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

Abstract

Provided is a depth measurement system comprising a plurality of depth measurement devices which each calculate a depth index value indicating the relative depth of a pattern on a sample, wherein: the plurality of depth measurement devices are classified into one reference device 1001 and an other correction target device 1002; the depth measurement devices each execute a depth measurement recipe for measuring the depth of a predetermined pattern in a measurement subject so as to calculate the depth index value of the predetermined pattern on the basis of a measurement value extracted from an obtained electronic image; and the correction target device stores a correction coefficient associated with the depth measurement recipe and outputs the depth index value of the predetermined pattern which has been corrected using a mathematical model to which the correction coefficient is applied.

Description

[Technical Field]

[0001] The present disclosure relates to a depth measurement device, a depth measurement system, and a depth index value calculation method for measuring the depth of a pattern, particularly the depth of a recess such as a hole or a groove. [Background technology]

[0002] In recent years, the need for measuring three-dimensional shapes has increased due to the increasing complexity and three-dimensionality of semiconductors, and a method for measuring three-dimensional shapes using a critical dimension scanning electron microscope (CEM) has been proposed. In Patent Document 1, for example, in the case of a groove structure, (groove width / groove bottom brightness) N , for hole structure (area of hole / luminance at bottom of hole) N It has been discovered that there is linearity between the line width or area of the pattern and the depth of the groove or hole, and a method has been disclosed for measuring the depth of recesses such as grooves and holes from the line width or area of the pattern and the brightness value (signal amount) inside (at the bottom) of the pattern. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2020 / 095346 Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, an index value proportional to depth (hereinafter referred to as a depth index value) is calculated from the line width or area of a pattern and the brightness value of the pattern bottom, and the absolute value of the pattern depth is calculated using a database that stores the relationship between previously measured pattern depths and depth index values. However, when this method is used to manage semiconductor device manufacturing processes, the line width, area, and brightness values of the pattern are measured using multiple depth measurement devices arranged on the manufacturing line to calculate the depth index value. However, because there are differences between the depth measurement devices due to various factors, there will also be differences between the devices in the depth index value calculated from these measurement values. This disclosure relates to correcting the differences in depth index values that occur between depth measurement devices. [Means for solving the problem]

[0005] A depth measurement system according to one aspect of the present disclosure includes a plurality of depth measurement devices, each of which calculates a depth index value indicating a relative depth of a pattern on a sample, the depth measurement system comprising: Each depth measurement device includes an electron optical system that irradiates an electron beam onto a sample, a detection system that detects electrons emitted from the sample irradiated with the electron beam, and a computer that executes a depth measurement recipe, which is an operating program for measuring the depth of a predetermined pattern in a measurement object, to control the electron optical system and the detection system and calculate a depth index value of the predetermined pattern based on a measurement value extracted from an electron image formed from an output from the detection system; The plurality of depth measuring devices are divided into one reference device and other devices to be corrected; The computer of the correction target device stores correction coefficients linked to the depth measurement recipe, and outputs depth index values of a predetermined pattern corrected using a mathematical model to which the correction coefficients are applied. [Effects of the Invention]

[0006] It is possible to reduce differences between devices caused by magnification errors between the reference device and the device to be corrected, differences in detection system gain, etc. Other objects and novel features will become apparent from the description of this specification and the accompanying drawings. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram of a depth measurement device. [Figure 2A] This is an example of a depth measurement system. [Figure 2B] FIG. 10 is a diagram showing a flow of correcting an instrument difference in a depth index value. [Figure 3] FIG. 10 is a diagram showing a flow of calculating a correction coefficient for a depth index value (correction method 1). [Figure 4A] 10 is an example of a correction coefficient management screen. [Figure 4B] 10 is an example of a correction coefficient editing screen. [Figure 5] FIG. 10 is a diagram showing a flow of calculating a correction coefficient for a depth index value (correction method 2). [Figure 6A] 10A and 10B are diagrams for explaining an example of calculating dimension values and brightness values from an SEM image. [Figure 6B] 10A and 10B are diagrams for explaining an example of calculating dimension values and brightness values from an SEM image. [Figure 7A] 10A and 10B are diagrams for explaining an example of calculating dimension values and brightness values from an SEM image. [Figure 7B] 10A and 10B are diagrams for explaining an example of calculating dimension values and brightness values from an SEM image. [Figure 8] FIG. 10 is a diagram showing a flow of calculating a correction coefficient for a depth index value (correction method 3). [Figure 9A] 10 is an example of a correction coefficient management screen. [Figure 9B] 10 is an example of a correction coefficient editing screen. [Figure 10] This is an example of a depth measurement system. [Figure 11] FIG. 10 is a diagram showing a calculation and operation flow of a correction coefficient in the depth measurement system. [Figure 12A] 10 is an example of a selection screen. [Figure 12B] 10 is an example of a calculation result display screen. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, the present embodiment will be described with reference to the accompanying drawings. In the accompanying drawings, functionally identical elements may be designated by the same or corresponding numerals. Note that the accompanying drawings show embodiments and implementation examples according to the principles of the present disclosure, but these are for understanding the present disclosure and are not to be used to interpret the present disclosure in a limiting manner. The descriptions in this specification are merely typical examples and are not intended to limit the scope or application of the present disclosure in any way.

[0009] Although the present embodiment has been described in sufficient detail to enable those skilled in the art to implement the present disclosure, it should be understood that other implementations and forms are possible, and that changes in configuration and structure and substitutions of various elements are possible without departing from the scope and spirit of the technical ideas of the present disclosure. Therefore, the following description should not be interpreted as being limited thereto.

