JP2628165B2 - X-ray exposure equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray exposure apparatus that performs high-resolution printing using X-rays via a reflection reduction optical system.
A small projection optical system that forms an image of an original such as a mask illuminated by X-rays at a predetermined reduction magnification; and a wafer or the like in which the original is arranged at an image forming position via the projection optical system. The present invention relates to an X-ray exposure apparatus for transferring an original pattern onto a substrate.

[Prior Art] Conventionally, in a semiconductor manufacturing process, an exposure apparatus such as a mask aligner or a stepper is often used for printing a circuit pattern of a mask or a reticle on a wafer.

In recent years, with the increasing integration of semiconductor chips such as ICs and LSIs, there has been a demand for an exposure apparatus capable of printing at a high resolution, which replaces the current exposure apparatus using deep ultraviolet light (DeepUV). The research and development of the equipment has been actively carried out. Generally, in this type of exposure apparatus, particularly a projection exposure apparatus such as a stepper, the minimum line width of printing called resolution (or resolution) is determined by the wavelength of light used and the numerical aperture of the projection optical system.

Regarding the numerical aperture, the larger the numerical aperture, the better the resolution is.However, if the numerical aperture is too large, the depth of focus becomes shallow, and there is a problem that the image is blurred with a slight defocus. Therefore, it is difficult to obtain high resolution. Therefore, attempts are usually made to obtain higher resolution by using light obtained from an excimer laser or the like or light having a short wavelength such as X-rays as light used for printing. In particular, an apparatus using X-rays has received a great deal of attention as a next-generation exposure apparatus, and an exposure apparatus using a proximity method using X-rays has been proposed.

[Problems to be Solved by the Invention] However, regarding the manufacture of VLSI after 64Mbit DRAM, it is difficult to obtain a submicron-order high resolution with high accuracy by the currently proposed X-ray exposure by the proximity method. And various problems such as a high pattern accuracy required for the mask.

An object of the present invention is a novel X-ray exposure apparatus that replaces the conventional X-ray exposure apparatus based on the proximity method, which has a high resolution of the order of submicrons and uses an X-ray capable of high-precision printing as a light source. An object of the present invention is to make it possible to perform efficient and highly accurate alignment in a reflection type reduction projection type X-ray exposure apparatus.

[Means for Solving the Problems] According to the present invention for achieving the above object, a mask stage for holding a mask, a wafer stage for holding a wafer, and a plurality of substrates each including at least one forcibly cooling unit are provided. X-ray reduction optical means for reducing and projecting the mask pattern illuminated with electromagnetic waves in the X-ray region onto the wafer, and an alignment mark provided on the wafer or wafer stage. Mark detecting means for irradiating light, reversing the light from the mark through the plurality of multilayer X-ray reflecting mirrors, and detecting enlarged image information of the mark.

[Operation] In this configuration, prior to exposure, information on the alignment is obtained, for example, visually or photoelectrically via the mark detecting means, and alignment of the wafer stage is performed based on this information. At this time, the alignment mark on the wafer stage is detected on the mask side enlarged by reversing the X-ray reduction optical means.

According to this, alignment information can be obtained with high accuracy,
Therefore, efficient and accurate alignment can be achieved.

In addition, the forced cooling means prevents deformation of the multilayer X-ray reflecting mirror due to heat, and performs more accurate alignment.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

First Embodiment FIG. 1 shows an X-ray reflection reduction type projection optical system that can be used in an exposure apparatus according to a first embodiment of the present invention. In the figure, MS is an object plane such as a mask, WF is an image plane such as a wafer, and M1, M2, and M3 are each X.
Reflector comprising a multilayer film for line reflection reduction imaging, in R1, R2, R3 is the multilayer film, the surface separation between the d _1, d ₂ and each reflector M1 M2, and the reflecting mirror M2 M3, l ₁ the image plane the object, i.e. the distance to the mask MS, a l ₂ reflecting mirror M1 from the reflecting mirror M1, that wafer WF
The distance to is shown. It is assumed that the values of d ₁ , d ₂ , l ₁ , l ₂ are measured along the optical axis O.

As described above, the reflection-reduction projection optical system shown in FIGS. 1 and 2 is configured such that the concave reflecting mirror M1 (hereinafter referred to as “concave mirror M1”) is sequentially arranged from the mask MS side.
It is written. ), A convex reflecting mirror M2 (hereinafter, referred to as “convex mirror M2”), a concave reflecting mirror M3 (hereinafter, referred to as “concave mirror M3”).
The circuit pattern of the mask MS is reduced and projected on the wafer WF, more specifically, on a resist applied on the surface of the wafer WF.

Usually, in an exposure apparatus used for producing a 64 Mbit or 256 Mbit class super LSI, the main specifications required for a projection optical system for performing surface projection as shown in FIGS. 1 and 4 are an ultra-high resolution, a large image plane. Size, no distortion, 64Mbit class
It is said that a minimum line width of 0.35 μm and an image plane size of 28 × 14 mm ² are required, and a 256 Mbit class requires a minimum line width of 0.25 μm and an image plane size of 40 × 20 mm ² . These requirements are generally contradictory, and no conventional optical system of this type simultaneously satisfies the above specifications. However, by using the projection optical system shown in the present embodiment, it is possible to satisfy the above-mentioned specifications.

In order to obtain a large image plane size in this type of optical system, it is most important that the flatness of the image plane is excellent, that is, the field curvature is properly corrected. Therefore, in the reflection reduction projection optical system shown in FIG.
The value of 3 and convex mirror paraxial curvature of M2 radius r _1, r _2, r ₃ is the following (1)
We have chosen to satisfy the formula.

0.9 <r ₂ / r ₁ + r ₂ / r ₃ <1.1 …… (1) Equation (1) is the Petzval sum (PETZVAL SUM: 1 / r ₁ −
1 / r ₂ + 1 / r ₃ ) is a conditional expression for reducing (1)
If the value exceeds the range of the expression, the required resolution cannot be obtained over the entire image plane size, and exposure satisfying the above-mentioned specifications becomes impossible. The closer the value of r ₂ / r ₁ + r ₂ / r ₃ in equation (1) is to 1, the closer the Petzval sum 1 / r ₁ −1 / r ₂ + 1 / r ₃ is to 0. That _{r 2 / r 1 + r 2} / r 3 = 1 is said to be the most ideal conditions.

Further, in order to satisfy the above-mentioned specification, it is necessary that aberrations other than the curvature of field, that is, spherical aberration, coma, astigmatism, and distortion are also satisfactorily corrected. In the system, the light emitted from the object is concave mirror M1, convex mirror M
2. The above-mentioned aberrations are corrected by reflecting in the order of the concave mirror M3 and using the convex mirror M2 as an aperture stop. In addition, by making at least one mirror surface of the three reflecting mirrors of the concave mirrors M1 and M3 and the convex mirror M2 aspherical, the above-described aberrations can be corrected more favorably. In particular, it is desirable to form the concave mirrors M1 and M3 with aspherical surfaces in order to improve the imaging performance. In other words, in order to remove the above-mentioned aberrations, so-called Seidel's five aberrations, the respective paraxial curvature radii of the concave mirrors M1 and M3 and the convex mirror M2 are appropriately determined in the reflection reduction projection optical system shown in FIG. Therefore, the Petzval sum is kept small, and mainly the distortion is removed by appropriately determining the distance between the surfaces, and other coma, astigmatism, and spherical aberration are corrected well by using an aspheric surface. I have.

FIG. 2 shows the geometrical optical aberration and the effective F of the optical system of FIG.
It is a graph which shows a relationship with a number. Lateral spherical aberrati is a representative of geometrical optical aberrations.
on) LSA can be approximated as being inversely proportional to the cube of the effective F number. In the expression, LSA = K / F ³ (2) (F is an effective F number, and K is a proportional constant).

FIG. 2 plots the relationship of the above equation for several values of K on a log-log graph.

Here, the proportional constant K means the value of the lateral spherical aberration when the effective F number is 1, and the value of K depends on the number of lenses (mirrors) constituting the optical system, the type and design of the optical system. Depends on the quality of the In a conventional optical stepper, a large number of lenses (10 or more) are used to achieve K ≒ 1 μm. However, in an X-ray reflection optical system such as the present optical system, since the ratio of absorption by the mirror is large, the number of mirrors to be used must be reduced as much as possible to increase the light amount.

In the case of an optical system of the type shown in the embodiment of the present invention in which the number of mirrors is 3 to 5, K is about 100 times larger than that of the optical stepper, and is in the order of K ≒ 100 μm.

The optical system of K = 100 μm is equivalent to K in the graph of FIG.
= 100 μm on a straight line. Therefore, for example, in order to reduce the aberration LSA to 0.35 μm or less in this optical system, it is understood from the equation (2) that the effective F number needs to be 6.6 or more.

However, when the F number is increased, the diameter of the blur due to diffraction increases. When the radius of the blur due to diffraction is evaluated using the Airy disk radius r ₀ , r ₀ = 1.22Fλ (3) Here, F is the effective number, and λ is the wavelength.

FIG. 3 is a double logarithmic graph showing the relationship of equation (3) for three types of r ₀ . According to this graph, for example,
When r ₀ <0.35 μm needs to be satisfied, it can be seen that it is necessary to select a combination of F and λ that satisfies the area below the lowermost straight line.

Therefore, in order to obtain the required resolution, the geometrical optical aberration shown in the graph of FIG.
Both the blur due to diffraction shown in the graph of FIG. 3 must be below the allowable amount.

For example, in the optical system of K = 100 μm, in order to satisfy the performance of LSA <0.35 μm and r ₀ <0.35 μm, since F> 6.6 from the graph of FIG. 2, it is necessary to satisfy the shaded portion of the graph of FIG. Must be a combination of the effective F number and the wavelength. However, in the optical system of this example, if light in the visible region is used, the influence of diffraction becomes large, and a submicron resolution cannot be obtained. In other words, by using light in the region of soft X-rays having a short wavelength,
For the first time, submicron resolution is possible.

As described above, in the optical system of the embodiment, both the geometrical optical aberration and the blur due to diffraction can be reduced to submicron or less in the soft X-ray wavelength region while the number of mirrors is small.

FIG. 4 is a schematic diagram in which the reflecting mirror in FIG. 1 is a multilayer reflecting mirror, and important parts are schematically illustrated and emphasized. The reflection reduction projection optical system shown in FIGS. 1 and 4 basically forms a coaxial optical system, and the mirror surfaces of the concave mirrors M1 and M3 are used only on one side. Note that at least one of the concave mirrors M1 and M3 and the convex mirror M2 is removed from the coaxial relationship, and the aberration can be further corrected by slightly tilting the optical axis O in the drawing.

FIG. 5 is an explanatory diagram showing an image plane when the reflection reduction projection optical system of FIG. 4 is used. In the figure, y indicates the image height, y _max indicates the maximum image height, y _min indicates the minimum image height, and y indicates the normal image plane.
_{The part where min} ≦ y ≦ _ymax is used. The luminous flux reaching this portion is not substantially blurred, and a uniform light amount distribution with an aperture efficiency of 100% can be obtained. FIG. 5 shows, as an example of the image plane to be used, a rectangular region in which the ratio of the long side to the short side is 2: 1 and the area is maximum. Needless to say, the above-mentioned various aberrations are satisfactorily corrected in this region. When assuming such a rectangular area as a used image plane, the short side of the rectangle is y _max −y _min , and the long side is Given by

The reflecting surfaces of the concave mirrors M1, M3 and the convex mirror M2 in the projection optical system shown in FIG. 4 are provided with a reflection film in order to efficiently reflect X-rays. This reflection film is formed of several tens of layers of multilayer films, and greatly improves the reflectance as compared with the case where no reflection film is provided. This type of multilayer reflective film is a combination of different materials such that the difference in refractive index between adjacent layers is large, for example, a multilayer film composed of a transition metal element having a high melting point and a semiconductor element, and a low melting point metal element. It can be formed from a multilayer film including a semiconductor element or a light metal element, a multilayer film including a white metal element and a semiconductor element, or the like. Specifically, tungsten W and carbon C, tantalum Ta and silicon Si,
Au and carbon C, rhenium Re and carbon C, zinc Pb and silicon
There are combinations of Si, ruthenium Ru and silicon Si, palladium Pb and silicon Si, rhodium Rh and silicon Si, ruthenium Ru and beryllium Be, ruthenium Ru and boron B, rhodium Rh and boron B, palladium Pd and boron B, and the like.

