Patent Number: 053655613
Section: summary

FIELD OF THE INVENTION AND RELATED ART This invention relates to exposure control in an exposure apparatus for use in the manufacture of semiconductor microcircuits. More particularly, the invention is concerned with exposure control suitably usable in an X-ray exposure apparatus, for example, for exposing a mask and a wafer with a radiation (X-rays) from a synchrotron or otherwise to print a pattern of the mask upon the wafer. In prior art X-ray exposure apparatuses, the amount of exposure is controlled in the following manner: (1) From the sensitivity, to X-rays used, of a radiation-sensitive material (called a "resist") applied to a wafer and from the illuminance in the field of irradiation of the X-rays from a source (the illuminance being determined from experience), the exposure time for the whole irradiation field on the wafer is determined. PA1 (2) An alternative is such that, as disclosed in Japanese Laid-Open Patent Application, Laid-Open No. Sho 60-198726, an X-ray detector is provided in the X-ray irradiation field and, while taking into account the variation in the X-ray illuminance with time, the exposure time for the whole irradiation field is determined. SUMMARY OF THE INVENTION In these prior art examples, the exposure time is determined uniformly over the entire irradiation field or an exposure region on a wafer. This involves a problem that, when there is non-uniformness in illuminance within the exposure region on the wafer, it is difficult to assure correct exposure throughout the exposure region. This causes inconveniences. For example, in X-ray lithography wherein a pattern of a linewidth on an order of 0.25 micron may be printed, it is possible that a semiconductor device formed on a wafer does not operate with a desired performance. The non-uniformness in illuminance may be reduced by placing a radiation source far remote from a mask and a wafer. With this method, however, the illuminance itself within the whole exposure region on the wafer is reduced. It is accordingly a primary object of the present invention to provide a system for controlling exposure in an exposure apparatus such as an X-ray exposure apparatus, by which the amount of radiation absorbed by a radiation-sensitive material in an exposure region can be made substantially uniform throughout every portion of the exposure region even if non-uniformness in illuminance is present within the exposure region. In accordance with one aspect of the present invention, to achieve this object, a shutter means having a leading edge and a trailing edge is provided and the moving speed of each of the leading edge and the trailing edge when they pass the exposure region for the controlled passage and interception of the radiation, is controlled to ensure that at different portions of the exposure region different exposure times are set as desired. These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.