Filling of nano-via holes by laser-assisted direct imprint

A new technique for filling narrow and high-aspect ratio nanoscale via holes by laser-assisted direct imprint has been proposed and developed. In the process, the filling material (e.g., metals or Si) is first deposited onto the nano-via holes by a deposition method that has a poor step coverage and hence fills the holes partially with voids. Then a mirror-flat transparent plate (mold) is pressed against the substrate, while an excimer laser pulse (XeCl, 308 nm wavelength, 20 ns pulse duration) shines through the mold. The laser pulse melts the filling material, and the flat mold presses the molten materials into the holes, filling them completely without voids. As examples, we successfully filled a hole array having 100 nm diameter, 500 nm depth (aspect ratio 5) and 200 nm inter-hole spacing (pitch) with e-beam evaporated silicon and copper. Besides superior step coverage and negligible thermal budget, this technique is fast and simple and doesn’t need a seed layer. Furthermore, it can planarize the wafer surface in addition to filling the holes. Clearly, this technique could be extended to other materials important for ICs metal interconnect, and may become an alternative to the dual damascene and CVD tungsten plug process used in the current ULSI fabrication. 2006 Elsevier B.V. All rights reserved.