CN117250830A

CN117250830A - Measuring method, measuring apparatus, lithographic apparatus, and article manufacturing method

Info

Publication number: CN117250830A
Application number: CN202310707304.0A
Authority: CN
Inventors: 山口涉
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 2022-06-16
Filing date: 2023-06-14
Publication date: 2023-12-19

Abstract

The invention provides a measuring method, a measuring apparatus, a lithographic apparatus and a method of manufacturing an article. A method of measurement, comprising: performing a preliminary measurement step, while varying combinations of parameter values of at least two different measurement parameters, performing preliminary measurements with respect to each combination; a processing step of performing processing to obtain a sensitivity distribution regarding each of the at least two measurement parameters as a distribution indicating sensitivity of a change in the measurement value as a function of the parameter value, based on the measurement value obtained in the performing preliminary measurement step; a determining step of determining a parameter value to be used with respect to each of the at least two measurement parameters based on a sensitivity distribution with respect to each of the at least two measurement parameters; and performing a main measurement based on the parameter values of each of the at least two measurement parameters determined in the determining step.

Description

Measuring method, measuring apparatus, lithographic apparatus, and article manufacturing method

Technical Field

The present invention relates to a measurement method, a measurement apparatus, a lithographic apparatus and a method of manufacturing an article.

Background

In a lithographic apparatus such as an exposure apparatus used in a lithographic process, it is important to accuracy of alignment between an exposure region (shot region) on a substrate and a master and accuracy of overlay registration between different layers on the substrate. As a method of measuring a mark formed on a substrate with high accuracy, there is a method of matching the wavelength of measurement light with physical characteristics or optical characteristics of the mark and its peripheral portion. The physical properties, structure and shape of the marks on the substrate may vary from process to process. Thus, selecting the optimal wavelength according to the label makes it possible to maximize the intensity and quality of the detection signal from the label and to achieve accurate measurement.

Japanese patent No. 4792833 discloses that the amount of misregistration with respect to a plurality of combinations of wavelength and focus position is obtained, and wavelength and focus position that minimize the variation (variation) of the amount of misregistration are set as measurement conditions.

When a mark formed on a substrate is measured, when a parameter value of a measured parameter is different from an optimal value, the intensity and quality of a detection signal from the mark may be reduced, resulting in a reduction in measurement accuracy.

Disclosure of Invention

The present invention provides a technique that is advantageous for achieving high measurement accuracy.

A first aspect of the invention provides a measurement method comprising: performing a preliminary measurement step, while varying combinations of parameter values of at least two different measurement parameters, performing preliminary measurements with respect to each combination; a processing step of performing processing to obtain a sensitivity distribution regarding each of the at least two measurement parameters as a distribution indicating sensitivity of a change in the measurement value as a function of the parameter value, based on the measurement value obtained in the performing preliminary measurement step; a determining step of determining a parameter value to be used with respect to each of the at least two measurement parameters based on a sensitivity distribution with respect to each of the at least two measurement parameters; and performing a main measurement based on the parameter values of each of the at least two measurement parameters determined in the determining step.

A second aspect of the present invention provides a method of manufacturing an article, comprising: measuring the position of a mark on a substrate according to the measurement method as defined in the first aspect, and transferring a pattern to the substrate based on the position of the mark; and obtaining an article by processing the substrate to which the pattern is transferred.

A third aspect of the present invention provides a measurement apparatus including a measurement unit and a controller, wherein the controller controls the measurement unit to perform preliminary measurement a plurality of times while changing a combination of parameter values of at least two different measurement parameters, obtains a sensitivity distribution regarding each of the at least two measurement parameters based on a measurement value obtained by the preliminary measurement as a distribution indicating sensitivity of a measurement value that varies with a parameter value, determines a parameter value to be used regarding each of the at least two measurement parameters based on the sensitivity distribution, and controls the measurement unit to perform main measurement in accordance with the determined parameter value of each of the at least two measurement parameters.

A fourth aspect of the invention provides a lithographic apparatus comprising: the measuring devices as defined in the third aspect, each of which is a position for measuring a mark provided on a substrate; and a positioning mechanism configured to position the substrate based on the position of the mark measured by the measuring device, wherein the lithographic apparatus is configured to transfer the pattern of the substrate.

A fifth aspect of the present invention provides a method of manufacturing an article, comprising: transferring a pattern to a substrate by using a lithographic apparatus as defined in the fourth aspect; and obtaining an article by processing the substrate to which the pattern is transferred.

Other aspects of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings.

Drawings

Fig. 1A and 1B are diagrams showing an arrangement of a measuring device according to a first embodiment;

fig. 2A to 2C are diagrams for explaining a problem;

fig. 3A and 3B are diagrams for explaining the arrangement and function of the wavelength variable unit in the measuring apparatus according to the first embodiment;

fig. 4 is a flowchart for explaining a measurement sequence in the measurement apparatus according to the first embodiment;

fig. 5A to 5C are diagrams for explaining a specific measurement process in the measurement apparatus according to the first embodiment;

fig. 6A and 6B are graphs for explaining a specific measurement process in the measurement apparatus according to the first embodiment;

fig. 7A to 7C are graphs for explaining specific measurement processing in the measurement apparatus according to the first embodiment;

fig. 8 is a flowchart for explaining a measurement sequence in the measurement apparatus according to the second embodiment;

fig. 9A and 9B are graphs for explaining a specific measurement process in the measurement apparatus according to the second embodiment;

fig. 10A to 10C are diagrams for explaining a specific measurement process in the measurement apparatus according to the second embodiment;

Fig. 11A to 11C are diagrams for explaining a measurement sequence in the measurement apparatus according to the third embodiment;

fig. 12 is a flowchart for explaining a measurement sequence in the measurement apparatus according to the fourth embodiment;

fig. 13 is a diagram for explaining the arrangement of an exposure apparatus according to the fifth embodiment; and

fig. 14 is a flowchart for explaining a sequence for exposing a substrate in the exposure apparatus.

Detailed Description

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following examples are not intended to limit the scope of the claimed invention. In the embodiments, a plurality of features are described, but the invention requiring all of these features is not limited, and a plurality of such features may be appropriately combined. In addition, in the drawings, the same or similar configurations are given the same reference numerals, and redundant description thereof is omitted.

Fig. 1A is a diagram schematically and exemplarily showing an arrangement of a measurement apparatus 100 according to a first embodiment. The measuring device 100 may be configured as a position detecting device that measures or detects a position of a target or a measurement object provided on the substrate 73. Alternatively, the measuring apparatus 100 may be configured as a coincidence detecting apparatus as follows: which measures the relative positions of a plurality of targets arranged on different layers on a substrate. As shown in fig. 1A, the measurement apparatus 100 includes a substrate stage WS holding a substrate 73, a measurement unit 50, and a controller 1100.

The substrate 73 is a measurement target member whose position or registration error is measured by the measurement device 100. The substrate 73 may be used, for example, for manufacturing devices such as semiconductor devices or liquid crystal display devices. The substrate 73 may be, for example, a wafer or a glass substrate. The substrate stage WS holds the substrate 73 via a substrate chuck (not shown), and may be driven or positioned by a substrate driving mechanism (not shown). The substrate driving mechanism includes a linear motor or the like, and can drive or position the substrate 73 held by the substrate stage WS by driving the substrate stage WS in the X-axis direction, the Y-axis direction, the Z-axis direction, and the rotation direction about the respective axes. The position of the substrate stage WS is monitored by, for example, a 6-axis laser interferometer 81 or the like, and the substrate stage WS is driven to a predetermined position under the control of the controller 1100. Note that in this specification, the direction is represented by an XYZ coordinate system in which the normal line of the surface of the measurement object member is the Z-axis direction. The six axes include an X-axis direction, a Y-axis direction, a Z-axis direction, rotation about the X-axis (ωx), rotation about the Y-axis (ωy), and rotation about the Z-axis (ωz). The Z-axis direction can be understood as the optical axis direction of the measuring apparatus 100 on the surface of the measurement object member.

The controller 1100 is formed of a computer (information processing device) including a CPU and a memory, and can define functions of the measurement device 100 by comprehensively controlling constituent elements of the measurement device 100 according to a program stored in a storage unit, for example. The controller 1100 may be configured to control a measurement process in the measurement apparatus 100 and a correction process (calculation process) of a measurement value obtained by the measurement apparatus 100.

Referring to fig. 1B, the arrangement of the measurement unit 50 will be described. The measurement unit 50 includes: an illumination system for illuminating the substrate 73 with light from the light source 61; and an imaging system (detection system) for forming light from the measurement pattern (mark) 72 provided on the substrate 73 as an image on the detection unit 75. The detection unit 75 includes a plurality of pixels that detect light from the measurement pattern 72, and functions as an image capturing unit that forms an image capturing area for capturing the measurement pattern 72 using the plurality of pixels. Here, the measurement pattern 72 as a measurement object or target may be a pattern for measuring an alignment error or a registration error in the substrate 73. The measurement object or target may include a plurality of measurement patterns 72. Note that the measurement object is not limited to the measurement pattern provided on the substrate, and may be, for example, a stage, a part of a stage, a moving object, or a part of a moving object. In addition, the information obtained by measurement is not limited to position information such as an absolute position or a relative position of the measurement object, and may be, for example, at least one of: the shape, speed, acceleration and temperature of the object are measured.

Referring to fig. 1B, light from a light source 61 is guided to the wavelength variable unit 40 via an 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 driving mechanism that drives the wavelength variable element. The driving mechanism includes a linear motor, and drives the wavelength variable element 42 in a predetermined direction (for example, the X-axis direction), thereby adjusting the wavelength (for example, the center wavelength and the wavelength width) of light that irradiates the measurement pattern 72 or the target. The position of the wavelength variable element is monitored, for example, by using an encoder or a sensor such as an interferometer, and can be positioned at a target location under the control of the controller 1100. By adjusting the position of the wavelength variable element with respect to the optical path of light having a wide band wavelength emitted from the light source 61 using the driving mechanism, the area where the light enters the wavelength variable element can be adjusted. This allows light having the target wavelength to pass through the wavelength variable element.

The light having passed through the wavelength variable unit 40 or the wavelength variable element is transmitted through the illumination optical system 63, and is guided to the illumination aperture stop 64. The beam diameter at illumination aperture stop 64 is smaller than the beam diameter at light source 61. The light having passed through the illumination aperture stop 64 is guided to the polarization beam splitter 68 via the relay lens 67. The polarizing beam splitter 68 transmits P-polarized light and reflects S-polarized light. The P-polarized light transmitted through the polarizing beam splitter 68 passes through the aperture stop 69 and the λ/4 plate 70, is converted into circularly polarized light, and kohler-illuminates a measurement pattern 72 provided in a substrate 73 via an objective optical system 71.

Note that the illumination optical system 63 may be provided with a light amount adjustment unit (not shown). For example, by providing a light amount adjustment unit capable of selecting a plurality of ND filters having different transmittances with respect to light from the light source 61, the intensity of light irradiating the substrate 73 can be adjusted.

Light reflected, diffracted, and scattered by the measurement pattern 72 provided in the substrate 73 passes through the λ/4 plate 70 via the objective optical system 71, and is guided to the aperture stop 69 upon conversion from circularly polarized light to S polarized light. Here, the polarization state of the light from the measurement pattern 72 is circular polarization opposite to that of the light illuminating the measurement pattern 72. Therefore, when 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 is counterclockwise circularly polarized. The light having passed through the aperture stop 69 is reflected by the polarizing beam splitter 68, and is guided to the detection unit 75 via the imaging optical system 74.

In this way, in the measurement unit 50, the polarizing beam splitter 68 separates the optical path of the light illuminating the substrate 73 and the optical path of the light from the substrate 73, and an image of the measurement pattern 72 arranged in the substrate 73 is formed in the detection unit 75. Based on the positional 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, the controller 1100 can obtain the position of the pattern element forming the measurement pattern 72 and the position of the measurement pattern 72.

A plurality of lenses and a detection aperture stop may be arranged between the polarizing beam splitter 68 and the detection unit 75. A plurality of aperture stops may be provided in each of the illumination aperture stop 64 and the detection aperture stop, the plurality of aperture stops enabling different numerical apertures to be set for the illumination system and the detection system. Thereby, a 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, can be adjusted.

Next, measurement parameters in the measurement apparatus 100 will be described. The measurement device 100 may preferably perform the measurement according to set parameter values of at least two parameters. The at least two measurement parameters may include, for example, at least two of: the center wavelength, wavelength width, σ value, polarization characteristic, and transmittance of the light of the measurement pattern are irradiated or detected, and the position (X, Y, Z) and inclination (ωx, ωy, ωz) of the measurement pattern with respect to the measurement unit 50. The polarization characteristic may be a polarization characteristic in the optical path in the measuring device 100 or the measuring unit. The transmittance may be a transmittance of an ND filter arranged in the optical path. The at least two measurement parameters may include: various types of arithmetic processing parameters set when the controller calculates a measured value from image information of a target.

The characteristics of the measurement pattern on the substrate (e.g., physical properties of the material, structure, shape, etc.) may vary depending on the process used to obtain the substrate. Therefore, in order to achieve accurate measurement, it is important to match the measurement parameters with the characteristics of the measurement pattern. The measurement parameters regarding the wavelength of light used for measurement will be exemplarily described below.

The measurement parameters regarding the wavelength of the light used for measurement may include, for example, two measurement parameters, namely a center wavelength and a wavelength width. Fig. 2A is a diagram showing wavelength characteristics of light having different center wavelengths. Two different center wavelengths are denoted by WL1 and WL2, respectively. Fig. 2B is a diagram showing wavelength characteristics of light having the same center wavelength but having different wavelength widths. The two different wavelength widths are denoted by Δwl1 and Δwl2, respectively. Setting an appropriate center wavelength and wavelength width for a measurement pattern formed on a substrate can maximize the intensity and quality of a signal from the measurement pattern and achieve accurate measurement.

Before describing in detail the method of setting measurement parameters according to the present embodiment, a method of setting measurement parameters in a coincidence checking device (measuring device) according to a comparative example will be described with reference to fig. 2C. The coincidence checking device according to the comparative example can obtain measurement data as shown in fig. 2C by measuring the coincidence error Mij of the measurement pattern with respect to each of the combinations of the plurality of focus positions Zi and the wavelength WLj. Fig. 2C is a diagram showing an example of the registration error M of the measurement pattern obtained with respect to each of the combinations of the plurality of focus positions Zi and the wavelength WLj. For example, the position of the measurement pattern obtained at the focus position Z1 under the measurement condition of the wavelength WL1 is denoted by M11. Based on the measurement data shown in fig. 2C, the overlay error variations A1 to Aj corresponding to the focus positions and the overlay error variations B1 to Bi corresponding to the wavelengths are calculated. Specifically, the overlay error variance A1 is calculated from the variance 3σ or range of the overlay errors M11 to Mi1 of the measurement patterns. The overlay error variance B1 is calculated from the variance 3σ or range of the overlay errors M11 to M1j of the measurement patterns. Based on the above results, the wavelength corresponding to the smallest variation in the overlay error variation A1 to Aj and the focus position corresponding to the smallest variation in the overlay error variation B1 to Bi are set as measurement parameters.

The magnitude relationship between the variation of the overlay error under each measurement condition may depend on both the focus position and the wavelength. The focus position Z1 and the wavelength WL1 are assumed to be optimal parameter values. Even in this case, if the measurement errors M12 and M21 are large, the misregistration error variation A1 and the misregistration error variation B1 are not minimized. Therefore, the optimum conditions (the focus position Z1 and the wavelength WL 1) are not set as the parameter values. Therefore, when using the variation of the overlay error under a single measurement condition (for example, only the center wavelength) as an evaluation index, it is difficult to accurately determine the optimum parameter value. In addition, when the center wavelength and the wavelength width of the determined wavelength characteristic are each not evaluated as a parameter value, the intensity and quality of the detection signal from the measurement pattern are not sufficiently optimized, and thus it is difficult to achieve high measurement accuracy.

The measurement apparatus 100 according to the present embodiment performs preliminary measurements a plurality of times while changing the combination of parameter values of a plurality of different measurement parameters. Then, the measurement apparatus 100 obtains a sensitivity distribution as a distribution indicating sensitivity of a measured value variation with a parameter value for each of a plurality of measurement parameters. The measurement apparatus 100 determines a parameter value to be used for each of a plurality of measurement parameters based on the sensitivity distribution, and performs a main measurement according to the parameter value determined for each of the plurality of measurement parameters. A method of setting the parameter value of the measurement parameter in the measurement apparatus according to the present embodiment will be described below.

Fig. 3A is a diagram showing an example of the arrangement of the wavelength variable unit 40. The wavelength variable unit 40 may include: a wavelength variable element 42, a holding member 45 holding the wavelength variable element 42, and a driving mechanism 47 driving the holding member 45 (the wavelength variable element 42). The driving mechanism 47 may adjust the incident area of light with respect to the wavelength variable element 42 by driving the wavelength variable unit 40 in a predetermined direction (e.g., X-direction or rotation about the Z-axis). This converts the light having a broadband wavelength emitted from the light source 61 into light having a wavelength corresponding to the incident area of the light with respect to the wavelength variable unit 40, thereby irradiating the substrate 73. In other words, based on the light having a broadband wavelength emitted from the light source 61, light having a wavelength corresponding to the incident area of the light with respect to the wavelength variable unit 40 is generated as illumination light, and the substrate 73 is irradiated with the illumination light.

