Browsing by Author "Lee, CS"

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2.4 V-operated enhancement-mode power PHEMTs for personal handy-phone system application
(2001)
Chen, SH
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Chang, EY
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Lin, YC
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Lee, CS
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友訊交大聯合研發中心
Enhacement-mode pseudomorphic high electron mobility transistors (E-PHEMTs) were developed for low voltage wireless communication applications. Under drain bias of 3.6 V, the device delivered a high output power density of 265.25 mW/mm (29.5dBm) with a power-added-efficiency (PAE) of 50.54 %. Under 1.9GHz pi/4-shifted quadrature phase shift keying(QPSK) modulation signal, the 3.36 mm devices meet personal handy-phone system (PHS) specification at an output power level of 22.42 dB with PAE of 35.12% under 2.4 V drain bias. The E-PHEMTs developed are adequate for low-voltage-operated PHS application.
A gold-free fully copper-metallized InP heterojunction bipolar transistor using non-alloyed ohmic contact and platinum diffusion barrier
(2005)
Chang, SW
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Chang, EY
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Lee, CS
;
Chen, KS
;
Tseng, CW
A gold-free, fully Cu-metallized InP heterojunction bipolar transistor using non-alloyed Ti/Pt/Cu and Pt/Ti/Pt/Cu ohmic contacts and platinum diffusion barrier has been successfully fabricated. The InGaAs/Ti/Pt/Cu ohmic structure was stable after annealing up to 350 degrees C as judged from the Auger depth profiles. A current-accelerated stress test was conducted on the device with a current density J(C) = 80kA/cm(2) for 24h, and the current gain showed no degradation after the current stress. The devices were also thermally annealed at 200 degrees C for 3 h and showed almost no change in the electrical parameters after the heat treatment. The results show that the Au-free, fully Cu-metallized InP heterojunction bipolar transistor (HBT) can be realized using non-alloyed ohmic contacts and Pt diffusion barrier.
A metamorphic high electron-mobitity transistor with reflowed submicron T-Gate for high-speed optoelectronics applications
(2003)
Lien, YC
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Chang, EY
;
Chu, LX
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Chang, HC
;
Lee, CS
A metamorphic high electron-mobility transistor (HEMT) manufactured with reflowed submicron T-gate using E-beam lithography for high-speed optoelectronics applications is developed. The In0.53Al0.47As/InGaAs HEMT uses InxAl1-xAs as the buffer layer between GaAs substrate and the InP lattice-matched HEMT structure. The T-gate developed has a gate length of 0.1 mum. The fabricated metamorphic HEMT has a saturation drain current of 280mA/mrn and a transconductance of 840mS/mm at V-DS=1.2V Noise figure for 160 mum gate-width device is less than 1 dB and the associated gain is up to 14dB at 18GHz. The device demonstrates a cut-off frequency f(T) of 150GHz and a maximum frequency f(MAX) up to 350GHz. The metamorphic HEMT developed has the potential for high-speed optoelectronics applications.
A novel I-line phase shift mask (PSM) technique for submicron T-Gate formation
(2001)
Fu, DK
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Chang, HC
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Fang, CY
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Lee, CS
;
Chang, EY
Submicron T-gate formation using I-line stepper with phase shift mask (PSM) technique [1,2,3] has become very attractive for GaAs MMIC technology due to its low capital investment and high throughput. In this paper a novel submicron (<0.2mum) T-gate technology using phase shift mask technique is reported. The 8% half-tone PSM was selected for the definition of the isolated narrow space. Before lithography, 2500Angstrom SiN film was deposited on the wafer. After I-line PSM exposure and RIE etch of the silicon nitride film, openings with less than 0.25mum wide were formed on the SiN film. To further reduce the dimension of the openings, the wafer was then deposited addition 500Angstrom nitride and etched back using RIE without any mask. Less than 0.2mum openings were formed on the wafer after the dry etch. The wafer was then coated with another layer of photoresist to form lift-off structure. Gate length of 0.185mum was obtained using this technique. This novel process is a high throughput T-gate process compared to conventional E-beam lithography technology for GaAs MMIC production.
