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Discharge of MNOS structures at elevated temperatures
World Abstracts on Microelectronics and Reliability maxima of which occur at 0.4 eV and 0.74 eV below the bottom of the conduction band. The results of the two techniques compared extremely well, lending confidence to the techniques. It is demonstrated that the techniques are capable of detecting small changes in the trap density, such as might occur due to ageing or temperature cycling. Impurity bands in moderately doped semiconductors and their effect of the MOS C - V freeze-out characteristics. H. D. BARBER, K. C. LEE and J. ERLE JONES. Solid-State Electronics 19, 365 (1976). An impurity concentration and temperature dependent model of the impurity band is presented for moderately doped semiconductors. This model is then applied to explain the freezing-out MOS C - V characteristics of 1.98 × 10 ~s cm -3 p-silicon. The results show that the shape of the impurity band and its temperature dependence significantly affect the shape of the C - V curve and its temperature dependence. The electron-hole drop and the impurity-induced semiconductor-metal transition. G. MAHLER and J. L. BIRMAN. Solid State Commun. 17, 1381 (1975). It is shown that metallic condensation should occur in Si even under condition of heavy doping. The density of delocalized donorelectrons strongly influences the equilibrium density of holes within the drop and in that fashion the half-width of the electron-hole recombination line. It is therefore possible to derive properties of the semiconductor-metal transition from a study of the electron-hole drop in doped samples. This is confirmed by an application to Si : P. Space-charge effect on excess carrier transport in semiconductors. Part II. Time evolution of the space-charge of excess carriers. ANDRZEJ OSTROWSKI. Electron Technology 8. (1) 43 (1975). In this part of the paper, time evolution of total space-charge produced by excess carrier generation of arbitrary space distribution, time-dependent and not necessarily neutral is studied. General expressions are derived for the total number of excess carriers and the moment of space-charge distribution for arbitrary form of generation function. Next, these expressions are specified for particular cases of generation : pulse, pulse neutral and periodic. The electronic properties of epitaxial layers. H. F. MATARE. Solid State Technology p. 36 (Feb. 1976). The particular case of the III-V heterojunction for light emission is developed and the reasons for the excellent properties for radiative recombination are outlined. The particular features of the Ga~All_xAs/GaAs junction with respect to dopant concentration and stoichiometry are considered and the influence of the temperature gradient for large size melts during liquid epitaxy is shown. A typical case of the chemical analysis of epitaxial layers using a microprobe is discussed. Layer stoichiometry can also be derived from measurements of photoluminescence and a refined method using modulated light injection combined with a double monochromator set-up is described. Furthermore, the wealth of available particle-injection methods (ions, electrons, nucleons, infrared radiation, molecular beams, thermal methods and X-rays) is briefly summarized and documented. Transient isothermal generation at the silicon-silicon oxide interface and the direct determination of interface trap distribution. J. G. SIMMONS and H. A. MAR. Solid-State Electronics 19, 369 (1976). The theory of transient isothermal generation through the the interface traps at the semiconductor-insulator interface is presented. The generation current (ly) vs time (t) characteristic is obtained in terms of the interface trap distribution throughout the bandgap.
