JP3336514B2 - X-ray reflection mask and X-ray projection exposure apparatus - 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 reflection type mask used in an X-ray lithography technique and an X-ray projection exposure apparatus provided with the mask.

[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. 12, an 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, there is no transparent substance and the reflectance on the substance surface is very low, so that ordinary optical elements such as lenses and mirrors cannot be used. For this reason, 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 the interference effect by matching the phases of the reflected light at each interface of the multilayer film. And a multilayer mirror for obtaining a higher reflectivity.

Although the oblique incidence mirror can obtain a reflectance close to 100%, it can be used only at oblique incidence where the oblique incidence angle (the incident angle measured from the reflection surface) is 10 degrees or less, and thus the aberration is corrected. It is difficult to configure an optical system. The multilayer mirror can reflect X-rays vertically,
A reflectance close to 00% cannot be obtained. On the longer wavelength side than the L-absorption edge (12.3 nm) of silicon, the highest reflectance is obtained when a multilayer film made of molybdenum and silicon is used. However, at a wavelength of 13 to 15 nm, 70% regardless of the incident angle.
It is about. On the shorter wavelength side than the L absorption edge of silicon,
A multilayer film having a reflectance of 30% or more at normal incidence has not been developed.

The X-ray source includes a synchrotron Ra
A light source that provides strong soft X-rays, such as a diation source or a laser plasma X-ray source, 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, a filter that transmits or reflects only X-rays of a predetermined wavelength, and the like, and illuminates the mask with X-rays of a predetermined wavelength. The mask includes a transmission mask and a reflection mask.
The transmissive mask is formed by forming a pattern on a thin membrane made of a substance that transmits X-rays well by providing a substance that absorbs X-rays in a predetermined shape. On the other hand, a reflective mask is a pattern in which a low-reflectance portion is provided in a predetermined shape on a multilayer film that reflects X-rays to form a pattern.

The transmission type mask must use a very fragile membrane having a thickness of about 0.1 μm or less in order to suppress absorption of X-rays, so that it has a practical size (for example, about 120 × 120 mm or more). Cannot be manufactured. On the other hand, since a thick substrate having sufficient mechanical strength can be used as the reflective mask, a reflective mask is used when applying the X-ray projection exposure technique 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 multilayer mirrors and the like, and is transferred to a photoresist applied on the wafer. . All the projection imaging optical systems need to be constituted by a reflection system using a multilayer mirror. Further, the reflectance of the multilayer mirror is not so high.
Therefore, in order to obtain a practical throughput, it is necessary to minimize the number of multilayer mirrors, and it is not easy to correct aberrations over a wide exposure area.

Therefore, for example, US Pat.
The required exposure area (for example, 3
(About 0 × 30 mm) at a time, and for example, as described in JP-A-4-333011,
An optical system has been devised in which a mask and a wafer are synchronously scanned while exposing an annular zone (for example, about 30 × 0.5 mm) to secure an exposure area of a required size.

Since the 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 the case of diffraction-limited imaging in which the aberration of the optical system is sufficiently small and the influence of the aberration can be neglected, the resolution 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 lighting.

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

On the other hand, the case where σ = 1 is referred to as imaging by incoherent illumination. In this case, the object is illuminated with a light beam having a divergence angle that fills the entire entrance side aperture of the imaging system. At this time, the OTF gradually decreases as the spatial frequency increases, but does not become 0 until the spatial frequency of 2NA / λ. Accordingly, although the contrast of the image is reduced, the incoherent illumination can resolve a pattern having a higher spatial frequency. In an illumination optical system of an exposure apparatus that requires a diffraction-limited resolution, partial coherent illumination of 0 <σ <1 is used in consideration of resolution and contrast.

