JPH09115820A - Scanning projection aligner and aligning method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To predict the focus characteristics of projection optical system or the focus state of mask pattern image accurately by operating the focus state of mark pattern image, obtained through synchronous scanning, from the synchronism error between a mark pattern corresponding to each position in scanning direction, a photosensitive substrate and a mask. SOLUTION: While moving a reticle stage RST and a wafer stage WST mounting a wafer W, the synchronism error of moving speed between both stages, i.e., the positional error between the measured position and design position of each stage, is detected by means of a stage controller 13. Based on the synchronism error and the shift of focus position of mark image or the variation of focus characteristics, a focus characteristics operating unit 14 corrects the output waveform of mark image obtained at each position of illuminating area thus determining the shift of focus position at the time of scanning exposure based on the focus position of a reticle R obtained as the central position of waveform. Dynamic characteristics of projection optical system PL are then predicted based on the focus position of each mark of the reticle R.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention sequentially scans a circuit pattern by illuminating the mask on which the circuit pattern is formed and scanning the mask and a photosensitive substrate in synchronization with an illuminated area on the mask. More specifically, the present invention relates to a scanning exposure apparatus that exposes a photosensitive substrate, and more specifically, predicts the image formation state of a pattern image of a mask that will be formed by synchronous scanning of the mask and the substrate before actual exposure. The present invention relates to a scanning type exposure apparatus and an exposure method.

[0002]

2. Description of the Related Art Conventionally, a projection exposure apparatus has been used as an apparatus for forming a circuit pattern of a semiconductor integrated circuit or a liquid crystal substrate on a semiconductor wafer by a photolithography technique. Such a projection exposure apparatus irradiates a reticle (mask) with illumination light made uniform by an illumination system to form a reticle pattern image on a photosensitive substrate via a projection optical system. This type of apparatus requires high-precision image forming characteristics to form a fine circuit pattern, and further, to expose a plurality of patterns in the same area on the substrate in an overlapping manner, an exposure process is performed. A high overlay accuracy is required between the layer to be exposed and the layer subjected to the previous exposure processing. For this reason, the image forming characteristics of the projection optical system are evaluated in advance before performing the overlay exposure, and the lens elements of the projection optical system are moved relative to each other in the optical axis direction so as to obtain appropriate image forming characteristics. Corrections such as changing the distance between the reticle and the principal point of the projection optical system have been made. As a method of pre-evaluating the imaging characteristics of the projection optical system, prior to the actual exposure, the photoresist on the wafer is exposed using the pattern of the test reticle with multiple marks, and the developed test pattern image is used. Conventionally, a method of comparing the mark coordinates of the mark and the mark coordinates on the reticle has been performed. However, such an evaluation method is disadvantageous in that it requires time and labor because it requires preliminary exposure and development steps, and also requires a special device for measuring an image.

The applicant of the present invention, in Japanese Patent Laid-Open No. 59-94032, provides a photoelectric sensor on a stage on which a photosensitive substrate is placed, and a test pattern of a reticle formed from a sensor output through a projection optical system. A method for directly observing position information has been disclosed. According to this method, not only the initial adjustment of the device, but also changes over time of the device, changes in the external environment such as atmospheric pressure and temperature, changes in the absorption characteristics of the illumination light by the imaging optical system,
Alternatively, it is possible to easily observe a change in the image forming characteristic caused by a change in the device condition such as the reticle illumination condition (solid angle, etc.), and it is also possible to correct the image forming characteristic based on the observation result. Recent projection exposure apparatuses are equipped with an image forming characteristic measuring mechanism of a projection optical system for performing this method. FIG. 7 shows an example of an imaging characteristic measuring mechanism of the projection optical system and an observation result. FIG. 7A shows a schematic structure of a projection exposure apparatus that exposes a mark pattern (test pattern) on the reticle R onto the wafer W, which is a photosensitive substrate, via the projection optical system PL. As shown in FIG.
Is placed on the wafer holder 5 of the wafer stage WST, and the reference plate 201 is arranged on the surface of the wafer stage WST at a position different from the wafer holder 5 in the X direction and at the same height as the surface of the wafer W. ing. When measuring the imaging characteristics of the projection optical system PL, the wafer stage WST is moved so that the reference plate 201 is located directly below the projection optical system PL, and the reticle R is illuminated with the illumination light IL to form the mark pattern image. Is imaged on the reference plate 201. The reference plate 201 has a slit 2 through which the illumination light IL passes.
One or a plurality of 02 are formed. Reference plate 201
A photoelectric sensor 203 that receives the light transmitted through the slit 202 is installed below the. Wafer stage WST
By moving the image in the horizontal direction (X direction), the image of the mark pattern 204 on the reticle R is transferred to the photoelectric sensor 203.
Can be received. FIG. 7B is a diagram conceptually showing the positional relationship between the mark pattern 204 of the reticle R and one slit 202 on the reference plate 201 when viewed from above the reticle R. The mark pattern 204 of the reticle R is shown in FIG.
Shows a movement relative to one slit 202 in the direction of the arrow. Further, FIG. 7C shows an output of the photoelectric sensor 203 in the moving direction (X direction), that is, an image of the mark pattern 204 transmitted through the slit 202. Various image forming characteristics of the projection optical system PL can be obtained from this output waveform. For example, the image contrast can be obtained by comparing the line width a obtained by slicing the signal waveform at an appropriate slice level with the reference line width (design value). The contrast of the image may be obtained by a predetermined calculation from the size of the peak b. It is also possible to obtain the contrast while moving the reference plate 201 in the optical axis AX direction of the projection optical system PL, and obtain the focus position, the field curvature, etc. from the position where the best contrast is obtained. Further, astigmatism can be obtained by changing the direction of the mark pattern 204 and performing measurement. In addition, the photoelectric sensor 20
By recording the coordinates of the wafer stage WST while detecting the image of the mark pattern 204 by 3, the center position c of the mark pattern is obtained in the wafer stage coordinate system,
From this, image distortion such as distortion can also be obtained.

In the projection exposure apparatus shown in FIG. 7 (a), alignment marks (alignment marks) for overlay exposure formed on the wafer W are formed adjacent to the projection optical system PL.
Alignment sensor (alignment sensor) 2 for reading
05 is provided. The sensor 205 detects the mark position by illuminating the alignment mark and receiving reflected light or diffracted light from the alignment mark. At this time, it is possible to capture the mark image as a two-dimensional image by using an image sensor as a sensor. When different reticle patterns are exposed on the same wafer W, if the positional relationship between the image of the specific pattern of the projection optical system PL or the reticle R and the detection position of the alignment sensor 205 changes, the exposure position on the wafer W changes. Overlay error occurs. The distance d between the projection optical system PL and the detection position of the alignment sensor or the distance between the image of the specific pattern of the reticle R and the detection position of the alignment sensor is called a baseline, and is a reference when overlay exposure is performed. It becomes a value. Since this distance (baseline) easily changes due to changes in the temperature of the device, it is necessary to periodically measure and maintain the set value. Therefore, the position of the mark pattern image of the reticle R is measured by the photoelectric sensor 203 prior to the overlay exposure, and then the wafer stage WST
By moving the sensor and measuring the slit 202 directly with the sensor 205, or by measuring the position of the alignment mark on the reference plate 201 where the positional relationship with the slit 202 is clear in advance, the baseline can be measured in advance. It is being appreciated.

[0005]

The above-mentioned method of measuring the image forming characteristic has been used in a collective exposure method (full field method) represented by a so-called step-and-repeat method. However, recently, a part of the pattern area of the reticle is illuminated in a slit shape or an arc shape,
The reticle pattern is sequentially exposed by scanning the reticle with respect to the illumination area and by scanning the photosensitive substrate with respect to the exposure area, which has a conjugate relationship with the illumination area with respect to the projection optical system, in synchronization with the scanning of the reticle. An exposure apparatus of a so-called slit scan exposure method (hereinafter referred to as a scanning exposure apparatus), which is a method of exposing on a substrate, has been developed. In this slit scan exposure method, the illumination area on the reticle is smaller than in the batch exposure method, and since only a part of the image field of the projection optical system is used for exposure, the distortion of the projected image is relatively small and the illuminance is easy to be uniform. There is an advantage. In addition, it is required to increase the exposure area in accordance with the increase in the area of semiconductor substrates, etc., but with this method, the exposure area in the scanning direction can be increased without enlarging the projection optical system itself or the image field of the projection optical system. There is also an advantage that can be increased.

