Bi/In thermal resist for both Si anisotropic wet etching and Si/SiO2 plasma etching

Glenn H. Chapman; Yuqiang Tu; Jun Peng

doi:10.1117/12.524690

30 December 2003 Bi/In thermal resist for both Si anisotropic wet etching and Si/SiO₂ plasma etching

Glenn H. Chapman, Yuqiang Tu, Jun Peng

Proceedings Volume 5342, Micromachining and Microfabrication Process Technology IX; (2003) https://doi.org/10.1117/12.524690
Event: Micromachining and Microfabrication, 2004, San Jose, California, United States

Abstract

Bi/In thermal resist is a bilayer structure of Bi over In films which can be exposed by laser with a wide range of wavelengths and can be developed by diluted RCA2 solutions. Current research shows bimetallic resist can work as etch masking layer for both dry plasma etching and wet anisotropic etching. It can act as both patterning and masking layers for Si and SiO₂ with plasma “dry” etch using CF₄/CHF₃. The etching condition is CF₄ flow rate 50 sccm, pressure 150 mTorr, and RF power 100 - 600W. The profile of etched structures can be tuned by adding CHF₃ and other gases such as Ar, and by changing the CF₄/CHF₃ ratio. Depending on the fluorocarbon plasma etching recipe the etch rate of laser exposed Bi/In can be as low as 0.1 nm/min, 500 times lower than organic photoresists. O₂ plasma ashing has little etching effect on exposed Bi/In. Bi/In also creates etch masking layers for alkaline-based (KOH, TMAH and EDP) “wet” anisotropic bulk Si etch without the need of SiO₂ masking steps. The laser exposed Bi/In etches two times more slowly than SiO₂. Experiment result shows that single metal Indium film exhibits thermal resist characteristics but at twice the exposure levels. It can be developed in diluted RCA2 solution and used as an etch mask layer for Si anisotropic etch. X-ray diffraction analysis shows that laser exposure causes both Bi and In single film to oxidize. In film may become amorphous when exposed to high laser power.

Citation Download Citation

Glenn H. Chapman, Yuqiang Tu, and Jun Peng "Bi/In thermal resist for both Si anisotropic wet etching and Si/SiO₂ plasma etching", Proc. SPIE 5342, Micromachining and Microfabrication Process Technology IX, (30 December 2003); https://doi.org/10.1117/12.524690

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