JPH11233416A - X-ray projection exposure equipment - Google Patents

Abstract

(57) [Summary] It is extremely difficult to increase the distance between a wafer and a reflecting mirror because the optical performance of an imaging optical system is reduced. Kind Code: A1 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, An X-ray projection imaging optical system for projecting and forming an image on a substrate, a mask stage for holding the mask, a substrate stage for holding the substrate, and position detection for optically detecting marks on the mask and the substrate An X-ray projection exposure apparatus having an optical system, wherein the projection imaging optical system includes a plurality of reflecting mirrors for reflecting X-rays, and at least one of the position detection optical systems is provided between the plurality of reflecting mirrors. An X-ray projection exposure apparatus, comprising:

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mirror projection system such as an X-ray optical system for forming a circuit pattern on a mask (or a reticle) on a substrate such as a wafer via a reflective imaging optical system. X suitable for transfer
The present invention relates to a line projection exposure apparatus.

[0002]

2. Description of the Related Art Conventionally, in an exposure apparatus for manufacturing a semiconductor, a circuit pattern formed on a mask (photomask) as an object plane is projected and transferred onto a sensitive substrate such as a wafer or a mask via an imaging optical system. I do. A resist is applied to the sensitive substrate, and the resist is exposed by exposing the resist to obtain a resist pattern.

The resolving power W of an exposure apparatus is determined mainly by the exposure wavelength λ and the numerical aperture NA of an image forming optical system, and is expressed by the following equation.

[0004]

W = kλ / NA (k: constant) Therefore, in order to improve the resolving power, it is necessary to shorten the wavelength or increase the numerical aperture. Currently, the exposure equipment used in semiconductor manufacturing mainly uses wavelengths.
Using i-line of 365 nm, a resolution of 0.5 μm is obtained at a numerical aperture of about 0.5. 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. Examples of the exposure light having a wavelength shorter than the i-line include an excimer laser, the wavelength of which is 248 nm in KrF,
193 nm for ArF, 0.25 μm for KrF, 0.18 μm for ArF
Is obtained. When an X-ray having a shorter wavelength is used as the exposure light, a resolution of 0.1 μm or less can be obtained at a wavelength of 13 nm, for example.

[0005] A conventional exposure apparatus mainly comprises a light source, an illumination optical system, and a projection imaging optical system. The projection image forming optical system includes a plurality of lenses or reflecting mirrors, and forms a pattern on a mask on a wafer. In order for the exposure apparatus to have a desired resolution, at least the imaging optical system needs to be an optical system having no aberration or almost no aberration. If the imaging optical system has an aberration, the cross-sectional shape of the resist pattern is degraded, adversely affecting the post-exposure process, and causing a problem that the image is distorted.

Further, the conventional semiconductor exposure apparatus is provided with a position detecting device (hereinafter referred to as an alignment device) so that a resist pattern can be formed at a predetermined position on a wafer provided with a circuit pattern. Thus, the positions of the mask and the wafer are detected, and the positions of the wafer and the mask are respectively adjusted by the wafer stage and the mask stage so that the reduced image of the mask is formed at a desired position on the wafer.

[0007] The alignment device includes, for example, an optical detection device. In this method, for example, a mark on a wafer is irradiated with illumination light, and the reflected light or the like is detected by a photodetector. When the wafer position changes, the signal output from the detector changes, so that the position of the wafer can be known. Similarly, the mark can be illuminated with illumination light, and the reflected light or the like can be detected by a photodetector to determine the position of the mask.

[0008] Since such an alignment apparatus can detect the positions of the marks on the wafer and the mask with high accuracy, the alignment between the mask and the wafer can be performed accurately. In the case of a conventional exposure apparatus, the alignment apparatus is disposed between the imaging optical system and the wafer or between the imaging optical system and the mask. FIG. 4 is a conceptual diagram of a part of a conventional exposure apparatus using i-line. The apparatus mainly includes a light source and an illumination optical system (not shown), a stage 15 of a mask 14, a projection imaging optical system 13, a stage 17 of a wafer 16, and an alignment device 18. The mask 14 is formed with a pattern of the same size or an enlarged size as the pattern to be drawn. The projection imaging optical system 13 includes a plurality of lenses and the like, and the mask 1
The pattern on 4 is imaged on wafer 16. The imaging optical system has a visual field having a diameter of about 20 mm, and transfers the pattern of the mask onto the wafer 16 collectively. The mark position of the mask and the wafer is determined by the alignment detecting device 18.
To detect.

