Measurement method, measurement device, lithography device and article production method

Abstract

To provide a technique advantageous in realizing a high measurement accuracy.SOLUTION: A measurement method includes: a preliminary measurement step of conducting a plurality of times of preliminary measurements while changing combinations of parameter values of a plurality of measurement parameters different from each other; a treatment step of obtaining a sensitivity distribution being a distribution of sensitivity showing a change in a measured value to a parameter value change, with regard to each of the plurality of measurement parameters, according to the measured value obtained at the preliminary measurement step; a determination step of determining a parameter value to be adopted for each of the plurality of measurement parameters, according to the sensitivity distribution for each of the plurality of measurement parameters; and a main measurement step of conducting a main measurement according to each parameter value of the plurality of measurement parameter determined at the determination step.SELECTED DRAWING: Figure 6

Description

Technical Field

[0005]

[0001] The present invention relates to a measurement method, a measurement apparatus, a lithography apparatus, and an article manufacturing method.

Background Art

[0002] In a lithography apparatus such as an exposure apparatus used in a lithography process, the alignment accuracy between the shot area of a substrate and a reticle, and the overlay accuracy between different layers on the substrate are important. As one method for measuring a mark formed on a substrate with high precision, there is a method of adapting the wavelength of measurement light to the physical or optical characteristics of the mark and its peripheral portion. The physical properties, structure, and shape of the material in the mark on the substrate can vary depending on the process. Therefore, by selecting an optimal wavelength according to the mark, the intensity and quality of the detection signal from the mark can be maximized, and high-precision measurement can be realized.

[0003] Patent Document 1 describes that for a plurality of combinations of wavelength and focus position, the amount of misalignment is obtained for each, and the wavelength and focus position at which the variation in the amount of misalignment is minimized are set as measurement conditions.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When measuring a mark formed on a substrate, if the parameter value of the measurement parameter is different from the optimal value, the intensity and quality of the detection signal from the mark may decrease, leading to a decrease in measurement accuracy

[0006] An object of the present invention is to provide a technique advantageous for achieving high measurement accuracy. [Means for solving the problem]

[0007] One aspect of the present invention relates to a measurement method, the measurement method comprising: a preliminary measurement step of performing preliminary measurements multiple times with different combinations of parameter values ​​for each of a plurality of mutually different measurement parameters; a processing step of obtaining a sensitivity distribution, which is a distribution of sensitivity indicating the change in the measured value in response to a change in the parameter value, for each of the plurality of measurement parameters based on the measured values ​​obtained in the preliminary measurement step; a determination step of determining the parameter value to be adopted for each of the plurality of measurement parameters based on the sensitivity distribution for each of the plurality of measurement parameters; and a main measurement step of performing the main measurement according to the parameter value of each of the plurality of measurement parameters determined in the determination step. [Effects of the Invention]

[0008] According to the present invention, a technology advantageous for achieving high measurement accuracy is provided. [Brief explanation of the drawing]

[0009] [Figure 1] A diagram showing the configuration of the measuring device according to the first embodiment. [Figure 2] A diagram to explain the problem. [Figure 3] A diagram illustrating the configuration and function of the wavelength tunable section in the measuring device of the first embodiment. [Figure 4] A diagram illustrating the measurement sequence in the measuring device of the first embodiment. [Figure 5] A diagram illustrating the specific measurement process in the measuring device of the first embodiment. [Figure 6] A diagram illustrating the specific measurement process in the measuring device of the first embodiment. [Figure 7] A diagram illustrating the specific measurement process in the measuring device of the first embodiment. [Figure 8] A diagram illustrating the measurement sequence in the measuring device of the second embodiment. [Figure 9] A diagram illustrating the specific measurement process in the measuring device of the second embodiment. [Figure 10] A diagram illustrating the specific measurement process in the measuring device of the second embodiment. [Figure 11] A diagram illustrating the measurement sequence in the measuring device of the third embodiment. [Figure 12] A diagram illustrating the measurement sequence in the measuring device of the fourth embodiment. [Figure 13] A diagram illustrating the configuration of the exposure apparatus according to the fifth embodiment. [Figure 14] A diagram illustrating the sequence of exposure processing for exposing a substrate. [Modes for carrying out the invention]

[0010] The embodiments will be described in detail below with reference to the attached drawings. Note that the following embodiments do not limit the invention as defined in the claims. While the embodiments describe multiple features, not all of these features are essential to the invention, and the features may be combined in any way. Furthermore, in the attached drawings, identical or similar configurations are given the same reference numerals, and redundant descriptions are omitted.

[0011] Figure 1(a) is a schematic and illustrative diagram showing the configuration of the measuring device 100 of the first embodiment. The measuring device 100 may be configured as a position detection device that measures or detects the position of a target or object to be measured provided on the substrate 73. Alternatively, the measuring device 100 may be configured as an overlay inspection device that measures the relative positions of a plurality of targets provided on different layers of the substrate. As shown in Figure 1(a), the measuring device 100 includes a substrate stage WS that holds the substrate 73, a measuring unit 50, and a control unit 1100.

[0012] The substrate 73 is a measurement target member whose position or misalignment error is measured by the measuring device 100. The substrate 73 can be used, for example, to manufacture devices such as semiconductor elements and liquid crystal display elements. The substrate 73 can be, for example, a wafer or a glass substrate. The substrate stage WS holds the substrate 73 via a substrate chuck (not shown) and can be driven or positioned by a substrate drive mechanism (not shown). The substrate drive mechanism includes, for example, a linear motor and drives the substrate stage WS in the X-axis direction, Y-axis direction, Z-axis direction, and the rotational directions of each axis, thereby driving or positioning the substrate 73 held by the substrate stage WS. The position of the substrate stage WS is monitored by, for example, a six-axis laser interferometer 81, and under the control of the control unit 1100, the substrate stage WS is driven to a predetermined position. In this specification, the direction is expressed by an XYZ coordinate system with the normal line of the surface of the measurement target member as the Z-axis direction. The six axes are the X-axis direction, Y-axis direction, Z-axis direction, rotation around the X-axis (ωX), rotation around the Y-axis (ωY), and rotation around the Z-axis (ωZ). The Z-axis direction may be understood as the optical axis direction of the measuring device 100 on the surface of the measurement target member.

[0013] The control unit 1100 is composed of a computer (information processing device) including a CPU and a memory, etc., and can define the functions of the measuring device 100 by comprehensively controlling the components of the measuring device 100 according to, for example, a program stored in the storage unit. The control unit 1100 can be configured to control the measurement process in the measuring device 100 and the correction process (arithmetic process) of the measurement values obtained by the measuring device 100.

[0014] The configuration of the measurement unit 50 will be described while referring to FIG. 1(b). The measurement unit 50 may include an illumination system that illuminates the substrate 73 using light from the light source 61, and an imaging system (detection system) that forms an image of the light from the measurement pattern (mark) 72 provided on the substrate 73 on the detection unit 75. The detection unit 75 includes a plurality of pixels that detect the light from the measurement pattern 72, and functions as an imaging unit that forms an imaging area for imaging the measurement pattern 72 by the plurality of pixels. Here, the measurement pattern 72 to be measured or targeted may be a pattern for measuring the alignment error or overlay error in the substrate 73. The measurement target or target may include a plurality of measurement patterns 72. Note that the measurement target is not limited to the measurement pattern provided on the substrate, and may be, for example, a stage or a part thereof, or a moving object or a part thereof. Further, the information obtained by the measurement is not limited to position information such as the absolute position or relative position of the measurement target, and may be, for example, at least one of the shape, speed, acceleration, and temperature of the measurement target.

[0015] As shown in FIG. 1(b), the light from the light source 61 is guided to the wavelength variable unit 40 through the illumination optical system 62. The light source 61 may be, for example, a laser light source, an LED, or a halogen lamp, but is not limited thereto. The wavelength variable unit 40 may include, for example, a wavelength variable element and a drive mechanism that drives the wavelength variable element. The drive mechanism includes a linear motor or the like, and by driving the wavelength variable element 42 along a predetermined direction (for example, the X-axis direction), the wavelength (for example, the center wavelength and the wavelength width) of the light that illuminates the measurement pattern 72 or the target can be adjusted. The position of the wavelength variable element is monitored using a sensor such as an encoder or an interferometer, for example, and can be positioned at the target position under the control of the control unit 1100. By adjusting the position of the wavelength variable element with respect to the optical path of the light having a wideband wavelength emitted from the light source 61 by the drive mechanism, the area where the light is incident on the wavelength variable element can be adjusted. Thereby, the light having the target wavelength passes through the wavelength variable element.

[0016] Light that has passed through the tunable section 40 or its tunable element is guided through the illumination optical system 63 to the illumination aperture diaphragm 64. The diameter of the light beam at the illumination aperture diaphragm 64 is smaller than the diameter of the light beam at the light source 61. The light that has passed through the illumination aperture diaphragm 64 is guided through the relay lens 67 to the polarizing beam splitter 68. The polarizing beam splitter 68 transmits P-polarized light and reflects S-polarized light. The P-polarized light that has passed through the polarizing beam splitter 68 is converted to circularly polarized light by passing through the aperture diaphragm 69 and the λ / 4 plate 70, and illuminates the measurement pattern 72 provided on the substrate 73 via the objective optical system 71.

[0017] The illumination optical system 63 may also be provided with a light intensity adjustment unit (not shown). For example, by providing a light intensity adjustment unit in which multiple ND filters with different transmittances are selectively arranged for light from the light source 61, the intensity of the light illuminating the substrate 73 can be adjusted.

[0018] Light reflected, diffracted, and scattered by the measurement pattern 72 on the substrate 73 passes through the objective optical system 71 and the λ / 4 plate 70, where it is converted from circularly polarized light to S-polarized light and guided to the aperture diaphragm 69. Here, the polarization state of the light from the measurement pattern 72 is the opposite of the circularly polarized light illuminating the measurement pattern 72. Therefore, if the polarization state of the light illuminating the measurement pattern 72 is clockwise circularly polarized, the polarization state of the light from the measurement pattern 72 will be counterclockwise circularly polarized. The light passing through the aperture diaphragm 69 is reflected by the polarizing beam splitter 68 and guided to the detection unit 75 via the imaging optical system 74.

[0019] In this way, the measurement unit 50 separates the optical path of light illuminating the substrate 73 from the optical path of light from the substrate 73 by the polarizing beam splitter 68, and an image of the measurement pattern 72 provided on the substrate 73 is formed in the detection unit 75. The control unit 1100 can acquire the positions of the pattern elements constituting the measurement pattern 72 and the position of the measurement pattern 72 based on the position information of the substrate stage WS obtained by the laser interferometer 81 and the waveform of the detection signal obtained by detecting the image of the measurement pattern 72.

[0020] Multiple lenses and detection aperture diaphragms may be arranged between the polarizing beam splitter 68 and the detection unit 75. Multiple aperture diaphragms may be provided for both the illumination aperture diaphragm 64 and the detection aperture diaphragm, allowing for different numerical apertures to be set for the illumination system and the detection system. This makes it possible to adjust the σ value, which is a coefficient representing the ratio of the numerical aperture of the illumination system to the numerical aperture of the detection system.

[0021] Next, the measurement parameters in the measuring device 100 will be described. Preferably, the measuring device 100 can perform measurements according to the set parameter values ​​of at least two parameters. The at least two measurement parameters may include, for example, at least two of the following: the central wavelength, wavelength width, σ value, polarization characteristics, transmittance, and the position (X, Y, Z) and tilt (ωX, ωY, ωZ) of the measurement pattern relative to the measuring unit 50. The deflection characteristics may be the deflection characteristics in the optical path of the measuring device 100 or the measuring unit. The transmittance may be the transmittance of an ND filter placed in the optical path. The at least two measurement parameters may also include various calculation processing parameters set by the control unit when calculating the measurement value from the target image information.

[0022] The characteristics of the measurement pattern on the substrate, such as the material properties, structure, and shape, can vary depending on the process used to obtain the substrate. Therefore, to achieve high-precision measurement, it is crucial to adapt the measurement parameters to the characteristics of the measurement pattern. Below, as an example of measurement parameters, we will describe measurement parameters related to the wavelength of light used in the measurement.

[0023] Two measurement parameters related to the wavelength of light used for measurement are, for example, the center wavelength and the wavelength width. Figure 2(a) shows the wavelength characteristics of light with different center wavelengths, where the two different center wavelengths are shown as WL1 and WL2, respectively. Figure 2(b) shows the wavelength characteristics of light having the same center wavelength but different wavelength widths, where the two different wavelength widths are shown as ΔWL1 and ΔWL2. By setting appropriate center wavelengths and wavelength widths for the measurement pattern formed on the substrate, the intensity and quality of the signal from the measurement pattern can be maximized, enabling high-precision measurement.

[0024] Before describing the details of how to set the measurement parameters in the embodiment, we will explain how to set the measurement parameters in the comparative example's superposition inspection device (measurement device) with reference to Figure 2(c). In the comparative example's superposition inspection device, measurement data as shown in Figure 2(c) can be obtained by measuring the superposition error Mij of the measurement pattern for each of the multiple combinations of focus position Zi and wavelength WLj. Figure 2(c) is a diagram showing an example of measurement data of the superposition error M of the measurement pattern obtained for each of the multiple combinations of focus position Zi and wavelength WLj. For example, the position of the measurement pattern obtained under the measurement conditions of wavelength WL1 at focus position Z1 is expressed as M11. Then, based on the measurement data shown in Figure 2(c), the variation in superposition error A1 to Aj according to the focus position and the variation in superposition error B1 to Bi according to the wavelength are calculated. As a specific example, the variation in superposition error A1 is calculated from the variation 3σ or range of the superposition error M11 to Mi1 of the measurement pattern. Furthermore, the superposition error variation B1 is calculated from the variation 3σ or range of the superposition errors M11 to M1j of the measurement patterns. Based on these results, the wavelength that minimizes the superposition error variation A1 to Aj and the focus position that minimizes the superposition error variation B1 to Bi are set as measurement parameters.

[0025] However, the relative magnitude of the superposition error variation under each measurement condition can depend on both the focus position and the wavelength. Even if the focus position Z1 and wavelength WL1 are optimal parameter values, if the measurement errors M12 and M21 are large, the superposition error variations A1 and B1 will not be minimized. Therefore, the optimal conditions (focus position Z1, wavelength WL1) cannot be set as parameter values. Consequently, when using the variation in superposition error under a single measurement condition (e.g., only the center wavelength) as an evaluation index, it is difficult to accurately determine the optimal parameter values. Furthermore, if the center wavelength and wavelength width, which determine the wavelength characteristics, are not evaluated as parameter values, the optimization of the intensity and quality of the detection signal from the measurement pattern will be insufficient, making it difficult to achieve high measurement accuracy.

[0026] Therefore, the measuring device 100 of this embodiment performs preliminary measurements multiple times, each with a different combination of parameter values ​​for a plurality of different measurement parameters. Based on the measurement values ​​obtained, the measuring device 100 obtains a sensitivity distribution for each of the plurality of measurement parameters, which is a distribution of sensitivity to changes in the measurement value in response to changes in the parameter value. Based on this sensitivity distribution, the measuring device 100 determines the parameter value to be adopted for each of the plurality of measurement parameters, and performs the main measurement according to the parameter value determined for each of the plurality of measurement parameters. The following describes how to set the parameter values ​​of the measurement parameters in the measuring device of this embodiment.

[0027] Figure 3(a) shows an example of the configuration of the wavelength tunable unit 40. The wavelength tunable unit 40 may include a wavelength tunable element 42, a holding member 45 that holds the wavelength tunable element 42, and a drive mechanism 47 that drives the holding member 45 (wavelength tunable element 42). By driving the wavelength tunable unit 40 in a predetermined direction (for example, rotation around the X direction or Z axis) with the drive mechanism 47, the incident area of ​​light on the wavelength tunable element 42 can be adjusted. As a result, broadband wavelength light emitted from the light source 61 is converted into light of a wavelength corresponding to the incident area of ​​the light on the wavelength tunable unit 40, illuminating the substrate 73. In other words, based on broadband wavelength light emitted from the light source 61, light of a wavelength corresponding to the incident area of ​​the light on the wavelength tunable unit 40 is generated as illumination light, and the substrate 73 is illuminated by this illumination light.

[0028] The tunable element 42 may be, for example, a transmission tunable filter or a transmission diffraction grating. This allows the control unit 1100 to adjust (change) the wavelength of light transmitted through the tunable element 42 by controlling its position or angle via the drive mechanism 47. A transmission tunable filter is, for example, a bandpass filter having a multilayer laminated film formed on the surface of a substrate, where the thickness of the multilayer laminated film may vary depending on the position in the wavelength change direction. Such a structure allows for a continuous change in the wavelength of transmitted light due to light interference.

[0029] Figure 3(b) illustrates the relationship between the wavelength of light transmitted through the tunable element 42 and the signal intensity when the tunable element 42 is moved to multiple positions in a predetermined direction by the drive mechanism 47. For example, if the position of the tunable element 42 in the X direction can be continuously adjusted, the central wavelength of the light transmitted through the tunable element 42 can be continuously changed by adjusting the position in the X direction from which light is incident on the tunable element 42. In addition, the tunable section 40 may be configured to include, for example, a tunable element 42 for short wavelength cutoff and a tunable element 42 for long wavelength cutoff, and to be driven individually. This makes it possible to arbitrarily change both the central wavelength and wavelength width of the transmitted light by controlling the tunable element 42 for short wavelength cutoff and the tunable element 42 for long wavelength cutoff.

[0030] Next, the sequence of the measurement process in the first embodiment will be described with reference to Figure 4. In the measurement process, parameter values ​​for measurement parameters are set, and measurements are performed according to those parameter values. Furthermore, as described above, the measurement process is carried out by the control unit 1100 comprehensively controlling each part of the measuring device 100.

[0031] When the measurement process begins, first, in S131, a process may be performed to align the relative positions of the substrate 73 and the measurement unit 50 under the control of the control unit 1100. Specifically, an image sensor may be used in the detection unit 75 of the measurement unit 50, and the substrate stage WS holding the substrate 73 may be driven so that an image of the measurement pattern 72 is formed in the imaging area of ​​the image sensor. The adjustment of the position of the substrate 73 in the Z-axis direction (optical axis direction, or direction along the light beam) relative to the measurement unit 50 may be called focus adjustment. In focus adjustment, for example, the signal intensity of at least one pattern constituting the measurement pattern 72 may be determined, and the substrate stage WS holding the substrate 73 may be positioned so that the signal intensity and its change are equal to or greater than a target value. Alternatively, in focus adjustment, the signal intensity of each of the multiple patterns constituting the measurement pattern 72 may be determined, and the substrate stage WS holding the substrate 73 may be positioned so that the signal intensity of both and their change are equal to or greater than a target value.

