JPH07115049A - Reduction projection aligner - Google Patents

Abstract

PURPOSE:To enable easy change of numerical aperture without causing geometric distortion of accuracy and troubles by dust. CONSTITUTION:Light emitted from a light source 1 passes through a reflection mirror 2 and a fly's eye lens 3, passes through a diaphragm 4, further passes through a relay lens 5, a reflection mirror 6 and a condenser lens 7 and lights a reticle 8. Light which passed through the reticle 8 and obtained information enters a reduction projection lens 9. A liquid crystal display 12 is installed in a pupil surface of the reduction projection lens 9. The liquid crystal display 12 can generate an arbitrary image by an electric signal by an electric signal generator 13. Light passed through the reduction projection lens 9 exposes a silicon substrate 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reduction projection exposure apparatus used for forming a fine pattern in a semiconductor device manufacturing process or the like.

[0002]

2. Description of the Related Art The miniaturization of semiconductor devices has progressed remarkably and 0.5
Semiconductor devices having a design rule of μm or less have been manufactured. Of the manufacturing process of such a semiconductor device,
In a lithography process of drawing a desired circuit pattern on a semiconductor substrate, a method of transferring a pattern drawn on a reticle to a resist on a silicon substrate by a reduction projection exposure apparatus (stepper) is generally used.

FIG. 2 is a diagram showing an optical system of a conventional reduction projection exposure apparatus. In FIG. 2, the light emitted from the light source 1 passes through the reflecting mirror 2, the fly-eye lens 3 and the diaphragm 4, and further illuminates the reticle 8 via the relay lens 5, the reflecting mirror 6 and the condenser lens 7. The light is diffracted by the pattern on the reticle 8 and enters the reduction projection lens 9 with the pattern information. Then, the silicon substrate 11 is reduced and exposed. The reduction projection lens 9 is composed of a large number of lenses, and its pupil plane shows a light intensity distribution in a form in which the reticle pattern information is Fourier transformed.

The pattern information having a high spatial frequency of the reticle 8 passes through a portion far from the center of the pupil plane, and the low spatial frequency pattern information passes near the center. The numerical aperture of the reduction projection lens 9 is uniquely determined by the size of the pupil plane. In the reduction projection lens having the same focal length, the wider the pupil plane is, the higher the numerical aperture is. Therefore, the pattern having a high spatial frequency on the reticle 8 is formed. Since the information of up to can be transmitted, the resolution is high. However, a reduction projection lens with a high numerical aperture has a shallow depth of focus. When pattern formation is performed using the resolution projection lens near the limit of resolution, an optimum value is generated for the numerical aperture due to the trade-off between the steps of the silicon substrate 11 and the fineness of the pattern. Conventionally, the numerical aperture has often been adjusted by replacing the metal plate filter 10 on the pupil plane.

[0005]

As described above, in the reduction projection exposure apparatus which is forced to be used near the resolution limit of the apparatus, the numerical aperture of the reduction projection lens 9 is changed according to the step or pattern size of the silicon substrate 11. Need to change. In this case, the pupil plane of the reduction projection lens 9 is one surface in the lens barrel of the lens, and the metal plate filter 1 is provided on that portion.
It is necessary to set 0. When this metal plate filter 10 is replaced, a physical change operation is performed on a part of a precise lens, which may cause a defect in accuracy and dust. Further, designing and manufacturing are required each time to obtain a desired filter, which requires an extremely large amount of labor and time.

It is an object of the present invention to provide a reduction projection exposure apparatus which can easily change the numerical aperture without causing a precision error and a defect due to dust.

[0007]

According to another aspect of the reduction projection exposure apparatus of the present invention, by applying an electric signal from the outside to the pupil plane of the reduction projection lens, the transmittance with respect to the exposure light is changed in whole or in part. It has a filter. A reduction projection exposure apparatus according to a second aspect is the reduction projection exposure apparatus according to the first aspect, wherein the filter is composed of a liquid crystal display plate in which liquid crystal is sealed in a flat transparent container having transparent pattern electrodes.

