JP3358097B2 - X-ray projection exposure equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray projection exposure apparatus used for X-ray lithography and the like.

[0002]

2. Description of the Related Art In recent years, with the miniaturization of semiconductor integrated circuit elements, conventional ultraviolet rays (wavelengths 193 to 436) have been used in order to improve the resolution of an optical system limited by the diffraction limit of light.
nm) instead of soft X-rays having a shorter wavelength (wavelength 5 nm).
Projection lithography technology using ２０20 nm) has been developed. As shown in FIG. 5, an X-ray projection exposure apparatus used in this technique mainly includes an X-ray source, an illumination optical system, a mask and a mask stage, a projection imaging optical system, a wafer stage, and the like.

[0003] In the X-ray wavelength range, no transparent substance exists and the reflectance on the substance surface is very low, so that ordinary optical elements such as lenses and mirrors cannot be used. Therefore, the optical system for X-rays uses an oblique incidence mirror that reflects the X-rays incident on the reflecting surface from an oblique direction using total reflection, and matches the phases of the reflected light at each interface of the multilayer film. It is composed of a multilayer mirror or the like that obtains a high reflectance by the interference effect.

[0004] An oblique incidence mirror can obtain a reflectance close to 100%, but can be used only at an oblique incidence with an oblique incidence angle (incident angle measured from a reflecting surface) of 10 degrees or less. Although a multilayer mirror can reflect X-rays vertically, it cannot provide a reflectance close to 100%. Silicon L
On the longer wavelength side than the absorption edge (12.3 nm), the highest reflectance is obtained when a multilayer film composed of molybdenum and silicon is used.
It is about 0%. On the shorter wavelength side than the L absorption edge of silicon, a multilayer film capable of obtaining a reflectance of 30% or more at normal incidence has not been developed.

The X-ray source includes a synchrotron Ra
diation Source) or laser plasma X-ray source,
A light source capable of obtaining strong soft X-rays is used. A synchrotron light source utilizes electromagnetic waves emitted in a tangential direction of an electron orbit when electrons moving at a speed close to the speed of light are deflected in a traveling direction by a magnetic field. Laser plasma X
When the target is irradiated with a strong laser pulse, the evaporated source material is turned into plasma, from which electromagnetic waves including X-rays are emitted.

The illumination optical system includes an oblique incidence mirror, a multilayer mirror, and a filter that transmits or reflects only X-rays of a predetermined (desired) wavelength, and illuminates the mask with X-rays of a desired wavelength. As the mask, a transmission mask and a reflection mask are known. The transmission mask is X
X on a thin membrane made of a material that transmits light well
A pattern is formed by providing a line absorbing material in a predetermined shape (pattern). On the other hand, the reflection type mask has a pattern formed by providing a low-reflectance portion in a predetermined shape on a multilayer film that reflects X-rays.

In a transmission type mask, a very fragile membrane having a thickness of about 0.1 μm or less must be used in order to suppress absorption of X-rays. Therefore, a mask having a practical size (100 mm or more) cannot be manufactured. On the other hand, a thick substrate having sufficient mechanical strength can be used for the reflective mask. Therefore, when applying the X-ray projection exposure to actual semiconductor manufacturing, a reflective mask is used.

[0008] The pattern formed on such a mask is imaged on a photoresist-coated wafer by a projection imaging optical system composed of a plurality of multilayer mirrors and the like, and is transferred to the photoresist. You. All the projection imaging optical systems must be constituted by reflection systems (multilayer mirrors). Further, since the reflectance of the multilayer mirror is not so high, the number of mirrors must be reduced as much as possible to obtain a practical throughput. Therefore, it is difficult to correct aberrations over a wide exposure area.

Therefore, a ring field optical system as shown in FIG. 4 has been devised. This optical system 20 has an optical axis 2
Aberration is corrected in a narrow ring-shaped area (ring field) 22 that is separated from 1 by a predetermined distance. Mask 2
The ring field 22a on 3 is projected and imaged on the ring field 22b on the wafer 24. Wafer 2
4 is 0.5 mm in the width direction of the annular zone.
Although only a small area can be taken, a wide range can be used in the direction along the annular zone because the optical system 20 is rotationally symmetric.

At the time of exposure, as shown in FIG. 4, for example, an arc-shaped exposure region 25b having a length of about 120 mm is used on a mask, and the mask 23 and the wafer 24 are moved at a speed ratio corresponding to the reduction magnification. By scanning synchronously, 3
An exposure area having a practical size of about 0 × 30 mm is secured. Since the X-rays are absorbed by the atmosphere and attenuated, all the optical paths of the X-rays are maintained at a predetermined degree of vacuum.

