Improvement of self-aligned dual patterning using spin-on-carbon mandrel

As the logic industry marches toward the 5nm technology node, multiple patterning schemes are intensively used to achieve sub-193nm lithography resolution for line and space definition. Several sources are reporting the need to use Self Aligned Dual Patterning (SADP) with EUV lithography. Implementing those spacer-based pitch splitting techniques is not trivial; they require major design changes and restrictions along with the additional patterning steps. They also increase manufacturing cost and process complexity. A faster, cost-effective option would be advantageous. Spin-on-carbon (SOC) is a promising candidate for first mandrel formation compared to alternatives such as Chemical Vapor Deposition (CVD) materials due to its lower cost and high-throughput. There are several benefits of using SOC as a first mandrel for SADP such as minimal recess in the floor during mandrel formation and high selectivity during the spacer etch and mandrel pull process. However, during the deposition of the spacer material, usually oxide or nitride, the carbon mandrel can be eroded, and the shape can be distorted, affecting the shape of the spacer in the next step. To enable the use of SOC for first mandrel, mandrel treatment and spacer shape optimization need to be addressed. In this paper, we will investigate a method to protect and preserve the shape of the carbon mandrel by using a direct current superposition (DCS) on a capacitively-coupled plasma (CCP) chamber. Then, we will review spacer etch development to reach the required final shape. Finally, we will perform a step-by-step roughness analysis and consider additional smoothing options.