[0008]

In the reduction projection exposure apparatus of the present invention, an arbitrary pattern can be drawn on the filter on the pupil plane by an external electric signal. Therefore, when changing the numerical aperture, the filter must be physically replaced. Not only is it unnecessary, but it is possible to instantly form a desired filter simply by changing the electric signal.

[0009]

EXAMPLES The present invention will be described in detail below with reference to examples. FIG. 1 shows an optical system of a reduction projection exposure apparatus according to the present invention. The light emitted from the light source 1 passes through the reflecting mirror 2 and the fly-eye lens 3, then passes through the diaphragm 4, and further illuminates the reticle 8 via the relay lens 5, the reflecting mirror 6, and the condenser lens 7. The light that has passed the reticle and obtained information enters the reduction projection lens 9. This reduction projection lens 9
The liquid crystal display board 12 is installed on the pupil plane of the. The liquid crystal display plate 12 is one in which liquid crystal is sealed in a flat transparent container having transparent pattern electrodes formed thereon, and an arbitrary image can be generated by applying an electric signal from the electric signal generator 13 to the transparent pattern electrodes. it can. The light that has passed through the reduction projection lens 9 exposes the silicon substrate 11.

The liquid crystal display panel 12 has an image area of 25 cm × 25.
The size of one pixel in cm is about 250 μm × 250 μm. The wavelength of the light source of the reduction projection exposure apparatus in the embodiment is 3
65 nm, the polarization degree of the illumination system is 0.6. Further, the numerical aperture of the reduction projection lens 9 at the time of full aperture is 0.5. Next, the characteristics at the time of forming a resist pattern by the reduction projection exposure apparatus of this embodiment will be compared with the conventional method. First, an aperture pattern having a circular shape of 11.5 cm from the center of the reduction projection lens 9 as an example is formed on the liquid crystal display plate 12, and the numerical aperture is 0.4.
5, a line-and-space pattern was exposed on the positive photoresist. At this time, it was possible to resolve a pattern of 0.40 μm. This value was exactly the same as when the metal plate filter was used. Next,
When an aperture pattern 20 cm from the center was formed on the liquid crystal display plate 12 and the same printing was performed with the numerical aperture of the reduction projection lens 9 being 0.4, a pattern of 0.44 μm was resolved. This value was also the same as when the metal plate filter was used.

As described above, it was confirmed that even if a liquid crystal display plate was used instead of the metal plate filter, the same effect was obtained. The filter is not limited to the liquid crystal display plate, and any filter can be used as long as it can freely change the light opaque portion by an electric signal.

[0012]

In the reduction projection exposure apparatus of the present invention, the numerical aperture of the reduction projection lens can be easily changed by an electric signal from the outside, and the lens is not physically operated at all. The accuracy and the like can be kept high, and the efficiency of use of the device is extremely high.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of an optical system of a reduction projection exposure apparatus according to an embodiment of the present invention.

FIG. 2 is a conceptual diagram of an optical system of a conventional reduction projection exposure apparatus.

[Explanation of symbols]

 1 Light Source 2 Reflector 3 Fly-eye Lens 4 Aperture 5 Relay Lens 6 Reflector 7 Condenser Lens 8 Reticle 9 Reduction Projection Lens 11 Silicon Substrate 12 Liquid Crystal Display 13 Electric Signal Generator

Claims (2)

[Claims] 1. A reduction projection exposure apparatus provided with a filter whose transmittance for exposure light changes on the entire or a part of the pupil surface of a reduction projection lens when an electric signal is applied from the outside. 2. The reduction projection exposure apparatus according to claim 1, wherein the filter is a liquid crystal display plate in which liquid crystal is enclosed in a flat transparent container having transparent pattern electrodes.