A novel contact hole shrink process for the 65-nm-node and beyond

Patterning of sub-100nm contacts for sub-90-nm-node devices is one of the primary challenges of photolithography today. The challenge involves achieving the desired resolution while maintaining manufacturable process windows. Increases in numerical aperture and reductions in target CDs will continue to shrink process windows and increase mask error factor resulting in larger CD variation. Several techniques such as RELACS, SAFIER, and resist reflow have been developed to improve the resolution of darkfield patterns such as contacts and trenches. These techniques are all post-develop processes applied to the patterned resist. Reflow is a fast process with low cost of ownership, but has two major disadvantages of high temperature sensitivity and large proximity bias. SAFIER and RELACS both have much slower throughput and higher cost of ownership than reflow. SAFIER also is sensitive to temperature and has large proximity bias. In this paper, a novel process is described that reduces the diameter of contact holes in resist up to 25nm without proximity effects. This process uniformly swells the resist film resulting in a shrink of patterned holes or trenches. Results are shown for 248nm and 193nm single layer resists, and a 193nm bilayer resist. This process has the potential to be high throughput with low cost of ownership similar to reflow techniques but without the proximity effects and thermal sensitivity observed with reflow.