Mark measurement method, measurement device, exposure device, calculation device, program, and recording medium

Abstract

This mark measurement method involves: acquiring a first image by measuring, under a first measurement condition, an overlay mark formed by overlaying, with a deviation on a first axis of a reference coordinate system, a first pattern group in which lines and spaces are repeatedly formed at a certain pitch on the first axis on one layer on a substrate onto a second pattern group in which lines and spaces are repeatedly formed at the certain pitch on the first axis in another layer different from the one layer; acquiring a second image by measuring the overlay mark under a second measurement condition different from the first measurement condition; acquiring a first mark position of the overlay mark on the first axis from the first image and a second mark position of the overlay mark on the first axis from the second image; and obtaining, from the first mark position and the second mark position, an absolute position of at least one of the first pattern group or the second pattern group in a first axis direction of the reference coordinate system.

Description

Mark measurement method, measurement device, exposure device, calculation device, program, and storage medium

[0001] The present invention relates to a mark measurement method, a measurement apparatus, an exposure apparatus, a calculation apparatus, a program, and a storage medium.

[0002] In lithography processes for manufacturing semiconductor devices, FPDs, and the like, multiple circuit patterns are overlaid on a substrate such as a wafer or glass plate to form the semiconductor device, etc. However, if the overlay accuracy between the layers is poor, the semiconductor device, etc., will not exhibit the desired circuit characteristics, and in some cases, the manufactured semiconductor device, etc. will be defective. For this reason, an overlay mark consisting of patterns formed on two different layers is imaged, and the overlay accuracy between the two different layers is measured from the imaged image.

[0003] For example, Patent Document 1 discloses a method for measuring an overlay mark, which acquires an image of the overlay mark and acquires, from the acquired image, the amount of relative positional deviation between a first pattern group formed on a first layer and a second pattern group formed on a second layer.

[0004] Special Publication No. 2004-508711

[0005] As patterns become finer, market demands for mark measurement are increasing. In measuring overlay marks, there is also a demand for smaller overlay marks, faster measurement speeds, and improved measurement accuracy. It is an object of the present invention to provide an improved overlay mark measurement method that meets at least one of these demands.

[0006] In the present disclosure, an overlay mark formed by overlapping patterns formed on two different layers is measured. Overlapping patterns formed on two different layers refers to at least a partial region of a pattern formed on one layer being stacked with at least a partial region of the other layer in a direction perpendicular to the substrate surface. There are various types of such overlay marks, including a Diffraction-Based Overlay mark (hereinafter referred to as a "DBO mark") that uses diffracted light to detect an overlay mark formed by overlapping with a positional misalignment (hereinafter, the positional misalignment may be simply referred to as "misalignment"), and a Fringe-Based Overlay mark that detects a moiré pattern formed by the overlap to measure the misalignment between the two layers.

[0007] The present inventors have created a measurement method for measuring the absolute position of the patterns of each layer that constitutes a DBO mark in a reference coordinate system. When an arbitrary point in a measurement device is set as the coordinate origin, the absolute position represents the shift position of the overlay mark from the coordinate origin. In this specification, measurement that measures the absolute position of a pattern is referred to as "absolute position measurement" of the pattern. Absolute position measurement has a measurement concept that is significantly different from known relative position measurement that measures the relative displacement between patterns. The advantages of absolute position measurement will be described later.

[0008] According to one aspect of the mark measurement method of the present disclosure, the method includes: measuring, under first measurement conditions, an overlay mark formed by superimposing, with a shift, a first pattern group, in one layer on a substrate, on a first axis of a reference coordinate system, where lines and spaces are repeated at a constant pitch on the first axis, and a second pattern group, in another layer different from the first layer, where lines and spaces are repeated at the constant pitch on the first axis, on the first axis; measuring, under first measurement conditions, an overlay mark formed by superimposing, with a shift, a first image; measuring, under second measurement conditions different from the first measurement conditions, an overlay mark on the first axis; acquiring, from the first image, a first mark position (d x m1) of the overlay mark on the first axis, and acquiring, from the second image, a second mark position (d x m2) of the overlay mark on the first axis; and determining, from the first mark position and the second mark position, an absolute position in the first axial direction, in which the first axis extends, for at least one of the first pattern group and the second pattern group.

[0009] In this specification, a pattern formed on one layer refers to a pattern formed on and in contact with one layer, and a pattern formed on another layer refers to a pattern formed on and in contact with the other layer.

[0010] In the mark measurement method, the first pattern group and the second pattern group are arranged with a shift of a predetermined shift amount (d) along a first axis direction in which the first axis extends in a reference state without any shift, and an absolute position in the first axis direction in the reference coordinate system may be determined for at least one of the first pattern group and the second pattern group using a sensitivity coefficient (r) calculated from a first reference position (dxl0) in the reference state, the first mark position (dxm1) acquired under the first measurement conditions, the second mark position (dxm2) acquired under the second measurement conditions, and the shift amount (d).

[0011] In the mark measurement method, the first pattern group and the second pattern group are arranged with a shift of a predetermined shift amount (d) along a first axis direction in which the first axis extends in a reference state without any shift, the overlay mark is arranged in each of two regions, a first overlap region and a second overlap region, which are spaced apart from each other in the first axis direction, and a first pattern group spacing (CMLdl) which is the distance in the first axis direction between the first pattern group included in the first overlap region and the first pattern group included in the overlap region may be a different value from a second pattern group spacing (CMLdu) which is the distance in the first axis direction between the second pattern group included in the first overlap region and the second pattern group included in the overlap region.

[0012] In the mark measurement method, the first pattern group spacing (CMLdl) may be the second pattern group spacing (CMLdu) plus twice the shift amount (i.e., the shift amount by which the first pattern group and the second pattern group are displaced in a reference state without any shift).

[0013] In the mark measurement method, the position of the midpoint of the first pattern group interval (CMLdl) and the midpoint of the second pattern group interval (CMLdu) in the first axial direction may be the same.

[0014] In the mark measurement method, the other layer may be an upper layer than the one layer, and the width of the first pattern included in the first pattern group may be wider than the width of the second pattern included in the second pattern group.

[0015] 3. The mark measurement method of claim 2, wherein determining the absolute position includes: acquiring from the first image a first distance (CMLm1) that is a distance in the first direction between the overlay mark in the first overlap region and the overlay mark in the overlap region; acquiring from the second image a second distance (CMLm2) that is a distance in the first direction between the overlay mark in the first overlap region and the overlay mark in the overlap region; determining a first sensitivity coefficient (r1) of the first pattern group and the second pattern group under the first measurement condition using the acquired first distance (CMLm1), the first pattern group distance (CMLdl), and the shift amount (d); and determining a second sensitivity coefficient (r2) of the first pattern group and the second pattern group under the second measurement condition using the acquired second distance (CMLm2), the first pattern group distance (CMLdl), and the shift amount (d).

[0016] 8. The mark measurement method according to claim 7, further comprising: calculating the first sensitivity coefficient (r1) using the following equation (1); and calculating the second sensitivity coefficient (r2) using the following equation (2). Here, CMLm1 represents the first distance between the first overlapping area and the overlapping area obtained from the first image of the overlay mark, CMLm2 represents the second distance between the first overlapping area and the overlapping area obtained from the second image of the overlay mark, CMLdl represents the design value of the first pattern group distance between the first pattern group included in the first overlapping area and the first pattern group included in the overlapping area, and d represents the shift amount in the first axis direction between the first pattern group and the second pattern group in a reference state without any misalignment.

[0017] The mark measurement method according to claim 8, further comprising: determining at least one of the absolute position (dxm) of the first pattern group and the absolute position (dxs) of the second pattern group using equation (3). Here, dxl represents the absolute position of the first pattern group in the first axis direction of the reference coordinate system, dxu represents the absolute position of the second pattern group in the first axis direction of the reference coordinate system, dxm1 represents the measurement position of the overlay mark obtained from the first image, and dxm2 represents the measurement position of the overlay mark obtained from the second image.

[0018] The mark measurement method may include adding a correction value for a rotation error component of the overlay mark with respect to the reference coordinate system to at least one of the first distance (CMLm1) and the second distance (CMLm2).

[0019] The mark measuring method may include adding a correction value for a lens aberration component of an imaging optical system for the overlay mark to at least one of the first distance (CMLm1) and the second distance (CMLm2).

[0020] The mark measurement method may include: additionally acquiring images of the overlay mark under one or more measurement conditions different from the first measurement condition and the second measurement condition; and determining an absolute position in the first axis direction for at least one of the first pattern group and the second pattern group from a first mark position (dxm1) acquired from the first image, a second mark position (dxm2) acquired from the second image, and an additional mark position acquired from an image under the one or more additional measurement conditions.

[0021] In the mark measurement method, the first measurement condition and the second measurement condition may differ in at least one of the wavelength of the illumination light, the focus state of the pattern group, the numerical aperture NA of the measurement optical system, the illumination σ of the measurement optical system, and the polarization state of the illumination light.

[0022] The mark measurement method may include selecting the first measurement condition and the second measurement condition based on at least one of signal quality, the number of measurement errors, the number of abnormal measurement values ​​detected, a repeatability coefficient, and a measurement accuracy coefficient.

[0023] The overlay mark may include an overlay mark formed by superimposing, on the one layer, a third pattern group in which lines and spaces are repeatedly formed at a constant pitch P2 on a second axis perpendicular to the first axis, and, on the other layer, a fourth pattern group in which lines and spaces are repeatedly formed at the constant pitch P2 on the second axis, with a shift, on the second axis, and may include determining an absolute position in the second axis direction for at least one of the third pattern group and the fourth pattern group from the measurement position of the first image and the measurement position of the second image.

[0024] The mark measurement method may include determining absolute positions in the first axis direction for both the first pattern group and the second pattern group, and calculating a relative positional deviation amount in the first axis direction between the first pattern group and the second pattern group from the absolute position in the first axis direction of the first pattern group and the absolute position in the first axis direction of the second pattern group.

[0025] The mark measurement method may include: determining absolute positions in the first axis direction for both the first pattern group and the second pattern group; and calculating a relative positional deviation amount between the first pattern group and the second pattern group in the first axis direction from the absolute position of the first pattern group in the first axis direction and the absolute position of the second pattern group in the first axis direction; and determining absolute positions in the second axis direction for both the third pattern and the fourth pattern; and calculating a relative positional deviation amount between the third pattern and the fourth pattern in the second axis direction from the absolute position of the third pattern in the second axis direction and the absolute position of the fourth pattern in the second axis direction.

[0026] According to one aspect of the measurement apparatus, there is provided a measurement apparatus for measuring a mark formed on a substrate, comprising: a stage that can move while holding the substrate on which the overlay mark is formed; an acquisition unit that acquires an image of the overlay mark; and a control unit that determines the absolute position by applying the mark measurement method described above to the image of the overlay mark acquired by the acquisition unit.

[0027] According to one aspect of the measurement device, there is provided a measurement device that measures a mark formed on a substrate, the measurement device comprising: a movable stage that holds a substrate on which an overlay mark is formed, the overlay mark being composed of a first pattern formed on one layer and a second pattern formed on another layer different from the first layer; an acquisition unit that acquires an image of the overlay mark; and a control unit that controls the stage and the acquisition unit, wherein the acquisition unit includes an illumination unit that illuminates the overlay mark and an imaging unit that forms an image of the overlay mark, and the control unit controls the illumination unit to measure the overlay mark under a plurality of mutually different measurement conditions, inputs from the acquisition unit the images of the overlay mark formed by the imaging unit for each of the plurality of measurement conditions, and determines the absolute position of at least one of the first pattern group and the second pattern group based on the images of the overlay mark for each of the plurality of measurement conditions.

[0028] According to one aspect of the exposure apparatus, there is provided an exposure apparatus that exposes a substrate with exposure light, the exposure apparatus comprising: a stage that can move while holding the substrate on which the overlay mark is formed; an acquisition unit that acquires an image of the overlay mark; and a control unit that determines the absolute position by executing the mark measurement method described above based on the image of the overlay mark acquired by the acquisition unit.

[0029] According to one aspect of the arithmetic device, the arithmetic device has an input unit that inputs information related to an image of the overlay mark formed on a substrate, a calculation unit that determines the absolute position by executing the mark measurement method described in any one of claims 1 to 17, and an output unit that outputs information related to the absolute position calculated by the calculation unit.

[0030] According to one aspect of the program, the program causes a measurement apparatus or an exposure apparatus to execute the mark measurement method described above.

[0031] According to one aspect of the storage medium, the storage medium stores a program for causing a measurement apparatus or an exposure apparatus to execute the mark measurement method described above.