[0010] In the following description of the embodiments, an example in which the present disclosure is applied to a scanning electron microscope (SEM) using an electron beam as a depth measurement device or depth measurement system is shown. However, this embodiment should not be interpreted as being limiting, and the present disclosure can also be applied to devices and systems that use other microscopes, such as a transmission electron microscope (TEM), a projection electron microscope, or a surface-illumination electron microscope, instead of a scanning electron microscope. The present disclosure can also be applied to devices and systems configured using the above-mentioned electron microscope with multiple electron beams (multibeams), or to general observation systems.

[0011] Furthermore, in the functions, operations, processing, and flow of the embodiments described below, the flow of each element and each step will be described primarily with the "computer," "overall control unit," and "management computer" as the subject (acting entity), but the description may also be with the "depth measurement device" or "depth measurement system" as the subject (acting entity), or with the "various programs" executed by the computer as the subject (acting entity). Some or all of the programs may be realized by dedicated hardware, or may be modularized. The various programs may be installed in the computer system by a program distribution server or storage media.

[0012] As semiconductor devices become more complex and miniaturized, etching has become an important process that determines the quality of the device. The depth measurement device of this embodiment calculates a depth index value that indicates the relative depth of a pattern based on two-dimensional pattern dimension values and brightness values inside the pattern obtained using a scanning electron microscope.

[0013] 1 is a schematic diagram of a depth measurement device for measuring the depth of a pattern. The depth measurement 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.

[0014] The imaging unit 101 includes an electron gun 106, a focusing lens 108 that focuses an electron beam 107 emitted from the electron gun 106, and a focusing lens 109 that further focuses the electron beam 107 that has passed through the focusing lens 108. The imaging unit 101 also includes a deflector 110 that deflects the electron beam 107, and an objective lens 111 that controls the height at which the electron beam 107 is focused. The imaging unit 101 also includes a shutter 130 that partially restricts the passage of the electron beam 107, a blanking deflector 131 that restricts the electron beam 107 from reaching the sample 112 by deflecting the electron beam 107 off the optical axis, and a blanking electrode 132 that receives the electron beam 107 deflected by the blanking deflector 131.

[0015] The electron beam 107 passes through the optical elements related to electron beam irradiation and scanning (these optical elements are collectively referred to as the electron optical system) provided in the scanning electron microscope as described above, and is irradiated onto a sample 112 placed on a stage 113. Emitted electrons 114, such as secondary electrons (SE) and backscattered electrons (BSE), emitted from the sample by irradiation with the electron beam 107 are guided in a predetermined direction by a deflector 115 (first secondary electron aligner) for deflecting the emitted electrons. The deflector 115 is a so-called Wien filter, which selectively deflects the emitted electrons 114 in a predetermined direction without deflecting the electron beam 107.

[0016] The emitted electrons 114 that pass through a detection aperture 116 provided for angular discrimination of the emitted electrons 114 are guided by a deflector 123 (second secondary electron aligner) to a detector 119 arranged off-axis. A detector 121 is also provided for detecting secondary electrons (tertiary electrons 120) generated by the collision of the emitted electrons 114 with the detection aperture 116. An energy filter 122 is provided immediately before the detector 119, and by energy discrimination, it is possible to selectively detect secondary electrons that are emitted vertically upward from the bottom of a semiconductor pattern formed on the sample 112 and have a passing trajectory near the optical axis. The optical elements involved in the detection of the emitted electrons 114 as described above are collectively referred to as a detection system.

[0017] The signal processing unit 103 generates an SEM image based on the output from the detection system. The signal processing unit 103 generates image data by storing the detection signals in a frame memory or the like in synchronization with the scanning of a scanning deflector (not shown). When storing the detection signals in the frame memory, the detection signals are stored at positions corresponding to the scanning positions of the frame memory, thereby generating a signal profile (one-dimensional information) and an SEM image (two-dimensional information).

[0018] The electron optical system and detection system of the imaging unit 101 as described above are controlled by an overall control unit 102. The overall control unit 102, input / output unit 104, and storage unit 105 are implemented as a computer 100. In response to a user instruction from the input / output unit 104, the overall control unit 102 reads out programs and data stored in the storage unit 105 and executes processing. By executing the programs stored in the storage unit 105, the overall control unit 102 executes control processing for obtaining an SEM image of the sample by the imaging unit 101, arithmetic processing for calculating a depth index value, and the like.

[0019] This section explains how to measure depth using the depth measurement device shown in Figure 1. The depth measurement device in Figure 1 captures an SEM image of a pattern that includes recesses. From the captured SEM image, the pattern dimension value or pattern area of the recesses and the brightness value inside the pattern are measured, and a depth index value is calculated. The depth index value is expressed by (Equation 1). N is an arbitrary positive number, and an appropriate value is set according to the pattern shape and sample material. (Formula 1) Depth index value = (pattern dimension value or pattern area / pattern brightness value) N Whether to use the pattern dimension value or the pattern area in calculating the depth index value depends on the shape of the two-dimensional recessed portion pattern. If the two-dimensional recessed portion pattern shape is an open pattern, the pattern dimension value is used. For example, for a trench pattern, the pattern dimension value of the groove width can be used. On the other hand, if the two-dimensional recessed portion pattern shape is a closed pattern, the pattern area is used. For example, for hole patterns and patterns with planar shapes such as ellipses, squares, and rectangles, the pattern area is used. [Example]

[0020] The flowchart in Figure 2B shows the procedure for correcting differences between depth measurement devices in a depth measurement system that uses multiple depth measurement devices, each of which calculates a depth index value, as shown in Figure 1. The measurement targets are mass-produced wafers, and we assume a situation in which the depth of a predetermined pattern formed on a mass-produced wafer is measured by multiple depth measurement devices arranged on a wafer manufacturing line.

