Charged particle beam device

Abstract

The present invention provides a technique that allows a cross section of a sample to be processed, while suppressing a curtaining effect. A charged particle beam device 100 is provided with: a stage 6 capable of mounting a sample 14; an ion beam tube 2 capable of applying an ion beam IB to the sample 14; and a curtaining effect prediction means for predicting a direction of the application of the ion beam IB that can suppress the curtaining effect when the cross section of the sample 14 is processed with the ion beam IB.

Description

Charged particle beam device

[0001] The present invention relates to a charged particle beam device, and more particularly to a charged particle beam device capable of processing a sample by irradiating an ion beam.

[0002] In the failure analysis of semiconductor devices, an observation sample is prepared, and an image of the failure location is acquired using a scanning electron microscope (SEM) or a transmission electron microscope (TEM). For preparing an observation sample, an FIB-SEM device capable of irradiating a focused ion beam (FIB) is generally used.

[0003] For example, Patent Document 1 discloses a method of obtaining cross-sectional information of a sample and performing cross-sectional processing with an ion beam while changing the irradiation amount of the ion beam based on the cross-sectional information. By this method, even when there are a plurality of substances with different hardnesses in the sample, flat cross-sectional processing can be performed with a uniform etching rate.

[0004] Japanese Patent Application Laid-Open No. 2015-109263

[0005] In recent years, the development of semiconductor devices having a complex three-dimensional structure with a layered structure has progressed. Therefore, a technique capable of suppressing the curtaining effect is required when performing continuous cross-sectional processing of a sample with a charged particle beam device such as an FIB-SEM device. Other problems and novel features will become apparent from the description of this specification and the accompanying drawings.

[0006] Among the embodiments disclosed in the present application, the outline of representative ones will be briefly described as follows.

[0007] A charged particle beam device according to an embodiment includes a stage on which a sample can be mounted, an ion beam column capable of irradiating an ion beam onto the sample, and curtaining effect prediction means for predicting an irradiation direction of the ion beam capable of suppressing a curtaining effect when processing a cross-section of the sample with the ion beam.

[0008] According to one embodiment, the cross-section of a sample can be processed while suppressing the curtaining effect.

[0009] This is a schematic diagram showing the charged particle beam apparatus in Embodiment 1. This is a schematic diagram showing the sample in Embodiment 1. This is a schematic diagram showing the BSE images of each layer of the sample in Embodiment 1. This is a flowchart showing each step included in the curtaining effect suppression means in Embodiment 1. This is a schematic diagram showing the state in Embodiment 1 where a part of the BSE image is selected as a selected region and line integration is performed. This is a graph showing the relationship between the position of the selected region and the line integration value of the brightness of the selected region in Embodiment 1. This is a schematic diagram showing the state in Embodiment 1 where the selected region is rotated from 0 degrees to 90 degrees. This is a graph showing the relationship between the rotation angle of the selected region and a plurality of dispersion values ​​corresponding to a predetermined rotation angle in Embodiment 1. This is a flowchart showing each step included in the sample processing method in Embodiment 1. This is a schematic diagram showing the state in Embodiment 1 where a part of the BSE image of another layer is selected as another selected region and line integration is performed. This is a schematic diagram showing the state in Embodiment 1 where another selected region is rotated from 0 degrees to 90 degrees. This is a graph showing the relationship between the rotation angle of another selected region and a plurality of dispersion values ​​corresponding to a predetermined rotation angle in Embodiment 1. This is a graph created by superimposing Figure 8 and Figure 12 in Embodiment 1. This is the GUI screen used when performing grouping in Embodiment 1. This is a schematic diagram showing how the stage is rotated when changing the irradiation direction of the ion beam in Embodiment 1. This is a schematic diagram showing cross-sectional design information and material density information in Embodiment 2. This is the GUI screen in Embodiment 3.

[0010] The embodiments will be described in detail below with reference to the drawings. In all the drawings used to describe the embodiments, the same reference numerals are used for members having the same function, and repeated descriptions of them will be omitted. In addition, in the following embodiments, descriptions of the same or similar parts will not be repeated unless it is particularly necessary.

[0011] Furthermore, the X, Y, and Z directions described in this application intersect and are orthogonal to each other. In this application, the Z direction is described as the vertical direction or depth direction of a certain structure.

[0012] (Embodiment 1) <Charged Particle Beam Apparatus> Figure 1 is a schematic diagram showing the charged particle beam apparatus 100 in Embodiment 1. The charged particle beam apparatus 100 is, for example, a FIB-SEM apparatus.

[0013] As shown in Figure 1, the charged particle beam apparatus 100 comprises a sample chamber 1, an ion beam tube 2, an electron beam tube 4, a stage 6, a signal detector 7, an integrated control device C0, an ion beam control device C1, an electron beam control device C2, a stage control device C3, and an image generation device C4. The ion beam tube 2 and the electron beam tube 4 are arranged orthogonally to each other.

[0014] The sample 14 used in Embodiment 1 is, for example, a thin piece on which a part of a semiconductor device is formed. The sample 14 includes a semiconductor substrate, a semiconductor element such as a transistor formed on the semiconductor substrate, and a plurality of wirings formed on the semiconductor element.

