Browsing by Author "Chen, CF"

Now showing 1 - 20 of 91

1.0 nm oxynitride dielectrics prepared by RTP in mixtures of N-2 and O-2 ambient
(2004)
Chang, KM
;
Yang, WC
;
Chen, CF
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This work presents a reliable method of growing aggressively scaled, 1.0 nm thick, gate dielectric in mixtures of N-2 and O-2 ambient at 900degreesC for 15 s by rapid thermal processing (RTP). These oxynitride films have excellent interface properties, 100 times lower leakage current density, and better charge trapping properties than rapid thermal oxidation SiO2 of identical thickness prepared in pure O-2 ambient. The effect of interfacial nitrogen concentration on the device characteristics with gate oxynitride films grown in various N-2/O-2 gas flow ratios was also investigated. The results demonstrate that the uniform nitrogen content increases with the N-2/O-2 gas flow ratio and that high-quality oxynitride films can be obtained by RTP in an optimum gas flow ratio of N-2/O-2 = 5/1 (slm). (C) 2004 The Electrochemical Society.
A new process-variation-immunity method for extracting capacitance coupling coefficients in flash memory cells
(2002-07-01)
Cho, CYS
;
Chen, MJ
;
Lin, JH
;
Chen, CF
;
電子工程學系及電子研究所
Overestimation of capacitance coupling coefficients in flash memory cells is encountered in the subthreshold slope method. By means of a two-parameters subthreshold current model I-D = I-o exp[q(V-GB - nV(SB))/nkT], a mathematical formulation of the subthreshold swing ratio in the subthreshold slope method is constructed to isolate the measurement errors caused by process variations from the errors traditionally caused by bulk capacitance coupling. To minimize the effect of process variations, a new method is developed based on the model. In this method, the control gate voltage shift due to weak body effect is measured in flash memory cells in subthreshold, while the corresponding slope factor n is adequately deduced from threshold voltage versus source-to-substrate bias measurement in dummy devices. The corrected capacitance coupling coefficients show large improvements compared to the design values, and the updated errors are found to be close to that caused solely by bulk capacitance coupling. The method is also fast since only a small source-to-substrate bias of 0.1 V is needed for implementation of weak body effect, and thereby it can be used as an in-line monitor of capacitance coupling coefficients.
A novel self-aligned highly reliable sidewall split-gate flash memory
(2006-03-01)
Cho, CYS
;
Chen, MJ
;
Chen, CF
;
Tuntasood, P
;
Fan, DT
A self-aligned sidewall split-gate Flash memory cell is fabricated with overerase immunity. Particularly, the sidewall corner of the floating-gate is deliberately rounded to release the electric field lines encountered in the poly-to-poly erase. The unit cell size of 12.7 F-2 (F is the feature size), formed in a 32-Mb NOR architecture, and the acceptable erase speed of 20 ms for block erase (512 K bits, 16 pages) are quite competitive. Endurance cycles up to 105 confirm the novel cell to be highly reliable as compared with the conventional source-side erase scheme. The bake experiment at 250 degrees C before and after program/erase cycles indicates the cell not only free of extrinsic defects in the manufacturing process but also experiencing excellent retention characteristics. Disturb effects during the programming and read-out operations are examined in detail and the operating conditions for disturbs inhibition are readily determined. We eventually elaborate on the differences between the proposed cell structure and existing ones, as well as on the NAND architecture application.
Bias effect on the growth of carbon nanotips using microwave plasma chemical vapor deposition
(2002-07-22)
Tsai, CL
;
Chen, CF
;
Wu, LK
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Carbon nanotips with a high-aspect ratio were directly grown on Pt films. Carbon nanotips grew up to 5.4 mum length and 64 nm diameter under a -120 V bias. Compared to the hollow structure of carbon nanotubes, transmission electron microscopy images indicate its solid body, which is made of graphite. Carbon nanotips possess good field emission characteristics, that is, a turn-on field of 1.5 V/mum and 761 muA/cm(2) under 2.2 V/mum. The Pt films provide a good conduction path for electron transport from the cathode to the emission site and do not act as catalysts. (C) 2002 American Institute of Physics.
Catalyzed growth model of carbon nanotubes by microwave plasma chemical vapor deposition using CH4 and CO2 gas mixtures
(2003-10-01)
Chen, M
;
Chen, CM
;
Koo, HS
;
Chen, CF
;
材料科學與工程學系
Catalyst growth carbon nanotubes (CNTs) have been synthesized successfully by microwave plasma chemical vapor deposition using CH4-CO2 gas sources, and Fe, Ti, Fe/Ti as catalysts. Significant difference of morphology in the carbon deposition was observed between Fe and Ti catalyst. By adjusting growth parameters of CH4 to CO2, a high yield of vertically aligned CNTs can be found in an Fe-deposited substrate. Ti is shown to be not suitable as a catalyst in CNT production. In the present work, we investigated the effect of H-2 plasma pretreatment on the CNT growth from the viewpoint of catalyst morphology, using Fe as the catalyst. After the H-2 pretreatment, significant catalyst particle sintering was observed and resulted in a broad size distribution of catalyst particles. The diameter of CNTs was governed by the catalyst particle size. The diameter of CNTs thus increased as the H-2 plasma pretreated time increased. The CNT diameters were distributed in the range approximately 10-20 nm when Fe-deposited substrate was not pretreated. However, the diameter of CNTs increased from 30 to 300 nm when Fe-deposited substrate was pretreated from 1 to 15 min. The CNT growth model in catalysts, as a function of a gas environment of CH4-CO2 gas mixture, was investigated. (C) 2003 Elsevier Science B.V. All rights reserved.
Characterization of bias-controlled carbon nanotubes
(2003-09-01)
Tsai, CL
;
Chen, CF
;
材料科學與工程學系
;
Department of Materials Science and Engineering
In this study, we focus on the immediately improving quality of growing carbon nanotubes without any pre- or post-treatment. The applied biases during the reaction can directly control the diameter and the quality of carbon nanotubes. This simple step skips additional treatments and is easily used in many deposition systems. The diameter of carbon nanotubes noticeably varies from 45 nm without any amorphous carbon (under + 80 V) to 120 nm (under - 120 V). Raman spectrums indicate that I-D/I-G ratio decreases with increasing positive bias. This implies applying positive bias could enhance the graphitization of carbon nanotubes. However, positive and negative bias effects slightly vary the field emission enhancement. In addition, carbon nanotubes grown under positive bias possess better field emission characterization. This results from the following reasons: (I) smaller diameter- (II) pure surface; (III) more graphitized structure; and (IV) higher field enhancement beta. (C) 2003 Elsevier Science B.V. All rights reserved.
Characterization of diamond films grown on amorphous SiO2
(1996-04-01)
Chen, CF
;
Leu, SY
;
Chen, SH
;
Yeh, WK
;
交大名義發表
Continuous diamond film growth on SiO2 was achieved by an effective pretreatment. Carbon implantation and diamond powder abrasion were used to enhance diamond nucleation on SiO2. The possibility of using two gas mixtures (CH4-CO2 and CH4-H-2) in order to achieve the growth of continuous diamond films on SiO2 was examined. The diamond film growth rate obtained using the CH4-CO2 gas mixture was 0.6 mu m/h which is roughly three times higher than that of the CH4-H-2 gas mixture. CH4-H-2 gas mixtures had a lower etching reaction rate than that of CH4-CO2 gas mixtures. The higher etching rate of the CH4-CO2 gas mixture was considered to be due to a higher concentration of active carbon radicals or carbon-containing species in the plasma. Scanning electron microscopy (SEM) and optical emission spectroscopy (OES) indicated that active carbon radicals and carbon-containing species are the major cause of pits arising at the surface. Using CH4-H-2 gas mixtures at a low microwave power gave the optimum reaction conditions for depositing diamond films on SiO2 layers.
Characterization of phosphorus-doped and boron-doped diamond-like carbon emitter arrays
(2001-11-01)
Tsai, CL
;
Chen, CF
;
Lin, CL
;
材料科學與工程學系
;
Department of Materials Science and Engineering
We synthesized phosphorus-doped and boron-doped emitters by using trimethylphosphite P(OCH3)(3) and trimethylborate B(OCH3)(3) as doping sources in a microwave plasma chemical vapor deposition system. Based on our experimental results from scanning electron microscopy and Raman spectra, there is much difference among undoped, phosphorus-doped, and boron-doped diamondlike material. In addition, doping both phosphorus and boron can enhance electric properties by reducing the turn-on voltage and can increase the emission current density. The turn-on voltages of undoped, boron-doped, and phosphorus-doped emitters in triode-type field emitter arrays are 15, 8, and 5 V, respectively. The emission currents of boron-doped and phosphorus-doped emitters are about 20 and 80 times larger than the undoped. (C) 2001 American Institute of Physics.
Comparison of characteristics and integration of copper diffusion-barrier dielectrics
(2006-03-01)
Wang, TC
;
Cheng, YL
;
Wang, YL
;
Hsieh, TE
;
Hwang, GJ
The characteristics of various copper (Cu) barrier layers, including SiN, SiCN, and SiCO, were investigated in this work. Carbon-based barrier films (SiCN and SiCO) improved the dielectric constant and line-to-line capacitance, but led to sacrifice in film deposition rate, diffusion-barrier performance, and adhesion strength to Cu in comparison with SiN films. In addition, SiN and SiCO films showed the superior electromigration (EM) performance and stress-induced void migration (SM) performance, respectively. Furthermore, the reliability results of SM and EM are strongly related to the barrier film stress characteristics and the adhesion strength between Cu layers. Therefore, optimization of the barrier layer stress and the enhancement of the interfacial condition between Cu and barrier films are crucial to significantly improve reliability. (c) 2005 Elsevier B.V. All rights reserved.
Comparison of the electronic structures of AIN nanotips grown on p- and n-type Si substrates
(2005-12-07)
Chiou, JW
;
Tsai, HM
;
Pao, CW
;
Dong, CL
;
Chang, CL
At and N K-edge x-ray absorption near-edge structure (XANES), scanning photoelectron microscopy (SPEM) and x-ray emission measurements were performed on AIN nanotips grown on p- and n-type Si substrates (p-AIN and n-AIN). Features and intensities in the Al and N K-edge XANES spectra of these AIN nanotips overall are similar. In contrast, the intensities of the valence-band SPEM spectra of p-AIN are apparently larger than those of n-AIN, which indicates that the valence-band density of states of p-AIN exceeds that of n-AIN. This result may be related to the observed enhancement of field-emission intensity of AIN nanotips grown on the p-type Si substrate.
Computerized tooth profile generation and analysis of characteristics of elliptical gears with circular-arc teeth
(2004-05-15)
Chen, CF
;
Tsay, CB
;
機械工程學系
;
Department of Mechanical Engineering
This study describes rack cutters with circular-arc profile teeth to generate elliptical gears which rotate about one of their foci. A mathematical model for elliptical gears with circular-arc teeth is developed according to gear theory. The influence of the design parameters, such as the number of teeth, gear module, pressure angle at the pitch point and the major-axis, are investigated. The effects of the circular-arc radius of the rack cutter on both the undercutting of teeth and on pointed teeth of the generated circular-arc elliptical gear are also studied. Three numerical examples are presented to elucidate the generation of gear tooth profiles using the proposed mathematical model, and to investigate the phenomena of tooth undercutting and pointed teeth. (C) 2003 Published by Elsevier B.V.
Density-controlled carbon nanotubes
(2005-03-01)
Hsu, CH
;
Chen, CF
;
Chen, CC
;
Chan, SY
;
材料科學與工程學系
We demonstrate that the field emission efficiency was greatly improved by reducing the density of carbon nanotubes (CNTs). In this study, catalyst composed of gold and nickel was deposited by e-gun evaporation before pre-treatment of furnace annealing. Carbon nanotubes were then gown on silicon substrate using bias-assisted microwave plasma chemical vapor deposition. Vertical aligned carbon nanotubes were grown with gas mixture of methane and hydrogen under external DC bias. The surface morphology and the tubular structure of carbon nanotubes were confirmed by electron microscopy and the density of carbon nanotubes could be controlled by the composition of the catalyst. The field emission properties were investigated through I-V measurement and the effects are discussed. (c) 2005 Elsevier B.V. All rights reserved.
Effect of deposition temperature and oxygen flow rate on properties of low dielectric constant SiCOH film prepared by plasma enhanced chemical vapor deposition using diethoxymethylsilane
(2006-02-24)
Cheng, YL
;
Wang, YL
;
Hwang, GJ
;
O'Neill, ML
;
Karwacki, EJ
Low dielectric constant (Low-k) films (SiCOH) were deposited from diethoxymethylsiliane [DEMS; SiH(CH3) (OC2H5)(2)] which has two ethoxy groups along with one methyl group attached to the silicon atoms. The deposited films have been characterized for different oxygen flows, ranging from 50 to 250 standard cubic centimeters per minute (seem). The growth rate is increased with the increasing oxygen (O-2) flow. The absorbance spectrum of Fourier transform infrared spectroscopy shows that the frequency of Si-O stretching vibration mode in the SiCOH film is shifted to a higher wave number with the increase of oxygen flow. It is deduced that the oxygen does not participate in a simple oxidative mechanism, and has no apparent impact on the methyl content even if the relative Si-O content of the deposited films is up to an O-2/DEMS flow rate ratio of 1:1. Also, the refractive index is decreased with increasing the oxygen flow and slightly increased with the deposition temperature. The dielectric constant of the SiCOH is investigated between 2.7 and 3.2, depending on the deposition temperature and O-2/DEMS flow rate ratio, which is lower than that of the current OSG films (k=2.9-3.3). SiCOH films deposited with DEMS only exhibit higher mechanical hardness and lower leakage current than those deposited with both DEMS and oxygen. (c) 2005 Elsevier B.V. All rights reserved.
Effect of nitrogen on diamond growth using unconventional gas mixtures
(1995-12-01)
Hong, TM
;
Chen, SH
;
Chiou, YS
;
Chen, CF
;
交大名義發表
The influence of nitrogen on the growth of diamond using unconventional gas mixtures of CH4-CO2 by microwave plasma chemical vapor deposition was investigated. A clear improvement in the surface morphology and quality of the diamond films indicates the beneficial effect of adding nitrogen to CH4-CO2 gas mixtures. However, most interestingly, for lower methane concentration, the addition of small amounts of nitrogen resulted in the formation of isolated diamond particles possessing a vacant ''cage-like'' structure with completed (100) facets. This result indicates that the continued addition of nitrogen gives rise to the deterioration of (111) facets and the retention of (100) facets. Analysis using Auger electron spectroscopy and secondary ion mass spectroscopy shows very low and uniform levels of nitrogen in the diamond films. Although the amount of atomic hydrogen in the ground state decreased and CN radicals increased with increasing amounts of added nitrogen, good-quality diamond films were deposited resulting from a larger amount of atomic oxygen and the decrease in the C-2 emissions in the gas phase under optimum conditions.
Effect of post-treatment on electrical properties of amorphous hydrogenated carbon films deposited by gridless ion beam deposition
(2003-01-01)
Chen, CF
;
Li, YW
;
Huang, HL
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Amorphous hydrogenated carbon (a-C:H) films were deposited from the gas mixtures of acetylene (C2H2) and argon (Ar) in a gridless ion beam deposition (GIBD) system fed with dc power. Vacuum annealing and hydrogen plasma treatment were performed on the a-C:H films and their effects on the physical and electrical properties of the films were investigated. Film structure and properties were investigated as a function of the C2H2 flow rate by Raman spectroscopy. Through the Raman spectra, we found that the Raman I-D/I-G intensity ratio increases as annealing temperature increases, which indicates a more graphite-like character in the annealed films. The dielectric constant of the annealed a-CA films was reduced from 3.8 to 2.9 and the thickness also slightly decreased with increasing annealing temperature. However, the leakage current density and dielectric constant of the hydrogen-plasma-treated a-C:H films were clearly lower than the as-deposited a-C:H films.
