Charged particle beam device

Abstract

A charged particle beam device (1) configured to irradiate a sample (8) with a charged particle beam (30), the charged particle beam device (1) comprising: a charged particle source (2) configured to irradiate the sample (8) with primary charged particles; a light source (13) configured to emit light to be emitted toward the sample (8); a detector (5) configured to detect secondary charged particles generated by irradiating the sample (8) with primary charged particles from the sample (8); an image processing unit (17) configured to generate an observation image of the sample (8) using the secondary charged particles detected by the detector (5); and a light control unit (14) configured to control an optical parameter representing a physical property of the light, wherein the light control unit (14) changes the polarization plane of the light as an optical parameter and causes the image processing unit (17) to generate observation images whose contrast corresponds to the changed polarization plane.

Description

Technical field

[0001] The present invention relates to a charged particle beam device that irradiates a sample with a charged particle beam. State of the art

[0002] In a semiconductor device manufacturing process, in-line control measurement using a scanning electron microscope (SEM) is an important control to increase yield. In particular, a low-voltage SEM (low-kV SEM), which uses an electron beam with an accelerating voltage of several kV or less, is very useful for controlling and measuring a two-dimensional shape such as a resist pattern in a lithography process and a gate pattern in a previous process, since the penetration depth of the electron beam is small and an image with rich surface information is obtained. Since organic materials such asFor example, when a resist and an antireflection layer used in a lithography process have similar compositions, or when silicon-based semiconductor materials constituting a transistor have similar compositions, it is difficult to obtain a difference in secondary electron emission from these materials. Since a sample made of such materials has low SEM image contrast, the detectability of an ultrafine structure or a defect of a semiconductor device is reduced. As a method for increasing detectability in SEM, a method for adjusting observation conditions such as an accelerating voltage and an irradiation current, and a technique for distinguishing the energy of electrons emitted from the sample are known.

[0003] PTL 1 discloses a method for controlling the image contrast of an SEM by irradiating an observation area of the SEM with light. Since excited charged particles are generated by light irradiation, the conductivity of a semiconductor or insulator changes. The difference in conductivity of the materials is reflected in the potential contrast of an SEM image. A location of poor conductivity in a semiconductor device or the like can be detected by controlling the potential contrast of the SEM by light irradiation. PTL 2 discloses a method for controlling the image contrast of an SEM by selecting different wavelengths of light, focusing on the light absorption characteristics that vary depending on the wavelength of the emitted light. List of reference literaturePatent literature PTL 1: JP 2003 - 151 483 A PTL 2: JP 5 190 119 B2 (corresponds to US 2011 / 0204228 A1)

[0004] US 2018 / 0364564 A1 shows another conventional charged particle beam device. Summary of the inventionTechnical problem

[0005] In PTL 1 and PTL 2, the image contrast of the SEM is controlled by determining the wavelength of light according to the different light absorption properties of the materials. However, since the light absorption properties of the material also strongly depend on optical parameters other than wavelength, the difference in light absorption properties cannot be sufficiently utilized by controlling only a single optical parameter. Furthermore, since the light absorption properties of a semiconductor device with a periodic structure depend not only on the material but also on the structure of the semiconductor device, it is difficult to control the image contrast of an SEM with high accuracy by controlling only a single optical parameter.

[0006] The present invention has been devised in view of the above problems, and an object of the invention is to provide a charged particle beam device capable of increasing the contrast of the observation image of a sample as much as possible in accordance with the light absorption characteristics different in each optical parameter. Solution to the problem

[0007] A charged particle beam device according to the present invention changes an optical parameter, such as the polarization plane of the light emitted to the sample, and generates an observation image whose contrast corresponds to the changed optical parameter. An optical parameter that maximizes the light absorption coefficient of the sample is determined according to a feature set of the shape structure of the sample. Beneficial effect

[0008] Since in the charged particle beam device according to the invention an observation image is acquired by irradiating the sample with light having different optical parameters, it is possible to increase the contrast of the observation image by using appropriate optical parameters according to the light absorption characteristics of the sample. Short description of the drawings [ Fig. 1] Fig. 1 is a configuration drawing of a charged particle beam device 1 according to a first embodiment. [ Fig. 2] Fig. Fig. 2 is a schematic diagram showing a configuration for irradiating a sample 8 with light emitted from a light source 13 after the light has been controlled to a wavelength / polarization plane / irradiation amount set by the user. [ Fig. 3A] Fig. 3A is a schematic diagram showing a configuration example in which a light control unit 14 controls optical parameters according to the conditions set via a setting input unit 21. [ Fig. 3B] Fig. Figure 3B is a schematic diagram showing a configuration example for controlling the wavelength and polarization plane of light. [ Fig. 4] Fig. 4 is a schematic diagram showing an example of a graphical user interface (GUI) provided by a display unit 20. [ Fig. 5] Fig. 5 is a schematic diagram showing an example of an SEM image acquired by adjusting the polarization plane according to a structural shape. [ Fig. 6] Fig. 6 is a configuration drawing of a charged particle beam device 1 according to a second embodiment. [ Fig. 7] Fig. 7 is a flowchart showing a method in which an optical parameter determination unit 15 determines optical parameters. [ Fig. 8A] Fig. 8A is a schematic diagram showing an example in which a Fourier transform is used as a method for extracting the feature amount of the shape of a sample having a periodic shape. [ Fig. 8B] Fig. Figure 8B is a schematic diagram showing a method for determining the polarization plane from the feature set. [ Fig. 9] Fig. 9 is a schematic diagram showing observation images obtained by extracting the feature amount of a structural shape from an SEM image of Sample 8 and using the optical parameter having the highest light absorption coefficient for each structure. [ Fig. 10] Fig. 10 is an example of a GUI provided by the display unit 20 in the second embodiment. [ Fig. 11A] Fig. 11A is a schematic diagram showing a configuration of the optical path when an irradiation ratio of the p-polarized light and the s-polarized light is measured and an irradiation amount of the light is adjusted according to the feature amount of a shape structure. [ Fig. 11B] Fig. Figure 11B is a schematic diagram showing a configuration of the beam path after adjusting the irradiation amount. [ Fig. 12A] Fig. Figure 12A is a schematic diagram showing an example of a method for extracting the feature set of the sample. [ Fig. 12B] Fig. 12B is a schematic diagram showing a method for determining the light irradiation conditions from a feature set extracted by a feature set extraction unit 18. [ Fig. 12C] Fig. Figure 12C is a schematic diagram showing an observation result when the irradiation amount per unit time is controlled for each polarization plane. [ Fig. 13] Fig. 13 is a schematic diagram showing an example of a GUI provided by the display unit 20 in a third embodiment. [ Fig. 14A] Fig. 14A is a schematic diagram showing an example in which an angle of light emitted to the sample 8 is controlled by adjusting the tilt angle of an XYZ stage 6. [ Fig. 14B] Fig. 14B shows an example in which the angle of the light irradiated to the sample 8 is adjusted by a mirror 35 installed outside an instrument case 23. [ Fig. 15A] Fig. 15A is a schematic diagram showing an example in which a brightness histogram of the SEM image is acquired in each of the X and Y directions. [ Fig. 15B] Fig. Figure 15B is a schematic diagram showing a method for maximizing contrast using a brightness histogram. [ Fig. 16] Fig. 16 is a schematic diagram showing an example of a GUI provided by the display unit 20 in a fourth embodiment. [ Fig. 17] Fig. 17 is a schematic diagram showing an example of an SEM image in which the image contrast of a magnetic domain of Sample 8 is increased. [ Fig. 18] Fig. 18 is a configuration drawing of the charged particle beam device 1 according to a sixth embodiment. [ Fig. 19] Fig. Figure 19 is a schematic diagram showing an SEM image acquired by a plurality of electron beam irradiations. [ Fig. 20] Fig. 20 is a schematic diagram showing a method for determining the light irradiation conditions from a feature set extracted by a feature set extraction unit 18. [ Fig. 21] Fig. 21 is a schematic diagram showing the effect of contrast control under a light irradiation condition according to a sixth embodiment. Description of embodiments<Grundprinzip der Erfindung>

