JPH0529196A - Exposure apparatus and manufacture of semiconductor chip using same - Google Patents

Abstract

PURPOSE:To accurately align a reticule with a wafer through a projection lens system by a light having a different wavelength from that of in exposure light by so providing one parallel flat surface plate inclined with respect to a meridional section of the lens system as to correct an astigmatism and a coma aberration generated via a projection lens by detecting means. CONSTITUTION:The exposure apparatus comprises a projection lens system 3 for projecting a first object pattern on a second object with an exposure light, and detecting means for illuminating the second object with a detected light having a different wavelength from that of the exposure light, receiving the detected light from the second object through the system 3 and detecting an image of a mark 14 on the second object. The system 3 is so composed as to correct the aberration of the light and to generate a predetermined astigmatism and a predetermined coma aberration for the detected light. One parallel flat surface plate 4 inclined with respect to a meridional section of the system 3 is so provided as to correct the astigmatism and the coma aberration generated by the projection lens by the detecting means.

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 a method of manufacturing a semiconductor chip using the same, and more particularly to a projection lens system (projection optical system) for forming a fine electronic circuit pattern such as IC or LSI formed on a reticle surface. And an exposure apparatus having a function of observing the state on the wafer surface through a projection lens system with light having a wavelength different from the light for this exposure. The present invention relates to a method of manufacturing a semiconductor chip.

[0002]

2. Description of the Related Art In a projection exposure apparatus for manufacturing semiconductors, the first
The circuit pattern of the reticle as an object is projected and exposed on the wafer as the second object by the projection lens system. Prior to this projection exposure, the alignment mark on the wafer is detected by observing the wafer surface with the observation device. The position of the reticle and the wafer are aligned, that is, alignment is performed based on the detection result.

The alignment accuracy at this time largely depends on the optical performance of the observation apparatus. Therefore, the performance of the observation device is an important factor in the exposure device.

Various types of devices that perform alignment using such an observation device have been proposed. For example, the present applicant has proposed an alignment system using such an observation device in Japanese Patent Laid-Open No. 58-25638.

In this publication, the circuit pattern of the reticle is projected and exposed on a wafer by a projection lens system using g-line (436 nm) light (exposure light), while the alignment system is exposed to H light.
The alignment mark of each of the reticle and the wafer is detected using light (alignment light) having a wavelength of 442 nm emitted from the e-Cd laser.

By constructing a so-called bi-telecentric optical system so that the projection lens system is telecentric on both the reticle side and the wafer side, when observing the wafer surface from the reticle side, the chief ray of alignment light is generated. It uses the feature that it is always perpendicular to the reticle surface. As a result, even if the type of IC to be manufactured is changed and the pattern size on the reticle surface is changed to change the observation position of the alignment system, the angle of the light incident on or reflected on the reticle surface can be kept unchanged. A highly accurate TTL on Axis system is constructed by utilizing the property.

The TTL on Axis system is to align a reticle and a wafer in an exposed state via a projection optical system for exposing.

The TTL on Axis alignment system using the light of the wavelength of the exposure light such as the g-line or the light equivalent to it as the alignment light as in the apparatus of the above-mentioned publication is a typical example of the method preferable in the detection accuracy of the alignment mark. is there.

[0009]

However, if the wavelength of the exposure light (exposure wavelength) and the wavelength of the alignment light (alignment wavelength) are made substantially equal to each other, a resist layer such as a multi-layered resist coated on the wafer will prevent the alignment light. The absorbed light reduces the reflected light from the alignment mark on the wafer surface, lowers the S / N ratio at the time of detecting the alignment mark, and causes a decrease in alignment accuracy.
For this reason, S /
It is necessary to improve the N ratio and the alignment accuracy.

When the alignment wavelength and the exposure wavelength are different from each other and the alignment mark is detected by the TTL method, various aberrations are satisfactorily corrected only for the exposure wavelength in the projection lens system. Aberrations, specifically axial chromatic aberration, lateral chromatic aberration, coma of other colors,
Astigmatism, spherical aberration, etc. occur, which makes it impossible to detect a good alignment mark, which causes a decrease in alignment accuracy.

Therefore, conventionally, various methods have been proposed for observing the wafer surface satisfactorily through the projection lens system with light having a wavelength other than the exposure wavelength. For example, when observing the wafer surface through a reticle, the position of the wafer surface is shifted in the optical axis direction of the projection lens system by the amount of focus shift due to the axial chromatic aberration that occurs in the projection lens system with respect to the alignment light used for observation. An auxiliary optical system that establishes a shared relationship between the reticle surface and the wafer surface and corrects axial chromatic aberration is provided between the reticle and the projection lens system, and this auxiliary optical system and the projection lens system form a reticle surface and a wafer. The method of establishing a mutual relationship with the face is adopted.

However, since none of these methods corrects other chromatic aberrations generated in the projection lens system, the alignment optical system forms an image of a radial pattern in which asymmetrical aberrations such as coma aberration and chromatic aberration of magnification do not occur. That is, the alignment mark is detected using only the image formation in the sagittal direction.

