A fast method for locating sample dislocations based on spherical aberration electron microscopy

Abstract

The present invention discloses a method for rapidly locating sample dislocations based on a spherical aberration electron microscope. The method utilizes an integrated differential contrast image to rapidly locate different types of dislocations in a sample, and obtains an image of the core atoms of the dislocation in a high-angle annular dark-field image. The method has precise positioning, is less dependent on the operator's subjective judgment, and saves time and effort.

Description

Technical Field

[0001] The invention belongs to the field of electronic information technology, and in particular relates to a method for quickly locating sample dislocation based on a spherical aberration electron microscope. Background Art

[0002] Dislocations are one of the most important defects in semiconductor materials. Numerous studies have shown that the presence of dislocations has a significant impact on the performance of various semiconductor optoelectronic and acoustic devices. Using spherical aberration-corrected transmission electron microscopy (TEM) to image the atomic structure of dislocation cores is an important part of semiconductor material defect research. Existing technical solutions are mainly divided into the following two categories:

[0003] 1. In transmission mode (TEM), adjust the sample to dual-beam conditions and capture dual-beam diffraction contrast images of different diffraction vectors to find the approximate location of the dislocation. Then switch to scanning transmission mode (STEM), rotate the crystal zone axis, and locate the dislocation based on the dual-beam diffraction contrast image.

[0004] 2. In scanning transmission mode (STEM), high-angle annular dark field (HAADF) and bright field (BF) images are collected simultaneously. Dislocations may appear as black spots in the bright field image, which can be used to determine the location of the dislocation.

[0005] However, both of these solutions have drawbacks. Solution 1 requires switching back and forth between transmission mode and scanning transmission mode, and the dislocation contrast in the two modes is inconsistent, making it inefficient. In solution 2, the dislocation contrast in brightfield images is still weak, especially at low magnifications. Therefore, it is necessary to switch back and forth between low and high magnifications to determine the dislocation location, which greatly tests the operator's judgment.

[0006] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for rapidly locating sample dislocations based on a spherical aberration electron microscope. The method can use an integrated differential contrast image (iDPC image) to rapidly locate different types of dislocations in a sample and obtain an image of the core atoms of the dislocation in a high-angle annular dark field image (HAADF image). The method has low reliance on the subjective judgment of the operator and saves time and effort.

[0008] In order to achieve the above object, a specific embodiment of the present invention provides the following technical solutions:

[0009] A method for quickly locating sample dislocation based on a spherical aberration electron microscope, comprising:

[0010] In the scanning transmission mode, determine the sample area to be photographed and perform calibration;

[0011] Adjust the imaging contrast and contrast of the detector in the spherical aberration electron microscope under the first condition, and realign the sample to be photographed;

[0012] Under the second condition and at a low magnification, a high-angle annular dark field image and an integral differential contrast image of the area to be photographed of the sample are simultaneously acquired, and the dislocation is quickly located in the high-angle annular dark field image by utilizing the contrast difference of the dislocation in the integral differential contrast image;

[0013] Under high magnification conditions, the core atomic image of the dislocation is obtained in the high-angle annular dark field image.

[0014] In one or more embodiments of the present invention, determining the sample area to be photographed and calibrating it includes:

[0015] Tilt the sample and align the sample's crystal axis to determine the area of ​​the sample to be photographed;

[0016] Obtain the location information of the area to be photographed and perform calibration.

[0017] In one or more embodiments of the present invention, the first condition includes:

[0018] In scanning transmission mode, and in integrated differential phase contrast imaging mode;

[0019] The camera length range in the spherical aberration electron microscope is 115mm-145mm, or the camera length in the spherical aberration electron microscope is 115mm or 145mm.

[0020] In one or more embodiments of the present invention, the detector is a four-quadrant detector;

[0021] Adjust the imaging contrast and contrast of the detector in the spherical aberration electron microscope, including:

[0022] An external vacuum area without samples is selected, and the gain and compensation of the four-quadrant detector in the spherical aberration electron microscope are adjusted so that the imaging contrast and contrast of the four-quadrant detector remain consistent.

[0023] In one or more embodiments of the present invention, the area of ​​the sample to be photographed is realigned according to the calibration, and the diffraction pattern is located in the center of the detector.

[0024] In one or more embodiments of the present invention, under the first condition, the imaging contrast and the contrast of the detector in the spherical aberration electron microscope are adjusted repeatedly for multiple times.