185
It is shown that a plot of l,,t vs logJ is a direct image of the energy distribution of the traps in the upper-half of the bandgap (in the case of an n-type semiconductor) and a plot of Igt vs loget is a direct image of the trap distribution in the lower-half of the bandgap. Frozen-in native defects in semiconductor compounds. K. I. HAGEMARK.J. phys. Chem. Solids 37. 461 (1976). A semiconductor compound M X is discussed from a thermodynamic point of view. The concentrations of some possible native point defects have been calculated as functions of the two thermodynamic parameters temperature T, and partial pressure of M, Pu. Three cases are discussed: (A) Complete equilibrium (M and X atoms are mobile). (B) Frozen-in X atoms only. (C) Completely frozen-in M and X atoms. In the two latter cases a two component-two phase system has three degrees of freedom, not two, as in the case of a complete equilibrium. Thus, the calculations illustrate the importance of the "'thermal history" of a crystal. Non-parabolicity and transverse mass of electron carriers in silicon. L. M. FALICOV. Solid State Commun. 18, (5) 669 (1976). It is shown that band structure effects give a small but not negligible contribution to the transverse cyclotron mass enhancement in silicon [100] field effect transistor devices. For carrier concentrations of about 8 x 1012 electrons per cm 2 the mass increases by approximately Am* = 0.005, i.e. 2.4%. In opposition to the many-body corrections, the band structure enhancement increases with concentration. Resonant interaction of acceptor states and optical phonons in silicon. H. R. CHANDRASEKHAR,A. K. RAMDAS and S. RODRIGUEZ. Solid State Commun. 18, (3) 405 (1976). The resonance broadening of line 2 in the excitation spectrum of gallium acceptors in silicon due to near coincidence of its energy with that of the zone center optical phonons, h~oo, has been confirmed under significantly improved experimental conditions. An additional feature labeled X and line 2 are interpreted as mixed excitations of the boundhole and the optical phonon. Under uniaxial stress, the stress induced components of line 2 which approach hco0 become more phonon-like and get "pinned" while the components of X become bound-hole-like as they recede from hco0, and exhibit a striking increase in intensity. Irradiation-induced compensation of n-type germaniumelectrical measurements. A. F. LEHAR and J. E. WHITEHOUSE. Solid State Commun. 17, (12) 1609 (1975). The temperature dependence of the Hall effect in an n-type germanium sample following each of a series of 2 MeV electron irradiations at 80 K has been analysed. It is shown that conversion to p-type proceeds by the introduction of defects which are acceptors contrary to the suggestion made recently that conversion proceeds by the removal of donors. Density of states determination of mixed semiconductors by neutron diffraction. R. BESERMAN and M. ZIGONE. W. DREXEL and C. MARTI. Solid State Commun. 18, (3) 419 (1976). The phonon density of states of mixed crystals has been determined by neutron diffraction in powders. In the "two mode type" mixed crystal ZnSxSe~_~, the great features of the host lattice density of states, are not modified up to an "'impurity" concentration of 25~o. On the other hand, the presence of Te in ZnSe~Tel_~ with x = 0.25, give rise to a "one-mode type" mixed crystal, the density of states of which is an average of that of the two components. These results justify that the eigenfrequencies of a twomodes type mixed crystal can be calculated using the un-
186
World Abstracts on Microelectronics and Reliability
perturbed host lattice density of states (additivity of Green's function).
Discharge of MNOS structures at elevated temperatures. LEIF LUNDKVIST.CHRISTER SVENSSONand BERTIL HANSSON. Solid-State Electronics 19, 221 (1976). The discharge behavior of MNOS structures without voltage applied, is investigated at temperatures from 25 to 300°C, for times from 10 min to about 1 week. The observed discharge behavior is explained by a theoretical model, including two discharge processes. The two processes are direct tunneling from traps and thermal excitation of these traps. It is shown that static retention times of more than 10 yr at 85~C is attainable. Also, discharge with voltage applied is investigated and shown to agree with the model when the voltage is small enough.
Fabrication and characteristics of MOS-FET's incorporating anodic aluminum oxide in the gate structure. R. K. RAYMOND and MUKUNDA B. DAS. Solid-State Eh,ctronic,s 19, 181 (1976). Anodic aluminum oxide films have been grown by means of a simple process which is compatible with the existing planar silicon IC fabrication technology. Device structures have been fabricated and tested in order to demonstrate the usefulness of anodized layers of evaporated aluminum in a multiple layer metallization scheme.
Results of anodization of thin aluminum layers on a silicon substrate indicate complete conversion of aluminum into aluminum oxide and in addition, formation of a thin underlying layer of silicon dioxide. For the anodic aluminum oxide a growth rate of 11.5 A/volt at a current density of 0.5 mA/cm 2 has been found to produce quite satisfactory quality of insulting layers. Experimental results are presented illustrating the C-V and l.-V characteristics of p-channel M O S - F E T ' s with both the partially anodized stacked-gate structure and the over-anodized double-oxide layer gate structure.
