Surface fluorination of polyimide thin films during CF4 + O2 reactive ion beam etching (RIBE) was investigated. The removal of the fluorinated layer by a subsequent oxygen ion beam etch was also studied. Electron spectroscopy for chemical analysis (ESCA) and Rutherford backscattering spectrometry (RBS) detected a fluorinated surface layer on the order of 100 A thick. Fluorine atom concentration in the surface of the film (as measured by RBS) and the etch rate of the film were measured as a function of several experimental parameters: ion energy, ion current density, etch time, and gas composition. The results are compared with theoretical predictions of the total number of fluorine atoms retained in the film after etching.

Polytetrafluoroethylene(PTFE), Polyvinylidene fluoride(PVFD), and Polymethylmethacrylate(PMMA) thin films have been bombarded with a H2 ion beam. The ion exposure time varied from 3 to 12 minutes corresponding to an ion dose of 1017H+/cm2 to 1018H+/cm2. ESCA spectra showed that the fluorine intensity from the fluorocarbon polymers decreased after H2 ion bombardment. Also the CF2 type bond groups observed in the fluorocarbon polymers decreased leaving only the hydrocarbon type bond groups (CH2) after H2 ion bombardment. We speculate that the hydrogen atoms abstract fluorine from the polymer which decreases the fluorine concentration. ESCA has been used to determine the effect of chemical vs. inert (H2 vs. He) ion bombardment on fluorocarbon polymers as a function of exposure time. The implication of these results to explain the differences between RIE and RIBE deposited polymers will be discussed.

We have used molecular beam methods and temperature programmed desorption to probe the reaction of several hydrocarbons with the Si(100) surface at cryogenic temperatures. It has been found that the kinetics of the surface reaction with the C=C bond can be strongly influenced by the production of active surface sites using prebombardment with Ar ions. The chemistry of the adsorbate is also influenced by electron bombardment of the adsorbed layer. Conversely, capping of active sites with atomic hydrogen retards the kinetics of the surface reaction. This work forms a first step in using the methods of surface kinetics and spectroscopy to probe the details of the elementary steps at work in chemical vapor deposition and plasma vapor deposition, leading to the production of SiC films.

Laser induced reactions of Mo(CO)6, CH3CH2OH, and NO adsorbed on Si(111)7 × 7 at 257 and 514 nm were studied and compared with thermally induced reactions under ultrahigh vacuum conditions utilizing laser induced desorption spectroscopy, thermal desorption spectroscopy, high resolution electron energy loss spectroscopy, and Auger electron spectroscopy. By using continuous wave laser irradiation, photolytic effects are clearly distinguished from pyrolytic effects. Mo(CO)6 and CH3CH2OH adsorbed on Si behave similarly as in the gas phase, whereas a substrate-mediated reaction channel is observed for NO adsorbed on Si.

Laser- and electron-assisted deposition of Fe on Si(111)-(7×7) surfaces using decomposition of Fe(CO)5 has been investigated with multiple internal reflection Fourier transform infrared, Auger electron and temperature programmed desorption spectroscopies and low energy electron diffraction under ultra-high vacuum conditions. No thermal reaction was apparent in temperature programmed desorption experiments: only molecular Fe(CO)5 desorption was observed at temperatures of 150 and 170 K, corresponding to desorption energies in the range of 7–10 kcal./mole. Fe(CO)5 decomposition could be induced using either incident 1.6 keV electrons or ultraviolet photons. Significant amounts of carbon were deposited from the electron induced decomposition, consistent with earlier reports on the Si(100) surface. In contrast, ultraviolet photolysis did not result in any detectable incorporation of carbon or oxygen into the iron deposits. No partially decarbonylated Fe(CO)x, x<5, fragments were detected subsequent to exposure to photons using infrared spectroscopy. However, a new, unresolved low frequency shoulder did appear in the infrared spectrum after exposing the Fe(CO)5 covered Si(111)-(7×7) crystal to the electron beam. Iron photodeposition was evident in the Auger electron spectra obtained subsequent to photolysis and annealing of the surface to either 300 K or 1000 K in order to desorb unreacted Fe(CO)5. These data suggest that there are no surface stable Fe(CO)x, x<5, species in the photodeposition process. Instead, photolysis yields Fe atoms directly, even at low temperatures. Annealing to temperatures on the order of 1000 K subsequent to iron deposition resulted in a significant decrease in the Fe:Si ratio as measured by Auger electron spectroscopy. In addition, CO could not be readsorbed on a surface where the Fe(CO)5 had been decomposed. This is attributed to dissolution of Fe into the bulk silicon crystal.

