Browsing by Author "Wang, SW"

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A new simple and reliable method to form a textured Si surface for the fabrication of a tunnel oxide film
(1998-05-01)
Chang, KM
;
Li, CH
;
Sheih, BS
;
Yang, JY
;
Wang, SW
In this work, a textured Si surface was formed with a new simple and reliable method for tunnel oxide fabrication. First, a thin poly-Si layer (12 nm thick) was deposited on Si surface and a 30-nm thick dry oxide film was then grown in O-2 ambient. This oxide film was served as a sacrificial oxide. The poly-Si film and Si substrate were both oxidized during thermal oxidization. After stripping this sacrificial oxide, a textured Si surface was obtained. Tunnel oxide grown on this textured Si surface has an asymmetrical J-E characteristics, less interface states generation and better reliability (larger Q(bd)) as compared to those of normal oxide.
A novel pretreatment technology for organic low-dielectric material to suppress copper diffusion and improve ashing resistance
(2000-06-01)
Chang, KM
;
Deng, IC
;
Tsai, YP
;
Wen, CY
;
Yeh, SJ
new novel pretreatment technology for integration of organic low-dielectric material in copper interconnects for ultralarge scale integration applications is developed. Using NH3 plasma treatment, two extremely important advantages were achieved in spin-on organic polymer (SOP), including the reduction of copper diffusion and the improvement of ashing resistance. A copper/SOP/Si capacitor structure is used to study the electrical characteristics of SOP film after ashing treatment or postanneal. Higher barrier capability and better ashing resistance can be achieved by the SOP layer after NH3 plasma treatment. After annealing at 500 degrees C for 60 min, secondary ion mass spectroscopy depths profile shows that the Cu atoms do not penetrate into the SOP when they are pretreated by NH3 plasma. Furthermore after the ashing step, the carbon atoms in the SOP film almost remain the same when they are pretreated by NH3 plasma. On the other hand, the concentration of carbon in as-cured SOP is no longer seen. The reason of improving ashing resistance and better barrier capability was due to the organic polymer film rearranging to form a carbon-containing silicon nitride film. (C) 2000 The Electrochemical Society. S0013-4651(99)10-007-7. Ail rights reserved.
An efficient and stable ray tracing algorithm for parametric surfaces
(2002-07-01)
Wang, SW
;
Shih, ZC
;
Chang, RC
;
資訊工程學系
;
Department of Computer Science
In this paper, we propose an efficient and stable algorithm for finding the ray-surface intersections. Newton's method and Bezier clipping are adapted to form the core of our algorithm. Ray coherence is used to find starting points for Newton iteration. We introduce an obstruction detection technique to verify whether an intersection point found by using Newton's method is the closest one. When Newton's method fails to achieve convergence, we use Bezier clipping as the substitution to find the intersection points. This combination achieves significant improvement in tracing primary rays. A similar approach also successfully improves the performance in tracing secondary rays.
An improved rendering technique for ray tracing Bezier and B-spline surfaces
(2000-09-01)
Wang, SW
;
Shih, ZC
;
Chang, RH
;
資訊工程學系
;
Department of Computer Science
Both numerical and subdivision methods are widely used approaches for ray tracing parametric surfaces. However, the expense of finding the ray-surface intersection points is a major drawback. Thus, simpler and less memory-intensive strategies are needed to improve these methods without further complicating them. This work presents an efficient algorithm for enhancing the performance of both numerical and subdivision methods. The proposed technique can be extended to most applications based on these two methods. The computational time of both approaches is improved by 16-40%. Copyright (C) 2000 John Wiley & Sons, Ltd.
Characteristics of selective chemical vapor deposition of tungsten on aluminum with a vapor phase precleaning technology
(1997-01-01)
Chang, KM
;
Yeh, TH
;
Wang, SW
;
Li, CH
;
電子工程學系及電子研究所
A simple and efficient precleaning of an aluminum surface with hydrochloric acid vapor prior to selective chemical vapor deposition of tungsten was investigated. The vapor phase precleaning was shown to remove the aluminum native oxide as well as reduce the aluminum fluorides formed at the W/Al interface during initial reaction of WF6 with the aluminum underlayer. It was found that the precleaning process is spontaneous and the removal rate of aluminum is related to the concentration of reactants used. After precleaning, the aluminum surface was free of oxide and covered with a large amount of Cl species that were examined by x-ray photoelectron spectroscopy. These Cl species occupy active sites on the wafer surface and prevent further adsorption of WF6 on the aluminum during the initial stage in selective deposition of tungsten. Therefore, the probability of reaction between WF6 and the underlying aluminum is greatly suppressed. By using a hydrochloric acid vapor to pretreat the aluminum trench and via hole patterned substrates, a smooth and dense tungsten film and low selectivity loss (<50 pcs/cm(2)) were obtained. A low concentration of aluminum fluorides accumulated at the W/Al interface that were involved in low via resistance was also observed.
Comprehensive study of plasma pretreatment process for thin gate oxide (<10 nm) fabricated by electron cyclotron resonance plasma oxidation
(1996-12-01)
Chang, KM
;
Li, CH
;
Fahn, FJ
;
Yeh, TH
;
Wang, SW
In this work, we comprehensively study the effect of ECR plasma pretreatment on ECR plasma grown SiO2 film. The ECR plasma grown gate oxide growth rate in the case of no plasma pretreatment is lower than that in the case of use of the plasma pretreatment step. Because the growth processes for these two methods (with and without pretreatment) differ only in terms of the initial surface conditions, the growth mechanisms are concluded to be determined by the initial Si surface conditions before plasma oxidation. The mid-gap interface states (Di(it-m)) of the ECR plasma grown SiO2 films in the case of plasma pretreatment are lower than those in the case of no plasma pretreatment. Through use of the plasma pretreatment process, the Si surface can be improved and cleaned before plasma oxidation. For SiO2 films pretreated with N-2 or Ar gas, the breakdown fields (E(bd)) are higher than those for SiO2 films not pretreated with N-2 or Ar gas. However, for NH3 gas pretreated films, the Ebd is lower than those for SiOz films pretreated with N-2 or Ar gas. This is because the NH3 gas contains H atoms which cause deterioration of F-N tunneling characteristics. Moreover, with the plasma pretreatment step, the stress-induced leakage currents (SILC) are lower than those without this step.
Dry etching of polysilicon with high selectivity using a chlorine-based plasma in an ECR reactor
(1996-07-01)
Chang, KM
;
Yeh, TH
;
Wang, SW
;
Li, CH
;
Yang, JY
Halogen-bearing gases have proved to be useful plasma discharge etchants for the fabrication of sub-micron poly-Si gate structures. In this paper, investigations of chlorine-based plasmas generated by an electron cyclotron resonance (ECR) reactor for poly-Si etching is studied. The influences of added oxygen, microwave power and RF power on etching characteristics are discussed. In addition, the etching mechanisms of the underlying oxide are developed. Finally, the Cl-2/HBr/O-2 mixed system is examined. The combined plasma exhibits the features of high selectivity, high anisotropy and high etching rate.
Dry etching of polysilicon with high selectivity using a chlorine-based plasma in an ECR reactor
(1996-07-01)
Chang, KM
;
Yeh, TH
;
Wang, SW
;
Li, CH
;
Yang, JY
Halogen-bearing gases have proved to be useful plasma discharge etchants for the fabrication of sub-micron poly-Si gate structures. In this paper, investigations of chlorine-based plasmas generated by an electron cyclotron resonance (ECR) reactor for poly-Si etching is studied. The influences of added oxygen, microwave power and RF power on etching characteristics are discussed. In addition, the etching mechanisms of the underlying oxide are developed. Finally, the Cl-2/HBr/O-2 mixed system is examined. The combined plasma exhibits the features of high selectivity, high anisotropy and high etching rate.
