Evaluation of EUV resist performance using interference lithography

Abstract

Extreme ultraviolet lithography (EUVL) stands as the most promising solution for the fabrication of future technology nodes in the semiconductor industry. Nonetheless, the successful introduction of EUVL into the extremely competitive and stringent high-volume manufacturing (HVM) phase remains uncertain partly because of the still limiting performance of EUV resists below 16 nm half-pitch (HP) resolution. Particularly, there exists a trade-off relationship between resolution (half-pitch), sensitivity (dose) and line-edge roughness (LER) that can be achieved with existing materials. This trade-off ultimately hampers their performance and extendibility towards future technology nodes. Here we present a comparative study of highly promising chemically amplified resists (CARs) that have been evaluated using the EUV interference lithography (EUV-IL) tool at the Swiss Light Source (SLS) synchrotron facility in the Paul Scherrer Institute (PSI). In this study we have focused on the performance qualification of different resists mainly for 18 nm and 16 nm half-pitch line/space resolution (L/S = 1:1). Among the most promising candidates tested, there are a few choices that allow for 16 nm HP resolution to be achieved with high exposure latitude (up to ~ 33%), low LER (down to 3.3 nm or ~ 20% of critical dimension CD) and low dose-to-size (or best-energy, BE) < 41 mJ/cm² values. Patterning was even demonstrated down to 12 nm HP with one of CARs (R1UL1) evaluated for their extendibility beyond the 16 nm HP resolution. 11 nm HP patterning with some pattern collapse and well resolved patterns down 12 nm were also demonstrated with another CAR (R15UL1) formulated for 16 nm HP resolution and below. With such resist it was possible even to obtain a small process window for 14 nm HP processing with an EL ~ 8% (BE ~ 37 mJ/cm², LER ~ 4.5 nm). Though encouraging, fulfilling all of the requirements necessary for high volume production, such as high resolution, low LER, high photon sensitivity (dose), and high exposure latitude (EL) simultaneously still remains challenging below 16 nm HP.