JPH06244084A - Method and device for exposure wherein holography is used - Google Patents

Abstract

PURPOSE:To enable proper alignment process of a wafer and a hologram by adjusting relative position relation between a hologram memory medium and a wafer to realize proper reproduction state of an alignment mark reproduced image at an alignment mark formation position on a wafer. CONSTITUTION:A pin hole 20 is illuminated by object illumination light B from an upper surface of a mask original disc 3 and a hologram memory medium 1 is irradiated with an object wave consisting of spherical divergent wave C diffracted here to form a hologram (holographic zone plate 4). A wafer 5 whereto resist us applied is arranged at a position wherein a mask is placed during hologram formation. Reproduction state of an alignment mark image on a wafer surface from the holographic zone plate 4 is detected as a focusing position (gap) of a hologram image, that is, misregistration information between a position of a hologram reproduced image stored in the hologram memory medium 1 and a mask position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure method and apparatus using holography, which has an alignment method and means for adjusting the relative positional relationship between a hologram and a wafer.

[0002]

2. Description of the Related Art In recent years, attention has been paid to a fine pattern exposure means using a holographic technique. In this exposure means, a mask having a predetermined circuit pattern or the like (mask pattern) is used, and a mask corresponding thereto is used. A step of forming a hologram of the pattern and a step of forming a reproduced image of the hologram of the mask pattern on the wafer and exposing the mask pattern are performed.

The reproduced image of the hologram by the holography technique is formed at the same position as the mask pattern at the time of hologram production with respect to the hologram. Therefore, the mask used in the hologram creating step is removed after the hologram is created, and instead, the wafer is fixed at the same position, and when the hologram is reproduced in this state, a hologram image is formed on the wafer (previous mask position), The mask pattern will be exposed on the wafer.

As described above, if the relative positional relationship between the wafer and the hologram (or hologram storage medium) at the time of transferring the mask pattern is not the same as the relative positional relationship between the mask pattern and the hologram at the time of producing the hologram, the mask pattern Since the hologram image is not accurately transferred onto the wafer, the relative positional relationship between them, for example, relative spacing (gap, Z direction), plane direction (xy direction), rotation, tilt, etc., is accurately positioned and the hologram image is transferred to the wafer. It is necessary to perform exposure work.

Here, as a conventional technique of lithography utilizing the holography technique, "method of exposing a hologram through a projection lens (Japanese Patent Laid-Open No. 3-235319) is used.
No.) "is known. This conventional technique transfers the fine pattern to the resist of the wafer by utilizing the fact that the aberration generated in the projection lens can be canceled by applying the holographic technique.

Generally, in order to produce a circuit pattern of a semiconductor, a liquid crystal or the like, it is necessary to expose the same wafer with a mask pattern a plurality of times, and alignment (xy alignment) with a pattern already formed on the wafer is required. ) Is required together with the detection of the gap (relative distance between the hologram and the mask or the top) for focus adjustment. (Hereinafter, adjustment of relative positional relationships such as xy alignment and gap alignment will be collectively referred to as alignment.) In the above-described alignment method of the prior art, the alignment pattern is recorded outside the circuit (liquid crystal) pattern. Therefore, the alignment is performed by overlapping the alignment patterns.

Further, as a hologram recording / reproducing method capable of reproducing high resolution, a holographic technique utilizing total internal reflection light in a hologram recording medium (hereinafter referred to as total reflection holography) is proposed by KA Stetson. Appl.Phys.Lett.Vol.11 Num.7 P.22
8 (1967)], but this document does not describe the alignment method.

On the other hand, the conventional example of the gap detection method in the exposure means using the total reflection holography is described in the document "Progress of Lithography Technology Utilizing Holography" [Solid Stat.
e Technology Japanese edition, November 1991]]. In this conventional technique, as shown in FIG. 9, a laser beam is vertically incident on the hologram recording medium 901 and the wafer 905, and the light reflected by the surface of the hologram storage medium 901 and the resist surface coated on the wafer 905 are reflected. The interference signal is detected by the detecting means 908, and the gap is detected by measuring the change of the interference signal due to the gap.

[0009]

In the prior art relating to the alignment described above, the relative position is detected by overlapping the patterns (marks), but the projection optical system is also used for the projection of the alignment pattern. Therefore, the influence of the aberration of the projection optical system remains in the adjustment of the relative positional relationship (positioning operation). Therefore, there is an advantage that the influence of the aberration is less on the hologram reproduction, but it is difficult to expose the fine pattern due to the limitation of the positioning accuracy particularly in the overlay exposure in which the exposure work is performed a plurality of times. Has become.

Furthermore, since the alignment mark is also enlarged by the projection optical system, a large observation optical system is required, and the restrictions on the arrangement of the entire apparatus are increased.
Especially when using total internal reflection holography, the prism is in contact with the hologram (recording medium), so the observation optical system cannot be brought close to the wafer due to the presence of this prism, so that it is possible to observe large alignment marks. It is difficult to increase the resolution of the optical system. In addition, when this alignment method is applied to the total reflection holography method, a projection area of a large alignment mark must be provided on the wafer, which causes a problem that the original circuit pattern forming area of the wafer is narrowed. Occurs.

Further, in the prior art relating to the gap detection, since the laser beam (parallel light flux) is made incident vertically on the wafer and the hologram recording medium, it is easily affected by multiple reflection between these two elements, and the gap There is a problem that the detection accuracy does not increase. Further, since the method is such that the gap during hologram recording is measured in advance and the measured value is adjusted at the time of reproduction, there is a problem that throughput is reduced due to precision measurement work such as gap detection during hologram creation. Furthermore, in the above-mentioned prior art, no means for adjusting the relative positional relationship other than the gap is disclosed.

On the other hand, when the hologram is deformed during operations such as hologram recording, fixing, and reproduction, for example, the hologram (hologram storage medium storing the hologram) may be contracted. The formation position also changes. For this reason, in the exposure process for the wafer, the wafer position needs to be corrected from the previous measurement position. However, in the above-described conventional technique, alignment including corrections corresponding to these hologram deformations (so-called focus position It is difficult to correct changes).

The present invention has been made in order to solve these problems, and it is possible to easily and accurately detect a relative positional relationship including gap detection, and at the same time, to provide a holography equipped with an alignment means capable of coping with hologram deformation. It is an object of the present invention to provide an exposure method and apparatus using the above.

[0014]

In order to achieve the above object, according to the invention of claim 1, diffracted light from a mask on which a desired pattern is formed is used as an object wave, and this is interfered with a reference wave to perform hologram recording. After the hologram is recorded on the medium, the hologram is irradiated with a reproduction wave conjugate with the reference wave to reproduce the mask pattern image on the wafer arranged in place of the mask, thereby transferring the mask pattern to the wafer. In the exposure method using holography, the step of storing a hologram for alignment as a hologram mark in the hologram recording medium by diffracted light from the alignment mark formed on the mask as an object wave, and reproducing the mask pattern image. Prior to the alignment mark image obtained by irradiating the hologram mark with a reproduction wave, A step of irradiating the wafer with raw light and detecting a reproduction state of the alignment mark reproduction image on the wafer surface, and detecting relative positional deviation information between the hologram recording medium and the wafer based on the detection result, And a step of correcting these relative positional relationships based on the positional deviation information, and an exposure method using holography.

According to a second aspect of the present invention, the transmitted diffracted light from the mask on which a desired pattern is formed is used as the object light, and the reference light and the diffracted light are interfered with each other to record a hologram on the hologram storage medium. By irradiating the hologram with reproduction light conjugate with the reference light and reproducing the mask pattern image on the wafer arranged in place of the mask,
In an exposure method using total reflection holography for transferring a pattern of a mask onto a wafer, a holographic zone plate for alignment on the hologram storage medium as transmitted light diffracted from an alignment mark of a predetermined shape formed on the mask as an object wave. Memorize
Prior to the reproduction of the mask pattern image, the wafer is irradiated with the reproduction light of the image of the alignment mark obtained by irradiating the holographic zone plate with the reproduction wave, and at the wafer surface of the alignment mark image reproduction light. By detecting reflected light or transmitted light of the alignment mark, and detecting the reproduction state of the alignment mark reproduction image on the wafer surface, and detecting the relative positional deviation information between the hologram recording medium and the wafer based on the detection result. Then, an exposure method using a total reflection hologram is provided, which comprises a step of correcting these relative positional relationships based on the positional deviation information.

According to a third aspect of the present invention, there is provided an exposure method using the total reflection hologram according to the second aspect, wherein the alignment mark image reproduction state detecting step is performed on the wafer surface of the alignment mark image reproduction light. The reflected state of the alignment mark is guided to the holographic zone plate, and the wavefront of the transmitted diffracted light is detected here to detect the reproduction state of the alignment mark reproduction image on the wafer surface. To do.

