Patent ID: 9305798
Filing Date: 2016-04-05
CPC Classification: H01L

Claim Text:
1. A method for etching a layer assembly comprising an intermediate layer sandwiched between an etch layer and a stop layer, the method comprising: in a region for forming a via contact to a contact portion of the stop layer, etching the etch layer using a first etchant, the etch layer comprising a first material and the first etchant comprising a first etch selectivity with respect to the etch layer and the intermediate layer; and etching the intermediate layer using a second etchant, the second etchant comprising a second etch selectivity with respect to the intermediate layer and the stop layer, wherein the second etchant is different from the first etchant, wherein the etch layer has a planar lower surface adjacent the intermediate layer and a non-planar upper surface over the contact portion of the stop layer, and wherein a thickness of the etch layer overlying the contact portion of the stop layer varies more than 10% around a mean value, wherein the etch layer has a variable thickness in the region to be etched for forming the via contact, and wherein the thickness is measured from the planar lower surface to the non-planar upper surface.