- Email: [email protected]
Electronic apparatus for measuring silver layer thickness on mirrors by means of eddy currents
Classified Abstracts 846--851
329
emission from emitter to base, and an alternative~space-charge limited injection theory.
of 10 -s torr. The resultant film is unattached by most of the etching baths used in semiconductor techniques, w.J.s.
G. T. Advani, et. al., Proc. Inst..Rad: Engrs., 50, June and July 1962, 1530 ; D. V. Geppert, ibid, 1527 ; D. Kahng, ibid, 1534; J. M. Levine, et. al., ibid, 1688-1689.
J. Delinas and M. Chappey, Le Vide, 18 (104), March/April 1963, 89-94.
30 : 56 846. The T.F.T., a new thin film transistor. U.S.A. This paper describes the construction and performance of a transistor of the " field-effect " type, constructed by thin film deposition. Unlike the conventional transistor, this device operates by the injection of majority carriers in this case into a semi-conductor---cadmium sulphide--having a wide energy gap. The transistor is built up on an insulating substrate by evaporating first two parallel strips of g o l d which act eventually as source and drain electrodes, then evaporating a layer of microcrystalline cadmium sulphide to cover the source and drain (except for two contact areas), thirdly, covering the semi-conductor with an insulating spacer layer of silicon monoxide, and finally evaporating another gold strip on top of the assembly. This latter is thus at the opposite side of the semi-conductor from the source and drain, and is opposite the gap between them. It is the control electrode, and known as the gate. A fine wire grille was used as a mask to allow deposition of a number of gold strips, to form electrodes of a number of devices, at the same time ; movement of the substrate before depositing the second set of strips controlled the source/gate spacing. Typical dimensions were : Semi-conductor layer 1 tzm thick, spacing between source and drain 5-50 ~m. Some alternative structures are also discussed, (a) in which the order of deposition is opposite to that outlined above : (b) in which all the electrodes are on the same side of the semi-conductor layer ; (c) a number of pairs of source and drain strips connected together to allow increased power dissipation; (d) a pentode-like structure using three " gates " ; and (e) a layer structure. In operation, the gate potential controls current flowing from source to drain, and pentode-like characteristics are shown for drain voltage and current in the ranges 0-10 V, 0-10 mA. There is an " enrichment " mode of operation, in which the gate is made positive by a few volts, effectively increasing the conductivity, and an alternative " depletion " mode, in which the gate is negative and operates by progressively " pinching o f f " the channel between source and drain. In either case, the gate offers a high-impedance control point, because of the insulating layer through which it acts. Some sim~le expressions for mutual conductance and gain-bandwidth product are derived ; typical figures so far obtained in practice are 25 mA/V, and 17 Mc/s, respectively. Current densities as high as 1000 Acm -2 are possible. M.D.A. P. K. Weimer, Proc. Inst. Rad. Engrs., 50[ June 1962, 1462-1469. 30 : 56 847, Capacitance between thin film conductors deposited on substrates of high relative permittivity. H. R. Kaiser and P. S. Castro, Proc. Instr. Rad. Engrs., 50, Oct. 1962, 2142. 30 56 848. The technique of depositing thin metallic films very close to each other in a vacuum and application of the method to the manufacture of field-effect transistors. France. The authors described how, by means of a suitable mask, thin layers of Cr and Au can be deposited by vacuum evaporation on a silicon crystal leaving a narrow line of discontinuity ( ~ 1 ~ wide) across the surface. The process is used in the manufacture of field effect transistors where the discontinuity forms a narrow channel between the electrodes contacting the metal film on the surface of the crystal. By means of this technique much narrower channels can be obtained than by the conventional photo-engraving process. The deposits are produced by successive evaporation of Cr and Au at pressures of the order
30 : 19 : 42 849. Comparison of two methods for measuring the thickness of thin co~atings of oxide films on :silicon. France. The tWO methods described are both optical. In the first the colour of the oxide is noted when viewed at normal incidence and the thickness determined from Newton's colour scale. The accuracy is better than ± 5 per cent in most cases, and ± 1 0 per cent for film thicknesses in excess of 10-~mm. The second method consists of measuring the desplacement of monochromatic interference fringes of equal thickness on passing a straight edge which has been coated with silver evaporated in vacuum. The accuracy in this case is of the order of ~-90/~. Oxide films on silicon are of importance in semi-conductor techniques due to their masking and protecting qualities. Thus, a knowledge of their thickness is of importance. In most cases an accuracy of 10 per cent. is sufficient and the first simple method can be used for films between 10 -4 and 10-3mm thick. W . J . S.
