Microstructures and high temperature isolation process for fabrication thereof
First Claim
1. A reactive ion etching process for fabricating a high aspect ratio, submicron, released single crystal structure having an electrically isolating segment, comprising:
- forming a first mask layer on a top surface of a single crystal silicon substrate;
patterning said first mask layer to produce a first mask defining a single crystal silicon structure of arbitrary shape to be formed in and surrounded by said substrate, said shape being independent of crystal orientation in said substrate and including at least a beam portion to be released, said patterning step including producing in said first mask a shape of an electrically isolating region for said structure of arbitrary shape;
reactive ion etching said substrate through the pattern defined by said first mask to produce corresponding deep trenches in said substrate surrounding the defined structure of arbitrary shape, said structure having a top surface covered by said first mask and having substantially vertical side walls;
initially thermally oxidizing said defined structure to produce a thermal oxide layer on said walls and on the bottom of said deep trenches, the thermal oxide layer extending at least partially through said single crystal silicon in said isolating region;
producing a second mask surrounding the isolating region;
stripping the thermal oxide from said side walls in the isolating region;
removing the second mask;
subsequently thermally oxidizing said defined structure to increase the thickness of said thermal oxide layer surrounding said isolating region and completely oxidizing the remaining silicon in said isolating region;
removing the thermal oxide layer from the floor of said trenches to expose said single crystal substrate; and
releasing at least said beam portion from its underlying substrate by reactive ion etching said exposed single crystal substrate in said trenches.
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Abstract
A method of fabricating released microelectromechanical and microoptomechanical structures having electrically isolating segments from single crystal silicon includes thermal oxidation steps. The structures are defined using a single mask patterning process, and the structure is partially thermally oxidized. This is followed by a second masking step which is used to define segments to be completely thermally oxidized, and a second oxidation step completes the fabrication of the isolating segment. Thereafter the structure is released from the underlying substrate.
186 Citations
11 Claims
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1. A reactive ion etching process for fabricating a high aspect ratio, submicron, released single crystal structure having an electrically isolating segment, comprising:
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forming a first mask layer on a top surface of a single crystal silicon substrate; patterning said first mask layer to produce a first mask defining a single crystal silicon structure of arbitrary shape to be formed in and surrounded by said substrate, said shape being independent of crystal orientation in said substrate and including at least a beam portion to be released, said patterning step including producing in said first mask a shape of an electrically isolating region for said structure of arbitrary shape; reactive ion etching said substrate through the pattern defined by said first mask to produce corresponding deep trenches in said substrate surrounding the defined structure of arbitrary shape, said structure having a top surface covered by said first mask and having substantially vertical side walls; initially thermally oxidizing said defined structure to produce a thermal oxide layer on said walls and on the bottom of said deep trenches, the thermal oxide layer extending at least partially through said single crystal silicon in said isolating region; producing a second mask surrounding the isolating region; stripping the thermal oxide from said side walls in the isolating region; removing the second mask; subsequently thermally oxidizing said defined structure to increase the thickness of said thermal oxide layer surrounding said isolating region and completely oxidizing the remaining silicon in said isolating region; removing the thermal oxide layer from the floor of said trenches to expose said single crystal substrate; and releasing at least said beam portion from its underlying substrate by reactive ion etching said exposed single crystal substrate in said trenches. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A reactive ion etching process for fabricating a submicron released single crystal structure having an electrically isolating segment, comprising:
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producing in a first mask layer on a single crystal substrate a pattern for a structure to be released, the pattern defining an electrically isolating region for the structure; producing deep trenches in said substrate through said mask layer, the trenches surrounding and defining the structure to be released; thermally oxidizing said defined structure to be released to completely oxidize said electrically isolating region while only partially oxidizing the remainder of said defined structure; and releasing said defined structure and oxidized electrically isolating region.
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Specification