JP2005302468A - Method and apparatus for displaying simulation image of charged particle beam device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for displaying simulation image of a charged particle beam device, which facilitate operator's or adjustor's mastering techniques for correcting aberration and understanding the procedures for the correction. <P>SOLUTION: The charged particle beam device having an aberration corrector comprises an operation input 44 which inputs a beam control condition from an operation; and a calculation means 45 which performs calculation for simulation on the basis of correction data of the beam control condition input from the operation input 44, to display a cross sectional shape of the beam after the correction and a simulation result of an image of a sample on a displaying means 50. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a simulation image display method and apparatus for a charged particle beam apparatus.
About.

  In a scanning electron microscope or a transmission electron microscope, an aberration correction apparatus is incorporated in an electron optical system for the purpose of observing a high resolution image or increasing a probe current density. As this aberration correction apparatus, a method has been proposed in which chromatic aberration is corrected by a combination of an electrostatic quadrupole and a magnetic quadrupole, and spherical aberration is corrected by a four-stage octupole. The principle is introduced in detail in Non-Patent Documents 1 to 3.

  Here, an outline of the principle of the aberration correction apparatus described above will be described with reference to FIG. In FIG. 4, an aberration correction device C is disposed in front of the objective lens 7. The aberration correction device C generates a magnetic potential distribution similar to the potential distribution generated by the four-stage electrostatic multipole 1, 2, 3, 4 and the second and third stages of the electrostatic multipole. Two-stage magnetic quadrupoles 5, 6 that form a superimposed magnetic field, and four-stage electrostatic octupoles 11, 12, that form an electric field superimposed on the electric field formed by the four-stage electrostatic quadrupole. 13 and 14.

In the configuration of FIG. 4, the charged particle beam incident from the left side of the drawing forms a reference charged particle beam trajectory by the four-stage electrostatic quadrupole 1, 2, 3, 4 and the objective lens 7. The charged particle beam is focused on the sample surface 15. In FIG. 8, the trajectory _{Rx in} the X direction and the trajectory _{Ry in the} Y direction of the particle beam are schematically drawn on the same plane.

The reference trajectory is a paraxial trajectory (which can be considered as a trajectory when there is no aberration), and the trajectory R _{y in the} Y direction passes through the center of the quadrupole 2 by the quadrupole 1 and the trajectory R in the X direction by the quadrupole 2. _This is a trajectory where _x passes through the center of the quadrupole 3 and finally the charged particle beam is focused on the sample surface by the quadrupoles 3 and 4 and the objective lens 7. In practice, these mutual adjustments are necessary for complete focus. At this time, the four-stage dipole is used for axial alignment.

Referring to FIG. 4 in more detail, the charged particle beam of the trajectory _{Rx in} the X direction is diffused by the quadrupole 1 (acting like a concave lens) and then focused by the quadrupole 2 (acting like a convex lens). After passing through the center of the quadrupole 3 and passing through the center of the quadrupole 3, the light is focused by the quadrupole 4 and travels toward the objective lens 7. On the other hand, the charged particle beam of the orbit R _{y in} the Y direction is focused by the quadrupole 1 so as to pass through the center of the quadrupole 2, and after passing through the center of the quadrupole 2, is focused by the quadrupole 3. After being diffused by the quadrupole 4, it goes to the objective lens 7. In this way, by combining the diffusing action of the quadrupole 1 acting on the X-direction trajectory R _x and the diffusing action of the quadrupole 4 acting on the Y-direction trajectory R _y , like a single concave or convex lens. Can work.

Next, chromatic aberration correction by the aberration correction apparatus C will be described. In order to first correct chromatic aberration in the system as shown in FIG. 4, the potential φ _q2 [V] of the electrostatic quadrupole 2 and the excitation J ₂ [ AT] (or magnetic position) is adjusted, and the chromatic aberration in the X direction is corrected to 0 as the entire lens system. Similarly, the potential φ _q3 [V] of the electrostatic quadrupole 3 and the excitation J ₃ [AT] of the magnetic quadrupole 6 are adjusted so as not to change the reference trajectory, and the chromatic aberration in the Y direction is reduced to 0 as the entire lens system. It is corrected.

Next, spherical aberration correction (third-order aperture aberration correction) will be described. When correcting the spherical aberration, after correcting the chromatic aberration in the X and Y directions, the spherical aberration in the X direction is corrected to 0 as the entire lens system by the potential φ _O2 [V] of the electrostatic octupole 12. The spherical aberration in the Y direction is corrected to 0 by the potential φ _O3 [V] of the electrostatic octupole 13.

  Next, the spherical aberration in the direction in which XY is synthesized is corrected to 0 by the electrostatic octupoles 11 and 14. In practice, alternate repeated adjustments are required. In addition, the superposition of the potential and excitation of the quadrupole and octupole uses a single 12-pole to change the potential and excitation applied to each 12-pole, dipole, quadrupole, hexapole, octupole, etc. Has been synthesized and put into practical use. This method is introduced in Non-Patent Document 4, for example.

That is, in the case of the electrostatic type, as shown in FIG. 5, the final-stage power supply _An (n (n) that can supply voltage independently to the twelve electrodes _Un (n = 1, 2,..., 12)). = 1, 2,..., 12) are connected to form a quadrupole field, the output voltage from the quadrupole power supply 20 is set to each final stage power supply A so that a field close to an ideal quadrupole field can be obtained. supplied to _n . Assuming the output voltage of the final-stage power supply A _n is proportional to the output voltage of the quadrupole power supply 20, 4 the ratio of the output voltage of the quadrupole power supply 20 becomes a value shown in Non-Patent Document 4 above. In addition, when an octupole field is created by overlapping this quadrupole field, the output voltage from the octupole power supply 28 is the output voltage of the quadrupole power supply 20 so that a field close to an ideal octupole field can be obtained. It is added and supplied to the final-stage power a _n. In the same way, a field in which a multipole field of 2n poles (n = 1, 2,... 6) is overlapped by one 12-pole element is obtained.

Next, in the case of the magnetic field type, as shown in FIG. 6, the final stage power supply B _{n that} can supply the excitation current independently to the coils of 12 magnets W _n (n = 1, 2,. When (n = 1, 2,..., 12) are connected to form a magnetic quadrupole field, the magnetic quadrupole power supply 15 is used so that a field close to an ideal magnetic quadrupole field can be obtained. Output voltage is supplied to each power source B _n . If it is assumed that the output current of the final stage power supply _Bn is proportional to the output voltage of the magnetic field type quadrupole power supply 15, the ratio of the output voltages is the ratio of the excitation force shown in Non-Patent Document 4 above. In the present invention, the superposition of multipole fields other than the magnetic field type quadrupole field is not explained, but by adding the voltage of the multipole field to the input voltage of the final stage power supply _Bn , the electrostatic type is added. Magnetic field type multipole field can be superimposed. Here, the yoke connecting the outside of each magnet W _n 6 magnetically is omitted.

Then, when superimposing the electrostatic and magnetic types, magnets W _n may be used a conductive magnetic material so that it can serve as the electrode U _n. In this case, the magnet coil is arranged to be electrically insulated from the electrode.

  In the following description, in order to simplify the description, it is described as if 2n poles are overlapped with each other, but in reality, the superposition of a plurality of multipole fields on one twelve pole is the voltage as described above. This is done by adding signals.

Note that it may be necessary to correct secondary aperture aberration due to four-stage hexapoles after chromatic aberration correction and before spherical aberration correction. The correction method is performed in the same procedure as the spherical aberration correction method. This second-order aperture aberration is generated depending on the mechanical accuracy of the aberration correction apparatus, but usually the correction amount is small and the influence on the high-order aberration is small in the range of the aberration correction apparatus. As a conventional apparatus of this type, an aberration correction apparatus for a charged particle beam apparatus capable of performing stable and optimal aberration correction for a long time is known (for example, see Patent Document 1).
JP 2003-203593 A H. Rose, Optik 33, Heft 1, 1-24 (1971) J. Zach, Optik 83, No.1, 30-40 (1989) J. Zach and M. Haider, Nucl. Instr. And Meth. In Phys. Res. A 363, 316-325 (1995) M. Haider et al., Optik 63, No. 1, 9-23 (1982)

  The aberration correction procedure according to the conventional technique is complicated as described above, and it is difficult to understand the directionality or symmetry of the image blur at each stage of the procedure. It took a considerable amount of education to learn and understand the procedure.

