Abstract:
Discloses is a scanning exposure apparatus which includes an illumination optical system for illuminating a pattern of an original through an opening being conjugate or approximately conjugate with the pattern of the original, and a changing mechanism for changing a width of the opening with respect to a scan direction of the original. The changing mechanism includes a light blocking plate, and a plurality of driving mechanisms for moving the light blocking plate. These driving mechanisms are provided at different positions with respect to the light blocking plate, and they are arranged to be driven by an actuator. At least one of the driving mechanisms includes a guiding mechanism for allowing a deviation between a position of an object to be driven by the actuator and a position of the light blocking plate, with respect to a direction different from a direction of displacement of the object to be driven.

Description:
FIELD OF THE INVENTION AND RELATED ART  
       [0001]     This invention relates generally to a scanning exposure apparatus. More particularly, the invention is directed to a scanning exposure apparatus to be used in a lithographic process, for manufacture of microdevices such as semiconductor devices (e.g. IC or LIS), liquid crystal display devices or thin film magnetic heads, for example.  
         [0002]     The manufacture of semiconductor devices, liquid crystal display devices or thin film magnetic heads, for example, uses a projection exposure apparatus in which, in order that a pattern formed on an original called a mask or a reticle (hereinafter, simply “mask”) is transferred onto a photosensitive substrate, comprising a silicon wafer substrate or a glass substrate having a photosensitive material (resist) applied to its surface (hereinafter, this substrate will be referred to simply as “wafer”), illumination light for sensitizing the resist is projected through the original onto the photosensitive substrate for exposure of the same.  
         [0003]     As regards such projection exposure, there are (i) proximity exposure method in which, while an original and a photosensitive substrate are placed in contact with each other or in proximity to each other, simultaneous exposure is carried out; (ii) mirror projection exposure method in which, through a mirror reflection optical system, an original and a photosensitive substrate are scanned by exposure light of arcuate shape; (iii) step-and-repeat exposure method using a step-and-repeat type reduction projection exposure apparatus (called a “stepper”) in which, while sequentially moving exposure regions on a substrate toward an exposure region of a projection optical system, a reduced image of the original is simultaneously transferred to each exposure region of the substrate.  
         [0004]     In an exposure apparatus based on step-and-repeat method (simultaneous exposure method), an effective imaging region has a circular shape. Since, however, semiconductor integrated circuits generally have a rectangular shape, originals to be used have a rectangular shape. Thus, in order to secure a largest transfer region in the simultaneous exposure, the region would have a rectangular shape that inscribes a circular imaging region of the projection optical system. Even in a largest transfer region, it would be a square shape having each side of 1/{square root}2 (square root of 2) of the diameter of the circle.  
         [0005]     On the other hand, an exposure method called slit-scan exposure method or step-and-scan method (hereinafter, “slit scan method”) has been proposed, according to which an exposure region of rectangular shape having a size approximately corresponding to the diameter of a circular imaging region of a projection optical system is used, and a mask and a wafer are scanningly and synchronously moved to thereby expand the transfer region.  
         [0006]     Such slit scan type projection exposure apparatus is described in detail in “O plus E”, February 1993, pp 96-99. This exposure apparatus has a rectangular exposure region and, with respect to each shot, scanning exposure is carried out by scanning a slit. When the scan exposure of one shot is completed, the wafer is moved stepwise toward the next shot position, and the scan exposure of the next shot is repeated similarly. By repeating the stepwise motion toward a subsequent shot and the exposure of the same, exposure of the whole wafer is carried out.  
         [0007]     In such slit scan method, where a projection optical system having an imaging region of the same size is used, a larger transfer region can be secured, as compared with the step-and-repeat method in which each transfer region is exposed simultaneously by using a projection lens. Namely, with respect to the scan direction, there is no restriction due to the optical system. Therefore, a size corresponding to the stroke of a scanning stage can be secured. With respect to a direction perpendicular to the scan direction, a transfer region of approximately {square root}2 (square root of 2) times can be secured.  
         [0008]     In the exposure apparatus for manufacture of semiconductor devices, enlargement of the transfer region and improvement of the resolving power have been desired to meet production of large-integration chips. Thus, usability of a projection optical system being smaller in size is very effective in respect to the optical performance and the cost as well. For this reason, the slit scan type exposure method becomes attractive as a main stream of future exposure apparatus.  
         [0009]      FIG. 10  illustrates the structure of a slit scan type projection exposure apparatus as disclosed in Japanese Laid-Open Patent Application, Publication No. 10-50599. In  FIG. 10 , illumination light emitted from a light source  1  is collected by an elliptical condensing mirror  2  and, after this, by means of optical integrators  9  and  14  ( 14   a ,  14   b ), superposition (averaging) of the image plane illuminance is carried out. After passing through a relay lens  42 , the light is projected on a movable blind (movable field stop)  32  having two movable blades. The movable blind  32  serves as a Fourier transform plane of the optical integrator  14 , and it is placed at a position optically conjugate with a mask  32 . Adjacent it, there is a fixed blind (field stop)  34 . The fixed blind  34  comprises a mechanical field stop having four knife edges, for example, that surround a rectangular opening. By means of the shape of this rectangular opening, the shape of an illumination region upon the mask  23  is determined. Namely, the illumination light as being restricted by the movable blind  32  and the fixed blind  34  and transmitted by way of a second relay lens  35 , a condenser lens  36  and a mirror  11 , illuminates the illumination region on the mask  23  with uniform illuminance distribution. Under the illumination condition described above and after the mask  23  and a wafer  25  are brought into alignment with each other by use of alignment mark  28 , the mask  23  and the wafer  25  are synchronously scanned in a first direction (hereinafter “scan direction) along the wafer  25  surface. By this, a photoresist applied to the wafer  25  surface is sensitized and the pattern formed on the mask  23  is transferred onto the wafer  25  precisely.  
         [0010]     In the slit scan type projection exposure apparatus, each exposure region on the wafer  25  is exposed by scan exposure based on a rectangular opening which is shorter than the length of these scan regions in the scan direction. Therefore, the integrated exposure amount in each exposure region should be controlled to assure that the integrated exposure amount of the rectangular opening becomes even for all the positions on the wafer  25 . If the integrated exposure amount is different depending on the position on the wafer  25 , it results in unevenness of integrated exposure amount inside each exposure region. This causes an error like illuminance non-uniformness in a step-and-repeat type exposure apparatus. As a solution for illuminance non-uniformness in a slit scan type exposure apparatus, particularly, in a constant-velocity exposure apparatus, Japanese Laid-Open Patent Applications, Publication No. 60-158449 and No. 7-66103 show the provision of a trapezoidal illuminance distribution in scan direction, in an attempt to uniforming the exposure amount on a wafer. According to this proposal, the change in illuminance with time during the exposure, at an arbitrary single point inside an exposure region of rectangular shape, on a wafer  25 , will have a trapezoidal shape such as shown in  FIG. 6A . This means that, in the constant-velocity scanning exposure, since the time base can be directly converted into the space base, a similar illuminance distribution is obtained with respect to the space base, as shown in  FIG. 6B .  
         [0011]     In the exposure amount control for constant-velocity scan exposure, the illuminance distribution of trapezoidal shape is regarded as a rectangular shape having the same height and the same area. More specifically, in  FIG. 6B , the trapezoidal illuminance distribution is approximated to a rectangular shape that has a width L of a line connecting the points where the triangular portions outside the rectangle having a width L and a height I and the triangular portions inside the rectangle have the same area, that is, a line that connects the points, in the slants at the opposite sides, of the level corresponding to a half of the maximum illuminance I, the rectangular shape having the same height as of the trapezoidal shape. The width L of this rectangle is taken as the slit width.  
         [0012]     The prior art described above is an example concerning exclusively to the correction of illuminance non-uniformness with respect to the scan direction. The shape of the opening of the fixed blind  34  is still rectangular, and the width of the opening in the scan direction has a constant value. Since the opening of the fixed blind  34  is rectangular, the shape of the opening projected on the mask  23  and the wafer  25  is, as a matter of course, rectangular. Therefore, unless the illuminance in a direction (hereinafter, “slit direction”) perpendicular to the scan direction as well is even, it results in non-uniformness of exposure.  
         [0013]     As described hereinbefore, the movable blind  32  is disposed at a position optically conjugate with the mask  23 , and the fixed blind  34  is disposed adjacent the movable blind  32 . However, at the fixed blind  34  position, a uniform illuminance distribution is not always provided within the illumination range. Namely, due to a change optical path length, for example, resulting from an error in the manufacture of optical elements disposed along the light path from the light source  1  to the fixed blind  34  or from an error in the assembling of them, generally, at the fixed blind  34  position there is small non-uniformness of illuminance along the plane orthogonal to the optical axis.  
         [0014]     Therefore, when the illumination region is restricted into a rectangular shape, by means of the fixed blind  34 , to illuminate the mask  32  and the wafer  25  is illuminated through the projection lens  22 , it results in dispersion of integrated exposure amount in dependence upon the exposure position. Thus, uniform exposure is unattainable and the resist applied to the wafer  25  is sensitized non-uniformly in dependence upon the location. Furthermore, even if the optical system is so adjusted to remove illuminance non-uniformness completely at the position of the fixed blind  34 , since the projection lens  22  for imaging the mask  23  upon the wafer  25  comprises ten or tens optical elements, due to a production error of these optical elements or non-uniformness of coating applied to these optical elements, the transmittance of the illumination light would involve partial non-uniformness.  
         [0015]      FIG. 2A  shows a distribution of illuminance i(x) of illumination light with respect to the scan direction, upon the mask  23 . Even if the illuminance distribution is even as illustrated, due to the non-uniformness of transmittance of the projection lens  22  as described above, the illuminance I(x) upon the wafer  25  would practically have an uneven distribution such as shown in  FIG. 2B .  
