Abstract:
A projection exposure apparatus includes a projection optical system arranged to project a pattern onto a substrate, a holding portion arranged to hold an optical element which propagates light toward the projection optical system, a mask having a transmission portion and being disposed on or near an image plane or object plane of the projection optical system or a plane conjugate to the image plane and the object plane, an actuator arranged to drive the mask along a plane of an image of the optical element formed by the projection optical system, and a measurement device arranged to measure an intensity of light while the mask is driven. The light emerges from the optical element, and passes through the projection optical system and the transmission portion of the mask. The measurement device includes a measurement surface positioned at a plane conjugate to a pupil plane of the projection optical system or a plane spaced apart from the mask enough to separately detect respective rays emerging from plural points of the pupil plane and passing through the transmission portion.

Description:
FIELD OF THE INVENTION 
     The present invention relates to an exposure apparatus for transferring a pattern on a mask onto a photosensitive substrate via a projection optical system. Such an exposure apparatus is used in lithography in manufacturing, e.g., a semiconductor element. 
     BACKGROUND OF THE INVENTION 
     The manufacture of a semiconductor element or the like by photolithography uses a projection exposure apparatus for transferring a circuit pattern or the like formed on a master (to be referred to as a reticle hereinafter) such as a reticle or photomask to a semiconductor wafer or the like coated with a photosensitive agent. An exposure apparatus of this type must accurately transfer a pattern on a reticle to a wafer at a predetermined magnification (reduction ratio). To meet this demand, the exposure apparatus must exploit a projection optical system which exhibits good imaging performance and suppresses aberration. In recent years, a pattern exceeding the general imaging performance of an optical system is often transferred along with further miniaturization of a semiconductor device. The transfer pattern, therefore, is more sensitive to the aberration of the optical system than a conventional pattern. On the other hand, the projection optical system must increase the exposure area and numerical aperture (NA), which makes aberration correction more difficult. 
     In this situation, demands are arising from measuring imaging performance, e.g., aberration, particularly, wavefront aberration of the projection optical system while the projection optical system is mounted in the exposure apparatus, i.e., is actually used for exposure. This is because measurement of aberration enables more precise lens adjustment corresponding to the state and device design almost free from the influence of aberration. 
     To meet these demands, the image intensity distribution is measured by a knife edge or slit, as a conventional means of obtaining imaging performance while the projection optical system is mounted in the exposure apparatus. Alternatively, the contrast of a pattern having a specific shape such as a bar chart is obtained. 
     In the method of obtaining the image intensity distribution by a knife edge or slit, the S/N ratio of image intensity distribution measurement must be about 10 6  or more in a projection optical system used for semiconductor lithography. This value is difficult to achieve. 
     To obtain wavefront aberration in the method of obtaining the contrast by using a bar chart, the contrasts of many bar charts must be obtained from a rough pitch to a pitch exceeding the resolution limit. This is not practical in terms of the formation of bar charts and measurement labor. 
     Further, these methods do not allow measurement of wavefront aberration. 
     As a method of obtaining wavefront aberration, an interferometer is used. However, the interferometer is generally used as an inspection device in the manufacture of a projection optical system, and is not practically mounted in the exposure apparatus in terms of the technique and cost because an interferometer made up of a prism, mirror, lens, and the like, and an interference illumination system having good coherence must be arranged near a reticle stage or wafer stage in the method using the interferometer. In general, the space near the wafer stage or reticle stage is limited, and the sizes of the interferometer and illumination system must, therefore, be limited. Limitations are also imposed in terms of heat generating and vibration, and the interferometer is difficult to mount. With recent decreases in exposure wavelength, an interferometer light source having good coherence in the exposure wavelength region does not exist or is very expensive. Thus, it is not practical in terms of the technique and cost to mount an interferometer type aberration measurement device in a projection exposure apparatus. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a projection exposure apparatus having a function of measuring the imaging performance, particularly, wavefront aberration of a projection optical system in a projection exposure apparatus. 
     According to the present invention, the foregoing object is attained by providing a projection exposure apparatus comprising: a projection optical system for projecting a pattern on a substrate; a holding portion for holding an optical element which propagates light toward the projection optical system; a mask which is arranged near an image plane or object plane of the projection optical system or a plane conjugate to the image plane and object plane and has a transmission portion; an actuator for driving the mask along a plane of an image of the optical element formed by the projection optical system; and a measurement device for measuring an intensity of light which emerges from the optical element, and passes through the projection optical system and the transmission portion of the mask while the mask is driven. 
     In a preferred embodiment, the apparatus further comprises an arithmetic device for calculating aberration of the projection optical system on the basis of a measurement result of the measurement device. 
     In a preferred embodiment, the apparatus further comprises an arithmetic device for calculating ray aberration of the projection optical system on the basis of a measurement result of the measurement device. 
     In a preferred embodiment, the apparatus further comprises an arithmetic device for calculating wavefront aberration of the projection optical system on the basis of a measurement result of the measurement device. 
     In a preferred embodiment, the optical element is arranged near the object plane of the projection optical system, and the mask is arranged near the image plane of the projection optical system. 
     In a preferred embodiment, the optical element includes a mask having a transmission portion, and light is emitted toward the projection optical system by illuminating the mask serving as the optical element by an illumination system. 
     In a preferred embodiment, the optical element is arranged near the image plane of the projection optical system, and the mask is arranged near the object plane of the projection optical system. 
     In a preferred embodiment, the optical element includes a mask having a transmission portion, and light is emitted toward the projection optical system by illuminating the mask serving as the optical element by an illumination system. 
     In a preferred embodiment, the projection exposure apparatus further comprises an illumination system, the optical element includes a reflecting member, and the reflecting member reflects, toward the projection optical system, light which is emitted by the illumination system and is incident on the reflecting member via the projection optical system. 
     In a preferred embodiment, the apparatus further comprises a reflecting mirror for deflecting light which emerges from the optical element and passes through the projection optical system, and guiding the light to the mask. 
     In a preferred embodiment, the optical element is arranged near the object plane of the projection optical system, the mask is arranged near a plane conjugate to the object plane of the projection optical system, the projection exposure apparatus further comprises a first reflecting mirror arranged on the image plane side of the projection optical system, and a second reflecting mirror for reflecting, toward the measurement device, light which is reflected by the first reflecting mirror and passes through the projection optical system, and light which emerges from the optical element passes through the projection optical system, is reflected by the first reflecting mirror, passes through the projection optical system again, is reflected by the second reflecting mirror, and guided to the mask. 
     In a preferred embodiment, the optical element and the mask are arranged near the object plane of the projection optical system, the projection exposure apparatus further comprises a reflecting mirror arranged on the image plane side of the projection optical system, and light which emerges from the optical element passes through the projection optical system, is reflected by the reflecting mirror, passes through the projection optical system again, and is guided to the mask. 
     In a preferred embodiment, the optical element and the mask are arranged near the image plane of the projection optical system, the projection exposure apparatus further comprises a reflecting mirror arranged on the object plane side of the projection optical system, and light which emerges from the optical element passes through the projection optical system, is reflected by the reflecting mirror, passes through the projection optical system again, and is guided to the mask. 
     In a preferred embodiment, a predetermined region near the image plane or object plane of the projection optical system falls within an isoplanatic region of the projection optical system. 
     In a preferred embodiment, the light which emerges from a predetermined region near the image plane or object plane of the projection optical system sufficiently covers a pupil of the projection optical system. 
     According to another aspect of the present invention, the foregoing object is attained by providing a projection exposure apparatus comprising: an illumination system; a projection optical system for projecting a pattern on a substrate; a holding portion for holding a first mask having a first transmission portion between the illumination system and the projection optical system; a second mask which is arranged near an image-side focal position of the projection optical system and has a second transmission portion; an actuator for driving the second mask along an image plane of the projection optical system; and a measurement device for measuring a change in intensity of light which is emitted by the illumination system and passes through the first transmission portion, the projection optical system, and the second transmission portion while the second mask is driven. 
     In a preferred embodiment, the apparatus further comprises an arithmetic device for calculating aberration of the projection optical system on the basis of a measurement result of the measurement device. 
     In a preferred embodiment, the apparatus further comprises an arithmetic device for calculating ray aberration of the projection optical system on the basis of a measurement result of the measurement device. 
     In a preferred embodiment, the apparatus further comprises an arithmetic device for calculating wavefront aberration of the projection optical system on the basis of a measurement result of the measurement device. 
     In a preferred embodiment, the apparatus further comprises an imaging optical system for imaging an exit pupil of the projection optical system on a measurement surface of the measurement device. 
     In a preferred embodiment, the actuator drives the measurement device and the imaging optical system together with the second mask. 
     In a preferred embodiment, the second mask, the imaging optical system, and the measurement device constitute an integral measurement unit, and the actuator drives the measurement unit along the image plane of the projection optical system. 
     In a preferred embodiment, the first mask has a plurality of first transmission portions. 
     In a preferred embodiment, the first mask has a transfer pattern to be transferred to the substrate, in addition to the first transmission portion. 
     In still another aspect of the present invention, the foregoing object is attained by providing a projection exposure apparatus comprising: an illumination system; a projection optical system for projecting a pattern on a substrate; a first holding portion for holding a first mask having a first transmission portion between the illumination system and the projection optical system; a first reflecting mirror arranged on an image plane side of the projection optical system; a second mask which is arranged between the illumination system and the projection optical system and has a second transmission portion; a second reflecting mirror for deflecting, toward the second transmission portion, light which is emitted by the illumination system, passes through the first transmission portion and the projection optical system, is reflected by the first reflecting mirror, and passes through the projection optical system again; an actuator for driving the second mask in a predetermined plane; and a measurement device for measuring an intensity of light which is emitted by the illumination system, passes through the first transmission portion of the first mask and the projection optical system, is reflected by the first reflecting mirror, passes through the projection optical system again, is reflected by the second reflecting mirror, and passes through the second transmission portion of the second mask while the second mask is driven. 
     In a preferred embodiment, the apparatus further comprises an arithmetic device for calculating aberration of the projection optical system on the basis of a measurement result of the measurement device. 
     In a preferred embodiment, the apparatus further comprises an arithmetic device for calculating ray aberration of the projection optical system on the basis of a measurement result of the measurement device. 
     In a preferred embodiment, the apparatus further comprises an arithmetic device for calculating wavefront aberration of the projection optical system on the basis of a measurement result of the measurement device. 
     In a preferred embodiment, the first reflecting mirror includes a spherical mirror. 
     In a preferred embodiment, the second reflecting mirror includes a half-mirror which transmits light emitted by the illumination system toward the projection optical system, and reflects, toward the second transmission portion of the second mask, light which is reflected by the first reflecting mirror and passes through the projection optical system. 
     In still another aspect of the present invention, the foregoing object is attained by providing a projection exposure apparatus comprising: an illumination system; a projection optical system for projecting a pattern on a substrate; a holding portion for holding a first mask having a first transmission portion between the illumination system and the projection optical system; a second mask which is arranged near an object plane of the projection optical system and has a second transmission portion; a reflecting mirror arranged on an image plane side of the projection optical system, light which is emitted by the illumination system, passes through the first transmission portion and the projection optical system, is reflected by the reflecting mirror, and passes through the projection optical system again being incident on the second transmission portion; an actuator for driving the second mask along the object plane of the projection optical system; and a measurement device for measuring an intensity of light which is emitted by the illumination system, passes through the first transmission portion and the projection optical system, is reflected by the reflecting mirror, passes through the projection optical system again, and passes through the second transmission portion while the second mask is driven. 
     In a preferred embodiment, the apparatus further comprises an arithmetic device for calculating aberration of the projection optical system on the basis of a measurement result of the measurement device. 
     In a preferred embodiment, the apparatus further comprises an arithmetic device for calculating ray aberration of the projection optical system on the basis of a measurement result of the measurement device. 
     In a preferred embodiment, the apparatus further comprises an arithmetic device for calculating wavefront aberration of the projection optical system on the basis of a measurement result of the measurement device. 
     In a preferred embodiment, the reflecting mirror includes a spherical mirror. 
