JP5157945B2 - Light irradiation device - Google Patents

Description

  The present invention relates to a light irradiation apparatus used in an exposure apparatus for manufacturing a semiconductor element, a printed circuit board, a liquid crystal substrate, and the like.

FIG. 12 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 via the wavelength selection filter 10 and the shutter 20.
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 8.

In the case of the apparatus shown in FIG. 12, a mask M is placed on the irradiated surface 8, and a mask pattern (not shown) formed on the mask M is coated with a photosensitive material such as a resist via a projection lens 7. Projected onto W and exposed. Note that a light irradiation device having the same configuration is used for an apparatus that exposes the mask pattern on the substrate W without bringing the projection lens 7 into close contact with the mask M and the substrate W.
In some cases, the object to be processed is arranged on the surface to be irradiated 8 instead of the mask M, irradiated with light, and the surface of the object to be processed is modified by a photochemical reaction. As such an example, there is a photo-alignment treatment of a photo-alignment film for a liquid crystal display element.
Hereinafter, an object to be irradiated with light from a light irradiation device such as a substrate or an alignment film is referred to as a workpiece.

  An integrator lens (also referred to as a fly-eye lens) is a lens in which about ten to hundred 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. In other words, the illuminance distribution of the light incident on the integrator lens 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 and irradiates uniformly. It becomes. By using the integrator lens as described above, the illuminance distribution on the irradiated surface can be about ± 5%.

FIG. 13 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. 13, light from a lamp (not shown) is collected, is incident on the integrator lens 4 from above, and is emitted from the integrator lens 4 via the collimator lens 6. Eight irradiation areas are irradiated.
The integrator lens 4 is composed of a first lens L1, a second lens L2, and a third lens L3, 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. It is assumed that the central portion has a high illuminance and a low peripheral portion.

The integrator lens 4 projects the light incident on each lens L onto the entire irradiation area. Light having an illuminance distribution indicated by A in the graph 1 is incident on the first lens L1, and is projected as light having an illuminance distribution indicated by A 'in the graph 2 on the entire irradiation region.
Similarly, light having an illuminance distribution of B in the graph 1 is incident on the second lens L2, 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 L3, and is projected as light having an illuminance distribution of C ′ in 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. As described above, by using the integrator lens, the illuminance distribution in the light irradiation region of the irradiated surface 8 can be reduced to ± 5% or less.

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. In such a case, if the cross-sectional shape of the individual lenses constituting the integrator lens 4 in the direction perpendicular to the optical axis is rectangular, the shape of the irradiation region becomes rectangular. As an example of using an integrator lens having a rectangular cross section of each lens, there is a light irradiation device described in Patent Document 1, for example.
Further, in such a light irradiation apparatus, means for selecting a wavelength on the light incident side of the integrator lens 4 in order to extract only light having a wavelength necessary for exposure from light emitted from the lamp 1, a so-called wavelength selection filter 10. Also, for example, as described in the illumination optical apparatus of Patent Document 2, it is also known from the past.
Many filters arranged on the light incident side of the integrator lens 4 are for blocking light having a wavelength shorter than a necessary wavelength.

JP 2002-237442 A JP-A-61-180435 JP 2004-245912 A

The wavelength selection filter (hereinafter simply referred to as a filter) is formed by depositing an inorganic multilayer film on a transparent substrate such as quartz or glass. The film to be formed is formed by setting the material and the film thickness in accordance with the wavelength of light to be blocked (transmitted).
In recent years, liquid crystal display substrates and printed circuit boards have been increased in area, and accordingly, it has been desired to expand the light irradiation region in the exposure apparatus. As a countermeasure, it has been proposed to combine a plurality of lamps and a condensing mirror as in the light irradiation device described in Patent Document 3, for example, and the light source is also enlarged.
As the size of the light source increases, the light (light) incident on the integrator lens also increases, and a filter disposed on the incident side of the integrator needs to be large. For example, in the case of a light irradiation device using four lamps side by side, the diameter of the light beam is about 700 mm.