[0011]

A telecentric optical system is used as a projection image forming optical system of a conventional projection exposure apparatus. The telecentric optical system is an optical system in which the principal ray is parallel to the optical axis at any point on the object plane or the image plane, and is called an object side telecentric and an image side telecentric, respectively. Usually, since the object plane and the image plane are perpendicular to the optical axis, these chief rays are incident perpendicularly to the mask and the wafer.

In a conventional exposure apparatus using ultraviolet light, a projection optical system which is telecentric on both the object side (mask side) and the image side (wafer side) is used. The advantages of using a telecentric optical system are that the magnification of the optical system does not change even when the mask or wafer moves in the optical axis direction, and that the resolution is constant on the image plane. These properties are very important for a lithographic apparatus that seeks diffraction-limited imaging performance.

However, in the conventional soft X-ray projection exposure apparatus as shown in FIG. 5, although it is possible to make the image side (wafer side) telecentric, since the reflection type mask 4 is used, the light incident on the mask is used. It is impossible to make the light (and the reflected light from the mask) perpendicular to the mask surface, and there is a serious problem that an optical system in which the object side (mask side) is telecentric cannot be used.

Even in such an arrangement, by using a projection imaging optical system having an object plane which is not perpendicular to the optical axis but inclined, the angle of incidence on the reflection mask is not perpendicular while satisfying the telecentric condition. It is theoretically possible. However, since the object plane is rotationally symmetric with respect to the optical axis, the object plane inclined with respect to the optical axis is not a plane. Therefore, in that case, a mask having a curvature must be used, which is impractical.

The present invention has been made in view of such a problem, and an X-ray capable of using a telecentric optical system on both the object side (mask side) and the image side (wafer side). An object of the present invention is to provide a projection exposure apparatus.

[0016]

SUMMARY OF THE INVENTION Therefore, the present invention firstly provides a method for producing an X-ray source comprising: at least an X-ray source; an illumination optical system for irradiating an X-ray emitted from the X-ray source onto a reflective mask; An X-ray projection exposure apparatus comprising: a projection imaging optical system configured to project and form an image of the formed pattern on a wafer;
The principal ray of the X-ray from the illumination optical system is vertically incident on the surface of the reflective mask, and the principal ray of the X-ray vertically reflected by the reflective mask is transmitted to the projection imaging optical system. An X-ray projection exposure apparatus having an X-ray beam splitter for incident parallel to the optical axis (Claim 1) "
I will provide a.

The present invention also provides a second aspect, wherein the X-ray beam splitter comprises at least a substrate having an opening and a self-supporting multilayer film formed on the substrate so as to cover the opening. An X-ray projection exposure apparatus according to claim 1 (claim 2). " The third aspect of the present invention is an X-ray projection exposure apparatus according to claim 2, wherein a beam-shaped support portion for supporting the self-supporting multilayer film is provided in an opening of the X-ray beam splitter. Claim 3) "is provided.

Further, the present invention provides a X-ray projection apparatus according to any one of claims 1 to 3, wherein a vibration means for vibrating the X-ray beam splitter in a direction parallel to a surface thereof is provided. Exposure apparatus (Claim 4) "is provided. Also,
Fifth, the present invention provides "a detecting means for detecting breakage of the X-ray beam splitter.
4. An X-ray projection exposure apparatus according to claim 4 (claim 5).

Further, the present invention provides, in a sixth aspect, a storage means for storing a plurality of X-ray beam splitters, and an X-ray beam splitter whose breakage has been detected by the detection means is stored in the storage means. An X-ray projection exposure apparatus according to claim 5, further comprising an exchange means for exchanging with the splitter. Also,
A seventh aspect of the present invention is the X-ray projection exposure apparatus according to any one of claims 1 to 6, wherein the X-ray beam splitter has a reflectance and a transmittance for use X-rays equal or substantially equal to each other. Claim 7) is provided.

[0020]

An example of an X-ray projection exposure apparatus according to the present invention will be described with reference to FIGS. In the apparatus shown in FIGS. 1 and 2, both the object side (mask side) and the image side (wafer side) use the ring-field projection imaging optical system 6 that is telecentric. The X-rays emitted from the X-ray source 2 are shaped by the illumination optical system 3 into an X-ray light beam whose principal rays are parallel to each other and large enough to irradiate an illumination area of a predetermined size. .

