Abstract:
A measuring apparatus according for measuring relative positions between a first mark on a movable reticle stage to hold a reticle, and a second mark on a movable object stage to hold an object to be exposed, the apparatus includes a detector for detecting light that has passed the first and second marks, and a processor for calculating the relative positions based on an output of the detector, wherein each of the first and second marks includes plural patterns to direct the light, at least ones of widths and intervals of the plural patterns being non-uniform.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to an exposure apparatus, and more particularly to a measuring apparatus for aligning a reticle and an object to be exposed relative to each other, an exposure apparatus having the same, and a device manufacturing method for using the exposure apparatus.  
         [0002]     Along with the recent demands for smaller and less expensive electronic apparatuses, an exposure apparatus that manufactures large-scale integrated circuits (“LSIs”) mounted in these exposure apparatuses is required to provide highly accurate exposure at the improved productivity. Thus, the exposure apparatus aligns a reticle with a wafer using a driver and an alignment means (such as a reticle reference mark formed on a reticle stage, a wafer reference mark formed on a wafer stage, and a photoelectric detector). The reticle and wafer reference marks generally include a rectangular single slit pattern. These patterns are similar but the wafer pattern is, for example, about ¼ or ⅕ as large as the reticle pattern.  
         [0003]     In alignment, the photoelectric detector detects the light that has transmitted through or is reflected on the reticle and wafer reference marks, and a driver aligns the reticle reference mark with the wafer reference mark based on the light intensity that has transmitted the masks. The driver moves the reticle and the wafer so as to maximize the light intensity. See Japanese Patent Publication No. 02-58766 (Patent Reference No. 1). As more precise exposure is required, the slit should be narrower for the improved alignment precision. However, the narrower slit makes the light intensity and the S/N ratio too low to provide accurate detections. One solution for this problem is to use plural, similarly shaped and regularly arranged slits for the alignment mark in order to increase the light intensity. See Japanese Patent Publication No. 04-30735 (Patent Reference No. 2).  
         [0004]     However, the alignment mark of Patent Reference No. 2 has plural peaks, requiring a long time for a detection of the maximum peak and causing a misdetection of the maximum peak. As a result, the throughput sometimes lowers, and the resolution and the overlay deteriorate.  
       BRIEF SUMMARY OF THE INVENTION  
       [0005]     Accordingly, it is an exemplary object of the present invention to provide a novel measurement technique directed to an alignment of a reticle and an object to be exposed relative to each other.  
         [0006]     A measuring apparatus according to one aspect of the present invention for measuring relative positions between a first mark on a movable reticle stage to hold a reticle, and a second mark on a movable object stage to hold an object to be exposed, the apparatus includes a detector for detecting light that has passed the first and second marks, and a processor for calculating the relative positions based on an output of the detector, wherein each of the first and second marks includes plural patterns to direct the light, at least ones of widths and intervals of the plural patterns being non-uniform.  
         [0007]     An exposure apparatus according to another aspect of the present invention for exposing an object to a pattern of a reticle, the apparatus includes a movable reticle stage to hold the reticle, a movable object stage to hold the object, the above measuring apparatus, and a controller to control positions of the movable reticle stage and the movable object stage based on a relative position measured by the measuring apparatus.  
         [0008]     A method of manufacturing a device according to another aspect of the present invention includes steps of exposing an object to a pattern of a reticle using the above exposure apparatus, developing the exposed object, and processing the developed object to manufacture the device. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a schematic structure of an exposure apparatus that includes an inventive alignment means.  
         [0010]      FIGS. 2A and 2B  are schematic plane view of a reticle reference mark and a wafer reference mark shown in  FIG. 1 .  
         [0011]      FIGS. 3A and 3B  are a table and a graph for explaining a pseudorandom noise (“PN”) code having a code length of 7 for the reticle and wafer reference marks shown in  FIG. 2 .  
         [0012]      FIGS. 4A and 4B  are graphs of the light intensity that transmits the wafer reference mark and is detected by a photoelectric detector in the inventive alignment means shown in  FIG. 1 .  
         [0013]      FIG. 5  is a schematic perspective view of a second embodiment of the wafer reference mark shown in  FIG. 2 .  
