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

Abstract

The purpose of the present invention is to provide an improved coincidence mark measurement method for reducing coincidence marks, increasing the measurement speed or improving the measurement accuracy. The mark measurement method includes: acquiring an image of overlap marks (OM1, OM2) formed by overlapping a first pattern (LS1) formed by repeating lines and lines at a first pitch P1 in a prescribed direction on one layer spaced on a substrate, and a second pattern (LS2) formed by repeating lines and lines at a second pitch P1 in a prescribed direction on the other layer; the second pattern (LS2) is formed by repeating lines and intervals on another layer different from the one layer in the prescribed direction at a second pitch P2 different from the first pitch P1; extracting a brightness signal of the coincidence mark in the specified direction from the acquired image of the coincidence mark (OM1, OM2); and determining an absolute position in the predetermined direction with respect to at least one of the first pattern and the second pattern on the basis of the extracted luminance signal.

Description

Technical Field

[0001] The present invention relates to a marking measurement method, a measuring device, an exposure device, a computing device, a program and a storage medium. Background Art

[0002] In the photolithography process for manufacturing semiconductor devices, multiple layers of circuit patterns are superimposed on a substrate such as a wafer or glass plate to form the semiconductor device. However, if the overlay accuracy between the layers is poor, the semiconductor device will not exhibit the specified circuit characteristics, and in some cases, the manufactured semiconductor device will be defective. Therefore, an overlay mark consisting of patterns formed on two different layers is photographed, and the overlay accuracy between the two different layers is measured based on the captured image.

[0003] For example, Patent Document 1 discloses a method for measuring a registration mark, in which an image of the registration mark is acquired and the relative misalignment amount between a first pattern formed on a first layer and a second pattern formed on a second layer is acquired from the acquired image.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application No. 2004-508711 Summary of the Invention

[0007] As patterns become increasingly miniaturized, market demands for mark measurement are increasing. In measuring overlay marks, there are also demands for smaller overlay marks, faster measurement speeds, or improved measurement accuracy. The present invention aims to provide an improved overlay mark measurement method that meets at least one of these requirements.

[0008] In the present disclosure, the overlap marks formed by the overlap of patterns formed on two different layers are measured. The overlap of patterns formed on two different layers means that the area of ​​at least a part of the pattern formed on a certain layer is superimposed on the area of ​​at least a part of the other layer in a direction perpendicular to the substrate surface. There are many types of such overlap marks, for example, a Diffraction Based Overlay mark (diffraction-based overlay measurement mark, DBO mark) that detects the offset of the two layers by detecting the light diffracted by the overlapped overlap mark, and a FBO mark (fringe-based overlay measurement mark, hereinafter referred to as "FBO mark") that detects the moiré pattern formed by the overlap to detect the offset of the two layers. The FBO mark is designed to intentionally overlap the patterns formed on two different layers to form a moiré pattern. It should be noted that marks that are not designed to intentionally overlap the patterns formed on two different layers, for example, marks that do not overlap when there is no alignment error but cause a large alignment error that causes overlap, are not included in the FBO mark.

[0009] The inventors of this application have developed a method for measuring the absolute position of the patterns that make up each layer of an FBO mark. Absolute position refers to the displacement of the coincidence mark relative to the coordinate origin, when an arbitrary point in the measurement device is set as the coordinate origin. In this specification, measuring the absolute position of a detection pattern is referred to as "absolute position measurement" of the pattern. Absolute position measurement has a measurement concept that differs significantly from relative position measurement, which measures the relative offset between known detection patterns. The advantages of absolute position measurement will be explained later.

[0010] One approach to labeling measurement methods includes:

[0011] Acquiring an image of a registration mark formed by overlapping a first pattern and a second pattern, wherein the first pattern is formed by lines and spaces repeating along a predetermined direction at a first pitch P1 on a layer on a substrate, and the second pattern is formed by lines and spaces repeating along the predetermined direction at a second pitch P2 different from the first pitch P1 on a layer different from the first pattern;

[0012] extracting a brightness signal of the registration mark in the prescribed direction from the acquired image of the registration mark; and

[0013] An absolute position in the predetermined direction is obtained for at least one of the first pattern and the second pattern based on the extracted brightness signal.

[0014] In this specification, a pattern formed on one layer refers to a pattern formed within one layer, and a pattern formed on another layer refers to a pattern formed within another layer.

[0015] The coincidence mark includes:

[0016] The first pattern is formed in a lower layer than the second pattern and a first region where a first registration mark formed by the second pattern overlapping the first pattern is located; and

[0017] The first pattern is formed in a layer above the second pattern and in a second region where a second registration mark formed by the first pattern overlapping the second pattern is located.

[0018] Based on the extracted brightness signal, determining the absolute position in the specified direction for at least one of the first pattern and the second pattern includes: determining the first moiré position X1 in the specified direction of the moiré fringes formed in the first area by overlapping the first pattern and the second pattern based on the brightness signal of the first coincidence mark; and determining the second moiré position X2 in the specified direction of the moiré fringes formed in the second area by overlapping the second pattern and the first pattern based on the brightness signal of the second coincidence mark.

[0019] The first pitch P1 and the second pitch P2 may be smaller than a resolution limit of an imaging unit that captures the registration mark.

[0020] It may also include obtaining at least one of the absolute position AP1 of the pattern provided in the upper layer in the predetermined direction by using equation (3) and the absolute position AP2 of the pattern provided in the lower layer in the predetermined direction by using equation (4).

[0021]

Mathematical formula 1

[0022]

[0023]

Mathematical formula 2

[0024]

[0025] One approach to labeling measurement methods includes:

[0026] Acquiring an image of a registration mark formed in a first area by overlapping a first pattern and a second pattern, wherein the first pattern is formed by lines and spaces repeating along a predetermined direction at a first pitch P1 on a layer on a substrate, and the second pattern is formed by lines and spaces repeating along the predetermined direction at a second pitch P2 different from the first pitch P1 on a layer different from the first pattern;

[0027] acquiring an image of a registration mark formed in the second area by overlapping a third pattern and a fourth pattern, wherein the third pattern is formed by lines and spaces being repeated along the prescribed direction at a third pitch P3 on the one layer, and the fourth pattern is formed by lines and spaces being repeated along the prescribed direction at a fourth pitch P4 different from the third pitch P3 on the other layer;

[0028] extracting a first luminance signal from the acquired image of the registration mark in the first area, the first luminance signal being a luminance signal in the prescribed direction of the registration mark formed in the first area;

[0029] extracting a second luminance signal from the acquired image of the registration mark in the second area, the second luminance signal being a luminance signal in the prescribed direction of the registration mark formed in the second area; and

[0030] An absolute position in the predetermined direction is determined for at least one of the first pattern, the second pattern, the third pattern, and the fourth pattern based on the extracted first and second luminance signals.

[0031] Alternatively, based on the extracted first brightness signal and the second brightness signal, determining the absolute position in a specified direction for at least one of the first pattern, the second pattern, the third pattern and the fourth pattern includes determining, based on the first brightness signal, a first moiré position X1 in the specified direction of the moiré fringes formed by the first pattern and the second pattern in the first area and a second moiré position X2 in the specified direction of the moiré fringes formed by the third pattern and the fourth pattern in the second area.

[0032] It may also include calculating at least one of the absolute position AP1 of the second pattern or the fourth pattern in the prescribed direction set on the other layer by formula (7) and the absolute position AP2 of the first pattern or the third pattern in the prescribed direction set on the one layer by formula (8).

[0033]

Mathematical formula 3

[0034]

[0035]

Mathematical formula 4

[0036]

[0037] Alternatively, determining the first moiré position in the predetermined direction or the second moiré position in the predetermined direction according to the brightness signal includes:

[0038] a. intercepting a signal length that is a positive integer multiple of the period of the moiré fringe from the brightness signal;

[0039] b. preparing a basis function of the moiré fringe signal;

[0040] c. calculating the inner product of the intercepted luminance signal and the basis function within the range of the intercepted signal length;

[0041] d. Based on the calculation result of the inner product, obtaining the frequency component of the moiré fringe signal and detecting the phase of the obtained frequency component;

[0042] e. Determine the first moiré position or the second moiré position based on the detected phase.

[0043] Alternatively, determining the absolute position of at least one of the first pattern and the second pattern in the predetermined direction based on the extracted luminance signal includes at least one of separating the luminance signal of the first pattern from the luminance signal and separating the luminance signal of the second pattern. It should be noted that the luminance signal of the first pattern and the luminance signal of the second pattern may be separated from the luminance signal, and instead of determining the absolute positions of the first and second patterns, the relative position of the first and second patterns in the predetermined direction may be directly determined.

[0044] Alternatively, separating at least one of the brightness signal of the first pattern and the brightness signal of the second pattern from the brightness signal includes:

[0045] a. A signal length that is a positive integer multiple of the period of the pattern to be separated is intercepted from the brightness signal;

[0046] b. preparing a basis function of the brightness signal of the pattern to be separated;

[0047] c. calculating the inner product of the intercepted luminance signal and the basis function within the range of the intercepted signal length; and

[0048] d. Obtaining the frequency component of the brightness signal of the pattern to be separated based on the calculation result of the inner product. It should be noted that the brightness signal separation method can also be applied to the case of obtaining the relative position between the first pattern and the second pattern in the specified direction.

[0049] The mark measurement method may further include resampling the brightness signal at a data pitch. Alternatively, the data pitch may be less than 1 / 2 of the period of the pattern to be separated and a positive integer multiple of the data pitch is a positive integer multiple of the period of the pattern to be separated.

[0050] The basis function may also be a sine function.

[0051] The marking measurement method may also include:

[0052] detecting a phase based on the acquired frequency component of the brightness signal of the pattern to be separated; and

[0053] The absolute position of the pattern is obtained based on the detected phase.

[0054] According to one embodiment, a marking measurement method is provided, comprising:

[0055] generating a brightness signal in the predetermined direction of a registration mark formed by overlapping a first pattern and a second pattern, wherein the first pattern is formed by lines and spaces being repeated along a predetermined direction at a first pitch P1 on a layer on a substrate, and the second pattern is formed by lines and spaces being repeated along the predetermined direction at a second pitch P2 different from the first pitch P1 on a layer different from the first pattern;

[0056] Separating and extracting a luminance signal of the first pattern from the luminance signal; and

[0057] The absolute position of the first pattern is calculated based on the extracted brightness signal of the first pattern.

[0058] The registration mark may also be formed by overlapping the first pattern and the second pattern in a common first region.

[0059] Alternatively, separating and extracting the brightness signal of the first pattern includes:

[0060] Extracting a signal length that is a positive integer multiple of the first interval from the brightness signal;

[0061] preparing a basis function of brightness variation of the first pattern; and

[0062] An inner product of the luminance signal and the basis function is calculated within the range of the truncated signal length.

[0063] Alternatively, the frequency component of the brightness signal of the first pattern may be acquired based on the calculation result of the inner product, and the absolute position of the first pattern may be calculated by detecting the phase of the acquired frequency component.

[0064] Alternatively, based on the extracted brightness signal, the first absolute position of the first pattern in the prescribed direction and the second absolute position of the second pattern in the prescribed direction are determined, and the relative misalignment between the first pattern and the second pattern in the prescribed direction is calculated based on the first absolute position and the second absolute position.

[0065] Alternatively, the predetermined direction may include a first direction and a second direction intersecting the first direction.

[0066] include:

[0067] deriving an absolute position of at least one of the first pattern or the second pattern in the first direction using the above-mentioned marking measurement method; and

[0068] The absolute position of at least one of the first pattern or the second pattern in the second direction is obtained using the above-mentioned marking measurement method.

[0069] Alternatively, the relative displacement between the first pattern and the second pattern in the first direction is calculated based on the absolute positions of the first pattern and the second pattern in the first direction.

[0070] A relative misalignment amount between the first pattern and the second pattern in the second direction is calculated based on the absolute positions of the first pattern and the second pattern in the second direction.

[0071] According to one embodiment, a measuring device for measuring a mark formed on a substrate is provided, comprising:

[0072] a platform configured to form a substrate with the registration mark;

[0073] a camera unit configured to capture the overlap mark; and

[0074] A control device performs control to measure the absolute position of at least one of the first pattern or the second pattern by executing the above-mentioned mark measurement method based on the image of the registration mark captured by the imaging unit.

