JPS62231198A - Curved crystal element for x-ray diffraction - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a 1F method for manufacturing a Johansson type curved crystal.

2. Description of the Related Art In the conventional LSI manufacturing process, a phototransfer method has generally been used to form a resist pattern. However, the optical transfer method is said to have a limit of 0.5 μm, and due to the influence of Fresnel diffraction and the small depth of focus, in order to form fine patterns of 1 μm or less, multilayer resist methods and CE
A process technology such as the L method must be used. That Z
), which complicates the process and causes a decrease in yield, and is expected to reach its limit in the near future. Electron beam direct writing and X-ray lithography are being considered as alternative means. However, the electron beam direct writing method has drawbacks such as the need to use multilayer resist in order to achieve throughput, stage joint accuracy, and high aspect ratio. On the other hand, X-ray lithography is considered particularly promising because it is a transfer process and is suitable for mass production, and since it uses light beams with wavelengths of several to several tens of amperes, the effect of diffraction is negligible in practical use. and 0.1
A degree of decapitation of up to about μm can be expected.

X-ray lithography can be roughly divided into two methods. One is the so-called proximity method, in which the X-ray mask and wafer are placed close to each other with a distance of about 10 μm, and the mask pattern is transferred by irradiating X-rays. This is a projection exposure method in which a projected image of a mask is transferred using a method.

The present invention relates to a Johansson-type curved crystal that is considered to be used as a light emitting element for illumination used in the subsequent projection exposure method. Since υC, a Johann type crystal has been used as a typical curved crystal for X-ray spectroscopy, but this Johann type crystal is a parallel plane crystal with lattice planes parallel to the crystal surface, with a radius equal to the diameter of a Rowland circle. By bending in only one direction along an arc such as It is designed to concentrate light. However, the curved crystal described above has large aberrations, and the X-rays emitted from the source near the optical axis near the center of the crystal satisfy the Bragg condition and ffi to a single point on the Rowland circle. As it moves away from the center, the incident X-rays no longer satisfy the Bragg angle. Furthermore, even if a light source is placed at a position around the crystal that satisfies the Bragg condition, the diffracted X-rays at the center point and the diffracted X-rays at the periphery have different focal points, so the light source is diffracted by the curved crystal. It is difficult to focus all the X-rays on the same location. There is also a Johansson-type curved crystal that eliminates aberrations by polishing the surface of the Johann-type curved crystal to a cylindrical surface similar to a Rowland circle, but since the curvature is only in one direction, light can only be focused on one plane. Therefore, it is not suitable as a focusing element for X-ray phosphorography, which requires three-dimensional light focusing.To be able to focus three-dimensional light, the crystal must have a double curvature. However, the in-situ crystal is not a spherical surface, but must be finished into a toroidal surface with different curvatures in two directions, making it difficult to manufacture f%.

C.1 Problems to be Solved by the Invention It is an object of the present invention to provide a method for easily manufacturing a Johansson crystal that can focus light on one spatial point.

20 Means for Solving Problems When the lattice plane is curved with a radius of curvature of 2Ro, the crystal surface is polished into a cylindrical surface beforehand so that the radius of curvature of the crystal surface becomes R8, and then the above The crystal was bent in a plane perpendicular to the cylindrical axis of the cylindrical polished surface so that the radius of curvature of the lattice plane was 2 Ro, and was also curved in a direction perpendicular thereto to make the crystal surface a toroidal surface.

E, because it is very difficult to polish to a toroidal surface, which is a curved surface with different curvature in two perpendicular directions,
After polishing the crystal to a pre-calculated curved surface before curving it,
By curving it, it became possible to easily produce a Johanshin-type crystal using the method of forming an I/rhoidal plane (Y).

Embodiment FIG. 1 shows an embodiment of the present invention. FIG. 1A shows a cross-sectional view of the crystal after bending, and FIG. 1B shows a cross-sectional view of the crystal before bending. Figure 2 shows a cross-sectional view of a Johansson-type curved crystal. In Figures 1 and 2, K is the curved crystal, C is the lattice plane, 0 is the center of curvature of the surface of the crystal, and Ro is the radius of curvature of the surface of the crystal. ,A
, Ao is the diffraction point of X-rays on the crystal surface in the paper plane, S is the X-ray source, F is the convergence point of the diffracted X-rays, B is 5B=SF and AO
B is the point on the circumference where the diameter is the center of curvature of the lattice plane, and IT is A. The intersection of B and SF, E is the incident point of the X-ray on the crystal surface that is not within the plane of the paper, and D is the intersection of the crystal plane passing through point Ao and the extension of line segment B/~.

