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Three-axis integrated MEMS accelerometer

  • US 7,318,349 B2
  • Filed: 06/04/2005
  • Issued: 01/15/2008
  • Est. Priority Date: 06/04/2005
  • Status: Expired due to Fees
First Claim
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1. A three-axis accelerometer for determining components of an inertial force vector with respect to an orthogonal coordinate system, the accelerometer comprising:

  • a sensor die having side 1 and opposite side 2, die made of a semiconductor substrate consisting of layer 1 and layer 2 of semiconductor materials attached to each other and having a at least one cavity at the interface between the layer 1 and layer 2, cavity made within the thickness of at least one of the layers 1 or 2;

    the cavity has overall dimensions and has a projection on the plane of side 1 of the sensor die;

    the sensor die comprising;

    a frame element consisting of part 1 having thickness and part 2 having uniform thickness smaller than thickness of part 1;

    part 2 is located within the projection of the cavity, surrounded by part 1 in the plane of side 1 and occupies an area on the side 1 of the sensor die;

    a proof mass element located within the semiconductor substrate, having overall dimensions, having a projection on the plane of side 1 of the sensor die and occupying an area on the side 1 of the sensor die;

    an elastic element having overall dimensions and occupying an area on the side 1 of the sensor die;

    elastic element mechanically couples the frame element and the proof mass element on side 1, wherein an inertial force applied to the proof mass element induces stress in the elastic element;

    mechanical-stress sensitive IC components located on elastic element and providing signals for determining components of applied inertial force;

    at least one digital signal processing circuit coupled to accelerometer for processing signals from stress-sensitive IC components;

    at least one cap having thickness and mechanically coupled to the frame element from at least the side 2 of the sensor die,whereby for the purpose of minimizing the area occupied by both proof mass element and elastic element on the side 1 of the sensor die without decreasing the sensor sensitivity;

    the area occupying by both proof mass element and elastic element on the side 1 of the sensor die is made smaller than the area occupying by part 2 of the frame on the side 1 of the sensor die;

    at least one digital signal processing circuit is integrated within part 2 of the sensor die frame;

    the overall dimensions of the cavity in the plane of side 1 of the sensor die exceed the corresponding overall dimensions of the elastic element and the elastic element is located within the projection of the cavity;

    at least two overall dimensions of the proof mass element exceed the corresponding overall dimensions of the elastic element andpart 2 of the frame at least partially is located within the projection of the proof mass element.

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