摘要:

Etching characteristics for GaAs and InP using an ultrahigh vacuum reactive ion beam etching (UHV‐RIBE) system have been classified. Using a horizontal electron cyclotron resonance (ECR) ion source, a uniform ion beam covering a large area is obtained, and etching at low pressure (≂10−5Torr) has become possible. The etching gas Cl2, is ionized at a gas pressure of 6×10−4Torr, and typical applied microwave power is 300 W. We have classified the etching behavior into three categories as a function of extraction voltage and tried to clarify the change of the edge profile and surface condition. It is possible to obtain a vertical mesa. The maximum etch rates for InP and GaAs are 2.0 μm/min and 1.2 μm/min at high temperature and high applied voltage. Under appropriate conditions almost comparable etch rates for GaAs and InP have been obtained.

ISSN:1071-1023    

DOI:10.1116/1.584560

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

Anodic oxide metal–insulator–semiconductor (MIS) structures have been prepared on (100)‐ and (111)B‐oriented samples ofn‐type InSb using either phosphoric or citric acid as the electrolyte. Interface properties have been evaluated using 1‐MHz capacitance–voltage (C–V) measurements as a function of temperature from ∼20 to 300 K. By comparing interface state density and fixed charge with preparation conditions for the dielectric, it is concluded that the data are consistent with the presence of elemental Sb at the interface, which acts as a hole trap.

ISSN:1071-1023    

DOI:10.1116/1.584562

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

Reactive ion etching of InP with CH4/H2mixtures, a promising process for optoelectronic device fabrication, has been studied to understand the mechanisms of etching and anisotropy. Special attention has been paid to the polymer film that deposits on inert surfaces in the discharge; deposition rates have been used as a monitor of the discharge chemistry as well as for process optimization. Surface analysis shows that under etching conditions that maximize the InP etch rate while minimizing polymer deposition, the hydrocarbon coverage on the InP surface equals typical ‘‘adventitious’’ carbon levels, and the surface is significantly depleted of P. The etch rate here is limited by the flux to the surface of hydrocarbon reactants responsible for In desorption. The absence of a significant hydrocarbon film on the vertical‐etched surfaces under conditions of 8:1 anisotropy precludes a surface inhibitor mechanism of anisotropy, implicating instead energy deposition via ion bombardment as the major contributor to the enhanced vertical etch rate. As the feedstock methane fraction is increased, more stoichiometric surfaces are obtained, the polymer deposition rate and the abundance of gas phase hydrocarbon oligomers increases, and ultimately, polymer forms on the InP. Here the InP etch rate is limited by transport through the permeable polymer overlayer. Reactions with polymer‐coated chamber walls are important in determining InP etch and polymer deposition rates, illustrating the need for chamber seasoning to obtain reproducible results. PH3is identified by mass spectrometry as the primary P‐containing volatile product, while the primary In‐containing volatile product remains unidentified.

ISSN:1071-1023    

DOI:10.1116/1.584564

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

Photochemical etching and deposition systems involve a range of laser‐induced and spontaneous processes occurring on rough, chemically heterogeneous surfaces. As such, they present an interesting opportunity for extending our understanding of surface photophysical and photochemical phenomena. In this article results of recent experiments investigating the effect of illumination on adsorption, dissociation, and desorption in such systems are described. Studies carried out under realistic film deposition and etching conditions are compared to studies of submonolayer assemblies on clean crystalline surfaces.

ISSN:1071-1023    

DOI:10.1116/1.584565

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

Real‐time ellipsometric characterization of the nucleation of hydrogenated amorphous silicon (a‐Si:H) prepared by plasma‐enhanced chemical vapor deposition (PECVD) on smooth, dense metal, and crystalline Si substrates is reviewed. The experimental results for photoelectronic qualitya‐Si:H from pure SiH4on Mo and Cr are consistent with the Volmer–Weber nucleation mode, with a separation of 40–50 Å between nucleation centers. Forc‐Si substrates, a new interpretation suggests that nucleation occurs on the same scale, but the geometry in the first monolayer is disklike. A well‐defined lobe and cusp in the data can be ascribed to surface smoothening by diffusion that results upon coalescence of these structures. For films from a pure SiH4plasma, the rates of coalescence and relaxation of substrate‐induced surface roughness on thick films are consistent with a diffusion length of ∼80 Å for the adsorbed precursors. For films prepared from a SiH4‐depleted plasma, the average surface diffusion length is reduced by at least a factor of 2. New results for the growth of μc‐Si:H ona‐Si:H films reveal an induction period of several minutes for the nucleation of microcrystallites. During this period a structurally defective 40–80 Å amorphous layer is deposited. Such a layer is expected to influence the properties of photoelectronic devices and compositionally modulated materials that use thin μc‐Si:H.

ISSN:1071-1023    

DOI:10.1116/1.584566

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

Band‐gap excitation promoted the adsorption of nitric oxide on diamond C(111)‐(2×1). In the absence of laser excitation the sticking probability for NO was ∼10−8. Laser excitation of the surface at 226 nm, with a duty cycle of 10−7, significantly enhanced the adsorption of NO. The time‐averaged reactive sticking probability for the laser‐irradiated surface increased by more than a factor of 100. However, the reaction saturated at ∼1.2% of a monolayer oxygen adatom coverage, indicative of adsorption mediated by defect sites. Similar behavior was observed on the diamond C(100)‐(1×1) surface. Translational activation of the adsorption of NO was also observed. The adsorption probability for NO accelerated to ∼280 meV by supersonic molecular‐beam techniques was ∼6×10−4for the diamond C(111)‐(2×1) surface, but again chemisorption saturated at ∼1.6% of a monolayer O adatom coverage.