[0075] According to one embodiment, an exposure device for exposing a substrate to exposure light is provided, comprising:

[0076] a platform configured to form a substrate with the registration mark;

[0077] a camera unit configured to capture the overlap mark; and

[0078] A control device performs control to measure the absolute position of at least one of the first pattern or the second pattern by executing the above-mentioned mark measurement method based on the image of the registration mark captured by the imaging unit.

[0079] According to one embodiment, a computing device is provided, comprising:

[0080] an input unit for inputting information related to the image of the registration mark formed on the substrate;

[0081] a calculation unit that calculates the absolute position of at least one of the first pattern or the second pattern by executing the above-mentioned marking measurement method; and

[0082] An output unit outputs information related to the absolute position of at least one of the first pattern or the second pattern calculated by the calculation unit.

[0083] According to one embodiment, there is provided a program for causing a measurement device or an exposure device to execute the above-described mark measurement method.

[0084] According to one embodiment, there is provided a storage medium storing a program for causing a measurement device or an exposure device to execute the above-described mark measurement method. BRIEF DESCRIPTION OF THE DRAWINGS

[0085] Figure 1 It is a conceptual diagram of coincidence marks and their formation process.

[0086] Figure 2 yes Figure 1 A partially enlarged cross-sectional view of the first coincidence mark among the coincidence marks.

[0087] Figure 3 yes Figure 1 A partially enlarged cross-sectional view of the second coincidence mark in the coincidence mark.

[0088] Figure 4 This is a diagram explaining the advantages of absolute value measurement.

[0089] Figure 5 1 is a diagram showing a registration mark and a luminance signal of an image obtained by capturing the registration mark.

[0090] Figure 6 It is a diagram illustrating separation of a luminance signal.

[0091] Figure 7A : is a flowchart showing a method of extracting a frequency component of a pattern that is desired to be extracted from a luminance signal.

[0092] Figure 7B This is a diagram illustrating separation of a luminance signal using the inner product method.

[0093] Figure 8 This is a conceptual diagram of a registration mark and its formation process according to another embodiment.

[0094] Figure 9 yes Figure 8 A partially enlarged cross-sectional view of the first coincidence mark among the coincidence marks.

[0095] Figure 10 yes Figure 8 A partially enlarged cross-sectional view of the fourth coincidence mark among the coincidence marks.

[0096] Figure 11 is a cross-sectional view of the first reference wafer.

[0097] Figure 12 is a cross-sectional view of the second reference wafer.

[0098] Figure 13 is a cross-sectional view of the third reference wafer.

[0099] Figure 14A It is a front view of the measuring device (viewed from the -Y direction).

[0100] Figure 14B It is a cross-sectional view of the measuring device in the XZ plane.

[0101] Figure 15 It is a cross-sectional view of the measuring device along the YZ plane.

[0102] Figure 16 This is a block diagram showing the input-output relationship of a control device configured around a control system of a measuring device.

[0103] Figure 17 This is a schematic diagram of an exposure device.

[0104] Figure 18 This is a block diagram showing the input and output relationship of the exposure control device included in the exposure apparatus. DETAILED DESCRIPTION

[0105] Hereinafter, the method for implementing the invention will be described with reference to the accompanying drawings. The accompanying drawings are schematically shown. The dimension ratios and quantities shown in the drawings may not necessarily be consistent with the actual dimension ratios and quantities. The accompanying drawings are appropriately represented using the XYZ coordinate system. The specification is described with reference to the XYZ coordinate system as appropriate. In this specification, when expressing a direction, when distinguishing between positive and negative directions, the positive and negative symbols are marked and shown in the form of "+X direction" and "-X direction". When expressing a direction without distinguishing between positive and negative directions, it is simply referred to as "X direction". That is, in this specification, the case of simply referring to "X direction" includes both "+X direction" and "-X direction". The same applies to the Y direction and the Z direction.

[0106] <First embodiment>

[0107] A first embodiment of the marking measurement method will be described.

[0108] [Coincidence Mark]

[0109] Reference Figure 1 、 Figure 2 and Figure 3To illustrate the coincidence mark. Figure 1 1 is a conceptual diagram of two overlay marks (OM1, OM2) formed on a substrate W1 and their formation process. Figure 2 1 is a partially enlarged cross-sectional view of a first registration mark OM1 formed in a first region on the substrate W1. Figure 3 It is a partially enlarged cross-sectional view of the second registration mark OM2 formed in the second region on the substrate W1.

[0110] like Figure 1 As shown, the first coincidence mark OM1 is an FBO mark formed by overlapping the second pattern LS2 and the first pattern LS1. The second coincidence mark OM2 is an FBO mark formed by overlapping the first pattern LS1 and the second pattern LS2. The first pattern LS1 is formed by lines and spaces extending in the Y direction repeated in the X direction at a first pitch P1. The second pattern LS2 is formed by lines and spaces extending in the Y direction repeated in the X direction at a second pitch P2. The first pitch P1 and the second pitch P2 are different values. In other words, the first coincidence mark OM1 and the second coincidence mark OM2 are both composed of two patterns (LS1, LS2) with different pitches, and the order of formation of the two patterns (LS1, LS2) is swapped.

[0111] The first pitch P1 of the first pattern LS1 and the second pitch P2 of the second pattern LS2 constituting the registration marks (OM1, OM2) are both 100 nm or more, preferably 1000 nm or less, and more preferably 200 nm or more and 720 nm or less.

[0112] The first area where the first overlap mark OM1 is formed and the second area where the first overlap mark OM2 is formed may be arranged close to each other to such an extent that they are in the same field of view of a camera photographing the overlap marks (OM1, OM2). Conversely, the first area and the second area may be arranged apart to such an extent that they are not in the same field of view of a camera photographing the overlap marks (OM1, OM2).

[0113] like Figure 2 As shown, in the first registration mark OM1, the first pattern LS1 is formed on the first layer 1 on the substrate W1. The second pattern LS2 is formed on the second layer 2 located above the first layer 1. Figure 3As shown, in the second overlap mark OM2, the second pattern LS2 is formed on the first layer 1 on the substrate W1. The first pattern LS1 is formed on the second layer 2 which is located above the first layer 1. The first pattern LS1 of the first overlap mark OM1 and the second pattern LS2 of the second overlap mark OM2 are formed on the same first layer 1. The second pattern LS2 of the first overlap mark OM1 and the first pattern LS1 of the second overlap mark OM2 are formed on the same second layer 2. Hereinafter, a pattern formed in the first layer 1 which is located below the second layer 2 will sometimes be referred to as a "lower layer pattern." A pattern formed in the second layer 2 which is located above the first layer 1 will sometimes be referred to as an "upper layer pattern."

[0114] An intermediate layer 3 having one or more layers may be formed between the first layer 1 and the second layer 2. The intermediate layer 3 is thin enough to allow the lower layer pattern formed in the first layer 1 to be measured using measurement light. The intermediate layer 3 being thin enough to be measured does not necessarily need to be thin enough to allow the lower layer pattern itself to be recognized in an image; it only needs to be thin enough to allow moiré fringes to be observed when the lower layer pattern overlaps with the upper layer pattern.

[0115] The moiré fringes are explained. When the coincidence marks (OM1, OM2) are photographed, moiré fringes formed by the interference of two patterns (LS1, LS2) with different spacings can be obtained in the image. Even in the case where the first spacing P1 or the second spacing P2 is less than the resolution limit of the imaging unit and the imaging unit cannot recognize the first pattern LS1 or the second pattern LS2, as long as the moiré fringes are formed and the pattern size of the moiré fringes is greater than the resolution limit of the imaging unit, the coincidence marks (OM1, OM2) can still be measured. Of course, in the case where the first spacing P1 or the second spacing P2 is greater than the resolution limit of the imaging unit and the imaging unit can recognize the first pattern LS1 or the second pattern LS2, the coincidence marks (OM1, OM2) can also be measured.

[0116] A plurality of coincidence marks (OM1, OM2) are arranged in correspondence with each shooting area in the scribe area within each shooting area of ​​the substrate W1. The coincidence marks (OM1, OM2) are preferably arranged in 10 to 50 numbers, for example. The coincidence marks may also be set in all shooting areas. There may also be more than 1,000 coincidence marks on the entire chip. The measurement of the coincidence marks does not necessarily measure all the coincidence marks on the substrate W1. Alternatively, a plurality of coincidence marks may be measured for each shooting area. In addition, the coincidence marks to be measured may also be selected according to the purpose of the measurement. Preferably, based on the measurement results of a plurality of coincidence marks, an enhanced global alignment (EGA) measurement of the arrangement of the shooting areas on the chip is calculated by a statistical method.

[0117] exist Figures 1 to 3In the figure, as the measurement object, there is shown an overlap mark having an upper pattern and a lower pattern formed by repeating lines and intervals extending in the Y direction in the X direction (hereinafter sometimes referred to as "overlap mark in the X direction"), but the shape of the overlap mark as the measurement object is not limited to this. An overlap mark having an upper pattern and a lower pattern formed by repeating lines and intervals in a direction intersecting the X direction may also be applied to the measurement object. In particular, it is preferred to apply an overlap mark having an upper pattern and a lower pattern repeated in the Y direction (hereinafter sometimes referred to as "overlap mark in the Y direction") to the measurement object. An overlap mark in which the overlap mark in the X direction and the overlap mark in the Y direction are arranged close to each other may also be used. In this case, since the overlap mark in the X direction and the overlap mark in the Y direction that are arranged close to each other can be brought into the same field of view, the movement of the observation position of the mark detection system MDS (described later) between the overlap marks can be reduced, and the measurement time can be shortened.

[0118] The composition and configuration of the coincidence marks can be implemented in a variety of ways. For example, it is also possible to configure two groups of coincidence marks (OM1, OM2). In addition, it is also possible to configure two groups of coincidence marks in the X direction (OMx1, OMx2) and two groups of coincidence marks in the Y direction (OMy1, OMy2), totaling four groups of coincidence marks, to be arranged close to each other. In the case of the four groups of coincidence marks, the two groups of coincidence marks in the X direction (OMx1, OMx2) can be arranged to be point-symmetrical, the coincidence marks in the Y direction (OMy1, OMy2) can be arranged to be point-symmetrical relative to the same point, the four groups of coincidence marks can be divided into four quadrants and arranged close to each other, or the four groups of coincidence marks can be arranged to be line-symmetrical relative to the X-axis direction or the Y-axis direction.

[0119] [Absolute position measurement of moiré fringes]

[0120] A light source irradiates detection light onto the registration marks (OM1, OM2), and an imaging unit captures the light reflected by the registration marks (OM1, OM2). The positions of the upper and lower layers of the pattern are determined from the captured images of the registration marks (OM1, OM2). Details of a measurement device equipped with a mark detection system for detecting registration marks, or an exposure device equipped with an alignment detection system for detecting registration marks, will be described later.

[0121] If the lower and upper patterns are misaligned, the position of the moiré fringes in the registration marks (OM1, OM2) changes. The inventors of this application have discovered that by measuring the absolute position of the moiré fringes in the registration marks (OM1, OM2), the absolute positions of the lower and upper patterns can be inversely calculated. A mark measurement method using this method is now described.

[0122] First, a luminance signal is extracted from the measured image of the coincidence marks (OM1, OM2). The absolute position (X1, X2) of the moiré fringe can be obtained based on the luminance signal IS. The absolute position X1 of the moiré fringe of the first coincidence mark OM1 (see Figure 1 Hereinafter, it may be referred to as "the first moiré position X1". ) is expressed as the distance in the X-axis direction between the position of the moiré fringe of the first coincidence mark OM1 and the coordinate origin SP. The absolute position X2 of the moiré fringe of the second coincidence mark OM2 (see Figure 1 . Hereinafter, it may be referred to as "the second moiré position X2". ) is represented as the distance in the X-axis direction between the position of the moiré fringe of the second coincidence mark OM2 and the coordinate origin SP. Figure 1 In the , the peak point near the center of the moiré fringes (interference fringes) of the coincidence marks (OM1, OM2) (the vertex of the second central peak of the three peaks contained in the interference fringes) is set as the position in the X direction of the moiré fringes of the coincidence marks (OM1, OM2). However, the position of the moiré fringes of the coincidence marks (OM1, OM2) can also be set based on other setting references. The coordinate origin SP can be set arbitrarily. The coordinate origin SP can also be set based on the coordinate system of the measurement device or exposure device.

[0123] The absolute position AP1 of the upper layer pattern in the X direction and the absolute position AP2 of the lower layer pattern in the X direction can be obtained from the first moiré position X1 and the second moiré position X2.

