JP6199591B2 - Light source apparatus and exposure apparatus - Google Patents

Description

  The present invention relates to a light source device for an exposure apparatus, and more particularly to a light source device and an exposure apparatus that use a plurality of array light sources having different wavelength characteristics.

  Conventionally, a lamp has been used as a light source of an exposure apparatus. Specifically, for example, in wiring pattern formation of printed circuit boards and solder resist film formation, spectral lines of 436 nm (g-line), 405 nm (h-line), 365 nm (i-line) are obtained from the sensitivity characteristics of the photosensitive material used. A strong mercury lamp was used as the light source. On the other hand, in recent years, a light source device that uses an LED as a light source instead of a mercury lamp has been developed in response to the demand for longer life of the light source and power saving. LEDs have the advantage of a longer life than mercury lamps, but on the other hand, the amount of light output by one LED element is smaller than that of mercury lamps, and the mercury lamps output broadband light including g-line, h-line, and i-line. On the other hand, since the LED outputs light with a specific narrow band wavelength, it cannot be used as it is as a light source for an exposure apparatus that requires broadband light.

  Therefore, a light amount equivalent to a mercury lamp is obtained by using an LED array light source composed of a large number of LEDs, and light having a plurality of wavelengths matching the sensitivity characteristics of the photosensitive material is obtained by using a plurality of LED array light sources having different wavelength characteristics. It has been proposed. In Patent Document 1, a lens array that forms an image of a light emitting portion of each LED element is overlaid on a plurality of LED array light sources having different wavelength characteristics, and a light emitting portion image is formed by superimposing condensed light beams from the lens array with a dichroic mirror. Is formed on the entrance surface of the integrator (light quantity uniformizing element).

  The projection exposure apparatus (stepper) of Patent Document 2 uses a light source device that combines light emitted from a plurality of LED array light sources having different wavelength characteristics using a dichroic mirror and forms an image on an incident surface of an integrator. In Patent Document 2, light from each LED element of the LED array light source enters the dichroic mirror as divergent light.

JP 2012-63390 A JP 2004-335949 A

  In general, it is known that a dichroic mirror shifts an edge wavelength at which light reflection and transmission are switched according to an incident angle of light. Further, when the wavelength difference between the transmitted light and the reflected light is small, there is a problem that the efficiency of using the light decreases due to the shift of the edge wavelength. Further, in Patent Document 1, an image of the LED array is formed at the integrator entrance, and light around the LED array is scattered at the entrance of the integrator, causing a light amount loss. Further, in the optical system in which the conjugate surface of the LED array is provided in the optical path as in Patent Document 1, the number of optical elements such as lenses increases, and as a result, a large space is required to install the light source device.

  In Patent Document 2, as the light emitted from the light source spreads, the area of the dichroic mirror increases, requiring a lot of space in the light source device. Further, in Patent Document 1 and Patent Document 2, since the optical path lengths from the LED array light sources to the first condenser lens incident position must be equal, the optical path length tends to increase as the number of LED arrays to be combined increases. There was more space needed. For this reason, these optical systems have a problem that they are larger than the lamp light source of the existing exposure apparatus and cannot be replaced with the light source of the existing exposure apparatus.

  The present invention has a small space loss exposure apparatus that can be used in place of a lamp light source of an existing exposure apparatus, with little light loss at the time of beam synthesis by a dichroic mirror (beam synthesis element), without the need to increase the size of the dichroic mirror. It aims at obtaining the light source device of.

  In the present invention, if light beams from a plurality of LED array light sources (array light sources) emitting different wavelengths are converted into parallel light beams and then incident on a dichroic mirror (light beam combining element), light loss is small and optical path length is not required. The present invention has been completed based on the viewpoint that a small light source device can be obtained.

