MEMS-based dual and single proof-mass accelerometer methods and apparatus
An integrated MEMS inertial sensor device includes one or more three-axis MEMS inertial sensor devices, such as accelerometers, with dual or single proof mass configurations. These designs can be compact and can decouple the motion of each axis to minimize the measurement errors due to cross-axis sensitivity. Some embodiments include a frame to decouple the motion of two axes and to provide geometric symmetry. Some embodiments also include double-folded springs. In a specific embodiment, the three axes of an integrated MEMS accelerometer device are entirely decoupled. Thus, the actuation of each axis, through a force due to acceleration, has little or substantially no effect on the other axes.
1. An integrated MEMS (Micro-Electro-Mechanical-Systems) inertial sensor device, the device comprising:
a substrate member having a surface region;
a first proof mass overlying the surface region;
a first frame overlying the surface region;
at least one frame spring physically coupled to the first frame and the first proof mass;
at least one first anchor physically coupled to the surface region;
at least one first spring physically coupled to the first frame and the first anchor, the first spring including a doubly-folded spring;
wherein the first proof mass is physically coupled to the first frame via the first spring, the first frame being physically coupled to the first anchor via the first spring;
a second proof mass overlying the surface region, the second proof mass having a center cavity, wherein the first proof mass is spatially disposed within the center cavity;
at least one second anchor physically coupled to the surface region; and
at least one second spring physically coupled to the second proof mass and the second anchor.
2. The device of claim 1 wherein the first frame is configured surrounding the perimeter of the first proof mass.
3. The device of claim 1 wherein the at least one frame spring comprises a doubly-folded spring, a singled folded spring, or a single beam spring.
4. The device of claim 1 wherein the first and second springs are configured with an “H”, an “I”, or a cross shaped arrangement.
5. The device of claim 1 wherein the second spring comprises a doubly-folded spring, a singled folded spring, or a single beam.
6. The device of claim 1 wherein the first proof mass, the first frame, the first anchor, and the first and frame springs are configured in a geometrically symmetric or anti-symmetric arrangement.
7. The device of claim 1 wherein the first and frame springs are configured in a rectangular arrangement within a vicinity of the perimeter of the first proof mass.
8. The device of claim 1 further comprising at least one electrode structure coupled to the surface region.
9. The device of claim 8 further comprising an IC layer overlying the surface region, the IC layer being electrically coupled to the electrode structure.
10. The device of claim 8 wherein the electrode structure comprises a differential electrode pair.
11. The device of claim 8 wherein the electrode structure is configured symmetrically or anti-symmetrically on the surface region.
12. The device of claim 11 wherein the first proof mass comprises a plurality of electrode cavities, the electrode structure comprising a plurality of differential electrode pairs, each of the plurality of differential electrode pairs being configured within one of the plurality of electrode cavities.
13. An integrated MEMS (Micro-Electro-Mechanical-Systems) inertial sensor device, the device comprising:
a substrate having a surface region;
an IC layer overlying the surface region;
a first proof mass overlying the surface region, the first proof mass having a plurality of electrode cavities;
a second proof mass overlying the surface region, the second proof mass having a center cavity, wherein the first proof mass is configured within the center cavity;
a frame overlying the surface region, the frame being configured within the center cavity, wherein the first proof mass is configured within the frame;
at least two doubly-folded springs physically coupled to the first proof mass and the frame;
at least two first anchors physically coupled to the surface region, the first anchors being configured within the center cavity;
at least two doubly-folded springs physically coupled to the first anchors and the frame;
at least two second anchors physically coupled to the surface region, the second anchors being configured within the center cavity;
at least two springs physically coupled to the second anchors and the second proof mass; and
a plurality of electrode structures coupled to the surface region, each of the plurality of electrode structures being configured within one of the plurality of electrode cavities, the plurality of electrode structures being electrically coupled to the IC layer.
14. The device of claim 13
wherein the second proof mass comprises a teeter totter proof mass overlying the surface region.
15. The device of claim 13 wherein the plurality of electrode structures comprises four groups of differential electrode pairs, two of the groups configured to be parallel to the x-axis, two of the groups configured to be parallel to the y-axis, each of the differential electrode pairs being configured within one of the plurality of electrode cavities in an anti-symmetrical arrangement.