| CPC H01L 21/32137 (2013.01) [H01L 21/3065 (2013.01); H01L 21/32139 (2013.01)] | 17 Claims |

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1. A method of patterning a substrate comprising:
(a) etching a substrate with a first etchant to form a recess to a first depth within the substrate, the substrate having a mask layer disposed thereon, wherein an etch byproduct from the substrate forms a clogging material at a top of the recess;
(b) depositing a passivation layer on the clogging material and sidewalls of the recess;
(c) performing a second etch operation with a second etchant on the passivation layer to remove the clogging material formed from the etch byproduct on the mask layer; and
(d) etching with the first etchant the recess to a second depth.
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