JP7105582B2 - Determination method, exposure method, exposure apparatus, article manufacturing method and program - Google Patents

Description

The present invention relates to a determination method, an exposure method, an exposure apparatus, an article manufacturing method, and a program.

Devices such as semiconductor devices and flat panel displays (FPDs) are manufactured through a photolithography process. In the photolithography process, a pattern of a mask or reticle (original) is projected onto a substrate such as a glass plate or wafer coated with a resist (photosensitive agent) through a projection optical system including lenses and mirrors. It includes an exposure step of exposing.

In the exposure process, it is necessary to precisely match the best focus position of the projection optical system, that is, the position where the mask pattern image is formed with the highest contrast, and the surface position of the substrate (surface coated with resist). be. If the best focus position of the projection optical system and the surface position of the substrate do not match, the image of the pattern on the mask will be blurred and the image of the desired pattern cannot be formed on the substrate.

Techniques for obtaining the best focus position of the projection optical system have been proposed in the past (see Patent Document 1). In the technique disclosed in Patent Document 1, first, the substrate is exposed through the focus measurement pattern in a state where the focus position of the substrate coated with the resist is set to the initial value (the image of the focus measurement pattern is projected onto the substrate). form above). Next, the substrate is exposed through the focus measurement pattern while the focus position of the substrate is changed by a predetermined step amount. Such change of the focus position of the substrate and exposure of the substrate are repeated until the focus position of the substrate reaches the lower limit or upper limit of the change range, and when the focus position of the substrate reaches the lower limit or upper limit of the change range, the substrate is developed. do. Next, the size of the resist image (pattern image) corresponding to the focus measurement pattern formed on the substrate after development is measured, and the least square method is used to approximate the size of the pattern image as a function of the focus position. do. Then, a threshold value that is smaller than the maximum value of the approximation function by a predetermined value is set, two points (focus positions) at which the threshold value and the approximation function intersect are obtained, and the intermediate position between the two points is determined by the projection optical system. is the best focus position. As described above, in the technique disclosed in Patent Document 1, in an ideal imaging state, the change in the size of the pattern image corresponding to the pattern for focus measurement formed on the substrate depending on the focus position is the best focus position. is symmetrical with respect to . This is because the effect of defocus on image formation is substantially the same on the plus side and the minus side.

JP-A-6-216004

However, in practice, there are cases where the change in the size of the pattern image corresponding to the focus measurement pattern formed on the substrate depending on the focus position is asymmetric with respect to the best focus position. A pattern image corresponding to the focus measurement pattern is formed at a different position on the substrate for each focus position. Therefore, when there is a factor that changes the size of the pattern image depending on the position on the substrate, the change in the size of the pattern image depending on the focus position becomes asymmetric with respect to the best focus position. Such factors include the difference in resist film thickness depending on the position on the substrate, the difference in the liquid amount and residence time of the developer during development due to the position on the substrate, and the difference in the intensity of flare light depending on the position on the substrate. be done. Also when the projection optical system has aberration such as spherical aberration, the change in the size of the pattern image depending on the focus position becomes asymmetric with respect to the best focus position.

In such a case, the approximation function obtained by approximating the size of the pattern image with the function of the focus position also has an asymmetric shape, so the best focus position changes greatly depending on where the threshold is set. Resulting in. Therefore, the best focus position obtained from the asymmetrical approximation function is considered to have low reliability (the difference from the true value is large). However, in the prior art, the reliability of the best focus position obtained from the approximation function cannot be quantitatively evaluated, so there is a possibility that the focus position with a large difference from the true value is set as the best focus position.

SUMMARY OF THE INVENTION It is an exemplary object of the present invention to provide an advantageous determination method for determining the best focus position of a projection optical system.

To achieve the above object, a determination method as one aspect of the present invention is a determination method for determining a best focus position of a projection optical system that projects a pattern of a mask onto a substrate, comprising: measurement values of the line width of the first measurement pattern or the intensity profile of the first measurement pattern , which are respectively transferred at a plurality of positions in the optical axis direction on the image plane side of the projection optical system; a first step of obtaining a function representing a relationship between each of the a third step of obtaining a second focus position that is the midpoint of two points where a second level different from the level intersects; and a third level between the function and the first level and the second level. determining the best focus position based on the first focus position, the second focus position, and the third focus position; and a fifth step.

Further objects or other aspects of the present invention will be made clear by preferred embodiments described below with reference to the accompanying drawings.

According to the present invention, for example, it is possible to provide an advantageous determination method for determining the best focus position of the projection optical system.

1 is a schematic diagram showing the configuration of an exposure apparatus; FIG. It is a figure which shows an example of a measurement pattern. 4 is a flowchart for explaining determination processing for determining the best focus position of the projection optical system; 4 is a diagram for specifically explaining S322, S324 and S326, S328, S332 and S334 of the determination processing shown in FIG. 3; FIG. 4 is a diagram for specifically explaining S322, S324 and S326, S328, S332 and S334 of the determination processing shown in FIG. 3; FIG. 4 is a diagram for specifically explaining S322, S324 and S326, S328, S332 and S334 of the determination processing shown in FIG. 3; FIG. FIG. 10 is a diagram for explaining determination processing for determining the best focus position of the projection optical system; 1 is a schematic diagram showing the configuration of an exposure apparatus; FIG.

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. In addition, in each figure, the same reference numerals are given to the same members, and redundant explanations are omitted.

As one aspect of the present invention, a determination method for determining the best focus position of an optical system that forms an image of light from an object plane onto an image plane will be described. In this embodiment, an example will be described in which the present invention is applied to determine the best focus position of a projection optical system used in an exposure apparatus for projecting a mask pattern onto a substrate. Here, the best focus position of the projection optical system is the position where the mask pattern image is formed with the highest contrast.

First, the exposure apparatus 100 will be described with reference to FIG. FIG. 1 is a schematic diagram showing the configuration of an exposure apparatus 100. As shown in FIG. The exposure apparatus 100 is a lithography apparatus used in a photolithography process, which is a manufacturing process for devices such as semiconductor devices and flat panel displays (FPDs). The exposure apparatus 100 exposes a substrate through a mask to transfer the pattern of the mask onto the substrate.

The exposure apparatus 100 has an illumination optical system 1, a projection optical system 7, a mask stage 22, a substrate stage 62, and a controller 80, as shown in FIG. Here, an XYZ coordinate system is defined such that the horizontal plane is the XY plane and the vertical direction is the Z-axis direction.

The exposure apparatus 100 irradiates the mask 21 with light emitted from a light source (not shown) through the illumination optical system 1 , and couples the light from the pattern of the mask 21 onto the substrate 61 through the projection optical system 7 . make an image Since the substrate 61 is coated with a resist (photosensitive agent), the pattern of the mask 21 is transferred to the substrate 61 through the subsequent development process.

When exposing the substrate 61, the mask stage 22 holding the mask 21 and the substrate stage 62 holding the substrate 61 are synchronously scanned in the ±Y directions. Thereby, the substrate 61 can be exposed in an area (mask pattern area) having a size larger than the projection area of the projection optical system 7 . When the scanning of the mask stage 22 and the substrate stage 62 is completed, the substrate stage 62 is stepped in the X direction and/or the Y direction by a fixed amount to expose another shot area of the substrate 61 . After the exposure of all shot areas on the substrate 61 is completed, the substrate 61 is unloaded from the exposure apparatus 100 and a new substrate is loaded into the exposure apparatus 100 .

The projection optical system 7 is a reflective optical system including a concave mirror 3, a trapezoidal mirror 4, and a convex mirror 5 in this embodiment. The projection optical system 7 is telecentric on both sides (object plane side and image plane side). In other words, the principal ray of light incident on the substrate 61 from the projection optical system 7 is parallel to the Z axis on both the object plane side and the image plane side.

The control unit 80 is composed of an information processing device (computer) including a CPU, memory, etc., and controls each unit of the exposure apparatus 100 according to a program stored in the memory. The control unit 80 performs an exposure process of exposing the substrate 61 and transferring the pattern of the mask 21 onto the substrate 61 by controlling the operation of each unit of the exposure apparatus 100 . In this embodiment, the control unit 80 also functions as a processing unit that performs determination processing for determining the best focus position of the projection optical system 7 . However, such determination processing does not necessarily have to be performed by the control unit 80, and may be performed by an information processing device external to the exposure apparatus 100, and the best focus position of the projection optical system 7 may be obtained from the information processing device.

When projecting the pattern of the mask 21 onto the substrate 61 via the projection optical system 7, the best focus position of the projection optical system 7 and the surface position of the substrate 61 (resist-coated surface) are precisely matched. There is a need. If the best focus position of the projection optical system 7 and the surface position of the substrate 61 do not match, the image of the pattern of the mask 21 formed on the substrate via the projection optical system 7 will be blurred. pattern cannot be formed on the substrate.

Therefore, in the present embodiment, determination processing for determining the best focus position of the projection optical system 7 is performed before exposing the substrate 61 . In the determination process, first, while changing the position (focus position) in the optical axis direction of the test substrate with respect to the projection optical system 7, that is, in the Z-axis direction, the image of the measurement pattern is projected onto the test substrate via the projection optical system 7. Project. Then, the line width of the resist image (pattern image) corresponding to the measurement pattern formed on the test substrate through the development process is measured, and the best focus position of the projection optical system 7 is determined based on the measurement result. The substrate 61 is exposed by matching the best focus position of the projection optical system 7 thus determined with the surface position of the substrate 61 . As a result, an image of a desired pattern can be formed on the substrate without blurring the image of the pattern of the mask 21 formed on the substrate via the projection optical system 7 . A determination process for determining the best focus position of the projection optical system 7 will be described later in detail. In the present embodiment, the test substrate is used as the object on which the image of the measurement pattern is projected via the projection optical system 7 in the determination process. may be used.

FIG. 2 is a diagram showing an example of a measurement pattern group 10 including a plurality of measurement patterns. The measurement pattern group 10 may be provided on the mask 21 or may be provided on a focus measurement mask different from the mask 21 . The measurement pattern group 10 includes, for example, four measurement patterns 101, 102, 103, and 104 whose extending directions are different from each other, as shown in FIG. Each of the measurement patterns 101 to 104 is an isolated single line pattern and is called an isolated line (iso) pattern. The measurement patterns 101 to 104 are used to determine the best focus position of the projection optical system 7 for the patterns in their extending directions. Therefore, the measurement pattern to be used among the measurement patterns 101 to 104 may be determined depending on which direction of the pattern formed on the mask 21 to determine the best focus position of the projection optical system 7 . The measurement patterns 101 to 104 are designed so that the line width of their images is maximized when the best focus position of the projection optical system 7 and the surface position of the substrate 61 match. Therefore, the line widths of the images of the measurement patterns 101 to 104 formed at each of a plurality of positions in the optical axis direction of the image plane side of the projection optical system 7, that is, in the Z-axis direction are measured. Thus, the best focus position of the projection optical system 7 can be obtained.

