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Hafnium-n type silicon Schottky barriers
World Abstracts on Microelectronics and Reliability
795
7. S E M I C O N D U C T O R I N T E G R A T E D CIRCUITS, DEVICES AND MATERIALS The far infrared absorption spectra of bound excitons in silicon. M. L. W. THEWALT, D. LABRIE and T. TIMUSK. Solid St. Comraun. 53 (12) 1049 0985). The first application of Fourier transform infrared spectroscopy to the measurement of the odd-parity excited states of a bound exciton is described. These results have reversed the prevailing model for this particular center, and allowed the even-parity excited states to be identified as well. All of these excited states can be put into excellent correspondence with acceptor states, providing the best existing confirmation of the pseudodonor/pseudo-acceptor model of isoelectronic bound exciton states. Possible refinements of the technique are discussed, along with some suggested areas for further studies. On shallow-deep instability of impurity level in semiconductors. G. MUKHOPADHYAY.Solid St. Commun. 53 (1) 47 (1985). The question of shallow-deep instability of the ground state of an impurity in a semiconductor is examined in terms of a model potential which is Coulombic at short distances (marked by r < b), and screened C o u l o m b at larger distances (r > b). It is shown that for b larger than a critical value b c the level rapidly becomes deeper, and the value of bc depends strongly on the effective mass # increasing rapidly with decreasing/~. Present status of arsenic planar diffusion sources. R. E. TRESSLER, H. J. BOEGLIN, J. MONKOWSKI,J. STACH, GABE DE MUNDA and CHARLESVOLK. Solid St. Technol. 165 (October 1984). Arsenic diffusions from a planar diffusion source based on the controlled dissociation of AlAsO4 have been demonstrated at low temperatures (975 1025"C) and at elevated temperatures (1000-1250"C) using a predeposition followed by drive-in. The diffusion profiles formed at low temperatures are characteristically flat, shallow and step-like and appear attractive for M O S structures. Essentially defect-free diffused regions result from the buried layer type of diffusion at 1200-1250°C with resistivities typical of other diffusion sources. These arsenic planar diffusion sources can be used in a typical diffusion tube in nitrogen with certain precautions taken to minimize oxygen contamination of the diffusion ambient. Complete exploration of the silicon gap at the Si-SiO 2 interface of MIS tunnel diodes using the conductance technique at various temperatures and illumination levels. M. EL-SAVED,G. PANANAKAKISand G. KAMARINOS. Solid-St. Electron. 28 (4) 345 (1985). Interface states density Ns,(E ) and capture crosssections a n and ffp of A I - S i O : Si (n-type) tunnel diodes (thickness ,~# 30 A) are studied using the conductance technique in the dark over the temperature range from 77 to 300 K and under illumination at room temperature. This new method allows the practical characterization of the entire silicon gap width, i.e. from 50 to 950 meV below the silicon conduction band edge. In accordance with other workers we observe that the U-shaped N~(E) profile does not depend on the temperature and that a n and ap decrease exponentially in the vicinity of the semiconductor energy bands. The above results are also in good agreement with those obtained from a numerical simulation of the I - V a characteristics of the studied diodes. Effects of heavy metal contamination from corrosive gas and dopant handling equipment in silicon wafer processing. K. M. EISELE and E. KLAUSMANN.Solid St. Technol. 177 (October 1984). Contamination by heavy metal atoms from stainless steel equipment components when diffusing into silicon wafers may seriously affect silicon device characteristics. The influence of deposited phosphorus-silicate glass resulting from the use of phosphorous-oxychloride as a liquid diffusion source is examined. Measurements of minority carrier life-
time were performed to determine the presence of unwanted impurities that m a y have been carried from the walls of the stainless steel vessels containing the doping gas, into the furnace tube. It was found that the minority carrier lifetime was not degraded; thus no significant a m o u n t s of heavy metals were transferred into the silicon.
