JPH07283105A - X-ray reflection mask and x-ray projection aligner - Google Patents

Abstract

PURPOSE:To provide a novel X-ray reflection mask which eliminates the need of a complicated illumination optical system and an optical integrator of low efficiency such as a fly's eye mirror and thereby enables improvement of through-put and an X-ray projection aligner with the mask. CONSTITUTION:An X-ray reflection mask is formed by forming a pattern consisting of a plurality of reflection parts 1 which reflect X-ray and a plurality of non reflection parts 2 which do not reflect X-ray on a substrate 3. In the mask, a surface of each reflection part 1 is a and relation of D/R<A is satisfied in a projecting surface or a recessed surface and an X-ray when an incidence side numerical aperture is A, width of each reflection part is D and a curvature radius of an arc is R in a projection imaging optical system for imaging reflection light from a mask on a wafer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray reflection type mask used in X-ray lithography and an X-ray projection exposure apparatus equipped with the mask.

[0002]

2. Description of the Related Art In recent years, with the miniaturization of semiconductor integrated circuit elements, in order to improve the resolution of an optical system which is limited by the diffraction limit of light, conventional ultraviolet rays (wavelengths 193 to 436) are used.
nm) instead of soft X-rays (wavelength 5)
˜20 nm) has been developed.

As shown in FIG. 12, the X-ray projection exposure apparatus used in this technique mainly comprises an X-ray source 32, an illumination optical system 33, a mask 34 and a mask stage 35, a projection imaging optical system 36, a wafer stage. 38 and the like. In the wavelength range of X-rays, since no transparent substance exists and the reflectance on the surface of the substance is very low, 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 X-rays obliquely incident on the reflecting surface using total reflection, and an interference effect by matching the phases of the reflected light at each interface of the multilayer film. It is composed of a multi-layered film mirror or the like that obtains higher reflectance.

The grazing incidence mirror can obtain a reflectance close to 100%, but since the grazing incidence angle (incident angle measured from the reflecting surface) can be used only at a grazing incidence of 10 degrees or less, the aberration is corrected. It is difficult to construct an optical system. The multilayer mirror can also reflect X-rays vertically, but 1
A reflectance close to 00% cannot be obtained. The highest reflectance is obtained when a multilayer film made of molybdenum and silicon is used on the wavelength side longer than the L absorption edge (12.3 nm) of silicon, but at a wavelength of 13 to 15 nm, the reflectance is 70% regardless of the incident angle.
It is a degree. On the shorter wavelength side than the L absorption edge of silicon,
A multilayer film that can obtain a reflectance of 30% or more at normal incidence has not been developed.

As an X-ray source, a synchrotron radiation source (Synchrotron Ra
A light source capable of obtaining intense soft X-rays such as a diation source) or a laser plasma X-ray source is used. The synchrotron radiation light source uses an electromagnetic wave radiated in a tangential direction of an electron orbit when an electron moving at a speed close to the speed of light is deflected in its traveling direction by a magnetic field. Laser plasma X
When the target is irradiated with a strong laser pulse, the radiation source is a material in which the vaporized target material is turned into plasma, and electromagnetic waves including X-rays are radiated from the plasma.

The illumination optical system is composed of a grazing incidence mirror, a multilayer mirror, a filter which transmits or reflects only X-rays of a predetermined wavelength, and illuminates the mask with X-rays of a predetermined wavelength. The mask includes a transmission type mask and a reflection type mask.
The transmissive mask has a pattern formed by providing a substance that absorbs X-rays in a predetermined shape on a thin membrane made of a substance that transmits X-rays well. On the other hand, the reflective mask is a pattern formed by providing a portion having a low reflectance in a predetermined shape on a multilayer film that reflects X-rays.

In order to suppress the absorption of X-rays, the transmissive mask must use a very fragile membrane having a thickness of about 0.1 μm or less, so that it has a practical size (for example, 120 × 120 mm or more). Cannot be manufactured. On the other hand, since the reflective mask can use a thick substrate having sufficient mechanical strength, the reflective mask is used when the X-ray projection exposure technique is applied to actual semiconductor manufacturing.

The pattern formed on such a mask is imaged on a wafer by a projection imaging optical system composed of a plurality of multi-layer film mirrors and transferred to a photoresist coated on the wafer. . It is necessary that the projection / imaging optical system is constructed of a reflective system using a multilayer mirror. Moreover, the reflectance of the multilayer mirror is not very high.
Therefore, in order to obtain a practical throughput, it is necessary to reduce the number of multilayer film mirrors as much as possible, and it is not easy to correct the aberration over the entire wide exposure area.

Therefore, for example, US Pat.
, The required exposure area (eg 3
In addition to an optical system for exposing (0 × 30 mm) at a time, as described in, for example, Japanese Patent Laid-Open No. 4-333011,
An optical system has also been devised which secures an exposure region of a required size by synchronously scanning a mask and a wafer while exposing a ring-shaped region (for example, about 30 × 0.5 mm).

Since X-rays are absorbed by the atmosphere and attenuated, the optical paths of the X-rays are all maintained at a predetermined degree of vacuum.
Generally, in diffraction-limited imaging in which the aberration of the optical system is sufficiently small and the influence of the aberration can be ignored, the resolving power of the optical system depends not only on the performance of the imaging system but also on the object (mask in the case of lithography). It depends on the way of lighting.

