JP2002083760A - X-ray projection aligner, x-ray projection exposure method, and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray projection aligner which can compensate for the magnification of projection and enables a desired fine pattern to be laid, with high accuracy on the circuit pattern on a wafer, prior to exposure. SOLUTION: An X-ray projection aligner, which consists of at least an X-ray source, an X-ray illumination optical system for applying X-rays generated from the X-ray source onto the mask having a prescribed pattern, a mirror for constituting an X-ray projection optical system for projecting the image of the pattern, receiving the X-rays from that mask onto the wafer where resist is applied and forming an image thereon; a lens barrel for holding the mirror; a wager stage for holding that wafer, a mask stage for holding that mask; a surface position detecting mechanism for detecting the surface positions of the wafer and mask; and a mark position detecting mechanism for detecting the positions of the marks made in those wafer and mask, and which possesses the function of correcting magnification of projection, and changing the positions of the mask and the wafer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit pattern on a photomask (mask or reticle) formed by a mirror projection system such as an X-ray optical system on a substrate such as a wafer via a reflective imaging optical system. The present invention relates to an X-ray projection exposure apparatus which is an apparatus suitable for transfer, an exposure method using the X-ray projection exposure apparatus, and a semiconductor device produced by the X-ray projection exposure apparatus.

[0002]

2. Description of the Related Art In a conventional exposure apparatus for manufacturing a semiconductor, a circuit pattern formed on a photomask (hereinafter, referred to as a mask) as an object plane is projected onto a substrate such as a wafer via an image forming apparatus. It is to be transcribed.

The exposure apparatus includes, for example, an exposure apparatus using an i-line of a high-pressure mercury lamp as an exposure light source. The exposure apparatus includes a light source, an illumination optical system, a projection optical system, and a stage for holding a mask. , A stage for holding a wafer, a surface position detecting mechanism, and a mark position detecting mechanism.

The surface position detecting mechanism irradiates a light beam obliquely onto a wafer, for example, and detects the reflected light beam with a photodetector. With this mechanism, the surface position of the wafer (the position of the projection optical system in the optical axis direction) can be known. The mark position detecting mechanism detects the positions of marks formed on the wafer and the mask by optical means.

[0005] The mask is formed with a pattern of the same size or an enlarged size as the pattern to be drawn on the wafer. The projection optical system is usually composed of a plurality of lenses and the like, and is configured so that the pattern on the mask can be imaged on the wafer and transferred collectively, and has a visual field of about 20 mm square. (For example, an area for two semiconductor chips) can be exposed collectively.

In recent years, the integration and performance of semiconductor exposure circuits have been further advanced, and it has become necessary to further improve the resolution. Generally, the resolving power W of an exposure apparatus is mainly determined by the exposure wavelength λ and the numerical aperture NA of the imaging optical system, and is expressed by the following equation. W = k ₁ λ / NA k ₁ : Constant Therefore, in order to improve the resolving power, it is necessary to shorten the wavelength or increase the numerical aperture. At present, as described above, an i-line having a wavelength of 365 nm is mainly used as an exposure light source of an exposure apparatus used for manufacturing a semiconductor, and a resolution of 0.5 μm is obtained at a numerical aperture of about 0.5. I have. Since it is difficult to increase the numerical aperture in terms of optical design, it is necessary to shorten the wavelength of exposure light in the future.

Therefore, in recent years, for example, an excimer laser has been used as exposure light having a wavelength shorter than the i-line. The wavelength is, for example, 248 nm for KrF and 193 nm for ArF.
Therefore, 0.25 μm for KrF and 0.25 μm for ArF.
A resolution of 18 μm is obtained.

Then, X having a shorter wavelength is used as the exposure light.
If a line is used, for example, if the wavelength is 13 nm, 0.1 μm
m or less. In the case of such an X-ray projection exposure apparatus using X-rays, it is difficult to design an optical system having a wide field of view since the projection image forming optical system must be constituted entirely by reflecting mirrors. On the other hand, if the exposure field of view of the projection optical system is formed in a ring shape, high resolution can be obtained within the elongated exposure field.

Further, at the time of exposure, by scanning the mask and the wafer, a semiconductor chip having a size of 20 mm square or more can be exposed by an imaging optical system having a small visual field. According to the X-ray projection exposure apparatus using such a method, a desired exposure area can be exposed. FIG. 7 shows a conceptual diagram of a part of the currently considered X-ray projection exposure apparatus. The device is mainly X
X-ray source 61, X-ray illumination optical system 62, X-ray projection optical system 5
1. The stage 53 of the mask 52, the stage 55 of the wafer 54, and the wafer surface position detecting mechanisms 57a and 57 for detecting the surface position of the wafer (the position in the optical axis direction of the X-ray projection optical system).
b, a mask surface position detecting mechanism (not shown) for detecting the surface position of the mask (the position in the optical axis direction of the X-ray projection optical system), and a wafer mark position detecting mechanism 60 for detecting the position of a mark formed on the wafer surface Mark position detecting mechanism (not shown) for detecting the position of a mark formed on the mask surface
It consists of.

The X-ray projection optical system 51 is composed of a plurality of reflecting mirrors and the like, and forms a pattern on a mask 52 on a wafer 54. The mask 52 is of a reflective type, and a circuit pattern is formed on its reflective surface. A multilayer film is provided on the surface of each reflector to increase the X-ray reflectivity. The X-ray projection optical system has an annular field of view, and transfers the pattern of a part of the annular area of the mask 52 onto the surface of the wafer 54.

