Non uniform recombination in thin silicon-on-sapphire films

World Abstracts on Microelectronics and Reliability Effects of annealing on localized states in amorphous Ge films. S. HASEGAWAand M. KITAGAWA.Solid St. Commun. 27, 855 (1978). Annealing behaviors of the activation energy for the electrical conduction E v that for the thermoelectric power E~, the optical gap E~pt, and the spin density in evaporated amorphous Ge are investigated. E~ is independent of E~ and Egopt, and the rates of variation of E~pt and Es with annealing temperature are connected by AE~Pt = 2.5AE#. It is suggested that the position of the Fermi level does not change with annealing in contrast with amorphous Si, and the edge of the localized tail state shifts with annealing. Piezoresistanee effect in Pbo,s2Sno.lsTe films. ANTONI ROGALSKIand JANUSZ RYBINSKI.Electron Technol. 11, (1/2) 75 (1978). Piezoresistance coefficient of longitudinal and transverse strain sensitivity has been measured in n- and p-type Pbo.s2Sno.lsTe films prepared on mica substrates and oriented in [111] direction. An attempt has been made to explain the dependence of the gauge factor on the angle between the stress direction and the current. Photocurreuts in silicon nitride films. FATEH MOHAMMAD NAZAR. Int. J. Electron. 45, (4) 401 (1978). Photocurrents in silicon nitride films deposited by pyrolytic reaction between silane and ammonia on silicon substrates of resistivities 0.01 f~-cm to 10f~-cm, both n and p-type, have been studied. Only nitride films on O.If~-cm p-Si and 10fl-cm n-Si substrates show photocurrents; the former being symmetric with polarity of the applied bias while the latter are strongly polarity dependent. It is suggested that the symmetric photocurrents which give log AI-V 1/2 behaviour may be due to the same localized levels giving rise to the dark Poole-Frenkel conduction. The asymmetric photocurrents may be a property of the Si3N4-Si interface. It is concluded that the type and resistivity of the silicon used as substrates definitely affect the electrical characteristics of the silicon nitride films deposited on them. Effect of reactive gas dopants on the MgP surface in AC plasma display panels. W. E. AHEARN and O. SAHNI. I B M J. Res. Dev. 22, (6) 622 (November 1978). Experimental results are presented for the influence of controlled levels of important reactive impurities (N2, 02, H20, CO2) on the aging characteristics of the operating voltages of ac plasma display panels. Details are also given of a novel method of modifying the electronic properties of MgO surfaces by discharge processing in an oxygen-doped Ne 0.117oAr Penning mixture. Electrical conduction in thin zinc rf sputtered films. C. R. TELLIER. Vueuum 28, (8/9) 321 (1978). Experiments on the thickness dependence variations in electrical resistance of thin rf sputtered zinc films before and after thermal ageing are consistent with a two-layers model: the first layer about 150 A thick is the thinner continuous layer that may be obtained; electronic conduction in the second layer occurs according to the Mayadas Shatzkes model related to polycrystalline films with a constant grain size. The linearized equations and the "effective Fuchs-Sondheimer" model previously reported are convenient tools for describing the conduction in the upper layer and allow an experimental determination of the carrier reflection coefficients at grain-boundaries and film surfaces. l / f noise in metal films : the role of the substrate. P. DUTTA, J. W. EBERHARD and P. M. HORN. Solid St. Commun. 27, 1389 (1978). We have examined the temperature dependence of voltage ("l/f") noise in Cu and Ag films on quartz and sapphire substrates. Our data suggest that two types of voltage noise occur simultaneously in metal films. One type of noise depends on the substrate and is weakly temperaturedependent; the remaining noise is strongly temperaturedependent and independent of the substrate. M.g. 19/3~C

201

An experimental study of the indium antimonide thin film transistor. A. VAN CALSTER.Solid-St. Electron. 22, 77 (1979). In this paper a survey is given of our experimental investigations on the InSb thin film transistor (TFT). The best characteristics were obtained on a two-sided thin film transistor, made by flash evaporations of InSb on a heated substrate of 250°C, followed by an annealing at 350°C for 30 minutes. Furthermore it was found that the presence of minority carriers obstruct the saturation of the transistor characteristics at room temperature. This negative influence of the minority carriers is weakened at lower temperatures, which makes the InSb TFT more attractive for operations in a cryogenic environment. Ultra-high vacuum systems for surface research. Y. MARGON1NSKI. Vclcuum 28, (12) 515. During the last 20 years, surface research has been one of the fastest growing fields in physics and physical chemistry. Yet such a development would have been impossible without a parallel advance in ultra-high vacuum (uhv) techniques. In this paper a short survey is given of uhv systems in surface research from 1927 to the present day, with special emphasis on the developments since the 1950s when NASA was established. To illustrate modern uhv technology, a detailed description is given of two commercially available systems, specially designed for surface research. Oxygen content and oxide barrier thickness in granular aluminium films. P. ZXEMANN, G. HElM and W. BUCKEL. Solid St. Commun. 27, 1131 (1978) Granular aluminium films were prepared by evaporation in an oxygen atmosphere. The oxygen content Co of the films was determined by Rutherford backscattering. The superconducting transition temperature Tc is measured as a function of the oxygen concentration. From the results the thickness of the oxide barriers is derived by applying a model of spherical granula. This model is confirmed by the observed linear dependence Tc oc Co. New substrate causes a stir. JERRY LYMAN. Electronics p. 94 (7 December 1978). Porcelain on steel could be key to size and cost barriers of conventional alumina material in thick-film hybrids. A phenomenological study of a.c. gas panels fabricated with vacuum-deposited dielectric layers. JOHN F. O'HANLON. I B M J. Res. Dev. 22, (6) 626 (November 1978). This paper presents the results of an experimental investigation of a.c. gas display panel parameters. The ignition and extinction voltages were measured for panels filled with Ne 0.1% Ar gas to pressures ranging from 0.75 x 104 Pa to 8 x 104 Pa (50 torr to 600 torr). The panels were constr ucted with chamber spacings, d, of 0.56 x 10 2cm to 2 x 10 2cm, and electrode widths, x, of 1.5 x l(I-3cm to 0.1 cm. Scaling of the Paschen minimum was not found to hold for the narrowest chamber spacing, The dependence of ignition voltage on linewidth was found to be proportional to e x p ( - 1 . 6 x / d ) for ( x / d ) < l. An electron diffusion process was invoked to explain this behavior. Non uniform recombination in thin silicon-on-sapphire films. SORIN CRISTOLOVEANU. ALAIN CHOVET a n d

GEORGES

KAMARINOS.Solid St. Electron. 21, 1563 (1978). Recombination parameters of SOS films are deduced from the study of the magnetoconcentration effect in double-injecting structures. The method of measurement is based on an original theory succinctly developed; it takes into account general SRH bulk and surface recombination laws; moreover inhomogeneous distributions of recombination centers are considered. Experimental results (current-voltage characteristics of such "magnetodiodes'), when analysed according to the proposed method, lead to more realistic values of the

202

World Abstracts on Microelectronics and Reliability

global recombination parameters (r,,, s~, Sz) of the SOS film. It is proved, for example, that the previous simplified analysis overestimates the carrier recombination velocity on the Si A1203 surface. On the contrary our method gives both a moderate value for this recombination velocity and lower carrier lifetime near the Sapphire interface, which well agrees with the continuity of recombination rates at the surface and in the underlying bulk; the higher recombination region is found to be 100-1000 A thick.

9. E L E C T R O N ,

ION

A compact high power semiconductor laser array. P. E. DOUGLAS. Microelectron. Reliab. 18, 163 (19781. The development of the semiconductor heterostructure diode laser has provided a very compact and efficient source of near monochromatic infra-red radiation. The device has found ready uses in range finding, weapon simulation, communication systems and for general field irradiation. For a number of applications however, power radiated from one laser chip is too low, and so methods of combining the outputs from several chips have been investigated with the particular aim of keeping the combined source as small as possible. This paper describes a particular method by which this has been achieved. An array of laser diodes with their outputs coupled together with fibre optic tapes has been developed to make a source whose dimensions depend basically on the number of lasers used and the tape size There is also a description of the method of coupling the output from the array to a system. Three practical embodiments employing laser stacks are described together with some of the problems involved. It is first desirable to consider briefly the properties of the single diode. Vector-scan E beam aims for wafers as well as masks. Electronics p. 68 (9 November 1978). Electron-beam machine

intended for production line achieves higher throughput with vector scanning.

Laser drilling of vias in dielectric for high density multilayer thick film circuits. T. COCCA and S. DAKESIAN.Solid St. TechnoL p. 63 (September 1978). The methodology whereby four mil vias can be fabricated in production using laser technology is described. A pulsed YAG laser was used to demonstrate the technique. A commercially available multilayer dielectric was used as the insulating medium. The conductor materials were fritless gold types. A RAYPAK digital microcircuit utilizing 60 gate beam lead arrays was used as the experimental vehicle to prove feasibility of laser drilling of the dielectric material. The circuit had two conductor levels insulated with dielectric and thirty-six laser drilled four mil vias. Once the laser energy output is adjusted so that each pulse completely drills one hole (vial the holes are consistent and uniform for that particular lot of material and dielectric thickness. In no instance did any tested unit indicate high resistivity at a four mil via. Work is continuing on multi-level substrates with four rail lines and spaces at each conductor level. A laser system with a programmable table will automate the laser drilling of vias. Thinning method for electron microscopy transparent silicon and germanium foils. (3. MAWR YON SYASZEWSKI.Micron 9, 207 (1978). A large amount of work has been done on tire preparation of germanium and silicon specimens for electron microscopy studies, due to the interest of these materials in the microelectronic industry. Modifications are presented here which have some advantages for the simplicity of specimen fabrication, the number of samples obtained and the size of the transparent area.

VCNR type characteristic in thin film amorphons Te G e - A s - S i films. Zv~ YANIV and ABRAtlAM SANDERICHIN. ]/UCt/Utn28, (12)1533). In the hope of further understanding the memory and switching effects of amorphous evaporated semi-conductor films, the current voltage curve of the quarternary system Te Ge As Si was experimentally examined and our findings are discussed belovx.

AND

LASER

BEAMS

Electrical and optical characteristics of evaporable-glassdielectric a.c, gas display panels. JOHN F. O'HANLON, K. C. PARK, A. REISMAN, R. HAVRELUK and J. G. CAHILI.. I B M J. Res. Dev. 22, (6) 613 (November 1978). This paper presents the characteristics of a prototype gas display panel fabricated with electron-beam deposited dielectric films. It is shown that panels with a 6-pm-thick dielectric layer and a 0.2-1Lm-thick MgO layer exhibit short stabilization times (15 mini, long life (20,O00h), small drift effects (< 0.5 V), and adequate brightness (21 cd/m2). The devices have a large dynamic write margin (> 10V) over a wide pressure range. Dielectric glass layers as thin as 3.2 itm were found to be stable. A panel with a small H20 impurity concentration was used to show that the hydrated MgO surface caused charge leakage and loss of memory margin, while a panel with an air leak confirmed that the surface saturated before the effects of gas contamination were observed. Effects of dislocations in silicon transistors with implanted emitters. C. BULL, P. ASHBURN, G. R. BOOKER and K. H. NICrtOLAS. Solid-St. Electron. 22, p. 95 (1979). Silicon bipolar transistors have been made by substituting a shallow phosphorus implantation for the standard emitter deposition used in the manufacture of linear integrated circuits. The imphmtation was followed by a high temperature heat treatment (drive-in), which caused the implanted ions to diffuse deeper into the semiconduclor to give emitter/base junction depths of typically 1.8 tim. When the high temperature heat treatment was performed in an oxidising atmosphere, the resulting transistors had lower gains and higher emitter/base leakages than the comparable standard diffused transistors. However, if an 1180~'C drive-in, in an inert atmosphere, was performed prior to the oxidation drive-in, high gains and low emitter/base leakages were obtained. Alternatively, if the oxidation drive-in was omitted, and instead an inert drive-in performed at any temperature between 1000 and 1180~C, high gains and low emitter/base leakages were again obtained. Etching and TEM studies revealed that the low gains and high emitter/base leakages were caused by emitter edge dislocations intersecting the emitter/base junction around the perimeter of the emitter. A mechanism is suggested to describe the formation of the emitter edge dislocations. Capacitance and doping profiles of ion-implanted, buriedchannel MOSFETS. G. LUBRERTSand B. C. BURKEV. SolidSt. Electron. 22, 47 (1979). Detailed capacitance measurements are presented of large-area, ion-implanted, buriedchannel MOSFETs. The gate capacitance was measured as a function of gate-substrate voltage with drain (source)substrate voltage as parameter. The MOSFETs were prepared on 10f~-cm, n-type, (111)Si. Boron ions with doses of 4 × 10 ~ and 8 × 1011/cm 2 were implanted through the gate oxide to a depth of 0.30--0.35 #m in the Si. The devices were subjected to heat treatments of 900 1100'C. Calculated capacitances based on a one-dimensional, partial-ionization model are in good agreement with experiment. The model is used to assess the validity of the C t' profiling technique based on the abrupt space-charge