The ratio of the numerical aperture of the illumination light to the incident numerical aperture of the imaging system is called the coherence factor σ. The case of σ = 0 is called image formation by coherent illumination, and in this case, the object is illuminated with a parallel light beam incident from a single direction. At this time, the transfer function (OTF) of the optical system is, as shown in FIG. 3, NA / λ (NA is the numerical aperture on the exit side of the imaging system,
λ shows a constant value up to the spatial frequency determined by the wavelength of the illumination light), but when it exceeds this spatial frequency, it becomes 0 and is not resolved.

On the other hand, the case of σ = 1 is called image formation by incoherent illumination. In this case, the object is illuminated with a ray having a divergence angle that fills the entire entrance side aperture of the image forming system. At this time, the OTF gradually decreases as the spatial frequency increases, but does not become 0 up to the spatial frequency of 2NA / λ. Therefore, although the image contrast is reduced, incoherent illumination can resolve a pattern with a higher spatial frequency. Partial coherent illumination of 0 <σ <1 is used for an illumination optical system of an exposure apparatus which requires a diffraction limit resolution, in consideration of resolution and contrast.

In an actual exposure apparatus, on the mask,
For example, in a wide area of about 120 × 120 mm,
It is required that the conditions of the partial coherent illumination as described above are satisfied and that the illuminance is uniform. As an illumination optical system satisfying such a condition, a Koehler illumination optical system as shown in FIG. 2 is widely and generally used. The function of the Koehler illumination system will be briefly described below.

The light beam emitted from the light source 20 is first converted into a parallel light beam by the first lens 21 and then incident on the optical integrator 22. The optical integrator 22 spatially splits the parallel light flux and focuses each split light flux, so that a multiplexed image 23 of the light source 20 is formed. In an exposure apparatus that uses ultraviolet light, a fly-eye lens is generally used as the optical integrator 22.

Next, the light rays diverging from the individual light source images 23 are converted into parallel light flux by the second lens 24, and thereafter,
Illuminate the object 25. Ray bundles emitted from different light source images 23 enter the object 25 from different directions. At this time, the thickness of the parallel light flux in the middle (between the first lens 21 and the optical integrator 22) determines the NA (numerical aperture) of the illumination light, and the divergence angle from the multiplexed light source image 23 is the illumination area. Will determine the size of. Since the light emitted from the point light source is converted into parallel light to illuminate the object, the illuminance unevenness is small. Moreover, it is easy to change the numerical aperture of the illumination.

In order to realize the Koehler illumination system as described above in the X-ray projection exposure apparatus, it is necessary to configure all optical systems equivalent to those shown in FIG. 2 with reflective optical systems using multilayer mirrors. is there.

[0017]

As an optical integrator that can be used for X-rays, there is a fly-eye mirror described in Japanese Patent Application No. 5-21577. This is a mirror in which a multilayer film is formed on a substrate provided with a large number of fine projections or depressions. As an illumination optical system using such a fly-eye mirror, for example, Japanese Patent Application No.
237654 describes an optical system for Koehler illumination of a ring-shaped area using a synchrotron radiation source, a fly-eye mirror, and a rotating mirror group.

However, the Koehler illumination optical system using such a fly-eye mirror requires a complicated optical system, so that the number of multilayer mirrors increases. Also,
Since the fly-eye mirror diverges the light rays, the loss of light amount becomes large. Therefore, there is a problem that the throughput of the X-ray projection exposure apparatus becomes considerably lower than a practically required value (for example, 30 sheets / 1 hour for an 8-inch wafer).

The present invention has been made in view of the above-mentioned conventional problems, and it is not necessary to use a complicated illumination optical system or a low-efficiency optical integrator such as a fly-eye mirror. An object of the present invention is to provide a novel X-ray reflection type mask that can be improved and an X-ray projection exposure apparatus including the mask.

[0020]

Therefore, in the first aspect of the present invention, "a pattern including a plurality of reflecting portions that reflect X-rays and a plurality of non-reflecting portions that do not reflect X-rays is formed on a substrate. In the X-ray reflection type mask, the projection imaging optical system for forming the reflected light from the mask on the wafer, in which the surface of each reflection part is a convex surface or a concave surface of a strip having an arcuate cross section. Of the incident side numerical aperture A, the width D of each of the reflecting portions, and the radius of curvature R of the arc, the convex surface or the concave surface satisfying the relationship of D / R <A. (Claim 1) "is provided.

A second aspect of the present invention is an "X-ray reflection type in which a pattern including a plurality of reflecting portions that reflect X-rays and a plurality of non-reflecting portions that do not reflect X-rays is formed on a substrate. In the mask, the surface of each of the reflecting portions is a convex surface or a concave surface of a strip having an arcuate cross section, and the incident side numerical aperture A of the projection image forming optical system for forming an image of the reflected light from the mask on the wafer. , A width D of each of the reflecting portions, and a radius of curvature R of the arc, a convex surface or a concave surface satisfying a relationship of 0.3 A <D / R <A. 2) ”is provided.

Further, a third aspect of the present invention is an "X-ray reflection type in which a pattern composed of a plurality of reflecting portions that reflect X-rays and a plurality of non-reflecting portions that do not reflect X-rays is formed on a substrate. In the mask, the surface of each of the reflecting portions is a convex surface or a concave surface of a strip having an arcuate cross section, and the incident side numerical aperture A of the projection image forming optical system for forming an image of the reflected light from the mask on the wafer. , The width D of each of the reflecting portions and the radius of curvature R of the arc, the convex surface or the concave surface satisfying the relationship of 0.5 A ≦ D / R ≦ 0.7 A. Item 3) ”is provided.

