JPH03215800A - X-ray exposing method - Google Patents

Abstract

PURPOSE:To increase an X-ray taking out area and to take out the strongest possible X-ray intensity by taking out the X-ray of a specified shape obtd. by reflecting and condensing synchrotron radiation light into the atmosphere via a beryllium window. CONSTITUTION:A troidal mirror (or cylindrical mirror) 2 is disposed in a beam line 15 consisting of a vacuum duct and the X-ray of the specified shape formed by reflecting and condensing the divergent light of the synchrotron radiation light 1 is taken out into the atmosphere via the beryllium window 5. The X-ray of this specified shape is used as a light source. The beryllium window 5 is formed by welding the beryllium window 5 by a sealing metal 4 with an electron beam to a beam line 15 consisting of the vacuum duct. The X-ray of the specified shape is taken out into the atmosphere in such a manner and a substrate to be exposed is disposed in the immediate neighborhood thereof. The substrate to be exposed is exposed by applying a required sufficient exposure thereto by the X-ray of the high intensity if the substrate is scanned by the X-ray.

Description

[Detailed Description of the Invention] [Summary] Regarding the light source in the X-ray exposure method, the area for extracting X-rays into the atmosphere is made as large as possible,
In an X-ray exposure method using synchrotron radiation as a light source, the synchrotron radiation is extracted from a beam line in a high vacuum, and the purpose is to extract as strong an X-ray intensity as possible. The diverging light is reflected and focused by a toroidal mirror or cylindrical mirror, and the light is focused to create an X with a certain width.
The X-ray is extracted into the atmosphere through a beryllium window having a similar shape, and the X-ray having a certain shape is used as irradiation light for exposure.

[Industrial application field]

The present invention relates to an X-ray exposure method, and particularly to a light source thereof.

There is a continuing trend for the degree of integration of semiconductor devices such as LSIs to increase approximately four times every 3.4 years, and this increase in degree of integration requires a reduction in the dimensions of the devices. The present invention provides an alternative to the conventional photo exposure method, which has reached its limit.
This is a proposal regarding the light source G of the line exposure method.

[Prior Art] Conventionally, a device pattern drawn on a mask (or reticle) was transferred onto a wafer surface using ultraviolet rays or deep ultraviolet rays. However, because the dimensions of the high-speed pattern to be transferred onto the entire surface of the wafer have been miniaturized to the same size or about twice the exposure wavelength of ultraviolet and deep ultraviolet rays, it has become difficult to accurately transfer the pattern onto the wafer surface. It has become extremely difficult to do so. Therefore, the NA of exposure equipment has to be increased. Efforts have been made to shorten the exposure wavelength and improve processing methods, but these are all approaching their technical limits.

In order to solve this difficult problem, a technology is being developed that uses X-rays whose exposure wavelength is two to three orders of magnitude smaller. but,
Conventional X-ray sources are thermionic bombardment type or pinch plasma generation, which has low X-ray intensity, and has drawbacks such as a diverging light source that places a burden on the exposure equipment, especially the alignment structure. Ta.

Therefore, synchrotron radiation (Synchrotron radiation) is used as an extremely strong X-ray source.
Exposure methods using n ; SR) are being researched;
This method is attracting attention as it is expected to improve throughput.

The following is an overview of the X-ray lithography technology using synchrotron radiation. This synchrotron radiation (hereinafter referred to as SR light) is used to transfer patterns by irradiating soft X-rays obtained from the synchrotron radiation. Then, such SR light is created with an electron storage ring. This electron storage ring consists of various electromagnets such as bending electromagnets that control electrons, an accelerating cavity that replenishes energy to electrons,
The electron beam accelerated from the linear accelerator is made to enter the storage ring and circulate inside the ring, and when moving at a speed close to the speed of light, The SR light is emitted in the tangential direction by changing the SR light, and the SR light is extracted from the beam line and used in lithography technology for microfabrication.

Figure 5 shows a schematic diagram of the electron storage ring.
0 is a linear accelerator, 11 is a storage ring, 12 is a bending electromagnet, 13 is an acceleration cavity, 14 is a vacuum duct, 15 is a beam line, and the pole is an SR light. In addition, other electromagnets such as a quadrupole electromagnet, a sextupole electromagnet, and a correction electromagnet are arranged in the same manner as the bending electromagnet.