This X-ray beam is first reflected (in the case of FIG. 1) or transmitted (in the case of FIG. 2) by the X-ray beam splitter 1, and then transmitted to the reflection type mask 4 by the principal ray (reflected light). Or transmitted light) is perpendicular.
Immediately before the reflective mask 4, it is preferable to provide a slit 9 for limiting an illumination area in an arc shape. The X-ray beam vertically reflected by the reflection mask 4 is transmitted (in the case of FIG. 1) or reflected (in the case of FIG. 2) by the X-ray beam splitter 1, and then incident on the projection imaging optical system 6. At this time, the direction of the principal ray of the incident X-ray beam parallel to the projection imaging optical system 6 and the optical axis of the projection imaging optical system 6 are made parallel. This makes it possible to configure a soft X-ray projection exposure apparatus in which the object side (mask side) is telecentric.

The wafer 7 is installed so that its surface is perpendicular to the optical axis of the projection imaging optical system 6.
Telecentric imaging is also performed on the image side (wafer side). The area that can be exposed at one time is, for example, 0.5 mm in width,
Since the mask stage 5 and the wafer stage 8 are exposed while being synchronously scanned (scanned) at a speed ratio corresponding to the reduction magnification of the projection imaging optical system 6, the exposure time is 30 × An exposure area of about 30 mm is obtained.

After exposing this area, the position of the wafer 7 is shifted (stepped), and the next exposure is performed. The entire surface of the wafer is exposed by repeating such a step-and-scan operation. X according to the present invention
It is preferable that the line beam splitter includes at least a substrate having an opening and a self-supporting multilayer film formed on the substrate so as to cover the opening. An example of the structure of such an X-ray beam splitter 1 is shown in FIG. 3 (FIG. 3A is a plan view, FIG. 3B is a cross-sectional view). A window (opening) 12 is formed on a substrate 11 having sufficient mechanical strength.
Is formed, and a self-supporting multilayer film 13 is formed so as to cover the opening 12. The opening 12 is formed in a generally rectangular shape larger than an arc-shaped region (indicated by a broken line in the figure) through which X-rays are transmitted and reflected.

It is preferable to provide a beam-shaped support for supporting the self-supporting multilayer film at the opening of the X-ray beam splitter. For example, when the strength of the self-supporting multilayer film 13 is insufficient and the self-supporting multilayer film 13 is hardly self-supporting in a large area, the self-supporting multilayer film 13 can be reinforced (supported) by the beam-shaped support portion 14 provided in the opening. X-ray beam splitter 1
Since it is installed at a position deviated from the focal point of the projection imaging optical system 6, even if such a support portion 14 is provided, the shadow of the support portion 14 will not be directly transferred onto the wafer 7, but the exposure region Causes uneven illumination.

Therefore, it is preferable to provide vibration means for vibrating the X-ray beam splitter in a direction parallel to the surface thereof. That is, by oscillating the X-ray beam splitter 1 in a plane parallel to the surface thereof, for example, in the longitudinal direction of the rectangular opening 12, the self-supporting multilayer film 13 that can prevent illuminance unevenness is reinforced by the support portion 14. Even if they are, they are fragile. That is, if the exposure is continued for a long time, there is a sufficient possibility that the self-supporting multilayer film 13 will be damaged halfway.

Therefore, it is preferable to provide a detecting means for detecting breakage of the X-ray beam splitter. That is, it is preferable to provide, for example, an X-ray detector as means for detecting breakage of the X-ray beam splitter 1. As the X-ray detector, an MCP (micro channel plate), a photomultiplier, an X-ray diode, an X-ray CCD, or the like can be used.

For example, in the case of the arrangement shown in FIG. 1, an X-ray detector 10a is installed at a position where X-rays from the illumination optical system 3 pass through the X-ray beam splitter 1, and X-rays to be detected are detected.
The breakage of the X-ray beam splitter 1 can be detected by the increase in the line intensity. Or X on slit 9
The X-ray beam splitter 1 can be detected by installing the X-ray detector 10b and detecting a decrease in the X-ray intensity detected.

In the case of the arrangement shown in FIG.
An X-ray detector 10b is installed on the upper side, and damage to the X-ray beam splitter 1 can be detected by an increase in detected X-ray intensity. In addition to the detecting means for detecting the damage of the X-ray beam splitter, a storing means for storing a plurality of X-ray beam splitters, and the X-ray beam splitter whose damage was detected by the detecting means were stored in the storing means. It is preferable to further provide an exchange means for exchanging with the X-ray beam splitter (claim 6).