A study of the fabrication of flip-chip bumps using dry-film
(2004)
Ke, ZT
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Lee, CS
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Shen, KH
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Chang, EY
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材料科學與工程學系
This work is to study the dry-film photoresist to form patterns for Flip-Chip bumps on 300 mm wafers. The so-called "double-deck metal seed layer" process was also applied in this study by using sputtered 1000 Angstrom Ti (Titanium) and 5000 Angstrom Cu (Copper) metal layers. By welding the metal and solder electroplating technology on the chip of the integrated circuits, Cu / Ni / Solder alloy fill zip hole under bumps metallization after solder re-flowing at 220degreesC. This research optimizes the parameters of the dry-film photoresist, lithography technology, metal sputtering technology and metal electroplating technology.
AIGaN Schottky characteristics after hybrid photo-enhanced wet and inductively coupled plasma etch
(2001)
Huang, WJ
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Fang, CY
;
Wong, JS
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Lee, CS
;
Chang, EY
AlGaN Schottky contact characteristics after hybrid photo-enhanced wet etch and Inductively coupled plasma etch (ICP) is studied. AlGaN was grown by MOCVD on sapphire substrate. KOH solution and 100mW/cm(2) UV illumination by Hg are lamp was used for photo-enhanced wet etch. Gas mixture of Cl-2 and N-2 was used for ICP etch. The Schottky metal used in this study is Ni/Au (100nm/100nm) and the Ohmic metal used is Al (100nm). Typical etch rates are 0.28nm/min and 265nm/min with a roughness of 0.6nm and 1.17nm for wet and dry etch respectively. The ICP process etches more rapidly but the etched surfaces are rougher when compared to the wet-etch process. After ICP etch at 600 watt for 60sec, the schottky diode has an ideality factor n=2.6, and the barrier height phi(B)=0.65 eV However, for the ICP etched sample followed by photo-enhanced wet chemical etch for 30mins, the sample has an ideality factor n=0.99, and the barrier height phi(B)=0.86 eV, and the breakdown voltage is recovered from 4V to 7.5V The study indicates that the wet chemical etch can remove the damage caused by ICP etching. Overall, the hybrid dry/wet etch process is a high etch rate process and cause very low damages on the etched surface.
AIGaN/GaN HEMT sub-bands study using low-temperature photoluminescence
(2001)
Fang, CY
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Lin, CF
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Lee, CS
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Chang, EY
;
Feng, MS
Al0.1Ga0.9N/GaN HEMTs (High Electron Mobility Transistor) structures with different delta-doping concentration and spacer thickness grown on sapphire by MOCVD are studied. The hall mobility is as high as 1333 cm(2)/V s. at room temperature and 6330 cm(2)/V s at 77 K. Obvious 2-DEG phenomena not clearly resolved in literatures before are observed by PL spectra measured at low temperature. The influences of delta-doping concentration and spacer thickness on the 2-DEG phenomena are discussed. Peaks red-shift of different HEMT structures due to temperature variation are observed in 2-DEG sub-bands as well as at the band-edge emission that is believed as a strong evidence of 2DEG sub-bands to valence bands transmission.
