JPH06244086A - Method and device for exposure wherein holography is used - Google Patents

Abstract

PURPOSE:To provide a method, device, etc., of exposure wherein holography is used which is provided with an alignment method which readily detects relative position relation in X-Y direction and also can cope with hologram deformation. CONSTITUTION:The title device is provided with a means for forming a hologram for alignment, a process for detecting diffraction wave E2 from a wafer provided to a wafer 5a though hologram for alignment and an alignment means for detecting or correcting relative misregistration between the wafer and the hologram based on the detection result in a holography exposure method.

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 detection of a gap (relative distance between hologram and mask or wafer) for focus adjustment. (Hereinafter, adjustment of relative positional relationships such as xy alignment and gap alignment is collectively referred to as alignment.) In the above-described alignment method of the related art, the alignment pattern is a circuit (liquid crystal).
The pattern is recorded on the outside of the pattern, and the alignment is performed by overlapping the patterns for alignment.

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. 12, a laser beam is vertically incident on the hologram recording medium 1201 and the wafer 1205, and the light reflected by the surface of the hologram storage medium 1201 and the resist surface coated on the wafer 1205 are reflected. The interference signal is detected by the detecting means 1208,
The gap is detected by measuring the change in 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 (holographic recording medium in which the hologram is stored) 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 various problems, and it is easy and accurate to detect a relative positional relationship in the xy directions and a gap, and a holography provided with an alignment method capable of dealing 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, in the invention according to claim 1 of the present application, diffracted light from a mask on which a desired pattern is formed is used as an object wave, and this is caused to interfere with a reference wave. After recording the hologram on the hologram recording medium, the hologram is irradiated with a reproduction wave conjugate with the reference wave to reproduce an image of the mask pattern on the wafer arranged in place of the mask, thereby forming the mask pattern on the wafer. In the exposure method using holography, the hologram pattern for alignment is stored in the hologram recording medium as an object wave of diffracted light from an alignment mark of a predetermined shape formed on the mask, and the mask pattern image Prior to the reproduction of the wafer, the wafer mark provided on the wafer surface is irradiated with illumination light having the same wavelength as the object wave. Irradiating the hologram mark with diffracted light obtained by detecting the transmitted detection light from the hologram mark by this, and relative displacement information between the hologram recording medium and the wafer based on the detection result. And correcting the relative positional relationship between them based on the positional deviation information, and an exposure method using holography.

According to a second aspect of the present invention, in the holographic exposure method according to the first aspect, the alignment mark has a zone plate shape, and the wafer mark is formed from the alignment mark at the time of forming the hologram mark. It is characterized in that the same diffracted wave as the object wave is generated.

According to the invention described in claim 3, in the exposure method using holography according to claim 1 or 2,
A step of detecting reference detection light obtained by irradiating the hologram mark with the same reference inspection light as the reference wave at the time of forming the hologram, and detecting relative positional deviation information between the hologram recording medium and the wafer based on the detection result. And a step of performing.

On the other hand, 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 the reference wave to record a hologram on the hologram recording medium, An exposure apparatus using holography that transfers a mask pattern onto a wafer by irradiating a hologram with a reproduction wave that is conjugate with the reference wave to reproduce an image of the mask pattern on the wafer, and generates a coherent light beam. A coherent 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 transmitted diffracted light generated from the alignment mark thereby is used as an object wave for forming the hologram mark, the hologram. Object-wave irradiation optical system for irradiating a recording medium, and coherence from the light source A reference wave irradiation optical system that irradiates the light flux into the hologram recording medium as a reference wave for forming a hologram mark so as to cause interference with the object wave in the hologram recording medium, and is formed on the wafer surface. A wafer mark illumination optical system that guides wafer mark illumination light having the same wavelength as the object wave to the wafer mark, and guides diffracted light at the wafer mark generated thereby to the hologram recording medium on which the alignment mark is formed,
A transmitted light detecting means for detecting diffracted light at the wafer mark transmitted through the hologram mark formed on the hologram recording medium as transmitted detection light; and the hologram recording medium based on the detection result of the transmitted light detecting means. An exposure apparatus using holography, comprising: a relative position detection unit that detects relative position deviation information with respect to the wafer.

According to a fifth aspect of the present invention, in the holographic exposure apparatus according to the fourth aspect, the alignment mark has a zone plate shape, and the wafer mark has the same object wave as the alignment mark. It is characterized by having a zone plate shape in which diffracted waves are generated.

According to a sixth aspect of the invention, in the holographic exposure apparatus according to the fourth or fifth aspect, the same reference inspection light as the reference wave is guided to the hologram mark, and the hologram mark Reference reflection light detection means for detecting reflected light, wherein the relative position detection means detects relative positional deviation information between the hologram recording medium and the wafer by utilizing a detection result of the reference reflection light detection means. Is characterized in that.

According to the invention described in claim 7,
In the exposure apparatus using holography according to 5 or 6, based on the detection result by the relative position detection means,
It is characterized by comprising a correction means for correcting the relative positional relationship between the hologram recording medium and the wafer.

[0021]

Since the present invention is constructed as described above, it has the following effects. First, in the present invention, in the alignment process of the hologram (recording medium) and the wafer which is performed prior to the holographic exposure (hologram reproduction) of the mask pattern, it is also characteristic that the alignment means also applies the holographic technique. Is.

Generally speaking, if the reproduction state of the alignment mark image by holography is proper, the reproduction image from the hologram of the mask pattern formed on the same hologram recording medium can also have a good reproduction state. Is used to perform alignment, and then the mask pattern is exposed (hologram reproduction).

That is, when the mask pattern hologram and the alignment hologram formed on the same hologram recording medium from the same mask are reproduced, the reproduced image maintains the relative positional relationship between the pattern on the mask and the alignment mark. Is formed. Utilizing this,
In order for the reproduction state of the alignment mark reproduction image at the alignment mark formation position on the wafer to be proper,
By adjusting the relative positional relationship between the hologram recording medium and the wafer, the alignment process between the wafer and the hologram for mask pattern exposure can be properly performed.

Here, in the holography technique, a hologram is formed by diffracted light from a predetermined mark, and the image of the mark is reproduced by the diffracted light from this hologram.
Therefore, the diffracted light from these marks and the hologram is important for forming and reproducing the hologram. In the present invention, focusing on the characteristics of diffracted light in this holography technique, it is possible to detect the relative positional relationship between the wafer and the hologram by utilizing the characteristics of various diffracted light generated from the alignment mark, hologram mark, and wafer mark. It is a feature.

As an example, the object wave generated from the alignment mark during hologram formation is diffracted light diffracted from the alignment mark under a predetermined diffraction condition, and is formed based on this object wave. The reproduced wave from the hologram passes through a path opposite to that of the object wave and is condensed at an image forming position to form an image of the alignment mark.

Further, for the hologram once formed,
When the same diffracted light as the object wave is irradiated, a part is diffracted by the hologram and a part is transmitted by the hologram. The light beam diffracted by the hologram originally travels the same path as the reference wave at the time of hologram formation because it is a light beam that interferes with the reference wave at the time of hologram formation.

For this reason, a wafer mark having a structure that produces diffracted light similar to an object wave is provided, and diffracted light produced by irradiating the wafer mark with a light beam having the same wavelength as the object wave (hereinafter referred to as diffracted wave). Shows the same characteristics as the object wave.
The state in which the diffracted wave from the wafer mark travels in the same path as the object wave is a state in which the diffracted wave from the wafer mark travels in the path opposite to the reproduction wave of the alignment mark image. The mark image is in a state of being accurately reproduced on the wafer mark.

Here, the state in which the alignment mark image is accurately formed on the wafer mark is the state in which the wafer and the hologram (recording medium) are accurately aligned. By detecting the progress of the diffracted wave, the reproduction state of the alignment mark, that is, the relative positional deviation between the wafer and the hologram can be detected.

As described above, in the present invention, when the relative positional relationship between the wafer and the hologram is detected, the diffracted wave from the wafer mark is used as the detection light, and the traveling state of the diffracted wave and the object wave or the reference to the hologram is used. The consistency of the wave with the diffracted light is detected.

Needless to say, 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 wafer mark and the mask pattern exposure position on the wafer.

Further, 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.

Since the present invention applies the holographic technique, uses diffracted light or the like as the detection light, and performs alignment using the detection results of these intensities, it does not observe the pattern itself. Therefore, the pattern observing optical system as in the prior art is not required, the alignment marks can be made finer, and the alignment accuracy can be improved. This is because the diffracted light (diffracted wave or the like) from the wafer mark or the hologram mark is used as the inspection light for detecting the relative position, so that the inspection light itself is less susceptible to the effects of multiple reflection and irregular reflection. This is because.

Further, when the hologram once formed is irradiated with the reference wave at the time of hologram formation, in addition to the light flux traveling on the same path as the reference wave at the time of hologram formation,
Part of the light is diffracted by the hologram and becomes a light beam that travels along the same path as the object wave at the time of hologram formation. If the characteristic of the reference wave for this hologram is used, when detecting the diffracted light from the wafer mark, the luminous flux generated by the irradiation of the reference wave for the hologram is used as the reference light, and the consistency between this reference light and the diffracted wave is used. By detecting the, the positional deviation information can be detected.

By the way, the alignment marks and the like used in the present invention are, for example, the light source to be used (from which the selected luminous flux).
It is preferable to use a zone plate-shaped mark (the zone plate may be concentric or linear) in which the focal length depending on the wavelength is matched with the gap. That is, by using a zone plate-shaped alignment mark, a wafer mark, a holographic zone plate (hologram mark), or the like, it is possible to use diffracted light that becomes predetermined convergent light or divergent light as the inspection light in the alignment work. .

As described above, when the relative position is detected, only the diffracted light is detected by utilizing the diffraction effect of the hologram or the zone plate, so that the influence of the noise light due to the multiple reflection on the wafer or the hologram recording medium, etc. In addition to the above, the relative position can be detected easily and accurately by applying a detecting means such as a convergent (imaging) point.

Further, for detecting the relative positional deviation information by detecting the above-mentioned diffracted waves, a method substantially similar to the position detecting means and the alignment means known as the method of the conventional exposure projection apparatus may be applied. Although possible, it is different from the conventional method in that holography is applied.
In addition, the positional relationship between these wafer marks can be detected by the arrangement and shape of these wafer marks, the scanning of the illumination light that causes the diffracted wave, and the like (for example, mechanical movement scanning and minute vibration scanning), and the detection result Accurate alignment work is performed by performing relative position adjustment based on the above.

Since the holographic exposure method and apparatus according to the present invention has the alignment means as described above, it is possible to perform easy and accurate alignment.
The alignment work can be performed in a short time, and the exposure work of a predetermined pattern can be performed in a state where the accurate relative positional relationship is maintained, so that overlay exposure of a plurality of patterns can be performed accurately and reliably.

In addition, since the holographic mark formed on the same hologram recording medium as the hologram of the mask pattern is used for relative position detection, there is no change in the image forming position caused by hologram deformation due to hologram contraction or the like. It is common with the mask pattern part.
For this reason, even if the image formation position of the reproduced image with respect to the hologram of the mask pattern changes, the hologram mark also changes, so that the change of the image formation position due to the hologram deformation is automatically corrected. There is.

The operation of the present invention will be individually described below. First, in the invention described in claim 1, in the exposure method using holography, the hologram mark for alignment is stored in the hologram recording medium using the diffracted light from the alignment mark of a predetermined shape formed on the mask as an object wave. The step of performing is performed. In the present invention, the hologram formed on the hologram recording medium based on the alignment mark is called a hologram mark.

By this step, the hologram for the alignment mark provided at the predetermined position of the mask is formed as a hologram mark on the hologram recording medium. The alignment mark is defined in a predetermined positional relationship with respect to a predetermined pattern (circuit pattern or the like) on the mask. Then, the hologram for this mask pattern is simultaneously (or separately) recorded on the hologram recording medium. When they are separately performed, the relative positional relationship between the mask and the hologram recording medium does not change. Then, when these holograms are reproduced, the positional relationship between the alignment mark image and the predetermined pattern image becomes similar to the positional relationship on the mask.

Next, the mask is removed, the wafer is mounted at the same position, the alignment work described later is performed, and then the exposure (transfer) work of the mask mark is performed. In addition, a hologram fixing operation or the like is performed as necessary.

In the present invention, in the alignment means, the hologram recording medium is provided with diffracted light (diffracted wave) obtained by irradiating the wafer mark provided on the wafer surface with illumination light having the same wavelength as the object wave at the time of hologram formation. And the transmission detection light (simple transmission light or transmission diffraction light) from the hologram mark formed thereon is performed. The alignment means in the present invention is characterized in that holographic technology is applied and diffracted light (diffracted wave) obtained by illuminating a wafer mark is used as inspection light for relative position detection.

That is, in the holographic technique, when a reproduction wave is made incident on the hologram during reproduction of the hologram, the light beam diffracted by the hologram becomes reproduction light and travels on an optical path opposite to the object wave during hologram formation. Focus on the image formation position. On the contrary, when the same light flux as the object wave at the time of hologram formation is made incident on this hologram, a light flux which is diffracted by the hologram and travels in a path opposite to the reproduction wave is obtained. In the present invention, these characteristics of this holographic technique are applied to alignment.

Therefore, in the present invention, the wafer mark and the illumination light for alignment are used so that a diffracted wave passing through the same path as the object wave from the alignment mark during hologram formation can be obtained. As described above, in the alignment means of the present invention, the light beam having the same wavelength as the object wave is used as the illumination light for alignment, and the wafer mark is irradiated with this illumination light. Then, the relative position is detected by detecting the transmission detection light obtained by irradiating the hologram mark with the diffracted wave from the wafer mark by the illumination light.

Here, when the hologram mark is irradiated with the diffracted wave, a part is diffracted by the hologram and a part is transmitted as it is. Therefore, as the transmitted detection light,
Either the transmitted diffracted light diffracted by the hologram or the simple transmitted light will be detected.

Then, a step of detecting the relative positional deviation state between the hologram recording medium and the wafer based on the detection result and correcting the relative positional relationship based on the detected state is performed. This relative position detection is, for example, in the case of detecting transmitted diffracted light from a hologram, by providing a means for detecting a light flux passing through a path in the direction opposite to the normal reproduction beam incident position on the hologram mark, The inspection light beam diffracted by is detected. In this case, if it is possible to detect from the wavefront of the inspection light that the inspection light is traveling exactly in the opposite direction to the optical axis of the reproduction wave, it is possible to detect that the wafer mark is accurately aligned. It will be possible.

