Modeling of stress-induced curvature in surface-micromachined devices

William D. Cowan; Victor M. Bright; Alex A. Elvin; David A. Koester

doi:10.1117/12.284554

2 September 1997 Modeling of stress-induced curvature in surface-micromachined devices

William D. Cowan, Victor M. Bright, Alex A. Elvin, David A. Koester

Proceedings Volume 3225, Microlithography and Metrology in Micromachining III; (1997) https://doi.org/10.1117/12.284554
Event: Micromachining and Microfabrication, 1997, Austin, TX, United States

Abstract

This paper compares measured to modeled stress-induced curvature of simple piston micromirrors. Two similar flexure-beam micromirror designs were fabricate using the 11th DARPA-supported multi-user MEMS processes (MUMPs) run. The test devices vary only in the MUMPs layers used for fabrication. In one case the mirror plate is the 1.5 micrometers thick Poly2 layer. The other mirror design employs stacked Poly1 and Poly2 layers for a total thickness of 3.5 micrometers . Both mirror structures are covered with the standard MUMPs metallization of approximately 200 angstrom of chromium and 0.5 micrometers of gold. Curvature of these devices was measured to within +/- 5 nm with a computer controlled microscope laser interferometer system. As intended, the increased thickness of the stacked polysilicon layers reduces the mirror curvature by a factor of 4. The two micromirror designs were modeled using IntelliCAD, a commercial CAD system for MEMS. The basis of analysis was the finite element method. Simulated results using MUMPs 11 film parameters showed qualitative agreement with measured data, but obvious quantitative differences. Subsequent remeasurement of the metal stress and use of the new value significantly improved model agreement with the measured data. The paper explores the effect of several film parameters on the modeled structures. Implications for MEMS film metrology, and test structures are considered.

Citation Download Citation

William D. Cowan, Victor M. Bright, Alex A. Elvin, and David A. Koester "Modeling of stress-induced curvature in surface-micromachined devices", Proc. SPIE 3225, Microlithography and Metrology in Micromachining III, (2 September 1997); https://doi.org/10.1117/12.284554

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available