Abstract

The IC and MEMS industry has been plagued by the problem of residual stresses that result from the deposition of materials on silicon. The residual stresses can induce the delamination of the thin firms, impede subsequent processing steps, or adversely effect the final geometry and performance of thicker films used in MEMS. The current research introduces a novel approach using a multi-layer sandwich composite approach to control residual stresses in a MEMS device, as well as to control the final geometry of the device. The method uses different materials and/or processing parameters, to create a stress - neutral laminate by balancing alternating layers of materials that individually possess tensile or compressive residual stresses.

The current method for controlling residual stress in a structured MEMS device includes selecting a total thickness and an overall equivalent stress for the structure. A thickness for each of at least one set of alternating first and second layers of deposited material is employed to control an internal stress with respect to the neutral axis of each material layer. Then, by alternating first and second layers, a MEMS type structure can be created based on the selected total thickness and desired overall equivalent stress. It will be demonstrated that there is more than one method that is effective in the control of resultant residual stresses and that either method can be useful in creating thicker firms for MEMS devices. It will be shown that the ability to control the final geometry of the device can be a powerful asset for the performance of MEMS devices.

The sandwich composite process also allows for the creation of a MEMS device that is much stronger, and has a higher natural resonance frequency, than using a homogenous material deposition. The additional strength and bandwidth provides MEMS designers the ability to create devices that up to now were difficult or almost impossible to manufacture.

Library of Congress Subject Headings

Thin films; Microelectromechanical systems--Design and construction; Cushioning materials; Shock (Mechanics); Semiconductor wafers

Publication Date

2005

Document Type

Thesis

Student Type

Graduate

Degree Name

Materials Science and Engineering (MS)

Department, Program, or Center

Center for Materials Science and Engineering

Advisor

Mark Kempski

Advisor/Committee Member

K.S.V. Santhanam

Comments

Physical copy available from RIT's Wallace Library at TK7872.T55 P37 2005

Campus

RIT – Main Campus

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