JP4229799B2 - Electron beam measurement or observation device, electron beam measurement or observation method - Google Patents

Description

  The present invention relates to an electron beam measuring apparatus and an electron beam measuring method for accurately performing three-dimensional measurement of a sample using a sample image captured by an electron microscope, and particularly to correction in an electron optical system of a scanning charged particle beam apparatus. The present invention relates to an improvement when adjusting so as to be suitable for image measurement.

  In a scanning charged particle beam apparatus such as a conventional scanning electron microscope (SEM), an off-axis aberration of an electron lens is corrected in order to increase the resolution of a scanning electron microscope image or the like. The off-axis aberration of the electron lens is performed, for example, by compensating for spherical aberration, coma aberration, field aberration, astigmatism, and field distortion. In addition, Zelzer's theorem is known for spherical aberration, and it is known that an axially symmetric electron lens used in an electron microscope or the like cannot reduce the spherical aberration to zero regardless of electrostatic type or magnetic type. It has been. Therefore, in order to compensate for spherical aberration, an aspherical mesh or an aspherical form is used as the electrostatic electrode shape or the magnetic pole shape.

  On the other hand, in the case of a transmission electron microscope (TEM), a sample is tilted, transmission images with different tilt angles are obtained, and stereo observation of the sample is performed using this as a left and right image. For example, as shown in Non-Patent Document 1, in the case of a scanning electron microscope (SEM), a sample is tilted or an electron beam is tilted to obtain reflected images having different tilt angles. Stereo observation is performed as left and right images. And, for example, as shown in Patent Documents 1 and 2, in the field of semiconductor manufacturing equipment, the stereo detection data obtained from the electron microscope is appropriately processed so that the sample image can be stereoscopically observed accurately and accurately, and Based on this, an electron beam apparatus and a data processing apparatus for an electron beam apparatus that can perform three-dimensional shape measurement have been proposed.

JP, 2002-270126, A [0005], FIG. 3, FIG. JP-A-2002-270127 [0005], FIG. 3, FIG. "Medical / biological electron microscopy" pp. 278-299, published in 1982

  However, particularly when trying to measure a sample such as a semiconductor chip or a silicon wafer, there is electron beam distortion or magnification distortion depending on the inclination direction or height direction of the sample. When electron beam distortion or magnification distortion is included in the measurement direction of the sample image, there is a problem that accuracy in measuring the sample by image measurement varies. In recent semiconductor microfabrication, for example, the pattern width formed on a chip is miniaturized to the submicron order, and the dimensional error allowed for three-dimensional shape measurement is more severe than in the past. Therefore, the conventional compensation method for off-axis aberrations of an electron lens such as spherical aberration has a problem that the accuracy required for stereo image measurement cannot be obtained.

  The present invention solves the above-mentioned problems, and by adjusting the correction in the electron optical system of the scanning charged particle beam apparatus so as to be suitable for image measurement, the accuracy can be achieved without depending on the inclination angle or height of the sample. It is an object to provide an electron beam measuring apparatus and an electron beam measuring method capable of measuring a three-dimensional image of a good sample.

  The electron beam measuring apparatus of the present invention that achieves the above object holds an electron optical system 2 that irradiates a sample 9 with an electron beam 7 emitted from an electron beam source 1 and the sample 9 as shown in FIG. The sample holder 3, the sample holder 3 and the irradiation electron beam 7 are relatively inclined to form a sample tilting part 5 that forms a state for acquiring a stereo image, and an electron beam detection that detects the electron beam 7 emitted from the sample 9 An electron beam measuring apparatus including the unit 4 is configured as follows. That is, the reference template held by the sample holder 3 and the irradiation electron beam 7 are relatively tilted by the sample tilting unit 5, and based on the stereo image of the reference template photographed by the electron beam detecting unit 4, The first measurement unit (for example, the measurement unit 20) for obtaining the form or coordinate value of the reference template, the measurement result of the reference template in the first measurement unit, and the known reference data regarding the reference template are compared, A calibration data creation unit 30 for creating calibration data of a stereo image photographed by the electron beam measuring device, and calibration is performed so as to reduce the aberration of the sample image detected by the electron beam detection unit 4 based on the calibration data. A calibration unit 40 to be performed, and a sample 9 placed on the sample holder 3 that has been calibrated by the calibration unit 40, and an inclined state formed by the sample tilting unit 5 Based on the stereo image of the sample 9 taken by the electron beam detecting section 4, a second measurement unit for obtaining a form or coordinate values of the sample 9 (e.g., form-coordinate measuring unit 50) and a.

  In the apparatus configured as described above, the electron beam apparatus of the electron beam measuring apparatus includes an electron beam source 1, an electron optical system 2, a sample holder 3, a sample tilting unit 5, and an electron beam detecting unit 4. A 1st measurement part image | photographs the reference | standard template of a predetermined inclination state with the electron beam detection part 4, and calculates | requires the form or coordinate value of a reference | standard template based on the acquired stereo image. The calibration data creation unit 30 creates calibration data of a stereo image photographed by the electron beam measurement apparatus by comparing the measurement result of the reference template in the first measurement unit with the known reference data regarding the reference template. The calibration unit 40 performs calibration based on the calibration data so as to reduce the aberration of the sample image detected by the electron beam detection unit 4. The second measurement unit is a sample 9 placed on the sample holder 3 that has been calibrated by the calibration unit 40, and was photographed by the electron beam detection unit 4 in an inclined state formed by the sample tilting unit 5. Based on the stereo image of the sample 9, the form or coordinate value of the sample 9 is obtained. In this way, by adjusting the correction in the electron optical system of the scanning charged particle beam apparatus so as to be suitable for image measurement, it is possible to accurately obtain a three-dimensional image of the sample without depending on the inclination angle or height of the sample. Measurement can be performed.

  In the electron beam measuring apparatus of the present invention, for example, as shown in FIG. 6, preferably, correction coefficients for a stereo image photographed by the electron beam detection unit 4 are further obtained for a plurality of tilt states formed by the sample tilt unit 5. Is stored in the correction coefficient storage unit 64, and an image correction unit 60 that reads out the correction coefficient corresponding to the tilt state where the stereo image was captured from the correction coefficient storage unit 64 and corrects the stereo image. Then, the second measuring unit (for example, the form / coordinate measuring unit 50) corrects the rough shape or coordinate value of the sample 9 photographed in the stereo image by the rough measuring unit 52 and the image correcting unit 60. A precision measurement unit 54 that obtains the form or coordinate value of the sample 9 based on the stereo image obtained, and the correction coefficient based on the form or coordinate value of the sample 9 obtained by the approximate measurement unit 52 by the image correction unit 60 The stereo image is corrected using the correction coefficient read from the storage unit 64.

  The electron beam observation apparatus of the present invention that achieves the above object holds an electron optical system 2 that irradiates a sample 9 with an electron beam 7 emitted from an electron beam source 1 and the sample 9 as shown in FIG. The sample holder 3, the sample holder 3 and the irradiation electron beam 7 are relatively inclined to form a sample tilting part 5 that forms a state for acquiring a stereo image, and an electron beam detection that detects the electron beam 7 emitted from the sample 9 An electron beam measuring apparatus including the unit 4 is configured as follows. That is, the reference template held by the sample holder 3 and the irradiation electron beam 7 are relatively tilted by the sample tilting unit 5, and based on the stereo image of the reference template photographed by the electron beam detecting unit 4, The first measurement unit (for example, the measurement unit 20) for obtaining the form or coordinate value of the reference template, the measurement result of the reference template in the first measurement unit, and the known reference data regarding the reference template are compared, Calibration data creation unit 30 for creating calibration data of a stereo image photographed by the electron beam measuring apparatus, and calibration is performed so as to reduce the aberration of the sample image detected by the electron beam detection unit 4 based on the calibration data. A calibration unit 40 and a sample 9 placed on the sample holder 3 to be calibrated by the calibration unit 40, and in a tilted state formed by the sample tilting unit 5 Based on the stereo image of the sample 9 photographed by the line detection unit 4, the second measurement unit (for example, the form / coordinate measurement unit 50) for obtaining the form or coordinate value of the sample 9 and the electron beam detection unit 4 detect And an image display unit 28 for displaying a stereo image of the sample 9 based on the electron beam.

