Low-k dielectric structure and method

Abstract

A low-k dielectric sacrificial material is formed within a microelectronic structure covered with a suitable porous or low density permeable material. At an appropriate time, the underlying sacrificial material is decomposed and diffused away through the overlying permeable material. As a result, at least one void is created, contributing to desirable dielectric characteristics.

1 . A method to make a microelectronic structure comprising: 
 forming a sacrificial dielectric layer adjacent a substrate layer;    forming a permeable layer upon the sacrificial dielectric layer;    decomposing a portion of the sacrificial dielectric layer to form a decomposition;    diffusing the decomposition through the permeable layer to form a void in a position previously occupied by a portion of the sacrificial dielectric layer.    
   
   
       2 . The method of  claim 1  wherein decomposing a portion of a sacrificial dielectric layer comprises heating a portion of the sacrificial dielectric layer above the thermal decomposition temperature for the sacrificial dielectric layer.  
   
   
       3 . The method of  claim 1  wherein decomposing a portion of a sacrificial dielectric layer comprises introducing a solvent to chemically decompose a portion of the sacrificial dielectric layer.  
   
   
       4 . The method of  claim 1  wherein diffusing the decomposition through the permeable layer comprises introducing a carrier plasma to the permeable layer to induce diffusion of the decomposition through the permeable layer to the carrier plasma.  
   
   
       5 . The method of  claim 1  further comprising forming a conductive layer across the sacrificial dielectric layer and the permeable layer before decomposition.  
   
   
       6 . The method of  claim 1  further comprising forming a conductive layer across the sacrificial dielectric layer before forming the permeable layer.  
   
   
       7 . The method of  claim 6  further comprising forming a shunt layer over the conductive layer before forming the permeable layer.  
   
   
       8 . The method of  claim 1  further comprising forming an additional dielectric layer between the substrate layer and the sacrificial dielectric layer, the additional dielectric layer comprising a dielectric material which does not substantially decompose during decomposing the sacrificial dielectric layer.  
   
   
       9 . The method of  claim 1  wherein the sacrificial dielectric layer comprises a polymer.  
   
   
       10 . The method of  claim 9  wherein the sacrificial dielectric layer comprises a polymer from the group consisting of polynorbornene, polycyclohexene, polypropylene oxide, polyethylene oxide, polystyrene, poly(p-phenylene), polyxylene, cross-linked PMMA, polyarylene, and poly(aryl ether).  
   
   
       11 . The method of  claim 1  wherein the permeable layer comprises a siloxane-based polymer or a carbon doped oxide.  
   
   
       12 . The method of  claim 5  wherein the permeable layer comprises a material from the group consisting of silicon dioxide, silicon nitride, aluminum oxide, aluminum phosphate, boron nitride, mesoporous silica, aluminosilicate, and fluorinated silicate glass.  
   
   
       13 . A microelectronic structure comprising: 
 substrate layer;    a permeable layer;    a sacrificial dielectric layer between the substrate layer and the permeable layer; and    a conductive layer extending across the sacrificial dielectric layer between the substrate layer and permeable layer;    the permeable layer being permeable to a decomposition comprising a portion of the sacrificial dielectric layer.    
   
   
       14 . The microelectronic structure of  claim 13  wherein the sacrificial dielectric layer has a lower thermal decomposition temperature than the permeable layer.  
   
   
       15 . The microelectronic structure of  claim 13  wherein the sacrificial dielectric layer is susceptible to a chemically decomposing agent which is substantially ineffective on the permeable layer.  
   
   
       16 . The microelectronic structure of  claim 13  further comprising an additional dielectric layer between the substrate layer and the sacrificial dielectric layer, the additional dielectric layer comprising a dielectric material which does not substantially decompose during decomposing the sacrificial dielectric layer.  
   
   
       17 . The microelectronic structure of  claim 13  wherein the conductive layer is formed across the permeable layer.  
   
   
       18 . The microelectronic structure of  claim 13  wherein the conductive layer does not cross the permeable layer, the permeable layer blanket covering exposed portions of the conductive layer and sacrificial dielectric layer.  
   
   
       19 . The microelectronic structure of  claim 18  further comprising a shunt layer between the permeable layer and exposed portions of the conductive layers.  
   
   
       20 . The microelectronic structure of  claim 13  wherein the sacrificial dielectric layer comprises a polymer.  
   
   
       21 . The microelectronic structure of  claim 20  wherein the sacrificial dielectric layer comprises a polymer from the group consisting of polynorbornene, polycyclohexene, polypropylene oxide, polyethylene oxide, polystyrene, poly(p-phenylene), polyxylene, cross-linked PMMA, polyarylene, and poly(aryl ether).  
   
   
       22 . The microelectronic structure of  claim 13  wherein the permeable layer comprises a siloxane-based polymer or a carbon doped oxide.  
   
   
       23 . The microelectronic structure of  claim 17  wherein the permeable layer comprises a material from the group consisting of silicon dioxide, silicon nitride, aluminum oxide, aluminum phosphate, boron nitride, mesoporous silica, aluminosilicate, and fluorinated silicate glass.  
   
   
       24 . The microelectronic structure of  claim 13  wherein the sacrificial dielectric layer defines one or more voids occupying at least a portion of the volume occupied by the sacrificial dielectric layer.  
   
   
       25 . The microelectronic structure of  claim 24  wherein the one or more voids occupy more than about 70% of the volume occupied by the sacrificial dielectric layer.  
   
   
       26 . The microelectronic structure of  claim 24  wherein the one or more voids are formed by decomposing a portion of the sacrificial dielectric layer to form a decomposition, and diffusing the decomposition away through the permeable layer after forming the conductive layer.