Method for preparing electron energy loss spectrum sample

Abstract

The invention provides a method for preparing an electron energy loss spectrum sample, and the method comprises the steps: positioning a defect region in a device through an electron beam absorption current method, and making a first positioning mark adjacent to the defect region, a focused ion beam is used for thinning in the first direction to obtain a first sample containing the first positioning mark and the defect area, the distance between the first positioning mark and the defect area in the second direction is obtained, the second direction is perpendicular to the first direction, and on the basis of the distance and the size of the defect area, the defect area is obtained. And making a second positioning mark, and thinning the first sample in a second direction by using a focused ion beam by taking the second positioning mark as a reference to obtain a second sample containing the defect area. The method can be used for accurately preparing the electron energy loss spectrum thin sample with tiny defects.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor manufacturing, and more specifically, relates to a method for preparing samples for electron energy loss spectroscopy. Background Art

[0002] The gate oxide layer is a very thin insulating material in a Metal-Oxide-Semiconductor (MOS) device, usually silicon dioxide (SiO2), located between the gate and the substrate. Its main function is to isolate the gate and the substrate and control the flow of current simultaneously. Gate oxide leakage refers to the phenomenon that current leaks through the insulating layer (gate oxide layer) between the gate and the substrate when the MOS transistor is in the off state. As the transistor size continues to shrink and the power supply voltage decreases, the thickness of the gate oxide layer also continues to decrease, resulting in an exponential increase in the gate leakage current.

[0003] Gate oxide leakage can lead to a reduction in the battery life of low-power devices, limit the signal holding time. Especially in the off state, the leakage will cause unnecessary energy consumption and a decline in device performance. After gate oxide leakage occurs, failure analysis needs to be carried out to analyze the chemical composition and elemental valence states of the defects, and then determine the cause of failure.

[0004] In semiconductor failure analysis, generally after locating the failure position by electron beam induced current, a sample with a thickness greater than 200 nm is prepared according to the circuit near the failure position by using focused ion beam technology. For gate oxide leakage, since the defect size is too small for the scanning electron microscope to see the defect position, Figure 1 For a schematic diagram of preparing a sample containing a defect area by using focused ion beam technology, please refer to Figure 1 , at the failure position circled by the blue box in the scanning electron microscope, the defect is invisible. However, when using electron energy loss spectroscopy to analyze the chemical composition and elemental valence states of the defects, the sample needs to be as thin as possible, otherwise the multiple scattering will affect the analysis effect due to the too thick sample. However, when further thinning the sample due to the too small defect size, the defect may be cut off.

[0005] ‌ Summary of the Invention The purpose of the present invention is to provide a method for preparing samples for electron energy loss spectroscopy, which can solve the problem that the defect is invisible during the sample preparation process by using focused ion beam technology, resulting in the inability to accurately prepare a sample with a defect during the sample thinning process.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is: The present invention provides a method for preparing samples for electron energy loss spectroscopy, and the method includes: Locate the defective area in the device by the electron beam absorption current method; Fabricate a first positioning mark adjacent to the defective area, and use a focused ion beam to thin in a first direction to obtain a first sample including the first positioning mark and the defective area; Obtain the distance between the first positioning mark and the defective area in a second direction, where the second direction is perpendicular to the first direction; Fabricate a second positioning mark based on the distance and the size of the defective area; Taking the second positioning mark as a reference, use a focused ion beam to thin the first sample in the second direction to obtain a second sample including the defective area.

[0007] In one embodiment, fabricating a first positioning mark adjacent to the defective area and using a focused ion beam to thin in a first direction to obtain a first sample including the defective area includes: Fabricate a first electron beam protection layer on the device, where the area of the first electron beam protection layer is larger than the area of the first positioning mark; Fabricate the first positioning mark on the first electron beam protection layer; Fabricate a first ion beam protection layer on the first electron beam protection layer.

[0008] In one embodiment, obtaining the distance between the first positioning mark and the defective area in a second direction includes: Use a transmission electron microscope to obtain the distance between the first positioning mark and the defective area in a second direction.

[0009] In one embodiment, the thickness of the first sample in the first direction is greater than or equal to 200 nm.

[0010] In one embodiment, fabricating a second positioning mark based on the positional relationship and the size of the defective area includes: fabricating a second protection layer on the upper surface of the defective position, where the area of the second protection layer is larger than the area of the defective area; Fabricate the second positioning mark on the second protection layer.

[0011] In one embodiment, fabricating a second positioning mark based on the distance and the size of the defective area includes: the width of the second positioning mark in the second direction is equivalent to the width of the defective area.

[0012] In one embodiment, taking the second positioning mark as a reference and using a focused ion beam to thin the first sample in the second direction to obtain a second sample including the defective area includes: Thin the first sample in the second direction based on the width of the defect area to obtain the second sample.

