Radiation and photochemistry of onium salt acid generators in chemically amplified resists

Tagawa, Seiichi; Nagahara, Seiji; Iwamoto, Toshiyuki; Wakita, Masanori; Kozawa, Takahiro; Yamamoto, Yukio; Werst, D.W.; Trifunac, A. D.

doi:10.1117/12.388304

Cited by 128 publications

(101 citation statements)

References 5 publications

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“…However, the reaction mechanisms of the pattern formation processes change drastically from the photochemistry in KrF/ArF photoresists to radiation chemistry in EUV/EB resists, 7-9 especially acid generation processes. 8 A standard resist pattern formation model of EUV CARs including radiation chemistry was proposed by Kozawa et al (2001). 9 Based on this model, the RLS trade-off problem of EUV resists has been improving steadily due to worldwide research efforts.…”

Section: -5mentioning

confidence: 99%

“…The difference between EB and EUV resists is the energy absorption processes. [7][8][9] The EB-and EUV-induced radiation chemistry in CARs has been discussed from the perspective of the configuration of spurs, acid yield, and acid distribution. 10 Recently our research group found that the resist sensitivity in the EUV/soft X-ray region can be estimated from the exposure results at any wavelength in this region 11,12 and also from the exposure results for EB.…”

Section: -5mentioning

confidence: 99%

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Estimation of resist sensitivity for extreme ultraviolet lithography using an electron beam

2016

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It is a challenge to obtain sufficient extreme ultraviolet (EUV) exposure time for fundamental research on developing a new class of high sensitivity resists for extreme ultraviolet lithography (EUVL) because there are few EUV exposure tools that are very expensive. In this paper, we introduce an easy method for predicting EUV resist sensitivity by using conventional electron beam (EB) sources. If the chemical reactions induced by two ionizing sources (EB and EUV) are the same, the required absorbed energies corresponding to each required exposure dose (sensitivity) for the EB and EUV would be almost equivalent. Based on this theory, we calculated the resist sensitivities for the EUV/soft X-ray region. The estimated sensitivities were found to be comparable to the experimentally obtained sensitivities. It was concluded that EB is a very useful exposure tool that accelerates the development of new resists and sensitivity enhancement processes for 13.5 nm EUVL and 6.x nm beyond-EUVL (BEUVL).

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Section: -5mentioning

confidence: 99%

Section: -5mentioning

confidence: 99%

Estimation of resist sensitivity for extreme ultraviolet lithography using an electron beam

2016

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“…We note that the peak in the secondary electron energy distribution is approximately 10 eV [25], and that such low energy electrons can have mean free paths of several nanometers [30]: these factors, combined with the "scavenging" picture [21], requires that these low energy electrons be accounted for carefully in CA materials. We note that it has been suggested that the PAG, through the scavenging effect, limits the range of thermalized electrons [20,21]. Figure 9 shows the results of a simulation that does so, and indicates that the beam broadening in the resist as a consequence of these processes is approximately 10 nm.…”

Section: Energy Deposition Distributionmentioning

confidence: 84%

“…This would lead one to imagine that the number of electrons necessary would have to be increased to account for the reduced probability of a "hit" on a PAG molecule. Recent work [20,21], however, has suggested that ionization events in the base polymer can also result in acid generation through an electron "scavenging" process, substantially increasing the efficiency with which incident electrons are converted into acid species. The situation in CA materials increases in complexity when one considers the role of acid diffusion and its effect on the developed image.…”

Section: Statisticsmentioning

confidence: 99%

Resist Requirements and Limitations for Nanoscale Electron-Beam Patterning

2002

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Electron beam lithography still represents the most effective way to pattern materials at the nanoscale, especially in the case of structures, which are not indefinitely repeating a simple motif. The success of e-beam lithography depends on the availability of suitable resists. There is a substantial variety of resist materials, from PMMA to calixarenes, to choose from to achieve high resolution in electron-beam lithography. However, these materials suffer from the limitation of poor sensitivity and poor contrast.In both direct-write and projection e-beam systems the maximum beam current for a given resolution is limited by space-charge effects. In order to make the most efficient use of the available current, the resist must be as sensitive as possible. This leads, naturally, to the use of chemically amplified (CA) systems. Unfortunately, in the quest for ever smaller feature sizes and higher throughputs, even chemically amplified materials are limited: ultimately, sensitivity and resolution are not independent. Current resists already operate in the regime of < 1 electron/nm 2 . In this situation detailed models are the only way to understand material performance and limits.Resist requirements, including sensitivity, etch selectivity, environmental stability, outgassing, and line-edge roughness as they pertain to, high-voltage (100 kV) direct write and projection electron-beam exposure systems are described. Experimental results obtained on CA resists in the SCALPEL ® exposure system are presented and the fundamental sensitivity limits of CA and conventional materials in terms of shot-noise and resolution limits in terms of electron-beam solid interactions are discussed.

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“…It is important to clarify the reaction mechanisms from the point of view of the effective development of microlithography techniques. Many papers on product analysis of acid genertor for KrF (248 nm) excimar laser and i-line (365 mn) have been reported [8][9][10][11][12][13]. And papers on flash photolysis of acid generator, such as a 347 nm nano-second flash and a 265 nm femto-second flash have been reported [14,15].…”

Section: Introductionmentioning

confidence: 99%