Inspection method and charged particle beam apparatus

Abstract

Provided is an inspection method for inspecting the electrical characteristics of a pattern on a sample where a pattern 102 comprising a conductor or a semiconductor has been formed in a dielectric region 101. A secondary electron image is acquired by scanning a charged particle beam on the sample. A feature amount is calculated on the basis of a luminance value of a third region 113, which is higher in luminance than a second region, that spreads toward a first region 111 side from a boundary between the first region 111 corresponding to a dielectric region in the secondary electron image and a second region 112 corresponding to the pattern. The electrical characteristics of the pattern are inspected on the basis of the feature amount.

Description

Technical Field

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[0001] The present invention relates to a charged particle beam apparatus that irradiates a sample with a charged particle beam, and particularly to an inspection method and a charged particle beam apparatus for inspecting the electrical and material properties of a sample.

Background Art

[0002] A charged particle beam apparatus, for example, a scanning electron microscope (hereinafter abbreviated as SEM), can identify a fine pattern on the order of nanometers with a focused electron beam. One of the observation methods of SEM is the potential contrast method. Potential contrast is a contrast that reflects the difference in the surface potential of a sample and reflects the conductivity of the sample. A technique for inspecting electrical property defects of semiconductor devices using this potential contrast method has been put into practical use. In the inspection of electrical property defects, defective locations are specified using the difference in the luminance of the patterns in the SEM image. Here, luminance refers to the degree of brightness of the signal of an image or pixel acquired by the charged particle beam apparatus, and is sometimes referred to as lightness. For example, in a pattern with high conductivity, the potential is low, so the luminance is high, and in a pattern with low conductivity, the potential is high, so the luminance is low. Therefore, defective portions with different conductivities can be detected from the difference in the luminance of the image. As a technique for improving the inspection sensitivity of electrical property defects by the potential contrast method, Patent Document 1 discloses a method of setting a region for analyzing luminance in a sample including a plurality of patterns to enhance the detection sensitivity of electrical property defects.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] To improve the detection sensitivity of electrical defects in a sample, it is important to increase the change in image brightness in response to changes in the potential of the area or pattern being inspected. The brightness of an SEM image depends on the amount of secondary electrons emitted from the sample, and the amount of secondary electrons emitted depends on the material. In the electrical property inspection of semiconductors, the material of the pattern used to evaluate conductivity is often metal or semiconductor, and these materials generally emit few secondary electrons. Therefore, the brightness of patterns made of metals and semiconductors is low, and consequently, the change in brightness in response to changes in potential is also small, making it difficult to detect electrical defects with high sensitivity.

[0005] This invention was made to solve these problems and aims to provide a technology for highly sensitive inspection of the electrical properties and material properties of patterns composed of metals and semiconductors. [Means for solving the problem]

[0006] An inspection method according to one embodiment of the present invention is an inspection method for inspecting the electrical properties of a pattern made of a conductor or semiconductor formed in a dielectric region of a sample, wherein a charged particle beam is scanned over the sample to acquire a secondary electron image, a feature quantity is calculated based on the brightness value of a third region that is brighter than the second region and extends from the boundary between a first region corresponding to the dielectric region and a second region corresponding to the pattern in the secondary electron image toward the first region, and the electrical properties of the pattern are inspected based on the feature quantity. [Effects of the Invention]

[0007] The electrical characteristics of the pattern can be inspected with high sensitivity. Other challenges and novel features will become apparent from the description and accompanying drawings herein. [Brief explanation of the drawing]

[0008] [Figure 1] This is an example of a pattern in an observed sample. [Figure 2] Figure 1 shows a schematic SEM image of the pattern. [Figure 3]This diagram illustrates the mechanism by which the third region arises. [Figure 4] This flowchart shows an example of an inspection method. [Figure 5A] This is an example of a SE (schematic) image. [Figure 5B] This is an example of a BSE image (schematic diagram). [Figure 5C] This is the luminance profile of the BSE image. [Figure 5D] These are the first and second regions extracted from the BSE image. [Figure 6A] This is an example of extraction from the third domain. [Figure 6B] This is an example of superimposing the SE image and the third domain. [Figure 7A] This is an example of the configuration of the charged particle beam apparatus in Example 1. [Figure 7B] This is an example of a hardware configuration for an information processing device. [Figure 8] This is an example of a GUI. [Figure 9A] This is one example of how test results can be displayed. [Figure 9B] This is one example of how test results can be displayed. [Figure 10] This flowchart shows an example of a method for determining electron beam conditions. [Figure 11A] This diagram illustrates a method for determining electron beam conditions by changing the focusing conditions. [Figure 11B] This diagram illustrates a method for determining electron beam conditions by changing the focusing conditions. [Figure 12A] This diagram illustrates a method for determining electron beam conditions by changing the focusing conditions. [Figure 12B] This diagram illustrates a method for determining electron beam conditions by changing the focusing conditions. [Figure 13] This is an example of the configuration of the charged particle beam apparatus in Example 3. [Figure 14A] This is an example of an SE image (schematic diagram) obtained by varying the intermittence conditions of the electron beam. [Figure 14B]This is a diagram for explaining a method of extracting third region segmentation from SE images (schematic diagrams) obtained by varying the intermittent conditions of an electron beam. [Figure 14C] This is an example of a display method for inspection results. [Figure 15] This is an example of the device configuration of the charged particle beam apparatus of Example 4. [Figure 16A] This is an example of SE images (schematic diagrams) obtained by varying light irradiation conditions. [Figure 16B] This is a diagram for explaining a method of extracting third region segmentation from SE images (schematic diagrams) obtained by varying light irradiation conditions. [Figure 16C] This is an example of a display method for inspection results.

