Charge particle beam device

Abstract

Charge particle beam device (1) irradiating a sample (8) with a charge particle beam (30), comprising: a charge particle source (2) configured to irradiate the sample (8) with primary charge particles (30); a light source (10) configured to emit light that is emitted towards the sample (8); a detector (5) configured to detect secondary charge particles generated by irradiating the sample (8) with primary charge particles from the sample (8); an image processing unit (18) configured to generate an observational image of the sample (8) using the secondary charge particles detected by the detector (5); and a light intensity control unit (14) configured to set an irradiance of light per unit of time, and an absorption properties measuring unit (13) configured to measure an amount of absorption of the light absorbed by the sample (8); characterized in that the charge particle device (1) further comprises: a storage unit (27) configured to store correspondence data describing a correspondence between the amount of absorption measured by the absorption properties measuring unit (13) and the light irradiance per unit time, wherein the light intensity control unit (14) causes the image processing unit to produce a multitude of observation images, each exhibiting a different contrast, by changing the irradiance of the light per unit of time, wherein the sample (8) has a property that the emission quantity of secondary charge particles changes depending on the light irradiation intensity per unit time, The light intensity control unit (14) sets the light irradiation intensity per unit time to a first intensity, so that the sample (8) emits secondary charge particles in a first emission quantity corresponding to the first intensity, and then causes the image processing unit to produce an observation image, and The light intensity control unit (14) adjusts the light irradiation intensity per unit time to a second intensity that differs from the first intensity, so that the sample (8) emits secondary charge particles in a second emission quantity corresponding to the second intensity, and then causes the image processing unit to produce an observation image, wherein the light intensity control unit (14) determines the first intensity and the second intensity according to the correspondence described in the correspondence data.

Description

Technical field

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

[0002] In semiconductor manufacturing processes, inline inspection and measurement using a scanning electron microscope (SEM) is a crucial step towards increasing yield. In particular, a low-voltage SEM (low-kV SEM), which uses an electron beam with an accelerating voltage of a few kV or less, is very useful for inspecting and measuring two-dimensional shapes, such as resist structures in a lithography process and gate structures in a previous process. This is because the electron beam has a shallow penetration depth and can capture an image with rich surface information. However, since organic materials such as...Since a resist and an antireflection layer used in the lithography process have similar compositions, or silicon-based semiconductor materials used in a transistor have similar compositions, it is difficult to distinguish between these materials in their secondary electron emission. Because a sample made of such materials exhibits low image contrast in a scanning electron microscope (SEM), the detectability of ultrafine structures or defects in semiconductor devices is reduced. Known methods for increasing detectability in an SEM include adjusting observation conditions such as accelerating voltage and irradiation current, as well as techniques for distinguishing the energy of the electrons emitted by the sample. However, depending on the conditions, resolution and imaging speed can be problematic.

[0003] PTL 1 discloses a method for controlling the image contrast of a scanning electron microscope (SEM) by irradiating an observation area of ​​the SEM with light. Since charge carriers are generated by light irradiation, the conductivity of a semiconductor or insulator changes. A difference in conductivity between materials is reflected in a potential contrast of an SEM image. A poorly conducting area in a semiconductor device or the like can be detected by controlling the potential contrast of the SEM through light irradiation.

[0004] PTL 2 discloses a method for controlling the image contrast of an SEM by selecting a wavelength of light for a sample configured from multiple layers, with a focus on the light absorption properties which vary depending on the wavelength of the emitted light.

[0005] Documents US 2021 / 0066029A1 and DE 112018007852T5 each disclose charge particle beam devices according to the preamble of claim 1. List of reference literature Patent literature PTL 1: JP 2003 151 483 A PTL 2: Japanese patent application JP 2010 536 656 A Summary of the invention: Technical problem

[0006] In both PTL 1 and PTL 2, the SEM image contrast is controlled according to a wavelength-dependent difference in the absorption properties of materials. Both are capable of increasing the image contrast between materials that exhibit a large difference in the wavelength dependence of their absorption properties. However, many similar materials, such as silicon materials with different doping types and densities or organic materials with similar compositions, exhibit a similar wavelength dependence of their absorption properties. For a sample composed of these materials, it can be difficult to obtain a sufficiently distinct difference in absorption properties.

[0007] The present invention was conceived in view of the above problem, and one object of the invention is to provide a charge particle beam device that is capable of capturing a high-contrast observation image even with a sample whose light absorption properties depend on a wavelength of light. Solution to the problem

[0008] To solve the problem, the inventor proposes a charge particle beam device with the features of claim 1. A charge particle beam device according to the invention irradiates a sample with light and simultaneously produces an observation image of the sample, generating a plurality of observation images, each exhibiting a different contrast, by changing the light irradiation intensity per unit time. Beneficial effect

[0009] According to the inventive charge particle beam device, it is possible to control the amount of secondary electrons emitted by the sample by adjusting the light irradiation intensity per unit time according to the light absorption properties. This makes it possible to increase the contrast of the observed images even for similar materials that have similar light absorption properties with respect to a given wavelength. Brief description of the drawings Fig. Figure 1 is a schematic configuration drawing of a charge particle beam device 1 according to a first embodiment. Fig. Figure 2 shows a configuration example of an absorption properties measurement unit 13. Fig. Figure 3 is a flowchart of a procedure for acquiring an observational image of sample 8 by the charge particle beam device 1. Fig. Figure 4 is a graph that shows a relationship between light irradiance per unit of time I r and a light absorption intensity I a shows. Fig. Figure 5 is a graph showing the relationship between the light irradiance I r per unit of time and an emission quantity of secondary electrons. Fig. Figure 6 is an example of a graphical user interface (GUI) 61, which is displayed by a picture display unit 25. Fig. Figure 7 is an example cross-sectional view of sample 8. Fig. Figure 8 shows exemplary observation images that were recorded under three light irradiation intensity conditions per unit of time. Fig. Figure 9 is a schematic configuration drawing of a charge particle beam device 1 according to a second embodiment. Fig. Figure 10 is a flowchart of a procedure for acquiring an observational image of sample 8 by the charge particle beam device 1. Fig. Figure 11 is a schematic configuration drawing of a pulse laser 10 and a light intensity adjustment unit 11 in the second embodiment. Fig. Figure 12 is an exemplary relationship between a light absorption property measured in S1001 and a light irradiance per unit time. Fig. Figure 13 is an exemplary cross-sectional view of sample 8. Fig. Figure 14 is a graph showing the relationship between a correction amount ΔC of a secondary electron detection signal and the light irradiation intensity per unit time in the second embodiment. Fig. Figure 15 shows exemplary observation images that were recorded under three light irradiation intensity conditions per unit of time. Fig. Figure 16 is a time diagram showing the respective times of electron beam irradiation / pulsed laser irradiation / secondary electron detection. Fig. Figure 17 is an example of the GUI 61, which is displayed by the image display unit 25 in a third embodiment. Fig. Figure 18 is an exemplary cross-sectional view of sample 8. Fig. Figure 19 shows exemplary observational images that were captured under each irradiation condition by the electron beam. Fig. Figure 20 shows a configuration example of an absorption properties measurement unit 13. Fig. Figure 21 shows a configuration example for the absorption properties measurement unit 13. Fig. Figure 22 shows exemplary observation images that were recorded under three light irradiation intensity conditions per unit of time. Fig. Figure 23 is a schematic configuration drawing of the charge particle beam device 1 according to a fifth embodiment. Fig. Figure 24 is a graph showing the energy distribution of the secondary electrons when a light pulse is emitted with different light irradiation intensities. Fig. Figure 25 shows exemplary observation images that were recorded under two light irradiation intensity conditions per unit of time and with an energy filter 231. Fig. Figure 26 is a schematic configuration drawing of the charge particle beam device 1 according to a sixth embodiment. Fig. Figure 27 is an exemplary cross-sectional view of sample 8. Fig. Figure 28 shows exemplary observation images that were recorded under two light irradiation intensity conditions. Description of embodiments<Grundprinzip der Erfindung>

