Borderless dual damascene contact
 A method is disclosed for forming self-aligned, borderless contact and vias together and simultaneously with relaxed photolithographic alignment tolerances using a modified dual damascene process having two etch-stop layers. A first etch-stop layer is formed over a first dielectric layer. A second dielectric layer and a second etch-stop layer are next formed sequentially over the first etch-stop layer. Contact/via hole pattern is etched into the first etch-stop layer using a first photoresist layer. A second photoresist layer, patterned with metal line trench pattern, is formed over the contact/via patterned first etch-stop layer. The contact/via hole openings are etched into the first dielectric layer until the second etch-stop layer is reached. Then, both the first and second etch-stop layers are etched through the openings. The openings in the first and second etch-stop layers are both extended by etching the second and first dielectric layers, respectively, until the former opening reaches the second etch-stop layer, and the latter reaches the underlying substructure of devices within the semiconductor substrate. Thus, a combination of contact via interconnects, without borders, and self-aligned with respect to metal lines with relaxed photolithographic tolerances is formed together and simultaneously using a modified dual damascene process having two etch-stop layers. 
Taiwan Semiconductor for Manufacturing Company
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Yu-Hua Cheng-Yeh James (Cheng-Ming)
Lee Shih Wu