| 摘要 |
PROBLEM TO BE SOLVED: To directly evaluate the performance of the detection system and to obtain a high precision alignment by making the alignment marks having a different step construction on an object, integrally rotating the object, making measurements in plural conditions and confirming the measurements. SOLUTION: Two alignment marks are provided leaving a distance L on an Si wafer. The marks are provided with, for example, the steps havingλ/8 and 3λ/8 steps whereλis the wavelength of the frequency used by the detection optical system. Since signal distortion and the generation direction of offsets correspond to each other and if aberration residue exists in the detection system, error offsetsΔ1 andΔ2 are respectively generated in arrow signs of1 and of2 directions with respect to each mark and a distance L0 between the marks L0 becomes L+Δ1+Δ2. Then, a similar measurement is made by rotating the wafer by 180 degrees, error offsetsΔ1 andΔ2 are respectively generated in the signs of1 and of2 directions and the distance between the marks L180=L-Δ1-Δ2 is measured. Then, one half of the difference of two measured values (Δ1+Δ2) is made an evaluation value and the detection system is adjusted so that the value becomes less than a specified value. |
