THREE-AXIS INERTIAL SENSOR AND METHOD OF FORMING
First Claim
1. A process of fabricating a three-axis inertial sensor comprising a z-axis sensing device, an x-axis sensing device, and a y-axis sensing device, the process comprising:
- providing a silicon-on-oxide (SOI) wafer comprising a first conductive layer separated from a second conductive layer by an insulative buried oxide (BOX) layer;
fabricating the SOI wafer to partially define in the first conductive layer thereof at least a portion of a proof mass for the z-axis sensing device, at least a portion of a proof mass for the x-axis sensing device, and at least a portion of a proof mass for the y-axis sensing device;
depositing a conductive deposited layer on the SOI wafer and over the first conductive layer;
patterning the deposited layer to define at least one suspension spring for the proof mass of the z-axis sensing device;
bonding the SOI wafer to a substrate so that the first conductive layer of the SOI wafer faces the substrate;
etching the second conductive layer of the SOI wafer to form a fixed electrode of the z-axis sensing device; and
then etching portions of the BOX layer to fully release the proof masses and define a capacitive gap between the fixed electrode and the proof mass of the z-axis sensing device.
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Abstract
A three-axis inertial sensor and a process for its fabrication using an silicon-on-oxide (SOI) wafer as a starting material. The SOI wafer has a first conductive layer separated from a second conductive layer by an insulative buried oxide (BOX) layer. The SOI wafer is fabricated to partially define in its first conductive layer at least portions of proof masses for z, x, and y-axis sensing devices of the sensor. After a conductive deposited layer is deposited and patterned to form a suspension spring for the proof mass of the z-axis sensing device, the SOI wafer is bonded to a substrate that preferably carries interface circuitry for the z, x, and y-axis devices, with the SOI wafer being oriented so that its first conductive layer faces the substrate. Portions of the BOX layer are then etched to fully release the proof masses.
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Citations
24 Claims
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1. A process of fabricating a three-axis inertial sensor comprising a z-axis sensing device, an x-axis sensing device, and a y-axis sensing device, the process comprising:
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providing a silicon-on-oxide (SOI) wafer comprising a first conductive layer separated from a second conductive layer by an insulative buried oxide (BOX) layer;
fabricating the SOI wafer to partially define in the first conductive layer thereof at least a portion of a proof mass for the z-axis sensing device, at least a portion of a proof mass for the x-axis sensing device, and at least a portion of a proof mass for the y-axis sensing device;
depositing a conductive deposited layer on the SOI wafer and over the first conductive layer;
patterning the deposited layer to define at least one suspension spring for the proof mass of the z-axis sensing device;
bonding the SOI wafer to a substrate so that the first conductive layer of the SOI wafer faces the substrate;
etching the second conductive layer of the SOI wafer to form a fixed electrode of the z-axis sensing device; and
thenetching portions of the BOX layer to fully release the proof masses and define a capacitive gap between the fixed electrode and the proof mass of the z-axis sensing device. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A three-axis inertial sensor having a z-axis sensing device with a proof mass associated therewith, an x-axis sensing device with a proof mass associated therewith, and a y-axis sensing device with a proof mass associated therewith, the sensor comprising:
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a silicon-on-oxide (SOI) wafer comprising a first conductive layer separated from a second conductive layer by an insulative buried oxide (BOX) layer;
at least portions of the proof masses for the z-axis, x-axis, and y-axis sensing devices being at least partially defined in the first conductive layer of the SOI wafer;
at least one suspension spring for the proof mass of the z-axis sensing device patterned in a conductive deposited layer on the SOI wafer;
a fixed electrode of the z-axis sensing device defined by a portion of the second conductive layer of the SOI wafer;
a capacitive gap between the fixed electrode and the proof mass of the z-axis sensing device resulting from removal of a portion of the BOX layer; and
a substrate bonded to the SOI wafer, the first conductive layer of the SOI wafer facing the substrate. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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Specification