In a fourth aspect of the present invention, a pattern is formed on a substrate, which includes a plurality of reflecting portions having a width D1 that reflects X-rays and a plurality of non-reflecting portions having a width D2 that does not reflect X-rays. In the X-ray reflection type mask, the numerical aperture NA of the exit side of the projection imaging optical system that forms the reflected light from the mask on the wafer, the width D1 of each reflection portion, and the width D2 of each non-reflection portion. , Between the wavelength X of the X-ray used, D1 + D2 <
The surface of the reflecting portion satisfying the relationship of σ × λ / NA (0 <σ <1) is a convex surface or a concave surface of a strip having an arc-shaped cross section, and the reflected light from the mask is imaged on the wafer. A convex surface or a concave surface satisfying the relationship of D1 / R <A among the entrance-side numerical aperture A of the projection imaging optical system, the width D1 of each of the reflecting portions, and the radius of curvature R of the arc, and the above relationship is not satisfied. There is provided an X-ray reflection type mask (claim 4), characterized in that the surface of the reflection portion is a flat surface.

In a fifth aspect of the present invention, a pattern is formed on a substrate, which includes a plurality of reflecting portions having a width D1 that reflects X-rays and a plurality of non-reflecting portions having a width D2 that does not reflect X-rays. In the X-ray reflection type mask, the numerical aperture NA of the exit side of the projection imaging optical system that forms the reflected light from the mask on the wafer, the width D1 of each reflection portion, and the width D2 of each non-reflection portion. , Between the wavelength X of the X-ray used, D1 + D2 <
The surface of the reflection part satisfying the relationship of σ × λ / NA (0.3 <σ <1) is a convex surface or a concave surface of a strip having an arc-shaped cross section, and the reflected light from the mask is imaged on the wafer. 0.3 A <D1 between the entrance-side numerical aperture A of the projection imaging optical system, the width D1 of each of the reflecting portions, and the radius of curvature R of the arc.
The X-ray reflection type mask (claim 5) is characterized in that it has a convex surface or a concave surface that satisfies the relationship of / R <A, and the surface of the reflecting portion that does not satisfy the relationship is a flat surface.

A sixth aspect of the present invention is that "a pattern is formed on a substrate, which is composed of a plurality of reflecting portions having a width D1 that reflects X-rays and a plurality of non-reflecting portions having a width D2 that does not reflect X-rays. In the X-ray reflection type mask, the numerical aperture NA of the exit side of the projection imaging optical system that forms the reflected light from the mask on the wafer, the width D1 of each reflection portion, and the width D2 of each non-reflection portion. , Between the wavelength X of the X-ray used, D1 + D2 <
The surface of the reflection part satisfying the relationship of σ × λ / NA (0.5 ≦ σ ≦ 0.7) is a convex surface or a concave surface of a strip having an arc-shaped cross section, and the reflected light from the mask is imaged on the wafer. Between the numerical aperture A on the incident side of the projection imaging optical system, the width D1 of each reflecting portion, and the radius of curvature R of the arc, 0.5 A ≦ D /
An X-ray reflection type mask (claim 6), characterized in that it is a convex surface or a concave surface that satisfies the relationship of R ≦ 0.7 A, and the surface of the reflecting portion that does not satisfy the relationship is a flat surface.

In a seventh aspect of the present invention, "a multilayer film that reflects X-rays of a predetermined wavelength is formed on each of the reflection portions, and the multilayer film and the X-rays on the multilayer film are formed on each of the non-reflection portions. An X-ray reflective mask (claim 7) according to claims 1 to 6, which is formed by stacking absorption films. The eighth aspect of the present invention is that "a multilayer film that reflects X-rays of a predetermined wavelength is formed in each of the reflection portions, and a multilayer film in which the periodic structure of the multilayer film is destroyed is formed in each of the non-reflection portions. An X-ray reflection type mask (claim 8) according to claims 1 to 6 is provided.

In a ninth aspect of the present invention, "the X-ray reflection type mask according to any one of claims 1 to 6, wherein a multilayer film that reflects X-rays of a predetermined wavelength is formed only on each of the reflecting portions. (Claim 9) "is provided. The tenth aspect of the present invention is "at least an X-ray source, the X-ray reflective mask according to any one of claims 1 to 9, and a projection connection for projecting an image of a pattern formed on the mask onto a wafer. And an X-ray projection exposure apparatus (Claim 10) including an image optical system.

The eleventh aspect of the present invention is "at least X
A radiation source, the X-ray reflection type mask according to claim 1, an illumination optical system that illuminates X-rays emitted from the X-ray source with a parallel light flux on the mask, and is formed on the mask. An X-ray projection exposure apparatus (claim 11) including a projection imaging optical system that projects and forms an image of the pattern on a wafer.

[0029]

In the conventional X-ray reflection type mask, the incident light (X
Since the line) is specularly reflected, a complicated illumination system such as Koehler illumination is necessary to perform partial coherent imaging. On the other hand, in the present invention, for example, as shown in FIG. 1, each reflecting portion 1 of the reflective mask is formed into a curved surface (a convex surface or a concave surface of a strip having an arcuate cross section), thereby making the incident light beam incident on the mask itself. Since a function for diverging the light is provided, even if the mask is illuminated with a parallel light flux, it is possible to realize image formation equivalent to partial coherent illumination. Therefore, a complicated illumination system as in the past is not required. The principle will be described below.

