Device, control method for same, and program

Abstract

A charged particle beam device 100 has an electron gun 102, a deflector 104, a detector 108, a sample stage 105 on which a sample 106 is placed, and a controller 109. Herein, the controller 109, upon receiving an instruction to create a captured image: (1) receives a VC method application region designation; (2) receives, from the detector, a secondary electron detection signal of the sample while sending a control signal generated on the basis of a predetermined scan trajectory to the deflector; and (3) generates a captured image on the basis of the secondary electron detection signal. The captured image includes a first partial region suitable for a VC method and a second partial region suitable for surface observation of the sample.

Description

Apparatus, control method thereof, and program

[0001] The present invention relates to an apparatus, a control method and a program thereof, and more particularly to an apparatus such as an electron beam apparatus and a semiconductor inspection apparatus using the same, and a control method and a program thereof.

[0002] Patent Literature 1 describes a technology related to a charged particle beam device as an electron beam device. Patent Literature 1 discloses a scanning electron microscope (hereinafter also referred to as SEM) that scans a sample multiple times with a charged particle beam, detects emitted electrons, and generates an output image. Patent Literature 1 also discloses that an image with a uniform brightness level across the entire field of view is generated by normalizing the brightness value of each pixel in a scan area by the irradiation time of the charged particle beam.

[0003] Japanese Patent Application Laid-Open No. 2015-210903

[0004] Scanning electron microscopes are used in a wide range of fields, including semiconductor devices, electronics, advanced materials, biology, and pharmaceuticals. In particular, in the field of semiconductor devices, as semiconductors become increasingly miniaturized and complex, in addition to conventional SEM observation, voltage contrast (VC) observation is also used. This technique involves irradiating a surface with an electron beam and observing the potential contrast resulting from the potential difference generated on the charged surface to observe faults and defects. However, as semiconductors become increasingly miniaturized, contrast sensitivity decreases, requiring time to find optimal scanning parameters. This requires precise positioning during observation, necessitating extra steps such as preliminary observations to confirm positional validity. As semiconductors are expected to continue to become increasingly miniaturized and complex, improving the contrast of the VC method, shortening observation times, and shortening turnaround times (TATs) are essential.

[0005] The charged particle beam device described in Patent Document 1 normalizes the cumulative brightness value per unit area of ​​the sample surface by the cumulative electron beam irradiation time for that area when a single captured image contains regions on the sample where the scanning speed is different or where secondary electrons are unlikely to be generated. This technology aligns the brightness levels of images of regions with different scanning conditions when the amount of electrons irradiated per unit area varies due to differences in scanning conditions such as scanning speed or overlapping scanning. Patent Document 1 only teaches using the cumulative electron beam irradiation time to normalize the brightness levels, but does not recognize the improvement of contrast, shortening of observation time, and shortening of turnaround time (TAT) in the VC method. Patent Document 1 also does not recognize the need to acquire captured images in VC observation by taking into account the shape, area, material, etc. of the object being observed.

[0006] An object of the present invention is to provide an apparatus capable of improving contrast, shortening observation time, and shortening TAT, and a method for controlling the same.

[0007] Other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[0008] A brief summary of a representative embodiment of the present invention will be given below.

[0009] That is, in a representative embodiment, an apparatus is disclosed that includes an electron gun, a deflector, a detector, a sample stage on which a sample is placed, and a controller. When the controller receives an instruction to create an image, it: (1) receives a designation of an area to which the VC method is applied, (2) receives a secondary electron detection signal from the sample from the detector while sending a control signal generated based on a predetermined scanning trajectory to the deflector, and (3) generates an image based on the secondary electron detection signal. The image includes a first partial area suitable for the VC method and a second partial area suitable for observing the surface of the sample.

[0010] To briefly explain the effects obtained by a representative embodiment of the invention disclosed in this application, it is possible to provide an apparatus and a control method thereof that can improve contrast, shorten observation time, and shorten TAT.

[0011] 6 is a block diagram showing the configuration of a charged particle beam device according to an embodiment; FIG. 7 is a timing chart showing the relationship between an image generation control signal and pixel data according to an embodiment; FIG. 8 is a block diagram showing an example of a pixel coefficient storage unit according to an embodiment; FIG. 9 is a block diagram showing an example of a pixel integration processing unit according to an embodiment; FIG. 10 is a flowchart showing the operation of a controller according to an embodiment; FIG. 11 is a plan view showing an example of a captured image acquired by scanning a sample using a charged particle beam device according to an embodiment; and FIG. 12 is a schematic plan view showing an example of a scan pattern when scanning a sample to acquire the captured image of FIG.

[0012] In the following embodiments, when the number of elements is mentioned, it is not limited to a specific number, and may be greater than or less than a specific number, unless otherwise specified or clearly limited in principle. Furthermore, in the following embodiments, the elements are not necessarily essential, unless otherwise specified or clearly considered not to be essential in principle. Furthermore, in the following embodiments, when the shape, positional relationship, etc. of elements are mentioned, it is intended to include those that are substantially similar or approximate to the shape, etc., unless otherwise specified or clearly considered not to be essential in principle. The same applies to the above numerical values ​​and ranges.

[0013] In addition, in all the drawings for explaining the embodiments, the same components are generally designated by the same reference numerals, and repeated explanations thereof will be omitted.

