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3941. Effects of accumulated film layers on the accuracy of quartz film thickness monitors. (USA)
Classified abstracts 3938-3946 and 0.43, respectively. The theory presented should hold over a much wider range of E/p than that for which experimental results are available. P H Vidaud and A yon Engel, J PhysD: Appl Phys, 11 (10), 1978, 1397-1404. 12 3938. Work functions and structures of alkaline-earth thin films. (USA) The work functions of thin and ultra-thin films of barium were studied by means of photoemission. The films were obtained by thermal evaporation and condensation on a quartz substrate in ultra-high vacuum. The mass-thickness dependence of the quantum yield is dominated by a single peak. The work function cl~ shows a minimum and reaches a constant value for the thick films. The structures of calcium, strontium and barium were studied using the replication and the zinc-coverage technique. The mass thicknesses ranged from 0.5 to 100 rim. Three main structures were observed: granular, lacunar and quasicontinuous structures. The work-function minimum is always observed with passage of the granular film to the lacunar film. (France). L Gaudart et al, J applPhys, 49 (7), 1978, 4105--4110.
III. V a c u u m
applications
30. EVAPORATION A N D DEPOSITION I N VACUO 30 3939. Electron trapping in SiO2 due to electron-beam deposition of aluminum. (USA) Electron trapping in the SiO2 layer of n-channel polycrystalline silicon-SiO2-silicon field-effect transistors with electron-beamevaporated aluminum was studied. The increased electron trapping was attributed to the X-rays generated when the electron beam impinged on the aluminum target. Traps with low-field capture crosssections greater than 10 -~3 cm 2 are associated with the X-rayinduced positively charged centres, while traps with low-field capture cross-sections of about 1 × 10-L5 cm 2 are associated with the X-rayinduced neutral centres. For the silicon-gate devices, both traps could be effectively reduced by annealing in dry forming gas at 550°C for 20 rain. As reported earlier, the capture cross-section of the positively charged traps has a strong field dependence of approximately E.x -3 and is approximately independent of temperature. The field dependence of the capture cross-section of the neutral traps is much weaker, with roughly a a = aoexp(-- bEo,) dependence, where ao = 1.6× 10 - i s cm 2 and b = 7.35 × 10 -~ cm V -~. A possible origin of these neutral traps is displaced bonds forming polarization potential wells. T H Ning, J appl Phys, 49 (7), 1978, 4077-4082. 30 3940. Uhv facility for metal-semlconductor thin-film studies. (USA) A unique multifunction apparatus consisting of a surface analysis chamber operating at 1 × 10 -a Pa connected by a 4.5 m long beam line to a 3.75 MeV Van de Graaff accelerator operating at 1 × 10 -+ Pa is described. The bakeable, all-metal sealed beam line contains collimating, blocking, focusing and steering facilities for the MeV ion beam and is differentially pumped with a turbomolecular pump to 4 × 10 -7 Pa after a mild (100°C) bakeout. The chamber contains surface preparation equipment, a double-pass C M A for AES and ELS, and facilities for metal evaporation at P ___ 8 × 10 -~ Pa from an electron-beam source while simultaneously performing MEED. A specially designed manipulator allows samples to be cleaned, annealed, and characterized prior to in situ evaporation. The resulting metal-semiconductor couple may also be annealed in situ and characterized by AES, MEED and Rutherford Backscattering Spectroscopy. C A Crider et al, J Vac Sci Technol, 15 (2), 1978, 215-218. 3O 3941. Effects of accumulated film layers on the accuracy of quartz film thickness monitors. (USA) The effect of accumulation layers on the accuracy of quartz thin-film thickness monitors is evaluated. Use of an expanded plane wave ultrasonic propagation theory correctly accounts for observed experimental data. The magnitude of the maximum errors calculated for simply reversing the order of a series of aluminum gold deposits is on the order of 5 %. If one totally neglects intervening layers, multiple
film propagation and non-linearity can produce errors greater than
50%. J S Heyman and W E Miller, J Vac Sci Technol, 15 (2), 1978, 219-222. 30 3942. Electron spectroscopic study of oxygen-plasma-treated polymer surfaces. (USA) Oxygen plasma treatment of ABS polymer surfaces has the effect of increasing the adhesion of evaporated metal films on those surfaces. To help understand this, surfaces of commercial ABS and polypropylene were examined with ESCA both before and after oxygen plasma treatment. The plasma treatment was found to change the basic chemical nature of the polymer surface by increasing the number of single and double bonds between carbon and oxygen atoms. It is suspected that these additional carbon-oxygen chemical bonds affect the adhesion between polymers and metals. In addition to the carbonoxygen bond formation, the plasma treatment removed residual impurities of silicon and increased the residual amounts of other metallic impurities originating in the bulk. The binding energies of these metallic impurities are all indicative of oxides. J A Burkstrand, J Vac Sci Technol, 15 (2), 1978, 223-226. 3O 3943. Thickness dependence of an amorphous overlayer Ge film on the electrical conductivity of ultra-thin Pt films. (USA) The resistance of ultra-thin Pt films as influenced by amorphous Ge thin over layers has been studied. The ratio of change in resistance of the Pt films with overlays of the amorphous Ge is negligibly small for continuous Pt films but is much larger for semicontinuous and discontinuous Pt films, especially for discontinuous ones: as order, these ratio are 10 -2, 1 and 102, respectively. The changes in resistance of semicontinuous and discontinuous Pt films markedly depend o n c e thickness of the overlay. With the thickness of the overlay, at the resistance increases slightly for semicontinuous Pt films lind decreases rapidly for the discontinuous one and then decreases for both films to a saturation value ( ~ 6 0 A). The decreases in resistance of both Pt films with the thickness of the overlay can be explained by electrical conduction of the localized states in the energy gap of the overlay. (Japan). S Ogawa, J Vac Sci Technol, 15 (2), 1978, 363-365. 3O 3944. Reflectance and structure of evaporated chromium and molybdenum films. (USA) Chromium and molybdenum films deposited in high vacuum at room temperature are shown to have anomalously low optical reflectance throughout the 0.2-2.5/zm wavelength range. Deposition at about 700°C for chromium and 1000°C for molybdenum, or postdeposition annealing, gives films with bulk reflectance. X-ray diffraction and transmission electron microscopy show the films deposited at room temperature to be very fine grained (70-100 A grain size). Electrical resistivity of the fine grained films is high (3-5 times bulk). High-temperature deposition or annealing gives larger grains (>400 A) and lower resistivity. A simple model accounts for the resistivity behaviour. J E Nestell J r and R W Christy, J Vac Sci Technol, 15 (2), 1978, 366-369. 30 3945. Thin-film NiCr resistor. (USA) Reactively evaporated NiCr resistors have been produced with slightly negative temperature coefficients of resistance. Evidence from the transmission electron microscope and Auger electron microprobe show these to be cermet structures with multiple conduction mechanisms. A theoretical model initially proposed by Neugebauer for discontinuous films is applied to these thin-film structures and expanded for the multiple conduction mechanisms and effect of expansion mismatch between the substrate and film. D M Buczek, J Vac Sci Technol, 15 (2), 1978, 370-372. 3O 3946. Synthesis and physical properties of superconducting compound films formed by the electron-beam codeposition of the elements. (USA) Electron-beam codeposition of the elements to form certain high critical temperature superconducting materials, in particular A-15 compounds, has proven to be very useful in research directed at understanding and improving their superconducting properties. This work has used the close control of three or more evaporant sources to reproducibly make specimens that permit studies across selected
195
III. V a c u u m
applications
30. EVAPORATION A N D DEPOSITION I N VACUO 30 3939. Electron trapping in SiO2 due to electron-beam deposition of aluminum. (USA) Electron trapping in the SiO2 layer of n-channel polycrystalline silicon-SiO2-silicon field-effect transistors with electron-beamevaporated aluminum was studied. The increased electron trapping was attributed to the X-rays generated when the electron beam impinged on the aluminum target. Traps with low-field capture crosssections greater than 10 -~3 cm 2 are associated with the X-rayinduced positively charged centres, while traps with low-field capture cross-sections of about 1 × 10-L5 cm 2 are associated with the X-rayinduced neutral centres. For the silicon-gate devices, both traps could be effectively reduced by annealing in dry forming gas at 550°C for 20 rain. As reported earlier, the capture cross-section of the positively charged traps has a strong field dependence of approximately E.x -3 and is approximately independent of temperature. The field dependence of the capture cross-section of the neutral traps is much weaker, with roughly a a = aoexp(-- bEo,) dependence, where ao = 1.6× 10 - i s cm 2 and b = 7.35 × 10 -~ cm V -~. A possible origin of these neutral traps is displaced bonds forming polarization potential wells. T H Ning, J appl Phys, 49 (7), 1978, 4077-4082. 30 3940. Uhv facility for metal-semlconductor thin-film studies. (USA) A unique multifunction apparatus consisting of a surface analysis chamber operating at 1 × 10 -a Pa connected by a 4.5 m long beam line to a 3.75 MeV Van de Graaff accelerator operating at 1 × 10 -+ Pa is described. The bakeable, all-metal sealed beam line contains collimating, blocking, focusing and steering facilities for the MeV ion beam and is differentially pumped with a turbomolecular pump to 4 × 10 -7 Pa after a mild (100°C) bakeout. The chamber contains surface preparation equipment, a double-pass C M A for AES and ELS, and facilities for metal evaporation at P ___ 8 × 10 -~ Pa from an electron-beam source while simultaneously performing MEED. A specially designed manipulator allows samples to be cleaned, annealed, and characterized prior to in situ evaporation. The resulting metal-semiconductor couple may also be annealed in situ and characterized by AES, MEED and Rutherford Backscattering Spectroscopy. C A Crider et al, J Vac Sci Technol, 15 (2), 1978, 215-218. 3O 3941. Effects of accumulated film layers on the accuracy of quartz film thickness monitors. (USA) The effect of accumulation layers on the accuracy of quartz thin-film thickness monitors is evaluated. Use of an expanded plane wave ultrasonic propagation theory correctly accounts for observed experimental data. The magnitude of the maximum errors calculated for simply reversing the order of a series of aluminum gold deposits is on the order of 5 %. If one totally neglects intervening layers, multiple
film propagation and non-linearity can produce errors greater than
50%. J S Heyman and W E Miller, J Vac Sci Technol, 15 (2), 1978, 219-222. 30 3942. Electron spectroscopic study of oxygen-plasma-treated polymer surfaces. (USA) Oxygen plasma treatment of ABS polymer surfaces has the effect of increasing the adhesion of evaporated metal films on those surfaces. To help understand this, surfaces of commercial ABS and polypropylene were examined with ESCA both before and after oxygen plasma treatment. The plasma treatment was found to change the basic chemical nature of the polymer surface by increasing the number of single and double bonds between carbon and oxygen atoms. It is suspected that these additional carbon-oxygen chemical bonds affect the adhesion between polymers and metals. In addition to the carbonoxygen bond formation, the plasma treatment removed residual impurities of silicon and increased the residual amounts of other metallic impurities originating in the bulk. The binding energies of these metallic impurities are all indicative of oxides. J A Burkstrand, J Vac Sci Technol, 15 (2), 1978, 223-226. 3O 3943. Thickness dependence of an amorphous overlayer Ge film on the electrical conductivity of ultra-thin Pt films. (USA) The resistance of ultra-thin Pt films as influenced by amorphous Ge thin over layers has been studied. The ratio of change in resistance of the Pt films with overlays of the amorphous Ge is negligibly small for continuous Pt films but is much larger for semicontinuous and discontinuous Pt films, especially for discontinuous ones: as order, these ratio are 10 -2, 1 and 102, respectively. The changes in resistance of semicontinuous and discontinuous Pt films markedly depend o n c e thickness of the overlay. With the thickness of the overlay, at the resistance increases slightly for semicontinuous Pt films lind decreases rapidly for the discontinuous one and then decreases for both films to a saturation value ( ~ 6 0 A). The decreases in resistance of both Pt films with the thickness of the overlay can be explained by electrical conduction of the localized states in the energy gap of the overlay. (Japan). S Ogawa, J Vac Sci Technol, 15 (2), 1978, 363-365. 3O 3944. Reflectance and structure of evaporated chromium and molybdenum films. (USA) Chromium and molybdenum films deposited in high vacuum at room temperature are shown to have anomalously low optical reflectance throughout the 0.2-2.5/zm wavelength range. Deposition at about 700°C for chromium and 1000°C for molybdenum, or postdeposition annealing, gives films with bulk reflectance. X-ray diffraction and transmission electron microscopy show the films deposited at room temperature to be very fine grained (70-100 A grain size). Electrical resistivity of the fine grained films is high (3-5 times bulk). High-temperature deposition or annealing gives larger grains (>400 A) and lower resistivity. A simple model accounts for the resistivity behaviour. J E Nestell J r and R W Christy, J Vac Sci Technol, 15 (2), 1978, 366-369. 30 3945. Thin-film NiCr resistor. (USA) Reactively evaporated NiCr resistors have been produced with slightly negative temperature coefficients of resistance. Evidence from the transmission electron microscope and Auger electron microprobe show these to be cermet structures with multiple conduction mechanisms. A theoretical model initially proposed by Neugebauer for discontinuous films is applied to these thin-film structures and expanded for the multiple conduction mechanisms and effect of expansion mismatch between the substrate and film. D M Buczek, J Vac Sci Technol, 15 (2), 1978, 370-372. 3O 3946. Synthesis and physical properties of superconducting compound films formed by the electron-beam codeposition of the elements. (USA) Electron-beam codeposition of the elements to form certain high critical temperature superconducting materials, in particular A-15 compounds, has proven to be very useful in research directed at understanding and improving their superconducting properties. This work has used the close control of three or more evaporant sources to reproducibly make specimens that permit studies across selected
195