Browsing by Author "LOU, YS"

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A CHARACTERIZATION TECHNIQUE FOR THE DEGRADATION CHARACTERISTICS OF TI/SI SCHOTTKY-BARRIER DIODES AND OHMIC CONTACTS AFTER THERMAL SILICIDATION
(1994-02-01)
LOU, YS
;
WU, CY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The effects of thermal silicidation on both the nonideal current-voltage characteristics of the Schottky-banier diodes and the degradation properties of the ohmic contacts have been self-consistently characterized by using a simple interfacial-layer theory. The abruptly changed nonideality of the measured I-V characteristics as TiSi2 is formed can be interpreted as the variations of the interface properties, such as the thermal-equlibrium barrier height, the interfacial-layer capacitance, and the density distribution of the interface state. Moreover, different work functions for Ti and TiSi2 and the change of the dominant type of the interface states and their density distributions are shown to be responsible for the fluctuations of the thermal-equilibrium barrier height after thermal silicidation. Furthermore, the interface parameters extracted from the fabricated Schottky-barrier diodes are used to calculate and compare the simultaneously-processed specific contact resistivities, and satisfactory agreement is obtained. Thus, the silicidation-related degradation characteristics of the ohmic contacts can be directly related to the variations of the interface properties at the Ti/Si interface.
A NEW OXIDATION-RESISTANT COSI2 PROCESS FOR SELF-ALIGNED SILICIDATION (SALICIDE) TECHNOLOGY
(1993-01-01)
LOU, YS
;
WU, CY
;
CHENG, HC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This paper presents a new oxidation-resistant and self-aligned CoSi2 process using amorphous-Si (a-Si)/Co bilayer metallization. It is shown that, even in an environment without introducing any flowing inert gas, the detrimental reaction between Co metal and ambient impurities, e.g. O2 and H2O, can be completely impeded by a covered thin a-Si layer during the thermal silicidation cycle. Moreover, despite a capped a-Si layer over Co film, the satisfactory self-aligned silicidation properties can be retained if the initial silicidation temperature is kept below 500-degrees-C in N2 ambient. Furthermore, the dependences of both oxidation-resistant and self-aligned silicidation properties on the thicknesses of a-Si and Co films are studied in detail. Based on experimental analysis, the allowed process window for the a-Si film thickness can be determined and is shown to increase with increasing the Co film thickness. An empirical process rule is experimentally obtained to determine the optimal thickness relation between a-Si and Co films for the a-Si/Co bilayer process. Thus, a simple and practical self-aligned CoSi2 process with extremely high immunity to ambient impurities is proposed for SALICIDE applications.
A SELF-CONSISTENT CHARACTERIZATION METHODOLOGY FOR SCHOTTKY-BARRIER DIODES AND OHMIC CONTACTS
(1994-04-01)
LOU, YS
;
WU, CY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Based on the simple interfacial-layer theory, the extraction methods for the interface parameters of the metal-semiconductor contact have been developed and applied to characterize both the Schottky-barrier diodes and the ohmic contacts in a self-consistent manner. It has been shown that the physical parameters at the metal-semiconductor interface can be extracted from the I-V characteristics of the Schottky-barrier diodes and the degradation of the thermal-equilibrium barrier height due to the thermal cycle can be directly modeled in terms of the extracted interface parameters. Besides, using the extracted parameters, the specified surface-treatment process can be evaluated by the extracted thermal-equilibrium barrier height, and thus the strongly process-dependent specific contact resistivity rho(c) of the ohmic contacts can be theoretically calculated by a modified tunneling model considering the impurity band. Furthermore, by comparing the simulated results and the measured rho(c) data deduced from the Al and Ti contacts on both doping types of the Si-substrate, satisfactory agreements have been obtained.
LATERAL TITANIUM SILICIDE GROWTH AND ITS SUPPRESSION USING THE A-SI/TI BILAYER STRUCTURE
(1995-03-01)
LOU, YS
;
WU, CY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The effects of internal oxygen impurities released from the TiSiO2 reaction on the lateral silicide growth using the a-Si/Ti bilayer structure are presented. The lateral silicide growth can be effectively retarded by internal oxygen impurities using a-Si/Ti bilayer process after silicidation at a temperature below 700 degrees C. Compared with the simultaneously processed single Ti layer process, it is observed that both high-level oxygen impurities and their redistribution in the possible Si-diffusion paths play the same important role on the suppression of the lateral silicide growth. Finally, the oxygen redistribution-dependent kinetics is developed to give a self-consistent explanation fo; the experimental observations from both the single Ti layer process and the a-Si/Ti bilayer process.
THE EFFECTS OF IMPURITY BANDS ON THE ELECTRICAL CHARACTERISTICS OF METAL-SEMICONDUCTOR OHMIC CONTACTS
(1995-01-01)
LOU, YS
;
WU, CY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The effects of semiconductor heavy doping on the I-V characteristics and the specific contact resistivity rho(c) of semiconductor-metal ohmic contacts have been theoretically studied by incorporating the band-edge-tailing and impurity band effects. The Fermi level and the effective conduction band edge have been recalculated to determine the electron population and the bandgap narrowing. When the available electrons with higher transmission probability, which dominate the tunneling process, have been reduced by the presence of an impurity band, the tunneling current density becomes lower and hence the specific contact resistivity becomes higher for the case with the impurity band than that without the impurity band. Considering the physical properties inherent in a heavily-doped semiconductor, it is possible to explain the deviations of the experimental data from the theoretical results obtained from the conventionally used tunneling theory for the ohmic contacts. Furthermore, by comparing the simulated results and the measured rho(c) data deduced from the Al and Ti contacts on both doping types of the Si-substrate, satisfactory agreements have been obtained.
THE PROCESS WINDOW OF A-SI/TI BILAYER METALLIZATION FOR AN OXIDATION-RESISTANT AND SELF-ALIGNED TISI2 PROCESS
(1992-08-01)
LOU, YS
;
WU, CY
;
CHENG, HC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The dependences of both oxidation-resistant and self-aligned silicidation properties on the thicknesses of top amorphous-Si (a-Si) and Ti metal in an a-Si/Ti bilayer process are presented. It is shown that a thin silicide layer formed during the reaction between a-Si and Ti films becomes a stable oxidation and nitridation barrier for oxygen- and nitrogen-related impurities. Moreover, the formation sequence of the silicide phase depends on not only the annealing temperature but also the thickness of Ti film. In addition, the preferential orientation of the silicide phase after annealing at high temperature also shows a strong dependence of the thickness of Ti film, which is attributed to the difference of the grain size in the polycrystalline silicide film. The allowed process window for the a-Si thickness can be determined experimentally and a reproducible and homogeneous self-aligned TiSi2 film can be easily obtained by using the a-Si/Ti bilayer process in SALICIDE applications despite of high-level contaminations of oxygen impurities in both the as-deposited Ti film and the annealing ambient.