However, the filter is formed by forming an inorganic vapor deposition film on a glass plate or the like (hereinafter collectively referred to as a glass plate) as described above. As a practical matter, it is difficult to form a vapor-deposited film with uniform characteristics over the entire surface of a large-area glass plate so that the wavelength to be blocked (transmitted) does not shift, and is currently about 250 mm to 300 mm square. Up to. Therefore, it is difficult to manufacture a filter used in a large light irradiation apparatus from a single glass plate.
As a result of intensive studies, we have considered that a plurality of small filter plates are held on a frame (holding frame) by the crosspiece and used as one large filter. However, the frame and its rail are usually made of metal from the viewpoint of durability and cost. If it does so, a frame and a cross will become opaque, and the thickness of a cross will also be about 5 mm-10 mm. When such a filter is arranged in the optical path, even if the outer frame of the frame is arranged outside the light beam, the crosspiece shields the light and produces a shadow, reducing the uniformity of the illuminance distribution on the light irradiation surface. I will let you.
The present invention has been made to solve the above-described conventional problems, and an object of the present invention is to provide a light irradiation device including a filter that holds a plurality of filter plates by a frame and its crosspieces on a light irradiation surface. This is to prevent a decrease in the uniformity of the illuminance distribution.

In order to solve the above problems, in the present invention, a light source and a plurality of lenses having a light incident / exit surface that is rectangular (that is, a rectangular cross section perpendicular to the optical axis) are arranged side by side. An integrator lens that makes light incident and uniforms the illuminance distribution on the light irradiation surface; and a filter that transmits only light in a specific wavelength range among the light emitted from the light source, the filter comprising a plurality of filters In a light irradiation apparatus configured by holding a plate with a frame and a frame bar, each of the rectangles of the integrator lens has a direction in which the frame of the filter frame extends in a region where the filter is irradiated with light. Arrange so that it is oblique to the direction of the side (so as not to be parallel) and not parallel to the diagonal of the rectangle of the integrator lens.
Here, the illuminance of the light incident on the filter and integrator lens is strong in the central part of the light beam (near the optical axis), so if it is arranged so that the filter beam does not cover this part, the influence of the beam shadow will be reduced. It can be made smaller, and a decrease in the uniformity of the illuminance distribution can be prevented. In other words, it is desirable to prevent the crosspieces from being arranged on the lens through which the optical axis passes and the lens adjacent thereto.
Further, in the region where the filter is irradiated with light, all the crosspieces of the filter should be arranged so as to be oblique to the side of the integrator lens and not parallel to the diagonal of the lens. Desirably, in this way, the influence of the shadow of the crosspiece can be effectively reduced.

  In the present invention, the direction in which the crosspieces of the filter frame extend is inclined with respect to the direction of each side of the integrator lens and is not parallel to the rectangular diagonal of the integrator lens. The shadow of the crosspiece is not added in the irradiation area of the irradiated surface by the action of the integrator lens, and the shadow of the frame crossing is dispersed on the light irradiation surface to prevent the uniformity of the illuminance distribution from being lowered. Can do.

It is a figure which shows schematic structure of the light irradiation apparatus of the Example of this invention. It is a figure which shows the structure of the filter of the Example of this invention. It is the figure which looked at the integrator lens from the light-incidence side. It is a figure (view seen from the light-incidence side) which shows the example of arrangement | positioning of the filter with respect to the integrator lens of the Example of this invention. It is a figure (perspective view) which shows the example of arrangement | positioning of the filter with respect to the integrator lens of the Example of this invention. It is a figure (1) explaining the reason which can prevent the fall of illumination intensity distribution in this invention. It is a figure (2) explaining the reason which can prevent the fall of illumination intensity distribution in this invention. It is a figure explaining arrangement | positioning of the filter in case each lens of an integrator lens is square. It is a figure explaining the example of preferable arrangement | positioning of the filter crosspiece with respect to each lens of an integrator lens. It is a figure which shows the structural example at the time of arrange | positioning the filter of this invention to the output side of an integrator lens. When the integrator lens 4 is composed of the light incident side lens group 4a and the light exit side lens group 4b, the filter of the present invention is disposed between the light incident side and the light exit side lens group of the integrator lens. It is a figure which shows the example of a structure. It is a figure which shows the structural example of the light irradiation apparatus used as light source devices, such as the conventional exposure apparatus. It is a figure which shows the mode of uniformity of the illumination distribution by an integrator lens.

FIG. 1 is a diagram showing a schematic configuration of a light irradiation apparatus according to an embodiment of the present invention. The same number is attached | subjected about the thing of the same structure as FIG.
In the present embodiment, the light source H includes two lamps 1a and 1b and two pieces of light that reflect and collect light from each lamp so that an irradiation area having a wide area can be obtained on the irradiated surface 8. It is comprised from the condensing mirrors 2a and 2b. Since the configuration is basically the same as that of a conventional light irradiation apparatus, a description thereof will be omitted.
The light emitted from the light source H has its optical path turned back by the first reflecting mirror 3 and enters the integrator lens 4 via the filter 10 and the shutter 20 for wavelength selection.
The light emitted from the integrator lens 4 is reflected by the second reflecting mirror 5, converted into parallel light by the collimator lens 6, and irradiated on the irradiated surface 8.

