Direct fabrication of multi-tier structures in dielectric materials for dual damascene processing

In the back end of line (BEOL) processing of advanced microprocessors several levels (ten or more) of wiring and associated via (interconnects) are required. Through these wiring-via levels signal and power can be carried throughout the chip and to the chip carrier. The semiconductor industry uses the dual damascene approach to fabricate a wiring- and a via-level simultaneously. However, the dual damascene processing requires more than twenty process steps for one wiring-via level. For an advanced microprocessor with more than ten wiring-via levels the step count for interconnects exceeds that for front end processing. Currently, the dual damascene processing is becoming the most time-consuming step in the processing sequence and affects the throughput of the semiconductor industry essentially. In this work we present a novel approach to fabricate a multi-tier structure for dual damascene processing based on UV nanoimprint lithography (UV-NIL). By using a soft polymer (PDMS) template with multi-tier patterns, a dual damascene structure for one wiring level and one via level can be directly imprinted in a functional dielectric material simultaneously. This UV-NIL based dual damascene processing reduces the total process steps drastically. The possibility of UV-NIL for dual damascene processing and imprintable dielectric materials as interlayer dielectric (ILD) will be discussed.