[0015] The sample chamber 1 is fitted with an ion beam tube 2 capable of irradiating the sample 14 with an ion beam IB. The ion beam tube 2 includes all the necessary components of an FIB device, such as an ion source 3 for generating the ion beam IB, a lens for focusing the ion beam IB, and a deflection system for scanning and shifting the ion beam IB.

[0016] The ion beam control device C1 is electrically connected to the ion beam tube 2 and controls the operation of the ion beam tube 2. For example, the irradiation of the ion beam IB from the ion source 3 and the driving of the deflection system are controlled by the ion beam control device C1.

[0017] The sample chamber 1 is fitted with an electron beam tube 4 capable of irradiating the sample 14 with an electron beam EB1. The electron beam tube 4 includes all the necessary components of a SEM device, such as an electron source 5 for generating the electron beam EB1, a lens for focusing the electron beam EB1, and a deflection system for scanning and shifting the electron beam EB1.

[0018] The electron beam control device C2 is electrically connected to the electron beam tube 4 and controls the operation of the electron beam tube 4. For example, the generation of the electron beam EB1 from the electron source 5 and the driving of the deflection system are controlled by the electron beam control device C2.

[0019] A stage 6 is provided inside the sample chamber 1. The stage 6 can accommodate a sample 14. The stage control device C3 is electrically connected to the stage 6 and controls the operation of the stage 6. With the sample 14 loaded, the stage 6 can be moved planar, vertically, rotated, and tilted by the stage control device C3.

[0020] A signal detector 7 is provided inside the sample chamber 1. The signal detector 7 can detect secondary electrons or backscattered electrons emitted from the sample 14 as a signal EB2 when the sample 14 is irradiated with the electron beam EB1.

[0021] The image generation device C4 is electrically connected to the signal detector 7 and controls the operation of the signal detector 7. The image generation device C4 includes a processing circuit that performs calculations on the signal EB2 detected by the signal detector 7 and converts it into an image. Therefore, the image generation device C4 can convert the signal EB2 into an image of the sample 14 (SEM image, BSE image).

[0022] The integrated control unit C0 is a processing unit that includes a semiconductor integrated circuit, such as a CPU. The integrated control unit C0 is electrically connected to and controls each of the ion beam control unit C1, electron beam control unit C2, stage control unit C3, and image generation unit C4. Therefore, it can be said that the control performed by each unit C1 to C4 is performed by the integrated control unit C0. For this reason, the integrated control unit C0 is sometimes simply referred to as the "control unit".

[0023] Furthermore, the integrated control unit C0 includes a computer 8. The computer 8 includes a curtaining effect prediction module 9, an angle change judgment module 10, and a storage device 11. The input device 12 and the display device 13 are electrically connected to the computer 8.

[0024] The input device 12 is a device for the operator to input instructions such as inputting information about the sample 14, changing the irradiation conditions of the ion beam IB and electron beam EB1, and changing the position of the stage 6. The input device 12 is, for example, a keyboard or mouse. The display device 13 displays a GUI screen, etc. On the GUI screen, the input of various instructions from the input device 12 can be confirmed, and acquired SEM images and BSE images can also be confirmed.

[0025] As will be explained in detail later, the charged particle beam apparatus 100 includes a curtening effect prediction means for predicting the irradiation direction of the ion beam IB that can suppress the curtening effect when processing the cross-section of the sample 14 with the ion beam IB. The curtening effect prediction means is performed using a curtening effect prediction module 9 and is based on a BSE image of the cut cross-section of the sample 14, or on the cross-sectional design information and material density information of the sample 14.

[0026] The angle change determination module 10 determines whether or not to change the incident direction of the ion beam IB when performing continuous cross-sectional processing of the sample 14 by ion beam IB irradiation, based on the prediction results of the curtaining effect prediction means.

[0027] The storage device 11 is, for example, a hard disk or flash memory. Various types of information obtained by the charged particle beam apparatus 100 can be stored in the storage device 11 and read from the storage device 11. For example, the storage device 11 stores SEM images and BSE images of the sample 14, as well as various types of information obtained by the curtaining effect prediction module 9 and the angle change judgment module 10.

[0028] Computer 8 can reflect information from the curtening effect prediction module 9, the angle change judgment module 10, and the storage device 11 to the integrated control device C0. As a result, the integrated control device C0 can control the operation of the stage 6 and suppress the curtening effect when irradiating the sample 14 with the ion beam IB.

[0029] As shown in Figure 2, the sample 14 includes layers 14A and 14B, each having a predetermined thickness. Layer 14B is located at a different depth than layer 14A and has a different cross-sectional structure. After irradiating the sample 14 with an ion beam IB and cutting the sample 14, the sample 14 is irradiated with an electron beam EB1. The backscattered electrons emitted from the sample 14 are detected as a signal EB2 by a signal detector 7, and the signal EB2 can be converted into a BSE image of the sample 14 by an image generation device C4.

[0030] Figure 3 shows BSE images 21 of a cross-section contained in layer 14A and BSE images 22 of a cross-section contained in layer 14B.

[0031] <Curtening Effect Prediction Means> The curtening effect prediction means in Embodiment 1 will be described below with reference to Figure 4. Steps S1 to S8 included in the curtening effect prediction means will be described below as shown in Figure 4, but Figures 5 to 8 will be used as needed.

