Abstract: A method for pull back SiN to increase rounding effect in a shallow trench isolation process, comprising 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 shallow trenches by etching; dry etching the Si3N4 layer; using high density plasma chemical vapor deposition oxide fill to fill in the shallow trenches; leveling the oxide fill; rounding the shallow trench corners; and removing the Si3N4 layer. After the removal of the Si3N4 layer, multiple cleaning processes are required.

Abstract: A fluoride silicate glass (FSG) layer, comprising a plasma enhanced oxide layer (PEOX layer) on a surface of the FSG layer, is positioned on a substrate of a semiconductor wafer. An etching tank, employed as a plug hole or a trench, is formed in the FSG layer. A first plasma ashing process, using oxygen or a gas mixture of nitride and hydrogen as a reacting gas, is then performed to remove fluorine atoms for a predetermined thickness of a surface of the etching tank. A wet cleaning process is performed thereafter. By performing a second plasma ashing process, using oxygen or a gas mixture of nitride and hydrogen as a reacting gas, residual fluorine atoms are removed for the predetermined thickness of the surface of the etching tank. Finally, the etching tank is filled with a conductive material so as to form a conductor.