JPH0567557A - Arc-shaped dark-field illumination apparatus - Google Patents

Abstract

PURPOSE:To simply provide a dark-field illumination apparatus in an aligner wherein a high-intensity far ultraviolet light source such as an excimer laser is used. CONSTITUTION:A light flux which is radiated form a laser light source 21 is converted into an arc-shaped parallel beam of light by means of an arc-shaped illumination optical system 22; a secondary light source plane 25 is formed by means of a conical optical system. The image of the secondary light-source plane is formed on a pupil plane 29 in a projection optical system 28 after a reticle 27 has been illuminated in an arc shape by using an image-formation optical system 26. Thereby, it is possible to obtain a dark-field illumination apparatus in which an image-formation characteristic with reference to a high spatial frequency component is enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illumination optical system used in a fine pattern printing apparatus for manufacturing integrated circuits. Projection optics are used to print fine patterns onto a wafer to fabricate integrated circuits. Among them, the catoptric projection optical system or catadioptric projection optical system is an optical system that includes a plurality of reflecting mirrors and performs printing using an arcuate illumination light flux. The present invention, as an illumination system of this type of optical system,
In particular, the present invention relates to a device for producing an arc-shaped dark-field illumination luminous flux using a laser such as an excimer laser as a light source.

[0002]

2. Description of the Related Art In recent years, the degree of integration of semiconductor integrated circuits has become higher and higher, and the precision of fine pattern printing in an exposure apparatus is also required to be high. FIG. 7 shows an image forming optical system configuration of a 1: 1 reflection type projection exposure apparatus, for example. It is composed of a concave mirror 71 and a convex mirror 72. The reticle 73 is irradiated with arcuate illumination light 74, the pattern on the reticle is projected onto the wafer 75, and the reticle 73 and the wafer 75 are scanned in the opposite directions for exposure. When performing projection exposure using such a catoptric system or catadioptric system, it is necessary to realize arcuate illumination as described above. In order to obtain such an arcuate illumination, for example, Japanese Patent Laid-Open No. 59-21611 as shown in FIG.
8 discloses a circular arc illumination device using a collimated light beam as a light source. This is as shown in FIG.
Nine-sided lens 81, 82, reflecting mirror 83, cylindrical lens 8
4, a cylindrical reflecting mirror 85 and a diffusing plate 86, which converge the parallel light flux 87 at the position of the diffusing plate 86 in an edged manner.

On the other hand, as is well known, for exposure, the resolution has been improved by using light of a shorter wavelength, but in the case of performing deep ultraviolet exposure, an excimer laser having a higher output than that of a conventional ultra-high pressure mercury lamp. It is considered promising to use light sources such as. However, when a laser such as an excimer laser is used as the light source, speckles due to the coherence of the laser light are removed, the reticle is uniformly illuminated, and the light source image is at a suitable level at the entrance pupil of the imaging optical system. An illumination system with a wide spread is required. Therefore, in the case of an illumination optical system for laser exposure, a diffuser plate such as a fly-eye lens array is used to form a secondary light source with low coherence, and the image of this secondary light source is formed on the pupil plane of the projection optical system. Design to image.

[0004]

However, in the above-mentioned conventional example, since the shape of the secondary light source image is determined by the diffuser plate, it is possible to control the secondary light source image on the pupil plane of the projection optical system. It is not suitable for a method of obtaining a resolution effect. Therefore, the present invention provides an exposure illumination device having a simple dark-field illumination function in the arc illumination device.

[0005]

In order to solve the above-mentioned problems, a dark field illumination device of the present invention is a secondary light source based on a parallel light plateau, an arc illumination optical system, a conical optical system, and a conical optical system. And an image forming optical system for forming an image on the pupil plane of the projection optical system.

[0006]

According to the present invention, in particular, in the arcuate illumination device, the reticle illuminates the good image area of the imaging optical system, that is, the dark field illumination area that exactly coincides with the arcuate area in which the aberration is corrected by the secondary light source. Make it on the surface. Here, by using a circular light source arranged on a circular arc as the secondary light source and not illuminating the 0th-order light component region on the pupil plane, a dark-field illumination effect that improves the imaging characteristics for high spatial frequency components is obtained. Expected to get. Therefore, the present invention is suitable for use in a semiconductor exposure apparatus that uses a circular good image area to synchronously scan a reticle and a wafer to transfer a pattern.

[0007]

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

FIG. 1 shows an embodiment of the present invention in which the reflecting mirror shown in FIG. 2 is used as a conical optical system. The conical optical system shown in FIG. 2 has a conical reflecting mirror 11 arranged in an arc shape on a diffusion plate 12.
It is a configuration in which is arranged.

The luminous flux emitted from the laser light source 21 is converted into an arc-shaped parallel light by an arc-shaped illumination optical system (for example, the optical system shown in FIG. 8 is used) 22. Next, the arc-shaped light beam is converted into a conical optical system, that is, a diffusion plate 23 having a conical reflecting mirror.
Thus, the secondary light source surface 25 is formed by following the optical path 24 without being shielded. At this time, when passing through the diffusing surface of the diffusing plate, a phase difference is generated in each optical path, and it is possible to reduce generation of speckle due to laser coherence. The image of the secondary light source surface is illuminated by the imaging optical system 26 on the reticle 27 in an arc shape, and is formed on the pupil plane 29 of the projection optical system 28. As described above, the arc-shaped dark-field illumination area can be obtained on the pupil plane of the projection optical system by a simple means.

FIG. 3 shows a second embodiment of the conical optical system which uses a transmission lens. By arranging the concave conical taper 32 on the diffusion plate 31, the annular illumination can be obtained by the prism action of the glass material of the diffusion plate as in the first embodiment. The optical path at this time is shown in FIG. Diffusion plate 41
Due to the concave conical taper 42 on the top, the incident parallel light beam 43
Along the optical path 44, dark field illumination is realized. A similar effect can be obtained with a convex taper, in which case the optical path of FIG. 5 is followed. When the parallel light flux 53 is incident on the convex taper 52 on the diffusion plate 51, it becomes an annular optical path 53 and dark field illumination is realized. Those utilizing the prism action can be arranged in an array and can be used for a wide light beam, and the conical taper is arranged in an array on the diffusion plate 61 as shown in FIG. By doing so, an annular optical path 64 is obtained even for a wide incident light beam 65, and dark field illumination is realized.

[0011]

As described above, according to the arc illuminator of the present invention, dark field illumination can be easily realized in exposure using a laser such as an excimer laser, and excellent for high spatial frequency components. The resolution is obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing an example.

FIG. 2 is a diagram showing an example of a conical optical system.

FIG. 3 is a diagram showing a second example of the conical optical system.

FIG. 4 is an optical path diagram of a conical optical system.

FIG. 5 is an optical path diagram of a conical optical system.

FIG. 6 is an optical path diagram when transmissive conical optical systems are arranged in an array.

FIG. 7 is a diagram showing an image forming optical system of a reflective exposure apparatus.

FIG. 8 is a diagram of a conventional arc illumination device using a collimated light beam as a light source.

[Explanation of symbols]

 11 Conical Reflecting Mirror 12 Diffusing Plate 21 Laser Light Source 22 Circular Illuminating Optical System 23 Diffusing Plate with Conical Reflecting Mirror 24 Optical Path 25 Secondary Light Source Surface 26 Imaging Optical System 27 Reticle 28 Projection Optical System 29 Pupil Surface 31 Diffusing Plate 32 Concave conical taper 41 diffuser plate 42 concave conical taper 43 incident light beam 44 optical path 51 diffuser plate 52 convex conical taper 53 incident optical path 54 optical path 61 diffuser plate 62 conical taper array 63 incident light beam 64 outgoing light beam 71 concave mirror 72 Convex mirror 73 Reticle 74 Arcuate illumination light 75 Wafer 81, 82 Spherical mirror 83 Reflector 84 Cylindrical lens 85 Cylindrical reflector 86 Diffuser

Claims (1)

[Claims] 1. A light source that emits a parallel light flux, an arc illumination optical system that converts the parallel light flux into a light flux having an arc cross section, a conical optical system that forms a secondary light source image, and a conical optical system. An arc-shaped dark-field illumination device comprising: an imaging optical system for forming a secondary light source image on a pupil plane of a projection optical system.