- Email: [email protected]
ION instabilities in MOS structures
World Abstracts on Microelectronics and Reliability time to non-availability and number of served customers for a reliability system undergoing failure and repair. On prediction o| survival time |or individual systems. J. F. LAWLESS. IEEE Trans. Reliab. R-23, 236 (1974). The problem of predicting length of life (survival time) of an individual system is discussed. The predictions are based on previous test data on the types of components involved in the system. As a preliminary the classical, Bayesian, and fiducial probability approaches to prediction are outlined. The use of prediction techniques is then discussed by means of examples, with some special attention being given to the problem of predicting the life of an r-out-of-k:G system whose components have exponentially distributed lifetimes.
Finding the better of two similar designs by Monte Curio techniques. P. W. BECKER. IEEE Trans. Reliab. R-23, 242 (1974). During the iterative design of a system (or circuit) the designer is often faced with the problem of ranking two designs according to some criterion. If the system elements have uncertain values, each system manifestation can be evaluated as to whether or not it meets some performance criterion. The fraction which meets or exceeds the criterion is called the yield. Monte Carlo techniques can be used to simulate the population of systems and thus to estimate the ranking of two designs. The first result presented in the paper is a derivation of the probability that one design is better than another, along with confidence limits for that probability. If the two designs are topologically the same, i.e., they differ only in the nominal values and actual distributions of true parameter values, then the same set of random numbers can be used for one simulation of each design. Due to the similarity there may be a positive correlation between the 2 results which can then be used to narrow the confidence limits from the crude method mentioned above. The second result is a derivation of these narrow confidence limits.
Methods for calculating the reliability function for systems subjected to random stresses. T. A. TUMOLILLO. IEEE Trans. Reliab. R-23, 256 (1974). The reliability function is calculated for components and systems which are subjected to stresses arriving randomly in time at a given average rate. The component is assumed to exist in a finite number of states, each of which is affected differently by the applied stress. During normal operation, failure rates are assigned to each of the states of the component; when the stress is applied, the failure rates for each state change to a new value. By defining the transitions among the states as a first order Markov process, the average probability of no failure prior to and including time t is calculated for the cases where the sets of failure rates are either discrete or continuous. The solution for the average probability is given as a matrix equation and several methods for reducing the equation to a useable form are examined. In addition, the theory of failure and repair processes is reviewed and methods for simplifying the calculation of the reliability of a system are presented.
Intrinsic safety foils explosive situations. R. J. REDDING and A. KRIGMAN. Electronics, February 6, 1975. p. 91. Commercially available safety barriers are simplifying the design of circuits that must operate in dangerous environments, and they offer a practical alternative to purging or spark-proof housings.
A sequential testing procedure for a system's state identiflcution. J. HALPERN. IEEE Trans. Reliab. R-23, 267 (t974). The system and its components have only two
339
states: complete success or complete failure. The components' states are random variables and the system's state depends deterministically on the states of its elements. This paper assumes the state of the system is unknown and presents a sequential testing procedure of the components in order to determine the system's state. The procedure minimizes the expected number of necessary tests for a wide class of systems. The procedure is needed when the system is entirely or partially consumed upon its use, e.g., the firing of a missile, and one wishes to know the system's state without actually operating the system.
On the design of fault diagnostic networks for combinational logic circuits. A. PALIT,A. SEN GUPTA,M. S. BAsu and A. K. CHOUDHURY. Int. J. Electron. 38, 25 (1975). The paper describes an easy method for the detection and location of all single faults of the stuck-at-zero and stuck-at-one type in a combinational network. It is shown that the test inputs can be applied in sequence to identify some of the faulty lines whose diagnosis is otherwise ambiguous. The faults on the rest of the network lines are diagnosed with an additional combinational network, which is virtually faultless. The design procedure for this cost-oriented additional logic block is discussed. An algorithm is included for the diagnosis of fault ab initio.
Specialized scanning electron microscopy voltage contrast techniques for LSI failure analysis. B. PIWCZVK and W. SIu. Proc. IEEE Reliability Physics Syrup. April 2-4, 1974. p. 49. Several scanning electron microscopy voltage contrast techniques used for integrated circuit failure analysis are compared. A newer, simpler technique permitting the elimination of the topographic image information while retaining the voltage contrast information is described. This technique called Selective Voltage Contrast (SVC) also permits the viewing of voltages in a circuit as imposed by individual input level changes. Examples of the application of the technique are shown using bipolar integrated circuits and a charge coupled memory device.
Instabilities in double dielectric structures. M. H. WOODS. Proc. IEEE Reliability Physics Syrup. April 2-4, 1974. p. 259. Double dielectric structures are used in devices and integrated circuits for the purposes of stabilization and encapsulation, increased breakdown strength, or for active operation as in MNOS and MAOS memory transistors. Instabilities are shown to arise from polarization, alkali migration and fixed interface charges, conductivity differences and the formation of slow and fast oxide states due to the application of high electric fields in memory devices. ION instabilities in MOS structures. R. J. KRIEGLER. Proc. IEEE Reliability Physics Symp. April 2-4, 1974. p. 250. Sodium and a few other alkali metal impurities, introduced during processing into the SiO2 gate insulator of MOS devices, are easily ionized and are sufficiently mobile even at low temperatures to cause a considerable drift of the electrical characteristics of MOS devices. This paper reviews methods of detecting the presence of mobile ions and discusses techniques for reducing the concentration of impurities or eliminating their deleterious electrical effect.
Leak detection of integrated circuits and other semiconductor devices on multilayer circuit boards. A. G. STANLEY, C. M. RADER and G. NEFF. Proc. IEEE Reliability Physics Syrup. April 2-4, 1974. p. 239. The radioisotope leak test has been modified to detect leaks, in integrated circuits and other devices mounted onto multilayer circuit boards, over the entire range from 10-'-10 -s atm. cc per
340
World Abstracts on Microelectronics and Reliability
second. The method combines radiation shielding techniques with three sequential tests using krypton-85. The test program has succeeded in detecting a significant number of leaky components on electronic boards for a high reliability space application.
A failure analysis technique for locating the fail site in MOSFET (LSI) logic chips with sputtered SIO2 passivation. A. A. VIELE. Proc. IEEE Reliability Physics Symposium. April 2-4, 1974. p. 16. This paper describes a technique used successfully to locate the fail site in MOSFET (LSI) Logic Chips. It is used to analyze modules or chips which fail functionally during electrical test. Signal tracing is employed to locate the fail site while dynamically exercising the chip. This technique emphasizes the analysis of AC fails (timing problems) and chips with sputtered SiO2 (Quartz) passivation. A new approach to fault locating T1 repeatered lines. S. GHOSH. Telecommunications. November 1974. p. 39. Since the introduction of digital transmission of voice signals in the early 1960's, the D/T1 digital carrier system has grown to be the most widely used exchange area carrier system in the national telephone network. The T1 line has always been regarded as the weakest link in the whole system, primarily because it is part of the outside plant sometimes stretching over many miles of open countryside. Therefore, the engineering practice for maintenance of T1 line has been directed towards providing facilities that permit easy and quick identification of a faulty repeater or line section from the central office.
Graph representation and diagnosis for multiunit faults. H. NAKANO and Y. NAKANISHI. IEEE Trans. Reliab. R-23, 320 (1974). A method using graph theory is proposed for the detection and the location of a multiunit fault in a system. The method requires only a slight increase in the number of internal monitoring terminals over the number required for the l-unit fault diagnosis. A graph representation of a system initially leads to a rectangular diagnostic matrix. An algorithm is developed for constructing a square reachability matrix from the diagnostic matrix. A graph derived from the reachability matrix permits diagnosis of multiunit faults.
A truncated sequential test for constant failure rate. A. SALVIA and R. SUICH. IEEE Trans. Reliab. R-24, 77 (1975). This paper presents a truncated sequential procedure for testing if the failure rate of a device is constant versus a linearly increasing failure rate. A number of items, N, are placed on test and their failure times are recorded sequentially. After each observation one decides either to accept or reject a constant failure rate or to wait for another observation. Simulation under various parametric conditions yields information on the initial choice of N, average sample sizes, and points on the OC curve. Selection of the various parametric conditions is discussed. An example illustrates the use of the test.
Appro~fimately optimum confidence bounds on seriesand parullel-system reliability for systems with binomial subsystem data. N. R. MANN. IEEE Trans. Reliab. R-23, 295 (1974). A method is derived for obtaining either randomized or nonrandomized lower confidence bounds on the reliability of independent series or parallel systems when subsystem data are binomially distributed. Both types of confidence bounds agree with published values of optimum confidence bounds to within about a unit in the second significant figure. In using the method derived for obtaining nonrandomized confidence bounds there is no difficulty with the number of subsystems in the system or of a requirement of equal sample sizes, as with the
standard method of obtaining the optimum bounds. Existence of subsystems for which no failures are observed also presents no difficulty, in contrast to the maximumlikelihood and likelihood ratio approximations. Numerical comparisons are made between optimum confidence bounds and those based on other approximating methods.
Numerical solution and inference for interval-reliability of repairable components. R. L. RACICOT. IEEE Trans. Reliab. R-24, 57 (1975). The renewal and intervalreliability functions for repairable components are solved for given general probability distribution of renewal interarrival times. Two powerful numerical methods are (1) A finite difference approach wherein the renewal equation is written in discrete form and then the resulting system of algebraic equations is solved recursively. (2) Transforms of the renewal equation are treated and Fourier series expansions are used. The Fourier series approach has a wider range of applicability than finite difference in that it can be used to solve the complete renewal problem. A new equivalent form of the interval-reliability integral equation leads to a computationally faster scheme (by a factor of 10) and a simplified approximate solution for high reliability components. A numerical solution for confidence intervals has also been generated for the average interval-reliability of a component within a system, given component failure data, using a pseudoBayesian approach. The goal is to choose priors that lead to classical limits and not the usual Bayesian limits. The intervals yield close-to-exact frequency limits depending on sample size, Weibull shape parameter and the true reliability.
Determination of reliability using event-based Monte Carlo simulation. S. J. KAMAT and M. W. RILEY. IEEE Trans. Reliab. R-24, 73 (1975). The reliability of a system can be found analytically, given the time-to-failure distribution for each element and the system configuration. Such analysis becomes increasingly difficult as the complexity of a system increases. This paper presents a Monte Carlo simulation procedure to estimate the reliability of a complex system with relative ease. A computer program, written in FORTRAN IV G Level code for an IBM 360/65 computer, finds all minimal tie-sets from the system configuration, which is provided as a coded reliability flow graph. Each replication in the simulation involves a search through the minimal tie-sets to identify the success or failure of the system for each value of the required time of satisfactory performance. The reliability of the system is then estimated as a tabulated function of time.
Availability models ot maintained systems. F. A. TILLMAN and S. CHATTERJEE. IEEE Trans. Reliab. R-24, 69 (1975). The concept of availability includes reliability as well as preventive and corrective maintenance. An availability model which includes both aspects of this problem is proposed in this paper. The model includes the following decision variables: 1. failure rates and repair rates of individual units 2. the time period for perfect-preventive maintenance for a given mission time 3. the optimal failure and repair rates as a function of design costs, corrective and preventive maintenance costs. The objective is to minimize the design and operating costs where the availability requirements are satisfied. An example is solved for a system with n subsystems in series where two units in parallel comprise each subsystem. The general approach is applicable to solving other complex availability problems.
Finding the better of two similar designs by Monte Curio techniques. P. W. BECKER. IEEE Trans. Reliab. R-23, 242 (1974). During the iterative design of a system (or circuit) the designer is often faced with the problem of ranking two designs according to some criterion. If the system elements have uncertain values, each system manifestation can be evaluated as to whether or not it meets some performance criterion. The fraction which meets or exceeds the criterion is called the yield. Monte Carlo techniques can be used to simulate the population of systems and thus to estimate the ranking of two designs. The first result presented in the paper is a derivation of the probability that one design is better than another, along with confidence limits for that probability. If the two designs are topologically the same, i.e., they differ only in the nominal values and actual distributions of true parameter values, then the same set of random numbers can be used for one simulation of each design. Due to the similarity there may be a positive correlation between the 2 results which can then be used to narrow the confidence limits from the crude method mentioned above. The second result is a derivation of these narrow confidence limits.
Methods for calculating the reliability function for systems subjected to random stresses. T. A. TUMOLILLO. IEEE Trans. Reliab. R-23, 256 (1974). The reliability function is calculated for components and systems which are subjected to stresses arriving randomly in time at a given average rate. The component is assumed to exist in a finite number of states, each of which is affected differently by the applied stress. During normal operation, failure rates are assigned to each of the states of the component; when the stress is applied, the failure rates for each state change to a new value. By defining the transitions among the states as a first order Markov process, the average probability of no failure prior to and including time t is calculated for the cases where the sets of failure rates are either discrete or continuous. The solution for the average probability is given as a matrix equation and several methods for reducing the equation to a useable form are examined. In addition, the theory of failure and repair processes is reviewed and methods for simplifying the calculation of the reliability of a system are presented.
Intrinsic safety foils explosive situations. R. J. REDDING and A. KRIGMAN. Electronics, February 6, 1975. p. 91. Commercially available safety barriers are simplifying the design of circuits that must operate in dangerous environments, and they offer a practical alternative to purging or spark-proof housings.
A sequential testing procedure for a system's state identiflcution. J. HALPERN. IEEE Trans. Reliab. R-23, 267 (t974). The system and its components have only two
339
states: complete success or complete failure. The components' states are random variables and the system's state depends deterministically on the states of its elements. This paper assumes the state of the system is unknown and presents a sequential testing procedure of the components in order to determine the system's state. The procedure minimizes the expected number of necessary tests for a wide class of systems. The procedure is needed when the system is entirely or partially consumed upon its use, e.g., the firing of a missile, and one wishes to know the system's state without actually operating the system.
On the design of fault diagnostic networks for combinational logic circuits. A. PALIT,A. SEN GUPTA,M. S. BAsu and A. K. CHOUDHURY. Int. J. Electron. 38, 25 (1975). The paper describes an easy method for the detection and location of all single faults of the stuck-at-zero and stuck-at-one type in a combinational network. It is shown that the test inputs can be applied in sequence to identify some of the faulty lines whose diagnosis is otherwise ambiguous. The faults on the rest of the network lines are diagnosed with an additional combinational network, which is virtually faultless. The design procedure for this cost-oriented additional logic block is discussed. An algorithm is included for the diagnosis of fault ab initio.
Specialized scanning electron microscopy voltage contrast techniques for LSI failure analysis. B. PIWCZVK and W. SIu. Proc. IEEE Reliability Physics Syrup. April 2-4, 1974. p. 49. Several scanning electron microscopy voltage contrast techniques used for integrated circuit failure analysis are compared. A newer, simpler technique permitting the elimination of the topographic image information while retaining the voltage contrast information is described. This technique called Selective Voltage Contrast (SVC) also permits the viewing of voltages in a circuit as imposed by individual input level changes. Examples of the application of the technique are shown using bipolar integrated circuits and a charge coupled memory device.
Instabilities in double dielectric structures. M. H. WOODS. Proc. IEEE Reliability Physics Syrup. April 2-4, 1974. p. 259. Double dielectric structures are used in devices and integrated circuits for the purposes of stabilization and encapsulation, increased breakdown strength, or for active operation as in MNOS and MAOS memory transistors. Instabilities are shown to arise from polarization, alkali migration and fixed interface charges, conductivity differences and the formation of slow and fast oxide states due to the application of high electric fields in memory devices. ION instabilities in MOS structures. R. J. KRIEGLER. Proc. IEEE Reliability Physics Symp. April 2-4, 1974. p. 250. Sodium and a few other alkali metal impurities, introduced during processing into the SiO2 gate insulator of MOS devices, are easily ionized and are sufficiently mobile even at low temperatures to cause a considerable drift of the electrical characteristics of MOS devices. This paper reviews methods of detecting the presence of mobile ions and discusses techniques for reducing the concentration of impurities or eliminating their deleterious electrical effect.
Leak detection of integrated circuits and other semiconductor devices on multilayer circuit boards. A. G. STANLEY, C. M. RADER and G. NEFF. Proc. IEEE Reliability Physics Syrup. April 2-4, 1974. p. 239. The radioisotope leak test has been modified to detect leaks, in integrated circuits and other devices mounted onto multilayer circuit boards, over the entire range from 10-'-10 -s atm. cc per
340
World Abstracts on Microelectronics and Reliability
second. The method combines radiation shielding techniques with three sequential tests using krypton-85. The test program has succeeded in detecting a significant number of leaky components on electronic boards for a high reliability space application.
A failure analysis technique for locating the fail site in MOSFET (LSI) logic chips with sputtered SIO2 passivation. A. A. VIELE. Proc. IEEE Reliability Physics Symposium. April 2-4, 1974. p. 16. This paper describes a technique used successfully to locate the fail site in MOSFET (LSI) Logic Chips. It is used to analyze modules or chips which fail functionally during electrical test. Signal tracing is employed to locate the fail site while dynamically exercising the chip. This technique emphasizes the analysis of AC fails (timing problems) and chips with sputtered SiO2 (Quartz) passivation. A new approach to fault locating T1 repeatered lines. S. GHOSH. Telecommunications. November 1974. p. 39. Since the introduction of digital transmission of voice signals in the early 1960's, the D/T1 digital carrier system has grown to be the most widely used exchange area carrier system in the national telephone network. The T1 line has always been regarded as the weakest link in the whole system, primarily because it is part of the outside plant sometimes stretching over many miles of open countryside. Therefore, the engineering practice for maintenance of T1 line has been directed towards providing facilities that permit easy and quick identification of a faulty repeater or line section from the central office.
Graph representation and diagnosis for multiunit faults. H. NAKANO and Y. NAKANISHI. IEEE Trans. Reliab. R-23, 320 (1974). A method using graph theory is proposed for the detection and the location of a multiunit fault in a system. The method requires only a slight increase in the number of internal monitoring terminals over the number required for the l-unit fault diagnosis. A graph representation of a system initially leads to a rectangular diagnostic matrix. An algorithm is developed for constructing a square reachability matrix from the diagnostic matrix. A graph derived from the reachability matrix permits diagnosis of multiunit faults.
A truncated sequential test for constant failure rate. A. SALVIA and R. SUICH. IEEE Trans. Reliab. R-24, 77 (1975). This paper presents a truncated sequential procedure for testing if the failure rate of a device is constant versus a linearly increasing failure rate. A number of items, N, are placed on test and their failure times are recorded sequentially. After each observation one decides either to accept or reject a constant failure rate or to wait for another observation. Simulation under various parametric conditions yields information on the initial choice of N, average sample sizes, and points on the OC curve. Selection of the various parametric conditions is discussed. An example illustrates the use of the test.
Appro~fimately optimum confidence bounds on seriesand parullel-system reliability for systems with binomial subsystem data. N. R. MANN. IEEE Trans. Reliab. R-23, 295 (1974). A method is derived for obtaining either randomized or nonrandomized lower confidence bounds on the reliability of independent series or parallel systems when subsystem data are binomially distributed. Both types of confidence bounds agree with published values of optimum confidence bounds to within about a unit in the second significant figure. In using the method derived for obtaining nonrandomized confidence bounds there is no difficulty with the number of subsystems in the system or of a requirement of equal sample sizes, as with the
standard method of obtaining the optimum bounds. Existence of subsystems for which no failures are observed also presents no difficulty, in contrast to the maximumlikelihood and likelihood ratio approximations. Numerical comparisons are made between optimum confidence bounds and those based on other approximating methods.
Numerical solution and inference for interval-reliability of repairable components. R. L. RACICOT. IEEE Trans. Reliab. R-24, 57 (1975). The renewal and intervalreliability functions for repairable components are solved for given general probability distribution of renewal interarrival times. Two powerful numerical methods are (1) A finite difference approach wherein the renewal equation is written in discrete form and then the resulting system of algebraic equations is solved recursively. (2) Transforms of the renewal equation are treated and Fourier series expansions are used. The Fourier series approach has a wider range of applicability than finite difference in that it can be used to solve the complete renewal problem. A new equivalent form of the interval-reliability integral equation leads to a computationally faster scheme (by a factor of 10) and a simplified approximate solution for high reliability components. A numerical solution for confidence intervals has also been generated for the average interval-reliability of a component within a system, given component failure data, using a pseudoBayesian approach. The goal is to choose priors that lead to classical limits and not the usual Bayesian limits. The intervals yield close-to-exact frequency limits depending on sample size, Weibull shape parameter and the true reliability.
Determination of reliability using event-based Monte Carlo simulation. S. J. KAMAT and M. W. RILEY. IEEE Trans. Reliab. R-24, 73 (1975). The reliability of a system can be found analytically, given the time-to-failure distribution for each element and the system configuration. Such analysis becomes increasingly difficult as the complexity of a system increases. This paper presents a Monte Carlo simulation procedure to estimate the reliability of a complex system with relative ease. A computer program, written in FORTRAN IV G Level code for an IBM 360/65 computer, finds all minimal tie-sets from the system configuration, which is provided as a coded reliability flow graph. Each replication in the simulation involves a search through the minimal tie-sets to identify the success or failure of the system for each value of the required time of satisfactory performance. The reliability of the system is then estimated as a tabulated function of time.
Availability models ot maintained systems. F. A. TILLMAN and S. CHATTERJEE. IEEE Trans. Reliab. R-24, 69 (1975). The concept of availability includes reliability as well as preventive and corrective maintenance. An availability model which includes both aspects of this problem is proposed in this paper. The model includes the following decision variables: 1. failure rates and repair rates of individual units 2. the time period for perfect-preventive maintenance for a given mission time 3. the optimal failure and repair rates as a function of design costs, corrective and preventive maintenance costs. The objective is to minimize the design and operating costs where the availability requirements are satisfied. An example is solved for a system with n subsystems in series where two units in parallel comprise each subsystem. The general approach is applicable to solving other complex availability problems.