JPS60166951A - Illuminating optical device - Google Patents

Abstract

PURPOSE:To control the spreading angle of luminous fluxes and to improve the utilizing efficiency and exposing efficiency of luminous fluxes by forming laser light having a short coherence length to plural divergent luminous fluxes by a light integrator and making the diverging origin thereof and a front side focal plane approximately coincident with each other. CONSTITUTION:Laser light 2 of the parallel luminous fluxes from an excimer laser body 1 is made into plural divergent luminous fluxes by a light integrator 4 and the main rays thereof are again made into parallel luminous fluxes by a collimator lens 5. Said fluxes irradiate a surface 3 to be irradiated in the position of the focal plane of the lens 5. The irradiating diameter and spreading angle A of the light on the surface 3 can be controlled to desired sizes by selecting adequately the individual lens diameters of the integrator 4, the diameter over the entire part thereof and the focal length of the lens 5 by which the utilizing efficiency and exposing efficiency of the luminous fluxes are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an illumination optical device used in a semiconductor exposure apparatus using an excimer laser or the like as a light source.

[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 region of the wavelength region of 200 to 300 (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, if such a light source is used in a semiconductor exposure device, the exposure time will be There was a tendency for the throughput to deteriorate.

However, in recent years, semiconductor exposure using excimer laser light has improved the efficiency and illuminance of optical systems due to its high brightness as a light source and its good directivity, and has attracted attention in particular as a light source for the above-mentioned lithography. There are also reports of semiconductor exposure experiments. However, all of these methods use the contact/pro-shimity method to directly irradiate the laser beam 2 from the excimer laser body 1 onto the irradiated surface 3 as shown in FIG.

By the way, when using a semiconductor exposure device to expose a fine pattern on a silicon wafer, etc., it is necessary to pay attention to the spread angle of the light beam on the irradiated surface, such as a sea urchin. Although this does not have much effect on the contact method, In the gloximity method and especially in the projection method, there is a large shadow threat, and in particular, it is expected that the shadow effect on the resolution performance due to exposure will be large.

However, if the laser beam is directly irradiated onto the irradiated surface as mentioned above, the divergence angle of the light beam at the irradiated surface is equal to the divergence angle of the laser beam of the excimer laser itself, and the amount is Generally, commercially available excimer lasers have a power of several m rad fj degrees, which is very small. In addition, it has been nearly impossible to control various quantities such as the divergence angle of the light beam on the irradiated surface and the size of the irradiation range on the irradiated surface.

[Object of the Invention] In view of the above points, the present invention has been made to eliminate the above drawbacks. Even when a light source such as an excimer laser is used, the spread angle of the light beam and the size of the irradiation range on the irradiated surface are small. It is an object of the present invention to provide an illumination optical device that improves the utilization efficiency of the luminous flux from the light source and the exposure efficiency by controlling various quantities such as the above to desired values.

〔Example〕

Embodiments of the illumination optical device according to the present invention will be described below with reference to the drawings.

FIGS. 2 and 3 show one embodiment of the present invention, with FIG. 2 being an explanatory diagram of an illumination optical device, and FIG. 3 being a partially enlarged view of a light integrator used in FIG. In the figure, 1
is an excimer laser body that emits excimer laser light, 2 is a laser beam, 3 is an irradiated surface such as a mask used for semiconductor exposure, and 4 is a group of tiny lenses like a fly's eye, a self-imaging fiber bundle or a group of mirrors. When the light integrator 4 is a convex lens group as shown in FIG. , the light integrator 4 may be a concave lens group), and A is the divergence angle of the light beam on the irradiated surface 3. Note that the rear focal plane of the collimator lens 5 substantially coincides with the irradiated surface 3.

Furthermore, since the light beam from a conventional light source is not a crime, it is common practice to place a field lens on the exit side of the light integrator to increase efficiency, but as in the present invention, an excimer laser is used as the light source. Because of the parallelism of the laser beam, a field lens is not used as shown in Figure 3.

A parallel beam of laser light 2 emitted from the excimer laser body 1 is converted into a plurality of diverging beams by a light integrator 4 as shown in FIG. The irradiated surface 3 located at the focal plane of the lens 5 is irradiated.At this time, the diameter of one light inch gator lens is d5, the focal length is f, the entire diameter of the light integrator 4 is D, and the collimator lens When the focal length of 5 is F and the irradiation diameter of the light on the irradiated surface 3 is 2, the following relationship approximately holds true.

Therefore, in the case of this embodiment as well, each parameter d, D.

] It is possible to obtain the desired diameter I and divergence angle by appropriately selecting the diameter I.

However, what is important here is that if the overall diameter of the light integrator 4 is made larger than the diameter S of the laser beam 2, the desired divergence angle cannot be obtained; conversely, when D<S, the light integrator 4 The diameter S of the laser beam 2 and the overall diameter of the light integrator 4 must be matched to avoid effectively using the luminous flux of the part of the laser beam 2 that protrudes from the laser beam 2 (this will reduce the efficiency of the optical system). .

Therefore, as shown in FIG. 3, an optical system for beam shaping is arranged between the excimer laser main body 1 and the light integrator 4. In the figure, 1, 6 and 7 are convex lenses arranged so that their focal points coincide with each other, and they constitute a beam expanding lens.As a result, the beam diameter of the laser beam 2 from the excimer laser body 1 is The light is magnified and enters the ride integrator 4. In the case of this embodiment, the above-mentioned two equations regarding the spread angle A of the light beam and the irradiation diameter I of the irradiated surface also hold true.

In addition to this, the present invention may be implemented using a well-known optical system that reduces the diameter of the laser beam from the excimer laser main body, so that the reduced laser beam beam is incident on the light integrator.

Flu K also has a rectangular cross section of the excimer laser beam, and its vertical and horizontal lengths are different, so in order to make the vertical and horizontal beam condensing state the same, a cylindrical laser beam with different power is used. It is also possible to use an anamorphic system in which lenses are orthogonally combined.

In addition, in the case of the present invention, the light used is laser light, and its coherency may have an adverse effect when projecting and exposing the fine pattern of a mask onto a silicon wafer. Since the coherent hta is shorter than the amount of aberration experienced in the subsequent optical system, it does not pose a problem. In particular, in this embodiment, excimer laser light is used as the laser light, but any other laser light such as excimer laser light may be used as long as it satisfies condition 1.

(Effects of the Invention) Second, as described in detail regarding the present invention, it has become possible to control the spread angle of the luminous flux of the light source used and the irradiation range on the irradiated surface. When used in an apparatus, etc., there is no generation of interference fringes due to laser light, uniform exposure is achieved, and an exposure apparatus with high illuminance and high throughput can be realized.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of a conventional example, Fig. 2 is an explanatory diagram of an embodiment of the present invention, Fig. 3 is an enlarged explanatory diagram of the light integrator in Fig. 2, and Fig. 4 is an explanatory diagram of another embodiment of the present invention. It is an explanatory diagram of an example. ■ is the excimer laser body, 2 is the laser beam, 3 is the irradiated surface, 4 is the light integrator, 5 is the collimator lens,
6 and 7 are convex lenses. Patent applicant Canon Co., Ltd.

Claims (1)

[Claims] a light source that emits a laser beam with a short coherence length; a light integrator that is disposed in front of the light source and converts the laser beam into a plurality of diverging beams; An illumination optical device comprising: a convergent lens arranged in front of the light integrator so as to coincide with the light integrator.