Method for locating characteristic defects of cadmium zinc telluride sample and method for preparing cadmium zinc telluride sample

Abstract

This invention relates to a method for locating characteristic defects in cadmium zinc telluride (CZT) samples and a method for preparing CZT samples. The location method includes the following steps: determining the positions of internal feature points on the sample under an infrared transmission microscope; establishing marking features on the sample surface using FIB-SEM; and determining the relative position of the internal feature points projected onto the sample surface by establishing a geometric relationship between the virtual position of the internal feature points projected onto the sample surface and the marking features. The preparation method uses these relative positions to prepare CZT samples. The location method of this invention can simply and effectively establish the positional relationship between internal feature points and surface features, accurately locating internal defect features in CZT samples. This allows for convenient and rapid determination of the specific location for preparing transmission electron microscopy (TEM) samples, thus improving the quality of TEM samples.

Description

Technical Field

[0001] This invention relates to the field of cadmium zinc telluride (CZN) materials technology, and in particular to a method for locating characteristic defects in CZN samples and a method for preparing CZN samples. Background Technology

[0002] Cd 1-X Zn X Te crystal is a compound crystal composed of cadmium (Cd), zinc (Zn), and tellurium (Te). It is an important semiconductor material with a wide range of applications, especially in detector fabrication. Not only can it be used as a detector material itself, but it can also be perfectly matched with mercury cadmium telluride (MCT) materials through compositional adjustments, serving as a substrate material for infrared detector development.

[0003] Due to Cd 1-X Zn X The Te single-crystal growth environment results in a large number of typical crystal defects, mainly including dislocations, twins, stacking faults, small-angle grain boundaries, inclusions / precipitates, etc. Currently, studying the characteristics and composition of these defects has become crucial for improving Cd. 1- X Zn X Te single crystal quality is a key breakthrough. In the study of crystal defects, transmission electron microscopy (TEM) is an important tool. It involves preparing TEM samples containing defect feature points and observing and analyzing them using a TEM microscope.

[0004] Therefore, it is necessary to select the portion of the wafer containing defect feature points for transmission electron microscopy (TEM) sample preparation. In related technologies, TEM sample preparation methods generally include: sample selection, choosing materials containing the desired defect feature points for preparation; followed by subsequent processing such as cutting, grinding, thinning, etching, cleaning, and polishing. After preparation, the required high-resolution image is obtained using a TEM. 1-X Zn X Te single crystals are generally prepared for transmission electron microscopy (TEM) samples at the wafer stage. Because inclusions and precipitates on the surface are extremely easy to detach during wafer processing, it is not conducive to TEM sample preparation. Moreover, since TEM sample preparation is carried out using a dual-beam scanning electron microscope (FIB-SEM) system, the imaging modes of the electron beam and ion beam limit it to the observation and analysis of the material surface, and it is impossible to observe the internal defect features of the sample. This makes it impossible to accurately locate the internal defect positions and to prepare samples containing defect feature points inside. Summary of the Invention

[0005] To overcome the defects existing in the above-mentioned transmission electron microscopy sample preparation process, the technical problem to be solved by the present invention is to provide a method for locating characteristic defects of cadmium zinc telluride (CZT) samples and a method for preparing CZT samples, which can accurately locate the internal defect features of CZT samples.

[0006] Regarding the method for locating characteristic defects in cadmium zinc telluride samples, the method of the present invention for solving the above-mentioned technical problem includes the following steps: determining the positions of internal feature points of the sample under an infrared transmission microscope; establishing marking features on the sample surface using FIB-SEM; and determining the relative position of the internal feature points projected onto the sample surface by establishing a geometric relationship between the virtual position of the internal feature points projected onto the sample surface and the marking features. Wherein, the position of the internal feature point is any position within the vicinity of the internal feature point; and the marking feature is a mark at any position near the region of the internal feature point.

[0007] This method utilizes infrared transmission microscopy (IRS) to measure the distance between internal feature points and surface markers in cadmium zinc telluride (CZD) samples. By continuously marking these points using FIB-SEM, the relative positions of the feature points and markers are clarified, allowing for precise localization of internal defects within the CZD samples. This enables the preparation of transmission electron microscopy (TEM) samples at the designated feature point locations. This simple and effective method establishes the positional relationship between internal and surface features, facilitating the rapid and convenient determination of the specific locations for TEM sample preparation. It provides a foundation for efficient TEM sample preparation and promotes improved sample quality.