As exposure X-rays, soft X-rays of about 13 nm, which provide high reflectivity with a multilayer film, are used, and such soft X-rays have a large absorption by air. Therefore, at least the mask, the wafer, and the X-ray projection optical system are arranged in a vacuum chamber 56 so that the optical path of the X-ray is kept in a vacuum, and the inside of the chamber is evacuated by a vacuum pump.

The projection exposure apparatus can obtain a high resolution near the image plane position of the projection optical system. Therefore, the wafer
It is necessary to arrange the surface position to be exposed near the image plane position of the projection optical system. The range (length in the optical axis direction) in which the projection optical system exhibits high resolution is referred to as the depth of focus. DOF
F is mainly determined by the exposure wavelength λ and the numerical aperture NA of the imaging optical system, and is expressed by the following equation.

DOF = k ₂ λ / NA ² k ₂ : constant For example, if the numerical aperture is 0.5 at a wavelength of 365 nm and the constant is 1, the DOF is 1.5 μm, the numerical aperture is 0.1 at a wavelength of 13 nm, and the constant is 0.1. Is 1, the DOF is 1.3 μm. Further, when the numerical aperture is 0.25 and the constant is 1 at a wavelength of 13 nm, the DOF is 0.2 μm. Therefore, X
A line projection exposure apparatus uses a surface position detection mechanism with higher accuracy than a conventional exposure apparatus using i-line. As the surface position detecting mechanism, an optical detecting means or an electric detecting means is used.

Further, since a semiconductor device has a circuit formed over a plurality of layers, even when a semiconductor device is formed by an X-ray projection exposure apparatus, high-precision overlay exposure is performed on a circuit already formed on a wafer. Perform For this purpose, a mechanism for precisely detecting at least the positions of the mask and the wafer during exposure is required. This mechanism uses a mark position detection mechanism that detects a mark formed on a wafer and a mask by optical means.

In a conventional projection exposure apparatus, an optical detecting means has been used as a surface position detecting mechanism, a wafer mark position detecting mechanism, and a mask mark position detecting mechanism.

[0016]

When a semiconductor device is manufactured, processes such as application and etching of a resist apply a thermal load to the wafer, so that the wafer is deformed by irreversible thermal expansion and contraction. Therefore, the circuit pattern on the wafer is not always a pattern having the same dimension as the design value, and may be a slightly enlarged or reduced pattern.

Therefore, the exposure apparatus needs a function of correcting the projection magnification so that the overlay exposure can be performed with high accuracy even on such a wafer. In a conventional exposure apparatus using i-line, as a method of correcting the projection magnification, the refractive index is changed by changing the pressure of a gas (air, nitrogen gas, or the like) in a space through which light beams of the projection optical system pass. The method is adopted.

However, in an X-ray projection exposure apparatus using soft X-rays, it is necessary to maintain the optical path of the X-rays in a vacuum in order to prevent absorption of the soft X-rays by air, and a conventional gas pressure change Cannot perform magnification correction using. After all, at present, there has been a problem that the projection magnification cannot be corrected by the X-ray projection exposure apparatus, and it is difficult to perform high-accuracy overlay exposure.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has an X-ray projection system capable of correcting a projection magnification and exposing a desired fine pattern to a circuit pattern on a wafer with high accuracy. An object of the present invention is to provide an exposure apparatus.

[0020]

Therefore, the present invention firstly provides an "X-ray illumination optical system for irradiating at least an X-ray source and an X-ray generated from the X-ray source onto a mask having a predetermined pattern. A mirror that constitutes an X-ray projection optical system that receives an X-ray from the mask and projects and forms an image of the pattern on a resist-coated wafer; a lens barrel that holds the mirror; A wafer stage for holding, a mask stage for holding the mask, a surface position detecting mechanism for detecting surface positions of the wafer and the mask, and a mark position detecting mechanism for detecting positions of marks formed on the wafer and the mask; An X-ray projection exposure apparatus comprising the function of correcting the projection magnification by changing the positions of the mask and the wafer.
(Claim 1) "is provided.

Further, the present invention secondly provides "X-ray according to claim 1, characterized in that it has a function of correcting the detection range of said surface position detection mechanism according to the positional change amount of said mask and wafer. And a projection exposure apparatus. 3. The X-ray projection apparatus according to claim 1, further comprising a function of correcting a detection range of the mark position detection mechanism in accordance with a position change amount of the mask and the wafer. Exposure apparatus (Claim 3) "
I will provide a.

Further, the present invention fourthly has a function of correcting an irradiation position of the X-ray illuminating optical system on the mask surface in accordance with the position change amount of the mask. 3. The X-ray projection exposure apparatus according to any one of (3) to (4).

The fifth aspect of the present invention is that the surface position detecting mechanism is an optical detecting means, and the detection range is corrected by adjusting the position of the whole or a part of the surface position detecting mechanism. An X-ray projection exposure apparatus according to any one of claims 2 to 4, characterized in that (claim 5).

Also, the present invention provides a sixth aspect in which "the surface position detection mechanism is an optical detection means, and the correction of the detection range is performed by adjusting the position or angle of at least one optical element constituting the surface position detection mechanism. The X-ray projection exposure apparatus according to any one of claims 2 to 4, characterized by:

The present invention seventhly provides an "X-ray projection exposure apparatus according to claim 6, wherein the adjustment of the angle of the optical element is an adjustment of the angle of the harbing." I will provide a. Eighth, the present invention provides an "X-ray projection exposure apparatus according to claim 6, wherein the adjustment of the position of the optical element is an adjustment of the position of a slit." .

