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Electrical and thermal stability of AuGeNi OHMIC contacts to GaAs fabricated with in situ RF sputter cleaning
388
World Abstracts on Microelectronics and Reliability
7. SEMICONDUCTOR INTEGRATED CIRCUITS, DEVICES AND MATERIALS Investigation of the Si-SiO 2 interface by surface inversion currents. J. KASSABOVand D. DIMITROV. Solid-St. Electron. 29(4), 477 (1986). An analytical solution for the current-voltage characteristics of inversion layers on p-type silicon (including drift and diffusion) is presented. The method is developed to give information on the equilibrium surface potential and to provide accurate values of the electron mobility and fixed oxide charge. Since the experimental samples are bare Si-SiO2 structures the data obtained are not influenced by the presence of a gate electrode as in usual MOS structures. Classification of macroscopic defects contained in p-type EFG ribbon silicon. C. T. Ho, D. B. SANDSTROMand C. E. DUBE. Solid-St. Electron. 29 (5), 495 (1986). Recombination behavior of the grown-in defects contained in p-type ribbon silicon has been examined. Minority carrier lifetime at various defect sites was measured as a function of temperature by the electron beam induced current (EBIC) method. Based on the lifetime vs temperature characteristics, we classify the defects into three macroscopic ( > 2 0 p m scale) categories: (1) plastically deformed single crystal region; (2) dislocation arrays with associated impurity atmosphere; and (3) crystallographic structural line boundaries including twins and grain boundaries. The recombination processes described by category (2) include a set of shallow electron donor traps near the dislocation core with apparent activation energies E c - E , = 0.66-0.087eV. The recombination lifetime category (3) can be described by Shockley-Read-Hall statistics with a recombination level located at the lower half of the band gap. Under the measurement condition, the activation energies of the acceptor-like center in category (3) were found to be E~--Ev = 0.086-0.114eV. The recombination properties of category (1) and (2) defects are consistent with the presence of compensating donor states in the p-type ribbon. Thus, it is believed that these types of defects are primarily responsible for the observed minority carrier lifetime dependence on the photoexcitation level in the EFG ribbon silicon. Electrical and thermal stability of AuGeNi O H M I C contacts to GaAs fabricated with in situ RF sputter cleaning. A. CALLEGARI, D. LACEY and E. T.-S. PAN. Solid-St. Electron. 29(5), 523 0986). In situ RF sputter cleaning of the GaAs surface before the AuGeNi deposition gave low contact resistance gc ~- 0.1 fl-mm. When the contacts were annealed at 4000C for 57 hours, R~ ~< 0.6 ~ - m m was obtained. This is still an acceptable value for 1 #m gate MESFET process. With low sputtering voltages or short sputtering times, contact resistance was large and non-uniform. Normally a short alloying time of 2 rain at 440°C is used for ohmic contact formation. For the process described here, alloying
times as long as 15 min at 430* gave low contact resistances /~-~ 0.2 fl-mm. When the AuGe films were deposited from two separate sources of Au and Ge ("layered" process) low contact resistances/~c = 0.2 f~-mm were obtained. However, this "layered" process did not show the same kind of uniformity and low contact resistance that was obtained when the AuGe film was deposited from a single "eutectic" source.
New oxygen related shallow thermal donor centres in Czoehralski-grown silicon. H. NAVARRO,J. GRIFFIN, J. WEBER and L. GENZEL. Solid St. Commun. 58(3), 151 (1986). A series of previously undetected effective-mass like oxygen related donor centres is observed in Czochralski-grown silicon (CzSi) by means of Phototbermal Ionization Spectroscopy. The new set of donors is shallower in energy than any of the known series of nine oxygen thermal donors reported in CzSi. The ionization energies of the new set of donors are between 34.7 and 37.4meV. The new donor centres also appear as a result of thermally annealing the samples at 450°C. Theoretical study of thermal properties for Si-Ge system. H.MATSUO KAGAYA,Y. KITANI and T. SOMA.Solid St. Commun. 58(6), 399 (1986). Using our presented treatment with the volume effect on the force constants of the pure constituent, we study the thermal properties of Si-Ge solid solution from first principle in the electronic theory of solids. The specific heat at constant volume of Sil_xGe ~ solid solution is monotonous function of the concentration x and is approximately given by the linear interpolation of atomic fraction. The Griineisen constant and the thermal expansion coefficient of Si~_xGex system have the characteristic concentration dependence. The almost constant value at high temperatures and the negative minimum at low temperature of the Grfineisen constant are not monotonous as function of x, and show a maximum near X = 0.7 and a minimum near x = 0.2, respectively. Then, the linear thermal expansion coefficient at low and high temperatures deviate largely from the linear interpolation of the atomic fraction. Investigation and interpretation of adsorption on silicon surfaces. CrI. KLEINT. Vacuum 36(5), 267 (1986). A review is given of some experimental investigations of hydrogen adsorption on silicon surfaces by thermodesorption and reflection electron energy loss spectroscopy. The interpretation of REEL adsorbate spectra by application of the dielectric model and the density of states model is discussed. The latter serves for simulation of the adsorbate loss spectra by local densities of states for hydrogen absorbed on silicon. Further the utility of the LDOS concept to explain the hydrogen spectra is demonstrated.