[0008] As an improvement to the method for locating characteristic defects in cadmium zinc telluride samples, two marking features are used, namely, point markings, denoted as mark a and mark b. The distance between the internal feature point and mark a is determined by infrared transmission microscopy and denoted as l. a The distance between the internal feature point and the label b is denoted as l. b Using FIB-SEM with marker a as the center and length l as the length, a Etch a mark with radius b; with mark b as the center and length l as the radius. bEtching marks are made around a radius, and two etched marks intersect. The intersection point of the two etched marks is used to determine the relative position closest to the virtual position of the feature point projected onto the sample surface. By establishing two marker features, the relative position of the feature point and the marker point can be determined efficiently and quickly. The etching marks clearly establish the geometric relationship between the virtual position of the feature point projected onto the sample surface and the marker features. The relative position of the feature point projected onto the sample surface is the location of one of the intersection points formed by the etched marks. Then, transmission electron microscopy (TEM) sample preparation can be performed based on the relative position, enabling more efficient and accurate localization of internal defect features in cadmium zinc telluride (CZN) samples, thus improving the quality of TEM samples.

[0009] As an improvement to the method for locating characteristic defects in cadmium zinc telluride samples, the etching mark is a circular mark, and one of the intersection points is the closest relative position of the virtual position of the feature point projected onto the sample surface. The use of circular marks is convenient for operation, provides clear markings, and facilitates observation and measurement.

[0010] Regarding the preparation method of zinc cadmium telluride samples, the preparation method of the present invention for solving the above-mentioned technical problems further includes: preparing transmission electron microscopy samples according to the relative positions.

[0011] The tellurium zinc cadmium sample preparation method provided by this invention implements the steps of the above-mentioned positioning method. The beneficial effects of the tellurium zinc cadmium sample preparation method include the beneficial effects of the above-mentioned positioning method. On this basis, the beneficial effects achieved by the tellurium zinc cadmium sample preparation method are the same as the beneficial effects of the above-mentioned positioning method, and will not be repeated here.

[0012] As an improvement to the method for preparing zinc cadmium telluride samples, before preparing the transmission electron microscope (TEM) sample based on the relative position, the method further includes: determining whether the distance between the obtained relative position and the virtual position of the orthographic projection of the nearest feature point onto the sample surface is less than a threshold; if the determination result is yes, preparing the TEM sample based on the relative position.

[0013] As an improvement to the sample preparation method for zinc cadmium telluride, in the case of a negative result, the second relative position that is closest to the virtual position of the orthographic projection of the feature point on the sample surface is determined.

[0014] In the above preparation method, determining the second relative position closest to the virtual position of the feature point's orthographic projection on the sample surface includes: observing the distance between the feature point and the relative position under an infrared transmission microscope, denoted as l. c The angle formed by the virtual line connecting the feature points and their relative positions, and the virtual line connecting the relative positions and the marked features, is denoted as α; in FIB-SEM, based on the distance l cThe etched marking feature, denoted as mark c, is located at the position of mark c. This position is the second relative position closest to the virtual position of the feature point's orthographic projection onto the sample surface. This step further corrects the accuracy of the relative position, allowing for a more precise determination of the closest position to the feature point's orthographic projection on the sample surface, until the relative position is directly above the internal feature point. This supports the determination of the optimal defect feature point location under different research conditions, based on the specific research object and objective. The transmission electron microscope sample is then prepared based on this second relative position.

[0015] The above-described method for preparing zinc-cadmium telluride samples implements the steps of the above-described positioning method. The beneficial effects of the zinc-cadmium telluride sample preparation method include the beneficial effects of the above-described positioning method. On this basis, the above-described zinc-cadmium telluride sample preparation method also determines the second relative position closest to the virtual position of the orthographic projection of the feature point on the sample surface through a second feature marking process. Compared with the relative position closest to the virtual position of the orthographic projection of the feature point on the sample surface obtained in a single step, the second relative position obtained by the above-described preparation method is closer to the virtual position of the orthographic projection of the feature point on the sample surface. The positioning result is more accurate, which is a further correction of the aforementioned relative position and further reduces the error. Attached Figure Description

[0016] Figure 1 This is a flowchart of a method for locating characteristic defects in cadmium zinc telluride samples according to an embodiment of the present invention.

[0017] Figure 2 This is a schematic diagram of the location of feature points under an infrared microscope according to an embodiment of the present invention;

[0018] Figure 3 This is a schematic diagram of two cross marks made under FIB-SEM according to an embodiment of the present invention;

[0019] Figure 4 This is a schematic diagram of distance measurement under an infrared transmission microscope according to an embodiment of the present invention;

[0020] Figure 5 A schematic diagram illustrating the determination of location by drawing a graphic under FIB-SEM according to an embodiment of the present invention;

[0021] Figure 6 This is a schematic diagram of position correction according to an embodiment of the present invention; Detailed Implementation

[0022] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments.

[0023] The steps described in the specification and the flowcharts in the accompanying drawings of this invention are not necessarily to be strictly followed according to the step numbers; the execution order of the steps can be changed. Furthermore, certain steps can be omitted, multiple steps can be combined into one step, and / or one step can be broken down into multiple steps.

