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Thermocompression bondability of bare copper leads
World Abstracts continued from page 37
Reactive sputter etching of thin films for pattern delineation R. N. CASTELLANO IEEE Trans. Components, tlybrids, Mf~t Technol. Chmt-l, (4) 397 (December 1978). Thin films of several metals, commonly used in integrated circuit fabrication, were reactively sputter-etched in an oxygen atmosphere with a focused ion beam. A decrease in the sputter-etch rate was observed as the partial pressure of oxygen was increased from 1.5 × 10 -6 to 1 × 10 -4 torr. This decrease was attributed to a buildup of a surface layer of adsorbed oxygen on the target. The partial pressure of oxygen corresponding to this decrease in sputter-etch rate of most metals was calculated on the basis of the thermodynamic properties of the compound formed. There was excellent correlation between calculated and experimental values. For integrated circuit fabrication, a suitable metal can be chosen as a thin-film mask which has a transition pressure lower than those metals on the substrate to be sputter-etched for pattern generation. This transition pressure can be predicted prior to processing.
Lead forming and outer lead bond pattern design for tape-bonded hybrids WILLIAM R. RODRIGUES DE MIRANDA, RUDOLPH G. OSWALD and DON BROWN IEEE Trans. Components, ttybrids, Mfij Technol. Chmt.-l, (4) 377 (December 1978). Tape automated bonding (TAB) has progressed to such an extent that hybrid devices are now being designed and built with this technology. In contrast with monolithic device configurations, where inner and outer lead bonds are coplanar, the hybrid device requires the leads to descend from the chip top surface level to the substrate level. It is desirable that the leads follow a carefully designed trajectory to match a substrate bonding pattern of a definite repeatable design. Funded by contracts from the U.S. Army Electronics Command (ECOM) and by internal sources, Honeywell Avionics Division developed a number of different designs for lead forming and outer lead bonding. These designs are now matured to the point that they are being standardized and incorporated into manual and automatic bonding equipment built by the Jade Corporation. They are also being submitted to American Society for Testing and Materials (ASTM) for consideration.
Thermocompression bondability of bare copper leads NICHOLAS T. PANOUSIS
IEEE Trans. Components, Hybrids, Mfg Technol. Chmt-I, (4) 372 (December 1978). Thermocompression bondability of bare (unplated) Cu leads to TiPdAu films on alumina substrates was investigated. This is an extension of earlier work to reduce the Au-plating thickness on Cu leads. Initial bondability, prebond shelf life, and long-term reliability were evaluated. The results follow. (1) Initial bondability is satisfactory provided suitable bond deformation is used. (2) Prebond shelf life is described by t(SL) = 7.5 x 10-~o exp (0.80+ 0.2eV/kT) where t(SL) is the time in hours to unacceptable bondability. The mechanism causing loss of bondability is surface oxidation of the Cu leads. A prebond shelf life (without recleaning) of about two years is indicated for storage at room temperature. (3) Long-term reliability is described by t(LT) = 9.7 x 10-1°exp (l.0+__0.2eV/kT) where t(LT) is the time in hours to unacceptable bond strengths. The mechanism causing loss of bond strength with time is believed to be interdiffusion of the Cu lead with the Au metallization. A life-time of greater than 40 years at 50:C is predicted. Comparisons between the present findings for bare Cu leads and those previously obtained using Au-plated Cu leads are presented. They indicate that the bare Cu leads have less processing and safety margin. But for many applications, bare Cu leads should be acceptable.
Chip--module package interfaces DONALD P. SERAPHIM
3.
Discrete Devices
Thick film distributed notch filters K. E. G. PITT
31icroelectronics 9, (1) 18 (1978). Series distributed RC notch filters have recently been developed in thick film construction in addition to the more well-known thin film form. Preliminary results are discussed that show their potential as frequency sensitive components. Technology limitations so far restrict tile implementation of their full potential usage. A realistic approach to thick film resistor design A. E. GUTTENSOHN Solid St. Technol. p. 73 (September 1978). A resistor design method has been developed which takes into account the dependency of the fired value of a thick film resistor upon its length (L), termination effect (T.E.), width (W), thickness (t) and layout environment. The development of this design approach is discussed in detail. A relationship has been empirically established to select resistor length based upon resistor power requirements and termination effects. Once length is determined, other empirical relationships involving length, thickness and fired resistor value establish resistor width. Corrections for length can then be made to account for severe resistor layout environments which may effect print thickness due to squeegee direction. Examples of actual resistor designs are noted and discussed.
Time dependence of ion-mlgratlon effects in NiCr resistor films U. SMITH and R. HOFFMANN
Electrocomp. Sci. Technol. 5, 159 (1978). This paper reports the effects of ion-migration on NiCr-resistor films sputtered on the substrates Coming 0211 and 7059. Graphs showing the. influence of magnitude and polarity of the bias potential, of the separation between resistor and counter-electrode, and of reversal of bias polarity are given for Coming 0211 substrates at a temperature of 100~C and in a relative humidity of 0.7 % for periods of time ranging up to I000 hours. Results for resistors having a NiCr-oxide layer between the film and the Corning 0211 substrate as well as for NiCr resistors on Coming 7059 substrate are also presented. Previous use of a biaselectrode at positive potential is shown to lead to a depletion-recovery effect. The physical interpretation of the experimental features is given in terms of a model involving anodie oxidation at the positive electrode and formation of a low conductivity deposit at the negative electrode. 64-pin QUIP keeps microprocessor chips cool and accessible WILLIAM LATTIN, TERRY MATHIASEN and STEVEN GROVENDER Electronics p. 130 (4 January 1979). Three-part design has low thermal resistance; readily removable chipcarrier has exposed contacts to ease testing.
Electrical properties of the MIS capacitor under illumination ANDRZEJ JAKUBOWSKI and STANISLAW KRAWCZYK Electron Technol. 11, (1/2)3 (1978). The paper presents an attempt of a single quantitative analysis of the semiconductor parameters and the static and dynamic parameters of the MIS capacitor in quasi-equilibrium conditions. The equilibrium conditions in semiconductor are disturbed by light-induced electronhole pair generation. The illumination level is characterized in terms of an effective generation rate. The more relevant relations between the semiconductor and MIS capacitor parameters and the effective generation rate are presented in the form of diagrams. The physical interpretation of the processes occurring during illumination of the MIS structure is also given.
IEEE Trans. Components, tlybrids, Mfg Technol. Chmt-I, (3) 305 (September 1978). The direction of progress for printed circuit board technology is illustrated through a design example using LSI chips and multichip modules. The interface requirements between the chips and modules and between the modules and the printed-circuit board are described. The use of large-scale integrated circuits in large systems is shown to require substantial increases in interconnection density at the module and the printed-circuit board. Approaches to providing the increased interconnection are described.
38
Thin-film layers shrink rf inductors to chip size Electronics p. 41 (1 February 1979). Instead of adding turns by depositing film on a flat surface. Thinco fabricates the turns vertically, depositing alternate layers of metal and silicon-dioxide dielectric on an alumina substrate. Furthermore, the components - Thineo has produced capacitors, too - are batchproduced in a vacuum chamber during only a single vacuum pumpdown.
Reactive sputter etching of thin films for pattern delineation R. N. CASTELLANO IEEE Trans. Components, tlybrids, Mf~t Technol. Chmt-l, (4) 397 (December 1978). Thin films of several metals, commonly used in integrated circuit fabrication, were reactively sputter-etched in an oxygen atmosphere with a focused ion beam. A decrease in the sputter-etch rate was observed as the partial pressure of oxygen was increased from 1.5 × 10 -6 to 1 × 10 -4 torr. This decrease was attributed to a buildup of a surface layer of adsorbed oxygen on the target. The partial pressure of oxygen corresponding to this decrease in sputter-etch rate of most metals was calculated on the basis of the thermodynamic properties of the compound formed. There was excellent correlation between calculated and experimental values. For integrated circuit fabrication, a suitable metal can be chosen as a thin-film mask which has a transition pressure lower than those metals on the substrate to be sputter-etched for pattern generation. This transition pressure can be predicted prior to processing.
Lead forming and outer lead bond pattern design for tape-bonded hybrids WILLIAM R. RODRIGUES DE MIRANDA, RUDOLPH G. OSWALD and DON BROWN IEEE Trans. Components, ttybrids, Mfij Technol. Chmt.-l, (4) 377 (December 1978). Tape automated bonding (TAB) has progressed to such an extent that hybrid devices are now being designed and built with this technology. In contrast with monolithic device configurations, where inner and outer lead bonds are coplanar, the hybrid device requires the leads to descend from the chip top surface level to the substrate level. It is desirable that the leads follow a carefully designed trajectory to match a substrate bonding pattern of a definite repeatable design. Funded by contracts from the U.S. Army Electronics Command (ECOM) and by internal sources, Honeywell Avionics Division developed a number of different designs for lead forming and outer lead bonding. These designs are now matured to the point that they are being standardized and incorporated into manual and automatic bonding equipment built by the Jade Corporation. They are also being submitted to American Society for Testing and Materials (ASTM) for consideration.