J. Eucinas, Le Vide, 18 (104), March/April 1963, 95-99. 30 : 19 850. Thin film thickness measurement using silver-modified Newton's rings. U.S.A. Many interference techniques have been employed for the thickness measurement of thin films. An interference technique which is inexpensive and easy to operate consists of a silvered lens placed over a stepped film with silver overlay. 'The resultant interference pattern when viewed in reflection is a series of sharp dark rings against a bright background, modified Newton's rings. The step in the film to be measured causes a shift in the rings from which the thickness is calculated. Step heights in silver films, vacuum deposited on fire-polished microscope slides, of 160 and 170A were measured. (Author) B. J. Stern, Rev. Sci. Instrum., 34 (2), Feb. 1963, 152-155. 30 : 56 851. Vapour sources for vacuum deposition of superconductive thin-film circuitry. U.S.A. Radiatively-heated ovens have been used as vapour sources for vacuum deposition of superconductive films, primarily tin and lead. They delivered uniform deposition rates in the entire range tested from tenths of angstroms per second to 100 A/sec. For the experimental arrangement employed, a deposition rate of 1/~/sec. is found by calculation to correspond to an effusion rate from the oven of 2 × 10-Smoles/cm2/sec. By effectively reducing the length of the oven opening to zero and increasing the ratio of oven diameter to opening diameter to about four, an emission characteristic of a surface source was obtained for the same range of deposition rates. For one such oven of typical dimensions, a chart is included by use of which compromise may be made between effective source enlargement, due to self-scattering effects at the source, and deposition rate. (Authors) A. J. Learn and R. S. Spriggs, Rev. Sci. Instrum., 34 (2), Feb. 1963, 179-182. 30 : 41 : 33 Domain pattern in eleetrodeposited nickel-iron thin films. See Abstr. No. 861. 30 • 56 Electronic apparatus for measuring silver layer thickness on mirrors by means of eddy currents. See Abstr. No. 877.
329
emission from emitter to base, and an alternative~space-charge limited injection theory.
of 10 -s torr. The resultant film is unattached by most of the etching baths used in semiconductor techniques, w.J.s.
G. T. Advani, et. al., Proc. Inst..Rad: Engrs., 50, June and July 1962, 1530 ; D. V. Geppert, ibid, 1527 ; D. Kahng, ibid, 1534; J. M. Levine, et. al., ibid, 1688-1689.
J. Delinas and M. Chappey, Le Vide, 18 (104), March/April 1963, 89-94.
30 : 56 846. The T.F.T., a new thin film transistor. U.S.A. This paper describes the construction and performance of a transistor of the " field-effect " type, constructed by thin film deposition. Unlike the conventional transistor, this device operates by the injection of majority carriers in this case into a semi-conductor---cadmium sulphide--having a wide energy gap. The transistor is built up on an insulating substrate by evaporating first two parallel strips of g o l d which act eventually as source and drain electrodes, then evaporating a layer of microcrystalline cadmium sulphide to cover the source and drain (except for two contact areas), thirdly, covering the semi-conductor with an insulating spacer layer of silicon monoxide, and finally evaporating another gold strip on top of the assembly. This latter is thus at the opposite side of the semi-conductor from the source and drain, and is opposite the gap between them. It is the control electrode, and known as the gate. A fine wire grille was used as a mask to allow deposition of a number of gold strips, to form electrodes of a number of devices, at the same time ; movement of the substrate before depositing the second set of strips controlled the source/gate spacing. Typical dimensions were : Semi-conductor layer 1 tzm thick, spacing between source and drain 5-50 ~m. Some alternative structures are also discussed, (a) in which the order of deposition is opposite to that outlined above : (b) in which all the electrodes are on the same side of the semi-conductor layer ; (c) a number of pairs of source and drain strips connected together to allow increased power dissipation; (d) a pentode-like structure using three " gates " ; and (e) a layer structure. In operation, the gate potential controls current flowing from source to drain, and pentode-like characteristics are shown for drain voltage and current in the ranges 0-10 V, 0-10 mA. There is an " enrichment " mode of operation, in which the gate is made positive by a few volts, effectively increasing the conductivity, and an alternative " depletion " mode, in which the gate is negative and operates by progressively " pinching o f f " the channel between source and drain. In either case, the gate offers a high-impedance control point, because of the insulating layer through which it acts. Some sim~le expressions for mutual conductance and gain-bandwidth product are derived ; typical figures so far obtained in practice are 25 mA/V, and 17 Mc/s, respectively. Current densities as high as 1000 Acm -2 are possible. M.D.A. P. K. Weimer, Proc. Inst. Rad. Engrs., 50[ June 1962, 1462-1469. 