Comparison study for 3x-nm contact hole CD uniformity between EUV lithography and ArF immersion double patterning

Abstract

In order to continue scaling down the feature sizes of the devices, EUV lithography is regarded as the most powerful candidate for patterning. So It has being studied to overcome the several issues such as source power for high throughput to apply volume production, mask defectivity from mask blank, RLS (Resolution, LWR & Sensitivity) trade off, which is the intrinsic property of EUV resist, and so on. For 2x nm node DRAM, dense contact hole, which has 3x nm half pitch (hp), has been issued to be made so far. There are two well-known methods for pattering; hole double patterning with ArF immersion lithography and single patterning with EUV lithography. EUV is more simple solution than hole double patterning for 3xnm hp dense contact hole, if it has large process window and comparable CD uniformity. Fortunately, EUV process already has larger process window than that of ArF immersion because its k1 value is a little bit high. But CD (critical dimension) uniformity and pattern profile were very poor in our initial result. Therefore it needs a lot of efforts to improve and compete against double patterning. The double patterning performance for 3xnm hp contact hole has been shown last year. In this paper, we will investigate on improving CD uniformity and pattern profile for 3x nm hp contact hole with several methods. Finally, the performance of EUV, which is achieved by our experiments, is being compared with that of double patterning in terms of CD uniformity and pattern profile.