MEASUREMENT OF LINE WIDTH

PURPOSE:To precisely measure the actual dimension of exposure pattern line width by a method wherein a vernier pattern provided with a standard dimen sion pattern part and a variable dimension part is previously formed in a photo mask. CONSTITUTION:A vernier pattern 2 is previously formed in a photo-mask 1 to be arranged corresponding to the position of the monitor pellet of a wafer. The pattern 2 is provided with a standard dimension pattern part 3 and a variable dimension pattern part 4 adjacent to the pattern 3. Within the standard dimension pattern part 3, multiple standard dimension positive patterns 10, 11 mutually in equal line width and the standard dimension negative pattern 20, 21 in equal line width to that of the standard dimension positive patterns 10, 11 are alternately arrayed in one lateral line. The variable dimension pattern 4 is provided with variable dimension positive patterns 30, 31... and variable dimension negative patterns 40, 41... Within an exposure pattern, the line width can be measured precisely by detecting a linear position.