Laser-induced thermochemical reactions have been investigated for GaAs in a CCl2F2 gas ambient using an argon-ion laser. The chemical compositions of the reaction products deposited on the etched groove were measured by Auger electron spectroscopy (AES). The conditions of laser power, scan speed, and CC12F2 gas pressure under which the etching reaction occurs without deposition of the residue were clarified. High etching rates up to 267 μm/s and an aspect ratio of 4.5 have been achieved by a single scan of a laser beam. Microprobe photoluminescence and Raman scattering measurement were carried out on the etched surface to characterize damage induced by this processing.

A SiO2 insulator and contact holes were simultaneously fabricated at room temperature by ArF and KrF excimer lasers. In this method, NF3 and O2 gases were employed for the reaction gas. When the ArF laser beam irradiated the NF3 and O2 gases in the presence of Si, SiFn and NO2 were produced by photo-chemical reaction. The SiFn adsorbed on the Si substrate pulled out O atoms from the NO2 to form a SiO2 layer. At the same time, the patterned KrF laser beam projected on the substrate and ablated the part exposed to fabricate contact holes. As the results, the simultaneous fabrication of SiO2 insulator with the 700 Å film thickness and selective pattern with the 10 μm width was demonstrated.

We report excimer laser induced etching of GaAs samples covered with a layer of condensed Cl2. The experiments were performed at low temperatures (120-150 K) and in a chlorine ambient (PC12=1-40 mTorr). Spatially well-resolved, anisotropic etching has been demonstrated with an observed etch rate of 0.25 Å/pulse (0.1 μm/min for typical parameters). The etch rate is characterized as a function of the various system parameters (pressure, temperature, laser rep-rate, etc.), and a model is proposed to describe the etching mechanism.

The ablation of single crystal MgO irradiated with 248 nm excimer laser light is studied by means of time resolved spectroscopy and quadrupole mass spectrometry. Luminescence spectra and SEM observations indicate that repeated laser bombardment gradually increases the density of potentially absorbing defects. In polished samples, this progressive growth is preceded by an initial clean-up (reduction) of surface damage. Unlike many wide band gap materials, defect production in MgO by electronic mechanisms is not likely. Chemical etch techniques indicate the presence of high dislocation densities in regions etched by the laser, suggesting that point defect production by dislocation motion is important. The ablation plume is composed of charged particles, including cluster ions, as well as a high density of excited neutrals. The growth of the plume with repeated bombardment correlates with defect formation as indicated by luminescence intensities.

Laser-induced desorption (LID) of In and Ga from Si(100) under ultra-high vacuum conditions is investigated. The frequency doubled 532 nm, 2-6 ns output of a Nd:YAG laser is focussed to 0. 14±0.03 J/cm2 on the Si surface to induce desorption. Desorbed In or Ga atoms are detected by laser-induced fluorescence initiated by a pulsed dye laser propagating in front of the surface. LID occurs by thermal desorption with approximate desorption energies and pre-exponential factors in agreement with literature values from previous isothermal desorption measurements. Experiments at higher coverages suggest that desorption occurs predominantly from the two-dimensional (2D) adsorbate layer with little desorption occurring directly from adsorbate islands. The 2D layer is resupplied by either diffusion out of adsorbate islands or by diffusion of incorporated adsorbate out of the bulk. Adsorbate-enhanced laser-induced surface damage is also observed; only 0.2 monolayer of In reduces the number of laser pulses required to observe damage by greater than a factor of 30.

A laser etching process was used to etch air-bearing surface patterns (cavities) on sliders for magnetic recording heads. Results on projection through mask as well as maskless etching of patterns on the TiC-A12O3 ceramic substrate and encapsulant alumina film on the surface are described. Pattern dimensions and location, along with laser operating parameters, are defined via a computer software program in the maskless etching process, and no external hard masks were used. A combination of maskless etching processes, using a Q-switched Nd:YAG laser for most of the ceramic substrate material in the back of the cavity and an excimer laser system for the alumina coating and nearby areas in the front, was found to give the best results.

