WO2018043423A1

WO2018043423A1 - Illuminating optical system, lithography device, and article manufacturing method

Info

Publication number: WO2018043423A1
Application number: PCT/JP2017/030779
Authority: WO
Inventors: 広美須田
Original assignee: キヤノン株式会社
Priority date: 2016-08-30
Filing date: 2017-08-28
Publication date: 2018-03-08
Also published as: KR20190040294A; CN109643069B; JP2018036425A; CN109643069A; TW201820045A; KR102212855B1; JP6761306B2; TWI645261B

Abstract

Provided is an illuminating optical system that illuminates, using light emitted from a light source, a surface to be illuminated. This illuminating optical system has: an optical integrator that is 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 to be inputted to the optical integrator. The optical integrator is a rod-type optical integrator that reflects inputted light by an internal surface. The illuminating optical system changes the position of the adjustment unit in the direction perpendicular to the optical axis of the illuminating optical system, thereby changing illuminance on the surface to be illuminated.

Description

Illumination optical system, lithographic apparatus, and article manufacturing method

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

In an exposure apparatus that projects a pattern formed on a mask onto a substrate coated with a photosensitive material such as a resist, improvement in illuminance uniformity on an illuminated surface such as a mask surface or a substrate surface is required. As a technique for improving the illuminance uniformity, it is known to use an illumination optical system including a rod-type optical integrator. By using a rod-type optical integrator, the illumination light from the secondary light source formed according to the number of internal reflections in the rod can be overlapped at the rod exit end to make the illuminance distribution uniform on the rod exit surface. it can.

However, in an illumination optical system equipped with a rod-type optical integrator, non-uniformity in the illumination distribution on the illuminated surface results as a result of various factors such as dirt and decentering of the optical system and unevenness of the antireflection film. May be allowed. In response to this problem, Patent Document 1 has a configuration in which a plurality of light amount adjustment units provided corresponding to a plurality of secondary light source images are arranged at positions that are optically conjugate with the exit surface of the rod-type optical integrator. Is disclosed.

However, in the illumination optical system disclosed in Patent Document 1, when the angle distribution (hereinafter referred to as “effective light source distribution”) to be collected on the illuminated surface is determined, the illuminance distribution correction amount on the illuminated surface is fixed. It becomes. Therefore, it has been difficult to correct illuminance non-uniformity (hereinafter referred to as “illuminance unevenness”) unique to each machine, which occurs due to the film formation state of the antireflection film, assembly accuracy, and the like. Further, when the optical element deteriorates after long-term use of the apparatus and the illuminance unevenness changes with time, it is necessary to replace the adjustment unit as appropriate.

JP 2000-269114 A

According to one aspect of the present invention, there is provided an illumination optical system that illuminates an illuminated surface using light from a light source, the optical integrator disposed between the light source and the illuminated surface, and the optical integrator And an optical filter having an adjustment unit that adjusts the intensity of light incident on the optical integrator. A plurality of first regions in which images in the same direction are formed on the exit end face of the integrator; and a plurality of second regions in which an image having a mirror image relationship with the image is formed on the exit end surface, The adjustment unit is provided at least in the first region, and the position of the adjustment unit in a direction perpendicular to the optical axis of the illumination optical system Illumination optical system and changes the illuminance on the illuminated surface is provided by changing.

The figure which shows the structure of exposure apparatus. The schematic diagram which shows the relationship between an adjustment part and a secondary light source. The figure which shows the imaging relationship of an adjustment part and an optical integrator injection | emission end surface. The figure which shows the example of arrangement | positioning of the adjustment part on an optical filter. The figure which shows the example of arrangement | positioning of the adjustment part on an optical filter. The figure explaining the effect | action of an optical filter. The figure explaining the correction method of illumination intensity nonuniformity. The figure explaining the correction method of illumination intensity nonuniformity. The figure explaining the correction method of illumination intensity nonuniformity. The flowchart which shows the correction | amendment procedure of inclined illumination intensity nonuniformity. The flowchart which shows the correction | amendment procedure of illumination intensity nonuniformity symmetrical to an optical axis. The figure explaining the effect | action of an optical filter. The figure explaining the effect | action of an optical filter. The figure explaining the correction method of illumination intensity nonuniformity. The figure explaining the correction method of illumination intensity nonuniformity. The figure explaining the effect | action of an optical filter. The figure explaining the effect | action of an optical filter. The figure explaining the effect | action of an optical filter. The figure explaining the effect | action of an optical filter.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to the following embodiment, The following embodiment shows only the specific example of implementation of this invention. Moreover, not all combinations of features described in the following embodiments are indispensable for solving the problems of the present invention.