[0032] 1 is a conceptual diagram of an example of an overlay mark and its formation process. FIG. 2 is an enlarged cross-sectional view of a first overlay mark in the overlay mark of FIG. 1. FIG. 3 is a conceptual diagram of a method for extracting a luminance signal from an image of an overlay mark. FIG. 4 is a diagram explaining advantages of absolute value measurement. FIG. 5 is a diagram of a second overlay mark as a further example. FIG. 6 is an enlarged cross-sectional view of the second overlay mark shown in FIG. 5. FIG. 7 is a diagram of an overlay mark and signal waveforms acquired from its image. FIG. 8 is a diagram of two signal waveforms acquired from images of the same overlay mark captured under different measurement conditions. FIG. 9 is a diagram of a specific example of pattern group spacing based on a different definition. FIG. 10 is a diagram of a third overlay mark as a further example. FIG. 11 is a diagram of an overlay mark rotated in conjunction with rotation of the substrate. FIG. 12 is a diagram of a method for measuring lens aberration components of an imaging optical system. FIG. 13 is a diagram of a method for measuring lens aberration components of an imaging optical system. FIG. 14 is a diagram of a method for measuring lens aberration components of an imaging optical system. FIG. 15 is a front view (viewed from the -Y direction) of a measurement apparatus. FIG. 16 is a cross-sectional view of the measurement apparatus in the XZ plane. FIG. 17 is a cross-sectional view of the measurement apparatus in the YZ plane. It is a block diagram showing the input / output relationship of a control device that mainly configures the control system of the measurement device. It is a diagram showing details of a mark detection system. It is a schematic diagram of an exposure apparatus. It is a block diagram showing the input / output relationship of an exposure control device provided in the exposure apparatus.

[0033] Hereinafter, embodiments of the invention will be described with reference to the drawings. The drawings are shown schematically. The dimensional ratios and numbers shown in the drawings do not necessarily correspond to the actual dimensional ratios and numbers. The drawings are shown using the XYZ coordinate system as appropriate. The specification will be explained with reference to the XYZ coordinate system as appropriate. In this specification, when expressing a direction, a positive or negative sign is added, such as "+X direction" and "-X direction." When expressing a direction without distinguishing between positive and negative, it is simply referred to as "X direction." In other words, in this specification, when simply referring to the "X direction," both the "+X direction" and the "-X direction" are included. The same applies to the Y direction and the Z direction.

[0034] <Mark Measurement Method> An embodiment of the mark measurement method will be described.

[0035] [Overlay Mark] One aspect of an overlay mark will be described with reference to Figures 1 and 2. Figure 1 is a conceptual diagram of an overlay mark OM1 formed on a wafer W and the process of forming the mark. Figure 2 is an enlarged cross-sectional view of the overlay mark OM1.

[0036] As shown in FIG. 1 , the overlay mark OM1 is composed of a first pattern group LSl and a second pattern group LSu. The second pattern group LSu is formed to be superimposed on the first pattern group LSl with a shift on the X axis. The overlay mark OM1 is a DBO mark. The first pattern group LSl is a line-and-space pattern in which line patterns S1 extending in the Y direction are repeatedly formed in the X direction at predetermined intervals. The second pattern group LSu is a line-and-space pattern in which line patterns S2 extending in the Y direction are repeatedly formed in the X direction at predetermined intervals.

[0037] The pitch P1 of the first pattern group LSl and the pitch P1 of the second pattern group LSu are the same value. The pitch P1 is preferably 100 nm or more and 1000 nm or less, and more preferably 200 nm or more and 900 nm or less.

[0038] The X-direction width Lw1 of the line pattern S1 in the first pattern group LSl is larger than the X-direction width Lw2 of the line pattern S2 in the second pattern group LSu. In the overlay mark OM1 shown in FIG. 2, the position of the +X-side end of the line pattern S1 in the first pattern group LSl on the X-axis overlaps with the position of the +X-side end of the line pattern S2 in the second pattern group LSu, and both are located on a straight line A1. On the other hand, the position of the −X-side end of the line pattern S1 in the first pattern group LSl on the X-axis does not overlap with the position of the −X-side end of the line pattern S2 in the second pattern group LSu. The center of the line pattern S2 is shifted by a shift amount d1 relative to the center of the line pattern S1. The shift amount d1 can also be said to be the shift amount d1 of the second pattern group LSu in the X-axis direction relative to the first pattern group LSl. The shift amount d1 is, for example, 40 nm or less, preferably 20 nm or less.

[0039] The overlay mark OM1 may be configured such that, in a reference state without misalignment, both ends of the line pattern S1 in the first pattern group LS1 in the X direction do not overlap both ends of the line pattern S2 in the second pattern group LSu in the X direction. Also, the width Lw1 in the X direction of the line pattern S1 in the first pattern group LS1 may be smaller than the width Lw2 in the X direction of the line pattern S2 in the second pattern group LSu.

[0040] In this embodiment, the first pattern group LSl and the second pattern group LSu are both line patterns laminated on an underlayer, but at least one of the first pattern group LSl and the second pattern group LSu may be configured as a trench pattern formed by carving a groove from the surface of the underlayer. In other words, the combination of the first pattern group LSl and the second pattern group LSu forms any one of a line pattern-line pattern, a line pattern-trench pattern, a trench pattern-line pattern, and a trench pattern-trench pattern.

[0041] 2 , in the overlay mark OM1 disclosed in this embodiment, the first pattern group LSl is formed on a first layer 1 on the wafer W. The second pattern group LSu is formed on a second layer 2 located above the first layer 1. Hereinafter, the first pattern group LSl formed on the first layer 1 may be referred to as the “lower layer pattern group.” The second pattern group LSu formed on the second layer 2 may be referred to as the “upper layer pattern group.”

[0042] In the overlay mark OM1 of this embodiment, the layer including the upper-layer pattern group is the uppermost layer, but other layers may be present above the layer including the upper-layer pattern group. The other layers are thin enough that the lower-layer pattern group can be measured with measurement light. In the overlay mark OM1 of this embodiment, an intermediate layer 3 is present between the first layer 1 and the second layer 2. The intermediate layer 3 is thin enough that the lower-layer pattern group can be measured with measurement light, but the thickness is not important as long as the lower-layer pattern group can be measured. The intermediate layer 3 may be composed of one layer or multiple layers. The intermediate layer 3 may not be present. In the overlay mark OM1 of this embodiment, the layer including the lower-layer pattern group is the first layer (lowest layer), but other layers may be present below the layer including the lower-layer pattern group. In other words, the lower-layer pattern group is not limited to patterns formed on the first layer.

[0043] A plurality of overlay marks OM1 may be arranged in scribe line regions or the like within each shot area of ​​the wafer W in correspondence with each shot area. For example, 10 to 50 overlay marks OM1 may be arranged. An overlay mark OM1 may be provided for every shot. More than 1,000 overlay marks OM1 may be provided across the entire substrate. When measuring the overlay marks OM1, it is not necessary to measure all overlay marks on the wafer W. Alternatively, multiple overlay marks may be measured for each shot area. Furthermore, overlay marks to be measured may be selected depending on the purpose of the measurement. Enhanced global alignment (EGA) measurement may be performed, in which the arrangement of shot areas on the substrate is calculated using a statistical method from the measurement results of multiple overlay marks.

[0044] [Position Measurement of Overlay Mark] As described above, the overlay mark OM1 is a DBO mark. A common method for measuring a DBO mark is to use a light receiving element to measure the light intensity of the diffracted light component of the overlay mark OM1 and obtain the overlay error from the asymmetry of the measured light intensity. Measuring light intensity does not require imaging using a light receiving element. However, this embodiment does not employ a common measurement method. Instead, the overlay mark OM1 is imaged using an FIA (Field Image Alignment) alignment sensor, which is a type of imaging alignment sensor that uses image processing. Illumination light generated under specified illumination conditions is irradiated onto the overlay mark OM1, and the reflected light is imaged on the imaging element of the FIA ​​alignment sensor. The mark position of the overlay mark OM1 is finally calculated from the image acquired by the imaging element. Details of a measurement device that has the FIA ​​alignment sensor and a mark detection system that detects the overlay mark, or an exposure apparatus that has the FIA ​​alignment sensor and an alignment detection system that detects the overlay mark, will be described later.

[0045] The mechanism for measuring the position of the overlay mark OM1 will now be described. First, a method for extracting a luminance signal from an image of the overlay mark OM1 will be described with reference to FIG. 3. FIG. 3 is a conceptual diagram showing a method for extracting a luminance signal from an acquired image of the overlay mark OM1. The signal luminance is obtained at each position on an arbitrary straight line A4 that crosses the image of the overlay mark OM1. The signal luminance at each position can be represented as a signal waveform IS. In this embodiment, the straight line A4 extends in the X direction. Therefore, the signal waveform IS shown in FIG. 3 represents the signal luminance of the overlay mark OM1 in the X direction.

[0046] The overlay mark OM1 is used to measure the relative displacement of the upper layer pattern group with respect to the lower layer pattern group. The resolution of the FIA ​​alignment sensor is not high enough to measure the relative displacement amount on the order of nanometers directly from the signal waveform.

[0047] Therefore, the inventor devised a method for determining the absolute positions of the upper and lower layer pattern groups relative to the reference coordinate system, by utilizing the fact that differences in measurement conditions, including the illumination conditions of the illumination light, have different effects on the image captured by the FIA ​​system alignment sensor between the lower layer pattern group and the upper layer pattern group, i.e., the fact that differences in measurement conditions change the shape of the signal waveform of the overlay mark OM1 composed of the upper layer pattern group on the lower layer pattern group.

[0048] The image of the overlay mark OM1 captured by the FIA-system alignment sensor is an image formed by combining light reflected from the upper layer pattern group and light reflected from the lower layer pattern group. When this image is converted into a luminance signal by an imaging element and a signal waveform IS is obtained, the signal waveform is a mixture of signals due to the light reflected from the upper layer pattern group (hereinafter referred to as "signals from the upper layer pattern group") and signals due to the light reflected from the lower layer pattern group (hereinafter referred to as "signals from the lower layer pattern group"). The mixture ratio of the signals from the upper layer pattern group and the lower layer pattern group contained in the signal waveform of the overlay mark OM1 is not necessarily 1:1.

[0049] That is, the degree of influence of the signals from the upper-layer pattern group and the lower-layer pattern group on the signal waveform of the overlay mark OM1 varies depending on the measurement conditions. Depending on the measurement conditions, there may be cases where the signals from the upper-layer pattern group have a greater influence than the signals from the lower-layer pattern group, or cases where the signals from the lower-layer pattern group have a greater influence than the signals from the upper-layer pattern group. Differences in measurement conditions change the signal waveform of the overlay mark OM1. The change in the signal waveform changes the calculation result of the position of that signal, i.e., the position information of the pattern group obtained from the overlay mark OM1.

[0050] The sensitivity coefficient is an index relating to the degree of influence (sensitivity) of the amount of misalignment of the upper-layer pattern group relative to the lower-layer pattern group on the positional information of the pattern group obtained from the signal waveform of the overlay mark OM1. In other words, the sensitivity coefficient is an index indicating the sensitivity with which the signals from the upper-layer pattern group and the lower-layer pattern group influence the signal waveform of the overlay mark OM1. For example, if the signals from the upper-layer pattern group and the lower-layer pattern group are mixed in a 1:1 ratio, the influence of the signals from the upper-layer pattern group and the lower-layer pattern group can be considered equal, and the sensitivity coefficient is 0.5. The sensitivity coefficient varies depending on the measurement conditions. In other words, the influence of the signals from the upper-layer pattern group on the signal waveform of the overlay mark OM1 and the influence of the signals from the lower-layer pattern group on the signal waveform of the overlay mark OM1 differ between the first measurement condition and the second measurement condition. Therefore, the sensitivity coefficient under the first measurement condition differs from the sensitivity coefficient under the second measurement condition, which differs from the first measurement condition. As such, the sensitivity coefficient can take on a variety of values ​​depending on the measurement conditions. The sensitivity coefficient usually ranges in value from 0 to 1. However, in some cases, the sensitivity coefficient may be greater than 1 or may be a negative value.

[0051] The first mark position dxm1 of the overlay mark OM1 acquired under the first measurement conditions is expressed as shown in equation (4) using the first sensitivity coefficient r1, the absolute position dxl of the first pattern group LS1 (lower layer pattern group) in the X-axis direction, and the absolute position dxu of the second pattern group LSu (upper layer pattern group) in the X-axis direction: dxm1 = r1(dxu-dxl)+dxl (4)

[0052] Similarly, the second mark position dxm2 of the overlay mark OM1 acquired under the second measurement conditions is expressed as shown in equation (5) using the second sensitivity coefficient r2, the absolute position dxl of the first pattern group LS1 in the X-axis direction, and the absolute position dxu of the second pattern group in the X-axis direction: dxm2 = r2(dxu-dxl)+dxl (5)

[0053] By combining and transforming equations (4) and (5), the following equation (3) can be obtained.

[0054] What can be seen from equation (3) is that when the first sensitivity coefficient r1 and the first mark position dxm1 under the first measurement condition, and the second sensitivity coefficient r2 and the second mark position dxm2 under the second measurement condition are known, it is possible to determine the absolute position dxl of the first pattern group LSl in the X-axis direction and the absolute position dxu of the second pattern group LSu in the X-axis direction. In other words, by capturing images of the overlay mark OM1 under the first measurement condition and under a second measurement condition different from the first measurement condition, it is possible to obtain the absolute positions (dxl, dxu) of the upper layer pattern group (second pattern group LSu) and the lower layer pattern group (first pattern group LSl), that is, how much they are shifted relative to the reference coordinate system.