[0032] In step S1, after machining the sample 14, an electron beam EB1 is irradiated onto the sample 14 to obtain a BSE image of the machined cross-section of the sample 14. Here, an example of a BSE image 21 of a cross-section contained in layer 14A of the sample 14 shown in Figure 3 is presented.

[0033] In step S2, as shown in Figure 5, the curtaining effect prediction module 9 selects a portion of the acquired BSE image 21 as a selected region 23. The selected region 23 is, for example, rectangular. Here, the size of the selected region 23 is such that it does not extend beyond the BSE image 21 even when the selected region 23 is rotated.

[0034] In step S3, as shown in Figure 5, the curtaining effect prediction module 9 performs line integration of the brightness of the selected region 23 using multiple lines 24 in the x-axis direction on the selected region 23, and obtains the graph shown in Figure 6. Figure 6 is a graph 25 showing the relationship between the position of the selected region 23 in the y-axis direction perpendicular to the x-axis direction and the line integration value of the brightness of the selected region 23.

[0035] In step S4, as shown in Figure 6, the curtaining effect prediction module 9 acquires graph 25, and then, based on graph 25, calculates the average value 26 of all lines 24 and calculates the luminance variance value 27.

[0036] In step S5, as shown in Figure 7, the curtaining effect prediction module 9 rotates the selected area 23 from 0 degrees to 90 degrees. Furthermore, by repeating steps S3 and S4 for each predetermined rotation angle, multiple variance values ​​27 corresponding to the predetermined rotation angle are calculated. The predetermined rotation angle is arbitrary, but for example, it is 1 degree.

[0037] In step S6, the curtening effect prediction module 9 determines whether the selected area 23 has rotated 90 degrees. If it has rotated 90 degrees (YES), the next step is step S7. If it has not rotated 90 degrees (NO), step S5 is repeated.

[0038] In step S7, as shown in Figure 8, the curtaining effect prediction module 9 acquires a graph 28 showing the relationship between the rotation angle of the selected region 23 and a plurality of variance values ​​27 corresponding to a predetermined rotation angle. Since the rotation angle is the angle from the horizontal axis of the acquired BSE image 21 of the cross-section of the sample 14, the rotation angle can be considered as the irradiation direction of the ion beam IB.

[0039] In step S8, the curtaining effect prediction module 9 identifies a specific variance value that is relatively low among several variance values ​​27, based on the graph 28. Next, the curtaining effect prediction module 9 determines a specific rotation angle 29a corresponding to the specific variance value as the irradiation direction of the ion beam IB when processing the cross-section of the sample 14.

[0040] The curtaining effect is caused by the difference in the sputtering rate on the scanning line of the ion beam IB. Since the sputtering rate is due to the material density, in the BSE image, a contrast according to the material density can be obtained. That is, the luminance of the BSE image is correlated with the sputtering rate. A large dispersion value of the luminance means a large difference in the sputtering rate and means that the curtaining effect is likely to occur.

[0041] Therefore, in the graph 28, by selecting a specific dispersion value that is a relatively low value among the plurality of dispersion values 27, the specific rotation angle 29a corresponding to the specific dispersion value can be selected as the irradiation direction of the ion beam IB that can suppress the curtaining effect.

[0042] Also, in the graph 28, there are provided an allowable dispersion value 31 that is a value higher than the specific dispersion value and is set to a value considering the variation in the irradiation direction of the ion beam IB, and ranges 30a, 30b, 30c of the allowable rotation angle corresponding to the allowable dispersion value 31.

[0043] In the graph 28, there may be a plurality of specific rotation angles 29a, 29b, 29c corresponding to a plurality of specific dispersion values and ranges 30a, 30b, 30c of a plurality of allowable rotation angles. In that case, the specific rotation angle 29a included within the widest range 30a of the plurality of allowable rotation angles is determined as the irradiation direction of the ion beam IB that can suppress the curtaining effect.

[0044] For example, when actually processing a sample using the ion beam IB, due to a misalignment of the sample mounted on the stage 6 or the like, the irradiation direction of the ion beam IB may deviate from the optimal angle. In such a case, as a location where the influence of the curtaining effect is small, the widest range of the allowable rotation angle is selected. When comparing the ranges 30a, 30b, 30c of the plurality of allowable rotation angles, since the range 30a of the allowable rotation angle is the widest, by setting the specific rotation angle 29a as the irradiation direction of the ion beam IB, the influence of the curtaining effect can be most suppressed.

[0045] Thus, by using the curtaining effect prediction means in Embodiment 1, it is possible to predict the irradiation direction of the ion beam IB that can suppress the curtaining effect. Since the cross-section of the sample is processed from the predicted irradiation direction of the ion beam IB, the curtaining effect can be suppressed.

[0046] <Sample processing method> The sample processing method in Embodiment 1 will be described below with reference to FIG. 9. Hereinafter, as shown in FIG. 9, steps S11 to S18 included in the sample processing method will be described, and FIGS. 10 to 15 will be used as necessary.

[0047] In Embodiment 1, the sample 14 shown in FIG. 2 and the sample 50 having the same structure as the sample 14 are prepared in advance. After determining the optimal irradiation direction of the ion beam IB when processing each cross-section using the sample 14, continuous cross-section processing of the sample 50 is performed by the ion beam IB.