Photochemical dry etching and surface modification of different polymers, e.g., poly-methylmethacrylate (PMMA), polyimid (PI) and poly-ethylene terephthalate (PET) was achieved with an incoherent excimer UV source. Decomposition and etch rates of PMMA were determined as a function of UV intensity and exposure time at different wavelengths λ = 172 nm (Xe2*), λ = 222 nm (KrCI*) and λ = 308 nm (XeCI*). The morphology of the exposed area of PMMA was investigated with SEM. The etching of the polymers can be explained as a result of extensive photooxidation. The results are compared with data obtained from mercury lamp and excimer laser experiments.

We study acoustic effects associated with the ablation of polyimide under water confinement. Ablation launches a shock in the target. After the shock propagates into the surrounding water we measure its velocity with an optical probe system. In the water the shocks decay after propagating a few hundred microns. The peak shock pressure scales with the square root of the laser fluence. Our observations can be explained by a simple model that interprets the generated pressures as being due to the heating of a confined ideal gas.

Excimer lasers sources of 193nm and 157 nm wavelength were used to obtain new photoablation etching rates for several materials of interest to the microelectronics industry. The harder 157nm radiation provided lower ablation rates and smaller threshold fluences for Polyimide and Polymethyl Methacrylate (PMMA) than with 193nm. For normally robust materials like quartz and Teflon (PTFE), the 157nm laser produced clean and smooth ablation sites with low threshold fluences of 620mJ/cm2 and 68mJ/cm2, respectively, features impossible to obtain with conventional excimer lasers at longer wavelengths. The data should help define new micromachining applications of these two materials for the electronic, optical or medical industry. Results are also reported for GaAs and InP based materials which are found to undergo moderate etch rates of 30-80nm/pulse at fluences of ∼3J/cm2, but suffer thermal damage and material segregation due to surface melting.

The surface debris that results from KrF excimer laser ablation of polyimide has been investigated as a function of the pressure. and atomic or molecular weight of several ambient gases: H2, He. Ne, air, Ar, Kr, and Xe. A linear relation between the measured debris radius and the inverse third root of the ambient pressure was found to exist, consistent with the predictions of blast wave theory. No measureable debris could be observed using helium or hydrogen gases up to 1 atm. similar to previous reports on helium. The derived value of the blast energy. equal to about 5% of the incident pulse energy, was used to estimate a nascent blast pressure of approximately 150 atm. By making the assumption that surface debris will form if the ablation fragments are confined in a “small” volume for a “sufficient” time, then conclusions from blast wave theory suggest how to decrease the amount of generated debris.

Resistless etching of thermal oxide silicon filmes were demonstrated by ArF & KrF excimer lasers, and CC12F2 gases. CC12F2 was decomposed by ArF excimer laser light, and CF2 radicals were produced. These radicals, which have absorption band nearby 250nm, were vary stable. Then the circuit pattarned KrF laser light was irradiated on the SiO2 in an atomsphere of CF2 radicals. As thse result, the etching pattern of 2 μ m width was performed.

Using holographic interferometry the surface laser plasma generation in high pressure gases has been investigated. Additional information about the generation of surface cover laser plasma, optical breakdown in the presence of aerosol particles and condensation front forming in high pressure gases is given.

Excimer laser radiation at 248 nm has been used for the maskless and selective removal of chromium (Cr) contamination from polyimide surfaces containing gold (Au) metallizations. Ablation thresholds and rates have been determined in air, vacuum, and oxygen. These results have been used to establish the optimum ablation medium and a corresponding process window that allows for selective removal of Cr from polyimide. The substantial differences between the ablated and unexposed regions of the polyimide surface have been established by electrical measurements, while the variations in their respective surface morphologies have been examined using optical and scanning electron microscopy. Quantitative determinations of Cr on the ablated and unablated regions of polyimide have been performed, using secondary ion mass spectrometry, to establish the threshold for the complete removal of Cr.