The wavelength variable element 42 may be, for example, a transmissive wavelength variable filter or a transmissive diffraction grating. This allows the controller 1100 to adjust (change) the wavelength of light transmitted through the wavelength variable element 42 by controlling the position or angle of the wavelength variable element 42 with the driving mechanism 47. The transmission-type wavelength variable filter is, for example, a bandpass filter in which a multilayer film is formed on the surface of a substrate, and may be configured to change the thickness of the multilayer film according to the position in the wavelength variation direction. This structure makes it possible to continuously change the wavelength of transmitted light by using light interference.

Fig. 3B is a diagram exemplarily showing a relationship between the wavelength of light transmitted through the wavelength variable element 42 and the signal intensity in the case where the driving mechanism 47 moves the wavelength variable element 42 to a plurality of positions in a predetermined direction. For example, in the case where the position of the wavelength variable element 42 in the X direction can be continuously adjusted, the center wavelength of the light transmitted through the wavelength variable element 42 can be continuously changed by adjusting the incidence position of the light with respect to the wavelength variable element 42 in the X direction. In addition, the wavelength variable unit 40 may include a short wavelength cut-off wavelength variable element 42 and a long wavelength cut-off wavelength variable element 42, and be configured to drive them individually. With this configuration, both the center wavelength and the wavelength width of the transmitted light can be arbitrarily changed by controlling the short-wavelength cut-off wavelength variable element 42 and the long-wavelength cut-off wavelength variable element 42.

The sequence of the measurement processing in the first embodiment will be described later with reference to fig. 4. In the measurement process, a parameter value of a measurement parameter is set, and measurement is performed according to the parameter value. As described above, the controller 1100 performs the measurement process by comprehensively controlling the constituent elements of the measurement apparatus 100.

When the measurement process starts, first, in step S131, a process of matching the relative positions of the substrate 73 and the measurement unit 50 may be performed under the control of the controller 1100. Specifically, an image capturing element may be used as the detection unit 75 in the measurement unit 50, and the substrate stage WS of the holding substrate 73 may be driven to form an image of the measurement pattern 72 in an image capturing area of the image capturing element. The adjustment of the position of the substrate 73 in the Z-axis direction (the optical axis direction or the direction along the light beam) with respect to the measurement unit 50 may be referred to as focus adjustment. In the focus adjustment, for example, a signal intensity based on at least one pattern constituting the measurement pattern 72 is obtained, and the substrate stage WS holding the substrate 73 may be positioned such that the signal intensity and its variation are equal to or greater than a target value. Alternatively, at the time of focus adjustment, signal intensities based on a plurality of patterns constituting the measurement pattern 72 may also be obtained, and the substrate stage WS holding the substrate 73 may be positioned so that the signal intensities and their variations are equal to or greater than the target values.

In step S132, under the control of the controller 1100, while changing the combination of parameter values of at least two different measurement parameters, images of the measurement pattern 72 on the substrate 73 may be obtained (imaged) a plurality of times by using the detection unit 75. The process may be understood as part of a preliminary measurement process in which preliminary measurements are made for each combination while varying the combination of parameter values for a plurality of different measurement parameters. The image of the measurement pattern 72 can be understood as intermediate information for obtaining the measurement value. The plurality of different measurement parameters may include, for example, a center wavelength and a wavelength width that may be controlled by the wavelength variable unit 40. The case of selecting the center wavelength and the wavelength width as a plurality of different measurement parameters will be exemplified below. However, other measurement parameters may be selected.

Step S133 is a process that can be arbitrarily performed. In step S133, the controller 1100 performs a synthesis process of generating a synthesized image by using the plurality of images obtained in step S132. Step S133 may be understood as a part of an estimation process of estimating an estimated value obtained for a combination different from that which has undergone preliminary measurement, based on the image obtained as intermediate information in step S132. The synthesis process in step S133 will be described in detail later.

In step S134, the controller 1100 performs: a first process of calculating the position (measured value) of the measurement pattern based on the image obtained in step S132 and a second process of calculating the position (measured value) of the measurement pattern based on the composite image generated in step S133. In step S134, the measurement value is not limited to the position information of the measurement pattern, and may be signal intensity information of the measurement pattern or waveform evaluation value information representing the characteristics of the signal waveform. The signal intensity information and the waveform evaluation value information of the measurement pattern will be described in detail later. If step S133 is not performed, the second process in step S134 is also not performed.

In this case, the first processing in step S132 and step S134 can be understood as: a preliminary measurement process of preliminary measurement is performed with respect to a combination of respective parameter values of a plurality of different measurement parameters. In addition, step S132 can be understood as: a detection process of detecting an image as intermediate information for obtaining a measured value from a measurement object. In addition, the first process in step S134 can be understood as: a calculation process of calculating a measurement value based on an image as intermediate information.

Further, the second processing in step S133 and step S134 may be understood as the following estimation processing: based on the image obtained as intermediate information obtained in step S132, measurement values obtained for combinations different from those that have undergone preliminary measurement are estimated. In this case, in the detection process, the image of the measurement object may be detected as intermediate information. In the estimation process, a synthetic image is generated from a plurality of images as intermediate information, and a measurement value obtained for a combination different from that which has undergone preliminary measurement may be estimated based on the synthetic image.

In step S135, the controller 1100 may calculate a sensitivity distribution with respect to at least two measurement parameters as a distribution indicating sensitivity of a measurement value variation of the measurement pattern as a function of a parameter value, based on the measurement values obtained in step S134. As the sensitivity distribution indicating the variation of the measurement value with the variation of the parameter value, for example, a sensitivity distribution indicating the variation of the measurement value with the variation of the center wavelength and a sensitivity distribution indicating the variation of the measurement value with the variation of the wavelength width can also be obtained. The sensitivity profile includes at least two types of sensitivity corresponding to at least two parameter values, respectively. The method of calculating the sensitivity distribution will be described in detail later.

In step S136, the controller 1100 may determine parameter values for at least two measurement parameters based on the sensitivity distribution calculated in step S135. This step can be understood as a determination process as follows: the parameter values to be used in relation to the respective measurement parameters are determined based on the sensitivity distribution in relation to the respective measurement parameters. This determination process makes it possible to determine the optimum center wavelength and the optimum wavelength width (a combination thereof).

In step S137, the detection unit 75 may obtain image information of the measurement pattern 72 according to the respective parameter values of the plurality of measurement parameters determined in step S136 under the control of the controller 1100, and may measure the position of the measurement pattern 72 based on the image information. This step can be understood as a main measurement process (determination process) of performing main measurement based on the parameter values of the respective measurement parameters determined in step S135.

The method of synthesizing the plurality of images in step S133 will be described below with reference to fig. 5A to 5C. The following is a description of a method of setting two measurement parameters (specifically, a center wavelength and a wavelength width). Fig. 5A shows an image 76a including a measurement pattern 72a obtained by the detection unit 75 under the condition that the center wavelength is 480nm and the wavelength width is ±10 nm. Fig. 5B shows an image 76B obtained by the detection unit 75 under the condition that the center wavelength is 500nm and the wavelength width is ±10 nm. The images 76a and 76B shown in fig. 5A and 5B, respectively, schematically show images obtained in the detection unit 75 at ND filter transmittance of 40% and 60% and accumulation time of 10 ms, respectively. The image 76a and the image 76b exhibit characteristics that the pattern portion and the non-pattern portion have different signal intensities, respectively, due to the difference in parameter values.

Fig. 5C shows a synthesized image 76C obtained by performing synthesis processing on the image 76a and the image 76b based on the reference luminance. In this case, the reference luminance refers to a luminance calculated from measurement conditions (parameter values) regarding the amount of light and set as a reference at the time of detecting each image, and is obtained in order to match the luminances of the plurality of images at the time of the combining process. Let Ta and Tb be ND filter transmittance, ca and Cb be accumulation time at the time of detection of the two images 76a and 76b for the synthesis process, and the luminance Sa and the luminance Sb of the images 76a and 76b can be represented by equations (1) and (2) given below.

Sa＝1/(Ca×Ta)...(1)

Sb＝1/(Cb×Tb)...(2)

If Ta < Tb and Ca < Cb, the high luminance Sa is the reference luminance, and the ratio of the luminance Sb to the reference luminance Sa is 0.67 obtained by the equations (1) and (2) and the measurement condition shown in fig. 5B. By multiplying the pixel output of the image 76b by the ratio of the luminance to the reference luminance to generate an image, and synthesizing the generated image with the image 76a having the reference luminance, a synthesized image 76c corresponding to an image detected under the condition that the center wavelength is 490nm and the wavelength width is ±20nm can be generated. This makes it possible to shorten the time required to determine the optimal center wavelength and the optimal wavelength width, as compared with the case where images are obtained with respect to all combinations of a plurality of desired center wavelengths and a plurality of desired wavelength widths.

