Charged particle beam system

Abstract

The present disclosure provides a charged particle beam system in which an image generation condition for evaluating a beam adjustment condition can be properly set. The charged particle beam system has an adjustment deflector for adjusting the trajectory of a beam incident to a scanning deflector and an optical element and comprises a user interface configured so as to display an image and a partial region of the image selected by the user. The charged particle beam system is configured so as to cause the user interface to display an input portion (170) for allowing the user to set the image (initial screen 151), the partial region (152), and at least one of a first parameter relating to the scanning speed of the scanning deflector and a second parameter relating to the change rate of the optical element (refer to FIG. 6).

Description

Technical Field

[0001] The present disclosure relates to a charged particle beam system, and more particularly to a charged particle beam system provided with an adjustment element used to appropriately pass a beam through optical elements such as lenses and aberration correctors.

Background Art

[0002] Charged particle beam systems such as scanning electron microscopes (SEM) and focused ion beam (FIB) devices are used for observing and analyzing fine structures using images generated based on detection of secondary electrons and the like generated by irradiation of a charged particle beam, and for processing using a sputtering phenomenon when irradiating a sample with a charged particle beam. Charged particle beam systems are mainly widely used in the semiconductor field, the material field, and the bio field. In these fields, with the miniaturization of observation samples, further improvement in image resolution, analysis, and processing accuracy are required.

[0003] To achieve this, it is important to narrow the diameter of the charged particle beam. To narrow the beam diameter, it is an important operation to adjust the beam irradiation axis so as to reduce lens aberration (hereinafter referred to as optical axis adjustment). In other words, the operation of matching the ideal optical axis of an optical element such as an electromagnetic lens with the beam orbit becomes important.

[0004] In this regard, for example, Patent Document 1 describes performing axis adjustment (wobbler adjustment method) based on the amount of image shift generated by a wobbler.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the wobbler adjustment method disclosed in Patent Document 1, adjustment conditions by adjustment elements such as an axis adjustment deflector are derived based on the amount of movement and the direction of movement of an object in an image before and after a change in an optical element. When evaluating such an amount of movement and the direction of movement, it is desirable to use an image generated under appropriate conditions. In view of such a situation, the present disclosure proposes a technique for appropriately setting image generation conditions for evaluating adjustment conditions of a charged particle beam.

Means for Solving the Problems

[0007] As one aspect for achieving the above object, the present disclosure provides a charged particle beam column including a scanning deflector that scans a beam emitted from a charged particle source, an optical element that adjusts the beam, and an adjustment deflector that adjusts the trajectory of the beam incident on the optical element, and a charged particle beam system including one or more computer subsystems connected to the charged particle beam column and controlling the scanning deflector and the adjustment deflector, wherein the one or more computer subsystems include a user interface configured to display an image output from the charged particle beam column and a partial region of the image selected by a user, and the one or more computer subsystems are configured to periodically change an optical condition of the optical element, generate an image based on a signal output from the charged particle beam column when the optical condition of the optical element is periodically changed, and display an input unit for allowing the user to set at least one of a first parameter related to a scanning speed of the scanning deflector and a second parameter related to a change speed of the optical element on the user interface.

[0008] Further features related to the present disclosure will become apparent from the description in this specification and the accompanying drawings. Also, aspects of the present disclosure are achieved and realized by elements and combinations of various elements, and aspects of the following detailed description and appended claims. It should be understood that the description in this specification is merely a typical example and does not limit the scope of the claims or the application examples of the present disclosure in any sense.

Advantages of the Invention

[0009] According to the above configuration, it becomes possible to appropriately set the image generation conditions for evaluating the adjustment conditions of the beam.

Brief Description of the Drawings

[0010]

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Mode for Carrying Out the Invention

[0011] (1) Embodiment <Regarding Wobbling and Its Improvement Points> Optical axis adjustment in a charged particle beam system means passing a beam (charged particle beam) through the ideal optical axis of an optical element such as a lens. At this time, a method of periodically changing the excitation current (lens strength) of the lens to be adjusted is called wobbling.

[0012] When the beam is deviated from the ideal optical axis, if the lens strength is periodically changed, the beam is deflected by the lens action, and the object in the field of view appears to move. On the other hand, when the beam passes through the lens along the ideal optical axis, even if the lens strength is changed, since the focusing condition of the beam changes, although the focus condition changes, there is no movement of the object. That is, by performing adjustment with an adjustment element (such as an alignment deflector) so that the object in the field of view does not move even when wobbling is performed, the beam trajectory can be made to coincide with the ideal optical axis. In the following description, such an optical axis adjustment method is called wobbler adjustment.

[0013] The ideal beam irradiation axis of the lens varies depending on the surface height position of the sample that focuses the beam. Therefore, for precise optical axis adjustment to achieve image observation with reduced aberration, it is desirable to perform the adjustment at a surface height equivalent to the surface height of the sample to be observed.

[0014] Observation samples of the charged particle beam system include those with non-uniform surface heights. That is, when setting the region for obtaining the final image and the region for wobbler adjustment at different positions to avoid overlapping irradiation of the observation region, the height of the sample surface may change (differ) between the observation position and a position away from the observation position (wobbler adjustment region). Therefore, it is desirable to set the wobbler adjustment region near the observation position where the height conditions are relatively close.

[0015] Also, in FIB, samples placed on a mesh or a lamella may be the objects of processing observation. At this time, the surface of the sample placed on the mesh or lamella may be inclined with respect to the optical axis. Therefore, since the sample height changes (differs) between the observation position and a position away from the observation position, it is desirable to perform wobbler adjustment near the observation position.