For example, a plurality of spare X-ray beam splitters are stored in the storage means in advance. As soon as damage is detected, the replacement means replaces the new one (spare X
(Beam beam splitter). By providing such means, it is not necessary to stop the operation even if the X-ray beam splitter is broken, and the operating rate of the X-ray projection exposure apparatus can be increased.

By the way, the X-ray beam splitter 1
When a line is incident, part of the line is reflected, part is transmitted, and the rest is absorbed by the multilayer film 13. In the soft X-ray projection exposure apparatus according to the present invention (for example, FIGS. 1 and 2), the X-rays emitted from the illumination optical system 3 are transmitted to the X-ray beam splitter before reaching the projection imaging optical system 6. 1 performs one reflection and one transmission.

Therefore, the intensity of X-rays incident on the projection imaging optical system 6 is proportional to R × T, where T is the reflectance of the multilayer film 13 and R is the transmittance. Since R + T + A is constant (A is the absorption of the multilayer film), when R = T, R × T becomes maximum, and the intensity of the X-ray incident on the projection imaging optical system 6 becomes maximum. Therefore, it is preferable that the reflectivity and the transmissivity of the X-ray beam splitter with respect to the used X-ray are equal or substantially equal (claim 7). Increasing the number of layers of the multilayer film 13 increases the reflectivity and decreases the transmittance, so that this condition (R = T)
It is preferable to select an appropriate number of layers so as to satisfy the above.

As the multilayer film according to the present invention, for example,
Among the combinations of molybdenum / silicon, molybdenum / silicon compound, ruthenium / silicon, ruthenium / silicon compound, rhodium / silicon, rhodium / silicon compound, and the like, those obtained by alternately laminating a plurality of times by any one combination are preferable. Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an example of a method for manufacturing an X-ray beam splitter according to the present invention will be described. FIG. 6 is a diagram showing a first method for manufacturing an X-ray beam splitter. First,
Reduced pressure CV on the back side of silicon wafer 61 polished on both sides
0.1 μm thick by D (Chemical Vapor Deposition)
m silicon nitride (Si ₃ N ₄ ) film is formed.

A photoresist is applied thereon, and the resist is patterned by photolithography.
The resist at the portion that will become the window (opening) of the line beam splitter is removed. The resist as a mask, RIE of the silicon nitride film using the CF ₄ gas (Reacti
Etching by ve ion etching to form a silicon nitride film 62 from which a window (opening) of the X-ray beam splitter has been removed (FIG. 6A).

Next, a multilayer film 63 of molybdenum and silicon (silicon) is formed on the surface of the silicon wafer 61 by high-frequency magnetron sputtering (FIG. 6).
b). The cycle length and the number of layers of the multilayer film 63 are appropriately set to values that can obtain a desired incident angle, reflectance, and transmittance of the X-ray beam splitter. Finally, using the silicon nitride film 62 on the back surface as a mask, the silicon wafer 61 is etched with a KOH aqueous solution to form a window (opening) 64.
To form Since the silicon on the side where the multilayer film is formed is also affected by the KOH aqueous solution, the first layer of the multilayer film (the first layer formed on the silicon wafer) is molybdenum. Since the silicon wafer 61 in the remaining portion of the silicon nitride film 62 remains without being etched, the support portion 65 of the multilayer film 63 is formed. (FIG. 6c) FIG. 7 is a view showing a second method of manufacturing the X-ray beam splitter.

First, a photoresist 7 having a thickness of about 1 μm is formed on the surface of a substrate 71 such as a silicon wafer.
2 is applied. A multi-layer film 73 of molybdenum and silicon is formed thereon by high-frequency magnetron sputtering (FIG. 7A). The cycle length and the number of layers of the multilayer film 73 are X
A desired angle of incidence of the line beam splitter and a value at which a reflectance or a transmittance is obtained are appropriately set.

Generally, a thin film formed by sputtering often has a compressive stress. Here, the film forming conditions are adjusted so that the internal stress of the multilayer film is close to zero. Specifically, the gas pressure at the time of film formation is normally set (for example, 5 mTorr).
Slightly higher than the above (for example, about 20 mTorr)
Alternatively, the internal stress can be reduced by heating the substrate to, for example, about 100 ° C. during film formation.

Next, the substrate 71 having the multilayer film 73 formed on the surface is immersed in an organic solvent such as acetone. Then, since the resist 72 is dissolved in the organic solvent, the multilayer film 73 is peeled off from the substrate 71. This multilayer film 7
7 (FIG. 7b) by scooping it and attaching it to another substrate 74 on which a window (opening) 75 and a support portion 76 have been formed in advance using an adhesive, as shown in FIG. 7c. The X-ray beam splitter is completed.

Next, an example of the characteristics of the X-ray beam splitter thus manufactured will be described. FIG. 8 shows the reflectance (solid line) and transmittance (dashed line) of an X-ray beam splitter used at a wavelength of 13 nm and an incident angle of 45 degrees. In the multilayer film, the thickness of the molybdenum layer is 3.2 nm, the thickness of the silicon layer is 6.4 nm, the number of stacked layers is 12 pairs, and the total thickness is 11 nm.
5.2 nm. Since the reflectance is 33% and the transmittance is 34%, the efficiency (product of the reflectance and the transmittance) of the X-ray beam splitter is 11%.

FIG. 9 shows the reflectance (solid line) and transmittance (dashed line) of an X-ray beam splitter used at a wavelength of 13 nm and an incident angle of 15 degrees. The multilayer film has a molybdenum layer thickness of 2.
The thickness is 3 nm, the thickness of the silicon layer is 4.6 nm, the number of stacked layers is 13 pairs, and the total thickness is 89.7 nm. The reflectivity is 39
% And the transmittance is 43%, the efficiency (product of the reflectance and the transmittance) of this X-ray beam splitter is 17%.

FIG. 10 shows the reflectance (solid line) and transmittance (dashed line) of an X-ray beam splitter used at a wavelength of 13 nm and an incident angle of 60 degrees. In a multilayer film, the thickness of the molybdenum layer is
4.8 nm, the thickness of the silicon layer is 9.6 nm, the number of stacked layers is four pairs, and the total thickness is 57.6 nm. The reflectance is 41
% And the transmittance is 33%, the efficiency (product of the reflectance and the transmittance) of the X-ray beam splitter is 14%.

The above three X-ray beam splitters are used for non-polarized X-rays, and are used when a laser plasma X-ray source is used as a light source. Since the emitted light is linearly polarized light, the configuration of the multilayer film is slightly different in that case.
FIG. 11 shows an incident angle of 45 nm for s-polarized light having a wavelength of 13 nm.
Of X-ray beam splitter used in degrees (solid line)
And the transmittance (broken line). In the multilayer film, the thickness of the molybdenum layer is 3.2 nm, the thickness of the silicon layer is 6.4 nm, the number of stacked layers is 6 pairs, and the total thickness is 57.6 nm. Since the reflectance is 38% and the transmittance is 44%, the efficiency (product of the reflectance and the transmittance) of the X-ray beam splitter is 17%.

Next, an embodiment of the X-ray projection exposure apparatus according to the present invention will be specifically described. FIG.
1 is a first embodiment of an X-ray projection exposure apparatus according to the present invention using a 5-degree X-ray beam splitter. Such devices are:
It is installed in a vacuum chamber (not shown) and operates under a predetermined degree of vacuum. When a laser plasma X-ray source is used as the X-ray source 2, an X-ray having the characteristics shown in FIG.
When a line beam splitter is used and a radiation light source is used, an X-ray beam splitter having characteristics shown in FIG. 11 is used. In the latter case, the optical axis of the projection imaging optical system 6 is
It is arranged to be perpendicular to the electron orbit plane (usually horizontal plane) of the synchrotron radiation light source.

The X-rays emitted from the illumination optical system 3 are reflected by the X-ray beam splitter 1 and then vertically incident on a mask 4 held on a mask stage 5. The intensity of the X-ray transmitted through the X-ray beam splitter 1 is monitored by an X-ray detector (an example of a detecting unit) 10a. Mask 4
Immediately before, a slit 9 having an arc-shaped opening for limiting an exposure area is provided. An X-ray detector (an example of a detecting means) 10b is also provided on this slit, and monitors the intensity of the X-ray.

When the X-ray beam splitter 1 is damaged,
Since the output of the X-ray detector 10a increases and the output of the X-ray detector 10b decreases, breakage can be immediately detected. The X-rays reflected perpendicularly by the mask 4 enter the X-ray beam splitter 1 again, pass through the X-ray beam splitter 1, and then enter the projection / imaging optical system 6. In this embodiment, the projection imaging optical system 6
An optical system composed of four aspherical reflecting surfaces was used. Each reflecting surface is coated with a multilayer film made of molybdenum and silicon for reflecting X-rays.

This optical system is a telecentric optical system on both the object side (mask side) and the image side (wafer side). The image side (wafer side) numerical aperture of this optical system is
0.08, the reduction ratio is 1/4, at a wavelength of 13 nm
It has a resolution of 0.1 μm. The projection imaging optical system 6 forms an image of a mask pattern on the surface of the wafer 7 held on the wafer stage 8.

Since the area to be exposed at a time is a thin arc-shaped area having a width of 0.5 mm and a length of 30 mm, the mask stage 5 and the wafer stage 8 are moved to move the mask 4 and the wafer 7 according to the reduction ratio. The entire pattern on the mask 4 is transferred to an exposure area of 30 mm square by performing synchronous scanning (scanning) at the set speed ratio. After exposing one exposure area on the wafer 7, the wafer stage 8
Is moved to shift the position of the wafer 7 (stepping), and the next exposure area is scanned again to transfer the pattern.

By repeating such a step-and-scan operation, a pattern is transferred onto the entire surface of the wafer 7 having a diameter of 8 inches to 12 inches. The X-ray projection exposure apparatus of the present embodiment is provided with a vibration driving means (an example of a vibration means) 101 for vibrating the X-ray beam splitter 1 in the plane thereof, thereby reinforcing (supporting) the self-supporting multilayer film. ) Prevents unevenness in the illuminance of the exposure area due to the beam (support portion).

In the exposure apparatus of this embodiment, a spare X
X-ray beam splitter storage section (an example of storage means) 103 for storing 20 X-ray beam splitters, and storage section 1
A transport unit (an example of an exchange unit) 102 that transports and exchanges the X-ray beam splitter from 03 to a position at the time of use is provided. As soon as the X-ray detector 10 (10a, 10b) detects the damage of the X-ray beam splitter 1, the X-ray beam splitter 1 damaged by the transport means 102 is replaced with a spare part stored in the storage unit 103. Is done.

Since it is not necessary to break the vacuum and replace the X-ray beam splitter 1 and evacuate again to a predetermined degree of vacuum, the operation stop time of the exposure apparatus is minimized (to several tens of seconds).
The throughput can be greatly improved. FIG. 13 shows a second embodiment of the X-ray projection exposure apparatus according to the present invention using an X-ray beam splitter having an incident angle of 15 degrees. Such an apparatus is installed in a vacuum chamber (not shown) and operates under a predetermined degree of vacuum.

As the X-ray source 2, a laser plasma X-ray source is used. X-rays emitted from the illumination optical system 3 are reflected by the X-ray beam splitter 1 and then reflected by a mask stage 5.
Incident on the mask 4 held in the vertical direction. The intensity of the X-ray transmitted through the X-ray beam splitter 1 is monitored by an X-ray detector (an example of a detecting unit) 10a. Immediately before the mask 4, a slit 9 having an arc-shaped opening for limiting an exposure area is provided. An X-ray detector (an example of a detecting means) 10b is provided also on this slit,
Monitor the strength of the line.

When the X-ray beam splitter 1 is damaged,
Since the output of the X-ray detector 10a increases and the output of the X-ray detector 10b decreases, breakage can be immediately detected. The X-rays reflected perpendicularly by the mask 4 enter the X-ray beam splitter 1 again, pass through the X-ray beam splitter 1, and then enter the projection / imaging optical system 6. In this embodiment, the projection imaging optical system 6
Used an optical system composed of two aspherical reflecting surfaces. Each reflecting surface is coated with a multilayer film made of molybdenum and silicon for reflecting X-rays.

This optical system is a telecentric optical system on both the object side (mask side) and the image side (wafer side). The image side (wafer side) numerical aperture of this optical system is 0.
08, the reduction ratio is 1/4, and is 0.
It has a resolution of 1 μm. The projection imaging optical system 6 forms an image of a mask pattern on the surface of the wafer 7 held on the wafer stage 8.

Since the area to be exposed at one time is a thin arc-shaped area having a width of 0.5 mm and a length of 30 mm, the mask 4 and the wafer 7 are synchronously scanned at a speed ratio according to the reduction magnification. Thereby, the entire pattern on the mask 4 is transferred to an exposure area of 30 mm square. After exposing one exposure area on the wafer 7, the position of the wafer 7 is shifted (stepped) by moving the wafer stage 8, and the next exposure area is scanned again to transfer the pattern.

By repeating such a step-and-scan operation, a pattern is transferred onto the entire surface of the wafer 7 having a diameter of 8 inches to 12 inches. The X-ray projection exposure apparatus of the present embodiment is provided with a vibration driving means (an example of a vibration means) 101 for vibrating the X-ray beam splitter 1 in the plane thereof, thereby reinforcing (supporting) the self-supporting multilayer film. ) Prevents unevenness in the illuminance of the exposure area due to the beam (support portion).

In the exposure apparatus of this embodiment, a spare X
X-ray beam splitter storage section (an example of storage means) 103 for storing 20 X-ray beam splitters, and storage section 1
A transport unit (an example of an exchange unit) 102 that transports and exchanges the X-ray beam splitter from 03 to a position at the time of use is provided. As soon as the X-ray detector 10 (10a, 10b) detects the damage of the X-ray beam splitter 1, the X-ray beam splitter 1 damaged by the transport means 102 is replaced with a spare part stored in the storage unit 103. Is done.

Since it is not necessary to break the vacuum and replace the X-ray beam splitter 1 and evacuate it again to a predetermined degree of vacuum, the operation stop time of the exposure apparatus is minimized (to several tens of seconds).
The throughput can be greatly improved. FIG. 14 shows a third embodiment of the X-ray projection exposure apparatus according to the present invention using an X-ray beam splitter having an incident angle of 60 degrees. Such an apparatus is installed in a vacuum chamber (not shown) and operates under a predetermined degree of vacuum.

As the X-ray source 2, a laser plasma X-ray source is used. The X-rays emitted from the illumination optical system 3 are transmitted through the X-ray beam splitter 1 and then vertically incident on a mask 4 held on a mask stage 5. Immediately before the mask 4, a slit 9 having an arcuate opening for limiting an exposure area is provided. An X-ray detector 10b is provided on this slit to monitor the intensity of the X-ray.

When the X-ray beam splitter 1 is damaged,
Since the output of the X-ray detector 10b decreases, damage can be immediately detected. The X-rays reflected perpendicularly by the mask 4 enter the X-ray beam splitter 1 again, are reflected from the X-ray beam splitter 1, and then enter the projection imaging optical system 6. In this embodiment, an Offner optical system that reflects three times on two spherical reflecting surfaces is used as the projection imaging optical system 6. On each reflective surface,
A multilayer film made of molybdenum and silicon for reflecting X-rays is coated.

This optical system is a telecentric optical system on both the object side (mask side) and the image side (wafer side). The image side (wafer side) numerical aperture of this optical system is 0.
08, reduction ratio is 1 ×, 0.1 at wavelength 13nm
It has a resolution of μm. In order to prevent interference between the mask stage 5 and the wafer stage 8, a planar multilayer mirror 141 for bending an X-ray beam is provided after the projection imaging optical system 6.

The projection imaging optical system 6 forms an image of a mask pattern on the surface of the wafer 7 held on the wafer stage 8. Since the area exposed at a time is a thin arc-shaped area having a width of 0.5 mm and a length of 30 mm, the mask 4 and the wafer 7 are synchronously scanned (scanned) at the same speed to form an exposure area of 30 mm square. The entire pattern on the mask 4 is transferred.

After exposing one exposure area on the wafer 7, the wafer stage 8 is moved to shift the position of the wafer 7 (stepping), and the next exposure area is scanned again to transfer a pattern. By repeating such a step-and-scan operation, a pattern is transferred onto the entire surface of the wafer 7 having a diameter of 8 inches to 12 inches.

The X-ray projection exposure apparatus of this embodiment is provided with a vibration driving means (an example of a vibration means) 101 for vibrating the X-ray beam splitter 1 in the plane thereof. The illuminance unevenness of the exposure area is prevented from being caused by the reinforcing (supporting) beams (supporting portions). Further, the exposure apparatus of the present embodiment has two spare X-ray beam splitters.
X-ray beam splitter storage section (an example of storage means) 103 for storing 0 sheets, and X is moved from storage section 103 to a position for use
A transport unit (an example of an exchange unit) 102 that transports and exchanges the line beam splitter is provided.

As soon as the X-ray detector 10 detects that the X-ray beam splitter 1 is damaged, the conveying means 102
The X-ray beam splitter 1 damaged by the
It is exchanged for the spare part stored in 03. Since it is not necessary to break the vacuum and replace the X-ray beam splitter 1 and evacuate it again to a predetermined degree of vacuum, the operation stop time of the exposure apparatus can be minimized (to several tens of seconds). Significantly improved.

[0065]

As described above, according to the present invention, the angle of incidence of X-rays on the reflection type mask can be made vertical.
It is possible to use an object-side (mask-side) telecentric projection imaging optical system that cannot be used in a conventional X-ray projection exposure apparatus, and it is possible to greatly improve the imaging performance of the exposure apparatus.

Since the reflection angle of the X-ray beam splitter according to the present invention can be set to an arbitrary value, the components of the exposure apparatus (X-ray source, illumination optical system, mask stage, projection imaging optical system) System, wafer stage, etc.)
The degree of freedom in the arrangement of the exposure apparatus is increased, and the entire exposure apparatus can be designed to be compact.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an example of an X-ray projection exposure apparatus of the present invention.

