Process for micromechanical fabrication
First Claim
1. A process for fabricating a micromachined structure, said process comprising the steps of:
- selecting a starting wafer having a first single crystal silicon substrate with at least one dielectric surface and a second single crystal silicon substrate bonded to said at least one dielectric surface of said first silicon substrate;
masking, patterning and diffusing said second single crystal silicon substrate with a first impurity in selected regions forming at least one of an electrode region and an anchor region;
depositing a first sacrificial layer of single crystal silicon over said at least one of said electrode region and said anchor region, forming a gap spacer;
depositing a first device layer of single crystal silicon over said gap spacer, said first device layer being doped in selected areas with an impurity to impart etch resistance to form a first device layer that has etch resistant areas;
masking and patterning said first device layer forming a suitable geometry for said micromachined structure; and
etching away said first sacrificial layer of single crystal silicon leaving said micromachined structure while preserving said dielectric surface.
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Abstract
An improved process for fabricating micromechanical devices having movable members, such as gyros and accelerometers. A starting wafer includes an oxidized silicon wafer which has been wafer bonded to a second silicon wafer which has a thin N layer on a P substrate. The wafer is patterned, doped and etched in a series of process steps which include the deposition of epitaxial layers to configure critical device dimensions and geometry. Metallizations are deposited for electrical/electronic interconnections. The process includes an ability to integrate on-chip electronics on the silicon substrate. Alignment difficulties and thermal mismatch associated with prior art processes are minimized.
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Citations
19 Claims
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1. A process for fabricating a micromachined structure, said process comprising the steps of:
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selecting a starting wafer having a first single crystal silicon substrate with at least one dielectric surface and a second single crystal silicon substrate bonded to said at least one dielectric surface of said first silicon substrate; masking, patterning and diffusing said second single crystal silicon substrate with a first impurity in selected regions forming at least one of an electrode region and an anchor region; depositing a first sacrificial layer of single crystal silicon over said at least one of said electrode region and said anchor region, forming a gap spacer; depositing a first device layer of single crystal silicon over said gap spacer, said first device layer being doped in selected areas with an impurity to impart etch resistance to form a first device layer that has etch resistant areas; masking and patterning said first device layer forming a suitable geometry for said micromachined structure; and
etching away said first sacrificial layer of single crystal silicon leaving said micromachined structure while preserving said dielectric surface. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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Specification