A light source device according to the present invention includes a first array light source in which a plurality of light source elements that emit light having a first wavelength characteristic are arranged, and each light source element that makes the light having the first wavelength characteristic parallel light. A first lens array in which collimator lenses corresponding to the first lens array are arranged, a second array light source in which a plurality of light source elements that emit light having a second wavelength characteristic different from the first wavelength characteristic are arranged, and the second A second lens array in which collimator lenses corresponding to the respective light source elements are arrayed, and a light having a third wavelength characteristic different from the first and second wavelength characteristics. A third array light source in which a plurality of light source elements are arranged, a third lens array in which collimator lenses corresponding to the respective light source elements are arranged to make the light of the third wavelength characteristic parallel light, The first lens A first combined light beam is formed by combining the parallel light having the first wavelength characteristic formed by the ray and the parallel light having the second wavelength characteristic formed by the second lens array so as to share the principal ray axis. And the first synthesized light beam and the parallel light having the third wavelength characteristic formed by the third lens array are synthesized so as to share the principal ray axis. And a condenser lens for condensing the second synthesized light beam and making it incident on the light quantity uniformizing element, and the wavelength characteristics of the first array light source and the second array light source are either Is the longest wavelength, the other is the shortest wavelength, and the wavelength characteristic of the third array light source is an intermediate wavelength between the longest wavelength and the shortest wavelength .

  It is practical that the first optical combining element and the second optical combining element are constituted by first and second dichroic mirrors, respectively. At least one of the first and second dichroic mirrors is arranged so that the incident angle of the light beam from the first to third array light sources to the dichroic mirror is smaller than 45 °.

  More specifically, the incident angle of the light beam from the first array light source is 45 ° in the first dichroic mirror, and the incident angle of the light beam from the third array light source is 45 ° in the second dichroic mirror. It is good to arrange so that it may become small.

The profile of the energy distribution of the light beam incident on the incident surface of the light quantity uniformizing element continuously changes so that the central portion is high and the peripheral portion is low.

It is preferable that a large number of light source elements of the array light source are arranged in a grid pattern or a staggered pattern.

  In another aspect, the present invention is an exposure apparatus using the light source device described above.

  In the light source device of the present invention, the light emitted from the LED array light source (array light source) is incident on the dichroic mirror (light beam combining element) in a parallel light state, so that the loss due to the change in the incident angle due to the difference in the incident location is suppressed. Therefore, an efficient light source device can be realized. Furthermore, since the light beams are combined in the parallel light state, the dichroic mirror does not become large, and the optical path of the parallel light portion can be set to a free length, so even in an optical system that combines three or more array light sources. A space-saving light source device can be realized.

It is a block diagram which shows the whole structure of the exposure apparatus containing the light source device by this invention. It is an optical block diagram which shows 1st embodiment of the light source device by this invention. It is an optical block diagram which shows 2nd embodiment of the light source device by this invention. It is a top view which shows one Embodiment of a LED array light source. It is a top view which shows another embodiment of a LED array light source. It is a graph which shows light quantity distribution of the light which injects into the incident end surface of the rod integrator of an illumination optical system. It is a graph which shows the incident angle with respect to a dichroic mirror, and the transmittance | permeability (reflectance) characteristic. It is a graph which shows another incident angle with respect to a dichroic mirror, and the transmittance | permeability (reflectance) characteristic.

  FIG. 1 shows an entire exposure apparatus 10 including a light source device 11 targeted by the present invention. In FIG. 1, arrows indicate light, and straight lines indicate connection of control signals. The light emitted from the light source device 11 driven by the power supply device 12 enters the illumination optical system 13, and the light emitted from the illumination optical system 13 enters the pattern drawing unit 14. The pattern drawing means 14 irradiates the substrate W placed on the exposure table 15 with the light incident from the illumination optical system 13. A photosensitive material is applied or laminated on the substrate W. The power supply device 12, the pattern drawing unit 14, and the exposure table 15 are controlled by the control device 16.