[0016] Furthermore, there are samples with characteristics vulnerable to charged particle beam irradiation, such as resist patterns of semiconductor devices. When observing such samples, it is desirable to reduce the charged particle beam irradiation dose.

[0017] Due to such circumstances, it can be said that a region that is different from the observation region but close to the observation region is a region suitable for the wobbler adjustment region.

[0018] In order to set both the observation region and the wobbler setting region to appropriate regions as described above, first, a low-magnification image (wide FOV (Field Of View) image: the first image) is obtained so that the observation region is included. While grasping the position of the observation region within the first image, it is desirable to set a region that is close to the observation region (the acquisition region of the second image) and has a small height difference from the observation region as the wobbler setting region (the acquisition region of the third image). However, this is not the case when there is a steep slope near the observation region or the observation region is surrounded by a member that is easily charged.

[0019] On the one hand, in SEM or the like, the scanning time can be changed. Specifically, the scanning time can be adjusted by adjusting the scanning signal supplied from a power source or the like connected to the scanning deflector. The adjustment of the scanning time can be performed, for example, in units of frames (one two-dimensional scanning unit). By this adjustment, it becomes possible to select high-speed scanning for the purpose of reducing the beam irradiation amount (dose amount) or low-speed scanning for the purpose of improving the dose amount to ensure sufficient signals (secondary electron amount).

[0020] As described above, it is desirable to set the scanning time and the wobbler setting area according to the observation purpose and the sample conditions. However, through the inventors' studies, it has become clear that depending on the setting conditions, unnecessary striped patterns may appear in the image of the wobbler setting area.

[0021] FIG. 1 is a schematic diagram of an image in which a third image (an image obtained in the wobbler setting area) is superimposed on a first image (low-magnification image). More specifically, an example is shown in which a real-time image for evaluating image displacement due to wobbling is superimposed on a previously obtained low-magnification image. By performing such a superimposed display, it becomes possible to evaluate whether the conditions for obtaining the third image, such as the scanning time (frame time) and the wobbler time (for example, in the case of an electromagnetic lens, the time for one cycle of the excitation current), are appropriate.

[0022] Also, when generating the third image, if the irradiation time per pixel (Dwell time, described later) is set to be longer than that of the first image, the contrast within the wobbler setting area can be increased with respect to the first image, and the visibility of image shake can be enhanced. On the other hand, when the irradiation time (Dwell time) of the third image is made to coincide with that of the first image, the generation conditions of the first image and the third image can be made to coincide. For this reason, the presence of the stripe pattern appearing in the third image can be judged by relative comparison with the first image. By storing such conditions in a storage medium in advance and providing options such as a high-contrast mode (Dwell time is long compared to other modes) and a low-dose mode (Dwell time is short compared to other modes) on the user interface, it becomes possible to select appropriate generation conditions for the wobbling image according to the sample situation, the operator's preference, etc.

[0023] When an operator sets a wobbler scanning area (dotted frame in FIG. 1: acquisition area of the third image), the beam is scanned within this area. When wobbling is performed in this state, periodic image movement occurs due to the wobbler of the lens (periodic excitation change of the lens).

[0024] Here, when the frame time (scanning time per frame of the wobbler selection area) is set to be slower than the wobbler time (time for one cycle of lens excitation change), multiple image movements occur within one frame, and this phenomenon is expressed as a stripe pattern in the image as shown in FIG. 1. When such stripe patterns are mixed in the image shake due to wobbling, appropriate evaluation of the image shake cannot be performed, and as a result, it may be difficult to perform high-precision alignment (optical axis adjustment). Therefore, it is desirable to perform wobbling under appropriate settings, but it is considered that it takes time to find appropriate setting conditions.

[0025] <Configuration and operation of a charged particle beam system, and method for adjusting the optical axis> The configuration and operation of a charged particle beam system and a method for adjusting the optical axis, which can appropriately set the wobbler conditions, will be described below.

[0026] A charged particle beam system capable of appropriately setting wobbler conditions includes, as one aspect, an optical element group including a scanning deflector that scans a beam emitted from a charged particle source, a lens that focuses the beam, and an (alignment) deflector that deflects the trajectory of the beam incident on the lens, and at least one computer system that controls the optical element group. Further, in the charged particle beam system, an image obtained by irradiating a sample with a beam is displayed on a display device. One or more computer systems cause the display device to display an input field for inputting at least one of (i) a scanning speed or (ii) a change time when changing the lens condition of the lens with a predetermined change width, together with a frame indicating the selected region, according to the size of the region selected by a selection device (such as a pointing device) that selects an arbitrary region of the image. According to the charged particle beam system, it becomes easy for an operator to search for wobbler-adjustable setting conditions, and the adjustment workability is greatly improved.

[0027] Hereinafter, an SEM system will be described as an example of one aspect of the charged particle beam system, but the present invention is not limited thereto, and it is also applicable to, for example, FIB-SEM, scanning transmission electron microscope (STEM), etc. In all the following drawings, those having the same function are denoted by the same reference numerals, and repeated description thereof will be omitted.

[0028] FIG. 2 is a diagram showing a schematic configuration example of an SEM system 100 according to the present embodiment. The SEM system 100 includes an electron beam source 101, an alignment deflector 102, a focusing lens 103, an objective lens 104, optical elements such as a scanning deflector 105, and the like. The electron beam 107 emitted from the electron beam source 101 passes through these components and is irradiated onto the sample 123.

