JP2877619B2 - Lighting equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illumination optical system of a reduction projection exposure apparatus used for manufacturing semiconductor integrated circuits and the like, and more particularly to an illumination apparatus and a projection exposure apparatus suitable for transferring a fine pattern.

[0002]

2. Description of the Related Art Generally, in an exposure optical system including an illumination optical system and an image forming optical system, resolution is improved by making an illumination light source into a ring shape. For example, in JP-A-61-91662 and JP-A-61-276217, a special stop is provided immediately after a secondary light source of a projection exposure apparatus, and a light intensity distribution applied to a reticle (mask substrate) is adjusted at a central portion. It is disclosed that the peripheral portion is made larger.

Japanese Patent Application Laid-Open No. 59-49514 discloses an annular illuminating device that converts light from a light source into cylindrical light with an optical member, and then converts the light into a circular light beam with a circular aperture stop. Japanese Patent Application Laid-Open No. 63-304624 discloses that a secondary light source image is corrected by measuring the light intensity distribution of the secondary light source so as to be suitable for the process, and furthermore, by moving the bright spot position of the lamp in the optical axis direction. It is disclosed that the peripheral portion of the light intensity applied to the reticle is made higher than the central portion.

[0004]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Application Laid-Open No. 61-91 is disclosed.
In the methods disclosed in Japanese Patent Application Publication No. 662 and Japanese Patent Application Laid-Open No. 61-276217, there is a problem that the illuminance on the reticle is significantly reduced due to a large light loss caused by an aperture disposed immediately after the secondary light source. In the method disclosed in JP-A-59-49514, the decrease in illuminance is alleviated,
Since the light from the light source is converted into cylindrical light and then into annular light, there is a problem that the optical member becomes complicated.

Japanese Patent Application Laid-Open No. 63-304624 discloses a method for correctly measuring the light intensity on the entrance pupil according to the pattern size and the same shape. There is no disclosure of a method for improving the resolution by lowering the resolution. In each of the above prior arts,
It is not always possible to obtain the optimum intensity distribution of the zonal luminous flux according to the pattern size and shape of the reticle, and there is also a problem that the number of adjustment work steps for obtaining the intensity distribution suitable for each pattern is large. Met. An object of the present illumination is to provide an illumination apparatus and a projection exposure apparatus capable of relatively easily obtaining illumination conditions of various patterns including the above-mentioned annular illumination with little loss of light.

[0006]

In order to solve the above problems, a light source is arranged near a first focal point of an ellipsoidal mirror, and light condensed near the second focal point is irradiated on a multi-beam generating member. In an illuminating device that irradiates the light emitted from the multi-beam generating member to a mask substrate (reticle) via a condenser lens, the light intensity distribution on the multi-beam generating member is made annular by changing the position of the elliptical mirror. To do.

In addition, the light source and the elliptical mirror are integrally held and their positions are changed, or at least the multi-beam generating member, the condenser lens and the sample stage are integrally held and their positions are changed. Further, a lens system for changing the light condensing position is provided between the light source and the multi-beam generating member. Further, a variable diaphragm device is mounted on the entrance surface or the exit surface of the multi-beam generating member.

The lenticular lens changes the intensity distribution of the reflected light from the ellipsoidal mirror, and the lenticular lens has a peripheral focal length shorter than a central focal length. Alternatively, the central portion has a concave lens characteristic, and the peripheral portion has a convex lens characteristic. In addition, a plurality of lenticular lenses having different optical characteristic values can be exchanged. Further, in the projection exposure apparatus, the light irradiated on the mask substrate by each of the above-mentioned illumination devices is projected onto the wafer by the projection lens.

[0009]

The position of the elliptical mirror is changed by fixing the light source, or the position of the light source and the elliptical mirror held together is changed, or at least the multi-beam generating member, the condenser lens and the sample stage are integrated. By holding and changing the position, the light intensity distribution on the multi-beam generating member changes to an annular shape or a flat shape. A lens system provided between the light source and the multi-beam generating member similarly changes the light intensity distribution on the multi-beam generating member. Further, the variable stop device provided on the entrance surface or the exit surface of the multi-beam generating member makes the incident light amount of the reticle constant.

In the lenticular lens, the focal length of the peripheral portion is made shorter than that of the central portion, or the central portion has a concave lens characteristic and the peripheral portion has a convex lens characteristic. Is changed into a ring shape or a flat shape. Further, by replacing the lenticular lens, the intensity distribution of the reflected light is changed. Further, the projection exposure apparatus using each of the above illumination devices can irradiate various annular or flat light onto the mask substrate without lowering the illuminance.

[0011]

FIG. 1 is a block diagram showing an optical system of a projection exposure apparatus using an illumination device according to the present invention. In FIG. 1, light from a substantial light source 100 of a mercury lamp 1 is reflected by an ellipsoidal mirror 2 and condensed with a slight spread near a second focal position of the ellipsoidal mirror 2. Reference numeral 3 denotes this light condensing position. This light is applied to the reticle 6 via the multi-beam generating member 4 and the condenser lens 5, and the pattern on the reticle 6 is imaged on the wafer 9 via the projection lens 7. In an actual exposure optical system, a reflecting mirror is provided between the elliptical mirror 2 and the reticle 6 to bend the optical path. However, since the exposure optical system is shown in a basic concept in FIG. Is omitted.

At this time, the emission surface 4a of the multi-beam generating member 4
Are equivalently the illumination light source of the reticle 6, and the reticle 6 is illuminated by its light intensity distribution.
As shown in FIG. 1, when the light condensing position 3 is far from the incident surface of the multi-beam generating member 4, the light intensity distribution on the incident surface of the multi-beam generating member 4 has a central portion as shown in FIG. 2. The periphery is weak and has a strong annular shape.
Has a similar annular shape.

It is known that the resolution is improved by the above-mentioned annular light intensity distribution, which is called an annular illumination method.
Actually, it is necessary to optimally set the light intensity distribution according to the shape and distribution of the pattern on the reticle 6. When the light condensing position 3 is made to coincide with the incident surface of the multi-beam generating member 4,
The light intensity on the emission surface 4a of the multi-beam generating member 4 changes to a uniform distribution as shown in FIG.

As described above, by changing the distance between the light condensing position 3 and the incident surface of the multi-beam generating member 4, the irradiation light distribution on the reticle 6 can be continuously changed from the annular shape to the uniform distribution. Therefore, the irradiation light can be set to an optimum distribution shape necessary for improving the resolution in accordance with the pattern on the reticle 6.

In the method disclosed in Japanese Patent Application Laid-Open No. 63-304624, the mercury lamp 1 is moved in the direction of the optical axis to move the condensing position 3 with respect to the incident surface of the multi-beam generating member 4. However, since the mercury lamp 1 operates at a high temperature, its moving mechanism is required to have heat resistance, thermal stability, and the like, and in addition, the light distribution by the moving mechanism easily causes a shadow in the light distribution. The positions of the elliptical mirror 2, the multi-beam generating member 4, and the like are moved, and the condensing position 3 is moved by another method.

[Embodiment 1] In this embodiment, the moving mechanism 10
Enables the elliptical mirror 2 to move. Moving mechanism 1
By setting 0, the light condensing position 3 is set from the position of the light receiving surface of the multi-beam generating member 4 to a position away from the multi-beam generating member 4 as shown in FIG. It can be set arbitrarily to a distribution like 2, 3. Since the mercury lamp 1 has an elongated shape, the elliptical mirror 2
A small hole as shown in FIG. These small holes are effective for cooling the mercury lamp 1 and allow the reflected light from the central part of the ellipsoidal mirror 2 to escape, so that a ring-shaped distribution as shown in FIG.

FIG. 5 shows the conventional pattern contrast and pattern size (line-and-space size or spatial frequency) transferred by a projection exposure apparatus using the illumination apparatus of FIG. FIG. 6 is a characteristic diagram shown in comparison with the performance of the projection exposure apparatus of FIG. Thus, according to the present invention, approximately 0.3
It can be seen that the contrast at line and space dimensions above μm is significantly improved.

[Embodiment 2] In order to form an image of the pattern of the reticle 6 on the wafer 9 correctly, the exit surface of the multi-beam generating member 4 and the entrance pupil 8 thereof are optically incompatible with the condenser lens 5. Must be set to the position. For this reason, if only the multi-beam generating member 4 is moved, the position of the light condensing position 3 with respect to the incident surface can be moved, but the above-mentioned optical complication condition is broken. Therefore, in this embodiment, the mercury lamp 1 and the ellipsoidal mirror 2 are used as shown in FIG. 6 or FIG.
Or the portion including the multi-beam generating member 4, the condenser lens 5, the reticle 6, the projection lens 7, and the wafer 9 is moved.

In FIG. 6, a mercury lamp 1 and an ellipsoidal mirror 2 are shown.
Is fixed on the table 21 and the table 21 is moved by the moving mechanism 11. In FIG. 7, the multi-beam generating member 4, the condenser lens 5, the reticle 6, the projection lens 7, and the like are fixed on the table 22, and the table 22 is moved by the moving mechanism 12.
By such a movement, the position of the light condensing position 3 with respect to the multi-beam generating member 4 can be moved and the emission light distribution thereof can be continuously changed while maintaining the above-mentioned optically harmful condition.

[Embodiment 3] In this embodiment, a mercury lamp 1, an ellipsoidal mirror 2, a multi-beam generating member 4, a condenser lens 5, a reticle 6, a projection lens 7, and a wafer 9
With the positional relationship such as being fixed, only the position of the light condensing position 3 is moved and moved by the lens system. As shown in FIG. 8, the above lens system is composed of, for example, a concave lens 50 and a convex lens 5.
1. The positional relationship between the two lenses is set, for example, such that the focal point of the concave lens 50 coincides with the focal point 3 and the convex lens 51 can move in the optical axis direction.

With the above arrangement, the light emitted from the concave lens 50 is converted into a parallel light beam, and condensed at the focal point 31 by the convex lens 51. Therefore, since the light condensing position 3 has equivalently moved to the focal point 31, the convex lens 51
, The light condensing position 3 can be continuously moved. Note that if the focus of the concave lens 50 is shifted from the light condensing position 3, the parallel light beam cannot be obtained. However, the same effect can be obtained because the convex lens 51 can narrow the parallel light beam.

The same effect can be obtained by replacing the lens system with a zoom lens or another optical system capable of independently controlling the magnification and the image point. In addition, if the lens system is configured to be detachable so that the most frequently used annular light distribution is obtained when the lens system is not provided, many exposure operations can be performed without adjusting the lens system. Since the above-mentioned lens system can be used only in a relatively special case where the correction is performed quickly and the orbicular zone light distribution needs to be corrected, the overall efficiency can be improved in the exposure operation using a large number of reticles. . In the first to third embodiments, the average illuminance of the reticle 6 may change due to the change in the annular light distribution. In such a case, for example, as shown in FIG. 9, a variable diaphragm device having a plurality of diaphragms 42 having different apertures on a rotating disk 41 is provided.
Adjust the average illuminance.

[Embodiment 4] The above annular light distribution can also be obtained by an aspheric lens. However, since an aspherical lens is usually difficult to manufacture and is expensive, in this embodiment, an aspherical lenticular lens (Lentikular lens) is used.
Use e). Lenticular lenses are usually
Used to lighten thick and heavy lenses, for example,
A hatched portion of the aspherical lens shown by a solid line in FIG. 10A is extracted and configured into a flat plate shape as shown in FIG.

FIG. 11 is a view for explaining the state of light focusing by the lenticular lens. Lenticular lens 6
0 is formed so that the portion cut out concentrically with respect to the center thereof becomes a substantial portion of a convex lens having a different focal length. That is, the focal length of the peripheral portion of the lenticular lens 60 is set short, and the focal length of the central portion is set relatively long. As a result, for example, in the aa cross section, a ring-shaped luminous flux distribution with a high density in the peripheral portion can be obtained, and if the light receiving surface of the multi-beam generating member 4 is arranged at this position, the same light density as in FIG. 2 can be obtained. Can be.

Similar zonal luminous flux distribution can be obtained even if the center of the lenticular lens 60 has a concave lens characteristic and the peripheral portion has a convex lens characteristic. Further, since it is no longer necessary for the lenticular lens 60 to have an annular light distribution, the elliptical mirror 2 may be replaced with a simple parabolic mirror or the like so as to make the reflected light density uniform. Good. Also,
Since the lenticular lens is thin and light, it can be easily replaced and detached. Therefore, as shown in FIG. 12, a plurality of lenticular lenses having different asphericity can be attached to the rotating ring 70 so as to be replaceable. As a result, the user can select the required annular light distribution very quickly only by rotating the rotary ring 70, so that the adjustment work is eliminated and the number of working steps can be greatly reduced.

[0026]

By changing the position of the elliptical mirror, the position of the light source and the elliptical mirror held together, or the position of the multi-beam generating member, the condenser lens and the sample stage held integrally, the projection exposure apparatus can be used. The reticle can be illuminated with light having an annular intensity distribution, thereby improving the definition of exposure. Further, by providing a lens system between the light source and the multi-beam generating member, similar annular light can be obtained.

Further, by providing a variable diaphragm device on the entrance surface or exit surface of the multi-beam generating member, the incident light amount of the reticle can be made constant regardless of the annular intensity distribution. In addition, similar annular light can be obtained by condensing the reflected light from the ellipsoidal mirror with a lenticular lens having an aspherical characteristic, and further, by adjusting a plurality of lenticular lenses, without adjustment. The intensity distribution of the annular light can be changed.

[Brief description of the drawings]

FIG. 1 is a side view of a first embodiment of the present invention.

FIGS. 2 and 3 are light intensity distribution diagrams on a multi-beam generating member incident surface in FIG.

FIG. 4 is a partial side view of the first embodiment of the present invention.

FIG. 5 is a contrast characteristic diagram according to the first embodiment of the present invention.

6 and 7 are side views of Embodiment 2 of the present invention.

FIG. 8 is a partial side view of a third embodiment of the present invention.

FIG. 9 is a side view in the case where a variable aperture is provided in Embodiments 1 to 3 of the present invention.

FIG. 10 is a sectional view of a lenticular lens.

FIG. 11 is an explanatory diagram of a light-collecting characteristic of a lenticular lens in Embodiment 4 of the present invention.

FIG. 12 is a diagram illustrating a configuration example of a fourth embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Mercury lamp, 2 ... Ellipsoidal mirror, 3 ... 2nd focus, 4 ... Multi-beam generating member, 5 ... Condenser lens, 6 ... Reticle, 7 ... Projection lens, 8 ... Projection lens entrance pupil, 9 ... Wafer, 10, 11, 12: moving mechanism, 21, 22, ...,
42 ... Aperture, 50 ... Concave lens, 51 ... Convex lens, 60 ...
Lenticular lenses, 41, 70 ... rotating ring.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-3-202148 (JP, A) JP-A-59-155843 (JP, A) JP-A-50-129045 (JP, A) 119646 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) H01L 21/027

Claims (9)

(57) [Claims] 1. A light source is disposed near a first focal point of an ellipsoidal mirror, and light condensed near the second focal point is irradiated on a multi-beam generating member, and light emitted from the multi-beam generating member is passed through a condenser lens. An illumination device for irradiating a mask substrate (reticle) through the illumination device, wherein a means for changing a position of the ellipsoidal mirror is provided. 2. A light source is disposed near a first focal point of an ellipsoidal mirror, and light condensed near the second focal point is radiated to a multi-beam generating member, and light emitted from the multi-beam generating member is passed through a condenser lens. An illumination device for irradiating the mask substrate with the light source and the ellipsoidal mirror integrally, and a second holding device for integrally holding at least the multi-beam generating member, the condenser lens, and the sample stage. A lighting device, comprising: holding means; and means for changing a position of the first holding means and / or the second holding means. 3. The illuminating device according to claim 1, wherein a variable stop device is attached to an entrance surface or an exit surface of the multi-beam generating member. 4. A light source is arranged near a first focal point of an ellipsoidal mirror, and light condensed near the second focal point is radiated to a multi-beam generating member, and light emitted from the multi-beam generating member is passed through a condenser lens. An illumination device for irradiating the mask substrate with the light source, between the light source and the multi- beam generating member in the optical axis direction of the light source
An illumination system, wherein a lens system whose focusing position is changed by the movement of the lens is provided, and a variable diaphragm device is attached to an entrance surface or an exit surface of the multi-beam generating member. 5. A movable light source is disposed near a first focal point of an ellipsoidal mirror, and light condensed near the second focal point is irradiated on a multi-beam generating member, and light emitted from the multi-beam generating member is condensed by a condenser lens. A illuminating device for irradiating a mask substrate (reticle) via a light source, wherein a variable stop device is attached to an entrance surface or an exit surface of the multi-beam generating member. 6. A light source is arranged near a first focal point of an ellipsoidal mirror.
The light focused near the second focus on the multi-beam generating member.
And a condenser lens for emitting light emitted from the multi-beam generating member.
Illumination device that irradiates the mask substrate (reticle) through the
A lenticular lens between the light source and the multi-beam generating member.
Wherein the intensity distribution of the reflected light from the ellipsoidal mirror is changed. 7. The illuminating device according to claim 6, wherein the lenticular lens has a focal length at a peripheral portion shorter than that at a central portion of the lenticular lens. 8. The illuminating device according to claim 6, wherein the lenticular lens has a concave lens characteristic at a central portion and a convex lens characteristic at a peripheral portion thereof. 9. The illuminating device according to claim 6, wherein a plurality of said lenticular lenses having different optical characteristic values are provided, and means for replacing said plurality of lenticular lenses is provided. Lighting device characterized by the following.