Embodiments for Carrying Out the Invention

[0009] A semiconductor device is composed of a pattern of a metal or semiconductor having conductivity and a dielectric region electrically insulated therefrom. Since the boundary of the dielectric region in contact with the pattern of the metal or semiconductor has the same potential as the potential of the pattern, a potential gradient is generated in the dielectric region. That is, the potential of the pattern is also reflected in the dielectric region in contact with the pattern of the metal or semiconductor. Generally, the amount of secondary electrons emitted from a dielectric is larger than that from a metal or semiconductor, and the sensitivity to potential is also higher. Therefore, in the inspection of the electrical characteristics of a pattern of a metal or semiconductor, by analyzing the change in the luminance of the dielectric region in contact with the pattern of the metal or semiconductor, the inspection of the electrical characteristics can be made highly sensitive.

[0010] Hereinafter, embodiments will be described with reference to the drawings. In the drawings, the same parts are denoted by the same reference numerals, and the redundant description thereof will be omitted as appropriate. It should be noted that the attached drawings are for facilitating the explanation and understanding of the invention, and there are points where the shapes, dimensions, ratios, etc. in each figure are different from those of the actual device.

Examples

[0011] The following examples show an example where an electron beam is used as the charged particle beam. However, it is not limited to an electron beam as long as it is a charged particle beam capable of forming a charge on the sample. When an electron beam is irradiated onto a sample, signal electrons are emitted from the sample. A SEM scans the sample surface by scanning it with an electron beam and detecting the signal electrons from the sample to create an image. The image obtained in this way is called an SEM image. Figure 1 shows an example of a sample pattern to be inspected. A cross-sectional view and a top view are shown for the normal pattern 100N and the defective pattern 100D, respectively. Note that the cross-sectional view shows the cross section along line AA' in the top view. A contact plug 102 made of tungsten is formed so as to be surrounded by an interlayer film 101 on which SiO2 has been deposited. In the normal pattern 100N, the contact plug 102 is connected to the lower layer wiring 103, whereas in the defective pattern 100D, the contact plug 102 is not connected to the lower layer wiring 103, resulting in an electrical connection failure.

[0012] Figure 2 shows SEM images (secondary electron (SE) images) 110N and 110D acquired for the normal pattern 100N and the defective pattern 100D, along with cross-sectional views. The normal pattern 100N and the defective pattern 100D are the same as those shown in Figure 1. From the difference in brightness in the SEM image, the first region 111 representing the interlayer film 101 and the second region representing the contact plug 102 can be distinguished. Here, at the boundary between the first region 111 and the second region 112, there is a region with higher brightness than the second region 112, which is called the third region 113. As can be seen by comparing with the cross-sectional view, there is no actual pattern corresponding to the third region 113. In defect inspection using the potential contrast method with SEM images, good / defective judgment is made by the difference in brightness. Therefore, the larger the difference in brightness between good and defective, the higher the defect detection sensitivity. The brightness of the second region 112 in the defective pattern SEM image 110D is only slightly lower than that of the second region 112 in the normal pattern SEM image 110N. Therefore, it is difficult to detect this difference and determine whether the pattern is good or defective.

[0013] In contrast, the brightness of the third region 113 in the defective pattern SEM image 110D is significantly reduced compared to the brightness of the third region 113 in the normal pattern SEM image 110N.

[0014] Here, we will explain the mechanism by which the third region 113 occurs in the SEM image using Figure 3. Figure 3 shows the cross-sectional view, brightness distribution, and potential distribution for the normal pattern 100N and the defective pattern 100D, respectively. As shown in the potential distribution of the normal pattern 100N, the contact plug 102 is electrically connected to the underlying wiring 103 and is not charged, so its potential is low. On the other hand, the interlayer film 101, which is a dielectric, becomes highly charged by the electron beam, increasing its potential. However, since the boundary where the contact plug 102 touches is at the same potential as the contact plug 102, a potential gradient is generated in the interlayer film 101 as it moves away from the contact plug 102. The region where this potential gradient occurs is the third region 113. The magnitude of the potential gradient generated in the interlayer film 101 depends on the potential of the contact plug 102.

[0015] As shown in the potential distribution of the defective pattern 100D, the contact plug 102 is not in contact with the underlying wiring 103 in the defective pattern 100D and is therefore electrically floating. The dielectric interlayer film 101 has a high potential due to charging, similar to the case of the normal pattern 100N. The contact plug 102 also has a rising potential due to the charging of the interlayer film 101.