We have investigated the decomposition of single-crystal InP surfaces irradiated by a 193 nm ArF excimer laser. These studies provide insight into mechanisms of thermal decomposition, surface diffusion and epitaxy. Pulsed laser exposure leads to evolution of P2 from the surface which is detected by resonance fluorescence resulting from a fortuitous overlap of the v″ = 0 with the laser frequency. P2-evolution occurs above a threshold fluence of 0.12 J/cm2 and lags the peak laser intensity by ∼20 nsec. These observations are explained by a thermally activated decomposition mechanism, as opposed to any direct, photochemical ejection process. Peak surface temperatures have been calculated and are used to predict P2 yields as a function of fluence and time which are in good agreement with experiments. These findings are also discussed in relation to previous studies of excimer laser stimulated growth of InP.

The sticking coefficient for molecular oxygen on GaAs(110) up to about one-halft monolayer coverage can be enhanced by two or three orders of magnitude when the semiconductor surface is illuminated by an argon ion laser with intensities of 5 W/cm2 or less. Previous work has shown that this effect is nonthermal and roughly independent of wavelength for above-bandgap radiation, implying that photogenerated electrons and/or holes are responsible in some way. In this paper we present recent work which shows that transfer of energy from the GaAs to oxygen molecules physisorbed on the surface causes the breakup of the oxygen and so enhances the reaction. This conclusion comes from comparison of our photoemission results for O2 and N2O exposures made under the same conditions, N2O being chosen since only 1.7 eV is needed to remove the oxygen atom as opposed to the 5.1eV required to break an O-O bond. Nitrous oxide, in contrast to O2, shows only slight photoenhancement and has a much lower activation energy for the dissociative sticking coefficient, demonstrating that removal of the dissociation of O2 as a reaction step also removes the major part of the activation energy barrier to oxygen chemisorption. Since N20 and photoenhanced O2 have similar kinetics, we conclude that the breakup of O2 is the reaction step accelerated by illumination. Another clue to the nature of the photoenhancement comes from our finding that both n- and p-type GaAs display similar O2 laser enhancement ratios. An estimate of the carrier concentrations at the surface predicts that electrons and holes are present in equal amounts at the surfaces of both doping types, however, so this result does not distinguish between single-carrier and recombination-related enhancement mechanisms.

The main features of evaporation of organic molecules from Van der Waals films with resonant IR photons and ablation of organic material and fragments from polymers with UV photons, resulting from time-of-flight experiments, are discussed. These results point to a photothermal mechanism. The experimental facts known so far can be explained using thermodynamic and kinetic arguments. No principal difference is found for breaking Van der Waals bonds with IR photons and chemical bonds employing UV photons.

We investigate the nature of the electronic transitions which lead to the desorption of ions from adsorbate-covered metal and semiconductor surfaces. F+ desorption from F/Si occurs via a Knotek-Feibelman mechanism, while H+ desorption from H/Si and O+ from CO/metals involve multi-electron transitions. The desorption of CO+ from CO/metals and NO+ from NO/Si apparently occurs via a simple Menzel-Gomer-Redhead mechanism.

We present experimental results which suggest a new mechanism for the production of excited atoms and ions by electron bombardment of alkali-halides. Doppler shift measurements show that the electronically excited atoms have a thermal velocity distribution in equilibrium with the surface temperature. Measurements of the absolute yield of excited atoms, the distribution of population among the excited states, and the dependence of yield on incident electron current support a model in which excited atoms are produced by gas-phase collisions between desorbed ground-state atoms and secondary electrons. Similarly, gas-phase ionization of ground-state neutrals by secondary electrons accounts for a substantial portion of the positive ions produced by electron bombardment of alkali-halides.

A low energy, broad beam electron source was used to induce chemical reactions on surfaces. Electron beam energies were selected to maximize the emission of secondary electrons, for the purpose of determining if these low energy electrons contributed to the overall reaction. Room temperature silicon oxidation showed maximum terminal oxide thickness (35 Å) at the primary electron energy that produced the maximum secondary electron flux (300 eV). XPS showed these films to be mostly sub-oxide in nature. Similar results were obtained in analogous experiments using tetraethoxysilane to deposit SiO2 and using iron pentacarbonyl to deposit Fe. By increasing the incident angle of the electron beam to 70 degrees from the normal, the deposition yields of SiO2 and Fe increased by 45% and 30%, respectively. This again was thought to be a result of secondary electron contributions, as the secondary yield increased by a factor of two upon tilting the beam.

