JP7340167B2 - Illumination optical system, exposure equipment, and device manufacturing method - Google Patents

Description

The present invention relates to an illumination optical system, an exposure apparatus, and a device manufacturing method.

Exposure apparatuses used in the manufacturing process of semiconductor devices, flat panel displays, MEMS (microelectromechanical systems), and the like are known.

In recent years, a solid-state ultraviolet light source using gallium nitride or the like has been developed, and it has been proposed to apply this type of solid-state ultraviolet light source to an illumination device of an exposure apparatus (see, for example, Patent Document 1). In solid-state ultraviolet light sources, the absolute value of the amount of light emitted by each chip is not very large. Therefore, in order to obtain the required high illuminance on the irradiated surface, it is necessary to combine the light from the plurality of chips and guide it to the illumination device. At this time, the lighting device is required to have high illuminance uniformity over the entire area on the predetermined surface through which the illumination light passes.

US Patent Application Publication No. 2005/0219493A1

In the first form, in the illumination optical system that illuminates the illuminated surface,
a first light emitting section that emits first illumination light from a first light emitting surface;
a second light emitting section that emits second illumination light from a second light emitting surface arranged at a distance from the first light emitting surface;
a light collecting member having a first light collecting part that collects the first illumination light from the first light emitting surface and a second light collecting part that collects the second illumination light from the second light emitting surface;
At least a portion of the first illumination light that has passed through the first light condensing section and the second illumination light that has passed through the second light condensing section is converted into a conjugate surface that is optically conjugate with the irradiated surface or a conjugate surface that is optically conjugate with the irradiated surface. To provide an illumination optical system characterized by comprising a relay optical system for superimposing planes.

In a second embodiment, an exposure apparatus is provided, comprising the illumination optical system of the first embodiment for illuminating a predetermined pattern installed on the irradiated surface, and exposing the predetermined pattern onto a substrate. .

In a third form, using the exposure apparatus of the second form, exposing the predetermined pattern to the substrate;
developing the substrate onto which the predetermined pattern has been transferred, and forming a mask layer having a shape corresponding to the predetermined pattern on the surface of the substrate;
There is provided a device manufacturing method characterized by comprising: processing the surface of the substrate through the mask layer.

1 is a diagram schematically showing the configuration of an exposure apparatus according to an embodiment. 2 is a diagram schematically showing the internal configuration of the illumination optical system in FIG. 1. FIG. FIG. 6 is a diagram showing how images of a plurality of light emitting surfaces are formed near the light emitting end of a lens element. FIG. 3 is a diagram showing radiation angle characteristics of an LED light source. The chip and the collector lens are shown as viewed from the exit end of the lens element. FIG. 7 is a diagram showing a numerical example in which a plurality of collector lenses are arranged almost densely. It is a figure which shows schematically the modification using a lens array. FIG. 7 is a diagram schematically showing a modification example in which light from a light source is guided by a light guide. FIG. 7 is a diagram schematically showing a modification example in which modified illumination is performed using a diffractive optical element. FIG. 7 is a diagram schematically showing a modification in which a fly-eye lens is omitted. FIG. 3 is a diagram showing a state in which a plurality of chips are lit in a circular shape. FIG. 3 is a diagram illustrating a state in which a plurality of chips are lit in an annular shape. 3 is a flowchart showing a manufacturing process of a semiconductor device. 1 is a flowchart showing a manufacturing process of a liquid crystal device such as a liquid crystal display element.

Embodiments will be described below based on the accompanying drawings. FIG. 1 is a diagram schematically showing the configuration of an exposure apparatus according to an embodiment. In FIG. 1, the Z-axis is in the normal direction of the image plane of the projection optical system PL (that is, the direction of the optical axis AX of the projection optical system PL: the vertical direction in the plane of the paper in FIG. 1), and the Z-axis is in the image plane of the projection optical system PL. The X-axis is set parallel to the paper surface of FIG. 1, and the Y-axis is set perpendicular to the paper surface of FIG. 1 within the image plane of the projection optical system PL.

Referring to FIG. 1, the exposure apparatus of this embodiment includes an illumination optical system IL that illuminates a mask (reticle) M on which a pattern to be transferred is formed. The internal configuration of the illumination optical system IL will be described later with reference to FIG. 2. The illumination optical system IL illuminates, for example, the entire rectangular pattern area of the mask M, or an elongated slit-shaped area (for example, a rectangular area) along the X direction in the entire pattern area.

Light from the pattern of the mask M passes through the projection optical system PL to form a pattern image of the mask M on a unit exposure area of the substrate W coated with a photosensitive resist. That is, in the unit exposure area of the substrate W, a rectangular area similar to the entire pattern area of the mask M, or a rectangular area elongated in the X direction ( A mask pattern image is formed in the static exposure area).

The substrate W is a single crystal wafer of silicon or the like in the case of a semiconductor exposure apparatus, and is a glass plate called a plate in the case of a liquid crystal exposure apparatus. The mask M is made of a light-transmitting member, and the pattern formed on its surface has a shape necessary for forming a semiconductor element or a liquid crystal display element. In particular, when using the optical proximity effect, the image formed on the substrate W and the pattern formed on the mask M do not necessarily have similar shapes depending on the magnification of the projection optical system PL. do not have.

Mask M is held substantially parallel to the XY plane on mask stage MS. The mask stage MS has a built-in mechanism for moving the mask M in the X direction, the Y direction, the rotation direction around the Z axis, and the like. The substrate W is held substantially parallel to the XY plane on the substrate stage WS. The substrate stage WS has a mechanism for moving the substrate stage WS (and thus the substrate W) in the X direction, the Y direction, the Z direction, the rotation direction around the X axis, the rotation direction around the Y axis, and the rotation direction around the Z axis. It has been incorporated.

