KR102212855B1 - Illumination optical system, lithographic apparatus, and article manufacturing method - Google Patents

Abstract

An illumination optical system is provided for illuminating a surface to be illuminated using light from a light source. The illumination optical system includes an optical integrator disposed between a light source and a surface to be illuminated, and an optical filter having an adjustment unit that adjusts the intensity of light incident on the optical integrator. The optical integrator is a rod-type optical integrator that reflects incident light from the inner surface. The illumination optical system changes the illuminance on the surface to be illuminated by changing the position of the adjustment portion in the direction perpendicular to the optical axis of the illumination optical system.

Description

Illumination optical system, lithographic apparatus, and article manufacturing method

The present invention relates to an illumination optical system, a lithographic apparatus, and a method of manufacturing an article.

In an exposure apparatus for projecting a pattern formed on a mask onto a substrate coated with a photosensitive material such as a resist, it is desired to improve the uniformity of illuminance on a surface to be illuminated such as a mask surface or a substrate surface. As a method of improving the illuminance uniformity, it is known to use an illumination optical system equipped with a rod-type optical integrator. By using the rod-type optical integrator, the illumination light from the secondary light source formed in accordance with the number of internal reflections in the rod is superimposed at the rod exit end, so that the distribution of illuminance on the rod exit surface can be uniform.

However, in an illumination optical system equipped with a rod-type optical integrator, irregularities may be observed in the illumination distribution on the surface to be illuminated due to various factors such as contamination or eccentricity of the optical system, and non-uniformity of the antireflection film. In response to this problem, Patent Document 1 discloses a configuration in which a plurality of light quantity adjustment units provided corresponding to a plurality of secondary light sources are disposed at a position that is optically conjugated with the exit surface of a rod-type optical integrator. .

However, in the illumination optical system disclosed in Patent Literature 1, when the angular distribution (hereinafter referred to as "effective light source distribution") to be focused on the surface to be illuminated is determined, the amount of correction of the illuminance distribution on the surface to be illuminated is fixed. Therefore, it has been difficult to correct the illuminance nonuniformity (hereinafter referred to as "illuminance nonuniformity") inherent to each substrate that occurs depending on the film-forming state of the antireflection film, assembly precision, and the like. Further, when the device is used for a long period of time and the optical element is deteriorated and the illuminance unevenness changes over time, it is necessary to appropriately replace the adjustment unit.

Japanese Patent Publication No. 2000-269114

According to an aspect of the present invention, there is provided an illumination optical system that illuminates a surface to be illuminated using light from a light source, an optical integrator disposed between the light source and the surface to be illuminated, and light incident on the optical integrator. It has an optical filter having an adjustment part for adjusting the intensity, and the optical integrator is a rod-type optical integrator that reflects incident light from an inner surface, and the optical filter is each other at the exit end surface of the rod-type optical integrator. A plurality of first regions in which images in the same direction are formed, and a plurality of second regions in which images having a mirror-like relationship with respect to the image are formed on the ejection end surface, and the adjustment unit is provided in at least the first region And there is provided an illumination optical system characterized in that by changing the position of the adjustment unit in a direction perpendicular to the optical axis of the illumination optical system, the illuminance on the surface to be illuminated is changed.

1 is a diagram showing a configuration of an exposure apparatus.
Fig. 2 is a schematic diagram showing a relationship between an adjustment unit and a secondary light source.
Fig. 3A is a diagram showing an imaging relationship between an adjustment unit and an exit end surface of an optical integrator.
3B is a diagram showing an example of an arrangement of an adjustment unit on an optical filter.
3C is a diagram showing an example of an arrangement of an adjustment unit on an optical filter.
4 is a diagram for explaining an action of an optical filter.
5A is a diagram for explaining a method of correcting illuminance unevenness.
5B is a diagram for explaining a method of correcting illuminance unevenness.
5C is a diagram for explaining a method of correcting illuminance unevenness.
Fig. 6 is a flow chart showing a procedure for correcting an inclined illuminance unevenness.
Fig. 7 is a flowchart showing a procedure for correcting an optical axis symmetrical illuminance non-uniformity.
8A is a diagram for explaining an operation of an optical filter.
8B is a diagram for explaining an operation of an optical filter.
9A is a diagram explaining a method of correcting illuminance unevenness.
9B is a diagram explaining a method of correcting illuminance unevenness.
10A is a diagram for explaining an operation of an optical filter.
10B is a diagram for explaining an action of an optical filter.
11A is a diagram for explaining an operation of an optical filter.
11B is a diagram for explaining an action of an optical filter.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the present invention is not limited to the following embodiments, and the following embodiments are only showing specific examples of the embodiments of the present invention. In addition, it cannot be said that all combinations of features described in the following embodiments are essential for solving the problems of the present invention.

