Depth measuring device, depth measuring system, and depth index value calculation method

Abstract

A depth measurement system has a plurality of depth measurement devices that each calculate a depth index value indicating a relative depth of a pattern on a sample, wherein the plurality of depth measurement devices are divided into one reference device (1001) and other correction target devices (1002), the depth measurement devices each perform a depth measurement process that measures a depth of a predetermined pattern in a measurement object, thereby calculating a depth index value of the predetermined pattern from a measurement value extracted from an obtained electronic image, and the correction target devices store a correction coefficient associated with the depth measurement process and output a depth index value of the predetermined pattern that is corrected using a mathematical model to which the correction coefficient is applied.

Description

Technical Field

[0001] This disclosure relates to a depth measuring device, a depth measuring system, and a method for calculating depth index values ​​for measuring the depth of patterns, particularly the depth of recesses such as holes and grooves. Background Technology

[0002] In recent years, due to the increasing complexity and three-dimensionality of semiconductors, the demand for measuring three-dimensional shapes has increased, leading to the development of methods using Critical Dimension-Scanning Electron Microscopes (SEMs) to measure three-dimensional shapes. For example, Patent Document 1 found that in trench structures (trench width / trench bottom brightness)... N In hole construction (hole area / hole bottom brightness) N A method for measuring the depth of recesses such as slots and holes is disclosed, which has a linear relationship with the depth of the pattern and is based on the line width or area of ​​the pattern and the brightness value (signal) of the inner side (bottom) of the pattern.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: International Publication No. 2020 / 095346 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] In Patent Document 1, a depth-proportional index value (hereinafter referred to as the depth index value) is calculated based on the line width or area of ​​the pattern and the brightness value at the bottom of the pattern. The absolute value of the pattern depth is calculated using a pre-stored database containing the relationship between measured pattern depths and depth index values. However, when this method is intended for use in the management of semiconductor device manufacturing processes, multiple depth measuring devices are configured on the production line to measure the line width, area, and brightness value of the pattern used to calculate the depth index value. However, due to various factors, there are machine differences between the depth measuring devices, resulting in machine differences in the depth index value calculated based on these measurements. This disclosure relates to the correction of machine differences in depth index values ​​generated between depth measuring devices.

[0008] Methods for solving problems

[0009] One aspect of the depth measurement system disclosed herein includes multiple depth measuring devices, each of which calculates a depth index value representing the relative depth of a pattern on a sample. Each depth measuring device includes: an electron-optical system that irradiates an electron beam onto the sample; a detection system that detects emitted electrons emitted by the sample irradiated with the electron beam; and a computer that controls the electron-optical system and the detection system by executing an action procedure, i.e., a depth measurement process, to measure the depth of a predetermined pattern in the measurement object. Based on measurement values ​​extracted from an electron image, the computer calculates the depth index value of the predetermined pattern. The electron image is formed from the output of the detection system. The multiple depth measuring devices are divided into a reference device and other calibration target devices. The computer of the calibration target device stores correction coefficients associated with the depth measurement process and outputs the depth index value of the predetermined pattern after correction using a mathematical model applying the correction coefficients.

[0010] Invention Effects

[0011] It can reduce mechanical errors caused by magnification errors between the reference device and the device being calibrated, as well as differences in detection system gain. Other issues and new features will become clear from the description and accompanying drawings in this specification. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of a depth measuring device.

[0013] Figure 2A This is an example of a depth measurement system.

[0014] Figure 2B This is a diagram illustrating the machine error correction process for depth index values.

[0015] Figure 3 This is a diagram showing the calculation process of the correction coefficient for the depth index value (correction method 1).

[0016] Figure 4A This is an example of a screen that manages correction coefficients.

[0017] Figure 4B This is an example of a screen for editing correction coefficients.

[0018] Figure 5 This is a diagram showing the calculation process of the correction coefficient for the depth index value (correction method 2).

[0019] Figure 6A This is a diagram used to illustrate an example of calculating size and brightness values ​​based on SEM images.

[0020] Figure 6B This is a diagram used to illustrate an example of calculating size and brightness values ​​based on SEM images.

[0021] Figure 7A This is a diagram used to illustrate an example of calculating size and brightness values ​​based on SEM images.

[0022] Figure 7B This is a diagram used to illustrate an example of calculating size and brightness values ​​based on SEM images.

[0023] Figure 8 This is a diagram showing the calculation process of the correction coefficient for the depth index value (correction method 3).

[0024] Figure 9A This is an example of a screen that manages correction coefficients.

[0025] Figure 9B This is an example of a screen for editing correction coefficients.

[0026] Figure 10 This is an example of a depth measurement system.

[0027] Figure 11 It is a diagram showing the calculation and application process of the correction coefficients in a depth measurement system.

[0028] Figure 12A This is an example of selecting a screen.

[0029] Figure 12B This is an example of a screen displaying calculation results. Detailed Implementation

[0030] Hereinafter, this embodiment will be described with reference to the accompanying drawings. In the drawings, functionally identical elements are sometimes shown with the same or corresponding numbers. Furthermore, the drawings illustrate embodiments and installation examples that follow the principles of this disclosure, but they are for the purpose of understanding this disclosure and are in no way intended to limit its interpretation. The descriptions in this specification are merely typical examples and do not limit the scope of patent protection or application of this disclosure in any sense.

[0031] In this embodiment, the description has been provided in sufficient detail by those skilled in the art for the purpose of implementing this disclosure. However, other installations and methods may also be used. It should be understood that structural and constructional changes and substitutions of various elements can be made without departing from the scope and spirit of the technical concept of this disclosure. Therefore, the following description is not intended to be limited to this.