[0014] Hereinafter, embodiments will be described with reference to the drawings. In the following embodiments, a scanning electron microscope will be described as an example of a charged particle beam device, but the present invention is not limited to a scanning electron microscope and can be applied to other charged particle beam devices.

[0015] <Overview of the Embodiments> In the embodiments, a semiconductor device is observed using a charged particle beam device equipped with a scanning electron microscope, and in particular, a semiconductor device is observed using VC observation. When observing a semiconductor device using a charged particle beam device using the VC method, it is important to increase the contrast (brightness level) ratio between an image captured in a region to which the VC method is applied (hereinafter also referred to as a VC method application region) and an image captured in a region to which the VC method is not applied (hereinafter also referred to as a region outside the VC method application region). Note that the image captured in the region outside the VC method application region corresponds to an image captured by performing a normal surface scan of a region to which the VC method is not applied.

[0016] In a charged particle beam device according to an embodiment, the scanning speed can be arbitrarily changed within one scanning line. For example, a VC method application region on a sample is scanned at a first scanning speed, and a region outside the VC method application region on the same line on the sample is scanned at a second scanning speed different from the first scanning speed. When an image of a predetermined field of view of the charged particle beam device is defined as one frame, an image including a partial image of the VC method application region and a partial image outside the VC method application region is acquired within one frame in one scan.

[0017] Here, pixel data of a partial image corresponding to the VC method application area on the sample is multiplied by a first pixel coefficient determined based on the characteristics of the plug in the VC method application area, such as the shape, material, area, etc. Conversely, pixel data of a partial image corresponding to an area outside the VC method application area on the sample is multiplied by a second pixel coefficient determined based on a second scanning speed.

[0018] As a result, with the charged particle beam device according to the embodiment, it is possible to acquire one frame of an image within an observation field (predetermined field of view) including a partial image of the VC method application region and a partial image outside the VC method application region in a single scan, making it possible to understand the validity of the position of the VC method application region and its relationship with other structures on the sample that appear outside the VC method application region, and it is also possible to acquire the image in one go with a normal scan. This eliminates the need for preliminary observation work, which involves confirming the position and then performing VC method observation, thereby shortening the observation time and TAT.

[0019] In addition, images in the VC method application area are generated by multiplying pixel data by a first pixel coefficient that takes into account the charging characteristics due to the shape, material, area, etc. of the plug in the VC method application area, so it is possible to increase the contrast compared to images outside the VC method application area.

[0020] 1 is a block diagram showing the configuration of a charged particle beam device according to an embodiment. In FIG. 1, reference numeral 100 denotes a charged particle beam device according to embodiment 1. The charged particle beam device 100 includes a scanning electron microscope 101 and a controller 109 that controls the scanning electron microscope 101.

[0021] <Scanning Electron Microscope> The scanning electron microscope 101 includes an electron gun 102, a scanning deflector (hereinafter also simply referred to as a deflector) 104, a sample stage 105, and a detector 108.

[0022] An electron beam 103 emitted from an electron gun 102 is deflected by a deflector 104 and focused on a sample 106 placed on a sample stage 105. When the sample 106 is irradiated with the electron beam 103, it emits secondary electrons 107. The emitted secondary electrons 107 are detected by a detector 108 and transmitted as a detection signal to a controller 109. The controller 109 performs signal processing on the received detection signal to generate an image 120 of the sample 106.

[0023] 1 illustrates a pair of opposing deflectors 104 to avoid complicating the drawing, but more specifically, two pairs of deflectors 104 that are substantially orthogonal to each other are provided in the scanning electron microscope 101. The two pairs of deflectors 104 are composed of a pair of deflectors (X-direction deflectors) that scan the electron beam 103 in the X direction over the sample 106, and a pair of deflectors (Y-direction deflectors) that scan the electron beam 103 in the Y direction over the sample 106. Control signals are supplied to the X-direction deflector and the Y-direction deflector from a controller 109, and the X-direction deflector and the Y-direction deflector deflect the electron beam 103 in accordance with the control signals from the controller 109. The control signals from the controller 109 are composed of an X / Y control signal (indicated as X / Y in FIG. 1) that instructs movement of the electron beam 103 in the X and Y directions, and an electron beam irradiation time signal (indicated as irradiation time in FIG. 1) that instructs the irradiation time during which the electron beam 103 is irradiated onto the sample 106. The deflector 104 controls the electron beam 103 in accordance with the X / Y control signal and the electron beam irradiation time signal.

[0024] <Controller> Next, we will explain the controller 109. The controller 109 controls the scanning of the electron beam in the scanning electron microscope 101 based on scanning conditions and parameters set by a user (not shown), and generates a captured image based on a detection signal from the scanning electron microscope 101.

[0025] First, the setting of scanning conditions and parameters by the user will be described. Here, an example will be described in which the user sets (instructs) scanning conditions and parameters to the controller 109 using an input device (not shown) and a display device (not shown) connected to the controller 109. Also, although not particularly limited, here, a case will be described in which the user sets scanning conditions and parameters using a graphic user interface (GUI). Of course, the method for setting scanning conditions and parameters is not limited to this, but by using a GUI, the user can make settings while checking them, making the setting easier.

[0026] 1, reference numeral 110 denotes a GUI screen displayed on the display device by the controller 109. A user operates input devices such as a mouse and a keyboard to make selections or input numerical values ​​for items displayed on the GUI screen 110.

[0027] In this embodiment, one GUI screen 110 is made up of three areas 111, 112 and 113 and an image size designation area, although this is not a particular limitation.

[0028] <<<Area 111: Scanning Method>>> The user selects the scanning method of the electron beam 103 in area 111. That is, in the example shown in FIG. 1, the scanning methods are composed of three scanning methods: raster, flat, and snake. The user selects one of these three scanning methods in area 111. The electron beam 103 moves by deflection by a deflector so as to match the trajectory (scanning trajectory) determined by the selected scanning method. Note that in the example shown in FIG. 1, raster is selected as the scanning method of the electron beam 103, and raster trajectory is selected as the scanning trajectory.

[0029] <<<Area 112: VC Method Applicable Area>>> In area 112, the user sets parameters (inputs numerical values) related to scanning of the VC method applicable area. The number of VC method applicable areas set on the sample 106 is not limited to one. That is, multiple VC method applicable areas may be set on the sample 106. Area 112 shown in FIG. 1 includes a VC method applicable area number, which is an area for specifying the number of VC method applicable areas, and a numerical value of "2" is set therein. This makes it possible to set two VC method applicable areas. Of course, the numerical value set for the VC method applicable area number may be "1" or "3" or greater.

[0030] In the embodiment, the parameters of the VC method application region include information about the position of the VC method application region on the sample 106 (indicated as "position" in FIG. 1), an irradiation time for irradiating the surface of the sample 106 corresponding to each pixel in the VC method application region with the electron beam 103, and a pixel coefficient of each pixel of the captured image corresponding to the position on the sample 106 irradiated with the electron beam 103. Since the next pixel is scanned after the value set for the irradiation time has elapsed, the irradiation time can be considered as a scanning speed, and is indicated as the scanning speed in FIG. 1.

[0031] The scanning speed and pixel coefficient for each pixel in the VC application area can be set by directly inputting values ​​on the GUI screen 110 using an input device. Alternatively, for example, a setting file containing parameters for each pixel can be prepared in advance and loaded into the controller 109. Here, the pixel coefficient for the VC application area is set as a parameter taking into account the shape, area, and material of the plug in the portion of the sample 106 corresponding to each target pixel. This results in a pixel coefficient that is independent of the scanning speed. In other words, the pixel coefficient is a coefficient that takes into account the characteristics of the VC application area of ​​the sample 106, independent of the scanning speed. This allows for optimization of both the irradiation time and the VC contrast of the captured image, thereby shortening the TAT for observation and improving the observation accuracy.

[0032] For example, by slowing down the scanning speed within the VC method application region, it is possible to lengthen the irradiation time of the electron beam within the VC method application region and thereby increase the contrast of the VC method application region relative to the non-VC method application region. However, for example, if the VC method application region is small and the irradiation time is long, it is possible that the VC method application region may be damaged, so slowing down the scanning speed is undesirable. In contrast, in the embodiment, a pixel coefficient determined taking into account the shape, area, material, etc., without depending on the scanning speed is integrated with the pixels of the VC method application region to acquire an image of the VC method application region. By using an appropriate pixel coefficient that increases the integrated value, it is possible to increase the scanning speed and shorten the irradiation time, while improving (raising) the contrast of the VC method application region relative to the non-VC method application region.

[0033] The user may set the position of the VC method application area by directly inputting a numerical value on the GUI screen 110 using an input device, or, for example, by loading design data for the sample 106 and setting a predetermined position in the design data as information regarding the position of the VC method application area, or by using a position on the sample 106 as a known marker and setting the relative position from the marker to the predetermined position as information regarding the position of the VC method application area.

[0034] <<<Area 113: Outside VC Method Application Area>>> In area 113, the user sets parameters related to scanning of areas outside the VC method application area. Areas outside the VC method application area correspond to areas where normal surface scanning is performed, and in area 113, the user sets parameters (by inputting numerical values) related to scanning of areas where normal surface scanning is performed. Parameters for areas where normal surface scanning is performed include, for example, the scanning speed and pixel coefficient, and the user sets these in area 113. Of course, the scanning speed and pixel coefficient may be changed for each pixel.

[0035] <<<Image Size Designation Area>>> In addition to the three areas described above, the GUI screen 110 also includes an area for designating the size of the captured image to be acquired (image size), as an item to be set by the user. In the example of Fig. 1, the user directly inputs the value 800 x 600 as the image size into the image size designation area.

[0036] <<Configuration of Controller>> Next, an example configuration of the controller 109 will be described. The controller 109 includes a scanning trajectory generation unit 114, a control signal generation unit 115, a pixel coefficient storage unit 116, a pixel accumulation processing unit 117, an A / D (analog / digital) conversion unit 118, and a pixel memory 119. The controller 109 includes a processor, which executes a program stored in a non-volatile memory (not shown) to implement the scanning trajectory generation unit 114, the control signal generation unit 115, the pixel coefficient storage unit 116, the pixel accumulation processing unit 117, and the like. Examples of the processor include a CPU and a GPU, but other semiconductor devices may also be used as long as they are capable of executing predetermined processing. Of course, these units may also be implemented by combining logic circuits, sequential circuits, and the like.

