Browsing by Author "Chen, HW"

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A method for measuring the complex refractive index of a turbid medium
(2005)
Jian, ZC
;
Lin, JY
;
Hsieh, PJ
;
Chen, HW
;
Su, DC
Based on the heterodyne interferometry and Fresnel equations, an alternative method for measuring the complex refractive index of a turbid medium. A light beam is incident on the boundary between a right-angle prism and a turbid medium. The phase difference between s- and p- polarizations of the reflected light occurs. The phase difference depends on then incident angle and the complex refractive index of a turbid medium-, their relation can be derived from Fresnel equations. The phase difference can be measured accurately with the heterodyne interferometry. Because there are two unknown parameters to be estimated, at least the phase differences under two different conditions should be measured. Then, these measured data are substituted into the derived relation, and a set simultaneous equation is obtained. If the simultaneous equation is solved. the complex refractive index can be estimated. Because the reflected light from the boundary is measured, the scattering noises coming from the turbidity of the tested medium can be greatly reduced. In addition, this method has some merits such as simple optical setup, high sensitivity, high stability, and suitability for a little amount of the tested medium in its native state (without dilution).
A spread spectrum clock generator for EMI reduction
(2001-12-01)
Chen, HW
;
Wu, JC
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電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This paper described a new method to generate a spread spectrum clock for the purpose of EMI reduction. This method uses two phase-locked loops (PLL). The output of the first PLL is locked to its input of 14.318-MHz, The VCO in this PLL is used to produce 32 outputs with the same frequency and each with 11.25 degrees phase variation. A digital spread spectrum generator uses these 32 signals to generate the desired spread spectrum signal by phase hopping technique. These two circuits form a spread spect ruin digital PLL (SSDPLL). The second PLL is configured as a conventional frequency synthesizer. It can be programmed to generate the desired frequencies. The second PLL also serves as a low pass filter of the output of the SSDPLL to smooth out frequency variation. This circuit was implemented with a 0.6 mum single poly CMOS process. The active areas of the SSDPLL and the synthesizer are 826 x 396 mum(2) and 790 x 298 mum(2), respectively. The, total power consumption is 99 mW at 3.3 V supply. The peak power of the spread spectrum clock is reduced by 10 dBm at 14.318 MHz output with a 2.34% frequency spreading. The reduction of peak power increases with output frequency.
Channel backscattering characteristics of strained PMOSFETs with embedded SiGe source/drain
(2005)
Lin, HN
;
Chen, HW
;
Ko, CH
;
Ge, CH
;
Lin, HC
Channel backscattering ratios of PMOSFETs with various embedded SiGe source/drain structures are analyzed in terms of the scattering theory We found that both the backscattering ratio and injection velocity are greatly influenced by the location and recess depth of SiGe source/drain. Although the strain-enhanced injection velocity is beneficial to the current gain, the accompanying backscattering ratio increase adversely impacts the overall performance, and therefore a trade-off exists between injection velocity and backscattering ratio during the optimization of such strain technique. The mechanism of increased backscattering ratio under uniaxial compressive strain is also investigated.
Channel backscattering characteristics of uniaxially strained nanoscale CMOSFETs
(2005-09-01)
Lin, HN
;
Chen, HW
;
Ko, CH
;
Ge, CH
;
Lin, HC
Channel backscattering characteristics of uniaxially strained nanoscale CMOSFETs are reported for the first time. Channel backscattering ratio increases and decreases under uniaxial tensile and compressive strain, respectively. It is found that in sub-100-nm devices, strain-induced modulation of carrier mean-free path for backscattering and reduction in kBT layer thickness are responsible for the different behaviors of backscattering ratio. Nevertheless, the source-side injection velocity improves irrespective of the strain polarities. The impact of channel backscattering ratio on drive current is also analyzed in terms,of ballistic efficiency and injection velocity.