Further, the present invention ninthly states that the surface position detecting mechanism is an electric detecting means, and the detection range is corrected by adjusting the position of a detector constituting the surface position detecting mechanism. An X-ray projection exposure apparatus according to any one of claims 2 to 4, characterized in that the present invention provides (9).

The tenth aspect of the present invention is that the mark position detecting mechanism is an optical detecting means, and the detection range is corrected by adjusting a position or an angle of an optical system constituting the mark position detecting mechanism. An X-ray projection exposure apparatus according to any one of claims 3 to 9, wherein the X-ray projection exposure apparatus (10) is provided.

Also, the present invention provides an eleventh aspect in which "the mark position detection mechanism is an optical detection means, and the correction of the detection range is performed by at least one of the mark position detection mechanisms.
10. The X according to claim 3, wherein the position or the angle of the two optical elements is adjusted.
Line projection exposure equipment. (Claim 11) is provided.

The present invention twelfthly states that "the function of correcting the irradiation position of the X-ray illumination optical system is achieved by adjusting the position or angle of at least one optical element constituting the X-ray illumination optical system. 4. The method according to claim 4, wherein
2. The X-ray projection exposure apparatus according to claim 1. (Claim 1
2) ”.

In the thirteenth aspect of the present invention, the X-ray projection exposure apparatus according to the twelfth aspect, wherein the optical element is a plane mirror disposed closest to the mask. "I will provide a. In the fourteenth aspect of the present invention, in the exposure method using the X-ray projection exposure apparatus according to any one of claims 1 to 13, the projection magnification is corrected by changing a position of the mask and the wafer, Correcting the detection range of the surface position detection mechanism based on the amount of change in the position, or correcting the detection range of the mark position detection mechanism, or correcting the irradiation position of the X-ray illumination optical system, Based on the position of the mark detected by the detection mechanism and the value of the surface position of the wafer and the mask detected by the surface position detection mechanism, the mask stage and the wafer stage are driven to move the mask to a desired position on the wafer. An X-ray projection exposure method characterized by forming a projected image of the formed circuit pattern.

Further, in the present invention, it is preferable that the correction of the projection magnification is performed based on a value of the projection magnification calculated from an interval between a plurality of marks detected by the mark position detection mechanism. 15. The X-ray projection exposure method according to 14.
(Claim 15) "is provided.

The present invention is directed to a sixteenth aspect of the present invention.
A semiconductor device manufactured by performing exposure using the X-ray projection exposure apparatus according to any one of claims 3 to 13 by the exposure method according to claim 14 or 15. (Claim 1
6) ”.

[0033]

FIG. 1 is a schematic view of an X-ray projection exposure apparatus according to the present invention. This device mainly consists of an X-ray source (not shown)
And an X-ray illumination optical system (not shown), an X-ray projection optical system 1, a stage 3 for holding a mask 2, a stage 5 for holding a wafer 4, a vacuum chamber 6, and a wafer surface position detecting mechanism 7.
a, 7b and a mask surface position detecting mechanism 8a, 8b.

The mask 2 is formed with a pattern of the same size or an enlarged size as a pattern to be drawn on the wafer 4, and the pattern is imaged on the surface of the wafer 4 via the X-ray projection optical system 1. ing. The X-ray projection optical system 1 has a ring-shaped or similar visual field, and transfers a pattern of a partial area of the mask 2 onto the surface of the wafer 4. At the time of exposure, a desired area can be exposed by synchronously scanning the mask and the wafer at a constant speed.

Wafer stage 3 and mask stage 5
Is an adjusting mechanism 3a driven in the optical axis direction of the X-ray projection optical system,
5a, and the projection magnification can be corrected by driving this adjustment mechanism. Such an adjustment mechanism preferably operates in a vacuum, and preferably includes a vacuum actuator for that purpose. For example, a vacuum stepping motor or a piezoelectric element may be used as the vacuum actuator.

The magnification of the X-ray projection optical system is determined by the width of the annular zone on the mask and on the wafer. In the case of an X-ray projection exposure apparatus, as shown in FIG. 2, the X-ray projection optical system uses a non-telecentric optical system on the mask side and moves the mask in the optical axis direction of the X-ray projection optical system to increase the magnification. Can be corrected.

Although the amount of magnification to be corrected is determined by the amount of deformation of the wafer, it has been confirmed by experiments that the amount is approximately ^10.sup.-4 . The magnification correction amount ΔM includes the X-ray incident angle θ on the mask, the orbicular zone radius R on the mask, and the mask movement amount Zm.
ΔM = Zm · tan θ / R. For example, if θ is 2 ° and R is 120 mm, 1
The Zm required for the magnification correction of 0 ^-4 is about 340 μm.

Further, when the position of the mask is changed, the plane of projection by the X-ray projection optical system also moves in the optical axis direction, so that the position of the wafer is also changed. Assuming that the magnification of the projection optical system is M, the movement amount Zw of the wafer is approximately the following value. Zw = M ² · Zm For example, if the magnification of the optical system is 1/4, when the mask is moved 340 μm for magnification correction, the movement amount of the wafer is about 21 μm.

As described above, the projection magnification can be corrected by changing the positions of the mask and the wafer.
When the detection range of the surface position detection mechanism that detects the surface position of the mask and wafer or the mark position detection mechanism that detects the mark position is narrow, and the position of the mask and wafer moves out of the detection range with magnification correction May be provided with a function of correcting the detection range as described below.

The surface position detecting mechanism optically or electrically detects the surface position of the wafer and the mask (the position in the optical axis direction of the X-ray projection optical system). Optical detection methods include a method of obliquely irradiating the wafer and mask surface with light and measuring the position of the reflected light, and a method of vertically irradiating a laser or the like to perform interference measurement. Has described a mechanism for obliquely incident a light beam on the wafer surface among the mechanisms for optically detecting as an example of a wafer surface position detection mechanism.

