AVS 46th International Symposium
    The Science of Micro-Electro-Mechanical Systems Topical Conference Thursday Sessions
       Session MM+MI-ThM

Paper MM+MI-ThM8
A New Chemistry for Rapid Etching of SiO@sub2@

Thursday, October 28, 1999, 10:40 am, Room 620

Session: Processing and Integration Technology
Presenter: C.I.H. Ashby, Sandia National Laboratories
Authors: C.I.H. Ashby, Sandia National Laboratories
C.M. Matzke, Sandia National Laboratories
L. Griego, Sandia National Laboratories
Correspondent: Click to Email
Plasma etching of SiO@sub2@ has traditionally been achieved using a fluorocarbon-based plasma. Very fast SiO@sub2@ etch rates (> 1 µm/min) are obtained using high-density plasmas and CH@subx@F@suby@ source gases. Although these plasmas provide fast preferential etching of SiO@sub2@ vs. Si by controlled deposition of a polymer, that same polymer deposition makes CH@subx@F@suby@ processes unsuitable for applications where the surface chemical properties of the SiO@sub2@ are important. Fabrication of deep trenches in fused SiO@sub2@ without chemical alteration of the SiO@sub2@ surface by a fluoropolymer deposit is essential for applications such as electrophoretic and electro-osmotic separations using microfabricated channels ("chemlab on a chip"). Rapid (0.4 µm/min) etching of fused silica has been achieved without the use of polymerizing fluorocarbon gases by the addition of N@sub2@ to SF@sub6@/Ar mixtures in an electron-cyclotron-resonance (ECR) reactor. Addition of N@sub2@ to SF@sub6@ increases the etch rate of SiO@sub2@ by up to 30%. After deep (10 µm) trench etching, the smoothness of the etched surface is comparable to that of unetched SiO@sub2@. Nitrogen might play two roles in enhancing SiO@sub2@ etching: 1) increasing the F atom concentration and/or 2) facilitating the etching of the SiO@sub2@ matrix through the formation of volatile NO@subx@ products. Optical emission studies using Ar actinometry suggest the second mechanism dominates under our plasma conditions. Process characteristics under a variety of plasma conditions will be presented. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under Contract DE-AC04-94AL85000.