It is assumed that the two images for the synthesizing process are synthesized without matching the reference values of the detected amounts of light of the two images. In this case, the image actually obtained and the image formed by the synthesis process are different in signal intensity of the pattern portion and the non-pattern portion. Therefore, it is difficult to accurately obtain a combination of the optimum center wavelength and the optimum wavelength width. For this reason, in step S133, the synthesizing process is preferably performed when the reference values of the detected amounts of light of the two images are matched. This makes it possible to accurately determine the combination of the optimum center wavelength and the optimum wavelength width. Although the method of calculating the luminance by using the ND filter transmittance and the accumulation time according to equation (1) and equation (2) has been described above, the present invention is not limited to this method. For example, a current value for controlling the output of the light source 61 and a gain set for the detection unit 75 may be set.

Next, a method of calculating the position information of the measurement pattern in step S134 will be described. The position of the measurement pattern 72 may be calculated by processing the image of the measurement pattern 72 obtained in step S133 using, for example, a template matching method. The template matching method can detect a position where the highest correlation occurs as a center position of the measurement pattern by calculating the correlation between the signal obtained in step S133 and the model signal (template) obtained in advance. Obtaining the center of gravity center pixel position of the region having several pixels on the left and right sides from the peak position of the correlation value function makes it possible to achieve a resolution of 1/10 pixel to 1/50 pixel.

A method of calculating the sensitivity distribution in step S135 will be described below with reference to fig. 6A and 6B. As an example of the sensitivity distribution, a sensitivity distribution indicating a change in the measurement value with respect to a change in the center wavelength (in short, a sensitivity distribution with respect to a change in the center wavelength) will be exemplarily described. The sensitivity distribution with respect to the center wavelength variation is a set of sensitivities indicating a measured value variation with respect to the center wavelength variation, and includes at least two sensitivities. The sensitivity distribution with respect to the change in the center wavelength is an index for determining the value of the center wavelength as the measurement parameter for measurement in step S136.

Fig. 6A is a graph showing a relationship between position information (measured value) of a measurement pattern and a center wavelength. The abscissa represents the center wavelength (written as "wavelength"), and the ordinate represents the positional information of the measurement pattern (written as "measurement value"). The center wavelengths WL3 and WL4 refer to the center wavelength of light. While the surface of the substrate 73 is aligned with the best focus position of the measurement unit 50, let M23 be a measurement value obtained by measuring the position of the measurement pattern 72 with light having the center wavelength WL3, and let M24 be a measurement value obtained by measuring the position of the measurement pattern 72 with light having the center wavelength WL 4. Fig. 6B is a graph showing a wavelength sensitivity distribution indicating a measured value change of the measurement pattern 72 with respect to a center wavelength change. The abscissa represents the center wavelength, and the ordinate represents the variation of the measured value calculated from the measured value shown in fig. 6A. For example, the center wavelength dWL3 and the measured value change dMw3 are represented by equation (3) and equation (4), respectively.

dWL3＝(WL3+WL4)÷2...(3)

dMw3＝(M24-M23)÷(WL4-WL3)...(4)

Next, a method of determining the parameter value of the measurement parameter in step S136 (determination process) will be described. In step S136, the parameter value to be used is determined based on the sensitivity distribution calculated in step S135. The parameter value indicating low sensitivity is preferably selected as the determination criterion in step S136. From another point of view, in step S136 (determination processing), the parameter values to be used are preferably determined so that the sensitivity in the sensitivity distribution is worse than the predetermined sensitivity in the parameter values to be used. From a further point of view, in step S136 (determination process), the parameter values to be used are preferably determined so that the sensitivity in the sensitivity distribution is lower than the predetermined sensitivity in the parameter values to be used. From a further point of view, in step S136 (determination processing), the parameter values to be used are preferably determined so that the sensitivity in the sensitivity distribution is the minimum value among the parameter values to be used.

The above-described reason for the determination of the parameter values will be described below with reference to fig. 7A to 7C. Fig. 7A is a graph exemplarily showing reflected light from the measurement pattern 72 and the non-pattern portion on a cross section of the substrate 73. The substrate 73 is constituted of a first layer L1 and a second layer L2, and has two boundary surfaces S1 and S2. On the boundary surface S1, the measurement pattern 72 has a step of a height d with respect to the non-pattern portion. Let L1A be the reflected light from the measurement pattern 72 on the boundary surface S1, L1B be the reflected light from the non-pattern portion, and L2A and L2B be the reflected light from the measurement pattern 72 and the non-pattern portion on the boundary surface S2. In the measurement unit 50, the interference light between the reflected light L1A and the reflected light L2A and the interference light between the reflected light L1B and the reflected light L2B become reflected light LA from the measurement pattern 72 and reflected light LB from the non-pattern portion, respectively, each of which is detected.

Fig. 7B is a graph showing an example of signal intensity information corresponding to the position X and including the reflected light LA from the pattern portion and the reflected light LB from the non-pattern portion shown in fig. 7A. In this case, as the signal intensity difference between the reflected light LA and the reflected light LB decreases, the signal contrast decreases, thereby making it more difficult to detect the position of the measurement pattern. The signal intensity difference between the reflected light LA and the reflected light LB varies according to the phase difference Δ of the step d originating from the measurement pattern 72, and the phase difference Δ is represented by equation (5) given below by using the refractive index n, the step d, and the wavelength of the second layer L2.

Δ＝2nd×2π/λ...(5)

According to equation (5), if the refractive index n or the step difference of the second layer L2 of the measurement pattern 72 is different, the phase difference Δ is changed. As described above, the change in the phase difference Δ causes a change in the signal contrast. With this variation, measurement errors may occur, resulting in a decrease in measurement accuracy.

In this case, as indicated by equation (5), since the change in the center wavelength corresponds to the variation in the phase difference Δ, the sensitivity indicating the change in the measurement value with the change in the center wavelength corresponds to the variation in the measurement value with respect to the variation in the phase difference. Therefore, in step S136 of the present embodiment, a parameter value indicating low sensitivity indicating a change in the measured value with respect to a change in the center wavelength is selected, and measurement errors accompanying process changes can be reduced.

Fig. 7C is a graph showing an example of signal strength information. In this case, the waveform evaluation value information refers to an index indicating the quality of the signal waveform generated based on the output from the detection unit 75. An example of the waveform evaluation value information is a value obtained by quantifying asymmetry of a signal waveform of the measurement pattern. For example, referring to fig. 7A, let TL and BL be the maximum and minimum values of the signal intensity in the left section of the signal waveform, TR and BR be the maximum and minimum values of the signal intensity in the right section of the signal waveform, respectively, and ML and MR be the signal intensity of the central portion of the signal waveform, respectively. As indicated by equation (6) given below, the asymmetry ES between the left section and the right section of the signal waveform may be obtained as a measured value in step S134.

ES＝(TL-BL)/(TL+BL)-(TR-BR)/(TR+BR)...(6)

The method of calculating the asymmetry is not limited to equation (6). For example, a center position of the signal waveform may be defined, and asymmetry of the signal waveform may be defined based on signal intensities in a predetermined position range in left and right sections with respect to the center position. In addition, the waveform evaluation value information is not limited to asymmetry, and the contrast of the measurement pattern may be evaluated as indicated by equation (7) given below.

EC＝{(TL-BL)/(TL+BL)+(TR-BR)/(TR+BR)}/2...(7)

As described above, instead of the position information of the measurement pattern, waveform evaluation value information may be obtained as the measurement value, and the parameter value of the measurement parameter may be determined based on the signal intensity information of the measurement pattern or the sensitivity of the waveform evaluation value information.

As described above, in the first embodiment, the sensitivity distribution with respect to each of the plurality of measurement parameters is obtained, and the parameter value to be used is determined for each of the plurality of measurement parameters based on the sensitivity distribution. This enables quick and accurate measurement of the measurement object.

The measuring device and the measuring process according to the second embodiment will be described below with reference to fig. 8. The second embodiment is different from the first embodiment in a method of calculating sensitivity for setting a parameter value of a measurement parameter, but is the same as the first embodiment in other configurations. Matters not mentioned here may correspond to the first embodiment.

