JPS62274716A - X-ray exposure equipment - Google Patents

Abstract

PURPOSE:To prevent the influence of secondary electrons which causes problems in the case of pattern transfer applying X-rays, and improve the accuracy of pattern transfer, by arranging a mirror reflecting all the X-rays with the same angle between an X-ray source and a light receiving surface. CONSTITUTION:When a 2-dimensional plane X-Y wherein an X-ray source 1 is situated at the origin is considered, an X-ray 3 radiated from the light source is expressed by y=ax((a) is a constant). Writing a mirror 2 as y=f(x) the intersection 4 of the mirror 2 and the X-ray 3 is given by a point x0 which satisfies ax0=f(x0). Then the tangent of reflection angle can be written as {f'(x0)-a}/{a+af'(x0)} which must be constant for all values of (a). Letting this value be (c), f'(x0)={f(x0)+cx0}/{x-cf(x0)} is derived from the two equations above. The function f (x) is obtained by solving the above differential equation, and the mirror may be manufactured according to the function. A 3-dimensional mirror 2 can be constituted by rotating this shape arround a center axis (y).

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to X-ray lithography, and particularly to Xa chrysolography suitable for highly accurate microfabrication.

[Conventional technology]

In x4 lithography, the mask and base substrate are x#!
As the secondary electrons are absorbed, secondary electrons are emitted in various directions, which act on the resist and reduce the transfer accuracy. For this reason, conventionally, for example, Monthly Vacuum Science and Technology, Vol. 82, 1-3
Monthly issue, 1984, pp. 63-67 (Y, 5ait
oh etc. “Sub+*1 cron p*ttsrnrap
lication using a high con
trust mask and two ayer r
esist in X-ray lithography
y,” J.

Vac, Sci, Technol, Vol, B
2 (IL Jan, -Mar.

1984, p. 63-p. 67), a method has been proposed in which a polymer film is laminated on a mask or a workpiece to absorb secondary electrons.

[Problem that the invention seeks to solve]

In the above-mentioned conventional technology, the process is complicated, and the non-uniformity of the film thickness deteriorates the transfer accuracy. An object of the present invention is to prevent the influence of secondary electrons without causing such drawbacks.

[Means for solving philosophical issues]

The above object is achieved by reflecting the X-rays once by a mirror. At this time, all the X-rays used for exposure must be reflected at the same angle.

The conceptual diagram is shown in Fig. 1.

[Effect]

Of the secondary electrons generated by X-rays, those that reduce transfer accuracy are due to X-rays with relatively short wavelengths. In particular, when a rotating anticathode type radiation source is used, continuous X-rays contain short wavelength components, which have an adverse effect.

By reflecting the X-rays with a mirror, it is possible to remove X-rays with wavelengths shorter than the X-rays to be exposed, and ultimately prevent the influence of secondary electrons. At this time, if the reflection angle on the mirror is not constant, a difference in the X-ray wavelength distribution will occur depending on one reflection angle, causing non-uniformity on the exposure surface.

〔Example〕

The present invention will be explained in detail below.

A case will be described in which a rotating anode-type radiation source targeting Si is used as an X-ray source. The accelerating voltage of electrons is 17
kV. The wavelength of the characteristic X-ray (S i Kα) at this time is 7.1A.

The design of the mirror is done as follows. This will be explained according to FIG. The X-ray source 1 is placed at the origin and considered within the X-Y two-dimensional plane. X-rays 3 generated from the light source are expressed as y=ax (a is a constant). If the mirror 2 is written as y=f (x), the intersection point 4 between the mirror and the X-ray becomes the point xo that satisfies axo=f(xo). The tangent of the reflection angle at this time is (f'(x
It can be written as o)-a)/(1+a f'(xo)). This value may be made constant for all a.

Letting this value be C, f' (xo) = (
f(xo)+cxo)/(x-cf(xo)). All that is required is to solve this differential equation to obtain the function f (x), and then manufacture the mirror according to that function. This differential equation cannot be solved analytically, but must be solved numerically. By rotating this shape around the y-axis, a three-dimensional mirror is formed. This mirror was made by inputting the above numerical calculation results into an NC machine tool, processing a quartz plate, and depositing platinum or gold on its surface to a thickness of 500 mm.

Figure 3 shows an x equipped with a mirror designed according to this method.
The configuration of the i-exposure device is shown. The reflection angle was set to 1.5°, so that X-rays with a wavelength of 4.7 Å or less were not reflected and were removed.A pattern was formed on the X-ray resist using the apparatus. W is evaporated onto a Si substrate, and an X-ray resist (RE5000P, Hitachi Chemical) is applied on top of it.
formed a pattern. FIG. 4 shows changes in pattern dimensions depending on exposure time. The white spots are those obtained using a conventional exposure method that does not use a mirror, and the black spots are those obtained using an exposure apparatus according to the present invention. As is clear from the figure, the black dots show more dimensional stability with respect to exposure time.

If the size of the mirror is approximately 71, the mirror is 1'+3
The intensity change at a distance of 00 nw was less than ±5%.

〔Effect of the invention〕

As is clear from the above embodiments, according to the present invention, short wavelength components of X-rays can be removed, and therefore the influence of secondary electrons, which is a problem when transferring patterns using X-rays, can be prevented.

This makes it possible to improve pattern transfer accuracy.
It becomes possible to improve productivity.

[Brief explanation of the drawing]

Figure 1 is a conceptual diagram of the present invention, Figure 2 is a diagram for explaining the mirror design method according to the present invention, Figure 3 is an ellipse diagram of the xHc exposure apparatus, and Figure 4 shows the pattern dimensional accuracy of the resist. FIG. 1...x, ml, 2...mirror, 3...X-ray, 4
...Intersection of xa and mirror, 5...X-ray source chamber, 6...He chamber, 7...Bsg, 8...
・) l mask.

Claims (1)

[Scope of Claims] 1. An X-ray exposure apparatus characterized by having a mirror between an X-ray source and a strong light surface that reflects all X-rays at the same angle. 2. The shape of the reflective surface of the above mirror is f'(x)={f(x
)+cx}/{x-cf(x)} (where c=tanθ
The X-ray exposure apparatus according to claim 1, wherein the X-ray exposure apparatus is a mirror expressed by a function f(x) that satisfies the following: ; θ is a reflection angle. 3. The shape of the reflective surface of the above mirror is x=Ae^α^(^f^_^1^)^-^α^(^0^
), α(f_1)=▲There are mathematical formulas, chemical formulas, tables, etc.▼
(A, constant, c= tanθ; θ is the reflection angle, f_1=1-c{[f(x)]
2. The X-ray exposure apparatus according to claim 1, wherein the X-ray exposure apparatus is a mirror expressed by a function f(x) of the form /x}).