ISSN:1071-1023    

DOI:10.1116/1.584567

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

Electron energy‐loss spectroscopy (EELS) and reflection high‐energy electron diffraction (RHEED) have been used to investigate thermal and photothermal reactions in dihydride (1×1)::2H surfaces obtained by dosing clean Si(100)2×1 surfaces to a saturation exposure (≊2×1017cm−2) of Si2H6at 300 K. With 15‐s anneals at progressively higher temperatures, the (1×1)::2H was transformed to a (2×1):H monohydride phase at temperatures between 655 and 725 K and most of the remaining H evolved by 765 K. Complete recovery of the initial clean‐surface EELS spectrum and 2×1 RHEED pattern, signaling deposition of one layer of epitaxial Si(100)2×1, was obtained between 845 and 955 K. One pulse of 120 mJ cm−2ArF laser‐beam irradiation resulted in significant hydrogen evolution from Si2H6‐saturated dihydride surfaces at 300 K and complete hydrogen desorption, with the reestablishment of the initial clean‐surface EELS spectrum, at 525 K. The mechanism was found to be photothermal rather than photolytic and the maximum temperature during the ≊20‐ns pulse (at 525‐K starting temperature) was calculated to be 800 K. RHEED patterns from dihydride surfaces irradiated at 525 K were 2×1, but with slightly weakened half‐order diffraction spot intensities. In initial film growth experiments using continuous Si2H6dosing and pulsed ArF laser irradiation, epitaxial Si was obtained at a steady‐state temperature of 525 K.

ISSN:1071-1023    

DOI:10.1116/1.584568

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

Multiple internal reflection (MIR) infrared spectroscopy has been used to study the adsorption of H and Si2H6on the Si(111)‐7×7 surface at 200 and 400 K. Both adsorbates react with the Si(111)‐7×7 surface to yield a variety of silicon hydrides with similar temperature dependence. Adsorption of atomic hydrogen at 400 K produces three different monohydrides with characteristic vibrational frequencies of 2076, 2086, and 2095 cm−1. At 200 K hydrogen adsorption produces a surface dihydride with a stretching frequency of 2119 cm−1and a trihydride with a stretch frequency of 2143 cm−1in addition to the three surface monohydrides. Adsorption of Si2H6on Si(111)‐7×7 at 400 K yields a single absorption feature centered at 2096 cm−1attributed to surface SiH species. The broad featureless spectrum is indicative of surface disorder due to the deposition of additional surface silicon atoms from the adsorbed disilane. At 200 K the adsorption of Si2H6yields a sharp vibrational feature at 2154 cm−1over a broad background centered at 2126 cm−1characteristic of a surface trihydride species (SiH3). The temperature dependence of the formation of surface hydrides is similar for both adsorbates. Lower adsorption temperatures favor the formation of higher hydrides. Differences are observed in the sequential appearance of absorption bands for adsorption of atomic hydrogen as opposed to the coverage‐independent vibrational spectra observed for the adsorption of Si2H6.

ISSN:1071-1023    

DOI:10.1116/1.584569

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

W deposition, using a WF6source by electron beam induced surface reaction, has been studied by Auger electron spectroscopy (AES) and transmission electron microscopy (TEM). The initial growth process has been observedinsituby AES and TEM. As a result, it became clear that a growth rate for W is ∼1 Å/min at 2×10−7Torr and β‐W clusters are formed by electron beam irradiation of the WF6adlayer. Moreover, it has been observed that W layers are formed by coalescing the W clusters by electron beam irradiation at 5×10−7Torr WF6gas pressure. Furthermore, a nanostructure involving a W rod with a 15‐nm diameter has been demonstrated by using electron beam induced surface reaction. Direct writing onto Si, GaAs, and poly(methylmethacrylate) (PMMA) resist have been demonstrated by electron beam induced surface reaction using XeF2, Cl2, and ClF3sources. The electron beam stimulated etched depth is proportional to the electron dose. A 0.5‐μm linewidth Si and PMMA resist patterns have been fabricated at 4×10−3and 2×10−3C/cm2doses, respectively. The PMMA resist etched depth profile control has been demonstrated by changing doses. GaAs etching has been achieved by heating the substrate.

ISSN:1071-1023    

DOI:10.1116/1.584570

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

Selected area epitaxy of CdTe onto GaAs(100)2°→(110) substrates is reported where a frequency‐doubled argon ion laser, output wavelength of 257 nm, is used to photolytically decompose the precursors. Photodissociation of the precursors dimethyl telluride, dimethyl ditelluride, diethyl telluride, and dimethyl cadmium have been investigated for their suitability in terms of their ultraviolet absorption spectra and thermal stability. Diethyl telluride or dimethyl telluride have strong absorptions at 257 nm and have good thermal stabilities yielding high photoenhancement factors. Nucleation of CdTe onto GaAs substrates has revealed the need to remove the native oxide for epitaxial growth. HeNe laser thin‐film interference has indicated a 4‐min nucleation delay for pyrolytic precursor decomposition. Photopatterned CdTe epitaxy has been demonstrated at 300 °C for a two‐dimensional mesa pattern obtained by shadow masking and a bar pattern obtained by projection onto the surface. Deposition due to vapor diffusion of Cd and Te was only evident at high laser intensities. At low intensities feature definition is very good with feature sizes ∼100 μm. These results are explained by surface‐rate‐limiting kinetics that can be stimulated by the laser radiation. Such a mechanism could be laser‐stimulated hydrocarbon desorption.

ISSN:1071-1023    

DOI:10.1116/1.584571

出版商:American Vacuum Society    

年代:1989

数据来源: AIP