FIG. 2 shows the structure of the filter 10 according to the present embodiment. The nine rectangular filter plates 10a are formed by a rectangular frame (holding frame) 10b and four bars 10c formed vertically and horizontally on the frame 10b. The retained filter is shown. 2A is a plan view of the filter 10 viewed from the light incident side, and FIG. 2B is a cross-sectional view taken along the line AA of FIG.
The filter 10 includes a plurality of filter plates 10a, a frame (holding frame) 10b that holds each filter plate 10a, and a crosspiece 10c that is disposed parallel to the frame 10b.
As described above, the filter plate 10a is obtained by depositing an inorganic multilayer film on a transparent substrate such as quartz or glass, and is, for example, a square having a side of 250 mm to 300 mm.
A frame (holding frame) 10b for holding the filter plate 10a and its crosspiece 10c are made of aluminum, the width of the crosspiece 10c of the frame 10b is 5 mm to 10 mm, and a recess is formed inside, and each filter plate 10a It is fitted and held in the recess.

FIG. 3 is a view of the integrator lens 4 as viewed from the light incident side. In the figure, 3 × 6 = 18 lenses L having a rectangular cross section perpendicular to the optical axis, which are formed in accordance with the shape of the light irradiation region, are arranged. The number of lenses L of the integrator lens 4 used in the actual light irradiation apparatus is 80 to 100.
4 and 5 are diagrams showing the configuration of the embodiment of the present invention when the filter 10 shown in FIG. 2 is arranged on the light incident side of the integrator lens 4 shown in FIG. 4 is a view of the integrator lens 4 and the filter 10 as viewed from the light incident side, and FIG. 5 is a perspective view thereof.

As shown in FIG. 4, the filter 10 is configured so that the crosspiece 10c of the frame 10b is inclined with respect to the side of each lens L of the integrator lens 4 (the frame 10b is inclined with respect to the direction in which the lenses L are arranged). However, it is arranged so that it is not parallel to the diagonal of each lens.
That is, when the beam 10c of each frame 10b is projected on the light incident surface of each lens L in the optical axis direction, the direction of the linear shadow of each beam 10c is parallel to each side of each rectangular lens L. So that the lens is not parallel to the diagonal line of the rectangle of each lens.
By disposing the frame crosspiece 10c in this way, it is possible to prevent a reduction in the uniformity of the illuminance distribution on the irradiated surface due to the shadow created by the frame crosspiece 10c.
In FIG. 4, for easy understanding, the frame 10 b of the filter 10 is shown extremely thick with respect to the size of the integrator lens 4. Actually, it is a little thinner, and the shadow of the frame bar 10c projected onto the entrance surface of the integrator lens is also thinner.

The reason why the illuminance distribution can be prevented from being lowered by arranging the crosspieces 10c of the frame 10b of the filter 10 so as to be inclined with respect to the direction of each side of the integrator lens 4 as described above is shown in FIGS. Use and explain.
FIG. 6A is a view of the integrator lens 4 as viewed from the light incident side. The integrator lens 4 is assumed to be composed of nine lenses indicated by the numbers L1 to L9 and having a square cross section. It is assumed that light shown as a circular light irradiation area (light beam) is incident on the integrator lens.
6B and 6C are diagrams in which the filter 10 is arranged on the light incident side of the integrator lens 4.
In order to simplify the explanation, here, the filter 10 is assumed that two filter plates 10a are held by a frame (filter frame) 10b, and one crosspiece 10c between the two filter plates 10a is an integrator. It is assumed that a shadow is cast on the light incident surface of the lens 4.
FIG. 6B shows a case where the crosspieces 10c of the frame 10b of the filter 10 are arranged in parallel with the sides of the lenses L of the integrator lens 4 (the frame 10b is in parallel with the sides of the rectangular lens). FIG. 6C shows a case where the crosspieces 10c of the frame 10b of the filter 10 are arranged obliquely with respect to the direction in which the lenses of the integrator lens are arranged (the frame 10b is obliquely with respect to the sides of the rectangular lens). .

