New methods for measuring mechanical properties of thin films in micromachining: Beam pull-in voltage (VPI) method and long beam deflection (LBD) method
✍ Scribed by Quanbo Zou; Zhijian Li; Litian Liu
- Publisher
- Elsevier Science
- Year
- 1995
- Tongue
- English
- Weight
- 506 KB
- Volume
- 48
- Category
- Article
- ISSN
- 0924-4247
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✦ Synopsis
New stress-measurement methods for determining both tensile and compressive stress and Young's modulus in surface micromachining are presented. The investigation is concentrated on the development of two techniques: (1) beam pull-in voltage (\left(V_{\mathrm{PI}}\right)) and (2) long beam deflection (LBD). The (V_{\mathrm{PI}}) method is based on the pulling down of the upper electrode (beam) when the voltage between two electrodes exceeds a critical level. Both tensile and compressive stress and Young's modulus of a thin film can be derived using this method. the LBD method, on the other hand, converts the axial strain in the beam into a transverse deflection (w(x)) after the structure is released to be free standing; this deflection is large enough to be measured easily. These techniques have been analysed and tested experimentally. A comparison with other known stressmeasurement techniques shows good agreement using polysilicon films. Both techniques have been shown to be quite promising for simple and accurate on-chip thin-film stress measurements.