[0032] Furthermore, in the following description of embodiments, an example of applying this disclosure to a scanning electron microscope (SEM) using electron beams is shown as a depth measurement device or system. However, this embodiment should not be interpreted as limiting; this disclosure can also be applied to devices and systems that use other microscopes such as transmission electron microscopes (TEM), projection electron microscopes, and surface illumination electron microscopes instead of scanning electron microscopes. Additionally, this disclosure can also be applied to devices and systems that use multiple electron beams to construct the aforementioned electron microscopes, or to general observation systems.

[0033] Furthermore, in the following description of the implementation methods, the functions, actions, processes, and flows are primarily described using "computer," "overall control unit," and "management computer" as the subjects (action subjects) to explain the flow of each element and step. However, "depth measurement device" and "depth measurement system" can also be described using "various programs" executed by the computer as the subjects (action subjects). Part or all of the programs can be implemented using dedicated hardware, or they can be modularized. Various programs can also be installed on the computer system via a program distribution server or storage medium.

[0034] As semiconductor devices become increasingly complex and miniaturized, etching has become a crucial process affecting device quality. The depth measurement device in this embodiment calculates a depth index value representing the relative depth of the pattern based on two-dimensional pattern size values ​​obtained using a scanning electron microscope and the brightness values ​​of the inner side of the pattern.

[0035] Figure 1 This is a schematic diagram of a depth measuring device for measuring the depth of a pattern. The depth measuring device includes an imaging unit 101, an overall control unit 102, a signal processing unit 103, an input / output unit 104, and a storage unit 105.

[0036] The imaging unit 101 includes an electron gun 106, a converging lens 108 for converging the electron beam 107 emitted from the electron gun 106, and a converging lens 109 for further converging the electron beam 107 that has passed through the converging lens 108. The imaging unit 101 also includes a deflector 110 for deflecting the electron beam 107 and an objective lens 111 for controlling the convergence height of the electron beam 107. In addition, it is provided with: a shutter 130, which partially restricts the passage of the electron beam 107; a blanking deflector 131, which restricts the electron beam from reaching the sample 112 by deflecting the electron beam 107 out of the optical axis; and a blanking electrode 132, which receives the electron beam 107 after it has been deflected by the blanking deflector 131.

[0037] An electron beam 107, passing through optical elements (collectively referred to as the electron optical system) within a scanning electron microscope as described above, which are related to electron beam irradiation and scanning, irradiates a sample 112 placed on a stage 113. Secondary electrons (SE) and backscattered electrons (BSE) emitted from the sample by the electron beam 107 are guided in a predetermined direction by a deflector 115 (first and second electron aligner). The deflector 115 is a so-called Wien filter that does not deflect the electron beam 107 but selectively deflects the emitted electrons 114 in a predetermined direction.

[0038] The emitted electron 114, having passed through the detection aperture 116 provided for angle discrimination of the emitted electron 114, is guided by the deflector 123 (secondary electron aligner) to the detector 119 disposed off-axis. Additionally, a detector 121 is provided for detecting secondary electrons (tertiary electrons 120) generated by the collision of the emitted electron 114 with the detection aperture 116. An energy filter 122 is provided directly in front of the detector 119, enabling selective detection of secondary electrons emitted vertically upward from the bottom of the semiconductor pattern formed on the sample 112 and having a passing trajectory near the optical axis through energy discrimination. These optical elements related to the detection of the emitted electron 114 are collectively referred to as the detection system.

[0039] In the signal processing unit 103, an SEM image is generated based on the output from the detection system. In the signal processing unit 103, detection signals are stored in a frame memory or similar medium in sync with the scanning of a scanning deflector (not shown) to generate image data. When storing the detection signals in the frame memory, the detection signals are stored at positions corresponding to the scanning positions in the frame memory, thereby generating a signal distribution (one-dimensional information) and an SEM image (two-dimensional information).

[0040] The electro-optical system and detection system of the imaging unit 101 described above are controlled by the overall control unit 102. The overall control unit 102, the input / output unit 104, and the storage unit 105 are installed as a computer 100. The overall control unit 102 receives instructions from the user from the input / output unit 104, reads the programs and data stored in the storage unit 105, and performs processing. By executing the programs stored in the storage unit 105, control processing for acquiring SEM images of the sample through the imaging unit 101, calculation processing for calculating depth index values, etc., are performed.

[0041] It shows in Figure 1 The method for measuring depth in the depth measuring device shown. Figure 1A depth measuring device is used to capture a SEM image of the pattern containing the recess. Based on the captured SEM image, the size or area of ​​the recess and the brightness value of the inner side of the pattern are measured to calculate the depth index value. The depth index value is represented by (Equation 1). N is an arbitrary positive number, set to an appropriate value corresponding to the shape of the pattern and the material of the sample.

[0042] (Equation 1)

[0043] Depth index value = (pattern size or pattern area / pattern brightness value) N

[0044] In calculating the depth index value, whether to use the pattern size value or the pattern area depends on the shape of the two-dimensional pattern of the recess. When the two-dimensional pattern of the recess is an open pattern, the pattern size value is used. For example, in a groove pattern, the pattern size value of the groove width can be used. On the other hand, when the two-dimensional pattern of the recess is a closed pattern, the pattern area is used. For example, in patterns with planar shapes such as holes, ellipses, squares, and rectangles, the pattern area is used.

[0045] Example 1

[0046] exist Figure 2B The flowchart shows the use of multiple units Figure 1 The diagram illustrates the steps for correcting machine discrepancies between depth measuring devices in a depth measuring system that calculates depth index values ​​separately. The object of measurement is a mass-produced wafer, and the scenario envisions a situation where multiple depth measuring devices configured on a wafer production line are used to measure the depth of a predetermined pattern formed on the mass-produced wafer.

