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Effects of oxygen in silicon on device processing
662
World Abstracts on Microelectronics and Reliability
Performance analysis of sub-micron gate GaAs MESFETS. O. L. EL-SAYED, S. EL-GHAZALY,G. SALMER and M. LEEEBVRE. Solid-St. Electron. 30, 643 (1987). A novel 2-D numerical model incorporating nonstationary electron dynamics is used to investigate the complex transport phenomena governing the operation of sub-micron gate GaAs MESFET's. A detailed theoretical analysis of different phenomena observed in subhalf micron devices is given. These include velocity overshoot, stationary and travelling domain formation, soft pinch off, excess drain current etc. The small signal parameters ~,,, .qe and Co, and their dependence on bias condition are evaluated. The effects of physical quantities such as mobility and interface barrier on carrier injection and transport and consequently on device performance are presented. Drift and diffusion of charge carriers in silicon and their empirical relation to the electronic field. M. A. OMAR and L. REGGIANL Solid-St. Electron. 30, 693 (1987). Simple empirical formulae, with three adjustable parameters, are employed in describing the drift velocity and longitudinal diffusion coefficient of charge carriers in purified silicon, over a wide range of electric field 110 10 ~ V/cm). The effects of the latice temperature for the range 77 430 K are also considered and a comparison with the experimental data is made. The
8. T H I C K -
AND
THIN-FILM
COMPONENTS,
Polymer thick film systems and surface mount techniques. A. K. COUSENS and J. S. ~¢VHITAKER.Microelectron. J. 18, 22 (1987). "Addition of surface mounting components to a thick film circuit produces a hybrid. The substrate may be either thick or thin film and with or without passive components already deposited on it" ... K.E. Pitt. The production of hybrid circuits using thick film pastes based on ceramic and glass binder systems with printed resistors and surface mounted components is well established. The extension of surface mount technologies to the printed circuit board (subtractive process) industries is well under way. New components for surface mounting and new processes for joining these components to circuits are developing. This paper is concerned with innovation in the area of film circuits for hybrid circuit manufacture. Polymer thick films are evaluated in terms of their performance, and also the feasibility of surface mounting components onto polymer thick film circuits to produce hybrids.
9. E L E C T R O N ,
ION
AND
proposed formulae can be useful for device simulation using silicon. Effects of oxygen in silicon on device processing. T. M. BROWN. Semiconductor int., 223 (May 1987). Optimum oxygen concentration in silicon wafers improves mechanical strength and intrinsic gettering. Interfacial properties of metal overlayers on III-V compounds. I. LINDAU. Vacuum 3% 385 (1987). This paper gives a short review of the interfacial properties of a few selected metal/Ill V systems prepared under atomically clean conditions. It is pointed out that a detailed understanding can now be obtained on an atomic scale about both the interfacial growth and the compositions of reaction products. Theory of defect complexes at semiconductor surfaces. SHANG-FEN REN and R. E. ALLEN.Solid St. Commun. 64, 589, (1987). We report calculations of deep levels associated with defect complexes at semiconductor surfaces. For the antistructure defect (Asc;,, GaAs) at the (1 1 0) surface of GaAs, the results are qualitatively the same as the sum of those for the individual antisite defects A s ~ and GaA~ a donor level and two acceptor levels within the band gap.
HYBRID
AND
MATERIALS
Hybrid ICs changing fast in a fast-changing world. S. KAMEI. JEE, Japan, 28 (May 1987). The hybrid IC market will continue to grow this year, expanding and solidifying the market base steadily. This industry has received attention for its high value-added products and an increasing number of enterprises have been entering the field. This year onwards, however, they will have to face a severe screening for survival. In spite of that, hybrid IC applications are being expanded steadily; well over 200 hybrid IC manufacturers are contributing greately to the technological advance and market expansion, while making market competition more severe. This trend will continue in 1987. Advances in hybrid chip placement. J. A. M. VAN BUUL and R. S. GNANT. Semiconductor int., 102 (September 19871. Developments in traditional SMD mounting techniques can also benefit the production of hybrid circuits.