However, if the marks are detected through the projection lens system only by using the image formation in the sagittal direction, it is possible to obtain a high resolution in an exposure apparatus which needs to transfer a submicron minute pattern onto a wafer with high resolution. It is difficult to perform accurate alignment and high-precision magnification control.

The magnification of the projection lens system changes with changes in atmospheric pressure, and the wafer is partially distorted due to processing such as development and etching. Therefore, the exposure apparatus is required to have a function of detecting such a change in magnification and distortion of the wafer to control the magnification of the projection lens system.

Therefore, as a method of detecting a change in magnification and distortion of the wafer, an image of a mark on the wafer is formed through a projection lens system, and a change in the image forming position in the meridional direction (radiation direction) is detected. It is conceivable, however, that the conventional image forming method of the radial pattern, that is, the mark image forming method using only the image formation in the sagittal direction cannot accurately detect such a change in the image forming position in the meridional direction.

Further, as in the prior art, only the image formation in the sagittal direction, the information of the mark position obtained through one alignment optical system is one-dimensional, and one alignment optical system is used for two-dimensional information. It was not possible to obtain accurate information on the proper mark position.

On the other hand, the applicant of the present invention is disclosed in Japanese Patent Laid-Open No. 62-28.
In Japanese Patent No. 1422, one plane-parallel plate is arranged to be inclined with respect to the meridional section of the projection lens system, and two planes are arranged in a plane orthogonal to the plane in which the plane-parallel plate is inclined.
By utilizing the image forming means having three parallel plane plates as a whole in which the parallel plane plates are inclined with respect to each other, the astigmatism and coma generated from the projection lens system due to the difference in the wavelength of the exposure light and the alignment light are used. We propose an exposure system that corrects aberrations and aligns the reticle and wafer with high accuracy.

The present invention is a further improvement of the exposure apparatus proposed in the applicant's earlier application, and it is meridional when detecting a mark through a projection lens system with detection light (alignment light) having a wavelength different from that of the exposure light. An object of the present invention is to provide an exposure apparatus capable of detecting the position of a mark image with respect to a direction and having an improved mark detection function, and a method of manufacturing a semiconductor chip using the exposure apparatus.

[0019]

An exposure apparatus according to the present invention comprises a projection lens system for projecting a pattern of a first object onto a second object with exposure light, and a second detection light system with detection light having a wavelength different from that of the exposure light. In an apparatus having a detection means for illuminating an object and receiving the detection light from the second object via the projection lens system to detect an image of a mark on the second object, the projection lens system includes the exposure device. The aberration correction is performed on the light, and the detection light is configured to generate a predetermined astigmatism and a predetermined coma, and the detection means generates the astigmatism. It is characterized in that it comprises a plane-parallel plate tilted with respect to the meridional section of the projection lens system so as to correct the aberration and the coma.

In addition, the exposure apparatus of the present invention illuminates the second object with a projection lens system for projecting the pattern of the first object onto the second object with the exposure light, and with detection light having a wavelength different from that of the exposure light. Then, in a device having a detection means for receiving the detection light from the second object via the projection lens system and detecting the image of the mark on the second object, the projection lens system is On the other hand, the aberration correction is performed, and the detection light is configured to generate a predetermined astigmatism and a predetermined coma, and the detection means generates the astigmatism and the astigmatism. A projection lens system for projecting a pattern of a first object onto a second object with exposure light, comprising two parallel plane plates tilted with respect to a meridional section of the projection lens system so as to correct the coma aberration; The center wavelength is different from the exposure light A detection unit that illuminates the second object with detection light having a predetermined bandwidth, receives the detection light from the second object via the projection lens system, and detects the image of the mark on the second object. In the apparatus having the projection lens system, the projection lens system is configured to perform aberration correction on the exposure light, and generate predetermined astigmatism, predetermined coma and predetermined chromatic aberration of magnification for the detection light. The detecting means includes a single plane parallel plate inclined with respect to the meridional cross section of the projection lens system so as to correct the astigmatism, the coma and the lateral chromatic aberration generated in the projection lens, and Second pattern of the first object with exposure light
A projection lens system for projecting onto an object and the exposure light illuminates a second object with detection light having a predetermined bandwidth having a different central wavelength, and the detection light from the second object is passed through the projection lens system. In the device having a detecting means for receiving and receiving the image of the mark on the second object, the projection lens system is aberration-corrected with respect to the exposure light and a predetermined non-correction with respect to the detection light. The projection lens is configured to generate a point aberration, a predetermined coma aberration, and a predetermined magnification chromatic aberration, and the detection unit corrects the astigmatism, the coma aberration, and the magnification chromatic aberration generated in the projection lens. It is characterized by having two parallel plane plates inclined with respect to the meridional section of the system.

