JPH06177003A - Projection exposure and projection aligner exposing device - Google Patents

Abstract

(57) [Abstract] [Purpose] To obtain an X-ray reduction projection exposure method for performing transfer with a high-precision pattern having no local thermal expansion. An exposure projection apparatus that performs pattern transfer using an imaging optical system 95 including a reflective mask 81, a multilayer-film reflective mirror, etc. is provided with a heating means 101 for uniformizing the surface expansion of the reflective mask 81 by beam irradiation. .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure method and apparatus for forming an image by exposing or irradiating vacuum ultraviolet rays or X-rays, particularly for pattern transfer of semiconductors.

[0002]

2. Description of the Related Art In order to improve the integration degree and operating speed of solid state elements of LSI, circuit patterns are being miniaturized.
At present, a reduction projection exposure method in which an exposure light source is ultraviolet rays is widely used for forming these circuit patterns. The resolution of this method depends on the exposure wavelength λ and the numerical aperture NA of the projection optical system. The resolution limit has been improved by increasing the numerical aperture NA. However, the above method is approaching its limit due to the reduction of the depth of focus and the difficulty of the refraction optical system (lens) design and manufacturing technique. 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 = 365 n)
m) and a KrF excimer laser (λ = 248 nm). The resolution is improved by shortening the exposure wavelength.
However, due to the theoretical limit of the wavelength of the ultraviolet light used for exposure, the extension of conventional optical exposure technology
It is difficult to obtain a resolution of 0.1 μm (100 nm) or less.

On the other hand, as a method of forming a fine pattern, there is a proximity equal-magnification X-ray exposure method in which the wavelength of light used for exposure 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 a mask is transferred to a resist on a wafer. A transmission type mask called a unit size X-ray mask is used in the proximity unit size X-ray exposure method. 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 is made of a light element material such as Si, SiN, SiC, and C and has a thickness of about 2 μm. As a portion that absorbs X-rays in the above-mentioned equal-magnification X-ray mask, a thickness called an absorber is 0.5 μm to 1.0 μm.
To some extent, the circuit pattern made of heavy metals such as W, Au, Ta,
It is formed on the membrane. Since the circuit pattern is formed on the membrane having a very low rigidity in the equal-magnification X-ray mask, the heavy metal internal stress of the absorber or the external force when the X-ray mask is mounted on a predetermined exposure apparatus causes the circuit to move. There is a problem that the pattern is distorted and a desired circuit pattern cannot be transferred to the resist on the wafer. Especially, in the case of the proximity equal-magnification X-ray exposure method, the pattern of the equal-magnification X-ray mask is 1: 1
Since it is transferred to the resist at the same magnification, the pattern distortion on the same size X-ray mask is transferred to the resist one to one. The problem that distortion occurs in the pattern of a uniform-magnification X-ray mask having low rigidity has become a major problem in the proximity uniform-magnification X-ray exposure method.

Against the background described above, an X-ray reduction projection exposure method using vacuum ultraviolet rays or soft X-rays as an exposure light source has been receiving attention in recent years. For example, Japanese Journal of Applied Physics (Japanese Jou
rnal of Applied Physics), 1991,30, 11
Volume B, p. 3051. FIG. 3 shows an example of an exposure optical system of the X-ray reduction projection exposure method. Vacuum ultraviolet rays or soft X-rays 411 are used as exposure light and are obliquely incident at an incident angle 42 of θ to illuminate the reflective mask 81 in a vacuum. The incident angle θ differs for various optical systems, but is approximately 1
It is about 15 ° to 15 °. In order to create a working area, direct incidence with an incident angle 42 of 0 ° is impossible with the exposure optical system of the X-ray reduction projection exposure method. The reflective mask 81 is formed with the multilayer film 2 capable of specularly reflecting vacuum ultraviolet rays or soft X-rays.
A predetermined pattern is formed on the multilayer film 2. The vacuum ultraviolet rays or soft X-rays reflected from the reflective mask are reflected by the convex mirror 92, further reflected by the concave mirror 91, and then reach the wafer 82 to form a predetermined pattern. The convex mirror 92 and the concave mirror 91 each have a multilayer film 7
Are formed. Generally in such an optical system,
When the xyz coordinate system is adopted as shown in FIG. 3, the x direction is called the meridional direction and the y direction is called the ball absent direction. Further, in order to expand the illumination area of the mask 81 and the exposure area of the wafer 82 with the optical system as shown in the figure, the mask 81 is moved in the meridional direction on the wafer 8
The scanning may be performed in synchronization with 2. Since the wavelength of vacuum ultraviolet rays or soft X-rays used for exposure and illumination is about 20 nm to 5 nm, the theoretical resolution which depends on the wavelength of the exposure light is improved.