Fig. 8 is a flowchart showing a sequence of measurement processing in the second embodiment. As in the first embodiment, the controller 1100 shown in fig. 1A performs this measurement process by comprehensively controlling the constituent elements of the measurement apparatus 100. When the measurement process starts, first, in step S231, a process of matching the relative positions of the substrate 73 and the measurement unit 50 may be performed under the control of the controller 1100. In step S232, under the control of the controller 1100, while changing the combination of parameter values of at least two different measurement parameters, images of the measurement pattern 72 provided on the substrate 73 may be obtained (photographed) a plurality of times by using the detection unit 75. This process can be understood as: a part of a preliminary measurement process of performing preliminary measurements for each combination while changing the combination of parameter values of a plurality of different measurement parameters. The plurality of different measurement parameters may include, for example, a center wavelength and a wavelength width that may be controlled by the wavelength variable unit 40. The following is a description of the case where the center wavelength and the wavelength width are selected as a plurality of different measurement parameters. In the second embodiment, the sensitivity of the measurement value to the shift (defocus) of the surface of the substrate 73 from the best focus position of the measurement unit 50 is considered. Step S232 includes an operation of driving the substrate stage WS holding the substrate 73 by a predetermined amount in the Z direction, and images of the measurement pattern 72 may be obtained (photographed) by the detection unit 75 at respective different positions in the Z direction.

Step S233 is a process that can be arbitrarily performed. In step S233, the controller 1100 performs a synthesis process of generating a synthesized image by using the plurality of image information obtained in step S232. In step S234, the controller 1100 performs: a first process of calculating the position (measured value) of the measurement pattern based on the image obtained in step S232; and a second process of calculating the position (measured value) of the measurement pattern based on the composite image generated in step S233.

The first processing in step S232 and step S234 may be understood as a preliminary measurement processing of performing preliminary measurements with respect to a combination of parameter values of a plurality of different measurement parameters. Step S232 can be understood as a detection process of detecting an image, which is intermediate information for obtaining a measured value, from a measurement object. The first process in step S234 may be understood as a calculation process of calculating a measured value based on an image as intermediate information.

The second process in step S233 and step S234 can be understood as an estimation process as follows: based on the image obtained in step S232 as intermediate information, measurement values obtained for combinations different from those that have undergone preliminary measurement are estimated. In this case, in the detection process, the image of the measurement object may be detected as intermediate information. In the estimation process, a synthetic image may be generated from a plurality of images as intermediate information, and a measurement value obtained for a combination different from that which has undergone preliminary measurement may be estimated based on the synthetic image.

In step S235, the controller 1100 may calculate a sensitivity distribution with respect to at least two measurement parameters as a distribution indicating sensitivity of a measurement value variation of the measurement pattern as a function of a parameter value, based on the measurement values obtained in step S234. As the sensitivity distribution indicating the variation of the measurement value with the variation of the parameter value, for example, a sensitivity distribution indicating the variation of the measurement value with the variation of the center wavelength and a sensitivity distribution indicating the variation of the measurement value with the variation of the wavelength width can be obtained. The sensitivity profile includes: at least two sensitivities respectively corresponding to the at least two measurement parameters. The method of calculating the sensitivity distribution will be described in detail later.

In step S236, the controller 1100 may determine parameter values of at least two measurement parameters based on the sensitivity distribution calculated in step S235. This step can be understood as a determination process as follows: parameter values to be used for the respective measurement parameters are determined based on sensitivity distribution with respect to the respective measurement parameters. This determination process makes it possible to determine the optimum center wavelength and the optimum wavelength width (a combination thereof).

In step S237, the detection unit 75 may obtain image information of the measurement pattern 72 according to the respective parameter values of the plurality of measurement parameters determined in step S236 under the control of the controller 1100, and may measure the position of the measurement pattern 72 based on the image information. This step can be understood as a main measurement process of performing main measurement based on the parameter values of the respective measurement parameters determined in step S235 (determination process).

In the second embodiment, the sensitivity to the change in the parameter value of the measurement parameter with respect to the change in the measurement value (focus sensitivity) with the change in the focus state (defocus change) can be used to determine the parameter value. For example, the sensitivity to the change in the center wavelength (in short, the focus sensitivity to the change in the center wavelength) with respect to the measured value change with the focus state (focus sensitivity) can be used to determine the parameter value. In addition, the sensitivity of the wavelength width to the change in the measured value (focus sensitivity) (in short, focus sensitivity to the change in the wavelength width) can be used to determine the parameter value. If a relative angular shift occurs between the normal of the surface of the substrate 73 and the optical axis of the measuring unit 50, the measured value changes with a deterioration in the relative focus position of the substrate 73 and the measuring unit 50. Therefore, by selecting parameter values representing low focus sensitivity with respect to at least two measurement parameters (in this case, the center wavelength and the wavelength width), deterioration of the measurement value can be reduced, and high-precision measurement can be achieved.

In step S232, for example, an image of a measurement pattern may be obtained for each of different positions in the Z-axis direction. In step S234, the position (measured value) of the measurement pattern may be calculated for the image information obtained in step S232 and the synthesized image generated in step S233. Similar to fig. 6A, fig. 9A is a graph showing a relationship between the position (measured value) of the measurement pattern and the center wavelength. The abscissa represents the center wavelength and the ordinate represents the measured value. The wavelengths WL3 and WL4 refer to the center wavelength of light illuminating the substrate and the center wavelength of light detected from the substrate. In the case shown in fig. 9A, as in fig. 6A, a measured value change with a change in the center wavelength is obtained while the substrate 73 is aligned with the best focus position of the measurement unit 50 and the substrate 73 is also aligned with the defocus position. For example, let M14 and M24 be measurement values of the measurement pattern 72 using light having the center wavelength WL4 at the best focus position Z1 and the defocus position Z2. Similarly, let M16 and M26 be measurement values of the measurement pattern 72 using light having the center wavelength WL 6.

In step S235, for at least two measurement parameters, a sensitivity is calculated, which is indicative of a measured value change of the measurement pattern as a function of a parameter value of the measurement parameter. In this case, for example, a change in the center wavelength and the wavelength width is considered as a change in the parameter value. In addition, a change in focus sensitivity is considered as a change in measurement value.

Fig. 9B is a graph showing a relationship between the center wavelength and a measured value change (focus sensitivity) of the measurement pattern 72 according to a focus state change. The abscissa represents the center wavelength, and the ordinate represents the measured value variation calculated from the measured value shown in fig. 9A. The measured value changes dMz and dMz are represented by equation (8) and equation (9) given below, respectively.

dMz4＝M14-M24...(8)

dMz6＝M16-M26...(9)

In step S236, the controller 1100 may determine parameter values for at least two measurement parameters, respectively, based on the sensitivity distribution calculated in step S235. Selecting a parameter value representing low focus sensitivity with respect to each measurement parameter can minimize a variation in the measurement value due to, for example, a variation in the parameter value, thereby realizing accurate measurement.

Instead of the above-described determination method based on one index, the parameter values of the respective measurement parameters may be determined by using a determination method based on a plurality of indexes. For example, the parameter values, i.e., the sensitivity distribution with respect to the change in the center wavelength in the first embodiment and the focus sensitivity with respect to the change in the center wavelength in the second embodiment, may also be determined based on two indices. In determining the parameter values based on a plurality of indices (sensitivities), a weighting function may be set to adjust the relative influence of the sensitivities. For example, the two sensitivities may be weighted in consideration of the difference in the degree of influence between the wavelength variation and the focus variation in the process variation. This can suppress a change in the measured value (measurement error) with respect to a wavelength change and a focus change accompanying a process variation.

The above is a description of calculating the sensitivity by using the single measurement pattern 72 on the substrate 73. However, the sensitivity may be calculated by using the measurement pattern 72 formed at a different position. For example, as shown in fig. 10A, the wavelength sensitivity and the focus sensitivity may be obtained by detecting images of a plurality of measurement patterns 72a and 72b formed on the substrate 73 and calculating measurement values based on the obtained image information. As shown in fig. 10B, the sensitivity Sa and the sensitivity Sb corresponding to the measurement pattern 72a and the measurement pattern 72B can be obtained.

In determining the parameter value of the measurement parameter from two or more parameter value candidates, it is preferable to determine the measurement parameter based on an average value or variation of the sensitivity Sa and the sensitivity Sb at the same wavelength to minimize an error caused when measuring a plurality of measurement parameters on the substrate. By this operation, it is also possible to minimize a measurement error corresponding to a position on the substrate 73, for example, due to a thickness variation of the substrate 73.

Each of the measurement parameters such as the wavelength, sigma value, and polarization of the light used by the measurement unit 50 may also be weighted. For example, after calculating the wavelength sensitivity distribution based on the obtained measurement values, the sensitivity distribution shown in fig. 10B may be integrated with the weighting function W1 of each wavelength as shown in fig. 10C. Specific examples of the weighting include a change in signal contrast according to the wavelength of the measurement pattern 72, measurement accuracy or a measurement time difference accompanied by a sigma value difference. This makes it possible to suppress a decrease in measurement accuracy or an increase in measurement time by calculating sensitivity when a predetermined weight is added to the measurement value obtained with respect to the measurement pattern 72.