By the way, the S emitted from such an electron storage ring
In the X-ray exposure method that irradiates R light, since SR light has a continuous spectrum in a wide wavelength range from the microwave band to the X-ray region, short-wavelength
It removes line components and removes long wavelength components using an absorption filter such as a beryllium window, and then exposes using X-rays with a wavelength slightly longer than 5, for example, in the wavelength range of 5 to 15. be.

[Problem to be solved by the invention]

However, even if X-rays are produced by SR light, they will attenuate significantly if they are extracted through the atmosphere over a long distance.
It is important to make the X-rays less than mm, and for this purpose, a beam line (consisting of a vacuum duct) maintained in a high vacuum (vacuum level 10-' to 10-' Torr) is used to attenuate the generated X-rays. However, for reasons such as the difficulty of handling in a high vacuum, it is preferable to carry out exposure in the atmosphere. A method is being considered in which a beryllium (Be) window, which is easily transparent to X-rays, is used to extract it into the atmosphere.Beryllium has a small atomic number and high mechanical strength, making it suitable as an X-ray transparent window. However, it is appropriate to set the thickness to about 10 to 100 μm; if the thickness is too thin, the mechanical strength will be weak and it will be easily damaged, and if the thickness is too thick, the X-rays will attenuate and the X-ray intensity will decrease. become.

On the other hand, the relationship between the thickness and size (width x length) of a beryllium (Be) window is determined by the limit with which it can withstand atmospheric pressure.
It is necessary to keep it below 5Kg/ms+z. Furthermore, in order to increase the X-ray intensity, the intake angle (the area from which the SR light is extracted) must be increased.

The present invention is an X-ray exposure method that aims to improve these problems, increase the area for extracting X-rays into the atmosphere as much as possible, and extract as strong an X-ray intensity as possible. This is what we propose.

(Means for solving the problem) The problem is to extract the synchrotron radiation from a beam line in a high vacuum, and to reflect and condense the diverging synchrotron radiation with a toroidal mirror or a cylindrical mirror. , an X-ray exposure method in which focused X-rays of a certain shape with a width are taken out into the atmosphere through a similarly shaped beryllium window, and the X-rays of a certain shape are used as irradiation light for exposure. solved by.

[For production]

That is, the present invention provides a toroidal mirror in a beam line consisting of a vacuum duct.
; annular surface mirror) or cylindrical force mirror (Cy
1indrical Mirror; cylindrical mirror)
is placed, reflected and focused X-rays of a certain shape (for example, arcuate) are taken out into the atmosphere through a helium window, and the X-rays of a certain shape are used as a light source.

In this way, the width of the helium window can be reduced by making the shape of the helium window approximately match the fixed shape reflected by those mirrors. And, for example, the width of the certain shape is 3 to 4
For n+m, set the width of the beryllium window to 4 to 5IIllI1
Create it with some leeway.

Then, the internal stress of helium (45Kg/mm
In order to withstand 2), the thickness of the beryllium window can be reduced to 25 μm, and by making the beryllium thinner, the intensity of X-rays extracted into the atmosphere will increase.

〔Example] Examples will be described in detail below with reference to the drawings.

? FIG. 1 is a diagram of the main parts for creating a fixed-shaped Xi according to the present invention, and the figure shows a configuration in a high vacuum in which a storage ring 11 is taken out to a beam line and a fixed-shaped X-ray is created. The symbol 1l is the storage ring, l is the SR light (synchrotron radiation), and 2 is the 1-roidal mirror. 3 is an X-ray of a certain shape, PH1 was taken out from the storage ring]? The horizontal beam spread angle of light 1, Psi is the beam spread angle in the dark blue direction of SR light 1 extracted from the storage ring, and P is the distance between the storage ring and the toroidal mirror. Z is the distance between the toroidal mirror and the fixed-shaped (arcuous) X-ray;
For example, the arcuate X-rays 3 are X-rays that are transmitted through a beryllium window and radiated into the atmosphere.

Figure 2 shows a perspective view of a toroidal mirror, which has a shape that can efficiently collect light from the left and right sides, and is made of materials that easily reflect SR light, such as
Platinum (Pt), gold (Au), silicon oxide (SiO)
■). The symbol R in the figure indicates the radius of curvature in the horizontal direction with respect to the direction of incidence of the SR light on the mirror, and R2 indicates the radius of curvature in the vertical direction with respect to the direction of incidence of the SR light on the mirror.

