Melvin Berkenblit

Plastic Deformation in Epitaxial Ge Layers Grown on Single Crystal Semi‐Insulating GaAs

The compatibility of Ge and , in terms of their temperature dependent mechanical properties, is described in this paper. Examination at room temperature of epitaxial Ge layers grown on wafers of single crystal, semi‐insulating , at substrate temperatures of 700°C by pyrolytic dissociation of , reveals evidence of plastic deformation immediately following the epitaxial deposition process. Plastic deformation is observed in epitaxial Ge layers grown at 350°C, by disproportionation of , only after a subsequent annealing cycle to at least 500°C. The low substrate temperature Ge films, however, show elastic bending of thin substrates after deposition and cooling to room temperature. Based on these observations, it is possible to estimate the differential thermal expansion coefficient between Ge and , and to use this result to estimate the critical shear stress for plastic deformation under low strain rate conditions . Interface dislocations are not observed.

The epitaxial growth of ZnO on sapphire and MgAl spinel using the vapor phase reaction of Zn and H2O

The gas phase reaction of Zn and H2O in a He carrier gas has been used as the basis for the chemical vapor deposition of ZnO on sapphire and MgAl spinel. Deposit characteristics were studied as a function of reactor linear gas stream velocity, Zn/H2O vapor phase ratio, temperature and substrate preparation. It was round that the substrate support can influence the surface morphology significantly and that in situ pretreatment can affect epitaxial relationships between deposit and substrate. Transparent, visually smooth deposits of (11–24) ZnO can be obtained on chemically polished (0001) sapphire at 815°C using average linear gas stream velocities, ν, of 6-12 cm/sec referenced to room temperature in conjunction with a Zn/H2O reactor input-pressure ratio of 0.02–0.09 (using Zn reactor pressures of 1.2–5.0 × 10−3 atm) . The substrates are given an H2O in situ pretreatment at 900°C prior to deposition at ν = 3 cm/sec with the partial pressure of H2O in He = 5.7 × 10 atm.

The equilibrium constant for the reaction of ZnO + H2 and the chemical vapor transport of zno via the Zn + H2O reaction

Using a gas transpiration method, the equilibrium constant for the reaction ZnO(s) + H2(v)⇄ Zn(v) + H2O(v) was determined directly in the temperature interval 592–950°C. The data are described by the equation log10K = [-11.794 × 103/T] + 8.040 with ΔH° = 53.97 Kcal/mole and ΔS° = 36.79 e.u. Based on this Information, vapor-solid gas concentration curves useful for defining conditions for the chemical vapor transport of ZnO via the reverse of the above reaction have been computer calculated.

Nitridation of silicon in a multiwafer plasma system

Silicon wafers were nitrided in a multiwafer plasma system at low temperatures (< 850°C). An argon plasma (400 kHz rf plasma) was used to which small quantities (approximately 2–8 %) of NH3, N2 or mixtures of N2 and H2 were added. As the rf power was increased, the film thickness as well as the etch rate (in buffered HF) increased. The rate of film growth was found to be slower than that for oxidation in a similar type of plasma system. The effects of variation of power and gas composition on film composition and etch rate are discussed.

Heat dissipation from silicon chips in a vertical plate, elevated pressure cold wall system

The heat dissipation effects of elevated pressure and cold gas temperature on vertically configured module mounted and free hanging chips were examined. It was found that with both types of chips, the thermal resistance (temperature rise x area/power) varies linearly with pressure in a log-log plot. A free hanging chip exhibits a (-1/3) power dependency on pressure while the module mounted chip exhibits a (-1/5) power dependency on pressure. The thermal resistance of the module mounted chip also appears to exhibit a dependency on gas temperature, but not on the difference in temperature between the chip and cold gas. The thermal resistance of the module mounted chip is some 5x lower than that of the free hanging chip, demonstrating that the module acts to a degree as a thermal expander. The efficiency is less than 20% based on the fact that the module area is some 30x greater than the chip area. For the module mounted chip, and a combination of a liquid nitrogen gas temperature and 1500 psi ambient atmosphere pressure, > 30 W/chip (0.180 in. × 0.180 in.) (0.46 cm × 0.46 cm), can be dissipated with a temperature rise to 85°C. This translates to a heat dissipation capability of more than 900 W/in2.

The formation of ß SiC on Si

Abstractß-SiC was formed on Si substrates in an horizontal, rf powered reactor. The reaction of Si with CH4} was either directly at temperatures of 1200-1350‡C or by a two step reaction in which CH4} was first cracked at 900‡C and then the deposited C reacted with Si at temperatures of 1200-1350‡C. Important features of the study were the minimization of contam-inants from susceptor and substrate support materials, removal of native oxides and a novel susceptor design. A rectangular, TaC coated Ta susceptor was used in conjunction with sapphire supports. Preheated He was used as a carrier gas. Growth characteristics and film structure are presented as a function of CH4} concentration and substrate temperature.

Thermal forming of niobium oxide switchable resistors

A controlled thermal process has been developed for the production of niobium oxide switchable resistors (NOSR), that are suitable for a medium speed, random access, read-write memory application. In particular, the voltage necessary to form the NOSR from the as-fabricated state to the bistable switchable resistor state has been reduced to approximately 2V at 1 mA. The thermal process increases the oxygen vacancy level in the niobium oxide, thereby lowering the bulk resistivity. The applied voltage now primarily appears across the niobium oxide-counterelectrode barrier, and as a consequence a lower external voltage is necessary to produce the same field in this vicinity. The presence of Sb or Bi on the oxide during the heat treatment lowers the subsequent current necessary for forming.

Anomalous Thermal Behavior of Boron‐Doped Low‐Temperature Ge Epitaxial Layers

Recently, conditions have been defined for the growth of mirror‐smooth layers of Ge on either Ge or semi‐insulating by the disproportionation reaction. In attempting to dope such layers with p‐type impurities under the defined surface‐rate‐limited growth conditions, it was observed that order‐of‐magnitude decreases in resistivity occurred on heating the grown layers to temperatures higher than the original growth temperature. This indicated that impurities were initially incorporated in an electrically inactive state. Results are presented which show this behavior to be increasingly pronounced for fast growth rates and low substrate temperatures, and growth conditions to minimize the effect are defined.