[0032] In S132, under the control of the control unit 1100, the detection unit 75 may acquire (image) an image of the measurement pattern 72 on the substrate 73 multiple times, while varying the combination of parameter values ​​for at least two different measurement parameters. This can be understood as part of a preliminary measurement process in which preliminary measurements are performed for each combination while varying the combination of parameter values ​​for multiple different measurement parameters. The image of the measurement pattern 72 can be understood as intermediate information for obtaining measurement values. Examples of multiple different measurement parameters include a center wavelength and a wavelength width that can be controlled by the wavelength tunable unit 40. Below, an example in which a center wavelength and a wavelength width are selected as multiple different measurement parameters will be described, but other measurement parameters may be selected.

[0033] S133 is an optional step. In S133, a synthesis process is performed to generate a composite image using multiple images acquired in S132. S133 can be understood as part of an estimation process that estimates the measured values ​​obtained in combinations different from those used for preliminary measurements, based on the images obtained as intermediate information in S132. The synthesis process in S133 will be explained in detail later.

[0034] In S134, the control unit 1100 performs a first process to calculate the position (measured value) of the measurement pattern based on the image acquired in S132, and a second process to calculate the position (measured value) of the measurement pattern based on the composite image generated in S133. In S134, the measured value is not limited to the position information of the measurement pattern, but may also be signal strength information of the measurement pattern, or waveform evaluation value information that indicates the characteristics of the signal waveform. The signal strength information and waveform evaluation value information of the measurement pattern will be explained in detail later. Note that if S133 is not executed, the second process in S134 is also not executed.

[0035] Here, the first processes in S132 and S134 can be understood as preliminary measurement steps in which preliminary measurements are taken for each combination of parameter values ​​of multiple different measurement parameters. Furthermore, S132 can be understood as a detection step in which an image is detected from the measurement target as intermediate information for obtaining measurement values. Furthermore, the first process in S134 can be understood as a calculation step in which measurement values ​​are calculated based on the image as intermediate information.

[0036] Furthermore, the second processing in S133 and S134 can be understood as an estimation process that estimates the measurement values ​​obtained in combinations different from the combinations for which preliminary measurements were taken, based on the images obtained as intermediate information in S132. Here, in the detection process, the image of the object to be measured may be detected as intermediate information. In the estimation process, a composite image is generated from multiple images as intermediate information, and based on this composite image, the measurement values ​​obtained in combinations different from the combinations for which preliminary measurements were taken may be estimated.

[0037] In S135, the control unit 1100 may calculate a sensitivity distribution for at least two measurement parameters based on the measurement values ​​obtained in S134. This sensitivity distribution is a distribution of sensitivity that shows the change in the measurement value of the measurement pattern in response to changes in parameter values. As a sensitivity distribution that shows the change in the measurement value in response to changes in parameter values, for example, a sensitivity distribution that shows the change in the measurement value in response to changes in the center wavelength and a sensitivity distribution that shows the change in the measurement value in response to changes in the wavelength width may be obtained. The sensitivity distribution includes at least two sensitivities corresponding to at least two parameter values. The method for calculating the sensitivity distribution will be explained in detail later.

[0038] In S136, the control unit 1100 may determine parameter values ​​for at least two measurement parameters based on the sensitivity distribution calculated in S135. This can be understood as a decision step in which the parameter values ​​to be adopted for each of the multiple measurement parameters are determined based on the sensitivity distribution for each of the multiple measurement parameters. This determination process allows us to determine the optimal center wavelength and wavelength width (or combination thereof).

[0039] In S137, under the control of the control unit 1100, the detection unit 75 acquires image information of the measurement pattern 72 according to the parameter values ​​of each of the multiple measurement parameters determined in S136, and the position of the measurement pattern 72 can be measured based on that image information. This can be understood as the main measurement step, in which the main measurement is performed according to the parameter values ​​of each of the multiple measurement parameters determined in S135 (determination step).

[0040] The following describes the method for combining multiple images in S133, with reference to Figure 5. Here, we will explain how to set two measurement parameters, specifically the center wavelength and wavelength width. Figure 5(a) shows image 76a, which includes the measurement pattern 72a acquired by the detection unit 75 under the conditions of a center wavelength of 480 nm and a wavelength width of ±10 nm. Figure 5(b) shows image 76b, which was acquired by the detection unit 75 under the conditions of a center wavelength of 500 nm and a wavelength width of ±10 nm. Images 76a and 76b shown in Figures 5(a) and 5(b), respectively, schematically represent images acquired with ND filter transmittances of 40% and 60%, and an accumulation time of 10 msec for the detection unit 75. Images 76a and 76b exhibit the characteristic that the signal intensity of the patterned and non-patterned areas differs from each other depending on the parameter values.

[0041] Figure 5(c) shows a composite image 76c obtained by combining image 76a and image 76b based on a reference brightness. Here, the reference brightness refers to the standard brightness calculated from the measurement conditions (parameter values) related to the amount of light set when detecting each image, and is obtained for the purpose of matching the brightness of multiple images when performing the composite processing. If the transmittance of the ND filter used to detect the two images 76a and 76b used in the composite processing is Ta and Tb, and the accumulation time is Ca and Cb, then the brightness Sa and Sb of images 76a and 76b can be expressed by the following (Equation 1) and (Equation 2).

[0042] Sa = 1 / (Ca × Ta) (Equation 1) Sb = 1 / (Cb × Tb) (Equation 2) When Ta < Tb and Ca < Cb, the higher-luminance Sa is the reference luminance. From Equation (1), Equation (2), and the measurement conditions shown in FIG. 5(b), the ratio of luminance Sb to the reference luminance Sa is obtained as 0.67. Then, an image is generated by multiplying the pixel output of image 76b by the ratio of luminance to the reference luminance, and the generated image is combined with the reference-luminance image 76a to generate a composite image 76c corresponding to the image detected under the conditions of a center wavelength of 490 nm and a wavelength width of ±20 nm. As a result, compared with the case of obtaining images for all combinations of a plurality of required center wavelengths and a plurality of required wavelength widths, the time required to determine the optimal center wavelength and wavelength width can be shortened.

[0043] If image synthesis is performed without matching the reference values of the detection light amounts of the two images used in the synthesis process, there will be a difference in the signal intensities of the pattern part and the non-pattern part between the actually acquired image and the image formed by the synthesis process. Therefore, it is difficult to accurately obtain the optimal combination of the center wavelength and the wavelength width. For this reason, in S133, it is preferable to perform the synthesis process with the reference values of the detection light amounts of the two images matched, whereby the optimal combination of the center wavelength and the wavelength width can be accurately determined. In addition, in Equation (1) and Equation (2), the method of calculating the luminance using the transmittance of the ND filter and the accumulation time is described, but it is not limited thereto. For example, the current value for controlling the output of the light source 61 and the gain set for the detection unit 75 may be set.

[0044] Next, the method for calculating the position information of the measurement pattern in S134 will be explained. The position of the measurement pattern 72 can be calculated by processing the image of the measurement pattern 72 acquired in S133, for example, using the template matching method. In the template matching method, the position with the highest correlation can be detected as the center position of the measurement pattern by performing a correlation calculation between the signal acquired in S133 and a model signal (template) acquired in advance. By determining the centroid pixel position of a region of several pixels to the left and right of the peak position in the function of the correlation value, a resolution of 1 / 10 to 1 / 50 pixels can be achieved.

[0045] The method for calculating the sensitivity distribution in S135 will be explained below with reference to Figure 6. As an example of a sensitivity distribution, a sensitivity distribution that shows the change in measured values ​​in response to a change in the central wavelength (simply put, the sensitivity distribution to a change in the central wavelength) will be explained here as an example. The sensitivity distribution to a change in the central wavelength is a set of sensitivities that show the change in measured values ​​in response to a change in the central wavelength, and includes at least two sensitivities. The sensitivity distribution to a change in the central wavelength serves as an indicator for determining the value of the central wavelength as a measurement parameter to be adopted for measurement in S136.

[0046] Figure 6(a) shows the relationship between the position information (measured value) of the measurement pattern and the central wavelength, with the central wavelength (labeled "wavelength") on the horizontal axis and the position information of the measurement pattern (labeled "measured value") on the vertical axis. Central wavelengths WL3 and WL4 refer to the central wavelength of light. With the surface of the substrate 73 aligned to the best focus position of the measurement unit 50, the measured value when the position of the measurement pattern 72 is measured with light of central wavelength WL3 is denoted as M23, and the measured value when the position of the measurement pattern 72 is measured with light of central wavelength WL4 is denoted as M24. Figure 6(b) shows the wavelength sensitivity distribution that indicates the change in the measured value of the measurement pattern 72 in response to a change in the central wavelength, with the central wavelength on the horizontal axis and the change in the measured value calculated from the measured value shown in Figure 6(a) on the vertical axis. As an example, the central wavelength dWL3 and the change in measured value dMw3 are expressed by (Equation 3) and (Equation 4), respectively.

[0047] dWL3=(WL3+WL4)÷2 (Formula 3) dMw3=(M24-M23)÷(WL4-WL3) (Formula 4) Next, the method for determining the parameter values ​​of the measurement parameters in S136 (determination step) will be explained. In S136, the parameter values ​​to be adopted are determined based on the sensitivity distribution calculated in S135. As a criterion for judgment in S136, it is preferable to select parameter values ​​that show low sensitivity. From another perspective, in S136 (determination step), it is preferable to determine the parameter values ​​to be adopted such that the sensitivity in the sensitivity distribution is less sensitive than a predetermined sensitivity for the parameter values ​​to be adopted. From yet another perspective, in S136 (determination step), it is preferable to determine the parameter values ​​to be adopted such that the sensitivity in the sensitivity distribution is the minimum for the parameter values ​​to be adopted.

[0048] The above reasons for determining the parameter values ​​will be explained below using Figure 7. Figure 7(a) is a diagram illustrating reflected light from the measurement pattern 72 and the non-patterned area in a cross-section of the substrate 73. The substrate 73 is composed of a first layer L1 and a second layer L2 and has two interface surfaces S1 and S2. At interface surface S1, the measurement pattern 72 has a step of height d relative to the non-patterned area. The reflected light from the measurement pattern 72 at interface surface S1 is denoted as L1A, and the reflected light from the non-patterned area as L1B. At interface surface S2, the reflected light from the measurement pattern 72 and the non-patterned area are denoted as L2A and L2B, respectively. In the measurement unit 50, the interference light of reflected light L1A and L2A, and the interference light of reflected light L1B and L2B become the reflected light LA ​​from the measurement pattern 72 and the reflected light LB from the non-patterned area, respectively, and are detected.

[0049] Figure 7(b) is a diagram showing an example of signal intensity information for position X, and includes reflected light LA ​​from the patterned area and reflected light LB from the non-patterned area shown in Figure 7(a). Here, the smaller the difference in signal intensity between reflected light LA ​​and LB, the lower the signal contrast becomes, and the more difficult it is to detect the position of the measurement pattern. The difference in signal intensity between reflected light L1 and L2 changes according to the phase difference Δ caused by the step d of the measurement pattern 72, and the phase difference Δ is expressed by the following equation (5) using the refractive index n of the second layer L2, the step d, and the wavelength λ.

[0050] Δ = 2nd × 2π / λ (Equation 5) (Equation 5) If there are variations in the refractive index n and step height d of the second layer L2 in the measurement pattern 72, the phase difference Δ will change. As mentioned above, a change in the phase difference Δ leads to a change in signal contrast, which may result in measurement errors and a decrease in measurement accuracy.

[0051] Here, as shown in (Equation 5), the change in the center wavelength corresponds to the variation in the phase difference Δ, so the sensitivity that indicates the change in the measured value to the change in the center wavelength corresponds to the variation in the measured value to the variation in the phase difference. For this reason, in S136 of this embodiment, by selecting a parameter value that has a small sensitivity that indicates the change in the measured value to the change in the center wavelength, measurement errors associated with process changes can be reduced.

[0052] Figure 7(c) shows an example of signal strength information. Here, waveform evaluation value information refers to an index indicating the quality of the signal waveform generated based on the output of the detection unit 75. An example of waveform evaluation value information is a value that quantifies the asymmetry of the signal waveform of the measurement pattern. For example, in Figure 7(a), the maximum value of the signal strength in the left section of the signal waveform is TL and the minimum value is BL, the maximum value of the signal strength in the right section is TR and the minimum value is BR, and the signal strength in the central part of the signal waveform is ML and MR. Then, as shown in (Equation 6) below, the asymmetry ES between the left and right sections of the signal waveform may be obtained as a measured value in S134.

[0053] ES=(TL−BL) / (TL+BL)−(TR−BR) / (TR+BR) (Equation 6) The method for calculating asymmetry is not limited to (Equation 6). For example, the asymmetry of the signal waveform may be defined based on the signal intensity within predetermined position ranges in the left and right sections relative to the center position. Furthermore, the waveform evaluation value information is not limited to asymmetry. For example, the contrast of the measurement pattern may be evaluated as shown in (Equation 7) below.

[0054] EC={(TL−BL) / (TL+BL)+(TR−BR) / (TR+BR)} / 2 (Equation 7) As described above, instead of obtaining positional information of the measurement pattern, waveform evaluation value information may be used as the measured value, and the parameter values ​​of the measurement parameters may be determined based on the signal intensity information of the measurement pattern and the sensitivity of the waveform evaluation value information.

[0055] As described above, in the first embodiment, the sensitivity distribution for each of the multiple measurement parameters is determined, and based on that sensitivity distribution, the parameter value to be adopted for each of the multiple measurement parameters is determined. This makes it possible to measure the object to be measured quickly and with high accuracy.

[0056] The measurement device and measurement process in the second embodiment will be described below with reference to Figure 8. The difference between the second embodiment and the first embodiment lies in the method for calculating sensitivity for setting the parameter values ​​of the measurement parameters; all other configurations are the same as in the first embodiment. Matters not mentioned here may follow those of the first embodiment.

[0057] Figure 8 shows the sequence of the measurement process in the second embodiment. This measurement process is performed by the control unit 1100 shown in Figure 1 comprehensively controlling each part of the measurement device 100, similar to the first embodiment. When the measurement process starts, first, in S231, a process to align the relative positions of the substrate 73 and the measurement unit 50 may be performed under the control of the control unit 1100. In S232, under the control of the control unit 1100, the detection unit 75 may acquire (image) an image of the measurement pattern 72 provided on the substrate 73 multiple times, while varying the combination of parameter values ​​for at least two different measurement parameters. This can be understood as part of a preliminary measurement process in which preliminary measurements are performed for each combination while varying the combination of parameter values ​​for multiple different measurement parameters. Examples of multiple different measurement parameters include a center wavelength and a wavelength width that can be controlled by the wavelength tunable unit 40. Below, an example in which a center wavelength and a wavelength width are selected as multiple different measurement parameters will be described. Furthermore, in the second embodiment, the sensitivity of the measured value to the displacement (defocus) of the surface of the substrate 73 from the best focus position of the measurement unit 50 is taken into consideration. Therefore, S232 includes the operation of driving the substrate stage WS holding the substrate 73 by a predetermined amount in the Z direction, so that an image of the measurement pattern 72 can be acquired (imaged) by the detection unit 75 at each of the different positions in the Z direction.

[0058] S233 is an optional step. In S233, the control unit 1100 performs a synthesis process to generate a composite image using the multiple image information acquired in S232. In S234, the control unit 1100 performs a first process to calculate the position (measured value) of the measurement pattern based on the image acquired in S232, and a second process to calculate the position (measured value) of the measurement pattern based on the composite image generated in S233.

[0059] Here, the first processes in S232 and S234 can be understood as preliminary measurement steps in which preliminary measurements are performed on each combination of parameter values ​​of multiple different measurement parameters. Furthermore, S232 can be understood as a detection step in which an image serving as intermediate information for obtaining measurement values ​​is detected from the measurement target. Furthermore, the first process in S234 can be understood as a calculation step in which measurement values ​​are calculated based on the image serving as intermediate information.

[0060] Furthermore, the second processing in S233 and S234 can be understood as an estimation process that estimates the measured values ​​obtained in combinations different from the combinations for which preliminary measurements were taken, based on the images obtained as intermediate information in S232. Here, in the detection process, the image of the object to be measured may be detected as intermediate information. In the estimation process, a composite image is generated from multiple images as intermediate information, and based on this composite image, the measured values ​​obtained in combinations different from the combinations for which preliminary measurements were taken may be estimated.

[0061] In S235, the control unit 1100 may calculate a sensitivity distribution for at least two measurement parameters based on the measurement values ​​obtained in S234. This sensitivity distribution is a distribution of sensitivity that shows the change in the measurement value of the measurement pattern in response to changes in parameter values. As a sensitivity distribution that shows the change in the measurement value in response to changes in parameter values, for example, a sensitivity distribution that shows the change in the measurement value in response to changes in the center wavelength and a sensitivity distribution that shows the change in the measurement value in response to changes in the wavelength width may be obtained. The sensitivity distribution includes at least two sensitivities corresponding to at least two measurement parameters. The method for calculating the sensitivity distribution will be explained in detail later.

[0062] In S236, the control unit 1100 can determine parameter values ​​for at least two measurement parameters based on the sensitivity distribution calculated in S235. This can be understood as a decision step in which the parameter values ​​to be adopted for each of the multiple measurement parameters are determined based on the sensitivity distribution for each of the multiple measurement parameters. This determination process allows us to determine the optimal center wavelength and wavelength width (or combination thereof).

[0063] In S237, under the control of the control unit 1100, the detection unit 75 acquires image information of the measurement pattern 72 according to the parameter values ​​of each of the multiple measurement parameters determined in S236, and the position of the measurement pattern 72 can be measured based on that image information. This can be understood as the main measurement step, in which the main measurement is performed according to the parameter values ​​of each of the multiple measurement parameters determined in S235 (determination step).

[0064] In the second embodiment, the sensitivity of the measurement parameter to changes in the parameter value of the measurement parameter, which corresponds to changes in the measured value (focus sensitivity) in response to changes in the focus state (changes in defocus), can be used to determine the parameter value. For example, the sensitivity of the measurement parameter to changes in the center wavelength (simply put, the sensitivity of the focus sensitivity to changes in the center wavelength), which corresponds to changes in the focus state (changes in defocus), can be used to determine the parameter value. Also, the sensitivity of the measurement parameter to changes in the wavelength width (simply put, the sensitivity of the focus sensitivity to changes in the wavelength width), which corresponds to changes in the focus state (changes in defocus), can be used to determine the parameter value. If there is a relative angular misalignment between the normal to the surface of the substrate 73 and the optical axis of the measurement unit 50, the measured value will change due to the relative focus position fluctuation between the substrate 73 and the measurement unit 50. Therefore, by selecting parameter values ​​with low focus sensitivity for at least two measurement parameters (here, the center wavelength and the wavelength width), it is possible to reduce the variability of the measured value and achieve high-precision measurement.