  More specifically, the illumination optical system 13 includes an integrator (light amount equalizing element) that uniformizes the in-plane light amount distribution of light emitted from the light source device 11 such as a rod integrator, and is further suitable for the pattern drawing unit 14. Forming shaped illumination light. The pattern drawing unit 14 converts the illumination light incident from the illumination optical system 13 into pattern light for forming a pattern on the photosensitive material on the substrate W. The illumination optical system 13 may include a shutter, a light amount adjusting unit, and the like.

  For the pattern drawing unit 14, for example, a light modulation element such as DMD can be used, or a light blocking unit such as a reticle can be used. Further, a projection optical system for projecting the pattern light onto the photosensitive material may be further provided. A light shielding means such as a reticle can be brought close to or in contact with the photosensitive material. The pattern drawing unit 14 and the optical system associated therewith are appropriately designed according to the application of the exposure apparatus 10. The exposure table 15 may also serve as a substrate alignment unit, a substrate transfer unit, or the like as necessary. The shape and the like of the exposure table are designed in a timely manner according to the substrate.

  The present invention is applied to the light source device 11 of the exposure apparatus 10 configured as described above, for example, and FIG. 2 shows the first embodiment.

  The light source device 11 of this embodiment includes a first LED array light source 21 that oscillates light with a first wavelength characteristic (365 nm), a second LED array light source 22 that oscillates light with a second wavelength characteristic (405 nm), And a third LED array light source 23 that oscillates light having a wavelength characteristic of 3 (385 nm), and synthesizes light having these different wavelength characteristics in order from the upstream. The first to third LED array light sources 21, 22, and 23 have the same configuration except for the oscillation wavelength, a plurality of LED elements 21a that oscillate 365 nm light, and a plurality of LED elements 22a that oscillate 405 nm light, A plurality of LED elements 23a that oscillate 385 nm light are provided. In FIG. 2, for convenience of illustration, three LED elements 21a, 22a, and 23a are drawn side by side. However, in reality, a large number of these LED elements 21a, 22a, and 23a are arranged vertically and horizontally on the same plane. It has become. 4 and 5 show specific examples of the planar arrangement. In the example of FIG. 4, the LED elements 21a, 22a, and 23a are arranged vertically and horizontally in a lattice shape (matrix shape). In the example of FIG. Arranged vertically and horizontally. In the staggered arrangement, when the arrangement pitch of the LED elements 21a, 22a, and 23a in each row is p, the pitch of the LED elements 21a, 22a, and 23a is shifted by p / 2 in the upper and lower rows. This staggered arrangement can increase the density of the LED elements and suppress the loss of light taken in by the illumination optical system, compared to the lattice arrangement.

  On the first to third LED array light sources 21, 22, and 23, lens arrays 31, 32, and 33 are arranged to overlap each other. Each of the lens arrays 31, 32, and 33 includes a plurality of collimator lenses 31a, 32a, and 33a corresponding to the LED elements 21a, 22a, and 23a, each of which emits divergent light from the LED elements 21a, 22a, and 23a as a parallel light flux. ing. Strictly speaking, the LED element emits surface light, but since the light emitting area is sufficiently small with respect to the size of the optical system, it can be said to be substantially a point light source. Therefore, the light emitted from the LED element is collimated using a collimator lens. It can be made a luminous flux. The parallel light beam here does not have to be completely parallel light, but may have an angle with respect to the optical axis (for example, within 2 °) as long as it can be regarded as substantially parallel light. The planar arrangement of the collimator lenses 31a, 32a, and 33a is the same as the planar arrangement of the LED elements 21a, 22a, and 23a, and both are shown in FIGS. As is well known, the light from the light emitting portions of the LED elements 21a, 22a, and 23a is divergent light, whereas the collimator lenses 31a, 32a, and 33a are divergent light in units of the LED elements 21a, 22a, and 23a. Is a parallel light flux. That is, the optical axes of the LED elements 21a, 22a, and 23a that are converted into parallel light beams by the collimator lenses 31a, 32a, and 33a are parallel to each other and independent from each other, and are not in a shared relationship. For convenience of the following explanation, the center of the parallel light flux group formed by the first LED array light source 21 and the lens array 31, the second LED array light source 22 and the lens array 32, and the third LED array light source 23 and the lens array 33 is used. The optical axes are defined as main optical axes 21X, 22X, and 23X.