[0016] This section explains the principle of defect inspection based on the difference in SEM brightness distribution that reflects this difference in potential distribution. The amount of secondary electrons emitted from tungsten, the material of a typical contact plug 102, is low. Therefore, the amount of emission hardly changes in response to differences in the potential of the contact plug 102, and the change in brightness of the resulting SEM image is also small. As a result, the difference in brightness between the second region 112 of the normal pattern SEM image 110N and the second region 112 of the defective pattern SEM image 110D is small, resulting in low detection sensitivity. In contrast, SiO2, the material of the interlayer film 101, emits a large amount of secondary electrons, and the amount of emission changes significantly in response to differences in potential. As mentioned above, the magnitude of the potential gradient of the interlayer film 101, which appears as the third region 113, reflects the difference in the potential of the contact plug 102. Therefore, by analyzing the difference in brightness of the third region 113, it becomes possible to inspect the electrical characteristics of the contact plug 102 with high sensitivity.

[0017] ≪Explanation of the flowchart≫ One form of implementation, the inspection method, will be explained following the flowchart in Figure 4. An example of the configuration of a charged particle beam apparatus used in this inspection method is shown in Figure 7A, and its details will be described later.

[0018] (Step 100) The electron beam is irradiated onto the sample according to the electron beam conditions (charged particle beam conditions) set by the user.

[0019] (Step 101) Secondary electrons emitted from the sample 8 by electron beam irradiation are detected by the electron detector 5 and imaged. The SEM image generated based on the detection signal of the secondary electrons is called an SE image. An example of an SE image (schematic diagram) is shown in Figure 5A.

[0020] (Step 102) Structural information corresponding to the SE image 200 (Figure 5A) is referenced from the region storage unit 38, and the first and second regions of the SE image 200 are extracted. The first region is the region occupied by a dielectric, such as an interlayer film, and the second region is the region occupied by a conductor or semiconductor, such as a contact plug. Here, an example of using a BSE image as the structural information used for extraction is shown. A BSE image (backscattered electron image) is an SEM image imaged based on the detection signal of BSE (backscattered electrons, backscattered electrons). An example of a BSE image used for region extraction (schematic diagram) is shown in Figure 5B. The BSE image 210 may be the BSE image acquired simultaneously with the SE image 200 by the BSE detector when Step 101 is executed, or a separately acquired BSE image may be used. Because semiconductors and conductors have a higher BSE emission rate compared to dielectrics, the contact plug is displayed brighter in the BSE image compared to the interlayer film, and the difference in materials can be clearly observed, making it easy to determine the boundary between the interlayer film (dielectric region) and the contact plug (conductor or semiconductor pattern). Therefore, as shown in Figure 5C, the bright frequency distribution of the BSE image 210 is set as the second region and the dark frequency distribution as the first region from the luminance profile. As a result, the boundary between the first and second regions (the contour lines of the contact plugs) is extracted, as shown in Figure 5D. In this example, contact plugs 201 and 202 with different shapes are extracted within the same field of view.

[0021] Structural information may be provided using X-ray images that allow for the identification of different material types, or CAD data. The user may also arbitrarily specify a region from the acquired SE image.

[0022] (Step 103) In Step 103, a third region (the region where a potential gradient occurs in the dielectric region (first region)) is defined for the image (SE image) acquired in Step 101, based on the first and second regions extracted in Step 102. Figure 6A shows the extraction results of the third regions 203 and 204, extracted based on the first and second regions extracted in Step 102. As an example of how to define the third region, it can be defined as having a width of 10 pixels inward (towards the second region) and 20 pixels outward (towards the first region) from the boundary between the first and second regions shown in Figure 5D. The appearance of the third region in the SE image is influenced by the trajectory of secondary electrons in the electron beam device, so the third region is defined to include to some extent the area inside the boundary identified by the structural information. Therefore, as shown in Figure 6B, it is advisable to display the SE image 200 (see Figure 5A) and the defined third regions 203 and 204 (see Figure 6A) superimposed, allowing the user to verify whether the third regions defined based on structural information actually adequately cover the bright areas of the SE image. By adjusting the definition of the third regions on the superimposed image in this way, it becomes possible to reliably extract the appropriate third regions. The size of the third regions can be specified in pixels or in actual dimensions.

[0023] Furthermore, the size of the third region can be defined for contact plugs 201 and 202, which have different sizes. That is, contact plugs 201 and 202 can define different pixel sizes inside and outside the boundary as the third region. Since the potential gradient generated in the interlayer film differs depending on the shape and material of the contact plug, it is preferable to define the third region for each contact plug with a different shape or material. The second region can be automatically classified based on differences such as the brightness value of the BSE image, the brightness difference of the SE image, material differences based on X-rays emitted during electron beam irradiation, CAD data, or the area and outer size of the SEM image, and the third region can be defined for each classification.

[0024] (Step 104) From the SE image acquired in Step 101, the luminance values ​​of the third region defined in Step 103 are extracted.

