JP2012043816A - Sample potential information detection method and charged particle beam device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device each detecting a compensation value of changes of device condition to be changed by potential measurement on a surface of a sample by using charged particle beams or sample charging, while suppressing potential changes of the sample induced by irradiation of the charged particle beams.SOLUTION: For achieving above purposes, each of a method and a device applies, in a state in which charged particle beams are applied onto a sample, voltage to the sample so as to get a state (hereinafter referred to as a mirror state) in which the charged particle beams do not reach the sample, and detects information about the sample potential by using signals obtained at that time.

Description

  The present invention relates to a charged particle beam irradiation method and a charged particle beam apparatus for irradiating a sample with a charged particle beam, and in particular, a sample potential information detection method suitable for measuring a sample potential and a sample potential detection. The present invention relates to a charged particle beam apparatus.

In recent years, especially with the advancement of semiconductor devices, semiconductor measurement / inspection technology has become increasingly important. A scanning electron microscope represented by a CD-SEM (Critical Dimension-Scanning Electron Microscope) is formed on a semiconductor device by scanning an electron beam on the sample and detecting electrons such as secondary electrons emitted from the sample. This is a device for measuring the measured pattern. In such an apparatus, in order to perform high-precision measurement and inspection, it is necessary to set the conditions of the apparatus appropriately. However, in recent devices, there is an electron beam irradiation or an influence of a semiconductor process. There is a sample to which electrification adheres. In particular, insulating samples such as resists, insulating films, and low-k materials are known as samples that are easily charged.

  If the sample is charged, the electron trajectory is bent, causing astigmatism and image blurring. In order to properly focus on such a charged sample, a technique for measuring the amount of charge and controlling the voltage applied to the sample so as to cancel the influence of charging is disclosed in Patent Document 1 and Patent Document 2, described in Patent Document 3.

  Patent Document 4 describes a technique for detecting a field emission current or a tunnel current emitted from a metal needle having a sharp tip in order to measure a sample potential in a non-contact manner.

JP-A-4-229541 Japanese Patent Laid-Open No. 10-125271 JP 2001-236915 A JP-A-1-214769

  Each of the techniques described in Patent Documents 1 to 3 relates to a technique for measuring the charge amount on a sample and adjusting the apparatus conditions based on the measurement, and is obtained based on irradiation of an electron beam to the sample. Since the amount of charge is measured by detecting the signal, charging is induced by irradiation of the electron beam, and there is a problem that it is difficult to measure the amount of charge before irradiation of the electron beam. .

  On the other hand, according to the technique described in Patent Document 4, it is possible to measure the potential of the sample surface without inducing charging by an electron beam. When it is large, there is a problem of discharge.

  The object of the present invention is to suppress the potential change of the sample induced by the irradiation of the charged particle beam, while measuring the potential of the sample surface using the charged particle beam, or to provide a compensation value for fluctuations in apparatus conditions that change due to the sample charging. It is in the provision of a method and apparatus for detection.

  In order to achieve the above object, according to the present invention, in a state where a charged particle beam is irradiated toward a sample, the charged particle beam does not reach the sample (hereinafter also referred to as a mirror state) and Thus, a method and an apparatus for detecting information on a sample potential by applying a voltage to a sample and using a signal obtained at that time are provided.

  In a preferred example of the present invention, the charged particle beam emitted from the charged particle source is irradiated toward the sample, and the potential of the sample is based on the charged particles reflected without reaching the sample. In the sample potential measurement method for obtaining the charged particle source, when the value of the retarding voltage for decelerating the charged particle beam is larger than the value of the acceleration voltage for accelerating the charged particle beam emitted from the charged particle source. And information on the trajectory of the charged particles detected by the charged particle detector disposed between the charged particle beam and the objective lens for focusing the charged particle beam, and the charge detected by the charged particle detector at a predetermined sample potential Provided is a method and apparatus for determining the potential of the sample based on the difference from the information on the trajectory of particles.

  According to the configuration as described above, the sample potential or the adjustment condition of the apparatus is detected from the information obtained without irradiating the sample with the charged particle beam. Detection of potential or the like is possible.

The figure explaining the outline of a scanning electron microscope. The figure explaining other structures of a scanning electron microscope. The figure showing the change by the charging potential of the image formed by a mirror electron. FIG. 10 is a diagram for explaining a method for detecting a shift amount of mirror electrons (Example 3); FIG. 10 is a diagram for explaining a method for detecting the amount of deviation of mirror electrons (Example 4). FIG. 10 is a diagram for explaining a method for detecting the amount of deviation of mirror electrons (Example 5). FIG. 10 is a diagram for explaining a method for detecting the amount of deviation of mirror electrons (Example 6). (Example 7) explaining the method to detect the deviation | shift amount of a mirror electron. The figure explaining further another structure of a scanning electron microscope. The figure which shows the example of the processing signal formation method. The figure explaining the principle of the electric potential measurement using a mirror electron.

  In recent years, miniaturization and high integration of ULSI elements have been rapidly advanced, and device processing with a processing size of several tens of nanometers is being performed. In addition, multilayering using a variety of new materials is progressing, such as the adoption of a low dielectric constant film and a metal gate film for speeding up, and a three-layer resist for enhancing resistance to etching. For this reason, there is a strict requirement for dimensional accuracy (CD) management during ULSI processing.

  Insulators such as resists, insulating films, and low-k materials are often used in semiconductor processing processes, but the surface of the insulator is charged by electron beam irradiation. When charged, the amount of secondary electrons trying to escape from the sample surface is changed, or the trajectory of the primary electron beam is bent, so that the image of the scanning electron microscope is distorted. As a result, it is difficult to measure true processing dimensions and shapes. For example, with an ArF resist, it becomes impossible to determine whether line edge roughness (LER) has occurred in the etching process or whether the dimension is incorrectly measured by charging with an electron microscope. In addition, in high-aspect contact hole observation, there are problems that the shape of the contact hole is distorted and that it is difficult to distinguish between the upper and lower diameters of the hole.

  In addition to spatial changes due to electron movement / diffusion, charging changes spatially / temporally, such as decay due to hole / electron recombination. Moreover, it is positively charged or negatively charged by the energy of electrons incident on the sample surface. Therefore, it is important to control charging. As a result of the bending of the electron trajectory due to electrification, a portion where the image cannot be formed (astigmatism) or blurring of the image occurs. The function of focusing the electrons at a predetermined position and automatically adjusting the focus (autofocus) also causes problems such as deviation from the original focus position due to charging, and it takes time to adjust the focus. It is important to know the magnitude and distribution of the charging potential.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram illustrating an outline of a scanning electron microscope. In the following description, a scanning electron microscope (SEM) that scans an electron beam on a sample will be described as an example. However, the present invention is not limited to this. For example, a FIB (Focused Ion beam) apparatus (focusing) is used. It can also be applied to other charged particle beam devices such as ion beam devices. However, it is necessary to change the polarity of the voltage applied to the sample depending on the polarity of the beam charge. FIG. 1 only illustrates an example of a scanning electron microscope, and the present invention can be applied to a scanning electron microscope having a configuration different from that shown in FIG. 1 as long as the gist of the invention is not changed. .

  In the scanning electron microscope described in FIG. 1, an extraction voltage is applied between the field emission cathode 11 and the extraction electrode 12, and a primary electron beam is extracted.

  The primary electron beam 1 thus extracted is accelerated by the acceleration electrode 13 and is subjected to focusing by the condenser lens 14 and scanning deflection by the upper scanning deflector 21 and the lower scanning deflector 22. The deflection intensities of the upper scanning deflector 21 and the lower scanning deflector 22 are adjusted so as to scan the sample 23 two-dimensionally with the lens center of the objective lens 17 as a fulcrum.

  The deflected primary electron beam 1 is further accelerated by a subsequent acceleration voltage 19 in an acceleration cylinder 18 provided in the path of the objective lens 17. The post-accelerated primary electron beam 1 is narrowed by the lens action of the objective lens 17. The cylindrical cylinder 20 is grounded, and forms an electric field that accelerates the primary electron beam 1 between the cylindrical cylinder 20 and the acceleration cylinder 18.

  Electrons such as secondary electrons and backscattered electrons emitted from the sample are caused by an electric field formed between a negative voltage (hereinafter also referred to as a retarding voltage) applied to the sample and the accelerating cylinder 18. It is accelerated in the direction opposite to the irradiation direction of the primary electron beam 1 and detected by the detector 29.

  The electrons detected by the detector 29 are displayed on an image display device (not shown) in synchronization with the scanning signal supplied to the scanning deflector. The obtained image is stored in a frame memory (not shown). The current or voltage supplied to and applied to each component of the scanning electron microscope shown in FIG. 1 may be controlled using a control device provided separately from the main body of the scanning electron microscope.

  A method for measuring the potential of a sample using an electron beam and an apparatus for realizing the method will be described below.

  First, assuming that the acceleration energy of electrons is Ee and the sample potential is Vr, | −Vr | is set to a state larger than Ee. The acceleration energy Ee is determined by the potential difference between the field emission cathode 11 and the acceleration electrode 13.

  When the electron beam is emitted toward the sample in this state, the incident electrons are reflected immediately above without entering the sample (this electron is called a mirror electron). The reflected mirror electrons move in the opposite direction in the lens system. A detector is arranged in the lens system to detect the arrival position of the mirror electrons, and the difference “shift” between the passing position of the incident electrons and the arrival position of the mirror electrons is detected. If there is no sample charging, the electron follows the same trajectory as the incident electrons and is reflected, so this deviation amount reflects the value of the sample potential Vr. Therefore, by measuring the relationship between the deviation amount and Vr in advance, the sample potential can be obtained from the deviation amount.

  Note that the “deviation” (difference) in this example is obtained by detecting the spread and position change of the mirror electrons projected on the detector, or the two-dimensional deviation of the image formed by the mirror electrons. It is also possible to obtain the sample potential by detecting the rotation between images and the difference in image blur.

  The relationship between the deviation amount and the sample potential can be obtained, for example, as follows. The object position when the sample height is Z and the sample potential is Vr1 is Zc. In this state, the parameters of the lens system are adjusted to bring the lens into focus.

  The position of the detector is assumed to be in the height direction z1. The detection position of the mirror electrons at this time is assumed to be Zr1 (x1, y1, z1). This is used as a reference value. Next, the sample potential is set to Vr2, the beam is emitted with the same energy, and the arrival position Zr2 (x2, y2, z1) of the mirror electrons at this time is obtained from the detector. A deviation amount between Zr1 and Zr2 is obtained, and a Vr-Zr correlation curve representing a correlation between the difference and the potential is obtained. At this time, as the number of data sets (Vr, Zr) increases, a correlation curve with higher accuracy can be obtained. In this state, if the arrival position of the mirror electrons when observing the charged sample is Zr3, the sample potential can be obtained from the Vr-Zr correlation curve. Since no electron beam is incident on the sample, the charged potential can be measured without changing the state.

  Here, Vr is changed as a method of obtaining the correlation curve, but there are other methods. For example, when the objective lens is composed of a magnetic field coil, it is considered that the relationship between the image plane position Z and the zero-time current Ic that excites the objective lens is known, so only Zr1 of the mirror electrons at the reference value. If measured, an arbitrary charged state Vr3 can be estimated from a change in the amount of deviation when the exciting current is changed. In addition, the Vr-Zr correlation curve can be obtained by changing the sample height, the booster voltage Vb, the object point position of the primary electrons with respect to the objective lens, and other parameters.

  When detecting the spread or deviation of the beam projected on the detector, it is desirable to use a detector in which a plurality of detection elements are two-dimensionally expanded. The arrival position or distribution of the mirror electrons can be obtained from the output signals of the plurality of detection elements, and the deviation from the reference value can be obtained.

  Further, if the shift amount is detected using an image, the shift amount can be detected more easily. The mirror electrons are reflected just above the sample and are affected by the beam path and structure when passing through the lens system. In order to acquire an image, the position of the incident beam may be scanned. Thereby, the shape of the structure of the beam path is formed as an image.

Further, when detecting the rotation of the image, the amount of rotation of the structure displayed in the projected image is monitored. Specifically, a method of obtaining the sample potential from the rotation angle when the focus is adjusted by changing the excitation current to the structure under the reference mirror condition, or the amount of change in the rotation angle when the excitation current is changed from the reference condition There is a method for obtaining the sample potential from (dθ / dI _obj ). Although the method using the relationship between the excitation current and the rotation angle of the objective lens has been described above, the parameters related to the optical conditions at the time of mirroring, such as the sample current Vr or the object point position of the primary electrons, the booster voltage, and the sample height. The sample potential can be measured even if it is replaced with. In addition, the shape of the structure is preferably a shape with little contrast, such as a single arrow or an “upper” character. Further, by obtaining the correlation between the amount of rotation and the sample potential, if the sample potential is estimated from the amount of rotation under a plurality of conditions obtained by the monitor, the sample potential can be measured with higher accuracy. In addition, since the focus of the electron beam changes by adjusting the voltage applied to the sample, if the correlation between the degree of image blur and the sample potential is obtained in advance, the sample potential corresponding to the degree of blur is set. Can be detected. The blur is detected by arranging a plurality of detectors in two dimensions. 1. a method for directly measuring the beam distribution on the detection surface; There is a method of using the edge of a structure having the same size as the spot system on the detection surface. 2. When this method is used, a wide range of blur amounts can be measured with high accuracy by arranging a plurality of sizes of structures.

  As described above, the sample potential can be specified by monitoring the rotation amount, blur, magnification, image distortion, or a combination of these information.

  A preferred example for measuring the sample potential will be described below with reference to the drawings.

  It is assumed that the sample 23 is charged to a certain potential. A stage voltage control system 43 applies a potential Vr to the sample. Here, Vr is given so as to be sufficiently larger than the acceleration energy Ee of electrons. The acceleration energy Ee referred to here indicates a value before being decelerated by the voltage applied to the sample. For example, when Ee is 2 keV, it is larger than about −2200V. Since the sample charge amount is considered to be about minus 200 V at most from minus several hundred, it is sufficient that the absolute value is larger than −2200 V. In this way, an equipotential surface 2 of −2000 V is formed at a position above the sample. This potential surface is called a mirror surface, where the primary electron beam is reflected and returned upward.

  This electron is called a mirror electron 3. The mirror electrons 3 that have passed through the lens system reach the detector 29. The detector 29 detects the position Zr3 (x3, y3, zr) of the mirror electron 3. Here, zr is a position in the height direction. The computing unit 40 calculates the “deviation” from the reference value Zr1 prepared in advance for the information of Zr3. The charged potential Vr3 of the sample is calculated from this “deviation” amount based on the “correlation curve between mirror electron position and potential”. This information is sent to the analyzer 41, and a control system parameter signal is set in order to control the charged state therein. As the control system, for example, there are an objective lens control system 42, a stage voltage control system 43, and an acceleration voltage control system 44, which respectively set an excitation current, a stage voltage, and electron extraction / acceleration energy, thereby changing the charged state. Control.

  The relationship between the deviation amount and the sample potential can be obtained, for example, as follows. The object position when the sample height is Z and the sample potential is Vr1 is Zc. In this state, the parameters of the lens system are adjusted to bring the lens into focus. The position of the detector is assumed to be in the height direction z1. As shown in FIG. 11, the detection position of the mirror electrons at this time is Zr1 (x1, y1, z1). This is used as a reference value. At this time, it is better to use a conductor or semiconductor sample which is not charged or not charged. Next, the sample potential is set to Vr2, the beam is emitted with the same energy, and the arrival position Zr2 (x2, y2, z1) of the mirror electrons at this time is obtained from the detector.

  A deviation amount between Zr1 and Zr2 is obtained, and a Vr-Zr correlation curve representing a correlation between the difference and the potential is obtained. At this time, if there are many (Vr, Zr) data sets, a correlation curve with higher accuracy can be obtained. In this state, if the arrival position of the mirror electrons when observing the charged sample is Zr3, the sample potential can be obtained from the Vr-Zr correlation curve.

  An image with the above standard value is set as S1, and this is set as a reference image. Similarly to the above, an image obtained when the sample potential Vr2 is changed is also acquired as a reference image, and a Vr-S correlation curve is created. In this state, the image signal of the sample to be measured is detected by the detector, and the charged potential Vr3 is calculated by comparing the image S3 with the previous reference image.

  When the deviation from the incident position is detected by an image, various detection image objects can be considered according to the configuration of the scanning electron microscope as described above.

  For example, the position of the hole or structure and the degree of blurring of the image of the hole or structure are obtained from the amount of contrast change at the edge of the hole or structure. In addition, it is conceivable to determine the degree of blurring of holes and structures from the area change. It is also conceivable to detect the rotation angle from the reference image of the hole or structure. Another possibility is to look at the brightness of the entire image.

  In addition to the lens system, a reflector (in this example, an electrode for causing electrons accelerated by the retarding voltage to collide with secondary electrons generated by a separately provided secondary electron detector) Or structures such as meshes, or objects that are intentionally marked, for example, the hole shape is made triangular or polygonal for reference, or an arrow is placed in the lens system. May be.

  In the following embodiment, another method for detecting the deviation will be specifically described.

  FIG. 2 is a diagram for explaining a second embodiment for detecting the sample potential. The primary electron beam 1 focused by the condenser lens 14 and passing through the stop 15 is deflected by using the upper scanning deflector 21 and the lower scanning deflector 22.

  At this time, as in the first embodiment, the potential applied to the sample is set so that the absolute value of the sample voltage is larger than the acceleration energy of the primary electron beam 1 when passing through the objective lens 17. The primary electron beam 1 does not reach the sample 23, is reflected by the mirror surface 2, and returns to the detector 29 as mirror electrons 3. When the primary electron beam 1 is deflected by the upper scanning deflector 21 and the lower scanning deflector 22, the return trajectory of the mirror electrons 3 also changes. Therefore, when the primary electron beam 1 is detected by the detector 29 and imaged by the computing unit 40, the mirror electrons are transformed. The shape of the hole or structure passed through is reflected in the image.

  For example, if a mesh 30 (which constitutes an energy filter) is placed in the lens system, and the detector 29 has a beam transmission port 31, the mesh electrons and holes shown in FIG. A captured image is obtained.

  FIG. 3A shows a state where the charging potential is 0 when the charging potential of the sample is defined as charging potential = sample potential−set potential of the sample.

  That is, it is an image when it is not charged, and FIG. 3B is an image when the charging potential is 100V. When the electric potential is changed or changed, the position of the hole in the center and the shaded portion of the mesh move. These images are registered in advance in the computing unit 40 as images (reference images) with known potentials.

  Next, the primary electron beam 1 is scanned with respect to the sample 23 whose potential is unknown, and an image of the mirror electrons 3 is acquired. The potential of the sample 23 is obtained by comparing this image with the reference image and calculating.

  In this example, the charge amount is detected by comparing a mesh image obtained by detecting mirror electrons with a mesh image acquired in advance and detecting the amount of deviation. At this time, the sample potential can be measured by substituting the detected shift amount into an approximate function indicating the correlation between the shift amount and the sample potential.

  At this time, the image to be compared is preferably an image obtained when the sample potential is 0 V in the sense of detecting the shift amount, but is not limited to this. For example, when the sample potential is 100 V By comparing the obtained image with the detected image, the amount of deviation from the image obtained when the sample potential is 0 V may be obtained.

  FIG. 4 is a diagram for explaining a third embodiment for detecting the sample potential. Among the reference images with known potentials, for example, the image 50a of the beam passage opening and the mesh image 50b are observed. On the other hand, the sample 23 with an unknown potential is observed, and the image (image 51a of the beam passage opening) is observed. , A mesh image 51b) is obtained. The movement distance l of the hole position is detected, and the charging potential φ is obtained from a correlation curve prepared in advance. Although the center position of the hole is taken here as the movement distance, the movement distance of a specific part of the mesh may be used.

  FIG. 5 is a diagram for explaining a fourth embodiment for detecting the sample potential, and is for explaining a method for obtaining a deviation caused by charging. In this example, the deviation is obtained from the distribution change of the luminance I of the image. The distribution of the luminance I in this direction is obtained by setting x as the direction crossing the beam passage image 51a. At this time, the intensity at the edge part Xmax of the displayed hole is determined as Imax, the intensity at the center part Xmin of the hole is determined as Imin, and a part where the image intensity I is equal to (Imax + Imin) / 2 is determined as Xh. If Δx = | Xmax−Xh | is defined, Δx is a half width.

  This Δx is used as a judgment value for the deviation amount. Here, when the charging potential changes (lower graph), the half-value width Δx also changes. When the change of the inverse value Δx of the signal intensity is obtained using the detector 29 and the computing unit 40, the charging potential can be obtained. Instead of the half width of the luminance, the radius of the hole displayed in the image 51a of the beam passage aperture may be used.

  FIG. 6 is a diagram for explaining a fifth embodiment for detecting the sample potential, and for explaining a method for obtaining a deviation due to charging. A change in the area of the image is used as an index of displacement. The area S0 of the contour of the beam passing port image 50a or the mesh image 50b in the reference image with a known potential is obtained by changing several types of voltages.

  The primary electron beam 1 is scanned with respect to the sample 23 whose potential is unknown, and an image formed by the mirror electrons 3 is acquired. At this time, an area S1 of a hole in the image 51a of the beam passage opening or the outline of the mesh image 51b is obtained. The area is compared with the above S0 by the calculator 40, and the potential of the sample 23 is obtained by calculating.

  FIG. 7 is a diagram for explaining a sixth embodiment for detecting the sample potential, and is for explaining a method for obtaining a deviation due to charging. The rotation angle is detected from the image of the hole obtained by the image or the position of the specific location of the structure. Several types of samples 23 with known potentials are prepared, and an image by the mirror electrons 3 is acquired. For example, the change positions 52a, 52b and 52c of the beam passage opening accompanying the potential change of the beam passage opening position 53 at the time of the potential measurement are obtained, and the curvature radius R and the center position are obtained from the curve obtained by fitting the locus 54 of the beam passage opening position. Find O.

  In the case of a sample whose charging potential is unknown, the beam passage opening position 53 at the time of potential measurement obtained by scanning is detected, and from the change position 52a of the beam passage opening accompanying the potential change of the beam passage opening position 53 at the time of potential measurement. Is obtained.

  Using the computing unit 40, the charging potential is calculated from the locus 54 of the beam passage position corresponding to θ. Here, the hole through which the beam passes has been described, but it may be obtained from the change in the angle of the image of another structure.

  FIG. 8 is a diagram for explaining a seventh embodiment for detecting the sample potential, and is for explaining a method for obtaining a deviation due to charging. Specifically, this is a method of obtaining the deviation from the incident position of the mirror electrons 3 from the change in luminance of the hole or structure obtained in the image.

In the hole image 57, the luminance of the specific portion 55 is integrated to obtain a luminance integrated value It.
The charging potential of the sample is obtained from the magnitude of It using the fact that the area and brightness of the specific portion 55 change when the potential of the sample 23 is different.

  FIG. 9 is a view for explaining an eighth embodiment for detecting the sample potential, and is a schematic view of a scanning electron microscope for carrying out the potential measuring method in this embodiment. A plurality of detectors 29b are arranged at the position where the mirror electrons 3 are detected, and the arrival position and amount of the mirror electrons 3 are detected.

  The detected signal is transmitted to the second computing unit 45, and addition / subtraction of the signal, detection and filtering of the peak position P are performed, and processed signal data is created (see FIG. 10). This signal is compared and calculated by a calculator 40 with a reference value signal to obtain a charging potential.

  As described above, according to the preferred embodiment of the present invention, the charge amount can be measured without causing the electron beam to reach the sample. Charge measurement is possible. In the above-described example, the example in which the charge amount is measured based on the relationship between the sample potential and the arrival position of the mirror electrons has been described. However, the present invention is not limited to this example. Then, the compensation value of the parameter to be adjusted may be detected without measuring the charge amount by obtaining a correlation with the other device parameter to be adjusted in advance.

1 Primary electron beam 2 Equipotential surface (mirror surface)
3 Mirror Electron 11 Field Emission Cathode 12 Extraction Electrode 14 Acceleration Electrode 14 Condenser Lens 15 Aperture 17 Objective Lens 18 Acceleration Cylinder 20 Cylindrical Cylinder 21 Upper Scanning Deflector 22 Lower Scanning Deflector 23 Sample 24 Holder 29 Detector 29b Multiple Detectors 40 computing unit 41 analyzer 42 objective lens control system 43 stage voltage control system 44 acceleration voltage control system 45 second computing unit 50a, 51a beam passage image 50b, 51b mesh image 51 image 52a, 52b at the time of potential measurement , 52c Change position of beam passage opening 53 due to potential change Beam passage opening position 54 when measuring potential Potential locus of beam passage opening 55 Specific location 58 Correlation curve

Claims (8)

In a sample potential measurement method for obtaining the potential of the sample based on charged particles reflected without reaching the sample in a state where the charged particle beam emitted from the charged particle source is irradiated toward the sample,
Than the value of the acceleration voltage that accelerates the charged particle beam emitted from the charged particle source,
When the value of the retarding voltage for decelerating the charged particle beam is large,
Information on the trajectory of the charged particles detected by a charged particle detector disposed between the charged particle source and an objective lens that focuses the charged particle beam;
Based on the difference from the information about the trajectory of the charged particles detected by the charged particle detector at a predetermined sample potential,
A method for measuring a sample potential, wherein the potential of the sample is obtained. In claim 1,
Information on the trajectory of the charged particles is
A method for measuring a sample potential, characterized in that the information is information on a position where a charged particle reflected without reaching the sample by an electric field formed by the retarding voltage reaches the charged particle detector. In claim 2,
The potential of the sample is obtained based on the difference between the arrival position of the charged particle with respect to the charged particle detector and the arrival position of the charged particle with respect to the particle detector obtained at the predetermined sample potential. Sample potential measurement method. In claim 2,
Information about the arrival position of the reflected charged particles with respect to the charged particle detector is as follows:
A method of measuring a sample potential, which is a spread or position of the charged particles projected on the charged particle detector. In claim 1,
Information on the trajectory of the charged particles is
Detected by the charged particle detector,
A sample potential measuring method, which relates to an image formed on the basis of charged particles reflected without reaching the sample by an electric field formed by the retarding voltage. In claim 5,
An image formed based on the charged particles;
Based on the amount of movement, blur, and / or rotation between images obtained at the predetermined sample potential,
A method for measuring a sample potential, wherein the potential of the sample is obtained. In claim 1,
Information regarding the trajectory of the charged particles detected by the charged particle detector at the predetermined sample potential and the relationship between the predetermined sample potential are obtained in advance,
A sample potential measuring method, wherein the potential of the sample is obtained based on the obtained relationship. A charged particle source;
An objective lens for focusing the charged particle beam emitted from the charged particle source;
A charged particle detector disposed between the charged particle source and the objective lens;
A power source for applying a voltage to decelerate the charged particle beam to the sample;
In a charged particle beam apparatus provided with a control device for controlling the voltage,
The controller is
In a state where the charged particle beam is irradiated from the charged particle source toward the sample,
Information on the trajectory of the charged particles detected when a voltage higher than the value of the acceleration voltage for accelerating the charged particle beam emitted from the charged particle source is applied to the sample;
Based on the difference from the information about the trajectory of charged particles detected at a given sample potential,
A charged particle beam apparatus characterized by obtaining a potential of the sample.

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