The surface position detecting mechanism has an irradiating section 7a for irradiating the wafer 4 with the light beam 12a and a detecting section 7b for detecting the reflected light from the wafer. This device irradiates the surface of the wafer obliquely and measures the reflected light with the photodetector of the detection unit to detect the surface position of the wafer.

The irradiating section 7a of the surface position detecting mechanism includes, for example, a light source (not shown) and an illumination optical system (not shown) for irradiating the light emitted from the light source to the slit 13a as shown in FIG. It comprises optical systems 15a and 16a for condensing the luminous flux on the wafer. Also, the detecting unit 7
b includes optical systems 15b and 16b for condensing light reflected from the wafer on the slit 13b, and a photodiode (not shown) for detecting the intensity of light transmitted through the slit.

As the light source, it is preferable to use a white light source containing visible light or infrared light which does not expose the resist. By using this white light source, it is possible to reduce the influence of interference caused by the reflected light on the wafer surface and the resist surface applied thereon, and it is possible to perform highly accurate position detection.

The surface position detection mechanism has a function of changing the detection range in accordance with the position of the wafer surface after movement. This makes it possible to arrange the position of the wafer surface within the detection range. The mechanism for changing the detection range includes, for example, a surface position detection mechanism 7a as shown in FIG.
This is a mechanism for moving the position of 7b by the stages 9a and 9b. By moving these simultaneously in the same direction in the optical axis direction of the X-ray projection optical system, the detection range can be moved. The movement amount may be set to a value substantially equal to the movement amount of the wafer accompanying the magnification correction.

Such a method of changing the detection range is applicable to means other than the optical detection means. For example, when an electrostatic sensor, which is an example of an electric detection unit, is used as the detection mechanism, the sensor may be moved in the same manner. The method of correcting the detection range in the optical detection means is not limited to the above. For example, the detection range may be corrected by adjusting the optical path or the focal position by changing the position or the angle of the optical element constituting the optical system. More specifically, for example, as shown in FIG. 3, parallel flat plates (harvings) 14a and 14b are inserted obliquely with respect to the optical path,
The optical path may be corrected by adjusting the angle. Alternatively, the optical paths may be corrected by moving the slits 13a and 13b in parallel.

It is preferable that such an adjusting mechanism be operated in a vacuum.
a, 17b, 18a, 18b.
For example, a vacuum stepping motor or a piezoelectric element may be used as the vacuum actuator.

A similar mechanism may be provided for the surface position detecting mechanism for detecting the mask surface position. FIG. 4 is a schematic diagram of an X-ray projection exposure apparatus according to the present invention. The apparatus mainly includes an X-ray source (not shown) and an X-ray illumination optical system (not shown), an X-ray projection optical system 1, a stage 3 for holding a mask 2, a stage 5 for holding a wafer 4, and a vacuum chamber 6.
, A wafer surface position detecting mechanism (not shown), a mask surface position detecting mechanism (not shown), a wafer mark position detecting mechanism 20, and a mask mark position detecting mechanism 21.

The wafer mark position detecting mechanism is an apparatus for detecting, for example, the positions of a mark on a wafer and a mark on a wafer stage by optical means or the like. The wafer stage and the mask stage are driven based on the positional information of the mask and the wafer obtained from these two mechanisms to expose a pattern on the mask to a desired position on the wafer.

For example, as shown in FIG. 5, a mechanism such as an optical microscope is used for a wafer mark position detecting mechanism. An enlarged image of the mark is detected by an image detector 26 such as a CCD, and the position of the mark is detected by image processing. In such a case, the wafer mark position detection mechanism includes a light source (not shown) that emits light that does not expose the resist, such as visible light or infrared light.
An illumination optical system (not shown) for irradiating the mark with light emitted from the light source, detection optical systems 27 and 28 for enlarging and projecting the image of the mark onto the detector, and a detector 26 such as a CCD may be used. By obtaining a high-contrast mark image by increasing the numerical aperture of the detection optical system, highly accurate mark position detection can be performed.

The mark position detection mechanism has a function of changing the detection range in accordance with the positions of the wafer and the mask surface after movement. This makes it possible to arrange the position of the mark within the detection range. The mechanism for changing the detection range is, for example, a mechanism for moving the mark position detection mechanism position by the moving stages 22 and 23 as shown in FIG. By moving these in the optical axis direction of the X-ray projection optical system, the detection range can be moved. The movement amount may be set to a value substantially equal to the movement amount of the wafer accompanying the magnification correction.

Such a method of changing the detection range is applicable to means other than the optical detection means. For example, even when an electron beam is used as the detection mechanism, the detection mechanism may be similarly moved. The method of correcting the detection range in the optical detection means is not limited to the above. For example, the detection range may be corrected by adjusting the optical path or the focal position by changing the position or the angle of the optical element constituting the optical system. As a more specific example, when a two-dimensional image of a mark is obtained, the focal position is corrected by changing the position of the imaging lens 28 shown in FIG. 5, or the position of the detector 26 is changed to the image forming surface of the mark image. By changing the position or the like, a high-contrast image of the mark may be formed on the detector.

It is preferable that such an adjusting mechanism be operated in a vacuum.
It is preferable to have 9, 30. For example, a vacuum stepping motor or a piezoelectric element may be used as the vacuum actuator. FIG. 6 is a schematic view of a part of the X-ray projection exposure apparatus according to the present invention.

This apparatus mainly holds an X-ray source (not shown), an X-ray illumination optical system 40, an X-ray projection optical system (not shown), a stage 3 for holding the mask 2, and a wafer (not shown). Stage (not shown), vacuum chamber (not shown), wafer surface position detection mechanism (not shown), mask surface position detection mechanism (not shown), wafer mark position detection mechanism (not shown), and mask mark position detection mechanism (not shown) (Shown).

The X-ray illumination optical system is an optical system for irradiating a desired position on the mask with X-rays in an annular shape. The X-ray illumination optical system includes at least one or more mirrors, reflects X-rays emitted from a light source, and irradiates the X-rays onto a mask. Illumination is performed so that the illuminance and the converging angle (coherency) of the X-rays are uniform within the X-ray irradiation range on the mask. X
X-rays irradiated onto the mask by the line irradiation optical system are obliquely incident on the mask (slightly inclined from the vertical). Therefore, when the position of the mask changes, the position of the X-ray irradiated on the mask also changes.

In the X-ray projection exposure apparatus according to the present invention, the X-ray illumination optical system has a function of moving the irradiation position in accordance with the movement of the mask accompanying the magnification correction. For example, as shown in FIG. 6, when the surface position of the mask is moved from the initial position 42a to the position 42b after the magnification correction, the X-ray beam incident on the mask is changed from the initial light beam 41a to the light beam after the magnification correction. 41b.

The irradiation position is preferably adjusted by adjusting the position and angle of a mirror constituting the X-ray illumination optical system. Further, at this time, it is preferable to adjust the incident angle to the mask, the uniformity of X-ray illuminance, and the uniformity of coherency because the exposure resolution does not change.

For example, the mirror for adjusting the position and angle may be a mirror closest to the mask. Thus, a change in the optical performance of the illumination optical system due to the adjustment can be minimized. Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited to these Examples.

[0058]

Embodiment 1 FIG. 1 shows an X-ray projection exposure apparatus according to a first embodiment of the present invention. This apparatus mainly includes an X-ray source (not shown), an X-ray illumination optical system (not shown), an X-ray projection optical system (barrel) 1, a stage 3 for holding a mask 2, and a stage 5 for holding a wafer 4. , Vacuum chamber 6, wafer surface position detection mechanisms 7a and 7b, mask surface position detection mechanism 8
a, 8b.

The present apparatus uses a laser plasma X-ray source as an X-ray source, and X-rays emitted therefrom are irradiated on a mask 2 via an X-ray illumination optical system. At this time, the exposure wavelength is 13.
The thickness was 5 nm, and a reflection type mask 2 was used. The X-rays 11 a reflected by the mask 2 pass through the X-ray projection optical system 1 and reach the wafer 4, and the mask pattern is reduced and transferred onto the wafer 4.

The X-ray projection optical system 1 is composed of four reflecting mirrors, has a magnification of 1/4, and has an annular exposure field of 2 mm in width and 30 mm in length. The four reflecting mirrors are supported in the lens barrel. By making the lens barrel made of Invar, thermal deformation is less likely to occur. The reflecting mirror has an aspherical reflecting surface, and the surface of the reflecting mirror has Mo / Mo for improving the reflectivity of X-rays.
A Si multilayer film is coated. At the time of exposure, the mask 2 and the wafer 4 are scanned by the stages 3 and 5, respectively. The scanning speed of the wafer is always one of the scanning speed of the mask.
/ 4. As a result, the pattern on the mask can be transferred onto the wafer in a reduced size of 1/4.

The wafer surface position detecting mechanism includes an irradiating section 7a and a detecting section 7b. The irradiating unit includes a light source, a slit, an optical system for illuminating the slit, and an optical system for irradiating the image of the slit onto the wafer (both are not shown). A halogen lamp was used as a light source, and visible white light emitted from the halogen lamp was irradiated onto the wafer. The slit had a plurality of openings, and the images of these openings were transferred to an exposure area on the wafer. A detection unit, a slit, an optical system that transfers a reprojection image of the image formed on the wafer onto the slit,
It is formed of a photodiode that detects the intensity of the light beam transmitted through the slit (both are not shown). The optical system has a vibrating mirror that periodically changes the optical path of the light beam, and periodically changes the position of the reprojected image on the slit. In this way, the surface positions at a plurality of points on the wafer were simultaneously detected.

The mask surface position detecting mechanism was constituted by an electrostatic sensor. A plurality of electrostatic sensors were arranged near the X-ray incident position on the mask surface. At this time, the electrostatic sensor was arranged so as not to come into contact with the mask surface, and was arranged so as not to interfere with the optical path of the X-ray. The detection ranges of the wafer surface position detection mechanism and the mask surface position detection mechanism were about 4 μm and about 100 μm, respectively.

In the X-ray projection exposure apparatus according to this embodiment, the surface position detecting mechanism is fixed to a one-axis stage, and the stage is fixed to a lens barrel of the X-ray projection optical system. When performing magnification correction, the stage was driven to move the detection range of the surface position detection mechanism. Then, at the time of exposure, the surface positions of the wafer and the mask can always be detected. The stage stroke is about 400 μm and about 30 μm, respectively, for the surface position detection mechanism for the mask and the wafer.
μm.

When the stage was driven, the position of the surface position detecting mechanism was measured with a laser interferometer, and the amount of movement was matched with the amount of movement of the mask and wafer accompanying magnification correction. Even when the magnification of 10 ^-4 is corrected by the above mechanism, the wafer position and the mask height are set to 0.1 by the surface position detection mechanism.
It could be detected with high accuracy of less than μm. The exposure apparatus according to the present invention sets the wafer position to X based on the detection result.
Exposure is performed in accordance with the image plane position and the exposure position of the line projection optical system to form a resist pattern having a minimum size of 0.08 μm on the semiconductor chip 1 on the wafer, which is a desired area.
A desired shape could be obtained over the entire area of the individual region. Furthermore, devices could be manufactured with a high yield even for a wafer having a large amount of deformation due to the process.

[0065]

Embodiment 2 FIG. 3 shows a part of an X-ray projection exposure apparatus according to a second embodiment of the present invention. This apparatus is an enlarged view of a part of the wafer surface position detecting mechanism shown in FIG.

The surface position detecting mechanism is provided with harbing mechanisms 14a and 14b for changing an optical path. In the X-ray projection exposure apparatus according to the present embodiment, the wafer surface position detecting mechanism is directly fixed to the lens barrel of the X-ray projection optical system. When performing magnification correction, the harbing was driven to move the detection range of the surface position detection mechanism. Then, at the time of exposure, the surface position of the wafer can be always detected. The moving amount of the detection range due to the driving of the harbing was set to about 30 μm.

Harving was driven by a vacuum stepping motor, and the amount of movement was controlled by the number of driving steps when driving the harbing. The relationship between the number of driving steps and the amount of movement of the detection range was checked in advance, and the harbing was driven so that the amount of movement of the detection range matched the amount of movement of the wafer accompanying magnification correction.

Even when the magnification of ^10.sup.-4 was corrected by the above mechanism, the height of the wafer and the mask could be detected with high accuracy of 0.1 .mu.m or less by the surface position detecting mechanism. The exposure apparatus according to the present invention exposes the wafer position to the image plane position and the exposure position of the X-ray projection optical system based on the detection result, thereby obtaining a minimum size of 0.08.
A μm resist pattern could be obtained in a desired shape over the entire surface of one desired semiconductor chip on the wafer. Furthermore, even for a wafer having a large amount of deformation due to the process, devices could be manufactured with high yield and high throughput.

[0069]

[Embodiment 3] FIG. 4 shows a third embodiment X of the present invention.
1 shows a line projection exposure apparatus. The apparatus mainly includes an X-ray source (not shown) and an X-ray illumination optical system (not shown), an X-ray projection optical system 1, a stage 3 for holding a mask 2, a stage 5 for holding a wafer 4, and a vacuum chamber 6. , Wafer surface position detection mechanism (not shown), and mask surface position detection mechanism (not shown)
, A wafer mark position detecting mechanism 20 and a mask mark position detecting mechanism 21.

The exposure apparatus according to this embodiment is obtained by adding a wafer mark position detection mechanism 20 and a mask mark position detection mechanism 21 to the exposure apparatus of the first embodiment. Wafer mark position detecting mechanism 20 and mask mark position detecting mechanism 2
1 used a special optical microscope. An enlarged image of the mark on the wafer and the mask was captured by a CCD, and the positions of the wafer and the mask were detected by image processing.

The detection ranges of the wafer mark position detection mechanism and the mask mark position detection mechanism were about 2 μm and about 32 μm, respectively. In the X-ray projection exposure apparatus according to the present embodiment, the mark position detecting mechanism is fixed to a one-axis stage, and the stage is fixed to a lens barrel of the X-ray projection optical system. When performing magnification correction, the stage was driven to move the detection range of the mark position detection mechanism. Then, at the time of exposure, the mark positions of the wafer and the mask can be detected with high accuracy. The stroke of the stage was about 400 μm and about 30 μm for the mark position detection mechanism for the mask and the wafer, respectively.

When the stage was driven, the position of the mark position detecting mechanism was measured with a laser interferometer, and the amount of movement was matched with the amount of movement of the mask and wafer accompanying magnification correction. Even when the magnification of 10 ⁻⁴ was corrected by the above mechanism, the position of the mark on the wafer and the mask could be detected with high accuracy of 10 nm or less by the mark position detection mechanism. The exposure apparatus according to the present invention exposes an exposure pattern on a circuit pattern formed on a wafer surface with high accuracy based on the detection result, and exposes the minimum size to 0.08 μm.
Can be obtained in a desired shape on the entire surface of one desired area of the semiconductor chip on the wafer. Furthermore, devices could be manufactured with a high yield even for a wafer having a large amount of deformation due to the process.

[0073]

Fourth Embodiment FIG. 5 shows a part of an X-ray projection exposure apparatus according to a fourth embodiment of the present invention. This apparatus is an enlarged view of a part of the wafer mark position detecting mechanism shown in FIG.

The mark position detecting mechanism is provided with a vacuum actuator 30 as an adjusting mechanism of the lens 28 for changing the focal length. In the X-ray projection exposure apparatus according to the present embodiment, the mark position detecting mechanism is directly fixed to the lens barrel of the X-ray projection optical system. When performing magnification correction, the vacuum actuator was driven to move the detection range of the mark position detection mechanism. Then, at the time of exposure, the mark position of the wafer can always be detected. The amount of movement of the detection range by driving the vacuum actuator was about 30 μm.

A piezoelectric element was used as a vacuum actuator. When adjusting the lens, the amount of movement was monitored by an electrostatic sensor. The piezoelectric element was driven so that the movement amount of the detection range was matched with the movement amount of the wafer accompanying the magnification correction. Even when the magnification of 10 ⁻⁴ was corrected by the above mechanism, the position of the mark on the wafer and the mask could be detected with high accuracy of 10 nm or less by the mark position detection mechanism. The exposure apparatus according to the present invention exposes the exposure pattern on the circuit pattern formed on the wafer surface with high accuracy based on the detection result, and performs exposure with a minimum size of 0.08.
A μm resist pattern could be obtained in a desired shape over the entire surface of one desired semiconductor chip on the wafer. Furthermore, even for a wafer having a large amount of deformation due to the process, devices could be manufactured with high yield and high throughput.

[0076]

Embodiment 5 FIG. 6 shows a part of an X-ray projection exposure apparatus according to a fifth embodiment of the present invention. The exposure apparatus according to the present embodiment is obtained by replacing the X-ray illumination optical system of the exposure apparatus according to the first embodiment with the optical system according to the present invention.

The X-ray illumination optical system 40 includes a light source (not shown)
A plurality of mirrors for condensing the X-rays emitted from the X-ray, an integrator for generating a plurality of secondary light sources from the X-rays reflected by the mirrors, and an X-ray projection optical system It is composed of a plurality of mirrors that focus light on the entrance pupil plane. All mirrors were coated on their surfaces with a multilayer film.

Further, the X-ray illuminating optical system is provided with a mechanism capable of changing the position of the X-ray irradiated on the mask surface. The mechanism is a mirror constituting the X-ray illumination optical system,
A mechanism to adjust the position and angle of the mirror at the downstream end closest to the mask. The mirror was a plane mirror. A piezoelectric element was used for the drive mechanism of the mirror.

When correcting the magnification, the position and angle of the plane mirror were adjusted so that the optical path of the reflected X-rays 11a from the mask did not change. With the above mechanism, 10 ^-4
Even when the magnification was corrected, it was possible to keep the X-ray illumination state of the mask unchanged. An exposure apparatus according to the present invention exposes an exposure pattern onto a circuit pattern formed on a wafer surface with high accuracy by superposing the exposure pattern on the wafer.
A 7 μm resist pattern could be obtained in a desired shape on the entire surface of one desired semiconductor chip region on the wafer. Furthermore, even for a wafer having a large amount of deformation due to the process, devices could be manufactured with high yield and high throughput.

[0080]

[Embodiment 6] The wafer coated with the resist was exposed by the X-ray projection exposure apparatus shown in the fifth embodiment. At the time of exposure, marks on the wafer surface were detected in advance by a mark position detecting mechanism, and the intervals between the marks were measured. Then, the optimum magnification correction amount for exposure was calculated from the difference between the measured value and the design value. Then, the mask and the wafer were moved in the optical axis direction of the X-ray projection optical system, respectively, so that the magnification was corrected.

The detection ranges of the surface position detection mechanism and the mark position detection mechanism were moved according to the movement amounts of the wafer and the mask at this time. Further, the X-ray irradiation position on the mask surface of the X-ray illumination optical system was adjusted. Further, marks on the wafer surface and the mask surface were detected by a wafer mark position detecting mechanism and a mask mark position detecting mechanism. Then, the wafer stage was driven to adjust the wafer position so that the projection pattern was formed on the circuit pattern already formed on the wafer surface with a desired overlay accuracy or less. Further, based on the detection result of the surface position detecting mechanism, the wafer stage was driven so that the wafer surface coincided with the image forming position of the X-ray projection optical system, and the position of the wafer was adjusted.

Scanning of the wafer stage and the mask stage was started, and exposure was performed. During the exposure, the height of the wafer and the mask is maintained by the surface position detecting mechanism. By the above-described exposure method, a resist pattern having a minimum size of 0.07 μm was obtained in a desired shape over a whole area of one semiconductor chip on a wafer which is a desired area. The overlay accuracy at this time was 10 nm or less.

[0083]

Embodiment 7 Using the X-ray projection exposure apparatus described in the fifth embodiment, a semiconductor device was manufactured by the exposure method described in the sixth embodiment. The device was a 16 GB (gigabyte) DRAM. In this device, 22 layers of circuits were formed, and 15 layers were exposed by the X-ray projection exposure apparatus according to the present invention. Since the remaining seven layers had a minimum pattern size of 0.15 μm or more, they were exposed with an excimer laser exposure device. During each exposure, resist coating, doping,
A device circuit was manufactured by performing processes such as annealing, etching, and deposition. Finally, the silicon wafer was cut and divided into chips, and each chip was packed in a ceramic package.

The semiconductor device manufactured as described above is
It has desired electrical characteristics while having a large capacity of 16 GB.

[0085]

As described above, according to the X-ray projection exposure apparatus of the present invention, a sufficient range of magnification correction can be performed without impairing the overlay accuracy, focusing accuracy, and mask illumination performance. As a result, exposure can be performed with high overlay accuracy and high throughput even on a process wafer having a large deformation amount.

[Brief description of the drawings]

FIG. 1 is a schematic view of an X-ray projection exposure apparatus according to the present invention.

FIG. 2 is a diagram showing a method of correcting magnification in an X-ray projection exposure apparatus according to the present invention.

FIG. 3 is a partially enlarged view of a surface position detecting mechanism of the X-ray projection exposure apparatus according to the present invention.

FIG. 4 is a schematic view of an X-ray projection exposure apparatus according to the present invention.

FIG. 5 is a partially enlarged view of a mark position detecting mechanism of the X-ray projection exposure apparatus according to the present invention.

FIG. 6 is a schematic diagram showing an X-ray illumination optical system of the X-ray projection exposure apparatus according to the present invention.

