Patent ID: 8368220
Filing Date: 2013-02-05
Classification: H01L

Abstract:
1. A dual damascene with recessed steps for anchoring a conductive filling comprising: a dielectric layer, comprising at least two relatively higher density portions and a contiguous relatively lower density portion sandwiched between the at least two relatively higher density portions, said relatively lower density portion having a thickness greater than about 68 percent of a total thickness of said dielectric layer; a dual damascene opening extending through a full thickness of the dielectric layer; a major portion of trench and via portions of said dual damascene extending through a full thickness of said lower density layer, the relatively higher density layer having a thickness at least about ⅕ as thick as the relatively lower density layer, said relatively higher density layers comprising carbon and nitrogen; and a lowermost relatively higher density portion comprises an etch stop layer and an uppermost relatively higher density portion comprises a polish stop layer, said etch stop layer and said polish stop layer having a greater resistance to dielectric plasma etching compared to said relatively lower density portion; wherein, the opening in the lower density layer has third and fourth lateral dimensions that are relatively larger by between about 20 Angstroms and about 150 Angstroms compared to at least a first lateral dimension of the opening in the lowermost relatively higher density layer and a second lateral dimension of the opening in the uppermost relatively higher density layer, the relatively lower density layer comprising at least one pair of recessed steps, and undercut regions below the uppermost relatively higher density portion have equal lateral dimension; wherein said anchored conductive filling consists of a top and a bottom coplanar with a respective top and bottom of said dielectric layer.