Novel EUV Resist Materials Design for 14 nm Half Pitch and below

Abstract

Polymers with a different Tg and activation energy were prepared to clarify influences of acid diffusion on resolution at 15 nm half-pitch (hp) and 14 nm hp using a EUV micro-field exposure tool (MET) at LBNL. Resolution on such a narrow pattern was limited by collapse and pinching. Clear relationship between pinching numbers and polymer Tg indicates that acid diffusion is one of major contributors on the pinching. In addition, polymers with a low thermal activation energy (Ea) on deprotection were effective for reducing pinching. This is probably originated from its high chemically amplification character even in low post-exposure bake (PEB) temperature to obtain both large chemical contrast and short acid diffusion. On the other hand, a good correlation between a cleanable outgassing amount and Ea indicates trade-off relationship between outgassing and resolution. Advantages of n-butyl acetate (nBA) developer have been investigated in viewpoint of dissolution uniformity. Surface roughness of a non-patterned resist film at half-exposed area, which was well correlated with LWR, was measured by AFM as indicator of uniformity in development process. To avoid any differences in resist chemistry other than development process, cross linking negative tone resist was applied for this study. The surface roughness obtained by nBA, which is conventional negative-tone imaging (NTI) developer, was 32 % lower than that obtained by 2.38 % TMAH solution. NTI resist system with a nBA developer and optimized resist reduced LWR from 4.8 nm to 3.0 nm in comparison with conventional positive tone resist with a 2.38 % TMAH developer. In addition, advantage on semi-dense trench patterning was well defined. New EUV sensitizer with 1.15 times higher EUV absorption resulted in 1.15 times higher acid yield by EUV exposure. Lithography performance of the new EUV sensitizer has been investigated by MET at SEMATECH Albany. Sensitivity was indeed improved from 20 mJ/cm 2 to 17 mJ/cm 2 according to the acid yield increase, but resolution was significantly degraded.

Molecular Glass Resists Based on 9,9′-Spirobifluorene Derivatives: Pendant Effect and Comprehensive Evaluation in Extreme Ultraviolet Lithography

“…Outgassing of resists has drawn much attention due to its impact on throughput and damages to optics. Several studies have been reported that polymer resists with low thermal activation energy upon deprotection are liable to outgassing. , Our previous work has revealed that the outgassing is primarily from the protecting groups and the skeleton is stable almost without outgassing under the EUV exposure . Therefore, the effects of different acid labile pendant groups on outgassing of the MG resists is essential for the molecule design.…”

“…The higher PEB temperatures for SP-AD and SP-BU resists further confirmed the hypothesis. The results are consistent with previous study about the relationship between E a and outgassing, suggesting that a low E a resist tends to release volatile species due to its high thermal reactivity even at room temperature.…”

Resist material options for extreme ultraviolet lithography

“…A significant improvement in the resolution has been expected for EUV lithography because of the reduction in the wavelength. The resolution of EUV lithography with chemically amplified resist processes has already reached the sub-16-nm region [5,6]. The focus of the resist development is shifting to the 11-nm half-pitch node.…”

Ultrasensitive metal-organic cluster resist for patterning of single exposure high numerical aperture extreme ultraviolet lithography applications

“…The biggest challenges for the successful implementation of EUVL for leading-edge logic devices and likely for futuristic fab-out DRAM, is the unavailability of compatible defect-free photoresists and mechanistic rapport to the scaling of feature size down to single-digit resolution 12 , 17 – 19 Note that there is no program to make through the direct write (maskless) tools, including electron beam lithography (EBL) 20 – 26 and helium ion beam lithography (HIBL) for mass production of IC chips to date 20 , 27 – 29 It suggests maskless tools can be used to counter the scarcity of rarely accessible EUV tools to resist developers for screening/prototyping of the futuristic logic nodes resists and low-volume production.…”