[0048] In step S11, continuous cross-section processing of the sample 14 is performed by the ion beam IB, and by irradiating each cross-section with the electron beam EB1, a BSE image of each cross-section is acquired. The BSE image of each cross-section and the depth information of each cross-section are linked to each other and stored in the storage device 11 as a dataset.

[0049] In step S12, the operator reads out the dataset of the sample 14 from the storage device 11 and selects a rectangular area at the location where the curtaining effect is to be prevented among the BSE images. The curtaining effect prediction module 9 selects the location selected by the operator as the selection area 23. That is, the curtaining effect prediction module 9 selects a part of each BSE image as the selection area 23.

[0050] In step S13, steps S3 to S8 of the curtaining effect prediction means are performed for each BSE image.

[0051] In the following explanation, to make the explanation easier to understand, we will use two examples of BSE images with different depths: BSE image 21 of a cross-section contained in layer 14A of sample 14, and BSE image 22 of a cross-section contained in layer 14B of sample 14. The processing for BSE image 21 is the same as that described in steps S3 to S8 (Figures 5 to 8). The processing for BSE image 22 is also the same as that described in steps S3 to S8.

[0052] As shown in Figure 10, a portion of the BSE image 22 is selected as a selection region 23, which is the same region as the selection region 23 of the BSE image 21. Line integration is performed on the brightness of the selection region 23 of the BSE image 22 along the x-axis. Subsequently, although not shown in the figure, a graph like that shown in Figure 6 is obtained and the variance value is calculated. That is, a graph is obtained that shows the relationship between the position of the selection region 23 in the y-axis direction and the line integration value of the brightness of the selection region 23, and the variance value is calculated based on the graph.

[0053] As shown in Figure 11, the selected region 23 of the BSE image 22 is rotated from 0 to 90 degrees, and multiple variance values ​​corresponding to a predetermined rotation angle are calculated. As shown in Figure 12, a graph 32 is obtained showing the relationship between the rotation angle of the selected region 23 of the BSE image 22 and the multiple variance values ​​corresponding to the predetermined rotation angle. Based on the graph 32, a specific variance value that is relatively low among the multiple variance values ​​is identified, and a specific rotation angle 33a corresponding to the specific variance value is determined as the irradiation direction of the ion beam IB when processing the cross section contained in the layer 14B of the sample 14.

[0054] Furthermore, Graph 32, similar to Graph 28 in Figure 8, includes an allowable variance value 31 and a range of allowable rotation angles 34a corresponding to the allowable variance value 31. If there are multiple ranges of allowable rotation angles in Graph 32 other than the range of allowable rotation angles 34a, the specific rotation angle included in the widest range of allowable rotation angles is determined as the irradiation direction of the ion beam IB that can suppress the curtaining effect.

[0055] The processing results for BSE images 21, such as graph 28, and the processing results for BSE images 22, such as graph 32, are stored in the storage device 11.

[0056] In step S14, the angle change determination module 10 reads a graph from the storage device 11 showing the relationship between the rotation angle of the selected region 23 and a plurality of variance values ​​corresponding to a predetermined rotation angle for each BSE image, and compares these. For example, as shown in Figure 13, the angle change determination module 10 reads the graph 28 of the BSE image 21 and the graph 32 of the BSE image 22 from the storage device 11 and compares them.

[0057] In step S15, the angle change determination module 10 determines whether or not an angle change is necessary for the irradiation direction of the ion beam IB, based on whether or not the range of permissible rotation angles for each BSE image overlap.

[0058] For example, we will explain how to determine whether or not it is necessary to change the angle of the ion beam IB irradiation direction when switching from a cross-section contained in layer 14A to a cross-section contained in layer 14B.

[0059] As shown in Figure 13, the range of permissible rotation angles 30a for the BSE image 21 and the range of permissible rotation angles 34a for the BSE image 22 do not overlap. In this case, it is necessary to change the irradiation direction of the ion beam IB from the irradiation direction corresponding to a specific rotation angle 29a to the irradiation direction corresponding to a specific rotation angle 33a.

[0060] On the other hand, if the range of permissible rotation angles 30a and 34a overlap, the ion beam IB is irradiated onto layer 14B without changing the irradiation direction of the ion beam IB in layer 14A.

[0061] When there are many BSE images, those with the same ion beam (IB) irradiation direction can be grouped together. In other words, those with overlapping allowable rotation angle ranges can also be grouped together. When performing continuous cross-sectional processing of a sample, the number of groups corresponds to the number of times the ion beam (IB) irradiation direction is switched.

[0062] The BSE images and depth information for each cross-section are linked to each other and stored in the storage device 11. Therefore, by performing this grouping, when performing continuous cross-sectional machining of a sample, the work of determining whether the range of permissible rotation angles overlaps at regular depth intervals can be omitted, thereby shortening the work time required for continuous cross-sectional machining.

[0063] In step S15, as shown in Figure 14, the angle change determination module 10 groups graphs 42 showing the irradiation direction of the ion beam IB and multiple dispersion values ​​for all cross-sections of the sample 14 read from the storage device 11, and outputs the irradiation direction of the ion beam IB and depth information for each cross-section of the sample 14 in each group on the GUI screen 40.

[0064] Figure 14 shows the GUI screen (graphic user interface screen) 40 used when performing grouping. As shown in Figure 14, the GUI screen 40 is equipped with buttons 41 to display graphs and images, a button 43 to perform grouping, a data screen 44 to display the grouping results, a button 45 to display a graph showing the irradiation direction of the ion beam IB for each group and multiple dispersion values, and a button 46 to save the grouping results.

[0065] Button 41 allows the user to select one or more locations from slice No. 1 to No. n, and the corresponding locations are displayed as graph 42. Furthermore, after grouping in step S15, the locations selected as representative cross-sections within each group are marked. For example, slices No. 1 and k are grouped together, and slice No. k is selected as the representative ion beam IB irradiation direction for this group.

[0066] The button 43 for performing grouping includes an "Auto" button 47 and a "Manual" button 48. Pressing the "Auto" button 47 automatically groups the graphs 42 of all cross-sections of the sample 14 on the GUI screen 40. After entering the number of groupings, pressing the "Manual" button 48 groups the graphs 42 of all cross-sections of the sample 14 according to the number entered by the operator.

[0067] The data screen 44 displays the irradiation direction (optimal angle) of the ion beam IB for each group, the depth information of each cross-section of the sample 14, and the range of the allowable rotation angle. In step S16, the information shown on the data screen 44 can be saved to the storage device 11 by pressing button 46.

[0068] In step S17, as shown in Figure 15, continuous cross-sectional machining is performed on sample 50, which has the same structure as sample 14. During this process, the integrated control device C0 controls the rotation of the stage 6 based on the information in the storage device 11.

[0069] First, with the sample 50 mounted on the stage 6, when processing the cross-section contained in layer 14A of the sample 50 using the ion beam IB, the stage 6 is rotated so that the irradiation direction of the ion beam IB becomes the irradiation direction of a predetermined group, and then the sample 50 is irradiated with the ion beam IB.

[0070] After processing the cross-section contained in layer 14A of sample 50, when processing the cross-section contained in layer 14B of sample 50 using the ion beam IB, the irradiation direction of the group corresponding to the depth of that cross-section is determined based on the information in the storage device 11. If a change of group is necessary, that is, if the ranges of their respective allowable rotation angles do not overlap, the stage 6 is rotated so that the irradiation direction of the ion beam IB is changed to the irradiation direction of the other group, and then the ion beam IB is irradiated onto sample 50.

[0071] Furthermore, when processing other cross-sections in layer 14A of sample 50 using ion beam IB after processing a predetermined cross-section in layer 14A of sample 50, it may not be necessary to change the group. That is, if the ranges of their respective allowable rotation angles overlap, the ion beam IB is irradiated onto sample 50 without changing the irradiation direction of the ion beam IB.

[0072] As described above, in Embodiment 1, the cross-section of the sample 50 is processed from the irradiation direction of the ion beam IB predicted using the curtaining effect prediction means. Therefore, even if the sample 50 is a semiconductor device with a complex three-dimensional structure having a layered structure, the curtaining effect can be suppressed when performing continuous cross-sectional processing of the sample 50.

[0073] (Embodiment 2) The charged particle beam apparatus 100 in Embodiment 2 will be described below with reference to Figure 16. In the following description, the differences from Embodiment 1 will be mainly explained, and points that overlap with Embodiment 1 will not be explained.

[0074] In Embodiment 1, the irradiation direction of the ion beam IB that could suppress the curtaining effect was determined by utilizing the BSE image and the variance value of brightness. In Embodiment 2, instead of the BSE image and the variance value of brightness, the cross-sectional design information and material density information of the sample 14 are used.

[0075] Figure 16 shows cross-sectional design information 60 and material density information 61 of a sample 14, which were fabricated using, for example, CAD (Computer-Aided Design). The cross-sectional design information 60 and material density information 61 are stored in a storage device 11.

[0076] As described in Embodiment 1, differences in material density correlate with differences in sputtering rate and appear as contrast in the BSE image. That is, by providing material density information 61 as reference information to the cross-sectional design information 60 of the sample 14, the irradiation direction of the ion beam IB that can suppress the curtaining effect can be determined, similar to Embodiment 1.

[0077] In Embodiment 2, in steps S1 to S8 of Figure 4 of Embodiment 1 and steps S11 to S17 of Figure 9 of Embodiment 1, the BSE image is replaced with material density information 61, and the luminance variance value is replaced with the material density variance value. As a result, in Embodiment 2 as well, a graph showing the relationship between the rotation angle of the selected region and a plurality of variance values ​​corresponding to a predetermined rotation angle can be obtained, as shown in Figures 8, 12, and 13.

[0078] Therefore, in Embodiment 2 as well, by using the curtaining effect prediction means, the irradiation direction of the ion beam IB that can suppress the curtaining effect can be predicted. Since the cross-section of the sample is processed from this predicted ion beam IB irradiation direction, the curtaining effect can be suppressed when performing continuous cross-sectional processing of the sample.

[0079] Furthermore, in Embodiment 1, after determining the optimal irradiation direction of the ion beam IB when processing each cross-section using the sample 14, continuous cross-sectional processing of the sample 50 was performed using the ion beam IB.

[0080] In contrast, in Embodiment 2, the optimal irradiation direction of the ion beam IB when processing each cross-section is determined using the cross-sectional design information 60 and material density information 61 of the sample 14. Therefore, even if there is no sample 50 and only one sample 14 exists, the optimal irradiation direction of the ion beam IB can be determined, and continuous cross-sectional processing of the sample 14 can be performed using the ion beam IB.