  In the electron beam measuring or observing apparatus of the present invention, for example, as shown in FIGS. 1 and 16, the sample tilting unit 5 preferably changes the irradiation direction of the electron beam of the electron optical system 2 with respect to the sample 9. The sample holder 3 and the irradiation electron beam 7 are relatively inclined by at least one sample inclination aspect of the sample inclination aspect of 1 and the second sample inclination aspect in which the sample holder 3 is inclined with respect to the electron beam. It is good to be configured.

  In the electron beam measurement or observation apparatus of the present invention, preferably, calibration data creation unit 30 creates calibration data of the tilt amount of sample tilting unit 5, and calibration unit 40 calibrates the tilt amount of sample tilting unit 5. It is good to be comprised so that it may be.

  In the electron beam measurement or observation apparatus of the present invention, preferably, the calibration data creation unit 30 creates calibration data of the irradiation direction of the irradiation electron beam 7 of the electron optical system 2, and the calibration unit 40 creates the calibration data of the electron optical system 2. It is good to be comprised so that the irradiation direction of the irradiation electron beam 7 may be calibrated.

  In the electron beam measurement or observation apparatus of the present invention, preferably, the calibration data creation unit 30 creates calibration data relating to the magnification of the electron optical system 2, and the calibration unit 40 calibrates the scanning range of the electron optical system 2. It is good to be configured as follows.

  In the electron beam measurement or observation apparatus of the present invention, preferably, the calibration data creation unit 30 creates calibration data related to distortion correction of the electron optical system 2, and the calibration unit 40 scans the scanning coil of the electron optical system 2. Is preferably calibrated.

  The electron beam measuring method of the present invention that achieves the above object holds the sample 9 and the electron optical system 2 that irradiates the sample 9 with the electron beam 7 emitted from the electron beam source 1 as shown in FIG. The sample holder 3, the sample holder 3 and the irradiation electron beam 7 are relatively inclined to form a sample tilting part 5 that forms a state for acquiring a stereo image, and an electron beam detection that detects the electron beam 7 emitted from the sample 9 An electron beam measuring method using an electron beam measuring apparatus having a unit 4, which includes the following steps. That is, the reference template held by the sample holder 3 and the irradiation electron beam 7 are relatively tilted by the sample tilting unit 5, and based on the stereo image of the reference template photographed by the electron beam detecting unit 4, The first measurement step (S102, S104, S106) for obtaining the form or coordinate value of the reference template, the measurement result of the reference template in the first measurement step, and the known reference data regarding the reference template are compared, Calibration data creation step (S108) for creating calibration data of a stereo image photographed by the electron beam measuring apparatus, and calibration so as to reduce the aberration of the sample image detected by the electron beam detector 4 based on the calibration data. A calibration step for performing (S110), and a sample placed on the sample holder 3 to be calibrated by the calibration step The second measurement step (S112, for obtaining the form or coordinate value of the sample 9 based on the stereo image of the sample 9 taken by the electron beam detector 4 in the inclined state formed by the sample inclined portion 5 S114 and S116) are executed by the computer.

  The electron beam measurement method of the present invention that achieves the above object holds an electron optical system 2 that irradiates a sample 9 with an electron beam 7 emitted from an electron beam source 1 and the sample 9 as shown in FIG. The sample holder 3, the sample holder 3 and the irradiation electron beam 7 are relatively inclined to form a sample tilting part 5 that forms a state for acquiring a stereo image, and an electron beam detection that detects the electron beam 7 emitted from the sample 9 An electron beam measuring method using an electron beam measuring apparatus having a unit 4, which includes the following steps. That is, the reference template held by the sample holder and the irradiation electron beam 7 are relatively inclined by the sample inclined portion 5, and based on the stereo image of the reference template photographed by the electron beam detecting portion 4, the reference The first measurement step (S202, S204, S206) for obtaining the template form or coordinate value, the measurement result of the reference template in the first measurement step, and the known reference data related to the reference template are compared, Calibration data creation step (S208) for creating calibration data of a stereo image photographed by the electron beam measuring device, and calibration is performed so as to reduce the aberration of the sample image detected by the electron beam detector 4 based on the calibration data. The calibration step (S210) to be performed and the electron beam detector for a plurality of inclined states formed by the sample inclined part 5 A correction coefficient storage step (S212) for storing a correction coefficient for a stereo image photographed by the above, and a sample 9 placed on the sample holder 3 that has been calibrated by the calibration step. A rough measurement step (S214, S216, S218) for obtaining a rough form or coordinate value of the sample 9 based on a stereo image of the sample 9 photographed by the electron beam detector 4 in an inclined state, and a stereo image is photographed. The correction coefficient corresponding to the inclined state is read from the correction coefficient stored in the correction coefficient storage step, and the correction coefficient is applied to the form or coordinate value of the sample 9 obtained in the approximate measurement step. An image correction step (S220, S222) for correcting the stereo image, and a step corrected by the image correction step. It is intended to execute precise measurements determining the form or coordinate values of the sample 9 on the basis of the O image and (S224) to the computer.

  The electron beam observation method of the present invention that achieves the above object includes an electron optical system 2 that irradiates a sample 9 with an electron beam 7 emitted from an electron beam source 1, and a sample 9, as shown in FIG. The sample holder 3, the sample holder 3 and the irradiation electron beam 7 are relatively inclined to form a sample tilting part 5 that forms a state for acquiring a stereo image, and an electron beam detection that detects the electron beam 7 emitted from the sample 9 An electron beam measuring method using an electron beam measuring apparatus having a unit 4, which includes the following steps. That is, the reference template held by the sample holder and the irradiation electron beam 7 are relatively inclined by the sample inclined portion 5, and based on the stereo image of the reference template photographed by the electron beam detecting portion 4, the reference The first measurement step (S102, S104, S106) for obtaining the form or coordinate value of the template, the measurement result of the reference template in the first measurement step, and the known reference data related to the reference template are compared, Calibration data creation step (S108) for creating calibration data of a stereo image photographed by the electron beam measuring apparatus, and calibration is performed so as to reduce the aberration of the sample image detected by the electron beam detector 4 based on the calibration data. A calibration step (S110) to be performed, and a sample 9 placed on the sample holder 3 to be calibrated by the calibration step. Thus, the second measurement step (S112, S114) for obtaining the form or coordinate value of the sample 9 based on the stereo image of the sample 9 photographed by the electron beam detection unit 4 in the tilted state formed by the sample tilting unit 5. , S116) and an image display step (S118) for displaying a stereo image of the sample 9 based on the electron beam detected by the electron beam detector 4 is executed by the computer.

  The electron beam measuring apparatus of the present invention that achieves the above object holds an electron optical system 2 that irradiates a sample 9 with an electron beam 7 emitted from an electron beam source 1, and a sample 9, as shown in FIG. The sample holder 3, the sample holder 3 and the irradiation electron beam 7 are relatively inclined to form a sample tilting part 5 that forms a state for acquiring a stereo image, and an electron beam detection that detects the electron beam 7 emitted from the sample 9 An electron beam measuring apparatus including the unit 4 is configured as follows. That is, a third measuring unit (for example, the form / coordinate measuring unit 50) for obtaining the form or coordinate value of the sample 9 based on the output corresponding to the stereo image obtained by the tilted state formed by the sample tilting part 5; The reference template is placed on the sample holder 3, the irradiation electron beam 7 and the reference template are relatively inclined, and based on the signal corresponding to the stereo image output from the electron beam detector 4, the form or coordinates of the reference template A slope for tilting the sample 9 by the sample tilting section 5 by comparing the first measurement unit for obtaining the value, the measurement result of the reference template in the first measuring section and the reference data known for the reference template A correction coefficient storage unit 64 that stores correction coefficients in a space other than the surface, and an image for correcting the image by reading out the corresponding correction coefficient from the correction coefficient storage unit 64 And a Tadashibu 60.

  For example, as shown in FIGS. 17 and 18, the third measuring unit obtains an approximate shape or coordinate value of the sample 9 based on the output corresponding to the stereo image of the electron beam detecting unit 4 (S402). The image correction unit 60 reads the corresponding image correction coefficient from the correction coefficient storage unit 64 and corrects the image based on the form or coordinate value of the sample 9 obtained in the rough measurement step. (S404, S406) and the third measurement unit executes a precise measurement step (S408) for obtaining the form or coordinate value of the sample 9 based on the corrected stereo image corrected by the image correction unit 60.