[0021] As shown in FIG. 2A, in order to suppress differences in depth index values calculated by multiple depth measurement devices, one of the multiple depth measurement devices is designated as a reference device 1001, and correction is performed to align the measurement values of the other devices (referred to as correction target devices 1002) with the measurement values of the reference device. Any one of the multiple depth measurement devices is selected as the reference device 1001. Both the reference device 1001 and the correction target device 1002 have the same device configuration shown in FIG. 1, and it is desirable that the overall control units 102 (computers 100) of each device are connected to each other via a network 1003. The flowchart of FIG. 2B will now be described.

[0022] In any one of the multiple depth measurement devices (which may be the reference device or the device to be corrected), necessary information such as the layout of the wafer to be measured, coordinates of the measurement pattern, and measurement conditions is input from the input / output unit 104 to create a measurement recipe (operation program) for depth measurement, and the created measurement recipe is stored in the memory unit 105. The created measurement recipe is deployed to the other depth measurement devices and stored (step 201).

[0023] Next, in each of the correction target devices 1002, an instrument difference correction coefficient for the depth index value is input from the input / output unit 104 and stored in the storage unit 105 (step 202). The method for determining the instrument difference correction coefficient will be described in detail later, but the correction coefficient needs to be calculated and set in advance for each measurement sample, depth measurement condition, and correction target device.

[0024] Next, in each of the correction target devices 1002, the set machine difference correction coefficient is linked to the measurement recipe so as to be applied to the depth measurement results (step 203).

[0025] Each depth measurement device executes the depth measurement recipe, measures the dimension value and brightness value from the captured image, and calculates a depth index value (step 204). The depth index value is expressed by (Equation 1), and an appropriate value of N is set in the depth measurement recipe. At this time, if a correction coefficient for the depth index value is applied to the measurement recipe (YES in step 205), the depth measurement device corrects the depth index value using a mathematical model that corrects the depth index value to which the correction coefficient has been applied (step 206). The corrected measurement result is output to the input / output unit 104 and stored in the memory unit 105 (step 207). On the other hand, if a correction coefficient has not been set (NO in step 205), the measurement result is output to the input / output unit 104 without correction and stored in the memory unit 105 (step 207). A case where a correction coefficient has not been set includes a case where the depth measurement device is a reference device, or a case where the depth measurement device is a device to be corrected but a correction coefficient has not been set because the device difference is small enough to be considered zero.

[0026] In this way, by correcting the depth index value of the correction target device 1002 using the mathematical model, the magnification between the reference device 1001 and the correction target device 1002 can be error It is possible to reduce differences between instruments caused by differences in the gain of the detection system and other factors. Below, several examples of methods for correcting the depth index value will be described.

[0027] (Depth index value correction method 1) Correction method 1 uses a linear equation as a mathematical model for correcting the depth index value, and corrects the depth index value by linear correction. c , the depth index value I calculated by the correction target device 1002 in step 204 according to (Equation 1) o If the correction coefficients set in step 202 are A and B, the depth index value is corrected by the linear correction formula shown in (Formula 2). (Formula 2) I c =A·I o +B The flowchart in FIG. 3 shows the procedure for calculating the correction coefficients A and B when correcting for machine differences using correction method 1.

[0028] To perform fitting using the linear equation shown in (Equation 2) and find the correction coefficients A and B, it is necessary to perform depth measurements at multiple measurement points on the wafer to be measured. For this reason, in any one of the multiple depth measurement devices (which may be the reference device or the device to be corrected), necessary information such as the layout of the wafer to be measured, coordinates of the measurement pattern, and measurement conditions is input from the input / output unit 104 to create a depth measurement recipe (operation program) for calculating the correction coefficients, and this is stored in the memory unit 105. The created measurement recipe is deployed to other depth measurement devices and stored (step 301). This measurement recipe differs from the measurement recipe created in step 201 of FIG. 2B only in the measurement points.

[0029] The reference device 1001 executes the depth measurement recipe for calculating the correction coefficient, measures the pattern dimension value and the pattern brightness value, and calculates the depth index value from those values using (Equation 1) (step 302). Similarly, the correction target device 1002 executes the depth measurement recipe for calculating the correction coefficient for the same sample (measurement target), measures the pattern dimension value and the pattern brightness value, and calculates the depth index value from those values using (Equation 1) (step 303).

[0030] With the depth index value at each measurement point by the reference device 1001 as y and the depth index value at each measurement point by the correction target device as x, fitting is performed using a linear equation (y=Ax+B) to calculate correction coefficients A and B (step 304). The calculated correction coefficients A and B are registered in the storage unit 105 of the correction target device 1002 (step 305). It is confirmed whether correction coefficients have been registered for all correction target devices 1002, and if there is any correction target device that has not been registered, steps 303 to 305 are performed for that correction target device.

[0031] The magnitude of the instrumental error varies depending on the measurement conditions when measuring depth and the sample to be measured. Therefore, in principle, a correction coefficient must be determined for each depth measurement recipe (see step 201). On the other hand, if there is a depth measurement recipe with the same measurement conditions and measurement target related to the instrumental error for the relevant depth measurement recipe (for example, a measurement recipe with only the measurement point being different) and a correction coefficient has already been calculated, it is acceptable to reuse the correction coefficient calculated for the existing depth measurement recipe as is. In this case, calculation of a correction coefficient for the new depth measurement recipe can be omitted. Measurement conditions related to the instrumental error include optical conditions, shooting magnification, number of pixels, scanning method, etc.

