JP5478385B2 - Contrast / brightness adjustment method and charged particle beam apparatus - Google Patents

Description

  The present invention relates to a method and apparatus for adjusting contrast and brightness of an image, and more particularly, to a method and apparatus for adjusting contrast and brightness based on a focus condition.

  In the semiconductor market and the like, semiconductor devices and the like have been highly integrated and miniaturized, and there has been a demand for improved performance of charged particle beam apparatuses that perform observation, measurement, and inspection of these samples. For example, a scanning electron microscope (hereinafter abbreviated as “SEM (Scanning Electron Microscope)”) which is an embodiment of a charged particle beam apparatus is required to have high resolution and reproducibility.

  In order to perform observation, measurement, or inspection with an SEM based on an image having a high resolution, it is necessary that the brightness and contrast of the image be appropriately adjusted. This is done by appropriately setting the gain and offset (bias). Patent Document 1 discloses a method for adjusting contrast and brightness based on luminance information. First, a plurality of combinations of reference histograms for luminance and gain values and bias values to be set are prepared in advance. Example of adjusting contrast and brightness by comparing the histogram created from the sample image with the reference histogram, selecting the reference histogram that most closely approximates, and setting the gain and bias values according to the reference histogram It is shown.

JP-A-4-328234 (paragraphs 0003 to 0016)

  However, in the contrast / brightness adjustment method disclosed in Patent Document 1, when an image is blurred, the histogram created from the image is positioned on the lower luminance side than the histogram created from the image at the normal focus. There is a case. Therefore, when contrast / brightness adjustment is performed on such an image, the gain value and the offset value are set high. On the other hand, if the focus adjustment is performed while the gain value and the bias value are set to be high, the image becomes too bright this time, and contrast / brightness adjustment is required again.

  In recent years, ArF resists and low-k materials necessary for realizing miniaturization are sometimes used in semiconductor devices. However, the device characteristics of these materials necessary for miniaturization are easily changed by beam irradiation, and are observed by SEM. The pattern tends to shrink (shrink) or deform.

  From the above, it is required to efficiently adjust contrast and brightness while suppressing beam irradiation on the sample. In the following, a contrast / brightness adjustment method and an image processing apparatus for the purpose of adjusting an appropriate contrast or brightness while suppressing the amount of beam irradiation on the sample will be described.

  As one aspect for achieving the above object, a method for obtaining an index value indicating a defocus amount from a signal obtained by a charged particle beam apparatus or the like and adjusting the contrast and / or brightness of an image based on the index value And a device are proposed.

  According to the above configuration, the information necessary for adjusting the contrast and brightness can be obtained in a defocused state, so there is no need to perform contrast / brightness adjustment after the focus adjustment. Irradiation can be suppressed.

The block diagram of the image signal processing apparatus which adjusts contrast and brightness based on the index value which shows the focus shift calculated | required from the image or the observed image signal. The figure explaining the outline | summary of the focus shift | offset calculation part which calculates a focus shift | offset | difference index value. The figure explaining the outline | summary of a contrast brightness adjustment part. The figure explaining the relationship between the change of a focus, and the change of a histogram. The figure explaining an example of the adjustment process of contrast and brightness using the image signal processing apparatus illustrated in FIG. 1 is a schematic configuration diagram of a charged particle beam apparatus (part 1). 6 is a flowchart for explaining a process of adjusting contrast and brightness based on focus shift information and luminance information. Schematic block diagram (2) of a charged particle beam apparatus. The figure which showed the structure of the image signal processing apparatus which adjusts contrast and brightness based on the index value which shows the focus shift calculated | required from the lens control amount. The figure explaining the outline | summary of the focus shift | offset calculation part which calculates a focus shift | offset | difference index value. FIG. 3 is a schematic configuration diagram of a charged particle beam apparatus (part 3). 7 is a flowchart for explaining a process of obtaining a focus shift index value based on a lens control amount and adjusting contrast and brightness using the focus shift index value and luminance information. FIG. 4 is a schematic configuration diagram of a charged particle beam apparatus (part 4). The figure which shows an example of the GUI screen which sets the conditions for contrast and brightness adjustment. The figure which shows an example of the GUI screen which sets the conditions for performing contrast brightness adjustment automatically. The figure explaining an example of the target contrast determination table. The figure explaining an example of a target brightness determination table. The figure explaining an example of a gain value determination table. The figure explaining an example of a bias value determination table.

