JPH03108699A - Radiation beam transmitting window and attachment of radiation beam transmitting thin film to the same - Google Patents

Abstract

PURPOSE:To enable an exposure treatment of a transfering device side under an atmospheric condition and also to enable grading up transmissivity of a radiation beam by forming a radiation beam transmitting thin film to be spherical, protruding to a side of a radiation beam source, and by lessening its thickness gradually towards its center. CONSTITUTION:A radiation beam transmitting thin film 1 is formed spherical protrudingly to a side of a radiation beam source. By this treatment, the thin film 1 is made to endure a tensile stress working to the thin film 1 derived from pressure difference between the radiation beam source side and the transfering device 4 side. By using the thin film 1 being shaped spherically in this way, tensile stress sigma shown in the figure, is solely works to the thin film 1. Accordingly, even if a film thickness t is small, the tensile stress sigma can be arbitrarily applied, by selecting a spherical curvature R corresponding to the film thickness t. Also, in order to make intensity of the radiation beam obtained at the device 4 side, to be of almost the same everywhere, the film thickness t is formed so as to get thinner towards a spherical center part C of the thin film 1, at its periphery, and therewith all transmitting distances of the radiation beams through the film are made to be quite same at every position.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention uses synchrotron radiation to
The present invention relates to a radiation-transmitting window of an exposure apparatus for transferring a circuit pattern such as the above onto a plate-like object to be exposed such as a wafer, and a method of attaching a radiation-transmitting thin film to the window.

[Conventional technology]

With advances in highly integrated semiconductor (LSI) technology, the use of synchrotron radiation, including soft X-rays, is attracting attention in semiconductor lithography equipment, which transfers patterns on masks onto wafers with attached resist. As shown in Figure 11, this synchrotron radiation is produced when electrons with a speed close to the speed of light are bent by the magnetic field of a deflection magnet (31) in a high vacuum electron storage ring (30). The electromagnetic waves are emitted in the tangential direction of the orbit, but they have good parallelism and can produce strong soft X-rays, so the VLSI mask pattern with a submicron line width is transferred onto the exposure plate. It is expected to be the next generation X-ray source for X-ray exposure equipment.

In an actual exposure apparatus using the synchrotron radiation,
Synchrotron radiation emitted from the electron storage ring (30) is guided through the beam line (3) into the transfer device (4), where an X-ray mask (not shown), a wafer drive stage (not shown), etc. The structure is such that a mask pattern is transferred onto the surface of a plate-like object to be exposed (in this case, a resist 1- formed on a wafer by 'f1.rII) using various devices.

Of these, the inside of the beam line (3) is kept in vacuum to avoid adversely affecting the high vacuum state in the electron storage ring (30), while the transfer device (4) is In order to suppress the
0), and the inside is filled with air or other gas atmosphere (such as helium gas, which has a small effect of attenuating radiation light). Therefore, between the synchrotron radiation source side that emits synchrotron radiation light (electron storage ring (30) and beam line (3) in the figure) and the transfer device (4), there is a high vacuum area on the synchrotron radiation source side in the middle of the synchrotron radiation path. A radiation-transmitting thin film (1) such as a beryllium thin film is provided which separates the atmosphere from the transfer device (4) side and allows a part of the radiation to pass through.

[Problem that the invention seeks to solve]

FIG. 12 is a sectional view showing a conventional example of a synchrotron radiation transmitting window to which such a synchrotron radiation transmitting thin film (1) is attached. As shown in the figure, the vacuum flange (2) of the beam line (3)
The end side of the flat radiation-transmitting thin film (1) is attached to the window frame made of 2) etc. via the spacer (23), and the window frame material such as the stop flange (24) is further clamped from above. There is.

When a mask pattern is exposed by irradiation with synchrotron radiation, in order to obtain a practical throughput, the thickness of the synchrotron radiation transmitting thin film (1) must be made as thin as possible to reduce the attenuation of the radiation as much as possible.

However, the synchrotron radiation source side space and the transfer device (4) chamber (
40) Because there is a considerable pressure difference between the inner environment and the surrounding air,
When the thickness of the synchrotron radiation transmitting thin film (1) becomes thinner, in the structure of the synchrotron radiation transmitting window described above, the thin film (1) bulges toward the synchrotron radiation source side around its radial center. As shown in Figure 12, a large tensile stress is applied to this thin film (1).

Therefore, it is necessary to maintain the atmosphere on the side of the chamber (40) of the transfer device in a reduced pressure state, and it becomes necessary to strengthen the reduced pressure equipment and maintain and control the reduced pressure state, thereby increasing the radiation transmittance. This could potentially offset the throughput improvement of synchrotron phosphorography.

The present invention was devised in view of the above-mentioned problems of the prior art, and it improves the structure of the synchrotron radiation transmitting thin film itself attached to the synchrotron radiation transmitting window, so that the transfer device side can perform exposure even under atmospheric pressure atmosphere. The purpose is to improve the radiation transmittance through processing and thinning of the film, and also to describe a method for attaching such an improved radiation transmitting thin film to a radiation transmitting window. It is also proposed.

[Means for solving problems]

Therefore, as shown in FIG. 1, the synchrotron radiation transmitting window of the present invention has a synchrotron radiation transmitting thin film (1) in a spherical shape that protrudes toward the synchrotron radiation source side, so that This makes it possible to withstand the tensile stress that acts on the synchrotron radiation transmitting thin film (1) due to pressure differences.

When the radiation-transmitting thin film (1) is formed into a spherical shape and used in this way, only the tensile stress σ expressed by the following equation is applied to the thin film (1).

However, P: pressure R: radius of spherical curvature t: film thickness Therefore, even if the film thickness is thin, by selecting the corresponding radius of spherical curvature R, the tensile stress σ can be set to an arbitrary value.

However, if the thickness t of the spherical synchrotron radiation transmitting thin film (1) is the same at every position, as shown in FIG. Since synchrotron radiation light that travels straight through is parallel light, each transmission distance in the film in the straight direction is
It is smallest at the center of the membrane and gradually becomes thicker as it approaches the edges of the membrane layer. Therefore, the attenuation rate of the emitted light also increases toward the edge of the film layer.

In the present invention, in order to improve the tensile stress resistance of the synchrotron radiation transmitting thin film (1), it is not only made into a spherical shape, but also so that the synchrotron radiation intensity obtained on the transfer device (4) side is approximately equal at any position. In order to achieve this, as shown in Fig. 1, the film thickness t is gradually thinned around the spherical center C of the synchrotron radiation transmitting thin film (1) (to > tz >
tz), so that the transmission distance X of the emitted light through the film is the same at any position. As shown in Fig. 3, the specific configuration for forming the film thickness so that the transmission distance X of the synchrotron radiation through the film is the same at every position is as follows: Set Ri and outer curvature RO to be the same (Ri=Ro), and set these curvature radius center points m0 and mi to the same line C
All you have to do is make it eccentric at the top. Furthermore, if this synchrotron radiation transmitting thin film (1) is made of metal such as beryllium, the thin film (1) is formed into a spherical shape, and the thin film (1) is made of a metal such as beryllium.
) can be easily controlled by the vapor deposition method as described above.

Furthermore, according to the above equation 0, the smaller the radius of curvature R of the spherical surface is, the more the tensile stress σ applied to the synchrotron radiation transmitting thin film (1) increases.
can be made smaller.

On the other hand, when a thin film is formed with different film thicknesses in each part as described above, the smaller the radius of spherical curvature R, the thinner the thickness t' of the outer peripheral part of the thin film (1) becomes. The stress will increase, contrary to the equation 0. Therefore, the inventors of the present invention determined the optimum value of this radius of curvature R of the spherical surface.

That is, from Figure 4.

Furthermore, the reaction force F' that acts on the membrane outer periphery due to the resultant force F is: F'=πDXt'XσX sinθ
・・・・・・・ ■However, πDXt': Circumferential area sin θ From the two-way equation 00 balance (D-)" πXP= πDXt' X a X5in
O--■Substituting equation 0 into this equation 0 and substituting it, D: Aperture of the synchrotron radiation transmitting thin film, and thickness t' of the outer periphery of the thin film (1), t' = t-cos (1...・・・・・・・・・・・・
・・・・・・・・・・・・・・・・■And the transfer device (
4) side pressure is P, the resultant force F applied to the thin film (1) due to the pressure P is dσmax If we set 20 from the 0 equation, we get dθ, cos2θ=o, −, θ=”(=45° )It turns out that.