A determination process for determining the best focus position of the projection optical system 7 will be described in detail below with reference to FIG. In S302, the focus position of the test board is set to the initial focus position. Specifically, the test substrate coated with the resist is held by the substrate stage 62, and the substrate stage 62 is moved so that the focus position of the test substrate becomes the initial focus position. The initial focus position is set, for example, at the lower limit position (Z-coordinate minus side limit) or the upper limit position (Z-coordinate plus side limit) of the range (moving range) in which the test substrate is moved in the Z-axis direction. In this embodiment, it is assumed that the initial focus position is set at the lower limit position of the movement range.

In S304, the image of the measurement pattern is projected onto the test substrate via the projection optical system 7, and the test substrate is exposed. Specifically, a mask provided with the measurement pattern group 10 shown in FIG. formed on a substrate.

In S306, it is determined whether the focus position of the test board has reached the upper limit position of the movement range. If the focus position of the test board has not reached the upper limit position of the movement range, the process proceeds to S308.

In S308, the test substrate is stepped in the Z-axis direction. Specifically, the substrate stage holding the test substrate is moved in the Z-axis direction by a predetermined step amount. In this embodiment, since the initial focus position is set to the lower limit position of the movement range, the substrate stage is moved to the positive side of the Z coordinate so that the test substrate is raised. In S302, when the initial focus position is set to the upper limit position of the movement range, the substrate stage is moved to the Z coordinate minus side so that the test substrate descends.

At S310, the test substrate is stepped in the X-axis and/or Y-axis. Specifically, the substrate stage holding the test substrate is moved in the X-axis direction and/or the Y-axis direction by a predetermined step amount so that the unexposed area of the test substrate is exposed.

In this way, S304 to S310 are repeated until the focus position of the test board reaches the upper limit position of the movement range. Then, when the focus position of the test substrate reaches the upper limit position of the movement range, in S306, the process proceeds to S312.

At S<b>312 , the test substrate is unloaded from the exposure apparatus 100 . In S314, the test substrate carried out from the exposure apparatus 100 is developed.

In S316, a microscope is used to measure the resist image corresponding to the measurement pattern formed on the test substrate after development, that is, the line width of the measurement pattern transferred to the test substrate. Let Li be the measured value (measurement result) of the line width of the measurement pattern corresponding to the focus position Fi (i=0, 1, 2, . . . ) of the test substrate. If the line width of the measurement pattern cannot be measured because the resist image is deformed, the measured value Li of the line width of the measurement pattern corresponding to the focus position Fi is invalidated.

In S318, it is determined whether or not the number of measured values (effective measured values) of the measurement pattern obtained in S316 is equal to or less than a predetermined number (for example, 4 or less). If the number of measured values in the measurement pattern is equal to or less than the predetermined number, it is determined that there is a problem with the measurement conditions, and the process proceeds to S320. In S320, it is notified that the determination process for determining the best focus position of the projection optical system 7 has resulted in an error (error notification). and start over by exposing the test board. On the other hand, when the number of measured values of the measurement pattern is not equal to or less than the predetermined number, the process proceeds to S322.

In S322, an approximation function representing the relationship between the measured value Li of the measurement pattern obtained in S316 and the focus position Fi of the test substrate is acquired. Specifically, the measurement value Li of the measurement pattern obtained in S316 is subjected to function fitting by the method of least squares as a function of the focus position. A function used for function fitting is, for example, a fourth-order polynomial of the focus position. In this embodiment, an approximation function will be described as an example, but any function may be used as long as it indicates the relationship between the measured value Li of the measurement pattern obtained in S316 and the focus position Fi of the test substrate.

In S324, based on the approximate function obtained in S322, the maximum value M of the approximate function and the focus position FM corresponding to the maximum value M are obtained within a certain focus range.

In S326, three slice values T1, T2 and T3 are set for the approximate function obtained in S322 to obtain three focus positions F1C, F2C and F3C. The slice values T1, T2 and T3 are slice levels (straight lines) set to intersect the approximation function obtained in S322.

Specifically, first, a slice value T3 (level) is set, and a focus position F3C, which is the midpoint between two points where the approximation function obtained in S322 and the slice value T3 intersect, is obtained. Here, of the two points at which the approximation function acquired in S322 and the slice value T3 intersect, the point on the minus side is set as the focus position F3A, and the point on the plus side is set as the focus position F3B. Then, the average focus position F3C is obtained from the focus positions F3A and F3B. It is appropriate to set the slice value T3 to a value slightly smaller than the maximum value M of the approximation function obtained in S324. For example, T3=0.90×M based on the maximum value M of the approximation function. However, the slice value T3 may be a fixed value regardless of the maximum value M of the approximation function.

Next, using slice values T1 and T2 different from slice value T3, the focus position is obtained in the same manner. The slice value T1 is a value larger than the slice value T3 by a certain amount, and the slice value T2 is a value smaller than the slice value T3 by a certain amount. For example, T1=0.95*M and T2=0.85*M. Then, the focus position F1C, which is the midpoint between the two points where the approximation function acquired in S322 and the slice value T1 intersect, is obtained. Here, of the two points at which the approximation function acquired in S322 and the slice value T1 intersect, the point on the minus side is set as the focus position F1A, and the point on the plus side is set as the focus position F1B. Then, the average focus position F1C is obtained from the focus positions F1A and F1B. Similarly, the focus position F2C, which is the midpoint between the two points where the approximation function acquired in S322 and the slice value T2 intersect, is obtained. Here, of the two points at which the approximation function acquired in S322 and the slice value T2 intersect, the point on the minus side is set as the focus position F2A, and the point on the plus side is set as the focus position F2B. Then, the average focus position F2C is obtained from the focus positions F2A and F2B.

In S328, it is determined whether or not the three focus positions F1C, F2C, and F3C obtained in S326 meet the criteria. In this embodiment, S328 determines whether or not the focus position F3C obtained in S326 is appropriate (adopted) as the best focus position of the projection optical system . Specifically, the difference between the focus position F3C and the focus position F1C and the difference between the focus position F3C and the focus position F2C are obtained, and whether the absolute value of these differences is equal to or less than a threshold, that is, the following formula ( 1) and formula (2) are satisfied. If the approximation function obtained in S322 has a symmetrical shape with respect to the focus position, the values of |F1C-F3C| and |F2C-F3C| become small, so that formulas (1) and (2) are easily satisfied. On the other hand, if the approximation function obtained in S322 has an asymmetrical shape with respect to the focus position, the values of |F1C−F3C| and |F2C−F3C| Become.

|F1C-F3C|≦U (1)
|F2C-F3C|≦U (2)
In equations (1) and (2), U is a threshold.

The threshold value U needs to be set in advance based on the accuracy with which the best focus position of the projection optical system 7 is determined. For example, if it is necessary to determine the best focus position of the projection optical system 7 with an accuracy of about 1 μm, set U=1 μm.

If both equations (1) and (2) are satisfied, the focus position F3C is considered highly reliable (close to the true value) as the best focus position of the projection optical system 7 . Therefore, it is determined that the focus positions F1C, F2C, and F3C satisfy the criteria, and the process proceeds to S332.

On the other hand, if either one or both of the formulas (1) and (2) are not satisfied, the focus position F3C fluctuates greatly depending on the slice value. is considered to be unreliable (far from the true value). Therefore, it is determined that the focus positions F1C, F2C, and F3C do not meet the criteria, and the process proceeds to S330.

In S330, it is determined whether the intersection of the approximation function acquired in S322 and the slice value is 1 point or less, or whether the slice value has reached the limit of the preset change range. If the slice value becomes too small, the number of intersections between the approximation function obtained in S322 and the slice value may be one or less. If the intersection of the approximation function acquired in S322 and the slice value is 1 point or less, or if the slice value reaches the limit of the preset change range, the process proceeds to S320. On the other hand, if the intersection of the approximation function acquired in S322 and the slice value is not less than 1 point and the slice value has not reached the limit of the preset change range, the process proceeds to S332.

At S332, the slice values T1, T2 and T3 are changed. Specifically, each of the slice values T1, T2, and T3 is shifted by a predetermined amount so as to become smaller. For example, the slice value T3 is changed from T3=0.90*M to T3=0.80*M. Similarly, the slice value T1 is changed from T1=0.95×M to T1=0.85×M, and the slice value T2 is changed from T2=0.85×M to T2=0.75×M. . Then, in S326, the three focus positions F1C, F2C and F3C are obtained again.

In S334, the best focus position of the projection optical system 7 is determined. In the present embodiment, it is determined whether the focus position F3C is appropriate as the best focus position of the projection optical system 7, as described above. Therefore, when proceeding to S334, the focus position F3C obtained in S326 is determined (adopted) as the best focus position of the projection optical system .

4(a), 4(b), 5(a), 5(b) and 6, S322, S324 and S326, S328, S332 and S334 of the decision processing shown in FIG. A specific description will be given.

FIG. 4A is a diagram showing an example of the approximation function CC obtained in S322 and indicating the relationship between the measured value Li of the measurement pattern obtained in S316 and the focus position Fi of the test substrate. In FIG. 4A, the vertical axis indicates the measured value Li (line width) of the measurement pattern, and the horizontal axis indicates the focus position Fi of the test substrate (defocus amount from the best focus position of the projection optical system 7). showing. Also, the measured value Li of the measurement pattern is obtained at a focus pitch of about 4 μm.

FIG. 4B shows focus positions F1A, F1B, F1C, F2A, F2B, F2C, F3A, It is a figure which shows an example of F3B and F3C. In FIG. 4B, the vertical axis indicates the measured value Li (line width) of the measurement pattern, and the horizontal axis indicates the focus position Fi of the test substrate (defocus amount from the best focus position of the projection optical system 7). showing. Also, the slice value T1 is T1=0.95×M, the slice value T2 is T2=0.85×M, and the slice value T3 is T3=0.90×M.

Referring to FIG. 4B, focus positions F1C, F2C and F3C are substantially the same. Therefore, in S328, for example, if the threshold value U is set to U=1 μm, the formulas (1) and (2) are satisfied. In this case, the process proceeds to S334, and the focus position F3C is determined as the best focus position of the projection optical system .

FIG. 5A is a diagram showing an example of an approximation function CC' obtained in S322 that indicates the relationship between the measured value Li of the measurement pattern obtained in S316 and the focus position Fi of the test substrate. In FIG. 5A, the vertical axis indicates the measured value Li (line width) of the measurement pattern, and the horizontal axis indicates the focus position Fi of the test substrate (defocus amount from the best focus position of the projection optical system 7). showing. Also, the measured value Li of the measurement pattern is obtained at a focus pitch of about 4 μm.

FIG. 5(b) shows focus positions F1A′, F1B′, F1C′, and F2A obtained by setting slice values T1′, T2′, and T3′ for the approximation function CC′ shown in FIG. 5(a). It is a figure which shows an example of ', F2B', F2C', F3A', F3B' and F3C'. In FIG. 5B, the vertical axis indicates the measured value Li (line width) of the measurement pattern, and the horizontal axis indicates the focus position Fi of the test substrate (defocus amount from the best focus position of the projection optical system 7). showing. Also, the slice value T1′ is T1′=0.95×M′, the slice value T2′ is T2′=0.85×M′, and the slice value T3′ is T3′=0.90×M '. M' is the maximum value of the approximation function CC'.

Referring to FIG. 5B, there is a difference between the focus positions F1C', F2C' and F3C'. Therefore, in S328, for example, if the threshold U is set to U=1 μm, the equations (1) and (2) are not satisfied. In this case, when the process proceeds to S330 and then to S332, the slice value is changed. Here, the slice value T1′ is changed to the slice value T1″ (=0.85×M′), and the slice value T2′ is changed to the slice value T2″ (=0.75×M′). , the slice value T3′ is changed to the slice value T3″ (=0.80×M′).

FIG. 6 shows a case where slice values T1'', T2'' and T3'' are set for the approximation function CC' shown in FIG. 5(a). In this case, focus positions F1A'', F1B'', F1C'', F2A'', F2B'', F2C'', F3A'', F3B'' and F3C'' are obtained. In FIG. 6, the vertical axis indicates the measured value Li (line width) of the measurement pattern, and the horizontal axis indicates the focus position Fi of the test substrate (defocus amount from the best focus position of the projection optical system 7). .

Referring to FIG. 6, focus positions F1C'', F2C'' and F3C'' are substantially the same. Therefore, in S328, formulas (1) and (2) are satisfied. In this case, the process proceeds to S<b>334 to determine the focus position F<b>3 C″ as the best focus position of the projection optical system 7 .

As described above, in this embodiment, the reliability of the best focus position obtained from the approximation function indicating the relationship between the measurement result of the measurement pattern and the focus position is quantitatively evaluated. Therefore, even when the approximation function has an asymmetrical shape, it is possible to avoid using a focus position with a large difference from the true value as the best focus position of the projection optical system 7. can be determined as the best focus position of the projection optical system 7 . In other words, in this embodiment, the best focus position of the projection optical system 7 can be obtained with high accuracy compared to the conventional technique.

Further, the determination processing for determining the best focus position of the projection optical system 7 in this embodiment is not limited to the method described with reference to FIG. 3, and various methods can be adopted. For example, the slice values T1, T2, and T3 may be set as percentages from a fixed value (such as the set value of the best focus position) instead of percentages from the maximum value of the approximation function.

Further, in S304 to S310, instead of performing exposure while changing the focus position of the test substrate, the substrate stage 62 holding the test substrate may be exposed while being scanned in a direction inclined by a certain amount from the XY plane. . As a result, exposure at different focus positions can be collectively performed within one shot area.

Returning to S302, when the exposure to the test substrate is redone, instead of transferring the same measurement pattern again, a measurement pattern extending in the same direction as the measurement pattern and having a different line width is used. A pattern may be transferred. For example, when the resist image corresponding to the measurement pattern cannot be correctly formed due to factors such as the development process, the resist image corresponding to the measurement pattern can be correctly formed by using a measurement pattern having a larger line width.

Further, in S328, if at least one of the formulas (1) and (2) is not satisfied, instead of proceeding to S330, the process may return to S302 to re-expose the test substrate. In this case, as described above, measurement patterns extending in the same direction and having different line widths may be used. Note that if another measurement pattern extending in the same direction and having a different line width has already been transferred to the test substrate, exposure is not necessary, so the process proceeds to S316 to perform another measurement. The line width of the pattern should be measured.

Also, in S328, the following formula (3) may be used instead of the formulas (1) and (2). Then, if the formula (3) is satisfied, the process proceeds to S332, and if the formula (3) is not satisfied, the process proceeds to S330.

|F1C-F2C|≦U (3)
When formula (3) is used, the focus position F3C may be set as the best focus position of the projection optical system 7 in S334, but it is not limited to this. In other words, it is possible to set a focus position other than the focus position F3C as the best focus position of the projection optical system . For example, the best focus position of the projection optical system 7 may be a focus position that is located between the focus position F1C and the focus position F2C and that is not the focus position F3C. Specifically, the focus position corresponding to the middle point between the focus position F1C and the focus position F2C may be set as the best focus position of the projection optical system 7 . Alternatively, as shown in FIG. 7, a barycentric position F4 of the closed region 400 formed by the approximation function CC and the slice value T3 may be obtained, and the focus position corresponding to the barycentric position F4 may be set as the best focus position of the projection optical system . As shown in FIG. 7, the closed region 400 is defined by the approximation function CC and a line segment connecting two points where the approximation function CC and the slice value T3 intersect. and region 402 . The center-of-gravity position F4 is determined so that the area of the area 401 and the area of the area 402 are equal.

Moreover, in FIG. 3, the case where the measurement pattern is transferred to the test substrate has been described as an example. However, as shown in FIG. 8, a sensor 63 provided on the substrate stage 62 may measure the line width of the image of the measurement pattern. The sensor 63 detects the image of the measurement pattern via the projection optical system 7 and outputs (measures) the line width of the image of the measurement pattern. Further, the sensor 63 may measure the light intensity profile (maximum light intensity) of the image of the measurement pattern instead of the line width of the image of the measurement pattern. Note that the sensor 63 may be configured independently of the substrate stage 62 .

An exposure process (exposure method) in the exposure apparatus 100 will be described. First, the best focus position of the projection optical system 7 is determined by the determination method described above. Next, each part of the exposure apparatus 100 is adjusted based on the best focus position of the projection optical system 7 . Specifically, each part of the exposure apparatus 100 is adjusted so that the best focus position of the projection optical system 7 and the surface position of the substrate 61 are matched. Such adjustment includes at least one of adjusting at least one of the position and orientation of the substrate stage 62 and adjusting at least one of the position, orientation and surface shape of the optical element included in the projection optical system 7. include. With the best focus position of the projection optical system 7 and the surface position of the substrate 61 aligned, the substrate 61 is exposed through the projection optical system 7 to transfer the pattern of the mask 21 onto the substrate 61 . As described above, the exposure apparatus 100 can perform exposure while the best focus position of the projection optical system 7 and the surface position of the substrate 61 are aligned. can be done.

The method for manufacturing an article according to the embodiment of the present invention is suitable for manufacturing articles such as devices (semiconductor devices, magnetic storage media, liquid crystal display devices, etc.), color filters, optical components, and MEMS. This manufacturing method includes a step of exposing a substrate coated with a photosensitive agent and a step of developing the exposed photosensitive agent by the exposure method of the embodiment described above using the exposure apparatus 100 . Also, the circuit pattern is formed on the substrate by performing an etching process or an ion implantation process on the substrate using the pattern of the developed photosensitive agent as a mask. By repeating these steps of exposure, development, etching, etc., a circuit pattern consisting of a plurality of layers is formed on the substrate. In the post-process, the substrate on which the circuit pattern is formed is diced (processed), and chip mounting, bonding, and inspection processes are performed. Such manufacturing methods may also include other well-known steps (oxidation, deposition, deposition, doping, planarization, resist stripping, etc.). The method for manufacturing an article according to the present embodiment is advantageous in at least one of performance, quality, productivity and production cost of the article as compared with conventional methods.

The present invention supplies a program that implements one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and one or more processors in the computer of the system or device reads the program. It can also be realized by executing processing. It can also be implemented by a circuit (eg, an ASIC) that implements one or more functions.

Although the preferred embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist.

100: Exposure device 7: Projection optical system 10: Measurement pattern group 61: Substrate 80: Control unit 101 to 104: Measurement pattern

Claims (27)

A determination method for determining a best focus position of a projection optical system for projecting a pattern of a mask onto a substrate, comprising:
measured values of the line width of the first measurement pattern or the intensity profile of the first measurement pattern , which are respectively transferred at a plurality of positions in the optical axis direction on the image plane side of the projection optical system via the projection optical system; and a first step of obtaining a function indicating the relationship between each of the plurality of positions;
a second step of finding a first focus position that is the midpoint of two points where the function and the first level intersect;
a third step of determining a second focus position that is the midpoint of two points where the function and a second level different from the first level intersect;
a fourth step of determining a third focus position that is the midpoint of two points where the function and a third level between the first level and the second level intersect;
a fifth step of determining the best focus position based on the first focus position, the second focus position and the third focus position;
A determination method characterized by having In the fifth step, based on the third focus position, a first difference between the first focus position and the third focus position, and a second difference between the second focus position and the third focus position , determining the best focus position. A determination method for determining a best focus position of a projection optical system for projecting a pattern of a mask onto a substrate, comprising:
A function indicating the relationship between the measurement results of the first measurement pattern transferred at a plurality of positions in the optical axis direction on the image plane side of the projection optical system via the projection optical system and each of the plurality of positions. a first step of obtaining
a second step of finding a first focus position that is the midpoint of two points where the function and the first level intersect;
a third step of determining a second focus position that is the midpoint of two points where the function and a second level different from the first level intersect;
a fourth step of determining a third focus position that is the midpoint of two points where the function and a third level between the first level and the second level intersect;
a fifth step of determining the best focus position;
has
In the fifth step, when a first difference between the first focus position and the third focus position and a second difference between the second focus position and the third focus position are larger than a threshold,
determining a fourth focus position that is the midpoint between two points where the function and a fourth level obtained by shifting the first level by a predetermined amount are intersected;
determining a fifth focus position that is the midpoint between two points of intersection of the function and a fifth level obtained by shifting the second level by the predetermined amount;
determining a sixth focus position that is the midpoint between two points of intersection of the function and a sixth level obtained by shifting the third level by the predetermined amount;
determining the best focus position based on the sixth focus position, the difference between the fourth focus position and the sixth focus position, and the difference between the fifth focus position and the sixth focus position; ,
A determination method comprising: 4. The determination method according to claim 3, wherein the measurement result includes a line width of the first measurement pattern transferred to each of the plurality of positions or a light intensity profile of the first measurement pattern. 5. A method according to any one of the preceding claims, wherein said third level is the midpoint between said first level and said second level. 3. The determination method according to claim 2, wherein, in said fifth step, said third focus position is set as said best focus position when said first difference and said second difference are equal to or less than a threshold value. In the fifth step, when the first difference and the second difference are greater than a threshold,
obtaining a new function indicating the relationship between the measurement result of the first measurement pattern transferred again to each of the plurality of positions via the projection optical system and each of the plurality of positions;
determining a seventh focus position that is the midpoint of two points where the new function and the first level intersect;
determining an eighth focus position that is the midpoint of two points where the new function and the second level intersect;
determining a ninth focus position that is the midpoint of two points where the new function and the third level intersect;
determining the best focus position based on the ninth focus position, the difference between the seventh focus position and the ninth focus position, and the difference between the eighth focus position and the ninth focus position; ,
3. The method of claim 2, comprising: In the fifth step, when the first difference and the second difference are greater than a threshold,
A first measurement pattern transferred to each of the plurality of positions via the projection optical system, extending in the same direction as the first measurement pattern, and having a line width different from the line width of the first measurement pattern. Acquiring a new function indicating the relationship between the measurement results of two measurement patterns and each of the plurality of positions;
determining a tenth focus position that is the midpoint of two points where the new function and the first level intersect;
determining an eleventh focus position that is the midpoint of two points where the new function and the second level intersect;
determining a twelfth focus position that is the midpoint of two points where the new function and the third level intersect;
determining the best focus position based on the 12th focus position, the difference between the 10th focus position and the 12th focus position, and the difference between the 11th focus position and the 12th focus position; ,
3. The method of claim 2, comprising: 9. The determination method according to claim 8 , wherein said fifth step includes a step of transferring said second measurement pattern to each of said plurality of positions via said projection optical system. A determination method for determining a best focus position of a projection optical system for projecting a pattern of a mask onto a substrate, comprising:
measured values of the line width of the first measurement pattern or the intensity profile of the first measurement pattern, which are respectively transferred at a plurality of positions in the optical axis direction on the image plane side of the projection optical system via the projection optical system; and a first step of obtaining a function indicating the relationship between each of the plurality of positions;
a second step of finding a first focus position that is the midpoint of two points where the function and the first level intersect;
a third step of determining a second focus position that is the midpoint of two points where the function and a second level different from the first level intersect;
a fourth step of determining the best focus position based on the first focus position and the second focus position;
A determination method characterized by having 11. The determination method according to claim 10 , wherein in said fourth step, said best focus position is determined based on a difference between said first focus position and said second focus position. 11. In the fourth step, when the difference is equal to or less than a threshold, a third focus position between the first focus position and the second focus position is set as the best focus position. determination method described in . 13. The method of claim 12 , wherein the third focus position is a midpoint between the first focus position and the second focus position. The third focus position is a center-of-gravity position of a closed region defined by the function and a line segment connecting two points where the function and the third level intersect,
13. The method of claim 12 , wherein said third level is a level between said first level and said second level. An exposure method for exposing a substrate using an exposure apparatus having a projection optical system for projecting a pattern of a mask onto a substrate,
a first step of determining a best focus position of the projection optical system;
a second step of adjusting the exposure device based on the best focus position determined in the first step;
a third step of exposing the substrate using the exposure apparatus adjusted in the second step;
has
The first step is
measured values of the line width of the first measurement pattern or the intensity profile of the first measurement pattern, which are respectively transferred at a plurality of positions in the optical axis direction on the image plane side of the projection optical system via the projection optical system; and obtaining a function indicating the relationship between each of the plurality of positions;
determining a first focus position that is the midpoint of two points where the function and the first level intersect;
determining a second focus position that is the midpoint of two points where the function and a second level different from the first level intersect;
determining a third focus position that is the midpoint of two points where the function and a third level between the first level and the second level intersect;
determining the best focus position based on the first focus position, the second focus position and the third focus position;
An exposure method comprising: In the step of determining the best focus position, the third focus position, a first difference between the first focus position and the third focus position, and a second focus position between the second focus position and the third focus position 16. The exposure method according to claim 15, wherein the best focus position is determined based on the difference. An exposure method for exposing a substrate using an exposure apparatus having a projection optical system for projecting a pattern of a mask onto a substrate,
a first step of determining a best focus position of the projection optical system;
a second step of adjusting the exposure device based on the best focus position determined in the first step;
a third step of exposing the substrate using the exposure apparatus adjusted in the second step;
has
The first step is
A function indicating the relationship between the measurement results of the first measurement pattern transferred at a plurality of positions in the optical axis direction on the image plane side of the projection optical system via the projection optical system and each of the plurality of positions. and obtaining
determining a first focus position that is the midpoint of two points where the function and the first level intersect;
determining a second focus position that is the midpoint of two points where the function and a second level different from the first level intersect;
determining a third focus position that is the midpoint of two points where the function and a third level between the first level and the second level intersect;
if a first difference between the first focus position and the third focus position and a second difference between the second focus position and the third focus position are greater than a threshold, the function and the first level are combined by a predetermined amount; A fourth focus position, which is the middle point of two points where the fourth level shifted by Finding a fifth focus position that is the midpoint of the points, finding a sixth focus position that is the midpoint between two points where the function and the sixth level obtained by shifting the third level by the predetermined amount intersect, determining the best focus position based on the sixth focus position, the difference between the fourth focus position and the sixth focus position, and the difference between the fifth focus position and the sixth focus position; ,
An exposure method comprising: An exposure method for exposing a substrate using an exposure apparatus having a projection optical system for projecting a pattern of a mask onto a substrate,
a first step of determining a best focus position of the projection optical system;
a second step of adjusting the exposure device based on the best focus position determined in the first step;
a third step of exposing the substrate using the exposure apparatus adjusted in the second step;
has
The first step is
measured values of the line width of the first measurement pattern or the intensity profile of the first measurement pattern, which are respectively transferred at a plurality of positions in the optical axis direction on the image plane side of the projection optical system via the projection optical system; and obtaining a function indicating the relationship between each of the plurality of positions;
determining a first focus position that is the midpoint of two points where the function and the first level intersect;
determining a second focus position that is the midpoint of two points where the function and a second level different from the first level intersect;
determining the best focus position based on the first focus position and the second focus position;
An exposure method comprising: 19. The exposure method according to claim 18 , wherein in the step of determining said best focus position, said best focus position is determined based on a difference between said first focus position and said second focus position. The second step includes adjusting at least one of the position and orientation of a substrate stage that holds the substrate, and adjusting at least one of the position, orientation and surface shape of an optical element included in the projection optical system. 20. The exposure method according to any one of claims 15 to 19 , comprising at least one of the steps of: An exposure apparatus for exposing a substrate,
a projection optical system that projects a mask pattern onto the substrate;
a processing unit that performs processing for determining the best focus position of the projection optical system;
has
The processing unit is
measurement values of the line width of the first measurement pattern transferred via the projection optical system at a plurality of positions in the optical axis direction on the image plane side of the projection optical system, or the intensity profile of the first measurement pattern ; , obtaining a function indicating the relationship with each of the plurality of positions;
Finding a first focus position that is the midpoint between two points where the function and the first level intersect,
Obtaining a second focus position that is the midpoint between two points at which the function and a second level different from the first level intersect;
Finding a third focus position that is the midpoint between two points where the function and a third level between the first level and the second level intersect;
An exposure apparatus, wherein the best focus position is determined based on the first focus position, the second focus position and the third focus position. The processing unit, based on the third focus position, a first difference between the first focus position and the third focus position, and a second difference between the second focus position and the third focus position, 22. An exposure apparatus according to claim 21 , wherein said best focus position is determined. An exposure apparatus for exposing a substrate,
a projection optical system that projects a mask pattern onto the substrate;
a processing unit that performs processing for determining the best focus position of the projection optical system;
has
The processing unit is
A function indicating the relationship between the measurement results of the first measurement pattern transferred at a plurality of positions in the optical axis direction on the image plane side of the projection optical system via the projection optical system and each of the plurality of positions. and get
Finding a first focus position that is the midpoint between two points where the function and the first level intersect,
Obtaining a second focus position that is the midpoint between two points at which the function and a second level different from the first level intersect;
Finding a third focus position that is the midpoint between two points where the function and a third level between the first level and the second level intersect;
if a first difference between the first focus position and the third focus position and a second difference between the second focus position and the third focus position are greater than a threshold, the function and the first level are combined by a predetermined amount; A fourth focus position, which is the middle point of two points where the fourth level shifted by Finding a fifth focus position that is the midpoint of the points, finding a sixth focus position that is the midpoint between two points where the function and the sixth level obtained by shifting the third level by the predetermined amount intersect,
Determining the best focus position based on the sixth focus position, the difference between the fourth focus position and the sixth focus position, and the difference between the fifth focus position and the sixth focus position An exposure apparatus characterized by: An exposure apparatus for exposing a substrate,
a projection optical system that projects a mask pattern onto the substrate;
a processing unit that performs processing for determining the best focus position of the projection optical system;
has
The processing unit is
measured values of the line width of the first measurement pattern or the intensity profile of the first measurement pattern , which are respectively transferred at a plurality of positions in the optical axis direction on the image plane side of the projection optical system via the projection optical system; and obtain a function indicating the relationship between each of the plurality of positions,
Finding a first focus position that is the midpoint between two points where the function and the first level intersect,
Obtaining a second focus position that is the midpoint between two points at which the function and a second level different from the first level intersect;
An exposure apparatus, wherein the best focus position is determined based on the first focus position and the second focus position. 25. An exposure apparatus according to claim 24 , wherein said processing section determines said best focus position based on a difference between said first focus position and said second focus position. exposing a photosensitive agent coated on a substrate using the exposure method according to any one of claims 15 to 20 ;
developing the exposed photosensitive agent to form a pattern of the photosensitive agent;
a step of forming a pattern on the substrate based on the pattern of the developed photosensitive agent, and processing the patterned substrate to manufacture an article;
A method for manufacturing an article, comprising: A program for causing a computer to execute each step of the determination method according to any one of claims 1 to 14.

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