Isolation Structure for Stacked Dies

Abstract

An isolation structure for stacked dies is provided. A through-silicon via is formed in a semiconductor substrate. A backside of the semiconductor substrate is thinned to expose the through-silicon via. An isolation film is formed over the backside of the semiconductor substrate and the exposed portion of the through-silicon via. The isolation film is thinned to re-expose the through-silicon via, and conductive elements are formed on the through-silicon via. The conductive element may be, for example, a solder ball or a conductive pad. The conductive pad may be formed by depositing a seed layer and an overlying mask layer. The conductive pad is formed on the exposed seed layer. Thereafter, the mask layer and the unused seed layer may be removed.

1 . A semiconductor device comprising:
 a semiconductor substrate having a circuit side and a backside opposite the circuit side;   through-silicon vias extending through the semiconductor substrate, each of the through-silicon vias having a protruding portion from the backside of the semiconductor substrate;   an isolation film on the backside of the semiconductor substrate between adjacent ones of the through-silicon vias, the isolation film not extending beyond the top of the protruding portion of each of the through-silicon vias; and   a conductive element on the protruding portion of each of the through-silicon vias.   
     
     
         2 . The semiconductor device of  claim 1 , wherein the conductive element comprises a conducting seed layer on the protruding portion of each of the through-silicon vias and a conductive pad on the conducting seed layer. 
     
     
         3 . The semiconductor device of  claim 2 , wherein the conducting seed layer extends over a portion of the isolation film. 
     
     
         4 . The semiconductor device of  claim 2 , wherein the conductive pad comprises copper. 
     
     
         5 . The semiconductor device of  claim 1 , wherein the isolation film extends along sidewalls of the protruding portion of each of the through-silicon vias. 
     
     
         6 . The semiconductor device of  claim 1 , wherein the conductive element comprises a solder ball. 
     
     
         7 . The semiconductor device of  claim 1 , further comprising conductive bumps on the circuit side of the semiconductor substrate. 
     
     
         8 . A method of forming a semiconductor device, the method comprising:
 providing a semiconductor substrate having a through-silicon via extending from a circuit side partially through the semiconductor substrate;   thinning a backside of the semiconductor substrate such that the through-silicon via protrudes from the backside of the semiconductor substrate;   forming an isolation film over the backside of the semiconductor substrate and the through-silicon via;   thinning the isolation film such that the through-silicon via is exposed; and   forming a conductive element on the through-silicon via.   
     
     
         9 . The method of  claim 8 , wherein the forming the conductive element comprises forming a solder ball on the through-silicon via. 
     
     
         10 . The method of  claim 8 , wherein the forming the conductive element comprises:
 forming a seed layer over the through-silicon via; and   forming a metal pad over the seed layer.   
     
     
         11 . The method of  claim 8 , wherein a liner is interposed between the through-silicon via and the semiconductor substrate and further comprising removing the liner from over the through-silicon via. 
     
     
         12 . The method of  claim 11 , wherein the removing the liner is performed after the forming the isolation film. 
     
     
         13 . The method of  claim 11 , wherein the isolation film has a planar surface. 
     
     
         14 . A method of forming a semiconductor device, the method comprising:
 providing a semiconductor substrate, the semiconductor substrate having a first side and a second side opposite the first side, the semiconductor substrate having a through-silicon via extending from the first side partially through the semiconductor substrate;   exposing the through-silicon via such that at least a portion of the through-silicon via protrudes from the second side of the semiconductor substrate;   forming a dielectric layer over the second side of the semiconductor substrate;   forming a patterned mask over the dielectric layer, the dielectric layer over the through-silicon via being exposed; and   removing the dielectric layer over the through-silicon via.   
     
     
         15 . The method of  claim 14 , further comprising forming a conductive element over the through-silicon via. 
     
     
         16 . The method of  claim 15 , wherein the conductive element comprises solder. 
     
     
         17 . The method of  claim 14 , further comprising removing the patterned mask after the removing the dielectric layer. 
     
     
         18 . The method of  claim 14 , wherein a liner is interposed between the through-silicon via and the semiconductor substrate. 
     
     
         19 . The method of  claim 18 , further comprising removing the liner after the forming the patterned mask. 
     
     
         20 . The method of  claim 18 , wherein the liner extends along sidewalls of the portion of the through-silicon via protruding from the second side of the substrate.