| 摘要 |
PURPOSE:To enable highly accurate inspection of superimposition by observing a change in diffraction patterns formed at prescribed intervals (d) and d/2 on a semiconductor substrate and by utilizing an intensity ratio between an odd- order diffracted light and an even-order diffracted light. CONSTITUTION:Diffraction gratings 11 of a grating interval (d) are drawn on a wafer 10. A coherent light is made to fall on the gratings 11, diffracted lights generated from the gratings 11 are observed by a one-dimensional counter, and thereby a diffraction pattern is obtained. Next, the waver 10 is shifted slightly and then disposed at a position reached by a shift of d/2, and diffraction gratings of an interval (d) are drawn. Then diffraction gratings 12 are formed and a diffraction pattern is obtained. After the diffraction patterns thus obtained are standardized, an intensity ratio between an odd-order light and an even-order light is taken. More precise superimposition can be realized in proportion as this ratio (the intensity of the odd-order light/the intensity of the even-order light) comes near to 0. |
