CN112782940A - Aberration measuring method, article manufacturing method, and exposure apparatus - Google Patents
Aberration measuring method, article manufacturing method, and exposure apparatus Download PDFInfo
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- CN112782940A CN112782940A CN202011231381.6A CN202011231381A CN112782940A CN 112782940 A CN112782940 A CN 112782940A CN 202011231381 A CN202011231381 A CN 202011231381A CN 112782940 A CN112782940 A CN 112782940A
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- 238000004519 manufacturing process Methods 0.000 title claims abstract description 13
- 238000000034 method Methods 0.000 title claims description 41
- 230000003287 optical effect Effects 0.000 claims abstract description 125
- 238000009826 distribution Methods 0.000 claims abstract description 71
- 238000000691 measurement method Methods 0.000 claims abstract description 6
- 239000000758 substrate Substances 0.000 claims description 68
- 238000005259 measurement Methods 0.000 claims description 30
- 230000010354 integration Effects 0.000 claims description 14
- 238000012545 processing Methods 0.000 claims description 12
- 239000000463 material Substances 0.000 claims description 8
- 238000001514 detection method Methods 0.000 description 16
- 238000005286 illumination Methods 0.000 description 9
- 230000007246 mechanism Effects 0.000 description 8
- 230000008569 process Effects 0.000 description 8
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- 238000004088 simulation Methods 0.000 description 5
- 238000012546 transfer Methods 0.000 description 4
- 230000008859 change Effects 0.000 description 3
- 238000011161 development Methods 0.000 description 2
- 238000003384 imaging method Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 201000009310 astigmatism Diseases 0.000 description 1
- 239000004973 liquid crystal related substance Substances 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 1
- 229910052753 mercury Inorganic materials 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 238000000206 photolithography Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 230000002123 temporal effect Effects 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
- G01M11/02—Testing optical properties
- G01M11/0242—Testing optical properties by measuring geometrical properties or aberrations
- G01M11/0257—Testing optical properties by measuring geometrical properties or aberrations by analyzing the image formed by the object to be tested
- G01M11/0264—Testing optical properties by measuring geometrical properties or aberrations by analyzing the image formed by the object to be tested by using targets or reference patterns
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/70—Microphotolithographic exposure; Apparatus therefor
- G03F7/70483—Information management; Active and passive control; Testing; Wafer monitoring, e.g. pattern monitoring
- G03F7/70591—Testing optical components
- G03F7/706—Aberration measurement
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
- G01M11/02—Testing optical properties
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
- G01M11/02—Testing optical properties
- G01M11/0207—Details of measuring devices
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
- G01M11/02—Testing optical properties
- G01M11/0221—Testing optical properties by determining the optical axis or position of lenses
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
- G01M11/02—Testing optical properties
- G01M11/0242—Testing optical properties by measuring geometrical properties or aberrations
- G01M11/0271—Testing optical properties by measuring geometrical properties or aberrations by using interferometric methods
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/70—Microphotolithographic exposure; Apparatus therefor
- G03F7/70216—Mask projection systems
- G03F7/70258—Projection system adjustments, e.g. adjustments during exposure or alignment during assembly of projection system
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/027—Making masks on semiconductor bodies for further photolithographic processing not provided for in group H01L21/18 or H01L21/34
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- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Geometry (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- Manufacturing & Machinery (AREA)
- Computer Hardware Design (AREA)
- Microelectronics & Electronic Packaging (AREA)
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- Exposure And Positioning Against Photoresist Photosensitive Materials (AREA)
- Testing Of Optical Devices Or Fibers (AREA)
- Exposure Of Semiconductors, Excluding Electron Or Ion Beam Exposure (AREA)
Abstract
The present disclosure relates to an aberration measurement method, an article manufacturing method, and an exposure apparatus. The aberration measurement method includes: a step of measuring, at a plurality of positions in an optical axis direction of a projection optical system, light quantities of light transmitted through an object side mark disposed on an object side of the projection optical system, and an image side mark disposed on an image side of the projection optical system, thereby acquiring a light quantity distribution indicating a relationship between the positions in the optical axis direction and the light quantities; a step of obtaining a feature quantity indicating asymmetry in the light quantity distribution with a focal position of the projection optical system as a symmetry axis; and determining the amount of aberration of the projection optical system based on the feature amount.
Description
Technical Field
The invention relates to an aberration measuring method, an article manufacturing method and an exposure apparatus.
Background
Articles having a fine pattern such as a semiconductor element, a liquid crystal display element, a thin film magnetic head, and the like are manufactured by using a photolithography technique. At this time, an exposure apparatus is used which transfers the pattern of the original plate to the substrate by projecting the pattern of the original plate onto the substrate by a projection optical system. In order to transfer the pattern of the original plate to the substrate with high accuracy, it is necessary to adjust the aberration of the projection optical system. The aberration of the projection optical system may vary due to heat generated by irradiation of the exposure light, atmospheric pressure, or the like. Therefore, the aberration of the projection optical system should be adjusted during the exposure task or the like.
The specification of international publication No. 04/059710 describes the following method: the object side mark including the periodic pattern is projected onto the image surface side mark by the projection optical system, and the image surface side mark is measured while being scanned at a plurality of positions in the optical axis direction of the projection optical system. However, in the method described in international publication No. 04/059710, since it is necessary to scan the image surface side marks at a plurality of positions in the optical axis direction of the projection optical system, the time required for measurement is long.
Disclosure of Invention
The present invention provides a technique advantageous for measuring aberrations of a projection optical system in a short time.
The 1 st aspect of the present invention relates to an aberration measuring method including: a step of measuring, at a plurality of positions in an optical axis direction of a projection optical system, light quantities of light transmitted through an object side mark disposed on an object side of the projection optical system, and an image side mark disposed on an image side of the projection optical system, thereby acquiring a light quantity distribution indicating a relationship between the positions in the optical axis direction and the light quantities; a step of obtaining a feature quantity indicating asymmetry in the light quantity distribution with a focal position of the projection optical system as a symmetry axis; and determining the amount of aberration of the projection optical system based on the feature amount.
The 2 nd aspect of the invention relates to an article manufacturing method including: a measurement step of measuring an aberration amount of a projection optical system of an exposure apparatus in accordance with the aberration measurement method of the 1 st aspect; an adjustment step of adjusting an aberration of the projection optical system based on the aberration amount measured in the measurement step; an exposure step of exposing the substrate coated with the photosensitive material by the exposure device after the adjustment step; a developing step of developing the photosensitive material after the exposure step; and a processing step of processing the substrate subjected to the developing step, wherein the article manufacturing method obtains an article from the substrate subjected to the processing step.
The invention according to claim 3 is an exposure apparatus comprising a master stage, a projection optical system, a substrate stage, a light receiving unit disposed on the substrate stage, and a control unit, the light receiving unit measures, at a plurality of positions in an optical axis direction of the projection optical system, light quantities of light transmitted through an object side mark disposed on an object side of the projection optical system, and an image side mark disposed on an image side of the projection optical system, the control unit obtains a light quantity distribution indicating a relationship between the position in the optical axis direction and the light quantity based on an output from the light receiving unit, obtains a feature quantity indicating asymmetry in the light quantity distribution about a focal position of the projection optical system as a symmetry axis, and determines an amount of aberration of the projection optical system based on the feature quantity.
Drawings
Fig. 1 is a diagram showing a configuration example of an exposure apparatus according to embodiment 1.
Fig. 2 is a diagram showing a configuration example of the substrate mounting table.
Fig. 3 is a diagram illustrating a relationship of spherical aberration and an asymmetric component (feature quantity).
Fig. 4 is a diagram illustrating a light amount distribution.
Fig. 5 is a diagram illustrating a light amount distribution in a case where the projection optical system has spherical aberration.
Fig. 6 is a diagram showing steps of processing for generating characteristic information.
Fig. 7 is a diagram illustrating processing performed in the exposure apparatus.
(symbol description)
EXP: an exposure device; 1: original edition; 3: a substrate; 6: a projection optical system; 14: a light receiving part.
Detailed Description
Hereinafter, embodiments will be described in detail with reference to the drawings. The following embodiments do not limit the inventions according to the patent claims. In the embodiments, a plurality of features are described, but not all of the plurality of features are necessarily essential to the invention, and a plurality of features may be arbitrarily combined. In the drawings, the same or similar components are denoted by the same reference numerals, and redundant description thereof is omitted.
Hereinafter, embodiment 1 will be described. Fig. 1 shows a configuration example of an exposure apparatus EXP of embodiment 1. The exposure apparatus EXP may have a function of measuring an aberration (for example, spherical aberration) of the projection optical system 6, and adjusting the aberration of the projection optical system 6 according to the result of the measurement thereof. The exposure apparatus EXP projects the pattern of the original plate 1 onto the substrate 3 coated with the photosensitive material by the projection optical system 6, thereby transferring the pattern of the original plate 1 onto the substrate 3 (photosensitive material).
Hereinafter, a configuration example and an operation example of the exposure apparatus EXP will be described more specifically. The exposure apparatus EXP may include: a reticle stage 2 for supporting a reticle (reticle) 1; a substrate mounting table 4 for supporting the substrate 3; and an illumination optical system 5 that illuminates the original plate 1 supported by the original plate stage 2 with exposure light. The exposure apparatus EXP may further include: a projection optical system 6 that projects the pattern of the original plate 1 illuminated with the exposure light onto the substrate 3 supported by the substrate mounting table 4; and a control unit CNT for controlling the laser interferometers 10 and 12 and the exposure apparatus EXP. The exposure apparatus EXP may include a light receiving unit 14, an alignment detection system 16, and a focus detection system 15.
The exposure apparatus EXP is configured as a scanning exposure apparatus (scanning stepper) that transfers the pattern of the original plate 1 to the substrate 3 while scanning the original plate 1 and the substrate 3 in synchronization with each other in the scanning direction. However, the exposure apparatus EXP may be applied to an exposure apparatus (stepper) that makes the original plate 1 and the substrate 3 stationary and transfers the pattern of the original plate 1 to the substrate 3. In the following description, a direction coincident with the optical axis of the projection optical system 6 is referred to as a Z-axis direction, a direction parallel to a direction in which the original plate 1 and the substrate 3 are scanned in a plane parallel to the Z-axis direction is referred to as a Y-axis direction, and a direction (non-scanning direction) perpendicular to the Z-axis direction and the Y-axis direction is referred to as an X-axis direction. Directions around the X, Y, and Z axes are referred to as θ X, θ Y, and θ Z directions, respectively.
The illumination area of the original plate 1 is illuminated with exposure light having a uniform illuminance distribution by the illumination optical system 5. The illumination optical system 5 may include a plurality of illumination apertures (not shown) for setting illumination conditions, and any illumination aperture may be used. The illumination optical system 5 may include, for example, a mercury lamp, a KrF excimer laser, an ArF excimer laser, an F2 laser, or a light source such as an Extreme Ultraviolet (EUV) light source. The master stage 2 supports the master 1. The master stage 2 can drive the master 1 at least in the Y-axis direction, and preferably can drive the master 1 about 6 axes. The original plate mounting table 2 can be driven by a drive mechanism such as a linear motor.
The original plate mounting table 2 can be provided with a mirror 7. A laser interferometer 9 can be provided at a position opposed to the reflecting mirror 7. The positions of the original plate mounting table 2 in the X-axis and Y-axis directions and the rotation angle in the θ Z direction are measured in real time by the laser interferometer 9, and the measurement results can be supplied to the control unit CNT. The control unit CNT controls the position and rotation angle of the reticle 1 supported by the reticle stage 2 by controlling the position and rotation angle of the reticle stage 2 based on the measurement result supplied from the laser interferometer 9.
The projection optical system 6 can project the pattern of the original plate 1 onto the substrate 3 at a predetermined projection magnification (e.g., 1/4 or 1/5). The projection optical system 6 includes a plurality of optical elements including an optical element for adjusting an aberration (for example, spherical aberration) of the projection optical system 6. The substrate mounting table 4 supports the substrate 3. The substrate mounting table 4 is driven by a substrate driving mechanism not shown. The substrate driving mechanism may include: a Z-stage mechanism for driving the substrate stage 4 in the Z-axis direction; an XY stage mechanism for driving the Z stage mechanism in X-axis and Y-axis directions; and a base for supporting the XY loading table mechanism.
A reflecting mirror 8 can be provided on the substrate mounting table 4. A plurality of laser interferometers 10 and 12 (only two are shown) can be provided at positions facing the reflecting mirror 8. The positions of the substrate mounting table 4 in the X-axis, Y-axis, Z-axis directions and the rotation angle in the θ Z direction are measured in real time by the laser interferometer 10, and the measurement results can be supplied to the control unit CNT. The control unit CNT drives the substrate mounting table 4 based on the measurement results supplied from the laser interferometers 10 and 12, and controls the position and rotation angle of the substrate 3.
The control unit CNT may be constituted by, for example, PLD (Programmable Logic Device) such as FPGA (Field Programmable Gate Array), ASIC (Application Specific Integrated Circuit), general-purpose computer with a program incorporated therein, or a combination of all or a part of them.
As illustrated in fig. 2, 1 or more substrate reference plates 11 are provided on the substrate mounting table 4. The surface of the substrate reference plate 11 is located at substantially the same height as the surface of the substrate 3. On the substrate reference plate 11, a reference mark 18 used for measurement by the alignment detection system 16 and an image side mark 17 used for measurement by the light receiving unit 14 can be arranged. The relative positions of the reference mark 18 and the image-side mark 17 are known. Alternatively, the reference mark 18 and the image-side mark 17 may be a common mark. The reference mark 18 and the image-side mark 17 are marks arranged on the image-side (image surface or its vicinity) of the projection optical system 6. Similarly, a master reference plate 13 having an object-side mark is provided on the master stage 2. The object side mark of the original plate reference 13 is a mark disposed on the object side (object surface or its vicinity) of the projection optical system 6.
The relative position between the original plate mounting table 2 and the substrate mounting table 4 can be measured by measuring the relative position between the object-side mark of the original plate reference plate 13 and the image-side mark 17 of the substrate reference plate 11 using the light receiving unit 14. Specifically, the object side mark of the original plate reference 13 is illuminated by the illumination optical system 5. The light transmitted through the object side mark passes through the projection optical system 6, further passes through the image side mark 17 of the substrate reference plate 11, and enters the light receiving unit 14. The light receiving unit 14 detects the amount (intensity) of incident light. The light quantity of light incident on the light receiving unit 14 can be measured by the light receiving unit 14 while driving the substrate mounting table 4 in the X-axis direction, the Y-axis direction, and the Z-axis direction, respectively. Then, the X-axis and Y-axis positions and the Z-axis position (focus) of the object-side mark of the original plate reference plate 13 and the image-side mark 17 of the substrate reference plate 11 can be adjusted based on the change in the amount of light measured by the light receiving unit 14. The object side mark may be disposed on the original plate 1.
Fig. 4 (a) shows a light amount distribution in which the position of the substrate mounting table 4 in the X-axis direction (or the Y-axis direction) is taken as the horizontal axis and the light amount (intensity) of light entering the light receiving unit 14 at each position is taken as the vertical axis by a solid line. This light quantity distribution can be obtained by measuring the light quantities of the light transmitted through the object side mark, the projection optical system 6, and the image side mark 17 at a plurality of positions in the X-axis direction (or the Y-axis direction). In fig. 4 (a), the position at which the light amount exhibits the maximum value is the position of the substrate mounting table 4 when the position in the X-axis direction (or Y-axis direction) of the object-side mark coincides with the position in the X-axis direction (or Y-axis direction) of the image-side mark 17. The position at which the light amount exhibits the maximum value can be obtained by, for example, fitting a function to the light amount distribution, or centroid processing.
Fig. 4 (b) shows, by a solid line, a light quantity distribution in which the position of the substrate mounting table 4 in the Z-axis direction is taken on the horizontal axis and the light quantity (intensity) of light incident on the light receiving unit 14 at each position is taken on the vertical axis. This light quantity distribution can be obtained by measuring the light quantities of the light transmitted through the object side mark, the projection optical system 6, and the image side mark 17 at a plurality of positions in the optical axis direction (Z-axis direction) of the projection optical system 6. In fig. 4 (b), the position at which the light amount exhibits the maximum value is the position in the Z-axis direction of the substrate mounting table 4 at which the position in the Z-axis direction of the image side mark 17 coincides with the imaging position of the object side mark. In this way, a position where the light amount exhibits a maximum value in the light amount distribution in the optical axis direction of the projection optical system 6 is defined as a focal position. The position at which the light amount exhibits the maximum value can be obtained by, for example, fitting a function to the light amount distribution, or centroid processing.
The focus detection system 15 includes a projection system that projects detection light onto the surface of the substrate 3 and a light receiving system that receives reflected light from the substrate 3, and the result of focus detection by the focus detection system 15 is supplied to the control unit CNT. The control unit CNT can drive the Z stage mechanism based on the result of focus detection by the focus detection system 15 to adjust the position and the tilt angle of the substrate 3 in the Z axis direction.
The alignment detection system 16 may include: a projection system for projecting the detection light to the alignment mark 19 of the substrate 3 or the reference mark 18 of the substrate reference plate 11; and a light receiving system for receiving the reflected light from the alignment mark 19 or the reference mark 18. The result of the detection by the alignment detection system 16 is supplied to the control section CNT. The control unit CNT controls the positions of the substrate mounting table 4 in the X-axis direction and the Y-axis direction based on the detection result by the alignment detection system 16, and controls the positions of the substrate 3 in the X-axis direction and the Y-axis direction.
Hereinafter, a method of measuring the aberration of the projection optical system 6 will be described. Here, although a method of measuring spherical aberration as aberration of the projection optical system 6 is described, the method can also be applied to measurement of astigmatism. Fig. 4 (b) which has been explained exemplarily shows the light quantity distribution in the case where the projection optical system 6 does not have spherical aberration. The broken line 30 in fig. 4 (b) is the calculated focal position. The light amount distribution in fig. 4 (b) is symmetrical (line-symmetrical) with the broken line 30 as the axis of symmetry.
In fig. 5, the light amount distribution in a state where the projection optical system 6 has, for example, spherical aberration of 100m λ is shown by a solid line. The light quantity distribution can be acquired by measuring the light quantities of the light transmitted through the object side mark, the projection optical system 6, and the image side mark 17 at a plurality of positions in the optical axis direction (Z-axis direction) of the projection optical system 6. A broken line 31 in fig. 5 is a focal position calculated from the light amount distribution shown by the solid line in fig. 5. The light amount distribution shown in fig. 5 is asymmetrical (that is, not line-symmetrical) with the broken line 31 as the axis of symmetry.
In order to evaluate the asymmetry of the light amount distribution shown in fig. 5 (that is, the light amount distribution in the case where the projection optical system 6 has spherical aberration), a gaussian function g (z) represented by equation (1) is fitted to the light amount distribution. Here, the position of the substrate mounting table 4 in the optical axis direction is represented by z, the maximum light amount (intensity) in the light amount distribution is represented by a, the average value is represented by μ, the variance is represented by σ, and the constant term is represented by d. In addition, π is the circumferential ratio and exp is an exponential function.
[ formula 1 ]
The initial value of the fitting and the range of the fitting are preferably set so that the average value μ of the gaussian function after fitting is equal to the focal position. Since the gaussian function is a symmetric even function having the average value μ of the gaussian function as the axis of symmetry (origin), information indicating asymmetry of the light intensity distribution can be obtained by calculating the difference between the fitted gaussian function and the light intensity distribution. The asymmetric component (feature quantity) is calculated by integrating the difference over a predetermined integration interval-a to a centered on the focal position. Therefore, the asymmetric component AS when the measured light intensity distribution is represented by i (z) is expressed by the formula (2). Further, a can be arbitrarily determined.
[ formula 2 ]
In order to uniformize the influence of the light amount at the time of measurement, the detection sensitivity of the light receiving unit 14, and the like, the symmetric component S is calculated by integrating the fitted gaussian function in the same integration interval as that in the case of obtaining the asymmetric component as shown in equation (3).
[ formula 3 ]
By normalizing the asymmetric component AS with the symmetric component S, a normalized asymmetric component (normalized feature quantity) can be obtained. A straight line 32 in fig. 3 is characteristic information showing a relationship between the spherical aberration amount of the projection optical system 6 and the normalized asymmetric component (characteristic amount).
When the normalized asymmetric component obtained from the light amount distribution shown in fig. 5 is the asymmetric component indicated by reference numeral 35, the spherical aberration amount corresponding to the asymmetric component can be determined as the spherical aberration amount indicated by reference numeral 36 based on the characteristic information indicated by the straight line 32. Here, since the information indicated by the straight line 32 may differ depending on the measurement condition, it is preferable to obtain the characteristic information for each measurement condition.
The projection optical system 6 mounted on the exposure apparatus EXP can measure aberrations using a measuring instrument such as an interferometer at the stage of manufacture, and adjust the aberrations based on the result. However, even if the aberration of the projection optical system 6 is adjusted with high accuracy in the manufacturing stage, the aberration may be changed when the projection optical system 6 is mounted on the exposure apparatus EXP. In addition, the aberration of the projection optical system 6 may vary with time due to the influence of heat generated at the time of exposure and the environment of use (for example, air pressure). For example, it is considered that the amount of spherical aberration of the projection optical system 6 indicated by symbol 33 in fig. 3 changes to the amount of spherical aberration as indicated by symbol 34 due to the change with time. As described above, the above-described principle requires a technique for easily measuring the aberration of the projection optical system 6 in the exposure apparatus EXP.
According to the above method, even if the spherical aberration of the projection optical system 6 is generated due to temporal change, the spherical aberration of the projection optical system 6 can be measured in a short time. As described above, by preparing characteristic information (straight line 32) indicating the relationship between the spherical aberration amount of the projection optical system 6 and the normalized asymmetric component (characteristic amount), it is possible to obtain the asymmetric component from the measured light amount distribution and obtain the spherical aberration amount from the information and the asymmetric component.
The characteristic information can be obtained by simulation, for example. The image formed by the object side mark on the image side mark when the amount of spherical aberration changes can be calculated by simulation. Therefore, the amount of light that can be acquired by the light receiving unit 14 at each of the plurality of positions in the optical axis direction of the projection optical system 6 can be calculated by simulation for each of the plurality of spherical aberration amounts. In this way, the light amount distribution indicating the relationship between the position in the optical axis direction and the light amount corresponding to the position can be calculated for each of the plurality of spherical aberration amounts based on the light amounts obtained for the plurality of positions by simulation. Further, it is possible to obtain the asymmetric component of each of the plurality of light amount distributions corresponding to the plurality of spherical aberration amounts. This makes it possible to obtain characteristic information (straight line 32).
As a method of generating a plurality of spherical aberration amounts, there is a method of adjusting a driving amount (position) of at least 1 optical element among a plurality of optical elements constituting the projection optical system 6. Here, it is convenient to know the relationship between the driving amount and the spherical aberration amount, but the spherical aberration amount may be actually measured under the set driving amount. Characteristic information (straight line 32) can be obtained by obtaining a light amount distribution for each of the plurality of driving amounts, and obtaining an asymmetric component from the light amount distribution.
In fig. 6, steps of a process for generating characteristic information are shown. In step S310, the spherical aberration amount is set or changed. Next, in step S320, a light amount distribution indicating a relationship between a position in the optical axis direction and a light amount corresponding to the position is acquired with respect to the spherical aberration amount set or changed in step S310. This can be obtained by calculating the light amounts that can be acquired by the light receiving section 14 at a plurality of positions in the optical axis direction of the projection optical system 6 through simulation. Next, in step S330, a feature amount (asymmetric component) is obtained from the light amount distribution acquired in step S320. Next, in step S340, it is determined whether or not steps S320 and S330 are performed with respect to the other spherical aberration amount, and if steps S320 and S330 are performed with respect to the other spherical aberration amount, the process returns to step S310, and if not, the process proceeds to step S350. When returning to step S310, the spherical aberration amount is changed in step S310, and the process proceeds to step S320. In step S350, the characteristic information is generated from the feature amounts (asymmetric components) obtained for the plurality of spherical aberration amounts by repeating steps S310 to S330.
In fig. 7, a process implemented in the exposure apparatus EXP is shown. This process is controlled by the control unit CNT. In step S410, the control unit CNT determines whether or not to adjust the spherical aberration of the projection optical system 6. In step S410, the control unit CNT may determine to adjust the spherical aberration of the projection optical system 6 when exposure is completed for a predetermined number of substrates or a predetermined number of lots (1 lot may be constituted by a predetermined number of substrates), for example. Here, the step S420 may be used in combination with focus measurement performed prior to exposure of the substrate, and in this case, the step S410 is not necessary. Since the focus measurement is a measurement for adjusting the height of the imaging area of the substrate according to the image plane of the projection optical system 6, the same processing as in step S420 is performed to obtain the light amount distribution as illustrated in fig. 4 (b). Therefore, steps S430 to S450 can be performed using the light amount distribution obtained in the focus measurement.
In step S420, the control unit CNT causes the light receiving unit 14 to detect the light amount at each of a plurality of positions in the optical axis direction of the projection optical system 6, and acquires a light amount distribution indicating the relationship between the position in the optical axis direction and the light amount corresponding to the position based on the output from the light receiving unit 14. Next, in step S430, the control unit CNT obtains a feature amount (asymmetric component) from the light amount distribution acquired in step S420. In step S440, the control unit CNT determines the spherical aberration amount corresponding to the characteristic amount based on the characteristic information prepared in the processing shown in fig. 6 and the characteristic amount (asymmetric component) obtained in step S430. In step S450, the control unit CNT adjusts the spherical aberration of the projection optical system 6 so that the amount of spherical aberration determined in step S440 is reduced or made zero. This adjustment can be achieved by driving at least 1 optical element in the projection optical system 6. Step S450 may be performed only when the amount of spherical aberration determined in step S440 exceeds a predetermined threshold value.
In step S460, the control unit CNT performs exposure for transferring the pattern of the master 1 to the substrate 3. In step S470, the control unit CNT determines whether or not to end the processing in steps S410 to S470, and if not, returns to step S410.
Hereinafter, embodiment 2 will be described. Matters not mentioned as embodiment 2 can be in accordance with embodiment 1. The method of obtaining the feature quantity (asymmetric component) is not limited to fitting of a gaussian function. The control unit CNT can calculate the asymmetric component by fitting a polynomial function with the focal position as the origin as shown in equation (4) to the light amount distribution obtained by measurement, for example. Here, regarding the nth-order polynomial n (z), the coefficient of the i-order term is set to k _ i.
[ formula 4 ]
In this case, the integral value of only the even-order term of the polynomial function is set as a symmetric component, and the integral value of only the odd-order term of the polynomial function is set as an asymmetric component, and the asymmetric component, which is a characteristic quantity indicating the asymmetry of the light amount distribution, can be calculated. Embodiment 2 will be specifically described below.
The control unit CNT fits a polynomial function to the light amount distribution obtained by the measurement, and determines the aberration from the polynomial function. The light amount distribution shown in fig. 5 is asymmetrical (that is, not line-symmetrical) with the broken line 31 as the axis of symmetry. In order to evaluate the asymmetry of the light amount distribution shown in fig. 5 (that is, the light amount distribution when the projection optical system 6 has spherical aberration), the control unit CNT fits a polynomial function to the light amount distribution. Further, the control unit CNT obtains the feature value from the odd-numbered term of the fitted polynomial function. Specific examples thereof are described below.
The control unit CNT processes each of the even-numbered term and the odd-numbered term of the fitted polynomial function. The control unit CNT integrates the even-numbered terms in a predetermined integration interval (-a to a interval) centered around the focal position as shown in equation (5), and sets the value obtained by the integration as the symmetric component S.
[ FORMULA 5 ]
Further, AS shown in equation (6), the control unit CNT takes a value obtained by integrating the odd-numbered terms in a predetermined integration interval (-an interval from a to a) centered around the focal position AS the asymmetric component AS.
[ formula 6 ]
The control unit CNT calculates the asymmetric component AS a feature quantity indicating the asymmetry of the light amount distribution by normalizing the asymmetric component AS with the symmetric component S. Here, the width of the integration interval in expression (5) and the width of the integration interval in expression (6) may be set to be equal to each other.
Hereinafter, embodiment 3 will be described. Matters not mentioned as embodiment 3 can be in accordance with at least 1 of embodiments 1 and 2. The method of obtaining the feature amount (asymmetric component) is not limited to the method involving integration. The control unit CNT may calculate the asymmetry component as a feature quantity indicating the asymmetry of the light amount distribution based on a coefficient of a specific degree of a polynomial function fitted to the measured light amount distribution.
Hereinafter, embodiment 4 will be described. Matters not mentioned as embodiment 4 can be in accordance with at least 1 of embodiments 1 to 3. The method of finding the characteristic amount (asymmetric component) is not limited to the method involving fitting to a function of the light amount distribution obtained by measurement. For example, as shown in equation (7), the control unit CNT integrates the light amount distribution i (Z) obtained by measurement in a section (a section from Z0 to a) between the focal position Z0 and a position a at a predetermined distance in the positive direction from the focal position Z0, and obtains the integrated value α.
[ formula 7 ]
Further, as shown in equation (8), the control unit CNT integrates the light amount distribution i (Z) obtained by measurement with respect to a section (-a section to the focal position Z0) between the focal position Z0 and the position a at a predetermined distance in the negative direction, and obtains the integrated value β.
[ formula 8 ]
Then, the control unit CNT calculates an asymmetry component as a feature quantity indicating asymmetry of the light amount distribution from the two integrated values α and β. Here, the width of the integration interval in expression (7) and the width of the integration interval in expression (8) may be set to be equal to each other.
Next, a modification of the above embodiment will be described. As the feature quantity indicating the asymmetry of the light quantity distribution, the asymmetric component may be calculated from the shape of the light quantity distribution obtained by measurement. For example, the difference between the light amount distribution obtained by measurement and a plurality of light amount distributions corresponding to a plurality of spherical aberration amounts prepared in advance is taken. Then, the spherical aberration amount corresponding to the light amount distribution with the smallest difference can be determined as the spherical aberration amount corresponding to the light amount distribution obtained by the measurement.
The adjustment of the spherical aberration of the projection optical system 6 may be performed during the regular maintenance of the exposure apparatus EXP or may be performed during the interruption process of the exposure apparatus EXP.
When the measured spherical aberration of the projection optical system 6 exceeds the threshold value, the aberration of the projection optical system 6 may be measured and adjusted with higher accuracy by a method such as measuring a pattern shift and/or a shape in a result of actually exposing and developing a substrate with a Scanning Electron Microscope (SEM) and so forth to analogize the aberration amount. This is a method of measuring and adjusting the aberration of the projection optical system by a method of measuring the aberration of the projection optical system with higher accuracy only when the detected aberration exceeds a certain threshold value.
Hereinafter, a method for manufacturing an article to which the aberration measurement method is applied will be described. The article manufacturing method may include: a measurement step of measuring an amount of aberration of the projection optical system 6 of the exposure apparatus EXP in accordance with the aberration measurement method; and an adjustment step of adjusting the aberration of the projection optical system 6 based on the aberration amount measured in the measurement step. The article manufacturing method includes an exposure step of exposing a substrate coated with a photosensitive material to light using an exposure apparatus EXP after the adjustment step, a development step of developing the photosensitive material after the exposure step, and a treatment step of treating the substrate subjected to the development step, and obtains an article from the substrate subjected to the treatment step.
The present invention is not limited to the above embodiments, and various changes and modifications can be made without departing from the spirit and scope of the invention. Thus, the claims are added to disclose the scope of the invention.
Claims (11)
1. An aberration measuring method, comprising:
a step of measuring, at a plurality of positions in an optical axis direction of a projection optical system, light quantities of light transmitted through an object side mark disposed on an object side of the projection optical system, and an image side mark disposed on an image side of the projection optical system, thereby acquiring a light quantity distribution indicating a relationship between the positions in the optical axis direction and the light quantities;
a step of obtaining a feature quantity indicating asymmetry in the light quantity distribution with a focal position of the projection optical system as a symmetry axis; and
and determining the amount of aberration of the projection optical system based on the feature amount.
2. The aberration measuring method according to claim 1,
in the step of obtaining the feature amount, the feature amount is obtained from a difference between the light amount distribution and a gaussian function fitted to the light amount distribution.
3. The aberration measuring method according to claim 2,
in the step of obtaining the feature value, a value obtained by normalizing a value obtained by integrating the difference with respect to a predetermined integration section centered around the focal position by a value obtained by integrating the gaussian function with respect to the integration section is obtained as the feature value.
4. The aberration measuring method according to claim 1,
in the step of obtaining the feature amount, the feature amount is obtained from an odd-numbered term of a polynomial function fitted to the light amount distribution.
5. The aberration measuring method according to claim 4,
in the step of obtaining the feature amount, a value obtained by normalizing a value obtained by integrating the odd-numbered term with respect to an integration section with respect to a value obtained by integrating the even-numbered term of the polynomial function with respect to a predetermined integration section centered around the focal position is obtained as the feature amount.
6. The aberration measuring method according to claim 1,
in the step of obtaining the feature amount, the feature amount is obtained from a coefficient of a specific degree of a polynomial function fitted to the light amount distribution.
7. The aberration measuring method according to claim 1,
in the step of obtaining the feature amount, the feature amount is obtained from a value obtained by integrating the light amount distribution with respect to a section between the focal position and a position at a predetermined distance in a positive direction from the focal position and a value obtained by integrating the light amount distribution with respect to a section between a position at a predetermined distance in a negative direction from the focal position and the focal position.
8. The aberration measuring method according to claim 1,
in the step of determining the aberration amount, the aberration amount of the projection optical system is determined based on information indicating a relationship between the aberration amount of the projection optical system and the characteristic amount.
9. The aberration measuring method according to claim 1,
the aberration amount includes a spherical aberration amount.
10. A method of manufacturing an article, comprising:
a measurement step of measuring an aberration amount of a projection optical system of an exposure apparatus according to the aberration measurement method according to any one of claims 1 to 9;
an adjustment step of adjusting an aberration of the projection optical system based on the aberration amount measured in the measurement step;
an exposure step of exposing the substrate coated with the photosensitive material by the exposure device after the adjustment step;
a developing step of developing the photosensitive material after the exposure step; and
a processing step of processing the substrate subjected to the developing step,
the article manufacturing method obtains an article from the substrate subjected to the treatment step.
11. An exposure apparatus comprising a master stage, a projection optical system, a substrate stage, a light receiving unit disposed on the substrate stage, and a control unit,
the light receiving unit measures, at a plurality of positions in an optical axis direction of the projection optical system, light quantities of light transmitted through an object side mark disposed on an object side of the projection optical system, and an image side mark disposed on an image side of the projection optical system,
the control unit obtains a light quantity distribution indicating a relationship between the position in the optical axis direction and the light quantity based on an output from the light receiving unit, obtains a feature quantity indicating asymmetry in the light quantity distribution about a focal position of the projection optical system as a symmetry axis, and determines an amount of aberration of the projection optical system based on the feature quantity.
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| JP7377071B2 (en) | 2023-11-09 |
| KR20210056237A (en) | 2021-05-18 |
| TWI837431B (en) | 2024-04-01 |
| JP2021076721A (en) | 2021-05-20 |
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