However, unlike the batch exposure method, the slit scan exposure method moves the reticle over the illumination area while forming one image, so that even one image passes through different portions of the projection optical system. Will form an image. That is, by scanning the reticle with respect to the illumination area, while a certain point on the reticle pattern passes through the illumination area, the optical path forming the image thereof continuously moves in the projection optical system. On the other hand, in the conventional method of measuring the image forming characteristic, the reticle pattern (object point) does not move with respect to the illumination area, so that the light rays forming the image pass only one optical path in the image forming optical system. . Therefore,
In the slit scan method, even if the image forming characteristic is obtained by using the conventional image forming characteristic measuring method, it does not reflect the image forming characteristic in the actual exposure. For example, if the distortion of the image formed through multiple parts of the projection optical system is different, the image obtained by scanning exposure spreads due to that effect, and the contrast is lower than that of the image measured by the conventional imaging characteristic measurement method. Will be shown.

Further, in the slit scan exposure system, not only the problem of the projection optical system but also the synchronization deviation of the scanning speed of the reticle and the photosensitive substrate, the rotation error and the vertical movement of the reticle during the scanning of the reticle are caused by the projection optical system. Deteriorates imaging characteristics. Further, a deviation of the positional relationship between the reticle and the photosensitive substrate due to the vibration of the apparatus due to the scanning operation also deteriorates the image forming characteristics. Particularly, in the projection exposure apparatus, as described above, in order to superimpose and expose a plurality of patterns on the same region of the substrate, the alignment mark formed in advance on the photosensitive substrate is illuminated, and the diffracted light from the mark is radiated. It is equipped with an alignment system for receiving the light and detecting the position thereof. The baseline of this alignment system is measured with the wafer stage and reticle stage being stationary when detecting the alignment mark on the wafer.However, in the scanning exposure apparatus, the reticle pattern is measured during actual exposure in the wafer stage and reticle stage. Are projected and exposed on the wafer by moving together, there is a possibility that the baseline measured at rest and the baseline obtained during scanning may be different. These are problems peculiar to the scanning type exposure apparatus and cannot be solved by the conventional measuring method of the image forming characteristics.

An object of the present invention is to provide a scanning type exposure system with a mechanism capable of accurately predicting the image forming characteristics of the projection optical system or the image forming state of the pattern image of the mask before the actual exposure in the scanning type exposure system. To provide a device.

Another object of the present invention is to provide a scanning type exposure apparatus provided with a mechanism capable of accurately measuring the baseline of an alignment system in a scanning type exposure system.

Still another object of the present invention is to form a mark pattern image formed by synchronously scanning the mask and the photosensitive substrate with respect to the illumination area on the mask prior to the actual exposure process. It is an object of the present invention to provide a scanning type exposure method capable of accurately predicting the image forming characteristic of a projection optical system.

Still another object of the present invention is to provide a scanning exposure method capable of accurately measuring the baseline of an alignment system.

In the text, the term "illumination region" means a mask (reticle) defined by being illuminated with illumination light.
The upper region, which is usually limited in size by a field stop or the like arranged in the illumination optical system. The term "exposure area" refers to an area on a photosensitive substrate that is exposed by irradiation of illumination light through a projection optical system. The exposure area is a conjugate relationship (imaging relationship) between the illumination area and the projection optical system. )It is in. In a scanning type exposure apparatus, a mask normally moves in a one-dimensional direction with respect to the illumination area, and in synchronization therewith, a photosensitive substrate moves in a direction opposite to the one-dimensional direction with respect to the exposure area to perform scanning. Is done.

[0013]

According to a first aspect of the present invention, a mask stage for scanning an illumination area on a mask and the image of the pattern on the mask is projected on a photosensitive substrate. In the scanning exposure apparatus, the mask is provided with a projection optical system, and a substrate stage that scans the photosensitive substrate with respect to an exposure region conjugate with the illumination region and the projection optical system in synchronization with scanning of the mask. Photoelectric detection means for photoelectrically detecting the image of the upper mark pattern on the substrate stage, and a synchronization error caused by synchronous scanning of the photosensitive substrate and the mask, for example, for each position of the mask or the photosensitive substrate (or its average). Different values) and the photoelectric detection means respectively when the mark pattern is located at various positions in the scanning direction in the illumination area. Image formation state calculation means for calculating the image formation state of the mark pattern image obtained by the synchronous scanning from the image of the mark pattern corresponding to each detected position in the scanning direction and the synchronization error detected by the synchronization error detection means. And the image forming state of the mask pattern obtained by the synchronous scanning of the photosensitive substrate and the mask from the calculation result of the image forming state calculating means. Provided.

In the scanning type exposure apparatus of the present invention, the mask stage moves the mark pattern of the mask to various positions within the illumination area, and at each position, the photoelectric detection means produces an image (still image) of the mark pattern by the projection optical system. ) Is measured. The respective images are images formed by passing through different optical paths in the projection optical system. further,
The synchronization error detecting means synchronizes a stage velocity synchronization shift, a Z direction position shift of the photosensitive substrate, and a shift of the image forming state due to the vibration of the projection optical system with the movement of the mask stage and the substrate stage during the actual scanning exposure. Detect as an error. The image formation state calculation means corrects the image formation state of the image of the mark pattern detected when the mark pattern is located at each point in the illumination area by using the detected synchronization error, and corrects them. By superimposing the formed images, the image formation state of the image of the mark pattern that will be formed under the conditions of the actual scanning exposure can be calculated.

It is preferable that the scanning type exposure apparatus further comprises a correction means for correcting the image formation state according to the calculation result of the image formation state calculation means. When the calculated image forming state is different from the image forming state or the design value measured under the static condition as conventionally used, the image forming characteristic is corrected by the correcting means prior to the actual exposure. It becomes possible. This correction can be performed by controlling the scanning speed or the scanning direction between the mask stage and the substrate stage by the stage controller.

According to a second aspect of the present invention, a mask stage for scanning the mask with respect to an illumination area on the mask, a projection optical system for projecting an image of the pattern on the mask onto a photosensitive substrate, A scanning exposure apparatus comprising: a substrate stage that scans the photosensitive substrate with respect to an exposure region that is conjugate with the illumination region and the projection optical system in synchronization with the scanning of the mask. Photoelectric detection means for photoelectrically detecting the image of the mark pattern of,
A synchronization error detection unit that detects a synchronization error caused by the synchronous scanning of the photosensitive substrate and the mask, for example, for each position of the mask or the photosensitive substrate, and the mark pattern at various positions in the scanning direction in the illumination region. Position, the position of the image of the mark pattern is calculated from the image of the mark pattern corresponding to each position in the scanning direction detected by the photoelectric detection means and the synchronization error detected by the synchronization error detection means. The position of the calculated mark pattern image is provided with image position calculating means and position adjusting mark detecting means for illuminating the position adjusting mark formed on the photosensitive substrate and photoelectrically detecting light from the position adjusting mark. And a detection position of the alignment mark detection means, a baseline of the alignment mark detection means is determined. Scanning exposure apparatus is provided. Since the calculated image position of the mark pattern is an image formed under the same conditions as the actual scanning type exposure according to the same principle as in the scanning type exposure apparatus of the first aspect of the present invention, The baseline of the alignment mark detecting means can be determined on the basis of the image position of this image. By thus setting the baseline with the position of the image that will be formed by the actual scanning exposure as a reference, the exposure overlay due to the vibration of the projection optical system caused by the movement of the mask stage and the substrate stage. The error can be reduced, and the overlay accuracy of scanning exposure can be improved.

In the above scanning type exposure apparatus, the photoelectric detecting means includes a light receiving portion having a slit and a sensor for photoelectrically detecting the light transmitted through the slit, and the mark pattern image of the mask and the slit of the light receiving portion. By relatively moving and in the direction parallel to the scanning direction, the image of the mark pattern can be photoelectrically detected. The synchronization error may include a positional shift of each stage caused by the synchronous movement of the substrate stage and the mask stage, and a shift of the imaging characteristic due to the vibration of the projection optical system.