[0013] In an actual exposure apparatus,
For example, in a wide area of about 120 × 120 mm,
It is required that the conditions for partial coherent illumination as described above be satisfied and that the illuminance be uniform. As an illumination optical system satisfying such conditions, 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 enters the optical integrator 22. Since the optical integrator 22 spatially divides the parallel light beam and converges each of the divided light beams, a multiplexed image 23 of the light source 20 is formed. In an exposure apparatus using ultraviolet light, a fly-eye lens is generally used as the optical integrator 22.

Next, the light beams diverging from the individual light source images 23 are converted into parallel light beams by the second lens 24,
The object 25 is illuminated. Light beams emitted from different light source images 23 enter the object 25 from different directions. At this time, the thickness of the parallel light beam (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 be determined. Since the light emitted from the point light source is converted into parallel light to illuminate the object, the illuminance unevenness is small. It is also easy to change the numerical aperture of the lighting.

In the X-ray projection exposure apparatus, in order to realize the Koehler illumination system as described above, it is necessary to configure all the optical systems equivalent to those shown in FIG. 2 with reflection optical systems using a multilayer mirror. 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. An illumination optical system using such a fly-eye mirror is disclosed in, for example, Japanese Patent Application No. Hei.
237654 describes an optical system for Koehler-illuminating an annular zone using a radiation light source, a fly-eye mirror, and a rotating mirror group.

However, in the Koehler illumination optical system using such a fly-eye mirror, a complicated optical system is required, so that the number of multilayer mirrors increases. Also,
Since the light rays are diverged by the fly-eye mirror, the loss of the light amount increases. For this reason, there is a problem that the throughput of the X-ray projection exposure apparatus is considerably lower than a practically necessary value (for example, about 30 wafers / hour for an 8-inch wafer).

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

[0020]

For this purpose, the present invention firstly provides "a pattern formed on a substrate by a plurality of reflecting portions for reflecting X-rays and a plurality of non-reflecting portions for not reflecting X-rays. An X-ray reflection type mask, wherein the surface of each of the reflection portions is a convex or concave surface having an arc-shaped rectangular cross section, and forms a reflected light from the mask on a wafer. A convex or concave surface satisfying the relationship of D / R <A between a numerical aperture A on the incident side, a width D of each reflecting portion, and a radius of curvature R of the circular arc. (Claim 1) "is provided.

The present invention is also directed to a second aspect of the present invention is an X-ray reflection type in which a pattern comprising a plurality of reflection portions for reflecting X-rays and a plurality of non-reflection portions for not reflecting X-rays is formed on a substrate. In the mask, the surface of each reflecting portion is a convex or concave surface having a cross section of an arc-shaped strip, and the incident-side numerical aperture A of a projection imaging optical system for imaging reflected light from the mask on a wafer. An X-ray reflection type mask having a convex or concave surface satisfying a relationship of 0.3 A <D / R <A between a width D of each of the reflecting portions and a radius of curvature R of the arc. 2) ”.

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

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

The fifth aspect of the present invention is that a pattern formed on a substrate is formed of 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 X-ray reflection type mask, the exit-side numerical aperture NA of the projection imaging optical system that forms the reflected light from the mask on a wafer, the width D1 of each reflecting portion, and the width D2 of each non-reflecting portion , And the wavelength λ of the X-ray used, D1 + D2 <
The surface of the reflecting portion that satisfies the relationship of σ × λ / NA (0.3 <σ <1) is a convex surface or a concave surface of an arc-shaped strip, and the reflected light from the mask is imaged on a 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.
An X-ray reflection type mask (Claim 5) "characterized in that a convex or 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.

