JP7377071B2 - Aberration measurement method, article manufacturing method, and exposure device - Google Patents

Description

The present invention relates to an aberration measurement method, an article manufacturing method, and an exposure apparatus.

2. Description of the Related Art Articles having fine patterns, such as semiconductor devices, liquid crystal display devices, and thin film magnetic heads, are manufactured using photolithography technology. At that time, an exposure apparatus is used that transfers the pattern of the original onto the substrate by projecting the pattern of the original onto the substrate using a projection optical system. In order to transfer the pattern of the original onto the substrate with high precision, it is necessary to adjust the aberration of the projection optical system. The aberration of the projection optical system can vary depending on heat generated by exposure light, atmospheric pressure, and the like. Therefore, the aberrations of the projection optical system should be adjusted, such as during an exposure job.

Patent Document 1 discloses that an object-side mark including a periodic pattern is projected onto an image-side mark by a projection optical system, and the image-side mark is scanned at each of a plurality of positions in the optical axis direction of the projection optical system. The method of measurement is described. However, in the method described in Patent Document 1, it is necessary to scan the image plane side mark at each of a plurality of positions in the optical axis direction of the projection optical system, so the time required for measurement is long.

International Publication No. 04/059710

An object of the present invention is to provide an advantageous technique for measuring aberrations of a projection optical system in a short time.

One aspect of the present invention relates to an aberration measurement method, and the aberration measurement method includes: an object side mark placed on the object side of a projection optical system; an object side mark placed on the image side of the projection optical system; By measuring the amount of light transmitted through the image-side mark at a plurality of positions in the optical axis direction of the projection optical system, a light amount distribution indicating the relationship between the position in the optical axis direction and the light amount is obtained. a step of determining a feature amount indicating asymmetry with a focus position of the projection optical system as an axis of symmetry in the light amount distribution; and a step of determining an amount of aberration of the projection optical system from the feature amount, In the step of determining the feature amount, the feature amount is determined based on a difference between the light amount distribution and a Gaussian function fitted to the light amount distribution.

According to the present invention, an advantageous technique for measuring aberrations of a projection optical system in a short time is provided.

FIG. 1 is a diagram illustrating a configuration example of an exposure apparatus according to a first embodiment. The figure which shows the example of a structure of a board|substrate stage. FIG. 3 is a diagram illustrating the relationship between spherical aberration and an asymmetric component (feature amount). A diagram illustrating a light amount distribution. FIG. 3 is a diagram illustrating a light amount distribution when the projection optical system has spherical aberration. The figure which shows the procedure of the process for generating characteristic information. FIG. 3 is a diagram showing processing performed in an exposure apparatus.

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the claimed invention. Although a plurality of features are described in the embodiments, not all of these features are essential to the invention, and the plurality of features may be arbitrarily combined. Furthermore, in the accompanying drawings, the same or similar components are designated by the same reference numerals, and redundant description will be omitted.

The first embodiment will be described below. FIG. 1 shows an example of the configuration of an exposure apparatus EXP according to the first embodiment. The exposure apparatus EXP may have a function of measuring the aberration (for example, spherical aberration) of the projection optical system 6 and adjusting the aberration of the projection optical system 6 based on the measurement result. The exposure device EXP uses a projection optical system 6 to project the pattern of the original 1 onto the substrate 3 coated with a photosensitive material, thereby transferring the pattern of the original 1 onto the substrate 3 (photosensitive material).

Hereinafter, a configuration example and an operation example of the exposure apparatus EXP will be described in more detail. The exposure apparatus EXP can include an original stage 2 that supports an original (reticle) 1, a substrate stage 4 that supports a substrate 3, and an illumination optical system 5 that illuminates the original 1 supported by the original stage 2 with exposure light. . The exposure apparatus EXP also includes a projection optical system 6 that projects the pattern of the original plate 1 illuminated with exposure light onto the substrate 3 supported by the substrate stage 4, laser interferometers 10 and 12, and each component of the exposure apparatus EXP. A control unit CNT may be provided to control the elements. Further, the exposure apparatus EXP can include a light receiving section 14, an alignment detection system 16, and a focus detection system 15.

