JP2007335271A - Image processing method, image processing device, and charged particle beam device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing device in which image processing is possible without complicating a circuit configuration when the image processing that is highly flexible is carried out against images that is input with various scanning forms, and provide a charged particle beam device provided with the image processing device. <P>SOLUTION: In the charged particle beam device in which charged particle beams are scanned on a sample, in which signals generated from the sample are detected to form a sample image, an input means for setting a scanning mode of the charged particle beams, and the image processing device for forming the sample image according to the scanning mode set by the input means are provided. The image processing device has an arrangement changing control means for calculating address data on the sample corresponding to the scanning mode of the charged particle beams, and a sequential scanning type conversion means for changing arrangement of signals digitized according to values of the address data. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image processing method and an image processing apparatus in a charged particle beam apparatus such as a scanning electron microscope, an electron beam drawing apparatus, and an FIB (focused ion beam) apparatus.

  A charged particle beam apparatus is an apparatus that observes and processes a sample by irradiating the sample with a charged particle beam such as an electron beam or an ion beam. For example, in a scanning electron microscope, a sample image is formed by irradiating a sample with an electron beam and detecting secondary electrons and reflected electrons generated from the sample. Electron beam lithography equipment and FIB equipment perform pattern formation and processing by irradiating a sample with an electron beam or ion beam. Secondary electrons generated from the sample during irradiation with the electron beam or ion beam are emitted from the sample. A sample image can also be formed by detection.

  The scanning of the charged particle beam on the sample usually starts from the upper left corner of the rectangular observation area. Then, sequential scanning is adopted in which scanning is performed from the left end to the right end of the observation area along the X direction under an orthogonal XY coordinate system, and this X direction scanning is repeated while shifting by one scanning line in the Y direction. Yes. The sample image is displayed on the display device according to the scanning pattern of the charged particle beam, using the secondary electron signal generated from the sample by irradiation of the charged particle beam as a luminance signal.

  The charged particle beam apparatus is characterized in that the signal to noise ratio, that is, the S / N, is extremely poor because the detected signal is weak. For this reason, as a method for improving the S / N for the input signal, the same observation area is scanned a plurality of times, and frame integration processing is performed on the image signal in units of frames obtained by each scanning, Filter processing by convolution calculation is performed. Moreover, in order to improve the contrast of the image of the fine structure of the sample, a complicated contrast-enhanced filter process is performed.

  In this way, the sample image formed by using image processing is observed, the structure of the minute portion is analyzed and confirmed, and the size of the minute portion is determined from the sample image to perform dimension management. In particular, in a semiconductor device manufacturing process, a scanning electron microscope is used as a semiconductor inspection apparatus that performs daily dimensional management and the like.

  When used as a semiconductor inspection apparatus, good visibility by more complicated image processing is required for observing the hole bottom of a sample, and high throughput is also required. In response to these demands, a dedicated circuit configured with hardware executes basic image processing. When more complicated image processing is required, image data is once taken into an external computer and software is downloaded. Processing by wear. Basic image processing performed by a dedicated image processing circuit includes the above-described frame integration, filter processing, contrast enhancement, and the like. In a display device, an image signal processed by a dedicated circuit is temporarily stored in an image memory, and the stored signal is displayed on the display device.

  Since image formation by the charged particle beam apparatus is performed by secondary electrons generated from the sample, charge exchange occurs between the sample and the apparatus during the image formation process. The charging phenomenon resulting from the exchange of electric charges has an adverse effect on image formation, which is a problem in performing analysis and dimensional management. To solve this problem, it is possible to set multiple scanning patterns of charged particle beams, select the scanning pattern according to the symmetry of the sample, and combine the images from the multiple scanning patterns to form the sample image Thus, a technique for eliminating the influence of charging is known (for example, see Patent Document 1).

  Further, in the scanning electron microscope, when the scanning frequency of the scanning electron beam in the scanning vertical direction is observed at a low magnification, there is a problem that the sampling theorem is not satisfied and aliasing occurs on the observation image. In order to solve this problem, there is known a method for suppressing the occurrence of aliasing and reducing image noise while maintaining the resolution by offsetting the scanning interval of the electron beam and performing averaging (for example, patents). Reference 2).

JP-A-9-180667 JP-A-5-74402

  From these known techniques, using various scanning patterns of a charged particle beam in accordance with the purpose and material of observation is very effective in improving image quality such as charging and aliasing. However, image data acquired by various scanning patterns is different from image data acquired by sequential scanning, and has a different data configuration. Filter processing by convolution calculation is generally performed using a mask. However, when there are various scanning patterns, an arithmetic circuit that depends on the scanning pattern is required, which complicates the arithmetic circuit and increases costs. There is also a problem that the degree of freedom in filter design is also impaired.

  The present invention has been made to solve the above-mentioned problems caused by various scans, and its purpose is to perform image processing with a high degree of freedom on images input in various scan formats. An object of the present invention is to provide an image processing apparatus capable of image processing without complicating a circuit configuration and a charged particle beam apparatus including the image processing apparatus.

  In the charged particle beam apparatus that scans a charged particle beam on a sample, detects a signal generated from the sample, and forms a sample image, an input unit that sets a scanning mode of the charged particle beam; This can be achieved by a configuration including an image processing apparatus that forms the sample image in accordance with the scanning mode set by the input means.

  The image processing apparatus includes a rearrangement control unit that calculates address data on the sample corresponding to the scanning mode of the charged particle beam, and a sequential scanning format that rearranges the digitized signals according to the value of the address data. Conversion means.

  According to the present invention, an image processing apparatus capable of performing image processing without complicating a circuit configuration when performing image processing with a high degree of freedom for an image input in various scanning formats, and the image processing apparatus are provided. A charged particle beam apparatus can be obtained.

  Embodiments of the present invention will be described below with reference to the drawings. In the following description, in order to understand the present invention, many specific matters are shown, but the present invention is not limited to application to the examples shown in the following description. Also, in the examples, well-known circuits are shown in block diagram form in order to avoid unnecessarily obscuring the present invention by showing unnecessary details. In most cases, technical details regarding timing and the like are not necessary to understand the present invention, and descriptions that appear to be within the skill of ordinary digital circuit engineers are omitted.

FIG. 1 shows a scanning electron microscope (Scanning Electron Microscope) which is an embodiment to which the present invention is applied.
It is a block diagram which shows the main structures of Microscope. In the sample chamber 207, a sample stage 206 that can be moved by inverting the sample 205 is disposed. The sample chamber 207 is kept at a high vacuum by a vacuum pump (not shown). An electron gun 201 and an electron lens are arranged in the mirror body 208. An electron beam 209 generated from the electron gun 201 passes through the condenser lens 202, is converged by the objective lens 210, and is irradiated onto the sample 205. The deflecting lens 203 has a role of scanning the focused electron beam 209 on the sample 205 two-dimensionally.

  The scanning pattern of the electron beam 209 is determined by a deflection signal applied to the deflection lens 203. The deflection signal is generated by the deflection lens controller 10 of the lens control means 9. In the deflection lens controller 10, several patterns are prepared as deflection signals and can be selected.

The scanning pattern is selected by the operator using an input control means such as a mouse or a keyboard attached to the host computer 20 while viewing the screen displayed on the display 17 connected to the host computer 20.

FIG. 2 is a screen view showing an example of a GUI (Graphical User Interface) screen displayed on the display 17, and names of scanning patterns such as “raster scan”, “spiral scan”, and “reciprocal scan” as scan modes are displayed on the screen. Is displayed on the selection button 1001. When the operator determines a desired scanning mode through input control means such as a mouse and a keyboard and designates a corresponding selection button 1001, the host computer 20 recognizes this operation,
The SEM control means 21 is instructed to give a scan pattern selection control command.

  When a plurality of scanning patterns are required for one sample, the screen shown in FIG. 2 is displayed within the procedure for setting the electro-optical conditions including each scanning pattern. Is specified.

  Upon receiving the scanning mode selection control command, the SEM control unit 21 sets the operation parameters of the condenser lens 202, the deflection lens 203, and the objective lens 210 to the lens control unit 9 so as to correspond to the selected scanning mode. Give an instruction signal to control. The relationship between the scanning mode and these parameters is stored in advance in the SEM control means 21 as, for example, data in a look-up table format. The lens control unit 9 receives a control signal from the SEM control unit 21 and sets one of the scanning patterns stored in the deflection lens controller 10 to generate a deflection signal.

  The operator may want to perform a scan other than the scan mode prepared in advance. In this case, it is desirable that the operator can input an arbitrary scanning pattern while viewing the screen displayed on the display 17 connected to the host computer 20.

  FIG. 3 is a screen diagram showing an example of a GUI screen displayed on the display 17. A window 1002 for inputting an arbitrary scanning pattern with a scanning coordinate X on the screen, and a set button for confirming the input content. 1003, a window 1004 for inputting the scanning coordinate Y, and a set button 1005 for confirming the input contents are displayed. When the set button 1003 and the set button 1005 are designated, the scanning state is displayed in an area 1006 as an arrow. Etc., and is easy to understand for the operator.

  When the operator performs an operation of inputting a desired scanning pattern on the GUI screen shown in FIG. 3 through input control means such as a mouse and a keyboard, the host computer 20 recognizes this operation and the input scanning pattern. Is converted into coordinate information on the sample, and this coordinate information is passed to the SEM control means 21 in the control command format in the same manner as when the scanning mode described above is selected, and the coordinate information is set in the deflection lens controller 10. In setting the coordinate information in the deflection lens controller 10, the value of the look-up table stored in the memory of the deflection lens controller 10 is added or updated.

  When a new scanning pattern is set on the screen shown in FIG. 3, the new scanning mode name is displayed on the scanning mode screen shown in FIG. 2 by inputting a new name on a screen (not shown). .

When the setting of the prepared scanning mode or pattern of the arbitrary scanning mode is completed, the deflection lens controller 10 sends a setting completion command to the SEM control means 21. The SEM control unit 21 receives a setting completion command from the deflection lens controller 10 and sends a control command indicating the start of scanning to the scan control unit 19. The scan control unit 19
In response to a control command indicating the start of scanning from the SEM control unit 21, a scan control signal is sent to the lens control unit 9 and the preprocessing unit 11.

FIG. 4 is a time chart showing the relationship between the scan timing signal and the deflection waveform. FIG. 5 is a time chart showing the relationship between the scan timing signal and the coordinate data. In FIG. 4, the lens control means 9 that has received the scan control signal (4A), according to the scanning mode set in the deflection lens controller 10, is the X-direction deflection waveform (4B) and the Y-direction deflection waveform (4C). Is applied to the deflection lens 203 via the deflection lens controller 10 to scan the electron beam 209. FIG. 4 is an example of a deflection waveform, and shows a spiral scanning pattern. At the same time, the coordinate information of the scanning pattern is sent to the preprocessing unit 11 at the timing shown in the coordinate data (5B) shown in FIG.

  The electron beam 209 is two-dimensionally scanned by the deflecting lens 203, and a signal 211 generated by the interaction between the sample 205 and the electron beam 209 is detected by the detector 204. Examples of the signal 211 include a secondary electron signal, a reflected electron signal, an Auger electron signal, a characteristic X-ray signal, and a cathode luminescence signal. The detected signal 211 is amplified by the detector 204 and input to the preprocessing unit 11.

  FIG. 6 is a configuration diagram of the preprocessing unit 11. As shown in FIG. 6, the preprocessing unit 11 amplifies the input detection signal 211 by the amplifier 101 to a signal level suitable for the A / D converter 102 that converts an analog signal into a digital signal. The converter 102 converts the digital data 107. The digital data 107 is input to the sequential scanning format conversion means 105, converted into the sequential scanning format, and then sent to the image processing unit 106. A rewritable memory device is used for the progressive scanning format conversion means 105.

  The coordinate data (5B) shown in FIG. 5 is received by the rearrangement control means 104 of the preprocessing unit 11 shown in FIG. 6, and the write address in the sequential scanning format conversion means 105 is calculated. The address data (5C) calculated by the rearrangement control means 104 is input to the sequential scanning format conversion means 105 at the timing shown in FIG.

  The sequential scanning format conversion unit 105 arranges the input digital data 107 according to the value of the address data from the rearrangement control unit 104, so that the digital data 107 converted into the sequential scanning format is stored in the preprocessing unit 11. Will be placed in memory.

  In the embodiment described with reference to FIGS. 5 and 6, the timing at which the value of the address data calculated by the rearrangement control means 104 is sent to the sequential scanning format conversion means 105 is synchronized with the timing at which the digital data 107 is sent. is doing. When actually designing this circuit, a detailed design is required to synchronize the timings of both, but this is a problem that can be easily solved by a normal circuit engineer. Description of the circuit is omitted.

  When the image processing performed in the image processing unit 106 includes time-series data comparison, for example, mask processing, etc., it is necessary to configure a plurality of arithmetic circuits corresponding to a plurality of electron beam scanning modes. However, as in this embodiment, digital data in an arbitrary scanning mode can be handled by arranging the input digital data according to the value of the address data by the digital data arithmetic circuit in the progressive scanning format.

The digital data image-processed by the preprocessing unit 11 shown in FIG.
12. The digital data stored in the frame memory (1) 12 is stored in the frame memory (2) 13 and the frame memory (3) 14 through the input bus 18 under the control of the transfer control unit 15. The frame memory (2) 13 is an image processing PC
The frame memory (3) 14 is a frame memory for transfer to the host computer 20 for display on the display 17. Note that it is desirable that the control speed of the input bus 18 by the transfer control unit 15 is not lower than the transfer speed of the preprocessing unit 11 in order to ensure real-time performance.

  With the above configuration, it is possible to obtain an image processing circuit that can cope with various scanning modes of a charged particle beam and can avoid circuit complexity.

The block diagram which shows the main structures of the scanning electron microscope which is one Example to which this invention is applied. FIG. 6 is a screen diagram showing an example of a GUI screen displayed on the display 17. FIG. 6 is a screen diagram showing an example of a GUI screen displayed on the display 17. The time chart which shows the relationship between a scanning timing signal and a deflection waveform. The time chart which shows the relationship between a scanning timing signal and coordinate data. The block diagram of the pre-processing part 11. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 9 ... Lens control means, 10 ... Deflection lens controller, 11 ... Pre-processing part, 17 ... Display, 19 ... Scan control part, 20 ... Host computer, 21 ... SEM control means,
1001 ... Selection button, 1002, 1004 ... Window, 1003, 1005 ... Set button, 1006 ... Area.

Claims (9)

  In an image processing method for digitizing a signal obtained by scanning a sample with a charged particle beam and displaying an image on a display, the digitized signal is obtained according to the value of address data on the sample corresponding to the scanning mode of the charged particle beam. An image processing method comprising rearranging signals.   In an image processing apparatus for digitizing a signal obtained by scanning a sample with a charged particle beam and displaying an image on a display, rearrangement control means for calculating address data on the sample corresponding to the charged particle beam scanning mode; An image processing apparatus comprising: sequential scanning format conversion means for rearranging the digitized signals in accordance with the value of the address data.   3. The timing at which the value of the address data is sent to the sequential scanning format conversion means and the timing at which the digitized signal is sent to the sequential scanning format conversion means are synchronized with each other. Image processing device.   In a charged particle beam apparatus that scans a charged particle beam on a sample and detects a signal generated from the sample to form a sample image, an input unit for setting a scanning mode of the charged particle beam, and a setting by the input unit A charged particle beam apparatus comprising: an image processing apparatus that forms the sample image in accordance with the scanned mode.   The image processing apparatus includes a rearrangement control unit that calculates address data on a sample corresponding to the scanning mode of the charged particle beam, and a sequential scanning format conversion unit that rearranges the digitized signals according to the value of the address data. The charged particle beam apparatus according to claim 4, comprising:   The timing at which the value of the address data is sent to the sequential scanning format conversion means is synchronized with the timing at which the digitized signal is sent to the sequential scanning format conversion means. Image processing device.   In a charged particle beam apparatus that scans a charged particle beam on a sample and detects a signal generated from the sample to form a sample image, means for selecting a plurality of scanning modes having different patterns as the scanning mode of the charged particle beam And a charged particle beam apparatus comprising: an image processing apparatus that generates a display image by processing a plurality of sample images obtained under the selected scanning mode.   The charged particle beam apparatus according to claim 7, wherein the image processing apparatus is configured to superimpose or average a plurality of sample images. The charged particle beam apparatus according to claim 7, wherein the image processing apparatus includes means for sequentially converting the digitized sample image into a scanning format.

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