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Mass spectroscopy of background gases in glow-discharge sputtering of tantalum thin films
Classified
abstracts
12461253
to be refrigerated. A graphic control panel indicates the flow path with marked stations along it, with several detectors located at these stations. Gauges are attached and indicated on the panel for relating the stations. Cryo-Vat Inc, US Patent 3,3 13,117, Official Gaz US Patent O&e, 837 (2), 11th April 1967, 394. 26. AUTOMATIC
PROTECTIVE
AND CONTROL EQUIPMENT
26 1246. Simple system for temperature control and cycling in the range 4-300°K. (USA) A feedback system for temperature measurement, control and cycling in the range 4-300°K is described. The system can be easily assembled by adding a few off-the-shelf components to any standard thermoelectric set-up used in the same temperature range. The system is easily operated to control the temperature of a chamber eg the microwave cavity of an ESR spectrometer, well within 10-20K. P M Angelo et al, Rev Sci Znstrum, 38, 1967,415-419. 27. LEAK DETECTORS
AND LEAK DETECTION
27 1247. Testing the leak-proof encapsulation of semiconductor devices with the aid of radioactive tracer gas. (Czechoslovakia) A method is presented for the leak-testing of small devices, such as semiconductors, using krypton-85. The device is placed in gas with radioactivity of 3.85 x lOmamC/cms at 10 atm pressure for 30 hours and then the gamma radiation is measured. As both @and y rays are produced by Krss, the quantity of test gas absorbed on the external surfaces of the device is evaluated by measuring the p activity, since radiation of this type from the internal device space is shielded by the device walls. Test equipment allowing a sensitivity of lo-“’ torr-litre/sec is described. M Tauer, Sabopr Obzor, 28 (4), April 1967,233-237 (in Czech). 28. HEATING EQUIPMENT
AND THERMOMETERS
28 : 30 Measurements of the substrate temperature during a coating process and its influence on magnetic thin film properties. See abstract number 1257. 28
: 37
1248. Multipurpose vacuum furnace with induction electron beam and resistance heating. (Czechoslovakia) The furnace described is suitable for vacuum annealing, melting, welding, soldering and other processes, where resistance, RF induction or electron beam heating is used. The work chamber is pumped down to 10e6 torr by a diffusion pump. Tungsten or molybdenum resistance heating elements are employed for temperatures up to 1600°C with a hot zone 140 mm x 90 mm diameter. Two exchangeable guns with a common magnetic lens focusing are incorporated; one for currents up to 10 mA and accelerating voltages up to 100 kV, the second for currents up to several amperes and voltages up to 40 kV. Mechanical motion and electrical feedthroughs are also described. The heating sources may be applied simultaneously. Experience gained with the furnace in capillary soldering and electron beam welding are briefly discussed. L Zobac, Slabopr Obzor, 28 (3), March 1967, 146-152 (in Czech). 28 1249. Thermocouple calibration
at temperatures
above 2,OOO”C.
(USSR)
The design of a high-vacuum furnace for calibrating thermocouples is described. Using tungsten heaters a maximum temperature of 2,600”C can be attained. With this furnace WRe 5-WRe 20 thermocouples were calibrated and the expression for their thermo-emf was determined as E= -2,543.0+21.4114 Ta.0027894 Ta for E in microvolts and T in “C. G B Lapp et al, Izmerit Tekh, No 2, Feb 1967, 82-83 (in Russian).
effect and electrical conductivity of Ni thin films. See abstract number 1206. 30 : 22 Feasibility study of thin film tunnel cathodes. See abstract number 1238. 30 1250. Optical film materials and their applications. (USA) This paper gives a survey of materials suitable for the preparation of dielectric films for interference coatings, highly reflecting metallic films, and semi-transparent coatings for neutral density filters and sunglasses. It is shown that improved vacuum-deposition techniques and treatments, such as evaporation by electron bombardment, film deposition under ultrahigh vacuum conditions and at extremely high rates, reactive evaporation in an oxygen atmosphere, and ultraviolet irradiation after the film deposition, have greatly increased the number and improved the quality of film materials for optical applications. The most important factors for producing dielectric films with high transmittance and metallic coatings with high reflectance are discussed. Coatings suitable for controlling the temperature of satellites and space vehicles are described. G Haas and E Ritter, J Vat Sci Technol, 4 (2), March/April 1967, 71-79. 30
1251. Investigation of sputtered &tantalum thin films. (USA) Sputtered B-tantalum thin films were produced in a two-chamber vacuum system (entrance chamber and sputtering chamber) with typical background pressure of 1 x lo-’ torr. Both the resistivity and sheet-resistance uniformity were almost entirely dependent on cathode voltage; a sheet resistance uniformity of & 1 per cent over a 3 by 4 inch substrate was achieved. The application of negativeanode bias voltage was found to control B-tantalum film resistivity; a 53 per cent reduction in resistivity was caused by a -200 V anode bias voltage applied during a 4 kV cathode sputtering run. A relationship between resistivity and plasma potential was found, which unifies both cathode voltage and anode-bias voltage effects. The electrostatic environment of the substrate appears to control the resulting Btantalum film properties. Continuous sputtering over a period of several days was required to initially achieve equilibrium conditions in the sputtering chamber. The application of directsubstrate negative bias voltage during clean-up reduced the fltantalum resistivity and, in some cases, produced a mixed structure of both bee and p-tantalum. H C Cook, J Vat Sci Technol, 4 (2), March/April 1967, 80-86. 30 1252. Mass
