Patent Number: 053234405
Section: summary

FIELD OF THE INVENTION AND RELATED ART This invention relates to an exposure apparatus for the manufacture of semiconductor devices such as ICs, LSIs, etc. More particularly, the invention is concerned with an X-ray exposure apparatus which uses radiation light as exposure light (printing light). In another aspect, the invention is concerned with a mask which is usable in such an X-ray exposure apparatus. As for the exposure light source in the exposure apparatus, in many cases a light source which produces visible light or ultraviolet light is used. In the exposure process using such a light source, the possibility of damaging a mask is very small. However, in the exposure process which uses synchrotron radiation light as a light source, having recently been proposed in an attempt to allow printing of very fine patterns, it has been reported that there is a possibility of a change in the characteristics of a mask ("Radiation Damage Effects in Boron Nitride Mask Membranes Subjected to X-ray Exposures" by W. A. Johnson, R. A. Levy, D. J. Resnick, T. E. Sanders, A. W. Yanof, H. Betz, H. Hunber and H. Oertel, "Journal of Vacuum Science & Technology", B. Vol. 5, No. 1, Jan/Feb 1987). This generates a necessity of replacing an over-exposed mask and, in order to properly determine the timing of replacement, it is necessary to accurately detect the dose of each mask. However, conventional exposure apparatuses are not equipped with such a function. SUMMARY OF THE INVENTION Since conventional exposure apparatuses are not equipped with the function of detecting the dose of each mask, there is a possibility that during exposure the dose of the mask goes beyond the limit of an allowable dose, resulting in failure of correct exposure. Since the manufacture of ICs, LSIs, etc. based on radiation light involves several tens of repetitions of an exposure process and the exposure time itself should be controlled very strictly, if correct exposure ends in failure, all the preceding exposure processes are wasted. This is a heavy loss. It is accordingly a primary object of the present invention to provide an exposure apparatus with which the dose of each mask can be detected accurately. It is another object of the present invention to provide a mask suitably usable in such an exposure apparatus. In accordance with an aspect of the present invention, an X-ray exposure apparatus which uses radiation light as exposure light includes display means; detecting means for detecting in each exposure the amount of exposure absorbed by a mask during the exposure; storing means for memorizing an accumulated dose of the mask; and control means for causing said display means to display a dose of the mask, wherein the does to be displayed corresponds to the sum of the accumulated dose memorized in said storing means and the amount of exposure detected by said detecting means. Each mask may be equipped with such a storing means. The control means may be arranged to compare the sum of the accumulated dose and the detected exposure amount, with a predetermined allowable dose and to cause the display means to display the result of the comparison. Mask replacing means may be provided such that, when the control means discriminates an excess of the sum of the accumulated dose and the detected exposure amount beyond the predetermined allowable dose, the mask replacing means operates to replace the mask by another. Since in an exposure of a mask, the exposure amount (dose) of the mask in that exposure is detected by the detecting means and the exposure amount converted into an accumulated dose memorized in the storing means is displayed in the display means, it is possible to obtain an accurate dose of each mask. 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.