[0025] Figure 7A shows the configuration of the charged particle beam apparatus (electron beam apparatus) 1, which is an inspection device. The charged particle beam apparatus 1 comprises a charged particle optical system (electron optical system), a stage mechanism system, a beam control system, an image processing system, and an input / output system. The charged particle optical system includes an electron gun 2, a deflector 3, an electron lens 4, and an electron detector 5. The stage mechanism system includes an XYZ stage (sample stage) 6 on which the sample 8 to be inspected is placed. The inside of the housing 9 is controlled to a high vacuum, and the charged particle optical system and the stage mechanism system are installed there. The beam control system includes a charged particle beam control unit 30, a charged particle beam output unit 31, a charged particle beam scanning unit 32, a charged particle beam focusing unit 33, and a detection unit 34. The image processing system includes an image generation unit 35, a region storage unit 38, a region extraction unit 39, and a feature extraction unit 40. The input / output system includes an observation condition setting unit 36 ​​and an input / display unit 37, the input / display unit 37 further including a condition input unit 41 and an image display unit 42. The observation condition setting unit 36 ​​writes control values ​​to the charged particle beam control unit 30 based on the electron beam observation conditions set in the condition input unit 41. According to the written control values, the electron gun 2, deflector 3, electron lens 4, and electron detector 5 are controlled in the set operation via the charged particle beam output unit 31, charged particle beam scanning unit 32, charged particle beam focusing unit 33, and detection unit 34.

[0026] In Figure 7A, the blocks (functional units) enclosed by dotted rectangles indicate functional units executed by the information processing device 10. The information processing device 10 includes a processor (CPU) 11, memory 12, storage device 13, input / output ports 14, network interface 15, and bus 16, as shown in Figure 7B. The processor 11 functions as a functional unit that provides predetermined functions by executing processing according to programs loaded into the memory 12. The storage device 13 stores data and programs used by the functional units. The storage device 13 uses a non-volatile storage medium such as an HDD (Hard Disk Drive) or SSD (Solid State Drive). The input / output ports 14 are connected to input devices such as keyboards and pointing devices, and output devices such as displays (display devices) (collectively referred to as input / output devices), and perform signal exchange between the information processing device 10 and the input / output devices. The network interface 15 enables communication with other information processing devices via a network. These components of the information processing device 10 are connected to each other via the bus 16.

[0027] The electron beam accelerated by the electron gun 2 is focused by the electron lens 4 and irradiated onto the sample 8. The electron lens 4 controls the spot size of the electron beam focused onto the sample surface. The irradiation position and range (e.g., magnification) on the sample are controlled by the deflector 3. The electron beam is controlled by the electron beam conditions set in the observation condition setting unit 36: acceleration voltage, irradiation current, irradiation position, magnification, irradiation range, and focus size. Electrons emitted from the sample 8 by the electron beam irradiation are detected by the electron detector 5 and become detection signals, which are then imaged by the image generation unit 35. The region storage unit 38 stores structural information of the observed sample (such as the size and material of the conductor or semiconductor pattern). The sample pattern data can be input and saved from the SEM image, or CAD data can be input and saved from an external source. Furthermore, the user can specify the data by capturing an SEM image. The region extraction unit 39 extracts the first and second regions from the SEM image (SE image) generated by the image generation unit 35 and the structural information of the region storage unit 38, and extracts the third region according to the region size setting value of the third region set in the condition input unit 41. The feature extraction unit 40 extracts the brightness of the third region extracted by the region extraction unit 39 from the SEM image and outputs it to the input / display unit 37.

[0028] Figure 8 shows an example of the GUI output to the display device. In the charged particle beam condition setting unit 310, basic observation conditions such as acceleration voltage, irradiation current, scanning speed, magnification, and focus size can be set. The observed SEM image is displayed in the image display unit 301. By using the pull-down menu, it is possible to select and display acquired SEM images such as SE images originating from secondary electron signals and BSE images originating from BSE.

[0029] The region setting unit 320 separates the acquired SE image into a first region and a second region, and sets conditions for extracting a third region. Structural information for extracting the first and second regions is read into the region selection unit 321. Here, an example is shown in which the BSE image acquired simultaneously when acquiring the secondary electron image of the image display unit 301 is used as structural information. The first and second regions are extracted from the BSE image displayed in the region selection unit 321. Boundary extraction between the first and second regions is assumed to be performed automatically from the brightness profile of the BSE image, but the first and second regions may also be manually separated from the manual setting unit 325.

[0030] Next, the third region, which occurs at the boundary between the first and second regions, is extracted. To do this, the range region setting unit 323 sets the range of the third region by defining the areas inside and outside the boundary. In this example, it is set by the pixel size from the boundary. Furthermore, if there are plugs of different sizes (second region) or plugs made of different materials (second region) within the same field of view, a plug type setting unit 324 is provided so that the size of the third region can be defined for each. The third region extracted according to the conditions set in the range region setting unit 323 is displayed in the third region extraction unit 322.

[0031] Furthermore, the third region confirmation unit 327 displays the extracted third region superimposed on the secondary electron image displayed on the image display unit 301. The layer selection unit 326 can be set to check the secondary electron image and the third region alternately or superimposed. This allows, for example, the definition of the third region to be corrected so that it does not include sufficiently dark areas of the first region or the second region if the set third region includes those areas.

[0032] Next, the feature extraction unit 40 extracts the luminance value of the third region from the secondary electron image and outputs a luminance profile 329. Here, the luminance region of the third region can be specified using the display profile region specification 328, and the image (SE image) of the third region of the specified luminance region is displayed on the extracted region luminance display unit 330.