spectrometry of background gases in glow-discharge sputtering of tantalum thin films. (USA) The composition of the ambient atmosphere during the sputtering of tantalum films in argon glow discharges has been studied by means of a mass spectrometer adapted both for residual analysis of vacua between 10-9-10-6 torr, and process monitoring at pressures of (1&50)x 1O-s torr. The partial pressures of a number of residuals were found to increase immediately upon initiation of the discharge in both an oil diffusion and a turbomolecular pump system. The total background gas levels during the discharge were in the 1 x 10m6 -5 x 1O-4 torr range, with the major component being hydrogen, and smaller contributions from water vapour and methane. The pressure increase of these species resulted from ion bombardment decomposition of adsorbed surface layers, and exhibited two maxima. The first is attributed to desorption from the electrodes and the second to desorption from the bell jar wall. The spectrometer was used for detailed studies of the gettering of deliberate additions of Na, CH4 and Ha during sputtering in argon. Considerable differences were found in the effect of the glow discharge on those gases, with the gettering of CH, and Ha exhibiting a complex time dependence. Tantalum films sputtered without deliberate gas additions, were found to be of the beta-tantalum form even when the dischargegenerated background was reduced to about 1 x 1Om8torr by long presputtering. (Author) J Sosniak, J Vat Sci Technol, 4 (2), March/April 1967, 87-93. 30 1253. Caesium ion sputtering of aluminium copper and titanium. (USA)
III.
Vacuum
30. EVAPORATION
applications AND SPUTTERING
30 : 16 Influence of Cs, Ba, Th and Cu adsorption and electric field on the Hall
Sputtering measurements were carried out to evaluate the materials for an electrode in caesium ion engines. Sputtering yields of the polycrystalline metals were measured as a function of caesium ion energy in the range 0.5-15 keV. The yield of powder metallurgy copper was also measured for caesium ion energies of 2, 5 and 7 keV. 423
abstracts
12461253
to be refrigerated. A graphic control panel indicates the flow path with marked stations along it, with several detectors located at these stations. Gauges are attached and indicated on the panel for relating the stations. Cryo-Vat Inc, US Patent 3,3 13,117, Official Gaz US Patent O&e, 837 (2), 11th April 1967, 394. 26. AUTOMATIC
PROTECTIVE
AND CONTROL EQUIPMENT
26 1246. Simple system for temperature control and cycling in the range 4-300°K. (USA) A feedback system for temperature measurement, control and cycling in the range 4-300°K is described. The system can be easily assembled by adding a few off-the-shelf components to any standard thermoelectric set-up used in the same temperature range. The system is easily operated to control the temperature of a chamber eg the microwave cavity of an ESR spectrometer, well within 10-20K. P M Angelo et al, Rev Sci Znstrum, 38, 1967,415-419. 27. LEAK DETECTORS
AND LEAK DETECTION
27 1247. Testing the leak-proof encapsulation of semiconductor devices with the aid of radioactive tracer gas. (Czechoslovakia) A method is presented for the leak-testing of small devices, such as semiconductors, using krypton-85. The device is placed in gas with radioactivity of 3.85 x lOmamC/cms at 10 atm pressure for 30 hours and then the gamma radiation is measured. As both @and y rays are produced by Krss, the quantity of test gas absorbed on the external surfaces of the device is evaluated by measuring the p activity, since radiation of this type from the internal device space is shielded by the device walls. Test equipment allowing a sensitivity of lo-“’ torr-litre/sec is described. M Tauer, Sabopr Obzor, 28 (4), April 1967,233-237 (in Czech). 28. HEATING EQUIPMENT
AND THERMOMETERS
28 : 30 Measurements of the substrate temperature during a coating process and its influence on magnetic thin film properties. See abstract number 1257. 28
: 37
1248. Multipurpose vacuum furnace with induction electron beam and resistance heating. (Czechoslovakia) The furnace described is suitable for vacuum annealing, melting, welding, soldering and other processes, where resistance, RF induction or electron beam heating is used. The work chamber is pumped down to 10e6 torr by a diffusion pump. Tungsten or molybdenum resistance heating elements are employed for temperatures up to 1600°C with a hot zone 140 mm x 90 mm diameter. Two exchangeable guns with a common magnetic lens focusing are incorporated; one for currents up to 10 mA and accelerating voltages up to 100 kV, the second for currents up to several amperes and voltages up to 40 kV. Mechanical motion and electrical feedthroughs are also described. The heating sources may be applied simultaneously. Experience gained with the furnace in capillary soldering and electron beam welding are briefly discussed. L Zobac, Slabopr Obzor, 28 (3), March 1967, 146-152 (in Czech). 28 1249. Thermocouple calibration
at temperatures
above 2,OOO”C.