[0055] Furthermore, even if the sensitivity coefficients under the first illumination condition and the second illumination condition are not known, the sensitivity coefficient r can be calculated from the first reference position dxl0 in the reference state, the mark position of the overlay mark OM1 acquired under the first measurement condition (first mark position dxm1), the mark position of the overlay mark OM1 acquired under the second measurement condition (second mark position dxm2), and the shift amount in the X-axis direction between the first pattern group and the second pattern group in the reference state. Then, once the sensitivity coefficient r is known, it is possible to obtain the absolute positions, i.e., the amount of deviation of the upper layer pattern group and the lower layer pattern group from the reference coordinate system, as described above.

[0056] Measurement conditions that cause the sensitivity of signals from the upper layer pattern group to differ from the sensitivity of signals from the lower layer pattern group include (1) the numerical aperture NA of the measurement optical system, (2) the illumination σ of the measurement optical system, (3) the wavelength of the illumination light, (4) the polarization state of the illumination light, and (5) the focusing state of the pattern group. The first measurement condition and the second measurement condition differ in at least one of these measurement conditions. The method for selecting the measurement conditions will be described later.

[0057] Advantages of Absolute Position Measurement The advantages of measuring the absolute positions of the upper and lower layer patterns will be described with reference to FIG. 4 . First, it will be explained how the relative positions determined by relative position measurement can also be easily determined by absolute position measurement. Once the absolute position AP1 in the X direction of the upper layer patterns constituting the overlay mark OM1 (the position of the upper layer patterns relative to the coordinate origin SP of the measurement device) and the absolute position AP2 in the X direction of the lower layer patterns constituting the overlay mark OM1 (the position of the lower layer patterns relative to the coordinate origin SP of the measurement device) are determined, the overlay error ΔAP between the upper and lower layer patterns can be obtained by calculating the difference between AP1 and AP2. In other words, once the absolute positions (AP1, AP2) of the upper layer pattern group (first pattern group LS1) and the lower layer pattern group (second pattern group LSu) are known, the relative overlay error ΔP of the upper layer pattern group relative to the lower layer pattern group can be determined simply by calculating the difference in the absolute positions of the two patterns.

[0058] Next, the advantages unique to absolute position measurement will be described. Typically, the measurement of the overlay mark provides the relative misalignment between the upper and lower layer patterns. Therefore, simply looking at the measurement results of the relative misalignment of the overlay mark makes it impossible to determine which of the upper and lower layer patterns is misaligned from its design position (ideal position). Even if the position of the lower layer pattern is misaligned from its design position, if the upper layer pattern is correctly aligned with the lower layer pattern, the misalignment between the upper and lower layer patterns will ultimately fall within a predetermined range. However, even if the relative misalignment between the upper and lower layer patterns falls within a predetermined range, as many layers are repeatedly overlaid, the misalignment (error from the design position) accumulates, resulting in a large overall misalignment. This problem can be solved by performing absolute position measurement. Absolute position measurement measures the misalignment of the pattern on each layer from its design position, thereby correcting the pattern position on each layer based on the design position, thereby preventing the cumulative misalignment described above.

[0059] More specifically, by measuring the absolute positions of the upper layer pattern group and the lower layer pattern group, it is possible to obtain the alignment errors of the multiple shot areas formed in the upper layer pattern group and the multiple shot areas formed in the lower layer pattern group, respectively. This makes it possible to determine which layer's positional misalignment (alignment error) is causing the overlay error between the upper layer pattern group and the lower layer pattern group. Furthermore, by feeding back the alignment error to one or both of the exposure tools that exposed the upper layer pattern group and the lower layer pattern group, it is possible to reduce the overlay error.

[0060] [Second Overlay Mark] The shape of the overlay mark to be measured is not limited to the shapes described above. Further examples of overlay marks will be disclosed. Figure 5 is a top view of overlay mark OM2. Figure 6 is an enlarged cross-sectional view of overlay mark OM2.

[0061] The overlay mark OM2 is composed of two regions, a first overlap region 6 and a second overlap region 7, and the two overlap regions (6, 7) are spaced apart in the X-axis direction. Each of the two overlap regions (6, 7) is formed by stacking a first pattern group LSl on a second pattern group LSu. The first overlap region 6 is the same as the overlay mark OM1 shown in FIG. 1 . That is, in the first overlap region 6, the upper layer pattern group and the lower layer pattern group have the same pitch P1, and in the reference state, their +X-side end positions on the X-axis overlap, but their −X-side end positions do not overlap. The second overlap region 7 is a mirror image pattern of the first overlap region 6. That is, in the second overlap region 7, the upper layer pattern group and the lower layer pattern group have the same pitch P1, and in the reference state, their −X-side end positions on the X-axis overlap, but their +X-axis positions do not overlap. In the first pattern group LSl, the mark structure in the first overlap region 6 and the mark structure in the second overlap region 7 are in a line-symmetric relationship with each other about a straight line A2-1, which is the center line of the first pattern group LSl. In the second pattern group LSu, the mark structure in the first overlap region 6 and the mark structure in the second overlap region 7 are in a line-symmetric relationship with each other about a straight line A2-2, which is the center line of the first pattern group LSl. Here, the reference state refers to a state in which the straight line A2-1 of the first pattern group LSl and the straight line A2-2 of the second pattern group LSu coincide with each other.

[0062] 6 , in the overlay mark OM2, the shortest distance in the X-axis direction between the first pattern group LSl included in the first overlap region 6 and the first pattern group LSl included in the second overlap region 7 is referred to as the first pattern group interval CMLdl, and the shortest distance in the X-axis direction between the second pattern group LSu included in the first overlap region 6 and the second pattern group LSu included in the second overlap region 7 is referred to as the second pattern group interval CMLdu. The overlay mark OM2 is designed so that the first pattern group interval CMLdl has a different value from the second pattern group interval CMLdu. Furthermore, the reference position of the two first pattern groups LSl (first reference position dxl0) is the midpoint when the first pattern group interval CMLdl is represented by a line segment, and the reference position of the two second pattern groups LSu (second reference position dxu0) is the midpoint when the second pattern group interval CMLdu is represented by a line segment. The first reference position dxl0 is on the line A2-1, and the second reference position dxu0 is on the line A2-2. Note that CML is an abbreviation for Center Mark Length.

[0063] 5 and 6, the first pattern group LSl and the second pattern group LSu are in a positional relationship that forms a reference state without any misalignment. In the reference state, the first reference position dxl0 of the first pattern group LSl and the second reference position dxu0 of the second pattern group LSu overlap in the X direction.

[0064] 6 , in the overlay mark OM2 in a reference state in which the misalignment between the first pattern group LSl and the second pattern group LSu is zero, the first reference position dxl0 and the second reference position dxu0 overlap in the X direction, but in reality, the amount of misalignment between the first pattern group LSl and the second pattern group LSu varies depending on the misalignment between the lower layer on which the first pattern group LSl is formed and the upper layer on which the second pattern group LSu is formed, as well as the distortion of each layer. In other words, in many cases, the midpoint of the first pattern group spacing CMLdl (first reference position dxl0) and the midpoint of the second pattern group spacing CMLdu (second reference position dxu0) are misaligned in the X direction, and the amount of misalignment is not fixed to a single value.

[0065] 6, the second pattern group interval CMLdu is designed to be larger than the first pattern group interval CMLdl, but the first pattern group interval CMLdl may also be designed to be larger than the second pattern group interval CMLdu. The first pattern group interval CMLdl may be the second pattern group interval CMLdu plus twice the shift amount d1. In other words, the following equation (6) may be satisfied: CMLdl = CMLdu + 2d1 (6)

[0066] 7 is a diagram showing the overlay mark OM2 and a signal waveform IS representing the signal brightness at each position on a line A4 that intersects the acquired image of the overlay mark OM2. In this embodiment, the line A4 is along the X direction. The signal waveform IS reflects the misalignment that occurs between the first pattern group LSl and the second pattern group LSu. Because the overlapping manner (positional relationship when overlapping) of the first pattern group LSl and the second pattern group LSu differs between the first overlapping region 6 and the second overlapping region 7, a difference occurs between the signal waveform obtained from the first overlapping region 6 and the signal waveform obtained from the second overlapping region 7.

[0067] 5 and 6 illustrate a reference state in which the deviation between the first pattern group LSl and the second pattern group LSu is zero, and therefore the signal waveform obtained from the first overlapping region 6 and the signal waveform obtained from the second overlapping region 7 are in a line-symmetric relationship with respect to the line A5. If there is a deviation between the first pattern group LSl and the second pattern group LSu, it is naturally conceivable that the signal waveform obtained from the first overlapping region 6 and the signal waveform obtained from the second overlapping region 7 will not be in a line-symmetric relationship.

[0068] As described above, the shape of the signal waveform changes depending on the measurement conditions. Fig. 8 is a diagram showing a signal waveform IS1 acquired from the overlay mark OM2 imaged under a first illumination condition, and a signal waveform IS2 acquired from the overlay mark OM2 imaged under a second measurement condition that is different from the first measurement condition.

[0069] From signal waveform IS1, a first interval CMLm1 can be obtained, which is the interval in the X direction between the signal waveform obtained from the first overlap region 6 and the signal waveform obtained from the second overlap region 7. Similarly, from signal waveform IS2, a second interval CMLm2 can be obtained, which is the interval in the X direction between the signal waveform obtained from the first overlap region 6 of overlay mark OM2 and the signal waveform obtained from the second overlap region 7.

[0070] The measurement position (first mark position) dxm1 of the overlay mark OM1 obtained from the signal waveform IS1 is set to the midpoint in the X direction between the signal waveform obtained from the first overlap region 6 and the signal waveform obtained from the second overlap region 7. Similarly, the measurement position (second mark position) dxm2 of the overlay mark OM1 obtained from the signal waveform IS2 is set to the midpoint in the X direction between the signal waveform obtained from the first overlap region 6 and the signal waveform obtained from the second overlap region 7.

[0071] The interval (CMLm1, CMLm2) between the signal waveforms obtained from the two overlapping regions (6, 7) reflects a mixture of the first pattern group interval CMLdl in the first pattern group LSl (lower layer pattern group) and the second pattern group interval CMLdu in the second pattern group LSu (upper layer pattern group). Although the signal waveforms IS1 and IS2 of both pattern groups are signal waveforms obtained from the same overlay mark OM1, the first interval CMLm1 and the second interval CMLm2 have different values ​​because the sensitivity coefficients differ depending on the measurement conditions.

[0072] The first sensitivity coefficient r1 under the first measurement conditions can be expressed by equation (1) using three parameters: (1) the first spacing CMLm1 obtained from the signal waveform IS1 acquired from the overlay mark OM2 imaged under the first measurement conditions; (2) the first pattern group spacing CMLdl in the first pattern group LSl (lower layer pattern group); and (3) the shift amount d in the X direction of the second pattern group LSu relative to the first pattern group LSl.

[0073] Similarly, the second sensitivity coefficient r2 under the second measurement conditions can be expressed by equation (2) using three parameters: (1) the second spacing CMLm2 obtained from the signal waveform IS2 acquired from the overlay mark OM2 imaged under the second measurement conditions, (2) the first pattern group spacing CMLdl in the first pattern group LSl (lower layer pattern group), and (3) the shift amount d of the second pattern group LSu in the X direction relative to the first pattern group LSl.

[0074] Here, the reason for introducing the pattern group intervals (CMLdl, CMLdu) will be explained. As described above, the first pattern group LSl (lower layer pattern group) and the second pattern group LSu (upper layer pattern group) are usually overlaid with a relative misalignment. In this state, when the overlay mark OM is measured under two different measurement conditions, two relative positional misalignment amounts between the first pattern group LSl and the second pattern group LSu are obtained corresponding to the measurement conditions. Since it is impossible to determine whether these two misalignment amounts are caused by differences in the sensitivity coefficients or by an overlay misalignment, the sensitivity coefficient r cannot be calculated. Therefore, different known pattern group intervals (CMLdl, CMLdu) are set for the first pattern group LSl and the second pattern group LSu, and these are measured under different measurement conditions to obtain the intervals (CMLm1, CMLm2), which makes it possible to calculate the sensitivity coefficient r using the above-described formulas (1) and (2).

[0075] In this way, once the first mark position dxm1 and first sensitivity coefficient r1 under the first measurement condition of the overlay mark OM2, and the second mark position dxm2 and second sensitivity coefficient r2 under the second measurement condition are determined, the absolute positions of the first pattern group LSl (lower layer pattern group) and the second pattern group LSu (upper layer pattern group) can be found using equation (3).

[0076] In the above, as shown in FIG. 6 , the pattern group interval (CMLdl, CMLdu) was defined as the shortest distance in the X direction between two overlapping regions (6, 7) in the pattern groups (LSl, LSu) of the same layer. However, the pattern group interval need only represent the pattern group interval between the overlapping regions, and does not necessarily have to be the shortest distance. For example, the position of the pattern group (LSl, LSu) included in the first overlapping region 6 may be set to the average value of the positions of multiple lines constituting the pattern group, and the position of the pattern group (LSl, LSu) included in the second overlapping region 7 may be set to the average value of the positions of multiple lines constituting the pattern group, and the distance therebetween may be defined as the pattern group interval (CMLdl, CMLdu).