[0033] Figure 9A is an example of a GUI created by the input / display unit 37 to present to the user the brightness trend of the third region obtained by performing the inspection flow of Example 1 on the wafer surface. For example, the average value of the brightness of the third region observed for each chip formed on the wafer is calculated, and the average brightness of the third region is divided into 6 groups. The wafer surface distribution is shown in Figure 9A, and the frequency distribution is shown in Figure 9B. The horizontal axis is the average brightness value, and the vertical axis is the frequency. Normal and defective judgments can be made from the brightness values, and the threshold for determining normal and defective can be arbitrarily set by the user, or it can be determined from electrical characteristics acquired by another device such as a prober or TEM.

[0034] By using Example 1, the first region (dielectric region such as an interlayer film) and the second region (conductor or semiconductor pattern such as a contact plug) can be identified, the third region extracted, and the brightness value of the third region can be obtained, thereby enabling highly sensitive inspection of the electrical characteristics of the second region. [Examples]

[0035] Example 2 describes an inspection method for determining the charged particle beam condition (electron beam condition) that yields the highest brightness value in the third region by comparing the brightness values ​​obtained by irradiating with an electron beam under multiple charged particle beam conditions.

[0036] Figure 10 shows the inspection flow for determining the electron beam conditions that result in high brightness in the third region. Step 110 sets multiple electron beam conditions. For example, electron beam conditions with different focus conditions are set. Multiple electron beam conditions can be set in the charged particle beam condition setting unit 310 on the GUI shown in Figure 8. Next, in Step 111, SEM images (SE images) are acquired for each electron beam condition set in Step 110. In Step 112, the first and second regions are extracted from the SE images for each electron beam condition using structural information, similar to Step 102 in the flowchart of Figure 4. In Step 113, the third region is defined for each SE image acquired for each electron beam condition. The method for defining the third region for each SE image is the same as in Step 103 in the flowchart of Figure 4. If there are second regions with different areas or materials within the same field of view, the third region is defined for each classification of the second region. In Step 114, the brightness values ​​of the third regions extracted in Step 113 are extracted. In Step 115, the brightness values ​​of the third region for each electron beam condition are compared. In Step 116, the electron beam condition with the highest brightness value in the third region among the electron beam conditions compared in Step 115 is determined to be the optimal electron beam condition (charged particle beam condition).

[0037] An example of determining the optimal electron beam conditions using the flowchart in Figure 10 will be explained. Figure 11A is a cross-sectional view of the sample 51 to be observed. A dielectric TEOS film 55 is formed on a Si substrate 53, and Poly-Si lines 54 are embedded in the TEOS film 55. Two types of electron beam conditions with different focusing conditions are used. Figure 11B shows the observation results for sample 51 under focusing conditions A and B. Focusing condition A is the focusing condition in which the contour of the sample surface is sharpest (just focus condition), and a secondary electron image 220 (schematic diagram) is obtained. Focusing condition B is a focusing condition in which the focal diameter is larger than that of focusing condition A (defocus condition), and a secondary electron image 230 (schematic diagram) is obtained. When the electron beam focusing condition is changed, the area of ​​the third region generated in the second region changes according to the electron beam condition, so the width of the third region is set for each electron beam condition. The third region 221 is extracted from SE image 220, and the third region 231 is extracted from SE image 230. Comparing the brightness profiles of the third region under focusing condition A (SE image 220) and focusing condition B (SE image 230), profile 232 under the electron beam condition with a larger focus diameter has a higher brightness value than profile 222 under the electron beam condition with a smaller focus diameter. In other words, focusing condition B reflects the potential gradient with higher sensitivity, so focusing condition B can be determined as the optimal condition.

[0038] A modified method for determining electron beam conditions will be described. Figure 12A is a cross-sectional view of the sample 52 being observed. The basic structure is the same as the sample 51 shown in Figure 11A, but of the four linear Poly-Si lines 54, only one Poly-Si line 54a is shallower. As a result, the thickness of the TEOS film 55 between the Poly-Si line 54 and the Si substrate 53 increases, increasing the capacitance and resistance and reducing the discharge amount. Therefore, it becomes more easily charged than the other three Poly-Si lines 54. Consequently, the potential gradient becomes smaller compared to the other three Poly-Si lines, resulting in a smaller brightness value in the third region.

[0039] Figure 12B shows the observation results for sample 52 under focusing conditions A and B. Focusing conditions A and B are the same as the electron beam conditions used to acquire the secondary electron image shown in Figure 11B. From SE image 223 under focusing condition A and SE image 233 under focusing condition B, brightness profiles 226 and 236 for the third region are obtained, respectively. Profiles 224 and 234 are frequency distributions representing the Poly-Si line 54a, respectively, and profiles 225 and 235 are frequency distributions representing the other three Poly-Si lines, respectively. As shown in Figure 12B, the brightness variation in the third region is greater under focusing condition B than under focusing condition A. In other words, focusing condition B allows for more sensitive detection of the potential state of the Poly-Si line (second region) than focusing condition A. Thus, the electron beam conditions may be determined so that the variation in brightness values ​​is large within the same field of view or within the wafer.