[0010] The basic principle of the invention will first be explained, followed by a discussion of specific embodiments. The present invention irradiates a sample to be observed with light in order to excite a charge carrier within the sample. The sample is then in an excited state. In the excited state, the amount of secondary electrons emitted increases in proportion to the amount of light absorbed. However, when photoelectrons are emitted from the sample by the light irradiation, the sample transitions into a depleted state, in which there is a lack of electrons. In the depleted state, the amount of secondary electrons emitted decreases in proportion to the amount of light absorbed.

[0011] An increase or decrease ΔS of the secondary electrons caused by light irradiation is expressed by expression 1. A represents the amount of light absorption, and z represents the distance from the direction of incidence of the light. [Expression 1] ΔS∝±∫dA / dz⋅dz

[0012] The dependence of the light absorption quantity dA / dz on the direction of incidence is expressed by expression 2. α1 to α3 represent absorption coefficients of a material, where α1 represents a linear absorption term and α2 and α3 represent non-linear absorption terms of the second and third order, respectively. Here, terms up to the third order are described, but higher-order terms have also been confirmed. r This represents the irradiance of the light applied to the sample per unit of time. Parameters for controlling the light irradiance per unit of time include the average power of a pulsed laser, the energy per pulse, the peak intensity per pulse, the pulse width of the pulsed laser, the number of light pulses emitted per unit of time, the frequency of the light pulses, the area of ​​a light spot, the wavelength of the light, the polarization, and similar factors. [Expression 2] dA / dz=α1⋅Ir+α2⋅Ir2+α3⋅Ir3

[0013] When the light irradiation intensity is low, the linear absorption term becomes dominant due to single-photon absorption. If the wavelength of the light lies within an absorption band of the material, the sample absorbs light and transitions to an excited state. In the excited state, the secondary electron emission power increases. When the light irradiation intensity is high, the nonlinear absorption term becomes dominant due to multiphoton absorption. Even if the wavelength of the light does not lie within the absorption band of the material, the sample absorbs light and transitions from an excited state to a depleted state, in which photoelectrons are emitted. In the depleted state, the secondary electron emission power decreases.This means that the amount of secondary electrons emitted can be controlled by adjusting an absorption property according to the irradiance of the light, either as single-photon or multi-photon absorption. Photophysical parameters that confirm nonlinear absorption include the absorption coefficient, the reflection coefficient, polarization modulation, wavelength modulation, photoelectron emission, and the like.

[0014] The present invention provides, using the above principle, a charge particle beam device which, even with materials having similar absorption properties with respect to a wavelength of light, makes it possible to obtain an observation image with high detectability by adjusting the irradiation intensity of the light per unit of time, in which the contrast of structures or defects is increased. <Erste Ausführungsform>

[0015] A first embodiment of the present invention describes a charge particle beam device that irradiates an observation area with a pulsed laser, the light irradiation intensity of which per unit time is controlled according to the light absorption properties of a sample, and increases the contrast of an observation image.

[0016] Fig. Figure 1 is a schematic configuration drawing of a charge particle beam device 1 according to the first embodiment. The charge particle beam device 1 is configured as a scanning electron microscope that irradiates a sample 8 with an electron beam (primary charge particle) to acquire an observational image of the sample 8. The charge particle beam device 1 comprises an electron optical system, a stage mechanism, a light pulse irradiation system, a light absorption properties measurement system, a control system, an image processing system, and an operating system. A storage device 27 is described below.

[0017] The electron-optical system comprises an electron gun 2, a deflection device 3, an electron lens 4, and an electron detector 5. The stage mechanism includes an XYZ stage 6 and a sample holder 7. The interior of a housing 9 is maintained at a high vacuum and accommodates the electron-optical system and the stage mechanism. The light pulse irradiation system comprises a pulsed laser 10 and a light intensity control unit 11. Light is emitted to the sample 8 through a light pulse introduction unit 12 located in the housing 9. An absorption properties measurement unit 13 detects a light pulse reflected from the sample 8.

[0018] The control system comprises an electron gun control unit 14, a deflection signal control unit 15, an electron lens control unit 16, a detector control unit 17, a table position control unit 18, a pulse laser control unit 19, a light intensity setting control unit 20, an absorption properties measurement control unit 21, a control transmission unit 22, and a detection signal acquisition unit 26. The control transmission unit 22 writes and controls a control value in each of the control units based on input information received from an operator interface 23. The image processing system comprises an image generation unit 24 and an image display unit 25.

[0019] An electron beam accelerated by the electron gun 2 is focused by the electron lens 4 and emitted towards the sample 8. The deflection device 3 controls the irradiation position of the electron beam on the sample 8. The electron detector 5 detects emission electrons (secondary charge particles) emitted by the sample 8 when it is irradiated with the electron beam. The user interface 23 is a functional unit that allows a user to input an accelerating voltage, an irradiation current, a deflection condition, a detection scanning condition, an electron lens condition, and the like.

[0020] A light pulse emitted by the pulsed laser 10 is directed to the position on the sample 8 irradiated by the electron beam. The light intensity control unit 11 is a device that controls the irradiation intensity of a light pulsed laser per unit time. The electron detector 5 detects secondary electrons emitted by the sample 8. The secondary electrons include both low-energy emission electrons from the sample and high-energy backscattered electrons. The image generation unit 24 generates a SEM image (observation image) of the sample 8 using a detection signal detected by the electron detector 5, and the image display unit 25 displays this image.

[0021] Fig. Figure 2 shows a configuration example of the absorption properties measuring unit 13. A pulsed laser beam, whose irradiation intensity has been set by the light intensity setting unit 11, is split by a beam splitter 30 before being emitted to sample 8. An irradiation light detector 31 detects a signal corresponding to the intensity of the light emitted to sample 8. The light intensity is calibrated according to a division ratio of the beam splitter 30. The pulsed laser beam emitted to sample 8 is reflected by the sample 8, and a reflection light detector 32, located opposite the beam splitter, detects a signal corresponding to the light intensity. A subtractor 33 determines a difference signal between the signals detected by the irradiation light detector 31 and the reflection light detector 32, respectively. A signal detector 34 digitizes the light absorption intensity based on this difference signal.