The use of a pulsed UV excimer laser based process for the incorporation of dopant impurities into Si is described. The process can result in high concentration shallow box like profiles suitable for submicron VLSI device fabrication. The process consists of exposure of the clean silicon surface to a doping gas (B2H6, AsH3, PH3) then driving the adsorbed monolayers of dopant into the Si by a melt-regrowth process initiated by a pulsed XeCl excimer laser. Modeling of the process allows prediction of the resulting doping profiles and electrical properties of the doped layers. Excellent crystal quality of the doped layers is found even without a postdoping anneal. Also, recent results indicate that post doping annealing may not be needed for improvement of the electrical characteristics of the doped layers provided certain conditions are met. Detailed descriptions of the process, results, modeling and device fabrication are presented.

Nickel and doped polysilicon lines can be written at speeds exceeding 1000 microns/sec using laser direct-write deposition. We explore the roles of gas pressure, composition, and laser power in determining writing speed and line morphology. The use of a surface layer of amorphous silicon provides optical absorption, thermal and electrical insulation which help to maintain high, relatively stable, surface temperature.

Laser direct-write deposition is used to interconnect CMOS gate arrays by means of computer controlled laser pantography. Complex circuits, such as an array of five 16-stage shift registers and one 16-stage counter have been successfully fabricated and tested.

Laser-controlled chemical deposition and etching techniques were used to modify integrated circuits. This work used a pulsed laser to initiate and control the etching, by chlorine gas, of aluminum conductors. New conducting paths were then formed by laser-chemical vapor deposition of highly-doped silicon from silane and diborane. Improved conductivity of laser-deposited connectors was achieved by the selective deposition of tungsten on the silicon. These techniques were used to “rewire” an integrated circuit allowing the full evaluation of the corrected circuit design.

Laser-direct-writing processes are employed to fabricate a GaAs digital integrated circuit. The lithography-free techniques deposit and etch conductors and resistors, and remove insulating layers, thus enabling multilevel interconnections. These combined directwrite processes provide the flexibility of clip-lead prototyping on a micrometer scale.

Quarter micrometer period diffraction gratings having depth-to-spacing ratios around 0.5 have been photochemically etched in p-GaAs using direct holographic illumination with 257 nm UV light. The results suggest the interaction of the incident light with the etched grating. The etch process is represented with the aid of a potential-pH diagram calculated from literature data.

Grooves have been etched photoelectrochemically into a (100) n-GaAs surface using a 100 cycle/mm grating mask to define the illuminated area. The degree of mask undercutting and the shape of the groove bottom are shown to be functions of doping density and crystallographic orientation. High doping density gives rise to reduced undercutting, presumably due to a lesser extent of surface diffusion of photogenerated holes.

It is well recognized that Vycor brand porous glass impregnated with a photosensitive organometallic compound can be used to produce refractive index patterns upon photolysis [1–3]. For instance, a metal carbonyl such as Mn2(CO)10 adsorbed into the porous glass matrix has been used to photopattern high resolution phase gratings albeit with low diffraction efficiencies due to the low refractive index change (Δn) so produced [1].

We have developed a new rapid isothermal processing technique for the deposition of epitaxial dielectric films (II–VIa fluorides and their mixtures) on silicon and ccmpound semiconductors. In this process, epitaxial dielectric films are deposited in an e-beam system at room teqperature and subsequently subjected to in-situ rapid isothermal annealing by using incoherent light sources incorporated in the e-beam system. Epitaxial dielectric films of CaF2 and CaxS1−xF2 have been deposited on Si, GaAs and InP. In this paper, prelimilifty results of electrical and structural characteristics of. epitaxial dielectric films on Si and cupourd semiconductors are presented.

AℓN deposited by D.C. triode sputtering and spin-on, phosphorus-doped glass (PSG) layers on GaAs and InP were investigated as encapsulants. These films have similar expansion coefficients to both GaAs and InP, minimizing the amount of strain induced in the near-surface region of the underlying wafer. We have quantified this effect by direct measurements of the stress in the films and by using secondary ion mass spectrometry profiling to measure the redistribution of Cr and Fe in encapsulated GaAs and InP respectively during high temperature processing. The dopant redistribution is considerably less for the AℓN and PSG films compared to the more conventional SiO2 and Si3N4 layers. The interaction of the films with the substrate at elevated temperatures is minimal as determined by Auger profiling and the electrical properties of the surface after removal of the encapsulants. The composition of the films remains essentially constant after annealing, as measured by Rutherford backscattering, and the thickness uniformity over large wafer diameters (2″) can be excellent with close control of the deposition parameters. The activation characteristics of low dose, Si-implanted layers in GaAs using either PSG or AℓN are comparable to those obtained using capless annealing or SiO2 or Si3N4 encapsulation.