Tham khảo tài liệu 'mems and microstructures in aerospace applications - robert osiander et al (eds) part 13', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 298 MEMS and Microstructures in Aerospace Applications The goal of contamination control at the design level is to minimize contamination sources and to remove contaminants from MEMS devices whenever it is feasible on-ground or on-orbit. By eliminating contaminants before they ever have chance to generate this design level contamination control is not only effective but also very cost-saving. Unfortunately this critical stage of contamination control is often neglected due to the lack of the involvement from a contamination engineer. Material selections for MEMS devices are critical for effective contamination control. Single-crystal Si polysilicon Si3N4 and SiO2 and other materials are well recognized for constructing MEMS devices. In addition SiC shape memory alloy SMA metals permalloy and high-temperature superconductive materials are potential candidates. Although these materials have certain unique properties which are attractive for certain MEMS applications contamination issues may result from the usage of these materials. For example silica material used in fiber optics is brittle and is prone to fracture including delayed fracture. Contamination Controls during Fabrication Contamination concerns start at the beginning of the MEMS fabrication life. Problem areas in the foundry can be with both inferior materials and chemicals or due to inadequate or not followed processing steps. Entire lots due to the homogeneous nature of fabrication runs may need to be destroyed due to contamination related yield losses such as streamers corrosion and other results from impurities or improper processing. The greater concern at the foundry level is allowing contamination to reside with a lot only to appear at a later date found through failure of the component. At the foundry level the most common source of contamination is organics that have not been adequately removed. Most foundries ship product with the photoresists still present which protect the MEMS from .