The wafer mark preferably has the same structure as the alignment mark, but it does not necessarily have to be completely the same. At least, it may have a configuration in which a diffracted wave that passes through the same path as the object wave diffracted by the alignment mark at the time of hologram formation (even if partially) is obtained.

For example, the alignment mark is formed on the mask, and the object wave is obtained by the transmitted or reflected diffracted light. However, even if the transmission type alignment mark is used, the wafer mark is reflected. It can also be used as a type mark. This is because the wafer mark is formed on the wafer, but when a circuit board or the like is manufactured, a wafer that is not a transmissive type is often used. A reflective mark configuration that can obtain a diffracted wave that passes through the same path as the above may be used.

When the present invention is applied to a transparent electrode structure or the like on a glass substrate, the glass substrate can be used for the wafer in the present invention. In such a case, the wafer mark is also of the transmission diffraction type. It is also possible to use a mark (having substantially the same configuration as the alignment mark).

Here, in the invention described in claim 2, in the exposure method using holography according to claim 1,
The alignment mark has a zone plate shape,
It is characterized in that the wafer mark has the same diffracted wave as the object wave from the alignment mark when the hologram mark is formed.

This is because the shape of the alignment mark is preferably the shape of the zone plate. That is, when the zone plate is used as the mark, the diffracted light generated from the mark becomes convergent light that converges to any one of the marks, so that the progress of the diffracted light can be easily detected.

When the zone plate is applied, the object wave from the alignment mark becomes diffracted light which is converged on the hologram recording medium by adopting a structure adapted to the wavelength used and the gap. Further, if the alignment mark is formed by a linear zone plate, a linear (linear) hologram mark is formed by the object wave from here. Then, the wafer mark also has a similar linear zone plate configuration, so that the inspection light that converges the diffracted wave from the wafer mark toward the hologram recording medium can be obtained.

When the wafer and the hologram are accurately aligned, the diffracted wave converges on a hologram mark which is a linear hologram, and the diffracted light from this is also obtained as a linear inspection light. Therefore, the detection can be easily performed.

Separately from this, when the focal point of the object wave or the like by the zone plate is configured to obtain a light beam which is focused on another position instead of on the hologram recording medium, the focal point is detected. As a result, the relative positional relationship between the wafer and the hologram can be detected. For example, when a zone plate-shaped alignment mark and a wafer mark are used, the state where the diffracted light from the wafer mark is focused at the same position where the diffracted light (object wave) from the alignment mark is focused is the relative position. The relationship will be accurately aligned. In this case, as the transmitted detection light, the diffracted light flux (converging point thereof) from the wafer mark that has simply passed through the hologram mark may be detected.

Further, the alignment mark and the wafer mark may be deformed such that one is a continuous linear mark and the other is a divided mark, and the like, so that the xy alignment can be easily detected. . That is,
The shapes do not necessarily have to be the same as each other, and it is sufficient that the diffraction waves that are the same as the object waves can be obtained by the inspection light even if they are partial.

Then, the relative positional deviation between the hologram (recording medium) and the wafer is corrected on the basis of the relative positional relationship information (deviation amount and direction etc.) obtained from these detection information, whereby the alignment is performed. Complete.
Further, the exposure operation is performed by reproducing the hologram of the mask pattern in the state where the alignment is accurately performed. In this case, since the alignment process as described above is performed, accurate overlay exposure can be performed even when a plurality of wafers are overlaid.

Next, in the invention described in claim 3, in the exposure method using holography according to claim 1 or 2, the hologram mark is irradiated with the same reference inspection light as the reference wave at the time of hologram formation. A step of detecting the reference detection light obtained as described above, and a step of detecting relative positional deviation information between the hologram recording medium and the wafer based on the detection result are provided.

In the present invention, among the characteristics of holography,
When a hologram formed once is irradiated with the same light flux as the reference wave at the time of hologram formation, the characteristics of the light flux obtained from the hologram are utilized. That is, when the hologram is irradiated with the same light flux as the reference wave, part of the light travels in the same manner as when the hologram was formed, but part of the light is diffracted by the hologram.

Here, as in the hologram formation, the reference detection light transmitted or reflected through the hologram becomes a light beam which travels in the opposite direction on the path of the reproduction wave (conjugate with the reference wave) for reproducing the hologram. The light beam diffracted by the hologram travels along the same path as (the transmitted light of) the object wave with which the hologram is irradiated.

Therefore, in the exposure method using holography according to claim 1 or 2, when the diffracted light or the transmitted light from the hologram is detected as the detection light or the transmitted detection light, these are opposite to the reproduction wave ( The reference detection light described above may be used as the reference light because it detects whether or not it coincides with the optical path of), or whether or not it coincides with the focusing point of the object wave.

That is, when the diffracted light generated by the irradiation of the hologram mark of the diffracted wave and the reference detection light, or the hologram mark transmitted light of the diffracted wave and the reference detection light (diffracted light) match, the wafer and the hologram are separated. Will be detected to be in an accurately aligned state.

Next, an apparatus for carrying out the above-described exposure method using holography according to the present invention will be described. In the following invention, the one applied to an exposure apparatus utilizing so-called total reflection holography is shown, but the method according to the present invention is not limited to this, and an exposure apparatus utilizing holography by another method is used. Can also be applied.

According to a fourth aspect of the present invention, the diffracted light from the mask on which a desired pattern is formed is used as an object wave,
After the hologram is recorded on the hologram recording medium by interfering this with the reference wave, the hologram is irradiated with a reproduction wave conjugate with the reference wave to reproduce an image of the mask pattern on the wafer arranged in place of the mask. An exposure apparatus using holography in which the mask pattern is transferred onto the wafer by performing the above, and further has the following configuration.

First, a coherent light source for generating a coherent light beam is provided as a light source for forming a hologram mark from an alignment mark. This light source may be the same one as that used when forming the hologram from the mask pattern, or may be a different means (including wavelength) besides this. If a wavelength different from the wavelength for the mask pattern is used, it should be used as a light beam for alignment that has a wavelength that reacts with the hologram recording medium but does not react (sensitize) with the wafer (resist). Is preferred.

That is, in forming a hologram mark on a hologram recording medium, a hologram can be formed as long as it has a wavelength sensitive to the hologram recording medium. Therefore, it is not always the same as the wavelength for the mask pattern. You don't have to. Then, the alignment mark image is accurately reproduced by reproducing with the light of the same wavelength as when the hologram mark is formed, and similarly, the light source (for alignment) when obtaining the diffracted wave from the wafer mark has the same wavelength. Alignment can be performed accurately by using one.

Since the alignment work is performed before the hologram transfer of the mask pattern, if the alignment work is performed with light having the same wavelength as the mask pattern reproduction (formation), the resist on the wafer is exposed. . In order to avoid this, for example, the alignment mark formation position of the mask is set to the pattern formation position so that the light beam irradiating the wafer mark and the diffracted light diffracted from it will not affect the reproduction (area) of the mask pattern. Or a cover means for hiding a necessary portion of the wafer at the time of alignment is required.

Next, using the coherent light beam from the light source, the hologram from the alignment mark is formed as a hologram mark by the object wave irradiation optical system and the reference wave irradiation optical system. If the alignment mark formed on the mask is composed of, for example, a pinhole, when the light flux of the object wave irradiation optical system irradiates the alignment mark, the transmitted diffracted light from here emits radial divergent light (object wave). ) And irradiate the hologram recording medium. On the other hand, the coherent light beam is emitted from the back surface side of the hologram recording medium to the irradiation position of the object wave by the reference wave irradiation optical system. Then, a hologram is formed on the hologram recording medium by the mutual interference of these lights. In addition,
The hologram mark in this case becomes a holographic zone plate.

When the alignment mark formed on the mask is, for example, in the shape of a zone plate, the hologram mark is formed at the position where the converged light from this alignment mark irradiates the hologram recording medium. For example, when using a linear zone plate with the gap distance as the focal length as the alignment mark,
Since an object wave that converges on the hologram recording medium is obtained, a hologram mark composed of a linear hologram is formed.

As described above, the alignment mark is formed in advance on the mask together with the desired pattern. After the mask is fixed to the hologram recording medium, the hologram is formed from the alignment mark and the mask pattern. These steps may be performed simultaneously or separately, but in any case, it is essential that the relative spacing positional relationship of the mask to the hologram recording medium is the same. Further, a hologram mark fixing operation or the like is performed as needed, similar to the mask pattern hologram.

Next, in the apparatus according to the present invention, diffracted light at the wafer mark by the wafer mark illumination light having the same wavelength as the object wave is used as the inspection light flux for alignment of the alignment means. That is, in the alignment work, the wafer mark illumination optical system guides the wafer mark illumination light having the same wavelength as the object wave at the time of hologram formation to the wafer mark, and diffracted light (diffracted wave) at the wafer mark is applied to the hologram mark. To the holographic recording medium on which is formed.

Here, as in the case of the above-described method invention, a wafer mark having a structure capable of obtaining the same diffracted light as the object wave from the alignment mark is used. When the relative positional relationship between the wafer and the hologram recording medium is accurate, the diffracted wave from the wafer mark enters the hologram mark along the same path as the object wave. In other words, the diffracted light from the wafer mark is used as virtual image reproduction light (a light flux traveling in a path opposite to the reproduction light) from the alignment mark image.

Then, the transmitted diffracted light or the simple transmitted light at the hologram mark by this diffracted wave is detected by the transmitted light detecting means, and the relative position detecting means detects the relative position between the wafer and the hologram based on the detection result. Do. For example, in the case of detecting transmitted diffracted light, in the state where the virtual image reproduction light is accurately aligned, detection is performed through a path opposite to the hologram reproduction wave (the same path as the reference wave during hologram formation). When light is obtained and there is a positional shift between them, the detected light deviates from this path. Therefore, the relative position shift state is detected from the state of the detection light.

Next, in the invention described in claim 5, the alignment mark has a zone plate shape, and the wafer mark has a zone plate shape in which the same diffracted wave as the object wave from the alignment mark is generated. Characterize. When the transmitted light detecting means detects the simple transmitted light by using the alignment mark and the wafer mark as the zone plate as described above, the position shift state is detected by detecting the converged position of the diffracted wave by the action of the zone plate. Can be easily detected.

Further, when the gap between the wafer and the hologram is configured to match the focal length of the zone plate and the diffracted light of the hologram mark of the diffracted wave is detected, the diffracted wave converges on the hologram mark. Since it becomes a light beam, the detection intensity becomes strong and the S / N ratio and the like are improved, so that the detection becomes easy.

Next, in the invention described in claim 6, the exposure apparatus using the holography described in claim 4 or 5 is provided with a reference reflected light detection means, and the detection result is used for relative position deviation detection. The relative position detecting means detects the relative positional deviation between the wafer and the hologram.

In the present invention, when the reference inspection light is incident on the hologram mark, the light beam passes through the same path as the object wave at the time of hologram formation, or the light beam passes through a path opposite to the reproduction wave (not conjugate to the reference wave). The characteristics of the holography technology that obtains the luminous flux are used. That is, when the detected light matches these light fluxes, it is possible to detect that the wafer mark has the same positional relationship with the hologram as the alignment mark.

Therefore, using this reference inspection light as the reference light,
The relative positional relationship between the wafer and the hologram (recording medium) is detected by comparing and detecting the real image detection light or the transmission detection light in the above invention. The relative position detecting means may be of any type such as one that detects a convergence point or one that detects a wavefront in accordance with the detection light used.

Next, in the invention described in claim 7,
An exposure apparatus using holography according to any one of claims 4, 5 and 6 is provided with a correction unit that performs alignment adjustment work based on the detection result of each relative positional relationship. The correction means may be any one that can adjust the fixed position of the wafer or the hologram recording medium, and can be adjusted by adjusting the position of the gap or the xy direction, or the tilt or rotation of the wafer based on the above detection result. A proper relative positional relationship can be achieved in the focused state.

Since the wafer is often supported so as to be replaceable with the mask and the hologram (recording medium) is often fixed, at least the position adjusting means may be provided on the wafer fixing means side. . Further, these correction means may be provided with a control means for interlocking with the movement adjusting means for the wafer or the like corresponding to the above detection result and correcting the position of the wafer or the like to adjust the relative positional relationship. preferable.

In the method and apparatus according to the present invention described above, in order to improve work efficiency, the gap in the previous hologram forming step is measured in advance, and the wafer is roughly aligned according to the measured value. It is preferable to operate. 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.

[0081]

The present invention will be described in more detail with reference to the following examples. It should be noted that the following embodiments describe the application of the present invention to the exposure method and apparatus using total internal reflection holography, but the present invention is not limited to this and may be applied to other methods of holography. It is possible.

First, a schematic structure of an exposure apparatus using holography according to this embodiment will be described with reference to FIG. In this holographic exposure apparatus, a prism 102 having an isosceles right triangle in cross section is used, and the short side is a horizontal upper surface, and the hologram recording medium 101 is arranged and fixed on the upper side. Further, a mask 103 is supported and fixed by a fixing means 106 with a predetermined gap (about 100 μm) opened above it. The hologram recording layer of the hologram recording medium 101 uses a photopolymer or the like that does not require development. On the mask 103, a desired circuit pattern (not shown) and an alignment mark for gap detection are electron beam-drawn.

The fixing means 106 mounts a mask at the time of hologram formation, but during the alignment work and the exposure work, the mask is replaced with a wafer to support and fix it. The mask and the wafer are supported at a plurality of positions. In addition, the fixed state is configured to be variable at each support position, and the lateral direction (xy direction) including tilt and rotation is also included.
And is vertically movable (gap) individually.

On the other hand, this embodiment is provided with a light source (not shown) that produces a coherent light beam (wavelength λ ₁ ) for the circuit pattern and a coherent light beam (wavelength λ ₂ ) for the alignment mark. In the present embodiment, the light flux emitted from the Ar laser is wavelength-divided to extract light fluxes of two wavelengths, but separate light sources may be used, or light fluxes of the same wavelength may be used in some cases.

In order to form the hologram of the alignment mark, the reference light A and the object illumination light B which are coherent light fluxes (wavelength λ ₂ ) are supplied from the back surface side of the hologram recording medium 101 and the top surface of the mask master 3, respectively. The light source means may be configured to be guided from the side. In this embodiment, a light beam (wavelength λ ₂ ) wavelength-selected from a light beam emitted from an Ar laser (not shown) is amplitude-divided at an appropriate ratio, and then a beam expander (not shown) produces parallel light beams. Wave A and object illumination light B are converted.

