The 10 nm technology class DRAM devices have already advanced with different patterning schemes using EUV [1-3]. Such efforts rely heavily on the choice of the underlayers, resist and the source-mask optimized (SMO) illumination mode. In this work, these concepts were explored in a single mask solution to pattern 42 nm pitch, Local Interconnect and periphery landing pad (LILP). To provide a more industry relevant solution, the use of Chemically Amplified Resists(CARs) has been adopted to pattern pillars and line/space (LS) patterns simultaneously. In addition, the following parameters have been evaluated to achieve the best printability of the two types of structures: (i) CARs tailored for high and low dose process (CAR-A and CAR-B), (ii) different underlayers (UL0, UL1, UL2), (iii) post exposure bake (PEB) conditions to determine the effect of dose-to-size and impact on the local CD uniformity (LCDU) in pillars and line width roughness (LWR) for LS. The performance comparison of different process options was done based on roughness/LCDU and dose-to-size (D-t-s).
This paper is organized as follows:
1. Experimental Method- Different combination of underlayers and resist screening using a single EUV source and mask. Optimization of the mask CDs and the overlapping process performance of pillars and LS based on the metrology inspection.
2. Underlayer performance- Choice of the underlayer based on printability performance and roughness/LCDU for a fixed resist coated on different underlayers.
3. Resist performance- Defect-free process window (PW) evaluation with different CAR coated on the best performing underlayer.
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