[0124] Moiré fringes are formed by the interference of the first pattern LS1 and the second pattern LS2. The first moiré position X1 and the second moiré position X2, which are the absolute positions of the moiré fringes in the overlap marks (OM1, OM2), can be expressed by equations (1) and (2) using the absolute position AP1 and AP2 of the upper and lower patterns in the X direction, respectively, and the first pitch P1 and second pitch P2 of the first and second patterns LS1, respectively.

[0125]

Mathematical formula 5

[0126]

[0127]

Mathematical formula 6

[0128]

[0129] Next, by solving AP1 and AP2 from equations (1) and (2), the following equations (3) and (4) can be obtained.

[0130]

Mathematical formula 7

[0131]

[0132]

Mathematical formula 8

[0133]

[0134] The first pitch P1 of the first pattern LS1 and the second pitch P2 of the second pattern LS2 are known. Using equations (3) and (4), the absolute position AP1 of the upper pattern in the X direction and the absolute position AP2 of the lower pattern in the X direction can be calculated from the absolute positions (X1, X2) of the two moiré fringes.

[0135] [Advantages of absolute position measurement]

[0136] Reference Figure 4 The advantages of absolute position measurement are explained below. When the absolute position AP1 of the upper pattern in the X direction and the absolute position AP2 of the lower pattern in the X direction are clearly determined, the relative error ΔAP of the overlap between the upper and lower patterns is obtained by calculating the difference between AP1 and AP2. In addition, when the absolute position AP1 of the upper pattern in the X direction, the absolute position AP2 of the lower pattern in the X direction, and the overlap error ΔAP are clearly determined, for example, the absolute position U2 of the lower pattern of the overlap mark OM3 can be inferred based on the measurement result of the absolute position U1 of only the upper pattern in the other overlap mark OM3. Although not shown in the figure, conversely, the absolute position U2 of the lower pattern of the other overlap mark OM3 can also be measured and the absolute position U1 of the upper pattern can be inferred by calculation. Through these inferences, the measurement speed of the overlap measurement can be increased or the measurement accuracy can be improved. On the other hand, in a method that directly measures the relative positions of the upper and lower patterns without measuring their absolute positions from the registration mark, it is impossible to infer the positions of the upper or lower patterns in other registration marks OM3. In other words, the above-mentioned effect is achieved only by measuring the absolute positions of the upper and lower patterns.

[0137] Furthermore, by separately measuring the absolute positions of the upper and lower patterns, the alignment errors of the multiple shot regions formed in the upper and lower patterns can be determined. This allows the determination of which layer's misalignment (alignment error) causes the overlay error between the upper and lower patterns. Furthermore, by feeding this alignment error back to one or both of the exposure devices exposing the upper and lower patterns, overlay errors can be reduced.

[0138] <Second embodiment>

[0139] A second embodiment of the mark measurement method will be described. Features common to the first embodiment will be omitted. For example, features related to the structure of the superimposed mark are the same as those of the first embodiment, and reference can be made to the description of the first embodiment.

[0140] [Position measurement based on separation of luminance signals]

[0141] As a method for acquiring the positions of the upper and lower patterns from images of the registration marks (OM1, OM2), the inventors of the present application have proposed a method for separating luminance signals obtained by imaging the registration marks.

[0142] Figure 5 This diagram conceptually illustrates the extraction of a brightness signal IS in the width direction of a pattern (the direction in which the line and space pattern repeats) from an image captured of an overlay mark OM. The brightness signal IS is plotted as a graph with the width direction of the pattern (the direction in which the line and space pattern repeats) on the horizontal axis and the brightness (intensity) of the signal obtained from the image on the vertical axis.

[0143] Reference Figure 6 Explain the separation of luminance signal. Figure 5 As shown, Figure 6 The brightness signal IS shown on the left side of the image is obtained by imaging the registration mark OM. The brightness signal IS includes components of reflected light from the upper pattern, reflected light from the lower pattern, and interference light between the upper and lower patterns (i.e., light that forms moiré fringes). Because each of these components has a unique frequency, the brightness signal IS can be frequency-decomposed. Figure 6 1 and 2. The luminance signal IS is subjected to frequency decomposition to extract a signal component 82 based on reflected light from the upper pattern, a signal component 81 based on reflected light from the lower pattern, and a signal component 83 based on interference light between the upper and lower patterns.

[0144] By detecting the phase based on the extracted signal component 82 based on the reflected light from the upper pattern, the absolute position AP1 of the upper pattern in the X direction can be determined. Similarly, for the lower pattern, by detecting the phase based on the signal component 81, the absolute position AP2 of the lower pattern in the X direction can be determined. The advantages of determining the absolute positions (AP1, AP2) of the upper and lower patterns are the same as those described in the first embodiment.

[0145] [Separation of Luminance Signal Using Inner Product Method]

[0146] Conventionally, as a method for extracting specific frequency components from a luminance signal containing multiple frequencies, a method using a discrete Fourier transform (hereinafter sometimes referred to as "DFT") is known. The DFT can be applied to the separation of the luminance signal IS described above. However, when using the DFT to determine the absolute position of the upper and lower patterns, the signals of the separated upper and lower patterns contain a large phase error. Therefore, the detected position error increases. According to the analysis of the inventors of the present application, one of the reasons for this is that the signal to which the DFT is applied is assumed to be an infinite length signal, while the actual luminance signal IS is a finite length signal.

[0147] Therefore, the inventors of the present application propose a method of extracting a specific frequency component from the actual brightness signal IS, thereby separating a signal of a pattern to be separated from the brightness signal IS. Figure 7A and Figure 7B This method will be described in detail. Figure 7A : is a flowchart showing a method of extracting a frequency component of a pattern desired to be extracted from the luminance signal IS. Figure 7B The left side of FIG. 1 is an example of a brightness signal IS obtained from an image, and the right side is an example of a basis function of a signal to be extracted.

[0148] Reference Figure 7A An example of this method is described. First, an image of the overlapping mark is acquired (step S1). Next, a one-dimensional brightness signal IS is created along a specified direction (for example, the X direction) based on the image data (step S2). Next, the brightness signal is resampled in such a way that a positive integer multiple of the data spacing d becomes a positive integer multiple of the period of the pattern to be separated (step S3). At this time, the data spacing d is set so that the data spacing d is less than half the period of the pattern to be separated. Next, the brightness signal IS is intercepted at a positive integer multiple of the period of the pattern to be separated (step S4). In parallel with the above process or in advance, a basis function corresponding to the period of the pattern to be separated is prepared (step S5).

[0149] Here, Figure 7B The signal 84 on the left side of the figure represents a signal of finite length obtained by cutting a signal length that is a positive integer multiple of the period of the pattern to be extracted from the brightness signal IS. The signal 84 shows a plurality of resampling points 86 resampled at the data pitch d. Figure 7B In the example of , there are 29 resampling points 86. Therefore, the signal 84 has a length that is 28 times (a positive integer multiple) the data interval d. Figure 7B The curve 85 on the right side of the graph is the basis function of the frequency to be extracted. As the basis function, a sine function with a length that is a positive integer multiple of the period of the frequency to be extracted can be used. Figure 7B, a sine function with four cycles is shown as the basis function. That is, 28 times (a positive integer multiple) the data pitch d becomes four cycles of the basis function (a positive integer multiple of one cycle), and signal 84 is a signal extracted from the luminance signal IS with four cycles (a positive integer multiple) of the basis function.

[0150] Next, the inner product of the signal 84 and the basis function shown in the curve 85 is calculated within the intercepted signal range (step S6). In this way, the frequency component to be extracted can be more accurately extracted from the finite length signal 84. Then, the phase and amplitude are calculated based on the result of the inner product calculation (step S7). Next, the position of the pattern to be separated is calculated based on the calculated phase (step S8). The position of the pattern as the calculation result is output (step S9). By calculating the phase of the frequency component extracted in this way, the position of the pattern to be separated (the absolute position of the upper pattern or the lower pattern) can be more accurately determined.

[0151] This signal separation method is sometimes referred to as signal separation using the inner product method. Signal separation using the inner product method can accurately calculate the position of the pattern compared to signal separation using DFT. It should be noted that it is preferred that the basis function of the frequency you want to extract is selected in a manner that is orthogonal to the function of the frequency you want to exclude (that is, frequencies other than the frequency you want to extract, noise components). By selecting in this way, the influence of the frequency you want to exclude can be eliminated. In addition, in the case where the signal 84 can be intercepted from the brightness signal IS at a positive integer multiple of the period of the spacing of the pattern to be separated, resampling (interpolation processing) can also be omitted.

[0152] The above describes how to determine the absolute X-direction position AP1 of the upper pattern and the absolute X-direction position AP2 of the lower pattern based on the luminance signal IS. Alternatively, the interference light signal component 83 (i.e., the light forming the moiré fringes) between the upper and lower patterns can be separated from the luminance signal IS, and the absolute X-direction position of the moiré fringes can be detected based on this signal component 83. Specifically, after resampling the luminance signal IS by truncating the signal length at a positive integer multiple of the moiré fringes' pitch, the inner product of the frequency of the moiré fringes signal and the basis function is calculated. Thus, by extracting the frequency component of the moiré fringes signal and detecting the phase of the extracted frequency component, the absolute position of the moiré fringes can be determined based on the phase. Separating the moiré fringe signal from the brightness signal IS and detecting the absolute position of the moiré fringe is not a necessary process in this second embodiment. However, if the absolute position of the moiré fringe can be detected, the absolute position AP1 of the upper pattern in the X direction and the absolute position AP2 of the lower pattern in the X direction can be calculated using equations (1) to (4) described in the first embodiment.

[0153] Signal separation using the inner product method is a method for accurately separating the luminance signal IS. However, it is also possible to determine not only the absolute position of the upper or lower pattern but also the relative position of the upper and lower patterns based on the separated signal components. In other words, luminance signal separation using the inner product method can be used not only for absolute position measurement but also for relative position measurement.

[0154] <Third embodiment>

[0155] [Another embodiment of the overlap mark]

[0156] A third embodiment of the marking measurement method will be described. Figure 8 、 Figure 9 and Figure 10 The features of the measured overlap marks are described. Features of the third embodiment that are common to the first and second embodiments are omitted. For example, regarding the overlap mark measurement method, any portion not included in the following description can be referenced to the description of the first and second embodiments.

[0157] Figure 8 1 is a conceptual diagram of two overlay marks (OM1 and OM4) formed on a substrate W1 and their formation process. Figure 9 is a partially enlarged cross-sectional view of a first registration mark OM1 formed in a first region on the substrate W1. Figure 10 3 is a partially enlarged cross-sectional view of the second registration mark OM4 formed in the second region on the substrate W1.

[0158] like Figure 8 As shown, the first overlap mark OM1 is an FBO mark formed by overlapping the second pattern LS2 and the first pattern LS1. The fourth overlap mark OM4 is an FBO mark formed by overlapping the fourth pattern LS4 and the third pattern LS3. The first pattern LS1 is formed by lines and spaces extending in the Y direction repeating in the X direction at a first pitch P1. The second pattern LS2 is formed by lines and spaces extending in the Y direction repeating in the X direction at a second pitch P2. The third pattern LS3 is formed by lines and spaces extending in the Y direction repeating in the X direction at a third pitch P3. The fourth pattern LS4 is formed by lines and spaces extending in the Y direction repeating in the X direction at a fourth pitch P4. The first pitch P1 and the second pitch P2 are different values. The third pitch P3 and the fourth pitch P4 are different values.

[0159] The difference between the coincidence mark disclosed in the third embodiment and the coincidence mark disclosed in the first embodiment is that the first pitch P1 and the fourth pitch P4 are different values ​​from each other, and the second pitch P2 and the third pitch P3 are different values ​​from each other. Figure 9As shown, the lower pattern in the first registration mark OM1 is the first pattern LS1, and the upper pattern is the second pattern LS2. Figure 10 As shown, the fourth coincidence mark OM4 is not Figure 9 In the form where the formation order of the two patterns (LS1, LS2) shown is reversed, the lower pattern is the third pattern LS3 and the upper pattern is the fourth pattern LS4.

[0160] Even with two coincidence marks (OM1, OM4) composed of these four patterns (LS1 to LS4), the absolute position of the moiré fringes can be measured. It should be noted that, assuming that the first and fourth pitches P1 and P4 are the same value, and the second and third pitches P2 and P3 are the same value, the coincidence mark is equivalent to the coincidence mark described in the first embodiment in which the order of formation of the two patterns (LS1 and LS2) is reversed. Therefore, the absolute position of the moiré fringes can naturally be measured.

[0161] A method of obtaining the absolute position AP1 and the absolute position AP2 of the upper layer pattern in the X direction from the first moiré position X1 of the registration mark OM1 and the second moiré position X2 of the registration mark OM4 will be described.

[0162] First, the first moiré position X1 and the second moiré position X2, which are the absolute positions of the moiré fringes in the overlap marks (OM1 and OM4), are formulated. These moiré positions (X1 and X2) can be expressed using the absolute position AP1 and the absolute position AP2 of the upper pattern in the X direction, as well as the first pitch P1 of the first pattern LS1, the second pitch P2 of the second pattern LS2, the third pitch P3 of the third pattern LS3, and the fourth pitch P4 of the fourth pattern LS4, using equations (5) and (6), respectively.

[0163]

Mathematical formula 9

[0164]

[0165]

Mathematical formula 10

[0166]

[0167] Next, by solving AP1 and AP2 according to equations (5) and (6), the following equations (7) and (8) can be obtained.

[0168]

Mathematical formula 11

[0169]

[0170]

Mathematical formula 12

[0171]

[0172] The first pitch P1 of the first pattern LS1, the second pitch P2 of the second pattern LS2, the third pitch P3 of the third pattern LS3, and the fourth pitch P4 of the fourth pattern LS4 are known. Using equations (7) and (8), the absolute position AP1 of the upper pattern in the X direction and the absolute position AP2 of the lower pattern in the X direction can be calculated based on the absolute positions (X1, X2) of the two moiré fringes.

[0173] The above describes three embodiments of the mark measurement method. The above mark measurement method can be incorporated into the measurement device or exposure device described later to measure the overlay mark. Details of the measurement device and exposure device will be described later. Furthermore, the above mark measurement method can also be used to measure overlay marks formed on the reference substrate described below. This is described in detail below.

[0174] <Use of reference substrate>

[0175] When a substrate is adsorbed on a substrate holder, the substrate may sometimes be deformed. In particular, the form and amount of deformation of the substrate may differ between different substrate holders. Furthermore, the difference in the form and amount of deformation of the substrate may affect the measurement results of the overlap mark. The overlap measurement device and the exposure device equipped with the overlap measurement device have inherent substrate holders. Therefore, even when measuring the same substrate, the measurement results may be different between different measurement devices, between the measurement device and the exposure device, and between different exposure devices. In addition, even when measuring the same substrate with the same device, the form and amount of deformation of the substrate may change each time it is adsorbed on the substrate holder, resulting in different measurement results.

[0176] Overlay measurement is used to match the measurement performance of multiple measuring devices or exposure devices, or to periodically calibrate the measurement accuracy of a measuring device or exposure device. Errors in overlay measurement caused by differences in substrate holders and the timing of substrate placement can reduce inspection results, the accuracy of measurement performance matching, and the accuracy of calibration. Therefore, when performing overlay measurement for these purposes, it is preferable to use a high-precision substrate that is less likely to affect the measurement results. For example, a reference substrate, which is less likely to deform even when attached to a substrate holder than a substrate used in product manufacturing, is preferably used as a high-precision substrate.

[0177] As a reference substrate, it is preferable to use a reference wafer with an external shape similar to that of the wafer used for product manufacturing. Using a reference wafer can reduce the amount of deformation of the substrate when it is adsorbed onto the substrate holder, compared to wafers used for product manufacturing (e.g., single crystal silicon wafers). Furthermore, the reproducibility of the deformation of the reference wafer is higher than that of the wafer used for product manufacturing. Therefore, by using a reference wafer, errors caused by substrate deformation can be eliminated during overlay measurements for matching between measurement devices or exposure devices, as well as during regular overlay measurements to check the measurement accuracy of the measurement devices or exposure devices, thereby improving the measurement accuracy of the measurement devices, the measurement accuracy of the exposure devices, and the overlay accuracy.

[0178] The reference wafer has a different structure from the single crystal silicon wafer used in product manufacturing. The reference wafer is preferably a multilayer structure rather than a single layer structure. Here, a three-layer reference wafer is specifically described, enabling high-precision overlay measurement.

[0179] A three-layer reference wafer has a central layer located in the thickness direction and two layers sandwiching the central layer. Because different functions can be assigned to the wafer between the central layer and the two layers, a three-layer reference wafer can be easily designed to improve measurement accuracy. Furthermore, if the two layers sandwiching the central layer are made of the same material, the thermal expansion coefficients are consistent on both sides, making it possible to design a wafer that deforms minimally with temperature changes. The following is an example of a three-layer reference wafer.

[0180] [First reference wafer]

[0181] Figure 11 A cross-sectional view of the first reference wafer RF1 is shown. The first reference wafer RF1 includes a base material 91 made of single-crystal silicon, a first layer 92 provided on one surface of the base material 91, and a second layer 93 provided on the other surface of the base material 91. For example, SiC (silicon carbide) is used as the first layer 92 and the second layer 93. SiC has a higher hardness than the base material 91 made of single-crystal silicon. In the first reference wafer RF1, the surface hardness is higher than the internal hardness, making it a wafer resistant to deformation.

[0182] The first layer 92 and the second layer 93 may be made of substantially the same material. The first layer 92 and the second layer 93 may also be designed to have substantially the same thickness. However, this is not limiting. For example, the first layer 92 and the second layer 93 may be intentionally made of different materials, or may be intentionally designed to have different thicknesses. The thickness of the first layer 92 and the second layer 93 may also be thicker than that of the base material 91.

[0183] [Second reference wafer]

[0184] Figure 12The second reference wafer RF2 is shown. The second reference wafer RF2 includes a base material 94 made of a non-metallic material, a first layer 95 provided on one surface of the base material 94, and a second layer 96 provided on the other surface of the base material 94. For example, ceramics are used as the base material. Ceramics have high hardness and are resistant to deformation. As a result, the second reference wafer RF2 becomes a wafer that is more resistant to deformation than single crystal silicon wafers used for product manufacturing. In addition, ceramics have advantages such as high chemical resistance and can be cleaned with hydrofluoric acid, and high heat resistance. As ceramics, for example, polycrystals of aluminum oxide are used. Polycrystals of aluminum oxide have a high Young's modulus and their physical properties are close to those of sapphire, making them suitable for base materials.

[0185] The first layer 95 and the second layer 96 may also have a small thickness that can be called a film, for example, a thickness of less than 1 μm. The first layer 95 and the second layer 96 are preferably less than 600 nm in thickness. The first layer 95 and the second layer 96 are preferably silicon, for example. If a silicon film is formed on the surface of the base material 94, the surface of the second reference wafer RF2 can be processed to the same level of surface roughness as the wafer used for product manufacturing by grinding the silicon film with CMP or the like. The surface roughness Ra of the pattern forming side of the second reference wafer RF2 can be, for example, less than 5 nm, preferably less than 1 nm. In addition, since the first layer 95 and the second layer 96 function as a protective layer to prevent metal contamination, metal contamination can be reduced by using the second reference wafer RF2.

[0186] In the above description, the first layer 95 and the second layer 96 are made of substantially the same material, but different materials may be intentionally selected for the first layer 95 and the second layer 96. The first layer 95 and the second layer 96 may be designed to have substantially the same thickness, or they may intentionally have different thicknesses.

[0187] [Third reference wafer]

[0188] Figure 13 The third reference wafer RF3 is shown. The third reference wafer RF3 includes a central layer 97 made of a resin or the like, a first layer 98 provided on one surface of central layer 97, and a second layer 99 provided on the other surface of central layer 97. Central layer 97 is made of, for example, polyimide. Polyimide is excellent as a reference wafer in terms of heat resistance, chemical resistance, and Young's modulus.

[0189] Unlike the first and second reference wafers RF1 and RF2, the third reference wafer RF3 uses a softer material for its central layer 97, which is less hard than the first and second layers 98 and 99. Consequently, localized strain within the third reference wafer RF3 is less likely to diffuse and propagate. As a result, the third reference wafer RF3 is able to suppress strain overall compared to single crystal silicon wafers used in product manufacturing.

[0190] The resin used for the center layer 97 may be a material used as an adhesive for bonding the first layer 98 and the second layer 99. The resin used for the center layer 97 may be a thermosetting resin or a photocurable resin.

[0191] First layer 98 and second layer 99 are made of, for example, single crystal silicon. Since the surface is made of single crystal silicon, it can be formed into a surface similar to that of wafers used for product manufacturing. Furthermore, since single crystal silicon is easily polished, first layer 98 and second layer 99 can be polished to a thickness similar to that of wafers used for product manufacturing.

[0192] exist Figure 13 In the third reference wafer RF3 shown, the thickness of central layer 97 is preferably thinner than that of first layer 98 and second layer 99. The thickness of second layer 99 can be, for example, 50 μm or less, preferably 30 μm or less, for example, preferably 5 μm or more, preferably 10 μm or more. The thickness of first layer 98 is preferably thicker than that of second layer 99. The thickness of first layer 98 is preferably 300 μm or more, preferably 500 μm or more. The thickness of second layer 99 is preferably 200 μm or less, preferably 150 μm or less. The first layer 98 and second layer 99 can be made of substantially the same material, or they can be made of intentionally different materials.

[0193] <Measuring device>

[0194] An example of a measuring device for measuring the above-mentioned registration mark is shown. Figure 14A A front view (viewed from the −Y direction) of the measuring device 100 is shown with some parts omitted. Figure 14B A cross-sectional view of the measuring device 100 cut along an XZ plane passing through an optical axis AX1 of a mark detection system MDS described later is shown with some omissions. Figure 15 A cross-sectional view of the measuring device 100 cut along a YZ plane passing through the optical axis AX1 is partially omitted. Figure 14A 、 Figure 14B and Figure 15 The measuring device 100 shown in FIG. 1 is housed in a housing (not shown).

[0195] The measuring device 100 is provided with a mark detection system MDS for detecting the above-mentioned overlap mark OM. In the following, the direction of the optical axis AX1 of the mark detection system MDS is set to the Z-axis direction. In the plane orthogonal to the Z-axis, the direction in which the movable platform described later moves with a long stroke is set to the Y-axis direction. The direction orthogonal to the Z-axis and the Y-axis is set to the X-axis direction. The rotation (tilt) directions around the X-axis, the Y-axis and the Z-axis are set to the θx, θy and θz directions, respectively. The mark detection system MDS has an L-shaped appearance when viewed from the side (for example, viewed from the +X direction). The mark detection system MDS has a cylindrical lens barrel at the lower end (front end) of the mark detection system MDS. An optical system (for example, a diffraction optical system) composed of a plurality of lens elements having an optical axis AX1 in the Z-axis direction is housed inside the lens barrel. 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.

[0196] The measuring device 100 includes: a platform 12 (see Figure 14A ); a wafer slider 10 (hereinafter sometimes referred to as "slider 10") configured on the platform 12 and holding the wafer W and capable of slight movement. Figure 14A ); a drive system 20 for driving the sliding member 10 (in Figure 14A Not shown, see Figure 16 ); measuring the position information of the slide 10 relative to the platform 12 of the first position measurement system 30 (in Figure 14A Not shown, see Figure 14B 、 Figure 15 、 Figure 16 ); a mark detection system MDS for detecting a mark on a wafer W carried (or held) on the slide 10; a second position measurement system 50 (in Figure 14A Not shown, see Figure 16 ); and control means 60 (in Figure 14A Not shown, see Figure 16 ). It should be noted that the wafer W includes the above-mentioned reference substrate and a substrate for product manufacturing.

[0197] The platform 12 has an upper surface that is substantially parallel to the XY plane perpendicular to the optical axis AX1. The slide 10 can move relative to the platform 12 in the X-axis and Y-axis directions with a specified stroke, and can move slightly (micro-displacement) in the Z-axis, θx, θy and θz directions. The first position measurement system 30 measures the position information of the slide 10 relative to the platform 12 in each direction (hereinafter referred to as "6 degrees of freedom directions") of the X-axis, Y-axis, Z-axis, θx, θy and θz. The control device 60 can also control the drive system 20 to drive the slide 10, and obtain measurement information based on the first position measurement system 30 and measurement information based on the second position measurement system 50, and use the mark detection system MDS to obtain the position information of multiple marks on the chip W held on the slide 10.