In a conventional exposure apparatus using i-rays or the like, the projection image forming optical system can be constituted by a lens, so that an optical system having a visual field of 20 mm square or more can be designed, and a desired area can be obtained. (For example, an area for two semiconductor chips) could be exposed at once. On the other hand, if an attempt is made to design an imaging optical system for X-rays in order to obtain higher resolution, the field of view becomes small, and a desired region cannot be exposed at a time. Therefore, there is a method in which a semiconductor chip having a size of 20 mm square or more is exposed by an imaging optical system having a small visual field by scanning a mask and a wafer at the time of exposure. In this way, a desired exposure area can be exposed even with an X-ray projection exposure apparatus.

For example, when exposing with X-rays having a wavelength of 13 nm,
By forming the exposure field of view of the projection imaging optical system in an annular shape, a high resolution can be obtained. FIG. 5 is a conceptual diagram of a part of the X-ray projection exposure apparatus. The apparatus mainly includes an X-ray source 1, an X-ray illumination optical system 2, a stage 5 of a mask 4, an X-ray projection imaging optical system 3, and a stage 7 of a wafer 6. Mask 4
Is formed with a pattern of the same size or an enlarged size as the pattern to be drawn. The projection imaging optical system 3 includes a plurality of reflecting mirrors and the like, and forms a pattern on the mask 4 on the wafer 6. The imaging optical system has an annular field of view,
The pattern of a part of the annular zone of the mask 4 is
Transfer to the top. At the time of exposure, the mask 4 is irradiated with X-rays 91 and the reflected X-rays 92 are incident on the wafer 6 through the X-ray projection imaging optical system 3. By synchronously scanning the mask 4 and the wafer 6 at a constant speed, a desired region (for example, a region for one semiconductor chip) is exposed.

[0011]

However, in the case of an X-ray projection exposure apparatus, a part of the reflecting mirror (reflecting mirror 34 in FIG. 5) constituting the imaging optical system is close to the wafer due to restrictions on optical design. Often placed. Therefore, it is difficult to dispose the optical system of the alignment device between the imaging optical system and the wafer. Because if the position of the reflector closest to the wafer among the reflectors that make up the imaging optical system is moved away from the wafer in order to increase the distance between the wafer and the reflector, the imaging performance of the imaging optical system will decrease. However, the desired pattern cannot be projected, and when the reflector closest to the wafer among the reflectors constituting the imaging optical system is thinned, the rigidity of the mirror is reduced, making it difficult to manufacture a highly accurate mirror. Because it becomes. Thus, increasing the distance between the wafer and the reflector is
It is extremely difficult to reduce the optical performance of the imaging optical system.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide an X-ray projection exposure apparatus capable of detecting an alignment without deteriorating the optical performance of an imaging optical system.

[0013]

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. An X-ray projection imaging optical system that receives an X-ray from the mask and projects and forms an image of the pattern on a substrate, a mask stage that holds the mask, a substrate stage that holds the substrate, An X-ray projection exposure apparatus having a position detection optical system for optically detecting a mark on a mask and a substrate, wherein the projection imaging optical system includes a plurality of reflecting mirrors for reflecting X-rays, and An X-ray projection exposure apparatus, wherein at least a part of the position detection optical system is arranged between reflecting mirrors.

The present invention also provides a second aspect of the invention wherein "at least a part of the position detecting optical system includes a reflecting mirror closest to a substrate among a plurality of reflecting mirrors constituting the projection imaging optical system; 2. The X-ray projection exposure apparatus according to claim 1, wherein the apparatus is disposed between close reflectors.
Further, the present invention is a third aspect, "the position detection optical system illuminates at least a mark provided on a mask with an illumination optical system,
The light beam reflected by the mark on the mask is guided to the mark on the substrate via the reflecting mirror of the X-ray projection imaging optical system, and the mark provided on the substrate is detected by the detection optical system. Item 3. An X-ray projection exposure apparatus according to any one of Items 1 to 2. (Claim 3) "is provided.

Further, the present invention provides a fourth aspect in which "the position detecting optical system illuminates at least a mark provided on the substrate by an illumination optical system, and reflects a light beam reflected by the substrate by the X-ray projection imaging optical system. 3. The X-ray projection exposure apparatus according to claim 1, wherein the mark is guided to a mark on the mask via a mirror, and the mark provided on the mask is detected by a detection optical system. I will provide a.

