Method of rounding a top corner of trench

Abstract

A method for pull back SiN to increase rounding effect in a shallow trench isolation process, includes the acts of preparing a substrate of Si and forming a SiO2 layer on the substrate, forming a Si3N4 layer on the SiO2 layer, defining Si3N4 trenches by plasma etching; etching the remaining Si3N4 with SF6/HBr gas, etching SiO2 layer to form a platform and enhance the rounding of the platform, etching the substrate to have a third shallow trench and a reinforced platform, filling the third shallow trench with oxide, leveling the oxide, which uses a CMP to level the filled oxide, and removing the Si3N4 layer, wherein after the removal of the Si3N4 layer, multiple cleaning processes are required.

Dependencies are inferred from the claim text.