ETCH STOP STRUCTURE

摘要

A buried etch stop layer (208) for fabricating stepped etched structures has a patterned recess (211). The etch stop layer is buried between etchable first (201) and second (202) layers. The recessed patterned buried etch stop layer can be made by forming a portion of the etch stop layer (204) on one of the etchable layers, etching the recess into it, then wafer bonding the etch stop layer (208) between the first (201) and second (202) layers. Once the buried etch stop layer has been formed, the process for fabricating stepped structures starts with patterning the first layer (201) and etching it to reveal a portion of the recessed area of the etch stop (211). Selective removal by etching of the revealed area is done to remove its entire thickness in the recessed area (211) but only to remove a partial thickness of the remaining revealed area (212). This is followed by selective etching of the revealed area of the second layer, masked by the remaining revealed area (212), so as to transfer a portion of the recess pattern into the second layer, optionally down to a membrane layer (214). This provides improved etch uniformity for stepped etched structures, including those with membranes.