         [0014]      FIGS. 6A and 6B  are schematic perspective views of a third embodiment of the wafer reference mark shown in  FIG. 2 .  
         [0015]      FIGS. 7A and 7B  are graphs of a signal relating to the wafer reference mark of the third embodiment from the photoelectric detector shown in  FIGS. 6A and 6B .  
         [0016]      FIG. 8  is a schematic perspective view of a fourth embodiment of a wafer reference mark shown in  FIG. 2 .  
         [0017]      FIG. 9  is a flowchart of an alignment method using the alignment means shown in  FIG. 9 .  
         [0018]      FIG. 10  is a flowchart for explaining the way of manufacturing devices (such as semiconductor chips such as ICs and LCDs and CCDs) using the exposure apparatus shown in  FIG. 1 .  
         [0019]      FIG. 11  is a detailed flowchart of Step  4  in  FIG. 10 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]     With reference to the accompanying drawings, a description will now be given of an alignment means  100  and an exposure apparatus  200  having the same according one aspect of the present invention. Here,  FIG. 1  shows a structure of the exposure apparatus  200 . The alignment means  100  serves to detect a position for an alignment, and includes a reticle reference mark  120 , a wafer reference mark  130  and a photoelectric detector  160 . The alignment means  100  is arranged in the exposure apparatus  200 , and executes an alignment in cooperation with a driver  330 , which is described later.  
         [0021]     The reticle reference mark  120  serves to reflect and absorb the light. The reticle reference mark  120  is arranged on a reticle stage  230 , which will be described later, and includes, as shown in  FIG. 2A , patterns  121  to  128  that reflect the detection light for an alignment, change the light intensity in accordance with an offset amount, and have different widths and intervals. Three or more patterns are preferable. Here,  FIG. 2A  is a plan view of the reticle reference mark  120 .  
         [0022]     The patterns  121  to  124  are orthogonal to the patterns  125  to  128 . A width A of the patterns  121  and  123  is different from a width B of the patterns  122  and  124 ; a width A′ of the patterns  125  and  127  is different from a width B′ of the patterns  126  and  128 . An interval D between the patterns  122  and  123  is different from an interval C between the patterns  121  and  122  and between the patterns  123  and  124 . An interval D′ between the patterns  126  and  127  is different from an interval C′ between the patterns  125  and  126  and between the patterns  127  and  128 . The adjacent marks thus have different widths and intervals. The width A of the patterns  121  and  123  is greater than the width B of the patterns  122  and  124 , and the width A′ of the patterns  125  and  127  is greater than the width B′ of the patterns  126  and  128 .  
         [0023]     Although the alignment mark in Patent Reference No. 1 has a single slit pattern suitable for an easy detection of a peak position, the pattern should be narrower in order to improve the detecting precision. Even when Patent Reference No. 1 attempts to provide accurate alignments with the narrower pattern, the reduced light intensity lowers the maximum peak value and makes the peak detection difficult. An alignment mark in Patent Reference No. 2 has plural patterns so as to increase the light intensity, but the detected plural peak positions make difficult to find the maximum peak position.  
         [0024]     On the other hand, the reticle reference mark  120  of this embodiment has the narrow patterns  122 ,  124 ,  126  and  128  so as to improve the precision of the peak detection, and wide patterns  121 ,  123 ,  125  and  127  so as to increase the light intensity. Due to these patterns  121  to  128 , the exposure apparatus  200  is less likely to provide an alignment based on an erroneous peak. The exposure apparatus  200  maintains the resolution due to the accurate alignment. A sudden peak of the light intensity accelerates the peak detections without thorough scanning of the mark. This precise and easy alignment improves the throughput and productivity. The patterns  121  to  124  are used for an alignment between the reticle  220  and object  250  in an X direction, and the patterns  125  to  128  are used for an alignment between them in a Y direction.  
         [0025]     The reticle reference mark  120  reflects the exposure light on the patterns  121  to  128 , and absorbs the exposure light on a mark frame  129 . The patterns  121 - 128  may be slits that transmit the exposure light in accordance with a structure of the exposure apparatus  200 . The reticle reference mark  120  is not limited to this embodiment with respect to the number of patterns, the interval and the width. The above effect is available by using either a mark width or a mark interval, for example, while this embodiment uses a pseudorandom noise (“PN”) code pattern.  
         [0026]     The PN means a bit string that imitates a random noise. The PN code periodically repeats the random bit string. For example, the PN code periodically repeats “1110100”. The PN code is characterized as shown in  FIGS. 3A and 3B  in that a code phase peaks when the PN code shifts by a code length of 7 of “1110100” and all codes overlap each other or when a phase shift is 0 and 7. When a light projection by the reticle reference mark  120  is defined as “1” (at patterns  121  to  124  or patterns  125  to  128 ) and the light shielding by it is defined as “0”, the light intensity enhances when all the patterns  121  to  124  or all the patterns  125  to  128  overlap the wafer reference marks  131  to  134  or the marks  135  to  138 , which will be described later. This configuration facilitates the peak determination, and the alignment means  100  is less likely to provide an alignment based on an erroneous peak. The exposure apparatus  200  that has the alignment means  100  realizes the precise alignment and fine processing. A sudden peak of the light intensity accelerates peak detections without thorough scanning of the mark. This precise and easy alignment improves the throughput and productivity. Here,  FIGS. 3A and 3B  are a table and a graph for explaining a PN code having a code length of  7 . More specifically,  FIG. 3A  is a table that correlates a phase shift with a code correlation, and  FIG. 3B  is a graph that shows a relationship between a code correlation and a bit shift.  
         [0027]     The wafer reference mark  130  serves to transmit and absorb the light. The wafer reference mark  130  is arranged on a wafer stage  260 , which will be described later, and includes, as shown in  FIG. 2B , patterns that transmit and reflect the detection light for alignment, have different widths or intervals, and change the light intensity in accordance with the shift amount. Here,  FIG. 2B  is a plane view of the wafer reference mark  130 . Although the wafer reference mark  130  is similar to the reticle reference mark  120 , the patterns  131  to  138  transmit, not reflect, the light. The wafer reference mark  130  is about ¼ or ⅕ as large as the reticle reference marks  120 . Other than that, the wafer reference mark  130  is the same as the reticle reference mark  120 , and a description will be omitted. Of course, the wafer reference mark  130  may reflect the light.  
         [0028]     The photoelectric detector  160  serves to detect the incident light intensity. The photoelectric detector  160  detects the light intensity that transmits the wafer reference mark  130 , and arranges a light intensity detector  162  below the wafer reference mark  130 . The light intensity detector  162  is so dimensioned that it can detect a mark in one direction or measure the patterns  121  to  124  or the patterns  125  to  128 . Thus, the photoelectric detector  160  detects positions of the reticle  220  and object  250  separately in the X and Y directions.  FIGS. 4A and 4B  show light intensity measurement results by the photoelectric detector  160 .  FIG. 4A and 4B  are graphs of the light intensities that transmit the wafer reference mark  130  and are detected by the photoelectric detector  160 .  FIG. 4A  is the graph generated from a PN code pattern having a code length of  127 . In  FIG. 4A , a pattern of 100 bits is drawn with a minimum critical dimension (“CD”) of 1 μm in an area of 100 μm. Since only one peak is detected during scanning, a misdetection of the peak will not happen. The exposure apparatus  200  that has the alignment means  100  realizes the precise alignment and improves the resolution. A sudden peak of the light intensity accelerates a detection of the maximum peak without thorough scanning of the mark. This precise and easy alignment improves the throughput and productivity. Even if the peak position shifts slightly, there is a sufficient light intensity and movements of the wafer stage  260  in a direction that increases the light intensity facilitate the peak search. The curve fitting and detecting of the center of gravity makes the resolution of the peak detection smaller than the minimum CD of the pattern.  
         [0029]      FIG. 4B  shows five peaks arranged at regular intervals as a result of scanning of a PN code pattern having a code length of  31  is drawn by three cycles +a. While the plural peaks sacrifice the searching easiness to some extent, the accuracy improves with the detections of the plural peaks by averaging and peak interval calculations. As a result, the exposure apparatus  200  that has the alignment means  100  realizes the precise alignment and fine processing. Since the code length determines the number of peaks and the code length is defined as 2 n-1  (n: integer), the code string is properly selected in the design. The photoelectric detector  160  can use another type.  
         [0030]     With reference to  FIG. 5 , a description will now be given of an alignment means  100 A.  FIG. 5  is a perspective view of a wafer reference mark  130 A as a second embodiment of the wafer reference mark  130 .  FIG. 5  shows a two-section photoelectric detector  160 A having light receiving surfaces corresponding to patterns use to detect the X and Y directions in the wafer reference mark  130 A. The two-element photoelectric detector  160 A detects peaks in the X and Y directions simultaneously, providing a prompt measurement and alignment, unlike the one-element photoelectric detector that repeats the measurement for each direction. This precise and easy alignment improves the throughput and productivity. The reticle reference mark  120  can also be changed like the wafer reference mark  130 A.  
         [0031]     With reference to  FIGS. 6A and 6B , a description will now be given of an alignment means  100 B.  FIG. 6A  is a perspective view of a wafer reference mark  130 B as a third embodiment of the wafer reference mark  130 .  FIG. 6B  shows the wafer reference mark  130 B having a pair of two-element patterns used to detect the X and Y directions and a four-section photoelectric detector  160 B. The wafer reference mark  130 B&#39;s patterns corresponding to xa and xb shift from the reticle reference mark  120  by half a pitch of the minimum CD. This configuration obtains a matching position between the signal strengths from the xa and xb patterns, and accelerates the alignment by saving scanning in the X direction, as shown in  FIG. 7A . This applies similarly to the Y direction as shown in  FIG. 7B . This configuration facilitates the peak determination, and the alignment means  100 B is less likely to provide an alignment based on an erroneous peak. The exposure apparatus  200  that includes the alignment means  100 B can maintain the resolution due to the highly accurate alignment. A sudden peak of the light intensity provides a quick positional detection without scanning of all the peaks. This precise and easy alignment improves the throughput and productivity. Here,  FIGS. 7A and 7B  are graphs of signals from the photoelectric detector and the wafer reference mark  130 B of the third embodiment. The reticle reference mark  120  can also be changed like the wafer reference mark  130 B.  
         [0032]     With reference to  FIG. 8 , a description will now be given of an alignment means  100 C.  FIG. 8  is a perspective view of a wafer reference mark  130 C as a fourth embodiment of the wafer reference mark  130 .  
         [0033]     Similar to the third embodiment,  FIG. 8  shows a four-section photoelectric detector  160 C having light receiving surface corresponding to a pair of two-element patterns used to detect the X and Y directions. This embodiment differs from the third embodiment in that two patterns that are sensitive to the X and Y directions are stepped. Thereby, this configuration obtains a matching position between two elements&#39; signals without scanning in the z (or focus) direction, and provides rapider alignment than the third embodiment. This configuration facilitates the peak determination, and the alignment means  100 C is less likely to provide an alignment based on an erroneous peak. The exposure apparatus  200  that includes the alignment means  100 C can maintain the resolution due to the highly accurate alignment. A sudden peak of the light intensity provides a quick positional detection without scanning of all the peaks. This precise and easy alignment improves the throughput and productivity. The step needs to smaller than the depth of focus (“DOF”) determined by the exposure light&#39;s wavelength λ and the projection optical system  240 &#39;s NA (DOF=kλ(NA) 2  k: constant). While this embodiment measures positions in the X, Y and Z positions by providing a step to one of the marks in the X and Y directions, only the X and Z or Y and Z directions may be measured. The reticle reference mark  120  can also be changed like the wafer reference mark  130 C.  
         [0034]     Referring now to  FIG. 1 , a description will be given of the exemplary exposure apparatus  200 . The exposure apparatus  200  includes, as shown in  FIG. 1 , an illumination apparatus  210  that illuminates a reticle (or a mask)  220  which has a circuit pattern, a reticle stage  230  that supports the reticle  220 , a projection optical system  240  that projects the illuminated reticle pattern onto a object  250 , and a wafer stage  260  that supports the object  250 .  
