Patent ID: 9093480
Filing Date: 2015-07-28
Classification: H01L

Abstract:
1. A method of making a semiconductor device, comprising: forming a stack of a first set of alternating layers of a first material and a second material, a first etch stop layer, and a second set of alternating layers of the first material and the second material over a substrate, the first set of alternating layers constituting a lower portion of the stack, the second set of alternating layers constituting an upper portion of the stack, and the first etch stop layer being located between the lower portion and the upper portion of the stack and comprising a material different from the first material and the second material; forming a hard mask over the stack; patterning the hard mask to form at least one hard mask opening which exposes the stack; etching the upper portion of the stack through the at least one hard mask opening to form at least one opening extending partially through the upper portion of the stack to the first etch stop layer; forming a masking layer on a sidewall and bottom surface of the at least one opening; removing the masking layer from the bottom surface of the at least one opening while leaving the masking layer on the sidewall of the at least one opening; and further etching the at least one opening to extend the at least one opening through the first etch stop layer and further through the lower portion of the stack while the masking layer remains on the sidewall of the at least one opening.