JPH06177019A - Optical element and its manufacture - Google Patents

Abstract

PURPOSE:To improve yield in optical loss by laminating multi-layer films on a smooth-surface substrate to the thickness larger than the number of lamination at which reflectivity saturates, for inspection, and removing defects from an upper layer if the multi-layer has a defect. CONSTITUTION:A thin film layer 119 is vapor-deposited on a substrate 11 having an ultra-smooth surface, then two kinds of material are alternately laminated, for forming a multi-layer film 21. Here, inspection is carried out with an optical microscope and an x-ray microscope, to remove a defective layer-pair. Then, inspection is carried out again with the optical microscope and x-ray microscope, and until actually reflectivity saturates itself, layer-pairs are laminated, and a resist is coated on it, so that patterns 22 and 2203 of a reflective mask are formed. Then, inspection is carried out again with the optical microscope and x-ray microscope, to confirm that no defect exist, respectively. With this, at an inspection/repair process, yield of expensive multi-layer film optical elements becomes greater, significantly contributing to reduced manufacturing costs of optical elements.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element such as a reflective mask used for reduced X-ray lithography for transferring semiconductor patterns, which is used for image formation by exposure or irradiation with vacuum ultraviolet rays or X-rays, and a method for manufacturing the same. It is about.

[0002]

2. Description of the Related Art In order to improve the degree of integration and operation speed of solid-state elements in LSI, circuit patterns are becoming finer. At present, a reduction projection exposure method in which an exposure light source is ultraviolet rays is widely used for forming these patterns. The resolution of the exposure method is proportional to the exposure wavelength λ and inversely proportional to the numerical aperture NA of the projection optical system. The resolution limit has been improved by increasing the numerical aperture NA. However, this method is approaching its limit due to the reduction of the depth of focus and the difficulty in designing and manufacturing the refractive optical system (lens). For this reason, means for shortening the exposure wavelength λ has been implemented. For example, from the g-line (λ = 435.8 nm) of a mercury lamp to the i-line (λ = 3)
65 nm) and a KrF excimer laser (λ = 249
nm) and the like. The resolution is improved by shortening the exposure wavelength. However, it is almost impossible to obtain a resolution of 0.1 μm (100 nm) or less from the theoretical limit based on the size of the wavelength of ultraviolet rays used for exposure.

On the other hand, as a method for forming a fine pattern, there is a proximity equal-magnification X-ray lithography in which an exposure wavelength is a soft X-ray of about 0.5 nm to 2 nm. Since this method has a short exposure wavelength, it is possible in principle to obtain a high resolution of 0.1 μm or less. Generally, in order to form a circuit pattern on a desired element, a pattern on the mask is transferred to a resist mask on the wafer. In the above-mentioned proximity equal-magnification X-ray lithography, a transmission type mask called an equal-magnification X-ray mask is used.
The X-ray permeable portion of the equal-magnification X-ray mask is formed of a thin film, which is usually called a membrane and has a thickness of about 2 μm, which is formed of a light element material such as Si, SiN, SiC, and C. Further, the portion that absorbs X-rays in the equal-magnification X-ray mask has a thickness of about 0.5 μm to 1.0 μm called an absorber on the membrane, and W, Au,
A circuit pattern made of a heavy metal such as Ta is formed.
Therefore, since the circuit pattern is formed on the membrane of the above-mentioned equal-magnification X-ray mask having a very low rigidity, the internal stress of the heavy metal as the absorber and the external force when the X-ray mask is mounted on the predetermined exposure apparatus. As a result, the circuit pattern is distorted and a desired circuit pattern cannot be transferred to the resist on the wafer. Especially, in the proximity equal-magnification X-ray lithography, the pattern of the equal-magnification X-ray mask is transferred to the resist at the equal magnification of 1: 1. Therefore, the pattern distortion on the equal-magnification X-ray mask is 1: 1 to the resist. Transcribed. The problem of causing distortion in the pattern of the same-size X-ray mask, which has low rigidity, is
This is a big problem in the near-magnification X-ray lithography.

On the basis of the above background, reduction X-ray lithography using vacuum ultraviolet rays or soft X-rays as an exposure light source has recently attracted attention. For example, Japanese Journal of Applied Physics
rnal of Applied Physics) 1991, No. 30, 11
Volume B, p. 3051. FIG. 6 shows an example of an exposure optical system for reduction X-ray lithography. Vacuum ultraviolet rays or soft X-rays 411 are used as an exposure light source, and are obliquely incident at an incident angle 42 of θ to illuminate the reflective mask 81. θ
The incident angle 42 of is different from various optical systems, but is about 1 ° to 15 °. In order to create a working area, direct incidence with an incident angle of 0 ° is not possible with the exposure optics of reduced X-ray lithography. The reflective mask 81 is formed with the multilayer film 2 capable of specularly reflecting vacuum ultraviolet rays or soft X-rays.
The vacuum ultraviolet rays or the soft X-rays 411 reflected from the reflective mask 81 are reflected by the convex mirror 92, and further the concave mirror 9
It is reflected at 1 and forms an image on the wafer 82. The convex mirror 9
2 and the concave mirror 91, the multilayer film 2 is formed on the entire surface of the mirror. Generally, in such an optical system, when the xyz coordinate system is adopted as shown in FIG. 6, the x direction is the meridional direction and the y direction is the sagittal direction.