In the invention described in claim 4, the diffracted light from the mask on which a desired pattern is formed is used as an object wave, and this is interfered with a reference wave to record a hologram on a hologram recording medium, and then the reference light is referred to. A holographic exposure apparatus that transfers a mask pattern onto a wafer by irradiating a hologram with a reproduction wave that is conjugate with a wave to reproduce an image of the mask pattern on a wafer that is arranged instead of the mask. A coherent light source for generating a coherent light beam, and a coherent light beam from the light source,
An object wave irradiating optical system for irradiating the position where the alignment mark of the mask is formed and irradiating the diffracted light generated by the alignment mark thereby into the hologram recording medium as an object wave for forming a hologram mark, A coherent light beam from the light source, as a reference wave for forming a hologram mark, so as to cause interference with the object wave in the hologram recording medium, a reference wave irradiation optical system for irradiating into the hologram recording medium,
Reproduction of irradiating the hologram mark formed on the hologram recording medium with a conjugate wave of the reference wave as a reproduction wave and irradiating the wafer surface with alignment mark reproduction light obtained from the hologram mark by the reproduction wave irradiation. A wave irradiation optical system, a reproduction image detecting means for detecting a reproduction state of an alignment mark image formed on the wafer surface by the alignment mark reproducing light, and the hologram recording based on a detection result of the reproduction image detecting means. There is provided an exposure apparatus using holography, comprising: a relative position detecting unit that detects relative positional deviation information between a medium and the wafer.

According to a fifth aspect of the present invention, the transmitted diffracted light from the mask on which a desired pattern is formed is used as object light, and this is interfered with the reference light to record a hologram on the hologram storage medium, and then the hologram is recorded. By irradiating the hologram with reproduction light conjugate with the reference light and reproducing the mask pattern image on the wafer arranged in place of the mask,
In a hologram exposure apparatus using a total reflection hologram for transferring a mask pattern to a wafer, a coherent light source for generating a coherent light flux, and a coherent light flux from the light source are guided to a position where an alignment mark of the mask is formed, An object wave irradiation optical system that irradiates the transmitted diffraction light generated from the alignment mark as an object wave for forming a hologram mark into the hologram storage medium and a coherent light beam from the light source thereby to form a hologram mark. As a reference wave, a reference wave irradiating optical system that irradiates the hologram storage medium so as to cause total interference with the inner surface of the hologram storage medium from the side opposite to the mask and to cause interference with the object wave in the hologram storage medium; Hologram mark formed on recording medium On the other hand, a reproduction wave irradiation optical system for irradiating the conjugate wave of the reference wave as a reproduction wave and irradiating the wafer surface with the alignment mark reproduction light obtained from the hologram mark by the reproduction wave irradiation, and the alignment mark reproduction light. Based on the detection result of the reproduction image detecting means for detecting the reproduction state of the alignment mark image formed on the wafer surface, and the relative positional deviation information between the hologram recording medium and the wafer. An exposure apparatus using total reflection holography, comprising: a relative position detecting unit for detecting.

According to a sixth aspect of the present invention, there is provided the holographic exposure apparatus according to the fourth or fifth aspect, wherein the reproduction image detecting means reflects the alignment mark reproduction light reflected or transmitted by the wafer surface. Is detected to detect the reproduction state of the alignment mark image.

According to a seventh aspect of the invention, there is provided the exposure apparatus using the holography according to the fourth or fifth aspect, wherein the reproduced image detecting means outputs the alignment mark reproducing light reflected on the wafer surface. The reproduction state of the alignment mark image is detected by guiding the hologram mark and detecting the diffracted light at the hologram mark.

According to the invention described in claim 8,
5. The hologram exposure apparatus according to 5, 6, or 7, further comprising a correction unit that corrects a relative positional relationship between the hologram storage medium and the wafer based on a detection result of the relative position detection unit. And

[0022]

The present invention is configured as described above, but in the alignment process of the hologram (recording medium) and the wafer performed prior to the holographic exposure (hologram reproduction) of the mask pattern, the alignment using the holographic technique is also applied. It is characteristic to have means. Generally speaking, if the reproduction state of the alignment mark image is proper, it is possible to obtain the reproduction image from the hologram of the mask pattern formed on the same hologram recording medium as well having a similar reproduction state. The alignment is performed so that the reproduced image by the reproduced light from the hologram mark becomes appropriate, and then the mask pattern is exposed (hologram reproduction).

That is, when the pattern hologram and the alignment hologram formed on the same hologram recording medium are respectively reproduced, the reproduced images are formed by maintaining the relative positional relationship between the pattern on the mask and the alignment mark. To be done. By utilizing this, the relative positional relationship between the hologram recording medium and the wafer is adjusted so that the reproduction state of the alignment mark reproduced image at the alignment mark formation position on the wafer becomes appropriate, and thus the wafer in the mask pattern exposure is adjusted. The alignment process with the hologram can be properly performed.

Explaining with an example, at least the reconstructed image of the alignment hologram is accurately focused on the wafer surface and reconstructed, the position of the proper gap between the hologram and the reconstructed image forming position (Z direction). Since it is recognized that the wafer is placed at the relative position of (1), the gap can be aligned in the relative positional relationship between the wafer and the hologram.

Further, by detecting the reproduction state of the reproduction image of the alignment hologram at the position where the alignment pattern is formed on the wafer, it is possible to detect (adjust) the relative position in the XY direction by adjusting the relative positional relationship between them. Will be things. Explaining with a specific example, if a means for detecting the reproduction light from the alignment hologram is provided only at the alignment pattern forming position on the wafer, X-
If the relative displacement in the Y direction has occurred, the reproduction light from the alignment hologram cannot be detected, so the relative position between the wafer and the hologram may be adjusted so that this can be detected.

It is needless to say that the relative positional relationship between the alignment mark and the mask pattern on the mask is the same as the relative positional relationship between the alignment mark image forming position and the mask pattern image forming position (exposure position) on the wafer. Yes.

The means for detecting the reproduced light from the alignment hologram is not particularly limited as long as it can detect the reproduced state of the reproduced image. For example, since the reproduction light is diffracted light that is condensed at the reproduction image forming position, the reproduction light is condensed on the wafer surface so that the condensed state (intensity) of the reproduction light is maximized on the wafer surface. Means such as one that adjusts the relative positional relationship by detecting the intensity of transmitted light or reflected light, and one that simply observes the reproduced image formed on the wafer surface by the reproduced light can be considered.

In addition, by performing the above relative position detecting step at a plurality of positions on the wafer, relative position detection (adjustment) with respect to the tilt and rotation of the wafer and the hologram (recording medium) can be performed. There is. It should be noted that these relative positional relationship detecting means may be ones that simultaneously detect the relative positions in the gap, the XY direction, or the like, or ones that individually detect each other.

The present invention is suitable for an exposure method and apparatus using so-called total reflection holography, which adopts a method of forming a hologram by using total reflection light in a hologram recording medium using a predetermined prism. However, it is also possible to apply the present invention to an exposure method and apparatus using another type of holographic technology.

Next, individual actions of the invention according to each claim of the present application will be described. First, the invention according to claim 1 is
Diffracted light from the mask on which a desired pattern is formed is used as an object wave, and this is interfered with a reference wave to record a hologram on a hologram recording medium, and then a reproduction wave conjugate with the reference wave is applied to the hologram. In the exposure method using holography in which the image of the mask pattern is reproduced on the wafer arranged in place of the mask to transfer the mask pattern onto the wafer, the holographic technique is also applied to the alignment means.

In the holographic exposure, since the mask pattern is exposed on the wafer by the reproduced image of the hologram, the holographic exposure is not limited to the so-called total reflection type holography, but is also formed on the same hologram recording medium in any type of holographic exposure. Since the reproduced image formation position from the hologram is reproduced while maintaining the above-mentioned positional relationship, it is possible to perform alignment using this.

The following steps are required to perform the alignment applying this holographic technique. First, it is necessary to store the hologram for alignment as a hologram mark in the hologram recording medium by using the diffracted light from the alignment mark formed on the mask as an object wave. A step of recording the alignment hologram on the same hologram recording medium as the mask pattern,
The mask pattern hologram forming step is performed while maintaining the relative positional relationship between the mask and the hologram recording medium at the time of forming the alignment hologram. Any of these hologram forming steps may be performed first.

Next, prior to the reproduction of the mask pattern image, the wafer is irradiated with the reproduction light of the alignment mark image obtained by irradiating the hologram mark with a reproduction wave, and the wafer of the alignment mark reproduction image is irradiated. The step of detecting the reproduction state on the surface is performed. this is,
This is a step of forming a reproduction image of the alignment mark. By detecting the reproduction state of the reproduction image on the wafer,
The relative positional relationship is detected by the method described above.
Since this step is performed as part of the alignment for reproducing the mask pattern, it is performed before reproducing the mask pattern image. Incidentally, in order to prevent the pattern formation position of the wafer from being unnecessarily exposed to light during the alignment, it is desirable to shield the pattern formation position by some means.

