Patent ID: 8632690

Claim:
A method for processing a substrate, comprising: introducing a first etchant into a reactor cell wherein the reactor cell is operable to isolate a region of a surface of a substrate; introducing a fluid into the reactor cell while the first etchant remains in the reactor cell; after initiating the introducing the fluid, removing contents of the reactor cell through a first removal line and a second removal line, wherein the first removal line extends further into the reactor cell than the second removal line; maintaining a level of the contents of the reactor cell above an inlet to the first removal line while removing the contents so that the isolated region of the surface of the substrate remains submerged by the contents of the reactor cell during the processing; introducing a second etchant into the reactor cell while removing the contents of the reactor cell through the first removal line and the second removal line; and continuing the introducing of the second etchant until a concentration of the second etchant is at a desired level, wherein the isolated region of the surface of the substrate continues to remain submerged during the introducing of the second etchant.