JPH07221012A - Aligner - Google Patents

Abstract

PURPOSE:To provide aligner with a small focal shift in transfer pattern even when a large mask is used. CONSTITUTION:In an aligner, a pattern is formed on a first substrate by an optical projection system with the same magnification. Then, the pattern is projected and exposed onto a second substrate 23. The aligner includes positional detecting means 1A to 8A, 1B to 8B, 10, and 11 and position controlling means 24 and 28. One of the first and second boards is adjusted in position by the position controlling means 24 and 28 on the basis of positional information detected from the positional detecting means 1A to 8A, 1B to 8B, 10, and 11 to keep substantially a constant space between the first and second boards.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus, and more particularly to focusing in an exposure apparatus.

[0002]

2. Description of the Related Art FIG. 7 is a diagram schematically showing the structure of a conventional exposure apparatus. In FIG. 7, the pattern formed on the fixed mask (for example, reticle) 121 is transferred onto the substrate 123 via the projection optical system 122. In this case, focus detection, that is, position detection with respect to the image plane of the projection optical system is performed by the focus detection optical system for the substrate to be exposed.
It was done only for 23.

In the focus detection optical system, for example, an LED
Light emitted from such a light source 101 is reflected by a mirror 104 via a lens 102 and a field slit 103. The light reflected by the mirror 104 enters the mirror 107 via the aperture stop 105 and the lens 106. The light reflected by the mirror 107 is obliquely incident on the substrate 123, is specularly reflected, and is incident on the mirror 107 '. The light reflected by the mirror 107 'is incident on the mirror 109 via the lens 106' and the aperture stop 108. The light reflected by the mirror 109 is received by the image sensor 111.

In FIG. 7, when the substrate 123 moves upward in the figure to a position 123 '(shown by a broken line in the figure),
The light receiving position of the reflected light from the substrate 123 on the image sensor 111 is shifted downward in the drawing. In this way, the movement of the substrate in the vertical direction in the figure can be detected based on the light receiving position of the reflected light from the substrate, and the substrate is positioned at the predetermined position so that the reflected light is received at the predetermined position. As described above, the positioning of the substrate was controlled.

[0005]

As described above, in the conventional exposure apparatus, focus detection is performed only on the surface of the substrate which is the object to be exposed. Therefore, when the size of the mask becomes large and the bending of the mask due to its own weight and the surface inclination (taper) due to the manufacturing error become apparent, even if the focus detection of only the substrate that is the object to be exposed is performed, the bending or taper of the mask is caused. However, there is an inconvenience that defocus occurs in the transfer pattern due to the above. The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an exposure apparatus in which the transfer pattern defocusing is small even for a large mask.

[0006]

In order to solve the above-mentioned problems, in the present invention, a projection optical system (22) having substantially the same magnification is used.
In an exposure apparatus which projects and exposes a pattern formed on a first substrate (21) onto a second substrate (23) via a substrate, position information of the first substrate and the second substrate is detected. Position detecting means (1A to 8A, 1B to 8)
B, 10, 11) and the position information detected by the position detecting means, the first substrate so as to keep the distance between the first substrate and the second substrate substantially constant. An exposure apparatus is provided which further comprises a positioning control means (24, 28) for controlling the positioning of at least one of the second substrates.

According to a preferred aspect of the present invention, the position detecting means (1A to 8A, 1B to 8B, 10, 11) is
Light incident means (1A to 7A, 1B to 7B) for obliquely incidenting a light beam on the first substrate and the second substrate.
And a light receiving means (11) for receiving the reflected light from each of the first substrate and the second substrate, and the positioning control means (24, 28) is provided from the first substrate. Positioning of at least one of the first substrate and the second substrate is controlled on the basis of the position where the reflected light is received and the position where the reflected light from the second substrate is received.

According to a further preferred aspect, the light incident means includes first light incident means (1A to 7A) for obliquely injecting a light beam onto the first substrate, and light incident on the second substrate. Second light incidence means (1) for obliquely entering the beam
B to 7B). In this case, depending on the light quantity of the reflected light from the first substrate and the light quantity of the reflected light from the second substrate, the light quantity of the light source of the first light incident means and the light quantity of the second light incident means of the second light incident means may be changed. It is preferable to include light quantity control means (27A, 27B) for controlling the light quantity of the light source. Further, the exposure apparatus includes a light receiving means (1
As 1), a first light receiving means (11A) for receiving the reflected light from the first substrate and a second light receiving means (11B) for receiving the reflected light from the second substrate. And the sensitivity of the first light receiving means and the sensitivity of the second light receiving means according to the light quantity of the reflected light from the first substrate and the light quantity of the reflected light from the second substrate. Sensitivity control means (24A, 2) for controlling each
4B) is preferably provided.

[0009]

As described above, in the present invention, the exposure for transferring the pattern formed on the mask, which is the first substrate, onto the substrate to be exposed, which is the second substrate, through the projection optical system having substantially the same magnification. In the device, detect the position information of the mask and substrate,
The distance between the mask and the substrate is controlled to be substantially constant based on this position information. At this time, if the light amount of the light source obliquely incident on the first substrate and the light amount of the light source obliquely incident on the second substrate are independently controlled, the reflectivity of the mask, which is the first substrate, Even if the reflectance of the exposed substrate, which is the second substrate, is significantly different, the difference in the amount of reflected light from each substrate exceeds the dynamic range of the light receiving sensor, and signal processing becomes impossible, and the S / N ratio deteriorates. It is possible to prevent a decrease in accuracy due to the deterioration.

Similarly, the sensitivity of the first light receiving sensor that receives the reflected light from the first substrate and the sensitivity of the first light receiving sensor that receives the reflected light from the second substrate are independently controlled. According to this structure, even if the reflectance of the mask that is the first substrate and the reflectance of the exposed substrate that is the second substrate are significantly different, the input gain of the sensor is appropriately changed and the reflected light from each substrate is changed. It is possible to avoid the inability to perform signal processing and the deterioration of the S / N ratio due to the difference in the light amount. Further, as will be described later, in an exposure apparatus in which the projection optical system has substantially the same magnification, by making the distance between the mask and the substrate substantially constant, defocus of the transfer pattern can be substantially avoided.

In an exposure apparatus of approximately 1 × magnification, the mask becomes larger as the photosensitive substrate becomes larger, so that the bending of the mask due to its own weight and the inclination of the surface become apparent. Further, since the mask becomes large, projection exposure is performed while scanning the mask and the substrate relative to the projection optical system. Therefore, even if the focus detection is performed only on the substrate as in the conventional case, the transfer pattern is likely to be defocused over the scanning range. Therefore,
After preliminary scanning is performed in the non-exposure state, the position information of the mask and the substrate is detected at a plurality of points, and the distance between the mask and the substrate is adjusted based on the position information so that the distance is as constant as possible over the scanning range. It is preferable to perform projection exposure.

Even in a general exposure apparatus in which the projection optical system is not the same size, the position information of the mask and the position information of the substrate are detected, and at least one of the mask and the substrate is controlled to move so that the distance becomes a predetermined distance. As a result, defocus of the transfer pattern can be substantially avoided. In this case, it is preferable to move the mask and the substrate to predetermined positions based on the detected mask position information and substrate position information. As described above, according to the present invention, the positional information of the mask and the substrate is detected by using, for example, the grazing incidence focus detection optical system, and the distance between the mask and the substrate is controlled so as to be constant or keep a predetermined distance. Defocus can be substantially avoided.

[0013]

Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a perspective view showing the structure of an exposure apparatus according to an embodiment of the present invention. 2 is a diagram showing the configuration of the position detection system of the exposure apparatus of FIG. As shown in FIGS. 1 and 2, in the exposure apparatus of the present embodiment, the pattern formed on the mask 21 is uniformly illuminated by an illumination means (not shown), and is a substrate via the unit-magnification projection optical system 22. Plate 2
Transfer to 3.