A measuring device according to a third embodiment will be described below. Matters not mentioned here may correspond to the first embodiment. A coincidence measuring apparatus (coincidence checking apparatus) that measures the relative positions of a plurality of measurement patterns formed on different layers on the substrate 73 will be described with reference to fig. 11A to 11C.

Fig. 11A is a diagram exemplarily showing an image of the measurement pattern 72 formed on the detection surface of the detection unit 75 shown in fig. 1B. The measurement pattern 72 may include a first pattern group P1 and a second pattern group P2 formed on different layers, respectively. The detection unit 75 may include a two-dimensional image capturing element having a plurality of pixels in the X and Y directions. The controller 1100 may generate signal waveforms representing the first pattern group P1 and the second pattern group P2, respectively, based on the output from the detection unit 75.

Fig. 11B shows a signal waveform SW generated by integrating the signal intensity of the pattern on each pixel of the detection unit 75 in the Y direction in fig. 11A as an example of a signal waveform generated based on the output from the detection unit 75 shown in fig. 11A. In integrating the signal intensity on each pixel of the detection unit 75, the number of pixels to be integrated is preferably set based on the size information of the pattern. Waveforms S1 and S2 shown in fig. 11B refer to changes in signal intensities of the first pattern group P1 and the second pattern group P2 in the signal waveform SW. In addition, the measured values X1 and X2 correspond to the center position of the first pattern group P1 and the center position of the second pattern group P2, respectively, calculated by the controller 1100 based on the waveforms S1 and S2, respectively. For example, calculating the difference between the measured value X1 and the measured value X2 will calculate the relative positional shift of the first pattern group P1 and the second pattern group P2 in the X direction. In calculating the relative positional shift in the Y direction, a first pattern group and a second pattern group composed of a plurality of patterns formed on the substrate along the Y direction, in which the longitudinal direction of each pattern coincides with the X direction, may be used. Then, a signal waveform is generated by integrating the signal intensities of the patterns on the respective pixels in the X direction, and the relative positional shift is calculated from the measured value difference between the respective pattern groups as the relative positional shift in the X direction.

Fig. 11C is a flowchart showing a sequence of measurement processing for determining a measurement parameter. The controller 1100 shown in fig. 1A performs measurement processing by comprehensively controlling constituent elements of the measurement apparatus 100. When the measurement process starts, first, a process of matching the relative positions of the substrate 73 and the measurement unit 50 is performed in step S331. In this case, as shown in fig. 11A, both the first pattern group P1 and the second pattern group P2 are aligned with the detection unit 75. In step S332, the detection unit 75 may obtain images of the first pattern group P1 and the second pattern group P2 provided on the substrate 73 a plurality of times while changing the combination of the parameter values of at least two different measurement parameters. This process may be performed in the same manner as in step S132 or step S232. In step S333, the controller 1100 performs a synthesis process of generating a synthesized image by using the plurality of pieces of image information obtained in step S332. In step S334, the controller 1100 calculates the positions (measured values) of the first pattern group P1 and the second pattern group P2 for the image information obtained in step S332 and the composite image generated in step S333. In step S335, the controller 1100 calculates the sensitivity of the measured values of the first pattern group P1 and the second pattern group P2 to the variation of the parameter values for at least two measured parameters.

In step S336, the controller 1100 determines parameter values for at least two measurement parameters based on the sensitivity distribution calculated in step S335. In step S337, the detection unit 75 obtains image information of the first pattern group P1 and the second pattern group P2 according to the parameter values of the plurality of measurement parameters determined in step S336 under the control of the controller 1100. The positions of the first pattern group P1 and the second pattern group P2 may be measured based on the image information.

A method of measuring the positions of the first pattern group P1 and the second pattern group P2 formed on different layers on the substrate 73 will be exemplarily described. There are two ways to align the substrate 73 with the measurement unit 50. In the first method, the first pattern group P1 and the second pattern group P2 are each individually aligned with the best focus position of the measurement unit 50, and the positions of the first pattern group P1 and the second pattern group P2 are each measured. In the second method, the positions of the first pattern group P1 and the second pattern group P2 may be measured while the substrate 73 and the detection unit 75 are aligned with a given focus position.

When the first method is used, in step S335, the sensitivity distribution is obtained according to the first embodiment, the second embodiment, or the like with reference to the best focus positions of the first pattern group P1 and the second pattern group P2. When the second method is used, in step S335, a sensitivity distribution can be obtained according to the first embodiment, the second embodiment, or the like with reference to the common focus position. The common focus position may be determined based on the intensity and quality of the detection signal from each of the first pattern group P1 and the second pattern group P2.

As described above, in the third embodiment, the positions of a plurality of measurement parameters formed on different layers of the substrate 73 are measured while changing the combination of the parameter values of at least two different measurement parameters. Then, the sensitivity distribution is calculated based on the measured value obtained by this operation. Parameter values for at least two measurement parameters are then determined based on the sensitivity distribution. This makes it possible to reduce errors in the coincidence measurement and to achieve accurate coincidence by selecting parameter values that vary little with measured value changes such as changes in wavelength or focus. In this embodiment, this makes it possible to provide a registration inspection apparatus that can quickly and accurately measure a registration error of a pattern on a substrate.

A measuring apparatus (measurement pattern monitor) that measures a characteristic change of a measurement pattern formed on a substrate according to a fourth embodiment will be described below. Matters not mentioned here may correspond to the first embodiment. As a fourth embodiment, a measurement device and a measurement process according to the fourth embodiment will be described with reference to fig. 12. The fourth embodiment is different from the first embodiment in a method of determining a parameter value of a measurement parameter.

First, a measuring device (measurement pattern monitor) that measures a characteristic change of a measurement pattern will be described. It is assumed that the substrate has been deformed or the structure/characteristics have been changed in a processing step such as heating of the substrate or film formation. In this case, as the signal intensity information of the obtained measurement pattern changes, the alignment accuracy of the substrate or the registration accuracy of the pattern on the substrate deteriorates. Therefore, the presence/absence of an abnormality in each processing step is detected by measuring (monitoring) the characteristics of the measurement pattern using the measurement device, thereby designating the processing device as the cause of the characteristic change of the measurement pattern. Therefore, changing the alignment or setting conditions of the processing apparatus or re-checking the structure or processing steps of the measurement pattern can reduce the occurrence of defective products accompanied by deterioration of the alignment accuracy of the substrate or deterioration of the registration accuracy of the pattern.

Fig. 12 is a flowchart showing a sequence of measurement processing according to the fourth embodiment. Step S431 to step S435 are the same as step S131 to step S135 shown in fig. 4, and thus a description thereof will be omitted.

Next, a method of determining the parameter value of the measurement parameter in step S436 (determination process) will be described. In step S436, a parameter value to be used is determined based on the sensitivity distribution calculated in step S435. The parameter value indicating high sensitivity is preferably selected as the determination criterion in step S436. From another point of view, in step S436 (determination process), the parameter values to be used are preferably determined so that the sensitivity in the sensitivity distribution is more sensitive than a predetermined sensitivity in the parameter values to be used. From a further angle, in step S436 (determination process), the parameter values to be used are preferably determined so that the sensitivity in the sensitivity distribution is higher than a predetermined sensitivity in the parameter values to be used. From a further angle, in step S436 (determination process), the parameter values to be used are preferably determined so that the sensitivity in the sensitivity distribution is the maximum value among the parameter values to be used.

Note that, when measurement processing is performed with respect to a plurality of measurement patterns, the sensitivity of each of the plurality of measurement patterns is obtained as described with reference to fig. 10B in the second embodiment. For example, it is preferable to determine the measurement parameters based on the average or variation of the sensitivities Sa and Sb at the same wavelength to maximize the error caused when measuring a plurality of measurement patterns on the substrate. By this operation, for example, the measurement error corresponding to the position on the substrate 73 due to the thickness variation of the substrate 73 can also be maximized.

The reason for the description above regarding the determination of the parameter values will be described below. In step S136 of the first embodiment, in order to reduce the measurement error accompanying the process variation, a parameter value representing low sensitivity indicating a variation of the measurement value with a variation of the center wavelength is selected. On the other hand, the measurement apparatus (measurement pattern monitor) according to the present embodiment needs to accurately detect a change in the measurement value accompanying a process change. Thus, process variations can be accurately detected by selecting parameter values that represent high sensitivity indicative of measured value variations as a function of center wavelength.

