AVS 51st International Symposium
    MEMS and NEMS Tuesday Sessions
       Session MN+MS+PS+TF-TuA

Paper MN+MS+PS+TF-TuA6
Deep Reactive Ion Etching of Silicon Structures for Profile and Morphology Control

Tuesday, November 16, 2004, 3:00 pm, Room 213C

Session: Nano/MEMS Manufacturing and Plasmas
Presenter: R.J. Shul, Sandia National Laboratories
Authors: R.J. Shul, Sandia National Laboratories
M.G. Blain, Sandia National Laboratories
S.G. Rich, Sandia National Laboratories
S.A. Zmuda, Sandia National Laboratories
Correspondent: Click to Email
Deep reactive ion etching (DRIE) of Si or the Bosch process relies on an iterative etch/deposition process where a sidewall etch inhibitor is formed to prevent lateral etching of the Si thus resulting in highly anisotropic etch profiles at reasonably high etch rates. The formation of deep, high-aspect ratio, straight-wall Si structures achieved with this process has been used to fabricate chemical and biological sensors, micro-fluidic devices, and mechanical actuators and gears. However as device designs become more complicated and aspect ratios increase, conventional DRIE processes often cannot meet the demands. For example, high-aspect ratio features etched to depths greater than 150 microns often become tapered and rough with unacceptably slow etch rates. This observation is often referred to as RIE lag or aspect ratio dependent etching and is attributed to reduced diffusion of neutral reactants and etch product species and reduced ion transport to the feature bottom as the depth increases. In many cases the etch will actually terminate due to either inefficient etching or polymer deposition dominating the process. We will report on the use of the DRIE platform to fabricate deep, high-aspect ratio Si features incorporating a process in which etch parameters are incrementally varied during each cycle of the process. The use of this in-situ variable etch process has resulted in a high degree of profile control and smooth etch morphologies while maintaining reasonably fast etch rates for high aspect ratio features. Etch results using this process will be reported as a function of cathode power, etch and deposition time, and reactive gas flow. These results will be compared to results obtained using conventional DRIE processes. 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.