  Hereinafter, specific examples of a method and an apparatus for performing contrast / brightness adjustment and a computer program for calculating conditions for performing the above adjustment in the computer based on information on defocus of the obtained image are used. I will explain.

  The image signal processing apparatus described in the present embodiment includes a focus deviation calculation unit that calculates an index value indicating a focus deviation, a contrast and brightness that are adjustment targets based on the focus deviation index value, and a gain of the signal amplifier. Contrast / brightness adjusting means for determining a value and a bias value are provided.

  In the method, apparatus, and computer program described in the present embodiment, it is assumed (estimated or a relationship is defined in advance) that an appropriate brightness is obtained at the normal focus by measuring an index value indicating a focus shift. Adjust contrast and brightness. According to such a configuration, it is not necessary to perform contrast / brightness adjustment again after focus adjustment, and beam irradiation onto the sample can be reduced, so that device characteristic deterioration can be suppressed and apparatus throughput can be improved.

  In the following description, an SEM will be described as an example of an image forming apparatus or a signal acquisition apparatus. However, the present invention is not limited to this. For example, two images obtained by irradiating a sample with an ion beam made of helium ions or liquid metal ions. Other charged particle beam devices such as focused ion beam devices that acquire images and signals by detecting secondary electrons and secondary ions are applied as image forming devices or signal acquisition devices. May be.

  Hereinafter, specific embodiments will be described in detail with reference to FIGS. 1 to 5.

  FIG. 1 is a diagram illustrating an aspect of an image signal processing apparatus. The image signal processing apparatus 10 includes a focus deviation calculation unit 13, a luminance information extraction unit 14, and a contrast / brightness adjustment unit 15 whose adjustment target is a signal amplifier. In the present embodiment, it is assumed that the image signal processing apparatus 10 is generally composed of a computer having a CPU (Central Processing Unit) and a memory, and executes signal processing therein by digital processing. However, you may comprise by hard wired.

  The focus deviation calculation unit 13 receives the image 11 or the observation image signal 12 formed by electrons emitted from the sample, calculates the focus deviation of the image or the observation image signal, and outputs a focus deviation index value 16. Defocus is the degree of deviation between the focused state and the current focused state. This is the difference between the focus evaluation value such as the sharpness of the signal when the beam is focused and the lens control amount, and the focus evaluation value and lens control amount of the signal acquired in the current focus state. A parameter that changes according to the difference or the magnitude of the difference is used as an index value. Also, the focus shift can be obtained based on the difference between the focus evaluation value before and after the autofocus and the lens control amount, and the lens control amount at the time of focusing obtained based on the change in the focus evaluation value with respect to the change in the lens control amount. Can also be obtained based on the difference between this predicted value and the current lens control amount.

  The luminance information extraction unit 14 receives the image 11 or the observation image signal 12 and outputs luminance information 17 of the image or observation image signal. The luminance information 17 becomes the current contrast and brightness of the image 11 or the observed image signal 12.

  The contrast / brightness adjustment unit 15 receives the focus deviation index value 16 calculated by the focus deviation calculation unit 13 and the luminance information 17 extracted by the luminance information extraction unit 14 as an input to obtain appropriate contrast and brightness at the normal focus. The control signal 18 of the signal amplifier for changing is output. The control signal of the signal amplifier indicates a gain value and a bias value for setting to the signal amplifier.

  Details of the focus deviation calculation unit will be described with reference to FIG. The focus deviation calculation unit 20 includes a signal parameter extraction unit 21, a normal focus parameter output unit 22, and a focus deviation extraction unit 25, and has a function of calculating the focus deviation index value 16 from the image 11 or the observed image signal 12. Have.

  The signal parameter extraction unit 21 extracts a signal parameter 23 from the image 11 or the observed image signal 12. If the input is an image, the signal parameter can be composed of, for example, information such as the sharpness and histogram obtained from the image, and the standard deviation in the gradation value of each pixel. If the input is an observation image signal, for example, it can be composed of information such as the period, amplitude, and phase of the observation image signal.

  The positive focus parameter output unit 22 outputs a positive focus parameter 24 according to the image 11 or the observed image signal 12. The normal focus parameter is configured by measuring information at the normal focus with respect to the signal parameter in advance. The focus shift extraction unit 25 obtains a difference between the signal parameter 23 and the regular focus parameter 24 and outputs a focus shift index value 16.