Substituting this into the above equation 0 and expressing the relationship between the aperture of the thin film (1) and the radius of spherical curvature R, the following is obtained. Therefore, the optimum value of the radius of spherical curvature R can be found from this relational expression.

Furthermore, as shown in Fig. 5, a rectangular opening (
2a), and a thin film (1) is placed there from the transfer device (4) side.
), the optimum value of the radius of curvature R of one spherical surface may be determined by setting the diagonal length Q of the opening (2a) as the diameter of the thin film (1).

Furthermore, the second to fourth inventions provide an attachment method for attaching a spherically shaped radiation-transmitting thin film (1) to a window frame (2) of a radiation-transmitting window.

That is, even if the first invention makes it possible to reduce the tensile stress acting on the film surface by making the synchrotron radiation transmitting thin film (1) spherical in shape, it is possible to reduce the tensile stress acting on the film surface by making the synchrotron radiation transmitting thin film (1) spherical. When it comes to actually attaching it to the clamp part of 2),
As shown in the conventional example in FIG. 12, when the end side of the synchrotron radiation transmitting thin film (1) is clamped between vertical surfaces such as flange surfaces, It bends toward the radiation source side at a portion, and bending stress is generated there. Therefore, the second to fourth inventions further improve the method of attaching such a spherical synchrotron radiation transmitting thin film (1), thereby avoiding the generation of local stress as described above, and uniformly distributing it over the entire surface of the film. This is so that a certain stress (tensile stress) is applied.

As shown in FIG. 6, the mounting method of the second invention is to form a tapered surface (20) on the transfer device (4) side of the window frame (2) for clamping the synchrotron radiation transmitting thin film (1). Tapered surface (
20), the spherical protruding surface of the synchrotron radiation transmitting thin film (1) is brought into contact with the thin film (1), and the end side of the thin film (1) is clamped to the window frame (2).

As shown in FIG. 7, the mounting method of the third invention is to attach a spherical seat (21) in accordance with the spherical curvature of the synchrotron radiation transmitting thin film (1).
is formed on the transfer device (4) side of the window frame (2), and the end side of the radiation-transmitting thin film (1) is adhered to this spherical seat (21).

As shown in FIG. 8, the mounting method of the fourth invention is such that the end side of the synchrotron radiation transmitting thin film (1) is integrally molded to form the window frame (2) of the synchrotron radiation transmitting window. ), and a radiation-transmitting thin film (1) is formed together with the radiation-transmitting thin film (1).

〔Example〕

Hereinafter, an embodiment of a method for attaching a radiation-transmitting thin film in a radiation-transmitting window according to the second invention will be shown, and a specific configuration of the radiation-transmitting window of the invention will be described.

FIG. 9 shows a radiation-transmitting thin film (1
) is a vertical cross-sectional view showing the structure of the radiation transmitting window attached.

This radiation-transmitting thin film (1) is made of beryllium and is formed into a spherical shape by vapor deposition, and the film thickness is formed to gradually become thinner around the spherical center C.

Furthermore, the peripheral side of this thin film (1) is made to extend in the direction of the spherical surface that touches points A and A' in the figure, and has a truncated cone-shaped radial extension that is integrally formed with the spherical part. Part (1a)
is provided.

In this embodiment, a tapered surface (20) is formed on the transfer device (4) side of the window frame (2) of the synchrotron radiation transmitting window, and the radially extending portion (1a) is formed on the tapered surface (20). surface contact, and the end side of this radial extension part (1a) is a presser metal fitting (
50) is fixed to the window frame (2).

As described above, in this embodiment, the part of the synchrotron radiation transmitting thin film ( ) that separates the high vacuum region on the synchrotron radiation source side and the chamber atmosphere on the transfer device (4) side has a spherical shape protruding toward the synchrotron radiation source side. Because of this, the tensile stress acting on the film surface can be reduced, and therefore, no problem will occur even if the film thickness is reduced to increase the radiation transmittance. Further, since the film thickness is adjusted at each part as described above, there is no large difference in the intensity of the emitted light depending on the position of the emitted light transmitted through the thin film (1).

Further, according to the method of attaching the synchrotron radiation transmitting thin film (1) shown in this example, the side surface (radially extending portion (la) in this example) of the spherical thin film (1) is attached to the window frame ( 2), and only the end side is fixed to the window frame (2), so only a uniform tensile stress acts on the membrane surface, and other local The generation of stress can be avoided. Moreover, since the synchrotron radiation transmitting thin film (1) is integrally provided with the radial extension part (1a) as described above, the cross-sectional area of the film passing through the point A-A' is compared to the cross-sectional area of the film passing through the point A-A'.
' The cross-sectional area of the membrane passing through the point becomes larger, and the presser metal fitting (50
), the tensile stress is further relaxed at points B and B'.

FIG. 10 shows a radiation-transmitting thin film (
1) is a vertical cross-sectional view showing another embodiment of the attached radiation light transmitting window; FIG.

In this example, the structure of the radiation-transmitting thin film (1) itself is the same as that of the previous example except that the radial extension part (1a) is not provided, so the details thereof will be omitted.

Here, the tapered surface formed on the window frame (29) is a spherical seat (20a) formed to match the spherical curvature of the synchrotron radiation transmitting thin film (1), and the thin film (20a) is attached to the spherical seat (20a). 1
) is brought into surface contact with the spherical protruding surface of the radiant light transmitting thin film (1 )
The end side of is fixed to the window frame (2).

In this way, if the spherical seat (20a) is provided, the spherical synchrotron radiation transmitting thin film (1) is brought into contact with it, and the entire end side is fixed there, the synchrotron radiation will be transmitted through the entire surface contact area. By clamping the periphery of the end of the transparent thin film (1), a lamp force of about 1 strength can be obtained without generating local stress on the film surface.

〔Effect of the invention〕

As described in detail above, according to the synchrotron radiation transmitting window having the structure of the present invention, since the synchrotron radiation transmitting thin film attached thereto has a spherical structure, even if the film surface is made thin, the height on the synchrotron radiation source side is It becomes possible to sufficiently withstand a large pressure difference between the vacuum region and the atmosphere inside the chamber on the transfer device side. Therefore, it is possible to increase the synchrotron radiation transmittance and improve the throughput of synchrotron radiation lithography, and it is also possible to maintain the pressure of the atmosphere inside the chamber at about atmospheric pressure, which eliminates the need for reinforcement of decompression equipment. It has excellent effects such as eliminating Furthermore, even if the synchrotron radiation transmitting thin film is made into a spherical shape, the thickness of the film is formed so that it gradually becomes thinner around the center of the thin film, so when parallel synchrotron radiation passes through the film, The attenuation rate of is the same at any membrane position.

As a result, the intensity of the transmitted radiation light is approximately equal at any position.

Furthermore, according to the second to fourth methods for attaching a synchrotron radiation transmitting thin film, the spherical synchrotron radiation transmitting thin film can be attached to the window frame of the synchrotron radiation transmitting window while avoiding the generation of local stress.
Therefore, it is possible to prevent breakage at the thin film clamp portion.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing the basic configuration of the present invention, Fig. 2 is an explanatory diagram showing the relationship between the thickness of the synchrotron radiation transmitting thin film and the synchrotron radiation transmission distance, and Fig. 3 is the optimum film surface shape of the synchrotron radiation transmitting thin film. 4 is a sectional view showing the film surface shape for convenience in order to find the optimum value of the radius of spherical curvature of the synchrotron radiation transmitting thin film.
The figure is a perspective view showing a state in which a spherical synchrotron radiation transmitting thin film is exposed and attached to a rectangular opening of a window frame, and FIG. 6 is an explanatory diagram showing a method for attaching a synchrotron radiation transmitting thin film according to the second invention. ,
FIG. 7 is an explanatory diagram showing a method of attaching a synchrotron radiation transmitting thin film according to the third invention, FIG. 8 is an explanatory diagram showing a method of attaching a synchrotron radiation transmitting thin film according to the fourth invention, and FIG. 9 is an explanatory diagram showing a method of attaching a synchrotron radiation transmitting thin film according to the fourth invention. FIG. 10 is a cross-sectional view showing an embodiment of a synchrotron radiation transmitting window to which a spherical synchrotron radiation transmitting thin film is attached, and FIG. 11 is an explanatory diagram showing an outline of X-ray lithography using synchrotron radiation, and FIG. 12 is a sectional view showing the structure of a conventional radiation transmitting window. In the figure, (1) is a synchrotron radiation transmitting thin film, (2) is a window frame, and (20
) is a tapered surface, (20a) (21) is a spherical seat, (3)
(4) shows the beam line, and (4) shows the transfer device. 1! IFiA Figure 4 Figure 11 Figure 2 Figure 2? n 0 Procedural amendment dated October lb, 1989

