回折格子による高精度位置合わせ法(第3報) : 単一・倍ピッチ2重回折格子法のプロセス適用性

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This paper describes the adaptability of a newly proposed mask-and-wafer alignment technique for semiconductor processing. This new single and double-pitch dual grating method uses gratings as alignment marks. Shape change in gratings due to processing and the consequent effect on gap and lateral displacement detection signals are discussed both theoretically and experimentally. When a gap detection signal has a sharp peak at a gap setting point where the aperture ratio is from 0.3 to 0.4,and when a lateral displacement detection signal has a simple triangular waveform where the aperture ratio is from 0.5 to 0.8,and the step width ratio is from 0.4 to 0.6,a high gap and lateral displacement detection accuracy is achieved. These theoretical calculations agreed well with experimental results. Transparent films such as resist, SiO_2,and poly-Si, and opaque films such as A1,which are deposited on a wafer grating mark during processing, decrease signal intensity because of the interference that results from the thickness of their multiple films. They also make the grating edge round, but they hardly change the signal waveform. High reflectivity films such as A1 only degrade the lateral displacement detection signal waveform due to multiple reflection between the mask and wafer. As this makes detection accuracy low, decreasing reflectivity is necessary.
公益社団法人精密工学会の論文
1989-06-05