Integrated large area microstructures and micromechanical devices
First Claim
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1. A process for fabricating a solid, large area platform mounted in a cavity in a wafer and supported for motion with respect to the wafer by integral, flexible, supports, comprising:
- producing on a top surface of the wafer a first pattern defining the size, shape and location of the large area platform and the supports for the platform;
etching through said first pattern to produce in a top portion of the wafer top surface trenches surrounding mesas corresponding to said platform and said supports;
producing on a bottom surface of the wafer a second pattern corresponding to the size, shape and location of said platform;
etching through said second pattern to produce in a bottom portion of the wafer a bottom trench corresponding to said platform, the bottom trench being aligned with but spaced below the top trench surrounding the mesa corresponding to said platform;
further etching the top trenches to cause the top surface trench surrounding the mesa corresponding to said platform to intersect said bottom trench to produce a though trench to free said platform; and
additionally etching said top trenches to undercut said mesas to release said supports from the wafer underlying the supports, the ends of said supports being integral with and cantilevered from the wafer and the platform and extending therebetween to support the platform.
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Abstract
Deep reactive ion etching creates a single mask MEMS structure 20-50 ηm deep on the top surface of a wafer. Thereafter, a bottom surface etch cooperates with trenches formed in the MEMS structure to provide through trenches which release large area structures of arbitrary shape and having a thickness up to that of the wafer. The released structure is supported in the wafer by MEMS support beams and motion is detected and affected by MEMS sensors and actuators, respectively.
43 Citations
29 Claims
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1. A process for fabricating a solid, large area platform mounted in a cavity in a wafer and supported for motion with respect to the wafer by integral, flexible, supports, comprising:
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producing on a top surface of the wafer a first pattern defining the size, shape and location of the large area platform and the supports for the platform;
etching through said first pattern to produce in a top portion of the wafer top surface trenches surrounding mesas corresponding to said platform and said supports;
producing on a bottom surface of the wafer a second pattern corresponding to the size, shape and location of said platform;
etching through said second pattern to produce in a bottom portion of the wafer a bottom trench corresponding to said platform, the bottom trench being aligned with but spaced below the top trench surrounding the mesa corresponding to said platform;
further etching the top trenches to cause the top surface trench surrounding the mesa corresponding to said platform to intersect said bottom trench to produce a though trench to free said platform; and
additionally etching said top trenches to undercut said mesas to release said supports from the wafer underlying the supports, the ends of said supports being integral with and cantilevered from the wafer and the platform and extending therebetween to support the platform. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A process for fabricating a micromechanical device comprising:
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producing a first pattern on the top surface of a substrate;
etching said pattern to form a first trench in the substrate with a depth of less than twenty (20) percent of the substrate thickness;
producing a second pattern on the bottom surface of the substrate;
etching said second pattern to form a second trench in the substrate with a depth which is less than the thickness of the substrate minus the depth of the trench formed from the top surface;
further etching said top surface trench to cause the bottom of said first trench to intersect with said second trench. - View Dependent Claims (12, 13, 14, 20, 21, 22)
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15. A process for fabricating a micromechanical device comprising:
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producing a first pattern on the top surface of a substrate;
etching said pattern to form a plurality of top trenches in the substrate with a depth of less than twenty (20) percent of the substrate thickness;
producing a second pattern on the bottom surface of the substrate, said second pattern being aligned with the top surface pattern so that at least one structure defined by said second pattern lies directly opposite at least one trench formed from the top surface;
etching said second pattern to form a bottom trench in the substrate with a depth which is less than the thickness of the substrate minus the depth of the trench formed from the top surface;
further etching said top surface trenches to cause lateral etching in at least one pair of adjacent trenches to undercut and thereby release the structure between them, and to cause vertical etching of the bottom of at least one top trench to cause it to intersect with the bottom trench previously formed by etching from the bottom surface.
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16. A process for fabricating a solid, large area platform mounted in a cavity in a wafer by integral, flexible supports, comprising:
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producing on a top surface of the water a first pattern defining the size, shape and location of a large area platform, supports for the platform, and electrodes for the platform;
etching through said first pattern to produce in a top portion of the wafer top surface trenches surrounding mesas corresponding to said platform, said supports and said electrodes;
depositing a protective layer on said mesas, the walls of said trenches and the bottom surfaces of said trenches;
producing on a bottom surface of the wafer a second pattern corresponding to the size, shape and location of said platform and vertically aligned with said first pattern;
etching through said second pattern to produce in a bottom portion of the wafer a bottom trench corresponding to said platform, the bottom trench being aligned with but spaced below the top trench surrounding the mesa corresponding to said platform;
removing the protective layer from the bottom surfaces of the top trenches; and
further etching the top trenches vertically to cause the top surface trench surrounding the mesa corresponding to said platform to intersect said bottom trench to produce a through trench to free said platform, and to horizontally undercut said mesas to release said supports and said electrodes from the wafer underlying the supports and electrodes, the ends of said supports being integral with and cantilevered from the wafer and the platform and extending therebetween to support the platform. - View Dependent Claims (17, 18, 19)
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23. A process for fabricating a large area, solid microelectromechanical platform supported by released, integral, flexible supports, comprising:
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etching the top side of a wafer to form top trenches defining the platform and supports connected to the platform;
etching the bottom side of the wafer to form bottom trenches aligned with the top trenches;
further etching from the top side of the wafer to connect the trenches defining the platform to free the platform; and
laterally underetching the supports to release them, thereby enabling the platform to move with respect to the wafer. - View Dependent Claims (24, 25, 26, 27, 28, 29)
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Specification