World Abstracts on Microelectronics and Reliability
evaluation of lifetime from the measurements and a low sensitivity of the results to surface conditions. The method is limited to layers thicker than a diffusion-length. In thinner layers only the lifetime of minority-carriers in the substrate can be determined from the frequency dependence of the photo-current.
Design of high reliability Mica capacitor for submarine cable repeaters. RYOICHI KANEOYA, SHIGEO KONDO, and KAORU SHINOZAKI. Abstracts-Trans. Inst. Electron. Commun. Engrs. Japan. 57, 25 (1974). In submarine cable repeaters, very high reliability as well as high precision is essential. In this paper, description is made on the design, fabrication and properties, etc. of high reliability mica capacitors. The role of crystal defects in transistor operation at high power levels. H. AHARONI and A. BAR-LEV. Microelectronics 6, 11 (1975). When a transistor structure is analyzed, one usually assumes that it is a perfectly periodic crystal structure with the addition, perhaps, of a certain density of recombination centres. This enables one to calculate a set of breakdown voltages for the transistor. If operation at high power levels is desired an additional analysis of thermal resistances and capacitances is also made. If, however, actual transistors are made and tested, one finds large differences among equivalent transistors in their behaviour at high power, in the voltages at which avalanche starts and in the current-voltage-time combination at which a hot spot forms and the transistor undergoes secondary breakdown. The actual values found will be less than those expected. This is a direct consequence of the fact that the crystal, in which the transistor is built, is not a perfect periodic structure as assumed, but includes many crystal defects. Some of these defects were in the original grown crystal, but most of them were actually introduced into it during the process of transistor manufacturing. These defects become important when the transistor is operating near its maximum ratings because the doping levels and the energy band structure is distorted around them and consequently the local electrical field is higher, making them the points at which avalanche starts. Current may also be channelled along a fault because of conductivity changes. They also distort the planar structure of the junction and because of that may bring the transistor into premature breakdown. We aim to discuss in this paper the role of defects during transistor operation and show the mechanism by which they influence it.
found to be almost independent of thickness and microscopic observations in transmission did not show the occurrence of "single-hole" and "propagating" breakdowns, as observed by Klein et al. in evaporated film systems. The I - V characteristics in the "non-destructive" phase have also been studied and the observed maximum breakdown voltage has been distinguished from the "maximum voltage breakdown" observed by Klein et al.
Thin oxide film effect on silicon N÷P diodes breakdown voltage. K. MATSUMOTOR and Y. HANETA. NEC Research & DevelopmentNo. 35, p. 21 (1974). In a pn diode made in silicon by the planar technique, the situation always arises that the breakdown voltage before walk-out can be modulated by the external surface electric field. The same is true with integrated circuits and MOS transistors. This paper reports the relation gained experimentally between the breakdown voltage before walk-out and the gate voltage. Especially, the influence of the substrate impurity concentration and the oxide thickness is investigated. Then, it is shown that, in high substrate resistivity, the breakdown voltage is proportional to approximately the square root of the oxide thickness and that, in low substrate resistivity, the breakdown voltage is proportional to a lower value than the square root of the oxide thickness. Experiments were carried out on MOS transistors. Degradation studies in GaAso.6Po.4 Light-emitting diodes. R. H. WEISSMAN, W. L. SNYDER, G. T. IKARI and T. L. LARSEN. Proc. IEEE Reliability Physics Syrup. April 2-4, 1974. p. 273. The light output of a Ga(As, P) electroluminescent (EL) diode, measured at a fixed value of forward current, generally decreases with time when the diode is operated under forward bias. The degradation characteristics of such devices can be highly variable as exemplified by the selected data from eight GaAso.~Po.4 LED's. [These diodes were stressed (operated) at 50 A/cm 2 and an ambient temperature (TA) of 25°C, and were measured at 20 A/cm:.] It is evident that some LED's degrade very rapidly; i.e., the light output decreases to less than 5t)°/,, of the initial value when stressed for as short a time as a few hundred hours. Others exhibit excellent stability--the degradation after 1000 hours stress being less than 10%. The objectives of the present investigation were to determine the cause for rapid degradation observed in some GaAso.6Po., L E D ' s and to elucidate the mechanism by which such devices proceed to the point of failure.
Interdiflnsion in electropinted tin-nickel on gold. M. VIKRAM RAO, M. MITCHELL and R. N. ANDERSON. SolidSt. Technol. p. 47, November, 1974. Tin-nickel plating has good properties that make it attractive for use by the electronics industry in circuit board manufacture. One question not previously answered is whether diffusion of the tin or nickel into the gold, or vice versa, would occur and shorten the useful life of the circuit. This article experimentally examines the interdiffusion of Sn-Ni on Au and concludes that there is no problem in the use of the Sn-Ni plate.
Failure mechanism on accelerated A.C. test for high voltage capacitors. J. BURNHAM and E. WONG. Proc. IEEE Reliability Physics Syrup. April 2-4, 1974. p. 223. A highly accelerated a.c. life test for high voltage d.c. capacitors has been developed which is useful for solid dielectric capacitors such as mica paper and high dielectric constant ceramics with low a.c. losses. The test utilizes the fact that corona intensity on a.c. is several orders of magnitude higher than on d.c. It is shown that the mechanism of failure involves electrochemical erosion for both the mica paper and the ceramic dielectric material. The life times follow a power law with an exponent of 26 for mica paper and 31-100 for the ceramic.
Destructive D.C. breakdown in "built-up" barium stearate films. V. K. AGARWAL and V. K. SRIVASTAVA. Electrocompnt. Sci. and Teehnol. 1, 87 (1974). The thickness dependence of maximum breakdown voltage (d.c.) leading to the destruction of the film has been reported for "built-up" barium stearate films in the thickness range (400,~-1000,~). These films were chosen because of their promising applications for making dielectric devices, and because their thickness is accurately known and controllable (within 25,~). The breakdown voltage is
Techniques in failure analysis of MOS Devices. J. J. GAJDA. Proc. IEEE Reliability Physics Symp. April 2-4 1974. p. 30. The greatest concern on MOS devices is the physical integrity of the gate oxide. Leakage paths and/or shorts through defect sites in the exide are a major device reliability problem. Optical microscopy is tedious and often does not resolve the defects. With this in mind, copper decoration techniques were developed that could reveal oxide failure sites down to 0-1 p~m size. The technique has isolated various failure mechanisms on