According to a third aspect of the present invention, a mask stage for scanning the mask with respect to an illumination area on the mask, a projection optical system for projecting an image of the pattern on the mask onto a photosensitive substrate, A scanning exposure apparatus comprising: a substrate stage that scans the photosensitive substrate with respect to an exposure region that is conjugate with respect to the illumination region and the projection optical system in synchronization with scanning of the mask. A detection system that illuminates a mark pattern installed on the image plane and detects an image of the mark pattern by the projection optical system on the image plane or the object plane, and is generated by synchronous scanning of the photosensitive substrate and the mask. For example, a synchronization error detecting unit that detects a synchronization error for each position of the mask or the photosensitive substrate, and when the mark pattern is located at various positions in the scanning direction. The image forming state of the mark pattern image obtained by the synchronous scanning is calculated from the image of the mark pattern corresponding to each position in the scanning direction detected by the detection system and the synchronization error detected by the synchronization error detecting means. Image state calculating means, and predicting the image forming state of the image of the mask pattern obtained by the synchronous scanning of the photosensitive substrate and the mask from the calculation result of the image forming state calculating means. A mold exposure apparatus is provided. In this device, a mark pattern provided on the object plane or image plane of the projection optical system, for example, an image of the mark pattern formed on either the mask or the photosensitive substrate by the projection optical system is displayed on the image plane or the object. Detection is performed by a detection device installed on the surface, for example, the mask stage or the substrate stage. According to the same principle as that of the scanning type exposure apparatus of the first aspect, it is possible to predict the image formation state of the image of the mask pattern which will be formed in the actual scanning exposure.

According to a fourth aspect of the present invention, while illuminating the mask, the illumination area on the mask is scanned with the mask, and an exposure area conjugate with the illumination area and the projection optical system is exposed. In the scanning exposure method, in which the pattern of the mask is exposed on the photosensitive substrate via the projection optical system by scanning the photosensitive substrate in synchronization with the scanning of the mask, a mark on the mask is exposed before the exposure. Patterns are arranged at various positions in the scanning direction within the illumination area, and the image of the mark pattern at each position by the projection optical system is photoelectrically detected, and the photosensitive substrate and the mask are the same as in actual scanning exposure. The marks corresponding to the respective positions in the scanning direction photoelectrically detected by detecting the synchronization error generated by the synchronous scanning at the scanning speed at each position of the mask or the photosensitive substrate. Calculating the image formation state of the image of the mark pattern obtained by the synchronous scanning from the image of the turn and the detected synchronization error, whereby the mask pattern of the mask pattern obtained by the synchronous scanning of the mask and the photosensitive substrate. The scanning exposure method is provided, which is characterized by predicting an image formation characteristic of an image.

In the scanning type exposure method of the present invention, the mark pattern on the mask is moved to various positions within the illumination area, and the image of the mark pattern by the projection optical system (still image) is maintained with the mask stage fixed at each position. ) Is detected photoelectrically. The images are images formed by passing through different optical paths in the projection optical system.
Further, by synchronously scanning the photosensitive substrate and the mask in advance, the stage speed is not synchronized with the movement of the mask stage and the photosensitive substrate during the actual scanning exposure, the substrate stage is displaced in the Z direction, and the projection optical system. The deviation of the imaging characteristic due to the vibration of is detected as a synchronization error. Correcting the image formation state of the image of the mark pattern detected when the mark pattern is located at each point in the illumination area by using the detected synchronization error, and superimposing the corrected images. Thus, it is possible to measure an image of a mark pattern formed under the same conditions as in actual scanning exposure.

According to a fifth aspect of the present invention, a projection exposure apparatus having means for detecting an alignment mark formed on a photosensitive substrate is used to illuminate a mask while illuminating an area on the mask. Scan the mask against
A scanning type which exposes the pattern of the mask on the photosensitive substrate via the projection optical system by scanning the photosensitive substrate with respect to an exposure region conjugate with the illumination region and the projection optical system in synchronization with the scanning of the mask. In the exposure method, prior to the exposure, the mark pattern on the mask is arranged at various positions in the scanning direction within the illumination area, and the image of the mark pattern at each position by the projection optical system is photoelectrically detected. , Synchronously scanning the photosensitive substrate and the mask, detecting a synchronization error caused by the synchronous scanning for each position of the mask or the photosensitive substrate, and the image of the mark pattern at each position in the scanning direction photoelectrically detected The position of the image of the mark pattern on the mask is calculated from the detected synchronization error, and the position of the calculated mark pattern image and the position of the photosensitive substrate are calculated. The scanning exposure method and a detecting position of the means for detecting the alignment mark, characterized in that to determine the baseline of the alignment mark detection means. Since the image of the calculated mark pattern is an image formed under the same conditions as the actual scanning type exposure on the same principle as in the scanning type exposure method of the fourth aspect of the present invention, The baseline of the alignment mark detecting means can be determined on the basis of the image position of the image. As a result, it is possible to reduce the exposure overlay error due to the vibration of the projection optical system or the like that occurs due to the movement of the mask stage and the substrate stage.

In the scanning exposure method of the present invention, an image of the mark pattern formed by the projection optical system is obtained by relatively moving the mark pattern image and the light receiving portion of the photoelectric detecting means in a direction parallel to the scanning direction. It can be detected photoelectrically.

According to a sixth aspect of the present invention, there is provided a method of manufacturing a microdevice using the scanning exposure apparatus of the present invention.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a scanning type exposure apparatus according to the present invention will be described below with reference to the drawings. Figure 1 shows the reticle R
An example of a scanning-type projection exposure apparatus that exposes the wafer W and the wafer W while scanning the illumination area of the reticle R in synchronization with each other. This projection exposure apparatus includes a light source and an illumination optical system (both not shown), a reticle stage RST that moves a reticle R in the scanning direction, a projection optical system PL that projects a pattern image formed on the reticle R onto a wafer W, a wafer. Wafer stage WS that moves W in synchronization with scanning of reticle R
Wafer alignment system 30 for aligning T and wafers
˜35, it is mainly composed of the photoconductor 3 for evaluating the imaging characteristics in advance. The light source and the illumination optical system are generally arranged above the reticle stage RST in FIG. As the illumination light source, an ultraviolet light source such as i-line or g-line which is a bright line of an ultra-high pressure mercury lamp, KrF or ArF excimer laser light, or metal vapor laser light is used. The illumination optical system is composed of a fly-eye lens for achieving uniform illuminance, a shutter for opening and closing the optical path, a variable blind and a relay lens for limiting the illumination area, and the like from the light source and the illumination optical system. The reticle R on which a circuit pattern or the like is drawn is illuminated with the illumination light IL at a substantially uniform illuminance and at a predetermined solid angle. In recent years, in order to increase the resolving power, the illumination optical system has a mechanism capable of zonal illumination, inclined illumination, or the like.

The reticle stage RST has a projection optical system P.
It is installed above L and can be moved at a predetermined scanning speed in the scanning direction (X direction) by a reticle drive unit (not shown) composed of a linear motor or the like. The reticle stage RST is provided with a movable mirror 6 that reflects the laser beam from the interferometer 7 fixed to the end in the X direction, and the position of the reticle stage RST in the scanning direction is determined by the interferometer 7 in units of 0.01 μm, for example. To be measured. The measurement result by the interferometer 7 is sent to the stage controller 13, and the reticle stage RST is always positioned with high accuracy.
A reticle holder (not shown) is installed on the reticle stage RST, and the reticle R is adsorbed and held on the reticle holder by a vacuum chuck or the like. Further, a reticle alignment system (not shown) facing the optical axis AX is mounted above the reticle stage RST, and the reference mark formed on the reticle R by this reticle alignment system is observed to detect the reticle R. The initial position of reticle stage RST is determined so that it can be accurately positioned at a predetermined reference position. Therefore, the position of the reticle R can be adjusted with sufficiently high accuracy simply by measuring the position of the reticle stage RST with the movable mirror 6 and the interferometer 7. The drive unit of reticle stage RST is controlled by stage controller 13.

On reticle stage RST, reticle R is illuminated by a rectangular (slit-shaped) illumination area having a length in a direction (Y direction) perpendicular to the scanning direction (X direction) of reticle R. This illumination region is defined by a field stop (not shown), and the field stop is usually arranged above the reticle stage and on a plane conjugate with the reticle R or in the vicinity thereof.

The illumination light passing through the reticle R is incident on the projection optical system PL, and the circuit pattern image of the reticle R by the projection optical system PL is a photosensitizer (photoresist) at the time of actual exposure.
Is formed on the wafer W coated with. Projection optical system PL
, A plurality of lens elements are accommodated such that the optical axis AX is a common optical axis. The projection optical system PL is provided with a flange portion 24 on its outer peripheral portion (lens barrel) and in the central portion in the optical axis direction, and is fixed to the mount 50 of the exposure apparatus main body by the flange portion 24. The projection magnification of the pattern image of the reticle R projected on the wafer W is determined by the magnification and arrangement of the lens elements of the projection optical system PL, and is usually reduced to 1/5 or 1/4 by the projection optical system PL.