  On the main optical axis 21X of the first LED array light source 21, a first dichroic mirror 41, a second dichroic mirror 42, and a condenser lens 43 are arranged in this order. The rod integrator 13a is located. The incident angle of the main optical axis 21X with respect to the first dichroic mirror 41 (the angle between the main optical axis 21X and the normal of the incident surface of the mirror 41) is α, and the incident of the main optical axis 21X with respect to the second dichroic mirror 42 The angle (angle formed by the main optical axis 21X and the normal of the incident surface of the mirror 42) is β.

  The second LED array light source 22 is arranged so that the main optical axis 22X incident on the back surface of the first dichroic mirror 41 and reflected coincides with the main optical axis 21X, and the third LED array light source 23 is the second dichroic. The main optical axis 23X incident on the back surface of the mirror 42 and reflected is arranged so as to coincide with the main optical axis 21X (and the main optical axis 22X). The incident angle of the main optical axis 22X with respect to the first dichroic mirror 41 (the angle formed by the main optical axis 22X and the normal line of the back surface of the mirror 41) is γ. In this embodiment, α = γ = 45 °. It is. Further, the incident angle of the main optical axis 23X with respect to the second dichroic mirror 42 (the angle formed between the main optical axis 23X and the normal line of the back surface incident surface of the mirror 42) is δ. In this embodiment, β = δ = 25 ° (β = δ <45 °).

  The first dichroic mirror 41 has a characteristic of transmitting the wavelength characteristic light from the first LED array light source 21 and reflecting the wavelength characteristic light from the second LED array light source 22. The second dichroic mirror 42 has a characteristic of transmitting light having the wavelength characteristics from the first LED array light source 21 and the second LED array light source 22 while reflecting light having the wavelength characteristics from the third LED array light source 23. ing.

  That is, the first dichroic mirror 41 and the second dichroic mirror 42 are designed and manufactured as multilayer films in consideration of the installation angles α, β, γ, and δ so as to obtain the above transmission and reflection characteristics.

  Therefore, the first dichroic mirror 41 and the second dichroic mirror 42 described above are provided from the first LED array light source 21 and the lens array 31, the second LED array light source 22 and the lens array 32, and the third LED array light source 23 and the lens array 33. The parallel light beam group is synthesized, and the synthesized light is condensed by the condenser lens 43 onto the incident end face 13 b of the rod integrator 13 a of the illumination optical system 13. The rod integrator 13a is a well-known light quantity uniformizing element that emits light with a uniform in-plane light quantity distribution of an incident light beam.

  In the present embodiment, the light beam from the first LED array light source 21 incident on the first dichroic mirror 41 and the light beam from the second LED array light source 22, the light beam from the first LED array light source 21 incident on the second dichroic mirror 42, The luminous flux from the second LED array light source 22 and the luminous flux from the third LED array light source 23 are both parallel luminous flux (group). For this reason, light is incident at a fixed angle in any part of the first dichroic mirror 41 and the second dichroic mirror 42 (there is no variation in incident angle depending on the incident position of the light), and is transmitted or reflected through the dichroic mirror. The ratio of light to be fixed is constant. Therefore, by appropriately designing the reflection and transmission edge wavelengths of the dichroic mirror, it is possible to minimize light loss at the dichroic mirror.