[0029] These optical elements are controlled by an electron beam source control unit 111, an alignment deflector control unit 112, a focusing lens control unit 113, an objective lens control unit 114, and a scanning deflector control unit 115. The sample 123 is placed on a sample stage 122 installed in a vacuum chamber 121. The electron beam 107 is focused by a focusing lens 103 and an objective lens 104, and scanned onto the sample 123 by a scanning deflector 105. At this time, secondary electrons and reflected electrons are emitted from the surface of the sample 123, and these are detected by a detector 108.

[0030] The integrated computer 130 is composed of one or more computer subsystems, and executes control of the components of the SEM and image generation (image processing) based on the output of the detector. The one or more computer systems include a storage medium storing programs for executing image processing and apparatus control as described later, a processor for executing the programs, and the like. Specifically, the integrated computer 130 performs control of the control units 111 to 115 of each optical element and image generation based on the output of the detector 108.

[0031] A controller 131 (an input device such as a pointing device like a keyboard or a mouse) and an image display device 132 are connected to the integrated computer 130. The operator inputs control information such as irradiation conditions of the beam (hereinafter, in the SEM system 100, it means an electron beam) to the integrated computer 130 from the controller 131. The integrated computer 130 controls each component in the SEM system 100 according to the input information. Further, the integrated computer 130 causes the image display device 132 to display the irradiation conditions of the beam input together with the SEM image and a designated area on the SEM image by a pointing device or the like. The image display device may be, for example, a stationary display device (display) or a tablet-type display device, and its type is not limited.

[0032] In the beam passing through the condenser lens 103 and the objective lens 104 and passing through a position deviated from the ideal optical axis of these optical elements, the aberration increases. The smaller the aberration, the narrower the electron beam can be focused. Therefore, in order to observe the sample 123 with higher resolution, optical axis adjustment to pass the beam through the ideal optical axis is required.

[0033] As described above, the periodic change of the excitation of the lens to be adjusted in this optical adjustment is particularly called wobbler. The alignment deflector 102 for wobbler adjustment is controlled by an X alignment deflector 102a that deflects the charged particle beam in the X-axis direction and a Y alignment deflector 102b that deflects the charged particle beam in the Y-axis direction. By combining the alignment deflectors 102a and 102b, the electron beam can be deflected two-dimensionally. In this embodiment, an example in which the optical element mainly to be adjusted for optical axis adjustment is an electromagnetic lens will be described, but other lenses such as electrostatic lenses and other optical elements such as anastigmators may be used. Also, different alignment deflectors may be provided for each optical element. In this embodiment, the optical axis direction is defined as the Z direction.

[0034] In wobbler, a wobbler signal for periodically changing the excitation is sent from the integrated computer 130 to the condenser lens 103 and the objective lens 104 to be adjusted, and the lens focusing action is periodically changed. When the electron beam passes through the ideal optical axis of the lens to be adjusted, since it passes through the lens vertically, during the execution of wobbler, the focusing position of the lens periodically changes in the optical axis (Z) direction from the sample surface and does not move in the XY direction. Therefore, the center position of the observed image does not change, and image blurring occurs periodically.

[0035] On the other hand, when the beam passes through a position deviated from the ideal optical axis of the lens, since the beam passes through the lens obliquely, during the execution of wobbler, the focusing position of the lens changes in the Z direction and also changes in the XY direction. Therefore, the center position of the observed image repeatedly reciprocates in a predetermined direction, and image blurring occurs periodically.

[0036] In wobbler adjustment, the operator observes the periodic image movement, and the alignment deflectors 102a and 102b are adjusted by the alignment deflector control unit 112 so that the image movement becomes small, thereby controlling the beam to pass through the ideal optical axis.

[0037] The adjustment values of the alignment deflectors 102a and 102b during the wobbler adjustment described above strictly vary depending on the focusing position of the lens, that is, the surface height of the observation sample (sample 123). This is because the ideal optical axis of the lens changes depending on the focusing position of the lens. Among the observation target samples of the charged particle beam system, there are those with height differences (there is a positional difference in the Z direction). Therefore, the sample height may change between the observation position and a position away from the observation position. For this reason, by setting the wobbler adjustment field of view at a position near the observation position (field of view) or a position that can be regarded as having the same height as the observation position, the image shake during wobbling can be accurately evaluated. For example, particularly in the case of machining observation with FIB, when placing the sample on the mesh or lamella, the sample surface is inclined with respect to the optical axis. Therefore, the sample height changes between the observation position and a position away from the observation position. For this reason, it is desirable to perform wobbler adjustment near the observation position.

[0038] Furthermore, among the samples 123 to be observed by the SEM system 100, there are those with characteristics vulnerable to beam irradiation. Therefore, in order to suppress the beam irradiation amount per unit area, it is desirable to perform beam irradiation for wobbler adjustment at a position different from the observation position.

[0039] As described above, it is desirable to perform wobbler adjustment at a position different from the observation position but having the same conditions as the observation position. In order to achieve this, it is desirable to generate an image that allows the operator to select the beam scanning area during wobbler adjustment.

[0040] <Regarding the wobbler selection area> FIG. 3 is a diagram showing an example in which a frame (area 152: partial area) indicating a selection area for the wobbler is superimposed on the initial screen 151 (first image). The frame (area 152) is set to be adjustable to any position and size with a pointing device or the like. Specifically, the operator selects a scanning area (area 152) with a selection device (pointing device or the like) 133 that selects an arbitrary area within the initial screen 151. This selected area becomes the scanning area for the wobbler. Then, the integrated computer 130 controls the scanning deflector control unit 115 so that the beam is scanned in the area corresponding to the wobbler scanning area within the initial screen 151.

[0041] The initial screen 151 for performing this area selection (setting area 152) is image data acquired before scanning area 152 and stored in a storage medium, and is obtained by scanning an area wider than the wobbler scanning (selection) area. Note that the time for one cycle of the lens excitation change is called the wobbler time, and the time required for the beam to scan the selected area is called the frame time.