[0005]

Illumination of the mask in a vacuum causes the following problems. As an illumination light source that emits vacuum ultraviolet rays or soft X-rays, for example, synchrotron radiation light can be considered. The above synchrotron radiation light is a light source having a high intensity and a continuous spectrum with respect to wavelength. In the region where the reflectance of the reflective mask for incident light is low, the incident light is almost absorbed by the mask. Even in a region where the multilayer film is formed and the reflectance is high, the reflectance is not 100%. Moreover, since only light having a wavelength that substantially satisfies the Bragg condition determined by the cycle length of the multilayer film and the incident angle of incident light is reflected, only a part of the wavelength region of a light source having a bandwidth such as synchrotron radiation is reflected. To reflect. Therefore, the incident light component that does not reflect the incident light is absorbed by the mask, and most of it becomes thermal energy. While the mask is being irradiated by this heat, the temperature of the mask rises and the mask thermally expands. Therefore, in the X-ray reduction projection exposure due to the thermal expansion of the mask, there arises a problem that the pattern of the mask cannot be imaged and transferred as a desired pattern on the resist on the wafer.

In particular, when the light source is a light source with high intensity such as synchrotron radiation, the surface of the illuminated optical element such as a mask thermally expands. For example, Heisei 3
The Ministry of Education, Culture, Sports, Science and Technology's Grant-in-Aid for Scientific Research “X-ray Imaging Optics” 3rd Open Symposium Proceedings Collection p26-30. 4A and 4B show a state in which the surface vicinity region 52 of the illumination region 51 in the optical element 81 such as a mask is thermally expanded. FIG. 4A is a plan view of the mask and FIG. 4B is a sectional view thereof.

Further, when the mask 81 and the wafer (not shown) are synchronously scanned to enlarge the illumination area 51 of the mask and the exposure area of the wafer, the direction in which the mask moves by the synchronous scanning as shown in FIG. In conjunction with 55, the area 52 near the surface of the illuminated and thermally expanded mask apparently moves on the mask surface. 5 shows the state immediately after the start of the synchronous scanning, and FIG. 6 shows the state immediately before the end of the synchronous scanning. Both are (a)
Is a plan view of the mask and (b) is a sectional view thereof. Area 5
6 is an area of the mask which has already been illuminated by the synchronous scanning. Therefore, it may be difficult to accurately form and transfer the mask pattern as a desired pattern on the resist on the wafer.

In order to avoid the problem of thermal expansion of the mask, as described in JP-A-63-313640,
A cooling medium is often brought into contact with the back surface of the mask to forcibly cool it and avoid a temperature rise of the mask. The above cooling method is effective when a thermal equilibrium state is established. However, the development in which the surface of the optical element such as the illuminated mask thermally expands is in a non-equilibrium state, so forced cooling from the back surface of the optical element avoids the development in which the surface of the optical element locally expands. Not effective to do.

It is an object of the present invention to provide an X-ray reduction exposure projection method for performing transfer with a high precision pattern having no local thermal expansion.

[0010]

SUMMARY OF THE INVENTION The above objects are drawn to the first optical element by illuminating the first optical element with a light source that emits a beam in at least a vacuum ultraviolet region or an X-ray region. In a projection exposure method for reducing and transferring a pattern onto a substrate via an imaging optical system including a second optical element,
This is achieved by performing pattern transfer while heating the region other than the region irradiated with the beam continuously or intermittently when illuminating the first optical element with the beam.

[0011]

In the projection exposure method of the present invention, when illuminating the mask, which is the first optical element, as shown in FIG.
The region 53 other than the above is heated continuously or intermittently. In the area illuminated by the beam, the surface vicinity 52 expands as shown in FIG. 1B as described above. On the other hand, a region 5 other than the region 51 irradiated with the beam
Since 3 is also heated continuously or intermittently, the vicinity 54 of the surface expands as shown in FIG. 1 (b). Therefore, the entire mask surface expands, which solves the problem that a desired pattern cannot be imaged and transferred due to local thermal expansion. Further, when the mask and the wafer on which the mask pattern is imaged are synchronously scanned, the local thermal expansion does not move on the mask surface, so the method of the present invention is particularly effective. Here, there is a possibility that a desired pattern may be entirely expanded by thermal expansion of the entire mask. In this case, if the position and size of the pattern formed on the mask are corrected in advance by the amount of thermal expansion, the pattern having the desired position and size can be imaged and transferred. Further, forced cooling may be performed from a surface different from the surface on which the beam is incident on the mask.

The timing of heating the mask as an optical element according to the method of the present invention is such that the pattern transfer is performed when the pattern transfer is being performed by the beam irradiation in the vacuum ultraviolet region or the X-ray region, and the beam is blocked to transfer the pattern. It is desirable to make the thermal expansion uniform on the mask surface by not performing heating or reducing the heating amount when the above is not performed. Further, the heating means desirably limits the heating amount of the heating means in accordance with the incident amount of the beam incident on the optical element. Examples of the heating means include infrared rays, visible rays, ultraviolet rays, vacuum ultraviolet rays, and X-rays. If at least one of the beams is irradiated, it is easy to control the timing of illumination and heating of the optical element.

[0013]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 shows an illumination method of an optical element which is one embodiment of the projection exposure method of the present invention, (a) is an illumination method, (b) is a diagram showing a cross section of the element, and FIG. It is a figure which shows one Example of the projection exposure apparatus which carries out X-ray reduction projection exposure of the optical element.

The mask 81 of the optical element in the projection exposure method of the present invention shown in FIG. 1 has a region having a relatively low reflectance with respect to vacuum ultraviolet rays or X-rays and a refractive index with respect to vacuum ultraviolet rays or X-rays. A region having a high reflectance formed by a multilayer film in which at least two different substances are alternately laminated,
It is arranged according to a predetermined pattern. The mask 81
Is irradiated with a vacuum ultraviolet ray or an X-ray beam in the projection exposure method, and FIG.
The area 51 shown in (a) is locally heated, and the area 51 shown in FIG.
As shown in the sectional view of FIG. However, in the projection exposure method of the present invention, when the mask 81 is irradiated, the pattern transfer is performed while continuously or intermittently heating the area other than the irradiation area 51, and thus the area 53 other than the irradiation area 51. Is also heated and near the surface 54
Is expanded, and the entire surface of the mask 81 is expanded. Therefore, the phenomenon of local thermal expansion disappears, and a desired pattern can be imaged and transferred. Further, when the mask and the wafer are synchronously scanned, the position and size of the pattern formed on the mask are corrected in advance by an amount corresponding to the thermal expansion to form an error caused by the expansion of the desired pattern as a whole. It is possible to prevent the above and obtain a desired pattern.

Next, a transfer experiment conducted by mounting the above mask on the embodiment of the X-ray projection exposure apparatus shown in FIG. 2 will be described. In FIG. 2, a mask 81 and a wafer 82 that is a substrate
Are the mask stage 83 and the wafer stage 8 respectively.
It is installed in 4. The mask stage 83 has a structure capable of forcibly cooling the mask 81.

First, the relative position between the mask 81 and the wafer 82 is detected by using the alignment device 85, and the control device 8
6, the alignment is performed via the drive devices 87 and 88. The X-rays emitted from the X-ray source 89, which is synchrotron radiation, are condensed by the reflecting mirror 90, and the shutter 98 and the window 9 are collected.
7, the arc region on the mask 81 is illuminated in vacuum. The X-ray source 89 may be a laser plasma X-ray source or the like in addition to the synchrotron radiation light. In order to avoid local thermal expansion that occurs near the surface of the illumination area of the mask, the heating light source 10 is provided in the area of the mask 81 other than the illumination area.
The heating light beam 101 is irradiated by 2. The heating control means 103 is mounted so that the energy amount of the heating light beam 101 can be controlled according to the energy amount of the incident X-ray 411.
The mask 104 that shields the heating light beam 101 is configured so that the heating light beam 101 does not irradiate the illumination area of the X-ray 411. Further, the slits 99 interlocking with the synchronous scanning of the mask 81 and the wafer 82 prevent the heating light beam 101 from hitting the area other than the mask 81 of the optical element. The shutter 100 is linked with the shutter 98.

The positional relationship between the mask and the incident X-ray was set so 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 are composed of X-rays having a wavelength of about 13 nm, and the imaging optical system 95 including the reflecting mirrors 91, 92, 93 and 94 magnifies the wafer 82 by a factor of 1/5.
To form an image. The reflecting mirrors 91, 92, 93 and 94 are formed by depositing 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 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 to the wafer. By the above method,
It was possible to obtain on the wafer 82 a pattern with a magnification of ⅕ that was faithful to the mask pattern.

The pattern may be formed by previously correcting the position and size of the pattern formed on the mask 81, which is an optical element, by the amount of thermal expansion. Further, not only the mask, which is the first optical element, but also the optical element such as the imaging optical system may be heated or forcibly cooled as described above.

The materials for the multilayer film usable in the present invention include Ni / C, Ru / BN, Rh / BN, Mo / SiC and Ni.
Cr / C, Ni / V, Ni / Ti, W / C, Ru / C, Rh /
C, Ru / BN, Rh / B ₄ C, RhRu / BN, Ru / B ₄
C, Mo / Si, Pd / BN, Ag / BN, Mo / SiN, M
Any material capable of forming a multilayer film, such as o / B ₄ C, Mo / C, Ru / Be, etc., can be used.

Further, in the present invention, only the case of the reflection type mask as the first optical element has been described, but the first optical element is not limited to the reflection type mask, and a diffraction grating, a linear zone plate, etc. It can also be applied to an optical element having the fine pattern of (3) on the reflecting surface.

[0021]

As described above, the projection exposure method and the projection exposure apparatus according to the present invention illuminate the first optical element with a light source that emits a beam in at least a vacuum ultraviolet region or an X-ray region, and In a projection exposure method for reducing and transferring a pattern drawn on one optical element onto a substrate via an imaging optical system including a second optical element, when irradiating the beam to the first optical element, Heating for uniformizing the thermal expansion of the surface of the first optical element caused by beam irradiation by performing pattern transfer while continuously or intermittently heating an area other than the area irradiated with the beam. Since the means is provided, local expansion of the surface of the first optical element can be prevented, and highly reliable pattern transfer can be performed.

[Brief description of drawings]

FIG. 1 shows a first optical element in one embodiment of a projection exposure method according to the present invention, in which (a) is an element illumination method,
(B) is a figure which shows each cross section of the said element.

FIG. 2 is a diagram showing an embodiment of a projection exposure apparatus for performing X-ray reduction projection exposure on the first optical element.

FIG. 3 is a diagram showing an exposure optical system of a conventional projection exposure method.

FIG. 4 is a diagram showing a first optical element in a conventional projection exposure method, (a) is a method of illuminating the element, and (b) is a diagram showing a cross section of the element.

FIG. 5 is a diagram showing a first optical element immediately after the start of synchronous scanning in conventional projection exposure, (a) is a method of illuminating the element, and (b) is a diagram showing a cross section of the element.

FIG. 6 shows a first optical element immediately before the end of synchronous scanning in conventional projection exposure, (a) is a method of illuminating the element, and (b) is a diagram showing a cross section of the element.

[Explanation of symbols]

 51 ... Beam irradiation area 53 ... Area other than irradiation area 81 ... First optical element (mask) 82 ... Substrate (wafer) 89 ... Light source 91, 92, 93, 94 ... Reflector 95 ... Imaging optical system 101 ... Heating Means 411 ... Beam

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Eiji Takeda 1-280 Higashi Koigokubo, Kokubunji City, Tokyo Metropolitan Research Center, Hitachi, Ltd.

Claims (11)

[Claims] 1. A light source which emits a beam in at least a vacuum ultraviolet ray region or an X-ray region is used to irradiate a first optical element, and the pattern drawn on the first optical element is changed to a second optical element. In a projection exposure method of reducing and transferring onto a substrate via an imaging optical system including, when irradiating the first optical element with the beam, a region other than a region irradiated with the beam is continuously or intermittently A projection exposure method characterized in that pattern transfer is performed while heating the film. 2. The heating of the first optical element is performed when the pattern transfer is performed by beam irradiation in the vacuum ultraviolet ray region or the X-ray region, and the beam is blocked and the pattern transfer is performed. Do not heat when not in
Alternatively, the projection exposure method according to claim 1, wherein the heating amount is reduced. 3. The projection exposure method according to claim 1, wherein the first optical element performs synchronous scanning with a substrate for reducing and transferring the pattern. 4. A light source that emits a beam of vacuum ultraviolet rays or X-rays, an illuminating device that illuminates the beam onto a first optical element, and a reflected beam from the first optical element that is focused on a substrate. An image forming optical means including a second optical element;
In the projection exposure apparatus comprising the optical element and the positioning means for moving or positioning the substrate to a desired position, a heating means for heating the first optical element is provided. 5. The projection exposure apparatus according to claim 4, wherein the heating means controls the heating amount according to the incident amount of the beam incident on the first optical element. 6. The projection according to claim 4, wherein the heating means is irradiation of at least one beam of infrared rays, visible rays, ultraviolet rays, vacuum ultraviolet rays, and X-rays. Exposure equipment. 7. The projection exposure apparatus according to claim 4, wherein a surface of the first optical element different from a surface on which the beam is incident is cooled by a cooling means. 8. The first optical element comprises a region having a relatively low reflectance for vacuum ultraviolet rays or X-rays and at least two kinds of substances having different refractive indices for vacuum ultraviolet rays or X-rays, which are alternately laminated. 8. The region having a high reflectance formed by the multilayer film described above is arranged on a substrate according to a predetermined pattern, according to any one of claims 4 or 5 or 7. Projection exposure device. 9. The imaging optical means is vacuum ultraviolet ray or X-ray.
5. A reflection mirror, which is a second optical element formed of a multilayer film in which at least two kinds of substances having different refractive indexes with respect to a line are alternately laminated, and is configured. Projection exposure equipment. 10. The projection exposure apparatus according to claim 4, wherein the light source that emits the vacuum ultraviolet ray or the X-ray beam is synchrotron radiation light. 11. A first optical element comprising a region having a low reflectance and a region having a high reflectance arranged according to a predetermined pattern.
9. The position and size of the predetermined pattern are formed by previously correcting them by an amount of thermal expansion.
The projection exposure apparatus described.