Development of spin-on-carbon hard mask for advanced node

Abstract

Spin-on-carbon (SOC) hard mask is useful for multilayer lithography process because of its high etch resistance, low cost of ownership, low defectivity, high alignment accuracy, good gap filling and planarization for topography. SOC is a high carbon containing polymer solution and as a coating material, the polymers need to be soluble in organic solvent and insoluble after curing for coating upper layer materials. High carbon content (>80%) of SOC is very important for good etch resistance. As the semiconductor industry is moving to 2X nm node and beyond, further improvement of SOC properties mentioned above is required to achieve higher resolution. We synthesized a series of novel monomers and high carbon polymers applicable for SOC applications of advanced nodes. The optimized SOC was a PGMEA based formulation, had high carbon content 90%, excellent filling/leveling properties, and adequate etching properties applicable to trilayer process. The SOC successfully transferred patterns from resist into substrate and the SOC patterns did not show deformation or wiggling down to CD 40nm. This paper describes some of the SOC polymer chemistry and the performance of an optimized SOC formulation.