Localized Deposition of Polysilicon for MEMS Post-Fabrication Processing

In this paper, the localized deposition of polysilicon is demonstrated on suspended and attached microbeams. The microbeams are 1, 2 and 5μm wide; 0.5, 1.5 and 2μm thick; and 50 and 100 μm long. Polysilicon is deposited by thermal decomposition of silane gas on the electrically-heated structures. The peak temperature of each microbeam is estimated using finite element analysis and an electro-thermal analysis is discussed. The deposited silicon is amorphous or polycrystalline, depending on the process conditions. The deposition rates are much higher than those of conventional LPCVD polysilicon. Localized polysilicon deposition is useful in MEMS post-fabrication processes such as tuning resonators and sealing packages.