JPH0950959A - Projection aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate the high precision alignment between a mask and a wafer by a method wherein a first detecting light from a substrate mark is detected without passing through a projection optical method, a mask mark is lit by a second detecting light through the projection optical system and a light from the mask mark is detected. SOLUTION: A lighting light is applied to a wafer 5 and a reflected light from the wafer 5 is transmitted through the half mirror of an alignment coaxial optical system 1 and focused on the image pickup surface of an image pickup device. The output of the image pickup device is supplied to a control system 13. Image information consisting of a wafer mark and a pair of index marks is obtained from the control system 13. By subjecting the image information to the image processing, the position of the wafer mark is detected. A beat interference light LM from a mask mark on a mask 4 is subjected to the photoelectric conversion by a photodetector 9 and a mask mark signal is generated and supplied to the control system 13. The difference between the phase of a reference signal and the phase of the mask mark signal is detected by the control system 13 and the position of the mask mark is detected in accordance with the detected phase difference.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure apparatus used in a photolithography process for manufacturing a semiconductor device, a liquid crystal display device or the like, and more particularly to an alignment for aligning a mask and a photosensitive substrate. A reduction projection type exposure apparatus having a system.

[0002]

2. Description of the Related Art Most of the successive exposure type projection exposure apparatuses which have been put into practical use at present are for optically aligning a reticle as a mask and a wafer (or a glass plate etc.) as a photosensitive substrate. An alignment system is incorporated. In such an alignment system, various alignment methods are used. As a highly accurate alignment method among these various alignment methods, an alignment mark (reticle mark) formed around the circuit pattern of the reticle and an alignment mark (wafer mark) formed in each shot area on the wafer are used. A TTR (through the reticle) method is known in which detection is performed simultaneously via a projection optical system.

In an alignment system of the TTR system, a relative displacement between a reticle mark and a wafer mark is measured by an alignment system disposed above a reticle, and the displacement is maintained in a predetermined relationship. The position or rotation angle of at least one of the reticle and the wafer is finely adjusted. By the way, there are various types of TTR type alignment systems.

For example, in the alignment system disclosed in JP-A-3-3224, a correction lens for correcting axial chromatic aberration with respect to alignment light is provided in the projection optical system,
A correction optical system for correcting lateral chromatic aberration with respect to the alignment light is provided near the reticle. In this case, monochromatic light such as laser light is used as alignment light in order to easily perform chromatic aberration correction. Further, in the alignment system disclosed in Japanese Patent Application Laid-Open No. 5-160001 filed by the present applicant, a correction optical element (PGC) for correcting axial chromatic aberration with respect to alignment light and controlling lateral chromatic aberration is used as a reticle. It is placed between the mask.

On the other hand, as an alignment system other than the TTR system, a so-called off-axis system alignment system is known. In the off-axis type alignment system,
The wafer mark is observed by the wafer observation system, and the reticle mark is observed by the reticle observation system different from the wafer observation system without passing through the projection optical system. As described above, in the off-axis method, the optical axis of the wafer observation system and the optical axis of the reticle observation system are largely separated from the optical axis of the projection optical system. In other words, the observation visual field of the wafer observation system and the exposure area on the wafer, and the observation visual field of the reticle observation system and the transfer target area on the reticle are largely separated from each other.

By the way, the demand for large integration of semiconductor elements is increasing year by year, and the pattern rule (line width) of the required circuit pattern is becoming smaller and smaller. It is known that the line width that can be resolved by the projection optical system becomes smaller in proportion to the wavelength, and in order to expose a circuit pattern with a smaller pattern rule, the wavelength of light used for exposure can be shortened. Good. Recently, for example, excimer laser light (wavelength 193 nm) or KrF using ArF as a medium is used.
There has been proposed a projection exposure apparatus using an excimer laser beam (wavelength 249 nm) with a medium of.

[0007]

In a projection exposure apparatus that performs exposure with the above-mentioned excimer laser light (wavelength 193 nm or 248 nm, etc.), the projection optical system favorably corrects aberrations with respect to the excimer laser light that is the exposure light. Has been done. Therefore, when red light (wavelength 600 nm to 800 nm) is used as alignment light in order to avoid exposure of the resist applied on the wafer, a large chromatic aberration (axial chromatic aberration, lateral chromatic aberration) with respect to the alignment light in the projection optical system is used. Etc.) occurs.

Therefore, in the alignment system disclosed in JP-A-3-3224, monochromatic light is used as the alignment light, and the axial chromatic aberration for the alignment monochromatic light is corrected by the correction lens provided in the projection optical system. There is. In the alignment system disclosed in JP-A-5-160001, monochromatic light such as laser light is used as alignment light, and a correction optical element (PGC) such as a phase grating is used to obtain chromatic aberration with respect to the alignment monochromatic light. We are making corrections.

