Methods and apparatus of creating airgap in dielectric layers for the reduction of rc delay

Abstract

A method and apparatus for generating air gaps in a dielectric material of an interconnect structure. One embodiment provides a method for forming a semiconductor structure comprising depositing a first dielectric layer on a substrate, forming trenches in the first dielectric layer, filling the trenches with a conductive material, planarizing the conductive material to expose the first dielectric layer, depositing a dielectric barrier film on the conductive material and exposed first dielectric layer, depositing a hard mask layer over the dielectric barrier film, forming a pattern in the dielectric barrier film and the hard mask layer to expose selected regions of the substrate, oxidizing at least a portion of the first dielectric layer in the selected region of the substrate, removing oxidized portion of the first dielectric layer to form reversed trenches around the conductive material, and forming air gaps in the reversed trenches while depositing a second dielectric material in the reversed trenches.

1 . A method for forming a dielectric structure having air gaps, comprising:
 depositing a first dielectric layer on a substrate;   depositing a second dielectric layer on the first dielectric layer;   forming trench-via structures in the first and second dielectric layer, wherein vias are formed in the first dielectric layer and trenches are formed in the second dielectric layer;   filling the trench-via structures with a conductive material;   planarizing the conductive material to expose the second dielectric layer;   depositing a dielectric barrier film on the conductive material and exposed second dielectric layer;   forming a pattern in the dielectric barrier film and the hard mask layer to expose selected regions of the substrate;   removing the second dielectric layer in the selected regions of the substrate to form reversed trenches around the conductive material filled in the trenches; and   forming air gaps in the reversed trenches while depositing a third dielectric material in the reversed trenches.   
     
     
         2 . The method of  claim 1 , wherein depositing the second dielectric layer comprises:
 depositing a silicon/oxygen containing material having labile organic group; and   curing the silicon/oxygen containing material to form microscopic gas pockets that uniformly dispersed in the first dielectric layer.   
     
     
         3 . The method of  claim 1 , wherein removing the second dielectric layer comprising etching the second dielectric layer exposed by the pattern. 
     
     
         4 . The method of  claim 3 , wherein the first dielectric layer and second dielectric layer are different in property such that the first dielectric layer serves as an etch stop during etching the second dielectric layer. 
     
     
         5 . The method of  claim 3 , wherein etching the second dielectric layer is performed using a masked dry etch process. 
     
     
         6 . The method of  claim 1 , further comprising lining the reversed trenches with a dielectric barrier prior to forming air gaps. 
     
     
         7 . The method of  claim 6 , wherein the third dielectric material comprises a dielectric barrier material deposited non-conformally in the reversed trenches so that the air gaps are formed and sealed within the dielectric barrier material. 
     
     
         8 . The method of  claim 6 , wherein the third dielectric material comprises an interlayer dielectric material deposited non-conformally in the reversed trenches so that the air gaps are formed and sealed within the interlayer dielectric material. 
     
     
         9 . The method of  claim 1 , wherein the third dielectric material comprises a dielectric barrier material deposited non-conformally in the reversed trenches so that the air gaps are formed and sealed within the dielectric barrier material. 
     
     
         10 . The method of  claim 9 , further comprising polishing the third dielectric material without breaking the air gaps. 
     
     
         11 . The method of  claim 1 , wherein the third dielectric material comprises an interlayer dielectric material deposited non-conformally in the reversed trenches so that the air gaps are formed and sealed within the interlayer dielectric material. 
     
     
         12 . The method of  claim 11 , further comprising polishing the third dielectric material without breaking the air gaps. 
     
     
         13 . A method for forming a dielectric structure having air gaps, comprising:
 depositing an interlayer dielectric material layer on a substrate;   depositing a porous dielectric layer on the interlayer dielectric material layer;   forming trench-via structures in the interlayer dielectric material layer and the porous dielectric layer;   depositing a metallic diffusion barrier over the trench-via structure;   filling the trench-via structures with a conductive material;   planarizing the conductive material to expose the porous dielectric layer;   removing the porous dielectric layer in selected regions of the substrate to form reversed trenches around the conductive material filled in the trenches; and   forming air gaps in the reversed trenches while depositing a non-conformal dielectric material in the reversed trenches.   
     
     
         14 . The method of  claim 13 , wherein depositing the porous dielectric layer comprises:
 depositing a silicon/oxygen containing material having labile organic group; and   curing the silicon/oxygen containing material to form microscopic gas pockets that uniformly dispersed in the porous dielectric layer.   
     
     
         15 . The method of  claim 14 , wherein removing the porous dielectric layer comprising etching the porous dielectric layer to expose the interlayer dielectric material layer. 
     
     
         16 . The method of  claim 15 , wherein the interlayer dielectric material layer and porous dielectric layer are different in property such that the interlayer dielectric material layer serves as an etch stop during etching of the porous dielectric layer. 
     
     
         17 . The method of  claim 15 , wherein the non-conformal dielectric material comprises a dielectric barrier material deposited non-conformally in the reversed trenches so that the air gaps are formed and sealed within the dielectric barrier material. 
     
     
         18 . The method of  claim 15 , wherein the non-conformal dielectric material comprises a dielectric barrier material deposited non-conformally in the reversed trenches so that the air gaps are formed and sealed within the dielectric barrier material. 
     
     
         19 . The method of  claim 17 , further comprising lining the reversed trenches with a dielectric barrier prior to forming air gaps. 
     
     
         20 . The method of  claim 15 , comprising polishing the non-conformal dielectric material without breaking the air gaps.