Further, the present invention provides, fifthly, an "X-ray projection exposure apparatus according to any one of claims 1 to 4, wherein a moving mechanism is provided in the position detecting optical system (claim 5)." I do. Further, the present invention provides a sixth aspect of the present invention, wherein the numerical aperture of the position detection optical system is not more than half the numerical aperture of the X-ray projection imaging optical system. Line projection exposure equipment.
(Claim 6) "is provided.

Further, the present invention provides a seventh aspect of the present invention, wherein at least a part of the position detecting optical system arranged between the plurality of reflecting mirrors has a half mirror. A line projection exposure apparatus. The present invention eighthly provides an "X-ray projection exposure apparatus according to any one of claims 1 to 7, wherein a temperature adjusting mechanism is provided in the position detection optical system."

[0018]

FIG. 1 is a schematic diagram of an X-ray projection exposure apparatus according to an embodiment of the present invention. This apparatus mainly includes an X-ray source 1, an X-ray illumination optical system 2, an X-ray projection imaging optical system 3, a stage 5 for holding a mask 4, a wafer stage 7 for holding a wafer 6, and alignment detection devices 81 and 82. It consists of. The mask 4 is formed with a pattern of the same size or an enlarged size as the pattern to be drawn. The X-ray projection imaging optical system 3 includes a plurality of reflecting mirrors, and forms an image of the pattern on the mask 4 on the wafer 6. The X-ray projection imaging optical system 3 has a field of view such as an annular zone, and transfers a pattern of a partial area of the mask 4 onto the wafer 6. At the time of exposure, a desired region is exposed by synchronously scanning the mask and the wafer at a constant speed. In the present embodiment,
For example, a laser plasma X-ray source was used as the X-ray source, the exposure wavelength was 13 nm, the mask 4 was a reflective mask, and the transfer magnification was 1/4. Since the transfer magnification is 1/4, the speed of the wafer stage is set to 1/4 of the speed of the mask stage. In FIG. 1, the X-ray luminous flux used for the X-ray exposure is omitted for simplicity, but is similar to the conventional technique shown in FIG.

The X-ray projection imaging optical system 3 comprises a plurality of reflecting mirrors 31 to 34 for reflecting X-rays. It is preferable to coat the surface of the reflecting mirror with a multilayer film in order to improve the reflectivity of X-rays. The alignment detecting devices 81 and 82 are devices for optically detecting the positions of the marks on the mask 4 and the wafer 6, and the illumination optical system 8 for illuminating at least the marks.
1 and a detection optical system 82 for detecting light from the mark. In the present embodiment, an alignment apparatus that performs FIA type alignment is used, but another alignment apparatus may be used. It is preferable that the light beam for alignment detection is reflected by the reflecting mirror of the X-ray projection imaging optical system, because the positioning including the influence of the projection imaging optical system can be performed. When the X-ray projection imaging optical system is formed of a reflecting mirror as in the present invention, good alignment can be performed because alignment light (for example, white light in the present embodiment) does not cause chromatic aberration. Can be. In the present embodiment, as shown in FIG. 1, the illumination optical system 81 is provided on a mark provided on the mask 4.
The light 86 is reflected by the mask 4, and the light 86 reflected by the mask 4 is reflected by the reflecting mirrors 31 to 34 of the X-ray projection imaging optical system 3 and guided to the wafer 6 as a light 87. Further, the light beam 88 reflected on the wafer 8 is detected by the detection optical system 82. The mark on the mask 4 is projected on the wafer 6 by the X-ray projection imaging optical system 3. The projected image and the mark on the wafer are detected by the detection optical system 82, and the positional relationship between the mask and the wafer can be obtained from the positional relationship between the projected image of the mask mark and the wafer mark. The detection optical system 82 for observing the mark image on the wafer 6 is partially disposed between a plurality of reflecting mirrors constituting the X-ray projection imaging optical system 3 (that is, in the X-ray projection imaging optical system 3). Therefore, the detection light from the mark on the wafer 6 can be detected without forming an unreasonable space between the reflecting mirror 34 and the wafer 6, so that the alignment can be detected satisfactorily. In the present embodiment, the mark 6
Although a reflecting mirror for guiding the detection light from the mirror is arranged between the reflecting mirrors 31 and 34, there is no particular limitation on which part of the alignment device is provided, and the detection light from the mark 6 can be detected. As shown in FIG.
What is necessary is just to arrange | position between two reflectors. In addition, any location may be used as long as the detection light from the mark 6 can be detected. However, if it is located between the reflecting mirrors 31 and 34, the detection optical system 82 of the alignment device is brought closer to the wafer 6. This is preferable because, for example, it is possible to prevent S / N from being deteriorated due to a decrease in the intensity of the detection light by another reflecting mirror.

The illumination optical system 81 and the detection optical system 82
The arrangement may be reversed as shown in FIG. In the apparatus shown in FIG. 2, the mark provided on the wafer 6 is irradiated with the light beam 85 by the illumination optical system 81 and the light beam 86
The light flux 87 is guided to the mask 4 by being reflected by the reflecting mirrors 31 to 34 of the line projection imaging optical system 3. Further, the light beam 88 reflected on the mask 4 is detected by the detection optical system 82. It is also possible to directly detect the mark on the wafer 6 without passing through the mask 4, and in this case, the detection light from the mark on the wafer 6 that has passed through the X-ray projection imaging optical system 3 is directly detected by the optical detection system. What is necessary is just to lead to 82. In the case of FIG. 2, a part of the alignment device arranged between the plurality of mirrors is a reflecting mirror constituting the illumination optical system 81. FIG. 1 also shows the case where the illumination optical system 81 and the detection optical system 82 are arranged in reverse.
By arranging a part of the alignment device between the plurality of reflecting mirrors, it is possible to irradiate a desired position on the wafer with alignment light, as in
The alignment device can be configured without creating an extra space between the wafer and the wafer 6. In the case of the apparatus shown in FIG. 2, if the illumination optical system 81 is disposed between the reflecting mirrors 31 and 34, the illumination optical system can be brought closer to the wafer 6. It is preferable because the strength can be prevented from dropping.

When the alignment light beam is reflected by the reflecting mirror of the X-ray imaging optical system, it is preferable that the light beam incident on the wafer and the reflected light beam do not interfere with each other. As a means for achieving this, it is preferable that the numerical aperture of the optical system of the alignment apparatus be equal to or less than half the numerical aperture of the X-ray projection imaging optical system. FIG. 1 shows the light beams 85 to 88 of the alignment apparatus. However, since the numerical aperture of the alignment optical system is set to half the numerical aperture of the X-ray projection imaging optical system, the light beam 87 incident on the wafer is The reflected light beam 88 does not interfere. In FIG. 2, similarly, the light beam 85 and the light beam 86 do not interfere.

A half mirror may be used as a part of the alignment optical system. FIG. 3 shows a part of an apparatus using a half mirror 88 as a part of an illumination optical system. In this way, a light beam incident on the wafer and a light beam reflected therefrom are
Part of the optical path can be shared, and the mark can be detected. It is preferable to use a pellicle mirror as the half mirror because the influence of refraction at the half mirror is reduced. Of course, the alignment apparatus may be configured as shown in FIG. 1 and a half mirror may be used as a part of the detection optical system.

The alignment marks are preferably arranged around the exposure field of the X-ray imaging optical system. In particular, in the case of an annular visual field, if marks are arranged around both ends of the annular direction of the arc, the marks on the mask are precisely projected on the wafer. When a part of the alignment detection device blocks X-rays as exposure light, it is preferable to provide the alignment detection device 8 with a moving mechanism 83 so that the alignment device can be evacuated during exposure. This moving mechanism may be performed mechanically, for example. At the time of exposure, all or a part of the alignment detection device can be retracted. In FIGS. 1 and 2, the moving mechanism is provided in both the illumination optical system 81 and the detection optical system 82, but may be provided in either one as necessary. The position of the alignment device may be changed by the moving mechanism 83 to detect a plurality of marks on the mask and the wafer. At this time, it is preferable that the alignment detecting device 8 be translated in a plane perpendicular to the optical axis of the projection imaging optical system 3. Further, when detecting a plurality of marks, the wafer stage and the mask stage may be synchronized with each other, or when detecting a plurality of marks on the wafer for one mark having a mask, only the mask stage may be used. You may move to measure.