  According to the electron beam measurement or observation apparatus of the present invention, the calibration data creation unit compares the measurement result of the reference template in the first measurement unit with the known reference data related to the reference template, and the electron beam measurement apparatus Since the calibration data of the stereo image to be photographed is created and the calibration is performed so as to reduce the aberration of the sample image detected by the electron beam detector 4 based on the calibration data, the calibration unit By adjusting the correction in the electron optical system of the scanning charged particle beam apparatus so as to be suitable for image measurement, accurate three-dimensional image measurement of the sample can be performed without depending on the tilt angle or height of the sample. .

[principle]
The principle of the present invention will be described below with reference to the drawings. 2A and 2B are explanatory diagrams of the tilted state in the sample holder of the electron beam measuring apparatus. FIG. 2A shows the tilted state with the horizontal state as the reference state, and FIG. 2B shows the tilted state with the tilted state as the reference state. Shows when to do. The tilted state with respect to the sample holder 3 is a first mode (see FIG. 2A) tilted at an arbitrary angle (± θ) from the reference state with the horizontal state as a reference state, and a state tilted at a predetermined angle (Φ). As a reference state, there is a second mode (see FIG. 2B) in which an arbitrary angle (± θ) is inclined from the reference state. In the tilted state, the angle between the reference template 9a and the sample 9 placed on the sample holder 3 and the incident electron beam is adjusted, and the left and right images of the sample necessary for stereo image measurement can be acquired by the electron beam measuring device. It becomes a state. Here, the thickness of the reference template 9a is assumed to be t.

  FIG. 3A is a diagram for explaining the distribution of targets arranged on a planar reference template. A plurality of accurately measured targets 9b are arranged on the flat reference template 9a. Here, the target 9b is also referred to as a measurement reference point or a feature point, and refers to a mark that is easily formed on the surface of the reference template 9a. The reference template 9a is placed on the sample holder 3 of the electron beam apparatus 10 and has a horizontal or inclined posture.

  FIG. 3B is an explanatory diagram of a three-dimensional reference template. Here, a case where a planar reference template is stacked in three stages is shown. In the three-dimensional reference template, the height of the reference template 9c is the same as that obtained by integrating the thicknesses of the planar reference templates at each stage. That is, the three-dimensional solid reference template 9c is placed on the sample holder 3 to be in an arbitrary inclined state. The arbitrary tilt state refers to the tilt state of the three-dimensional solid reference template 9c at the tilt angle selected as the angle of the space so that calibration can be performed in the space where the object to be measured can exist. Say. When a three-dimensional reference template 9c having an arbitrary inclination state is photographed, the image distortion in the height direction can be calculated based on the reference target at each height projected in the photographed image. Therefore, the compensation value of the magnetic field potential or electrostatic potential of the electron optical system of the electron beam measuring device is calculated so as to compensate the calculated image distortion value in the height direction, and the electron beam detecting unit of the electron beam measuring device is calculated. By performing calibration so as to reduce the aberration of the sample image detected at 4, it is possible to calibrate the space in the height direction (for example, the optical axis direction of the beam).

  In the apparatus configured as described above, the electron beam measuring apparatus acquires a target position on the reference template image for each inclination angle, and acquires calibration data for removing image distortion in the reference template height direction. Next, a sample 9 instead of the reference template is placed on the sample holder 3 and an image of the sample 9 is acquired by an electron beam measuring apparatus using the sample 9 as an object at an arbitrary inclination angle.

  Even when the electron beam measuring apparatus is calibrated as described above, if image distortion required for image measurement still remains, the image correcting unit 60 is used to determine the approximate height and position of the sample 9, The image of the sample 9 is corrected. That is, each inclination angle of the reference template 9a used for correction of the electron beam measuring apparatus 2 is known from the approximate height and position of the subject (sample 9), and the distortion pattern of the image at the inclination angle determines the inclination angle at the inclination angle. Image distortion in each part of the subject can be calculated. The calculation of the image distortion in each part of the subject is performed while calculating the whole for each subject, and then the image of the sample 9 is corrected so as to compensate for this image distortion. Alternatively, it may be calculated as an image distortion pattern at each height (space) of the electron beam measuring apparatus, and this image distortion pattern may be stored in the memory of the electron beam measuring apparatus. That is, using the target position information of the reference template 9a as shown in FIG. 3A, the distortion coefficient of the target of the reference template 9a at each inclination angle can be acquired.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram illustrating a first embodiment of the present invention, and shows a case where a stereo image is obtained by adjusting a tilt angle of an object by adjusting a rotation angle of a holder that holds the object. . In the figure, an electron beam apparatus 10 (scanning microscope) as an image forming optical system in an electron beam measuring apparatus includes an electron beam source 1 that emits an electron beam 7 and an electron that irradiates an object 9 with an electron beam (beam) 7. Optical system 2, sample holder 3 that holds the object 9 in a tiltable manner, a magnification changing unit 6 that changes the magnification of the electron optical system 2, a scanning power supply 6 a that supplies power to the magnification changing unit 6, and a detection that detects the electron beam 7 The secondary electron conversion target 8 that attenuates the energy of secondary electrons emitted from the object 9 and reflects the energy to the detector 4. It has. The beam tilt control unit 5a as the tilt control unit 5 that controls the tilt of the electron beam 7 is not used in the first embodiment, but is used in a third embodiment to be described later.

  The electron optical system 2 includes a condenser lens 2a that changes the electron flow density, opening angle, irradiation area, etc. of the electron beam 7 emitted from the electron beam source 1, and a deflection lens 2b that controls the incident angle of the electron beam 7 on the sample surface. A scanning lens 2c that deflects the finely focused electron beam 7 to scan the sample surface two-dimensionally, and an objective lens 2d that focuses the incident probe on the sample surface along with the function of the final stage reduction lens. ing. In accordance with the magnification change command of the magnification changing unit 6, the region on the sample surface where the electron beam 7 is scanned by the scanning lens 2c is determined. The beam tilt control unit 5b sends a tilt control signal to the sample holder 3, and the sample holder 3L in the first posture in which the sample holder 3 and the irradiation electron beam 7 form the first relative tilt angle, and the second relative Switching is made between the sample holder 3R in the second posture having an inclination angle.

Three-dimensional coordinate system _{C L} of the object 9 to be placed on the sample holder 3L in the first posture, when an electron beam device 10 as a fixed coordinate _system, the _{(X L, Y L, Z} L) . Also, three-dimensional coordinate system _{C R} of the object 9 to be placed on the sample holder 3R second posture, when an electron beam device 10 as a fixed coordinate _{system, (X R, Y R,} Z R) It becomes. In addition, although the relative inclination angle of the sample holder 3 and the irradiation electron beam 7 by the holder inclination control unit 5b is set to be switched between two ways of rising to the right and rising to the left, here, two steps are illustrated. However, in order to obtain stereo detection data, a minimum of two stages is required. For example, when a yaw axis, a pitch axis, and a roll axis are set as the three-dimensional coordinate system of the object 9, the yaw axis corresponds to the Z axis, the pitch axis corresponds to the X axis, and the roll axis corresponds to the Y axis.

  The object 9 is, for example, a semiconductor chip such as a silicon semiconductor or a gallium / arsenic semiconductor, but may be an electronic component such as a power transistor, a diode, or a thyristor, or a glass such as a liquid crystal panel or an organic EL panel. The display device parts used may be used. Under typical scanning microscope observation conditions, the electron beam source 1 is applied to −3 kV, and the object 9 is applied to −2.4 kV. The secondary electrons emitted from the object 9 collide with the secondary electron conversion target 8 and the energy is weakened and detected by the detector 4.

  The electron beam measuring apparatus includes a measurement unit 20 as a first measurement unit, a calibration data creation unit 30, a known reference data storage unit 32, a calibration unit 40, an electron lens aberration compensation unit 42, and a configuration as a second measurement unit. A coordinate measuring unit 50 is provided.

  The measuring unit 20 relatively inclines the reference templates 9a and 9c held by the sample holder 3 and the irradiation electron beam 7 by the sample inclining unit 5, and the reference templates 9a and 9c photographed by the electron beam detecting unit 4 are used. The form or coordinate value of the reference templates 9a and 9c is obtained based on the stereo image. The measuring unit 20 includes an incident angle adjusting unit 22, an image forming unit 24, a reference template measuring unit 26, and a display device 28.

