Anti-Getter: Expandable Polymer Microspheres for MEMS Devices
AssigneeRobert Bosch GmbH
InventorsAshwin K. Samarao, Gary O'Brien, Ando Feyh
Life of this patent
Estimating the term…
Abstract
A method of fabricating a MEMS device includes depositing an expandable material into a first recess of a cap wafer. The cap wafer includes a plurality of walls that surround and define the first recess and a second recess. The cap wafer is bonded to a MEMS wafer including a first MEMS device and a second MEMS device. The first MEMS device is encapsulated in the first recess, and the second MEMS device is encapsulated in the second recess. The expandable material is then heated to at least an activation temperature to cause the expandable material to expand after the first recess has been sealed. The expansion of the expandable material causes a reduction in volume of the first recess.
Claims19
A method of fabricating a microelectromechanical system (MEMS) device, comprising:
- depositing an expandable material into a first recess of a cap wafer, the cap wafer including a plurality of walls that surround and define the first recess and a second recess, the expandable material not being deposited into the second recess, the plurality of walls including at least one dividing wall that separates the first recess from the second recess, the expandable material having an activation temperature at which the expandable material expands;
- pressing the cap wafer onto a MEMS wafer, the MEMS wafer including a first MEMS device and a second MEMS device which are integrated into the same MEMS wafer, the plurality of walls of the cap wafer being pressed against the MEMS wafer such that the first MEMS device is encapsulated in the first recess and the second MEMS device is encapsulated in the second recess, the first recess having a first pressure level and the second recess having a second pressure level, the first and second pressure levels being substantially equal when the cap wafer is pressed onto the MEMS wafer;
- and
- heating the cap wafer and the MEMS wafer with the cap wafer pressed onto the MEMS wafer to a bonding temperature, the bonding temperature causing the plurality of walls of the cap wafer to bond to MEMS wafer such that a first volume is sealed within the first recess and a second volume is sealed within the second recess, the bonding temperature being greater than the activation temperature such that the expandable material expands within the first recess after the first volume is sealed within the first recess.
A method of fabricating a microelectromechanical system (MEMS) device, comprising:
- depositing an expandable material into a first recess of a cap wafer, the cap wafer including a plurality of walls that surround and define the first recess and a second recess, the expandable material not being deposited into the second recess, the plurality of walls including at least one dividing wall that separates the first recess from the second recess, the expandable material having an activation temperature at which the expandable material expands;
- bonding the cap wafer onto a MEMS wafer, the MEMS wafer including a first MEMS device and a second MEMS device which are integrated into the same MEMS wafer, the plurality of walls of the cap wafer being bonded to the MEMS wafer such that the first MEMS device is encapsulated in the first recess and the second MEMS device is encapsulated in the second recess, the bonding resulting in a first volume being sealed within the first recess and a second volume being sealed within the second recess, the first volume being sealed at a first pressure level and the second volume being sealed at a second pressure level;
- and
- heating the expandable material to the activation temperature such that the expandable material expands within the first recess.
A microelectromechanical system (MEMS) device comprising:
- a MEMS wafer including a first MEMS device and a second MEMS device;
- a cap wafer bonded to the MEMS wafer, the cap wafer including a first recess that encapsulates the first MEMS device and a second recess that encapsulates the second MEMS device, a first volume being sealed in the first recess and a second volume being sealed in the second recess;
- and
- expanded polymer microspheres sealed within in the first recess, the polymer microspheres having been heated to an activation temperature to cause expansion of the polymer microspheres.
Dependencies are inferred from the claim text.