Stress redistribution during silicon micromachining
- Hohns Hopkins Univ., Baltimore, MD (United States)
Failure of MEMS structures is often caused by stresses generated during silicon micromachining process. Residual stresses develop during deposition of the structural and sacrificial layers on a substrate due to thermal expansion mismatch and crystal growth. These stresses redistribute as the sacrificial layer is etched away, causing stress concentration in the multilayer, and sometimes leading to cracking and buckling of the structural layer. To set the stage for a systematic micromechanics study of silicon micromachining process, an initial analysis is carried out for the stress redistribution during etching. The structural and sacrificial layers and the substrate are taken to be linear elastic, with prescribed residual stresses. Under plane strain conditions, the sacrificial layer is assumed to undergo a gradual property change, mimicking the etching process of the layer. Contours of the stress distributions in the structural layer are obtained by performing finite element calculations. Buckling of the structural layer is also analyzed based on the stress distribution and the relative dimensions of the layer. The implications of these results on the design of etching patterns in alleviating the detrimental effects of residual stresses are discussed.
- OSTI ID:
- 175277
- Report Number(s):
- CONF-950686--
- Country of Publication:
- United States
- Language:
- English
Similar Records
Properties of low residual stress silicon oxynitrides used as a sacrificial layer
Planar silicon fabrication process for high-aspect-ratio micromachined parts