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Electron beam harmlessly probes high-density chips
Mask making for custom VLSI Semiconductor Prod. p.37 (1980). As integration rises into the VLSI level, the technical requirements in all areas are enhanced, and the contribution of the mask tooling phase in supporting both the design and the manufacturing cycles becomes even more critical. This paper examines the role of mask-making in the design and manufacture of custom VLSI circuits. It describes the critical aspects of both the design creation and prove-out phase and the following volume manufacturing activity and discusses the contribution required from a mask-making facility in this environment. Characteristics of metal-semiconductor contacts fabricated by the electroless deposition method A. K. D A T r A , K. GHOSH, N. K. D. CHOWDHURY and A. N. DAW Solid-St. Electron. 23, 905 (1980). Metal-semiconductor contacts have been fabricated by electroless deposition of Cu on chemically cleaned n-type silicon and their characteristics studied. The values of barrier height and the ideaIity factor are found to be comparable to those of vacuum evaporated contacts. A non-linearity in the 1/C2 vs V plot has been observed and the same has been satisfactorily explained by taking surface state capacitance into consideration.
3.
Testing
Electric measurement of impurity concentration in p-type epitaxially grown and ion-implanted base regions A. Z. INCECIK and H. W. POTZL Solid-St. Electron. 23, 1229 (1980). A new destruction free method of evaluation of the impurity densities in the base region of a p-epitaxial transistor based on the GummelPoon model of the bipolar transistor is presented. An Early voltage measurement method is used to determine the impurity densities at the edges of the base region and the Gummel number of the base from the change of the Gummel charge Qb. The feasibility of our method is demonstrated by experimental results which are also used to determine the error ranges of the method which are within ---20%. The method is very easy to apply because it only used d.c. current and voltage measurements. Electrical Rutherford backscattering and transmission electron microsoupy studies of furnace annealed zinc implanted GaAs S. S. KLILAR, B. J. SEALY, K. G. STEPHENS, D. SADANA and G. R. B O O K E R Solid-St. Electron. 23, 831 (1980). Electrical, Rutherford backscattering and transmission electron microscopy measurements have been carried out on GaAs samples implanted with 150keV, 1.1015 zinc ions/era2 and furnace annealed in the temperature range from room temperature to 900°C. A correlation between three types of measurement technique was established and four distinct annealing stages have been identified. For perfect recrystallisation and maximum electrical activation and annealing temperature of 900°C is required. The maximum peak hole concentration was in the range 1-2.1019 holes/cm3. Electron beam harmlessly probes hlgh-density chips J. G O S C H Electronics p. 65 (1980). Beam diameter could easily be reduced to 0.1 micrometer to test 1-ttm-wide features. Scanning light spot analysis of faulty solar cells K. L E H O V E C and A. FEDOTOWSKY Solid-St. Electron. 23,565 (1980). Current output patterns of a solar cell panel exposed to a scanning light spot are computed for fault-free and for faulty cell containing either cracks with leakage conductances across the exposed junction at the crack, or point shorts in series with various spreading resistances. Low light level, uniform attenuation length, and an external panel termination of low impedance are assumed. It is shown that various boundary conditions can be satisfied by appropriate imaging techniques. A general equivalency theorem for the ceil output of an illuminated point with that of an illuminated line through that point parallel to the finger electrode is derived and utilised. The preferred attenuation length of about half the finger electrode spacing can be achieved by modulating
the light beam at an appropriate frequency which is typically in the low MHz range. Output patterns generated by a modulated light beam are compared with those obtained by unmodulated light. Stimulus unit simplifies failure anal~'sls M. MARSHALL Electronics p. 171 (1980). Servicing microprocessor-based boards using signature analysis no longer requires a built-in stimulus. Yield model for productivity optimisation of VLSI memory chips with redundancy and partially good product C. H. STAPPER, A. N. McLAREN and M. DRECKMANN IBM J. Res Develop. 24(3)398 (1980). A model with mixed Poisson statistics has been developed for calculating the yield for memory chips with redundant lines and for partially good product. The mixing process requires two parameters which are readily obtained from product data. The product is described in the model by critical areas which depend on the circuit's sensitivity to defects, and they can be determined in a systematic way. The process is represented in the model by defect densities and gross yield losses. These are measured with defect monitors independently of product type. This paper shows how the yield for any product can be calculated given the critical areas, defect density, and mixing parameter. Future yields are forecast by using expected improvements in defect densities. Examples show good agreement between actual and calculated yields.
4.
Applications
LSI helps telephones go digital D. K. MELVIN 1EEE Spectrum. p. 30 (1980). Low-cost, high-density chips accelerate the digital design of switching systems, terminals and networks. LSI circuit for AC motor speed control B. G. STARR and J. C. F. Van LOON Electron. Components Applic. 2(4) 219 (1980). The disadvantages of Pulse Width Modulation (PWM) speed control systems for a.c. motors have now been overcome by the development of a purpose-designed LSI circuit for signal generation. This article describes the internal organisation of the circuit. There is a full description of the various input/output facilities, and detailed user advice is given. The article is the third in a series describing our PWM speed control system. Magnetic bubble reliability testing- component and sytem level aspects J. E. DAVIES IEEE 18th Annual Proceedings, Reliability Physics 1980, Las Vegas, Nevada, p. 83 (1980). Magnetic bubble memory components are extremely attractive for applications requiring high density, non-volatility and solid-state reliability. Operating lifetest and:accelerated stress test results are presented to classify the component error rates. Built-in error correction at the system level can improve error rates by several orders of magnitude. Calculated and measured error correction data are presented. Theremoelectric heat pumps cool packages electronically D. A. ZESKIND Electronics p. 109 (1980). Decreased costs and improved reliability of these solid-state modules warrant a new look at a versatile thermal management technology.