Chemistry of Ti(OiPr)Cl-3 with chloride and oxygen-containing ligands: The roles of alkoxide and solvents in the six-coordinate titanium complexes
(1996-03-27)
Gau, HM
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Lee, CS
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Lin, CC
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Jiang, MK
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Ho, YC
Ti((OPr)-Pr-i)Cl-3 reacts easily with various ligands to form a series of six-coordinate complexes, [Ti((OPr)-Pr-i)Cl-5](2-)(HAm+)(2) (Am = NEt(3) (7a) or NC5H5 (7b)), Ti((OPr)-Pr-i)Cl(3)L(2) (L = THF (8) or PhCHO (9)), Ti((OPr)-Pr-i)-Cl-3(PhCHO)(Et(2)O) (10), and [Ti((OPr)-Pr-i)Cl-2(mu-Cl)(PhC(O)OMe)](2) (11). Upon dissolution of 7a in THF, 8 was obtained. When 1 mol equiv of HNEt(3)Cl was added to 8, [Ti((OPr)-Pr-i)Cl-4(THF)](-)(HNEt(3))+ (12) was obtained. With the addition of another 1 mol equiv of HNEt(3)Cl, 12 was converted to 7a. One THF in 8 can be removed in vacuo to give the chloride-bridged dimer [Ti((OPr)-Pr-i)Cl-2(mu-Cl)(THF)](2) (13) which can be converted back to 8 by dissolving in THF. 13 was found to react with 2 mol equiv of HNEt(3)Cl or PhCHO to give 12 and Ti((OPr)-Pr-i)Cl-3(PhCHO)(THF) (14), respectively. The molecular structures of 7b, 8, and 10-13 show short Ti-(OPr)-Pr-i distances, and the relative bonding order of (OPr)-O---Pr-i > Cl-, THF > Et(2)O > PhCHO > mu-Cl- > RC(O)OMe is discussed based on the solid state structures. This bonding sequence is very useful for the prediction of the geometry for six-coordinate complexes of early transition metals with the following principle: The strongest ligand prefers a trans position to the weakest ligand, and the second strongest ligand favors a trans position to the second weakest ligand in the complex. Kinetically, the trans position to the isopropoxide is rather labile for substitution, and the lability of the trans ligand ensures the effectiveness of titanium alkoxides for subsequent reactions or as catalysts in many asymmetric organic syntheses.
Effect of the transition metal on the synthesis of quaternary sulfides MPb8In17S34 (M = Cu, Ag, Au)
(2006-02-20)
Wang, KC
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Lee, CS
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應用化學系
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Department of Applied Chemistry
Quaternary sulfides MPb8In17S34 (M = Cu, Ag, Au) were synthesized at 1123 K from their elements in stoichiometric ratios. These compounds crystallize in monoclinic space group P2(1)/m. The crystal structures feature combinations of (2)(infinity)[InS2] (NaCl111-type) and (2)(infinity)[MPb2In3S6] (NaCl100-type) slabs. These compounds are semiconductors with band gaps near 1.3 eV.
Gold-free fully cu-metallized InGaP/GaAs heterojunction bipolar transistor
(2005-01-01)
Chang, SW
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Chang, EY
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Biswas, D
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Lee, CS
;
Chen, KS
A gold-free, fully Cu-metallized InGaP/GaAs heterejunction bipolar transistor using platinum as the diffusion barrier has been successfully fabricated. The HBT uses Pd/Ge and Pt/Ti/Pt/Cu for n-type and p(+)-type ohmic contacts, respectively, and Ti/Pt/Cu for interconnect metals with platinum as the diffusion barrier. The Ti/Pt/Cu structure was stable during annealing up to 350degreesC judging from the X-ray diffraction (XRD) data and sheet resistance. A current-accelerated stress test was conducted on the device with a current density J(C) = 140 kA/cm(2) for 24 h, and the current gain showed no degradation. The devices were also thermally annealed at 250degreesC,for 24 h and showed little change. We have successfully demonstrated that an Au-free, fully Cu-metallized HBT can be realized using Pt as the diffusion barrier and Pd/Ge and Pt/Ti/Pt/Cu as the ohmic contacts.
