Polymer-Structure Dependence of Acid Generation in Chemically Amplified Extreme Ultraviolet Resists

Negative-tone imaging (NTI) with EUV exposure has major advantages with respect to line-width roughness (LWR) and resolution due in part to polymer swelling and favorable dissolution mechanics. In NTI process, both resist and organic solvents play important roles in determining lithography performances. The present study describes novel chemically amplified resist materials based on NTI technology with EUV using specific organic solvents. Lithographic performances of NTI process were described in this paper under exposures using ASML NXE:3300 EUV scanner at imec. It is emphasized that 14 nm hp was nicely resolved under exposure dose of 37 mJ/cm 2 without any bridge and collapse, which are attributed to the low swelling character of NTI process. Although 13 nm hp resolution was potentially obtained, a pattern collapse still restricts its resolution in case coating resist film thickness is 40 nm. Dark mask limitation due mainly to mask defectivity issue makes NTI with EUV favorable approach for printing block mask to produce logic circuit. A good resolution of CD-X 21 nm/CD-Y 32 nm was obtained for block mask pattern using NTI with usable process window and dose of 49 mJ/cm 2 . Minimum resolution now reaches CD-X 17 nm / CD-Y 23 nm for the block. A 21 nm block mask resolution was not affected by exposure dose and explored toward low dose down to 18 mJ/cm 2 by reducing quencher loading. In addition, there was a negligible amount of increase in LCDU for isolated dot pattern when decreasing exposure dose from 66 mJ/cm 2 to 24 mJ/cm 2 . On the other hand, there appeared tradeoff relationship between LCDU and dose for dense dot pattern, indicating photon-shot noise restriction, but strong dependency on patterning features. Design to improve acid generation efficiency was described based on acid generation mechanism in traditional chemically amplified materials which contains photoacid generator (PAG) and polymer. Conventional EUV absorber which comprises of organic compounds is expected to have 1.6 times higher EUV absorption than polyhydroxystyrene based on calculation. However, observed value of acid amount was comparable or significantly worse than polyhydroxystyrene.

Section: El (%)mentioning

confidence: 99%

Negative-tone Imaging with EUV Exposure toward 13 nm hp

Tsubaki

Nihashi

Tsuchihashi

et al. 2016

“…Sensitization mechanism of EUV resist has been well investigated by many researchers [30][31][32][33][34][35][36][37][38][39][40]. Absorption of high-energy EUV light (13.5 nm) mainly by polymer is the first step of EUV sensitization.…”

Section: Noise Mitigation Approach (1): Dissolution Uniformity Of Nbamentioning

confidence: 99%

“…This electron is then trapped by PAG through reductive electron transfer and activates PAG to generate acid. It has been reported that acid generation yield under EUV exposure is strongly affected by polymer structure [32][33][34][35][36], PAG structure [37][38][39], and its loadings [38][39][40], respectively.…”

Section: Noise Mitigation Approach (1): Dissolution Uniformity Of Nbamentioning

confidence: 99%

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

Tarutani

Tsubaki

Fujimori

et al. 2014

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.

“…[4][5][6]9] The acid generation mechanism for EUV resists is analogous to that of EB resists. [7][8][9] However, the absorption of incident EUV photon conforms to Lambert's Law in EUV resists as well as KrF and ArF photoresists. Thus, it is clarified that EUV resists have some similarity to those in both photoresists and EB resists.…”

Section: Introductionmentioning

confidence: 99%

Dissolution Kinetics in Polymer-Bound and Polymer-Blended Photo-Acid Generators

Yamamoto

Kozawa

Tagawa

2012

Self Cite

In the fabrication beyond 16 nm node, the uniform distribution of acid generators in resist matrix is a serious concern. Recently, the incorporation of acid generators to polymers via covalent bonds has attracted much attention in order to overcome the compatibility problem of acid generators with polymers and reduce the diffusion lengths of acid, which leads to high resolution and low line edge roughness (LER). However, understanding of the resist dissolution kinetics in polymer-bounded and polymer-blended photo-acid generator (PAG) for extreme ultraviolet (EUV) lithography is insufficient. Therefore, it is significantly important to clarify the effect of binding acid generator with polymer on the dissolution kinetics. In this study, dissolution kinetics in polymer-bound and polymer-blended PAG was investigated to understand inherent EUV resist characteristics. The development rate R(E,Z) at different depth position in resist film was determined in polymer-bounded and polymer-blended PAG using resist development analyzer (RDA-800EUV) measurement system. The difference of R(E,Z) in polymer-bounded and polymer-blended PAG was observed. Also, the preliminary evaluation of resist profile for EUV chemically amplified resists was performed by using PROLITH and parameters obtained with EUV exposure tool. Furthermore, the resist patterns were produced by electron beam and the SEM observation results were compared with the PROLITH simulation results.