Variable-shaped e-beam lithography enabling process development for future copper damascene technology

To realize fast and efficient integrated circuits the interconnect system gains an increasing importance. In particular, this is the case for logic and processor circuits with up to 12 metallization layers. In order to optimize this technology and the according processes it is desirable to generate flexible test structures in small lot production. In opposition to standard optical lithography using masks, Electron Beam Direct Write (EBDW) lithography can rapidly deliver special test structures at low cost. Furthermore, critical dimensions of future technology nodes which are not yet manufacturable by standard optical lithography tools can be produced. In this paper we demonstrate the potential of the 50 kV variable shaped EBDW cluster for patterning of future back-end-of-line (BEOL) structures on full 200 mm wafers. The patterned wafers have been used to develop next generation copper damascene interconnect processes for critical dimensions down to 50 nm.