Browsing by Author "Wu, Yew-Chung"

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Method for lift off GaN pseudomask epitaxy layer using wafer bonding way
(2005-08-25)
Wu, Yew-Chung
;
Lin, Pei-Yen
;
Peng, Hsien-Chih
The epitaxial lateral overgrowth (ELOG) GaN obtains the dangling structure by using wet etching and the transferred substrate to separate from the GaN epitaxy layer by using stress concentration of thermal expansion coefficient of the transferred substrate. It is useful to separate of the GaN epitaxy layer and transferred substrate by using anneal of wafer bonding. The present invention is to provide high selective etching rate, no damage to epitaxial film, low cost, and feasibility for larger commercial sizes. The wet etching method can not damage the separated epitaxial substrate, thus the substrate can be reused. There are various choices of handling substrate for bonding, not limited by the epitaxial method. When the epitaxial film is applied in devices, the low defect density of the epitaxial film can enhance the lifetime and efficiency of the devices. The addition of this improved fabrication process does not require expensive equipment. Moreover, it will reduce the production cost. The epitaxy substrate is a recyclable substrate after separation of wet etching method and the transferred epitaxy layer obtain low defect density, lifetime improvement and low cost.
Method for lifting offGaN pseudomask epitaxy layerusing wafer bonding way
(2005-08-25)
Wu, Yew-Chung
;
Lin, Pei-Yen
;
Peng, Hsien-Chih
Present invention is a method for lifting off GaN pseudomask epitaxy layer using wafer bonding way, wherein GaN epitaxy is obtained by way of selective area growth on a seed and the growth is in a way of pseudomask growth over a substrate. Owing to the different thermal expansion coefficients of the substrate and the GaN seed, by way of annealing and wafer bonding, the GaN epitaxy layer and the epitaxy substrate can be separated, or the GaN epitaxy substrate can be transferred onto another substrate. Thereby, the epitaxy substrate separated is not spoiled during the transferring procedure and can be reused, which lowers the cost; and high-quality GaN epitaxy layer can be transferred to various kinds of substrates for various kinds of usage and for solving the problems of difficulties in the production or the utilization of the substrate (such as difficulties in the cutting, the conductivity, the heat-sinking, and so on.)
The investigation of interfacial and crystallographic observation in the Ni(V)/SAC/OSP Cu solder joints with high and low silver content during thermal cycling test
(2015-12-01)
Lee, Christine Jill
;
Chen, Wei-Yu
;
Chou, Tzu-Ting
;
Lee, Tae-Kyu
;
Wu, Yew-Chung
This study investigated the microstructure and grain orientation of Ni(V)/SAC396/OSP Cu and Ni(V)/SAC105/OSP Cu solder joints during thermal cycling test (TCT). In general, adjusting Ag content in solders influenced the performance of thermal cycling (TC). Nevertheless, it is still crucial to find the optimal condition of Ag and related mechanisms of crack formation during TCT. This study applied FE-SEM to observe the crack propagation and the precipitation of Sn-Ag IMCs in the solders. Moreover, FE-EPMA and EBSD were used to detect the elemental distribution and grain orientation near the cracks, respectively. The locations of crack initiation are strongly related to the CTE mismatch between Si chip and solder alloy. Besides, the large number of Ag3Sn precipitations in the joint with high Ag content efficiently hinder the crack propagation due to the effects of precipitation hardening. It is revealed that the Ni(V)/SAC396/OSP Cu exhibits good thermal stability during thermal cycle test.