The sixth aspect of the present invention is that a pattern formed on a substrate is formed by a plurality of reflective portions having a width D1 that reflects X-rays and a plurality of non-reflective portions having a width D2 that does not reflect X-rays. In the X-ray reflection type mask, the exit-side numerical aperture NA of the projection imaging optical system that forms the reflected light from the mask on a wafer, the width D1 of each reflecting portion, and the width D2 of each non-reflecting portion , And the wavelength λ of the X-ray used, D1 + D2 <
The surface of the reflecting portion that satisfies the relationship of σ × λ / NA (0.5 ≦ σ ≦ 0.7) is a convex surface or a concave surface of an arc-shaped strip, and the reflected light from the mask is imaged on a wafer. 0.5 A ≦ D / D between the entrance-side numerical aperture A of the projection imaging optical system, the width D 1 of each of the reflecting portions, and the radius of curvature R of the arc.
An X-ray reflection type mask (Claim 6), wherein a convex or concave surface that satisfies the relationship of R ≦ 0.7 A and the surface of the reflecting portion that does not satisfy the above relationship is a flat surface.

Also, the present invention provides a seventh aspect in which "each of the reflecting portions is formed with a multilayer film for reflecting X-rays of a predetermined wavelength, and each of the non-reflecting portions is formed of the multilayer film and the X-ray thereon. An X-ray reflection type mask (Claim 7) according to any one of claims 1 to 6, wherein the X-ray reflection mask is formed by laminating absorption films. Further, the present invention eighthly provides that "a multilayer film for reflecting X-rays of a predetermined wavelength is formed in each of the reflecting portions, and a multilayer film in which the periodic structure of the multilayer film is destroyed is formed in each of the non-reflecting portions. An X-ray reflection mask according to any one of claims 1 to 6 (claim 8) "is provided.

According to a ninth aspect of the present invention, there is provided an X-ray reflection mask according to any one of claims 1 to 6, wherein a multilayer film for reflecting X-rays of a predetermined wavelength is formed only on each of said reflecting portions. (Claim 9) is provided. Further, the present invention is a twelfth aspect of the present invention that provides at least an X-ray source, an X-ray reflection mask according to claims 1 to 9, and a projection imaging method for projecting an image of a pattern formed on the mask onto a wafer. An X-ray projection exposure apparatus comprising: an image optical system;

Further, the present invention provides an eleventh embodiment of the present invention, wherein "at least X
A radiation source, an X-ray reflection mask according to claim 1, an illumination optical system configured to illuminate the X-ray radiated from the X-ray source on the mask with a parallel light beam, and formed on the mask. X-ray projection exposure apparatus (Claim 11), comprising: a projection imaging optical system for projecting and forming an image of the pattern on a wafer.

[0029]

In the conventional X-ray reflection mask, the incident light (X
(Line) reflects specularly, so that a complex illumination system such as Koehler illumination was required 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 an arc-shaped strip) so that the incident light is incident on the mask itself. Is provided, an image equivalent to partial coherent illumination can be realized even if the mask is illuminated with a parallel light beam. Therefore, a complicated illumination system as in the related art is not required. The principle will be described below.

For example, as shown in FIGS. 7 and 8, when a parallel light beam is incident on the reflecting portion 1 having a convex or concave surface having the cross section of an arc-shaped strip, the reflected light is reflected in different directions depending on the incident position. So they diverge and reflect.
If the center of the arc is O and the radius is R, and the incident angle is sufficiently small, that is, close to normal incidence, and the approximation of the paraxial ray is used, the focal point F of the reflecting surface moves from the center O of the circle to the direction of the incident ray. It is in the position of R / 2.

When a parallel light beam enters such a reflecting portion 1, the reflected light becomes a light beam diverging from the focal point F. Assuming that the width of the reflecting portion 1 is D and half of 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 spread angle of the ray diverging from the focal point F is 2θ on one side. That is, despite illuminating the mask with a parallel beam, the reflected beam has a divergence angle of D / R, which illuminates a normal reflective mask with illumination light having a numerical aperture equal to D / R. Is equivalent to

Therefore, if the radius of curvature R of the arc is set so as to satisfy σA = D / R (0 <σ <1), where A is the numerical aperture on the incident side of the projection imaging optical system, illumination by a parallel light beam Thereby, 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).
It is preferable to set the range of ≦ 0.7 (claim 3).

Also, the exit-side numerical aperture NA of the projection imaging optical system that forms the reflected light from the mask on the wafer,
D1 + D2 <[sigma] * [lambda] / NA between the width D1 of each reflecting portion, the width D2 of each non-reflecting portion, and the wavelength [lambda] of the X-ray used.
A projection imaging optical system that forms a convex or concave surface of a strip having an arc-shaped cross section on the surface of the reflecting portion satisfying the relationship of (0 <σ <1), and forms reflected light from the mask on a wafer. Between the incident-side numerical aperture A, the width D1 of each of the reflecting portions, and the radius of curvature R of the arc, a convex surface or a concave surface satisfying the relationship of D1 / R <A, and the surface of the reflecting portion not satisfying the above relationship is defined as As is clear from FIG. 3, in a pattern having a spatial frequency lower than NA / λ, a higher-contrast image can be obtained by coherent illumination with σ = 0. Therefore, for such a pattern, it is preferable that the reflecting portion be a flat surface.

On the other hand, a pattern whose spatial frequency is higher than NA / λ is not resolved when σ = 0. Therefore, for such a pattern, it is preferable that the reflecting portion be the convex surface or the concave surface, and thereby, an image can be formed by partial coherent illumination of 0 <σ <1. You can get an image up to. Here, in order to achieve both good image contrast and high resolution, the coherence factor σ is set in the range of 0.3 <σ <1 and the relationship is set to 0.3 A <D1 / R <A. (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 set to 0.5 A ≦ D / R ≦ 0.7 A (claim 6).

It is preferable that a multilayer film for reflecting X-rays of a predetermined wavelength is formed on each of the reflection portions, and that the non-reflection portion is formed by laminating the multilayer film and an X-ray absorption film thereon. (Claim 7). Alternatively, X of a predetermined wavelength is applied to each of the reflecting portions.
It is preferable that a multilayer film that reflects lines is formed, and a multilayer film in which the periodic structure of the multilayer film is destroyed is formed in each of the non-reflection portions.

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

The X-ray reflection mask according to any one of claims 1 to 9 comprises at least an X-ray source and an illumination optical system for illuminating the mask with X-rays radiated from the X-ray source with a parallel light beam. ,
It is preferable to provide an X-ray projection exposure apparatus having a projection image forming optical system for projecting and forming an image of a pattern formed on a mask on a wafer (claim 11). As the X-ray reflection multilayer film according to the present invention, for example, molybdenum / silicon, molybdenum / silicon compound, ruthenium / silicon,
It is preferable to use a combination of ruthenium / silicon compound, rhodium / silicon, rhodium / silicon compound, etc., which is 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 mask according to the present invention, in order to perform 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. For this reason, it is possible to avoid a loss of light amount due to repeated reflection by the multilayer mirror, and to improve the throughput of the exposure apparatus.

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 having a divergent angle. Is illuminated with parallel light, only light rays reflected by fine, ie, high spatial frequency, pattern portions have angular spread. Further, in the conventional illumination system, the light beam spreads in all directions symmetrically with respect to the optical axis. However, in the optical system using the X-ray reflection type mask according to the present invention, the light beam spreads with respect to the line and space pattern. Light rays spread only in the vertical direction, that is, the direction in which the spatial frequency of the pattern is high.

For the above reasons (two points), in the present invention, only the luminous flux corresponding to the required pattern has a divergence angle. This almost eliminates the loss of light quantity, and from this point on, the efficiency of the entire optical system is improved and the throughput of the exposure apparatus is improved. In addition, since the reflective mask is illuminated with a parallel light beam, 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]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the configuration of an X-ray reflection type mask according to the present invention will be described. FIG. 4 is a schematic sectional view of the 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 serving as the reflecting portion 1 was formed as a convex surface (FIG. 4A) or a concave surface (FIG. 4B) having an arc-shaped strip.

The radius of curvature of the convex surface or the concave surface (the cross section of which is arc-shaped) is appropriately set as described in the section of action (claims 1 to 6).
) Was set. In this embodiment, a multilayer film (X-ray reflection multilayer film) 4 for reflecting X-rays is formed on the entire surface of the substrate 3. The material constituting the multilayer film is appropriately selected according to the wavelength of the X-ray to be used. For example, for the X-ray near the wavelength of 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 evaporation.

The non-reflective portion 2 has a multilayer film 4
An absorber layer 5 made of a substance that absorbs X-rays was further formed thereon. As the absorber, for example, a substance such as gold, tungsten, tantalum, or nickel was used. After the absorber layer 5 is formed on the entire surface of the multilayer film 4 by a method such as sputtering or vacuum deposition, only the absorber layer on the reflecting portion 1 is formed by a method such as reactive ion etching. Formed by removal.

Alternatively, the absorber layer 5 is prepared by coating only the multilayer film on the reflecting portion 1 with a photoresist in advance, and sputtering, vacuum deposition or the like on the multilayer film not coated with the photoresist. After the absorber layer was formed by the method described above, the layer was formed by a so-called lift-off method in which only the absorber layer on the reflecting portion 1 was removed together with the photoresist. FIG. 5 is a schematic sectional view of an X-ray reflection type mask according to a second embodiment of the present invention. On the substrate 3 made of quartz, silicon, or the like, the surface of the portion serving as the reflecting portion 1 was formed as a convex surface (FIG. 5a) or a concave surface (FIG. 5b) of an arc-shaped strip.

The radius of curvature of the convex surface or the concave surface (the cross section of which is arc-shaped) is appropriately set as described in the section of operation.
6). In this embodiment, the X-ray reflection multilayer film 4 is formed only on the reflection part 1 of the substrate 3. The X-ray reflection multilayer film 4 forms a multilayer film on the entire surface of the substrate 3 by a method such as sputtering or vacuum deposition, and then removes only the multilayer film of the non-reflection portion 2 by a method such as reactive ion etching. Formed.

Alternatively, the X-ray reflective multilayer film 4 covers only the substrate surface of the non-reflective portion 2 in advance with a photoresist or the like.
On it and on the surface of the substrate not covered with photoresist,
After a multilayer film was formed by a method such as sputtering or vacuum deposition, the film was formed by a so-called lift-off method in which only the multilayer film on the non-reflective portion 2 was removed together with the photoresist. The same material as that used in the first embodiment was used as the material constituting the multilayer film.

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

In this embodiment, a multilayer film 4 for reflecting X-rays is formed on the entire surface of the substrate 3. The same material as that of the first embodiment was used for the material constituting the multilayer film. The multilayer film 4 was formed by a method such as sputtering or vacuum evaporation. The non-reflective portion 2 is formed by destroying the periodic structure of only the portion of the multilayer film 4 where the non-reflective portion is formed and lowering the reflectance.

In order to selectively destroy the periodic structure of the multilayer film 4, only the multilayer film of the reflection section 1 is covered with a photoresist or the like and protected in advance, and a large diameter (a few mm) of a Kauffman ion source or the like is used. Using an ion source, ions such as argon are accelerated at several to several hundred kilovolts, and the entire surface of the substrate is irradiated, and then the photoresist is 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 to be formed. Next, an embodiment of an X-ray projection exposure apparatus having an X-ray reflection type mask according to the present invention will be described below.

