Browsing by Author "Liu, CP"

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Characterization and reliability of low dielectric constant fluorosilicate glass and silicon rich oxide process for deep sub-micron device application
(2001-11-01)
Cheng, YL
;
Wang, YL
;
Liu, CW
;
Wu, YL
;
Lo, KY
Fluorosilicate Glass (FSG) with low dielectric constant currently has been replaced as an alternative to SiO2 for device speed improvement. However, several integration aspects, such as Fluorine (F) distribution, F thermal stability, gap fill capability, capacitance reduction and via resistance of FSG prepared by the high density plasma (HDP) chemical vapor deposition (CVD) method are of concern for sub-0.18-mum devices. In this study, HDP-FSG films show different F concentrations at different locations on an 8-inch wafer. In addition, the FSG film shows poor thermal stability and F diffuses out of the film after high temperature annealing and the pressure cook test (PCT). However, the thermal stability of FSG film can be improved by capping with an oxide layer. The results indicate that silicon rich oxide (SRO) has a better effect at blocking the F diffusion out of FSG films at high temperature than plasma enhanced oxide (PE-OX). For the gap fill capability, HDP-FSG can fill all 0.23-mum gaps and some of the 0.21-mum gaps with an aspect ratio <3.8 but not the 0.19-mum gaps. A 8000 Angstrom HDP-FSG film with 600 Angstrom USG liner and 2000 Angstrom cap layer shows approximately 7.5 to 7.7% capacitance reduction on 0.23/0.23-mum gaps when compared with USG (undoped silicate glass). In addition, FSG has a larger capacitance reduction on the wider metal lines than the thinner metal lines at the same gap size due to a capacitance fringe effect. The via resistance for 0.26 mum unlanded via (which allow minor photo mis-alignment) of HDP-FSG film is also similar to that of USG. (C) 2001 Elsevier Science B.V. All rights reserved.
Characterization and thermal stability of fluorosilicate glass films deposited by high density plasma chemical vapor deposition with different bias power
(2006-03-01)
Hsiao, WC
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Liu, CP
;
Wang, YL
;
Cheng, YL
;
材料科學與工程學系
High-density plasma chemical vapor deposition (HDP-CVD) fluorosilicate glass (FSG) films were evaluated for the application of intermetal dielectric (IMD) materials in current devices. Film characteristics were examined as a function of deposition/sputter etch (D/S) ratio, which was controlled by the bias power in HDP-CVD. FTIR spectra show that the positions of Si-O and Si-F peaks are independent of the bias power, but the Si-O shifted to a higher wave number and Si-F-2 appeared upon annealing for the films deposited at lower bias power. Stress hysteresis of the FSG films after the first thermal cycle shows a nonequilibrium nature of the microstructure related to impurity content, especially for the film deposited with lower bias power. Thermal desorption of H2O, F, O-2 and Ar were examined, while most of the desorption behaviour can be related to the physical pore structure and pore quantity. (c) 2005 Elsevier B.V. All rights reserved.
Direct COSi2 thin-film formation with homogeneous nanograin-size distribution by oxide-mediated silicidation
(2004-09-01)
Chang, JJ
;
Liu, CP
;
Chen, SW
;
Chang, CC
;
Hsieh, TE
By annealing at 460 degreesC for 120 s followed by 600 degreesC 120 s, nanocrystalline CoSi2 thin film with an average grain size of 5 nm can be directly formed from a Co/SiOx/Si multilayer with the SiOx, as a mediated layer. It is found that annealing at 460 degreesC for enough time is crucial for generating enough diffusion channels within the SiOx, layer. After these channels are created, subsequent annealing at 600 degreesC keeps these channels open and is responsible for rapid grain growth. In other words, by using two-step annealing, nucleation and growth processes can be effectively controlled and, hence, the resulting microstructure. The homogeneous nanograin-size distribution is important for ultralarge-scale integration technology below 90 nm to prevent resistance degradation induced by CoSi2, agglomeration. (C) 2004 American Vacuum Society.
Effect of deposition temperature, on thermal stability in high-density plasma chemical vapor deposition fluorine-doped silicon dioxide
(2004-05-01)
Cheng, YL
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Wang, YL
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Chen, HW
;
Lan, JL
;
Liu, CP
Thermal stability of fluorine-doped silicon dioxide films deposited by high-density plasma chemical vapor deposition as a function of deposition temperature were investigated in this study. Both thermal desorption spectrum and annealing test results show that SiOF films deposited above 400 degreesC have better thermal stability. Furnace annealing data indicate that non -Si-F- bonding fluorine does exist in low-deposition-temperature SiOF films. Furthermore, secondary-ion mass spectrometer results also reveal that the fluorine in SiOF films with a lower-deposition temperature is easily diffused out and turned into the underlayer, which results in less thermally stable SiOF films. Moreover, short-loop simulation results have been subsequently tested and it was concluded that the deposition temperature of the SiOF film is extremely important for thermal stability. (C) 2004 American Vacuum Society.