FIG. 7 is a diagram showing the illuminance distribution when the filter 10 is arranged on the light incident side of the integrator lens 4 as shown in FIG. This figure is created with the same image as FIG.
FIGS. 7A, 7B, and 7C are illuminance distributions in the case of FIG. 6B, and FIGS. 7D, 7E, and 7F are illuminance distributions in the case of FIG. 6C. is there.
7A and 7D show the illuminance distribution of the light emitted from each lens, FIGS. 7B and 7E show the illuminance distribution obtained by adding them, and FIGS. 7C and 7F show the irradiated surface. An illuminance distribution image of the entire light irradiation area is shown.
As described above, the integrator lens 4 projects the light incident on each lens onto the entire irradiated area of the irradiated surface. However, in the case of FIG. 6B, the shadow of the frame crosses the center of the lenses L2, L5, and L8 of the integrator lens vertically.
For this reason, as shown in FIG. 7A, the illuminance distribution of the light projected by the lens L5 onto the irradiation region is such that the illuminance at the center portion is reduced. Similarly, the illuminance distribution of the light projected by the lenses L2 and L8 also has a reduced illuminance at the central portion.

When these illuminance distributions are added in the irradiation area of the irradiated surface by the action of the integrator lens, the low-illuminance portions of the lenses L2, L5, and L8 are also added, as shown in FIG. 7B. Become. Therefore, the added illuminance distribution is such that the illuminance at the central portion is extremely low (dark) compared to the other portions.
As a result, as shown in FIG. 7C, an extremely low (dark) area of illuminance crosses the irradiation area of the irradiated surface. Therefore, a desired uniformity of illuminance distribution (for example, ± 5%) cannot be obtained in the light irradiation region.
In contrast to this, in the case of FIG. 6C, the shadow of the frame is oblique to the direction in which the lenses are arranged, and the shadow of the frame crosses the lenses L2, L5, and L8. The lens L2 is located on the right side, the lens L5 is located near the center, and the lens L8 is located on the left side. Therefore, as shown in FIG. 7 (d), the illuminance distribution of the light projected by the lens L5 onto the irradiation area is a reduced illuminance at the center portion, but the illuminance distribution of the light projected by the lens L2 is The illuminance distribution of the right portion is reduced, and the illuminance distribution of the light projected by the lens L8 is that of the left portion of which the illuminance is reduced, and the low illuminance portions do not match.

Therefore, when these illuminance distributions are added in the irradiation area of the irradiated surface, the low-illuminance portions of the lenses L2, L5, and L8 do not overlap in the irradiation area as shown in FIG. Although there is an influence of the shadow of the frame, there is no region where the illuminance is extremely low (dark).
As a result, as shown in FIG. 7 (f), the irradiance area of the surface to be irradiated crosses three castles with slightly low illuminance (dark), but there is little decrease in illuminance at that portion. Therefore, a desired uniformity of illuminance distribution (for example, ± 5%) can be obtained in the light irradiation region.
In FIG. 4, the frame 10b of the filter 10 is arranged so as to intersect at about 45 ° with respect to the direction of the side of each lens L of the integrator lens 4 (direction in which the lenses are arranged). 45 ° is not always optimal. In short, it is important that the same position of each lens L is not darkened.
Therefore, when the crosspieces 10c of the frame 10b are arranged obliquely with respect to the direction of the side of each lens L of the integrator lens 4, it is necessary to arrange them so that they are not parallel to (or do not match) the diagonal lines of each lens. .

For example, as shown in FIG. 8A, when the cross section of the integrator lens 4 cut by a plane perpendicular to the optical axis of each lens L is a square, the cross direction of the lenses L on the crosspiece 10c of the frame 10b. If the frame is arranged at 45 °, the shadow of the frame crosses the diagonal of each lens of the integrator lens (becomes parallel). Therefore, the shadow of the frame crosses the lens L3, L5, and L7 at the same position. Is done. Therefore, as described in FIG. 7, the portions with low illuminance are added, and the portion with extremely low illuminance crosses the light irradiation region diagonally.
Therefore, in such a case, as shown in FIG. 8B, the angle of the side of each lens L of the crosspiece 10c of the filter 10 is adjusted, and the shadow of the crosspiece 10c is projected onto each lens L. Try to make the position different.

Here, since the illuminance of the light incident on the integrator lens 4 is strong in the central portion of the light beam (near the optical axis), if the crosspiece 10c of the filter 10 is disposed on this portion, the influence of the shadow of the crosspiece 10c is affected. It appears greatly.
For example, when the crosspiece 10c of the filter 10 passes through the central portion of the integrator lens 4 as shown in FIGS. 6B and 6C, the integrator in which light with high illuminance enters as shown in FIG. The influence of the shadow of the crosspiece 10c appears strongly on the light passing through the lens L5 at the center of the lens 4.
Therefore, if the crosspiece 10c of the filter 10 is not arranged on the lens arranged in the center portion of the light beam of the integrator lens, the influence of the shadow of the crosspiece 10c can be reduced. In the example of FIG. 6, it is desirable not to dispose the crosspiece 10c of the filter 10 on the lens L5 in the central portion of the integrator lens 4, that is, the lens through which the optical axis of the light beam passes (and / or the lens adjacent to the optical axis).
Although FIG. 6 shows a case where nine lenses L are arranged, as described above, the number of integrator lenses used in an actual light irradiation apparatus is larger. For example, as shown in FIG. 9, when the number of lenses L of the integrator 4 is 66 and the optical axis passes between the lenses L30, L31, L42, and L43, the lenses L30 and L31 adjacent to the optical axis. , L42, L43 so that the crosspiece 10c of the filter 10 is not applied.
As described above, the influence of the shadow of the crosspiece 10c can be reduced by preventing the crosspiece 10c of the filter 10 from being arranged on the lens through which the optical axis of the light beam passes (and / or the lens adjacent to the optical axis). Can do.

In the above-described embodiment, the example in which the filter is disposed on the light incident side of the integrator lens is shown, but the present invention can be applied to other cases.
FIG. 10 shows an example in which the filter 10 is arranged on the output side of the integrator lens 4. Other configurations are the same as those shown in FIG. 1, and the same configurations as those in FIG.
When the filter 10 of the present invention is disposed on the exit side of the integrator lens 4, if the distance from the integrator lens 4 is long, the shadow of the cross 10c of the frame 10b of the filter 10 is projected as it is onto the irradiated surface. However, if it is close to the output side of the integrator lens 4 and before the position where the light emitted from each lens overlaps (the side close to the integrator lens 4), the crosspiece 10c of the filter 10 is in the direction of the side of each lens L. By arranging them so as to be oblique and not parallel to the diagonal line of the lens, the same effect as shown in the above embodiment can be obtained.
That is, when the filter 10 is disposed near the exit side of the integrator lens 4 and the beam 10c is projected on the light incident / exit surface of each lens L in the optical axis direction, the shadow direction of each beam 10c is rectangular. The illuminance distribution on the surface to be irradiated by the shadow formed by the crosspiece 10c of the frame is arranged so as not to be parallel to each side of each lens L of the shape and not to be parallel to the diagonal of the rectangle of each lens. A decrease in uniformity can be prevented.

FIG. 11 shows an example in which the filter 10 of the present invention is disposed between both lens groups 4a and 4b when the integrator lens 4 is composed of a light incident side lens group 4a and a light emission side lens group 4b.
In a large light irradiation apparatus, in order to prevent an increase in cost due to an increase in the size of the integrator lens 4, the integrator lens 4 includes a lens group 4a on the light incident side and a lens on the light emission side as shown in FIG. In some cases, the group 4b may be divided. In such a case, it is conceivable to arrange the filter 10 between both lens groups. Even in such a case, the crosspiece 10c of the filter 10 is oblique to the direction of the side of each lens L constituting the integrator lens (the direction in which the lenses L are arranged) and is parallel to the diagonal line of the lens L. By arranging so that it does not become, the same effect as what was shown in the above-mentioned example can be given.

DESCRIPTION OF SYMBOLS 1a, 1b Lamp 2a, 2b Condenser mirror 3 1st reflective mirror 4 Integrator lens 5 2nd reflective mirror 6 Collimator lens 8 Irradiation surface 10 Filter 10a Filter board 10b Frame 10c Crosspiece 20 Shutter L1-L9 Lens H Light source

Claims (1)

A light source and an integrator lens that arranges a plurality of rectangular lenses side by side to make the light from the light source incident to make the illuminance distribution uniform on the light irradiation surface, and a specific wavelength range of the light emitted from the light source In the light irradiation device provided with a filter that transmits only the light of
The filter is configured by holding a plurality of filter plates by a frame and a crosspiece of the frame,
The light irradiation apparatus, wherein the crosspiece is disposed so as to be inclined with respect to a direction of a side of the plurality of lenses of the integrator lens and not parallel to a diagonal line of the lens.

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