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Electron-beam lithography draws a finer line
554
World Abstracts on Microelectronics and Reliability
Rheology and modelling of the spin coating process, B. D. WASHO. I B M J. Res. Develop. p. 190 (March 1977t. This study examines the spin coating process both experimentally and from a fundamental point of view. The analysis has produced a model and a quantitative relationship between spin coating thickness and pertinent material and process variables. The model predicts that the simplest and most reproducible results occur in a region which is independent of thickness and time and is characterized by low steady state radial flow on the suhstrate. The model also includes a time-dependent term, shown to be important for the region of high radial flow--fluids of relatively low viscosity and process conditions of relatively high speed and/or long times. Experimentally, Newtonian-like polyamide in iso-amyl alcohol solutions was examined on large rotating substrates, and measurements showed excellent correlation with the model. The sensitivity of the spin coating process to substrate size and shape is also reported and a comparison with other data in the literature, particularly on photoresist solutions, is presented. The potential applicability of the model to non-ideal fluids is also developed. Ultrasonic wire welding. Part I--Wedge-wedge bonding of aluminium wires. K. I. JOHNSON, M. H. SCOTT and D. A. EDSON. Solid St. Technol. p. 50 (March 1977). The effect of the major welding parameters and thick film conditions on weld quality have been systematically examined when ultrasonically welding 25 #m diameter A1 wires to Pd-Ag, Pd-Au and Au thick film substrates, with a view to improving the reliability and quality of such welds. A light cell/: fibre optic vibration monitor of suitable frequency response (up to 100 kHz) has been developed so as to enable the measurement of this critical parameter. The monitor has been used to check the output of a number of welding machines, and has identified faults which could substantially reduce bonding yield. Welding settings have been established which give maximum tolerance to fluctuations in conditions when wedge welding 25 #m diameter Al- l ~;Si wires to Pd-Ag, Pd-Au and Au circuitry. Use of very short (5 msec), high amplitude pulses gives substantial increase in tolerance to variation of vibration amplitude ( - + 25~'~;) for the first two materials. The Al/Pd-Ag and Al/Au combinations were more weldable and gave higher pull strengths than the A1/Pd-Au combination (-0.1) and ~0.06 N respectively). The effect of Pd-Ag film storage ira various environments for up to 162 days, of thickness variation (8-13 #m) and of firing temperature {850 + 10C) on A1 wire weldability was investigated. No significant reduction was established over these ranges. Electron-beam lithography draws a finer line. T. H. P. CHANG, M. HATZAKIS, A. D. WILSON and A. N. BROtRS. Electronics p. 89 (May 12, 1977). Before LSI circuits can become any more complex, line widths must drop below l/~m---which means switching from optical to electronbeam fabrication.
field conductivity shows that p, is not suiticient to characterize ohmic contacts. It is shown that the contact noise (]2/. f law is valid up to 500 MHz and that noise measurements are much more sensitive to contact behavior than first order coefficients. Contact noise may he important at intermediate bias but is proved to b~. negligible both at very low and very high bias. Moreover it has been possible to define a contact quality factor which provides a quantitative characterization of contact behavior
Magnetron sputtering of SiO2 an alternative to chemical vapor deposition. KAREL URBANEK.Solid St. Tcch,ol. p. S7 (April 1977). Using an r.f. magnetron rather than a conventional diode for r.f. sputtering, a deposition rate almost an order of magnitude greater was obtained Although no subslrate bias was used, excellent step, coverage was achieved. In addition substrate damage was minimized. Although possibly not yet suitable lor deposition of the gate oxide, it holds great promise for interlayer insulation, Low pressure CVD production processes for poly, nitdde and oxide. RICrlARD S. ROSLER. Solid St. Tectvlol, p 63 {April 1977). The past year has seen the introduction of low pressure CVD reactors throughout the semiconductor industry. These reactors represent a significant breakthrough m terms of cost. productivity, and uniformity. The effects of the important processing variables upon thickness uniformity, growth rate and load size are described for depositions of polycrystalline silicon, silicon nitride. and silicon dioxide. Masks for printing thick-film circuits. (L C. 1)t B~v. Microelectron. Reliab. 