For example, as shown in FIGS. 7 and 8, when a parallel light beam enters a reflecting portion 1 which is a convex surface or a concave surface of a strip having an arcuate cross section, the reflected light has a different reflection direction depending on the incident position. So it reflects as if diverging.
Using the paraxial ray approximation where the center of the arc is O and the radius is R, and the incident angle is sufficiently small, that is, near normal incidence, the focal point F of the reflecting surface is from the center O of the circle to the direction of the incident ray. It is in the R / 2 position.

When a parallel light beam is incident on such a reflecting portion 1, the reflected light becomes a bundle of rays diverging from the focal point F. Assuming that the width of the reflecting portion 1 is D and half the angle extending from the center O to the reflecting portion 1 is θ, θ is sufficiently small, so that D = 2Rθ holds. This is equal to D / R because the divergence angle of the rays diverging from the focal point F is 2θ on one side. That is, even though the mask is illuminated with a parallel light flux, its reflected light flux has a divergence angle of D / R, which illuminates a normal reflective mask with illumination light whose numerical aperture is equal to D / R. Is equivalent to the case.

Therefore, if the incident side numerical aperture of the projection imaging optical system is A and the radius of curvature R of the arc is set so as to satisfy σA = D / R (0 <σ <1), illumination by a parallel light beam is performed. According to this, partial coherent imaging with a coherence factor σ can be realized (claim 1). In order to achieve both good image contrast and high resolution, the coherence factor σ is preferably set in the range of 0.3 <σ <1 (Claim 2), especially 0.5 ≦ σ
It is preferable to set it in the range of ≤0.7 (claim 3).

Further, the numerical aperture NA on the exit side of the projection imaging optical system for focusing the light reflected from the mask on the wafer,
Between the width D1 of each reflection portion, the width D2 of each non-reflection portion, and the wavelength λ of the X-ray used, D1 + D2 <σ × λ / NA
A projection imaging optical system in which the surface of the reflecting portion satisfying the relationship of (0 <σ <1) is a convex surface or a concave surface of a strip having an arcuate cross section, and forms the reflected light from the mask on a wafer. Of the incident side numerical aperture A, the width D1 of each of the reflecting portions, and the radius of curvature R of the circular arc is a convex surface or a concave surface that satisfies the relationship of D1 / R <A, and the surface of the reflecting portion that does not satisfy the relationship is It is preferable to use a flat surface (claim 4). As is clear from FIG. 3, in the case of a pattern having a spatial frequency lower than NA / λ, a high-contrast image can be obtained by imaging with coherent illumination of σ = 0. Therefore, for such a pattern, it is preferable that the reflecting portion is a flat surface.

On the other hand, a pattern having a spatial frequency higher than NA / λ is not resolved when σ = 0. Therefore, for such a pattern, it is preferable that the reflection portion is the convex surface or the concave surface. By this, the image formation by the partial coherent illumination of 0 <σ <1 can be realized, and thus the high spatial frequency is achieved. You can even get a statue. Here, in order to achieve both good image contrast and high resolution, the coherence factor σ should be set in the range of 0.3 <σ <1, and the relation should be 0.3 A <D1 / R <A. Preferably (Claim 5) In particular, it is preferable that the coherence factor σ is set in a range of 0.5 ≤ σ ≤ 0.7 and the relationship is 0.5 A ≤ D / R ≤ 0.7 A (Claim 6).

It is preferable that a multilayer film that reflects X-rays of a predetermined wavelength is formed on each of the reflecting portions, and the multilayer film and an X-ray absorbing film thereon are laminated on each of the non-reflecting portions. (Claim 7). Alternatively, each of the reflecting portions has an X of a predetermined wavelength.
It is preferable to form a multilayer film that reflects a line, and to form a multilayer film in which the periodic structure of the multilayer film is destroyed in each of the non-reflective portions (claim 8).

Alternatively, the X of a predetermined wavelength is provided only in each of the reflecting portions.
It is preferable to form a multilayer film that reflects rays (claim 9). Further, the X-ray reflection type mask according to claim 1,
It is preferably provided in an X-ray projection exposure apparatus having at least an X-ray source and a projection imaging optical system for projecting an image of a pattern formed on a mask onto a wafer (claim 10).

Further, at least the X-ray reflection type mask according to any one of claims 1 to 9, and an illumination optical system for illuminating the X-rays emitted from the X-ray source on the mask with a parallel light beam. ,
It is preferably provided in an X-ray projection exposure apparatus having a projection imaging optical system for projecting an image of a pattern formed on a mask onto a wafer (claim 11). Examples of the X-ray reflective multilayer film according to the present invention include molybdenum / silicon, molybdenum / silicon compounds, ruthenium / silicon,
It is preferable that the ruthenium / silicon compound, the rhodium / silicon compound, the rhodium / silicon compound, and the like are alternately laminated a plurality of times.

As the X-ray absorbing film according to the present invention, for example, a thin film of gold, tungsten, tantalum, nickel or the like is preferable. As described above, according to the X-ray reflection type mask of the present invention, in order to perform the partial coherent imaging, a complicated illumination system such as a Koehler illumination system is not required, and the illumination optical system is greatly simplified. can do. Therefore, it is possible to avoid the loss of the light amount due to the repeated reflection by the multilayer mirror, and the throughput of the exposure apparatus is improved.

