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1379. Reduction of nodules in electron-gun-evaporated Au films
Classified abstracts
1376-l 384
encountered in this type of definition. Two types of ion bombardment are considered which include conventional sputtering systems and ion guns. Five major problem areas in backsputter definition are considered: (i) relative removal rates of mask and pattern films; (ii) secondary mask defects; (iii) redeposition effects; (iv) substrate temperature; and (v) radiation damage. The principles of backsputter definition are then developed. This includes a discussion of sputter yield vs angle of incidence, forward ion scattering effects which result in the trenching phenomenon, redeposition effects, and reactive backsputtering. It was concluded from this analysis that an ion-beam approach with substrate tilt and rotation relative to the ion beam is the optimum configuration for backsputter definition. The design of a low-voltage triode backsputtering system (LVBS) is discussed which is capableof generating iow-energy (-200 eV), high-current-density (l-5 mA/cm*). and large-diameter (in excess of 12 in. (30.48 cm)) ion beams. This system eliminates. many of the usual problems associated with conventional sputtering systems and is readily adapted to large-scale manufacturing requirements. A characterization of the system is presented which includes measurements of: (i) plasma and beam properties; (ii) substrate temperatures as a function of beam potential and current density; (iii) film removal rates; (iv) application to pattern definition; and (v) application to device processing. T C Tisone and P D Cruzan, J Vat Sci Technol, 12 (3), 1975,677-688.
30 1376. Target and substrate interactions in bias sputter deposition. (USA) During bias sputter deposition, the accumulation rate is found to vary significantly with impressed substrate bias. In the case of rf bias sputter deposition, the rate may increase or decrease depending on the biasing method. Measurements of the harmonic content of the radiation from a rf sputtering discharge have been made as a function of impressed substrate bias, both dc and rf, and for self bias obtained by tuning of the substrate circuit. These measurements indicate that for rf sputter deposition with dc bias, the target and substrates are non-interacting. For rf self-bias operation, the two circuits interact strongly, modifying the discharge characteristics to allow the dissipation of greater amounts of useful power. G J Kominiak, J Vuc Sci Technol, 12 (3), 1975, 689-692. 1377. Nucleation
and growth of rf triode-sputtered
30 gold mms. (USA)
The nucleation and growth of rf triode-sputtered gold films, whose electrical and optical properties were previously reported, are described in detail. Electron micrographs show that the rate of formation of nucleated particles is greater than 2 x 1012 cm-’ s-l. The resultant island particle density at a nominal film thickness (NFT) of 10 A is 2 x 1Ol2 cm-*. Linear alignment (chaining) of tiny nucleated island particles is observed. The growth of the island particles as irregularly shaped flattened platelets is attributed to the influence of electron charge. The islands become completely interconnected by tiny gold bridges when the surface coverage is 50% at a NFT of 30 A. Diffraction mode and off-axis dark-field microscopy reveal that the island particles are composed of randomly oriented crystallites. Histograms of the crystallite size distribution for a large number of films showed that the crystallite size increases with NFT up to 100 A; above 100 A the mean crystallite size remains constant ai 85 A. R H Cornely et al, J Vuc Sci Technol, 12 (3), 1975, 693-698. 1378. Hi&rate
30 physical vapour deposition of refractory metals. (USA)
Molybdeium, niobium, and vanadium bulk deposits produced by hieh-rate ohvsical vaoour deposition techniques (HRPVD) were anilysed fbr-impurit; content, grain size and morphology, yield strength, hardness, and bend ductility. Yield strengths of MO and Nb were comparable to those of wrought material having equivalent grain sizes, while the yield strength of vapour-deposited V was superior to that of wrought V because of its ultrafine (0.7 pm) grain size. Ultrafine-grained refractory metals, such as the V deposits produced in this study, may greatly reduce void formation and growth which causes dimensional changes and degradation of mechanical properties in reactor structural components. It is suggested that HRPVD techniques may be used to prepare fine-grained materials having superior resistance to swelling induced by fast-neutron irradiation. M A Sherman et al, J Vat Sci Technol, 12 (3), 1975, 697-703.
