縮小投影露光装置用合わせマークの高精度検出法 (第3報)

2波長・2傾角照明, 回折光検出方式

抄録

An alignment mark illumination and detection technique is described in which the alignment error caused by the alignment pattern depth and the resist thickness asymmetry is reduced. For the alignment mark, a diffraction pattern which gives a high contrast signal is used. 2-wavelength laser (488, 543 nm) is diverged in 2 directions by a double refraction prism and illuminates the alignment mark vertically and with 26.2 degree inclination. The first order diffraction light is detected. The variation in the detected signal is 30% in the range of 0.6-2.5 pm of pattern depth and resist thickness, compared with the signal detected by the single wavelength light illumination. The experimental result gives a detection error of ± 0.045 μm (3σ) for a wafer in the worst condition.