In a Koehler illumination system using a fly-eye mirror in a conventional X-ray projection exposure apparatus, any pattern on the mask is illuminated with a light beam bundle having a divergence angle. Is illuminated with parallel light, only the light rays reflected by a fine pattern portion, that is, a pattern portion having a high spatial frequency, have an angular spread. Further, in the conventional illumination system, the light flux spreads symmetrically with respect to the optical axis in all directions. However, in the optical system using the X-ray reflection type mask according to the present invention, the line and space pattern The light rays spread only in the vertical direction, that is, in the direction in which the spatial frequency of the pattern is high.

For the above reasons (2 points), in the present invention, only the ray bundle for the required pattern has a divergence angle, so that there is a divergence such as in a conventional illumination system using a fly-eye mirror. The loss of the light amount due to is almost eliminated, and also from this point, the efficiency of the entire optical system is improved and the throughput of the exposure apparatus is improved. Further, since the reflection type mask is illuminated by the parallel light flux, the illuminance unevenness is small.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0042]

First, the structure of an X-ray reflection type mask according to the present invention will be described. FIG. 4 is a schematic sectional view of an X-ray reflection type mask according to the first embodiment of the present invention. On the substrate 3 made of quartz, silicon, or the like, the surface of the portion to be the reflection portion 1 was a convex surface (FIG. 4a) or a concave surface (FIG. 4b) which a strip having an arcuate cross section had.

The radius of curvature of the convex surface or the concave surface (having an arcuate cross section) is appropriately determined as described in the section of operation (claims 1 to 6).
It was set). In this example, a multilayer film (X-ray reflective multilayer film) 4 that reflects X-rays was formed on the entire surface of the substrate 3. The material forming the multilayer film is appropriately selected according to the wavelength of the X-ray used. For example, for X-rays having a wavelength of about 13 nm, the multilayer film 4 made of molybdenum and silicon (silicon) was used. The multilayer film 4 was formed by a method such as sputtering or vacuum deposition.

The multilayer film 4 is formed on the portion which will be the non-reflecting portion 2.
An absorber layer 5 made of a substance that absorbs X-rays was further formed on the top. For the absorber, for example, a substance such as gold, tungsten, tantalum, nickel or the like was used. As for the absorber layer 5, after forming an absorber layer on the entire surface of the multilayer film 4 by a method such as sputtering or vacuum deposition, only the absorber layer on the reflection part 1 is formed by a method such as reactive ion etching. It was formed by removing.

Alternatively, as for the absorber layer 5, only the multilayer film on the reflecting portion 1 is previously coated with a photoresist, and the multilayer film not covered with the photoresist is sputtered or vacuum deposited on the multilayer film. After the absorber layer is formed by the method described above, only the absorber layer on the reflection portion 1 is removed together with the photoresist by a so-called lift-off method. FIG. 5 is a schematic sectional view of an X-ray reflection type mask which is a second embodiment of the present invention. On the substrate 3 made of quartz, silicon, or the like, the surface of the portion to be the reflection portion 1 was a convex surface (FIG. 5a) or a concave surface (FIG. 5b) that a strip having an arc-shaped cross section had.

The radius of curvature of the convex surface or the concave surface (having an arcuate cross section) is appropriately set as described in the section of the operation (claim 1
~ 6)). In this example, the X-ray reflective multilayer film 4 was formed only on the reflective portion 1 of the substrate 3. For the X-ray reflection multilayer film 4, after forming a multilayer film on the entire surface of the substrate 3 by a method such as sputtering or vacuum deposition, only the multilayer film of the non-reflective portion 2 is removed by a method such as reactive ion etching. Formed by.

Alternatively, in the X-ray reflection multilayer film 4, only the substrate surface of the non-reflecting portion 2 is previously coated with photoresist or the like,
On top of that and on the surface of the substrate not covered with photoresist,
After forming a multi-layer film by a method such as sputtering or vacuum deposition, the so-called lift-off method is used in which only the multi-layer film on the non-reflective portion 2 is removed together with the photoresist. The same material as that of the first embodiment was used as the material forming the multilayer film.

FIG. 6 is a schematic sectional view of an X-ray reflection type mask which is a third embodiment of the present invention. On the substrate 3 made of quartz, silicon, or the like, the surface of the portion to be the reflection portion 1 was a convex surface (FIG. 5a) or a concave surface (FIG. 5b) that a strip having an arc-shaped cross section had. The radius of curvature of the convex surface or the concave surface (having an arcuate cross section) is appropriately determined as described in the section of the action (claims 1 to 1).
6) was set).

In this embodiment, the multilayer film 4 which reflects X-rays is formed on the entire surface of the substrate 3. The same material as that of the first embodiment was used as the material forming the multilayer film. The multilayer film 4 was formed by a method such as sputtering or vacuum evaporation. The non-reflecting portion 2 was formed by breaking the periodic structure of only the multilayer film 4 in the portion forming the non-reflecting portion to reduce the reflectance.

In order to selectively destroy the periodic structure of the multi-layer film 4, only the multi-layer film of the reflection part 1 is previously protected by coating it with a photoresist or the like, and a Kaufman ion source or the like having a large diameter (several mm). (A few tens of mm) An ion source was used to accelerate ions of argon or the like at a few to a few hundred kilovolts to irradiate the entire substrate surface, and then the photoresist was removed.

