Patent Number: 053352599
Section: summary

FIELD OF THE INVENTION AND RELATED ART This invention relates to an X-ray exposure apparatus which uses synchrotron radiation light as illumination light. Development of such semiconductor device manufacturing exposure apparatuses of the type that use synchrotron radiation light has advanced. Generally, the synchrotron radiation X-rays have a small divergence angle with respect to the direction (y-axis direction) perpendicular to the orbit plane of a charged particle accumulation ring (light source). To compensate for this, some measures may be required: for example, placing a swingable or fixed convex mirror on the path of light from the light source to a substrate such as a wafer to thereby expand the divergence angle with respect to the y-axis direction. The synchrotron radiation X-rays as expanded by such a mirror in the y-axis direction have an intensity distribution which is uniform in the direction (x-axis direction) perpendicular to the y-axis direction, but which is uneven in the y-axis direction. To compensate for this, it may be necessary to provide a shutter between the mirror and the substrate and to control the moving speed of the shutter. Alternatively, it may be necessary to control the scanning speed of a mask stage or a wafer stage. By these measures, non-uniformness of exposure amount due to the distribution of X-ray intensity may be corrected and non-uniform exposure of the substrate may be prevented. On the other hand, the substrate is placed in a reduced pressure chamber having a reduced pressure ambience of helium gas, for example. The synchrotron radiation X-rays expanded by the mirror go through a beam duct which is maintained under a vacuum of about 10.sup.-9 and, after passing through an X-ray transmission film such as a beryllium thin film, enter the reduced pressure chamber. The amount of X-ray absorption by such an X-ray transmission film is uneven due to non-uniformness in thickness of the film, for example. This causes non-uniform exposure of a substrate. When the tolerance of linewidth error for a fine pattern to be printed by exposure is .+-.2.5%, such non-uniform exposure resulting from the X-ray transmission film should desirably be not more than 1% (while taking into account the non-uniformness in exposure to be caused by a mask, for example, which is also to be irradiated). However, it has been found that, in a case when a beryllium film is used as the X-ray transmission film and when the center wavelength of the synchrotron radiation X-rays expanded by a mirror is 10 angstroms non-uniform exposure of 1% can be caused by even a very small non-uniformness in thickness of about 0.3 micron of the beryllium film. It is however very difficult to reduce the non-uniformness in thickness of the X-ray transmission film such as a beryllium film, to the very small amount as above. As an example, generally a beryllium film can be produced by a rolling method or a vacuum deposition method. With the rolling method, non-uniformness thickness easily occurs in a stripe-like fashion in the rolling direction. As a result, the thickness distribution has an approximately one-dimensional shape, in the direction perpendicular to the rolling direction. With the vacuum deposition method, while the non-uniformness is not as large as by the rolling method, there easily occurs non-uniformness of in thickness due to a vacuum deposition device or during the rolling operation to be executed after the deposition. In many cases, such non-uniformness also appears in a one-dimensional distribution. Usually, a beryllium film of a thickness of 20 microns has a non-uniformness in thickness of about 2-5 microns. Thus, the non-uniformness of exposure resulting from this largely exceeds the aforementioned tolerance. SUMMARY OF THE INVENTION It is accordingly an object of the present invention to provide an improved X-ray exposure apparatus by which non-uniform exposure due to such non-uniform thickness of an X-ray transmission film may be reduced considerably. It is another object of the present invention to provide an improved semiconductor device manufacturing method by which non-uniformness in exposure can be reduced and by which semiconductor devices of a higher degree of integration can be manufactured. 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.