Evaluation of advanced chemical mechanical planarization techniques for copper damascene interconnect
(2004-01-30)
Chen, KW
;
Wang, YL
;
Liu, CP
;
Yang, K
;
Chang, L
According to rapid development of CMP technology, the difference of polishing methods would be applied for copper damascene interconnect. These methods include conventional rotary, linear, oscillation platform. The advantages of these platform would highlighted in uniformity control, stability of removal rate, planarization efficiency, throughput promotion, lower cost of ownership, even dishing and erosion effect integrated with slurry. This paper presented our experience to compare the uniformity, removal rate and planarization efficiency of Cu-CMP between various polishing platforms. In convection, the rotary or oscillation platform would be usually applied in oxide and tungsten CMP, due to the robust air-back carrier and rigid platen to polish the wafer, which performs the good reliability on wafer-to-wafer thickness and endpoint detection. However, the linear polisher is made of the air-bearing moving belt and self-rotated carrier and would provide the wider uniformity and planarization control window than others. In addition,, the simulation model would explain the difference from mechanic design and wafer moving paths between various polishing techniques. Hence, the trade-off advantage and application between various platforms would be compensated and integrated with slurry, conditioners and coming thickness profile from copper plating. It can achieve the optimization of Cu-CMP process. (C) 2003 Elsevier B.V. All rights reserved.
Formation of pyramid-like nanostructures during cobalt film growth by magnetron sputtering
(2005-04-01)
Liu, CP
;
Chang, JJ
;
Chen, SW
;
Chung, HC
;
Wang, YL
Cobalt pyramid-like nanostructures with sharp tips were formed on the surfaces of cobalt thin films grown by magnetron sputtering only when a negative bias was applied. There are two types of pyramids, which grew on top of a columnar grain structure directly from Si(001) substrates. The formation of pyramid-like nanostructures is only selective to a epsilon-Co (hcp) thin film but not a alpha-Co (fcc) thin film, where the basal plane is 10 (1) over bar0 with several well-defined low-energy faceted planes. When grown on Si(111) substrates, the shape of the basal plane changes to a pentagon or other polygon. The island nucleation seems to depend on adatom energy, sputtering rate and the interface stress between the Co thin film and the substrate, but growth is significantly determined by the minimum surface configuration of the structure.
High-selectivity damascene chemical mechanical polishing
(2006-03-01)
Chiu, SY
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Wang, YL
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Liu, CP
;
Chang, SC
;
Hwang, GJ
In this study, multi-step chemical mechanical polishing (CMP) with different copper removal rates and polishing pads is used to eliminate topography efficiently and to reduce micro-scratches on copper films. In colloidal-silica-based slurry, the polishing behaviors of copper, tantalum and silicon dioxide are found to relate to that kind of alkaline additives. The size of cations from alkaline additives influences the zeta potential of slurries, so as to vary the material removal rate. The addition of small-sized K+ from KOH provides high removal selectivity of tantalum/copper and oxide/copper, so as to benefit the reduction of copper dishing. (c) 2005 Elsevier B.V All rights reserved.
Integration of a stack of two fluorine doped silicon oxide film with ULSI interconnect metallization
(2004-01-15)
Cheng, YL
;
Wang, YL
;
Liu, CP
;
Wu, YL
;
Lo, KY
Recently, fluorosilicate glass (FSG) has received much attention for application in microelectronics manufacturing due to its low dielectric constant and stable gap-filling ability. Although FSG films have been demonstrated as potential inter metal dielectrics (IMD) for sub-micron devices, integrating a stack of two fluorine doped silicon oxide film deposited on a high-density plasma chemical vapor deposition (HDP-CVD) system for gap filling and a plasma-enhanced chemical vapor deposition (PECVD) system for throughput has not been fully investigated. In this research, an excellent and exceptionally stable process was demonstrated for a stack of HDP-CVD FSG and PECVD FSG layers. Cracks that result from multi-level metal technology were eliminated when higher compressive stress PECVD FSG film was implemented as a capping layer. An 11% capacitance reduction was achieved when comparing a stack of FSG films to undoped silicon oxide. No problem occurred for photo, via etching and chemical mechanical polishing of FSG film. The FSG layer stack's via resistance (Rc(-)Via) as well as a full HDP-FSG scheme is comparable. These results are very promising for the integration of FSG films as inter metal dielectric for devices. (C) 2003 Elsevier B.V. All rights reserved.