Then, the step of detecting the relative positional deviation information between the hologram recording medium and the wafer based on the detection result and correcting the relative positional relationship between them is performed based on the positional deviation information. As described above, by detecting whether or not the reproduction state of the hologram mark is proper, it is possible to identify the presence or absence of the relative positional deviation between the wafer and the hologram. Therefore, the relative positional deviation information is detected from this detection result. It

Further, the alignment is completed by adjusting the relative positional relationship between the wafer and the hologram (recording medium) so that the reproduction state of the hologram mark becomes appropriate based on the positional deviation information. By reproducing the hologram of the mask pattern in such a state that the alignment is properly performed, an appropriate mask pattern image is exposed at a predetermined position on the wafer.

Next, the invention described in claim 2 is an exposure method using a so-called total reflection holography technique (total reflection holography), in which the same total reflection holography technique is applied to alignment. Furthermore, it is characteristic that an alignment mark is used so that the hologram mark becomes a holographic zone plate.

That is, in the present invention, a hologram (recording medium)
When detecting the relative positional relationship (including gap detection) between the wafer and the wafer, the holographic zone plate is applied, and the light flux (reproducing light) that converges (images) to the image formation position as detection light for alignment is used. The relative positional deviation information is detected from the focused state (reproduced state) of this light flux on the wafer surface. The detection of the focused state is performed, for example, by detecting the intensity of the transmitted light or the reflected light on the wafer surface or the wavefront.

First, in forming a hologram from an alignment mark according to the present invention, a holographic zone plate for alignment is formed on the hologram storage medium as an object wave of transmitted diffracted light from an alignment mark having a predetermined shape formed on a mask. It is performed by the process of storing.
In this hologram forming step, divergent light diffracted by the pattern of the alignment mark provided on the mask is used to form the hologram on the hologram recording medium similarly to the mask pattern.

The alignment mark may have any structure as long as the hologram formed from this alignment mark has a function as a holographic zone plate. In other words, when the hologram for alignment is irradiated with the reproduced wave, the hologram having the function of condensing the reproduced light there to the image forming position (that is, the holographic zone plate) is aligned with the mark. It may be provided as a mark on the mask.

As an example, a slit, a pinhole, or the like may be considered, but the invention is not limited to these, and any structure may be used as long as the transmitted diffracted light from the mark becomes divergent light. For example, when an alignment mark composed of a pinhole is used, a concentric holographic zone plate is formed, and in the case of a slit, a holographic zone plate composed of a striped pattern in a strip-shaped area is a hologram. It will be formed on a recording medium.

The step of forming the holographic zone plate may be carried out simultaneously with or separately from the step of forming the hologram of the desired pattern on the mask. When forming (and reproducing) the holographic zone plate, light having a wavelength different from the wavelength used for hologram forming (and reproducing) of the mask pattern may be used.

Then, prior to the reproduction of the mask pattern image, the wafer is irradiated with the reproduction light of the image of the alignment mark obtained by irradiating the holographic zone plate with the reproduction wave, and the alignment mark image reproduction light is emitted. By detecting the reflected light or transmitted light on the wafer surface, the step of detecting the reproduction state of the reproduction image of the alignment mark on the wafer surface is performed. Then, the alignment is completed by the process of detecting the relative positional deviation information between the wafer and the hologram (recording medium) based on the detection result, and correcting the relative positional relationship between them based on the positional deviation information.

In the present invention, since the holographic zone plate is applied as a hologram for alignment, the reproduction light of the alignment mark image becomes a light beam which is focused on the image forming position. Therefore, if only the gap is taken as an example, the state where the reproduction light is accurately focused on the wafer surface is the state where the alignment mark image is reproduced accurately. The reproduced state of the mark image can be detected by detecting the focused state of the reproduced light on the wafer surface.

Further, by performing the above-mentioned detection at the alignment mark image forming position on the wafer, it is possible to simultaneously detect the positional deviation state in the XY direction from the relative positional deviation state between the image forming position and the focusing position. Therefore, if these are detected at a plurality of positions on the wafer surface, it is possible to detect the relative positional deviation and the state such as inclination and rotation.

As described above, since the relative positional relationship between the wafer and the hologram on which the alignment mark is accurately reproduced is the relative positional relationship at which the mask pattern is accurately exposed on the wafer at the same time, after the above alignment is completed. The mask pattern is reproduced (exposed).

By the way, the reproduction state of the alignment mark image on the wafer surface can be detected by detecting the converging state of the reproduction light, and the converging state can be detected by, for example, the following means. As an example, when the reproduction light is reproduced at an appropriate gap interval, the reproduction light is a light flux that is most densely focused on the wafer surface. Therefore, when the intensity of the reproduction light irradiated on the wafer surface is maximum. Can detect that the gap is proper.

As another means, focusing on the fact that the reproduction light is a diffracted wave diffracted by the holographic zone plate, the wafer surface is detected by detecting the wavefront of the reproduction light reflected or transmitted by the wafer surface. The condensed state on the surface can be detected.

Here, in the invention described in claim 3, a means for detecting the relative position by the wavefront detection is shown. The present invention is the exposure method using the total reflection hologram according to claim 2, wherein in the alignment mark image reproduction state detecting step, the reflection light on the wafer surface of the alignment mark image reproduction light is reflected by the holographic zone. By reproducing the alignment mark reproduced image on the wafer surface by detecting the wavefront of the transmitted diffracted light there while being guided to the plate.

In the present invention, the reproduction light of the alignment mark image (diffracted wave from the holographic zone plate)
Is reflected on the wafer surface, then is made incident on the holographic zone again, and the wavefront is detected by detecting the transmitted diffracted light there. Below,
For simplicity of explanation, only gap detection will be described as an example. However, if a reflecting portion is provided only on the alignment mark image forming position on the wafer surface, misalignment in the XY direction can be detected as described above. Will be things.

Since the reproduction light of the alignment mark image is focused light which is diffracted from the holographic zone plate and condensed at the image forming position as described above, when the reproduction light is reflected on the wafer surface, it is divergent light. Becomes In other words, the reflected light becomes divergent light from the alignment mark image formed on the wafer surface, and enters the holographic zone plate again.

Here, if the reproduction state of the alignment mark image (the gap between the wafer and the hologram) is accurate (the state where the wafer is in focus), the same image as the alignment mark is formed on the wafer surface. Then, the reflected light (light flux from the alignment mark image) from here passes through the same path (the same path as the divergent light from the alignment mark at the time of hologram formation) in the opposite direction to the convergent light at the time of image formation, and is reflected and diverged. It again enters the holographic zone plate as light.

The reflected divergent light incident on the holographic zone plate is diffracted here, and the characteristic of the holographic technique appears in the traveling direction of the reflected diffracted light. That is, since the object wave and the reference wave (reflected light) interfere with each other in the hologram recording medium during hologram formation, the same light flux as the object wave during hologram formation is applied to the hologram once formed. When irradiated, it is diffracted by the hologram and travels along the same path as the reference wave (reflected light from the hologram recording medium) at the time of hologram formation.

Since the path of (reflected light of) the reference wave is a light beam traveling in the path opposite to the reproduced wave (parallel light conjugate with the reference wave) at the time of hologram reproduction, the reproduced image of the alignment mark is the wafer. When the light is accurately focused on the surface, the diffracted light reflected by the holographic zone plate is also parallel light that passes through a path opposite to the reproduction wave.

However, when the alignment mark image is not accurately reproduced, that is, when the gap between the wafer and the hologram storage medium is not accurately aligned with the focus state, the reflected and divergent light on the wafer surface is This is different from the object wave at the time of hologram formation, and the diffracted light reflected by the holographic zone plate is not parallel but converged or divergent light.

Therefore, the wavefront of this reflected diffracted light (parallel,
By detecting the convergence or divergence, it is possible to detect the reproduction state of the alignment mark image, that is, the difference (deviation) in the gap between the hologram (storage medium) and the wafer with respect to the formation position (focus position) of the hologram and the reproduction image. Becomes

Further, regarding the gap alignment, the position deviation from the focus state is detected from the detection result of the wavefront, and the relative distance between the wafer and the hologram storage medium is corrected based on this detection result to reproduce the hologram image. Focusing (gap adjustment) can be performed.

