JP3918440B2 - Light irradiation device with illuminance distribution uniform filter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light irradiation apparatus that is used as a light source device of an exposure apparatus used in the manufacture of integrated circuits, liquid crystal display elements, and the like, and particularly requires light having a uniform irradiation area. In the irradiation apparatus, an illuminance distribution uniformizing filter capable of reducing only the illuminance of the peripheral portion and uniformizing the illuminance distribution of the irradiation region by a simple method even when the illuminance of the peripheral portion of the irradiation region is high. It is related with the provided light irradiation apparatus.
[0002]
[Prior art]
FIG. 9 shows a configuration example of a light irradiation apparatus used as a light source apparatus such as a conventional exposure apparatus.
In the figure, the light emitted from the lamp 1 is collected by the condenser mirror 2, the optical path is turned back by the first reflecting mirror 3, and enters the integrator lens 4.
The integrator lens 4 has a function of making the illuminance distribution of the light incident on the lens 4 uniform on the irradiated surface. The light emitted from the integrator lens 4 is reflected by the second reflecting mirror 5 and enters the collimator lens 6. The light emitted from the collimator lens 6 becomes parallel light and is irradiated on the irradiated surface.
In the case of FIG. 9, the mask M is placed on the irradiated surface, and the mask pattern formed on the mask M is projected onto the substrate W through the projection lens 7 and exposed. Note that the configuration of the light irradiation apparatus is the same for an apparatus that exposes the mask pattern on the substrate without bringing the projection lens 7 into close contact with the mask M and the substrate W.
In addition, there is a case where an object to be processed (hereinafter also referred to as a workpiece) is arranged on the surface to be irradiated instead of the mask M, and the surface of the object to be processed is modified by a photochemical reaction by irradiating light. For example, a photo-alignment film for a liquid crystal display element is disposed and a photo-alignment process is performed.
[0003]
The integrator lens 4 (also referred to as a fly-eye lens) is a lens in which dozens to dozens of lenses are arranged in parallel in the vertical and horizontal directions. Each of the lenses divides incident light, and the divided light is superimposed on the irradiation surface to make the illuminance distribution uniform. That is, the illuminance distribution of the light incident on the integrator lens 4 is non-uniform, and even if the intensity of the light incident on each lens is different, the emitted light irradiates the same irradiation surface so that the uniform illuminance is obtained. Distribution.
By using the integrator lens 4 as described above, the illuminance distribution on the irradiated surface can be about ± 5%.
FIG. 10 shows how the illuminance distribution is made uniform by the integrator lens. In addition, although the integrator lens comprised from three lenses is shown in the figure for easy description, actually, dozens to dozens of lenses are provided.
In FIG. 10, light from a lamp (not shown) is collected, enters the integrator lens 4 from the upper side of the figure, and irradiates the irradiation area of the irradiated surface at the lower side of the figure through the collimator lens 6.
The integrator lens 4 is composed of a first lens 4a, a second lens 4b, and a third lens 4c, and the illuminance distribution in the horizontal direction of the drawing of light incident on the integrator lens 4 is as shown in graph 1 in the figure. Suppose that it is a simple shape.
The integrator lens 4 projects the light incident on each lens over the entire irradiation area. The light having the illuminance distribution of A in the graph 1 is incident on the first lens 4a, and is projected as light having the illuminance distribution of A 'in the graph 2 on the entire irradiation region.
[0004]
Similarly, light having an illuminance distribution of B in the graph 1 is incident on the second lens 4b, and is projected as light having an illuminance distribution of B 'in the graph 2 on the entire irradiation region. Light having an illuminance distribution of C in the graph 1 is incident on the third lens 4c, and is projected as light having an illuminance distribution as in C 'of the graph 2 on the entire irradiation region.
In the irradiation region, the illuminance distributions A ′, B ′, and C ′ are added. As a result, the illuminance distribution in the irradiation region is as shown in the graph 3. Compared to the graph 1, the illuminance distribution of the graph 3 is made uniform.
If the number of lenses constituting the integrator lens is increased, such a uniform effect of the illuminance distribution can be obtained. The illuminance distribution in the light irradiation area can be made ± 5% or less by the integrator lens.
Recently, however, a more uniform illuminance distribution, for example, ± 3% or less, has been demanded for reasons such as miniaturization of processing accuracy of an object to be processed and a stable processing process.
[0005]
When exposing a rectangular workpiece such as a liquid crystal substrate or a printed circuit board, the shape of the light emitted from the light irradiation device is made to be rectangular according to the shape of the workpiece. If the cross-sectional shape of each lens constituting the integrator lens 4 in the direction perpendicular to the optical axis is made rectangular, the shape of the irradiation region becomes rectangular.