<First embodiment>

1 is a schematic diagram showing a configuration of an exposure apparatus 100 according to the present embodiment. The exposure apparatus 100 is used, for example, in a lithography process in a manufacturing process of a semiconductor device, and exposes the image of a pattern formed on the reticle R (mask) onto a wafer W, which is a substrate ( It is a projection type exposure apparatus that transfers). In Fig. 1, the Z axis is taken along the normal direction of the wafer W, and the X axis and the Y axis are taken in a direction perpendicular to each other in a plane parallel to the wafer W plane. The exposure apparatus 100 includes an illumination optical system 101, a reticle stage 102, a projection optical system 103, a wafer stage 104, and a control unit 105.

The illumination optical system 101 adjusts light (luminous flux) from the discharge lamp 1 serving as a light source to illuminate the reticle R serving as an illuminated region. The discharge lamp 1 may be, for example, an ultra-high pressure mercury lamp that supplies light such as an i-line (wavelength 365 nm). Further, the present invention is not limited thereto, for example, a KrF excimer laser that supplies light of a wavelength of 248 nm, an ArF excimer laser that supplies light of a wavelength of 193 nm, and an F2 laser that supplies light of a wavelength of 157 nm may be used. In addition, when the illumination optical system 101 and the projection optical system 103 are constituted by a reflective refractometer or a reflecting system, charged particle beams such as X-rays and electron beams may be used as the light source.

The reticle R is, for example, a quartz glass original plate on which a pattern to be transferred (for example, a circuit pattern) is formed on the wafer W. The reticle stage 102 holds the reticle R and is movable in the X and Y axis directions. The projection optical system 103 projects the light that has passed through the reticle R onto the wafer W at a predetermined magnification. The wafer W is a substrate containing, for example, single crystal silicon on which a resist (photosensitive material) is applied on its surface. The wafer stage 104 holds the wafer W through a wafer chuck (not shown), and in each axis direction of X, Y, and Z (in some cases, each of the rotation directions ωx, ωy, and ωz are included) It is operating as. The wafer stage 104 may be driven by the wafer stage driver 114.

The illumination optical system 101, in order from the discharge lamp 1 toward the reticle R, which is an area to be illuminated, is an elliptical mirror 2, a first relay optical system 3, an optical integrator 4, and And a second relay optical system 5. The elliptical mirror 2 is a condensing mirror that condenses the light (beam) radiated from the discharge lamp 1 at the second focal position F2. The light emitting portion in the bulb portion of the discharge lamp 1 is disposed in the vicinity of the first focal point F1 of the elliptical mirror 2, for example. The first relay optical system 3 as an imaging optical system includes a front lens group 3a (first lens) including a singular or plural lens, and a lens rear group 3b (second lens) including a singular or plural lens Includes. The entire lens group 3a makes the light from the light source parallel light. The lens rear group 3b condenses light, which has become parallel light by the lens rear group 3a, on the incident end surface 4a of the optical integrator 4. The second focal position F2 and the incident end surface 4a of the optical integrator 4 are optically conjugated by the front lens group 3a and the rear lens group 3b. In the present embodiment, the optical axis of the illumination optical system 101, particularly the optical system including the first relay optical system 3, the optical integrator 4, and the second relay optical system 5, is in the Z-axis direction.

In the present embodiment, the optical integrator 4 is a rod-type optical integrator that reflects incident light from the inner surface and forms a plurality of secondary light source images corresponding to the number of reflections. The shape of the optical integrator 4 is, for example, a square pillar. That is, the shape of the incident end surface and the exit end surface parallel to the XY plane of the optical integrator 4 is a rectangle of the surface to be illuminated and the top. Above all, such a shape is an example, and does not impede the application of a member having the same action as the optical integrator 4. For example, the optical integrator 4 may be composed of a hollow rod forming a reflective surface therein. Further, the cross-sectional shape of the incident end face 4a and the exit end face 4b of the optical integrator 4 in the XY plane may be a polygon other than a square.

