Passivation of aluminum for micromachining silicon sensors

Ani Duan; Xuyuan Chen

doi:10.1117/12.775407

30 April 2008 Passivation of aluminum for micromachining silicon sensors

Ani Duan, Xuyuan Chen

Proceedings Volume 6959, Micro (MEMS) and Nanotechnologies for Space, Defense, and Security II; 695912 (2008) https://doi.org/10.1117/12.775407
Event: SPIE Defense and Security Symposium, 2008, Orlando, Florida, United States

Abstract

When wafer with patterned Al connections will be machined by wet etching as subsequent microfabrications, silicon nitride (SiN) is used as passivation and mask layer. We use low temperature deposition process, e.g., plasma-enhanced chemical vapor deposition (PECVD), for depositing SiN. What we experienced is that the wet etching by using Tetramethyl Ammonium Hydroxide (TMAH-water) solution leads the failure of micromachining MEMS sensors and actuators. Damage of aluminum connection by the etching solution is found as the killer reason. In this paper, we have investigated the etching of Al in different TMAH solutions. The result shows that due to deposition of SiN after Al metallization, pinholes are always formed on SiN because of the Al crystal hillocks formed during the SiN deposition. The edge of the Al pattern is not perfectly covered because of poor step coverage of PECVD SiN on Al. The in situ method for passivation of the aluminum during the wet etching has been used. By adding the surfactants, the passivation technique for Al during the Si micromachining in TMAH-water solution is achieved. The quality of Si anisotropic wet etching which includes etching rate, surface roughness and undercutting have been affected significantly.

Citation Download Citation

Ani Duan and Xuyuan Chen "Passivation of aluminum for micromachining silicon sensors", Proc. SPIE 6959, Micro (MEMS) and Nanotechnologies for Space, Defense, and Security II, 695912 (30 April 2008); https://doi.org/10.1117/12.775407

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