Method for providing a MEMS device with a plurality of sealed enclosures having uneven standoff structures and MEMS device thereof
A method for forming a MEMS device includes coupling a MEMS substrate and a base substrate. The MEMS substrate and the base substrate contain at least two enclosures. One enclosures has a first vertical gap between the bonding surface of the MEMS substrate and the bonding surface of the base substrate that is less than a second vertical gap between the bonding surface of the MEMS substrate and the bonding surface of the base substrate than another of the enclosures to provide a height difference between the first vertical gap and the second vertical gap. The method includes bonding the bonding surfaces of the one of the two enclosures at a first pressure to provide a first sealed enclosure. The method includes bonding the bonding surfaces of other of the two enclosures at a second pressure to provide a second sealed enclosure.
1. A method comprising:
coupling a microelectromechanical system (MEMS) substrate and a base substrate, wherein the MEMS substrate and the base substrate contain at least two enclosures, wherein one of the at least two enclosures has a first vertical gap between the bonding surface of the MEMS substrate and the bonding surface of the base substrate that is less than a second vertical gap between the bonding surface of the MEMS substrate and the bonding surface of the base substrate to provide a height difference between the first vertical gap and the second vertical gap, wherein the MEMS substrate include first and second sets of standoffs with bonding surfaces on the first and second sets of standoffs, wherein the first and second sets of standoffs are etched from a same level of a same device layer, and wherein a first length of the first set of standoffs is greater than a second length of the second set of standoffs to result in the height difference between the first vertical gap and the second vertical gap;
bonding the bonding surfaces of the one of the two enclosures to provide a first sealed enclosure at a first pressure; and
bonding the bonding surfaces of the another of the two enclosures to provide a second sealed enclosure at a second pressure.
2. The method of claim 1 , wherein the base substrate includes first and second sets of bonding pads, wherein the first set of bonding pads and the first set of standoffs define the one of the at least two enclosures and the second set of bonding pads and the second set of standoffs define the another of the two enclosures.
3. The method of claim 2 , wherein the height of the first set of bonding pads is greater than the height of the second set of bonding pads to provide the height difference.
4. The method of claim 1 , wherein the bonding surfaces of the MEMS substrate and the base substrate comprises any of copper, gold, tin, tantalum, lead, tungsten, aluminum, or germanium.
5. The method of claim 1 , wherein the first pressure bonding step and the second pressure bonding step comprise providing eutectic bonds.
6. The method of claim 1 , wherein the first pressure is less than the second pressure.
7. The method of claim 1 , wherein the first pressure is greater than the second pressure.
8. The method of claim 1 , wherein there is at least one MEMS structure inside the first and second sealed enclosures.
9. The method of claim 8 , wherein the at least one MEMS structure includes any of a gyroscope, an accelerometers, a magnetometer, a pressure sensor, a microphones or a radio-frequency component.
10. The method of claim 1 , wherein the first pressure bonding step and the second pressure bonding step provides a hermetic seal.
11. The method of claim 1 , wherein the first pressure bonding step and the second pressure bonding step comprise providing an electrical connection between the MEMS substrate and the base substrate.
12. The method of claim 1 , wherein the base substrate comprises a silicon substrate.
13. The method of claim 1 , wherein the base substrate comprises electrical circuits.
14. A MEMS device, comprising:
a MEMS substrate coupled to a base substrate, wherein the MEMS substrate and the base substrate form and contain at least two enclosures, wherein each of the at least two enclosures contains a movable MEMS structure, wherein each of the at least two enclosures is defined by a continuous standoff structure, wherein one of the at least two enclosures has a first standoff structure that is shorter than a second standoff structure than another of the at least two enclosures, wherein the first standoff structure and the second standoff structure protrude from a same level of a same device layer, wherein the one of the at least two enclosures has a first pressure and the another of the at least two enclosures enclosure has a second pressure.
15. The MEMS device of claim 14 , wherein the standoff structure and the movable MEMS structure are composed of the same material.
16. The MEMS device of claim 15 , wherein the material comprises silicon.
17. The MEMS device of claim 14 , wherein the base substrate comprises one or more electrical circuits.
18. The MEMS device of claim 14 , wherein the standoff structure is composed of aluminum.