Between the discharge lamp 1 and the optical integrator 4, in the vicinity of the reticle R, that is, the conjugated surface S1 that is conjugated with the wafer W, the optical filter 6 is disposed perpendicular to the optical axis. do. The optical filter 6 is configured to be movable two-dimensionally along the XY plane, and the movement is performed by the filter drive unit 7, for example. The optical filter 6 is included in the first relay optical system 3, as shown in FIG. 1, and may be disposed between the front lens group 3a and the rear lens group 3b. The optical filter 6 has a plurality of adjustment units for adjusting the intensity of light incident on the optical integrator 4, provided corresponding to the number of secondary light source images formed by the optical integrator 4. The optical action of the optical filter 6 will be described later in detail.

The lens rear group 3b is disposed at a position separated by a focal length from the position of the virtual image surface S2 of the secondary light source formed by the optical integrator 4, and is substantially parallel to the optical axis from the optical filter 6 The illumination light emitted by the light is once condensed on this virtual image surface S2.

The incident end surface 4a of the optical integrator 4 is disposed in the vicinity of the virtual image surface S2. The illumination light condensed by the lens rear group 3b is reflected a plurality of times from the inner surface of the optical integrator 4 and is emitted. The illumination light emitted from the optical integrator 4 is emitted so as to be directed from a virtual image of a discrete secondary light source corresponding to the number of reflections. For this reason, the angle of the illumination light emitted from the optical integrator 4 corresponds to the emission angle of the illumination light from the virtual image of the secondary light source disposed on the virtual image surface S2.

The exit end surface 4b of the optical integrator 4 is overlapped by a plurality of light source images arranged on the virtual image surface S2, and is uniformly illuminated. The light emitted from the exit end surface 4b of the optical integrator 4 passes through the second relay optical system 5 and then illuminates the reticle R, which is a surface to be illuminated. The second relay optical system 5 includes an entire lens group 5a including a single lens or a plurality of lenses in which light from the exit end surface 4b of the optical integrator 4 becomes parallel light. The lens front group 5a is configured to be movable in the optical axis direction (Z axis direction) of the second relay optical system 5. The second relay optical system 5 further includes a lens rear group 5b including a single or a plurality of lenses for condensing light in parallel light from the front lens group 5a on the surface to be illuminated. The entire lens group 5a is moved by the lens driving unit 51. By moving the front lens group 5a in the optical axis direction, distortion can be changed while substantially not changing the focal length. With this action, it is possible to move the peripheral illuminance up and down by the movement of the front lens group 5a.

In this embodiment, the exit end surface 4b of the optical integrator 4 is disposed at the focal position on the front side of the front lens group 5a, and the exit end surface 4b of the optical integrator 4 is , It is optically conjugated with the reticle (R) which is the surface to be illuminated. Further, strictly, in order to avoid transferring foreign matters on the ejection end face 4b of the optical integrator 4, the position of the ejection end face 4b may be slightly shifted from the conjugate. Then, the light emitted from the reticle R, that is, the image of the mask pattern is transferred onto the wafer W through the projection optical system 103.

The illuminance distribution measuring unit 115 measures the illuminance distribution in the reticle R which is the surface to be illuminated. The control unit 105 controls the discharge lamp 1, the filter driving unit 7, the lens driving unit 51, the wafer stage driving unit 114, and the illuminance distribution measuring unit 115. The control unit 105 may include a storage unit 105a that stores various types of data necessary for control.

Next, the optical action of the optical filter 6 will be described. 2 is a diagram schematically showing a relationship between a plurality of adjustment units provided on an optical filter and a plurality of secondary light sources formed by the optical integrator 4. FIG. 2 shows an optical path of illumination light emitted from the optical filter 6 in parallel to the optical axis. The adjustment unit 60 on the optical axis provided on the optical filter 6 adjusts the intensity of the light flux from the secondary light source 40 that is not reflected from the inner surface of the optical integrator 4. In addition, the pair of adjusting parts 61a, 61b adjacent to both outer sides of the adjusting part 60 is the intensity of the light flux from the secondary light source images 41a, 41b reflected once from the inner surface of the optical integrator 4 Adjust. In addition, the pair of adjusting parts 62a, 62b adjacent to both outer sides of the adjusting parts 61a, 61b are reflected twice from the inner surface of the optical integrator 4, and the light flux from the secondary light source images 42a, 42b Adjust the intensity of According to this configuration, it is possible to independently control the transmittance of each of the plurality of secondary light sources formed by the optical integrator 4.

The adjustment units 60, 61a, 61b, 62a, 62b are disposed in the vicinity of the ejection end surface 4b of the optical integrator 4 and the conjugated surface S1 that is conjugated. Therefore, the shape of one adjustment part corresponds to the illumination area on the reticle R or wafer W of FIG. 1, and the transmittance distribution of the adjustment parts 60, 61a, 61b, 62a, 62b is the wafer W ) Is reflected in the illumination distribution of the illumination area.

3A is a diagram for explaining an imaging relationship between each adjustment unit in the optical filter 6 and the exit end surface 4b of the optical integrator 4. In the optical integrator 4, the light flux from an adjacent secondary light source is reversed. For this reason, when the direction of the image formed on the exit end surface 4b of the optical integrator 4 is "F", the images of the adjacent adjustment portions are in the opposite direction and are in a mirror image relationship with each other.

3B is a schematic diagram of the optical filter 6 disposed in the vicinity of the conjugated surface S1 as viewed from the incident side. Here, a pattern filter (or a light blocking member) is used as an adjustment part. In this embodiment, the plurality of pattern filters constituting the plurality of adjustment units are disposed at predetermined positions on the optical filter corresponding to the mirror image relationship on the plurality of secondary light sources of the optical integrator 4. . The optical filter 6 includes a plurality of first regions A and B, and a plurality of second regions that are regions excluding the first region. Here, the plurality of first regions A and B are regions in which images in the same direction are formed on the exit end surface 4b of the optical integrator 4. Further, the plurality of second regions are regions in which an image having a mirror image relationship with respect to the image of the first region is formed on the exit end surface 4b of the optical integrator 4. In this embodiment, on the surface of the optical filter 6, corresponding to the plurality of secondary light sources of the optical integrator 4, rectangular pattern filters 6A and 6B are respectively provided with a plurality of first regions ( It is arranged in A, B). Further, the pattern filters 6A and 6B may be disposed in at least a part of the plurality of first regions A and B, not all of them.

In this embodiment, as the pattern filters 6A and 6B, by disposing circular pattern filters of different sizes, each pattern filter portion has an effect as shown in FIGS. 4A and 4B. have. By appropriately adjusting the diameter, transmittance, and arrangement of each pattern filter, finally, on the surface to be illuminated, as shown in Fig. 4(C) showing the sum of Figs. 4(A) and (B), approximately In proportion to the square of the height, the effect of increasing the illuminance of the periphery of the illuminated surface is obtained.

In general, in the illumination optical system of a projection exposure apparatus, if the uniformity of the numerical aperture on the surface to be illuminated and the uniformity of the illuminance distribution are tried to be compatible, the peripheral illuminance decreases according to the angular characteristics of the antireflection film used for the lens. There is a tendency. Therefore, the optical filter having the effect of increasing the ambient illuminance as in the present embodiment is effective for correcting the illuminance distribution.

Further, the light flux incident on the optical integrator 4 is adjusted to have a symmetrical illuminance distribution with respect to the optical axis. As a result, the distribution of the effective light source on the surface to be illuminated becomes symmetric with respect to the main light beam, so that no image shift occurs with respect to defocus. Thereby, exposure in good telecentricity can be realized.

For example, when the illumination light incident on the optical integrator 4 has an asymmetrical illuminance distribution with respect to the optical axis, the symmetry of the effective light source distribution is lost, and the image performance is affected in the form of a shift in telecentricity. However, according to the present embodiment, since the arrangement of the pattern filters is optically symmetric, the shift in telecentricity hardly occurs.

In the present embodiment, two types of pattern filters 6A and 6B are used as the adjustment units, but by changing the density of a fine dot pattern, for example, one type of pattern is approximately proportional to the square of the image height. It is also possible to create an illuminance distribution.

Hereinafter, a method of correcting illuminance unevenness as shown in FIG. 5A will be described. The illuminance non-uniformity of FIG. 5A can be decomposed into an inclined illuminance non-uniformity as shown in FIG. 5B and an optical-axis symmetrical arc shape as shown in FIG. have. These can be separated by calculating the average illuminance and inclination component for each image height from the illuminance distribution.