[0032] 4A and 4B show GUI screens for the correction target device 1002 to register the correction coefficients A and B in step 305. FIG.

[0033] 4A shows the correction coefficient management screen. The correction coefficient management table 400 allows the correction coefficients A and B registered in the correction target device 1002 to be checked all at once. The correction coefficients are managed by management number 401, and a condition name 402 and correction coefficient values (A, B) 403, 404 are registered for each management number. The condition name 402 registers the measurement conditions and measurement target related to the above-mentioned machine difference. By checking the condition name 402, the user can determine whether to calculate a correction coefficient or apply a registered correction coefficient.

[0034] The correction coefficient management table 400 can be edited using the edit button 405. It is also possible to add a new record or select a management number 401 and edit the condition name 402 and correction coefficient values 403 and 404. FIG. 4B shows the correction coefficient editing screen. When a management number is selected and the edit button 405 is pressed, the management number of the correction coefficient currently selected on the editing screen is displayed in the management number display field 410, the correction coefficient registered with that management number is displayed in the correction coefficient value display field 411, and the condition name is displayed in the condition name display field 412. The management number for saving a new correction coefficient is entered in the management number input field 413, the correction coefficient calculated using the flowchart of FIG. 3 is entered in the correction coefficient value input field 414, and the condition name to be registered is entered in the condition name input field 415. Then, by pressing the apply button 416, the correction coefficient management table 400 is updated.

[0035] (Depth index value correction method 2) The method for correcting the depth index value is not limited to the above. Correction method 2 is a method in which correction coefficient A is fixed to 1 and only correction coefficient B is set in the mathematical model (Equation 2) of correction method 1. The procedure for calculating correction coefficient B is shown in the flowchart of Figure 5. Steps 301 to 303, 305, and 306 are the same as those in the flowchart of Figure 3, so redundant explanations will be omitted. In correction method 2, the difference between the average values of the depth index values calculated by the reference device and the device to be corrected is found, and this difference is used as correction coefficient B (step 504).

[0036] The GUI screen for registering and managing the correction coefficients is similar to the screens shown in FIGS. 4A and 4B, but the correction coefficient A is fixed to 1 or the correction coefficient A is not displayed.

[0037] In the case of correction method 2, there is no need to fit to a linear equation, and the correction coefficient is calculated by calculating the offset amount from the average value of the depth index values calculated by each device, so it is possible to obtain the correction coefficient value more easily than in correction method 1.

[0038] (Depth index value correction method 3) In correction method 3, the pattern dimension value or pattern area and brightness value are corrected using appropriate mathematical models, and the depth index value is calculated from the corrected values, thereby nonlinearly correcting the depth index value. Figures 6A and 6B show an example of calculating the trench width and brightness value from SEM images of the same trench pattern taken by depth inspection devices α and β. The trench patterns in SEM images 601 and 602 are measured at different magnifications depending on the device. error The brightness and groove width vary depending on the equipment and detection system. The groove width obtained from the SEM image 601 captured by the equipment α (reference equipment) shown in FIG. 6A is W α , the brightness value of the trench bottom is GL α and the groove width obtained from the SEM image 602 captured by the apparatus β (the apparatus to be corrected) shown in FIG. 6B is represented as W β , the brightness value of the trench bottom is GL β The trench width and brightness values are calculated as the average values of multiple trench patterns.

[0039] Depth index value I of device α and β α , I β is calculated using Equation 3. (Formula 3) I α =(W α / GL α ) N I β =(W β / GL β ) N When the instrument difference is not corrected, the depth index value I α , I β will not have the same value.

[0040] In correction method 3, the pattern dimension value and the brightness value inside the pattern are corrected using a mathematical model. For example, when correction is performed using a linear mathematical model, the correction coefficient A for the pattern dimension value is CD ,B CD and the correction coefficient A for the luminance value GL ,B GL are calculated in advance, and these correction coefficients are registered in the correction target device 1002 in advance.

[0041] Depth index value I of the correction target device 1002 β is the groove width W corrected by a mathematical model using a correction coefficient, as shown in (Equation 4). β ' , brightness value GL β ' to obtain the depth index value I β ' is corrected to '. (Formula 4) W β ' =A CD ·W β +B CD GL β ' =A GL ·GL β +B GL I β ' =(W β ' / GL β ' ) N By using (Equation 4), it is possible to correct for differences in the depth index value of an unclosed pattern such as a trench pattern.

[0042] An example of calculating the pattern area and brightness value from SEM images of the same hole pattern taken by the depth inspection devices α and β shown in Figures 7A and 7B is shown. The hole diameter calculated from the SEM image 701 taken by the reference device (device α) shown in Figure 7A is D α , the brightness value of the hole bottom is GL α and the hole diameter obtained from the SEM image 702 captured by the correction target apparatus (apparatus β) shown in FIG. 7B is represented as D β , the brightness value of the hole bottom is GL β As in the case of trench patterns, the hole diameter and brightness value may be calculated as the average values of a plurality of hole patterns.

[0043] Depth index value I of device α and β α , I β is calculated using Equation 5. (Formula 5) S α =π (D α / 2) 2 S β=π (D β / 2) 2 I α =(S α / GL α ) N I β =(S β / GL β ) N When the instrument difference is not corrected, the depth index value I α , I β will not have the same value.