In the method of manufacturing a semiconductor chip of the present invention, the image of the alignment mark on the wafer is detected through a projection lens system using detection light that does not expose the wafer, and the wafer obtained based on the detection is detected. Position information of the wafer is aligned, and the circuit pattern of the mask is illuminated with exposure light that exposes the wafer to project and transfer the image of the circuit pattern onto the wafer through the projection lens system. Then, in the method of manufacturing a semiconductor chip, the projection lens system is configured to correct aberrations with respect to the exposure light, and to generate predetermined astigmatism and predetermined coma with respect to the detection light. The astigmatism and the coma produced in the projection lens during the detection are tilted with respect to the meridional section of the projection lens system. The image of the alignment mark on the wafer is detected through the projection lens system using the detection light that does not expose the wafer, and the position of the wafer obtained based on the detection. Positioning the wafer according to the information, illuminating the circuit pattern of the mask with exposure light that exposes the wafer to project an image of the circuit pattern onto the wafer through the projection lens system, and transfer the image. In the method of manufacturing a semiconductor chip, the projection lens system is configured to perform aberration correction on the exposure light and generate predetermined astigmatism and predetermined coma aberration with respect to the detection light. And two parallel planes in which the astigmatism and the coma generated in the projection lens during the detection are inclined with respect to the meridional section of the projection lens system. Is characterized such that the corrected using.

[0022]

1 is a schematic view of an optical system of an embodiment when the present invention is applied to an exposure apparatus for semiconductor manufacturing. In the figure, reference numeral 1 denotes a reticle as a first object, which is placed on the reticle stage 28. A wafer 2 is a second object, and an alignment mark 14 is provided on the surface of the wafer. A projection optical system 3 is composed of a projection lens system and projects a circuit pattern or the like on the surface of the reticle 1 onto the surface of the wafer 2.

Reference numeral 21 denotes a θ, Z stage on which the wafer 2 is mounted, and θ rotation of the wafer 2 and focus adjustment, that is, adjustment in the Z direction are performed. The θ and Z stage 21 is mounted on an XY stage 22 for performing a step operation with high accuracy. An optical square 23, which serves as a reference for measuring the stage position, is placed on the XY stage 22, and the optical square 23 is monitored by a laser interferometer 24.

In the present embodiment, the alignment between the reticle 1 and the wafer 2 is performed indirectly by aligning the reference marks whose positional relationship is determined in advance. Alternatively, it is assumed that an actual resist image pattern or the like is aligned and exposed to measure the error (offset), and thereafter the offset processing is performed in consideration of the value.

Next, a method for detecting the position of the mark 14 on the surface of the wafer 2 will be described. 63 is a light source, which is composed of a white light source such as a halogen lamp. Of the light flux from the light source 63, the wavelength selection filter 66 has a predetermined wavelength width different from that of the exposure light (for example, wavelength 633 ± 20n).
m, half-value width 40 nm), and a linearly polarized light beam having a polarization plane in a predetermined direction is reflected by a polarization beam splitter 67 via a condenser lens 62.

The light beam reflected by the polarization beam splitter 67 is converted into circularly polarized light by the λ / 4 plate 65 and a correction lens 18 for correcting spherical aberration and chromatic aberration and one parallel sheet having optical properties described later and inclined in a predetermined direction. After being reflected by the mirror M1 via the plane plate 4, the light is incident on the projection lens system 3.

Here, the plane-parallel plate 4 is arranged at a predetermined angle with respect to the meridional section of the projection lens system 3, and the projection lens system 3 is caused by the difference in the wavelength of the exposure light and the detection light (alignment light) as described later. The astigmatism, coma, chromatic aberration, etc., which occur due to The light flux incident on the projection lens system 3 illuminates the mark 14 on the surface of the wafer 2 after emission.

The reflected light from the mark 14 on the surface of the wafer 2 returns to the projection lens system 3, the mirror M1, the plane-parallel plate 4, the correction optical system 18 and the original optical path in order and enters the λ / 4 plate 65. The light flux that has passed through the λ / 4 plate 65 has a polarization plane of 90
It becomes a linearly polarized light that has been rotated by a degree, and this time it passes through the polarization beam splitter 67 and is incident on the CCD (imaging device) 19, and an image of the mark 14 (mark image) is formed on the surface thereof.

At this time, the positional relationship of the wafer 2 is obtained by observing (measuring) the position of the mark image formed on the surface of the CCD 19. For example, the deviation of the mark image from the reference position (reference mark) on the CCD 19 surface is obtained.

Thus, in this embodiment, the elements 63, 66,
The deviation of the mark on the surface of the wafer 2 from the reference mark is detected through the projection lens system 3 by the detecting means having 62, 67, 65, 18, 4, M1, and 19. Then, the detection of the mark image at this time is performed by forming the mark image on the surface of the CCD 19 by the image forming means having the elements M1, 4, and 18.

Next, a method of aligning the mark 1a provided on the reticle 1 with the reference mark 64 provided on the main body will be described.

Of the light beam from the light source 68, the wavelength selection filter 68 allows a light beam having a predetermined wavelength width to pass through, is condensed by the condenser lens 62, and is reflected by the half mirror 61. Then, the mark 1a and the reference mark 64 are illuminated by the light flux reflected by the half mirror and passing through the correction lens 18 and the mirror 17. The reflected light from the mark 1a and the reference mark 64 returns to the mirror 17, the correction lens 18 and the original optical path in order, passes through the half mirror 61 and is incident on the CCD 19 surface, and both mark images are formed on the surface. ing. Based on the positional relationship between both mark images at this time, the reticle 2 is aligned with the main body.

