Browsing by Author "Wu, WF"

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Barrier capability of TaNx films deposited by different nitrogen flow rate against Cu diffusion in Cu/TaNx/n(+)-p junction diodes
(2001-01-01)
Yang, WL
;
Wu, WF
;
Liu, DG
;
Wu, CC
;
Ou, KL
This paper investigates the barrier capability of tantalum nitride (TaNx) layers against Cu diffusion. The TaNx layers were reactively sputtered in contact holes to a thickness of 50 nm by using a different nitrogen flow rate. Results indicate that the TaNx layers fail to be a diffusion barrier due to a relative high resistivity for nitrogen flow ratios exceeding 10%. in addition, we found that the phase of alpha -Ta(-N) functions as an effective barrier against Cu diffusion and that Cu/TaN(3-5%)/n(+)-p junction diodes are able to sustain a 30 min furnace anneal up to 500 degreesC without causing degradation of the electrical characteristics. The high-temperature failure of barrier capability for the TaNx layers is due to interdiffusion of Cu and Si across the TaNx film structure to form Cu3Si. The surface roughness and the film structure of TaNx layers determine the ability of Cu and Si interdiffusion. (C) 2001 Elsevier Science Ltd. All rights reserved.
Carbon nanotubes grown using cobalt silicide as catalyst and hydrogen pretreatment
(2005-12-01)
Wen, HC
;
Yang, KH
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Ou, KL
;
Wu, WF
;
Luo, RC
Cobalt catalytic-layers 25 mn were deposited by sputtering on silicon substrates. At the pretreatments, hydrogen plasma was conducted for 4-16 min at 600 degrees C in a MPCVD system. Pretreated samples were characterized using SEM and AFM. Surface morphologies of catalytic-layers were changed after hydrogen plasma pretreatments. The cobalt layers became discontinuous and some nanoparticles were formed. With pretreatments for a long time, nanoparticles tended to agglomerate to reduce surface energy and larger nanoparticles were observed. It is believed that the optimum pretreatment condition for the growth of carbon nanotubes could be achieved because relatively high growth failure and nanofibers (> 100 nm) was observed for shorter and longer than 12 min pretreatment, respectively. It is found that the hydrogen pretreatment is a crucial step for the making of nucleation sites in the synthesis of carbon nanotubes using cobalt silicide as catalyst on Si substrates. After the pretreatment, mixture gases of hydrogen and methane were then flowed into the chamber for 12 min, samples were characterized using SEM, TEM and Raman spectrum. Carbon atoms were adsorbed on the islands of catalysts, and then diffused into the edge of nanotubes. Cobalt silicides were formed due to high processing temperature, and cobalt atoms tended to diffuse and stay on the silicon substrates, which enhance carbon nanotubes to grow under the root growth mechanism. (c) 2005 Elsevier B.V. All rights reserved.
Characterization of TiN film grown by low-pressure-chemical-vapor-deposition
(1997-10-31)
Mei, YJ
;
Chang, TC
;
Hu, JC
;
Chen, LJ
;
Yang, YL
Conformal TiN films were deposited by thermal low-pressure-chemical-vapor-deposition (LPCVD) in a rotating disk reactor, using TiCl4 and NH3 with N-2 as a dilution gas. TiN plug with 0.05 mu m contact size was achieved. No void formation was observed in the TiN plug. The result demonstrated that LPCVD-TiN can be used to fill very small contact holes. The excellent step coverage and uniformity resulted from a surface-reaction-rate-limited deposition. The resistivity of TiN film was reduced to 133 mu Omega cm by in-situ NH3 plasma post-treatment. The concentration of chlorine in the TiN him was measured to be less than 2 atomic % (at.%) by Auger electron spectroscope measurement. For Al deposited on TiN, the Al orientation was found to be dependent on the deposition method of Al film, but not on the underlying TiN orientation. (C) 1997 Elsevier Science S.A.
Deposition of indium tin oxide films on polycarbonate substrates by radio-frequency magnetron sputtering
(1997-04-20)
Wu, WF
;
Chiou, BS
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Indium tin oxide (ITO) films have been deposited onto polycarbonate (PC) substrates by radio frequency (rf) magnetron sputtering. The influence of the oxygen content during sputtering on the film morphology, and the electrical and optical properties of the films have been investigated. Both the refractive index and the extinction coefficient decrease with increasing oxygen content. In this study, the figures of merit T-10/R-sh of the films are higher than those for low-temperature sputtered films reported in the literature. (C) 1997 Elsevier Science S.A.