(USSR)
The design of a high-vacuum furnace for calibrating thermocouples is described. Using tungsten heaters a maximum temperature of 2,600”C can be attained. With this furnace WRe 5-WRe 20 thermocouples were calibrated and the expression for their thermo-emf was determined as E= -2,543.0+21.4114 Ta.0027894 Ta for E in microvolts and T in “C. G B Lapp et al, Izmerit Tekh, No 2, Feb 1967, 82-83 (in Russian).
effect and electrical conductivity of Ni thin films. See abstract number 1206. 30 : 22 Feasibility study of thin film tunnel cathodes. See abstract number 1238. 30 1250. Optical film materials and their applications. (USA) This paper gives a survey of materials suitable for the preparation of dielectric films for interference coatings, highly reflecting metallic films, and semi-transparent coatings for neutral density filters and sunglasses. It is shown that improved vacuum-deposition techniques and treatments, such as evaporation by electron bombardment, film deposition under ultrahigh vacuum conditions and at extremely high rates, reactive evaporation in an oxygen atmosphere, and ultraviolet irradiation after the film deposition, have greatly increased the number and improved the quality of film materials for optical applications. The most important factors for producing dielectric films with high transmittance and metallic coatings with high reflectance are discussed. Coatings suitable for controlling the temperature of satellites and space vehicles are described. G Haas and E Ritter, J Vat Sci Technol, 4 (2), March/April 1967, 71-79. 30
1251. Investigation of sputtered &tantalum thin films. (USA) Sputtered B-tantalum thin films were produced in a two-chamber vacuum system (entrance chamber and sputtering chamber) with typical background pressure of 1 x lo-’ torr. Both the resistivity and sheet-resistance uniformity were almost entirely dependent on cathode voltage; a sheet resistance uniformity of & 1 per cent over a 3 by 4 inch substrate was achieved. The application of negativeanode bias voltage was found to control B-tantalum film resistivity; a 53 per cent reduction in resistivity was caused by a -200 V anode bias voltage applied during a 4 kV cathode sputtering run. A relationship between resistivity and plasma potential was found, which unifies both cathode voltage and anode-bias voltage effects. The electrostatic environment of the substrate appears to control the resulting Btantalum film properties. Continuous sputtering over a period of several days was required to initially achieve equilibrium conditions in the sputtering chamber. The application of directsubstrate negative bias voltage during clean-up reduced the fltantalum resistivity and, in some cases, produced a mixed structure of both bee and p-tantalum. H C Cook, J Vat Sci Technol, 4 (2), March/April 1967, 80-86. 30 1252. Mass
spectrometry of background gases in glow-discharge sputtering of tantalum thin films. (USA) The composition of the ambient atmosphere during the sputtering of tantalum films in argon glow discharges has been studied by means of a mass spectrometer adapted both for residual analysis of vacua between 10-9-10-6 torr, and process monitoring at pressures of (1&50)x 1O-s torr. The partial pressures of a number of residuals were found to increase immediately upon initiation of the discharge in both an oil diffusion and a turbomolecular pump system. The total background gas levels during the discharge were in the 1 x 10m6 -5 x 1O-4 torr range, with the major component being hydrogen, and smaller contributions from water vapour and methane. The pressure increase of these species resulted from ion bombardment decomposition of adsorbed surface layers, and exhibited two maxima. The first is attributed to desorption from the electrodes and the second to desorption from the bell jar wall. The spectrometer was used for detailed studies of the gettering of deliberate additions of Na, CH4 and Ha during sputtering in argon. Considerable differences were found in the effect of the glow discharge on those gases, with the gettering of CH, and Ha exhibiting a complex time dependence. Tantalum films sputtered without deliberate gas additions, were found to be of the beta-tantalum form even when the dischargegenerated background was reduced to about 1 x 1Om8torr by long presputtering. (Author) J Sosniak, J Vat Sci Technol, 4 (2), March/April 1967, 87-93. 30 1253. Caesium ion sputtering of aluminium copper and titanium. (USA)
III.
Vacuum
30. EVAPORATION
applications AND SPUTTERING
30 : 16 Influence of Cs, Ba, Th and Cu adsorption and electric field on the Hall
Sputtering measurements were carried out to evaluate the materials for an electrode in caesium ion engines. Sputtering yields of the polycrystalline metals were measured as a function of caesium ion energy in the range 0.5-15 keV. The yield of powder metallurgy copper was also measured for caesium ion energies of 2, 5 and 7 keV. 423