Packaging Nanoporous Energetic Silicon For On-Chip Mems Applications
Authors: Wayne A. Churaman, Collin R. Becker, Christopher J. Morris, Luke J. Currano, and Chia-Chen Wu, and Michael J. Sailor Company: U.S. Army Research Laboratory and University of California, San Diego, Department of Chemistry and Biochemistry Date Published: 10/3/2011
IWLPC (Wafer-Level Packaging)
Abstract: Energetic materials are generally composed of a fuel and an oxidizer, which react to produce an exothermic reaction. Many common oxidizers are susceptible to moisture absorption, resulting in degradation of the reaction and lower energy released. In this paper, we show two separate packaging techniques to promote longer shelf-life of nanoporous energetic silicon with sodium perchlorate oxidizer, which is extremely hygroscopic. An encapsulation layer of parylene-C, deposited through a vaporization and condensation process, results in decreased moisture uptake by the sodium perchlorate. Subsequently, the shelf-life of the nanoporous energetic silicon increases from 1 minute to approximately 20 hours, when exposed continuously to relative humidity (RH) in the range of 45-60%. We also show initial results to chemically modify the surface of the porous silicon to slow down water infiltration into the pores, resulting in increased shelf-life of at least 32 minutes at 45% RH. Because nanoporous silicon is fabricated on a p-type boron doped silicon wafer, it can be integrated with MEMS using traditional bulk micromachining techniques.