In this embodiment, a plurality of detecting means for detecting marks on the surface of the wafer 2 and an optical system for aligning the reticle with the main body are provided symmetrically with respect to the optical axis of the projection lens system 3.

In the present embodiment, as described above, by providing one parallel plane plate 4 in the optical path of the detection optical system for detecting the mark 15 on the surface of the wafer 2, the exposure light and the detection light are detected. Of astigmatism and coma produced by the projection lens system 3 due to the difference in the wavelength of the reticle 1 is corrected in both the sagittal plane and the meridional plane, and the mark 14 on the wafer 2 is satisfactorily detected. The relative alignment with the wafer 2 is performed with high accuracy. After that, the pattern on the surface of the reticle 1 is projected and exposed on the surface of the wafer 2 by the projection lens system 3, and the semiconductor chip is manufactured through known development processing and the like.

Next, the optical function of the plane parallel plate 4 used in this embodiment will be described.

Generally, as shown in FIG. 2, thickness d and refractive index N
It is assumed that a light beam having a divergence angle μ is incident on the plane-parallel plate 201 such that the principal ray PR thereof has an angle θ (θ = 45 ° in the figure). At this time, the astigmatism AS and the coma aberration CM generated from the plane-parallel plate 201 are W. Smith
Author of "Modern Optical Engineer"
As shown in “ring”, AS = d · θ ² (N ² −1) / N ³ CM = d · μ ² · θ (N ² −1) / (2N ³ ).

That is, the astigmatism AS is the square of the incident angle θ,
Coma aberration CM is proportional to the incident angle θ. Therefore, as shown in FIG. 3, when the two parallel plane plates 301 and 302 having the same thickness are arranged at the angle θ and the angle −θ with respect to the principal ray PR, the astigmatism AS is larger than that in the case of FIG. Although it is doubled, the coma aberrations CM cancel each other out and become 0.

Applicant's earlier JP-A-62-281422
In the exposure apparatus according to the publication, the coma aberration is corrected by adjusting the thickness and inclination of one parallel plane plate CM, and the thickness and inclination of the two parallel plane plates AS1 and AS2 are adjusted and the plane parallel plate CM is adjusted. Astigmatism generated from the entire optical system including is corrected.

That is, the coma aberration of the entire optical system is corrected by one parallel plane plate CM, and the two parallel plane plates AS1 and A
By S2, the astigmatism of the entire optical system including the astigmatism generated in the plane-parallel plate CM is corrected.

On the other hand, in the present invention, by setting the various aberrations of the projection lens system to appropriate values, the wavelengths of the exposure light and the detection light (alignment light) can be adjusted by using one parallel plane plate. Due to the difference, astigmatism, coma aberration, chromatic aberration, etc. generated from the projection lens system are well corrected while the overall size of the device is reduced. For example, a projection lens system whose aberration is corrected with a wavelength of g-line has a wavelength of 63 from a He-Ne laser.
It is difficult to bring the amount of aberration within an allowable value when using a light flux of 2.8 nm unless a refraction system is used, for example, a mirror optical system is not used.

On the other hand, in the present invention, it is impossible to eliminate the alignment aberration of the projection lens system (within the allowable value) as described above, but it is designed to have the residual aberration so as to have a predetermined value. For example, in the exposure apparatus shown in FIG. 1, the residual aberration amount of the projection lens system has different signs of the astigmatism AS and the coma aberration CM generated from the one parallel plane plate 201 shown in FIG. As a result, it is possible to correct astigmatism and coma by using only one plane-parallel plate.

As described above, in the present invention, by properly controlling the aberration amount of the projection lens system in advance, various aberrations caused by the projection lens system due to the difference in wavelength are corrected by one parallel plane plate, and the mark 14 on the wafer 2 surface is corrected. Is observed well.

In addition, in the present invention, when observing the mark 14 on the surface of the wafer 2, the angle of view of the projection lens system and the wavelength used may be used as variables and changed. As a method of changing the angle of view, there is a method of changing the irradiation position of the mark on the surface of the wafer 2. The wavelength can be changed by changing the wavelength selection filter.

Next, a specific numerical example when a plane parallel plate is used will be shown.

The wavelength of the detection light is 632.8 nm, the NA of the light beam is 0.1 (the imaging magnification of the projection lens system is ⅕, and NA = 0.5 and μ = tan on the reduced wafer side).
^-1 (0.1) = 5.7 °).

Here, when the inclination in FIG. 2 is the angle θ, the thickness d, and the refractive index N has the following values, the coma aberration CM and astigmatism AS generated from one parallel plane plate are as follows. .

[0047]

[Table 1] BK7: Nd = 1.51633 νd = 64.1 F6: Nd = 1.63636 νd = 35.4 To obtain the coma aberration CM and the astigmatism AS at this time from the three parallel plane plates (C)

[0048]

[Table 2] Becomes Coma aberration C when using one parallel plane plate
When M and astigmatism AS are

[0049]

[Table 3] To obtain the same coma aberration CM and astigmatism AS from three parallel plane plates (e)

[0050]

[Table 4] In order to evaluate compactness, which is a measure of the length of the optical path when the plane-parallel plate is arranged in the optical path, the length D of the plane-parallel plate in the optical axis direction is defined as shown in FIG. Comparing the above (d) and (e) as an example (however, d = 4 is used in (e)), the effective diameter EA is 10, 20, 30,
40

[0051]

[Table 5] Becomes That is, in (d) and (e), even when one parallel plane plate is used, EA = 24.57 or more and the use of (d) shortens the length D and downsizes the entire optical system.

Therefore, in (e), the parallel plane plate is actually 3
It can be seen that the length corresponding to the length D is further increased because the number of sheets is used, and the optical system of (d) is smaller in size.

Next, the correction of the chromatic aberration of magnification of the projection lens system will be described by taking the conditions (a) and (b) described above as an example.
Now, assuming that the wavelength range is wavelength 633 ± 20 mm, wavelength λ = 61
Center wavelength λ = 633 nm of 3 nm and wavelength λ = 653 nm
The color shift amount ΔLT shown in FIG.

[0054]

[Table 6] Thus, when the glass material changes, the color shift amount ΔLT changes (inversely proportional to the Abbe number νd).

Further, as shown in the above (a) and (b), even if the glass material is changed, the coma aberration CM and the astigmatism AS hardly change. Therefore, in the present embodiment, first, various aberrations are set by variables other than the glass material (the aberration is other than the chromatic aberration of magnification), and finally the glass material is determined to correct the chromatic aberration of magnification.

At this time, the projection lens system 3 is designed in advance so that the direction of coma and the direction of chromatic aberration of magnification can be corrected by the plane-parallel plate 4. Further, since the color shift amount ΔLT on the plane-parallel plate 4 is constant even if the angle of view changes, the projection lens system 3
Can be corrected only at a limited image height (position of the mark 14). For this reason, in this embodiment, the projection lens system 3 is set so that the change of the chromatic aberration of magnification is small in the image height range near the position of the mark 14 and at least corresponding to the width of the mark 14.

When a light beam with a narrow band width is used as the detection light in this embodiment, it is not necessary to correct the chromatic aberration of magnification.

In the first embodiment shown in FIG. 1, the case where one parallel plane plate is used is shown, but the optical path length is somewhat longer, but the use of two parallel plane plates produces the same effect as described above. Obtainable.

In this case, when the projection lens system has no coma and only astigmatism remains, the plane-parallel plate 4 of FIG.
As shown in FIG. 3, the two parallel plane plates 301, 30
It suffices to arrange the two at an angle. If the signs of astigmatism are different (the value obtained by subtracting the sagittal image plane from the meridional image plane is negative or positive), the two parallel plane plates 3 shown in FIG.
01 and 302 may be arranged in a state of being rotated 90 degrees about the optical axis 303.

In addition, as shown in FIG. 5, two parallel plane plates 50 having different thickness d, inclination angle θ, and refractive index N are used.
1,502 may be used. In this case, astigmatism AS and coma aberration CM are

[0061]

[Equation 1] Becomes

Therefore, in consideration of the residual aberration of the taking lens system, if two parallel plane plates having different thickness d, inclination angle θ and refractive index N are properly used, the aberration can be corrected more favorably. Further, as the plane parallel plate, a back surface reflection type mirror having a back surface as a reflection surface may be used instead of the transmission type.

FIGS. 6 and 7 are schematic views of the main parts of the exposure apparatus according to the second and third embodiments of the present invention. In the embodiment shown in FIGS. 6 and 7, the mark 14 on the wafer 2 surface is imaged through the projection lens system 3 in the vicinity of the alignment mark 1a on the reticle 1 surface. Both the mark 1a and the mark image on the wafer 2 are imaged by the CCD 1
It is formed in sequence on 9 surfaces. Then, the positions of both marks with respect to the reference mark are observed (measured), and thereby the relative alignment between the reticle 1 and the wafer 2 is performed. This point is different from the first embodiment of FIG. 1, and other configurations are substantially the same as the first embodiment.

Next, the second embodiment of FIG. 6 will be described focusing on the configuration different from the first embodiment of FIG. First, when observing the mark 14 on the wafer 2, the light beam from the light source 64 for observing the mark 1a on the reticle 1 surface, which will be described later, is emitted from the mark 1
This is done when a is not illuminated. Therefore, the light source 6
4 is turned off, or the light flux is blocked by shutter means (not shown) or the like.

Of the light flux from the light source 63, the light flux of a predetermined wavelength width (wavelength 633 ± 20n) is obtained by the wavelength selection filter 66.
m, full width at half maximum (40 nm) and then condensed by the condenser lens 62, and linearly polarized light polarized in a predetermined direction is passed by the polarization beam splitter 43a. Then, in the following order, circularly polarized light is formed by the λ / 4 plate 65a, the plane parallel plate 4 that corrects astigmatism and coma, the correction lens 45 that corrects spherical aberration and axial chromatic aberration, the mirror 45, and the half mirror 41.
The mark 14 on the wafer 2 surface is illuminated by the correction lens 18, the mirror 17, the reticle 1, and the projection lens system 3.

The reflected light from the mark 14 on the surface of the wafer 2 returns to the original optical path and forms a mark image in the vicinity of the mark 1a of the reticle 1 formed by the projection lens 3.
After that, the mirror 17, the correction lens 18, and the half mirror 41
Reflected by the mirror 44, the correction lens 45, the plane-parallel plate 4, and the λ / 4 plate 65a to become linearly polarized light whose polarization direction is rotated by 90 degrees from the previous one, and this time the polarization beam splitter 43a.
And the other polarization beam splitter 43b, and a mark image is formed on the surface of the CCD 19. As a result, the mark 14 on the wafer 2 surface formed on the CCD 19 surface
Is observing the mark image. For example, CCD of the mark image
The amount of deviation from the reference mark on the surface 19 is detected.

Next, when observing the mark 1a on the surface of the reticle 1, the light from the light source 63 is prevented from entering the surface of the wafer 2.

Of the light flux from the light source 64, a wavelength selection filter 69 having optical characteristics different from those of the wavelength selection filter 66.
In b, only a light beam in a predetermined wavelength range (wavelength 680 ± 20 nm) is passed and condensed by a condenser lens 62b, and only a linearly polarized light polarized in a predetermined direction is reflected by a polarization beam splitter 43b.

Thereafter, the λ / 4 plate 65b is sequentially converted into circularly polarized light, passes through the relay lens 42 and the half mirror 41, and illuminates the mark 1a on the surface of the reticle 1 through the correction lens 18 and the mirror 17.

The reflected light from the mark 1a of the reticle 1 returns to the original optical path, that is, passes through the mirror 17, the correction lens 18, and the half mirror 41, the relay lens 42, the λ / 4 plate 6
At 5b, it becomes linearly polarized light whose polarization direction is rotated by 90 degrees, and this time it passes through the polarization beam splitter 43b,
An image of the mark 1a is formed on the surface of the CCD 19.

At this time, a part of the light flux from the light source 64 passes through the reticle 1 and passes through the projection lens system 3 to the wafer 2
Illuminate the mark 14 on the surface. And mark 1 at this time
The reflected light from 4 returns to the original optical path and enters the CCD 19 surface.

Therefore, in this embodiment, the mark 1 on the surface of the wafer 2 is used.
The on-axis chromatic aberration of the projection lens system 3 is controlled so that the image forming position based on the reflected light from the lens 4 is largely defocused from the CCD 19 surface, and the mark 1a of the reticle 1 is well focused on the CCD 19 surface. ing.

At this time, when the aberration of the projection lens system is not corrected as described above, the wafer 2 is moved by the XY stage 22 so that the light beam from the light source 64 does not enter the mark 14 on the surface of the wafer 2.

In this embodiment, the mark image of the mark 1a of the reticle 1 on the CCD 19 surface is observed in this way. For example, the amount of deviation of the mark image from the reference mark on the CCD surface is detected. In this embodiment, the relative alignment between the reticle 1 and the wafer 2 is performed as described above.

In the third embodiment shown in FIG. 7, the projection lens system 3 is configured to be telecentric on both the incident side and the exit side, and the detection means 701 composed of the elements below the mirror 17 is provided as the optical axis of the projection lens system 3. It is configured to be movable in a direction orthogonal to the. This makes it possible to align the reticle 1 and the wafer 2 regardless of the position of the alignment mark 1a on the surface of the reticle 1.

At this time, an offset occurs due to the attitude of the detecting means 701 when the detecting means 701 is moved. For example, when the mirror 17 is tilted at an angle α, assuming that the axial chromatic aberration on the reticle side of the light flux with a wavelength of 633 nm of the projection lens system 3 is L and the projection magnification is 1/5, Ltan (2α / 5)
However, an offset occurs in terms of wafer surface. Therefore, in this embodiment, the wavelength selection filter 69b has the same wavelength (g-lin) as the exposure light whose aberration is corrected by the projection lens diameter 3.
The one having the optical property of passing through e) is used. The offset (baseline) is corrected by using the stage reference mark 20 having a mark on the XY stage 22 at the same height as the wafer 2.

That is, when only the exposure light (g-line) and the light having the wavelength 633 ± 20 nm and the light having the wavelength 680 ± 20 nm are used, the measurement difference between the reticle 1 and the stage reference mark 20 is used as an offset.

In this embodiment, the reticle 1 and CCD
The relay lens 42 and the correction lens 18 which are the image forming system between the lens 19 and 19 are aberration-corrected with the exposure light and the wavelength of 680 ± 20 nm. The beam splitter 41b has a dichroic characteristic that allows exposure light to pass therethrough. At this time, the λ / 4 plate 65b for the wavelength of 680 nm does not act as a complete λ / 4 plate with the exposure light.

However, the fact that it does not function as a perfect λ / 4 plate is that the amount of light incident on the surface of the CCD 19 simply decreases. Therefore, the light source 64 that can detect the exposure light used only by the stage reference mark 20 is used to improve the inconvenience at this time.

The range in which the image height of the projection lens system 3 is changed is such that aberration fluctuations can be ignored, and when the aberration changes significantly, the parallel plane plate 4 for correcting astigmatism and coma is used. The tilt angle θ is changed by rotating, or parallel plane plates having different thickness and materials are used.

FIG. 8 is a schematic view of the essential portions of Embodiment 4 of the present invention. In the figure, 25 is a laser, and laser 25
The light beam from the laser beam is emitted to the alignment mark 15 on the wafer surface 2 via the mirror 26 and the light projecting lens 27.

Reference numeral 81 is a mirror, and 100 is an observing optical system, which has a single plane-parallel plate 4 tilted with respect to the meridional section of the projection lens system 3.

In this embodiment, the plane-parallel plate 4 constitutes an optical system which corrects the chromatic astigmatism and coma produced in the projection lens system 3.

Reference numerals 10, 11, and 12 are mirrors, and 8 is a correction lens unit. Reference numeral 16 is an alignment mark on the reticle 1 side, which is formed by the projection lens system 3 and the observation optical system 100.
5 is provided at a position where an image is formed.

Reference numeral 17 is a mirror, 18a is an alignment scope, and 19 is a CCD for observing the state on the reticle 1 surface and the wafer 2 surface.

As described above, in this embodiment, the elements 25 and 2 are
6, 27, 4, 100, 12, 17, 18, 19 are detection means, and the alignment mark 1 on the wafer 2 is provided.
5 is detected via the projection lens system 3. This detection is performed by projecting the image of the mark 15 onto the CCD 19 by the image forming means having the elements 4, 100, 12, 17, and 18, and the contrast of the image of the mark 15 is improved by the action of the optical system 4. I am letting you.

In this embodiment, the circuit pattern on the surface of the reticle 1 is projected onto the surface of the wafer 2 by the projection lens system 3 with the exposure light of the g-line (436 nm). On the other hand, the mark 15 on the surface of the wafer 2 has a wavelength of 633n from the He-Ne laser 25.
The projection lens system 3 and the observation optical system 10 are illuminated with m detection light.
By 0, a mark image is formed on the surface of the reticle 1 near the reticle-side alignment mark.
Then, the alignment scope 18 simultaneously observes the relationship between both marks. In the present embodiment, it is not necessary to move and fix the observation optical system 100 along with the movement of the alignment image height, but in the following description, the alignment image height is fixed for simplicity.

In general, the projection lens system 3 is well corrected for aberrations at the projection wavelength of the g-line, but is not sufficiently corrected at the alignment wavelength. Especially due to chromatic aberrations,
For example, a lot of axial chromatic aberration, lateral chromatic aberration, chromatic spherical aberration, chromatic coma, and chromatic astigmatism remain.

Therefore, when the surface of the wafer 2 is considered as the object surface, the mark 15 on the surface of the wafer 2 is imaged above the surface of the reticle 1 in many cases due to various aberrations.

For example, the projection magnification of the projection lens system 3 is 1/5.
If the axial chromatic aberration on the wafer side is 300 μm when the magnification is doubled, the image of the wafer 2 on the reticle side is 0.3 × 5 ² =
The image is formed on the reticle 1 by 7.5 (mm).

Therefore, it becomes difficult to observe the pattern on the surface of the reticle 1 and the pattern on the surface of the wafer 2 at the same time, and various corrections for matching both pattern images between the reticle and the projection lens system have been conventionally performed. The optical system is arranged and corrected. However, it is difficult to perform perfect aberration correction with this correction optical system, and it is generally difficult to make a good observation.

In this embodiment, the reticle 1 and the projection lens system 3
And the observation optical system 1 in which aberrations are satisfactorily corrected not only in the sagittal direction but also in all directions including the meridional direction.
By arranging 00, the pattern on the surface of the reticle 1 and the pattern on the surface of the wafer 2 are matched, the observation of both patterns is made good, and highly accurate alignment is possible.

[0093]

According to the present invention, by adopting the above-mentioned structure, the pattern of the first object can be changed to the second pattern by the projection lens system.
When detecting a mark on the second object through the projection lens system with light having a wavelength different from the wavelength used when projecting on the object, various aberrations generated in the projection lens system are corrected well, and a clear mark image is obtained. It is possible to achieve an exposure apparatus capable of observing.

In particular, when the present invention is applied to an exposure apparatus for semiconductor manufacturing, both the reticle surface and the wafer surface can be observed as clear images.
It is possible to perform a two-dimensional alignment of y and θ with high accuracy, and thereby obtain a semiconductor chip manufacturing method capable of manufacturing high density semiconductor chips.

[Brief description of drawings]

FIG. 1 is a schematic view of a main part of a first embodiment of an exposure apparatus of the present invention.

FIG. 2 is an explanatory diagram of various aberrations generated from one inclined plane-parallel plate.

FIG. 3 is an explanatory diagram of various aberrations generated from two inclined plane-parallel plates.

FIG. 4 is an explanatory diagram showing an amount of color misregistration and an optical path length generated from an inclined plane-parallel plate.

FIG. 5 is an explanatory diagram of various aberrations generated from two parallel plane plates having different inclined thicknesses and different materials.

FIG. 6 is a schematic view of the essential portions of Embodiment 2 of the exposure apparatus of the present invention.

FIG. 7 is a schematic view of a main part of a third embodiment of an exposure apparatus of the present invention.

FIG. 8 is a schematic view of the essential portions of Embodiment 4 of the exposure apparatus of the present invention.

[Explanation of symbols]

1 reticle 2 wafers 3 Projection lens system 4 Parallel plane plate 14,15 mark 18 Correction lens 19 CCD 25 light sources 62 condenser lens 63 light source 64 mark 65, 65a, 65b λ / 4 66,69,69b Wavelength selection filter

Claims (10)

[Claims] 1. A projection lens system for projecting a pattern of a first object onto a second object with exposure light, and a second object illuminated with detection light having a wavelength different from that of the exposure light. In a device having a detection means for receiving the detection light through the projection lens system and detecting an image of a mark on the second object, the projection lens system is aberration-corrected with respect to the exposure light. Along with the detection light, a predetermined astigmatism and a predetermined coma aberration are generated, and the projection unit corrects the astigmatism and the coma aberration generated by the projection lens by the detection unit. An exposure apparatus comprising a plane-parallel plate tilted with respect to a meridional section of a lens system. 2. The exposure apparatus according to claim 1, wherein the plane parallel plate is composed of a back surface reflection type mirror whose back surface is a reflection surface. 3. A projection lens system for projecting a pattern of a first object onto a second object with exposure light, and a second object illuminated with detection light having a wavelength different from that of the exposure light. In a device having a detection means for receiving the detection light through the projection lens system and detecting an image of a mark on the second object, the projection lens system is such that aberration is corrected for the exposure light. In addition, it is configured to generate a predetermined astigmatism and a predetermined coma aberration with respect to the detection light, and the detecting means corrects the astigmatism and the coma aberration generated in the projection lens. An exposure apparatus comprising two plane-parallel plates tilted with respect to a meridional section of a projection lens system. 4. The exposure apparatus according to claim 3, wherein the parallel plane plate is composed of a back surface reflection type mirror whose back surface is a reflection surface. 5. A projection lens system for projecting a pattern of a first object onto a second object with exposure light, and illuminating the second object with detection light having a predetermined bandwidth whose central wavelength is different from that of the exposure light, In a device having a detection means for receiving the detection light from the second object via the projection lens system and detecting an image of a mark on the second object, the projection lens system has an aberration with respect to the exposure light. The astigmatism generated by the projection lens is corrected and is configured to generate a predetermined astigmatism, a predetermined coma aberration, and a predetermined chromatic aberration of magnification with respect to the detection light. An exposure apparatus comprising a single plane-parallel plate inclined with respect to a meridional section of the projection lens system so as to correct aberration, the coma aberration, and the chromatic aberration of magnification. 6. The exposure apparatus according to claim 5, wherein the plane parallel plate is composed of a back surface reflection type mirror whose back surface is a reflection surface. 7. A projection lens system for projecting a pattern of a first object onto a second object with exposure light, and illuminating the second object with detection light having a predetermined bandwidth whose central wavelength is different from that of the exposure light, In a device having a detection means for receiving the detection light from the second object via the projection lens system and detecting an image of a mark on the second object, the projection lens system has an aberration with respect to the exposure light. The astigmatism generated by the projection lens is corrected and is configured to generate a predetermined astigmatism, a predetermined coma aberration, and a predetermined chromatic aberration of magnification with respect to the detection light. An exposure apparatus comprising two parallel plane plates tilted with respect to a meridional section of the projection lens system so as to correct aberration, the coma aberration, and the chromatic aberration of magnification. 8. The exposure apparatus according to claim 5, wherein the plane parallel plate is a back surface reflection type mirror whose back surface is a reflection surface. 9. An image of an alignment mark on the wafer is detected through a projection lens system using detection light that does not expose the wafer, and the wafer is aligned based on the position information of the wafer obtained based on the detection. In the method for producing a semiconductor chip, the method comprises: illuminating a circuit pattern of a mask with exposure light that exposes the wafer, projecting and transferring an image of the circuit pattern onto the wafer through the projection lens system, The projection lens system is configured to perform aberration correction on the exposure light and to generate a predetermined astigmatism and a predetermined coma aberration with respect to the detection light. The astigmatism and the coma produced in the projection lens are corrected by using one parallel plane plate inclined with respect to the meridional section of the projection lens system. And manufacturing method. 10. An image of an alignment mark on the wafer is detected through a projection lens system using detection light that does not expose the wafer, and the wafer is aligned based on the position information of the wafer obtained based on the detection. In the method for producing a semiconductor chip, the method comprises: illuminating a circuit pattern of a mask with exposure light that exposes the wafer, projecting and transferring an image of the circuit pattern onto the wafer through the projection lens system, The projection lens system is configured to perform aberration correction on the exposure light and to generate a predetermined astigmatism and a predetermined coma aberration with respect to the detection light. The astigmatism and the coma generated in the projection lens are corrected by using two parallel plane plates inclined with respect to the meridional section of the projection lens system. Manufacturing method.