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NASA NTRS1982

Wafering insight provided by the ODE method

The orientation-dependent etching method of slicing was investigated to see if it could be used to form more slices from high quality silicon crystals than can be achieved by mechanical slicing methods. Orientation-dependent slicing uses preferential etching down narrow slots in a silicon slab on form slices. The method has several possible advantages including high slicing yield (sq m/kg), plane parallel, thin slices, ready for processing and the chance of high throughput and low costs. There are limitations in the need for simple crystals, and in restricted depth of slicing.

Soclof, S. I.↗

NASA NTRS1981

Surface flashover arc orientation on Mylar film

A study of the arc discharge patterns and resultant damage patterns on thin Mylar films exposed to a 20 keV electron beam is described. In particular, it is established that there is a broad directional correlation among the directions associated with visible linear arcs, damage tracks, the 'slow' optical direction and the longitudinal marks left on the films surface as a result of chemical etching. Transverse etch marks also appear to be associated with secondary groups of damage track directions. The 'fast' optical direction is associated with the absence of visible arcs or arc damage.

Gossland, M.↗

NASA NTRS1984

Modified Fabrication for InGaAsP Strip Laser

Improved fabrication of InGaAsP stripe lasers involves replacement of oxide stripe in quaternary laser by an n-type layer of InP grown on top of quaternary cap layer. Process allows use of stop etch that selectively removes InP and does not etch InGaAsP, making fabrication especially convenient.

Ladany, I.↗

NASA NTRS1982

Bread board float zone experiment system for high purity silicon

A breadboard float zone experimental system has been established at Westech Systems for use by NASA in the float zone experimental area. A used zoner of suitable size and flexibility was acquired and installed with the necessary utilities. Repairs, alignments and modifications were made to provide for dislocation free zoning of silicon. The zoner is capable of studying process parameters used in growing silicon in gravity and is flexible to allow trying of new features that will test concepts of zoning in microgravity. Characterizing the state of the art molten zones of a growing silicon crystal will establish the data base against which improvements of zoning in gravity or growing in microgravity can be compared. 25 mm diameter was chosen as the reference size, since growth in microgravity will be at that diameter or smaller for about the next 6 years. Dislocation free crystals were growtn in the 100 and 111 orientations, using a wide set of growth conditions. The zone shape at one set of conditions was measured, by simultaneously aluminum doping and freezing the zone, lengthwise slabbing and delineating by etching. The whole set of crystals, grown under various conditions, were slabbed, polished and striation etched, revealing the growth interface shape and the periodic and aperiodic natures of the striations.

Kern, E. L.↗

NASA NTRS1982

Holographic fabrication of gratings in metal substrates

A program for investigating the grain enlargement resulting from the laser recrystallization of a thin gallium arsenide film on a patterned substrate, a technique known as graphoepitaxy was evaluated. More specifically, the effects of recrystallizing an uncapped gallium arsenide film using a continuous wave neodymium YAG laser operating at 1.06 microns were studied. In an effort to minimize arsenic loss from the film, the specimens were held in an arsine atmosphere during recrystallization. Two methods for fabricating patterned substrates were developed, one using reactive ion etching of a molybdenum film on both sapphire and silicon substates and another by preferential wet etching of a silicon substrate onto which a film of molybdenum was subsequently deposited.

Fletcher, R. M.↗

NASA NTRS1983

Techniques for the correction of topographical effects in scanning Auger electron microscopy

A number of ratioing methods for correcting Auger images and linescans for topographical contrast are tested using anisotropically etched silicon substrates covered with Au or Ag. Thirteen well-defined angles of incidence are present on each polyhedron produced on the Si by this etching. If N1 electrons are counted at the energy of an Auger peak and N2 are counted in the background above the peak, then N1, N1 - N2, (N1 - N2)/(N1 + N2) are measured and compared as methods of eliminating topographical contrast. The latter method gives the best compensation but can be further improved by using a measurement of the sample absorption current. Various other improvements are discussed.

Prutton, M.↗

NASA NTRS1985

Bonding Heat-Resistant Fabric to Tile

Acid etching, densification, and silica cement ensure strong bond. Key step in preparation for bonding to glazed tile is etching quartz fabric and tile with acid. This increases adhesion of silica cement used to form bond. Procedures use high-temperature materials exclusively and therefore suitable for securing flexible seals and heat barriers around doors and viewing ports in furnaces and kilns.