[0065] In S232, for example, images of the measurement pattern can be acquired for each of the different positions in the Z-axis direction. In S234, the position (measured value) of the measurement pattern can be calculated from the image information acquired in S232 and the composite image generated in S233. Figure 9(a), similar to Figure 6(a), is a diagram showing the relationship between the position (measured value) of the measurement pattern and the center wavelength, with the center wavelength on the horizontal axis and the measured value on the vertical axis. Wavelengths WL3 and WL4 refer to the center wavelengths of the light illuminating the substrate and the light detected from the substrate. In the example of Figure 9(a), similar to Figure 6(a), the change in the measured value in response to the change in the center wavelength is determined not only when the substrate 73 is aligned to the best focus position of the measurement unit 50, but also when the substrate 73 is aligned to the defocus position. For example, at the best focus position Z1 and the defocus position Z2, the measured values ​​of the measurement pattern 72 with light of center wavelength WL4 are M14 and M24, respectively. Similarly, the measured values ​​of measurement pattern 72 using light with a central wavelength of WL6 are denoted as M16 and M26.

[0066] In S235, sensitivity is calculated for at least two measurement parameters, indicating how the measured value of the measurement pattern changes in response to changes in the parameter values ​​of the measurement parameters. Here, changes in the central wavelength and wavelength width are considered as changes in the parameter values. Changes in focus sensitivity are also considered as changes in the measured value.

[0067] Figure 9(b) shows the relationship between the change in measured values ​​(focus sensitivity) of measurement pattern 72 in response to a change in focus state and the center wavelength. The horizontal axis shows the center wavelength, and the vertical axis shows the change in measured values ​​calculated from the measured values ​​shown in Figure 9(a). The change in measured values ​​dMz4 and dMz6 are expressed by the following equations (8) and (9), respectively.

[0068] dMz4=M14-M24 (formula 8) dMz6=M16-M26 (Formula 9) In S236, the control unit 1100 can determine parameter values ​​for at least two measurement parameters based on the sensitivity distribution calculated in S235. By selecting parameter values ​​with low sensitivity for each measurement parameter, for example, changes in the measured value caused by fluctuations in the parameter value can be minimized, thereby achieving highly accurate measurement.

[0069] Regarding the determination of the parameter values ​​for each measurement parameter, instead of determining them based on a single indicator as described above, a method based on multiple indicators may be adopted. For example, the parameter values ​​may be determined based on both the sensitivity distribution to changes in the center wavelength in the first embodiment and the focus sensitivity to changes in the center wavelength in the second embodiment. When determining parameter values ​​based on multiple indicators (sensitivity), a weighting function may be set to adjust for the relative influence of each sensitivity. For example, the two sensitivities may be weighted to take into account the difference in the influence of wavelength changes and focus changes in process variations. This makes it possible to suppress changes in measured values ​​(measurement errors) in response to wavelength changes and focus changes associated with process variations.

[0070] Up to this point, we have described the calculation of sensitivity using a single measurement pattern 72 on the substrate 73, but sensitivity may also be calculated using multiple measurement patterns 72 formed at different locations. For example, as shown in Figure 10(a), images may be detected at multiple measurement patterns 72a and 72b formed on the substrate 73, and measurement values ​​may be calculated based on the acquired image information to determine wavelength sensitivity and focus sensitivity. Then, as shown in Figure 10(b), the sensitivity Sa and Sb for measurement patterns 72a and 72b may be determined, respectively.

[0071] When determining the parameter values ​​of measurement parameters from two or more candidate parameter values, it is preferable to determine the measurement parameters based on the average value or variation of sensitivity Sa and Sb at the same wavelength, so as to minimize the error that occurs when measuring multiple measurement patterns on the substrate. This may minimize, for example, measurement errors that depend on the position on the substrate 73 due to variations in the film thickness of the substrate 73.

[0072] Furthermore, weighting may be applied to each of the measurement parameters used by the measurement unit 50, such as the wavelength of light, σ value, and polarization. For example, after calculating the wavelength sensitivity distribution based on the acquired measurement values, a wavelength-specific weighting function W1, as shown in Figure 10(c), can be integrated into the sensitivity distribution shown in Figure 10(b). Specific examples of weighting include changes in signal contrast according to wavelength in the measurement pattern 72, and differences in measurement accuracy and measurement time due to differences in σ values. By doing so, a decrease in measurement accuracy and an increase in measurement time can be suppressed by adding predetermined weights to the measurement values ​​acquired for the measurement pattern 72 and calculating the sensitivity.

[0073] The following describes a measuring device according to the third embodiment. Matters not mentioned herein may follow those of the first embodiment. As the third embodiment, a superposition measuring device (superposition inspection device) for measuring the relative positions of multiple measuring patterns formed on different layers on a substrate 73 will be described with reference to Figure 11.

[0074] Figure 11(a) illustrates an image of a measurement pattern 72 formed on the detection surface of the detection unit 75 shown in Figure 1(b). The measurement pattern 72 may include a first pattern group P1 and a second pattern group P2 formed on different layers. The detection unit 75 may include a two-dimensional image sensor having multiple pixels in the X and Y directions. The control unit 1100 can generate signal waveforms for the first pattern group P1 and the second pattern group P2 based on the output from the detection unit 75.

[0075] Figure 11(b) shows a signal waveform SW generated by integrating the signal intensity of the pattern at each pixel of the detection unit 75 in the Y direction of Figure 11(a), as an example of a signal waveform generated based on the output of the detection unit 75 shown in Figure 11(a). For the integration of signal intensity at each pixel of the detection unit 75, it is preferable to set the number of pixels to be integrated based on the dimensional information of the pattern. Waveforms S1 and S2 shown in Figure 11(b) represent the changes in signal intensity of the first pattern group P1 and the second pattern group P2 in the signal waveform SW. Measured values ​​X1 and X2 are the center positions of the first pattern group P1 and the second pattern group P2, respectively, calculated by the control unit 1100 based on waveforms S1 and S2. For example, by calculating the difference between measured value X1 and measured value X2, the relative positional shift between the first pattern group P1 and the second pattern group P2 in the X direction can be calculated. To calculate the relative positional displacement in the Y direction, for example, a first pattern group and a second pattern group can be used, each consisting of multiple patterns formed on the substrate along the Y direction, with the longitudinal direction of the pattern being equal to the X direction. Then, a signal waveform is generated by integrating the signal intensity of the pattern at each pixel in the X direction, and the relative positional displacement is calculated from the difference in measured values ​​of each pattern group, similar to the relative positional displacement in the X direction.

[0076] Figure 11(c) is a diagram showing the sequence of measurement processing for determining measurement parameters in this embodiment. The measurement processing is performed by the control unit 1100 shown in Figure 1 comprehensively controlling each part of the measurement device 100. When the measurement processing starts, in S331, a process is executed to align the relative positions of the substrate 73 and the measurement unit 50. Here, as shown in Figure 11(a), both the first pattern group P1 and the second pattern group P2 are aligned with respect to the detection unit 75. In S332, the detection unit 75 may acquire images of the first pattern group P1 and the second pattern group P2 provided on the substrate 73 multiple times, while varying the combination of parameter values ​​for at least two different measurement parameters. This process can be performed, for example, in the same way as in S132 or S232. In S333, the control unit 1100 performs a synthesis process to generate a composite image using the multiple image information acquired in S332. In S334, the control unit 1100 calculates the positions (measured values) of the first pattern group P1 and the second pattern group P2, respectively, for the image information acquired in S332 and the composite image generated in S333. In S335, the control unit 1100 calculates the sensitivity of the measured values ​​of the first pattern group P1 and the second pattern group P2 to changes in parameter values ​​for at least two measurement parameters.

[0077] In S336, the control unit 1100 may determine parameter values ​​for at least two measurement parameters based on the sensitivity distribution calculated in S335. In S337, under the control of the control unit 1100, the detection unit 75 may acquire image information of the first pattern group P1 and the second pattern group P2 according to the parameter values ​​of each of the multiple measurement parameters determined in S336. Based on this image information, the positions of the first pattern group P1 and the second pattern group P2 may be measured.

[0078] Here, a representative example of a method for measuring the positions of a first pattern group P1 and a second pattern group P2 formed on different layers of the substrate 73 will be described. There are two methods for aligning the substrate 73 with the measurement unit 50. In the first method, the positions of the first pattern group P1 and the second pattern group P2 are measured by individually aligning each of them to the best focus position of the measurement unit 50. In the second method, the positions of the first pattern group P1 and the second pattern group P2 can be measured with the substrate 73 and the detection unit 75 aligned to a certain focus position.

[0079] If the first method is adopted, in S335, the sensitivity distribution may be determined according to the first or second embodiment, etc., based on the best focus positions of the first pattern group P1 and the second pattern group P2, respectively. If the second method is adopted, in S335, the sensitivity distribution may be determined according to the first or second embodiment, etc., based on a common focus position. The common focus position may be determined based on the intensity and quality of the detection signals from the first pattern group P1 and the second pattern group P2.

