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Proceedings Paper

Thick polysilicon processing for MEMS transducer fabrication
Author(s): Paul L. Bergstrom; David R. Bosch; Guy Averett
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Paper 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.

Paper Details

Date Published: 3 September 1999
PDF: 10 pages
Proc. SPIE 3875, Materials and Device Characterization in Micromachining II, (3 September 1999); doi: 10.1117/12.360458
Show Author Affiliations
Paul L. Bergstrom, Motorola (United States)
David R. Bosch, Motorola (United States)
Guy Averett, Motorola (United States)

Published in SPIE Proceedings Vol. 3875:
Materials and Device Characterization in Micromachining II
Yuli Vladimirsky; Craig R. Friedrich, Editor(s)

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