Characterization of heteroepitaxial silicon on sapphire by UV reflectometry. M. T. DUFFY, G. W. CULLEN,R. A. SOLTIS,G. HARnEKE and J. R. SANDERCOCK. R C A Rev. 46 19 (March 1985). In previous work we described an optical reflectance technique used for quality control purposes in the qualification of silicon-on-sapphire (SOS) films. The procedure, applicable to film thicknesses on the 0.5-0.6 ,um range, was based on specular reflectance measurements at two wavelengths, 280 n m and 400 nm. Because of recent interest in SOS films in the 0.2-0.3 p.m thickness range, the measurement procedure has been modified to evaluate films in both thickness ranges using the same instrumentation as before. The modified procedure, based on measurements at one wavelength (280 nm), eliminates optical interference effects in the case of the thinner films and increases the sensitivity of the measurement technique. Hafnium-n type silicon Schottky barriers. A. RADZISZEWSKI and T. SKRABKA. Solid-St. Electron. 28 (7) 707 (1985). This paper describes the electrical properties of hafnium-/ntype/silicon contacts. These contacts were found to be Schottky barriers with a low barrier height. Polished and chemically cleaned (111) silicon wafers with a donor concentration Na = 7 x 1022 m -3 were used to fabricate experimental Schottky barrier structures. For the Schotty barrier height (Pbn and the ideality factor n values were found of 0.47 V and 1.07-1.11, respectively. It is concluded that due to their low forward voltage drop and good rectifying properties, Hf-nSi contacts can be applied in microwave Schottky barrier diodes. Microscopic models of Hg +, Au ° and Pt- isoelectronic interstitial impurities in silicon. J. L. A. ALVES,J. R. LEITE,V. M. S. GOMES and L. V. C. ASSALI. Solid St. Commun. 55 (4) 333 (1985). Rigourous self-consistent field electronic structure calculations have been carried out, for the first time, for the tetrahedal-site interstitial Hg +, Au ° and Pt isoelectronic impurities in silicon. Compact and fully occupied e(d) and t2(d) levels below the valence band are introduced by mercury and gold impurities, which interact weakly with the host lattice. The presence of a hyperdeep s-like level close to the bottom of the valence band is a relevant feature of the analysed impurities. No shallow donor action was detected for the impurities which are stable in the non paramagnetic Hg 2 +, Au ÷ and Pt ° charge state configurations. Oxygen behaviour in liquid phase expitaxial GaAs. J. S. C. CHANG, D. W. KISKER and D. A. STEVENSON. Solid-St. Electron. 28 (5) 479 (1985). The oxygen activity in the gallium solvent was controlled and measured by an electrochemical method, during the liquid phase epitaxy of GaAs. This technique, in combination with SIMS analysis of GaAs grown from O is saturated melts, was used to determine the oxygen distribution coefficient at 840°C. In this temperature region, the low solubility of oxygen in liquid gallium combined with a distribution coefficient < 10 -3 leads to m a x i m u m oxygen levels in the ~< 1016 c m - 3 range. The behavior of oxygen in three layers, with significant differences in oxygen concentration, was evaluated by photoluminescence and deep level transient spectroscopy, and no direct relationship was observed between the energy levels in the PL or DLTS spectra and the oxygen concentration in epitaxial GaAs. Measuring and modeling minority carrier transport in heavily
795
7. S E M I C O N D U C T O R I N T E G R A T E D CIRCUITS, DEVICES AND MATERIALS The far infrared absorption spectra of bound excitons in silicon. M. L. W. THEWALT, D. LABRIE and T. TIMUSK. Solid St. Comraun. 53 (12) 1049 0985). The first application of Fourier transform infrared spectroscopy to the measurement of the odd-parity excited states of a bound exciton is described. These results have reversed the prevailing model for this particular center, and allowed the even-parity excited states to be identified as well. All of these excited states can be put into excellent correspondence with acceptor states, providing the best existing confirmation of the pseudodonor/pseudo-acceptor model of isoelectronic bound exciton states. Possible refinements of the technique are discussed, along with some suggested areas for further studies. On shallow-deep instability of impurity level in semiconductors. G. MUKHOPADHYAY.Solid St. Commun. 53 (1) 47 (1985). The question of shallow-deep instability of the ground state of an impurity in a semiconductor is examined in terms of a model potential which is Coulombic at short distances (marked by r < b), and screened C o u l o m b at larger distances (r > b). It is shown that for b larger than a critical value b c the level rapidly becomes deeper, and the value of bc depends strongly on the effective mass # increasing rapidly with decreasing/~. Present status of arsenic planar diffusion sources. R. E. TRESSLER, H. J. BOEGLIN, J. MONKOWSKI,J. STACH, GABE DE MUNDA and CHARLESVOLK. Solid St. Technol. 165 (October 1984). Arsenic diffusions from a planar diffusion source based on the controlled dissociation of AlAsO4 have been demonstrated at low temperatures (975 1025"C) and at elevated temperatures (1000-1250"C) using a predeposition followed by drive-in. The diffusion profiles formed at low temperatures are characteristically flat, shallow and step-like and appear attractive for M O S structures. Essentially defect-free diffused regions result from the buried layer type of diffusion at 1200-1250°C with resistivities typical of other diffusion sources. These arsenic planar diffusion sources can be used in a typical diffusion tube in nitrogen with certain precautions taken to minimize oxygen contamination of the diffusion ambient. Complete exploration of the silicon gap at the Si-SiO 2 interface of MIS tunnel diodes using the conductance technique at various temperatures and illumination levels. M. EL-SAVED,G. PANANAKAKISand G. KAMARINOS. Solid-St. Electron. 28 (4) 345 (1985). Interface states density Ns,(E ) and capture crosssections a n and ffp of A I - S i O : Si (n-type) tunnel diodes (thickness ,~# 30 A) are studied using the conductance technique in the dark over the temperature range from 77 to 300 K and under illumination at room temperature. This new method allows the practical characterization of the entire silicon gap width, i.e. from 50 to 950 meV below the silicon conduction band edge. In accordance with other workers we observe that the U-shaped N~(E) profile does not depend on the temperature and that a n and ap decrease exponentially in the vicinity of the semiconductor energy bands. The above results are also in good agreement with those obtained from a numerical simulation of the I - V a characteristics of the studied diodes. Effects of heavy metal contamination from corrosive gas and dopant handling equipment in silicon wafer processing. K. M. EISELE and E. KLAUSMANN.Solid St. Technol. 177 (October 1984). Contamination by heavy metal atoms from stainless steel equipment components when diffusing into silicon wafers may seriously affect silicon device characteristics. The influence of deposited phosphorus-silicate glass resulting from the use of phosphorous-oxychloride as a liquid diffusion source is examined. Measurements of minority carrier life-
time were performed to determine the presence of unwanted impurities that m a y have been carried from the walls of the stainless steel vessels containing the doping gas, into the furnace tube. It was found that the minority carrier lifetime was not degraded; thus no significant a m o u n t s of heavy metals were transferred into the silicon.
Characterization of heteroepitaxial silicon on sapphire by UV reflectometry. M. T. DUFFY, G. W. CULLEN,R. A. SOLTIS,G. HARnEKE and J. R. SANDERCOCK. R C A Rev. 46 19 (March 1985). In previous work we described an optical reflectance technique used for quality control purposes in the qualification of silicon-on-sapphire (SOS) films. The procedure, applicable to film thicknesses on the 0.5-0.6 ,um range, was based on specular reflectance measurements at two wavelengths, 280 n m and 400 nm. Because of recent interest in SOS films in the 0.2-0.3 p.m thickness range, the measurement procedure has been modified to evaluate films in both thickness ranges using the same instrumentation as before. The modified procedure, based on measurements at one wavelength (280 nm), eliminates optical interference effects in the case of the thinner films and increases the sensitivity of the measurement technique. Hafnium-n type silicon Schottky barriers. A. RADZISZEWSKI and T. SKRABKA. Solid-St. Electron. 28 (7) 707 (1985). This paper describes the electrical properties of hafnium-/ntype/silicon contacts. These contacts were found to be Schottky barriers with a low barrier height. Polished and chemically cleaned (111) silicon wafers with a donor concentration Na = 7 x 1022 m -3 were used to fabricate experimental Schottky barrier structures. For the Schotty barrier height (Pbn and the ideality factor n values were found of 0.47 V and 1.07-1.11, respectively. It is concluded that due to their low forward voltage drop and good rectifying properties, Hf-nSi contacts can be applied in microwave Schottky barrier diodes. Microscopic models of Hg +, Au ° and Pt- isoelectronic interstitial impurities in silicon. J. L. A. ALVES,J. R. LEITE,V. M. S. GOMES and L. V. C. ASSALI. Solid St. Commun. 55 (4) 333 (1985). Rigourous self-consistent field electronic structure calculations have been carried out, for the first time, for the tetrahedal-site interstitial Hg +, Au ° and Pt isoelectronic impurities in silicon. Compact and fully occupied e(d) and t2(d) levels below the valence band are introduced by mercury and gold impurities, which interact weakly with the host lattice. The presence of a hyperdeep s-like level close to the bottom of the valence band is a relevant feature of the analysed impurities. No shallow donor action was detected for the impurities which are stable in the non paramagnetic Hg 2 +, Au ÷ and Pt ° charge state configurations. Oxygen behaviour in liquid phase expitaxial GaAs. J. S. C. CHANG, D. W. KISKER and D. A. STEVENSON. Solid-St. Electron. 28 (5) 479 (1985). The oxygen activity in the gallium solvent was controlled and measured by an electrochemical method, during the liquid phase epitaxy of GaAs. This technique, in combination with SIMS analysis of GaAs grown from O is saturated melts, was used to determine the oxygen distribution coefficient at 840°C. In this temperature region, the low solubility of oxygen in liquid gallium combined with a distribution coefficient < 10 -3 leads to m a x i m u m oxygen levels in the ~< 1016 c m - 3 range. The behavior of oxygen in three layers, with significant differences in oxygen concentration, was evaluated by photoluminescence and deep level transient spectroscopy, and no direct relationship was observed between the energy levels in the PL or DLTS spectra and the oxygen concentration in epitaxial GaAs. Measuring and modeling minority carrier transport in heavily