  Next, details of the contrast / brightness adjusting unit will be described with reference to FIG. The contrast / brightness adjustment unit 30 includes a target contrast determination unit 31, a target brightness determination unit 32, a gain value determination unit 35, and a bias value determination unit 36. Based on the focus deviation index value 16, the contrast / brightness adjustment unit 30 Brightness is determined, and the gain value and bias value of the signal amplifier are determined from the target contrast 33, the target brightness 34, and the luminance information 17.

  The target contrast determination unit 31 receives the focus deviation index value 16 and outputs a target contrast 33. This target contrast is a target value for adjusting the contrast of the image 11 or the observed image signal 12. The output target contrast is prepared in advance as a table by measuring the relationship between the focus deviation index value and the contrast in advance. The relationship may be given as a calculation formula. Further, for example, the relationship between the focus deviation index value 16 and the target contrast or contrast adjustment amount is tabulated in advance, the contrast adjustment amount is read based on the input index value, and gain control is performed according to the adjustment amount. Alternatively, the relationship between the input index value and the gain value may be tabulated in advance, and the gain value may be read based on the input index value. The same applies to the target brightness determination unit described later. Such tables and arithmetic expressions are stored in advance in a predetermined storage medium, and can be read out as necessary. The storage medium may be provided in the image signal processing apparatus, or may be stored in an external storage medium so that it can be read out as necessary. The expression indicating the relationship between the focus deviation index value and the contrast can be expressed by a primary or multi-order arithmetic expression, and the contrast is obtained by substituting the focus deviation evaluation value into the arithmetic expression. It is good to do so.

  FIG. 16 is a diagram illustrating an example of the target contrast determination table. In this table, the relationship between a plurality of target contrasts and a plurality of defocus index values is tabulated. A gain value determination unit 35, which will be described later, determines a gain value based on, for example, the difference between the current contrast and the target contrast, and controls the signal amplifier. When the contrast adjustment amount is stored in the table, a gain value determination unit 35 described later determines a gain value corresponding to the adjustment amount and controls the signal amplifier.

  The target brightness determination unit 32 receives the focus deviation index value 16 and outputs a target brightness 34. This target brightness is a target value for adjusting the brightness of the image 11 or the observed image signal 12. The target brightness to be output is prepared as a table by measuring the relationship between the focus deviation index value and the brightness in advance. The relationship may be given as a calculation formula. FIG. 17 is a diagram illustrating an example of the target brightness determination table. The concept is the same as the target contrast determination table.

  The gain value determination unit 35 receives the target contrast 33 and the luminance information 17 and outputs the gain value of the control signal 18 of the signal amplifier. The output gain value is determined in advance by measuring the relationship between contrast and luminance information and the gain value of the signal amplifier, and inputting the target contrast and luminance information (current contrast). FIG. 18 is a diagram illustrating an example of the gain value determination table. In this table, for each combination of the current luminance (current contrast) and the target contrast, the gain value of the signal amplifier (in this example, the DAC value or the control amount of another amplifier may be registered) is registered. ing.

  The bias value determination unit 36 receives the target brightness 34 and the luminance information 17 and outputs the bias value of the control signal 18 of the signal amplifier. The output bias value is determined in advance by measuring the relationship between brightness, luminance information, and the bias value of the signal amplifier, and inputting the target brightness and luminance information (current brightness). FIG. 19 is a diagram illustrating an example of the bias value determination table. The concept is the same as that of the gain value determination table.

  The control signal 18 (gain value / bias value) of the signal amplifier determined by the contrast / brightness adjustment unit 30 is output to the signal amplifier, and the signal amplifier controls the observation image signal using the control signal of the signal amplifier. Then, the contrast and brightness of the image are set as target values.

  When the focus adjustment is performed in the state where the target contrast and the target brightness are set, the contrast and the brightness become appropriate at the normal focus. A change in contrast and brightness of an image or observation image signal at that time will be described.

  First, changes in image contrast and brightness will be described with reference to FIG. The description uses a histogram created from the gradation value of the brightness of each pixel from the image. The horizontal axis is the gradation value, and the vertical axis is the number of pixels having the gradation value.