[0025] In one or more embodiments of the present invention, the second condition includes:

[0026] In scanning transmission mode, and in simultaneous integrated differential phase contrast and high-angle annular dark field imaging modes;

[0027] The camera length range in the spherical aberration electron microscope is 115mm-145mm, or the camera length in the spherical aberration electron microscope is 115mm or 145mm.

[0028] In one or more embodiments of the present invention, the low multiple ranges from 225Kx to 1.3Mx; or the low multiples include: 225Kx, 320Kx, 450Kx, 640Kx, 910K, and 1.3Mx.

[0029] In one or more embodiments of the present invention, before the step of simultaneously acquiring the high-angle annular dark field image and the integrated differential contrast image of the area to be photographed of the sample, the method further includes:

[0030] Under the second condition, the contrast and intensity of the high-angle annular dark field image are adjusted by adjusting the offset and gain of the high-angle annular dark field image so that the contrast and intensity of the high-angle annular dark field image are at appropriate values ​​to obtain a clear image with distinct contrast.

[0031] In one or more embodiments of the present invention, the high multiple range is 2.55Mx-14.5Mx; or

[0032] The high multiples include: 2.55Mx, 3.6Mx, 5.1Mx, 7.2Mx, 10Mx, and 14.5Mx.

[0033] Compared with the existing technology, the method for quickly locating sample dislocations based on spherical aberration electron microscopy of the present invention uses the large contrast difference of dislocations in iDPC images at low magnification to quickly locate different types of dislocations in the sample, and obtains the core atomic image of the dislocation through the HAADF image obtained at the same time. The operation is simple and the dislocation positioning is accurate.

[0034] In spherical aberration electron microscopes, the conventional iDPC mode (integrated differential phase contrast imaging mode) is mainly used for light atom imaging and needs to be used under the condition of a camera length of 285mm. The camera length where the HAADF image is located is generally 115mm or 145mm. If you want to acquire high-level HAADF and iDPC images at the same position of the sample, you need to switch the camera length back and forth, which also involves adjusting the focal length, which is very cumbersome. In the present invention, when acquiring HAADF and iDPC images simultaneously, the camera length of the electron microscope in iDPC mode can always be maintained at 115mm or 145mm, without the need for switching back and forth, making operation simpler.

[0035] The method for quickly locating sample dislocations based on a spherical aberration electron microscope of the present invention has very obvious contrast of dislocations in iDPC images under low magnification conditions, so it is less dependent on the subjective judgment of the operator, saving time and effort. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0037] Figure 1 This is a flow chart of a method for rapid sample dislocation location based on a spherical aberration electron microscope in one embodiment of the present invention;

[0038] Figure 2 Figure 1 is a comparison of high-angle annular dark field (HAADF) images and integrated differential contrast images (iDPC) images simultaneously imaging dislocations at low magnifications in one embodiment of the present invention, where a is the HAADF image and b is the iDPC image.

[0039] Figure 3 This is a comparison diagram of high-resolution imaging of dislocations by a high-angle annular dark field image (HAADF image) and an integrated differential contrast image (iDPC image) in one embodiment of the present invention, where a is the HAADF image and b is the iDPC image. DETAILED DESCRIPTION

[0040] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0041] The traditional atomic imaging method uses a high-angle annular dark-field detector to collect high-angle scattered electrons. The advantage is that it can achieve atomic contrast imaging and is insensitive to sample thickness. The disadvantage is that the dislocation contrast is weak and difficult to locate at low magnifications, especially in samples with low dislocation density. It is difficult to quickly and accurately locate dislocations.

[0042] As the electron beam passes through a sample, it is deflected by the electric and magnetic fields within the sample, causing the diffraction pattern to shift relative to the detector center. Integrated differential phase contrast imaging (iDPC) uses a segmented STEM detector to measure the shift in the diffraction pattern as the electron beam scans. Any sample is composed of atoms, which consist of positively charged nuclei and negatively charged electrons. These charges generate an electric vector field, a scalar field with an electrostatic potential gradient. The electrostatic potential field has a distinct maximum at the location of the nucleus, a natural reflection of the atomic arrangement in the sample. Imaging the electrostatic potential field is the ultimate goal of electron microscopy, and iDPC directly provides this ideal imaging feature. For thin samples, iDPC is a direct phase imaging technique that can provide direct information about the sample's structure and composition. Because its imaging is linear, compared to high-angle annular dark-field imaging, it can image both light and heavy elements. It is highly sensitive to dislocations in semiconductor samples and enables rapid dislocation localization.