[0044] Depth index value I of the correction target device 1002 β As shown in (Equation 6), the hole diameter DW corrected by the mathematical model using the correction coefficient is β ' , brightness value GL β ' to obtain the depth index value I β ' is corrected to '. (Formula 6) D β ' =A CD D β +B CD GL β ' =A GL ·GL β +B GL S β ' =π·(D β ' / 2) 2 I β ' =(S β ' / GL β ' ) N By using (Equation 6), it is possible to correct for differences between machines in the depth index value of a closed pattern such as a hole pattern. Machine differences can also be corrected in the same way for closed patterns other than hole patterns. All that is required is to apply a calculation method for the area S according to the pattern shape.

[0045] Correction coefficient A when correcting for machine differences using correction method 3 CD ,B CD ,A GL ,B GLThe calculation procedure is shown in the flowchart of Figure 8.

[0046] In any one of the multiple depth measurement devices (which may be the reference device or the device to be corrected), necessary information such as the layout of the wafer to be measured, coordinates of the measurement pattern, and measurement conditions is input from the input / output unit 104 to create a depth measurement recipe (operation program) for calculating correction coefficients, and store it in the memory unit 105. The created measurement recipe is deployed to the other depth measurement devices and stored (step 801).

[0047] The reference device 1001 executes the depth measurement recipe for calculating the correction coefficients and measures the pattern dimension values and pattern brightness values (step 802). Similarly, the correction target device 1002 executes the depth measurement recipe for calculating the correction coefficients for the same sample and measures the pattern dimension values and pattern brightness values (step 803). Let y be the dimension value at each measurement point by the reference device 1001, and x be the dimension value at each measurement point by the correction target device, and then use the linear equation (y=A CD x+B CD ) and perform fitting using the correction coefficient A CD ,B CD Similarly, the luminance value at each measurement point by the reference device 1001 is set to y, and the luminance value at each measurement point by the correction target device is set to x, and the linear equation (y=A GL x+B GL ) and perform fitting using the correction coefficient A GL ,B GL (Step 805). CD ,B CD ,A GL ,B GL are registered in the storage unit 105 of the correction target device 1002 (step 806). It is checked whether the correction coefficients are registered in all correction target devices 1002, and if there is any correction target device that is not registered, steps 803 to 806 are performed for that correction target device.

[0048] 9A and 9B, the correction target device 1002 calculates the correction coefficient A CD ,B CD ,AGL ,B GL 4A and 4B, the GUI screen for registering the user ID and password is the same as that shown in FIG. 4A and B, so a duplicated explanation will be omitted.

[0049] FIG. 9A shows a correction coefficient management screen. The correction coefficients registered in the correction target device 1002 can be checked all at once using the correction coefficient management table 900. This is the same as the correction coefficient management screen shown in FIG. 4A, but the correction coefficient value can be a correction coefficient value for a dimension value (A CD ,B CD ) 901, the brightness correction coefficient value (A GL ,B GL ) 902 are registered. Fig. 9B shows a correction coefficient editing screen. Similar to the correction coefficient editing screen shown in Fig. 4B, it is provided with a correction coefficient value display field 911 that displays the correction coefficient for dimension values, a correction coefficient value display field 912 that displays the correction coefficient for brightness values, and correction coefficient value input fields 913 and 914 for inputting the correction coefficient for dimension values and the correction coefficient for brightness values calculated in the flowchart of Fig. 8, respectively.

[0050] In correction method 3, a mathematical model is created to correct both the dimension value and the brightness value, so that it is possible to correct instrument differences not only in depth index values, but also in measurements that use only brightness values, and in measurement values calculated using brightness values other than depth index values. [Example]

[0051] In the second embodiment, an operation method and a depth measurement system are described that automatically calculate and manage correction coefficients required to correct the instrumental difference of the depth index value described in the first embodiment using a mathematical model. In one aspect of the depth measurement system of this embodiment, as shown in FIG. 2A, a plurality of depth measurement devices 1001, 1002 are connected to a network 1003 so that they can access each other. On the other hand, FIG. 10 shows another aspect of the depth measurement system of this embodiment, in which a management computer 1004 is further connected to the network 1003. The management computer 1004 has a function of managing the correction coefficients registered in each device.

[0052] The procedure for calculating and using the correction coefficients in the depth measurement system of Fig. 10 will be described with reference to the flowchart of Fig. 11 and the GUI screens of Figs. 12A and 12B. Here, an example of calculating the correction coefficients based on correction method 3 described in Example 1 will be described. The same applies to calculating the correction coefficients based on other correction methods.

[0053] In any one of the multiple depth measurement devices in the depth measurement system, necessary information such as the layout of the wafer to be measured, coordinates of the measurement pattern, and measurement conditions is input from the input / output unit 104 to create a depth measurement recipe (operation program) for calculating correction coefficients, and the program is stored in the storage unit 105. The created measurement recipe is deployed to the other depth measurement devices and stored (step 1101). Each device in the depth measurement system executes the depth measurement recipe for calculating correction coefficients, and measures pattern dimension values and pattern brightness values (step 1102).

[0054] 12A is displayed on the management computer 1004. The selection screen 1200 is provided with a classification 1201 into a reference device and a correction target device. The selection list 1200 is provided with a device name column 1202, a measurement recipe column 1203, and a measurement data column 1204.