[0024] The conventional method for observing inclusions and precipitates within cadmium zinc telluride (CdZZ) wafers is to use an infrared transmission microscope (IRM). IRM is a microscope used to observe and analyze the infrared radiation characteristics of materials. Unlike ordinary optical microscopes, IRM uses an infrared light source and an infrared detector, allowing for the observation and analysis of the absorption, transmission, and reflection characteristics of materials in the infrared band. Equipped with an infrared light source and an infrared detector in the 0.4–1.8 μm wavelength range, it enables signal detection. (The last sentence appears to be incomplete and possibly refers to CdZZ / C ... 1-X Zn X Te crystals have a wide band gap and high infrared transmittance in the infrared radiation band of 0.9–30 μm. Therefore, infrared transmission microscopes can be used to observe and locate feature points inside cadmium zinc telluride wafers. At the same time, the instrument can also be used to observe the surface of cadmium zinc telluride wafers.

[0025] The first embodiment of this invention provides a method for locating characteristic defects in cadmium zinc telluride (CZN) samples, enabling the preparation of transmission electron microscopy (TEM) samples at the defect feature points. The method includes the following specific steps: determining the positions of internal feature points under an infrared transmission microscope; establishing marking features on the sample surface using FIB-SEM; determining the relative position of the internal feature points projected onto the sample surface by establishing a geometric relationship between the virtual position of the internal feature points projected onto the sample surface and the marking features; and preparing the TEM sample based on the relative position. By observing the distance between the internal feature points of the CZN sample and the markings on the material surface through infrared transmission microscopy, and by continuously marking with FIB-SEM, the relative position of the feature points and the marking points is clarified, allowing for precise location of internal defect features in the CZN sample, thereby enabling the preparation of TEM samples at the feature point locations. This method simply and effectively establishes the positional relationship between internal feature points and surface features, thus enabling convenient and rapid determination of the specific location for preparing TEM samples, providing a foundation for efficient TEM sample preparation and promoting improved TEM sample quality.

[0026] In practice, Figure 1 This is a flowchart of an embodiment of the present invention, such as... Figure 1 As shown, step S101 involves observing the sample using an infrared transmission microscope to locate internal feature points and confirm their approximate positions within the sample. First, the initial sample is placed under the infrared transmission microscope, and then observed. At this point, the positions of defect feature points in the initial sample can be preliminarily observed, for example, as... Figure 2 The diagram shows a schematic representation of the feature point locations under an infrared microscope according to an embodiment of the present invention. It is worth noting that the approximate locations of the defect feature points in the initial sample only need to be determined.

[0027] Step S102: Load the sample into the FIB-SEM and mark the approximate area of ​​the sample's characteristic points, denoted as point markers a and b. The FIB-SEM is a dual-beam scanning electron microscope system, which combines focused ion beam etching (FIB) and scanning electron microscopy (SEM). It can remove material surfaces through ion beam etching while simultaneously observing and analyzing the sample using scanning electron microscopy. In this embodiment, the marking pattern consists of two lines of specific length intersecting to form a mark. The intersection of mark a and mark b is set at a specific distance, for example, as shown below. Figure 3 As shown, Figure 3 The diagram shows two cross marks made under FIB-SEM according to an embodiment of the present invention. Specifically, the two lines are set to a length of 30 μm, and the distance between the intersection of mark a and the intersection of mark b is set to 80 μm.

[0028] Step S103, as follows Figure 4 As shown, Figure 4 This diagram illustrates a distance measurement under an infrared transmission microscope according to an embodiment of the present invention. A sample marked with labels a and b is taken out and observed under the infrared transmission microscope. The distance between the internal feature point and the two cross-shaped marks a and b is determined and denoted as l. a and l b Among them, l a The distance between the intersection of marker a and the location of the defect feature point in the initial sample determined in step S101 is l. b The distance between the intersection of marker b and the location of the defect feature point in the initial sample determined in step S101.

[0029] Step S104, as follows Figure 5 As shown, Figure 5 This diagram illustrates the method for determining the position of a graphic using FIB-SEM according to an embodiment of the present invention. Based on the distance between the internal feature points and the two cross marks observed under an infrared transmission microscope in step S103, FIB-SEM is used with the intersection of mark a as the center and a length l... a A circular mark is etched with a radius of 1; then, using FIB-SEM with the intersection of mark b as the center and a length l, a circular mark is etched. bCircular marks are etched around the radius. The intersection of two of these circular marks represents the closest point on the sample surface where the feature point's orthographic projection is located. Then, infrared spectroscopy is used to confirm the location of one of the intersection points under a microscope, confirming this closest point on the sample surface. The transmission electron microscopy (TEM) sample can then be prepared at this location. It's important to note that this intersection point is the point between the two circles closest to the feature point; the point on the sample surface where the feature point's orthographic projection is located is directly above the sample's thickness. It's worth noting that the circular marks in this embodiment are a specific operational method and do not limit the determination of the closest point on the sample surface; the same effect can be achieved using arc-shaped marks.

