Microbolometer contact systems and methods

Abstract

Systems and methods are directed to contacts for an infrared detector. For example, an infrared imaging device includes a substrate having a first metal layer and an infrared detector array coupled to the substrate via a plurality of contacts. Each contact includes for an embodiment a second metal layer formed on the first metal layer; a third metal layer formed on the second metal layer, wherein the third metal layer at least partially fills an inner portion of the contact; and a first passivation layer formed on the third metal layer.

What is claimed as new and desired to be protected is: 
     
         1 . An infrared imaging device comprising:
 a substrate having a first metal layer;   an infrared detector array coupled to the substrate via a plurality of contacts, wherein each contact comprises:   a second metal layer formed on the first metal layer;   a third metal layer formed on the second metal layer, wherein the third metal layer at least partially fills an inner portion of the contact; and   a first passivation layer formed on the third metal layer.   
     
     
         2 . The infrared imaging device of  claim 1 , wherein a readout integrated circuit is formed within the substrate. 
     
     
         3 . The infrared imaging device of  claim 1 , wherein the infrared detector array comprises a plurality of microbolometers, and wherein the second metal layer forms part of a leg metal layer to couple with a corresponding leg of the microbolometer. 
     
     
         4 . The infrared imaging device of  claim 1 , wherein the contact further comprises a second passivation layer formed on the second metal layer on a side opposite of where the third metal layer is formed, wherein the second passivation layer is disposed at a top portion of the contact distant from the first metal layer. 
     
     
         5 . The infrared imaging device of  claim 4 , wherein the first passivation layer is made of silicon dioxide, and wherein the second passivation layer is made of silicon nitride. 
     
     
         6 . The infrared imaging device of  claim 1 , wherein the second metal layer is formed directly on the first metal layer. 
     
     
         7 . The infrared imaging device of  claim 1 , wherein the infrared detector array comprises a plurality of microbolometers, and wherein each microbolometer comprises a resistive material forming a bridge. 
     
     
         8 . The infrared imaging device of  claim 7 , wherein each microbolometer comprises further comprises legs coupling the resistive material to the second metal layer, wherein the first metal layer forms part of a readout integrated circuit within the substrate 
     
     
         9 . The infrared imaging device of  claim 1 , wherein the third metal layer completely fills the inner portion of the contact. 
     
     
         10 . A method of forming a contact on a substrate for an infrared detector array, the method comprising:
 applying a polyimide coating on the substrate;   applying a passivation layer on the polyimide coating;   applying a photoresist pattern on the passivation layer;   etching to expose a first metal layer on the substrate;   depositing a second metal layer on the first metal layer;   applying a photoresist pattern on the second metal layer; and   depositing a third metal layer on the second metal layer to at least partially fill an inner portion of the contact.   
     
     
         11 . The method of  claim 10 , wherein the depositing the third metal layer on the second metal layer to at least partially fill the inner portion of the contact comprises depositing the third metal layer on the second metal layer to completely fill the inner portion of the contact. 
     
     
         12 . The method of  claim 10 , further comprising:
 applying a first passivation layer on the third metal layer and a portion of the second metal layer; and   etching to release and provide the contact.   
     
     
         13 . The method of  claim 12 , wherein the depositing the third metal layer on the second metal layer to at least partially fill the inner portion of the contact comprises depositing the third metal layer on the second metal layer to completely fill the inner portion of the contact. 
     
     
         14 . The method of  claim 10 , further comprising applying a photoresist pattern to the substrate. 
     
     
         15 . The method of  claim 14 , further comprising depositing the first metal layer on the substrate, wherein the first metal layer is coupled to a readout integrated circuit formed within the substrate. 
     
     
         16 . The method of  claim 15 , wherein the passivation layer is disposed at a top portion of the contact distant from the first metal layer. 
     
     
         17 . The method of  claim 10 , further comprising applying a photoresist pattern on the passivation layer before depositing the second metal layer. 
     
     
         18 . The method of  claim 15 , wherein the depositing the third metal layer comprises lifting-off a portion of the third metal layer and removing the photoresist. 
     
     
         19 . The method of  claim 16 , wherein the etching to release comprises:
 applying a photoresist pattern over the third metal layer;   performing ion milling; and   removing the photoresist pattern remaining.   
     
     
         20 . The method of  claim 15 , wherein the infrared detector array comprises a plurality of microbolometers, and wherein the second metal layer forms part of a leg metal layer to couple with a corresponding leg of the microbolometer.