Liquid crystal technique as a failure analysis tool A. GOEL and A. GRAY
IEEE 18th Annual Proceedings, Reliability Physics 1980, Las Vegas, Nevada, p. 115 (1980). This paper describes a method for identifying location of hot spots• shorts on MOS intergrated circuits using liquid crystal technique. Several articles have been published discussing the theory and principles of this technique. This paper will concentrate on the practical aspects of the method. 43
3.
Testing
Electric measurement of impurity concentration in p-type epitaxially grown and ion-implanted base regions A. Z. INCECIK and H. W. POTZL Solid-St. Electron. 23, 1229 (1980). A new destruction free method of evaluation of the impurity densities in the base region of a p-epitaxial transistor based on the GummelPoon model of the bipolar transistor is presented. An Early voltage measurement method is used to determine the impurity densities at the edges of the base region and the Gummel number of the base from the change of the Gummel charge Qb. The feasibility of our method is demonstrated by experimental results which are also used to determine the error ranges of the method which are within ---20%. The method is very easy to apply because it only used d.c. current and voltage measurements. Electrical Rutherford backscattering and transmission electron microsoupy studies of furnace annealed zinc implanted GaAs S. S. KLILAR, B. J. SEALY, K. G. STEPHENS, D. SADANA and G. R. B O O K E R Solid-St. Electron. 23, 831 (1980). Electrical, Rutherford backscattering and transmission electron microscopy measurements have been carried out on GaAs samples implanted with 150keV, 1.1015 zinc ions/era2 and furnace annealed in the temperature range from room temperature to 900°C. A correlation between three types of measurement technique was established and four distinct annealing stages have been identified. For perfect recrystallisation and maximum electrical activation and annealing temperature of 900°C is required. The maximum peak hole concentration was in the range 1-2.1019 holes/cm3. Electron beam harmlessly probes hlgh-density chips J. G O S C H Electronics p. 65 (1980). Beam diameter could easily be reduced to 0.1 micrometer to test 1-ttm-wide features. Scanning light spot analysis of faulty solar cells K. L E H O V E C and A. FEDOTOWSKY Solid-St. Electron. 23,565 (1980). Current output patterns of a solar cell panel exposed to a scanning light spot are computed for fault-free and for faulty cell containing either cracks with leakage conductances across the exposed junction at the crack, or point shorts in series with various spreading resistances. Low light level, uniform attenuation length, and an external panel termination of low impedance are assumed. It is shown that various boundary conditions can be satisfied by appropriate imaging techniques. A general equivalency theorem for the ceil output of an illuminated point with that of an illuminated line through that point parallel to the finger electrode is derived and utilised. The preferred attenuation length of about half the finger electrode spacing can be achieved by modulating
the light beam at an appropriate frequency which is typically in the low MHz range. Output patterns generated by a modulated light beam are compared with those obtained by unmodulated light. Stimulus unit simplifies failure anal~'sls M. MARSHALL Electronics p. 171 (1980). Servicing microprocessor-based boards using signature analysis no longer requires a built-in stimulus. Yield model for productivity optimisation of VLSI memory chips with redundancy and partially good product C. H. STAPPER, A. N. McLAREN and M. DRECKMANN IBM J. Res Develop. 24(3)398 (1980). A model with mixed Poisson statistics has been developed for calculating the yield for memory chips with redundant lines and for partially good product. The mixing process requires two parameters which are readily obtained from product data. The product is described in the model by critical areas which depend on the circuit's sensitivity to defects, and they can be determined in a systematic way. The process is represented in the model by defect densities and gross yield losses. These are measured with defect monitors independently of product type. This paper shows how the yield for any product can be calculated given the critical areas, defect density, and mixing parameter. Future yields are forecast by using expected improvements in defect densities. Examples show good agreement between actual and calculated yields.
4.
Applications
LSI helps telephones go digital D. K. MELVIN 1EEE Spectrum. p. 30 (1980). Low-cost, high-density chips accelerate the digital design of switching systems, terminals and networks. LSI circuit for AC motor speed control B. G. STARR and J. C. F. Van LOON Electron. Components Applic. 2(4) 219 (1980). The disadvantages of Pulse Width Modulation (PWM) speed control systems for a.c. motors have now been overcome by the development of a purpose-designed LSI circuit for signal generation. This article describes the internal organisation of the circuit. There is a full description of the various input/output facilities, and detailed user advice is given. The article is the third in a series describing our PWM speed control system. Magnetic bubble reliability testing- component and sytem level aspects J. E. DAVIES IEEE 18th Annual Proceedings, Reliability Physics 1980, Las Vegas, Nevada, p. 83 (1980). Magnetic bubble memory components are extremely attractive for applications requiring high density, non-volatility and solid-state reliability. Operating lifetest and:accelerated stress test results are presented to classify the component error rates. Built-in error correction at the system level can improve error rates by several orders of magnitude. Calculated and measured error correction data are presented. Theremoelectric heat pumps cool packages electronically D. A. ZESKIND Electronics p. 109 (1980). Decreased costs and improved reliability of these solid-state modules warrant a new look at a versatile thermal management technology.
Liquid crystal technique as a failure analysis tool A. GOEL and A. GRAY
IEEE 18th Annual Proceedings, Reliability Physics 1980, Las Vegas, Nevada, p. 115 (1980). This paper describes a method for identifying location of hot spots• shorts on MOS intergrated circuits using liquid crystal technique. Several articles have been published discussing the theory and principles of this technique. This paper will concentrate on the practical aspects of the method. 43