Further, a plurality of alignment detecting devices may be provided to detect a plurality of points on the wafer. It is preferable that the alignment detecting device 8 be provided with a temperature adjusting mechanism 84.
As the temperature adjustment mechanism, water cooling, a refrigerant, a Peltier element, or the like can be used. Accordingly, the heat generated from the alignment apparatus can be suppressed, so that the influence of heat on the projection imaging optical system can be suppressed, and the thermal deformation of the projection imaging optical system can be suppressed. It is easier to maintain the desired aberrations of the system.

Exposure by the above-described apparatus allowed the mask pattern to be projected and transferred to a desired position on the wafer.
As a result, a resist pattern with a minimum size of 0.1 μm
It could be obtained at a desired position over the entire area of one semiconductor chip on the wafer, and a highly accurate device could be manufactured. On the other hand, in the case of the conventional X-ray projection exposure apparatus, since the X-ray imaging projection optical system is designed so that the alignment apparatus can be arranged, the imaging performance is poor, and a resist pattern having a desired shape is formed in a part of the exposure area. Could not be obtained.

[0026]

As described above, according to the X-ray projection exposure apparatus of the present invention, while the aberration of the projection imaging optical system is set to a desired value,
An alignment device can be arranged. Further, by providing a moving mechanism, a plurality of points on the wafer can be detected. As a result, the mask pattern can be projected and transferred to a desired position on the wafer, and a highly accurate device can be manufactured.

[Brief description of the drawings]

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

FIG. 2 is a schematic diagram showing an X-ray projection exposure apparatus according to an embodiment of the present invention.

FIG. 3 is a schematic diagram illustrating an X-ray projection exposure apparatus according to an embodiment of the present invention.

FIG. 4 is a schematic diagram of a conventional i-line projection exposure apparatus.

FIG. 5 is a schematic view of a conventional X-ray projection exposure apparatus.

[Description of Signs of Main Parts]

 1. . . X-ray source 2. . . Illumination optical system 3,. . . 13. Projection imaging optical system 4, 14. . . Mask 5,15. . . Mask stage 6,16. . . Wafer 7,17. . . Wafer stage 18. . . Alignment device 19 i-ray 31-34 X-ray reflecting mirror 81 Illumination optical system 82 Detector 83 Moving mechanism 84 Temperature adjusting mechanism 85-88 Alignment light beam 89: half mirror 90-92. . . X-ray

Claims (8)

[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, X-ray projection imaging optical system for projecting and forming an image on a substrate, a mask stage for holding the mask, a substrate stage for holding the substrate, and a position for optically detecting a mark on the mask and the substrate An X-ray projection exposure apparatus having a detection optical system, wherein the projection imaging optical system includes a plurality of reflecting mirrors for reflecting X-rays, and at least the position detection optical system is provided between the plurality of reflecting mirrors. An X-ray projection exposure apparatus characterized in that a part thereof is arranged. 2. The apparatus according to claim 1, wherein at least a part of said position detecting optical system includes:
2. The X-ray projection exposure according to claim 1, wherein the X-ray projection exposure device is arranged between a reflector closest to the substrate and a reflector closest to the second among the plurality of reflectors constituting the projection imaging optical system. apparatus. 3. The position detecting optical system illuminates at least a mark provided on the mask with an illumination optical system, and transmits a light beam reflected by the mark on the mask via a reflecting mirror of the X-ray projection imaging optical system. The mark guided on the substrate, and the mark provided on the substrate is detected by a detection optical system.
3. The X-ray projection exposure apparatus according to claim 1. 4. The position detecting optical system illuminates at least a mark provided on a substrate with an illumination optical system, and illuminates a light beam reflected by the substrate on a mask via a reflecting mirror of the X-ray projection imaging optical system. 3. The X-ray projection exposure apparatus according to claim 1, wherein the mark is guided to a mark, and the mark provided on the mask is detected by a detection optical system. 5. An X-ray projection exposure apparatus according to claim 1, wherein a moving mechanism is provided in said position detecting optical system. 6. An X-ray projection exposure apparatus according to claim 1, wherein a numerical aperture of said position detecting optical system is not more than 1/2 of a numerical aperture of said X-ray projection imaging optical system. . 7. The X-ray projection exposure apparatus according to claim 1, wherein at least a part of the position detecting optical system disposed between the plurality of reflecting mirrors has a half mirror. 8. An X-ray projection exposure apparatus according to claim 1, wherein a temperature adjusting mechanism is provided in said position detecting optical system.