Further, as described above, if the reflecting portion is provided only at the alignment mark image forming position, X is determined from the presence or absence of reflected light.
-Since it is possible to detect misalignment information in the Y direction, holograms (recording media) other than gaps can be applied by applying the detection of the wavefront.
It is also possible to adjust the relative positional relationship between the wafer and the wafer. It is also possible to detect the intensity and the like at the same time with the same detection system at the time of the wavefront detection, and relative position detection and adjustment may be performed based on these information.

As described above, in the present invention, since the light that converges (images) on the wafer is used as the inspection light for alignment, compared with the conventional vertical light incidence method, it is possible to use the light in the gap interval or at other positions. The influence of multiple reflections is extremely small.

Further, since the holographic zone plate formed on the hologram recording medium is used as the image forming means of the detection light as in the case of the hologram of the mask pattern, the change of the focus position caused by the deformation of the hologram due to the contraction of the hologram, for example. Also becomes common with the circuit pattern portion. Therefore, even if the focus position of the reproduced image with respect to the hologram of the mask pattern changes, the focus position of the reproduced image of the holographic zone plate also changes.

Therefore, if the relative positional relationship such as the focus adjustment is adjusted by the alignment hologram, the change in the relative position of the mask pattern with respect to the hologram deformation such as the focus is automatically corrected. .

Next, the invention according to claim 4 of the present application relates to an apparatus for carrying out an exposure method using a holographic technique. The apparatus according to the present invention uses, as an object wave, the diffracted light from the mask on which a desired pattern is formed, interferes with the reference wave to record a hologram on a hologram recording medium, and then reproduces the conjugate wave with the reference wave. An exposure device using holography, in which a mask pattern is transferred onto a wafer by irradiating a hologram with a wave to reproduce an image of the mask pattern on a wafer arranged in place of the mask, and applied a holographic technique. It is provided with means for detecting the relative position of the wafer and the hologram (recording medium).

First, a coherent light source for generating a coherent light beam is provided as a light source for forming a hologram mark for alignment on the hologram recording medium from an alignment mark provided on a mask. This light source may be the same one as that used when forming the hologram from the mask pattern, or may be different means (including wavelength). When a wavelength different from the wavelength for the mask pattern is used, it is preferable to use a wavelength that does not react (sensitize) to the wafer (resist) but reacts to the hologram storage medium.

That is, the formation of the hologram mark on the hologram storage medium is not necessarily the same as the wavelength for the mask pattern, but a hologram is formed if the wavelength is sensitive to the hologram storage medium. it can.
Then, the alignment mark image is accurately reproduced by reproducing with the light of the same wavelength as that at the time of formation, so that the alignment mark image can be accurately reproduced by using this. Even in this case, since the alignment mark image is formed at a position corresponding to the mask position at the time of hologram formation, the formation position of the horogram reproduction image does not change even if a light flux having a wavelength different from that of the mask pattern image is used. .

Further, since the alignment work including the relative position detection is performed before the hologram exposure of the mask pattern, if the alignment work is performed with the light of the same wavelength as the mask pattern reproduction (formation), the resist on the wafer becomes unnecessary. There may be a problem of exposure. In order to avoid this, for example, the alignment mark formation position of the mask should be spatially separated from the pattern formation position so that the light (diffracted light, etc.) when reproducing the alignment mark image does not affect the reproduction of the mask pattern image. Or a means for hiding a necessary portion of the wafer (for example, a mask pattern transfer region) is required.

Next, the coherent light beam from the light source is used to form the hologram from the alignment mark as a hologram mark on the hologram recording medium by the object wave irradiation optical system and the reference wave irradiation optical system. The hologram mark formation itself is not particularly limited as long as it uses a holographic technique, but at least the respective light beams are guided so that the object wave from the alignment mark interferes with the reference wave in the hologram recording medium. Optical means are required.

In the apparatus according to the present invention, the alignment mark is irradiated by the object wave irradiation optical system, and the hologram recording medium is irradiated by the diffracted light (object wave) generated from the alignment mark, while the hologram is irradiated by the reference wave irradiation optical system. A reference wave is irradiated in the storage medium so as to interfere with the object wave. Then, a hologram mark is formed on the hologram storage medium by the mutual interference of these lights.

Here, an alignment mark is formed in advance on the mask together with a desired pattern, and after the mask is fixed to the hologram storage medium, a hologram forming process from the hologram mark and the mask pattern is performed. These steps may be performed simultaneously or separately, but in any case, it is essential that the relative positional relationship between the hologram storage medium and the mask is the same. Further, a hologram mark fixing operation or the like is performed as needed, similar to the mask pattern hologram.

After these hologram forming steps are completed, the mask is removed and the wafer is inserted at the same position.
It should be noted that it is preferable that a rough preliminary alignment be performed when the wafer is inserted. Then, the hologram mark is reproduced before the reproduction (exposure) of the mask pattern image to detect and adjust the relative position between the wafer and the hologram (recording medium), and after accurate alignment is completed, the mask pattern is exposed. Work is done.

In the apparatus according to the present invention, the reproduction wave irradiating optical system irradiates the hologram mark with the reproduction wave to obtain the reproduction light of the alignment mark image formed of the light beam diffracted here. This reproduction light is condensed at the image forming position of the alignment mark image, but since the image forming position is the mask (alignment mark) position at the time of hologram formation, the wafer surface arranged in place of the mask is irradiated. Will be done.

Then, the reproduction state of the alignment mark image on the wafer surface by the reproduction light is detected by the reproduction image detecting means. As long as the detection means can detect the reproduction state of the hologram image formed on the wafer surface, for example, as described above, the intensity or wavefront is obtained, or the hologram image is observed as a real image using an observation system or the like. Any method such as one may be used.

From the detection result, the relative position detecting means detects the relative positional deviation information between the wafer and the hologram (recording medium), and based on this information, the relative positional relationship between the wafer and the hologram recording medium is adjusted to achieve alignment. After that, the mask pattern is exposed.

Next, in the invention described in claim 5, the hologram exposure apparatus using the so-called total reflection holography technique is provided with the relative position detecting means also using the total reflection holography technique. In the device according to the present invention, a coherent light source for generating a coherent light beam is provided as a light source for forming the hologram mark by the alignment mark, and the light beam from the light source is provided by the object wave irradiation optical system and the reference wave irradiation optical system. Leads to masks and hologram recording media.

The object wave irradiation optical system guides the light flux so that the transmitted diffracted light generated from the alignment mark of the mask irradiates the hologram storage medium as an object wave for forming the hologram mark, and the reference wave irradiation optical system is used. Is a reference wave for forming a hologram mark, which is totally reflected on the inner surface of the hologram storage medium from the side opposite to the mask and guides the light flux so as to cause interference with the object wave in the hologram storage medium. . Then, a hologram mark is formed in the hologram recording medium by the interference action of these object waves and reference waves.

As an example, if the alignment mark of the mask to be used is composed of, for example, a pinhole, when the light beam from the object wave irradiation optical system irradiates the alignment mark, the transmitted diffracted light from this is radial. It becomes divergent light and illuminates the hologram storage medium. On the other hand, the reference wave irradiation optical system irradiates the back surface side of the hologram storage medium with a coherent light beam at a similar position. Then, a concentric holographic zone plate is formed on the hologram storage medium by these mutual lights.

An alignment mark is formed in advance on the mask together with a desired pattern. After the mask is fixed to the hologram storage medium, a hologram is formed from the holographic zone plate and the mask pattern. These steps may be performed simultaneously or separately, but in any case, it is essential that the relative gap (gap) between the mask and the hologram storage medium is the same. Further, after performing work such as fixing of the hologram as necessary, the mask is removed, the wafer is inserted and the relative position of the inserted wafer to the hologram (recording medium) is detected.

Next, when the hologram wave is irradiated with a predetermined reproduction wave by the reproduction wave irradiation optical system, reproduction light of an alignment mark image is obtained, and the reproduction light of the alignment mark formed on the wafer surface is obtained. The reproduction state is detected by the reproduction image detecting means, and based on the detection result, relative position deviation information between the hologram (recording medium) and the wafer is detected by the relative position detecting means. Based on this
The alignment is completed by adjusting the relative positional relationship between the wafer and the hologram recording medium.

In the exposure apparatus according to the sixth aspect of the invention, the reproduction image detecting means detects the reproduction state of the alignment mark image by detecting the alignment mark reproduction light reflected or transmitted by the wafer surface. . Also in the present invention, the means for detecting the reproduction state of the alignment mark image may be any means such as intensity, wavefront, or real image detection, and is not particularly limited.

Then, when the material of the wafer substrate is, for example, a glass substrate, or when a penetrating portion such as a pinhole or a slit is provided at the alignment mark image forming position on the wafer, the wafer is transmitted. It is also possible to detect the image formation state by detecting the reproduction light. On the other hand, it goes without saying that the reflected light may be detected by providing a reflecting portion on the wafer surface as described above.