  The incident angle adjustment unit 22 adjusts the posture of the object 9 (including the reference templates 9a and 9c), and the electron beam 7 projected onto the object 9 by the electron beam apparatus 10 and the object 9 are relative to each other. The incident angle is adjusted so that a stereo image can be formed for the object 9. That is, the incident angle adjustment unit 22 adjusts the posture of the object 9 by sending a control signal to the holder inclination control unit 5b. Further, the incident angle adjusting unit 22 sends a control signal to the holder tilt control unit 5b to adjust the reference plane scanned by the electron beam 7 emitted from the electron beam source 1 and form a stereo image. Left and right images can be formed. The image forming unit 24 creates an image on the sample surface using the secondary electron beam detected by the detector 4 when the scanning lens 2c scans the region on the sample surface. The reference template measurement unit 26 obtains the form or coordinate values of the reference templates 9a and 9c based on the stereo images of the reference templates 9a and 9c photographed by the electron beam detection unit 4. The display device 28 displays left and right images of a stereo image of the object 9 (including the reference templates 9a and 9c) photographed by the electron beam detection unit 4, and for example, a CRT or a liquid crystal display is used.

The calibration data creation unit 30 compares the measurement result of the reference template in the measurement unit 20 with the known reference data regarding the reference templates 9a and 9c, and creates calibration data of a stereo image photographed by the electron beam measurement apparatus. . The known reference data storage unit 32 stores target positions provided in the reference templates 9a and 9c. The calibration data of the electron beam measuring apparatus created by the calibration data creation unit 30 includes the following.
(1) Calibration data of the tilt amount of the sample tilt portion 5.
(2) Calibration data of the irradiation direction with respect to the irradiation electron beam 7 of the electron optical system 2.
(3) Calibration data relating to the magnification of the electron optical system 2.
(4) Calibration data relating to distortion correction of the electron optical system 2.

The calibration unit 40 performs calibration based on the calibration data so as to reduce the aberration of the sample image detected by the electron beam detection unit 4. The calibration unit 40 has the following modes according to the calibration data of the electron beam measuring apparatus created by the calibration data creation unit 30 described above.
(1) The calibration unit 40 is configured so that the tilt amount of the sample tilting unit 5 is calibrated.
(2) The calibration unit 40 is configured so that the irradiation direction of the irradiation electron beam 7 of the electron optical system 2 is calibrated.
(3) The calibration unit 40 is configured so that the scanning range of the electron optical system 2 is calibrated.
(4) The calibration unit 40 is configured so that the scanning direction of the scanning coil of the electron optical system 2 is calibrated.

  The electron lens aberration compensation unit 42 compensates the distribution state of the magnetic field potential and electrostatic potential of the electron lens constituting the electron optical system 2 in accordance with the calibration signal output from the calibration unit 40, thereby reducing the aberration of the sample image. Thus, the electron optical system 2 suitable for image measurement is adjusted. When the electron beam apparatus 10 has an electromagnetic prism called ExB that separates the secondary electrons emitted from the sample 9 from the electron beam 7 emitted from the electron beam source 1 and sends them to the electron beam detector 4, the calibration is performed. The electron optical system 2 to be calibrated by the unit 40 includes an electromagnetic prism called ExB.

  The form / coordinate measuring unit 50 is a sample 9 placed on the sample holder 3 that has been calibrated by the calibrating unit 40, and is photographed by the electron beam detecting unit 4 in a tilted state formed by the sample tilting unit 5. On the basis of the stereo image of the sample 9, the form or coordinate value of the sample 9 is obtained. The form / coordinate measuring unit 50 uses the incident angle adjusting unit 22, the image forming unit 24, and the display device 28 of the measuring unit 20 in common with the reference template measuring unit 26.

  Next, a calibration procedure of the electron beam apparatus necessary for stereo image measurement by the apparatus configured as described above will be described. FIG. 4 is a flowchart of electron beam measurement including a calibration procedure for the electron beam apparatus according to the first embodiment of the present invention. FIG. 4 shows a processing flow in which the electron beam apparatus is calibrated using the reference templates 9a and 9c, and then the sample image measurement is performed (S100). First, the reference templates 9a and 9c are placed on the sample holder 3, and the sample holder 3 or the electron beam 7 is shifted to an inclined state (S102). For example, a tilt control signal is sent to the sample holder 3 by the beam tilt control unit 5b, and the relative incident angle between the electron beam 7 and the object 9 is adjusted by the incident angle adjusting unit 22. This inclination angle is set with respect to the inclination angle of the reference templates 9a and 9c to be measured. For example, the inclination angle is set to the inclination state shown in FIG. 2A or the inclination state shown in FIG. When there are a plurality of inclination angles, it is preferable to set the inclination angles to angles that can be measured in advance and acquire images.

  The measurement unit 20 acquires tilt images of the reference templates 9a and 9c obtained from the electron beam detection unit 4 (S104). Then, the measurement unit 20 obtains the forms or coordinate values of the reference templates 9a and 9c based on the stereo images of the reference templates 9a and 9c photographed by the electron beam detection unit 4 (S106). Regarding the processing of S106, it is preferable to use target detection and stereo matching processing which will be described later.

  The calibration data creation unit 30 creates calibration data of a stereo image photographed by the electron beam apparatus 10 by comparing the measurement result of the reference templates 9a and 9c in S106 with the known reference data regarding the reference templates 9a and 9c. (S108). Based on the calibration data, the calibration unit 40 calibrates the electron beam apparatus 10 so as to reduce the aberration of the sample image detected by the electron beam detection unit 4 (S110).

  Next, the sample (measurement object) 9 is placed on the sample holder 3 (S112). Then, the electron beam 7 or the sample holder 3 is placed in a desired inclination state, and the sample 9 is photographed by the electron beam detector 4 (S114). For example, when a three-dimensional image measurement of the sample 9 is performed, a desired tilt state is selected such that an angle with a small blind spot or an angle at which a target to be measured is particularly well photographed. Then, based on the stereo image of the sample 9 in a desired tilt state, the form or coordinate value of the sample 9 is obtained (S116). In order to observe the sample, a stereo image of the sample 9 is displayed on the display device 28 based on the electron beam detected by the electron beam detector 4 (S118). If the form or coordinate value of the sample 9 can be acquired, a return is returned (S120).

[Parallel projection]
Here, parallel projection, which is a precondition for the calibration procedure of the electron beam apparatus, will be described. Since the electron microscope has a wide range of magnifications from low magnification to high magnification (ex. 2 to several million times), the electron optical system 2 can be regarded as center projection at low magnification and parallel projection at high magnification. The magnification that can be regarded as parallel projection is preferably determined based on the calculation accuracy of the deviation correction parameter. For example, 1000 or 10000 times is used as the reference magnification. The displacement correction parameter is a parameter for correcting the displacement of the left and right images of the sample so that the stereoscopic image can be stereoscopically viewed.

すると、対象座標系７４で選択した原点（Ｘｏ，Ｙｏ，Ｚｏ）とオリエンテーション行列Ａを用いて、次のように表せる。

ここで、オリエンテーション行列Ａの要素ａi,jに関しては、回転行列の要素ａi,jが画像座標系７２の対象座標系７４を構成する３軸Ｘ，Ｙ，Ｚに対する傾きω、φ、κを用いて、次のように表せる。

FIG. 5 is an explanatory diagram of parallel projection. In the case of parallel projection, if the coordinate system (X _R , Y _R , Z _R ) taking rotation into consideration is used as the target coordinate system 74 and K1 and K2 are selected as the scale factors, the following equation is established.

Then, using the origin (Xo, Yo, Zo) selected in the target coordinate system 74 and the orientation matrix A, it can be expressed as follows.

Here, for the elements a i, j of the orientation matrix A, the inclinations ω, φ, κ of the rotation matrix elements a i, j with respect to the three axes X, Y, Z constituting the target coordinate system 74 of the image coordinate system 72 are used. And can be expressed as:

  In the calculation of the displacement correction parameter, six external orientation elements ω, φ, κ, Xo, Yo, and Zo included in the expressions (1) and (2) are obtained. In other words, these six external orientation elements are calculated from the above equations by forming an observation equation by using at least three reference marks and sequentially resolving them. Specifically, an approximate value of an unknown variable is given, Taylor expansion around the approximate value is linearized, a correction amount is obtained by the least square method, the approximate value is corrected, and the same operation is repeated to obtain a convergence solution These six external orientation elements can be obtained by an approximate solution method. Further, instead of the formulas (1) and (2), the calculation may be performed by appropriately adopting from various calculation formulas used as external orientation in single photo orientation, relative orientation, and other aerial triangulation.

