MEMS membrane overtravel stop
A micro electrical mechanical system (MEMS) device in one embodiment includes a substrate defining a back cavity, a membrane above the back cavity, a back plate above the membrane, and a first overtravel stop (OTS) positioned at least partially directly beneath the membrane and supported by the back plate.
1. A micro electrical mechanical system (MEMS) device comprising:
a substrate defining a back cavity;
a membrane including a first surface and an opposite second surface and located above the back cavity;
a back plate counter electrode formed in a back plate layer and located in opposition to the membrane first surface, the back plate supported directly or indirectly by the substrate; and
a first overtravel stop (OTS) located at least partially in opposition to the membrane second surface and at least partially overlapping a released movable portion of the membrane and supported directly or indirectly by the back plate layer.
2. The MEMS device of claim 1 further comprising a socket layer, wherein:
the socket layer is above the substrate;
the membrane is above the socket layer; and
the back plate is above the membrane.
3. The MEMS device of claim 1 further comprising a socket layer, wherein:
the back plate is above the substrate;
the membrane is above the back plate; and
the socket layer is above the membrane.
4. The MEMS device of claim 1 , further comprising:
a spring supporting the membrane; and
an electrically isolating back plate anchor extending downwardly from the back plate and supporting the spring, wherein the first OTS is supported by the back plate.
5. The MEMS device of claim 4 , wherein the first OTS comprises:
a first OTS anchor operatively supported by the spring; and
a first ring portion directly supported by the first OTS anchor and spaced apart from a second ring portion which is directly supported by a second OTS anchor of a second OTS.
6. The MEMS device of claim 4 , wherein the first OTS comprises:
a first ring portion;
a second ring portion encircled by the first ring portion; and
a plurality of struts extending between the first ring portion and the second ring portion.
7. The MEMS device of claim 4 , further comprising:
an oxide portion located between the spring and the first OTS, the oxide portion electrically isolating the first OTS from the spring; and
a feeder portion extending above the substrate and in electrical communication with the first OTS, at least a portion of the feeder portion at a same level as the membrane.
8. The MEMS device of claim 4 , further comprising:
a second OTS positioned inwardly from the first OTS, the second OTS supported by the back plate through a downwardly extending support post.
9. The MEMS device of claim 8 , wherein the downwardly extending support post is integrally formed with the back plate.
10. The MEMS device of claim 9 , further comprising:
an oxide portion located between the support post and the second OTS.
11. The MEMS device of claim 4 , further comprising:
an anti-stiction bump extending downwardly from the back plate;
an electrically isolated portion of the membrane positioned in opposition to the anti-stiction bump;
a bridge portion located below the isolated portion of the membrane and supported by the membrane; and
an oxide portion located between the isolated portion of the membrane and the bridge portion and electrically isolating the isolated portion of the membrane from the bridge portion.