     In still another aspect of the present invention, the foregoing object is attained by providing a projection exposure apparatus comprising: a substrate stage; a projection optical system for projecting a pattern on a substrate on the substrate stage; a first mask which is arranged between the projection optical system and the substrate stage and has a first transmission portion; and illumination system for illuminating the first transmission portion; a second mask which is arranged between the projection optical system and the substrate stage and has a second transmission portion; a reflecting mirror arranged on an object side of the projection optical system, light which is emitted by the illumination system, passes through the first transmission portion and the projection optical system, is reflected by the reflecting mirror, and passes through the projection optical system again being incident on the second transmission portion; an actuator for driving the second mask along an image plane of the projection optical system; and a measurement device for measuring an intensity of light which is emitted by the illumination system, passes through the first transmission portion and the projection optical system, is reflected by the reflecting mirror, passes through the projection optical system again, and passes through the second transmission portion while the second mask is driven. 
     In a preferred embodiment, the apparatus further comprises an arithmetic device for calculating aberration of the projection optical system on the basis of a measurement result of the measurement device. 
     In a preferred embodiment, the apparatus further comprises an arithmetic device for calculating ray aberration of the projection optical system on the basis of a measurement result of the measurement device. 
     In a preferred embodiment, the apparatus further comprises an arithmetic device for calculating wavefront aberration of the projection optical system on the basis of a measurement result of the measurement device. 
     In a preferred embodiment, the reflecting mirror includes a spherical mirror. 
     In still another aspect of the present invention, the foregoing object is attained by a method of measuring aberration of a projection optical system in a projection exposure apparatus for projecting a pattern on a substrate via the projection optical system, the projection exposure apparatus having a projection optical system for projecting a pattern on a substrate, a holding portion for holding an optical element which propagates light toward the projection optical system, and a mask which is arranged near an image plane or object plane of the projection optical system or a plane conjugate to the image plane and object plane and has a transmission portion, the method comprising: the measurement step of measuring an intensity of light which emerges from the optical element, and passes through the projection optical system and the transmission portion of the mask while the mask is driven along a plane of an image of the optical element formed by the projection optical system; and the arithmetic step of calculating aberration of the projection optical system on the basis of a measurement result obtained in the measurement step. 
     In still another aspect of the present invention, the foregoing object is attained by providing a method of measuring aberration of a projection optical system in a projection exposure apparatus for projecting a pattern on a substrate via the projection optical system, the projection exposure apparatus having an illumination system, a projection optical system for projecting a pattern on a substrate, a holding portion for holding a first mask having a first transmission portion between the illumination system and the projection optical system, and a second mask which is arranged near an image-side focal position of the projection optical system and has a second transmission portion, the method comprising: the measurement step of measuring a change in intensity of light which is emitted by the illumination system and passes through the first transmission portion, the projection optical system, and the second transmission portion while the second mask is driven along an image plane of the projection optical system; and the arithmetic step of calculating aberration of the projection optical system on the basis of a measurement result obtained in the measurement step. 
     In still another aspect of the present invention, the foregoing object is attained by providing a method of measuring aberration of a projection optical system in a projection exposure apparatus for projecting a pattern on a substrate via the projection optical system, the projection exposure apparatus having an illumination system, a projection optical system for projecting a pattern on a substrate, a first holding portion for holding a first mask having a first transmission portion between the illumination system and the projection optical system; a first reflecting mirror arranged on an image plane side of the projection optical system, a second mask which is arranged between the illumination system and the projection optical system and has a second transmission portion, and a second reflecting mirror for deflecting, toward the second transmission portion, light which is emitted by the illumination system, passes through the first transmission portion and the projection optical system, is reflected by the first reflecting mirror, and passes through the projection optical system again, the method comprising: the measurement step of measuring an intensity of light which is emitted by the illumination system, passes through the first transmission portion of the first mask and the projection optical system, is reflected by the first reflecting mirror, passes through the projection optical system again, is reflected by the second reflecting mirror, and passes through the second transmission portion of the second mask while the second mask is driven in a predetermined plane; and the arithmetic step of calculating aberration of the projection optical system on the basis of a measurement result obtained in the measurement step. 
     In still another aspect of the present invention, the foregoing object is attained by providing a method of measuring aberration of a projection optical system in a projection exposure apparatus for projecting a pattern on a substrate via the projection optical system, the projection exposure apparatus having an illuminating system, a projection optical system for projecting a pattern on a substrate, a holding portion for holding a first mask having a first transmission portion between the illumination system and the projection optical system, a second mask which is arranged near an object plane of the projection optical system and has a second transmission portion, and a reflecting mirror arranged on an image plane side of the projection optical system, light which is emitted by the illumination system, passes through the first transmission portion and the projection optical system, is reflected by the reflecting mirror, and passes through the projection optical system again being incident on the second transmission portion, the method comprising: the measurement step of measuring an intensity of light which is emitted by the illumination system, passes through the first transmission portion and the projection optical system, is reflected by the reflecting mirror, passes through the projection optical system again, and passes through the second transmission portion while the second mask is driven along the object plane of the projection optical system; and the arithmetic step of calculating aberration of the projection optical system on the basis of a measurement result obtained in the measurement step. 
     In still another aspect of the present invention, the foregoing object is attained by providing a method of measuring aberration of a projection optical system in a projection exposure apparatus for projecting a pattern on a substrate via the projection optical system, the projection exposure apparatus having a substrate stage, a projection optical system for projecting a pattern on a substrate on the substrate stage, a first mask which is arranged between the projection optical system and the substrate stage and has a first transmission portion, an illumination system for illuminating the first transmission portion, a second mask which is arranged between the projection optical system and the substrate stage and has a second transmission portion, and a reflecting mirror arranged on an object side of the projection optical system, light which is emitted by the illumination system, passes through the first transmission portion and the projection optical system, is reflected by the reflecting mirror, and passes through the projection optical system again being incident on the second transmission portion, the method comprising: the measurement step of measuring an intensity of light which is emitted by the illumination system, passes through the first transmission portion and the projection optical system, is reflected by the reflecting mirror, passes through the projection optical system again, and passes through the second transmission portion while the second mask is driven along an image plane of the projection optical system; and an arithmetic step of calculating aberration of the projection optical system on the basis of a measurement result obtained in the measurement step. 
     In still another aspect of the present invention, the foregoing object is attained by providing a transfer method of transferring a pattern to a substrate by using a projection exposure apparatus, the projection exposure apparatus having a projection optical system for projecting a pattern on a substrate, a holding portion for holding an optical element which propagates light toward the projection optical system, and a mask which is arranged near an image plane or object plane of the projection optical system or a plane conjugate to the image plane and object plane and has a transmission portion, the method comprising: the measurement step of measuring an intensity of light which emerges from the optical element, and passes through the projection optical system and the transmission portion of the mask while the mask is driven along a plane of an image of the optical element formed by the projection optical system; the arithmetic step of calculating aberration of the projection optical system on the basis of a measurement result obtained in the measurement step; the adjustment step of adjusting the projection optical system on the basis of aberration obtained in the arithmetic step; and the transfer step of transferring a pattern to the substrate by using the projection exposure apparatus in which the projection optical system is adjusted. 
     In still another aspect of the present invention, the foregoing object is attained by providing a transfer method of transferring a pattern to a substrate by using a projection exposure apparatus, the projection exposure apparatus having an illumination system, a projection optical system for projecting a pattern on a substrate, a holding portion for holding a first mask having a first transmission portion between the illumination system and the projection optical system, and a second mask which is arranged near an image-side focal position of the projection optical system and has a second transmission portion, the method comprising: the measurement step of measuring a change in intensity of light which is emitted by the illumination system and passes through the first transmission portion, the projection optical system, and the second transmission portion while the second mask is driven along an image of the projection optical system; the arithmetic step of calculating aberration of the projection optical system on the basis of a measurement result obtained in the measurement step; the adjustment step of adjusting the projection optical system on the basis of aberration obtained in the arithmetic step; and the transfer step of transferring a pattern to the substrate by using the projection exposure apparatus in which the projection optical system is adjusted. 
     In still another aspect of the present invention, the foregoing object is attained by providing a transfer method of transferring a pattern to a substrate by using a projection exposure apparatus, the projection exposure apparatus having an illumination system, a projection optical system for projecting a pattern on a substrate, a first holding portion for holding a first mask having a first transmission portion between the illumination system and the projection optical system; a first reflecting mirror arranged on an image plane side of the projection optical system, a second mask which is arranged between the illumination system and the projection optical system and has a second transmission portion, and a second reflecting mirror for deflecting, toward the second transmission portion, light which is emitted by the illumination system, passes through the first transmission portion and the projection optical system, is reflected by the first reflecting mirror, and passes through the projection optical system again, the method comprising: the measurement step of measuring an intensity of light which is emitted by the illumination system, passes through the first transmission portion of the first mask and the projection optical system, is reflected by the first reflecting mirror, passes through the projection optical system again, is reflected by the second reflecting mirror, and passes through the second transmission portion of the second mask while the second mask is driven in a predetermined plane; the arithmetic step of calculating aberration of the projection optical system on the basis of a measurement result obtained in the measurement step; the adjustment step of adjusting the projection optical system on the basis of aberration obtained in the arithmetic step; and the transfer step of transferring a pattern to the substrate by using the projection exposure apparatus in which the projection optical system is adjusted. 
     In still another aspect of the present invention, the foregoing object is attained by providing a transfer method of transferring a pattern to a substrate by using a projection exposure apparatus, the projection exposure apparatus having an illumination system, a projection optical system for projecting a pattern on a substrate, a holding portion for holding a first mask having a first transmission portion between the illumination system and the projection optical system, a second mask which is arranged near an object plane of the projection optical system and has a second transmission portion, and a reflecting mirror arranged on an image plane side of the projection optical system, light which is emitted by the illumination system, passes through the first transmission portion and the projection optical system, is reflected by the reflecting mirror, and passes through the projection optical system again being incident on the second transmission portion, the method comprising: the measurement step of measuring an intensity of light which is emitted by the illumination system, is reflected by the reflection mirror, passes through the projection optical system again, and passes through the second transmission portion while the second mask is driven along the object plane of the projection optical system; the arithmetic step of calculating aberration of the projection optical system on the basis of a measurement result obtained in the measurement step; the adjustment step of adjusting the projection optical system on the basis of aberration obtained in the arithmetic step; and the transfer step of transferring a pattern to the substrate by using the projection exposure apparatus in which the projection optical system is adjusted. 
     In still another aspect of the present invention, the foregoing object is attained by providing a transfer method of transferring a pattern to a substrate by using a projection exposure apparatus, the projection exposure apparatus having a substrate stage, a projection optical system for projecting a pattern on a substrate on the substrate stage, a first mask which is arranged between the projection optical system and the substrate stage and has a first transmission portion, an illumination system for illuminating the first transmission portion, a second mask which is arranged between the projection optical system and the substrate stage and has a second transmission portion, and a reflecting mirror arranged on an object side of the projection optical system, light which is emitted by the illumination system, passes through the first transmission portion and the projection optical system, is reflected by the reflecting mirror, and passes through the projection optical system again being incident on the second transmission portion, the method comprising: the measurement step of measuring an intensity of light which is emitted by the illumination system, passes through the first transmission portion and the projection optical system, is reflected by the reflecting mirror, passes through the projection optical system again, and passes through the second transmission portion while the second mask is driven along an image plane of the projection optical system; the arithmetic step of calculating aberration of the projection optical system on the basis of a measurement result obtained in the measurement step; the adjustment step of adjusting the projection optical system on the basis of aberration obtained in the arithmetic step; and the transfer step of transferring a pattern to the substrate by using the projection exposure apparatus in which the projection optical system is adjusted. 