Deposition of indium tin oxide films on polycarbonate substrates by radio-frequency magnetron sputtering
(1997-04-20)
Wu, WF
;
Chiou, BS
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Indium tin oxide (ITO) films have been deposited onto polycarbonate (PC) substrates by radio frequency (rf) magnetron sputtering. The influence of the oxygen content during sputtering on the film morphology, and the electrical and optical properties of the films have been investigated. Both the refractive index and the extinction coefficient decrease with increasing oxygen content. In this study, the figures of merit T-10/R-sh of the films are higher than those for low-temperature sputtered films reported in the literature. (C) 1997 Elsevier Science S.A.
Effect of aluminum seed layer on the crystallographic texture and electromigration resistance of physical vapor deposited copper interconnect
(2000-12-01)
Chin, YL
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Chiou, BS
;
Wu, WF
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The effects of an Al underlayer with respect to texture control and electromigration (EM) resistance of Cu films are investigated in this study. The Al underlayer enhances the (111) texture of Cu films and the surface smoothness of the annealed Cu film. The same cubic crystal structure (face-centercd cubic) and small difference of the nearest interatomic distance of the (111) plane between Cu and Al result in the increase of the peak ratio I((111))/I-(200) of Cu films. The thicker the Al film, the more preferred the Cu (111) orientation. The resistivity of the Cu/AI bilayer film, which increases at about 0.2 mu Omega .cm per 1-nm-thick Al underlayer, is smaller than the reported value of single phase Cu(Al) solution. The EM resistance of Cu interconnects is also improved when the Al underlayer is present. The mean time to failure (MTF) of Cu interconnects with a 5-nm-thick Al underlayer is longer by one order of magnitude than that without an Al underlayer at 240 degreesC and 12 MA/cm(2).
Effect of oxygen concentration in the sputtering ambient on the microstructure, electrical and optical properties of radio-frequency magnetron-sputtered indium tin oxide films
(1996-02-01)
Wu, WF
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Chiou, BS
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Indium tin oxide (ITO) films have been prepared by radio-frequency (rf) magnetron sputtering. The effect oi oxygen concentration in the sputtering ambient on the structure and properties oi ITO films are investigated. The films have a preferred orientation in the (440) plane. The presence of oxygen during sputtering enhances the crystallization of the film. Film grain size increases as more oxygen is added. According to the XPS measurements, the addition of oxygen reduces the oxygen-deficient region of the film. Hence the optical transmittance of the film is improved while film conductivity decreases.
Effect of the tantalum barrier layer on the electromigration and stress migration resistance of physical-vapor-deposited copper interconnect
(2002-05-01)
Chin, YL
;
Chiou, BS
;
Wu, WF
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The effects of a Ta barrier layer on electromigration and stress migration of Cu films are investigated. The Ta barrier layer enhances both the (111) texture and the median grain size of the annealed Cu films. At 225degreesC, the electromigration mean time to failure (225degreesC-MTF) of Ta/Cu/Ta multilayer interconnects is about two times longer than that of Cu monolayer interconnects. After 500 thermal cycles, the 225degreesC-MTF of Ta/Cu/Ta multilayer interconnects does not change and is about three times longer than that of Cu monolayer interconnects. The activation energy E-a of electromigration of Ta/Cu/Ta multilayer interconnects is 0.77 eV, which is higher than that of Cu monolayer interconnects (0.65 eV). Since the Ta/Cu/Ta specimen has enhanced crystallographic texture and larger grain size. it has both higher electromigration endurance and thermal stress resistance than Cu. However. the measured MTF is shorter than that predicted by an equation proposed by Vaidya and Sinha [Thin Solid Films 75 (1981) 253]. The shorter MTF and smaller E-a values for the Ta/Cu/Ta multilayer compared to the predicted ones are due to the weak Ta/Cu interface, A lifetime of 100 years is predicted for Ta/Cu/Ta multilayer interconnects with and without 500 thermal cycle stress.
