A study on the material design for the reduction of LWR

Tsubaki, Hideaki; Yamanaka, Tsukasa; Nishiyama, Fumiyuki; Shitabatake, Koji

doi:10.1117/12.712157

Cited by 6 publications

(6 citation statements)

References 11 publications

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“…The author supports the theory that the photochemical generation of acid and the corresponding catalytic reaction with the acid liable group on the polymer during the PEB are critical factors to the formation of LWR 13 . Resist researchers have demonstrated that the surface roughness (AFM) generated from a spin coated film including bake and development is relatively low.…”

Section: Line Width Roughness (Lwr)supporting

confidence: 58%

Resist fundamentals for resolution, LER, and sensitivity (RLS) performance tradeoffs and their relation to micro-bridging defects

Rathsack

Nafus

Hatakeyama

et al. 2009

Advances in Resist Materials and Processing Technology XXVI

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High NA immersion and EUV lithography processes are challenged to meet stringent control requirements for the 22 nm node and beyond. Lithography processes must balance resolution, LWR and sensitivity (RLS) performance tradeoffs while scaling resist thickness to 100 nm and below 1-3 . Hardware modules including coat, bake and development seek to enable resist processes to balance RLS limitations. The focus of this paper is to study the fundamentals of the RLS performance tradeoffs through a combination of calibrated resist simulations and experiments.This work seeks to extend the RLS learning through the creation of calibrated resist models that capture the exposure kinetics, acid diffusion properties, deprotection kinetics and dissolution response as a function of PAG loading in a 193 nm polymer system. The calibrated resist models are used to quantify the resolution and sensitivity performance tradeoffs as well as the degradation of resist contrast relative to image contrast at small dimensions.Calibrated resist simulations are capable of quantifying resolution and sensitivity tradeoffs, but lack the ability to model LWR. LWR is challenging to simulate (lattice models) and to measure; due to the dependence on spectral frequency. This paper seeks to use micro-bridging experiments as means to better understand the statistical nature of LWR. Microbridging analysis produces a statistical distribution of "discrete bridging events" that encompasses practical variations across scanner, track and resist. Micro-bridging and LWR experiments are done using a 1.2 NA immersion system on 45 nm space structures (90 nm pitch) as a means to demonstrate the concept, but the methodology can also be used to study EUVL processes as the technology matures. The understanding of the RLS performance tradeoffs enables TEL to develop future hardware and processes that support industry scaling goals.

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Section: Line Width Roughness (Lwr)supporting

confidence: 58%

Resist fundamentals for resolution, LER, and sensitivity (RLS) performance tradeoffs and their relation to micro-bridging defects

Rathsack

Nafus

Hatakeyama

et al. 2009

Advances in Resist Materials and Processing Technology XXVI

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“…6 Many studies have revealed that most important process in CAR is post-exposure bake (PEB) process because deprotection reaction and diffusion kinetics of acid generated from photoacid generator (PAG) directly determines resolution and sensitivity. [8][9][10][11][12] Especially suppression of acid diffusion is dominant contributor to improve resolution and LWR in such a narrow pitch patterning. This approach, however, causes sensitivity loss, therefore, different material designs are strongly required based on a comprehensive understanding of reaction and diffusion processes during PEB process.…”

Section: Introductionmentioning

confidence: 99%

Novel EUV resist materials design for 14nm half pitch and below

et al. 2014

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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.

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“…CAR serves as a key technology for photolithography of 20 nm hp patterning and below because of its high sensitivity and resolution [6]. Many studies have revealed that most important process in CAR is post-exposure bake (PEB) process because deprotection reaction and diffusion kinetics of acid generated by photoacid generator (PAG) directly determines resolution and sensitivity [7][8][9][10][11][12]. Therefore, tight control of acid diffusion and deprotection reaction opens up key routes to improve resolution and sensitivity with a reasonable process window.…”

Section: Introductionmentioning

confidence: 99%

EUV Resist Materials Design for 15 nm Half Pitch and Below

Tsubaki

Tarutani

Inoue

et al. 2013

J. Photopol. Sci. Technol.

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Chemically amplified resist materials with a different sensitivity were prepared to investigate impact of sensitivity on resolution at 15 nm half-pitch (hp) using a EUV microfield exposure tool (MET) at SEMATECH Berkeley. Sensitivity at least slower than 30 mJ/cm 2 was required to resolve 15 nm hp patterns using current EUV resists. It is noteworthy that resolution of 15 nm hp was limited by not only pattern collapse but also pinching of patterns. The same tendency is observed in E-beam patterning at 20 nm hp. A strong relationship between pinching and sensitivity in E-beam exposure indicates contribution of photon-shot noise on the pinching. Clear correlation between diffusion length and pinching using the E-beam exposure indicates that acid diffusion is another contributor on the pinching. Bound PAG into polymer and molecular PAG with a big anchor group showed almost same character on pinching. Key conclusion here is even in a molecular PAG, we can control acid diffusion to achieve 15 nm hp resolution capability. Strategy to improve sensitivity is to utilize resist with high deprotection efficiency. Polymer with a low thermal activation energy on deprotection (low Ea polymer) was demonstrated as a key technology to achieve 15 nm hp resolution with a faster sensitivity below 26 mJ/cm 2. Special rinse material was effective for reducing LWR by ~ 20%. Sensitivity dependency of outgassing have been systematically discussed at first. A good linear correlation between a cleanable outgassing amount and exposure energy strongly indicates tradeoff relationship between outgassing and sensitivity. Applying a new EUV topcoat to resist demonstrated reduction of outgassing from 7.39 nm to below 0.1 nm with maintaining resolution.

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A study on the material design for the reduction of LWR

Cited by 6 publications

References 11 publications

Resist fundamentals for resolution, LER, and sensitivity (RLS) performance tradeoffs and their relation to micro-bridging defects

Resist fundamentals for resolution, LER, and sensitivity (RLS) performance tradeoffs and their relation to micro-bridging defects

Novel EUV resist materials design for 14nm half pitch and below

EUV Resist Materials Design for 15 nm Half Pitch and Below

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