 Hereinafter, specific examples of the multilayer reflective film will be described.

<Multilayer Reflection Film for X-rays with Wavelength of 114.0 °> Example 1-1 If the different materials constituting the multilayer film are a first material and a second material, the first material is Ru and the second material is Si. By setting the film thicknesses to 36.4 ° and 23.5 °, 41 layers were laminated, and a reflectance of 38.6% was obtained at an incident angle of 0 ° (normal incidence).
As a result of laminating C on the uppermost layer of 5 ° as a protective film, a reflectance of 37.9% was obtained at an incident angle of 0 °. Each film thickness is 3
By stacking 41 layers at 9.1 ° and 25.2 °, a reflectance of 40.1% was obtained at an incident angle of 20 °. C as a protective film
Was laminated on the uppermost layer of 5 °, and as a result, a reflectance of 39.4% was obtained at an incident angle of 20 °.

Example 1-2 When the first substance is Pd and the second substance is Si, the thickness of each layer is 31.3 ° and 28.0 °, and 41 layers are laminated, a reflectance of 26.1% is obtained at an incident angle of 0 °. Was done. By setting the film thicknesses to 33.3Å and 30.1Å, respectively,
A reflectance of 6.7% was obtained.

<Multilayer Reflection Film for X-rays with Wavelength of 112.7 °> Example 1-3 The first material is Ru, the second material is Be, and the film thicknesses are 26.6 ° and 30.6 °, and 41 layers are laminated to form an incident angle. At 0 °, a reflectance of 77.2% was obtained. Incident angle by stacking 41 layers with each film thickness 27.4Å and 33.4Å
A reflectance of 79.9% was obtained at 20 °.

<Multilayer Reflection Film for X-rays with a Wavelength of 108.7 °> Example 1-4 The first material is Rh, the second material is Si, and the film thicknesses are 33.4 ° and 23.4 °, respectively. At 0 °, a reflectivity of 33.2% was obtained. Incident angle by stacking 41 layers with each film thickness of 48.2Å and 28.8Å
A reflectance of 38.7% was obtained at 40 °.

<Multilayer Reflection Film for X-rays with a Wavelength of 82.1 °> Example 1-5 The first material is Ru, the second material is B, and the film thickness is 20.1 ° and 21.8 °. At an angle of 0 °, a reflectance of 18.0% was obtained. Incident angle by stacking 41 layers with each film thickness 21.3Å and 23.4Å
A reflectance of 21.6% was obtained at 20 °.

Example 1-6 The first substance was Rh, the second substance was B, and the respective film thicknesses were 20.0 ° and 21.9 °. By stacking 41 layers, a reflectance of 15.7% was obtained at an incident angle of 0 °. . Each film thickness
Incident angle of 20 by stacking 41 layers at 21.0Å and 23.6Å
With ゜, a reflectance of 18.8% was obtained.

Example 1-7 Assuming that the first substance is Pd and the second substance is B, the respective film thicknesses are 19.4 ° and 22.4 °, and by stacking 41 layers, a reflectance of 13.2% is obtained at an incident angle of 0 °. Was. Incident angle by stacking 41 layers with each film thickness 20.6Å and 24.0Å
A reflectance of 15.7% was obtained at 20 °.

Although the multilayer reflective film described above is for X-rays having a wavelength of 80 to 120 °, the multilayer reflective film for X-rays in other wavelength ranges is also designed by appropriately selecting a combination of the above-described substances. Obtainable. Further, the first substance and the second substance may not only be composed of a single element, but may be composed of a synthetic substance of a plurality of elements.

Hereinafter, numerical examples of the projection optical system shown in FIGS. 1 and 4 will be described. In the projection optical system of the present invention, at least one of the concave mirrors M1 and M3 and the convex mirror M2 is used in order to favorably correct various aberrations.
The number of reflecting mirrors is preferably an aspherical surface, and each of the following numerical examples adopts a configuration including at least one aspherical reflecting mirror.

In the following numerical examples, Ki (i = 1, 2, 3) is the aspherical coefficient of the i-th surface counted from the object side, and the aspherical shape can be represented by the following equation.

Here, X is the coordinate in the optical axis direction, H is the distance from the optical axis in the vertical direction, and ri is (i = 1, 2, 3) is the i-th number counted from the object side.
It represents the paraxial radius of curvature of the th surface. Also, l ₁ , l
₂ , d ₁ and d ₂ are concave mirrors M as described with reference to FIG.
It shows the distance from 1 to the mask MS, the distance from the reflecting mirror M1 to the wafer WF, the surface distance between the concave mirror M1 and the convex mirror M2, and the surface distance between the convex mirror M2 and the concave mirror M3.

Example 1-8 l ₁ = -1288.7 mm l ₂ = -298.9 mm _{K 1 = -2.26097 K 2 = -0.12295} K 3 = 0.11246 ( performance) spatial frequency 1500lp / 80% distortion rate at 85% 13.3Å when MTF wavelength = 0 in mm = -0.3% EXAMPLE 1-9 l ₁ = -2577.4mm l ₂ = -597.9mm K ₁ = -2.26097 K ₂ = -0.12295 K ₃ = 0.11246 (Performance) MTF at spatial frequency 2000 lp / mm 75% when wavelength = 0 75% when 13.3 ° Distortion = -0.24% Example 1-10 l ₁ = -2577.4mm l ₂ = -597.9mm K ₁ = -2.26097 K ₂ = -0.12295 K ₃ = 0.11246 (Performance) MTF at spatial frequency 1500 lp / mm 70% when wavelength = 0 70% when 13.3 1 60% at 100Å 40% at 20040 Distortion = -0.2% Example 1-11 l ₁ = −3000.0mm l ₂ = −602.5mm _{K 1 = -0.94278 K 2 = -0.07146} K 3 = 0.14283 ( performance) 45% distortion rate at 65% 200 Å at 80% 100 Å at 80% 13.3Å when MTF wavelength = 0 in the spatial frequency 1500lp / mm = 0.00005% or less Example 1-12 l ₁ = -4500.0mm l ₂ = -903.6mm 35% distortion rate when _{K 1 = -0.94301 K 2 = -0.08049} K 3 = 0.14261 ( performance) 40% 200 Å at 50% 100 Å at 50% 13.3Å when MTF wavelength = 0 in the spatial frequency 2000lp / mm = 0.00004% or less Example 1-13 l ₁ = −3000.0mm l ₂ = −602.7mm _{K 1 = -0.93900 K 2 = 0} . ( Spherical) K ₃ = 0.14403 (performance) at 55% 200 Å at 60% 100 Å at 60% 13.3Å when MTF wavelength = 0 in the spatial frequency 1500lp / mm 45 % Distortion 0.01 μm or less Example 1-14 l ₁ = -1431.1mm l ₂ = -719.0mm _{K 1 = -1.72866 K 2 = -1.60435} K 3 = -0.78100 ( performance) 14% at 45% 200 Å at 75% 100 Å at 80% 13.3Å when MTF wavelength = 0 in the spatial frequency 1500lp / mm distortion 0.1 μm Example 1-15 l ₁ = −934.6mm l ₂ = −1054.2mm _{K 1 = -1.82882 K 2 = -1.83789} K 3 = -1.19285 ( performance) 0% when the 30% 200 Å at 65% 100 Å at 70% 13.3Å when MTF wavelength = 0 in the spatial frequency 1500lp / mm distortion 0.1 μm In Examples 1-8 to 1-10, concave mirrors M1 and M3 were convex mirrors M.
2 shows the case where they are arranged at the same position at substantially the same distance from each other,
Embodiments 1-8 and 1-10 are designed for manufacturing a 64 Mbit class LSI, and Embodiment 1-9 is designed for manufacturing a 256 Mbit class LSI. The projection optical systems of Examples 1-8 to 1-10 are relatively compact and have high resolution, but tend to have some distortion. In this case, the correction can be performed by producing the mask by giving the mask pattern itself distortion that is opposite to the distortion generated by the projection optical system and that cannot be corrected.

Embodiments 1-11 to 1-15 show the case where the concave mirror M3 is arranged between the concave mirror M1 and the convex mirror M2, and in each embodiment, approximately 1/1 / the distance between the concave mirror M1 and the convex mirror M2. A concave mirror M3 is arranged at a position separated by a distance of 2. Example 1-11 and Example 1-12 are 64 Mbit class and 256 Mbit class LSI, respectively.
Designed for manufacturing, it provides a bright optics with almost complete removal of distortion and an effective F-number of 13. In Example 1-13, the convex mirror M2 is a spherical surface, and a 64Mbit class LS
When designed for manufacturing, Example 1-14 has a projection magnification of 1
Example 1-15 shows an example in which the projection magnification is set to 1 and the design is made for the production of a 64 Mbit class LSI. Example 1
-8 to Example 1-13 are all examples in which the reduction magnification is 1/5, and all the examples other than Example 1-13 are three reflecting mirrors (M1, M2, M
This is an example in which 3) is configured with an aspherical surface.

The projection optical system described above uses three reflecting mirrors M1, M2, and M3, but the projection optical system applicable to the projection exposure apparatus is not limited to the above embodiments. For example, an optical design may be performed by adding a fourth reflecting mirror of M4. In order to reflect X-rays efficiently, a multilayer reflective film may be used as described above. However, even if a multilayer reflective film is used, an increase in the number of reflecting mirrors inevitably increases the loss of X-rays. Therefore, it is desirable that the number of reflecting mirrors constituting the projection optical system is small.

The projection optical system is used not only for the above-described surface projection but also for a system in which a predetermined image height with small aberration is projected through an arc-shaped slit or the like, and a mask and a wafer are simultaneously scanned and sequentially transferred. it can.

FIGS. 6A and 6B and FIGS. 7A to 7D are aberration diagrams for the projection optical system of FIG. 1 and the fourth embodiment. 6 (A) and 6 (B), (A) shows astigmatism, (B) shows distortion, and FIGS.
(D) shows the lateral aberration at different object heights. Seventh
In the figure, (A) has a height of 185 mm, and (B) has a height of 160.
mm, (C) shows the case where the object height is 130 mm, and (D) shows the case where the object height is 100 mm. 6 (A) and 6 (B), the ordinate represents the object height, M represents a meridional surface, and S represents a sagittal surface.

As can be seen from the aberration diagrams in FIGS. 6 and 7, sufficient aberration correction has been made for this type of projection optical system.
In particular, the distortion in FIG. 6B is almost zero, and the aberration is not shown. Further, aberration correction was achieved over a wide range so as to be sufficiently satisfied as an optical system applicable to a surface projection type exposure apparatus requiring a wide exposure area. Further, the present invention provides an optical system having MTF characteristics sufficient to obtain a submicron order resolution.

FIG. 8 is a principle diagram for explaining the reason why the illumination light to the mask MS is non-perpendicularly incident in FIGS. In an exposure apparatus or the like, when a mask pattern is printed on a wafer, it is preferable that the mask pattern is vertically illuminated on the wafer so as to form a so-called telecentric illumination system. In the figure, MM is the reflecting mirrors M1, M2, M3 of FIGS.
Where IP is its entrance pupil position, FF is the front focus position, and PL is the principal ray passing through the center of the mask MS and passing through the front focus FF. In order for the pattern of the mask MS to be vertically (or almost vertically) incident on the wafer WF, the mask MS
Must pass through the front focus FF from the center of
The surrounding light must also pass through the entrance pupil. Therefore, when the obliquely incident (non-perpendicularly incident) light L is applied to the mask MS as shown in the drawing, most of the light can be incident perpendicularly and / or almost perpendicularly on the mask WF. This is a preferable configuration in a system that uses one side of the reflection optical system that is symmetric with respect to the optical axis. This principle can be used for telescopes and microscopes.

Second Embodiment FIG. 9 is a schematic diagram showing an X-ray reflection reduction type projection optical system used in an exposure apparatus according to a second embodiment of the present invention.

In the case where the optical system shown in FIGS. 1 and 4 is used, when a wafer stage (not shown) is moved to print a plurality of shots stepwise over the entire surface of the wafer WF, a light beam incident on the reflecting mirror M1 from the mask MS is blocked. There is a possibility that. The optical system of FIG. 9 solves this, and the fourth reflecting mirror M0
The movement range of the wafer WF is free from the influence of the optical system. In order to illuminate the wafer WF with incident light, the reflecting mirror M0 is not limited to the 45-degree slant as shown in FIG. 9 but may be installed at another angle.

 Examples of a multilayer film suitable for the reflector M0 are shown below.

<Multilayer Reflection Film for X-rays with Wavelength of 114.0 °> Example 2-1 The first material is Ru, the second material is Si, and the respective film thicknesses are 55.4 ° and 34.3 °, and the incident angle is obtained by stacking 41 layers. At 45 °, a reflectivity of 43.8% was obtained.

Example 2-2 Assuming that the first material is Pd and the second material is Si, the respective film thicknesses are 44.5 ° and 42.3 °, and 41 layers are laminated to obtain a reflectance of 29.1% at an incident angle of 45 °. Was.

<Multilayer Reflection Film for X-Ray with Wavelength of 112.7 °> Example 2-3 The first material is Ru, the second material is Be, and the film thicknesses are 30.2 ° and 49.7 °, respectively, and 41 layers are laminated to form an incident angle. At 45 °, a reflectance of 85.3% was obtained.

<Multilayer Reflection Film for X-rays with a Wavelength of 108.7 °> Example 2-4 The first material is Rh, the second material is Si, and the film thicknesses are 52.7 ° and 31.9 °, respectively. At 45 °, a reflectance of 39.5% was obtained.

<Multilayer Reflection Film for X-rays with a Wavelength of 82.1 °> Example 2-5 The first material is Ru, the second material is B, and the film thicknesses are 27.6 ° and 32.8 °, respectively, and 41 layers are laminated to form an incident angle. At 45 °, a reflectivity of 41.8% was obtained.

Example 2-6 Assuming that the first material is Ru and the second material is B, the thickness of each material is 26.7 ° and 33.5 °, and 41 layers are laminated to obtain a reflectance of 36.6% at an incident angle of 45 °. Was.

Example 2-7 Assuming that the first substance is Pd and the second substance is B, the film thicknesses of the respective substances are 25.9 ° and 34.2 °, and 41 layers are laminated to obtain a reflectance of 30.2% at an incident angle of 45 °. Was.

Third Embodiment FIG. 10 is a schematic diagram showing a configuration of an X-ray reflection reduction type projection optical system used in an exposure apparatus according to a third embodiment of the present invention.

The optical system in FIG. 9 is an example of a type in which exposure light is transmitted through the mask MS, whereas the optical system in FIG. 10 uses the mask as a reflection type.

This embodiment matches the principle of FIG. 6 well and is preferable. This is because, when the mask MS is used in the reflection type, if the illumination light is incident on the mask MS non-perpendicularly, the image of the circuit pattern of the mask can be efficiently sent to the reflecting mirror M1 side.

In the case of a reflective mask, the forced cooling means
It is preferable that an electronic cooling mechanism such as a CO, for example, a water cooling mechanism or a Peltier element can be attached.

Furthermore, it is preferable to attach such forced cooling means C1, C2, etc. to the reflecting mirrors M1, M2, etc., because they do not thermally expand. In this case, if it is attached to at least the first few reflecting mirrors, it may not be necessary for subsequent reflecting mirrors. This is because the first few sheets may be at the highest temperature. Of course, it may be attached to all reflecting mirrors.

Note that the advantage of non-perpendicular incidence shown using this reflective mask also applies to the example of the optical system shown in FIGS. 11, 12, and 13 below.

Fourth Embodiment FIG. 11 is a schematic diagram showing a configuration of an X-ray reflection reduction type projection optical system used in an exposure apparatus according to a fourth embodiment of the present invention. In this optical system, the X-ray beam SR from the SOR light source
Is reflected by the reflector MTR and is incident non-perpendicularly on the mask MS. The reflector MTR is a mask MS
In order to scan the circuit pattern surface, a wide exposure area is secured. This reflector MT
As R, a glancing type, a multi-layer type, or the like can be used.
Also in this embodiment, it is preferable to attach forced cooling means to the reflecting mirrors M0 and M1. Further, the X-ray guide tube from the SOR light source usually extends in the tangential direction of the ring, and the tube can be shared by an apparatus having a long distance from the mask MS to the reflecting mirror M1 as in this embodiment. The device does not become large.

Fifth Embodiment FIG. 12 is a schematic diagram showing a configuration of an X-ray reflection reduction projection optical system used in an exposure apparatus according to a fifth embodiment of the present invention. In this optical system, the X-ray beam is scanned in the vertical direction inside the SOR light source, and the mask MS is set at a predetermined angle inclined from the vertical direction so as to be also non-perpendicular.

Sixth Embodiment FIG. 13 is a schematic diagram showing a configuration of an X-ray reflection reduction type projection optical system used in an exposure apparatus according to a sixth embodiment of the present invention. In this optical system, the mask MS and the wafer WF are arranged vertically and in parallel, and the illumination light is not cut off. This is suitable for printing a plurality of shots by moving the wafer to step noise.

Seventh Embodiment FIG. 14 is a configuration diagram of an exposure apparatus according to a seventh embodiment of the present invention.

In this exposure apparatus, the mask MS is disposed vertically, the wafer WF is mounted on a horizontal stage so as to be suitable for the SOR light source, and the optical system is the reflection system shown in FIGS. 9, 11, and 12 described above. Optical systems may be used.

In the figure, reference numeral 1 denotes a mask stage for supporting a mask MS, which can be moved in a two-dimensional direction by a driving device (not shown). Two
Reference numerals A, 2B, and 2C denote alignment marks provided on the mask stage 1, which are formed at three different points on the mask stage 1 as shown in the present embodiment, and are used for detecting the orthogonality with the wafer and / or the wafer stage. used. Reference numeral 3 denotes a light guide member through which X-rays pass, which directs X-rays emitted from an X-ray source (not shown) and transmitted through the mask MS to a projection optical system described later. Reference numeral 4 denotes a lens barrel that houses a projection optical system including a plurality of reflecting mirrors, and is connected to the light guide member 3.
Reference numerals 10, 11 and 12 denote first, second and third stage alignment scopes, respectively, which have a function of observing the above-described alignment marks 2A, 2B and 2C and the alignment marks 6A, 6B and 6C on the member 50, respectively. .

Reference numerals 20 and 21 denote first and second mask / wafer alignment scopes, respectively. The positions of the corresponding alignment marks on the side of the mask MS and the wafer WF are observed through a projection optical system to thereby align the mask MS and the wafer WF. Perform alignment. M0, M1, M2, and M3 are the above-mentioned multilayer film reflecting mirrors. In particular, M1, M2, and M3 constitute a reduction projection optical system, and the reflecting mirror M0
Is a bending mirror for directing the X-rays that have entered the interior of the lens barrel 4 through the light guide member 3 to the reflecting mirror M1 at a predetermined angle.

Since only one half of the reflecting mirror M1 is used with respect to the optical axis O as shown in FIGS.
It is better to keep it for the relation of jigs when processing the multilayer film and to promote heat radiation. Alternatively, the entire circular mirror surface may be subjected to multi-layer processing to use only half. The reflecting mirror M3 has a hole h1 for X-ray passage at an eccentric position. The hole h1 is provided before processing the multilayer film, and performs the processing of the multilayer film in a state of being filled, and removes the filling after completion. In this way, the distortion generated at the time of drilling can be eliminated. The reflecting mirror M2 is fixed to a support plate SS having a hole h2.

Next, reference numerals 50, 51, and 52 denote stage constituent members constituting a wafer stage. The constituent member 50 has a wafer chuck for supporting and fixing the wafer WF, and has a stage alignment mark 6A, 6B used for alignment on its upper surface. , 6C are provided. The constituent member 51 has the constituent member 50 mounted thereon, and is movable on the constituent member 52 in the X direction as indicated by the arrow in the figure. The constituent member 52 is movable in the Y direction as shown by the arrow in the figure, and the constituent members 51 and 52 constitute a so-called XY stage. 70 and 71 are driving devices for moving the constituent members 51 and 52 in the X direction and the Y direction, respectively.
It consists of a step motor and the like. The component member 50 is rotatable in the θ direction by a driving device (not shown). The component member 50 is moved up and down by piezoelectric elements P1, P2, and P3 arranged on the lower surface as shown in FIG. Reference numerals 90, 91 and 92 denote stage control length measuring devices which can measure the position or the amount of movement of the wafer displaced in the X and Y directions with high accuracy. As the stage control length measuring devices 90, 91, 92, an interferometer-type length measuring device capable of optically measuring the length without contact is suitable.

The projection exposure apparatus shown in FIG. 14 is an apparatus for subjecting the pattern image of the mask MS to reduction projection by the reflecting mirrors M1, M2, and M3 and exposing the wafer WF by surface projection, and the wafer is exposed by a so-called step-and-repeat method. On the FW, baking is performed for each chip or a plurality of chips separated by a scribe line. The mask MS is supported by a mask holder (not shown) on the mask stage 1, and the wafer WF is attracted to a wafer chuck (not shown) and fixed to the wafer stage. After the alignment of the wafer WF and the mask MS, which will be described later, is completed, exposure as described below is performed.

X-rays emitted from an X-ray source (not shown) illuminate the mask MS, and the circuit pattern of the mask MS includes a light guide member 3, a reflecting mirror M0,
Then, an image is formed on a predetermined area on the wafer WF via a reduction projection optical system including the reflecting mirrors M1, M2, and M3. That is, according to the present apparatus, information on the circuit pattern of the mask MS is transmitted to the wafer WF in the form of an X-ray intensity distribution, and the circuit pattern is transferred to a photoconductor (resist) for X-ray applied on the wafer WF. Is formed. The X-rays to be used can be in any wavelength range according to the characteristics of the photoreceptor and the projection optical system. However, if an X-ray source that emits X-rays in the desired wavelength range cannot be obtained, BN (boron / The mask MS may be illuminated via an X-ray filter having a predetermined absorption characteristic such as a nitroid. After the printing of one chip or a plurality of chips is completed in one shot, the wafer stage is moved (stepped) by the driving devices 70 and 71 to feed an area including the chips or the plurality of chips adjacent to the effective printing range of the projection optical system. After the mask MS and the chip to be printed on the wafer WF are again aligned, the chip is printed by X-rays (repeat). This operation is performed on a plurality of chips on the wafer WF in a predetermined order, and all of the plurality of chips separated by scribe lines on the wafer W are exposed by a large number of shots. The exposed wafer WF is automatically replaced with an unexposed wafer WF, and the above-described exposure process is performed again.

An example of an alignment procedure in the present embodiment will be described below.

In FIG. 14, the driving members 70, 71
By moving the wafer stage composed of 1,52, the alignment marks 6A, 6B, 6C on the component member 50 are moved to the stage alignment scope through the projection optical system composed of the reflecting mirrors M1, M2, M3.
Position so that observation is possible sequentially with 10, 11, and 12.

That is, first, the semiconductor laser head LZ mounted on the lower surface of the support plate SS is driven and turned on. Next, the stage is moved so that the alignment mark 6A on the wafer stage comes to a position facing the hole h2. Next, focus detection is performed by the alignment scope 12 using the alignment mark 2A of the mask stage 1 and the alignment mark 6A of the wafer stage. At this time, the wafer stage is moved up and down for focusing by the piezoelectric element P1. Similarly, the marks 6B and 6C sequentially face the hole h2, focus detection is performed by the marks 2B and 2C and the scopes 11 and 10, the piezoelectric elements P2 and P3 are sequentially operated, and the wafer stage moves up and down. Thus, three marks 2A, 2B, 2C and three marks 6A, 6B, 6C
Is set at the in-focus position, so that the orthogonality between the mask stage and the wafer stage is accurately secured. Immediately after each focus detection of each point, the shift amounts in the X and Y directions are sequentially measured and stored using the marks 2A, 2B and 2C and the marks 6A, 6B and 6C. At this time, the correction driving can be performed using the motors 70 and 71.

Since the distance between the mask MS and the wafer WF is long in the apparatus of the present embodiment, the orthogonality correction between the mask MS and the wafer WF is useful. Also, in the case of the optical system shown in FIGS. 1, 4, 8, and 13, the parallelism between the mask MS and the wafer WF can be similarly corrected. In addition, by detecting the alignment marks 6A, 6B, and 6C of the wafer stage with the illumination light that has traveled backward through the reduction optical system in this way, for example, when the reduction ratio is 1/5, the detection can be performed by magnifying five times. preferable.

Information about the alignment from the alignment scope 10, 11, 12 can be obtained visually or photoelectrically,
Various known methods may be used.

Now, of the exposure areas on the wafer WF held on the component member 50, the areas exposed by the first one shot, for example, the positions of the areas of one chip separated by orthogonal scribe lines and the alignment marks 6A, By determining the positional relationship with 6B and 6C in advance, after the above-described stage alignment is completed, the wafer stage composed of the constituent members 50, 51, and 52 is moved based on the positional relationship, and the first one shot on the wafer WF is shot. The region can be sent to the vicinity of the image forming position of the mask MS by the projection optical system. A predetermined pair of alignment marks WM are provided around the area to be exposed in the first one shot on the wafer WF, that is, on the scribe line,
The alignment marks and the alignment marks (not shown) formed on the mask MS are visually or photoelectrically observed through the mask / wafer alignment scopes 20 and 21 to perform more accurate alignment.

Further, the wavelength of the semiconductor laser head LZ as a light source for the above-described alignment is, for example, 780 nm to 850 nm,
For example, the wavelength is one or two orders of magnitude longer than the wavelength of X-rays for exposure of 100 °, and the reflecting surface of the multilayer mirror can reflect laser light very well, just like a mere gloss layer of gold. Further, the alignment mark on the wafer WF or the wafer stage is reflected in the order of the reflecting mirrors M3, M2, and M1 and proceeds toward the mask MS.
It can be observed at double magnification.

At this time, for example, even if two types of semiconductor laser wavelengths, for example, 780 nm and 850 nm, are used for two types of resists, the reflecting mirror has essentially no wavelength dependency on the wavelength of this order, so it is always used. This is preferable because a high degree of alignment accuracy can be maintained.

After the above alignment is completed, the above-described exposure process is started. If the positional relationship and the order of exposure between the region exposed in the first shot and each region sequentially exposed by step and repeat are given to a control device (not shown), The exposure area subsequent to the area to be exposed can always be sent to an accurate position by stepping (moving) the wafer stage with high precision through the control device. It is not necessary to perform alignment between the wafer and the wafer WF. In particular, in order to improve the throughput, the alignment is performed only for the first shot described above, and the remaining shots are set on the stage, compared to the method of aligning the mask MS and the wafer WF for each shot (die-by-die alignment). It is more preferable to use a method in which the exposure area is accurately sent by the mechanical accuracy of the above.

The projection exposure apparatus shown in FIG. 14 is used in a vacuum state in order to perform exposure using X-rays. For example, the inside of the apparatus is evacuated by an evacuation unit (not shown) such as a vacuum pump, and exposure is performed in a vacuum state of about 10 ⁻⁶ Torr. It is desirable that the degree of vacuum inside the apparatus is higher. In the present projection exposure apparatus, exposure is performed in a high vacuum to ultra-high vacuum state. At this time, the above-described reflector cooling means is useful.

Also, instead of vacuuming the inside of the device,
Replace the atmosphere consisting of N ₂ and O ₂ with light elements such as H and He,
Exposure may be performed by filling a light element into the inside of the apparatus.
For example, the front side of the mask MS (X-ray irradiation side), the back side of the mask MS (in the lens barrel 3), and the upper surface of the wafer WF are all filled with He and flow at a constant speed in FIG. Then, these light elements have substantially zero absorption of X-rays and have better heat absorption than vacuum, so that the mask MS and the reflecting mirror are not distorted by heat. Exposure by such a method results in beryllium
The number of X-ray transmission windows made of Be is also minimized, and attenuation can be minimized, so that X-rays can be used effectively. On the other hand, for example, if the upper part of the mask is a He chamber, the lower lens barrel 3 is a vacuum chamber, and the upper part of the wafer is an atmosphere chamber, a B window is required at each boundary, and X-ray attenuation is increased. He is safer because H burns easily. Even when the mirror is filled with He, the aforementioned forced cooling means may be added to the mirror.

Also, when the wavelength of X-rays used for exposure is large, the effect on the human body and the like is small due to the large absorption of various substances. Absent. On the other hand, if the wavelength of X-rays becomes shorter, the absorption of various substances becomes smaller. Therefore, it is preferable to provide an X-ray shield depending on the wavelength of X-rays to be used.

As described above, according to the projection exposure apparatus as shown in FIG. 14, since the pattern of the mask illuminated by the X-rays is imaged on the wafer through the projection optical system and the exposure is performed, the reduction magnification is set as the projection optical system. By using what you have,
The precision with respect to the pattern of the mask is eased as compared with the conventional proximity method, and the manufacture of the mask is facilitated. It goes without saying that the resolution can be improved by reducing and projecting. Further, the degree of freedom of the X-ray source that can be used is increased, and the apparatus has high versatility. Further, accurate gap measurement and interval adjustment between the mask and the wafer required by the proximity method are not required.

As described above, two types of X-ray masks, a reflection type and a transmission type, can be used as the mask used in the present invention. The transmission type X-ray mask includes an X-ray absorber and a mask substrate that supports the X-ray absorber, and the mask substrate is patterned by the X-ray absorber. As a material of the X-ray absorber, Au, Ta, W, or the like, which has a high X-ray absorption rate and is easy to process, can be used. On the other hand, as a material of the mask substrate, an organic polymer or an inorganic substance can be used. Examples of the organic polymer include polyimide, mylar, and Kapton, and examples of the inorganic substance include Si, SiC, Si ₃ N ₄ , Ti, and BN in which B is diffused. Also, a SiN substrate, a composite substrate of polyimide and BN, and the like can be used.

The reflection type X-ray mask is a mask in which a pattern is drawn using a material having a high reflectance on a mask substrate having a low reflectance, and for example, a thick mask made of a material having a low electron density (light element material) such as Si. It is possible to use a mask in which a pattern is drawn on a substrate with a substance having a high electron density (heavy element substance) such as Au, or a multilayer reflective film made of Ti and Ni is patterned on a mask substrate.

The mask MS used in the present invention must be appropriately selected according to the wavelength of the X-ray used. For example, for X-rays having a wavelength of about several degrees to several tens of degrees, the mask material described above can be selected. For X-rays having a relatively long wavelength of several tens to several hundreds of degrees, the above-described mask material can be used. Is not preferred because absorption is too large. This several tens to several hundreds of X
As the line mask, it is preferable to form a mask by making holes in the X-ray absorbing member or reflecting member according to the circuit pattern.

Further, as the X-ray source used in the present invention, a so-called electron beam-excited X-ray source that irradiates a solid metal with an electron beam to generate X-rays, a laser plasma, a rare gas plasma, Source using surface discharge plasma, SO
A radiation source using synchrotron radiation represented by R (Synchrotron Orbital Radiation) is used.

Further, a photoreceptor for X-rays used for exposure, that is, a resist is made of various materials from high-sensitivity to relatively low-sensitivity, depending on the energy density of X-rays for exposure which differs depending on the X-ray source used. You can choose. For example, negative-type X-ray resist materials include polyglycidyl methacrylate-CO-ethyl acrylate (COP), polyglycidyl methacrylate maleic acid adduct (SEL-N), polydiaryl orthophthalate, epoxidized polybutadiene, and polystyrene TTF. There are metal-containing salt resist materials, halogen-containing polyvinyl ether resist materials, and halogen-containing polyacrylate resist materials. Positive X-ray resist materials include polymethyl methacrylate (PM
MA), polyhexafluorobutyl methacrylate, polytetrafluoropropyl methacrylate, polymethacrylonitrile, poly (MMA) -CO-trichloroethyl methacrylate), polybutene-1-sulfone, and a metal-containing salt resist material, polytrichloroethyl methacrylate, Examples include polymethyl methacrylate-CO-dimethylmethylene malonate (PMMA-CO-DMM), a copolymer of n-hexylaldehyde and n-butyraldehyde, and polychloroacetaldehyde.

[Effects of the Invention] As described above, according to the present invention, alignment information can be obtained with high accuracy, so that alignment can be performed efficiently and with high accuracy.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing the configuration of an X-ray reflection projection reduction optical system that can be used in an exposure apparatus according to a first embodiment of the present invention. FIGS. 2 and 3 illustrate the principle of the optical system in FIG. FIG. 4 is a schematic diagram showing an example in which a multilayer reflector is used in the optical system of FIG. 1 and important parts are schematically illustrated and emphasized. FIG. 5 is an optical system of FIG. FIGS. 6A and 6B are graphs showing an example of astigmatism and distortion of the optical system of FIG. 1, and FIGS. 7A to 7D. Is a graph showing an example of lateral aberration at different object heights in the optical system of FIG. 1; FIG. 8 is an explanatory diagram for explaining the reason why illumination light is incident non-perpendicularly on the mask of FIGS. FIG. 9 shows a reflection type optical system according to a second embodiment of the present invention suitable for printing a plurality of shots by moving a wafer stepwise. FIG. 10 is a schematic diagram showing a configuration of a system, FIG. 10 is a schematic diagram showing a configuration of an optical system according to a third embodiment of the present invention in which the transmission type mask of the optical system in FIG. Is a schematic diagram showing a configuration of an optical system according to a fourth embodiment of the present invention in which a horizontal X-ray luminous flux from a SOR light source is totally reflected and scanned by a reflecting mirror. FIG. FIG. 13 is a schematic view showing a configuration of an optical system according to a fifth embodiment of the present invention, which is installed at an angle. FIG. FIG. 14 is a schematic diagram showing the configuration of an optical system according to a sixth embodiment of the present invention suitable for printing a plurality of shots. FIG. 14 is a seventh embodiment of the present invention using the optical system shown in FIGS. FIG. 15 is a configuration diagram showing the configuration of a reflection reduction projection type X-ray exposure apparatus according to an embodiment, and FIG. FIG. 15 is a partially enlarged sectional view of a wafer stage of the apparatus shown in FIG. MS: Mask, M0 ', M0 to M3, MTR: Reflector, R1 to R3: Multilayer reflective film, WF: Wafer, FF: Front focal position, IP: Entrance pupil position, PL: Chief ray, MM: Copying mirror O, O ', O ", O: optical axis, C0, C1, C2: cooling means, L: light flux, SR: X-ray light flux from SOR light source, 1: mask stage, 2A , 2B, 2C, 6A, 6B, 6C: alignment mark, 3: light guide member, 4: lens barrel, 10, 11, 12: stage alignment scope, 20, 21: mask / wafer alignment scope, 50, 51, 52 : Stage constituent members, 70, 71: drive device, P1 to P3: piezoelectric element, 90 to 92: length measuring device for stage control, h1, h2: hole, WM: alignment mark, LZ: laser head.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shigentaro Ogura 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Takuo Kariya 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (72) Inventor Yoshiaki Fukuda 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Yasuo Kawai 3-30-2, Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Setsuo Minami 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-62-65327 (JP, A) JP-A-62-9632 (JP, A) JP-A-53-42679 (JP, A) JP-A-63-312638 (JP, A)

Claims (2)

(57) [Claims] An apparatus includes a mask stage for holding a mask, a wafer stage for holding a wafer, and a plurality of multilayer X-ray reflecting mirrors each provided with at least one forced cooling means. X for reducing and projecting the illuminated mask pattern onto the wafer
Line reducing optical means, and irradiating the alignment mark provided on the wafer or wafer stage with light, and reversing the light from the mark through the plurality of multilayer X-ray reflecting mirrors to enlarge image information of the mark. An X-ray exposure apparatus, comprising: mark detection means for detecting the following. 2. An X-ray exposure apparatus according to claim 1, wherein at least one of said plurality of multilayer X-ray reflecting mirrors is an aspherical reflecting mirror.