Method of fabrication of large area micromechanical devices
First Claim
1. A method of creating a balanced stress micromechanical structure having at least first, second and third sides, wherein said structure is defined by diffusing a mass of silicon with a dopant, said method comprising the steps of:
- etching a tub in said mass of silicon, said tub defining at least one of said at least first, second and third sides of said structure;
doping said tub by applying an etch stop diffusion comprising said dopant to all exposed surfaces of said tub;
filling said tub with a silicon backfill to create a filled surface defining at least another of said first, second and third sides;
diffusing said filled surface with said dopant to create an envelope having a sealed relatively lightly doped interior bulk, said envelope comprising said at least first, second and third sides; and
etching said balanced stress micromechanical structure free from said mass of silicon.
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Accused Products
Abstract
A method of fabrication of micromechanical devices enables the production of large area micromechanical transducer structures which are symmetric, stress balanced structures relatively devoid of geometric distortions. Micromechanical transducer structures are fabricated implementing processes and physical characteristics which overcome the unbalanced stresses occurring in high concentration diffusion planar structures that cause problematic geometric distortions that restrict physical size. Large increases in the practical size of micromechanical devices which may be fabricated are achieved while permitting greater depths of structural features, without the resultant concentration and stress distortions. Multilevel, balanced stress structures can be created which are of varying geometries at each level to produce a "sculpted" structure.
121 Citations
25 Claims
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1. A method of creating a balanced stress micromechanical structure having at least first, second and third sides, wherein said structure is defined by diffusing a mass of silicon with a dopant, said method comprising the steps of:
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etching a tub in said mass of silicon, said tub defining at least one of said at least first, second and third sides of said structure; doping said tub by applying an etch stop diffusion comprising said dopant to all exposed surfaces of said tub; filling said tub with a silicon backfill to create a filled surface defining at least another of said first, second and third sides; diffusing said filled surface with said dopant to create an envelope having a sealed relatively lightly doped interior bulk, said envelope comprising said at least first, second and third sides; and etching said balanced stress micromechanical structure free from said mass of silicon. - View Dependent Claims (2, 3, 4, 5)
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6. A balanced stress micromechanical structure having a selected shape and at least a first and a second selected dimension, comprising:
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a mass of silicon; means for selectively providing etch resistance to said mass of silicon to generate etch resistant silicon integral with said mass of silicon, said means for selectively providing etch resistance being disposed in at least one pattern to provide at least some patterned etch resistant silicon; wherein said mass of silicon is exposed to etching means for selectively etching said mass of silicon while retaining said at least some patterned etch resistant silicon; and means for preventing geometric distortion or said at least some patterned etch resistant silicon upon freeing said at least some patterned etch resistant silicon from said silicon mass. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13)
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14. A method of creating a planar balanced stress micromechanical structure in a mass of silicon, said method comprising the steps of:
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etching a plurality of grooves in said mass of silicon; doping said plurality of grooves by applying an etch stop diffusion to all exposed surfaces of said grooves to create an etch resistant corrugated lower surface; filling said plurality of grooves with a silicon to create a filled surface of said planar balanced stress micromechanical structure; diffusing said filled surface with an etch stop diffusion to create an etch resistant upper planar surface; and etching said planar balanced stress micromechanical structure substantially free from said silicon mass. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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21. A method of fabricating a balanced stress micromechanical structure in a mass of silicon, said method comprising the steps of:
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applying a etch stop dopant in a pattern on a first surface of said mass of silicon; growing an intermediate layer of silicon over said etch stop dopant patterned on said first surface of said mass of silicon; applying a second etch stop dopant in a second pattern on said intermediated layer of silicon; and etching said balanced stress micromechanical structure substantially free from said mass of silicon. - View Dependent Claims (22, 23, 24, 25)
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Specification