[0043] Based on this, the present invention provides a method for quickly locating sample dislocations based on a spherical aberration electron microscope. It uses integrated differential contrast images (iDPC images) to quickly locate different types of dislocations in the sample, and obtains the core atomic image of the dislocation in the high-angle annular dark field image (HAADF image). The positioning is precise, less dependent on the operator's subjective judgment, and saves time and effort.

[0044] like Figure 1 As shown, a method for quickly locating sample dislocations based on a spherical aberration electron microscope in one embodiment of the present invention includes the following steps:

[0045] S1: In the scanning transmission mode, tilt the sample and align the sample crystal axis to determine the area to be photographed, obtain the position information of the area to be photographed, and perform calibration.

[0046] S2: In the scanning transmission mode and the integral differential phase contrast imaging mode, the camera length in the spherical aberration electron microscope is set to 115mm-145mm or 115mm or 145mm, and an external vacuum area that does not contain the sample is selected. The imaging contrast and contrast of the four-quadrant detector in the spherical aberration electron microscope are adjusted multiple times as needed to keep the imaging contrast and contrast of the four-quadrant detector consistent. According to the calibration, the sample area to be photographed is realigned, and the diffraction pattern is located in the center of the four-quadrant detector.

[0047] S3: In the scanning transmission mode, and in the simultaneous imaging mode of integral differential phase contrast and high-angle annular dark field, the camera length in the spherical aberration electron microscope remains at the camera length of 115mm-145mm or 115mm or 145mm in step S2, and the magnification of the spherical aberration electron microscope is adjusted so that it is under low magnification conditions such as 225Kx-1.3Mx, specifically: 225Kx, 320Kx, 450Kx, 640Kx, 910Kx, 1.3Mx, and the contrast and contrast of the high-angle annular dark field image are adjusted by adjusting the offset and gain of the high-angle annular dark field image. After the contrast and contrast of the high-angle annular dark field image are at appropriate values, the high-angle annular dark field image and the integral differential phase contrast image of the sample area to be photographed are collected at the same time. The appropriate value may be understood as the range of the contrast and the contrast of the high-angle annular dark field image when adjusting the contrast and the contrast of the high-angle annular dark field image until a clear atomic image with distinct contrast is obtained.

[0048] S4: Rapidly locate dislocations in high-angle annular dark-field images using the contrast difference of dislocations in the integrated differential contrast image.

[0049] S5: Adjust the magnification of the spherical aberration electron microscope so that it is under high magnification conditions such as 2.55Mx-14.5Mx, specifically: 2.55Mx, 3.6Mx, 5.1Mx, 7.2Mx, 10Mx, 14.5Mx, and obtain the core atomic image of the dislocation in the high-angle annular dark field image according to the positioning of the dislocation in the high-angle annular dark field image under low magnification conditions.

[0050] The following is a detailed description using a specific embodiment as an example to facilitate further understanding of the technical solution of the present invention.

[0051] First, in the scanning transmission mode (STEM), the sample crystal axis is rotated straight, the area to be photographed is found and determined, and the position information is saved for calibration.

[0052] Secondly, the integrated differential phase contrast imaging (iDPC) mode was selected in the scanning transmission mode, and the camera length was selected as 115 mm.

[0053] Select the integral differential phase contrast imaging mode only, find a vacuum area outside the sample, adjust the imaging contrast and contrast of the four-quadrant detector of the DF4 probe of the spherical aberration electron microscope to be consistent, return to the sample area to be photographed according to the calibration, and use the multi-function knobs X and Y on the spherical aberration electron microscope control panel to adjust the position of the diffraction pattern displayed on the fluorescent screen to keep the diffraction pattern in the center of the detector.

[0054] Switch the integrated differential phase contrast imaging mode to the integrated differential phase contrast and high-angle annular dark field simultaneous imaging mode, keep the camera length at 115mm, adjust the magnification of the spherical aberration electron microscope to a low magnification, such as 225Kx, and adjust the offset and gain of the high-angle annular dark field image to the appropriate values ​​of contrast and contrast to obtain a clear and contrasted image. Then, collect the HAADF image and iDPC image simultaneously. The acquisition results are shown in Figure 2. Figure 2 shown.

[0055] Next, refer to Figure 2 As shown, the high contrast of the dislocation in the iDPC image is used to locate the exact position in the iDPC image. At the same time, the dislocation is also accurately located in the HAADF image based on the position information of the dislocation in the iDPC image.

[0056] Finally, reference Figure 3 As shown, the magnification of the spherical aberration electron microscope is adjusted so that it is under high magnification conditions, such as 10Mx, and the core atomic image of the dislocation in the high-angle annular dark field image is obtained based on the positioning of the dislocation in the high-angle annular dark field image under low magnification conditions.