FIG. 2 is a configuration diagram showing another example of the X-ray projection exposure apparatus of the present invention.

FIG. 3 is a schematic plan view (a) and a schematic cross-sectional view (b) showing an example of an X-ray beam splitter according to the present invention.

FIG. 4 is a schematic perspective view showing an example of a ring field optical system.

FIG. 5 is a configuration diagram showing an example of a conventional soft X-ray projection exposure apparatus.

FIG. 6 is a schematic sectional view illustrating an example (first manufacturing method) of a method of manufacturing an X-ray beam splitter according to the present invention.

FIG. 7 is a schematic cross-sectional view illustrating an example (second manufacturing method) of a method of manufacturing an X-ray beam splitter according to the present invention.

FIG. 8 is a reflection and transmission characteristic diagram of a first X-ray beam splitter used in the example.

FIG. 9 is a graph showing the reflection and transmission characteristics of a second X-ray beam splitter used in an example.

FIG. 10 is a graph showing the reflection and transmission characteristics of a third X-ray beam splitter used in an example.

FIG. 11 is a reflection and transmission characteristic diagram of a fourth X-ray beam splitter used in the example.

FIG. 12 is a configuration diagram showing a first embodiment of an X-ray projection exposure apparatus according to the present invention.

FIG. 13 is a configuration diagram showing a second embodiment of the X-ray projection exposure apparatus according to the present invention.

FIG. 14 is a configuration diagram showing a third embodiment of the X-ray projection exposure apparatus according to the present invention.

[Explanation of Signs of Main Parts]

DESCRIPTION OF SYMBOLS 1 X-ray beam splitter 2 X-ray source 3 Illumination optical system 4 Reflective mask 5 Mask stage 6 Projection imaging optical system 7 Wafer 8 Wafer stage 9 Slit 10 X-ray detector (an example of a detection means) 11 Substrate 12 Window part ( (Opening) 13 Multilayer 14 Support 20 Ring field optical system 21 Optical axis 22 Ring field 23 Mask 24 Wafer 25 Arc-shaped exposure region 61 Silicon wafer 62 Silicon nitride film 63 Multilayer film 64 Window (opening) 65 Support Unit 71 Silicon wafer 72 Resist layer 73 Multi-layer film 74 Substrate 75 Window (opening) 76 Support unit 101 X-ray beam splitter vibration driving unit (an example of a vibration unit) 102 X-ray beam splitter transport unit (an example of an exchange unit) 103 X-ray beam splitter storage (Example of storage means)

────────────────────────────────────────────────── ─── Continued on the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 21/027 G03F 7/20 INSPEC (DIALOG) WPI (DIALOG)

Claims (7)

(57) [Claims] At least an X-ray source, an illumination optical system for irradiating an X-ray emitted from the X-ray source onto a reflective mask, and an image of a pattern formed on the mask projected and formed on a wafer An X-ray projection exposure apparatus comprising a projection imaging optical system, wherein an X-ray principal ray from the illumination optical system is vertically incident on the surface of the reflective mask, and the X-ray is vertically reflected by the reflective mask. An X-ray projection exposure apparatus, comprising: an X-ray beam splitter that causes the principal ray of the light to enter the projection imaging optical system in parallel with the optical axis of the optical system. 2. The X-ray beam splitter according to claim 1, wherein the X-ray beam splitter includes at least a substrate having an opening and a free-standing multilayer film formed on the substrate so as to cover the opening. The X-ray projection exposure apparatus according to claim 1. 3. An X-ray projection exposure apparatus according to claim 2, wherein a beam-shaped support portion for supporting said self-supporting multilayer film is provided at an opening of said X-ray beam splitter. 4. An X-ray projection exposure apparatus according to claim 1, further comprising a vibration means for vibrating said X-ray beam splitter in a direction parallel to a surface thereof. 5. A detecting means for detecting breakage of said X-ray beam splitter.
The X-ray projection exposure apparatus according to claim 1. 6. A storage means for storing a plurality of X-ray beam splitters, and an X-ray beam splitter whose damage has been detected by said detection means is stored in said storage means.
6. An X-ray projection exposure apparatus according to claim 5, further comprising an exchange means for exchanging with the X-ray beam splitter. 7. The X-ray beam splitter according to claim 1, wherein
7. An X-ray projection exposure apparatus according to claim 1, wherein the reflectance and the transmittance for rays are equal or substantially equal.