In step S437, the detection unit 75 obtains image information of the measurement pattern 72 according to the parameter value of each of the plurality of measurement parameters determined in step S436 under the control of the controller 1100, and may measure characteristic information of the measurement pattern 72 based on the image information. This step may be understood as a main measurement process of performing main measurement based on the parameter value of each of the plurality of measurement parameters determined in step S436 (determination process). Examples of the characteristic information of the measurement pattern 72 include the position of the measurement pattern 72, signal strength information, and waveform evaluation value information.

In step S438, the characteristic information of the measurement pattern 72 obtained in step S437 is compared with the reference information to obtain the amount of change in the characteristic information of the measurement pattern. Examples of the reference information include characteristic information and design value information of the measurement pattern 72, and simulation results obtained in advance.

As described above, in the fourth embodiment, sensitivity distribution with respect to each measurement parameter is obtained, and parameter values to be used are determined for each measurement parameter based on the sensitivity distribution. This makes it possible to quickly and accurately measure a change in physical information of a measurement parameter in the measurement apparatus (measurement pattern monitor) according to the present embodiment.

A lithographic apparatus incorporating the above-described measurement apparatus will be described. The lithographic apparatus may be, for example, an exposure apparatus, an imprint apparatus, or an electron beam drawing apparatus. Fig. 13 is a schematic diagram showing an arrangement of an exposure apparatus EXA as an example of a lithographic apparatus. The exposure apparatus EXA is a photolithography apparatus which is used in a photolithography process which is a manufacturing process of an article or a device such as a semiconductor device or a liquid crystal display device, and forms a pattern on the substrate 83. The exposure apparatus EXA exposes the substrate 83 via the reticle 31 serving as a master, thereby transferring the pattern of the reticle 31 to the substrate 83. In the present embodiment, the exposure apparatus EXA adopts a step-and-scan method, but a step-and-repeat method or other exposure method may also be adopted.

As shown in fig. 13, the exposure apparatus EXA includes an illumination optical system 801, a reticle stage RS holding the reticle 31, a projection optical system 32, a substrate stage WS holding the substrate 83, a position measuring apparatus 550, and a controller 1200.

The illumination optical system 801 is an optical system that illuminates an illuminated surface using light from the light source unit 800. The light source unit 800 includes, for example, a laser. The laser includes: an Arf excimer laser having a wavelength of about 193nm, a KrF excimer laser having a wavelength of about 248nm, or the like, but the type of light source is not limited to an excimer laser. For example, the light source unit 800 may use F having a wavelength of about 157nm ₂ A laser or EUV (extreme ultraviolet) having a wavelength of 20nm or less is used as a light source.

In the present embodiment, the illumination optical system 801 shapes light from the light source unit 800 into slit light having a predetermined shape suitable for exposure, and illuminates the reticle 31. The illumination optical system 801 has a function of uniformly illuminating the reticle 31 and a polarized illumination function. The illumination optical system 801 includes, for example, a lens, a reflecting mirror, an optical integrator, a diaphragm, and the like, and is formed by sequentially arranging a condenser lens, a fly-eye lens, an aperture diaphragm, a condenser lens, a slit, and an imaging optical system.

The reticle 31 is formed of quartz, for example. The reticle 31 forms a pattern (circuit pattern) to be transferred to the substrate 83.

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 driving mechanism includes a linear motor or the like, and is capable of moving the reticle 31 held by the reticle stage RS by driving the reticle stage RS in the X-axis direction, the Y-axis direction, the Z-axis direction, and the rotation direction about the respective axes. Note that the position of the reticle 31 is measured by a light oblique incidence type reticle position measuring unit (not shown), and the reticle 31 is arranged at a predetermined position via the reticle stage RS.

The projection optical system 32 has a function of imaging light from the object plane into the image plane. In the present embodiment, the projection optical system 32 projects light (diffracted light) having passed through the pattern of the reticle 31 onto the substrate 83, thereby forming an image of the pattern of the reticle 31 on the substrate. As the projection optical system 32, an optical system formed of a plurality of lens elements, an optical system including a plurality of lens elements and at least one concave mirror (catadioptric optical system), an optical system including a plurality of lens elements and at least one diffractive optical element such as kinoform, or the like is used.

A photoresist is applied to the substrate 83. The substrate 83 is a processing target object to which the pattern of the reticle 31 is transferred, and includes a wafer, a liquid crystal substrate, another processing target substrate, and the like.

The substrate stage WS holds a substrate 83 via a substrate chuck (not shown), and is connected to a substrate driving mechanism (not shown). The substrate driving mechanism includes a linear motor or the like, and can move the substrate 83 held by the substrate stage WS by driving the substrate stage WS in the X-axis direction, the Y-axis direction, the Z-axis direction, and the rotation direction about the respective axes. The reference plate 39 is disposed on the substrate stage WS.

The position of the reticle stage RS and the position of the substrate stage WS are monitored by, for example, a 6-axis laser interferometer 91 or the like, and the reticle stage RS and the substrate stage WS are driven at a constant speed ratio under the control of the controller 1200.

The controller 1200 is formed of a computer (information processing apparatus) including a CPU, a memory, and the like, and operates the exposure apparatus EXA by comprehensively controlling respective units of the exposure apparatus EXA according to a program stored in a storage unit, for example. The controller 1200 controls: an exposure process of transferring the pattern of the reticle 31 to the substrate 83 by exposing the substrate 83 through the reticle 31. Further, in the present embodiment, the controller 1200 controls: a measurement process in the position measurement device 550 and a correction process (calculation process) of the measurement value obtained by the position measurement device 550. In this manner, the controller 1200 also serves as part of the position measurement device 550.

In the exposure apparatus EXA, light (diffracted light) having 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 optically conjugate relation. By scanning the reticle 31 and the substrate 83 at the speed ratio of the reduction ratio of the projection optical system 32, the pattern of the reticle 31 is transferred to the substrate 83.

The position measurement device 550 is a measurement device for measuring the position of the target object. In the present embodiment, the position measuring device 550 measures the position of a mark such as an alignment mark provided in the substrate 83. The position measurement device 550 includes a wavelength variable unit. The wavelength variable unit is composed of a wavelength variable element and a holding member. The controller drives the wavelength variable unit in the X direction by using a driving mechanism (not shown).

Referring to fig. 14, a sequence of exposure processing for transferring the pattern of the reticle 31 onto the substrate 83 by exposing the substrate 83 via the reticle 31 will be described. As described above, the controller 1200 comprehensively controls the respective units of the exposure apparatus EXA to perform the exposure process.

In step S101, the substrate 83 is loaded into the exposure apparatus EXA. In step S102, the surface (height) of the substrate 83 is detected by a shape measuring device (not shown) to measure the surface shape of the entire substrate 83.

In step S103, calibration is performed. More specifically, the wafer stage WS is driven to position the fiducial marks on the optical axis of the position measurement device 550 based on the designed coordinate positions of the fiducial marks provided on the fiducial plate 39 in the stage coordinate system. Then, the positional shift of the reference mark with respect to the optical axis of the position measurement device 550 is measured, and the stage coordinate system is reset based on the positional shift so that the origin of the stage coordinate system coincides with the optical axis of the position measurement device 550. Next, based on the designed positional relationship between the optical axis of the position measuring device 550 and the optical axis of the projection optical system 32, the substrate stage WS is driven to position the reference mark on the optical axis of the exposure light. Then, the positional shift of The reference mark with respect to The optical axis of The exposure light is measured by a TTL (Through The Lens) measurement system via The projection optical system 32.

In step S104, a baseline between the optical axis of the position measurement device 550 and the optical axis of the projection optical system 32 is determined based on the calibration result obtained in step S103. In step S105, the position measuring device 550 measures the position of the mark provided in the substrate 83.

In step S106, global alignment is performed. More specifically, based on the measurement result obtained in step S105, the offset, magnification, and rotation with respect to the exposure area array on the substrate 83 are calculated, and the regularity of the exposure area array is obtained. Then, correction coefficients are obtained according to the regularity of the array of the base line and the exposure area, and the substrate 83 is aligned with the reticle 31 (exposure light) based on the correction coefficients.

In step S107, the substrate 83 is exposed while the reticle 31 and the substrate 83 are scanned in the scanning direction (Y direction). At this time, by driving the substrate stage WS in the Z direction and the oblique direction based on the surface shape of the substrate 83 measured by the shape measuring device, an operation of sequentially adjusting the surface of the substrate 83 to the imaging plane of the projection optical system 32 is also performed.

In step S108, it is determined whether or not the exposure of all the exposure areas of the substrate 83 is completed (i.e., whether or not there is no unexposed exposure area). If the exposure of all the exposure areas of the substrate 83 is not completed, the process returns to step S107, and steps S107 and S108 are repeated until the exposure of all the exposure areas is completed. On the other hand, if the exposure of all the exposure areas of the substrate 83 is completed, the process advances to step S109, and the substrate 83 is unloaded from the exposure apparatus EXA.

In the present embodiment, the position of the mark is measured by using each of a plurality of different measurement parameters, and the sensitivity of each measurement value corresponding to the deterioration of the measurement parameters is calculated with respect to at least two or more measurement parameters. The measurement parameters to be used for the measurement are determined based on the sensitivity. This makes it possible to reduce errors in alignment measurement and achieve accurate alignment. Accordingly, the present embodiment can provide a position measuring device that can quickly and accurately measure the position of a pattern on a substrate.

An article manufacturing method of manufacturing an article by using the above-described lithographic apparatus will be exemplarily described. The article manufacturing method is suitable for manufacturing articles such as devices (semiconductor devices, magnetic storage media, liquid crystal display devices, and the like), for example. The manufacturing method comprises the following steps: a step of exposing (forming a pattern on) a substrate on which a photosensitive agent is applied by using an exposure device EXA, and a step of developing (processing the substrate) the exposed substrate. In addition, the manufacturing method may include other well-known steps (oxidation, film formation, deposition, doping, planarization, etching, resist removal, dicing, bonding, packaging, and the like). The article manufacturing method of the present embodiment is more advantageous than the conventional method in at least one of the performance, quality, productivity, and production cost of the article. Note that the above-described article manufacturing method can be performed by using a lithographic apparatus such as an imprint apparatus or a drawing apparatus.

Other embodiments

The embodiment(s) of the present invention may also be implemented as follows: a computer of a system or apparatus that reads out and executes computer-executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be more fully referred to as a "non-transitory computer-readable storage medium") to perform the functions of one or more of the above-described embodiments and/or that includes one or more circuits (e.g., an Application Specific Integrated Circuit (ASIC)) for performing the functions of one or more of the above-described embodiments; and methods performed by a computer of the system or apparatus, e.g., reading and executing computer-executable instructions from a storage medium to perform the functions of one or more of the above-described embodiment(s), and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may include one or more processors (e.g., a Central Processing Unit (CPU), micro-processing unit (MPU)), and may include a separate computer or a network of separate processors to read out and execute the computer-executable instructions. The computer-executable instructions may be provided to the computer, for example, from a network or a storage medium. The storage medium may include, for example, one or more of a hard disk, random Access Memory (RAM), read Only Memory (ROM), memory of a distributed computing system, optical disks such as Compact Discs (CDs), digital Versatile Discs (DVDs), or blu-ray discs (BD) TM), flash memory devices, and memory cards.

Other embodiments

The embodiments of the present invention can also be realized by a method in which software (program) that performs the functions of the above embodiments is supplied to a system or apparatus, a computer of the system or apparatus or a Central Processing Unit (CPU), a Micro Processing Unit (MPU), or the like, through a network or various storage mediums, and the program is read out and performed.

While the invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims

1. A method of measurement, comprising:

performing a preliminary measurement step, while varying combinations of parameter values of at least two different measurement parameters, performing preliminary measurements with respect to each combination;

a processing step of performing processing to obtain a sensitivity distribution regarding each of the at least two measurement parameters as a distribution indicating sensitivity of a change in the measurement value as a function of the parameter value, based on the measurement value obtained in the performing preliminary measurement step;

A determining step of determining a parameter value to be used with respect to each of the at least two measurement parameters based on a sensitivity distribution with respect to each of the at least two measurement parameters; and

a main measurement step of performing a main measurement based on the parameter values of each of the at least two measurement parameters determined in the determination step.

2. The method of measurement according to claim 1,

wherein, in the preliminary measurement step and the main measurement step, the position information of the target is measured.

3. The method of measurement according to claim 2,

wherein the at least two measurement parameters include a center wavelength of light illuminating the target and a wavelength width of the light.

4. The method of measurement according to claim 2,

wherein the at least two measurement parameters include: at least two of a center wavelength, a wavelength width, and a value of light irradiating the target, polarization characteristics in an optical path of a measuring device measuring the target, transmittance of an ND filter arranged in the optical path, a position of the target, and an inclination of the target.

5. The method of measurement according to claim 2,

Wherein one of the at least two measurement parameters comprises: the position of the target in a direction along an optical path of a position detection device that detects the position of the target.

6. The method of measurement according to claim 2,

wherein in the determining step, a parameter value to be used is determined with respect to each of the at least two measurement parameters based on the sensitivity distribution with respect to each of the at least two measurement parameters and a weighting function assigned to each of the at least two measurement parameters.

7. The method of measurement according to claim 1,

wherein the step of performing the preliminary measurement comprises: detecting intermediate information for obtaining a measurement value from a measurement object, and calculating the measurement value based on the intermediate information, and

the processing steps comprise: based on the intermediate information, a measurement value obtained with a combination different from a combination used to make the preliminary measurement is estimated, and based on the measurement value estimated in the estimation, calculation is performed to obtain a sensitivity distribution with respect to each of the at least two measurement parameters.

8. The method of measurement according to claim 7,

Wherein in the detection, an image of the measurement object is detected as the intermediate information, and

in the estimation, a synthetic image as the intermediate information is generated from a plurality of images, and a measurement value obtained with a combination different from a combination used to make the preliminary measurement is estimated based on the synthetic image.

9. The method of measurement according to claim 1,

wherein in the determining step, the parameter values to be used are determined such that the sensitivity in the sensitivity distribution is worse than a predetermined sensitivity in the parameter values to be used.

10. The method of measurement according to claim 1,

wherein in the determining step, the parameter values to be used are determined such that the sensitivity in the sensitivity distribution is lower than a predetermined sensitivity in the parameter values to be used.

11. The method of measurement according to claim 1,

wherein in the determining step, parameter values to be used are determined such that the sensitivity in the sensitivity distribution is the smallest of the parameter values to be used.

12. The method of measurement according to claim 1,

wherein in the preliminary measurement step and the main measurement step, signal strength information or waveform evaluation value information of the target is measured.

13. The method of measurement according to claim 2,

wherein in the determining step, at least one of an average value and a variance of the sensitivity distribution is calculated based on the sensitivity distribution with respect to each of the plurality of targets, and a parameter value to be used is determined based on the sensitivity of at least one of the average value and the variance of the sensitivity distribution.

14. The method of measurement according to claim 1,

wherein in the determining step, the parameter values to be used are determined such that the sensitivity in the sensitivity distribution is more sensitive than a predetermined sensitivity in the parameter values to be used.

15. The method of measurement according to claim 1,

wherein in the determining step, the parameter values to be used are determined such that the sensitivity in the sensitivity distribution is higher than a predetermined sensitivity in the parameter values to be used.

16. The method of measurement according to claim 1,

wherein in the determining step, parameter values to be used are determined such that the sensitivity in the sensitivity distribution is the maximum of the parameter values to be used.

17. A method of manufacturing an article, comprising:

measuring a position of a mark on a substrate according to the measuring method of any one of claims 1 to 16, and transferring a pattern to the substrate based on the position of the mark; and

The article is obtained by processing a substrate transferred with a pattern.

18. A measuring device comprises a measuring unit and a controller,

wherein the controller controls the measurement unit to perform preliminary measurements a plurality of times while changing a combination of parameter values of at least two different measurement parameters, obtains a sensitivity distribution regarding each of the at least two measurement parameters based on a measurement value obtained by the preliminary measurements, the sensitivity distribution being a distribution indicating sensitivity of a measurement value change with a parameter value change, determines a parameter value to be used regarding each of the at least two measurement parameters based on the sensitivity distribution, and controls the measurement unit to perform main measurements according to the determined parameter value of each of the at least two measurement parameters.

19. The measurement device according to claim 18, further comprising a wavelength variable unit configured to change a wavelength of light that irradiates a measurement object;

wherein the controller controls the wavelength variable unit based on the parameter values determined for each of the at least two measured parameters.

20. The measurement device of claim 19, wherein the wavelength variable unit comprises: a wavelength variable element having a transmission wavelength that changes along a predetermined direction; and a driving mechanism configured to drive the wavelength variable element.

21. The measurement device according to claim 20, wherein the wavelength variable unit is configured to change a center wavelength and a wavelength width of light that irradiates the measurement object, and

the at least two measurement parameters include a center wavelength and a wavelength width.

22. The measurement apparatus according to claim 18, wherein the measurement unit measures position information of a target.

23. A lithographic apparatus, comprising:

the measurement device according to any one of claims 18 to 22, configured to measure a position of a marker provided on a substrate; and

a positioning mechanism configured to position the substrate based on the position of the mark measured by the measuring device,

wherein the lithographic apparatus is configured to transfer a pattern of the substrate.

24. A method of manufacturing an article, comprising:

transferring a pattern to a substrate by using the lithographic apparatus of claim 23; and

the article is obtained by processing a substrate transferred with a pattern.