Further, in the apparatus according to the invention described in claim 7, the reproduction image detecting means guides the reproduction light of the alignment mark reflected on the wafer surface to the hologram mark and diffracted light at the hologram mark. Is detected to detect the reproduction state of the alignment mark image.

In the present invention, as described above, the holographic technique is applied to guide the reproduction light reflected on the wafer surface to the hologram mark again, and the characteristic of the diffracted light here is utilized to reproduce the alignment mark image. Detect the condition. As this detecting means, the means explained in the above-mentioned method invention may be used.

The detection of the reproduction state will be outlined with an example. The alignment mark in the present invention preferably has a configuration in which a holographic zone plate is formed as a hologram mark. Suppose that the alignment mark is composed of pinholes and only gap detection is taken as an example.The wafer fixed at the original mask position is diffracted by the holographic zone plate based on the light flux from the reproduction wave irradiation optical system. Then, the light flux that converges (images) at the focus position (appropriate gap) is used.

That is, if the reproduction wave irradiating optical system irradiates the holographic zone plate with a reproduction wave that is conjugate with the reference wave as in the case of normal hologram reproduction, the diffracted light from here irradiates an image of the alignment mark (pinhole). Reproduce.
Here, since a light beam that converges to the focus position is obtained from the holographic zone plate, the state where the wafer surface matches the focus position is focused (focus).
It becomes a state.

Then, as described above, if the reproduction light from the holographic zone plate is incident on the wafer surface in this focused state, the reflected light on the wafer surface passes through the same path as the incident light and is holographic again. The diffracted light that has entered the zone plate travels through the same path as that of the previous irradiation reproduction light (parallel light) and travels.

However, when the wafer surface goes out of focus,
The diffracted light is not a parallel light but a light flux that converges or diverges. Therefore, by detecting the wavefront of the reflected diffracted light by the reflected wave detecting means, it can be detected that the wafer surface is deviated from the focus position if at least it is clear that the light is not parallel light. Further, the relative position detecting means detects the positional deviation information of the wafer surface with respect to the in-focus state based on the detection result. Then, the gap is adjusted based on this detection result, and the hologram of the mask pattern is reproduced in a state where the wafer surface is accurately focused, whereby the mask pattern is accurately transferred to the wafer.

In order to improve the working efficiency, it is preferable to measure the gap in the previous hologram forming step in advance and roughly align the wafer according to the measured value. Even in this case, if the hologram is deformed, for example, the focus position will be different from the measured value, but by performing the alignment of the present invention, accurate focus adjustment corrected from the measured value can be achieved. Done.

As described in the method invention, the relative positional deviation information such as the XY directions and the rotational inclination can be detected by a means such as providing a reflecting portion only at the alignment mark image forming position on the wafer surface.

In the apparatus according to the invention described in claim 8,
Correction means is provided for correcting the relative positional relationship between the hologram storage medium and the wafer based on the detection result of the relative position detection means. By this correction means, the wafer and the hologram recording medium are relatively moved so that they are accurately aligned based on the relative position information of the wafer and the hologram (recording medium), thereby completing the alignment. Then, by reproducing the hologram of the mask pattern, the mask pattern image is accurately formed on the exposed region of the wafer.

The correction means for performing this final alignment adjustment work is only required to be able to adjust at least the fixed position of the wafer, and the gap, the fixed position in the XY directions, etc. can be determined based on the previous detection result. Preferably, it can be adjusted at a plurality of positions on the peripheral portion of the wafer. In addition,
It is also possible to fix the fixed positions of both the hologram recording medium and the wafer.

[0089]

The present invention will be described in more detail with reference to the following examples. First, in the hologram exposure means according to one embodiment of the present invention, a pinhole-shaped mark is used as an alignment mark, and a holographic zone plate formed from this mark is used for relative position detection for alignment. In order to simplify the description, only the relative gap (gap) detection between the wafer and the hologram recording medium will be described as an example.

First, the formation of a hologram for alignment will be described with reference to FIG. 1. In this embodiment, the so-called total reflection holography technique is applied, and the basic arrangement configuration when creating a hologram by this is applied. Is as shown in FIG. In this figure, the hologram recording medium 1
Are arranged so as to be held on the upper surface of the prism 2, and the mask master 3 is fixedly supported with a gap of about 100 μm kept from the hologram recording medium 1.

As the hologram recording medium 1, a photopolymer or the like which does not require development is used.
A desired circuit pattern (not shown) and a pinhole 20 as an alignment mark for gap detection are electron beam-drawn, and the relative positional relationship between the mask pattern and the alignment mark is predetermined.

In order to form a hologram (holographic zone plate) of the alignment mark, the pinhole 20 is illuminated by the object clearing light B from the upper surface side of the mask master 3, and the spherical diverging wave C diffracted here is used. The hologram recording medium 1 is irradiated with the object wave. Further, a reference wave A, which is a luminous flux coherent to the object illumination light B, is guided from the back surface side of the hologram recording medium 1 so as to be totally reflected inside the mask master 3 and to interfere with the previous object wave.

In the light source means in this embodiment, the luminous flux emitted from an Ar laser (not shown) is amplitude-divided at an appropriate ratio and then converted into a reference wave A and an object illumination light B which are parallel luminous fluxes by a beam expander. , Are led to respective irradiation positions as shown in the figure.

When the object illumination light B illuminates the pinhole 20 which is a mask mark on the mask 3, a diverging spherical wave C due to transmitted diffracted light is generated from the back surface side of the mask 3,
It enters the hologram recording medium 1. At the same time, the reference wave A is made incident on the hologram recording medium 1 from the prism 2 side, is guided to the irradiation area of the divergent spherical wave C and is totally reflected on the inner surface, so that these two lights are reflected in the hologram recording medium 1. In the holographic zone plate 4 is recorded (formed) as a hologram of the alignment mark by the interference action.

In order to reproduce the alignment mark image from the hologram recorded here, the holographic zone plate 4 is used as an image forming element, and parallel light conjugate with the reference light A is used as a reproduction wave for forming the hologram image. It may be incident as detection light, which will be referred to as detection light D. Figure 1
As shown in FIG. 5, the detection light D is incident on (the holographic zone plate 4 forming position of) the hologram recording medium 1 to obtain a light beam condensed at the position of the pinhole 20 of the mask.

The circuit pattern (mask pattern) formed on the mask 3 is in the same gap as the gap where the holographic zone plate 4 is recorded.
A separately recorded mask pattern reference optical system and object optical system are used to record as a pattern hologram on the hologram storage medium 1.

Next, the mask 3 is removed, and the wafer 5 is mounted at the same position to perform the exposure work. The exposure of the mask pattern on the wafer 3 is performed by detecting the gap between the wafer 5 and the hologram (storage medium 1). After the alignment work is performed, the mask pattern is exposed on the resist of the wafer 5. Therefore, the illumination light wavelength for recording the mask pattern as a hologram (the same wavelength as the wavelength of the reproduction light) is such that the resist applied to the wafer 5 is exposed, and the holographic zone plate 4 for gap detection is used. Recording (and reproduction) is preferably performed using light in a wavelength range that is not sensitive to the resist.
If the two kinds of holograms recorded in this way are reproduced at their respective recording wavelengths, unnecessary exposure (exposure) to the resist during the gap detection will not occur.

Next, the gap detecting means in this embodiment will be described with reference to FIG. In this figure, a resist-coated wafer 5 is placed at the position where the mask 3 was placed when the hologram was formed. Wafer 5
Is supported by an electrically drivable holding device 6, and is configured so that fine adjustment of the gap and the like can be performed by a control means (not shown).

In this embodiment, the gap is adjusted by changing the supporting position of the wafer while the hologram storage medium 1 is fixed, but any relative positional relationship (gap) between the wafer and the hologram can be adjusted. It is not limited to this method. Further, it is preferable to have a structure capable of relative movement in the lateral direction (XY direction),
In order to adjust the relative rotation and inclination, these holding means may be provided at a plurality of positions and separately controlled.

The gap is detected by irradiating the holographic zone plate 4 with the detection light D as described above. The detection light D, after passing through the beam splitter 7, enters the prism 2 and undergoes total internal reflection once, then enters the hologram recording medium 1 and illuminates the holographic zone plate 4. Further, the detection light D is
The reproduction image of the alignment mark (pinhole 20) is formed by being diffracted by the holographic zone plate 4.

At this time, the diffracted light from the holographic zone plate 4 is converted into convergent light E so that the position where the mask is placed becomes the focus position, and irradiates the wafer 5. The convergent light E forms an alignment mark image on the wafer 5, but at the same time, it is reflected by the wafer 5 and enters the holographic zone plate 4 again. Then, it is diffracted here and propagates in the opposite direction on the optical path of the detection light D, and this is used as the signal light S for relative position detection.

The signal light S is totally reflected in the prism 2 and then is emitted and guided to the beam splitter 7, where it is reflected and enters the detection optical system 8. The signal light S becomes a plane wave conjugate with the detection light D when the wafer 5 is accurately arranged at the position where the mask was placed, that is, when the wafer 5 is at the focus position of the convergent light E. . In other words, if the alignment mark image is reproduced accurately, the signal light S becomes a plane wave.

However, when the wafer 5 is arranged with a gap larger than the proper gap interval, the signal light S becomes convergent light, and conversely, when the wafer 5 is arranged with a smaller gap, it becomes divergent light. Therefore, by measuring the wavefront of the signal light S by the detection optical system 8, it is possible to detect the position deviation state of the hologram from the focus position, and it is possible to adjust to the optimum gap based on the relative position deviation information.

Thus, in this embodiment, the reproduction state of the alignment mark image from the holographic zone plate 4 on the wafer surface is stored in the focus position (gap) of the hologram image, that is, in the hologram storage medium 1. It is directly detected as positional deviation information between the formation position of the reproduced image of the hologram and the mask position. Therefore, even if the hologram reproduction image formation position changes (from the mask position) due to, for example, hologram deformation, the focus position can be accurately detected and the gap can be adjusted according to the changed state.

That is, the above-mentioned convergent light E is a light flux that forms a reproduced image of the alignment mark, and since the alignment mark in this embodiment is the pinhole 20, it is the light flux that accurately converges on the wafer 5. It becomes a light beam that accurately forms a reproduced image of the alignment mark. Therefore, since the state in which the reproduced image of the alignment mark is accurately formed on the surface of the wafer 5 is the state in which the hologram is focused, it is possible to detect whether or not the hologram is accurately converged on the surface of the wafer 5. , A gap (focus position) misregistration state (that is, a reproduction state of an alignment mark image) can be detected.

Next, a means for detecting the gap by detecting the wavefront of the signal light S will be described. The basic concept of the gap detection optical system 8 in this embodiment is to detect the deviation of the signal light S from the parallel light. As this kind of detection method, a spot width measurement method, an astigmatism method, and oblique incidence are used. Method, knife edge method, Foucault method, critical angle method, etc. ("Recent optical contact roughness measurement method" O plus E, April 1985, p.
71), the spot width measuring method, and the oblique incidence method [X-ray lithography] are known. In the present invention, any of these may be used, and it is not limited to these as long as the wavefront of the signal light S can be detected.

First, an embodiment to which the spot width measuring method is applied will be described. The detection optical system in this embodiment is
As shown in FIG. 3, it is roughly composed of a convex lens 309 and a photodiode array 310 arranged at the focal position thereof. In this embodiment, the signal light S is the convex lens 3
The light beam is focused on the photodiode array 310 by the light source 09, and its spot diameter is minimum when the wavefront of the signal light S is a flat surface, and is larger than that in other cases.

That is, the wavefront of the signal light S becomes a plane when the signal light S becomes a parallel light. In this case, the convex lens 309 causes the signal light S to converge at its focal position (becomes a spot light). ), When the signal light S is convergent light or divergent light, the converging position deviates from the original focus position.
Therefore, the deviation of the wavefront of the signal light S from the planar state can be detected by detecting the converged state of the signal light S by the photodiode array 310 arranged at the original focus position.

In the present embodiment, the state where the wavefront of the signal light S is flat is when the resist surface and the focus position of the holographic zone plate 4 are in agreement, so that the photodiode array 310 is used. By electrically driving the holding device 6 so that the detected spot diameter is minimized, the focus position can be detected (gap alignment).

The other detection methods described above can also be used by appropriately exchanging the detection optical system. Among them, the critical angle method and the astigmatism method have the characteristics peculiar to the total reflection hologram. It is also possible to take an arrangement using. Examples in which these are applied will be described below.

FIG. 4 is a conceptual diagram of an embodiment to which a detection method using the critical angle method is applied. In this embodiment, the reference wave A ₁ when forming the holographic zone plate 404 is guided as follows. First,
After entering the prism 402, the reference wave A ₁ is totally reflected on the inner surface of the hologram recording medium 402, and then the prism 4
It is adjusted so that it will be incident on the (a) plane of No. 02 at a critical angle. Then, at the time of detecting the gap, the detection light D ₁ conjugate with the reference wave A ₁ is made incident on the prism (a) surface at a critical angle θc, and the light flux totally reflected here is guided to the holographic zone plate 404. .

In the present embodiment, the detection light D ₁ is totally reflected by the (a) surface and then diffracted by the holographic zone plate 404, and the diffracted light here becomes the reproduction light of the alignment mark image and the image forming position. Is focused on. This reproduction light is reflected by the wafer 405, then propagates in the same path in the opposite direction, is reflected by the half mirror 407, and enters the gap detection optical system 408.

The gap detection optical system 408 is roughly composed of a condenser lens 411, a two-divided detector 412 and the like. The signal light S ₁ in this embodiment is condensed by the lens 411 and is incident on the two-divided detector 412. To do. The light receiving portion of the two-divided detector 412 is arranged so that the lens 411 can generate a synchronization signal at the optimum focus position.
Is aligned to the focal position of.

As described above, when the wafer 405 is not in the optimum focus position of the hologram reproduction image, the signal light S ₁
Becomes a diverging wave or a converging wave, so that the incident angle of the signal light S _{1 on} the prism (a) surface partially changes. Therefore, part of the signal light S ₁ exceeds the critical angle, and this part is not totally reflected. For example, when the signal light S ₁ is a divergent wave, the light flux in the upper half of the figure has an incident angle that exceeds the critical angle when reflected on the (a) plane. For this reason, since a part of the light is transmitted instead of being totally reflected in this part, the intensity of the reflected light from this part is reduced.

In this state, the signal light S reflected by the (a) surface
_{When 1} is incident on the two-divided detector 412, the intensity of the signal light from the portion that does not undergo total reflection becomes weaker than the other portions. Therefore, upon detection by the two-divided detector 412, an asymmetric signal in which the detection intensity is partially changed is generated.

As described above, when the wafer 405 is not at the optimum focus position of the hologram, the signal light S ₁ becomes a diverging wave or a converging wave, so that an asymmetric signal is generated at the time of detection by the two-divided detector 412. Wafer 40
The positional deviation from the focus position of 5 can be detected. And
The focus position is detected and the gap is adjusted by driving the position changing means (not shown) of the wafer 405 according to the deviation of the light amount and adjusting so as to obtain the synchronization signal.

Next, an embodiment to which a detection method using the astigmatism method is applied will be described. In the astigmatism method, it is necessary to generate a convergent light having astigmatism by using a cylindrical lens or the like in the detection optical system, but a similar effect is obtained when the wavefronts of the recording light and the reproducing light of the holographic zone plate are , Astigmatism is also obtained.

The embodiment shown in FIG. 5 is an example of a detecting means to which the astigmatism method is applied, and the recording light A having astigmatism is used.
_The holographic zone plate 504 is recorded by ₂ . Then, when a plane wave as the detection light D ₂ is incident on the holographic zone plate 504 thus formed, the signal light S ₂ reflected and returned on the wafer surface has astigmatism. According to this method, an astigmatism optical system can be configured without using a cylindrical lens in the detection optical system 508.

The detection optical system 508 is composed of the condenser lens 5
13 and a four-division detector 514. The four-division detector 514 includes a lens 51 as a light receiving portion.
It is aligned at the three focal positions.

When the signal light S ₂ is detected with such an arrangement, when the wafer is not at the focus position of the hologram, an asymmetrical detection signal is generated from the 4-division detector 514 according to astigmatism. Therefore, the focus position can be detected and the gap can be adjusted by driving the wafer moving unit so that a symmetrical signal is obtained from the four-division detector 514 in accordance with this detection signal. In addition, here the holographic zone plate 5
The case where the recording light A _{2 of} 04 has astigmatism has been described, but the same detection and the like can be performed even if a plane wave is used as recording light and the detection light has astigmatism.

Next, an embodiment to which the oblique incidence method is applied will be described with reference to FIG. As shown in this figure, the parallel light D ₃ for detection in the oblique incidence method is incident asymmetrically with respect to the optical axis of the holographic zone plate 604. The holographic zone plate 604 is produced by the pinhole pattern of the mask as in the above-mentioned embodiment.

Then, when the wafer 605 is at the focus position of the hologram reproduction image, the detection light D ₃ is diffracted by the holographic zone plate 604, and then a → b →
It travels along the path of c and becomes the signal light S _3, and the mirror 6
The mirror 615, the lens 613, and the like are adjusted so that after being reflected by 15, the light is condensed on the optical axis of the lens 613.