Holt, J. W.↗

NASA NTRS1982

High density circuit technology, part 3

Dry processing - both etching and deposition - and present/future trends in semiconductor technology are discussed. In addition to a description of the basic apparatus, terminology, advantages, glow discharge phenomena, gas-surface chemistries, and key operational parameters for both dry etching and plasma deposition processes, a comprehensive survey of dry processing equipment (via vendor listing) is also included. The following topics are also discussed: fine-line photolithography, low-temperature processing, packaging for dense VLSI die, the role of integrated optics, and VLSI and technology innovations.

Wade, T. E.↗

NASA NTRS1982

Development of a polysilicon process based on chemical vapor deposition, phase 1 and phase 2

High-purity polycrystalline silicon was produced in an experimental, intermediate and advanced CVD reactor. Data from the intermediate and advanced reactors confirmed earlier results obtained in the experimental reactor. Solar cells were fabricated by Westinghouse Electric and Applied Solar Research Corporation which met or exceeded baseline cell efficiencies. Feedstocks containing trichlorosilane or silicon tetrachloride are not viable as etch promoters to reduce silicon deposition on bell jars. Neither are they capable of meeting program goals for the 1000 MT/yr plant. Post-run CH1 etch was found to be a reasonably effective method of reducing silicon deposition on bell jars. Using dichlorosilane as feedstock met the low-cost solar array deposition goal (2.0 gh-1-cm-1), however, conversion efficiency was approximately 10% lower than the targeted value of 40 mole percent (32 to 36% achieved), and power consumption was approximately 20 kWh/kg over target at the reactor.

Plahutnik, F.↗

NASA NTRS1984

Formation of ion damage tracks

A new model is proposed to explain both localized damage regions and preferential etching of damage tracks caused by the passage of energetic ions in insulators. The formation of each region of extended defects is initiated by the Auger decay of a vacancy produced in an inner electronic shell of an atom of the insulator by an incident ion. This decay produces an intense source of ionization within a small volume around the decaying atom, which causes decomposition of the material in a manner similar to that observed in pulsed laser irradiation. The resulting chemical or crystalline modification of the material is the latent track, which can be preferentially etched due to its changed structure.

Tombrello, T. A.↗

NASA NTRS1984

Solar cosmic ray produced neon in lunar soils and their implication for gas-rich meteorite studies

Characteristic neon isotopic ratios, produced due to solar cosmic ray spallation (SCR) in lunar soils, are useful in deciphering and estimating the relative contributions of SCR and GCR spallation. To delineate these features, etched mineral grains from mature and immature lunar soils (14148 and 61221 respectively) were analyzed using mass spectrometry. The SF-Ne composition deduced in this work agrees with that obtained from earlier etched lunar pyroxene studies. The data points for mature soil 14148 define a line which significantly deviates from the 61221 tie line. This deviation is attributed to the presence of SCR spallation component. In this context, neon isotopic compositions (step-wise heating) in Pantar and Leighton dark portions were studied and compared with that of Fayetteville. The meteorite data points deviate significantly from the tie line joining SF-Ne and GCR (pyroxene) end points. This deviation is attributed to SCR-spallation in gas-rich chondrites.

Nautiyal, C. M.↗

NASA NTRS1986

Reducing Sodium Contamination in MOS Devices

Method of removing positive ions from oxides in metal-oxide-semiconductor (MOS) transistors and intergrated circuits ensure freedom from contamination by sodium and other mobile positive ions. Electric field applied during oxide growth to push mobile Na + ions to surface. After cooling from growth temperature, field turned off and Na + contaminated surface layer etched away. New method intended to suplement established methods of minimizing ion contamination, such as scrupulous cleanliness in processing, purging with hydrogen chloride to react with and remove contaminants, and growing extra-thick gate oxide, then etching it to remove large portion of contaminants concentrated near surface.

Dehaye, R. F.↗

NASA NTRS1986

Electrochemical Process Makes Fine Needles

Electrochemical process makes fine tungsten needles for use as microscopic probes or field-emission cathodes. Etching vessel filled with dense, inert lower liquid covered by less-dense, caustic etching solution. Newly formed needle breaks off upper part of wire in etchant and falls into can in inert liquid below. Improved process does not require close monitoring and left unattended for an indefinite time.