FIG. 9 is a schematic structural view of an X-ray projection exposure apparatus according to a fourth embodiment of the present invention. A radiation light source is used as the X-ray source, and an illumination optical system is not particularly provided. The X-ray reflection type mask 34 is illuminated with a substantially parallel X-ray light beam 30 from the radiation light source. The projection imaging optical system 36 includes four spherical surfaces 4.
An optical system of round reflection was used. This optical system is 30 × 30m
m is an optical system that collectively exposes an area of m
/ 4, the exit side numerical aperture NA = 0.06, and the wavelength λ =
A molybdenum / silicon multilayer reflecting 13 nm X-rays is formed. The diffraction limit in the image formation by coherent illumination of this optical system is that the spatial frequency is NA / λ = 4.
600 cycles / mm, that is, 0.11 μm line and space.

The X-ray reflection type mask 34 has a line and space pattern corresponding to the diffraction limit of 0.44 μm or more corresponding to the diffraction limit in the image formation by coherent illumination. The reflecting portion in was formed as a convex or concave surface of a strip having an arc-shaped cross section. The radius of curvature R of the convex surface or the concave surface (the cross section of which is arc-shaped) has a coherence factor of σ, the projection imaging optical system 3
Assuming that the entrance-side numerical aperture of No. 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 for a pattern of width D is given by R = D / (σ × NA × M).

In this embodiment, the coherence factor σ
= 0.5, so that 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 as a convex surface or a concave surface having an arc-shaped strip (the arc is given by this equation. With a large radius of curvature). In the case of using the conventional X-ray reflection type mask in the X-ray projection exposure apparatus of the present embodiment, it is possible to resolve only up to 0.11 μm line and space. By using this, resolution up to 0.08 μm line and space became possible. Further, since no illumination optical system was used, the loss of light amount was eliminated, and the throughput was increased by 20 times or more as compared with the case where the conventional Koehler illumination optical system was used.

FIG. 10 is a schematic structural view of an X-ray projection exposure apparatus according to a 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 substantially parallel X-ray beam 30 from the radiation light source. As the projection imaging optical system 36, an optical system composed of two aspherical surfaces was used. This optical system is an optical system for exposing a ring-shaped area having a radius of 30 mm and a width of 0.5 mm.
The exit side numerical aperture NA = 0.08 and the reflection surface has a wavelength λ = 13n.
A molybdenum / silicon multilayer film that reflects m X-rays is formed. The diffraction limit in the image formation by coherent illumination of this optical system is such that the spatial frequency is NA / λ = 6150.
Period / mm, that is, 0.08 μm line and space.

The X-ray reflection mask 34 has a line and space pattern corresponding to a diffraction limit of 0.32 μm or more corresponding to the diffraction limit in image formation by coherent illumination. The reflecting portion in was formed as a convex or concave surface of a strip having an arc-shaped cross section. The radius of curvature R of the convex surface or the concave surface (the cross section of which is arc-shaped) has a coherence factor of σ, the projection imaging optical system 3
Assuming that the entrance-side numerical aperture of No. 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 for a pattern of width D is given by R = D / (σ × NA × M).

In this embodiment, the coherence factor σ
= 0.5, so 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 a convex surface or a concave surface of an arc-shaped strip (the arc is given by this equation. With a large radius of curvature). In the case of using the conventional X-ray reflection type mask in the X-ray projection exposure apparatus of the present embodiment, it is possible to resolve only up to 0.08 μm line and space. By using this, resolution up to 0.06 μm line and space became possible. In addition, since the illumination optical system is simple and a fly-eye mirror having a large loss due to scattering is not used, the loss of light quantity is eliminated, and the throughput is more than five times as compared with the case where a conventional Koehler illumination optical system is used. Has increased.

FIG. 11 is a schematic structural view of an X-ray projection exposure apparatus according to a sixth embodiment of the present invention. As the X-ray source, a laser plasma light source 43 was used, and an illumination optical system including one rotating parabolic mirror 44 was used. Laser plasma light source 43
Are arranged at the focal point of the parabolic mirror 44, and the X-ray diverging from the light source 43 becomes a parallel light beam after being reflected by the parabolic mirror 44, and illuminates the area 42 on the arc 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 width
A molybdenum / silicon multilayer that exposes a 0.5 mm annular zone area, has a reduction ratio of M = 1/4, a numerical aperture on the exit side NA = 0.1, and reflects X-rays having a wavelength of λ = 13 nm on a reflecting surface. A film is formed. The diffraction limit in the image formation by coherent illumination of this optical system is that the spatial frequency is N
A / λ = 7700 cycles / mm, that is, 0.065 μm line and space.