As shown in the figure, when the mask 21 and the plate 23 become large, the effective fields of view of the projection optical system 22 are 25 and 26 on the mask 21 and the plate 23, respectively.
Only the range of can be secured. In this case, the mask 21 and the plate 23 are integrally moved relative to the projection optical system 22 in the direction of the arrow in the figure, that is, by performing exposure scanning in one direction, the entire desired wide exposure area is projected and exposed. To do.

As shown in the figure, for example, an oblique incidence focus detection optical system can be used as the position detection system of the exposure apparatus of the present invention. The position detection system shown in the figure has two light sources 1A each having means capable of varying the amount of light.
And 1B. The light emitted from the light source 1A (1B) is reflected by the lens 2A (2B) and the field slit 3A (3).
It is reflected upward (downward) in the figure by the mirror 4 via B). The light reflected by the mirror 4 has an aperture stop 5A (5B).
And the mirror 7A (7B) via the lens 6A (6B)
Incident on.

The light reflected to the left in the figure by the mirror 7A (7B) obliquely enters the mask 21 (plate 23), is specularly reflected and enters the mirror 7A '(7B'). Mirror 7
The light reflected downward (upper) in the figure by A '(7B') enters the prism 10 via the lens 6A '(6B') and the aperture stop 8A (8B). The two reflected lights respectively deflected to the left in the figure by the prism 10 are received by a common two-dimensional sensor (or one-dimensional sensor such as CCD) 11. The sensor 11 detects the position and the light amount of the two reflected lights, and an electric signal corresponding to the light amount is generated by the signal processing unit 24.
Is output to. When the signal processing unit 24 determines that the electric signals corresponding to the two reflected lights are out of the input range of the sensor 11, the two light source control devices 27.
A proper light quantity command is output to either one or both of A and 27B to control the light quantity of the light sources 1A and 1B. Each light source 1
An algorithm for obtaining the above-mentioned appropriate light amount command for A and 1B is shown in the flowchart of FIG. The signal processing unit 24 can be realized by, for example, a microcomputer and peripheral circuits for signal input / output. As shown in the flowchart of FIG. 3, the signal processing unit 2
4, an electric signal corresponding to each reflected light is detected by the sensor 11
When it is within the input range of, the light amount control is not performed for the corresponding light source. On the contrary, when the electric signal corresponding to each reflected light is not within the input range of the sensor 11,
When the magnitude of the signal is too small, the light quantity of the corresponding light source is increased by a predetermined amount, and when the magnitude of the signal is too large, the light quantity of the corresponding light source is decreased by a predetermined amount.

As described above, two slit images corresponding to the mask 21 and the plate 23 are projected on the two-dimensional sensor 11, and the signal processing unit 24 and the light source control device 2 are provided.
Proper electrical signals can be obtained by the cooperation of 7A, 27B and the light sources 1A, 1B. In addition, the visual field slit 3A is set so that the longitudinal direction of the slit image is a direction perpendicular to the paper surface of FIG.
And 3B are configured. When the mask 21 and the plate 23 are at the predetermined positions shown by the solid lines in the figure, the distance between the two slit images formed on the two-dimensional sensor 11 is L.

In FIG. 2, the mask 21 moves upward in the drawing to a position 21 '(shown by a broken line in the drawing), and the plate 23 moves upward in the drawing to 23' (shown by a broken line in the drawing). )
At the position of, the light receiving position of the reflected light from the mask 21 and the plate 23 on the two-dimensional sensor 11 is shifted downward in the drawing. As a result, as shown by the broken line in the figure, the distance between the two slit images that have been displaced is L '. By the way, when the mask 21 and the plate 23 move in the same direction in the figure by the same distance, that is, the mask 2
If the distance between 1 and the plate 23 is constant, the optical system is constructed symmetrically so that L and L ′ are equal in size.

FIG. 4 is a view showing the conjugate relation between the unit-magnification projection optical system, the mask and the plate. In FIG. 4, the pattern formed on the mask 31 is the same-magnification projection optical system 32.
An image is formed on a substrate 33 such as a plate through the. When the mask 31 moves upward in the drawing by a distance d and reaches the position 31 'as shown by the broken line, the pattern image forming position is the substrate 3
It moves upward in the figure by a distance d from the position of 3. That is, if the substrate 33 is moved to the position shown by the broken line in the drawing so that the distance between the mask 31 and the substrate 33 is kept constant, the conjugate relationship is maintained and the defocus of the transfer pattern does not occur.

Therefore, in the exposure apparatus as shown in FIGS. 1 and 2, at least one of the mask 21 and the plate 23 is controlled by the drive control unit 28 and the drive units 29 and 30 so that the distances L and L'are always constant. If one of them is controlled to move, defocus of the transfer pattern can be substantially avoided. Further, the reflected light from the mask 21 and the plate 23 travels along the optical path indicated by the solid line in FIG. 2 and is received at a predetermined position on the two-dimensional sensor 11, respectively.
Both the mask 21 and the plate 23 may be moved and controlled so that the respective 3 are positioned at predetermined positions.

FIG. 5 is a diagram showing a state in which the mask is bent by its own weight and the plate surface is inclined.
Shows the state of the mask and the plate before the preliminary scanning (non-exposure), and FIG. 9B shows the state of the mask and the plate whose position is corrected after the preliminary scanning. Generally, since the mask is supported on the periphery, bending due to its own weight becomes a problem. Further, since the plate is entirely supported by the stage, flexural deformation is not a problem, but surface inclination is a problem.

As shown in FIG. 5 (a), when the mask 41 is bent by its own weight and the surface of the plate 43 is inclined, for example, the distance between the mask 41 and the plate 43 is predetermined at the center O of the mask 41. Even if the distance is held at the distance H, the distance between the mask 41 and the plate 43 cannot be maintained at the predetermined distance H in the scanning direction (indicated by an arrow in the drawing). As a result, the unit magnification projection optical system 4 is scanned while scanning in the direction of the arrow in the figure.
When the pattern formed on the mask 41 is transferred to the plate 43 via 2, the defocus does not occur near the center O ′ of the plate 43, but the defocus of the transferred pattern occurs in the peripheral region.

Therefore, using the position detection optical system of FIG.
The position information of the mask 41 and the plate 43 is detected while performing preliminary scanning in the non-exposure state. Based on the detected position information, at least one of the mask 41 and the plate 43 is positionally controlled so that the deviation between the distance between the mask 41 and the plate 43 and the predetermined distance H becomes as small as possible in the scanning direction. In this way, as shown in FIG. 5B, the positioning correction is performed after the preliminary scanning, and the pattern formed on the mask 41 is transferred to the plate 43 through the unit-magnification projection optical system 42.
Transfer onto the plate 43, projection exposure can be performed without defocusing the transfer pattern over substantially the entire surface of the plate 43.

FIG. 6 is a diagram showing the configuration of another position detecting optical system. The position detection optical system shown in FIG.
It is equipped with one light source 51. The light emitted from the light source 51 enters the beam splitter 54 through the lens 52 and the field slit 53. The light incident on the beam splitter 54 is split into a reflected light beam that travels upward in the figure and a transmitted light beam that travels leftward in the figure. The reflected light beam has an aperture stop 55A.
And obliquely enters the mask 21 through the objective lens 56A having a relatively large aperture. On the other hand, the transmitted light beam is transmitted through the aperture stop 55.
B is obliquely incident on the plate 23 via B and the objective lens 56B having a relatively large aperture.

The light reflected by the mask 21 and the plate 23 enters the prism 60 via the lenses 56A and 56B, and the aperture stops 55A and 55B, respectively. The two reflected lights that have entered the prism 60 are both deflected to the left in the drawing, and respectively enter the corresponding two-dimensional sensors (or one-dimensional sensors such as CCDs) 11A and 11B. In each of the sensors 11A and 11B, the position and light amount of the corresponding reflected light is converted into an electric signal.

