Selective chemical vapor deposition of tungsten for microdynamic structures
First Claim
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1. A method of forming a microdynamic structure, comprising:
- forming on a top surface of a substrate wafer a first dielectric layer;
forming a second layer of silicon dioxide on a top surface of said first layer to produce a composite dielectric wafer;
patterning and etching said composite dielectric wafer to produce at least one channel in said wafer, said channel extending partially through said second layer and having a bottom wall in said silicon dioxide layer, the bottom wall being spaced above said top surface of said first layer;
implanting silicon in said silicon dioxide bottom wall of said channel;
selectively depositing a refractory metal in said channel to fill said channel;
depositing an isolation mask on said first layer to and on said refractory metal to mask said refractory metal in said channel;
etching said silicon dioxide layer in the region surrounding at least a part of said metal-filled channel to produce a cavity and to free said metal to provide a cantilever beam extending into said cavity.
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Abstract
A selective chemical vapor deposition (CVD) tungsten process is used to fabricate three-dimensional tungsten cantilever beams on a substrate. Two beams form micromechanical tweezers that move in three dimensions by the application of potential differences between the beams, and between the beams and the silicon substrate. A high deposition rate selective tungsten CVD process is used to fabricate beams of greater than 3 micrometers thickness in patterned, CVD silicon dioxide trenches ion-implanted with silicon. Tweezers 200 micrometers in length with a cross section of 2.7 by 2.5 micrometers will close upon application of a voltage of less than 150 volts.
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Citations
14 Claims
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1. A method of forming a microdynamic structure, comprising:
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forming on a top surface of a substrate wafer a first dielectric layer;
forming a second layer of silicon dioxide on a top surface of said first layer to produce a composite dielectric wafer;patterning and etching said composite dielectric wafer to produce at least one channel in said wafer, said channel extending partially through said second layer and having a bottom wall in said silicon dioxide layer, the bottom wall being spaced above said top surface of said first layer; implanting silicon in said silicon dioxide bottom wall of said channel; selectively depositing a refractory metal in said channel to fill said channel; depositing an isolation mask on said first layer to and on said refractory metal to mask said refractory metal in said channel; etching said silicon dioxide layer in the region surrounding at least a part of said metal-filled channel to produce a cavity and to free said metal to provide a cantilever beam extending into said cavity. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of forming a microdynamic structure comprising:
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providing a wafer including an insulating layer covered by a tungsten seeding layer; depositing a layer of silicon dioxide on said tungsten seeding layer; etching through said layer of silicon dioxide at least one elongated channel having a bottom wall formed by said tungsten seeding layer, said channel serving as a mold for formation of said microdynamic structure; selectively depositing tungsten by chemical vapor deposition in said channel, said tungsten seeding in said channel on said bottom wall of said channel and filling said channel to form an elongated tungsten structure in said silicon dioxide layer; and selectively removing a portion of said silicon dioxide layer surrounding said tungsten-filled channel to form a cavity around at least a part of said tungsten structure to release said structure and to form a cantilever tungsten beam extending into said cavity. - View Dependent Claims (11, 12, 13, 14)
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Specification