Patent ID: 8476142

Claim:
A method of processing a patterned substrate having a narrow trench and an open area, the method comprising: flowing a silicon-containing precursor and ozone (O 3 ) into a substrate processing region containing the patterned substrate; forming a dense portion of silicon oxide, filling the narrow trench and covering an exposed horizontal surface of the open area; forming a porous portion of silicon oxide over the dense portion, wherein the porous portion predominantly forms above the narrow trench and not within the narrow trench; and stripping the porous portion of the silicon oxide using a wet etch, wherein the open area is the bottom of a wide trench and the wide trench contain material from both the dense portion and the porous portion prior to the stripping operation, and wherein the operation of stripping the porous portion further comprises removing the dense portion of silicon oxide above the open area such that the open area is again exposed.