JPS62294234A - Exposure device - Google Patents

Abstract

PURPOSE:To set the height of a reduction projection exposure device to a required minimum value by arranging a concave reflective mirror in the optical path between an excimer laser light source optical system and a reticle. CONSTITUTION:A concaves reflective mirror 3 is arranged in the optical path between the optical system of an excimer light source 1 and a reticle 4 to make a condenser lens unnecessary. Consequently, a height l2 is considerably shortened, and a height l1+l2 of the reduction projection exposure device is held down to a required minimum value.

Description

DETAILED DESCRIPTION OF THE INVENTION 3. Detailed Description of the Invention Field of Industrial Application The present invention relates to an exposure apparatus, particularly an exposure apparatus using photolithography technology used in the manufacture of semiconductor devices.

More specifically, it relates to an exposure device that uses discontinuous, e.g., pulsed energy beams, more specifically excimer laser, etc., devised to realize ultra-fine processing in one step of photolithography in semiconductor device manufacturing. .

2. Description of the Related Art Conventionally, reduction projection exposure apparatuses (steppers) using an ultra-high pressure mercury lamp as a light source have already been commercially available for microfabrication of semiconductor devices, particularly LSIs, VLSIs, and the like. However, conventional steppers only use the q-ray (43
6 nm) and i-line (365 nm), the resolution was limited to 0.8 μm for q-line and 0.6 μm for i-line. At these wavelengths, it will be nearly impossible to obtain the 0.5 μm resolution required for 4M or 1eM bit production in the future.

Therefore, in recent years, XeC, which has a shorter wavelength than the q-line and i-line, has been
l! (308 nm), KrF (249 nm), ArF (
Development of an exposure apparatus using an excimer light source such as 193 nm) is now being considered.

Problems to be Solved by the Invention However, reduction projection exposure using an excimer laser has the following problems.

1) Since the exposure wavelength is short, there is a limited range in material selection for the optical material glass (glass material) used in the reduction projection lens due to transmittance. By the way, KrF (249nm),
At the laser wavelength of ArF (193 nm), quartz (Si
It is limited to two types: O2) and goldstone (CaF2). Therefore, in designing a reduction projection lens, various aberrations such as chromatic aberration must be corrected in units of a fraction of a wavelength by utilizing the slight difference in refractive index and dispersion of the glass materials that constitute the lens. However, as mentioned above, the materials that can be used for deep ultraviolet light such as excimer laser light are limited, so when designing a reduction projection lens, the only method used is to gradually change the radius of curvature of the spherical surface of a material with the same refractive index. However, there is a problem in that the reduction projection lens alone is extremely long, about 1 m.

(2) On the other hand, in not only excimer lasers but also reduction projection exposure apparatuses, it is necessary to make the occupied area or the height of the apparatus as small and low as possible. However, if the above-mentioned lens is used in a general optical system for reduction projection exposure, a configuration as shown in FIG. 2 will be obtained. The light emitted from the excimer laser 7 is transmitted to the integrator 2. It involves an illumination optical system 9 that uses a vertical condenser lens for converging light onto a lens 11 with a length 13 of about 1 m by a flat mirror 8, which uniformly illuminates the reticle 1o and has a lens length 11. is transferred to Weno-12 through a reduction projection lens 11 that is about 1 m long.

Therefore, in the conventional device shown in Fig. 2, an illumination optical system 9 is required, 11+13 is long, about 2 m, and the height of the device itself is very high, more than 2 m, and a pattern of about 0.6 μm can be formed. In ultra-high-precision exposure equipment, optical axis misalignment and the like occur, which is extremely inconvenient. If the height is further increased, problems such as vibration will increase design difficulties, and if an excimer light source 7 that generates a vibration sound every time it oscillates is used, this height problem becomes even more serious. There is a problem in that it is very difficult to arrange an optical system for alignment between the Ueno 1-12 and the reticle 10.

Therefore, in the present invention, in excimer reduction projection exposure, by arranging a concave reflecting mirror between the optical path axis of the laser light source optical system and the reticle, the height of the entire optical system, or in other words, the reduction projection exposure apparatus, can be reduced. The aim is to keep it to the minimum necessary.