First, a method of correcting the irregularity of illuminance of the inclined shape of Fig. 5B will be described. As described above, the optical filter 6 of the present embodiment has an effect of increasing the illuminance of the peripheral portion in proportion to approximately the square of the image height. At this time, if the incident end surface 4a of the optical integrator 4 is equivalent to the surface to be illuminated, and a normalized XY coordinate system, the effect z of the illumination distribution adjustment by the optical filter 6 is z = a ( It can be written as x ² + y ² ). Where a is a constant.

The pattern filters 6A, 6B of the optical filter 6 are in at least a part of the plurality of first regions A, B in which images in the same direction are formed on the exit end surface 4b of the optical integrator 4 It is placed. The optical filter 6 is movable in a direction along a plurality of first regions A and B and a plurality of second regions that are other regions, that is, a direction along the XY plane. That is, it is possible to change the position of the optical filter 6 in the direction (X direction or Y direction) perpendicular to the optical axis (Z axis) of the illumination optical system. Here, even if the optical filter 6 is moved in the direction along the XY plane, the effect of the change in the illuminance distribution on the surface to be illuminated imparted by the pattern filters 6A and 6B does not cancel each other.

Therefore, the effect z'of the illumination distribution adjustment by the optical filter 6 when the optical filter 6 is moved by a predetermined distance δ in the X and Y directions is z'= a((x+δ) ² +( It can be written as y+δ) ² ). Where a is a constant. In other words, since the x and y first-order terms depending on δ are generated, an inclined roughness distribution can be generated.

6 is a flowchart showing a procedure for correcting irregularity in illuminance of an inclined shape. In S601, the control unit 105 calculates the illuminance non-uniformity on the surface to be illuminated based on the illuminance distribution data measured by the illuminance distribution measurement unit 115 (irradiance non-uniformity measurement 1). Assuming that the maximum value of the illuminance value on the surface to be illuminated is Smax and the minimum value is Smin, the illuminance non-uniformity S is calculated, for example, by the following equation.

S=(Smax-Smin)/(Smax+Smin)

Thereafter, the control unit 105 moves the optical filter 6 a predetermined distance δ in the X direction in S602, and measures the illuminance unevenness on the surface to be illuminated in S603 (irradiance unevenness measurement 2). Next, the control unit 105 moves the optical filter 6 a predetermined distance δ in the Y direction in S604, and measures the illuminance unevenness on the surface to be illuminated in S605 (irradiance unevenness measurement 3). Thereafter, in S606, the control unit 105 calculates the amount of change in the illuminance unevenness from the results of illuminance unevenness measurements 1, 2, and 3, and stores it in the storage unit 105a. This amount of change corresponds to the inclination of the above-described inclined roughness distribution.

Next, in S607, the control unit 105 calculates the movement direction and the movement amount of the optical filter 6 based on the change amount calculated in S606. Then, the control unit 105 moves the optical filter 6 by the filter driver 7 in the calculated direction by the calculated movement amount.

After that, in S609 again, the control unit 105 measures the illuminance non-uniformity on the surface to be illuminated (irradiance non-uniformity measurement 4), and in S610, it checks whether the illuminance non-uniformity converges within a predetermined allowable range. Here, if the illuminance unevenness converges within the allowable range, the process ends. On the other hand, if the illuminance unevenness does not converge within the allowable range, the process proceeds to S611, the result of illuminance unevenness measurement 4 is fed back, and returns to S607 to recalculate the moving direction and the amount of movement of the optical filter 6.

Next, a method of correcting the symmetrical illuminance unevenness of FIG. 5C will be described with reference to the flowchart of FIG. 7. When the symmetrical illuminance unevenness occurs, the peripheral illuminance correction amount is adjusted. As described above, the second relay optical system 5 has a configuration in which distortion is changed while substantially not changing the focal length by moving the front lens group 5a in the optical axis direction. Accordingly, it is possible to vertically move the peripheral illuminance by the movement of the front lens group 5a.

In S701, the control unit 105 obtains, by the illuminance distribution measuring unit 115, the amount of change in the illuminance of the outermost periphery of the surface to be illuminated when the front lens group 5a is moved by a predetermined distance Δ in the optical axis direction, and calculates the change amount. It is stored in the storage unit 105a (irradiance nonuniformity measurement 1). In addition, this S701 may be performed in advance by simulation or the like. In S702, the control unit 105 calculates the amount of movement of the front lens group 5a in the optical axis direction based on this change amount. In S703, the control unit 105 moves the entire lens group 5a in the optical axis direction by the lens driving unit 51 by the calculated movement amount.