[0198] More specifically, the platform 12 has a rectangular (or square) shape when viewed from above. The top surface of the platform 12 is finished to a very high degree of flatness, forming a guide surface for the movement of the slider 10. The platform 12 is made of a material with a low thermal expansion coefficient, also known as a zero-expansion material (e.g., Invar-type alloy, ultra-low expansion cast steel, or ultra-low expansion glass ceramic).

[0199] Alternatively, a cavity may be formed on the platform 12, and the vibration isolation device 14 may be disposed inside the cavity (see Figure 15 ). The vibration isolation device 14 may also be provided in plurality. Although not shown in the figure, the platform 12 has cavities in three locations, and three vibration isolation devices 14 are arranged in each cavity. The platform 12 is supported by the three vibration isolation devices 14. On the upper surface of the base frame 16 provided on the floor and parallel to the XY plane, the platform 12 is supported at three points in such a manner that the upper surface is roughly parallel to the XY plane. It should be noted that the number of vibration isolation devices 14 is not limited to three.

[0200] The vibration isolation device 14 can also constitute at least a part of an active vibration isolation system (Active Vibration Isolation System, also called "AVIS"). The vibration isolation device 14 can also selectively include an accelerometer, a displacement sensor (such as an electrostatic capacitance sensor, etc.) and an actuator (such as a voice coil motor, etc.) and an air spring (air mount, isolator) that functions as an air damper. The internal pressure of the gas in the gas chamber of the air spring is high, and it is difficult to ensure the control response (for example, up to about 20Hz). Therefore, if the vibration isolation device 14 includes both an actuator and an air spring, high-response control can be achieved by controlling the actuator. In addition, if the actuator is controlled according to the output of the accelerometer (not shown), higher-response control can be achieved. Micro-vibrations such as floor vibrations can also be isolated by air springs. The vibration isolation device 14 can avoid vibrations between the platform 12 and the base frame 16 (see Figure 14B) between the vibration. It should be noted that a hydraulic damper can also be used instead of the air spring.

[0201] The upper end surface of the vibration isolation device 14 is connected to the platform 12. Gas (e.g., compressed air) can be supplied to the air spring via a gas supply port (not shown). The air spring expands and contracts in the Z-axis direction with a predetermined stroke (e.g., approximately 1 mm) depending on the amount of gas filled within (changes in the compressed air pressure). Therefore, by using the air springs in each of the three vibration isolation devices 14 to independently move three locations of the platform 12 up and down from below, the positions of the platform 12 and the slider 10 supported thereon in the Z-axis, θx, and θy directions can be arbitrarily adjusted.

[0202] The actuator of the vibration isolation device 14 drives the stage 12 not only in the Z-axis direction but also in the X-axis and Y-axis directions.

[0203] The three vibration isolation devices 14 are connected to the control device 60 (see Figure 16 ). It should be noted that the three vibration isolation devices 14 may also be respectively equipped with actuators capable of moving the platform 12 in, for example, 6 degrees of freedom directions rather than the X-axis direction, the Y-axis direction, and the Z-axis direction. The control device 60 always controls the actuators of the three vibration isolation devices 14 in real time. The control is preferably performed based on the relative position information of the mark detection system MDS and the platform 12 measured by the second position measurement system 50. The control may also be performed on the head 32 (see Figure 14B 、 Figure 15 The position of the platform 12 in the six degrees of freedom (DOF) direction is maintained in a desired positional relationship relative to the marker detection system MDS. It should be noted that feedforward control can also be performed on each of the three vibration isolation devices 14. For example, the control device 60 can also perform feedforward control on each of the three vibration isolation devices 14 based on the measurement information of the first position measurement system 30.

[0204] like Figure 15As shown, four bearings 18 are installed on the sliding member 10. In this embodiment, air static pressure bearings (air bearings) are used as the bearings 18. One bearing 18 is installed at each of the four corners of the bottom surface of the sliding member 10. The bearing surface of each bearing 18 is installed in a state that is approximately flush with the lower surface of the sliding member 10. Pressurized air is sprayed from the four bearings 18 toward the platform 12. And, the sliding member 10 is floated from the platform 12 by the static pressure (pressure in the gap) between the bearing surface of the pressurized air and the upper surface (guide surface) of the platform 12. The interval (gap, clearance) between the bottom surface of the sliding member 10 and the upper surface of the platform 12 is preferably less than 10 μm, preferably less than 5 μm. In this embodiment, as the material of the sliding member 10, zero expansion glass (for example, Zerodur from Schott, etc.) which is a kind of zero expansion material is used.

[0205] A recess 10a is formed on the upper portion of the slider 10. The recess 10a has an inner diameter that is larger than the diameter of the wafer W. When viewed from above, the recess 10a has a substantially circular shape. A wafer holder WH having a diameter substantially the same as that of the wafer W is arranged inside the recess 10a. As the wafer holder WH, a vacuum chuck, an electrostatic chuck, a mechanical chuck, or the like can be used. As an example, a pin chuck type vacuum chuck can also be used. The wafer W is held by adsorption by the wafer holder WH so that the upper surface of the wafer W is substantially flush with the upper surface of the slider 10. The wafer holder WH has a plurality of suction ports. The plurality of suction ports are connected to the vacuum pump 11 (see FIG. 1 ) via a vacuum piping system (not shown). Figure 16 The control device 60 controls the opening and closing of the vacuum pump 11 and the output of the operation.

[0206] The slider 10 is provided with vertically movable pins (not shown) for moving the wafer W up and down on the wafer holder WH. When unloading the wafer W from the wafer holder WH, the vertically movable pins are raised to lift the wafer W from the wafer holder WH. This makes it easier for the arm of the wafer transport system 70 to hold the wafer. When the wafer holder WH is caused to adsorb the wafer W, the vertically movable pins are lowered to bring the lower surface of the wafer W into close contact with the wafer holder WH. The vertically movable pins are moved up and down by the drive device 13 controlled by the control device 60 (see FIG. 1 ). Figure 16 ).

[0207] For example, it is preferable that the wafer holder WH can suction-hold a wafer having a diameter of 300 mm. It should be noted that if the wafer transport system 70 includes a non-contact holding member (e.g., a Bernoulli chuck) that suction-holds the wafer on the wafer holder WH from above, the vertically movable pins may not be provided on the slider 10.

[0208] like Figure 14B and Figure 15As shown, a two-dimensional grating (hereinafter referred to as "grating") RG1 is arranged horizontally (parallel to the surface of wafer W) in an area slightly larger than the wafer W on the lower surface of slider 10. Grating RG1 includes a reflective diffraction grating (X diffraction grating) periodic along the X-axis and a reflective diffraction grating (Y diffraction grating) periodic along the Y-axis. The pitch of the grating lines of the X and Y diffraction gratings is set to, for example, 1 μm.

[0209] like Figure 16 As shown, 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 slide 10 in the X-axis direction. The second drive device 20B integrally drives the slide 10 in the Y-axis direction with the first drive device 20A.

[0210] like Figure 15 As shown, a pair of movable members 22a including a magnet unit (or coil unit) is provided on the side surface of the slider 10 on the -Y side. When viewed from the side, the pair of movable members 22a are in an inverted L shape and are fixed at a predetermined interval in the X-axis direction. Figure 15 As shown, a pair of movable members 22b including a magnet unit (or coil unit) is provided on the side surface of the slider 10 on the +Y side. The pair of movable members 22b are fixed at a predetermined interval in the X-axis direction. The pair of movable members 22a and the pair of movable members 22b are arranged symmetrically. The movable members 22a and 22b are respectively supported in a non-contact manner on the upper surfaces of a pair of plate members 24a and 24b extending in the X-axis direction and substantially parallel to the XY plane.

[0211] like Figure 15 As shown, stators 26a and 26b, each composed of a coil unit (or magnet unit), are disposed on the upper surfaces of the pair of plate members 24a and 24b in the region excluding the two ends in the X-axis direction. Electromagnetic interaction between the pair of movable elements 22a and the stators 26a generates a driving force (electromagnetic force) that drives the pair of movable elements 22a in the X-axis and Y-axis directions.

[0212] A pair of movable members 22a and fixed members 26a constitute an XY linear motor 28A (see FIG. 2 ) which generates driving forces in the X-axis direction and the Y-axis direction. Figure 16 A pair of movable parts 22b and fixed parts 26b constitute an XY linear motor 28B that generates driving forces in the X-axis direction and the Y-axis direction (see Figure 16 The slide 10 is driven in the X-axis direction by an XY linear motor 28A and an XY linear motor 28B at a predetermined stroke.

[0213] The first drive device 20A can make the XY linear motor 28A and the XY linear motor 28B generate different driving forces in the X-axis direction. As a result, the slide 10 is driven in the θz direction. The first drive device 20A is controlled by the control device 60 (see Figure 16 The first drive device 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 drive device 20A does not necessarily generate a driving force in the Y-axis direction.

[0214] The movable platform 24 is configured to be separated from a pair of plate members (24a, 24b) by a predetermined distance in the X-axis direction, and has a pair of connecting members (24c, 24d) extending in the Y-axis direction. Step portions are respectively formed at both ends of the connecting members (24c, 24d) in the Y-axis direction. Furthermore, in a state where one end and the other end in the longitudinal direction of the plate member 24a are placed on the step portions on the -Y side of the connecting members (24c, 24d), the connecting members (24c, 24d) are integrated with the plate member 24a. In addition, in a state where one end and the other end in the longitudinal direction of the plate member 24b are placed on the step portions on the +Y side of the connecting members (24c, 24d), the connecting members 24c, 24d are integrated with the plate member 24b (see Figure 14B That is, in this manner, a pair of plate members (24a, 24b) are connected by a pair of connecting members (24c, 24d) to form a movable platform 24 in a rectangular frame shape.

[0215] like Figure 14A As shown, a pair of linear guides (27a, 27b) extending in the Y-axis direction are fixed to the base frame 16 (see Figure 14B ) near both ends of the upper surface in the X-axis direction. Inside one linear guide 27a located on the +X side, a stator 25a (see FIG. 1 ) of a Y-axis linear motor 29A composed of a coil unit (or magnet unit) covering substantially the entire length in the Y-axis direction is housed near the upper surface and the -X side surface. Figure 14B). A movable part 23a is arranged opposite to the upper surface and the -X side surface of the linear guide 27a. The movable part 23a has a magnet unit (or coil unit) with an L-shaped cross-section, and together with the fixed part 25a, constitutes the Y-axis linear motor 29A. Air bearings that spray pressurized air toward the opposite surfaces are fixed respectively on the lower surface and the +X side surface of the movable part 23a, which are opposite to the upper surface and the -X side surface of the linear guide 27a. As the air bearing fixed on the +X side surface of the movable part 23a, a vacuum preload type air bearing is preferably used. The vacuum preload type air bearing can easily maintain the interval (gap, gap) in the X-axis direction between the movable part 23a and the linear guide 27a at a constant value by balancing the static pressure of the pressurized air between the bearing surface and the -X side surface of the linear guide 27a and the vacuum preload.

[0216] X-guides 19, consisting of multiple (e.g., two) rectangular parallelepiped members, are fixed to the upper surface of the movable member 23a at predetermined intervals in the Y-axis direction. Sliding members 21, each with an inverted U-shaped cross section, which together with the X-guides 19 form a uniaxial guide mechanism, engage non-contact with each of the two X-guides 19. Air bearings are provided on each of the three surfaces of the sliding members 21 that face the X-guides 19. The two sliding members 21 are fixed to the lower surface (the -Z side) of the connecting member 24c.

[0217] The other linear guide 27b located on the -X side houses the stator 25b of the Y-axis linear motor 29B composed of a coil unit (or magnet unit). The linear guide 27b is symmetrical and has the same structure as the linear guide 27a (see Figure 14B ). The movable part 23b is arranged opposite to the upper surface and the +X side surface of the linear guide 27b. The movable part 23b is the same as the movable part 23a (symmetrical on both sides), and has a magnet unit (or coil unit) with an L-shaped cross-section. The movable part 23b and the fixed part 25b together constitute the Y-axis linear motor 29B. On the lower surface and the -X side surface of the movable part 23b, air bearings are fixed respectively opposite to the upper surface and the +X side surface of the linear guide 27b. As the air bearing fixed to the -X side surface of the movable part 23b, a vacuum preload type air bearing is used. The vacuum preload type air bearing can easily maintain the interval (gap, gap) in the X-axis direction between the movable part 23b and the linear guide 27b at a constant value.

[0218] Similar to the above, two uniaxial guide devices composed of the X guide 19 and the sliding member 21 that non-contactly engages with the X guide 19 are provided between the upper surface of the movable element 23 b and the bottom surface of the connecting member 24 d .