[0057] Compared with the existing technology, the method for quickly locating sample dislocations based on spherical aberration electron microscopy of the present invention uses the large contrast difference of dislocations in iDPC images at low magnification to quickly locate different types of dislocations in the sample, and obtains the core atomic image of the dislocation through the HAADF image obtained at the same time. The operation is simple and the dislocation positioning is accurate.

[0058] In spherical aberration electron microscopes, the conventional iDPC mode (integrated differential phase contrast imaging mode) is mainly used for light atom imaging and needs to be used under the condition of a camera length of 285mm. The camera length of the HAADF image is generally 115mm or 145mm. If you want to acquire high-level HAADF and iDPC images of the same sample position, you need to switch the camera length back and forth, which also involves adjusting the focal length, which is very cumbersome. In the present invention, when acquiring HAADF and iDPC images simultaneously, the camera length of the electron microscope in DPC mode can always be maintained at 115mm or 145mm, without the need for switching back and forth, making the operation simpler.

[0059] The method for quickly locating sample dislocations based on a spherical aberration electron microscope of the present invention has very obvious contrast of dislocations in iDPC images under low magnification conditions, so it is less dependent on the subjective judgment of the operator, saving time and effort.

[0060] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

[0061] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A method for rapid location of sample dislocation based on spherical aberration electron microscopy, characterized in that: include: In the scanning transmission mode, determine the sample area to be photographed and perform calibration; Under a first condition, adjusting the imaging contrast and contrast of the detector in the spherical aberration electron microscope and realigning the sample area to be imaged, the first condition being an integral differential phase contrast imaging mode in a scanning transmission mode; Under the second condition and at a low magnification, a high-angle annular dark field image and an integral differential contrast image of the area to be photographed of the sample are simultaneously acquired, and the contrast difference of the dislocation in the integral differential contrast image is used to quickly locate the dislocation in the high-angle annular dark field image. The second condition is a simultaneous imaging mode of integral differential phase contrast and high-angle annular dark field in a scanning transmission mode. Under high magnification conditions, the core atomic image of the dislocation is obtained in the high-angle annular dark field image.

2. The method for rapid location of sample dislocation based on spherical aberration electron microscopy according to claim 1, characterized in that: Determine the sample area to be photographed and perform calibration, including: Tilt the sample and align the sample's crystal axis to determine the area of ​​the sample to be photographed; Obtain the location information of the area to be photographed and perform calibration.

3. The method for rapid sample dislocation location based on spherical aberration electron microscopy according to claim 1, characterized in that: Under the first condition: The camera length range in spherical aberration electron microscope is 115mm-145mm.

4. The method for rapid sample dislocation location based on spherical aberration electron microscopy according to claim 1, characterized in that: The detector is a four-quadrant detector; Adjust the imaging contrast and contrast of the detector in the spherical aberration electron microscope, including: An external vacuum area without samples is selected, and the compensation and gain of the four-quadrant detector imaging in the spherical aberration electron microscope are adjusted respectively so that the imaging contrast and contrast of the four-quadrant detector remain consistent.

5. The method for rapid sample dislocation location based on spherical aberration electron microscopy according to claim 1, characterized in that: According to the calibration, the area of ​​the sample to be photographed is realigned so that the diffraction pattern is located in the center of the detector.

6. The method for rapid sample dislocation location based on spherical aberration electron microscopy according to claim 1, characterized in that: Under the first condition, the imaging contrast and the contrast of the detector in the spherical aberration electron microscope are adjusted repeatedly.

7. The method for rapid sample dislocation location based on spherical aberration electron microscopy according to claim 1, characterized in that: Under the second condition: The camera length range in spherical aberration electron microscope is 115mm-145mm.

8. The method for rapid sample dislocation location based on spherical aberration electron microscopy according to claim 1, characterized in that: The low magnification range is 225Kx-1.3Mx.

9. The method for rapid sample dislocation location based on spherical aberration electron microscopy according to claim 1, characterized in that: Before the step of simultaneously acquiring the high-angle annular dark field image and the integral differential contrast image of the sample area to be photographed, the method further includes: Under the second condition, the contrast and the intensity of the high-angle annular dark field image are adjusted by adjusting the compensation and gain of the high-angle annular dark field image.

10. The method for rapid sample dislocation location based on spherical aberration electron microscopy according to claim 1, characterized in that: The high magnification range is 2.55Mx-14.5Mx.

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