  By setting the gain value and the bias value of the control signal of the signal amplifier output from the contrast / brightness adjustment unit 30 with respect to the histogram 40 before adjustment, the histogram 41 after adjustment is changed. The gain value is adjusted to the target contrast 33 by adjusting the width of the histogram, and the bias value is set to the target brightness 34 by adjusting the degree of brightness of the entire image by changing the position of the histogram of the display image.

  When focus adjustment is performed in this state, the contrast and brightness of the adjusted histogram 41 change so as to overlap the shape of the histogram 44 at the normal focus, and an image with appropriate brightness at the normal focus is obtained.

  Next, changes in contrast and brightness of the observation image signal will be described with reference to FIG. In the contrast adjustment of the observation image signal, the maximum value of the observation image signal is changed. By multiplying the observed image signal (FIG. 5a) by a gain value (amplification degree) that is a control signal of the signal amplifier output from the contrast / brightness adjusting unit 30 (FIG. 5b), the maximum value of the observed image signal is changed. Adjust the ratio of white and black parts on the image.

  In the brightness adjustment of the observation image signal, the average value of the observation image signal is changed. By adding the bias value, which is the control signal of the signal amplifier output from the contrast / brightness adjusting unit 30, to the observed image signal (FIG. 5c), and changing the average value of the observed image signal, the degree of brightness of the entire image Adjust. The observation image signal obtained by these becomes the adjusted observation image signal 53 (FIG. 5d) set to the target contrast and the target brightness.

  When focus adjustment is performed in this state, the contrast and brightness of the observation image signal 53 after adjustment change so as to overlap with the shape of the observation image signal at the normal focus (FIG. 5e), and appropriate brightness at the normal focus. This is an observation image signal that can generate an image.

  According to the present embodiment, since an appropriate contrast / brightness correction value can be obtained in a defocused state, an image acquisition based on beam scanning is performed after the focus adjustment to derive the correction value. There is nothing. Therefore, it is effective in suppressing the beam irradiation amount on the sample and suppressing the processing time.

  Hereinafter, an example in which the above-described image signal device is applied to a charged particle beam device will be described with reference to FIGS. As illustrated in FIG. 6, an image signal processing apparatus 10 that processes an image signal obtained by the charged particle beam apparatus is connected to an output side of the charged particle beam apparatus.

  The charged particle beam device 60 includes a signal amplifier 70 that amplifies a detection signal output from the detector in a mirror body 61 that houses a beam source 64, a focusing lens 62, an objective lens 65, a detector 69, an XY stage 68, and the like. A display image generation unit 71 that generates an observation image signal 12 output from the signal amplifier as a display image, an image signal processing device 10, and an image display 72 are connected.

  In the mirror 61, when the charged particle beam 63 emitted from the beam source 64 is irradiated onto the sample 66, secondary electrons and reflected electrons are emitted from the sample portion irradiated with the charged particle beam 63, and the detector. 69 detects them. The detected signal is amplified by the signal amplifier 70 and output to the display image generation unit 71 as the observation image signal 12. At this time, the deflection of the charged particle beam 63 is controlled so as to scan the observation region of the sample 66. The sample 66 is fixed to a sample holder 67 installed on the XY stage 68, and the center position of the observation region of the sample 66 is determined by horizontal movement control of the XY stage 68. When focus adjustment is performed on the sample 66, the objective lens controller 73 controls the objective lens 65 to converge the charged particle beam 63.

  The display image generation unit 71 receives the observation image signal 12 output from the signal amplifier 70 as an input, generates a bitmap image 11, and stores it in an image memory including a RAM (Random Access Memory) or the like. The image signal processing apparatus 10 receives the image 11 stored in the image memory, calculates an index value indicating defocus, and determines a control signal 18 of the signal amplifier based on the index value.

  The operation of the image signal processing apparatus 10 when applied to a charged particle beam apparatus will be described using the flowchart of FIG. First, the image 11 generated from the display image generation unit 71 is acquired (step S10). Next, the luminance information extraction unit 14 extracts luminance information of the image (step S11). Next, the focus shift calculation unit 13 calculates the focus shift index value of the image (step S12). A target value (target contrast and target brightness) is determined from the extracted luminance information and the calculated defocus index value (step S13). Next, the luminance information extracted from the image is compared with the target value (step S14).

  If the luminance information does not reach the target value in the determination of step 14, it is determined that contrast / brightness adjustment is necessary, and the contrast / brightness adjustment unit 15 determines the target value (target contrast and target brightness) from A gain value and a bias value are determined (step S15). The determined gain value and bias value are set in the signal amplifier 70, and the contrast and brightness of the image are adjusted (step S16).

  On the other hand, if the luminance information has reached the target value in the determination in step 14 in which the image is acquired and the luminance information extracted from the image is compared with the target value, the contrast / brightness adjustment is terminated, and the image display In 72, an image after contrast / brightness adjustment is displayed. The image display 72 may display an image being adjusted for the purpose of confirming a change in contrast and brightness.

  As described above, in a charged particle beam device having an image processing signal device that performs contrast / brightness adjustment based on an index value indicating a focus shift obtained from an image, the contrast / brightness adjustment is repeatedly performed. Brightness can be as close as possible to the target value.

  As illustrated in FIG. 8, instead of the image 11, the observation image signal 12 output from the signal amplifier 70 is directly input to the image signal processing device 10, and the index value indicating the luminance information and the focus shift is calculated. The control signal 18 of the signal amplifier can be determined based on the luminance information and the index value.

  FIG. 9 is a diagram illustrating an example of an image signal processing apparatus that performs contrast / brightness adjustment based on the lens control amount 74 and the image 11 or the observed image signal 12. The image signal processing device 90 includes a focus deviation calculation unit 91, a luminance information extraction unit 14, and a contrast / brightness adjustment unit 15 whose adjustment target is a signal amplifier. In the present embodiment, it is assumed that the image signal processing device 90 is generally configured by a computer having a CPU (Central Processing Unit) and a memory, and executes signal processing therein by digital processing. However, you may comprise by hard wired.

  The focus shift calculation unit 91 receives the lens control amount 74 for controlling the focus and outputs the focus shift index value 16. The luminance information extraction unit 14 receives the image 11 or the observation image signal 12 and outputs luminance information 17 of the image or observation image signal. The luminance information 17 becomes the current contrast and brightness of the image 11 or the image observation signal 12.

  The contrast / brightness adjustment unit 15 receives the focus deviation index value 16 calculated by the focus deviation calculation unit 91 and the luminance information 17 extracted by the luminance information extraction unit 14 as input, and obtains appropriate contrast and brightness at the normal focus. The control signal 18 of the signal amplifier for changing is output. The control signal of the signal amplifier indicates a gain value and a bias value for setting to the signal amplifier.

  Details of the focus deviation calculation unit will be described with reference to FIG. The focus shift calculation unit 100 includes a normal focus lens control amount output unit 101 and a focus shift extraction unit 102, and has a function of calculating the focus shift index value 16 from the lens control amount 74. The lens control amount output unit 101 at the time of normal focus has a lens control amount at the time of normal focus registered in advance, and outputs a lens control amount 103 at the time of normal focus. Further, a mechanism in which the output value of the lens control amount at the normal focus differs depending on the observation condition of the sample may be incorporated. The focus shift extraction unit 102 obtains the difference between the lens control amount 74 and the normal focus lens control amount 103 and outputs the focus shift index value 16. The contrast / brightness adjusting unit 15 has the same configuration as that of the first embodiment.

  According to the present embodiment, an appropriate contrast / brightness correction value can be obtained in a defocused state, which is effective in suppressing the amount of beam irradiation on the sample and the processing time.

  FIG. 11 is a diagram for explaining another example in which an image signal processing apparatus is applied to a charged particle beam apparatus. Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 11 to 13 as appropriate. The mirror body 61 has the same configuration as that of the second embodiment. The image signal processing device 90 receives the lens control amount 74 of the objective lens control unit and the image 11 stored in the image memory, calculates an index value indicating a focus shift, and controls the signal amplifier based on the index value. The signal 18 is determined.

  The operation of the image signal processing apparatus 90 when applied to a charged particle beam apparatus will be described using the flowchart of FIG. First, the lens control amount 74 of the objective lens control unit 73 and the image 11 generated from the display image generation unit 71 are acquired (step S20). Next, the luminance information extraction unit 14 extracts luminance information of the image (step S21). Next, the focus deviation calculation unit 91 calculates the focus deviation index value 16 from the lens control amount (step S22). A target value (target contrast and target brightness) is determined from the extracted luminance information and the calculated defocus index value (step S23). Next, the luminance information extracted from the image is compared with the target value (step S24).