         [0016]     The non-uniformness of transmittance produced at the projection lens  22  will be explained in more detail.  FIG. 8A  illustrates an effective region of a projection lens  22 , upon a wafer  25 . Generally, the projection lens  22  is constituted by a combination of optical elements having a circular outer peripheral shape. Thus, the lens itself has a circular effective portion  81 . As described hereinbefore, in the slit scan type exposure apparatus, in order to perform the scan exposure with a wide width, a rectangular exposure region  82  inside the lens effective portion  81  is used. Here, generally, the non-uniformness of illuminance resulting from a manufacturing error of the optical elements, non-uniformness of the coating applied to the optical elements, or an error in the assembling, is produced in a distribution having correlation with respect to the radial direction of the optical elements. Hence, the illuminance distribution within the rectangular exposure region has a shape like a portion of a spindle shape, as shown in  FIG. 9 . If the mask  23  and the wafer  25  are synchronously scanned by use of exposure light having such illuminance distribution, the result is that the integrated exposure amount in the scan direction contains large illuminance non-uniformness in dependence upon the location.  
         [0017]     As a measure for such inconveniences, Japanese Laid-Open Patent Application, Publication No. 62-193125 proposes a projection exposure apparatus in which a liquid crystal shutter is inserted into the light path of illumination light, thereby to control the irradiation area of exposure light as desired. For those positions where the exposure light has a low intensity and the integrated exposure amount is insufficient, the width of the opening in the scan direction is enlarged, while on the other hand, for those positions where the exposure light has a large intensity and the integrated exposure amount is excessive, the width of the opening in the scan direction is narrowed. Although this document describes the function and structure for changing the opening width, it does not refer to the manner how to determine the opening width to attain efficient projection exposure.  
         [0018]     For example, where the photosensitivity (speed) of a resist (photosensitive material) applied to a wafer  25  is Pr, the exposure amount per unit time to be applied to the wafer  25  surface is Qw, the width of the opening of the fixed blind  34  in the scan direction as projected on the wafer  25  is Lw, and the movement velocity of the wafer  25  in the scan direction is Vw, since the integrated exposure amount upon the wafer  25  is equivalent to the resist photosensitivity and it follows that: 
 
 Pr =( Qw×Lw )/ Vw   (1) 
 
 it can be rewritten as: 
 
 Vw =( Qw×Lw )/ Pr   (2) 
 
 Thus, if the resist photosensitivity Pr is 2,000 J/m 2 , the exposure amount per unit applied to the wafer  25  surface  25  (hereinafter, “wafer surface illuminance”) Qw is 30,000 W/m 2 , the opening width Lw in the scan direction is 10 mm, then the scan speed Vw of the wafer  25  is 0.15 m/sec. If, however, the output of the light source  1  is lowered and the wafer surface illuminance Qw decreases to 20,000 W/m 2 , the scan speed Vw is lowered to 0.10 m/sec. This means that the time required for exposure is prolonged and that the productivity is lowered. 
 
         [0019]     Here, from equation (2), the scan speed can be made higher by enlarging the opening width Lw in the scan direction. On the other hand, the projection lens  22  has a predetermined effective view angle with which best optical performance is attainable. Therefore, the opening width cannot be expanded as desired. It is seen from the above that, in the structure proposed by this patent document, even for local adjustment of the opening width in the scan direction to meet illuminance non-uniformness, it is necessary to determine how to set the opening width to assure efficient exposure.  
         [0020]     Japanese Laid-Open Patent Application, Publication No. 2001-244183 proposes (as first and second inventions) a measure for the inconveniences described above, and it discloses a structure that enable local adjustment for reducing and removing illuminance non-uniformness to be produced on a wafer, while effectively utilizing the view angle of a projection lens. Also, this document shows (as second and third inventions) a structure that enables adjustment for reducing and removing non-uniformness of illuminance, with respect to different exposure conditions to be used in the exposure apparatus.  
         [0021]     More specifically, Japanese Laid-Open Patent Application, Publication No. 2001-244183 proposes an adjusting mechanism ( FIGS. 1 and 5 ) having a light blocking plate  66  ( 66   a ,  66   b ) mounted with tilt with respect to the optical axis of illumination light for removing local unevenness of exposure light applied to a wafer  25 . The light blocking plate  66  is provided in the form of a pair ( 66   a ,  66   b ) at positions opposed to each other with respect to the optical axis, and they can be deformed in response to push and pull of push rod  51   a ,  51   b ,  51   c ,  51   d , and  51   e . By changing the shape of the light blocking plate  66  as desired, the shape of an opening area  60  for the illumination light is determined.  
