MEMS device with reduced dynamic stress and methods
A structure for a MEMS device includes a MEMS layer comprising a mass portion and a spring portion, a substrate coupled to the MEMS layer, wherein the substrate comprises a planar region and an stopper region, wherein the MEMS device and the substrate are oriented in a plurality of relative orientations in response to an external force, wherein the spring portion and the stopper region are configured to disengagingly impact when the external force exceeds a first threshold force, wherein the mass portion and the planar region are configured to disengagingly impact when the external force exceeds a second threshold force, and wherein the second threshold force exceeds the first threshold force.
1. A structure for a MEMS device comprising:
a MEMS layer comprising a mass portion and a spring portion;
a substrate coupled to the MEMS layer, wherein the substrate is vertically disposed relative to the MEMS layer, wherein the substrate comprises a planar region and a stopper region;
wherein the MEMS layer is configured to be displaced relative to the substrate in an in-plane direction that is parallel to the substrate and configured to be displaced relative to the substrate in an out-of-plane direction that is towards and away from the substrate;
wherein the MEMS device and the substrate are oriented in a plurality of relative orientations in response to an external force in the out-of-plane direction;
wherein the spring portion and the stopper region are configured to contact when the external force in the out-of-plane direction exceeds a first threshold force;
wherein the spring portion is configured to provide a disengaging force in the out-of-plane direction against the stopper region;
wherein the mass portion and the planar region are configured to contact when the external force in the out-of-plane direction exceeds a second threshold force;
wherein the second threshold force exceeds the first threshold force.
2. The structure of claim 1 wherein the spring portion is selected from a group consisting of: a torsion spring, a leaf spring.
3. The structure of claim 1
wherein the substrate comprises an insulating layer and a metal layer overlying the insulating layer; and
wherein the stopper region comprises a pillar-like structure formed within the metal layer extending down to the insulating layer, and a bumper region overlying the pillar-like structure.
4. The structure of claim 1 wherein the spring portion and the stopper region are configured to impact in response to the external force in the out-of-plane direction exceeding the second threshold before the mass portion and the planar region impact in response to the external force in the out-of-plane direction exceeding the second threshold force.
5. The structure of claim 1 wherein the MEMS device is selected from a group consisting of: an accelerometer and a gyroscope.
6. The structure of claim 1 wherein the second threshold force exceeds 30G.
7. The structure of claim 1 :
wherein the MEMS layer, comprise a lateral spring portion, and an anchor portion, wherein the MEMS layer is coupled to the substrate by the anchor portion; and
wherein the MEMS layer is configured to be displaced relative to the substrate in an in-plane direction that is parallel to the substrate;
wherein the MEMS device and the anchor portion are oriented in a plurality of relative orientations in response to an external force in the in-plane direction;
wherein the mass portion and the lateral spring portion are configured to contact when the external force in the in-plane directions exceeds a third threshold force;
wherein the lateral spring portion is configured to provide a disengaging force in the in-plane direction against the mass portion;
wherein the mass portion and the anchor portion are configured to contact when the external force in the in-plane directions exceeds a fourth threshold force; and
wherein the fourth threshold force exceeds the third threshold force.
8. The structure of claim 7 wherein the spring portion and the mass portion are configured to impact in response to the external force in the in-plane direction exceeding the fourth threshold before the mass portion and the anchor portion impact in response to the external force in the in-plane direction exceeding the fourth threshold force.
9. The structure of claim 7 wherein the MEMS device is selected from a group consisting of: an accelerometer and a gyroscope.
10. The structure of claim 7 wherein the first threshold force is within a range of 10G to 30G.
11. A method for a MEMS device including a MEMS layer having a mass portion and a spring portion, and a substrate having a planar region and a stopper region, the method comprising:
subjecting the MEMS device to a first external force in an out-of-plane direction towards the planar region, whereby the spring portion and the stopper region impact in response to the first external force in the out-of-plane direction, wherein the mass portion and the planar region do not impact in response to the first external force in the out-of-plane direction, wherein the first external force in the out-of-plane directions exceeds a first threshold force;
subjecting the MEMS device to a second external force in the out-of-plane direction towards the planar region, whereby the spring portion and the stopper region impact and the mass portion and the planar region impact in response to the second external force in the out-of-plane direction, wherein the second external force in the out-of-plane direction exceeds a second threshold force, and wherein the second threshold force exceeds the first threshold force; and subsequently
separating the mass portion and the planar region apart in response to a separation force associated with the spring portion and the stopper region impacting.
12. The method of claim 11 wherein the MEMS device includes a torsion portion, and
wherein the separating the spring portion and the stopper region apart comprises having the torsion portion separate the spring portion and the stopper region.
13. The method of claim 11 wherein the subjecting the MEMS device to the second external force in the out-of-plane direction comprises: reducing a force of the mass portion and the planar region impacting in response to the separation force associated with the spring portion and the stopper region impacting.
14. The method of claim 11 further comprising determining force data from the MEMS device in response to the first external force.
15. The method of claim 11 wherein the MEMS device is selected from a group consisting of: an accelerometer and a gyroscope.
16. The method of claim 11 wherein the second threshold force exceeds 30G.
17. The method of claim 11 wherein the first threshold is within a range of 10G to 30G.
18. The method of claim 11
wherein the MEMS layer comprises a lateral spring portion and an anchor portion, wherein the anchor portion is coupled to the planar region;
the method further comprising:
subjecting the MEMS device to a third external force in an in-plane direction parallel to the planar region, whereby the mass portion and the lateral spring portion impact in response to the third external force in the in-plane direction, wherein the mass portion and the anchor portion region do not impact in response to the third external force in the in-plane direction, wherein the third external force in the in-plane directions exceeds a third threshold force;
subjecting the MEMS device to a fourth external force in the in-plane direction parallel to the planar region, whereby the mass portion and the lateral spring portion impact in response to the fourth external force in the in-plane direction, wherein the mass portion and the anchor portion region impact in response to the fourth external force in the in-plane direction, wherein the fourth external force in the in-plane directions exceeds a fourth threshold force;
and subsequently
separating the mass portion and the anchor portion apart in response to a separation force associated with the mass portion and the lateral spring portion impacting.
19. The method of claim 18 wherein a perturbation to the MEMS device comprises the first external force in the in-plane direction and the third external force in the out-of-plane direction.
20. The method of claim 11 wherein the subjecting the MEMS device to the first external force in the out-of-plane direction towards the planar region, further comprises: dissipating an impact between the spring portion and the stopper region from the stopper region to an underlying substrate layer via one or more pillars, while bypassing an intervening metal layer.