Browsing by Author "Yeh, TH"

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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.
Amorphouslike chemical vapor deposited tungsten diffusion barrier for copper metallization and effects of nitrogen addition
(1997-08-01)
Chang, KM
;
Yeh, TH
;
Deng, IC
;
Shih, CW
;
電子工程學系及電子研究所
In this article, we propose an amorphouslike chemical vapor deposited tungsten (CVD-W) thin him as a diffusion barrier for copper metallization. Experimental results gave no evidence of interdiffusion and structural change for Cu/amorphouslike CVD-W/Si samples annealed up to 675 degrees C for 30 min in N-2. At higher temperatures (700 degrees C), Cu penetration results in the formation of eta ''-Cu3Si precipitates at the CVD-W/Si interface. This is due to the crystallization of the amorphouslike CVD-W film above 650 degrees C, rendering the grain-boundary structure and, hence, fast pathways for Cu diffusion. The Cu/amorphouslike CVD-W/p(+)n diodes, thus, sustain large increases in reverse leakage current. In addition, the effects of nitrogen addition by using an in situ nitridation on the amorphouslike CVD-W film are also discussed. The effectiveness of the nitrided barrier is attributed to the blocking of the grain boundaries in the tungsten film by nitrogen atoms. This slows down Cu diffusion significantly. Physical and chemical analyses indicate that interfaces in the Cu/WNx/W/Si multilayer maintain their integrity while the annealing is carried out at 750 degrees C. Moreover, the reverse leakage current densities of Cu/WNx/W/p(+)n diodes remain at 10(-7) A/cm(2) after 725 degrees C annealing. (C) 1997 American Institute of Physics.
Amorphouslike chemical vapor deposited tungsten diffusion barrier for copper metallization and effects of nitrogen addition
(1997-08-01)
Chang, KM
;
Yeh, TH
;
Deng, IC
;
Shih, CW
;
電子工程學系及電子研究所
In this article, we propose an amorphouslike chemical vapor deposited tungsten (CVD-W) thin him as a diffusion barrier for copper metallization. Experimental results gave no evidence of interdiffusion and structural change for Cu/amorphouslike CVD-W/Si samples annealed up to 675 degrees C for 30 min in N-2. At higher temperatures (700 degrees C), Cu penetration results in the formation of eta ''-Cu3Si precipitates at the CVD-W/Si interface. This is due to the crystallization of the amorphouslike CVD-W film above 650 degrees C, rendering the grain-boundary structure and, hence, fast pathways for Cu diffusion. The Cu/amorphouslike CVD-W/p(+)n diodes, thus, sustain large increases in reverse leakage current. In addition, the effects of nitrogen addition by using an in situ nitridation on the amorphouslike CVD-W film are also discussed. The effectiveness of the nitrided barrier is attributed to the blocking of the grain boundaries in the tungsten film by nitrogen atoms. This slows down Cu diffusion significantly. Physical and chemical analyses indicate that interfaces in the Cu/WNx/W/Si multilayer maintain their integrity while the annealing is carried out at 750 degrees C. Moreover, the reverse leakage current densities of Cu/WNx/W/p(+)n diodes remain at 10(-7) A/cm(2) after 725 degrees C annealing. (C) 1997 American Institute of Physics.
Barrier characteristics of chemical vapor deposited amorphous-like tungsten silicide with in situ nitrogen plasma treatment
(1999-07-01)
Chang, KM
;
Deng, IC
;
Yeh, TH
;
Shih, CW
;
電子工程學系及電子研究所
Our team investigated the characteristics of inserting an 80 nm amorphous-like WSi1.6N0.5N/WSi1.6 barrier layer between aluminum film and a shallow diode to retard aluminum and silicon interdiffusion. In one chamber without breaking vacuum, we used a nitrogen plasma treatment to stuff nitrogen atoms into the grain boundaries of amorphous-like tungsten silicide film. The nitrogen atoms eliminated the fast diffusion paths of film, thus giving the amorphous-like tungsten silicide film a smaller diffusion coefficient. We then examined the failure of diodes with amorphous-like WSi1.6N0.5/WSi1.6 barriers which were annealed at 575 degrees C for 30 min and which had leakage currents of 10(7) and 10(8) nA/cm(2). These diodes failed due to the diffusion of aluminum along the sidewalls of the barriers and the field oxide interface. In the search for a solution to this problem we investigated the use of tetraethylorthosilicate, which is known for its thermal stability as a stress buffer. In this experiment we used tetraelhylorthosilicate to form a "contact array structure" which in turn prevented diode failure at 575 degrees C annealing for 30 min, and furthermore, the diodes in the contact array structure only began to show evidence of degradation at 600 degrees C. (C) 1999 The Electrochemical Society. S0013-4651(98)09-086-7. All rights reserved.
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.
Design of microstrip bandpass filters with a dual-passband response
(2005-04-01)
Kuo, JT
;
Yeh, TH
;
Yeh, CC
;
電信工程研究所
;
Institute of Communications Engineering
This paper presents a rigorous design of microstrip bandpass filters with a dual-passband response in parallel-coupled and vertical-stacked configurations. Based on resonance characteristics of a stepped impedance resonator (SIR), the second resonant frequency can be tuned over a wide range by adjusting its structure parameters. Emphasis is placed on filter synthesis for simultaneously matching in-band response and singly loaded Q by using tapped input/output couplings for the two designated passbands. Fractional bandwidth design graphs are used to determine proper geometric parameters of each coupled stage when filter specification is given. Realizable fractional bandwidths of the two passbands for a coupled SIR structure are clearly depicted in fractional bandwidth design graphs. Several experimental litters are fabricated and measured to demonstrate the design.
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.
Highly selective etching for polysilicon and etch-induced damage to gate oxide with halogen-bearing electron-cyclotron-resonance plasma
(1996-09-01)
Chang, KM
;
Yeh, TH
;
Deng, IC
;
Lin, HC
;
電子工程學系及電子研究所
The investigations of polysilicon etching with three halogen-bearing plasmas (SF6, Cl-2, and HBr) in an electron-cyclotron-resonance reactor have been made. We examine the etching characteristics which include etching rate, anisotropy, and selectivity based on the discussions of the chemical and electrical properties of the F, Cl, and Br radicals, It was found that the degree of anisotropy strongly depends on the deposition of a silicon halide film on sidewall and on the spontaneous etching properties of three halogen plasma mixtures. The selectivity to oxide is related to the amount of silicon halides that are produced during etching poly-Si and the electrically polarized level of these products when they adsorb on the oxide surface. We find that the selectivity on oxide is approximately infinite for the HBr system and over 90 for the Cl-2 system. In addition, the effects of oxygen addition, microwave power, and rf power are also investigated. It was found that the maximum etching rate and selectivity of SF6, Cl-2, and HBr plasmas occurred at concentrations of added oxygen at about 7.5%, 5%, and 3% total flow rates, respectively. The suitable range for the microwave power applied is from 250 to 300 CV and the most respectable value of applied rf power is about 35 W. Concurrently, the local surface charging causing damage to the gate oxide during the overetching period is studied. It is observed that low device yield, large flatband voltage V-fb shift, and high interface-state density D-it are correlated with longer overetch and high antenna ratio structure of the device. A more obvious degradation is observed in the SF6 gaseous system than in Cl-2 and HBr ones. Finally, the influence of magnetic coil current on device damage is also addressed. (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.
Nitridation of fine grain chemical vapor deposited tungsten film as diffusion barrier for aluminum metallization
(1997-04-15)
Chang, KM
;
Yeh, TH
;
Deng, IC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A novel tungsten nitride (WNx) film for diffusion barrier applications has been prepared by nitridation of a fine grain chemical vapor deposited tungsten (CVD-W) film. The fine grain CVD-W is deposited at 300 degrees C in a low pressure chemical vapor deposition reactor with a SiH4/WF6 flow rate of 12.5/5 seem under a total gas pressure of 100 mTorr. The subsequent nitridation process is executed in nitrogen plasma at 300 degrees C without breaking vacuum. The thickness of WN, layer as examined by secondary ion mass spectroscopy is 50 nm after 5 min exposure to nitrogen plasma. X-ray photoelectron spectroscopy spectra shows that the atomic ratio of tungsten to nitrogen in WNx, layer is 2:1. According to the analysis by Auger electron spectroscopy and the measurement of n(+)p junction leakage current, the Al/WNx/W/Si multilayer maintains excellent interfacial stability after furnace annealing at 575 degrees C for 30 min. The effectiveness of W2N barrier is attributed to stuffing grain boundaries with nitrogen atoms which eliminates the rapid diffusion paths in fine grain CVD-W films. (C) 1997 American Institute of Physics.
Nitridation of fine grain chemical vapor deposited tungsten film as diffusion barrier for aluminum metallization
(1997-04-15)
Chang, KM
;
Yeh, TH
;
Deng, IC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A novel tungsten nitride (WNx) film for diffusion barrier applications has been prepared by nitridation of a fine grain chemical vapor deposited tungsten (CVD-W) film. The fine grain CVD-W is deposited at 300 degrees C in a low pressure chemical vapor deposition reactor with a SiH4/WF6 flow rate of 12.5/5 seem under a total gas pressure of 100 mTorr. The subsequent nitridation process is executed in nitrogen plasma at 300 degrees C without breaking vacuum. The thickness of WN, layer as examined by secondary ion mass spectroscopy is 50 nm after 5 min exposure to nitrogen plasma. X-ray photoelectron spectroscopy spectra shows that the atomic ratio of tungsten to nitrogen in WNx, layer is 2:1. According to the analysis by Auger electron spectroscopy and the measurement of n(+)p junction leakage current, the Al/WNx/W/Si multilayer maintains excellent interfacial stability after furnace annealing at 575 degrees C for 30 min. The effectiveness of W2N barrier is attributed to stuffing grain boundaries with nitrogen atoms which eliminates the rapid diffusion paths in fine grain CVD-W films. (C) 1997 American Institute of Physics.
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