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/cm 2 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/cm 2 , 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.

EUV/Soft X-Ray Interference Lithography

“…EUV-IL enabled the characterization and development of new EUV resist materials before commercial EUV exposure tools became available. EUV resist has been performed on the EUV-IL beamline at SLS [25] and on the XIL beamline at SSRF [26]. Line structures of new EUV resist material with HP of 12 nm have been fabricated at the EUV-IL beamline at SLS, as shown in Figure 12.…”

“…The EUV resist test result, done by XIL-II at SLS (reproduced with permission from[25] ©(2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE)).…”

Photolithography reaches 6 nm half-pitch using EUV light

“…Further increase in the resolution will severely test the capabilities of the beamline experimental setup, the characteristics of high resolution EUV photoresists [10], and the fabrication of high quality IL masks. In the first case, the effect of source extension and of mechanical vibrations plays a role in resolution improvement and limitations.…”

State-of-the-art EUV materials and processes for the 7nm node and beyond

“…At PSI, for instance, we have had the opportunity to test many state-of-the-art CARs from vendors from all around the world and several promising candidates that simultaneously meet sensitivity, LWR and EL high performance requirements for the 7 and 5 nm logic node (16 nm and 13 nm half-pitch HP, respectively) for HVM have been identified for further investigation [2][3][4]. Although several CARs have been additionally found to be excellent performing down to 13 nm HP and even well resolved down to 12 nm and 11 nm, it has been demonstrated that alternative material solutions for HVM performance for upcoming technology nodes are still needed [2][3][4]. For that reason, the performance of alternative resist platforms such as Sn-based metal organic resist from Inpria Corp. and a negative tone CAR molecular resist from Irresistible Materials have been previously investigated [5,6].…”