| 摘要 |
PURPOSE:To enhance the alignment accuracy by a method wherein a change in the strength of an alignment signal with reference to the position coordinates of a stage is stored into a memory and the position of the stage is controlled on the basis of an output from the memory. CONSTITUTION:An alignment beam 1 scans an alignment mark on a wafer 108; when the beam 1 reaches an edge part of a mark 2, the scattered light is generated. This detection light and the direct light reach a space filter 6 via a lens 106 and a beam-slitter 101. Then, the scattered light which has passed through the filter 6 is converted into a digital signal by a photoelectric transduc er 7 and is then stored into a memory 113. This A/D conversion is executed synchronously with a position pulse which is generated by a laser interferometer 111 to calculate the position coordinates of a stage 109. As a result, when the stage 109 is scanned, a change in the strength of an alignment signal with reference to the position coordinates of the stage 109 is stored into a memory 113. Then, a CPU 115 calculates an alignment position on the basis of an output from the memory 113 and the position of the stage 109 is detected via a control ler 112. |
