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16 December 1992 An automatic angular positioning of mask with wafer using modified moire technique
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Proceedings Volume 1622, Emerging Optoelectronic Technologies; (1992)
Event: Emerging OE Technologies, Bangalore, India, 1991, Bangalore, India
An automatic and accurate technique for angular positioning of mask with respect to wafer is reported.. Alignment marks are in the form of gratings and the moire signal is obtained by the relative displacement between the gratings. The higher slope region of the moire signal is used to obtain higher sensitivity and better position control accuracy. The experiments are performed with 25 micrometer pitch gratings and Piezo- Electric Transducer is used for the angular displacement. The angular -7 accuracy of the order of 2 x 10 radian is reported with a time constant of 0.2 sec. In the recent years, use of moire interference technique for mask to wafer alignment has attracted much attention especially in VLSI fabrication technology where a highly accurate linear and angular positioning is involved. In this technique the alignment marks are in the form of gratings. A laser beam is passed normally through a mask grating and reflected from the wafer grating. Intensity variation in the reflection mode due to relative angular rotation is detected by a photodetector and converted into the electrical signal, known as moire signal.
© (1992) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Brahm Pal Singh, Dr. Kowsalya, Rina Sharma, Ram Narain, Alok K. Kanjilal, Ramesh P. Singh, Vijay Trimbak Chitnis, and Yoshihisa Uchida "An automatic angular positioning of mask with wafer using modified moire technique", Proc. SPIE 1622, Emerging Optoelectronic Technologies, (16 December 1992);


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