[0047] like Figure 2A As shown, in order to suppress machine errors based on depth index values ​​calculated from multiple depth measuring devices, a calibration is performed where any one of the multiple depth measuring devices is used as a reference device 1001, and the measured values ​​of the other devices (referred to as calibration target devices 1002) are made consistent with the measured values ​​of the reference device. The reference device 1001 is selected from any one of the multiple depth measuring devices. Both the reference device 1001 and the calibration target device 1002 have identical... Figure 1 In the illustrated device structure, the overall control unit 102 (computer 100) of each device is preferably interconnected via a network 1003. Hereinafter, [the following will describe...] Figure 2B The flowchart is used for illustration.

[0048] In any one of the multiple depth measurement devices (which can be either a reference device or a calibration device), the required information such as the layout of the wafer to be measured, the coordinates of the measurement pattern, and the measurement conditions are input from the input / output unit 104. A measurement process (action program) for depth measurement is then created and stored in the storage unit 105. The created measurement process is then expanded and stored in other depth measurement devices (step 201).

[0049] Next, in each calibration target device 1002, the machine error correction coefficient of the depth index value is input from the input / output unit 104 and stored in the storage unit 105 (step 202). The details of the method for determining the machine error correction coefficient will be described later, but the correction coefficient needs to be calculated and set in advance for each measurement sample, depth measurement conditions, and calibration target device.

[0050] Next, in each calibration device 1002, the measurement process is associated with the setting machine error correction coefficient in a manner that applies the depth measurement result (step 203).

[0051] Each depth measuring device performs a depth measurement process, measuring the size and brightness values ​​of the captured image to calculate a depth index value (step 204). The depth index value is represented by (Equation 1), and an appropriate value of N is set in the depth measurement process. At this time, if a correction coefficient for the depth index value is applied to the measurement process (step 205: Yes), the depth measuring device corrects the depth index value using a mathematical model that corrects the depth index value with the applied correction coefficient (step 206). The corrected measurement result is output to the input / output unit 104 and stored in the storage unit 105 (step 207). On the other hand, if no correction coefficient is set (step 205: No), the measurement result is output to the input / output unit 104 without correction and stored in the storage unit 105 (step 207). The cases where no correction coefficient is set include: the depth measuring device being a reference device; and the depth measuring device being a calibration target device, but the error is so small that it can be considered as 0, and therefore no correction coefficient is set.

[0052] In this way, by using a mathematical model to correct the depth index value of the calibration target device 1002, the mechanical error between the reference device 1001 and the calibration target device 1002 caused by magnification error, gain difference of the detection system, and other factors can be reduced. Several examples of methods for correcting the depth index value are explained below.

[0053] (Method 1 for correcting depth index values)

[0054] Correction Method 1 uses a linear equation as the mathematical model for correcting the depth index value, and corrects the depth index value through linear correction. When the corrected depth index value I... cThe depth index value I calculated by the calibration object device 1002 in step 204 according to (Equation 1) o When the correction coefficients set in step 202 are A and B, the depth index value is corrected by the linear correction formula shown in (Equation 2).

[0055] (Equation 2)

[0056] I c =A·I o +B

[0057] Figure 3 The flowchart illustrates the calculation steps for correction coefficients A and B when performing machine error correction using correction method 1.

[0058] The correction coefficients A and B are obtained by fitting the linear equation shown in Equation 2. Therefore, depth measurement of the target wafer at multiple measurement points is required. Thus, in any one of the multiple depth measurement devices (which can be either a reference device or a calibration device), the necessary information such as the layout of the wafer to be measured, the coordinates of the measurement pattern, and the measurement conditions are input from the input / output unit 104. A depth measurement process (action program) for calculating the correction coefficients is then created and stored in the storage unit 105. The created measurement process is then expanded to other depth measurement devices and stored (step 301). This process becomes a measurement-only measurement point and... Figure 2B The measurement process in step 201 is different from the measurement process.

[0059] The reference device 1001 performs a depth measurement process for calculating the correction coefficient, measuring the pattern size and pattern brightness values, and calculates the depth index value based on these values ​​using (Equation 1) (step 302). Similarly, the calibration object device 1002 performs a depth measurement process for calculating the correction coefficient on the same sample (measurement object), measuring the pattern size and pattern brightness values, and calculates the depth index value based on these values ​​using (Equation 1) (step 303).

[0060] The depth index values ​​at each measurement point of the reference device 1001 are set as y, and the depth index values ​​at each measurement point of the calibration target device are set as x. A linear formula (y = Ax + B) is used for fitting, and correction coefficients A and B are calculated (step 304). The calculated correction coefficients A and B are registered in the storage unit 105 of the calibration target device 1002 (step 305). It is confirmed whether correction coefficients are registered in all calibration target devices 1002. If there are unregistered calibration target devices, steps 303 to 305 are performed on that calibration target device.

[0061] The magnitude of machine error varies depending on the measurement conditions during depth measurement and the sample being measured. Therefore, in principle, a correction factor needs to be determined for each depth measurement process (refer to step 201). On the other hand, regarding this depth measurement process, if there is a depth measurement process with the same measurement conditions and measurement object (e.g., a process with different measurement points) and the correction factor has already been calculated, the correction factor calculated for the existing depth measurement process can be directly used. In this case, the calculation of the correction factor for the new depth measurement process can be omitted. Measurement conditions related to machine error include optical conditions, magnification, pixel count, scanning method, etc.

[0062] Figure 4A and Figure 4B The GUI screen showing the registration of correction coefficients A and B by the correction object device 1002 in step 305 is shown.

