Browsing by Author "Chang, L"

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Alkylation of nanoporous silica thin films by high density plasma chemical vapor deposition of a-SIC : H
(2004-05-01)
Pan, FM
;
Wu, BW
;
Cho, AT
;
Tsai, KC
;
Tsai, TG
Film stacks of a-SiC:H and molecularly templated nanoporous silica thin films have been prepared, and alkylation of pore surfaces of the nanoporous silica layer by the a-SiC:H layer was studied. The a-SiC:H thin films were deposited by high-density plasma chemical vapor deposition (HDP-CVD) using trimethylsilane (3MS) as the precursor. Carbon is found to uniformly distribute in the thin nanoporous silica film, and the carbon content in the nanoporous film decreases with increasing the a-SiC:H deposition temperature. We used the modified Sanderson formalism to estimate the corresponding Si(2p) and C(1s) electron energies in x-ray photoelectron spectra (XPS) for possible terminal species on pore surfaces in the nanoporous silica layer. According to the XPS analysis and thermal desorption mass spectroscopy, the terminal species are probably in the chemical form of alkoxyl structures. The alkoxyl terminal groups introduced into the nanoporous silica thin film are believed to stem from hydrocarbons trapped in microvoids in the a-SiC:H film, which are formed during the HDP-CVD deposition. The terminal alkoxyl groups in the nanoporous silica layer can greatly enhance the hydrophobicity of the nanoporous silica dielectric, and hence improve the dielectric property of the film stack of a-SiC:H/nanoporous silica. An effective dielectric constant smaller than 1.7 can be obtained for the film stacks. (C) 2004 American Vacuum Society.
Backside copper metallization of GaAs MESFET's using Ta and TaN as diffusion barrier
(2000)
Chang, EY
;
Chen, CY
;
Chang, L
;
Chen, SH
;
材料科學與工程學系
Backside copper metallization of GaAs MESFET's ( Metal Semiconductor Field Effect Transistor) using Ta and TaN as the diffusion barrier layers was studied. A thin diffusion barrier Ta(40nm) or TaN(40nm) was sputtered on the GaAs substrate as the diffusion barrier for copper metallization. Material reactions of these films with GaAs substrate at different annealing temperatures were characterized by X-ray diffraction, Auger electron spectroscopy and transmission electron microscopy. Copper and diffusion barrier layer films were very stable up to 500 degrees C. At higher temperatures, Ta atoms started to react with GaAs substrate to form TaAs and TaAs, and Cu atoms started to penetrate into the GaAs substrate. The backside of the GaAs MESFET's was metallized using these Cu/Ta and Cu/TaN films. After 300 degrees C 2 hr annealing, the MESFET's showed very little change in the device characteristics. The experimental results show that both Ta and TaN are good diffusion barriers for backside copper metallization in GaAs devices.
Backside copper metallization of GaAs MESFETs using TaN as the diffusion barrier
(2001-06-01)
Chen, CY
;
Chang, EY
;
Chang, L
;
Chen, SH
;
材料科學與工程學系
Backside copper metallization of GaAs MESFETs using TaN as the diffusion barrier was studied. A thin TaN layer of 40 nm was sputtered on the GaAs substrate before copper firm metallization. As judged from the data of X-ray diffraction (XRD), Anger electron spectroscopy (AES), and cross-sectional transmission electron microscopy (TEM), the Cu/TaN films with GaAs were very stable without interfacial interaction up to 550 OC annealing, The copper metallized MESFETs were thermally stressed at 300 degreesC, The devices showed very little change in the device characteristics (<3 %) after thermal stress, and the changes of the electrical parameters and RF characteristics of the devices after thermal stress were of the same order as those devices without Cu metallization, These results show that TaN is a good diffusion barrier for Cu in GaAs devices and the Cu/TaN films can be used for the backside copper metallization of GaAs MESFETs.
Bandgap mapping for III-V quantum well by electron spectroscopy imaging
(2004)
Tsai, JS
;
Kai, JJ
;
Chang, L
;
Chen, FR
;
材料科學與工程學系
The concept of bandgap mapping' was proposed originally to map the inhomogeneity of band energy in III-V semiconductors with a spatial resolution of a few nanometres in a scanning transmission electron microscope with the focus beam mode. In this paper, several techniques were developed to demonstrate the possibility to map the distribution of bandgap energies for GaN/AlN quantum-well structures using electron spectroscopy imaging (ESI). The phase correlation function was used to register different energy-loss images among ESI series with an accuracy of 1 pixel. The energy dispersion of ESI series was improved by a fast Fourier transform interpolation method. An iterative multivariable least square algorithm was derived to refine the fitting of the single scattering distribution to an analytic form of the density of states function alpha(E Eg)(0.5). The inhomogeneity of the band energy of the quantum well can be revealed from the band-energy map. A threshold filter method is applied to estimate the average value and SD of the bandgap energy from barrier and well regions in the energy map. The average bandgap energy of AlN and GaN is determined to be 5.62 +/- 0.35 and 3.87 +/- 0.36 eV, respectively. The effect of delocalization on the accuracy of band-energy determination is discussed. The 2sigma(Eg), accuracy of this analysis is comparable to half of the energy resolution of the ESI experiment.
Characterization of diamond nanoplatelets
(2004-04-01)
Chen, HG
;
Chang, L
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Diamond deposition at a temperature above 1000 degreesC was carried out in a microwave plasma chemical vapor deposition reactor using a 3% CH4/H-2 gas mixture. A polycrystalline diamond substrate was coated with a thin film of nickel in 100-nm thickness before deposition. Electron microscopy characterization of electron diffraction, high-resolution imaging, and electron energy loss spectroscopy shows that the diamonds deposited exhibit regular shapes in triangles and parallelogram with well-faceted surfaces. These diamond platelets are single crystallites with a uniform thickness of approximately 30-70 nm and length of several hundred nanometers to a few micrometers. The platelet morphology suggests that it is formed by lateral growth. Also, it was found that the diamonds are covered with a 1 to 2-nm thick graphite films in epitaxy. (C) 2003 Elsevier B.V. All rights reserved.
Chemical vapor deposition of epitaxial zinc oxide thin films on gallium nitride/sapphire substrates
(2004)
Hou, WC
;
Lin, BW
;
Chang, L
;
Lin, TS
;
Lin, CW
High-quality ZnO thin films were formed on (0002) oriented GaN/sapphire substrates by chemical vapor deposition (CVD) of Zinc acetylacetonate (Zn(C5H7O2)(2)) and oxygen. The surface morphology and crystallinity of the deposited ZnO thin films have been investigated using atomic force microscopy and X-ray diffraction. Low temperature photoluminescence spectra show that there is a sharp band edge emission positioned at 3.37 eV and the deep level emission is hardly seen. High-resolution transmission electron microscopy in cross section shows that ZnO is directly grown on GaN in epitaxy without any interlayer, and the ZnO/GaN interface remains atomically flat. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA. Weinheim.
Chemical vapor deposition of uniform and high-quality diamond films by bias-enhanced nucleation method
(2006-03-01)
Yan, JK
;
Chang, L
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Diamond films on 1 x 1 cm(2) Si (100) substrates were synthesized by microwave plasma chemical vapor deposition (MWCVD) using mixture of methane and hydrogen gases. Bias-enhanced nucleation method was used to avoid any mechanical pretreatments. Distribution of deposited diamond crystallites in terms of density, size, and morphology has been significantly improved over all the Si substrate surface area by using a novel designed Mo anode. Films were characterized from the center to the edges of substrates using scanning electron microscopy, transmission electron microscope, and Raman analysis. The results also show that uniform diamond films can be obtained by short bias nucleation period using a dome-shaped Mo anode. The diamond crystallites were directly deposited on Si substrate. Using 2% CH4 in the growth stage, high quality diamond films in the < 100 > texture can be obtained with relatively smooth surface. (c) 2005 Elsevier B.V. All rights reserved.
