Patent ID: 7318349

Claim:
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 and part 2 of the frame at least partially is located within the projection of the proof mass element.