Effect of adding Ar on the thermal stability of chemical vapor deposited fluorinated silicon oxide using an indirect fluorinating precursor
(1997-05-12)
Chang, KM
;
Wang, SW
;
Li, CH
;
Yeh, TH
;
Yang, JY
For a low dielectric constant intermetal dielectric application, fluorinated silicon oxide (FxSiOy) films were deposited in an electron cyclotron resonance chemical vapor deposition system, with SiH4, O-2, and CF4 as the reaction gases. Since the CF4 is an indirect fluorinating precursor, the fluorinating mechanism resembles that of the oxide etching by a fluorocarbon plasma. Thermal stability of the incorporated fluorine (and hence, the dielectric constant) relies heavily on the deposition parameters and technologies. According to experimental results, adding Ar gas during deposition can improve the thermal stability of incorporated fluorine. Such an improvement is due to the fact that Ar sputtering enhances the removal of weakly bonded silicon fluoride on the as-deposited film surface, thereby elevating the mean bonding strength of fluoride remaining in the oxide. (C) 1997 American Institute of Physics.
Effects of gas ratio on electrical properties of electron-cyclotron-resonance nitride films grown at room temperature
(1996-06-01)
Chang, KM
;
Tsai, JY
;
Li, CH
;
Yeh, TH
;
Wang, SW
The effects on the electrical properties of electron-cyclotron-resonance (ECR) nitride films grown at room temperature with different SiH4/N-2 gas ratios from 7 sccm/43 seem to 2 sccm/48 seem are systematically investigated. Superior properties of the films with low bulk trap density 8X10(17) cm(-3), small trap cross section, high breakdown strength 12.12 MV/cm, and near-stoichiometric refractive index 2.0 are obtained when the gas ratio SiH4/N-2 is 5 sccm/45 sccm, the microwave power is 210 W, and the chamber pressure is 0.5 mTorr. With the microwave power, total gas flow rate, and total pressure unchanged, the decrease in SiH4/N-2 ratio lower than 5/45 results in larger trap density and some lower breakdown strength. On the other side, increasing SiH4/N-2 ratio results in higher hydrogen content, lower breakdown strength, and films which are easily degraded during consecutive voltage sweep. High microwave power will eliminate the weak bonds and strengthen the electrical stability of the high SiH4/N-2 ratio film. (C) 1996 American Institute of Physics.
Effects of gas ratio on electrical properties of electron-cyclotron-resonance nitride films grown at room temperature
(1996-06-01)
Chang, KM
;
Tsai, JY
;
Li, CH
;
Yeh, TH
;
Wang, SW
The effects on the electrical properties of electron-cyclotron-resonance (ECR) nitride films grown at room temperature with different SiH4/N-2 gas ratios from 7 sccm/43 seem to 2 sccm/48 seem are systematically investigated. Superior properties of the films with low bulk trap density 8X10(17) cm(-3), small trap cross section, high breakdown strength 12.12 MV/cm, and near-stoichiometric refractive index 2.0 are obtained when the gas ratio SiH4/N-2 is 5 sccm/45 sccm, the microwave power is 210 W, and the chamber pressure is 0.5 mTorr. With the microwave power, total gas flow rate, and total pressure unchanged, the decrease in SiH4/N-2 ratio lower than 5/45 results in larger trap density and some lower breakdown strength. On the other side, increasing SiH4/N-2 ratio results in higher hydrogen content, lower breakdown strength, and films which are easily degraded during consecutive voltage sweep. High microwave power will eliminate the weak bonds and strengthen the electrical stability of the high SiH4/N-2 ratio film. (C) 1996 American Institute of Physics.
Influences of damage and contamination from reactive ion etching on selective tungsten deposition in a low-pressure chemical-vapor-deposition reactor
(1996-09-01)
Chang, KM
;
Yeh, TH
;
Wang, SW
;
Li, CH
;
電子工程學系及電子研究所
Reactive ion etching (RIE) used in contact hole formation can result in damage and contamination of the underlying silicon substrate. In this work, influences of these phenomena on selective tungsten deposition in a low-pressure chemical-vapor-deposition reactor have been studied. The damage was generated because of ion bombardment and radiation-induced bonding changes in silicon lattices. It causes large Si consumption, rough W/Si interface during tungsten deposition, and large leakage current of W/Si Schottky structure. Simultaneously, contamination occurred with two forms of residual layers and impurity permeation layers in fluorocarbon-based RIE chemistries. The CF4/CHF3/O-2 RIE of oxide produces the SiFxCyOz complex layers deposited on the sidewall and on the Si surface as well as the embedding of impurities such as F and C in the Si substrate. The creep-up, selectivity loss, lateral encroachment, high W film resistivity, and rough W/Si interface have been observed in the contaminated samples. Accordingly, a post-RTE etching technique used to remove the damage and contaminants before tungsten growth has been developed. A CF4/O-2 plasma etching followed with an O-2 plasma ashing step exhibits the capability of efficient surface cleaning. The excellent characteristics of W films such as elimination of encroachment and creep-up, low selectivity loss (i.e., 0.25 pcs/cm(2)), low resistivity of W films, smooth W/Si interface, and very low leakage current of W/Si contacts are thus obtained. (C) 1996 American Institute of Physics.
Influences of deposition temperature on thermal stability and moisture resistance of chemical vapor deposited fluorinated silicon oxide by using indirect fluorinating precursor
(1996-08-26)
Chang, KM
;
Wang, SW
;
Wu, CJ
;
Yeh, TH
;
Li, CH
In this letter, fluorinated silicon oxide (FxSiOy) films were deposited in the electron cyclotron resonance (ECR) chemical vapor deposition system with SiH4, O-2, and CF4 as the reaction gases. The CF4, in contrast to SiF4 or FSi(OC2H5)(3) used in other reports, is an indirect fluorinating source. The fluorinating mechanism is similar to that of the etching of oxide by fluorocarbon plasma, therefore, the thermal stability of the incorporated fluorine must strongly depend on the deposition temperature. It is found that the thermal stability and moisture resistance are greatly improved by increasing the deposition temperature. However, the higher deposition temperature also results in a higher compressed stress and dielectric constant. Besides, to get the moisture resistance, the deposition temperature must be above 300 degrees C. On the other hand, ECR-SiO2 (without fluorination), even deposited at room temperature, is shown to have a good water resistance. Therefore, by choosing deposition temperature for FxSiOy to have enough thermal tolerance and capping with ECR-SiO2, the moisture resistor is suggested for the inter metal dielectric applications.
Influences of deposition temperature on thermal stability and moisture resistance of chemical vapor deposited fluorinated silicon oxide by using indirect fluorinating precursor
(1996-08-26)
Chang, KM
;
Wang, SW
;
Wu, CJ
;
Yeh, TH
;
Li, CH
In this letter, fluorinated silicon oxide (FxSiOy) films were deposited in the electron cyclotron resonance (ECR) chemical vapor deposition system with SiH4, O-2, and CF4 as the reaction gases. The CF4, in contrast to SiF4 or FSi(OC2H5)(3) used in other reports, is an indirect fluorinating source. The fluorinating mechanism is similar to that of the etching of oxide by fluorocarbon plasma, therefore, the thermal stability of the incorporated fluorine must strongly depend on the deposition temperature. It is found that the thermal stability and moisture resistance are greatly improved by increasing the deposition temperature. However, the higher deposition temperature also results in a higher compressed stress and dielectric constant. Besides, to get the moisture resistance, the deposition temperature must be above 300 degrees C. On the other hand, ECR-SiO2 (without fluorination), even deposited at room temperature, is shown to have a good water resistance. Therefore, by choosing deposition temperature for FxSiOy to have enough thermal tolerance and capping with ECR-SiO2, the moisture resistor is suggested for the inter metal dielectric applications.
Leakage performance and breakdown mechanism of silicon-rich oxide and fluorinated oxide prepared by electron cyclotron resonance chemical vapor deposition
(1997-05-01)
Chang, KM
;
Wang, SW
;
Yeh, TH
;
Li, CH
;
Luo, JJ
The characteristics of silicon-rich oxide and fluorinated oxide (FxSiOy) films deposited in an electron cyclotron resonance chemical vapor deposition system with SiH4 and O-2 as the oxide sources and CF4 as the fluorinating precursor are investigated in this work. According to experimental results, the dangling bonds in Si-rich oxide behave as positively by charged electron traps and degrade the dielectric strength by lowering the barrier height for Fowler-Nordheim tunneling. On the other hand, a small amount of incorporated F atoms will passivate and neutralize these excess Si dangling bonds, thereby elevating the dielectric strength. However, too much incorporated F will degrade the pretunneling leakage performance owing to the porosity and fatigues structure in FxSiOy film. The high leakage and even breakdown at low field strongly limits the incorporated F concentration in FxSiOy film and the lowering of dielectric constant.
New techniques for simulation of ion implantation by numerical integration of Boltzmann transport equation
(1998-01-01)
Wang, SW
;
Guo, SF
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
New techniques for more accurate and efficient simulation of ion implantations by a stepwise numerical integration of the Boltzmann transport equation (BTE) have been developed in this work. Instead of using uniform energy grid, a non-uniform grid is employed to construct the momentum distribution matrix. A more accurate simulation result is obtained for heavy ions implanted into silicon. In the same time, rather than utilizing the conventional Lindhard, Nielsen and Schoitt (LNS) approximation, an exact evaluation of the integrals involving the nuclear differential scattering cross-section (d sigma(n) = 2 pi p dp) is proposed. The impact parameter p as a function of ion energy E and scattering angle phi is obtained by solving the magic formula iteratively and an interpolation techniques is devised during the simulation process. The simulation time using exact evaluation is about 3.5 times faster than that using the Littmark and Ziegler (LZ) spline fitted cross-section function for phosphorus implantation into silicon.
New techniques for simulation of ion implantation by numerical integration of Boltzmann transport equation
(1998-01-01)
Wang, SW
;
Guo, SF
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
New techniques for more accurate and efficient simulation of ion implantations by a stepwise numerical integration of the Boltzmann transport equation (BTE) have been developed in this work. Instead of using uniform energy grid, a non-uniform grid is employed to construct the momentum distribution matrix. A more accurate simulation result is obtained for heavy ions implanted into silicon. In the same time, rather than utilizing the conventional Lindhard, Nielsen and Schoitt (LNS) approximation, an exact evaluation of the integrals involving the nuclear differential scattering cross-section (d sigma(n) = 2 pi p dp) is proposed. The impact parameter p as a function of ion energy E and scattering angle phi is obtained by solving the magic formula iteratively and an interpolation techniques is devised during the simulation process. The simulation time using exact evaluation is about 3.5 times faster than that using the Littmark and Ziegler (LZ) spline fitted cross-section function for phosphorus implantation into silicon.
Novel single-poly EEPROM with damascene control-gate structure
(2005-10-01)
Sung, HC
;
Lei, TF
;
Hsu, TH
;
Wang, SW
;
Kao, YC
A novel single-poly EEPROM using damascene control gate (CG) structure is presented in this letter. The CG is tungsten (W) line made by a damascene process, and intergate dielectric is Al2O3 grown by atomic layer deposition (ALD). The program and erase mechanism is the same as the one for traditional stacked-gate cell, which uses the channel hot electron injection for programming and Fowler-Nordheim tunneling for channel erasing. With the high dielectric constant (K) property of Al2O3, we can perform the program and erase function with a voltage less than 6.5 V, which can be handled by 3.3 V devices instead of traditional high voltage devices. In the process compatibility aspect, this new cell needs only two extra masking steps over the standard CMOS process, and the high-kappa material is deposited in the back-end metallization steps without the contamination concerns on the front-end process. Therefore, this new technology is suitable for embedded application. In this letter, the good cell performance is demonstrated; such as, fast programming/erasing, good endurance and data retention.
Parallel simulation of ion implantation for multi-component targets using Boltzmann transport equation
(1998-07-01)
Wang, SW
;
Guo, SF
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A stepwise Boltzmann transport equation (BTE) simulation using non-uniform energy grid momentum matrix and exact nuclear scattering cross-section is successfully parallelized.to simulate the ion implantation of multi-component targets. Assuming that the interactions of ion with different target atoms are independent, the scattering of ions with different components can be calculated concurrently by different processors. It is developed on CONVEX SPP-1000 and the software environment of parallel virtual machine (PVM) with a master-slave paradigm. A speedup of 3.3 has been obtained for the simulation of As ions implanted into AZ1350 (C6.2H6O1N0.15S0.06) which is composed of five components. In addition, our new scheme gives better agreement with the experimental results for heavy ion implantation than the conventional method using a uniform energy grid and approximated scattering function.
Reactive ion etching of compound semiconductors grown by MOCVD technique with BCl3/SF6/Ar mixtures
(1995)
Chang, KM
;
Tsai, JY
;
Yeh, CB
;
Yeh, TH
;
Wang, SW