Browsing by Author "LIN, HC"

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ABRUPTNESS OF GE COMPOSITION AT THE SI/SIGE INTERFACE GROWN BY ULTRAHIGH-VACUUM CHEMICAL-VAPOR-DEPOSITION
(1995-08-21)
TSAI, WC
;
CHANG, CY
;
JUNG, TG
;
LIOU, TS
;
HUANG, GW
A model is proposed to estimate the interfacial abruptness of the Si/SiGe heterojunction. In this model, a transition region with linearly graded Ge composition is assumed at the Si/SiGe interface. The Ge composition x of Si/SiGe quantum well grown by ultrahigh vacuum chemical vapor deposition at 550 degrees C is found to increase with the deposition time as deposition at the same gas phase composition. This phenomenon can be explained by this model and the fitting results match the measured data. The thickness of the transition region and the transition time can be extracted from these fittings. The transition thicknesses are found to be about 1.9 nm or thinner as grown at 550 degrees C or below. (C) 1995 American Institute of Physics.
ADAPTIVE LOAD BALANCING FOR PARALLEL QUEUES WITH TRAFFIC CONSTRAINTS
(1984)
YUM, TP
;
LIN, HC
;
資訊工程學系
;
Department of Computer Science
ANOMALOUS DOPING BEHAVIOR OF IN-SITU BORON-DOPED POLYCRYSTALLINE SILICON DEPOSITED BY ULTRAHIGH-VACUUM CHEMICAL-VAPOR-DEPOSITION
(1993-09-13)
LIN, HC
;
LIN, HY
;
CHANG, CY
;
LEI, TF
;
WANG, PJ
The deposition of in situ heavily boron-doped polycrystalline silicon (poly-Si) films was studied using an ultrahigh vacuum/chemical vapor deposition system. Fully activated carrier concentrations up to 3X10(20) cm-3 were obtained for the as-deposited films grown at 550-degrees-C. For boron concentration beyond this level, the crystallinity of poly-Si films degraded with increasing boron concentration, which resulted in an anomalous rise in resistivity. This crystallinity degradation occurred at a higher rate for films grown on a SiO2 surface than those grown on an undoped poly-Si surface. It is attributed to the preferential adsorption of boron atoms on the SiO2 surface. Under a high B2H6 flux condition, a large amount of boron atoms would accumulate on the SiO2 Surface before the formation of Si nuclei, and thus disturbs the subsequent film deposition and grain growth processes.
CHARACTERISTICS OF BORON-DIFFUSION IN POLYSILICON SILICON SYSTEMS WITH A THIN SI-B LAYER AS DIFFUSION SOURCE
(1995-02-01)
CHEN, TP
;
LEI, TF
;
LIN, HC
;
CHANG, CY
;
電子工程學系及電子研究所
A new material, Si-B layer, as boron diffusion source for polysilicon/silicon systems, has been investigated. The Si-B layer was deposited on polysilicon in an ultrahigh vacuum chemical vapor deposition (UHV/CVD) system at 550 degrees C. The characteristics of boron diffusion in Si-B layer/polysilicon/silicon systems have been investigated by using secondary ion mass spectroscopy (SIMS) and cross-sectional transmission electron microscopy (XTEM). To remove the Si-B layer after the drive-in step, the Si-B layer was oxidized completely during thermal drive-in stage and removed with a diluted hydrofluoric acid. The effects of thermal oxidation of Si-B layer on boron diffusion profiles and polysilicon structures were analyzed. It was found that the boron profiles within the polysilicon are slightly dependent on the oxidation of Si-B layer. Moreover, the polysilicon grain size for Si-B layer source were enlarged, as compared with conventional BF2+-implanted polysilicon source. It is attributed to the effects of the gettering of oxygen impurity by the Si-B layer and secondary grain growth during Si-B layer oxidation. In addition, the boron diffusion profiles in the silicon substrate for Si-B layer source exhibited a more shallow junction depth and less sensitivity to the thermal budget, as compared with BF2+-implanted polysilicon source. This is considered to be the effect of the smaller surface concentration, C-s, in the silicon substrate for Si-B layer source.
CHARACTERISTICS OF POLYCRYSTALLINE FILMS GROWN BY ULTRAHIGH-VACUUM CHEMICAL-VAPOR-DEPOSITION SYSTEM
(1995-12-01)
LIN, HY
;
LEI, TF
;
LIN, HC
;
CHANG, CY
;
TWU, RC
In situ boron-doped polycrystalline Si1-xGex (poly-Si1-xGex) films deposited by ultrahigh vacuum chemical vapor deposition (UHV/CVD) system were characterized. Optimum fitted values of grain boundary trap state densities, 4.0 x 10(12) cm(-2) and 4.9 x 10(12) cm(-2) were obtained for poly-Si and poly-Si0.79Ge0.21, respectively. The extracted average carrier concentration in the grain agrees with secondary ion mass spectroscopy (SIMS) analysis. In turn, we found that these films are suitable Hall elements to sense magnetic field. Experimental results show that the sensitivity decreased with the increasing input current, which can be well explained using the thermionic emission theory. Finally, we use these films to fabricate thin film transistors.
CHARACTERIZATION OF THE SI/SIGE HETEROJUNCTION DIODE GROWN BY ULTRAHIGH-VACUUM CHEMICAL-VAPOR-DEPOSITION
(1994-10-15)
JUNG, TG
;
CHANG, CY
;
LIU, CS
;
CHANG, TC
;
LIN, HC
The unipolar Si/SiGe heterojunction diode grown by ultrahigh vacuum chemical vapor deposition at 550-degrees-C is demonstrated. The dark current density measured at 77 K is (2.5 +/- 0.1) x 10(-7) A/cm2 for the barrier height of 176 +/- 8 meV, at a reverse bias of 1 V. The barrier heights are measured from the activation analysis of the saturation current and compared to the theoretical values. The barrier height decreases as the thickness of the SiGe strained layer exceeds the critical thickness.
DEPOSITION OF IN-SITU BORON-DOPED POLYCRYSTALLINE SILICON FILMS AT REDUCED PRESSURES
(1994-02-07)
LIN, HC
;
LIN, HY
;
CHANG, CY
;
LEI, TF
;
WANG, PJ
We report on the deposition of in situ boron-doped polycrystalline Si films on the SiO2 surface with reduced growth pressures at 550 degrees C. The deposition rate of these films decreased as the doping level was greater than 10(19) cm(-3). Such a result is in sharp contrast to what has been observed previously for similar films grown with conventional low pressure chemical vapor deposition techniques. It was also found that the incubation time prior to the deposition of these films diminished as the doping level was increased to 3x10(20) cm(-3) or higher. It is attributed to the preferential adsorption of boron atoms on the SiO2 surface at the initial stage of growth, which facilitates the nucleation of Si.
EFFECT OF BORON DOPING ON THE STRUCTURAL-PROPERTIES OF POLYCRYSTALLINE SILICON FILMS GROWN AT REDUCED PRESSURES
(1994-08-01)
LIN, HC
;
LIN, HY
;
CHANG, CY
;
JUNG, TG
;
WANG, PJ
The deposition and properties of in situ boron-doped polycrystalline silicon (poly-Si) films grown at 550-degrees-C were investigated using an ultrahigh vacuum chemical vapor deposition system. It is observed that, if the doping level is high enough, the boron incorporation would significantly reduce the deposition rate, impede the grain growth, and degrade the crystallinity of the poly-Si films. We also found that the preferential adsorption of boron atoms on the SiO2 surface at the initial stage of deposition shortened the incubation time of deposition. The property of trapping states at the grain boundary is also examined, and a density of about 4.7 X 10(12) CM-2 is obtained for poly-Si films with a doping level less than 2.2 X 10(19) cm-3.
EFFECTS OF ANNEALING CONDITIONS ON THE PHASE-STABILITY AND SUPERCONDUCTING PROPERTIES OF DC SPUTTERING TLBACACUO THIN-FILMS
(1993-12-01)
LIN, HC
;
LI, MH
;
LI, JJ
;
JANG, FI
;
FU, CM
We have studied the influence of heat treatment on the properties of the superconducting transition and critical current on the TiBaCaCuO thin films prepared by DC sputtering. The superconducting transition temperature is increasing as the maximum annealing temperature is raised. The XRD analysis reveals the evolution of the major phase of the films from 2212 phase to 2223 phase, when the films were annealed at maximum temperature varied from 895-degrees-C to 922-degrees-C. The surface morphology of the sample reveals the formation of the intergrowth of grains by partial melting, which may associated with the evolution of cntical current for the annealed films.