The principle of convergence of X-rays will be explained regarding the Johansson type curved crystal shown in FIG. On the Rowland circle on the paper, that is, on the circumference of the radius RO centered on point 0, the center of curvature B of the lattice surface
A radiation source S is placed at a position on the Roland circumference in a direction that satisfies Bragg's condition at a point Aθ where the direction BAo and the same line segment BAO intersect with the crystal surface, and the center of curvature point 0 of the surface of the crystal is If point F is set at a position symmetrical to S with respect to minute BAo, points S, B, and F are on the circumference along the crystal surface, and 5I3=BF, so 1 at point A: i S A B = l B A F-π/'2-
θB × θ8 ; Bragg angle) is added by 151, and all normals to the lattice plane pass through point B, so
From the X-ray source S to the curved crystal, a surface with a curvature Ro,
All the diffracted X-rays of the X-rays emitted to point A of α converge to point F. In addition, if the crystal plane is also curved to become a plane of rotation about the line segment SF, then Similarly, all diffracted X-rays converge on point F without aberration.

Such a curved crystal is made by curving it into an arc shape centered on point B in the plane of the paper, and by curving a flat plate crystal into a plane of rotation with SF as the axis in the direction perpendicular to the plane of the paper. The resulting crystal is A in the paper. It can be manufactured by polishing in a circular shape with SF as the axis in the direction perpendicular to the plane of the paper so that B is the diameter, but such a polished surface is difficult to actually manufacture once. Therefore, the present invention aims to produce the above-mentioned three-dimensional Johann type curved crystal by a method of polishing and then curving, rather than curving and then polishing. The method will be explained in Fig. 1. Fig. 1B is a cross-sectional view of the crystal before bending, and Fig. 1A is a cross-sectional view of the crystal after bending. Determining the angle θ and the radius of curvature Ro of the crystal surface in the crystal, AOD=2Roθ AD=2R□ (1-CO!+θ), and if we set X=AOD, and y=A stone, then the polishing before the crystal is curved. The coordinates of surface A are expressed as (x, y>, and the xy
When we find the relational expression, the following expression holds true when Ro>>x.

y=2Ro (1-cos x/2Ro) −(1
1ζx”/ 4 Ro---0-(■L52Ro-
7Ui ding)"-x"-...=131 When formula (3) is transformed, (y-2Ro)2+x"= (2Ro, z,...
,,,, (4 degrees, indicating that the crystal surface is a curved surface with a radius of 2RO of 219, which is the radius of curvature after curvature.

Further, ADH=2RoSjn2θB.

As shown in FIG. 1B, the function y is a function representing the cross section of the surface of the crystal with the lattice plane AoD as the reference (X axis) when the curved crystal is returned to a flat plate. Therefore, for a flat crystal as shown in FIG.
1. After processing into a cylindrical surface as expressed by either formula (3), curve the crystal surface in a plane perpendicular to the cylinder axis so that the radius of curvature is R8, and then A surface, that is, a surface without curvature, has a radius of curvature of A. By curving the crystal so that it becomes a toroidal surface having a curved surface H, a curved crystal with good retention properties can be obtained. Equation (1) is a rigorous study of crystals12
It is a function of the cross section of the surface, and the formula (21 represents the cross section when approximated as R8>>x. However, since this is a foreign body line, the product 1
Ya is difficult. Therefore, equation (3) is obtained by further approximating this using a circle with a radius of 2R8.

- As a specific example, wavelength ^ = 5, X of 40625 A
Ge (111
) is used. SA, )=FAo=750mm, θ
a = 56.2.77deg, RO = 450.87, A
H8=623.8mm. The value of X is 1m1II or l
An example of calculating y when taking a value up to >40 mm.Units shown in Figure 3A are perspective views of the crystal when polished as shown in the table above, and Figure 3B is a perspective view of the same crystal. A perspective view of the crystal when curved in two directions is shown.

According to the present invention, ultra-LS that requires ultra-fine patterns
For X-ray lithography, which is considered as a manufacturing process for I, it has become easier to manufacture a curved crystal that has no aberration and has a three-dimensional light focusing function, which is an essential X-ray focusing element.

[Brief explanation of drawings]

Figure 1 (21 is an embodiment of the present invention; Figure A is a cross-sectional view of the crystal after bending; Figure B is a cross-sectional view of the crystal before bending; Figure 2 is a cross-sectional view of the Johansson-type curved crystal; Figure 3). is A in the process diagram of the present invention
Figure A is a perspective view of the polished crystal before bending, and Figure B is a perspective view of the completed curved crystal after bending.

Claims (1)

[Claims] When the lattice plane is curved with a radius of curvature of 2R_0, the crystal surface is polished into a cylindrical surface before bending so that the radius of curvature of the crystal surface becomes R_0, and then the crystal is polished so that the radius of curvature of the crystal surface becomes R_0. A curved crystal element for X-ray diffraction, which is bent in a plane perpendicular to the cylindrical axis of the cylindrical polished surface and curved in a direction perpendicular to it so that the crystal surface becomes 2R_0, so that the crystal surface is a toroidal surface.