[0077] 9 shows a specific example of a pattern group interval defined by the positions of the above-mentioned multiple lines. In FIG. 9, in the first pattern group LSl, the distance between the center of gravity C6 of the first overlap region 6 (i.e., the average value of the positions of the six lines in the first overlap region) and the center of gravity C7 of the second overlap region 7 (i.e., the average value of the positions of the six lines in the second overlap region) is defined as the first pattern group interval CMLdl. Similarly, in the second pattern group LSu, the distance between the center of gravity C6 of the first overlap region 6 and the center of gravity C7 of the second overlap region 7 is defined as the second pattern group interval CMLdu. In this case, for the first interval CMLm1 and the second interval CMLm2, the positions of the pattern group (LSl, LSu) included in the first overlap region 6 are similarly calculated from the average value of the signal positions of the multiple lines that make up the pattern group, and the positions of the pattern group (LSl, LSu) included in the second overlap region 7 are calculated from the average value of the signal positions of the multiple lines that make up the pattern group, and these distances are applied to the above equations (1) and (2) as the first interval CMLm1 and the second interval CMLm2. By combining the definition of the pattern group interval (CMLdl, CMLdu) of the mark itself with the definitions of the intervals CMLm1 and CMLm2 found from the signal waveforms (IS1, IS2), the absolute position of the first pattern group LSl (lower layer pattern group) and the absolute position of the second pattern group LSu (upper layer pattern group) can be found in the same manner as above, even if the pattern group interval is defined as in the example shown in FIG.

[0078] In this way, by averaging the positions of multiple patterns, the averaging effect improves the accuracy of position calculation. It is also possible to exclude signals from some of the multiple lines included in the signal waveforms (IS1, IS2) of the pattern group and calculate the position of the pattern group from the remaining lines. For example, if the signal of a line at the edge of the pattern group cannot be properly detected and the signal waveform at that edge is distorted, the accuracy of calculating the position of the pattern group can be improved by excluding the signal waveform of the distorted portion and calculating the position.

[0079] The above describes measuring one overlay mark under two measurement conditions and acquiring images for each. However, images may be acquired additionally under one or more measurement conditions. In other words, one overlay mark may be measured under three or more measurement conditions. Then, the absolute position (dxl, dxu) in the X direction may be calculated for at least one of the first pattern group LSl and the second pattern group LSu from the first mark position dxm1 acquired from the first image, the second mark position dxm2 acquired from the second image, and the additional mark positions (dx3, ...) acquired from the additionally acquired images under the one or more measurement conditions.

[0080] When there are three or more measurement conditions, the absolute position (dxl, dxu) in the X direction is solved using the least squares method. For example, when there are i images acquired by illuminating with i measurement conditions, the absolute position (dxl, dxu) in the X direction can be found by the following equation (7). In this case, regularization (such as ridge regression) or weighted least squares may be used in addition to the least squares method.

[0081] [Third Overlay Mark] FIG. 10 discloses another example of an overlay mark. The overlay mark OM3 is composed of a first overlap region 6, a second overlap region 7, a third overlap region 8, and a fourth overlap region 9. Each overlap region is formed by overlaying a first pattern group LSl, which is a lower layer pattern group, with a misalignment between the first and second pattern groups LSu. In FIG. 10 , the first overlap region 6 is located in the second quadrant, the above-mentioned second overlap region 7 is located in the fourth quadrant, the third overlap region 8 is located in the first quadrant, and the fourth overlap region 9 is located in the third quadrant. Using the overlay mark OM3, it is possible to determine not only the absolute positions (dxl, dxu) of the first overlap region 6 and the overlap region 7 in the X direction, but also the absolute position dym of the first pattern group LSl in the Y direction and the absolute position dys of the second pattern group LSu in the Y direction for the third overlap region 8 and the fourth overlap region 9.

[0082] The third overlapping region 8 and the fourth overlapping region 9 are formed by overlapping the third pattern group LSly and the fourth pattern group LSuy with a shift on the Y axis. In both the third pattern group and the fourth pattern group, lines and spaces extending in the X direction are formed at equal pitches and repeatedly in the Y direction. The line width in the third pattern group is thicker than the line width in the fourth pattern group.

[0083] [Selection of Optimal Measurement Conditions] As described above, the measurement conditions that cause the sensitivity of signals from upper-layer patterns to differ from the sensitivity of signals from lower-layer patterns include (1) the numerical aperture NA of the measurement optical system, (2) the illumination σ of the measurement optical system, (3) the wavelength of the illumination light, (4) the polarization state of the illumination light, and (5) the focusing state of the pattern group. Methods for selecting measurement conditions that optimize these measurement conditions include (I) the number of measurement errors, (II) signal quality, (III) the number of abnormal measurement values ​​detected, (IV) the repeatability coefficient, and (V) the measurement accuracy coefficient.

[0084] (I) The number of measurement errors is the number of times a signal could not be recognized from the image. The clarity of the mark image changes depending on the combination of measurement conditions; if the mark image is unclear, it may be impossible to recognize the signal from the image. It is preferable to select a combination of measurement conditions that reduces the number of measurement errors.

[0085] (II) Signal quality refers to the quality of the signal waveform. The amplitude and period of the signal waveform obtained vary depending on the combination of measurement conditions. It is preferable to select a combination of measurement conditions that is easy to use for analyzing the signal waveform.

[0086] (III) The number of abnormal measurement values ​​detected is the number of abnormal measurement values ​​contained in the signal waveform. The number of abnormal measurement values ​​varies depending on the combination of measurement conditions. It is preferable to select a combination of measurement conditions that produces the fewest abnormal measurement values.

[0087] (IV) The repeatability coefficient is an index representing the variation in the determined absolute position dxl of the first pattern group LSl or the absolute position dxu of the second pattern group LSu, and is represented by Δdxl and Δdxu, respectively. The smaller Δdxl and Δdxu are, the better, and ideally, Δdxl = 0 and Δdxu = 0. The repeatability coefficients (Δdxl, Δdxu) are affected by the reproducibility Δdxi of the mark position under each measurement condition. For example, if the repeatability of the mark position obtained under two measurement conditions is Δdxm1 and Δdxm2, the repeatability coefficients (Δdxl, Δdxu) are represented by the following equations (8) and (9). Note that in equations (8) and (9), r1 and r2 represent the sensitivity coefficients under the two measurement conditions, as described above.

[0088] (V) The measurement accuracy coefficient is an index of accuracy that indicates how close a measurement value is to the true value. The measurement accuracy coefficient V1 is expressed by the following equation (10). In equation (10), r1 and r2 represent the sensitivity coefficients under the two measurement conditions, as described above. σ1 and σ2 respectively represent the standard deviations of the sensitivity coefficients, which differ for each measurement point on the same substrate.

[0089] The method for changing the measurement conditions will be described later together with the structure of the mark detection system MDS.

[0090] [Correction of Rotation Error Component of Overlay Mark] If the substrate is placed on the stage in a state rotated from the reference coordinate system (ideal position), the overlay mark will also rotate. Figure 11 shows how the overlay mark OM3 rotates with respect to the reference coordinate system as the substrate rotates. Note that, for ease of understanding, the rotation angle shown in Figure 11 is shown to be larger than the actual expected rotation angle.

[0091] The frames indicated by thick lines in Figure 11 represent the original positions of the first overlap region 6, the second overlap region 7, the third overlap region 8, and the fourth overlap region 9 of the overlay mark OM3. The frames indicated by two-dot chain lines in Figure 11 represent the rotated states of the first overlap region 6, the second overlap region 7, the third overlap region 8, and the fourth overlap region 9 of the overlay mark OM3. Although the overlap of the patterns of the overlap regions (6, 7, 8, 9) is omitted, please refer to Figure 10 for details.

[0092] The rotation of the patterns in each overlapping region (6, 7, 8, 9) is reflected in the displacement of the centers of gravity (C6, C7, C8, C9) of each overlapping region (6, 7, 8, 9). When the centers of gravity (C6, C7, C8, C9) are displaced, the spacing CML between the patterns in the overlapping regions changes. For example, the spacing between the patterns, which is the distance between the centers of gravity C6 and C7, changes from CMLx1 to CMLx2.

[0093] Therefore, when the overlay mark is measured while the substrate is rotated, a rotational error component is included in the interval (CMLm1, CMLm2) between the signal waveforms obtained from the two overlapping regions (6, 7) of the pattern groups (LSl, LSu) constituting the overlay mark. As a result, the sensitivity coefficients (r1, r2) calculated from the interval between the signal waveforms include a rotational error component, and therefore the absolute position (dxl, dxu) in the X direction cannot be accurately determined.

[0094] Therefore, it is advisable to add a correction value for the rotation error component of the overlay mark to the interval between the signal waveforms (CMLm1, CMLm2). The correction value is set from the amount of rotation error calculated from the rotation angle of the substrate. The rotation angle of the substrate is determined by measuring multiple overlay marks OM3 or other alignment marks. Note that this correction method uses the stage positioning control used to calculate the rotation angle as an absolutely correct index. It is advisable to separately calibrate the stage positioning control using an accuracy maintenance method.

[0095] [Correction of Lens Aberration Components of the Imaging Optical System] When the imaging optical system includes lens aberration, the captured image is distorted, resulting in a distorted signal waveform. The distortion of the signal waveform generates an error in the interval (CMLm1, CMLm2) between the signal waveforms in the overlapping region. In other words, the interval (CMLm1, CMLm2) between the signal waveforms includes a lens aberration error component of the imaging optical system. Therefore, the sensitivity coefficients (r1, r2) calculated from the interval between the signal waveforms include a rotational error component, and therefore the absolute position (dxl, dxu) in the X direction cannot be accurately determined.

[0096] Therefore, a correction value for the lens aberration component of the imaging optical system of the overlay mark may be added to at least one of the first distance (CMLm1) and the second distance (CMLm2).

[0097] 12A to 12E are diagrams showing a method for measuring the lens aberration components of an imaging optical system. With reference to these diagrams, one method for determining the correction values ​​for the lens aberration components of an imaging optical system will be described.

[0098] (1) First, as shown in Fig. 12A, the entire overlay mark OM3 is imaged. In Fig. 12A to Fig. 12E, the area S01 enclosed by a thick line is the imaged area. The interval CMLm1 between signal waveforms obtained from the imaged result includes a lens aberration component.

[0099] (2) Second, as shown in Fig. 12B, of the overlay mark OM3, only the first overlap region 6 is imaged. When imaging the first overlap region 6, the stage on which the substrate is placed is moved so that the first overlap region 6 is positioned at the center of the imaging optical system.

[0100] (3) Third, as shown in Fig. 12C, of ​​the overlay mark OM3, only the overlap region 7 is imaged. When imaging the overlap region 7, the stage on which the substrate is placed is moved so that the overlap region 7 is positioned at the center of the imaging optical system.

[0101] (4) Fourth, as shown in Fig. 12D, of the overlay mark OM3, only the third overlap region 8 is imaged. When imaging the third overlap region 8, the stage on which the substrate is placed is moved so that the third overlap region 8 is positioned at the center of the imaging optical system.

[0102] (5) Fifth, as shown in Fig. 12E, of the overlay mark OM3, only the fourth overlap region 9 is imaged. When imaging the fourth overlap region 9, the stage on which the substrate is placed is moved so that the fourth overlap region 9 is positioned at the center of the imaging optical system.

[0103] If there is no lens aberration in the imaging optical system, the distance CMLm1 calculated in (1) should match the distance the stage moved during imaging in (2) and (3). However, if there is lens aberration in the imaging optical system, the distance will not match. The difference between the distance CMLm1 calculated in (1) and the distance the stage moved during imaging in (2) and (3) can be used as the correction value for the lens aberration component in the X direction. Similarly, the difference between the distance (CML) between the overlapping regions in the Y direction obtained from the images calculated in (1) and the distance the stage moved during imaging in (4) and (5) can be used as the correction value for the lens aberration component in the Y direction. Note that this correction method uses the stage positioning control used to calculate the rotation angle as an absolutely correct index. It is recommended that the stage positioning control be separately calibrated using an accuracy maintenance method.

[0104] <Measurement Apparatus> [Overview of the Measurement Apparatus] An example of a measurement apparatus for measuring the above-described overlay mark is shown. FIG. 13A shows a front view (viewed from the -Y direction) of the measurement apparatus 100, with some parts omitted. FIG. 13B shows a cross-sectional view of the measurement apparatus 100 taken along an XZ plane passing through the optical axis AX1 of the mark detection system MDS (described later), with some parts omitted. FIG. 14 shows a cross-sectional view of the measurement apparatus 100 taken along a YZ plane passing through the optical axis AX1, with some parts omitted. Note that the measurement apparatus 100 shown in FIGS. 13A, 13B, and 14 is housed in a housing (not shown). FIG. 15 shows a block diagram illustrating the input / output relationship of the control device 60, which centrally constitutes the control system of the measurement apparatus 100 according to this embodiment. FIG. 16 shows details of the mark detection system MDS.

