Abstract
The dissolution behavior of a simple combination of poly(4-hydroxystyrene) films and tetramethylammonium hydroxide aqueous solution was analyzed to gain a fundamental understanding of the ...effects of film thickness and alkaline concentration on the dissolution kinetics of chemically amplified resists. Films of four different thicknesses, from thick (approximately 900 nm) to thin (approximately 50 nm), were developed in 22 different developers of different concentrations. The dissolution behavior of each combination was observed using a quartz crystal microbalance. Differences in dissolution kinetics due to film thickness were observed even between relatively thick films such as 900 and 500 nm thick films in dilute developers. These differences were considered to be caused by the diffusion of the solution into the films. Thin films also showed characteristic behavior with dilution. This behavior was due to the interaction between the substrate and the films, unlike in the case of thick films.
Metal oxide nanocluster resists have recently attracted considerable attention for use in extreme ultraviolet lithography. In this study, radiation-induced reactions of carboxylic acids used as the ...ligands of metal oxide nanocluster resists were investigated using a pulse radiolysis method. Upon the irradiation of the aqueous solutions of calboxylic acids with an electron beam, radical dianions of carboxylates were generated under the basic condition. From the comparison between pulse radiolyses under acidic and basic conditions, the kinetics of the radical dianions was clarified. For aromatic carboxylates, anion radicals of carboxylic acids were generated through the reaction of their dianions with H2O. For unsaturated carboxylates, their radicals were generated through the reaction of their radical dianions with H2O. The carboxylic anions and vinyl groups were protonated for dianions of aromatic and unsaturated carboxylates, respectively. The proton dynamics control is important for the stable performance of metal oxide nanocluster resists.
Abstract
Understanding the dissolution kinetics of resist materials is essential for their efficient development. In this study, we investigated the dissolution kinetics of poly(4-hydroxystyrene) ...(PHS) with a weight-average molecular weight (
M
w
) of 8000–30 000 and a polydispersity index (
M
w
/M
n
) of 1.07–1.20. The dissolution kinetics of PHS films was observed in tetramethylammonium hydroxide (TMAH) aqueous developers by a quartz crystal microbalance (QCM) method. The TMAH concentration was changed from 0 to 2.38 wt%. The formation of a thick transient swelling layer at these
M
w
/M
n
values was suppressed compared with that at
M
w
/M
n
> 2. QCM data were analyzed using the polynomial regression to clarify the effects of
M
w
and
M
w
/M
n
on the dissolution kinetics in a narrow polydispersity region. Both dissolving and swelling kinetics largely depended on
M
w
/
M
n
.
M
w
had little effect in 2.38 wt% TMAH developer; however, it had a large effect on the swelling when 2.38 wt% TMAH developer was diluted.
The radiation-induced reactions of ligands play an important role in the sensitization of metal oxide nanocluster resists. However, the details in the radiation chemistry of ligands for metal oxide ...nanocluster resists are still unknown. In this study, the radiation-induced reactions of carboxylic acid ligands were investigated using a pulse radiolysis method. The rate constants for the reactions of molecular and ionic forms of tiglic, angelic, o-toluic, and p-toluic acids with hydrated electrons were determined. The rate constants for the reactions of tiglic, angelic, benzoic, o-toluic, and p-toluic acids with dodecane radical cations were also determined. The radical ions of tiglic and angelic acids were more unstable than those of benzoic, o-toluic, and p-toluic acids. The results obtained in this study indicate that the molecular structures of ligands affect their reactivity to cationic and anion species and the stability of their radical cations and anions.
The resolution of lithography used for the high-volume production of semiconductor devices has been improved to meet the market demands for highly integrated circuits. With the reduction in feature ...size, the molecular size becomes non-negligible in the resist material design. In this study, the excluded volume effects caused by adding high-concentration acid generators were investigated for triphenylsulfonium nonaflate. The resist film density was measured by X-ray diffractometry. The dependences of absorption coefficient and protected unit concentration on acid generator weight ratio were calculated from the measured film density. Using these values, the effects on the decomposition yield of acid generators, the protected unit fluctuation, and the line edge roughness (LER) were evaluated by simulation on the basis of sensitization and reaction mechanisms of chemically amplified extreme ultraviolet resists. The positive effects of the increase in acid generator weight ratio on LER were predominant below the acid generator weight ratio of 0.3, while the negative effects became equivalent to the positive effects above the acid generator weight ratio of 0.3 owing to the excluded volume effects.
Extreme ultraviolet (EUV) lithography is the most promising candidate technique for the high-volume production of semiconductor devices with half-pitches of sub-10 nm. An anion-bound polymer, in ...which the anion part of onium salts is polymerized, has attracted much attention from the viewpoint of the control of acid diffusion. In this study, we modeled the acid generation processes in the anion-bound chemically amplified resists upon exposure to EUV radiation and developed a Monte Carlo simulation code. Using the developed simulation code, the dependence of the quantum efficiency of acid generation on the concentration of acid generator units was calculated. The calculated quantum efficiencies well agreed with the experimental values with a fitting error of less than 10%. The thermalization distance was considered to be approximately 3 nm. The blur of proton distribution intrinsic to the reaction mechanisms of anion-bound chemically amplified resists was roughly estimated to be 4.5-6.5 nm.
The uniformity of acid generator distribution and the length of acid diffusion are serious problems in the development of resist materials used for the 16 nm node and below. Anion-bound polymers in ...which the anion part of onium salts is polymerized have attracted much attention for solving these problems. In this study, the reaction mechanism of an anion-bound polymer in cyclohexanone was clarified using pulse radiolysis. The design of an efficient electron and hole transfer system is essential to the enhancement of resist performance.
Extreme ultraviolet (EUV) lithography is the most promising candidate for the high-volume production of semiconductor devices with half-pitches of sub-10 nm. An anion-bound polymer (ABP), in which ...the anion part of onium salts is polymerized, has attracted much attention from the viewpoint of the control of acid diffusion. In this study, the acid generation mechanism in ABP films was investigated using electron (pulse), γ, and EUV radiolyses. On the basis of experimental results, the acid generation mechanism in anion-bound chemically amplified resists was proposed. The major path for proton generation in the absence of effective proton sources is considered to be the reaction of phenyl radicals with diphenylsulfide radical cations that are produced through hole transfer to the decomposition products of onium salts.
EUV lithography is one of candidates for the high-volume manufacturing of semiconductor devices with sub-10 nm critical dimension. An anion-bound polymer, in which the anion part of onium salts is ...introduced into main chain polymer, has attracted much attention for sub-10 nm fabrication. We have modeled the acid generation of anion-bound resists and developed a simulation code for facilitating the development and improvement of resist materials and processes for EUV lithography 1. In this study, the acid quantum efficiency of acid generation was investigated using the developed simulation code. The quantum efficiency did not depend on the thermalization distance. The increase in the efficiency of acid generation from an electronically excited state of the resist and the suppression of the reaction between phenyl radicals are important for the improvement of quantum efficiency.
EUV lithography is one of the most promising candidate technologies for high volume manufacturing(HVM) of 7nm node beyond. To apply EUV lithography to HVM, high resolution and fast sensitivity with ...low roughness are required. To improve sensitivity, we developed novel PAG that includes electron withdrawing group (EWG). The PAG showed high acid generation efficiency from our experimental results. Increasing proton source unit in resist matrix also produces high acid generation efficiency. By using the novel PAG and increasing proton source unit ratio in resist matrix, we developed novel resists that produces high resolution patterns with reasonable sensitivity.
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