[0022] Fig. Figure 3 is a flowchart of a procedure for acquiring an observational image of sample 8 using the charge particle beam device 1. Each step of the process is described below. Fig. 3 described. (FIG. 3: Steps S301 to S303)

[0023] The table mechanism moves the sample 8 into an observation position (S301). The control transmission unit 22 sets the accelerating voltage, irradiation current, magnification, and sampling time as basic electron beam observation conditions according to the information entered at the operator interface 23 (S302). The pulse laser control unit 19 sets the wavelength of the pulse laser (S303). It is desirable to set the laser wavelength based on a wavelength band in which the sample 8 absorbs light. (FIG. 3: Step S304)

[0024] The control transmission unit 22 measures the light absorption properties of the sample 8 while changing the irradiance of the light per unit time. The light irradiance is controlled by the light intensity setting unit 11. The absorption properties measuring unit 13 performs light absorption measurements. The control transmission unit 22 stores data in the storage device 27, which, based on the measurement result, describes a correspondence between the light irradiance and the light absorption properties. An example of this correspondence is described below with reference to... Fig. 4 described. (FIG. 3: Step S305)

[0025] The control transmission unit 22 sets a threshold value for the light irradiance per unit time based on the result of step S304. This threshold value can be determined, for example, depending on which light absorption property of expression 2 is dominant: the linear absorption element (α1) or the nonlinear absorption element (from α2 onwards). A specific example of a criterion for determining the threshold value is given below with reference to... Fig. 4 described. (FIG. 3: Step S304 and S305: Supplement No. 1)

[0026] In this workflow, an analysis result is stored and used in S304 in storage device 27. However, the correspondence between light irradiance and light absorption properties under different conditions can also have been analyzed beforehand, and the result can be stored as a database in storage device 27. This eliminates the need to perform steps S304 and S305 every time an observation image is acquired. (FIG. 3: Step S304 and S305: Supplement No. 2)

[0027] Storage device 27 can be configured from a suitable device capable of storing the measurement result and its corresponding value. For example, if the measurement result and its corresponding value are pre-stored in a database and used, storage device 27 can be configured from a non-volatile storage device. If the measurement result and its corresponding value are captured each time this process is executed, storage device 27 can be configured from a storage device for the temporary storage of the measurement result and its corresponding value. These devices can be combined. (FIG. 3: Steps S306 to S308)

[0028] Based on the results from S304 and S305, the control transmission unit 22 sets one or more light irradiation intensities as observation conditions (S306). Here, an observation condition need not be the threshold value set in S305 itself, but can be a suitable value close to the threshold, as described below. The control transmission unit 22 adjusts the irradiation intensity via the light intensity setting unit 11 so that the irradiation intensity corresponds to the light irradiation intensity set as an observation condition (S307). The control transmission unit 22 irradiates the sample 8 with an electron beam and with a light pulse, the irradiation intensity of which per unit time has been set, and acquires an observation image via the image generation unit 24 (S308).

[0029] Fig. Figure 4 is a graph that shows a relationship between light irradiance per unit of time I r and a light absorption intensity I a shows. In S304, the in Fig. The relationship shown in Figure 4 was measured. Here, the relationship between the light absorption properties and the light irradiance per unit time is shown when sample 8 consists of silicon (Si) and silicon nitride (SiN). From the absorption properties of silicon, Figure 41 shows that the light absorption intensity I a transitions from a linear to a non-linear characteristic when the light irradiance I r approximately 150 MW / cm² per unit of time 2 The absorption properties of silicon nitride (42) maintain a linear characteristic until the light irradiation intensity I is reached. r approximately 300 MW / cm² 2 / µs achieved.

[0030] In S305, the control transmission unit 22 can define an irradiation intensity at which the absorption properties 41 (Si) change from linear to nonlinear as a threshold value I rth(Si) set, and an irradiation intensity at which the absorption properties 42 (SiN) change from linear to nonlinear, as a threshold value I rth(SiN) adjust. The meaning of these thresholds is explained with reference to Fig. 5 described.

[0031] Fig. Figure 5 is a graph that shows a relationship between the light irradiance I r per unit of time and an emission quantity of secondary electrons. With increasing I r The emission quantity of secondary electrons 51 from silicon increases, and when I r approximately 150 MW / cm² 2 Once it reaches / µs or more, it gradually decreases. The emission of secondary electrons 52 from silicon nitride increases to about 300 MW / cm². 2 / µs. In the present description, the phenomenon of the increase and decrease in the emission quantity of secondary electrons is referred to as the secondary electron modulation effect. The inventors have found that this modulation effect occurs when the absorption properties change from linear to nonlinear. Therefore, in Fig. 5 the irradiation intensities at which the emission quantity of secondary electrons begins to decrease, each corresponding to threshold I rth(Si) and the threshold I rth(SiN) .

[0032] To increase the contrast of the observation image for each of the materials, it is desirable to adjust the observation condition such that the emission quantity of secondary electrons differs significantly for each material. This corresponds to a large difference between the emission quantities of secondary electrons 51 and 52 in Fig. 5. It is assumed that such a high-contrast observational condition occurs at irradiance intensities close to the thresholds at which the emission levels of secondary electrons begin to decrease. Therefore, in Fig. 5. Three observation conditions were set for contrast comparison: Condition a (0 MW / cm²) 2 / µs), condition b (70 MW / cm²) 2 / µs) and condition c (350 MW / cm²) 2 / µs). An example of observational images under these conditions is described below.

[0033] Fig. Figure 6 is an example of a graphical user interface (GUI) 61, which is displayed by the image display unit 25. Basic observation conditions such as the accelerating voltage 62, the irradiation current 63, the magnification 64, and the scanning speed 65 are adjustable on the GUI 61. The image display section 66 shows the observation image.An “Irradiation Conditions” setting section 67 comprises (a) a “Wavelength” setting section 68 to set the wavelength of a light pulse, (b) an absorption properties analysis section 69 to acquire (or retrieve from a database) the absorption properties of a sample, (c) an absorption properties display section 70 to display the absorption properties, and (d) an “Irradiation Intensity” setting section to set, based on the light irradiation intensity conditions per unit time determined on the “Absorption Properties” display section 70, an average power 71 of the light pulse, a pulse width 72, a frequency 73 of the light pulse, and an irradiation diameter 74 of the light pulse. Fig. In section 6, two wavelengths can be selected as the light pulse wavelength. Additionally, three conditions can be set as the light irradiation intensity condition per unit of time. Other parameters can also be set on the GUI 61.

[0034] Fig. Figure 7 is an example cross-sectional view of sample 8. Fig. Figure 4 shows an example composed of silicon 75 and silicon nitride 76. A line-structured thin film of silicon nitride 76 is deposited on the silicon 75. The electron beam observation conditions were an accelerating voltage of 0.5 kV, an irradiation current of 100 pA, a magnification of 100,000x, and a scanning rate of a TV scan rate. The wavelength of a light pulse was 355 nm. As shown in Fig. Figure 5 shows that the light irradiance per unit of time was 0 MW / cm². 2 / µs, 70 MW / cm 2 / µs and 350 MW / cm² 2The microsecond setting was used. The average luminous flux at the respective irradiance intensities was 0 mW, 44 mW and 220 mW.

[0035] Fig. Figure 8 shows exemplary observation images that were recorded under three light irradiance intensity conditions per unit of time. Conditions a to c were recorded in Fig. 5 described. In the observational image acquired under condition a, silicon 75 and silicon nitride 76 exhibit the same image brightness, and the structure is poorly discernible. In the observational image acquired under condition b, both silicon 75 and silicon nitride 76 achieve high image brightness, and the structure is highly discernible. In the observational image acquired under condition c, silicon 75 has low image brightness, while silicon nitride 76 has high image brightness. It can be seen that the observational image acquired under condition c achieves the highest contrast.

[0036] The same effect can also be obtained if the charge particle beam device 1 according to the first embodiment is implemented with a delaying system in which a voltage is applied to the XYZ table 6, the sample holder 7 and the sample 8 in order to reduce the electron energy emitted to the sample. <Zusammenfassung der ersten Ausführungsform>

[0037] The charge particle beam device 1 according to the first embodiment makes it possible to control the amount of secondary electrons emitted by the sample 8 by adjusting the irradiation intensity per unit time of the light actually emitted according to the light absorption properties, which depend on the light irradiation intensity per unit time. Even with similar materials that have similar absorption properties with respect to a given wavelength of light, it is therefore possible to increase the contrast of the observed image and thereby improve the detectability of a defect and the structure of the sample 8. <Zweite Ausführungsform>

[0038] When sample 8 is irradiated with light, photoelectrons can be emitted from sample 8. These photoelectrons act as noise for secondary electrons. Therefore, in the second embodiment of the invention, a configuration example is described that eliminates the influence of the photoelectrons on the secondary electron detection result.

[0039] Fig. Figure 9 is a schematic configuration drawing of a charge particle beam device 1 according to the second embodiment. The charge particle beam device 1 according to the second embodiment comprises the configuration described in the first embodiment and also includes a photoelectron detector 91, a photovoltaic current meter 92, a circuit breaker 93, and a signal corrector 94. The photoelectron detector 91 detects photoelectrons from the sample 8 resulting from irradiation with the light pulse. The photovoltaic current meter 92 measures a current flowing through the sample 8 when it is irradiated with light. The circuit breaker 93 interrupts the electron beam. The signal corrector 94 corrects a secondary electron detection signal or the brightness of an observation image based on the photoelectron detection signal detected by the photoelectron detector 91.Since the remaining configuration is identical to that of the first embodiment, the following discussion will mainly focus on the differences.

[0040] Fig. Figure 10 is a flowchart of a procedure for acquiring an observational image of sample 8 by the charge particle beam device 1. In the flowchart of Fig. 10 was added to the schedule in Fig. Step S1002 was inserted between S307 and S308, and S304 was replaced by S1001. The remaining steps correspond to those in Fig. 3. (FIG. 10: Step S1001)

[0041] The control transmission unit 22 measures the light absorption properties of the sample 8 while changing the irradiance of the light per unit time. The light absorption properties can be measured based on the emission quantity of photoelectrons detected by the photoelectron detector 91 or on the photovoltaic current measured by the photovoltaic current meter 92. The relationship between the emission quantity of photoelectrons and the light absorption quantity, or the relationship between the photovoltaic current and the light absorption quantity, can, for example, be measured in advance, and the measurement results can be stored in the storage device 27. (FIG 10: Step S1002)

[0042] The signal corrector 94 corrects the secondary electron detection signal based on the light absorption properties measured in S1001. That is, the influence of light irradiation on the secondary electron detection signal is eliminated by subtracting the secondary electron detection signal obtained when sample 8 is irradiated with light (but not with the electron beam) from the secondary electron detection signal obtained when sample 8 is irradiated with both the electron beam and light. The secondary electron detection signal obtained when sample 8 is irradiated with light (but not with the electron beam) can be determined from the detection result in S1001.

[0043] Fig. Figure 11 is a schematic configuration drawing of the pulsed laser 10 and the light intensity control unit 11 in the second embodiment. A laser oscillator (or laser amplifier) ​​111 emits the light pulse. A wavelength converter 112 is configured with a nonlinear optical component and the like, and controls the wavelength of the light pulse. A pulse picker 113 is configured with a component with an electron optical effect or a component with a magneto-optical effect and controls the frequency of the light pulse. A pulse spread controller 114 is configured with a pair of prisms and the like, and controls the pulse width of the light pulse. A polarization controller 115 is configured using a birefringent component or the like and controls a polarization plane of the light pulse.An average luminous intensity controller 116 is configured with a variable density neutral density (ND) filter or the like and adjusts the average luminous intensity of the light pulse. Furthermore, the light pulse introduction unit 12 can be configured with a zoom lens or the like, so that the irradiation diameter of the light pulse can be controlled.

[0044] Fig. Figure 12 is an example of a relationship between the light absorption properties measured in S1001 and the light irradiance per unit time. Here, the absorption properties of P-type and N-type silicon, which contain different types of impurities, are analyzed. The measurement was performed by detecting the photoelectrons with the photoelectron detector 91. The electron beam was interrupted by the interrupter 93. The wavelength of the light pulse was 405 nm. At this wavelength, there is no light energy (eV) available that reaches the vacuum level of silicon, and therefore no photoelectrons are emitted if the light pulse is absorbed linearly. With increasing light irradiance per unit time, photoelectrons are emitted by multiphoton absorption, which is a nonlinear process.

[0045] Fig. Figure 12 shows a relationship between the light irradiance I r per unit of time and an emission intensity S ph of photoelectrons in P-type and N-type silicon. P-type silicon 121 emits photoelectrons with a light irradiance per unit time of 4 MW / cm². 2 / µs as the threshold, while N-type silicon has 122 photoelectrons with a threshold of 12 MW / cm². 2 emitted / µs. Fig. Figure 12 shows an example in which the photoelectrons were detected with the photoelectron detector 91, but when the photovoltaic current measuring device 92 is used, the photovoltaic current emitted by the sample 8 can be measured, resulting in the same threshold values ​​as in Fig. 12.

[0046] Fig. Figure 13 is an exemplary cross-sectional view of sample 8. On a surface of the P-type silicon 131, N-type silicon 132 is bonded and formed, and a hole structure of a silicon oxide thin film 133 is formed on it. A defect 134 is a location where the N-type silicon 132 is misaligned with the hole structure of the silicon oxide thin film 133.

[0047] In the second embodiment, the same GUI is used as in the first embodiment. The SEM observation conditions were an accelerating voltage of 1.0 kV, an irradiation current of 500 pA, a magnification of 200,000x, and a scanning rate twice the TV sampling rate. The condition a for the light irradiation intensity per unit time was set to 0.0 MW / cm². 2 / µs set, condition b set to 4 MW / cm 2 / µs, and the condition c is set to 12 MW / cm² 2 / µs. Condition b also included a light pulse frequency of 100 MHz, an average power of 16 mW, a pulse width of 1000 femtoseconds, and an irradiation diameter of 50 µm. Condition c also included a light pulse frequency of 50 MHz, an average power of 54 mW, a pulse width of 800 femtoseconds, and an irradiation diameter of 60 µm.

[0048] Fig. Figure 14 is a graph showing the relationship between a correction factor ΔC of the secondary electron detection signal and the light irradiance per unit time in the second embodiment. The correction factor ΔC was added to the relationship between the light irradiance I r per unit of time and the emission intensity S ph the photoelectrons that are in Fig. Figure 12 shows that the surface area ratio of P-type silicon 131 to N-type silicon 132 in sample 8 is determined. In the second embodiment, this ratio was set to 50%.

[0049] Fig. Figure 15 shows exemplary observation images acquired under three light irradiation intensity conditions per unit time. In the observation image acquired under condition a, the P-type silicon 131 and the N-type silicon 132 exhibit the same image brightness, the structure is poorly discernible, and the defect is not visually detectable. In the observation image acquired under condition b, the discernibility of the P-type silicon 131 and the N-type silicon 132 is improved, but defect detection is insufficient. In the observation image acquired under condition c, the image brightness of the P-type silicon 131 is low, and the structure contrast is highest. The visual detectability of a defect 156 is sufficient when the observation image is acquired under condition c.

[0050] As a method for removing the influence of the photoelectrons from the secondary electron signal, it is possible to remove the influence of the photoelectrons from the secondary electron signal detected by the electron detector 5 by controlling a voltage applied to an energy filter in the electron lens control unit 16. <Zusammenfassung der zweiten Ausführungsform>

[0051] The charge particle beam device 1 according to the second embodiment corrects the secondary electron detection signal by removing the influence of the photoelectrons emitted from the sample 8 when it is irradiated with light. This makes it possible to improve the contrast of the observed image of the sample 8, thereby enhancing the detectability of the defect and the structure. <Dritte Ausführungsform>

[0052] In a third embodiment of the present invention, an example is described in which the sample 8 is intermittently irradiated with the electron beam. The detectability of the sample 8 can be improved by comparing the observed image when the electron beam is emitted with the observed image when no electron beam is emitted. The configuration of the charge particle beam device 1 is the same as that of the second embodiment. By interrupting the electron beam with the interrupter 93, an irradiation period and a non-irradiation period (interval period) of the electron beam can be controlled.

[0053] Fig. Figure 16 is a timing diagram showing the respective times of electron beam irradiation / pulsed laser irradiation / secondary electron detection. The control transmission unit 22 controls an irradiation period 161 and an interval period 162 of the electron beam by controlling the interrupter 93. In the third embodiment, a light pulse 163 of the pulsed laser is controlled at a constant frequency, independent of the irradiation period 161 and the interval period 162. The light pulse 163 can be emitted simultaneously with the irradiation period 161 and simultaneously with the interval period 162. A time 164, at which secondary electrons are detected, is synchronized with the irradiation period 161. The time 164, at which secondary electrons are detected, is to be synchronized with the irradiation period 161, taking into account a transit time of the secondary electrons and a delay time due to a switching delay of the electron detector 5.

[0054] Fig. Figure 17 is an example of the GUI 61 displayed by the image display unit 25 in the third embodiment. In the third embodiment, in addition to the GUI 61 described in the first embodiment, a setting section “Irradiation Period” 171 and a setting section “Interval Period” 172 were added.

[0055] Fig. Figure 18 shows an exemplary cross-sectional view of sample 8. N-type silicon 182 is bonded and formed on the surface of the P-type silicon 181. A silicon oxide thin film 183 is provided on the surface, and a hole structure is formed in the silicon oxide thin film 183. A polysilicon contact pin 184 is formed in the hole structure. A defect 185 is injected with high-density N-type silicon. A defect 186 has a thin residual layer between the contact pin 184 and the N-type silicon 182. A defect 187 has a residual layer that is thicker than that of the defect 186.

[0056] In the third embodiment, the observation conditions were an accelerating voltage of 0.3 kV, an irradiation current of 50 pA, a 50,000-fold observation magnification, and the sampling rate of the TV scan rate. For intermittent emission of the electron beam, the irradiation period was 200 ns and the interval period was 3.2 µs. In the third embodiment, the relationship between the light absorption properties of the sample 8 and the light irradiation intensity per unit time was recorded using the photovoltaic current measuring device 92. As shown in the display section “Absorption Properties” 70 in Fig. As shown in Figure 17, conditions a to c were defined as light irradiances per unit time based on the absorption properties. Condition a was 0.0 MW / cm². 2 / µs. Condition b was 16 MW / cm². 2 / µs. The condition c was 30 MW / cm². 2 / µs. Conditions corresponding to these conditions were set in the “Irradiation Conditions” section 67.

[0057] Fig. Figure 19 shows exemplary observational images acquired under each electron beam irradiation condition. In the observational image acquired under condition a, by continuously irradiating the sample with the electron beam for 5 µs or longer, the contact pins 192 are visible, but the defects are not. In the observational image acquired under condition b, by continuously irradiating the sample with the electron beam for 5 µs or longer, a depletion layer of the junction becomes conductive due to the linear absorption of the light pulse, causing a normal contact pin 194 to light up. However, a defect exhibiting high-density N-type silicon with weak linear absorption (the defect 185 in Figure 19) is visible. Fig. 18), and errors with residual layer (errors 186 and 187 in Fig. 18) are electrically charged by electron beam irradiation, which keeps the brightness of the contact pin low. In the observational image acquired under condition c, by continuously irradiating the sample with the electron beam for 5 µs or longer, the depletion layer of the junction with the high-density N-type silicon also becomes conductive due to nonlinear absorption, causing a defect 196 to appear bright. In the observational image acquired under condition c by intermittent irradiation with an electron beam irradiation period of 200 ns and an interval period of 3.2 µs, a defect 198, which has a thin residual layer between the contact pin and the N-type silicon, and a defect 199, which has a thicker residual layer than that of defect 198, are visible as grayscale contrast. Under this condition, error 198, which has a high capacity, is brighter than error 199, which has a low capacity.

[0058] A difference image 200 was created by the difference between the two mean observation images (condition b: 5 µs) (condition c: 5 µs) of Fig. 19. The error of the transition on the underside of the contact pin can be extracted from the difference image 200. A difference image 201 was generated by the difference between the two lower observation images (condition c: 5 µs) (condition c: 200 ns) of Fig. 19 formed. From the difference image 201, residual layer defects with different layer thicknesses on the underside of the contact pin can be extracted. <Zusammenfassung der dritten Ausführungsform>

[0059] The charge particle beam device 1 according to the third embodiment generates an observation image while intermittently irradiating the sample 8 with the electron beam by switching between a period in which the sample 8 is irradiated with the electron beam and a period in which the sample is not irradiated with the electron beam. This makes it possible to acquire an observation image with a different contrast than an observation image acquired by continuously irradiating the sample 8 with the electron beam. This enables the differentiation and detection of electrical faults with different electrical properties. <Vierte Ausführungsform>

[0060] Fig. Figure 20 shows a configuration example of an absorption properties measurement unit 13. Here, a configuration for detecting a polarization plane of light is shown. A light pulse reflected from the sample 8 is elliptically polarized by a waveplate 211 and split into S-polarized and P-polarized light by a birefringent component 212. A photodetector 213 detects the light intensity of the S-polarized light, and a photodetector 214 detects the light intensity of the P-polarized light. A subtractor 215 calculates a difference between the light intensity of the S-polarized light and the light intensity of the P-polarized light. A signal detector 216 digitizes the calculation result as the intensity of the elliptically polarized light. Digital processing can be used instead of an analog circuit to determine the difference signal.

[0061] Fig. Figure 21 shows a configuration example of an absorption properties measurement unit 13. Here, a configuration for detecting a harmonic generated by nonlinear absorption is shown. A harmonic light pulse generated by the sample 8 is spectrally decomposed by a diffraction grating 217. The light intensity for each spectrum is detected by a light intensity sensor 218, which has a plurality of sensor components in a single line, fabricated using a silicon process. The light intensity of each wavelength detected by the light intensity sensor 218 is digitized by the signal detector 219. In the fourth embodiment, the emitting light pulse was circularly polarized light, and the wavelength was 700 nm.The threshold of light irradiance per unit time at which linear becomes nonlinear is an irradiance at which the light pulse becomes elliptically polarized light, or an irradiance at which a second harmonic with 350 nm is generated.

[0062] In the fourth embodiment, the process plan was divided into Fig. 3 and the GUI in Fig. 6. In the fourth embodiment, a sample made of an organic-inorganic hybrid material with a dielectric mixed with an organic substance was used. The conditions a to c were defined as the light irradiation intensity per unit time according to the threshold of the light irradiation intensity per unit time at which the plane of polarization of sample 8 changes due to light pulse irradiation or the second harmonic occurs. Condition a was 0.0 MW / cm². 2 / µs. Condition b was 4 MW / cm².2 / µs. The condition c was 10 MW / cm². 2 / µs. Condition b also included a light pulse frequency of 100 MHz, an average power of 14 mW, a pulse width of 220 femtoseconds, and an irradiation diameter of 100 µm. Condition c also included a light pulse frequency of 100 MHz, an average power of 35 mW, a pulse width of 220 femtoseconds, and an irradiation diameter of 100 µm.

[0063] Fig. Figure 22 is an example of observational images acquired under three light irradiation intensity conditions per unit time. In the observational image acquired under condition a, the organic substance 222 and the dielectric 223, which are the basic components of the hybrid material, exhibit the same image brightness, and the visibility of a dielectric domain is low. In the observational image acquired under condition b, the dielectric is excited by linear absorption, so that the secondary electrons emitted by the dielectric 225 increase, and the dielectric domains are clearly visible. In the observational image acquired under condition c, nonlinear absorption occurs in each of the dielectrics, which have different complex dielectric constants, thereby reducing the secondary electron emission.In the observation image, which was captured under condition c, dielectrics 227, which have different complex dielectric constants, can be identified by the gray levels corresponding to the difference in the complex dielectric constant.

[0064] The charge particle beam device 1 according to the fourth embodiment makes it possible to distinguish and detect domains with different dielectric constants of the sample 8. In the fourth embodiment, two configuration examples of the absorption property measuring unit 13 for detecting the plane of polarization and the wavelength were shown; however, it is not necessary to detect both properties, and only the plane of polarization or the wavelength can be detected. <Fünfte Ausführungsform>

[0065] In a fifth embodiment of the invention, in addition to the configurations described in the first to fourth embodiments, a configuration example is described in which the contrast of the observed image is increased by distinguishing the energy of the secondary electrons. The other configurations correspond to those in the first to fourth embodiments.

[0066] Fig. Figure 23 is a schematic configuration drawing of the charge particle beam device 1 according to the fifth embodiment. Here, a configuration example is described which, in addition to the configuration described in the first embodiment, includes an energy filter 231, which distinguishes the energy of the secondary electrons, and an energy filter control unit 232, which controls a voltage applied to the energy filter 231. The user specifies a voltage to be applied to the energy filter 231 via the user interface 23, and the energy filter control unit 232 regulates the voltage accordingly. An energy spectrometer, such as a spectrometer with a Wien filter, can also be used instead of the energy filter 231.

[0067] In the fifth embodiment, the Fig. Sample 8, shown in Figure 7, was used. The observation conditions were an accelerating voltage of 0.5 kV, an irradiation current of 100 pA, a 100,000x observation magnification, and a sampling rate of a TV scan rate. The wavelength of the light pulse was 355 nm. Regarding the light irradiation intensity per unit time, as in the first embodiment, condition a and condition b were set as the light irradiation intensities based on the relationship between the absorption properties and the light irradiation intensity per unit time. Condition a was set to 0 MW / cm². 2 / µs set, and as condition b 350 MW / cm 2 / µs. Furthermore, the average power levels were set based on the two configured light irradiation intensity conditions per unit of time. The average power level was 0 mW and 220 mW, respectively.

[0068] Fig. Figure 24 is a graph showing the energy distribution of secondary electrons when a light pulse corresponding to the light irradiation intensities is emitted. For a light pulse of 0 MW / cm² 2 At a rate of / µs (i.e., without light irradiation), there is virtually no difference between silicon 241 and silicon nitride 242. When the light pulse is 350 MW / cm² 2 When a light pulse of 350 MW / cm² is emitted, the silicon nitride is in a linear absorption state, and the secondary electron emission power is high. It can be seen that in this state, the peak intensity in the energy distribution of the secondary electrons of silicon nitride 243 is high and the peak is shifted towards a lower energy side. The silicon, which is exposed to the light pulse of 350 MW / cm², 2When irradiated for µs, the silicon nitride 244 is in a nonlinear absorption state, and the emission of secondary electrons is suppressed. It can be seen that in this state, the peak intensity in the energy distribution of the secondary electrons of silicon nitride 244 is low and the peak is shifted towards a high-energy side. Fig. Figure 24 shows that the energy filter 231 makes it possible to increase the difference in secondary electron yields in addition to the difference in emission power. In the fifth embodiment, a filter voltage V was used. EF Set to 4V.

[0069] Fig. Figure 25 shows exemplary observational images acquired with the energy filter 231 under two light irradiation intensity conditions per unit time. In the observational image acquired under condition a, silicon 252 and silicon nitride 253 exhibit the same image brightness, and the structure is poorly discernible. In the observational image acquired under condition b, the difference in image brightness between silicon 252 and silicon nitride 253 is greater, and the structure is more discernible. In the observational image acquired with the energy filter 231 (the filter voltage was 4 V) under condition b, it can be seen that the image contrast between silicon 252 and silicon nitride 253 is increased by the difference in energy, and the structure is further enhanced. <Zusammenfassung der fünften Ausführungsform>

[0070] The charge particle beam device 1 according to the fifth embodiment makes it possible to enhance the contrast of the observation image by using the differentiation of the energy of the secondary electrons in addition to adjusting the light irradiation intensity per unit of time, as described in the first to fourth embodiments. <Sechste Ausführungsform>

[0071] Fig. Figure 26 is a schematic configuration drawing of the charge particle beam device 1 according to a sixth embodiment of the present invention. The sixth embodiment describes a configuration example in which the properties of the sample 8 are identified based on the secondary electron detection signal or the observation image itself, instead of using the absorption property measuring unit 13 and the absorption property measuring control unit 21. The in Fig. The configuration shown in Figure 26 corresponds to the configuration described in the first embodiment, except that the absorption properties measuring unit 13 and the absorption properties measuring control unit 21 are omitted.

[0072] In the sixth embodiment, the light irradiance conditions set to condition a and condition b per unit time were used. Condition a was 10.0 MW / cm². 2 / µs. Condition b was 100 MW / cm². 2 / µs. Condition a also includes an average power of the light pulse of 400 mW. Condition b also includes an average power of the light pulse of 4000 mW.

[0073] Fig. Figure 27 is an exemplary cross-sectional view of sample 8. On a surface of P-type silicon 271, low-density N-type silicon 272 and high-density N-type silicon 273 are formed. A low-density N-type silicon basin 274 is also formed on the surface of the P-type silicon 271. Low-density P-type silicon 275 and high-density P-type silicon 276 are formed on a surface of the N-type silicon basin 274.

[0074] Fig. Figure 28 shows exemplary observational images acquired under two light irradiation intensity conditions. In the observational image acquired under condition a, the N-type silicon 282 and P-type silicon 283 are clearly distinguishable. From the observational image acquired under condition a, the type of impurity and an energy band of the material can be deduced. In the observational image acquired under condition b, a difference in density can be distinguished between the low-density N-type silicon 285 and the high-density N-type silicon 286 based on the difference in image brightness. Similarly, the low-density P-type silicon 287 and the high-density P-type silicon 288 can be distinguished based on a difference in image brightness. From the observational image acquired under condition b, the density of the impurities and the electronic structure of the material can be deduced.

[0075] The charge particle beam device 1 according to the sixth embodiment makes it possible to distinguish and identify different types of properties of the sample 8 based on observational images, each of which was recorded under different light irradiation intensity conditions per unit of time. <Modifikationen der Erfindung>

[0076] The present invention is not limited to the embodiments described above, but includes various modifications. For example, the embodiments described above may have been described in detail for ease of understanding and are not necessarily limited to those that have all the configurations described above. Furthermore, a part of a configuration of one embodiment may be replaced by the configuration of another embodiment, and the configuration of another embodiment may be added to the configuration of one embodiment. A part of the configuration of each embodiment may be added to, deleted from, or replaced by another configuration.

[0077] In the above embodiments, it is possible to select one or more wavelengths by using a tunable laser as the pulsed laser 10, the wavelength of which can be selected by parametric oscillation. A pulsed laser with a single wavelength can be used, or a wavelength conversion unit that generates a harmonic of the light. Since an image with uniform image contrast can be acquired in the irradiation area of ​​the light pulse, it is desirable that the irradiation area of ​​the light pulse be wider than the deflection area of ​​the electron beam controlled by the deflection device 3. However, the present invention is not limited to a deviation between the irradiation area of ​​the light pulse and the deflection area. The light pulse and the electron beam can be emitted simultaneously or at different times.

[0078] In the above embodiments, it is possible to use an ND filter as the light intensity control unit 11, which is capable of changing the density to control the average power of a laser. An optical attenuator can also be used as an optical system for controlling the average power. The following can also be used as the light intensity control unit 11: (a) a pulse picker or the like, which uses a component with an electro-optic effect or a component with a magneto-optic effect, which serves to control the pulse frequency and the number of emitted pulses; (b) an optical system for controlling pulse scattering or the like, which is configured with a pair of prisms and serves to control a pulse width; and (c) a condenser lens, which serves to control an irradiation area of ​​a light pulse.In addition, an optical branch, a pulse stacker, a wavelength converter, a polarization regulator, and similar devices can be used. These devices can be used in combination.

[0079] Fig. Figure 2 illustrates that an absorption intensity, representing light absorption properties, is determined from a difference signal between the incident and reflected light. However, it is also possible to use the light intensity of the reflected light. The difference signal can also be calculated digitally instead of using an analog circuit.

[0080] In the second embodiment, the photoelectron detector 91 can be used together with the electron detector 5. In this second embodiment, the photoelectron detector 91 and the photovoltaic current measuring device 92 are used in combination to measure the photoelectrons from the sample 8; however, only one of them can also be used. A reflection light detector for the reflection light from the sample 8, a polarization plane detector for the reflection light from the sample 8, a wavelength detector for the reflection light from the sample 8, and the like can also be used as the absorption properties measuring unit 13.

[0081] The interrupter 93 can be an electron beam interrupting device configured with a parallel electrode and an aperture. The electron beam can also be interrupted in the deflection device 3, or a shield such as a valve on the optical axis of the electron beam can be used.

[0082] In the embodiments described above, the control transmission unit 22 can be configured using hardware, such as circuits in which the functions are implemented, or it can be configured by having software in which the functions are implemented executed by an arithmetic unit. The same applies to the functional units (electron gun control unit 14, deflection signal control unit 15, electron lens control unit 16, detector control unit 17, table position control unit 18, pulse laser control unit 19, light intensity adjustment control unit 20, absorption properties measurement control unit 21, and the like) that are controlled by the control transmission unit 22. This also applies to the image generation unit 24.

[0083] In the embodiments described above, an example configuration for acquiring observational images of sample 8 was presented in which the charge particle beam device 1 is configured as a scanning electron microscope. However, the present invention is also applicable to other charge particle beam devices. That is, the invention is applicable to other charge particle beam devices that adjust a secondary charge particle emission power by irradiating sample 8 with light. List of reference symbols 1 Charge particle beam device 2 electron beam guns 3. Deflection device 4 electron lens 5 electron detector 6 XYZ table 7 Sample holders 8 Sample 9 cases 10 pulse lasers 11 Light intensity adjustment unit 12 Light pulse introduction unit 13 Absorption properties - measuring unit 14 Electron beam gun control unit 15 Deflection signal control unit 16 electron lens control unit 17 Detector control unit 18 Table position control unit 19 Pulse laser control unit 20 Light intensity adjustment control unit 21 Absorption properties measuring control unit 22 Control and transmission unit 23 User interface 24 Image generation unit 25 Image display unit 30 beam splitters 31 Irradiation light detector 32 Reflection light detector 33 subtractors 34 Signal detector 51 Silicon 52 Silicon nitride 61 GUI (graphical user interface) 66 Image display section 67 Setting section “Irradiation conditions” 68 Setting section “Wavelength” 69 Absorption properties analysis section 70 Display section “Absorption properties” 75 silicon 76 Silicon nitride 91 Photoelectron detector 92 Photovoltaic current measuring device 93 interrupters 94 Signal corrector 111 Laser oscillator (or laser amplifier) 112 wavelength converters 113 Pulse Pickers 114 Pulse Spread Controller 115 Polarization controller 116 Average power controllers 121 P-type silicon 122 N-type silicon 131 P-type silicon 132 N-type silicon 133 Silicon oxide thin film 134 errors 152 P-type silicon 153 N-type silicon 156 errors 161 irradiation period 162 Interval period 163 light pulses 171 Setting section “Irradiation period” 172 Setting section “Interval period” 181 P-type silicon 182 N-type silicon 183 Silicon oxide thin film 184 Contact pin 185 errors 186 errors 187 errors 192 Contact pin 194 Contact pin 196 errors 198 errors 199 errors 200 difference image 201 Difference image 211 wave plate 212 birefringent component 213 Photodetector 214 Photodetector 215 subtractors 216 Signal detector 217 Diffraction gratings 218 Light intensity sensor 219 Signal detector 222 organic substance 223 Dielectric 225 Dielectric 227 Dielectric 231 Energy filters 232 Energy filter control unit 252 silicon 253 Silicon nitride 271 P-type silicon 272 N-type silicon 273 N-type silicon 274 N-type silicon tub 275 P-type silicon 276 P-type silicon 282 N-type silicon 283 P-type silicon 285 N-type silicon 286 N-type silicon 287 P-type silicon 288 P-type silicon

Claims

Charge particle beam device (1) irradiating a sample (8) with a charge particle beam (30), comprising: a charge particle source (2) configured to irradiate the sample (8) with primary charge particles (30); a light source (10) configured to emit light that is emitted to the sample (8); a detector (5) configured to detect secondary charge particles generated by irradiating the sample (8) with primary charge particles; an image processing unit (18) configured to generate an observation image of the sample (8) using the secondary charge particles detected by the detector (5); a light intensity control unit (14) configured to set an irradiation intensity of the light per unit time; and an absorption properties measurement unit (13) configured toto measure the amount of absorption of the light absorbed by the sample (8); characterized in that the charge particle device (1) further comprises: a storage unit (27) configured to store correspondence data describing a correspondence between the amount of absorption measured by the absorption properties measuring unit (13) and the light irradiance per unit time, wherein the light intensity control unit (14) causes the image processing unit to generate a plurality of observation images, each exhibiting a different contrast, by changing the irradiance of the light per unit time, wherein the sample (8) has a property such that an emission quantity of secondary charge particles changes depending on the light irradiance per unit time, and the light intensity control unit (14) sets the light irradiance per unit time to a first intensity.such that the sample (8) emits secondary charge particles in a first emission quantity corresponding to the first intensity, and then causes the image processing unit to produce an observation image, and the light intensity control unit (14) adjusts the light irradiation intensity per unit time to a second intensity that differs from the first intensity, such that the sample (8) emits secondary charge particles in a second emission quantity corresponding to the second intensity, and then causes the image processing unit to produce an observation image, wherein the light intensity control unit (14) determines the first intensity and the second intensity according to the correspondence described in the correspondence data. Charge particle beam device (1) according to claim 1, wherein the light intensity control unit (14) adjusts the light irradiation intensity per unit time to a third intensity which lies between the first intensity and the second intensity, such that the sample (8) emits secondary charge particles in a third emission quantity corresponding to the third intensity, and then causes the image processing unit to produce an observation image, and the third emission quantity is greater than the first emission quantity, and the second emission quantity is less than the first emission quantity. Charge particle beam device (1) according to claim 2, wherein an absorption quantity of the light absorbed by the sample (8) has a first component that is proportional to a first power of the light irradiation intensity per unit time, and a second component that is proportional to a second or higher power of the light irradiation intensity per unit time, the second component becoming greater than or equal to the first component when the light irradiation intensity per unit time is greater than or equal to the third intensity, and becoming less than the first component when the light irradiation intensity per unit time is less than the third intensity, the light intensity control unit (14) adjusts the light irradiation intensity per unit time to the second intensity, such that the second component becomes greater than the first component in the absorption quantity.and the light intensity control unit (14) adjusts the light irradiance per unit time to the first intensity, so that the first component becomes greater than the second component in the amount of absorption. Charge particle beam device (1) according to claim 2, wherein an absorption quantity of the light absorbed by the sample (8) has a first component that is proportional to a first power of the light irradiation intensity per unit time, and a second component that is proportional to a second or higher power of the light irradiation intensity per unit time, and the light intensity control unit (14) controls the light irradiation intensity per unit time such that the second component becomes larger in the absorption quantity than the first component, so that the emission quantity becomes smaller than that which would be the case if the first component were larger than the second component. Charge particle beam device (1) according to claim 1, further comprising: a signal quantity correction unit configured to correct a signal quantity of secondary charge particles detected by the detector according to the absorption quantity measured by the absorption properties measuring unit (13). Charge particle beam device (1) according to claim 5, wherein the signal quantity correction unit corrects a detection result detected by the detector by subtracting from a first signal quantity of secondary charge particles detected by the detector when the sample (8) is irradiated with light and not with primary charge particles a second signal quantity of secondary charge particles detected by the detector when the sample (8) is irradiated with light and not with primary charge particles. Charge particle beam device (1) according to claim 1, wherein the light intensity control unit (14) is configured to switch between an irradiation period in which the sample (8) is irradiated with primary charge particles and an interval period in which the sample (8) is not irradiated with primary charge particles, and the image processing unit generates a plurality of observation images, each exhibiting a different contrast, by generating a first observation image of the sample while the sample is continuously irradiated with primary charge particles, and a second observation image of the sample while the sample (8) is intermittently irradiated with primary charge particles, switching between an irradiation period and an interval period. Charge particle beam device (1) according to claim 1, further comprising: an energy filter configured to distinguish the secondary charge particles incident on the detector according to the energy of the secondary charge particles. Charge particle beam device (1) according to claim 1, wherein the light intensity control unit (14) controls one or more parameters including the average light power, the peak intensity of the light, the pulse width of the light, the irradiation period of the light pulse, the irradiation area of ​​the light on a surface of the sample (8), the wavelength of the light and the polarization of the light. Charge particle beam device (1) according to claim 1, wherein the light intensity control unit (14) is configured with one or more optical attenuators, optical branches, pulse stackers, pulse pickers, light wavelength converters, polarization controllers and condenser lenses. Charge particle beam device (1) according to claim 1, wherein the absorption properties measuring unit (13) is configured with one or more reflection light detectors for the light reflected by the sample (8), polarization plane detectors for the light reflected by the sample (8), wavelength detectors for the light reflected by the sample, photoelectron detectors for photoelectrons emitted by the sample (8), and photovoltaic detectors for the photovoltage generated in the sample (8).

Images