<First Embodiment>
FIG. 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 semiconductor device manufacturing process, and exposes (transfers) an image of a pattern formed on a reticle R (mask) onto a wafer W that is a substrate. It is an exposure apparatus. 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 directions perpendicular to each other in a plane parallel to the wafer W surface. 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 (light flux) from the discharge lamp 1 that is a light source to illuminate the reticle R that is an illuminated area. The discharge lamp 1 can be, for example, an ultrahigh pressure mercury lamp that supplies light such as i-line (wavelength 365 nm). For example, a KrF excimer laser that supplies light with a wavelength of 248 nm, an ArF excimer laser that supplies light with a wavelength of 193 nm, and an F2 laser that supplies light with a wavelength of 157 nm may be used. Further, when the illumination optical system 101 and the projection optical system 103 are configured by a catadioptric system or a reflective system, a charged particle beam such as an X-ray or an electron beam may be used as the light source.

The reticle R is an original plate made of, for example, quartz glass 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 made of, for example, single crystal silicon and having a resist (photosensitive material) coated on the surface thereof. The wafer stage 104 holds the wafer W via a wafer chuck (not shown) and is movable in the respective axial directions of X, Y, and Z (which may include ωx, ωy, and ωz that are the respective rotation directions). . The wafer stage 104 can be driven by a wafer stage drive unit 114.

The illumination optical system 101 includes an elliptical mirror 2, a first relay optical system 3, an optical integrator 4, and a second relay optical system 5 in order from the discharge lamp 1 toward the reticle R that is an illuminated area. The elliptical mirror 2 is a condensing mirror that condenses the light (light flux) emitted from the discharge lamp 1 at the second focal position F2. The light emitting part in the bulb part of the discharge lamp 1 is arranged 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 lens front group 3a (first lens) composed of one or more lenses and a lens rear group 3b (second lens) composed of one or more lenses. Including. The front lens group 3a converts light from the light source into parallel light. The rear lens group 3 b condenses the light that has been converted into parallel light by the rear lens group 3 a onto the incident end face 4 a of the optical integrator 4. By the lens front group 3a and the lens rear group 3b, the second focal position F2 and the incident end face 4a of the optical integrator 4 are optically conjugate. 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 set to the Z-axis direction.

In this embodiment, the optical integrator 4 is a rod-type optical integrator that reflects incident light on 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 quadrangular prism. 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 similar to the illuminated surface. However, such a shape is merely an example, and does not hinder the application of a member having the same function as the optical integrator 4. For example, the optical integrator 4 may be composed of a hollow rod that forms a reflective surface inside. Further, the cross-sectional shape of the incident end surface 4a and the exit end surface 4b of the optical integrator 4 on the XY plane may be a polygon other than a quadrangle.

Between the discharge lamp 1 and the optical integrator 4, an optical filter 6 is arranged in the vicinity of the reticle R, that is, the conjugate plane S1 conjugate with the wafer W, perpendicular to the optical axis. The optical filter 6 is configured to be movable two-dimensionally along the XY plane, and the movement is performed by, for example, the filter driving unit 7. For example, as shown in FIG. 1, the optical filter 6 is included in the first relay optical system 3 and can be disposed between the lens front group 3a and the lens rear group 3b. The optical filter 6 has a plurality of adjustment units that adjust 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 in detail later.

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

The incident end face 4a of the optical integrator 4 is disposed in the vicinity of the virtual image plane S2. The illumination light collected by the rear lens group 3b is reflected a plurality of times on the inner surface of the optical integrator 4 and emitted. Illumination light emitted from the optical integrator 4 is emitted as if traveling 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 arranged on the virtual image plane S2.

The exit end surface 4b of the optical integrator 4 is superimposed and illuminated uniformly by a plurality of light source images arranged on the virtual image plane S2. The light emitted from the emission end surface 4b of the optical integrator 4 is transmitted through the second relay optical system 5, and then illuminates the reticle R, which is the illuminated surface. The second relay optical system 5 includes a lens front group 5a composed of a single lens or a plurality of lenses for converting light from the emission end face 4b of the optical integrator 4 into 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 composed of a single lens or a plurality of lenses for condensing the light that has been converted into parallel light by the lens front group 5a onto the surface to be illuminated. The lens front unit 5a is moved by the lens driving unit 51. By moving the lens front group 5a in the optical axis direction, the distortion can be changed while substantially not changing the focal length. With this action, the peripheral illuminance can be increased or decreased by the movement of the lens front group 5a.

In the present embodiment, the exit end surface 4b of the optical integrator 4 is disposed at the front focal position of the lens front group 5a, and the exit end surface 4b of the optical integrator 4 is optically conjugate with the reticle R that is the illuminated surface. It has become. Strictly speaking, the position of the injection end face 4b may be slightly shifted from the conjugate in order to avoid the transfer of foreign matter on the injection end face 4b of the optical integrator 4. Then, the light emitted from the reticle R, that is, the image of the mask pattern, is transferred onto the wafer W via the projection optical system 103.

The illuminance distribution measuring unit 115 measures the illuminance distribution on the reticle R that 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 can include a storage unit 105a that stores various data necessary for control.

Next, the optical action of the optical filter 6 will be described. FIG. 2 is a diagram schematically illustrating a relationship between a plurality of adjustment units provided on the 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 beam from the secondary light source 40 that is not reflected by the inner surface of the optical integrator 4. A pair of

adjustment units

61 a and 61 b adjacent to both outer sides of the adjustment unit 60 adjust the intensity of the light beam from the secondary

light source images

41 a and 41 b that are reflected once by the inner surface of the optical integrator 4. Further, a pair of

adjustment units

62 a and 62 b adjacent to both outer sides of the

adjustment units

61 a and 61 b adjust the intensity of the light beam from the secondary

light source images

42 a and 42 b reflected twice by the inner surface of the optical integrator 4. According to such a configuration, the transmittance can be controlled independently for each of the light beams of the plurality of secondary light sources formed by the optical integrator 4.

The adjusting

units

60, 61a, 61b, 62a, 62b are disposed in the vicinity of the conjugate surface S1 conjugate with the emission end surface 4b of the optical integrator 4. Accordingly, the shape of one adjustment unit corresponds to the illumination area on the reticle R or the wafer W in FIG. 1, and the transmittance distribution of the

adjustment units

60, 61 a, 61 b, 62 a, 62 b is on the wafer W. It is reflected in the illuminance distribution of the illumination area.

FIG. 3A is a diagram for explaining the imaging relationship between each adjustment unit in the optical filter 6 and the exit end face 4b of the optical integrator 4. FIG. In the optical integrator 4, the light beam from the adjacent secondary light source is inverted. For this reason, when the direction of the image formed on the exit end face 4b of the optical integrator 4 is “F”, the images of the adjacent adjustment units are opposite to each other and are in a mirror image relationship with each other.

FIG. 3B is a schematic view of the optical filter 6 disposed in the vicinity of the conjugate plane S1 as viewed from the incident side. Here, a pattern filter (or a light shielding member) is used as the adjustment unit. In the present embodiment, the plurality of pattern filters constituting the plurality of adjustment units are arranged at predetermined positions on the optical filter corresponding to the mirror image relationship in the plurality of secondary light source images 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 other than the first region. Here, the plurality of first areas A and B are areas in which images in the same direction are formed on the emission end face 4 b of the optical integrator 4. The plurality of second regions are regions where an image having a mirror image relationship with the image of the first region is formed on the emission end face 4 b of the optical integrator 4. In the present embodiment, rectangular pattern filters 6A and 6B are arranged on the surface of the optical filter 6 in the plurality of first regions A and B, corresponding to the plurality of secondary light source images of the optical integrator 4, respectively. Yes. Note that the pattern filters 6A and 6B may be arranged in at least a part of the plurality of first regions A and B instead of all of the first regions A and B.