[Lens distortion correction]
When obtaining up to the distortion aberration of the electron lens constituting the electron optical system 2, it is possible to correct by Equation (4) by preparing a plurality of reference marks and obtaining images from a plurality of directions. That is, if the x and y coordinates obtained by further correcting the lens distortion in the equations (1) and (2) are x ′ and y ′, the following equation is established.
x ′ = x + Δx (4)
y ′ = y + Δy
Here, when k1 and k2 are radial lens distortion coefficients, the following equation is used.

  The distortion of the electron lens is calculated by the successive approximation method by applying the above equation by measuring the image coordinates and the target coordinates. In the calculation of the distortion of the electronic lens, the lens distortion coefficient increases as an unknown variable. Therefore, it is preferable to further increase the reference point, measure the image coordinates and the target coordinates, and calculate by the fitting successive approximation method. In addition, the lens distortion coefficient is the radial lens distortion in the equation (5), but in addition to the tangential lens distortion, the spiral lens distortion, and other elements necessary for correcting the distortion aberration of the electronic lens, the expression (5) is added. If a lens distortion coefficient is calculated | required, those calibration (calibration) will be attained. For example, if the beam is scanned so as to correct the lens distortion using the obtained lens distortion coefficient, a corrected image can be acquired as a result. Alternatively, lens distortion in an image can be corrected by storing lens distortion in a memory and performing beam scanning so as to correct the lens distortion.

  FIG. 6 is a block diagram illustrating a second embodiment of the present invention. In the figure, the electron beam measurement apparatus includes an image in addition to the measurement unit 20, the calibration data creation unit 30, the known reference data storage unit 32, the calibration unit 40, the electron lens aberration compensation unit 42, and the form / coordinate measurement unit 50. A correction unit 60, an image correction coefficient calculation unit 62, and a correction coefficient storage unit 64 are provided.

  The form / coordinate measuring unit 50 includes a rough measuring unit 52 and a precision measuring unit 54. The approximate measurement unit 52 obtains an approximate form or coordinate value of the sample 9 photographed in the stereo image. The precision measurement unit 54 obtains the form or coordinate value of the sample 9 based on the stereo image corrected by the image correction unit 60.

  The image correction unit 60 reads from the correction coefficient storage unit 64 a correction coefficient corresponding to the tilt state where the stereo image is captured based on the form or coordinate value of the sample 9 obtained by the approximate measurement unit 52, and the stereo image is read out. Correct it. The image correction coefficient calculation unit 62 calculates correction coefficients for a stereo image captured by the electron beam detection unit 4 for a plurality of tilt states formed by the sample tilt unit 5. The correction coefficient calculation process will be described in detail later. The correction coefficient storage unit 64 stores the correction coefficient calculated by the image correction coefficient calculation unit 62 for each of a plurality of tilt states formed by the sample tilt unit 5.

  Next, a calibration procedure of the electron beam apparatus necessary for stereo image measurement by the apparatus configured as described above will be described. FIG. 7 is a flowchart of electron beam measurement including a calibration procedure for the electron beam apparatus according to the second embodiment of the present invention. FIG. 7 shows a processing flow in which the electron beam apparatus is calibrated using the reference templates 9a and 9c, and then the sample image is measured (S200). First, S202 to S210 are the same as those described in S102 to S110. That is, the reference templates 9a and 9c are placed on the sample holder 3, and the sample holder 3 or the electron beam 7 is shifted to an inclined state (S202). The measurement unit 20 acquires tilt images of the reference templates 9a and 9c obtained from the electron beam detection unit 4 (S204). Then, the measurement unit 20 obtains the forms or coordinate values of the reference templates 9a and 9c based on the stereo images of the reference templates 9a and 9c photographed by the electron beam detection unit 4 (S206). The calibration data creation unit 30 creates calibration data of a stereo image photographed by the electron beam apparatus 10 by comparing the measurement results of the reference templates 9a and 9c in S206 with the known reference data regarding the reference templates 9a and 9c. (S208). The calibration unit 40 calibrates the electron beam apparatus 10 based on the calibration data so as to reduce the aberration of the sample image detected by the electron beam detection unit 4 (S210). The image correction coefficient calculation unit 62 calculates correction coefficients for the stereo image photographed by the electron beam detection unit 4 for a plurality of tilt states formed by the sample tilt unit 5 and stores them in the correction coefficient storage unit 64 ( S212).

  Next, the sample (measurement object) 9 is placed on the sample holder 3 (S214). Then, the electron beam 7 or the sample holder 3 is set in a desired inclination state, and the sample 9 is photographed by the electron beam detector 4 (S216). For example, when a three-dimensional image measurement of the sample 9 is performed, a desired tilt state is selected such that an angle with a small blind spot or an angle at which a target to be measured is particularly well photographed. Then, based on the stereo image of the sample 9 in a desired tilt state, the rough measurement unit 52 obtains the form or coordinate value of the sample 9 (S218).

  The image correction unit 60 reads out a correction coefficient corresponding to the tilt state where the stereo image is captured from the correction coefficient stored in the correction coefficient storage unit 64 (S220). Then, the image correcting unit 60 applies the correction coefficient read in S220 to the form or coordinate value of the sample 9 obtained by the approximate measuring unit 52 to correct the stereo image (S222). The precision measurement unit 54 obtains the form or coordinate value of the sample 9 based on the stereo image corrected by the image correction unit 60 (S224). If the form or the coordinate value of the sample 9 can be acquired precisely, a return is returned (S226). Preferably, a stereo image corrected by the image correction unit 60 is displayed on the display device 28 in order to observe the sample.

  Next, an example of processing performed in S106 and S116 in FIG. 4 and S206 and S218 in FIG. 7 will be described. In this process, the forms or coordinate values of the reference templates 9a and 9c and the sample 9 are obtained based on the stereo images of the reference templates 9a and 9c and the sample 9 in a desired tilt state. FIGS. 8A and 8B are diagrams for explaining the left and right images of the stereo image captured by the electron beam detection unit 4 and the image in the reference state. FIG. 8A is a non-reference image, and FIG. 8B is a reference image and image conversion processing. A non-reference image (C) shows an image in a reference state processed by the image coordinate conversion process. The non-reference image is subjected to image conversion processing using the first image correction coefficient to the inclined state of the reference image. Further, the image of FIG. 8B is subjected to image coordinate conversion processing. In the image coordinate conversion process, the reference image and the image-converted non-reference image are coordinate-converted into an image in which the relative inclination angle of the sample inclination part 5 is in the reference state. For example, the measurement part 20 or the form / coordinate measurement is performed. This is performed by the unit 50. In the coordinate conversion, no special correction is applied to the image distortion state, so that the image processing is simpler than the image conversion. In addition, by converting the coordinates to the image in the reference state, it becomes easy to use the captured image of the sample captured in the inclined state.

  FIG. 9 is a flowchart for explaining an example of processing for obtaining the form or coordinate value of the reference template. FIG. 9 shows a measurement flow in which the measurement unit 20 measures a correction coefficient for image conversion processing using the reference templates 9a and 9c (S300). First, the reference templates 9a and 9c are placed on the sample holder 3 (S302). Next, the sample holder 3 or the electron beam 7 is shifted to an inclined state (S304). Next, the electron beam measurement apparatus acquires an inclination image of the reference template obtained from the electron beam detector 4 (S306). Then, the electron beam measuring apparatus determines whether the number of images necessary for the tilt image acquisition process has been acquired (S308). In S308, if the required number of images has not yet been reached, the process returns to S304 to obtain further tilted images.

  If the required number of images has been reached in S308, the measurement unit 20 acquires a reference template image in a reference inclination state, for example, an image in the horizontal direction (inclination angle 0 degree) (S310). If the design values or measurement values of the reference templates 9a and 9c are known, the design values or existing measurement values may be used together with the image measurement or instead of the image measurement. Further, if the beam system is adjusted at an inclination angle of 0 °, a reference template image at an inclination angle of 0 ° may be set as a reference inclination state.

