Wafer level hermetically sealed mems device

Abstract

A hermetically sealed microelectromechanical system (MEMS) package includes a MEMS switch having a movable portion and a stationary portion with an electrical contact thereon. A glass lid is anodically bonded to the MEMS switch to form a sealed cavity over the movable portion of the MEMS switch. The glass lid includes a contact aperture to allow access to the electrical contact on the stationary portion of the MEMS switch. A family of body-implantable hermetically-sealed MEMS packages are provided according to certain aspects and embodiments of the present invention.

1 . A method of forming a MEMS package comprising:
 fabricating a MEMS switching device having a movable portion and a stationary portion;   forming switch metallization on at least the movable portion of the MEMS switching device and contact metallization on the stationary portion of the MEMS switching device; and   anodically bonding a glass lid to the MEMS switching device to form a sealed cavity over the movable portion of the MEMS switching device, the glass lid including a contact aperture to allow access to the contact metallization on the stationary portion of the MEMS switching device.   
     
     
         2 . A method according to  claim 1 , wherein forming switch metallization and contact metallization comprises:
 attaching a masking structure to the MEMS switching device, the masking structure having a plurality of through holes;   depositing the contact metallization and the switch metallization through the through holes on the MEMS switching device; and   detaching the masking structure from the MEMS switching device.   
     
     
         3 . A method according to  claim 2 , wherein the masking structure includes a silicon shadow mask. 
     
     
         4 . A method according to  claim 2 , wherein the through holes includes potassium-hydroxide etched in the silicon shadow mask. 
     
     
         5 . A method according to  claim 2 , wherein the masking structure includes wax for attachment and is detached from the MEMS switching device by heating the wax. 
     
     
         6 . A method according to  claim 1 , wherein anodically bonding the glass lid to the MEMS switching device is performed at an anodic bonding voltage that is less than 100 Volts greater than an actuation voltage of the MEMS switching device. 
     
     
         7 . A method according to  claim 13 , wherein the actuation voltage of the MEMS switching device is about 150 Volts and the anodic bonding voltage is about 230 Volts. 
     
     
         8 . A method according to  claim 1 , wherein anodically bonding the glass lid to the MEMS switching device is performed at an anodic bonding temperature that does not affect electrical contacting qualities of the contact metallization and the switch metallization. 
     
     
         9 . A method according to  claim 8 , wherein the contact metallization and the switch metallization is composed of titanium-ruthenium. 
     
     
         10 . A method according to  claim 7 , wherein the anodic bonding temperature is about 365° C. 
     
     
         11 . A method according to  claim 1 , wherein the glass lid is composed of a material having a thermal coefficient of expansion (TCE) that is similar to a TCE of the MEMS switching device. 
     
     
         12 . A method according to  claim 10 , wherein the glass lid includes Pyrex. 
     
     
         13 . A method of forming a MEMS package comprising:
 fabricating a MEMS switching device having a movable portion and a stationary portion;   forming switch metallization on at least the movable portion of the MEMS switching device and contact metallization on the stationary portion of the MEMS switching device; and   anodically bonding a glass lid to the MEMS switching device to form a sealed cavity over the movable portion of the MEMS switching device, the glass lid including a contact aperture to allow access to the contact metallization on the stationary portion of the MEMS switching device,   wherein forming switch metallization and contact metallization comprises:
 attaching a masking structure to the MEMS switching device, the masking structure having a plurality of through holes; 
 depositing the contact metallization and the switch metallization through the through holes on the MEMS switching device; and 
 detaching the masking structure from the MEMS switching device. 
   
     
     
         14 . A method of forming a MEMS package comprising:
 fabricating a MEMS switching device having a movable portion and a stationary portion;   forming switch metallization on at least the movable portion of the MEMS switching device and contact metallization on the stationary portion of the MEMS switching device; and   anodically bonding a glass lid to the MEMS switching device to form a sealed cavity over the movable portion of the MEMS switching device, the glass lid including a contact aperture aligned directly over the electrical contact to allow access to the contact metallization on the stationary portion of the MEMS switching device.   
     
     
         15 . A method of forming a MEMS package comprising:
 fabricating a MEMS switching device having a movable portion and a stationary portion;   depositing selectively switch metallization on at least the movable portion of the MEMS switching device and contact metallization on the stationary portion of the MEMS switching device; and   anodically bonding a glass lid to the MEMS switching device to form a sealed cavity over the movable portion of the MEMS switching device, the glass lid including a contact aperture aligned directly over the electrical contact to allow access to the contact metallization on the stationary portion of the MEMS switching device.