Integration of MOCVD titanium nitride with collimated titanium and ion metal plasma titanium for 0.18-mu m logic process
(2001-11-01)
Lan, JK
;
Wang, YL
;
Lo, KY
;
Liu, CP
;
Liu, CW
Both collimated titanium (CO-Ti) and ion metal plasma titanium (IMP-Ti) have been widely used for plug liner layers. The focused ion beam (FIB) images of these films show that the IMP-Ti surface is granular and the CO-Ti surface is amorphous. It is concluded that the lower reflectivity and resistivity of IMP-Ti films are caused by the fact that IMP-Ti has a larger grain than that of the CO-Ti films. We define a grain size factor (GF) and find that the activation energy of grain growth of IMP-Ti film is 3.8 times larger than that of CO-Ti film. The electric measurement of vias resistance shows that IMP-Ti plug liner gives 13.6% higher via resistance and broader distribution than that of the CO-Ti plug liner. From the experimental data, we can conclude that there are three factors that make the IMP Ti plug liner process have higher vias resistance. These three factors are IMP-Ti resistivity, IMP-Ti thickness and CVD TiN thickness. (C) 2001 Elsevier Science B.V. All rights reserved.
Mechanisms of circular defects for shallow trench isolation oxide deposition
(2003-09-01)
Lan, JK
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Wang, YL
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Liu, CP
;
Chao, CG
;
Ay, CY
Shallow trench isolation (STI) is extensively used as the isolation method beyond 0.18 mum generation. This study explored the formation of circular defects in high-density plasma (HDP) STI deposition. Circular defects were caused by the burst flow of silane reactive gas. The defect maps were coincident with the silane flow field. Fourier transform infrared and secondary-ion-mass spectroscopy data exhibited that the silane-burst flow formed a silicon rich oxide (SRO) film. This SRO film existed between the STI oxide and liner oxide. The circular defects were easily found using optical microscopy (OM) for STI with SRO film. Scanning electron microscopy and transmission electron microscopy photographs show that these defects include bubbles and concavities. When SRO fully covers the liner oxide, bubbles easily form by delamination between SRO film and liner oxide. This correlates with the high tensile stress produced by the SRO film. Besides this, higher STI deposition temperatures yield more bubbles. When SRO discontinuously forms on the liner oxide, the concavities were induced by the variation of STI deposition rate on SRO film and liner oxide. The surface charge difference between the SRO film and the liner oxide is the driving force for the generation of concavities. (C) 2003 American Vacuum Society.
Modified polycrystalline silicon chemical-vapor deposition process for improving roughness at oxide/polycrystalline silicon interface
(2005-01-24)
Chang, JJ
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Hsieh, TE
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Wang, YL
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Tseng, WT
;
Liu, CP
A new modified low pressure chemical-vapor deposition process for stacked polysilicon (poly-Si) films is developed in this study. The proposed stacked film process combines polysilicon with amorphous silicon films. In this process, polysilicon film was deposited first at 630degreesC, followed by a continuous temperature decrease down to 560degreesC for the deposition of amorphous silicon film. It was found that the doped stacked polysilicon films deposited by this process result in lowering of surface roughness, together with reduction of the (311) phase of the doped amorphous silicon and (110) phase of the doped polysilicon. As a consequence, device performance based on the stacked films also improves. Results of surface roughness analysis indicated that the doped stacked polysilicon film has a root-mean square surface roughness (Rrms) of 78 A, which is smaller than those of doped conventional (630degreesC) polysilicon film (Rrms=97 A), and doped amorphous silicon film (Rrms=123 A, deposited at 560degreesC). Transmission electron microscopic (TEM) observation performed at oxide/polysilicon interface showed that the conventional (630degreesC) oxide/polysilicon interface has high angle grain boundaries on the polysilicon side, which may induce leakage current around the interfacial area. (C) 2004 Elsevier B.V. All rights reserved.
Moisture resistance and thermal stability of fluorine-incorporation siloxane-based low-dielectric-constant material
(2004-01-30)
Cheng, YL
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Wang, YL
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Wu, YL
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Liu, CP
;
Liu, CW
The low dielectric constant (low-k) of organo-silica-glass (OSG) and fluorine-incorporated OSG (OFSG) materials produced from plasma-enhanced chemical vapor deposition of trimethylsilane are thermally stable to greater than 600 degreesC. FTIR analysis indicates that Si-CH3 bonds and Si-F bonds remain intact to temperatures well above that normally encountered during integrated circuit manufacture, allowing these materials to maintain a low-k value. While OFSG materials proved to have less hydrolytic resistant than their non-fluorinated analogs during high pressure, high temperature water exposure (pressure cooker test), their leakage current was found to be lower than OSG films before and after wafer exposure. The measured properties of OFSG blanket films suggest that this material is sufficiently robust to ensure stability of reliability after the fabrication. (C) 2003 Elsevier B.V. All rights reserved.
Monitor and eliminate the circular defects in HDP-STI deposition through oxynitride/oxide composite liner
(2004-01-30)
Lan, JK
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Wang, YL
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Liu, CP
;
Lee, WH
;
Ay, C
This paper investigates. the monitor and elimination methods for the circular defects in high-density-plasma shallow trench isolation (HDP-STI) deposition process. The optical measurement method can monitor the circular defects in early stage. When the thickness of silane-burst film exceeds 7.8 nm, the fit-error can alert the circular defects. The oxynitride/oxide composite liner can eliminate the circular defects. Besides this, the oxynitride/oxide composite liner can also improve the breakdown strength of the STI oxide. The breakdown strength of the STI oxide increases, respectively, 375 and 30% in the wafer center and edge. The uniformity of the STI breakdown strength was reduced from greater than 200% to less than 10% using the composite liner. The traditional N2O plasma treatment for stabilizing the oxynitride film is harmful in the HDP-STI process. The N2O plasma treatment shows the worst circular defect performance. (C) 2003 Elsevier B.V. All rights reserved.
Novel slurry solution for dishing elimination in copper process beyond 0.1-mu m technology
(2006-03-01)
Chen, KW
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Wang, YL
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Liu, CP
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Chang, L
;
Li, FY
The reduction of the copper dishing was investigated by optimizing the copper CMP processes. The reduction method is a novel copper slurry with the organic passivation agent used during the copper polishing to reduce the copper dishing level. The passivation mechanism of the copper polishing was proposed. With the optimized condition of the copper ECD and CMP, the resistivity deviation of 180-mu m square metal pads with 10-80% pattern densities was reduced from over 30% to less than 10%. The amount of the copper dishing was reduced from around 150 nm to less than 30 nm. Finally, 10% increase of wafer yield and better process reliability were achieved. (c) 2005 Elsevier B.V. All rights reserved.
Study of diffusion and quality control for CoSi2 formation by oxide-mediated cobalt silicidation with Ti capping
(2005-09-01)
Chang, JJ
;
Liu, CP
;
Hsieh, TE
;
Wang, YL
;
材料科學與工程學系
The mechanism for the enhancement Of COSi2 thin film formation and film quality control by oxide-mediated cobalt silicidation with a Ti-capping layer is discussed. It is found that Ti absorbs oxygen from the SiOx layer, which induces weak points in the SiOx layer and then enhances Co diffusion as well as COSi2 formation. The control of the reactions between Ti and SiOx is significant because a low reaction rate cannot form a suitable thickness Of CoSi2 film, whereas a high reaction rate tends to form the highly resistive CoSi phase. In addition, to maintain the SiOx layer still existing after annealing is also important because if no SiOx layer remains, unreacted Co would react with Si directly to form the highly resistive phase of CoSi, leading to the smooth interface between CoSi2 and Si and dense bulk CoSi2 thin film being destroyed. (c) 2005 American Vacuum Society.
Study on precipitations of fluorine-doped silicon oxide
(2004-01-30)
Wu, J
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Wang, YL
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Liu, CP
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Chang, SC
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Kuo, CT
Precipitation on fluorine-doped silicon oxide film (SiOF) was observed while exposure to air for a prolonged period of time (>4 h). Most of the precipitates are less than 1 mum and clustered at wafer center. Under SEM view, the precipitation shows hexagonal shape, and mainly composed of Si and O. SIMS analysis showed that SiOF films without F precipitates showed leveling F% profile, whereas SIMS result for SiOF films with precipitations shows increasing gradient with depth. In this study, factors affecting the precipitation of SiOF film were investigated. Humidity in environment was found to be one of the essential elements for the onset of precipitation. Process optimization and control methodologies were also investigated for precipitation prevention to provide a more robust and stable SiOF film, hence ensuring the reliability of device performance. (C) 2003 Elsevier B.V. All rights reserved.
The application of electrochemical metrologies for investigating chemical mechanical polishing of Al with a Ti barrier layer
(2003-11-15)
Chiu, SY
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Wang, YL
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Liu, CP
;
Lan, JK
;
Ay, C
In situ electrochemical measurements were performed for Al and Ti disks in various slurries during polishing and static conditions. The electrochemical results obtained from the corrosion potential drop of Al polishing have verified that the maximum removal rate of metal CMP can be achieved when the removal rate of the surface oxide was equal to its growth rate. However, Ti polishing did not exist maximum removal rate. The effects of H2O2%, pH values and pressure on the Al and Ti polishing behaviors were explored by using potentiodynamic scan. The corrosion potential drop was found to be a good index for polishing removal rate. The corrosion potential drop changed with increasing H2O2% for Al polishing and there existed a maximum value. But the corrosion potential drop increased with increasing H2O2% for Ti polishing. The pH value had different effects on Al and Ti polishing. Higher pH values gave higher Al removal rate but lower Ti removal rate. The Al polishing showed more pressure sensitive than Ti polishing did. The galvanic current was measured for AIM polishing. For slurry with 6 vol.% H2O2 and pH = 4, the abraded Al electrode obtained a negative current, which implied Ti oxidation was enhanced. (C) 2003 Elsevier B.V. All rights reserved.
The study of diffusion and nucleation for COSi2 formation by oxide-mediated cobalt silicidation
(2006-02-24)
Chang, JJ
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Liu, CP
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Hsieh, TE
;
Wang, YL
;
材料科學與工程學系
The role of cobalt in oxide-mediated silicidation is studied in terms of diffusion and nucleation by varying annealing conditions, oxide thickness and implantation in Si substrate. Electroscopic imaging in transmission electron microscopy shows that SiOx act as a one-way diffusion barrier reducing the Co effective concentration at the cobalt silicide growth interface leading to CoSi2 as the first formation phase during silicidation. X-ray photoelectron spectroscopy analysis shows that unreacted Co coexists with CoSi2 at the interface between the SiOx layer and Si substrate, implying that Co diffusion rate is faster than CoSi, nucleation rate. An Si-implanted substrate can increase the CoSi2 nucleation rate and reduce the Co accumulation. (c) 2005 Elsevier B.V. All rights reserved.
Two-color resonant four-wave mixing spectroscopy of highly predissociated levels in the (A)over-tilde(2)A(1) state of CH3S
(2005-03-22)
Liu, CP
;
Reid, SA
;
Lee, YP
;
應用化學系
;
Department of Applied Chemistry
We report results of two-color resonant four-wave mixing experiments on highly predissociated levels of the methylthio (or thiomethoxy) radical CH3S in its first excited electronic state A (2)A(1). Following photolysis of jet-cooled dimethyl disulfide at 248 nm, the spectra were measured with a hole-burning scheme in which the probe laser excited specific rotational transitions in band 3(3). The spectral simplification afforded by the two-color method allows accurate determination of line positions and homogeneous linewidths, which are reported for the C-S stretching states 3(v)(v=3-7) and combination states 1(1)3(v)(v=0-2), 2(1)3(v)(v=3-6), and 1(1)2(1)3(v)(v=0,1) involving the symmetric CH3 stretching (nu(1)) mode and the CH3 umbrella (nu(2)) mode. The spectra show pronounced mode specificity, as the homogeneous linewidth of levels with similar energies varies up to two orders of magnitude; nu(3) is clearly a promoting mode for dissociation. Derived vibrational wave numbers omega(1)('), omega(2)('), and omega(3)(') of the A state agree satisfactorily with ab initio predictions.
Uniform COSi2 nano-nucleus formation by oxide mediated silicidation with a Ti capping layer
(2006-03-01)
Chang, JJ
;
Hsieh, TE
;
Liu, CP
;
Wang, YL
;
材料科學與工程學系
The nucleation stage toward CoSi2 with average island size of about 4 nm and uniform island size distribution is obtained from a TiN/Co/ Ti/Co/SiOx/Si multilayer with the SiOx as a mediated layer by annealing at 460 degrees C for 240 s followed by 600 degrees C 240 s. It is found that Ti capping layer can enhance Co diffusion into the Si substrate at higher temperature (600 degrees C 240 s) annealing, which results in larger nucleus size (average grain size about 12 nm) but nonuniform nucleus size distribution. However, two-step annealing for 460 degrees C 240 s followed by 600 degrees C 240 s results in a smaller average nucleus size with better nucleus size distribution. The mechanism responsible for the discrepancy is discussed in the paper. (c) 2005 Elsevier B.V. All rights reserved.