[0037] Once the user has completed setting the scanning conditions and parameters on the GUI screen 110, they are loaded into the scanning trajectory generation unit 114. Of the loaded scanning conditions and parameters, the scanning trajectory generation unit 114 supplies the scanning trajectory (scanning method), scanning speed, position of the scanning area, and image size parameters to the control signal generation unit 115, and supplies the position of the scanning area and pixel coefficient parameters to the pixel coefficient storage unit 116. Note that the position of the scanning area here refers to the position of the VC method application area and the position outside the VC method application area. Hereinafter, in this specification, when there is no need to distinguish between the VC method application area and the area outside the VC method application area, these will also be referred to as the scanning area.

[0038] The control signal generating unit 115 inputs a control signal (X / Y control signal: X / Y) for controlling the deflector 104 and an electron beam irradiation time signal (irradiation time) calculated from the scanning time to the scanning electron microscope 101. At the same time, the control signal generating unit 115 supplies an image generation control signal for generating an image of the sample 106 to the pixel coefficient storage unit 116 and the pixel integration processing unit 117, thereby controlling the generation of the image.

[0039] The pixel coefficient storage unit 116 stores pixel coefficients set by the user and sequentially outputs the stored pixel coefficients to the pixel accumulation processing unit 117. The pixel coefficient storage unit 116 is supplied with the positions and pixel coefficients read by the scanning trajectory generation unit 114 and the image generation control signal generated by the control signal generation unit 115.

[0040] As will be described in detail later with reference to FIG. 3 , the pixel coefficient storage unit 116 includes a look-up table (hereinafter also referred to as an LUT). The pixel coefficients supplied to the pixel coefficient storage unit 116 are stored and held in the LUT. The LUT has at least the same number of elements as the number of pixels in one frame of the captured image, and the pixel coefficient for that pixel set (designated) by the user is stored in the LUT element at coordinates corresponding to the pixel coordinates of the captured image. The pixel coefficient storage unit 116 also monitors the image generation control signal from the control signal generation unit 115, and upon determining that the integration process for the current pixel has been completed, updates the coordinate address indicating the current LUT element and outputs the pixel coefficient stored in the LUT element indicated by the updated coordinate address.

[0041] The A / D conversion unit 118 converts the detection signal from the detector 108 according to the secondary electrons 107 into a digital signal and outputs it as an input signal.

[0042] The pixel integration processing unit 117 performs integration processing on the input signal converted into a digital signal by the A / D conversion unit 118 based on the image generation control signal and pixel coefficients, and stores the pixel data 202 obtained by integrating the input signal a number of times calculated from the scanning speed specified by the user in the pixel memory 119.When scanning of one frame is completed, the acquired captured image 120 is output.

[0043] Completion of the setting of the scanning conditions and parameters and reading of the same by the scanning trajectory generation unit 114 can be regarded as an instruction to the controller 109 to create the captured image 120. Furthermore, reading of the setting related to the VC method application area can be regarded as reception of a VC method application area designation by the controller 109.

[0044] <<<Image Generation Control Signals, Pixel Data>>> Next, the timing of the image generation control signals and pixel data 202 will be described with reference to the drawings. FIG. 2 is a timing diagram showing the relationship between the image generation control signals and pixel data according to an embodiment. In FIG. 2, the horizontal axis represents time and the vertical axis represents voltage. The clock signal CLK shown in FIG. 2 represents a reference clock signal. Although not particularly limited, the controller 109 operates in synchronization with this clock signal CLK.

[0045] As shown in FIG. 2, the image generation control signal 201 includes a frame control signal 203, a line control signal 204, and a pixel switching signal 205, and each of these signals (203 to 205) changes based on the rising edge (hereinafter simply referred to as the rising edge) of the clock signal CLK.

[0046] Each of the frame control signal 203, the line control signal 204 and the pixel switching signal 205 is generated by the control signal generating unit 115 shown in FIG.

[0047] The frame control signal 203 is asserted (high level) at the start of scanning. The period during which the frame control signal 203 is continuously asserted indicates that an area within the same frame is being scanned. When scanning of an entire frame is completed, the frame control signal 203 is negated.

[0048] The line control signal 204 is a signal that indicates line switching during scanning. The line control signal 204 is asserted at the start of scanning for each line, and is negated when scanning of that line is completed. If, for example, raster (trajectory) is set as the scanning method (scanning trajectory), the line control signal 204 is asserted while scanning one line, and is negated when scanning of that line is completed. Thereafter, the direction of the deflector 104 is controlled to the scanning start position of the next line, and the line control signal 204 continues to be negated during the period until scanning begins (blanket period).

[0049] The pixel switching signal 205 is a control signal indicating pixel switching. The pixel switching signal 205 is asserted for only one pulse when irradiation of the electron beam 103 for an irradiation time calculated from the scanning speed set (specified) by the user is completed for an area on the sample 106 corresponding to one pixel. The number of cycles of the clock signal CLK from the rising edge of the previous pixel switching signal 205 to the rising edge of the next pixel switching signal 205 is the number of integrations per pixel in the pixel integration processing unit 117.

[0050] That is, if the scanning speed of a certain region (VC method application region) designated by the user is fast and the beam irradiation time on the surface of that region on the sample 106 is short, the interval (the interval between rising edges) of the pixel switching signal 205 becomes short and the number of pixel integrations in the pixel integration processing unit 117 also decreases. On the other hand, if the scanning speed designated by the user is slow, the beam irradiation time on the surface of that region on the sample 106 becomes long, so the interval of the pixel switching signal 205 becomes long and the number of pixel integrations in the pixel integration processing unit 117 also increases.