Alternatively, in order to selectively destroy the periodic structure of the multilayer film 4, a focused ion beam (beam diameter) accelerated to several hundred kilovolts using a liquid metal ion source such as gallium is used.
0.1 μm or less) was selectively applied to the multilayer film in the portion where the non-reflection portion is formed. Next, an embodiment of the X-ray projection exposure apparatus provided with the X-ray reflection type mask according to the present invention will be described below.

FIG. 9 is a schematic block diagram of an X-ray projection exposure apparatus which is the fourth embodiment of the present invention. A synchrotron radiation source is used as the X-ray source, and no illumination optical system is provided. The X-ray reflective mask 34 is illuminated by the X-ray luminous flux 30 from the synchrotron radiation source. The projection / imaging optical system 36 has four spherical surfaces composed of two spherical surfaces.
An optical system with multiple reflections was used. This optical system is 30x30m
This is an optical system that collectively exposes the area m, and the reduction ratio is M = 1.
/ 4, the numerical aperture NA on the exit side is 0.06, and the reflection surface has a wavelength λ =
A molybdenum / silicon multilayer film that reflects 13 nm X-rays is formed. The diffraction limit of image formation by coherent illumination of this optical system has a spatial frequency of NA / λ = 4.
600 cycles / mm, that is, 0.11 μm line and space.

The X-ray reflection type mask 34 has a pattern having a dimension of 0.44 μm or less, in which the reflecting portion of a pattern having a dimension of 0.44 μm or more in line and space corresponding to the diffraction limit in image formation by coherent illumination is a flat surface as usual. The reflecting portion in was a convex surface or a concave surface which a rectangular strip had. The radius of curvature R of the convex surface or concave surface (circular cross section) has a coherence factor σ, and the projection imaging optical system 3
Assuming that the incident side numerical aperture of 6 is A and the width of the reflecting portion on the mask is D, the condition of σA = D / R may be satisfied as described above.
Since A = NA × M, the radius of curvature R is given by R = D / (σ × NA × M) for a pattern of width D.

In this embodiment, the coherence factor σ
= 0.5, R = 133 × D. That is, the reflection portion of the line-and-space pattern of 0.44 μm or less on the X-ray reflection type mask 34 is formed on the convex surface or the concave surface of the rectangular strip having the cross section (the arc is given by this formula. With a radius of curvature). In the X-ray projection exposure apparatus of the present embodiment, when the conventional X-ray reflection type mask is used, it is possible to resolve only 0.11 μm line and space, but the X-ray reflection type mask according to the present invention is used. By using it, it became possible to resolve up to 0.08 μm line and space. Further, since the illumination optical system is not used at all, there is no loss of light quantity, and the throughput is increased by 20 times or more as compared with the case where the conventional Koehler illumination optical system is used.

FIG. 10 is a schematic block diagram of an X-ray projection exposure apparatus which is the fifth embodiment of the present invention. A radiation light source was used as the X-ray source, and an illumination optical system including a cylindrical mirror 40 and a conical mirror 41 having the same rotation axis AX was used. The illumination optical system illuminates the arc-shaped region 42 on the reflective mask 34 with the X-ray light flux 30 which is substantially parallel from the radiation light source. As the projection imaging optical system 36, an optical system composed of two aspherical surfaces is used. This optical system is an optical system that exposes a ring-shaped region having a radius of 30 mm and a width of 0.5 mm, and a reduction magnification M = 1/4,
Emission-side numerical aperture NA = 0.08, reflection surface has wavelength λ = 13n
A molybdenum / silicon multilayer film that reflects the X-rays of m is formed. The diffraction limit of image formation by coherent illumination of this optical system is such that the spatial frequency is NA / λ = 6150.
Cycle / mm, that is, 0.08 μm line and space.

In the X-ray reflection type mask 34, the reflection portion in the pattern having a line and space of 0.32 μm or more corresponding to the diffraction limit in the image formation by the coherent illumination is a flat surface as in the conventional case, and the pattern of 0.32 μm or less is used. The reflecting portion in was a convex surface or a concave surface which a rectangular strip had. The radius of curvature R of the convex surface or concave surface (circular cross section) has a coherence factor σ, and the projection imaging optical system 3
Assuming that the incident side numerical aperture of 6 is A and the width of the reflecting portion on the mask is D, the condition of σA = D / R may be satisfied as described above.
Since A = NA × M, the radius of curvature R is given by R = D / (σ × NA × M) for a pattern of width D.

In this embodiment, the coherence factor σ
= 0.5, R = 100 × D. That is, the reflection portion of the line-and-space pattern of 0.32 μm or less on the X-ray reflection type mask 34 is formed on the convex surface or the concave surface of the strip having an arc-shaped cross section (the arc is given by this formula. With a radius of curvature). In the X-ray projection exposure apparatus of the present embodiment, when the conventional X-ray reflection type mask is used, it is possible to resolve up to 0.08 μm line and space, but the X-ray reflection type mask according to the present invention is used. By using it, it became possible to resolve up to 0.06 μm line and space. Also, since the illumination optical system is simple and a fly-eye mirror, which causes a large loss due to scattering, is not used, there is no loss of light quantity, and the throughput is 5 times or more compared to the case where a conventional Koehler illumination optical system is used. Increased to.