30 1379. Reduction of nodules in electron-gun-evaporated Au films. (USA) When gold is evaporated from an electron beam source, spitting from
the molten charge results in nodules on the deposited film. Au was evaporated from carbon and tungsten crucibles in an attempt to understand and reduce nodule formation. A carbon scum on the melt surface, nonwetting of crucible walls, and crucible surface roughness are all felt to contribute to nodule production. W-2’% ThOl crucibles with a 0.4 p surface finish have been employed for Au evaporation, as they exhibit the following advantages: (1) Exceptionally long life and virtual indestructibility; (2) an evaporation rate 2-3 times higher than that for carbon crucibles; and (3) 15 nodules > 13 f~ diam per 100 cm2 substrate, at a deposition rate of 12,000 @min. L G Feinstein and M J Bill, J Vuc Sci Technol, 12 (3), 1975, 704-708.
1380. Evaporator patterns. (USA)
facility
for deposition
of multielement
30 thin-film
A versatile mask changer and evaporator is described for use in fabricating experimental thin-film circuits. Its operation is demonstrated for two examples: the preparation of the integrated sensor (512 x 512 units, each containing active and passive elements) and the optical three-colour-stripe filter having each colour 340 layers spaced within 8 p side-by-side, up to 2 in. sq area (approx. 25 cm’). L H Meray, J Vat Sci Technol, 12 (3), 1975, 709-712. 1381. Departure from Knudsen’s tion of indium. (USA)
30 cosine law during the boat evapora-
It is shown that Knudsen’s cosine law for free molecular flow is not obeyed in the case of vacuum evaporation of indium for film deposition from MO boats. (AIP) (India) S D Rawat, J Vat Sci Technol, 12 (3), 1975, 725-726. 30:33 1382. An evaporator for vacuum installations. (USSR) A new form of metal evaporator furnished with a vapour condenser
mounted above the tank containing the metal to be evaporated is described; the crucible is placed directly in the tank in question. This arrangement reduces the amount of power consumed and increases the period of continuous operation of the apparatus. The crucible is provided with double walls and is linked to the tank through a channel in the bottom; between the double walls is a spiral heater. In order to reduce the loss of metal and increase the uninterrupted working time, the condenser returns the condensed metal vapour directly to the tank. M I Vinogradov et al, Soviet Patent, class c 23 c, 13/12, No. 413218, claimed 27 July 1970, pub/d 3 June 1974 (in Russian). 1383.
Device
for studying
the condensation
of materials
30:47 in wcuo.
(USSR) An instrument for continuously recording the deposition rate of vacuum-evaporated materials is described. The evaporator and condenser are mounted on a common base, and the body of the vacuum chamber (including the inspection windows) is made of heat-resistant glass, being fixed on the base in such a manner that the inspection windows and the condenser form an additional, semi-independent vacuum chamber. The vapour from the material being evaporated passes into this chamber from the evaporator and moves along the condenser, on which it settles. The vapour is prevented from settling on the inspection window by means of an extra heater. The condensation process may then be followed through a microscope, using either reflected or transmitted light. M M Spivak et al, Soviet Patent, class G 01 p, 25158, No. 406152, claimed 11 October 1971, publd 18 April 1974 (in Russian). 30 1384. Metal evaporator.
