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Some reliability aspects of carbon film resistors
World Abstracts on Microelectronics and Reliability Nevada. 1975. p. 107. Experiments are carried out to understand the electromigration-induced failure mechanism in thin-film Au conductors. The activation energy for the atom transport and the magnitude of the current exponent in the failure equation are obtained. The role of surface coverage on the reliability of Au stripes is studied. The underlying mode of atom transport and the possible sources of flux divergences are discussed in terms of these results.
Width dependence of electromigration life in AI-Cu, AICn-Si and Ag conductors. G A. SCOGGAN, B. N AGARWALA, P. P. PERESSINI, and A. BROUILLARD. 13th Ann. Proc. Reliability Physics Syrup., Nevada. 1975. p. 151. The electromigration lifetimes of thin-film A1-Cu, A1Cu-Si, and Ag conductors were measured as a function of stripe width. Both the median lifetime and the standard deviation of the lognormal failure distribution were observed to depend strongly on the stripe width; this finding indicates that a narrower stripe is less reliable. This width dependence is interpreted in terms of the microstructural characteristics of the films. Acceleration factors for plastic encapsulated semiconductor devices and their relationship to field performance. B REICH. Microelectron. & Reliab. 14, 63 (1975). The relationship between junction temperature and failure rate for hermetically sealed transistors and integrated circuits is well known and accepted. Those involved in the study of plastic semiconductor reliability are seeking a similar relationship. Many such relationships involving different stress parameters have been promulgated over the past three to five years. These relationships yield acceleration factors which differ greatly when one attempts their application from an accelerated stress condition to some operating use condition. This paper reviews the acceleration factors which have been put forth for plastic devices operating or tested with reverse bias applied. The acceleration factors are then tested against available data, accelerated, non-controlled and controlled field data. The results indicate, in some instances large differences between actual results and those predicted by the acceleration models. More data of this type is needed to test the models already promulgated as well as those which might be added in the future. Degradation mechanisms in rewritable n-channel FAMOS devices. R. C. DOCKERTY. 13th Ann. Proc. Reliability Physics Syrup. Nevada. p. 6, 1975. Electrically rewritable n-channel FAMOS devices were fabricated with a floating polycrystalline silicon gate and an AI control gate. The A1 gate is used to control injection of holes or electrons from the avalanching drain diffusion onto the floating gate. Charge retention by the floating gate and device degradation due to multiple write/erase cycling is discussed. Susceptibility of microwelds in hybrid microcircuits to corrosion degradation. J. L. JELLISON. 13th Ann. Proc. Reliability Physics Syrup. Nevada. p. 70, 1975. Analysis of broken ultrasonic AI-Ag bonds involving SEM electron microprobe, ion microprobe, and Auger electron spectroscopy indicated that failure was due to corrosion. Subsequent environmental tests demonstrated that AI-Ag bonds are highly susceptible to corrosion, but A1-Au and Au-A1 bonds are less so. No evidence of corrosion of Au-Ag bonds was found. Migrated-gold resistive shorts in microcircuits. A. SHUMKA and R. R. PIETY. 13th Ann. Proc. Reliability Physics Syrup. Nevada. p. 93, 1975. Failures, failure modes and failure mechanisms related to the formation of
405
migrated-gold resistive shorts (MGRS) in gold-metallized microcircuits will be described. Also, three different methods of screening devices for MGRS will be presented and the impact MGRS can have on device reliability will be discussed.
Effects of fast temperature cycling on alumium and gold metal systems. A. C. MACPHERSON, W. H. WEISENBERGER, H. M. DAY and A. CHRISTOU. 13th Ann. Proc. Reliability Physics Syrup., Nevada. p. 113, 1975. Microwave power transistors in a radar system may undergo - 1 0 '~ fast heating and cooling cycles during lifetime. Controlled temperature cycling tests have been carried out on AI, passivated A1, and gold metallization systems using both a special test pattern and commercially available transistors. Significant visible and electrical changes were observed for A1, glassed A1 and a laboratory T a - P t Ta-Au system, but not for a commercial gold transistor. Reliability evaluation of hermetic integrated circuit chips in plastic packages. H. KHAJEZADEH and A. S. ROSE. 13th Ann. Proc. Reliability Physics Syrup. Nevada. p. 87, 1975. Previous studies of the basic failure mechanisms of conventional plastic-encapsulated integrated circuits have led to improvements in materials and processes which have yielded two orders of magnitude improvement in reliability. Additionally, it has been demonstrated that, where severe environmental conditions are encountered, enhanced reliability is provided by device surfaces passivated with a silicon nitride dielectric and metallized with a titanium, platinum, gold interconnecting system. Failures associated with gold electroplating under severe humiditybias conditions are avoided by the deposition of a dielectric layer over the metallization pattern. Subsequent thermal, electrical, and moisture stress testing has confirmed earlier indications that predicted lifetimes greater than l0 Thr can be anticipated for these types of integrated circuits when they are operated at a maximum rated temperature of 125°C. An automated dual-in-line-package assembly system has been evaluated that provides plastic packages in which the conventional wire bonds have been eliminated and replaced with thermocompression bonds of metal beams to both the device and the lead-frame bond sites. The advantages gained from this type of assembly system are discussed. Migratory gold resistive shorts: chemical aspects of a failure mechanism. F. J. GRUNTHANER, T. W. GRISWOLD and P. J. CLENDENING. 13th Ann. Proc. Reliab. Physics Syrup. Nevada. p. 99, 1975. Integrated-circuit devices using the Ti/W/Au metal system are subject to failure mechanisms based on electrolytic corrosion. The migratory gold resistive short (MGRS) failure mode is one example of this mechanism and results in the formation of filamentary or dendritic deposits of gold between adjacent stripes on the IC chip. This reaction requires the presence of a sufficient amount of water, a bias voltage between adjacent stripes, and the activation of the cathodic (-) stripe. Gold ions are transported from anode to cathode through a film of moisture adsorbed on the surface of the chip; halide ions are probably involved in the transfer. Their presence is verified experimentally by x-ray photoelectron spectroscopy. Some of the chemical and electrostatic factors involved in the MGRS mechanism are discussed in this paper, including the questions of a threshold level of moisture and contamination. Some reliability aspects of carbon film resistors. J. S. BORA. The Q.R. J , India May 1975, p. 71. The present paper provides useful information regarding the permanent increase in resistance value with time at various levels of power, temperature and voltage. Life-testing of
406
World Abstracts on Microelectronics and Reliability
resistors, although started with a small sample size, gives encouraging results. Large sample sizc (550-1000) and long test durations (800-1000 hr at each level) are recommended for life-tests. As no data is available for indigenous components regarding failure rates and deviation of parameters with time, better experiments can be designed based on this experience.
The corrosive activity of fluxes. A. BOCHENEK and B. WOZNIAKOWSKI. Microelectron. & Reliab, 14, 295 (1975). The corrosive effects of fluxes on conductive paths are one of the major factors limiting the reliability of electronic equipment. The process begins from the moment when flux touches the metal surface and lasts during the process of soldering, until the apparatus is washed. Every one can notice the effects of the corrosive action of flux residues when equipment is used. Obviously, the constructor and the technologist of assembly should know about magnitude of corrosive activity of particular types of fluxes in order to choose the right type, to design thickness and arrangement of conductive paths, and to control the assembly parameters, as well. High reliability photodiodes for space applications, M BRILMAN. Microelectron. & Reliab. 