Thermocompression bondability of bare copper leads NICHOLAS T. PANOUSIS
IEEE Trans. Components, Hybrids, Mfg Technol. Chmt-I, (4) 372 (December 1978). Thermocompression bondability of bare (unplated) Cu leads to TiPdAu films on alumina substrates was investigated. This is an extension of earlier work to reduce the Au-plating thickness on Cu leads. Initial bondability, prebond shelf life, and long-term reliability were evaluated. The results follow. (1) Initial bondability is satisfactory provided suitable bond deformation is used. (2) Prebond shelf life is described by t(SL) = 7.5 x 10-~o exp (0.80+ 0.2eV/kT) where t(SL) is the time in hours to unacceptable bondability. The mechanism causing loss of bondability is surface oxidation of the Cu leads. A prebond shelf life (without recleaning) of about two years is indicated for storage at room temperature. (3) Long-term reliability is described by t(LT) = 9.7 x 10-1°exp (l.0+__0.2eV/kT) where t(LT) is the time in hours to unacceptable bond strengths. The mechanism causing loss of bond strength with time is believed to be interdiffusion of the Cu lead with the Au metallization. A life-time of greater than 40 years at 50:C is predicted. Comparisons between the present findings for bare Cu leads and those previously obtained using Au-plated Cu leads are presented. They indicate that the bare Cu leads have less processing and safety margin. But for many applications, bare Cu leads should be acceptable.
Chip--module package interfaces DONALD P. SERAPHIM
3.
Discrete Devices
Thick film distributed notch filters K. E. G. PITT
31icroelectronics 9, (1) 18 (1978). Series distributed RC notch filters have recently been developed in thick film construction in addition to the more well-known thin film form. Preliminary results are discussed that show their potential as frequency sensitive components. Technology limitations so far restrict tile implementation of their full potential usage. A realistic approach to thick film resistor design A. E. GUTTENSOHN Solid St. Technol. p. 73 (September 1978). A resistor design method has been developed which takes into account the dependency of the fired value of a thick film resistor upon its length (L), termination effect (T.E.), width (W), thickness (t) and layout environment. The development of this design approach is discussed in detail. A relationship has been empirically established to select resistor length based upon resistor power requirements and termination effects. Once length is determined, other empirical relationships involving length, thickness and fired resistor value establish resistor width. Corrections for length can then be made to account for severe resistor layout environments which may effect print thickness due to squeegee direction. Examples of actual resistor designs are noted and discussed.
Time dependence of ion-mlgratlon effects in NiCr resistor films U. SMITH and R. HOFFMANN
Electrocomp. Sci. Technol. 5, 159 (1978). This paper reports the effects of ion-migration on NiCr-resistor films sputtered on the substrates Coming 0211 and 7059. Graphs showing the. influence of magnitude and polarity of the bias potential, of the separation between resistor and counter-electrode, and of reversal of bias polarity are given for Coming 0211 substrates at a temperature of 100~C and in a relative humidity of 0.7 % for periods of time ranging up to I000 hours. Results for resistors having a NiCr-oxide layer between the film and the Corning 0211 substrate as well as for NiCr resistors on Coming 7059 substrate are also presented. Previous use of a biaselectrode at positive potential is shown to lead to a depletion-recovery effect. The physical interpretation of the experimental features is given in terms of a model involving anodie oxidation at the positive electrode and formation of a low conductivity deposit at the negative electrode. 64-pin QUIP keeps microprocessor chips cool and accessible WILLIAM LATTIN, TERRY MATHIASEN and STEVEN GROVENDER Electronics p. 130 (4 January 1979). Three-part design has low thermal resistance; readily removable chipcarrier has exposed contacts to ease testing.
Electrical properties of the MIS capacitor under illumination ANDRZEJ JAKUBOWSKI and STANISLAW KRAWCZYK Electron Technol. 11, (1/2)3 (1978). The paper presents an attempt of a single quantitative analysis of the semiconductor parameters and the static and dynamic parameters of the MIS capacitor in quasi-equilibrium conditions. The equilibrium conditions in semiconductor are disturbed by light-induced electronhole pair generation. The illumination level is characterized in terms of an effective generation rate. The more relevant relations between the semiconductor and MIS capacitor parameters and the effective generation rate are presented in the form of diagrams. The physical interpretation of the processes occurring during illumination of the MIS structure is also given.
IEEE Trans. Components, tlybrids, Mfg Technol. Chmt-I, (3) 305 (September 1978). The direction of progress for printed circuit board technology is illustrated through a design example using LSI chips and multichip modules. The interface requirements between the chips and modules and between the modules and the printed-circuit board are described. The use of large-scale integrated circuits in large systems is shown to require substantial increases in interconnection density at the module and the printed-circuit board. Approaches to providing the increased interconnection are described.
38
Thin-film layers shrink rf inductors to chip size Electronics p. 41 (1 February 1979). Instead of adding turns by depositing film on a flat surface. Thinco fabricates the turns vertically, depositing alternate layers of metal and silicon-dioxide dielectric on an alumina substrate. Furthermore, the components - Thineo has produced capacitors, too - are batchproduced in a vacuum chamber during only a single vacuum pumpdown.