A conventional reflective X-ray mask is, for example, an Extended Abstracts of the 18th Conference on Solid Solid Devices and Materials (Extended Abstracts of the 18th C).
onference on Solid State Devices and Material)
(1986), p17-p20, a region where the multilayer film exists in a region having a high reflectance, and a region where a multilayer film or a multilayer film structure does not exist in a region having a low reflectance or no reflectivity. Formed as. The X-ray mask shown in FIG. 7A irradiates the multilayer film 2 on the substrate 1 with the focused ion beam 5 to change the quality in the direction perpendicular to the substrate 1,
A region having a low reflectance or the non-reflecting portion 3 is formed, and a pattern is formed in a region of the multilayer film 2 having a high reflectance.

Further, in the example shown in FIG. 7B, a predetermined portion of the multilayer film 2 on the substrate 1 is removed to form a portion without the multilayer film, that is, the non-reflection portion 3. Substrate 1 used here as an optical element such as a reflecting mirror or an X-ray mask
Requires a super-smooth substrate without roughness in order to obtain high reflectance, and is generally expensive.

Further, as described in JP-A-64-4021, a predetermined thickness and shape are formed on the multilayer film 2 directly attached to the ultra-smooth substrate 1 shown in FIG. 7C. There is also an example of a reflection type X-ray mask in which the absorber pattern 35 is formed and used as a non-reflecting portion.

Furthermore, another example of the reflection type X-ray mask is described in JP-A-1-152725. That is, as shown in FIG. 7D, the surface of the substrate 1 of the reflective mask is partially removed in advance by etching to form a concavo-convex structure 33 to form a predetermined pattern, and then the multilayer film is formed on the surface of the substrate 1. 2 is formed, and the convex structure portion serves as a reflecting portion and the concave structure portion 34 serves as a non-reflecting portion.

When the wavelength of vacuum ultraviolet rays or X-rays used for exposure or irradiation is small, vacuum ultraviolet rays or X-rays are used.
In order to increase the reflectance of the multilayer film with respect to the line, it is necessary to increase the number of laminated layers of the multilayer film. For example, in order to obtain a high reflectance, 50 layer pairs or more at an X-ray wavelength of 13 nm is used.
The number of layers required is about 100 layer pairs or more for nm, and about 150 layer pairs or more for 7 nm.

[0010]

However, the more films that are stacked as described above, the greater the possibility that defects will occur in the stacked films. Since a multilayer film having a defect cannot obtain a desired reflectance, an optical element is inspected after manufacturing the element, and if a defect is found, the multilayer film having a defect becomes a defective product. Therefore, the yield of the optical element is reduced and the cost of manufacturing the optical element is increased.

In order to increase the resolution as described above,
Although it is necessary to shorten the wavelength or increase the NA, there is a limit to shortening the wavelength or increasing the NA because of the balance of the depth of focus and the like. In order to avoid this problem, JP-A-4-11891
As described in Japanese Patent Publication No. 4, when a natural number is n and an incident angle of vacuum ultraviolet rays or X-rays used for exposure or irradiation is θ at a desired position on a substrate of an optical element, it is approximately λ · (2n−1). / (4 · cos θ) is provided to form a multi-layer film, and a predetermined pattern is adjacent to or adjacent to a predetermined pattern. -1) / (4 ・ cos θ)
By arranging so as to become, it becomes possible to transfer and image a fine pattern exceeding the resolution limit of the imaging optical system. However, when a defect occurs in the multilayer film laminated on the substrate, the correction of the multilayer film is not taken into consideration, so that there is a problem that the multilayer film becomes a defective product and the yield of optical elements decreases.

[0012]

[Problems to be Solved by the Invention] The above problems are
In an optical element in which a multilayer film having a region having a relatively low reflectance with respect to vacuum ultraviolet rays or X-rays and a region having a relatively high reflectance with respect to X-rays is arranged in accordance with a predetermined pattern, a laminate in which the reflectance with respect to the vacuum ultraviolet rays or X-rays is saturated. By stacking the multilayer film having a thickness of several layers or more on a smooth substrate, it is possible to solve the problem by inspecting and removing the defect from the upper layer when the multilayer film has a defect.

Further, the above-mentioned defects in the multilayer film can be solved by removing the defects one by one from the upper layer or laminating the multilayer films thereafter.

Further, the above-mentioned multilayer film is formed by vacuum ultraviolet rays or X
A region having a relatively high reflectance and a region having a relatively low reflectance with respect to the line are arranged according to a predetermined pattern, and the height of the pattern of the high reflectance region adjacent or adjacent to the line is λ · (2n−1) / (4・ Cos
By removing from the upper layer so as to change only θ), the resolving power of the optical element can be increased, and the kind of the surface material of the high reflectance region in the above multilayer film and the thickness of one layer thereof should be the same. As a result, it is possible to improve the fineness of the pattern on which the optical element is transferred or imaged.

[0015]

First, let us consider the relationship between the number of layers of a multilayer film in which two kinds of substances having different optical constants for vacuum ultraviolet rays or X-rays are alternately laminated and the reflectance for the vacuum ultraviolet rays or X-rays. A, B, and C shown in FIG. 8 have an incident angle of 5 ° and have wavelengths of vacuum ultraviolet rays or X-rays of about 13, 10, and 7, respectively.
Mo whose period length is designed to show peak reflectance in nm
2 shows the relationship between the reflectance and the number of laminated layers (number of laminated layers) of the multilayer films of / Si, Ru / BN, and Ru / BN. In either case, as the number of stacked layers increases, each reflectance increases with a small vibration. Furthermore, when the number of stacked layers is about 50 layers for 13 nm and about 100 layers for 10 nm, and 150 layers for 7 nm, the above-mentioned reflectances are saturated with a small vibration. If the wavelength of vacuum ultraviolet rays or X-rays used becomes smaller, the number of laminated layers also increases, so that the film thickness of the entire multilayer film also increases. This indicates that the penetration depth of vacuum ultraviolet rays or X-rays into each multilayer film increases as the wavelength becomes shorter. If a defect occurs during the lamination of the multilayer film, the desired reflectance cannot be obtained.

A, B, and C shown in FIG. 9 have wavelengths of 13 nm and 10 n, respectively, when there are defects in the number of laminated pairs of 30 layers, 50 layers, and 100 layers, respectively.
This is the reflectance for X-rays of m and 7 nm. It is shown that the reflectance is saturated just before the number of laminated layers with defects, and the reflectance is reduced even if the number of laminated layers is more than that. A of FIG.
As shown in B and C, by removing the above-mentioned multilayer film from the upper layer of the multilayer film to the place where there is a defect, each multilayer film shows the maximum reflectance in each number of stacks. Further, after removing the defective multilayer film, a new multilayer film having no defect is laminated to reproduce an optical element having a multilayer film having high reflectance.

Further, the number of laminated layers of the multi-layered film is set to be thicker than the number of laminated layers at which the reflectance of the multi-layered film with respect to vacuum ultraviolet rays or X-rays is saturated, and the multi-layered film is relatively reflected with respect to the vacuum ultraviolet rays or X-rays. When a region having a high reflectance and a region having a low reflectance are arranged in the multilayer film according to a predetermined pattern,
When a defect occurs on the surface of the multilayer film pattern, the reflectance in a saturated state can be obtained by removing a predetermined number of multilayer films from the upper layer of the multilayer film. For example, wavelength 1
In the case of laminating 150 layers of a multilayer film for 0 nm, the above X
When a region having a high reflectance and a region having a low reflectance with respect to the line are arranged in the multilayer film according to a predetermined pattern,
About 10 layer pairs are removed from the surface of the defective multi-layer film pattern, which has a reduced reflectance due to the occurrence of defects on the surface of the multi-layer film pattern. In this case, the number of laminated multilayer films of the optical element is 140 layer pairs, but this laminated pair has a saturated reflectance with respect to the above X-rays, and has a reflectance equivalent to that of a good quality multilayer film of 150 layer pairs.

By the way, in FIG. 11, the incident angle is 5 °, the number of laminated Mo / Si multilayer films whose period length is designed so that the X-ray wavelength has a peak reflectance at about 13 nm, and the phase of the amplitude reflectance is shown. It shows the relationship of. The phase of the amplitude reflectivity is also saturated by vibrating at the number of laminated layers where the reflectivity is saturated. The phase of the amplitude reflectance is different when the surface of the multilayer film is a metal layer of Mo and when it is a Si layer.