LASER
Scanned electron beam alloyed OHMIC contacts to n-GaAs. T. S. KAKUR and A. G. NASSIBIAN.Solid-St. Electron. 30, 619 (1987). Scanned electron beam (SEB) is used for the alloying of evaporated AuGe Ni metallisation on n-type GaAs so as to realise high quality ohmic contacts to n-GaAs. The contact quality is studied for various incident beam energy, scanning time and metallisation thickness. The electrical properties of the contacts are characterised by contact resistivity measurements and it is found that the contact resistivity for SEB alloyed contacts is lower than furnace alloyed contacts and it is independent of metallisation thickness. The optical and Scanning Electron Microscopic observation of surface and subsurface morphology establishes that SEB alloyed contacts have smooth and uniform morphology compared to furnace alloyed contacts. The electron microprobe analysis confirms that the contact constituents are uniformly distributed over the entire contact area. Penetration depth of gold in GaAs is studied by Rutherford Backscattering Techniques which shows that the penetration of gold for SEB contact is far less than furnace alloyed contacts and is independent of metallisation thickness. High temperature ageing tests confirm that SEB
CIRCUITS
BEAM
TECHNIQUES
alloyed contacts undergo less ageing degradation compared to furnace alloyed contacts. Fowler-Nordheim tunneling in implanted MOS devices. D. R. WOLTERS and H. L. PEEK. Solid-St. Electron. 30, 835 (1987). Current-voltage curves of thermally oxidized silicon with polysilicon gates have been measured and interpreted with the Fowler Nordheim model of tunneling electrons through the energy barrier at one of the interfaces of the dielectric, The measurements were done on wafers which have been implanted with various doses As + ions. From the F N curves the barrier height and the pre-exponential term have been extracted. The barrier height and the pre-exponential term decrease substantially if the dose was larger than 10 J4/cm2. Although the Fowler-Nordheim plots shifted and had different slopes, it is shown that the expression following the model is still applicable. It was verified whether the current density was homogeneous over the area. When however the As + implantation was performed with the gate as a mask, the Fowler-Nordheim curves turned out to be kinked. This kinked curve suggests that it is composed of two straight lines. The steep part of the curve is thought to
World Abstracts on Microelectronics and Reliability
Performance analysis of sub-micron gate GaAs MESFETS. O. L. EL-SAYED, S. EL-GHAZALY,G. SALMER and M. LEEEBVRE. Solid-St. Electron. 30, 643 (1987). A novel 2-D numerical model incorporating nonstationary electron dynamics is used to investigate the complex transport phenomena governing the operation of sub-micron gate GaAs MESFET's. A detailed theoretical analysis of different phenomena observed in subhalf micron devices is given. These include velocity overshoot, stationary and travelling domain formation, soft pinch off, excess drain current etc. The small signal parameters ~,,, .qe and Co, and their dependence on bias condition are evaluated. The effects of physical quantities such as mobility and interface barrier on carrier injection and transport and consequently on device performance are presented. Drift and diffusion of charge carriers in silicon and their empirical relation to the electronic field. M. A. OMAR and L. REGGIANL Solid-St. Electron. 30, 693 (1987). Simple empirical formulae, with three adjustable parameters, are employed in describing the drift velocity and longitudinal diffusion coefficient of charge carriers in purified silicon, over a wide range of electric field 110 10 ~ V/cm). The effects of the latice temperature for the range 77 430 K are also considered and a comparison with the experimental data is made. The
8. T H I C K -
AND
THIN-FILM
COMPONENTS,
Polymer thick film systems and surface mount techniques. A. K. COUSENS and J. S. ~¢VHITAKER.Microelectron. J. 18, 22 (1987). "Addition of surface mounting components to a thick film circuit produces a hybrid. The substrate may be either thick or thin film and with or without passive components already deposited on it" ... K.E. Pitt. The production of hybrid circuits using thick film pastes based on ceramic and glass binder systems with printed resistors and surface mounted components is well established. The extension of surface mount technologies to the printed circuit board (subtractive process) industries is well under way. New components for surface mounting and new processes for joining these components to circuits are developing. This paper is concerned with innovation in the area of film circuits for hybrid circuit manufacture. Polymer thick films are evaluated in terms of their performance, and also the feasibility of surface mounting components onto polymer thick film circuits to produce hybrids.
