Browsing by Author "Lee, Cheng-Shih"

Now showing 1 - 8 of 8

A Cu-based alloyed ohmic contact system on n-type GaAs
(2007-12-03)
Chen, Ke-Shian
;
Chang, Edward Yi
;
Lin, Chia-Ching
;
Lee, Cheng-Shih
;
Huang, Wei-Ching
An alloyed Pd/Ge/Cu Ohmic contact to n-type GaAs is reported for the first time. The Pd/Ge/Cu Ohmic contact exhibited a very low specific contact resistance of 5.73x10(-7) Omega cm(2) at a low annealing temperature of 250 degrees C. This result is comparable to the reported Pd/Ge and Au/Ge/Ni Ohmic contact systems to n-type GaAs with doping concentrations about 1x10(18) cm(-3). The Ohmic contact formation mechanisms and microstructure evolution were investigated using secondary ion mass spectrometry, x-ray diffraction, transmission electron microscopy, and energy dispersive spectrometer. The Ohmic contact behavior was related to the formation of Cu(3)Ge and PdGa(x)As(y) compounds after annealing. (c) 2007 American Institute of Physics.
[ADJUSTABLE COLLIMATOR AND SPUTTERING APPARATUS WITH THE SAME]
(2005-09-08)
Lee, Cheng-Shih
;
Chang, Edward Yi
An adjustable collimator and a sputtering apparatus with the same are provided. The adjustable collimator comprises an adjustable main body, first and second collimating elements. The adjustable main body has an interior space, a top portion, a bottom portion and an adjuster between the top portion and the bottom portion. The adjuster is adapted for adjusting a relative distance between the top portion and the bottom portion. A first collimating element fixed inside the interior space of the top portion in a manner to move with the top portion and a second collimating element fixed inside the interior space of the bottom portion to move with the bottom portion. When the adjustable collimator applies to sputtering apparatus, it can easily control the incident angel of the molecule of the sputtering material by adjusting a relative distance between the top and bottom portion.
Application of Pd/Ge/Cu alloyed ohmic contact system to n-type GaAs for fully Cu-metallized InGaP/GaAs HBTs
(2009-02-01)
Chen, Ke-Shian
;
Chang, Edward Yi
;
Lin, Chia-Ching
;
Lee, Cheng-Shih
;
材料科學與工程學系
Use of the Pd/Ge/Cu multilayers as the emitter and collector ohmic metal for the fully Cu-metallized InGaP/GaAs heterojunction bipolar transistors is studied. The Pd/Ge/Cu ohmic contact exhibited a very low contact resistance of 5.73 x 10(-7) Omega cm(2) at a low annealing temperature (250 degrees C) and the microstructure evolution of Pd/Ge/Cu ohmic contact was investigated using transmission electron microscopy and energy dispersive spectrometer. We also did some comparisons between the Pd/Ge/Cu, Pd/Ge/Ti/Pt/Cu, and the traditional Au/Ge/Ni/Au ohmic contact structures to n-type GaAs. The common emitter I-V curves and Gummel plot of these Cu-metallized HBTs using Pd/Ge/Cu ohmic contact and Cu interconnects showed similar electrical characteristics as those HBTs with conventional Au-metallization. The cutoff frequency (f(T)) of 3 x 20-mu m-emitter-area devices was about 38 GHz. During both the current-accelerated stress test (110 kA/cm(2) stress for 24 h) and the thermal stability test (annealing at 250 degrees C for 24 h), the fully Cu-metallized HBT with Pd/Ge/Cu ohmic contact and Cu interconnects showed almost no obvious degradation in electrical characteristics. The results show that the Pd/Ge/Cu ohmic contact in combination with the Cu interconnects can be used on HBT devices to achieve the Au-free fully Cu-metallized lnGaP/GaAs HBTs, and the devices exhibit good device performance. (C) 2008 Elsevier Ltd. All rights reserved.
