Surface micromachined differential microphone
First Claim
1. A method of forming a miniature, surface micromachined, differential microphone, the steps comprising:
- a) depositing a sacrificial layer on a top surface of a silicon wafer;
b) depositing a diaphragm material on an upper surface of said sacrificial layer;
c) etching said diaphragm material layer to isolate a diaphragm therein; and
d) removing at least a portion of said sacrificial layer from a region beneath said defined diaphragm, further comprising at least one of;
forming comb sense fingers along at least a portion of a perimeter of said diaphragm as a sub-step of etching step (c); and
forming a conductive layer intermediate said top surface of said silicon wafer and said sacrificial layer.
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Accused Products
Abstract
A method of forming a miniature, surface micromachined, differential microphone, comprising depositing a sacrificial layer on a surface of a silicon wafer; depositing a diaphragm material on a surface of the sacrificial layer; etching the diaphragm material layer to isolate a diaphragm; and removing a portion of the sacrificial layer beneath the defined diaphragm. A diaphragm formed in the diaphragm material layer is supported by a hinge and otherwise isolated from a remaining portion of the diaphragm material layer by a slit adjacent a perimeter of the diaphragm. An enclosed back volume beneath the diaphragm has a depth defined by a thickness of the sacrificial layer, and communicates with an external region via the slit. A transducer may be provided for producing an electrical signal responsive to a displacement of the diaphragm.
19 Citations
20 Claims
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1. A method of forming a miniature, surface micromachined, differential microphone, the steps comprising:
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a) depositing a sacrificial layer on a top surface of a silicon wafer; b) depositing a diaphragm material on an upper surface of said sacrificial layer; c) etching said diaphragm material layer to isolate a diaphragm therein; and d) removing at least a portion of said sacrificial layer from a region beneath said defined diaphragm, further comprising at least one of; forming comb sense fingers along at least a portion of a perimeter of said diaphragm as a sub-step of etching step (c); and forming a conductive layer intermediate said top surface of said silicon wafer and said sacrificial layer. - View Dependent Claims (2, 3, 4, 5)
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6. A miniature, surface micromachined, differential microphone, comprising:
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a) a silicon substrate; b) a sacrificial layer deposited upon an upper surface of said silicon substrate; c) a diaphragm material layer deposited on an upper surface of said sacrificial layer; d) a diaphragm and supporting hinge formed from said diaphragm material layer, said diaphragm being isolated from a surrounding portion of said diaphragm material layer except at said hinge by a slit formed in the diaphragm material layer adjacent a perimeter of said diaphragm; e) an enclosed back volume beneath said diaphragm having a depth defined by a thickness of said sacrificial layer, said back volume communicating with a region external thereto only via said slit; and at least one of;
a plurality of comb sense fingers disposed along at least a portion of a perimeter of said diaphragm, and a conductive layer intermediate said upper surface of said silicon substrate and said upper surface of said sacrificial layer. - View Dependent Claims (7, 8, 9, 10)
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11. In a miniature, surface micromachined, differential microphone, comprising a diaphragm having a perimeter and a plurality of comb sense fingers disposed along at least a portion of the perimeter formed from a diaphragm material layer and a supporting hinge formed from the diaphragm material layer, and an enclosed back volume beneath said diaphragm and having a side surface and a bottom surface and having a hole in one of said side and said bottom surfaces allowing communication between the back volume and a region external thereto, the improvement comprising:
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a) a slit disposed between the perimeter of said diaphragm and a surrounding portion of said diaphragm material layer from which said diaphragm is isolated; and b) the enclosed back volume beneath said diaphragm and having the side surface and the bottom surface, each of the side and said bottom surfaces being isolated from a region external to the enclosed back volume except via said slit.
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12. A microphone, comprising:
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a substrate, having deposited on a surface thereof a sacrificial layer, and a diaphragm layer disposed on top of said sacrificial layer, an aperture being formed through said diaphragm layer, and at least a portion of said sacrificial layer beneath the diaphragm layer being removed, resulting in a diaphragm with a void between said diaphragm layer and said substrate, wherein said diaphragm has an axis of rotational movement in response to acoustic waves which is substantially parallel to a plane of said diaphragm; a transducer for producing an electrical signal responsive to a displacement of said diaphragm with respect to said substrate due to acoustic waves, comprising at least one of;
a plurality of comb sense fingers disposed along at least a portion of a perimeter of said diaphragm, and a conductive layer intermediate said substrate and said sacrificial layer. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20)
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Specification