JPS60247643A - 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 [Technical Field] The present invention relates to an optical device that reduces the adverse effects of interference when printing fine patterns using coherent light.

[Prior art]

Conventionally, ultra-high-pressure water lamps or ultra-high-pressure Xe-Hg lamps have been mainly used as light sources for semiconductor exposure equipment that prints fine patterns such as LSIs using optical phosphorography techniques. However, recently, lasers (such as excimer lasers) that emit light at high output in the ultraviolet region, which is the wavelength used in photophosphorography, have been developed and are attracting attention as new light sources for semiconductor exposure equipment. Laser light generally has high brightness and directivity, so when used as a light source, high efficiency of a condensing optical system can be achieved, but the strong coherence characteristic of laser light is a drawback. That is, speckles occur on the mask surface and the image surface due to the interference of the laser beams, impairing the reproducibility of fine pattern images.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical device in which speckles do not occur even when a fine pattern is printed using a laser beam or the like by eliminating the above drawbacks and weakening the coherence of a beam of light.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. First, the basic concept of the present invention is shown in FIG.

l is a laser. Reference numeral 2 denotes a mask having an integrated circuit pattern, and a wafer is placed behind the mask 2 in close proximity or with a projection system in between. 3 to 4 are optical systems for controlling the beam flux. The laser light emitted from the laser l is
It passes through the optical system 3 and is branched into n ray bundles at point A, and these ray bundles respectively reach points P, IF5. After passing through . By the way, between AP and B, between AP2B..., AP
If the difference in optical path length between nB is set to exceed the coherence distance of the laser beam, the coherence will be weakened after point B, and the occurrence of speckles can therefore be reduced.

Next, as an embodiment of the present invention, FIG. 2 shows a configuration diagram of an optical device using optical fibers.

1.2 in the figure is equivalent to the component with the same number in Figure 1, and 3
a is a beam expander, 4a is a lens array, 4b
is a condenser lens. Furthermore, Fl.

F2. ..., Fn indicates optical fiber,
The optical path lengths of the sequential optical fibers are made to have a difference greater than the coherence length of the laser beams. In this figure, the optical fibers are arranged one-dimensionally, but in a device that irradiates a planar object all at once, they are arranged two-dimensionally.

The beam is expanded in diameter by the expander 3a, enters the bundle of optical fibers, and is branched into n bundles of light rays. After each of the light beams passes through an optical fiber, they are combined again by the lens array 4a and the condenser lens 4b, and the mask 2 is irradiated. However, since the optical path difference between each bundle of light rays has already exceeded the coherence distance, only the plurality of light rays passing through one optical fiber can interfere on the surface of the mask 20.

Therefore, the occurrence of speckles on the surface of the mask 2 is reduced. Furthermore, it is clear that this effect becomes more pronounced as the number n of optical fibers increases.

〔Effect of the invention〕

As explained above, according to the present invention, the occurrence of speckles can be prevented by weakening the coherence of the light beam. Therefore, by applying the optical device according to the present invention to an apparatus for printing fine patterns on LSIs, etc., it becomes possible to use a high-brightness light source such as a laser, and high efficiency of the apparatus can be achieved.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the basic concept of an optical device according to the present invention, and FIG. 2 is a configuration diagram of an optical device using optical fibers according to an embodiment of the present invention. ■・・・・・・・・・Ref f-, 2° old °° mask drop 3.4・・・・Optical system for controlling the beam flux. 3a・・・・・・Beam expander. 4a......Lens array. 4b・・・・・・Condenser lens. P, ~Pn-old... Branch optical path. F1~Fn...Optical fiber. Figure 1 Figure 2

Claims (1)

[Claims] The incident light having a long coherence length is branched into a plurality of beam bundles, each of the plurality of beam bundles is guided to a branched optical path, and an optical path difference greater than the coherence length is provided between each beam bundle in the branched optical path. An optical device that then superimposes each of the beam bundles again.