  Subsequently, the measurement unit 20 performs variable coefficient acquisition processing (S312 to S318). First, the measurement unit 20 selects one of the tilted images in a stereo pair, that is, the left and right images of the stereo image obtained from the electron beam detection unit 4 as a reference image (S312). Next, target detection is performed on the tilted images that are a stereo pair (S314). As for the reference image, when an image having an inclination angle of 0 degrees is acquired, target detection is performed. In this case, since the approximate arrangement relationship of the feature points is known, miscorrespondence can be avoided, and by performing a series of processes described in <i> to <v> below, several target feature points are designated. Image measurement can be performed only by (automatic recognition) even if a point similar to the target exists in the image.

<I>: When the sample is a semiconductor chip, the approximate position of the pattern is read. In this case, if the design value of the semiconductor chip or the pattern interval is known, the known value is used. This is the reference point coordinate.
<Ii>: A point corresponding to three or more points on the reference image and the search image is roughly designated. This is the image coordinate.
<Iii>: Each parameter of the reference image and the search image is calculated by the following formula.
That is, the reference point coordinates corresponding to the image coordinates are substituted into the quadratic projective transformation expression shown in Expression (6), and the observation equation is established to obtain parameters b1 to b8.
X = (b1 * x + b2 * y + b3) / (b7 * x + b8 * y + 1) (6)
Y = (b4 * x + b5 * y + b6) / (b7 * x + b8 * y + 1)
Here, X and Y represent image coordinates, and x and y represent reference point coordinates.

<Iv>: Based on the obtained parameters b1 to b8, all pattern positions on the image are calculated for the reference image and the search image.
<V>: A stereo matching process is performed and measured around the obtained position corresponding to each pattern.

[Stereo matching processing]
Next, a matching method using an area-based normalized correlation coefficient will be described as an example of stereo matching processing. FIG. 10 is an explanatory diagram of the matching method using the normalized correlation coefficient, in which the right image in the figure is the reference image and the left image is the search image. Here, M is a reference data block in a reference image composed of N pieces of data, and I is a search data block in a search image starting from coordinates (U, V).

  In the matching method using the normalized correlation coefficient, the similarity between the reference data block M and the search data block I at each position is obtained from the correlation coefficient while performing a raster scan of the reference data block M in the search data block I. Is the method. Here, the raster scanning means that the reference data block M is moved from the left to the right in the search data block I, goes down to the right end of the search data block I, returns to the left end, and the search data block I is moved from the left to the right. The scanning state moved to. If the maximum position of the correlation coefficient value R is searched, the same location as the reference data block M in the search data block I can be searched.

M = M (Xi, Yi) 1 ≦ i ≦ N (7)
I = I (U + Xi, V + Yi) (8)
Then, the normalized correlation coefficient R (U, V) is
R (U, V) = (NΣIiMi−ΣIiΣMi)
/ SQRT [{NΣIi ² − (ΣIi) ² } × {NΣMi ² − (ΣMi) ² }] (9)
It becomes. The correlation coefficient value R always takes a value from −1 to +1. When the correlation coefficient value R is +1, the template and the search image are completely matched.

  Then, the image correction coefficient calculation unit 62 uses the reference image selected in S <b> 312, and uses the correspondence relationship of the stereo pair image with respect to the non-reference image of the inclined image that is a stereo pair. A first image correction coefficient that determines the image distortion state of the reference image is obtained (S316). The first image correction coefficient obtained in S316 is stored in, for example, the correction coefficient storage unit 64 in a state where it can be used by, for example, the measurement unit 20, the form / coordinate measurement unit 50, and the image correction unit 60 (S318). The first image correction coefficient is modeled using points detected by the parallel projection calibration method, approximated using a method of curve approximation by the least square method, affine transformation, etc., and used for the approximation The coefficient for performing the image conversion process while correcting the image distortion by various arithmetic processes such as a method for determining the image is obtained.

[Affine transformation formula]
Here, affine transformation will be described as an example of image conversion processing.
x ′ = b1x + b2y + b3 (10)
y ′ = b4x + b5y + b6
These coefficients b1,..., B6 are calculated by the successive approximation method by measuring four or more corresponding points on the left and right images. Therefore, the coordinate values detected by the target may be used for the left and right images of the stereo pair image and calculated. Next, conversion coefficients are similarly calculated for the detection position of the reference image selected in S312 and the target position or reference value (design value) of the image acquired at an inclination angle of 0 degrees.

  FIG. 11 is a flowchart for explaining an example of processing for obtaining the form or coordinate value of a sample. FIG. 11 illustrates a flow in the case of performing a three-dimensional image measurement on the sample 9 using the first image correction coefficient obtained in S316 of FIG. 9 (S350). First, the measurement object 9 is placed on the sample holder 3 (S352). Then, the electron beam 7 or the sample holder 3 is brought into a desired inclined state (S354). For example, when a three-dimensional image measurement of the sample 9 is performed, a desired tilt state is selected such that an angle with a small blind spot or an angle at which a target to be measured is particularly well photographed. And the stereo pair image of the sample 9 in a desired inclination state is acquired (S356). Then, the reference image selection process of the measurement unit 20 selects either one of the tilted images forming a stereo pair, that is, the left and right images of the stereo image obtained from the electron beam detection unit 4 as a reference image (S358). Next, target detection is performed for the tilted images that are a stereo pair (S360).

  The image conversion process of the measurement unit 20 converts the non-reference images of the left and right images of the stereo image using the first image correction coefficient (S362). Subsequently, in the image coordinate conversion process of the measurement unit 20, the reference image and the non-reference image image-converted by the image conversion process of the measurement unit 20 are converted into an image in which the relative inclination angle of the sample inclination unit 5 is in the reference state. Coordinate conversion is performed (S364). The form / coordinate measuring unit 50 performs stereo matching processing using the non-reference image and the reference image that have been coordinate-converted by the image coordinate conversion processing of the measuring unit 20 as a stereo image (S366).

  Then, the form / coordinate measuring unit 50 performs stereo image measurement, calculates the three-dimensional coordinates of the photographed sample 9, and obtains the shape and coordinate values of the sample (S368). In the above embodiment, the case where the stereo matching process is performed after the image conversion process and the image coordinate conversion process of the measurement unit 20 has been described. However, the present invention is not limited to this, and the stereo matching process is performed. May be performed after the image conversion process of the measurement unit 20 and before the image coordinate conversion process of the measurement unit 20.

  Further, between S364 and S366, the non-reference image and the reference image that have been coordinate-transformed by the image coordinate transformation process of the measurement unit 20, and the image of the reference image relative to the image in which the relative tilt angle of the sample tilting unit 5 is in the reference state A step of image conversion of the reference image and the non-reference image may be inserted using the second image correction coefficient for removing the distortion state. When the image distortion state of the electron beam apparatus 10 is different between the inclination state suitable for photographing the sample and the relative inclination angle of the sample inclination portion 5 in the reference state, the image is converted by the image coordinate conversion processing of the measurement unit 20. By correcting the non-reference image and the reference image using the second image correction coefficient, the shape or coordinate value of the sample by the form / coordinate measuring unit can be accurately obtained.

[Height measurement]
Next, a case where a parameter for correcting lens distortion in the height direction of the measurement target 9 is included with respect to the first image correction coefficient will be described. With respect to the sample 9 placed on the sample holder 3, as shown in FIG. 2B, height correction at each inclination angle Φ is possible. Therefore, spatial correction may be performed at the angle, and the distortion correction coefficient of the height at each angle may be included in the first image correction coefficient and stored. Then, to photograph the object 9 to be measured by inclining the tilt angle Φ, the electron beam 7 or the observation optical axis tilting mechanism is provided, the electron beam 7 is tilted by tilting the angle Φ, and the object 9 to be measured is photographed. Is equivalent to things. FIG. 12 is a perspective view for explaining the coordinate system of the sample holder 3. In the coordinate system of the sample holder 3, the Y axis is the rotation axis, and the angle θ is the clockwise direction in the + direction.

