JPH02184853A - illumination optical device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an illumination optical device for an apparatus for projecting and exposing patterns of ICs, LSIs, etc.

(Prior Art) Conventionally, this type of illumination optical device is known, for example, as shown in FIG. 6. That is, the parallel light flux supplied from the light source 1 forms a plurality of convergence points by the plurality of lens elements constituting the optical integrator 2,
It forms a so-called secondary light source. The multiple light beams from this secondary light source are guided to the irradiated surface by a condenser lens, and these light beams illuminate the irradiated surface in a superimposed manner to average and smooth the illuminance. .

However, if the luminous flux supplied from the light al has an asymmetric intensity distribution (luminous flux density distribution) as shown in FIG. This cannot be canceled out, and a deviation occurs in the illuminance distribution even on the irradiated surface, making it difficult to uniformly illuminate the irradiated surface.

Therefore, in order to solve this problem, for example, Japanese Patent Application Laid-Open No. 6292912 proposed by the same applicant as the present case,
In JP-A-62-92913, an optical integrator formed by alternately arranging positive and negative lens elements is provided, and +1x and 1x lens elements are alternately arranged closer to the light source than the optical integrator. A lens assembly was provided.

(Problems to be Solved by the Invention) However, although uniform illumination can certainly be expected with the above configuration, the configuration of the optical integrator or the lens assembly disposed closer to the light source is complicated. It becomes difficult to reduce costs due to manufacturing adjustments and an increase in the number of parts.

In particular, in recent years, the manufacturing of semiconductor devices (VLSI, etc.) has progressed in miniaturization and higher density, and in order to cope with this, exposure equipment that uses a short wavelength, high output excimer laser, etc. as a light source has been introduced. It is emerging. Excimer lasers and the like use a vibrating mirror as a light scanning means to form multiple condensing points in the optical integrator between the optical path between the light source and the optical integrator to oscillate a rectangular beam with high coherency. By shaking it, a substantially incoherent light beam is obtained. However, since the spatial coherency of the light beam supplied from an excimer laser or the like differs greatly in the vertical and horizontal directions within the beam, it is necessary to adjust the way in which a vibrating mirror or the like used as the optical scanning means is swung.

Furthermore, if the light flux that illuminates a reticle (mask) and a substrate such as a wafer contains a lot of polarized light in a specific direction, the line width of the pattern on the reticle printed on the wafer will be parallel to the polarization direction. There are also very different problems in the vertical direction.

Therefore, the present invention has been made in view of the above problems, and it is possible to reduce costs, achieve uniform illumination even when the light flux supplied from the light source has an asymmetric intensity distribution, and provide a This eliminates the need to adjust the swing angle of the optical scanning means even if the coherency of the light beam supplied by the light source is asymmetric, and furthermore, even if the light beam supplied from the light source contains a lot of polarized light in a specific direction, it can be It is an object of the present invention to provide a high-performance illumination optical device that can accurately transfer a pattern image onto a substrate such as a wafer regardless of direction.

(Means for Solving the Problems) In order to achieve the above object, the present invention includes a light source means 10 that supplies a parallel light beam, and a plurality of secondary light sources formed by the parallel light beam, as shown in FIG. An optical integrator 30 that transmits light from this secondary light source to an irradiated surface 50.
In the illumination optical system that includes the condenser lens 40 that guides the
It has a light beam rotation means 20 that rotates the light beam.

The light beam rotation means 20 is a rotatable optical member that inverts the light beam component in one direction within the cross section of the light beam and is provided so that the optical axes of the incident light beam and the emitted light beam are located on the same or straight line. It is preferable that it be configured.

(Function) The present invention rotates a luminous flux using a luminous flux rotation means. As a result, uniform illumination on a time average basis can be achieved, and coherency can be made rotationally symmetrical, so there is no need to adjust the way the scanning means is swung. Furthermore, even if the light flux supplied from the light source contains a large amount of polarized light in a specific direction, the image of a pattern such as a reticle (mask) can be accurately transferred onto a substrate such as a wafer regardless of the direction.

(Embodiment) FIG. 1 shows a schematic layout diagram of an embodiment of the present invention, and the embodiment will be described in detail based on this diagram.

