Seal for surface acoustic wave devices

Abstract

One embodiment disclosed relates to a method for sealing an active area of a surface acoustic wave (SAW) device on a wafer. The method includes providing a sacrificial material over at least the active area of the SAW device, depositing a seal coating over the wafer so that the seal coating covers the sacrificial material, and replacing the sacrificial material with a target atmosphere. Another embodiment disclosed relates to an SAW device sealed at the wafer level (i.e. prior to separation of the die from the wafer). The device includes an active area to be protected, an electrical contact area, and a lithographically-formed structure sealing at least the active area and leaving at least a portion of the electrical contact area exposed.

1 - 16  (canceled)  
     
     
         17 . A surface acoustic wave (SAW) device sealed at the wafer level, the device comprising: 
 an active area to be protected;    an electrical contact area; and    a lithographically-formed structure sealing at least the active area and leaving at least a portion of the electrical contact area exposed.    
     
     
         18 . The device of  claim 17 , wherein the lithographically-formed structure comprises a glassy material.  
     
     
         19 . The device of  claim 17 , wherein the SAW device is fabricated on a substrate from a group of substrates consisting of lithium tantalate, lithium niobate, and quartz.  
     
     
         20 . A lithographically-fabricated surface acoustic wave (SAW) device, the SAW device comprising: 
 means for carrying a surface acoustic wave; and    a wafer-level means for sealing the means for carrying the surface acoustic wave.    
     
     
         21 . The SAW device of  claim 20 , wherein the means for carrying the surface acoustic wave comprises a transducer structure.  
     
     
         22 . The SAW device of  claim 21 , wherein the transducer structure comprises aluminum pattered into interdigitated electrode fingers.  
     
     
         23 . The SAW device of  claim 20 , wherein the wafer-level means for sealing comprises a lithographically-formed structure sealing at least the means for carrying.  
     
     
         24 . The SAW device of  claim 23 , further comprising electrical contact areas coupled to the means for carrying, and wherein the wafer-level means for sealing leaves exposed at least a portion of the electrical contact areas.  
     
     
         25 . The device of  claim 17 , wherein the lithographically-formed structure comprises a material of a thickness so as to be impermeable to undesired contaminants.  
     
     
         26 . The device of  claim 17 , wherein the lithographically-formed structure comprises silicon dioxide.  
     
     
         27 . The device of  claim 17 , wherein the lithographically-formed structure comprises silicon nitride.  
     
     
         28 . The device of  claim 17 , wherein the lithographically-formed structure comprises a metal.  
     
     
         29 . The device of  claim 18 , wherein the glassy material comprises a spin-on-glass.  
     
     
         30 . The device of  claim 18 , wherein the glassy material comprises a sputtered glass.  
     
     
         31 . The device of  claim 17 , wherein the SAW device is fabricated on a lithium tantalate substrate.  
     
     
         32 . The device of  claim 17 , wherein the SAW device is fabricated on a lithium niobate substrate.  
     
     
         33 . The device of  claim 17 , wherein the SAW device is fabricated on a quartz substrate.