In the step-and-repeat method, a pattern image of the mask M is exposed all at once to one unit exposure area among a plurality of unit exposure areas set vertically and horizontally on the substrate W. After that, the control system CR positions another unit exposure area of the substrate W with respect to the projection optical system PL by moving the substrate stage WS in steps along the XY plane. In this way, the operation of exposing the pattern image of the mask M onto the unit exposure area of the substrate W at once is repeated.

In the step-and-scan method, the control system CR moves the pattern image of the mask M onto the substrate W while moving the mask stage MS and the substrate stage WS in the Y direction at a speed ratio according to the projection magnification of the projection optical system PL. One unit exposure area is scanned and exposed. After that, the control system CR positions another unit exposure area of the substrate W with respect to the projection optical system PL by moving the substrate stage WS in steps along the XY plane. In this way, the operation of scanning and exposing the pattern image of the mask M onto the unit exposure area of the substrate W is repeated.

That is, in the step-and-scan method, the mask stage MS and the substrate stage WS, and furthermore the mask M and the substrate W, are moved along the Y direction, which is the short side direction of a rectangular (generally slit-shaped) stationary exposure area. By moving (scanning) synchronously, an area on the substrate W having a width equal to the long side of the stationary exposure area and a length corresponding to the scanning amount (movement amount) of the substrate W is formed. The mask pattern is scanned and exposed.

Referring to FIG. 2, the illumination optical system IL of this embodiment includes an LED (Light Emission Diode) light source 1 as a solid-state light source. The LED light source 1 includes a plurality of light emitting parts arranged at intervals in the vertical and horizontal directions. Each light emitting section has a solid state light emitting element 1a that emits illumination light from a light emitting surface. In the following description, the solid state light emitting device 1a having a light emitting surface will be referred to as a chip 1a. However, in FIG. 2 and related figures, in order to make the explanation easier to understand and the drawings clearer, the LED light source 1 has a total of six chips, two rows in the X direction and three rows in the Y direction. 1a, and its light emitting surface is circular. Note that the light emitting surface in this embodiment can be the surface of the chip 1a from which light is emitted.

Illumination light emitted from the light emitting surfaces of the six chips 1a is focused by six collector lenses 2 arranged to correspond to the respective chips 1a, and then sent to the fly-eye lens 4 via the relay lens 3. incident. Each collector lens 2 is arranged so that its front focal position substantially coincides with the position of the light emitting surface of the corresponding chip 1a. Furthermore, the front focal position of the relay lens 3 substantially coincides with the plane on which the rear focal position of each collector lens 2 is located. Each collector lens 2 is arranged so that its optical axis is substantially parallel to the optical axis of the relay lens 3 (and thus the optical axis AXi of the illumination optical system IL).

The fly's eye lens 4 is an optical integrator having a large number of lens elements (wavefront splitting elements) 4a arranged in parallel. In FIG. 2 and related figures, in order to facilitate understanding of the explanation and clarify the drawings, the fly-eye lenses 4 are arranged in five rows in the X direction and in three rows in the Y direction, as shown in FIG. There are a total of 15 lens elements 4a, and each lens element 4a has a rectangular cross section elongated in the X direction. Further, it is assumed that the 15 lens elements 4a are densely arranged, and the cross section of the fly's eye lens 4 is approximately square.

Therefore, as shown by the thin solid line in FIG. 2, the light emitted from the center of the light emitting surface of each chip 1a passes through the corresponding collector lens 2 and becomes a substantially parallel light beam, leading to a path substantially parallel to the optical axis AXi. It enters the relay lens 3 along the line. The six substantially parallel light beams incident on the relay lens 3 are converged on the incident side surface of the fly's eye lens 4 located near the rear focal position.

As shown by the broken line in FIG. 2, the light emitted from the end of the light emitting surface of each chip 1a in a direction approximately parallel to the optical axis of the collector lens 2 (and in turn approximately parallel to the optical axis AXi of the illumination optical system IL) is emitted from the end of the light emitting surface of each chip 1a. After converging near the rear focal plane of the lens 2, the light is projected onto the incident side surface of the fly's eye lens 4 located near the rear focal plane by the action of the relay lens 3. In this way, the illumination light from each chip 1a passes through the corresponding collector lens 2 and relay lens 3, and is superimposed on the incident side surface of the fly's eye lens 4.

That is, the images of the circular light emitting surfaces of each chip 1a of the LED light source 1 are formed so as to substantially overlap each other on the incident side surface of the fly's eye lens 4. At this time, the light emitting surface of each chip 1a of the LED light source 1 is enlarged and projected by the action of the collector lens 2 and the relay lens 3 to a size that covers the effective area of the incident side surface of the fly's eye lens 4.

Each lens element 4a is configured such that the focal position of its entrance side surface substantially coincides with the position of its exit surface, and the focal position of its exit surface substantially coincides with the entrance surface. Further, each lens element 4a is arranged so that its optical axis is substantially parallel to the optical axis AXi of the illumination optical system IL. The light flux incident on the fly's eye lens 4 is wavefront-divided by a plurality of lens elements 4a, and as shown in FIG. An image 21 of the light emitting surface is formed.

In FIG. 3, it is assumed that the illumination light from each chip 1a is superimposed over a region covering the entire incident side surface of the illustrated 15 lens elements 4a. Actually, as described above, a circular illumination field centered on the optical axis AXi is formed on the inside of the substantially square entrance side surface of the fly's eye lens 4. In order to correspond to the circular illumination field formed on the incident side surface, a large number of small light sources 21 are distributed at the output end of the fly's eye lens 4 within a circular area centered on the optical axis AXi. is formed.

The light flux that has passed through the plurality of lens elements 4a of the fly-eye lens 4 illuminates the mask M via the aperture stop 5 and the condenser lens 6, which are arranged near the exit end. The condenser lens 6 is arranged so that its front focal position approximately coincides with the position of the exit end of the fly's eye lens 4, and its rear focal position approximately coincides with the position of the pattern surface of the mask M. That is, the incident side surface of each lens element 4a and the pattern surface of the mask M are arranged to be optically substantially conjugate. The aperture diaphragm 5 has, for example, a circular aperture (light transmitting portion) centered on the optical axis AXi. Here, the surface on which the aperture stop 5 is arranged is optically conjugate with the surface on which a projection aperture stop (not shown) for determining the numerical aperture of the projection optical system PL is arranged.