Claims (8)

[Claims] (1) Installed between the beam line that extracts synchrotron radiation from the synchrotron radiation source side and the transfer device, separating the high vacuum area on the synchrotron radiation source side from the chamber atmosphere on the transfer device side, and transmitting the synchrotron radiation light. In a synchrotron radiation transmitting window provided with a synchrotron radiation transmitting thin film, the synchrotron radiation transmitting thin film is formed into a spherical shape that protrudes toward the synchrotron radiation source side, and the synchrotron radiation transmitting thin film has a spherical shape around the central part of the synchrotron radiation transmitting thin film. A synchrotron radiation transmitting window characterized by being formed so that the film thickness gradually becomes thinner. (2) In the synchrotron radiation transmitting window described in the preceding paragraph, the inner radius of curvature and the outer radius of curvature of the spherical surface of the synchrotron radiation transmitting thin film are made the same, and the center points of these radii of curvature are eccentrically arranged on the same line,
2. The synchrotron radiation transmitting window according to claim 1, wherein the synchrotron radiation transmitting thin film is formed so that the film thickness becomes gradually thinner around the spherical center of the synchrotron radiation transmitting thin film. (3) In the synchrotron radiation transmitting window according to claims 1 and 2, the radial radiation is 3. The radiation light transmitting window according to claim 1, wherein the light transmitting thin film is formed into a spherical shape. ▲Contains mathematical formulas, chemical formulas, tables, etc.▼ (4) When attaching the spherical synchrotron radiation transmitting thin film according to claims 1 to 3 to a synchrotron radiation transmitting window, a tapered surface is formed on the transfer device side of the window frame of the synchrotron radiation transmitting window. and the spherical protruding surface of the synchrotron radiation transmitting thin film is brought into contact with the tapered surface, and the end side of the synchrotron radiation transmitting thin film is fixed to the window frame. How to attach the thin film. (5) In the method for attaching a synchrotron radiation transmitting thin film in a synchrotron radiation transmitting window described in the preceding paragraph, the circumferential side portion of the synchrotron radiation transmitting thin film is extended in the direction of its spherical surface to provide a radially extending portion, and the radially extending portion is provided. 5. A method for attaching a radiation-transmitting thin film to a radiation-transmitting window according to claim 4, wherein the radially extending portion is brought into contact with the tapered surface, and the end portion of the radially extending portion is fixed to the window frame. (6) In the method for attaching a synchrotron radiation transmitting thin film in a synchrotron radiation transmitting window as set forth in claim 4, a tapered surface formed on the transfer device side of the window frame of the synchrotron radiation transmitting window is attached so that the synchrotron radiation transmits through the window. A spherical seat formed to match the spherical curvature of the thin film, with the spherical protruding surface of the radiation transmitting thin film in contact with the spherical seat, and an R-shaped surface formed from the opposite side to match the curvature. A method for attaching a synchrotron radiation transmitting thin film in a synchrotron radiation transmitting window according to claim 4, characterized in that the end side of the synchrotron radiation transmitting thin film is fixed to the window frame by applying a backing metal having a . (7) When attaching the spherical synchrotron radiation transmitting thin film according to claims 1 to 3 to a synchrotron radiation transmitting window, the synchrotron radiation transmitting thin film is attached to the transfer device side on the window frame of the synchrotron radiation transmitting window. A method for attaching a synchrotron radiation transmitting thin film to a synchrotron radiation transmitting window, characterized in that a spherical seat is formed in accordance with the spherical curvature of the thin film, and an end side of the synchrotron radiation transmitting thin film is adhered to the spherical seat. (8) When the spherical synchrotron radiation transmitting thin film according to claims 1 to 3 is attached to a synchrotron radiation transmitting window, the end side of the synchrotron radiation transmitting thin film becomes the window frame of the synchrotron radiation transmitting window. A method for attaching a radiation-transmitting thin film to a radiation-transmitting window, characterized in that the radiation-transmitting thin film is formed integrally with the window frame as described above.