[0219] The movable platform 24 is supported from below by movable members (23a, 23b) by means of two uniaxial guide devices on each of the +X and -X sides (four in total), and is capable of moving along the X-axis on the movable members 23a, 23b. Therefore, when the slider 10 is driven along the X-axis by the first drive device 20A described above, the reaction force to the driving force acts on the movable platform 24, which is provided with the fixed members (26a, 26b). As a result, the movable platform 24 moves in the opposite direction to the slider 10 in accordance with the law of conservation of momentum. In other words, the generation of vibrations caused by the reaction force to the driving force of the slider 10 in the X-axis direction is prevented (or effectively suppressed) by the movement of the movable platform 24. In other words, the movable platform 24 functions as a counterweight when the slider 10 moves in the X-axis direction. However, it is not necessarily necessary for the movable platform 24 to function as a counterweight. It should be noted that a counterweight (not shown) may be additionally provided for preventing (or effectively suppressing) the generation of vibration caused by the driving force of the slider 10 relative to the movable table 24 in the Y-axis direction.

[0220] Y-axis linear motor 29A generates a driving force (electromagnetic force) to drive movable element 23a in the Y-axis direction through electromagnetic interaction between movable element 23a and fixed element 25a. Y-axis linear motor 29B generates a driving force (electromagnetic force) to drive movable element 23b in the Y-axis direction through electromagnetic interaction between movable element 23b and fixed element 25b.

[0221] The driving force in the Y-axis direction generated by the Y-axis linear motors (29A, 29B) acts on the movable platform 24 via two uniaxial guide devices on the +X side and the -X side. As a result, the slider 10 is driven in the Y-axis direction together with the movable platform 24. That is, in this embodiment, the second driving device 20B (see FIG. 2 ) that drives the slider 10 in the Y-axis direction is composed of the movable platform 24, the four uniaxial guide devices, and the pair of Y-axis linear motors (29A, 29B). Figure 16 ).

[0222] In this embodiment, the pair of Y-axis linear motors (29A, 29B) are physically separated from the platform 12 and are vibration-isolated by the three vibration isolation devices 14. It should be noted that the linear guides (27a, 27b) of the fixing members (25a, 25b) provided with the pair of Y-axis linear motors (29A, 29B) can also be configured to be movable relative to the base frame 16 (see Figure 14B ) moves in the Y-axis direction and functions as a counterweight when the slider 10 is driven in the Y-axis direction.

[0223] In this embodiment, an image processing-based FIA (Field Image Alignment) system is used as the mark detection system MDS. As an example of a mark detection method using the FIA ​​system, the following method is described: a broadband detection beam generated by an illumination light source such as a halogen lamp is irradiated onto a target mark, and an image sensor (such as a CCD) is used to capture an image of the target mark formed on a light-receiving surface by light reflected from the target mark, as well as an image of an indicator (not shown) (e.g., an indicator pattern provided on an internal indicator plate), and image signals of these images are output.

[0224] The imaging signal from the mark detection system MDS is supplied to the control device 60 via the signal processing device 49 (see Figure 16 ). The measuring apparatus 100 is configured to be able to switch and set (select) the measurement conditions (also referred to as alignment measurement conditions) of the mark using the mark detection system MDS.

[0225] The alignment measurement conditions that can be switched include irradiation conditions for illuminating the target mark with detection light, light reception conditions for receiving light from the mark, and signal processing conditions for processing the photoelectric conversion signal obtained from the received light from the mark. By switching alignment measurement conditions, FBO and / or DBO marks can be measured under different measurement conditions, allowing the absolute position of the two layers with the marks formed and the amount of misalignment between the two layers to be determined. The irradiation and light reception conditions are switched and set by the control unit 60 via the mark detection system MDS, while the signal processing conditions are switched and set by the control unit 60 via the signal processing unit 49.

[0226] The irradiation conditions to be switched and set may also include at least one of the wavelength of the detection light irradiated onto the mark from the optical system of the mark detection system MDS, the amount of the detection light, and the NA and σ of the optical system. Furthermore, the light reception conditions to be switched and set may also include at least one of the order of diffracted light generated from the mark and the wavelength of the light generated from the mark.

[0227] The upper surface of the wafer held on the slider 10 is coated with a sensitive agent (resist). Accordingly, detection light having a wavelength that is insensitive to the resist is preferably used. For example, it is preferable to irradiate the registration mark with broadband light that is insensitive to the resist coated on the wafer. For example, the light source may be a white light source that irradiates light with a wavelength within the wavelength range of 350 to 850 nm.

[0228] As a method for switching the wavelength of the detection light in the illumination conditions, for example, a method can be adopted in which a filter used in the wavelength selection mechanism of the mark detection system MDS is selectively set on the optical path of the illumination light from the illumination light source. In addition, the settings of the illumination field stop, illumination aperture stop, and imaging aperture stop (for example, including an imaging aperture stop with an annular light-shielding shape and used in conjunction with the annular illumination aperture stop) or the states of these stop can be controlled. In this way, the illumination conditions (normal illumination / distorted illumination), dark field / bright field detection method, the numerical aperture NA or σ of the optical system, or the illumination light amount can be set to the desired state.

[0229] The signal processing conditions for the switching settings include at least the selection of the waveform analysis (waveform processing) algorithm used in the signal processing device 49, the selection of the signal processing algorithm such as the EGA calculation model, and at least one of the selection of multiple parameters used in each selected signal processing algorithm.

[0230] For example, U.S. Patent Application Publication No. 2008 / 0013073 discloses an FIA system capable of switching and setting alignment measurement conditions. The mark detection system MDS of this embodiment can also employ an FIA system having the same configuration as that disclosed in the aforementioned U.S. Patent Application Publication. It should be noted that the aforementioned U.S. Patent Application Publication discloses changing the illumination aperture diaphragm from a conventional circular transmissive portion to one having an annular transmissive portion, and arranging a phase difference plate at a position proximal to the imaging aperture diaphragm. Furthermore, this change and configuration enables the FIA ​​system (alignment sensor) to function as a phase-contrast microscope-type sensor. As one of the light-receiving conditions, the FIA ​​system also discloses imparting a specified phase difference to diffracted light of a specified order generated from the mark. In this embodiment, the mark detection system MDS also includes an alignment autofocus function for adjusting the focal position of the optical system.

[0231] The signal processing device 49 is a computing device comprising: an input unit for inputting information related to the image of the registration mark; a computing unit for calculating the absolute position of at least one of the first or second patterns based on the input information; and an output unit for outputting information related to the absolute position of at least one of the first or second patterns calculated by the computing unit. The signal processing device 49 processes the imaging signal output as a detection signal from the mark detection system MDS, calculates position information of the target mark relative to the detection center, and outputs the information 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 or second patterns based on the input information, and a storage medium storing the program. The program can also be installed in the measuring device from a program distribution server or storage medium on a network.

[0232] In this embodiment, the signal processing device 49 and the control device 60 are shown as separate bodies, but the signal processing device 49 and the control device 60 may be integrated. For example, the control device 60 may function as the arithmetic device included in the signal processing device 49.

[0233] As the mark detection system MDS, a beam scanner-type alignment system may be used that scans measurement light in a predetermined direction relative to the target mark while the slider 10 is moved in a predetermined direction. In this embodiment, the mark detection system MDS includes an alignment autofocus function. However, instead of or in addition to this, the measurement unit may include an oblique-incidence multi-point focus position detection system similar to the focus position detection system (e.g., the system disclosed in U.S. Patent No. 5,448,332).

[0234] like Figure 14B and Figure 15 As shown, the first position measurement system 30 includes a head 32, which is positioned within a recess formed in the upper surface of the platform 12 and fixed to the platform 12. The upper surface of the head 32 faces the lower surface of the slider 10 (the surface on which the grating RG1 is formed). A predetermined gap (clearance, clearance) is formed between the upper surface of the head 32 and the lower surface of the slider 10. The gap in this section may be, for example, a few millimeters.

[0235] like Figure 16As shown, the first position measurement system 30 includes an encoder system 33 and an interferometer system 35. The encoder system 33 irradiates multiple light beams from the head 32 onto the measurement portion on the lower surface of the slider 10 (the surface where the grating RG1 is formed) and receives multiple return light beams from the measurement portion on the lower surface of the slider 10 (for example, multiple diffracted light beams from the grating RG1). This allows position information of the slider 10 to be acquired. The encoder system 33 includes an X linear encoder 33x that measures the position of the slider 10 in the X-axis direction and a pair of Y linear encoders (33ya, 33yb) that measure the position of the slider 10 in the Y-axis direction. The interferometer system 35 includes four laser interferometers (35a, 35b, 35c, 35d).

[0236] As encoder system 33, a diffraction interferometry head similar to the encoder head disclosed in, for example, U.S. Patent No. 7,238,931 and U.S. Patent Application Publication No. 2007 / 288121 (hereinafter referred to as "head" as appropriate) may be used. It should be noted that the head includes a light source, a light receiving system (including a photodetector), and an optical system. However, in this embodiment, at least the optical system is disposed within the housing of head 32, facing grating RG1. Alternatively, at least one of the light source and the light receiving system may be disposed outside the housing of head 32.

[0237] In this embodiment, the measurement of the position information of the slide 10 in the X-axis direction and the Y-axis direction has a common detection point. The control device 60 always controls the actuators of the three vibration isolation devices 14 in real time so that the position of the detection point in the XY plane is consistent with the detection center of the mark detection system MDS. This control is based on the relative position information of the mark detection system MDS and the platform 12 measured by the second position measurement system 50. Therefore, in this embodiment, the control device 60 uses the encoder system 33 to measure the position information of the slide 10 in the XY plane directly below the detection center of the mark detection system MDS (on the back side of the slide 10) when measuring the alignment mark on the chip W placed on the slide 10. In addition, the control device 60 measures the rotation amount of the slide 10 in the θz direction based on the difference in the measurement values ​​of a pair of Y heads (37ya, 37yb).

[0238] To measure the Z-axis position and the rotational amounts in the θx and θy directions of the slider 10, it is sufficient to direct the light beams into three different points on the surface formed with the grating RG1. Thus, only three Z heads (e.g., laser interferometers) are required. It should be noted that a protective glass can be provided on the lower surface of the slider 10 to protect the grating RG1, and a wavelength-selective filter can be provided. This wavelength-selective filter allows the measurement beams from the encoder system 33 to pass through the protective glass surface while preventing the measurement beams from the interferometer system 35 from passing through.

[0239] As can be seen from the above description, the control device 60 can measure the position of the slider 10 in the six degrees of freedom directions by using the encoder system 33 and the interferometer system 35 of the first position measurement system 30. In this case, because the optical path length of the measurement beam in air is short and approximately constant in the encoder system 33, the influence of air ripples can be largely ignored. Therefore, the encoder system 33 can be used to measure the position information of the slider 10 in the XY plane (including the θz direction) with high precision. In addition, the detection points on the actual grating RG1 in the X-axis and Y-axis directions by the encoder system 33 and the detection points on the lower surface of the slider 10 in the Z-axis direction by the interferometer system 35 are aligned with the detection center of the mark detection system MDS in the XY plane. Therefore, the occurrence of so-called Abbe errors caused by the offset between the detection points and the detection center of the mark detection system MDS in the XY plane can be suppressed to a substantially negligible level. Therefore, the control device 60 can measure the position of the sliding part 10 in the X-axis direction, Y-axis direction and Z-axis direction with high precision by using the first position measurement system 30 without generating Abbe error caused by the offset of the detection point and the detection center of the mark detection system MDS in the XY plane.

[0240] like Figure 14A and Figure 14B As shown, the second position measurement system 50 includes a pair of heads (52A, 52B) respectively provided on the lower surfaces of one end and the other end of the head mounting member 51 in the longitudinal direction, and scale members (54A, 54B) arranged opposite the heads (52A, 52B). The upper surfaces of the scale members (54A, 54B) are formed at the same height as the surface of the wafer W held by the wafer holder WH. Reflective two-dimensional gratings (RG2a, RG2b) are formed on the upper surfaces of the scale members (54A, 54B). The two-dimensional gratings (hereinafter referred to as gratings) (RG2a, RG2b) each include a reflective diffraction grating (X diffraction grating) with a periodic direction along the X-axis and a reflective diffraction grating (Y diffraction grating) with a periodic direction along the Y-axis. The pitch of the grating lines of the X diffraction grating and the Y diffraction grating is set to, for example, 1 μm.

[0241] The scale components (54A, 54B) are made of a material with a low thermal expansion coefficient (such as the above-mentioned zero expansion material), such as Figure 14A and Figure 14B As shown, they are fixed to the platform 12 by support members 56. In this embodiment, the sizes of the scale members (54A, 54B) and the support member 56 are determined so that the gratings (RG2a, RG2b) and the heads (52A, 52B) face each other with a gap of about several mm.

[0242] like Figure 16 As shown, in this embodiment, the second position measurement system 50 includes two 4-axis encoders (581, 582). The 4-axis encoder 581 (see FIG. 1 ) is composed of an XZ linear encoder 58X1 and a YZ linear encoder 58Y1, which measures the position information of the stage 12 relative to the mark detection system MDS in the X-axis, Y-axis, Z-axis, and θx directions. Figure 16 Similarly, the XZ linear encoder 58X2 and the YZ linear encoder 58Y2 constitute a 4-axis encoder 582 for measuring the position information of the platform 12 relative to the mark detection system MDS in the X-axis, Y-axis, Z-axis and θx directions (see Figure 16 In this case, based on the position information of the platform 12 relative to the mark detection system MDS related to the Z-axis direction measured by the four-axis encoders (581, 582), the position information of the platform 12 relative to the mark detection system MDS related to the θy direction is calculated (measured). Based on the position information of the platform 12 relative to the mark detection system MDS related to the Y-axis direction measured by the four-axis encoders (581, 582), the position information of the platform 12 relative to the mark detection system MDS related to the θz direction is calculated (measured).

[0243] The second position measurement system 50, comprised of the four-axis encoder 581 and the four-axis encoder 582, measures position information of the stage 12 in the six degrees of freedom (DOF) relative to the mark detection system MDS, i.e., information on the relative position of the mark detection system MDS and the stage 12 in the six DOF directions. This information, measured by the second position measurement system 50, is constantly supplied to the 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 to ensure that the detection point of the first position measurement system 30 is aligned with the detection center of the mark detection system MDS in the desired positional relationship. Specifically, the actuators of the three vibration isolation devices 14 are controlled so that the detection point of the first position measurement system 30 and the detection center of the mark detection system MDS coincide within the XY plane, for example, at the nanometer level, and that the surface of the wafer W on the slider 10 coincides with the detection position of the mark detection system MDS. In this case, for example, the reference axis LV coincides with the aforementioned straight line CL. It should be noted that as long as the detection point of the first position measurement system 30 and the detection center of the mark detection system MDS can be controlled to have the desired positional relationship, the second position measurement system 50 may not be able to measure relative position information in all directions of the six degrees of freedom.

[0244] Figure 16 The block diagram of the input and output relationship of the control device 60, which is composed of the control system of the measuring device 100 of this embodiment, is shown in FIG. The control device 60 includes a workstation (or microcomputer) and performs comprehensive control on the components of the measuring device 100. Figure 16 As shown, the measuring device 100 has Figure 1 The components shown in FIG are arranged together in a wafer transfer system 70 in the chamber. The wafer transfer system 70 is composed of, for example, a horizontal multi-joint robot.

[0245] The aforementioned measuring device may also be a separate device from the exposure device. The measuring device may be arranged separately from the exposure device or adjacent to the exposure device. Next, an example of an exposure device equipped with an alignment detection system for detecting the aforementioned overlay mark is shown below.

[0246] <Exposure device>

[0247] like Figure 17As shown, exposure apparatus 200 includes an illumination system IOP, a reticle stage RST that holds a reticle R, a projection unit PU that projects an image of a pattern formed on reticle R onto a wafer W coated with a sensitive agent (resist), a wafer stage WST that holds wafer W and moves it within the XY plane, and control systems for these components. Exposure apparatus 200 includes a projection optical system PL having an optical axis AX in the Z-axis direction parallel to the optical axis AX1 of the mark detection system MDS described above. Exposure apparatus 200 can also be used for semiconductor device manufacturing or FPD manufacturing.

[0248] The illumination system IOP includes a light source and an illumination optical system connected to the light source via a light transmission optical system. The illumination light (exposure light) IL is used to illuminate the reticle R set (limited) by the reticle mask (masking system) along the X-axis direction ( Figure 17 The illumination system IOP is illuminated by a slit-shaped illumination area IAR extending elongated (in a direction perpendicular to the paper). The configuration of the illumination system IOP is disclosed, for example, in U.S. Patent Application Publication No. 2003 / 0025890. Here, ArF excimer laser light (wavelength 193 nm) is used as the illumination light IL, for example.

[0249] The reticle platform RST is configured in the lighting system IOP Figure 9 The reticle stage RST can be driven by a reticle stage drive system 211 (in the Figure 17 Not shown, see Figure 18 ) is driven slightly in the horizontal plane (XY plane) on a reticle platform (not shown), and can be moved in the scanning direction ( Figure 17 The Y-axis direction (left and right direction) is driven within the specified stroke range.

[0250] On reticle stage RST, reticle R is placed, on which a pattern area and a plurality of marks with known positional relationships with the pattern area are formed on the -Z side surface (pattern surface). The position information of reticle stage RST in the XY plane (including rotation information in the θz direction) is always detected by reticle interferometer 214 with the aid of movable mirror 212 (or a reflective surface formed on the end face of reticle stage RST) at a resolution of, for example, about 0.25 nm. The measurement information of reticle interferometer 214 is transmitted to exposure control device 220 (see Figure 18 It should be noted that the position information of the reticle stage RST in the XY plane may also be measured by an encoder instead of the reticle interferometer 214 .

[0251] The projection unit PU is configured on the reticle platform RST Figure 9. Projection unit PU includes a lens barrel 240 and a projection optical system PL retained in the lens barrel 240. The projection optical system PL is, for example, telecentric on both sides and has a specified projection magnification (for example, 1 / 4 times, 1 / 5 times or 1 / 8 times, etc.). The reticle R is configured in such a way that the first surface (object surface) of the projection optical system PL is roughly consistent with the pattern surface, and the chip W with the surface coated with a resist (sensing agent) is configured on the second surface (image surface) side of the projection optical system PL. Therefore, when the illumination area IAR on the reticle R is illuminated by the illumination light IL from the illumination system IOP, a reduced image of the circuit pattern of the reticle R within the illumination area IAR (a reduced image of a part of the circuit pattern) is formed by the illumination light IL passing through the reticle R via the projection optical system PL in an area (hereinafter also referred to as the exposure area) IA on the chip W that is conjugate with the illumination area IAR. In addition, by synchronously driving the reticle stage RST and the chip stage WST, the reticle R is moved relative to the illumination area IAR (illumination light IL) along the scanning direction (Y-axis direction), and the chip W is moved relative to the exposure area IA (illumination light IL) along the scanning direction (Y-axis direction), thereby scanning and exposing one shooting area on the chip W.

[0252] After exposure, the pattern of the reticle R is transferred to the shooting area. As the projection optical system PL, as an example, a diffraction system consisting of a plurality of (for example, about 10 to 20) diffraction optical elements (lens elements) arranged only along the optical axis AX parallel to the Z-axis direction is used. Among the plurality of lens elements constituting the projection optical system PL, the plurality of lens elements on the object plane side (reticle R side) become movable lenses that are driven by a driving element (for example, a piezoelectric element, etc.) not shown in the figure in translation along the Z-axis direction (the optical axis direction of the projection optical system PL) and can be driven in the inclined direction relative to the XY plane (i.e., the θx direction and the θy direction). In addition, the imaging characteristic correction controller 248 (in Figure 17 Not shown, see Figure 18 By independently adjusting the applied voltage to each drive element based on instructions from the exposure control device 220, each movable lens can be driven individually, thereby adjusting various imaging characteristics of the projection optical system PL (magnification, distortion, astigmatism, coma, field curvature, etc.). It should be noted that, instead of or in addition to the movement of the movable lens, an airtight chamber can be provided between adjacent specific lens elements within the lens barrel 240, and the pressure of the gas within the airtight chamber can be controlled by the imaging characteristic correction controller 248. Alternatively, a configuration can be adopted in which the center wavelength of the illumination light IL can be shifted by the imaging characteristic correction controller 248. These configurations can also adjust the imaging characteristics of the projection optical system PL.

[0253] The wafer stage WST is driven by a stage drive system 224 (in the Figure 17 The wafer W is driven on wafer stage 222 along the X-axis and Y-axis directions with a predetermined stroke, and is also slightly driven in the Z-axis, θx, θy, and θz directions. Wafer W is held on wafer stage WST by a wafer holder (not shown) by vacuum adsorption or the like. It should be noted that, in place of wafer stage WST, a stage assembly may be used that includes a first stage that moves in the X-axis, Y-axis, and θz directions, and a second stage that moves slightly in the Z-axis, θx, and θy directions on the first stage.

[0254] The position information of wafer stage WST within the XY plane (including rotation information (deflection amount (rotation amount θz in the θz direction), pitch amount (rotation amount θx in the θx direction), and roll amount (rotation amount θy in the θy direction))) is always detected by interferometer system 218 using movable mirror 216 (or a reflective surface formed on the end face of wafer stage WST) with a resolution of, for example, approximately 0.25 nm. It should be noted that the position information of wafer stage WST within the XY plane can also be measured using encoder system 33 instead of interferometer system 218.

[0255] The measurement information of the interferometer system 218 is supplied to the exposure control device 220 (see Figure 18 Exposure control device 220 controls the position of wafer stage WST in the XY plane (including rotation in the θz direction) via stage drive system 224 based on the measurement information from interferometer system 218 .

[0256] In addition, Figure 17 The figure is omitted, but the Z-axis position and tilt of the surface of the wafer W are determined by a focus sensor AFS (see FIG. 1 ) which is composed of a multi-point focus position detection system of an oblique incidence method disclosed in the specification of U.S. Patent No. 5,448,332. Figure 10 ) measurement. The measurement information of the focus sensor AFS is also supplied to the exposure control device 220 (see Figure 10 ).

[0257] Furthermore, a reference plate FP is fixed to wafer stage WST, the surface of which is at the same height as the surface of wafer W. Formed on the surface of reference plate FP are a first fiducial mark used for baseline measurement by alignment detection system AS, a pair of second fiducial marks detected by the reticle alignment detection system, and the like.

[0258] An alignment detection system AS for detecting alignment marks (including the aforementioned overlay marks) formed on the wafer W or the first reference mark is provided on the side of the lens barrel 240 of the projection unit PU. The alignment detection system AS includes an imaging unit for capturing images of the alignment marks and a light source (for example, a halogen lamp) that radiates broadband light. The alignment detection system AS employs an image processing method that measures the mark position by processing an image obtained by capturing the illuminated mark. This image processing method utilizes an FIA system, a type of imaging alignment sensor. The exposure control device 220 functions as a computing device comprising: an input unit for inputting information related to the image of the overlay mark; a computing unit for calculating the absolute position of at least one of the first pattern or the second pattern based on the input information; and an output unit for outputting information related to the absolute position of at least one of the first pattern or the second pattern calculated by the computing unit. The computing device includes a program for causing the exposure device to execute the aforementioned mark measurement method and a storage medium storing the program. The program can also be installed in an existing exposure device from a program distribution server or storage medium on a network.

[0259] In exposure apparatus 200, a pair of reticle alignment detection systems 213 (in the X-axis direction) are further provided above reticle stage RST at a predetermined distance therebetween. The reticle alignment detection systems 213 are capable of simultaneously detecting a pair of reticle marks located at the same Y position on reticle R placed on reticle stage RST. Figure 17 Not shown, see Figure 18 The detection result of the mark by the reticle alignment detection system 213 is supplied to the exposure control device 220.

[0260] Figure 18 The input and output relationship of the exposure control device 220 is shown in a block diagram. Figure 18 As shown, in addition to the aforementioned components, exposure apparatus 200 also includes a wafer transfer system 270 connected to an exposure control device 220 for transferring wafers. Exposure control device 220 includes a microcomputer or a workstation, and comprehensively controls the entire apparatus including the aforementioned components. Wafer transfer system 270 is comprised of, for example, a horizontal articulated robot.

[0261] Description of Reference Numerals

[0262] 1: First layer

[0263] 2: Second layer

[0264] 3: Middle layer

[0265] 10: (wafer) sliding part

[0266] 10a: (Slider) Recess

[0267] 11: Vacuum pump

[0268] 12: Platform

[0269] 14: Vibration isolation device

[0270] 16: Base frame

[0271] 18: Bearings

[0272] 19: X guide

[0273] 20: Drive system

[0274] 20A: First drive unit

[0275] 20B: Second drive unit

[0276] 21: Sliding parts

[0277] 22: Second floor

[0278] 22a, 22b: Movable parts

[0279] 23: The third floor

[0280] 23a, 23b: Movable parts

[0281] 24: Movable Platform

[0282] 24a, 24b: Plate components

[0283] 24c, 24d: Connecting parts

[0284] 25a, 25b, 26a, 26b: Fixing parts

[0285] 27a, 27b: Linear guides

[0286] 28A, 28B: XY linear motor

[0287] 29A, 29B: Y-axis linear motor

[0288] 30: First position measurement system

[0289] 32: Head

[0290] 33: Encoder system

[0291] 33x: X linear encoder

[0292] 35: Interferometer system

[0293] 49: Signal processing device

[0294] 50: Second position measurement system

[0295] 51: Head mounting parts

[0296] 56: Supporting parts

[0297] 581, 582: 4-axis encoder

[0298] 58X1, 58X2: XZ linear encoder

[0299] 58Y1, 58Y2: YZ linear encoder

[0300] 60: Control device

[0301] 70: Wafer transport system

[0302] 81, 82, 83: signal components

[0303] 84: Signal

[0304] 85: Curve

[0305] 86: Resample point

[0306] 91, 94: base material

[0307] 92, 95, 98: First floor

[0308] 93, 96, 99: Second level

[0309] 94: base material

[0310] 97: Central level

[0311] 100: Measuring device

[0312] 200: Exposure device

[0313] 211: (Exposure device) reticle platform drive system

[0314] 212, 216: (Exposure device) moving mirror

[0315] 213: (Exposure device) Reticle alignment detection system

[0316] 214: (Exposure device) Reticle interferometer

[0317] 218: (Exposure device) Interferometer system

[0318] 220: Exposure control device

[0319] 222: (Exposure device) Wafer work platform

[0320] 224: (Exposure device) platform drive system

[0321] 240: (Exposure device) barrel

[0322] 248: (Exposure device) Imaging characteristics correction controller

[0323] 270: (Exposure device) Wafer transport system

[0324] AFS: Focus Sensor

[0325] AS: Alignment Detection System

[0326] AX, AX1: Optical axis

[0327] FP: Reference Plate

[0328] G1: (basis function) curve

[0329] IA: Exposure Area

[0330] IAR: Illumination Area

[0331] IL: Illumination Light

[0332] IOP: Lighting System

[0333] IS: Luminance signal

[0334] L: cross section

[0335] LV: Reference axis

[0336] MDS: Mark Detection System

[0337] PL: Projection Optics

[0338] PU: Projection Unit

[0339] R: Reticle

[0340] RF1: First reference wafer

[0341] RF2: Second reference wafer

[0342] RF3: Third reference chip

[0343] RG1: Grating

[0344] RG2a, 2G2b: Two-dimensional gratings

[0345] RST: Reticle Platform

[0346] W: chip

[0347] W1: substrate

[0348] WH: (measuring device) wafer holder

[0349] WST: (Exposure device) wafer stage.

Claims

1. A marking measurement method, comprising: Acquiring an image of a registration mark formed by overlapping a first pattern and a second pattern, wherein the first pattern is formed by lines and spaces repeating along a predetermined direction at a first pitch P1 on a layer on a substrate, and the second pattern is formed by lines and spaces repeating along the predetermined direction at a second pitch P2 different from the first pitch P1 on a layer different from the first pattern; extracting a brightness signal of the registration mark in the prescribed direction from the acquired image of the registration mark; as well as An absolute position in the predetermined direction is obtained for at least one of the first pattern and the second pattern based on the extracted brightness signal.

2. The marking measurement method according to claim 1, wherein: The coincidence mark includes: The first pattern is formed in a lower layer than the second pattern and a first region where a first registration mark formed by the second pattern overlapping the first pattern is located; and The first pattern is formed in a layer above the second pattern and in a second region where a second registration mark formed by the first pattern overlapping the second pattern is located. Based on the extracted brightness signal, determining the absolute position in the specified direction for at least one of the first pattern and the second pattern includes: based on the brightness signal of the first coincidence mark, determining the first moiré position X1 in the specified direction of the moiré fringes formed in the first area by overlapping the first pattern and the second pattern; based on the brightness signal of the second coincidence mark, determining the second moiré position X2 in the specified direction of the moiré fringes formed in the second area by overlapping the second pattern and the first pattern.

3. The marking measurement method according to claim 2, wherein: The first pitch P1 and the second pitch P2 are smaller than a resolution limit of an imaging unit that captures the registration mark.

4. The marking measurement method according to claim 2 or 3, wherein: The method includes obtaining at least one of the absolute position AP1 of the pattern provided on the upper layer in the predetermined direction by using the formula (3) and the absolute position AP2 of the pattern provided on the lower layer in the predetermined direction by using the formula (4). 【Mathematical formula 1】 【Mathematical formula 2】 5. A marking measurement method, comprising: Acquiring an image of a registration mark formed in a first area by overlapping a first pattern and a second pattern, wherein the first pattern is formed by lines and spaces repeating along a predetermined direction at a first pitch P1 on a layer on a substrate, and the second pattern is formed by lines and spaces repeating along the predetermined direction at a second pitch P2 different from the first pitch P1 on a layer different from the first pattern; acquiring an image of a registration mark formed in the second area by overlapping a third pattern and a fourth pattern, wherein the third pattern is formed by lines and spaces being repeated along the prescribed direction at a third pitch P3 on the one layer, and the fourth pattern is formed by lines and spaces being repeated along the prescribed direction at a fourth pitch P4 different from the third pitch P3 on the other layer; extracting a first luminance signal from the acquired image of the registration mark in the first area, the first luminance signal being a luminance signal in the prescribed direction of the registration mark formed in the first area; extracting a second luminance signal from the acquired image of the registration mark in the second area, the second luminance signal being a luminance signal in the prescribed direction of the registration mark formed in the second area; as well as An absolute position in the predetermined direction is determined for at least one of the first pattern, the second pattern, the third pattern, and the fourth pattern based on the extracted first and second luminance signals.

6. The marking measurement method according to claim 5, wherein: Based on the extracted first brightness signal and the second brightness signal, calculating the absolute position in a specified direction for at least one of the first pattern, the second pattern, the third pattern and the fourth pattern includes: calculating the first moiré position X1 in the specified direction of the moiré fringes formed by the first pattern and the second pattern in the first area, and the second moiré position X2 in the specified direction of the moiré fringes formed by the third pattern and the fourth pattern in the second area based on the first brightness signal.

7. The marking measurement method according to claim 5 or 6, wherein: The method comprises calculating at least one of the absolute position AP1 of the second pattern or the fourth pattern provided on the other layer in the prescribed direction by using formula (7) and the absolute position AP2 of the first pattern or the third pattern provided on the first layer in the prescribed direction by using formula (8), 【Mathematical formula 3】 【Mathematical formula 4】 8. The marking measurement method according to any one of claims 2 to 4 and 6, wherein: Determining the first moiré position in the specified direction or the second moiré position in the specified direction according to the brightness signal includes: a. extracting a signal length that is a positive integer multiple of the period of the moiré fringe from the brightness signal; b. preparing a basis function of the moiré fringe signal; c. calculating the inner product of the intercepted luminance signal and the basis function within the range of the intercepted signal length; d. obtaining the frequency component of the moire fringe signal and detecting the phase of the obtained frequency component based on the calculation result of the inner product; and e. Determine the first moiré position or the second moiré position based on the detected phase.

9. The marking measurement method according to claim 1, wherein: Determining the absolute position of at least one of the first pattern and the second pattern in the specified direction based on the extracted brightness signal includes: separating the brightness signal of the first pattern from the brightness signal, and separating at least one of the brightness signal of the second pattern from the brightness signal.

10. The marking measurement method according to claim 9, wherein: Separating at least one of the brightness signal of the first pattern and the brightness signal of the second pattern from the brightness signal includes: a. A signal length that is a positive integer multiple of the period of the pattern to be separated is extracted from the brightness signal; b. preparing a basis function of the brightness signal of the pattern to be separated; c. calculating the inner product of the intercepted luminance signal and the basis function within the range of the intercepted signal length; and d. According to the calculation result of the inner product, obtain the frequency component of the brightness signal of the pattern to be separated.

11. The marking measurement method according to claim 8 or 10, wherein: It also includes a process of resampling the brightness signal at a data pitch, wherein the data pitch is less than 1 / 2 of the period of the pattern to be separated, and a positive integer multiple of the data pitch is a positive integer multiple of the period of the pattern to be separated.

12. The marking measurement method according to any one of claims 8, 10 and 11, wherein: The basis function is a sine function.

13. The marking measurement method according to claim 10, comprising: detecting a phase according to the acquired frequency component of the brightness signal of the pattern to be separated; as well as The absolute position of the pattern is obtained based on the detected phase.

14. A marking measurement method, comprising: generating a brightness signal in the predetermined direction of a registration mark formed by overlapping a first pattern and a second pattern, wherein the first pattern is formed by lines and spaces being repeated along a predetermined direction at a first pitch P1 on a layer on a substrate, and the second pattern is formed by lines and spaces being repeated along the predetermined direction at a second pitch P2 different from the first pitch P1 on a layer different from the first pattern; separating and extracting a brightness signal of the first pattern from the brightness signal; and The absolute position of the first pattern is calculated based on the extracted brightness signal of the first pattern.

15. The marking measurement method according to claim 14, wherein: The registration mark is formed by overlapping the first pattern and the second pattern in a common first region.

16. The marking measurement method according to claim 14 or 15, wherein: Separating and extracting the brightness signal of the first pattern includes: Extracting a signal length that is a positive integer multiple of the first interval from the brightness signal; preparing a basis function of brightness variation of the first pattern; and An inner product of the luminance signal and the basis function is calculated within the range of the truncated signal length.

17. The marking measurement method according to claim 16, wherein: The frequency component of the brightness signal of the first pattern is obtained according to the calculation result of the inner product, and the absolute position of the first pattern is calculated by detecting the phase of the obtained frequency component.

18. The marking measurement method according to any one of claims 1 to 17, wherein: Based on the extracted brightness signal, the first absolute position of the first pattern in the specified direction and the second absolute position of the second pattern in the specified direction are determined, and the relative misalignment between the first pattern and the second pattern in the specified direction is calculated based on the first absolute position and the second absolute position.

19. A marking measurement method, wherein: The prescribed direction includes a first direction and a second direction intersecting the first direction. The marking measurement method comprises: obtaining an absolute position of at least one of the first pattern and the second pattern in the first direction using the marking measurement method according to any one of claims 1 to 18; and The absolute position of at least one of the first pattern and the second pattern in the second direction is obtained using the marker measurement method according to any one of claims 1 to 18.

20. The marking measurement method according to claim 19, wherein: Calculating a relative offset between the first pattern and the second pattern in the first direction according to the absolute positions of the first pattern and the second pattern in the first direction, A relative displacement amount between the first pattern and the second pattern in the second direction is calculated based on the absolute positions of the first pattern and the second pattern in the second direction.

21. A measuring device for measuring a mark formed on a substrate, the measuring device comprising: a platform configured to form a substrate with registration marks; a camera unit for photographing the overlap mark; as well as A control device performs control to measure the absolute position of at least one of the first pattern and the second pattern by executing the mark measurement method according to any one of claims 1 to 20 based on the image of the registration mark captured by the imaging unit.

22. An exposure device for exposing a substrate with exposure light, the exposure device comprising: a platform configured to form a substrate with registration marks; a camera unit for photographing the overlap mark; as well as A control device performs control to measure the absolute position of at least one of the first pattern and the second pattern by executing the mark measurement method according to any one of claims 1 to 20 based on the image of the registration mark captured by the imaging unit.

23. A computing device comprising: an input unit that inputs information related to an image of a registration mark formed on a substrate; a calculation unit for calculating an absolute position of at least one of the first pattern and the second pattern by executing the mark measurement method according to any one of claims 1 to 20; as well as An output unit outputs information related to the absolute position of at least one of the first pattern and the second pattern calculated by the calculation unit. 24 . A program for causing a measuring device or an exposure device to execute the marking measurement method according to claim 1 . 25 . A storage medium storing a program for causing a measuring device or an exposure device to execute the mark measurement method according to claim 1 .

Images