When the alignment mark on the mask 103 is illuminated by the object illumination light B, an object wave C is generated by the transmitted diffracted light from the back surface side, and the hologram recording medium 101.
Incident on. 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 previous object wave C, and is totally reflected inside the hologram recording medium 101, so that these two lights are emitted. Hologram marks are recorded (formed) in 101 by interfering with each other.

In order to reproduce the hologram mark recorded here, parallel light conjugate with the reference wave A may be incident as a reproduction wave, which will be referred to as a reproduction wave D. As shown in FIG. 1, a light flux having the same wavelength, which is incident on the path where the reference wave A is emitted from the prism 102 in the opposite direction, is incident on the long side of the prism 102 to undergo total internal reflection, and then is reflected on the hologram recording medium 1. The reproduction light D is obtained by making the light incident. When the hologram wave is irradiated with this reproduction wave D, a light beam that is condensed (imaged) at the position of the alignment mark on the mask is obtained as reproduction light.

The circuit pattern (not shown) formed on the mask 103 uses the reference optical system and the object optical system for the pattern in the same state as the relative positional relationship between the mask recording the hologram mark and the hologram recording medium. And recorded on the hologram recording medium 101 as a pattern hologram.

The light flux for the circuit pattern has a pattern light flux (wavelength λ ₁ ) obtained by wavelength-selecting the light flux emitted from the Ar laser (not shown), and is amplitude-divided by the half mirror 110 at an appropriate ratio.
111b, the reference beam A ₂ and the object illumination light B, which are parallel light fluxes.
Is converted to _2, further dichroic mirror 112a which reflects the wavelength lambda ₁ transmitted through the wavelength lambda _2, is reflected by 112b, each hologram recording medium 101 and the mask 1
It is led to 03.

The object illumination light B ₂ illuminates the circuit pattern forming area of the mask 103, and illuminates the hologram recording medium 101 with the transmitted diffracted light (object wave) by the circuit pattern. In this object wave irradiation area, the hologram recording medium 101
The reference wave A ₂ is radiated from the back side of and the internal reflection is performed. The interference of these light beams forms a pattern hologram based on the circuit pattern.

Next, the mask 103 is removed, the wafer is mounted at the same position, and the wafer is exposed. For the exposure of the wafer, after performing the alignment work such as the gap detection between the wafer and the hologram (recording medium 1) and the alignment in the xy directions, a reproduced image of the pattern hologram is formed on the resist of the wafer to form the circuit pattern. The procedure is such that the resist is exposed (transferred).

Here, the illumination light wavelength (the same wavelength as the reproduction light wavelength for recording the circuit pattern as a hologram,
In this embodiment, λ ₁ ) is used so that the resist applied to the wafer is exposed, and recording (and reproduction) of the hologram mark for alignment is performed in the wavelength region not exposed to the resist (λ _{2 in} this embodiment). ) Is preferable.

If the two kinds of holograms thus recorded are reproduced at the same wavelength as each recording wavelength, unnecessary exposure (exposure) to the resist during the alignment work will not occur. When using a light beam for alignment with the same wavelength as that for the circuit pattern,
It is necessary to spatially sufficiently separate the mutual marks or to take measures such as a shielding means for covering the circuit pattern transfer area of the wafer during the alignment work.

Further, the illumination light to the alignment mark when recording the hologram mark has been described as a parallel light flux obtained by expanding the light flux from the light source with the beam expander, but the alignment mark is illuminated with the light condensed by the objective lens. However, it is possible to increase the efficiency of irradiation light.

Next, the alignment means of the present invention will be described with reference to the drawings based on individual embodiments.

First, a first embodiment of the alignment means according to the present invention will be described with reference to FIGS. 4 and 5. In this embodiment, an alignment zone plate 32 formed of a linear zone plate-shaped slit is used as an alignment mark, and a reflective wafer zone plate 52 having the same shape as the alignment zone plate 32 is used as a mask mark. Then, as the inspection light at the time of alignment, a light beam that directly illuminates the mask zone plate 52 is used, and the reflected diffracted light here is used as a diffracted wave. In the present embodiment, this reflected diffracted wave is made incident on the hologram recording medium, and the diffracted light at the hologram mark 42 formed there is detected to perform relative position detection and alignment.

The method of forming a hologram from the alignment mark formed on the mask 3a is the same as the means shown in FIG. In this embodiment, the alignment zone plate 32 is used as the alignment mark, and the configuration of the zone plate is such that the wavelength of the illumination light used (λ
It is designed so that the gap distance becomes the focal length according to ₂ ). Therefore, when the object illumination light is applied to the alignment zone plate 32, the transmitted diffracted light (object wave) from the alignment zone plate 32 becomes a light beam that converges at the focal position.

That is, the object wave from the alignment zone plate 32 becomes a converging cylindrical wave C ₂ which converges on the hologram recording medium 1a, and the linear hologram mark 42 is formed by irradiating it with the reference wave A _4. To be done.

Next, a hologram having a circuit pattern is formed on the hologram recording medium while maintaining the relative positional relationship between the mask and the hologram recording medium. The hologram is fixed and exposed as necessary. Then, the mask 3 and the wafer 5 are exchanged, and the wafer 5 is held in a state of being substantially aligned with the position where the mask 3 was arranged.
Place by. This rough alignment is not always necessary, but considering the improvement of throughput, it is desirable to perform it in the same manner as the conventional method.

The holding means 6 has a structure capable of being electrically driven, and moves the mounted wafer 5a or the like in the horizontal direction (xy direction) and the vertical direction (z direction) for each holding position. The moving direction and the moving amount are adjusted by the control means (not shown). In this embodiment, the relative positional relationship is adjusted by changing the supporting position of the wafer 5a with the hologram recording medium 1a fixed.
The method is not limited to this method as long as the relative positional relationship between the wafer and the hologram (gap, xy direction, etc.) can be adjusted.

The wafer 5a has already been subjected to patterning once or more, and as shown in FIG. 5, the wafer 5a has the wafer zone plate 52 described above as a wafer mark.
Is formed, and its configuration and arrangement are the same as those of the alignment zone plate 32 in the mask, except that it is of a reflective type. Then, during the alignment operation, the wafer zone plate 52 is irradiated with the wafer mark illumination light D ₂ having the same wavelength as the object illumination light (reference light) at the time of hologram formation.

The wafer mark illumination light D ₂ is emitted perpendicularly to the wafer surface, but since the reflection type is used as the wafer mark, it is also emitted perpendicularly to the hologram recording medium 1a, and the hologram mark The light flux that has passed through the light source is used. The wafer mark illumination light D ₂ is vertically incident from one short side of the prism 2a,
The one with total reflection at the long side of is used. In this embodiment, the light source for illuminating the wafer mark is different from the light source for forming the hologram mark, but the same light source may be used.

When the wafer mark illumination light D ₂ is applied to the wafer zone plate 52, the reflected diffracted wave from the wafer zone plate 52 becomes a convergent cylindrical wave E ₂ and converges on the focal position of the wafer zone plate 52. As described above, since the wafer zone plate 52 has the same configuration as the alignment zone plate 32, when the wafer 5a is at the same position as the mask 3a, the converging cylindrical wave E _{2 as the} detection light is on the hologram recording medium 1a. And the hologram mark 42 is irradiated.