30 : 56 847, Capacitance between thin film conductors deposited on substrates of high relative permittivity. H. R. Kaiser and P. S. Castro, Proc. Instr. Rad. Engrs., 50, Oct. 1962, 2142. 30 56 848. The technique of depositing thin metallic films very close to each other in a vacuum and application of the method to the manufacture of field-effect transistors. France. The authors described how, by means of a suitable mask, thin layers of Cr and Au can be deposited by vacuum evaporation on a silicon crystal leaving a narrow line of discontinuity ( ~ 1 ~ wide) across the surface. The process is used in the manufacture of field effect transistors where the discontinuity forms a narrow channel between the electrodes contacting the metal film on the surface of the crystal. By means of this technique much narrower channels can be obtained than by the conventional photo-engraving process. The deposits are produced by successive evaporation of Cr and Au at pressures of the order
30 : 19 : 42 849. Comparison of two methods for measuring the thickness of thin co~atings of oxide films on :silicon. France. The tWO methods described are both optical. In the first the colour of the oxide is noted when viewed at normal incidence and the thickness determined from Newton's colour scale. The accuracy is better than ± 5 per cent in most cases, and ± 1 0 per cent for film thicknesses in excess of 10-~mm. The second method consists of measuring the desplacement of monochromatic interference fringes of equal thickness on passing a straight edge which has been coated with silver evaporated in vacuum. The accuracy in this case is of the order of ~-90/~. Oxide films on silicon are of importance in semi-conductor techniques due to their masking and protecting qualities. Thus, a knowledge of their thickness is of importance. In most cases an accuracy of 10 per cent. is sufficient and the first simple method can be used for films between 10 -4 and 10-3mm thick. W . J . S.
J. Eucinas, Le Vide, 18 (104), March/April 1963, 95-99. 30 : 19 850. Thin film thickness measurement using silver-modified Newton's rings. U.S.A. Many interference techniques have been employed for the thickness measurement of thin films. An interference technique which is inexpensive and easy to operate consists of a silvered lens placed over a stepped film with silver overlay. 'The resultant interference pattern when viewed in reflection is a series of sharp dark rings against a bright background, modified Newton's rings. The step in the film to be measured causes a shift in the rings from which the thickness is calculated. Step heights in silver films, vacuum deposited on fire-polished microscope slides, of 160 and 170A were measured. (Author) B. J. Stern, Rev. Sci. Instrum., 34 (2), Feb. 1963, 152-155. 30 : 56 851. Vapour sources for vacuum deposition of superconductive thin-film circuitry. U.S.A. Radiatively-heated ovens have been used as vapour sources for vacuum deposition of superconductive films, primarily tin and lead. They delivered uniform deposition rates in the entire range tested from tenths of angstroms per second to 100 A/sec. For the experimental arrangement employed, a deposition rate of 1/~/sec. is found by calculation to correspond to an effusion rate from the oven of 2 × 10-Smoles/cm2/sec. By effectively reducing the length of the oven opening to zero and increasing the ratio of oven diameter to opening diameter to about four, an emission characteristic of a surface source was obtained for the same range of deposition rates. For one such oven of typical dimensions, a chart is included by use of which compromise may be made between effective source enlargement, due to self-scattering effects at the source, and deposition rate. (Authors) A. J. Learn and R. S. Spriggs, Rev. Sci. Instrum., 34 (2), Feb. 1963, 179-182. 30 : 41 : 33 Domain pattern in eleetrodeposited nickel-iron thin films. See Abstr. No. 861. 30 • 56 Electronic apparatus for measuring silver layer thickness on mirrors by means of eddy currents. See Abstr. No. 877.