Further, the image of the aperture stop 5 viewed from the exit side of the illumination optical system IL is the exit pupil of the illumination optical system, and the aperture stop 5 is arranged at a position optically conjugate with the exit pupil of the illumination optical system. The surface that is visible can be called the illumination pupil. In this illumination pupil, a secondary light source (generally, a predetermined light intensity distribution in the illumination pupil) is formed as a substantial surface light source consisting of a large number of light emitting parts by the plurality of lens elements 4a of the fly's eye lens. Ru. In other words, the light from the plurality of lens elements 4a of the fly's eye lens 4 is distributed to the illumination pupil. The illumination pupil is a position where the illumination surface becomes the Fourier transform plane of the illumination pupil due to the action of the optical system between the illumination pupil and the illuminated surface (mask or wafer in the case of exposure equipment). may be defined.

In addition, when the number of wavefront divisions (the number of lens elements 4a) by the fly-eye lens 4 is relatively large, the global light intensity distribution formed on the incident surface of the fly-eye lens 4 and the global light intensity distribution of the entire secondary light source It shows a high correlation with the light intensity distribution (pupil intensity distribution). Therefore, the light intensity distribution on the entrance surface of the fly's eye lens 4 and the surface optically conjugate with the entrance surface may also be referred to as the pupil intensity distribution.

The light beams from the plurality of lens elements 4a of the fly's eye lens 4 are restricted by the aperture of the aperture stop 5, and then illuminate the mask M in a superimposed manner via the condenser lens 6. As a result, an elongated rectangular illumination area is formed on the pattern surface (illuminated surface) of the mask M along the X direction. In this way, the lights divided by the incident side surface of the fly's eye lens 4 are projected through the condenser lens 6 so that they almost overlap each other in the illumination area of the mask M, and the illuminance in the illumination area is averaged. be exposed.

In this embodiment, the range expressed as the vicinity does not indicate the depth of focus (1/2) × (λ/NA ² ) by the numerical aperture NA of the imaging light beam, where the wavelength of light is λ. It shows a range of approximately 2×(λ/NA ² ) in which the decrease in light amount due to the spread of the illumination light beam is negligible. In the case of the LED light source 1, each chip 1a as a light emitting part is considered to be an almost completely diffused light source, as shown in FIG. In FIG. 4, the radial direction corresponds to the radiation intensity of light, and the azimuth (direction of rotation around the origin) corresponds to the radiation angle of light.

Therefore, the illuminance of the light that travels obliquely at an angle θ from each chip 1a is cosθ times the illuminance of the light that travels in the normal direction at an angle 0 from the light emitting surface of each chip 1a. That is, in order to take in the light from each chip 1a as efficiently as possible, it is necessary to use the collector lens 2 to take in light that is largely tilted from the normal to the light emitting surface of each chip 1a. However, when the collector lens 2 takes in the light that is highly tilted, the amount of peripheral light of the light flux that has passed through the collector lens 2 is attenuated by cos θ compared to the amount of light at the center.

For example, if the incident side surface of the fly's eye lens 4 is configured to be illuminated according to the prior art disclosed in U.S. Patent Application Publication No. 2005/0219493A1, the amount of peripheral light on the incident side surface of the fly's eye lens 4 is A non-uniform illuminance distribution is formed in which the amount of light is attenuated by cosθ compared to the central light amount. In this case, in the fly's eye lens 4, the incident light beam is divided by the plurality of lens elements 4a and overlapped on the irradiated surface, so even if the illuminance distribution of the incident light beam on the fly's eye lens 4 is uneven, At the top, a nearly uniform illuminance distribution can be obtained.

However, the light beam divided by the fly's eye lens 4 passes through each lens element 4a and reaches the output end of the fly's eye lens 4. Since the output end of the fly-eye lens 4 is placed near the front focal point of the condenser lens 6, the state of the light intensity distribution at the output end of the fly-eye lens 4 and the angular light intensity of the light beam illuminating the mask M can be controlled. This corresponds to the state of the distribution. In other words, due to the uneven light intensity distribution in which the peripheral light intensity is smaller than the center light intensity at the exit end of the fly-eye lens 4, the incident light beam illuminating the mask M has a higher incidence than the vertically incident light at an incident angle of 0 degrees. Nonuniform irradiation angle characteristics in which the intensity of light with a larger angle is lower are obtained. Here, the irradiation angle characteristic can be said to be the uniformity of light intensity with respect to the incident angle of illumination light.

In the exposure apparatus, an aperture stop 5 is provided near the exit end of the fly's eye lens 4 to limit the angular range of the illumination light beam. In order to resolve finer patterns, it is necessary to introduce diffracted light with a larger diffraction angle into the projection optical system PL. The diffraction angle of the diffracted light due to light from the periphery of the illumination light beam is the maximum diffraction angle that can be taken in, so if the intensity of the light at the periphery of the angular distribution of the illumination light (light with a large incident angle) is weak, a fine pattern of diffracted light will be generated. There is a problem in that the intensity is weak and sufficient contrast cannot be obtained.

Furthermore, when performing modified illumination, the aperture of the aperture stop 5 may be formed into a ring shape in order to make the light intensity distribution in the illumination pupil into a ring shape. In this case as well, it is desirable that the irradiation angle characteristics of the illumination light to the irradiated surface be uniform in order to minimize the decrease in the amount of light. In this embodiment, the image of the light emitting surface of each chip 1a, which is considered to be an almost completely diffused light source, is projected onto the incident side surface of the fly's eye lens 4 so as to almost overlap with each other, so that the light enters the fly's eye lens 4. It is possible to make the light quantity distribution of the luminous flux substantially uniform, and in turn, it is possible to make the irradiation angle characteristics of the illumination light onto the irradiated surface substantially uniform.

