State-of-the-art lithography is often severely influenced by defects that are smaller than the resolution limit of the mask inspection system. However, the mask inspection suffers from noises comparable to signal of the small defect, due to illumination nonuniformity, laser speckle, and fluctuation of the sensor signal. In order to overcome these issues, we propose a novel mask defect inspection method that uses detection optics for polarization variation. This inspection method uses the variation of polarization states which are caused by form birefringence in the mask feature. Thus the defect signals in the polarization-variation image can be obtained with sufficient intensity for much smaller defects than the wavelength. However since pattern edges are especially emphasized in the polarization-variation images, the images can not faithfully be acquired the mask pattern. To avoid these problems, we simultaneously use both conventional transmitted inspection images and the polarization variation images. By using numerical simulation, this paper discusses the validity of the mask inspection method that detects the polarization variation. The simulated results show that this new inspection method is quite effective for 20-nm-size defect and smaller ones.
[1]
Satoshi Endo,et al.
Detection of half-tone PSM pinhole with DUV reflected light source
,
2002,
Photomask Japan.
[2]
Katsura Otaki,et al.
Polarization Effect on Signal from Optical ROM Using Solid Immersion Lens
,
2000
.
[3]
Osamu Suga,et al.
Study of EUVL mask defect inspection using 199-nm inspection tool with super-resolution method
,
2009,
Photomask Technology.
[4]
T. Gaylord,et al.
Formulation for stable and efficient implementation of the rigorous coupled-wave analysis of binary gratings
,
1995
.
[5]
M. Totzeck,et al.
Numerical simulation of high-NA quantitative polarization microscopy and corresponding near-fields
,
2001
.
[6]
Donis G. Flagello,et al.
Polarization influence on imaging
,
2005
.
[7]
Jari Turunen,et al.
Eigenmode method for electromagnetic synthesis of diffractive elements with three-dimensional profiles
,
1994
.
[8]
D. Flagello,et al.
Polarization effects associated with hyper-numerical-aperture (>1) lithography
,
2005
.
[9]
Konstantinos Adam,et al.
Polarization effects in immersion lithography
,
2005
.