FIG. 11 is a schematic block diagram of an X-ray projection exposure apparatus which is the sixth embodiment of the present invention. A laser plasma light source 43 was used as the X-ray source, and an illumination optical system consisting of a single rotating parabolic mirror 44 was used. Laser plasma light source 43
Is arranged at the focal point of the rotating parabolic mirror 44, and the X-ray diverging from the light source 43 becomes a parallel light flux after being reflected by the rotating parabolic mirror 44 and illuminates the arcuate area 42 on the reflective mask 34. .

As the projection imaging optical system 36, an optical system composed of four aspherical surfaces was used. This optical system has a radius of 30 mm and a width
This is an optical system that exposes a 0.5 mm ring-shaped area, with a reduction ratio M = 1/4, an emission-side numerical aperture NA = 0.1, and a reflective surface that reflects a molybdenum / silicon multilayer that reflects X-rays with a wavelength λ = 13 nm. A film is formed. The spatial limit of the diffraction limit in image formation by coherent illumination of this optical system is N
A / λ = 7700 cycles / mm, that is, 0.065 μm line and space.

In the X-ray reflection type mask 34, the reflection portion in the pattern of line and space of 0.26 μm or more corresponding to the diffraction limit in the image formation by the coherent illumination has a flat surface as in the conventional case, and the pattern of 0.26 μm or less is used. The reflecting portion in was a convex surface or a concave surface which a rectangular strip had. The radius of curvature R of the convex surface or concave surface (circular cross section) has a coherence factor σ, and the projection imaging optical system 3
Assuming that the incident side numerical aperture of 6 is A and the width of the reflecting portion on the mask is D, the condition of σA = D / R may be satisfied as described above.
Since A = NA × M, the radius of curvature R is given by R = D / (σ × NA × M) for a pattern of width D.

In this embodiment, the coherence factor σ
= 0.5, R = 80 × D. That is, the reflection portion of the line-and-space pattern of 0.26 μm or less on the X-ray reflection type mask 34 is formed on the convex surface or the concave surface of the strip having an arc-shaped cross section (the arc is given by this formula. With a radius of curvature). When the conventional X-ray reflection type mask is used in the X-ray projection exposure apparatus of the present embodiment, it is possible to resolve up to 0.065 μm line and space, but the X-ray reflection type mask according to the present invention is used. By using it, it became possible to resolve up to 0.05 μm line and space. Moreover, since the illumination optical system is simple and a fly-eye mirror, which causes a large loss due to scattering, is not used, there is no loss of light quantity, and the throughput is four times or more compared to the case where a conventional Koehler illumination optical system is used. Increased.

[0062]

As described above, according to the present invention, it is possible to realize image formation equivalent to image formation by partial coherent illumination without using a complicated illumination optical system as in the prior art. It is possible to maximize the performance of the optical system. Further, since the illumination optical system is simplified, it is possible to significantly reduce the loss of the light amount due to the illumination optical system, and the throughput of the X-ray projection exposure apparatus can be improved accordingly.

Further, since the complicated illumination optical system is unnecessary, there is an effect that the manufacturing cost of the X-ray exposure apparatus is reduced.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a configuration of a reflective mask of the present invention. a is a sectional view and b is a perspective view.

FIG. 2 is a diagram illustrating the concept of a conventional Koehler illumination optical system.

FIG. 3 is a diagram illustrating a transfer function (OTF) of an optical system.

FIG. 4 is a diagram showing a structure of an X-ray reflection type mask of a first embodiment according to the present invention.

FIG. 5 is a diagram showing a structure of an X-ray reflection type mask according to a second embodiment of the present invention.

FIG. 6 is a diagram showing the structure of an X-ray reflective mask according to a third embodiment of the present invention.

FIG. 7 is an X-ray reflective mask (convex reflective surface) according to the present invention.
It is a figure explaining the function of.

FIG. 8 is an X-ray reflective mask (concave reflective surface) according to the present invention.
It is a figure explaining the function of.

FIG. 9 is a diagram showing the configuration of an X-ray reduction projection exposure apparatus according to the fourth embodiment of the present invention.

FIG. 10 is a diagram showing the structure of an X-ray reduction projection exposure apparatus according to the fifth embodiment of the present invention.

FIG. 11 is a view showing the arrangement of an X-ray reduction projection exposure apparatus according to the sixth embodiment of the present invention.

FIG. 12 is a diagram showing a configuration of a conventional X-ray reduction projection exposure apparatus.

[Explanation of symbols for main parts]

 1 ... Reflective part 2 ... Non-reflective part 3 ... Substrate 4 ... X-ray reflective multilayer film 5 ... X-ray absorber layer 20 ... Light source 21 ... First lens 22 ... Optical integrator 23 ... Multiplexed light source image 24 ... Second lens 25 ... Illuminated object 30 ... Parallel X-ray luminous flux 32 ... X-ray source 33 ... Illumination optical system 34 ... X-ray reflection type mask 35 ... Mask stage 36 ... Projection imaging optical system 37 ... Wafer 38 ... Wafer stage 40 ... Cylindrical mirror 41 ... Conical mirror 42 ... Arc-shaped illumination area 43 ... Laser plasma X-ray source 44 ... Rotating elliptical mirror

Claims (11)

