Local observation method, program, recording medium, and electron beam application device

Abstract

To provide an electron beam application device for implementing a local observation method capable of observing a bottom part of a groove part with higher accuracy.SOLUTION: An electron beam application device irradiates an irradiation target with an electron beam emitted from a photocathode, and acquires a detected signal. A local observation method implements; a positional information setting step of setting positional information of a groove part of the irradiation target; a first electron beam parameter setting step of setting an electron beam parameter of the electron beam irradiated to the irradiation target; an electron beam irradiation step of irradiating the groove part with the electron beam based on the electron beam parameters set in the positional information setting step and the first electron beam parameter setting step; and a detection step of detecting, by with the detector, an emitted object emitted from the groove part and generating the detected signal. In the first electron beam parameter setting step, a size of the electron beam of when reaching an opening of the groove part is set to a size capable of suppressing generation of an electric field in the groove part.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The disclosure in this application relates to a local observation method for an irradiation object using an electron beam application device, a program for implementing the local observation method in the electron beam application device, a recording medium on which the program is recorded, and an electron beam application device. [Background technology]

[0002] In semiconductor manufacturing processes, dimensional control of patterns formed on substrates is performed. Patent Document 1 describes a method for measuring the dimensions of hole or groove patterns, particularly those with a high aspect ratio, using a primary electron beam irradiation means that scans and irradiates a pattern formed on a substrate with a primary electron beam, a backscattered electron detection means that detects backscattered electrons that have penetrated sidewalls of the hole or groove pattern among backscattered electrons emitted from the substrate irradiated with the primary electron beam by the primary electron beam irradiation means, an electron beam image generation means that generates an electron beam image corresponding to the intensity distribution of the backscattered electrons detected by the backscattered electron detection means, and a depth estimation means that determines a boundary region between a dark region existing within a bright region on the electron beam image generated by the electron beam image generation means and the bright region, and estimates the depth of the hole or groove pattern from information on the brightness of the dark region within the determined boundary region. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6316578 Summary of the Invention [Problem to be solved by the invention]

[0004] The invention described in Patent Document 1 employs a method for detecting backscattered electrons that have penetrated the sidewalls of a hole or groove pattern, and therefore requires the use of a highly accelerated electron beam of 30 kV or more. However, the use of a highly accelerated electron beam causes problems such as heating and charging of the sample.

[0005] Therefore, there is a need for a method and apparatus for observing the bottom of a groove with a relatively high aspect ratio formed in a substrate, based on a principle different from that of Patent Document 1.

[0006] The disclosure of this application has been made to solve the above-mentioned problems. As a result of intensive research, the inventors have newly discovered that (1) when an electron beam is generated using a photocathode, it is possible to easily generate an electron beam with different electron beam parameters for each local area to be observed, and (2) therefore, by setting the size of the electron beam when it reaches the opening of the groove to a size that can suppress the generation of an electric field within the groove, it is possible to observe the bottom of a groove with a relatively high aspect ratio.

[0007] That is, the disclosure of the present application relates to a local observation method that allows more accurate observation of the bottom of a groove, a program for implementing the local observation method in an electron beam application device, a recording medium on which the program is recorded, and an electron beam application device. [Means for solving the problem]

[0008] The present application relates to a local observation method, a program for implementing the local observation method in an electron beam application device, a recording medium on which the program is recorded, and an electron beam application device, which are described below.

[0009] (1) A method for locally observing an irradiated object using an electron beam application device, comprising: The local observation method is a method for observing at least a groove portion formed in the irradiation target, The electron beam application device is A light source and a photocathode that generates releasable electrons in response to receiving excitation light irradiated from the light source; an anode capable of forming an electric field between itself and the photocathode, which extracts the releasable electrons by the formed electric field to form an electron beam; a detector that detects emissions emitted from the irradiation target irradiated with the electron beam and generates a detection signal; A control unit; Including, The local observation method includes: a position information setting step of setting at least position information of the groove portion in the irradiation target; a first electron beam parameter setting step of setting electron beam parameters of the electron beam to be irradiated onto the irradiation target; an electron beam irradiation step of irradiating the groove with an electron beam based on the electron beam parameters set in the position information setting step and the first electron beam parameter setting step; a detection step of detecting, with the detector, an amount of emitted material emitted from the groove portion irradiated with the electron beam in the electron beam irradiation step, and generating a detection signal; and In the first electron beam parameter setting step, at least the size of the electron beam when it reaches the opening of the groove is set to a size that can suppress the generation of an electric field in the groove. Local observation method. (2) The position information setting step is performed based on design information of the irradiation target. The local observation method according to (1) above. (3) before the position information setting step, a step of acquiring position information of the groove portion is included, The groove position information acquisition step includes: irradiating the irradiation target with an electron beam; a detection step of detecting an amount of emitted material emitted from an irradiation area irradiated with the electron beam by the detector and generating a detection signal; a detection data output step of outputting the detection signal generated in the detection step in association with position information of the irradiation area; and The control unit controls so that the position information setting step is performed based on the detection data associated with the position information of the irradiation area output in the detection data output step. The local observation method according to (1) above. (4) the first electron beam parameter setting step includes setting a focal length of the electron beam that has passed through the opening of the groove portion; The focal length is Calculation is performed based on design information of the irradiation target, When an electron beam is irradiated onto the groove, the electron beam is focused at the bottom of the groove. The local observation method according to (1) above. (5) The control unit further comprising a second electron beam parameter setting step of setting a focal length longer than the focal length preset in the first electron beam parameter setting step; and an electron beam irradiation step of irradiating the groove with an electron beam based on the electron beam parameters set in the second electron beam parameter setting step. The local observation method according to (1) above. (6) The control unit further comprising a third electron beam parameter setting step of setting a focal length shorter than the focal length preset in the first electron beam parameter setting step; and an electron beam irradiation step of irradiating the groove with an electron beam based on the electron beam parameters set in the third electron beam parameter setting step. The local observation method according to (1) above. (7) The control unit changes at least one selected from the electron beam current, the magnitude of the electron beam acceleration energy, the electron beam shape, the electron beam emission time, and the electron beam emittance, which are predetermined in the first electron beam parameter setting step. The local observation method according to (1) above. (8) The control unit The electron beam is controlled so as to be irradiated to areas other than the grooves based on electron beam parameters different from the first electron beam parameters set in the first electron beam parameter setting step. The local observation method according to (1) above. (9) The control unit a light amount adjusting step of adjusting the amount of light reaching the photocathode from the light source so that the signal intensity of the detection signal detected in the detection step becomes a preset value; a step of repeating the electron beam irradiation step, the detection step, and the light amount adjustment step so that the signal intensity of the detection signal approaches a preset value; a detection data output step of outputting light amount adjustment data when the signal intensity of the detection signal approaches a preset value as detection data of the groove portion; Contains The local observation method according to (1) above. (10) After the detection data output step is performed, The control unit changing at least one of the electron beam parameters set in the first electron beam parameter setting step, and using the changed electron beam parameter; the light amount adjusting step; a step of repeating the electron beam irradiation step, the detection step, and the light amount adjustment step so that the signal intensity of the detection signal approaches a preset value; a detection data output step of outputting light amount adjustment data when the signal intensity of the detection signal approaches a preset value as detection data of the groove portion; To carry out The local observation method according to (9) above. (11) The electron beam application device is scanning electron microscope, Electron beam inspection equipment, or Semiconductor inspection equipment, is The local observation method according to (1) above. (12) A program for causing the control unit of the electron beam application device to execute each of the steps described in any one of (1) to (11) above. (13) A computer-readable recording medium on which the program described in (12) above is recorded. (14) a light source; a photocathode that generates releasable electrons in response to receiving excitation light irradiated from the light source; an anode capable of forming an electric field between itself and the photocathode, which extracts the releasable electrons by the formed electric field to form an electron beam; a detector that detects emissions emitted from the irradiation target irradiated with the electron beam and generates a detection signal; A control unit; An electron beam application device comprising: The control unit stores the program described in (12) above. Electron beam application equipment. [Effects of the Invention]

[0010] The local observation method using the electron beam application device disclosed in the present application makes it possible to observe the bottom of a groove. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram schematically showing an electron beam application apparatus 1 according to the first embodiment. [Figure 2] FIG. 2 shows an example of an irradiation target S, where FIG. 2a is a schematic top view of the irradiation target S, and FIG. 2b is a cross-sectional view taken along the arrow xx in FIG. 2a. [Figure 3] 3A and 3B are diagrams showing other examples of the irradiation target S, in which FIG. 3A is a schematic top view of the irradiation target S, and FIG. 3B is a cross-sectional view taken along the arrow xx in FIG. 3A. [Figure 4] Figure 4 is a schematic cross-sectional view of the irradiation target S, Figure 4a is a diagram for explaining the problems with conventional local observation methods, and Figure 4b is a diagram for explaining the principle by which the bottom of a groove can be observed using the local observation method disclosed in the present application. [Figure 5] 5A and 5B are schematic diagrams for explaining the first electron beam parameter setting step (ST2), in which FIG. 5A is a schematic top view of the irradiation target S, and FIG. 5B is a cross-sectional view taken along the arrow xx in FIG. 5A. [Figure 6] 6a to 6c are schematic cross-sectional views of the irradiation target S, and are schematic views for explaining the first electron beam parameter setting step (ST2). [Figure 7] FIG. 7 is a flowchart of the local observation method. [Figure 8] FIG. 8 is a schematic diagram for explaining an example of control of electron beam parameters set by the control unit 6. In FIG. [Figure 9] FIG. 9 is an enlarged view of the photocathode 3 portion of the electron beam application apparatus 1A according to the second embodiment. [Figure 10] 10a to 10c are schematic diagrams for explaining the setting of the focal length. [Figure 11] 11a and 11b are schematic diagrams illustrating an example of the detection step (ST4). [Figure 12] FIG. 12 is a diagram showing an image of the groove portion of the sample used in the example. [Figure 13] FIG. 13 is a photograph in place of a drawing, in which FIG. 13a is an SEM image of the groove and the surrounding area of the groove obtained in the position information acquisition step of Example 2, and FIG. 13b is an SEM image obtained by implementing the local observation method. [Figure 14] FIG. 14 is a photograph substituted for a drawing, which is image data synthesized based on the detection data (light intensity adjustment data) of the sample obtained in Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, a local observation method, a program for executing the local observation method in an electron beam application device, a recording medium on which the program is recorded, and an electron beam application device will be described in detail with reference to the drawings. Note that in this specification, components having similar functions are assigned the same or similar reference numerals. Furthermore, repeated descriptions of components assigned the same or similar reference numerals may be omitted.

[0013] Furthermore, for ease of understanding, the position, size, range, etc. of each component shown in the drawings may not represent the actual position, size, range, etc. Therefore, the disclosure in this application is not necessarily limited to the position, size, range, etc. disclosed in the drawings.

[0014] (First embodiment of electron beam application device and first embodiment of local observation method) An electron beam application apparatus 1 according to a first embodiment and a local observation method according to the first embodiment will be described with reference to FIGS. 1 to 8. FIG. 1 is a diagram schematically illustrating the electron beam application apparatus 1 according to the first embodiment. FIG. 2 is a diagram illustrating an example of an irradiation target S, where FIG. 2a is a schematic top view of the irradiation target S and FIG. 2b is a cross-sectional view taken along the line xx in FIG. 2a. FIG. 3 is a diagram illustrating another example of the irradiation target S, where FIG. 3a is a schematic top view of the irradiation target S and FIG. 3b is a cross-sectional view taken along the line xx in FIG. 3a. FIG. 4 is a schematic cross-sectional view of the irradiation target S, where FIG. 4a is a diagram illustrating problems with a conventional local observation method, and FIG. 4b is a diagram illustrating the principle by which the bottom of a groove can be observed using the local observation method disclosed in the present application. FIG. 5 is a schematic diagram illustrating the first electron beam parameter setting step (ST2), where FIG. 5a is a schematic top view of the irradiation target S and FIG. 5b is a cross-sectional view taken along the line xx in FIG. 5a. 6a to 6c are schematic cross-sectional views of the irradiation target S, and are schematic diagrams for explaining the first electron beam parameter setting step (ST2). Fig. 7 is a flowchart of a local observation method. Fig. 8 is a schematic diagram for explaining an example of control of the electron beam parameters set by the control unit 6.

[0015] The electron beam application device 1 according to the first embodiment shown in FIG. 1 includes at least a light source 2, a photocathode 3, an anode 4, a detector 5, and a control unit 6. The electron beam application device 1 may also optionally include a power supply 7, an electron beam deflector 8, and an objective lens 9. FIG. 1 shows an example in which the electron beam application device 1 is formed separately into an electron gun portion 1a and a counterpart device 1b (the portion of the electron beam application device 1 excluding the electron gun portion 1a). Alternatively, the electron beam application device 1 may be formed as an integrated unit. Furthermore, although not shown, the electron beam application device 1 may include known components according to the type of the electron beam application device 1.

[0016] The light source 2 is not particularly limited as long as it can emit an electron beam B by irradiating the photocathode 3 with excitation light L. Examples of the light source 2 include a high-output (watt-class), high-frequency (several hundred MHz), ultrashort pulse laser light source, a relatively inexpensive laser diode, an LED, etc. The excitation light L to be irradiated may be either pulsed light or continuous light, and may be adjusted appropriately depending on the purpose. In the example shown in FIG. 1, the light source 2 is disposed outside the vacuum chamber CB, and the excitation light L is irradiated onto the first surface (the surface on the anode 4 side) of the photocathode 3. Alternatively, the light source 2 may be disposed inside the vacuum chamber CB. The excitation light L may also be irradiated onto the second surface (the surface opposite the anode 4) of the photocathode 3.

[0017] The photocathode 3 generates electrons that can be emitted in response to receiving excitation light L irradiated from the light source 2. The principle by which the photocathode 3 generates electrons that can be emitted in response to receiving excitation light L is publicly known (see, for example, Japanese Patent No. 5808021).

[0018] The photocathode 3 is formed of a substrate such as quartz glass or sapphire glass and a photocathode film (not shown) bonded to the first surface of the substrate (the surface on the anode 4 side). The photocathode material for forming the photocathode film is not particularly limited as long as it can generate electrons that can be released when irradiated with excitation light, and examples include materials that require EA surface treatment and materials that do not require EA surface treatment. Materials that require EA surface treatment include, for example, III-V semiconductor materials and II-VI semiconductor materials. Specific examples include AlN, CeTe, GaN, compounds of one or more alkali metals and Sb, AlAs, GaP, GaAs, GaSb, InAs, and mixed crystals thereof. Other examples include metals, such as Mg, Cu, Nb, LaB6, SeB6, and Ag. The photocathode 3 can be produced by subjecting the photocathode material to EA surface treatment. The photocathode 3 not only allows for selection of excitation light in the near-ultraviolet to infrared wavelength range according to the gap energy of the semiconductor, but also enables electron beam source performance (quantum yield, durability, monochromaticity, time response, degree of spin polarization) according to the application of the electron beam to be achieved by selecting the semiconductor material and structure.

[0019] Examples of materials that do not require EA surface treatment include simple metals such as Cu, Mg, Sm, Tb, and Y, alloys, metal compounds, diamond, WBaO, and CsTe. Photocathodes that do not require EA surface treatment can be fabricated by known methods (see, for example, Japanese Patent No. 3537779). The contents of Japanese Patent No. 3537779 are incorporated herein by reference in their entirety.

[0020] In this specification, the terms "photocathode" and "cathode" are used to refer to something that emits an electron beam, and "cathode" to refer to the opposite electrode of an "anode." However, the symbol 3 is used for both "photocathode" and "cathode."

[0021] There are no particular limitations on the anode 4 as long as it can form an electric field together with the cathode 3, and any anode 4 commonly used in the field of electron guns may be used. By forming an electric field between the cathode 3 and the anode 4, electrons that are generated in the photocathode 3 by irradiation with excitation light L and can be emitted are extracted, forming an electron beam B.

[0022] FIG. 1 shows an example in which a power supply 7 is connected to the cathode 3 to form an electric field between the cathode 3 and the anode 4, but there are no particular restrictions on the placement of the power supply 7 as long as a potential difference is generated between the cathode 3 and the anode 4.

[0023] The detector 5 detects the amount of emitted matter SB emitted from the irradiation target S irradiated with the electron beam B. The emitted matter SB refers to a signal emitted from the irradiation target S when irradiated with the electron beam B, and examples thereof include secondary electrons, backscattered electrons, characteristic X-rays, Auger electrons, cathodoluminescence, and transmitted electrons. The detector 5 is not particularly limited as long as it can detect the emission of these emitted matter SB, and any known detector or detection method may be used. Note that, as described later in the explanation of the principle of the local observation method disclosed in the present application, the local observation method according to the embodiment suppresses the generation of an electric field within the trench T. Therefore, the electron beam B can easily reach the bottom of the trench T, and the detector 5 may detect the absorbed current incident on the irradiation target S. Note that the absorbed current refers to electrons incident on the irradiation target S that flow to ground as absorbed electrons. As described above, the absorbed current is electrons emitted from the irradiation target S irradiated with the electron beam B, and therefore the absorbed current is also included in the emitted matter SB.

[0024] The control unit 6 may be a processor (CPU), a general-purpose computer equipped with a CPU, or the like.

[0025] The electron beam deflection device 8 scans the formed electron beam B over the irradiation target S. The electron beam deflection device 8 may be a known device such as a deflection electrode that generates an electric field in a direction intersecting the traveling direction of the electron beam B.

[0026] The objective lens 9 is not particularly limited as long as it can focus the emitted electron beam B toward the irradiation target S, and any known objective lens 9 may be used.

[0027] Next, the local observation method disclosed in the present application (in other words, the control contents and program contents of the control unit 6 provided in the electron beam application apparatus 1) will be described with reference to FIGS.

[0028] The local observation method includes a position information setting step (ST1), a first electron beam parameter setting step (ST2), an electron beam irradiation step (ST3), and a detection step (ST4).

[0029] The position information setting step (ST1) sets at least position information of a trench T in the irradiation target S. The trench T refers to a portion of the irradiation target S with a large aspect ratio, in other words, a recessed portion that is larger than other portions on the irradiation surface S1 of the irradiation target S that is irradiated with the electron beam B. FIG. 2 shows an example of the irradiation target S, which is a trench with a high aspect ratio formed in a semiconductor wafer. FIG. 3 shows another example of the irradiation target S, which is a deep hole formed in a substrate. The irradiation target S may be a substrate or the like on which the trench T is artificially formed, or may be a substrate on which the trench T is non-artificially formed. Furthermore, as shown in FIG. 3, the trench T may be covered by a component of the irradiation target S except for the opening T1. Alternatively, as shown in FIG. 2, a portion other than the opening T1 may be covered by a component of the irradiation target S (forming a sidewall), and the other portion may be open.

[0030] Position information of the trench T in the irradiation target S may be set based on, for example, design information. When manufacturing a semiconductor wafer, the location where the trench T will be formed is designed in advance. Therefore, in the example shown in FIG. 2, if it is desired to locally observe the state of the bottom T3 of the trench T, the control unit 6 may set position information of the bottom T3 so that the electron beam B is irradiated onto the bottom T3. Furthermore, if it is desired to also observe the peripheral portion of the trench T, it is desired to set position information including the trench T and the peripheral portion to be observed.

[0031] Next, the first electron beam parameter setting step (ST2) will be described with reference to Fig. 2 and Fig. 4 to Fig. 6. A conventional electron beam application apparatus 1 generally includes an electron beam deflection device 8 that deflects the electron beam B emitted from the photocathode 3. The electron beam deflection device 8 causes the electron beam B to scan the irradiation target S (for example, from the upper left to the lower right of the irradiation target S shown in Fig. 2).

[0032] Incidentally, when scanning the irradiation target S using a conventional electron beam application device 1, the electron beam parameters of the electron beam B are usually the same. In other words, the groove portion T of the irradiation target S and the portion other than the groove portion T are irradiated with the electron beam B having the same electron beam parameters. However, as shown in FIG. 4a, when the electron beam B having the same electron beam parameters is irradiated while scanning the irradiation target S, there are cases where the emitted matter SB emitted from the irradiation target S irradiated with the electron beam B is not observed. The reasons for this are thought to be: (1) when the electron beam B is irradiated onto the periphery of the opening T1 and the wall surface T2 of the groove portion T of the irradiation target S, electric charges accumulate on the irradiated irradiation target S; (2) the accumulated electric charges generate an electric field within the groove portion T; (3) a: the generated electric field prevents the emitted material SB from being emitted out of the opening T1 and causes it to remain within the groove portion T; b: the electron beam B is affected by the generated electric field and has difficulty reaching the bottom T3 of the groove portion T; and c: the emitted material SB that has remained within the groove portion T due to the above-mentioned a prevents the electron beam B from proceeding to the bottom T3 of the groove portion T; and (4) as a result, the emitted material SB could not be detected by the detector 5.

[0033] On the other hand, in the electron beam application apparatus 1 according to the first embodiment and the local observation method according to the first embodiment, the electron beam B is formed using the photocathode 3. Forming the electron beam B using the photocathode 3 allows for easy setting of electron beam parameters (such as beam size) according to the irradiation location on the irradiation target S. Therefore, as shown in FIG. 4b, by setting the size of the electron beam B irradiated onto at least the groove T to a size that can suppress the generation of an electric field within the groove T, unlike the example shown in FIG. 4a, the emitted matter SB is more likely to be emitted from the opening T1. As a result, the detector 5 can detect the emitted matter SB. Furthermore, suppressing the generation of an electric field within the groove T makes it easier for the electron beam B to reach the bottom T3 of the groove T. Therefore, the detector 5 may detect emitted matter B that is not emitted from the opening T1, such as an absorbed current incident on the irradiation target S.

[0034] Next, the electron beam parameters set in the first electron beam parameter setting step (ST2) will be described with reference to Fig. 5. Examples of the electron beam parameters include the size of the electron beam, the focal length of the electron beam, the electron beam current, the magnitude of the acceleration energy of the electron beam, the shape of the electron beam, and the emittance of the electron beam. When the electron beam B is irradiated, the parameters required for irradiating the electron beam B and the values of these parameters are set in advance, and the electron beam B is irradiated based on the set electron beam parameters and values. In the first electron beam parameter setting step (ST2), of the preset electron beam parameters, at least the size of the electron beam B when it reaches the groove T is set in accordance with the size of the groove T.

[0035] 4a, when the electron beam B is irradiated onto the periphery of the opening T1 of the groove T or onto the wall surface T2, charge accumulates on the irradiation target S, making it difficult for the emitted material SB to be emitted from the opening T1 and / or making it difficult for the electron beam B to reach the bottom T3 of the groove T. Therefore, the size of the electron beam B when it reaches the groove T is preferably a size that can suppress the generation of an electric field within the groove T, in other words, a size that will result in an electric field that can detect the emitted material SB even if an electric field is generated within the groove T, and more preferably a size that will not generate an electric field within the groove T.

[0036] The size of the groove T at which no electric field is generated may be determined appropriately taking into consideration the material of the irradiation target S, the shape of the groove T, and the like. In the example shown in FIG. 5, the groove T is formed by two perpendicular and parallel wall surfaces T2. In this case, as shown in FIG. 5a, the opening T1 of the groove T is rectangular (the area surrounded by diagonal lines in FIG. 5a), and the shortest length of the opening T1 is the short side w1. In this specification, the shortest length of the opening T1 is defined as the size w1 of the opening T1. Note that, although not shown, if the shape of the opening T1 is other than rectangular, the size w1 of the opening T1 may be determined as the shortest length when the opening T1 is sandwiched between imaginary parallel lines. For example, if the opening T1 is circular, the size w1 of the opening T1 is the diameter, and if the opening T1 is elliptical, the size w1 of the opening T1 is the minor axis.

[0037] In order to prevent the irradiated electron beam B from generating an electric field within the groove portion T, as shown in Figure 6a, when the size w1 of the opening T1 is 1, the size w2 of the electron beam B when it reaches the groove portion T (more specifically, the opening T1) can be set to be less than 1, 0.95 or less, 0.9 or less, 0.85 or less, 0.8 or less, 0.75 or less, 0.7 or less, 0.65 or less, 0.6 or less, 0.55 or less, 0.5 or less, 0.45 or less, 0.35 or less, 0.3 or less, 0.25 or less, 0.2 or less, 0.15 or less, 0.1 or less, 0.05 or less, 0.01 or less, etc.

[0038] The size w2 of the electron beam B may also be determined as an absolute value. The lower limit of the size w2 of the electron beam B generated by the photocathode 3 is approximately 0.3 nm. Therefore, the size w2 of the electron beam B may be 0.3 nm or more, 1 nm or more, 2.5 nm or more, 5 nm or more, 7.5 nm or more, 10 nm or more, 12.5 nm or more, 15 nm or more, 17.5 nm or more, 20 nm or more, 22.5 nm or more, 25 nm or more, or 30 nm or more, as long as it does not exceed the size w1 of the groove T. Note that the size w2 of the electron beam B refers to the diameter if the shape of the electron beam B when it reaches the opening T1 is approximately circular, or the longest length when the electron beam B is sandwiched between imaginary parallel lines if the shape is other than approximately circular. If the size w2 of the electron beam B is significantly smaller than the opening T1 (e.g., less than half), the electron beam B may be scanned within the groove T.

[0039] As described above, even if an electric field is generated in the groove T, the problem of the present application can be solved as long as the electric field is strong enough to detect the emitted matter SB. The strength of the generated electric field varies depending on the current amount and irradiation time of the irradiated electron beam B. Therefore, as shown in FIG. 6b, the size w2 of the electron beam B when it reaches the opening T1 of the groove T may be larger than the size w1 of the opening T1, as long as it is within a range in which the emitted matter SB can be detected even if an electric field is generated.

[0040] 6c, the groove T may be tapered so that the area of the bottom T3 is smaller than the area of the opening T1. In this case, in addition to the relationship between w1 and w2 shown in FIGS. 6a and 6b, it is preferable to have a shape such that the electron beam B does not irradiate the wall surface T2 of the groove T, or to have an electric field that is strong enough to detect emitted matter SB even if the electron beam B irradiates the wall surface T2. Specifically, if the size of the bottom T3 is defined as w3, the size of the electron beam B irradiated to the bottom T3 should be smaller than w3. Of course, the size of the electron beam B irradiated to the bottom T3 may be larger than w3 as long as the electric field is strong enough to detect emitted matter SB.

[0041] Next, an example of control of electron beam parameters set by the control unit 6 will be described with reference to FIG. 8. Note that the following description is one example of control. Other control may be used as long as it is within the scope of the technical concept disclosed in this application. Also, to avoid complicating the drawings, some of the circuits and components from the control unit 6 may be omitted.

[0042] First, the size w2 of the electron beam B when it reaches the aperture T1 will be described. The size w2 of the electron beam B can be controlled by changing the size of the excitation light L irradiated onto the photocathode 3. The larger the size of the excitation light L, the larger the size w2 of the electron beam B. Therefore, the control unit 6 can control an excitation light size adjustment device 62, such as a lens or liquid crystal shutter, so that the size w2 of the electron beam B is set to the set size. Alternatively, or optionally, an electron beam size adjustment device 63, such as an electromagnetic lens or aperture, may be provided on the optical axis of the emitted electron beam B, and the control unit 6 may control the electron beam size adjustment device 63. Furthermore, alternatively, or optionally, an intermediate electrode 64 may be formed between the cathode 3 and the anode 4. The control unit 6 (1) controls the power supply 7 to adjust the potential difference between the cathode 3, the intermediate electrode 64, and the anode 4, or (2) controls the movement of the intermediate electrode 64 to adjust the relative positional relationship between the cathode 3, the intermediate electrode 64, and the anode 4, thereby adjusting the focal position of the electron beam B when it reaches the counterpart device 1b; in other words, it is possible to control the size of the electron beam B when it reaches the opening T1 of the groove T in the irradiation target S. The configuration of the intermediate electrode 64, the control method, and the principle of controlling the focal position are described in detail in Japanese Patent No. 6466020. The contents of Japanese Patent No. 6466020 are incorporated herein by reference.

[0043] Furthermore, in addition to the size w2 of the electron beam B, the size of the electron beam B irradiated onto the bottom T3 may optionally be narrowed down to be smaller than w2, in other words, the electron beam B in the groove T may be controlled to be focused toward the bottom T3. In this case, the electron beam application device 1 may be configured to include an objective lens 9, and the focusing strength of the objective lens 9 may be adjusted. The stronger the focusing strength of the objective lens 9, the more the electron beam B can be focused.

[0044] In the electron beam application device 1 according to the first embodiment and the local observation method according to the first embodiment, the size w2 of the electron beam B (optionally the size of the bottom T3 irradiated) may be set based on the design information of the irradiation target S.

[0045] Next, an example of control of electron beam parameters other than the size w2 of the electron beam B (optionally the size irradiated onto the bottom T3) set by the control unit 6 will be described.

[0046] Control will be described when the parameter to be set is the current of the electron beam B. In this specification, "electron beam current" refers to the magnitude of the electron quantity (current value) contained in the irradiated electron beam B. The current of the electron beam B depends on the light quantity of the excitation light L irradiated to the photocathode 3. Therefore, when the current of the electron beam B is set as a parameter, the control unit 6 controls the light quantity of the excitation light L irradiated to the photocathode 3 so that the current value of the electron beam B becomes the set value. In the example shown in FIG. 1, the control unit 6 controls the light quantity of the light source 2. Alternatively, as shown in FIG. 8, a light quantity adjustment device 61 such as a liquid crystal shutter may be provided between the light source 2 and the photocathode 3, and the light quantity of the light source 2 may be kept constant and the light quantity reaching the photocathode 3 may be controlled by controlling the liquid crystal shutter.

[0047] The magnitude of the acceleration energy of electron beam B can be controlled by changing the electric field strength between the cathode 3 and the anode 4. The greater the voltage difference between the cathode 3 and the anode 4, the greater the acceleration energy. Therefore, when the magnitude of the acceleration energy of electron beam B is set as a parameter, the control unit 6 simply controls the voltage of the power supply 7 so that the magnitude of the acceleration energy of electron beam B becomes the set value.

[0048] The shape of the electron beam B can be controlled by providing an electron beam shape adjustment device 65, such as an electromagnetic lens or an aperture, on the optical axis of the emitted electron beam B. Therefore, when the shape of the electron beam B is set as a parameter, the control unit 6 can control the electron beam shape adjustment device 65 so that the electron beam B has the set shape. Alternatively, the shape of the electron beam B may be controlled by adjusting the shape of the excitation light L irradiated onto the photocathode 3 using a device similar to the excitation light size adjustment device 62, such as a lens or a liquid crystal shutter.

[0049] The emission time of the electron beam B can be controlled by the emission time of the excitation light L emitted by the light source 2. Therefore, when the emission time of the electron beam B is set as an electron beam parameter, the control unit 6 controls the ON / OFF of the light source 2 so as to achieve the set emission time of the electron beam B. Alternatively, although not shown, a shutter may be provided between the light source 2 and the photocathode 3, and the control unit 6 may control the emission time of the electron beam B by controlling the shutter.

[0050] The emittance of the electron beam B can be controlled by the wavelength of the excitation light L emitted by the light source 2. Therefore, when the emittance of the electron beam B is set as a parameter, the control unit 6 simply controls the wavelength of the excitation light L so as to achieve the set emittance of the electron beam B. Although not shown in the figure, a known tunable filter may be provided between the light source 2 and the photocathode 3, and the tunable filter may be controlled by the control unit 6.

[0051] As described above, in the first electron beam parameter setting step (ST2), among the preset electron beam parameters, at least the size w2 of the electron beam B when it reaches the groove T is set in accordance with the size of the groove T. Optionally, in the first electron beam parameter setting step (ST2), parameters other than the size w2 of the electron beam B may also be set (changed) from preset values to new values.

[0052] For example, the local observation method disclosed in the present application can locally observe only the bottom T3 of the trench T based on the position information of the trench T. Alternatively, the trench T and the peripheral portion of the trench T may be simultaneously observed by irradiating the trench T with the electron beam B as well as the peripheral portion of the trench T. However, if a strong electron beam is irradiated on the peripheral portion of the trench T, an electric field may be generated within the trench T, which may make it difficult for the electron beam B irradiated on the trench T to reach the bottom T3 of the trench T and / or may make it difficult for the emitted material SB to be emitted outside the opening T1. Therefore, as shown in FIG. 4b, when the electron beam Bw is irradiated on the peripheral portion of the trench T, the electron beam parameters of the electron beam Bw may be set so that no electric field is generated within the trench T or so that the electric field is strong enough not to affect the detection of the emitted material SB by the detector 5. Specifically, to obtain a weak electron beam Bw, the current value of the electron beam Bw may be reduced or the irradiation time of the electron beam Bw may be shortened. In addition, if it is expected that an electric field will be generated within the groove T when the electron beam Bw is irradiated onto the peripheral portion of the groove T, the electron beam parameters of the electron beam B irradiated onto the groove T may be set (changed) in addition to the size w2, such as (1) increasing the acceleration energy of the electron beam B to make it easier for the electron beam B to reach the bottom T3 even when affected by the electric field generated within the groove T, or (2) increasing the current amount of the electron beam B and / or lengthening the irradiation time of the electron beam B to increase the amount of emitted material SB and make it easier for the detector 5 to detect the emitted material SB.

[0053] That is, in the first electron beam parameter setting process (ST2), (1) in order to suppress the generation of an electric field within the groove T due to the electron beam B being locally irradiated onto the groove T, at least the size w2 of the electron beam B when it reaches the opening T1 of the groove T is set, and (2) additional electron beam parameters other than the size w2 of the electron beam B may be set depending on the irradiation conditions of the electron beam Bw on the peripheral portion of the groove T, etc.

[0054] In the electron beam irradiation step (ST3), the groove T is irradiated with an electron beam B based on the electron beam parameters set in the position information setting step (ST1) and the first electron beam parameter setting step (ST2). When only the groove T is to be locally observed, in the electron beam irradiation step (ST3), the groove T may be irradiated with an electron beam B having the electron beam parameters set in the first electron beam parameter setting step (ST2). Although not limited thereto, when the electron beam application device 1 has an electron beam deflector 8, the control unit 6 may control the electron beam deflector 8 to irradiate the groove T with the electron beam B. Alternatively, the electron beam B may be irradiated to the groove T by the control unit 6 controlling the position of the excitation light L irradiated to the photocathode 3 without using the electron beam deflector 8.

[0055] In the electron beam irradiation step (ST3), the electron beam B may optionally be irradiated to areas other than the trench T (for example, the peripheral portion of the trench T or the entire irradiation target S). In this case, an electron beam (for example, the above-mentioned electron beam Bw) having electron beam parameters different from the electron beam parameters of the electron beam B irradiated to the trench T may be irradiated.

[0056] In the detection step (ST4), the detector 5 detects the amount of emitted material SB emitted from the irradiation target S irradiated with the electron beam B, and generates a detection signal. Note that in the disclosure of the present application, the electron beam B having the electron beam parameters set in the first electron beam parameter setting step (ST2) is described with particular attention to the groove portion T, but it is of course also possible to irradiate the electron beam B onto areas other than the groove portion T and detect the emitted material SB.

[0057] The electron beam application apparatus 1 according to the first embodiment and the local observation method according to the first embodiment provide the following effects. (1) Even if the irradiation target S has a trench T with a large aspect ratio, the bottom T3 of the trench T can be observed. Therefore, even during the manufacturing process of a semiconductor wafer or the like, it is possible to observe whether the bottom T3 of the trench T is manufactured as designed. Depending on the results of the observation, even if a defect occurs at each stage of the manufacturing process, the cause can be identified. (2) The invention described in Patent Document 1 requires an acceleration energy of 30 kV or more. On the other hand, the electron beam application device 1 according to the first embodiment and the local observation method according to the first embodiment use the photocathode 3 as the electron beam source, and therefore can be performed with an acceleration energy lower than 30 kV. This allows the device to be made smaller.

[0058] (Second embodiment of electron beam application device and second embodiment of local observation method) An electron beam application apparatus 1A and a local observation method according to the second embodiment will be described with reference to Figures 1 to 9. Figure 9 is an enlarged view of the photocathode 3 portion of the electron beam application apparatus 1A according to the second embodiment.

[0059] The electron beam application apparatus 1A according to the second embodiment differs from the electron beam application apparatus 1 according to the first embodiment in that excitation light L from a light source is irradiated onto two or more different locations on the photocathode 3 so that two or more electron beams B are extracted from the photocathode 3, but is otherwise the same as the electron beam application apparatus 1 according to the first embodiment. Therefore, in the second embodiment, differences from the first embodiment will be mainly described, and repeated descriptions of matters already described in the first embodiment will be omitted. Therefore, it goes without saying that matters already described in the first embodiment can be adopted in the second embodiment, even if they are not explicitly described in the second embodiment.

[0060] Although not shown, in order to irradiate two or more different locations on the photocathode 3 with excitation light L from the light source 2, multiple light sources 2 may be provided. Alternatively, excitation light L may be split into two or more beams from a single light source 2 using an excitation light splitting device such as a splitter or a spatial light phase modulator, and then irradiated onto the photocathode 3. When electron beams B are extracted from two or more different locations on the photocathode 3, if the amount of emitted material SB is detected with a single detector 5, the timing of irradiation of the electron beams B may be staggered. Furthermore, if electron beams B are irradiated at the same timing, detectors 5 may be provided according to the number of electron beams B to be irradiated simultaneously. Although not shown, two or more photocathode 3 may be provided, and electron beams B may be extracted from different photocathode 3, respectively.

[0061] In the local observation method according to the second embodiment, except that multiple electron beams B are irradiated, the position information setting step (ST1), the first electron beam parameter setting step (ST2), the electron beam irradiation step (ST3), and the detection step (ST4) may be performed in the same manner as in the first embodiment.

[0062] The electron beam application apparatus 1A and the local observation method according to the second embodiment can irradiate a plurality of electron beams B to the trench T. Therefore, in addition to the effects achieved by the electron beam application apparatus 1 and the local observation method according to the first embodiment, the following effects are achieved. (1) Even when there are multiple grooves T, the electron beam B can be irradiated onto each groove. (2) Multiple electron beams B can be irradiated simultaneously, greatly improving observation efficiency.

[0063] Examples of the electron beam application device 1 include a scanning electron microscope, an electron beam inspection device, and a semiconductor inspection device.

[0064] (Example of configuration that can be adopted in embodiments of the electron beam application device and the local observation method) Next, an optional additional configuration example that can be adopted in the electron beam application apparatus 1, 1A and the local observation method according to the first and second embodiments will be described. Note that the following description will be given as a process of the local observation method, but in the case of the electron beam application apparatus 1, 1A, it corresponds to the control content of the control unit 6.

[0065] (Groove position information acquisition process) The local observation method may perform a groove position information acquisition step before the position information setting step (ST1). The groove position information acquisition step includes the steps of: irradiating an irradiation target S with an electron beam B; detecting the amount of emitted material SB emitted from the irradiation region irradiated with the electron beam B using a detector 5 to generate a detection signal; and outputting the detection signal generated in the detection step in association with position information of the irradiation region (e.g., scanning information of the electron beam deflector 8 in the first and second embodiments). The position information setting step (ST1) is performed based on the detection data associated with the position information of the irradiation region output in the detection data output step. Note that when performing the groove position information acquisition step, it is desirable to minimize charge accumulation in the peripheral portion of the groove T. Therefore, it is desirable to irradiate the electron beam irradiated in the groove position information acquisition step based on electron beam parameters different from the first electron beam parameters, such as by reducing the electron beam current value or shortening the electron beam emission time, compared to the electron beam B irradiated to the groove T.

[0066] When the groove position information acquisition process is carried out, even if the design position information of the groove T in the irradiation target S is unknown, the position information of the groove T (and the surrounding area of the groove T) can be acquired by actually irradiating the irradiation target S with the electron beam B.

[0067] (Focal length setting) Setting of the focal length will be described with reference to Fig. 10. The first electron beam parameter setting step (ST2) may include setting of the focal length of the electron beam B that has passed through the opening T1 of the groove T. The electron beam B emitted from the photocathode 3 has acceleration energy due to the electric field formed by the photocathode 3 and the anode 4. Therefore, the electron beam B that has passed through the opening T1 can reach the bottom T3 of the groove T.

[0068] However, as shown in Fig. 10b, when the focus F of the electron beam B is located closer to the opening T1 than the bottom T3, the electron beam B beyond the focus F begins to spread, and the spread electron beam B is irradiated onto the bottom T3. On the other hand, as shown in Fig. 10c, when the focus F of the electron beam B is located further beyond the bottom T3, the spread electron beam B is irradiated onto the bottom T3.

[0069] Therefore, in order to obtain an image of the bottom T3 with higher resolution, the focal length may be set, as necessary, to a distance at which the electron beam B is focused on the bottom T3 of the trench T. The focal length can be adjusted by controlling the intermediate electrode 64 shown in FIG. 8 and / or the objective lens 9. Note that the control method for the intermediate electrode 64 and the control method for the objective lens 9 have already been explained in the first electron beam parameter setting step (ST2). Therefore, detailed explanation will be omitted to avoid redundancy.

[0070] If design information for the irradiation target S is available, the focal length is calculated based on that design information, and is set to a distance at which the electron beam B will focus on the bottom T3 of the groove T when irradiated with the electron beam B onto the groove T, as shown in Figure 10a.

[0071] If there is no design information for the irradiation target S, the position of the groove can be determined by performing the groove position information acquisition process as described above. However, the groove position information acquisition process cannot measure the aspect ratio of the groove T. In this case, the local observation method is first performed to determine whether the image of the bottom T3 obtained is clear or blurred. This determination may be made by the operator or the control unit 6. If the image of the bottom T3 is clear, the local observation method is terminated. If the control unit 6 determines that the image is blurred, it may perform (1) a second electron beam parameter setting process in which the focal length is set longer than the focal length previously set in the first electron beam parameter setting process, or (2) a third electron beam parameter setting process in which the focal length is set shorter than the focal length previously set in the first electron beam parameter setting process, and then (3) an electron beam irradiation process in which the electron beam is irradiated onto the groove T using the electron beam parameters set in the second electron beam parameter setting process or the electron beam parameters set in the third electron beam parameter setting process. Furthermore, when the electron beam irradiation step (3) is performed, the position information setting step (ST1) can use the already set position information of the groove portion, so there is no need to perform the position information setting step (ST1) again. After the electron beam irradiation step (3) is performed, the detection step (ST4) can be performed.

[0072] (Electron beam parameter settings) As described above, in the first electron beam parameter setting step, at least the size w2 of the electron beam B when it reaches the groove T is set, and the other electron beam parameters may be left unchanged from their predetermined values. Alternatively, at least one selected from the electron beam current, the magnitude of the electron beam acceleration energy, the electron beam shape, the electron beam emission time, and the electron beam emittance may be changed from its predetermined value. When performing the second electron beam parameter setting step or the third electron beam parameter setting step, at least one selected from the electron beam current, the magnitude of the electron beam acceleration energy, the electron beam shape, the electron beam emission time, and the electron beam emittance may also be changed from its predetermined value. Note that in the second electron beam parameter setting step or the third electron beam parameter setting step, the size w2 of the electron beam B set in the first electron beam parameter setting step may be changed as necessary.

[0073] Furthermore, even when design information is available, it is conceivable that the shape, aspect ratio, etc. of the trench T of the irradiation target S that is actually manufactured may differ from the design information. In such a case, when the local observation method is performed based on the first electron beam parameters set on the basis of the design information, it is conceivable that the bottom T3 of the trench T may not be observed. In such a case, it is sufficient to reset the electron beam parameters, including the size w2 of the electron beam B, and perform the local observation method again.

[0074] (Detection step (ST4)) The detection step (ST4) described above detects the amount of the emitted material SB emitted from the irradiation target S. Then, based on the amount of the emitted material SB detected in the detection step (ST4), the state of the bottom part T3 can be observed. Alternatively, the control unit 6 may control the amount of the emitted material SB emitted from the irradiation target S so that it approaches a preset value. Note that the preset value is a value (detector sensitivity) that is arbitrarily set within a range that does not exceed the maximum value (dynamic range) of the signal that can be processed by the detector 5. More specifically, the control unit 6 a light intensity adjusting step of adjusting the amount of light reaching the photocathode 3 from the light source 2 so that the signal intensity of the detection signal detected in the detection step (ST4) becomes a preset value; a step of repeating the electron beam irradiation step (ST3), the detection step (ST4), and the light intensity adjustment step so that the signal intensity of the detection signal approaches a preset value; a detection data output step of outputting light amount adjustment data when the signal intensity of the detection signal approaches a preset value as detection data for the groove portion T; may be implemented.

[0075] The principle that light intensity adjustment data in which the signal intensity of the detection signal approaches a preset value can be used as detection data for the irradiation target S is described in detail in Japanese Patent Nos. 6968481 and 7154671, and therefore a description of the specific principles, procedures, etc. will be omitted in this specification. The matters described in Japanese Patent Nos. 6968481 and 7154671 are incorporated herein by reference.

[0076] In the inventions described in Japanese Patent Nos. 6,968,481 and 7,154,671, the light intensity adjustment data obtained when the signal intensity of the detection signal reaches a preset value (5 in FIG. 11a) is used as the detection data, as shown in FIG. 11a. However, in the local observation method disclosed in the present application, the signal intensity does not necessarily have to be the same as the preset value; it only needs to approach the preset value, as shown in FIG. 11b. Although not limited thereto, "approaching" in this specification means approaching a signal intensity of at least approximately 20% of the preset signal intensity value. "Approaching" may also mean at least approximately 30%, 40%, 50%, 60%, 70%, 80%, or 90% of the preset signal intensity value. Of course, as shown in FIG. 11a, the average measured signal intensity may be 100% of the preset signal intensity value.

[0077] Furthermore, in this specification, "the signal intensity of the detection signal approaches a preset value" means that the average value of the measured signal intensity when the electron beam B is irradiated so as to scan the groove T (or the groove T and its surrounding area) falls within ±20% of the preset value. In the example shown in FIG. 11b, the preset value is 5, so if the average value of the measured signal intensity is between 1 and 9, it can be said that "the signal intensity of the detection signal approaches a preset value." The preset value is defined as X, and the range of signal intensity when approaching the preset value X by Y% can be expressed by the following formula. X-(X×(100%-Y%) / 100)~X+(X×(100%-Y%) / 100)

[0078] If the range of signal strength expressed by the above formula exceeds the dynamic range, the range of signal strength may be defined as the range expressed by the above formula and within the dynamic range.

[0079] Furthermore, if the image obtained after the detection data output step is performed is unclear, the control unit 6 optionally changing at least one of the electron beam parameters set in the first electron beam parameter setting step, and using the changed electron beam parameter; Light intensity adjustment process, a step of repeating the electron beam irradiation step, the detection step, and the light amount adjustment step so that the signal intensity of the detection signal approaches a preset value; a detection data output step of outputting light amount adjustment data when the signal intensity of the detection signal approaches a preset value as detection data of the groove portion; may be carried out repeatedly.

[0080] At least one of the electron beam parameters to be changed includes the size w2 of the electron beam B, the focal length of the electron beam, the current of the electron beam, the magnitude of the acceleration energy of the electron beam, the shape of the electron beam, the emission time of the electron beam, and the emittance of the electron beam.

[0081] Note that the configuration examples that can be employed in the above-described embodiments of the electron beam application apparatus 1, 1A, and local observation method are merely examples. Configuration examples not exemplified may also be employed as long as they are within the scope of the technical concept disclosed in this application. Furthermore, any one or more of the various embodiments and configuration examples may be combined.

[0082] (Embodiments of a program and a recording medium) The above-described embodiments of the electron beam application apparatus 1, 1A and the local observation method, as well as examples of configurations that can be employed in the embodiments, can be implemented by controlling the control unit 6 of the electron beam application apparatus 1, 1A. Therefore, it is sufficient if a program created to enable each step shown in FIG. 7 (including examples of configurations that can be employed) to be implemented is installed in the control unit 6. The program may also be provided by being recorded on a readable recording medium. The local observation method disclosed in the present application can be implemented by installing the program disclosed in the present application in the control unit 6 of the conventional electron beam application apparatus 1, 1A.

[0083] The following examples are provided to specifically explain the embodiments disclosed in the present application, but these examples are merely for the purpose of explaining the embodiments and are not intended to limit or restrict the scope of the invention disclosed in the present application. [Example]

[0084] [Production of electron beam application device 1] Example 1 A laser light source (iBeamSmart manufactured by Toptica) was used as the light source 2. The photocathode 3 was an InGaN photocathode fabricated using a known method described in Daiki SATO et al. 2016 Jpn. J. Appl. Phys. 55 05FH05. EA treatment of the photocathode surface was performed using a known method. The fabricated electron gun was replaced with the electron gun of a commercially available SEM. The specifications of the commercially available SEM included a cold field emission electron source (CFE) for the electron gun and a deflection coil as the electron beam deflector 8. The electron beam acceleration voltage was a maximum of 30 kV, and observations at a maximum magnification of 1,000,000 times were possible. A program was created and improved for the control unit 6 of the electron beam application device 1 so that it could perform each of the steps described in the embodiment.

[0085] [Implementation of local observation method] (sample) A semiconductor wafer with a trench was used as the sample. Figure 12 shows an image of the trench of the sample used. The trench opening size was 1 μm, the depth was 30 μm, and the aspect ratio was 30.

[0086] <Example 2> (1) Groove position information acquisition process Using the electron beam application device 1 prepared in Example 1, an electron beam having the following electron beam parameters was irradiated onto the sample while scanning it. The focal length was set based on the aspect ratio of the sample so that the focus was on the bottom. In Example 2, secondary electrons emitted to the outside from the opening of the groove were detected by a detector. Acceleration voltage: 10kV ·Magnification: 8000x Probe current: 100pA Probe size (width of the electron beam when passing through the groove opening w2): 30 nm

[0087] Figure 13a shows an SEM image of the groove and its surrounding area obtained in the groove position information acquisition step.

[0088] (2) Implementation of local observation methods Based on the groove position information obtained in (1) above, the electron beam was irradiated under the same conditions as in (1) above, except that the probe current of the electron beam when irradiating the middle groove among the three grooves was set to 1 nA. Figure 13b shows the resulting SEM image.

[0089] Example 3 Position information was set so that the groove and its surrounding area shown in FIG. 13a were the irradiation area, and the sample was irradiated with electron beam B using the electron beam application device 1 prepared in Example 1. Then, the light intensity of the light source 2 was adjusted so that the signal intensity of the detection signal detected by the detector 5 was a preset value (a value at which the detection signal is the same regardless of the location on the sample). Light intensity adjustment data that resulted in the signal intensity of the detection signal being approximately 25% of the preset value was output as detection data for the sample. Then, an image was synthesized based on the detection data (data for adjusting the light intensity (intensity) of the light source 2). Figure 14 shows the image data synthesized in Example 3. The electron beam parameters are as follows: Acceleration voltage: 10kV ·Magnification: 8000x Probe size (width of the electron beam when passing through the groove opening w2): 30 nm Modulate the intensity of light source 2 from 1mW to 100mW

[0090] The areas circled in the photographs of Figures 13 and 14 are deposits at the bottom of the grooves. Almost no deposits were observed in the area circled in Figure 13(a). On the other hand, in Figure 13(b), where only the central groove was irradiated with an electron beam at a high current value, deposits in the central groove were clearly observed. Furthermore, in the method of Example 3, where the light intensity of light source 2 was adjusted so that the signal intensity of the detection signal detected by detector 5 reached a preset value, deposits were observed in the left and central grooves.

[0091] The reason why no deposits were observed in the left side of the groove in Figures 13(a) and 13(b) is thought to be because the electron beam was irradiated around the groove, generating an electric field within the groove. The reason why deposits were observed in the center of the groove in Figure 13(b) is thought to be because the electron beam was irradiated with an intensity greater than the effect of the generated electric field. From these results, for example, if you want to observe only the bottom of the groove locally, you can accurately observe the condition of the bottom of the groove by irradiating only the groove with an electron beam of size w2 set in the first electron beam parameter setting process, without irradiating the peripheral area of the groove with the electron beam. Furthermore, when irradiating the peripheral area of the groove with the electron beam Bw, it was confirmed that the electron beam parameters for the electron beam B irradiated to the groove should be set taking into account the size w2 of the electron beam B and the electric field generated within the groove by the electron beam Bw irradiated to the peripheral area of the groove.

[0092] 14, the detection method of Example 3 differs from Example 2 in the detection principle, and therefore deposits on the bottom of the grooves could be confirmed by irradiating the grooves and their peripheral areas with an electron beam so that the signal strength of the detection signal was the same. From the above results, in Example 3, position information was set so that the grooves and their peripheral areas were the irradiation area, but the state of the irradiated grooves and their bottoms can be observed with high accuracy even without setting position information about the grooves. [Industrial Applicability]

[0093] The electron beam application device and local observation method using the electron beam application device disclosed in the present application make it possible to observe the bottom of a trench with a high aspect ratio, and are therefore useful for manufacturers of electron microscopes and electron beam inspection devices, as well as businesses that inspect and observe irradiated objects. [Explanation of symbols]

[0094] 1, 1A, 1B...electron beam application device, 1a...electron gun portion, 1b...counterpart device, 2...light source, 3...photocathode (cathode), 4...anode, 5...detector, 6...controller, 61...light intensity adjuster, 62...excitation light size adjuster, 63...electron beam size adjuster, 64...intermediate electrode, 65...electron beam shape adjuster, 7...power supply, 8...electron beam deflector, 9...objective lens, B, Bw...electron beam, CB...vacuum chamber Chamber, F... focus, L... excitation light, S... irradiation target, S1... irradiation surface, SB... emitted material, ST1... position information setting process, ST2... first electron beam parameter setting process, ST3... electron beam irradiation process, ST4... detection process, T... groove, T1... groove opening, T2... groove wall, T3... groove bottom, w1... size of opening T1, w2... size of electron beam B when reaching opening T1, w3... size of electron beam B irradiated to bottom T3

Claims

1. A method for locally observing an irradiation object using an electron beam application device, comprising: The local observation method is a method for observing at least a groove portion formed in the irradiation target, The electron beam application device is A light source and a photocathode that generates releasable electrons in response to receiving excitation light irradiated from the light source; an anode capable of forming an electric field between itself and the photocathode, which extracts the releasable electrons by the formed electric field to form an electron beam; a detector that detects emissions emitted from the irradiation target irradiated with the electron beam and generates a detection signal; A control unit; Including, The local observation method includes: a position information setting step of setting at least position information of the groove portion in the irradiation target; a first electron beam parameter setting step of setting electron beam parameters of the electron beam to be irradiated onto the irradiation target; an electron beam irradiation step of irradiating the groove with an electron beam based on the electron beam parameters set in the position information setting step and the first electron beam parameter setting step; a detection step of detecting, with the detector, an amount of emitted material emitted from the groove portion irradiated with the electron beam in the electron beam irradiation step, and generating a detection signal; and In the first electron beam parameter setting step, at least the size of the electron beam when it reaches the opening of the groove is set to a size that can suppress the generation of an electric field in the groove. Local observation method.

2. The position information setting step is performed based on design information of the irradiation target. The local observation method according to claim 1 .

3. a step of acquiring position information of the groove portion before the step of setting position information, The groove position information acquisition step includes: irradiating the irradiation target with an electron beam; a detection step of detecting an amount of emitted material emitted from an irradiation area irradiated with the electron beam by the detector and generating a detection signal; a detection data output step of outputting the detection signal generated in the detection step in association with position information of the irradiation area; and The control unit controls so that the position information setting step is performed based on the detection data associated with the position information of the irradiation area output in the detection data output step. The local observation method according to claim 1 .

4. the first electron beam parameter setting step includes setting a focal length of the electron beam that has passed through the opening of the groove portion; The focal length is Calculation is performed based on design information of the irradiation target, When an electron beam is irradiated onto the groove, the electron beam is focused at the bottom of the groove. The local observation method according to claim 1 .

5. The control unit further comprising a second electron beam parameter setting step of setting a focal length longer than the focal length preset in the first electron beam parameter setting step; an electron beam irradiation step of irradiating the groove with an electron beam based on the electron beam parameters set in the second electron beam parameter setting step; The local observation method according to claim 1 .

6. The control unit a third electron beam parameter setting step of setting a focal length shorter than the focal length preset in the first electron beam parameter setting step; and an electron beam irradiation step of irradiating the groove with an electron beam based on the electron beam parameters set in the third electron beam parameter setting step. The local observation method according to claim 1 .

7. The control unit changes at least one selected from the current of the electron beam, the magnitude of the acceleration energy of the electron beam, the shape of the electron beam, the emission time of the electron beam, and the emittance of the electron beam, which are predetermined in the first electron beam parameter setting step. The local observation method according to claim 1 .

8. The control unit Control is performed so that the electron beam is irradiated to portions other than the groove portion based on electron beam parameters different from the first electron beam parameters set in the first electron beam parameter setting step. The local observation method according to claim 1 .

9. The control unit a light amount adjusting step of adjusting the amount of light reaching the photocathode from the light source so that the signal intensity of the detection signal detected in the detection step becomes a preset value; a step of repeating the electron beam irradiation step, the detection step, and the light amount adjustment step so that the signal intensity of the detection signal approaches a preset value; a detection data output step of outputting light amount adjustment data when the signal intensity of the detection signal approaches a preset value as detection data of the groove portion; Contains The local observation method according to claim 1 .

10. After the detection data output step is performed, The control unit changing at least one of the electron beam parameters set in the first electron beam parameter setting step, and using the changed electron beam parameter; the light amount adjusting step; a step of repeating the electron beam irradiation step, the detection step, and the light amount adjustment step so that the signal intensity of the detection signal approaches a preset value; a detection data output step of outputting light amount adjustment data when the signal intensity of the detection signal approaches a preset value as detection data of the groove portion; To carry out The local observation method according to claim 9 .

11. The electron beam application device is scanning electron microscope, Electron beam inspection equipment, or Semiconductor inspection equipment, is The local observation method according to claim 1 .

12. 12. A program for causing the control unit of the electron beam application device to execute each step according to claim 1.

13. A computer-readable recording medium on which the program according to claim 12 is recorded.

14. A light source and a photocathode that generates releasable electrons in response to receiving excitation light irradiated from the light source; an anode capable of forming an electric field between itself and the photocathode, which extracts the releasable electrons by the formed electric field to form an electron beam; a detector that detects emissions emitted from the irradiation target irradiated with the electron beam and generates a detection signal; A control unit; An electron beam application device comprising: The control unit stores the program according to claim 12. Electron beam application equipment.

Images