| 摘要 |
An automatic alignment apparatus comprises reference marks formed at the right-hand and left-hand sides of each of a semiconductor wafer and a mask, each of the reference marks comprising two mark elements extending in two different directions. These reference marks are formed such that when the mask and wafer are overlapped with each other, diffracted lights in different directions are produced from adjacent ones of the mark elements on the mask and wafer. A first and a second source of coherent light are provided for illuminating the right-hand and the left-hand marks, respectively, on the mask and wafer with a coherent spot light. First and second scanning means are provided for scanning the right-hand and the left-hand marks, respectively, on the mask and wafer by the spot light so that the diffracted lights are produced from the mark elements of the wafer and mask in one stroke of scanning. First to fourth detector means are used for respectively detecting the diffracted lights in one direction and the diffracted lights in the other direction produced from the right-hand marks on the wafer and mask and the diffracted lights in one direction and the diffracted lights in the other direction produced from the left-hand marks on the wafer and mask and for photoelectrically converting the diffracted lights respectively. Wafer and mask position signals for the alignment of the wafer and mask may be separately produced by the first to fourth detector means.
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