Thereafter, in S704 again, the control unit 105 obtains the amount of change in the illuminance of the outermost periphery of the illuminated surface when the front lens group 5a is moved by a predetermined distance Δ in the optical axis direction (irradiance unevenness measurement 2), and in S705 , It is checked whether the variation amount converges within a predetermined allowable range. Here, if the amount of variation converges within the allowable range, the process is ended. On the other hand, if the amount of variation does not converge within the allowable range, the process proceeds to S706, the result of the illuminance non-uniformity measurement 2 is fed back, and the flow returns to S703 to recalculate the movement amount of the optical filter 6. In this way, the control unit 105 feedback-controls the movement amount of the optical filter 6 so that the illuminance unevenness calculated from the illuminance distribution measured by the illuminance distribution measuring unit 115 converges within the allowable range.

By performing both movement of the optical filter 6 according to the control procedure of Fig. 6 and driving of the entire lens group according to the control procedure of Fig. 7 described above, more precise correction can be performed. At this time, the control procedure of Fig. 6 and the control procedure of Fig. 7 by the control unit 105 may be executed in series or in parallel along a time series.

Further, the execution result of each of the control procedure in Fig. 6 and the control procedure in Fig. 7 can be stored in the storage unit 105a. When executed again under the same lighting conditions, the execution result can be called from the storage unit 105a and each element can be driven to the optimum position. Thereby, the same procedure as in Figs. 6 and 7 is omitted, and it is possible to quickly correct the inclined illuminance unevenness and concentric circular illuminance unevenness (optical axis symmetric illuminance unevenness).

In addition, when the illumination optical system is used for a long period of time, it is considered that the transmittance of any lens in the device is deteriorated, resulting in uneven illumination of a rotationally asymmetric oblique shape. Even in such a case, by performing the control procedure of Figs. 6 and 7 again, it is possible to correct the inclined illuminance unevenness and the concentric circular illuminance unevenness (optical axis symmetric illuminance unevenness).

In addition, in Japanese Unexamined Patent Application Publication No. 2001-35564, for example, an optical filter is disposed in the vicinity of the incident surface of an optical integrator in which a plurality of microlenses are two-dimensionally arranged at a predetermined pitch. The optical filter has a light amount adjusting unit capable of adjusting the amount of transmitted light in a plurality of regions each corresponding to a plurality of microlenses constituting the optical integrator. Even with such a configuration, it is possible to control the illuminance unevenness by moving the optical filter along the XY plane.

However, since an optical integrator in which a plurality of microlenses are arranged two-dimensionally at a predetermined pitch is generally expensive, the rod-type optical integrator according to the present embodiment is inexpensive. According to the configuration of the present embodiment using a rod-type optical integrator, an arrangement location of each adjustment unit is determined using the one having an image forming relationship as shown in Fig. 3A. Specifically, the plurality of adjustment portions are disposed on the optical filter so that the image direction of each adjustment portion formed on the exit end surface of the rod-type optical integrator becomes the same direction by the light transmitted through each of the plurality of adjustment portions. Thereby, it is possible to control the illuminance unevenness.

<2nd embodiment>

Next, an illumination optical system according to a second embodiment will be described. The schematic configuration of the device is the same as in FIG. 1. 3C is a schematic diagram of the optical filter 6 according to the present embodiment as viewed from the incident side. On the surface of the optical filter 6, corresponding to the plurality of secondary light sources of the optical integrator 4, a rectangular pattern filter 6C is disposed in a plurality of first regions C, and a rectangular pattern The filter 6D is disposed in the plurality of second regions D. Further, the pattern filters 6C and 6D may be disposed in at least a part of the plurality of first regions C and the plurality of second regions D, respectively, not all of them. Here, the plurality of first regions C are regions in which images in the same direction are formed on the exit end surface 4b of the optical integrator 4. Further, the plurality of second regions D is a region in which an image having a mirror-like relationship with respect to the images of the plurality of first regions C is formed on the exit end surface 4b of the optical integrator 4.

In the present embodiment, the pattern filter 6C has an effect of increasing the illuminance of the peripheral portion of the illuminated surface in proportion to the square of the image height, as shown in Fig. 8A. Further, the pattern filter 6D has the opposite characteristic, that is, the effect of lowering the illuminance of the peripheral portion in proportion to the square of the image height, as shown in Fig. 8B. By the combination of the pattern filters 6C and 6D, as a whole, it is comprised so that the effect of the illuminance distribution change may cancel each other.

