Method of improving a shallow trench isolation gapfill process

Abstract

A method of forming a graded trench for a shallow trench isolation region is provided. The method includes providing a semiconductor substrate with a substrate region. The method further includes forming a pad oxide layer overlying the substrate region. Additionally, the method includes forming an etch stop layer overlying the pad oxide layer. The method further includes patterning the etch stop layer and the pad oxide layer to expose a portion of the substrate region. In addition, the method includes forming a trench within an exposed portion of the substrate region, the trench having sidewalls and a bottom and a first depth. The method additionally includes forming a dielectric layer overlying the trench sidewalls, the trench bottom, and mesa regions adjacent to the trench. The method further includes removing a first portion of the dielectric layer from the trench bottom to expose the substrate region with a second portion of the dielectric layer remaining on the sidewalls of the trench. In addition, the method includes etching the substrate region to increase the depth of at least a portion of the trench to a second depth. Also, the method includes removing the second portion of the dielectric layer from the trench.

1 . A trench located on and extending into the semiconductor substrate comprising:
 a trench bottom and a trench opening;   a first trench sidewall region;   a first step region adjacent to the first trench sidewall region, the first step region being substantially parallel to the trench bottom and forming a first angle with the first trench sidewall region; and   a second trench sidewall region, the second trench sidewall region forming a second angle with the trench bottom.   
     
     
         2 . The trench of  claim 1  further comprising:
 a second step region adjacent to the second trench sidewall region, the second step region being substantially parallel to the trench bottom; and 
 a third trench sidewall region, the third trench sidewall region forming a third angle with the second step region. 
 
     
     
         3 . The trench of  claim 1  wherein the first and second angles are between and including 90 and 120 degrees. 
     
     
         4 . The trench of  claim 1  wherein the first and second angles are both 90 degrees.