[Claims] 1. An X-ray reflective mask comprising a substrate and a pattern formed of a plurality of reflecting portions that reflect X-rays and a plurality of non-reflecting portions that do not reflect X-rays. Is a convex surface or a concave surface of a strip having an arcuate cross section, and the incident side numerical aperture A of the projection imaging optical system for forming an image of the reflected light from the mask on the wafer,
Between the width D of each of the reflecting portions and the radius of curvature R of the arc,
An X-ray reflection type mask having a convex surface or a concave surface satisfying the relationship of D / R <A. 2. An X-ray reflection type mask having a pattern formed on a substrate, comprising a plurality of reflection portions that reflect X-rays and a plurality of non-reflection portions that do not reflect X-rays. Is a convex surface or a concave surface of a strip having an arcuate cross section, and the incident side numerical aperture A of the projection imaging optical system for forming an image of the reflected light from the mask on the wafer,
Between the width D of each of the reflecting portions and the radius of curvature R of the arc,
An X-ray reflection type mask having a convex surface or a concave surface satisfying the relationship of 0.3 A <D / R <A. 3. An X-ray reflection type mask comprising a substrate, on which a pattern composed of a plurality of reflection portions that reflect X-rays and a plurality of non-reflection portions that does not reflect X-rays is formed. Is a convex surface or a concave surface of a strip having an arcuate cross section, and the incident side numerical aperture A of the projection imaging optical system for forming an image of the reflected light from the mask on the wafer,
Between the width D of each of the reflecting portions and the radius of curvature R of the arc,
An X-ray reflection type mask having a convex surface or a concave surface satisfying the relationship of 0.5 A ≦ D / R ≦ 0.7 A. 4. An X-ray reflection type mask formed on a substrate with a pattern including a plurality of reflection portions having a width D1 that reflects X-rays and a plurality of non-reflection portions having a width D2 that does not reflect X-rays. In, the numerical aperture NA on the exit side of the projection imaging optical system that forms the reflected light from the mask on the wafer, and the width D of each of the reflecting portions
1, the width of each non-reflecting portion, the wavelength λ of the X-ray to be used, and the surface of the reflecting portion satisfying the relationship of D1 + D2 <σ × λ / NA (0 <σ <1). The convex or concave surface of the arc-shaped strip, which is the entrance-side numerical aperture A of the projection imaging optical system that forms the reflected light from the mask on the wafer, the width D1 of each of the reflecting portions, and the radius of curvature of the arc. A convex surface or a concave surface satisfying a relationship of D1 / R <A with R,
An X-ray reflection type mask, wherein the surface of the reflecting portion that does not satisfy the above relation is a flat surface. 5. An X-ray reflection type mask formed on a substrate by forming a pattern including a plurality of reflection portions having a width D1 that reflects X-rays and a plurality of non-reflection portions having a width D2 that does not reflect X-rays. In, the numerical aperture NA on the exit side of the projection imaging optical system that forms the reflected light from the mask on the wafer, and the width D of each of the reflecting portions
1, the width D2 of each of the non-reflecting portions, and the wavelength λ of the X-ray to be used, the surface of the reflecting portion satisfying the relationship of D1 + D2 <σ × λ / NA (0.3 <σ <1) has a circular cross section. The convex or concave surface of the arc-shaped strip, which is the entrance-side numerical aperture A of the projection imaging optical system that forms the reflected light from the mask on the wafer, the width D1 of each of the reflecting portions, and the radius of curvature of the arc. An X-ray reflection type mask having a convex surface or a concave surface satisfying a relationship of 0.3 A <D1 / R <A with R and a flat surface of a reflecting portion not satisfying the above relationship. 6. An X-ray reflection type mask formed on a substrate with a pattern including a plurality of reflection portions having a width D1 that reflects X-rays and a plurality of non-reflection portions having a width D2 that does not reflect X-rays. In, the numerical aperture NA on the exit side of the projection imaging optical system that forms the reflected light from the mask on the wafer, and the width D of each of the reflecting portions
1, the width D2 of each non-reflecting portion, and the wavelength λ of X-rays used, the surface of the reflecting portion satisfying the relationship of D1 + D2 <σ × λ / NA (0.5 ≦ σ ≦ 0.7) The convex or concave surface of the arc-shaped strip, which is the entrance-side numerical aperture A of the projection imaging optical system that forms the reflected light from the mask on the wafer, the width D1 of each of the reflecting portions, and the radius of curvature of the arc. An X-ray reflection type mask having a convex surface or a concave surface satisfying a relation of 0.5 A ≦ D / R ≦ 0.7 A with R, and a surface of a reflecting portion not satisfying the above relation being a flat surface. 7. A multilayer film that reflects X-rays of a predetermined wavelength is formed on each of the reflection portions, and the multilayer film and an X-ray absorption film thereon are laminated on each of the non-reflection portions. The X-ray reflection type mask according to claim 1, wherein 8. A multilayer film that reflects X-rays of a predetermined wavelength is formed on each of the reflection portions, and a multilayer film in which the periodic structure of the multilayer film is destroyed is formed on each of the non-reflection portions. The X-ray reflection type mask according to claim 1, wherein 9. A multilayer film that reflects X-rays of a predetermined wavelength is formed only on each of the reflecting portions.
X-ray reflection type mask according to. 10. An X-ray source, an X-ray reflection type mask according to claim 1, and a projection imaging optical system for projecting an image of a pattern formed on the mask onto a wafer. An X-ray projection exposure apparatus comprising: 11. At least an X-ray source, the X-ray reflective mask according to claim 1, and X emitted from the X-ray source.
X-ray projection exposure apparatus including an illumination optical system that illuminates a line on the mask with a parallel light flux, and a projection imaging optical system that projects and forms an image of a pattern formed on the mask on a wafer .