16, 69 0977) Thick-fihn circuits are printed on Alumina suhstrates by off-contact or contact printing process through a correctly generated pattern on screens. The present paper describes these and compares the various types used for printing thick-film circuits, Though metal masks are suitable for fine line printing, for most applications sensitized bichromated emulsions or Diazo emulsions can be used to generate a mask, Aluminium corrosion in the presence of phosphosilicate glass and moisture. ROBERT B. COMIZZOLI. RCA Review 37, 483 (December 1976). Using a test pattern typical of IC dimensions, cathodic corrosion o1" aluminum lines tinder phosphosilicate glass (PSG) layers was related to phosphorus content of the passivafion glass. I,ittle or no corrosion occurs for phosphorus concentration up to about 5 wt3~;. At 7.7 wt";, phosphorus, serious corrosion occurs in a short time. A sequential procedure for evaluating corrosion effects in plastic packaged IC's is described, and tests using this procedure confirm previous models of corrosion. Measurement of aluminum-line resistance is used as a sensitive determinant of corrosion
The DryOx process for etching silicon dioxide. RICtIARD L. BERSIN and RICHARD F. REICHEI~DERFER.Solid St. Technol. p. 78 (April 1977). Anhydrous hydrogen fluoride is Low noise "'OHMIC" contacts on n-type silicon. M. ROt,- used in a new dry process for etching silicon dioxide withLAND, J. P . NOUGIER, D. GASQUET and R. ALABEDRA. out damaging the underlying layer of silicon. The process Solid-St. Electron. 20, 323 (1977). A technique is given for etches silicon dioxide with high precision and true specificity. At prescribed temperature and pressures, the hydropreparation of low noise ohmic contacts on n-type silicon using silver-silicon eutectic. It allows reaching electric fields gen fluoride has no effect on silicon, silicon nitride, aluup to 20 kV cm- ~ in a wide range of resistivities and lattice minum or other common materials. The process can be temperatures (300-6°K). Interface chemical composition used in two ways: "'permeation etching," in which etching and structure is studied using scanning electron micro- occurs under a coating of negative photoresist, or the discopy and X-ray analysis. Contact resistivity p~ is studied rect etching approach. This article describes the new techversus bulk resistivity p and lattice temperature "E High nique's development and applications.
World Abstracts on Microelectronics and Reliability
Rheology and modelling of the spin coating process, B. D. WASHO. I B M J. Res. Develop. p. 190 (March 1977t. This study examines the spin coating process both experimentally and from a fundamental point of view. The analysis has produced a model and a quantitative relationship between spin coating thickness and pertinent material and process variables. The model predicts that the simplest and most reproducible results occur in a region which is independent of thickness and time and is characterized by low steady state radial flow on the suhstrate. The model also includes a time-dependent term, shown to be important for the region of high radial flow--fluids of relatively low viscosity and process conditions of relatively high speed and/or long times. Experimentally, Newtonian-like polyamide in iso-amyl alcohol solutions was examined on large rotating substrates, and measurements showed excellent correlation with the model. The sensitivity of the spin coating process to substrate size and shape is also reported and a comparison with other data in the literature, particularly on photoresist solutions, is presented. The potential applicability of the model to non-ideal fluids is also developed. Ultrasonic wire welding. Part I--Wedge-wedge bonding of aluminium wires. K. I. JOHNSON, M. H. SCOTT and D. A. EDSON. Solid St. Technol. p. 50 (March 1977). The effect of the major welding parameters and thick film conditions on weld quality have been systematically examined when ultrasonically welding 25 #m diameter A1 wires to Pd-Ag, Pd-Au and Au thick film substrates, with a view to improving the reliability and quality of such welds. A light cell/: fibre optic vibration monitor of suitable frequency response (up to 100 kHz) has been developed so as to enable the measurement of this critical parameter. The monitor has been used to check the output of a number of welding machines, and has identified faults which could substantially reduce bonding yield. Welding settings have been established which give maximum tolerance to fluctuations in conditions when wedge welding 25 #m diameter Al- l ~;Si wires to Pd-Ag, Pd-Au and Au circuitry. Use of very short (5 msec), high amplitude pulses gives substantial increase in tolerance to variation of vibration amplitude ( - + 25~'~;) for the first two materials. The Al/Pd-Ag and Al/Au combinations were more weldable and gave higher pull strengths than the A1/Pd-Au combination (-0.1) and ~0.06 N respectively). The effect of Pd-Ag film storage ira various environments for up to 162 days, of thickness variation (8-13 #m) and of firing temperature {850 + 10C) on A1 wire weldability was investigated. No significant reduction was established over these ranges. Electron-beam lithography draws a finer line. T. H. P. CHANG, M. HATZAKIS, A. D. WILSON and A. N. BROtRS. Electronics p. 89 (May 12, 1977). Before LSI circuits can become any more complex, line widths must drop below l/~m---which means switching from optical to electronbeam fabrication.