14, 305 (1975). This paper presents the techniques used to manufacture a high performance silicon photodetector having several precisely defined photosensitive areas. The principle of the device design is based on a PIN structure. Metallic layers are used to mask parasitic photosensitive areas. The metal layers are used in such a way that they do not degrade the electrical characteristics of the junction. Special care has been taken during manufacturing to assure the reliability of the product, which is to be used in a meteorological satellite. Problems were encountered in defining significant tests characterizing the reliability of the device under various environmental conditions. The reliability characterization is difficult due to the semiconductor and optical aspects of the structure. Tests were therefore imposed to specifically monitor the reliability of either the electrical or opticalparameters. The device was then required to withstand both sets of reliability tests. A comparative reliability evaluation of CMOS. A maturing technology. D. J. BURNS and V. C. KAPFER. Proc. Reliability and Maintainability Syrup. Washington D.C.p. 354, 28-30 January, 1975. A reliability evaluation program consisting of 180 C/MOS devices from 4 vendors has been in progress at RADC for about 2 years. The date codes for these devices range from 1969 to 1973. The testing program included storage temperature, thermal shock, moisture resistance w/bias, temperature cycling w/bias, and bias power and temperature step stress (BPATSS). The results are presented detailing the predominant failure modes and mechanisms which were induced by this stress testing program. Evaluation testing of integrated circuits. R. A. HOMAN and M. W. ROSSMAN. Proc. Reliability and Maintainability Syrup. Washington D.C., p. 372, 28-30 January, 1975. Evaluation/qualification test approaches applied to various types of integrated circuits are summarized. Linear devices as well as C-MOS and TTL digitals were evaluated. Among the evaluation techniques utilized were 3. C I R C U I T
AND
SYSTEMS
RELIABILITY,
Reliability case history of an airborne air data computer, T. MURATA. IEEE Trans. Reliab. R-24. (2) 98 1975. The life of an airborne Air Data computer and some of its
computerized circuit modeling and simulation for purposes of nominal, worst case, and sensitivity analyses. physical construction analysis, node voltage probing on both digital and linear devices, characterization by means of exploratory and design limit testing. Other tests performed were environmental, burn-in, life, specification limit, and functional tests. The data analysis approach, typical results and observations on the effectiveness of the various techniques are presented.
Reverse bias stresses on emitter-base junctions. R. F. HAYTHORNTHWAITE and R. E. THOMAS. Proc. 1975 Canadian SRE Reliability Syrup. Ottawa, p. 231, 10 May, 1975. Evidence is presented showing that the gain degradation mechanism in bipolar transistors subjected to either high temperature reverse bias (HTRB) stressing or emitter base avalanche (EBA) breakdown stressing is similar. The study was conducted to determine if the short EBA test could be substituted for the much longer HTRB test in predicting transistor stability under operating conditions. Reliability of interconnections on microcircuits. D. L. FRESH. Proc. Reliability and Maintainability Syrup. Washington D.C., p. 568, 28-30 January, 1975. Defects in metal interconnection patterns constitute a significant factor in the reliability of semiconductor microcircuits. Electrical opens, occurring in the vacuum-deposited metal films, have achieved considerable notoriety and have been the basis for reliability studies by numerous investigators. The application of the scanning electron microscope (SEM) is becoming relatively widespread in detecting these defects in metallization. Considerable work has recently been directed toward improving the SEM procedures and techniques, including the preparation of a test method in MIL-STD format. The current status of the SEM test method; its utility, suitability, and acceptance in detecting defects in metal interconnection patterns; and its extension and applicability to other types of defects in high reliability semiconductor microcircuits are discussed. On computer-oriented design of microstrip amplifiers with component tolerance assignment. E. MARAZZ1, V A MONACO, A. BRINI and V. SOLARO. Aha Frequenza XLIV (4), 174 (1975). Component parameter tolerances can cause performance degradation of some circuits during mass-production. Production yield estimates relative to both circuit response specifications and given component tolerances and techniques for increasing yield without reducing tolerances or introducing expensive adjustments are topics of interest in circuit design. These design aspects are illustrated using a 2 GHz thin-film microstrip reflection amplifier. Inspection and supervision of cable quality, during fabrication, using an auto-test unit TM02. M. CADE, P. FENOUILLET, A. CLAUSTRE and J. C. LEROY. Cables and Transmission, 29 (2) 213 1975. (In French). Following important work into statistical control process of urban cables at the factory sites, carried out by the Centre National d'Etudes des T616communications, the French Company S.A.T. has studied and developed an auto-test unit designed to test out cables during fabrication. After going over the principles underlying a verification of cable parameters, the expos6 sets out a table of auto-test measurements TM02, an instrument which proves to be very useful when assessing cable quality. MAINTENANCE
AND
REDUNDANCY
components have been observed in the field and in the laboratory. This paper treats 3 aspects of the reliability. Part 1 shows the relationship of predicted to actual MTBF
Width dependence of electromigration life in AI-Cu, AICn-Si and Ag conductors. G A. SCOGGAN, B. N AGARWALA, P. P. PERESSINI, and A. BROUILLARD. 13th Ann. Proc. Reliability Physics Syrup., Nevada. 1975. p. 151. The electromigration lifetimes of thin-film A1-Cu, A1Cu-Si, and Ag conductors were measured as a function of stripe width. Both the median lifetime and the standard deviation of the lognormal failure distribution were observed to depend strongly on the stripe width; this finding indicates that a narrower stripe is less reliable. This width dependence is interpreted in terms of the microstructural characteristics of the films. Acceleration factors for plastic encapsulated semiconductor devices and their relationship to field performance. B REICH. Microelectron. & Reliab. 14, 63 (1975). The relationship between junction temperature and failure rate for hermetically sealed transistors and integrated circuits is well known and accepted. Those involved in the study of plastic semiconductor reliability are seeking a similar relationship. Many such relationships involving different stress parameters have been promulgated over the past three to five years. These relationships yield acceleration factors which differ greatly when one attempts their application from an accelerated stress condition to some operating use condition. This paper reviews the acceleration factors which have been put forth for plastic devices operating or tested with reverse bias applied. The acceleration factors are then tested against available data, accelerated, non-controlled and controlled field data. The results indicate, in some instances large differences between actual results and those predicted by the acceleration models. More data of this type is needed to test the models already promulgated as well as those which might be added in the future. Degradation mechanisms in rewritable n-channel FAMOS devices. R. C. DOCKERTY. 13th Ann. Proc. Reliability Physics Syrup. Nevada. p. 6, 1975. Electrically rewritable n-channel FAMOS devices were fabricated with a floating polycrystalline silicon gate and an AI control gate. The A1 gate is used to control injection of holes or electrons from the avalanching drain diffusion onto the floating gate. Charge retention by the floating gate and device degradation due to multiple write/erase cycling is discussed. Susceptibility of microwelds in hybrid microcircuits to corrosion degradation. J. L. JELLISON. 13th Ann. Proc. Reliability Physics Syrup. Nevada. p. 70, 1975. Analysis of broken ultrasonic AI-Ag bonds involving SEM electron microprobe, ion microprobe, and Auger electron spectroscopy indicated that failure was due to corrosion. Subsequent environmental tests demonstrated that AI-Ag bonds are highly susceptible to corrosion, but A1-Au and Au-A1 bonds are less so. No evidence of corrosion of Au-Ag bonds was found. Migrated-gold resistive shorts in microcircuits. A. SHUMKA and R. R. PIETY. 13th Ann. Proc. Reliability Physics Syrup. Nevada. p. 93, 1975. Failures, failure modes and failure mechanisms related to the formation of
405
migrated-gold resistive shorts (MGRS) in gold-metallized microcircuits will be described. Also, three different methods of screening devices for MGRS will be presented and the impact MGRS can have on device reliability will be discussed.
Effects of fast temperature cycling on alumium and gold metal systems. A. C. MACPHERSON, W. H. WEISENBERGER, H. M. DAY and A. CHRISTOU. 13th Ann. Proc. Reliability Physics Syrup., Nevada. p. 113, 1975. Microwave power transistors in a radar system may undergo - 1 0 '~ fast heating and cooling cycles during lifetime. Controlled temperature cycling tests have been carried out on AI, passivated A1, and gold metallization systems using both a special test pattern and commercially available transistors. Significant visible and electrical changes were observed for A1, glassed A1 and a laboratory T a - P t Ta-Au system, but not for a commercial gold transistor. Reliability evaluation of hermetic integrated circuit chips in plastic packages. H. KHAJEZADEH and A. S. ROSE. 13th Ann. Proc. Reliability Physics Syrup. Nevada. p. 87, 1975. Previous studies of the basic failure mechanisms of conventional plastic-encapsulated integrated circuits have led to improvements in materials and processes which have yielded two orders of magnitude improvement in reliability. Additionally, it has been demonstrated that, where severe environmental conditions are encountered, enhanced reliability is provided by device surfaces passivated with a silicon nitride dielectric and metallized with a titanium, platinum, gold interconnecting system. Failures associated with gold electroplating under severe humiditybias conditions are avoided by the deposition of a dielectric layer over the metallization pattern. Subsequent thermal, electrical, and moisture stress testing has confirmed earlier indications that predicted lifetimes greater than l0 Thr can be anticipated for these types of integrated circuits when they are operated at a maximum rated temperature of 125°C. An automated dual-in-line-package assembly system has been evaluated that provides plastic packages in which the conventional wire bonds have been eliminated and replaced with thermocompression bonds of metal beams to both the device and the lead-frame bond sites. The advantages gained from this type of assembly system are discussed. Migratory gold resistive shorts: chemical aspects of a failure mechanism. F. J. GRUNTHANER, T. W. GRISWOLD and P. J. CLENDENING. 13th Ann. Proc. Reliab. Physics Syrup. Nevada. p. 99, 1975. Integrated-circuit devices using the Ti/W/Au metal system are subject to failure mechanisms based on electrolytic corrosion. The migratory gold resistive short (MGRS) failure mode is one example of this mechanism and results in the formation of filamentary or dendritic deposits of gold between adjacent stripes on the IC chip. This reaction requires the presence of a sufficient amount of water, a bias voltage between adjacent stripes, and the activation of the cathodic (-) stripe. Gold ions are transported from anode to cathode through a film of moisture adsorbed on the surface of the chip; halide ions are probably involved in the transfer. Their presence is verified experimentally by x-ray photoelectron spectroscopy. Some of the chemical and electrostatic factors involved in the MGRS mechanism are discussed in this paper, including the questions of a threshold level of moisture and contamination. Some reliability aspects of carbon film resistors. J. S. BORA. The Q.R. J , India May 1975, p. 71. The present paper provides useful information regarding the permanent increase in resistance value with time at various levels of power, temperature and voltage. Life-testing of
406
World Abstracts on Microelectronics and Reliability
resistors, although started with a small sample size, gives encouraging results. Large sample sizc (550-1000) and long test durations (800-1000 hr at each level) are recommended for life-tests. As no data is available for indigenous components regarding failure rates and deviation of parameters with time, better experiments can be designed based on this experience.
The corrosive activity of fluxes. A. BOCHENEK and B. WOZNIAKOWSKI. Microelectron. & Reliab, 14, 295 (1975). The corrosive effects of fluxes on conductive paths are one of the major factors limiting the reliability of electronic equipment. The process begins from the moment when flux touches the metal surface and lasts during the process of soldering, until the apparatus is washed. Every one can notice the effects of the corrosive action of flux residues when equipment is used. Obviously, the constructor and the technologist of assembly should know about magnitude of corrosive activity of particular types of fluxes in order to choose the right type, to design thickness and arrangement of conductive paths, and to control the assembly parameters, as well. High reliability photodiodes for space applications, M BRILMAN. Microelectron. & Reliab. 14, 305 (1975). This paper presents the techniques used to manufacture a high performance silicon photodetector having several precisely defined photosensitive areas. The principle of the device design is based on a PIN structure. Metallic layers are used to mask parasitic photosensitive areas. The metal layers are used in such a way that they do not degrade the electrical characteristics of the junction. Special care has been taken during manufacturing to assure the reliability of the product, which is to be used in a meteorological satellite. Problems were encountered in defining significant tests characterizing the reliability of the device under various environmental conditions. The reliability characterization is difficult due to the semiconductor and optical aspects of the structure. Tests were therefore imposed to specifically monitor the reliability of either the electrical or opticalparameters. The device was then required to withstand both sets of reliability tests. A comparative reliability evaluation of CMOS. A maturing technology. D. J. BURNS and V. C. KAPFER. Proc. Reliability and Maintainability Syrup. Washington D.C.p. 354, 28-30 January, 1975. A reliability evaluation program consisting of 180 C/MOS devices from 4 vendors has been in progress at RADC for about 2 years. The date codes for these devices range from 1969 to 1973. The testing program included storage temperature, thermal shock, moisture resistance w/bias, temperature cycling w/bias, and bias power and temperature step stress (BPATSS). The results are presented detailing the predominant failure modes and mechanisms which were induced by this stress testing program. Evaluation testing of integrated circuits. R. A. HOMAN and M. W. ROSSMAN. Proc. Reliability and Maintainability Syrup. Washington D.C., p. 372, 28-30 January, 1975. Evaluation/qualification test approaches applied to various types of integrated circuits are summarized. Linear devices as well as C-MOS and TTL digitals were evaluated. Among the evaluation techniques utilized were 3. C I R C U I T
AND
SYSTEMS
RELIABILITY,
Reliability case history of an airborne air data computer, T. MURATA. IEEE Trans. Reliab. R-24. (2) 98 1975. The life of an airborne Air Data computer and some of its
computerized circuit modeling and simulation for purposes of nominal, worst case, and sensitivity analyses. physical construction analysis, node voltage probing on both digital and linear devices, characterization by means of exploratory and design limit testing. Other tests performed were environmental, burn-in, life, specification limit, and functional tests. The data analysis approach, typical results and observations on the effectiveness of the various techniques are presented.
Reverse bias stresses on emitter-base junctions. R. F. HAYTHORNTHWAITE and R. E. THOMAS. Proc. 1975 Canadian SRE Reliability Syrup. Ottawa, p. 231, 10 May, 1975. Evidence is presented showing that the gain degradation mechanism in bipolar transistors subjected to either high temperature reverse bias (HTRB) stressing or emitter base avalanche (EBA) breakdown stressing is similar. The study was conducted to determine if the short EBA test could be substituted for the much longer HTRB test in predicting transistor stability under operating conditions. Reliability of interconnections on microcircuits. D. L. FRESH. Proc. Reliability and Maintainability Syrup. Washington D.C., p. 568, 28-30 January, 1975. Defects in metal interconnection patterns constitute a significant factor in the reliability of semiconductor microcircuits. Electrical opens, occurring in the vacuum-deposited metal films, have achieved considerable notoriety and have been the basis for reliability studies by numerous investigators. The application of the scanning electron microscope (SEM) is becoming relatively widespread in detecting these defects in metallization. Considerable work has recently been directed toward improving the SEM procedures and techniques, including the preparation of a test method in MIL-STD format. The current status of the SEM test method; its utility, suitability, and acceptance in detecting defects in metal interconnection patterns; and its extension and applicability to other types of defects in high reliability semiconductor microcircuits are discussed. On computer-oriented design of microstrip amplifiers with component tolerance assignment. E. MARAZZ1, V A MONACO, A. BRINI and V. SOLARO. Aha Frequenza XLIV (4), 174 (1975). Component parameter tolerances can cause performance degradation of some circuits during mass-production. Production yield estimates relative to both circuit response specifications and given component tolerances and techniques for increasing yield without reducing tolerances or introducing expensive adjustments are topics of interest in circuit design. These design aspects are illustrated using a 2 GHz thin-film microstrip reflection amplifier. Inspection and supervision of cable quality, during fabrication, using an auto-test unit TM02. M. CADE, P. FENOUILLET, A. CLAUSTRE and J. C. LEROY. Cables and Transmission, 29 (2) 213 1975. (In French). Following important work into statistical control process of urban cables at the factory sites, carried out by the Centre National d'Etudes des T616communications, the French Company S.A.T. has studied and developed an auto-test unit designed to test out cables during fabrication. After going over the principles underlying a verification of cable parameters, the expos6 sets out a table of auto-test measurements TM02, an instrument which proves to be very useful when assessing cable quality. MAINTENANCE
AND
REDUNDANCY
components have been observed in the field and in the laboratory. This paper treats 3 aspects of the reliability. Part 1 shows the relationship of predicted to actual MTBF