         [0035]     The exposure apparatus  200  is a projection exposure apparatus that exposes onto the object  250  a circuit pattern on the reticle  220  in a step-and-scan manner. Of course, the present invention is applicable to a step-and-repeat exposure apparatus (“stepper”). Such an exposure apparatus is suitable for a sub-micron or quarter-micron lithography process. The instant embodiment exemplarily describes a step-and-scan exposure apparatus (which is also called “scanner”). “The step-and-scan manner”, as is used herein, is an exposure method that exposes a mask pattern onto a wafer by continuously scanning the wafer relative to the mask, and by moving the wafer stepwise to the next exposure area to be shot after one shot of exposure. “The step-and-repeat manner” is another exposure method that moves a wafer stepwise to an exposure area for the next shot every short of cell projection.  
         [0036]     The illumination apparatus  210  illuminates the reticle  220  that has a circuit pattern to be transferred, and includes a light source unit  212  and an illumination optical system  214 .  
         [0037]     The light source unit  212  uses a laser as a light source. The laser may use, for example, an ArF excimer laser with a wavelength of approximately 193 nm, an KrF excimer laser with a wavelength of approximately 248 nm, and an F 2  laser with a wavelength of approximately 157 nm, etc. The type of laser is not limited to the excimer laser, and a YAG laser may be used, for example. The number of laser units is not limited. For example, two independently acting solid lasers would cause no coherence between these solid lasers and significantly reduce speckles resulting from the coherence. An optical system may swing linearly or rotationally so as to reduce the speckles. When the light source unit  212  uses laser, it is desirable to employ the light shaping optical system that shapes a parallel beam from a laser source into a desired beam shape, and an incoherently turning optical system that turns a coherent laser beam into an incoherent one. A light source applicable to the light source unit  212  is not limited to a laser. One or more lamps, such as a mercury lamp and a xenon lamp, may be used.  
         [0038]     The illumination optical system  214  is an optical system that illuminates the reticle  220 , and includes a lens, a mirror, a light integrator, a stop, and the like. For example, a condenser lens, a fly-eye lens, an aperture stop, a condenser lens, a slit, and an imaging optical system are arranged in this order. The illumination optical system  214  can use any light regardless of whether it is the on-axial or off-axial light. The light integrator may include a fly-eye lens or an integrator formed by stacking two sets of cylindrical lens array plates (or lenticular lenses), and be replaced with an optical rod or a diffractive element.  
         [0039]     The reticle  220  is made for example, of quartz, and has a circuit pattern (or an image) to be transferred. It is supported and driven by a reticle stage (not shown). The diffracted light emitted from the reticle  220  passes the projection optical system  240 , and then projected onto the object  250 . The object  250  is a semiconductor wafer or a liquid crystal substrate, and the photoresist is applied on the object  250 . The reticle  220  and the object  250  are located in an optically conjugate relationship. Since the exposure apparatus  200  of the instant embodiment is a scanner, the reticle  220  and the object  250  are scanned at a speed of the reduction ratio. Thus, the pattern on the reticle  220  is transferred to the object  250 . If the exposure apparatus  200  is a stepper, the reticle  220  and the object  250  remain stationary during exposure.  
         [0040]     The reticle stage  230  supports the reticle  220  via a reticle chuck (not shown), and is connected to a moving mechanism (not shown). The moving mechanism (not shown) includes a linear motor, and moves the reticle stage  230  and the reticle  220  in and around the XYZ directions. Here, the Y-axis is a scan direction on the reticle  220  or object  250  surface, the X-axis is a perpendicular direction to the Y-axis, and the Z-axis is a direction perpendicular to the surface of the reticle  220  or the object  250 .  
         [0041]     The projection optical system  240  may use an optical system solely including a plurality of lens elements, a catadioptric optical system including a plurality of lens elements and at least one concave mirror, an optical system including a plurality of lens elements and at least one diffractive optical element such as a kinoform, and a full mirror type optical system, and so on. Any necessary correction of the chromatic aberrations may use a plurality of lens units made from glass materials having different dispersion values (Abbe values) or can arrange a diffractive optical element such that it disperses in a direction opposite to that of the lens unit.  
         [0042]     The photoresist is applied to the object  250 . A photoresist application step includes a pretreatment, an adhesion accelerator application treatment, a photoresist application treatment, and a pre-bake treatment. The pretreatment includes cleaning, drying, etc. The adhesion accelerator application treatment is a surface reforming process so as to enhance the adhesion, between the photoresist and a base (i.e., a process to increase the hydrophobicity by applying a surface active agent), through a coat or vaporous process using an organic film such as HMDS (Hexamethyl-disilazane). The pre-bake treatment is a baking (or burning) step, softer than that after development, which removes the solvent.  
         [0043]     The wafer stage  260  supports the object  250 . The wafer stage  260  may use any structure known in the art, and a detailed description of its structure and operation will be omitted. The wafer stage  260  may use, for example, a linear motor to move the object  250  in the XY directions. The reticle  220  and object  250  are, for example, scanned synchronously, and the positions of the wafer stage  260  and reticle stage  230  are monitored, for example, by a laser interferometer so that both are driven at a constant speed ratio. The wafer stage  260  is installed on a stage stool supported on the floor and the like, for example, via a damper. The reticle stage and the projection optical system  240  are installed on a barrel stool (not shown) which is supported, for example, via a damper to a base frame on the floor.  
         [0044]     A controller (or processor)  300  controls a driver  350 , which will be described later, based on a measurement result by a measurement part  330 , which will be described later.  
         [0045]     The measurement part  330  serves to measure positions of the reticle stage  230  and the wafer stage  260 , and send the positions to the controller  300 .  
         [0046]     The driver  350  serves to drive the reticle stage  230  and the wafer stage  260  under control by the controller  300 .  
         [0047]     Referring now to  FIG. 9 , a description will be given of a position detecting method and an alignment method. Here,  FIG. 9  shows a flowchart of the position detecting method and alignment method using the alignment means.  
         [0048]     First, the reticle stage  230  and the wafer stage  260  are driven (step  1002 ). Here, the controller  300  reads location information from the measurement part  330 , and instructs the driver  350  to drive the reticle stage  230  and the wafer stage  260  in the X and Y directions. Then, the measurement part  330  measures heights of the reticle stage  230  and the wafer stage  260  to drive the reticle stage  230  and the wafer stage  260  in the Z direction. The driver  350  drives the reticle stage  230  and the wafer stage  260  so that the focus accords with the imaging surface of the projection optical system  240 .  
         [0049]     Next, the photoelectric detector  160  scans in the X direction the light that has transmitted the wafer reference mark  130 , and detects a peak of the light intensity (step  1004 ). The detected peak is sent to the controller  300  (step  1006 ). The scan may proceed with the left or right direction as long as it is along the X direction. The controller  300  obtains a peak position or location information from the photoelectric detector  160  and stores a scan position of the wafer stage  260  for scanning in the X direction. The controller  300  sequentially stores the peak position generated by the scanning.  
         [0050]     Next, the photoelectric detector  160  scans in the Y direction the light that has transmitted the wafer reference mark  130 , and detects a peak of the light intensity (step  1008 ). The detected peak is sent to the controller  300  (step  1010 ). Similar to steps  1004  and  1006 , the scan may proceed with the left or right direction as long as it is along the Y direction. The controller  300  obtains a peak position from the photoelectric detector  160 , and stores a scan position of the wafer stage  260  for scanning in the Y direction. The controller  300  sequentially stores the peak position generated by the scanning. The alignment means  100 A to  100 C of the above embodiments provide quick positional detections through simultaneous scanning in the X and Y directions. The precise and easy alignments improve the throughput and productivity.  
         [0051]     The reticle stage  230  and the wafer stage  260  are adjusted based on the peak positions in the X and Y directions (step  1012 ). Here, the controller  300  refers to the stored peak positions, and obtains the maximum peak position in each of the X and Y directions. Since the starting positions of the reticle stage  230  and the wafer stage  260  are known, the maximum peak position can be easily obtained by calculating a distance from the starting position to the maximum peak position. Once the maximum peak position is obtained, the reticle stage  230  and the wafer stage  260  are driven to the peak position.  
         [0052]     The reticle stage  230  and the wafer stage  260  are driven in the Z direction (step  1014 ). For the alignment in the Z direction, a measurement part (not shown) measures a focal point, detects the only peak at the focal point, and stores the Z coordinate and peak position of the peak in the controller  300 .  
         [0053]     It is determined whether the peak positions in the X, Y and Z directions are higher than signal levels of predetermined thresholds (step  1016 ). The alignment ends when the peak positions in the X, Y and Z directions are higher than the signal levels of the predetermined thresholds (step  1018 ). When the peak positions in the X, Y and Z directions are lower than the signal levels of the predetermined thresholds, the peak positions in the X, Y and Z directions are updated as initial positions and the procedure returns to step  1002  (step  1020 ). This method cannot obtain a sufficient signal level unless the other axes are almost properly aligned. Thus, when the positional offset is large, the procedure needs to be repeated in this way.  
         [0054]     While this embodiment is suitable for a reflection reticle for the EUV exposes apparatus, the present invention is also applicable to an exposure apparatus that uses the i-line, KrF excimer laser, ArF excimer laser and F 2  laser for the light source. This alignment method facilitates the peak determination, and the alignment means  100  is less likely to provide an alignment based on an erroneous peak. The exposure apparatus  200  that has the alignment means  100  can maintain the resolution due to the highly accurate alignment. A sudden peak of the light intensity accelerates the positional detection without thorough scanning. This precise and easy alignment improves the throughput and productivity.  
         [0055]     In exposure, the light emitted from the light source unit  212 , e.g., Koehler-illuminated the reticle  220  via the illumination optical system  214 . The light that passes the reticle  220  and reflects the reticle pattern is imaged onto the object  250  by the projection optical system  240 . The illumination optical system  214  and the projection optical system  240  used by the exposure apparatus  200  has lens etc. and can transmit ultraviolet light, far ultraviolet light and vacuum ultraviolet light with high transmittance. Thus, the exposure apparatus  200  can provide devices, such as a semiconductor device, a LCD device, an image-pickup device, such as a CCD, and a thin film magnetic head, with a high throughput and economical efficiency.  
         [0056]     Referring now to  FIGS. 10 and 11 , a description will now be given of a device manufacturing method that uses the above exposure apparatus  200 .  
         [0057]      FIG. 10  is a flowchart for explaining the way of manufacturing devices (i.e., semiconductor chips such as IC and LSI, LCDs, CCDs, etc.). A description will now be given of the fabrication of a semiconductor chip as an example. Step  1  (circuit design) designs a semiconductor device circuit. Step  2  (reticle fabrication) forms a reticle having a designed circuit pattern. Step  3  (wafer preparation) manufactures a wafer using materials such as silicon. Step  4  (wafer process), which is also referred to as a pretreatment, forms the actual circuitry on the wafer through photolithography of the present invention using the mask and wafer. Step  5  (assembly), which is also referred to as a posttreatment, forms into a semiconductor chip the wafer formed in Step  4  and includes an assembly step (e.g., dicing, bonding), a packaging step (chip sealing), and the like. Step  6  (inspection) performs various tests for the semiconductor device made in Step  5 , such as a validity test and a durability test. Through these steps, a semiconductor device is finished and shipped (Step  7 ).  
         [0058]      FIG. 11  is a detailed flowchart of the wafer process in Step  4 . Step  11  (oxidation) oxidizes the wafer&#39;s surface. Step  12  (CVD) forms an insulating film on the wafer&#39;s surface. Step  13  (electrode formation) forms electrodes on the wafer by vapor arrangement and the like. Step  14  (ion implantation) implants ions into the wafer. Step  15  (resist process) applies a photosensitive material onto the wafer. Step  16  (exposure) uses the exposure apparatus  200  to expose a circuit pattern on the mask onto the wafer. Step  17  (development) develops the exposed wafer. Step  18  (etching) etches parts other than a developed resist image. Step  19  (resist stripping) removes unused resist after etching. These steps are repeated to form multilayer circuit patterns on the wafer. The device manufacturing method of the instant embodiment can fabricate higher quality devices than the conventional ones.  
         [0059]     Thus, the above embodiments can provide an alignment means for achieving highly accurate and easy alignments, and an exposure apparatus having the alignment means.  
         [0060]     This application claims a foreign priority benefit based on Japanese Patent Applications No. 2004-165878, filed on Jun. 3, 2004, which is hereby incorporated by reference herein in its entirety as if fully set forth herein.