Micro-fluid ejection device and method for assembling a micro-fluid ejection device by wafer-to-wafer bonding

Abstract

A micro-fluid ejection device is assembled by wafer-to-wafer bonding at a temperature below about 150° C. a first silicon oxide layer of a first wafer, having flow features patterned in the first silicon oxide layer on an actuator chip in a first silicon substrate of the first wafer, to a second silicon oxide layer of a second wafer, defining a nozzle plate on a second silicon substrate of the second wafer. Nozzle holes are formed in the nozzle plate in alignment with actuator elements of the actuator chip of the first wafer either before or after bonding the first and second wafers together. The second silicon substrate of the second wafer is used as a handle and then removed from the silicon oxide layer of the second wafer after bonding the first and second wafers together.

1 . A micro-fluid ejection device, comprising:
 an actuator chip in a first wafer adjacent a front surface of a first silicon substrate thereof also having a back surface opposite said front surface, at least one fluid supply passage in said first silicon substrate between said front and back surfaces and at least one actuator element on said front surface;   a flow feature patterned in a first silicon oxide layer on said front surface of said first silicon substrate so as to define at least one ejection chamber overlying said actuator element of said actuator chip and in flow communication with said fluid supply passage; and   a nozzle plate in a second wafer defined by a second silicon oxide layer thereof attached by a wafer-to-wafer bond formed at a temperature below about 150° C. to said flow features of said first silicon oxide layer of said first wafer at an interface of said first and second silicon oxide layers with one another, said nozzle plate having at least one nozzle hole substantially in alignment with said actuator element of said actuator chip and defined through said nozzle plate from an interior surface contiguous with said ejection chamber to an exterior surface thereof.   
   
   
       2 . The device of  claim 1  wherein said exterior surface of said nozzle plate is formed by removal of a second silicon substrate from said second silicon oxide layer of said second wafer. 
   
   
       3 . The device of  claim 1  wherein said exterior surface of said nozzle plate is formed by grinding away said second silicon substrate from said second silicon oxide layer and polishing said exterior surface. 
   
   
       4 . The device of  claim 1  wherein said exterior surface of said nozzle plate is formed by dry etching away said second silicon substrate from said second silicon oxide layer. 
   
   
       5 . The device of  claim 1  wherein said bond is a fusion bond. 
   
   
       6 . A method for assembling a micro-fluid ejection device, comprising:
 wafer-to-wafer bonding at a temperature below about 150° C. an actuator chip-and-flow features silicon oxide layer-bearing first wafer with a nozzle plate silicon oxide layer-bearing second wafer at a silicon oxide layer-to-silicon oxide layer interface between the first and second wafers.   
   
   
       7 . The method of  claim 6  further comprising:
 removing a silicon substrate handle from the silicon oxide layer of the second wafer after bonding the first and second wafers together.   
   
   
       8 . The method of  claim 7  further comprising:
 forming nozzle holes in the nozzle plate defined by the silicon oxide layer of the second wafer after said bonding of the first and second wafers together and after said removing of said silicon substrate handle.   
   
   
       9 . The method of  claim 8  wherein said forming nozzle holes in the nozzle plate includes:
 optically aligning the nozzle plate with actuator elements of the actuator chip through the silicon oxide layer of the second wafer forming the nozzle plate which is transparent; and   patterning and etching the nozzle holes into the nozzle plate optically aligned with the actuator elements of the actuator chip.   
   
   
       10 . The method of  claim 6  further comprising:
 forming nozzle holes in the nozzle plate defined by the silicon oxide layer of the second wafer before bonding the first and second wafers together.   
   
   
       11 . A method for assembling a micro-fluid ejection device, comprising:
 positioning separate first and second wafers together such that the wafers meet at an interface between respective first and second silicon oxide layers on corresponding first and second silicon substrates of the respective first and second wafers; and   wafer-to-wafer bonding the first and second wafers together at the interface at a temperature below 150° C. such that flow features patterned in the first silicon oxide layer on an actuator chip in the first silicon substrate of the first waver are bonded to a nozzle plate defined by the second silicon oxide layer on the second silicon substrate of the second wafer.   
   
   
       12 . The method of  claim 11  further comprising:
 removing the second silicon substrate from the second silicon oxide layer of the second wafer after said bonding of the first and second wafers together.   
   
   
       13 . The method of  claim 12  wherein said removing includes grinding away the second silicon substrate from the second silicon oxide layer. 
   
   
       14 . The method of  claim 12 , wherein said removing includes dry etching away the second silicon substrate from the second silicon oxide layer. 
   
   
       15 . The method of  claim 12  further comprising:
 prior to said removing the second silicon substrate, using the second silicon substrate as a handle to facilitate said positioning of the second wafer relative to the first wafer.   
   
   
       16 . The method of  claim 12  further comprising:
 forming nozzle holes in the nozzle plate after said wafer-to-wafer bonding of the first and second wafers and after said removing of the second silicon substrate from the second silicon oxide layer of the second wafer.   
   
   
       17 . The method of  claim 16  wherein said forming nozzle holes in the nozzle plate includes optically aligning the nozzle plate with the actuator elements of the actuator chip through the second silicon oxide layer forming the nozzle plate which is transparent. 
   
   
       18 . The method of  claim 17  wherein said forming nozzles in the nozzle plate further includes patterning and etching the nozzle holes into the nozzle plate optically aligned with the actuator elements of the actuator chip. 
   
   
       19 . The method of  claim 11  further comprising:
 forming nozzle holes in the nozzle plate before said wafer-to-wafer bonding of the first and second wafers together.   
   
   
       20 . The method of  claim 19  wherein said forming nozzle holes includes infrared aligning the nozzle plate with fiducials on the actuator chip and then patterning and etching the nozzle holes into the nozzle plate.