JP2606797B2 - Illumination device and illumination method using the same - Google Patents

Description

The present invention relates to a lighting device and a lighting method using the same.
Especially in semiconductor manufacturing, when using a light source such as a high-intensity laser with good coherence to prove the mask surface or reticle surface on which the fine pattern of the electronic circuit or the like to be irradiated is formed, light interference occurs. The present invention relates to an illumination device that performs uniform illumination by reducing illumination unevenness due to interference fringes on a surface to be irradiated and an illumination method using the same.

(Prior Art) A recent semiconductor device manufacturing technology requires a lithography technology capable of forming a high-density electronic circuit pattern as electronic circuits become more highly integrated.

Generally, when an electronic circuit pattern on a mask or reticle surface is transferred onto a wafer surface, the resolution line width of the electronic circuit pattern transferred onto the wafer surface is proportional to the wavelength of the light source. For this reason, far-ultraviolet light with a wavelength of 200 to 300 nm (deep UV region)
For example, an ultra-high pressure mercury lamp, a xenon mercury lamp, or the like that oscillates at a short wavelength is used. However, these light sources have low luminance and no directivity, and the photosensitivity of the photoresist applied on the wafer surface is low, so that the exposure time becomes longer and the throughput is reduced.

On the other hand, recently, a light source having an oscillation wavelength in a deep UV region called an excimer laser has been developed, and various applications to lithography technology have been studied because of its high brightness, monochromaticity, directivity, and the like. However, when an excimer laser is used, the coherence inherent to the laser is often used, that is, the coherence is good. , Irregular interference fringes occur. This interference fringe causes illumination unevenness and printing error, and is a major cause of lowering the resolution of the mask pattern image.

As a method of reducing coherence, for example, there is a method of condensing a light beam from a laser in a spot shape and optically scanning a pupil plane of the condenser lens when guiding the light beam to a condenser lens. Has the disadvantage that the illuminance non-uniformity of the light flux appears directly. Although there is a method of directly scanning the irradiated surface, this method has a drawback that it is difficult to completely scan the irradiated surface. In addition, for example, there is a method in which scanning is performed by changing the incident angle of a light beam to a secondary light source forming means such as a fly-eye lens. This method relatively reduces illuminance unevenness. There are drawbacks such as difficulty in erasing interference fringes caused by the above.

(Problems to be Solved by the Invention) The present invention is intended to reduce interference fringes that cause illuminance unevenness that occurs on a surface to be irradiated when a high-intensity light source having good coherence such as a laser is used. It is an object of the present invention to provide a lighting device capable of uniformly illuminating an irradiation surface and a lighting method using the same.

(Means for Solving the Problems) (1-1) A lighting device according to the present invention includes a secondary light source forming means for forming a secondary light source by receiving coherent light from a light source;
An optical system for causing a light beam from each part of the secondary light source to be incident on a surface to be irradiated and superimposing the light beam on the surface to be illuminated. A light intensity distribution on the surface to be illuminated when the coherent light is incident on the secondary light source forming means at a plurality of different incident angles by the scanning means. A detecting means is provided, and the scanning means is controlled according to an output of the detecting means.

(2-1) An exposure apparatus according to the present invention includes: a secondary light source forming unit configured to form a secondary light source by receiving coherent light from a light source;
An optical system for causing a light beam from each part of the secondary light source to be incident on the reticle and superimposing the light beam, and exposing the substrate with a reticle pattern illuminated by the light beam from each part of the secondary light source. Scanning means for changing the incident angle of the coherent light with respect to the secondary light source forming means is provided between the light source and the secondary light source forming means, and the scanning means changes the coherent light at a plurality of different incident angles. When the light is incident on the secondary light source forming means, a detecting means for detecting a light intensity distribution on the surface to be irradiated is provided, and the scanning means is controlled in accordance with an output of the detecting means.

(3-1) The illumination method according to the present invention is directed to an illumination method in which a secondary light source is formed by coherent light from a light source, and a light beam from each part of the secondary light source is incident on a surface to be illuminated and overlaps. When the coherent light is made incident on the secondary light source forming unit at a plurality of different incident angles by a scanning unit, a light intensity distribution on the illuminated surface is detected, and the scanning unit is controlled according to the detection result. It is characterized by.

