Sequential Infiltration Synthesis for Line Edge Roughness Mitigation of EUV Resist

Abstract

It is well known that high line-edge roughness (LER) and line-width roughness (LWR) are one of the key problems hindering utilization of extreme ultraviolet lithography (EUVL) in fabrication of semiconductor devices at advanced technology nodes where pattern with sub-20 nm half pitch lines and spaces is required. Sequential infiltration synthesis (SIS) has never been used before in lithography for line-edge roughness mitigation, but this concept has proved its value for 14 nm half pitch block copolymer lines formed by directed self-assembly. During this process an inorganic scaffold is being deposited inside the resist material after performing several sequential infiltration cycles with metal-organic precursor and its oxidizing agent. Etching in oxygen atmosphere after is required to transform former resist pattern into metal oxide one and improve (up to 40%) the pattern roughness. In this paper, for the first time we demonstrate feasibility of sequential infiltration synthesis (SIS) for smoothing of EUV resist lines.

Atomic layer deposition and its derivatives for extreme ultraviolet (EUV) photoresist applications

“…In 2017, Baryshnikova et al were the first to demonstrate the use of the SIS process to reduce the LER by infiltrating trimethylaluminum (TMA) and water (H 2 O) into EUV polymer-based resist, forming aluminum oxide (AlO x ) throughout the resist matrix. 27) Although the LER of EUV line patterns decreased from 3.5 to 2.1 nm after O 2 /Ar plasma ashing step, the authors reported ∼60% shrinkage for 26 nm lines due to the loss of organic components and densification of the metal oxide network. 27) It is notable that this direct conversion of infiltrated resist patterns into inorganic replicas has been first reported by Nam et al for SU-8, a negative-tone photoresist, and has been used for fabricating semiconducting metaloxide-based nanoelectronic devices.…”

“…27) Although the LER of EUV line patterns decreased from 3.5 to 2.1 nm after O 2 /Ar plasma ashing step, the authors reported ∼60% shrinkage for 26 nm lines due to the loss of organic components and densification of the metal oxide network. 27) It is notable that this direct conversion of infiltrated resist patterns into inorganic replicas has been first reported by Nam et al for SU-8, a negative-tone photoresist, and has been used for fabricating semiconducting metaloxide-based nanoelectronic devices. [48][49][50] Meanwhile, Vanelderen et al also observed 10% and 20% improvements in LWR and LER, in comparison to reference samples, after the line patterns were transferred into the first layer of the device structure stack with SIS-modified EUV resist as etch mask.…”

“…Over the years, there has been an increasing number of reported studies utilizing ALD and its modified forms to improve the EUV patterning process and develop advanced inorganic-organic hybrid resist technology. For example, besides improving the feature roughness of patterned organic EUV resist, [27][28][29] ALD-based techniques can also increase the thickness of resist pattern/ mask for reactive ion etching as well as the intrinsic etch resistance by either selectively adding more materials on the pattern surface, [29][30][31] or infusing inorganic elements into the patterned organic resist matrix. 32,33) On the other hand, instead of modifying the already patterned EUV resist, ALD and its modified techniques can be leveraged to synthesize novel hybrid EUV resist thin films that can be then subjected to EUVL.…”

Depth profiles of aluminum component in sequential infiltration synthesis-treated electron beam resist films analyzed by time-of-flight secondary ion mass spectrometry

“…14) In-situ spectroscopic ellipsometry provides an insight into time-resolved infiltration progress of diffusion, adsorption, and entrapped behaviors of TMA in PMMA thin films. 15) SIS has been recently applied to nanotechnology, in particular, to nanolithography such as directed self-assembly (DSA) lithography, 6) electron beam lithography, 16,17) extreme ultraviolet (EUV) lithography, 18,19) and nanoimprint lithography (NIL). 20) This arises from the reason because the improvement of etching durability of organic polymer resist materials by organic-inorganic hybridization [21][22][23] is intended.…”

“…It has been reported in EUV lithography that SIS brings the reduction of line edge roughness of resist patterns through shrinkage process in addition to improved etching durability. 18,19) We have studied the improvement of dry etching durability of ultraviolet (UV)-cured resists for NIL and positive-tone resists for electron beam lithography. For UV-NIL, we synthesized trimethylsilyl-containing acrylate monomers and investigated the etching durability of the UV-cured resists to oxygen reactive ion etching (O 2 RIE), because the trimethylsilyl groups were oxidized to inorganic silica during O 2 RIE.…”