The means to solve the problem, that is, the configuration of the optical path order, are as follows: an excimer laser optical system as a light generation source, an integrator system to ensure uniformity of the laser beam and shape the beam, and a conventional mirror and illumination optical system. Transform the optical path (change direction) instead of
A concave reflecting mirror is placed between the optical path of the reticle and the excimer laser light source, and is used in place of the condenser lens used in the conventional illumination optical system 9. Further, preferably, the reflective surface of the concave mirror is composed of a multilayer film made of, for example, a high reflectance aluminum film and a dielectric film.

Therefore, in the present invention, by arranging the above-mentioned concave reflecting mirror between the optical path of the excimer laser light source optical system and the reticle, the height of the apparatus can be reduced and the degree of freedom can be increased in the design of the optical system. Furthermore, it has a great effect on anti-vibration measures, and is especially suitable for high-precision equipment that forms ultra-fine patterns on wafers by exposure.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to FIG. That is, for example, a KrF excimer laser light source (
Using an oscillation wavelength (249 nm) 1 and a laser light source, the integrator 2 shapes and homogenizes the oscillated and emitted light from this light source. This integrator 2 has a function of expanding the beam diameter and emitting it. Furthermore, a concave mirror 3 whose curvature and aperture are determined so that it can illuminate the effective area of the reticle and enter the entrance pupil of the reduction projection lens 6 is arranged in the optical path between the integrator 2 and the reticle 4. Then, the pattern of the reticle 4 is exposed onto the wafer (semiconductor substrate) 6 through the lens 6. In this embodiment, optical axes o1 and 0
Although the mirror 3 was installed so that the optical axes o and +02 are vertical, the lengths of the optical axes o and +02 can be made arbitrary by changing the curvature of the concave mirror 3.

Further, the reflective surface of the concave mirror 3 was first coated with a multilayer film consisting of a high reflectance aluminum film and a dielectric film in order to increase the reflectance. According to these conditions, a reflectance of 99 cm or more was obtained.

In the optical system shown in FIG. 1, the conventional condenser lens can be omitted, so 12 can be considerably shorter than 13, and the device height is 1. +12 can now be held as low as approximately 1.6m.

Figure 2 shows an example in which a relatively heavy excimer light source 1 is installed diagonally upward at the bottom so that the intersection angle of optical axes 01 and 02 is an acute angle. This is extremely effective as a countermeasure.

The height of the entire device! , +lI2 become shorter, the deviation of the optical axis o2 due to vibration is suppressed, and the exposure apparatus becomes extremely high-performance for a submicron pattern type exposure apparatus. When exposing an ultra-fine pattern of about 0.6 μm to a resist on the wafer 6, the resolution deteriorates even if the optical axis 02 is shifted by several μm. Therefore, being able to reduce the height by as much as several 1 ocW1 is extremely useful for forming ultra-fine exposure patterns without causing deviation of the optical axis.

Effects of the Invention In an excimer laser exposure device, by using the configuration of the present invention, that is, arranging a concave mirror between the excimer laser optical system and the reticle, a conventional condenser lens is not required, and the height of the device can be reduced. , the degree of simplicity and freedom in designing a compact and highly accurate excimer exposure device and optical system will be expanded. Moreover, it is highly effective in terms of anti-vibration measures, and the present invention has extremely excellent effects in forming ultra-fine patterns in semiconductor devices and the like.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an excimer exposure apparatus according to one embodiment of the present invention, FIG. 2 is a schematic diagram of an apparatus according to another embodiment, and FIG. 3 is a schematic diagram of a conventional reduction projection exposure apparatus. . 1... Excimer light source, 3... Concave mirror, 4... Reticle, 6... Reduction projection lens, 6... Wafer 0 Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure mirror ink b-7 Figure 2 3

Claims (2)

[Claims] (1) In an exposure apparatus having an optical system including a reduction projection lens, a wafer stage, a reticle stage, and an excimer laser light source, a concave reflecting mirror is disposed in the optical path between the reticle stage and the excimer laser light source, and the An exposure apparatus characterized in that excimer laser light from a light source is reflected by the reflecting mirror and irradiated onto the wafer through the reticle lens. (2) The exposure apparatus according to claim 1, wherein the reflective surface of the concave reflective mirror is made of a multilayer film consisting of a high reflectance aluminum film and a dielectric film.