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RF sputtering of zinc sulphide
330
WORLD
ABSTRACTS
ON MICROELECTRONICS
facilities; hence, the work can be done by a small selfcontained unit. In consequence, the time to produce a new circuit is very short. *RF sputtering of z i n c sulphide. R. J. WOODWARD. Signals Res. ~ Dev. Estab., Christchurch, Hants. June (1970), pp. 32. (1091-7203) T72-00679M SRDE-REP70029. Describes work done of the R F sputtering of zinc sulphide doped thin films on to silicon. Details of the sputtering process and an assessment of equipment improvements are included.
Sputtering multilayered conductor films. D. G. MUTH. J. Vac. Sci. Technol. 8, No. 1, January-February (1971), p. 99. R.f. sputtering techniques were used to deposit multilayer conductor films with Au as the top conducting layer. Appreciable interdiffusion of the layered films occurred during sputtering, with a resultant increase in the Au resistivity. The heating attributable to electron bombardment during sputtering caused the films to heat to 290°C at 0"5 kW of applied power, and as high as 550°C at 2.0 kW. After sputtering a two-layer film on NiChrome-Au at 1"0 and 2'0 kW, for example, Ni and Cr were detected throughout the 12,000-A Au layer. When sputtering at 2"0 kW., the underlying NiCr film also reacted with the Au to form an intermetallic compound, Au4Cr. Other conductor film systems included in this study were Ti-Au, T i - P d Au, Ta-Au, and Mo-Au.
The use of perfluoroalkyl polyether fluids in v a c u u m pumps. M. A. BAKER, L. HOLLAND and L. LAURENSON. Vacuum 21, No. 10 (1971), p. 479. A fluorocarbon fluid ("Fomblin")* has been investigated as a lubricant for a rotary mechanical pump. Although the backstreaming rate was only marginally (30 per cent) less than that of a mineral oil the emitted vapour and fragmented species (CF~, CF3, C3F3) were resistant to the formation of carbonaceous and polymerized films (as occurs with hydrocarbons or silicone vapours) when exposed to electron bombardment. Resistance to polymerization and carbon deposition may arise from the low adsorption time and high bond strength of CFradicals. The fluorocarbon fluid can also be evaporated by electron bombardment without leaving a decomposition residue. A rotary pump was operated at 110°C for 500 hr without signs of wear so that vapour with a saturated vp at this temperature may be pumped without gas-ballasting. The fluid shows marked resistance to reaction with exhausted gases (e.g. fluorinated species) and can afford corrosion protection to the pump. In conclusion experiments show that an all fluorocarbon system is possible with both diffusion and rotary pumps charged with the fluid, such an arrangement would be of value for electron beam systems if fluorocarbon radicals could be tolerated. However, the high cost of the fluid will currently restrict its use.
Basic requirements of equipments for manufacturing thin-film e l e m e n t s by sputtering. G. KH. SATAROV. Elektron. Tekh. Mikroelektron. 3 (1970), p. 13.
AND RELIABILITY
(In Russian.) Basic requirements of equipments for manufacturing thin-film elements by ion sputtering are discussed including permissible pressure of residual gases, working pressure of plasma-forming gas, exhausting rate, protection against oil vapour penetration, electrical voltage on the target, localization of plasma, placing of substrates, uniformity of layers, stability of supplying voltages, purification and mixing of gases, and target cooling.
Termination materials for thin-film resistors. J. S. FISHER and P. M. HALL. Proc. I E E E 59, No. 10 (1971), p. 1418. The resistance of a thin film resistor can be considered as consisting of three parts: (1) the resistance of the resistor material; (2) the resistance of the termination material; and (3) the interracial resistance. The aging of the interracial resistance can dominate the aging of low valued resistors, especially under corrosive conditions. The interfacial resistance using a distributed parameter analysis is treated and a figure of merit which can be used to describe the aging of the interface is defined. Also, a sensitive method of measuring this quantity is introduced and a sampling of data on several different termination material systems is presented. The best results were obtained with T i - P d - A u . The conclusions drawn from the figure of merit are corroborated by adhesion and thermocompression bond strength studies.
The structure of thick films and techniques for attaching flip chip microcircuits. K. I. JOHNSON, M. H. SCOTT, W. BATTARBEEand R. GRmcS. Proc. Tech. Prog. I N T E R N E P C O N '71, Brighton. 19-21 October (1971), p. 227. Components are joined to thick film circuits by soldering, by eutectic bonding (for silicon chips being back bonded) and by thermocompression and ultrasonic bonding (for fine wires). Devices for face down bonding, flip chips, are normally joined by soldering, but difficulties are sometimes encountered. Moreover, for some applications, solderless bonding is desirable. This is practicable with thin film circuitry, but not hitherto for thick films. Among the complicating factors are the relative roughness of thick films, the small contact areas involved, the fragile nature of the devices and the high joint yield and reliability required. Work was therefore undertaken to determine the structural characteristics of various thick film inks, subsequently assessing the feasibility of ultrasonically welding flip chips to such films. Concurrently with the first stage, a fluxless reflow soldering technique has been developed that has significant advantages over previously described reflow solder techniques. Section 1 of the paper deals with the examination of the structure of conducting thick films and Section 2 with flip chip attachment, primarily by reflow soldering.
S o m e problems of performance in thin film deposition by evaporation and condensation in v a c u u m . A. S. VALEEV and V. L. EVDOKIMOV. Elektron. Tekh. Mikroelektron. 4 (1970), p. 40. (In Russian.) Criteria are presented which enable comparison of different systems for the vacuum deposition of thin films and selection of
WORLD
ABSTRACTS
ON MICROELECTRONICS
facilities; hence, the work can be done by a small selfcontained unit. In consequence, the time to produce a new circuit is very short. *RF sputtering of z i n c sulphide. R. J. WOODWARD. Signals Res. ~ Dev. Estab., Christchurch, Hants. June (1970), pp. 32. (1091-7203) T72-00679M SRDE-REP70029. Describes work done of the R F sputtering of zinc sulphide doped thin films on to silicon. Details of the sputtering process and an assessment of equipment improvements are included.
Sputtering multilayered conductor films. D. G. MUTH. J. Vac. Sci. Technol. 8, No. 1, January-February (1971), p. 99. R.f. sputtering techniques were used to deposit multilayer conductor films with Au as the top conducting layer. Appreciable interdiffusion of the layered films occurred during sputtering, with a resultant increase in the Au resistivity. The heating attributable to electron bombardment during sputtering caused the films to heat to 290°C at 0"5 kW of applied power, and as high as 550°C at 2.0 kW. After sputtering a two-layer film on NiChrome-Au at 1"0 and 2'0 kW, for example, Ni and Cr were detected throughout the 12,000-A Au layer. When sputtering at 2"0 kW., the underlying NiCr film also reacted with the Au to form an intermetallic compound, Au4Cr. Other conductor film systems included in this study were Ti-Au, T i - P d Au, Ta-Au, and Mo-Au.
The use of perfluoroalkyl polyether fluids in v a c u u m pumps. M. A. BAKER, L. HOLLAND and L. LAURENSON. Vacuum 21, No. 10 (1971), p. 479. A fluorocarbon fluid ("Fomblin")* has been investigated as a lubricant for a rotary mechanical pump. Although the backstreaming rate was only marginally (30 per cent) less than that of a mineral oil the emitted vapour and fragmented species (CF~, CF3, C3F3) were resistant to the formation of carbonaceous and polymerized films (as occurs with hydrocarbons or silicone vapours) when exposed to electron bombardment. Resistance to polymerization and carbon deposition may arise from the low adsorption time and high bond strength of CFradicals. The fluorocarbon fluid can also be evaporated by electron bombardment without leaving a decomposition residue. A rotary pump was operated at 110°C for 500 hr without signs of wear so that vapour with a saturated vp at this temperature may be pumped without gas-ballasting. The fluid shows marked resistance to reaction with exhausted gases (e.g. fluorinated species) and can afford corrosion protection to the pump. In conclusion experiments show that an all fluorocarbon system is possible with both diffusion and rotary pumps charged with the fluid, such an arrangement would be of value for electron beam systems if fluorocarbon radicals could be tolerated. However, the high cost of the fluid will currently restrict its use.
Basic requirements of equipments for manufacturing thin-film e l e m e n t s by sputtering. G. KH. SATAROV. Elektron. Tekh. Mikroelektron. 3 (1970), p. 13.
AND RELIABILITY
(In Russian.) Basic requirements of equipments for manufacturing thin-film elements by ion sputtering are discussed including permissible pressure of residual gases, working pressure of plasma-forming gas, exhausting rate, protection against oil vapour penetration, electrical voltage on the target, localization of plasma, placing of substrates, uniformity of layers, stability of supplying voltages, purification and mixing of gases, and target cooling.
Termination materials for thin-film resistors. J. S. FISHER and P. M. HALL. Proc. I E E E 59, No. 10 (1971), p. 1418. The resistance of a thin film resistor can be considered as consisting of three parts: (1) the resistance of the resistor material; (2) the resistance of the termination material; and (3) the interracial resistance. The aging of the interracial resistance can dominate the aging of low valued resistors, especially under corrosive conditions. The interfacial resistance using a distributed parameter analysis is treated and a figure of merit which can be used to describe the aging of the interface is defined. Also, a sensitive method of measuring this quantity is introduced and a sampling of data on several different termination material systems is presented. The best results were obtained with T i - P d - A u . The conclusions drawn from the figure of merit are corroborated by adhesion and thermocompression bond strength studies.
The structure of thick films and techniques for attaching flip chip microcircuits. K. I. JOHNSON, M. H. SCOTT, W. BATTARBEEand R. GRmcS. Proc. Tech. Prog. I N T E R N E P C O N '71, Brighton. 19-21 October (1971), p. 227. Components are joined to thick film circuits by soldering, by eutectic bonding (for silicon chips being back bonded) and by thermocompression and ultrasonic bonding (for fine wires). Devices for face down bonding, flip chips, are normally joined by soldering, but difficulties are sometimes encountered. Moreover, for some applications, solderless bonding is desirable. This is practicable with thin film circuitry, but not hitherto for thick films. Among the complicating factors are the relative roughness of thick films, the small contact areas involved, the fragile nature of the devices and the high joint yield and reliability required. Work was therefore undertaken to determine the structural characteristics of various thick film inks, subsequently assessing the feasibility of ultrasonically welding flip chips to such films. Concurrently with the first stage, a fluxless reflow soldering technique has been developed that has significant advantages over previously described reflow solder techniques. Section 1 of the paper deals with the examination of the structure of conducting thick films and Section 2 with flip chip attachment, primarily by reflow soldering.
S o m e problems of performance in thin film deposition by evaporation and condensation in v a c u u m . A. S. VALEEV and V. L. EVDOKIMOV. Elektron. Tekh. Mikroelektron. 4 (1970), p. 40. (In Russian.) Criteria are presented which enable comparison of different systems for the vacuum deposition of thin films and selection of