(USSR)
An improved version of an existing metal evaporator is described. In order to increase the accuracy with which the level of the melt is determined, and also in order to protect the contact element from becoming coated with evaporated metal, the contact element is supplied with an autonomous heating system. The elements may accordingly be raised to a temperature high enough to prevent metal vapour from being condensed upon it. The autonomous supply system is of the simplest kind, incorporating a standard current source and a coil-type relay. The contact element so furnished acts as an electric 531
1376-l 384
encountered in this type of definition. Two types of ion bombardment are considered which include conventional sputtering systems and ion guns. Five major problem areas in backsputter definition are considered: (i) relative removal rates of mask and pattern films; (ii) secondary mask defects; (iii) redeposition effects; (iv) substrate temperature; and (v) radiation damage. The principles of backsputter definition are then developed. This includes a discussion of sputter yield vs angle of incidence, forward ion scattering effects which result in the trenching phenomenon, redeposition effects, and reactive backsputtering. It was concluded from this analysis that an ion-beam approach with substrate tilt and rotation relative to the ion beam is the optimum configuration for backsputter definition. The design of a low-voltage triode backsputtering system (LVBS) is discussed which is capableof generating iow-energy (-200 eV), high-current-density (l-5 mA/cm*). and large-diameter (in excess of 12 in. (30.48 cm)) ion beams. This system eliminates. many of the usual problems associated with conventional sputtering systems and is readily adapted to large-scale manufacturing requirements. A characterization of the system is presented which includes measurements of: (i) plasma and beam properties; (ii) substrate temperatures as a function of beam potential and current density; (iii) film removal rates; (iv) application to pattern definition; and (v) application to device processing. T C Tisone and P D Cruzan, J Vat Sci Technol, 12 (3), 1975,677-688.
30 1376. Target and substrate interactions in bias sputter deposition. (USA) During bias sputter deposition, the accumulation rate is found to vary significantly with impressed substrate bias. In the case of rf bias sputter deposition, the rate may increase or decrease depending on the biasing method. Measurements of the harmonic content of the radiation from a rf sputtering discharge have been made as a function of impressed substrate bias, both dc and rf, and for self bias obtained by tuning of the substrate circuit. These measurements indicate that for rf sputter deposition with dc bias, the target and substrates are non-interacting. For rf self-bias operation, the two circuits interact strongly, modifying the discharge characteristics to allow the dissipation of greater amounts of useful power. G J Kominiak, J Vuc Sci Technol, 12 (3), 1975, 689-692. 1377. Nucleation
and growth of rf triode-sputtered
30 gold mms. (USA)
The nucleation and growth of rf triode-sputtered gold films, whose electrical and optical properties were previously reported, are described in detail. Electron micrographs show that the rate of formation of nucleated particles is greater than 2 x 1012 cm-’ s-l. The resultant island particle density at a nominal film thickness (NFT) of 10 A is 2 x 1Ol2 cm-*. Linear alignment (chaining) of tiny nucleated island particles is observed. The growth of the island particles as irregularly shaped flattened platelets is attributed to the influence of electron charge. The islands become completely interconnected by tiny gold bridges when the surface coverage is 50% at a NFT of 30 A. Diffraction mode and off-axis dark-field microscopy reveal that the island particles are composed of randomly oriented crystallites. Histograms of the crystallite size distribution for a large number of films showed that the crystallite size increases with NFT up to 100 A; above 100 A the mean crystallite size remains constant ai 85 A. R H Cornely et al, J Vuc Sci Technol, 12 (3), 1975, 693-698. 1378. Hi&rate
30 physical vapour deposition of refractory metals. (USA)
Molybdeium, niobium, and vanadium bulk deposits produced by hieh-rate ohvsical vaoour deposition techniques (HRPVD) were anilysed fbr-impurit; content, grain size and morphology, yield strength, hardness, and bend ductility. Yield strengths of MO and Nb were comparable to those of wrought material having equivalent grain sizes, while the yield strength of vapour-deposited V was superior to that of wrought V because of its ultrafine (0.7 pm) grain size. Ultrafine-grained refractory metals, such as the V deposits produced in this study, may greatly reduce void formation and growth which causes dimensional changes and degradation of mechanical properties in reactor structural components. It is suggested that HRPVD techniques may be used to prepare fine-grained materials having superior resistance to swelling induced by fast-neutron irradiation. M A Sherman et al, J Vat Sci Technol, 12 (3), 1975, 697-703.