  If the brightness information does not reach the target value in the determination of step 24, it is determined that contrast / brightness adjustment is necessary, and the contrast / brightness adjustment unit 15 determines the target value (target contrast and target brightness) from A gain value and a bias value are determined (step S25). The determined gain value and bias value are set in the signal amplifier 70, and the contrast and brightness of the image are adjusted (step S26).

  On the other hand, if the luminance information has reached the target value in the determination of step 24 in which the lens control amount and the image are acquired and the luminance information extracted from the image and the target value determined from the lens control amount are compared, The brightness adjustment is terminated, and the image after contrast / brightness adjustment is displayed on the image display 72. The image display 72 may display an image being adjusted for the purpose of confirming a change in contrast and brightness.

  As described above, in a charged particle beam apparatus having an image processing signal device that performs contrast / brightness adjustment based on an index value indicating a focus shift obtained from a lens control amount, by repeatedly performing contrast / brightness adjustment, Contrast and brightness can be as close as possible to the target values.

  In addition, as illustrated in FIG. 13, instead of the image 11, the observation image signal 12 output from the signal amplifier 70 is input and luminance information is extracted, and the control signal 18 of the signal amplifier is obtained based on the luminance information. It can also be determined. In this embodiment, the lens control amount of the objective lens control unit is used. However, other lens control amounts may be used as long as they are used for focus adjustment. For example, in the case of an electromagnetic lens, an excitation current may be used, and in the case of an electrostatic lens, an applied voltage may be used. Moreover, the parameter which shows the value which changes according to lens intensity like the DAC value used for control of these lenses may be used.

  FIG. 14 is a diagram illustrating an example of a GUI (Graphical User Interface) screen for performing contrast / brightness adjustment. This screen is displayed on the image display 72, and the operator uses this screen to set execution conditions and adjust contrast and brightness.

  First, the operator activates the execution screen 400 on the image display 72 and determines whether or not to perform contrast / brightness adjustment from the sample image displayed on the image display screen 407. Next, as an adjustment method, an adjustment 402 based only on luminance information or an adjustment 403 based on focus deviation is selected, and an automatic adjustment button 401 is pressed. In response to pressing of the automatic adjustment button 401, contrast / brightness adjustment is started by the previously selected adjustment method.

  The adjustment 402 only for luminance information is a mode in which contrast and brightness are adjusted so that the luminance becomes a preset target value without considering focus shift. The adjustment 403 based on the focus shift is a mode for adjusting the contrast and the brightness by calculating an index value indicating the focus shift in accordance with the processing flow of FIG. 7 or FIG. In the adjustment 403 based on the focus deviation, the target contrast and the target brightness at the time of adjustment can be set as in the conditions A404, B405, and C406, and the operator can adjust according to the pattern shape, for example. Conditions can be selected. The image display screen 407 displays a sample image after contrast / brightness adjustment, which is used for visual confirmation of whether or not the adjustment is properly performed. For example, when contrast / brightness adjustment clearly fails, the operator can determine whether readjustment is necessary by looking at the state of the image display screen 407. After finishing the contrast / brightness adjustment, the operator presses a close button 408 to close the execution screen 400 and finish the adjustment.

  As described above, by preparing means for selecting and executing adjustment based only on luminance information and adjustment based on focus deviation from the execution screen, the optimum adjustment means can be obtained based on the usage conditions of the charged particle beam apparatus. It becomes possible to select.

  In this embodiment, the button is used as the function selection unit, but the expression of the adjustment type selection method is not limited to this.

  FIG. 15 is a diagram for explaining an example of a condition setting screen (GUI screen) for setting conditions for performing automatic operation in the charged particle beam apparatus. The condition setting screen 500 is displayed on the image display 72 as one of recipe files for performing automatic operation.

  First, the operator activates the condition setting screen 500 and then selects the sample pattern flag 501 or the adjustment-specific pattern flag 502 used for contrast / brightness adjustment. By selecting the flag 501 or 502, it is determined whether to use the sample on the stage or the adjustment pattern. When the sample pattern flag 501 is selected, the pattern stage coordinates, the sample image acquisition magnification, and the number of frames for acquiring the sample image are also input from the numerical value input windows 503, 504, and 505, respectively. When the adjustment dedicated pattern flag 502 is selected, the stage coordinates, the magnification, and the number of frames that are stored in advance are set in the respective numerical value input windows. Note that the number of frames set here is the number of scan image integrations for forming a pattern image.