In a method of manufacturing an optical element including a step of removing a multilayer film from an upper layer, a multilayer film in which at least two kinds of substances having different optical constants with respect to vacuum ultraviolet rays or X-rays are alternately laminated on a substrate. The number of stacked layers is set to be larger than the penetration depth of the vacuum ultraviolet rays or X-rays, and a region having a high reflectance and a region having a low reflectance with respect to the vacuum ultraviolet rays or the X-rays are formed according to a predetermined pattern. It is arranged in a multilayer film and the height of the pattern in the adjacent area with high reflectance is
By changing by (2n−1) / (4 · cos θ), the relative phase of the X-rays reflected from the adjacent pattern of the region having high reflectance is inverted as shown in FIG. The intensity distribution of the line changes as shown in FIG. 1C, and the contrast of adjacent image patterns increases. Here, it is desirable that the surface materials of adjacent regions having high reflectance are made the same so that the phases of the amplitude reflectance are aligned. This is because when the material of the first layer forming the pattern surface of the adjacent high reflectance region is different,
As shown in FIG. 11, the relative phase difference of the amplitude with respect to the reflected light from the pattern in the adjacent region having high reflectance is 180.
The contrast of adjacent patterns does not increase so much. FIG. 12 shows a conventional reflective mask,
The structure is shown in (a), and (b) and (c)
Shows changes in phase and intensity of vacuum ultraviolet rays or X-rays reflected from the mask.

Further, when the height difference between adjacent or adjacent high reflectance patterns is m · (da + db), the value of m can be determined so that the following relational expression holds. desirable.

M · (da + db) = λ · (2n−1) / (4 · cos
θ) Here, m and n are natural numbers, and da is a multilayer film 1
The film thickness of the layer, db is the film thickness of another layer forming the multilayer film, λ
Is the wavelength of vacuum ultraviolet rays or X-rays used for illuminating or exposing the optical element, and θ is the incident angle of vacuum ultraviolet rays or X-rays used for illuminating or exposing the optical element. For example, da is M
The film thickness is 2.58 nm for the o film and BN film for the db is 2.
58 nm, 81 layers of Mo films, and 80 layers of BN films are alternately laminated, and the thickness is changed to give m = 17 and n = 18 at λ = 10 nm and θ = 5 °. When the Mo film and the BN film are removed one by one from the upper layer of the multilayer film, the relative phase with respect to the X-ray reflected from the pattern of the adjacent high reflectance region is inverted by 180 °, and the image contrast of the adjacent pattern is increased. Will increase. The Mo film is exposed on the outermost surface of each of the adjacent patterns having high reflectance. Here, it is desirable that the accuracy of the height difference between the patterns in the adjacent or adjacent regions having high reflectance is within about 5% with respect to the cycle length of the multilayer film. Where m
= 17, n = 18, the left side of the above equation is 87.72 nm,
The right side is 87.83 nm. This difference is 0.11 nm, and the error is 2% when the cycle length of the multilayer film is 5.16 nm.
There is no problem.

[0022]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a diagram showing an embodiment of an optical element according to the present invention,
2 is a diagram showing a manufacturing process flow of the above optical element, FIG. 3 is a diagram showing an example of an optical element having a defect in a multilayer film, FIG. 4 is a diagram showing an example of an optical element pattern formed by this embodiment,
FIG. 5 is a diagram showing an X-ray projection exposure apparatus on which the optical element according to the present invention is mounted.

First Embodiment A first embodiment shown in FIG. 1 exemplifies a reflection type mask as an optical element, (a) is a sectional view of the above element, (b) is a diagram showing an amplitude distribution of reflected light, ( FIG. 3C is a diagram showing the intensity distribution of the reflected light. The reflective mask is shown in FIG.
As shown in FIG. 3, at least two kinds of substances having different optical constants for vacuum ultraviolet rays or X-rays are alternately laminated on the substrate 11 to form the multilayer film 21, and the reflectance for vacuum ultraviolet rays or X-rays is relatively high. An optical element in which a low region and a high region are arranged in the multilayer film 21 according to a predetermined pattern, and each of the multilayer films 2 forming the pattern.
The reference numerals 2, 2203 are thicker than the number of laminated layers at which the reflectance with respect to the vacuum ultraviolet ray or the X-ray is saturated, and are laminated on the smooth substrate 11 through the thin film layer 119 of aluminum to form the pattern with high reflectance. 22 and the high-reflectance multilayer film 2203 adjacent to or close to each other, λ · (2n−
There is a height difference of 1) / (4 · cos θ). Therefore, the phase of X-rays or the like reflected from the pattern is inverted by the height difference Δ on the surface of the multilayer film forming the pattern, cancels each other out in the region where the reflectance is relatively low, and the contrast of adjacent image patterns increases. To do.

Next, an example of manufacturing the reflective X-ray mask will be described. The part shown in FIG. 2 shows the manufacturing process of the above embodiment. Silicon substrate or Si with ultra-smooth surface
A thin film layer 119 of an aluminum (Al) film that protects the substrate 11 when removing the multilayer film is vapor-deposited to a thickness of 200 nm on the C substrate 11 by magnetron sputtering, which is one of the sputtering vapor deposition methods. At this time, the pressure of the sputtering gas is desirably as low as possible. Next, a carbon (C) film having a thickness of 1.27 nm and a nickel (Ni) film having a thickness of 1.27 nm are alternately formed to form a multilayer film 21.
At this time, each layer of 20 layers was inspected with an optical microscope and an X-ray microscope. The inspection after stacking 160 layers was found that the multilayer film 21 had a defect. At this time, the reflectance for X-rays having a wavelength of 5 nm was 25%. Therefore, 20 layer pairs were removed from 160 layer pairs to make 140 layer pairs. Again, every 20 layer pairs were inspected with an optical microscope and an X-ray microscope, and a total of 200 layer pairs in which the reflectance was substantially saturated were laminated. A resist was applied thereon to form a reflection type mask as shown in FIG. 1 (a), which was again inspected with an optical microscope and an X-ray microscope, and it was confirmed that there was no defect in each.

Second Embodiment Similar to the above embodiment, an aluminum (Al) film 119 is vapor-deposited to a thickness of 200 nm on a silicon substrate or SiC substrate 11 having an ultra-smooth surface by magnetron sputtering, and then ruthenium (Ru). A 1.78 nm thick film and a 1.78 nm thick boron nitride (BN) film are alternately laminated to form a multilayer film. At this time, each stack of 10 layer pairs was inspected by an optical microscope and an X-ray microscope, and it was found by inspection after stacking 120 layer pairs that the multilayer film had a defect. Therefore, the Ru film and the BN film are removed one by one from the 120 layer pair,
Each time one layer was removed, inspection was performed with an optical microscope and an X-ray microscope. In order to remove the Ru film and the BN film one by one, the temperature of the sample substrate was cooled to −100 ° C., and digital etching was used in which carbon tetrafluoride gas was adsorbed on the sample surface for etching. When the removal and inspection were repeated for each layer, a defect was found in the 115th layer pair, and up to the 110th layer pair was removed. After that, the Ru film and the BN film are alternately laminated again, and a total of 150 layer pairs are laminated while inspecting with an optical microscope and an X-ray microscope for every 10 layer pairs.
It was confirmed that there were no defects. A reflection type mask was formed in the same manner as in the first example, and it was again inspected with an optical microscope and an X-ray microscope to confirm that there was no defect.

Third Embodiment Further, similarly to the above-mentioned embodiment, a silicon substrate or a SiC substrate 11 having an ultra-smooth surface is coated with an aluminum (Al) film 119 at a thickness of 200 n by a magnetron sputtering method.
After vapor deposition to a thickness of m, molybdenum (Mo) film 2.58
nm thickness and boron nitride (BN) film 2.58 nm thickness were alternately laminated to form a multilayer film. At this time, an inspection with an optical microscope and an X-ray microscope is performed for each stack of 10 layers.
Up to 50 pairs of layers were laminated, but inspection revealed that the multilayer film had no defects. At this time, the reflectance for X-rays having a wavelength of 10 nm was 35%. A reflective mask was formed in the same manner as in the above example, but it was found by inspection with an optical microscope and an X-ray microscope that there were defects on the surface of the multilayer film pattern. It is considered that the above defects were generated during the pattern forming process of the reflective mask. Therefore, the Mo film and the BN film were removed one by one from the surface of the multilayer film 150 layer pairs, and a total of 10 layer pairs were removed. Optical microscope and X again
Inspection with a line microscope confirmed that there were no defects. In this example, the reflectance was saturated in the Mo layer 241 layer and the BN layer 240 layer, but after that, a reflective mask similar to that in the above example was formed, and it was confirmed by inspection with both microscopes that there was no defect. FIG. 3A is a diagram showing defects 2202 existing on the surface of the multilayer film pattern 22, and FIG. 3B is a diagram showing a defect-free reflective mask obtained by removing the defects 2202.

Fourth Embodiment Next, a molybdenum (Mo) film 2.5 is formed on the aluminum (Al) film 119 formed in the same manner as in the above respective embodiments.
A multilayer film was formed by alternately stacking a 8 nm thick boron nitride (BN) film and a 2.58 nm thick boron nitride (BN) film. At this time, each layer of 10 layers was inspected with an optical microscope and an X-ray microscope.
Up to 150.5 layer pairs were laminated (Mo 151 layer and BN1
A total of 301 layers were alternately laminated with 50 layers), and the inspection result showed that there were no defects in the multilayer film. The reflectance for X-rays having a wavelength of 10 nm was 35%. A reflective mask was formed in the same manner as in the above example to form a multilayer film pattern. Further, when the difference in height between the patterns of the above-described regions of high reflectance that are adjacent or close to each other is m (da + db), the value of m was determined so that the following relational expression approximately holds.

