Process for producing surface micromechanical structures
First Claim
1. A method for fabricating, on a silicon wafer, at least one micromechanical structure which is at least partially free-standing above a silicon substrate at a distance that is approximately equal to a thickness of a sacrificial layer and is at least partially mounted to the silicon substrate, comprising the steps of:
- (a) depositing the sacrificial layer on the silicon substrate;
(b) depositing a second layer on the sacrificial layer, the second layer being patterned;
(c) performing a vapor-phase etching process including the steps of removing, in an etching operation, the sacrificial layer without removing the second layer by subjecting the silicon wafer to a vapor phase of a mixture, of hydrofluoric acid and water to expose the micromechanical structure, and heating the silicon wafer to adjust an etching rate by controlling the water content on a surface of the silicon wafer.
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Abstract
A method for fabricating surface-micromechanical structures wherein a sacrificial layer, in particular of silicon oxide, is deposited on a silicon substrate represented by a silicon wafer, the sacrificial layer being patterned. Onto the sacrificial layer, a second layer, in particular of polysilicon, is deposited and is likewise patterned. The sacrificial layer is removed in an etching operation by means of an etching medium which attacks the sacrificial layer but not the second layer, structures being formed as a result of which are free-standing above the silicon substrate at a distance equal to the thickness of the removed sacrificial layer and are anchored at certain sites on the silicon substrate. According to the invention, for the purpose of etching and exposing, the micromechanical structures are exposed to the vapor phase of a mixture of anhydrous hydrofluoric acid and water in a vapor-phase etching process. This makes it possible to dispense with laborious rinsing operations and sublimation operations.
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Citations
12 Claims
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1. A method for fabricating, on a silicon wafer, at least one micromechanical structure which is at least partially free-standing above a silicon substrate at a distance that is approximately equal to a thickness of a sacrificial layer and is at least partially mounted to the silicon substrate, comprising the steps of:
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(a) depositing the sacrificial layer on the silicon substrate; (b) depositing a second layer on the sacrificial layer, the second layer being patterned; (c) performing a vapor-phase etching process including the steps of removing, in an etching operation, the sacrificial layer without removing the second layer by subjecting the silicon wafer to a vapor phase of a mixture, of hydrofluoric acid and water to expose the micromechanical structure, and heating the silicon wafer to adjust an etching rate by controlling the water content on a surface of the silicon wafer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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Specification