Method for overpressure protected pressure sensor
First Claim
1. A method for fabricating a mechanical overpressure stop on a pressure sensor having a silicon substrate and a sensing diaphragm comprising the steps ofdepositing a layer of sacrificial material to form a spacer on said silicon substrate adjacent to said sensing diaphragm,depositing a metalization layer on said silicon substrate and said spacer,depositing a layer of dry film resist upon said metalization layer, wherein said dry resist layer is deposited in successive layers each less than approximately twenty-five micrometers thick, each layer being patterned in registry with a previously deposited resist layer before deposit of a subsequent layer,removing a portion of said resist layer at locations adjacent to said spacer to partially expose said metalization layer,depositing a metal layer upon exposed positions of said metalization layer to form said mechanical overpressure stop, andremoving the remainder of said resist layer and said spacer.
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Accused Products
Abstract
A structure and method of fabrication is provided for a micromechanical overrange protected pressure sensor. A pressure sensor having a silicon substrate is provided with a cavity and a deformable diaphragm wherein deflection of the diaphragm in response to pressure is limited by a forward pressure stop. A method is provided for electrodepositing a metal layer which is attached to the substrate adjacent to the diaphragm to provide a reverse pressure stop in response to pressure supplied to the underside of a diaphragm. The metal layer has a relatively low thermal coefficient of expansion and is patterned through use of a photo-resist layer. A previously deposited precision spacer between the diaphragm and reverse pressure stop is removed to provide a precision gap between the reverse pressure stop and the diaphragm.
Micromechanical elements of relatively great size, yet having precision dimensions or positioning are herein fabricated by lithography of patterned resist films up to several hundred microns thick, exposed and developed to great depth with faithful pattern delineation. The patterns formed by development of the exposed resist are then metallized, preferably by pulse electroplating, to form structural or mechanical elements. Deep film patterning may be achieved by laying down successive layers of a dry film resist and exposing each layer after it is deposited.
56 Citations
26 Claims
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1. A method for fabricating a mechanical overpressure stop on a pressure sensor having a silicon substrate and a sensing diaphragm comprising the steps of
depositing a layer of sacrificial material to form a spacer on said silicon substrate adjacent to said sensing diaphragm, depositing a metalization layer on said silicon substrate and said spacer, depositing a layer of dry film resist upon said metalization layer, wherein said dry resist layer is deposited in successive layers each less than approximately twenty-five micrometers thick, each layer being patterned in registry with a previously deposited resist layer before deposit of a subsequent layer, removing a portion of said resist layer at locations adjacent to said spacer to partially expose said metalization layer, depositing a metal layer upon exposed positions of said metalization layer to form said mechanical overpressure stop, and removing the remainder of said resist layer and said spacer.
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14. A method of fabricating metal mechanical structures having an out-of-plane offset greater than ten micrometers, said method comprising the steps of
forming, patterning and developing a dry film resist layer to provide a patterned surface onto which metal is deposited to thereby achieve a selected pattern of metal, and characterized in that said step of forming, patterning and developing deposits the resist layer with a thickness greater than ten micrometers in successive layers each less than approximately twenty five micrometers thick, patterns each said deposited layer in registry with a previous layer before deposit of a subsequent layer, and develops said patterned resist layer substantially uniformly in vertical sections extending through its thickness.
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26. A method of forming a metal structure on a surface of a workpiece, said method comprising the steps of
premetalizing the surface with a metal layer, depositing a plurality of dry film resist layers on the workpiece, wherein each said layer is patterned by exposure to an obliquely extending radiation to pattern said layer in registry with a previously deposited layer before deposit of a subsequent layer, developing portions of said resist layers exposed to the radiation to form a pattern having a shape of the metal structure in said resist layers, and metalizing the pattern to form the metal structure.
Specification