Integrated electroacoustic transducer
First Claim
1. An electroacoustic transducer formed within a semiconductor substrate comprisingan essentially nontensioned diaphragm comprising a semiconductor material having a mechanical bending moment stiffness such that it vibrates in response to an input signal at audio and/or ultrasonic frequencies;
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Accused Products
Abstract
An electroacoustic transducer, primarily in the form of a capacitive microphone, for incorporation into a semiconductor substrate. The vibrating element comprises a largely nontensioned diaphragm, such as an epitaxial layer formed on the semiconductor substrate, so as to greatly reduce its mechanical stiffness. The substrate is etched away in the desired area to define the diaphragm and form an acoustic cavity. A continuous array of microscopic holes is formed in the backplate to cut down the lateral flow of air in the gap between capacitor electrodes. Narrow gaps made possible by the hole array allow low voltage diaphragm biasing. In at least one embodiment, the acoustic input can be provided through the air hole array. An acoustic port may be added to alter the frequency response of the device, and a back closure provided to act as a rear acoustic cavity and an EMI shield.
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Citations
26 Claims
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1. An electroacoustic transducer formed within a semiconductor substrate comprising
an essentially nontensioned diaphragm comprising a semiconductor material having a mechanical bending moment stiffness such that it vibrates in response to an input signal at audio and/or ultrasonic frequencies; - and
a pair of electrodes placed with respect to said diaphragm so that the electric field between the electrodes varies in relationship with the vibrating diaphragm to permit conversion between electrical and acoustic signals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 16)
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11. An electroacoustic transducer formed within a semiconductor substrate comprising:
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a diaphragm which vibrates in response to an input signal at audio and/or ultrasonic frequencies; a pair of electrodes placed with respect to said diaphragm so that the electric field between the electrodes varies in relation to the vibrating diaphragm to permit conversion between electrical and acoustic signals, the electrodes defining an air gap therebetween; and acoustic venting means comprising a continuous array of small holes extending through one of the electrodes to the air gap, said array covering essentially the entire area of that electrode which is co-extensive with the diaphragm, where the density of the holes in the array is at least 50 per mm2 and the diameter of the holes is less than 100 μ
m. - View Dependent Claims (12, 13, 14, 15, 17, 18, 19, 20, 21)
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22. An electroacoustic transducer formed within a semiconductor substrate comprising:
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a diaphragm which vibrates in response to an input signal at audio and/or ultrasonic frequencies; a front acoustic cavity defined by a portion of the semiconductor substrate adjacent to the diaphragm; a pair of electrodes placed with respect to said diaphragm so that the electric field between the electrodes varies in relation with the vibrating diaphragm to permit conversion between electrical and acoustic signals and so that an air gap is formed between the electrodes; a back acoustic cavity adjacent to one of the electrodes and defined by a member which also shields the transducer from electromagnetic interference; acoustic venting means comprising an array of holes connecting the air gap to the back acoustic cavity; and an acoustic port defined by an element adjacent to the front acoustic cavity, the size of the port being such as to produce a desired frequency response characteristic for the transducer. - View Dependent Claims (23, 24, 25, 26)
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Specification