M · (da + db) = λ · (2n−1) / (4 · cos
θ) where m and n are natural numbers and da is molybdenum (Mo)
The thickness of the film, db is the thickness of a boron nitride (BN) film, λ is the wavelength of vacuum ultraviolet rays or X-rays used for illuminating or exposing an optical element, and θ is the vacuum ultraviolet ray or X used for illuminating or exposing an optical element. The angle of incidence of the line. From the upper layer of the multilayer film, M so that the film thickness is changed to give m = 17 and n = 18.
The o film and the BN film were removed one by one. The Mo film is exposed on both outermost surfaces of the adjacent patterns having high reflectance.
Inspection by an optical microscope and an X-ray microscope confirmed that there were no defects. Here, it is desirable that the accuracy of the height difference between the patterns of the adjacent or adjacent areas of high reflectance is within about 5% with respect to the cycle length of the multilayer film, but in this embodiment, m = 17. , N = 18, the left side of the above equation is 87.72.
nm, and the right side is 87.83 nm. This difference is 0.11
There is no problem because the error is about 2% for the cycle length of the multilayer film of 5.16 nm.

FIG. 4 shows an example of the pattern formed in this embodiment. (A) shows a high reflectance multilayer film region 2203 having a phase difference of (2n−1) π from the multilayer film region 22 having high reflectance.
And (b) show a pattern in which stripes are alternately arranged close to each other. (B) surrounds the high reflectance region 22 (2
(c-1) is a diagram showing a pattern in which high reflectance regions 2203 having a phase difference of (n-1) π are arranged close to each other, and (c) shows high reflectance having a (2n-1) π phase difference around the high reflectance region 22. The figure shows a pattern in which the index regions 2203 are adjacent and juxtaposed at intervals, and (d) shows a high reflectance region 22 having a phase difference of (2n-1) π on both sides of the high reflectance region 22.
FIG. 3 is a diagram showing a pattern in which 03 is adjacently arranged in a stripe shape.

Fifth Embodiment FIG. 5 shows an X-ray projection exposure apparatus on which a transfer experiment was carried out by mounting the reflection type mask manufactured in the above embodiment. In FIG. 5, the mask 81 and the wafer 82 are mounted on the mask stage 83 and the wafer stage 84, respectively. First,
The relative position between the mask 81 and the wafer 82 is detected using the alignment device 85, and the drive device 8 is controlled by the control device 86.
Alignment is performed via 7, 88. The X-ray emitted from the X-ray source 89 is condensed by the reflecting mirror 90, and the arc area on the mask 81 is illuminated. The positional relationship between the mask 81 and the incident X-ray 411 was set such that the minor axis direction of the thinner pattern was the sagittal direction of the incident X-ray and the major axis direction of the thinner pattern was the meridional direction of the incident X-ray. The X-rays reflected by the mask 81 are X-rays having a wavelength near 10 nm, and
An image is formed on the wafer 82 at a magnification of ⅕ by an image forming optical system 95 composed of 1, 92, 93 and 94. Reflector 9
1, 92, 93, and 94 are Mo similar to the mask 81.
A / BN-based multilayer film is deposited, and the cycle length of each multilayer film is adjusted so that the wavelengths of the reflected X-rays match. The mask 81 and the wafer 82 were synchronously scanned according to the magnification, and the pattern on the entire surface of the mask was transferred onto the wafer 82. By this method,
A pattern with a width of 0.07 μm could be obtained in a 30 mm square area on the wafer 82.

Sixth Embodiment Before forming a predetermined pattern on the multilayer film formed in the fifth embodiment, the multilayer film is mounted on the X-ray projection exposure apparatus shown in FIG. Transfer to the upper resist and inspected for defects in the multilayer film. The X-rays reflected by the multilayer film are composed of X-rays having a wavelength near 10 nm, and
An image forming optical system 95 composed of 1, 92, 93 and 94 forms an image on the resist on the wafer 82 at a magnification of 1/5.
The reflecting mirrors 91, 92, 93 and 94 are vapor-deposited Mo / BN multilayer films similar to the mask 81, and the cycle length of each multilayer film is adjusted so that the wavelengths of the reflected X-rays coincide with each other. The mask and the wafer were synchronously scanned according to the magnification, and the entire surface of the multilayer film was transferred to the resist on the wafer. After developing the resist, by inspecting the residual film characteristics of the resist on the wafer,
It was possible to confirm the presence or absence of defects on the entire surface of the multilayer film.

In each of the above-mentioned embodiments, the materials used for the multilayer film are Ni / C, Ru / BN, Rh / BN, Mo / Si.
Although the case of the C-based multilayer film has been described, the present invention is not limited to the above-mentioned materials. For example, NiCr / C, Ni / V,
Ni / Ti, W / C, Ru / C, Rh / C, Ru / B
N, Rh / B ₄ C, RhRu / BN, Ru / B ₄ C, Mo
/ Si, Pd / BN, Ag / BN, Mo / SiN, Mo
Any material capable of forming a multilayer film such as / B ₄ C, Mo / C, Ru / Be can be used.

Further, although the above-mentioned embodiment describes only the case of the reflection type mask, it is not limited to the reflection type mask,
It can also be applied to an optical element having a fine pattern on the reflecting surface such as a diffraction grating or a linear zone plate.

[0034]

As described above, in the optical element and the method for manufacturing the same according to the present invention, a multilayer film having a region having a relatively low reflectance and a region having a relatively high vacuum ultraviolet ray or X-ray reflectance is provided on a substrate. In the optical element arranged according to the pattern, the multilayer film is laminated on a smooth substrate with a thickness equal to or larger than the number of laminated layers where the reflectance with respect to the vacuum ultraviolet ray or the X-ray is saturated, and according to the formation of the multilayer film and a predetermined pattern. By including the inspection step and the defect removal step in the step of arranging the layers, the yield of the expensive multilayer optical element in the inspection and correction process becomes large, which can greatly contribute to the reduction of the manufacturing cost of the optical element and the manufacturing of the present invention. By transferring and imaging an optical element according to the method, the phase of the beam reflected from the adjacent pattern of the high reflectance region is inverted, and the contrast of the adjacent pattern is changed. There is increasing, it is possible to increase the resolution of the pattern image.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of an optical element according to the present invention,
(A) is a figure which shows the cross section of a multilayer film pattern, (b) is a figure which shows the amplitude distribution of reflected light, (c) is a figure which shows the intensity distribution of reflected light.

FIG. 2 is a diagram showing a manufacturing process flow of the optical element.

3A and 3B are diagrams showing an example of an optical element having a defect in a multilayer film, FIG. 3A is a diagram showing a multilayer film having a defect, and FIG. 3B is a diagram showing a multilayer film from which a defective portion is removed.

FIG. 4 is a view showing an example of a pattern formed in this embodiment,
(A) is a diagram showing a pattern in which a multilayer film in which a phase difference is (2n-1) π in a high reflectance region is alternately arranged in proximity to each other in a stripe shape, and (b) surrounds the high reflectance region (2n-1). A diagram showing a pattern in which high reflectance regions in which phases are different by π are close to each other,
(C) is a diagram showing a pattern in which (2n-1) high reflectance regions having different π phases are juxtaposed adjacent to each other around the high reflectance region, and (d) is (2n-) on both sides of the high reflectance region. 1) A diagram showing a pattern in which high reflectance regions having different π phases are adjacent to each other.

FIG. 5 is a diagram showing an X-ray projection exposure apparatus on which the optical element of the present invention is mounted.

FIG. 6 is a diagram showing an exposure optical system of a conventional X-ray reduction projection exposure method.

FIG. 7 is a diagram showing a conventional reflective mask, and includes (a) to
(D) is sectional drawing of the mask formed with the respectively different method.

FIG. 8 is a diagram showing the number of stacked multilayer films and the reflectance of reflected X-rays.

FIG. 9 is a diagram showing the relationship between the number of stacked multilayer films having a defect and the reflectance.

FIG. 10 is a diagram showing the relationship between the number of stacked layers and the reflectance when the defective multilayer film is removed.

FIG. 11 is a diagram showing the relationship between the number of stacked multilayer films and the phase of amplitude reflectance.

12A and 12B are diagrams showing a conventional optical element, FIG. 12A is a sectional view of the element, FIG. 12B is a diagram showing an amplitude distribution of reflected light, and FIG. 12C is a diagram showing an intensity distribution of reflected light.

[Explanation of Codes] 11 ... Substrate 21 ... Multilayer Film 22, 2203 ... Multilayer Film 89 for Forming Pattern 89 ... X-ray Source 119 ... Thin Film Layer 2202 ... Defect

Front page continuation (72) Inventor Eiji Takeda 1-280 Higashi Koikekubo, Kokubunji, Tokyo Inside Hitachi Central Research Laboratory

Claims (15)

[Claims] 1. An optical element in which a multilayer film having a region having a relatively low reflectance and a region having a relatively high vacuum ultraviolet ray or X-ray on a substrate is arranged according to a predetermined pattern. An optical element, characterized in that the multilayer film is thicker than the number of laminated layers at which the reflectance for X-rays is saturated and is laminated on a smooth substrate. 2. The high reflectance region is a multi-layer film which is changed so as to substantially satisfy the following equation when the height of at least one pattern is m · (da + db). The optical element according to claim 1, wherein m · (da + db) = λ · (2n−1) / (4 · cos
θ) where m and n are natural numbers, da is the thickness of one layer forming the multilayer film, db is the thickness of another layer forming the multilayer film, and λ is a vacuum ultraviolet ray used for illumination or exposure of the optical element. Or X
The wavelength of the ray, θ is the incident angle of vacuum ultraviolet ray or X-ray used for illumination or exposure of the optical element. 3. The optical element according to claim 1, wherein in the multilayer film having the low reflectance region and the high reflectance region, the surface materials of adjacent regions having high reflectance are the same. 4. The optical element according to claim 1 or 3, wherein the multilayer film has at least one thin film layer formed between the multilayer film and the substrate. 5. A step of alternately laminating at least two kinds of substances having optical constants different from those of vacuum ultraviolet rays or X-rays on a substrate to form a multilayer film, and a step of relatively laminating to vacuum ultraviolet rays or X-rays. A region having a high reflectance and a region having a low reflectance are arranged in the multilayer film according to a predetermined pattern, a step of inspecting an optical element formed by the step, and a step of correcting the optical element. And a step of removing the defect from the upper layer of the multilayer film when the multilayer film has a defect. 6. The step of forming a multilayer film by laminating at least two kinds of substances having different optical constants is performed after the step of forming at least one thin film layer on the substrate. The method for manufacturing the optical element according to claim 5. 7. The method of manufacturing an optical element according to claim 5, wherein the step of removing the defects from the upper layer of the multilayer film includes the step of removing the multilayer film one layer at a time from the upper layer. 8. The multilayer film according to claim 5, wherein the multilayer film is laminated in a thickness equal to or larger than the number of laminated layers at which the reflectance with respect to the vacuum ultraviolet ray or the X-ray is saturated. Optical element manufacturing method. 9. The method of manufacturing an optical element according to claim 5, wherein the step of inspecting the optical element includes an inspection by an X-ray microscope at least in part. 10. In the step of inspecting the optical element, at least a part of the optical element is exposed and transferred to a material to be exposed,
The method for manufacturing an optical element according to claim 5, wherein the material to be exposed is inspected. 11. The step of alternately laminating at least two kinds of substances having different optical constants to form a multilayer film includes at least one step of inspecting the optical element in the middle of the step. 7. The method for manufacturing an optical element according to claim 5, which is characterized in that. 12. A multilayer film in which at least two kinds of substances having different optical constants with respect to vacuum ultraviolet rays or X-rays are alternately laminated on a substrate, and the number of laminated layers is defined as the reflectance of the multilayer film with respect to vacuum ultraviolet rays or X-rays. And the step of stacking the stacked layers to a thickness equal to or larger than the number of stacked layers that saturates.
A step of arranging a region having a high relative reflectance and a region having a low relative reflectance of a line according to a predetermined pattern, and a height of at least one pattern of the high reflectance region which is adjacent to or adjacent to each other are approximately λ · (2n -1) / (4 · cos θ), a method of manufacturing an optical element, including the step of removing the multilayer film from the upper layer, where n is a natural number and λ is a vacuum ultraviolet ray used for illumination or exposure of the optical element. Or X-ray wavelength, θ
Is the incident angle of vacuum ultraviolet rays or X-rays used for illumination or exposure of the optical element. 13. The height of the pattern in the adjacent or adjacent multilayer region having a high reflectance includes the step of removing the multilayer film from the upper layer so that the following equation is satisfied. Item 12. A method for manufacturing an optical element according to item 12, m · (da + db) = λ · (2n−1) / (4 · cos
θ) where m and n are natural numbers, da is the thickness of one layer forming the multilayer film, db is the thickness of another layer forming the multilayer film, and λ is a vacuum ultraviolet ray used for illumination or exposure of the optical element. Or X
The wavelength of the ray, θ is the incident angle of vacuum ultraviolet ray or X-ray used for illumination or exposure of the optical element. 14. The step of alternately laminating at least two kinds of substances having different optical constants to form a multilayer film is performed after the step of forming at least one thin film layer on the substrate. Claim 12 or claim 13
A method for manufacturing the optical element described in 1. 15. The height of the pattern in the multi-layer film region adjacent to or adjacent to each other and having a high reflectance is approximately λ · (2n−1) /
15. The method according to claim 12, further comprising the step of removing the multilayer film from the upper layer one by one so as to change the height by (4 · cos θ). Of manufacturing a finished optical element.