Copper metalized ohmic contact electrode of compound device
(2007-07-12)
Lee, Cheng-Shih
;
Chang, Edward Yi
;
Chen, Ke-Shian
The present invention provides an ohmic contact for a copper metallization whose heat diffusion is improved and cost is reduced. Therein, the ohmic contact is formed through a depositing and an annealing of three metal layers of Pd, Ge and Cu; and, the contact resistance of the ohmic contact is adjusted by the thicknesses of the three layers.
Copper-airbridged low-noise GaAs PHEMT with Ti/WNx/Ti diffusion barrier for high-frequency applications
(2006-08-01)
Lee, Cheng-Shih
;
Lien, Yi-Chung
;
Chang, Edward Yi
;
Chang, Huang-Choung
;
Chen, Szu-Houng
A GaAs pseudomorphic HEMT (PHEMT) with Cu-metallized interconnects was successfully developed. Sputtered WNx was used as the diffusion barrier and Ti was used as the adhesion layer to improve the adhesion between WNx/Cu interface in the thin-metal structure. After copper metallization, the PHEMTs were passivated with silicon nitride to avoid copper oxidation. The Cu-airbridged PHEMT showed the saturation I-DS was 250 mA/mm and the g(m) was 456 mS/mm. The Ti adhesion layer plays a significant role on the g(m) and V-p uniformity of the Cu-metallized PHEMTs. The GaAs PHEMTs with Ti/WNx/Ti/Cu multilayer have better noise figure and associated gain than those of the devices without the Ti adhesion layer. The fabricated Cu-metallized GaAs PHEMT with Ti/WNx/Ti/Cu multilayer has a noise figure of 0.76 dB and an associated gain of 8.8 dB at 16 GHz. The cutoff frequency (f(T)) is 70 GHz when biased at V-DS = 1.5 V. These results show that the Ti/WNx/Ti multilayer can serve as a good diffusion barrier for Cu metallization process of airbridge interconnects on GaAs low-noise PHEMTs.
Cu-metalized compound semiconductor device
(2006-12-28)
Chang, Edward Yi
;
Chang, Shang-Wen
;
Lee, Cheng-Shih
The present invention is a compound semiconductor device characterized in that it is Cu-metalized to improved the reliability of the device and to greatly reduce the cost of production.
INTERCONNECT OF GROUP III- V SEMICONDUCTOR DEVICE AND FABRICATION METHOD FOR MAKING THE SAME
(2007-02-22)
Lee, Cheng-Shih
;
Chang, Edward Yi
;
Chang, Huang-Choung
An interconnect of the group III-V semiconductor device and the fabrication method for making the same are described. The interconnect includes a first adhesion layer, a diffusion barrier layer for preventing the copper from diffusing, a second adhesion layer and a copper wire line. Because a stacked-layer structure of the first adhesion layer/diffusion barrier layer/second adhesion layer is located between the copper wire line and the group III-V semiconductor device, the adhesion between the diffusion barrier layer and other materials is improved. Therefore, the yield of the device is increased.
Method of fabricating copper metallization on backside of gallium arsenide devices
(2005-04-21)
Chang, Edward Yi
;
Lee, Cheng-Shih
A bi-level structure based on copper metallization technique has been applied to backside of gallium arsenide (GaAs) devices. The foundation where the structure stands on is device substrate backside, on which a layer of diffusion barrier is deposited first, and to the top of it, a layer of copper metallization is plated to enhance device performance. The barrier layer can be selected from tungsten (W), tungsten nitride (WN), or titanium tungsten nitride (TiWN) by sputtering or evaporating, which effectively prevents copper from diffusing into GaAs substrate. The layer of copper metallization, formed by employing anyone of sputtering, evaporating, or electroplating, proves to offer attractive thermal and electrical conductivity and mechanical strength and the like. Moreover, these characteristic improvements coupled with a fascinating part, low cost, would benefit and motivate global GaAs fabs.