Theoretical and experimental study of MOS transistors nonuniformly doped by SILOX technique. G. DOUCET, F. VAN DE WIELE and P. JESPERS. Solid-State Electronics 19, 191 (1976). A simple one-dimensional analytical model is presented for MOS transistors having a single type net impurity concentration substrate which is non uniform. Closed form expressions for the drain current, the threshold voltage, the pinchoff voltage and the low frequency small-signal parameters are given as a function of the equilibrium majority carrier distribution. Experimental results for n-channel MOS transistors nonuniformly doped by means of the SILOX process are presented and compared to the results of the theoretical model. The SILOX process is described in Section 5
8. THICK- AND THIN-FILM COMPONENTS, HYBRID CIRCUITS
AND MATERIALS Thick-film advances simplify complex hybrid module design. Prof. PETER KIRBY. Electronic Engineering p. 35 (March 1976). Hybrid thick-film circuits are now being produced in large quantities for many applications throughout the world. A superficial examination of product might suggest that there has been little change in the technology since the thick-film hybrid process originated in the early 1960s. This is incorrect. Every state of the production process has been the subject of significant improvement. A thick-film wide band amplifier. D. R. HETHERINTON. IERE Col!f. Hybrid Microelectronics, Loughborough p. 69. 9-11 Sept. 1975. The paper describes the conversion from printed circuit to thick-film hybrid circuit technology of a wide band amplifier used in the input of a video tape recorder, The amplifier specification is 14 dB gain from 40 to 860 mHz. The thick-film layout is described in detail and the performance differences between plastic 'T' pack active devices and naked chip epoxy bonded devices are shown. A fast thick-film amplifier. J. ROBERTSON and B. ANDERSON. IERE Coqfi Hybrid Microelectronics, Loughborough p. 77. 9 11 Sept. 1975, This paper describes a thick-film hybrid preamplifier which was produced as a joint venture between Nuclear Enterprises Limited and Edinburgh University. The preamplifier functioned as an amplifier with a 50fl input impedance between a photomultiplier tube and a discriminator stage. It was designed to provide a gain of 4 with a risetime < 1 nsec. Small size was dictated by transit time and capacitance considerations but also by the requirement to stack 8 preamplifier circuits vertically within a 1,35 in. (34.3 ram) wide NIMS module.
Thick-film directional coupler design--a comparison of theories. PETER L. BAINBRIDGEand RONALD J. ROBERTSON. IERE Co~f Hybrid Microelectronics, Loughborough p. 83. 9 11 Sept. 1975. The paper describes the design of 10 dB and 20 dB directional couplers using two different theories.
One method used computer programmes to determine the dimensions and the other used design data curves. The performance of the thick-film couplers in the frequency range 1 2 GHz is compared and various improvements are suggested.
High frequency characteristics of meandering line-resistors with regard to the design of thin-film circuits. H. GRUNDNER and H. FECHNER. IERE Conf. Hybrid Microelectronics. Loughborough p. 63.9-1t Sept. 1975. The paper describes the high frequency behaviour of meandering line-resistors manufactured in thin-film technology. By means of a developed lumped-distributed model the frequency characteristic of such resistors in an arbitrary rectangular area is computed. The results, which are in good agreement with the outcome of measurements are plotted in diagrams. For a given power requirement, resistor area, resistance valuc and a required limiting frequency one can get quickly the shape of the meandering lines, the resistor-line width and the number of squares for a resistor, fulfilling the required frequency-specification.
A hybrid thin-film multichannel biotelemetry transmitter. JOHN H. FILSHIE and IAIN J. MCGEE. IERE Conf. Hybrid Microelectronies, Loughborough p. 49. 9 11 Sept. 1975. The requirements of a modern biotelemetry system are discussed together with the problems of measuring biological parameters. Hybrid thin-film methods provide a good solution to the problem. Multi-channel F M / F M VHF radiotransmitters for measuring temperature and biopotentials have been designed and constructed. A radio-frequencyoperated switch is also described which allows implanted transmitters to be switched remotely.
