JP2010129516A - Scanning electron microscope, discharge electron detected value estimation method, sem image simulation method, and its program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: a method for highly precisely estimating a detection value of emitted electrons obtained by actual observation; a method for highly precisely simulating an SEM image obtained by actual observation; and a scanning electron microscope having an electronic optical system or the like set therein, so that a dummy SEM image is actually obtained. <P>SOLUTION: In the discharge electron detection value estimation method, an electromagnetic field distribution EM of the electronic optical system 4 in an electron microscope body 1 is calculated, while detection values of first emitted electrons 50 from a sample 5 in the electromagnetic field distribution EM and second emitted electrons 52 emitted from the electronic optical system by collision with the first emitted electrons are calculated by a Monte Carlo method. The detection value is obtained for every incident position of an electron beam 2 to the sample 5, and SEM images are formed corresponding to the detected value. When a desired image is selected and designated from among the SEM images, the electronic optical system or the like is set to the simulated conditions and such an SEM image can be actually observed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a scanning electron microscope, an emission electron detection value estimation method, an SEM image simulation method, and a program thereof.

  A calculation method using a Monte Carlo method is generally known as a method for obtaining electrons emitted from a sample by an electron beam. In this method, the number of emitted electrons, the energy, and the emission angle of both electrons are calculated by reproducible using repeated processes and random numbers of reflected electrons and secondary electrons generated by electrons incident on the sample. The Reflected electrons refer to electrons emitted from a sample whose energy is, for example, 50 eV or more, and secondary electrons are electrons whose energy is less than 50 eV. When the scanning electron microscope (so-called SEM) actually obtains a microscopic image (so-called SEM image), the secondary electrons are generally detected.

  Patent Document 1 discloses an electron beam simulation technique for calculating the optimum focus value of an electron beam from the signal amount of emitted electrons obtained by the Monte Carlo method in order to improve the accuracy of the length measurement SEM. According to this document, Monte Carlo simulation of emitted electrons due to collision of an incident electron beam assuming an intensity distribution is performed, and the total amount of secondary electrons obtained for each incident position and incident angle is used as the signal amount of the SEM image. This document describes a method and means for improving the accuracy of simulation, and does not set the conditions of an electron optical system or the like so as to obtain an SEM image desired by an operator.

Note that a calculation method using a difference method, a finite element method, or the like is well known for calculating an electric field distribution and a magnetic field distribution generated by an electron optical system such as a magnetic lens and an electric field lens ([0054] of Patent Document 1). I won't go into details.
JP 2007-218711 A

  The electrons emitted from the sample are deflected by the magnetic or electric field generated by the electron optical system, and then collected and detected by the electric field generated by the detector. Such electrons contribute to the formation of the SEM image. However, depending on the emission angle or energy of the emitted electrons, it may be blocked by an electron optical system such as an objective lens or may collide with a part other than the detection unit of the detector, thereby not contributing to the formation of the SEM image. There is also. That is, the electrons contributing to the formation of the SEM image are a part of all the emitted electrons.

  The detector basically detects the low energy electrons (secondary electrons) described above, but also detects high energy electrons (reflected electrons) depending on the emission angle and energy of the emitted electrons. Further, there may be a case where secondary electrons are emitted from a structural member such as an electron optical system due to reflected electrons, and the secondary electrons are detected.

  Since the SEM image actually obtained contains these electrons, it is often different from the SEM image formed using only the electrons emitted from the sample. In addition, the obtained SEM image may change due to a change in the configuration of the electron optical system or the like.

  Therefore, the present invention provides an emission electron detection value estimation method for accurately estimating a detection value of emitted electrons obtained by actual observation, and an SEM image simulation method for accurately simulating an SEM image obtained by actual observation, and The purpose is to provide the program. Furthermore, the present invention has a function of estimating the detected electron emission value or SEM image simulation function according to the above-described method, and can scan a part or all of the electron optical system or the like so that a desired simulation result can be obtained even by actual observation. The purpose is to provide an electron microscope.

  The invention according to claim 1 is a method for estimating an emission electron detection value, wherein a first step of pre-calculating an electromagnetic field distribution generated by an electron optical system and a detector in a scanning electron microscope is installed in the electromagnetic field distribution. A second step of inputting sample data relating to at least the shape and composition of the sample and an incident condition of an electron beam incident on the sample; and from the sample by the electron beam based on the input sample data and the incident condition A first step of calculating a first emission electron of the first emission electron by a Monte Carlo method, and calculating a trajectory of the first emission electron in the electromagnetic field distribution based on a parameter of the first emission electron obtained by the third step And counting the first emitted electrons reaching the detector based on the calculation result of the fourth step and the fourth step. And a sixth step of calculating the average value of the count values obtained in the fifth step as an estimated detection value by repeating each of the steps 3 to 5 a predetermined number of times. It is characterized by that.

  According to a second aspect of the present invention, in the fourth step, when the first emission electron collides with the electron optical system or the like, the electron beam is emitted from the electron optical system or the like by the collision instead of the fourth step. The second emission electrons are calculated by the Monte Carlo method. In the fifth step, the orbits of the second emission electrons in the electromagnetic field distribution are obtained by the fourth step instead of the fifth step. The calculation is based on the parameters of the second emission electrons, and the second emission electrons reaching the detector are counted.

  The invention according to claim 3 is an SEM image simulation method, comprising the detection value estimation method according to claim 1, and further, the sixth step is performed for each incident position of the incident beam. Performing an estimated detection value for each incident position, and generating simulated SEM image data in which intensities corresponding to the estimated detection values are arranged in association with the incident positions. To do.

  According to a fourth aspect of the present invention, there is provided a method for estimating an emission electron detection value, wherein a first step of calculating in advance an electromagnetic field distribution generated by an electron optical system and a detector in a scanning electron microscope, and emission from a sample position in the electromagnetic field distribution A second step of setting a plurality of different combinations of energy and emission angle of the emitted electrons, a third step of calculating an orbit of the emitted electrons in the electromagnetic field distribution based on the plurality of combinations, Based on the calculation result of the third step, the emitted electrons that reach the detector are counted, the count value is used as a reference value, and a detection value reference table that associates each combination with the reference value is created. A fourth step, sample data on at least the shape and composition of the sample placed at the sample position, and the incident condition of the electron beam incident on the sample. A sixth step of calculating a first emission electron from the sample by the electron beam based on the inputted sample data and the incident condition by a Monte Carlo method, For all the first emission electrons calculated in the step, the emission electrons in the detection value reference table having the smallest difference in energy and emission angle are selected, and the sum of the reference values of the selected emission electrons is selected. A seventh step of calculating a value, an average value of each total value obtained by repeating the sixth and seventh steps a predetermined number of times, and calculating the average value of the emitted electrons from the incident position And an eighth step as a detection value.

  According to a fifth aspect of the present invention, in the third step, when the emitted electrons collide with the electron optical system or the like, the second emission electrons emitted from the electron optical system or the like due to the collision are calculated by the Monte Carlo method. A tenth step of calculating a trajectory of the second emitted electrons in the electromagnetic field distribution based on a parameter of the second emitted electrons obtained by the ninth step, and the detection An eleventh step of counting the second emitted electrons that have reached the chamber, wherein the ninth to eleventh steps are executed a plurality of times, and the obtained count values of the second emitted electrons are averaged. And added to the reference value.

  The invention of claim 6 is an SEM image simulation method, comprising the detection value estimation method according to claim 4, and further, the eighth step is performed for each incident position of the incident beam. And calculating simulated estimated values, and generating simulated SEM image data in which intensities corresponding to the estimated detected values are arranged in association with the incident positions.

  The invention according to claim 7 is an emission electron detection value estimation program, wherein a computer is installed in the electromagnetic field distribution, the first means for calculating in advance the electromagnetic field distribution generated by the electron optical system and the detector in the scanning electron microscope. Second means for inputting sample data relating to at least the shape and composition of the sample to be processed and the incident condition of the electron beam incident on the sample, and the electron beam based on the input sample data and the incident condition. Third means for calculating the first emission electrons from the sample by the Monte Carlo method, and the trajectory of the first emission electrons in the electromagnetic field distribution are based on the parameters of the first emission electrons obtained by the third means. And a fourth means for calculating the first emission electrons reaching the detector based on a calculation result by the fourth means. And the third to fifth means are repeated a predetermined number of times to function as sixth means for calculating an average value of count values obtained by the fifth means as an estimated detection value. And

  According to an eighth aspect of the present invention, in the fourth means, when the first emission electron collides with the electron optical system or the like, the second emission electron emitted from the electron optical system or the like by the collision is calculated by the Monte Carlo method. The fifth means calculates the trajectory of the second emission electrons in the electromagnetic field distribution based on the parameter of the second emission electrons obtained by the fourth means.

