Thick polysilicon processing for MEMS transducer fabrication

Paul L. Bergstrom; David R. Bosch; Guy Averett

doi:10.1117/12.360458

3 September 1999 Thick polysilicon processing for MEMS transducer fabrication

Paul L. Bergstrom, David R. Bosch, Guy Averett

Proceedings Volume 3875, Materials and Device Characterization in Micromachining II; (1999) https://doi.org/10.1117/12.360458
Event: Symposium on Micromachining and Microfabrication, 1999, Santa Clara, CA, United States

Abstract

The fabrication of thick polysilicon films for MEMS transducer devices has significant impact on manufacturing process cost and cycle time. Standard polysilicon processing for films greater than two microns result in prohibitive cycle times for production. This study investigates the effect of deposition conditions on film morphology and mechanical properties and manufacturability for 3 micrometers polysilicon films. The study investigated deposition temperatures ranging from 580 degree(s)C to 1050 degree(s)C, gas flow rates, and deposition pressures on across-wafer and across- load uniformity, film morphology studied using AFM, XRD, and TEM, and blanket film intrinsic stresses. The goal was a high deposition rate low residual stress polysilicon film with morphology resembling the standard polysilicon deposition process. The study demonstrated that film morphology was stable between 605 degree(s)C and 700 degree(s)C with a transition in film properties occurring above that temperature. Intrinsic stresses followed the expected trends with compressive films above 603 degree(s)C. Increasing temperature and pressure resulted in increased deposition rates and decreased across-wafer and across-load thickness uniformities. No attempt was made to optimize the processes or hardware configurations to improve uniformities. The process investigation demonstrated increased deposition rates with acceptable as-deposited film morphology and intrinsic stresses. The study confirmed morphology and stress trends with pressure and temperature.

Citation Download Citation

Paul L. Bergstrom, David R. Bosch, and Guy Averett "Thick polysilicon processing for MEMS transducer fabrication", Proc. SPIE 3875, Materials and Device Characterization in Micromachining II, (3 September 1999); https://doi.org/10.1117/12.360458

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KEYWORDS

Silicon films

Semiconducting wafers

Low pressure chemical vapor deposition

Transmission electron microscopy

Atomic force microscopy

Surface roughness

Manufacturing

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