[0030] As a further improvement to the method for locating internal characteristic defects in cadmium zinc telluride samples of the present invention, the optimal location of defect feature points needs to be determined according to the specific research object and target under different research conditions. If the feature point location obtained according to the above steps deviates significantly from the target value required by the experiment, the following steps can be used to correct the location to ensure sample quality.

[0031] Step S105: Is the intersection of the two circles closest to the feature point directly above the thickness direction of the feature point? If the error between the obtained relative position and the target value is within a set threshold, then prepare the transmission electron microscope sample according to the relative position. If the error between the obtained relative position and the target value is greater than the set threshold, then proceed to steps S106 and S107.

[0032] Step S106, as follows Figure 6 As shown, Figure 6 The diagram illustrates the position correction method according to an embodiment of the present invention. The distance between the feature point and the nearest intersection point of the two circles (to reduce error) is observed under an infrared transmission microscope and denoted as l. c The angle formed by the virtual line connecting the feature point to the nearest intersection of the two circles and the virtual line connecting the nearest intersection of the two circles to the intersection of the mark 'a' is denoted as α. In other words, l c The distance between the nearest intersection of the two circles in step S104, i.e., the position closest to the orthographic projection of the feature point on the sample surface, and the position of the defect feature point in the initial sample determined in step S101.

[0033] Next, in step S107, as follows: Figure 6 As shown, under FIB-SEM, based on distance l cA cross mark of a specific line length is etched at angle α, denoted as c; for example, a cross mark with a line length of 20 μm is specifically set. This correction step allows for more precise determination that the cross mark c is the surface mark directly above the internal feature point, at which a transmission electron microscope (TEM) sample can be prepared. If the feature point position obtained according to the above steps still deviates from the experimental target value, further position correction can be performed using steps S105 and S106 to obtain a position closer to the orthographic projection of the feature point onto the sample's upper surface.

[0034] Through the description of specific embodiments, a more in-depth and specific understanding should be gained of the technical means and effects adopted by the present invention to achieve the intended purpose. However, the accompanying drawings are only provided for reference and illustration and are not intended to limit the present invention.

Claims

1. A method for preparing a zinc cadmium telluride sample, characterized in that, The process involves locating internal defect features in cadmium zinc telluride (CZN) samples to prepare transmission electron microscopy (TEM) samples at these characteristic locations, including: The location of internal feature points in the sample was determined using an infrared transmission microscope; Marking features were established on the sample surface using FIB-SEM. By establishing the virtual position of the orthographic projection of the internal feature points of the sample onto the sample surface and the geometric relationship between the marked features, the relative position of the orthographic projection of the internal feature points of the sample onto the sample surface is determined. The marking feature has two parts, namely, point marking, and the marking feature is denoted as mark a and mark b; By establishing the virtual position of the orthographic projection of the internal feature points onto the sample surface and the geometric relationship between the marked feature: the distance between the internal feature points and the mark a is determined by infrared transmission microscopy, denoted as . The distances between the internal feature points and the label b are denoted as . Using FIB-SEM with marker 'a' as the center and length as the distance, Etch markings are made with radius as the center; with mark b as the center and length as the radius as the radius. Etching marks are made for the radius, and two etching marks intersect. The relative position closest to the virtual position of the feature point projected onto the sample surface is determined based on the intersection of the two etching marks. Determine whether the distance between the obtained relative position and the virtual position of the closest feature point projected onto the sample surface is less than a threshold. If the determination result is yes, the transmission electron microscope sample is prepared according to the relative position; If the judgment result is negative, determine the second relative position that is closest to the virtual position of the feature point projected onto the sample surface; Determining the second relative position closest to the virtual position of the feature point's orthographic projection on the sample surface includes: observing the distance between the feature point and the relative position under an infrared transmission microscope, denoted as . The angle formed by the virtual line connecting the feature points and their relative positions, and the virtual line connecting the relative positions and the marked features, is denoted as α; in FIB-SEM, based on distance... The etching mark feature with angle α is denoted as mark c. The position of mark c is the second relative position that is closest to the virtual position of the feature point projected onto the sample surface. Transmission electron microscopy sample preparation is performed based on the second relative position.

2. The preparation method according to claim 1, characterized in that, The location of the internal feature point is any position within the range of the internal feature points of the sample.

3. The preparation method according to claim 1, characterized in that, The marking feature is a mark at any position near the internal feature point region.

4. The preparation method according to claim 1, characterized in that, The etching mark is a circular mark. The intersection point of two etching marks that is closest to the feature point is the closest relative position of the virtual position of the feature point projected onto the sample surface.

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