The optical illumination device according to the embodiment of the present invention includes a light beam a10 as a parallel light flux supplying means for supplying a parallel light flux, and a trapezoidal prism 20 as a light flux rotation means rotatable around the optical axis.
, an optical integrator 30 made up of a plurality of lens elements, and a condenser lens 40 are arranged, respectively.

The parallel light beam supplied from the light aio is refracted at the slope 21 of the trapezoidal prism, reflected at the bottom surface 22, refracted at the slope 23, and exits again as a parallel light beam.

Here, the trapezoidal prism 20 is provided so that the optical axes of the incident light beam and the exit light beam are located on the same straight line.

For example, as shown in FIG. 1, if the light beam in the plane of the paper in the section A' has an intensity distribution as shown in FIG. 2, when this light beam passes through the trapezoidal prism 20,
As shown by the solid line in FIG. 3, the luminous flux intensity in the plane of the paper in the BB' section has a distribution in which the upper and lower sides are inverted (180° inverted) with the optical axis as the boundary.

On the other hand, if the light beam in the direction perpendicular to the plane of the paper in the AA' section has an intensity distribution as shown in FIG. The luminous flux intensity does not change as shown by the breakdown in FIG. That is, the trapezoidal prism 20 has a function of inverting the luminous flux component in one direction within the illumination luminous flux cross section.

In this way, the parallel light beam whose light beam component in one direction in the cross section of the light beam is inverted by the trapezoidal prism 20 enters the optical integrator 30 consisting of a collection of lens elements,
A plurality of condensing points are formed within the same plane on the exit side, essentially forming a secondary light source. A plurality of light beams from each condensing point of this secondary light source are illuminated by a condenser lens 40 so as to be superimposed on an irradiated surface 50.

Although not shown in FIG. 1 of the present invention, the irradiated surface 50
A projection objective lens may be provided behind the
This projection objective lens is an optical integrator 30
Preferably, the secondary light source formed by is reimaged at the pupil position of this projection objective and is arranged in such a way that a so-called Köhler illumination is substantially achieved. Then, a reticle or the like is placed at a position corresponding to the irradiated surface 50,
When a substrate such as a wafer is placed at a position conjugate with the reticle with respect to the projection objective lens, an image of a pattern on the reticle can be transferred onto the substrate.

Now, as shown in FIG. 2, when a parallel light beam having an asymmetric intensity distribution is supplied along the plane of the paper from the light source IO shown in FIG.
By passing through 0, the same effect as described above is applied in the paper direction. Therefore, the parallel light flux on the exit side of the trapezoidal prism 20 has a light flux intensity distribution in which the upper and lower sides are inverted (180° inverted) with the optical axis as the boundary, as shown by the solid line in FIG.

Therefore, if the trapezoidal prism 20 is rotated by 1/4 around the optical axis, the light beam is rotated by 1/2 as shown by the broken line in FIG. Then, when the trapezoidal prism 20 is further rotated by 1/4, the light beam is rotated by 1/2 and becomes as shown by the solid line in FIG. 3 again. For this reason, the optical integrator 30
The plurality of light beams from the secondary light source formed by the above rotation are similarly rotated to illuminate the irradiated surface 50 in a superimposed manner.

Therefore, if the trapezoidal prism 20 is rotated n times so that the light flux rotates an integer number of times within one exposure time, the light flux rotated 2n times will have a uniform light amount and illuminance per time average on the irradiated surface 50. It can be illuminated so that This makes it possible to achieve the same state in which the illuminated surface 50 is uniformly illuminated by a light beam having a uniform and rotationally symmetrical intensity distribution.

Therefore, since the amount of light for exposure is uniform over the entire exposure area, the coating is applied to the irradiated surface 50 or a substrate such as a wafer provided at a position conjugate to the irradiated surface 50 with respect to the projection objective lens (not shown). The applied resist can be exposed uniformly and uniformly.

In addition, when exposing with multiple pulsed lights using an excimer laser or the like that oscillates pulsed light at high output as a light source, the trapezoidal prism 20 is rotated so that the pulsed light rotates exactly once in one exposure. In addition, the pulsed light may be rotated by an integer number of rotations for one exposure, but in this case,
It is more effective to increase the number of pulses per exposure.