Except in special cases, when forming a pattern with an exposure device, it is undesirable for the resolution to differ depending on the direction of the pattern. Therefore, it is desirable that the aperture of the aperture stop 5 is rotationally symmetrical about the optical axis AXi so that the angular range of the illumination light beam does not have azimuth dependence. Here, the term ``no azimuth dependence of the angular range of the illumination luminous flux" means that the angular range of the illumination luminous flux on the plane that includes the principal ray (meridional plane) varies when the meridional plane is rotated about the principal ray. It can be said that the angle is also constant. In the case of normal illumination in which the illumination light flux is limited to a predetermined aperture angle, the aperture of the aperture stop 5 is circular. When the light emitting surface of each chip 1a is rectangular, the aperture stop 5 is arranged so that the circular opening is almost inscribed in the rectangular illumination field formed at the output end of the fly's eye lens 4. Become.

Here, since the light incident on the outside of the circular opening cannot pass through the aperture stop 5, the light blocked by the aperture stop 5 does not contribute to illumination and results in a loss of light quantity. Even if the circular aperture is arranged so as to be completely inscribed in the square illumination field, more than 20% of the light cannot pass through the aperture stop 5. If the light-emitting surface of the chip 1a, which is the light-emitting part of the LED light source 1, is circular when viewed from the optical axis AXi direction, it will be similar to the circular shape of the aperture of the aperture stop 5, and light will be emitted from each chip 1a. Light loss can be minimized.

By increasing the number of pairs of the chip 1a of the LED light source 1 and the collector lens 2, it is possible to increase the illuminance on the patterned surface of the mask M, which is the irradiated surface (and thus on the exposed surface of the substrate 1). However, in the fly-eye lens 4, light emitted from a lens element 4a different from (for example, adjacent to) the lens element 4a into which the light has entered is largely bent and is not captured by the condenser lens 6, or even if it is captured, it does not illuminate the lens element 4a. It ends up reaching outside the area. Therefore, the light emitted from the chip 1a of the LED light source 1 needs to enter the exit surface of the lens element 4a of the fly's eye lens 4.

That is, as shown in FIG. 5, the light emitting surface of each chip 1a of the LED light source 1 and each collector lens 2 are such that the light emitting end of the lens element 4a of the fly's eye lens 4 is projected by the fly's eye lens 4 and the relay lens 3. It must be located within the specified range. FIG. 5 shows each chip 1a and each collector lens 2 of the LED light source 1 as viewed from the output end of the lens element 4a.

In FIG. 5, a rectangular region 4aa indicated by a two-dot chain line indicates a range in which the output end of the fly's eye element 4 is projected by the fly's eye lens 4 and the relay lens 7. Each chip 1a of the LED light source 1 and each collector lens 2 must be included within the rectangular area 4aa. More precisely, each spot of light from the light emitting surface of each chip 1a formed at the rear focal position of each collector lens 2 is formed by the light emitting end of the fly's eye element 4 formed by the fly's eye lens 4 and the relay lens 7. It must be within the projected range 4aa.

In order to effectively take in the light from each chip 1a of the LED light source 1, the effective diameter of each collector lens 2 is larger than the effective diameter of each chip 1a. In the LED light source 1, the plurality of chips 1a are not in contact with each other. As a result, better cooling efficiency can be achieved by passing the cooling medium (cooling liquid) for cooling each chip 1a of the LED light source 1 not only through the back side of the chip 1a but also through the front side other than the light emitting surface. It is possible to obtain.

Hereinafter, with the image-side numerical aperture of the projection optical system PL 0.8 and the illumination coherence factor (σ value) 0.8, one pattern of the mask M is applied to a rectangular unit exposure area of 30 mm x 10 mm on the substrate W. A numerical example will be shown when applied to the illumination optical system IL of an exposure apparatus that performs reduction exposure at a magnification of /4. In order to carry out reduction exposure at a magnification of 1/4, an illumination area having four times the size of the unit exposure area, that is, a rectangular illumination area of 120 mm x 40 mm, is required on the mask M. The pattern area on the mask M is set to be slightly smaller than the illumination area, taking into account installation errors of the mask M and the like.

Since the coherence factor of illumination is 0.8, the numerical aperture of 0.8 on the substrate W is multiplied by the magnification 1/4 and the coherence factor of illumination 0.8, which is the value obtained by multiplying the numerical aperture of 0.16 ( It is necessary to irradiate the illumination area of the mask M with light of uniform intensity over an angular range of 9.2° (converted to an angle of 9.2°). As an example, the focal length of the collector lens 2 can be 400 mm, and the inner diameter (diameter) of the circular opening of the aperture stop 5 can be 128 mmφ.

The focal length of the fly's eye lens 4 can be 20 mm, and the cross-sectional shape of the lens element 4a can be a rectangle of 6 mm x 2 mm. The cross-sectional size of the lens element 4a of 6 mm x 2 mm is the same as the size of an illumination area of 120 mm x 40 mm on the mask M projected by the relay lens 6 and the fly's eye lens 4. Since the fly's eye lens 4 needs to fill at least the inner region of the circular opening of the aperture stop 5, it is constituted by, for example, 22 stages x 64 stages of lens elements 4a.

The focal length of the condenser lens 3 is 400 mm, the focal length of the collector lens 2 is 3 mm, and the light from the chip 1a having a circular light emitting surface with a diameter of 1 mm in the LED light source 1 is transmitted to the incident side surface of the fly's eye lens 4. The image is enlarged and projected onto a circular area with a diameter of 133 mmφ. At this time, in the fly's eye lens 4, it is necessary that the illumination light illuminates the entire surface of the lens element 4a, which corresponds to the outermost periphery of the circular opening of the aperture stop 5. The light incident on the partial area of the lens element 4a corresponding to the outside of the circular opening of the aperture stop 5 does not contribute to illumination and results in a loss of light quantity, but in order to maintain the uniformity of the irradiation angle characteristics of the illumination light. This is a necessary loss.

