回折格子によるマスクとウエハの間隙設定法

概要

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This paper presents a mask-wafer gap setting method for X-ray lithography, using dual gratings. The mask gratings and the wafer gratings are arranged at right angles with regard to each other, so that the diffraction light intensity varies only with the mask-wafer gap variation, independently from the lateral displacement. Two pairs of those dual gratings, which consist of different pitch mask gratings and same pitch wafer gratings, were used as gap setting marks. Diffraction light intensity differences ΔI(0.1) = I_1(0.1 - I_2(O.1) from those pairs were used for gap setting signal. In order to avoid the gap setting error caused by the ripples in the signal, the wafer stage was scanned for several microns in the gap direction. During scanning, ΔI and relative displacement of the wafer stage were sampled to calculate the regression line. The mask-wafer gap was set at the point where the regression line became zero. The gap setting point had good agreement with the calculated gap. A wide gap setting range, 0-60 μm, was obtained. Moreover, O.4 μm(3δ) gap setting repeatability has been achieved.
公益社団法人精密工学会の論文
1989-05-05