Low-noise metamorphic HEMTs with reflowed 0.1 mu m T-gate
(2004-06-01)
Lien, YC
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Chang, EY
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Chang, HC
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Chu, LH
;
Huang, GW
A 0.1-mum T-gate fabricated using e-beam lithography and thermally reflow process was developed and applied to the manufacture of the low-noise metamorphic high electron-mobility transistors (MHEMTs). The T-gate developed using the thermally reflowed e-beam resist technique had a gate length of 0.1 mum and compatible with the MHEMT fabrication process. The MHEMT manufactured demonstrates a cutoff frequency f(T) of 154 GHz and a maximum frequency f(max). of 300 GHz. The noise figure for the 160 mum gate-width device is less than 1 dB and the associated gain is up to 14 dB at 18 GHz. This is the first report of a 0.1 mum MHEMT device manufactured using the reflowed e-beam resist process for T-gate formation.
Microstructural evolution of Cu/Ta/GaAs multilayers with thermal annealing
(2004)
Wu, WC
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Chen, CY
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Lee, CS
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Chang, EY
;
Chang, L
Copper metallization for GaAs was evaluated by using Cu/Ta/GaAs multilayers for its thermal stability. A thin Ta layer of 30 nm thickness was sputtered on the GaAs substrate as the diffusion barrier before copper film metallization. As judged from the results of sheet resistance, X-ray diffraction, Auger electron spectroscopy and transmission electron microscopy, the Cu/Ta films on GaAs were very stable up to 500 degreesC without Cu migration into GaAs. After 550 degreesC annealing, the interfacial mixing of Ta with GaAs substrate occurred, resulting in the formation of TaGa2 and TaAs2, and the diffusion of Ga and As through the Ta layer formed the Cu3Ga and Cu3As phases at the Cu/Ta interface. After 600 degreesC annealing, the reaction of GaAs with Ta and Cu formed TaAs and Cu3Ga, as a result of Cu migration and interfacial instability.
Relaxation dynamics and structural characterization of organic nanoparticles with enhanced emission
(2005-07-21)
Bhongale, CJ
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Chang, CW
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Lee, CS
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Diau, EWG
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Hsu, CS
With a reprecipitation method, we prepared fluorescent organic nanoparticles of 1,4-di[(E)-2-phenyl-1-propenyl]-benzene (PPB) that feature weak emission in solution but exhibit blue-shifted absorption and strong emission as aggregates. Picosecond fluorescent transients of these PPB nanoparticles showed biexponential decay, described with a consecutive kinetic model involving two emissive states. X-ray diffraction patterns of PPB nanocrystals indicate long-range packing structures of two types, one the same as in a single crystal and the other not yet determined. PPB molecules in a crystal show an arrangement of a herringbone type with three benzene rings in a PPB unit being nearly planar and two methyl groups of the unit pointing along the same direction, in contrast to the twisted structure of an isolated PPB molecule. Fluorescence transients of PPB on a femtosecond scale indicate an efficient channel for isomerization that is activated for free PPB in solution but inhibited in PPB forming nanoparticles, demonstrating the significance of molecular geometry and twisting motions that affect the relaxation dynamics in the excited state. The versatile techniques combined in this work provide strong evidence to improve our understanding of optical properties in organic nanoparticles dependent on size.
Study of Ti/W/Cu, Ti/Co/Cu, and Ti/Mo/Cu multilayer structures as Schottky metals for GaAs diodes
(2004-07-01)
Chang, HC
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Lee, CS
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Chen, SH
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Chang, EY
;
He, J
Schottky structures with copper and refractory metals as diffusion barrier for GaAs Schottky diodes were evaluated. These structures have lower series resistances than the conventionally used Ti/Pt/Au structure. Based on the electrical and material characteristics, the Ti/W/Cu and Ti/Mo/Cu Schottky structures are thermally stable up to 400degreesC; the Ti/Co/Cu Schottky structure is thermally stable up to 300degreesC. Overall, the copper-metallized Schottky structures have excellent electrical characteristics and thermal stability, and can be used as the Schottky metals for GaAs devices.
Study of titanium tungsten nitride and tungsten nitride Schottky contacts on n-GaN
(2003-07-01)
Lee, CS
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Chang, EY
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Chang, L
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Fang, CY
;
Huang, YL
The Schottky diode behaviors of the TiWNx and the WNx Schottky contacts to n-GaN were investigated at different annealing temperatures. Both TiWNx and WNx films were deposited by the reactive DC sputtering method. The WNx/n-GaN contact exhibited excellent electrical characteristics even after rapid-thermal annealing up to 850degreesC for 10s. The ideality factor and barrier height remained 1.09 and 0.8OeV, respectively, after 850degreesC annealing. However, the TiWNx/n-GaN contact was thermally stable only up to 650degreesC annealing; the values of the ideality factor and the barrier height were 1.14 and 0.76 eV, respectively, after 650degreesC annealing and started to degrade when annealed at higher temperatures. The deterioration of the TiWNx/n-GaN contact at higher temperatures was due to the inter-diffusion of the TiWN film and the GaN material.
Use of Ti/W/Cu, Ti/Co/Cu and Ti/Mo/Cu multi-layer metals as Schottky metals for GaAs Schottky diodes
(2002)
Lee, CS
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Chang, EY
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He, JJ
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材料科學與工程學系
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Department of Materials Science and Engineering
New Schottky structures (Ti/W/Cu, Ti/Co/Cu, Ti/Mo/Cu),with copper and refractory diffusion barrier metal, for GaAs Schottky diodes were evaluated. For the widely used Ti/Pt/Au Schottky diode, the thick overcoat gold layer was replaced with copper; Pi layer was replaced with the transition metals such as W, Co and Mo. The choice of the refractory metals was I based on their resistivity and the capability as the anti-diffusion barrier. The multi-layer metals were sputtered on the surface of n-GaAs. The Schottky metals were annealed at 15.0degreesC-300degreesC after deposition. Them ideality. factor and Schottky barrier height are 1.08/0.78eV, 1.07/0.71eV and 1.06/0.76eV for Ti/W/Cu, Ti/Co/Cu and Ti/Mo/Cu. structure respectively after annealing at 150degreesC for 2 minutes. The electrical properties of these contacts are, comparable with the typical Ti/Pt/Au Schottky diode which has an ideality factor close to 1.07. From the XkD results, the Ti/W/Cu and Ti/Mo/Cu Schottky structures are thermally stable after annealing up to 400degreesC for 30 minutes; Ti/Mo/Cu Schottky structure is. thermally stable up to 300degreesC annealing for 30min These results show that the new. Schottky. structure's have excellent electrical characteristics compare to the traditional Ti/Pt/Au structure and can be used as the Schottky metals for GaAs devices.
Use of WNX as the diffusion barrier for interconnect copper metallization of InGaP-GaAs HBTs
(2004-07-01)
Chang, SW
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Chang, EY
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Lee, CS
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Chen, KS
;
Tseng, CW
Use of WNX as the diffusion barrier for interconnect copper metallization of InGaP-GaAs heterojunction bipolar transistors (HBTs) was studied. The WNX (40 nm) and Cu (400 nm) films were deposited sequentially on the InGaP-GaAs HBT wafers as the diffusion barrier and interconnect metallization layer, respectively, using the sputtering method. As judged from the data of scanning electron microscopy, X-ray diffraction, Auger electron spectroscopy, and sheet resistance, the Cu-WNX-SiN and Cu-WNX-Au structures were very stable up to 550 degreesC and 400 degreesC annealing, respectively. Current accelerated stress test was conducted on the Cu-WNX metallized HBTs with V-CE = 2 V, J(C) = 140 kA/cm(2) and stressed for 55 h, the current gain (beta) of these HBTs showed no degradation and was still higher than 100 after the stress test. The Cu-WNX metallized HBTs were also thermally annealed at 250 degreesC for 25 h and showed no degradation in the device characteristics after the annealing. For comparison, HBTs with An interconnect metallization were also processed, and these two kinds of devices showed similar characteristics after the stress tests. From these results, it is demonstrated that WNX is a good diffusion barrier for the interconnection copper metallization of GaAs HBTs.