The X-ray reflection type mask 34 has a line and space pattern corresponding to the diffraction limit of 0.26 μm or more corresponding to the diffraction limit in the image formation by coherent illumination. The reflecting portion in was formed as a convex or concave surface of a strip having an arc-shaped cross section. The radius of curvature R of the convex surface or the concave surface (the cross section of which is arc-shaped) has a coherence factor of σ, the projection imaging optical system 3
Assuming that the entrance-side numerical aperture of No. 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 for a pattern of width D is given by R = D / (σ × NA × M).

In this embodiment, the coherence factor σ
= 0.5, so that 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 a convex surface or a concave surface of an arc-shaped strip (the arc is given by this equation. With a large radius of curvature). In the case of using the conventional X-ray reflection type mask in the X-ray projection exposure apparatus of the present embodiment, it is possible to resolve only up to 0.065 μm line and space. By using this, it has become possible to resolve up to 0.05 μm line and space. In addition, since the illumination optical system is simple and a fly-eye mirror, which has a large loss due to scattering, is not used, there is no loss of light amount, and the throughput is four times or more as compared with 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 an image equivalent to an image formed by partial coherent illumination without using a complicated illumination optical system as in the prior art. The performance of the optical system can be maximized. Further, since the illumination optical system is simplified, it is possible to greatly reduce the loss of light amount due to the illumination optical system, and accordingly, it is possible to improve the throughput of the X-ray projection exposure apparatus.

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

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a reflective mask of the present invention. a shows a sectional view, and b shows 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 configuration of an X-ray reflection type mask of the first embodiment according to the present invention.

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

FIG. 6 is a view showing a configuration of an X-ray reflection type mask of a third embodiment according to the present invention.

FIG. 7 is an X-ray reflection type mask (convex reflection surface) according to the present invention.
FIG. 4 is a diagram for explaining the function of FIG.

FIG. 8 is an X-ray reflection type mask (concave reflection surface) according to the present invention.
FIG. 4 is a diagram for explaining the function of FIG.

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

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

FIG. 11 is a diagram showing a configuration of an X-ray reduction projection exposure apparatus according to a 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 Signs of Main Parts]

 DESCRIPTION OF SYMBOLS 1 ... Reflection part 2 ... Non-reflection part 3 ... Substrate 4 ... X-ray reflection 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 beam 32 ... X-ray source 33 ... Illumination optical system 34 X-ray reflective 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 ... Spheroidal mirror

Claims (11)

(57) [Claims] 1. An X-ray reflection mask comprising a substrate and a pattern formed of a plurality of reflection portions for reflecting X-rays and a plurality of non-reflection portions for not reflecting X-rays. Is a convex or concave surface having an arc-shaped strip in cross section, and an incident-side numerical aperture A of a projection imaging optical system that forms reflected light from the mask on a wafer.
Between the width D of each reflecting portion and the radius of curvature R of the arc,
An X-ray reflection type mask having a convex surface or a concave surface satisfying a relationship of D / R <A. 2. An X-ray reflection mask comprising a substrate and a pattern formed of a plurality of reflection portions for reflecting X-rays and a plurality of non-reflection portions for not reflecting X-rays. Is a convex or concave surface having an arc-shaped strip in cross section, and an incident-side numerical aperture A of a projection imaging optical system that forms reflected light from the mask on a wafer.
Between the width D of each reflecting portion and the radius of curvature R of the arc,
An X-ray reflection type mask having a convex surface or a concave surface satisfying a relationship of 0.3 A <D / R <A. 3. 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 or concave surface having an arc-shaped strip in cross section, and an incident-side numerical aperture A of a projection imaging optical system that forms reflected light from the mask on a wafer.
Between the width D of each reflecting portion and the radius of curvature R of the arc,
An X-ray reflection type mask having a convex or concave surface satisfying a relationship of 0.5 A ≦ D / R ≦ 0.7 A. 4. 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 above, the exit-side numerical aperture NA of the projection imaging optical system that forms the reflected light from the mask on the wafer, and the width D of each reflecting portion
1. The cross section of the surface of the reflecting portion satisfying the relationship of D1 + D2 <σ × λ / NA (0 <σ <1) between the width D2 of each non-reflecting portion and the wavelength λ of the X-ray used. The convex or concave surface of the arc-shaped strip, 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 reflecting portion, the radius of curvature of the arc Between R and a convex or concave surface satisfying the relationship of D1 / R <A,
An X-ray reflection type mask, wherein the surface of the reflection portion that does not satisfy the above relationship is a flat surface. 5. An X-ray reflection mask having a pattern formed on a substrate, comprising 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 above, the exit-side numerical aperture NA of the projection imaging optical system that forms the reflected light from the mask on the wafer, and the width D of each reflecting portion
1. The cross section of the surface of the reflecting portion satisfying the relationship of D1 + D2 <σ × λ / NA (0.3 <σ <1) between the width D2 of each non-reflecting portion and the wavelength λ of the X-ray used. The convex or concave surface of the arc-shaped strip, 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 reflecting portion, the radius of curvature of the arc An X-ray reflection mask comprising: a convex surface or a concave surface satisfying a relationship of 0.3 A <D1 / R <A with R; and a surface of a reflecting portion that does not satisfy the relationship is a flat surface. 6. An X-ray reflective mask comprising a substrate and a pattern formed of a plurality of reflective portions having a width D1 for reflecting X-rays and a plurality of non-reflective portions having a width D2 for not reflecting X-rays. In the above, the exit-side numerical aperture NA of the projection imaging optical system that forms the reflected light from the mask on the wafer, and the width D of each reflecting portion
1. The cross section of the surface of the reflecting portion satisfying the relationship of D1 + D2 <σ × λ / NA (0.5 ≦ σ ≦ 0.7) between the width D2 of each non-reflecting portion and the wavelength λ of the X-ray to be used. The convex or concave surface of the arc-shaped strip, 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 reflecting portion, the radius of curvature of the arc An X-ray reflection mask comprising: a convex surface or a concave surface satisfying a relationship of 0.5 A ≦ D / R ≦ 0.7 A with respect to R; 7. A multi-layer film for reflecting X-rays of a predetermined wavelength is formed on each of said reflecting portions, and said non-reflecting portion is formed by laminating said multi-layer film and an X-ray absorbing film thereon. 7. The X-ray reflection type mask according to claim 1, wherein: 8. A multi-layer film for reflecting X-rays of a predetermined wavelength is formed on each of the reflecting portions, and a multi-layer film in which a periodic structure of the multi-layer film is destroyed is formed on each of the non-reflecting portions. 7. The X-ray reflection type mask according to claim 1, wherein: 9. A multi-layer film for reflecting X-rays of a predetermined wavelength is formed only on each of said reflection portions.
7. The X-ray reflection type mask according to any one of items 1 to 6. 10. An X-ray source, an X-ray reflection mask according to claim 1, and a projection imaging optical system configured to project and image an image of a pattern formed on the mask on a wafer. X-ray projection exposure apparatus comprising: 11. An X-ray source, the X-ray reflection mask according to claim 1, and X-rays radiated from the X-ray source.
An X-ray projection exposure apparatus comprising: an illumination optical system for illuminating a line with a parallel light beam on the mask; and a projection imaging optical system for projecting and imaging an image of a pattern formed on the mask on a wafer. .