[0081] (Embodiment 3) The charged particle beam apparatus 100 in Embodiment 3 will be described below with reference to Figure 17. In the following description, the differences from Embodiment 1 will be mainly explained, and points that overlap with Embodiment 1 will not be explained.

[0082] Embodiment 1 assumed the existence of a sample 50 having the same structure as sample 14. Embodiment 3 assumes the existence of only one sample 14, and that the cross-sectional design information and material density information of sample 14 cannot be obtained, as in Embodiment 2.

[0083] In this case, with the sample 14 mounted on the stage 6, when processing the cross section contained in layer 14A of the sample 14 using the ion beam IB, first, steps S1 to S8 of the curtaining effect prediction means are performed. Next, the stage 6 is rotated so that the irradiation direction of the ion beam IB becomes the irradiation direction determined by the curtaining effect prediction means, and processing of the cross section contained in layer 14A of the sample 14 is continued.

[0084] Subsequently, when the processed cross-section switches to a cross-section included in layer 14B, steps S1 to S8 of the curtaining effect prediction means are performed first for the cross-section included in layer 14B. Next, the stage 6 is rotated so that the irradiation direction of the ion beam IB becomes the irradiation direction determined by the curtaining effect prediction means, and processing of the cross-section included in layer 14B of the sample 14 is continued.

[0085] Figure 17 shows the GUI screen 70 in Embodiment 3. The GUI screen 70 is provided with a display screen 71 that shows the BSE image of the cross-section when the current ion beam IB irradiation direction was determined, and the BSE image of the current processing cross-section. The display screen 71 also displays the irradiation direction (optimal angle) of the ion beam IB predicted by the curtaining effect prediction means. Comparing these two BSE images can be used as a basis for deciding when to switch the irradiation direction of the ion beam IB.

[0086] The GUI screen 70 is equipped with a button 72 for automatically switching the irradiation direction of the ion beam IB, and a button 73 for the operator to confirm the recommended settings when a switch is recommended.

[0087] By pressing button 72, for example, when switching from a cross-section contained in layer 14A to a cross-section contained in layer 14B, steps S1 to S8 of the curtaining effect prediction means are automatically performed, and the processing of the cross-section is continued.

[0088] By pressing button 73, for example, when switching from a cross-section contained in layer 14A to a cross-section contained in layer 14B, a message box 74 is displayed recommending a change in the irradiation direction of the ion beam IB. After reviewing the message box 74, the operator can select whether or not to actually change the irradiation direction of the ion beam IB on the message box 74.

[0089] The GUI screen 70 is provided with buttons 75 for setting the range of the allowable rotation angle. Buttons 75 include an "Auto" button 76 and a "Manual" button 77. For example, referring to Figure 8, pressing the "Auto" button 76 automatically calculates the allowable variance value 31, which is expected to have little effect from the curtening effect, and automatically sets the recommended range of the allowable rotation angle 30a. Pressing the "Manual" button 77 sets the range of the allowable rotation angle according to the value entered by the operator.

[0090] The GUI screen 70 is provided with a button 78 for displaying a graph. By pressing the button 78, a graph like Figure 8 is displayed showing the BSE image of the cross-section when the irradiation direction of the ion beam IB, which is currently displayed on the display screen 71, is determined. One or more graphs can be displayed simultaneously. The area corresponding to the graph currently displayed on the display screen 71 is marked.

[0091] As described above, in Embodiment 3, even when only one sample 14 exists, the cross-section of the sample 14 is processed from the irradiation direction of the ion beam IB predicted by the curtaining effect prediction means, so the curtaining effect can be suppressed when performing continuous cross-sectional processing of the sample 14.

[0092] Although the present invention has been specifically described above based on the embodiments described above, the present invention is not limited to the embodiments described above and can be modified in various ways without departing from the spirit of the invention.

[0093] 100 Charged Particle Beam Apparatus 1 Sample Chamber 2 Ion Beam Tube 3 Ion Source 4 Electron Beam Tube 5 Electron Source 6 Stage 7 Signal Detector 8 Computer 9 Curtening Effect Prediction Module 10 Angle Change Judgment Module 11 Storage Device 12 Input Device 13 Display Device 14 Sample 14A, 14B Sample Layers 21, 22 BSE Image 23 Selected Region 24 Line 25 Graph 26 Mean Value 27 Variance Value 28 Graph 29a, 29b, 29c Specific Rotation Angle 30a, 30b, 30c Allowable Rotation Angle Range 31 Allowable Variance Value 32 Graph 33a Specific Rotation Angle 34a Allowable Rotation Angle Range 35 Graph 40 GUI Screen 41, 43, 45, 46, 47, 48 Button 42 Graph 44 Data screen 50 Sample 60 Cross-sectional design information 61 Material density information 70 GUI screen 71 Display screen 72, 73, 75, 76, 77, 78 Buttons 74 Message box C0 Integrated control unit (control unit) C1 Ion beam control unit C2 Electron beam control unit C3 Stage control unit C4 Image generation unit EB1 Electron beam EB2 Signal (secondary electrons, backscattered electrons) IB Ion beam

