), respectively. The rates of metal deposition, the purity of the deposited metals and the electrical properties of the deposits are a direct result of the chemical and physical properties of the precursor and the metal.

Laser writing of high quality metal interconnects has been demonstrated by several authors. However, the use of this technique for customizing integrated circuits (ICs) has been very limited. One significant problem has been the contact resistance between the laser written metal and the existing IC metallization. The existing IC metallization is usually aluminum and spontaneously forms an oxide (-50 A) upon exposure to air. The high reactivity of aluminum in air precludes the use of cleaning to remove the native oxide thus preventing high quality contacts. Switching to a noble metal such as gold would solve the contact problem but would have several undesirable effects such as poor adhesion and increased cost. In this paper, we report on the use of refractory metal overcoats on aluminum metallization to solve the contact problem. Our laser written metal is gold obtained by the pyrolytic decomposition of a spin-on gold metallo-organic ink. The resistivity of the laser written gold is approximately 30 µS2-cm. With proper cleaning, the typical contact resistance between the refractory metal coated aluminum and the laser written gold is 30 S2 for a 3 gm x 3µm contact (-3 1.1i2-cm2). This value is sufficient for a wide range of IC interconnect problems. A significant advantage of this metallization is its growing use in the IC industry. This allows customizing and/or repairing ICs without requiring any specialized processing.

An excimer laser-based system for planarization of aluminum alloys has been developed. The patented planarization process utilizes a 308 nm XeC1 laser to melt and reflow the aluminum film after metal deposition. Contacts and vias of submicron geometry are filled after laser melting without thermal degradation of the underlying structure. The effect of laser fluence on the planarization process as well as the effect of the contact pattern, contact profile and barrier metal to the planarization process are discussed. Insufficient laser energy causes grain boundary separation and metal cracking as a result of grain boundary scattering and preferential melting of Al at the grain boundary. A threshold energy of greater than 3.0 J/cm2 at a substrate temperature of 4000C is required to completely melt flow aluminum in the entire laser spot without grain boundary separation. Finally, a high throughput Al planarization process has been developed on the XMR Model 7100 planarization system.