The signal processing unit 24 judges the magnitude of the signal converted by each of the sensors 11A and 11B. If the signal magnitude is outside the proper input range of each sensor, the magnitude of the signal is calculated. Gain controller 24 so that is within the proper input range of each sensor.
The input gain of each sensor is changed by A and 24B.
When the sensor is, for example, a CCD, the input gain can be changed by changing the storage time. Further, the algorithm for obtaining the input gain command in the signal processing unit 24 is realized by an algorithm in which the "light source light amount command" is read as the "sensor input gain command" in FIG. The operation of the position detection optical system shown in FIG. 6 is the same as the operation of the position detection optical system of FIG. 2, and a duplicate description will be omitted. However, in FIG.
When the mask 21 and the plate 23 move upward in the figure, the reflected light receiving position on the two-dimensional sensor 11 also moves upward in the figure, which is the opposite of the case of the position detection optical system in FIG.

In the above embodiment, if the slit-shaped light beam is compressed in the longitudinal direction through the cylindrical lens and received by the one-dimensional sensor, the received light amount increases, so that the S / N ratio is improved and the pattern is improved. The averaging effect of can be expected. Further, in the above-described embodiment, the example in which the oblique incidence focus detection optical system is used as the position detection system has been described, but other suitable position detection means can be used.

Further, although the present invention has been described with reference to the exposure apparatus having the same-magnification projection optical system in the above-mentioned embodiments, the mask position information and the substrate position can be also obtained in the exposure apparatus having the non-magnification projection optical system. Based on the information, it is possible to avoid the defocus of the transfer pattern by performing positioning control so that the distance between the mask and the substrate becomes a predetermined distance, or the position of the mask and the position of the substrate become a predetermined position. it can.

Consider, for example, the case where the projection optical system 22 has a reduction magnification of 1 / M in the embodiments shown in FIGS. Here, in the method of detecting the image forming position of the slit image on the two-dimensional sensor 11, when the magnification of the lens 6A and the magnification of the lens 6B are equal, the field slit 3A for forming an image on the two-dimensional sensor 11 is used. image as the movement amount (image by light through a mask 21) is ^doubled M movement amount of the image of the field slits 3B (image due to the light through the plate 23), the positioning of the mask 21 or plate 23 Should be controlled. In the method of detecting the interval between the slit images on the two-dimensional sensor 11, the field slit 3A is used.
It is only necessary to control so that the distance between the image of 1 and the image of the field slit 3B becomes constant. Further, the two-dimensional sensor 11 is provided so that the magnifications of the lenses 6A and 6B are different (for example, when the projection optical system is 1 / M, the magnification of the lens 6A is 1 / M ² of the magnification of the lens 6B). You may comprise so that the above space | interval may become fixed. The configuration as described above is not limited to the case where the projection optical system 22 has the reduction magnification, but can be applied to the case where the projection optical system 22 has the enlargement magnification.

In the above embodiment, the mask 2
1 and only the positional relationship at one point on the plate 23 is detected, but when the sizes of the mask 21 and the plate 23 are very large, position detection is performed at a plurality of points in the scanning orthogonal direction of the mask 21 and the plate 23. You may go. In this case, a plurality of position detection systems are provided,
The position of at least one of the mask 21 and the plate 23 may be controlled based on the detection result of these position detection systems. Further, instead of the two-dimensional sensor 11 in each embodiment, a one-dimensional sensor such as a CCD can be applied as described above.

[0031]

As described above, according to the present invention, the positional information of the mask and the substrate is detected by utilizing, for example, the grazing incidence focus detection optical system, and in the case of the unit magnification projection optical system, the distance between the mask and the substrate is reduced. Positioning control is performed so that a constant interval is maintained. As a result, it is possible to perform projection exposure with a small transfer pattern defocus even for a large mask.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of an exposure apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a position detection system of the exposure apparatus of FIG.

FIG. 3 is a flowchart showing an algorithm for obtaining an appropriate light amount command for each of the light sources of FIGS. 1 and 2.

FIG. 4 is a diagram showing a conjugate relationship between a unit-magnification projection optical system, a mask, and a plate.

FIG. 5 is a diagram showing a state in which the mask is bent by its own weight and the plate surface is tapered, (a) shows the state of the mask and plate before preliminary scanning (non-exposure), and (b).
Shows the state of the mask and the plate whose position is corrected after the preliminary scanning.

FIG. 6 is a diagram showing a configuration of another position detection optical system.

FIG. 7 is a diagram schematically showing a configuration of a conventional exposure apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 light source 2, 6 lens 3 field slit 4, 7 mirror 5, 8 aperture stop 6 lens 10 prism 11 one-dimensional sensor such as a two-dimensional sensor or CCD 21 mask 22 projection optical system 23 substrate 24 signal processing unit 24A, 24B gain Controller 27A, 27B Light source control device 28 Drive control device 29, 30 Drive device

Claims (11)

[Claims] 1. An exposure apparatus for projecting and exposing a pattern formed on a first substrate onto a second substrate through a projection optical system of substantially equal magnification, wherein the first substrate and the second substrate Position detecting means for detecting the position information of, and based on the position information detected by the position detecting means, so as to keep the distance between the first substrate and the second substrate substantially constant, An exposure apparatus comprising a positioning control means for controlling the positioning of at least one of the first substrate and the second substrate. 2. The position detecting means includes a light incident means for obliquely incidenting a light beam on the first substrate and the second substrate, and each of the first substrate and the second substrate. A light receiving unit for receiving the reflected light of the first substrate, the positioning control unit based on the position of receiving the reflected light from the first substrate and the position of receiving the reflected light from the second substrate. , The first substrate and the second
2. The exposure apparatus according to claim 1, wherein the positioning of at least one of the substrates is controlled. 3. The light incident means includes a first light incident means for obliquely incidenting a light beam on the first substrate, and a second light incident means for obliquely incident a light beam on the second substrate. The exposure apparatus according to claim 2, further comprising a light incident unit. 4. The light amount of the light source of the first light incident unit and the second light incident unit according to the light amount of the reflected light from the first substrate and the light amount of the reflected light from the second substrate. 4. The exposure apparatus according to claim 3, further comprising light amount control means for controlling the light amount of each of the light sources. 5. The exposure device, as the light receiving means,
The first substrate includes a first light receiving unit for receiving the reflected light from the first substrate and a second light receiving unit for receiving the reflected light from the second substrate, and the first substrate. Sensitivity control means for controlling the sensitivity of the first light receiving means and the sensitivity of the second light receiving means in accordance with the amount of reflected light from the substrate and the amount of reflected light from the second substrate. The exposure apparatus according to claim 2, wherein: 6. The positioning control means, based on the relative positional relationship between the position where the reflected light from the first substrate is received and the position where the reflected light from the second substrate is received, The exposure apparatus according to claim 2, wherein positioning of at least one of the first substrate and the second substrate is controlled. 7. The positioning control means determines the first substrate and the first substrate based on the position where the reflected light from the first substrate is received and the position where the reflected light from the second substrate is received. The exposure apparatus according to claim 2, wherein the two substrates are moved to respective predetermined positions. 8. An apparatus for performing projection exposure while scanning the first substrate and the second substrate in one direction with respect to the projection optical system, wherein the position detecting means is a pre-exposure preparatory unit. Position information at a plurality of points on the first substrate and the second substrate is detected during scanning, and the positioning control unit determines the first position based on the position information of the position detecting unit at the plurality of points. Positioning of at least one of the first substrate and the second substrate is controlled so as to keep the distance between the substrate and the second substrate substantially constant over the scanning range. The exposure apparatus according to any one of claims 1 to 7. 9. The exposure apparatus according to claim 8, wherein the position detecting means detects position information over substantially the entire surfaces of the first substrate and the second substrate in the preliminary scanning. 10. An exposure apparatus which projects and exposes a pattern formed on a first substrate onto a second substrate via a projection optical system, comprising: position information of the first substrate and the second substrate. A position detecting means for detecting position information, and a distance between the first substrate and the second substrate is a predetermined distance based on the position information of the first substrate and the position information of the second substrate. Thus, the exposure apparatus is provided with a positioning control means for controlling the positioning of at least one of the first substrate and the second substrate. 11. The positioning control means moves each of the first substrate and the second substrate to a predetermined position based on the position information of the first substrate and the position information of the second substrate. The exposure apparatus according to claim 10, wherein: