JP5348152B2 - Charged particle beam adjustment method and charged particle beam apparatus - Google Patents

Description

  The present invention relates to a charged particle beam apparatus, and more particularly to a charged particle beam apparatus suitable for correcting a deviation of an optical axis of a charged particle optical system and stably obtaining a high resolution image.

  In a charged particle beam apparatus typified by a scanning electron microscope, desired information (for example, a sample image) is obtained from a sample by scanning a finely focused charged particle beam on the sample. In such a charged particle beam apparatus, if there is a deviation in the optical axis with respect to the lens, lens aberration occurs and the resolution of the sample image decreases, so high-precision axis adjustment is required to obtain a sample image with high resolution. It is. Therefore, in the conventional axis adjustment, the excitation current of the objective lens is periodically changed, and the operating conditions of the axis adjustment deflector (aligner) are manually adjusted so as to minimize the movement at that time. Japanese Patent Laid-Open No. 2000-195453 discloses a technique for automatically performing such adjustment. According to this description, a technique for changing the excitation set value of the alignment coil based on the transition of the electron beam irradiation position that changes between two excitation conditions of the objective lens is disclosed. Furthermore, Japanese Patent Laid-Open No. 2000-331637 discloses a technique for performing focus correction from two electron microscope images obtained under different optical conditions based on detection of positional deviation between the two.

  Moreover, if it deviates from the center of the astigmatism corrector that performs astigmatism correction of the charged particle beam, the field of view moves when adjusting astigmatism, and adjustment becomes difficult. Therefore, another aligner (deflector) that controls the position of charged particles on the sample in conjunction with the operation of the astigmatism corrector is provided, and the setting value (astigmatism corrector) of the astigmatism corrector changes. The field of view is corrected so that the observed image does not move when the astigmatism is adjusted by canceling the movement of the image with respect to. At this time, a signal proportional to the set value of the astigmatism corrector is input to the aligner for correcting field deviation, but this proportionality factor must be determined so that the image movement is canceled when adjusting astigmatism. I must. In order to perform this adjustment, an astigmatism corrector setting value (such as current) is periodically changed to find a proportional coefficient that minimizes image movement at this time.

JP 2000-195453 A JP 2000-331637 A

  In order to manually adjust the optical axis as described above, an experience-backed technique is required, and adjustment accuracy varies depending on the operator, and adjustment may take time. Also, in the above-described adjustment by automation, it is necessary to store adjustment parameters that change depending on the optical conditions for each optical condition, and registration work is required each time the optical conditions are changed. Further, even if the optical system is used under the same optical conditions, there is a problem that adjustment based on the registered parameters becomes difficult due to a change with time of the optical axis. There is also a possibility that the operator may perform observation or the like based on the deteriorated sample image without noticing that the axis is shifted.

  An object of the present invention is to provide a charged particle beam device and a charged particle beam device that can easily adjust the optical axis even when the optical condition is changed or the state of the charged particle beam changes due to a change in the optical axis over time. It is to provide an adjustment method.

  In order to achieve the above object, in the present invention, when the axis of the charged particle beam is adjusted with respect to the optical element that affects the charged particle beam by the alignment deflector, the deflection condition of the alignment deflector is set to the first state. In addition, the optical element is changed to at least two states, a first deviation between the first sample image and the second sample image obtained at that time is detected, and the deflection condition of the alignment deflector is set to the second state. In this case, the optical element is changed to at least two states, the second deviation between the third sample image and the fourth sample image obtained at that time is detected, and based on the information on the two deviations. Thus, a charged particle beam adjusting method and a charged particle beam apparatus for determining an operating condition of the alignment deflector are provided.

  According to such a configuration, highly accurate axis adjustment is possible regardless of the optical conditions of the charged particle beam.

  According to the present invention, it is possible to perform highly accurate axis adjustment regardless of the optical conditions of the charged particle beam apparatus.

1 is a schematic configuration diagram of a scanning electron microscope that is an example of the present invention. Schematic processing flow for correcting an axial deviation with respect to the objective lens. The principle figure which correct | amends the axial shift with respect to an objective lens. 3 is a schematic process flow for correcting an axis deviation with respect to an astigmatism corrector. An example of a message when axis deviation is detected. An example of the axis misalignment detection process which added the image quality determination process. The figure which shows the setting screen for setting the environment of automatic axis deviation correction. The figure which shows the example of a display of a correction amount graph.

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

  FIG. 1 is a schematic configuration diagram of a scanning electron microscope which is an example of the present invention. A voltage is applied between the cathode 1 and the first anode 2 by a high voltage control power source 20 controlled by a microprocessor (CPU) 40, and the primary electron beam 4 is drawn from the cathode 1 with a predetermined emission current. An acceleration voltage is applied between the cathode 1 and the second anode 3 by a high-voltage control power source 20 controlled by the CPU 40, and the primary electron beam 4 emitted from the cathode 1 is accelerated and proceeds to the subsequent lens system. The primary electron beam 4 is converged by the converging lens 5 controlled by the lens control power source 21, and after the unnecessary region of the primary electron beam is removed by the diaphragm plate 8, the converging lens 6 controlled by the lens control power source 22, And the objective lens 7 controlled by the objective lens control power source 23 is converged as a minute spot on the sample 10. The objective lens 7 can take various forms such as an in-lens system, an out-lens system, and a snorkel system (semi-in-lens system). A retarding method is also possible in which a negative voltage is applied to the sample to decelerate the primary electron beam. Furthermore, each lens may be composed of an electrostatic lens composed of a plurality of electrodes.

  The primary electron beam 4 is scanned two-dimensionally on the sample 10 by the scanning coil 9. The secondary signal 12 such as secondary electrons generated from the sample 10 by the irradiation of the primary electron beam travels to the upper part of the objective lens 7 and is then separated from the primary electrons by the orthogonal electromagnetic field generator 11 for secondary signal separation. And detected by the secondary signal detector 13. The signal detected by the secondary signal detector 13 is amplified by the signal amplifier 14 and then transferred to the image memory 25 and displayed on the image display device 26 as a sample image.

  A one-stage deflection coil 51 is arranged near or at the same position as the scanning coil 9 and operates as an aligner for the objective lens. In addition, an octupole astigmatism correction coil 52 for correcting astigmatism in the X and Y directions is disposed between the objective lens and the diaphragm plate. An aligner 53 for correcting the axial deviation of the astigmatism correction coil is disposed in the vicinity of the astigmatism correction coil or at the same position.

  In addition to the sample image, the image display device 26 displays various operation buttons for setting the electron optical system and scanning conditions, as well as buttons for checking the axis conditions and instructing the start of automatic axis alignment. it can.

  When focus adjustment is performed in a state where the primary electron beam has passed a position deviated from the center of the objective lens (in a state where the axis is deviated), the field of view moves with the focus adjustment. When the operator notices an axis shift, the start of the axis alignment process can be instructed by an operation such as clicking a process start button displayed on the display device with a mouse. When receiving an axis alignment command from the operator, the control CPU 40 starts processing along the flow of FIG. 2 or FIG.

  In the description of FIG. 1, the control processor unit is described as being integrated with or equivalent to the scanning electron microscope. However, the control processor unit is not limited to this, and a control processor provided separately from the scanning electron microscope body is described below. Processing as described may be performed. In this case, a detection signal detected by the secondary signal detector 13 is transmitted to the control processor, or a signal is transmitted from the control processor to a lens or a deflector of the scanning electron microscope, and via the transmission medium. An input / output terminal for inputting / outputting a transmitted signal is required. Alternatively, a program for performing the processing described below may be registered in a storage medium, and the program may be executed by a control processor that has an image memory and supplies necessary signals to the scanning electron microscope.

Example 1
The processing flow of FIG. 2 will be described in detail below.

First step:
A current condition of the objective lens 7 or a condition determined based on the current condition (for example, a condition in which the focus is slightly shifted from the current focus condition) is set as the condition 1 in the objective lens 7. Next, the current condition of the aligner 51 or a predetermined condition is set as the condition 1 of the aligner 51. The image 1 is acquired under the objective lens condition 1 and the aligner condition 1.

Second step:
With the condition of the aligner 51 as it is, an image 2 is acquired by setting a second focus condition in which only the objective lens condition is defocused by a predetermined value with respect to the objective lens condition 1.

Third step, fourth step:
A condition obtained by shifting the condition of the aligner 51 by a predetermined value with respect to the condition 1 is set as the condition 2 and is set in the aligner 51. Then, the objective lens conditions are set to Condition 1 and Condition 2 in the same manner as in Steps 1 and 2, and the respective images (image 3 and image 4) are acquired.

Step 5:
An image is acquired again under the same conditions as image 1 and is registered as image 5.

Step 6:
The parallax (image shift) between the image 1 and the image 2 is detected by image processing, and this is registered as the parallax 1. The parallax between the images can be detected from, for example, the image shift amount that maximizes the image correlation value by obtaining the image correlation while shifting the images of the image 1 and the image 2 in units of pixels. In addition, any image processing capable of detecting parallax can be applied to the present embodiment.

Step 7:
The parallax between the images 3 and 4 is detected by image processing and registered as parallax 2.

Step 8:
The parallax between image 1 and image 5 is detected by image processing and registered as parallax 3. Since the image 1 and the image 5 are acquired under the same conditions, if there is a deviation (parallax 3) between these images, the deviation is created by a sample or beam drift. That is, when the optical condition of the charged particle beam is set to a certain state (first state) and then the optical condition is set to another state (second state), and then the first state is set again, the above 2 Sample images are detected in each of the first states, and the drift is calculated based on the deviation between the two.

Step 9:
The drift component is detected from the parallax 3, and the drift component is corrected (removed) for the parallax 1 and the parallax 2. For example, if the capture interval between the images 1 and 5 is t seconds, the drift (d) per unit time (seconds) is expressed by d = (parallax 3) / t. On the other hand, if the capture intervals of the images 1 and 2 and the images 3 and 4 are T12 and T34, the parallax 1 and the parallax 2 include drift components of d × T12 and d × T34, respectively. Therefore, by subtracting the drift component from the parallax 1 and the parallax 2, it is possible to calculate an accurate parallax due to the axis deviation.

Step 10 and Step 11:
The optimum value of the aligner 51 is calculated from the parallax 1 and the parallax 2 that have been drift-corrected, and set to the aligner.

  The processing flow of FIG. 2 is described in a procedure with which the operation can be easily understood. However, the order of capturing images does not affect the processing except for the first and last images (for drift correction). In actual processing, in order to speed up the processing, for example, the objective lens condition 7 is set to the condition 1 and the images 1 and 3 are successively captured, and then the objective lens condition 7 is set to the condition 2 Image 2 and image 4 can be captured continuously. Since the objective lens of an electron microscope is usually composed of a magnetic field lens, since the inductance is large, a method of continuously controlling an aligner that is small in inductance and capable of high-speed control is practically effective.

  The principle of correcting (correcting) the axial deviation with respect to the objective lens in the processing flow of FIG. 2 will be described with reference to FIG. In the state where the axis is deviated, the beam off-axis amount at the position (deflection surface) of the aligner 51 is WAL (complex variable: XAL + j · YAL, j: imaginary unit), and the tilt of the beam relative to the optical axis at this position is WAL ′ (Complex variable), trajectory calculation based on electron optical theory (paraxial theory) is possible. In the case of a magnetic field type objective lens, if the image shift amount (parallax) generated when the lens current value is changed from I1 to I2 by ΔI (= I1−I2) is ΔWi (complex variable: ΔXi + j · ΔYi), the trajectory By calculation, ΔWi can be expressed as follows.

ΔWi = K · ΔI · (WAL · A + WAL ′ · B) (1)
Here, K, A, and B are parameters (complex numbers) that are determined by the off-axis state at the time of measurement and the operating conditions of the objective lens (acceleration voltage, focal length of the objective lens, object point position of the objective lens, etc.). is there. The state in which the axis is deviated with respect to the objective lens means that ΔWi has a value other than 0 in Equation (1). Therefore, conventionally, the current of the objective lens is periodically changed by ΔI, the operator recognizes the image shift ΔWi at this time, and the aligner conditions are adjusted so as to eliminate the image shift. That is, the optimum value of the aligner for correcting the axial deviation indicates a condition in which the right side of the equation (1) is 0 regardless of ΔI. If you export this condition,
(WAL · A + WAL '· B) = 0 (2)
Thus, the operating condition of the aligner that satisfies this condition is the optimum value. If there is an axis misalignment, the aligner deflection surface also involves the tilt of the incident beam. If this is WAL0 'and the deflection angle (control value) by the aligner is WAL1', WAL '= WAL0' + WAL1 '(3)
It is represented by Therefore, the purpose of the axis adjustment function is to obtain the aligner condition WAL1 ′ (the optimum value of the aligner) that satisfies the equation (2). When the aligner is composed of electromagnetic coils, the deflection angle WAL1 'is proportional to the coil current of the aligner.

From the above relationship, rewriting equation (1)
ΔWi = ΔI · (A1 + WAL1 ′ · B1) (4)
Is obtained. Here, A1 and B1 summarize the following terms.

A1 = K ・ (WAL ・ A + WAL0 ′ ・ B) (5)
B1 = KB (6)
From equation (4), the optimum value WAL1 ′ of the aligner is given by WAL1 ′ = − A1 / B1 (7). Therefore, the optimum value of the aligner can be calculated by obtaining A1 and B1. In Expression (4), ΔI is the current change amount of the objective lens and can be determined in advance as a known value. Therefore, if the aligner is set to two predetermined conditions and the parallax ΔWi with respect to ΔI is detected by image processing in each of them, an equation for obtaining the unknowns A1 and B1 is obtained from the equation (4). Since A1 and B1 can be solved from this equation, the optimum condition of the aligner can be determined from Equation (7).

  That is, an n-order equation is solved for unknowns such as A and B under the condition that the parallax ΔWi obtained when the aligner is set to two predetermined conditions is small (ideally zero). Thus, a condition that does not depend on the operating condition of the electron optical system can be derived. Based on this condition, an aligner condition (aligner excitation condition) can be derived. Note that the aligner 51 has an arrangement or structure capable of two-dimensionally controlling a beam passing position on at least the main surface of the objective lens. If the deflection fulcrum of the beam by the aligner exists in the vicinity of the main surface of the objective lens, the state of the axial deviation with respect to the objective lens cannot be controlled. That is, in the case of an alignment deflector (aligner) using an electromagnetic coil as in the embodiment of the present invention, it becomes possible to detect an excitation current (deflection signal) to the coil that changes depending on optical conditions. For example, since the excitation current that changes depending on the change in the excitation condition of the objective lens and the magnitude of the retarding voltage applied to the sample can be detected based on the optical conditions at the time of observation, different parameters are set for each optical condition. It is not necessary to register, and even if the beam condition changes due to changes over time, it becomes possible to detect the excitation current to the appropriate alignment coil in the changed state.

  As described above, according to the embodiment of the present invention, it is possible to cope with the changing state of the axis deviation and the operating conditions of the optical element of the charged particle optical system (for example, beam energy, focal length, optical magnification, etc.) Can be easily realized.

  The magnitude of the axis deviation can be quantified by the magnitude of the parallax ΔWi with respect to ΔI. Therefore, for example, when an operation with the possibility of causing an axis deviation such as a sample exchange or a change in conditions of the electron optical system is performed, the axis deviation can be detected in advance by executing a process for detecting the parallax ΔWi due to ΔI. can do. Further, when ΔWi exceeds a predetermined value, a message can be displayed informing the operator that the axis adjustment is necessary. FIG. 5 shows an example of a message screen when axis deviation is detected. The operator can execute the axis adjustment process by the input means according to this message, if necessary. For example, the input means can click on an icon displayed on the message screen (for example, FIG. 5) or another dedicated icon displayed on the monitor with a mouse, or specify a processing command from the menu screen. Can take form.

(Example 2)
On the other hand, the astigmatism corrector 52 can also be automatically adjusted in this embodiment. In the astigmatism corrector, the action of converging the beam and the action of diverging the beam occur in different directions in a plane orthogonal to the optical axis. Therefore, if the beam does not pass through the center of the astigmatism correction field, it will be deflected in a direction corresponding to the deviation from the center of the astigmatism correction field. At this time, since the deflection action also changes in conjunction with the correction of astigmatism, the image moves in conjunction with the adjustment operation of astigmatism, making the adjustment operation difficult. In order to correct this, conventionally, a signal linked to the signal (Xstg, Ystg) of the astigmatism corrector 52 is inputted to another aligner 53, and the astigmatism corrector is detected by the movement of the image generated in the aligner 53. The movement of the image due to is canceled. At this time, if the signal (complex variable) input to the aligner 53 is Ws1, Ws1 is expressed by the following equation.

Ws1 = Ksx · Xstg + Ksy · Ystg (8)
Here, Ksx and Ksy are coefficients represented by complex variables. Assuming that the signals (Xstg, Ystg) of the astigmatism corrector are changed separately by ΔXstg, ΔYstg, respectively, the movements (parallax) ΔWix, ΔWiy of the observation image corresponding to each change are as follows. .

ΔWix = ΔXstg · (Asx + Bx · Ksx) (9)
ΔWiy = ΔYstg · (Asy + By · Ksy) (10)
Here, Asx and Asy are complex variables whose values are determined in accordance with the axial deviation of the beam with respect to the astigmatism corrector. Ksx and Ksy represent axis adjustment parameters (complex variables) controlled by the apparatus. Bx and By are complex variables determined by the position of the aligner, the deflection sensitivity, the conditions of the electron optical system, and the like. Conventionally, modulation signals of ΔXstg and ΔYstg are respectively added to the astigmatism corrector, and the operator recognizes the image movement (ΔWix, ΔWiy) at that time, and manual adjustment of the parameters Ksx, Ksy is performed so as to eliminate this. It was broken.

  This is the axis adjustment operation for the astigmatism corrector. That is, the operation of aligning the axis with the astigmatism corrector corresponds to obtaining the coefficients Ksx and Ksy at which ΔWix and ΔWiy are 0 regardless of ΔXstg and ΔYstg in the equations (9) and (10). . It should be noted that ΔWix and ΔWiy are ideally zero, but the present invention is not limited to this, and the coefficient may be obtained under the condition that ΔW is small so as to be close to zero. The forms of the equations (9) and (10) are exactly the same as the equation (4) shown above, and the current value change (ΔI) of the objective lens is changed to the signal changes (ΔXstg, ΔYstg) of the astigmatism corrector. In other words, the optimal control parameters (Ksx, Ksy) for the aligner 53 can be obtained by parallax detection and its calculation processing. A processing flow for this is shown in FIG. The aligner for correcting the visual field shift by the astigmatism corrector is for correcting the position of the beam on the sample, and must be disposed at a position where the position on the sample can be controlled.

  The magnitude of the axis deviation with respect to the astigmatism corrector can be quantified by image deviation (parallax) when a change in ΔXstg and ΔYstg is given to the signal of the astigmatism corrector. For this reason, in this embodiment, as in the case of the axis deviation with respect to the objective lens described above, operations that may change the state of the optical axis (change in acceleration voltage, sample exchange, change in focus position, etc.) are performed. In this case, parallax detection can be performed to display and notify the operator of the state of the axis deviation. According to this display, the operator can instruct execution of the axis alignment processing of the astigmatism corrector by using the input means displayed on the screen, if necessary. The input means can take various forms, for example, by clicking a dedicated icon displayed on the monitor with a mouse or designating processing from a menu screen.

  In the embodiment of the present invention, when the operator erroneously instructs the axis adjustment process in an inappropriate image state (a state in which the focus is significantly shifted or an image state that includes almost no structural information), a malfunction of the process is caused. Can be prevented. This function will be described with reference to the processing flow of FIG. When instructed to start the axis misalignment detection process or the axis adjustment process, the CPU 40 first captures the current image and executes a process of quantifying the captured image (image quality quantification). This processing by the quantification means quantifies whether there is structural information necessary for parallax detection in the image. As an output of this processing, for example, the image can be subjected to Fourier transform, and a quantitative value Fi calculated by the following expression from the result can be used.

Fi = ΣΣ [F (fx, fy) · fx ⁿ · fy ⁿ ] (11)
Here, F (fx, fy) represents a two-dimensional Fourier transform (FFT) of the image, and fx, fy represents a spatial frequency. By using a real number or an integer of 1 or more as the index n, it is possible to appropriately quantify the image quality. That is, if there is no structural information in the image, F (fx, fy) becomes a very small value in a region where fx, fy is greater than 0. Therefore, structural information appropriate for the image quality is obtained from the calculation result of Expression (11). It is possible to determine whether or not there is. If the quantitative value Fi is less than or less than a predetermined value, an alarm may be generated based on a determination that the quantitative value Fi is not suitable for the alignment signal calculation. This alarm may be by display or sound as shown in FIG.

(Example 3)
FIG. 7 is a diagram for explaining a third embodiment of the present invention, and is a diagram showing a setting screen for setting an automatic axis deviation correction environment displayed on the image display device. The operator of the scanning electron microscope sets the automatic axis adjustment environment from this screen. In the case of the present embodiment, an example of setting with the pointing device 60 on the setting screen will be described. First, the operator determines whether or not aperture alignment is to be automatically performed, and selects one of “correction based on parallax detection”, “predetermined value correction”, and “no”. “Correction based on parallax detection” is a mode in which axis deviation correction is performed in the steps described in the first embodiment. If this mode is selected, it is possible to obtain a stable axis correction accuracy for a long time regardless of the temporal change of the primary electron beam. “Default value correction” is a pre-registered memory that is not shown in the figure, which stores the axial deviation that occurs for each objective lens excitation condition and the distance between the sample and the objective lens (a plurality of optical conditions such as working distance). In this mode, when conditions are set, the axis is adjusted with the registered axis adjustment conditions. This mode may be selected, for example, when no change in axis deviation occurs over time or when almost the same axis deviation is recognized even when the optical conditions are changed. In this setting, correction is performed based on a default value, so that detection time for axis adjustment conditions and calculation time are not required, and processing time can be improved. “No” is a mode in which the axis is not adjusted, and it is desirable to select it in an environment in which no axis deviation occurs.

  As described above, if a plurality of correction modes can be selected on the environment setting screen, it is possible to select appropriate correction conditions based on the use conditions, environment, and the like of the scanning electron microscope.

  Next, the operator selects automatic axis adjustment timing. For example, if the frequency of axis misalignment is high, set “every analysis point” in consideration of the accuracy of the axis tones and correct the axis misalignment at each measurement point so that the axis misalignment does not occur much. If there is, it is preferable to select “every wafer” in consideration of the throughput, and to correct the axis deviation every time the wafer to be measured by the scanning electron microscope is replaced. By providing such options, it is possible to select an appropriate axis deviation correction timing based on the use conditions, environment, etc. of the scanning electron microscope. If “when a predetermined value is exceeded” is selected, the parallax ΔWi with respect to the objective lens current change amount ΔI is detected for each analysis point or for each wafer, and when ΔWi exceeds a predetermined value, “correction based on parallax detection”. Is done. In addition, when “user setting” is selected, the axis adjustment is performed at an axis adjustment timing separately registered in advance.

  Next, the operator selects whether or not to register the correction amount graph. The correction amount graph here is displayed on the image display device in the form as shown in FIG. In the technique shown in the first embodiment, the coil current to the astigmatism corrector aligner 53 is finally calculated. The difference between the coil current and the coil current before correction is how much the beam is deviated from the optical axis. By plotting this degree and graphing it, it is possible to determine the transition of the degree of axis deviation. If the transition of this axis deviation shows a substantially constant value, it is determined that the state of the subsequent axis deviation is also the same, and by switching to the “default value correction” above, “parallax detection” The detection time and calculation time of the axis adjustment condition required for “correction based on” can be eliminated, and the throughput can be improved. By displaying such a graph, it is possible to entrust the operator to make a determination for performing appropriate automatic axis adjustment, and to set appropriate axis adjustment conditions.

  The graph shown in FIG. 8B is an example in which the measurement result of the semiconductor pattern width is displayed superimposed on the correction amount graph of FIG. The measurement of the semiconductor pattern width is formed based on the detected amount of secondary electrons or reflected electrons obtained by scanning an electron beam one-dimensionally or two-dimensionally on a semiconductor device having a pattern to be measured. This is done by measuring the width of the line profile. The length measurement result of the target pattern thus obtained and the pattern dimension error based on the design information are plotted superimposed on the correction amount graph shown in FIG.

  In FIG. 8 (b), the part indicated by a is because the parallax ΔWi exceeds a predetermined range or there is no structural information necessary for parallax detection (the quantitative value Fi described in the second embodiment is If the value is less than or less than a certain value), the length is measured under the condition that “correction based on parallax detection” is not performed. It is desirable to distinguish and display this part from other parts such as by changing the color so that it can be distinguished from the case where the correction amount is zero. In the following description, a case where length measurement is performed without performing “correction based on parallax detection” when the parallax ΔWi exceeds a predetermined range will be described, but the present invention is not limited to this. It is also possible to generate an alarm for prompting, etc. and stop automatic length measurement. In addition, when length measurement is continued even though “correction based on parallax detection” is not performed, the obtained length measurement value may be incorrect. In such a case, in order to confirm whether or not the length measurement was correctly performed later, the sample image obtained at the time of length measurement along with the length measurement value, the line profile, or the optical conditions of the electron microscope It is good to store at least one of them. The operator can judge the reliability of the length measurement by comparing the length measurement result obtained together with the information.

  Next, the operator selects what processing is to be performed when the parallax ΔWi exceeds a predetermined range, or when the set value Fi is less than or less than a certain value. When “stop length measurement” is selected, the length measurement that is being performed automatically and continuously is stopped, and the electron beam is blanked by a blanking mechanism (not shown) so as to be in a standby state. At this time, a message as shown in FIG. 5 may be displayed on the image display screen. Of these, “continue” is a mode in which length measurement is performed without performing “correction based on parallax detection”. “Continue with sample image registration” is a mode for registering a sample image and the like obtained without performing “correction based on parallax detection” together with the length measurement result as described above. “Switch to default value correction” is effective when “correction based on parallax detection” cannot be performed and the state of the axis deviation is known to some extent. In this mode, the axis deviation is performed based on a correction amount registered in advance. Further, it may be possible to skip to the next vertex without performing length measurement. Naturally, the environment setting screen described so far can also be applied for stigma alignment.

  In addition, in order to determine whether or not the automatic axis adjustment described in this embodiment is properly performed, at least four sample images used for performing “correction based on parallax detection” are displayed on an image display screen. It may be displayed in real time. In the above description, the axis adjustment for the objective lens and the astigmatism corrector has been described. However, the present invention is not limited to this, and general optical elements for charged particle beams that need to be adjusted with an alignment deflector. It is applicable to. Furthermore, the present invention can be applied not only to an electron microscope but also to all charged particle beam apparatuses that focus a charged particle beam using a focused ion beam or an axially symmetric lens system.

  DESCRIPTION OF SYMBOLS 1 ... Cathode, 2 ... First anode, 3 ... Second anode, 4 ... Primary electron beam, 5 ... First convergent lens, 6 ... Second convergent lens, 7 ... Objective lens, 8 ... Diaphragm plate, 9 ... Scanning coil DESCRIPTION OF SYMBOLS 10 ... Sample, 11 ... Orthogonal electromagnetic field (EXB) generator for secondary signal separation, 12 ... Secondary signal, 13 ... Detector for secondary signal, 14a ... Signal amplifier, 20 ... High-voltage control power supply, 21 ... First One converging lens control power source, 22 ... second converging lens control power source, 23 ... objective lens control power source, 24 ... scanning coil control power source, 25 ... image memory, 26 ... image display device, 31 ... objective lens aligner control power source, 32 ... astigmatism corrector control power supply, 33 ... astigmatism corrector aligner control power supply, 40 ... control CPU, 51 ... objective lens aligner, 52 ... astigmatism corrector, 53 ... astigmatism corrector aligner.

Claims (11)

A charged particle source, an objective lens that focuses the charged particle beam emitted from the charged particle source, an alignment deflector that adjusts the axis of the charged particle beam with respect to the objective lens, and irradiation of the charged particle beam In a charged particle beam adjustment method of a charged particle beam apparatus, comprising a detector for detecting the obtained secondary charged particles, and forming a sample image based on the output of the detector,
When the deflection condition of the alignment deflector is set to the first state, the focusing condition of the objective lens is changed to two states, and the first sample image and the second sample image obtained at that time are changed. Detecting a shift of 1
When the deflection condition of the alignment deflector is set to the second state, the focusing condition of the objective lens is changed to at least two states, and the third sample image and the fourth sample image obtained at that time are changed. Detecting a second shift,
Applying the information of the first deviation and the second deviation to an expression for deriving the deviation of the sample image with respect to the change of the alignment condition, calculating an unknown that varies depending on the operating condition of the charged particle beam optical system,
A charged particle beam adjustment method, characterized in that an alignment condition is obtained from a condition in which the calculated unknown and the focusing condition of the objective lens are changed to two conditions to reduce image displacement. The charged particle beam adjustment method according to claim 1,
After the first and third sample images are obtained by changing the alignment deflector from the first state to the second state in a state where the objective lens is in a certain focusing condition, the objective lens is A charged particle beam adjusting method, wherein the objective lens and the alignment deflector are controlled so as to obtain the second and fourth sample images under other focusing conditions. The charged particle beam adjustment method according to claim 1,
After acquiring the at least four sample images, the drift amount is calculated based on the deviation between the fifth sample image and the first sample image obtained by returning to the optical conditions when the first sample image is acquired again. A charged particle beam adjustment method characterized by calculating. The charged particle beam adjustment method according to claim 1,
The first sample image, the second sample image, determines whether any one of said third sample image and the fourth sample image is suitable for operation of the Alignment condition,
A charged particle beam adjustment method characterized by generating an alarm when it is determined that the calculation is not suitable. The charged particle beam adjustment method according to claim 1,
Quantifying the image of the sample image;
A charged particle beam adjustment method, characterized by generating an alarm when a quantified quantitative value is less than a predetermined value or less than a predetermined value. A charged particle source, an objective lens that focuses the charged particle beam emitted from the charged particle source, an alignment deflector that adjusts the axis of the charged particle beam with respect to the objective lens, and irradiation of the charged particle beam In a charged particle beam apparatus comprising a detector for detecting the obtained secondary charged particles, and forming a sample image based on the output of the detector,
A first sample image and a second sample image obtained by changing the focusing condition of the objective lens to two states when the deflection condition of the alignment deflector is in the first state; A memory for storing a third sample image and a fourth sample image obtained by changing the focusing condition of the objective lens into two states when the deflection condition is in the second state;
Based on the first shift between the first sample image and the second sample image and the second shift between the third and fourth sample images, it varies depending on the operating conditions of the charged particle beam optical system. calculating the unknown, charged particle beam apparatus characterized by comprising a control unit for calculating the alignment conditions of the alignment deflector. The charged particle beam apparatus according to claim 6,
Wherein the control device, a charged particle beam apparatus characterized by computing the Alignment condition on the basis of the condition deviation of the sample image obtained by the condition is changed to the two states of the objective lens is reduced. The charged particle beam apparatus according to claim 6,
After obtaining the first and third sample images, the control device changes the alignment deflector from the first state to the second state with the objective lens in a certain focusing condition. The charged particle beam apparatus controls the objective lens and the alignment deflector so as to obtain the second and fourth sample images in a state where the objective lens is in another focusing condition. The charged particle beam apparatus according to claim 6,
After acquiring the at least four sample images, the control device reverts the fifth sample image obtained by returning to the optical condition when the first sample image is acquired again to the deviation of the first sample image. A charged particle beam device characterized in that a drift amount is calculated on the basis thereof. The charged particle beam apparatus according to claim 6,
Means for calculating alignment conditions by the alignment deflector based on information obtained from the sample image;
Said first sample image, the second sample image, means for determining whether any one of said third sample image and the fourth sample image is suitable for operation of the Alignment condition,
A charged particle beam apparatus comprising: means for generating an alarm when the means determines that the calculation is not suitable. The charged particle beam apparatus according to claim 6,
Means for calculating alignment conditions by the alignment deflector based on information obtained from the sample image;
Means for quantifying the image of the sample image;
A charged particle beam apparatus comprising: means for generating an alarm when a quantitative value quantified by the means is equal to or less than a predetermined value or less than a predetermined value.

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