Effective repair to ultra-low-k dielectric material (k-2.0) by hexamethyidisilazane treatment
(2002-07-01)
Mor, YS
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Chang, TC
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Liu, PT
;
Tsai, TM
;
Chen, CW
O-2 plasma ashing is commonly used to remove photoresist. The effect of O-2 plasma ashing on the porous organosilicate glass (CH3SiO1.5)(n), one of the spin-on materials, is investigated. O2 plasma can oxidize the methyl groups in porous organosilicate glass (POSG), which leads to the formation of Si-OH groups. The hydrophilic Si-OH groups will induce moisture uptake so that electrical degradation will occur in POSG film. Pure hexamethyldisilazane (HMDS) vapor (100% HMDS) can react with the Si-OH groups in POSG film. It converts hydrophilic Si-OH groups into hydrophobic Si-O-Si(CH3)(3) groups against moisture uptake. The leakage current density decreases by a factor of 2-3 and the dielectric constant decreases from 3.62 to 2.4 when O-2 plasma-damaged POSG undergoes HMDS treatment at 80degreesC for 15 min. Therefore, HMDS treatment is the effective technique to repair the electrical degradation to POSG film during photoresist stripping processing. (C) 2002 American Vacuum Society.
Effects of ammonia plasma treatment on the surface characteristics of carbon fibers
(2006-02-24)
Wen, HC
;
Yang, K
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Ou, KL
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Wu, WF
;
Chou, CP
Carbon fibers were grown from cobalt catalysts with larger size (> 100 nm), and the size distribution can be controlled by pretreatment. Pretreated cobalt catalytic-layers were observed as islands, which can enhance the growth of carbon fibers. The carbon fibers were treated by ammonia plasma in a PECVD system. High-energy ammonia plasma not only can cause damage but also adsorb on carbon fibers. The ammonia plasma treatment resulted in the etching effect. It is also observed that the more treatment time, the more disorder in structures of carbon fibers. The N-H functional groups were found on the surfaces of ammonia plasma treated carbon fibers and this observation can be further investigated to develop chemical sensor application. (c) 2005 Elsevier B.V. All rights reserved.
Effects of nitrogen plasma treatment on tantalum diffusion barriers in copper metallization
(2003-02-01)
Wu, WF
;
Ou, KL
;
Chou, CP
;
Wu, CC
;
機械工程學系
In this study, the barrier properties of ultrathin Ta, TaN, and nitrogen plasma-treated Ta films were investigated by Cu/Ta(N)/Si structure. The barrier properties were evaluated by sheet resistance, film stress, X-ray diffraction, transmission electron microscopy, scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. Nitrogen plasma-treated Ta films possess better barrier performance than sputtered Ta and TaN films. The sheet resistance of Cu/Ta/Si and Cu/TaN/Si increases, apparently, after annealing at 600 and 625degreesC, respectively. The Cu/30 min plasma-treated Ta/Si is fairly stable up to annealing at 700degreesC for 1 h. Diffusion resistance of the plasma-treated Ta barrier is more effective. It is believed that a new amorphous layer forms on the surface of Ta film after plasma treatment. The new amorphous layer possesses some nanocrystalline Ta2N phases with lattice constant 0.305 nm. It is believed that the amorphous layer containing some nanocrystals can alleviate Cu diffusion into the Si substrate and, hence, improve barrier performance. (C) 2003 The Electrochemical Society.
Electromigration and integration aspects for the copper-SiLK system
(2004-07-01)
Tseng, HS
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Chiou, BS
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Wu, WF
;
Ho, CC
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電子工程學系及電子研究所
In this study, the thermal characteristics and electromigration (EM) resistance of two dielectrics, SiLK(TM) and SiO2, are investigated to evaluate the feasibility of low dielectric-constant SiLK for intermetal. dielectric applications. Liftoff patterning was employed to fabricate the Cu interconnect for the EM test, and the Taguchi method was used in the experimental design to identify the key parameters for a successful liftoff. It was shown that the thermal impedance of the metal lines passivated with SiLK is 14% higher than that of metal lines passivated with SiO2. On the basis of the thermal impedance and temperature rise of the interconnect, it was concluded that the major heat transfer path is via the underlayer dielectric to the Si substrate. The activation energy of EM for Cu passivated with SiLK is smaller, and the EM lifetime is shorter than that of Cu passivated with SiO2. Possible mechanisms are discussed.
Eliminating dielectric degradation of low-k organosilicate glass by trimethylchlorosilane treatment
(2002-07-01)
Chang, TC
;
Liu, PT
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Mor, YS
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Tsai, TM
;
Chen, CW
The interaction between low-k organosilicate glass (OSG) and photoresist removal is investigated. O-2 plasma ashing and chemical wet stripper are commonly performed to remove photoresist (PR) in integrated circuit fabrication. However, O-2 plasma or wet stripper will attack function groups and cause Si-OH group formation in OSG film during PR removal processing. The Si-OH groups often lead to moisture uptake and consequently dielectric degradation will occur in OSG film. Trimethylchlorosilane (TMCS) treatment can negate the damage in the OSG film after the PR removal process. In addition, chemical TMCS can react with Si-OH groups and reduces moisture uptake so that the dielectric characteristic of OSG can be maintained. Hence, TMCS treatment is a promising method for photoresist removal. (C) 2002 American Vacuum Society.
High-reliability Ta2O5 metal-insulator-metal capacitors with Cu-based electrodes
(2006)
Tsai, KC
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Wu, WF
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Chao, CG
;
Kuan, CP
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材料科學與工程學系
The properties of tantalum oxide (Ta2O5) metal-insulator-metal (MIM) capacitors with Al/Ta/Cu/Ta bottom electrodes were investigated. An ultrathin Al film successfully suppresses oxygen diffusion in the Ta2O5 MIM capacitor with the Cu-based electrode. The electrical characteristics and reliability of Ta2O5 MIM capacitors are improved by addition of ultrathin Al films. Ta2O5 MIM capacitors have low leakage current density (1 nA/cm(2) at 1 MV/cm) and high breakdown field (5.2 MV/cm at 10(-6) A/cm(2)). The decrease in leakage current is attributed to the formation of a dense and uniform Al2O3 layer, which has self-protection property and stops further oxygen diffusion into the tantalum contact. The dominant conduction mechanism of leakage current is the Poole-Frenkel effect at electric fields above 1.5 MV/cm. (c) 2006 The Electrochemical Society.
Highly (111) textured titanium nitride layers for sub- quarter-micrometer Al metallization
(1999-07-01)
Wu, WF
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Lin, CC
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Huang, CC
;
Lin, HC
;
Chang, TC
Texture improved TiN films were prepared by a two-step deposition process. A thin uncollimated TiN layer is deposited first at low substrate temperature and sputtering power. This layer has poor step coverage and high resistivity, but acts as a crystallographic seed layer for the subsequent collimated TiN layer deposited at high substrate temperature and sputtering power. The TiN layer stack is deposited sequentially without vacuum break. The resulting TiN layer has a low resistivity of 72.25 mu Omega cm, high <111> preferred orientation, and improved bottom coverage in sub-quarter-micrometer contact holes and trenches. (C) 1999 The Electrochemical Society. S1099-0062(99)01-023-8. All rights reserved.
Improved TaN barrier layer against Cu diffusion by formation of an amorphous layer using plasma treatment
(2002-09-01)
Ou, KL
;
Wu, WF
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Chou, CP
;
Chiou, SY
;
Wu, CC
The thermal stability and electrical properties of plasma-treated TaN films have been investigated by Cu/TaN/Si systems. The properties of diffusion barrier were evaluated by sheet resistance, x-ray diffraction (XRD), transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS), energy-dispersive spectroscopy (EDS), Auger electron microscopy (AES), and reverse-biased junction leakage current. A new amorphous layer is found to form on the surface of TaN film after the plasma treatment, Plasma-treated TaN films show better barrier performance than untreated TaN films. The sheet resistance of Cu/TaN(10 nm)/Si increases apparently after annealing at 625 degreesC for 1 h, while the Cu/plasma-treated TaN(10 nm)/Si is fairly stable up to annealing at 750 degreesC. The resistance to copper diffusion in plasma-treated TaN film is more effective. This is attributed that an amorphous layer that forms on the surface of TaN film after the plasma treatment. The thermal stabilities of Cu/TaN/n(+)-p junction diodes are enhanced by plasma treatment. The Cu/TaN(10 nm)/n(+)-p and Cu/TaN(50 nm)/n(+)-p junction diodes result in large reverse-biased junction leakage currents after annealing at 525 and 575 degreesC, respectively. On the other hand, plasma-treated TaN diffusion barriers improve the integrity of junction diodes up to 650 degreesC. Nano crystallization and stuffing effects of plasma treatments are believed to impede Cu diffusion into the Si substrate and hence improve the barrier performance. (C) 2002 American Vacuum Society.
Improving the electrical integrity of Cu-CoSi2 contacted n(+)p junction diodes using nitrogen-incorporated Ta films as a diffusion barrier
(2002-11-01)
Yang, WL
;
Wu, WF
;
You, HC
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Ou, KL
;
Lei, TF
The study on improving the electrical integrity Of Cu-CoSi2 contacted-junction diodes by using the reactively sputtered TaNx as a diffusion barrier is presented in this paper. In this study, the Cu(300 nm)-CoSi2 (50 nm)/n(+)p junction diodes were intact with respect to metallurgical reaction up to a 350 degreesC thermal annealing while the electrical characteristics started to degrade after annealing at 300 degreesC in N-2 ambient for 30 min. With the addition of a 50-nm-thick TaNx diffusion barrier between Cu and CoSi2, the junction diodes were able to sustain annealing up to 600 degreesC without losing the basic integrity of the device characteristics, and no metallurgical reaction could be observed even after a 750 degreesC annealing in furnace. In addition, the structure of TaNx layers deposited on CoSi2 at various nitrogen flow rates has been investigated. The TaNx film with small grain sizes deposited at nitrogen flow ratios exceeding 10% shows better barrier capability against Cu diffusion than the others.
Influence of N2O plasma treatment on microstructure and thermal stability of WNx barriers for Cu interconnection
(2004-05-01)
Tsai, KC
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Wu, WF
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Chen, JC
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Pan, TJ
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Chao, CG
Thermal stabilities of Cu-contacted n(+)-p junctions with tungsten nitride (WNx) diffusion barriers deposited at various nitrogen flow ratios are investigated. N2O plasma treatment is applied to improve thermal stability and barrier performance of WNx film. Sheet resistance Of Cu/N2O plasma-treated WNx/Si is fairly stable even after annealing at 750degreesC for 30 min. Moreover, N2O plasma treatment enables the Cu/WNx/n(+)-p junction-diodes to sustain thermal annealing at 600 degreesC without electrical degradation. Auger electron spectroscopy depth profiles show that Cu diffusion through the N2O plasma-treated WNx barrier is extremely limited, even after annealing at 675 degreesC. Analyses of transmission electron microscopy and x-ray photoemission spectroscopy show that nitridation and oxidation on the WNx barrier occur and an amorphous layer is formed after N2O plasma treatment. (C) 2004 American Vacuum Society.
Mechanical and optical properties of ITO films with anti-reflective and anti-wear coatings
(1997-05-01)
Wu, WF
;
Chiou, BS
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
In this study, radio frequency (rf) magnetron sputtered ITO films were coated with reactively sputtered SiO2 films. The microhardness, pull-off strength, scratch adhesion strength, optical transmittance and reflectance of the SiO1/ITO/substrate system are investigated. Coating of SiO2 enhances both the hardness and pull-off strength and reduces the scratch critical load of the system. The optical transmittance in the visible range is also improved with the addition of SiO2.
Novel multilayered Ti/TiN diffusion barrier for Al metallization
(2005-08-01)
Wu, WF
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Tsai, KC
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Chao, CG
;
Chen, JC
;
Ou, KL
A novel, multilayered Ti/TiN diffusion barrier is proposed and successfully applied for Al metallization. The multilayered Ti/TiN structure is effective in enhancing the barrier properties since the very thin Ti layer inserted into titanium nitride (TiN) barrier can cause disruption of the TiN columnar growth and reduction of open grain boundaries resulting in retarded interdiffusion between metal and silicon. Multilayered Ti/TiN films are deposited sequentially by sputtering without breaking vacuum. It is found that TiN grain boundaries are discontinuous when a Ti layer is inserted into TiN. Multilayered Ti/TiN has a better barrier performance than single-layer TiN in Al metallization. However, the barrier performance is related to the number and thickness of the inserted Ti layers, because increasing titanium will enhance chemical reactions between Al and barrier layers, and produce more titanium-aluminum compounds. The total thickness of introduced Ti layers should be reduced to improve barrier performance.