摘要:

A series of silicon oxynitride thin films prepared by plasma enhanced chemical vapor deposition was characterized by Fourier transform infrared (FTIR), wavelength dispersive x ray, and ultraviolet/visible spectroscopies. Changes in deep‐UV transparency and in composition of these and similar films on silicon, sapphire, and quartz wafers were then studied as a function of exposure to the output at 193 nm of an ArF excimer laser. Single‐pulse and high‐repetition‐rate exposures at different average pulse energies were performed. No changes were observed in the single‐pulse experiments, while the films increased in UV transparency and decreased in hydrogen content in the high‐repetition‐rate experiments. The effects observed were greater for films on quartz and sapphire, than for films on silicon. While not precluding a UV photon assisted mechanism, these results suggest that the changes in transparency and composition occur via local heating of the film. On the basis of a 10‐μm film, the laser exposure of the film on quartz increased its transparency at 200 nm from 1% T before irradiation to 10% T, a contrast of 10, while the film on sapphire increased from 10% T before irradiation to 25% T, a contrast of 2.5. The primary effect of the irradiation upon composition was to reduce both the NH and SiH contents; however, these results, when compared with data on unirradiated samples with a variety of compositions, indicate that it was the change in SiH content that most directly affected the UV transparency. Thus the photomodifiable, UV absorbing defect is associated with SiH bonds in the glass. Changes in other features of the FTIR spectra were also observed. Overall, the local modification of the UV transparency of silicon oxynitride thin films was readily achieved by current excimer laser technology. While the effect occurred for films on silicon, the results show that the greatest contrast at the lowest laser fiuence would be achieved in heavily hydrogenated films on quartz.

ISSN:0734-211X    

DOI:10.1116/1.584765

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

A new method of maintaining window transparency in photochemical vapor deposition (photo‐CVD) has been developed in which the window is continuously etched clean during the deposition process. This technique is demonstrated in the deposition ofa‐Si:H(F) by direct photo‐CVD of Si2H6using XeF2as an etchant. XeF2is also used to clean the chamber between runs. Fluorine may be incorporated in the films via either gas phase or surface reactions with XeF2. The optoelectronic quality ofa‐Si:H:F decreases with F incorporation, which suggests that this technique may be particularly suited to the deposition of μc‐Si:H(F) anda‐SiGe :H(F) anda‐SiC :H(F) alloys wherein fluorinated process gases are preferentially employed.

ISSN:0734-211X    

DOI:10.1116/1.584766

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

Deposition of silicon from silane discharges is studied in diode and hollow‐cathode systems. Using the single‐target (‘‘diode’’) configuration as a reference, it is shown that discharge confinement results in substantial increases in deposition rate and efficiency. The ‘‘target‐confined hollow cathode’’ exhibits the best performance; in comparison with a diode discharge at 2‐Pa silane pressure, rates are 20–50× higher at fixed applied rf voltage and 5× higher at fixed input power density. Alternatively, for a fixed deposition rate this new configuration allows the applied rf voltage to be reduced by ∼10 and the power density to be reduced by ∼20, again at a 2‐Pa pressure. Planarizing films are obtained at low pressures and/or low gas flows, while high pressures yield more directional deposition over surface steps. Good agreement with this profile study, and with our deposition rate data, is given by a model wherein ion bombardment is the dominant film forming and etching mechanism at low pressures, and wherein trapping of both excited neutrals and of electrons may contribute to the high efficiencies and rates observed.

ISSN:0734-211X    

DOI:10.1116/1.584767

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

High‐density, nonvolatile, associative electronic memories based on neural network models require large arrays of highly uniform, small area, resistive connections (synapses). Such passive, two terminal resistors (very weak connections, 105to 106Ω for a 1000×1000 matrix) are uncommon in the current very large scale integration (VLSI) technology. We report on a solid‐state, resistance tailorable, programmable‐once, binary, nonvolatile memory switch based on manganese oxide (MnOx) thin films. MnOxexhibits irreversible memory switching from a conducting (on) to an insulating (off) state, with the off to on resistance ratio of greater than 104. The switching mechanism is current triggered chemical transformation of a conductive MnO2−Δto an insulating Mn2O3state. The energy required for the ‘‘switching’’ is of the order of 4 to 20 nJ/μm2. Apart from the high density information storage in such MnOxmicroswitch arrays as programmable read only memory (PROM), the ‘‘tailorable MnOxfusible links’’ may also be suited for post‐fabrication, ‘‘function‐specific programming’’ of microcircuit architectures.