[0080] As described above, in the third embodiment, the positions of multiple measurement patterns formed on different layers of the substrate 73 are measured while varying the combination of parameter values ​​for at least two different measurement parameters. A sensitivity distribution is then calculated based on the measurement values ​​obtained. Based on this sensitivity distribution, the parameter values ​​for at least two measurement parameters are determined. This makes it possible to reduce errors in superposition measurement and achieve high-precision superposition by selecting parameter values ​​that show small changes in measurement values ​​in response to changes in parameter values, such as wavelength changes or focus changes. Therefore, in this embodiment, it is possible to provide a superposition inspection device that can measure the superposition error of patterns on a substrate at high speed and with high precision.

[0081] The following describes a fourth embodiment, a measuring device (measurement pattern monitor) for measuring characteristic changes of a measurement pattern formed on a substrate. Matters not mentioned here may follow the first embodiment. The fourth embodiment will be described with reference to Figure 12, describing the measuring device and measurement process in the fourth embodiment. The difference between the fourth embodiment and the first embodiment is the method for determining the parameter values ​​of the measurement parameters.

[0082] First, we will explain the function of the measuring device (measurement pattern monitor) that measures changes in the characteristics of the measurement pattern. If deformation or changes in structure and characteristics of the substrate occur during processing steps such as heating or film deposition of the substrate, the signal strength information of the acquired measurement pattern will change, causing the measured value to change and deteriorating the alignment accuracy of the substrate and the overlapping accuracy of the patterns on the substrate. Therefore, by measuring (monitoring) the characteristics of the measurement pattern using the measuring device, it is possible to detect the presence or absence of abnormalities in each processing step and identify the processing device that is causing the change in the characteristics of the measurement parameters. As a result, for example, by calibrating the relevant processing device, changing the setting conditions, or reviewing the structure of the measurement pattern and processing steps, it is possible to reduce the occurrence of defective products due to the deterioration of the alignment accuracy of the substrate and the overlapping accuracy of the patterns.

[0083] Figure 12 shows the sequence of the measurement process in the fourth embodiment. Since steps S431 to S435 are the same as steps S131 to S135 shown in Figure 4, their explanation is omitted here.

[0084] Next, the method for determining the parameter values ​​of the measurement parameters in S436 (determination step) will be explained. In S436, the parameter values ​​to be adopted are determined based on the sensitivity distribution calculated in S435. As a criterion for judgment in S436, it is preferable to select parameter values ​​that show high sensitivity. From another perspective, in S436 (determination step), it is preferable to determine the parameter values ​​to be adopted such that the sensitivity in the sensitivity distribution is more sensitive than a predetermined sensitivity at the parameter values ​​to be adopted. From yet another perspective, in S436 (determination step), it is preferable to determine the parameter values ​​to be adopted such that the sensitivity in the sensitivity distribution is greater than a predetermined sensitivity at the parameter values ​​to be adopted. From yet another perspective, in S436 (determination step), it is preferable to determine the parameter values ​​to be adopted such that the sensitivity in the sensitivity distribution is maximized at the parameter values ​​to be adopted.

[0085] When performing measurement processing for multiple measurement patterns, the sensitivity of each of the multiple measurement patterns is determined, as explained using Figure 10(b) in the second embodiment. Then, it is preferable to determine the measurement parameters so as to maximize the error that occurs when measuring multiple measurement patterns on the substrate, for example, based on the average value or variation of the sensitivity Sa and Sb at the same wavelength. This may maximize, for example, the measurement error that corresponds to the position on the substrate 73 due to variations in the film thickness of the substrate 73.

[0086] The following explains the reasons for determining the parameter values. In S136 of the first embodiment, a parameter value with low sensitivity to changes in the measured value in response to changes in the center wavelength was selected in order to reduce measurement errors associated with process changes. On the other hand, the measuring device (measurement pattern monitor) of this embodiment needs to detect changes in the measured value associated with process changes with high accuracy. Therefore, by selecting a parameter value with high sensitivity to changes in the measured value in response to changes in the center wavelength, it becomes possible to detect process changes with high accuracy.

[0087] In S437, under the control of the control unit 1100, the detection unit 75 acquires image information of the measurement pattern 72 according to the parameter values ​​of each of the multiple measurement parameters determined in S436, and characteristic information of the measurement pattern 72 can be measured based on that image information. This can be understood as the main measurement step, in which the main measurement is performed according to the parameter values ​​of each of the multiple measurement parameters determined in S436 (determination step). Examples of characteristic information of the measurement pattern 72 include the position and signal strength information of the measurement pattern 72, and waveform evaluation value information.

[0088] In S438, the characteristic information of the measurement pattern 72 acquired in S437 is compared with reference information to determine the change in the characteristic information of the measurement pattern. Examples of reference information include previously acquired characteristic information of the measurement pattern 72, design value information, and simulation results.

[0089] As described above, in the fourth embodiment, the sensitivity distribution for each of the measurement parameters is determined, and based on that sensitivity distribution, the parameter values ​​to be adopted for each of the plurality of measurement parameters are determined. As a result, the measurement device (measurement pattern monitor) of this embodiment can measure changes in the physical property information of the measurement pattern at high speed and with high accuracy.

[0090] The following describes a lithography apparatus incorporating the above-mentioned measuring device. The lithography apparatus may be, for example, an exposure apparatus, an imprint apparatus, or an electron beam lithography apparatus. Figure 13 is a schematic diagram showing the configuration of an exposure apparatus EXA as an example of a lithography apparatus. The exposure apparatus EXA is a lithography apparatus used in the lithography process, which is a manufacturing process for articles or devices such as semiconductor elements or liquid crystal display elements, to form a pattern on a substrate 83. The exposure apparatus EXA exposes the substrate 83 through a reticle 31, which is the master plate, and transfers the pattern of the reticle 31 to the substrate 83. In this embodiment, the exposure apparatus EXA employs a step-and-scan method, but it is also possible to employ a step-and-repeat method or other exposure methods.

[0091] As shown in Figure 13, the exposure apparatus EXA includes an illumination optical system 801, a reticle stage RS that holds the reticle 31, a projection optical system 32, a substrate stage WS that holds the substrate 83, a position measuring device 550, and a control unit 1200.

[0092] The illumination optical system 801 is an optical system that illuminates the surface to be illuminated using light from the light source unit 800. The light source unit 800 includes, for example, a laser. The laser includes ArF excimer lasers with a wavelength of approximately 193 nm, KrF excimer lasers with a wavelength of approximately 248 nm, etc., but the type of light source is not limited to excimer lasers. For example, the light source unit 800 may use an F2 laser with a wavelength of approximately 157 nm or an EUV (Extreme ultraviolet) laser with a wavelength of 20 nm or less as the light source.

[0093] In this embodiment, the illumination optical system 801 shapes the light from the light source 800 into slit light having a predetermined shape optimal for exposure, and illuminates the reticle 31. The illumination optical system 801 has the function of uniformly illuminating the reticle 31 and the function of polarized illumination. The illumination optical system 801 includes, for example, lenses, mirrors, optical integrators, and apertures, and is configured by arranging a condenser lens, a fly-eye lens, an aperture diaphragm, a condenser lens, a slit, and an imaging optical system in that order.

[0094] The reticle 31 is made of, for example, quartz. The reticle 31 has a pattern (circuit pattern) formed on it that should be transferred to the substrate 83.

[0095] The reticle stage RS holds the reticle 31 via a reticle chuck (not shown) and is connected to a reticle drive mechanism (not shown). The reticle drive mechanism includes a linear motor and drives the reticle stage RS in the X-axis, Y-axis, Z-axis, and rotational directions of each axis, thereby moving the reticle 31 held by the reticle stage RS. The position of the reticle 31 is measured by a reticle position measuring unit (not shown) of the oblique incidence system, and the reticle 31 is positioned at a predetermined position via the reticle stage RS.

[0096] The projection optical system 32 has the function of forming an image of light from the object surface onto the image plane. In this embodiment, the projection optical system 32 projects light (diffracted light) that has passed through the pattern of the reticle 31 onto the substrate 83, forming an image of the pattern of the reticle 31 on the substrate. The projection optical system 32 can be an optical system consisting of a plurality of lens elements, an optical system including a plurality of lens elements and at least one concave mirror (catedioptric optical system), or an optical system including a plurality of lens elements and at least one diffractive optical element such as a kinoform.

[0097] A photoresist is coated onto the substrate 83. The substrate 83 is a workpiece onto which the pattern of the reticle 31 is transferred, and includes wafers, liquid crystal substrates, and other workpieces.

[0098] The substrate stage WS holds the substrate 83 via a substrate chuck (not shown) and is connected to a substrate drive mechanism (not shown). The substrate drive mechanism includes a linear motor and drives the substrate stage WS in the X-axis direction, Y-axis direction, Z-axis direction, and rotational direction of each axis, thereby moving the substrate 83 held by the substrate stage WS. A reference plate 39 is also provided on the substrate stage WS.

[0099] The positions of the reticle stage RS and the substrate stage WS are monitored, for example, by a 6-axis laser interferometer 91, and the reticle stage RS and the substrate stage WS are driven at a constant speed ratio under the control of the control unit 1200.

[0100] The control unit 1200 is composed of a computer (information processing device) including a CPU and memory, and for example, it comprehensively controls each part of the exposure device EXA according to a program stored in the memory unit to operate the exposure device EXA. The control unit 1200 controls the exposure process in which the substrate 83 is exposed via the reticle 31 and the pattern of the reticle 31 is transferred to the substrate 83. In this embodiment, the control unit 1200 also controls the measurement process in the position measuring device 550 and the correction process (calculation process) of the measured values ​​obtained by the position measuring device 550. Thus, the control unit 1200 also functions as part of the position measuring device 550.

[0101] In the exposure apparatus EXA, light (diffracted light) that has passed through the reticle 31 is projected onto the substrate 83 via the projection optical system 32. The reticle 31 and the substrate 83 are arranged in an optically conjugate relationship. By scanning the reticle 31 and the substrate 83 at a speed ratio equal to the reduction ratio of the projection optical system 32, the pattern of the reticle 31 is transferred to the substrate 83.

[0102] The position measuring device 550 is a measuring device that measures the position of an object. In this embodiment, the position measuring device 550 measures the position of a mark 82, such as an alignment mark, provided on the substrate 83. The wavelength tunable means 540 consists of a wavelength tunable element and a holding member, and is driven in the X direction by the control unit using a drive mechanism (not shown).

[0103] Referring to Figure 14, the exposure process sequence for exposing the substrate 83 via the reticle 31 and transferring the pattern of the reticle 31 to the substrate 83 will be described. As described above, the exposure process is performed by the control unit 1200 comprehensively controlling each part of the exposure apparatus EXA.

[0104] In S101, the substrate 83 is loaded into the exposure apparatus EXA. In S102, the surface (height) of the substrate 83 is detected by a shape measuring device (not shown) and the surface shape of the entire substrate 83 is measured.

[0105] In S103, calibration is performed. Specifically, the substrate stage WS is driven so that the reference mark is positioned on the optical axis of the position measuring device 550, based on the design coordinate position of the reference mark provided on the reference plate 39 in the stage coordinate system. Next, the positional deviation of the reference mark relative to the optical axis of the position measuring device 550 is measured, and based on the positional deviation, the stage coordinate system is reset so that the origin of the stage coordinate system coincides with the optical axis of the position measuring device 550. Then, the substrate stage WS is driven so that the reference mark is positioned on the optical axis of the exposure light, based on the design positional relationship between the optical axis of the position measuring device 550 and the optical axis of the projection optical system 32. Finally, the positional deviation of the reference mark relative to the optical axis of the exposure light is measured via the projection optical system 32 using a TTL (through-the-lens) measurement system.

[0106] In S104, the baseline between the optical axis of the position measuring device 550 and the optical axis of the projection optical system 32 is determined based on the calibration results in S103. In S105, the position measuring device 550 measures the position of the mark 82 provided on the substrate 83.

[0107] In S106, global alignment is performed. Specifically, based on the measurement results in S105, the shift, magnitude, and rotation of the shot area arrangement on the substrate 83 are calculated to determine the regularity of the shot area arrangement. Then, a correction coefficient is determined from the regularity of the shot area arrangement and the baseline, and the substrate 83 is aligned with the reticle 31 (exposure light) based on the correction coefficient.

[0108] In S107, the substrate 83 is exposed while scanning the reticle 31 and the substrate 83 in the scanning direction (Y direction). At this time, based on the surface shape of the substrate 83 measured by the shape measuring device, the substrate stage WS is driven in the Z direction and tilt direction to sequentially align the surface of the substrate 83 with the imaging plane of the projection optical system 32.

[0109] In S108, it is determined whether exposure has been completed for all shot areas of the substrate 83 (i.e., whether there are any unexposed shot areas). If exposure has not been completed for all shot areas of the substrate 83, the process proceeds to S107, and steps S107 and S108 are repeated until exposure has been completed for all shot areas. On the other hand, if exposure has been completed for all shot areas of the substrate 83, the process proceeds to S109, and the substrate 83 is removed from the exposure apparatus EXA.

[0110] In this embodiment, the position of mark 82 is measured using multiple different measurement parameters, and the sensitivity of the measured value to the variation in the measurement parameters is calculated for at least two or more candidate measurement parameters. Then, the measurement parameters to be used for measurement are determined based on the sensitivity. This reduces errors in alignment measurement and enables high-precision alignment. Therefore, this embodiment provides a position measuring device that can measure the position of a pattern on a substrate at high speed and with high precision.

[0111] A method for manufacturing articles using the lithography apparatus described above will be explained exemplified. The method is suitable for manufacturing articles such as devices (semiconductor elements, magnetic storage media, liquid crystal display elements, etc.). The manufacturing method includes the steps of exposing a substrate coated with a photosensitive agent (forming a pattern on the substrate) using an exposure apparatus EXA, and developing the exposed substrate (processing the substrate). The manufacturing method may also include other well-known steps (oxidation, film formation, vapor deposition, doping, planarization, etching, resist stripping, dicing, bonding, packaging, etc.). The method for manufacturing articles in this embodiment is advantageous compared to conventional methods in at least one of the performance, quality, productivity, and production cost of the articles. The method for manufacturing articles described above may also be carried out using lithography apparatus such as an imprint apparatus or a drawing apparatus.

[0112] This specification and the drawings disclose the following measurement methods, measuring devices, lithography devices, and methods for manufacturing articles. (Item 1) A preliminary measurement step in which preliminary measurements are performed for each combination while varying the combination of parameter values ​​for at least two different measurement parameters, A processing step to obtain a sensitivity distribution, which is a sensitivity distribution showing the change in the measured value in response to a change in the parameter value, based on the measured values ​​obtained in the preliminary measurement step, for each of the at least two measured parameters, A determination step of determining the parameter value to be adopted for each of the at least two measurement parameters based on the sensitivity distribution for each of the at least two measurement parameters, A measurement step in which the measurement is performed according to the parameter values ​​of each of the at least two measurement parameters determined in the determination step, A measurement method characterized by including (Item 2) In the preliminary measurement step and the main measurement step, the target's position information is measured. The measurement method described in item 1, characterized by the following: (Item 3) The at least two measurement parameters include the central wavelength of the light illuminating the target and the wavelength width of the light, The measurement method described in item 2, characterized by the following: (Item 4) The at least two measurement parameters include the central wavelength, wavelength width, and σ value of the light illuminating the target; the polarization characteristics in the optical path of the measuring device for measuring the target; the transmittance of the ND filter placed in the optical path; the position of the target; and the tilt of the target. The measurement method described in item 2, characterized by the following: (Item 5) One of the at least two measurement parameters includes the position of the target in a direction along the optical path of a position detection device that detects the position of the target, The measurement method described in item 2, characterized by the following: (Item 6) In the determination step, the parameter values ​​to be adopted for each of the at least two measurement parameters are determined based on the sensitivity distribution for each of the at least two measurement parameters and the weight function given for each of the at least two measurement parameters. A measurement method according to any one of items 2 to 5, characterized by the following: (Item 7) The preliminary measurement step includes a detection step of detecting intermediate information from the object to be measured in order to obtain a measurement value, and a calculation step of calculating a measurement value based on the intermediate information. The aforementioned processing step is: An estimation step is performed to estimate the measured values ​​obtained in combinations different from the combinations for which the preliminary measurements were taken, based on the aforementioned intermediate information. A calculation step is included in which the sensitivity distribution is obtained for each of the at least two measurement parameters based on the measured values ​​obtained in the preliminary measurement step and the measured values ​​estimated in the estimation step, A measurement method according to any one of items 1 to 6, characterized by the following: (Item 8) In the detection step, the image of the object to be measured is detected as the intermediate information, The estimation step involves generating a composite image from the multiple images used as intermediate information, and estimating the measurement values ​​obtained in combinations different from the combinations used for the preliminary measurements, based on the composite image. The measurement method described in item 7, characterized by the following: (Item 9) In the determination step, the parameter value to be adopted is determined such that the sensitivity in the sensitivity distribution is less sensitive than a predetermined sensitivity at the parameter value to be adopted. A measurement method according to any one of items 1 to 8, characterized by the following: (Item 10) In the determination step, the parameter values ​​to be adopted are determined such that the sensitivity in the sensitivity distribution is smaller than a predetermined sensitivity in the parameter values ​​to be adopted. A measurement method according to any one of items 1 to 9, characterized by the following: (Item 11) In the determination step, the parameter value to be adopted is determined such that the sensitivity in the sensitivity distribution is minimized at the parameter value to be adopted. A measurement method according to any one of items 1 to 9, characterized by the following: (Item 12) In the preliminary measurement step and the main measurement step, target signal intensity information or waveform evaluation value information is measured. The measurement method described in item 1, characterized by the following: (Item 13) In the determination step, based on the sensitivity distribution of each of the multiple targets, at least one of the mean value and variability of the sensitivity distribution is calculated, and the parameter value to be adopted is determined based on the sensitivity in at least one of the mean value and variability of the sensitivity distribution. The measurement method according to item 2 or 12, characterized by the features described herein. (Item 14) In the determination step, the parameter value to be adopted is determined such that the sensitivity in the sensitivity distribution is more sensitive than a predetermined sensitivity at the parameter value to be adopted. The measurement method described in item 1, characterized by the following: (Item 15) In the determination step, the parameter values ​​to be adopted are determined such that the sensitivity in the sensitivity distribution is greater than a predetermined sensitivity in the parameter values ​​to be adopted. The measurement method described in item 1, characterized by the features described in item 17. A step of measuring the position of a mark on a substrate according to the measurement method described in any one of items 1 to 16, and transferring a pattern to the substrate based on the position of the mark, A step of obtaining an article by processing the substrate onto which the pattern has been transferred, A method for manufacturing articles, characterized by including the following: (Item 18) A measuring device comprising a measuring unit and a control unit, The control unit controls the measurement unit to perform preliminary measurements multiple times, each with different combinations of parameter values ​​for at least two different measurement parameters; based on the measurement values ​​obtained from the preliminary measurements, obtain a sensitivity distribution for each of the at least two measurement parameters, which is a distribution of sensitivity to changes in the measurement value in response to changes in the parameter value; determine the parameter value to be adopted for each of the at least two measurement parameters based on the sensitivity distribution; and control the measurement unit to perform the main measurement according to the parameter value determined for each of the at least two measurement parameters. A measuring device characterized by the following features. (Item 19) It further includes a wavelength tunable unit that changes the wavelength of the light illuminating the object to be measured, The control unit controls the tunable wavelength unit based on the parameter values ​​determined for each of the at least two measurement parameters. The measuring device described in item 18, characterized by the features described herein. (Item 20) The wavelength-tunable section includes a wavelength-tunable element whose transmission wavelength changes along a predetermined direction, and a drive mechanism for driving the wavelength-tunable element. The measuring device described in item 19, characterized by the features described herein. (Item 21) The wavelength-tunable unit can change the central wavelength and wavelength width of the light illuminating the object to be measured. The at least two measurement parameters include the center wavelength and the wavelength width, The measuring device described in item 20, characterized by the following: (Item 22) The measurement unit measures the target's position information. A measuring device according to any one of items 18 to 21, characterized by the features described herein. (Item 23) Lithography apparatus, A measuring device according to any one of items 18 to 22, configured to measure the position of a mark provided on a circuit board, The system includes a positioning mechanism that positions the substrate based on the position of the mark measured using the measuring device, A lithography apparatus characterized by being configured to transfer the pattern onto the aforementioned substrate. (Item 24) The process of transferring a pattern onto a substrate using the lithography apparatus described in item 23, A step of obtaining an article by processing the substrate onto which the pattern has been transferred, A method for manufacturing articles, characterized by including the following:

[0113] The invention is not limited to the embodiments described above, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, claims are attached to disclose the scope of the invention. [Explanation of symbols]

[0114] 40: Wavelength tunable unit, 50: Measurement unit, 100: Measurement device, 1100: Control unit

Claims

1. a preliminary measurement step of performing preliminary measurement for each combination of at least two different measurement parameters while changing the combination of parameter values; a processing step of executing a process of determining a change in a measurement value with respect to a change in a parameter value for each of the at least two measurement parameters based on the measurement value obtained in the preliminary measurement step; a determining step of determining a parameter value to be adopted for each of the at least two measurement parameters based on the change in the measurement value obtained in the processing step for each of the at least two measurement parameters; a main measurement step of performing a main measurement in accordance with the respective parameter values ​​of the at least two measurement parameters determined in the determination step; A measuring method comprising:

2. In the preliminary measurement step and the main measurement step, position information of a target is measured.

2. The measuring method according to claim 1 .

3. the at least two measurement parameters include a central wavelength of light illuminating the target and a wavelength width of the light; 3. The measuring method according to claim 2.

4. the at least two measurement parameters include at least two of a central wavelength, a wavelength width, and a σ value of light illuminating the target, polarization characteristics in an optical path of a measurement device that measures the target, a transmittance of an ND filter disposed in the optical path, a position of the target, and an inclination of the target; 3. The measuring method according to claim 2.

5. one of the at least two measurement parameters includes a position of the target in a direction along an optical path of a position detection device that detects the position of the target; 3. The measuring method according to claim 2.

6. In the processing step, a sensitivity distribution is obtained, which is a distribution of sensitivities indicating changes in the measurement values, In the determination step, a parameter value to be adopted is determined for each of the at least two measurement parameters based on the sensitivity distribution for each of the at least two measurement parameters and a weighting function assigned to each of the at least two measurement parameters.

3. The measuring method according to claim 2.

7. In the processing step, a sensitivity distribution is obtained, which is a distribution of sensitivities indicating changes in the measurement values, the preliminary measurement step includes a detection step of detecting intermediate information from a measurement object for obtaining a measurement value, and a calculation step of calculating the measurement value based on the intermediate information, The processing step comprises: an estimation step of estimating, based on the intermediate information, a measurement value to be obtained in a combination different from the combination in which the preliminary measurement was performed; a calculation step of obtaining the sensitivity distribution for each of the at least two measurement parameters based on the measurement values ​​obtained in the preliminary measurement step and the measurement values ​​estimated in the estimation step, 2. The measuring method according to claim 1 .

8. In the detecting step, an image of the measurement object is detected as the intermediate information; the estimation step generates a composite image from the plurality of images as the intermediate information, and estimates, based on the composite image, a measurement value obtained in a combination different from the combination used in the preliminary measurement.

8. The measuring method according to claim 7.

9. In the processing step, a sensitivity distribution is obtained, which is a distribution of sensitivities indicating changes in the measurement values, In the determining step, the parameter value to be adopted is determined so that the sensitivity in the sensitivity distribution is less sensitive than a predetermined sensitivity at the parameter value to be adopted.

2. The measuring method according to claim 1 .

10. In the processing step, a sensitivity distribution is obtained, which is a distribution of sensitivities indicating changes in the measurement values, In the determining step, the parameter value to be adopted is determined so that the sensitivity in the sensitivity distribution is smaller than a predetermined sensitivity at the parameter value to be adopted.

2. The measuring method according to claim 1 .

11. In the processing step, a sensitivity distribution is obtained, which is a distribution of sensitivities indicating changes in the measurement values, In the determining step, the parameter value to be adopted is determined so that the sensitivity in the sensitivity distribution is minimized at the parameter value to be adopted.

2. The measuring method according to claim 1 .

12. In the preliminary measurement step and the main measurement step, signal intensity information or waveform evaluation value information of the target is measured.

2. The measuring method according to claim 1 .

13. In the processing step, a sensitivity distribution is obtained, which is a distribution of sensitivities indicating changes in the measurement values, In the determination step, at least one of an average value and a variation of the sensitivity distribution is calculated based on the sensitivity distribution of each of the plurality of targets, and the parameter value to be adopted is determined based on the sensitivity of at least one of the average value and the variation of the sensitivity distribution.

13. The measuring method according to claim 2 or 12.

14. In the processing step, a sensitivity distribution is obtained, which is a distribution of sensitivities indicating changes in the measurement values, In the determining step, the parameter value to be adopted is determined so that the sensitivity in the sensitivity distribution is higher than a predetermined sensitivity at the parameter value to be adopted.

2. The measuring method according to claim 1 .

15. In the processing step, a sensitivity distribution is obtained, which is a distribution of sensitivities indicating changes in the measurement values, In the determining step, the parameter value to be adopted is determined so that the sensitivity in the sensitivity distribution is greater than a predetermined sensitivity at the parameter value to be adopted.

2. The measuring method according to claim 1 .

16. In the processing step, a sensitivity distribution is obtained, which is a distribution of sensitivities indicating changes in the measurement values, In the determining step, the parameter value to be adopted is determined so that the sensitivity in the sensitivity distribution is maximized at the parameter value to be adopted.

2. The measuring method according to claim 1 .

17. a step of measuring the position of a mark on a substrate according to the measurement method of claim 1 and transferring a pattern onto the substrate based on the position of the mark; processing the substrate to which the pattern has been transferred to obtain an article; A method for manufacturing an article, comprising:

18. A measurement device including a measurement unit and a control unit, the control unit controls the measurement unit to perform preliminary measurements multiple times while varying combinations of parameter values ​​for at least two mutually different measurement parameters, executes a process for determining a change in parameter value for each of the at least two measurement parameters based on the measurement values ​​obtained by the preliminary measurements, determines a parameter value to be adopted for each of the at least two measurement parameters based on the change in the measurement value determined by the process for each of the at least two measurement parameters, and controls the measurement unit to perform main measurements in accordance with the parameter values ​​determined for each of the at least two measurement parameters. A measuring device characterized by:

19. further comprising a wavelength variable unit that changes the wavelength of the light that illuminates the measurement object; the control unit controls the wavelength tuner based on the parameter values ​​determined for each of the at least two measurement parameters.

19. The measuring device according to claim 18.

20. the wavelength tunable unit includes a wavelength tunable element whose transmission wavelength changes along a predetermined direction, and a drive mechanism that drives the wavelength tunable element; 20. The measuring device according to claim 19.

21. the wavelength variable unit is capable of changing a central wavelength and a wavelength width of light that illuminates the measurement object, the at least two measurement parameters include the central wavelength and the wavelength width; 21. The measuring device according to claim 20.

22. The measurement unit measures position information of a target.

19. The measuring device according to claim 18.

23. 1. A lithographic apparatus comprising:

23. The measurement device according to any one of claims 18 to 22, configured to measure the position of a mark provided on a substrate; a positioning mechanism that positions the substrate based on the position of the mark measured using the measurement device, A lithographic apparatus configured to transfer a pattern onto the substrate.

24. Transferring a pattern onto a substrate using a lithographic apparatus according to claim 23; processing the substrate to which the pattern has been transferred to obtain an article; A method for manufacturing an article, comprising:

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