Note that the SR light is converted into a short wavelength X by this toroidal mirror.
The line component is removed, and the long wavelength component is removed by a beryllium window, which will be described next, to emit X-rays with wavelengths of about 5 to 15.

Next, to explain specific numerical values and examples of the shape of emitted X-rays, Figures 3(a) and 3(b) are diagrams showing the shape of X-rays;
a) is the shape of the irradiation onto the toroidal mirror. The figure (b) shows the shape in which the beryllium window is irradiated (the shape in which it is taken out into the atmosphere;
(constant shape of X-ray 3). Listing the values for that, the values are R, = 165mm, R2 = 1100
00mmP=3000mm, GA=
34mradPsi = 1.4mrad, PH1
=35mradH= 18.0608mm Here, G^ is the incident angle at which the SR light enters the toroidal mirror, and H is the width of the SR light irradiated onto the beryllium window. As a result, arcuate X-rays as shown in FIG. 3(b) can be taken out from the beryllium window. If Z - 10,000 mm, the width of the arch of the X-ray 3 is approximately 3 to 4 mm.The dimensions of the rectangle including the entire arch are 14.8 mm x 40 mm.Therefore, the width of the arch is 3 to 4 mm, and the width of the arch is approximately 3 to 4 mm. window width 4
It is sufficient to use a bow-shaped window with a margin of about 5+nn+.

FIGS. 4(a) and 4(b) are views showing the beryllium window according to the present invention, where (a) is a side sectional view of the beryllium window portion, and FIG. 4(b) is a plan view of the helillium window. , a helium window 5 is electron beam welded to a beam line 15 consisting of a vacuum duct using a sealing metal 4, and the plane portion other than the helium window 5 shown in FIG. It is composed of In addition, in FIG. 4(b), the helium window 5 is shown as a portion surrounded by a dotted line, and the diagonal line within the helium window 5 shows the X-ray 3 having a certain shape.

In this way, by forming the arcuate beryllium window 5 with a width of 4 to 5IIIl1, which has a slight margin for the arcuate X-ray shape with a width of 3 to 4 mm, the thickness of the beryllium can be reduced to about 25 μm, and the X that can be taken out into the atmosphere. It is possible to reduce the attenuation of the rays and extract high-intensity X-rays. in this case,
If the beryllium window shape is 14.8m + x 40m
If the window is made into a rectangular window of m, the internal stress cannot be reduced to 45 Kg/mm2 or less unless the beryllium thickness is increased to about 50 μm, and such a thick beryllium thickness will exponentially attenuate the X-ray intensity. Become.

In this way, X-rays of a certain shape (arcuous shape) are taken out into the atmosphere, a substrate to be exposed is placed nearby, and the substrate to be exposed is scanned by X-rays.
The X-ray exposure method can be exposed with a sufficient amount of light required for X-ray exposure, thereby improving the throughput of the X-ray exposure method and greatly contributing to its generalization.

In addition, although the above example was explained using a toroidal mirror (mirror with an annular surface), it is also possible to use a cylindrical mirror.
(A mirror with a cylindrical surface) can be used to obtain substantially the same effect, and the present invention is not limited to the above-mentioned toroidal mirror.

[Effects of the Invention] As is clear from the above explanation, according to the present invention, exposure can be performed using X-rays with sufficient intensity as a light source,
It will bring us closer to the generalization of line exposure, and will significantly contribute to improving the performance of semiconductor devices such as [, Sl, etc.].

[Brief explanation of drawings]

Figure 1 is a diagram of the main parts for creating X-rays of a certain shape according to the present invention, Figure 2 is a perspective view of a toroidal mirror, Figures 3 (a) and (b) are diagrams showing the shape of X-rays, Figure 4(a). (b) is a diagram showing a helium window according to the present invention, and FIG. 5 is a schematic diagram of an electron storage ring. In the figure, l is the SR light, 2 is the toroidal mirror, 3 is the X-ray of a fixed shape, 5 is the beryllium window, 11 is the storage ring, l5 is the beam line Figure 5

Claims (1)

[Claims] In an X-ray exposure method using synchrotron radiation as a light source, the synchrotron radiation is extracted from a beam line in a high vacuum, and the diverging light of the synchrotron radiation is transmitted using a toroidal mirror or a cylindrical mirror. The X-rays are reflected and focused, the X-rays of a certain shape with a width are taken out into the atmosphere through a similarly shaped beryllium window, and the X-rays of the certain shape are used as irradiation light for exposure. An X-ray exposure method characterized by: