Relative and Absolute Pressure Sensor Combined on Chip
First Claim
1. A method for manufacturing a pressure measurement system in a wafer for measuring an absolute and a relative pressure, the method comprising:
- a first step wherein a shallow cavity and a deep cavity are etched in a base wafer, such that the depth of the shallow cavity is smaller than the depth of the deep cavity;
a second step wherein a top wafer is applied to the base wafer;
a third step wherein the top wafer is thinned for forming a first membrane over the shallow cavity and for forming a second membrane over the deep cavity, and wherein elements are formed in the top wafer, the elements allowing performing pressure measurements resulting in a first sensor and a second sensor, respectively; and
a fourth step wherein back thinning is applied on the base wafer such that the deep cavity is opened from the backside of the base wafer and that the shallow cavity is still closed by the backside of the base wafer;
wherein the system can be used for measuring an absolute pressure using the first sensor and a relative pressure using the second sensor, and wherein the etching of the first step defines the edges of the first membrane and of the second membrane in respectively the sensors formed from the shallow and the deep cavity.
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Abstract
A method for manufacturing a system in a wafer for measuring an absolute and a relative pressure includes etching a shallow and a deep cavity in the wafer. A top wafer is applied and the top wafer is thinned for forming a first respectively second membrane over the shallow respectively deep cavity, and for forming in the top wafer first respectively second bondpads at the first respectively second membrane resulting in a first respectively second sensor. Back grinding the wafer results in an opened deep cavity and a still closed shallow cavity. The first bondpads of the first sensor measure an absolute pressure and the second bondpads of the second sensor measure a relative pressure. The etching in the first step defines the edges of the first membrane and of the second membrane in respectively the sensors formed from the shallow and the deep cavity.
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Citations
18 Claims
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1. A method for manufacturing a pressure measurement system in a wafer for measuring an absolute and a relative pressure, the method comprising:
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a first step wherein a shallow cavity and a deep cavity are etched in a base wafer, such that the depth of the shallow cavity is smaller than the depth of the deep cavity; a second step wherein a top wafer is applied to the base wafer; a third step wherein the top wafer is thinned for forming a first membrane over the shallow cavity and for forming a second membrane over the deep cavity, and wherein elements are formed in the top wafer, the elements allowing performing pressure measurements resulting in a first sensor and a second sensor, respectively; and a fourth step wherein back thinning is applied on the base wafer such that the deep cavity is opened from the backside of the base wafer and that the shallow cavity is still closed by the backside of the base wafer; wherein the system can be used for measuring an absolute pressure using the first sensor and a relative pressure using the second sensor, and wherein the etching of the first step defines the edges of the first membrane and of the second membrane in respectively the sensors formed from the shallow and the deep cavity. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A pressure measurement system for measuring both an absolute and a relative pressure, the system comprising:
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a base wafer comprising a closed shallow cavity with a first membrane over the shallow cavity forming an absolute pressure sensor, and on the same base wafer, an open deep cavity, with and a second membrane over the deep cavity forming a relative second pressure sensor, wherein the edge of the first membrane respectively second membrane is determined by the shallow cavity respectively the open deep cavity forming the sensors. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18)
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18. A flow meter according to claim 17, wherein the first membrane of the absolute pressure sensor is in the first part of the cavity.
Specification