A microcomputer controlled alignment system using moire sensors

This paper deals with an automatic and precision alignment technique for proximity printing in x-ray lithography, using two pairs of moire gratings, with moire signals from each pair being 180.deg. out of phase with each other. We constructed an automatic and precision alignment experimental system which could measure both transmitted moire signals and reflected moire signals at the same time. The automatic alignment was achieved using transmitted moire signals and also reflected moire signals as a control signal for a stage driver. The alignment position of the system was monitored not only by a control signal but also by a non-control signal. The effect of transmitted and reflected moire signals upon alignment accuracy was discussed. We concluded that the technique using diffracted moire signals is a viable automatic and precision alignment technique.