The reticle pattern in the slit-shaped illumination area (the center substantially coincides with the optical axis AX) on the reticle R is projected onto the wafer W via the projection optical system PL. Since the projection image on the wafer W has an inverted image relationship with the pattern of the reticle R via the projection optical system PL, when the reticle R is scanned at the speed Vr in the −X direction (or + X direction) during exposure, the wafer W W is in the + X direction (or −) opposite to the reticle R.
In the X direction), scanning is performed at a speed Vw in synchronization with the reticle R,
The pattern of the reticle R is sequentially exposed on the entire surface of the shot area on the wafer W. The scanning speed ratio (Vr / Vw) is determined by the reduction ratio of the projection optical system PL described above.

The wafer W is vacuum-sucked to the wafer holder 5 held on the wafer stage WST. Wafer stage WST is configured not only to move in the scanning direction (X direction) described above, but also to move in a direction (Y direction) perpendicular to the scanning direction so that each of a plurality of shot areas on the wafer can be scanned and exposed. Therefore, the operation of scanning each shot area on the wafer W and the operation of moving to the exposure start position of the next shot area are repeated. Wafer stage WST can also be finely moved in the optical axis AX direction (Z direction) of projection optical system PL. Further, wafer stage WST can be tilted with respect to optical axis AX by a leveling stage (not shown). Wafer stage WST is driven by a wafer stage drive unit (not shown) such as a motor,
The moving speed is adjusted according to the ratio (Vr / Vw).
The movable mirror 8 is fixed to the end of the wafer stage WST,
The laser beam from the interferometer 9 is reflected by the moving mirror 8,
By detecting the reflected light with the interferometer 9, the position of the wafer stage WST in the XY plane (hereinafter referred to as the wafer stage coordinate system) is constantly monitored. The reflected light from the movable mirror 8 is, for example, 0.01 μm
It is detected with about the same resolution. The wafer stage drive unit is controlled by the stage controller 13 to move the wafer stage WST in synchronization with the reticle stage RST. The stage controller 13 collectively manages the scanning of each stage and the adjustment of the projection optical system PL accompanying it.

The scanning type exposure apparatus shown in FIG. 1 includes wafer alignment systems 30 to 35 adjacent to the projection optical system PL. The wafer alignment system is formed on the wafer W in order to expose a new pattern on a layer which has been exposed and processed, for example, etched, vapor-deposited, etc., on the wafer W in the previous process with high precision. It is an optical detection system for detecting the alignment mark (alignment mark) that is present. As the light source 30 of the wafer alignment system, a laser, a halogen lamp, or the like that emits light having a wavelength that is non-photosensitive to the photoresist film on the wafer W is used. The illumination light emitted from the light source 30 passes through the half mirror 33, the mirror 34, and the wafer W by the mirror 35.
Illuminate the top alignment mark. Reflected light or diffracted light from the alignment mark on the wafer W passes through a path opposite to the illumination light, passes through the half mirror 33, and is photoelectrically converted in the light receiving unit 31. The signal from the light receiving unit 31 is amplified to a sufficient output by the amplifier 32, and the signal is sent to the stage controller 13 that also functions as an alignment control system. The optical axis AX of the projection optical system PL and the optical axis AX2 of the alignment system are set as close to each other as possible and are separated by a constant interval. By maintaining this distance stable, an accurate positional relationship between the pattern of the reticle R and the shot area of the wafer W is maintained when overlay exposure is performed. The optical axis AX and the optical axis AX2 are usually called the baseline of the alignment system, but in the present invention,
As will be described later, the baseline is defined based on the projected image of the mark formed on the reticle R. Instead of the light receiving unit 31 of the wafer alignment system, a two-dimensional image pickup device such as CCD may be used.

The projection exposure apparatus shown in FIG. 1 further comprises a light projector 10 for irradiating the image plane of the projection optical system PL with light rays in an oblique direction and a light receiver 11 for receiving the reflected light from the image plane. A Z direction position sensor is provided. The Z-direction position sensor can be configured, for example, to project a slit image or a pinhole image from the projector 10 onto the wafer W and receive the reflected light through the slit or the pinhole, and the projection optical system PL. When the wafer W is positioned on the optimum image plane of, the reflected light is adjusted to enter the slit or the pinhole. By providing a plurality of these sensors, after detecting the inclination of the surface of the wafer W,
It is also possible to perform the correction by inclining the wafer stage WST by the above-described leveling stage so that the entire exposure area on the wafer W matches the optimum image plane of the projection optical system PL. The light emitted from the projector is selected to have a wavelength that does not expose the photosensitizer.

The scanning exposure operation of the scanning exposure apparatus having the above structure will be described with reference to FIG. FIG. 2 (a)
FIG. 3 is a conceptual view of the reticle R as seen from above, showing a projection optical system P
The rectangular illumination area IA is defined within a circle representing the L image field. The pattern on the reticle R is sequentially illuminated by moving the reticle R in the scanning direction (X direction) with respect to the illumination area IA, and all the patterns existing in the scanning direction of the reticle R are scanned by one time. Illuminated. The illumination time is determined by the time required for each pattern to cross the illumination area IA, that is, the size of the pattern and the scanning speed. The scanning speed is determined by the sensitivity of the photosensitive agent, the intensity of illumination light, and the like. Fig. 2 (a)
Shows the case where the reticle R is scanned in the X direction at the velocity Vr. The reticle pattern irradiated in the illumination area IA is projected onto the exposure area EA on the wafer W by the projection optical system PL.
An image is formed at a reduction magnification of. This state is shown in FIG. 2B when the wafer W is viewed from above. As described above, the speed Vw of the wafer W is determined by the speed Vr of the reticle R times the reduction magnification of the projection optical system PL, and the image on the wafer W has a mirror image relationship with the pattern of the reticle R, so that the wafer W is opposite to the reticle R. -
Move in the X direction. Then, when the scanning of the reticle R is completed once, the image of the entire surface of the reticle R is formed on the wafer W in the area SH.
Formed. By repeating this operation, a so-called step-and-scan exposure is performed in which a plurality of patterns of the reticle R are exposed on almost the entire surface of the wafer W.

Returning to FIG. 1, the wafer W is placed on the surface of the wafer stage WST at a position different from the wafer holder 5 in the X direction.
The pattern plate 2 for measuring the image-forming characteristics is installed at a height substantially matching the upper surface of the. The pattern plate 2 is formed by the Z-direction position sensor (10, 11) and the wafer stage WST.
The position of the upper surface of the pattern plate 2 is adjusted so as to coincide with the image plane of the projection optical system PL. When measuring the imaging characteristics of projection optical system PL in advance, wafer stage WST is moved in the X direction so that pattern plate 2 is located directly below projection optical system PL. As a result, the pattern of the reticle R illuminated with the illumination light IL is imaged on the pattern plate 2 via the projection optical system PL. A slit-shaped opening 1 is formed in the center of the pattern plate 2, and a photoelectric sensor 4 for measuring the intensity of illumination light passing through the opening 1 is installed inside the wafer stage WST and below the pattern plate 2. Has been done. The photoelectric sensor 4 has an area sufficient to receive all light rays passing through the opening 1. The configuration of the image formation characteristic measuring system using the pattern plate 2 (which functions as a light receiving portion of the photoelectric sensor 4) and the photoelectric sensor 4 is used in the conventional collective exposure type projection exposure apparatus as shown in FIG. The configuration is similar to that of a static imaging characteristic measurement system. Therefore, as described in the section of the prior art, the static projection image of the mark pattern of the reticle R formed by passing through one fixed optical path of the projection optical system PL is projected onto the pattern plate 2 by the projection optical system. After moving to the imaging position of the system PL, the wafer stage WST and the reticle stage RST are stopped, and then the wafer stage W is illuminated while illuminating the test mark.
It can be measured by slightly moving ST. Since the wafer stage WST and the reticle stage RST are movable in the scanning exposure apparatus, the wafer stage WST
Instead of ST, reticle stage RST may be slightly moved to measure a still image. As described above, in the scanning exposure apparatus, it is necessary to optimally adjust the imaging characteristics in a stationary state, that is, the imaging characteristics when the reticle R and the wafer W are not scanned, prior to actual exposure. Is also necessary, and it is desirable to correct the obtained image-forming characteristics by using an appropriate correction means. For example, if the calculated magnification deviates from the target magnification, a deviation of the magnification of the image formed by scanning will occur in the non-scanning direction, and the image quality in the scanning direction will deteriorate. Therefore, for example, the reticle R
And change the optical path length of the projection optical system PL,
It is possible to use a known method in which a part of the L lens element is driven in the optical axis AX direction or is tilted with respect to the optical axis AX to correct the magnification and distortion. Further, the shift of the focal position, the inclination of the image plane, etc. are corrected by giving an offset to the Z-direction position sensor (10, 11). The present invention is based on the premise that the image forming characteristic in the stationary state is optimized, and a method for measuring the image forming state of the image of the pattern of the reticle R which may be generated by the actual scanning exposure and the correction thereof. Provide a way.

Next, using the scanning exposure apparatus shown in FIG. 1, according to the scanning exposure method of the present invention, a method of measuring (predicting) the image forming characteristics of the image of the pattern of the reticle R generated by the scanning exposure. explain. As the reticle R, a dedicated test reticle in which a test pattern is drawn with a plurality of marks, or a reticle pattern including a plurality of test marks around the manufacturing reticle as shown in FIG. 3 can be used. Or reticle stage RST
It is also possible to use a dedicated image-forming characteristic measurement pattern installed above. Normally, it is sufficient to cover the inside of the illumination area, so only the peripheral pattern is sufficient. However, when the traveling speed and inclination of the reticle R differ depending on the position on the reticle stage RST, almost all of the reticle stage RST is covered. A measurable test reticle is advantageous. However, if such a dedicated reticle R is used, the reticle exchange operation becomes complicated, so it is desirable to properly use the reticle. In the present invention, a reticle R for manufacturing a circuit pattern, as shown in FIG. 3, is provided with four test marks M _{1 to} M on each of two opposite sides of the reticle pattern region 40.
A reticle pattern containing ₈ was used.

In order to measure the image forming characteristic according to the scanning exposure method of the present invention, wafer stage WST is moved so that pattern plate 2 is located at the image forming position below projection optical system PL. Then, as shown in FIG. 4 (a), the reticle R
Marks M ₁ of various positions x _R = x ₁ , x ₂ , x in the scanning direction (arrow (X) direction) in the illumination area IA.
₃ are sequentially moved to · · · x _n, to measure the image of the mark M ₁ in the x _R position. First, the reticle stage RS
By moving T, the mark M ₁ is positioned at x ₁ in the scanning direction. At this time, the image of the mark M ₁ is formed at any position on the pattern plate 2. Then, with the reticle stage RST stopped, the wafer stage WST is moved by a small amount in the scanning direction (X direction or −X direction) to scan the pattern plate 2 with respect to the projection image of the mark M _{1 by} the projection optical system PL. To do. It is desirable to move wafer stage WST as slowly as possible so as not to adversely affect the image forming characteristics of the mark due to the vibration of the stage. The mark M passes through the opening 1 of the pattern plate 2 by the above scanning.
The image ₁ is detected by the photoelectric sensor 4. Photoelectric sensor 4
The signal waveform detected by is shown in the graph at x _R = x ₁ in FIG. 4 (b). The horizontal axis X _{p of the} graph is the photoelectric sensor 4
It is assumed that the position in the upper scanning direction (X direction) (X coordinate X _p on the photoelectric sensor 4) is indicated and the center of the signal waveform is detected by X _P1 . The center position of the signal waveform can also be expressed by using the wafer stage X coordinate system, that is, the position in the X direction of the wafer stage measured by the interferometer 9 for the wafer stage WST. The X _p coordinate system on the photoelectric sensor 4 is used for comparison in order to compare the center positions of the images formed accordingly. However, the center position X _P1 of the signal waveform is converted to the wafer stage coordinate system and stored in the imaging characteristic detection system 12 for later processing. The vertical axis represents the intensity of received light (arbitrary scale). After the detection of the projected image of the mark M ₁ in the case where the mark M ₁ is positioned in the first position of the illumination area (x _R = x ₁₎ has been completed, the mark M ₁ by moving the reticle stage RST illumination area To the next scanning direction position (x _R = x ₂ ). Then, at that position, as in the case of x _R = x ₁ , the wafer stage WST is moved in the scanning direction while the reticle stage RST is stopped to form a projection image of the mark M _{1 by} the projection optical system PL. The pattern plate 2 is scanned. The signal waveform output by the sensor 4 is shown in the graph of x _R = x _{2 in} FIG. 4 (b). Comparing the output waveform when the mark M ₁ is located at x = x ₁ and the output waveform when it is located at x _R = x ₂ , the center position X _P2 of the signal waveform is ΔX ₁₂ = X _P2- X Only _{P1 is} different. This means that if the mark M ₁ is located at x _R = x ₁ and x _R = x ₂ ,
The light forming these images passes through different optical paths in the projection optical system PL, and the influence of the distortion of the obtained image is different due to the aberration of the lens element of the projection optical system PL. Next, reticle stage RS
By moving T to move the mark M ₁ to the next scanning direction position (x _R = x ₃ ) in the illuminated area, x _R = x ₁ and x _R =
The projected image is detected in the same manner as in the case of x ₂ . Output waveform when mark M ₁ is located at x _R = x ₃ and x _R = x
The output waveform when located at position ₂ has a center position of ΔX ₂₃ = X _P2 −X _P3 due to the difference in the influence of distortion.
Only different. In this way, the reticle stage RST
Thus, the mark M ₁ is sequentially moved to the next scanning direction position in the illumination area, and x _R = x _n, that is, each x _R is reached until the x _R position closest to the scanning end side in the illumination area IA is reached. The detection of the projected image is performed at each position. After measuring the projected image at x = x _n , the respective positions x ₁ , x ₂ , x ₃ ... x _n in the scanning direction (the arrow direction in FIG. 4A) in the illumination area IA.
The n output waveforms of the projected image of the mark M ₁ in FIG.
These output waveforms and the center position in the wafer stage X coordinate system are stored in the imaging characteristic detection system 12, respectively.
Since the output waveforms are images formed by light passing through different portions of the projection optical system PL, respectively, the image forming characteristics of the images at the time of scanning exposure in which the images are formed on the same principle. Reflects. From the obtained output waveform and the center position in the wafer stage coordinate system, the image formation characteristic detection system 12 obtains the image formation characteristics of those images, for example, magnification, distortion, etc., and for each position of the mark pattern x _R. It may be stored in the imaging characteristic detection system 12. In the detection by the photoelectric sensor 4, when the illumination light IL is not constant due to the pulse oscillation of the laser or the like, the output of the photoelectric sensor is also affected. Therefore, for example, the laser power for each pulse is measured by a power meter or the like, It is necessary to normalize the output of the photoelectric sensor 4 with the laser power.

Further, according to the present invention, the image forming characteristics of the image formed by the light passing through the different optical paths of the projection optical system PL will be generated by the synchronous movement of the reticle stage RST and the wafer stage WST. It is corrected by the amount of change in the image forming characteristic based on the error. Such correction is performed by the image forming characteristic calculator 14 (corresponding to the image forming characteristic calculating means and the image position calculating means), and the image forming characteristic of the image generated by the actual exposure in the scanning type exposure method is predicted by the correction. can do. First, a method for obtaining the positional deviation and the amount of change in the imaging characteristic based on the synchronization error will be described below. The wafer W is placed on the wafer stage WST, and the reticle stage R is moved at the same scanning speed as in the actual exposure.
By monitoring the signals of the interferometers 7 and 9 for each stage while moving ST and wafer stage WST, a synchronization error of the moving speed of both stages, that is, reticle stage RST and wafer stage W at a predetermined time.
The deviation between the ST measurement position and each planned design position is detected. At this time, the interferometer can detect not only the positional error in the X and Y directions but also the rotational error of the wafer. The stage controller 13 calculates these positional deviations. The values of these positional deviations and rotation errors are determined for each position of the reticle stage RST and the wafer stage WST, for example, when the reticle stage RST is at a predetermined position, the wafer stage position scheduled from the synchronous speed with the reticle stage RST. It is observed how much the wafer stage position is deviated with respect to the position of the wafer stage WST (represented by the wafer stage coordinate system).
It is stored in the stage controller 13 as data for each.

