| 摘要 |
PURPOSE:To expand the apparent focal depth of a projection align, at the same time, minimizing the reduction of its throughput by providing a special relationship between the characteristics of the open and close control of the shutter and the characteristics of the shift control of the optical axis direction. CONSTITUTION:The continuous shift of a wafer and the surface of a projected image in the optical axis direction is controlled so that the existence probability can be maximized at the two points apart in a distance approximately equal to the focal depth of a projection lens, and in the middle of such points, the existence probability is suppressed to an extent that no degradation of the contrast of the exposed resist pattern is invited. Thus, during an exposure period for a time, the surface of the projected image and the photosensitive board are shifted interrelatedly in the optical axis direction with the speed characteristics which are controlled in advance in order to maximize the existence probability at least two locations in the optical axis direction. Therefore, it is possible to obtain the expansion effect of the focal depth without lowering the processing capacity of the photosensitive board per hour extremely. Also, the illuminance variation characteristics of the illuminating rays on the mask are obtained in advance before the regular exposure to the photosensitive board. The total exposure amount for the shot area can be controlled accurately. |