In the detection optical system 608 in this embodiment, the two-divided detector 61 is located at the condensing position of the lens 613.
7 is arranged, and when the wafer 605 is not in the focus position of the hologram, the signal light S ₃ is incident on a position deviated from the central portion of the two-divided detector 617.
Therefore, by driving the moving means of the wafer 605 while measuring the differential signal detected here, the focus position of the hologram is synchronously detected and the gap can be adjusted.

In each of the above embodiments, the method of measuring the gap between one point on the wafer and the hologram (recording medium) has been described. As shown in FIG. 7, the holographic zone plate for detecting the gap is provided at a plurality of positions. It is also possible to record at (for example, three points) and detect the tilt between the wafer and the hologram at the same time.

Further, the illumination light for the alignment mark when recording the hologram for alignment has been described as a parallel light flux obtained by expanding the light flux from the light source with the beam expander. However, as shown in FIG. By illuminating the alignment mark with the condensed light, it is possible to improve the illumination efficiency of the irradiation light.

On the other hand, in the case where the alignment mark is not a pinhole but a slit-like one as in the above embodiment, a holographic zone plate (linear holographic zone plate) formed in a band-shaped region is used. However, relative position detection such as gap detection can be performed by the same method as in each of the above embodiments. Which one should be selected may be selected as appropriate when pinholes or slits are selected in consideration of arrangement conditions of the mask pattern and alignment marks with respect to the mask, and may be mixed when a plurality of alignment marks are provided.

Next, an embodiment for detecting and adjusting the relative positional deviation in the XY directions according to the present invention will be described. In each of the above-mentioned embodiments, the positional deviation of the gap is detected by detecting the reflected light on the wafer surface.
The following can be considered as a simple application of this.

First, by providing the reflecting portion only at the position where the alignment mark image is formed on the wafer surface, it is detected by the detection system whether or not the reproduction light of the alignment mark image is reflected by the wafer surface (or change in detection intensity thereof). By
The relative positional deviation in the X and Y directions can be detected.

This is because when a pinhole-shaped alignment mark is used, by providing a similar pinhole at the alignment mark image forming position, the detection system for detecting the transmitted light from (the pinhole of) the wafer. It is also possible to detect.

Further, as shown in FIG. 10A, slit marks 1020 are arranged as alignment marks in the XY directions, and as shown in FIG. 10B, a plurality of pinholes are arranged in the XY directions. It is conceivable to use the mark 1021 or the like. In these cases, the slit mark 10
By detecting the reproduction state over the entire length of the hologram reproduction image of 20 or by detecting the reproduction state of each of the hologram reproduction images of the pinhole mark 1021, the misalignment state in the XY directions can be detected.

Next, when the mark (hologram) to which these zone plates are applied is used in the detection system, the dynamic range of the detection system is determined by the size of the zone plate. For this reason, if the zone plate is made larger, the respective displacements can be detected even if the relative positional displacement is large, so that it can be used for the rough alignment.

Therefore, for example, with respect to the alignment mark for XY alignment (holographic mark corresponding thereto), if no other rough alignment means is provided, it is a region which has little influence on the circuit pattern etc. in addition to that for precise alignment. It is also possible to provide a large alignment mark on the.

Focusing on the gap detection, the gap detection sensitivity (accuracy) needs to suppress an error within the depth of focus during hologram exposure of the circuit pattern. In the present invention and the respective embodiments of the present invention, the reproduction state of the actual hologram mark is detected, so that the reproduction state in the alignment system is appropriate. It is extremely easy to perform the alignment within the depth of focus in hologram exposure of the circuit pattern.

Here, considering the accuracy of the gap detection, increasing the divergence (convergence) angle of the (diffracted) light beam generated from the pinhole or zone plate used in the present invention and each embodiment, in other words, N.S. A. Raising the value improves the detection sensitivity. For this purpose, it is necessary to reduce the diameter of the pinhole (increasing the divergence angle) and narrowing the line width of the zone plate (decreasing the convergence angle). Since there is a limit to what can be done or to miniaturize the zone plate, it is often difficult to manufacture.

Therefore, a method of using the high-order diffracted light of the zone plate can be considered as a practical countermeasure. Although the intensity of the high-order diffracted light becomes weaker than that of the low-order diffracted light, the detection itself has no problem with the light intensity if the method detects the wavefront state. However, the first-order light and the third-order light (or the fifth-order light or the seventh-order light) cannot be distinguished only by the wavefront, but by roughly aligning the gap interval in advance in the vicinity of the condensing position of the diffracted light to be detected. By setting this, only the diffracted light of the required order can be detected, so that if this method is adopted, more precise gap alignment can be performed.

Although the embodiments to which the holographic zone plate is applied have been described above, the present invention can also be applied to the case where other marks are used. For example, depending on the configuration and method of the holographic exposure apparatus, the hologram reproduced image for alignment may be directly observed. With such a holographic exposure apparatus, for example, by providing an observation means for directly observing the alignment mark image formation position, if the alignment mark image on the wafer is directly detected, the reproduction state of the alignment mark image is also directly detected. It will be possible.

Further, as shown in FIG. 11, it is also possible to provide a mark which is easy to compare with the alignment mark on the wafer surface and detect the relative positional deviation information by superimposing it on the reproduced image of the hologram mark. FIG. 1A shows a case where a partial projection portion (which may be a reflection portion or a transmission portion) is provided at the alignment mark image forming position on the wafer. For example, on the partial projection portion 1110, When a reproduced image is formed from the hologram formed by the alignment mark 1100, the alignment mark image 1101 and the projection unit 1 are formed.
A detection image 1120 is obtained from the observation optical system of 110. Further, FIG. 2B shows a case where a mark 1140 that is easy to compare with the alignment mark is provided at the previous image forming position, and in this case, a detected image 1150 is obtained.

Therefore, the relative positional deviation information can be detected from these detected images, and the relative position between the wafer and the hologram (recording medium) can be determined by, for example, the wafer supporting means capable of adjusting the relative position in the XY directions. Adjust the position,
The alignment is complete.

The observation optical system is not particularly limited as long as it can detect the alignment mark image or the reproduction state thereof. As an example, in the holographic exposure apparatus to which the so-called total reflection holography technology is applied as in each of the above embodiments, the alignment mark is formed by providing an observation optical system for observing the alignment mark image formation position as shown in FIG. The reproduction state of the image can be directly detected.

In this figure, the hologram recording medium 12
When the reproduction wave D ₁₂ is applied to the hologram mark 1204 formed on 01, the reproduction image of the alignment mark is formed on the wafer 1205. Here, when the wafer 1205 uses an opaque substrate, the alignment mark image formed on the wafer surface may be detected by the observation system 1282 that observes the prism 1202 in a meeting. When the wafer 1205 uses a transparent substrate such as a glass substrate, the observation optical system 1280 provided on the wafer 1205 may detect the alignment image and the like.

Further, instead of these observation systems, a predetermined optical system and an image sensor or the like arranged at a position conjugate with the alignment mark image forming position of this optical system detect the reproduced alignment mark image on the wafer. You may provide what you do.

It is needless to say that the present invention can be carried out even if the exposure means using the holographic technique according to the other method is provided with a means capable of detecting the alignment mark image formed on the wafer.

[0143]

As described above, according to the present invention, when the relative position between the wafer and the hologram (recording medium) is detected, the holography technique is applied, so that the alignment is preliminarily performed before the hologram reproduction of the wafer mark. Since the hologram of the mark is reproduced and the reproduction state is detected and the alignment can be performed, the mask pattern can be exposed in a state in which the mark is optimally aligned for the reproduction of the hologram.

That is, prior to the reproduction of the mask pattern,
Gap alignment needs to be performed within the depth of focus for reproduction image formation during hologram reproduction, but a proper reproduction state of the alignment mark mark means that gap adjustment has been performed within this depth of focus. However, the use of the alignment means of the present invention has an advantage that alignment of a gap within an appropriate depth of focus, which has been difficult in the past, can be performed easily and accurately.

Further, since the hologram mark produced on the hologram recording medium is used and the reproduction light composed of the diffracted light by the hologram mark is used as the detection light for detecting the relative position, there is no gap between the gaps as in the conventional case. Noise due to the effects of multiple reflections in the system has been reduced, and the relative position detection system has been dramatically improved. Therefore, relative alignment can be accurately performed during exposure of the mask pattern, and thus exposure transfer can be performed more accurately.