  The present invention has been made in view of such a problem, and a simulation image of a charged particle beam apparatus that makes it easy for an operator or a coordinator to learn the aberration correction technique and understand the procedure. It is an object to provide a display method and apparatus.

  According to the first aspect of the present invention, in the charged particle beam apparatus including the aberration correction unit, the calculation unit performs a simulation calculation based on the correction data of the beam control condition from the operation unit, and calculates the beam cross-sectional shape and the sample image after the calculation. The simulation result is displayed on the display means.

  According to a second aspect of the present invention, the calculation means calculates the trajectory and aberration coefficient of the charged particle from the electromagnetic field applied to the particle optical system, and the two-dimensional current of the charged particle at the sample surface position from the aberration coefficient. A density distribution is calculated, an image when the sample surface is scanned using the probe of the current density distribution is calculated, and at least one of the calculation results is displayed on a display means.

The invention according to claim 3 is characterized in that the calculation means calculates a third-order or less aperture aberration coefficient as the aberration coefficient.
The invention according to claim 4 is characterized in that the calculation means calculates a first-order chromatic aberration coefficient as the aberration coefficient.

The invention according to claim 5 is characterized in that the calculation means calculates a distribution when the sample surface position is arbitrarily shifted as the current density distribution.
According to a sixth aspect of the present invention, in a charged particle beam apparatus including an aberration corrector, an operation input unit that inputs a beam control condition from the operation unit, and correction data of the beam control condition input from the operation input unit are used. And a calculation means for performing a simulation calculation and displaying the corrected cross-sectional shape of the beam and the simulation result of the sample image on the display means.

  According to the first aspect of the present invention, since the calculation results at each correction stage at the time of aberration correction are displayed on the display means, it is easy for an operator or an adjuster to learn the aberration correction technique and understand the procedure. Can be.

  According to the second aspect of the present invention, based on the two-dimensional current density distribution of charged particles, an image when the sample surface is scanned using the probe of the current density distribution can be displayed on the display means. Therefore, it is possible to make it easy for an operator or a coordinator to learn the aberration correction technique and understand the procedure.

According to a third aspect of the present invention, the calculating means can calculate a third or lower order aberration coefficient as an aberration coefficient.
According to a fourth aspect of the present invention, the calculating means can calculate a primary chromatic aberration coefficient as an aberration coefficient.

According to the fifth aspect of the invention, the pre-calculation means can calculate the distribution when the sample position is arbitrarily shifted.
According to the sixth aspect of the present invention, when the aberration correction is calculated by the aberration corrector, the simulation calculation result is displayed by the display means. Therefore, the operator or the adjuster learns the aberration correction technique and understands the procedure. To make it easier to do.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, 31 is an objective aperture provided along the optical path, and 32 to 35 are four-stage electrostatic multipoles. Among these multipoles, 33 and 34 also have a function as a magnetic field type multipole capable of superimposing a magnetic potential distribution similar to the potential distribution. Reference numeral 36 denotes an objective lens (OL) for irradiating the sample surface with an electron beam, and reference numeral 37 denotes a sample surface.

  38 is a first stage multipole electrode power supply, 39 is a second stage multipole electrode / coil power supply, 40 is a third stage multipole electrode / coil power supply, 41 is a fourth stage multipole power supply, and 42 is an objective. This is the power supply for the lens. These power sources are power sources for generating a dipole electric field, a quadrupole electric field, a hexapole electric field, an octupole electric field, and a quadrupole magnetic field in the electrostatic multipole elements 32-35. A control unit 43 controls the power supplies 38 to 42 based on the setting in the operation input unit 44. For example, a computer is used as the control unit 43. An operation input unit 44 is connected to the control unit 43 and inputs various commands. As the operation input unit 44, for example, a keyboard, a mouse, a knob or the like is used. Reference numeral 45 denotes an arithmetic unit that is connected to the operation input unit 44 and that performs arithmetic calculations and outputs the results, which characterizes the present invention.

  Data necessary for calculating the simulation state is stored in advance in the calculation unit 45. For example, data such as how an image is obtained when the objective lens knob is rotated in a certain direction is stored in advance. Reference numeral 50 denotes a display unit that displays an image. For example, a CRT or a liquid crystal display device is used as the display unit 50.