FIG. 13 is a front view showing the relationship between an image and a sample when the measurement object 9 is irradiated with an electron beam. From geometric relationship,
Left image Lx = (X × cos θ + Z × sin θ) × s (11)
Ly = Y
Right image Rx = (X × cos θ−Z × sin θ) × s (12)
Ry = Y
s: Resolution (1 pixel)
Thus, when the three-dimensional coordinates are obtained from the orientation matrix in consideration of the rotation angle of the image and the sample, the following is obtained.
X = Lx + Rx (13)
Z = Lx−Rx
Y = Ly = Ry
As shown in FIG. 14, the expression (13) is effective only when the left and right images have an angle across the Z axis as the shooting direction of the stereo image. Next, a formula that can be used without depending on the angle is derived. FIG. 15 shows a case where the left and right images are inclined by θ1 and θ2 with respect to the Z axis, respectively, as the shooting direction of the stereo image.

The angle of the left image is θ1, and the angle of the right image is θ2, and a Z ′ axis obtained by inclining the Z axis by θ ′ is assumed. Here, it is assumed that the left and right photographing directions of the stereo image in FIG. 14 are symmetrical with respect to the Z ′ axis. Then, by applying the pseudo coordinates (X ′, Y ′, Z ′), the angle of the image becomes θ ′ ± θ, and the equation (12) is used to further change to the coordinates XYZ later by θ 'Rotate.
Z ′ = ((Lx−Rx) / (2 × sin θ)) × s (14)
X ′ = ((Lx + Rx) / (2 × cos θ)) × s
Y '= Ly = Ry
Therefore, the following equation is established.
X = X ′ × cos θ′−Z ′ × sin θ ′ (15)
Z = X ′ × sin θ ′ + Z ′ × cos θ ′
Y = Y '

  Therefore, the expression (13) or the expression (15) is applied according to the tilt state of the sample 9, and the lens distortion in the height direction of the measurement target object 9 is corrected with respect to the tilt image that is a stereo pair. . That is, using the electron beam measuring apparatus, the object to be measured whose lens distortion is corrected using the approximate position and height of the object 9 to be measured and the height correction parameter included in the first image correction coefficient. Nine stereo pair images are generated. Here, it is possible to display the generated stereo pair image of the measurement object 9 on a display device such as a CRT of the electron beam measuring device.

  In the second embodiment, the left and right images of the stereo pair image are used as the reference image, the image coordinates on the reference image side of the non-reference image are corrected, the stereo matching process is performed, and the sample 9 is further converted into the reference coordinates. Is calculated (see FIG. 8). In this way, by correcting the image coordinates on the reference image side of the non-reference image, matching the distortion of the left and right images reduces the rate of mismatching during stereo matching processing and improves the reliability of stereo matching. There is an advantage.

  FIG. 16 is an overall configuration block diagram for explaining the third embodiment of the present invention. In the first and second embodiments, the holder is tilted when a stereo image is obtained. However, the third embodiment shows a case where a stereo image is obtained by deflecting an electron beam of a scanning microscope. Here, in FIG. 16, the same reference numerals are given to the same components as those in FIG. Here, a beam tilt control unit 5 a is provided as the tilt control unit 5 that controls the tilt of the electron beam 7. The beam tilt control unit 5a sends a tilt control signal to the deflecting lens 2b, and the electron beam 7R having the first relative tilt angle between the sample holder 3 and the irradiation electron beam 7 and the electron having the second relative tilt angle. Switching with line 7L. Note that the relative tilt angle between the sample holder 3 and the irradiation electron beam 7 by the beam tilt control unit 5a is not limited to two but may be set in multiple stages, but at least two are necessary to obtain stereo detection data. is there.

  FIG. 17 is an overall configuration block diagram for explaining the fourth embodiment of the present invention. In the figure, the electron beam measuring apparatus includes a configuration / coordinate measuring unit 50, an image correcting unit 60, an image correction coefficient calculating unit 62, a correction as a third measuring unit in addition to the measuring unit 20 described in the first embodiment. A coefficient storage unit 64 is provided. The form / coordinate measuring unit 50 is provided with a function of executing a rough measurement step S402 and a precise measurement step S408. The image correction unit 60 is provided with a function of executing an image correction step (S404, S406). In the first to third embodiments, the calibration data creation unit 30, the known reference data storage unit 32, the calibration unit 40, and the electron lens aberration compensation unit 42 are provided in order to perform the calibration procedure of the electron beam apparatus. Reference numeral 4 shows a case where the image correction is performed independently on the assumption that the calibration procedure of the electron beam apparatus has been completed.

  Next, the operation of the apparatus configured as described above will be described. FIG. 18 is a flowchart of electron beam measurement in Example 4 of the present invention. In the approximate measurement step, the form / coordinate measuring unit 50 obtains the approximate form or coordinate value of the sample 9 based on the output corresponding to the stereo image of the electron beam detecting unit 4 (S402). In the image correction step, the image correction unit 60 reads the corresponding image correction coefficient from the correction coefficient storage unit 64 based on the form or coordinate value of the sample 9 obtained in the rough measurement step (S404), and this image correction coefficient Is used to correct the stereo image (S406). In the precise measurement step, the form / coordinate measuring unit 50 obtains the form or coordinate value of the sample 9 based on the corrected stereo image corrected by the image correcting unit 60 (S408). If the form or the coordinate value of the sample 9 can be acquired accurately, the process returns (S410). Preferably, a stereo image corrected by the image correction unit 60 is displayed on the display device 28 in order to observe the sample.

  In the above-described embodiment, the calibration data of the electron beam measuring apparatus created by the calibration data creation unit includes the calibration data of the tilt amount of the sample tilting unit 5 and the irradiation direction of the electron optical system 2 with respect to the irradiation electron beam 7. Although the calibration data regarding the magnification of the electron optical system 2 and the calibration data regarding the distortion correction of the electron optical system 2 are shown, the present invention is not limited to this. The calibration data may be any data that can be calibrated by the calibration unit so as to reduce the aberration of the sample image detected by the electron beam detection unit 4.

BRIEF DESCRIPTION OF THE DRAWINGS It is a whole block diagram explaining Example 1 of this invention. It is explanatory drawing of the inclination state in the sample holder of an electron beam measuring apparatus. (A) is an explanatory diagram of a planar reference template, and (B) is an explanatory diagram of a three-dimensional reference template. It is a flowchart of the electron beam measurement including the calibration procedure of the electron beam apparatus in Example 1 of this invention. It is explanatory drawing of parallel projection. It is a block diagram explaining a second embodiment of the present invention. It is a flowchart of the electron beam measurement including the calibration procedure of the electron beam apparatus in Example 2 of this invention. It is a figure explaining the right-and-left image of the stereo image image | photographed with the electron beam detection part 4, and the image in a reference | standard state. It is a flowchart explaining an example of the process which calculates | requires the form or coordinate value of a reference | standard template. It is explanatory drawing of the matching method by a normalized correlation coefficient. It is a flowchart explaining an example of the process which calculates | requires the form or coordinate value of a sample. 3 is a perspective view for explaining a coordinate system of a sample holder 3. FIG. It is a front view which shows the relationship between an image and a sample when the measurement object 9 is irradiated with an electron beam. As a stereo image shooting direction, a case where the left and right images have an angle with the Z axis interposed therebetween is shown. As a stereo image capturing direction, the left and right images are inclined by θ1 and θ2 with respect to the Z axis, respectively. It is a whole block diagram explaining Example 3 of the present invention. It is a whole block diagram explaining Example 4 of the present invention. . It is a flowchart of the electron beam measurement in Example 4 of this invention.

