Patent Number: 052767256
Section: summary

FIELD OF THE INVENTION AND RELATED ART This invention relates to an exposure system for transferring onto a workpiece a pattern formed on an original. More particularly, the invention is concerned with an exposure system which uses a synchrotron orbital radiation (SOR) beam as an exposure energy and which is arranged to execute axis alignment between the exposure beam and a pattern transferring exposure station of the exposure system. In the field of the manufacture of semiconductor microcircuit devices such as integrated circuits (ICs), large scaled integrated circuits (LSIs) and the like, many proposals have been made to an exposure system using X-rays of a wavelength of an order of 1-150 angstroms, for example, in an attempt to meet the requirement of higher-resolution printing with further increase in the density of semiconductor devices. Among these X-ray exposure systems, those which use a synchrotron orbital radiation beam having high luminance are considered effective. In such an exposure system, a mask and a wafer are disposed opposed to each other and in parallel to each other with a predetermined gap (clearance) maintained therebetween. A synchrotron orbital radiation beam is projected perpendicularly to the mask and the wafer, within a predetermined exposure area, by which a pattern formed on the mask is transferred onto the wafer having a suitable radiation-sensitive surface layer. Since, however, the structure of a light source device for providing the synchrotron orbital radiation beam is very bulky as compared with a simple light source device used in traditional exposure systems, it is difficult to provide a major assembly of an exposure system, including a pattern transferring exposure station, as a unit with such a synchrotron orbital radiation source device. In consideration of this difficulty, the major assembly of the exposure system has to be separated from the radiation source device. This results in the possibility of a change in the relative attitude of the radiation source device and the major assembly of the exposure system, which causes an undesirable change in the angle of incidence of the exposure beam upon the pattern transferring exposure station. If this occurs, the pattern of the mask can not be transferred correctly and accurately. Where a reflection mirror is used to set the angle of radiation of a synchrotron orbital radiation beam, if the set angle of such reflection mirror is not correct, the radiation beam flux can not impinge on a mask or wafer exactly perpendicularly or, in some cases, the position of incidence of the radiation beam flux deviates. SUMMARY OF THE INVENTION In consideration of the foregoing, the present invention aims at solving problems involved in the axis alignment between a pattern transferring exposure station of an exposure system and an exposure beam such as a synchrotron orbital radiation beam, to thereby allow the exposure beam to be projected perpendicularly upon an original or a workpiece, placed in the pattern transferring exposure station within a predetermined positional relationship and to execute higher-precision printing with less pattern transfer distortion. In another aspect, the invention aims at accomplishing the axis alignment with an inexpensive structure. Briefly, in accordance with an aspect of the present invention, there is provided an exposure system using a synchrotron orbital radiation beam, supplied from a radiation source, and including a pattern transferring exposure station effective to transfer, by exposure, a pattern formed on an original, such as a mask, onto a workpiece, such as a semiconductor wafer, wherein light in a visible region or a region adjacent thereto, which is contained in the synchrotron orbital radiation beam supplied from the radiation source, is used to accomplish axis alignment between the radiation source and the pattern transferring exposure station. This allows axis alignment without the necessity of an X-ray detector which is expensive. In one preferred form of the present invention, the exposure apparatus usable with a mask having a pattern and a wafer having a radiation-sensitive surface layer, for transferring with a radiation energy beam the pattern of the mask to the wafer, comprises: a mask supporting member for supporting the mask; PA1 a wafer supporting member for supporting the wafer; PA1 means for projecting a beam, which is thinner than the radiation energy beam and which advances along or about the axis of the radiation energy beam, upon said reflective member; PA1 means for observing a positional relationship between the indication pattern and a spot formed by projection of the thinner beam upon said reflective member; and PA1 means for correcting a relationship between the indication pattern and the spot, on the basis of the observation. a reflective member having a reflection surface and an indication pattern, said reflective member being supported by one of said mask supporting member and said wafer supporting member; In another preferred form, the exposure apparatus further comprises: a projector having an axis which is coaxial with or substantially coaxial with the axis of the radiation energy beam, said projector having a masking member which can be projected upon said reflective member supported by one of said mask supporting member and said wafer supporting member; an optical system effective to re-image the masking member projected upon said reflective member, said re-imaging optical system having an axis which is coaxial with the axis of the radiation energy beam; and means for correcting any inclination of said reflective member to bring the position of the image as formed as a result of the re-imaging into a predetermined relationship with respect to the axis of said re-imaging optical system. 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.