SUBMICRON-DIMENSIONAL MEASUREMENT WITH 2-LASER-BEAM SCANNING USING AN ACOUSTOOPTIC DEFLECTOR

A new submicron-order dimensional measurement system using a two-laser-beam scanning method and measurement results are described. Two fine spot beams, slightly separated, which are generated from an acoustooptic deflector, are scanned at 0.02 mum steps on an object by driving a signal which has two frequency components. The synthetic light intensity distribution of the two beams is adjusted to a particular distribution according to the dimension to be measured by varying that of the frequency. The shape of the reflected light intensity signal is adjusted to the particular U-shaped signal by controlling the synthetic light intensity distribution. From the value of the frequency which controls the U-shaped signal, the submicron dimensions can be measured with accuracies of +/-0.02 mum.