As described above, in the conventional TTR type alignment system, it is necessary to use alignment light having a narrow wavelength width such as monochromatic light in order to suppress the influence of chromatic aberration generated in the projection optical system. As a result, there is an inconvenience that the detection accuracy is deteriorated due to the influence of interference caused by the resist applied on the wafer.

In the off-axis type alignment system described above, since the wafer is observed using the light having a relatively wide wavelength width, it is possible to reduce the influence of interference due to the resist. However, since the exposure region and the wafer observation visual field are widely separated, it is necessary to move the wafer mark two-dimensionally during alignment.
As a result, there is a disadvantage that offset drift occurs between the reticle observation system and the wafer observation system, and the accuracy is lowered.

The present invention has been made in view of the above-mentioned problems, and provides a projection exposure apparatus capable of performing highly accurate alignment between a mask and a wafer while suppressing the influence of interference due to resist and the occurrence of offset drift. The purpose is to do.

[0012]

In order to solve the above problems, in the present invention, an exposure illumination optical system for illuminating a mask on which a predetermined pattern is formed with an exposure light beam, and the mask. A projection optical system for projecting a pattern on a photosensitive substrate, a relative position of the substrate and the mask based on a substrate mark formed on the substrate and a mask mark formed on the mask In the projection exposure apparatus provided with an alignment system for detecting, the alignment system illuminates the first detection light having a broadband wavelength to the substrate mark without passing through the projection optical system, and the first detection light from the substrate mark is emitted. By receiving the detection light without passing through the projection optical system, a substrate mark detection optical system for detecting the substrate mark, and a second detection light through the projection optical system. Illuminating the mask mark, by receiving the light from the mask mark, to provide a projection exposure apparatus characterized by comprising: a mask mark detecting optical system for detecting the mask marks.

According to a preferred aspect of the present invention, the substrate mark detecting optical system has the first wavelength having the wide band wavelength.
Light source means for illuminating the substrate mark for supplying detection light,
Deflection means arranged between the projection optical system and the substrate for deflecting the first detection light from the substrate mark illuminating light source means to illuminate the substrate mark by epi-illumination; An image detection optical system for detecting an image of the substrate mark based on the first detection light.

Further, the mask mark detection optical system illuminates the second detection light having a wavelength different from that of the exposure light flux onto the substrate through the deflecting means, and the second detection reflected by the substrate. Light source means for illuminating the mask mark for guiding light to the mask mark, light receiving means for receiving the second detection light from the mask mark illuminated by the light source means for illuminating the mask mark, and the substrate, It is preferable to include a correction unit disposed between the mask and the substrate to correct the chromatic aberration of the projection optical system with respect to the reflected second detection light.

According to another aspect of the present invention, an exposure illumination optical system for illuminating a mask having a predetermined pattern with an exposure light beam, and the mask pattern on a photosensitive substrate. A projection optical system for projecting onto a substrate, and an alignment system for detecting a relative position between the substrate and the mask based on a substrate mark formed on the substrate and a mask mark formed on the mask In the projection exposure apparatus, the alignment system illuminates the substrate mark with a first detection light having a wide wavelength without passing through the projection optical system, and the first detection light from the substrate mark is supplied to the projection optical system. By receiving the light without passing through the substrate mark detection optical system for detecting the substrate mark, and illuminating the mask mark with the second detection light, and passing through the projection optical system. By receiving the light from the serial mask mark, to provide a projection exposure apparatus characterized by comprising: a mask mark detecting optical system for detecting the mask marks.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the substrate mark is illuminated with the first detection light having a wide band wavelength without passing through the projection optical system, and the first detection light from the substrate mark is received without passing through the projection optical system. Thus, the board mark is detected. Further, the mask mark is detected by illuminating the substrate with the second detection light without passing through the projection optical system and receiving the second detection light from the substrate through the projection optical system and the mask mark.

As described above, according to the present invention, since the substrate mark is detected by using the first detection light having the broadband wavelength without passing through the projection optical system, the influence of the resist interference can be reduced. Further, in the above-described configuration of the present invention, a configuration in which the substrate mark is detected in the vicinity of the exposure area (illumination area) on the substrate is also possible. In this case, since it is not necessary to move the substrate when detecting the substrate mark, it is possible to avoid the occurrence of offset drift as in the conventional off-axis method. Therefore, the projection exposure apparatus of the present invention enables highly accurate alignment between the mask and the substrate.

Further, in the above-mentioned configuration of the present invention, it is possible to configure the substrate mark detecting optical system and the mask mark detecting optical system substantially coaxially. As a result, the influence of the fluctuation of the optical axis of each detection optical system can be removed, and stable alignment without drift becomes possible. It should be noted that specifically, the substrate mark detection optical system deflects the first detection light by a deflecting unit arranged between the projection optical system and the substrate to illuminate the substrate mark with epi-illumination. Then, the image of the substrate mark is detected based on the reflected light from the substrate mark with respect to the first detection light. In this case, it is preferable to detect the image of the substrate mark inside the effective visual field of the projection optical system on the substrate and in a region outside the illumination region of the exposure illumination optical system on the substrate.

On the other hand, in the mask mark detection optical system, the substrate is illuminated with the second detection light having a wavelength different from that of the exposure light through the above-mentioned deflecting means. The second detection light is preferably monochromatic light, for example, laser light. The second detection light specularly reflected on the substrate reaches the mask mark via the projection optical system. At that time, for example, the correction means provided in the projection optical system corrects the chromatic aberration of the projection optical system with respect to the second detection light. At that time, if it is a single color, the correction is easy. Then, the mask mark is detected by receiving the detection light from the mask mark for the second detection light. The mask mark is made by etching chromium etc., and unlike the wafer mark covered with resist,
No error occurs even if detection is performed with monochromatic light. The above-mentioned correction means is, for example, a diffraction grating formed on a transparent substrate,
It is preferable to deflect the second detection light and guide it to the mask mark.

The above-mentioned deflecting means has a reflecting surface for reflecting, for example, the first detection light and the second detection light toward the substrate. Then, it is preferable that a light transmitting portion for transmitting the second detection light specularly reflected on the substrate toward the projection optical system is formed on the reflecting surface. in this case,
By forming the above-described reflective surface as a total reflective surface, it is possible to minimize the light amount loss of each detection light and improve the detection accuracy.

Further, the deflecting means is disposed in the optical path between the projection optical system and the substrate, and has a plane parallel plate for transmitting the exposure light through the projection optical system, and a prism member having the above-mentioned reflecting surface. It is preferable that the parallel flat plate and the prism member are integrally formed. In this case, the plane-parallel plate makes it possible to hold the reflecting surface in a stable manner, and since the area in which the second detection light is exposed to the atmosphere outside the prism member becomes small, it becomes less susceptible to air fluctuations, and the detection is performed. Accuracy is improved.

According to another aspect of the present invention, the mask mark can be detected by illuminating the mask with the second detection light and receiving the second detection light from the mask through the projection optical system. In this case, the mask mark detection optical system,
The mask is directly illuminated with the second detection light having a wavelength different from the exposure light. The second detection light transmitted through the mask reaches the surface of the substrate via the projection optical system. At that time, the correcting means provided in the projection optical system corrects the chromatic aberration of the projection optical system with respect to the second detection light. Then, the mask mark is detected by receiving the second detection light reflected by the surface of the substrate via the above-mentioned deflecting means.

Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a diagram schematically showing the configuration of a projection exposure apparatus according to the first embodiment of the present invention. The present embodiment is an example in which the present invention is applied to a so-called lens scan type projection exposure apparatus that performs exposure while moving the mask and the wafer relative to the projection optical system. In FIG. 1, the z-axis is parallel to the optical axis of the projection optical system, the x-axis is parallel to the plane of FIG. 1 in the plane perpendicular to the optical axis, and the x-axis is parallel to the z-axis and the x-axis. Each y-axis is set.

The illustrated projection exposure apparatus has an excimer laser beam (wavelength 249) using, for example, KrF or ArF as a medium.
nm or 193 nm), and an illumination optical system 11 for uniformly illuminating the mask 4 with exposure light. The mask 4 is supported on the mask stage 12, and the mask stage 12 is xy perpendicular to the optical axis of the projection optical system 3.
It can move two-dimensionally in a plane. The x-direction movement amount and the y-direction movement amount of the mask stage 12 and thus the mask 4 are constantly measured by the laser interferometer 10. The output of the laser interferometer 10 is supplied to the control system 13.

For example, the light transmitted through the mask 4 on which the circuit pattern is formed reaches the wafer 5 which is a photosensitive substrate through the projection optical system 3, and a pattern image of the mask 4 is formed on the wafer 5. The wafer 5 is supported on the wafer stage 6 via a wafer holder (not shown). The wafer stage 6 is two-dimensionally driven in an xy plane perpendicular to the optical axis of the projection optical system 3. The amount of movement of the wafer stage 6 and thus of the wafer 5 in the x direction and the amount of movement in the y direction are constantly measured by the laser interferometer 7. The output of the laser interferometer 7 is supplied to the control system 13.

