Ultraviolet cross-link gap fill materials and planarization applications for patterning metal trenches in 32-45 nm via first dual damascene process

In the dual damascene (DD) process using the via-first trench-last approach, a planarizing thermally cured material is used to minimize thickness variation across the vias. The coating planarization is followed by photoresist application and lithography on vias. The major problem with this process is the large thickness bias observed as via pattern pitch and density change across the wafer. The thickness bias between the open field and dense via arrays is not acceptable for advanced lithography and leads to narrow process windows and problems during the subsequent trench etch steps. In this study, UV-cured gap fill materials are proposed as planarizing layers under a photoresist. UV-cured gap fill materials show good planarization, via fill properties (no voids), etch selectivity, minimal outgassing during curing, excellent resistance to solvents and photoresist intermixing when compared with thermally cured films. This novel method using UV curing to reduce thickness bias in gap fill materials is one of the most promising processes ready to be incorporated into the mass production of patterning metal trenches by the 32-45 nm via-first DD process.