  Next, ON / OFF of contrast / brightness adjustment is selected. If the contrast / brightness adjustment flag 506 is ON, adjustment is performed. Since the adjustment is not performed if the flag 506 is OFF, it is desirable to select under the condition that the contrast / brightness adjustment is not necessary.

  When the contrast / brightness adjustment flag 506 is ON, either an adjustment 507 based only on luminance information or an adjustment 508 based on focus deviation can be selected as an adjustment method. The adjustment 507 only for luminance information is a mode in which contrast and brightness are adjusted so that the luminance becomes a preset target value without considering focus shift.

  The adjustment based on the focus shift 508 is a mode for adjusting the contrast and the brightness by calculating an index value indicating the focus shift in accordance with the processing flow of FIGS. In the adjustment 508 based on the focus shift, the target contrast and the target brightness at the time of adjustment can be set as in the conditions A509, B510, and C511, and the operator can adjust according to the pattern shape, for example. Conditions can be selected.

  Next, the operator selects the timing of contrast / brightness adjustment during execution of automatic operation. For example, when the frequency of contrast / brightness adjustment is high, 512 for each analysis point or 513 before focus adjustment is set, and contrast and brightness are adjusted for each analysis point or for each focus adjustment. If the difference in pattern brightness does not occur much, it is better to select 514 for each sample exchange in consideration of the throughput, and to adjust the contrast and brightness each time the sample used in the charged particle beam apparatus is exchanged. . By providing such an option, it is possible to select an optimal contrast / brightness adjustment timing based on the use conditions of the charged particle beam apparatus, the material of the sample, and the like.

  In addition, it is also possible to select the user setting 515 and perform contrast / brightness adjustment at a timing separately registered in advance.

  As described above, if the contrast / brightness adjustment based on the focus shift can be selected as one of the recipe files on the condition setting screen, it can also be applied during automatic operation.

  In the present embodiment, the flag is used to explain the condition setting screen of the automatic driving function, but the notation of the flag and the expression of the adjustment type selection method are not limited thereto.

  When contrast and brightness are adjusted based on luminance, it is necessary to scan the sample with an electron beam after focus adjustment in order to form an image for that purpose. On the other hand, in the adjustment using the focus deviation index value, the contrast and the like are adjusted based on the predicted value.

  For example, if it is acceptable to irradiate the sample with an electron beam, it may be desirable to adjust contrast or the like based on the luminance of the image. Therefore, as in the GUI screen illustrated in FIG. 15, a mode for adjusting contrast / brightness based on luminance information and a mode for adjusting contrast / brightness based on focus deviation information can be arbitrarily switched. With this configuration, the apparatus conditions can be set in consideration of the type of sample and the accuracy of contrast / brightness adjustment.

10, 90 Image signal processing device 11 Image 12 Observation image signal 13, 20, 91, 100 Focus deviation calculation unit 14 Luminance information extraction unit 15, 30 Contrast / brightness adjustment unit 16 Focus deviation index value 17 Luminance information 18 Control of signal amplifier Signal (Gain value / Bias value)
DESCRIPTION OF SYMBOLS 21 Signal parameter extraction part 22 Positive focus parameter output part 23 Signal parameter 24 Positive focus parameter 25,102 Focus shift extraction part 31 Target contrast determination part 32 Target brightness determination part 33 Target contrast 34 Target brightness 35 Gain value determination part 36 Bias value determination Part 40 Histogram 41 before adjustment Histogram 42 after adjustment Histogram width change (contrast)
43 Histogram position change (brightness)
44 Histogram at proper focus (appropriate brightness)
50 Observation image signal 51 before adjustment 51 Maximum value adjustment by multiplying gain value (target contrast)
52 Average value adjustment by adding bias values (target brightness)
53 Observation image signal after adjustment (target contrast and target brightness)
54 Change in contrast / brightness of observation image signal 60 charged particle beam device 61 mirror body 62 focusing lens 63 charged particle beam 64 beam source 65 objective lens 66 sample 67 sample holder 68 XY stage 69 detector 70 signal amplifier 71 display image generation unit 72 Image Display 73 Objective Lens Control Unit 74 Lens Control Amount 80 Charged Particle Beam Device (Observation Image Signal)
101 Lens control amount output unit 103 at the time of positive focus Lens control amount 110 at the time of positive focus Charged particle beam device (image + lens control amount)
120 Charged particle beam device (observation image signal + lens control amount)

Claims (10)

A charged particle source that emits a charged particle beam, a detector that detects a signal obtained based on irradiation of the sample with the charged particle beam, and an image that forms an image based on the signal detected by the detector In a charged particle beam apparatus equipped with a signal processing device,
The image signal processing apparatus includes: a focus deviation calculation unit that obtains an index value of focus deviation of the charged particle beam based on the detected signal; and a focus deviation index value obtained by the focus deviation calculation unit. A contrast / brightness adjustment unit that adjusts the contrast and brightness of the image, and the contrast / brightness adjustment unit includes the focus deviation index value, the target contrast, the contrast adjustment amount, or the gain value of the amplifier of the detector. A signal for adjusting the contrast based on a table in which the relationship is registered, or an arithmetic expression indicating a relationship between the focus deviation index value and a target contrast, a contrast adjustment amount, or a gain value of the amplifier of the detector A charged particle beam device characterized by generating A charged particle source that emits a charged particle beam, a detector that detects a signal obtained based on irradiation of the sample with the charged particle beam, and an image that forms an image based on the signal detected by the detector In a charged particle beam apparatus equipped with a signal processing device ,
The image processing apparatus includes a focus deviation calculation unit that obtains an index value of a focus deviation of the charged particle beam based on the detected signal, and a focus deviation index value obtained by the focus deviation calculation unit. A contrast / brightness adjustment unit that adjusts the contrast and brightness of the image, and the contrast / brightness adjustment unit includes the focus deviation index value, the target brightness, the brightness adjustment amount, or the bias value of the amplifier of the detector; A signal for adjusting the brightness based on a table in which a relationship is registered, or an arithmetic expression indicating a relationship between the focus deviation index value and the target brightness, the brightness adjustment amount, or the bias value of the amplifier of the detector. A charged particle beam device generated. In claim 1 or 2 ,
The image processing apparatus, the charged particle beam based on the focus evaluation value of the autofocus before and after the charged particle beam apparatus according to claim Rukoto determined the focus shift evaluation value. In claim 1 or 2 ,
The charged particle beam apparatus, wherein the image processing apparatus obtains the defocus index value based on a lens control amount of the charged particle beam. In claim 1 or 2 ,
The image processing apparatus includes a luminance information of the image, the focus error on the basis of the index value, the detector amplifier charged particle beam apparatus characterized that you generate a control signal. In a contrast / brightness adjustment method for adjusting the contrast and brightness of an image obtained when a charged particle beam is irradiated onto a sample,
  Based on irradiation of the charged particle beam to the sample, an index value of defocus of the charged particle beam is obtained, and the defocus index value, target contrast, contrast adjustment amount, or gain value of the amplifier of the detector A signal for adjusting the contrast based on a table in which the relationship is registered, or an arithmetic expression indicating a relationship between the focus deviation index value and a target contrast, a contrast adjustment amount, or a gain value of the amplifier of the detector A method for adjusting contrast and brightness. In a contrast / brightness adjustment method for adjusting the contrast and brightness of an image obtained when a charged particle beam is irradiated onto a sample,
Based on irradiation of the charged particle beam to the sample, an index value of defocus of the charged particle beam is obtained, and the defocus index value , target brightness, brightness adjustment amount, or bias value of the detector amplifier Or a signal for adjusting the brightness based on an arithmetic expression indicating a relationship between the focus deviation index value and the target brightness, the brightness adjustment amount, or the bias value of the amplifier of the detector. A method for adjusting contrast and brightness. In claim 6 or 7,
On the basis of the focus evaluation value of the autofocus before and after the charged particle beam, contrast brightness adjustment method comprising Rukoto determined the focus deviation index value. In claim 6 or 7,
Based on the lens control amount of the charged particle beam, contrast brightness adjustment method comprising Rukoto determined the focus shift evaluation value. In claim 6 or 7,
And luminance information of the image, the focus error on the basis of the index value, contrast brightness adjustment method characterized that you generate a control signal of the amplifier of the detector.

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