[0055] In the reference device record of the selection list 1200, the user selects the name of the device to be used as the reference device from the device name column 1202 using a pull-down menu (step 1103). When the reference device is selected, a depth measurement recipe for calculating correction coefficients held by the device becomes selectable. Then, the user selects a depth measurement recipe for calculating correction coefficients held by the reference device from the measurement recipe column 1203 using a pull-down menu (step 1104). When a depth measurement recipe for calculating correction coefficients is selected, measurement data acquired by the device by executing the depth measurement recipe for calculating correction coefficients becomes selectable. Then, the user selects measurement data held by the reference device from the measurement data column 1204 using a pull-down menu (step 1105).

[0056] Next, in the correction target device record of the selection list 1200, the user selects the name of the device to be corrected from the device name field 1202 using a pull-down menu (step 1106). When the correction target device is selected, it becomes possible to select a depth measurement recipe for calculating correction coefficients held by the device. Then, the user selects a depth measurement recipe for calculating correction coefficients held by the device to be corrected from the measurement recipe field 1203 using a pull-down menu (step 1107). When a depth measurement recipe for calculating correction coefficients is selected, it becomes possible to select measurement data acquired by the device by executing the depth measurement recipe for calculating correction coefficients. Then, the user selects measurement data held by the device to be corrected from the measurement data field 1204 using a pull-down menu (step 1108).

[0057] By pressing the execute button 1205 on the selection screen (FIG. 12A), fitting is performed on the measurement results of the selected reference device and correction target device, and a correction coefficient (A CD ,B CD ,A GL ,B GL ) is calculated (step 1109), and the fitting result and the calculated correction coefficient are displayed on the calculation result display screen shown in FIG.

[0058] The calculation result display screen shown in FIG. 12B will now be described. Measurement results 1211 before application of correction and measurement results 1212 after application of correction based on the calculated correction coefficient are displayed. In both cases, the vertical axis represents the measurement results of the reference device, while the horizontal axis of graph 1211 represents the measurement results of the correction target device before correction, and the horizontal axis of graph 1212 represents the measurement results of the correction target device after correction. This makes it possible to compare the correspondence between the values of the reference device and the values of the correction target device before and after correction. The data to be displayed as the measurement results can be selected in data selection field 1210. Here, an example is shown in which a depth index value is selected, but dimension values or brightness values can also be selected using a pull-down menu. The correction coefficient calculated by fitting is displayed in correction coefficient display area 1214, and the inter-device difference index before and after correction is displayed in inter-device difference index display area 1215. The user compares the displayed graphs 1211 and 1212 and checks the change in the inter-device difference index displayed in the inter-device difference index display section 1215 to confirm whether the machine difference has been sufficiently reduced by the correction using the correction coefficient (step 1111). For example, by comparing the graphs 1211 and 1212, it can be seen that the depth index value after correction of the correction target device is more consistent with the depth index value of the reference device than the depth index value before correction. Also, here, the inter-device difference index Acc is calculated using (Equation 7). (Formula 7) Acc = |Average of x values - Average of y values| / Average of y values Here, the value x is the depth index value or measurement value of the correction target device, and the value y is the depth index value or measurement value of the reference device. The values are the depth index value or measurement value selected in the data selection field 1210. The smaller the difference between the average value of the value x and the average value of the value y, the smaller the value of the index Acc.

[0059] If the correction coefficient is not appropriate (No in step 1111), the measurement conditions of the depth measurement recipe for calculating the correction coefficient are reviewed, and the process is repeated from step 1101. If the correction coefficient is appropriate (Yes in step 1111), the management number is entered in the management number input field 1213 on the calculation result display screen (FIG. 12B), and the calculated correction coefficient is registered in the correction target device by pressing the save button 1216 (step 1112). At this time, it is preferable to automatically register the measurement target and measurement conditions as conditions under which the correction coefficient can be applied. This will cause them to be displayed in the correction coefficient management table 900 (FIG. 9A). This is performed for all correction target devices (step 1113). As described above, the management computer 1004 can calculate and manage correction coefficients for all correction target devices in the depth measurement system.

[0060] In the case of the depth measurement system shown in Fig. 2A, the process from step 1104 to step 1112 is performed for each apparatus to be corrected, thereby executing the flowchart of Fig. 11. In this case, each apparatus to be corrected calculates and manages the correction coefficients to be applied to that apparatus. That is, the apparatus to be corrected in step 1106 is that apparatus, and the display screens of Figs. 12A and 12B are also displayed on the computer of that apparatus.

[0061] In this embodiment, the user can easily calculate and register correction coefficients by selecting appropriate measurement data according to the depth measurement system program, thereby reducing the differences between instruments in the measurement values. [Explanation of symbols]

[0062] 100: computer, 101: imaging unit, 102: overall control unit, 103: signal processing unit, 104: input / output unit, 105: memory unit, 106: electron gun, 107: electron beam, 108, 109: focusing lens, 110: deflector, 111: objective lens, 112: sample, 113: stage, 114: emitted electrons, 115: deflector, 116: detection aperture, 119, 121: detector, 120: tertiary electrons, 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 columns, 411, 911, 912: correction coefficient value display column, 412: condition name display column, 413: control number input column, 414, 913, 914: correction coefficient value input column, 415: condition name input column, 416: apply button, 601, 602, 701, 702: SEM image, 1001: reference device, 1002: correction target device, 1003: network, 1004: management computer, 1200: selection list, 1201: classification, 1202: device name column, 1203: measurement recipe column, 1204: measurement data column, 1205: execute button, 1210: data selection column, 1211, 1212: measurement results, 1213: control number input column, 1214: correction coefficient display section, 1215: inter-device difference index display section, 1216: save button.