  Reference numeral 51 denotes a secondary electron detector disposed in the vicinity of the sample surface 37. The output of the secondary electron detector 51 is input to the control unit 43. The control unit 43 gives measurement image information to the display unit 50. On the other hand, the calculation unit 45 provides a simulation image. As a result, the measurement image A and the simulation image B are displayed on the display unit 50. The operation of the apparatus configured as described above will be described as follows.

  The gist of the present invention is as follows. For example, it is assumed that a beginner is operating this aberration correction apparatus. Therefore, an actually measured image is displayed on the display unit 50, but it is not a satisfactory image. For example, it is assumed that a blurred image is displayed. In such a case, since the beginner does not know how to change which part of the image, the operation may not be performed. In such a case, a simulation image is displayed on the display unit 50 in advance. It is assumed that the displayed image is a blurred image. The operator operates the knob of the operation input unit 44 to recognize how the image displayed on the display unit 50 changes as a result. That is, when the operator turns the knob of the operation input unit 44 to the right, for example, it is assumed that the blurred image has become a clear image.

  Therefore, the operator erases the simulation image to make only the measurement image, and turns the operation knob clockwise as described above. As a result, the measurement image becomes a focused image. In this way, adjustment is performed in a state in which the actual change in the measurement image is recognized in advance from the image change due to the simulation. As a result of this adjustment, the control unit 43 gives a control signal to the power supplies 38 to 42 to drive in a direction in which aberrations are eliminated. Then, a focused image is obtained on the display unit 50.

  Hereinafter, the present invention will be described in detail. First, in the initial state, the sample surface 37 is irradiated with an electron beam, and secondary electrons emitted from the surface are detected by the detector 51. Note that the image to be detected need not be secondary electrons, and may be emitted electrons or the like. The control unit 43 receives the image signal from the detector 51, performs predetermined image processing, and then causes the display unit 50 to display an image. Here, it is assumed that the image displayed on the display unit 50 is not a clear image.

  Therefore, the operator operates the operation input unit 44 to transmit a command to the control unit 43 to set the apparatus in the simulation mode. In the simulation mode, the control unit 43 displays a simulation image on the display unit 50 in addition to the measurement image. Therefore, the operator refers to the simulation image and adjusts so that the simulation image becomes clear by turning, for example, a knob from the operation input unit 44 when the image is not clear.

  The operator stores the operation procedure when the knob of the operation input unit 44 is adjusted so that the image becomes clear. Then, only the measurement image is displayed on the display unit 50, and adjustment is performed so that the measurement image becomes clear by operating a knob or the like according to the procedure performed by the simulation. Specifically, in accordance with the adjustment from the operation input unit 44, the control unit 43 controls the power supplies 38 to 42 to correct aberrations. As a result, it is possible to make it easy for an operator or a coordinator to learn the aberration correction technique and understand the procedure.

  FIG. 2 is an explanatory diagram of the simulation according to the present invention. Reference numeral 60 denotes an image before simulation. Here, when the operator operates the operation input unit 44, the central image 60 changes. 61 is an image with noise in the horizontal direction, 62 is an image with noise in the horizontal direction, 63 is an image with noise in the vertical direction, and 64 is an image with noise in the vertical direction. Here, for example, it is assumed that the adjustment knob is turned with respect to the image 61 so that the image becomes a clear image as indicated by 60. When the adjustment knob is turned, the calculation unit 35 stores the calculation formula for turning the adjustment knob, so that the calculation according to the state of the input operation procedure is performed and displayed on the display unit 50.

  The operator remembers the operation sequence at this time. Also, remember the operation sequence that makes the images clear for the other images 62 to 64. Therefore, the simulation image is deleted and the actually measured image is displayed on the display unit 50. When the measurement image is an image with noise, the operator can obtain a clear image as indicated by 60 by rotating the operation knob. The above operation is exactly the same for the 62 to 64 images.

  For example, each time the operation input unit 44 is operated to correct aberration using the electrostatic multipole elements 32 to 35, the set value is sent to the calculation unit 45. The calculation unit 45 has in advance electromagnetic field data when a unit voltage or unit current is applied to the electrostatic multipole elements 32 to 35, and is actually added based on the set value set by the operation input unit 44. The electromagnetic field is calculated. Using the electromagnetic field, the trajectory and aberration coefficient of the charged particles are calculated.

  A current density distribution of charged particles at the sample surface position is calculated from the obtained aberration coefficient, and an image when the sample surface is scanned using the current density distribution as a probe is calculated. FIG. 3 is an explanatory diagram of the simulation operation. (A) is a trajectory of the charged particle beam, (b) is a cross-sectional shape of the charged particle beam for scanning the sample, (c) is an image to be changed, (d) is a charged particle beam shown in (a). It is an image obtained by calculation as a result of using and scanning the sample shown in (c). Among such images, images at each stage, for example, images such as (b) and (d) are displayed on the display unit 50.

  By doing in this way, based on the two-dimensional current distribution density of the charged particles, an image when the sample surface is scanned using the probe of the current density distribution can be displayed on the display unit 50. An operator or a coordinator can easily learn the aberration correction technique and understand the procedure.

  As described above, according to the present invention, since the state of the current density distribution is displayed on the display unit in real time, it is easy to understand what each procedure of aberration correction has. . As a result, the period required for the operator or the adjuster to learn the aberration correction technique can be shortened.

  According to the present invention, the calculation unit 45 can calculate a third-order or lower aperture aberration coefficient as the aberration coefficient. Further, a primary chromatic aberration coefficient can be calculated as the aberration coefficient. In addition, the distribution when the sample position is arbitrarily shifted can be calculated. Such calculation results can be displayed by sending image data from the calculation unit 45 to the display unit 50. As a result, the operator or adjuster can recognize an image of each aberration coefficient.

  In the above-described embodiment, the case where the operation input unit 44 and the control unit 43 are connected has been described. However, the embodiment of the present invention is not limited to this, and the operation input unit 44 and the control unit 43 are not limited thereto. It is also possible not to connect them.

  The present invention is used for adjusting a scanning electron microscope, an electron probe microanalyzer, an Auger electron spectrometer, an ion microprobe, a transmission electron microscope, and the like.

It is a block diagram which shows one embodiment of this invention. It is explanatory drawing of the simulation by this invention. It is explanatory drawing of simulation operation | movement. It is a figure for demonstrating the principle of an aberration correction apparatus. It is a figure which shows the method of using an electrostatic type 12 pole as a 12 or less electrostatic type multipole. It is a figure which shows the method of using a magnetic field type | mold 12 pole as a 12 or less electromagnetic field type | mold multipole.

Explanation of symbols

Reference Signs List 31 Object diaphragm 32 Electrostatic multipole 33 Electrostatic multipole 34 Electrostatic multipole 35 Electrostatic multipole 36 Objective lens 37 Sample 38 Power supply 39 Power supply 40 Power supply 41 Power supply 42 Power supply 43 Control section 44 Operation input section 45 Arithmetic unit 50 Display unit 51 Detector

Claims (6)

  In a charged particle beam apparatus including an aberration correction unit, a calculation unit performs a simulation calculation based on correction data of a beam control condition from an operation unit, and displays a beam cross-sectional shape and a sample image simulation result after the calculation on a display unit. A simulation image display method for a charged particle beam apparatus, characterized in that it is configured as described above.   The calculation means calculates the trajectory and aberration coefficient of the charged particles from the electromagnetic field applied to the particle optical system, calculates the two-dimensional current density distribution of the charged particles at the sample surface position from the aberration coefficient, 2. A simulation image of a charged particle beam apparatus according to claim 1, wherein an image obtained by scanning a sample surface using a probe having a density distribution is calculated, and at least one of the calculation results is displayed on a display means. Display method.   3. The simulation image display method according to claim 2, wherein the calculation means calculates a third-order or lower aperture aberration coefficient as the aberration coefficient.   The simulation image display method according to claim 2, wherein the calculation unit calculates a first-order chromatic aberration coefficient as the aberration coefficient.   The simulation image display method according to claim 2, wherein the calculation means calculates a distribution when the sample surface position is arbitrarily shifted as the current density distribution. In a charged particle beam apparatus including an aberration corrector, an operation input unit that inputs beam control conditions from the operation unit;
A calculation unit that performs a simulation calculation based on the correction data of the beam control condition input from the operation input unit, and displays the cross-sectional shape of the beam after correction and the simulation result of the sample image on a display unit;
A simulation image display device for a charged particle beam device.