In the present embodiment, by arranging circular pattern filters having different sizes as the pattern filters 6A and 6B, each pattern filter portion has an effect as shown in FIGS. 4A and 4B. ing. By appropriately adjusting the diameter, transmittance, and arrangement of each pattern filter, finally, on the surface to be illuminated, as shown in FIG. 4C representing the sum of FIGS. 4A and 4B, approximately. An effect of increasing the illuminance at the periphery of the illuminated surface in proportion to the square of the image height can be obtained.

In general, in an illumination optical system of a projection exposure apparatus, when trying to achieve both the uniformity of the numerical aperture on the surface to be illuminated and the uniformity of the illuminance distribution, the ambient illuminance decreases due to the angular characteristics of the antireflection film used for the lens. There is a tendency. For this reason, an optical filter having an effect of increasing the illuminance in the vicinity as in the present embodiment is effective in correcting the illuminance distribution.

Further, the light beam incident on the optical integrator 4 is adjusted so as to have an illuminance distribution symmetric with respect to the optical axis. As a result, the effective light source distribution on the illuminated surface is symmetric with respect to the chief ray, so that no image shift occurs with respect to defocusing. Thereby, exposure with good telecentricity can be realized.

If the illumination light incident on the optical integrator 4 has an asymmetric 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 telecentricity shift. . However, according to the present embodiment, since the arrangement of the pattern filter is symmetric with respect to the optical axis, the telecentricity shift hardly occurs.

In this embodiment, two types of pattern filters 6A and 6B are used as the adjustment unit. However, for example, by changing the density of fine dot patterns, 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 for correcting illuminance unevenness as shown in FIG. 5A will be described. The illuminance unevenness in FIG. 5A is decomposed into an inclined illuminance unevenness as shown in FIG. 5B and an illuminance unevenness in which the illuminance decreases as it goes to the periphery as shown in FIG. 5C. can do. These can be separated from each other by calculating the average illuminance and inclination component by image height from the illuminance distribution.

First, a method of correcting the inclined illuminance unevenness in FIG. 5B will be described. As described above, the optical filter 6 of this embodiment has an effect of increasing the illuminance at the peripheral portion in proportion to the square of the image height. At this time, if the incident end face 4a of the optical integrator 4 is equivalent to the illuminated surface and is a normalized XY coordinate system, the effect z of the illuminance distribution adjustment by the optical filter 6 is z = a (x ² + y ² ). Can be written. Here, a is a constant.

The pattern filters 6A and 6B of the optical filter 6 are disposed in at least a part of the plurality of first regions A and B in which images in the same direction are formed on the exit end face 4b of the optical integrator 4. The optical filter 6 is movable in a direction along the plurality of first regions A and B and the plurality of second regions which 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 a 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 effects of the illuminance distribution change on the illuminated surface provided by the pattern filters 6A and 6B are not canceled out.

Therefore, the effect z ′ of the illuminance distribution adjustment by the optical filter 6 when the optical filter 6 is moved by the predetermined distance δ in the X direction and the Y direction can be written as z ′ = a ((x + δ) ² + (y + δ) ² ). Here, a is a constant. That is, since the first-order terms of x and y depending on δ are generated, an inclined illuminance distribution can be generated.

FIG. 6 is a flowchart showing a correction procedure for inclined uneven illuminance. In step S601, the control unit 105 calculates illuminance unevenness on the illuminated surface based on the illuminance distribution data measured by the illuminance distribution measuring unit 115 (illuminance unevenness measurement 1). If the maximum value of the illuminance value on the surface to be illuminated is Smax and the minimum value is Smin, the illuminance unevenness S is calculated by the following equation, for example.
S = (Smax−Smin) / (Smax + Smin)
Thereafter, the control unit 105 moves the optical filter 6 by a predetermined distance δ in the X direction in S602, and measures illuminance unevenness on the illuminated surface in S603 (illuminance unevenness measurement 2). Next, the control unit 105 moves the optical filter 6 by a predetermined distance δ in the Y direction in S604, and measures the illuminance unevenness on the illuminated surface in S605 (illuminance unevenness measurement 3). Thereafter, in step S606, the control unit 105 calculates the amount of change in illuminance unevenness from the results of the

illuminance unevenness measurements

1, 2, and 3, and stores the change in the storage unit 105a. This change amount corresponds to the inclination of the above-described inclined illuminance 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 causes the filter driving unit 7 to move the optical filter 6 by the calculated movement amount in the calculated direction.

Thereafter, in S609, the control unit 105 again measures the illuminance unevenness on the surface to be illuminated (illuminance unevenness measurement 4), and confirms whether the illuminance unevenness is within a predetermined allowable range in S610. If the illuminance unevenness is within the allowable range, the process ends. On the other hand, if the illuminance unevenness is not within the allowable range, the process proceeds to S611, the result of the illuminance unevenness measurement 4 is fed back, and the process returns to S607 to recalculate the moving direction and the moving amount of the optical filter 6.

Next, a method of correcting illuminance unevenness that is symmetric with respect to the optical axis in FIG. 5C will be described with reference to the flowchart in FIG. When illuminance unevenness symmetric to the optical axis occurs, the peripheral illuminance correction amount is adjusted. As described above, the second relay optical system 5 has a configuration in which the distortion is changed while the focal length is not substantially changed by moving the lens front group 5a in the optical axis direction. Thereby, the peripheral illuminance can be increased or decreased by the movement of the lens front group 5a.

In S701, the control unit 105 obtains the amount of change in illuminance at the outermost peripheral portion of the illuminated surface when the illuminance distribution measurement unit 115 moves the lens front group 5a by a predetermined distance Δ in the optical axis direction. Is stored in the storage unit 105a (illuminance unevenness measurement 1). Note that S701 may be performed in advance by simulation or the like. In S702, the control unit 105 calculates the amount of movement of the lens front group 5a in the optical axis direction based on the amount of change. In step S <b> 703, the control unit 105 causes the lens driving unit 51 to move the lens front group 5 a in the optical axis direction by the calculated movement amount.

Thereafter, in S704, the control unit 105 again obtains the amount of change in illuminance at the outermost peripheral portion of the illuminated surface when the lens front group 5a is moved by a predetermined distance Δ in the optical axis direction (illuminance unevenness measurement 2), and S705. Then, it is confirmed whether the fluctuation amount is within a predetermined allowable range. If the fluctuation amount is within the allowable range, the process ends. On the other hand, if the fluctuation amount is not within the allowable range, the process proceeds to S706, the result of the illuminance unevenness measurement 2 is fed back, the process returns to S703, and the movement amount of the optical filter 6 is recalculated. As described above, 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 measurement unit 115 falls within the allowable range.
By performing both the movement of the optical filter 6 according to the control procedure of FIG. 6 and the driving of the front 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 performed by the control unit 105 may be executed in series along a time series, or may be executed in parallel.

Note that the execution results of the control procedure of FIG. 6 and the control procedure of FIG. 7 can be stored in the storage unit 105a. When it is executed again under the same illumination conditions, each element can be driven to the optimum position by calling the execution result from the storage unit 105a. Thereby, the procedures as shown in FIGS. 6 and 7 can be omitted, and the correction of the inclined uneven illuminance and the concentric uneven illuminance (illuminance unevenness symmetric to the optical axis) can be performed quickly.

Further, when the illumination optical system is used for a long period of time, it is considered that the transmittance of any lens in the apparatus is deteriorated, and rotationally asymmetric inclined uneven illumination is generated. Even in such a case, the control procedure shown in FIGS. 6 and 7 may be executed again to correct the inclined illuminance unevenness and the concentric illuminance unevenness (illuminance unevenness symmetric to the optical axis). .

For example, in Japanese Patent Application Laid-Open No. 2001-135564, an optical filter is arranged in the vicinity of an 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 adjustment unit that can adjust the amount of transmitted light in a plurality of regions respectively corresponding to a plurality of microlenses constituting the optical integrator. Even with such a configuration, it is possible to control illuminance unevenness by moving the optical filter along the XY plane.

However, since the optical integrator in which a plurality of microlenses are two-dimensionally arranged at a predetermined pitch is generally expensive, the rod-type optical integrator according to the present embodiment is lower in cost. According to the configuration of the present embodiment using the rod-type optical integrator, the arrangement position of each adjustment unit is determined by utilizing the imaging relationship as shown in FIG. 3A. Specifically, the plurality of adjustment units are arranged so that the direction of the image of each adjustment unit formed on the exit end face of the rod-type optical integrator is the same by the light transmitted through each of the plurality of adjustment units. Placed on top. Thereby, illuminance unevenness control is possible.

Second Embodiment
Next, an illumination optical system according to the second embodiment will be described. The schematic configuration of the apparatus is the same as that shown in FIG. FIG. 3C is a schematic view of the optical filter 6 according to the present embodiment as viewed from the incident side. On the surface of the optical filter 6, rectangular pattern filters 6 </ b> C are arranged in a plurality of first regions C corresponding to a plurality of secondary light source images of the optical integrator 4, and a rectangular pattern filter 6 </ b> D is a plurality of rectangular pattern filters 6 </ b> D. Arranged in the second region D. Note that the pattern filters 6C and 6D may be arranged in at least a part of the plurality of first regions C and the plurality of second regions D, respectively. Here, the plurality of first regions C are regions in which images in the same direction are formed on the emission end surface 4 b of the optical integrator 4. The plurality of second regions D are regions where images having a mirror image relationship with the images of the plurality of first regions C are formed on the emission end face 4 b of the optical integrator 4.

In the present embodiment, the pattern filter 6C has the effect of increasing the illuminance at the peripheral portion of the illuminated surface approximately in proportion to the square of the image height as shown in FIG. 8A. The pattern filter 6D has the opposite characteristic, that is, the effect of lowering the illuminance at the peripheral portion approximately in proportion to the square of the image height as shown in FIG. 8B. As a whole, the combination of the pattern filters 6C and 6D is configured to cancel the effects of the illuminance distribution change.

Hereinafter, a method of correcting the uneven illuminance as shown in FIG. 9A will be described. If the incident end surface 4a of the optical integrator 4 is equivalent to an illuminated surface and is a normalized XY coordinate system, the effect z of the optical filter 6 is expressed as z = ax ² −ax for the sake of simplicity and expressed only in one dimension in the X direction. ² = 0 and does not affect the illuminance distribution. Here, a is a constant.

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

Also in this embodiment, by executing the same procedure as that in the flowchart of FIG. 6, it is possible to correct the uneven illumination unevenness so as to be flat as shown in FIG. 9B. Thus, when the secondary illuminance decrease of the secondary shape is originally small and the inclined illuminance unevenness is dominant, the configuration of the adjustment unit as in this embodiment is effective for correcting the illuminance distribution.

<Third Embodiment>
Next, an illumination optical system according to the third embodiment will be described. In the present embodiment, the effects of the pattern filters 6C and 6D in the second embodiment are different. The pattern filter 6C in the present embodiment has an effect that the illuminance distribution changes approximately in proportion to the cube of the image height as shown in FIG. 10A. The pattern filter 6D has the opposite characteristic, that is, an effect that the illuminance distribution changes approximately in proportion to the cube of the image height as shown in FIG. 10B. As a whole, the combination of the pattern filters 6C and 6D is configured to cancel the effects of the illuminance distribution change.

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

The effect z ′ when the optical filter 6 is moved by a predetermined distance δ in the X direction is z ′ = a (x + δ) ³ −a (x−δ) ³ because the direction of δ changes in the pattern filters 6C and 6D. . In the present embodiment, since a quadratic term of x depending on δ is generated, a concentric secondary illuminance distribution can be generated.

Also in the present embodiment, by executing the same procedure as in the flowchart of FIG. 6, the secondary shape illuminance distribution as shown in FIG. 11A can be corrected to be flat as shown in FIG. 11B. As described above, when there is originally no inclined illuminance unevenness and concentric secondary illuminance unevenness is dominant, the configuration of the adjustment unit as in this embodiment is effective for illuminance distribution correction.
Even if the illuminance distribution to be corrected is a third-order or higher order shape, illuminance unevenness correction can be performed by appropriately setting the transmittance distribution of the pattern filter.

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

<Embodiment of article manufacturing method>
The article manufacturing method according to 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. The article manufacturing method of this embodiment uses a lithography apparatus (such as an exposure apparatus, an imprint apparatus, or a drawing apparatus) to transfer an original pattern to a substrate, and processes the substrate on which the pattern has been transferred in this process. Including the step of. Further, the manufacturing method includes other well-known steps (oxidation, film formation, vapor deposition, doping, planarization, etching, resist stripping, dicing, bonding, packaging, and the like). The article manufacturing method of this embodiment is advantageous in at least one of the performance, quality, productivity, and production cost of the article as compared with the conventional method.

The present invention is not limited to the above embodiment, and various changes and modifications can be made without departing from the spirit and scope of the present invention. Therefore, in order to make the scope of the present invention public, the following claims are attached.

This application claims priority based on Japanese Patent Application No. 2016-168546 filed on Aug. 30, 2016, the entire contents of which are incorporated herein by reference.

Claims

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 illuminated surface;
An optical filter having an adjustment unit for adjusting the intensity of light incident on the optical integrator;
Have
The optical integrator is a rod-type optical integrator that reflects incident light on its inner surface,
The optical filter includes a plurality of first regions in which images in the same direction are formed on the exit end face of the rod-type optical integrator, and a plurality of images in which an image having a mirror image relationship with the image is formed on the exit end face. And a second region of
The adjustment unit is provided at least in the first region,
The illumination optical system, wherein the illuminance on the illuminated surface is changed by changing the position of the adjustment unit in a direction perpendicular to the optical axis of the illumination optical system.
2. The illumination optical system according to claim 1, wherein the adjusting unit is not provided in the second region, but is provided in the plurality of first regions.
The adjustment unit is disposed in the plurality of first regions and the plurality of second regions,
The characteristic of the illuminance distribution on the illuminated surface adjusted by the adjusting unit in the first region is different from the characteristic of the illuminance distribution on the illuminated surface adjusted by the adjusting unit in the second region. The illumination optical system according to claim 1.
A first relay optical system that is disposed between the light source and the optical integrator and guides the light from the light source to the optical integrator;
The first relay optical system includes a first lens that collimates light from a light source, and a second lens that condenses the light that has been collimated by the first lens onto the incident end surface of the optical integrator. ,
The illumination optical system according to claim 1, wherein the optical filter is disposed between the first lens and the second lens.
It further has a measuring unit that measures the illuminance distribution on the illuminated surface,
The illumination optical system according to claim 1, wherein the position of the optical filter is changed based on the illuminance distribution measured by the measurement unit.
A control unit for controlling the driving of the optical filter;
The illumination according to claim 5, wherein the control unit feedback-controls driving of the optical filter so that illuminance unevenness calculated from the illuminance distribution measured by the measurement unit is within an allowable range. Optical system.
A second relay optical system that is disposed between the optical integrator and the illuminated surface and guides light from the exit end surface of the optical integrator to the illuminated surface;
The second relay optical system is a third lens that collimates light from the exit end face of the optical integrator and is configured to be movable in the optical axis direction of the second relay optical system. Including
The control unit further feedback-controls driving of the third lens so that illuminance unevenness calculated from the illuminance distribution measured by the measurement unit falls within an allowable range. The illumination optical system described.
A lithographic apparatus for forming an original pattern on a substrate,
The illumination optical system according to claim 1, which illuminates the original plate;
A projection optical system for projecting the pattern onto the substrate;
A lithographic apparatus comprising:
Forming a pattern on a substrate using the lithographic apparatus according to claim 8;
Processing the substrate on which the pattern is formed in the step;
An article manufacturing method comprising obtaining an article from a processed substrate.