Characterization of interfacial layer of ultrathin Zr silicate on Si(100) using spectroscopic ellipsometry and HRTEM
(2004-05-01)
Ahn, H
;
Chen, HW
;
Landheer, D
;
Wu, X
;
Chou, LJ
Optical properties and the film thickness of interfacial layer formed between the ultrathin as-deposited Zr silicate films and the Si substrate were investigated by the variable-angle spectroscopic ellipsometry (SE), the high-resolution transmission electron microscopy (HRTEM), and X-ray photoelectron spectroscopy (XPS). Five Zr silicate films were deposited by using oxygen-based Zr(O-i-Pr)(2)(thd)(2) and Si(O-t-Bu)(2)(thd)(2) as precursors in a pulse-mode metalorganic chemical-vapor deposition (MOCVD) apparatus to investigate the influence of the choice of ambient gas (oxygen or NO) on the formation of the interfacial layers during the oxidation and the deposition of the Zr silicate films. HRTEM images clearly show the existence of the amorphous interfacial layer below the Zr silicate layer. The interfacial layers are found to be Zr-free from the XPS study. In SE analysis, the interfacial layers were described best as the mixture of SiO2 and SiO in the Bruggeman effective medium approximation (BEMA). The evident reduction of the interfacial layer due to the intentionally grown ultrathin oxynitride buffer layer was observed for the Zr silicate film deposited under a carefully designed growing condition. Any source of oxygen during the growth of the film results in the thicker, but self-limited interfacial layer. (C) 2004 Elsevier B.V. All rights reserved.
Characterization of thin ZrO2 films deposited using Zr(O '-Pr)(2)(thd)(2) and O-2 on Si(100)
(2002-05-01)
Chen, HW
;
Landheer, D
;
Wu, X
;
Moisa, S
;
Sproule, GI
The properties of ZrO2 films deposited using molecular oxygen and a recently developed precursor, zirconium Zr(O-i-Pr)(2)(thd)(2) have been investigated. The organometallic was dissolved as a 0.15 molar solution in octane and introduced into the deposition chamber using a liquid injection system. The deposition rate was insensitive to molecular oxygen flow but changed with liquid injection rate and was thermally activated in the range 390 degreesC-550 degreesC. Carbon concentrations, <0.1 at.%, the detection limit of the x-ray photoelectron spectroscopy depth profiling measurements, were obtained at the lowest deposition temperatures and deposition rates. High-resolution transmission electron microscopy showed the films to be polycrystalline as deposited, with a zirconium silicate interfacial layer. After proper annealing treatments, an equivalent oxide thickness (EOT) of around 2.3 urn has been achieved for a 5.2 nm thick film, with a leakage current two orders of magnitude lower than that Of SiO2 with the same EOT. Promising capacitance-voltage characteristics were also achieved, but some improvements are required if these films are to be used as a gate insulator. (C) 2002 American Vacuum Society.
Conductivity enhancement mechanism of the poly(ethylene oxide)/modified-clay-LiClO4 systems
(2002-07-01)
Chen, HW
;
Chiu, CY
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
This study demonstrates that adding clay that was organically modified by dimethyldioctadecylammonium chloride (DDAC) and d2000 surfactants increases the ionic conductivity of polymeric electrolyte. A.C. impedance, differential scanning calorimetric (DSC), and Fourier transform infrared (FTIR) studies revealed that the silicate layers strongly interact with the dopant salt lithium perchlorate (LiClO4) within a poly(ethylene oxide) (PEO)/clay/LiClO4 system. DSC characterization verified that the addition of a small amount of the organic clay reduces the glass-transition temperature of PEO as a result of the interaction between the negative charge in the clay and the lithium cation. Additionally, the strength of such a specific interaction depends on the extent of PEO intercalation. With respect to the interaction between the silicate layer and the lithium cation, three types of complexes are assumed. In complex I, lithium cation is distributed within the PEO phase. In complex II, lithium cation resides in an PEO/exfoliated-clay environment. In complex III, the lithium cation is located in PEO/ agglomerated-clay domains. More clay favors complex III over complexes II and I, reducing the interaction between the silicate layers and the lithium cations because of strong self-aggregation among the silicate layers. Notably, the (PEO)(8)LiClO4/DDACmodified clay (DDAC-mClay) composition can form a nanocomposite electrolyte with high ionic conductivity (8 x 10(-5) S/cm) at room temperature. (C) 2002 Wiley Periodicals, Inc.