Here, from the characteristics of the holographic technique, when the hologram is irradiated with the same light flux as the object wave at the time of hologram formation, a diffracted wave traveling in a path opposite to the reproduction wave for the hologram is obtained. That is, in the case of irradiating a hologram with a reproduction wave, a reproduction wave traveling in a path opposite to the object wave is obtained, and a light flux in a path opposite to that in the case where a hologram reproduction image is formed by this is used in this embodiment. We are using.

Therefore, utilizing this characteristic, the converging cylindrical wave E
_The transmission diffracted light F ₂ obtained when the hologram mark 42 is irradiated by ₂ is detected at a position opposite to the incident path of the reproduction wave (or at a position where the reflected light of the reference light travels during hologram formation), which is not shown. It is possible to detect whether or not the wafer and the hologram are accurately aligned by the detection by the instrument.

Therefore, the detection intensity in the detection means changes depending on whether or not the hologram mark 42 is present at the convergence position of the converging cylindrical wave E ₂ , and the detection intensity becomes maximum in the state of being accurately aligned. The holding means 6a is controlled and operated based on the information to perform the alignment.

Since the transmitted diffracted light F ₂ in this embodiment travels in a direction completely different from the wafer mark illumination light D ₂ and the simple reflected light on the wafer surface thereof, etc. A good detection signal with less noise can be obtained without being affected.

Also in the present embodiment, it is preferable that the alignment be roughly performed when the wafer 5a is mounted.
In order to detect the rotation in the y direction and in the plane thereof, it is preferable to individually provide alignment marks having longitudinal directions in both the xy directions as shown in FIG.

Further, in this embodiment, the reflection type wafer zone plate 52 is used as the wafer mark. However, when the transmission material is used as the material of the wafer, or the wafer mark including the transmission slit is used. It is also possible to do so. In this case, by irradiating the wafer mark with the same light flux as the object illumination light at the time of forming the hologram as the wafer mark illumination light, the transmitted diffracted light from the wafer mark may be used as the detection light as in the above-described embodiment. It is also possible to use the wafer mark illumination optical system also as the object illumination optical system at the time of hologram formation.

Next, the formation of hologram marks for alignment in the second embodiment of the alignment means according to the present invention will be described with reference to FIG. In this example,
Alignment zone plate 33 formed of concentric zone plate-shaped transparent regions as alignment marks
And a reflective wafer zone plate 53 having the same shape as the alignment zone plate 33 as a mask mark.
To use.

Also in this embodiment, the method of forming a hologram from the alignment mark formed on the mask 3b is almost the same as that of the above embodiment. Here, although the alignment zone plate 33 is used as the alignment mark in this embodiment, the shape of the zone plate is such that the focal length depending on the wavelength of the illumination light used is longer than the gap interval, that is, the alignment zone plate 33 diffracts light. The converged spherical wave C ₃ thus formed does not converge on the hologram recording medium 1b but converges at a position where it passes through the hologram recording medium.

Therefore, the alignment zone plate 3
When the object illuminating light B ₆ is irradiated to the object ₃ , a converging spherical wave C ₃ is obtained as an object wave, and the hologram recording medium is irradiated while the converging spherical wave C ₃ is converging and the reference wave is applied to the same position from the back surface side. A ₆ is irradiated, and the hologram mark 43 is formed by these interferences. Then, in this state, a hologram based on the circuit pattern of the mask 3b is formed, then the mask 3b is removed, and the wafer 5b is mounted on the holding device 6b.

Next, a third embodiment of the alignment method using the alignment mark 43 will be described with reference to FIG. In this embodiment, the wafer zone plate 53 as a wafer mark also has the same structure as the above embodiment.
As shown in the figure, the wafer illumination light D ₄ composed of a parallel light flux having the same wavelength as the object wave and the reference wave at the time of hologram formation is totally reflected by the long side portion of the prism 2c, and the hologram recording medium 1
Irradiation is perpendicular to b, the hologram mark 43 is transmitted, and the wafer zone plate 53 is irradiated vertically. The wafer illumination light D ₄ is reflected and diffracted by the wafer zone plate 53 to become a convergent wave E ₄ , and enters the hologram recording medium 1b again.

If the convergent position of the convergent wave E ₄ coincides with the convergent position of the convergent spherical wave C ₃ which is the object wave at the time of hologram formation, that is, if the wafer 5b is in the accurately aligned state, The convergent wave E ₄ is generated by the wafer zone plate 53.
The transmitted diffracted light F ₄ is diffracted by and propagates in the same direction as the traveling direction of the reference wave A ₆ at the time of hologram formation (opposite direction to the hologram reproduction wave).

By providing a detector (not shown) in the traveling direction of the reference wave A ₆ , the transmitted diffracted light F ₄ is detected, and when the detected intensity is maximum, the wafer 5b is accurately aligned. In this state, the detection intensity becomes weak both when the gaps in the xy directions are incorrect and when the gap is incorrect. Therefore, the alignment is performed by moving the wafer 5b by the holding means 6c so that the detection intensity of the transmitted diffracted light F ₄ is maximized.

Next, another embodiment of the alignment method using the same alignment mark 43 as the third embodiment will be described with reference to FIG. In the fourth embodiment, the diffraction light from the wafer mark is used by using the wafer mark illumination light as in the above embodiments, and the wafer zone plate 53 as the wafer mark also has the same configuration as in the above embodiments. . The difference between this embodiment and the above embodiment is that the convergent wave E
_The point is that not the diffracted light when the hologram mark 43 by ₄ is irradiated, but the simple transmitted light is used as the detection light.
The detection light composed of this simple transmitted light is referred to as transmitted convergent light E ₆ .

As described above, due to the characteristics of the holographic technology, when the convergent position of the transmitted convergent light E ₆ coincides with the convergent position of the object wave during hologram formation, the wafer 5b becomes a hologram (recording medium). Since the position is accurately aligned, the relative position relationship between the wafer and the hologram can be detected by detecting the convergence position of the transmitted convergent light E ₆ . To detect the convergent position of the transmitted convergent light E ₆ , for example, a lens system having one focus is provided at the proper convergent position in the detecting means, and a photoelectric detector or the like is provided at the other focus position of this lens system, and this detection is performed. This is possible by detecting the detection state in the container.

By the way, in the present embodiment, the characteristics of the holography technique are further applied, and another light flux that converges on the convergence position of the previous object wave is used as the reference light, and this reference light and the transmitted convergent light E ₆ are combined. By detecting the deviation (consistency), the convergence state of the transmitted convergent light E ₆ is detected. That is, in this embodiment, the hologram mark 4 is used during alignment.
The same hologram illuminating light D ₆ as the reference wave at the time of hologram formation is applied to 3 and the reflected diffracted light from the hologram mark 43 is used as the reference light.

This is one of the characteristics of holography technology.
When a hologram once formed is irradiated with the same light flux as the reference wave at the time of hologram formation, diffracted light passing through the same path as the object wave at the time of hologram formation passes through the hologram (recording medium) and travels. It is an application of what can be obtained.

Utilizing this characteristic, the reflected diffraction light G ₁ from the hologram mark 43 of the hologram illumination light D ₆ is
Since the same path as (the transmitted light of) the object wave at the time of hologram formation is passed, when the reflected diffracted light G ₁ and the previously transmitted convergent light E ₆ match, the wafer is accurately aligned. It is possible to detect that there is. Therefore, the alignment is completed by detecting the reflected diffracted light G ₁ and the transmitted convergent light E ₆ by a detection means (not shown) and controlling the driving of the holding means 6 so that they coincide with each other.