Further, since the reproduction light from the hologram mark formed on the same hologram recording medium as the mask pattern is used for relative position detection (alignment), the hologram (recording medium) is temporarily deformed and a hologram reproduction image is formed. Even if the position changes, the alignment mark (holographic mark) portion itself is deformed similarly to the pattern portion (hologram thereof). Therefore, if the reproduction state of the alignment mark image (after deformation) is proper, the reproduction state of the mask pattern (after deformation) is also proper, and the optimum reproduction image formation position corresponding to the hologram deformation is set. Can be detected. Therefore, there is an advantage that a complicated pattern correction means as in the prior art is not required and accurate pattern transfer can be performed even if hologram deformation or the like occurs.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an arrangement configuration of a holographic zone plate producing means for collecting gap detection light used in a hologram exposure method according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the arrangement and the like of the gap detecting means of the above embodiment.

FIG. 3 is an explanatory diagram showing a wavefront detecting means for signal light in the above-described embodiment, and a detection optical system and the like in an embodiment to which a spot width measuring method is applied.

FIG. 4 is an explanatory diagram showing a wavefront detecting means for signal light in another embodiment, which shows a detection optical system and the like in an embodiment to which the critical angle method is applied.

FIG. 5 is an explanatory diagram showing a wavefront detection means for signal light in another example, and a detection optical system and the like in an example to which an astigmatism method is applied.

FIG. 6 is an explanatory view showing a wavefront detecting means for signal light in another embodiment, showing a detection optical system and the like in an embodiment to which the oblique incidence method is applied.

FIG. 7 is an explanatory view showing a gap detecting means in another embodiment, and a detection optical system and the like for detecting gaps at a plurality of positions.

FIG. 8 is an explanatory diagram showing a schematic configuration of a holographic zone plate forming means in another embodiment.

FIG. 9 is an explanatory diagram showing a conventional example of a gap detection unit.

FIG. 10 is an explanatory diagram showing an example of an alignment mark according to another embodiment.

FIG. 11 is an explanatory diagram showing a reproduction state of an alignment mark and an alignment mark image on a wafer in another embodiment.

FIG. 12 is an explanatory diagram showing a schematic arrangement configuration of an observation optical system for observing an alignment mark image on a wafer in another example.

[Explanation of symbols]

1; hologram recording medium, 2; prism, 3; mask,
4; holographic zone plate, 5; wafer,
6; holding mechanism, 7; beam splitter, 8; detection optical system, 9; convex lens, 10; photodiode array, 1
DESCRIPTION OF SYMBOLS 1; Convex lens, 12; 2 division detector, 13; Convex lens, 14; 4 division detector, 15; Mirror, 1
6; convex lens, 17; two-divided detector, 18; objective lens

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinki Magome 3 2-3 Marunouchi, Chiyoda-ku, Tokyo Nikon (72) Inventor Naomasa Shiraishi 3 2-3 Marunouchi, Chiyoda-ku, Tokyo Company Nikon (72) Inventor Hiroshi Shirahiro Marunouchi 3 2-3, Tokyo, Chiyoda-ku, Tokyo Stock Company Nikon (72) Inventor Toshio Matsuura Marunouchi 3 2-3, Chiyoda-ku, Tokyo Stock Company Nikon

Claims (8)

[Claims] 1. A diffracted light from a mask on which a desired pattern is formed is used as an object wave, and this is interfered with a reference wave to record a hologram on a hologram recording medium, and then a reproduction wave conjugate with the reference wave is generated. An exposure method using holography in which a mask pattern is transferred onto a wafer by irradiating a hologram to reproduce an image of the mask pattern on the wafer arranged in place of the mask, and an alignment mark formed on the mask A step of storing a hologram for alignment in the hologram recording medium as a hologram mark by using the diffracted light from the object wave as an object wave, and the alignment obtained by irradiating the hologram mark with a reproduced wave prior to the reproduction of the mask pattern image. While irradiating the wafer with the reproduction light of the mark image,
The step of detecting the reproduction state of the reproduced image of the alignment mark on the wafer surface, the relative positional deviation information between the hologram recording medium and the wafer is detected based on the detection result, and the relative positional deviation information is detected based on the positional deviation information. An exposure method using holography, which comprises: a step of correcting the positional relationship. 2. A transmitted light diffracted from a mask on which a desired pattern is formed is used as object light, and this is interfered with a reference light to record a hologram on a hologram storage medium, and then a reproduction light conjugate with the reference light. In the exposure method using total reflection holography in which the mask pattern is transferred onto the wafer by irradiating the hologram with the hologram to reproduce the image of the mask pattern on the wafer arranged in place of the mask. A step of storing the holographic zone plate for alignment in the hologram storage medium as an object wave of transmitted diffracted light from an alignment mark having a predetermined shape; and reproducing the holographic zone plate before reproducing the mask pattern image. The reproduction light of the image of the alignment mark obtained by irradiating a wave A step of detecting the reproduction state of the alignment mark reproduced image on the wafer surface by irradiating the wafer and detecting reflected light or transmitted light of the alignment mark image reproduced light on the wafer surface; And a step of detecting relative positional deviation information between the hologram recording medium and the wafer based on the above, and correcting the relative positional relationship between them based on this positional deviation information. Method. 3. The step of detecting the reproduction state of the alignment mark image guides the reflection light of the alignment mark image reproduction light on the wafer surface to the holographic zone plate and detects the wavefront of the transmitted diffraction light there. 3. The reproduction state of the reproduction image of the alignment mark on the wafer surface is detected by the method described above.
An exposure method using the total reflection hologram described in 1. 4. A diffracted light from a mask on which a desired pattern is formed is used as an object wave, and this is interfered with a reference wave to record a hologram on a hologram recording medium, and then a reproduction wave conjugate with the reference wave is generated. An exposure apparatus using holography for transferring a mask pattern onto a wafer by irradiating a hologram to reproduce an image of the mask pattern on a wafer arranged in place of the mask, and is a coherent light source for generating a coherent light beam. The light source and a coherent light beam from the light source are guided to a position where the alignment mark of the mask is formed, and the diffracted light generated by the alignment mark thereby is used as an object wave for forming the hologram mark, and the hologram recording medium. An object wave irradiation optical system for irradiating the inside, and a coherent light beam from the light source A reference wave irradiating optical system for irradiating the hologram recording medium into the hologram recording medium as a reference wave for forming the hologram mark so as to cause interference with the object wave in the hologram recording medium; A reproduction wave irradiation optical system for irradiating the hologram mark with a conjugate wave of the reference wave as a reproduction wave and for irradiating the wafer surface with the alignment mark reproduction light obtained from the hologram mark by the reproduction wave irradiation, Reproduction image detection means for detecting the reproduction state of the alignment mark image formed on the wafer surface by the alignment mark reproduction light, and the relative between the hologram recording medium and the wafer based on the detection result of the reproduction image detection means. A relative position detecting means for detecting positional deviation information; Exposure equipment using. 5. A transmitted light diffracted from a mask on which a desired pattern is formed is used as object light, and this is interfered with a reference light to record a hologram on a hologram storage medium, and then reproduction light conjugate with the reference light is obtained. In the hologram exposure apparatus using a total reflection hologram that transfers the mask pattern onto the wafer by irradiating the hologram with the hologram to reproduce the image of the mask pattern on the wafer arranged in place of the mask. A coherent light source for causing, and a coherent light flux from the light source is guided to a position where the alignment mark of the mask is formed, and transmitted diffracted light generated from the alignment mark thereby is an object wave for hologram mark formation, An object wave irradiation optical system for irradiating the hologram storage medium, As a reference wave for forming a hologram mark, these coherent light beams are totally reflected on the inner surface of the hologram storage medium from the side opposite to the mask, and interfere with the object wave in the hologram storage medium. A reference wave irradiation optical system for irradiating, and a hologram mark formed on the hologram recording medium, irradiating a conjugate wave of the reference wave as a reproduction wave, and reproducing an alignment mark obtained from the hologram mark by irradiation of the reproduction wave. A reproduction wave irradiation optical system that irradiates the wafer surface with light, a reproduction image detection unit that detects a reproduction state of an alignment mark image formed on the wafer surface by the alignment mark reproduction light, and a reproduction image detection unit. Information on relative displacement between the hologram recording medium and the wafer is obtained based on the detection result. Exposure apparatus using the total reflection holography and relative position detection means for output, comprising the to. 6. The reproduction image detecting means detects the reproduction state of the alignment mark image by detecting the alignment mark reproduction light reflected or transmitted by the wafer surface. Or an exposure apparatus using the holography described in 5. 7. The reproduced image detecting means guides the reproduced light of the alignment mark reflected on the wafer surface to the hologram mark, and detects the diffracted light at the hologram mark to detect the reproduced state of the alignment mark image. The exposure apparatus using holography according to claim 4 or 5, wherein the exposure apparatus is for detecting. 8. A correction means for correcting the relative positional relationship between the hologram storage medium and the wafer based on the detection result of the relative position detection means. 7. The hologram exposure apparatus according to 7.