Determination of 1-hydroxypyrene in children urine using column-switching liquid chromatography and fluorescence detection
(2004-06-15)
Kuo, CT
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Chen, HW
;
Chen, JL
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環境工程研究所
;
Institute of Environmental Engineering
This study developed an acid hydrolysis method instead of using enzyme extraction, equipped with column-switching system for the pretreatment of samples, in the determination of 1-hydroxypyrene in the urine from children and pyrene in airborne particulates. We collected both types of samples from areas near a petrochemical industry and rural areas as reference. Samples were first treated with acid hydrolysis and followed by solvent extraction prior to being injected into the separation system for the determination with high performance liquid chromatography and fluorescence. A column-switching system was on-line with a C-18 separation column to remove matrix interference and obtain a stable baseline of the chromatogram. The eluent used to separate the 1-hydroxypyrene was 60% (v/v) aqueous acetonitrile solution. A fluorescence detector was used to monitor 1-hydroxypyrene at lambda(ex) = 348 nm and lambda(em) = 388nm, and pyrene at lambda(ex) = 331 nm and lambda(em) = 390 nm. Both calibration graphs were linear with very good correlation coefficients (r > 0.999) and the detection limits were ca. 2 pg (5 ng/l). Results showed that there was a significant association between 1-hydroxypyrene levels in urine specimens and pyrene levels in airborne particulate samples (r = 0.68, P < 0.05). The average levels of pyrene in the particulates (0.18 versus 0.09 ng/m(3)) and of 1-hydroxypyrene in urine specimens (155.9 versus 110.2 ng/g creatinine) were higher for the petrochemical area than for the rural area. This method is stable and sensitive for measuring polycyclic aromatic hydrocarbons in environmental samples. (C) 2003 Elsevier B.V. All rights reserved.
Effect of CF4 plasma pretreatment on low temperature oxides
(2002-12-01)
Chang, TY
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Chen, HW
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Lei, TF
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Chao, TS
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電子工程學系及電子研究所
This study describes a novel technique for forming low temperature oxides (<350 degreesC) using a replacement metal gate process. Low temperature oxides were generated by N2O plasma in a PECVD system with pretreatment in CF4. Fabricated oxides demonstrate excellent current-voltage (I-V) characteristics, such as low leakage current, high breakdown charge and good reliability. Experimental results indicate that CF4 plasma treatment can significantly improve the mobility and resistance against hot carrier stress of MOSFETs. With excellent electrical properties, this technique is suitable for fabrication low temperature devices.
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
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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.
Hydrogen bonding effect on the poly(ethylene oxide), phenolic resin, and lithium perchlorate-based solid-state electrolyte
(2004-01-15)
Chen, HW
;
Jiang, CH
;
Wu, HD
;
Chang, FC
;
應用化學系
The interaction behavior of solid-state polymer electrolytes composed of poly(ethylene oxide) (PEO)/novolac-type phenolic resin and lithium perchlorate (Li-ClO4) was investigated in detail by DSC, FTIR, ac impedance, DEA, solid-state NMR, and TGA. The hydrogen bonding between the hydroxyl group of phenolic and ether oxygen of the PEO results in higher basicity of the PEO. The higher basicity of the ether group can dissolve the lithium salts more easily and results in a greater fraction of "free" anions and thus higher ionic conductivity. DEA results demonstrated that addition of the phenolic increases the dielectric constant because of the partially negative charge on the ether group induced by the hydrogen bonding interaction between ether oxygen and the hydroxyl group. The study showed that the blend of PEO(100)/LiClO4(25)/phenolic(15) possesses the highest ionic conductivity (1.5 X 10(-5) S cm(-1)) with dimensional stability. (C) 2003 Wiley Periodicals, Inc.
Improvement of low-temperature gate dielectric formed in N2O plasma by an additional CF4 pretreatment process
(2002-07-01)
Chang, TY
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Lei, TF
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Chao, TS
;
Wen, HC
;
Chen, HW
This study describes a novel technique to form low temperature oxide (<350 &DEG;C). Low-temperature oxides were formed by N2O plasma in the plasma-enhanced chemical vapor deposition (PECVD) system with a CF4 pretreatment. These oxides demonstrate excellent current-voltage (I-V) characteristics comparable to thermally grown oxides. Experimental results indicate that CF4 plasma treatment can significantly improve the reliability of low-temperature oxides. With excellent electrical properties, the technique is highly promising for low-temperature processes.
Initialization characteristics and their effects on the erasability of phase change optical disks using transmission electron microscopy
(1999-03-01)
Chen, HW
;
Hsieh, TE
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Liu, JR
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Shieh, HPD
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材料科學與工程學系
We investigated the microstructure of phase change optical disks subjected to various initialization conditions using transmission electron microscopy (TEM). The effects of initialization powers on the erase ratio of phase change optical disks and corresponding microstructure changes were also studied. It was found that the increase of initialization power enlarged the width of the recrystallization band formed in the recording media of the disk. A wide recrystallization band was effective for decreasing the residual signal level hence the erase ratio increased. Disk dynamic test and TEM study results also revealed the deterioration of carrier-to-noice ratio (CNR) characteristic and the increasing trend of erase ratio was reduced when a substantial amount of coarse grains appeared in the crystalline region. This elucidates the necessity for phase change optical disks to have good heat dissipation property in order to suppress the formation of coarse granular structures.
Interaction mechanism of a novel polymer electrolyte composed of poly(acrylonitrile), lithium triflate, and mineral clay
(2001-10-15)
Chen, HW
;
Chang, FC
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應用化學系
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Department of Applied Chemistry
The addition of optimum cetyl pyridium chloride (CPC)-modified montmorillonite (CM) increases the ionic conductivity of poly(acrylonitrile)-based electrolytes by roughly two orders of magnitude. Specific interactions between the silicate layer, the nitrile group, and the lithium cation were investigated by FTIR, solid-state NMR, dielectric analyzer, and alternating current impedance. IR and NMR spectra confirm that the negative charges in the silicate layers alter the ionic charge environment of the PAN-based electrolyte composites, which have the same function as the polar group in PAN. The optimum CM content to achieve the maximum ionic conductivity is 6 phr. However, untreated montmorillonite leads to insignificant polymer intercalation, the negative charges in the silicate layers fail to appreciably disturb the attractive force of the lithium salt, and the resulting conductivity improvement is also less than that of the CM additives. (C) 2001 John Wiley & Sons, Inc.
Investigating the effect of miscibility on the ionic conductivity of LiClO4/PEO/PCL ternary blends
(2004-11-02)
Chiu, CY
;
Chen, HW
;
Kuo, SW
;
Huang, CF
;
Chang, FC
We demonstrate that miscibility affects the ionic conductivity of ternary polymer blends of lithium perchlorate (LiClO4), poly(ethylene oxide) (PEO), and poly(E-caprolactone) (PCL). Although individually these three binary blends are fully miscible, a closed immiscibility loop exists in the ternary blend phase diagram as a result of the complicated interactions among LiClO4, PEO, and PCL. The addition of PCL suppresses the crystallization of PEO and results in higher ionic conductivity. FTIR spectroscopy studies indicate that an excess PCL content causes immiscibility, which results in PCL being excluded from the ternary blends. Consequently, the maximum ionic conductivity (6.3 x 10(-7) S cm(-1)) at ambient temperature of ternary blends having a fixed LiClO4 content (25 wt %) is at a composition of 25/60/15 (LiClO4:PEO:PCL).
Investigation of DC hot-carrier degradation at elevated temperatures for n-channel metal-oxide-semiconductor field-effect-transistor of 0.13 mu m technology
(2006-04-01)
Lin, JC
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Chen, SY
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Chen, HW
;
Jhou, ZW
;
Lin, HC
In this study, n-channel metal-oxide-semiconductor field-effect transistors (nMOSFETs) having 20 and 32 angstrom gate oxide thicknesses of 0.13 mu m technology were used to investigate DC hot-carrier reliability at elevated temperatures up to 125 degrees C. The research also focused on the degradation of analog properties after hot-carrier injection. On the basis of the results of experiments, the hot-carrier degradation of I-d.op (drain current defined on the basis of analog applications) is found to be the worst case among those of three types of drain current from room temperature to 125 degrees C. This result should provide valuable insight to analog circuit designers. As to the reverse temperature effect, the substrate current (I-b) commonly accepted as the parameter for,monitoring the drain-avalanche-hot-carrier (DAHC) effect should be modified since the drain current (I-d) degradation and I-b variations versus temperature have different trends. For the devices having a gate oxide thinner than 20 angstrom, we suggest that the worst condition in considering hot-carrier reliability should be placed at elevated temperatures.
Ionic conductivity enhancement of the plasticized PMMA/LiClO4 polymer nanocomposite electrolyte containing clay
(2002-09-01)
Chen, HW
;
Lin, TP
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
This work has demonstrated that the addition of an optimum content of dimethyldioctadecylammonium chloride (DDAC)-modified montmorillonite clay (Dclay) enhances the ionic conductivity of the plasticized poly(methyl methacrylate)-based electrolyte by nearly 40 times higher than the plain system. Specific interactions among silicate layer, carbonyl group (C=O) and lithium cation have been investigated using Fourier-transform infrared (FTIR), solid-state NMR, alternating current impedance. The FTIR characterization confirms that both of the relative fractions of 'complexed' C=O sites and 'free' anions increase with the increase of the Delay content, indicating that strong interaction exists between the C=O group and the lithium salt. In addition, the solid-state NMR demonstrates that the interaction between the PMMA and the clay mineral is insignificant. The addition of clay mineral promotes the dissociation of the lithium salt and thus, the specific interaction can be enhanced between the C=O and the free lithium cation. However, the balanced attractive forces among silicate layers, C=O groups, lithium cations and anions is critical to result in the higher ionic conductivity. (C) 2002 Elsevier Science Ltd. All rights reserved.
Mismatches after hot-carrier injection in advanced complementary metal-oxide-semiconductor technology particularly for analog applications
(2006-04-01)
Chen, SY
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Lin, JC
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Chen, HW
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Lin, HC
;
Jhou, ZW
In this paper, the impact of hot carrier stress on the mismatch properties of n and p metal-oxide-semiconductor (MOS) field-effect transistors (FETs) with different sizes produced using 0.15 mu m complementary MOS (CMOS) technology is presented for the first time. The research reveals that hot-carrier injection (HCI) does degrade the matching properties of MOSFETs. The degree of degradation closely depends on the strength of the HC effect. Thus, it is found that, under the stress condition of drain avalanche hot carrier (DAHC), the properties of nMOSFETs rapidly and greatly become worse, but the changes are small for pMOSFETs. For analog circuit parameters, it is found that the after-stress lines of n and pMOSFETs exhibit a cross point in sigma (Delta V-t,V-op) drawings. It is suggested that the cross point can be used to indicate the minimal size in order for n and p pairs to have the same degree of Delta V-t.op mismatch in designing analog circuits. In addition, interpretations for the differences between n and pMOSFETs and between Delta V-t,V-op and I-ds,I-op mismatches are provided with experimental verifications.
New VLSI architecture of Reed Solomon decoder with erasure function
(1995)
Chen, HW
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Wu, JC
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Huang, GS
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Lee, JC
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Chang, SS
Novel polymer electrolyte composed of poly(ethylene oxide), lithium triflate, and benzimidazole
(2004-01-15)
Chen, HW
;
Xu, HY
;
Huang, CF
;
Chang, FC
;
應用化學系
This work has demonstrated that the incorporation of benzimidazole derivatives, 2,2'-p-phenylene-bisindole (PPBI), enhances the ionic conductivity of a poly(ethylene oxide) (PEO)-based electrolyte by 20 times more than the plain system. Specific interactions among amino group, ethyl oxide, and lithium cation were investigated using differential scanning calorimetry (DSC), FTIR, and alternating current impedance. The DSC characterization confirms that the initial addition of PPBI is able to enhance the PEO crystallinity attributed to the interaction between the negative charge from the amino group and the lithium cation. Three types of complexes are present: complex I is present in the PEO phase, complex 11 resides at interphase, and complex III is located within the PPBI domain. Complex II plays the key role in stabilizing these two microstructure phases. FTIR spectra confirm that because of the presence of PPBI one is able to dissolve lithium salts more easily than in the plain electrolyte system and thus increase the fraction of free ions. (C) 2003 Wiley Periodicals, Inc.