Hereinafter, a method of correcting unevenness of illuminance in an inclined shape as shown in Fig. 9A will be described. When the incident end surface 4a of the optical integrator 4 is equivalent to the surface to be illuminated, and a normalized XY coordinate system, the effect z of the optical filter 6 is, if only one dimension in the X direction is shown, z =ax ² -ax ² =0, which does not affect the illuminance distribution. Where a is a constant.

The effect z'when the optical filter 6 is moved by a predetermined distance δ in the X direction is because the direction of δ is changed in the pattern filters 6C and 6D, so z'=a(x+δ) ² -a(x It can be written as -δ) ² . That is, since a first-order term of x depending on δ is generated, an inclined roughness distribution can be generated.

Also in the present embodiment, by performing the same procedure as in the flowchart of FIG. 6, it is possible to correct the irregularity of illuminance in the oblique shape so as to be flat as shown in FIG. 9B. As described above, in the case where the decrease in the peripheral illuminance of the original secondary shape is small, and the illuminance unevenness of the oblique shape is dominant, the configuration of the adjustment unit as in the present embodiment is effective for correcting the illuminance distribution.

<Third embodiment>

Next, an illumination optical system according to a third embodiment will be described. In this embodiment, the effects of the pattern filters 6C and 6D in the second embodiment are different. The pattern filter 6C in this embodiment has an effect of changing the illuminance distribution in proportion to the third power of the image height, as shown in Fig. 10A. Further, the pattern filter 6D has the opposite characteristic, that is, an effect of changing the illuminance distribution in proportion to the third power of the image height, as shown in Fig. 10B. By the combination of the pattern filters 6C and 6D, as a whole, it is comprised so that the effect of the illuminance distribution change may cancel each other.

As in the second embodiment, the effect z of the optical filter 6 is z=ax ³ -ax ³ =0, so long as only one dimension in the X direction is shown, and does not affect the illuminance distribution. Where a is a constant.

The effect z'when the optical filter 6 is moved by a predetermined distance δ in the X direction is because the direction of δ is changed in the pattern filters 6C and 6D, so z'=a(x+δ) ³ -a(x -δ) ³ In this embodiment, since a second-order term of x depending on δ is generated, a concentric second-order roughness distribution can be generated.

Also in this embodiment, by executing the procedure similar to that of the flowchart of FIG. 6, the illuminance distribution of the secondary shape as shown in FIG. 11A can be corrected so as to be flat as shown in FIG. 11B. As described above, in the case where there is no roughness irregularity of the original inclined shape and the secondary roughness irregularity of the concentric circle is dominant, the configuration of the adjustment unit as in the present embodiment is effective for correcting the illumination distribution.

Further, even if the illuminance distribution to be corrected is a higher-order shape after the third order, it is possible to correct illuminance unevenness by appropriately setting the transmittance distribution of the pattern filter.

According to each of the above embodiments, a technique advantageous for improving the correction performance of illuminance unevenness is provided.

<Embodiment of an article manufacturing method>

The article manufacturing method in the embodiment of the present invention is suitable for manufacturing an article such as a micro device such as a semiconductor device or an element having a fine structure, for example. The article manufacturing method of the present embodiment includes a process of transferring a pattern of an original to a substrate using the lithographic apparatus (exposure apparatus, imprint apparatus, drawing apparatus, etc.), and a process of processing the substrate to which the pattern has been transferred. Include. In addition, this manufacturing method includes other well-known processes (oxidation, film formation, vapor deposition, doping, planarization, etching, resist stripping, dicing, bonding, packaging, etc.). The article manufacturing method of the present embodiment is more advantageous than the conventional method in at least one of the performance, quality, productivity, and production cost of the article.

The present invention is not limited to the above embodiments, and various changes and modifications are possible without departing from the spirit and scope of the present invention. Accordingly, the following claims are appended to clarify the scope of the present invention.

This application claims priority based on Japanese Patent Application No. 2016-168546 filed on August 30, 2016, and uses all the description contents here.