If the collector lens 2 attempts to take in light in the range up to 0.8 in terms of numerical aperture (light in the range up to 53.1 degrees in angle) out of the light from the chip 1a, the collector lens 2 will capture at least 5.8 degrees in numerical aperture. A diameter of 8mmφ is required. Actually, the collector lens 2 needs to have a diameter of about 8 mmφ for aberration correction. The set of the chip 1a and the collector lens 2 must fall within a range 4aa of 120 mm x 40 mm, which is the projection of the output end of the 6 mm x 2 mm lens element 4a by the fly's eye lens 4 and the relay lens 3.

As shown in FIG. 6, a maximum of 73 collector lenses 2 each having a diameter of 8 mmφ can be arranged in a projection range 4aa of 120 mm×40 mm. When the output per chip 1a is 1W, the light output from the 73 chips 1a of the LED light source 1 is 73W. Since the take-in angle of the collector lens 2 is 0.8 in terms of numerical aperture, the take-in efficiency is 0.8 squared, which is 64%.

The optical surface of the illumination optical system IL is calculated by multiplying the area ratio of the aperture of the aperture stop 5 to the illumination field formed on the incident side surface of the fly-eye lens 4 and dividing the capture efficiency of 64% by the area of the illumination region by multiplying the light output by 73W. The illuminance can be calculated by ignoring the effects of reflection on the glass and absorption of light by the glass material. When the above calculation is performed, an illuminance of 14.35 W/cm ² is obtained in a unit exposure area of the substrate W. Assuming that the loss of light amount due to reflection on the optical surfaces of the illumination optical system IL and the projection optical system PL and absorption by the glass material is about 70%, an illuminance of 10 W/cm ² can be obtained in a unit exposure area of the substrate W.

As described above, in the illumination optical system IL of this embodiment, light from the light emitting surfaces of the plurality of chips 1a is focused by the plurality of collector lenses 2 having optical axes substantially parallel to each other. Then, the light beams that have passed through the plurality of collector lenses 2 are superimposed by the relay lens 3 on the incident side surface of the fly's eye lens 4, which is located at a position that is almost optically conjugate with the pattern surface of the mask M, which is the irradiated surface. , the light beams from the light emitting surfaces of the plurality of chips 1a are combined.

In other words, the image of the light emitting surface of each chip 1a is projected onto the incident side surface of the fly's eye lens 4 so as to substantially overlap. As a result, the distribution of the amount of light incident on the fly's eye lens 4 can be made substantially uniform. Note that the incident side surface of the fly's eye lens 4 can be regarded as a region on a predetermined surface through which illumination light passes.

Then, the illuminance distribution of the illumination light that enters the patterned surface of the mask M, which is the irradiated surface, can be made substantially uniform, and the irradiation angle characteristics of the illumination light that enters the patterned surface can be made substantially uniform. That is, in this embodiment, it is possible to achieve high illumination intensity in the illumination area by combining the light fluxes from the light emitting surfaces of the plurality of chips 1a while achieving uniformity of illuminance and uniformity of irradiation angle characteristics in the illumination area on the mask M. I can do it.

In the embodiment described above, the same number of collector lenses 2 as chips 1a are individually arranged to correspond to the plurality of chips 1a arranged at intervals. However, without being limited thereto, instead of the plural collector lenses 2 arranged individually, a lens array 12 in which a plurality of lenses 12a are formed on a single light-transmissive substrate as shown in FIG. 7 may be used. May be used. That is, a modification example in which a plurality of collector lenses 2 in the embodiment of FIG. 2 are integrally formed is possible.

In general, the collector lens 2 in the embodiment of FIG. 2 functions as a light condensing section that condenses illumination light from the light emitting surface of the corresponding chip 1a. As this condensing section, not only a lens having a refractive effect but also a mirror having a reflecting effect, a diffractive optical element having a diffractive effect, etc. can be used. Further, a light collecting member in which a plurality of light collecting parts are individually provided, or a light collecting member in which a plurality of light collecting parts are integrally formed can be used.

Since the chip 1a, which is the light emitting part, is formed on the substrate by a semiconductor process, its positional accuracy is extremely high. On the other hand, when the number of chips 1a to be synthesized increases, it is difficult to arrange a large number of collector lenses 2 while aligning their optical axes. Therefore, a light condensing member such as the lens array 12 in which multiple light condensing parts are integrally formed is also manufactured with high precision using a semiconductor process, and alignment marks are placed on both the LED light source 1 and the lens array 12. By providing these alignment marks and overlapping these alignment marks, there is an advantage that positioning work of a large number of light condensing parts with respect to a large number of chips 1a is facilitated.

In the embodiment described above, the illumination light from each chip 1a is transmitted through the corresponding collector lens 2 and relay lens 3 to a fly's eye that is arranged to be optically almost conjugate with the patterned surface of the mask M, which is the irradiated surface. They are superimposed on the incident side surface of the lens 4. That is, a conjugate surface that is optically conjugate with the patterned surface of the mask M, which is the irradiated surface, substantially coincides with the incident side surface of the plurality of lens elements 4a of the fly's eye lens 4. However, without being limited thereto, the conjugate surface may be positioned between a relay lens (relay optical system) and a condenser lens (condenser optical system), and the illumination light from a plurality of light emitting surfaces may be directed to the conjugate surface. They may be configured to at least partially overlap.

In other words, regarding the optical system consisting of each collector lens 2 and relay lens 3, there is a conjugate surface that has an optically conjugate relationship with the light emitting surface of each chip 1a, and a surface on the incident side of the plurality of lens elements 4a of the fly eye lens 4. The positional relationship in the optical axis direction may not be the same as that of the optical axis. At this time, on the incident side surfaces of the plurality of lens elements 4a of the fly's eye lens 4, the illumination lights from the plurality of light emitting surfaces partially overlap. Here, by changing the above-mentioned positional relationship, the illuminance distribution on the incident side surface of the plurality of lens elements 4a of the fly's eye lens 4 can be changed.