It is needless to say that a transmissive wafer mark can be used in these embodiments as in the above-mentioned embodiments. Further, by providing a plurality of sets of alignment marks and the like as shown in FIG. 3, accurate relative position detection and alignment can be performed. In each of the above embodiments, the relative position is detected by providing the marks at the corners.

The alignment method using the reference light described at the end can also be applied to the other embodiments described above. For example, when the hologram mark is irradiated with the hologram illumination light D ₆ , simple reflected light G ₂ is generated in addition to the reflected diffracted light G ₁ , but the simple reflected light G ₂ is the same as the reference wave at the time of hologram formation (reproduction). It becomes the reference light that travels in the path opposite to the wave). Therefore, the relative position of the wafer and the hologram can be detected by comparing and detecting the reference light (simple reflected light G ₂ ) as the reference light of the previous embodiment.

Although the detecting means is omitted in the above embodiments, the invention can be applied to the invention as long as at least the intensity of the detection light can be detected. However, in the case of detecting a minute positional deviation or the like, a minute positional deviation can be detected by combining the light source means for the detection light with the line scanning means, the minute deflection angle vibration scanning means or the like.

Further, the detecting means may employ not only the intensity but also the wavefront of the detection light or the like to detect the relative positional deviation. For example, as in the embodiment shown in FIG. 7, a detector that detects when the detection light (diffracted light F ₄ ) becomes parallel light (aligned state) can detect the deviation of the detection light from parallel light. Anything will do.

As the detection method, a spot width measuring method, an astigmatism method, an oblique incidence method, a knife edge method, a Foucault method, a critical angle method or the like ("Recent roughness measuring method by optical contact" O plus E April 1985 issue, p71), spot width measurement method, oblique incidence method [X-ray lithography] are known. In the present invention, any of these may be used,
It is not limited to these as long as the wavefront of the detection light can be detected.

An embodiment of these detecting means will be described with reference to FIGS. This embodiment of the detection system is used as the detection system of the embodiment shown in FIG. 7, and can be applied to the case of detecting whether or not the light flux to be detected is parallel light. In this embodiment, the traveling state of the transmitted diffracted light F ₄ is detected, and each member is arranged with reference to the traveling direction (optical axis) of the reference wave during hologram formation.

Here, in the state where the gap is displaced, that is, in the defocused state, the transmitted diffracted light F ₄ becomes divergent light or convergent light. On the other hand, when the gap is accurate and lateral deviation (positional deviation in the XY directions) occurs, the transmitted diffracted light F ₄ is parallel light, but the traveling direction changes. Changes in these wavefronts are detected by applying the astigmatism method. The astigmatism method is usually used for autofocus, and if the principle is applied as it is, gap detection can be performed.

In this embodiment, the transmitted diffracted light F ₄ is incident on the four-division detector 917 arranged at the focal position of the optical system including the cylindrical lens 913. Here, the four-division detector 917 is, as shown in FIG.
It is divided into light receiving portions K _{1 to} K ₄ corresponding to the XY directions. In this embodiment, when the relative positional relationship between the wafer and the hologram is accurate, the transmitted diffracted light F ₄ becomes parallel light, so that it becomes a light beam condensed at the central portion of the four-division detector 917, and each light receiving portion K. The detection intensities from _{1 to} K ₄ are equal.

On the other hand, as shown in FIG. 11, when the gap position is deviated, the light is deformed into an elliptical shape and is condensed, and the detection intensities of the adjacent light receiving portions are different.
Furthermore, if there is a displacement in the X-Y direction,
The condensing point is deviated from the center, and the detection intensity from each light receiving unit is different.

As described above, since the change of the light collecting condition corresponding to the gap and the positional deviation in the XY directions appears as shown in FIG. 11, the corresponding change state of the detection intensity in each light receiving portion is shown. By detecting, the relative positional deviation between the wafer and the hologram can be detected.

Specifically, by utilizing the fact that the light beam incident on the four-division detector 917 becomes circular when the gap is correct, the outputs from the four light receiving parts K _{1 to} K ₄ are calculated based on the following equations. Calculate the number S.

S = ((K ₁ + K ₃ )-(K ₂ + K ₄ ))
/ (K ₁ + K ₂ + K ₃ + K ₄ ) When this numerical value S is S = 0, the correct gap is obtained.

On the other hand, when the displacement in the X-Y directions occurs, the detected wavefront curvature does not change but changes in the traveling direction. Therefore, the position of the spot on the four-division detector 917 may move in the lateral displacement direction. Becomes In this case,
T _X and T _{Y, which} are expressed by the following equations, are signals representing lateral deviations in the X and Y directions in the figure, respectively. When lateral deviation does not occur, T _X and T _Y generate signals respectively. Not (T _X
= T _Y = 0).

T _X = ((K ₂ + K ₃ )-(K ₁ + K
_{4)) / (K 1 =} + K 2 + K 3 + K 4) T Y ((K 3 + K 4) - (K 1 + K 2)) / (K 1 +
K ₂ + K ₃ + K ₄ )

As described above, in the present embodiment, the optical system to which the astigmatism method is applied is used, and the above-mentioned numerical values are obtained from the output signal from the four-division detector to obtain the relative positional deviation information between the wafer and the hologram. Is detected, and alignment is performed by adjusting the relative positional relationship based on this.

In the above-described embodiment, the gap and the xy-direction alignment are performed at the same time. However, depending on the method of the detecting means, the detection intensity alone may be due to the gap shift or the xy-direction shift. If it is difficult to make the determination, a detection system for gap detection may be provided separately. Furthermore, it is possible to record the detection system for gap detection at a plurality of positions (for example, three points) and simultaneously detect the tilt of the wafer.

Furthermore, pinholes (or concentric zone plates) and slits (or linear zone plates) have been separately described as alignment marks, hologram marks, or wafer marks, but which is selected? The circuit pattern of the mask and the alignment mark may be appropriately selected in consideration of the layout condition for the mask, the layout condition on the wafer, etc. When a plurality of alignment marks are provided, these may be mixed.

The dynamic range of the detection system in the third embodiment is determined by the size of the zone plate. Therefore, if the size of the zone plate is increased, it is possible to detect the displacement even if the relative displacement is large.
It can also be used for rough alignment. And
After that, it is also possible to perform highly accurate alignment by using the detection means or the like of the first or second embodiment, and further, by using the alignment means shown in each embodiment in combination, the relative alignment can be achieved. The dynamic range of position measurement can be expanded and relative position detection can be performed with high accuracy.

On the other hand, focusing on gap detection, it is necessary to suppress the error in the gap detection sensitivity (accuracy) within the depth of focus during hologram exposure of the circuit pattern. Since the present invention and the respective embodiments of the present invention are the same as those for detecting the actual reproduction state of the hologram mark, it can be detected that the reproduction state in the alignment system is proper. Therefore, it is extremely easy to perform the alignment within the depth of focus in the subsequent hologram exposure of the circuit pattern.

Here, considering the accuracy of the gap detection, increasing the convergence angle of the (diffracted) light beam generated from the zone plate used in the present invention and each of the embodiments, in other words, N.M. A. Raising the value improves the detection sensitivity. For this purpose, it is necessary to reduce the line width of the zone plate, but it is often difficult to miniaturize the fine pinhole holes and the zone plate because there is a limit.

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 if it is a method of detecting in the wavefront state. However, since the first-order light and the third-order light (or fifth-order light or seventh-order light) cannot be distinguished only by the wavefront, only the diffracted light of the necessary order can be detected by roughly aligning these diffraction focusing positions. By keeping the gap interval closer to the position, more precise gap alignment can be performed.

[0142]

As described above, according to the exposure method or apparatus using holography according to the present invention, the holography technique is applied to the alignment means, and therefore, the observation optics for position detection as in the prior art. It has the advantage of not requiring a system. Furthermore, because the wafer mark illumination light and the diffracted wave from it are used as the inspection inspection light flux for alignment, and the transmitted light and diffracted light by the hologram are detected, noise light due to multiple reflections in the gap interval is reduced, for example. Therefore, the detection accuracy of the relative positional relationship is improved.

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.

Therefore, the focus position at the time of exposing the mask pattern can be accurately detected, so that the exposure transfer can be performed more accurately. Furthermore, because the alignment between the wafer and the hologram can be performed accurately and easily,
In particular, there is an advantage that overlay exposure can be performed in an accurately aligned state for an exposure target that requires overlay exposure. Therefore, according to the present invention, there is an advantage that the throughput in the exposure operation is improved and the yield of finished products is improved.

When the hologram mark formed on the hologram recording medium is used for detection as described in the embodiment, even if the hologram is deformed, the hologram mark (holographic zone plate) itself is also a pattern part. Since it is deformed in the same manner as (hologram of), it becomes possible to perform alignment with the optimum image forming position corresponding to the deformation of the hologram, and it is not necessary to use complicated correction means as in the past, and exposure transfer accuracy of patterns etc. There is an advantage to improve.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of an embodiment of an exposure apparatus using holography according to the present invention.

FIG. 2 is an explanatory diagram showing a circuit pattern of a mask and an arrangement configuration of alignment marks in the first embodiment.

FIG. 3 is an explanatory diagram showing a circuit pattern of a mask and an arrangement configuration of alignment marks according to another embodiment.

FIG. 4 is an explanatory diagram showing an arrangement configuration at the time of producing a hologram in the alignment means used in the hologram exposure method according to the first embodiment of the present invention.

FIG. 5 is an explanatory diagram showing an arrangement configuration and the like at the time of relative position detection in the alignment means of the first embodiment of the present invention.

FIG. 6 is an explanatory diagram showing an arrangement configuration at the time of producing a hologram in the alignment means used in the hologram exposure method according to the second embodiment of the present invention.

FIG. 7 is an explanatory diagram showing an arrangement configuration and the like at the time of relative position detection in the alignment means of the third exemplary embodiment of the present invention.

FIG. 8 is an explanatory diagram showing another example of the arrangement and the like at the time of relative position detection in the alignment means of the fourth exemplary embodiment of the present invention.

FIG. 9 is an explanatory diagram showing an example of the arrangement and the like of relative position detection means in the alignment means of the third embodiment.

10 is an explanatory diagram showing a schematic configuration of a four-divided detector in FIG.

FIG. 11 is an explanatory diagram showing a relationship between a light beam incident on the four-division detector in FIG. 9 and a positional deviation state.

FIG. 12 is an explanatory diagram showing an example of a conventional alignment means.

[Explanation of symbols]

1a, 1b, 101; hologram recording medium, 2a, 2b, 2c, 102; prism, 3a, 3b, 103; mask, 5a, 5b; wafer, 6a, 6b, 6c, 6d, 106; holding mechanism, 32, 33 Alignment marks, 42, 43; hologram marks, 52, 53; wafer marks, A, A ₄ , A ₆ ; alignment mark hologram reference light, B, B ₄ , B ₆ ; alignment mark hologram object illumination light , C, C ₂ , C ₃ ; transmitted diffracted light (object wave) from the alignment mark, D: hologram reproduction wave for hologram mark, D ₂ , D ₄ , D ₅ ; wafer mark illumination light, D ₆ ; hologram illumination Light, E ₂ , E ₄ , E ₅ ; Reflected and diffracted light from wafer mark, F ₁ , F ₂ , F ₃ , F ₄ , F ₅ ; Detection light, A ₂ ; Pattern hologram reference light , B ₂ ; holographic object illumination light for pattern, G ₁ , G ₂ ; reference light for alignment, 110; beam splitter (half mirror), 111 a, 111 b; beam expander, 112 a, 112 b; dichroic mirror,

 ─────────────────────────────────────────────────── ─── 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 (7)

[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 a predetermined shape formed on the mask The step of storing the hologram mark for alignment in the hologram recording medium as the object wave using the diffracted light from the alignment mark as an object wave, and before the reproduction of the mask pattern image, the illumination light having the same wavelength as the object wave is applied to the wafer surface. The hologram mark is irradiated with the diffracted light obtained by irradiating the wafer mark provided on the Along with this, the step of detecting the transmitted detection light from the hologram mark by this, the relative positional deviation information between the hologram recording medium and the wafer is detected based on the detection result, and these relative positions are detected based on this positional deviation information. An exposure method using holography, comprising: a step of correcting the relationship. 2. The alignment mark has a zone plate shape, and the wafer mark is configured to generate the same diffracted wave as the object wave from the alignment mark at the time of forming the hologram mark. An exposure method using the described holography. 3. A step of detecting a reference detection light obtained by irradiating the hologram mark with the same reference inspection light as the reference wave at the time of forming the hologram, and the relative between the hologram recording medium and the wafer based on the detection result. An exposure method using holography according to claim 1 or 2, further comprising: a step of detecting positional deviation information. 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 a mask pattern on the wafer, wherein a coherent light source for generating a coherent light beam, and a coherent light source from the light source. Object wave irradiation for guiding the light flux to the position where the alignment mark of the mask is formed, and irradiating the diffracted diffracted light generated thereby from the alignment mark into the hologram recording medium as an object wave for forming the hologram mark. An optical system and a coherent light beam from the light source are used to form a hologram mark. A reference wave irradiation optical system that irradiates the hologram recording medium into the hologram recording medium so as to cause interference with the object wave in the hologram recording medium, and a wafer mark formed on the wafer surface to the object. A wafer mark illumination optical system that guides the wafer mark illumination light having the same wavelength as the wave and guides the diffracted light at the wafer mark generated thereby to the hologram recording medium on which the alignment mark is formed; and a wafer mark illumination optical system formed on the hologram recording medium. Relative positional deviation information between the hologram recording medium and the wafer based on a detection result of the transmitted light detecting unit that detects diffracted light at the wafer mark that has passed through the hologram mark as transmitted detection light. An exposure apparatus using holography, comprising: a relative position detecting means for detecting 5. The alignment mark has a zone plate shape, and the wafer mark has a zone plate shape in which the same diffracted wave as the object wave from the alignment mark is generated. Exposure equipment using holography. 6. A reference reflected light detection unit that guides the same reference inspection light as the reference wave to the hologram mark and detects the reflected light at the hologram mark, wherein the relative position detection unit includes the reference reflection light. The holographic exposure apparatus according to claim 4 or 5, wherein relative position shift information between the hologram recording medium and the wafer is detected by using a detection result of a light detection unit. 7. A correction means for correcting the relative positional relationship between the hologram recording medium and the wafer based on the detection result of the relative position detection means. An exposure apparatus using the holography described in 1.