Effect of pulse frequency on leveling and resistivity of copper coatings
(2002-05-01)
Chen, CF
;
Lin, KC
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Pulse-and DC-plated copper films on wafers were investigated with respect to their applicability as advanced interconnect materials. Pulse frequency was varied to determine its influence on the topography, grain size, and electrical resistivity of electroplated copper films. Morphology and scanning electron microscopy (SEM) studies were conducted on these samples. Smooth and dense coatings were obtained at the optimal frequency of 100 Hz, which displayed the smallest electrical resistance. The leveling capacity of submicron features was also optimized at this frequency.
Effects of ammonia plasma treatment on the electrical properties of plasma-enhanced chemical vapor deposition amorphous hydrogenated silicon carbide films
(2002-09-01)
Li, YW
;
Chen, CF
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Amorphous hydrogenated silicon carbide (a-SiC:H) films were deposited from a mixture of silane and methane gases using the plasma-enhanced chemical vapor deposition (PECVD) process. The properties of the film. following ammonia plasma treatment, are reported. A lower silane flow rate reduces the refractive index, but increases the carbon content and the optical band gap. Increasing the carbon concentration of the a-SiC:H films reduces the dielectric constant. The films were treated with ammonia plasma for various treatment periods. The original Film has a smooth surface with a roughness of 0.231 nm but increasing the ammonia plasma treatment period gradually roughens the surface. The chemical bonding nature of the a-SIC:H films with higher silicon content was investigated by X-ray photoelectron spectro.scop, Various nitrogen ioni/ation species reacted with Si to promote the formation of silicon nitride. As a result, although the dielectric constant of the a-SiC:H films, increased slightly, the leakage current density declined as the ammonia plasma treatment time increased.
Effects of the relationship between resistivity and additive chemistries in electrochemically deposited copper films
(2002-04-01)
Chen, CF
;
Lin, KC
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The room-temperature electrical resistance of copper films on silicon wafers deposited from acid-copper sulfuric solutions is a function of grain size and impurity content. These properties were examined by a series of additive chemistries used in plating baths. The trapped impurities and the functional characteristics of additives were analyzed by X-ray photoelectron spectroscopy (XPS) and cyclic voltammetric stripping (CVS) measurements, The impurity scattering effect on the resistances depends on the charge factor for different dopants. On the other hand, the effect of grain-boundary scattering on the resistances will depend on the extent of activation overpotential of various additive chemistries. Evidence suggests that additive chemistries with a higher overpotential would create a higher resistivity due to larger grain-boundary scattering and greater impurity incorporation into copper films.
Electrical and reliability characteristics of 1nm ultrathin oxynitride gate dielectric prepared by RTP
(2003)
Yang, WC
;
Chen, CF
;
Chang, KM
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Ultra low leakage and highly reliable 1 nm gate oxynitride films were successfully developed. Ultrathin oxynitride films were prepared by RTP in N-2/O-2 = 5/1 (slm) optimum mixed gas ambient These films show excellent interface properties, significantly low gate leakage current, and superior enhanced reliability. Moreover, interface trap generation under higher field stressing was also investigated.
Electrical characteristics and annealing study of boron-doped polycrystalline diamond films
(1995-12-01)
Chen, SH
;
Chen, SL
;
Tsai, MH
;
Shyu, JJ
;
Chen, CF
Annealing processes are an important area of fundamental research within the field of diamond electronic applications. In this study, annealing was applied to as-grown boron-doped diamond films. The current-voltage (I-V) characteristics of the Al/boron-doped diamond films were also investigated. First, the conductivity of films was examined to determine the effect of annealing on boron-doped diamond films. Experimental results indicated that the activation energy for the as-deposited diamond films (intrinsic or light boron-doped) is about 0.38 eV. After annealing, the activation energy did not change. However, the activation energy of the heavily doped films remarkably would change to 0.014 eV after annealing. Next, Fourier transform infrared spectroscopy (FTIR) and cathodoluminescence (CL) were performed to understand more clearly the correlation between the activation energy and the annealing effect on B-doped diamond films. These results revealed that for the lightly B-doped films, the boron atoms were effectively activated at the substitutional site. For the heavily doped case, boron was initially located in an inactive site (e.g., grain boundary, interstitial or clustering sites) and would diffuse into the substitutional site after 900 degrees C annealing.