[0105] Measurement apparatus 100 includes a mark detection system MDS for detecting the above-described overlay mark OM. Mark detection system MDS includes a light source and illumination optical system that can illuminate the above-described overlay marks (OM1, OM2, OM3) under a plurality of measurement conditions, and an FIA alignment sensor that captures the overlay marks (OM1, OM2, OM3). Details of mark detection system MDS will be described later.

[0106] Hereinafter, the direction of the optical axis AX1 of the mark detection system MDS is referred to as the Z-axis direction. The direction in which a stage (described later) moves over a long stroke in a plane perpendicular to the Z-axis is referred to as the Y-axis direction. The direction perpendicular to the Z-axis and Y-axis is referred to as the X-axis direction. The directions of rotation (tilt) around the X-axis, Y-axis, and Z-axis are referred to as the θx, θy, and θz directions, respectively. The mark detection system MDS has an L-shaped outer shape when viewed from the side (e.g., when viewed from the +X direction). The mark detection system MDS is equipped with a cylindrical lens barrel at its lower end (tip). The lens barrel houses an optical system (e.g., a refractive optical system) consisting of multiple lens elements with an optical axis AX1 in the Z-axis direction. In this specification, the optical axis AX1 of the optical system housed inside the lens barrel is referred to as the optical axis AX1 of the mark detection system MDS.

[0107] The measurement apparatus 100 includes a base 12 (see FIG. 13A), a wafer stage 10 (hereinafter sometimes abbreviated as "stage 10"; see FIG. 13A) that is placed on the base 12 and that is capable of holding a wafer W and making minute movements, a drive system 20 that drives the stage 10 (not shown in FIG. 13A, see FIG. 15), a first position measurement system 30 that measures position information of the stage 10 relative to the base 12 (not shown in FIG. 13A, see FIGS. 13B and 15), a measurement unit having a mark detection system MDS that detects marks on the wafer W mounted on (or held by) the stage 10, a second position measurement system 50 (not shown in FIG. 13A, see FIG. 15) that measures relative position information between the mark detection system MDS and the base 12, and a control device 60 (not shown in FIG. 13A, see FIG. 15).

[0108] [Surface Plate] The surface plate 12 has an upper surface substantially parallel to the XY plane perpendicular to the optical axis AX1. The stage 10 is movable relative to the surface plate 12 in the X-axis and Y-axis directions by a predetermined stroke, and can also be moved slightly (displaced slightly) in the Z-axis, θx, θy, and θz directions. The first position measurement system 30 measures position information of the stage 10 relative to the surface plate 12 in each of the X-axis, Y-axis, Z-axis, θx, θy, and θz directions (hereinafter referred to as "six degrees of freedom"). The control device 60 may acquire measurement information from the first position measurement system 30 and measurement information from the second position measurement system 50 while controlling the driving of the stage 10 by the drive system 20, and may use the mark detection system MDS to determine position information of multiple marks on the wafer W held on the stage 10.

[0109] More specifically, the surface plate 12 has a rectangular (or square) shape in a plan view. The top surface of the surface plate 12 is finished to have an extremely high degree of flatness, and functions as a guide surface when moving the stage 10. The surface plate 12 is made of a material with a low thermal expansion coefficient, also known as a zero-expansion material, such as an invar alloy, extremely low-expansion cast steel, or extremely low-expansion glass ceramics.

[0110] [Vibration Isolation Device] A cavity may be formed in the surface plate 12, and the vibration isolation device 14 may be disposed inside the cavity (see FIG. 14). A plurality of vibration isolation devices 14 may be provided. Although not shown in the figure, the surface plate 12 has three cavities, and three vibration isolation devices 14 are disposed in each cavity. The surface plate 12 is supported by the three vibration isolation devices 14. The surface plate 12 is supported at three points on the upper surface of a base frame 16 installed on the floor, which is parallel to the XY plane, so that the upper surface is approximately parallel to the XY plane. Note that the number of vibration isolation devices 14 is not limited to three.

[0111] The vibration isolation device 14 may constitute at least a part of an active vibration isolation system (also referred to as "AVIS"). The vibration isolation device 14 may optionally include an accelerometer, a displacement sensor (e.g., a capacitance sensor), an actuator (e.g., a voice coil motor), and an air mount functioning as an air damper. The internal gas pressure in the gas chamber of the air mount is high, making it difficult to ensure control response (e.g., up to about 20 Hz). Therefore, if the vibration isolation device 14 includes both an actuator and an air mount, high-response control is possible by controlling the actuator. Furthermore, controlling the actuator according to the output of an accelerometer (not shown) enables even higher-response control. Micro-vibrations such as floor vibrations may be isolated by the air mount. The vibration isolation device 14 can prevent vibration transmission between the surface plate 12 and the base frame 16 (see 14B). Note that a hydraulic damper may be used instead of the air mount.

[0112] The upper end surfaces of the vibration isolation devices 14 are connected to the surface plate 12. Gas (e.g., compressed air) can be supplied to the air mounts via a gas supply port (not shown), and the air mounts expand and contract in the Z-axis direction at a predetermined stroke (e.g., a stroke of 0.5 mm or more and 2 mm or less) depending on the amount of gas filled therein (pressure change of the compressed air). Therefore, by using the air mounts of each of the three vibration isolation devices 14 to individually move three locations on the surface plate 12 up and down from below, the positions of the surface plate 12 and the stage 10 levitated and supported thereon can be arbitrarily adjusted in the Z-axis direction, the θx direction, and the θy direction.

[0113] The three vibration isolation apparatuses 14 are connected to a control device 60 (see FIG. 15 ). Each of the three vibration isolation apparatuses 14 may include an actuator capable of moving the surface plate 12 in six degrees of freedom, not limited to the X-axis, Y-axis, and Z-axis directions. The control device 60 constantly controls the actuators of the three vibration isolation apparatuses 14 in real time. This control may be performed based on relative position information between the mark detection system MDS and the surface plate 12 measured by the second position measurement system 50. This control may be performed so that the position of the surface plate 12, to which the head unit 32 (see FIGS. 13B and 14 ) of the first position measurement system 30 is fixed, in the six degrees of freedom directions, maintains a desired positional relationship with the mark detection system MDS. Each of the three vibration isolation apparatuses 14 may be feedforward controlled. For example, the control device 60 may perform feedforward control of each of the three vibration isolation apparatuses 14 based on measurement information from the first position measurement system 30.

[0114] [Stage] As shown in FIG. 14 , four bearings 18 are attached to the stage 10. In this embodiment, air bearings are used as the bearings 18. One bearing 18 is attached to each of the four corners of the bottom surface of the stage 10. The bearing surface of each bearing 18 is attached so that it is substantially flush with the underside of the stage 10. Pressurized air is ejected from the four bearings 18 toward the base plate 12. The static pressure (gap pressure) between the bearing surface of the pressurized air and the upper surface (guide surface) of the base plate 12 causes the stage 10 to float above the base plate 12. The clearance (gap) between the bottom surface of the stage 10 and the upper surface of the base plate 12 is preferably 10 μm or less, and more preferably 5 μm or less. In this embodiment, the stage 10 is made of zero-expansion glass (e.g., Zerodur by Schott Corporation), a type of zero-expansion material.

[0115] As shown in FIG. 14 , a recess 10a is formed in the upper portion of the stage 10. The recess 10a has an inner diameter larger than the diameter of the wafer W. In a plan view, the recess 10a has a substantially circular shape. A wafer holder WH having a diameter substantially equal to that of the wafer W is disposed within the recess 10a. The wafer holder WH may be a vacuum chuck, an electrostatic chuck, or a mechanical chuck. For example, a pin-type vacuum chuck may be used. The wafer W is held by suction on the wafer holder WH so that the top surface of the wafer W is substantially flush with the top surface of the stage 10. The wafer holder WH has multiple suction ports. The multiple suction ports are connected to a vacuum pump 11 (see FIG. 15 ) via a vacuum piping system (not shown). A control device 60 controls the on / off operation and output of the vacuum pump 11. For example, the wafer holder WH may be capable of suction-holding a wafer having a diameter of 300 mm.

[0116] 13B and 14 , a two-dimensional grating (hereinafter simply referred to as the grating) RG1 is arranged horizontally (parallel to the surface of the wafer W) in an area slightly larger than the wafer W on the underside of the stage 10. The grating RG1 includes a reflective diffraction grating (X diffraction grating) whose periodic direction is in the X-axis direction, and a reflective diffraction grating (Y diffraction grating) whose periodic direction is in the Y-axis direction. The pitch of the grating lines of the X diffraction grating and the Y diffraction grating is set to, for example, 1 μm.

[0117] [Drive System] As shown in Figure 15, the drive system 20 includes a first drive device 20A and a second drive device 20B. The first drive device 20A includes XY linear motors (28A, 28B). The second drive device 20B includes XY linear motors (29A, 29B). The first drive device 20A drives the stage 10 in the X-axis direction. The second drive device 20B, together with the first drive device 20A, drives the stage 10 in the Y-axis direction.

[0118] As shown in FIG. 14, a pair of movers 22a equipped with magnet units (or coil units) is provided on the side surface on the -Y side of the stage 10. The pair of movers 22a are inverted L-shaped in side view and are fixed at a predetermined distance in the X-axis direction. As shown in FIG. 14, a pair of movers 22b equipped with magnet units (or coil units) is provided on the side surface on the +Y side of the stage 10. The pair of movers 22b are fixed at a predetermined distance in the X-axis direction. The pair of movers 22a and the pair of movers 22b are arranged symmetrically. The movers 22a, 22b are supported in a non-contact manner on the upper surfaces of a pair of plate members 24a, 24b extending in the X-axis direction, which are substantially parallel to the XY plane.

[0119] 14, stators 26a, 26b, each consisting of a coil unit (or a magnet unit), are disposed on the upper surface of each of the pair of plate members 24a, 24b in an area excluding both ends in the X-axis direction. Electromagnetic interaction between the pair of movers 22a and the stator 26a generates driving forces (electromagnetic forces) that drive the pair of movers 22a in the X-axis and Y-axis directions.

[0120] The pair of mover 22a and stator 26a constitutes an XY linear motor 28A (see FIG. 15) that generates driving forces in the X-axis and Y-axis directions. The pair of mover 22b and stator 26b constitutes an XY linear motor 28B (see FIG. 15) that generates driving forces in the X-axis and Y-axis directions. The stage 10 is driven in the X-axis direction by a predetermined stroke by the XY linear motor 28A and XY linear motor 28B.

[0121] The first driving unit 20A can vary the magnitude of the driving force in the X-axis direction generated by the XY linear motor 28A and the XY linear motor 28B. This drives the stage 10 in the θz direction. The first driving unit 20A is controlled by the control unit 60 (see FIG. 15). The first driving unit 20A generates not only a driving force in the X-axis direction, but also a driving force in the Y-axis direction. However, the first driving unit 20A does not necessarily have to generate a driving force in the Y-axis direction.

[0122] The stage driving unit 24 has a pair of plate members (24a, 24b) and a pair of connecting members (24c, 24d) arranged a predetermined distance apart in the X-axis direction and each extending in the Y-axis direction. Step portions are formed on both ends of the connecting members (24c, 24d) in the Y-axis direction. The connecting members (24c, 24d) and the plate member 24a are integrated with each other by placing one end and the other end of the plate member 24a in the longitudinal direction on the -Y-side step portions of each connecting member (24c, 24d). The connecting members (24c, 24d) and the plate member 24b are integrated with each other by placing one end and the other end of the plate member 24b in the longitudinal direction on the +Y-side step portions of each connecting member (24c, 24d) (see FIG. 13B). That is, in this manner, a pair of plate members (24a, 24b) are connected by a pair of connecting members (24c, 24d), and a rectangular frame-shaped stage driving unit 24 is configured.

[0123] As shown in FIG. 13A, a pair of linear guides (27a, 27b) extending in the Y-axis direction are fixed to the upper surface of the base frame 16 (see FIG. 13B) near both ends in the X-axis direction. One of the linear guides, 27a, located on the +X side, houses a stator 25a (see FIG. 13B) of a Y-axis linear motor 29A, which is comprised of a coil unit (or magnet unit) extending over substantially the entire length in the Y-axis direction near the upper surface and the -X side surface. A mover 23a is disposed facing the upper surface and the -X side surface of the linear guide 27a. The mover 23a has a magnet unit (or coil unit) with an L-shaped cross section, and together with the stator 25a, constitutes the Y-axis linear motor 29A. Air bearings that eject pressurized air toward the opposing surfaces are fixed to the lower surface and the +X side surface of the mover 23a, which face the upper surface and the -X side surface of the linear guide 27a, respectively. Preferably, a vacuum preload air bearing is used as the air bearing fixed to the +X side surface of mover 23 a. A vacuum preload air bearing easily maintains a constant clearance (gap) in the X-axis direction between mover 23 a and linear guide 27 a due to the balance between the static pressure of the pressurized air between the bearing surface and the −X side surface of linear guide 27 a and the vacuum preload force.

[0124] A plurality of X guides 19, for example two rectangular parallelepiped members, are fixed on the upper surface of mover 23a at a predetermined distance in the Y-axis direction. Slide member 21, which has an inverted U-shaped cross section and constitutes a uniaxial guide device together with X guide 19, is engaged without contact with each of the two X guides 19. Air bearings are provided on each of the three surfaces of slide member 21 facing X guide 19. The two slide members 21 are each fixed to the lower surface (the surface on the -Z side) of connecting member 24c.

[0125] The other linear guide 27b, located on the -X side, houses a stator 25b of a Y-axis linear motor 29B, which is composed of a coil unit (or magnet unit). Linear guide 27b is configured similarly to linear guide 27a, but with a bilateral symmetry (see FIG. 13B). A mover 23b is disposed facing the top surface and +X side surface of linear guide 27b. The mover 23b has a magnet unit (or coil unit) with an L-shaped cross section, similar to mover 23a (although bilaterally symmetrical). Mover 23b, together with stator 25b, constitutes Y-axis linear motor 29B. Air bearings are fixed to the bottom surface and -X side surface of mover 23b, facing the top surface and +X side surface of linear guide 27b, respectively. A vacuum preload air bearing is used as the air bearing fixed to the -X side surface of mover 23b. The vacuum preload type air bearing makes it easy to maintain the clearance (gap) in the X-axis direction between the mover 23b and the linear guide 27b at a constant value.

[0126] As described above, two uniaxial guide devices each composed of an X guide 19 and a slide member 21 that engages with the X guide 19 without contact are provided between the top surface of the mover 23b and the bottom surface of the connecting member 24d.

[0127] The stage driver 24 is supported from below by movers (23a, 23b) via two uniaxial guide devices (four in total), one on each of the +X and -X sides, and is movable in the X-axis direction on the movers 23a, 23b. Therefore, when the stage 10 is driven in the X-axis direction by the first driver 20A described above, a reaction force of the driving force acts on the stage driver 24, which is provided with the stators (26a, 26b). As a result, the stage driver 24 moves in the opposite direction to the stage 10 in accordance with the law of conservation of momentum. That is, the movement of the stage driver 24 prevents (or effectively suppresses) the generation of vibrations caused by the reaction force of the driving force in the X-axis direction on the stage 10. That is, the stage driver 24 functions as a countermass when the stage 10 moves in the X-axis direction. However, the stage driver 24 does not necessarily have to function as a countermass. A counter mass (not shown) may be additionally provided to the stage driving unit 24 to prevent (or effectively suppress) the generation of vibrations caused by the driving force that drives the stage 10 in the Y-axis direction.

[0128] Y-axis linear motor 29A generates a driving force (electromagnetic force) that drives mover 23a in the Y-axis direction through electromagnetic interaction between mover 23a and stator 25a. Y-axis linear motor 29B generates a driving force (electromagnetic force) that drives mover 23b in the Y-axis direction through electromagnetic interaction between mover 23b and stator 25b.

[0129] The driving force in the Y-axis direction generated by the Y-axis linear motors (29A, 29B) acts on the stage driving unit 24 via two uniaxial guide devices on each of the +X and −X sides. This causes the stage 10 to be driven in the Y-axis direction integrally with the stage driving unit 24. That is, in this embodiment, the stage driving unit 24, the four uniaxial guide devices, and the pair of Y-axis linear motors (29A, 29B) constitute a second driving unit 20B (see FIG. 15) that drives the stage 10 in the Y-axis direction.

[0130] In this embodiment, the pair of Y-axis linear motors (29A, 29B) are physically separated from the base plate 12, and are also vibrationally separated by the three vibration isolation devices 14. Note that the linear guides (27a, 27b) on which the stators (25a, 25b) of the pair of Y-axis linear motors (29A, 29B) are respectively provided may be configured to be movable in the Y-axis direction relative to the base frame 16 (see FIG. 13B) and may function as counter masses when the stage 10 is driven in the Y-axis direction.

[0131] [Mark Detection System] Next, details of the mark detection system MDS that detects the overlay marks OM (OM1, OM2, OM3) will be described with reference to Fig. 16. The measurement apparatus 100 includes a mark detection system MDS that is an off-axis FIA (Field Image Alignment) type alignment sensor.

[0132] In the mark detection system MDS, broadband illumination light (wideband light) emitted from a light source 241 such as a halogen lamp passes through a condenser lens 242 , a wavelength selection mechanism 243 and a polarization switching mechanism 251 and is incident on an illumination field stop 244 .

[0133] The polarization switching mechanism 251 is a mechanism for setting the polarization state of the illumination light to a desired state. The polarization switching mechanism 251 is equipped with multiple polarization filters arranged circumferentially on a rotatable disk. By rotating the disk, the illumination light can pass through different polarization filters. In addition to the polarization filters, plain glass with no polarizing effect may be placed on the disk. By providing the polarization switching mechanism 251, the polarization state of the illumination light, which is one of the measurement conditions, can be changed.

[0134] The wavelength selection mechanism 243 is a mechanism for transmitting only a light beam having a wavelength range that is not photosensitive to the photoresist applied to the wafer W and that is also suitable for detecting the overlay mark OM and the like of the detection target (alignment target). By using the wavelength selection mechanism 243, it is possible to change the wavelength of the illumination light, which is one of the measurement conditions.

[0135] The wavelength selection mechanism 243 includes, for example, a plurality of filters that each extract light of a different wavelength, and a filter driver that places one of the plurality of filters on the optical path of the broadband light emitted from the light source 241. In this embodiment, the wavelength selection mechanism 243 includes four filters that transmit a light beam with a wavelength of 530 to 620 nm (green light), a light beam with a wavelength of 620 to 710 nm (orange light), a light beam with a wavelength of 710 to 800 nm (red light), and a light beam with a wavelength of 530 to 800 nm (white light), respectively.

[0136] It is preferable that the filter used for wavelength selection is placed at a position conjugate with the light source 241 and where color unevenness is unlikely to occur. Furthermore, the filter is not limited to the type that transmits a predetermined wavelength range as described above. A wavelength cut filter that cuts off a predetermined wavelength range may be used, and multiple wavelength cut filters may be combined to extract and transmit only the desired wavelength.

[0137] The light source 241 may be a solid-state light source such as an LED or LD. In this case, multiple solid-state light sources with different narrow bands are prepared and selectively turned on and off. This allows the wavelength of the illumination light to be changed in a short time without using a wavelength filter.

[0138] The illumination light DL transmitted through the transmission portion of the illumination field stop 244 passes through a relay lens 245 and enters an illumination aperture stop 246 (263). Furthermore, the illumination light DL passes through a beam splitter 247 and an objective lens 253 to illuminate a desired illumination area, such as an area including an overlay mark OM, the position of which is to be detected on the wafer W. The illumination field stop 244 is substantially conjugate (in an imaging relationship) with the surface of the wafer W (the surface on which the overlay mark OM is located). Therefore, the illumination area on the wafer W can be limited depending on the shape and size of the transmission portion of the illumination field stop 244.

[0139] The illumination aperture stop 246 (263) is disposed at a plane (referred to as the illumination system pupil plane) H1 that is optically Fourier transform-related with respect to the wafer surface (overlay mark OM) via the objective lens 253 and the beam splitter 247. The illumination aperture stop 246 (263) is available in two types: an illumination aperture stop 246 having a normal circular transmission portion, and an illumination aperture stop 263 having an annular transmission portion. The illumination aperture stop 246 (263) is designed to allow selection between these two types. When measuring the overlay mark OM using normal illumination (so-called normal illumination), the illumination aperture stop 246 is disposed on the illumination optical path. When measuring the overlay mark OM using so-called modified illumination (or annular illumination as oblique illumination), the illumination aperture stop 263 is disposed on the illumination optical path. The illumination aperture stop 246 may include multiple circular aperture stops with different aperture diameters of the circular transmission portion. Changing the illumination aperture stop allows the illumination σ of the measurement optical system, which is one of the measurement conditions, to be changed.

[0140] The light beam reflected from the illumination area including the overlay mark on the wafer W is incident via the objective lens 253 and the beam splitter 247 on an imaging aperture stop 249 having a circular opening located at a plane (referred to as the imaging system pupil plane) H2 that has an optical Fourier transform relationship with the surface of the wafer W. Note that this imaging aperture stop 249 may be configured as an imaging aperture stop with an annular light-shielding portion, as disclosed in Japanese Patent Laid-Open Publication No. 8-306609, that can be inserted and removed from the imaging optical path and used in conjunction with the illumination aperture stop 263 described above to perform dark-field detection. If the wafer mark is a low-level step mark, dark-field detection is preferably performed; if it is a high-level step mark, the imaging aperture stop is preferably retracted from the optical path and bright-field detection is performed. By changing the combined aperture stop, the numerical aperture NA of the measurement optical system, which is one of the measurement conditions, can be changed.

[0141] The light beam that has passed through the imaging aperture stop 249 is condensed by the imaging lens 250 and focused on an image pickup element 254 such as a CCD. As a result, an image of the overlay mark is formed on the imaging surface of the image pickup element 254.

[0142] The image captured by the image sensor 254 is supplied to the control device 60 via the signal processing device 49. The control device 60 includes a workstation (or a microcomputer) and the like, and controls all components of the measurement device 100. The measurement device 100 selects measurement conditions for the overlay marks OM (OM1, OM2, OM3) using the mark detection system MDS, and controls the mark detection system MDS and the stage driving unit 24 in accordance with the selected measurement conditions.

[0143] Image processing-based alignment sensors capable of switching or selecting measurement conditions are disclosed in further detail in, for example, U.S. Patent Application Publication No. 2008 / 0013073. The mark detection system MDS of this embodiment can employ a configuration similar to that disclosed therein. While the focus state of the mark detection system MDS on the overlay mark OM can be optically changed by changing the focal length of the objective lens 253 of the mark detection system MDS, in this embodiment, it is changed by moving the stage 10, which holds the wafer W on which the overlay mark is formed, in the optical axis direction (Z-axis direction) of the mark detection system MDS. In other words, the focus state, which is one of the measurement conditions, can be changed by adjusting the position of the stage 10 in the Z-axis direction. To detect the focus state, the mark detection system MDS may be equipped with an alignment focus system that detects the surface position of the wafer W.

[0144] Furthermore, a beam scanning type alignment system that scans a measurement light beam in a predetermined direction relative to the target mark while the stage 10 is moving in the predetermined direction may be used as the mark detection system MDS. Furthermore, in this embodiment, the mark detection system MDS has an alignment autofocus function, but instead of or in addition to this, the measurement unit 40 may be equipped with a focal position detection system, for example, an oblique incidence type multi-point focal position detection system similar to that disclosed in U.S. Pat. No. 5,448,332, etc.

[0145] The function of signal processing device 49 (see FIG. 15 or 16 ) will be described. Signal processing device 49 is a calculation device that has an input unit that inputs information related to the image of overlay mark OM, a calculation unit that calculates the absolute position (dxl, dxu) of at least one of first pattern group LSl or second pattern group LSu from the input information, and an output unit that outputs information related to the absolute position (dxl, dxu) of at least one of first pattern group LSl or second pattern group LSu calculated by the calculation unit.

[0146] The signal processing device 49 processes the imaging signal output as a detection signal from the mark detection system MDS, performs signal processing to calculate position information of the target mark relative to the detection center, and outputs the signal to the control device 60. The signal processing device 49 includes a program for calculating the absolute position of at least one of the first pattern group LSl or the second pattern group LSu from the input information, and a storage medium on which the program is stored. The program may be installed in the measurement device from a program distribution server on the network or from the storage medium.

[0147] The signal processing performed by the signal processing device 49 includes at least one of the following: a waveform analysis (waveform processing) algorithm to be used in the signal processing device 49, selection of a signal processing algorithm such as an EGA calculation model, and selection of various parameters to be used in each selected signal processing algorithm.

[0148] 15 and 16, the signal processing device 49 is shown as being separate from the control device 60, but the signal processing device 49 and the control device 60 may be integrated together. For example, the control device 60 may have the function of the arithmetic device that the signal processing device 49 has.

[0149] 13B and 14, the first position measurement system 30 is disposed in a recess formed in the upper surface of the surface plate 12 and has a head unit 32 fixed to the surface plate 12. The upper surface of the head unit 32 faces the lower surface of the stage 10 (the surface on which the grating RG1 is formed). A predetermined clearance (gap) is formed between the upper surface of the head unit 32 and the lower surface of the stage 10. The clearance referred to in this paragraph may be, for example, a clearance of about several mm (for example, 1 mm or more and 5 mm or less).

[0150] As shown in FIG. 15 , the first position measurement system 30 includes an encoder system 33 and an interferometer system 35. The encoder system 33 irradiates a plurality of beams from the head unit 32 onto a measurement unit on the underside of the stage 10 (the surface on which the grating RG1 is formed) and receives a plurality of return beams from the measurement unit on the underside of the stage 10 (e.g., a plurality of diffracted beams from the grating RG1). This allows position information of the stage 10 to be acquired. The encoder system 33 includes an X linear encoder 33x that measures the position of the stage 10 in the X-axis direction and a pair of Y linear encoders (33ya, 33yb) that measure the position of the stage 10 in the Y-axis direction. The interferometer system 35 includes four laser interferometers (35a, 35b, 35c, 35d) and measures the position of the stage 10 in the Z-axis direction and the amount of rotation in the θx and θy directions.

[0151] A diffraction interference type head similar to the encoder head (hereinafter simply referred to as the head as appropriate) disclosed in, for example, U.S. Patent No. 7,238,931 and U.S. Patent Application Publication No. 2007 / 288,121 may be used as the encoder system 33. The head includes a light source, a light receiving system (including a photodetector), and an optical system, but in this embodiment, it is sufficient that at least the optical system is disposed inside the housing of the head unit 32 facing the grating RG1, and at least one of the light source and the light receiving system may be disposed outside the housing of the head unit 32.

[0152] In this embodiment, by using encoder system 33, control device 60 can measure position information within the XY plane of stage 10 when measuring an alignment mark on wafer W placed on stage 10. Control device 60 also measures the amount of rotation of stage 10 in the θz direction based on the difference between the measurement values ​​of the pair of Y heads (37ya, 37yb).

[0153] In order to measure the position of the stage 10 in the Z-axis direction and the amount of rotation in the θx and θy directions, the four laser interferometers (35a, 35b, 35c, 35d) of the interferometer system 35 measure the position in the Z-axis direction and the amount of rotation in the θx and θy directions by irradiating beams at four different points on the surface on which the grating RG1 is formed. In principle, it is sufficient to be able to measure the positions in the Z-axis direction at three different points on the measurement surface, so three laser interferometers may be used.

[0154] As can be seen from the above description, the control device 60 can measure the position of the stage 10 in six degrees of freedom by using the encoder system 33 and interferometer system 35 of the first position measurement system 30 .

[0155] As shown in FIGS. 13A and 13B , the second position measurement system 50 includes a pair of head units (52A, 52B) respectively provided on the underside of one longitudinal end and the other longitudinal end of the head mounting member 51, and scale members (54A, 54B) disposed opposite the head units (52A, 52B). The upper surfaces of the scale members (54A, 54B) are flush with the surface of the wafer W held by the wafer holder WH. A reflective two-dimensional grating (RG2a, RG2b) is formed on the upper surface of each of the scale members (54A, 54B). The two-dimensional gratings (hereinafter abbreviated as gratings) (RG2a, RG2b) each include a reflective diffraction grating (X diffraction grating) whose periodic direction is in the X-axis direction and a reflective diffraction grating (Y diffraction grating) whose periodic direction is in the Y-axis direction. The grating line pitch of the X diffraction grating and the Y diffraction grating is set to, for example, 1 μm.

[0156] The scale members (54A, 54B) may be made of a material with a low thermal expansion coefficient, such as the zero-expansion material described above. As shown in Figures 13A and 13B, the scale members (54A, 54B) are fixed to the surface plate 12 via support members 56. In this embodiment, the dimensions of the scale members (54A, 54B) and support members 56 are determined so that the gratings (RG2a, RG2b) and the head portions (52A, 52B) face each other with a gap of about several millimeters between them.

[0157] As shown in FIG. 15, in this embodiment, the second position measurement system 50 includes two four-axis encoders (58 １ , 58 ２ ) XZ Linear Encoder 58X １ and YZ linear encoder 58Y １ A four-axis encoder 58 measures position information of the surface plate 12 in the X-axis, Y-axis, Z-axis, and θx directions relative to the mark detection system MDS. １ (See FIG. 15.) Similarly, the XZ linear encoder 58X ２ and YZ linear encoder 58Y ２ A four-axis encoder 58 measures position information of the surface plate 12 in the X-axis, Y-axis, Z-axis, and θx directions relative to the mark detection system MDS. ２ In this case, a four-axis encoder (58 １ , 58 ２ Based on the position information of the surface plate 12 in the Z-axis direction relative to the mark detection system MDS measured by the four-axis encoder (58), the position information of the surface plate 12 in the θy direction relative to the mark detection system MDS is obtained (measured). １ , 58 ２ ) is measured, the position information of the surface plate 12 in the θz direction relative to the mark detection system MDS is obtained (measured).

[0158] 4-axis encoder 58 １ and 4-axis encoder 58 ２This constitutes a second position measurement system 50 that measures position information of the surface plate 12 in six degrees of freedom with respect to the mark detection system MDS, i.e., information on the relative position in six degrees of freedom between the mark detection system MDS and the surface plate 12. Information on the relative position in six degrees of freedom between the mark detection system MDS and the surface plate 12 measured by the second position measurement system 50 is constantly supplied to a control device 60. Based on this relative position information, the control device 60 controls the actuators of the three vibration isolation devices 14 in real time so that the detection point of the first position measurement system 30 has a desired positional relationship with the detection center of the mark detection system MDS.

[0159] [Wafer Transfer System] The measuring apparatus 100 includes a wafer transfer system 70 arranged in a chamber together with the components shown in FIG. 1 . The wafer transfer system 70 is, for example, a horizontal articulated robot. The wafer transfer system 70 may include a non-contact holding member (e.g., a Bernoulli chuck) that suction-holds the wafer on the wafer holder WH from above without contact. The measuring apparatus 100 described above is a separate device independent of the exposure apparatus. However, the measuring apparatus 100 may also be an apparatus integrated with the exposure apparatus. An example of an exposure apparatus equipped with an alignment detection system for detecting the above-described overlay marks (OM1, OM2, OM3) is shown below.

[0160] 17 , exposure apparatus 200 includes an illumination system IOP, a reticle stage RST that holds reticle R, a projection unit PU that projects an image of a pattern formed on reticle R onto a wafer W coated with a photosensitive agent (resist), a wafer stage WST that holds wafer W and moves within the XY plane, and a control system for these. Exposure apparatus 200 includes a projection optical system PL that has an optical axis AX in the Z-axis direction that is parallel to the optical axis AX1 of the mark detection system MDS described above. Although exposure apparatus 200 of this embodiment is an exposure apparatus used for manufacturing semiconductor elements, the features of exposure apparatus 200 can be applied to exposure apparatuses used for manufacturing FPDs.

[0161] Illumination system IOP includes a light source and an illumination optical system connected to the light source via a light-transmitting optical system, and illuminates, with approximately uniform illuminance, a slit-shaped illumination area IAR that extends elongatedly in the X-axis direction (a direction perpendicular to the plane of the paper in FIG. 17 ) on reticle R, which is set (limited) by a reticle blind (masking system), with exposure light IL. The configuration of illumination system IOP is disclosed, for example, in U.S. Patent Application Publication No. 2003 / 0025890. Here, as an example, ArF excimer laser light (wavelength 193 nm) is used as exposure light IL.

[0162] Reticle stage RST is disposed below illumination system IOP in Fig. 9. Reticle stage RST can be driven by a reticle stage drive system 211 (not shown in Fig. 17, see Fig. 18) that includes, for example, a linear motor or the like, to move minutely within a horizontal plane (XY plane) on a reticle stage base (not shown), and can also be driven within a predetermined stroke range in the scanning direction (the Y-axis direction, which is the left-right direction in Fig. 17).

[0163] A reticle R is placed on the reticle stage RST. The reticle R has a pattern area and a plurality of marks whose positional relationship with the pattern area is known, formed on its -Z side surface (pattern surface). Position information (including rotation information in the θz direction) of the reticle stage RST in the XY plane is constantly detected by a reticle interferometer 214 via a movable mirror 212 (or a reflecting surface formed on the end surface of the reticle stage RST) with a resolution of, for example, about 0.25 nm. The measurement information of the reticle interferometer 214 is supplied to an exposure control device 220 (see FIG. 18). The position information of the reticle stage RST in the XY plane described above may also be measured by an encoder instead of the reticle interferometer 214.

[0164] The projection unit PU is disposed below the reticle stage RST in FIG. 9 . The projection unit PU includes a lens barrel 240 and a projection optical system PL held within the lens barrel 240. The projection optical system PL is, for example, double-telecentric and has a predetermined projection magnification (e.g., ¼, ⅕, or ⅛). The reticle R is disposed so that its pattern surface substantially coincides with the first surface (object plane) of the projection optical system PL, and a wafer W, whose surface is coated with a resist (sensitizer), is disposed on the second surface (image plane) of the projection optical system PL. Therefore, when an illumination area IAR on the reticle R is illuminated by exposure light IL from the illumination system IOP, the exposure light IL that has passed through the reticle R forms a reduced image of the circuit pattern of the reticle R within the illumination area IAR (a reduced image of a portion of the circuit pattern) in an area IA on the wafer W that is conjugate to the illumination area IAR, via the projection optical system PL. Then, by synchronously driving the reticle stage RST and the wafer stage WST, the reticle R is moved relative to the illumination area IAR (exposure light IL) in the scanning direction (Y-axis direction), and the wafer W is moved relative to the exposure area IA (exposure light IL) in the scanning direction (Y-axis direction), thereby scanning and exposing one shot area on the wafer W.

[0165] Exposure is performed, and the pattern of the reticle R is transferred to the shot area. The projection optical system PL, for example, is a refractive system consisting of multiple, for example, approximately 10 to 20, refractive optical elements (lens elements) arranged along an optical axis AX parallel to the Z-axis direction. Of the multiple lens elements constituting the projection optical system PL, multiple lens elements on the object plane side (the reticle R side) are movable lenses that can be shifted in the Z-axis direction (the optical axis direction of the projection optical system PL) and in tilt directions relative to the XY plane (i.e., the θx direction and the θy direction) by drive elements (not shown), such as piezoelectric elements. The imaging characteristic correction controller 248 (not shown in FIG. 17 , see FIG. 18 ) independently adjusts the voltages applied to each drive element based on instructions from the exposure control device 220, thereby individually driving each movable lens and adjusting various imaging characteristics of the projection optical system PL (such as magnification, distortion, astigmatism, coma, and field curvature). Instead of or in addition to moving the movable lens, an airtight chamber may be provided between specific adjacent lens elements inside the lens barrel 240, and the pressure of the gas inside the airtight chamber may be controlled by the imaging characteristics correction controller 248, or a configuration may be adopted in which the central wavelength of the exposure light IL can be shifted by the imaging characteristics correction controller 248. These configurations also make it possible to adjust the imaging characteristics of the projection optical system PL.

[0166] Wafer stage WST is driven by a stage drive system 224 (shown as a block in FIG. 10 for convenience) including a planar motor or a linear motor or the like over a predetermined stroke in the X-axis and Y-axis directions on wafer stage base 222, and is also finely driven in the Z-axis, θx, θy, and θz directions. Wafer W is held on wafer stage WST by vacuum suction or the like via a wafer holder (not shown). Note that instead of wafer stage WST, a stage device may be used that includes a first stage that moves in the X-axis, Y-axis, and θz directions, and a second stage that finely moves on the first stage in the Z-axis, θx, and θy directions.

[0167] Position information within the XY plane of wafer stage WST (including rotation information expressed as the amount of yawing (amount of rotation θz in the θz direction), amount of pitching (amount of rotation θx in the θx direction), or amount of rolling (amount of rotation θy in the θy direction)) is constantly detected by interferometer system 218 via movable mirror 216 (or a reflective surface formed on the end face of wafer stage WST) with a resolution of, for example, about 0.25 nm. Note that position information within the XY plane of wafer stage WST may also be measured by encoder system 33 instead of interferometer system 218.

[0168] The measurement information of the interferometer system 218 is supplied to an exposure control device 220 (see FIG. 18 ). Based on the measurement information of the interferometer system 218, the exposure control device 220 controls the position of the wafer stage WST in the XY plane (including rotation in the θz direction) via a stage drive system 224.

[0169] 17, the position in the Z-axis direction and the tilt amount of the surface of the wafer W are measured by a focus sensor AFS (see FIG. 10) consisting of a multi-point focal position detection system of the oblique incidence type disclosed in, for example, U.S. Patent No. 5,448,332, etc. Measurement information of this focus sensor AFS is also supplied to the exposure controller 220 (see FIG. 10).

[0170] Additionally, a reference plate FP is fixed on the wafer stage WST, and its surface is at the same height as the surface of the wafer W. On the surface of this reference plate FP, a first reference mark used for baseline measurement of the alignment detection system AS, and a pair of second reference marks detected by the reticle alignment detection system are formed.

[0171] An alignment detection system AS is provided on the side of the lens barrel 240 of the projection unit PU, detecting alignment marks (including the above-mentioned overlay marks) or first reference marks formed on the wafer W. The alignment detection system AS has a configuration similar to the mark detection system MDS in the measurement apparatus 100. The exposure control device 220 functions as a calculation device having an input unit that inputs information related to images of the overlay marks (OM1, OM2, OM3), a calculation unit that calculates the absolute position of at least one of the first pattern group or the second pattern group from the input information, and an output unit that outputs information related to the absolute position of at least one of the first pattern group or the second pattern group calculated by the calculation unit. The calculation unit includes a program for causing the exposure apparatus to execute the above-mentioned mark measurement method, and a storage medium on which the program is stored. The program may be installed in an existing exposure apparatus from a program distribution server on a network or a storage medium.

[0172] Furthermore, in exposure apparatus 200, a pair of reticle alignment detection systems 213 (not shown in FIG. 17, see FIG. 18) are provided above reticle stage RST, spaced a predetermined distance apart in the X-axis direction, and are capable of simultaneously detecting a pair of reticle marks at the same Y position on reticle R placed on reticle stage RST. The results of mark detection by reticle alignment detection systems 213 are supplied to exposure controller 220.

[0173] 18 is a block diagram showing the input / output relationships of exposure control device 220. As shown in FIG. 18, in addition to the above-mentioned components, exposure apparatus 200 also includes a wafer transport system 270 that transports wafers and is connected to exposure control device 220. Exposure control device 220 includes a microcomputer, a workstation, or the like, and performs overall control of the entire apparatus including the above-mentioned components. Wafer transport system 270 is composed of, for example, a horizontal articulated robot. While this specification has described a method and apparatus for measuring overlay mark OM provided on wafer W, similar measurement methods and apparatus can also be used for substrates other than wafers (FPD substrates and printed circuit boards).

[0174] 1: First layer 2: Second layer 3: Intermediate layer 6: First overlapping region 7: Second overlapping region 8: Third overlapping region 9: Fourth overlapping region 10: Wafer stage 10a: Recess 11: Vacuum pump 12: Surface plate 14: Vibration isolator 16: Base frame 18: Bearing 19: X guide 20: Drive system 20A: First drive device 20B: Second drive device 21: Slide member 22a, 22b, 23a, 23b: Movable element 24: Stage drive unit 24a, 24b: Plate member 24c, 24d: Connecting member 25a, 25b, 26a, 26b: Stator 27a, 27b: Linear guide 28A, 28B: XY linear motor 29A, 29B: Y-axis linear motor 30: First position measurement system 32: Head section 33: Encoder system 33x: X linear encoder 35: Interferometer system 40: Measurement unit 49: Signal processing device 50: Second position measurement system 51: Head mounting member 56: Support member 58X1, 58X2: XZ linear encoder 58Y1, 58Y2: YZ linear encoder 60: Control device 70: Wafer transfer system 100: Measurement device 200: Exposure device 211: Reticle stage drive system 212: Movable mirror 213: Reticle alignment detection system 214: Reticle interferometer 216: Movable mirror 218: Interferometer system 220: Exposure control device 222: Wafer stage surface plate 224: Stage drive system 240: Lens barrel 241: Light source 242 : Condenser lens 243 : Wavelength selection mechanism 244 : Illumination field stop 245 : Relay lens 246 : Illumination aperture stop 247 : Beam splitter 248 : Imaging characteristic correction controller 249 : Imaging aperture stop 250 : Imaging lens 251 : Polarization switching mechanism 253 : Objective lens 254 : Image pickup element 263 : Illumination aperture stop 270 : Wafer transport system 581,582: 4-axis encoder AFS: Focus sensor AP1, AP2: Absolute position AS: Alignment detection system AX, AX1: Optical axis C6, C7: Center of gravity (of pattern overlap area) CMLdl: First pattern group interval CMLdu: Second pattern group interval CMLm1: First interval CMLm2: Second interval DL: Illumination light FP: Reference plate IA: Exposure area IAR: Illumination area IL: Exposure light IOP: Illumination system IS, IS1, IS2: Signal waveform LSl: First pattern group LSu: Second pattern group LSly: Third pattern group LSuy: Fourth pattern group MDS: Mark detection system OM, OM1, OM2, OM3: Overlay mark P1, P2: Pitch PL: Projection optical system PU : Projection unit R: Reticle RG1: Grating RST: Reticle stage S01: Area S1, S2: Line pattern SP: Coordinate origin W: Wafer WH: Wafer holder WST: Wafer stage dxl: Absolute position (of first pattern group or lower layer pattern group) dxl0: First reference position (of first pattern group or lower layer pattern group) dxm1: First mark position (measured under first measurement conditions) dxm2: Second mark position (measured under second measurement conditions) dxu: Absolute position (of second pattern group or upper layer pattern group) dxu0: Second reference position (of second pattern group or upper layer pattern group) r, r1, r2: Sensitivity coefficients ΔAP: Overlay error,

Claims

1. A mark measurement method including: measuring, under first measurement conditions, an overlay mark formed by overlapping, with a shift, a first pattern group, on one layer on a substrate, in which lines and spaces are formed repeatedly at a constant pitch on a first axis of a reference coordinate system, and a second pattern group, on another layer different from the first layer, in which lines and spaces are formed repeatedly on the first axis at the constant pitch, on the first axis; measuring, under first measurement conditions, the overlay mark to obtain a first image; measuring, under second measurement conditions different from the first measurement conditions, the overlay mark to obtain a second image; obtaining, from the first image, a first mark position on the first axis of the overlay mark, and obtaining, from the second image, a second mark position on the first axis of the overlay mark; and determining, from the first mark position and the second mark position, an absolute position in the first axial direction in which the first axis extends, for at least one of the first pattern group and the second pattern group.

2. A mark measurement method according to claim 1, wherein the first pattern group and the second pattern group are arranged with a shift along the first axis direction by a predetermined shift amount in a reference state without any shift, and an absolute position in the first axis direction in the reference coordinate system is determined for at least one of the first pattern group and the second pattern group using a sensitivity coefficient determined from a first reference position in the reference state, the first mark position acquired under the first measurement conditions, the second mark position acquired under the second measurement conditions, and the shift amount.

3. A mark measurement method according to claim 1 or 2, wherein the first pattern group and the second pattern group are arranged with a predetermined shift amount along the first axis direction in a reference state without any shift, the overlay marks are arranged in each of two areas, a first overlap area and a second overlap area, which are spaced apart in the first axis direction, and a first pattern group interval, which is the distance in the first axis direction between the first pattern group included in the first overlap area and the first pattern group included in the overlap area, is a different value from a second pattern group interval, which is the distance in the first axis direction between the second pattern group included in the first overlap area and the second pattern group included in the overlap area.

4. The mark measurement method according to claim 3, wherein the first pattern group interval is equal to the second pattern group interval plus twice the shift amount.

5. A mark measurement method according to claim 3 or 4, wherein the midpoint of the first pattern group interval and the midpoint of the second pattern group interval are located at the same position in the first axis direction.

6. A mark measurement method according to any one of claims 1 to 5, wherein the other layer is a layer above the one layer, and the width of a first pattern included in the first pattern group is wider than the width of a second pattern included in the second pattern group.

7. The mark measurement method according to claim 3, wherein determining the absolute position includes: acquiring from the first image a first interval that is the interval in the first axis direction between the overlay mark in the first overlap region and the overlay mark in the overlap region; acquiring from the second image a second interval that is the interval in the first axis direction between the overlay mark in the first overlap region and the overlay mark in the overlap region; determining a first sensitivity coefficient of the first pattern group and the second pattern group under the first measurement conditions using the acquired first interval, the first pattern group interval, and the shift amount; and determining a second sensitivity coefficient of the first pattern group and the second pattern group under the second measurement conditions using the acquired second interval, the first pattern group interval, and the shift amount.

8. The mark measurement method according to claim 7, comprising: determining the first sensitivity coefficient r1 using the following equation (1); and determining the second sensitivity coefficient r2 using the following equation (2). Here, CMLm1 represents the first distance between the first overlapping area and the overlapping area obtained from the first image of the overlay mark, CMLm2 represents the second distance between the first overlapping area and the overlapping area obtained from the second image of the overlay mark, CMLdl represents the design value of the first pattern group distance between the first pattern group included in the first overlapping area and the first pattern group included in the overlapping area, and d represents the shift amount in the first axis direction between the first pattern group and the second pattern group in a reference state without any misalignment.

9. The mark measurement method according to claim 8, further comprising determining at least one of the absolute positions of the first pattern group and the second pattern group using equation (3). Here, dxl represents the absolute position of the first pattern group in the first axis direction of the reference coordinate system, dxu represents the absolute position of the second pattern group in the first axis direction of the reference coordinate system, dxm1 represents the measurement position of the overlay mark obtained from the first image, and dxm2 represents the measurement position of the overlay mark obtained from the second image.

10. A mark measurement method according to any one of claims 7 to 9, comprising adding a correction value for a rotation error component of the overlay mark relative to the reference coordinate system to at least one of the first interval and the second interval.

11. The mark measurement method according to any one of claims 7 to 10, further comprising adding a correction value for a lens aberration component of an imaging optical system for the overlay mark to at least one of the first distance and the second distance.

12. A mark measurement method according to any one of claims 1 to 11, comprising: additionally acquiring images of the overlay mark under one or more measurement conditions different from the first measurement condition and the second measurement condition; and determining an absolute position in the first axis direction for at least one of the first pattern group and the second pattern group from the first mark position acquired from the first image, the second mark position acquired from the second image, and an additional mark position acquired from an image under the one or more additional measurement conditions.

13. A mark measurement method according to any one of claims 1 to 12, wherein the first measurement condition and the second measurement condition differ in at least one of the wavelength of the illumination light, the focusing state of the pattern group, the numerical aperture NA of the measurement optical system, the illumination σ of the measurement optical system, and the polarization state of the illumination light.

14. A mark measurement method according to any one of claims 1 to 13, comprising selecting the first measurement conditions and the second measurement conditions based on at least one of signal quality, the number of measurement errors, the number of abnormal measurement values ​​detected, a repeatability coefficient, and a measurement accuracy coefficient.

15. The mark measurement method according to any one of claims 1 to 14, wherein the overlay mark includes an overlay mark formed by superimposing, on the one layer, a third pattern group in which lines and spaces are repeatedly formed at a constant pitch P2 on a second axis perpendicular to the first axis, and, on the other layer, a fourth pattern group in which lines and spaces are repeatedly formed on the second axis at the constant pitch P2, with a deviation on the second axis, and includes determining, from the measurement position of the first image and the measurement position of the second image, an absolute position in the second axial direction in which the second axis extends, for at least one of the third pattern group and the fourth pattern group.

16. A mark measurement method according to any one of claims 1 to 15, comprising: determining absolute positions in the first axis direction for both the first pattern group and the second pattern group; and calculating a relative positional deviation amount in the first axis direction between the first pattern group and the second pattern group from the absolute position in the first axis direction of the first pattern group and the absolute position in the first axis direction of the second pattern group.

17. A mark measurement method according to claim 15, comprising: determining absolute positions in the first axial direction for both the first pattern group and the second pattern group; and calculating a relative positional deviation amount between the first pattern group and the second pattern group in the first axial direction from the absolute position of the first pattern group in the first axial direction and the absolute position of the second pattern group in the first axial direction; and determining absolute positions in the second axial direction for both the third pattern and the fourth pattern; and calculating a relative positional deviation amount between the third pattern and the fourth pattern in the second axial direction from the absolute position of the third pattern in the second axial direction and the absolute position of the fourth pattern in the second axial direction.

18. A measurement device for measuring a mark formed on a substrate, comprising: a movable stage that holds the substrate on which the overlay mark is formed; an acquisition unit that acquires an image of the overlay mark; and a control unit that determines the absolute position by executing the mark measurement method according to any one of claims 1 to 17 on the image of the overlay mark acquired by the acquisition unit.

19. A measurement device for measuring a mark formed on a substrate, comprising: a movable stage that holds a substrate on which an overlay mark is formed, the overlay mark being composed of a first pattern group formed on one layer and a second pattern group formed on another layer different from the first layer; an acquisition unit that acquires an image of the overlay mark; and a control unit that controls the stage and the acquisition unit, wherein the acquisition unit includes an illumination unit that illuminates the overlay mark and an imaging unit that forms an image of the overlay mark, and the control unit controls the illumination unit to measure the overlay mark under a plurality of mutually different measurement conditions, inputs from the acquisition unit the images of the overlay mark formed by the imaging unit for each of the plurality of measurement conditions, and determines the absolute position of at least one of the first pattern group and the second pattern group based on the images of the overlay mark for each of the plurality of measurement conditions.

20. An exposure apparatus that exposes a substrate with exposure light, comprising: a stage that can move while holding the substrate on which the overlay mark is formed; an acquisition unit that acquires an image of the overlay mark; and a control unit that determines the absolute position by executing the mark measurement method according to any one of claims 1 to 17, based on the image of the overlay mark acquired by the acquisition unit.

21. A computing device having: an input unit for inputting information relating to an image of the overlay mark formed on a substrate; a computing unit for determining the absolute position by executing the mark measurement method according to any one of claims 1 to 17; and an output unit for outputting information relating to the absolute position calculated by the computing unit.

22. A program for causing a measurement apparatus or an exposure apparatus to execute the mark measurement method according to any one of claims 1 to 17.

23. A storage medium storing a program for causing a measurement apparatus or exposure apparatus to execute the mark measurement method according to any one of claims 1 to 17.

Images