Patent Number: 053902270
Section: summary

The present invention relates to an exposure apparatus wherein a pattern of an original is transferred or printed on a substrate facing the original with an exposure beam. In an exposure apparatus used for manufacturing semiconductor devices, a pattern formed in the original such as a mask or a reticle is projected onto a substrate such as a wafer or glass, using an exposure beam, by which a photoresist applied on the substrate is exposed to the pattern, so that the pattern is transferred onto the resist. In this case, means for limiting the exposure beam is provided, as the case may be, so as to prevent unnecessary portions of the exposure beam directed to the mask or the reticle from reaching the mask or the reticle. For example, in a pattern exposure for manufacturing an integrated circuit, scribe lines are provided around a regular square or rectangular circuit pattern area. The scribe lines have a width of 50-100 microns and have alignment marks for aligning the mask and the wafer. If the exposure beam is applied over the whole surface of the mask, the alignment marks in the scribe lines are also printed on the wafer together with the circuit pattern. One method of avoiding this is that blades having linear blocking edges are used to cover the scribe lines to prevent the scribe line from being exposed to the exposure beam. Particularly, in an X-ray exposure apparatus, the light (radiation) applied to the mask is not reflected by the mask but is absorbed thereby, and therefore, it is converted to thermal energy with the result of production of thermal deformation in a mask, as contrasted to the other exposure apparatus. Therefore, it is preferable that the means for limiting the exposure beam is provided to prevent the light from reaching the unnecessary part of the mask. SUMMARY OF THE INVENTION However, in such an apparatus as described above, the region to which the exposure beam is limited changes in accordance with the size of the circuit pattern, and therefore, the necessity results to move the blades in accordance with the size of the circuit pattern. This further necessitates an actuator and guiding mechanism for moving the blades in predetermined directions, thus making the entire structure of the apparatus complicated. Since the positioning of the blades has to be highly accurate, the guiding mechanism has to have high rigidity and high rectilinearity, and in addition, position detecting means having high resolution is required, with the result that the weight and the cost of the apparatus is increased. In the X-ray exposure apparatus, the use, as in the conventional apparatus, of the blades for limiting the exposure beam is effective to suppress the temperature rise attributable to the absorption of the exposure beam energy by the mask itself. However, this results in the temperature rise of the blade limiting the exposure beam. In the exposure apparatus, particularly, wherein the highly accurate alignment is required, even a small thermal deformation of a constituent member as well as the thermal deformation of the mask is a problem, and therefore, the temperature rise of the blades is not preferable. Accordingly, it is a principal object of the present invention to provide an exposure apparatus wherein the exposure beam is effectively limited, and the temperature rise is suppressed, with a simple structure. According to an aspect of the present invention, there is provided an exposure apparatus comprising exposure means for transferring a pattern of an original onto a substrate, deviation detecting means for detecting a deviation between alignment marks of the original and the substrate, positioning means for positioning the deviation detecting means and exposure beam limiting means for limiting the exposure beam provided by the exposure means, wherein the exposure beam limiting means is mounted integrally with the deviation detecting means. In an embodiment, four of the deviation detecting means are provided in the respective orientations different by 90 degrees, and the exposure beam limiting means is provided with a plate having a linear edge for limiting the exposure beam, and wherein an amount of projection of the edge into the exposure view angle region is not more than L.sub.A .times.l.sub.min /(2.times.L.sub.M) where L.sub.M and L.sub.A are distances, measured along the optical axis of the exposure beam, to the original from a point of origin of the divergence of the exposure beam provided by the exposure means and the edge of the plate, respectively; and l.sub.min is a length of a side of the minimum angle of view limited by the exposure beam limiting means. In an embodiment, the exposure beam limiting means is provided with a fine displacing means for displacing the plate in the direction perpendicular to the edge by a small distance. Thus, the deviation detecting means for detecting the amount of deviation between the original and the substrate facing each other and the exposure limiting means, are integrally moved by the positioning means during the operation. Therefore, it is not necessary to employ a moving and positioning means exclusively for the exposure beam limiting means. In addition, the positioning of the exposure beam limiting means is effected by the positioning of the deviation detecting means integral therewith relative to the alignment mark, and therefore, the position of the exposure beam limiting means is very accurately determined in accordance with the view angle. In an embodiment, the exposure beam limiting means is provided with cooling means, and therefore, even if the X-rays are used for the exposure beam, the temperature rise of the exposure beam limiting means is suppressed, thus assuring a highly precise alignment. When the deviation detecting means (alignment unit) having, as a principal function, for executing the positioning relative to the alignment mark on the scribe line carries the exposure beam limiting means (blade), the alignment unit moves in two dimensions in accordance with the change of the size of the view angle and the position in the scribe line where the alignment mark is depicted. For this reason, some problems arise. That is, the adjacent blades are more interfered with each other than in the conventional masking blade which is movable only in the direction perpendicular to the scribe line. In addition, the space required to allow movement of the blade has to be free and cannot accommodate any other parts. Accordingly, it is a second object of the present invention to provide an exposure apparatus wherein a blade for limiting the exposure beam is integral with the alignment unit with high compactness. According to this aspect of the present invention, there is provided an exposure apparatus comprising exposure means for transferring a pattern of an original onto a substrate, first exposure beam limiting means for limiting the exposure beam provided by the exposure means to an angle of view necessary and sufficient to irradiate the maximum angle of view, deviation detecting means for detecting the deviation between the alignment mark of the original and the alignment mark of the substrate, displacing means for displacing and positioning the deviation detecting means in accordance with a position of the alignment mark of the original and second exposure means control means having a blade in the form of a plate fixed to the deviation detecting means to further limit the exposure means to a proper angle of view, wherein the length of the blade measured in the direction perpendicular to the view angle limiting edge is slightly larger than (l.sub.EX -l.sub.min)/2, where l.sub.EX is a length of the maximum exposure view angle in the direction perpendicular to the view angle limiting edge; and l.sub.min is the length of the minimum exposure view angle in the same direction, and the length of the blade measured along the edge is slightly larger than l.sub.max +l.sub.STG, where l.sub.STG is a distance through which the detecting means moves along the edge by the displacing means, and adjacent ones of the blades are mounted to the deviation detecting means at different levels. With this structure, the view angle (irradiation area) in which the exposure beam is irradiated during the exposure operation is changeable from the maximum exposure view angle to the minimum exposure view angle in accordance with the size of the circuit pattern of the original, and in addition, the position of the alignment mark in the scribe line of the original changes together in two dimensions. In the alignment operation prior to the exposure operation, the deviation detecting means displaces in accordance with the position of the alignment mark to detect the alignment mark. Since the blade moves together, the blade can cover the portion not requiring the exposure, such as the scribe line. Also, since the dimensions of the blade are defined in the manner described above, they are made of sufficient and minimum dimensions so as to cover the portion not requiring the exposure over the entire range of the changeable view angle, thus minimizing the wasteful space. In other words, the exposure beam is limited properly by the positioning of the detecting means. 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.