In the following, the exposure apparatus EXP is configured as a scanning exposure apparatus (scanning stepper) that transfers the pattern of the original 1 onto the substrate 3 while scanning the original 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 transfers the pattern of the original 1 onto the substrate 3 by keeping the original 1 and the substrate 3 stationary. In the following description, the direction that coincides with the optical axis of the projection optical system 6 will be referred to as the Z-axis direction, and the direction parallel to the direction in which the original 1 and the substrate 3 are scanned within a plane perpendicular to the Z-axis direction will be referred to as the Y-axis direction. The direction (non-scanning direction) perpendicular to the Z-axis direction and the Y-axis direction is defined as the X-axis direction. Further, directions around the X-axis, Y-axis, and Z-axis are respectively referred to as θX, θY, and θZ directions.

The illumination area of the original 1 is illuminated by an illumination optical system 5 with exposure light having a uniform illuminance distribution. The illumination optical system 5 can include a plurality of illumination apertures (not shown) for setting illumination conditions, and any illumination aperture can be used. The illumination optical system 5 may include a light source such as a mercury lamp, a KrF excimer laser, an ArF excimer laser, an F2 laser, or an extreme ultra violet (EUV light) light source. Original stage 2 supports original version 1. The original stage 2 can drive the original 1 at least in the Y-axis direction, and preferably can drive the original 1 about six axes. The original stage 2 can be driven by a drive mechanism such as a linear motor.

A mirror 7 may be provided on the original stage 2. A laser interferometer 9 may be provided at a position facing the mirror 7. The position of the original stage 2 in the X-axis and Y-axis directions and the rotation angle in the θZ 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 original stage 2 by controlling the position and rotation angle of the original stage 2 based on the measurement results supplied from the laser interferometer 9. .

The projection optical system 6 can project the pattern of the original 1 onto the substrate 3 at a predetermined projection magnification (for example, 1/4 or 1/5). The projection optical system 6 includes a plurality of optical elements, and the plurality of optical elements include optical elements for adjusting aberrations (for example, spherical aberration) of the projection optical system 6. The substrate stage 4 supports the substrate 3. The substrate stage 4 is driven by a substrate drive mechanism (not shown). The substrate drive mechanism may include a Z stage mechanism that drives the substrate stage 4 in the Z-axis direction, an XY stage mechanism that drives the Z stage mechanism in the X-axis and Y-axis directions, and a base that supports the XY stage mechanism. .

A mirror 8 may be provided on the substrate stage 4 . A plurality of laser interferometers 10 and 12 (only two are shown) may be provided at positions facing the mirror 8. The position of the substrate stage 4 in the X-axis, Y-axis, and Z-axis directions and the rotation angle in the θZ 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 controls the position and rotation angle of the substrate 3 by driving the substrate stage 4 based on the measurement results supplied from the laser interferometers 10 and 12.

The control unit CNT is, for example, a PLD (Programmable Logic Device) such as FPGA (Field Programmable Gate Array), or an ASIC (Application Specific Integrated). Abbreviation for Circuit), or a general-purpose computer with a built-in program It may be configured by a computer or a combination of all or part of these.

As illustrated in FIG. 2, the substrate stage 4 is provided with one or more substrate reference plates 11. The surface of the substrate reference plate 11 is located at approximately the same height as the surface of the substrate 3. On the substrate reference plate 11, a reference mark 18 used by the alignment detection system 16 for measurement and an image-side mark 17 used by the light receiving section 14 for measurement 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 plane side (at or near the image plane) of the projection optical system 6. Similarly, the original stage 2 is provided with an original reference plate 13 having an object side mark. The object side mark of the original reference plate 13 is a mark placed on the object side (at or near the object surface) of the projection optical system 6.

The relative position between the original stage 2 and the substrate stage 4 can be measured by measuring the relative position between the object side mark of the original reference plate 13 and the image side mark 17 of the substrate reference plate 11 using the light receiving section 14. Specifically, the object side mark of the original reference plate 13 is illuminated by the illumination optical system 5. The light that has passed through the object-side mark passes through the projection optical system 6 and further passes through the image-side mark 17 of the substrate reference plate 11 and enters the light receiving section 14 . The light receiving unit 14 detects the amount (intensity) of the incident light. While driving the substrate stage 4 in the X-axis direction, Y-axis direction, and Z-axis direction, the light receiving section 14 can measure the amount of light incident thereon. Based on the change in the amount of light measured by the light receiving unit 14, the positions of the object-side mark on the original reference plate 13 and the image-side mark 17 on the substrate reference plate 11 in the X-axis direction and Y-axis direction, and in the Z-axis direction are determined. The position (focus) of the image can be adjusted. The object side mark may be placed on the original plate 1.

In FIG. 4(a), the horizontal axis represents the position of the substrate stage 4 in the X-axis direction (or Y-axis direction), and the vertical axis represents the amount (intensity) of light incident on the light receiving unit 14 at each position. The light intensity distribution is shown by a solid line. This light amount distribution can be obtained by measuring the amount of 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 Y-axis direction). In FIG. 4(a), the position where the amount of light shows the maximum value is the same as the position of the object-side mark in the X-axis direction (or Y-axis direction) and the position of the image-side mark 17 in the X-axis direction (or Y-axis direction). This is the position of the substrate stage 4 when they match. The position where the amount of light shows the maximum value can be determined, for example, by fitting a function to the distribution of light amount, or by performing center-of-gravity processing.

In FIG. 4(b), the solid line shows the light amount distribution, where the horizontal axis represents the position of the substrate stage 4 in the Z-axis direction, and the vertical axis represents the amount (intensity) of light incident on the light receiving section 14 at each position. has been done. This light amount distribution is obtained by measuring the amount of light transmitted through the object-side mark, the projection optical system 6, and the image-side mark 17 at multiple positions in the optical axis direction (Z-axis direction) of the projection optical system 6. be able to. In FIG. 4(b), the position where the amount of light shows the maximum value is the position of the substrate stage 4 in the Z-axis direction where the position of the image-side mark 17 in the Z-axis direction coincides with the imaging position of the object-side mark. . In this way, the position where the light amount shows the maximum value in the light amount distribution in the optical axis direction of the projection optical system 6 is defined as the focus position. The position where the amount of light shows the maximum value can be determined, for example, by fitting a function to the distribution of light amount, or by performing center-of-gravity processing.

The focus detection system 15 includes a projection system that projects detection light onto the surface of the substrate 3 and a light reception system that receives reflected light from the substrate 3, and the focus detection result by the focus detection system 15 is supplied to the control unit CNT. be done. The control unit CNT can drive the Z stage mechanism based on the result of focus detection by the focus detection system 15 and adjust the position and inclination angle of the substrate 3 in the Z-axis direction.

The alignment detection system 16 includes a projection system that projects detection light onto the alignment mark 19 of the substrate 3 or the reference mark 18 of the substrate reference plate 11, and a light receiving system that receives reflected light from the alignment mark 19 or the reference mark 18. sell. The results of detection by the alignment detection system 16 are supplied to the control unit CNT. The control unit CNT controls the position of the substrate 3 in the X-axis direction and the Y-axis direction by controlling the position of the substrate stage 4 in the X-axis direction and the Y-axis direction based on the detection result by the alignment detection system 16. Control.

Hereinafter, a method of measuring the aberration of the projection optical system 6 will be explained. Note that although a method for measuring spherical aberration as the aberration of the projection optical system 6 will be described here, this method is also applicable to measuring astigmatism. FIG. 4B, which has already been described, exemplarily shows the light amount distribution when the projection optical system 6 does not have spherical aberration. A dotted line 30 in FIG. 4(b) is the calculated focus position. The light amount distribution in FIG. 4(b) is symmetrical (line symmetrical) with the dotted line 30 as the axis of symmetry.

In FIG. 5, the light amount distribution in a state where the projection optical system 6 has a spherical aberration of, for example, 100 mλ is shown by a solid line. The light amount distribution is obtained by measuring the amount of 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. Can be done. A dotted line 31 in FIG. 5 is the focus position calculated from the light amount distribution shown by the solid line in FIG. The light amount distribution shown in FIG. 5 is asymmetrical with respect to the axis of symmetry about the dotted line 31 (that is, it is not line symmetrical).

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), a Gaussian function Fit (z). Here, the position of the substrate stage 4 in the optical axis direction is z, the maximum light amount (intensity) in the light amount distribution is A, the average is μ, the dispersion is σ, and the constant term is d. Further, π is pi, and exp is an exponential function.

・・・（１）

...(1)

The initial value of fitting and the range of fitting are preferably set so that the average μ of the Gaussian function after fitting is equal to the focus position. The Gaussian function is a symmetric even function with the average μ of the Gaussian function as the axis of symmetry (origin), so by calculating the difference between the fitted Gaussian function and the light intensity distribution, we can show the asymmetry of the light intensity distribution. You can get information. An asymmetrical component (feature amount) is calculated by integrating this difference over a predetermined integration interval from -a to a centered on the focus position. Therefore, when the measured light amount distribution is I(z), the asymmetric component AS is expressed by equation (2). Note that a can be arbitrarily determined.

・・・（２）

...(2)

In addition, in order to equalize the effects of the light intensity during measurement and the detection sensitivity of the light receiving unit 14, the fitted Gaussian function is set to be the same as the integral interval when determining the asymmetric component, as shown in equation (3). The symmetrical component S is calculated by integrating over the integration interval of .

・・・（３）

...(3)

By normalizing the asymmetric component AS with the symmetric component S, a normalized asymmetric component (normalized feature amount) can be obtained. A straight line 32 in FIG. 3 is characteristic information indicating the relationship between the amount of spherical aberration of the projection optical system 6 and the normalized asymmetric component (feature amount).

If the normalized asymmetric component obtained from the light intensity distribution shown in FIG. The amount of aberration can be determined as the amount of spherical aberration indicated by reference numeral 36. Here, since the information shown on the straight line 32 may vary depending on the measurement conditions, it is desirable that the characteristic information is obtained for each measurement condition.

The aberrations of the projection optical system 6 mounted on the exposure apparatus EXP are measured using a measuring instrument such as an interferometer during the manufacturing stage, and the aberrations can be adjusted based on the results. However, even if the aberrations of the projection optical system 6 are adjusted with high precision at the manufacturing stage, the aberrations may have changed by the time the projection optical system 6 is mounted on the exposure apparatus EXP. Further, the aberration of the projection optical system 6 may change over time due to the heat generated during exposure and the environment in which it is used (for example, atmospheric pressure). For example, it is conceivable that the amount of spherical aberration of the projection optical system 6 indicated by the reference numeral 33 in FIG. 3 changes to the amount of spherical aberration shown by the reference numeral 34 due to changes over time. Due to the above-mentioned circumstances, there has been a need for a technique for easily measuring the aberrations 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 occurs due to changes over time, the spherical aberration of the projection optical system 6 can be measured in a short time. As mentioned above, by preparing in advance the characteristic information (straight line 32) that indicates the relationship between the amount of spherical aberration of the projection optical system 6 and the normalized asymmetric component (feature amount), it is possible to determine the asymmetric shape from the measured light amount distribution. The amount of spherical aberration can be determined based on the information and the asymmetric component.

Characteristic information can be obtained, for example, by simulation. The image formed by the object-side mark on the image-side mark when the amount of spherical aberration is changed can be calculated by simulation. Therefore, for each of the plurality of spherical aberration amounts, the amount of light that can be acquired by the light receiving section 14 at each of the plurality of positions in the optical axis direction of the projection optical system 6 can be calculated by simulation. In this way, for each of the multiple amounts of spherical aberration, it is possible to calculate the light amount distribution that shows the relationship between the position in the optical axis direction and the light amount corresponding to that position from the light amount obtained at multiple positions by simulation. . Then, each asymmetric component of a plurality of light quantity distributions corresponding to a plurality of amounts of spherical aberration can be obtained. Thereby, characteristic information (straight line 32) can be obtained.

As a method for generating a plurality of amounts of spherical aberration, there is a method of adjusting the drive amount (position) of at least one of the plurality of optical elements constituting the projection optical system 6. Here, it is convenient that the relationship between the drive amount and the spherical aberration amount is known, but the spherical aberration amount may be actually measured under a set drive amount. Characteristic information (straight line 32) can be obtained by determining the light amount distribution for each of the plurality of drive amounts and determining the asymmetric component from the light amount distribution.

FIG. 6 shows a processing procedure for generating characteristic information. In step S310, the amount of spherical aberration is set or changed. Next, in step S320, for the amount of spherical aberration set or changed in step S310, a light amount distribution indicating the relationship between the position in the optical axis direction and the amount of light corresponding to that position is obtained. This can be done by calculating by simulation the amount of light that can be acquired by the light receiving section 14 at each of a plurality of positions in the optical axis direction of the projection optical system 6. 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 steps S320 and S330 are to be executed for other amounts of spherical aberration, and if steps S320 and S330 are to be executed for other amounts of spherical aberration, the process returns to step S310; otherwise, Proceed to step S350. If the process returns to step S310, the amount of spherical aberration is changed in step S310, and the process proceeds to step S320. In step S350, characteristic information is generated from the feature amounts (asymmetric components) obtained for each of the plurality of spherical aberration amounts by repeating steps S310 to S330.

FIG. 7 shows the processing performed in the exposure apparatus EXP. This process is controlled by the control unit CNT. In step S410, the control unit CNT determines whether to adjust the spherical aberration of the projection optical system 6. In step S410, the control unit CNT adjusts the spherical aberration of the projection optical system 6, for example, when exposure has been completed for a predetermined number of substrates or a predetermined number of lots (one lot may be composed of a predetermined number of substrates). It can be determined that Here, step S420 may be used together with focus measurement performed prior to exposing the substrate, and in this case, step S410 is unnecessary. The focus measurement is a measurement for adjusting the height of the shot area of the substrate according to the image plane of the projection optical system 6, and for this purpose, a process similar to step S420 is performed, and a process as illustrated in FIG. 7 is performed. A light intensity distribution is obtained. Therefore, steps S430 to S450 can be performed using the light amount distribution obtained in this focus measurement.

In step S420, the control unit CNT causes the light receiving unit 14 to detect the amount of light at each of a plurality of positions in the optical axis direction of the projection optical system 6, and based on the output from the light receiving unit 14, the control unit CNT detects the position in the optical axis direction and its position. Obtain a light amount distribution that shows the relationship between the light amount corresponding to the position. Next, in step S430, the control unit CNT obtains a feature amount (asymmetric component) from the light amount distribution obtained in step S420. In step S440, the control unit CNT determines the amount of spherical aberration corresponding to the feature amount based on the characteristic information prepared in the process shown in FIG. 6 and the feature 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 zero. This adjustment can be made by driving at least one optical element of the projection optical system 6. Step S450 may be performed only when the amount of spherical aberration determined in step S440 exceeds a preset threshold.

In step S460, the control unit CNT performs exposure to transfer the pattern of the original 1 onto 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 it does not end, the process returns to step S410.

The second embodiment will be described below. Matters not mentioned in the second embodiment may follow the first embodiment. The method for determining the feature amount (asymmetric component) is not limited to Gaussian function fitting. For example, the control unit CNT can calculate the asymmetric component by fitting a polynomial function with the origin at the focus position to the light amount distribution obtained by measurement, as shown in equation (4). Here, it is assumed that the coefficient of the i-th term of the n-th degree polynomial N(z) is k_i.

・・・（４）

...(4)

In this case, the asymmetric component, which is a feature value indicating the asymmetry of the light intensity distribution, is calculated using the integral value of only the even-order term of the polynomial function as the symmetric component, and the integral value of only the odd-number order term of the polynomial function as the asymmetric component. be able to. The second embodiment will be specifically described below.

The control unit CNT fits a polynomial function to the light amount distribution obtained by measurement, and determines the aberration based on the polynomial function. The light amount distribution shown in FIG. 5 is asymmetrical with respect to the axis of symmetry about the dotted line 31 (that is, it is not line symmetrical). 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 this light amount distribution. . Furthermore, the control unit CNT obtains a feature amount based on the odd-order term of the fitted polynomial function. A specific example will be explained below.

The control unit CNT processes even-order terms and odd-order terms among the plurality of terms of the fitted polynomial function. As shown in Equation (5), the control unit CNT integrates the even-order terms in a predetermined integration interval (interval from -a to a) centered on the focus position, and the value obtained thereby is symmetrically Let it be component S.

・・・（５）

...(5)

In addition, as shown in equation (6), the control unit CNT integrates the odd-order terms in a predetermined integration interval (interval from -a to a) centered on the focus position, and converts the value into the asymmetric component AS. do.

・・・（６）

...(6)

The control unit CNT normalizes the asymmetric component AS with the symmetric component S, thereby calculating the asymmetric component as a feature amount indicating the asymmetry of the light amount distribution. Here, the width of the integral interval in equation (5) and the width of the integral interval in equation (6) can be set equal.

The third embodiment will be described below. Matters not mentioned in the third embodiment may follow at least one of the first and second embodiments. The method for determining the feature amount (asymmetric component) is not limited to a method involving integration. The control unit CNT may calculate an asymmetric component as a feature amount indicating the asymmetry of the light amount distribution based on a coefficient of a specific degree of a polynomial function fitted to the light amount distribution obtained by measurement.

The fourth embodiment will be described below. Matters not mentioned in the fourth embodiment may follow at least one of the first to third embodiments. The method for determining the feature amount (asymmetric component) is not limited to a method that involves fitting a function to the light amount distribution obtained by measurement. For example, as shown in equation (7), the control unit CNT changes the light amount distribution I(z) obtained by measurement between the focus position Z0 and a position a at a predetermined distance in the positive direction from the focus position Z0. The integral value α is determined by integrating the interval (interval from Z0 to a).

・・・（７）

...(7)

Further, as shown in equation (8), the control unit CNT converts the light amount distribution I(z) obtained by measurement into an interval (-a to the focus position Z0) to obtain an integral value β.

・・・（８）

...(8)

Then, the control unit CNT calculates an asymmetric component as a feature amount indicating the asymmetry of the light amount distribution based on the two integral values α and β. Here, the width of the integral interval in equation (7) and the width of the integral interval in equation (8) can be set equal.

Modifications of the above embodiment will be described below. The asymmetric component, which is a feature indicating the asymmetry of the light amount distribution, may be calculated based on the shape of the light amount 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 amounts of spherical aberration prepared in advance is calculated. Then, the amount of spherical aberration corresponding to the light amount distribution with the smallest difference can be determined as the amount of spherical aberration corresponding to the light amount distribution obtained by measurement.

Adjustment of the spherical aberration of the projection optical system 6 may be performed during regular maintenance of the exposure apparatus EXP, or may be performed while the exposure apparatus EXP is suspending processing.

If the measured spherical aberration of the projection optical system 6 exceeds a threshold, the amount of aberration can be estimated by measuring the pattern shift and/or shape of the result of actually exposing and developing the substrate using a scanning electron microscope (SEM) or the like. The aberrations of the projection optical system 6 may be measured and adjusted with higher precision using a method such as the following. This uses the aberration measurement method of the embodiment to detect the aberration of the projection optical system, and only when the detected aberration exceeds a certain threshold, measures the aberration of the projection optical system using a more accurate method. , is the method of adjustment.

Hereinafter, an article manufacturing method to which the above aberration measurement method is applied will be explained. The article manufacturing method includes a measurement step of measuring the amount of aberration of the projection optical system 6 of the exposure apparatus EXP according to the aberration measurement method described above, and adjusting the aberration of the projection optical system 6 based on the amount of aberration measured in the measurement step. and an adjustment step. The article manufacturing method also includes an exposure step of exposing a substrate coated with a photosensitive material using an exposure device EXP after the adjustment step, a developing step of developing the photosensitive material after the exposure step, and a development step of developing the photosensitive material after the exposure step. and a processing step of processing the substrate that has undergone the development step, and an article is obtained from the substrate that has undergone the processing step.

The invention is not limited to the embodiments described above, and various changes and modifications can be made without departing from the spirit and scope of the invention. Therefore, the following claims are hereby appended to disclose the scope of the invention.

EXP: Exposure device, 1: Original plate, 3: Substrate, 6: Projection optical system, 14: Light receiving unit

Claims (12)

The amount of light transmitted through the object-side mark placed on the object side of the projection optical system, the projection optical system, and the image-side mark placed on the image side of the projection optical system is calculated based on the optical axis of the projection optical system. obtaining a light amount distribution indicating a relationship between a position in the optical axis direction and the light amount by measuring at a plurality of positions in the direction;
obtaining a feature amount indicating asymmetry with the focus position of the projection optical system as an axis of symmetry in the light amount distribution;
determining an amount of aberration of the projection optical system from the feature amount,
In the step of determining the feature amount, the feature amount is determined based on a difference between the light amount distribution and a Gaussian function fitted to the light amount distribution.
An aberration measurement method characterized by the following. In the step of determining the feature quantity, a value obtained by integrating the difference over a predetermined integral interval centered on the focus position is normalized by a value obtained by integrating the Gaussian function over the integral interval, as the feature quantity. demand,
The aberration measuring method according to claim 1 , characterized in that: The amount of light transmitted through the object-side mark placed on the object side of the projection optical system, the projection optical system, and the image-side mark placed on the image side of the projection optical system is calculated based on the optical axis of the projection optical system. obtaining a light amount distribution indicating a relationship between a position in the optical axis direction and the light amount by measuring at a plurality of positions in the direction;
obtaining a feature amount indicating asymmetry with the focus position of the projection optical system as an axis of symmetry in the light amount distribution;
determining an amount of aberration of the projection optical system from the feature amount,
In the step of determining the feature amount, the feature amount is determined based on an odd-order term of a polynomial function fitted to the light amount distribution.
An aberration measurement method characterized by the following. In the step of determining the feature amount, a value obtained by integrating the odd-order term over a predetermined integration interval centered on the focus position is normalized by a value obtained by integrating the even-order term of the polynomial function over the integration interval, Obtained as the feature quantity,
The aberration measuring method according to claim 3 , characterized in that: The amount of light transmitted through the object-side mark placed on the object side of the projection optical system, the projection optical system, and the image-side mark placed on the image side of the projection optical system is calculated based on the optical axis of the projection optical system. obtaining a light amount distribution indicating a relationship between a position in the optical axis direction and the light amount by measuring at a plurality of positions in the direction;
obtaining a feature amount indicating asymmetry with the focus position of the projection optical system as an axis of symmetry in the light amount distribution;
determining an amount of aberration of the projection optical system from the feature amount,
In the step of determining the feature amount, the feature amount is determined based on a coefficient of a specific degree of a polynomial function fitted to the light amount distribution.
An aberration measurement method characterized by the following. The amount of light transmitted through the object-side mark placed on the object side of the projection optical system, the projection optical system, and the image-side mark placed on the image side of the projection optical system is calculated based on the optical axis of the projection optical system. obtaining a light amount distribution indicating a relationship between a position in the optical axis direction and the light amount by measuring at a plurality of positions in the direction;
obtaining a feature amount indicating asymmetry with the focus position of the projection optical system as an axis of symmetry in the light amount distribution;
determining an amount of aberration of the projection optical system from the feature amount,
In the step of determining the feature amount, a value obtained by integrating the light intensity distribution for an interval between the focus position and a position at a predetermined distance in the positive direction from the focus position, and a position at the predetermined distance in the negative direction from the focus position. and a value obtained by integrating the light amount distribution for the section between and the focus position, and determining the feature amount based on
An aberration measurement method characterized by the following. The amount of light transmitted through the object-side mark placed on the object side of the projection optical system, the projection optical system, and the image-side mark placed on the image side of the projection optical system is calculated based on the optical axis of the projection optical system. obtaining a light amount distribution indicating a relationship between a position in the optical axis direction and the light amount by measuring at a plurality of positions in the direction;
obtaining a feature amount indicating asymmetry with the focus position of the projection optical system as an axis of symmetry in the light amount distribution;
determining an amount of aberration of the projection optical system from the feature amount,
In the step of determining the feature amount, the feature amount is determined based on a difference between the light amount distribution and an even function fitted to the light amount distribution.
An aberration measurement method characterized by the following. In the step of determining the amount of aberration, the amount of aberration of the projection optical system is determined based on information indicating the relationship between the amount of aberration of the projection optical system and the feature amount.
The aberration measuring method according to any one of claims 1 to 7. The amount of aberration includes an amount of spherical aberration,
The aberration measuring method according to any one of claims 1 to 8. a measuring step of measuring the amount of aberration of the projection optical system of the exposure apparatus according to the aberration measuring method according to any one of claims 1 to 9;
an adjustment step of adjusting the aberration of the projection optical system based on the amount of aberration measured in the measurement step;
After the adjustment step, an exposure step of exposing the substrate coated with the photosensitive material using the exposure device;
After the exposure step, a developing step of developing the photosensitive material;
a treatment step of treating the substrate that has undergone the development step,
A method for manufacturing an article, characterized in that an article is obtained from the substrate that has undergone the treatment step. An exposure apparatus comprising an original stage, a projection optical system, a substrate stage, a light receiving section disposed on the substrate stage, and a control section,
The light receiving unit detects the amount of light that has passed through an object side mark placed on the object side of the projection optical system, the projection optical system, and an image side mark placed on the image side of the projection optical system. Measured at multiple positions in the optical axis direction of the projection optical system,
The control unit determines a light amount distribution indicating a relationship between a position in the optical axis direction and the light amount based on the output from the light receiving portion, and sets a focus position of the projection optical system in the light amount distribution as an axis of symmetry. determining a feature amount indicating asymmetry, and determining an amount of aberration of the projection optical system from the feature amount;
The control unit includes:
The feature amount is determined based on the difference between the light amount distribution and a Gaussian function fitted to the light amount distribution, or
The feature amount is determined based on an odd-order term of a polynomial function fitted to the light amount distribution, or
The feature amount is determined based on a coefficient of a specific degree of a polynomial function fitted to the light amount distribution, or
a value obtained by integrating the light intensity distribution for a section between the focus position and a position at a predetermined distance in the positive direction from the focus position, and a value between the position at the predetermined distance in the negative direction from the focus position and the focus position. determining the feature amount based on a value obtained by integrating the light amount distribution for the section;
An exposure device characterized by: An exposure apparatus comprising an original stage, a projection optical system, a substrate stage, a light receiving section disposed on the substrate stage, and a control section,
The light receiving unit detects the amount of light that has passed through an object side mark placed on the object side of the projection optical system, the projection optical system, and an image side mark placed on the image side of the projection optical system. Measured at multiple positions in the optical axis direction of the projection optical system,
The control unit determines a light amount distribution indicating a relationship between a position in the optical axis direction and the light amount based on the output from the light receiving portion, and sets a focus position of the projection optical system in the light amount distribution as an axis of symmetry. determining a feature amount indicating asymmetry, and determining an amount of aberration of the projection optical system from the feature amount;
The control unit calculates the feature amount based on a difference between the light amount distribution and an even function fitted to the light amount distribution.
An exposure device characterized by:

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