| 摘要 |
PURPOSE:To eliminate virtual displacement of position by making equal the magnification factors of magnified pictures of a pair of alignment marks through disposition of compensating lens in the optical paths branched by the half mirror. CONSTITUTION:The light reflected from the alignment mark 12 of mask 11 passes the optical path A and focuses a picture 12' with magnification factor MA, when a concave lens 28 with focal distance fc is inserted into the optical path B of the mark 14 of wafer 15, the focal point moves to the point 14'' from 14'. When the distance between the lens 28 and the positions 14', 14'' is respectively considered as a and b, the mangification factor MB'=S4/S3Xb/a,b=(1/fc +1/a)<-1>. Therefore, when MB'=MA by selecting fc, and the distance between the optical axis 9a of the objective lens 9 and the alignment marks 12, 14 is R, a virtual displacement (MAXMB')XR can be reduced to zero. Moreover, further accurate alignment can be realized under the conditions that the interval epsilon between the wafer 15 and mask 11 is smaller than 10mun, the mark 12 of mask is composed of the parallel two lines in the width of 10mun or less and the mark 14 of mask consists of the lines in the width of 10um or less radially arranged for the center of exposing area. |
