Methods of forming shallow trench isolation structures in semiconductor devices

Abstract

Methods of forming a shallow trench isolation structures in semiconductor devices are disclosed. A disclosed method comprises forming a first oxide layer, a nitride layer, and a second oxide layer on a substrate; forming a trench defining first and second active areas by etching the second oxide layer, the nitride layer, the first oxide layer, and the substrate in a predetermined area; forming a third oxide layer along an inside of the trench; forming a fourth oxide layer to fill up the trench; forming a sacrificial oxide layer on the fourth oxide layer; and removing the sacrificial oxide layer, the fourth oxide layer, the third oxide layer, the second oxide layer, and the nitride layer so as to form the shallow trench isolation. Thus, it is possible to minimize the damage of a narrow active area when forming an element isolation area through an STI process.

1 . A method of forming a shallow trench isolation structure in a semiconductor device comprising:
 forming a first oxide layer, a nitride layer, and a second oxide layer above a substrate;   forming a second oxide layer pattern, a nitride layer pattern, and a first oxide layer pattern to expose a shallow trench isolation region in the substrate by etching the second oxide layer, the nitride layer, and the first oxide layer;   forming a trench in the substrate by etching the shallow trench isolation region using the second oxide layer pattern as a mask;   forming a third oxide layer on a wall of the trench;   forming a fourth oxide layer on the substrate to fill the trench;   forming a sacrificial oxide layer on the fourth oxide layer;   removing the sacrificial oxide layer, the fourth oxide layer, the third oxide layer pattern, and the second oxide layer pattern until the nitride layer pattern is exposed; and   removing the nitride layer pattern by a chemical mechanical polishing process.   
   
   
       2 . A method as defined in  claim 1 , wherein the sacrificial oxide layer is formed by an SOG (Spin on Glass) method. 
   
   
       3 . A method as defined in  claim 2 , further comprising performing a heat treatment in an oxygen atmosphere at a temperature over about 1,000° C., after forming the sacrificial oxide layer. 
   
   
       4 . A method as defined in  claim 1 , wherein the third oxide layer has a thickness of about 10˜100 Å. 
   
   
       5 . A method as defined in  claim 1 , wherein the sacrificial oxide layer, portions of the fourth oxide layer, portions of the third oxide layer, and the second oxide layer are removed by blanket etching. 
   
   
       6 . A method as defined in  claim 1 , further comprising an etching process to remove a nitride residue using a phosphoric acid (H 3 PO 4 ) after performing the chemical mechanical polishing process. 
   
   
       7 . A method as defined in  claim 1 , further comprising forming a first photoresist pattern over the second oxide layer to define the shallow trench isolation region. 
   
   
       8 . A method as defined in  claim 7 , further comprising removing the photoresist pattern prior to etching the substrate in the shallow trench isolation region. 
   
   
       9 . A method as defined in  claim 1 , wherein forming the third oxide layer comprises low pressure chemical vapor deposition of a TEOS layer. 
   
   
       10 . A method as defined in  claim 1 , wherein filling the trench with the fourth oxide layer comprises high density plasma chemical vapor deposition of an oxide layer. 
   
   
       11 . A method as defined in  claim 7 , wherein the first photoresist pattern also defines first and second active regions. 
   
   
       12 . A method as defined in  claim 11 , wherein the first active region has a greater width than the second active region. 
   
   
       13 . A method as defined in  claim 1 , wherein an upper surface of the fourth oxide layer is substantially coplanar with the upper surface of the first oxide layer. 
   
   
       14 . A method as defined in  claim 1 , wherein removing the nitride layer pattern exposes an upper surface of the first oxide layer.