US-12617670-B2 - MEMS bump stopper surface features

US12617670B2US 12617670 B2US12617670 B2US 12617670B2US-12617670-B2

Abstract

A microelectromechanical system (MEMS) sensor assembly comprises a substrate, a bump stopper extending from the substrate, and a sensor suspended relative to the substrate. The sensor is configured to move relative to the substrate, wherein the bump stopper is configured to restrain the sensor travel distance and prevent contact between the sensor and the substrate. The bump stopper has a surface facing the sensor, wherein an area of contact between the sensor and the surface is less than the total area of the surface.

Inventors

Ken Deng
Bing Yu
Michael Pedersen
Nicholas Palcheck
Jeremy Johnson
Richard Li-Chen Chen

Assignees

KNOWLES ELECTRONICS, LLC

Dates

Publication Date: 20260505
Application Date: 20221222

Claims (9)

1 . A microelectromechanical system (MEMS) sensor assembly, comprising: a substrate; a bump stopper extending from the substrate; and a sensor suspended relative to the substrate, the sensor configured to move relative to the substrate, wherein the bump stopper is configured to restrain the sensor travel distance and prevent contact between the sensor and the substrate, the bump stopper having a surface facing the sensor; wherein an area of contact between the sensor and the surface is less than the total area of the surface; wherein the surface includes a region of recess and one or more regions that protrude toward the sensor relative to the rest of the surface; and wherein said region of recess is curved.
2 . The MEMS sensor assembly of claim 1 , wherein said region of recess is convex.
3 . The MEMS sensor assembly of claim 1 , wherein said region of recess is concave.
4 . The MEMS sensor assembly of claim 1 , wherein the one or more regions have a protrusion distance in a range between about 10 nm and about 400 nm.
5 . A microelectromechanical system (MEMS) sensor assembly, comprising: a substrate; a sensor suspended relative to the substrate, the sensor configured to move relative to the substrate; and a bump stopper extending from the substrate at a first end of the bump stopper, the bump stopper having a surface facing the sensor on a second end distal from the substrate, wherein the bump stopper is configured to restrain the sensor travel distance and prevent contact between the sensor and the substrate; wherein an area of contact area between the sensor and the surface is less than the total area of the surface; and wherein the surface includes a region of recess surrounded by one or more regions that protrude toward the sensor relative to the rest of the surface; and wherein said region of recess is one of concave and convex.
6 . The MEMS sensor assembly of claim 5 , wherein the one or more regions have a protrusion distance in a range between about 10 nm and about 400 nm.
7 . The MEMS sensor assembly of claim 5 , wherein the bump stopper has a plan view shape selected from the group of shapes consisting of an oval, an ellipse, a rectangle, a rectangle having rounded corners, and combinations thereof.
8 . The MEMS sensor assembly of claim 7 , wherein the one or more regions have a plan view shape selected from the group of shapes consisting of an oval, an ellipse, a rectangle, a rectangle having rounded corners, and combinations thereof.
9 . A microelectromechanical system (MEMS) sensor assembly, comprising: a substrate; a sensor suspended relative to the substrate, the sensor configured to move relative to the substrate; and a bump stopper extending from the substrate at a first end of the bump stopper, the bump stopper having a surface facing the sensor on a second end distal from the substrate, wherein the bump stopper is configured to restrain the sensor travel distance and prevent contact between the sensor and the substrate; wherein an area of contact area between the sensor and the surface is less than the total area of the surface; wherein the surface includes a region of recess surrounded by one or more regions that protrude toward the sensor relative to the rest of the surface; and wherein said region of recess is a non-flat surface and said one or more regions that protrude are planar surfaces.

Description

FIELD OF THE DISCLOSURE The present disclosure relates to microelectromechanical systems (MEMS) bump stoppers, and more particularly to MEMS bump stoppers having features that reduce contact surface area resulting in a reduced stiction force upon contact. BACKGROUND Bump stoppers are an effective way to prevent damage to MEMS devices under high dynamic loads. However, stiction upon contact between the bump stoppers and contacted components can be problematic as a major failure mode in MEMS devices. Because the force of stiction between surfaces is proportional to contact area, reducing the cross-sectional size of the bump stoppers can effectively lower the stiction force. However, a smaller sized bump stopper results in a smaller bonding area between the bump stopper and a substrate, which can compromise the bonding strength of the bump stoppers, making them vulnerable to failures including debonding, breakage, and sinking into the substrate underneath. DRAWINGS The foregoing and other features of the present disclosure will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. These drawings depict only several embodiments in accordance with the disclosure and are, therefore, not to be considered limiting of its scope. FIG. 1 illustrates a schematic cross-sectional view of an exemplary MEMS sensor assembly according to an embodiment. FIG. 2 is an exemplary bump stopper according to an embodiment. FIG. 3 is an exemplary bump stopper according to another embodiment. FIG. 4 is an exemplary bump stopper according to a further embodiment. FIG. 5 is an exemplary bump stopper according to yet another embodiment. FIG. 6 is an exemplary bump stopper according to a still further embodiment. FIG. 7 is an exemplary bump stopper according to still another embodiment. FIG. 8 is a schematic cross sectional view of an exemplary bump stopper according to an embodiment. FIG. 9 is a schematic cross sectional view of an exemplary bump stopper according to another embodiment. FIG. 10 is a schematic cross sectional view of an exemplary bump stopper according to a further embodiment. FIG. 11 is perspective view of the exemplary bump stopper illustrated in FIG. 9. FIG. 12 is perspective view of the exemplary bump stopper illustrated in FIG. 10. FIG. 13 is a schematic cross sectional view of an exemplary bump stopper according to yet another embodiment. FIG. 14 is a schematic cross sectional view of an exemplary bump stopper according to yet a further embodiment. FIG. 15 is perspective view of the exemplary bump stopper illustrated in FIG. 13. FIG. 16 is perspective view of the exemplary bump stopper illustrated in FIG. 14. FIG. 17 is a schematic cross sectional view of an exemplary bump stopper according to yet a further embodiment. FIG. 18 is perspective view of the exemplary bump stopper illustrated in FIG. 17. DETAILED DESCRIPTION According to an embodiment, a MEMS sensor assembly comprises a substrate, a bump stopper extending from the substrate, and a sensor suspended relative to the substrate. The sensor is configured to move relative to the substrate, wherein the bump stopper is configured to restrain the sensor travel distance and prevent contact between the sensor and the substrate. The bump stopper has a surface facing the sensor, wherein an area of contact between the sensor and the surface is less than the total area of the surface. In an embodiment the surface is convex. In an embodiment the surface is concave. In an embodiment the surface includes one or more regions that protrude toward the sensor relative to the rest of the surface. In an embodiment the one or more regions have a protrusion distance in a range between about 10 nm and about 400 nm. According to some embodiments the bump stopper has a plan view shape selected from the group of shapes consisting of an oval, an ellipse, a rectangle, a rectangle having rounded corners, and combinations thereof. According to some embodiments the one or more regions have a plan view shape selected from the group of shapes consisting of an oval, an ellipse, a rectangle, a rectangle having rounded corners, and combinations thereof. In an embodiment, a process for manufacturing a bump stop for a MEMS sensor comprises the steps of providing a substrate having a surface, depositing a first material onto a first portion of the surface, depositing a second material onto the first material and the rest of the surface, polishing the first and second materials to create a planar surface on the first material and one or more recesses in the second material relative to the planar surface, and depositing bump stop material over regions of the planar surface and the one or more recesses. In an embodiment the bump stop material is deposited onto a first region of the planar surface and a second region of a recess at least partially surrounded by the first region. In an embodiment the first region entirely sur