[0063] Figure 4A The calibration coefficient management screen is displayed. Through the calibration coefficient management table 400, calibration coefficients A and B registered in the calibration object device 1002 can be simultaneously viewed. Calibration coefficients are managed by management number 401, and each management number is registered with a condition name 402 and calibration coefficient values ​​(A, B) 403 and 404. The condition name 402 registers the measurement conditions and measurement objects related to the aforementioned machine error. By checking the condition name 402, the user can determine whether to calculate the calibration coefficient or apply a registered calibration coefficient.

[0064] You can edit the correction coefficient management table 400 using the edit button 405. You can also add new records, or select management number 401 to edit the condition name 402, correction coefficient values ​​403 and 404. Figure 4B The correction coefficient editing screen is displayed. When a management number is selected and the edit button 405 is pressed, the management number of the currently selected correction coefficient is displayed in the management number display bar 410, the correction coefficient registered with that management number is displayed in the correction coefficient value display bar 411, and the condition name is displayed in the condition name display bar 412. Entering the management number of the newly saved correction coefficient into the management number input bar 413 will... Figure 3 The correction coefficients obtained from the flowchart are entered into the correction coefficient value input field 414, and the registered condition names are entered into the condition name input field 415. Then, the correction coefficient management table 400 is updated by pressing the apply button 416.

[0065] (Method 2 for correcting depth index values)

[0066] The methods for correcting depth index values ​​are not limited to those described above. In the mathematical model (Equation 2) of Correction Method 1, Correction Method 2 fixes the correction coefficient A to 1 and sets only the correction coefficient B. Figure 5The flowchart illustrates the steps for calculating the correction factor B. Steps 301–303, 305, and 306 are... Figure 3 The flowchart is the same as that of the previous one, so repeated explanations are omitted. In correction method 2, the difference between the value of the depth index calculated in the reference device and the average value calculated in the correction target device is obtained, and this difference is set as the correction coefficient B (step 504).

[0067] The GUI screen for registering and managing correction coefficients is also similar to... Figure 4A , Figure 4B The displayed screen is the same, becoming a screen where the correction factor A is fixed at 1 or there is no correction factor A.

[0068] In the case of correction method 2, it is not necessary to fit to a linear equation. The correction coefficient is calculated by calculating the offset based on the average value of the depth index calculated by each device. Therefore, the correction coefficient value can be obtained more easily than in correction method 1.

[0069] (Method 3 for correcting depth index values)

[0070] In correction method 3, the pattern size value or pattern area and brightness value are corrected using a suitable mathematical model, and the depth index value is calculated based on the corrected values, thereby non-linearly correcting the depth index value. This is illustrated by... Figure 6A , Figure 6B The example shown illustrates the calculation of groove width and brightness values ​​using SEM images of the same groove pattern captured by depth inspection devices α and β. The groove patterns in SEM images 601 and 602 exhibit differences in brightness and groove width due to magnification errors of each device and machine errors of the inspection system. W... α Indicates according to Figure 6A The groove width, calculated from the SEM image 601 taken by the device α (as a reference device), is used in GL. α The brightness value at the bottom of the trench is represented by W. β Indicates according to Figure 6B The groove width obtained from the SEM image 602 taken by the device β (as the calibration object) is calculated using GL. β This represents the brightness value at the bottom of the groove. Additionally, the groove width and brightness value are calculated as the average of multiple groove patterns.

[0071] Depth index values ​​I of devices α and β α I β Calculated using (Equation 3).

[0072] (Equation 3)

[0073] I α =(W α / GL α ) N

[0074] I β =(W β / GL β ) N

[0075] Without machine error correction, due to machine error, the depth index value I... α I β They are not the same value.

[0076] In correction method 3, the pattern size value and the brightness value inside the pattern are corrected using mathematical models. For example, in the case where correction is performed using a linear mathematical model, a correction coefficient A for the pattern size value is calculated. CD B CD And the correction factor A for the brightness value GL B GL These correction coefficients are pre-registered in the correction object device 1002.

[0077] As shown in Equation 4, the depth index value I of the calibration target device 1002 β The slot width W is corrected using a mathematical model with correction coefficients. β ', Brightness value GL β ', Corrected to depth index value I β '.

[0078] (Equation 4)

[0079] W β '=A CD ·W β +B CD

[0080] GL β '=A GL ·GL β +B GL

[0081] I β '=(W β ' / GL β ') N

[0082] By using (Equation 4), it is possible to correct the error in the depth index value of non-closed patterns such as groove patterns.

[0083] It shows according to Figure 7A , Figure 7B The example shown is an example of calculating the pattern area and brightness values ​​using SEM images of the same aperture pattern captured by depth inspection devices α and β. Using D... α Indicates by Figure 7AThe aperture determined from SEM image 701 taken by the reference device (device α) is calculated using GL. α The brightness value at the bottom of the aperture is represented by D. β Indicates by Figure 7B The aperture determined from the SEM image 702 taken by the calibration device (device β) shown is calculated using GL. β This represents the brightness value at the bottom of the hole. Furthermore, similar to the case of groove patterns, the hole diameter and brightness value can be calculated as the average of multiple hole patterns.

[0084] Depth index values ​​I of devices α and β α I β Calculated using (Equation 5).

[0085] (Equation 5)

[0086] S α =π·(D α / 2) 2

[0087] S β =π·(D β / 2) 2

[0088] I α =(S α / GL α ) N

[0089] I β =(S β / GL β ) N

[0090] Without machine error correction, the depth index value I α I β Because of machine differences, rather than the same value.

