Static pressure compensation of resonant integrated microbeam sensors
First Claim
1. A sensing device including:
- a silicon substrate having a substantially rigid first region comprising a rim and a second region compressing a diaphragm surrounded by the rim and more flexible than the rim, the diaphragm flexing in response to variations in a first parameter;
an elongate primary vibratory element having opposite first and second end portions fixed with respect to the substrate to position the primary vibratory element along the second region, for lengthwise extension and contraction of the primary vibratory element responsive to the flexing of the second region, said extension and contraction varying a primary natural resonant frequency of the primary vibratory element, said primary vibratory element comprising an elongate polysilicon beam located at and perpendicular to an edge of the diaphragm;
an elongate secondary vibratory element fixed with respect to the substrate, said secondary vibratory element having a secondary natural resonant frequency variable in response to changes in a second parameter, while substantially unaffected by variations in the first parameter; and
a means for sensing the primary and secondary resonant frequencies and for generating an output representing the primary parameter compensated for the effect of the secondary parameter, based on said primary and secondary natural resonant frequencies.
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Accused Products
Abstract
A temperature and static pressure compensated differential pressure sensor includes a semiconductor substrate in which a flexible, pressure responsive diaphragm is formed. A pressure responsive resonant microbeam is fabricated at the diaphragm periphery. For temperature compensation, a secondary resonant microbeam sensor is fabricated on the substrate at a peripheral location beyond the point of substrate attachment to a pressure tube or other support. For static pressure compensation, another secondary resonant microbeam can be positioned remote from the diaphragm and at a location of maximum substrate response to static pressure. A further resonant microbeam can be mounted at the diaphragm center to augment the signal due to diaphragm deflections. Also disclosed is an accelerometer including a proof mass, a rigid rim surrounding the proof mass, and a series of narrow, flexible bridges supporting the proof mass relative to the rim. The bridges flex responsive to accelerations, thus to allow the proof mass to move relative to the rim. At least one of the bridges incorporates a resonant microbeam for measuring acceleration by virtue of the induced strain from flexure of its associated bridge. For temperature compensation, a secondary resonant microbeam is fabricated along the rim.
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Citations
25 Claims
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1. A sensing device including:
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a silicon substrate having a substantially rigid first region comprising a rim and a second region compressing a diaphragm surrounded by the rim and more flexible than the rim, the diaphragm flexing in response to variations in a first parameter; an elongate primary vibratory element having opposite first and second end portions fixed with respect to the substrate to position the primary vibratory element along the second region, for lengthwise extension and contraction of the primary vibratory element responsive to the flexing of the second region, said extension and contraction varying a primary natural resonant frequency of the primary vibratory element, said primary vibratory element comprising an elongate polysilicon beam located at and perpendicular to an edge of the diaphragm; an elongate secondary vibratory element fixed with respect to the substrate, said secondary vibratory element having a secondary natural resonant frequency variable in response to changes in a second parameter, while substantially unaffected by variations in the first parameter; and a means for sensing the primary and secondary resonant frequencies and for generating an output representing the primary parameter compensated for the effect of the secondary parameter, based on said primary and secondary natural resonant frequencies. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A sensing device including:
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a semiconductor substrate including a flexible region that undergoes flexing in response to variations in a first parameter, and a rigid region adjacent to the flexible region and not flexing in response to said variations in the first parameter; an elongate primary vibratory element formed of a semiconductor material and having opposite first and second end portions fixed to said flexible region of the substrate for lengthwise extension and contraction of the primary vibratory element responsive to the flexing of the flexible region, said extension and contraction varying a primary natural resonant frequency at which the primary vibratory element tends to oscillate, said primary natural resonant frequency further varying with changes in a second variable condition; an elongate secondary vibratory element formed of a semiconductor material and having opposite first and second end portions fixed to said rigid region of the substrate for lengthwise extension and contraction of the secondary vibratory element responsive to variations in the second parameter, said extension and contraction varying a secondary natural resonant frequency at which the secondary vibratory element tends to oscillate; a primary resonant frequency sensing means for sensing the primary natural resonant frequency and generating a primary frequency signal based on the primary resonant frequency; a secondary frequency sensing means for sensing the secondary natural resonant frequency and for generating a secondary frequency signal based on the secondary resonant frequency; a means for receiving the primary and secondary frequency signals and for generating an output representing the first variable condition compensated for the effect of the second variable condition, based on said frequency signals. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A sensing device including:
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A semiconductor substrate having a flexible region that undergoes flexing in response to changes in a first variable condition, and a rigid region adjacent the flexible region that does not flex in response to the changes in the first variable condition; an elongate primary vibratory element formed of a semiconductor material and having first and second opposite ends fixed to the flexible region of the substrate for lengthwise extension and contraction of the primary vibratory element responsive to the flexing of the flexible region and responsive to changes in a second variable condition; an elongate secondary vibratory element formed of a semiconductor material and having opposite first and second end portions fixed to the rigid region of the substrate for lengthwise extension and contraction of the secondary vibratory element responsive to said changes in the second variable condition; wherein the primary vibratory element and the secondary vibratory element have respective primary and secondary natural resonant frequencies that vary with the lengthwise extension and contraction of the primary and secondary vibratory elements, respectively; and a means for sensing the primary and secondary natural resonant frequencies and for generating an output representing the first variable condition compensated for the effect of the second variable condition, based on said primary and secondary natural resonant frequencies. - View Dependent Claims (22, 23, 24, 25)
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Specification