A simple hybrid thick-film hand pass filter. D. P. HEYWOOD. IERE Conf. Hybrid Microelectronics, Loughborough p. 43. 9-11 Sept. 1975. It is shown that inductors can be replaced by a very simple form of gyrator for filters demanding only moderate values of Q, giving a saving in space and
185
It is shown that a plot of l,,t vs logJ is a direct image of the energy distribution of the traps in the upper-half of the bandgap (in the case of an n-type semiconductor) and a plot of Igt vs loget is a direct image of the trap distribution in the lower-half of the bandgap. Frozen-in native defects in semiconductor compounds. K. I. HAGEMARK.J. phys. Chem. Solids 37. 461 (1976). A semiconductor compound M X is discussed from a thermodynamic point of view. The concentrations of some possible native point defects have been calculated as functions of the two thermodynamic parameters temperature T, and partial pressure of M, Pu. Three cases are discussed: (A) Complete equilibrium (M and X atoms are mobile). (B) Frozen-in X atoms only. (C) Completely frozen-in M and X atoms. In the two latter cases a two component-two phase system has three degrees of freedom, not two, as in the case of a complete equilibrium. Thus, the calculations illustrate the importance of the "'thermal history" of a crystal. Non-parabolicity and transverse mass of electron carriers in silicon. L. M. FALICOV. Solid State Commun. 18, (5) 669 (1976). It is shown that band structure effects give a small but not negligible contribution to the transverse cyclotron mass enhancement in silicon [100] field effect transistor devices. For carrier concentrations of about 8 x 1012 electrons per cm 2 the mass increases by approximately Am* = 0.005, i.e. 2.4%. In opposition to the many-body corrections, the band structure enhancement increases with concentration. Resonant interaction of acceptor states and optical phonons in silicon. H. R. CHANDRASEKHAR,A. K. RAMDAS and S. RODRIGUEZ. Solid State Commun. 18, (3) 405 (1976). The resonance broadening of line 2 in the excitation spectrum of gallium acceptors in silicon due to near coincidence of its energy with that of the zone center optical phonons, h~oo, has been confirmed under significantly improved experimental conditions. An additional feature labeled X and line 2 are interpreted as mixed excitations of the boundhole and the optical phonon. Under uniaxial stress, the stress induced components of line 2 which approach hco0 become more phonon-like and get "pinned" while the components of X become bound-hole-like as they recede from hco0, and exhibit a striking increase in intensity. Irradiation-induced compensation of n-type germaniumelectrical measurements. A. F. LEHAR and J. E. WHITEHOUSE. Solid State Commun. 17, (12) 1609 (1975). The temperature dependence of the Hall effect in an n-type germanium sample following each of a series of 2 MeV electron irradiations at 80 K has been analysed. It is shown that conversion to p-type proceeds by the introduction of defects which are acceptors contrary to the suggestion made recently that conversion proceeds by the removal of donors. Density of states determination of mixed semiconductors by neutron diffraction. R. BESERMAN and M. ZIGONE. W. DREXEL and C. MARTI. Solid State Commun. 18, (3) 419 (1976). The phonon density of states of mixed crystals has been determined by neutron diffraction in powders. In the "two mode type" mixed crystal ZnSxSe~_~, the great features of the host lattice density of states, are not modified up to an "'impurity" concentration of 25~o. On the other hand, the presence of Te in ZnSe~Tel_~ with x = 0.25, give rise to a "one-mode type" mixed crystal, the density of states of which is an average of that of the two components. These results justify that the eigenfrequencies of a twomodes type mixed crystal can be calculated using the un-
186
World Abstracts on Microelectronics and Reliability
perturbed host lattice density of states (additivity of Green's function).
Discharge of MNOS structures at elevated temperatures. LEIF LUNDKVIST.CHRISTER SVENSSONand BERTIL HANSSON. Solid-State Electronics 19, 221 (1976). The discharge behavior of MNOS structures without voltage applied, is investigated at temperatures from 25 to 300°C, for times from 10 min to about 1 week. The observed discharge behavior is explained by a theoretical model, including two discharge processes. The two processes are direct tunneling from traps and thermal excitation of these traps. It is shown that static retention times of more than 10 yr at 85~C is attainable. Also, discharge with voltage applied is investigated and shown to agree with the model when the voltage is small enough.
Fabrication and characteristics of MOS-FET's incorporating anodic aluminum oxide in the gate structure. R. K. RAYMOND and MUKUNDA B. DAS. Solid-State Eh,ctronic,s 19, 181 (1976). Anodic aluminum oxide films have been grown by means of a simple process which is compatible with the existing planar silicon IC fabrication technology. Device structures have been fabricated and tested in order to demonstrate the usefulness of anodized layers of evaporated aluminum in a multiple layer metallization scheme.
Results of anodization of thin aluminum layers on a silicon substrate indicate complete conversion of aluminum into aluminum oxide and in addition, formation of a thin underlying layer of silicon dioxide. For the anodic aluminum oxide a growth rate of 11.5 A/volt at a current density of 0.5 mA/cm 2 has been found to produce quite satisfactory quality of insulting layers. Experimental results are presented illustrating the C-V and l.-V characteristics of p-channel M O S - F E T ' s with both the partially anodized stacked-gate structure and the over-anodized double-oxide layer gate structure.