[0051] The pixel data 202 is data obtained by integrating an input signal, which is a detection signal from the detection unit 108 converted into a digital signal by the A / D conversion unit 118, using a pixel coefficient specified by the user for the number of cycles of the clock signal CLK until the pixel switching signal 205 is asserted again. For example, the pixel data 202 indicated by "D0" indicates a value obtained by integrating the pixel coefficient for two cycles of the clock signal CLK (two-pixel integration). Similarly, the pixel data 202 indicated by "D2" indicates a value obtained by integrating the pixel coefficient for four cycles of the clock signal CLK (four-pixel integration).

[0052] <<<Pixel Coefficient Storage Unit>>> Fig. 3 is a block diagram showing an example of a pixel coefficient storage unit according to an embodiment. As shown in Fig. 3, the pixel coefficient storage unit 116 includes at least an address counter 301 and an LUT 302.

[0053] 3, in the LUT 302, a plurality of elements are stored at addresses (intersections of the X and Y coordinates) of an array specified by an X coordinate (X) and a Y coordinate (Y). The array configured by the X and Y coordinates corresponds to one frame. That is, each pixel in one frame corresponds to an address specified by the X and Y coordinates, and the elements stored at the addresses correspond to the pixels.

[0054] At each address of the LUT 302, a pixel coefficient 303 for each pixel set by the user on the GUI screen 110 is stored as an element. That is, the pixel coefficients 303 from the scanning trajectory generation unit 114 are stored in the LUT 302. At this time, the address of the LUT 302 to store the pixel coefficients 303 is determined by a parameter indicating the position of the scanning area from the scanning trajectory generation unit 114. Note that in FIG. 3, "a0" to "a3" shown as pixel coefficients 303 correspond to the pixel data "D0" to "D3" shown in FIG. 2. That is, "a0" is a pixel coefficient corresponding to pixel data "D0", and "a2" is a pixel coefficient corresponding to pixel data "D2".

[0055] The address counter 301 is supplied with a frame control signal 203, a line control signal 204, and a pixel switching signal 205. Based on these signals, the address counter 301 generates an address that identifies an element of the LUT 302. A pixel coefficient stored in the LUT 302 is selected by the address generated by the address counter 301, and the selected pixel coefficient is output from the pixel coefficient storage unit 116 as a pixel coefficient 303.

[0056] The address generated by the address counter 301 is also used as an address indicating an element of the image memory 119 shown in Fig. 1. That is, in the image memory 119, the pixel data 202 corresponding to the address specified by the address generated by the address counter 301 is stored.

[0057] <<<Pixel Integration Processing Unit>>> Figure 4 is a block diagram showing an example of a pixel integration processing unit according to an embodiment. As shown in Figure 4, the pixel integration processing unit 117 includes at least a multiplier 401, an adder 402, a flip-flop circuit (hereinafter also referred to as an FF circuit) 403 that holds data during integration processing, and a latch circuit 404 that stores data after integration processing and outputs it to the image memory 119 as pixel data. The pixel integration processing unit 117 receives at least an input signal 405 obtained by converting a secondary electron signal detected by the detector 108 (Figure 1) into a digital signal using the A / D conversion unit 118 (Figure 1), the pixel coefficient 303 output from the pixel coefficient storage unit 116 (Figure 3), the frame control signal 203, and the pixel switching signal 205.

[0058] The multiplier 401 multiplies the input signal 405 by the pixel coefficient 303 and outputs the multiplication result to the adder 402. The adder 402 adds the previous multiplication result held in the FF circuit 403 to the current multiplication result, and updates the value stored in the FF circuit 403 with the addition result.

[0059] The frame control signal 203 is input to both an FF circuit 403 and a latch circuit 404, and the FF circuit 403 and the latch circuit 404 are each reset by the rising edge of the frame control signal 203. The FF circuit 403 is also reset by the rising edge of the pixel switching signal 205. In contrast, the latch circuit 404 is enabled by the rising edge of the pixel switching signal 205.

[0060] The FF circuit 403 is reset by the rising edge of the frame control signal 203, so that the FF circuit 403 is reset at the start of one frame. The FF circuit 403 is also reset by the rising edge of the pixel switching signal 205. In other words, the addition result of the adder 402 is accumulated in the FF circuit 403 during the period from when the pixel switching signal 205 rises until the next rise.

[0061] For example, when the pixel data 202 is "D0," as shown in FIG. 2 , the pixel switching signal 205 rises once and then rises again two cycles of the clock signal CLK. As a result, during the first cycle of the clock signal CLK, the input signal 405 and "a0" of the pixel coefficient 303 are multiplied by the multiplier 401, and the multiplication result and the output of the reset FF circuit 403 are added by the adder 402 and stored in the FF circuit 403. During the second cycle of the clock signal CLK, the input signal 405 and "a0" of the pixel coefficient 303 are multiplied by the multiplier 401, and the multiplication result and the multiplication result of the first cycle stored in the FF circuit 403 are added by the adder 402 and stored in the FF circuit 403. Although the example has been described using the case where pixel data 202 is "D0," in other cases (e.g., D1 to D3), the number of times to be accumulated is similarly determined according to the rising interval of pixel switching signal 205 (the number of cycles of clock signal CLK).

[0062] The latch circuit 404 is also reset by the rising edge of the frame control signal 203, so that the latch circuit 404 is reset at the start of one frame. After that, the latch circuit 404 is enabled by the rising edge of the pixel switching signal 205. In the enabled state, the latch circuit 404 takes in the output of the FF circuit 403 and outputs it as pixel data 202.

[0063] 3 and 4, "a0" to "a3" indicate pixel coefficients (first pixel coefficients) set based on the characteristics of the VC method application area. In this case, the position of the VC method application area on the sample 106 is expressed in X and Y coordinates as (X0, Y0) to (X3, Y0). Although not shown in FIGS. 3 and 4, pixel coefficients (second pixel coefficients) set for areas outside the VC method application area are also stored in the LUT and are integrated with the input signal in the pixel integration processing unit 117 shown in FIG. 4. For areas outside the VC method application area, the scanning speed is set to, for example, one cycle of the clock signal CLK, and the second pixel coefficients are set based on this scanning speed.

[0064] The area outside the VC method application area is, for example, the entire area in one frame excluding the VC method application area, which eliminates the need to set the position of the area outside the VC method application area as shown in FIG.

[0065] <<<Processing Flow>>> Figure 5 is a flowchart showing the operation of the controller according to the embodiment. Next, the operation of the pixel coefficient storage unit and pixel accumulation processing unit according to the first embodiment will be described using Figures 1 and 3 to 5. Here, the explanation will be given taking as an example a case where the user sets a raster trajectory as the scanning trajectory, as shown in Figure 1. Of course, the raster trajectory is just one example, and the present invention is not limited to this. Furthermore, it is assumed that pixel coefficients are supplied to the LUT 302 of the pixel coefficient storage unit 116 from the scanning trajectory generation unit 114, and that pixel coefficients have already been stored in each element of the LUT 302.

[0066] First, in step 500, the controller 109 starts a scan.

[0067] Next, in step 501, the controller 109 asserts the frame control signal 203 to initialize the image memory 119. The controller 109 also initializes the addresses (address values ​​indicating the X and Y coordinates) of the address counter 301 in the pixel coefficient storage unit 116. This initializes the address values ​​specifying the elements of the image memory 119 and the elements of the LUT 302.

[0068] In step 502, the controller 109 uses the address counter 301 to select an element designated by the address value initialized in step 501 from the elements of the LUT 302 in the pixel coefficient storage unit 116, reads out (updates) the pixel coefficient 303 stored in the selected element, and, in response to the rising edge of the frame control signal 203, initializes the FF circuit 403 in the pixel integration processing unit 117 and initializes the pixel data (pixel value) 202 latched in the latch circuit 404.

[0069] Then, in step 503, the controller 109 executes an integration process in the pixel integration processing unit 117 using the read pixel coefficients 303 and the input signal. That is, the integration process is executed using the multiplier 401, adder 402, and FF circuit 403 shown in FIG. 4. Each time this integration process is completed, the controller 109 determines in step 504 whether the pixel switch signal 205 is asserted. In other words, each time the clock signal CLK shown in FIG. 2 rises, it is determined whether the pixel switch signal 205 is rising.

[0070] If it is determined in step 504 that the pixel switch signal 205 is not asserted (No), the controller 109 repeats the accumulation process of step 503 to obtain an accumulated value until the pixel switch signal 205 is asserted. In other words, multiplication is performed between the same pixel coefficient and the same input signal for the number of cycles of the clock signal CLK from when the pixel switch signal 205 is asserted, negated, and then asserted again, and the result is added to the previous multiplication result to obtain an accumulated value.

[0071] If the pixel switch signal 205 is asserted in step 504 (Yes), the controller 109 enables the latch circuit 404 in step 505, updates the latch circuit 404, updates the pixel data 202, and stores it in the pixel memory 119. That is, the updated pixel data 202 is stored in the pixel memory 119, and the current address value (X coordinate) is updated. At this time, the pixel data 202 stored in the pixel memory 119 is pixel data acquired by performing integration processing between the pixel coefficient and the input signal in the pixel integration processing unit 117 for the number of cycles of the clock signal CLK in the interval between rising edges of the pixel switch signal 205.

[0072] Next, in step 506, the controller 109 determines whether a line switch has occurred based on the line control signal 204. If the line control signal 204 is not negated, the controller 109 determines that a line switch has not occurred, and returns to step 502 to execute the process. That is, in step 502, the controller 109 initializes the pixel values ​​and updates the pixel coefficients, and in steps 503 and 504, it executes an accumulation process using the updated pixel coefficients and the updated input signal, and in step 505, it stores the pixel data obtained by the accumulation process at the updated address value.

[0073] The address value is updated in step 505 by updating the address generated by the address counter 301 in the pixel coefficient storage unit 116 in response to the rising edge of the pixel switching signal 205. For example, if the current address (X coordinate, Y coordinate) generated by the address counter 301 is (X0, Y0), the address counter 301 updates the address to (X1, Y0) in response to the rising edge of the pixel switching signal 205. The control signal (X / Y control signal) output by the control signal generation unit 115 to control the deflector 104 corresponds to the address generated by the address counter 301. Therefore, when the address value generated by the address counter 301 is updated, the position on the sample 106 irradiated with the electron beam 103 also changes accordingly, and the A / D conversion unit 118 outputs an input signal according to the secondary electrons from the position irradiated with the electron beam 103. Therefore, when the address value generated by the address counter 301 is updated, the input signal input to the multiplier 401 is also updated. That is, the updated pixel coefficient and the input signal corresponding to the secondary electrons at the position on the sample 106 corresponding to the updated address value are supplied to the multiplier 401, and multiplication is performed between them.