Claims (10)

It is an illumination optical system that uses light from a light source to illuminate a surface to be illuminated,
An optical integrator disposed between the light source and the surface to be illuminated,
Optical filter having an adjustment unit that adjusts the intensity of light incident on the optical integrator
Have,
The optical integrator is a rod-type optical integrator that reflects incident light from an inner surface,
The optical filter may include a plurality of first regions in which images in the same direction are formed on an emission end surface of the rod-type optical integrator, and a plurality of first regions in which an image having a mirror image relationship with respect to the image is formed on the emission end surface Contains 2 areas,
The adjustment unit is not provided in the plurality of second regions, but is provided in the plurality of first regions,
An image formed on an exit end surface of the rod-type optical integrator by light from the adjustment unit provided in the plurality of first regions, and the rod-type optical integrator by light from the plurality of second regions Illuminating the illuminated surface with an image formed on the end surface,
An illumination optical system, characterized in that, by changing a position of the adjustment unit in a direction perpendicular to an optical axis of the illumination optical system, the illuminance on the surface to be illuminated is changed. It is an illumination optical system that uses light from a light source to illuminate a surface to be illuminated,
An optical integrator disposed between the light source and the surface to be illuminated,
Optical filter having an adjustment unit that adjusts the intensity of light incident on the optical integrator
Have,
The optical integrator is a rod-type optical integrator that reflects incident light from an inner surface,
The optical filter may include a plurality of first regions in which images in the same direction are formed on an emission end surface of the rod-type optical integrator, and a plurality of first regions in which an image having a mirror image relationship with respect to the image is formed on the emission end surface Contains 2 areas,
The adjustment unit is disposed in a part of the plurality of first regions and a part of the plurality of second regions,
The number of the adjustment units provided in a part of the plurality of first regions and the number of the adjustment parts provided in a part of the plurality of second regions are the same number,
The rod-type optical by the image formed on the exit end surface of the rod-type optical integrator by light from the adjustment unit provided in the plurality of first regions and the light from the adjustment unit provided in the plurality of second regions. Illuminating the illuminated surface with an image formed on the exit end surface of the integrator,
The characteristics of the illuminance distribution on the surface to be illuminated adjusted by the adjustment unit of the first region and the characteristics of the illumination distribution on the surface to be illuminated adjusted by the adjustment unit of the second region are different,
An illumination optical system, characterized in that, by changing a position of the adjustment unit in a direction perpendicular to an optical axis of the illumination optical system, the illumination intensity on the surface to be illuminated is changed. The method of claim 1,
Further comprising a first relay optical system disposed between the light source and the optical integrator and guiding light from the light source to the optical integrator,
The first relay optical system includes a first lens for converting light from a light source into parallel light, and a second lens for condensing light converted into parallel light by the first lens to an incidence end surface of the optical integrator. ,
The optical filter is an illumination optical system, characterized in that disposed between the first lens and the second lens. The method of claim 1,
Further comprising a measurement unit for measuring the distribution of illuminance on the surface to be illuminated,
An illumination optical system, characterized in that the position of the optical filter is changed based on the illuminance distribution measured by the measurement unit. The method of claim 4,
Further comprising a control unit for controlling the drive of the optical filter,
The control unit is an illumination optical system characterized in that feedback control of the driving of the optical filter so that the illuminance unevenness calculated from the illuminance distribution measured by the measurement unit converges within an allowable range. The method of claim 5,
Further comprising a second relay optical system disposed between the optical integrator and the surface to be illuminated, and guiding light from the exit end surface of the optical integrator to the surface to be illuminated,
The second relay optical system is a third lens that converts light from the exit end surface of the optical integrator into parallel light, and includes a third lens configured to be movable in the optical axis direction of the second relay optical system,
The control unit further controls the driving of the third lens in a feedback control so that the illuminance unevenness calculated from the illuminance distribution measured by the measuring unit converges within an allowable range. The method of claim 1,
The plurality of first regions are regions in which light from the plurality of first regions is reflected from the inner surface of the rod-type optical integrator to form an image on the exit end surface of the rod-type optical integrator. Illumination optical system. The method of claim 1,
Among the plurality of first regions, in a region in which light from the plurality of first regions is not reflected from the inner surface of the rod-type optical integrator and forms an image on the exit end surface of the rod-type optical integrator, the An illumination optical system, characterized in that no adjustment unit is provided. It is a lithographic apparatus for forming a pattern of an original plate on a substrate,
The illumination optical system according to claim 1 for illuminating the original plate disposed on the irradiated surface,
A projection optical system that projects the pattern onto the substrate
Lithographic apparatus comprising a. A step of forming a pattern on a substrate using the lithographic apparatus according to claim 9, and
Process of processing the substrate on which the pattern is formed in the process
A method of manufacturing an article comprising: obtaining an article from the processed substrate.

Images