[0091] As shown in Equation 6, the depth index value I of the calibration target device 1002 β The aperture DW was corrected using a mathematical model with correction coefficients. β ′ and brightness value GL β Corrected to depth index value I β ′.

[0092] (Equation 6)

[0093] D β '=A CD ·D β +B CD

[0094] GL β '=AGL ·GL β +B GL

[0095] S β '=π·(D β ' / 2) 2

[0096] I β '=(S β ' / GL β ') N

[0097] By using (Equation 6), the depth index value of closed patterns such as hole patterns can be corrected for mechanical errors. The same correction can be made for closed patterns other than hole patterns. This can be achieved by applying the calculation method for the area S corresponding to the pattern shape.

[0098] Figure 8 The flowchart shows the correction coefficient A when performing machine error correction using correction method 3. CD B CD A GL B GL The calculation steps.

[0099] In any one of the multiple depth measurement devices (which can be a reference device or a calibration target device), the necessary information such as the layout of the wafer to be measured, the coordinates of the measurement pattern, and the measurement conditions are input from the input / output unit 104. A depth measurement process (operation program) for calculating the calibration coefficient is then created and stored in the storage unit 105. The created measurement process is then expanded and stored in other depth measurement devices (step 801).

[0100] The reference device 1001 performs a depth measurement process for calculating the correction coefficient, measuring the pattern size and pattern brightness values ​​(step 802). Similarly, the calibration target device 1002 performs a depth measurement process for calculating the correction coefficient on the same sample, measuring the pattern size and pattern brightness values ​​(step 803).

[0101] Let the dimensional values ​​at each measuring point of the reference device 1001 be y, and the dimensional values ​​at each measuring point of the calibration object device be x. Then, use the linear equation (y = A...) CD x+B CD Perform the fitting and calculate the correction coefficient A. CD B CD (Step 804). Similarly, the brightness value at each measurement point of the reference device 1001 is set as y, and the brightness value at each measurement point of the calibration target device is set as x. Then, the brightness value is calculated using the linear formula (y = A). GL x+B GL Perform the fitting and calculate the correction coefficient A.GL B GL (Step 805). Calculate the correction coefficient A. CD B CD A GL B GL The calibration coefficient is registered in the storage unit 105 of the calibration target device 1002 (step 806). It is checked whether the calibration coefficient is registered in all the calibration target devices 1002. If there is an unregistered calibration target device, steps 803 to 806 are performed on that calibration target device.

[0102] Figure 9A and Figure 9B The calibration object device 1002 is shown registering the calibration coefficient A in step 806. CD B CD A GL B GL The GUI screen. (And) Figure 4A , Figure 4B The GUI screen shown is the same, so repeated descriptions are omitted.

[0103] Figure 9A The calibration coefficient management screen is displayed. Through the calibration coefficient management table 900, the calibration coefficients registered in the calibration target device 1002 can be simultaneously viewed. Figure 4A The correction factor management screen shown is the same, but the correction factor value (A) is registered as the dimension value. CD B CD 901. Correction coefficient value for brightness (A) GL B GL )902. Figure 9B The screen for editing the correction coefficients is shown. (Compared to...) Figure 4B The correction coefficient editing screen shown is the same, but it has a correction coefficient value display bar 911 for displaying the correction coefficient for the size value and a correction coefficient value display bar 912 for displaying the correction coefficient for the brightness value. These are respectively entered in... Figure 8 The correction coefficients for the size values ​​and the brightness values ​​obtained in the flowchart are entered in fields 913 and 914.

[0104] In correction method 3, mathematical models are created to correct the size value and the brightness value respectively. Therefore, machine error can be corrected not only for the depth index value, but also for the measurement value calculated using only the brightness value and the brightness value other than the depth index value.

[0105] Example 2

[0106] In Example 2, a method for automatically calculating and managing the correction coefficients required for correcting depth index values ​​using a mathematical model, as described in Example 1, and a depth measurement system are illustrated. One aspect of the depth measurement system in this embodiment is as follows: Figure 2A As shown, multiple depth measuring devices 1001 and 1002 are connected via network 1003 in a manner that allows them to access each other. On the other hand, Figure 10 In another embodiment of the depth measurement system, a management computer 1004 is also connected to the network 1003. The management computer 1004 has the function of managing the correction coefficients registered in each device.

[0107] use Figure 11 Flowcharts and Figure 12A , Figure 12B The GUI screen explains that in Figure 10 The steps for calculating and applying correction coefficients in a depth measurement system are described below. Here, an example of calculating correction coefficients based on correction method 3 described in the first embodiment is explained. The same applies when calculating correction coefficients based on other correction methods.

[0108] In any one of the multiple depth measuring devices in the depth measuring system, necessary information such as the layout of the wafer to be measured, the coordinates of the measurement pattern, and measurement conditions are input from the input / output unit 104 to create a depth measuring process (action program) for calculating correction coefficients, and it is stored in the storage unit 105. The created measurement process is then spread to other depth measuring devices and stored (step 1101). Each device in the depth measuring system executes the depth measuring process for calculating correction coefficients to measure the pattern size value and the pattern brightness value (step 1102).

[0109] Displayed in management computer 1004 Figure 12A The selection screen shown. Selection list 1200 is divided into reference device and calibration target device as section 1201. Selection list 1200 includes device name field 1202, measurement process field 1203, and measurement data field 1204.

[0110] In the reference device record of selection list 1200, the user selects the device name as the reference device from the device name field 1202 via drop-down (step 1103). When a reference device is selected, the depth measurement process for calculating the correction coefficient held by that device becomes selectable. Therefore, the user selects the depth measurement process for calculating the correction coefficient held by the reference device from the measurement process field 1203 via drop-down (step 1104). If the depth measurement process for calculating the correction coefficient is selected, the measurement data obtained by the device performing the depth measurement process for calculating the correction coefficient becomes selectable. Therefore, the user selects the measurement data held by the reference device from the measurement data field 1204 via drop-down (step 1105).