  The invention according to claim 9 is an SEM image simulation program, wherein the computer is arranged by associating each means according to any one of claims 7 and 8 with an intensity corresponding to the estimated detection value corresponding to the incident position. The sixth means is performed for each incident position of the incident beam and calculates an estimated detection value for each incident position.

  The invention according to claim 10 is an emission electron detection value estimation program, wherein a computer calculates in advance a first means for calculating an electromagnetic field distribution generated by an electron optical system and a detector in a scanning electron microscope, and A second means for setting a plurality of different combinations of the energy and emission angle of the emitted electrons emitted from the sample position; and a third means for calculating an orbit of the emitted electrons in the electromagnetic field distribution based on the plurality of combinations. And a detection value reference that associates each combination with the reference value by counting the emitted electrons that reach the detector and using the counted value as a reference value based on the calculation result by the means and the third means Fourth means for creating a table, sample data regarding at least the shape and composition of the sample placed at the sample position, and incidence of an electron beam incident on the sample A fifth means for inputting a result, a sixth means for calculating a first emission electron from the sample by the electron beam based on the inputted sample data and the incident condition by a Monte Carlo method; For all the first emission electrons calculated by the means of 6, the emission electrons in the detection value reference table having the smallest difference in energy and emission angle are selected, and the reference value of the selected emission electrons is selected. And calculating the average value of the total values obtained by repeating the sixth and seventh means a predetermined number of times, and calculating the average value from the incident position. It is made to function as an 8th means which calculates as an estimated detection value of this.

  In the invention of claim 11, when the emitted electrons collide with the electron optical system or the like in the trajectory calculation by the third means, the computer further emits the second from the electron optical system or the like due to the collision. Ninth means for calculating emitted electrons by the Monte Carlo method, and a second orbit for calculating the orbit of the second emitted electrons in the electromagnetic field distribution based on the parameters of the second emitted electrons obtained by the ninth means. The tenth means functions as an eleventh means for counting the second emitted electrons that have reached the detector, and the ninth to eleventh means are executed a plurality of times, and the second emitted electrons obtained are The count value is averaged and added to the reference value.

  The invention of claim 12 is an SEM image simulation program, wherein the computer is arranged by associating each means according to any one of claims 10 and 11 with an intensity corresponding to the estimated detection value corresponding to the incident position. The eighth means is performed for each incident position of the incident beam to calculate the estimated detection value.

  According to a thirteenth aspect of the present invention, in a scanning electron microscope including at least an electron optical system and a detector, an electromagnetic field distribution calculating unit that pre-calculates an electromagnetic field distribution generated by the electron optical system and the detector, and the electromagnetic field distribution calculating unit is installed in the electromagnetic field distribution. A data input unit for inputting sample data relating to at least the shape and composition of the sample and the incident condition of the electron beam incident on the sample, and from the sample by the electron beam based on the input sample data and the incident condition The emission electron calculation unit that calculates the first emission electron of the first emission electron by the Monte Carlo method, and the orbit of the first emission electron in the electromagnetic field distribution is calculated based on the parameter of the first emission electron obtained by the emission electron calculation unit Based on the calculation result of the electron trajectory calculation unit and the electron trajectory calculation unit. An electron counting unit that counts electrons, and each process of the emission electron calculating unit, the electron trajectory calculating unit, and the electron counting unit are executed a predetermined number of times for each incident position of the incident beam, and obtained by the electron counting unit. And a simulated SEM image for generating simulated SEM image data in which an intensity corresponding to the estimated detected value is arranged in association with each incident position. A data generation unit and a simulated SEM image display unit that displays a simulated SEM image based on the simulated SEM image data are provided.

  According to a fourteenth aspect of the present invention, in the orbit calculation by the electron orbit calculation unit, when the first emitted electrons collide with the electron optical system or the like, the emitted electron calculation unit emits from the electron optical system or the like by the collision. The second emitted electrons are calculated by the Monte Carlo method, and the electron trajectory calculation unit calculates the second emitted electron trajectory in the electromagnetic field distribution by the parameter of the second emitted electrons obtained by the emitted electron calculation unit. The electron counting unit further counts the second emitted electrons that reach the detector.

  According to a fifteenth aspect of the present invention, in a scanning electron microscope including at least an electron optical system and a detector, an electromagnetic field distribution calculation unit that calculates in advance an electromagnetic field distribution generated by the electron optical system and the detector, and a sample position in the electromagnetic field distribution A parameter setting unit that sets a plurality of different combinations of energy and emission angle of the emitted electrons that are emitted from, an electron trajectory calculating unit that calculates the trajectory of the emitted electrons in the electromagnetic field distribution based on the plurality of combinations, Based on a calculation result by the electron trajectory calculation unit, an electron counting unit that counts the emitted electrons that reach the detector, and a count value obtained by the electron counting unit is used as a reference value, and each combination and the reference value A detection value reference table creation unit that creates a detection value reference table in association with A data input unit for inputting sample data relating to the composition and an incident condition of an electron beam incident on the sample, and a first emission electron from the sample by the electron beam based on the input sample data and the incident condition. The emitted electron of the detected value reference table having the smallest difference in energy and emission angle with respect to all the first emitted electrons calculated by the emitted electron calculating unit calculated by the Monte Carlo method and the emitted electron calculating unit An estimated detection value calculation unit that calculates a total value of the reference values of the selected emitted electrons as an estimated detection value of the emitted electrons from the incident position, and an intensity corresponding to the estimated detection value in the incident position A simulated SEM image data generating unit that generates simulated SEM image data arranged in association with the SEM image, and an SEM image based on the simulated SEM image data. Comprising a SEM image display unit for the, by calculating is performed multiple times by the Monte Carlo method of the first emitted electrons, the reference value is characterized by being averaged.

  According to a sixteenth aspect of the present invention, when the emitted electrons collide with the electron optical system or the like in the orbit calculation by the electron orbit calculation unit, the emission electron calculation unit is emitted from the electron optical system or the like by the collision. The emitted electrons are calculated by the Monte Carlo method, and the electron trajectory calculation unit calculates the trajectory of the second emission electrons in the electromagnetic field distribution based on the parameters of the second emission electrons obtained by the emission electron calculation unit. The electron counting unit further counts the second emitted electrons reaching the detector, and the reference value is averaged by calculating the second emitted electrons by a Monte Carlo method a plurality of times. It is added to the reference value.

  According to a seventeenth aspect of the present invention, in a scanning electron microscope including at least an electron optical system including at least one electrode and a detector, a predetermined plurality of electromagnetic field distributions generated by the electron optical system and the detector are applied to the electrodes. Electromagnetic field distribution calculation unit for calculating in advance with respect to the voltage value, data input for inputting sample data on at least the shape and composition of the sample installed in each electromagnetic field distribution, and a plurality of incident positions of the electron beam incident on the sample And an emission electron calculation unit for calculating a first emission electron from the sample by the electron beam by a Monte Carlo method based on the input sample data, the incident position, and a plurality of incident energy values of the electron beam And an orbit of the first emission electrons in the electromagnetic field distribution, the first emission electrons obtained by the emission electron calculation unit An electron trajectory calculation unit that calculates based on parameters, an electron counting unit that counts the first emitted electrons that reach the detector among the trajectories calculated by the electron trajectory calculation unit, and Estimated by calculating the average value of the count values obtained by the electron counting unit as the estimated detection value of each incident position by repeatedly executing each process of the emitted electron calculating unit, the electron trajectory calculating unit, and the electron counting unit a predetermined number of times. A detection value calculation unit; and an optimal contrast selection unit that selects the incident energy and the voltage value of the combination having the highest contrast from the combination of the estimated detection values of the plurality of incident positions in the plurality of incident energy values; And an applied voltage setting unit that sets the incident energy and the voltage value to the electron optical system.

  In the invention of claim 18, when the first emission electrons collide with the electron optical system or the like in the orbit calculation by the electron orbit calculation unit, the emission electron calculation unit further emits from the electron optical system or the like by the collision. The second emitted electrons are calculated by the Monte Carlo method, and the electron trajectory calculation unit calculates the second emitted electron trajectory in the electromagnetic field distribution by the parameter of the second emitted electrons obtained by the emitted electron calculation unit. The electron counting unit further counts the second emitted electrons reaching the detector based on a calculation result by the electron trajectory calculating unit.

  According to a nineteenth aspect of the present invention, in a scanning electron microscope including at least an electron optical system including at least one electrode and a detector, an electromagnetic field distribution generated by the electron optical system and the detector is applied to the predetermined plurality of electrodes. Electromagnetic field distribution calculation unit for calculating in advance with respect to the voltage value, data input for inputting sample data on at least the shape and composition of the sample installed in each electromagnetic field distribution, and a plurality of incident positions of the electron beam incident on the sample And an emission electron calculation unit for calculating a first emission electron from the sample by the electron beam by a Monte Carlo method based on the input sample data, the incident position, and a plurality of incident energy values of the electron beam And an orbit of the first emission electrons in the electromagnetic field distribution, the first emission electrons obtained by the emission electron calculation unit An electron trajectory calculation unit that calculates based on parameters, an electron counting unit that counts the first emitted electrons that reach the detector among the trajectories calculated by the electron trajectory calculation unit, and Estimated by calculating the average value of the count values obtained by the electron counting unit as the estimated detection value of each incident position by repeatedly executing each process of the emitted electron calculating unit, the electron trajectory calculating unit, and the electron counting unit a predetermined number of times. The operator selects from the detected value calculation unit, the simulated SEM image list display data generation unit for displaying a list of all the simulated SEM images generated by the simulated SEM image data generation unit, and the simulated SEM images displayed as a list. An image selection unit; and an applied voltage setting unit that sets the incident energy and the voltage value corresponding to the selected simulated SEM image in the electron optical system.

  According to the present invention, since the electromagnetic field based on various conditions (that is, shape, applied voltage, ampere turn, etc.) of the actual electron optical system and detector of the scanning electron microscope is reproduced, the estimated detection value can be obtained with high accuracy. It can be calculated. Further, since the emission electrons are considered to be deflected by an actual electromagnetic field or blocked by physical components such as an electron optical system, the estimated detection value is close to the detection value obtained in the actual scanning electron microscope.

  Further, the electrons to be detected in the calculation of the estimated detection value can include not only electrons directly emitted from the sample but also electrons emitted when the emitted electrons collide with an electron optical system or the like. Therefore, the accuracy of the estimated detection value can be further increased.

  In addition, since the detection values from each position of the sample can be estimated, a simulated SEM image can be obtained by arranging these estimated detection values for each position to obtain image data. Since various simulated SEM images in which the setting conditions of the electron optical system and the incident conditions of incident electrons are changed are obtained before actual observation, it is not necessary to repeat trial and error of observation using an actual sample. Therefore, deterioration such as contamination of the sample by the electron beam is reduced.

  Furthermore, the electromagnetic field distribution generated by the electron optical system and detector of the scanning electron microscope is calculated in advance, and the number of detected electrons emitted from the sample position and the secondary electrons in the electromagnetic field distribution is determined by the emission condition of the emitted electrons. Each is obtained as a reference value, and these are stored as a detection value reference table. Then, by applying the energy, emission angle, etc. of the electrons emitted from the sample to the emission conditions of the emitted electrons in this detection value reference table, the detection value of the event that has emitted the electrons is obtained from the reference values in the detection value reference table. It is done. In other words, the number of electrons detected by the detector is stored as a detection value reference table for electrons of all emission conditions, so there is no need to separately calculate the trajectory of electrons emitted from the sample. The value can be easily estimated.

(First embodiment)
A first embodiment of the present invention will be described.

  FIG. 1 is a schematic diagram of a scanning electron microscope according to the first embodiment of the present invention. FIG. 2 is a block diagram of the control processing unit according to the first embodiment of the present invention.

  The scanning electron microscope according to the first embodiment includes a microscope main body 1, a power supply unit 8, and a control device 10. In the microscope main body 1, an electron gun 3 that generates an electron beam 2, an electron optical system 4 that focuses and deflects the electron beam 2, a sample stage 6 on which a sample 5 is provided, and electrons in the microscope main body 1. Is installed. The power supply unit 8 is controlled by the control device 10 and applies voltage or current to the electron gun 3 and the electron optical system 4. The electron gun 3 and the electron optical system 4 are disposed along the optical axis (not shown) of the electron beam 2, and the sample stage 6 is located on the optical axis.

  The electron optical system 4 includes an electrode or a magnetic pole that performs focusing, aberration correction, deflection, and the like of the electron beam 2 and an electrode or a magnetic pole that causes electrons to reach the detector 7. For example, as shown in FIG. 1, the electron optical system 4 includes a focusing lens 4a for focusing the electron beam 2, a deflector 4b for scanning the electron beam 2 on the sample 5, and an electron beam 2 focused by the focusing lens 4a. Is made up of an objective lens 4c for focusing the laser beam onto a finer electron beam. Further, for example, as shown in FIG. 3, electrodes 41, 42 and the like are provided before and after the objective lens 4c. The electrodes 41 and 42 generate an electric field for improving the efficiency of detecting electrons by the detector 7. In the example shown in FIG. 3, it is assumed that the objective lens 4c is a magnetic lens, and a coil 43 for excitation is provided.

  As shown in FIG. 1, the control device 10 includes a CPU 11, an internal storage unit 12, a power supply control unit 13, a signal processing unit 14, a control processing unit 15, an input unit (data input unit) 16, and a display unit. (SEM image display unit) 17 and external storage means 18 are provided. These are connected to each other by a bus. The internal storage unit 12 is, for example, a RAM or a ROM. The external storage means 18 is, for example, a removable medium such as a hard disk drive or a floppy (registered trademark) disk drive. The CPU 11 executes a program stored in the internal storage unit 12 and controls the power supply control unit 13, the signal processing unit 14, the control processing unit 15, and the like. The estimation of the emission electron detection value and the simulation of the SEM image according to the present invention are processed by the control processing unit 15. In addition, the CPU 11 scans the electron beam 2 on the sample by setting an electric field and a magnetic field generated by the electron optical system 4 via the power supply control unit 13 and the power supply unit 8. The detector 7 detects secondary electrons emitted from the sample 5 by the electron beam 2 and outputs a detection signal. The CPU 11 controls the signal processing unit that has received this detection signal to display the actual SEM image on the display unit 17.

  The control processing unit 15 includes an electromagnetic field distribution calculation unit 20, an emission electron calculation unit 21, an electron trajectory calculation unit 22, an electron counting unit 23, an estimated detection value calculation unit 24, and a simulated SEM image data generation unit 25. Prepare. While the program is being executed, the control processing unit 15 refers to the program, data, and the like stored in the program storage unit 30, the database 31, and the data storage unit 32 of the internal storage unit 12. Data from the input unit (data input unit) 16 is input to the control processing unit 15. For example, the shape and composition of the sample 5 and the set value of the electron optical system 4 are input from the input unit 16. The control processing unit 15 is also connected to a display unit (SEM image display unit) 17. For example, the display unit 17 displays image data generated by a simulated SEM image data generation unit 25 described later as a simulated SEM image.

  The control processing unit 15 may be mounted on a computer (not shown). In this case, the computer has a configuration in which the power supply control unit 13 and the signal processing unit 14 are omitted from the control device 10 of FIG. .

  Processing of the emission electron detection value estimation method and SEM image simulation method according to the first embodiment of the present invention will be described.

  4 and 5 are flowcharts showing respective processes of the emission electron detection value estimation method and the SEM image simulation method executed in the scanning electron microscope of the present embodiment, and FIG. 4 is a flowchart showing a procedure for creating basic electromagnetic field distribution data. FIG. 5 is a flowchart showing a procedure for creating an estimated detection value table using basic electromagnetic field distribution data and a procedure for displaying a simulated SEM image.

  In the present embodiment, first, an electromagnetic field distribution in a space including the sample 5, the electron optical system 4, and the detector 7 is calculated.

  As shown in FIG. 4, in the first step A1, element data including information such as the shape and position of each component member that generates an electric field or magnetic field, such as the electron optical system 4 and the detector 7, and applied voltage, applied ampere turn, etc. Enter. Element data is input from an input unit (data input unit) 16. The element data is confidential information and is input by a person who is not an operator (user) such as a designer or a developer. Further, instead of inputting the element data from the input unit 16, the element data may be read from the external storage device 18. Alternatively, the element data may be included in a program stored in the program storage unit 30 and the data may be read.

  Using the element data, the electromagnetic field distribution calculation unit 20 calculates each electric field distribution and each magnetic field distribution generated by each element as a basic electromagnetic field distribution (step A2). Each basic electromagnetic field distribution is an electromagnetic field distribution in which each element is generated in the space, and an electromagnetic field distribution used for electron trajectory calculation described later is obtained by superimposing the basic electromagnetic field distributions. Each calculated basic electromagnetic field distribution is stored and stored in the database 31 as basic electromagnetic field distribution data.

  Next, each process from calculation of an estimated detection value of emitted electrons using each basic electromagnetic field distribution data to display of a simulated SEM image will be described.

  As shown in FIG. 5, in step B1, the operator inputs the voltage applied to each element, electromagnetic field analysis data such as an ampere turn, and the incident conditions such as the acceleration voltage of the electron beam 2, the incident position, and the incident angle. Since a plurality of applied voltages and ampere turns input here are input, a plurality of electromagnetic field distributions are created. Next, the operator inputs one type of sample data such as the shape and composition of the sample 5. For example, in the case of the sample 5 as shown in FIG. 6, the operator inputs the component A and shape of the sample 5a and the component and shape of the sample 5b, and inputs the positions C and D at which the electron beam 2 is incident.

と表される。同様に、例えば、対物レンズ４ｃについての基礎磁場分布及びその要素データとして入力したコイル４３に印加されたアンペアターンをそれぞれＭ_ｏ（ｘ，ｙ，ｚ）、ＮＩ_ｓとし、更にオペレータによって入力されたアンペアターンをＮＩ_ｕとすると、対物レンズ４ｃによって生じる磁場分布Ｍ（ｘ，ｙ，ｚ）は、

と表される。 The electromagnetic field distribution calculation unit 20 reads each basic electromagnetic field distribution data stored and stored in the database 31 (step B2), and uses the electromagnetic field analysis data input by the operator, and the electric field distribution E and magnetic field distribution M in the space. (Hereinafter, for convenience, these distributions are collectively referred to as an electromagnetic field distribution EM) (step B3). The electromagnetic field distribution EM is obtained by multiplying each basic electromagnetic field distribution by a value obtained by dividing the voltage or ampere turn of the electromagnetic field analysis data by the applied voltage or ampere turn of the element data, and further superimposing them. For example, the basic electric field distribution for the electrode 41 and the applied voltage inputted as its element data are respectively E _t (x, y, z) and V _st, and the basic electric field distribution for the detector 7 and the application inputted as its element data If the voltages are E _d (x, y, z) and V _sd , respectively, and the applied voltages of the electrode 41 and the detector 7 input by the operator are V _ut and V _ud , respectively, these electrodes 41 and the detector 7. The electric field distribution E (x, y, z) generated by

It is expressed. Similarly, for example, the basic magnetic field distribution and the applied ampere turns in the coil 43 input as the element data of the objective lens 4c respectively _{M o (x, y, z} ), and NI _s, which is further input by the operator When the ampere turn is NI _u , the magnetic field distribution M (x, y, z) generated by the objective lens 4c is

It is expressed.

  Next, the emission electron calculation unit 21 calculates the number of electrons (first emission electrons) 50 (51) emitted from the sample 5 by the electron beam 2 based on the sample data of the sample 5 and the incident condition of the electron beam 2. The emission angles θz, θx, energy, etc. (see FIG. 6) are calculated by the Monte Carlo method (step B4).

  The electron trajectory calculation unit 22 uses the electromagnetic field distribution EM (that is, the electric field distribution E and the magnetic field distribution M) obtained in step B3 and each parameter of the first emitted electrons obtained in step B4, to calculate the first emitted electrons. The trajectory is calculated (step B5).

  Depending on the emission angle or energy, the first emission electrons may collide with the electron optical system 4 (first emission electrons 51 shown in FIG. 3). The CPU 11 determines whether or not this collision has occurred (step B6). If there is a collision (YES in step B6), the emitted electron calculation unit 21 again emits electrons from the electron optical system 4 due to the collision. The number of (second emission electrons) 52, the emission angle, energy, and the like are calculated by the Monte Carlo method (step B7). Then, the electron trajectory calculation unit 22 calculates the trajectory of the second emitted electrons using the electromagnetic field distribution EM obtained by the process of Step B3 and the parameters of the second emitted electrons obtained by Step B7 (Step B8). ). Note that there may be a case where the first emission electrons do not collide with the electron optical system 4 or a case where the secondary electron emission rate is extremely low (NO in step B6) depending on the material of the colliding electron optical system 4. Since the use of such a material is known to designers and the like, the processing from steps B6 to B8 may be omitted in advance. In this case, the process immediately proceeds from step B5 to step B9.

  By the processing so far, the trajectories of all the emitted electrons in the electromagnetic field distribution EM are obtained. In step B9, the electron counting unit 23 counts the number of trajectories that reach the detector 7 among all the trajectories, that is, the first and second emitted electrons detected by the detector 7. This count value is integrated as an integrated count value in the data storage unit 32.

  Since the Monte Carlo method is a calculation method using random numbers, it is necessary to perform repeated calculation to increase the calculation accuracy for the first emission electrons in Step B4 and the calculation accuracy for the second emission electrons in Step B7. Therefore, a predetermined number of times for calculating these values is set in advance, and the estimated detection value calculation unit 24 determines whether or not the calculation of steps B4 and B7 has been performed for the predetermined number of times (step B10). If NO in step B10 (NO in step B10), the process returns to step B4, and each process from the calculation of the first emission electrons is performed again. When the predetermined number of times has been reached (YES in step B10), a value obtained by dividing the integrated count value by the predetermined number of times is calculated as an estimated detection value (step B11). The estimated detection value is stored in the data storage unit 32. For example, as shown in FIG. 7, it is assumed that the number of first and second emitted electrons for the first time is three, and as a result, the number of detected electrons detected by the detector 7 is two. As a result of repeating such calculation 100 times, the total number of first and second emitted electrons is 297, and the total number of detected electrons is 187. Since the calculation was performed 100 times, the estimated detection value is 1.87 (= 187/100).

  In the processing from step B4 to B11, the emitted electrons are calculated for one incident position among the incident conditions input in step B1. When a plurality of incident positions of the electron beam 2 are set in step B1, the CPU 11 determines whether estimated detection values have been calculated for all these incident positions (step B12), and for all incident positions. If the estimated detection value is not calculated (NO in step B12), the process from step B4 is performed again by changing the incident position of the electron beam 2. If estimated detection values are calculated for all incident positions (YES in step B12), it is determined whether estimated detection values have been calculated for all electromagnetic field distributions calculated in step B3. (Step B13). If the estimated detection values are not calculated for all electromagnetic field distributions (NO in step B13), the process returns to step B4 to calculate the estimated detection values for the remaining electromagnetic field distributions. If the estimated detection values are calculated for all electromagnetic field distributions (YES in step B13), the process proceeds to the next step.

  At this time, estimated detection values are calculated for all electromagnetic field distributions EM and incident conditions. The CPU 11 creates these estimated detection values as an estimated detection value table (step B14) and stores them in the database 31.

  The simulated SEM image data generation unit 25 generates simulated SEM image data by arranging the intensity corresponding to each incident position from the estimated detection values in the estimated detection value table stored in the database 31 (step B15). When the simulated SEM image is displayed on the display unit 17 using the simulated SEM image data (step B16), the entire process is completed. In addition to the simulated SEM image data generating unit 25, the control processing unit 15 may include a simulated SEM image list display data generating unit 34 for displaying a list of all simulated SEM images. Can be observed.

  According to this embodiment, the electromagnetic field distribution generated by the electron optical system and detector of the scanning electron microscope is calculated, while the electrons emitted from the sample are calculated using the Monte Carlo method. Then, the trajectory of electrons passing through the electromagnetic field is calculated, and only the electrons that have reached the detector are obtained as estimated detection values.

  In addition, since the electromagnetic field is reproduced based on various conditions (that is, shape, applied voltage, amperage, etc.) of the actual electron optical system and detector of the scanning electron microscope, the estimated detection value can be calculated with high accuracy. Further, since the emission electrons are considered to be deflected by an actual electromagnetic field or blocked by physical components such as an electron optical system, the estimated detection value is close to the detection value obtained in the actual scanning electron microscope.

  Further, the electrons to be detected in the calculation of the estimated detection value can include not only electrons directly emitted from the sample but also electrons emitted when the emitted electrons collide with the electron optical system. Therefore, the accuracy of the estimated detection value can be further increased.

  In addition, since the detection values from each position of the sample can be estimated, a simulated SEM image can be obtained by arranging these estimated detection values for each position to obtain image data. Various simulated SEM images in which the setting conditions of the electron optical system and the incident conditions of incident electrons are changed can be obtained as individual display or list display before actual observation, so that it is not necessary to repeat trial and error of observation using an actual sample. . Therefore, deterioration such as contamination of the sample by the electron beam is reduced.

(Second Embodiment)
A second embodiment of the present invention will be described. The scanning electron microscope according to the second embodiment can obtain an optimum (or desired) contrast using the estimated detection value table described in the first embodiment, or a real SEM image of a simulated SEM image designated by a list display. This is a scanning electron microscope configured as described above.

  As shown in FIG. 9, the scanning electron microscope according to the second embodiment includes an optimum contrast selection unit 28 and an applied voltage setting unit 29 in the control processing unit 15 in addition to the configuration of the first embodiment. Further, as described later, a simulated SEM image list display data generation unit 34 and an image selection unit 35 may be further provided. In the scanning electron microscope according to the present embodiment, each process shown in FIG. 4 and the processes from Step B1 to Step B14 shown in FIG. 5 are performed, and then Step C1 shown in FIG. 10 is substituted for Step B15 and Step B16. To steps C7 are performed. That is, in the scanning electron microscope according to the second embodiment, the applied voltage and ampere turn of the electron optical system that provides the optimum contrast are selected based on the calculated estimated detection value, and actual observation using this selected value is performed. .

  Each process until the SEM image display in this embodiment is demonstrated.

  As described above, the description of each processing shown in FIG. 4 and the processing from step B1 to step B14 shown in FIG. 5 is omitted. However, in step B1, it is assumed that the operator has input observation positions on the sample 5 (for example, points C and D shown in FIG. 6). This observation position is equivalent to an incident position that is one of the incident conditions of the electron beam 2. And when the process of step B14 is complete | finished, the estimated detection value with respect to all the electromagnetic field distribution and incident conditions which an operator assumes is preserve | saved as an estimated detection value table. FIG. 8 is an example of the estimated detection value table. The estimated detection values when the electron beam 2 is incident on the points C and D on the sample 5 shown in FIG. 6 are calculated for each of the acceleration voltage and the set voltages of the electrodes 41 and 42.

  As shown in FIG. 10, the optimum contrast selection unit 28 (see FIG. 9) refers to the detection value estimated value table (see FIG. 8) (step C1), and the observation position of the sample 5 obtained for each combination of applied voltages. The difference between the estimated detection values at point C and point D is calculated (step C2).

  Next, the combination of applied voltages that gives the largest difference is selected (step C3). That is, a combination that selects the optimum contrast between the observation positions C and D in the SEM image is selected. In the example shown in FIG. 8, it can be seen that the difference between the estimated detection values in condition number 8 is the largest. Therefore, in this case, each applied voltage of the condition number 8 is selected as an optimal combination.

  As another calculation method of the optimum combination, a combination of applied voltages that maximizes the value of (difference between each estimated detection value) / (total sum of each estimated detection value) may be selected. According to this method, the combination of condition number 7 is selected as the optimal combination.

  The applied voltage setting unit 29 controls the power supply control unit 13 to set each applied voltage selected by the optimum contrast selecting unit 28 in the electron optical system 4 (see FIG. 1) (step C4).

  The power supply control unit 13 controls the electron beam 2 so as to scan the observation region including the observation positions C and D (step C5). Thereafter, the signal processing unit 14 processes the detection signal obtained from the detector 7 (step C6), and an SEM image is displayed on the display unit 17 (step C7).

  In this way, the operator compares estimated detection values at a plurality of positions on the sample based on the estimated detection value table, and selects and designates a combination (condition number) of an acceleration voltage, an applied voltage, and the like that provides an optimum contrast. Since the designated combination is set in the actual electron optical system, an SEM image having an optimum contrast can be obtained. Note that the above combination may include an ampere turn applied to a magnetic lens such as an objective lens. In addition, the control processing unit 15 according to the second embodiment may include a simulated SEM image list display data generation unit 34 and an image selection unit 35. In this case, the simulated SEM image list display data generation unit 34 generates image data for displaying a list of all the simulated SEM images generated by the simulated SEM image data generation unit 25. The image selection unit 35 detects a simulated SEM image selected and specified by the operator from this list, and conditions are specified for each component member such as an electron optical system and a detector. Therefore, the acceleration voltage at the time of acquiring the selected simulated SEM image A contrast SEM image based on the applied voltage and the like is obtained.

  According to the second embodiment of the present invention, the estimated detection value is calculated in consideration of various conditions of the actual electron optical system and detector of the scanning electron microscope. Therefore, the selected combination is close to the set value of the electron optical system in actual observation.

  Furthermore, since a combination of acceleration voltage, applied voltage, and the like that optimize the contrast between desired positions and a simulated SEM image are obtained before actual observation, it is not necessary to repeat trial and error using an actual sample. Therefore, it is possible to perform actual observation under the specified conditions while minimizing the deterioration of the sample due to the electron beam.

(Third embodiment)
A third embodiment of the present invention will be described.

  The scanning electron microscope according to the third embodiment of the present invention further includes a detector reference table creation unit in the control processing unit 15 of the first embodiment. Other configurations are the same as those in the first embodiment. The scanning electron microscope of the present embodiment is configured so that the calculation of the estimated detection value and the generation of the simulated SEM image data described in the first and second embodiments can be performed at high speed by using a detection value reference table described later. Scanning electron microscope.

  FIG. 11 is a block diagram of the control processing unit 15 according to the present embodiment. As shown in the figure, the control processing unit 15 includes a detection value reference table creation unit 33 in addition to the configuration of the first embodiment. The detection value reference table unit 33 detects electrons detected by the detector 7 with respect to different combinations of the set values of the electron optical system 4 and the emission angle, energy, and the like of electrons (emitted electrons) emitted from the mounting position of the sample 5. A detection value reference table representing the number of reference values (reference values to be described later) is created.

  12 and 13 are flowcharts of the emission electron detection value estimation method and the SEM image simulation method according to the third embodiment of the present invention, FIG. 12 is a flowchart showing a procedure for creating a detection value reference table, and FIG. 13 is a detection value. It is a flowchart which shows the display of the simulation SEM image using a reference table, or preparation of an estimated detection value table.

  Next, each process from calculation of an estimated detection value of emitted electrons using each basic electromagnetic field distribution data to display of a simulated SEM image will be described.

  Also in this embodiment, since the basic electromagnetic field distribution described in the first embodiment is necessary for the electron trajectory calculation, first, the processing from step A1 to step A3 shown in FIG. 4 is performed. Since these processes have been described in the first embodiment, a description thereof will be omitted.

  Next, the electromagnetic field distribution calculation unit 20 reads basic electromagnetic field distribution data from the database 31 (step D1), and further reads electromagnetic field analysis data (step D2). As described in the first embodiment, the electromagnetic field analysis data is set value data such as a voltage and an ampere turn applied to each element of the electron optical system 4 and the detector 7, and a predetermined value is previously set for each element. Is set. Or you may input from an operator like step B2 shown in FIG.

  The electromagnetic field distribution calculation unit 20 calculates the electromagnetic field distribution EM (that is, the electric field distribution E and the magnetic field distribution M) using each basic electromagnetic field distribution data and electromagnetic field analysis data (step D3). The calculation method is the same as the process of step B3 in the first embodiment.

  Next, the electron trajectory calculation unit 22 reads the emission condition data (step D4). The emission condition data has a plurality of combinations such as an emission position, an emission angle, energy, and the like for emitted electrons emitted from the attachment position of the sample 5 to the objective lens 4c side. For example, the energy is set at equal intervals or logarithmic intervals from a value close to 0 eV such as 0.1 eV to an energy equal to the acceleration voltage of the electron beam 2. Further, the emission angles are set at equal intervals in all directions (all θz and θx shown in FIG. 6) from the surface when the sample 5 is assumed to the objective lens 4c side. In addition, since the surface may be inclined, the value of the emission angle θz may exceed 90 degrees. The emission position is preferably set at the intersection between the surface of the sample 5 and the central axis of the electron optical system 4 (that is, the optical axis). You may specify the position of. The emission condition data may be input by the operator from the input unit 16 or may be stored in advance in the program storage unit 30 as a part of the program. Or CPU11 may create based on the above setting conditions.

  Using such emission condition data, the electron trajectory calculation unit 22 calculates the trajectory of outgoing electrons in the electromagnetic field distribution EM (step D5). Thereafter, the CPU 11 determines whether or not the emitted electrons collide with the electron optical system 4 (step D6). If there is a collision (YES in step D6), the emitted electron calculation unit 21 causes the electron optical to be detected by the collision. The number of electrons emitted from the system 4 (second emission electrons), the emission angle, energy, and the like are calculated by the Monte Carlo method (step D7). Then, the electron trajectory calculation unit 22 calculates the trajectory of the second emitted electrons in the electromagnetic field distribution EM obtained by the process of Step D3 (Step D8).

  In step D <b> 9, the electron counting unit 23 counts the number of trajectories of the second emitted electrons that reach the detector 7, that is, the second emitted electrons detected by the detector 7. Since this detection value (second emission electron detection value) depends on the parameter of the second emission electron by the Monte Carlo method, it is preferable to calculate this parameter many times in order to obtain it with high accuracy. Accordingly, in step D10, which is the next step, it is determined whether or not the second number of emitted electrons has been calculated a predetermined number of times. If the number has not been reached (NO in step D10), the process returns to step D7 to return to the second emission. Recalculate the electrons.

  When the second emission electrons are calculated a predetermined number of times by the Monte Carlo method (YES in step D10), the electron counting unit 23 averages the second emission electron detection values obtained in step D9 (step D11), and further The number of emitted electrons (emitted electron detection value) reaching the detector 7 from the emitted electron trajectory obtained in step D5 is counted, and the average value of the second emitted electron detected values and the emitted electron detected value are added together. Then, a reference value is calculated (step D12). That is, the reference value is the number of electrons detected by the detection value 7 under a certain emission electron emission condition.

  The CPU 11 determines whether or not the reference values for all electromagnetic field distributions EM and emission conditions have been calculated (step D13). If not calculated (NO in step D13), the CPU 11 returns to step D2 for electromagnetic field analysis. Read data.

  When all the reference values have been calculated (YES in step D13), a reference value table (detection value reference table) corresponding to the set value of the electron optical system 4 and the emission conditions of the emitted electrons is created, and the database 31 is created. And the process ends (step D14). FIG. 14 is an example of the detection value reference table, and represents reference values for the energy of the emitted electrons and the emission angle θz calculated at a certain set value of the electron optical system 4.

  Note that there are cases where the emitted electrons do not collide with the electron optical system 4 or the secondary electron emission rate is extremely low (NO in step D6) depending on the material of the colliding electron optical system 4. Since the use of such materials is known to designers and the like, the processing from steps D7 to D11 may be omitted in advance. In this case, the process immediately proceeds from step D6 to step D12.

  Next, a procedure for calculating an estimated detection value using the detection value reference table and a procedure for generating simulated SEM image data will be described.

  After the detection value reference table is created by the above processing, as shown in FIG. 13, the operator accelerates the electron beam 2 and the sample data including information such as the shape and composition of the sample 5 used for observation from the input unit 16. Input conditions such as voltage, incident position, incident angle, etc. are input (step E1).

  Based on the sample data of the sample 5 and the incident conditions of the electron beam 2, the emitted electron calculation unit 21 counts the number of electrons (first emission electrons) emitted from the sample 5 by the electron beam 2, the emission angle, and the energy. Is calculated by the Monte Carlo method (step E2).

  The estimated detection value calculation unit 24 selects, from the detection value reference table, emitted electrons with conditions close to the emission angle and energy of each first emitted electron (step E3). For example, it is assumed that the energy of the first emission electrons is 1.3 eV and the emission angle θz is 38 degrees. In this case, in the detection value reference table shown in FIG. 14, the closest emitted electron is an emitted electron having an energy of 1 eV and an emission angle of 45 degrees, and the reference value is 1. Therefore, the CPU 11 sets the number of electrons (estimated detection value) detected by the detector 7 due to the event of emitting the first emitted electrons to 1 (step E4). Alternatively, it is assumed that the energy of the first emission electrons is 999.8 eV and the emission angle is 41 degrees. In this case, the nearest outgoing electron in the detection value reference table has an energy of 1000 eV and an emission angle of 45 degrees, and its reference value is 1.87. Therefore, the CPU 11 sets the estimated detection value due to this event to 1.87. As described above, in step E4, the reference value of the emitted electron that minimizes the difference between the energy and the emission angle with respect to the first emission electron is selected, and the estimated detection value of the event in which this reference value emits the first emission electron. Set to

  Since the first emission electrons are calculated by the Monte Carlo method, it is necessary to perform repeated calculation to increase accuracy. Therefore, in step E5, the CPU 11 determines whether or not the first number of emitted electrons has been calculated a predetermined number of times. If the predetermined number of times has not been reached (NO in step E5), the CPU 11 returns to step E2 and performs the first emission. Recalculate the electrons by Monte Carlo method. When the predetermined number of times has been reached (YES in step E5), the CPU 11 averages the obtained plurality of estimated detection values (step E6).

  Next, the CPU 11 determines whether or not the estimated detection values are calculated for all the incident conditions (step E7). If not calculated (NO in step E7), the incident condition is changed, Return to Step E2. When estimated detection values are calculated for all incident conditions (YES in step E7), the CPU 11 further creates an averaged estimated detection value as an estimated detection value table (step E7) and stores it in the database 31. To do.

  At this time, estimated detection values are calculated for all the incident conditions. The CPU 11 creates these estimated detection values as an estimated detection value table (step E8) and stores them in the database 31.

  The simulated SEM image data generation unit 25 generates simulated SEM image data by arranging the intensity corresponding to each incident position from the estimated detection values in the estimated detection value table stored in the database 31 (step E9). When the simulated SEM image is displayed on the display unit 17 using the simulated SEM image data (step E10), the entire process is completed.

  According to this embodiment, the same effects as those of the first embodiment can be obtained, and furthermore, the calculation of the estimated detection value and the generation of the simulated SEM image data can be performed at high speed.

  In addition, in this embodiment, the electromagnetic field distribution generated by the electron optical system and detector of the scanning electron microscope is calculated in advance. Furthermore, the number of detected electrons emitted from the sample position in the electromagnetic field distribution and the secondary electrons resulting from the emitted electrons is obtained as a reference value for each emission condition of the emitted electrons, and these are stored as a detected value reference table. . Then, by applying the energy, emission angle, etc. of the electrons emitted from the sample to the emission conditions of the emitted electrons in the detection value reference table, the detection value of the event that has emitted the electrons is obtained from the reference values in the detection value reference table. . In other words, the number of electrons detected by the detector is stored as a detection value reference table for electrons of all emission conditions, so there is no need to separately calculate the trajectory of electrons emitted from the sample. Value estimation is fast and easy.

  Similarly to the first embodiment, the control processing unit 15 may include a simulated SEM image list display data generation unit 34 for displaying a list of all simulated SEM images (see FIG. 11). The list display of images can be observed.

(Fourth embodiment)
A fourth embodiment of the present invention will be described.

  The scanning electron microscope according to the fourth embodiment has the configurations of the second and third embodiments. That is, the scanning electron microscope is configured to obtain an SEM image having an optimum contrast using the estimated detection value table.

  In addition to the configuration of the third embodiment, the scanning electron microscope according to the fourth embodiment includes an optimal contrast selection unit 28 and an applied voltage setting unit 29 in the control processing unit 15 shown in FIG. 9 (not shown). In the scanning electron microscope according to the present embodiment, the processes shown in FIGS. 4 and 12 and the processes from Step E1 to Step E8 shown in FIG. 13 are performed. Next, instead of Step E9 and Step E10, FIG. Processing from step C1 to step C7 shown is performed. That is, in the scanning electron microscope according to the fourth embodiment, similarly to the second embodiment, the applied voltage and ampere turn of the electron optical system that provides the optimum contrast are selected based on the calculated estimated detection value. The actual observation using is performed.

  In this embodiment, the same effect as in the third embodiment can be obtained.

  In addition, since a combination of an acceleration voltage, an applied voltage, and the like that optimize the contrast between desired positions is obtained before actual observation, it is not necessary to repeat trial and error using an actual sample. Moreover, since the detection value reference table is used, the above combinations can be easily obtained. Therefore, actual observation can be performed in a state where deterioration of the sample due to the electron beam is minimized.

  The control processing unit 15 according to the present embodiment may include the simulated SEM image list display data generation unit 34 and the image selection unit 35 described in the second embodiment. In this case, all the simulated SEM images generated by the simulated SEM image data generation unit 25 are displayed in a list, and when the operator selects and designates from this list, the components such as the electron optical system and the detector are the conditions at the time of simulation. Therefore, a contrast SEM image based on the acceleration voltage, applied voltage, and the like at the time of obtaining the simulated SEM image is obtained.

It is a schematic diagram of the scanning electron microscope which concerns on this invention. It is a block diagram of the control processing part which concerns on 1st Embodiment of this invention. It is a schematic diagram around the objective lens according to the present invention. It is a flowchart which shows the preparation procedure of the basic electromagnetic field distribution data based on this invention. It is a flowchart which shows the preparation procedure of the estimated detection value table using the basic electromagnetic field distribution data which concerns on 1st Embodiment of this invention, and the display procedure of a simulation SEM image. It is a schematic diagram which shows an example of the sample used for this invention, and an example of an emitted electron or a 1st emission electron. It is a numerical table for demonstrating calculation of an estimated detection value. It is an example of the estimated detection value table of this invention. It is a block diagram of a control processing part concerning a 2nd embodiment of the present invention. It is a flowchart which shows the display procedure of the SEM image which concerns on 2nd Embodiment of this invention. It is a block diagram of the control processing part which concerns on 3rd Embodiment of this invention. It is a flowchart which shows the preparation procedure of the detection value reference table which concerns on this invention. It is a flowchart which shows the display procedure of the simulation SEM image which concerns on 3rd Embodiment of this invention. It is an example of the detection value reference table which concerns on 3rd Embodiment of this invention.

Explanation of symbols

1: microscope main body 2: electron beam 3: electron gun 4: electron optical system 4c: objective lens 7: detector 8: power supply unit 10: control device 11: CPU
15: Control processing unit 20: Electromagnetic field distribution calculation unit 21: Emission electron calculation unit 22: Electron trajectory calculation unit 23: Electron counting unit 24: Estimated detection value calculation unit 25: Simulated SEM image data generation unit 28: Optimal contrast selection unit 29 : Applied voltage setting unit 33: Detection value reference table creation unit

Claims (19)

A first step of pre-calculating the electromagnetic field distribution produced by the electron optics and detector in the scanning electron microscope;
A second step of inputting sample data relating to at least the shape and composition of a sample placed in the electromagnetic field distribution, and an incident condition of an electron beam incident on the sample;
A third step of calculating a first emission electron from the sample by the electron beam based on the input sample data and the incident condition by a Monte Carlo method;
A fourth step of calculating a trajectory of the first emission electrons in the electromagnetic field distribution based on a parameter of the first emission electrons obtained by the third step;
A fifth step of counting the first emitted electrons reaching the detector based on the calculation result of the fourth step;
A sixth step of calculating the average value of the count values obtained in the fifth step as an estimated detection value by repeating the third to fifth steps a predetermined number of times;
An emission electron detection value estimation method comprising: In the fourth step, when the first emission electron collides with the electron optical system or the like, the second emission electron emitted from the electron optical system or the like by the collision is replaced with the Monte Carlo method instead of the fourth step. Calculated by
In the fifth step, instead of the fifth step, the orbit of the second emission electron in the electromagnetic field distribution is calculated based on the parameter of the second emission electron obtained by the fourth step, The method according to claim 1, further comprising: counting second emitted electrons that reach the detector. The detection value estimation method according to claim 1, further comprising:
Performing the sixth step for each incident position of the incident beam to calculate an estimated detection value for each incident position;
Generating simulated SEM image data in which intensities corresponding to the estimated detection values are arranged in association with the incident positions. A first step of pre-calculating the electromagnetic field distribution produced by the electron optics and detector in the scanning electron microscope;
A second step of setting a plurality of different combinations of the energy and exit angle of the emitted electrons emitted from the sample position within the electromagnetic field distribution;
A third step of calculating a trajectory of the emitted electrons in the electromagnetic field distribution based on the plurality of combinations;
Based on the calculation result of the third step, the emitted electrons that reach the detector are counted, the counted value is used as a reference value, and a detection value reference table is created in which each combination is associated with the reference value. A fourth step to:
A fifth step of inputting sample data relating to at least the shape and composition of the sample placed at the sample position and an incident condition of an electron beam incident on the sample;
A sixth step of calculating a first emission electron from the sample by the electron beam based on the input sample data and the incident condition by a Monte Carlo method;
For all the first emission electrons calculated in the sixth step, select the emission electrons in the detection value reference table having the smallest difference in energy and emission angle, and select the emission electrons selected. A seventh step of calculating a total value of reference values;
Calculating an average value of the total values obtained by repeating the sixth and seventh steps a predetermined number of times, and setting the average value as an estimated detection value of the emitted electrons from the incident position;
An emission electron detection value estimation method comprising: In the third step, when the emitted electrons collide with the electron optical system or the like, a ninth step of calculating a second emission electron emitted from the electron optical system or the like by the collision by a Monte Carlo method;
A tenth step of calculating a trajectory of the second emission electrons in the electromagnetic field distribution based on a parameter of the second emission electrons obtained by the ninth step;
An eleventh step of counting the second emitted electrons that have reached the detector;
Further comprising
5. The emitted electrons according to claim 4, wherein the ninth to eleventh steps are executed a plurality of times, and the obtained count value of the second emitted electrons is averaged and added to the reference value. Detection value estimation method. The detection value estimation method according to claim 4, further comprising:
Performing the eighth step for each incident position of the incident beam and calculating an estimated detection value thereof;
Generating simulated SEM image data in which intensities corresponding to the estimated detection values are arranged in association with the incident positions. Computer
A first means for pre-calculating the electromagnetic field distribution produced by the electron optics and detector in the scanning electron microscope;
A second means for inputting sample data relating to at least the shape and composition of the sample placed in the electromagnetic field distribution and an incident condition of an electron beam incident on the sample;
A third means for calculating a first emission electron from the sample by the electron beam based on the input sample data and the incident condition by a Monte Carlo method;
A fourth means for calculating a trajectory of the first emission electrons in the electromagnetic field distribution based on a parameter of the first emission electrons obtained by the third means;
Fifth means for counting the first emitted electrons reaching the detector based on the calculation result by the fourth means;
The third to fifth means are repeated a predetermined number of times to function as sixth means for calculating an average value of the count values obtained by the fifth means as an estimated detection value. Electronic detection value estimation program. The fourth means calculates a second emission electron emitted from the electron optical system or the like by the collision when the first emission electron collides with the electron optical system or the like by a Monte Carlo method,
The said 5th means calculates the orbit of the said 2nd emission electron in electromagnetic field distribution based on the parameter of the said 2nd emission electron obtained by the said 4th means. The emitted electron detection value estimation program described. The computer,
Each means according to claim 7 or 8,
Function as means for generating simulated SEM image data in which the intensity according to the estimated detection value is arranged in association with the incident position;
The SEM image simulation program characterized in that the sixth means is performed for each incident position of the incident beam and calculates an estimated detection value for each incident position. Computer
A first means for pre-calculating the electromagnetic field distribution produced by the electron optics and detector in the scanning electron microscope;
A second means for setting a plurality of different combinations of the energy and exit angle of the emitted electrons emitted from the sample position within the electromagnetic field distribution;
A third means for calculating a trajectory of the emitted electrons in the electromagnetic field distribution based on the plurality of combinations;
Based on the calculation result by the third means, the emitted electrons reaching the detector are counted, the counted value is used as a reference value, and a detection value reference table in which each combination is associated with the reference value is created. A fourth means to:
Fifth means for inputting sample data relating to at least the shape and composition of the sample placed at the sample position and the incident condition of the electron beam incident on the sample;
Sixth means for calculating a first emission electron from the sample by the electron beam based on the input sample data and the incident condition by a Monte Carlo method;
For all the first emission electrons calculated by the sixth means, select the emission electrons in the detection value reference table having the smallest difference in energy and emission angle, and the selected emission electrons A seventh means for calculating the total value of the reference values;
As an eighth means for calculating an average value of the total values obtained by repeating the sixth and seventh means a predetermined number of times, and calculating the average value as an estimated detection value of the emitted electrons from the incident position. An emission electron detection value estimation program characterized by causing it to function. Said computer further
When the emitted electrons collide with the electron optical system or the like in the trajectory calculation by the third means, ninth means for calculating the second emitted electrons emitted from the electron optical system or the like by the collision by the Monte Carlo method When,
Tenth means for calculating a trajectory of the second emitted electrons in the electromagnetic field distribution based on a parameter of the second emitted electrons obtained by the ninth means;
Function as an eleventh means for counting the second emitted electrons that have reached the detector;
11. The emitted electrons according to claim 10, wherein the ninth to eleventh means are executed a plurality of times, and the obtained count value of the second emitted electrons is averaged and added to the reference value. Detection value estimation program. The computer,
Each means according to claim 10 or 11,
Function as means for generating simulated SEM image data in which the intensity according to the estimated detection value is arranged in association with the incident position;
The SEM image simulation program, wherein the eighth means is performed for each incident position of the incident beam to calculate an estimated detection value. In a scanning electron microscope comprising at least an electron optical system and a detector,
An electromagnetic field distribution calculation unit for calculating in advance the electromagnetic field distribution generated by the electron optical system and the detector;
A data input unit for inputting sample data relating to at least the shape and composition of the sample placed in the electromagnetic field distribution and an electron beam incident condition incident on the sample;
An emission electron calculation unit that calculates a first emission electron from the sample by the electron beam based on the input sample data and the incident condition by a Monte Carlo method;
An electron trajectory calculation unit that calculates a trajectory of the first emission electrons in the electromagnetic field distribution based on a parameter of the first emission electrons obtained by the emission electron calculation unit;
Based on the calculation result by the electron trajectory calculation unit, an electron counting unit that counts the first emitted electrons reaching the detector;
Each process of the emission electron calculation unit, the electron trajectory calculation unit, and the electron counting unit is executed a predetermined number of times for each incident position of the incident beam, and an average value of count values obtained by the electron counting unit is estimated and detected. An estimated detection value calculation unit to calculate as a value;
A simulated SEM image data generating unit that generates simulated SEM image data in which intensities corresponding to the estimated detection values are arranged in association with each incident position;
A simulated SEM image display unit for displaying a simulated SEM image based on the simulated SEM image data;
A scanning electron microscope comprising: In the orbit calculation by the electron orbit calculation unit, when the first emission electrons collide with the electron optical system or the like, the emission electron calculation unit calculates the second emission electrons emitted from the electron optical system or the like by the collision. Calculated by Monte Carlo method,
The electron trajectory calculation unit calculates the trajectory of the second emission electrons in the electromagnetic field distribution based on the parameters of the second emission electrons obtained by the emission electron calculation unit,
The scanning electron microscope according to claim 13, wherein the electron counting unit further counts the second emitted electrons that reach the detector. In a scanning electron microscope comprising at least an electron optical system and a detector,
An electromagnetic field distribution calculation unit for calculating in advance the electromagnetic field distribution generated by the electron optical system and the detector;
A parameter setting unit for setting a plurality of different combinations of energy and emission angle of emitted electrons emitted from the sample position in the electromagnetic field distribution;
Based on the plurality of combinations, an electron trajectory calculation unit that calculates a trajectory of the emitted electrons in the electromagnetic field distribution;
Based on the calculation result by the electron trajectory calculation unit, an electron counting unit that counts the emitted electrons reaching the detector;
A detection value reference table creating unit that creates a detection value reference table in which each of the combinations is associated with the reference value, using the count value obtained by the electronic counting unit as a reference value;
A data input unit for inputting sample data relating to at least the shape and composition of the sample placed at the sample position and the incident condition of the electron beam incident on the sample;
An emission electron calculation unit that calculates a first emission electron from the sample by the electron beam based on the input sample data and the incident condition by a Monte Carlo method;
For all the first emission electrons calculated by the emission electron calculation unit, select the emission electrons in the detection value reference table having the smallest difference in energy and emission angle, and the selected emission electrons An estimated detection value calculation unit that calculates a total value of reference values as an estimated detection value of emitted electrons from the incident position;
A simulated SEM image data generating unit that generates simulated SEM image data in which the intensity corresponding to the estimated detection value is arranged in association with the incident position;
An SEM image display unit for displaying an SEM image based on the simulated SEM image data;
With
The scanning electron microscope characterized in that the reference value is averaged by calculating the first emission electrons by a Monte Carlo method a plurality of times. When the emitted electrons collide with the electron optical system or the like in the orbit calculation by the electron orbit calculation unit, the emission electron calculation unit calculates the second emission electrons emitted from the electron optical system or the like by the collision by the Monte Carlo method. And
The electron trajectory calculation unit calculates the trajectory of the second emission electrons in an electromagnetic field distribution based on the parameters of the second emission electrons obtained by the emission electron calculation unit,
The electron counting unit further counts the second emitted electrons reaching the detector,
16. The scanning electron microscope according to claim 15, wherein the reference value is averaged and added to the reference value by performing calculation of the second emission electrons by a Monte Carlo method a plurality of times. In a scanning electron microscope comprising at least an electron optical system including at least one electrode and a detector,
An electromagnetic field distribution calculation unit for calculating in advance the electromagnetic field distribution generated by the electron optical system and the detector with respect to a predetermined plurality of voltage values applied to the electrodes;
A data input unit for inputting sample data on at least the shape and composition of the sample placed in each electromagnetic field distribution and a plurality of incident positions of an electron beam incident on the sample;
An emission electron calculation unit for calculating a first emission electron from the sample by the electron beam by a Monte Carlo method based on the input sample data and the incident position and a plurality of incident energy values of the electron beam;
An electron trajectory calculation unit that calculates a trajectory of the first emission electrons in the electromagnetic field distribution based on a parameter of the first emission electrons obtained by the emission electron calculation unit;
Among the trajectories calculated by the electron trajectory calculation unit, an electron counting unit that counts the first emitted electrons that reach the detector;
The emission electron calculation unit, the electron trajectory calculation unit, and the electron counting unit are repeatedly executed a predetermined number of times for each incident position, and the average value of the count values obtained by the electron counting unit is estimated for each incident position. An estimated detection value calculation unit for calculating as a detection value;
An optimal contrast selection unit that selects the incident energy and the voltage value of the combination having the highest contrast from the combination of the estimated detection values of the plurality of incident positions in the plurality of incident energy values;
An applied voltage setting section for setting the selected incident energy and the voltage value in the electron optical system;
A scanning electron microscope comprising: When the first emission electrons collide with the electron optical system or the like in the orbit calculation by the electron orbit calculation unit, the emission electron calculation unit further displays the second emission electrons emitted from the electron optical system or the like due to the collision. Calculated by Monte Carlo method,
The electron trajectory calculation unit calculates the trajectory of the second emission electrons in the electromagnetic field distribution based on the parameters of the second emission electrons obtained by the emission electron calculation unit,
The scanning electron microscope according to claim 17, wherein the electron counting unit further counts the second emitted electrons reaching the detector based on a calculation result by the electron trajectory calculating unit. In a scanning electron microscope comprising at least an electron optical system including at least one electrode and a detector,
An electromagnetic field distribution calculation unit for calculating in advance the electromagnetic field distribution generated by the electron optical system and the detector with respect to a predetermined plurality of voltage values applied to the electrodes;
A data input unit for inputting sample data on at least the shape and composition of the sample placed in each electromagnetic field distribution and a plurality of incident positions of an electron beam incident on the sample;
An emission electron calculation unit for calculating a first emission electron from the sample by the electron beam by a Monte Carlo method based on the input sample data and the incident position and a plurality of incident energy values of the electron beam;
An electron trajectory calculation unit that calculates a trajectory of the first emission electrons in the electromagnetic field distribution based on a parameter of the first emission electrons obtained by the emission electron calculation unit;
Among the trajectories calculated by the electron trajectory calculation unit, an electron counting unit that counts the first emitted electrons that reach the detector;
The emission electron calculation unit, the electron trajectory calculation unit, and the electron counting unit are repeatedly executed a predetermined number of times for each incident position, and the average value of the count values obtained by the electron counting unit is estimated for each incident position. An estimated detection value calculation unit for calculating as a detection value;
A simulated SEM image list display data generator for displaying a list of all simulated SEM images generated by the simulated SEM image data generator;
An image selection unit selected by the operator from the displayed simulated SEM images;
An applied voltage setting unit that sets the incident energy and the voltage value corresponding to the selected simulated SEM image in the electron optical system;
A scanning electron microscope comprising:

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