Micromechanical sensor with a guard band electrode and fabrication technique therefor
First Claim
1. A method of fabricating a micromechanical sensor comprising the steps of:
- providing a silicon substrate with a P+ epitaxial layer doped with boron to a concentration greater than approximately 1020 thereover;
selectively etching said silicon substrate so as to define a proof mass in said silicon substrate wherein said epitaxial layer provides an etch stop;
depositing a sense electrode responsive to an excitation signal on a glass substrate; and
bonding said epitaxial layer to said glass substrate to provide said sensor.
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Accused Products
Abstract
An electrostatically actuated micromechanical sensor having a guard band electrode for reducing the effect of transients associated with a dielectric substrate of the sensor. A proof mass, responsive to an input, is suspended over the substrate and one or more electrodes are disposed on the substrate in electrostatic communication with the proof mass to sense the input acceleration and/or to torque the proof mass back to a null position. A guard band electrode is disposed over the dielectric substrate in overlapping relationship with the electrodes and maintains the surface of the substrate at a reference potential, thereby shielding the proof mass from transients and enhancing the accuracy of the sensor. A dissolved wafer process for fabricating the micromechanical sensor is described in which the proof mass is defined by a boron doping step. An alternative fabrication technique is also described in which the proof mass is defined by an epitaxial layer.
176 Citations
9 Claims
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1. A method of fabricating a micromechanical sensor comprising the steps of:
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providing a silicon substrate with a P+ epitaxial layer doped with boron to a concentration greater than approximately 1020 thereover; selectively etching said silicon substrate so as to define a proof mass in said silicon substrate wherein said epitaxial layer provides an etch stop; depositing a sense electrode responsive to an excitation signal on a glass substrate; and bonding said epitaxial layer to said glass substrate to provide said sensor. - View Dependent Claims (2, 3, 4)
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5. A method of fabricating a micromechanical sensor comprising the steps of:
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providing a silicon substrate with an epitaxial layer thereover in which a proof mass of said sensor is formed; depositing a sense electrode responsive to an excitation signal on a glass substrate; bonding said epitaxial layer to said glass substrate to provide said sensor; and depositing a guard band electrode on said glass substrate in overlapping relationship with said sense electrode. - View Dependent Claims (6)
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7. A micromechanical sensor device comprising:
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a dielectric substrate having a surface; a proof mass comprising an epitaxial layer suspended over said surface of said dielectric substrate, said proof mass being responsive to an input stimulus and forming a first capacitor plate; a first electrode disposed over said surface of said dielectric substrate for coupling an excitation signal to said proof mass and forming a second capacitor plate; a second electrode for sensing out-of-plane deflection of said proof mass; an insulating layer disposed over said surface of said dielectric substrate in overlapping relationship with a portion of said first electrode and said second electrode; and a guard band electrode disposed over said insulating layer so as to overlap said portion of said first electrode and said portion of said second electrode, said guard band electrode receiving a reference potential for shielding said proof mass from spurious charge on said surface of the dielectric substrate. - View Dependent Claims (8, 9)
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Specification