Title :
Automatic angular alignment in mask aligner using computer controlled moire technique
Author :
Furuhashi, H. ; Hayashi, N. ; Watanabe, S. ; Higa, S. ; Uchida, Y. ; Singh, B.P. ; Kashyap, K.
Author_Institution :
Aichi Inst. of Technol., Toyota, Japan
Abstract :
A novel method for the automatic alignment of masks with respect to a wafer in a mask-aligner is developed and reported. Alignment marks are used in the form of gratings of 25 μm pitch. The effect of various parameters on moire fringes is studied theoretically and experimentally, and the results are found to be in good agreement. A computer controlled moire sensor is employed to obtain the angular alignment accuracy of the order of ±130 nanoradians. This high accuracy is maintained for more than 5 minutes. Feasibility experiments are performed for wafers of various sizes and very high accuracy is obtained in each case
Keywords :
diffraction gratings; integrated circuit manufacture; manufacturing processes; masks; moire fringes; process control; spatial variables control; alignment accuracy; automatic angular alignment; computer controlled moire technique; feasibility experiments; gratings; mask aligner; Automatic control; Circuits; Diffraction gratings; Energy consumption; Optical reflection; Optical sensors; Photodetectors; Signal generators; Signal processing; Very large scale integration;
Conference_Titel :
Industrial Electronics, Control, and Instrumentation, 1996., Proceedings of the 1996 IEEE IECON 22nd International Conference on
Conference_Location :
Taipei
Print_ISBN :
0-7803-2775-6
DOI :
10.1109/IECON.1996.566070
