All-silicon monolithic motion sensor with integrated conditioning circuit
First Claim
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1. A method for forming a monolithic motion sensor, the method comprising the steps of:
- providing a first semiconductor wafer characterized by a first electrical conductivity type;
forming a doped region of a second electrical conductivity type in a surface of the first semiconductor wafer;
selectively etching a trench in the doped region so as to form a micromachined motion sensing element therein;
forming conditioning circuitry for the micromachined motion sensing element on a second semiconductor wafer;
etching a recess in a surface of the second semiconductor wafer;
bonding the second semiconductor wafer to the first semiconductor wafer such that the recess encases the trench and forms an enclosure for the micromachined motion sensing element, and such that a portion of the second semiconductor wafer is disposed above bond pads on the surface of the first semiconductor wafer; and
removing the portion of the second semiconductor wafer so as to expose the bond pads on the surface of the first semiconductor wafer.
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Abstract
A motion sensor including a sensing wafer with a bulk micromachined sensing element, and a capping wafer on which is formed the conditioning circuitry for the sensor. The sensing and capping wafers are configured such that, when bonded together, the capping wafer encloses the sensing element to form a monolithic sensor. The capping wafer is further configured to expose bond pads on the sensing wafer, and to enable singulation of the two-wafer stack into individual dies. Wire bonds can be made to both wafers, such that the sensor can be packaged in essentially any way desired.
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Citations
30 Claims
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1. A method for forming a monolithic motion sensor, the method comprising the steps of:
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providing a first semiconductor wafer characterized by a first electrical conductivity type; forming a doped region of a second electrical conductivity type in a surface of the first semiconductor wafer; selectively etching a trench in the doped region so as to form a micromachined motion sensing element therein; forming conditioning circuitry for the micromachined motion sensing element on a second semiconductor wafer; etching a recess in a surface of the second semiconductor wafer; bonding the second semiconductor wafer to the first semiconductor wafer such that the recess encases the trench and forms an enclosure for the micromachined motion sensing element, and such that a portion of the second semiconductor wafer is disposed above bond pads on the surface of the first semiconductor wafer; and removing the portion of the second semiconductor wafer so as to expose the bond pads on the surface of the first semiconductor wafer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method for forming a monolithic motion sensor, the method comprising the steps of:
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providing an oxide region located below a surface of a first semiconductor wafer characterized by a first electrical conductivity type; forming a doped region of a second electrical conductivity type in the first semiconductor wafer, the doped region extending from the surface to the oxide region; selectively etching a trench in the doped region, the trench extending from the surface to the oxide region so as to yield a structural feature within the trench, such that the structural feature is formed by a portion of the doped region and is contiguous with the oxide region; selectively etching the oxide region so as to free the structural feature and thereby yield a micromachined motion sensing element; forming conditioning circuitry for the micromachined motion sensing element on a second semiconductor wafer; etching a recess in a surface of the second semiconductor wafer; bonding the second semiconductor wafer to the first semiconductor wafer such that the recess encases the trench and forms an enclosure for the micromachined motion sensing element, and such that a portion of the second semiconductor wafer is disposed above bond pads on the surface of the first semiconductor wafer; and removing the portion of the second semiconductor wafer so as to expose the bond pads on the surface of the first semiconductor wafer. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. A method for forming a monolithic motion sensor, the method comprising the steps of:
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providing a recess in a surface of a first semiconductor wafer characterized by a first electrical conductivity type; doping a wall of the recess to have a second electrical conductivity type; bonding a second semiconductor wafer to the first semiconductor wafer such that the recess is encased by the second semiconductor wafer and the first and second semiconductor wafers form a monolithic sensing wafer; forming a doped region of the second electrical conductivity type in the second semiconductor wafer, the doped region extending through the second semiconductor wafer to the wall of the recess such that the wall forms a buried interconnect; selectively etching a trench in the doped region, the trench extending through the second semiconductor wafer to the recess so as to yield a micromachined motion sensing element within the trench and above the buried interconnect; forming conditioning circuitry for the micromachined motion sensing element on a third semiconductor wafer; etching a recess in a surface of the third semiconductor wafer; bonding the third semiconductor wafer to the monolithic sensing wafer such that the recess encases the trench and forms an enclosure for the micromachined motion sensing element, and such that a portion of the third semiconductor wafer is disposed above bond pads on the surface of the monolithic sensing wafer; and removing the portion of the third semiconductor wafer so as to expose the bond pads on the surface of the monolithic sensing wafer. - View Dependent Claims (25, 26, 27, 28, 29, 30)
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Specification