Claims

A stage capable of mounting a sample, An ion beam tube capable of irradiating the aforementioned sample with an ion beam, When processing the cross-section of the sample with the ion beam, a means for predicting the irradiation direction of the ion beam that can suppress the curtening effect is provided, A charged particle beam apparatus equipped with the following features. 　 In the charged particle beam apparatus according to claim 1, An electron beam tube capable of irradiating the aforementioned sample with an electron beam, A signal detector capable of detecting reflected electrons emitted from the sample as a signal when the sample is irradiated with the electron beam, An image generation device capable of generating a BSE image from the detected signal, Furthermore, The aforementioned curtaining effect prediction means is (a) A step of obtaining a first BSE image of the first cross section by irradiating the first cross section of the first sample with the electron beam, (b) A step of selecting a portion of the first BSE image as a first selected region, (c) A step of performing line integration of the brightness of the first selected region in a first direction on the first selected region, (d) A step of obtaining a first graph showing the relationship between the position of the first selected region in a second direction orthogonal to the first direction and the line integrated value of the brightness of the first selected region, and calculating a first variance value based on the first graph. (e) A step of rotating the first selected region from 0 degrees to 90 degrees and repeating step (c) and step (d) for each predetermined rotation angle to calculate a plurality of first variance values ​​corresponding to the predetermined rotation angle. (f) A step of obtaining a second graph showing the relationship between the rotation angle of the first selected region and the plurality of first variance values ​​corresponding to the predetermined rotation angle, (g) A step of identifying a first specific variance value which is a relatively low value among the plurality of first variance values ​​based on the second graph, and determining a first specific rotation angle corresponding to the first specific variance value as the first irradiation direction of the ion beam when processing the first cross section. A charged particle beam apparatus having the following features. 　 In the charged particle beam apparatus according to claim 2, The second graph includes a first allowable variance value which is higher than the first specific variance value and is set to a value that takes into account the variation in the irradiation direction of the ion beam, and a range of the first allowable rotation angle corresponding to the first allowable variance value. A charged particle beam apparatus in which, in step (g) above, if there are multiple ranges of the first specific rotation angles and multiple ranges of the first allowable rotation angles in the second graph, the first specific rotation angle that falls within the widest range of the first allowable rotation angles is determined as the first irradiation direction. 　 In the charged particle beam apparatus according to claim 2, The aforementioned curtaining effect prediction means is (h) A step of obtaining a second BSE image of the second cross-section by irradiating the second cross-section of the first sample, which has a different depth from the first cross-section, (i) A step of selecting a portion of the second BSE image as the second selected region, which is the same region as the first selected region. (j) A step of performing line integration of the brightness of the second selected region in the first direction on the second selected region, (k) A step of obtaining a third graph showing the relationship between the position of the second selected region in the second direction and the line integrated value of the brightness of the second selected region, and calculating a second variance value based on the third graph. (l) A step of rotating the second selection region from 0 degrees to 90 degrees and repeating step (j) and step (k) for each predetermined rotation angle to calculate a plurality of second variance values ​​corresponding to the predetermined rotation angle. (m) A step of obtaining a fourth graph showing the relationship between the rotation angle of the second selected region and the plurality of second variance values ​​corresponding to the predetermined rotation angle, (n) A step of identifying a second specific variance value which is a relatively low value among the plurality of second variance values ​​based on the fourth graph, and determining a second specific rotation angle corresponding to the second specific variance value as the second irradiation direction of the ion beam when processing the second cross section. A charged particle beam apparatus further possessing the following. 　 In the charged particle beam apparatus according to claim 4, A charged particle beam apparatus in which, with a second sample having the same structure as the first sample mounted on the stage, the stage is rotated so that the irradiation direction of the ion beam becomes the first irradiation direction, and then the ion beam is irradiated onto the second sample. 　 In the charged particle beam apparatus according to claim 5, The second graph includes a first allowable dispersion value which is higher than the first specific dispersion value and is set considering the variation in the irradiation direction of the ion beam, and a range of the first allowable rotation angle corresponding to the first allowable dispersion value. The fourth graph includes a second allowable variance value which is higher than the second specific variance value and is set considering the variation in the irradiation direction of the ion beam, and a range of the second allowable rotation angle corresponding to the second allowable variance value. A charged particle beam apparatus that, after processing the first cross-section of the second sample, and when processing the second cross-section of the second sample using the ion beam, rotates the stage so that the irradiation direction of the ion beam is changed from the first irradiation direction to the second irradiation direction if the range of the first allowable rotation angle and the range of the second allowable rotation angle do not overlap, and then irradiates the second sample with the ion beam. 　 In the charged particle beam apparatus according to claim 5, The second graph includes a first allowable dispersion value which is higher than the first specific dispersion value and is set considering the variation in the irradiation direction of the ion beam, and a range of the first allowable rotation angle corresponding to the first allowable dispersion value. The fourth graph includes a second allowable variance value which is higher than the second specific variance value and is set considering the variation in the irradiation direction of the ion beam, and a range of the second allowable rotation angle corresponding to the second allowable variance value. A charged particle beam apparatus that, after processing the first cross-section of the second sample, processes the second cross-section of the second sample using the ion beam, and if the range of the first allowable rotation angle and the range of the second allowable rotation angle overlap, irradiates the second sample with the ion beam without changing the irradiation direction of the ion beam from the first irradiation direction. 　 In the charged particle beam apparatus according to claim 2, A charged particle beam apparatus in which, with the first sample mounted on the stage, when processing the first cross section of the first sample using the ion beam, after performing steps (a) to (g) of the curtaining effect prediction means, the stage is rotated so that the irradiation direction of the ion beam becomes the first irradiation direction, and the processing of the first cross section is continued. 　 In the charged particle beam apparatus according to claim 1, The device further comprises a storage device for storing cross-sectional design information and material density information of the aforementioned sample. The aforementioned curtaining effect prediction means is (a) A step of acquiring first cross-sectional design information and first material density information corresponding to the first cross-section of the first sample from the storage device, (b) A step of selecting a part of the first cross-sectional design information as a first selected region, (c) A step of performing line integration of the material density of the first selected region in a first direction on the first selected region, (d) A step of obtaining a first graph showing the relationship between the position of the first selected region in a second direction orthogonal to the first direction and the line integrated value of the material density of the first selected region, and calculating a first variance value based on the first graph. (e) A step of rotating the first selected region from 0 degrees to 90 degrees and repeating step (c) and step (d) for each predetermined rotation angle to calculate a plurality of first variance values ​​corresponding to the predetermined rotation angle. (f) A step of obtaining a second graph showing the relationship between the rotation angle of the first selected region and the plurality of first variance values ​​corresponding to the predetermined rotation angle, (g) A step of identifying a first specific variance value which is a relatively low value among the plurality of first variance values ​​based on the second graph, and determining a first specific rotation angle corresponding to the first specific variance value as the first irradiation direction of the ion beam when processing the first cross section. A charged particle beam apparatus having the following features. 　 In the charged particle beam apparatus according to claim 9, The second graph includes a first allowable variance value which is higher than the first specific variance value and is set to a value that takes into account the variation in the irradiation direction of the ion beam, and a range of the first allowable rotation angle corresponding to the first allowable variance value. A charged particle beam apparatus in which, in step (g) above, if there are multiple ranges of the first specific rotation angles and multiple ranges of the first allowable rotation angles in the second graph, the first specific rotation angle that falls within the widest range of the first allowable rotation angles is determined as the first irradiation direction. 　 In the charged particle beam apparatus according to claim 9, The aforementioned curtaining effect prediction means is (h) A step of acquiring second cross-sectional design information and second material density information corresponding to a second cross-sectional area of ​​the first sample that has a different depth from the first cross-sectional area. (i) A step of selecting a part of the second cross-sectional design information as the second selection region which is the same region as the first selection region, (j) A step of performing line integration of the material density of the second selected region in the first direction on the second selected region, (k) A step of obtaining a third graph showing the relationship between the position of the second selected region in the second direction and the line integrated value of the material density of the second selected region, and calculating a second variance value based on the third graph. (l) A step of rotating the second selection region from 0 degrees to 90 degrees and repeating step (j) and step (k) for each predetermined rotation angle to calculate a plurality of second variance values ​​corresponding to the predetermined rotation angle. (m) A step of obtaining a fourth graph showing the relationship between the rotation angle of the second selected region and the plurality of second variance values ​​corresponding to the predetermined rotation angle, (n) A step of identifying a second specific variance value which is a relatively low value among the plurality of second variance values ​​based on the fourth graph, and determining a second specific rotation angle corresponding to the second specific variance value as the second irradiation direction of the ion beam when processing the second cross section. A charged particle beam apparatus having the following features. 　 In the charged particle beam apparatus according to claim 11, A charged particle beam apparatus in which, with the first sample mounted on the stage, the stage is rotated so that the irradiation direction of the ion beam is the first irradiation direction, and then the ion beam is irradiated onto the first sample. 　 In the charged particle beam apparatus according to claim 12, The second graph includes a first allowable dispersion value which is higher than the first specific dispersion value and is set considering the variation in the irradiation direction of the ion beam, and a range of the first allowable rotation angle corresponding to the first allowable dispersion value. The fourth graph includes a second allowable variance value which is higher than the second specific variance value and is set considering the variation in the irradiation direction of the ion beam, and a range of the second allowable rotation angle corresponding to the second allowable variance value. A charged particle beam apparatus that, after processing the first cross-section, when processing the second cross-section using the ion beam, rotates the stage so that the irradiation direction of the ion beam is changed from the first irradiation direction to the second irradiation direction if the range of the first allowable rotation angle and the range of the second allowable rotation angle do not overlap, and then irradiates the first sample with the ion beam. 　 In the charged particle beam apparatus according to claim 12, The second graph includes a first allowable dispersion value which is higher than the first specific dispersion value and is set considering the variation in the irradiation direction of the ion beam, and a range of the first allowable rotation angle corresponding to the first allowable dispersion value. The fourth graph includes a second allowable variance value which is higher than the second specific variance value and is set considering the variation in the irradiation direction of the ion beam, and a range of the second allowable rotation angle corresponding to the second allowable variance value. A charged particle beam apparatus that, after processing the first cross-section, irradiates the first sample with the ion beam without changing the irradiation direction of the ion beam from the first irradiation direction when processing the second cross-section using the ion beam, if the range of the first allowable rotation angle and the range of the second allowable rotation angle overlap.

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