8. THICK- AND THIN-FILM COMPONENTS, HYBRID CIRCUITS AND MATERIALS Sizing hybrid packages for optimum reliability. H. SCOTT GOEDEKE.Proc. a. Reliab. M aintainab. Syrup., 403 (1986). The increasing use of hybrid microelectronics in avionics systems, due to their advantage in size and weight, has prompted the need for reliability optimized hybrid designs to meet the high probability of mission success required for these systems. To help satisfy this need, a method for minimizing the hybrid failure rate equation of MIL-HDBK-217D with respect to package size is presented in this paper. Since the hybrid failure rate increases with increasing lid seal perimeter and decreases with increasing substrate area there is some intermediate package size within producible limits which minimizes failure rate. The problem, therefore, is to find an
algorithm to accurately compute the minimum failure rate package size while taking producibility into consideration. To solve this problem, a mathematical derivation of the minimum failure rate package size from the MIL-HDBK217 failure rate equation was attempted. However, an approximation which yields accurate results only for large hybrid packages could be obtained. From this derivation an algorithm was found to calculate the exact minimum failure rate package size within the desired resolution. A FORTRAN computer program was written to evaluate this algorithm. The program was written to show hybrid failure rate sensitivity to variations in package size so that reliability-producibility trade studies could be evaluated. In
World Abstracts on Microelectronics and Reliability
7. SEMICONDUCTOR INTEGRATED CIRCUITS, DEVICES AND MATERIALS Investigation of the Si-SiO 2 interface by surface inversion currents. J. KASSABOVand D. DIMITROV. Solid-St. Electron. 29(4), 477 (1986). An analytical solution for the current-voltage characteristics of inversion layers on p-type silicon (including drift and diffusion) is presented. The method is developed to give information on the equilibrium surface potential and to provide accurate values of the electron mobility and fixed oxide charge. Since the experimental samples are bare Si-SiO2 structures the data obtained are not influenced by the presence of a gate electrode as in usual MOS structures. Classification of macroscopic defects contained in p-type EFG ribbon silicon. C. T. Ho, D. B. SANDSTROMand C. E. DUBE. Solid-St. Electron. 29 (5), 495 (1986). Recombination behavior of the grown-in defects contained in p-type ribbon silicon has been examined. Minority carrier lifetime at various defect sites was measured as a function of temperature by the electron beam induced current (EBIC) method. Based on the lifetime vs temperature characteristics, we classify the defects into three macroscopic ( > 2 0 p m scale) categories: (1) plastically deformed single crystal region; (2) dislocation arrays with associated impurity atmosphere; and (3) crystallographic structural line boundaries including twins and grain boundaries. The recombination processes described by category (2) include a set of shallow electron donor traps near the dislocation core with apparent activation energies E c - E , = 0.66-0.087eV. The recombination lifetime category (3) can be described by Shockley-Read-Hall statistics with a recombination level located at the lower half of the band gap. Under the measurement condition, the activation energies of the acceptor-like center in category (3) were found to be E~--Ev = 0.086-0.114eV. The recombination properties of category (1) and (2) defects are consistent with the presence of compensating donor states in the p-type ribbon. Thus, it is believed that these types of defects are primarily responsible for the observed minority carrier lifetime dependence on the photoexcitation level in the EFG ribbon silicon. Electrical and thermal stability of AuGeNi O H M I C contacts to GaAs fabricated with in situ RF sputter cleaning. A. CALLEGARI, D. LACEY and E. T.-S. PAN. Solid-St. Electron. 29(5), 523 0986). In situ RF sputter cleaning of the GaAs surface before the AuGeNi deposition gave low contact resistance gc ~- 0.1 fl-mm. When the contacts were annealed at 4000C for 57 hours, R~ ~< 0.6 ~ - m m was obtained. This is still an acceptable value for 1 #m gate MESFET process. With low sputtering voltages or short sputtering times, contact resistance was large and non-uniform. Normally a short alloying time of 2 rain at 440°C is used for ohmic contact formation. For the process described here, alloying
times as long as 15 min at 430* gave low contact resistances /~-~ 0.2 fl-mm. When the AuGe films were deposited from two separate sources of Au and Ge ("layered" process) low contact resistances/~c = 0.2 f~-mm were obtained. However, this "layered" process did not show the same kind of uniformity and low contact resistance that was obtained when the AuGe film was deposited from a single "eutectic" source.
New oxygen related shallow thermal donor centres in Czoehralski-grown silicon. H. NAVARRO,J. GRIFFIN, J. WEBER and L. GENZEL. Solid St. Commun. 58(3), 151 (1986). A series of previously undetected effective-mass like oxygen related donor centres is observed in Czochralski-grown silicon (CzSi) by means of Phototbermal Ionization Spectroscopy. The new set of donors is shallower in energy than any of the known series of nine oxygen thermal donors reported in CzSi. The ionization energies of the new set of donors are between 34.7 and 37.4meV. The new donor centres also appear as a result of thermally annealing the samples at 450°C. Theoretical study of thermal properties for Si-Ge system. H.MATSUO KAGAYA,Y. KITANI and T. SOMA.Solid St. Commun. 58(6), 399 (1986). Using our presented treatment with the volume effect on the force constants of the pure constituent, we study the thermal properties of Si-Ge solid solution from first principle in the electronic theory of solids. The specific heat at constant volume of Sil_xGe ~ solid solution is monotonous function of the concentration x and is approximately given by the linear interpolation of atomic fraction. The Griineisen constant and the thermal expansion coefficient of Si~_xGex system have the characteristic concentration dependence. The almost constant value at high temperatures and the negative minimum at low temperature of the Grfineisen constant are not monotonous as function of x, and show a maximum near X = 0.7 and a minimum near x = 0.2, respectively. Then, the linear thermal expansion coefficient at low and high temperatures deviate largely from the linear interpolation of the atomic fraction. Investigation and interpretation of adsorption on silicon surfaces. CrI. KLEINT. Vacuum 36(5), 267 (1986). A review is given of some experimental investigations of hydrogen adsorption on silicon surfaces by thermodesorption and reflection electron energy loss spectroscopy. The interpretation of REEL adsorbate spectra by application of the dielectric model and the density of states model is discussed. The latter serves for simulation of the adsorbate loss spectra by local densities of states for hydrogen absorbed on silicon. Further the utility of the LDOS concept to explain the hydrogen spectra is demonstrated.
8. THICK- AND THIN-FILM COMPONENTS, HYBRID CIRCUITS AND MATERIALS Sizing hybrid packages for optimum reliability. H. SCOTT GOEDEKE.Proc. a. Reliab. M aintainab. Syrup., 403 (1986). The increasing use of hybrid microelectronics in avionics systems, due to their advantage in size and weight, has prompted the need for reliability optimized hybrid designs to meet the high probability of mission success required for these systems. To help satisfy this need, a method for minimizing the hybrid failure rate equation of MIL-HDBK-217D with respect to package size is presented in this paper. Since the hybrid failure rate increases with increasing lid seal perimeter and decreases with increasing substrate area there is some intermediate package size within producible limits which minimizes failure rate. The problem, therefore, is to find an
algorithm to accurately compute the minimum failure rate package size while taking producibility into consideration. To solve this problem, a mathematical derivation of the minimum failure rate package size from the MIL-HDBK217 failure rate equation was attempted. However, an approximation which yields accurate results only for large hybrid packages could be obtained. From this derivation an algorithm was found to calculate the exact minimum failure rate package size within the desired resolution. A FORTRAN computer program was written to evaluate this algorithm. The program was written to show hybrid failure rate sensitivity to variations in package size so that reliability-producibility trade studies could be evaluated. In