     In still another aspect of the present invention, the foregoing object is attained by providing a method of manufacturing a device by using a projection exposure apparatus, the projection exposure apparatus having a projection optical system for projecting a pattern on a substrate, a holding portion for holding an optical element which propagates light toward the projection optical system, and a mask which is arranged near an image plane or object plane of the projection optical system or a plane conjugate to the image plane and object plane and has a transmission portion, the method comprising: the measurement step of measuring an intensity of light which emerges from the optical element, and passes through the projection optical system and the transmission portion of the mask while the mask is driven along a plane of an image of the optical element formed by the projection optical system; the arithmetic step of calculating aberration of the projection optical system on the basis of a measurement result obtained in the measurement step; the adjustment step of adjusting the projection optical system on the basis of the aberration obtained in the arithmetic step; the transfer step of transferring a pattern to a photosensitive member of the substrate coated with the photosensitive member by using the projection exposure apparatus in which the projection optical system is adjusted; and the developing step of developing the photosensitive member bearing the pattern. 
     In still another aspect of the present invention, the foregoing is attained by providing a method of manufacturing a device by using a projection exposure apparatus, the projection exposure apparatus having an illumination system, a projection optical system for projecting a pattern on a substrate, a holding portion for holding a first mask having a first transmission portion between the illumination system and the projection optical system, and a second mask which is arranged near an image-side focal position of the projection optical system and has a second transmission portion, the method comprising: the measurement step of measuring a change in intensity of light which is emitted by the illumination system and passes through the first transmission portion, the projection optical system, and the second transmission portion while the second mask is driven along an image plane of the projection optical system; the arithmetic step of calculating aberration of the projection optical system on the basis of a measurement result obtained in the measurement step; the adjustment step of adjusting the projection optical system on the basis of the aberration obtained in the arithmetic step; the transfer step of transferring a pattern to a photosensitive member of the substrate coated with the photosensitive member by using the projection exposure apparatus in which the projection optical system is adjusted; and the developing step of developing the photosensitive member bearing the pattern. 
     In still another aspect of the present invention, the foregoing is attained by providing a method of manufacturing a device by using a projection exposure apparatus, the projection exposure apparatus having an illumination system, a projection optical system for projecting a pattern on a substrate, a first holding portion for holding a first mask having a first transmission portion between the illumination system and the projection optical system; a first reflecting mirror arranged on an image plane side of the projection optical system, a second mask which is arranged between the illumination system and the projection optical system and has a second transmission portion, and a second reflecting mirror for deflecting, toward the second transmission portion, light which is emitted by the illumination system, passes through the first transmission portion and the projection optical system, is reflected by the first reflecting mirror, and passes through the projection optical system again, the method comprising: the measurement step of measuring an intensity of light which is emitted by the illumination system, passes through the first transmission portion of the first mask and the projection optical system, is reflected by the first reflecting mirror, passes through the projection optical system again, is reflected by the second reflecting mirror, and passes through the second transmission portion of the second mask while the second mask is driven in a predetermined plane; the arithmetic step of calculating aberration of the projection optical system on the basis of a measurement result obtained in the measurement step; the adjustment step of adjusting the projection optical system on the basis of the aberration obtained in the arithmetic step; the transfer step of transferring a pattern to a photosensitive member of the substrate coated with the photosensitive member by using the projection exposure apparatus in which the projection optical system is adjusted; and the developing step of developing the photosensitive member bearing the pattern. 
     In still another aspect of the present invention, the foregoing is attained by providing a method of manufacturing a device by using a projection exposure apparatus, the projection exposure apparatus having an illumination system, a projection optical system for projecting a pattern on a substrate, a holding portion for holding a first mask having a first transmission portion between the illumination system and the projection optical system, a second mask which is arranged near an object plane of the projection optical system and has a second transmission portion, and a reflecting mirror arranged on an image plane side of the projection optical system, light which is emitted by the illumination system, passes through the first transmission portion and the projection optical system, is reflected by the reflecting mirror, and passes through the projection optical system, again being incident on the second transmission portion, the method comprising: the measurement step of measuring an intensity of light which is emitted by the illumination system, passes through the first transmission portion and the projection optical system, is reflected by the reflecting mirror, passes through the projection optical system again, and passes through the second transmission portion while the second mask is driven along the object plane of the projection optical system; the arithmetic step of calculating aberration of the projection optical system on the basis of a measurement result obtained in the measurement step; the adjustment step of adjusting the projection optical system on the basis of the aberration obtained in the arithmetic step; the transfer step of transferring a pattern to a photosensitive member of the substrate coated with the photosensitive member by using the projection exposure apparatus in which the projection optical system is adjusted; and the developing step of developing the photosensitive member bearing the pattern. 
     In still another aspect of the present invention, the foregoing is attained by providing a method of manufacturing a device by using a projection exposure apparatus, the projection exposure apparatus having a substrate stage, a projection optical system for projecting a pattern on a substrate on the substrate stage, a first mask which is arranged between the projection optical system and the substrate stage and has a first transmission portion, an illumination system for illuminating the first transmission portion, a second mask which is arranged between the projection optical system and the substrate stage and has a second transmission portion, and a reflecting mirror arranged on an object side of the projection optical system, light which is emitted by the illumination system, passes through the first transmission portion and the projection optical system, is reflected by the reflecting mirror, and passes through the projection optical system again being incident on the second transmission portion, the method comprising: the measurement step of measuring an intensity of light which is emitted by the illumination system, passes through the first transmission portion and the projection optical system, is reflected by the reflecting mirror, passes through the projection optical system again, and passes through the second transmission portion while the second mask is driven along an image plane of the projection optical system; the arithmetic step of calculating aberration of the projection optical system on the basis of a measurement result obtained in the measurement step; the adjustment step of adjusting the projection optical system on the basis of the aberration obtained in the arithmetic step; the transfer step of transferring a pattern to a photosensitive member of the substrate coated with the photosensitive member by using the projection exposure apparatus in which the projection optical system is adjusted; and the developing step of developing the photosensitive member bearing the pattern. 
     Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the present invention and, together with the description, serve to explain the principles of the invention. 
         FIG. 1  is a view showing the optical path of a ray A which deviates from an ideal imaging point IP of an optical system with aberration; 
         FIG. 2  is a view showing the intensity distribution, of a beam having passed through a second transmission portion, on a light intensity distribution measurement device; 
         FIG. 3  is a view showing an example of a mask having a second transmission portion; 
         FIGS. 4A and 4B  are graphs showing the light intensity distributions of rays A and P shown in  FIG. 1  along the u and v axes on the measurement surface of the light intensity distribution measurement device; 
         FIG. 5  is a view for explaining a beam near the imaging point IP when the second transmission portion is a square aperture in an isoplanatic region; 
         FIGS. 6A and 6B  are graphs showing the light intensity distribution of beams A′ and P′ shown in  FIG. 5  along the u and v axes on the measurement surface of the light intensity distribution measurement device; 
         FIG. 7  is a schematic view showing a projection exposure apparatus according to the first embodiment of the present invention; 
         FIG. 8  is a view showing an example in which rectangular apertures are arrayed in a matrix as a first transmission portion; 
         FIG. 9  is a partial, enlarged view showing the second transmission portion T and light intensity distribution measurement device; 
         FIG. 10  is a graph for explaining the relationship between the exit pupil and the imaging plane of the projection optical system, a wavefront on the light intensity distribution measurement surface, and a ray; 
         FIG. 11  is a schematic view showing a projection exposure apparatus according to the second embodiment of the present invention; 
         FIG. 12  is a schematic view showing a second illumination system used for the projection exposure apparatus in  FIG. 11 ; 
         FIG. 13  is a schematic view showing a projection exposure apparatus according to the third embodiment of the present invention; 
         FIG. 14  is a schematic view showing a projection exposure apparatus according to the fourth embodiment of the present invention; 
         FIG. 15  is a view showing equations (3) to (6); 
         FIG. 16  is a view showing equations (7) to (12); 
         FIG. 17  is a view showing equations (13) to (16), (3′), (11′), and (12′); 
         FIG. 18  is a schematic view showing a projection exposure apparatus according to the fifth embodiment of the present invention; 
         FIG. 19  is a schematic view showing a projection exposure apparatus according to the sixth embodiment of the present invention; 
         FIG. 20  is a sectional view showing a measurement unit used in the projection exposure apparatus according to the sixth embodiment of the present invention; 
         FIG. 21  is a view for explaining an imaging state when the measurement unit moves; 
         FIG. 22  is a schematic view showing a projection exposure apparatus according to the seventh embodiment of the present invention; 
         FIG. 23 , is a partial, enlarged view showing the second transmission portion and light intensity distribution measurement device; 
         FIG. 24  is a schematic view showing a projection exposure apparatus according to the eighth embodiment of the present invention; 
         FIG. 25  is a partial, enlarged view showing the transmission portion and light intensity distribution measurement device; 
         FIGS. 26A and 26B  are graphs showing the light intensity distribution along with scan of a mask having a slit, in which  FIG. 26A  is a graph showing the light intensity of a principal ray, and  FIG. 26B  is a graph showing the light intensity as a function of the slit position; 
         FIG. 27  is a schematic view showing a projection exposure apparatus according to the ninth embodiment of the present invention; 
         FIG. 28  is an enlarged view showing the main part of the projection exposure apparatus according to the ninth embodiment of the present invention; 
         FIG. 29  is a schematic view showing a projection exposure apparatus according to the tenth embodiment of the present invention; 
         FIG. 30  is a flow chart showing a semiconductor device manufacturing process; and 
         FIG. 31  is a flow chart showing a wafer process. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The principle of the present invention will be explained. The present invention is based on the principle adopted in, e.g., the Foucalt test, wire test, phase modulation test, and Ronchi test (see, e.g., Daniel Malacara, “Optical Shop testing”, John Wiley &amp; Sons, Inc., page 231 (1978)). 
     In general, a beam coming from a point object converges to one imaging point in an ideal projection optical system free from any aberration, but does not converge to one point in the presence of aberration. 
       FIG. 1  shows the state of a beam near the imaging point. In  FIG. 1 , a ray A, which is emitted by an illumination system (not shown), passes through a first transmission portion (optical element) regarded as a point object formed on a first mask (not shown), passes through a projection optical system (not shown) and deviates from an ideal imaging performance IP. A second mask  17 M having a second transmission portion  17 T, and a light intensity distribution measurement device  18  for measuring the light intensity distribution of a beam having passed through the transmission portion  17 T are arranged near the imaging point. 
     Let coordinates (u, v) be the position of the second transmission portion  17 T on a plane perpendicular to the optical axis (not shown; vertical direction in  FIG. 1 ) of the projection optical system, and coordinates (x, y) be the position on the light intensity measurement surface of the light intensity distribution measurement device  18 . The position on the light intensity measurement surface of the light intensity distribution measurement device  18  is in one-to-one correspondence with the position on the exit pupil of the projection optical system. This can be realized by separating the light intensity distribution measurement device  18  from the image-side focal position of the projection optical system by a certain distance, or arranging an optical system which conjugates the position on the light intensity measurement surface and the position of the exit pupil of the projection optical system. 
     In  FIG. 1 , the ray A deviates from the ideal imaging point IP and is shielded by the non-transmission portion of the second mask  17 M owing to the aberration of the projection optical system. In this state, the light intensity distribution of a beam having passed through the second transmission portion  17 T of the second mask  17 M on the measurement surface of the light intensity distribution measurement device  18  exhibits a dark portion corresponding to the ray A. 
       FIG. 2  shows the intensity distribution of a beam having passed through the second transmission portion  17 T on the light intensity distribution measurement device  18 . I 0  (u, v) represents the light intensity of a portion corresponding to a principal ray P when the position of the second transmission portion  17 T is (u, v) and I a  (u, v) represents the light intensity of a portion corresponding to the ray A when the position of the second transmission portion  17 T is (u, v). I a  (u, v) is low because the ray A is shielded by the non-transmission portion of the second mask  17 M. 
     Letting (ε, η) be the ray aberration of the ray A, the light intensity at a portion corresponding to the ray A becomes equal to I 0  (u, v):
 
 I   a ( u, v )= I   0 ( u−ε, v−η ) 
 
when the second transmission portion  17 T is moved by (ε, η).
 
     For this reason, changes in light intensity at respective points on the light intensity distribution measurement device  18  are plotted while the position (u, v) or the second transmission portion  17 T is moved. As a result, a distribution shifted in phase by an amount corresponding to ray aberration (changes in intensity along with movement) can be obtained. This phase shift amount can be obtained to determine ray aberration. 
       FIG. 3  is a view showing the second mask  17 M having the second transmission portion  17 T. A square aperture is formed as the second transmission portion (optical element)  17 T in a non-transmission substrate. 
       FIG. 4A  is a graph showing the plots of the light intensities I a  (u, v) and I 0  (u, v) on the measurement surface of the light intensity distribution measurement device  18  along the u axis. In  FIG. 4A , the two plots have a phase shift of a ray aberration ε along the u axis. 
       FIG. 4B  is a graph showing the plots of the light intensities I a  (u, v) and I 0  (u, v) on the measurement surface of the light intensity distribution measurement device  18  along the v axis. In  FIG. 4B , the two plots have a phase shift of a ray aberration η along the v axis. 
     Since each point (x, y) on the light intensity measurement surface of the light intensity distribution measurement device  18  is in one-to-one correspondence with the exit pupil of the projection optical system, as described above, the ray aberration (ε, η) is regarded as aberration of a ray having passed through the point (x, y) on the exit pupil. 
     In the above description, the first transmission portion (optical element) arranged between the illumination system and the projection optical system is regarded as a point object. If the first transmission portion is an object smaller than the isoplanatic region of the projection optical system, the transmission portion need not be so small as to be regarded as a point object. In the isoplanatic region, aberration is regarded to be equal throughout this region. Imaging beams with the same aberration that pass through respective points of the first transmission portion are superimposed into the image of the first transmission portion. The plot obtained by scanning the image of the first transmission portion at the second transmission portion  17 T has a distribution obtained by superimposing, by size of the second pattern image, the plots in which the first transmission portion is regarded as the point object. 
       FIG. 5  shows a beam near the imaging point of the projection optical system when the first transmission portion arranged between the illumination system and the projection optical system is a square aperture in the isoplanatic region. A′ represents a beam corresponding to the ray A; and P′, a beam corresponding to the principal ray P. The sections of the two beams are squares equal in size because of the isoplanatic region, and the beam A′ deviates from the beam P′ by the aberration (ε, η) of the ray A. Let I′ 0 (u, v) be the light intensity of a portion corresponding to the beam P′ when the position of the second transmission portion  17 T is (u, v), and I′ a (u, v) be the light intensity of a portion corresponding to the beam A′. Then, as is apparent from  FIGS. 6A and 6B , we have
   I′   a ( u, v )= I′   0 ( u−ε, v−η ).  
     Changes in light intensity at respective points on the light intensity distribution measurement devices  18  are plotted while the position (u, v) of the second transmission portion  17 T is moved. Consequently, a distribution shifted in phase by an amount corresponding to ray aberration (changes along with movement) can be obtained. This phase shift amount can be obtained to determine ray aberration. The second transmission portion  17 T is the same as that shown in FIG.  3 . 
       FIG. 6A  is a graph showing the plots of the light intensities I′ a  (u, v) and I′ 0  (u, v) on the measurement surface of the light intensity distribution measurement device  18  along the u axis. In  FIG. 6A , the two plots have a phase shift of the ray aberration ε along the u axis. 
       FIG. 6B  is a graph showing the plots of the light intensities I′ a  (u, v) and I′ 0  (u, v) on the measurement surface of the light intensity distribution measurement device  18  along the v axis. In  FIG. 6B , the two plots have a phase shift of the ray aberration η along the v axis. 
     From this, as far as the first transmission portion falls within the isoplanatic region, the ray aberration (ε, η) can be obtained similarly to a case wherein the first transmission portion is regarded as a point object. 
     Letting R′ be the optical length between the position where the imaging beam crosses the reference sphere and the position where the imaging beam crosses the imaging plane, wavefront aberration φ and the ray aberration (ε, η) satisfy 
               ɛ   ⁢           ⁢     (     x   ,   y     )       =       R   ′     ⁢       ∂   ϕ       ∂   x                 (   1   )                 η   ⁡     (     x   ,   y     )       =       R   ′     ⁢       ∂   ϕ       ∂   y                 (   2   )             
 
