AVS 52nd International Symposium
    MEMS and NEMS Tuesday Sessions
       Session MN-TuM

Paper MN-TuM10
Deep Reactive Ion Etching of Membrane-Based Devices Using a Low-Frequency Bias

Tuesday, November 1, 2005, 11:20 am, Room 207

Session: Micro and Nano Fabrication Techniques for MEMS & NEMS
Presenter: R.J. Shul, Sandia National Laboratories
Authors: R.J. Shul, Sandia National Laboratories
J. Stevens, Sandia National Laboratories
R.P. Manginell, Sandia National Laboratories
M.G. Blain, Sandia National Laboratories
S.G. Rich, Sandia National Laboratories
S.A. Zmuda, Sandia National Laboratories
L.J. Sanchez, Sandia National Laboratories
M. DeVre, Unaxis USA Inc.
J. Shin, Unaxis USA Inc.
S.L. Lai, Unaxis USA Inc.
Correspondent: Click to Email
Deep reactive ion etching (DRIE) of Si or the Bosch process is essential in the fabrication of many membrane-based devices, especially chemical and biological sensors. The process relies on the ability of the DRIE process to essentially stop on the membrane film, typically a dielectric film such as SiO@sub2@ or SiN. The ability to stop on this film is due to the high etch selectivity of Si to the membrane film. Since the SiO@sub2@ or SiN membrane is an insulator, positive charge can build up on this film upon exposure to the plasma and notching at the foot of the feature can result. The positive charge causes ions accelerated from the plasma to assume a divergent path at the Si-insulator interface and causes preferential, lateral etching of the Si at the interface, allowing a notch to form. The notch can be several microns in both the lateral and vertical dimensions and can destroy the device. Notching can be minimized and often eliminated when a low-frequency or pulsed-bias is used. In this study, we will report on the results of deep Si etching of membrane devices using a low-frequency 100 kHz bias. We will compare the results for specific device applications where both high-frequency and low-frequency biasing has been incorporated and demonstrate the relative advantages of low-frequency techniques. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.