Aluminum thin film was deposited via a photochemical surface reaction of dimethylaluminum hydride (DMAH) using a deuterium lamp. The period required to initiate the film growth differed with substrate, and making use of this result the film could be grown preferentially on silicon nitride and silicon oxide layers rather than on wet-etched silicon. On the basis of an x-ray photoelectron spectroscopy the observed dependence of photodeposition on substrate surfaces can be attributed to how DMAH is chemisorbed initially.

A new laser direct-write process for patterning of metal on multichip modules has been developed. The process involves the laser modification of the non-conductive surface of a seed multilayer, converting it to a conductive surface, which can be electroplated with metal. The seed multilayer is composed of a TiW adhesion layer, onto which a Au film is sputtered, followed by an a-Si layer, which forms the non-conductive surface. The laser modifies the surface by alloying (or mixing) the Si and Au to form the conductive surface. This laser process has been shown to be capable of writing speeds of 2.5 m/s. With a silicon dioxide interlevel dielectric layer, the process works over a large range of laser power (Pmax/Pmin ∼ 5). A polyimide interlevel dielectric layer can be used without damage or loss of adhesion, although the process margin is substantially reduced (Pmax/Pmin ∼ 2).

We describe pyrolytic laser assisted chemical vapor deposition (LCVD) of copper onto silicon using a copper(I) hexafluoroacetylacetonate trimethylvinylsilane organometallic complex with 514.5 nm radiation from an Ar+ laser. Growth rates of 0.4-40 μm/min were obtained and at intermediate laser powers, the Cu lines had a resistivity comparable to that of bulk Cu. The line shape and morphology was strongly dependent upon laser power with volcano shapes appearing at higher powers. The growth was sensitive to the nature of the substrate suggesting that film nucleation was a critical element in the writing process.

An excimer-laser-based method for achieving selective-area oxide growth on polymer surfaces is described. This method uses high photon energy (6.4 eV, 7.9 eV) excimer laser irradiation to change hydrophobic surfaces (surface tension <20 erg/cm2) into hydrophilic surfaces. The hydrophobic growth surfaces are prepared by exposure of a polymer to halogen-containing plasmas. Selective growth is done by simultaneously exposing patterned, laser-modified surfaces to SiC14 and H2O; the reaction takes place only where the H2O adsorbs to form a condensed adlayer. After selective growth, oxygen etching of the polymer results in the desired resist pattern. When used with a plasma-deposited carbon polymer, the result is a new all-dry lithographic process.

Laser direct writing of tungsten from WF6 onto 0.6 μm thick films of silicon oxynitride on silicon using an argon-ion laser beam is investigated. XPS studies show that WF6 is chemisorbed on the oxynitride surface and that nitrogen plays a role in this adsorption. Deposits have good adhesion, columnar growth structure and resistivities ranging from 13 to 25 μΩ-cm. The deposition conditions significantly affect the deposit morphology and profile. In particular, increasing the hydrogen pressure increases the linewidth but reduces the thickness. Mass transport phenomena are invoked to explain these effects.

Laser Chemical Vapor Deposition of tungsten on GaAs from WF6 using a focused cw scanning argon-ion laser beam has been investigated. Lines have been produced using different mixtures of WF6:H2 and WF6:SiH4 and in some cases, without any reducing gas. Depositions are found to occur within a narrow process window, and are difficult to reproduce. In order to understand this process, we have performed surface analysis on GaAs samples exposed to WF6. X-Ray Photoelectron Spectroscopy studies on the interaction between WF6 and GaAs in the absence of laser illumination show that fluorinated tungsten compounds are present on the GaAs surface. Furthermore, the existence of a chemical reaction leading to the formation of GaF3 at the surface and to a loss of the stoichiometry of the substrate surface is detected. Possible mechanisms, and the effects of these reactions on the deposition process are discussed.

The origin of the ArF excimer laser induced luminescence from a WF6/H2/Ar gas mixture was investigated. The experiments prove that the emission originates from excited W clusters with a size of about 10-20 nm. The influence of the H2 and Ar concentrations, the laser fluence and the repetition rate on the light intensity was studied.