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On the effect of gate oxide thickness upon the hall mobility and other magneto-electrical characteristics in most structures
82
World Abstracts on Microelectronics and Reliability
(110), (100) and evaporated (amorphous) silicon subst rates. The degree of preferred orientation is markedly stronger on [111] Si. Ion channeling measurements confirm that in this case the c-direction of the Pd2Si is parallel with the [111] direction in the underlying Si. A new interpretation of the valence band density of states of amorphous group IV-semiconductors. J. TREUSCH and B. KRAMER. Solid St. Commun. 14, 169 (1974). The disappearance of significant structures in the density of states of the lower (s-like) valence bands of a m o r p h o u s G r o u p 1Vsemiconductors is explained as a consequence of fluctuations in second nearest neighbour positions which lead to an additional pseudopotential coefficient V(2oo). Silicon is treated as an example. An explanation is proposed for the different behaviour of III V compounds, where a doublet structure of the valence band density of states occurs also in the a m o r p h o u s phases. M I S capacitance and derivative of capacitance, with application to non-parabolic band semiconductors. M. MICI~AELand W. F. LEONARD. Solid St. Electron. 17, 71 (1974). Theoretical capacitance ( C - V ) and derivative of capacitance (C' V) curves for an MIS structure with a semiconductor having a non-parabolic conduction band and a parabolic valence band are calculated for single level trap, uniform and nonuniform surface state distributions. The Kane model is used to describe the non-parabolic conduction band. The effects of varying the hole effective mass, Kane matrix element, temperature, surface state densities (both donor and acceptor types), and the degeneracy factors for the surface states is examined. The computed results are based on Hgo.sCdo.zTe ZnS device parameters. On the effect of gate oxide thickness upon the hall mobility and other magneto-electrical characteristics in most structures. J. KASSABOV,N. VELCHEVand V. GANCHEVA.Solid St. Electron. 17, 41 (1974). P-Channel silicon MOS Halltrons with a different thickness of the oxide under the gate are studied. The measurements are performed in steady-state conditions at room temperature and in a weak magnetic field. Some conclusions about the surface conductivity, 8. T H I C K -
AND THIN-FILM
Hall mobility and Hall coefficient of carriers in the channel are given. The magneto-electrical characteristics are presented as a function of space charge, surface potential and free charge at the surface of the semiconductor. An explanation of the decrease of the surface conductivity in the nonlinear part of the curve of surface conductivity vs gate voltage is proposed. Screening of metallization step coverage on integrated circuits. D. L. CROSTHWAIT, JR., P. B. GHATE and D. M SMITH. IEEE l l t h Annual Proceedinys Reliability Physics. 254 (1973). Scanning electron microscopy is widely used to screen step coverage of interconnects on planar semiconductor devices. Utilization of this method has produced many sampling plans. This paper presents the results of a SEM examination of regional and slice-to-slice variances of oxide step contours and metal coverage. High-current pulse testing of aluminum stripes crossing oxide steps was also investigated as an electrical alternative to a SEM screen. The results of this study indicate that when slice-to-slice variances in oxide contour can occur, the quality of metallization must be judged on a slice basis and a SEM examination of each type step in a relatively small region adequately characterizes the slice, Measurement of low densities of surface states at the Si SiO 2interface. G. DECLERCK, R. VAN OVERSTRAETEN and G. BROUX. Solid St. Electronics 16, 1451 (1973). By a careful process Si-SiO2-interfaces can be made with a low oxide charge Qo~ and with a low surface states density N,,. For dry oxides on (100) N~-values as low as a few 10~ cm 2 eV are found on samples with an oxide charge density of 3"0 × 10~°cm 2 Only the Nicollian Goetzbcrger conductance method is proved to give reasonable results on these structures. The quasi-static low frequency C Vtechnique is in good agreement with the conductance technique for samples with N~-values higher than I'0 × 10 j ~ c m - 2 eV 1. The spatial fluctuation of surface potential, mainly caused by oxide charge fluctuations, is an important parameter when studying the high or low frequency C t'characteristics. Some irregularities in the experimental N~, 0-curves are explained.
COMPONENTS,
Thin film vacuum equipment. V. HOFFMAN. Solid St. Technol. 93 (Dec. 1973). In thin film deposition technology, the quality and properties of films are highly dependent upon the equipment utilized; and especially the pressure levels maintained during deposition. The equipment necessary for undertaking vacuum evaporation, sputtering and ion plating is reviewed with emphasis on the film properties. Also discussed are the relative advantages of different deposition sources, substrate fixturing, monitoring and control techniques, and vacuum pumping stations. Detailed data of typical evaporation and sputtering rates are listed for a variety of materials. Evaporation, sputtering and ion-plating; pros and cons. J. E. VARGA and W. A. BAILEY. Solid St. Technol. 79 (1973). The most generally practiced thin-film vacuum deposition methods, namely, evaporation, sputtering and ion-plating are reviewed. In the brief description of the salient features of each method, their advantages and drawbacks are pointed out with regard to obtainable film properties, operational
CIRCUITS
AND MATERIALS
considerations and economy. In as nearly quantitative form as possible, the three methods are compared. This comparison is "normalized" to a twenty-four inch diameter deposition chamber. Finally, the film properties, the operational considerations and the costs associated with each coating method are "'merit rated". Thus, for a specific task the most favorable trade-off selection can be made. Cylindrical diode continuous vacuum sputtering equipment for laboratory and high volume production. C. H. GEORGE. J. Vac. Sci. Technol. 10 (2), 393-397 (Mar. April 1973). To meet anticipated extremely large volume demands for integrated capacitor resistor tantalum thin film circuits, which require six to eight times the sputtering time of resistor circuits only, a cylindrical diode continuous sputtering machine was developed. An experimenta I vacuum head fitted to a 56-cm commerically available bell jar vacuum system and equipped with an air-locked separately pumped magazine was used to prove feasibility of the concept, to solve non-uniformity problems inherent in the cylindrical
World Abstracts on Microelectronics and Reliability
(110), (100) and evaporated (amorphous) silicon subst rates. The degree of preferred orientation is markedly stronger on [111] Si. Ion channeling measurements confirm that in this case the c-direction of the Pd2Si is parallel with the [111] direction in the underlying Si. A new interpretation of the valence band density of states of amorphous group IV-semiconductors. J. TREUSCH and B. KRAMER. Solid St. Commun. 14, 169 (1974). The disappearance of significant structures in the density of states of the lower (s-like) valence bands of a m o r p h o u s G r o u p 1Vsemiconductors is explained as a consequence of fluctuations in second nearest neighbour positions which lead to an additional pseudopotential coefficient V(2oo). Silicon is treated as an example. An explanation is proposed for the different behaviour of III V compounds, where a doublet structure of the valence band density of states occurs also in the a m o r p h o u s phases. M I S capacitance and derivative of capacitance, with application to non-parabolic band semiconductors. M. MICI~AELand W. F. LEONARD. Solid St. Electron. 17, 71 (1974). Theoretical capacitance ( C - V ) and derivative of capacitance (C' V) curves for an MIS structure with a semiconductor having a non-parabolic conduction band and a parabolic valence band are calculated for single level trap, uniform and nonuniform surface state distributions. The Kane model is used to describe the non-parabolic conduction band. The effects of varying the hole effective mass, Kane matrix element, temperature, surface state densities (both donor and acceptor types), and the degeneracy factors for the surface states is examined. The computed results are based on Hgo.sCdo.zTe ZnS device parameters. On the effect of gate oxide thickness upon the hall mobility and other magneto-electrical characteristics in most structures. J. KASSABOV,N. VELCHEVand V. GANCHEVA.Solid St. Electron. 17, 41 (1974). P-Channel silicon MOS Halltrons with a different thickness of the oxide under the gate are studied. The measurements are performed in steady-state conditions at room temperature and in a weak magnetic field. Some conclusions about the surface conductivity, 8. T H I C K -
