JPS60168133A - Illuminating optical device - Google Patents

Abstract

PURPOSE:To suppress the generation of an interference fringe on the surface to be irradiated, and to execute a uniform exposure by using plural laser light sources. CONSTITUTION:Laser lights emitted from laser light sources 1a, 1b are reflected by mirrors 2a, 2b, respectively, and led to conve lenses 4a, 4b, and on the other hand, laser light emitted from a laser light source 1c is led directly to a convex lens 4c as it is, the laser light which have passed through the convex lenses 4a, 4b and 4c, respectively, form secondary light sources A1, A2 and A3, and the respective divergent luminous fluxes irradiate uniformly the surface of a mask 6. Each secondary light source A1, A2 and A3 is formed by each separate laser light source 1a, 1b and 1c, therefore, the interference property between the luminous fluxes emitted from the secondary light sources A1, A2 and A3, respectively is low enough, and it does not occur that an interference fringe appears on the surface of the mask 6 and uniformity of an exposure of a wafer 7 is damaged.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an illumination optical device that uses an excimer laser or the like as a light source and is suitable for use in a semiconductor exposure apparatus.

[Prior art]

In recent years, there has been an increasing demand for forming fine patterns, and for this purpose, lithography using an optical system using light in the deep UV range of wavelengths from 200 to aao (nm) has been developed. In that case, an ultra-high-pressure mercury lamp or a xenon mercury lamp is often used as the light source, but since the light source has no directionality and its brightness is not necessarily sufficient, the light source cannot be used in semiconductor exposure equipment. When used, the exposure time becomes longer and the throughput tends to deteriorate.

Recently, the development of lasers that emit laser light in the short wavelength region has progressed, and it has become possible to use high-intensity laser light with a wavelength in the deep UV region as described above in semiconductor exposure equipment. .

By the way, in the case of a normal semiconductor exposure apparatus, it is known that a plurality of secondary light sources are formed in order to prevent the quality of an image formed on a wafer from being impaired due to the light diffraction effect due to a mask pattern.

However, even if a secondary light source is formed using a single laser that emits laser light within the above wavelength range, interference fringes will appear on the mask surface due to the high coherence of the laser light. , a serious drawback arises in that significant exposure unevenness occurs.

[Purpose of the invention]

In view of the above points, the present invention was proposed in order to solve the above drawbacks, and it eliminates the interference of light between a plurality of secondary light sources. It is an object of the present invention to provide an illumination optical device used in a semiconductor exposure apparatus, etc., which enables high-energy exposure using a laser light source while ensuring uniformity of exposure amount.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory diagram of an embodiment of the illumination optical device according to the present invention. In the figure, la and lb are laser light sources such as, for example, an injection locking reta excimer V-laser, which are arranged so as to emit laser light in a direction perpendicular to the optical axis 3. Similarly, reference numeral 1c denotes a laser light source, which is arranged so as to emit laser light in the direction of the optical axis 8. 2a
, 2b is a mirror that reflects the laser beams from the laser light sources la and lb, respectively, and directs them toward the optical axis 3. 4a, 4b, and 4c are convex lenses for forming secondary light sources, which incident and condense the laser beams in the direction of the optical axis 3 from the laser light sources 1a, 11)' and the IC, respectively, and form the secondary light sources AI, A2.
．． Form A3 respectively. 5 is a lens having a light convergence property, for example, a secondary light source Ax.

A2. It is arranged so as to have a focal plane on or near the plane containing A3. Reference numeral 6 denotes a mask for semiconductor exposure having a fine pattern, and is arranged at or near the other return plane of the lens 5. For example, a silicon wafer 7 is arranged behind this mask 6.

The laser beams emitted from the laser light sources 1a and lb are reflected by mirrors 2a and 2b, respectively, and are reflected by convex lenses 4a and 4b.
On the other hand, the laser light emitted from the laser light source IC is directly guided to the convex lens 4C, and the laser light after passing through the convex lenses 4a, 4b, 4c is sent to the secondary light sources AX, A2 . Form A3. Those secondary light sources AI,
A2. The respective diverging light beams emitted from A3 uniformly illuminate the surface of the mask 6. At this time, secondary light sources AI, A2. The divergent light beams emitted from Aa and Aa are superimposed on the surface of the mask 6, but in the present invention, each of the secondary light sources AI, A2 and A3 are formed by separate laser light sources la, lb, and lc. Therefore, the coherence between the light beams emitted from the secondary light sources AI and A2°83 is sufficiently low, and interference fringes appear on the mask 60 surface, which affects the uniformity of exposure of Ueno-7. There is no harm in doing so.

FIG. 2 is a block diagram of another embodiment of the present invention, and in the figure,
It is assumed that 9a, 9b, and 9c are semiconductor laser light sources whose light exit ports are located on the return plane of the lens 5, for example. Reference numeral 10 denotes a projection lens arranged between the mask 6 and the lens 7, and here the semiconductor laser light source 9a
, gb, and 9c play the role of secondary light sources, which is different from the above embodiment.

The laser light emitted from the semiconductor laser light sources 9 a+ 9 b+ 9 c is converted by the lens 5 into a luminous flux that uniformly illuminates the stripe cover 6, as in the above embodiment. The uniformly illuminated pattern on the mask 6 is transferred onto the wafer 7 by the projection lens lO. In this case as well, the semiconductor laser 9a,
Since the coherence between the light beams emitted from 9b and 9c is sufficiently low, no interference fringes appear on the surface of mask 6, and Ueno 7 is uniformly exposed.

In particular, since semiconductor lasers are small, it is easy to arrange a large number of semiconductor lasers in an IJ rack arrangement as shown in FIG. 8, which is convenient for implementing the present invention.

In the above embodiment, a convex lens is used to form the secondary light source, but it goes without saying that a concave lens may also be used.

〔Effect of the invention〕

As explained above, by using a plurality of laser light sources, the generation of interference fringes on the irradiated surface is suppressed, and various exposures are made possible. Furthermore, when the present invention is applied to a semiconductor exposure apparatus, it has the effect of achieving high illuminance and high throughput.

[Brief explanation of drawings]

FIG. 1 shows a first embodiment of the present invention, which is a configuration diagram of an illumination optical system using a plurality of laser light sources, and FIG. 2 shows a second embodiment.
A configuration diagram of an exposure optical system using multiple semiconductor laser light sources,
FIG. 8 is a diagram showing an arrangement of a plurality of semiconductor lasers. la, lb+ lc: laser light source, 2a, 2b: mirror, 8: optical axis (of illumination optical system), 4a, 4b+4C: convex lens (for beam expansion), 5: lens J6: mask, 7:
Wafer, 9a, 9b, 9c: semiconductor laser light source, 10:
Projection lens patent applicant: Canon Co., Ltd. Rororororororororororororororororororo 0 mouth Figure 3

Claims (1)

[Claims] A plurality of arranged laser light sources or each secondary light source formed by a plurality of laser light sources, and an optical means for superimposing the light beams from the laser light sources or the secondary light sources on the irradiated surface. An illumination optical device comprising: