Calibration method, detection system, exposure apparatus, article manufacturing method and program

Abstract

To provide a technique advantageous for calibrating a detection system for detecting a position of a detected object.SOLUTION: In a calibration method of a detection system having an illumination system for illuminating a detected object, and an imaging system for forming an image of light from the detected object on a photoelectric conversion element, the illumination system includes a plurality of first drawings arranged on a pupil surface of the illumination system and having different openings, and a plurality of second drawings arranged on a pupil surface of the imaging system and having different openings. The calibration method includes: a first step of acquiring a first defocus characteristic indicating a shift amount of an image in a state that each drawing is positioned in a first position shifted from a reference position, with respect to each of combinations of two drawings made by selecting one drawing each from the plurality of first drawings and the plurality of second drawings; and a second step of adjusting the respective positions so that the first drawings and the second drawings are positioned in the reference positions respectively based on a reference defocus characteristic indicating a shift amount of an image in a state that each drawing is positioned in the reference position, and the first defocus characteristic.SELECTED DRAWING: Figure 9

Description

Technical Field

[0001] The present invention relates to a calibration method, a detection system, an exposure apparatus, a method for manufacturing an article, and a program.

Background Art

[0002] In recent years, in exposure apparatuses used for manufacturing semiconductor elements and the like, as the resolution line width is miniaturized, improvement in the overlay accuracy (overlay precision) between a reticle and a substrate has been demanded. Since generally about 1 / 5 of the resolution line width is required for the overlay accuracy, as the miniaturization of semiconductor elements progresses, improvement in the overlay accuracy becomes increasingly important.

[0003] In order to improve the overlay accuracy, for example, there is a method of adjusting the position detection system included in the exposure apparatus with high precision. The position detection system generally includes an illumination system for illuminating an object to be detected (for example, a mark) provided on a substrate with detection (observation) light, and an imaging system for condensing the light from the object to be detected and detecting an image of the object to be detected. In order to realize a good imaging state of the position detection system, adjusting the aperture stop provided in the illumination system or the imaging system, that is, adjusting the position of the pupil, is one of the important technical problems that require high positioning accuracy. Therefore, a technique for adjusting the position of the aperture stop of at least one of the illumination system and the imaging system of the position detection system has been proposed (see Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in position-detection illumination and imaging systems, maintaining the pupil position adjusted using, for example, the techniques disclosed in Patent Documents 1 and 2, throughout the operating period of the exposure equipment at the user site is a significant technical challenge separate from the initial adjustment. Generally, encoders are used to store the pupil position adjusted in the position-detection illumination and imaging systems to address limitations in holding the aperture diaphragm due to mechanical precision and to deal with resetting the exposure equipment, including power interruptions. However, introducing encoders is costly, and the encoders themselves are heat sources, which can cause fluctuations in the refractive index of the air inside the exposure equipment. Furthermore, unlike the initial adjustment in the manufacturing process of the exposure equipment, there are significant constraints on adjustment tools and adjustment time at the user site. Therefore, in position-detection illumination and imaging systems, there is a need for a technology that allows for self-contained return to, for example, the initially adjusted pupil position within the exposure equipment without using encoders.

[0006] This invention has been made in view of the problems of the prior art, and its exemplary objective is to provide a technique advantageous for calibrating a detection system for detecting the position of an object under test. [Means for solving the problem]

[0007] To achieve the above objective, a calibration method as one aspect of the present invention is a calibration method for a detection system having an illumination system for illuminating an object to be tested and an imaging system for forming an image of light from the object to be tested on a photoelectric conversion element, wherein the illumination system includes a plurality of first apertures selectively arranged on the pupil plane of the illumination system and having apertures different from each other, and the imaging system includes a plurality of second apertures selectively arranged on the pupil plane of the imaging system and having apertures different from each other, and for each of at least two combinations of first apertures and second apertures configured by selecting one aperture each from the plurality of first apertures and the plurality of second apertures, the first aperture and the second apertures The present invention is characterized by comprising: a first step of acquiring a first defocus characteristic that shows the amount of shift of the image on the photoelectric conversion element with respect to the amount of defocus of the object under test when each is located at a first position shifted from a reference position; and a second step of adjusting the positions of the first and second apertures so that each of them is located at the reference position, based on a reference defocus characteristic that shows the amount of shift of the image on the photoelectric conversion element with respect to the amount of defocus of the object under test when each of the first and second apertures is located at the reference position, and the first defocus characteristic acquired in the first step.

[0008] Further objects or other aspects of the present invention will be revealed by embodiments described below with reference to the accompanying drawings. [Effects of the Invention]

[0009] According to the present invention, for example, it is possible to provide a technique that is advantageous for calibrating a detection system that detects the position of an object under test. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram showing the configuration of an exposure apparatus as one aspect of the present invention. [Figure 2] This diagram shows the detailed configuration of the stage reference plate. [Figure 3] This is a diagram showing the specific configuration of the position detection system. [Figure 4] This diagram shows the specific configuration of the switching mechanism. [Figure 5] This diagram shows the specific configuration of the switching mechanism. [Figure 6] This figure shows an example of the state of the position detection system. [Figure 7] This figure shows an example of the relationship between the drive amount of the substrate stage and the amount of variation in the defocus characteristics. [Figure 8] This is a diagram showing an example of alignment marks. [Figure 9] This is a flowchart explaining the calibration process (calibration method) for position detection systems. [Modes for carrying out the invention]

[0011] The embodiments will be described in detail below with reference to the attached drawings. Note that the following embodiments do not limit the invention as defined in the claims. While the embodiments describe multiple features, not all of these features are essential to the invention, and the features may be combined in any way. Furthermore, in the attached drawings, identical or similar configurations are given the same reference numerals, and redundant descriptions are omitted.

[0012] Figure 1 is a schematic diagram showing the configuration of an exposure apparatus 100 as one aspect of the present invention. The exposure apparatus 100 is a lithography apparatus that exposes a substrate through a master plate and forms a pattern on the substrate. The exposure apparatus 100 includes a master plate stage 2 that holds a master plate 1 (reticle or mask), a substrate stage 4 that holds a substrate 3, and an illumination optical system 5 that illuminates the master plate 1 held on the master plate stage 2. The exposure apparatus 100 also includes a projection optical system 6 that projects the pattern (image) of the master plate 1 onto the substrate 3 held on the substrate stage 4, and a control unit 17 that comprehensively controls the overall operation of the exposure apparatus 100.

[0013] In this embodiment, the exposure apparatus 100 is a scanning exposure apparatus (scanner) that transfers the pattern of the original plate 1 onto the substrate 3 while synchronously scanning the original plate 1 and the substrate 3 in the scanning direction (i.e., in the step-and-scan method). However, the exposure apparatus 100 may be an exposure apparatus (stepper) that fixes the original plate 1 (i.e., in the step-and-scan method) and transfers the pattern of the original plate 1 onto the substrate 3.

[0014] Hereinafter, as shown in FIG. 1, the direction that coincides with the optical axis of the projection optical system 6 (optical axis direction) is defined as the Z direction, the scanning direction of the original plate 1 and the substrate 3 within a plane perpendicular to the Z direction is defined as the Y direction, and the direction perpendicular to the Z direction and the Y direction (non-scanning direction) is defined as the X direction. Also, the directions around the X axis, Y axis, and Z axis are defined as the θX direction, θY direction, and θZ direction, respectively.

[0015] The illumination optical system 5 illuminates the original plate 1, specifically, a predetermined illumination area on the original plate, with light having a uniform illuminance distribution (exposure light). As the exposure light, g-line or i-line of a high-pressure mercury lamp, KrF excimer laser, ArF excimer laser, F2 laser, etc. are used. Also, in order to manufacture finer semiconductor elements, extreme ultraviolet light (EUV light) of several nm to several hundred nm may be used as the exposure light.

[0016] The original plate stage 2 holds the original plate 1 and is configured to be two-dimensionally movable within a plane perpendicular to the optical axis of the projection optical system 6, i.e., within the XY plane, and rotatable in the θZ direction. The original plate stage 2 is driven by a drive mechanism (not shown) such as a linear motor.

[0017] A mirror 7 is provided on the original plate stage 2. Also, a laser interferometer 9 is provided at a position facing the mirror 7. The two-dimensional position and the rotation angle of the original plate stage 2 (holding the original plate 1) are measured in real time by the laser interferometer 9, and such measurement results are output to the control unit 17. The control unit 17 controls the drive mechanism based on the measurement results of the laser interferometer 9 to position the original plate 1 held by the original plate stage 2.

[0018] The projection optical system 6 includes a plurality of optical elements and projects the pattern of the reticle 1 onto the substrate 3 at a predetermined projection magnification β. In this embodiment, the projection optical system 6 is, for example, a reduction optical system having a projection magnification β of 1 / 4 or 1 / 5.

[0019] The substrate stage 4 includes a Z stage that holds the substrate 3 via a chuck, an XY stage that supports the Z stage, and a base that supports the XY stage. The substrate stage 4 is driven by a drive mechanism 18 including a linear motor or the like.

[0020] A mirror 8 is provided on the substrate stage 4. Also, laser interferometers 10 and 12 for measuring the position of the substrate stage 4 are provided at positions facing the mirror 8. The positions of the substrate stage 4 in the X direction, Y direction, and θZ direction are measured in real time by the laser interferometer 10, and such measurement results are output to the control unit 17. Also, the positions of the substrate stage 4 in the Z direction, θX direction, and θY direction are measured in real time by the laser interferometer 12, and such measurement results are output to the control unit 17. The control unit 17 positions the substrate 3 held on the substrate stage 4 by controlling the drive mechanism 18 based on the measurement results of the laser interferometers 10 and 12.

[0021] A stage reference plate 11 is provided on the substrate stage 4 so as to be approximately at the same height as the surface of the substrate 3 held on the substrate stage 4. FIG. 2 is a diagram showing a detailed configuration of the stage reference plate 11 provided on the substrate stage 4. The stage reference plate 11 may be provided at one corner of the substrate stage 4, or may be provided at a plurality of corners of the substrate stage 4. Also, the stage reference plate 11 may be provided along the side of the substrate stage 4. In this embodiment, as shown in FIG. 2, three stage reference plates 11 are provided for the substrate stage 4.

[0022] As shown in Figure 2, the stage reference plate 11 is provided with reference marks 111 detected by the original plate position detection systems 13 and 14, and reference marks 112 detected by the position detection system 16. The stage reference plate 11 may have multiple reference marks 111 or multiple reference marks 112. The positional relationship (X direction and Y direction) between reference marks 111 and reference marks 112 is set to a predetermined positional relationship (i.e., it is known). Reference marks 111 and reference marks 112 may be the same mark.

[0023] The master plate position detection system 13 is located near the master plate stage 2. The master plate position detection system 13 detects a master plate reference mark (not shown) provided on the master plate 1 held on the master plate stage 2, and a reference mark 111 provided on the stage reference plate 11 on the substrate stage via the projection optical system 6. The master plate position detection system 13 uses the same light source as the light source used when actually exposing the substrate 3 to detect the master plate reference mark provided on the master plate 1 and the reference mark 111 via the projection optical system 6. Specifically, the master plate position detection system 13 detects the reflected light from the master plate reference mark and the reference mark 111 (reflective mark) with an image sensor (for example, a photoelectric conversion element such as a CCD camera). Based on the detection signal from the image sensor, alignment is performed between the master plate 1 and the substrate 3. In this process, by aligning the position and focus of the original plate reference mark on the original plate 1 and the reference mark 111 on the stage reference plate 11, the relative positional relationship (X, Y, Z) between the original plate 1 and the substrate 3 can be adjusted.

[0024] The original plate position detection system 14 is provided on the substrate stage 4. The original plate position detection system 14 is a transmissive detection system and is used when the reference mark 111 is a transmissive mark. The original plate position detection system 14 uses the same light source as the light source used when actually exposing the substrate 3 to detect the original plate reference mark provided on the original plate 1 and the reference mark 111 provided on the stage reference plate 11. Specifically, the original plate position detection system 14 detects the transmitted light that has passed through the original plate reference mark and the reference mark 111 using a light intensity sensor. At this time, while moving the substrate stage 4 in the X direction (or Y direction) and Z direction, the original plate position detection system 14 detects the amount of transmitted light. This makes it possible to align the position and focus of the original plate reference mark provided on the original plate 1 and the reference mark 111 provided on the stage reference plate 11.

[0025] Thus, whether using the original plate position detection system 13 or the original plate position detection system 14, the relative positional relationship (X, Y, Z) between the original plate 1 and the substrate 3 can be adjusted.

[0026] The focus detection system 15 includes a light projection system that projects light onto the surface of the substrate 3 at an oblique angle, and a light receiving system that receives the light reflected from the surface of the substrate 3. The focus detection system 15 detects the position of the substrate 3 in the Z direction (height direction) and outputs the detection result to the control unit 17. Based on the detection result of the focus detection system 15, the control unit 17 controls the drive mechanism 18 to adjust the position (focus position) and tilt angle of the substrate 3 held on the substrate stage 4 in the Z direction.

[0027] The position detection system 16 includes an illumination system that illuminates the alignment marks 19 and reference marks 112 on the stage reference plate 11, which are the objects under inspection on the substrate, and an imaging system that forms an image of the light (reflected light) from the alignment marks 19 and reference marks 112 on a photoelectric conversion element. The position detection system 16 detects the alignment marks 19 and reference marks 112 and outputs the detection result to the control unit 17. Based on the detection result of the position detection system 16 (position of the alignment marks 19), the control unit 17 controls the drive mechanism 18 that drives the substrate stage 4 and adjusts the position of the substrate 3 held on the substrate stage 4 in the X and Y directions.

[0028] Optical position detection systems for detecting (observing) alignment marks on a substrate are generally classified into two main types: off-axis detection systems and TTL (Through the Lens) detection systems. Off-axis detection systems optically detect alignment marks on the substrate without using a projection optical system. TTL detection systems detect alignment marks on the substrate using light of a different wavelength than the exposure light (non-exposure light) via a projection optical system. In this embodiment, the position detection system 16 is an off-axis detection system, but this does not limit the detection method. For example, if the position detection system 16 is a TTL detection system, the alignment marks 19 on the substrate 3 are detected via the projection optical system 6, but the basic configuration is the same as that of the off-axis detection system.

[0029] Figure 3 shows the specific configuration of the position detection system 16, including the illumination system ILS and the imaging system IMS. The position detection system 16 includes a light source 20, a first illumination optical system 21, a wavelength filter plate 22, a second illumination optical system 23, an aperture diaphragm plate 24, a third illumination optical system 25, a fourth illumination optical system 26, a polarizing beam splitter 27, an NA diaphragm 28, and a prism 29. Furthermore, the position detection system 16 includes a λ / 4 plate 30, an objective lens 31, a relay lens 32, a first imaging optical system 33, an aperture diaphragm plate 34, a second imaging optical system 35, an optical element for adjusting the wavelength shift difference 36, a photoelectric conversion element 37, and switching mechanisms 38 and 39.

[0030] In this embodiment, the light source 20 emits visible light (for example, light with a wavelength of 500 nm to 700 nm), blue wavelength light (for example, light with a wavelength of 450 nm to 550 nm (blue wavelength light)), and infrared light (for example, light with a wavelength of 700 nm to 1500 nm). The light (illumination light) guided from the light source 20 by a fiber or the like passes through the first illumination optical system 21, the wavelength filter plate 22, and the second illumination optical system 23, and reaches the aperture diaphragm plate 24 located at the pupil plane (optical Fourier transform plane with respect to the object plane) of the position detection system 16.

[0031] The wavelength filter plate 22 is equipped with multiple wavelength filters that transmit light through wavelength bands (transmission wavelength bands) that differ from each other. Under the control of the control unit 17, one wavelength filter is selected from the multiple wavelength filters and placed in the optical path of the position detection system 16. In this embodiment, the wavelength filter plate 22 is equipped with a wavelength filter that transmits visible light, a wavelength filter that transmits blue wavelength light, and a wavelength filter that transmits infrared light. By switching these wavelength filters on the wavelength filter plate 22, the wavelength band of light that illuminates the alignment marks 19 provided on the substrate 3 can be selected. In addition, the wavelength filter plate 22 may have a configuration that allows for the addition of new wavelength filters in addition to the multiple wavelength filters that are provided in advance.

[0032] The aperture diaphragm plate 24 has multiple aperture diaphragms 24a (first diaphragms) arranged on it, each having a different numerical aperture (aperture size, NA) and aperture shape. The multiple aperture diaphragms 24a are selectively positioned on the pupil plane of the illumination system ILS. In this embodiment, under the control of the control unit 17, the illumination mode for illuminating the alignment mark 19 can be changed by switching the aperture diaphragms 24a positioned on the optical path of the illumination system ILS of the position detection system 16, specifically on the pupil (pupil plane). Furthermore, the aperture diaphragm plate 24 may have a configuration that allows for the addition of new aperture diaphragms in addition to the multiple aperture diaphragms 24a that are provided in advance.

[0033] Various methods can be employed for the switching mechanism 38 that switches the aperture apertures 24a to be placed in the optical path of the ILS illumination system of the position detection system 16 in the aperture aperture plate 24. Figure 3 illustrates a switching mechanism 38 that employs a guide rail system to select the desired aperture aperture 24a to be placed in the optical path of the ILS illumination system by sliding the aperture aperture plate 24, in which multiple aperture apertures 24a are arranged in a straight line, in the Z direction. Furthermore, after selecting the desired aperture aperture 24a, the switching mechanism 38 can finely adjust the position of the aperture aperture 24a in the Z direction by slightly sliding the aperture aperture plate 24. Such operation can be achieved, for example, by having a linear / pulse motor in the switching mechanism 38.

[0034] The direction of operation of the aperture diaphragm 24 by the switching mechanism 38 does not need to be one-dimensional. For example, the switching mechanism 38 may operate the aperture diaphragm 24 two-dimensionally in a plane perpendicular to the optical axis of the illumination system ILS (in the ZX plane). The aperture diaphragm 24a, positioned in the optical path of the illumination system ILS, is adjusted in position (pupil adjustment) in the ZX plane in combination with the aperture diaphragm 34a, positioned in the optical path of the imaging system IMS, so that the overall imaging performance of the position detection system 16 is good.

[0035] Light passing through the aperture diaphragm plate 24 (aperture diaphragm 24a) is guided to the polarizing beam splitter 27 via the third illumination optical system 25 and the fourth illumination optical system 26. Of the light guided to the polarizing beam splitter 27, the S-polarized light perpendicular to the plane of the paper is reflected by the polarizing beam splitter 27 and passes through the NA diaphragm 28 and the prism 29. The NA diaphragm 28 is a variable NA diaphragm that can change the NA by changing the aperture amount under the control of the control unit 17. The prism 29 is used to branch the optical path to an optical system not shown. Light from the prism 29 passes through the λ / 4 plate 30 and is converted to circularly polarized light, which illuminates the alignment marks 19 provided on the substrate 3 via the objective lens 31.

[0036] The light diffracted at the alignment mark 19 (detection light) passes through the objective lens 31 and the λ / 4 plate 30, is converted to P-polarized light parallel to the plane of the paper, and passes through the prism 29 and NA aperture 28 to the polarizing beam splitter 27. The light that has passed through the polarizing beam splitter 27 passes through the relay lens 32, the first imaging optical system 33, and the aperture diaphragm plate 34.

[0037] The aperture diaphragm plate 34 has multiple aperture diaphragms 34a (second diaphragms) arranged on it, each having a different numerical aperture (aperture size, NA) and aperture shape. The multiple aperture diaphragms 34a are selectively positioned on the pupil plane of the imaging system IMS. In this embodiment, under the control of the control unit 17, the detection mode for detecting the alignment mark 19 can be changed by switching the aperture diaphragms 34a positioned on the optical path of the imaging system IMS of the position detection system 16, specifically on the pupil (pupil plane). Furthermore, the aperture diaphragm plate 34 may have a configuration that allows for the addition of new aperture diaphragms in addition to the multiple aperture diaphragms 34a that are provided in advance.

[0038] In the aperture diaphragm plate 34, various methods can be employed for the switching mechanism 39 to switch the aperture diaphragm 34a to be placed in the optical path of the imaging system IMS of the position detection system 16. Figure 3 illustrates a switching mechanism 39 employing a turret system that selects the desired aperture diaphragm 34a to be placed in the optical path of the imaging system IMS by rotating (driving) the aperture diaphragm plate 34, which has multiple aperture diaphragms 34a arranged on it, around a rotation axis 40. The aperture diaphragm plate 34 has multiple aperture diaphragms 34a arranged such that their diaphragm centers are located on a single circumference. Furthermore, after selecting the desired aperture diaphragm 34a, the switching mechanism 39 can finely adjust the rotation axis 40 in the plane of the paper (in the direction perpendicular to the optical axis of the imaging system). As a result, the aperture diaphragm 34a placed in the optical path of the imaging system IMS is positioned (pupil adjustment) in the XY plane in combination with the aperture diaphragm 24a placed in the optical path of the illumination system ILS so that the overall imaging performance of the position detection system 16 is good.

[0039] In this embodiment, the switching mechanisms 38 and 39 employ a guide rail system or a turret system as a method for switching the aperture diaphragm, but are not limited to these. For example, other methods may be used as long as it is possible to switch (select) the aperture diaphragm and fine-tune the aperture diaphragm.

[0040] Light passing through the aperture diaphragm 34 (aperture diaphragm 34a) reaches the photoelectric conversion element 37 (for example, an image sensor such as a CCD image sensor) via the second imaging optical system 35 and the wavelength shift difference adjustment optical member 36. The photoelectric conversion element 37 detects the light from the alignment mark 19, and the accumulation time can be extended until the intensity of such light exceeds a certain threshold. The accumulation time of the photoelectric conversion element 37 is controlled by the control unit 17.

[0041] In the exposure apparatus 100, the control unit 17 determines the amount of drive for the drive mechanism 18 that drives the substrate stage 4 based on the position information of the alignment marks 19 obtained by the position detection system 16, and performs exposure (overlay exposure) of the substrate 3.

[0042] The following describes the calibration method for the position detection system 16 in this embodiment and the effects obtained by this calibration method. First, the specific configurations of the switching mechanism 38 for switching the aperture diaphragm 24a arranged in the optical path of the illumination system ILS of the position detection system 16, and the switching mechanism 39 for switching the aperture diaphragm 34a arranged in the optical path of the imaging system IMS of the position detection system 16 will be described.

[0043] Figure 4 shows the specific configuration of the switching mechanism 38 employing a guide rail system. Referring to Figure 4, the aperture diaphragm plate 24 (light shielding plate) is attached to the guide rail 41 via a bearing 42 and is configured to be drivable in the Z direction by a gear 43. Multiple aperture diaphragms 24a with different NAs and shapes are arranged in a straight line on the aperture diaphragm plate 24. The positions (ranges) in which each aperture diaphragm 24a should be located on the aperture diaphragm plate 24 are indicated by circles labeled A to F. For example, the position of the circle labeled D is where the aperture diaphragm 24a to be placed in the optical path of the illumination system ILS of the position detection system 16 is located.

[0044] Figure 5 shows the specific configuration of the switching mechanism 39 employing a turret system. Referring to Figure 5, the aperture diaphragm plate 34 (light shielding plate) is configured to be rotatable (driven) around the rotation axis 40 by a gear 40a integrally provided with the rotation axis 40. The aperture diaphragm plate 34 has multiple aperture diaphragms 34a with different NAs and shapes, arranged such that the center of each diaphragm is located on a single circumference. In the aperture diaphragm plate 34, the positions (ranges) in which each aperture diaphragm 34a should be located are indicated by circles labeled positions a to g. For example, the position of the circle labeled position e is where the aperture diaphragm 34a to be placed in the optical path of the imaging system IMS of the position detection system 16 is located.

[0045] The number of aperture diaphragms 24a arranged on the aperture diaphragm plate 24 and the number of aperture diaphragms 34a arranged on the aperture diaphragm plate 34 may be the same or different. Also, the shape (aperture shape) of the aperture diaphragms 24a and 34a does not have to be circular, and the transmittance of their apertures does not have to be 100%.

[0046] As is clear from Figures 4 and 5, there are generally multiple combinations of aperture diaphragms 24a, which are placed in the optical path of the illumination system ILS of the position detection system 16, and aperture diaphragms 34a, which are placed in the optical path of the imaging system IMS of the position detection system 16. However, regardless of the combination of aperture diaphragms 24a and 34a, in order to maintain good imaging performance of the position detection system 16, it is necessary to adjust the positions of aperture diaphragms 24a and 34a to an optically desirable state. In the adjustment (calibration) of the position detection system 16, two evaluation indicators are used: the amount of lateral displacement when the alignment mark 19 provided on the substrate 3 is defocused, and the asymmetry of the image of the alignment mark 19 (the degree to which the image is asymmetrically distorted).

[0047] Figure 6 shows the state of the position detection system 16 before adjusting the aperture diaphragm 24a located in the optical path of the illumination system ILS. In Figure 6, the circles shown by thick solid lines (thick lines) indicate the state of the aperture diaphragm 34a located in the optical path of the imaging system IMS before adjustment. Referring to Figure 6, before adjusting the aperture diaphragm 24a, the optical axis of the light illuminating the substrate 3 (illumination light) is deviated from perpendicular to the substrate 3, so the direction of the zero-order diffracted light reflected by the substrate 3 is deviated from the center of the aperture diaphragm 34a before adjustment. As described above, since the aperture diaphragm 24a is located on the optical Fourier transform plane with respect to the surface on which the substrate 3 is located, adjusting the aperture diaphragm 24a is equivalent to adjusting the effective light source, i.e., the angle of light incident on the substrate 3 (incidence angle of illumination light). Therefore, in the state shown in Figure 6, by driving (adjusting) the aperture diaphragm 24a, the component of the tilted illumination light along the driving direction of the optical axis can be corrected. If these components are not corrected, it is clear that when the alignment marks 19 on the substrate are detected at different focus positions, the image of the alignment marks 19 will shift laterally, causing errors in the detection of the alignment marks 19's position.

[0048] In principle, the zero-order diffracted light reflected from the substrate 3 can also be adjusted to the center of the pupil on the detection side by driving (adjusting) the aperture diaphragm 34a, which is shown by the thick line in Figure 6. Since the aperture diaphragm 34a is located on the optical Fourier transform plane with respect to the photoelectric conversion element 37 (photoelectric conversion surface), adjusting the aperture diaphragm 34a is equivalent to selecting the order of the diffracted light from the substrate 3 that the photoelectric conversion element 37 detects.

[0049] Generally, diffracted light from an object with symmetry, such as the alignment mark 19, is generated symmetrically with positive and negative polarity around the zero-order diffracted light. Therefore, as described above, by adjusting the zero-order diffracted light to the center of the pupil on the detection side, the position detection system 16 can achieve a good imaging state with little distortion. However, if the illumination light is tilted, asymmetric distortion occurs in the image of the alignment mark 19, affecting the position detection accuracy of the alignment mark 19. This is mainly due to two factors: the alignment mark 19 actually has a three-dimensional thickness, and the reflected light from the substrate 3 passes through a region with low aberration correction away from the optical axis of the imaging system IMS.

[0050] Therefore, it is basically necessary to match the aperture diaphragm 24a and the aperture diaphragm 34a while taking two evaluation indices: the amount of lateral displacement when the alignment mark 19 provided on the substrate 3 is defocused, and the asymmetry of the image of the alignment mark 19. Here, matching the aperture diaphragm 24a and the aperture diaphragm 34a basically means aligning their centers (in an ideal state where the position detection system 16 has no aberrations). However, in cases where the coma aberration of the position detection system 16 is large, the aperture diaphragm 24a and the aperture diaphragm 34a may be slightly offset to block diffracted light passing through regions on the pupil plane where the aberration correction state is low, even if it impairs the symmetry of the diffracted light taken into the imaging system IMS.

[0051] In the introduction and operation of the exposure apparatus 100, a process (adjustment process) is usually provided to adjust the condition of the exposure apparatus 100 when it is shipped and installed, and to confirm that the condition is good. In the adjustment process, as described above, the initial positions of the aperture diaphragms 24a and 34a are determined by taking two evaluation indices: the amount of lateral displacement when the alignment mark 19 provided on the substrate 3 is defocused, and the asymmetry of the image of the alignment mark 19. For example, the initial positions of the aperture diaphragms 24a and 34a are determined (adjusted) so that the amount of lateral displacement and asymmetry of the image of the alignment mark 19 formed on the photoelectric conversion element when the alignment mark 19 is defocused fall within an acceptable range. In this embodiment, in order to use when actually introducing and operating the exposure apparatus 100 having a position detection system 16, the following data (initial data) is acquired for each of the aperture diaphragms 24a and 34a.

[0052] When the centers of the aperture diaphragms 24a and 34a deviate from their initial positions determined in the calibration process, there are generally four degrees of freedom regarding the drive (amount of drive) of the aperture diaphragms 24a and 34a to correct the deviation from the initial position. Specifically, there are two first-order independent directions in a plane perpendicular to the optical axis for each of the aperture diaphragms 24a and 34a. These two directions do not need to be orthogonal to each other, but here we will represent the two directions with subscripts x and y. Note that if a guide rail system as shown in Figure 4 is used as the switching mechanism for switching the aperture diaphragms in either the illumination system ILS or the imaging system IMS of the position detection system 16, the degrees of freedom regarding the drive of the aperture diaphragms 24a and 34a will be less than four.

[0053] In the calibration of the position detection system 16 during the operation of the exposure apparatus 100, if the aperture diaphragms 24a and 34a are shifted from their initial positions, the drive amount (correction drive amount) of the aperture diaphragms 24a and 34a is expressed as a four-vector in Equation 1 below as an unknown variable to be determined in order to correct this shift.

[0054]

number

[0055] In Equation 1, PILx represents the correction drive amount in the x-direction for the aperture diaphragm 24a located in the optical path of the illumination system ILS, and PILy represents the correction drive amount in the y-direction for the aperture diaphragm 24a located in the optical path of the illumination system ILS. Furthermore, PDLx represents the correction drive amount in the x-direction for the aperture diaphragm 34a located in the optical path of the imaging system IMS, and PDLy represents the correction drive amount in the y-direction for the aperture diaphragm 34a located in the optical path of the imaging system IMS.

[0056] The drive mechanism 18 drives the substrate stage 4 in the Z direction, while the position detection system 16 detects the alignment marks 19 for adjustment (calibration). The alignment marks 19 for adjustment do not need to be on the substrate 3; they only need to be on the substrate stage 4 and driven in the Z direction together with the substrate stage 4, for example, they may be on the stage reference plate 11. If the alignment marks 19 for adjustment are on the stage reference plate 11, the calibration method in this embodiment can be performed self-contained using only the components of the exposure apparatus 100.

[0057] If the optical axis of the ILS illumination system of the position detection system 16 is deviated from perpendicular to the plane on which the alignment marks 19 exist, the image of the alignment marks 19 detected by the photoelectric conversion element 37 will shift horizontally as the substrate stage 4 is driven in the Z direction. Therefore, the degree to which the optical axis of the light illuminating the substrate 3 is deviated from perpendicular to the substrate 3 can be evaluated from the direction (x and y directions) and amount of the shift of the alignment mark 19 image when the substrate stage 4 is driven in the Z direction by a small unit amount δZ. Hereinafter, the degree to which the illumination light is deviated from perpendicular to the substrate 3 (the amount of shift of the alignment mark 19 image on the photoelectric conversion element with respect to the amount of defocus of the alignment marks 19) will be used as an evaluation index and referred to as the defocus characteristic.

[0058] The amount by which the centers of the aperture diaphragms 24a and 34a deviate from their initial positions determined in the calibration process is usually small enough that the resulting defocus characteristics can be considered proportional to the amount of deviation. Therefore, in order to determine the four correction drive amounts represented by Equation 1, four independent linear relationships are sufficient.

[0059] To obtain these four independent linear relationships (equations), in this embodiment, first, two distinct combinations of aperture diaphragms 24a and 34a are selected from a plurality of combinations of aperture diaphragms 24a and 34a. Specifically, two distinct combinations of aperture diaphragms 24a and 34a are selected by selecting one aperture diaphragm from each of the plurality of aperture diaphragms 24a shown in Figure 4 and the plurality of aperture diaphragms 34a shown in Figure 5. In this embodiment, each of these two combinations is referred to as Mode 1 (first combination) and Mode 2 (second combination). Here, the combination of aperture diaphragms 24a and 34a selected as Mode 1 or Mode 2 may be reused from existing combinations for realizing illumination modes already set in the exposure apparatus 100, according to the purpose described below. As will be described later, a combination of aperture diaphragms having an optimized structure for the purpose of calibrating the position detection system 16 may be specially set.

[0060] In this way, when two combinations that realize Mode 1 and Mode 2 are selected, the amount of variation in the defocus characteristics can be expressed as a four-vector, as shown in Equation 2 below.

[0061]

number

[0062] In Equation 2, Δ1x represents the variation in the x-direction defocus characteristics in Mode 1, and Δ2x represents the variation in the x-direction defocus characteristics in Mode 2. Similarly, Δ1y represents the variation in the y-direction defocus characteristics in Mode 1, and Δ2y represents the variation in the y-direction defocus characteristics in Mode 2. Figure 7 illustrates the concept that these variations in defocus characteristics are proportional to the amount of drive of the substrate stage 4 in the Z-direction. Figure 7 shows the relationship between the amount of drive of the substrate stage 4 in the Z-direction and the variation in defocus characteristics, with the horizontal axis representing the amount of drive of the substrate stage 4 in the Z-direction and the vertical axis representing the defocus characteristics (variation).

[0063] In this embodiment, during the calibration process, the defocus characteristic values ​​(D01x, D02x, D01y, D02y) in the x and y directions for each of modes 1 and 2 at the completion of the initial adjustment are measured and acquired as initial data (reference defocus characteristics). Furthermore, by performing the following procedures (1), (2), (3), and (4), the variation vectors of the defocus characteristics when the aperture diaphragms 24a and 34a are varied by a unit amount within the pupil plane of the illumination system ILS and imaging system IMS, respectively, are acquired as initial data.

[0064] Procedure (1): Determine the variation vector (Δ1x, Δ2x, Δ1y, Δ2y) of the defocus characteristics when only the aperture diaphragm 24a placed in the optical path of the ILS illumination system of the position detection system 16 is varied by a unit amount in the x direction, and define this as (A, B, C, D).

[0065] Procedure (2): Determine the variation vector (Δ1x, Δ2x, Δ1y, Δ2y) of the defocus characteristics when only the aperture diaphragm 34a placed in the optical path of the imaging system IMS of the position detection system 16 is varied by a unit amount in the x direction, and define this as (E, F, G, H).

[0066] Procedure (3): Determine the variation vector (Δ1x, Δ2x, Δ1y, Δ2y) of the defocus characteristics when only the aperture diaphragm 24a placed in the optical path of the illumination system ILS of the position detection system 16 is varied by a unit amount in the y direction, and define this as (I, J, K, L).

[0067] Procedure (4): Determine the variation vector (Δ1x, Δ2x, Δ1y, Δ2y) of the defocus characteristics when only the aperture diaphragm 34a placed in the optical path of the imaging system IMS of the position detection system 16 is varied by a unit amount in the y direction, and define this as (M, N, O, P).

[0068] When the exposure apparatus 100 is put into operation and the aperture diaphragms 24a and 34a have shifted from their initial positions determined in the calibration process, the position detection system 16 needs to be calibrated (to adjust the positions of the aperture diaphragms 24a and 34a). The procedure described below is then performed.

[0069] First, with the aperture diaphragms 24a and 34a positioned at a location shifted from their initial position (first position), the defocus characteristic values ​​(D1x, D2x, D1y, D2y) in the x and y directions for each of modes 1 and 2 are measured and acquired. This allows us to determine the correction drive amounts (PILx, LDTx, PILy, DTy) for the aperture diaphragms 24a and 34a, which were unknowns in Equation 1, from the four-variable simultaneous equation shown in Equation 3.

[0070]

number

[0071] The solution to the system of four equations shown in Equation 3 is simple. Therefore, the solution may be performed by a unit with calculation capabilities in the exposure apparatus 100, such as the control unit 17, or by an external device (calculation unit) different from the exposure apparatus 100.

[0072] Based on the correction drive amount obtained from the four-equation system shown in Equation 3, the positions of the aperture diaphragms 24a and 34a are adjusted (returned to their initial positions) by controlling (driving) the switching mechanisms 38 and 39 respectively, thereby achieving calibration of the position detection system 16.

[0073] In this embodiment, the initial positions of the aperture diaphragms 24a and 34a determined in the calibration process are used as the reference positions, and the purpose described is simply to return the aperture diaphragms 24a and 34a to their initial positions if they deviate from those initial positions. However, the reference position, which is the position to which the aperture diaphragms 24a and 34a are returned, is not limited to the initial position but can be set to any position. Furthermore, if there is a need to intentionally change the characteristics of the position detection system 16 in order to accommodate the specific characteristics of individual process substrates, the left side of equation 3 may be set to the value of the defocus characteristic (target value) corresponding to an arbitrary target.

[0074] Furthermore, in this embodiment, the number of combinations (modes) of aperture diaphragms 24a and 34a required for calibration of the position detection system 16 is at least two. However, it is also possible to prepare more than two combinations, perform the procedure described above, and determine the correction drive amounts for aperture diaphragms 24a and 34a by comprehensively considering the results. For example, if there are N types of combinations, N(N-1) / 2 correction drive amounts (PILx, LDTx, PILy, DTy) can be obtained, and the weighted average value of these vectors may be adopted.

[0075] Furthermore, the alignment light (non-exposure light) used in the exposure apparatus 100 generally includes multiple wavelength bands, for example, at least two wavelength bands above 450 nm, in order to accommodate various processes. In such cases, wavelength-weighted averaging may be performed.

[0076] Next, we will describe the selection (combination) of aperture diaphragms 24a and 34a that is suitable for actual operation of the calibration method of the position detection system 16 in this embodiment. As is clear from Equation 3, in this embodiment, the correction drive amounts of aperture diaphragms 24a and 34a are determined from linear equations (a system of four linear equations). Therefore, if the value of the determinant of the coefficient matrix shown in Equation 4 is close to zero, the accuracy of the correction drive amounts (PILx, LDTx, PILy, DTy) of aperture diaphragms 24a and 34a obtained from Equation 3 will decrease. For this reason, it is necessary to set the value of the determinant of the coefficient matrix shown in Equation 4 to a value far from zero.

[0077]

number

[0078] As an alignment mark 19 that can be put into practical use in the exposure apparatus 100 (position detection system 16) and that can be simplified, an alignment mark 19A as shown in Figure 8 can be considered. Figure 8 shows an alignment mark 19A that includes a structure that generates diffracted light in only one of two orthogonal directions in a plane perpendicular to the optical axis of the position detection system 16 (in the XY plane). In the alignment mark 19A, due to the symmetry of the mark, diffracted light is generated only in the Y direction in the coordinate axes shown in Figure 8. Therefore, even if the aperture diaphragms 24a and 34a are driven in the X direction in the coordinate axes shown in Figure 8, it is considered that the defocus characteristics in the X direction will hardly change. In this way, by using an alignment mark 19A in which the direction in which no diffracted light is generated and the direction in which diffracted light is generated coincide with the X and Y directions in the position detection system 16, equation 4 can be approximated with high accuracy to a block diagonalization matrix as shown in the following equation 5.

[0079]

number

[0080] When the X and Y directions are separated, the determinant shown in Equation 5 becomes (AF-BE)·(KP-LO), which is the product of the determinants of the diagonal submatrices. Therefore, mode 1 and mode 2 (combinations of aperture diaphragm 24a and aperture diaphragm 34a) should be selected such that the values ​​of AF-BE and KP-LO are simultaneously far from zero.

[0081] It is possible to prepare two sets of such combinations of aperture diaphragms 24a and aperture diaphragms 34a. Here, as an example, aperture diaphragms 24a and aperture diaphragms 34a are assumed to have a common center (i.e., their centers overlap) and apertures that are nearly circular in shape with different radii. In this case, for Mode 1 and Mode 2, the aperture diaphragm 24a should differ significantly only in the radius of its opening (aperture diameter), while the aperture diaphragm 34a should have the same (identical) aperture diameter. Specifically, it is desirable that the aperture ratio between the aperture diaphragm 24a included in Mode 1 and the aperture diaphragm 24a included in Mode 2 be at least twice. Furthermore, the aperture diaphragms 34a included in Mode 1 and Mode 2, respectively, have a larger aperture diameter than the aperture diaphragms 24a included in Mode 1 and Mode 2. Such combinations are optically known; for example, a mode including a large aperture diaphragm 24a is a mode that prioritizes resolution, while a mode including a small aperture diaphragm 34a is a mode that prioritizes contrast.

[0082] The small aperture diameter of aperture 24a means that the diameter of light passing through aperture 34a is small, and that light passes inside aperture 34a. Therefore, in modes that prioritize contrast, the effect of the shift in aperture 34a on the defocus characteristics is extremely small compared to modes that prioritize resolution. This means that in equation 5, the values ​​of F and P are close to zero, so (AF-BE)·(KP-LO)≈BE·LO, and it is possible to avoid the value of the overall determinant being close to zero.

[0083] As described above, Table 1 below shows specific numerical examples of aperture 24a and aperture 34a in Mode 1 and Mode 2, respectively, when aperture 24a and aperture 34a have circular openings with a common center and different radii.

[0084] [Table 1]

[0085] Next, with reference to Figure 9, the calibration process (calibration method) for the position detection system 16 will be described. This process is carried out by the control unit 17 comprehensively controlling each part of the exposure apparatus 100, including the position detection system 16. In other words, the control unit 17 also functions as a processing unit that performs the calibration process for the position detection system 16. However, this does not preclude the possibility that an external device (information processing device) may perform the calibration process for the position detection system 16 by comprehensively controlling each part of the exposure apparatus 100, including the position detection system 16, instead of the control unit 17.

[0086] In this embodiment, the exposure apparatus 100 is configured so that the position detection system 16 can be calibrated at any time while the exposure apparatus 100 is in operation. However, the aperture diaphragm 24a and aperture diaphragm 34a actually deviate from the initial position determined in the calibration process when, for example, the power supply to the exposure apparatus 100 is interrupted and then the power supply to the exposure apparatus 100 is resumed (re-powering). Also, when the exposure apparatus 100 is reset for recovery operation in response to some trouble (reset), the aperture diaphragm 24a and aperture diaphragm 34a may deviate from the initial position determined in the calibration process. Therefore, by performing calibration of the position detection system 16 during such re-powering or resetting, the operational effectiveness of the exposure apparatus 100 can be improved. It should be noted that even during re-powering or resetting, the user may choose not to perform calibration of the position detection system 16.

[0087] Referring to Figure 9, in S101, the current defocus characteristics (D1x, D1y) in the pre-selected mode 1 (after the aperture diaphragms 24a and 34a have shifted from their initial positions) are acquired (measured). Specifically, the switching mechanisms 38 and 39 are driven to position the aperture diaphragm 24a, selected in mode 1, on the pupil plane of the illumination system ILS, and the aperture diaphragm 34a, also selected in mode 1, on the pupil plane of the imaging system IMS. The substrate stage 4 is also driven so that the alignment mark 19 is located within the field of view of the position detection system 16. Then, while driving the substrate stage 4 in the Z direction, the alignment mark 19 is detected by the position detection system 16, thereby acquiring the current defocus characteristics in mode 1.

[0088] In S102, the current defocus characteristics (D2x, D2y) in the pre-selected mode 2 (after the aperture diaphragms 24a and 34a have shifted from their initial positions) are acquired (measured). Specifically, the switching mechanisms 38 and 39 are driven to position the aperture diaphragm 24a, selected in mode 2, on the pupil plane of the illumination system ILS, and the aperture diaphragm 34a, also selected in mode 2, on the pupil plane of the imaging system IMS. The substrate stage 4 is also driven so that the alignment mark 19 is within the field of view of the position detection system 16. Then, while driving the substrate stage 4 in the Z direction, the alignment mark 19 is detected by the position detection system 16, thereby acquiring the current defocus characteristics in mode 2.

[0089] In this embodiment, in steps S101 and S102 (first step), the current defocus identification (first defocus characteristic) is acquired for each of modes 1 and 2.

[0090] In S103, the difference between the defocus characteristics of modes 1 and 2 (D01x, D02x, D01y, D02y) acquired in advance during the adjustment process and the current defocus characteristics of modes 1 and 2 (D1x, D2x, D1y, D2y) acquired in S101 and S102 is calculated.

[0091] In S104, the drive amounts for the aperture diaphragms 24a and 34a, i.e., the correction drive amounts (PILx, PILy, PDLx, PDLy), which are necessary to correct the deviation of the aperture diaphragms 24a and 34a from their initial positions, are determined. As described above, the correction drive amounts for the aperture diaphragms 24a and 34a can be determined from the four-variable simultaneous equations shown in Equation 3, based on the difference obtained in S103. Note that the various data, including the initial data necessary to determine the correction drive amounts for the aperture diaphragms 24a and 34a, i.e., to solve the four-variable simultaneous equations shown in Equation 3, may be read from a storage area provided in the exposure apparatus 100 or from an external storage area.

[0092] In S105, the aperture diaphragm 24a (switching mechanism 38) and aperture diaphragm 34a (switching mechanism 39) are driven according to the correction drive amounts (PILx, PILy, PDLx, PDLy) determined in S104 to adjust the positions of the aperture diaphragms 24a and 34a, respectively.

[0093] In this embodiment, in steps S103, S104, and S105 (second step), the positions of the aperture diaphragms 24a and 34a are adjusted (pupil adjustment) based on the reference defocus characteristics in modes 1 and 2, and the current defocus characteristics.

[0094] Thus, according to the calibration method for the position detection system 16 in this embodiment, calibration of the position detection system 16 can be performed self-contained at the user site at any time, without requiring any special tools other than those for the exposure apparatus 100. Furthermore, since an encoder for detecting the misalignment of the aperture diaphragms 24a and 34a (pupil position misalignment) is not required, it is possible to achieve both cost reduction and elimination of heat sources, while improving position detection accuracy. Therefore, according to this embodiment, an exposure apparatus 100 that is superior in terms of cost and overlay accuracy can be provided.

[0095] The method for manufacturing articles in the embodiments of the present invention is suitable for manufacturing articles such as flat panel displays, liquid crystal display elements, semiconductor elements, and MEMS. Such a manufacturing method includes the steps of exposing a substrate coated with a photosensitive material using the exposure apparatus 100 described above, and developing the exposed photosensitive material. Furthermore, an etching step or ion implantation step is performed on the substrate using the pattern of the developed photosensitive material as a mask to form a circuit pattern on the substrate. These steps of exposure, development, etching, etc. are repeated to form a circuit pattern consisting of multiple layers on the substrate. In a subsequent step, dicing (processing) is performed on the substrate on which the circuit pattern has been formed, followed by chip mounting, bonding, and inspection steps. Such a manufacturing method may also include other well-known steps (oxidation, film formation, vapor deposition, doping, planarization, resist peeling, etc.). The method for manufacturing articles in this embodiment is advantageous compared to conventional methods in at least one of the performance, quality, productivity, and production cost of the articles.

[0096] The present invention can also be realized by supplying a program that implements one or more of the functions of the above-described embodiments to a system or device via a network or storage medium, and by having one or more processors in the computer of that system or device read and execute the program. It can also be realized by a circuit (e.g., an ASIC) that implements one or more functions.

[0097] The disclosures herein include the following calibration methods, detection systems, exposure apparatuses, methods for manufacturing articles, and programs.

[0098] (Item 1) A calibration method for a detection system having an illumination system for illuminating an object under test and an imaging system for forming an image of light from the object under test on a photoelectric conversion element, The illumination system includes a plurality of first apertures selectively positioned on the pupil surface of the illumination system, each having a different aperture. The imaging system includes a plurality of second apertures selectively positioned on the pupil plane of the imaging system, each having a different aperture. A first step is to acquire a first defocus characteristic for each of at least two combinations of first and second apertures, each of which is formed by selecting one aperture from each of the plurality of first apertures and the plurality of second apertures, that shows the amount of shift of the image on the photoelectric conversion element with respect to the amount of defocus of the object under test when each of the first aperture and the second aperture is positioned at a first position shifted from a reference position; A second step involves adjusting the positions of the first and second apertures so that they are positioned at the reference position, based on a reference defocus characteristic that shows the amount of shift of the image on the photoelectric conversion element with respect to the amount of defocus of the object under test when the first and second apertures are each positioned at the reference position, and the first defocus characteristic acquired in the first step. A calibration method characterized by having the following features.

[0099] (Item 2) The calibration method according to item 1, characterized in that in the second step, the amount of drive required for the position adjustment of the first aperture and the second aperture is determined from the difference between the first defocus characteristic and the reference defocus characteristic, and the amount of change in the reference defocus characteristic when the first aperture and the second aperture are varied by a unit amount within the pupil plane of the illumination system and the pupil plane of the imaging system, respectively.

[0100] (Item 3) The calibration method according to item 2, characterized in that the reference defocus characteristics and the amount of variation of the reference defocus characteristics are obtained in advance before performing the first step.

[0101] (Item 4) The calibration method according to any one of items 1 to 3, characterized in that the first aperture positioned on the pupil plane of the illumination system and the second aperture positioned on the pupil plane of the imaging system have circular openings whose centers overlap and which have different radii.

[0102] (Item 5) The aforementioned at least two combinations include a first combination and a second combination, The calibration method according to any one of items 1 to 4, characterized in that the aperture ratio between the first aperture included in the first combination and the first aperture included in the second combination is 2 times or more.

[0103] (Item 6) The aforementioned at least two combinations include a first combination and a second combination, The second aperture included in the first combination and the second aperture included in the second combination have the same aperture diameter. The calibration method according to any one of items 1 to 4, characterized in that the second aperture included in the first combination and the second aperture included in the second combination have an aperture diameter larger than the aperture diameter of the first aperture.

[0104] (Item 7) The calibration method according to any one of items 1 to 6, characterized in that the light includes at least two wavelength bands of 450 nm or more.

[0105] (Item 8) The calibration method according to any one of items 1 to 7, characterized in that the object under test includes a structure that generates diffracted light in only one of two orthogonal directions in a plane perpendicular to the optical axis of the detection system.

[0106] (Item 9) The calibration method according to any one of items 1 to 8, characterized in that the reference position includes an initial position in which the positions of the first aperture and the second aperture are adjusted so that the amount of lateral displacement and asymmetry of the image formed on the photoelectric conversion element when the object under test is defocused falls within an acceptable range.

[0107] (Item 10) A detection system for detecting the position of an object under test, A lighting system for illuminating the object under test, An imaging system that forms an image of light from the object under test on a photoelectric conversion element, A processing unit that performs a calibration process for the detection system, It has, The illumination system includes a plurality of first apertures selectively positioned on the pupil surface of the illumination system, each having a different aperture. The imaging system includes a plurality of second apertures selectively positioned on the pupil plane of the imaging system, each having a different aperture. The aforementioned processing unit, For each of at least two combinations of first and second apertures, which are formed by selecting one aperture from each of the plurality of first apertures and the plurality of second apertures, a first defocus characteristic is obtained that shows the amount of shift of the image on the photoelectric conversion element with respect to the amount of defocus of the object under test when each of the first aperture and the second aperture is located at a first position shifted from the reference position. Based on a reference defocus characteristic that shows the amount of shift of the image on the photoelectric conversion element with respect to the amount of defocus of the object under test when the first aperture and the second aperture are each positioned in the reference position, and the first defocus characteristic, the positions of the first aperture and the second aperture are adjusted so that they are each positioned in the reference position. A detection system characterized by the following features.

[0108] (Item 11) An exposure apparatus for exposing a substrate, A detection system according to claim 10, which detects a mark provided on the substrate as an object to be tested, A control unit that adjusts the position of the substrate based on the position of the mark detected by the detection system, An exposure apparatus characterized by having the following features.

[0109] (Item 12) The process of exposing a substrate using the exposure apparatus described in item 11, A step of developing the exposed substrate, A process for manufacturing an article from the developed substrate, A method for manufacturing an article, characterized by having the following:

[0110] (Item 13) A program characterized by causing a computer to execute one of the calibration methods described in any one of items 1 through 9.

[0111] The invention is not limited to the embodiments described above, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, claims are attached to disclose the scope of the invention. [Explanation of Symbols]

[0112] 100: Exposure device 16: Position detection system 17: Control unit 24a, 34a: Aperture diaphragm 37: Photoelectric conversion element 38, 39: Switching mechanism ILS: Illumination system IMS: Imaging system

Claims

1. A calibration method for a detection system having an illumination system for illuminating an object under test and an imaging system for forming an image of light from the object under test on a photoelectric conversion element, The illumination system includes a plurality of first apertures selectively positioned on the pupil surface of the illumination system, each having a different aperture. The imaging system includes a plurality of second apertures selectively positioned on the pupil plane of the imaging system, each having a different aperture. A first step is to acquire a first defocus characteristic for each of at least two combinations of first and second apertures, which are formed by selecting one aperture from each of the plurality of first apertures and the plurality of second apertures, that shows the amount of shift of the image on the photoelectric conversion element with respect to the amount of defocus of the object under test when each of the first aperture and the second aperture is located at a first position shifted from a reference position, A second step involves adjusting the positions of the first and second apertures so that they are positioned at the reference position, based on a reference defocus characteristic that shows the amount of shift of the image on the photoelectric conversion element with respect to the amount of defocus of the object under test when the first and second apertures are each positioned at the reference position, and the first defocus characteristic acquired in the first step. A calibration method characterized by having the following features.

2. The calibration method according to claim 1, characterized in that in the second step, the amount of drive required for the position adjustment of the first aperture and the second aperture is determined from the difference between the first defocus characteristic and the reference defocus characteristic, and the amount of change in the reference defocus characteristic when the first aperture and the second aperture are varied by a unit amount within the pupil plane of the illumination system and the pupil plane of the imaging system, respectively.

3. The calibration method according to claim 2, characterized in that the reference defocus characteristics and the amount of variation of the reference defocus characteristics are obtained in advance before performing the first step.

4. The calibration method according to claim 1, characterized in that the first aperture positioned on the pupil plane of the illumination system and the second aperture positioned on the pupil plane of the imaging system have circular openings whose centers overlap and which have different radii.

5. The aforementioned at least two combinations include a first combination and a second combination, The calibration method according to claim 1, characterized in that the aperture ratio between the first aperture included in the first combination and the first aperture included in the second combination is 2 times or more.

6. The aforementioned at least two combinations include a first combination and a second combination, The second aperture included in the first combination and the second aperture included in the second combination have the same aperture diameter. The calibration method according to claim 1, characterized in that the second aperture included in the first combination and the second aperture included in the second combination have an aperture diameter larger than the aperture diameter of the first aperture.

7. The calibration method according to claim 1, characterized in that the light includes at least two wavelength bands of 450 nm or more.

8. The calibration method according to claim 1, characterized in that the object under test includes a structure that generates diffracted light in only one of two orthogonal directions in a plane perpendicular to the optical axis of the detection system.

9. The calibration method according to claim 1, characterized in that the reference position includes an initial position in which the positions of the first aperture and the second aperture are adjusted so that the amount of lateral displacement and asymmetry of the image formed on the photoelectric conversion element when the object under test is defocused falls within an acceptable range.

10. A detection system for detecting the position of an object under test, A lighting system for illuminating the object under test, An imaging system that forms an image of light from the object under test on a photoelectric conversion element, A processing unit that performs a calibration process for the detection system, It has, The illumination system includes a plurality of first apertures selectively positioned on the pupil surface of the illumination system, each having a different aperture. The imaging system includes a plurality of second apertures selectively positioned on the pupil plane of the imaging system, each having a different aperture. The aforementioned processing unit, For each of at least two combinations of first and second apertures, which are configured by selecting one aperture from each of the plurality of first apertures and the plurality of second apertures, a first defocus characteristic is obtained that shows the amount of shift of the image on the photoelectric conversion element with respect to the amount of defocus of the object under test when each of the first aperture and the second aperture is located at a first position shifted from the reference position. Based on a reference defocus characteristic that shows the amount of shift of the image on the photoelectric conversion element with respect to the amount of defocus of the object under test when the first aperture and the second aperture are each positioned in the reference position, and the first defocus characteristic, the positions of the first aperture and the second aperture are adjusted so that they are each positioned in the reference position. A detection system characterized by the following features.

11. An exposure apparatus for exposing a substrate, A detection system according to claim 10, which detects a mark provided on the substrate as an object to be tested, A control unit that adjusts the position of the substrate based on the position of the mark detected by the detection system, An exposure apparatus characterized by having the following features.

12. A step of exposing a substrate using the exposure apparatus described in claim 11, A step of developing the exposed substrate, A process for manufacturing an article from the developed substrate, A method for manufacturing an article, characterized by having the following:

13. A program characterized by causing a computer to execute the calibration method described in any one of claims 1 to 9.

Images