Fracture properties of polycrystalline silicon - a material for micro-electro-mechanical systems
- Univ. of California, Berkeley, CA (United States)
A great deal of research has been performed during the past few years to apply the microfabrication technology used for making integrated circuits to the manufacture of microscopic pressure sensors, accelerometers, and other micro-electro-mechanical systems (MEMS). One result of this work has been the choice of polycrystalline silicon (polysilicon) as a primary structural material employed in MEMS devices, particularly when the polysilicon has been doped with such elements as phosphorus for improved electrical and mechanical properties. As MEMS devices become more relied upon for real world applications, it will be necessary to establish design rules to ensure adequate product lifetimes. However, very little work has been done to deter- mine the failure mechanisms of polysilicon. The work presented here offers an experimental evaluation of the ultimate strength and fracture toughness of polysilicon with regard to the effects of exposure to hydrofluoric acid, a commonly used etchant in MEMS fabrication. A series of micromechanical structures have been designed to measure the strain at fracture and fracture toughness of a thin film. These test structures are patterned onto a thin film of polysilicon covering a silicon wafer using standard microfabrication techniques. Since the structures have dimensions on the order of microns, hundreds of multiple test structures are patterned on a single wafer providing a large amount of statistical data. Results using these structures indicate that prolonged exposure to HF can result in a decrease in the fracture strength of polysilicon.
- OSTI ID:
- 175276
- Report Number(s):
- CONF-950686-; TRN: 95:006111-0230
- Resource Relation:
- Conference: Joint applied mechanics and materials summer meeting, Los Angeles, CA (United States), 28-30 Jun 1995; Other Information: PBD: 1995; Related Information: Is Part Of AMD - MD `95: Summer conference; PB: 520 p.
- Country of Publication:
- United States
- Language:
- English
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