AND THIN-FILM
Hall mobility and Hall coefficient of carriers in the channel are given. The magneto-electrical characteristics are presented as a function of space charge, surface potential and free charge at the surface of the semiconductor. An explanation of the decrease of the surface conductivity in the nonlinear part of the curve of surface conductivity vs gate voltage is proposed. Screening of metallization step coverage on integrated circuits. D. L. CROSTHWAIT, JR., P. B. GHATE and D. M SMITH. IEEE l l t h Annual Proceedinys Reliability Physics. 254 (1973). Scanning electron microscopy is widely used to screen step coverage of interconnects on planar semiconductor devices. Utilization of this method has produced many sampling plans. This paper presents the results of a SEM examination of regional and slice-to-slice variances of oxide step contours and metal coverage. High-current pulse testing of aluminum stripes crossing oxide steps was also investigated as an electrical alternative to a SEM screen. The results of this study indicate that when slice-to-slice variances in oxide contour can occur, the quality of metallization must be judged on a slice basis and a SEM examination of each type step in a relatively small region adequately characterizes the slice, Measurement of low densities of surface states at the Si SiO 2interface. G. DECLERCK, R. VAN OVERSTRAETEN and G. BROUX. Solid St. Electronics 16, 1451 (1973). By a careful process Si-SiO2-interfaces can be made with a low oxide charge Qo~ and with a low surface states density N,,. For dry oxides on (100) N~-values as low as a few 10~ cm 2 eV are found on samples with an oxide charge density of 3"0 × 10~°cm 2 Only the Nicollian Goetzbcrger conductance method is proved to give reasonable results on these structures. The quasi-static low frequency C Vtechnique is in good agreement with the conductance technique for samples with N~-values higher than I'0 × 10 j ~ c m - 2 eV 1. The spatial fluctuation of surface potential, mainly caused by oxide charge fluctuations, is an important parameter when studying the high or low frequency C t'characteristics. Some irregularities in the experimental N~, 0-curves are explained.
COMPONENTS,
Thin film vacuum equipment. V. HOFFMAN. Solid St. Technol. 93 (Dec. 1973). In thin film deposition technology, the quality and properties of films are highly dependent upon the equipment utilized; and especially the pressure levels maintained during deposition. The equipment necessary for undertaking vacuum evaporation, sputtering and ion plating is reviewed with emphasis on the film properties. Also discussed are the relative advantages of different deposition sources, substrate fixturing, monitoring and control techniques, and vacuum pumping stations. Detailed data of typical evaporation and sputtering rates are listed for a variety of materials. Evaporation, sputtering and ion-plating; pros and cons. J. E. VARGA and W. A. BAILEY. Solid St. Technol. 79 (1973). The most generally practiced thin-film vacuum deposition methods, namely, evaporation, sputtering and ion-plating are reviewed. In the brief description of the salient features of each method, their advantages and drawbacks are pointed out with regard to obtainable film properties, operational
CIRCUITS
AND MATERIALS
considerations and economy. In as nearly quantitative form as possible, the three methods are compared. This comparison is "normalized" to a twenty-four inch diameter deposition chamber. Finally, the film properties, the operational considerations and the costs associated with each coating method are "'merit rated". Thus, for a specific task the most favorable trade-off selection can be made. Cylindrical diode continuous vacuum sputtering equipment for laboratory and high volume production. C. H. GEORGE. J. Vac. Sci. Technol. 10 (2), 393-397 (Mar. April 1973). To meet anticipated extremely large volume demands for integrated capacitor resistor tantalum thin film circuits, which require six to eight times the sputtering time of resistor circuits only, a cylindrical diode continuous sputtering machine was developed. An experimenta I vacuum head fitted to a 56-cm commerically available bell jar vacuum system and equipped with an air-locked separately pumped magazine was used to prove feasibility of the concept, to solve non-uniformity problems inherent in the cylindrical