Method for forming deep trench capacitor with liquid phase deposition oxide as collar oxide

Abstract

A method for forming a deep trench capacitor mainly utilizes a liquid phase deposition (LPD) oxide to form a collar oxide layer in the trench, followed by forming a conductive layer serving as an upper electrode of the deep trench capacitor, thereby avoiding collar oxide residue in the conductive layer and thus forming good electrical connection. And, the method of the present invention does not need a dry etch to remove the unnecessary collar oxide layer such that the process can be simplified.

1 - 7 . (canceled)  
   
   
       8 . A method for forming a trench capacitor comprising the steps of: 
 providing a substrate;    forming a mask layer of a predetermined pattern on the substrate to expose a portion of the substrate;    forming a trench in the exposed portion of the substrate;    filling the lower portion of the trench with a photoresist layer;    forming a low temperature oxide layer on the surface of the trench not covered by the photoresist layer;    removing the photoresist layer in the trench;    forming a conductive diffusion region in the substrate at the periphery of the portion of the trench not covered by the low temperature oxide layer;    forming a dielectric layer on the surfaces of the trench and the low temperature oxide layer; and    filling the trench with a conductive layer, and making the top of the conductive layer lower than the bottom of the low temperature oxide layer.    
   
   
       9 . (canceled)  
   
   
       10 . The method as claimed in  claim 8 , wherein the low temperature oxide layer is a liquid phase deposition oxide layer.  
   
   
       11 . The method as claimed in  claim 8 , wherein the conductive diffusion region is formed by use of Arsenic Silicon Glass (ASG) and heat treatment, or Gas Phase Diffusion (GDP).  
   
   
       12 . The method as claimed in  claim 8 , wherein the dielectric layer comprises a nitride layer.  
   
   
       13 . The method as claimed in  claim 12 , wherein the dielectric layer also comprises an oxide layer.  
   
   
       14 . The method as claimed in  claim 8 , wherein the conductive layer comprises a polysilicon layer.  
   
   
       15 . The method as claimed in  claim 8 , further comprising a step of removing the dielectric layer on the surface of the low temperature oxide layer, after the filling with the conductive layer.