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MOS semiconductor random access memory failure rate
410
World Abstracts on Microelectronics and Reliability
tracks) by stray currents located in electrified lines when thyristor fitted locomotives, using both a/c and d/c choppers, are running. The level of disturbance is compared with the permissible specifications, in particular those advised by CCITT, and solutions are proposed to reduce the levels met. Warranties--The easy way out. JAMES R. ANDERSON. Proc.
2. R E L I A B I L I T Y
OF
COMPONENTS,
Reliability assessment of small signal GaAs FETS. FRANCOIS BEHMANN. Microelectron. Reliab. 19, 107 (1979). The reliability of small signal GaAs FETs for applications in communication satellites is assessed including both Aluminum and Gold gate pad devices. The mean time to failure and dispersion are derived from life test data of biased devices. Failure criteria and mechanisms are discussed. Finally, the probability of success of the FET devices and their application in the spacecraft receivers are evaluated. Current/voltage characteristics of transistors operating in current-mode second breakdown. J. E. CARROLL and P. J. PROBERT. Solid-St. Electron Devices 3, (2) 41 (March 1979). The current/voltage characteristics of Si n-p-n transistors, when the device is pulsed into second breakdown for several nanoseconds, are studied. The collector/base characteristics have limits given by le = 0, which can be modelled approximately by neglecting recombination, and by Ib = 0 which requires recombination to be fully understood. This later condition is closely analagous to the Kirk effect with a plasma of holes and electrons close to the base region. In all these second-breakdown states the electron multiplication factor is low, typically less than 1.33, so that there is little useful multiplication gain. Second breakdown thus prevents the transistor from being used as a 3-terminal avalanche transistor. Failure at high current levels occurs most readily in the Ie = 0 state. The cutback in voltage and increase in current can be limited by tailoring the collector impurity profile. These two features suggest ways in which transistors may be improved to protect them against short pulse burnout via current-mode second breakdown. MOS semiconductor random access memory failure rate. J. E. ARSENAULTand D. C. ROBERTS. Microelectron. Reliab. 19, 81 (1979). Recent life test and field data on large semiconductor RAMs when compared with the applicable failure rate model of MIL-HDBK-217[1] indicates that the model yields highly pessimistic results. Using data based on the widely used 4K N M O S RAM an interim solution is proposed until revised models become available and some reasons are given for the disparity. Recent developments in gold conductor bonding performance and failure mechanisms. S. J. HOROW1TZ, D. J. GERRY, J. J. FELTEN, J. R. LARRY and R. M. ROS~NaERG. Solid St. 7echnol. p. 37 (March 1979). Technical developments in thick film gold conductors over the past five years are reviewed with emphasis on a new generation of conductors optimized to give improvement in circuit yield and reliability in specialized wire bonding operations. The improvement in ultrasonic aluminum wire bond reliability achieved by addition of a small amount of palladium to a gold conductor is discussed and microstructural studies to determine the mechanism are described. Important parameters in the design of a thick film gold conductor for high yield automatic thermosonic gold wire bonding are also considered and performance of a reduced thickness gold conductor is presented.
IEEE Reliab. Syrup., Washington, D.C., 23 25 January 1979, p. 413. The application of reliability warranties to Navy guided weapons is examined. Analysis techniques to determine the compatibility of the warranty concept for a weapon system are presented. The evaluation concludes that it is possible for the warranty to provide counter productive result i.e.. lower reliability at high cost.
TUBES,
TRANSISTORS
AND
ICs
Separation of surface and bulk gases in contact materials of vacuum switches--Determination of gases and effect on vacuum breakdown. KAZUH1DE MATSUMOTO,TADAO MORI, KIYOSHI FUKUI, NORIO KAWANA, MITSUO KASHIMURA, KEIICHI FURUYA and TADASHI KIKUCHI. IEEE Trans. Components, Hybrids, Mfo Technol. Chmt-2, (1) 4 (March 1979). Meaningful analysis for very small quantities of gases in contacts can be obtained only by the method which permits differentiating between surface and bulk gases. The graphite capsule method and copper bath method in vacuum fusion analysis were compared, and the surface area variation method and two-stage gas extraction method were investigated for the separation of surface and bulk gases. As a result of these investigations, the surface and bulk gas content of the copper-tellurium alloy can be determined by the surface area variation method. The bulk oxygen content of the ingot, forged- and vacuum-refined copper-tellurium alloy is 3.8 parts per million (ppm), 1.7ppm, and 0.1ppm, respectively. The surface oxygen content, however, is conversely 1.5/2g/cm 2, 2.4,ug/cm 2 and 3.7 #g/cm 2, respectively. In high vacuum, gases are released from the electrodes as the voltage is applied between the electrodes. The released gases increase exponentially whether the spark breakdowns occur or not. It is suggested that the released gas at the spark breakdown corresponds to surface gas, which is considered as water vapor mostly absorbed on the electrode. After the spark breakdowns occur repeatedly, water vapor from the surface layers is depleted, namely, the surface conditioning takes place. Therefore, the released gas without spark breakdown corresponds to the bulk gas, which is mostly hydrogen. Degradation of electrical contacts caused by oscillatory micromotion between the contact members. HELGE KONGSJORDEN, JOHN KULSET~S and JARLE SLETBAK.IEEE Trans. Components, Hybrids, Mf.q Technol. Chmt-2, (1) 32 (March 1979). The influence of oscillatory movement on the contact resistance is discussed on the basis of experiments with contacts in a crossed rod configuration, the contact members being AI-AI and Cu-Cu. Measurements were carried out for movements of amplitudes within the range 0.4-18/~m and mechanical loads between 20 170 N at frequencies 10 100cycles/h. The experimental results show that micromotion under certain conditions causes rapid and extensive degradation. For A1 contacts with load 20N, the resistance increases to 50 times the initial value after 200 cycles. Silicon wafer damage--Two useful investigation techniques. F. G. VIEWEG-GUTBERLET. Electron. Produc. p. 27 (May 1979). Any mechanical treatment to the surface of a silicon wafer causes lattice defects which partially extend into the bulk of the wafer. The defects are surrounded by a stress-field which may generate dislocations if the wafer is exposed to high temperatures as applied in semiconductor device technology. The damage crack distribution versus depth can be detected by an angle polish procedure, and the stressfield by means of X-ray section topography.
World Abstracts on Microelectronics and Reliability
tracks) by stray currents located in electrified lines when thyristor fitted locomotives, using both a/c and d/c choppers, are running. The level of disturbance is compared with the permissible specifications, in particular those advised by CCITT, and solutions are proposed to reduce the levels met. Warranties--The easy way out. JAMES R. ANDERSON. Proc.
2. R E L I A B I L I T Y
OF
COMPONENTS,
Reliability assessment of small signal GaAs FETS. FRANCOIS BEHMANN. Microelectron. Reliab. 19, 107 (1979). The reliability of small signal GaAs FETs for applications in communication satellites is assessed including both Aluminum and Gold gate pad devices. The mean time to failure and dispersion are derived from life test data of biased devices. Failure criteria and mechanisms are discussed. Finally, the probability of success of the FET devices and their application in the spacecraft receivers are evaluated. Current/voltage characteristics of transistors operating in current-mode second breakdown. J. E. CARROLL and P. J. PROBERT. Solid-St. Electron Devices 3, (2) 41 (March 1979). The current/voltage characteristics of Si n-p-n transistors, when the device is pulsed into second breakdown for several nanoseconds, are studied. The collector/base characteristics have limits given by le = 0, which can be modelled approximately by neglecting recombination, and by Ib = 0 which requires recombination to be fully understood. This later condition is closely analagous to the Kirk effect with a plasma of holes and electrons close to the base region. In all these second-breakdown states the electron multiplication factor is low, typically less than 1.33, so that there is little useful multiplication gain. Second breakdown thus prevents the transistor from being used as a 3-terminal avalanche transistor. Failure at high current levels occurs most readily in the Ie = 0 state. The cutback in voltage and increase in current can be limited by tailoring the collector impurity profile. These two features suggest ways in which transistors may be improved to protect them against short pulse burnout via current-mode second breakdown. MOS semiconductor random access memory failure rate. J. E. ARSENAULTand D. C. ROBERTS. Microelectron. Reliab. 19, 81 (1979). Recent life test and field data on large semiconductor RAMs when compared with the applicable failure rate model of MIL-HDBK-217[1] indicates that the model yields highly pessimistic results. Using data based on the widely used 4K N M O S RAM an interim solution is proposed until revised models become available and some reasons are given for the disparity. Recent developments in gold conductor bonding performance and failure mechanisms. S. J. HOROW1TZ, D. J. GERRY, J. J. FELTEN, J. R. LARRY and R. M. ROS~NaERG. Solid St. 7echnol. p. 37 (March 1979). Technical developments in thick film gold conductors over the past five years are reviewed with emphasis on a new generation of conductors optimized to give improvement in circuit yield and reliability in specialized wire bonding operations. The improvement in ultrasonic aluminum wire bond reliability achieved by addition of a small amount of palladium to a gold conductor is discussed and microstructural studies to determine the mechanism are described. Important parameters in the design of a thick film gold conductor for high yield automatic thermosonic gold wire bonding are also considered and performance of a reduced thickness gold conductor is presented.
IEEE Reliab. Syrup., Washington, D.C., 23 25 January 1979, p. 413. The application of reliability warranties to Navy guided weapons is examined. Analysis techniques to determine the compatibility of the warranty concept for a weapon system are presented. The evaluation concludes that it is possible for the warranty to provide counter productive result i.e.. lower reliability at high cost.
TUBES,
TRANSISTORS
AND
ICs
Separation of surface and bulk gases in contact materials of vacuum switches--Determination of gases and effect on vacuum breakdown. KAZUH1DE MATSUMOTO,TADAO MORI, KIYOSHI FUKUI, NORIO KAWANA, MITSUO KASHIMURA, KEIICHI FURUYA and TADASHI KIKUCHI. IEEE Trans. Components, Hybrids, Mfo Technol. Chmt-2, (1) 4 (March 1979). Meaningful analysis for very small quantities of gases in contacts can be obtained only by the method which permits differentiating between surface and bulk gases. The graphite capsule method and copper bath method in vacuum fusion analysis were compared, and the surface area variation method and two-stage gas extraction method were investigated for the separation of surface and bulk gases. As a result of these investigations, the surface and bulk gas content of the copper-tellurium alloy can be determined by the surface area variation method. The bulk oxygen content of the ingot, forged- and vacuum-refined copper-tellurium alloy is 3.8 parts per million (ppm), 1.7ppm, and 0.1ppm, respectively. The surface oxygen content, however, is conversely 1.5/2g/cm 2, 2.4,ug/cm 2 and 3.7 #g/cm 2, respectively. In high vacuum, gases are released from the electrodes as the voltage is applied between the electrodes. The released gases increase exponentially whether the spark breakdowns occur or not. It is suggested that the released gas at the spark breakdown corresponds to surface gas, which is considered as water vapor mostly absorbed on the electrode. After the spark breakdowns occur repeatedly, water vapor from the surface layers is depleted, namely, the surface conditioning takes place. Therefore, the released gas without spark breakdown corresponds to the bulk gas, which is mostly hydrogen. Degradation of electrical contacts caused by oscillatory micromotion between the contact members. HELGE KONGSJORDEN, JOHN KULSET~S and JARLE SLETBAK.IEEE Trans. Components, Hybrids, Mf.q Technol. Chmt-2, (1) 32 (March 1979). The influence of oscillatory movement on the contact resistance is discussed on the basis of experiments with contacts in a crossed rod configuration, the contact members being AI-AI and Cu-Cu. Measurements were carried out for movements of amplitudes within the range 0.4-18/~m and mechanical loads between 20 170 N at frequencies 10 100cycles/h. The experimental results show that micromotion under certain conditions causes rapid and extensive degradation. For A1 contacts with load 20N, the resistance increases to 50 times the initial value after 200 cycles. Silicon wafer damage--Two useful investigation techniques. F. G. VIEWEG-GUTBERLET. Electron. Produc. p. 27 (May 1979). Any mechanical treatment to the surface of a silicon wafer causes lattice defects which partially extend into the bulk of the wafer. The defects are surrounded by a stress-field which may generate dislocations if the wafer is exposed to high temperatures as applied in semiconductor device technology. The damage crack distribution versus depth can be detected by an angle polish procedure, and the stressfield by means of X-ray section topography.