[0009] In the following, the basic principle of the invention will be explained first, and then specific embodiments of the invention will be described. The present invention determines the light irradiation conditions (optical parameters) that produce the highest image contrast and offers an image contrast that enables high detectability of a structure or defect. The invention determines suitable light irradiation conditions that include a variety of light irradiation parameters (polarization plane, irradiation direction, irradiation angle, wavelength, irradiation period of the light, irradiation amount of the light per unit time). By irradiating the sample with light, charged particles in the sample are excited according to the number of photons, thereby changing their electronic state. The emission amount of secondary electrons under light irradiation satisfies expression (1).ΔS is the amplification amount of the emitted electrons by the light irradiation, α is the absorption coefficient of the material, and D. puls is the amount of light irradiation of the sample per unit time. ΔS∝α⋅Dpulse

[0010] The amount of light irradiation per unit time is expressed by expression (2). W ave is the average light output, f pulse is the frequency of a pulsed laser, and N shot is the number of pulses emitted per unit of time. For a continuous laser whose light oscillates continuously, the average light output corresponds to the irradiation quantity D cw of light per unit of time. Dpulse=(Wave / fpulse)⋅Nshot

[0011] The absorption coefficient α is expressed by expression (3), where κ is the extinction coefficient and λ is the wavelength of light. α=4πκ / λ

[0012] The extinction coefficient κ is expressed by expression (4). R is the reflectance versus light intensity, and θ is the phase shift of the light. κ=2R sin θ / (1+R−2R cos θ)

[0013] The reflectance R varies depending on whether the polarization plane is p-polarized light or s-polarized light and is expressed by expressions (5) and (6), respectively. R p is the reflectance of the p-polarized light, and R s is the reflectance of s-polarized light. N is the complex refractive index of the material, and φ is the angle of incidence. From this, it can be seen that the emission power of secondary electrons depends not only on the wavelength, but also on the amount of light irradiation per unit time, the polarization plane, and the angle of incidence of the light. Rp=|N2cos φ−N2−sin2φ|2 / |N2cosφ+N2−sin2φ|2 Rs=|cos φ−N2−sin2φ|2 / |cos φ+N2−sin2φ|2 <Erste Ausführungsform>

[0014] In the first embodiment of the present invention, a charged particle beam device is described that controls an amount of electrons emitted from the sample during electron beam irradiation by controlling the polarization plane and other optical parameters of an intermittently irradiated light to achieve image acquisition with high image contrast.

[0015] Fig. 1 is a configuration diagram of a charged particle beam apparatus 1 according to the first embodiment. The charged particle beam apparatus 1 is configured as a scanning electron microscope that acquires an observation image of the sample 8 by irradiating the sample 8 with an electron beam 30 (primary charged particles). The charged particle beam apparatus 1 includes an electron optical system, a stage mechanism system, an electron beam control system, a light irradiation system, and a main console 16.

[0016] The electron optical system includes an electron gun 2, a deflector 3, an electron lens 4, and a detector 5. The stage mechanism system includes the XYZ stage 6 and a sample holder 7. The electron beam control system includes an electron gun control unit 9, a deflection signal control unit 10, a detection control unit 11, and an electron lens control unit 12. The light irradiation system includes a light source 13, a light control unit 14, a light irradiation unit 24, and a setting input unit 21. The main console 16 includes an imaging system and an input and output system. The imaging system includes an image processing unit 17 and an image signal processing unit 19, whose detection scanning function is synchronized with a deflection signal. The input and output system includes an electron beam imaging condition setting input unit 21 and a display unit 20.

[0017] The electron beam 30 accelerated by the electron gun 2 is focused by the electron lens 4 and emitted toward the sample 8. The deflector 3 controls an irradiation position of the electron beam 30 on the sample 8. The detector 5 detects emitted electrons (secondary charged particles) emitted from the sample 8 by irradiating the sample 8 with the electron beam 30. The setting input unit 21 is a functional unit that allows a user to input an acceleration voltage, an irradiation current, a deflection condition, a detection scanning condition, an electron lens condition, and the like.

[0018] The light source 13 emits light toward the sample 8. The light source 13 is a laser capable of emitting a single wavelength or multiple wavelengths in the ultraviolet to near-infrared range. The light emitted by the light source 13 is emitted through a glass window 22 provided in the device housing 23 onto the sample 8, which is located in a vacuum. The light control unit 14 controls an optical parameter representing a physical property emitted by the light source 13. The user specifies the optical parameter for the light control unit 14 via the setting input unit 21.

[0019] Fig. 2 is a schematic diagram showing a configuration for irradiating the sample 8 with light emitted from the light source 13 after controlling it to the wavelength / polarization plane / irradiation amount set by the user. Generally, the polarization plane includes linearly polarized light and circularly polarized light. Linearly polarized light includes p-polarized light and s-polarized light, and circularly polarized light has left-circular and right-circular directions. The light irradiation unit 24 controls the wavelength / polarization plane / irradiation amount of the light to be emitted. The light irradiation unit 24 can be configured, for example, from a wavelength conversion unit, a polarization control unit, and an intensity control unit.The polarization control unit is a component capable of changing the polarization plane of the light and is, for example, a wire mesh type or a crystal type that utilizes a birefringence phenomenon of the material itself. The intensity control unit is capable of controlling the light intensity, for example, via a pulse width of the light. The light irradiation unit 24 is capable of changing the optical parameters using these devices.

[0020] Fig. 3A is a schematic diagram showing a configuration example in which the light control unit 14 controls optical parameters according to the conditions set via the setting input unit 21. The light control unit 14 controls optical parameters of the light emitted to the sample 8 by controlling the respective control components included in the light irradiation unit 24. The light control unit 14 also controls optical parameters such as the wavelength of the light emitted from the light source 13. Fig. Figure 3A is a schematic diagram showing a configuration example in which the polarization plane and the irradiation amount per unit time are controlled. The light irradiation unit 24 includes a polarization conversion plate 32 and a variable light amount filter 33, and the light control unit 14 controls the polarization conversion plate 32 and the variable light amount filter 33.

[0021] The light emitted by the light source 13 is converted by the polarization conversion disk 32 into a polarization plane specified by the setting input unit 21. The variable light quantity filter 33 controls the light quantity to achieve the irradiation quantity per unit time specified by the setting input unit 21. Light whose irradiation quantity per unit time and polarization plane have been adjusted is emitted to the sample 8 via an adjustment mirror 31 and the glass window 22.

[0022] Fig. 3B is a schematic diagram showing a configuration example in which the wavelength of light and the polarization plane are controlled. The light irradiation unit 24 includes a wavelength conversion unit 34 and the polarization conversion disk 32. The light emitted from the light source 13 is controlled by the wavelength conversion unit 34 to emit the light at the wavelength specified by the setting input unit 21, and the polarization plane is controlled by the polarization conversion disk 32.

[0023] Fig. 4 is a schematic diagram showing an example of a graphical user interface (GUI) provided by the display unit 20. The "image acquisition operation" setting area 206 is a field for setting the acceleration voltage / irradiation current / scanning speed / irradiation interval of the electron beam 30, and for setting the scanning period / irradiation amount per unit time / wavelength / irradiation angle / irradiation intensity (pulse width) of the light to be emitted. The "polarization plane" setting area 205 is a field for setting the polarization plane of the light. For example, one of p-polarized light, s-polarized light, circularly polarized light, or elliptically polarized light can be selected.The display area 201A displays an SEM image when no light is emitted, and the display area 201B displays the SEM image when light is emitted with the set polarization plane. A "difference image" display area 202 displays a difference image of the SEM images displayed in the display areas 201A and 201B. The image processing unit 17 generates the difference image by subtracting the SEM image without light irradiation from the SEM image with light irradiation. The user can confirm the contrast-enhancing effect of the light irradiation by checking a portion of the image highlighted by the light irradiation via the difference image. The "start imaging" button 203 is a button for instructing the charged particle beam device 1 to start imaging the observation image of the sample 8.The “Difference Image” button 204 is a button for instructing the charged particle beam device 1 to generate the difference image.

[0024] Fig. Figure 5 is a schematic diagram showing an example of an SEM image acquired by adjusting the polarization plane according to the pattern shape. A sample in which a resist 42 was coated on an anti-reflection layer 41 was used as Sample 8. The resist 42 formed on the anti-reflection layer 41 was formed as a microline pattern with different pitches. The wavelength at which the polarization plane was adjusted to Fig. In the evaluation shown in Figure 5, the absorption coefficients of the resist 42 and the anti-reflection layer 41 were the highest. The absorption coefficients were 200 nm for the resist 42 and 400 nm for the anti-reflection layer 41. The line pitch width was 500 nm for line pitch A and 250 nm for line pitch B. The electron beam irradiation conditions were an acceleration voltage of 0.8 keV, an irradiation current of 15 pA, and a scanning speed of a TV scanning rate. The light irradiation conditions were a wavelength of 400 nm, an irradiation light quantity per unit time of 100 mW, and the polarization plane of the p-polarized light and the s-polarized light. The irradiation angle was 30 degrees. The detection scanning frequency was 100 MHz.

[0025] At line pitch A, the image brightness of the anti-reflection layer 41 is brighter than that of the resist 42 when p-polarized light is emitted, thereby increasing the image contrast between the anti-reflection layer 41 and the resist 42. In contrast, the contrast between the anti-reflection layer 41 and the resist 42 is low when s-polarized light is emitted. Under these irradiation conditions, high image contrast is achieved because p-polarized light is efficiently absorbed by the anti-reflection layer 41. At line pitch B, the light is efficiently absorbed by the anti-reflection layer 41 when s-polarized light is emitted, thereby increasing the image contrast. In contrast, the image contrast is low when p-polarized light is emitted. <Erste Ausführungsform: Zusammenfassung>

[0026] The charged particle beam device 1 according to the first embodiment generates an observation image of the sample 8 for each optical parameter while changing the optical parameters including the polarization plane of the light, thereby generating observation images whose contrast differs for each optical parameter. This makes it possible to obtain an observation image for each optical parameter with a different contrast according to the light absorption characteristics of the sample 8. Thus, the visibility of the observation image can be increased by selecting the optical parameter according to the light absorption characteristics of the sample 8.

[0027] The charged particle beam device 1 according to the first embodiment generates observation images each having a different contrast according to each optical parameter, generates difference images between the observation images, and displays the difference image in the "difference image" display area 202. This allows the difference between the observation images with different contrasts to be clearly recognized.

[0028] Even if in Fig. 5 shows an example in which the polarization plane is set as an optical parameter, the contrast of the observation image can also be adjusted by adjusting other optical parameters according to the light absorption characteristics of the sample 8. For example, the irradiation amount of light per unit time, the pulse width, the irradiation angle (elevation angle), the wavelength, the irradiation direction (azimuth angle), the irradiation period of the light, and the like can be adjusted. The irradiation angle is an angle formed in a vertical plane between a perpendicular line (Z axis) and the electron beam 30. The irradiation direction is an angle formed in a horizontal plane between the electron beam 30 and one of the coordinate axes (XY axes). <Zweite Ausführungsform>

[0029] In a second embodiment of the present invention, a configuration example will be described in which the feature amount of the shape structure of the sample 8 is extracted and the optical parameter of the light irradiated to the sample 8 is then controlled according to the feature amount.

[0030] Fig. 6 is a configuration drawing of a charged particle beam device 1 according to the second embodiment. The charged particle beam device 1 according to the second embodiment includes, in addition to the configuration described in the first embodiment, a feature quantity extraction unit 18 and an optical parameter determination unit 15. The feature quantity extraction unit 18 detects a shape structure of the sample 8 and extracts the feature quantity of the shape structure. The optical parameter determination unit 15 determines, according to this feature quantity, a parameter that maximizes the absorption coefficient of the light irradiated onto the sample 8. The feature quantity extraction unit 18 extracts features such asthe size / density / period / area / contour line of the shape structure / photophysical properties of the material from which the sample 8 is made. The storage device 81 is described further below.

[0031] Fig. Fig. 7 is a flowchart showing a process in which the optical parameter determination unit 15 determines optical parameters. In the following, each step of Fig. 7 described. (FIG. 7: Steps S1 to S3)

[0032] The user places the sample 8, and the stage mechanism system moves the sample to an observation position (S1). The user sets irradiation conditions such as the irradiation current of the electron beam 30, and the image processing unit 17 acquires an SEM image of the sample 8 according to these irradiation conditions (S2). The feature quantity extraction unit 18 extracts the shape structure of the sample 8 and its feature quantity from the SEM image obtained in S2 (S3).

[0033] ( Fig. 7: Steps S4 to S6) The optical parameter determining unit 15 temporarily sets an optical parameter (e.g., the irradiation amount per unit time) to an arbitrary value (S4).

[0034] The light control unit 14 and the light irradiation unit 24 irradiate the sample 8 with light using this optical parameter (S5). The image processing unit 17 acquires the SEM image of the sample 8 and calculates the contrast of the SEM image (S6). Steps S4 to S6 are repeated, changing the value of the optical parameter. If, for example, the irradiation amount per unit time is temporarily set as the optical parameter in step S4, steps S4 to S6 are repeated over the entire adjustable numerical value range, changing the numerical value of the irradiation amount. (FIG. 7: Step S7)

[0035] The optical parameter determination unit 15 compares the contrast at each optical parameter value with the image contrast when no light is emitted. The optical parameter determination unit 15 applies the value that results in the maximum contrast. If the contrast is maximum when no light is emitted, the optical parameter "without irradiation" is applied. (FIG. 7: Steps S4 to S7)

[0036] Steps S4 to S7 are repeated for each combination of optical parameters. After steps S4 to S7 have been performed for the irradiation amount per unit time, steps S4 to S7 are performed, for example, for the wavelength. Corresponding steps are also performed for the other optical parameters. As an example combination of optical parameters, all parameters that can be set in the "Image Acquisition Process" setting area 206 of Fig. 4 can be set.