field conductivity shows that p, is not suiticient to characterize ohmic contacts. It is shown that the contact noise (]2/. f law is valid up to 500 MHz and that noise measurements are much more sensitive to contact behavior than first order coefficients. Contact noise may he important at intermediate bias but is proved to b~. negligible both at very low and very high bias. Moreover it has been possible to define a contact quality factor which provides a quantitative characterization of contact behavior
Magnetron sputtering of SiO2 an alternative to chemical vapor deposition. KAREL URBANEK.Solid St. Tcch,ol. p. S7 (April 1977). Using an r.f. magnetron rather than a conventional diode for r.f. sputtering, a deposition rate almost an order of magnitude greater was obtained Although no subslrate bias was used, excellent step, coverage was achieved. In addition substrate damage was minimized. Although possibly not yet suitable lor deposition of the gate oxide, it holds great promise for interlayer insulation, Low pressure CVD production processes for poly, nitdde and oxide. RICrlARD S. ROSLER. Solid St. Tectvlol, p 63 {April 1977). The past year has seen the introduction of low pressure CVD reactors throughout the semiconductor industry. These reactors represent a significant breakthrough m terms of cost. productivity, and uniformity. The effects of the important processing variables upon thickness uniformity, growth rate and load size are described for depositions of polycrystalline silicon, silicon nitride. and silicon dioxide. Masks for printing thick-film circuits. (L C. 1)t B~v. Microelectron. Reliab. 16, 69 0977) Thick-fihn circuits are printed on Alumina suhstrates by off-contact or contact printing process through a correctly generated pattern on screens. The present paper describes these and compares the various types used for printing thick-film circuits, Though metal masks are suitable for fine line printing, for most applications sensitized bichromated emulsions or Diazo emulsions can be used to generate a mask, Aluminium corrosion in the presence of phosphosilicate glass and moisture. ROBERT B. COMIZZOLI. RCA Review 37, 483 (December 1976). Using a test pattern typical of IC dimensions, cathodic corrosion o1" aluminum lines tinder phosphosilicate glass (PSG) layers was related to phosphorus content of the passivafion glass. I,ittle or no corrosion occurs for phosphorus concentration up to about 5 wt3~;. At 7.7 wt";, phosphorus, serious corrosion occurs in a short time. A sequential procedure for evaluating corrosion effects in plastic packaged IC's is described, and tests using this procedure confirm previous models of corrosion. Measurement of aluminum-line resistance is used as a sensitive determinant of corrosion
The DryOx process for etching silicon dioxide. RICtIARD L. BERSIN and RICHARD F. REICHEI~DERFER.Solid St. Technol. p. 78 (April 1977). Anhydrous hydrogen fluoride is Low noise "'OHMIC" contacts on n-type silicon. M. ROt,- used in a new dry process for etching silicon dioxide withLAND, J. P . NOUGIER, D. GASQUET and R. ALABEDRA. out damaging the underlying layer of silicon. The process Solid-St. Electron. 20, 323 (1977). A technique is given for etches silicon dioxide with high precision and true specificity. At prescribed temperature and pressures, the hydropreparation of low noise ohmic contacts on n-type silicon using silver-silicon eutectic. It allows reaching electric fields gen fluoride has no effect on silicon, silicon nitride, aluup to 20 kV cm- ~ in a wide range of resistivities and lattice minum or other common materials. The process can be temperatures (300-6°K). Interface chemical composition used in two ways: "'permeation etching," in which etching and structure is studied using scanning electron micro- occurs under a coating of negative photoresist, or the discopy and X-ray analysis. Contact resistivity p~ is studied rect etching approach. This article describes the new techversus bulk resistivity p and lattice temperature "E High nique's development and applications.