抄録
Thid paper describes a mask-to-wafer alignment technique for submicron X-ray lithography. A new alignment method is proposed to detect lateral displacement in the wide gap range accurately. Wafer grating pitch is twice as large as the mask grating pitch in order to avoid gap fluctuation influence on the lateral displacement detection signal. The dependence of the lateral displacement detection signal on gap fluctuations is disscussed both theoretically and experimentally. A highly sensitive and stable lateral displacement detection signal is obtained at the specific gap. The signal has a triangular wavefrom and hardly varies by gap fluctuations of a few microns from the specific gap. The gap range where the stable signal can be obtained, is fifty times larger than that of the conventional dual grating method. These experimental results agreed well with the theoretical calculation. By combining the double-pitch dual grating method and the single grating method mentioned in the 1st report, accuracies of ±0.02 μm in both the gap and lateral displacement servo-controls are achieved.
