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Surface adsorption and vacuum breakdown
552
A B S T R A C T S ON M [ C R O E L E C T R O N I C S
AND RELIABILITY
Nucleation and initial g r o w t h o f single-crystal films. R. F. ADAMSKYand R. E. LEBLANC. ffournat
of ['acuum Science Techt, ology, Vol. 2, No. 2, March April 1965, p. 79. The mechanism of epitaxial growth has been investigated by the study of the nucleation process and early growth stages of singlecrystal gold and silver films in (100) and (1"1l) orientations. Films were grown by evaporation on vacuumcleaved NaCI and mica cleavage planes, and on single-crystal NaCI films deposited on fresh mica cleavage surfaces. In the earliest observable period of growth, nuclei have been found to be as small as 5 .\ in size. These nuclei, which contain t0-20 atoms, strongly indicate that growth proceeds continuously from initial nuclei consisting of only a few atoms. In subsequent stages of growth, coalescence processes occur which are governed by mobility of atoms and clusters on the substrate material. Mobility is highest on the evaporated film substrates, a'nd leads to a decrease in nucleation density as a function of time because of rapid coalescence of the mobile nuclei. Nucleation rates have been measured as a function of substrate temperature and activation energies determined for the nucleation process. S u r f a c e adsorption and v a c u u m b r e a k d o w n . W. D. OWE.',-and J. BEY.-,'ox. Vacuum, Vol. 15, 3,o. 3, 1965, p. 123. The authors deal with the mechanism of the so-called "vacuum" electrical breakdown in the pressure range 10 -5 to I0 q ° torr. Electrical conduction at such low pressures is of fundamental interest because the initiation and build-up of current leading to breakdown is not yet fully understood. A parallel plate gap of 0'3 mm was used in the experiments, the applied voltage ranging to 10 kV. It appears that breakdown of the gap at 10 -5 tort is generally preceded by a sudden increase in gap current accompanied by a marked increase in gas pressure, probably due to release of gas from the electrodes under the influence of electron bombardment. This was confirmed by similar experiments at still lower pressures and it seems now established that electrical breakdown in a high vacuum can take place by the Townsend process when a sufficient increase in pressure has taken place.
Formation o f thin film circuits using preferential nucleation. H. L. CASWrLL and Y. BUDO.
Solid-State Electronics, Vol. 8, 1965, pp. 479-483. The binding energy for many metals on polymeric surfaces is dependent upon the degree of polymerization of the substrate. It has been demonstrated for lead, tin and silver that this difference can be made sufficiently great to allow images formed by electron or ultraviolet polymerization to be developed by coating the entire substrate with metal; the metal adhering only to the developed portion of the polymer film. A thin layer of the polymer material is then deposited over the metal layer to form a reliable insulation film and the preferential nucleation process again used to form a second metal film pattern. Multilayer circuit patterns have been fabricated with resolution of several microns. The technique is compatible with conventional thin film evaporation techniques and should be suited for the fabrication of high density, multilayer circuits. PbS t h i n film transistors. W. B. PZ.X.XESAKZR. Solid-State Electronics, Vol. 8, 1965, pp. 509-515. Thin-film transistors were prepared using evaporated PbS films. It is shown that films containing oxidized barriers to the conductivity have very little sensitivity to electric fields. However, nearly intrinsic films show a much larger field effect, and can be switched from n-type to p-type conduction by the field. Effective electron mobilities as high as 260 cm'-'/V-sec were obtained. Interesting effects due to nonuniform fields applied by the gate are illustrated and discussed. While the data can be qualitatively explained in terms of a simple model, the strong frequency dependence is not yet understood. The sensitivity to water vapor indicates, however, that surface states may play a strong role. Mobility variation and capacitive relaxation may also occur. Theoretical characteristics of insulated gate field effect devices. C. Ju.~'D. Solid-State Electronics, Vol. 8, 1965, pp. 375-379. One established a theory of the operation of the insulated gate field effect devices. This analysis takes into account, first, the saturation of the velocity of the carriers at high electric field, second, the presence of surface states at the dielectric semiconductor interface. Two types of operation are to be considered, either the channel is obtained by diffusion or epitaxial process or the channel is an inversion channel. In the second type the presence of surface states is the most important factor of operation. Stresses in evaporated silicon monoxide films. M. A. NOVICE. Vacuum, Vol. 14, pp. 385-392. Deposition pressure and source temperature are two parameters which were investigated and found to have a very significant effect on the stress and physical property of silicon monoxide films. By studying the way these parameters affect the stress introduced both during and after deposition, evaporation conditions may be established which will give rise to low stress, mechanically stable insulating films.
A B S T R A C T S ON M [ C R O E L E C T R O N I C S
AND RELIABILITY
Nucleation and initial g r o w t h o f single-crystal films. R. F. ADAMSKYand R. E. LEBLANC. ffournat
of ['acuum Science Techt, ology, Vol. 2, No. 2, March April 1965, p. 79. The mechanism of epitaxial growth has been investigated by the study of the nucleation process and early growth stages of singlecrystal gold and silver films in (100) and (1"1l) orientations. Films were grown by evaporation on vacuumcleaved NaCI and mica cleavage planes, and on single-crystal NaCI films deposited on fresh mica cleavage surfaces. In the earliest observable period of growth, nuclei have been found to be as small as 5 .\ in size. These nuclei, which contain t0-20 atoms, strongly indicate that growth proceeds continuously from initial nuclei consisting of only a few atoms. In subsequent stages of growth, coalescence processes occur which are governed by mobility of atoms and clusters on the substrate material. Mobility is highest on the evaporated film substrates, a'nd leads to a decrease in nucleation density as a function of time because of rapid coalescence of the mobile nuclei. Nucleation rates have been measured as a function of substrate temperature and activation energies determined for the nucleation process. S u r f a c e adsorption and v a c u u m b r e a k d o w n . W. D. OWE.',-and J. BEY.-,'ox. Vacuum, Vol. 15, 3,o. 3, 1965, p. 123. The authors deal with the mechanism of the so-called "vacuum" electrical breakdown in the pressure range 10 -5 to I0 q ° torr. Electrical conduction at such low pressures is of fundamental interest because the initiation and build-up of current leading to breakdown is not yet fully understood. A parallel plate gap of 0'3 mm was used in the experiments, the applied voltage ranging to 10 kV. It appears that breakdown of the gap at 10 -5 tort is generally preceded by a sudden increase in gap current accompanied by a marked increase in gas pressure, probably due to release of gas from the electrodes under the influence of electron bombardment. This was confirmed by similar experiments at still lower pressures and it seems now established that electrical breakdown in a high vacuum can take place by the Townsend process when a sufficient increase in pressure has taken place.
Formation o f thin film circuits using preferential nucleation. H. L. CASWrLL and Y. BUDO.
Solid-State Electronics, Vol. 8, 1965, pp. 479-483. The binding energy for many metals on polymeric surfaces is dependent upon the degree of polymerization of the substrate. It has been demonstrated for lead, tin and silver that this difference can be made sufficiently great to allow images formed by electron or ultraviolet polymerization to be developed by coating the entire substrate with metal; the metal adhering only to the developed portion of the polymer film. A thin layer of the polymer material is then deposited over the metal layer to form a reliable insulation film and the preferential nucleation process again used to form a second metal film pattern. Multilayer circuit patterns have been fabricated with resolution of several microns. The technique is compatible with conventional thin film evaporation techniques and should be suited for the fabrication of high density, multilayer circuits. PbS t h i n film transistors. W. B. PZ.X.XESAKZR. Solid-State Electronics, Vol. 8, 1965, pp. 509-515. Thin-film transistors were prepared using evaporated PbS films. It is shown that films containing oxidized barriers to the conductivity have very little sensitivity to electric fields. However, nearly intrinsic films show a much larger field effect, and can be switched from n-type to p-type conduction by the field. Effective electron mobilities as high as 260 cm'-'/V-sec were obtained. Interesting effects due to nonuniform fields applied by the gate are illustrated and discussed. While the data can be qualitatively explained in terms of a simple model, the strong frequency dependence is not yet understood. The sensitivity to water vapor indicates, however, that surface states may play a strong role. Mobility variation and capacitive relaxation may also occur. Theoretical characteristics of insulated gate field effect devices. C. Ju.~'D. Solid-State Electronics, Vol. 8, 1965, pp. 375-379. One established a theory of the operation of the insulated gate field effect devices. This analysis takes into account, first, the saturation of the velocity of the carriers at high electric field, second, the presence of surface states at the dielectric semiconductor interface. Two types of operation are to be considered, either the channel is obtained by diffusion or epitaxial process or the channel is an inversion channel. In the second type the presence of surface states is the most important factor of operation. Stresses in evaporated silicon monoxide films. M. A. NOVICE. Vacuum, Vol. 14, pp. 385-392. Deposition pressure and source temperature are two parameters which were investigated and found to have a very significant effect on the stress and physical property of silicon monoxide films. By studying the way these parameters affect the stress introduced both during and after deposition, evaporation conditions may be established which will give rise to low stress, mechanically stable insulating films.