(4-1) In the exposure method of the present invention, a secondary light source is formed by coherent light from a light source, and a luminous flux from each part of the secondary light source is incident on a reticle and is superimposed on the reticle pattern. In the exposure method of exposing a substrate, when the coherent light is incident on the secondary light source forming means at a plurality of different incident angles by a scanning means, a light intensity distribution on an irradiated surface is detected, and according to the detection result. And controlling the scanning means.

FIG. 1 is a schematic view of an optical system according to an embodiment of the present invention.
In FIG. 1, reference numeral 1 denotes a light source that emits a light beam having good coherence, such as an excimer laser. Reference numeral 2 denotes a scanning unit, which is composed of, for example, a movable mirror and scans a light beam from the light source 1 by rotation or vibration and makes the light beam enter the beam expander 4.
Reference numeral 5 denotes a secondary light source forming means, which comprises, for example, a plurality of fly-eye lenses and the like, and introduces a light beam expanded through the beam expander 4 from an incident surface 5a. Thus, a secondary light source surface is formed on the emission surface 5b of the secondary light source forming means 5.
Reference numeral 6 denotes a half mirror which divides a light beam emitted from the secondary light source surface 5b into two light beams. Reference numeral 7 denotes an illuminating unit, which is composed of, for example, a condenser lens or the like. Reference numeral 9 denotes an imaging lens (projection optical system),
The upper pattern is projected onto the image plane 10 of the wafer (substrate) at a predetermined magnification.

Numeral 11 designates sub-illuminating means, which is disposed at a position optically equivalent to the illuminating means 7 via the half mirror 6,
Are incident on a sub-irradiation surface 12 which is disposed at a position optically equivalent to the irradiation surface 8. Reference numeral 13 denotes a projection system, which includes a beam expander or a microscope, and is a sub-irradiated surface.
The illuminance distribution integrated on 12 is projected onto illuminance detecting means 14 such as a CCD. Numeral 15 denotes a scanning control means for controlling the scanning of the scanning means 2 in a predetermined sequence based on the output signal from the illuminance detecting means 14 to make the light beam incident on the secondary light source forming means 5 via the beam expander 4. Adjusting the corner.

In this embodiment, the scanning control unit 15 controls the scanning of the scanning unit 2 by using the output signal from the illuminance detecting unit 14 to change the incident angle of the light beam to the secondary light source forming unit 5 with the above configuration. Thus, the unevenness of the illuminance distribution on the irradiated surface 8 is adjusted.

FIG. 2 shows the secondary light source forming means 5 by the scanning of the scanning means 2.
FIG. 7 is an explanatory diagram showing an optical path of a light beam incident on the irradiated surface 8 when an incident angle of the light beam incident on the light incident surface 5a is changed.

When a fly-eye lens is used as the secondary light source forming means 5 as in the present embodiment, and this is arranged one-dimensionally, it is equivalent to one-dimensionally arranging a plurality of slits. For this reason, when the light beam is not scanned by the scanning means 2, that is, when a coherent light beam is incident on the fly-eye lens, the coherent light beams passing through each fly-eye lens interfere with each other on the irradiated surface 8, and for example, the third An interference fringe as shown in the figure is formed. As a result, the illuminance unevenness on the irradiated surface 8 becomes large. For example, when the pattern on the irradiated surface 8 is projected on the image forming surface 10 by the projection lens 9, this causes a large decrease in the imaging performance. come.

However, in the case of using a pulse laser such as an excimer laser, if the movable mirror constituting the scanning means 2 is simply vibrated to change the incident angle φ of the light beam to the secondary light source forming means 5 at random, the finite number of scans is obtained. The integrated illuminance distribution on the irradiated surface 8 is, for example, as shown in FIG. 4, and the illuminance unevenness cannot be completely removed.

Therefore, in the present embodiment, the illuminance distribution on the sub-illuminated surface 12 that is optically equivalent to the illuminance distribution on the illuminated surface 8 is detected by the illuminance detection unit 14 via the projection system 13, and the illuminance detection unit 14 at this time detects By controlling the scanning of the scanning means 2 in correspondence with the pulse emission timing by the scanning control means 15 based on the output signal, the illuminance distribution on the irradiated surface 8 becomes a uniform distribution as shown in FIG. 5, for example. Like that.

That is, the peak position and the peak interval of the Young's interference fringes generated for each scan are measured by the illuminance detecting means 14, information on the incident angle of the luminous flux to the secondary light source forming means 5 is obtained, and this is sequenced by the scanning control means 15. Thus, the scanning means 2 is controlled so that the incident angle φ of the light beam is adjusted so that the integrated distribution of all scans becomes a predetermined illuminance distribution. Thus, the uneven illuminance on the irradiated surface 8 is removed such that the peak position 3a causing the uneven illuminance unevenness shown in FIG. 3 moves at a predetermined speed in the direction of the arrow. At the same time, the light emitted from the secondary light source forming means 5 is made incoherent so that the optical performance of the entire apparatus can be substantially determined by the NA of the light beam from the secondary light source forming means.

In the present embodiment, if the intensity unevenness of the integrated illuminance distribution is obtained by the illuminance detecting means 14, the coherence degree of the secondary light source forming means, that is, the coherence degree on the irradiated surface can be obtained.

In the embodiment shown in FIG. 1, the illuminance detecting means 14 may be directly disposed on the sub-irradiated surface 12 without using the projection system 13. Further, the light beam from the light source 1 may be directly incident on the secondary light source forming means 5 without using the beam expander 4.

(Effect of the Invention) According to the present invention, the integrated illuminance distribution is detected by the illuminance detecting means arranged on the sub-illuminated surface which is optically equivalent to the illuminated surface, that is, the peak of the Young interference fringe on the illuminated surface. By detecting the position, peak interval, etc., and performing optimal scanning to make the light beam incident on the secondary light source forming means, it is possible to reduce illuminance unevenness on the irradiated surface when using a light source with good coherence. ,
An illumination device having an excellent illuminance distribution such that the coherence of the irradiated surface can be determined only by the NA of the illumination system, and an illumination method using the same can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic view of an optical system according to one embodiment of the present invention, FIG. 2 is an explanatory view of a part of FIG. 1, and FIG. 3 is an explanation of an integrated illuminance distribution on a surface to be irradiated when scanning is not performed. FIG. 4, FIG. 4 and FIG. 5 are explanatory diagrams of the integrated 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 illuminating means, 8 is an illuminated surface, 9 is an imaging lens, 10 is an imaging surface, 11 is a sub-illuminating means, 12 is a sub-illuminated surface, 13 is a projection system,
Reference numeral 14 denotes illuminance detection means, and 15 denotes scanning control means.

Claims (4)

(57) [Claims] 1. A secondary light source forming means for forming a secondary light source by receiving coherent light from a light source, and an optical device for causing light beams from respective portions of the secondary light source to be incident on a surface to be illuminated and to be superposed. A scanning means for changing an incident angle of the coherent light with respect to the secondary light source forming means is provided between the light source and the secondary light source forming means, and a plurality of different incident lights are provided by the scanning means. When the coherent light is incident on the secondary light source forming means at an angle, a detecting means for detecting a light intensity distribution on the illuminated surface is provided, and the scanning means is controlled in accordance with an output of the detecting means. Lighting device characterized by the following. 2. A secondary light source forming means for forming a secondary light source by receiving coherent light from a light source, and an optical system for superimposing and superimposing a light beam from each part of the secondary light source on a reticle. An exposure apparatus for exposing a substrate with a reticle pattern illuminated with a light beam from each portion of the secondary light source, wherein the scanning means for changing an incident angle of the coherent light with respect to the secondary light source forming means is provided. When the coherent light is incident on the secondary light source forming unit at a plurality of different incident angles by the scanning unit, the light intensity distribution on the surface to be illuminated is provided between the light source and the secondary light source forming unit. An exposure apparatus comprising: a detection unit; and controlling the scanning unit according to an output of the detection unit. 3. In an illumination method in which a secondary light source is formed by coherent light from a light source, and a light beam from each part of the secondary light source is made to impinge on a surface to be illuminated, a plurality of different light sources are scanned by a scanning means. When the coherent light is incident on the secondary light source forming means at an incident angle, a light intensity distribution on the surface to be illuminated is detected, and the scanning means is controlled in accordance with the detection result. 4. An exposure method for forming a secondary light source by coherent light from a light source, exposing a substrate with a pattern of the reticle by irradiating a light beam from each part of the secondary light source onto a reticle and superimposing the light beams. In the above, when the coherent light is made incident on the secondary light source forming means at a plurality of different incident angles by a scanning means, a light intensity distribution on a surface to be illuminated is detected, and the scanning means is controlled according to the detection result. An exposure method comprising: