Single-crystal-silicon 3D micromirror
First Claim
1. A method of fabricating a silicon mirror device comprising:
- providing a p-doped single crystal silicon substrate wafer having a frontside and a backside;
forming first and second n-doped regions at a surface of said substrate wherein said first n-doped regions have a first thickness and said second n-doped regions have a second thickness larger than said first thickness;
forming a hard mask on said backside of said wafer;
depositing a silicon oxide layer on said frontside of said wafer;
depositing an aluminum layer on said silicon oxide layer and patterning said aluminum layer to leave aluminum on said silicon oxide layer overlying some of said second n-doped regions to form thermal actuators;
depositing a dielectric layer overlying said patterned aluminum layer and said silicon oxide layer and patterning said dielectric layer to form a mask for flexible springs over portions of said first n-doped regions;
depositing and patterning a metal layer overlying said dielectric layer to form bond pads to said thermal actuators contacting said patterned aluminum layer through openings in said dielectric layer and to form reflecting mirror surfaces overlying others of said second n-doped regions not covered by said patterned aluminum layer to form micromirrors;
thereafter etching away said substrate from said backside of said wafer stopping at said first and second n-doped regions;
thereafter dicing said wafer into mirror array chips;
thereafter etching away said dielectric layer from said frontside of said wafer to expose portions of said first n-doped regions; and
etching away from said frontside said exposed first n-doped regions not covered by said mask to form flexible springs in said first n-doped regions wherein said second n-doped regions covered by said patterned aluminum layer form thermal actuators and said wherein said flexible springs connect said micromirrors to said thermal actuators.
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Accused Products
Abstract
In a 3D free space micromirror device, a mirror plate is joined with actuators through flexible springs where the other ends of the actuators have fixed support on the substrate. Single crystal silicon and aluminum are used as bi-morph materials with silicon dioxide providing electrical isolation between the two. Thickness variation in the microstructure is achieved by two-step p-n junction formed in a p-type substrate. Thick and thin n-silicon layer formation and DRIE cut mechanisms are employed in such a way that all the thick and thin silicon components of the structure are released simultaneously avoiding overetch which can be detrimental to the thin flexural springs. Working prototypes of the device have been found suitable for any optical switching array architecture where deflections up to 10 degrees are required.
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Citations
37 Claims
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1. A method of fabricating a silicon mirror device comprising:
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providing a p-doped single crystal silicon substrate wafer having a frontside and a backside;
forming first and second n-doped regions at a surface of said substrate wherein said first n-doped regions have a first thickness and said second n-doped regions have a second thickness larger than said first thickness;
forming a hard mask on said backside of said wafer;
depositing a silicon oxide layer on said frontside of said wafer;
depositing an aluminum layer on said silicon oxide layer and patterning said aluminum layer to leave aluminum on said silicon oxide layer overlying some of said second n-doped regions to form thermal actuators;
depositing a dielectric layer overlying said patterned aluminum layer and said silicon oxide layer and patterning said dielectric layer to form a mask for flexible springs over portions of said first n-doped regions;
depositing and patterning a metal layer overlying said dielectric layer to form bond pads to said thermal actuators contacting said patterned aluminum layer through openings in said dielectric layer and to form reflecting mirror surfaces overlying others of said second n-doped regions not covered by said patterned aluminum layer to form micromirrors;
thereafter etching away said substrate from said backside of said wafer stopping at said first and second n-doped regions;
thereafter dicing said wafer into mirror array chips;
thereafter etching away said dielectric layer from said frontside of said wafer to expose portions of said first n-doped regions; and
etching away from said frontside said exposed first n-doped regions not covered by said mask to form flexible springs in said first n-doped regions wherein said second n-doped regions covered by said patterned aluminum layer form thermal actuators and said wherein said flexible springs connect said micromirrors to said thermal actuators. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method of fabricating a silicon mirror device comprising:
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providing a p-doped single crystal silicon substrate wafer having a frontside and a backside;
forming first and second n-doped regions at a surface of said substrate wherein said first n-doped regions have a first thickness and said second n-doped regions have a second thickness larger than said first thickness;
forming a hard mask on said backside of said wafer;
depositing a silicon oxide layer on said frontside of said wafer;
depositing an aluminum layer on said silicon oxide layer and patterning said aluminum layer to leave aluminum on said silicon oxide layer overlying some of said second n-doped regions to form thermal actuators;
depositing a dielectric layer overlying said patterned aluminum layer and said silicon oxide layer and patterning said dielectric layer to form a mask for flexible springs over portions of said first n-doped regions;
depositing and patterning a metal layer overlying said dielectric layer to form bond pads to said thermal actuators contacting said patterned aluminum layer through openings in said dielectric layer and to form reflecting mirror surfaces overlying others of said second n-doped regions not covered by said patterned aluminum layer to form micromirrors;
thereafter etching away said substrate from said backside of said wafer stopping at said first and second n-doped regions;
thereafter dicing said wafer into mirror array chips;
thereafter etching away said dielectric layer from said frontside of said wafer to expose portions of said first n-doped regions; and
etching away from said frontside said exposed first n-doped regions not covered by said oxide mask to form flexible springs in said first n-doped regions wherein said second n-doped regions covered by said patterned aluminum layer form thermal actuators and wherein said flexible springs connect said micromirrors to said thermal actuators and wherein each mirror element in each of said mirror array chips comprises one micromirror and four thermal actuators. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
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27. A three-dimensional free space micromirror device comprising:
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single crystal silicon micromirrors;
single crystal silicon thermal actuators; and
single crystal silicon flexible springs connecting said thermal actuators to said micromirrors. - View Dependent Claims (28, 29, 30, 31, 32, 33, 34, 35, 36, 37)
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Specification