[0040] Using Example 2, it is possible to extract the brightness of the third region obtained under multiple electron beam conditions and determine the electron beam condition that maximizes the brightness difference between good and bad results. [Examples]

[0041] Example 3 shows an example using a pulsed charged particle beam apparatus capable of irradiating a sample with a pulsed electron beam. The sample is irradiated with a pulsed electron beam, and the signal electrons emitted from the sample are detected by an electron detector in synchronization with the pulsed electron beam to create an image. The degree of decay of the charge of the sample differs depending on the time constant based on the capacitance and resistance components of the pattern. The pulsed charged particle beam apparatus makes it possible to quantitatively grasp the transient phenomenon of charge. That is, based on the difference in brightness values ​​of the third region under electron beam conditions with different intermittence (interval) times, it is possible to quantitatively measure electrical characteristics such as resistance and capacitance values ​​with high sensitivity, in addition to determining whether the sample is defective or normal. Quantitative measurement of electrical characteristics requires acquiring multiple SE images with different intermittence conditions and utilizing the brightness changes in the acquired SE images. Therefore, while in Examples 1 and 2 it was sufficient to define the third region for each SE image, in Example 3, when performing quantitative analysis, the region for measuring brightness changes needs to be common to multiple SE images acquired with different intermittence conditions. To distinguish it from the third region of each SE image, the region set in common for multiple SE images is called the third region segmentation. To improve examination sensitivity, the third region segmentation is set so that the brightness difference of the SE images is as large as possible.

[0042] Figure 13 shows the configuration of the pulsed charged particle beam apparatus (pulsed electron beam apparatus) 1b, which is an inspection apparatus. The configuration is similar to the inspection apparatus shown in Figure 7A, but a beam breaker 7 is added to the charged particle optical system and an intermittent irradiation unit 43 is added to the beam control system as a mechanism for intermittently irradiating with an electron beam. The observation condition setting unit 36 ​​writes control values ​​to the charged particle beam control unit 30 and controls it based on the intermittent conditions of the electron beam set in the condition input unit 41. The intermittent irradiation unit 43 controls the beam breaker 7 so that the electron beam is irradiated to the sample 8 at the set intermittent irradiation time and timing according to the control values. The detection unit 34 detects secondary electrons using the electron detector 5 in synchronization with the pulsed electron beam controlled by the intermittent irradiation unit 43.

[0043] In Example 3, the difference in brightness of the SE image under a series of intermittent conditions of the electron beam is calculated, and the region where the brightness difference is large is set as the third region segmentation. Figure 14A shows the secondary electron images (schematic diagram) acquired for each electron beam irradiation interval (intermittent condition). Here, the intermittent conditions of the electron beam are 10 μsec and 100 μsec, with SE image 241 being the SE image under the 10 μsec intermittent condition and SE image 242 being the SE image under the 100 μsec intermittent condition.

[0044] Next, we will explain how to extract the third region segmentation from these two SE images using Figure 14B. First, a difference image of the secondary electron images under two discontinuation conditions is created. A difference image is an image whose brightness value is the brightness difference between two images, and the larger the brightness difference, the brighter it becomes (the brightness of the difference image is higher). Here, since the brightness difference due to the difference in discontinuation conditions in the third region of the SE image is larger than the brightness difference due to the difference in discontinuation conditions in the first and second regions of the SE image, the difference image 243, which uses the brightness difference as its brightness value, also shows a pattern similar to that of the SE image. From the brightness profile 244 in the difference image 243, the third region segmentation 245 is extracted based on the profile on the higher brightness side. For example, as shown in Figure 14B, it is good to set a threshold for the extracted brightness (region threshold) and set the brightness region above that as the third region segmentation. The threshold can be set arbitrarily by the user.

[0045] Next, for the extracted third-region segmentation 245, the brightness values ​​of SE image 241 (with a discontinuation condition of 10 μsec) and SE image 242 (with a discontinuation condition of 100 μsec) are obtained. Figure 14C shows an example of the output.

[0046] Furthermore, if there are third regions within the same field of view that have different brightness changes in response to the intermittent condition, third region segmentation may be extracted such that each region exhibits a larger brightness change in response to the intermittent condition. In other words, multiple types of third region segmentation may be extracted within the same field of view. An example of extracting multiple third region segmentation is shown in Example 4, which will be described later.

[0047] According to Example 3, it becomes possible to extract third-region segmentation such that the brightness change is large through multiple intermittent conditions, enabling highly sensitive quantitative inspection. [Examples]

[0048] Example 4 shows an example in which a charged particle beam apparatus is used, in which the charge state of the sample is controlled and observed by irradiating it with ultraviolet light, for example. In this case, in addition to the electron beam conditions, it is necessary to extract a third region segmentation common to multiple SE images such that the brightness change of the third region is large for each light irradiation condition.

