JPS61156736A - Exposing device - Google Patents

Abstract

PURPOSE:To reduce the adverse effect inflicted on a bright line spectrum and to obtain an exposing device having high resolving power by a method wherein a suitable filter is inserted into a part of the illumination system with which a projection optical system is illuminated, and a continuous spectrum is effectively cut. CONSTITUTION:The luminous flux emitted from a light source 2 is condensed on the field lens 3 arranged in the vicinity of the second focus by an oval mirror. The incidence angle of each luminous flux which is made incident on a filter element 5 is made small in such a manner that the center luminous flux in a field lens 3 becomes almost a parallel light by the first capacitor lens. After passing through a filter element 5, the luminous flux is introduced to an optical integrator 8. The filter element 5 is composed of a multilayer film which transmits the luminous flux having the narrow wavelength range of bright line spectrum necessary for projection and exposure, but it does not transmit other spectrum lights. As a result, a continuous spectrum can be cut effectively, and the adverse effect inflicting on the bright-line spectrum can be reduced.

Description

[Detailed Description of the Invention] (Technical Field) Is the present invention applicable to semiconductor manufacturing? The present invention relates to a one-dimensional device, and particularly to a projection exposure device suitable for transferring a mask on which a circuit pattern or the like is formed onto a silicon wafer or the like.

(Prior Art) Mercury lamps have traditionally been widely used as light sources for illumination in projection exposure apparatuses. As shown in Figure 2, this mercury lamp emits a large number of bright line spectra, with the H-line (405 nm) and E-line (546 nm) adjacent to each other near the G-line (436 nm), which is usually used most often. Existing. Conventionally, wavelengths shorter than the G-line are cut with a sharp-cut color filter, wavelengths longer than the G-line are cut with a cold mirror, and the spectral sensitivity of the resist itself decreases at wavelengths longer than zffM. was. However, the spectral sensitivity characteristics of color filters, gold mirrors, and resists are not sharp in terms of wavelength vs. transmittance or wavelength vs. reflectance, so h@ and e
Even if a can be cut, the continuous spectrum near ta remains in the printing light beam. Although the intensity of this continuous spectrum is smaller than that of the bright line spectrum, it has a wide wavelength range, so when considering the effect by integrating the wavelength intensity as a whole, it has a large effect on printing performance. Although the projection optical system used in the present invention is color-corrected for wavelength components within the spread of the emission line spectrum, chromatic aberration is not corrected for wavelengths in the continuous spectral region. When printing is performed, the in-focus bright line spectral component light and the out-of-focus continuous spectral component light overlap, which adversely affects the printing performance.

(Objective of the Present Invention) An object of the present invention is to provide an exposure apparatus suitable for semiconductor manufacturing that can obtain high resolution even when a light source that emits a continuous spectrum in addition to the bright line spectrum is used in the illumination system.

A further object of the present invention is to provide a high-performance exposure apparatus that eliminates the shadow 41 of the continuous spectrum by arranging a filter element having a predetermined spectral characteristic at a specific position of the illumination system.

(Main features of the g-light device for achieving the purpose of the present invention)
9. In an exposure apparatus for semiconductor manufacturing using a light source emitting a plurality of spectra in the illumination system, a filter element for selecting only a luminous flux of a predetermined wavelength from among the emission spectrum emitted from the light source is provided in a part of the illumination system. This is what we have set up.

Other features of the invention are detailed in the Examples.

(Example) FIG. 1 is a schematic diagram of an optical system according to an embodiment of the present invention.

In the figure, 1 is a circular mirror, 2 is a light source such as a mercury lamp, and 3 is a field lens. The light source 2 and the field lens 3 are arranged near the first and second focal points of the rectangular mirror 1, respectively.

4 is a first condenser lens, and a field lens 3 is located near the front focal point. 5 is the filter [-1
6 and 7 are reflecting mirrors, 8 is an optical integrator, 9 is a second condenser lens, and the optical integrator 8 is located near the front focal point. 10 is a reticle surface on which a circuit pattern is formed, 1) is a projection optical system, and 12 is a wafer.

The light beam emitted from the light source 2 is focused by the rectangular mirror 1 onto the field lens 3 arranged near the second focal point. The central light beams of the first condenser lens 41C and the shift field lens 3 are made to be substantially parallel lights, so that the angle of incidence of each light beam on the filter element 5 is made small. Then, the light is transmitted through the filter p-=child st- and then guided to the optical integrator 8.

Here, the filter element 5 transmits a narrow wavelength range of the bright line spectrum required for projection exposure and cuts out other spectral elements, and the filter element used in this embodiment is composed of a multilayer film. Because the molecule t and its characteristics shift due to this rounding and the difference in the angle of incidence of the light beam, the filter element is arranged at a position so that the angle of incidence of the light beam on the filter element is approximately constant, that is, it is small.

The selected light passes through the optical integrator 8 and is focused by the second condenser lens 9, uniformly illuminating the reticle surface 10t.

Then, the circuit pattern on the reticle surface 10 illuminated with light of a predetermined wavelength is projected onto the surface 12 by the projection optical system 1).

FIGS. 2 and 3 are diagrams showing the spectral characteristics of a mercury lamp and a filter element according to the present invention, respectively.