EFFECTS OF SIH4, GEH4, AND B2H6 ON THE NUCLEATION AND DEPOSITION OF POLYCRYSTALLINE SI1-XGEX FILMS
(1994-09-01)
LIN, HC
;
CHANG, CY
;
CHEN, WH
;
TSAI, WC
;
CHANG, TC
In this study, the effects of different reactants, namely, SiH4, GeH4 and B2H6, on the nucleation and deposition of polycrystalline silicon-germanium (poly-Si1-xGe(x)) films on oxide surface in an ultrahigh vacuum chemical vapor deposition reactor were explored. The results show that the addition of GeH4 tends to retard the nucleation process of poly films while B2H6 is preferential for adsorbing on the oxide surface. These effects lead to different incubation duration depending on the kind of reactants used. On the deposition of poly-Si1-xGe(x) films, it is observed that the Ge incorporation is only slightly related to the substrate type, but the deposition mode of poly-Si1-xGe(x) films is much different from that of epitaxial growth on Si(100). The incorporation of Ge atoms also overcomes the anomalous doping effect encountered in heavily boron-doped poly-Si films and allows extremely low resistivity (below 2 mOMEGA-cm) poly films to be obtained at low temperatures (less-than-or-equal-to550-degrees-C).
EPITAXY OF SI1-XGEX BY ULTRAHIGH-VACUUM CHEMICAL-VAPOR-DEPOSITION USING SI2H6 AND GEH4
(1995-07-15)
CHEN, LP
;
CHOU, TC
;
TSAI, WC
;
HUANG, GW
;
TSENG, HC
Disilane and germane were used to grow Si1-xGex epilayers at 550 degrees C by ultrahigh-vacuum chemical vapor deposition (UHVCVD). The solid composition x and growth rate of Si1-xGex were evaluated from double-crystal X-ray rocking curves and show very strong dependence on the total source gas flow rate ([GeH4]+[Si2H6]) and the gas ratio ([GeH4]/[GeH4]+[Si2H6]). The solid composition increases with increase of the gas ratio and also with increasing the total source flux by keeping gas ratio constant. The growth rate increases with the solid composition at lower values and then becomes saturated in the higher composition range (x>0.22). The results can be explained by the relationships of the source fluxes, relative incorporation efficiency at activated surface sites and hydrogen desorption under different growth conditions.
ESTIMATING PIT-EXCAVATION VOLUME USING CUBIC SPLINE VOLUME FORMULA
(1991-05-01)
CHEN, CS
;
LIN, HC
;
土木工程學系
;
Department of Civil Engineering
Current methods used for estimating the volume of pit escavation assumes that the ground profile between the grid points is linear (based on the trapezoidal rule), or nonlinear (based on Simpson's 1/3 and 3/8 formulas). Generally speaking, the nonlinear profile formulas provide better accuracy than the linear profile formulas. However, all the methods mentioned have a common drawback: The joints (grid points) of any two straight lines (the trapezoidal rule), quadratic polynomials (Simpson's 1/3 formula), or cubic polynomials (Simpson's 3/8 formula) form sharp corners. Consequently, these models may not describe the ground profile well. In this paper, formulas based on an extension of the cubic spline polynomial are presented. The grid of this new method is constructed by choosing the variational points of the ground profile and then dividing the pit's area into rectangles of unequal size. Therefore, the new formulas can be used for estimating the excavation volume of a pit divided into a grid with unequal intervals. Further, due to the characteristics of the cubic spline polynomial, a curve modeled by this polynomial can match the ground profile well. The new formulas should provide better accuracy than the other methods mentioned.
FABRICATION AND PROPERTIES OF DC-SPUTTERED TL-1223 SUPERCONDUCTING THIN-FILMS
(1995-06-01)
JUANG, JY
;
HORNG, JH
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LIN, HC
;
WANG, SJ
;
FU, CM
A multi-step deposition and post annealing scheme has been developed for preparing nearly single phase, c-axis oriented TlBa2Ca2Cu3O9 (Tl-1223) superconducting thin films by dc-sputtering. The effects of the compensates used during post annealing on final phase formation suggest the crucial role played by thermodynamic conditions and further validates the viability of the present process scheme. In particular, films obtained by the present process have shown, for the first time in this system, a critical current density (Jc) above 10(6) A/cm(2) at 17 K with a zero- resistance transition temperature (Tco) above 110 K. The results are attributed to the improvement of film morphology, specifically a decreased density of weak-linking.
FABRICATION OF P-CHANNEL POLYCRYSTALLINE SI1-XGEX THIN-FILM TRANSISTORS BY ULTRAHIGH-VACUUM CHEMICAL-VAPOR-DEPOSITION
(1994-09-26)
LIN, HC
;
JUNG, TG
;
LIN, HY
;
CHANG, CY
;
CHEN, LP
In this report, we present a novel approach for fabricating polycrystalline silicon-germanium thin-film transistors at low temperatures (less than or equal to 550 degrees C). A bottom gate configuration is used for this approach, and an i-Si1-xGex/i-Si/p(+)-Si1-yGey multilayer is deposited sequentially on the gate oxide using an ultra-high vacuum chemical vapor deposition technique. The i-Si1-xGex serves as the channel while the i-Si is used as a buffer layer for allowing p(+)-Si1-yGey to be etched selectively on. p-channel thin-film transistors with a held-effect mobility of 13 cm(2)/V s were achieved using this method, which is superior to those grown by low pressure chemical vapor deposition. Our results indicate that the deposition of poly-Si1-xGex/poly-Si multilayer structure would be a promising way for polycrystalline thin-film device applications.
GLOBAL EXISTENCE, ASYMPTOTICS AND UNIQUENESS FOR THE REFLECTION KERNEL OF THE ANGULARLY SHIFTED TRANSPORT-EQUATION
(1995-03-01)
JUANG, J
;
LIN, HC
;
NELSON, P
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應用數學系
;
Department of Applied Mathematics
A nonlinear integrodifferential initial value problem, which is induced from a ''simple transport model,'' is investigated. The underlying equation contains two parameters c and alpha. Here c (c greater than or equal to O) denotes the fraction of the scattering per collision and alpha (O less than or equal to alpha less than or equal to 1) is an angular shift. In this paper, we exploit the relationship between the solution in the half space and that in slab geometry. We are thus able to show that the problem has a unique, positive, uniformly bounded and globally defined solution for O less than or equal to c less than or equal to 1 and O less than or equal to alpha less than or equal to 1. Moreover, it is shown that such global solution converges to the minimal positive solution of the half space problem as the spatial variable approaches infinity (i.e. the slab becomes thicker).
GROWTH AND PROPERTIES OF SUBMILLIMETER SINGLE GRAIN TL2BA2CA2CU3O10+X SUPERCONDUCTING THIN-FILMS
(1995-10-02)
LIN, HC
;
UEN, TM
;
LIU, CK
;
JUANG, JY
;
WU, KH
Distinct crystalline superconducting grains of Tl2Ba2Ca2Cu3O10+x(Tl-2223) with sizes up to 150 mu mx150 mu mX1 mu m were prepared by a single target dc-sputtering process followed by proper postannealing at temperatures around 910 degrees C. A reactive ion etching process was developed to pattern an similar to 10 mu m wide bridge with four contact leads directly on a single grain to study its superconducting transport properties. The etching process was found to have only minimal effect on the superconducting transition temperature T-c, which was typically around 110 K. Grains grown on MgO(100) and LaAlO3(100) substrates, although, displaying somewhat different in-plane orientations, all had critical current densities J(c), well above 10(6) A/cm2 at 77 K. The existence of only one grain boundary, however, can reduce the J(c) by orders of magnitude. (C) 1995 American Institute of Physics.
GROWTH AND PROPERTIES OF SUBMILLIMETER SINGLE GRAIN TL2BA2CA2CU3O10+X SUPERCONDUCTING THIN-FILMS
(1995-10-02)
LIN, HC
;
UEN, TM
;
LIU, CK
;
JUANG, JY
;
WU, KH
Distinct crystalline superconducting grains of Tl2Ba2Ca2Cu3O10+x(Tl-2223) with sizes up to 150 mu mx150 mu mX1 mu m were prepared by a single target dc-sputtering process followed by proper postannealing at temperatures around 910 degrees C. A reactive ion etching process was developed to pattern an similar to 10 mu m wide bridge with four contact leads directly on a single grain to study its superconducting transport properties. The etching process was found to have only minimal effect on the superconducting transition temperature T-c, which was typically around 110 K. Grains grown on MgO(100) and LaAlO3(100) substrates, although, displaying somewhat different in-plane orientations, all had critical current densities J(c), well above 10(6) A/cm2 at 77 K. The existence of only one grain boundary, however, can reduce the J(c) by orders of magnitude. (C) 1995 American Institute of Physics.
GROWTH OF UNDOPED POLYCRYSTALLINE SI BY AN ULTRAHIGH-VACUUM CHEMICAL-VAPOR-DEPOSITION SYSTEM
(1993-09-06)
LIN, HC
;
LIN, HY
;
CHANG, CY
;
LEI, TF
;
WANG, PJ
Deposition of undoped polycrystalline-silicon (poly-Si) films on SiO2 using an ultrahigh vacuum chemical vapor deposition system was investigated. Poly-Si films with high crystallinity were obtained at a temperature as low as 525-degrees-C. The layer growth process was found to proceed with an activation energy of 44 +/- 2 kcal/mol, and is dominated by the desorption rate of surface-bonded hydrogen atoms. An incubation time was observed prior to the film deposition. This incubation period increased with decreasing growth temperature, resulting from slower nucleation and growth rates ai lower temperatures.
LOW-TEMPERATURE EPITAXIAL-GROWTH OF SILICON AND SILICON-GERMANIUM ALLOY BY ULTRAHIGH-VACUUM CHEMICAL-VAPOR-DEPOSITION
(1994-01-01)
JUNG, TG
;
CHANG, CY
;
CHANG, TC
;
LIN, HC
;
WANG, T
Low-temperature epitaxy of silicon and silicon-germanium alloy via an ultrahigh-vacuum chemical vapor deposition system was investigated. Bistable conditions were observed for silicon epitaxial growth performed within the temperature range of 550 degrees C to 800 degrees C. The activation energy of the SiGe growth rate was found to decrease as the germanium composition increased. The germanium atomic molar fraction in these epitaxial layers was tightly controlled by a computer-controlled gas source switching system. Si/SiGe superlattice structures of 20-period 5 nm Si/12 nm SiGe layers were grown to demonstrate the excellent controllability of this growth technique.
LOW-TEMPERATURE GROWTH OF SILICON-BORON LAYER AS SOLID DIFFUSION SOURCE FOR POLYSILICON CONTACTED P(+)-N SHALLOW JUNCTION
(1995-12-01)
LEI, TF
;
CHEN, TP
;
LIN, HC
;
CHANG, CY
;
電子工程學系及電子研究所
A new material, Si-B, is proposed as a solid diffusion source for fabrication of poly-Si contacted p(+)-n shallow junctions, The junction depth of the Si-B source diode has been measured and compared with that of a BF2+-implanted poly-Si source diode, It was found that the Si-B source diode had a much shallower junction and was less sensitive to thermal budget than the BF2+ source diode, This was attributed to the smaller surface concentration and diffusivity of boron in the silicon in Si-B source diodes. Regarding electrical characteristics of diodes with a junction depth over 500 Angstrom, a forward ideality factor of better than 1.01 over 8 decades and a reverse-current density lower than 0.5 nA/cm(2) at -5 V were obtained, As the junction depth shrank to 300 Angstrom, the ideality factor and reverse current density of diodes increased slightly to 1.05 and 1.16 nA/cm(2), respectively, These results demonstrated that a uniform ultrashallow p(+)-n junction can be obtained by using a thin Si-B layer as a diffusion source.