Ryuji Ohnishi

Backexposure Effect in Chemically Amplified Resist Process upon Exposure to Extreme Ultraviolet Radiation

With the progress in the resist development toward the realization of 22nm high volume production using extreme ultraviolet (EUV) lithography, practical issues such as defects, filtering, and etching durability have recently attracted much attention. The side wall profile of resist pattern si s among such issues. Although EUV radiation is hardly reflected at the resist-underlayer boundary, secondary electrons generated in the underlayer sensitize acid generators in the resist. In this study, the backexposure effect on the side wall profile of line-and-space patterns was theoretically investigated. The potential difference between the resist and the underlayer and the absorption coefficient of the underlayer significantly affected the sidewall profile. The image quality at the bottom of the resist layer was also improved by increasing the absorption coefficient of the underlayer. # 2011 The Japan Society of Applied Physics

Optimization of Photoacid Generator in Photoacid Generation-Bonded Resist

We developed and evaluated a photoacid generator (PAG)-bonded resist, a chemical amplified (CA) resist for decreasing line edge roughness (LER) and increasing sensitivity in extreme ultraviolet lithography (EUVL) and electron beam (EB) lithography. We investigated many samples to find an effective for the PAG-bonded resist. Under EB exposure, the LERs and resolutions of the PAG-bonded resist and PAG-blended resist which uses the same PAG and base polymer were compared. It was confirmed that the LER and resolution of the PAG-bonded resist are better than those of the PAG-blended resist. An LER of 3.5 nm in 75 nm line-and-space (L/S) and a resolution of 25 nm space were achieved. Under EUV exposure, a sensitivity of 5.0 mJ/cm2 was achieved.

Transmission Measurement Using Extreme Ultraviolet Light for the Development of Extreme Ultraviolet Resist

A transmission measurement system with high accuracy was installed in the BL10 beamline of the NewSUBARU synchrotron facility. We measured the transmittance of a resist using extreme ultraviolet (EUV) light, and evaluated the relation between the E0 sensitivity and the transmittance of the resist under EUV exposure. The measured transmittance was almost the same as the calculated value obtained using from the table of Henke atomic scattering factors. Furthermore, it is confirmed that there is a correlation between the photoabsorption coefficient of the anion of PAG and the E0 sensitivity under EUV exposure at a wavelength of 13.5 nm. Thus, increasing the atomic photoabsorption cross section of the anion of PAG is effective in increasing the sensitivity of the chemically amplified resist in EUVL.

Extreme Ultraviolet Resist Development at the University of Hyogo

A resist for extreme ultraviolet (EUV) lithography requires a small line edge roughness (LER) and a high sensitivity. The achievements of a small LER and a high sensitivity are discussed. One of the candidates for an EUV resist is a main-chain-decomposition-type chemically amplified (CA) resist, such as a methacrylate resist. As a result of outgassing-mass analysis of a methacrylate resist under EUV exposure, we confirmed that the main chain decomposed and this resist has a low outgassing rate compared with an ESCAP-type resist which is a high-annealing-temperature-type CA resist. Another candidate is a photo acid generator (PAG)-bonded CA resist, which has an advantage of a uniform density distribution in the resist system. This resist has an E0 sensitivity of 1.9 mJ/cm2 and a low outgassing rate under EUV exposure. Furthermore, a PAG-bonded resist has a LER of 3 nm (3σ) and a resolution of 30 nm under electron beam (EB) exposure. It is expected that a PAG-bonded CA resist has a good capability to achieve a small LER and high sensitivity for an EUV resist of a 32 nm node.

Development of under layer material for EUV lithography

For the next generation lithography (NGL), several technologies have been proposed to achieve the 22nm-node devices and beyond. Extreme ultraviolet (EUV) lithography is one of the candidates for the next generation lithography. For lithography processes, the Line width roughness (LWR) and the pattern collapse of resist are the most critical issues for NGL, because of the small target critical dimension (CD) size and high aspect ratio. In this study, we design the new concept of EUV Under layer (UL) material to meet these requirements and study the impact of polymer design for pattern collapse behavior, pattern profile and LWR control by using EUV exposure tool.

Development of Low Line Edge Roughness and Highly Sensitive Resist for Extreme Ultraviolet Lithography

We developed a novel chemically amplified resist to increase sensitivity and reduce line edge roughness (LER) in extreme ultraviolet (EUV) lithography. This resist consists of a base resin of which a photochemical acid generator (PAG) is bonded to the side chain this is called the PAG-bonded resist. Under EUV exposure, an E0 sensitivity of 1.9 mJ/cm2 and a low outgassing pressure of 2.5×10-6 Pa were achieved. Resolution and LER were obtained by electron beam (EB) exposure. Under EB exposure, an LER of 2.1 nm (3σ) for a 100 nm line and space (L/S) pattern was achieved by the PAG-bonded base resin. In addition, we improved this resist and an LER of 4.0 nm (3σ) for a 50 nm L/S pattern was achieved under EB exposure. These results demonstrate that the novel resist system has a good advantage in terms of high sensitivity and low LER.