In the rectangular irradiation region as described above, the illuminance is higher in the periphery of the irradiation region, and may not satisfy the required illuminance uniformity. The cause of this is the difference in reflectance and transmittance due to variations in the film thickness and the like of various deposited films provided on the surfaces of lenses and mirrors in the light irradiation device, as well as the design and assembly conditions of the optical system.
In order to improve the illuminance distribution in the irradiation region, it is known to provide an illuminance distribution correction filter 8 as shown by a dotted line in FIG.
[0006]
For example, Japanese Patent Application Laid-Open No. 56-55043 describes that an illuminance distribution correction filter is provided between an integrator lens and an irradiated surface.
The illuminance distribution correction filter is a filter having partially different light transmittances. For example, the illuminance distribution correction filter is manufactured by vapor-depositing a material that reflects or absorbs light having an irradiated wavelength on a quartz plate.
Further, for example, Japanese Patent Laid-Open No. 7-20320 describes in detail the structure of the illuminance distribution correction filter as described above.
As shown in paragraphs [0003] to [0004] of JP-A-7-20212, the illuminance distribution correction filter measures the illuminance distribution on the irradiated surface after assembling the light irradiating device, and this illuminance distribution. In other words, for example, if the illuminance at the periphery of the irradiation region is high, the light transmittance of the periphery is reduced. This is inserted into the optical path of the light irradiation device to make the illuminance distribution in the irradiation region uniform.
[0007]
[Problems to be solved by the invention]
The illuminance distribution correction filter is manufactured by depositing a material that reflects or absorbs light, an antireflection film, or the like on a quartz plate as disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 7-20320. Quartz purchase costs, vapor deposition costs, production time, etc. are expensive. For example, the manufacturing cost of the 200 × 200 mm illuminance distribution correction filter is about 200,000 yen even when simple correction is performed.
In addition, the illuminance of a portion that is not desired to be reduced is also reduced by the transmittance of the vapor deposition film provided on the quartz plate, and the illuminance is lowered as a whole irradiation region.
For example, if the irradiation area is rectangular and the peripheral area has a large illuminance, it is desirable to reduce the illuminance only at the peripheral area without reducing the illuminance at the central area of the irradiation area, and make the illuminance distribution uniform. However, when the conventional illuminance distribution correction filter is used, the illuminance distribution is made uniform, but the illuminance at the center of the irradiation area is also reduced by passing through the quartz plate, and the illuminance is reduced as a whole. As a result, the processing time of the object to be processed becomes longer and the throughput is lowered.
The present invention has been made in consideration of the above circumstances, and the object of the present invention is to reduce the man-hour and cost of manufacturing the illuminance distribution correction filter, and the irradiation area is rectangular, and the illuminance at the periphery is large. In this case, it is to provide a light irradiation device capable of adjusting the illuminance distribution by reducing the illuminance at only the peripheral portion without reducing the illuminance at the center of the irradiation region.
[0008]
[Means for Solving the Problems]
The illuminance distribution correction filter is composed of a metal wire stretched on a filter frame, and the metal wire is inserted into the light beam incident on the integrator lens.
In the present invention, the individual lenses constituting the integrator lens have a rectangular cross-sectional shape in the direction perpendicular to the optical axis, and the metal wire rod projects shadows due to the incident light onto the boundary lines of the individual lenses. The shadow is projected onto the irradiated surface, and the illuminance distribution on the irradiated surface is adjusted.
The shadows projected on the boundary lines of the individual lenses by the action of the integrator lens described in FIG. 10 are projected on the periphery of the irradiated surface corresponding to the boundary lines. For example, the metal wire rod is applied to the filter frame. If one wire is stretched, the illuminance on the two opposite sides around the irradiated surface can be reduced, and if the two metal wires are stretched perpendicular to the filter frame, the four sides around the illuminated surface are stretched. The illuminance can be reduced.
That is, a shadow produced by inserting a filter in which at least one or two metal wires are linearly inserted on the light incident side of the integrator lens and blocking the light incident on the integrator lens by the metal wire is described above. If projected onto the boundary line of the lenses constituting the integrator lens, the illuminance of the two opposing sides or the four surrounding sides of the irradiated surface can be reduced.
Further, only the illuminance around the irradiated surface is reduced, and the illuminance at the center of the irradiated surface is not reduced.
As described above, according to the present invention, it is possible to reduce the illuminance at the peripheral portion of the irradiation region without reducing the illuminance at the central portion only by stretching one or two metal wires on the filter frame. Further, unlike the prior art, neither a quartz plate nor vapor deposition work is required, and the manufacturing cost and the number of steps can be greatly reduced.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a configuration example of a light irradiation apparatus provided with an illuminance distribution uniformizing filter according to an embodiment of the present invention.