Explanation of symbols

9 Sample (object to be measured)
9a, 9c Reference template 10 Electron beam apparatus 20 Measurement unit 30 Calibration data creation unit 40 Calibration unit 50 Configuration / coordinate measurement unit 52 Approximate measurement unit 54 Precision measurement unit 60 Image correction unit 64 Correction coefficient storage unit

Claims (11)

An electron beam source that emits an electron beam, an electron optical system that irradiates the sample with the electron beam, a sample holder that holds the sample, and the sample holder and the irradiation electron beam that are relatively inclined to acquire a stereo image An electron beam measuring apparatus comprising an electron beam apparatus having a sample inclined part for forming a state and an electron beam detecting part for detecting an electron beam emitted from the sample;
Based on a stereo image of the reference template photographed by the electron beam detector, the reference template held by the sample holder and the irradiation electron beam are relatively inclined by the sample inclined portion, and the reference template is used. A first measuring unit for obtaining a form or coordinate value of;
The measurement result of the reference template in the first measurement unit is compared with the known reference data related to the reference template, and the stereo image taken by the electron beam measuring device is compared with the optical axis direction of the irradiation electron beam. A calibration data creation unit for creating calibration data for reducing image distortion in a certain height direction ;
A calibration unit that performs calibration based on the calibration data so as to reduce the aberration of the sample image detected by the electron beam detection unit;
A sample placed on a sample holder of the electron beam apparatus that has been calibrated by the calibration unit, the stereo of the sample taken by the electron beam detection unit in an inclined state formed by the sample inclination unit A second measurement unit for obtaining a form or coordinate value of the sample based on an image;
An electron beam measuring apparatus comprising: A correction coefficient storage unit that stores correction coefficients for a stereo image captured by the electron beam detection unit for a plurality of tilt states formed by the sample tilting unit;
An image correction unit that reads out a correction coefficient corresponding to the tilted state where the stereo image was captured from the correction coefficient storage unit and corrects the stereo image;
Comprising:
The second measuring unit obtains a schematic form or coordinate value of a sample captured in the stereo image, and a sample form or coordinate value based on the stereo image corrected by the image correcting unit. Have the precision measurement part you want;
The stereo image is corrected by the image correction unit using the correction coefficient read from the correction coefficient storage unit based on the form or coordinate value of the sample obtained by the approximate measurement unit. The electron beam measuring apparatus according to claim 1. An electron beam source that emits an electron beam, an electron optical system that irradiates the sample with the electron beam, a sample holder that holds the sample, and the sample holder and the irradiation electron beam that are relatively inclined to acquire a stereo image specimen rotation unit to form a state, an electron beam measuring apparatus including an electron beam apparatus having an electron beam detector for detecting the electron beam emitted from said sample;
Based on a stereo image of the reference template photographed by the electron beam detector, the reference template held by the sample holder and the irradiation electron beam are relatively inclined by the sample inclined portion, and the reference template is used. A first measuring unit for obtaining a form or coordinate value of;
The measurement result of the reference template in the first measurement unit is compared with the known reference data related to the reference template, and the stereo image taken by the electron beam measuring device is compared with the optical axis direction of the irradiation electron beam. A calibration data creation unit for creating calibration data for reducing image distortion in a certain height direction ;
A calibration unit that performs calibration based on the calibration data so as to reduce the aberration of the sample image detected by the electron beam detection unit;
A stereo image of the sample placed on the sample holder of the electron beam apparatus to be calibrated by the calibration unit and photographed by the electron beam detection unit in a tilted state formed by the sample tilting unit A second measuring unit for determining the form or coordinate value of the sample based on
An image display unit for displaying a stereo image of the sample based on the electron beam detected by the electron beam detection unit;
An electron beam measuring apparatus comprising: The sample tilting section includes at least a first sample tilting mode in which an electron beam irradiation direction of the electron optical system is changed with respect to the sample, and a second sample tilting mode in which the sample holder is tilted with respect to the electron beam. the one specimen rotation embodiment, the electron beam measuring equipment according to any one of claims 1 to 3 and configured to relatively inclined and said electron beam irradiation and the sample holder. Calibration data for the amount of tilt of the sample tilting section is created by the calibration data creating section;
The amount of inclination of the sample inclination part is calibrated by the calibration part;
Electron beam measurement apparatus according to any one of claims 1 to 4. The calibration data creation unit creates calibration data of the irradiation direction for the irradiation electron beam of the electron optical system;
The calibration direction calibrates the irradiation direction of the irradiation electron beam of the electron optical system;
Electron beam measurement apparatus according to any one of claims 1 to 4. Calibration data relating to the magnification of the electron optical system is created by the calibration data creating unit;
The scanning range of the electron optical system is calibrated by the calibration unit;
Electron beam measurement apparatus according to any one of claims 1 to 4. Calibration data relating to distortion correction of the electron optical system is created by the calibration data creation unit;
The calibration unit calibrates the scanning direction of the scanning coil of the electron optical system;
Electron beam measurement apparatus according to any one of claims 1 to 4. An electron beam source that emits an electron beam, an electron optical system that irradiates the sample with the electron beam, a sample holder that holds the sample, and the sample holder and the irradiation electron beam that are relatively inclined to acquire a stereo image An electron beam measurement method using an electron beam measurement apparatus comprising an electron beam apparatus having a sample inclined part that forms a state and an electron beam detection part that detects an electron beam emitted from the sample;
Based on a stereo image of the reference template photographed by the electron beam detector, the reference template held by the sample holder and the irradiation electron beam are relatively inclined by the sample inclined portion, and the reference template is used. A first measuring step for determining a form or coordinate value of;
The measurement result of the reference template in the first measurement step is compared with the known reference data related to the reference template, and the stereo image taken by the electron beam measuring device is compared with the optical axis direction of the irradiation electron beam. A calibration data creation step for creating calibration data for reducing image distortion in a certain height direction ;
A calibration step for performing calibration so as to reduce the aberration of the sample image detected by the electron beam detector based on the calibration data;
A stereo image of the sample placed on the sample holder of the electron beam apparatus to be calibrated by the calibration step and photographed by the electron beam detector in an inclined state formed by the sample inclined portion A second measuring step for determining the morphology or coordinate value of the sample based on
Electron beam measurement method for causing computer to execute. An electron beam source that emits an electron beam, an electron optical system that irradiates the sample with the electron beam, a sample holder that holds the sample, and the sample holder and the irradiation electron beam that are relatively inclined to acquire a stereo image An electron beam measurement method using an electron beam measurement apparatus comprising an electron beam apparatus having a sample inclined part that forms a state and an electron beam detection part that detects an electron beam emitted from the sample;
Based on a stereo image of the reference template photographed by the electron beam detector, the reference template held by the sample holder and the irradiation electron beam are relatively inclined by the sample inclined portion, and the reference template is used. A first measuring step for determining a form or coordinate value of;
The measurement result of the reference template in the first measurement step is compared with the known reference data related to the reference template, and the stereo image taken by the electron beam measuring device is compared with the optical axis direction of the irradiation electron beam. A calibration data creation step for creating calibration data for reducing image distortion in a certain height direction ;
A calibration step for performing calibration so as to reduce the aberration of the sample image detected by the electron beam detector based on the calibration data;
A correction coefficient storage step for storing correction coefficients for a stereo image photographed by the electron beam detector for a plurality of tilt states formed by the sample tilt section;
The sample placed on the sample holder of the electron beam apparatus that has been calibrated by the calibration step, and the stereo of the sample taken by the electron beam detector in an inclined state formed by the sample inclined part A rough measuring step for determining a rough shape or coordinate value of the sample based on the image;
A correction coefficient corresponding to the tilt state where the stereo image is taken is read from the correction coefficient stored in the correction coefficient storage step, and the correction is performed on the form or coordinate value of the sample obtained in the rough measurement step. An image modifying step of modifying the stereo image by applying a coefficient;
A precision measurement step for obtaining a form or coordinate value of the sample based on the stereo image corrected by the image correction step;
Electron beam measurement method for causing computer to execute. An electron beam source that emits an electron beam, an electron optical system that irradiates the sample with the electron beam, a sample holder that holds the sample, and the sample holder and the irradiation electron beam that are relatively inclined to acquire a stereo image An electron beam observation method using an electron beam measurement apparatus comprising an electron beam apparatus having a sample tilt part that forms a state and an electron beam detection part that detects an electron beam emitted from the sample;
Based on a stereo image of the reference template photographed by the electron beam detector, the reference template held by the sample holder and the irradiation electron beam are relatively inclined by the sample inclined portion, and the reference template is used. A first measuring step for determining a form or coordinate value of;
The measurement result of the reference template in the first measurement step is compared with the known reference data related to the reference template, and the stereo image taken by the electron beam measuring device is compared with the optical axis direction of the irradiation electron beam. A calibration data creation step for creating calibration data for reducing image distortion in a certain height direction ;
A calibration step for performing calibration so as to reduce the aberration of the sample image detected by the electron beam detector based on the calibration data;
A stereo image of the sample placed on the sample holder of the electron beam apparatus to be calibrated by the calibration step and photographed by the electron beam detector in an inclined state formed by the sample inclined portion A second measuring step for determining the morphology or coordinate value of the sample based on
An image display step for displaying a stereo image of the sample based on the electron beam detected by the electron beam detector;
Electron beam observation method that makes a computer execute.

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