Theoretical and experimental study of MOS transistors nonuniformly doped by SILOX technique. G. DOUCET, F. VAN DE WIELE and P. JESPERS. Solid-State Electronics 19, 191 (1976). A simple one-dimensional analytical model is presented for MOS transistors having a single type net impurity concentration substrate which is non uniform. Closed form expressions for the drain current, the threshold voltage, the pinchoff voltage and the low frequency small-signal parameters are given as a function of the equilibrium majority carrier distribution. Experimental results for n-channel MOS transistors nonuniformly doped by means of the SILOX process are presented and compared to the results of the theoretical model. The SILOX process is described in Section 5
8. THICK- AND THIN-FILM COMPONENTS, HYBRID CIRCUITS
AND MATERIALS Thick-film advances simplify complex hybrid module design. Prof. PETER KIRBY. Electronic Engineering p. 35 (March 1976). Hybrid thick-film circuits are now being produced in large quantities for many applications throughout the world. A superficial examination of product might suggest that there has been little change in the technology since the thick-film hybrid process originated in the early 1960s. This is incorrect. Every state of the production process has been the subject of significant improvement. A thick-film wide band amplifier. D. R. HETHERINTON. IERE Col!f. Hybrid Microelectronics, Loughborough p. 69. 9-11 Sept. 1975. The paper describes the conversion from printed circuit to thick-film hybrid circuit technology of a wide band amplifier used in the input of a video tape recorder, The amplifier specification is 14 dB gain from 40 to 860 mHz. The thick-film layout is described in detail and the performance differences between plastic 'T' pack active devices and naked chip epoxy bonded devices are shown. A fast thick-film amplifier. J. ROBERTSON and B. ANDERSON. IERE Coqfi Hybrid Microelectronics, Loughborough p. 77. 9 11 Sept. 1975, This paper describes a thick-film hybrid preamplifier which was produced as a joint venture between Nuclear Enterprises Limited and Edinburgh University. The preamplifier functioned as an amplifier with a 50fl input impedance between a photomultiplier tube and a discriminator stage. It was designed to provide a gain of 4 with a risetime < 1 nsec. Small size was dictated by transit time and capacitance considerations but also by the requirement to stack 8 preamplifier circuits vertically within a 1,35 in. (34.3 ram) wide NIMS module.
Thick-film directional coupler design--a comparison of theories. PETER L. BAINBRIDGEand RONALD J. ROBERTSON. IERE Co~f Hybrid Microelectronics, Loughborough p. 83. 9 11 Sept. 1975. The paper describes the design of 10 dB and 20 dB directional couplers using two different theories.
One method used computer programmes to determine the dimensions and the other used design data curves. The performance of the thick-film couplers in the frequency range 1 2 GHz is compared and various improvements are suggested.
High frequency characteristics of meandering line-resistors with regard to the design of thin-film circuits. H. GRUNDNER and H. FECHNER. IERE Conf. Hybrid Microelectronics. Loughborough p. 63.9-1t Sept. 1975. The paper describes the high frequency behaviour of meandering line-resistors manufactured in thin-film technology. By means of a developed lumped-distributed model the frequency characteristic of such resistors in an arbitrary rectangular area is computed. The results, which are in good agreement with the outcome of measurements are plotted in diagrams. For a given power requirement, resistor area, resistance valuc and a required limiting frequency one can get quickly the shape of the meandering lines, the resistor-line width and the number of squares for a resistor, fulfilling the required frequency-specification.
A hybrid thin-film multichannel biotelemetry transmitter. JOHN H. FILSHIE and IAIN J. MCGEE. IERE Conf. Hybrid Microelectronies, Loughborough p. 49. 9 11 Sept. 1975. The requirements of a modern biotelemetry system are discussed together with the problems of measuring biological parameters. Hybrid thin-film methods provide a good solution to the problem. Multi-channel F M / F M VHF radiotransmitters for measuring temperature and biopotentials have been designed and constructed. A radio-frequencyoperated switch is also described which allows implanted transmitters to be switched remotely.
A simple hybrid thick-film hand pass filter. D. P. HEYWOOD. IERE Conf. Hybrid Microelectronics, Loughborough p. 43. 9-11 Sept. 1975. It is shown that inductors can be replaced by a very simple form of gyrator for filters demanding only moderate values of Q, giving a saving in space and