The reason why the synchronous movement of reticle stage RST and wafer stage WST adversely affects the image forming characteristics of the pattern image of reticle R is caused by reticle stage R.
Not only the synchronous deviation between the moving speeds of ST and wafer stage WST, but also the positional deviation in the Z direction of the photosensitive substrate (due to the unevenness of the photosensitive substrate) mounted on wafer stage WST, and the projection optics during the movement of both stages. A deviation of the imaging characteristics of the projection optical system PL due to the vibration of the system PL can be considered. These causes are caused by the reticle stage RST and the wafer stage WS.
Since T can be measured by performing synchronous scanning before actual exposure, it can be included in the synchronous error in this specification. Therefore, not only the stage controller 13 but also Z
The direction position sensors 10 and 11 and the acceleration sensor 15 also function as synchronization error detecting means. The misalignment of the photosensitive substrate in the Z direction is detected by detecting the output of the Z direction sensor 11 during the synchronous movement, and determining the Z of the wafer W obtained in advance by experiment or calculation.
It can be calculated by using a relational expression between the positional deviation in the direction and the imaging characteristics, for example, the positional deviation in the Z direction of the wafer W and the amount of change in the focus position. The deviation of the imaging characteristics of the projection optical system PL due to the vibration of the projection optical system PL is, for example, as shown in FIG. 1, the accelerometer 15 mounted on the lens barrel portion of the projection optical system PL.
It can be obtained by observing the detection signal from and the relational expression between the movement amount of each of the projection optical system PL in the X, Y and Z directions and the change of the imaging characteristic, which is obtained in advance by calculation or experiment. The stage controller 13 determines the synchronization error and the amount of change in the imaging characteristic caused by the synchronization error for each position of the wafer stage WST or as an average value in one scan.
To memorize.

By using the thus obtained synchronization error and the deviation of the image forming position of the image of the mark M ₁ and the change of the image forming characteristic based on the synchronization error, the image forming characteristic calculator 14 is used for each position of the illumination area IA. The obtained output waveform of the image of the mark M ₁ (FIG. 4) is corrected. Here, a case where the image forming position of the image of the mark M ₁ in the scanning direction (X direction) is corrected will be described as an example.
The stage W stored in the stage controller 13
The total amount ΔX of the positional deviation amount in the scanning direction (X direction) caused by the synchronous deviation of the moving speed of ST and the vibration of the projection optical system PL.
_b is calculated for each position in the X direction of wafer stage WST.
Next, the total amount of positional deviation in the scanning direction (X direction) at the center position (represented and stored in the wafer stage coordinate system) of the output waveform of the image observed at each x _R position in the illumination area IA. The quantities ΔX _b1 , ΔX _b2 , ΔX _b3 ... ΔX _bn (synchronization error corresponding to each x position in the scanning direction in the illumination area IA) are extracted from the imaging characteristic detection system 12, and their values ΔX _b1 , Δ
The output waveform (FIG. 4 (b)) of the image observed at each x position in the illumination area IA is corrected by X _b2 , ΔX _b3 ... ΔX _bn . This is shown in Fig. 5 (a). For example, the output waveform of the image formed when the mark M ₁ is located at x _R = x ₁ in the illumination area IA is modified so that its center position is X _P1 + ΔX _b1 . Similarly, the mark M ₁ is x _R = within the illumination area IA.
The output waveforms of the images respectively formed at x ₂ , x ₃ ··· x _n , the center position is ΔX _b2 , ΔX _b3
・ ・ Correct by shifting by ΔX _bn . The output waveform of the image of the mark M ₁ thus obtained is formed on the photosensitive substrate by the projection optical system PL at the moment when the mark M ₁ is located at each position in the scanning direction of the illumination area in the actual scanning exposure. It represents an image that will be imaged.
Next, by adding m = _{1 to n to} the respective estimated image shapes P _m (x _p ) in the modified x ₁ to x _n shown in FIG. Obtain the output waveform as shown in (b). Center position X of the output waveform in Fig. 5 (b)
₀ 'represents the imaging position of the mark M ₁ of the reticle R. This image forming position corresponds to the image forming position of an image that would be formed by performing one scan in the actual scanning exposure.

In the above description, only the positional deviation amount in the scanning direction (X direction) is taken into consideration as the synchronization error, and the image forming state (image forming position) of the mark M ₁ located at each position in the scanning direction within the illumination area. However, as a synchronization error, the intensity P of the output waveform is corrected from the amount of positional deviation of the wafer W in the Z direction, or Y
It is also possible to correct the output waveform of the image in the Y direction from the amount of positional deviation in the direction. For these synchronization errors, the averaged synchronization error value that would be generated by one scan can be used instead of the value stored for each position in the scanning direction in the illumination area. In this case, the image forming state (image forming position) of the mark M ₁ located at each position in the scanning direction within the illumination area is corrected by the same value (synchronization error average value).

Further, in the above description, only M ₁ is used as the mark on the reticle R, but not only M ₁ but all the marks M _{1 to} M ₈ are still imaged by the same operation as described above. Can be detected at each position in the illumination area and corrected by the synchronization error corresponding to each point in the illumination area. The output waveforms of the marks M _{1 to} M ₈ before and after correction and the center position in the wafer stage coordinate system are also stored in the imaging characteristic detection system 12.

Next, from the image forming position of the mark M ₁ of the reticle R obtained as the center position X ₀ ′ of the output waveform of FIG. Ask for. From the position coordinates of the mark M ₁ on the reticle R and the magnification of the projection optical system PL, the position (design value) X ₀₁ where the mark M ₁ should be imaged on the photoelectric sensor 4 can be calculated. Therefore, by calculating ΔX = X ₀ ′ −X ₀₁ , the X-direction imaging position shift of the mark M ₁ of the reticle R caused by various causes including the synchronous movement of the reticle stage RST and wafer stage WST ( The difference between the design value and the actual exposure position) can be predicted.
Similarly, the image forming positions and the positional shifts of the other marks M _{2 to} M ₈ can be obtained.

Next, a method of predicting the dynamic image forming characteristic of the projection optical system PL in the actual scanning type exposure from the obtained one-dimensional or two-dimensional image forming position of each mark of the reticle R will be described. For example, when obtaining the contrast of an image as the image forming characteristic, the output waveform of the mark pattern obtained by the calculation as shown in FIG. 5B is sliced at an appropriate slice level to obtain each line width l Compare with a reference value. Alternatively, it can be obtained from the rising angles of the edges at both ends of the output waveform of each mark.

To obtain the image magnification as the image forming characteristic, the following method can be adopted. Imaging positions of a plurality of marks on the reticle R, for example, marks M ₁ and M _{5 on} the photoelectric sensor 4 are determined by the X coordinate system (for example, X ₁ , X ₅ ) of the wafer stage WST, and the wafer stage WST of the wafer stage WST. The magnification can be calculated from the distance between X ₁ and X ₅ in the coordinate system and the distance between the marks M ₁ and M ₅ on the reticle R in the X direction.

Further, the following method can be adopted to obtain the distortion as the image forming characteristic. For example, a set of two points A ₁ , A ₂ and B ₁ , B ₂ on the relatively inner side and the relatively outer side in the pattern area 40 of the reticle R has the same spacing A ₁ A ₂ and spacing B ₁ B _2. Thus, the image forming positions on the photoelectric sensor 4 are obtained in the coordinate system of wafer stage WST in the same manner as above. Next, the image forming position interval A ₁ A ₂ ′ and the interval B ₁ B ₂ ′ of the set of two points in the coordinate system of wafer stage WST are respectively obtained, and the difference (A ₁ A ₂ '-
The distortion can be obtained by calculating A ₁ A ₂ ) and (B ₁ B ₂ '-B ₁ B ₂ ) respectively and comparing them in consideration of the magnification.

In addition, from the measurement of the image forming position of the mark of the reticle R as described above, the scanning of the reticle R causes
The rotation amount of reticle R on reticle stage RST can be obtained. In this case, among the marks of the reticle R, for example, the marks M ₁ and M ₅ of Y on the photoelectric sensor 4
In the same manner as above, the image forming positions Y ₁ and Y ₅ in the direction are obtained respectively in the Y coordinate system of the wafer stage WST to obtain the difference ΔY, and how much the pattern of the reticle R is imaged in the Y direction. I understand. Also, this ΔY and M ₁
And the rotation amount θ of the reticle R can be calculated from the distance of M _{5 in} the X direction and the like.

Further, the positional deviation of the entire pattern of the reticle R can be obtained as follows. For example,
The reticle R is arranged on the reticle stage RST so that the center of the reticle R is located on the optical axis of the projection optical system PL, and the photoelectric sensor 4 detects 2 of each mark as described above.
After obtaining the three-dimensional image formation position in the wafer stage coordinate system,
The distance between the reference point (wafer stage coordinate system) on the photoelectric sensor 4 and the image forming position of each mark is obtained. And
By comparing those distances and the distances L _{1 to} L ₈ of the marks M _{1 to} M ₈ of the reticle R from the center of the reticle R in consideration of the magnification, the pattern of the reticle R in the scanning of the reticle R can be determined. Know the offset amount. In this case, the offset amount of the pattern of the reticle R can be obtained by comparing the distance from the center of the reticle R with respect to one mark and the distance between the image forming position and the reference point, but from the viewpoint of reproducibility, etc. It is preferable to calculate the offset amount from the average value by calculating the distance difference between the two marks M _{1 to} M ₈ .

When the image forming characteristic obtained as described above is not within the desired range, a predetermined operation for correcting the image forming characteristic can be performed. However, as a premise, the image forming characteristic (image forming characteristic of a still image) measured in a state where the stage is stationary is optimally adjusted, and further adjustment is difficult. As an adjustment method at this stage, it is possible to reduce synchronization deviation, vibration, and the like between the reticle R and the wafer W, which are deteriorated by scanning exposure. Generally, when the scanning speed is reduced, the load on the control system is reduced, and thus the synchronization accuracy is improved. It is also considered that vibration is reduced. Therefore, when the desired accuracy is not achieved in the displacement of the image forming position of the mark obtained as described above, a method of sending a signal to the stage controller 13 to reduce the scanning speed can be considered. When the scanning speed is decreased, the productivity (throughput) of the product is decreased, so it is optimal to decrease the speed within the range where the desired accuracy is obtained. For this reason,
The optimum speed can be selected by changing the scanning speed and measuring the imaging characteristics.

Next, a method of obtaining the baseline of the wafer alignment system from the one-dimensional or two-dimensional image formation position of each mark of the reticle R obtained as described above will be described. The measurement of the baseline can be performed using the measurement result of the image formation position and the image formation characteristic of the mark of the reticle R by the image formation characteristic calculator 14. Center position X of the output waveform in Fig. 5 (b)
_The image forming position of the mark M ₁ of the reticle R obtained as 0'is represented by the wafer stage coordinate system and is used as a reference point for baseline measurement during scanning exposure. Next, the wafer stage WST is moved in the X direction so that the photoelectric sensor 4 is located below the wafer alignment system, and the light source 30 of the alignment system irradiates the pattern plate 2 or the photoelectric sensor 4 with light to reflect the reflected light. It is detected by the light receiver 31. At this time, a specific portion of the pattern plate 2 or the photoelectric sensor 4 is set as a reference position. For example, one end defining the opening 1 of the pattern plate 2 is set as a reference position, and the end is defined as the light receiver 31.
May be detected. By taking in the signal of the interferometer 9 when the reference position is detected by the optical receiver 31 of the alignment system to the stage controller 13, the reference position can be known in the wafer stage coordinate system. Then, the baseline of the alignment system can be determined from the difference between the reference point of the baseline measurement and the reference position detected by the wafer alignment system. By thus defining the baseline of the alignment system, it is possible to accurately determine the position of the wafer W to be overlaid and exposed with the mark of the reticle R as a reference. Moreover, since the baseline can be obtained in a manner that takes in the relative positional deviation between the reticle R and the wafer W that occurs during scanning, the overlay accuracy in scanning exposure can be improved.

In the above embodiment, the slit-shaped opening 1 formed in the pattern plate 2 is provided as the light receiving portion of the photoelectric sensor. However, as shown in FIG. 6 (a), a square opening having a larger opening area is provided. The opening 1 ′ may be formed in the pattern plate 2. In this case, the photoelectric sensor installed below the opening 1 ′ has a size capable of receiving all the light passing through the opening 1 ′. For example, when the rectangular mark M ₁₀ formed on the reticle R passes through the opening 1 ′, the photoelectric sensor outputs a waveform signal as shown in FIG. 6B, and this signal is differentiated. By doing so, the waveform as shown in FIG. 6 (c) is obtained. In the waveform of FIG. 6 (c), the image contrast can be obtained from the line width a or the peak b, and the distortion can be obtained from the waveform center position c. The photoelectric sensor having such a large-area opening 1'has a larger signal range for measuring the integrated waveform, and therefore has a lower S / N than that having a slit-shaped opening. However, since the signals are not averaged by the slit width, there is an advantage that a signal closer to an actual image can be obtained. Further, there is an advantage that the measurement can be performed regardless of the type of the pattern on the reticle side.

In the above embodiment, the photoelectric sensor 4 is provided inside the wafer stage. However, a problem due to heat generation of the photoelectric sensor,
Alternatively, in order to avoid an inconvenience due to an increase in the weight of wafer stage WST, only a light receiving part, for example, only the incident end of an optical fiber is installed on the wafer stage, and the light received by the light receiving part is passed through the optical fiber or the like to the wafer stage. It can also be sent to a photoelectric sensor installed outside the.

In the above embodiment, the image forming characteristic of the reticle pattern is predicted by detecting the mark pattern installed on the object plane side of the projection optical system by the photoelectric sensor installed on the image plane side of the projection optical system. Conversely, the mark pattern installed on the image plane side of the projection optical system may be detected by a photoelectric sensor or the like installed on the object plane side of the projection optical system. For example, it is possible to illuminate a mark pattern formed on a wafer with an optical fiber or the like, and detect an image of the mark pattern by a projection optical system by a reticle stage or a sensor installed above the reticle stage.

Although the projection exposure apparatus of the above-described embodiment uses the projection optical system PL for semiconductor manufacturing, the present invention is a scanning exposure apparatus other than the scanning exposure apparatus using the projection optical system,
For example, it is similarly effective for a scanning type exposure apparatus using a mirror optical system.

[0053]

The scanning type exposure apparatus of the present invention measures and calculates the dynamic conditions of scanning exposure, that is, the image forming characteristics when the mask stage and the substrate stage are moving, before the actual exposure. Since it is equipped with a mechanism capable of adjusting, it is possible to predict in advance an error in the image forming characteristics or the like that occurs due to a unique cause of the scanning type exposure apparatus, thereby changing the exposure condition so as to correct the image forming characteristics. can do. Since the scanning type exposure apparatus of the present invention can determine the baseline of the wafer alignment system with reference to the image position of the reticle pattern that would be obtained in actual scanning type exposure, the scanning type exposure apparatus is highly accurate. Overlay exposure can be realized. Since the scanning type exposure method of the present invention measures and calculates the imaging characteristics and the wafer alignment system baseline under the dynamic conditions of the scanning type exposure, the scanning type exposure method is caused by a unique cause. It is possible to know in advance the image forming characteristic and the error of the baseline, etc., and thereby, the exposure condition and the scanning speed can be changed so as to correct the image forming characteristic and the baseline. Therefore,
By using the scanning exposure apparatus and the scanning exposure method of the present invention, microdevices such as semiconductor elements and liquid crystal elements can be manufactured with higher accuracy and higher efficiency.

[Brief description of the drawings]

FIG. 1 shows an outline of a configuration of a scanning exposure apparatus of the present invention including a mechanism capable of predicting an imaging characteristic during scanning exposure.

2A and 2B are diagrams illustrating a scanning exposure method by a scanning exposure apparatus according to an embodiment, FIG. 2A shows a state in which a reticle R is scanned with respect to an illumination area IA, and FIG. FIG. 7 is a diagram showing a state in which a wafer W is scanned in the opposite direction to the scanning direction of the reticle R with respect to the exposure area EA.

FIG. 3 is a plan view of a reticle including test marks M _{1 to} M ₈ used in the examples.

FIG. 4 is a diagram showing how mark images are formed when reference marks of a reticle are located at various positions in the scanning direction of an illumination area IA in the embodiment, and FIG. 4 (a) is an illumination area IA. 4B shows that the reference mark M ₁ moves along the X direction, and FIG. 4B shows the photoelectric sensor when the reference mark M ₁ is located at the X direction positions x ₁ , x ₂ and x ₃ of the illumination area IA. 3A and 3B show output waveforms of the image of the mark pattern M ₁ detected by.

FIG. 5 shows the waveform output of the image of the reference mark M ₁ of the reticle,
It is a figure which shows the method of correcting with a synchronization error, and FIG.
X ₁ , x in the illumination area IA after being corrected by the synchronization error
2B shows the output waveform of the mark pattern image corresponding to ₂ , x ₃ ... X _n , and FIG. 5B shows a mark which will be formed by one scan of the reference mark M ₁ with respect to the illumination area IA. The image of M ₁ is shown.

6A and 6B show a state in which an image of a mark pattern is detected by using a photoelectric sensor having a large area opening, FIG. 6A shows a positional relationship between the mark pattern and the opening, and FIG. Shows the output from the sensor, and FIG. 6 (c) shows the waveform obtained by differentiating the output waveform of FIG. 6 (b).

FIG. 7 is a diagram showing an outline of a conventional single-exposure projection exposure apparatus equipped with a measurement system for image formation characteristics, FIG. 7 (a) showing an outline of the apparatus configuration, and FIG. 7 (b) showing a mark pattern. Shows the positional relationship between the sensor and the opening, and FIG. 7 (c) shows the output waveform from the sensor.

[Explanation of symbols]

R reticle, W Wafer PL Projection optical system IA Illumination area EA Exposure area RST Reticle stage WST Wafer stage M ₁ Reticle mark 1 Aperture 2 Pattern plate 4 Photoelectric sensor 5 Wafer holder 7 Laser interferometer 10 Projector 12 Imaging characteristic detection system 13 Stage Controller 14 Image formation characteristic calculator 15 Acceleration sensor 30 Alignment system light source 31 Light receiving unit 202 Photoelectric sensor

Claims (12)

[Claims] 1. A mask stage for scanning an illumination area on a mask, the projection optical system for projecting an image of a pattern on the mask onto a photosensitive substrate, the illumination area and the projection optical system. In a scanning exposure apparatus including a substrate stage that scans the photosensitive substrate with respect to a conjugate exposure region in synchronization with scanning of the mask, an image of a mark pattern on the mask is photoelectrically detected on the substrate stage. Photoelectric detection means, synchronization error detection means for detecting a synchronization error caused by the synchronous scanning of the photosensitive substrate and the mask, and the photoelectric conversion when the mark pattern is located at various positions in the scanning direction within the illumination area. An image of the mark pattern corresponding to each scanning direction position detected by the detection means, and a synchronization error detected by the synchronization error detection means. Image forming state calculating means for calculating the image forming state of the mark pattern image obtained by synchronous scanning, and is obtained by synchronous scanning of the photosensitive substrate and the mask from the calculation result of the image forming state calculating means. The above-mentioned scanning type exposure apparatus, wherein the image formation state of a mask pattern image is predicted. 2. The scanning exposure apparatus according to claim 1, further comprising a correction unit for correcting the image formation state according to the predicted image formation state of the mask pattern image. 3. A mask stage for scanning an illumination area on a mask, a projection optical system for projecting an image of a pattern on the mask onto a photosensitive substrate, and the illumination area and the projection optical system. A scanning exposure apparatus comprising a substrate stage that scans the photosensitive substrate with respect to a conjugate exposure region in synchronization with the scanning of the mask, and photoelectrically detects an image of a mark pattern on the mask on the substrate stage. Photoelectric detection means, synchronization error detection means for detecting a synchronization error caused by the synchronous scanning of the photosensitive substrate and the mask, and the photoelectric conversion when the mark pattern is located at various positions in the scanning direction within the illumination area. An image of the mark pattern corresponding to each scanning direction position detected by the detection means, and a synchronization error detected by the synchronization error detection means. Image position calculation means for calculating the position of the image of the mark pattern, and alignment mark detection means for illuminating the alignment mark formed on the photosensitive substrate and photoelectrically detecting light from the alignment mark. The scanning exposure apparatus according to claim 1, further comprising: a baseline of the alignment mark detecting means, which is determined from the calculated position of the mark pattern image and the detection position of the alignment mark detecting means. 4. The photoelectric detecting means includes a light receiving portion having a slit and a sensor for photoelectrically detecting light transmitted through the slit, and the mark pattern image of the mask and the light receiving portion are parallel to the scanning direction. The scanning exposure apparatus according to any one of claims 1 to 3, wherein an image of the mark pattern is photoelectrically detected by relatively moving in a direction. 5. A mask stage for scanning an illumination area on a mask, the projection optical system for projecting an image of a pattern on the mask onto a photosensitive substrate, the illumination area and the projection optical system. In a scanning exposure apparatus including a substrate stage that scans the photosensitive substrate with respect to a conjugate exposure region in synchronization with scanning of the mask, a mark pattern provided on an object plane or an image plane of the projection optical system is provided. A detection system that illuminates and detects an image of the mark pattern by the projection optical system on the image plane or the object plane; and a synchronization error detection unit that detects a synchronization error caused by the synchronous scanning of the photosensitive substrate and the mask. Of the mark pattern corresponding to each scanning direction position detected by the detection system when the mark pattern is located at various positions in the scanning direction. Image forming state calculating means for calculating the image forming state of the mark pattern image obtained by synchronous scanning from the image and the synchronization error detected by the synchronization error detecting means, and the image forming state calculating means calculates the image forming state from the image forming state calculating means. The scanning type exposure apparatus, wherein the image formation state of a mask pattern image obtained by synchronous scanning of a photosensitive substrate and the mask is predicted. 6. The synchronization error includes displacement of each stage caused by synchronous movement of the substrate stage and the mask stage, displacement of the photosensitive substrate in the Z direction, and displacement of imaging characteristics due to vibration of the projection optical system. The scanning exposure apparatus according to any one of claims 1 to 5, characterized in that. 7. A method of manufacturing a microdevice using the scanning exposure apparatus according to claim 1. 8. While illuminating a mask, the mask is scanned with respect to an illumination area on the mask, and a photosensitive substrate is scanned with respect to an exposure area conjugate with the illumination area and the projection optical system. In a scanning type exposure method of exposing the pattern of the mask on a photosensitive substrate through a projection optical system by scanning in synchronization, prior to the exposure, the mark pattern on the mask is scanned in an illumination area in a scanning direction. Arranged at various positions, photoelectrically detecting an image of the mark pattern at each position by the projection optical system, synchronously scanning the photosensitive substrate and the mask at the same scanning speed as the actual scanning exposure, and synchronously scanning. The synchronization error caused by the above is detected for each position of the mask or the photosensitive substrate, and the image of the mark pattern corresponding to each position in the scanning direction photoelectrically detected and the detected The image formation characteristic of the image of the mark pattern obtained by the synchronous scanning based on the obtained synchronization error, thereby forming the image formation characteristic of the image of the mask pattern obtained by the synchronous scanning of the mask and the photosensitive substrate. The above-mentioned scanning type exposure method. 9. The image of the mark pattern corresponding to each position in the scanning direction which is photoelectrically detected is corrected by the detected synchronization error corresponding to each position in the scanning direction to be corrected at each position in the scanning direction. 9. The scanning type exposure method according to claim 8, wherein the image formation state of the image of the mark pattern obtained by the synchronous scanning is calculated by obtaining a mark pattern image and superimposing the corrected images. . 10. A projection exposure apparatus having means for detecting an alignment mark formed on a photosensitive substrate is used to scan the mask with respect to an illumination area on the mask while illuminating the mask. Scanning for exposing the pattern of the mask onto the photosensitive substrate via the projection optical system by scanning the photosensitive substrate with respect to an exposure region conjugate with the illumination region and the projection optical system in synchronization with the scanning of the mask In the mold exposure method, prior to the exposure, the mark patterns on the mask are arranged at various positions in the scanning direction in the illumination area, and the images of the mark patterns at the respective positions by the projection optical system are photoelectrically detected. Then, the photosensitive substrate and the mask are synchronously scanned at the same scanning speed as the actual scanning type exposure, and a synchronization error caused by the synchronous scanning is caused by the mask or the photosensitive substrate. Each position is detected, the position of the image of the mark pattern on the mask is calculated from the image of the mark pattern at each position in the scanning direction photoelectrically detected, and the detected synchronization error, and the calculation is performed. The above-mentioned scanning exposure method, wherein the baseline of the alignment mark detecting means is determined from the position of the mark pattern image and the detection position of the means for detecting the alignment mark of the photosensitive substrate. 11. An image of the mark pattern at each position in the scanning direction that is photoelectrically detected is corrected by the detected synchronization error corresponding to each position in the scanning direction, and the corrected position at each position in the scanning direction is corrected. The scanning exposure method according to claim 10, wherein the position of the image of the mark pattern obtained by synchronous scanning is obtained from the image obtained by superimposing the images of the respective mark patterns. 12. The image of the mark pattern formed by the projection optical system is photoelectrically detected by relatively moving the mark pattern image and the light receiving surface of the photoelectric detection means in a direction parallel to the scanning direction. The scanning exposure method according to claim 10 or 11.