         [0022]     Referring to  FIG. 5 , details of an adjusting blind  33  will be described. The light blocking plate  66  is a metal plate having a thickness 0.1 mm, and the surface thereof provides a diffusion surface processed by chemical etching. As shown in  FIG. 5 , the light blocking plate  66  is disposed with a tilt of about 40 deg. with respect to the optical axis of the illumination light. This angle is determined because of that, in the embodiments of Japanese Laid-Open Patent Application, Publication No. 2001-244183, a third relay lens  42  has a numerical aperture (NA) of about 0.35 and the illumination light has a divergent angle of about 19 deg. with respect to the optical axis. The angle is determined to be a sharper angle as compared with the divergence angle of the third relay lens  42  to ensure that, when the light blocking plate  66  is inserted just before the illumination light is focused on the movable blind  32  surface thereby to narrower the opening width, the opening width is determined by the optical-axis side edge of the light blocking plate  66 .  
         [0023]      FIG. 1  illustrates the state of deformation of the light blocking plate  66 . In this example, in accordance with normal illuminance non-uniformness upon the wafer  25 , the shape of the opening of the adjusting blind  33  is preset to a shape slightly different from a rectangle. While details of opening shape will be explained later, the opening shape  60  of this example has a pot-like shape as shown in  FIG. 1 , and the light blocking plate  66  is adjusted by the push rods  51   a - 51   e  in accordance with this opening shape  60 . However, where the optical-axis side edge of the light blocking plate  66  is straight and if the light blocking plate  66  is deformed by the push rods  51   a - 51   e  to meet this, since the light blocking plate  66  is disposed with a tilt with respect to the optical axis, the portion thereof to which deforming forces are applied would be deformed not only within the plane of the adjusting blind  33  but also along the optical axis direction. This inevitably produces a change of defocus amount with respect to the movable blind  32  which is at a position optically conjugate with the mask  23 .  
         [0024]     Even if the defocus amount changes as described, however, regarding the illuminance distribution on the wafer  25 , the result would be a mere change of the angle of the slant portions of the trapezoid shown in  FIG. 6A . Since the area of the trapezoid is unchanged, there is no change in the integrated illuminance. However, since the light blocking plate  66  has deformed in the optical axis direction as well, it becomes necessary to enlarge the spacing Δd between the movable blind  32  and the light blocking plates  66   a  and  66   b  of the adjusting blind  33 .  
         [0025]     In order to avoid this, the light blocking plate  66  of Japanese Laid-Open Patent Application, Publication No. 2001-244183 is formed with an elliptical edge shape as shown in  FIG. 1 . Thus, when the opening is deformed into a pot-like shape  60  as described, the edge of the light blocking plate  66  can be placed within the plane perpendicular to the optical axis.  
         [0026]     Of course, the opening shape  60  of the adjusting blind  33  is not used only in the normal state. However, since the amount of change of illuminance non-uniformness to be produced on the wafer  25  is only about 1% to 3% due to the change of illumination condition or changes of optical elements with time, the amount of deformation of the light blocking plate  66  is not large.  
         [0027]     Japanese Laid-Open Patent Application, Publication No. 2001-244183 proposes a first invention that concerns a projection exposure apparatus for transferring a pattern of an original onto a photosensitive substrate by synchronously scanning the original and the photosensitive substrate in a first direction, wherein there is exposure region shaping means for locally changing, with respect to a second direction perpendicular to the first direction, an opening width of an exposure region with respect to the first direction, the exposure region shaping means providing an adjusting function for shaping the exposure region into a desired shape to thereby remove local unevenness of exposure light quantity to be applied to the photosensitive substrate, and wherein a largest opening width with respect to the first direction of the exposure region shaping means corresponds to a largest view angle of a projection lens with respect to the first direction.  
         [0028]     With this arrangement, the opening width can be adjusted in accordance with local illuminance non-uniformness to be produced by an illumination optical system for producing illumination light and by the projection lens, such that a uniform exposure distribution can be provided. Additionally, in the opening width adjustment, the largest opening width is made to be equivalent to the largest view angle of the projection lens, by which a largest exposure amount is obtainable with the projection lens.  
         [0029]     As a result, the scan speed for synchronous scan exposure of the original and the photosensitive substrate can be a highest speed with respect to the projection lens, and the productivity of the exposure apparatus can be improved.  
         [0030]     Japanese Laid-Open Patent Application, Publication No. 2001-244183 proposes a second invention in relation to the first invention, in which the amount of illumination light on the same plane as of the photosensitive substrate and with respect to the slit direction is measured at different positions, and the exposure region shaping means is actuated so that the measured illumination light quantity becomes approximately even and non-uniformness is removed. Since the illuminance non-uniformness at a position where a resist (photosensitive material) is to be present in the exposure can be measured, factors contributable to the illuminance non-uniformness can be avoided.  
         [0031]     Japanese Laid-Open Patent Application, Publication No. 2001-244183 proposes a third invention in relation to the first invention, in which exposure light amount is locally adjusted every time the illumination condition to the original is changed. Even if optical elements in the light path are changed when the illumination condition for the original is changed, or there occurs illuminance non-uniformness when the portion of optical elements in the light path to be used is changed, the correction of illuminance non-uniformness can be carried out again. Thus, uniform exposure distribution is obtainable constantly.  