FIG. 7 is a schematic view of a conventional X-ray projection exposure apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... X-ray projection optical system (barrel) 2 ... Mask 3 ... Mask stage 3a ... Adjustment mechanism 4 ... Wafer 5 ... Wafer stage 5a ... Adjustment mechanism 6 ... Vacuum chamber 7a: Wafer surface position detection mechanism (irradiation unit) 7b: Wafer surface position detection mechanism (detection unit) 8a: Mask surface position detection mechanism (irradiation unit) 8b: Mask surface position detection Mechanism (detection unit) 9a, 9b, 10a, 10b ... Stage 11a, 11b ... X-ray 12a, 12b ... Light flux 13a, 13b ... Slit 14a, 14b ... Harving 15a, 15b ... -Lens 16a, 16b-Mirror 17a, 17b, 18a, 18b-Vacuum actuator 20-Wafer mark position detection mechanism 21-Mask mark position detection mechanism 2 2, 23 ... Stage 24, 25 ... Light flux 26 ... Image detector 27, 28 ... Imaging lens 29, 30 ... Vacuum actuator 40 ... X-ray illumination optical system 41a, 41b X-ray beam 42a, 42b Mask surface position 51 X-ray projection optical system 52 Mask 53 Mask stage 54 Wafer 55 Wafer stage 56 Vacuum chamber 57a Surface position detection mechanism (irradiation unit) 57b Surface position detection mechanism (detection unit) 58a, 58b Light flux 59a, 59b, 59c, 59d, 59e, 59f
X-ray 60: Wafer mark position detection mechanism 61: X-ray source 62: X-ray illumination optical system 63: Light flux 64a, 64b: Mask surface position 65a, 65b: Wafer surface Position 66: Optical axis of X-ray projection optical system

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G21K 5/00 G21K 5/02 X 5/02 H01L 21/30 531A

Claims (16)

[Claims] At least an X-ray source, an X-ray illumination optical system for irradiating an X-ray generated from the X-ray source onto a mask having a predetermined pattern, and receiving the X-ray from the mask, the pattern Constituting an X-ray projection optical system for projecting and forming an image on a resist-coated wafer, a lens barrel for holding the mirror, a wafer stage for holding the wafer, and a mask stage for holding the mask And a surface position detection mechanism for detecting the surface position of the wafer and the mask,
An X-ray projection exposure apparatus comprising a mark position detecting mechanism for detecting a position of a mark formed on the wafer and the mask, wherein an X-ray projection exposure apparatus has a function of correcting a projection magnification by changing the position of the mask and the wafer. X-ray projection exposure apparatus. 2. The X-ray projection exposure apparatus according to claim 1, further comprising a function of correcting a detection range of said surface position detection mechanism in accordance with an amount of position change of said mask and wafer. 3. The X-ray projection exposure apparatus according to claim 1, further comprising a function of correcting a detection range of the mark position detection mechanism according to a position change amount of the mask and the wafer. 4. The apparatus according to claim 1, further comprising a function of correcting an irradiation position of the X-ray illuminating optical system on the mask surface according to a position change amount of the mask. X-ray projection exposure apparatus. 5. The surface position detecting mechanism is an optical detecting means, and the detection range is corrected by adjusting the position of the whole or a part of the surface position detecting mechanism. The X-ray projection exposure apparatus according to any one of 2 to 4. 6. The surface position detecting mechanism is an optical detecting means, and the detection range is corrected by adjusting the position or angle of at least one optical element constituting the surface position detecting mechanism. The X-ray projection exposure apparatus according to any one of claims 2 to 4, wherein: 7. The X-ray projection exposure apparatus according to claim 6, wherein the adjustment of the angle of the optical element is an adjustment of the angle of the harbing. 8. The apparatus according to claim 6, wherein the adjustment of the position of the optical element is an adjustment of a position of a slit.
Line projection exposure equipment. 9. The surface position detecting mechanism is an electric detecting means, and the detection range is corrected by adjusting a position of a detector constituting the surface position detecting mechanism. The X-ray projection exposure apparatus according to any one of 2 to 4. 10. The mark position detecting mechanism is an optical detecting means, and the detection range is corrected by adjusting a position or an angle of an optical system constituting the mark position detecting mechanism. An X-ray projection exposure apparatus according to claim 3. 11. The mark position detecting mechanism is an optical detecting means, and the correction of the detection range is performed by adjusting the position or angle of at least one optical element constituting the mark position detecting mechanism. An X-ray projection exposure apparatus according to any one of claims 3 to 9, wherein: 12. A function of correcting an irradiation position of the X-ray illumination optical system includes a function of correcting at least one of the X-ray illumination optical systems.
The X-ray projection exposure apparatus according to any one of claims 4 to 11, wherein the X-ray projection exposure apparatus is performed by adjusting positions or angles of two optical elements. 13. An X-ray projection exposure apparatus according to claim 12, wherein said optical element is a plane mirror disposed closest to a mask. 14. An exposure method using the X-ray projection exposure apparatus according to claim 1, wherein the projection magnification is corrected by changing a position of the mask and the wafer, and a change amount of the position is corrected. The detection range of the surface position detection mechanism is corrected based on, or the detection range of the mark position detection mechanism is corrected, or the irradiation position of the X-ray illumination optical system is corrected, and the detection is performed by the mark position detection mechanism. A circuit pattern formed on the mask at a desired position on the wafer by driving the mask stage and the wafer stage based on the position of the mark and the value of the surface position of the wafer and the mask detected by the surface position detection mechanism. An X-ray projection exposure method comprising forming a projected image of 15. The X-ray projection exposure according to claim 14, wherein the correction of the projection magnification is performed based on a value of a projection magnification calculated from an interval between a plurality of marks detected by the mark position detection mechanism. Method. 16. A semiconductor device produced by using the X-ray projection exposure apparatus according to any one of claims 1 to 13 and performing exposure by the exposure method according to claim 14 or 15.