Shallow trench isolation having an etching stop layer and method for fabricating same

Abstract

A shallow trench isolation having an etching stop layer and its method of fabrication. The method utilizes a shield layer such as a silicon nitride layer to serve as an etching stop layer. The etching stop layer is formed in the top position of the shallow trench isolation.

What is claimed is:  
     
         1 . A method for fabricating a shallow trench isolation having an etching stop layer, comprising the steps of: 
 (a) providing a substrate;    (b) forming a stacked structure consisting of a first insulated layer, a conductive layer, and a first shield layer in sequence on said substrate;    (c) defining said stacked structure and said substrate so as to form a shallow trench;    (d) forming a second insulated layer over said substrate, to fill said shallow trench;    (e) etching said second insulated layer so as to leave a portion of said second insulated layer remaining in said shallow trench, and to form a concave portion in the top position of said shallow trench;    (f) removing said first shield layer;    (g) forming a second shield layer over said substrate, to fill said concave portion; and    (h) etching said second shield layer so as to leave a portion of said second shield layer in the concave portion, to serve as an etching stop layer.    
     
     
         2 . A method as claimed in  claim 1 , wherein said substrate is a silicon substrate.  
     
     
         3 . A method as claimed in  claim 1 , wherein said first insulated layer is a silicon oxide layer.  
     
     
         4 . A method as claimed in  claim 1 , wherein said conductive layer is a polysilicon layer.  
     
     
         5 . A method as claimed in  claim 1 , wherein said shield layer is a silicon nitride layer.  
     
     
         6 . A method as claimed in  claim 1 , wherein said second insulated layer is a silicon oxide layer.  
     
     
         7 . A method as claimed in  claim 1 , wherein said etching stop layer in the step (h) is a silicon nitride layer.  
     
     
         8 . A method as claimed in  claim 1 , wherein said first and second shield layers are silicon nitride layers deposited by low pressure chemical vapor deposition which uses SiH 2 Cl 2  and NH 3  as a reaction gas.  
     
     
         9 . A method as claimed in  claim 1 , wherein said concave portion in step (e) is formed by an etching back method.  
     
     
         10 . A method as claimed in  claim 1 , wherein said concave portion in step (e) is formed by the sequential steps of chemical mechanical polishing and dry etching.  
     
     
         11 . A method as claimed in  claim 1 , wherein said etching stop layer in step (h) is attained by removing a portion of said second shield layer using chemical mechanical polishing.  
     
     
         12 . A method for fabricating a shallow trench isolation having an etching stop layer, comprising the steps of: 
 (a) providing a silicon substrate;    (b) forming a stacked structure consisting of a first silicon oxide layer, a polysilicon layer, and a first silicon nitride layer in sequence on said silicon substrate;    (c) defining said stacked structure and said silicon substrate so as to form a shallow trench; (d) forming a second silicon oxide layer over said substrate, to fill said shallow trench using a high density plasma deposition;    (e) polishing said second silicon oxide layer so as to leave a portion of said second silicon oxide layer remaining in said shallow trench, and to form a concave portion in the top position of said shallow trench, by chemical mechanical polishing;    (f) removing said first silicon nitride layer;    (g) forming a second silicon nitride layer over said silicon substrate, to fill said concave portion; and    (h) polishing said second silicon nitride layer so as to leave a portion of said second silicon nitride layer in the concave portion, to serve as an etching stop layer.    
     
     
         13 . A shallow trench isolation having an etching stop layer, comprising: 
 a substrate in which is formed a shallow trench in the predetermined position;    an isolation structure filling in said shallow trench, wherein said isolation structure consists of an insulated layer and an etching stop layer disposed on said insulated layer.    
     
     
         14 . A shallow trench isolation as claimed in  claim 13 , wherein said substrate is a silicon substrate.  
     
     
         15 . A shallow trench isolation as claimed in  claim 13 , wherein said first insulated layer is a silicon oxide layer.  
     
     
         16 . A shallow trench isolation as claimed in  claim 13 , wherein said stop etching stop layer is a silicon nitride layer.  
     
     
         17 . A shallow trench isolation as claimed in  claim 13 , further comprising a silicon oxide layer, which is formed on the side walls and bottom of said shallow trench.  
     
     
         18 . A shallow trench isolation having an etching stop layer, comprising: 
 a silicon substrate in which is formed a shallow trench in the predetermined position;    an isolation structure filling in said shallow trench, wherein said isolation structure consists of a silicon oxide layer and a silicon nitride layer disposed on said silicon oxide layer.