[0037] Fig. 8A shows an example in which Fourier transform is used as a method for extracting the feature quantity of the shape of a sample with a periodic shape. The detector 5 detects electrons (secondary charged particles) emitted from the sample 8 by irradiating the sample 8 with the electron beam 30 according to the irradiation conditions set by the setting input unit 21. The image processing unit 17 converts the electron emission signal into an image. The feature quantity extraction unit 18 performs Fourier transform on the SEM image, analyzes the shape structure of the sample 8 through frequency analysis, and extracts feature quantities such as sizes and distances. The width from the image center to a bright spot or line is the feature frequency of each shape, and the feature size can be calculated from the inverse of the feature frequency.

[0038] In Fig. 8A is f x the structural frequency of the sample in the X-direction, and f y is the structural frequency in the Y-direction. In Fig. 8A it can be seen that f x is a value less than f y If P x is the structure density in the X-direction and P y the structure density in the Y-direction, P x a product of FOV (Field of View) and f x , and P y is a product of FOV and f y . In Fig. 8A is the structure density in the X-direction P x , where the structure frequency is low, lower than the structure density in the Y-direction P y where the structural frequency is high.

[0039] Fig. Figure 8B is a schematic diagram showing a method for determining the polarization plane from the feature set. The horizontal axis of Fig. 8B is the product of the wavelength λ of the light and the structure frequency f and corresponds to a parameter representing the diffraction efficiency. The vertical axis represents the absorption coefficient of the sample for p-polarized light and for s-polarized light, respectively. The graph can be obtained in advance by optical simulation or real measurement and stored in a database. Fig. Figure 8B shows the values at a wavelength λ1. At λ1f x the light absorption coefficient of sample 8 is higher for s-polarized light than for p-polarized light, and at λ1f y The light absorption coefficient of sample 8 is higher for p-polarized light. As shown in Expression (1), when sample 8 is irradiated with light having a polarization plane where its light absorption coefficient is large, the change in image brightness is larger and the contrast is higher.

[0040] In order to make the contrast-enhancing effect uniform in the X-direction of the structure and in the Y-direction of the structure, the light intensity I s of the s-polarized light and the light intensity I p of the p-polarized light can be adjusted by adjusting the light intensity I s of the s-polarized light and the light intensity I p of the p-polarized light by the respective product (α s P x , α p P y ) of the absorption coefficient α s , α p of s-polarized light and p-polarized light and the structure density P x , P y The details of this are explained in a third embodiment, which is described further below.

[0041] Fig. Figure 9 is a schematic diagram showing observation images obtained by extracting the feature amount of the structure shape from the SEM image of Sample 8 and using the optical parameter having the highest light absorption coefficient corresponding to each structure. Sample 8 used a sample in which an oxide layer 45 was formed on an underlying silicon substrate 43, and polysilicon 44 was formed on the oxide layer 45. The polysilicon 44 was formed in the shape of islands with different pitches in the X and Y directions. The electron beam irradiation conditions 30 were an acceleration voltage of 1.5 keV, an irradiation current of 300 pA, and a scanning speed of 150 ns / pixel. The light irradiation conditions were a wavelength of 535 nm, and irradiation was performed with p- or s-polarized light according to the structure whose contrast was to be increased.The detection sampling frequency was 400 MHz.

[0042] Out of Fig. 8B it can be seen that the absorption coefficient for s-polarized light at the structure frequency in the X-direction f x is high and the absorption coefficient for p-polarized light at the structure frequency in the Y-direction f y high. Here, taking into account the structural densities P x and P y and the absorption coefficient α s the irradiation amount of s-polarized light per unit time is set to 7 mW and the irradiation amount of p-polarized light per unit time is set to 10 mW. In the example of Fig. 9, the oxide layer 45 exhibits increased image contrast in the X direction of the patterned structure when s-polarized light is emitted, and the change in the Y direction of the pattern is small. In contrast, the image brightness of the oxide layer 45 in the Y direction of the pattern increases compared to the change in image brightness in the X direction of the pattern, and the contrast in the Y direction is increased when p-polarized light is emitted. This enables arbitrary contrast control by using light irradiation parameters whose polarization plane is adjusted according to the direction of the patterned shape.

[0043] Fig. Fig. 10 is an example of a GUI provided by the display unit 20 in the second embodiment. A feature set extraction panel 212 enables the selection of a feature set extraction method. In addition to the Fourier analysis of the observation image shown in Fig. 8A, a method for extracting feature quantities of the shape structure from the design data, a method for measuring the feature size on the observation image, and the like are given as examples.

[0044] If a correspondence between a feature set and optical parameters capable of maximizing the image contrast of the sample 8 with this feature set is stored in a database in advance, the optical parameter determination unit 15 can automatically determine the optical parameters corresponding to the extracted feature set by referencing the database. In this case, it is possible to display each optical parameter on the screen of Fig. 10 automatically select the feature sets according to the characteristics without the need to change the schedule of Fig. 7. The database can be configured, for example, by storing data describing the correspondence between a feature set and the optical parameters in the storage device 81.

[0045] The display areas 207 and 208 display observation images with various optical parameters. A "light irradiation conditions" monitoring area 209 displays the current value of each optical parameter. The "imaging conditions" display areas 210 and 211 display imaging conditions corresponding to the display areas 207 and 208, respectively. <Zweite Ausführungsform: Zusammenfassung>

[0046] The charged particle beam device 1 according to the second embodiment acquires an observation image by determining the optical parameters having the highest light absorption coefficient for a feature set of the sample 8, corresponding to that feature set, and emitting light with that optical parameter. This makes it possible to increase the contrast of the observation image for each shape structure of the sample 8 as much as possible.

[0047] The charged particle beam device 1 according to the second embodiment determines an optical parameter capable of increasing the contrast by referring to a database describing the correspondence between a feature quantity and the optical parameter, or by following the flowchart in Fig. 7, the optical parameter corresponding to the feature set is searched for. The use of a database allows for the rapid determination of the optimal optical parameter. If a database cannot be created in advance, it is possible to use the optical parameters Fig. 7. Furthermore, a database can be built by determining optical parameters that Fig. 7 are stored in the storage device 81. <Dritte Ausführungsform>

[0048] In the form structure, which in Fig. As described in Figure 9, the feature quantity in the X direction of the shaped structure and the feature quantity in the Y direction of the shaped structure are different from each other, and therefore the light absorption coefficients in the respective directions are different. Therefore, in a third embodiment of the present invention, a method for uniformly enhancing contrast in each observation direction is described, even when the feature quantity in the observation directions is different. The configuration of the charged particle beam device 1 is similar to that in the second embodiment.

[0049] Fig. 11A is a schematic diagram showing a configuration of the optical path when the irradiation ratio of the p-polarized light and the s-polarized light is measured and the irradiation amount of the light is adjusted according to the feature amount of the mold structure. The variable light amount filter 33 adjusts the irradiation amount per unit time. P-polarized light is emitted from the light source 13 and split into two optical paths by a non-polarizing beam splitter 47. In one optical path, the irradiation amount of the p-polarized light per unit time is adjusted by the variable light amount filter 33, and the irradiation amount of the p-polarized light per unit time is measured by a beam monitor 49.In the other beam path, after the polarization plane of the p-polarized light is converted into s-polarized light by the polarization conversion disk 32, the irradiation amount per unit time is adjusted by the variable light amount filter 33, and the irradiation amount of the s-polarized light per unit time is measured by a beam monitor 49.

[0050] Fig. Figure 11B is a schematic diagram showing the configuration of the beam path after adjusting the irradiation amount. The beam path configuration of Fig. According to the irradiation amount measured in Figure 11A, the light control unit 14 controls the irradiation amount according to the shape structure of the sample by a method described below. The beam monitor 49 is movable and is removed from the beam path once the adjustment of the irradiation amount per unit time is completed.

[0051] Fig. Figure 12A is a schematic diagram showing an example of a method for extracting the sample feature set. In Fig. 12A, the feature set extraction unit 18 acquires line profiles in the X and Y directions, respectively, and extracts feature sets such as a line size and a line pitch. In Fig. 12A, the line spacing is extracted as a feature set. The line spacing can be extracted, for example, as the brightness peak interval of the observation image. In Fig. 12A is L x the line spacing in the X direction and L y the line spacing in the Y direction.

[0052] Fig. 12B is a schematic diagram showing a method for determining the light irradiation conditions from the feature quantity extracted by the feature quantity extraction unit 18. In the graph of Fig. 12B, the horizontal axis represents a ratio of the wavelength λ to the line spacing L, and the vertical axis represents the absorption coefficient of the irradiation light by the sample 8. When the irradiation amount D p of p-polarized light per unit time and the irradiation amount D s of s-polarized light per unit time are equal, the contrast is uniform at each line pitch. The irradiation amount of each polarization plane per unit time is calculated using expressions (7) and (8). α P is an absorption coefficient of p-polarized light for wavelength λ and line spacing L, α s is an absorption coefficient of s-polarized light for wavelength λ and line spacing L, and D P puls and D S pulsare the irradiation amounts of p-polarized light and s-polarized light per unit time with which sample 8 is irradiated. By using one or both of D P puls and D S pulse is set so that D p = D s , the contrast can be made uniform in every direction. DP=DpulseP⋅αP DS=DpulseS⋅αS

[0053] Fig. 12C is a schematic diagram showing an observation result when the irradiation amount per unit time is controlled for each polarization plane. As Sample 8, a sample in which a structure of polysilicon 44 was formed on an underlying silicon carbide substrate 46 was used. The polysilicon 44 was formed in the form of islands with different pitches in the X and Y directions. The electron beam irradiation conditions 30 were an acceleration voltage of 0.3 keV, an irradiation current of 1 nA, and a scanning speed of 20 ns / pixel. The light irradiation conditions were a wavelength of 300 nm and a detection scan of 2 ns. The polarization plane and the irradiation amount per unit time were determined with reference to Fig. 12A and Fig. 12B so that the contrast was uniform.

[0054] From expressions (7) and (8), it is necessary to set the irradiation amount of p-polarized light per unit time to 2 / 3 of the irradiation amount of s-polarized light per unit time in order to obtain the contrast-enhancing effect at each line pitch λ1 / d x and λ1 / d y Under the condition “light irradiation OFF” in Fig. 12C, the contrast difference between the polysilicon 44 and the silicon carbide substrate 46 is small. In contrast, a uniform contrast-enhancing effect was confirmed when the light irradiation amount per unit time for each polarized light was adjusted according to the feature amount of the mold structure.

[0055] Although the variable light quantity filter 33 is used to control the irradiation amount per unit time in the third embodiment, in the case of a pulse laser, a pulse picker may be used instead of the variable light quantity filter 33 to set the pulse number of the p-polarized light per unit time to 2 / 3 of the pulse number of the s-polarized light per unit time.

[0056] Fig. Fig. 13 is a schematic diagram showing an example of a GUI provided by the display unit 20 in the third embodiment. In Fig. 13, the feature size is extracted as a feature quantity from the line profile. An SEM image when no light is emitted is displayed in the display area 201A, and an image acquired under the specified light irradiation conditions is displayed in the display area 201B. The "polarization plane ratio" setting area 213 is a scroll bar that can be used to manually adjust the proportion of s-polarized light and p-polarized light. An "irradiation amount" setting area 214 is a scroll bar that can be used to adjust the irradiation amount per unit time for both p-polarized light and s-polarized light. The "polarization type" selection button 216 is used to select the polarization plane. A "live image" display area 215 displays the SEM image during the extraction of the light irradiation conditions.The light control unit 14 selects the polarization plane of the light and the irradiation amount per unit time according to the feature amount of the sample 8 according to the method described above. The result of this selection is automatically displayed on the screen of . Fig. 13 is displayed. <Dritte Ausführungsform: Zusammenfassung>

[0057] The charged particle beam device 1 according to the third embodiment determines the optical parameters of the feature quantity according to the structural shape of the sample 8 and adjusts the irradiation amount per unit time according to the light absorption coefficient corresponding to each optical parameter. This makes it possible to uniform the contrast for each optical parameter. Thus, uniform contrast can be obtained even if the feature quantity of the sample 8 is different in each observation direction. <Vierte Ausführungsform>

[0058] In a fourth embodiment of the present invention, a configuration example will be described in which an optical parameter is determined at which the efficiency of electrons emitted from the sample 8 is maximum, thereby making it possible to obtain a high-contrast observation image. The charged particle beam device 1 according to the fourth embodiment includes, in addition to the configuration described in the first to third embodiments, a mechanism for adjusting the angle of light emitted toward the sample 8. A functional unit (for example, the light irradiation unit 24) that controls light irradiation conditions other than the angle can be installed in front of or behind the alignment mirror 31.

[0059] Fig. 14A is a schematic diagram showing an example in which an angle of light emitted to the sample 8 is controlled by adjusting an inclination angle of an XYZ stage 6. The light control unit 14 controls the angle of the light by specifying the inclination angle with respect to the XYZ stage 6.

[0060] Fig. 14B is a schematic diagram showing an example in which the angle of the light irradiated onto the sample 8 is adjusted by a mirror 35 installed outside the device body 23. The light control unit 14 controls the angle of the light by specifying the inclination angle with respect to the mirror 35.

[0061] By using a variable-wavelength pulse laser as the light source 13, for example, the pulse width and the number of irradiation pulses per unit time can be controlled. The pulse width and the number of irradiation pulses per unit time can be adjusted by the function of the pulse laser or by another function integrated in the optical irradiation system. For example, the pulse width can be adjusted by a Q-switch, and the number of irradiation pulses per unit time can be adjusted by a pulse picker with Pockels cells. The polarization of the pulsed laser can be adjusted by using a configuration similar to the third embodiment.

[0062] Fig. Figure 15A shows an example in which a brightness histogram of the SEM image was acquired in the X and Y directions. The sample 8 used corresponded to the Fig. 12A. The brightness histogram represents a frequency distribution of the brightness values of each pixel in the SEM image. Instead of the brightness histogram, a brightness difference histogram can also be used as long as the contrast can be optimized. Furthermore, luminance can be used instead of brightness. In the following, it is assumed that a brightness histogram is used.

[0063] Fig. Figure 15B shows a method for maximizing contrast using a brightness histogram. To maximize image contrast, it is sufficient to determine the optical parameter for which the frequency peak interval H of the brightness histogram is largest. In the example shown in Fig. As shown in Fig. 15B, the light control unit 14 first creates a brightness histogram while changing the wavelength and the polarization plane, and determines the wavelength and the polarization plane at which the peak interval H is maximum. Then, the light control unit 14 determines a light irradiation angle at which the peak interval H is maximum. Finally, the light control unit 14 determines the irradiation amount of light per unit time at which the peak interval H is maximum. The irradiation amount can be adjusted by, for example, a pulse width, the number of pulses per unit time, an average power of the pulsed laser, and the like.

[0064] The peak interval H can be maximized for each optical parameter. In addition to the Fig. 15B, the respective peak interval H can be maximized for the wavelength, the irradiation direction (azimuth angle) with respect to the sample, the irradiation period of the light, and the like. The parameters can be set in any order. An optimal value of the optical parameters can be set for each observation direction. When the optimal optical parameter is determined according to the feature amount of the sample 8 (for example, when the optimal optical parameter is determined by the method described in the first embodiment), only the other optical parameters are adjustable.For example, if p-polarized light is optimal in the X direction and s-polarized light is optimal in the Y direction, only the wavelength can be optimized for the brightness histogram in the X direction under the assumption of p-polarized light, and only the wavelength can be optimized for the brightness histogram in the Y direction under the assumption of s-polarized light.

[0065] Fig. 16 is an example of the GUI provided by the display unit 20 in the fourth embodiment. The user inputs the optical parameter for which the optimum value is sought and a search range in a "light irradiation conditions" selection area 217. The polarization plane to be emitted is checked in a polarization type selection area 222. The wavelength of the light to be emitted, the irradiation amount per unit time, the irradiation angle, the light irradiation interval, the irradiation direction (azimuth angle) of the light with respect to the sample, and the pulse width can be set. The display area 201A displays an SEM image when no light is emitted, and the display area 201B displays an image acquired using the optical parameter with the largest peak interval H. The "live image" display area 215 displays the SEM image during the optical parameter search.The "Image Processing" display area 221 displays a composite image or a difference image of the acquired images. The user selects an image file in an image selection area 218. Next, the user specifies an image calculation method in a "Calculation Method" selection area 219. For example, if a difference image of the images A and B selected in the image selection area 218 is to be output, a minus symbol is selected, and if a composite image is to be output, a plus symbol is selected. When the "Start Processing" button 220 is selected, the image processing unit 17 starts image processing. <Vierte Ausführungsform: Zusammenfassung>

[0066] The charged particle beam device 1 according to the fourth embodiment determines optical parameters such that the peak interval H in the brightness histogram of the SEM image is large. This makes it possible to optimize optical parameters to increase the structural contrast of the SEM image. <Fünfte Ausführungsform>

[0067] Although the above-described embodiment described an example in which the shaped structures on the sample 8 are linearly arranged and p-polarized light or s-polarized light is used depending on the observation direction, the invention is applicable to other shaped structures. In a fifth embodiment of the present invention, an example of increasing the contrast of an SEM image obtained by detecting the magnetic domains of a material will be described as an example thereof. The configuration of the charged particle beam device 1 is the same as that in the first and second embodiments. The polarization conversion plate 32 may be a λ / 2 polarization plate, a λ / 4 polarization plate, or a combination of a λ / 2 polarization plate and a λ / 4 polarization plate. Other components capable of converting the polarization plane may also be used. The GUI is the same as that shown in Fig. 16.

[0068] Fig. Figure 17 is a schematic diagram showing an example of an SEM image in which the image contrast of a magnetic domain of Sample 8 was increased. An iron thin film having domains that were magnetic domains was used as Sample 8. The electron beam irradiation conditions were an acceleration voltage of 0.5 keV, an irradiation current of 20 pA, and a scanning speed of 100 ns / pixel. The light irradiation conditions were a wavelength of 800 nm, and the polarization plane was (1) left-circularly polarized light and (2) right-circularly polarized light. When Sample 8, which has different magnetic domains, is irradiated with light having different right- and left-circular polarizations, different absorption coefficients are obtained for each magnetization axis due to magnetic circular dichroism.That is, the SEM image obtained under polarization-controlled light irradiation exhibits a contrast that reflects the state of the magnetic domains. In . Fig. 17 (1) the signal magnitude increases in areas that have magnetic domains with an upward component, while in Fig. 17 (2) the contrast increases in areas that have magnetic domains with a downward component. Furthermore, using the GUI of Fig. 16 a difference image ( Fig. 17 (3)) between (1) and (2) of Fig. 17. The generation of the difference image makes it possible to evaluate the influence of irradiation with different polarization types on the respective magnetic domains. <Sechste Ausführungsform>

[0069] Since the feature quantity in the X direction and the feature quantity in the Y direction are different in the shape structure of an SEM image acquired by a plurality of electron beam irradiations, the light absorption coefficients in the respective directions are different from each other. Therefore, in the sixth embodiment of the present invention, a method for uniformly enhancing the contrast in each observation direction in wide-field observation by a plurality of electron beam irradiations is described, even when the feature quantity in each observation direction is different. A charged particle beam device is described that controls the amount of electrons emitted from the sample during electron beam irradiation by controlling the polarization plane and other optical parameters of an intermittently irradiated light to achieve high-contrast image acquisition.

[0070] Fig. 18 is a configuration diagram of a charged particle beam apparatus 1 according to the sixth embodiment. The charged particle beam apparatus 1 is configured as a multi-beam scanning electron microscope that acquires an observation image of the sample 8 in a wide field of view by irradiating the sample 8 with electron beams 55, 56, 57 (primary charged particles). The charged particle beam apparatus 1 includes the electron optical system, the stage mechanism system, the electron beam control system, the light irradiation system, and the main console 16. The electron optical system includes a multi-beam optical device 50 that forms and irradiates a plurality of electron beams, and detectors 51, 52, and 53. The stage mechanism system includes the XYZ stage 6 and the sample holder 7.The electron beam control system includes a multi-beam electron beam control unit 61, a detection control unit (a) 58, a detection control unit (b) 59, and a detection control unit (c) 60. The light irradiation system includes the light source 13, the light control unit 14, the light irradiation unit 24, and the setting input unit 21. The main console 16 is equipped with an imaging system and an input / output system. The imaging system includes the image processing unit 17 and the image signal processing unit 19, whose detection scanning function is synchronized with the deflection signal. The input / output system includes the setting input unit 21 for the imaging conditions of the electron beams 55, 56, and 57 and the display unit 20. The feature quantity extraction unit 18 detects the shape structure of the sample 8 and extracts the feature quantity of the shape structure.The optical parameter determination unit 15 determines the parameter that maximizes the absorption coefficient of the light irradiated onto the sample 8 according to the feature quantity. The feature quantity extraction unit 18 extracts the feature quantity such as the size / density / period / area / contour line of the mold structure / photophysical properties of the material of which the sample 8 is made from the SEM image, the electron emission signal, the design data, and the like.

[0071] The electron beams 55, 56, and 57 accelerated by the multi-beam optical device 50 are emitted toward the sample 8, and the irradiation positions of the electron beams 55, 56, and 57 on the sample 8 are controlled. The detector 5 detects emitted electrons (secondary charged particles) emitted from the sample 8 by irradiating the sample 8 with the electron beams 55, 56, and 57. The setting input unit 21 is a functional unit that allows the user to input the acceleration voltage, irradiation current, deflection condition, detection scanning condition, electron lens condition, and the like.

[0072] Fig. Figure 19 is an SEM image acquired by multiple electron beam irradiations. Since SEM observation is performed by multiple electron beam irradiations, an area captured by one observation can be enlarged, as shown in Fig. 19. This enables the observation of a wide field of view, thereby capturing areas with different structural feature sets in one image. In the present embodiment, as shown in Fig. 19, an image of a sample was captured in which structures A and structures B with the same structure spacing but different structure formation directions were mixed in one field of view.

[0073] First, feature amount extraction of the shape structure is performed for each SEM image acquired by each detector. In the present embodiment, the line pitch of the sample structure was used as the method for extracting the feature amount of the shape structure of the sample, as in the third embodiment.

[0074] Fig. Fig. 20 is a schematic diagram showing a method for determining the light irradiation conditions from the feature quantity extracted by the feature quantity extraction unit 18 from each image acquired by the plurality of electron beam irradiations. In the graph of Fig. 20, the horizontal axis represents the ratio of the wavelength λ to the line spacing L, and the vertical axis represents the absorption coefficient of sample 8 for the irradiation light. The line spacing L A the structure A and the line spacing L B of structure B were applied. If the irradiation amount D A per unit of time with respect to the structure A and the irradiation amount D B per unit time with respect to structure B, the contrast is uniform at any line pitch. The irradiation amount of each polarization plane per unit time is calculated using expressions (9) and (10). DA=DpulseS⋅αS(A)+DpulseP⋅αP(A) DB=DpulseS⋅αS(B)+DpulseP⋅αP(B)

[0075] α P(A) is the absorption coefficient of p-polarized light with respect to the wavelength λ and the line spacing L A , α S(A) is the absorption coefficient of s-polarized light with respect to the wavelength λ and the line spacing L A , α P(B) is the absorption coefficient of p-polarized light with respect to the wavelength λ and the line spacing L B , and α S(B) is the absorption coefficient of s-polarized light with respect to the wavelength λ and the line spacing L B . D A and D B are the irradiation amounts per unit time of the p-polarized light and the s-polarized light with which the sample 8 is irradiated. By adjusting one or both of D P puls and D S pulse such that D A = DB , the contrast can be made uniform in every direction.

[0076] Fig. Figure 21 is a schematic diagram showing an observation result when the irradiation amount per unit time is controlled for each polarization plane. As Sample 8, a sample in which a pattern of polysilicon 71 was formed on an underlying silicon 70 was used. Although microline patterns with equal pitches in the X and Y directions were formed in the polysilicon 71, patterns A and patterns B were formed in phases rotated by 90 degrees. The electron beam irradiation conditions 30 were an acceleration voltage of 5.0 keV, an irradiation current of 5 nA, and a scanning speed of 100 ns / pixel. The light irradiation conditions were a wavelength of 405 nm and a detection scan of 20 ns. The polarization plane and the irradiation amount per unit time were determined with reference to Fig. 20 so that the contrast was uniform. The GUI corresponds to the one described in Fig. 13.

[0077] The observation was made on the sample with the Fig. 19. From expressions (9) and (10), it is clear that in order to make the contrast-enhancing effect uniform for each of the structures A and B, it is necessary to set the irradiation amount of the s- and p-polarized light per unit time with respect to the structure A to half of the irradiation amount of the s- and p-polarized light per unit time with respect to the structure B. Under the condition of "light irradiation OFF" in Fig. 21 (a), the contrast difference between the polysilicon 44 and the silicon arbid substrate 46 is small. When the SEM image, as in Fig. 21 (b), under the condition that light is emitted without extracting the feature amount of the shaped structure, the contrast difference between the silicon and polysilicon in structure B is small compared to the contrast between the silicon and polysilicon in structure A, and a uniform contrast-enhancing effect in structures A and B cannot be obtained. On the other hand, as a result of controlling the light irradiation amount per unit time for each polarized light according to the feature amount of the shaped structure, a uniform contrast-enhancing effect was confirmed in both structure A and structure B, as shown in Fig. 21 (c).

[0078] Although the variable light quantity filter is used to control the irradiation quantity per unit time in the sixth embodiment, in the case of the pulse laser, a pulse picker may be used instead of the variable light quantity filter to set the pulse number of the p-polarized light per unit time to 2 / 3 of the pulse number of the s-polarized light per unit time.

[0079] The charged particle beam device 1 according to the sixth embodiment determines the optical parameters of the feature quantity according to the structural shape of the sample 8 and adjusts the irradiation amount per unit time for each optical parameter according to the light absorption coefficient corresponding to each optical parameter. This enables uniform contrast for each optical parameter. Thus, uniform contrast can be obtained even if the feature quantity of the sample 8 is different in each observation direction, for example. <Modifikationen der Erfindung>

[0080] The present invention is not limited to the above embodiments, but includes various modifications. For example, the above embodiments may be described in detail for easier understanding of the invention and are not necessarily limited to those having all of the configurations described above. A part of a configuration of one embodiment may be replaced with a configuration of another embodiment, or a configuration of another embodiment may be added to the configuration of the embodiment. Furthermore, a part of the configuration of each embodiment may be combined with another configuration, omitted, or replaced with another configuration.

[0081] Although the above embodiments described an example in which the charged particle beam device 1 is configured as a scanning electron microscope as a configuration example for acquiring an observation image of the sample 8, the invention is also applicable to other charged particle beam devices. That is, the invention is applicable to other charged particle beam devices that adjust the emission power of secondary charged particles by irradiating the sample 8 with light.

[0082] Although a pulse laser is used as the light source 13 in the above embodiments, other light sources capable of emitting light may also be used. Fig. While an example in which polarized light is controlled using the polarization conversion plate 32 was described in Figure 3, the polarized light can also be controlled in other ways. For example, linearly polarized light can be converted into circularly polarized light or elliptically polarized light by using a λ / 4 polarization plate.

[0083] In the fourth embodiment, the configuration for adjusting the angle of incidence of the light is not limited to the Fig. 14A and Fig. 14B. For example, in Fig. 14B, the angle of incidence of the light can be controlled by adjusting an angle of the adjusting mirror 31.

[0084] In the above embodiments, as the photophysical property of the shape structure of the sample, an optical absorption coefficient of the material of the sample 8, an optical reflectance of the material of the sample 8, a dielectric constant of the material of the sample 8, an Abbe number of the material of the sample 8, an optical refractive index of the material of the sample 8, and the like are considered.

[0085] In the above embodiments, in order to ensure that the efficiency of the emitted electrons is increased by irradiating the sample 8 with light, it is desirable to irradiate the sample 8 with light at a time interval shorter than the period of irradiation of the sample 8 with the electron beam 30.

[0086] In the above embodiments, the main console 16 may be configured from an arithmetic unit such as a computer. Functional units (image processing unit 17, feature quantity extraction unit 18, and setting input unit 21), the light control unit 14, and the optical parameter determination unit 15 included in the main console 16 may be configured using hardware such as circuits in which the functions are implemented, or they may be configured by having the arithmetic unit execute software in which the functions are implemented. List of reference symbols 1 charged particle beam device 2 electron beam guns 3 Deflection device 4 Electron lens 5 Detector 6 XYZ table 7 sample holders 8 Sample 9 Electron gun control unit 10 Deflection signal control unit 11 Detection control unit 12 Electron lens control unit 13 Light source 14 Lighting control unit 15 Unit for determining optical parameters 16 Main console 17 Image processing unit 18 Feature set extraction unit 19 Image signal processing unit 20 display unit 21 Setting input unit 22 stained glass windows 23 housings 24 light irradiation unit 25 Irradiation light 30 electron beam 31 Adjustment mirror 32 Polarization conversion disc 33 variable light quantity filter 34 wavelength conversion unit 41 Anti-reflective coating 42 Resist 43 Silicon substrate 44 polysilicon 45 oxide layer 46 Silicon carbide substrate 47 Non-polarizing beam splitter 49 beam monitor 50 optical multi-beam device 51 Detector 52 detector 53 Detector 55: Electron beam 56: Electron beam 57: Electron beam 58 Detection control unit (a) 59 Detection control unit (b) 60 Detection control unit (c) 61 Multi-beam electron beam control unit 70 Silicon 71 polysilicon 81 Storage device 201A Display area 201B Display area 202 Display area “Difference image” 203 Start image button 204 Difference Image button 205 Polarization plane setting area 206 Image Capture Process Settings Area 207 Display area 208 display area 209 Monitoring area “Light irradiation conditions” 210 Display area “Image conditions” 211 Display area “Image conditions” 212 Feature set extraction field 213 Polarization plane ratio setting area 214 Irradiation amount setting area 215 Live image display area 216 -Polarization type selection button 217 Selection area “Light irradiation conditions” 218 Image selection area 219 Selection area “Calculation method” 220 Start processing button 221 Image processing display area 222 Polarization type selection area

Claims

[1] A charged particle beam device (1) configured to irradiate a sample (8) with a charged particle beam (30), the charged particle beam device (1) comprising: a charged particle source (2) configured to irradiate the sample (8) with primary charged particles; a light source (13) configured to emit light to be emitted toward the sample (8); a detector (5) configured to detect secondary charged particles generated by irradiating the sample (8) with primary charged particles from the sample (8); an image processing unit (17) configured to generate an observation image of the sample (8) using the secondary charged particles detected by the detector (5); and a light control unit (14) configured to control an optical parameter representing a physical property of the light, wherein the light control unit (14) changes the polarization plane of the light as an optical parameter and causes the image processing unit (17) to generate observation images whose contrast corresponds to the changed polarization plane. [2] Charged particle beam device (1) according to claim 1, wherein the light control unit (14) sets the polarization plane of the light as an optical parameter to a first polarization plane so that the sample (8) has a first light absorption coefficient corresponding to the first polarization plane, and then causes the image processing unit (17) to generate an observation image, the light control unit (14) sets the polarization plane of the light as an optical parameter to a second polarization plane different from the first polarization plane so that the sample (8) has a second light absorption coefficient corresponding to the second polarization plane, and then causes the image processing unit (17) to generate an observation image. [3] A charged particle beam device (1) according to claim 1, wherein the light control unit (14) controls as optical parameters at least one of: an angle formed between the light and a coordinate axis in a horizontal plane when the light is projected in a horizontal plane, an angle formed between the light and a coordinate axis in a vertical plane when the light is projected in a vertical plane, a wavelength of light, a period of light irradiation, and an amount of light irradiated per unit of time. [4] Charged particle beam device (1) according to claim 1, wherein the image processing unit (17) generates a first observation image of the sample (8) when the light control unit (14) has set the optical parameter to a first parameter, and a second observation image of the sample (8) when the light control unit (14) has set the optical parameter to a second parameter, the image processing unit (17) generates a difference image by determining a difference between the first observation image and the second observation image, and the charged particle beam device (1) further comprises a display unit (20) configured to display the difference image. [5] Charged particle beam device (1) according to claim 1, further comprising: a feature set extraction unit (18) configured to extract a feature set of a shape structure formed on the sample (8); and an optical parameter determining unit (15) configured to determine, in accordance with the feature set, the optical parameter that maximizes the light absorption coefficient of the sample (8) for the light. [6] Charged particle beam device (1) according to claim 5, further comprising: a storage unit (81) configured to store absorption coefficient data describing a correspondence between one or more of the optical parameters and the light absorption coefficients, wherein the optical parameter determination unit (15) determines the optical parameter with which the contrast of the observation image is as high as possible by referencing the absorption coefficient data. [7] A charged particle beam device (1) according to claim 5, wherein the feature set extraction unit (18) extracts as the feature set at least one of: a size of the mold structure, a surface density of the form structure, a repetition cycle of the form structure, a surface of the mold structure, a contour line of the form structure, and a photophysical property of the material from which the mold structure is made. [8] The charged particle beam device (1) according to claim 5, wherein the feature amount extraction unit (18) extracts the feature amount of the shape structure using the observation image or the design data. [9] Charged particle beam device (1) according to claim 5, wherein the light control unit (14) irradiates the sample (8) with light having each optical parameter by changing the optical parameter, and the image processing unit (17) acquires the observation image corresponding to the optical parameter at which the contrast is highest among the contrasts of the observation image when the sample (8) is irradiated with light having each optical parameter. [10] Charged particle beam device (1) according to claim 5, wherein the light control unit (14) is configured to control an irradiation amount of the light per unit time and a parameter other than the irradiation amount as an optical parameter, and the light control unit (14) adjusts the irradiation amount when the other parameter has been set to a first parameter and the irradiation amount when the other parameter has been set to a second parameter such that the difference between a first contrast of the observation image when the other parameter has been set to the first parameter and a second contrast of the observation image when the other parameter has been set to the second parameter is small. [11] Charged particle beam device (1) according to claim 10, wherein the light control unit (14) also comprises: a first measuring device configured to measure the irradiation amount of the light with the first parameter; and a second measuring device configured to measure the irradiation amount of the light with the second parameter, and the light control unit (14) controls the irradiation amount using the irradiation amount measured by the first measuring device, the irradiation amount measured by the second measuring device, the first absorption coefficient of the sample (8) for the light with the first parameter and the second absorption coefficient of the sample (8) for the light with the second parameter so that the difference between the first contrast and the second contrast is reduced. [12] Charged particle beam device (1) according to claim 1, wherein the light control unit (14) acquires a histogram of the luminance or brightness value of each pixel in the observation image or a histogram of the luminance or brightness difference of each pixel in the observation image, and the light control unit (14) adjusts the optical parameter so that a frequency peak interval on the histogram is maximized. [13] Charged particle beam device (1) according to claim 12, wherein the light control unit (14) is configured to control a first parameter and a second parameter as optical parameters, the light control unit (14) detects a first histogram as histograms when the optical parameter is the first parameter, and a second histogram when the optical parameter is the second parameter, and the light control unit (14) controls the first parameter so as to maximize a frequency peak interval on the first histogram and controls the second parameter so as to maximize a frequency peak interval on the second histogram. [14] Charged particle beam device (1) according to claim 1, wherein the light control unit (14) irradiates the sample (8) with light in every second time interval which is shorter than a first time interval in which the sample (8) is irradiated with primary charged particles, and the light control unit (14) controls the irradiation amount of light per unit time by controlling at least one of an average light intensity, a time width of light irradiation, a period of light irradiation, the second time interval, and a number of light irradiations per unit time. [15] The charged particle beam device (1) according to claim 7, wherein the photophysical property is at least one of an optical absorptivity of the material, an optical reflectivity of the material, a dielectric constant of the material, an Abbe number of the material, and an optical refractive index of the material.

Images