Selectively patterned periodic metal nanodots are prospective for use in photonic, plasmonic and magnetic storage
devices. Here, we proposed a simple method to fabricate metal nanodots by block copolymer self-assembly and electron beam lithography. Block copolymer self-assembly is a facile method to fabricate periodic nanostructures such as cylinder and sphere in a large area. These self-assembled nanostructures are useful as templates and scaffolds for the fabrication of periodic metal nanodots. In this study, we used polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) and fabricated perpendicular PMMA cylinders onto substrate in PS matrixes. After UV irradiation and immersion in acetic acid, cylindrical nanopores of PS were fabricated. We performed electron beam lithography onto these PS nanoporous thin films. PS is negative tone resist for electron beam lithography. If the electron dose was enough large for PS resist, nanoporous structures were fabricated only in exposed areas after development by solvent, which dissolves PS. We evaporated Au onto these patterned nanoporous templates and sonicated these metal evaporated films in tetrahydrofuran (THF). In consequence, metal nanodots were fabricated only in exposed areas. The diameter and pitch of these nanodots were approximately 20 nm and 40 nm, respectively. These values were almost equal to block copolymer self-assembled cylinder structures. Finally, we demonstrated a simple method for fabricating periodic metal nanodots only in selective areas.
Due to potential applications of Extreme Ultraviolet Lithography (EUVL) to 22 nm half-pitch (hp) generations, EUVL
is well researched. However, current SEMI standards about the chuck are based on only the local slope of roughness.
Herein chuck standards, which consider the spatial frequency of the chuck surface roughness as well as the local slope of
the shape, are proposed by examining the chuck roughness. To prevent a mask pattern shift when an EUVL mask is
clamped by an electrostatic chuck, the roughness height must be limited. Thus, the in-plane distortion (IPD) and
out-of-plane distortion (OPD) are introduced to evaluate the mask pattern shift. This research utilizes ANSYS to evaluate
the relationship between the spatial frequency of chuck roughness and IPD/OPD induced on the mask surface after an
EUVL mask is clamped by the chuck.
The IPD depends on the local slope of the surface roughness shape of the electrostatic chuck (ESC) as well as the
spatial frequency of the roughness. Therefore, re-polishing the chuck surface can decrease IPD. Moreover, the spatial
frequency of roughness must be considered when a mask pattern shift correction is performed according to the surface
roughness shape of the EUVL mask and ESC.
Profiling of optical surfaces with discontinuous steps by monochromatic interferometry has the ambiguity of multiples of a quarter wavelength. Wavelength-tuning interferometry can measure these surfaces with a unit of synthetic wavelength that is usually much larger than that of the original source. In order to solve this problem, the fractional phases of the interferograms before and after wavelength tuning should be carefully estimated. Phase-shifting interferometry with a mechanical phase shift by a PZT transducer determines the fractional phases of the interferograms with a resolution of better than one part in 250 of the wavelength. After subtracting the mechanical drift of the test surface during wavelength tuning, the absolute distance between the test surface and the reference surface is measured with an uncertainty better than a quarter wavelength. An optical flat with two gauge blocks 1 mm in height contacting the surface is measured by a Fizeau interferometer. Experimental results demonstrate that the surface profile can finally be measured with an accuracy of 20 nm.
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