         [0032]     Japanese Laid-Open Patent Application, Publication No. 2001-244183 proposed a fourth invention in relation to the third invention, in which the step of changing the illumination condition includes a step of measuring the illuminance distribution on the surface of the photosensitive substrate. Thus, the illumination condition change and the illuminance non-uniformness detection can be done uninterruptedly, in series. Inadvertent omission of measurement, for example, by an operator can be prevented.  
         [0033]     Although these examples refer to locally changing the opening width of a slit in the scan direction, there is no specific disclosure in regard to the structure that enables the adjustment. Furthermore, where the amount of change of 1% to 3% of the illuminance non-uniformness is going to be corrected by flexure of the slit made by a thin metal plate, if it is pushed or pulled simply in the scan direction, excessive stress is applied to the mechanism and the load to the actuator becomes excessively large. There is a risk of plastic deformation of the thin metal plate. It is therefore necessary to prepare means for easily deforming the variable slit, made of a thin metal plate, in its thickness direction. Furthermore, it would be necessary to choose a catadioptric system having a plurality of mirrors and lenses, as a projection optical system, from the standpoint of energy efficiency, chromatic aberration, and environment sensitivity, to meet a scanning projection exposure apparatus having an arcuate-shape slit opening.  
         [0034]     However, in a plane adjacent the edge of the slit and being conjugate with the mask, there is a blind mechanism for restricting the irradiation region on the mask. Therefore, the exposure non-uniformness adjusting mechanism and the blind mechanism will interfere with each other.  
       SUMMARY OF THE INVENTION  
       [0035]     It is accordingly an object of the present invention to provide an improved apparatus by which at least one of the inconveniences described above can be reduced or removed.  
         [0036]     It is another object of the present invention to provide an arrangement by which the width of an opening can be adjusted without excessive stress being applied to a changing mechanism for changing the opening width.  
         [0037]     In accordance with an aspect of the present invention, to achieve these objects, there is provided a scanning exposure apparatus, comprising: an illumination optical system for illuminating a pattern of an original through an opening being conjugate or approximately conjugate with the pattern of the original; and a changing mechanism for changing a width of the opening with respect to a scan direction of the original, said changing mechanism including a light blocking plate, and a plurality of driving mechanisms for moving said light blocking plate, said plurality of driving mechanisms being provided at different positions with respect to said light blocking plate and also being arranged to be driven by an actuator; wherein at least one of said plurality of driving mechanisms includes a guiding mechanism for allowing a deviation between a position of an object to be driven by said actuator and a position of said light blocking plate, with respect to a direction different from a direction of displacement of the object to be driven.  
         [0038]     Briefly, in accordance with the present invention, the opening width can be adjusted without causing excessive stress to the opening-width changing mechanism.  
         [0039]     These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0040]      FIG. 1  is a schematic view for explaining a structure for providing an opening shape adjusting function to exposure region shaping means according to a first embodiment of the present invention.  
         [0041]      FIGS. 2A and 2B  are graphs for explaining a difference between an illuminance distribution on a mask and an illuminance distribution on a wafer (photosensitive substrate).  
         [0042]      FIG. 3  is a schematic view for explaining the structure of an exposure non-uniformness adjusting slit mechanism, according to the first embodiment of the present invention.  
         [0043]      FIG. 4  is a schematic view for explaining the structure of an exposure non-uniformness adjusting slit mechanism, according to a second embodiment of the present invention.  
         [0044]      FIG. 5  is a schematic view for explaining an arrangement of a main portion of a projection exposure apparatus, according to the first and second embodiments of the present invention,  
         [0045]      FIGS. 6A and 6B  are graphs for explaining an intensity distribution of exposure light, upon a wafer.  
         [0046]      FIG. 7  is a schematic and diagrammatic view for explaining the structure of a projection exposure apparatus according to the first and second embodiments of the present invention.  
         [0047]      FIGS. 8A and 8B  are schematic views for explaining an effective range of a projection lens.  
         [0048]      FIG. 9  is a schematic view for explaining an illuminance distribution inside a rectangular exposure region.  
         [0049]      FIG. 10  is a schematic and diagrammatic view for explaining the structure of a conventional projection exposure apparatus.  
         [0050]      FIG. 11  is a flow chart for explaining the procedure of microdevice manufacturing processes.  
         [0051]      FIG. 12  is a flow chart for explaining details of a wafer process including in the procedure of  FIG. 11 . 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0052]     Preferred embodiments of the present invention will now be described with reference to the attached drawings.  
       Embodiment 1  
       [0053]     A first embodiment of the present invention will be described with reference to the drawings.  FIG. 7  shows the structure of a slit scan type projection exposure apparatus according to this embodiment. In  FIG. 7 , elements corresponding to those of  FIG. 10  are denoted by like numerals. The control method for controlling the projection exposure apparatus using an exposure non-uniformness adjusting slit mechanism of this embodiment may be that described in detail in Japanese Laid-Open Patent Application, Publication No. 2001-244183, and description thereof will be omitted here.  
         [0054]      FIG. 3  best shows the feature of the present invention. In  FIG. 3 , denoted at  66   a  is a fixed slit, and denoted at  66   b  is a variable slit that comprises a thin metal plate, constituting exposure non-uniformness adjusting means. The variable slit may be provided by any other member, as long as it is resiliently deformable. Denoted at  66   c  is a block mounted locally along the slit direction of the variable slit, and denoted at  66   d  is a block seat. Denoted at  66   e  is a pivotal motion guiding mechanism, and denoted at  66   f  and  66   g  are plane guiding mechanisms each having mutually orthogonal straight-motion guiding mechanisms. If the plane guiding mechanism is provided on a driving axis at the central portion, the in-plane position of the variable slit can not be fixed any more. Therefore, the plane guiding mechanism is not provided to such central driving axis.  
         [0055]     The forces to be applied to the variable slit (thin metal plate) from a plurality of driving axes are those in the upward and downward directions as viewed in  FIG. 3 , namely, in the directions substantially perpendicular to the optical axis of the illumination optical system (i.e., the widthwise direction of the slit defined by the illumination optical system, and the direction corresponding to the scan direction upon the mask or wafer). However, as long as the plural driving axes apply a force (displacement) to the variable slit in the same direction, a structure being arranged to apply, to the variable slit, a force in a direction inclined with respect to the optical axis of the illumination optical system, may be used.  
         [0056]     In this example, the driving axis at the center is not provided with a plane guiding mechanism but it is provided with a pivotal motion guiding mechanism. However, the pivotal motion guiding mechanism for the central driving axis may be omitted. Namely, it is possible that neither the plane guiding mechanism nor the pivotal motion guiding mechanism is provided to the driving axis at the central portion, and the structure may be arranged so that the position of the central portion of the thin metal plate of the variable slit as well as the tilt with respect to the optical axis of the illumination optical system are determined by the central driving axis.  
         [0057]     As a matter of course, the driving axis having no plane guiding mechanism such as described above may not be a central axis. It may be any one of plural driving axes that function to push or pull the variable slit in the scan direction (scan direction upon the reticle or width direction of the slit upon the reticle). On the other hand, in this embodiment, one pivotal motion guiding mechanism and two plane guiding mechanisms are provided in relation to a single driving axis. However, the two plane guiding mechanisms may be replaced by a single two-dimensional guiding mechanism. Alternatively, in place of one pivotal motion guiding mechanism and one plane guiding mechanism, a guiding mechanism (e.g. leaf springs) for confinement in a plane may be used.  
         [0058]     In the structure described above, when plural actuators cause pushing or pulling motion, the variable slit  66  is flexed and it is deformed in the thickness direction of the plate. At this time, the pivotal motion guiding mechanism  66   e  and the plane guiding mechanism  66   f  and  66   g  are moved, whereby the stress unnecessary for the variable slit deformation is dissipated into these guiding mechanisms. As a result, the load to the actuators is suppressed to minimum. Also, the risk of plastic deformation of the thin metal plate, constituting the variable slit  66   b , is reduced considerably.  
         [0059]     This embodiment uses an approximately parallel largest opening area  83  ( FIG. 8A ) positioned inside the rectangular exposure area  82 . The opening area  84  depicts the initial shape of the opening.  
         [0060]     In accordance with the functions described hereinbefore, by changing the opening width of the exposure non-uniformness adjusting slit locally within the range of the largest opening area  83  on the basis of the illuminance non-uniformness upon the wafer surface, the integrated exposure amount on the wafer surface as the slit scan exposure is carried out can be held substantially uniform.  
         [0061]     Here, the integrated exposure amount on the wafer  25  surface is measured by use of an illuminance non-uniformness sensor (light quantity sensor)  27  which is provided on the wafer stage that carries thereon a wafer (or a member being movable while carrying a wafer thereon). In response to the measurement, a main control system  9  controls the pushing and pulling motion of the actuators, whereby the slit width is adjusted at plural locations in the slit lengthwise direction (slit direction). Here, the measurement of the light quantity on the wafer using the illuminance non-uniformness sensor may be carried out every time the wafer is singly exposed in the scan direction, every time the wafer is exposed reciprocally in the scan direction, every time the wafer as a whole is exposed, every time wafers of a single lot are exposed, or every time any printing disorder of the wafer is found.  
         [0062]     Further, the slit may be substantially closed, if necessary.  
         [0063]     The exposure region shaping means, that is, the variable slit of the exposure non-uniformness adjusting slit mechanism, is made by a thin metal plate having resilience. It is disposed at the center of the edge of the thin metal plate, and at a position rotationally tilted about the slit direction as rotational axis.  
         [0064]     The movement direction of the mechanism for pushing and pulling this variable slit is in the scan direction. Thus, this mechanism does not interfere with the blind mechanism described hereinbefore. The deformation direction of the variable slit is parallel to the thickness direction of the thin metal plate, constituting the slit.  
         [0065]     In order to convert the movement direction of the mechanism for pushing and pulling the variable slit, into the deformation direction of the variable slit, members attached to plural locations on the thin metal plate may preferably be provided with a pivotal motion guiding mechanism having rotational axes taken on the slit direction and a direction perpendicular to the deformation direction of the variable slit. Furthermore, a pushing/pulling mechanism at the center may desirably be provided with such pivotal motion guiding mechanism only, while the remaining pushing/pulling mechanisms may be provided with a plane guiding mechanism as well as a pivotal motion mechanism.  
         [0066]     The exposure non-uniformness adjusting slit mechanism described above is applicable both to a case where the shape of the slit opening is approximately parallel and to a case where it is arcuate. Furthermore, in the exposure non-uniformness adjusting slit mechanism described above, even if excessive stress is produced in the thin metal plate that constitutes the variable slit, through the movements of the pivotal motion guiding mechanism and the plane guiding mechanism, the stress unnecessary for the deformation of the variable slit is dissipated into these guiding mechanisms. Therefore, the load to the actuators is suppressed to minimum. Also, the risk of plastic deformation of the thin metal plate, constituting the variable slit, is reduced considerably.  
       Embodiment 2  
       [0067]     The second embodiment differs from the first embodiment in that, although the first embodiment uses an approximately parallel slit, in the second embodiment the exposure non-uniformness adjusting slit mechanism is applied to locally changing the opening width of an arcuate slit in a catadioptric projection system. Those portions of the second embodiment not particularly described have a similar structure as of the first embodiment.  
         [0068]     In the second embodiment, an arcuate slit is produced by adapting a thin metal plate to follow the surface of an elliptic cylinder and by slicing the whole plate obliquely with respect to the axis of the elliptic cylinder. Through this process, the thin metal plate can have an edge of arcuate shape.  
         [0069]      FIG. 4  best shows the feature of the present invention. In  FIG. 4 , denoted at  66   a  is a fixed slit, and denoted at  66   b  is a variable slit that comprises a thin metal plate, constituting exposure non-uniformness adjusting means. Denoted at  66   c  is a block mounted locally along the slit direction of the variable slit, and denoted at  66   d  is a block seat. Denoted at  66   e  is a pivotal motion guiding mechanism, and denoted at  66   f  and  66   g  are plane guiding mechanisms each having mutually orthogonal straight-motion guiding mechanisms. If the plane guiding mechanism is provided on a driving axis at the central portion, the in-plane position of the variable slit can not be fixed any more. Therefore, the plane guiding mechanism is not provided to such central driving axis.  
         [0070]     In this example, the driving axis at the center is not provided with a plane guiding mechanism but it is provided with a pivotal motion guiding mechanism. However, the pivotal motion guiding mechanism for the central driving axis may be omitted. Namely, it is possible that neither the plane guiding mechanism nor the pivotal motion guiding mechanism is provided to the driving axis at the central portion, and the structure may be arranged so that the position of the central portion of the thin metal plate of the variable slit as well as the tilt with respect to the optical axis of the illumination optical system are determined by the central driving axis.  
         [0071]     As a matter of course, the driving axis having no plane guiding mechanism such as described above may not be a central axis. It may be any one of plural driving axes that function to push or pull the variable slit in the scan direction (scan direction upon the reticle or width direction of the slit upon the reticle). On the other hand, in this embodiment, one pivotal motion guiding mechanism and two plane guiding mechanisms are provided in relation to a single driving axis. However, the two plane guiding mechanisms may be replaced by a single two-dimensional guiding mechanism. Alternatively, in place of one pivotal motion guiding mechanism and one plane guiding mechanism, a guiding mechanism (e.g. leaf springs) for confinement in a plane may be used.  
         [0072]     In the structure described above, when plural actuators cause pushing or pulling motion, the variable slit  66  is flexed and it is deformed in the thickness direction of the plate. At this time, the pivotal motion guiding mechanism  66   e  and the plane guiding mechanism  66   f  and  66   g  are moved, whereby the stress unnecessary for the variable slit deformation is dissipated into these guiding mechanisms. As a result, the load to the actuators is suppressed to minimum. Also, the risk of plastic deformation of the thin metal plate, constituting the variable slit  66   b , is reduced considerably.  
         [0073]      FIG. 8B  shows an effective region of the projection lens  22 , upon the wafer  25  surface. Since, generally, a projection lens comprises a combination of optical elements having circular outer periphery, the lens itself has a circular effective portion  81 . However, as described hereinbefore, in slit scan type exposure apparatuses, in order to assure scan exposure with a large width, a rectangular exposure area  82  inside the lens effective portion  81  is used. In this embodiment, a catadioptric system having a plurality of mirrors and lenses is chosen as a projection optical system, from the standpoint of energy efficiency, chromatic aberration, and environment sensitivity, and it is applied to a scanning projection exposure apparatus having an arcuate-shape slit opening. Hence, an arcuate largest opening area  83  inside the rectangular exposure region  82  is used. The opening area  84  depicts the initial shape of the slit opening.  
         [0074]     In accordance with the functions described hereinbefore, by changing the opening width of the exposure non-uniformness adjusting slit locally within the range of the largest opening area  83  on the basis of the illuminance non-uniformness upon the wafer surface, the integrated exposure amount on the wafer surface as the slit scan exposure is carried out can be held substantially uniform.  
         [0075]     Here, the integrated exposure amount on the wafer  25  surface is measured by use of an illuminance non-uniformness sensor (light quantity sensor)  27  which is provided on the wafer stage that carries thereon a wafer (or a member being movable while carrying a wafer thereon). In response to the measurement, a main control system  9  controls the pushing and pulling motion of the actuators, whereby the slit width is adjusted at plural locations in the slit lengthwise direction (slit direction). Here, the measurement of the light quantity on the wafer using the illuminance non-uniformness sensor may be carried out every time the wafer is singly exposed in the scan direction, every time the wafer is exposed reciprocally in the scan direction, every time the wafer as a whole is exposed, every time wafers of a single lot are exposed, or every time any printing disorder of the wafer is found.  
         [0076]     Further, the slit may be substantially closed, if necessary.  
       Embodiment 3  
       [0077]     Next, an embodiment of a device manufacturing method which uses a projection exposure apparatus described above, will be explained as a third embodiment of the present invention.  
         [0078]      FIG. 11  is a flow chart for explaining the procedure of manufacturing various microdevices such as semiconductor chips (e.g., ICs or LSIs), liquid crystal panels, CCDs, thin film magnetic heads or micro-machines, for example. Step  1  is a design process for designing a circuit of a semiconductor device. Step  2  is a process for making a mask on the basis of the circuit pattern design. Step  3  is a process for preparing a wafer by using a material such as silicon. Step  4  is a wafer process which is called a pre-process wherein, by using the thus prepared mask and wafer, a circuit is formed on the wafer in practice, in accordance with lithography. Step  5  subsequent to this is an assembling step which is called a post-process wherein the wafer having been processed at step  4  is formed into semiconductor chips. This step includes an assembling (dicing and bonding) process and a packaging (chip sealing) process. Step  6  is an inspection step wherein an operation check, a durability check an so on, for the semiconductor devices produced by step  5 , are carried out. With these processes, semiconductor devices are produced, and they are shipped (step  7 ).  
         [0079]      FIG. 12  is a flow chart for explaining details of the wafer process. Step  11  is an oxidation process for oxidizing the surface of a wafer. Step  12  is a CVD process for forming an insulating film on the wafer surface. Step  13  is an electrode forming process for forming electrodes upon the wafer by vapor deposition. Step  14  is an ion implanting process for implanting ions to the wafer. Step  15  is a resist process for applying a resist (photosensitive material) to the wafer. Step  16  is an exposure process for printing, by exposure, the circuit pattern of the mask on the wafer through the exposure apparatus described above. Step  17  is a developing process for developing the exposed wafer. Step  18  is an etching process for removing portions other than the developed resist image. Step  19  is a resist separation process for separating the resist material remaining on the wafer after being subjected to the etching process. By repeating these processes, circuit patterns are superposedly formed on the wafer.  
         [0080]     With these processes, high density microdevices can be manufactured with a lower cost.  
         [0081]     In accordance with the embodiments of the present invention as described hereinbefore, the exposure non-uniformness adjusting slit mechanism is applicable both to an approximately parallel slit and to an arcuate slit. Even if excessive stress is produced in the thin metal plate that constitutes the variable slit, through the movements of the pivotal motion guiding mechanism and the plane guiding mechanism, the stress unnecessary for the deformation of the variable slit is dissipated into these guiding mechanisms. Therefore, the load to the actuators is suppressed to minimum. Also, the risk of plastic deformation of the thin metal plate, constituting the variable slit, is reduced considerably.  
         [0082]     Viewing the structure of a projection exposure apparatus, at a plane adjacent the edge of the slit and being optically conjugate with a mask, a blind mechanism for restricting the irradiation region on a mask would be provided. However, since in the embodiments of the present invention the pushing/pulling mechanism is accommodated in a direction perpendicular to the optical axis direction and the slit direction, unwanted interference between the exposure non-uniformness adjusting slit mechanism and the blind mechanism can be avoided.  
         [0083]     While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth and this application is intended to cover such modifications or changes as may come within the purposes of the improvements or the scope of the following claims.  
         [0084]     This application claims priority from Japanese Patent Application No. 2003-434549 filed Dec. 26, 2003, for which is hereby incorporated by reference.