     The wavefront aberration φ can be obtained from this relationship. The relationship is described in, e.g., Max Born, Emill Wolf, “Principles of Optics 6th Edition”, Chapter V, 1993, Pergamon Press. 
     According to the above-described method, a wavefront aberration measurement device can be formed with the same size as that of an imaging performance measurement device using a knife edge, slit, or bar chart, which is available for a projection exposure apparatus, and can be assembled in a projection exposure apparatus. 
     Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. 
     [First Embodiment] 
       FIG. 7  shows a projection exposure apparatus according to the first embodiment of the present invention. The projection exposure apparatus shown in  FIG. 7  has, as masks for measuring the imaging performance of a projection optical system  10 , a mask  12  having a first transmission portion (optical element)  11  and a mask  17 M having a second transmission portion  17 T. The mask  12  is held by a mask holder  12 H. The projection exposure apparatus has a light intensity distribution measurement device  18  as a device for measuring the imaging performance of the projection optical system  10 . A wafer is exposed to a device circuit pattern by the exposure apparatus, and then developed and etched. The mask  12  having a mask pattern  12 P such as a circuit pattern is held on the object plane of the projection optical system  10  in photolithography for a semiconductor wafer or the like. In the first embodiment, both the mask pattern  12 P and first transmission portion (optical element)  11  are formed on the mask  12 . Alternatively, the mask pattern  12 P and the first transmission portion  11  may be formed on separate masks. 
     In this embodiment, an illumination system  16  serves as both an illumination system for a circuit pattern (mask pattern) and an illumination system for the first transmission portion  11  serving as a measurement pattern. A beam emitted by the illumination system  16  passes through the mask  12 , which is arranged near the object plane (object-side focal position) of the projection optical system  10  and has the first transmission portion  11 . The beam forms the image of the first transmission portion  11  at the image-side focal position of the projection optical system  10  via the projection optical system  10 . The beam passes through the second transmission portion  17 T arranged near the imaging position of the image of the first transmission portion  11 , and reaches the measurement surface of the light intensity distribution measurement device  18  where the light intensity distribution is measured. The mask  17 M having the second transmission portion  17 T and the light intensity distribution measurement device  18  are mounted on a wafer stage  14 . The mask  17 M is aligned near the imaging position of the image of the first transmission portion  11 . A controller  19  controls an actuator ( 31  in  FIG. 9 ) to scan the mask  17 M (second transmission portion  17 T) in a plane (image plane) perpendicular to an optical axis AX of the projection optical system  10 . A signal processor  20  processes a signal of the light intensity distribution (change along with scan) measured by the light intensity distribution measurement device  18 , and obtains aberration such as wavefront aberration of the projection optical system  10 . The wafer stage  14  supports a wafer chuck  13  and is driven by a driving device  15 . 
     A beam emitted by the illumination system  16  is assumed to sufficiently cover the entrance pupil of the projection optical system  10  after it passes through the first transmission portion  11 . This is realized by an illumination system with σ=1 obtained by exchanging the aperture stop of the illumination system  16 . 
     The first transmission portion  11  is smaller than the isoplanatic region of the projection optical system  10 . For the projection system of a semiconductor exposure apparatus several percent of the screen size is regarded as a standard isoplanatic region. For a semiconductor exposure apparatus a 6″ mask, the first transmission portion  11  must be below several mm in size. 
       FIG. 8  shows an example in which rectangular apertures are arrayed as the first transmission portion  11  in a 10×10 matrix in the mask  12 . The imaging performance can be measured at a plurality of image points in the projection optical system  10  by arraying a plurality of first transmission portions  11  and measuring the imaging performance at the respective imaging positions. 
       FIG. 9  is a partial, enlarged view showing the second transmission portion  17 T and light intensity distribution measurement device  18 . The second transmission portion  17 T and light intensity distribution measurement device  18  are aligned by the wafer stage  14 , which holds them, so as to locate the second transmission portion  17 T near the imaging position of the image of the first transmission portion  11 . A position on the light intensity measurement surface (light-receiving surface) of the light intensity distribution measurement device  18  is in one-to-one correspondence with a position on the exit pupil of the projection optical system. This can be realized by separating the light intensity measurement surface of the light intensity distribution measurement device  18  from the imaging position of the projection optical system toward the optical axis AX by a certain distance. This can also be realized by using a pupil imaging optical system for imaging the exit pupil of the projection optical system  10  onto the light intensity measurement surface of the light intensity distribution measurement device  18 . The object-side focal position of the pupil imaging optical system coincides with the position of the second transmission portion  17 T, and its image-side focal position coincides with the light intensity measurement surface. The light intensity distribution measurement device  18  has, e.g., a solid-state image sensing element on which many pixels are two-dimensionally arrayed. The image sensing region of the solid-state image sensing element is determined to satisfactorily cover the pupil of the projection optical system  10 . 
     In this state, the second transmission portion  17 T is scanned by an actuator  31  in a plane perpendicular to the optical axis AX. The signal processor  20  detects, as a light intensity distribution, changes in light intensity at the respective light-receiving units (pixels) of the solid-stage image sensing element of the light intensity distribution measurement device  18  with respect to the position (u, v) of the second transmission portion  17 T. As a result, ray aberration (ε(x, y), η(x, y)) can be obtained. Note that (x, y) represents positional coordinates on the measurement surface of the light intensity distribution measurement device  18 , and is in one-to-one correspondence with coordinates on the exit pupil of the projection optical system  10 . The signal processor  20  calculates wavefront aberration φ (x, y) from the obtained ray aberration on the basis of equations (1) and (2) described above. 
     In general, R′ is an aberration-dependent amount, and calculating wavefront aberration by equations (1) and (2) requires complicated processing. 
     A practical example of calculating the wavefront aberration φ by equations (1) and (2) will be described. 
       FIG. 10  is a graph for explaining the relationship between the exit pupil and imaging plane of the projection optical system  10 , a wavefront on the light intensity distribution measurement surface, and a ray. In  FIG. 10 , X, Y, and Z define a coordinate system in which the center of the exit pupil of the projection optical system  10  is an origin and the optical axis AX is the z-axis. W represents the wavefront of an imaging beam from the first transmission portion  11  that is formed by the projection optical system  10  and passes through the center of the exit pupil; G, a reference spherical surface; C, the imaging surface of the projection optical system  10 ; D, the intensity distribution measurement surface of the light intensity distribution measurement device  18 ; O 1 , the center of the exit pupil of the projection optical system  10 ; and O 2 , the center of the reference spherical surface. 
     Further,
         P 1 : point at which the imaging beam from the first transmission portion  11  crosses the exit pupil plane   P 2 : point at which the imaging beam from the first transmission portion  11  crosses the imaging plane C   P 3 : point at which the imaging beam from the first transmission portion  11  crosses the intensity distribution measurement surface D of the light intensity distribution measurement device  18     Q 0 : point at which the maximum NA beam component of the imaging beam from the first transmission portion  11  crosses the reference spherical plane   Q 1 : point at which the imaging beam from the first transmission portion  11  crosses the wavefront W   Q 2 : point at which the imaging beam from the first transmission portion  11  crosses the reference sphere   Q 3 : point at which a straight line Q 2 Q 2  crosses the intensity distribution measurement surface D, i.e., the point at which the imaging beam from the first transmission portion  11  crosses the intensity distribution measurement surface D when no aberration exits   Q 4 : point at which a straight line Q 0 Q 2  crosses the intensity distribution measurement surface D, i.e., point at which the outermost imaging beam from the first pattern  11  crosses the intensity distribution measurement surface D when no aberration exists   R: radius of the reference sphere   R′: distance Q 2 P 2      L: distance Q 2 Q 3      L′: distance Q 2 P 3      φ: wavefront aberration (optical length Q 1 Q 2 ) of the projection optical system  10     (ε, η): ray aberration (line segment O 2 P 2 ) (α, β): ray aberration (line segment O 3 P 3 ) on the intensity distribution measurement surface D   H 0 : maximum radius of the exit pupil of the projection optical system  10     NA 0 : numerical aperture NA 0 =H 0 /R corresponding to the maximum radius of the exit pupil of the projection optical system  10     x- and y-coordinates: X- and Y-coordinates normalized by the maximum radius of the exit pupil of the projection optical system  10 
 
 X=H   0   ·x, Y=H   0   ·y  
   H′ 0 : maximum radius of a region where all beam components from the exit pupil of the projection optical system  10  without any aberration cross each other on the intensity distribution measurement surface
 
 H′   0   =NA   0 ·( L−R ) 
       

     From the above-mentioned relationship between wavefront aberration and ray aberration, we have 
       ɛ   =         R   ′     ⁢       ∂   ϕ       ∂   X         =       R   ⁡     (     1   +       Δ   ⁢           ⁢   R     R       )       ⁢       ∂   ϕ       ∂   X               
       η   =         R   ′     ⁢       ∂   ϕ       ∂   Y         =       R   ⁡     (     1   +       Δ   ⁢           ⁢   R     R       )       ⁢       ∂   ϕ       ∂   Y               
 
where ΔR=R′−R 
       α   =         L   ′     ⁢       ∂   ϕ       ∂   X         =       L   ⁡     (     1   +       Δ   ⁢           ⁢   L     L       )       ⁢       ∂   ϕ       ∂   X               
       β   =         L   ′     ⁢       ∂   ϕ       ∂   Y         =       L   ⁡     (     1   +       Δ   ⁢           ⁢   L     L       )       ⁢       ∂   ϕ       ∂   Y               
 
where ΔL=L′−L.
 
     When these equations are expressed by coordinates normalized by the maximum radius H 0 , we obtain equations (3), (4), (5), and (6) in FIG.  15 . 
     The relationship between the point Q 2  at which the imaging beam from the first transmission portion  11  crosses the reference sphere, and the point P 3  at which the imaging beam from the first transmission portion  11  crosses the intensity distribution measurement surface D is obtained. Let Q 3  (X′, Y′) be the point at which the beam crosses the intensity distribution measurement surface D when the beam emerges without any aberration from the point Q 2  (X′, Y′) at which the imaging beam from the first transmission portion  11  crosses the reference sphere, and P 3  (X″, Y″) be the point at which the imaging beam from the first transmission portion  11  crosses the intensity distribution measurement surface D. Then, since the beam deviates from the no-aberration position by the aberration, equations (7) and (8) in  FIG. 16  hold. 
     Letting Q 3  (X′, Y′) be the point at which the beam crosses the intensity distribution measurement surface D when the beam emerges without any aberration from the point Q 2  (X′, Y′), at which the imaging beam from the first transmission portion  11  crosses the reference sphere plane, equations (9) and (10) in  FIG. 16  hold from the relationship with the normalized coordinates in FIG.  10 . 
     From equations (7), (8), (9), and (10), we get 
           X   ″       H   0   ′       =           X   ′       H   0   ′       +     α     H   0   ′         =     x   +     α     H   0   ′               
           Y   ″       H   0   ′       =           Y   ′       H   0   ′       +     β     H   0   ′         =     y   +     β     H   0   ′               
 
     Hence, equations (11) and (12) in  FIG. 16  can be obtained as the relationship between the point Q 2  (x, y) at which the imaging beam from the first transmission portion  11  crosses the reference sphere, and the point P 3  (X″, Y″) at which the imaging beam from the first transmission portion  11  crosses the intensity distribution measurement surface D. 
     From equations (3), (4), (5), (6), (11), and (12), the relationship between wavefront aberration and ray aberration can be given by equations (3′) and (4′) in  FIG. 17  by the normalized coordinates (x, y) in the region where equations (13), (14), (15), and (16) in  FIG. 17  hold. 
     The relationship between the normalized coordinates (x, y) of the point Q 2  at which the imaging beam from the first transmission portion  11  crosses the reference sphere, and the point P 3  (X″, Y″) at which the imaging beam from the first transmission portion  11  crosses the intensity distribution measurement surface D is given by equations (11′) and (12′) in FIG.  17 . 
     In equations (9), (10), (11′), and (12′), NA 0  and H′ 0  are fixed values irrelevant to aberration, so that wavefront aberration can be calculated by general numerical integration. 
     For the projection optical system of a semiconductor apparatus, 
           Δ   ⁢           ⁢   R     R     ⁢           ⁢   and   ⁢           ⁢       Δ   ⁢           ⁢   L     L         
 
can be set to 10 −6  or less, and 
         α     H   0   ′       =           1     H   0   ′       ·     L   R     ·   ɛ     ⁢           ⁢   and   ⁢           ⁢     β     H   0   ′         =       1     H   0   ′       ·     L   R     ·   η           
 
η can be set to 10 −5  or less. Therefore, wavefront aberration can be practically calculated by equations (9), (10), (11′), and (12′).
 
     [Second Embodiment] 
     The second embodiment of the present invention will be explained with reference to FIG.  11 . The second embodiment relates to a projection exposure apparatus in which a first transmission portion  11  is arranged on the imaging plane of a circuit pattern (transfer pattern)  12 P of a reticle  12 , the first transmission portion  11  is illuminated under predetermined illumination conditions, and a second transmission portion  17 T is arranged near the imaging position of the image of the first transmission portion that is formed on the reticle  12  via a projection optical system  10 . The first transmission portion  11  is set on a wafer stage  14  and illuminated by a second illumination system  21  mounted on the wafer stage  14 . The second illumination system  21  as a light source can use light guided from a first illumination system  16  via a guide system  22  such as a fiber light guide. The first transmission portion  11  and second illumination system  21  are moved by the wafer stage  14  so as to locate the first transmission portion  11  at a position on the imaging plane of the transfer pattern  12 P, i.e., a position where aberration is measured. A beam from the first transmission portion  11  is formed by the projection optical system  10  into an image on the reticle  12  side of the projection optical system  10 . The imaging beam is deflected by a mirror  23 . A mask  17 M having the second transmission portion  17 T is arranged near the imaging position formed by the deflected beam. The mask  17 M is scanned by an actuator controlled by a controller  19  along a surface conjugate to the object plane (plane where the mask pattern  12 P is set) of the projection optical system  10 . The remaining same reference numerals as those in  FIG. 7  denote the same parts. 
       FIG. 12  shows an example of the second illumination system  21  in  FIG. 11. A  beam guided from the first illumination system  16  via the guide system  22  such as a fiber light guide emerges from a fiber light guide end  41 , and illuminates  11 M having the first transmission portion  11  so as to diverge to a beam having σ=1 or more to the projection optical system  10  via a condenser lens  42 . 
     [Third Embodiment] 
       FIG. 13  shows the third embodiment according to the present invention. In the third embodiment, an illumination system  16  illuminates a reflecting member (optical element)  110  corresponding to the first transmission portion  11  of the first embodiment via a projection optical system  10 , and the beam scattered and reflected by the reflecting member  110  is used to measure the wavefront aberration of the projection optical system. The reflecting member  110  is set on a wafer stage  14  and aligned by the wafer stage  14  to a position on the imaging plane of a reticle pattern  12 P, i.e., a position where aberration is measured. 
     In the third embodiment, the illumination system for illuminating the transfer pattern  12 P also serves as an illumination system for illuminating the reflecting member  110 . The illumination system illuminates the reflecting member  110  via a mask  12  having a transmission portion at a portion conjugate to the reflecting member  110 , a semitransparent mirror  24 , and the projection optical system  10 . In this case, the mask  12  may be eliminated. The beam scattered and reflected by the reflecting member  110  is formed by the projection optical system  10  into an image on the reticle side of the projection optical system  10 . The imaging beam is reflected by the semitransparent mirror  24  to deflect the optical path. A transmission portion  17 T is arranged near the imaging position formed by the deflected beam. A mask  17 M is scanned by an actuator controlled by a controller  19  along a surface conjugate to the object plane (plane where the mask pattern  12 P is set) of the projection optical system  10 . The remaining same reference numerals as those in  FIG. 7  denote the same parts. 
     [Fourth Embodiment] 
       FIG. 14  shows the fourth embodiment according to the present invention. In the fourth embodiment, a second illumination system  25  illuminates a reflecting member (optical element)  110  via a projection optical system  10 . That is, the fourth embodiment employs the second light source for illuminating the reflecting member  110 , in addition to a first light source  16  for illuminating a transfer pattern  12 P. The reflecting member  110  is set on a wafer stage  14  and aligned by the wafer stage  14  to a position where aberration on the imaging plane of the transfer pattern  12 P is measured. 
     The second illumination system  25  illuminates the reflecting member  110  via a mask  12  having a transmission portion at a portion conjugate to the reflecting member  110 , a semitransparent mirror  24 , and the projection optical system  10 . In this case, the mask  12  may be eliminated. The beam scattered and reflected by the reflecting member  110  is formed by the projection optical system  10  into an image on the mask side of the projection optical system  10 . The imaging beam is deflected by the semitransparent mirror  24 . A mask  17 M is arranged near the imaging position formed by the deflected beam. The mask  17 M is scanned by an actuator controlled by a controller  19  along a surface conjugate to the object plane (plane where the mask pattern  12 P is set) of the projection optical system  10 . The remaining same reference numerals as those in  FIG. 7  denote the same parts. 
     In the projection exposure apparatuses of the first to fourth embodiments described above, a plurality of lenses among a plurality of optical elements, which constitute the projection optical system  10 , are movable in the optical axis direction and/or a direction perpendicular to the optical axis. One or a plurality of aberrations (particularly, Seidel&#39;s five aberrations) in the optical system  10  can be corrected or optimized by moving one or a plurality of lenses by an aberration adjustment driving system (not shown) on the basis of wavefront aberration information obtained by using the above-mentioned methods and apparatuses. A means for adjusting the aberration of the projection optical system  10  includes not only a movable lens but also various known systems such as a movable mirror (when the optical system is a catadioptric system), a tiltable plane-parallel plate, and a pressure-controllable space. 
     [Fifth Embodiment] 
       FIG. 18  is a view showing a projection exposure apparatus according to the fifth embodiment of the present invention. A beam emitted by an illumination system  16  passes through a mask  12  having a first transmission portion (optical element)  11 , and forms the image of the first transmission portion  11  at the image-side focal position of a projection optical system  10  via this system  16 . The beam passes through a second transmission portion  17 T arranged near the imaging position of the first transmission portion  11 , and reaches the measurement surface of a light intensity distribution measurement device  18  where the light intensity distribution is measured. A second mask  17 M having the second transmission portion  17 T and the light intensity distribution measurement device  18  are mounted on a wafer stage  14  and aligned near the imaging position of the first transmission portion  11 . A controller  19  controls an actuator  31  to scan the mask  17 M in a plane perpendicular to an optical axis AX of the projection optical system  10 . A signal processor  20  processes a signal of the light intensity distribution (change along with scan) measured by the light intensity distribution measurement device  18 , and obtains the wavefront aberration of the projection optical system  10 . 
     Note that the first transmission portion  11  may be formed in a mask having a transfer pattern to be transferred to a wafer W. The first transmission portion  11  and transfer pattern may be illuminated by a common illumination system or separate illumination systems. 
     A beam emitted by the illumination system  16  is assumed to sufficiently cover the entrance pupil of the projection optical system  10  after it passes through the first transmission portion  11 . This is realized by, e.g., setting the numerical aperture of the illumination system  16  to be equal to that of the projection optical system  10  on the reticle  12  side. 
     The first transmission portion  11  is smaller than the isoplanatic region of the projection optical system  10 . For the projection system of a semiconductor exposure apparatus, several % of the screen size is regarded as a standard isoplanatic region. For a semiconductor exposure apparatus using a 6″ mask, the first transmission portion  11  is less than several mm in size. 
       FIG. 8  shows an example in which rectangular apertures are arrayed as the first transmission portion  11  in a 10×10 matrix in the mask  12 . The imaging performance of the projection optical system  10  can be measured at a plurality of image points by arraying a plurality of first transmission portions  11  and measuring the imaging performance at the respective imaging positions. 
       FIG. 9  is a partial, enlarged view showing the second transmission portion  17 T and light intensity distribution measurement device  18 . The second transmission portion  17 T and light intensity distribution measurement device  18  are aligned by the wafer stage  14  so as to locate the second transmission portion  17 T near the imaging position of the first transmission portion  11  (image-side focal position of the projection optical system  10 ). 
     A position on the light intensity measurement surface of the light intensity distribution measurement device  18  is in one-to-one correspondence with a position on the exit pupil of the projection optical system  10 . This can be realized by separating the light intensity distribution measurement device  18  from the imaging position of the projection optical system by some degree. This can also be realized by using a pupil imaging optical system for imaging the exit pupil of the projection optical system  10  onto the light intensity measurement surface of the light intensity distribution measurement device  18 . The object-side focal position of the pupil imaging optical system coincides with the position of the second transmission portion  17 T, and its image-side focal position coincides with the light intensity measurement surface. 
     The light intensity distribution measurement device  18  has, e.g., a solid-state image sensing element on which many pixels are two-dimensionally arrayed. The image sensing region of the solid-state image sensing element is determined to satisfactorily cover the pupil of the projection optical system  10 . 
     In this state, the second transmission portion  17 T is scanned by the actuator  31  in a plane perpendicular to the optical axis AX. The signal processor  20  receives changes in light intensity detected by the respective pixels of the solid-state image sensing element of the light intensity distribution measurement device  18  with respect to the position (u, v) of the second transmission portion  17 T. As a result, ray aberration (ε(x, y) η(x, y)) is obtained. Note that (x, y) represents positional coordinates on the measurement surface of the light intensity distribution measurement device  18 , and is in one-to-one correspondence with coordinates on the exit pupil of the projection optical system  10 . The signal processor  20  calculates wavefront aberration φ(x, y) from the obtained ray aberration on the basis of equations (1) and (2) described above. 
     [Sixth Embodiment] 
       FIG. 19  is a view showing a projection exposure apparatus according to the sixth embodiment of the present invention, which comprises first and second transmission portions and a light intensity distribution measurement device for measuring the imaging performance of a projection optical system. 
     An illumination system  16  illuminates a transfer pattern  12 P and first transmission portion  11 . The transfer pattern  12 P and first transmission portion  11  are formed on a mask  12 , but may be formed on separate masks. 
     In transferring the transfer pattern  12 P to a substrate, a beam emitted by the illumination system  16  passes through the transfer pattern  12 P, and forms the image of the transfer pattern  12 P at the image-side focal position of the projection optical system  10 , i.e., on a wafer W on a wafer stage  14 . 
     In the sixth embodiment, the illumination system  16 , the first transmission portion  11 , and a measurement unit  102  measure the wavefront aberration of the projection optical system  10 . The measurement unit  102  has an integral structure of a second transmission portion  17 T and light intensity distribution measurement device  104 . 
       FIG. 20  is a view showing the measurement unit  102  in detail. The measurement unit  102  comprises a pupil imaging optical system  103 , and the light intensity distribution measurement device  104  with a two-dimensional solid-state image sensing element  105  such as a CCD. 
     A beam emitted by the illumination system  16  passes through a plurality of transmission portions of the mask  12  having a plurality of first transmission portions  11  as shown in  FIG. 8 , passes through the projection optical system  10 , and forms the image of each first transmission portion  11  at the image-side focal position of the projection optical system  10 . The beam passes through the second transmission portion  17 T arranged near the imaging position of the first transmission portion  11 , and reaches via the pupil imaging optical system  103  the solid-state image sensing element  105  where the light intensity distribution is measured. 
     By driving the wafer stage as an actuator, the measurement unit  102  can scan a plane perpendicular to an optical axis AX of the projection optical system  10  and can measure changes in light intensity on the solid-state image sensing element  105  to measure the wavefront aberration of the projection optical system  10 , similar to the above embodiments. 
     The pupil imaging optical system  103  is a collimator lens having a focal length f, and is installed in the measurement unit  102  such that the object-side focal plane is located at the position of the second transmission portion  17 T and the image-side focal plane is located at the position of the light-receiving surface of the two-dimensional solid-state image sensing element  105 . The two-dimensional solid-state image sensing element  105  is conjugate to the exit pupil of the projection optical system  10  via the pupil imaging optical system  103 . 
       FIG. 21  shows an imaging state observed by a coordinate system using the measurement unit  102  as a reference when the measurement unit  102  moves from negative to positive directions along the x direction in FIG.  10 . The second transmission portion  17 T is not illustrated. 
     When the measurement unit  102  moves in the x direction, an imaging point at position A moves from A to B and C. The image of the first transmission portion  11  is formed at the position of the second transmission portion  17 T by the projection optical system  10 . The object-side focal plane of the pupil imaging optical system  103  coincides with the position of the second transmission portion  17 T, and the image-side focal plane of the pupil imaging optical system  103  coincides with the position of the light-receiving surface of the two-dimensional solid-state image sensing element  105 . The position of the image of the exit pupil of the projection optical system  10  that is formed on the two-dimensional solid-state image sensing element  105  does not move even when the measurement unit  102  moves. One point of the exit pupil is always imaged at one point on the two-dimensional solid-state image sensing element  105 . 
     By moving the measurement unit  102  in a direction perpendicular to the optical axis AX of the projection optical system  10  in this state, the wavefront aberration of the projection optical system  10  can be measured similarly to the above embodiments. 
     The sixth embodiment of the present invention can simplify elements arranged on the wafer stage  14  by using the measurement unit  102 , which is advantageous in mounting the apparatus. 
     [Seventh Embodiment] 
     The seventh embodiment according to the present invention will be described with reference to FIG.  22 . 
       FIG. 22  shows a projection exposure apparatus  100  according to the seventh embodiment. The projection exposure apparatus  100  comprises a mask  12  having a first transmission portion (optical element)  11  for measuring the imaging performance, an auxiliary illumination system  113 , a projection optical system  114 , a mask  115 A having a second transmission portion  115 , a light intensity distribution measurement device  116 , and a wafer stage  117 . 
     The first transmission portion  11  is formed in the mask  12  and is smaller than the isoplanatic region of the projection optical system  114 . For the projection system of a semiconductor exposure apparatus, several percent of the screen size is regarded as a standard isoplanatic region. For a semiconductor exposure apparatus using a 6″ mask, the first transmission portion  11  must be less than several mm in size.  FIG. 8  shows an example in which rectangular apertures are arrayed as the first transmission portion  11  in a 10×10 matrix in the mask  12 . The imaging performance can be measured at a plurality of image points by arraying a plurality of first transmission portions  11  and measuring the imaging performance at the respective imaging positions. 
     The auxiliary illumination system  113  also serves as a main illumination system in the seventh embodiment. A beam emitted by the auxiliary illumination system  113  is assumed to sufficiently cover the entrance pupil of the projection optical system  114  after it passes through the first transmission portion  11 . This is realized by changing the auxiliary illumination system  113  to an illumination system with σ=1. 
     The projection optical system  114  forms an image from a beam which is emitted by the auxiliary illumination system  113  and passes through the first transmission portion  11  and mask  12 . The imaging beam passes through the second transmission portion  115  arranged near the imaging position of the first transmission portion  11  and reaches the measurement surface of the light intensity distribution measurement device  116  where the light intensity distribution is measured. 
     The mask  115 A having the second transmission portion  115  and the light intensity distribution measurement device  116  are mounted on the wafer stage  117  and aligned near the imaging position of the first transmission portion  11 . The second transmission portion  115  is moved by an actuator  115 C controlled by a controller  115 D in a plane perpendicular to an optical axis P. The light intensity distribution measurement device  116  is connected to a light intensity distribution signal processor  116 A. 
     The wafer stage  117  has a wafer chuck  117 A and is driven by a driving device  117 B. 
       FIG. 23  is a partial, enlarged view showing the second transmission portion  115  and light intensity distribution measurement device  116 . 
     The second transmission portion  115  and light intensity distribution measurement device  116  are aligned by the wafer stage  117  so as to locate the second transmission portion  115  near the imaging position of the image of the first transmission portion  11 . A position on the light intensity measurement surface of the light intensity distribution measurement device  116  has a margin to such a degree a to ensure one-to-one correspondence with a position on the exit pupil of the projection optical system  114 . This can be realized by separating the light intensity distribution measurement device  116  from the imaging position of the projection optical system  114  to some extent. This can also be realized by using a pupil imaging optical system. 
     The light intensity distribution measurement device  116  is constituted such that the device  116  adopts a two-dimensional solid-state image sensing element, each pixel is set as a light-receiving unit, and the total of the sectional areas of beams received by respective light-receiving units satisfactorily covers the pupil area of the pupil of the projection optical system  114 . 
     The operation of the projection exposure apparatus  100  according to the seventh embodiment will be explained. 
     The second transmission portion  115  scans a plane perpendicular to the optical axis P by the actuator  115 C. The light intensity distribution signal processor  116 A performs a signal processing based on the above-mentioned principle for changes in light intensity at the respective light-receiving units (pixels) of the light intensity distribution measurement device  116  with respect to the position of the transmission portion  115 . Accordingly, ray aberration (ε(x, y), η(x, y)) can be obtained. Note that (x, y) represents positional coordinates on the light intensity measurement surface D of the light intensity distribution measurement device  116 , and coordinates on the exit pupil plane of the projection optical system  114 . The signal processor  116 A calculates wavefront aberration φ(x, y), from the obtained ray aberration by:
 
ε( x, y )= R′· ( αφ/αx )  (1) 
 
η( x, y )= R′· ( αφ/αy )  (2) 
 
     [Eighth Embodiment] 
     The eighth embodiment of the present invention will be described with reference to FIG.  24 . 
       FIG. 24  shows a projection exposure apparatus  200  according to the eighth embodiment of the present invention. The projection exposure apparatus  200  comprises a mask  221 A having a first transmission portion  221  for measuring the imaging performance, an auxiliary illumination system  223 , a projection optical system  224 , a mask  225 A having a second transmission portion  225 , a light intensity distribution measurement device  226 , a wafer stage  227 , a deflection optical system  228 , and a reflection optical system  229 . 
     The mask  221 A has the first transmission portion (optical element)  221  such as a circular aperture. 
     The auxiliary illumination system  223  is constituted such that an emitted beam passes through the mask  221 A having the first transmission portion  221  such as a circular aperture. The auxiliary illumination system  223  is, e.g., an illumination system with σ=1 wherein a beam having passed through the first transmission portion  221  sufficiently covers the entrance pupil of the projection optical system  224 . 
     The projection optical system  224  forms a beam which is emitted by the auxiliary illumination system  223  and passes through the deflection optical system  228 , into an image at the center of curvature of the reflection optical system  229  (to be described later). 
     The mask  225 A has the second transmission portion  225  such as an aperture slit. The second transmission portion  225  is movable by an actuator  225 C along the z and y directions perpendicular to the optical axis P of the projection optical system  224 , which is deflected by the deflection optical system  228 . The actuator  225 C is controlled by an actuator controller  225 D, and the moving amount of the actuator  225 C is transferred as data to a signal processor  226 A. 
     As shown in  FIG. 25 , the light intensity distribution measurement device  226  comprises a pupil imaging optical system  226 B and solid-state image sensing element  226 C. The solid-state image sensing element  226 C is conjugate to the entrance pupil of the projection optical system  224  via the pupil imaging optical system  226 B. 
     The deflection optical system  228  is formed from a semitransparent member (half-mirror). The deflection optical system  228  changes the optical path of a beam which is reflected by the reflection optical system  229  (to be described below) and passes through the projection optical system  224  again. The beam forms the image of the first transmission portion  221  on the deflected optical path, and passes through the second transmission portion  225  such as an aperture slit of the mask  225 A arranged near the image. The beam having passed through the second transmission portion  225  reaches the light intensity measurement surface of the light intensity distribution measurement device  226  where the light intensity is measured. 
     The reflection optical system  229  is formed from a spherical mirror arranged to make the center of curvature coincide with the imaging position of the beam which emerges from the first transmission portion  221 , passes through the projection optical system  224 , and forms an image. After the beam is reflected by the reflection optical system  229 , it passes through the projection optical system  224  again and forms an image near the second transmission portion  225 . 
     The operation of the projection exposure apparatus according to the eighth embodiment will be explained with reference to FIG.  25 . 
       FIG. 25  is a partial, enlarged view showing the second transmission portion  225  and light intensity distribution measurement device  226 . 
     The actuator  225 C moves the second transmission  225  in the −z to +z directions in  FIG. 25  such that a beam having passed through the projection optical system  224  twice (reciprocated beam) passes through an ideal imaging point P 0  of the image of the first transmission portion  221 . In scan, a principal ray Ao having passed through the center of the pupil of the projection optical system  224  passes the second transmission portion  225  while the upper end of the aperture slit serving as the second transmission portion  225  crosses the ideal imaging position Po and its lower end crosses the ideal imaging position Po. The light intensity of the beam is observed by the light intensity distribution measurement device  226 . 
     The light intensity distribution along with slit scan is shown as a graph by plotting the slit position on the abscissa and the light intensity on the ordinate, resulting in FIG.  26 B. The light intensity as a function of the slit position is obtained only during a period corresponding to a slit width L and a diameter ρ of the circular aperture image of the first transmission portion  221 . 
     A ray A having transverse aberration ε in the z direction in  FIG. 25  will be considered. This ray A passes through a position P 1  apart from th ideal imaging plane by ε in the z direction. The ray A, therefore, passes through the aperture slit while the upper end of the aperture slit as the second transmission portion  225  crosses P 1  and its lower end crosses P 1 . In the light intensity distribution as a function of the slit position at this time, the light intensity shape shifts by ε from the light intensity distribution of the principal ray Ao, as shown in FIG.  26 A. 
     In this manner, the shift amount of the light intensity shape for the principal ray Ao corresponds to the transverse aberration amount. The light intensity distribution measurement device  226  can measure the transverse aberration amount of the entire pupil plane in the z direction by obtaining changes in light intensity with respect to the position of the second transmission portion  225  and measuring the shift amount of the light intensity shape between the principal ray Ao and each pupil point. Similarly, the light intensity distribution measurement device  226  can measure transverse aberration η in the y direction by moving the second transmission portion  225  in the y direction. Note that the aperture slit in scan in the y direction is much longer in the y direction. 
     The obtained transverse aberration amount (ε, η) in the z and y directions are measured on the reticle side. Since the beam has passed through the projection optical system  224  twice, the relationship with wavefront aberration φ of the projection optical system  224  satisfies
 
ε=−(1 /NAo )·[α(2φ)/αx]  (17) 
 
η=−(1 /NAo )·[α(2φ)/αy]  (18) 
 
where NAo is the numerical aperture of the projection optical system  224  on the reticle side, and x and y are coordinates on the entrance pupil and are values normalized by the pupil diameter.
 
     The wavefront aberration φ of the projection optical system  224  can be obtained by measuring the transverse aberration amounts (ε, η) in the x and y directions for the entire pupil plane by using equations (17) and (18) described above. 
     In the eighth embodiment, the measured transverse aberration amounts (ε, η) receive the doubled influence of the wavefront aberration φ of the projection optical system  224 , and NA on the reticle side is smaller than NA on the wafer side. Hence, the transverse aberration is larger than that measured in the seventh embodiment. 
     For example, the reduction magnification of the projection optical system  224  is 5×. Letting E be the transverse aberration amount measured in the seventh embodiment and ε be the transverse aberration amount measured in the eighth embodiment, from equations (1) and (17) their ratio is:
 
 ε/E= 2·( NAi/Na   0 )=10   (19) 
 
In the eighth embodiment, a transverse aberration amount ten times that in the seventh embodiment is observed, and the measurement precision of the wavefront aberration φ greatly increases. Note that NAi is the numerical aperture of the projection optical system  224  on the wafer side, and calculation of equation (19) exploits the reduction magnification of the projection optical system  224 :
 
( NAi/NAo )=5. 
 
In the eighth embodiment, the angle of a beam having passed through a single pupil point is smaller on the reticle side than the wafer side, so that the arrangement of the pupil imaging optical system  226 B in the light intensity distribution measurement device  226  can be simplified.
 
     [Ninth Embodiment] 
     The ninth embodiment of the present invention will be described with reference to  FIGS. 27 and 28 . 
       FIG. 27  shows a projection exposure apparatus  300  according to the ninth embodiment of the present invention. Similar to the eighth embodiment, the projection exposure apparatus  300  comprises a mask  331 A having a first transmission portion  331 , an auxiliary illumination system  333 , a projection optical system  334 , a mask (e.g., common to  331 A) having a second transmission portion  335 , a wafer stage  337 , a reflection optical system  339 , and a light intensity distribution measurement device  336 . 
     The reflection optical system  339  uses a spherical mirror identical to that of the eighth embodiment. The center of curvature of the spherical mirror is decentered in a direction perpendicular to an optical axis P near the imaging position of the first transmission portion  331 . The image of the first transmission portion  331 , which is reflected by the reflection optical system  339  and passes through the projection optical system  334 , again is formed at a position deviated from the first transmission portion  331  in a direction perpendicular to the optical axis P. 
     As shown in  FIG. 28 , which is an enlarged view of the main part in  FIG. 27 , the light intensity distribution measurement device  336  comprises a reflecting mirror  336 D in addition to a pupil imaging optical system  336 B and solid-state image sensing element  336 C. The solid-state image sensing element  336 C is conjugate to the entrance pupil of the projection optical system  334  via the pupil imaging optical system  336 B. 
     Also, in the ninth embodiment, the second mask having the second transmission portion  335  such as a slit at an ideal imaging position Po is scanned, and the light intensity distribution measurement device  336  measures the light intensity distribution. The ninth embodiment is smaller in light quantity loss than the eighth embodiment because of the absence of the semitransparent optical axis deflection optical system  228 . 
     [Tenth Embodiment] 
     The tenth embodiment of the present invention will be described with reference to FIG.  29 . 
     In the tenth embodiment, shown in  FIG. 29 , a projection exposure apparatus  400  comprises a mask  441  having a first transmission portion, a mask  441 A, an auxiliary illumination system  443 , a projection optical system  444 , a mask  445  having a second transmission portion (scan pattern), a light intensity distribution measurement device  446 , a wafer stage  447 , a reflection optical system  449 , a guide optical system  440 A, and a light output system  440 B for outputting a beam propagating through the guide optical system  440 A. 
     In the tenth embodiment, the first mask  441  having the first transmission portion such as a circular aperture and the second mask  445  having the second transmission portion are arranged on the wafer stage  447 . The reflection optical system  449  has the center of curvature near the mask  441 A and is decentered from the optical axis of the projection optical system  444 . 
     The guide optical system  440 A guides a beam from the auxiliary illumination system  443  to the wafer side, and uses a light propagation means such as an optical fiber. 
     The light output system  440 B is equipped with the mask  441  having the first transmission portion such as a circular aperture, and outputs a beam guided by the guide optical system  440 A toward the projection optical system  444  via the transmission portion. 
     According to the tenth embodiment, a beam which passes through the transmission portion of the mask  441  and the projection optical system  444  is reflected by the reflection optical system  449 . The light which is reflected by the reflection optical system  449  and passes through the projection optical system  444  again forms an image in a plane which is perpendicular to the optical axis of the projection optical system  444  and coincides with the mask  441  having the transmission portion. The imaging beam scans the mask  445  having the second transmission portion, and the light intensity distribution is measured by the light intensity distribution measurement device  446 . A signal processor  446 A processes the position of the second transmission portion of the second mask  445  and the light intensity distribution, thereby measuring the aberration of the projection optical system  444 . 
     [Semiconductor Device Manufacturing Method] 
     An embodiment of a semiconductor device manufacturing method using the above-described projection exposure apparatus will be explained. 
       FIG. 30  is a flow chart for explaining the manufacture of a semiconductor device (e.g., a semiconductor chip such as an IC or LSI, a liquid crystal panel, a CCD, or the like). In step  1  (circuit design), a semiconductor device circuit is designed. In step  2  (mask formation), a mask having the designed circuit pattern is formed. In step  3  (wafer manufacture), a wafer is manufactured by using a material such as silicon. In step  4  (wafer process) called a pre-process, an actual circuit is formed on the wafer by lithography using a prepared mask and the wafer. Step  5  (assembly), called a post-process, is the step of forming a semiconductor chip by using the wafer formed in step  4 , and includes an assembly process (dicing and bonding) and a packaging process (chip encapsulation). In step  6  (inspection), inspections such as the operation confirmation test and durability test of the semiconductor device manufactured in step  5  are conducted. After these steps, the semiconductor device is completed and shipped (step  7 ). 
       FIG. 31  is a flow chart showing the wafer process in step  4  of  FIG. 30  in detail. In step  11  (oxidation), the wafer surface is oxidized. In step  12  (CVD), an insulating the film is formed on the wafer surface. In step  13  (electrode formation), an electrode is formed on the wafer by vapor deposition. In step  14  (ion implantation), ions are implanted in the wafer. In step  15  (resist processing), a photosensitive agent is applied to the wafer. In step  16  (exposure), the above-mentioned exposure apparatus exposes the wafer to the circuit pattern of a mask. In step  17  (developing), the exposed wafer is developed. In step  18  (etching), the resist is etched except for the developed resist image. In step  19  (resist removal), an unnecessary resist after etching is removed. These steps are repeated to form multiple circuit patterns on the wafer. 
     The manufacturing method of this embodiment can manufacture a high-precision semiconductor device, which is difficult to manufacture by a conventional method. 
     As has been described above, the present invention realizes measurement of the wavefront aberration of a projection optical system in a state in which the projection optical system can be actually used for exposure. The present invention enables more precise adjustment of the projection optical system and the design of a device, which is hardly influenced by aberration. 
     As many apparently widely different embodiments of the present invention can be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments except as defined in the claims.