Showing papers on "Isotropic etching published in 1985"

X‐ray photoelectron and Auger electron spectroscopic analysis of surface treatments and electrochemical decomposition of CuInSe2 photoelectrodes

Abstract: CuInSe2 photoanodes can be optimized for use in electrochemical photovoltaic cells, containing aqueous polyiodide as the electrolyte, by wet chemical etching in Br2MeOH and subsequent thermal treatment (air oxidation). Surface analyses show the formation of a rather clean, Cu‐depleted surface with some adsorbed oxygen after Br2/MeOH etch, and the formation of indium‐oxygen bonds after thermal treatment, in accordance with previous studies that show indium oxides to be the native ones on this semiconductor. Samples that underwent photoanodic decomposition in the iodide electrolyte and those that were purposely decomposed in acetonitrile showed severe to near‐total Cu depletion near their surface and the presence of lower valent Se. These data complement those from solution analyses and from electrochemical studies, to characterize the preferred decomposition path of CuInSe2 sufficiently to stabilize this type of photoelectrochemical cell. Our conclusions are based on the use of Auger parameters and, to a l...

Molecular beam epitaxial growth of GaAs on Si(211)

Abstract: The molecular beam epitaxial growth of GaAs on Si(211) has been investigated. Theoretical considerations had suggested the (211) orientation to be particularly suitable for the nucleation and growth of a zincblende‐type compound semiconductor on a diamond‐type elemental one. The experimental results support the theoretical prediction. Morphologies of thin (≤0.1 μm) (211) layers are substantially better than for (100) layers, which nucleate poorly and require large layer thicknesses (≂1μm) to yield good morphologies. When the (211) layer growth is initiated with a thin (GaAs/Al, Ga)As superlattice buffer (0.1 μm), consisting of 10 periods of 5+5 nm, the (211) morphology rivals that of GaAs(100) homoepitaxial growth. Chemical etching studies as well as transmission electron microscope investigations show the layers to have the (211)B orientation and to be free of antiphase domains, both as predicted. The (211) layers show strong photoluminescence at 4 K. Not intentionally doped layers are n type, with elect...

Epitaxial growth and characterization of CaF2 on Si

Abstract: CaF2 films have been grown epitaxially on (100) and (111) Si substrates by molecular beam epitaxy. These films have been characterized by electron microscopy, reflection high‐energy electron diffraction, Rutherford backscattering ion channeling, and back‐reflection Laue x‐ray diffraction. In addition, chemical etching has been used to reveal dislocations and to delineate cracks. Film cracking appears to be related to crystalline perfection through misfit dislocation mobility. It is possible to grow high quality, (xmin=3.0%) single‐crystal films on (111) Si which are free of cracks and atomically flat. However, the high free energy of the (100) surface in an ionic fluorite crystal prevents the growth of comparable CaF2 films on the (100) Si surface.

Substrate chemical etching prior to molecular‐beam epitaxy: An x‐ray photoelectron spectroscopy study of GaAs {001} surfaces etched by the H2SO4‐H2O2‐H2O solution

Abstract: X‐ray photoelectron spectroscopy has been performed in order to investigate the effects of the chemical etching of GaAs {001} surfaces by the H2SO4/H2O2/H2O solution used following the procedure currently practiced in the molecular‐beam‐epitaxy technique. It is demonstrated that, in contrast to what is generally believed, rinsing in running deionized water after etching does not produce any passivating oxide film on the surface. The surface‐oxidized phases are only due to the sample manipulation in air after etching. This oxidation process is enhanced by the sample heating for indium soldering on the sample holder. It is shown that the surface‐oxidized phases can be avoided by handling the sample under an inert atmosphere. Results of thermal desorption of the surface‐oxidized phases are also given.

Micromachining of silicon mechanical structures

Abstract: Refined and very exact processing procedures for producing geometrically highly precise silicon structures are described. The structures are micromachined utilizing wet chemical orientation and/or concentration etching techniques. The use of a specially designed and highly effective etching system is a significant refinement in the processing procedure. The structures have excellent large and small scale uniformity. Relief structures having features as small as 0.2 μm have been produced. We report on devices for three specific research applications: (1) Very high Q torsional oscillators useful for high sensitivity measurements in the study of the mechanical properties of single crystal silicon and also in the study of thin freely suspended liquid crystal films, (2) unstrained focusing x‐ray mirrors, and (3) μm level mechanical ‘‘shadow masks’’ useful for noncontaminative, in situ patterning of thin films deposited in MBE and/or other deposition systems.

Strengthened solid-state laser materials

Abstract: The tensile fracture strength of crystalline materials for high average power lasers has been increased by a factor of 15 using deep chemical polishing. Samples of gadolinium scandium gallium garnet, gadolinium gallium garnet, and yttrium aluminum garnet, which were prepared by conventional mechanical techniques to a high quality polish, were found to contain subsurface damage up to 50 μm in depth. When this damage was removed by deep chemical etching, the mean strength of small, four‐point flexure specimens increased from 155 to 2280 MPa; however, these samples were no longer optically flat after etching. Specimens in which the optical figure was restored by polishing after the etch had an intermediate strength of 630 MPa.

Surface acoustic wave devices and method of manufacture thereof

Abstract: A phase and amplitude compensated surface acoustic wave (SAW) structure is described in which computer controlled compensation is achieved by laser chemical etching of selective portions of a compound chemical film deposited on the surface of a piezoelectric SAW substrate in the path of propagation. The compound film comprises a layer of amplitude attenuating cermet material formed on the substrate and a phase compensating layer of molybdenum formed over the cermet material and in contact with the substrate surface.

Microwave apparatus for generating plasma afterglows

Abstract: A microwave apparatus for generating plasma afterglows for stripping and/or etching of photoresist and semiconductor material at a sufficiently high rate to allow single wafer processing in a fully automated reactor. The apparatus includes a stripping/etching chamber for plasma afterglow stripping of photoresist and selective isotropic etching of semiconductor material, such as polysilicon and silicon nitride, using a variety of etchant compositions which form reactive species in a plasma. In addition, the apparatus may be employed for anisotropic etching for semiconductive material by decoupling etchant generation from ion production and acceleration by using two plasma sources, i.e., microwave power and radio frequency (RF) power. Anisotropic etching is carried out in an etching chamber which subjects, in situ, a plasma afterglow to RF power and which is designed to operate in the reactive ion etch mode.

Effect of flow history on the morphology of thermotropic liquid crystalline copolyesters

Abstract: Morphological studies have been carried out on a thermotropic liquid crystalline copolyester based on poly(ethylene terephthalate) (PET) and para hydroxybenzoate (PHB) that has been subjected to different types of flow histories. Wide angle X-ray scattering investigations and chemical etching (n-propylamine is the etchant) in conjunction with electron microscopy studies conducted on end gated injection molded plaques of the 60 percent PHB and 80 percent PHB copolyesters indicate that a highly oriented skin region and a less oriented core region is present. Chemical etching studies performed on microtomed layers of end gated and center gated plaques show that the etching is less pronounced in the skin region and is more pronounced in the core. The microtomed layers of the end gated injection molded plaques when analyzed by ESCA indicate the presence of a “PHB rich” skin region and a “PET” rich core region. Biaxial orientation, as denoted by WAXS measurements, is observed when the 60 percent PHB copolyester is squeezed between lubricated parallel plates.

GaAs and AlGaAs anisotropic fine pattern etching using a new reactive ion beam etching system

Abstract: High aspect‐ratio anisotropic etching for GaAs has been obtained with Cl2 plasma in a new reactive ion beam etching (RIBE) system equipped with an ultrahigh vacuum chamber. A vertical wall with 0.5 μm thickness and 7 μm height was obtained at a 500 V ion extraction voltage and etching gas pressure of 8×10−4 Torr. A normalized etching rate was 2 ( μm/min)/(mA/cm2) which corresponds to a sputtering yield of 23 atoms/ion. Such a high aspect‐ratio etching was mainly owing to use of a high‐temperature (250 °C) baked photoresist mask with a sharp cut profile. GaAs and AlGaAs equirate etching, which is often difficult in the conventional reactive ion etching (RIE), has also been obtained using this system. It was found that decrease of the AlGaAs etching rate in the RIE is attributed to Al2O3 formation due to residual H2O during etching.

Selective etching characteristics of HF for AlxGa1-xAs/GaAs

Abstract: The first detailed report of the selective etching characteristics of an AlxGa1-xAs/GaAs DH wafer (x≥0.4) in an HF system is given. Selective etching at a cleaved facet and a calculation of the energy of activation are included.

Properties of high rate sputtered perpendicular recording media

Abstract: Double layered media for perpendicular magnetic recording were made by dc magnetron sputtering. The coercivity of the Co‐Cr layer was independent of deposition rate over the range from 0.006 to 1.2 μm/min, when the substrate temperature was kept constant during sputtering. Micro columnar structure of the Co‐Cr film was studied by chemical etching. Only the columns were dissolved leaving the column boundaries showing a microhoneycomb structure. From the composition analysis of the etchant, Cr segregated column boundaries were confirmed to exist even in the high rate sputtered films. The Permalloy back layer with coercivity below 1 Oe shows large noise pulses in the reproducing process. Increasing the coercivity to several Oersteds reduced the noise to the amplifier noise level without changing the signal level. Finally, a high recording performance was obtained for the media made by high rate sputtering.

Chlorine surface interaction and laser‐induced surface etching reactions

Abstract: Surface reaction and radiation‐enhanced desorption of product species are basic surface processes in laser‐induced chemical etching of solids. These processes have been studied in Cl2‐Si and a number of metal systems which depending on the reaction behavior are divided into three classes, namely, the spontaneous etching, the passive, and the diffusive reaction systems. Various gaseous and surface analyses including XPS, AES, time‐resolved mass spectrometry, and quartz‐crystal microbalance measurements are performed in conjunction with surface irradiation by UV and visible laser pulses. The surface chlorination reactions and the effects of laser irradiation, in particular, the nonthermal radiation effects are discussed.

Method for tapered dry etching

Abstract: Holes in substrates are produced by a photolithography-plasma dry etching method employing a positive photoresist mask such as poly(methyl methacrylate) which is capable of being isotropically eroded by plasma action. The result is simultaneous anisotropic etching of the substrate and isotropic erosion of the mask, producing tapered holes.

Method of manufacturing shadow mask

Abstract: A method of manufacturing a shadow mask comprises the steps of: forming photoresist films on two major surfaces of a sheet made of a shadow mask material; forming latent images by selectively exposing the photoresist films, respectively; developing the latent images to form photoresist film patterns, respectively; and spraying an etching solution for etching the shadow mask sheet having the photoresist film patterns onto the two major surfaces thereof to etch bared portions of the shadow mask sheet, wherein the photoresist film formed on one of the two major surfaces of the shadow mask sheet is thicker than that formed on the other of the two major surfaces. The step of spraying the etching solution comprises a first step and a subsequent second step, wherein an impact of the etching solution against the shadow mask sheet in the first step is greater than that in the second step.

Selective interhalogen etching of tantalum compounds and other semiconductor materials

Abstract: We find that gaseous ClF3 is an effective and selective etchant for a variety of transition metals and metal compounds. Kinetics were studied for etching α‐Ta (13–16 atom % N), Ta2N, and Ta2O5 in this gas, as a function of temperature and pressure, to provide effective activation energies of 4.0, 4.4, 7.7 kcal/mole, respectively. Relative etch rates measured in CF4/O2 and NF3 plasmas indicate that ClF3 gaseous etching has more than an order of magnitude better selectivity for nonoxidic metal compounds over the corresponding oxide. At 100 °C, selectivity for etching α‐Ta or Ta2N over Ta2O5 is more than 160:1. Other materials used in semiconductor manufacture, such as SixNy, W, TaSi2, and photoresist, were also briefly surveyed and the results suggest ClF3 holds promise for isotropic etching applications that require high selectivity.

Auger electron spectroscopic study of the etching of cadmium telluride and cadmium manganese telluride

Abstract: The surface compositions of Cd1−xMnxTe and CdTe that result from various chemical treatments have been studied by Auger electron spectroscopy. The depths of nonstoichiometric surface layers have been determined by sputter profiling. Bromine methanol and mineral acids leave surfaces depleted in Cd and Mn. The depth and degree of depletion is generally more severe for Mn than for Cd. Nearly stoichiometric surfaces result from soaking Cd1−xMnxTe and CdTe in water solutions with KOH. The depletion of Mn from the surface after bromine methanol etching can be reduced by dissolving Mn in the etch solution.

Low power ion-beam-assisted etching of indium phosphide

Abstract: Ion-beam-assisted etching is a dry etching technique in which the sputter etching component of an ion beam and the chemical etching component supplied by a localized reactive gas flux, such as chlorine, can be independently controlled. In this paper the etching properties of InP as a function of substrate temperature, ion-beam parameters, and reactive chlorine flux in such a system are presented. Sample temperatures greater than 150°C were required to achieve reasonable etch rates and surfaces that were free from an In rich surface layer. By controlling parameters, high aspect ratio structures with vertical side walls and good surface quality were obtained.

Plasma etching of silicon using fluorinated gas mixtures

Abstract: A method of plasma etching silicon using a fluorinated gas mixture. A mixture of CHF3 and SF6 is utilized in an etch chamber to form a plasma for etching silicon. The degree of anisotropy of the etch can be controlled by changing the percentage of CHF3 in the CHF3/SF6 mixture. The method does not adversely affect the etched surface so that no post-etch thermal process step is required to cure the silicon surface.

X-Ray Photoelectron Spectroscopy Study of GaAs (001) and InP (001) Cleaning Procedures Prior to Molecular Beam Epitaxy

Abstract: The effect of chemical etching by H2S04/H202/H20 (5/1/1) mixtures and of mechanopolishing by bromine-methanol diluted solution on GaAs (001) and InP (001) substrates for molecular beam epitaxy (MBE) has been studied using X-ray photoelectron spectroscopy (XPS). The final rinse in running deionized water does not produce any passivating oxide layer on the substrate surface. Oxidation observed on GaAs and InP after these cleaning procedures occurs during substrate handling in air. The H2S04/H202/H20 mixture produces arsenic rich surface layers having an atomic ratio As/Ga of 1.15, whereas the bromine-methanol mechanopolishing leads to an arsenic or phosphorus depleted surface with atomic ratios As/Ga=0.7 and P/In=0.65.

Co-Cr 垂直記録媒体の微視的偏析構造

Abstract: Microcolumnar structure of Co-Cr film has been studied with use of chemical etching. Only the columns are dissolved leaving the column boundaries a microhoneycomb structure. From the composional analysis of etchant after etching, Cr segregated column boundaries have been confirmed to exist even in the high rate sputtered Co-Cr films. The Co-Cr film with higher Hc shows sharper and narrower grain boundaries whose Cr content is also higher. It is concluded that degree of Cr segregation is very important factor for the control of the mametic oronerties of the Co-Cr films.

Composition‐selective photochemical etching of compound semiconductors

Abstract: Compound semiconductor materials differing only in the relative amounts of constituent atoms are very difficult to etch selectively using current chemical etching techniques. We have developed a photochemical etching process that solves this problem by utilizing the difference in band gap of GaAs1−xPx materials differing slightly in composition to produce a very high degree of etching selectivity between the materials. The concepts employed in this process have general applicability to other compound semiconductor material systems.

Local Temperature Rise during Laser Induced Etching of Gallium Arsenide in SiCl4 Atmosphere

Abstract: Localized etching of GaAs using an argon laser beam in an SiCl4 atmosphere has been performed for various laser powers to investigate the threshold power, i.e., the minimum local temperature, for pyrolytic etching. Local temperature rise during laser induced etching was measured by the peak shift of in situ photoluminescence and was also estimated by solving the three dimensional heat equation. It was found that the threshold power for pyrolytic etching at an SiCl4 pressure of 76 Torr was about 0.25 W, turning out to be about 190°C, which was in good agreement with the calculated temperature.

Dry etching method for selectively etching silicon nitride existing on silicon dioxide

Abstract: A dry etching method for selectively etching a silicon nitride having the generic formula Si x N y existing over a base of SiO 2 utilizing, as the etchant gas, a mixture of a fluorohydrocarbon in which the atomic ratio of F/C is smaller than 3:1, the mixture containing 30-70% of CO 2 on a flow rate basis. The presence of such a large amount of CO 2 in the etchant in combination with the particular fluorohydrocarbons is effective for enhancing the selective ratio of etching between Si x N y and SiO 2 and also for preventing formation of obstructive polymers of fluorocarbons.