[0111] Next, in the calibration target device record of selection list 1200, the user selects the device name as the calibration target device from the device name field 1202 via drop-down (step 1106). When the calibration target device is selected, the depth measurement process for calculating the calibration coefficient held by that device becomes selectable. Therefore, the user selects the depth measurement process for calculating the calibration coefficient held by the calibration target device from the measurement process field 1203 via drop-down (step 1107). If the depth measurement process for calculating the calibration coefficient is selected, the measurement data obtained by the device performing the depth measurement process for calculating the calibration coefficient becomes selectable. Therefore, the user selects the measurement data held by the calibration target device from the measurement data field 1204 via drop-down (step 1108).

[0112] By pressing the select screen ( Figure 12A The execution button 1205 is used to fit the measurement results of the selected reference device and calibration target device, and calculate the correction coefficient (A). CD B CD A GL B GL (Step 1109) Display the fitting results and calculated correction coefficients in Figure 12B The calculation result display screen shown is shown in step 1110. The calculation result display screen is displayed on the management computer 1004.

[0113] right Figure 12BThe calculation results are shown in the display screen. The screen displays the measurement results before calibration (1211) and the measurement results after calibration based on the calculated calibration coefficients (1212). The vertical axis represents the measurement results of the reference device. In graph 1211, the horizontal axis represents the measurement results of the calibration target device before calibration, and in graph 1212, the horizontal axis represents the measurement results of the calibration target device after calibration. Thus, the correspondence between the values ​​of the reference device and the calibration target device can be compared before and after calibration. The data displayed as measurement results can be selected in the data selection bar 1210. An example of selecting the depth index value is shown here, but size and brightness values ​​can also be selected via the dropdown menu. The calibration coefficients calculated by fitting are displayed in the calibration coefficient display unit 1214, and the inter-device difference index before and after calibration is displayed in the inter-device difference index display unit 1215. The user compares the displayed graphs 1211 and 1212, or confirms the changes in the inter-device difference index displayed in the inter-device difference index display unit 1215, thereby confirming whether the calibration using the calibration coefficients has sufficiently reduced the machine error (step 1111). For example, by comparing Figures 1211 and 1212, it can be seen that the corrected depth index value of the calibration target device is more consistent with the depth index value of the reference device than the uncorrected depth index value. Furthermore, the inter-device difference index Acc is calculated here using Equation 7.

[0114] (Equation 7)

[0115] Acc = |Average of x - Average of y| / Average of y

[0116] Here, value x is the depth index or measurement value of the calibration target device, and value y is the depth index or measurement value of the reference device. The value is set to the depth index or measurement value selected in the data selection bar 1210. The smaller the difference between the average value of x and the average value of y, the smaller the value of the index Acc.

[0117] If the correction factor is inappropriate (step 1111: No), modify the measurement conditions of the depth measurement process used to calculate the correction factor, and repeat the process from step 1101 onwards. If the correction factor is appropriate (step 1111: Yes), the calculation result will be displayed on the screen. Figure 12B In the management number input field 1213, the management number is set, and by pressing the save button 1216, the calculated correction coefficient is registered to the calibration target device (step 1112). At this time, as a condition for applying the correction coefficient, the measurement object and measurement conditions can be automatically registered. This is then displayed in the correction coefficient management table 900. Figure 9A This process is performed on all calibration target devices (step 1113). Through the above, the management computer 1004 is able to calculate and manage the calibration coefficients of all calibration target devices in the depth measurement system.

[0118] exist Figure 2A In the case of the depth measurement system shown, by performing steps 1104 to 1112 for each calibration target device, it is possible to perform... Figure 11 The flowchart is as follows. In this case, the calibration target device calculates and manages the calibration coefficients applied to the device. That is, the calibration target device in step 1106 is the device itself. Figure 12A , Figure 12B The display screen is also shown on the computer of the device.

[0119] In this embodiment, the user selects appropriate measurement data according to the program of the depth measurement system, thereby easily calculating and registering the correction coefficient, which can reduce the machine error of the measurement value.

[0120] Symbol Explanation

[0121] 100: Computer; 101: Imaging Unit; 102: Overall Control Unit; 103: Signal Processing Unit; 104: Input / Output Unit; 105: Storage Unit; 106: Electron Gun; 107: Electron Beam; 108, 109: Converging Lens; 110: Deflector; 111: Objective Lens; 112: Sample; 113: Stage; 114: Emitting Electron; 115: Deflector; 116: Detection Aperture; 119, 121: Detector; 120: Tertiary Electron; 122: Energy Filter; 123: Deflector; 130: Shutter; 131: Blanking Deflector; 132: Blanking Electrode; 400: Correction Coefficient Management Table; 401: Management Number; 402: Condition Name; 403, 404, 901, 902: Correction Coefficient Value; 405: Edit Button; 410: Management Number Display Bar; 411 911, 912: Calibration coefficient value display bar; 412: Condition name display bar; 413: Management number input bar; 414, 913, 914: Calibration coefficient value input bar; 415: Condition name input bar; 416: Application button; 601, 602, 701, 702: SEM image; 1001: Reference device; 1002: Calibration target device; 1003: Network; 1004: Management computer; 1200: Selection list; 1201 Division; 1202: Device name bar; 1203: Measurement process bar; 1204: Measurement data bar; 1205: Execute button; 1210: Data selection bar; 1211, 1212: Measurement result; 1213: Management number input bar; 1214: Calibration coefficient display section; 1215: Inter-device difference index display section; 1216: Save button.

Claims

1. A depth measurement system comprising a plurality of depth measuring devices, wherein the plurality of depth measuring devices respectively calculate a depth index value representing the relative depth of a pattern on a sample, characterized in that, The depth measuring devices each include: An electron optical system that irradiates an electron beam onto a sample; A detection system that detects emitted electrons from a sample irradiated by the electron beam; and A computer, through executing a depth measurement process—a procedure for measuring the depth of a predetermined pattern in a measurement object—controls the electro-optical system and the detection system. Based on the measurement values ​​extracted from the electronic image, it calculates the depth index value of the predetermined pattern, the electronic image being formed from the output of the detection system. The multiple depth measuring devices are divided into one reference device and other calibration devices. The computer of the calibration device stores calibration coefficients associated with the depth measurement process, and outputs the depth index value of the predetermined pattern after calibration using a mathematical model applied with the calibration coefficients. The computer of the calibration target device associates one or more calibration coefficients with the conditions for applying each calibration coefficient, and registers this information from the GUI screen in an updatable manner. The conditions include the measurement conditions for obtaining the object being measured and the electronic image.

2. The depth measurement system according to claim 1, characterized in that, The plurality of depth measuring devices control the electro-optical system and the detection system by performing a depth measurement process with the same measurement conditions and correction coefficients as the depth measurement process, extracting the measured values ​​from the electronic image, or calculating the depth index value of the predetermined pattern of the measured object based on the extracted measured values, wherein the electronic image is formed from the output of the detection system. The correction coefficient is either a correction coefficient obtained by fitting the measured value extracted by the depth measurement process for calculating the correction coefficient performed by the calibration target device to the measured value extracted by the depth measurement process for calculating the correction coefficient performed by the reference device, or a correction coefficient obtained by fitting the depth index value calculated by the depth measurement process for calculating the correction coefficient performed by the calibration target device to the depth index value calculated by the depth measurement process for calculating the correction coefficient performed by the reference device, according to the mathematical model.

3. The depth measurement system according to claim 1, characterized in that, The mathematical model is represented as I c =A I o +B, The I c It is the corrected depth index value, the I o The depth index value before correction is given, and A and B are the correction coefficients.

4. The depth measurement system according to claim 1, characterized in that, The mathematical model is represented as I c =I o +B, The I c It is the corrected depth index value, the I o It is the depth index value before correction, and B is the correction coefficient.

5. The depth measurement system according to claim 1, characterized in that, The depth index value is expressed as a function of the pattern's size and the brightness value of the inner side of the pattern. The mathematical model is represented by W. c =A CD W o +B CD and GL c =A GL GL o +B GL , The W c It is the corrected size value of the pattern, the W o The GL is the size value of the pattern before correction. c It is the brightness value of the inner side of the corrected pattern, the GL o It is the brightness value of the inner side of the pattern before correction, wherein A CD The B mentioned CD The A mentioned GL The B mentioned GL It is the correction coefficient.

6. The depth measurement system according to claim 2, characterized in that, The multiple depth measuring devices are connected via a network. The calibration target device obtains the measured value or calculated depth index value extracted by the reference device through the network during the depth measurement process for calculating the calibration coefficient, and calculates the calibration coefficient.

7. The depth measurement system according to claim 6, characterized in that, The computer of the calibration target device can display, in a comparative manner, the correspondence between the measured value of the reference device and the measured value of the calibration target device before calibration, and the correspondence between the measured value of the reference device and the measured value of the calibration target device after calibration, or can display, in a comparative manner, the correspondence between the depth index value of the reference device and the depth index value of the calibration target device before calibration, and the correspondence between the depth index value of the reference device and the depth index value of the calibration target device after calibration.

8. The depth measurement system according to claim 7, characterized in that, The computer of the calibration target device calculates an inter-device difference index representing the difference between the measured value or depth index value of the reference device and the measured value or depth index value of the calibration target device, and displays the change of the inter-device difference index before and after calibration.

9. The depth measurement system according to claim 2, characterized in that, The depth measurement system is equipped with a management computer. The multiple depth measurement devices and the management computer are connected via a network. The management computer obtains, via the network, the measured value or the calculated depth index value extracted by the reference device performing the depth measurement process for calculating the correction coefficient, and the measured value or the calculated depth index value extracted by the calibration target device performing the depth measurement process for calculating the correction coefficient, and calculates the correction coefficient of the calibration target device.

10. The depth measurement system according to claim 9, characterized in that, The management computer can display, in a comparative manner, the correspondence between the measured value of the reference device and the measured value of the calibration target device before calibration, and the correspondence between the measured value of the reference device and the measured value of the calibration target device after calibration; or it can display, in a comparative manner, the correspondence between the depth index value of the reference device and the depth index value of the calibration target device before calibration, and the correspondence between the depth index value of the reference device and the depth index value of the calibration target device after calibration.

11. The depth measurement system according to claim 10, characterized in that, The management computer calculates an inter-device difference index representing the difference between the measured value or depth index of the reference device and the measured value or depth index of the calibration target device, and displays the change of the inter-device difference index before and after calibration.

12. A depth measurement system comprising a plurality of depth measuring devices, wherein the plurality of depth measuring devices respectively calculate a depth index value representing the relative depth of a pattern on a sample, characterized in that, The depth measuring devices each include: An electron optical system that irradiates an electron beam onto a sample; A detection system that detects emitted electrons from a sample irradiated by the electron beam; and A computer, through executing a depth measurement process—a procedure for measuring the depth of a predetermined pattern in a measurement object—controls the electro-optical system and the detection system. Based on the measurement values ​​extracted from the electronic image, it calculates the depth index value of the predetermined pattern, the electronic image being formed from the output of the detection system. The multiple depth measuring devices are divided into one reference device and other calibration devices. The computer of the calibration device stores calibration coefficients associated with the depth measurement process, and outputs the depth index value of the predetermined pattern after calibration using a mathematical model applied with the calibration coefficients. The depth index value is expressed as a function of the pattern's size and the brightness value of the inner side of the pattern. The mathematical model is represented by W. c =A CD W o +B CD and GL c =A GL GL o +B GL , The W c The W is the corrected size value of the pattern. o The GL is the size value of the pattern before correction. c It is the brightness value of the inner side of the corrected pattern, the GL o It is the brightness value of the inner side of the pattern before correction, wherein A CD The B mentioned CD The A mentioned GL The B mentioned GL It is the correction coefficient.

13. A method for calculating a depth index value in a depth measurement system, the depth measurement system comprising multiple depth measuring devices, for calculating a depth index value representing the relative depth of a pattern of the object being measured, characterized in that, The depth measuring devices each include: An electron optical system that irradiates an electron beam onto a sample; A detection system that detects emitted electrons from a sample irradiated by the electron beam; and A computer, through executing a depth measurement process—a procedure for measuring the depth of a predetermined pattern in a measurement object—controls the electro-optical system and the detection system. Based on the measurement values ​​extracted from the electronic image, it calculates the depth index value of the predetermined pattern, the electronic image being formed from the output of the detection system. The multiple depth measuring devices are divided into one reference device and other calibration devices. The computer of the calibration device stores calibration coefficients associated with the depth measurement process. The reference device outputs the depth index value calculated by performing the depth measurement process. The calibration device uses a mathematical model that applies the calibration coefficients to calibrate and output the depth index value calculated during the depth measurement process. The computer of the calibration target device associates one or more calibration coefficients with the conditions for applying each calibration coefficient, and registers this information from the GUI screen in an updatable manner. The conditions include the measurement conditions for obtaining the object being measured and the electronic image.

14. The method for calculating depth index values ​​according to claim 13, characterized in that, The plurality of depth measuring devices control the electro-optical system and the detection system by performing a depth measurement process with the same measurement conditions and correction coefficients as the depth measurement process, extracting the measured values ​​from the electronic image, or calculating the depth index value of the predetermined pattern of the measured object based on the extracted measured values, wherein the electronic image is formed from the output of the detection system. The correction coefficient is either a correction coefficient obtained by fitting the measured value extracted by the depth measurement process for calculating the correction coefficient performed by the calibration target device to the measured value extracted by the depth measurement process for calculating the correction coefficient performed by the reference device, or a correction coefficient obtained by fitting the depth index value calculated by the depth measurement process for calculating the correction coefficient performed by the calibration target device to the depth index value calculated by the depth measurement process for calculating the correction coefficient performed by the reference device, according to the mathematical model.

15. The method for calculating depth index values ​​according to claim 14, characterized in that, The multiple depth measuring devices are connected via a network. The calibration target device obtains the measured value or calculated depth index value extracted by the reference device through the network during the depth measurement process for calculating the calibration coefficient, and calculates the calibration coefficient.

16. The method for calculating depth index values ​​according to claim 14, characterized in that, The depth measurement system is equipped with a management computer. The multiple depth measurement devices and the management computer are connected via a network. The management computer obtains, via the network, the measured value or the calculated depth index value extracted by the reference device performing the depth measurement process for calculating the correction coefficient, and the measured value or the calculated depth index value extracted by the calibration target device performing the depth measurement process for calculating the correction coefficient, and calculates the correction coefficient of the calibration target device.

17. A depth measuring device, comprising calculating a depth index value representing the relative depth of a pattern on a sample, characterized in that, The depth measuring device includes: An electron optical system that irradiates an electron beam onto a sample; A detection system that detects emitted electrons from a sample irradiated by the electron beam; and A computer, through executing a depth measurement process—a procedure for measuring the depth of a predetermined pattern in a measurement object—controls the electro-optical system and the detection system. Based on the measurement values ​​extracted from the electronic image, it calculates the depth index value of the predetermined pattern, the electronic image being formed from the output of the detection system. In a depth measurement system equipped with multiple depth measuring devices, the devices are divided into a reference device and a calibration device. When a device is classified as a calibration target, the computer stores calibration coefficients associated with the depth measurement process and outputs the depth index value of the predetermined pattern after calibration using a mathematical model applied to the calibration coefficients. When a device is classified as a correction target, the computer associates one or more correction coefficients with the conditions under which each correction coefficient is applied, and registers this information from the GUI screen in an updatable manner. The conditions include the measurement conditions for obtaining the object being measured and the electronic image.

18. The depth measuring device according to claim 17, characterized in that, The computer calculates a depth measurement process using correction coefficients under the same measurement conditions as the depth measurement process, controls the electro-optical system and the detection system, extracts the measured values ​​from the electronic image, or calculates the depth index value of the predetermined pattern of the measured object based on the extracted measured values. The electronic image is formed from the output of the detection system. The correction coefficient is a correction coefficient obtained by fitting the measured value extracted by the depth measurement device that is classified as the correction target device to the measured value extracted by the depth measurement device that is classified as the reference device to the depth measurement device that is classified as the correction target device through the depth measurement process for calculating the correction coefficient, according to the mathematical model; or it is a correction coefficient obtained by fitting the depth index value calculated by the depth measurement device that is classified as the correction target device to the depth index value calculated by the depth measurement device that is classified as the reference device through the depth measurement process for calculating the correction coefficient, according to the mathematical model.

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