Furaren Sogo Shinpojiumu Koen Yoshishu, 18, 125 (2000)

Fullerene derivatives as a 10-nm resolution electron beam resist

Furaren Sogo Shinpojiumu Koen Yoshishu, 18, 125 (2000)
T. Tada, T. Kanayama, A.P.G. Robinson, R.E. Palmer, M.T. Allen, J.A. Preece and K.D.M. Harris

A resist is one of the key elemenet of the electron beam (e-beam) lithography process. To realize nanofabrication using e-beam lithography, a resist material composed of small molecules is needed. We discovered that fullerene C60, whose molecular size is less than 1 nm, becomes insoluble in organic solvents after e-beam exposure. This means a C60 films works as a negative e-beam resist. However, its sensitivity is not high and the spin-coating method, which is commonly used for resist preparation, is not available for film preparation becuase of low viscosity of the solution. We discovered that chemical modification of C60 into so-called methanofullerene dramatically improves the resist properties

The methanfullerene (MTF) films are easily prepared by spin coating. The sensitivities of the methanofullerene resist are around 10^-3 C/cm^2 and one order of magnitude higher than that of C60 resist (0.01 C/cm^2). They have very high resolution and high dry etch durability comparable to C60, making this material very attractive for use in 10 nm scale lithography. To demonstrate the good performance of the resists, the nanometer scale patterns were defined in MTF film on a Si substrate. Lines with a width of 10-20 nm were formed and shown in Figure 1.

Raman spectra measurements show disappearance of the pentagonal pinch mode and appearance of a glassy carbon like peak after e-beam irradiation, which suggests that the repsonse of this material to e-beam is due to fragmentation of the C60 cage. This will be discussed in more detail.

This work is partly supported by NEDO through the management of the Angstrom Technology Patnership (ATP).

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