Furthermore, if the trapezoidal prism 20 is rotated at an appropriate rotational speed as described above, even if an excimer laser or the like is used in which the spatial coherency of the luminous flux differs greatly in the vertical and horizontal directions, not only the intensity distribution of the luminous flux but also the spatial Since the optical coherency is also rotationally symmetrical, there is no need to adjust the scanning state due to the vibration of a vibrating mirror (not shown) that is usually provided between the optical path of the light source 10 and the trapezoidal prism 20, which is very effective. Even if a light source that supplies a light beam having a component is used, as described above, if the trapezoidal prism 20 is rotated so that the polarized light beam is rotated by an integer, the reticle ( An image of a pattern such as a mask) can be accurately transferred onto a substrate such as a wafer regardless of direction.

Although the trapezoidal prism 20 has been described as the optical member rotatable around the optical axis of the present invention, the same effect can be expected by using an optical member such as a prism or a reflective member having an odd number of reflective surfaces instead. can. For example, as shown in FIG. 4, an optical member having three reflective surfaces is arranged so that the optical axes of the incident light beam and the outgoing light beam are located on the same straight line,
All you have to do is rotate it around this optical axis. Note that it is effective to use a reflective film with as little polarization property as possible for the reflective surface provided in the light beam rotation means in order to remove polarized light.

Although the light beam rotation means in the above embodiments functions as an image rotator, as shown in FIG. 5, cylindrical lenses may be arranged facing each other and rotated about the optical axis.

At this time, it is preferable that the cylindrical lenses arranged to face each other be constructed of Kevlar type in the plane direction perpendicular to the generatrix. Although this configuration is not strictly an image low cheater, it can function substantially equivalently for collimated parallel light beams.

Note that the present invention is suitable not only as an illumination optical system for a semiconductor exposure apparatus but also as an illumination optical system for a laser annealing apparatus, optical CVD, or the like.

〔Effect of the invention〕

As described above, according to the present invention, even if a luminous flux having an asymmetric luminous flux density distribution is supplied, the amount of light based on the time average power,
Uniform illuminance can be achieved.

Furthermore, even if a light source with high coherency is used,
This is very effective because it eliminates the need to adjust the way the scanning means swings to prevent speckles caused by coherency.

Furthermore, even if a light source that supplies a light beam with many polarized components in a specific direction is used, the rotated light beam illuminates a reticle (mask) and a substrate such as a wafer. This solves the problem that the line width of a pattern such as a reticle (mask) varies depending on the direction, and it is possible to accurately transfer an image of a pattern such as a reticle (mask) onto a substrate such as a wafer regardless of the direction.

Moreover, since it can be realized with a simple configuration, cost reduction can be easily achieved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an embodiment of the present invention. FIG. 2 is a diagram showing the intensity distribution in the state of i;1 when the beam passes through the beam rotation means. FIG. 3 is a diagram showing the intensity distribution after passing through the beam rotation means. FIG. 4 is a sectional view showing an example of a light beam rotation means having an odd number of reflecting surfaces. FIG. 5Δ is a cross-sectional view in a plane direction perpendicular to the generatrix of the cylindrical lenses arranged opposite to each other as the light beam rotation means. FIG. 5B is a cross-sectional view in a plane direction parallel to the generatrix of cylindrical lenses arranged opposite to each other as a beam rotation means. FIG. 6 is a schematic diagram of a conventional illumination optical device. [Description of main parts] t o --- One light source means 20 --- Luminous flux rotation means 30 --- Optical integrator 40 -- Condenser lens

Claims (1)

[Scope of Claims] 1) A parallel light beam supply means that supplies a parallel light beam, an optical integrator that forms a secondary light source using the parallel light beam, and a condenser lens that guides the light beam from the secondary light source to a surface to be illuminated. What is claimed is: 1. An illumination optical device comprising: a light beam rotation means for rotating a light beam, located closer to the light source than the optical integrator. 2) The light beam rotation means is constituted by a rotatable optical member that inverts a light beam component in one direction in a cross section of the light beam and is provided so that the optical axes of the incident light beam and the outgoing light beam are located on the same straight line. An illumination optical device according to claim 1, characterized in that: