Papers by Keyword: Dual Gate Oxide

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Authors: Didier Lévy, Sébastien Petitdidier, H. Bernard, F. Guyader, C. Dezauzier, C. Pizzetti
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Authors: Philippe Garnier, B. Pernet, Y. Gomez, C. Duluard, Alphonse Torres, David Barge, M. Gatefait, Didier Lévy
Abstract: Integrating multiple gate oxides on a same die requires a proper definition of their respective active area (fig. 1). First the thick gate oxide is grown, and covered by some photoresist. Then a wet etch removes this oxide on the die areas where the resist has been developed. Finally, after resist stripping and surface cleaning, the thin gate oxide is grown. The interaction between the thick oxide surface, the resist and the etchant makes the wet etch challenging. This paper deals with some characterizations and solutions to improve this process.
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Authors: Ki Hyung Ko, Myung Geun Song, Byung Kwon Cho, Bo Un Yoon, Yu Jin Cho, Tae Sung Kim
Abstract: PR-mask oxide wet etching process is generally applied for the formation of dual gate oxide (Gox) transistor (TR) with different thickness of gate oxide. Oxide residues, which could not be removed properly with conventional wet etching process by dHF was observed when PR rework process by strip with SPM and SC1 was preceded before oxide wet etching. The root cause on this oxide removal retardation issue was studied by XPS for the analysis of surface element, SEM for the observation of surface morphology and optical spectroscopy for the measurement of thickness of oxide. It was found that PR rework process is main factor for oxide residue, because no unetched oxide layer was observed after dHF etching if there was no PR rework. A model test showed that when NH4OH component was included during PR rework process, retardation of oxide etching was occurred. The abnormal high content of carbon ingredient on oxide surface after NH4OH treatment with SC1 or NH4OH only solution shows that some kind of blocking layer generated upon adsorbed NH4OH molecules on oxide surface may hinder oxide wet etching by HF. It is postulated that anionic molecules such as PAG (photoacid generator) or anionic surfactant arisen from PR developing process may be able to combine with NH4OH molecules, forming complex layer by electrostatic interaction. This assumption was clearly verified that no oxide residues was found after dHF etching if ozonated water (O3 DIW) treatment was applied between PR developing and oxide wet etching step, since O3DIW can remove organic component with high efficiency, resulting the elimination of blocking layer for wet etching process.
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Authors: Simon Y.M. Chooi, Sang-Yee Loong, Christopher Lim, Zainab Ismail, Tjin-Tjin Tjoa
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