JPS63106721A - Illuminating device - Google Patents

Abstract

PURPOSE:To reduce the variance of illuminance to attain a good illuminance distribution by detecting peak positions and intervals of peaks or the like of Young's interference fringes on a face to be irradiated and performing optimum scanning to make a luminous flux incident on a secondary light source forming means. CONSTITUTION:Peak positions and intervals of peaks of Young's interference fringes generated in every scanning are measured by an illuminance detecting means 14 with respect to the illuminance distribution on an auxiliary face 12 to be irradiated optically equivalent to that on a face 8 to be irradiated to obtain information of the angle of incident of the luminous flux on a secondary light source forming means 5. A scanning means 2 is controlled to adjust an angle phi of incidence of the luminous flux so that the integral distribution of all scannings may be a prescribed illuminance distribution by the sequence of a scanning control means 15. Thus, a peak position 3a causing the variance of illuminance is moved at a prescribed speed to eliminate the variance of illuminance on the face 8 to be irradiated. Further, the luminous flux emitted from the secondary light source forming means 5 is made incoherent to approximately determine the optical performance of the whole of a device by N.A of the luminous flux from the secondary light source forming means.

Description

Detailed Description of the Invention - (Industrial Application Field) The present invention relates to a lighting device, and in particular, in semiconductor manufacturing, a light source such as a high-intensity laser with good coherence is used to illuminate an irradiated surface such as an electronic circuit. The present invention relates to an illumination device that reduces illumination unevenness due to interference fringes on an irradiated surface caused by light interference when illuminating a mask surface, reticle surface, etc. on which a fine pattern is formed, and provides uniform illumination.

(Conventional technology) Recent semiconductor manufacturing technology includes high integration of electronic circuits.
There is a need for a lithography technique that can form high-density electronic circuit patterns.

Generally, when an electronic circuit pattern on a mask or reticle is transferred onto the surface of a sea urchin, the resolution line width of the electronic circuit pattern transferred onto the surface of the sea urchin is proportional to the wavelength of the light source.

For this reason, far ultraviolet light (deep UV) with a wavelength of 200 to 300 nm is used.
For example, ultra-high-pressure mercury lamps, xenon mercury lamps, etc., which oscillate short wavelengths in the region) are used. However, these light sources have low brightness and no directivity, and the photoresist applied to the surface of the sea urchin also has low photosensitivity, resulting in a long exposure time and a reduction in throughput.

On the other hand, recently, a light source called an excimer laser having an oscillation wavelength in the deep UV region has been developed, and its application to lithography technology is being studied in various ways because of its high brightness, monochromaticity, directivity, etc. However, when using an excimer laser, in many cases, due to the laser's unique coherence, that is, good coherence, the mask surface or sea urchin surface may be damaged due to imperfections on the mask surface or the surface of the sea urchin, or the optical characteristics of the illumination system. Irregular interference fringes appear on the surface.

These interference fringes cause errors in illumination unevenness and burn-in, and are a major cause of lowering the resolution of the mask pattern image.

One method for reducing coherence is, for example, to condense the light beam from a laser into a spot and optically scan the pupil plane of the condenser lens when guiding the light beam to a condenser lens. has the disadvantage that the uneven illuminance of the luminous flux is directly affected by the wind. There is also a method of directly scanning the irradiated surface, but this method has the disadvantage that it is difficult to completely scan the irradiated surface. In addition, there is a method of scanning by changing the angle of incidence of the light beam on the secondary light source forming means, such as a fly's eye lens, but this method relatively reduces illuminance unevenness, but the microscopic fly's eye lens There are drawbacks such as difficulty in erasing interference fringes that occur between the two.

(Problems to be Solved by the Invention) The present invention aims to reduce interference fringes that cause uneven illuminance that occurs on the irradiated surface when a high-intensity light source with good coherence, such as a laser, is used. The purpose of the present invention is to provide a lighting device that enables uniform illumination of an irradiation surface.

(Means for solving the problem) A light beam from a light source with good coherence is guided to a secondary light source forming means through a scanning means, and the light beam from the secondary light source forming means is used to illuminate the illumination means. When illuminating the irradiated surface, the scanning state of the scanning means is controlled by the scanning control means so that the integrated illuminance distribution on the irradiated surface falls within a preset illuminance distribution.

(Embodiment) FIG. 1 is a schematic diagram of an optical system according to an embodiment of the present invention. In the figure, reference numeral 1 denotes a light source that emits a highly coherent light beam, such as an excimer laser. Reference numeral 2 denotes a scanning means, which is composed of, for example, a movable mirror, and rotates or vibrates to scan the light beam from the light source 1 and make it enter the beam expander 4.

Reference numeral 5 denotes a secondary light source forming means, which is composed of, for example, a plurality of fly's eye lenses, and introduces the light beam expanded through the beam expander 4 from the entrance surface 5a. Thereby, a secondary light source surface is formed on the exit surface 5b of the secondary light source forming means 5. A half mirror 6 divides the light beam emitted from the secondary light source surface 5b into two light beams. Reference numeral 7 denotes an illumination means, which is composed of, for example, a condenser lens or the like, and makes the reflected light beam from the half mirror 6 incident on an irradiated surface 8, which is, for example, a mask surface or a reticle surface for semiconductor manufacturing. Reference numeral 9 denotes an imaging lens which projects the pattern on the irradiated surface 8 onto an imaging surface 10 such as a sea urchin surface at a predetermined magnification.

Reference numeral 11 denotes sub-illumination means, which is arranged at a position optically equivalent to the illumination means 7 through the half mirror 6.
The light flux that has passed through is made incident on a sub-liquid irradiation surface 12 which is arranged at a position optically equivalent to the irradiation surface 8. Reference numeral 13 denotes a projection system, which is composed of a beam expander, a microscope, etc., and projects an integrated illuminance distribution onto the auxiliary liquid irradiation surface 12 onto an illuminance detection means 14 such as a CCD. Reference numeral 15 denotes a scanning control means which controls the scanning of the scanning means 2 according to a predetermined sequence based on the output signal from the illuminance detection means 14, and makes the light flux incident on the secondary light source forming means 5 via the beam expander 4. Adjusting the corner.

In this embodiment, with the above configuration, the scanning control means 15 uses the output signal from the illuminance detection means 14 to control the scanning means 2.
The unevenness of the illuminance distribution on the irradiated surface 8 is adjusted by controlling the scanning of and changing the angle of incidence of the light beam onto the secondary light source forming means 5.

FIG. 2 is an explanatory diagram showing the optical path of the light beam incident on the irradiated surface 8 when the angle of incidence of the light beam incident on the incident surface 5a of the secondary light source forming means 5 is changed by scanning by the scanning means 2. .

As in this embodiment, when a fly's eye lens is used as the secondary light source forming means 5 and is arranged in a negative dimension, it is equivalently equivalent to arranging a plurality of slits in one dimension. Therefore, when the scanning means 2 does not scan the light beam, that is, when a coherent light beam is incident on the fly's eye lens, the coherent light beams that have passed through each fly's eye lens interfere with each other on the irradiated surface 8. Interference fringes as shown in the figure are formed. As a result, the illuminance unevenness on the irradiated surface 8 increases, which causes a significant decrease in imaging performance when, for example, a pattern on the irradiated surface 8 is projected onto the imaging surface 10 with the projection lens 9. come.

However, when using a pulsed laser such as an excimer laser, simply vibrating the movable mirror constituting the scanning means 2 and randomly changing the incident angle φ of the light beam to the secondary light source forming means 5 results in a finite amount of scanning. In terms of numbers, the integrated illuminance distribution on the irradiated surface 8 is as shown in FIG. 4, for example, and it is not possible to completely eliminate illuminance unevenness.

Therefore, in this embodiment, the illuminance distribution on the subliquid irradiation surface 12, which is optically equivalent to the illuminance distribution on the irradiated surface 8, is detected by the illuminance detection means 14 via the projection system 13, and By controlling the scanning of the scanning means 2 in accordance with the pulse emission timing by the scanning control sub-device 5 based on the output signal of I am trying to make it so that

That is, the illuminance detection means 14 measures the peak position and peak interval of Young's interference fringes that occur for each scan, obtains information on the incident angle of the light beam to the secondary light source forming means 5, and uses this information as the sequence of the scan control means 15. The scanning means 2 is controlled and the incident angle φ of the light beam is adjusted so that the integrated distribution of all scans becomes a predetermined illuminance distribution. As a result, the peak position 3a, which is the cause of the non-uniform illuminance unevenness shown in FIG. 3, moves at a predetermined speed in the direction of the arrow, thereby eliminating the illuminance unevenness on the irradiated surface 8. At the same time, the light flux emitted from the secondary light source forming means 5 is made incoherent, and the optical performance of the entire device is reduced to N of the light flux from the secondary light source forming means.
I made it possible to make a general decision with A.

In this embodiment, if the intensity unevenness of the cumulative illuminance distribution is determined by the illuminance detection means 14, the degree of coherence of the secondary light source forming means, that is, the degree of coherence at the irradiated surface can be determined.

In the embodiment shown in FIG. 1, the illuminance detection means 14 may be placed directly on the side illuminated surface 12 without using the projection system 13. Alternatively, the beam from the light source 1 may be made to directly enter the secondary light source forming means 5 without using the beam expander 4.

(Effects of the Invention) According to the present invention, the integrated illuminance distribution is detected by the illuminance detection means disposed on the subliquid irradiation surface that is optically equivalent to the irradiated surface,
In other words, when a light source with good coherence is used by detecting the peak position and peak interval of Young's interference fringes on the irradiated surface, performing optimal scanning, and making the light beam incident on the secondary light source forming means. It is possible to reduce the unevenness of illuminance on the irradiated surface, and to achieve an illumination device having a good illuminance distribution such that the coherence of the irradiated surface can be determined only by N and A of the illumination system.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of an optical system according to an embodiment of the present invention, Fig. 2 is an explanatory diagram of a part of Fig. 1, and Fig. 3 is an explanation of the cumulative illuminance distribution on the irradiated surface when no scanning is performed. 4 and 5 are explanatory diagrams of the cumulative illuminance distribution on the irradiated surface when scanning is performed. In the figure, 1 is a light source, 2 is a scanning means, 5 is a secondary light source forming means,
7 is an illumination means, 8 is an irradiation surface, 9 is an imaging lens, 10 is an image formation surface, 11 is a sub-illumination means, 12 is a sub-liquid irradiation surface, 13 is a projection system, 14 is an illuminance detection means, 15 is a scanning It is a control means. Patent applicant: Canon Co., Ltd. 1 time 1ζ Hem 3 Figure 4 Figure 5 Figure 5

Claims (2)

[Claims] (1) The light beam from the light source with good coherence is guided to the secondary light source forming means via the scanning means, and the light beam from the secondary light source forming means is used to illuminate the surface to be illuminated by the illumination means. An illumination device characterized in that the scanning state of the scanning means is controlled by a scanning control means so that the integrated illuminance distribution on the irradiated surface falls within a preset illuminance distribution. (2) The scanning means is constituted by a movable mirror, and the rotation or vibration of the movable mirror is controlled by the scanning control means to change the angle of incidence of the light beam from the light source onto the secondary light source forming means. Claim 1 characterized by
The lighting device described in Section 1.