[0042] As shown in FIG. 3, a frame display is performed, and the scanning deflector 105 is controlled to selectively scan the inside of the frame (area 152) to generate an image, and in that state, wobbling is performed to visually confirm the image of area 152.

[0043] Also, according to the user interface as illustrated in FIG. 3, when wobbling is executed within area 152 set to any position and size, while the wobbler adjustment image can be visually evaluated, a periodically blurred area image may be generated (see FIG. 4).

[0044] <Blurred image area generated during wobbler adjustment> FIG. 4 is a diagram illustrating a state in which an image area focused on the wobbler adjustment image (area 152) and an out-of-focus and blurred area periodically appear. Due to the wobbling of the electromagnetic lens, the focus state periodically fluctuates. In the example of FIG. 4, an in-focus area 401 and an out-of-focus area 402 alternately appear, seemingly as if a stripe pattern appears within area 152. In such a state, image shake may not be properly evaluated. The stripe pattern occurs when at least one of the size of the wobbler scanning area, the scanning speed, and the wobbler time is inappropriate.

[0045] When the frame time is set earlier than the wobbler time, the above-described stripe pattern does not occur, and the wobbler adjustment can be performed by the operator observing the image movement.

[0046] On the other hand, when the frame time is set later than the wobbler time, since the focus changes occur multiple times within one frame, a stripe pattern as illustrated in FIG. 4 occurs. That is, the image movement cannot be observed as an image change for each frame, and image adjustment becomes difficult.

[0047] From the above, as a generation condition of the wobbler adjustment image, it is desirable to shorten the frame time with respect to the wobbler time. To perform such a setting, first, it is conceivable to set the size of the wobbler scanning area smaller compared to the state in which the stripe pattern occurs. For example, in the case of an SEM system configured such that the frame time changes in proportion to the frame area (size of the scanning area) when setting the wobbler area, if the area of the wobbler scanning area is reduced, the frame time can be shortened compared to before the reduction. Note that limiting the area from the initial scanning area of the initial screen 151 to the wobbler scanning area is realized by reducing the beam scanning range of the scanning deflector from a predetermined scanning width. This is fundamentally different from changing the focusing position of the lens to increase the observation magnification and reducing the scanning area on the sample.

[0048] In addition, in order to shorten the frame time with respect to the wobble time, it is conceivable to set the scanning speed of the beam to be faster than that in the state where the stripe pattern is generated. Since the frame time becomes shorter in inverse proportion to the scanning speed, if the scanning speed is increased, the frame time can be shortened compared to before the increase. Furthermore, in order to shorten the frame time with respect to the wobble time, it is conceivable to set the wobble time to be longer than that in the state where the stripe pattern is generated.

[0049] <Wobble condition setting process> FIG. 5 is a flowchart showing a wobble condition setting process in an SEM system (charged particle beam system) 100 having a user interface as illustrated in FIG. 3.

[0050] The integrated computer 130 is composed of one or more computer subsystems and includes a storage medium in which a program for displaying a user interface on the image display device 132 is stored. Here, as setting conditions when performing wobble adjustment, a scanning speed Ss, a wobble time Tw, and a frame time Tf are set. In the wobble scanning area 152 selected by the operator, as long as Tw < Tf, appropriate wobble conditions have not been set.

[0051] Appropriate optical axis adjustment can be achieved by appropriately setting combinations of a plurality of parameters. However, the combinations of parameters are diverse, and it is desirable to perform settings according to the sample state in the initial screen 151.

[0052] In FIG. 5, when the operator sets the wobble scanning area Aw from the initial scanning area, the integrated computer 130 accepts the setting by the operator (step 501).

[0053] When the operator inputs (observation result) whether the image movement by the wobbler can be observed every time the image of one frame is updated (Tw > Tf), the integrated computer 130 determines the observation result by the operator. When the observation result is "image movement can be observed (Tw > Tf)" (Yes in step 502), the process proceeds to step 504. On the other hand, when the observation result is "image movement cannot be observed (Tw ≤ Tf)" (No in step 502), the process proceeds to step 503.

[0054] In step 503, the integrated computer 130 notifies the operator to re - set any one of the scanning speed Ss, the wobbler time Tw, and the frame time Tf, and accepts at least any one of Ss, Tw, and Aw re - set by the operator according to this notification. Then, the integrated computer 130 executes wobbler adjustment (step 504).

[0055] (2) Embodiment The above is the outline of the wobbler condition setting process. Hereinafter, each embodiment of the SEM system (charged particle beam system) 100 that can easily set appropriate conditions will be described in more detail.

Embodiment

[0056] FIG. 6 and FIG. 7 are diagrams showing an example of a GUI screen for setting wobbler conditions. FIG. 8 is a flowchart for explaining the setting process using these user interfaces.

[0057] Using the SEM system (charged particle beam system) 100, first, an initial scanning area is set to include the observation target area, and an initial screen 151 is acquired. The integrated computer 130 stores the image data of the initial screen 151 in a predetermined storage medium and displays it on a GUI screen as illustrated in FIG. 6 or FIG. 7. When the operator sets the wobbler scanning area Aw (area 152) on the initial screen 151 displayed on the GUI screen, the integrated computer 130 accepts the setting by the operator (step 801).

[0058] Based on the size information of the wobbler scanning area 152 and the initially set scanning speed during wobbler adjustment, the integrated computer 130 calculates the scanning time per frame (step 802).

[0059] When the operator selects a scanning area using the selection device (such as a pointing device) 133, the integrated computer 130 displays at least one input field 170 for the wobbler time or the scanning speed, together with a frame for specifying the wobbler scanning area 152, on the screen of the image display device 132 (step 803). At this time, the integrated computer 130 may also display an input field for setting the wobbler adjustment coefficient (hereinafter referred to as N). Also, the input field 170 may be automatically displayed in conjunction with the frame specifying the area 152, or may be manually displayed by a simple operation (such as mouse click or keyboard key input) using the selection device (such as a pointing device) 133. Note that the wobbler adjustment coefficient N is a natural number of 2 or more.

[0060] When the operator selects to change the scanning speed or the wobbler time, the integrated computer 130 selects the condition to change from these two conditions and the value of N (step 804).

[0061] Using the value of N selected in step 804, the integrated computer 130 calculates and applies the selected scanning speed or wobbler time value by the wobbler condition adjustment unit 134 so that "frame time × N = wobbler time" (steps 805, 806, 807).

[0062] The wobbler condition adjustment unit 134 can store the value of N as a table for each observation condition, and by using N as a default value, the operator can be saved the operation of setting the value of N.

[0063] Alternatively, by enabling the operator to arbitrarily set the value of N, it is possible to further improve the workability of wobbler adjustment. The signal-to-noise ratio (S / N ratio) of the observation image varies according to condition (i) the beam irradiation time (dwell time) per pixel, condition (ii) the beam irradiation dose (dose amount) per pixel, condition (iii) the ratio of the amount of electrons in the incident beam to the amount of electrons emitted from the sample (yield), condition (iv) the ratio of the electrons detected by the detector to the electrons emitted from the sample (detection efficiency), and so on.

[0064] The operator indirectly sets condition (i) by setting the scanning time or the like according to the observation purpose or the like. Since conditions (ii) to (iv) change according to the setting of condition (i), the conditions of (ii) to (iv) also change according to the operator's preference. That is, the frame time, which is inversely proportional to the scanning speed, may also vary from operator to operator.

[0065] On the other hand, for the wobbler time, there is an appropriate cycle of image movement that is easy for the operator to adjust. Therefore, depending on the operator, the frame time is diverse, and since there is an appropriate value range for the wobbler time, it is desirable to allow various settings for N as well. From the above, the operability is improved by enabling the operator to arbitrarily set the value of N according to each observation condition.

[0066] By enabling the setting of region 152 on the user interface and displaying the input field 170 in a state where it is possible to visually determine whether or not a stripe pattern appears within region 152, it becomes possible to select a region suitable for wobbling and set the conditions for wobbling at the same time. To enable such a setting, for example, among a plurality of buttons provided on the pointing device, one button is a button for selecting the vertex part of the frame when selecting region 152, and the other button is a display button for the input field 170 (the input field 170 is displayed by pressing the button). Also, the input field 170 may be automatically displayed after setting region 152.

[0067] Also, after selecting the appropriate area 152 and setting the wobbling conditions, it is desirable to enable control by the adjustment knob of the alignment deflector so that alignment can be performed promptly.

[0068] Note that FIGS. 6 and 7 show examples of input sections in which parameters that change according to the scanning speed and wobbling time, such as 2, 3, 4, ···, are used instead of directly inputting the scanning speed and wobbling time. However, an input field that can directly input the scanning speed and wobbling time may be provided, or an input section that adjusts the scanning speed and wobbling time by changing the position of a knob such as a control bar may be provided.

Example

[0069] FIG. 9 is a flowchart for explaining a process of performing optical axis adjustment using an SEM system (charged particle beam system) 100 equipped with a user interface.

[0070] The integrated computer 130 calculates the scanning time per frame based on the size and scanning speed of the wobbling scanning area 152 during wobbling adjustment. When the operator selects a scanning area using the selection device (pointing device, etc.) 133 and the wobbling scanning area 152 is specified on the image display device 132, the integrated computer 130 accepts the specification of the wobbling scanning area 152 (step 901).

[0071] The integrated computer 130 calculates the frame time Tf from the size information Aw of the wobbling scanning area and the scanning speed Ss set as the initial value (step 902). In the memory built into the integrated computer 130, for example, Tf = Aw × Ss × n (n is a predetermined coefficient) is stored in advance, and the integrated computer 130 calculates Tf that increases in proportion to the size of Aw.

[0072] Next, the integrated computer 130 reads out preset conditions (parameters and coefficients to be adjusted to satisfy Tw = N×Tf) from the memory, and obtains parameters that satisfy Tw = N×Tf (step 903 → step 904).

[0073] The integrated computer 130 sets (automatically sets) the parameters obtained by calculation, and controls each optical element (scanning deflector, objective lens, alignment deflector, etc.) provided in the charged particle beam apparatus so as to perform wobbler adjustment (step 905 → step 906). The automatic setting of the parameters is realized by the wobbler condition adjustment unit 134 based on the calculation result of the integrated computer 130 so that "frame time × N = wobbler time" or "frame time × N < wobbler time < predetermined time". Here, N is a wobbler adjustment coefficient, which is a natural number of 2 or more.

[0074] The wobbler condition adjustment unit 134 stores the value of N as a table for each observation condition, and stores which of the two conditions is to be automatically set so that the above formula holds. This stored value can be changed in advance during the wobbler adjustment operation. Thus, for the same reason as described in the first embodiment, it is possible to set an appropriate wobbler condition for each operator's observation condition. The input screen for this condition setting is not displayed together with a frame for designating the wobbler scanning area 152 for each wobbler adjustment, but is performed by the operator as a separate operation from the wobbler adjustment operation. Thereby, it is possible to reduce the display of the input field each time the wobbler is adjusted, and to shorten the operation time by automation.

[0075] In this embodiment, an example in which one input is used to obtain the other using an arithmetic expression including the frame time and the wobbler time has been described. However, instead of the arithmetic expression, two relation tables may be stored in a predetermined storage medium as related information of the two parameters, and the other may be obtained by referring to the relation tables.

Example

[0076] FIG. 10 is a diagram showing a configuration example of a user interface according to Example 3. Further, FIG. 11 is a flowchart for explaining an example of an optical axis adjustment process using the user interface illustrated in FIG. 10.

[0077] When the integrated computer 130 receives a setting of a scanning (selection) area 180 (Aw´) for optical axis adjustment on a GUI screen (FIG. 10) that displays an initial screen 151 by an operator (step 1101), it registers the shape and position of this scanning (selection) area 180 for optical axis adjustment in an internal memory (not shown) (step 1102). The scanning (selection) area 180 for optical axis adjustment is used as a scanning area during subsequent optical axis adjustment.

[0078] The integrated computer 130 displays an input field 181 where the scanning speed can be input on the image display device 132 together with a frame designating the scanning (selection) area 180 for optical axis adjustment selected by the operator (step 1103). Note that the input field 181 may be automatically displayed together with the frame designating the scanning (selection) area 180 for optical axis adjustment, or may be manually displayed by a simple operation (mouse click or keyboard key input) associated with the operation of a selection device (pointing device, etc.) 133 for designating the scanning (selection) area 180 for optical axis adjustment. In the above-described Example 1 and Example 2, mainly an example is described in which an operator observes image movement by a wobbler during optical axis adjustment and manually adjusts the beam irradiation axis. On the other hand, in automatic optical axis adjustment, it is desirable to perform adjustment based on image movement when the excitation of the lens is changed at a specific change step without executing the wobbler (without changing the lens excitation periodically). However, in both the above-described manual optical axis adjustment and automatic optical axis adjustment, it is desirable to ensure an S / N ratio sufficient to accurately recognize the presence of image shake and parallax in the image used during image adjustment. The S / N of the image depends on the beam irradiation time per pixel, that is, the scanning speed.

[0079] The operator evaluates the S / N of the image within the registered scanning (selection) area 180 for optical axis adjustment and inputs an instruction to the integrated computer 130 on whether to change to the specified scanning speed Ss. When the instruction by the operator indicates using the default value as the scanning speed (No in step 1104), the integrated computer 130 transfers the process to step 1107. When the instruction by the operator indicates using the desired input value as the scanning speed (Yes in step 1104), the integrated computer 130 transfers the process to step 1105.

[0080] When the operator inputs the scanning speed to the input field 181 so that the S / N becomes an appropriate value, the integrated computer 130 accepts the input value of the scanning speed (step 1105) and applies it (step 1106).

[0081] The integrated computer 130 controls each optical element (scanning deflector, objective lens, alignment deflector, etc.) provided in the charged particle beam apparatus so as to perform optical axis adjustment by setting the input value or the default value of the scanning speed as a parameter (step 1107).

[0082] As described above, according to Example 3, by setting the scanning speed as the default value, the operation of the operator to input the scanning speed can be omitted. Further, when the S / N is not appropriate, by enabling the operator to arbitrarily set the scanning speed, it becomes possible to set the scanning speed so as to obtain the desired S / N of the operator.

[0083] Normally, when the input field is to be displayed each time the scanning speed is input, it is necessary to move the mouse to the button. On the other hand, according to the charged particle beam system 100 configured to execute the flowchart illustrated in FIG. 11, the labor of moving the mouse can be reduced and the operation can be simplified.

Example

[0084] FIG. 12 is a diagram showing a configuration example of the user interface according to Example 4. FIG. 13 is a flowchart for explaining the optical axis adjustment process using the user interface illustrated in FIG. 12.

[0085] When the operator selects (sets) the optical axis adjustment scanning (selection) area 180 (Aw′) using the selection device (pointing device or the like) 133 (step 1301), the integrated computer 130 accepts the selection (setting), registers the shape and position of the optical axis adjustment scanning (selection) area 180 in the internal memory, and uses it as the scanning area during subsequent optical axis adjustment (step 1302).

[0086] The integrated computer 130 calculates the frame time based on the range of the optical axis scanning (selection) area 180 and the scanning speed during optical axis adjustment (step 1303).

[0087] The integrated computer 130 displays an input field 181 where the frame time can be input on the image display device 132 together with the frame designating the optical axis adjustment scanning (selection) area 180 selected by the operator. Note that the input field 181 may be automatically displayed together with the frame designating the optical axis adjustment scanning (selection) area 180, or may be manually displayed by a simple operation (mouse click or keyboard key input) associated with the operation of the selection device (pointing device or the like) 133 for designating the optical axis adjustment scanning (selection) area 180.

[0088] The S / N ratio of the image depends on the scanning speed, and since the frame time depends on the scanning speed, the S / N ratio of the image can be adjusted by the frame time. The operator observes the S / N ratio within the registered scanning (selection) area 180 for optical axis adjustment, determines whether to use the default value of the frame time for optical axis adjustment or change the default value and use the desired input value for optical axis adjustment, and inputs an instruction to the integrated computer 130. When the instruction by the operator indicates using the default value as the frame time (No in step 1305), the integrated computer 130 causes the process to proceed to step 1308. Also, when the instruction by the operator indicates using the desired input value as the frame time (Yes in step 1305), the integrated computer 130 causes the process to proceed to step 1306.

[0089] When the operator inputs the frame time into the input field 181 so that the S / N ratio becomes an appropriate value, the integrated computer 130 accepts the input value (step 1306) and applies it (step 1307).

[0090] The integrated computer 130 controls each optical element (scanning deflector, objective lens, alignment deflector, etc.) provided in the charged particle beam apparatus so as to perform optical axis adjustment by setting the input value (desired value of the operator) or the default value of the frame time as a parameter.

[0091] As described above, according to Example 4, by using the default value for the input value of the frame time, the operator can be saved the trouble of inputting the frame time. Also, by enabling the operator to arbitrarily set the frame time, it becomes possible to set the frame time so as to obtain the desired S / N ratio.

[0092] Normally, it is necessary to move the mouse to the button for displaying the input field for changing the image S / N ratio each time. On the other hand, according to the charged particle beam system configured to execute the flowchart illustrated in FIG. 13, the labor of moving the mouse can be reduced and the operation can be simplified.

Example

[0093] Example 5 will describe a charged particle beam system 100 having a function of notifying an operator whether or not the setting is appropriate based on the setting of the wobbler scanning area 152.

[0094] If the wobbler scanning area 152 is not set within a region having substantially the same height as the observation region, it may not be possible to appropriately evaluate image shaking. Further, if there is no edge or the like capable of specifying positions in at least two directions (x and y directions) within the field of view, it is not possible to evaluate two-dimensional image shaking.

[0095] When the wobbler scanning area 152 is set, it is possible to determine whether the setting is appropriate or not from the evaluation of the signal amount inside the area and the evaluation of the presence or absence of an edge using image processing. For example, if the integrated computer 130 notifies the operator by generating an error message notifying the result or changing the color of the frame of the area 152, it is possible to shorten the working time until the appropriate conditions are set.

[0096] For example, after the area 152 in FIG. 4 is set and an image is formed by scanning the area with a beam, if the obtained signal amount (secondary electron detection amount) is small, sufficient contrast may not be obtained. Therefore, when the signal amount is equal to or less than a predetermined value (a preset threshold value), the integrated computer 130 evaluates the output of the detector 108 and displays a message prompting to lower the scanning speed, for example, or displays a message (warning) prompting a response to increase the signal amount (for example, increasing the beam current). Thereby, the operator can recognize that wobbling may fail and can promptly perform an appropriate setting.

[0097] Furthermore, even if there are no edges or the like for evaluating image shake within the region 152, or if they are insufficient, wobbling may fail. In such a case, the integrated computer 130 may display a message prompting to reset the scanning region to a position where there is an object with clear contrast. Also, the integrated computer 130 may notify the operator of the possibility of wobbling failure by setting the color of the frame of the region 152 to a color indicating a warning (such as yellow or red (green display if the setting is appropriate)). Whether the contrast in the X direction and the contrast in the Y direction are clear may be determined, for example, by creating luminance profiles in two directions and determining whether the luminance difference between the maximum luminance and the minimum luminance is equal to or greater than a predetermined value, or by other contrast evaluation methods.

[0098] Also, when a stripe pattern occurs within the region 152, the evaluation using wobbling may fail. When the region 152 is determined, the initial value of the frame time is determined accordingly. Therefore, for example, the integrated computer 130 determines whether "frame time < wobble time (initial value)", and when this condition is not satisfied, it can notify that the proper setting has not been made by performing at least one of displaying a message prompting to increase the scanning time (scanning speed) (or increase the wobble time) and displaying a different display (identification display) from when the region 152 is properly set. Also, as a method for determining the presence or absence of a stripe pattern, the integrated computer 130 evaluates the spatial frequency in the Y direction (vertical direction) of the region 152, and determines whether the presence or absence of a stripe pattern by determining whether regions with low spatial frequency (regions out of focus with a blurred image) and regions with high spatial frequency (regions in focus where the structure of the sample is clearly represented) appear alternately.

[0099] As described above, since the initial generation conditions of the image required for wobbling are determined by the setting of the region 152, it is possible to quickly perform an appropriate setting by evaluating the suitability of the image in that state and outputting an appropriate message.

[0100] Also, it is conceivable to prohibit settings that would cause stripe patterns to be mixed into area 152 or that would affect proper image evaluation. FIG. 14 is a diagram showing a configuration example of a wobbler condition setting screen (GUI). In the wobbler condition setting screen illustrated in FIG. 14, the check box for the frame time is selected, but the input is prohibited so that conditions C and D cannot be selected (checked). The integrated computer 130 displays on the GUI screen so as not to allow selection of image generation conditions that would cause stripe patterns to be mixed into area 152. By doing so, it becomes possible to prevent image generation that may reduce the accuracy of axis misalignment evaluation.

[0101] (3) Others (v) The functions of the present embodiment can also be realized by software program codes. In this case, a storage medium recording the program codes is provided to a system or device, and a computer (or CPU or MPU) of the system or device reads the program codes stored in the storage medium. In this case, the program codes themselves read from the storage medium realize the functions of the above-described embodiment, and the program codes themselves and the storage medium storing them constitute the present disclosure. As a storage medium for supplying such program codes, for example, a flexible disk, CD-ROM, DVD-ROM, hard disk, optical disk, magneto-optical disk, CD-R, magnetic tape, non-volatile memory card, ROM, etc. are used.

[0102] Also, based on the instructions of the program codes, an OS (operating system) running on the computer, etc. may perform part or all of the actual processing, and the functions of the above-described embodiment may be realized by such processing. Further, after the program codes read from the storage medium are written into the memory on the computer, based on the instructions of the program codes, a CPU of the computer, etc. may perform part or all of the actual processing, and the functions of the above-described embodiment may be realized by such processing.

[0103] Furthermore, by distributing the program code of the software that realizes the functions of the embodiment via a network, it can be stored in a storage means such as a hard disk or memory of a system or device, or a storage medium such as a CD-RW or CD-R, and when in use, a computer (or CPU or MPU) of the system or device reads and executes the program code stored in the storage means or the storage medium.

[0104] Note that the processes and technologies described herein are not essentially related to any specific device and can also be implemented by an appropriate combination of components. Furthermore, a dedicated device may be constructed to execute the steps of the method described herein. Also, by appropriately combining a plurality of components disclosed in this embodiment, various technical elements can be formed. For example, some components may be deleted from all the components shown in the embodiment. Although the present disclosure has been described in relation to specific examples, these are for ease of understanding rather than for limitation. Those of ordinary skill in the art will readily appreciate that there are numerous combinations of hardware, software, and firmware suitable for implementing the technology of the present disclosure. For example, the described software can implement the technology of the present disclosure in a wide range of programming or scripting languages such as assembler, C / C++, perl, Shell, PHP, Java (registered trademark), etc.

[0105] Furthermore, in the above-described embodiment, the control lines and information lines show those considered necessary for explanation, and not necessarily all control lines and information lines are shown on the product. All the components may be interconnected.

[0106] In addition, those of ordinary skill in the art can clearly understand other implementations of the present disclosure from the consideration of the specification and embodiments of the present disclosure disclosed herein. The description content and specific examples in the specification are merely typical, and the scope and spirit of the present disclosure are shown in the following claims.

Explanation of Symbols

[0107] 101 Electron beam source 102 Alignment deflector 102a X alignment deflector 102b Y alignment deflector 103 Focusing lens 104 Objective lens 105 Scanning deflector 107 Electron beam 108 Detector 111 Electron beam source control unit 112 Alignment deflector control unit 113 Focusing lens control unit 114 Objective lens control unit 115 Scanning deflector control unit 121 Vacuum chamber 122 Sample stage 123 Sample 130 Integrated computer 131 Controller 132 Image display device 133 Selection device 134 Wobbler condition adjustment unit 151 Initial screen 152 Scanning area for wobbler 163 Image movement 170 Input field 180 Scanning (selection) area for optical axis adjustment 181 Input field

Claims

1. A charged particle beam column having a scanning deflector that scans a beam emitted from a charged particle source, an optical element that adjusts the beam, and an adjustment deflector that adjusts the trajectory of the beam incident on the optical element, and one or more computer subsystems connected to the charged particle beam column and controlling the scanning deflector and the adjustment deflector, wherein the one or more computer subsystems include a user interface configured to display an image output from the charged particle beam column and a partial region of the image selected by a user, the one or more computer subsystems periodically change the optical conditions of the optical element, generate an image based on a signal output from the charged particle beam column when the optical conditions of the optical element are periodically changed, and display, on the user interface, an input unit for allowing the user to set at least one of the generated image, the partial region, a first parameter related to the scanning speed of the scanning deflector, or a second parameter related to the changing speed of the optical element, the one or more computer subsystems, after one of the first parameter and the second parameter is set, identify a parameter that does not satisfy a predetermined condition among the other parameters and display it on the user interface in a charged particle beam system.

2. In claim 1, the one or more computer subsystems display, on the user interface, an image of a region wider than the partial region and an image of the partial region superimposed thereon in a charged particle beam system.

3. In claim 2, the image of the partial region and the image of the region wider than the partial region are obtained by different scans of the scanning deflector in a charged particle beam system.

4. In claim 1, the one or more computer subsystems are configured to calculate a scanning time per frame based on the partial region set on the user interface and the first parameter in a charged particle beam system.

5. In claim 4, The charged particle beam system, wherein the one or more computer subsystems are configured to generate an alarm when the change time of one cycle of the optical element is shorter than the scanning time per frame.

6. In claim 4, the charged particle beam system, wherein the one or more computer subsystems are configured to cause the user interface to display a message prompting to increase the scanning speed when the change time of one cycle of the optical element is shorter than the scanning time per frame.

7. In claim 4, the charged particle beam system, wherein the one or more computer subsystems are configured to cause the user interface to display a message prompting to slow down the change time of one cycle of the optical element when the change time of one cycle of the optical element is shorter than the scanning time per frame.

8. In claim 4, the charged particle beam system, wherein the user interface permits at least one input of the first parameter and the second parameter when the change time of one cycle of the optical element is longer than the scanning time per frame, and prohibits at least one input of the first parameter and the second parameter when the change time of one cycle of the optical element is shorter than the scanning time per frame.

9. A charged particle beam system comprising a scanning deflector that scans a beam emitted from a charged particle source, an optical element that adjusts the beam, and an adjustment deflector that adjusts the trajectory of the beam incident on the optical element, and one or more computer subsystems connected to the charged particle beam column and controlling the scanning deflector and the adjustment deflector, wherein the one or more computer subsystems include a user interface configured to display an image output from the charged particle beam column and a partial region of the image selected by the user. The charged particle beam system is configured such that at least one of the one or more computer subsystems controls at least one of the scanning deflector and the optical element so that a change time for one cycle of the optical element in the partial region is longer than a scanning time per frame, based on relationship information including a scanning speed of the scanning deflector and a change speed of the optical element.

10. In claim 9, the one or more computer subsystems are configured to display, on the user interface, an input unit for allowing a user to set at least one of the image, a partial region of the image, a first parameter related to a scanning speed of the scanning deflector, or a second parameter related to a change speed of the optical element, and is configured to determine the other of the first parameter or the second parameter based on one of the set first parameter or second parameter and the relationship information.

Images