In this way, the mask 4 is provided for the projection optical system 3.
The pattern of the mask 4 can be transferred onto one exposure region on the wafer 5 by performing scan exposure while moving the wafer 5 and the wafer 5 relatively in the x direction. Then, the pattern of the mask 4 can be sequentially transferred to each exposure region of the wafer 5 by repeating the above-described scan exposure while sequentially driving the wafer 5 two-dimensionally in the xy plane.

Furthermore, the projection exposure apparatus of FIG.
An alignment system is provided for detecting the relative position between the wafer 5 and the mask 4 based on the wafer mark formed above and the mask mark formed on the mask 4. The alignment system detects the wafer mark by using the wafer mark detection light (first detection light) having a wide wavelength, that is, the illumination light without passing through the projection optical system 3, and at the same time, the mask mark detection light (for detecting the mask mark) ( The second detection light), that is, the alignment coaxial optical system 1 for emitting the alignment light is provided.

In the present embodiment, when detecting a mask mark, a two-beam interference method, that is, LIA (Laser Inte
rferometric Alignment) method is used. In the two-beam interference type alignment, two-coherent (coherent) light beams (laser beams or the like) having a wavelength different from that of the exposure light are irradiated onto the diffraction grating-shaped mask mark from predetermined two directions to form a one-dimensional image. Interference fringes are formed and the position of the mask mark is specified by observing the interference fringes.

FIG. 2 is a diagram schematically showing the configuration of the alignment coaxial optical system 1 in FIG. In FIG.
The alignment coaxial optical system 1 includes a laser light source 20 as a light source that supplies alignment light having a wavelength different from the exposure light. As the laser light source 20, for example, a He-Ne laser that emits light having a wavelength of 633 nm can be used. The beam emitted from the laser light source 20 is split into two beams by the half mirror 21.

That is, the beam L1 transmitted through the half mirror 21 is incident on the first acoustooptic element 22. on the other hand,
The beam L2 reflected by the half mirror 21 enters the second acoustooptic device 24 via the half mirror 23. Here, the first acousto-optic element 22 is driven by a high frequency signal of frequency f1, and the second acousto-optic element 24 is driven by frequency f2.
It is driven by a high frequency signal of (f2 = f1−Δf).
The upper limit of the frequency difference Δf is defined by the responsiveness of the photoelectric detector 9 for detecting a mask mark, which will be described later. In this way, the laser light source 20, the half mirror 21, the half mirror 23, the first acousto-optic element 22, and the second acousto-optic element 24 constitute a two-beam generation means for generating a pair of coherent light beams.

The beams L1 and L2 which have passed through the first acousto-optic element 22 and the second acousto-optic element 24, respectively, pass through the half mirror 25 and are reflected by the half mirror 26, as shown by the broken line in the figure. It enters the condenser lens 27. The pair of beams L1 and L2 are condensed by the condenser lens 27, and then reflected by the prism assembly 2 arranged in the optical path between the projection optical system 3 and the wafer 5 via the relay lens system 28. It is incident on the surface 2a. The pair of beams L1 and L2 reflected by the reflecting surface 2a intersect on the wafer 5. Then, the pair of beams L1 and L2 specularly reflected on the wafer 5 pass through the reflecting surface 2a toward the mask 4 as described later. Thus, the above-mentioned two-beam generation means, the half mirror 25, the half mirror 26, the condenser lens 27, the relay lens system 28, and the reflecting surface 2a of the prism assembly 2 constitute a part of the mask mark detecting optical system. are doing.

Further, the alignment coaxial optical system 1 uses the wide band wavelength (for example, 500 nm) as the wafer mark detection light.
Illuminating light source 3 for supplying illuminating light having
0 is provided. The illumination light from the illumination light source 30 becomes a parallel light flux by the collimator lens 31, and then enters the half mirror 25. The illumination light reflected by the half mirror 25 enters the reflecting surface 2 a of the prism assembly 2 via the half mirror 26, the condenser lens 27, and the relay lens system 28. The illumination light reflected by the reflecting surface 2a illuminates the wafer mark WM formed on the wafer 5 by epi-illumination.

The reflected light from the wafer 5 with respect to the illumination light is
Reflective surface 2a, relay lens system 28, and condenser lens 27
It is incident on the half mirror 26 via. The light transmitted through the half mirror 26 forms an image on an image pickup surface of an image pickup device 33 such as a CCD via an image forming lens 32.
The output of the image sensor 33 is supplied to the control system 13. Incidentally, the half mirror 26 may be replaced with a polarization beam splitter. As is well known, when the polarization beam splitter is combined with a quarter-wave plate, the light amount loss is reduced. Therefore, this configuration may be adopted when the light amount is small. An index plate 34 is positioned on the wafer-side focal plane of the condenser lens 27. The index plate 34 has a pair of index marks 34a for observing the wafer mark.
And 34b, a reference lattice mark 34c for detecting a mask mark is formed.

Thus, in the control system 13, the image pickup device 33
Based on the output of, the image information including the wafer mark WM and the pair of index marks 34a and 34b can be obtained. Then, by processing the obtained image information, the position of the wafer mark WM can be detected.
In this way, the illumination light source 30, the collimator lens 31,
Half mirror 25, half mirror 26, condenser lens 2
7, the relay lens system 28, the reflecting surface 2a, the index plate 34, the imaging lens 32, and the image sensor 33 constitute a wafer mark detecting optical system for detecting a wafer mark.
The mask mark detection system and the wafer mark detection optical system share the half mirror 25, the half mirror 26, the condenser lens 27, and the relay lens system 28. Therefore, the mask mark detection system and the wafer mark detection optical system are so-called coaxial.

As shown in FIG. 1, the prism assembly 2 is disposed between the projection optical system 3 and the wafer 5, and the projection optical system 3
It functions as a plane-parallel plate with respect to the exposure light from the mask 4 via the. Further, as described above, the prism member having the reflecting surface 2a is integrally formed in the prism assembly 2, and the wafer 5 is illuminated by epi-illumination through the reflecting surface 2a, and at the same time, the pair of mask members for detecting the mask mark is detected. Beam LR
(L1 and L2) are guided onto the wafer 5.

FIG. 3 is a view for explaining the structure and operation of the prism assembly 2 of FIG. As shown in FIG. 3, a pair of beams LR (L1 and L
2) is incident on the projection optical system 3 via a pair of minute light transmitting portions 2b formed on the reflecting surface 2a. In this way, by forming the pair of minute light transmitting portions 2b on the reflecting surface 2a, the illumination light and the alignment light are totally reflected by the reflecting surface 2a, and the alignment light reflected on the substrate is totally transmitted. be able to. The reflecting surface 2a may be formed of a semi-transmissive film that transmits a part of light and reflects the remaining light. However, in this case, since the light amount loss occurs in both the illumination light and the alignment light, the detection accuracy may be reduced.

FIG. 4 is a view showing the arrangement of the effective field of view, the exposure area, and the wafer mark of the projection optical system on the wafer of FIG. As shown in FIG. 4, in the effective visual field A1 of the projection optical system 3 on the wafer 5, a rectangular exposure area (indicated by a shaded area in the figure) A2 extending in the y direction is formed, and the effective visual field A1 within the effective visual field A1 is formed. A wafer mark MW is formed at the left end in the figure. Thus, the wafer mark MW is formed outside the exposure area (that is, the illumination area by the illumination optical system 11), but is within the effective visual field A1.

Therefore, the portion of the reflecting surface 2a of the prism assembly 2 is arranged so as not to block the exposure light traveling toward the exposure area A2 on the wafer 5 via the projection optical system 3. Referring again to FIG. 1, the pair of beams LR that have entered the projection optical system 3 enter the correction optical element (PGC) 8 provided on the pupil plane of the projection optical system 3. The correction optical element 8 is, for example, a transparent substrate having a diffraction grating formed at a predetermined position.

As described above, the pair of beams LR once enter the wafer 5 and then pass through the projection optical system 3 and the mask 4
Be led to. Therefore, in order to avoid the exposure of the resist applied on the wafer 5, a pair of beams LR 6
Laser light having a wavelength of 00 nm or more is used.
On the other hand, since the projection optical system 3 is aberration-corrected with respect to the excimer laser light (wavelength 249 nm or 193 nm) that is the exposure light, a large chromatic aberration occurs for the pair of beams LR. Therefore, the correction optical element 8 described above corrects the axial chromatic aberration of the projection optical system 3 with respect to the pair of passing beams LR.

In this way, the pair of beams LR passing through the correction optical element 8 intersect (image) on the mask mark MM formed at a predetermined position on the mask 4. FIG. 5 shows a pattern area on the mask of FIG. 1, an effective visual field of the projection optical system,
It is a figure which shows arrangement | positioning of a transfer target area | region and a mask mark. As shown in FIG. 5, in the effective visual field A3 (indicated by a broken line in the figure) of the projection optical system 3 on the mask 4, a rectangular transfer target region extending in the y direction (indicated by a hatched portion in the figure).
A4 is formed. The transfer target area (that is, the illumination area by the illumination optical system 11) A4 extends along the y direction over the entire pattern area PA, and occupies a part of the pattern area PA along the x direction. Therefore, the transfer target area A4 scans the entire pattern area PA by moving the mask 4 along the x direction during scan exposure.

The pair of beams L on the mask 4
The conjugate position of R is the point P at the left end in the figure in the transfer target area A4.
1, that is, it is located in the pattern area PA. However, since the mask mark cannot be formed in the pattern area PA, the mask 4 is used in this embodiment.
The mask mark MM is formed at a position deviating from the pattern area PA along the direction orthogonal to the scanning direction of, ie, the y direction. The mask mark MM is, as shown in the figure,
For example, it is formed in a diffraction grating shape having a predetermined pitch along the x direction (measurement direction).

Therefore, the correction optical element 8 corrects the axial chromatic aberration with respect to the pair of beams LR and deflects (diffracts) the pair of beams LR so that the pair of beams LR on the mask mark MM on the mask 4. Cross. Referring again to FIG. 1, the pair of beams LR intersecting on the mask mark MM are respectively diffracted by the diffraction grating, and two ± 1st order transmitted diffracted lights are generated in the normal direction (z direction) of the mask 4. The generated two transmitted diffracted lights interfere with each other to generate beat interference light LM.

Beat interference light LM from the mask mark MM
Is photoelectrically converted by the photoelectric detector 9, and as a result, a mask mark signal is generated. This mask mark signal is supplied to the control system 13 having a built-in phase detection system. On the other hand, a pair of beams other than the above-mentioned pair of beams LR interferes as a reference beam at the standard diffraction grating 34c of the index plate 34,
Beat interference light is generated by this interference. The generated beat interference light is photoelectrically converted by a photoelectric detector (not shown) in the alignment coaxial optical system 1, and as a result, a reference signal is generated. This reference signal is also supplied to the control system 13.

In this way, the control system 13 detects the phase difference from the mask mark signal with reference to the phase of the reference signal. Then, based on the detected phase difference, the mask mark M
The position of M can be detected. In this way, the relative position between the wafer 5 and the mask 4 can be detected based on the obtained wafer mark position information and mask mark position information.

As described above, in this embodiment, the wafer mark is detected by observing the wafer using the illumination light having the broadband wavelength. Therefore, the influence of interference caused by the resist applied on the wafer can be minimized, and highly accurate wafer mark detection can be performed.
In this embodiment, the exposure area (illumination area) on the wafer
The wafer mark is detected in the vicinity of the outer side of, for example, in the effective visual field of the projection optical system. Therefore, since it is not necessary to move the wafer when detecting the wafer mark, it is possible to avoid the occurrence of offset drift as in the conventional off-axis method and improve the detection accuracy.

Further, in the present embodiment, the optical system for detecting the wafer mark and the optical system for detecting the mask mark share a part of the optical system and are constructed so-called coaxially. Therefore, the influence of the fluctuation of the optical axis of each detection optical system is removed, and stable detection without drift becomes possible, and the detection accuracy is improved. Further, in this embodiment, the prism assembly is interposed between the projection optical system and the wafer, and a part of the prism assembly is used as an incident prism (a prism member having the reflecting surface 2a) and the rest is used as a plane parallel plate. As a result, the relative distance (baseline amount) between the wafer mark detection optical system and the projection optical system can be reduced, and the reflective surface 2a can be stably held. Further, since the beam for mask mark detection is exposed to the atmosphere in a portion other than the prism member, the beam is less likely to be affected by fluctuations in air and the detection accuracy is improved.

FIG. 6 is a view schematically showing the arrangement of a projection exposure apparatus according to the second embodiment of the present invention. FIG.
FIG. 7 is a diagram showing the arrangement of a pattern area, an effective visual field of a projection optical system, a transfer target area, and a mask mark on the mask of FIG. 6. Further, FIG. 8 is a diagram for explaining the configuration and operation of the prism assembly 2 of FIG. The apparatus of the second embodiment has a configuration similar to that of the first embodiment, but differs from the first embodiment only in the configuration of the mask mark detection system. Therefore, in FIG. 6, elements having the same functions as those of the first embodiment are denoted by the same reference numerals as in FIG. Hereinafter, the second embodiment will be described focusing on the difference from the first embodiment.

The projection exposure apparatus of FIG. 6 is provided with an illumination system 90 for illuminating the mask mark MM formed at a predetermined position on the mask 4 with alignment light (non-exposure light) having a wavelength different from the exposure light. ing. As shown in FIG. 7, the second
In the embodiment, the diffraction grating mark having a predetermined pitch along the x direction and the diffraction grating mark having a predetermined pitch along the y direction are formed as the mask mark MM.

A pair of diffracted light of a predetermined order (for example, ± first-order diffracted light) LR of the diffracted and transmitted light generated by the mask mark MM with respect to the alignment light from the illumination system 90 enters the projection optical system 3. The pair of beams LR that have entered the projection optical system 3 are corrected for aberrations so as to intersect on the surface of the wafer 5 by the deflection (diffraction) action of the correction optical element 8 provided inside the projection optical system 3. Therefore, as shown in FIG. 8, the pair of beams LR through the projection optical system 3
(L1 and L2) are reflection surfaces 2a of the prism assembly 2
It intersects on the surface of the wafer 5 via the pair of minute light transmitting portions 2b formed above.