30 1379. Reduction of nodules in electron-gun-evaporated Au films. (USA) When gold is evaporated from an electron beam source, spitting from
the molten charge results in nodules on the deposited film. Au was evaporated from carbon and tungsten crucibles in an attempt to understand and reduce nodule formation. A carbon scum on the melt surface, nonwetting of crucible walls, and crucible surface roughness are all felt to contribute to nodule production. W-2’% ThOl crucibles with a 0.4 p surface finish have been employed for Au evaporation, as they exhibit the following advantages: (1) Exceptionally long life and virtual indestructibility; (2) an evaporation rate 2-3 times higher than that for carbon crucibles; and (3) 15 nodules > 13 f~ diam per 100 cm2 substrate, at a deposition rate of 12,000 @min. L G Feinstein and M J Bill, J Vuc Sci Technol, 12 (3), 1975, 704-708.
1380. Evaporator patterns. (USA)
facility
for deposition
of multielement
30 thin-film
A versatile mask changer and evaporator is described for use in fabricating experimental thin-film circuits. Its operation is demonstrated for two examples: the preparation of the integrated sensor (512 x 512 units, each containing active and passive elements) and the optical three-colour-stripe filter having each colour 340 layers spaced within 8 p side-by-side, up to 2 in. sq area (approx. 25 cm’). L H Meray, J Vat Sci Technol, 12 (3), 1975, 709-712. 1381. Departure from Knudsen’s tion of indium. (USA)
30 cosine law during the boat evapora-
It is shown that Knudsen’s cosine law for free molecular flow is not obeyed in the case of vacuum evaporation of indium for film deposition from MO boats. (AIP) (India) S D Rawat, J Vat Sci Technol, 12 (3), 1975, 725-726. 30:33 1382. An evaporator for vacuum installations. (USSR) A new form of metal evaporator furnished with a vapour condenser
mounted above the tank containing the metal to be evaporated is described; the crucible is placed directly in the tank in question. This arrangement reduces the amount of power consumed and increases the period of continuous operation of the apparatus. The crucible is provided with double walls and is linked to the tank through a channel in the bottom; between the double walls is a spiral heater. In order to reduce the loss of metal and increase the uninterrupted working time, the condenser returns the condensed metal vapour directly to the tank. M I Vinogradov et al, Soviet Patent, class c 23 c, 13/12, No. 413218, claimed 27 July 1970, pub/d 3 June 1974 (in Russian). 1383.
Device
for studying
the condensation
of materials
30:47 in wcuo.
(USSR) An instrument for continuously recording the deposition rate of vacuum-evaporated materials is described. The evaporator and condenser are mounted on a common base, and the body of the vacuum chamber (including the inspection windows) is made of heat-resistant glass, being fixed on the base in such a manner that the inspection windows and the condenser form an additional, semi-independent vacuum chamber. The vapour from the material being evaporated passes into this chamber from the evaporator and moves along the condenser, on which it settles. The vapour is prevented from settling on the inspection window by means of an extra heater. The condensation process may then be followed through a microscope, using either reflected or transmitted light. M M Spivak et al, Soviet Patent, class G 01 p, 25158, No. 406152, claimed 11 October 1971, publd 18 April 1974 (in Russian). 30 1384. Metal evaporator.
(USSR)
An improved version of an existing metal evaporator is described. In order to increase the accuracy with which the level of the melt is determined, and also in order to protect the contact element from becoming coated with evaporated metal, the contact element is supplied with an autonomous heating system. The elements may accordingly be raised to a temperature high enough to prevent metal vapour from being condensed upon it. The autonomous supply system is of the simplest kind, incorporating a standard current source and a coil-type relay. The contact element so furnished acts as an electric 531