JPS62265722A - Optical system for illumination - Google Patents

Abstract

PURPOSE:To uniformly illuminate the surface of split prism to be illuminated by introducing a luminous flux to a luminous flux splitting member having two split prisms made of a plurality of reflecting surfaces and an optical element disposed between the prisms and guiding the luminous flux emitted from the member to the surface to be illuminated to alleviate a speckle. CONSTITUTION:A split prism 5 is composed of a plurality of reflecting surfaces 5-1, 5-2, 5-3, ...reflecting an incident luminous flux of an S-polarized component at a predetermined rate and a full-reflecting surface 50. The luminous flux of a P-polarized component is rotated at a polarizing surface by an optical element 6 at 90 deg. to introduce it as the luminous flux of the S-polarized component to a split prism 7. The luminous fluxes divided in a plurality of the S- polarized component become the luminous flux of the P-polarized component, mostly reflected on a full-reflecting surface 70 to be emitted. After the flux is noninterfered to be emitted, the flux is guided to a fly eye lens 8, with the condensing point as a secondary light source surface, and the surface 10 to be illuminated is uniformly illuminated by a condenser lens 9 by using the luminous flux of uniform intensity distribution emitted from the light source surface by alleviating a speckle.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to illumination optical systems, and in particular, in semiconductor manufacturing, illumination of electronic circuits and other irradiated surfaces using a light source such as a high-intensity laser with good coherence. The present invention relates to an illumination optical system that completely reduces adverse effects such as uneven illumination on an irradiated surface due to original interference when illuminating a fine pattern, and enables uniform illumination.

(Conventional technology) Recent semiconductor manufacturing technology includes high integration of electronic circuits.
Lingraphy technology is claimed to be capable of forming high-density circuit patterns.

Generally, the circuit butter on the mask or reticle surface is completely removed.
- When transferring onto a surface - Sea urchin... The resolution line width of a circuit pattern transferred onto a surface is proportional to the wavelength of the light source. For this reason, for example, ultra-high pressure mercury lamps, xenon mercury lamps, etc., which use short wavelengths in the far ultraviolet (deep UV region) of 200 to 300 nm, are used. However, these light sources have low brightness and lack directivity, and the photoresist coated on the eight surfaces of the sea urchins also has low photosensitivity, resulting in a long exposure time and a decrease in throughput.

Recently, a light source with an oscillation wavelength in the deep UV region called the exClmar laser has been developed1.
Due to its advantages such as monochromaticity (%f4 degree) and 1-direction, various applications to phosphorography technology have been studied. However, when using an exhaust/malebou, there are many cases where the mask surface, square surface, etc. are covered due to the inherent coherency of the laser, imperfections in the striped surface or wafer surface, optical characteristics of the illumination system, etc. Irregular interference fringes, so-called speckles, occur on the irradiated surface. These speckles cause errors in illumination and printing and reduce the resolution of the mask pattern image.

(Problems to be solved by the invention) The present invention enables uniform illumination of the irradiated surface by reducing speckles that occur on the irradiated surface when a high-intensity light source with good laser coherence is used. The purpose is to provide a Tojiku illumination optical system.

A further object of the present invention is to average the speckles that occur on the mask surface or sea urchin surface when using a light source with good coherence such as an excimer laser.
An object of the present invention is to provide an illumination optical system suitable for an exposure apparatus for semiconductor manufacturing that enables fI image power.

(Means for resolving problem t-4) Two split prisms made up of a plurality of reflective surfaces each having a predetermined reflectance for the luminous flux from the light source, and a polarization plane placed between the two split prisms that can be rotated by 90 degrees. The beam is made incident on a beam splitting member having an optical element and a gold plate, and the beam emitted from the beam splitting member is guided to a surface to be irradiated.

The features of this pond water invention are described in the Examples.

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

In the same figure, one light source is used, for example, Ne-No in the visible range,
It consists of Ar laser, invisible excimer laser, etc. 2 is a light beam emitted from the light source 1, 3 is a beam shaper that expands or reduces the diameter of the light beam 2 in order to adapt it to the subsequent optical system, and 4 is a beam splitting member that divides the entire incident light beam into a plurality of beams. In addition, the plurality of light beams are emitted with different optical path differences between them. Denoted at 5 and 7 are splitting prisms that each constitute part or all of the beam splitting member 4, and each has a plurality of reflecting surfaces.These reflecting surfaces divide the incident beam into a plurality of beams having predetermined polarization components, and t A plurality of light beams are emitted by giving an optical path difference to each of them. For example, the polarization plane of the incident light beam is rotated by t-90 degrees by an optical element that constitutes a part of the 6-piece light beam splitting member 4. For example, 1Atf! i, consists of a long plate, a 90" optical rotator, etc. 7 Lia's eye lenses consisting of 8-digit microlenses form the h92-order light source surface. 9 is a condenser lens, a 10-digit mask, a reticle, etc. is the irradiated surface.

In this example, the S polarized light component emitted from light source 1 and the PIJ
A beam shaper 3 shapes the randomly polarized light 5J, 2 with two light components into a beam diameter of an appropriate size, so that the beam diameter is
41) The light is made incident on the splitting prism 5 of the member 4. Particularly, in this embodiment, the split prism 5t - S, which is relatively easy to manufacture.
A plurality of reflective surfaces 5-1, 5-2, 5-3, .
・The total reflection surface is raised! has been completed. As a result, the S-polarized component of the incident light beam is ``/l,!
-1°5-2. . . . divides the intensity into equal parts and reflects it as a light beam with a uniform intensity distribution, and further divides it into multiple reflective surfaces 5-1.5
-2. The distance between each reflective surface of ... should be maintained appropriately, preferably longer than the coherence distance to make it incoherent,
The so-called incoherence is emitted from the concave 9.

Most of the 10,000P polarized light beam is reflected by the total reflection surface 50 of the Jfl prism 5 and exits. So, what about the luminous flux of the P-polarized component? The plane of polarization is rotatably rotated by 90 degrees by the optical element 6, and the beam is made to enter a splitting prism 7 similar to the splitting prism 5 as a beam of S-polarized light. As a result, the split prism 5
Similarly, the light flux of the S lunar component is subject to multiple reflection theory7-1゜7-
2.7-3. The beam is divided into equal parts in terms of strength, and the beam is emitted after making it incoherent.

At this time, the nine luminous fluxes emitted from the splitting prism 5 are divided into a plurality of S-polarized components, and the nine luminous fluxes are transferred to the polarizing element 6 to become a luminous flux of the P-polarized components.The majority of them are totally reflected by the splitting prism 7 C1j70.
It is reflected and ejected.

In this way, in this embodiment, the S-polarized light component and the P-polarized light component incident on the light beam splitting member 4 are divided equally in terms of intensity to form a band-shaped light beam having an area-uniform intensity distribution. Fly-eye lens 8 that is emitted with interference
I am leading the way.

Then, using the light beam with a uniform g-degree distribution emitted from the condensing point of the primary eye lens 8 as the secondary light source surface 1, the condenser lens 9 completely reduces the occurrence of speckles on the irradiated surface 10 and makes it uniform. It is irradiating.

In addition, in case of non-implementation, the groove bottom may be formed by a plurality of reflecting surfaces of the dividing prism 7 that equally divide the P-polarized light component, thereby eliminating the need for the optical element 6.

FIG. 2 is an explanatory diagram of an embodiment of the grip of the light beam splitting member 4 shown in FIG. 1.

In the figure, 20 is a light beam splitting member, and 21 and 23 are splitting prisms similar to those shown in FIG. 1, which are arranged so that their reflecting surfaces are perpendicular to each other with respect to the direction in which the light travels. 22
is an optical element similar to that shown in FIG.

In the embodiment shown in FIG. 1, the diameter of the beam emitted from the beam splitting member 4 is band-shaped. On the other hand, in this embodiment, the splitting prisms 21 and 23t are arranged as described above, so that the incident light beam is expanded in the vertical and horizontal directions and then emitted.

In this embodiment, a light beam having a polarization state in one direction, for example, a light beam having an S-polarized component, is made incident on the light beam splitting member 20 using a stand-polarized laser or a polarizing plate in advance. Then, the light is emitted from the dividing prism 21 by dividing the light into equal parts in one-dimensional direction. Then, the plane of polarization is rotated by 90 degrees using the polarization cable 22, and the light beam is made incident on the splitting prism 23 so as to become an S-polarized light beam. As a result, the diameter of the light beam t-2 is expanded to have a two-dimensionally uniform intensity distribution, and the light beam is effectively rendered incoherent.

The beam splitting member shown in Figure 2 is designed to expand the diameter of the beam by making all the beams of polarized light that are polarized in one direction incident on the beam splitting member shown in Figure 2. In order to expand the luminous flux diameter two-dimensionally in the same way as the IJ, use two luminous flux splitting members 4 shown in Fig. 1 so that the directions of luminous flux expansion are orthogonal to each other as shown in Fig. 3. It should be placed in . In the figure, reference numerals 30 and 40 denote beam splitting members S31, 33, il, and 43, respectively, dividing prisms, and 32.degree. 42 an optical element for rotating the polarizing plane by 90''.

In FIG. 3, the incident light beam is expanded in one direction by the light beam splitting member 30, and then the light beam splitting member 40 is used to expand the incident light beam in one direction.
The luminous flux is fully expanded in a direction perpendicular to the direction in which the luminous flux is expanded, thereby enlarging the diameter of the luminous flux two-dimensionally as a whole.

(Effects of the Invention) According to the present invention, by providing a beam splitting member having the above-mentioned configuration in an optical system, it is possible to expand the beam size when using a laser beam with good coherence and to reduce the beam intensity. Speckles that occur on the irradiated surface to improve the appearance? This makes it possible to uniformly illuminate the irradiated surface while reducing the time required, thereby making it possible to achieve an entire illumination optical system particularly suitable for semiconductor manufacturing equipment.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an optical system according to one embodiment of the present invention, and FIGS. 2 and 3 are explanatory diagrams of other embodiments of a portion of FIG. 1, respectively. In the figure, 1) - is the light source, 2-digit luminous flux, 3-digit luminous flux shaper,
4, 20, 30.40 are luminous flux splitting members 1s and 7, respectively.
12+, 23, 31, 33, 41, 43 are split prisms, 6, 22.32.42 are polarization planes 'i
Optical element that rotates 90', 8 is a fly eye lens, 9
10 is a surface to be illuminated. Patent questioner: Canon Co., Ltd.

Claims (3)

[Claims] (1) A luminous flux splitting member that includes two splitting prisms that are composed of a plurality of reflective surfaces having a predetermined reflectance for the luminous flux from a light source, and an optical element that rotates the plane of polarization by 90 degrees, which is placed between the two splitting prisms. 1. An illumination optical system characterized in that a luminous flux is made incident on a luminous flux splitting member and a luminous flux emitted from the luminous flux splitting member is guided to an irradiated surface. (2) The illumination according to claim 1, wherein the plurality of reflecting surfaces of the splitting prism are configured to equally divide and reflect a luminous flux of polarized light components in one direction in terms of intensity. Optical system. (3) The illumination optical system according to claim 1, wherein the two splitting prisms are arranged such that the reflecting surfaces of the splitting prisms are orthogonal to each other with respect to the traveling direction of the light beam.