Thus, an image of the mask mark MM based on the interference between the pair of beams L1 and L2 is formed on the surface of the wafer 5. The light from the mask mark image is totally reflected by the reflecting surface 2a of the prism assembly 2 and then enters the second alignment coaxial optical system 100. FIG. 9 is a diagram schematically showing the configuration of the second alignment coaxial optical system 100 in FIG. The second alignment coaxial optical system 100 in the second example has a configuration similar to that of the alignment coaxial optical system 1 in the first example. However, the second
In the alignment coaxial optical system 100, the two-beam generation means (20 to 20) in the alignment coaxial optical system 1 of the first embodiment is used.
24) and the index plate 34 are not present.

The light from the mask mark image that has entered the second alignment coaxial optical system 100 enters the half mirror 26 via the relay lens system 28 and the condenser lens 27, as shown by the broken line in FIG. The light transmitted through the half mirror 26 passes through the image forming lens 32 and is, for example, CC.
An image is formed on the image pickup surface of the image pickup device 33 such as D. The output of the image sensor 33 is supplied to the control system 13. Thus
The control system 13 can detect the mask mark MM based on the output of the image sensor 33.

As described above, in the second embodiment, the image sensor 3
An image of the mask mark MM is formed together with an image of the wafer mark WM on the imaging surface of No. 3. That is, since the wafer mark WM and the mask mark MM can be detected at the same time within the same field of view, the wafer 5 and the mask 4 can be aligned with high accuracy. Further, as described above, in the second example, the heterodyne optical system used in the first example is unnecessary. Therefore, in the second alignment coaxial optical system, the two light flux generating means (20 to 2)
4) can be omitted, and the configuration of the system can be simplified.

In each of the above embodiments, the present invention is applied to the lens scan type projection exposure apparatus.
Obviously, the present invention can be applied to other general projection exposure apparatuses. Further, in each of the above-mentioned embodiments,
An example in which the present invention is applied to a projection exposure apparatus that uses excimer laser light as exposure light has been shown, but it is clear that the present invention can be applied to a general projection exposure apparatus that uses other exposure light.

[0054]

As described above, in the present invention, since the substrate mark is detected by using the light of the wide band wavelength without passing through the projection optical system, it is possible to reduce the influence of the interference due to the resist. Further, if the substrate mark is detected in the vicinity of the exposure area on the substrate, the occurrence of offset drift can be avoided. Therefore, the projection exposure apparatus of the present invention enables highly accurate alignment between the mask and the wafer. Further, the substrate mark detection optical system and the mask mark detection optical system can be configured so-called coaxially. In this case, the influence of the fluctuation of the optical axis of each detection optical system can be removed, and stable alignment without drift becomes possible, so that the detection accuracy is further improved.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a configuration of a projection exposure apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram schematically showing a configuration of an alignment coaxial optical system 1 in FIG.

3A and 3B are views for explaining the configuration and operation of the prism assembly 2 of FIG.

FIG. 4 is a diagram showing an arrangement of an effective field of view, an exposure area, and a wafer mark of the projection optical system on the wafer of FIG.

5 is a diagram showing the arrangement of a pattern area, an effective visual field of a projection optical system, a transfer target area, and a mask mark on the mask of FIG.

FIG. 6 is a diagram schematically showing a configuration of a projection exposure apparatus according to a second embodiment of the present invention.

7 is a diagram showing the arrangement of a pattern area, an effective visual field of a projection optical system, a transfer target area, and a mask mark on the mask of FIG.

8A and 8B are views for explaining the configuration and action of the prism assembly 2 of FIG.

9 is a second alignment coaxial optical system 10 in FIG.
It is a figure which shows the structure of 0 roughly.

[Explanation of symbols]

 1 Alignment Coaxial Optical System 2 Prism Assembly 3 Projection Optical System 4 Mask 5 Wafer 6 Wafer Stage 7, 10 Interferometer 8 Correction Optical Element 9 Photoelectric Detector 11 Illumination Optical System 12 Mask Stage 13 Control System 20 Laser Light Source 22, 24 Acoustic Optical element 30 Illuminating light source 31 Collimating lens 32 Imaging lens 33 Imaging element WM Wafer mark MM Mask mark 90 Illumination system 100 Second alignment coaxial optical system

Claims (11)

[Claims] 1. An exposure illumination optical system for illuminating a light flux for exposure on a mask on which a predetermined pattern is formed,
A projection optical system for projecting the mask pattern onto a photosensitive substrate, and a substrate relative to the mask based on a substrate mark formed on the substrate and a mask mark formed on the mask. In a projection exposure apparatus provided with an alignment system for detecting a position, the alignment system illuminates the substrate mark with a first detection light having a broadband wavelength without passing through the projection optical system, A substrate mark detection optical system for detecting the substrate mark by receiving the first detection light without passing through the projection optical system, and illuminating the mask mark with the second detection light through the projection optical system. And a mask mark detection optical system for detecting the mask mark by receiving light from the mask mark. Projection exposure system. 2. The substrate mark detection optical system is arranged between a substrate mark illumination light source means for supplying the first detection light having the broadband wavelength, and the projection optical system and the substrate. Deflection means for deflecting the first detection light from the substrate mark illuminating light source means to epi-illuminate the substrate mark, and an image of the substrate mark is detected based on the first detection light from the substrate mark. The projection exposure apparatus according to claim 1, further comprising an image detection optical system for performing the above. 3. The exposure illumination optical system forms an illumination area in an effective field of view of the projection optical system on the substrate, and the substrate mark detection optical system includes the projection optical system of the substrate. The projection exposure apparatus according to claim 2, wherein the projection exposure apparatus has a detection field of view in an area outside the illumination area. 4. The mask mark detection optical system illuminates the substrate with second detection light having a wavelength different from that of the light flux for exposure through the deflecting means, and the second detection light reflected by the substrate is detected. A mask mark illuminating light source unit for guiding light to the mask mark; a light receiving unit for receiving the second detection light from the mask mark illuminated by the mask mark illuminating light source unit; The correction means arranged between the mask and the substrate for correcting the chromatic aberration of the projection optical system with respect to the reflected second detection light, is further provided. The projection exposure apparatus according to. 5. The mask mark is a diffraction grating arrayed at a predetermined pitch along the measurement direction, and the mask mark illuminating light source means outputs the second detection light to the diffraction grating in a predetermined manner. In order to irradiate from two directions, it has 2 light flux production | generation means which produces | generates a pair of 2nd detection light of coherence, The said light-receiving means has the said 2nd detection light of a coherent pair from a predetermined 2 direction, said diffraction grating. 5. The diffracted light generated by irradiating the light is received.
3. The projection exposure apparatus according to claim 1. 6. The deflecting means has a reflection surface for reflecting the first detection light and the second detection light toward the substrate, and the reflection surface includes the first reflection light specularly reflected by the substrate. The projection exposure apparatus according to any one of claims 2 to 5, further comprising: a light transmission section that transmits the two detection lights toward the projection optical system. 7. The deflecting means includes a plane-parallel plate arranged in an optical path between the projection optical system and the substrate, and a prism member having the reflecting surface. The projection exposure apparatus according to claim 6, wherein the projection exposure apparatus is integrally formed with the prism member. 8. An exposure illumination optical system for illuminating a light flux for exposure on a mask having a predetermined pattern formed thereon,
A projection optical system for projecting the mask pattern onto a photosensitive substrate, and a substrate relative to the mask based on a substrate mark formed on the substrate and a mask mark formed on the mask. In a projection exposure apparatus provided with an alignment system for detecting a position, the alignment system illuminates the substrate mark with a first detection light having a broadband wavelength without passing through the projection optical system, By receiving the first detection light without passing through the projection optical system, a substrate mark detection optical system for detecting the substrate mark, and illuminating the mask mark with the second detection light, the projection optical system A mask mark detection optical system for detecting the mask mark by receiving light from the mask mark via the mask mark detection optical system. Projection exposure system. 9. The substrate mark detection optical system is arranged between a substrate mark illumination light source means for supplying the first detection light having the broadband wavelength, and the projection optical system and the substrate. Deflection means for deflecting the first detection light from the substrate mark illuminating light source means to epi-illuminate the substrate mark, and an image of the substrate mark is detected based on the first detection light from the substrate mark. The projection exposure apparatus according to claim 8, further comprising: a substrate mark image detection optical system for performing the above. 10. The mask mark detecting optical system is illuminated by the mask mark illuminating means for illuminating the mask mark with a second detecting light having a wavelength different from that of the exposure light flux. Mask mark image detection for receiving the second detection light from the mask mark via the projection optical system and the deflecting means, and detecting the image of the mask mark based on the received second detection light. An optical system; and a correction unit arranged between the mask and the substrate to correct the chromatic aberration of the projection optical system with respect to the second detection light from the mask mark. The projection exposure apparatus according to claim 9. 11. The projection exposure apparatus according to claim 9, wherein the substrate mark image detection optical system and the mask mark image detection optical system have the same image pickup device.