Semiconductor with Bottom-Side Wrap-Around Flange Contact

Abstract

A packaging technique for electronic devices includes wafer fabrication of flexible contacts on the bottom surface of the substrate underneath the active circuit. Inherently reliable contacts suitable for a variety of devices can be formed via a simple fabrication process with good wafer packing density. For one embodiment, a trench is formed from the back of the substrate, exposing an upper conductive layer on the top surface. A standoff is formed on the bottom surface of the substrate. A lower conductive layer is formed that runs from and electrically connects with the exposed portion of the upper conductive layer onto the substrate standoff. The standoff is removed, releasing the formed conductors, resulting in a flexible contact.

1 . A method of fabricating a contact for an electronic device, comprising:
 thinning the bottom surface of a substrate, the substrate having an electronic circuit that includes an electrical connection point on the top surface of the substrate, the thinning to expose a portion of the bottom surface of the electrical connection point;   forming a standoff below the bottom surface of the substrate;   forming a lower conductive layer that runs from the standoff and runs to and electrically couples with the exposed portion of the electrical connection point; and   removing at least a portion of the standoff to create a flexible conductor.   
     
     
         2 . The method of  claim 1 , wherein the electrical connection point comprises one of the following: gold, silver, nickel, titanium, aluminum, tungsten, copper, platinum, or a combination thereof. 
     
     
         3 . The method of  claim 1 , wherein the standoff is between 25 and 200 microns in height. 
     
     
         4 . The method of  claim 1 , further comprising:
 depositing an insulating layer on the bottom surface of the substrate prior to forming the standoff, wherein the electrical connection point remains exposed.   
     
     
         5 . The method of  claim 4 , further comprising:
 removing a portion of the insulating layer between the substrate and the conductive layer to create the flexible conductor.   
     
     
         6 . The method of  claim 1 , further comprising:
 forming an encapsulant layer above the top surface of the substrate.   
     
     
         7 . The method of  claim 1 , wherein the lower conductive layer comprises one of the following: gold, silver, nickel, titanium, aluminum, tungsten, copper, platinum, or a combination thereof. 
     
     
         8 . The method of  claim 1 , further comprising:
 depositing a second insulating layer on the bottom surface of the substrate after removing at least a portion of the standoff, wherein a lower portion of the flexible conductor remains exposed.   
     
     
         9 . The method of  claim 1 , wherein the lower conductive layer comprises a bottom layer to accept solder and a top layer to reject solder. 
     
     
         10 . The method of  claim 1 , wherein a barrier metal layer is deposited, prior to the conductive layer, on at least a portion of the area to be covered by the conductive layer. 
     
     
         11 . The method of  claim 1 , further comprising:
 coupling the flexible conductor with a printed circuit board using one or more of the following: solder, ultrasonic bonding, conductive epoxy, or plated conductors.   
     
     
         12 . A method of fabricating a contact for an electronic device, comprising:
 forming an upper conductive layer above the top surface of a substrate, the substrate having an electronic circuit that includes an electrical connection point, the upper conductive layer having an inner portion connected to the electrical connection point and an outer portion extending beyond the edge of the electronic circuit;   thinning the bottom surface of a substrate to expose a portion of the bottom surface of the upper conductive layer;   forming a standoff below the bottom surface of the substrate;   forming a lower conductive layer that runs from the standoff and runs to and electrically couples with the exposed portion of the upper conductive layer; and   removing at least a portion of the standoff to create a flexible conductor.   
     
     
         13 . The method of  claim 12 , wherein the electrical connection point comprises one of the following: gold, silver, nickel, titanium, aluminum, tungsten, copper, platinum, or a combination thereof. 
     
     
         14 . The method of  claim 12 , wherein the upper conductive layer comprises one of the following: gold, silver, nickel, titanium, aluminum, tungsten, copper, platinum, or a combination thereof. 
     
     
         15 . The method of  claim 12 , wherein the standoff is between 25 and 200 microns in height. 
     
     
         16 . The method of  claim 12 , further comprising:
 depositing an insulating layer on the bottom surface of the substrate prior to forming the standoff, wherein the upper conductive layer remains exposed.   
     
     
         17 . The method of  claim 16 , further comprising:
 removing a portion of the insulating layer between the substrate and the conductive layer to create the flexible conductor.   
     
     
         18 . The method of  claim 12 , further comprising:
 forming an encapsulant layer above the top surface of the substrate.   
     
     
         19 . The method of  claim 12 , wherein the lower conductive layer comprises one of the following: gold, silver, nickel, titanium, aluminum, tungsten, copper, platinum, or a combination thereof. 
     
     
         20 . The method of  claim 12 , further comprising:
 depositing a second insulating layer on the bottom surface of the substrate after removing at least a portion of the standoff, wherein a lower portion of the flexible conductor remains exposed.   
     
     
         21 . The method of  claim 12 , wherein the lower conductive layer comprises a bottom layer to accept solder and a top layer to reject solder. 
     
     
         22 . The method of  claim 12 , wherein a barrier metal layer is deposited, prior to the lower conductive layer, on at least a portion of the area to be covered by the conductive layer. 
     
     
         23 . The method of  claim 12 , further comprising:
 coupling the flexible conductor with a printed circuit board using one or more of the following: solder, ultrasonic bonding, conductive epoxy, or plated conductors.   
     
     
         24 . An electronic component package comprising:
 a flexible conductor on a bottom side of a substrate, the substrate having an electronic circuit, wherein a gap of air defines the space between a portion of the flexible conductor and a portion of the bottom side of the substrate.   
     
     
         25 . The electronic component package of  claim 24 , wherein the flexible conductor is electronically coupled with an electrical connection point on the top side of the substrate through a trench formed in the bottom side of the substrate. 
     
     
         26 . The electronic component package of  claim 25 , wherein the electrical connection point comprises one of the following: gold, silver, nickel, titanium, aluminum, tungsten, copper, platinum, or a combination thereof. 
     
     
         27 . The electronic component package of  claim 24 , further comprising:
 an insulating layer between a portion of the bottom surface of the substrate and the flexible conductor.   
     
     
         28 . The electronic component package of  claim 24 , further comprising:
 an encapsulant layer above the top surface of the substrate.   
     
     
         29 . The electronic component package of  claim 24 , wherein the flexible conductor comprises one of the following: gold, silver, nickel, titanium, aluminum, tungsten, copper, platinum, or a combination thereof. 
     
     
         30 . The electronic component package of  claim 24 , wherein the flexible conductor comprises a bottom layer to accept solder and a top layer to reject solder. 
     
     
         31 . The electronic component package of  claim 24 , further comprising:
 a barrier metal layer on the top side of the flexible conductor, the top side of the flexible conductor being the side closest to the substrate.   
     
     
         32 . The electronic component package of  claim 25 , wherein the flexible conductor is directly coupled to the electrical connection point on the top side of the substrate. 
     
     
         33 . The electronic component package of  claim 24 , wherein the flexible conductor is electronically coupled with an electrical connection point on the top side of the substrate by means of a through-silicon via formed in the bottom side of the substrate and the flexible conductor partially resides within the through-silicon via.