  In the present embodiment, the upstream first dichroic mirror 41 combines light from the first LED array light source 21 having the shortest wavelength (365 nm) and light from the second LED array light source 22 having the longest wavelength (405 nm). Subsequently, light from the third LED array light source 23 having an intermediate wavelength (385 nm) is synthesized in the second dichroic mirror 42 on the downstream side. Since there is a large wavelength difference between the oscillation wavelength of the first LED array light source 21 and the oscillation wavelength of the second LED array light source 22, the first dichroic mirror 41 has a margin of edge wavelength for switching between transmission and reflection. It can be taken big. For this reason, the incident angles α and γ to the first dichroic mirror 41 are set to 45 ° with the smallest mirror area and the best arrangement efficiency. In contrast, in the second dichroic mirror 42, the wavelength difference between the transmission wavelength and the reflection wavelength is small. For this reason, when the incident angle δ is 45 °, a part of the light incident on the second dichroic mirror 42 from the third LED array light source 23 is transmitted without being reflected, resulting in poor efficiency. Therefore, in the embodiment of FIG. 2, the incident angle δ of the main optical axis 23X to the second dichroic mirror 42 is set to 25 °, the width of the edge wavelength for switching between transmission and reflection is made narrower (the slope of the edge is steep). I have to. Thus, the light use efficiency of the light source device is improved by appropriately setting the angle of the dichroic mirror according to the interval of the wavelengths of the light to be combined.

  7 and 8 are diagrams showing the incident angle θ to the dichroic mirror, the incident wavelength nm, and the switching wavelength (transmittance) between transmission and reflection. FIG. 7 shows that the edge wavelength of the dichroic mirror has a width of about 20 nm when used at 45 °. On the other hand, when used at 25 °, the width of the edge wavelength is about 10 nm (FIG. 8). Therefore, when the wavelength interval of the light to be combined is narrow as shown in FIG. 8, it is desirable that the angle of the dichroic mirror is reduced and the width of the edge wavelength is narrow. Further, when the light incident on the dichroic mirror is not parallel light and the incident angle varies depending on the position, the position of the edge wavelength is shifted as shown in FIG. Therefore, when the whole dichroic mirror is seen, the result is the same as the width of the edge wavelength is widened. For example, when the incident angle has a width of 9 °, the width of the edge wavelength is substantially expanded by about 10 nm to be about 30 nm (FIG. 7).

  Furthermore, in the present embodiment, the distance from the lens arrays 31, 32, 33 of the first to third LED array light sources 21, 22, 23 to the condenser lens 43 is parallel light, and the first to third LEDs There is no conjugate plane of the array light sources 21, 22, 23. Therefore, the optical path length between the first to third LED array light sources 21, 22, 23 and the condenser lens 43 can be set to an arbitrary distance. That is, since there is no restriction on the optical path length from the first LED array light source 21 to the condenser lens 43, from the second LED array light source 22 to the condenser lens 43, and from the third LED array light source 23 to the condenser lens 43, the optical path design is highly flexible. Equipment can be saved.

  FIG. 6 shows a light amount distribution of a light beam incident on the incident end face 13b of the rod integrator 13a of the illumination optical system 13. In the present embodiment, the relationship from the LED element to the incident end surface 13b of the rod integrator is the Koehler illumination. The light condensed by the condenser lens 43 on the incident end face 13b of the rod integrator 13a is parallel light from all the LED elements. Therefore, the light intensity distribution on the incident end face 13b of the rod integrator 13a has the highest energy density at the center. The profile is high and has a continuous profile in which the energy density decreases toward the periphery, and the shape is a Gaussian distribution with a high central portion and a low peripheral portion. For this reason, even if the incident aperture size of the rod integrator 13a is small, it is possible to take in a large amount of light into the illumination optical system 13 and increase the light utilization efficiency.

  FIG. 3 shows a light source device 11 of FIG. 2 in which a third dichroic mirror 44 is arranged on the main optical axis 23X of the third LED array light source 23, and the second dichroic mirror 44 4 shows an embodiment of four-wavelength synthesis in which a group of parallel light beams from a fourth LED array light source 24 and a lens array 34 that oscillate light having an intermediate wavelength (400 nm) are incident. The fourth LED array light source 24 includes a plurality of LED elements 24a (see FIGS. 4 and 5) that oscillate 400 nm light, and the lens array 34 uses each diverging light from each LED element 24a as a parallel light flux. A plurality of collimator lenses 34a corresponding to the element 24a are provided. The third dichroic mirror 44 has a characteristic of transmitting 385 nm light from the third LED array light source 23 and reflecting 400 nm light from the fourth LED array light source 24. The incident angle of the main optical axis 23X with respect to the third dichroic mirror 44 (the angle between the main optical axis 23X and the normal of the incident surface of the mirror 43) is ε, and the incident of the main optical axis 24X with respect to the third dichroic mirror 44 The angle (angle formed by the main optical axis 24X and the normal line of the back surface incident surface of the mirror 44) is η.

  In the above-described embodiment, the LED array light sources 21 to 24 are shown as the array light source. However, it is also possible to use a semiconductor laser array light source or an optical fiber array light source in which a semiconductor laser element and an optical fiber are bundled. Further, although the dichroic mirrors 41 to 43 are exemplified as the light beam combining element, a light beam combining element such as a dichroic prism can also be used.

DESCRIPTION OF SYMBOLS 10 Exposure apparatus 11 Light source apparatus 12 Power supply apparatus 13 Illumination optical system 13a Rod integrator 14 Pattern drawing means 15 Exposure table 16 Control apparatus 21 1st LED array light source 22 2nd LED array light source 23 3rd LED array light source 24 4th LED array light source 21X 22X 23X 24X Optical axis 21a 22a 23a 24a LED element (light source element)
31 32 33 34 Lens array 31a 32a 33a 34a Collimator lens 41 First dichroic mirror 42 Second dichroic mirror 43 Condenser lens 44 Third dichroic mirror

Claims (4)

A first array light source in which a plurality of light source elements that emit light having a first wavelength characteristic are arranged;
A first lens array in which collimator lenses corresponding to the respective light source elements are arranged to make the light of the first wavelength characteristic parallel light,
A second array light source in which a plurality of light source elements that emit light having a second wavelength characteristic different from the first wavelength characteristic are arranged;
A second lens array in which collimator lenses corresponding to the respective light source elements are arranged to make the light of the second wavelength characteristic parallel light,
A third array light source in which a plurality of light source elements that emit light having a third wavelength characteristic different from the first and second wavelength characteristics are arranged;
A third lens array in which collimator lenses corresponding to the respective light source elements are arranged to make the light of the third wavelength characteristic parallel light,
The parallel light of the first wavelength characteristic formed by the first lens array and the parallel light of the second wavelength characteristic formed by the second lens array are combined so as to share the principal ray axis. A first optical combining element that is a first combined luminous flux;
A second optical combining element that combines the first combined light beam and the parallel light having the third wavelength characteristic formed by the third lens array so as to share the principal ray axis, and forms a second combined light beam;
A condenser lens that collects the second synthesized light beam and makes it incident on the light quantity uniformizing element;
Equipped with a,
One of the wavelength characteristics of the first array light source and the second array light source is the longest wavelength, the other is the shortest wavelength, and the wavelength characteristic of the third array light source is an intermediate wavelength between the longest wavelength and the shortest wavelength. A light source device characterized by that.   2. The light source device according to claim 1, wherein the first optical combining element and the second optical combining element are first and second dichroic mirrors, respectively, and at least one of the first and second dichroic mirrors is the dichroic mirror. A light source device arranged so that an incident angle of light beams from the first to third array light sources is smaller than 45 °.   3. The light source device according to claim 2, wherein the first dichroic mirror has an incident angle of light flux from the first array light source of 45 °, and the second dichroic mirror has an incident angle of light flux from the third array light source. A light source device arranged to be smaller than 45 °. An exposure apparatus using the light source device according to any one of claims 1 to 3 .

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