Chemical vapor deposition of zinc oxide thin films on Y2O3/Si substrates
(2004)
Lin, CW
;
Cheng, TY
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Chang, L
;
Juang, JY
;
材料科學與工程學系
Highly-oriented ZnO films were deposited on Y2O3/Si(111) and Y2O3/Si(100) substrates by atmospheric pressure metal-organic chemical vapor deposition (MOCVD) using zinc acetylacetonate (Zn(C5H7O2)(2)) and oxygen as sources. The substrate temperature and O-2 gas temperature were all kept at 500 degreesC. Y2O3, thermodynamically more stable than SiO2 and epitaxially formed on Si, is used as buffer layer. Epitaxial Y2O3 of 200 nm thickness were first grown by pulsed laser deposition on Si(111) and Si(100) substrates at 800 degreesC for 30 min. X-ray diffraction patterns of the samples only show sharp diffraction peaks of Y2O3{222} and ZnO{0002}. The photoluminescence spectra of ZnO show strong peaks of near the band edge and very weak peaks of deep-level emission at 7 K and room temperature. Cross-sectional transmission electron microscopy shows that the highly-oriented ZnO films has columnar structure with a grain size distribution of 600-850 Angstrom. Most of ZnO grains exhibit orientation relationship with Y2O3 as {0002}(ZnO)//{222}(Y2O3), <0110>(ZnO)//(112)(Y2O3), and <1120>(ZnO)//<110>(Y2O3). (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA. Weinheim.
Crack-free GaN/AlN distributed Bragg reflectors incorporated with GaN/AlN superlattices grown by metalorganic chemical vapor deposition
(2006-02-06)
Huang, GS
;
Lu, TC
;
Yao, HH
;
Kuo, HC
;
Wang, SC
A crack-free GaN/AlN distributed Bragg reflector (DBR) incorporated with GaN/AlN superlattice (SL) layers was grown on a c-plane sapphire substrate by metalorganic chemical vapor deposition. Three sets of half-wave layers consisting of 5.5 periods of GaN/AlN SL layers and GaN layer were inserted in every five pairs of the 20 pair GaN/AlN DBR structure to suppress the crack generation. The grown GaN/AlN DBRs with SL insertion layers showed no observable cracks in the structure and achieved high peak reflectivity of 97% at 399 nm with a stop band width of 14 nm. Based on the x-ray analysis, the reduction in the in-plane tensile stress in the DBR structure with insertion of SL layers could be responsible for the suppression of crack formation and achievement of high reflectivity. (c) 2006 American Institute of Physics.
Deposition of heteroepitaxial diamond on 6H-SiC single crystal by bias-enhanced microwave plasma chemical vapor deposition
(2000-04-01)
Chang, L
;
Yan, JE
;
Chen, FR
;
Kai, JJ
;
材料科學與工程學系
Deposition of heteroepitaxial diamond on substrates of 6H-SiC single crystal by a d.c. voltage biased-enhanced microwave plasma chemical vapor deposition method has been attempted. Various concentrations of methane (CH4) up to 10% in hydrogen (H-2) was used to evaluate its effect on epitaxy. Characterization of cross-sectional transmission electron microscopy with electron energy loss spectroscopy shows that an interlayer can form between diamond 6H-SiC, depending on the CH4 concentration. With low CH4 concentration, diamond was directly nucleated on 6H-SiC with an orientation relationship of diamond {111}//6H-SiC {0001} and diamond [110]//6H-SiC [11 (2) over bar 0]. (C) 2000 Elsevier Science S.A. All rights reserved.
Diamond deposition on Au/amorphotis Si thin films
(2004-04-01)
Kao, CK
;
Yan, JK
;
Chang, L
;
Cho, SY
;
Chen, HG
Au/amorphous Si/SiO2/Si structure was used as substrate for diamond deposition by microwave plasma CVD. The Au-Si phase diagram shows a eutectic point at 363 degreesC. At deposition temperatures of 700-800 degreesC, the Au and amorphous Si films were alloyed as liquid during deposition, which resulted in formation of an array of single crystalline Si whiskers. Microstructural characterization shows that the Si whiskers have a diameter in the range of 50 nm-5 mum with facet on the top surface. The Si whiskers are shown to be oriented along <311> directions. Diamond particles deposited are found only on top of the Si whiskers. The diamond particles can be either of polycrystalline or single crystalline characteristics. (C) 2004 Elsevier B.V. All rights reserved.
Diamond deposition on Si (111) and carbon face 6H-SiC (0001) substrates by positively biased pretreatment
(2002-03-01)
Chang, TF
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Chang, L
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The growth of textured diamond films on Si (111) and carbon face 6H-SiC (0001) has been achieved by positive bias-enhanced-nucleation in microwave plasma chemical vapor deposition. A bias voltage of + 100 to +300 V, 3% CH4 concentration in bias step, and 0.33% CH4 concentration in growth step were used to synthesize diamond films on Si and carbon face 6H-SiC. Highly oriented diamond films were observed by scanning electron microscopy and X-ray diffraction patterns. Cross-sectional transmission electron microscopy showed that the interface between diamond and Si substrate was smooth, while it was rough between diamond and SiC. It also showed that diamond films were directly grown on both substrates. (C) 2002 Elsevier Science B.V. All lights reserved.
Diamond growth onCoSi(2)/Si by bias-enhanced microwave plasma chemical vapor deposition method
(2001-11-01)
Chen, MR
;
Chang, L
;
Chang, DF
;
Chen, HG
;
材料科學與工程學系
Diamond was grown on polycrystalline CoSi2/Si substrates by bias-enhanced microwave plasma chemical vapor deposition. Both of the positive and negative biasing effects were investigated by microstructural characterization. It has been found that nucleation density can reach similar to 10(9) cm(-2) with positive biasing, much higher than with negative biasing. Cross-sectional transmission electron microscopy shows that diamond deposited by positive biasing grows on a relatively smooth CoSi2 surface, while the etching effect of ion bombardment during negative biasing results in a rough CoSi2 surface. The diamond morphology obtained with negative bias has a flat surface with a strong (1 0 0) texture. (C) 2001 Elsevier Science B.V. All rights reserved.
Diamond nucleation on Cu by using MPCVD with a biasing pretreatment
(2001-11-01)
Chuang, KL
;
Chang, L
;
Lu, CA
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Bias enhanced nucleation of diamond on polycrystalline Cu substrates has been investigated. With CH4 concentration increased, the nucleation density is increased and saturated at 10% CH4, but the quality of diamond is decreased. Bias voltages also play an important role on the nucleation of diamond. It is found that the nucleation density is highest when the voltage was set at -250 V. (C) 2001 Elsevier Science B.V. All rights reserved.
Diamond nucleation on Ni3Al substrate using bias enhanced nucleation method
(2005-02-01)
Chen, HG
;
Chang, L
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Diamond deposition with positive and negative bias enhanced nucleation (BEN) pretreatments on mirror-polished polycrystalline Ni3Al substrates has been investigated, respectively. It was found that diamond deposition on the substrates under both biasing exhibited significant variations among grains of different orientations. The substrate surface was found to be rough in the case of negative biasing, whereas it was smooth in the case of positive biasing. Thus, the correlation of the crystallographic orientation of grains on the samples with the diamond nucleation behavior was systematically characterized for the case of positive biasing by electron backscattered diffraction method with scanning electron microscopy. Diamond deposition on Ni3Al grains near (111) orientation results in higher nucleation densities, while the densities are low on (110) and (100) oriented grains. Also, the interfacial microstructure between diamond deposited and Ni3Al was characterized by cross-sectional transmission electron microscopy. (C) 2004 Elsevier B.V. All rights reserved.
Effect of trimethylsilylation on the film stress of mesoporous silica ultralow-k film stacks
(2006)
Chen, JY
;
Pan, FM
;
Lin, DX
;
Cho, AT
;
Chao, KJ
The film stress of the ultralow-k mesoporous silica thin film and the alpha-SiC:H/ mesoporous silica film stack was studied. The as-calcined mesoporous silica exhibits a tensile film stress due to its volume contraction during bake and calcination. Trimethylsilylation of the mesoporous film results in a spring-back effect and thereby improves the mechanical properties of the porous film. Deposition of a plasma-assisted alpha-SiC:H layer on the mesoporous silica thin film can also relieve the tensile stress, and even made the film stack become compressively stressed. This is ascribed to the stress compensation and alkoxylation occurring during the alpha-SiC:H deposition.
Effects of plasma treatment in the tungsten process for chemical vapor deposition titanium nitride barrier film beyond nanometer technology
(2006-03-01)
Chen, KW
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Wang, YL
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Chang, L
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Li, FY
;
Hwang, GJ
As the device shrunk to 100 nm, the CVD TiN barrier filling would be limited by the process window of contact for both step coverage and plasma treatment. This limitation not only affects the step coverage capability but also poses a challenge to the treatment of the organic film with the small contact hole. In this study, we investigated whether the plasma treatment of the TiN film barrier influences the subsequent tungsten deposition and causes the change of the gapfilling behavior. After the different RF plasma treatment, we found that the resistivity and impurity level of the thin TiN film can influence not only the contact resistance and uniformity, but also the product yield. The over-treatment contacts were found with porous voids in the poor tungsten deposition during the contact filling even after CMP polishing. The resistances of under-treatment contacts would be determined by the impurity level of TiN films. Hence, the optimized TiN deposition and treatment would be critical to the contact resistance and yield performance. (c) 2005 Elsevier B.V. All rights reserved.
Evaluation of advanced chemical mechanical planarization techniques for copper damascene interconnect
(2004-01-30)
Chen, KW
;
Wang, YL
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Liu, CP
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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.
Extension of HRTEM resolution by semi-blind deconvolution method and Gerchberg-Saxton algorithm: application to grain boundary and interface
(2001)
Chen, FR
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Ichnose, H
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Kai, JJ
;
Chang, L
;
材料科學與工程學系
A generalized maximum entropy method coupled with Gerchberg-Saxton algorithm has been developed to extend the resolution from high-resolution TEM image(s) for weak objects. The Gerchberg-Saxton algorithm restores spatial resolution by operating real space and reciprocal space projections cyclically. in our methodology, a generalized maximum entropy method (Kullback-Leibler cross entropy) dealing with weak objects is used as a real space (P1) projection. After P1 projection, not only are the phases within the input spatial frequencies improved, but also the phases in the next higher frequencies are extrapolated. An example of semi-blind deconvolution (P1 project only) to improve the resolution in SiC twin boundary is shown. The nature of the bonding in this twin boundary is Si-C but it was rotated 180degrees along the boundary normal. The optimum solution from P1 projection can be further improved by a P2 projection. The square roots of diffraction intensities from a diffraction pattern are then substituted to complete a cycle operation of the Gerchberg-Saxton algorithm. Application examples of Gerchberg-Saxton algorithm to solve the atomic structure of defects (2 x 1 interfacial reconstruction and dislocation) in NiSi2 / Si interfaces will be shown also.
Four-dimensional dielectric property image obtained from electron spectroscopic imaging series
(2001)
Lo, SC
;
Kai, JJ
;
Chen, FR
;
Chang, L
;
Chen, LC
We have demonstrated a new quantitative method to characterize two- dimensional distributions of energy-dependent dielectric function of materials from low loss electron spectroscopic image (ESI) series. Two problems associated with extracted image-spectrum from the low-loss image series, under-sampling and loss of energy resolution, were overcome by using fast Fourier transformation (FFT) interpolation and maximum entropy deconvolution method. in this study, Black Diamond(TM)/Si3N4/SiO2/Si-substrate dielectric layer designed for copper metallization was used as the sample. We show that the reconstructed (FFT interpolated and maximum entropy deconvoluted) image-spectrum obtained from ESI series images can be quantified with the same accuracy as conventional electron energy-loss spectroscopy spectra. Since the analysis of the dielectric function is sensitive to the local thickness of the specimen using Kramers-Kronig analysis, we also developed a new method to quantitatively determine the dielectric constant for low-k materials. We have determined the thickness of the Black Diamond using the extrapolated thickness method from the materials of known dielectric constants. Using Kramers-Kronig formula, the dielectric function map can be deduced front two-dimensional reconstructed single scattering spectra with providing the information of thickness. We proposed a four-dimensional data presentation for revealing the uniformity of the energy dependent property. The accuracy of our methods depends on the thickness determination and on the quality of the reconstructed spectra from the image series.