Electrode layer partitioning
A MEMS sensor includes a proof mass that is suspended over a substrate. A sense electrode is located on a top surface of the substrate parallel to the proof mass, and forms a capacitor with the proof mass. The sense electrodes have a plurality of slots that provide improved performance for the MEMS sensor. A measured value sensed by the MEMS sensor is determined based on the movement of the proof mass relative to the slotted sense electrode.
1. A system for providing for capacitive sensing of an external force on a microelectromechanical system (MEMS) device, the system comprising:
a substrate located in a first plane;
a movable component of a MEMS device layer, the MEMS device layer coupled to the substrate, wherein the movable component moves along a first axis in response to the external force; and
a sense electrode disposed on the substrate in the first plane, wherein a first capacitive sensing element is formed between the movable component and the first sense electrode, wherein the first capacitive sensing element is configured to be responsive to the motion of the movable component along the first axis,
wherein the sense electrode comprises a plurality of slots that substantially extend between two non-adjacent sides of the sense electrode, and wherein the plurality of slots comprise at least 8% of the surface area of the sense electrode and less than 20% of the surface area of the sense electrode.
2. The system of claim 1 , wherein the plurality of slots substantially extend between two parallel sides of the sense electrode.
3. The system of claim 2 , wherein the two parallel sides comprise two long sides of the sense electrode.
4. The system of claim 2 , wherein the two parallel sides comprise two short sides of the sense electrode.
5. The system of claim 1 , wherein the plurality of slots comprises a comb pattern.
6. The system of claim 1 , wherein the plurality of slots comprise a partial hexagonal pattern.
7. The system of claim 1 , wherein at least a portion of each of the plurality of slots is located parallel to another of the plurality of slots.
8. The system of claim 1 , wherein the first axis is perpendicular to the first plane.
9. The system of claim 1 , further comprising:
a second movable component of the MEMS device layer, wherein the second movable component moves along a second axis in response to the external force; and
a second sense electrode disposed on the substrate in the first plane, wherein a second capacitive sensing element is formed between the second movable component and the second sense electrode, wherein the second capacitive sensing element is configured to be responsive to the motion of the second movable component along the second axis, and wherein the second sense electrode comprises a second plurality of slots that substantially extend between two non-adjacent sides of the second sense electrode.
10. The system of claim 9 , further comprising a center point located in the first plane between the sense electrode and the second sense electrode, wherein the plurality of slots and the second plurality of slots are symmetrical about a line that passes through the center point in the first plane.
11. The system of claim 9 , further comprising a processing unit coupled to the first sense electrode and the second sense electrode to determine a value of an external force based on a combined measurement of the first capacitive sensing element and the second capacitive sensing element.
12. The system of claim 1 , wherein the plurality of slots comprises multiple angled slots.
13. The system of claim 12 , wherein three of the angled slots intersect at 120 degree angles.
14. The system of claim 1 , wherein the sense electrode comprises a folded strip electrode.
15. The system of claim 14 , wherein the length of the folded strip electrode is longer than the length of the perimeter of the sense electrode.
16. The system of claim 14 , wherein the folded strip electrode substantially forms a square wave pattern, a spiral pattern, a T-slot pattern, a Y-slot pattern, or a recessed slot pattern.
17. The system of claim 1 , further comprising:
a second sense electrode disposed on the substrate in the first plane, wherein a second capacitive sensing element is formed between one or more components of the MEMS device layer and the second sense electrode; and
processing circuitry coupled to the sense electrode and the second sense electrode to receive a first signal from the sense electrode and a second signal from the second sense electrode, the processing circuitry configured to combine the first signal and the second signal to output a signal responsive to movement of at least a portion of the MEMS device layer along the first axis.