In FIG. 1, the light emitted from the lamp 1 is collected by the condenser mirror 2, the optical path is turned back by the first reflecting mirror 3, and enters the integrator lens 4. On the light incident side of the integrator lens 4 is provided an illuminance distribution uniformizing filter 10 of the present invention in which a metal wire is stretched.
The individual lenses constituting the integrator lens 4 have a rectangular cross-sectional shape perpendicular to the optical axis, and the metal wire stretched over the illuminance distribution uniformizing filter 10 is shaded by the incident light, The integrator lens 4 is provided so as to be projected onto the boundary line between the individual lenses.
Light emitted from the integrator lens 4 with the illuminance distribution adjusted by the illuminance distribution uniforming filter 10 is reflected by the second reflecting mirror 5 and incident on the collimator lens 6 to become parallel light, which is irradiated onto the irradiated surface.
[0010]
FIG. 2 shows a specific configuration example of the illuminance distribution uniformizing filter according to the embodiment of the present invention that projects a shadow on the incident surface of the integrator lens.
As shown in the figure, the illuminance distribution uniform filter 10 includes a filter frame 11 and a metal wire 12 stretched on the frame.
The filter frame 11 is provided with an opening 11a through which a light beam incident on the integrator lens 4 passes. Further, the filter frame 11 is provided with a large number of through holes 11b through which the metal wire 12 is fixed.
The metal wire 12 is, for example, a 0.3 mm nickel wire, is stranded and is stretched over the filter frame 11 and fixed to the through hole 11b. The metal wire 12 is irradiated with intense condensed light and becomes high temperature. Therefore, a nickel wire was selected as a material having a relatively low expansion rate so that it does not easily oxidize and does not swell and sag. Moreover, it was made into the strand wire so that it might not meander or sag when it was stretched.
As described above, the metal wire 12 is stretched to a position where the shadow caused by the incident light is projected onto the boundary lines of the individual lenses of the integrator lens 4.
[0011]
The metal wire 12 is appropriately provided while measuring the illuminance distribution. As shown in FIG. 2, when one metal wire is provided on the filter frame and its shadow extends over a position where it is projected onto the boundary line of the integrator lens 4, it is covered as described later. The illuminance on the two opposite sides of the irradiated surface can be reduced.
Only one metal wire 12 may be provided in one vertical or horizontal direction as shown in FIG. 2, or may be provided in a cross shape one by one in the vertical and horizontal directions as shown in FIG. In this way, it is possible to reduce the illuminance on the four sides around the irradiated surface.
Furthermore, when performing a fine illuminance adjustment, a plurality of metal wires may be provided at one place as shown in FIG. 4, or at two places as shown in FIG. Moreover, as shown in FIG. 6, you may provide in a cross in several places.
In addition, the illuminance distribution can be adjusted by several means such as changing the thickness of the metal wire or changing the distance from the metal wire to the integrator lens.
[0012]
Next, the operation of the illuminance distribution uniformizing filter of the embodiment of the present invention will be described.
As described above, the integrator lens projects the light incident on each lens over the entire irradiation region.
This will be described below with reference to FIG.
Light enters the integrator lens 4 from above in FIG. Here, the integrator lens 4 is a compound lens formed by arranging a plurality of lenses having a rectangular cross-sectional shape in the vertical direction with respect to the optical axis of incident light in the vertical and horizontal directions.
The light emitted from the integrator lens 4 is projected onto the surface to be irradiated, and the shape of the irradiation region becomes a rectangular shape indicated by ABCD.
The light projected onto the vertex ABCD of the irradiation area is light incident on the position of ABCD of each lens constituting the integrator lens 4. For the sake of simplicity, the ABCD notation for each lens shows only the four central lenses, but the same applies to the other lenses.
[0013]
Here, it is assumed that the illuminance of the irradiation area ABCD is low in the central part and becomes higher toward the peripheral part as shown by a curve indicating the illuminance distribution. In order to improve such illuminance distribution, the following is performed.
As shown in FIG. 8, metal wires 12a and 12b are provided on the incident side of the integrator lens 4 to block incident light. Although the incident angle of the light incident on the integrator lens 4 depends on the optical system, for example, it has an angle range of 0 ° to ± 8 °, so that the shadow caused by this spreads and the boundaries of the individual lenses constituting the integrator lens The projected image is enlarged around the line.
By the way, this shadow is the darkest in each boundary line, and becomes thinner as the distance from the boundary line increases. Further, when the metal wire 12a is moved away from the integrator lens 4, the width of the shadow is widened and thinned as a whole, and when approaching, the width of the shadow is narrowed and darkened as a whole. This is convenient for making the illuminance distribution uniform when the peripheral illuminance is higher than the center of the irradiation region. That is, the metal wire 12a enlarges and projects a shadow on the boundary line of the lens in the AD and BC directions. Due to this shadow, the illuminance at the AD peripheral portion and the BC peripheral portion of the irradiation region is lowered and becomes the same as the illuminance at the center of the irradiation region. In addition, the metal wire 12b enlarges and projects a shadow on the boundary line of the lens in the AB and DC directions. Then, due to this shadow, the illuminance at the AB peripheral portion and the DC peripheral portion of the irradiation region becomes low, and becomes the same as the illuminance at the center of the irradiation region.
Here, the shadow of the portion where the metal wires 12a and 12b intersect becomes darker than the others. Therefore, the illuminances at the vertices A, B, C, and D of the irradiation areas corresponding to the intersecting parts are the parts where the illuminance is the highest, but are greatly reduced compared to the other, and the same as the illuminance at the center of the irradiation area become.
[0014]
As described above, by arranging the metal wires 12a and 12b so that the shadows are projected onto the boundary lines of the lenses constituting the integrator lens 4, without reducing the illuminance at the center of the irradiation area ABCD, The illuminance at the periphery can be lowered, and the illuminance distribution can be made uniform.
Similarly, for example, if only the metal wire 12a is provided and a shadow is projected on the boundary line of the lens in the AD and BC directions, the illuminance at the AD peripheral portion and the BC peripheral portion of the irradiation region can be lowered.
As described above, the method of providing the metal wire 12 is appropriately performed while measuring the illuminance distribution, but a plurality of metal wires are provided at one place, a plurality of metal wires are provided at a plurality of places, Since the shadow width and density can be changed by changing the thickness of the metal wire or changing the distance from the metal wire to the integrator lens, it can be adjusted to have a desired illuminance distribution.
[0015]
【The invention's effect】
As described above, the following effects can be obtained in the present invention.
(1) The illuminance distribution uniformizing filter of the present invention has a metal frame attached to a metallic frame, and the manufacturing cost is extremely low, which is tens of thousands of yen. The manufacturing cost can be reduced to 1/10 or less as compared with a filter using a conventional deposited film.
(2) Fine illuminance adjustment is possible only by attaching or removing the metal wire to the filter frame, and the uniformity of the illuminance distribution can be further improved by cut-and-try.
(3) Since there is no portion where no metal wire is provided, light is not attenuated. Therefore, it is possible to reduce the illuminance only at the peripheral portion without reducing the illuminance at the center of the irradiation region.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration example of a light irradiation apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating a specific configuration example (1) of an illuminance distribution uniformizing filter;
FIG. 3 is a diagram illustrating a specific configuration example (2) of an illuminance distribution uniformizing filter;
FIG. 4 is a diagram illustrating a specific configuration example (3) of an illuminance distribution uniformizing filter;
FIG. 5 is a diagram illustrating a specific configuration example (4) of an illuminance distribution uniformizing filter;
FIG. 6 is a diagram illustrating a specific configuration example (5) of an illuminance distribution uniformizing filter.
FIG. 7 is a diagram (1) illustrating an operation of an illuminance distribution uniformizing filter according to an embodiment of the present invention.
FIG. 8 is a diagram (2) illustrating an operation of the illuminance distribution uniformizing filter according to the embodiment of the present invention.
FIG. 9 is a diagram showing a configuration example of a light irradiation apparatus used as a light source apparatus such as a conventional exposure apparatus.
FIG. 10 is a diagram showing how the illuminance distribution is made uniform by an integrator lens.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Lamp 2 Condensing mirror 3 1st reflective mirror 4 Integrator lens 5 2nd reflective mirror 6 Collimator lens 10 Illuminance distribution equalization filter 11 Filter frame 11a opening 11b Through-hole 12 Metal wire

Claims (1)

In a light irradiation apparatus including an optical element including a light source and an integrator lens that projects light from the light source onto an irradiated surface,
The integrator lens is a compound lens configured by arranging a plurality of lenses having a rectangular cross-sectional shape in the vertical direction with respect to the optical axis of incident light in the vertical and horizontal directions,
A filter in which a metal wire is linearly inserted is inserted on the light incident side of the integrator lens, and a shadow caused by the metal wire blocking light incident on the integrator lens is a boundary between the lenses constituting the integrator lens. The light irradiation apparatus provided with the illuminance distribution uniformization filter characterized by being projected on a line.

Images