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Incoming inspection and delivery quality of integrated circuits
1160
Workl Abstracts on Microelectronics and Reliability
faults by a new test pattern generator, called the Enhanced Test Generator (ETG), is also described.
Voltage-testing of thin-film capacitors. T. M. BERLICKI. IEEE Trans. Reliab. R-33, 205 (1984). The influence of proof-test voltage and testing time on the working-life distribution of thin film capacitors is presented. The proof-test not only eliminates capacitors with low breakdown voltage, it decreases the working life of the remaining components. A short proof-test is proposed to avoid degrading the remaining components. The test method for estimating the distribution parameters is presented.
Gaseous cleaning beneath surface mounted components: evaluation using a beam lead test chip. J. M. COOK and JOHN J. HANNON. IEEE Trans. Components Hybrids Mf,q Technol. CHMT-7, 328 (1984). Temperature, humidity, bias (THB) accelerated aging at 85°C, 85 % relative humidity (RH), and + 1 0 Vdc bias has been used to evaluate the gaseous, oxidative cleaning beneath surface mounted components. In this instance the component was a Si test chip that had been beam lead bonded to a thin film header. This work has been performed to investigate the possibility of removing organic contamination from beneath various devices (e.g. chips, chip carriers, etc.) by the use of gaseous, oxidative methods. Current methods involve various combinations of organic solvents, detergents, and/or aqueous solutions of oxidants, and are expensive, difficult to control, and sometimes incompatible with various circuit materials. An integral part of this investigation has been to determine the species responsible for the oxidative removal and then to maximize its production and delivery to the circuits to be cleaned. A most useful tool for accomplishing this is electron paramagnetic resonance (EPR) spectroscopy, which detects the sorts of species involved (atoms and free radicals) both qualitatively and quantitatively. It has been unambiguously determined that 3p oxygen atoms are the most reactive species with little or no contribution from ~AO2. Knowing this, it was possible to develop gas mixtures that increase the atom concentration several-fold, and to find the operating conditions and reactor materials that deliver the most atoms to the reaction site. When these test circuits were cleaned in a system analogous to that used in the EPR studies, their performance under accelerated aging conditions was at least as good as those cleaned using the standard, wet, cleaning procedure. Likewise, circuits cleaned in a conventional plasma processor and using a gas mixture developed the same way, performed as well. Gaseous methods are shown to be viable alternatives to conventional wet cleaning methods currently used for cleaning beneath surface mounted components. Moreover the use of EPR has been shown to yield useful information about such processes.
New thick film capacitor dielectrics. S. J. STEIN, C. HUANG and P.BLESS. Solid St. Technol. 213 (1984). A new series of thick film dielectrics was developed for firing at 850-1000°C. Dielectric constant nominal values of 25, 50 and 100 were achieved during the course of the program. The electrical performance of different conductor electrode metallurgies was studied, as was the performance of blends of different members of the series. These dielectrics responded well to heat, voltage, and humidity tests. Laser trimming of the capacitors for adjustment is feasible as is subsequent overglazing. Q values of 100 200 have routinely been achieved.
A field study of connector reliability. THOMAS A. YAGER and KIMBERLY NIXON. IEEE Trans. Components Hybrids Mfg Technol. CHMT-7, 370 (1984). The objectives of this investigation were (1) to survey field support personnel on the reliability and use of connectors in electronic test and computer equipment; (2) to characterize the types of defects found on gold-plated edge card connector fingers from a
large sample of printed wire assemblies (PWA's), obtained randomly from customer sites; and (3) to characterize the chemistry of the most prevalent defects found on the edge card connector fingers. The field support survey provided information on proper selection, use, and care of connectors used in electronic equipment. The microscopic examination of PWA edge card connector fingers indicated that the presence of a film covering the gold surface was the predominant defect found. Other defects observed included wear scratches, dust, pore corrosion, and a build up of debris at the metal-to-metal contact area. Defects such as edge corrosion and creep were observed, but on only very few PWA's. Chemical analysis of the film on the connector fingers found it to be primarily organic.
Yield model for fault clusters within integrated circuits. C. H. STAPPER. IBM J Re,s. Det,. 28, 636 (1984). Generalized negative binomial statistics turns out to be a model of the fault distribution in very large chips or wafers with internal defect clusters. This is expected to influence large chip and full wafer redundancy requirements. Furthermore, the yield appears to be affected by an experimental dependence of the average number of faults on chip area.
Effects of ambient atmosphere on aluminum-copper wirebond reliability. DENNIS R. OLSEN and KRISTI L. JAMES. IEEE Trans. Components Hybrids Mfy Technol. CHMT-7, 357 (1984). The effect of ambient atmosphere on the stability of AI Cu bonds aged at 150 -300°C was studied. Dath show that atmosphere plays a major role in determining the failure mode of wires bonded and aged under otherwise identical conditions. Bonds aged in air, nitrogen, and vacuum all experienced an inital decrease in pull strength due to annealing of the wire. The mechanical strength of vacuum and nitrogen aged samples continued to degrade with time. A shift in the primary failure mode from wire breaks to bond lifts was noted. The pull strengths of air-aged samples remained stable through 1600 h. The dominant failure mode was wire breaks. AL Cu intermetallic phases were formed under all conditions. Surface diffusion was suggested by the presence of a groove at the bond perimeter. With time, the groove propagated along the metallic C u / C u intermetallic interface, undercutting the bond. The formation of copper oxides in air-aged samples retarded this process. An effective activation energy of 0.45 eV was calculated for the AI Cu failure mechanism in vacuum.
Incoming inspection and delivery quality of integrated circuits. F. M. WURNn<. Microelectron. Reliab. 24, 925 (1984). Improved delivery quality of integrated circuits and new rigorous quality specifications make acceptance sampling on the basis of attributes an increasingly important function. For economic reasons sampling tests will increasingly replace the 100 ~o incoming inspection. The cost of this incoming inspection on the component level has to be compared with the diagnosis and repair cost for replacing defective integrated circuits on assembled printed circuit boards. Both cost components must be adequately matched to the technical and economic needs of the customer. Quantitative relations between the cost of repair, the average outgoing quality (AOQ) and the number of assembled integrated circuits are explained and the rigorous quality requirements of the user justified from the cost viewpoint. The practical application of single and double sampling plans and of the corresponding operating characteristic curves, with special emphasis on integrated circuits, is presented in some detail. The use of the normalized operating characteristic field, originally published by the author, and containing all applicable sampling plans, is explained using some typical examples. Finally the average outgoing quality is discussed with the help of a double-normalized set of A O Q curves in dependence
World Abstracts on Microelectronics and Reliability on defectives in the sample and acceptance number c as a parameter. The characterization of delivery quality in defectives per million (DPM) calculated using a continuous sampling procedure with the constant sampling sizes and acceptance numbers as well as varying lot sizes and rejection rates is introduced, and a new rule of thumb relation connecting the AQL values with defectives per million is proposed.
Endurance tests on noble-metal sliding-contact materials for small horsepower d.c. motors. R. SCHNABLand B. GEHLERT. Feinwerktechnik Messtechnik 92, 389 (1984) in German. Sliding and tapping contacts made from noble metal or with a noble metal coating are used in potentiometer and small horsepower motor technology in particular when a high standard of current transmission is required. A number of articles have been published on the development and behaviour of materials for use in potentiometers and on the specific requirements they have to meet [1-4]. In this article, a report is therefore given on investigations into contact materials for d.c. motors. These are employed in large numbers as final control elements and driving members in modern electronic devices and systems.
Power GaAs MESFET: reliability aspects and failure mechanisms. C. CANALL,F. CASTALDO,F. FANTINI, D.
OGLIARI, M.VANzI, M. ZICOLILLO and
E. ZANONL Microelectron. Reliab. 24, 947 (1984). In this paper we analyse and discuss some failure analyses performed on power GaAs MESFET. The pieces came both from accelerated tests and from the field. More than one half of the examined devices revealed catastrophic failures with all terminals short circuited due to burn-out occuring in the active area of the FET. In a smaller number of cases devices came from circuits whose power output was decreased and showed parametric degradations such as: an increase in drain to sourch resistance, a remarkable effect of nonsaturation, a reduction of pinch-off voltage, an increase in the forward gate current. Auger analysis performed on failed transistors clearly reveals an interdiffusion of Au through the Ti and W layers in the gate metallizations, thus reaching the gate active region. Despite the unavailability of test patterns, prepared for the particular purpose, some possible explanations of the electrical characteristics of the parametrically failed devices are presented.
Accelerated life testing of small-geometry printed circuit boards. R. R. SUTHERLANDand I. D. E. VIDELO. Circuit World 11, 35 (1985).The accelerated life test methods used by British Telecom to demonstrate the probability of 20yr life of electronic components in non-hermetic packages have now been applied to small geometry printed circuit boards from four different manufacturers. The reliability hazards found included the migration of copper from conductor tracks through one dry-film solder resist, and the delamination of a second from the board. Wet-film solder resists caused comparatively minor problems. Migration of lead and tin across the exposed surface of a board between solder pads was also observed, probably due to inadequate cleaning.
Reliability compliance testing of electronic components for consumer electronics. E. PRZYBYL and E. PECIAKOWSKI. Electrocomp. Sci. Technol. 11, 261 (1985). In this paper the organisation of reliability compliance testing of electronic components in Poland is discussed. The aim of the testing is to find the reliability of the components to both producer and user and hence to establish reliability for the two parties. The system described is derived from standard methods and has two aims. These are:(1) To enable periodical checks of production to be made. (2) To estimate the reliability level of the components produced.
1161
Sampling plans are constructed on the basis of Weibull distributions. Individual life tests are performed to compare the reliability levels with those in the specification, and also to enable data to be accumulated for calculation of average failure rates. These tests are supervised by the quality centre UNITRA-ELECTRON. The centre is then in a position to provide reliability data on electronic components for the designers and producers of electronic equipment. The system of reliability compliance testing given in the paper will be effective if the tests are performed frequently. The aim is also to achieve results in the shortest possible time. In order to achieve these aims accelerated life testing has been investigated. Applicability of techniques, including that of accelerated life testing, to the study of reliability of polyester capacitors is examined.
Reliability characterization of high speed CMOS logic ICs. S. GOTTESFELD and L. GmaoNs. RCA Rev. 45, 179 (1984). Information is presented on the reliability testing of new high-speed CMOS devices known commercially as QMOS. The reliability characterization of the early development product is discussed and data is presented on more than 10,000plastic-packaged devices tested under accelerated stress conditions during and after product qualification. The data generated demonstrate a final plastic-packaged product with exceptionally good reliability as compared with the more mature LSTTL technology. Data is also presented to show excellent stability under extreme mechanical and enviromental stresses.
Determination of reliability from ramped voltage breakdown experiments: application to dual dielectric MIM capacitors. M. SHATZKES, M. Av-RoN and K. V. SRIKRISHAN. Proc. IEEE Reliab. Phys. Conf. 138 (1984). Ramped voltage breakdown experiments were used to derive the dependence of life-time, T(v), on the applied voltage for Ta20 5-Si3N4 dual dielectric capacitors. Techniques previously described allowed for recognition of defective capacitors, which break down early, and for the effect of trapping of injected carriers, which retards the breakdown. It is therefore possible to determine r(v) for charge-free nondefective capacitors--a quantity of interest for reliability. For nonoptimistic reliability projections, z(v) must be obtained over a range in voltage so that log z(v) vs v exhibits, at the lower portion of that range, an upward concavity. Projections thus obtained were verified in a life-test.
Reliability prediction using large MOS capacitors.
Eo DOMANGUE. RICHARD RIVERA and CLARK SHEPARD. Proc. IEEE Reliab. Phys. Conf. 140 (1984). Large MOS capacitors were used in a study of the dielectric breakdown mechanism to establish the relationship among the results of various test methods. Reliance on models was avoided through the use of a test vehicle which duplicated the structures of a 64K dynamic memory device. A method is proposed to predict device reliability using process monitors at the time of wafer manufacture.
Controlling the quality of soldering of PTH solder joints. C. LEA and F. H. HOWIE. Circuit World 11, 5 (1985). The efficiency of assembly of electronic components into PCBs relies on a large number of materials and processes being carefully specified and controlled. Improved production routes for PCBs and new soldering techniques frequently appear and yet, 40yrs after the first PCBs and nearly 30 yrs since the advent of wave soldering, the perennial problems have not been eliminated and the industry is still beset with trial and error adjustments of process parameters. Scientific research at N P L has progressed towards an understanding of the basic causes of the two main problems of PCB soldering: outgassing and lack of solderability.
Workl Abstracts on Microelectronics and Reliability
faults by a new test pattern generator, called the Enhanced Test Generator (ETG), is also described.
Voltage-testing of thin-film capacitors. T. M. BERLICKI. IEEE Trans. Reliab. R-33, 205 (1984). The influence of proof-test voltage and testing time on the working-life distribution of thin film capacitors is presented. The proof-test not only eliminates capacitors with low breakdown voltage, it decreases the working life of the remaining components. A short proof-test is proposed to avoid degrading the remaining components. The test method for estimating the distribution parameters is presented.
Gaseous cleaning beneath surface mounted components: evaluation using a beam lead test chip. J. M. COOK and JOHN J. HANNON. IEEE Trans. Components Hybrids Mf,q Technol. CHMT-7, 328 (1984). Temperature, humidity, bias (THB) accelerated aging at 85°C, 85 % relative humidity (RH), and + 1 0 Vdc bias has been used to evaluate the gaseous, oxidative cleaning beneath surface mounted components. In this instance the component was a Si test chip that had been beam lead bonded to a thin film header. This work has been performed to investigate the possibility of removing organic contamination from beneath various devices (e.g. chips, chip carriers, etc.) by the use of gaseous, oxidative methods. Current methods involve various combinations of organic solvents, detergents, and/or aqueous solutions of oxidants, and are expensive, difficult to control, and sometimes incompatible with various circuit materials. An integral part of this investigation has been to determine the species responsible for the oxidative removal and then to maximize its production and delivery to the circuits to be cleaned. A most useful tool for accomplishing this is electron paramagnetic resonance (EPR) spectroscopy, which detects the sorts of species involved (atoms and free radicals) both qualitatively and quantitatively. It has been unambiguously determined that 3p oxygen atoms are the most reactive species with little or no contribution from ~AO2. Knowing this, it was possible to develop gas mixtures that increase the atom concentration several-fold, and to find the operating conditions and reactor materials that deliver the most atoms to the reaction site. When these test circuits were cleaned in a system analogous to that used in the EPR studies, their performance under accelerated aging conditions was at least as good as those cleaned using the standard, wet, cleaning procedure. Likewise, circuits cleaned in a conventional plasma processor and using a gas mixture developed the same way, performed as well. Gaseous methods are shown to be viable alternatives to conventional wet cleaning methods currently used for cleaning beneath surface mounted components. Moreover the use of EPR has been shown to yield useful information about such processes.
New thick film capacitor dielectrics. S. J. STEIN, C. HUANG and P.BLESS. Solid St. Technol. 213 (1984). A new series of thick film dielectrics was developed for firing at 850-1000°C. Dielectric constant nominal values of 25, 50 and 100 were achieved during the course of the program. The electrical performance of different conductor electrode metallurgies was studied, as was the performance of blends of different members of the series. These dielectrics responded well to heat, voltage, and humidity tests. Laser trimming of the capacitors for adjustment is feasible as is subsequent overglazing. Q values of 100 200 have routinely been achieved.
A field study of connector reliability. THOMAS A. YAGER and KIMBERLY NIXON. IEEE Trans. Components Hybrids Mfg Technol. CHMT-7, 370 (1984). The objectives of this investigation were (1) to survey field support personnel on the reliability and use of connectors in electronic test and computer equipment; (2) to characterize the types of defects found on gold-plated edge card connector fingers from a
large sample of printed wire assemblies (PWA's), obtained randomly from customer sites; and (3) to characterize the chemistry of the most prevalent defects found on the edge card connector fingers. The field support survey provided information on proper selection, use, and care of connectors used in electronic equipment. The microscopic examination of PWA edge card connector fingers indicated that the presence of a film covering the gold surface was the predominant defect found. Other defects observed included wear scratches, dust, pore corrosion, and a build up of debris at the metal-to-metal contact area. Defects such as edge corrosion and creep were observed, but on only very few PWA's. Chemical analysis of the film on the connector fingers found it to be primarily organic.
Yield model for fault clusters within integrated circuits. C. H. STAPPER. IBM J Re,s. Det,. 28, 636 (1984). Generalized negative binomial statistics turns out to be a model of the fault distribution in very large chips or wafers with internal defect clusters. This is expected to influence large chip and full wafer redundancy requirements. Furthermore, the yield appears to be affected by an experimental dependence of the average number of faults on chip area.
Effects of ambient atmosphere on aluminum-copper wirebond reliability. DENNIS R. OLSEN and KRISTI L. JAMES. IEEE Trans. Components Hybrids Mfy Technol. CHMT-7, 357 (1984). The effect of ambient atmosphere on the stability of AI Cu bonds aged at 150 -300°C was studied. Dath show that atmosphere plays a major role in determining the failure mode of wires bonded and aged under otherwise identical conditions. Bonds aged in air, nitrogen, and vacuum all experienced an inital decrease in pull strength due to annealing of the wire. The mechanical strength of vacuum and nitrogen aged samples continued to degrade with time. A shift in the primary failure mode from wire breaks to bond lifts was noted. The pull strengths of air-aged samples remained stable through 1600 h. The dominant failure mode was wire breaks. AL Cu intermetallic phases were formed under all conditions. Surface diffusion was suggested by the presence of a groove at the bond perimeter. With time, the groove propagated along the metallic C u / C u intermetallic interface, undercutting the bond. The formation of copper oxides in air-aged samples retarded this process. An effective activation energy of 0.45 eV was calculated for the AI Cu failure mechanism in vacuum.
Incoming inspection and delivery quality of integrated circuits. F. M. WURNn<. Microelectron. Reliab. 24, 925 (1984). Improved delivery quality of integrated circuits and new rigorous quality specifications make acceptance sampling on the basis of attributes an increasingly important function. For economic reasons sampling tests will increasingly replace the 100 ~o incoming inspection. The cost of this incoming inspection on the component level has to be compared with the diagnosis and repair cost for replacing defective integrated circuits on assembled printed circuit boards. Both cost components must be adequately matched to the technical and economic needs of the customer. Quantitative relations between the cost of repair, the average outgoing quality (AOQ) and the number of assembled integrated circuits are explained and the rigorous quality requirements of the user justified from the cost viewpoint. The practical application of single and double sampling plans and of the corresponding operating characteristic curves, with special emphasis on integrated circuits, is presented in some detail. The use of the normalized operating characteristic field, originally published by the author, and containing all applicable sampling plans, is explained using some typical examples. Finally the average outgoing quality is discussed with the help of a double-normalized set of A O Q curves in dependence
World Abstracts on Microelectronics and Reliability on defectives in the sample and acceptance number c as a parameter. The characterization of delivery quality in defectives per million (DPM) calculated using a continuous sampling procedure with the constant sampling sizes and acceptance numbers as well as varying lot sizes and rejection rates is introduced, and a new rule of thumb relation connecting the AQL values with defectives per million is proposed.
Endurance tests on noble-metal sliding-contact materials for small horsepower d.c. motors. R. SCHNABLand B. GEHLERT. Feinwerktechnik Messtechnik 92, 389 (1984) in German. Sliding and tapping contacts made from noble metal or with a noble metal coating are used in potentiometer and small horsepower motor technology in particular when a high standard of current transmission is required. A number of articles have been published on the development and behaviour of materials for use in potentiometers and on the specific requirements they have to meet [1-4]. In this article, a report is therefore given on investigations into contact materials for d.c. motors. These are employed in large numbers as final control elements and driving members in modern electronic devices and systems.
Power GaAs MESFET: reliability aspects and failure mechanisms. C. CANALL,F. CASTALDO,F. FANTINI, D.
OGLIARI, M.VANzI, M. ZICOLILLO and
E. ZANONL Microelectron. Reliab. 24, 947 (1984). In this paper we analyse and discuss some failure analyses performed on power GaAs MESFET. The pieces came both from accelerated tests and from the field. More than one half of the examined devices revealed catastrophic failures with all terminals short circuited due to burn-out occuring in the active area of the FET. In a smaller number of cases devices came from circuits whose power output was decreased and showed parametric degradations such as: an increase in drain to sourch resistance, a remarkable effect of nonsaturation, a reduction of pinch-off voltage, an increase in the forward gate current. Auger analysis performed on failed transistors clearly reveals an interdiffusion of Au through the Ti and W layers in the gate metallizations, thus reaching the gate active region. Despite the unavailability of test patterns, prepared for the particular purpose, some possible explanations of the electrical characteristics of the parametrically failed devices are presented.
Accelerated life testing of small-geometry printed circuit boards. R. R. SUTHERLANDand I. D. E. VIDELO. Circuit World 11, 35 (1985).The accelerated life test methods used by British Telecom to demonstrate the probability of 20yr life of electronic components in non-hermetic packages have now been applied to small geometry printed circuit boards from four different manufacturers. The reliability hazards found included the migration of copper from conductor tracks through one dry-film solder resist, and the delamination of a second from the board. Wet-film solder resists caused comparatively minor problems. Migration of lead and tin across the exposed surface of a board between solder pads was also observed, probably due to inadequate cleaning.
Reliability compliance testing of electronic components for consumer electronics. E. PRZYBYL and E. PECIAKOWSKI. Electrocomp. Sci. Technol. 11, 261 (1985). In this paper the organisation of reliability compliance testing of electronic components in Poland is discussed. The aim of the testing is to find the reliability of the components to both producer and user and hence to establish reliability for the two parties. The system described is derived from standard methods and has two aims. These are:(1) To enable periodical checks of production to be made. (2) To estimate the reliability level of the components produced.
1161
Sampling plans are constructed on the basis of Weibull distributions. Individual life tests are performed to compare the reliability levels with those in the specification, and also to enable data to be accumulated for calculation of average failure rates. These tests are supervised by the quality centre UNITRA-ELECTRON. The centre is then in a position to provide reliability data on electronic components for the designers and producers of electronic equipment. The system of reliability compliance testing given in the paper will be effective if the tests are performed frequently. The aim is also to achieve results in the shortest possible time. In order to achieve these aims accelerated life testing has been investigated. Applicability of techniques, including that of accelerated life testing, to the study of reliability of polyester capacitors is examined.
Reliability characterization of high speed CMOS logic ICs. S. GOTTESFELD and L. GmaoNs. RCA Rev. 45, 179 (1984). Information is presented on the reliability testing of new high-speed CMOS devices known commercially as QMOS. The reliability characterization of the early development product is discussed and data is presented on more than 10,000plastic-packaged devices tested under accelerated stress conditions during and after product qualification. The data generated demonstrate a final plastic-packaged product with exceptionally good reliability as compared with the more mature LSTTL technology. Data is also presented to show excellent stability under extreme mechanical and enviromental stresses.
Determination of reliability from ramped voltage breakdown experiments: application to dual dielectric MIM capacitors. M. SHATZKES, M. Av-RoN and K. V. SRIKRISHAN. Proc. IEEE Reliab. Phys. Conf. 138 (1984). Ramped voltage breakdown experiments were used to derive the dependence of life-time, T(v), on the applied voltage for Ta20 5-Si3N4 dual dielectric capacitors. Techniques previously described allowed for recognition of defective capacitors, which break down early, and for the effect of trapping of injected carriers, which retards the breakdown. It is therefore possible to determine r(v) for charge-free nondefective capacitors--a quantity of interest for reliability. For nonoptimistic reliability projections, z(v) must be obtained over a range in voltage so that log z(v) vs v exhibits, at the lower portion of that range, an upward concavity. Projections thus obtained were verified in a life-test.
Reliability prediction using large MOS capacitors.
Eo DOMANGUE. RICHARD RIVERA and CLARK SHEPARD. Proc. IEEE Reliab. Phys. Conf. 140 (1984). Large MOS capacitors were used in a study of the dielectric breakdown mechanism to establish the relationship among the results of various test methods. Reliance on models was avoided through the use of a test vehicle which duplicated the structures of a 64K dynamic memory device. A method is proposed to predict device reliability using process monitors at the time of wafer manufacture.
Controlling the quality of soldering of PTH solder joints. C. LEA and F. H. HOWIE. Circuit World 11, 5 (1985). The efficiency of assembly of electronic components into PCBs relies on a large number of materials and processes being carefully specified and controlled. Improved production routes for PCBs and new soldering techniques frequently appear and yet, 40yrs after the first PCBs and nearly 30 yrs since the advent of wave soldering, the perennial problems have not been eliminated and the industry is still beset with trial and error adjustments of process parameters. Scientific research at N P L has progressed towards an understanding of the basic causes of the two main problems of PCB soldering: outgassing and lack of solderability.