ISSN:0734-211X    

DOI:10.1116/1.584768

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

The oxidation behavior of low‐pressure chemical vapor deposition silicon oxynitrides was investigated for layer compositions ranging from that of pure nitride to oxynitride with an atomic ratio of O/N=1. Oxidations were performed at 850–1000 °C in ambients having different H2O/O2flow ratios. Rutherford backscattering spectrometry and elastic recoil detection were employed to quantify the increase in oxygen content of the films upon oxidation. Hydrogen profiles in oxidized samples were measured using nuclear reaction analysis and elastic recoil detection. We observed that the oxidation rate for either oxynitride composition is nearly two orders of magnitude smaller than that of silicon. Linear oxidation kinetics were measured for the conditions applied in this study, which are indicative of a reaction‐controlled process. The activation energy of this process was determined to be 2 eV for silicon nitride and appeared to decrease with growing oxygen content in oxynitrides. The hydrogen profiles measured in oxidized samples showed a peak at the oxide/oxynitride interface. The size of this peak varies with oxidation conditions and film composition. A reaction mechanism for the oxidation of (oxy)‐nitride is proposed that relates the observed hydrogen accumulation to Si–NH and Si–OH groups at the oxidizing interface. The measured acceleration of the oxidation rate induced by adding small amounts of HCl to the ambient is interpreted in terms of enhanced transport of NH species to the surface. This effect is greatest for pure nitride and diminishes with increasing oxygen content in oxynitride material.

ISSN:0734-211X    

DOI:10.1116/1.584769

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

This paper investigates the effects of lateral confinement on the chemical kinetics of surface reactions that involve diffusive mass transport in the phase above the surface. The phenomena to be expected are illustrated by a theoretical treatment of the reaction typesA+D⇄2CorB⇄A+2C, whereAis a surface species, andBandCare both gaseous species. The case explored is one in which the back reaction due to the product speciesCis important. It is assumed that speciesBis the major constituent of the vapor, and remains so throughout the course of the reaction. The spatial profiles ofAandCas a function of time are found by the use of a Green’s function formalism and evaluated numerically for illustrative cases. The results of the calculations provide a possible explanation of the drastic rate enhancement produced in some cases by lateral confinement resulting from the use of focused energy beams. The possibility of dramatic lateral variation of chemical kinetics due to strong concentration gradients of the product species is demonstrated. The results could have application to a broad class of transportlimited surface processing reactions confined by focused beams or by lithographic masking.

ISSN:0734-211X    

DOI:10.1116/1.584770

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

Initial stages of GaAs growth on Si by molecular‐beam epitaxy were investigated byinsituphotoemission spectroscopy. The obtained results suggest that the first layer on Si is the As layer, and that the electronic structure of the Si surface exposed to As4depends on the exposure temperature. The interface structure between GaAs epilayers and Si substrates is discussed in terms of the initial process of the growth.

ISSN:0734-211X    

DOI:10.1116/1.584771

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

Flux distributions from Knudsen cell sources used in molecular‐beam epitaxy have been determined using Monte Carlo techniques. The increased beaming effect as the cell empties, which produces an increase in film thickness variation across the substrate, is found to be less pronounced than the widely used analytic theory of Clausing predicts. Tilting a full cell is shown to produce flux distributions which are asymmetric about the cell axis, but the effect decreases as the tilted cell empties.

ISSN:0734-211X    

DOI:10.1116/1.584772

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

We studied the influence of different fabrication techniques on the electrical properties ofn‐GaAs Schottky contacts. In comparison to the conventional technology for Schottky metallizations represented by wet chemical etching and thermal evaporation the pretreatment of the semiconductor surface was performed either by wet chemical or Ar+etching and the metallization step by evaporating, sputtering or by ion beam contacting. Diodes prepared by such procedures show very different electrical gehavior but no monotonic dependence of the barrier height from preparation parameters, especially from the ion energy. Whereas ion cleaning at 500 V results in barrier heights of ∼0.3 eV, cleaning at 1000 V gives a barrier of 0.4 eV. The implantation of the contact metal results in a barrier of 0.65 eV. DLTS measurements reveal a tendency of relationships between the barrier height and the dominating deep levels, thus supporting the model of Fermi levels pinning by defect states. DLTS further indicates a sensitive reaction of the EL 2 center on the metallization procedure.

ISSN:0734-211X    

DOI:10.1116/1.584773

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

A very low Schottky barrier height of 0.1 eV for aninsitufabricatedn+‐Si/GaAs interface is verified byC–Vmeasurement. The height is approximately equal to the conduction‐band discontinuity of the interface, in spite of a high density of misfit dislocations (lattice mismatch: 4%). Thermal stability of the interface is assured for annealing temperatures up to 850 °C. As an example application, an AlGaAs/GaAs metal–insulator semiconductor‐like heterostructure field effect transistor usingn+‐Si for gate material is successfully fabricated.

ISSN:0734-211X    

DOI:10.1116/1.584774

出版商:American Vacuum Society    

年代:1989

数据来源: AIP