9. E L E C T R O N ,
ION
AND
proposed formulae can be useful for device simulation using silicon. Effects of oxygen in silicon on device processing. T. M. BROWN. Semiconductor int., 223 (May 1987). Optimum oxygen concentration in silicon wafers improves mechanical strength and intrinsic gettering. Interfacial properties of metal overlayers on III-V compounds. I. LINDAU. Vacuum 3% 385 (1987). This paper gives a short review of the interfacial properties of a few selected metal/Ill V systems prepared under atomically clean conditions. It is pointed out that a detailed understanding can now be obtained on an atomic scale about both the interfacial growth and the compositions of reaction products. Theory of defect complexes at semiconductor surfaces. SHANG-FEN REN and R. E. ALLEN.Solid St. Commun. 64, 589, (1987). We report calculations of deep levels associated with defect complexes at semiconductor surfaces. For the antistructure defect (Asc;,, GaAs) at the (1 1 0) surface of GaAs, the results are qualitatively the same as the sum of those for the individual antisite defects A s ~ and GaA~ a donor level and two acceptor levels within the band gap.
HYBRID
AND
MATERIALS
Hybrid ICs changing fast in a fast-changing world. S. KAMEI. JEE, Japan, 28 (May 1987). The hybrid IC market will continue to grow this year, expanding and solidifying the market base steadily. This industry has received attention for its high value-added products and an increasing number of enterprises have been entering the field. This year onwards, however, they will have to face a severe screening for survival. In spite of that, hybrid IC applications are being expanded steadily; well over 200 hybrid IC manufacturers are contributing greately to the technological advance and market expansion, while making market competition more severe. This trend will continue in 1987. Advances in hybrid chip placement. J. A. M. VAN BUUL and R. S. GNANT. Semiconductor int., 102 (September 19871. Developments in traditional SMD mounting techniques can also benefit the production of hybrid circuits.
LASER
Scanned electron beam alloyed OHMIC contacts to n-GaAs. T. S. KAKUR and A. G. NASSIBIAN.Solid-St. Electron. 30, 619 (1987). Scanned electron beam (SEB) is used for the alloying of evaporated AuGe Ni metallisation on n-type GaAs so as to realise high quality ohmic contacts to n-GaAs. The contact quality is studied for various incident beam energy, scanning time and metallisation thickness. The electrical properties of the contacts are characterised by contact resistivity measurements and it is found that the contact resistivity for SEB alloyed contacts is lower than furnace alloyed contacts and it is independent of metallisation thickness. The optical and Scanning Electron Microscopic observation of surface and subsurface morphology establishes that SEB alloyed contacts have smooth and uniform morphology compared to furnace alloyed contacts. The electron microprobe analysis confirms that the contact constituents are uniformly distributed over the entire contact area. Penetration depth of gold in GaAs is studied by Rutherford Backscattering Techniques which shows that the penetration of gold for SEB contact is far less than furnace alloyed contacts and is independent of metallisation thickness. High temperature ageing tests confirm that SEB
CIRCUITS
BEAM
TECHNIQUES
alloyed contacts undergo less ageing degradation compared to furnace alloyed contacts. Fowler-Nordheim tunneling in implanted MOS devices. D. R. WOLTERS and H. L. PEEK. Solid-St. Electron. 30, 835 (1987). Current-voltage curves of thermally oxidized silicon with polysilicon gates have been measured and interpreted with the Fowler Nordheim model of tunneling electrons through the energy barrier at one of the interfaces of the dielectric, The measurements were done on wafers which have been implanted with various doses As + ions. From the F N curves the barrier height and the pre-exponential term have been extracted. The barrier height and the pre-exponential term decrease substantially if the dose was larger than 10 J4/cm2. Although the Fowler-Nordheim plots shifted and had different slopes, it is shown that the expression following the model is still applicable. It was verified whether the current density was homogeneous over the area. When however the As + implantation was performed with the gate as a mask, the Fowler-Nordheim curves turned out to be kinked. This kinked curve suggests that it is composed of two straight lines. The steep part of the curve is thought to