Photoresist scum free process for via first dual damascene process

摘要

An improved method of forming a dual damascene structure by a via first process is described. Via holes are formed in a damascene stack consisting of an etch stop layer, a dielectric layer, and a barrier layer. An i-line photoresist is coated on the substrate and fills the vias. An e-beam curing step is performed to render the photoresist components inactive towards adjacent layers. The photoresist is etched back to a level about 1600 Angstroms above the via bottom to form a plug. A second curing step may be performed and then a Deep UV resist is preferably coated and patterned to form a trench opening above the vias. There is no interaction between the Deep UV photoresist and the cured plug which thereby prevents scum or bridging defects from occurring. Fences during trench etch are avoided. Plug stabilization also prevents voids from forming during trench patterning.