[0049] Figure 15 shows the configuration of the pulsed charged particle beam apparatus (pulsed electron beam apparatus) 1c, which is an inspection apparatus. In addition to the configuration and functions of the inspection apparatus shown in Figure 13, a light source 44 for laser irradiation, an irradiation optical system 45, and a laser control unit 46 are added. The light source 44 uses a single-wavelength light source. The laser may be a tunable laser whose wavelength can be selected by parametric oscillation. Alternatively, a wavelength conversion unit that generates harmonics of light may be used. The irradiation area of ​​the light should preferably be wider than the deflection area of ​​the electron beam controlled by the deflector 3 in order to obtain an image with uniform image contrast. The light may be a continuously oscillating light source or a pulsed light source, or a continuous light source may be pulsed using an electro-optic modulator or an acousto-optic modulator. The light and electron beam may be irradiated simultaneously in time or at different timings in time. Secondary electrons emitted when the electron beam is irradiated onto the sample 8 that has been irradiated with light are detected by the electron detector 5. The detection signal detected by the electron detector 5 forms an SEM image in the image generation unit 35 and is displayed in the image display unit 42. Furthermore, a charged particle beam apparatus configuration is also possible, which adds a light source 44 for laser irradiation, an irradiation optical system 45, and a laser control unit 46 to the apparatus configuration and functions of the inspection apparatus shown in Figure 7A. In this case, a continuous charged particle beam will be irradiated onto the sample.

[0050] By irradiating sample 8 with light under different irradiation conditions, the brightness of the third region of the SE image of sample 8 changes. The procedure for determining the third region segmentation that shows the largest change in brightness with respect to the light irradiation conditions is described below. Figure 16A shows examples of secondary electron images acquired under user-defined electron beam observation conditions and light irradiation conditions. Here, the electron beam observation conditions are kept the same, and examples are shown where the light irradiation conditions are 10mW, 300mW, 500mW, and 1000mW.

[0051] Similar to Example 3, difference images of secondary electron images under these four light irradiation conditions are created. For example, if difference images are created for all four SE images in a brute-force manner, six difference images will be created. The method for extracting third-region segmentation that increases the brightness value of the difference image can be performed in the same way as in Example 3, as shown in Figure 16B. That is, a threshold for extracted brightness (region threshold) is set, and brightness regions with brightness profiles higher than this threshold are set as third-region segmentation.

[0052] Furthermore, if there are third regions within the same field of view that exhibit different brightness changes under different light illumination conditions, third region segmentation may be extracted such that each region exhibits a larger brightness change under different intermittent conditions. In Figure 16B, four types of third region segmentation are extracted. The differences between the types are indicated by the subscripts A to D. For each type of third region segmentation, third region segmentation may be extracted based on different difference images.

[0053] For the extracted third-region segmentations 251A to D, the brightness values ​​in the third-region segmentations extracted from the secondary electron images shown in Figure 16A are obtained. An example of the output is shown in Figure 16C.

[0054] According to Example 4, in addition to electron beam observation, it becomes possible to extract third-region segmentation where the brightness change is large from the brightness change of the third region when light is irradiated under each light irradiation condition, enabling highly sensitive quantitative inspection.

[0055] It should be noted that the present invention is not limited to the embodiments described above, and various modifications are included. For example, the embodiments described above are explained in detail to make the present invention easier to understand, and are not necessarily limited to those having all the configurations described. Furthermore, it is possible to replace parts of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add configurations from other embodiments to the configuration of one embodiment. In addition, it is possible to add, delete, or replace parts of the configuration of each embodiment with other configurations. [Explanation of Symbols]

[0056] 1,1b,1c: Charged particle beam apparatus, 2: Electron gun, 3: Deflector, 4: Electron lens, 5: Electron detector, 6: XYZ stage, 7: Beam cutoff, 8: Sample, 10: Information processing device, 11: Processor (CPU), 12: Memory, 13: Storage device, 14: Input / output port, 15: Network interface, 16: Bus, 31: Charged particle beam output unit, 32: Charged particle beam scanning unit, 33: Charged particle beam focusing unit, 34: Detection unit, 35: Image Image generation unit, 36: Observation condition setting unit, 37: Input / display unit, 38: Region storage unit, 39: Region extraction unit, 40: Feature extraction unit, 41: Condition input unit, 42: Image display unit, 43: Intermittent irradiation unit, 44: Light source, 45: Irradiation optical system, 46: Laser control unit, 51, 52: Sample, 53: Si substrate, 54: Poly-Si line, 55: TEOS film, 100N: Normal pattern, 100D: Defective pattern, 101: Interlayer film, 102: Contact plug, 103: Bottom Layer wiring, 110: SEM image, 111: First region, 112: Second region, 113: Third region, 200: SE image, 201, 202: Contact plug, 203, 204: Third region, 210: BSE image, 220, 230, 223, 233: Secondary electron image, 221, 231: Third region, 222, 232: Profile, 224, 225, 234, 235: Profile, 226, 236: Brightness profile, 241, 242: SE image, 243: Difference image Image, 244: Brightness profile, 245, 251: Third region segmentation, 301: Image display unit, 310: Charged particle beam condition setting unit, 320: Region setting unit, 321: Region selection unit, 322: Third region extraction unit, 323: Range region setting unit, 324: Plug type setting unit, 325: Manual setting unit, 326: Layer selection unit, 327: Third region confirmation unit, 328: Display profile region specification, 329: Brightness profile, 330: Extracted region brightness display unit.

Claims

1. A method for inspecting the electrical properties of a pattern made of a conductor or semiconductor formed in a dielectric region of a sample, A charged particle beam is scanned over the aforementioned sample to obtain a secondary electron image. A feature quantity is calculated based on the brightness value of a third region that is brighter than the second region and extends from the boundary between the first region corresponding to the dielectric region and the second region corresponding to the pattern in the secondary electron image toward the first region, An inspection method characterized by inspecting the electrical characteristics of the pattern based on the aforementioned feature quantities.

2. In claim 1, The inspection method is characterized in that the third region is generated by the potential gradient in the dielectric region of the sample.

3. In claim 1, An inspection method characterized by extracting the boundary based on the structural information of the sample.

4. In claim 3, An inspection method characterized by using a backscattered electron image or X-ray image obtained by scanning a charged particle beam over the sample, or CAD data of the sample, as structural information of the sample.

5. In claim 1, A first secondary electron image is obtained by scanning the sample with a charged particle beam under first charged particle beam conditions. A second secondary electron image is obtained by scanning the sample with a charged particle beam under second charged particle beam conditions. An inspection method characterized by determining the charged particle beam conditions for acquiring the secondary electron image based on a comparison of the brightness profile of the third region of the first secondary electron image and the brightness profile of the third region of the second secondary electron image.

6. In claim 5, An inspection method characterized in that the focusing diameter of the charged particle beam on the sample under the first charged particle beam condition and the focusing diameter of the charged particle beam on the sample under the second charged particle beam condition are different.

7. In claim 1, An inspection method characterized in that the charged particle beam conditions for acquiring the secondary electron image are defocus conditions.

8. A method for inspecting the electrical properties of a pattern made of a conductor or semiconductor formed in a dielectric region of a sample, A pulsed charged particle beam under first intermittent conditions is scanned over the sample to obtain a first secondary electron image. A second secondary electron image is obtained by scanning the sample with a pulsed charged particle beam under a second intermittent condition. Based on the luminance profile on the high-luminance side in the difference image between the first secondary electron image and the second secondary electron image, a first third region segmentation is extracted. An inspection method characterized by inspecting the electrical characteristics of the pattern based on feature quantities based on the brightness values ​​of the third region segmentation in the first secondary electron image and the second secondary electron image.

9. A method for inspecting the electrical properties of a pattern made of a conductor or semiconductor formed in a dielectric region of a sample, A charged particle beam is scanned over the sample irradiated with light under the first light irradiation conditions to obtain a first secondary electron image. A second secondary electron image is obtained by scanning a charged particle beam over the sample irradiated with light under the second light irradiation condition. A third region segmentation is extracted based on the luminance profile on the high-luminance side in the difference image between the first secondary electron image and the second secondary electron image. An inspection method characterized by inspecting the electrical characteristics of the pattern based on feature quantities based on the brightness values ​​of the third region segmentation in the first secondary electron image and the second secondary electron image.

10. In claim 8 or claim 9, The inspection method is characterized in that the third region segmentation is included in the high-luminance region generated by the potential gradient in the dielectric region of the sample in the first secondary electron image and the second secondary electron image.

11. A sample stage on which a sample having a pattern made of a conductor or semiconductor formed in a dielectric region is placed, A charged particle optical system that irradiates the sample with a charged particle beam, The system includes an information processing device that inspects the electrical characteristics of a pattern from a secondary electron image obtained by scanning the charged particle beam over the sample, The information processing device calculates a feature quantity based on the brightness value of a third region that is brighter than the second region and extends from the boundary between the first region corresponding to the dielectric region and the second region corresponding to the pattern in the secondary electron image toward the first region, and the charged particle beam apparatus inspects the electrical characteristics of the pattern based on the feature quantity.

12. In claim 11, The third region is a charged particle beam apparatus generated by the potential gradient in the dielectric region of the sample.

13. In claim 11, The secondary electron image is a charged particle beam apparatus in which the charged particle optical system scans the charged particle beam under defocus conditions over the sample to obtain the secondary electron image.

14. In claim 11, The charged particle optical system irradiates the sample with a pulsed charged particle beam. The information processing device extracts a first third region segmentation based on the high-luminance luminance profile in the difference image between a first secondary electron image obtained by scanning a pulsed charged particle beam under first intermittent conditions over the sample and a second secondary electron image obtained by scanning a pulsed charged particle beam under second intermittent conditions over the sample, and inspects the electrical characteristics of the pattern based on feature quantities based on the luminance values ​​of the third region segmentation in the first and second secondary electron images.

15. In claim 11, The charged particle optical system irradiates the sample with light, The information processing device extracts a third region segmentation based on the luminance profile on the high-luminance side of the difference image between a first secondary electron image obtained by scanning a charged particle beam over the sample irradiated with light under a first light irradiation condition and a second secondary electron image obtained by scanning a charged particle beam over the sample irradiated with light under a second light irradiation condition, and inspects the electrical characteristics of the pattern based on feature quantities based on the luminance values ​​of the third region segmentation in the first secondary electron image and the second secondary electron image.

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