Patent Number: 062722026
Section: summary

FIELD OF THE INVENTION AND RELATED ART This invention relates to an exposure method and, more particularly, to a proximity exposure method using X-rays, for example. The exposure method of the present invention is suitably applicable to the manufacture of various microdevices such as a semiconductor chip (e.g., IC or LSI), a display device (e.g., a liquid crystal panel), a detecting device (e.g., a magnetic head), and an image pickup device (e.g., a CCD), for example. FIG. 1 shows an example of an X-ray proximity exposure apparatus of a known type (Japanese Laid-Open Patent Application No. 2-100311). Denoted in the drawing at 1 is an X-ray source (light emission point) such as synchrotron orbital radiation (SOR), and denoted at 2 is an SOR X-ray beam being expanded in an X direction into a slit-like shape. Denoted at 3 is a convex mirror, made of SiC, for example, for expanding the slit-like X-ray beam 2 in a Y direction. Denoted at 2a is the X-ray beam having been expanded by the convex mirror 3 into an area shape. Denoted at 7 is a workpiece to be exposed, such as a semiconductor wafer having been coated with a resist, for example. Denoted at 10 is a mask. Denoted at 4 is a beryllium film for isolating an ambience at the SOR side and an ambience at the mask (and workpiece) side from each other. Denoted at 5 is a focal plane type shutter being provided for exposure amount adjustment. In an exposure operation, the mask 10 and the workpiece 7 are placed with a spacing (gap) of about 10 microns maintained therebetween. As the shutter 5 is opened, a slit-like high-luminance X-ray beam 2 from the SOR, for example, and being expanded into an area shape (X-ray beam 2a) by the convex mirror 3, is projected to the mask 10 and then to the workpiece 7, by which a pattern image of the mask 10 is transferred to the workpiece 7 at a unit magnification. As regards the X-rays in this case, a wavelength of about 0.5-20 nm is used. Therefore, in connection with the wavelength only, theoretically, a very high resolution of 0.05 micron (50 nm) or less will be obtainable. Practically, however, such a high-resolution mask itself is difficult to manufacture. If a mask of a nominal smallest linewidth of 0.05 micron is manufactured by use of a technique for production of a conventional mask of a smallest linewidth of 0.1 micron (100 nm), any positional error or any error in the line-and-space (linewidth and spacing) of a pattern produced will be transferred to a workpiece as a mask defect. It will cause a void in the pattern to be formed, or a positional deviation of the pattern. Further, a produced mask pattern may not have a proper linewidth or a sufficient thickness. On these occasions, a sufficient contrast will not be attainable, and the pattern will not be resolved satisfactorily. SUMMARY OF THE INVENTION It is accordingly an object of the present invention to provide an exposure method by which a pattern can be formed at a higher resolution and a higher precision, on the basis of a currently available X-ray exposure apparatus and a mask which can be produced in accordance with a current technique. It is another object of the present invention to provide an exposure method which enables accomplishment of resolution even in a strict condition under which the contrast is too low and the resolution is currently difficult to accomplish. 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.