The curve shown by the dotted line in FIG. 2 is the spectral transmittance when an interference filter, which is a narrowband transmission filter, is used as the filter element 6. Also, Figure 3 is from a book that combines two sharp cut filters A and B with different transmission bands to obtain the same effect as a narrow band transmission filter.If a multilayer film is used as a filter, both sides of the filter element 50. Multiple l-films, each with a different transmission band, can be deposited. Also, filter A.

If one side of B is a so-called glass filter that utilizes light absorption by dye etc., filter A or B is placed on one surface of it.
A similar effect can be obtained by depositing a multilayer film having the following characteristics. However, there is actually no glass filter that cuts the long wavelength side like filter A, and it is necessary to use a multilayer film to achieve this characteristic.

As described above, in this embodiment, the continuous spectrum light beam outside the predetermined bright line spectrum region is efficiently removed by the filter element, thereby achieving an exposure apparatus that can easily obtain high resolution.

FIGS. 4 and 5 are schematic diagrams of optical systems according to other preferred embodiments of the present invention. The same members as in FIG. 1 are given the same reference numerals.

A filter element 5 according to the embodiment shown in FIG. 4 is arranged between an optical integrator 8 and a reticle 100. What is important in this case is the problem of shading of the filter element 5.

The filter element 5 is constructed using a dielectric multilayer film in order to have sharp cut characteristics as described above, and its characteristics change according to the angle of incidence. Therefore, it is desirable that the state in which the light flux illuminating each point on the reticle 10 travels back through the filter element 5 is all the same. The embodiment shown in FIG. 4 is a case where the projection optical system on the reticle surface 10 side is a telescopic link.

Each light ray indicated by 15 in the figure is a chief ray for each point on the reticle surface 10. The principal rays are parallel according to the projection optical system. Therefore, the location in Figure 4, the reticle (filo
If the filter element 5 is placed between the condenser lens 9 of the illumination thread and the condenser lens 9 of the illumination thread, the angle t\j of the filter will be exactly the same for each point on the reticle surface, and no shading will occur.

Note that the filter element 5 is preferably installed at a location where the principal rays of the illumination light beam for each point on the reticle surface are parallel, and it is not necessarily necessary to install it between the reticle surface 10 and the condenser lens 9. is reticle surface 101N+1
is a non-telecentric projection optical system.
This is an example in which At is applied. Since the principal rays 15 incident on the reticle surface 10 are not parallel, it is not appropriate to arrange the filter 5 at the position shown in FIG. In this case, it is sufficient to create a part in the illumination system where the principal rays are parallel, and in Figure 5, exactly such a situation is created using the optical integrator 8.
The light is generated by the condensing system 21 located behind the
An IC filter system 5 is arranged. Of course, even in the case of an illumination system for a projection system where the reticle surface 10 side is telecentric, if a place is created in the illumination system V'3IfI% where the principal ray is parallel, the filter can be placed there instead of the arrangement shown in Fig. 4. I can do things. 22 is an optical member constituting a part of the illumination system.

In this embodiment, the filter element can be placed at a position where a predetermined 4-line spectrum light beam can be selected even if the light beams incident on the filter element are not strictly parallel, and unnecessary continuous spectrum light beams can be removed. (Effect of the present invention) According to the present invention, a part of the illumination system that illuminates the projection optical system
By inserting a filter element with an excess of 1C, it can be used to effectively cut the continuous spectrum and achieve a high resolution dew with reduced negative 4gI on the 14-win spectrum.

Furthermore, by easily cutting continuous spectrum light near the printing light, which was difficult to cut with conventional glass filters, it is possible to achieve an exposure device that eliminates the effects of spring chromatic aberration and improves image contrast. .

However, if you proactively set up a position in the illumination optical system where the principal rays of the light flux that illuminate each point on the reticle surface are parallel, and place the filter element at this position, the angle of incidence of the light rays that enter the filter element can be adjusted. can be made small, and the shift in the wavelength characteristics of the transmitted light of the filter element due to the deviation of the incident angle of the light beam can be slightly VC, and an exposure apparatus that can obtain a high resolution of 7'c can be achieved.

Brief explanation of the front screen Figures 1, 4, and 5 are schematic diagrams of an optical system according to an embodiment of the present invention, and Figures 2 and 3 are schematic diagrams of a light source and a filter element according to the present invention, respectively. It is an explanatory diagram of minute''/1% property.

In the figure, 1 is a round mirror, 2 is a light source, 3 is a field lens, and 4
is the first condenser lens, 5 is the filter element, 6,
7 is each a reflector, 8 is an optical integrator, 9
1 is a second condenser lens, 10 is a reticle surface, 1) is a projection optical system, and 12 is a surface.

Claims (3)

[Claims] (1) In an exposure apparatus for semiconductor manufacturing using a light source that emits a plurality of spectra in the illumination system, only a luminous flux of a predetermined wavelength is selected from among the emission spectra emitted from the light source as part of the illumination system. An exposure apparatus characterized by being provided with a filter element. (2) The exposure apparatus according to claim 1, wherein the filter element is provided at a position where principal rays of a luminous flux illuminating each point of the illuminated surface in the illumination system are substantially parallel. . (3) The exposure apparatus according to claim 1, wherein the filter element is configured to cut a continuous spectrum outside a predetermined bright line spectrum.