POSITION MARK AND USE THEREOF

Japanese Patent JPS57190317

A

PURPOSE:To detect the position of the mark position in a scanning direction and simultaneously one in a direction rectangular thereto, by determining the interval of stepwise differences constituted of grooves or projections as the function of the distance from th mark position. CONSTITUTION:The width SWX is scanned by beam equal to the mark length L in y direction to detect the x coordinate of the mark 4. The mark width W3= (x2+x3-x1-x4)/2 is obtained from the information available thereat with the scanning position SL=LX(W3-W2)/(W1-W2). The y coordinate of the mark 4 is previously almost cleared for the calculation of SL so that the scanning width SWY in x direction can be made narrower than in y direction to obtain y=(y1+ y2+y3+y4)/4 from the available information. In this constitution, mark position detection accuracy is the same as the case of L type for the scanning width SWY