In the embodiment described above, the LED light source 1 is used as the light source. However, the present invention is not limited thereto, and a light source having a plurality of light emitting parts arranged at intervals, such as a semiconductor laser array, can be used. Further, as shown in FIG. 8, a modification example is also possible in which light from a semiconductor laser (laser diode) 21 is made to enter an optical fiber (light guide) 23 through an input lens 22 and guided. In the modification shown in FIG. 8, the exit surfaces 23a of the plurality of optical fibers 23 are used as secondary light sources and are arranged near the front focal position of the collector lens 2. That is, the emission surfaces 23a of the plurality of optical fibers 23 in the modified example of FIG. 8 correspond to the emission surfaces of the plurality of chips 1a in the embodiment of FIG. The emission surface 23a as a light emitting surface has a shape such as a circle, a rectangle, or a polygon, as necessary. Note that the fiber core portion of the exit surface 23a of the plurality of optical fibers 23, that is, the portion from which light is emitted may be used as the light emitting surface.

Although FIG. 8 shows an example in which the light from the semiconductor laser 21 is guided to the optical fiber 23 by the input lens 22, various configurations are possible for the specific configuration in which the light from the semiconductor laser 21 is guided to the optical fiber 23. be. Furthermore, the light source 21 in the modified example of FIG. 8 is not limited to a semiconductor laser, and a solid state light emitting device such as a fiber laser or an LED can be used. When using an optical fiber (light guide), the light source placed in front of the optical fiber can be placed any distance apart, so the advantage is that sufficient cooling measures can be taken for the light emitting part. There is.

When a solid-state ultraviolet light source is used as in the embodiment described above, it has the advantage of a longer life than a conventional ultra-high pressure mercury lamp. Further, since there is no problem that the lamp can be replaced only after cooling, there is an advantage that the operating time of the device can be extended. Further, solid-state ultraviolet light sources have a higher light conversion efficiency than mercury lamps, and have the advantage of being able to reduce the amount of power used.

In the embodiment described above, the light from the circular light emitting surfaces of the plurality of chips 1a is superimposed on the incident side surface of the fly's eye lens 4 to form a circular illumination field. However, without being limited to this, a modification example in which the diffractive optical element 24 is arranged so as to be inserted into the optical path between the plurality of collector lenses 2 and the relay lens 3 is also possible, as shown in FIG. In FIG. 9, by arranging a diffractive optical element 24 as a deflecting member that changes the angle of incident light and outputs it near the front focal position of the relay lens 3, an arbitrary light can be applied to the incident side surface of the fly's eye lens 4. An example of forming a shaped illumination field (light amount distribution) is shown.

As an example, the diffractive optical element 24 is arranged near the front focal position of the relay lens 3, and transmits light from the circular light emitting surface of the chip 1a, which is the light emitting part, to the rear focal position of the relay lens 3. In turn, it is converted into a luminous flux having an annular shape or other desired cross-sectional shape on the incident side surface of the fly's eye lens 4. Since the pattern on the diffractive optical element 24 is formed by Fourier transformation, there is no position dependence, and the diffractive optical element 24 can be placed without being conscious of the position of the optical axis of the collector lens 2. In other words, by replacing the diffractive optical element 24 inserted in the optical path, the angular distribution of the illumination light can be changed to an arbitrary shape. That is, by inserting a diffractive optical element having desired characteristics into the optical path using an insertion/removal mechanism (not shown), the angular distribution of the illumination light can be selected as necessary. Note that the diffractive optical element 24 may be of a transmissive type or a reflective type. Further, instead of or in addition to the diffractive optical element 24, a refractive optical element such as an axicon prism or a reflective optical element such as an axicon mirror may be used.

In the embodiment described above, a fly's eye lens 4 having a large number of lens elements 4a arranged in parallel is used. However, the invention is not limited to this, and as shown in FIG. 10, a modification in which the fly's eye lens 4 and the condenser lens 6 are omitted is also possible. In the modification of FIG. 10, as shown in FIG. 11, the plurality of chips 31a of the LED light source 31 have a rectangular light emitting surface similar to the illumination area on the mask M (and in turn, similar to the unit exposure area on the substrate W). has. Further, an aperture stop 32 having a circular opening 32a is arranged near the front focal position of the relay lens 3, and a patterned surface of the mask M is arranged near the rear focal position of the relay lens 3.

In the case of a step-and-repeat exposure apparatus (stepper exposure machine), the field of view of the projection optical system PL is often circular, and the light emitting surface of the chip 31a is formed into a square or a square inscribed in the circular field of view. It is similar to a nearby rectangular shape. In a step-and-scan type exposure apparatus (scan type exposure machine), the field of view of the projection optical system PL is often rectangular, and the light emitting surface of the chip 31a is similar to the rectangular field of view. The light emitting surface of each chip 31a of the LED light source 31 is arranged near the front focal point of the corresponding collector lens 2, and the light emitted from one point on the light emitting surface is converted by the collector lens 2 into a substantially parallel beam of light. The light flux that has passed through each collector lens 2 is irradiated onto the mask M via the aperture diaphragm 32 and the relay lens 3.

Since the aperture stop 32 is arranged near the rear focal point position of the collector lens 2, the pair of the chip 31a and the collector lens 2 is placed inside the circular opening 32a of the aperture stop 32, as shown in FIG. must be located in FIG. 11 shows an example in which the chip 31a has a rectangular light emitting surface. In the modification shown in FIG. 10, the angular distribution of illumination light can be selected by selectively lighting up a plurality of chips 31a. As shown in FIG. 11, when all the chips 31a arranged inside the circular aperture 32a of the aperture stop 32 are lit, almost uniform normal illumination (circular illumination) is provided at a predetermined aperture. It can be carried out.