Claims

1. 1. A depth measurement system comprising a plurality of depth measurement devices, each of which calculates a depth index value indicating a relative depth of a pattern on a sample, the depth measurement system comprising: Each of the depth measurement devices comprises: an electron optical system that irradiates the sample with an electron beam; a detection system for detecting emitted electrons from the sample irradiated with the electron beam; a computer that controls the electron optical system and the detection system by executing a depth measurement recipe, which is an operating program for measuring the depth of a predetermined pattern on a measurement object, and calculates the depth index value of the predetermined pattern based on a measurement value extracted from an electron image formed from an output from the detection system, The plurality of depth measurement devices are divided into one reference device and other correction target devices; the computer of the correction target device stores a correction coefficient associated with the depth measurement recipe, and outputs the depth index value of the predetermined pattern corrected using a mathematical model to which the correction coefficient is applied; the computer of the correction target device associates one or more correction coefficients with conditions under which each of the correction coefficients is applied, and registers the correlation coefficients in an updatable manner from a GUI screen; The conditions include the measurement target and measurement conditions for acquiring the electron image.

2. In claim 1, the plurality of depth measurement devices execute a depth measurement recipe for calculating a correction coefficient, the measurement conditions of which are equal to those of the depth measurement recipe, to control the electron optical system and the detection system, thereby extracting the measurement values from an electron image formed from an output from the detection system, or calculating the depth index value of the predetermined pattern of the measurement object based on the extracted measurement values; A depth measurement system in which the correction coefficient is a correction coefficient obtained by fitting the measurement value extracted by executing the depth measurement recipe for calculating the correction coefficient in the correction target device to the measurement value extracted by executing the depth measurement recipe for calculating the correction coefficient in the reference device according to the mathematical model, or a correction coefficient obtained by fitting the depth index value calculated by executing the depth measurement recipe for calculating the correction coefficient in the correction target device to the depth index value calculated by executing the depth measurement recipe for calculating the correction coefficient in the reference device according to the mathematical model.

3. In claim 1, The mathematical model is ｃ = A.I. ｏ +B, I ｃ is the depth index value after correction, and I ｏ is the depth index value before correction, and A and B are the correction coefficients.

4. In claim 1, The mathematical model is ｃ =I ｏ +B, I ｃ is the depth index value after correction, and I ｏ is the depth index value before correction, and B is the correction coefficient.

5. In claim 1, the depth index value is expressed as a function of a dimension value of a pattern and a brightness value inside the pattern; The mathematical model is ｃ =A ＣＤ ・W ｏ +B ＣＤ and G.L. ｃ =A ＧＬ ・GL ｏ +B ＧＬ is expressed as The W ｃ is the dimension value of the pattern after correction, and W ｏ is the dimension value of the pattern before correction, and GL ｃ is the luminance value inside the pattern after correction, and GL ｏ is the luminance value inside the pattern before correction, and A ＣＤ , the above B ＣＤ , the above A ＧＬ , the above B ＧＬ wherein the correction coefficient is

6. In claim 2, the plurality of depth measuring devices are connected via a network, The correction target device is a depth measurement system that acquires the measurement value extracted or the depth index value calculated by the reference device by executing the depth measurement recipe for calculating the correction coefficient via the network and calculates the correction coefficient.

7. In claim 6, The computer of the correction target device displays a comparative relationship between the measurement value by the reference device and the measurement value before correction by the correction target device, and a comparative relationship between the measurement value by the reference device and the measurement value after correction by the correction target device, or a comparative relationship between the correspondence between the depth index value by the reference device and the depth index value before correction by the correction target device, and a comparative relationship between the depth index value by the reference device and the depth index value after correction by the correction target device.

8. In claim 7, A depth measurement system in which the computer of the device to be corrected calculates an inter-device difference index indicating the difference between the measurement value or the depth index value by the reference device and the measurement value or the depth index value by the device to be corrected, and displays the change in the inter-device difference index before and after correction.

9. In claim 2, a management computer; the plurality of depth measuring devices and the management computer are connected via a network, The management computer acquires, via the network, the measurement values or the calculated depth index values extracted by the reference device when the reference device executes the depth measurement recipe for calculating the correction coefficient, and the measurement values or the calculated depth index values extracted by the correction target device when the correction target device executes the depth measurement recipe for calculating the correction coefficient, and calculates the correction coefficient for the correction target device.

10. In claim 9, The management computer displays in a comparative manner the correspondence between the measurement value by the reference device and the measurement value before correction by the correction target device, and the correspondence between the measurement value by the reference device and the measurement value after correction by the correction target device, or the correspondence between the depth index value by the reference device and the depth index value before correction by the correction target device, and the correspondence between the depth index value by the reference device and the depth index value after correction by the correction target device.

11. In claim 10, The management computer calculates an inter-device difference index indicating the difference between the measurement value or the depth index value by the reference device and the measurement value or the depth index value by the device to be corrected, and displays the change in the inter-device difference index before and after correction.

12. A depth measurement system comprising a plurality of depth measurement devices, each of which calculates a depth index value indicative of a relative depth of a pattern on a sample, comprising: Each of the depth measurement devices comprises: an electron optical system that irradiates the sample with an electron beam; a detection system for detecting emitted electrons from the sample irradiated with the electron beam; a computer that controls the electron optical system and the detection system by executing a depth measurement recipe, which is an operating program for measuring the depth of a predetermined pattern on a measurement object, and calculates the depth index value of the predetermined pattern based on a measurement value extracted from an electron image formed from an output from the detection system, The plurality of depth measurement devices are divided into one reference device and other correction target devices; the computer of the correction target device stores a correction coefficient associated with the depth measurement recipe, and outputs the depth index value of the predetermined pattern corrected using a mathematical model to which the correction coefficient is applied; the depth index value is expressed as a function of a dimension value of a pattern and a brightness value inside the pattern; The mathematical model is expressed as W c =A CD ·W o +B CD and GL c =A GL ·GL o +B GL ; A depth measurement system in which W c is the dimensional value of the pattern after correction, W o is the dimensional value of the pattern before correction, GL c is the luminance value inside the pattern after correction, GL o is the luminance value inside the pattern before correction, and A CD , B CD , A GL , and B GL are the correction coefficients.

13. A depth index value calculation method for a depth measurement system that includes a plurality of depth measurement devices and calculates a depth index value that indicates a relative depth of a pattern to be measured, comprising: Each of the depth measurement devices comprises an electron optical system that irradiates an electron beam onto a sample, a detection system that detects electrons emitted from the sample irradiated with the electron beam, and a computer that controls the electron optical system and the detection system by executing a depth measurement recipe, which is an operating program for measuring the depth of a predetermined pattern in a measurement object, and calculates the depth index value of the predetermined pattern based on a measurement value extracted from an electron image formed from an output from the detection system, The plurality of depth measurement devices are divided into one reference device and other correction target devices; the computer of the correction target device stores a correction coefficient associated with the depth measurement recipe; the reference device executes the depth measurement recipe and outputs the calculated depth index value; the correction target apparatus corrects the depth index value calculated by executing the depth measurement recipe using a mathematical model to which the correction coefficient is applied, and outputs the corrected depth index value; the computer of the correction target device associates one or more correction coefficients with conditions under which each of the correction coefficients is applied, and registers the correlation coefficients in an updatable manner from a GUI screen; The conditions include the measurement conditions for acquiring the measurement object and the electron image.

14. In claim 13, the plurality of depth measurement devices execute a depth measurement recipe for calculating a correction coefficient, the measurement conditions of which are equal to those of the depth measurement recipe, to control the electron optical system and the detection system, thereby extracting the measurement values from an electron image formed from an output from the detection system, or calculating the depth index value of the predetermined pattern of the measurement object based on the extracted measurement values; A depth index value calculation method in which the correction coefficient is a correction coefficient obtained by fitting the measurement value extracted by executing the depth measurement recipe for calculating the correction coefficient in the correction target device to the measurement value extracted by executing the depth measurement recipe for calculating the correction coefficient in the reference device according to the mathematical model, or a correction coefficient obtained by fitting the depth index value calculated by executing the depth measurement recipe for calculating the correction coefficient in the correction target device to the depth index value calculated by executing the depth measurement recipe for calculating the correction coefficient in the reference device according to the mathematical model.

15. In claim 14, the plurality of depth measuring devices are connected via a network, A depth index value calculation method in which the correction target device acquires, via the network, the measurement value extracted or the depth index value calculated by the reference device executing the depth measurement recipe for calculating the correction coefficient, and calculates the correction coefficient.

16. In claim 14, the depth measurement system includes a management computer, and the plurality of depth measurement devices and the management computer are connected via a network; A depth index value calculation method in which the management computer acquires, via the network, the measurement values or the calculated depth index values extracted by the reference device when the reference device executes the depth measurement recipe for calculating the correction coefficient, and the measurement values or the calculated depth index values extracted by the correction target device when the correction target device executes the depth measurement recipe for calculating the correction coefficient, and calculates the correction coefficient for the correction target device.

17. 1. A depth measurement apparatus for calculating a depth index value indicating a relative depth of a pattern on a sample, comprising: an electron optical system that irradiates the electron beam onto the sample; a detection system for detecting emitted electrons from the sample irradiated with the electron beam; a computer that controls the electron optical system and the detection system by executing a depth measurement recipe, which is an operating program for measuring the depth of a predetermined pattern on a measurement object, and calculates the depth index value of the predetermined pattern based on a measurement value extracted from an electron image formed from an output from the detection system, In a depth measurement system including a plurality of the depth measurement devices, the depth measurement system is divided into a reference device and a correction target device, When the device is classified as the correction target device, the computer stores a correction coefficient associated with the depth measurement recipe, and outputs the depth index value of the predetermined pattern corrected using a mathematical model to which the correction coefficient is applied; When the device is classified as the correction target device, the computer associates one or more of the correction coefficients with conditions under which each of the correction coefficients is applied, and registers the associations in an updatable manner from a GUI screen; The conditions include the measurement target and measurement conditions for acquiring the electron image.

18. In claim 17, the computer executes a depth measurement recipe for calculating a correction coefficient, the measurement conditions of which are equal to those of the depth measurement recipe, to control the electron optical system and the detection system, thereby extracting the measurement value from an electron image formed from an output from the detection system, or calculates the depth index value of the predetermined pattern of the measurement object based on the extracted measurement value; The correction coefficient is a correction coefficient obtained by fitting the measurement value extracted by a depth measurement device classified as the correction target device executing the depth measurement recipe for correction coefficient calculation to the measurement value extracted by a depth measurement device classified as the reference device executing the depth measurement recipe for correction coefficient calculation according to the mathematical model, or a correction coefficient obtained by fitting the depth index value calculated by a depth measurement device classified as the correction target device executing the depth measurement recipe for correction coefficient calculation to the depth index value calculated by a depth measurement device classified as the reference device executing the depth measurement recipe for correction coefficient calculation according to the mathematical model.

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