[0074] On the other hand, if the controller 109 determines in step 506 that the line control signal 204 is negated and a line switch has occurred, the controller 109 then executes step 507. In step 507, the controller 109 determines, based on the frame control signal 203, whether one frame has ended.

[0075] In step 507, if the frame control signal 203 is not negated, the controller 109 determines that one frame has not ended, and then executes step 508.

[0076] In step 508, the controller 109 initializes and updates the address generated by the address counter 301. That is, in response to assertion of the line control signal 204, the address counter 301 updates the address value of the Y coordinate and initializes the address value of the X coordinate. That is, the address counter 301 initializes the value of the X coordinate indicating the position of the pixel and updates the value of the Y coordinate indicating the position of the line. Specifically, the address counter 301 outputs address values ​​(e.g., X0, Y1) in which the position of the line and the position of the pixel have been changed.

[0077] After step 508, the above-described steps 502 to 507 are executed. At this time, in step 502, the pixel coefficient specified by the address value (X0, Y1) is read out from the LUT 302, and the input signal input to the multiplier 401 is a signal based on secondary electrons at a position on the sample 106 specified by the X / Y control signal corresponding to the address value (X0, Y1).

[0078] When scanning of one frame is completed, the frame control signal 203 is negated. When scanning of one frame is completed, the controller 109 ends the pixel integration process in step 509. The pixel data 202 of one frame generated by the image integration process is stored in the image memory 119 and output to, for example, a display device as an image captured by scanning.

[0079] <<<Captured Image>>> An example of a captured image captured by the charged particle beam device 100 according to the embodiment will now be described. FIG. 6 is a plan view showing an example of a captured image acquired by scanning a sample once using the charged particle beam device according to the embodiment. FIG. 7 is a schematic plan view showing an example of a scan pattern when the sample is scanned to acquire the captured image of FIG. 6. FIGS. 6 and 7 show a case where the user sets scan conditions as in the GUI screen 110 shown in FIG. 1. That is, it is assumed that the scan trajectory is set to a raster trajectory as shown in FIG. 1.

[0080] Figures 6 and 7 show an example in which multiple VC method application areas with different areas and shapes, as well as areas outside the VC method application area, are set within the area of ​​sample 106 that is scanned in one go as one frame.

[0081] That is, in Figure 6, 120 indicates one frame of captured image obtained in one scan, 602_A and 602_B indicate partial images of the VC method application area with different areas and shapes, and 603 indicates a partial image of a normal surface scan outside the VC method application area.

[0082] To acquire the captured image shown in FIG. 6 , the charged particle beam device 100 according to the first embodiment scans the surface of the sample 106 using a scan pattern as shown in FIG. 7 . That is, the VC method application regions 702_A and 702_B of the sample 106, corresponding to the partial images 602_A and 602_B, are scanned with the electron beam 103 at a first scan speed. The non-VC method application region 703 of the sample 106, corresponding to the normal surface scan partial image 603, is scanned with the electron beam 103 at a second scan speed different from the first scan speed. Here, the second scan speed is set to a value faster than the first scan speed. Note that in FIG. 7 , the double-arrowed line RL indicates a retrace line, which is a switching portion of the raster trajectory and does not affect the acquisition of the captured image.

[0083] In the charged particle beam device according to the embodiment, when setting VC method application regions 702_A and 702_B on the sample 106, the user can arbitrarily set, for each of the VC method application regions 702_A and 702_B, the position of the region, the scanning speed for each pixel when scanning the region, and the pixel coefficient when scanning the region. Furthermore, for a region outside the VC method application region 703 on the sample 106, the user can arbitrarily set the scanning speed for each pixel when scanning the region and the pixel coefficient when scanning the region. By setting the scanning speed and pixel coefficient for the VC method application region and the scanning speed and pixel coefficient for the region outside the VC method application region to appropriate values, it is possible to acquire an image with improved VC contrast, which is the ratio between the VC method application region and the region outside the VC method application region.

[0084] 7 shows an example in which the same value of the first scanning speed is set for the multiple VC method application regions 702_A and 702_B, but the present invention is not limited to this. That is, when multiple VC method application regions (701_A, 701_B) exist on the sample 106 as shown in FIG. 7, different values ​​of the first scanning speed may be set for each VC method application region.

[0085] 7, multiple VC method application regions and non-VC method application regions are set on the same scanning orbit (line). By setting in this way, the scanning speed of the electron beam changes to a first scanning speed and a second scanning speed on the same scanning orbit.

[0086] 7, it is possible to obtain partial images 602_A and 602_B of the VC method application area and a regular surface scanning partial image 603 outside the VC method application area in a single scan, as shown in Fig. 6, and generate one frame of captured image 120. This makes it possible to omit the preliminary observation step that was conventionally required when performing VC observation, thereby realizing a shorter TAT for semiconductor observation and contributing to improved convenience of scanning because it is possible to grasp the validity of the position of structures shown in partial images within the VC method application area and the positional relationship with structures shown in partial images of areas outside the VC method application area where regular surface scanning is performed.

[0087] According to the embodiment, the user can arbitrarily set a pixel coefficient for each minute region on the sample, which corresponds to one pixel of the captured image, and can acquire an image with good VC contrast while shortening the beam irradiation time for that region. Furthermore, since a partial image of the VC method application region and a partial image obtained by performing a normal surface scan outside the VC method application region can be acquired as a single frame of captured image in a single scan, processes such as preliminary observation and confirmation of positional validity can be omitted, improving scanning convenience and shortening the observation time.

[0088] 7, VC method application regions 702_A and 702_B can be regarded as the first surface, and region 703 outside the VC method application region can be regarded as the second surface. In this case, scanning is performed at a first scanning speed on the first surface, and scanning is performed at a second scanning speed on the second surface. Furthermore, in FIG. 7, the solid line trajectory portion where scanning is performed at the first scanning speed can be regarded as the first scanning trajectory (first speed trajectory), and the dashed line trajectory portion where scanning is performed at the second speed can be regarded as the second scanning trajectory (second speed trajectory).

[0089] As described above, the user sets appropriate scanning speeds and pixel coefficients (first pixel coefficient, second pixel coefficient) for the VC method application area and outside the VC method application area, for example, on the GUI screen 110. Note that the scanning speed and pixel coefficients set for the area outside the VC method application area are, for example, scanning speeds and pixel coefficients suitable for normal surface scanning (surface observation), and the pixel coefficients for the area outside the VC method application area are set based on the scanning speed for the area outside the VC method application area.

[0090] In the first velocity trajectory, scanning is performed at a scanning speed suitable for the VC method, and images of a first partial region corresponding to the first surface (partial images 602_A, 602_B) are generated using an input signal based on secondary electrons from the first surface and pixel coefficients suitable for the VC method. In the second velocity trajectory, scanning is performed at a scanning speed suitable for normal surface scanning, and an image of a second partial region corresponding to the second surface (partial image 603) is generated using an input signal based on secondary electrons from the second surface and pixel coefficients suitable for normal surface scanning.

[0091] The invention made by the inventor has been specifically described above based on an embodiment, but it goes without saying that the present invention is not limited to the above embodiment and can be modified in various ways without departing from the gist of the invention.

[0092] REFERENCE SIGNS LIST 100 Charged particle beam device 101 Scanning electron microscope 102 Electron gun 104 Deflector 108 Detector 106 Sample 109 Controller 110 GUI screen 114 Scanning trajectory generation unit 115 Control signal generation unit 116 Pixel coefficient storage unit 117 Pixel integration processing unit 118 A / D conversion unit 119 Pixel memory

Claims

1. An apparatus having an electron gun, a deflector, a detector, a sample stage on which a sample is placed, and a controller, wherein the controller receives an instruction to create an captured image and: receives a designation of an application area of ​​the VC method; receives a secondary electron detection signal from the sample from the detector while sending a control signal generated based on a predetermined scanning trajectory to the deflector; and generates the captured image based on the secondary electron detection signal, wherein the captured image includes the following partial areas: a first partial area suitable for the VC method; and a second partial area suitable for observing the surface of the sample.

2. An apparatus according to claim 1, wherein the predetermined scanning trajectory includes: a first speed trajectory for scanning a first surface on the sample corresponding to the VC method application area designation at a first scanning speed suitable for the VC method; and a second speed trajectory for scanning a second surface on the sample not corresponding to the VC method application area designation at a second scanning speed faster than the first scanning speed, wherein the generation of an image of the first partial area is performed using a first coefficient, and the generation of an image of the second partial area is performed using a second coefficient determined based on the second scanning speed, and the first scanning speed and the first coefficient are values ​​determined based on the characteristics of the first surface.

3. An apparatus according to claim 2, wherein the first scanning speed and the second scanning speed correspond to a time during which the electron beam from the electron gun is irradiated onto the first surface and the second surface.

4. An apparatus according to claim 3, wherein the predetermined scanning trajectory includes one line of one scan by the electron beam, and within the same one line, the first surface is scanned at the first scanning speed and the second surface is scanned at the second scanning speed.

5. An apparatus according to claim 4, wherein an image of the first partial region is generated by calculating pixel data relating to the first surface based on the secondary electron detection signal and the first coefficient, and an image of the second partial region is generated by calculating pixel data relating to the second surface based on the secondary electron detection signal and the second coefficient.

6. An apparatus according to claim 5, wherein the image of the first partial region and the image of the second partial region are included in one frame acquired by one scan with the electron beam.

7. The device according to claim 1, wherein the instruction to create the captured image is given through a GUI.

8. A control method for an apparatus comprising an electron gun, a deflector, a detector, a sample stage on which a sample is placed, and a controller, wherein the controller receives a secondary electron detection signal from the sample from the detector while sending a control signal generated based on a predetermined scanning orbit to the deflector, and generates an image based on the secondary electron detection signal, wherein the controller generates a first image relating to a first partial region of the sample designated as a VC method application region, and generates a second image suitable for surface observation of the sample for a second partial region different from the first partial region.

9. A control method according to claim 8, wherein the controller scans a first surface on the sample corresponding to the first partial region designated as the VC method application region at a first scanning speed suitable for the VC method using the control signal, and generates the first image based on pixel data acquired by scanning and a first coefficient, and scans a second surface on the sample corresponding to the second partial region at a second scanning speed faster than the first scanning speed using the control signal, and generates the second image based on pixel data acquired by scanning and a second coefficient, wherein the first scanning speed and the first coefficient are values ​​determined based on the characteristics of the first surface.

10. A program for causing the controller to execute the control method according to claim 8 or 9.