On the other hand, as shown in FIG. 12, when only the peripheral chips 31a are lit in an annular shape inside the opening 32a, annular illumination can be performed. In FIG. 12, chips that are lit are indicated by reference numeral 31aa, and chips that are off are indicated by hatching and reference numeral 31ab. In reality, by providing a larger number of pairs of chips 31a and collector lenses 2 than in FIGS. 11 and 12, a finer annular pattern can be created. Furthermore, by inserting an anamorphic prism between the chip 31a and the collector lens 2, or by making the optical surface of the collector lens 2 a toric surface, even if the shape of the light emitting surface of the chip 31a is square, the mask M It can be transferred to the upper rectangular illumination area.

In this embodiment, the illumination area on the mask can be regarded as an area on a predetermined surface through which illumination light passes. Since the images of the light emitting surfaces of the respective chips 31a are projected onto this predetermined surface so as to almost overlap, the illuminance distribution of the illumination light in the region on this predetermined surface (the illumination region on the mask M) is approximately controlled. Can be done evenly.

In the above-described embodiment, the surface of the chip 1a from which light is emitted is defined as the light-emitting surface, but if a light-shielding member having an aperture of a predetermined shape is provided on the upper surface of the chip 1a, this aperture will emit light. To determine the area, the area of the aperture may be considered as the light emitting surface.

In each of the embodiments described above, the light from the plurality of light emitting surfaces is focused by the plurality of collector lenses 2 having optical axes substantially parallel to each other, but the optical axes of the plurality of collector lenses 2 do not have to be parallel to each other. When the optical axes of the plurality of collector lenses 2 are parallel to each other, the degree of superimposition of the light from the plurality of light emitting surfaces on a predetermined surface can be increased, but this makes the illuminance distribution on the predetermined surface non-uniform. In some cases, the optical axes of the plurality of collector lenses 2 may be made non-parallel to each other.

Further, each of the optical axes of the plurality of collector lenses 2 may be provided so as to deviate from the center position of the plurality of light emitting surfaces. Further, the lens in each of the above-described embodiments is not limited to a single lens, but may be a lens group consisting of a plurality of lenses. Moreover, it is not limited to a refractive optical member such as a lens, but may be a diffractive optical element that diffracts light or a reflective optical element that reflects light. Further, in each of the above-described embodiments, the fly-eye lens 4 has a plurality of lens elements arranged in parallel, but the plurality of lens elements may be provided integrally.

Further, in each of the embodiments described above, the aperture stop 5 is arranged on the illumination pupil plane, but the aperture stop 5 may be omitted. Further, in the embodiment shown in FIG. 8, a lamp may be used instead of the solid-state light emitting device. In this case, an image of the bright spot of the lamp may be formed at the input end of the optical fiber. Furthermore, an image of the lamp bright spot may be formed on a portion of the fiber core at the input end of the optical fiber.

The exposure apparatus of the above-described embodiment is manufactured by assembling various subsystems including each component listed in the claims of the present application so as to maintain predetermined mechanical accuracy, electrical accuracy, and optical accuracy. be done. In order to ensure these various types of accuracy, before and after this assembly, adjustments are made for various optical systems to achieve optical accuracy, various mechanical systems are adjusted to achieve mechanical accuracy, and various electrical systems are adjusted to achieve optical accuracy. is adjusted to achieve electrical accuracy. The process of assembling various subsystems into an exposure apparatus includes mechanical connections between the various subsystems, wiring connections of electric circuits, piping connections of air pressure circuits, and the like. Needless to say, before the process of assembling the various subsystems into the exposure apparatus, there is a process of assembling each subsystem individually. After the assembly process of various subsystems into the exposure apparatus is completed, comprehensive adjustment is performed to ensure various precisions of the exposure apparatus as a whole. Note that the exposure apparatus may be manufactured in a clean room where the temperature, cleanliness, etc. are controlled.

Next, a device manufacturing method using the exposure apparatus according to the above-described embodiment will be described. FIG. 13 is a flowchart showing the manufacturing process of a semiconductor device. As shown in FIG. 13, in the semiconductor device manufacturing process, a metal film is vapor-deposited on the wafer W that will become the substrate of the semiconductor device (step S40), and a photoresist, which is a photosensitive material, is applied on the vapor-deposited metal film. (Step S42). Next, using the projection exposure apparatus of the above-described embodiment, the pattern formed on the mask (reticle) M is transferred to each shot area on the wafer W (step S44: exposure step), and the wafer W after this transfer is completed. , that is, the photoresist to which the pattern has been transferred is developed (step S46: development step).

Thereafter, using the resist pattern generated on the surface of the wafer W in step S46 as a mask, processing such as etching is performed on the surface of the wafer W (step S48: processing step). Here, the resist pattern is a photoresist layer in which concavities and convexities are generated in a shape corresponding to the pattern transferred by the projection exposure apparatus of the above-described embodiment, and the concavities penetrate through the photoresist layer. It is. In step S48, the surface of the wafer W is processed through this resist pattern. The processing performed in step S48 includes, for example, at least one of etching the surface of the wafer W and forming a metal film or the like. In addition, in step S44, the projection exposure apparatus of the above-described embodiment transfers the pattern using the wafer W coated with photoresist as a photosensitive substrate.

FIG. 14 is a flowchart showing the manufacturing process of a liquid crystal device such as a liquid crystal display element. As shown in FIG. 14, in the liquid crystal device manufacturing process, a pattern forming process (step S50), a color filter forming process (step S52), a cell assembly process (step S54), and a module assembly process (step S56) are sequentially performed. In the pattern forming step of step S50, predetermined patterns such as a circuit pattern and an electrode pattern are formed on a glass substrate coated with a photoresist as a plate P using the projection exposure apparatus of the above-described embodiment. This pattern forming step includes an exposure step of transferring a pattern onto the photoresist layer using the projection exposure apparatus of the above-described embodiment, and development of the plate P to which the pattern has been transferred, that is, development of the photoresist layer on the glass substrate. The process includes a developing process to generate a photoresist layer having a shape corresponding to the pattern, and a processing process to process the surface of the glass substrate through the developed photoresist layer.

In the color filter forming process of step S52, a large number of sets of three dots corresponding to R (Red), G (Green), and B (Blue) are arranged in a matrix, or three dots of R, G, and B are arranged in a matrix. A color filter is formed by arranging a plurality of striped filter sets in the horizontal scanning direction. In the cell assembly process of step S54, a liquid crystal panel (liquid crystal cell) is assembled using the glass substrate on which a predetermined pattern is formed in step S50 and the color filter formed in step S52. Specifically, for example, a liquid crystal panel is formed by injecting liquid crystal between a glass substrate and a color filter. In the module assembly process of step S56, various parts such as an electric circuit and a backlight for performing display operations of the liquid crystal panel are attached to the liquid crystal panel assembled in step S54.

Furthermore, the above-described embodiments are not limited to application to exposure apparatuses for manufacturing semiconductor devices, and can be applied to, for example, liquid crystal display elements formed on rectangular glass plates or sheet-like flexible bodies, or plasma displays. The present invention can also be widely applied to exposure apparatuses for display devices such as, etc., and exposure apparatuses for manufacturing various devices such as image pickup elements (CCDs, etc.), micromachines, thin film magnetic heads, and DNA chips. Furthermore, the above-described embodiments can also be applied to an exposure process (exposure apparatus) when manufacturing a mask (photomask, reticle, etc.) on which a mask pattern of various devices is formed using a photolithography process. .

1 LED light source 1a chip (light emitting part)
2 Collector lens 3 Relay lens 4 Fly-eye lens 4a Lens element 5 Aperture stop 6 Condenser lens IL Illumination optical system M Mask MS Mask stage PL Projection optical system W Wafer WS Wafer stage CR Control system

Claims (18)

In the illumination optical system that illuminates the illuminated surface,
a first light emitting section that emits first illumination light from a first light emitting surface;
a second light emitting section that emits second illumination light from a second light emitting surface;
a light collecting member having a first light collecting part that collects the first illumination light ; and a second light collecting part that collects the second illumination light;
At least a portion of an image of the first light emitting surface caused by the first illumination light that has passed through the first light condensing section and an image of the second light emitting surface that is caused by the second illumination light that has passed through the second light condensing section. a relay optical system that overlaps the irradiated surface with a conjugate plane that is optically conjugate with the irradiated surface ;
an optical integrator having a plurality of wavefront splitting elements arranged in an optical path between the relay optical system and the irradiated surface;
a condenser optical system that superimposes a plurality of light beams wavefront-divided by the optical integrator on the irradiated surface,
the conjugate plane substantially coincides with the entrance plane of the optical integrator;
Front focal positions of the first light condensing section and the second light condensing section substantially coincide with the positions of the first light emitting surface and the second light emitting surface, respectively;
The front focus position of the relay optical system is on the plane where the rear focus positions of the first light condensing part and the second light condensing part are located,
An illumination optical system, wherein the incidence surface of the optical integrator is located near a rear focal plane of the relay optical system . The light condensing member and the relay optical system are arranged such that the incident surface of the optical integrator, the first light emitting surface, and the second light emitting surface are in an optically conjugate relationship with each other. Item 1. Illumination optical system according to item 1. The relay optical system is arranged such that the image of the first light emitting surface and the image of the second light emitting surface are larger than the size of the incident surface of one of the plurality of wave front splitting elements. The illumination optical system according to claim 1 or 2, which magnifies an image of the first light emitting surface and an image of the second light emitting surface . 4. The illumination optical system according to claim 3, wherein the image of the first light emitting surface and the image of the second light emitting surface are enlarged to a size that covers an effective area of the entrance surface of the optical integrator. The illumination optical system according to any one of claims 1 to 4, wherein an image of the first light emitting surface and an image of the second light emitting surface substantially overlap on the incident surface of the optical integrator. The first light collecting part of the light collecting member has a first lens, and the second light collecting part of the light collecting member has a second lens,
The illumination optical system according to claim 1, wherein the optical axis of the first lens and the optical axis of the second lens are parallel to each other. The illumination optical system according to claim 6, wherein the first lens and the second lens are integrally formed . further comprising an aperture stop provided on the exit end side of the optical integrator and having an opening through which part of the first illumination light and the second illumination light pass;
The illumination optical system according to any one of claims 1 to 7, wherein the shape of the opening is similar to the shapes of the first light emitting surface and the second light emitting surface. The illumination optical system according to claim 1, wherein the first light emitting surface and the second light emitting surface have a circular shape . 10. The deflection member according to claim 1, further comprising a deflection member that is inserted into an optical path between the light condensing member and the relay optical system and that changes the angle of incident light and emits it. Illumination optical system. The illumination optical system according to claim 10, wherein the deflection member is a diffractive optical element . 12. The illumination optical system according to claim 1, wherein the first light emitting section and the second light emitting section have solid state light emitting elements as a first light source and a second light source, respectively. The illumination optical system according to claim 12, wherein the solid state light emitting device is an LED . The first light emitting unit includes a first light guide that propagates light from the first light source,
The second light emitting unit includes a second light guide that propagates light from the second light source,
The first light emitting surface is an exit surface of the first light guide,
The illumination optical system according to claim 12 or 13, wherein the second light emitting surface is an exit surface of the second light guide. The illumination optical system according to claim 12, further comprising a cooling member that cools the solid-state light emitting element. comprising the illumination optical system according to any one of claims 1 to 15,
An exposure apparatus that illuminates a predetermined pattern of the irradiated surface with the illumination optical system and exposes the predetermined pattern onto a substrate. The exposure apparatus according to claim 16, further comprising a projection optical system that forms an image of the predetermined pattern on the substrate. exposing the predetermined pattern to the substrate using the exposure apparatus according to claim 16 or 17;
A device manufacturing method comprising: developing the substrate onto which the predetermined pattern has been transferred, and forming a shape corresponding to the predetermined pattern on the surface of the substrate.

Images