Watkins, J. L.↗

NASA NTRS1986

Multifunction Vacuum Chamber for IC Metallization

Vacuum system chamber processing multilayer metallization on integrated circuits (IC's) performs four operations ordinarily done in separated equipment. Chamber etches holes, removes photoresist, cleans by sputter etching, and deposits final layer of metal. Combinedfunction chamber costs less than separate equipment. Chamber avoids exposing integrated circuits to room air and, to oxidation and dust, between steps. Eliminates time spent in transferring circuits from one apparatus to next.

Routh, D. E.↗

NASA NTRS1987

Deformation and fracture of single-crystal and sintered polycrystalline silicon carbide produced by cavitation

An investigation was conducted to examine the deformation and fracture behavior of single-crystal and sintered polycrystalline SiC surfaces exposed to cavitation. Cavitation erosion experiments were conducted in distilled water at 25 C by using a magnetostrictive oscillator in close proximity (1 mm) to the surface of SiC. The horn frequency was 20 kHz, and the double amplitude of the vibrating disk was 50 microns. The results of the investigation indicate that the SiC (0001) surface could be deformed in a plastic manner during cavitation. Dislocation etch pits were formed when the surface was chemically etched. The number of defects, including dislocations in the SiC (0001) surface, increased with increasing exposure time to cavitation. The presence of intrinsic defects such as voids in the surficial layers of the sintered polycrystalline SiC determined the zones at which fractured grains and fracture pits (pores) were generated. Single-crystal SiC had superior erosion resistance to that of sintered polycrystalline SiC.

Miyoshi, Kazuhisa↗

NASA NTRS1987

Early changes in gradation styles and rates on Mars

The wide annulus of massifs and knobs of Isidis and Argyre provided sufficiently large areas for meaningful crater statistics of large craters. Counts were made over adjacent and nested areas in order to test consistency and to derive relative age of each basin. Within the Isidis annulus, charateristic terrains provided counting areas for dating contrasting surface process: channeled hummocky terrain, etched terrains, and intermassif channeled plains. The channeled hummocky terrain contains a high channel density of narrow valley networks cutting both primary Isidis features and old craters. The etched terrains represent a broad region outside the inner high relief massifs of southwestern Isidis where numerous irregular plateaus, mesas, and relict craters indicate a different style of erosion. The intermassif channeled plains occur along the inner mountainous ring. Shallow meandering channels form a large integrated drainage system that is linked to numerous smaller intermountainous basins. These ponds and interconnected tributaries extend beyond the primary inner massif ring through broad canyons.

Schultz, Peter H.↗

NASA NTRS1987

High temperature radiator materials for applications in the low Earth orbital environment

Radiators must be constructed of materials which have high emittance in order to efficiently radiate heat from high temperature space power systems. In addition, if these radiators are to be used for applications in the low Earth orbital environment, they must not be detrimentally affected by exposure to atomic oxygen. Four materials selected as candidate radiator materials (304 stainless steel, copper, titanium-6% aluminum-4% vanadium (Ti-6%Al-4%V), and niobium-1% zirconium (Nb-1%Zr)) were surface modified by acid etching, heat treating, abrading, sputter texturing, electrochemical etching, and combinations of the above in order to improve their emittance. Combination treatment techniques with heat treating as the second treatment provided about a factor of two improvement in emittance for 304 stainless steel, Ti-6%Al-4%V, and Nb-1%Zr. A factor of three improvement in emittance occurred for discharge chamber sputter textured copper. Exposure to atomic oxygen in an RF plasma asher did not significantly change the emittance of those samples that had been heat treated as part of their texturing process. An evaluation of oxygen penetration is needed to understand how oxidation affects the mechanical properties of these materials when heat treated.

Rutledge, Sharon K.↗

NASA NTRS1987

Low reflectance EUV materials - A comparative study

A study has been undertaken of the performance characteristics of a variety of surfaces and surface treatments for use on baffle materials in Extreme UV Explorer instrumentation, in order to ascertain which materials performed with the least overall scattering between 300 and 1200 A and thereby minimize this important background source. Seven scattering samples were measured: bead-blasted aluminum treated with alodine 600, bead-blasted aluminum, Kel-f, etched molybdenum, nickel-plated etched molybdenum, bead-blasted 304 stainless steel, and bead-blasted aluminum painted with Chemglaze Z-306. Attention is given to total reflectance of each material plotted against the graze angle for 304, 584, and 1216 A.

Jelinsky, Patrick↗