Patent ID: 8435902

Claim:
A method of etching silicon oxide from both a narrow trench and a wide trench on a surface of a patterned substrate in a substrate processing region of a substrate processing chamber, the method comprising: flowing a fluorine-containing precursor and a hydrogen-containing precursor into a remote plasma region fluidly coupled to the substrate processing region while forming a plasma in the remote plasma region to produce plasma effluents; etching the silicon oxide in each of the narrow trench and the wide trench by allowing the plasma effluents into the substrate processing region and forming solid by-products on the surface of a remaining silicon oxide in the narrow trench and the wide trench, wherein solid by-products over the narrow trench are taller than solid by-products over the wide trench; performing a partial sublimation, wherein the solid by-products of the wide trench are removed while the solid by-products of the narrow trench are only partially removed to form residual solid by-product in the narrow trench; flowing the plasma effluents into the substrate processing region again to remove silicon oxide from the wide trench at a linear rate greater than that of the narrow trench due to the residual solid by-products; and performing a full sublimation, wherein the residual solid by-products are removed from the narrow trench.