[0013] In one embodiment, after making the second positioning mark based on the positional relationship and the size of the defect area in the second direction, it further includes: making third positioning marks on both sides of the second positioning mark in the second direction, and the third positioning marks are used to identify the thinning direction.

[0014] In one embodiment, thinning the first sample in the second direction based on the width of the defect area to obtain the second sample includes: Use a first ion beam to thin until the third positioning mark initially appears; Use a second ion beam for fine thinning until the third positioning mark is completely exposed and then terminate. The power of the first ion beam is greater than the power of the second ion beam.

[0015] In one embodiment, it further includes: obtaining the electron energy loss spectrum of the final sample to obtain the chemical composition and element valence state of the defect area.

[0016] The method for preparing an electron energy loss spectrum sample provided by the present invention includes locating a defect area in a device by an electron beam absorption current method, making a first positioning mark adjacent to the defect area, using a focused ion beam to thin in a first direction to obtain a first sample including the first positioning mark and the defect area, obtaining the distance between the first positioning mark and the defect area in a second direction, the second direction being perpendicular to the first direction, making a second positioning mark based on the distance and the size of the defect area, and using the second positioning mark as a reference, using a focused ion beam to thin the first sample in the second direction to obtain a second sample including the defect area. This method thins in the first direction after locating the defect area in the device to make a first sample including the defect area and the first positioning mark, makes a second positioning mark based on the positional relationship between the first positioning mark and the defect area on the first sample and the size of the defect area, and uses the second positioning mark as a reference to thin the first sample in the second direction to obtain a second sample including the defect area. This method can accurately prepare an electron energy loss spectrum thin sample with a tiny defect retained. Description of the Drawings

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0018] Figure 1 Schematic diagram of preparing a sample containing a defect region using a focused ion beam technique; Figure 2 Schematic flow chart of the method for preparing an electron energy loss spectroscopy sample provided by an embodiment of the present invention; Figure 3 Schematic diagram of a first positioning mark and a defect region on a first sample after thinning in a first direction provided by an embodiment of the present invention; Figure 4 Schematic diagram of the positional relationship between a second positioning mark, a first positioning mark and the defect region provided by an embodiment of the present invention; Figure 5 Schematic diagram of the second positioning mark after being cut straight forward and backward along a second direction provided by an embodiment of the present invention; Figure 6 Schematic diagram of the first sample after thinning in a second direction provided by an embodiment of the present invention; Figure 7 Schematic diagram of using electron energy loss spectroscopy to characterize the chemical composition of a defect provided by an embodiment of the present invention; Figure 8 Schematic diagram of using electron energy loss spectroscopy to characterize the chemical composition of a defect provided by an embodiment of the present invention. Detailed implementation manners

[0019] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0020] In the description of the present invention, it should be understood that the terms "including" and "having", and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units does not necessarily have to be limited to those clearly listed steps or units, but may include other steps or units that are not clearly listed or are inherent to these processes, methods, products or devices.

[0021] It should be understood that the orientation or positional relationship indicated by the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and thus should not be construed as a limitation to the present invention.

[0022] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more such features. It should be understood that the term "and / or" used herein is merely a description of the relationship between associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0023] In semiconductor failure analysis, generally after the failure location is located by electron beam induced current, a sample with a thickness greater than 200 nm is prepared by focused ion beam technology according to the circuit near the failure location. For gate oxide leakage, since the defect size is too small for a scanning electron microscope to see the defect location, Figure 1 For a schematic diagram of preparing a sample containing a defect region in the focused ion beam technology, please refer to Figure 1 , at the failure location circled by the blue box in the scanning electron microscope, the defect is invisible. However, when analyzing the chemical composition and elemental valence state of the defect by electron energy loss spectroscopy, the sample needs to be as thin as possible, otherwise multiple scattering due to the too-thick sample will affect the analysis effect. However, when further thinning the sample due to the too-small defect size, the defect may be cut off. The present invention provides a method for preparing an electron energy loss spectroscopy sample based on the above problems.

[0024] The method for preparing an electron energy loss spectroscopy sample provided by the present invention will be described in detail below with reference to specific embodiments.

[0025] Figure 2 For a schematic flow chart of the method for preparing an electron energy loss spectroscopy sample provided by an embodiment of the present invention, please refer to Figure 2 , this embodiment provides a method for preparing an electron energy loss spectroscopy sample, and the method includes: S101. Locate the defect region in the device by electron beam induced current method; Specifically, the electron beam absorption current method of this embodiment is an electron beam technology for locating defective areas in a device. Its principle is to irradiate an electron beam on a sample. When the electron beam scans to a certain point, if this point is a metal wire and is electrically connected through a nano-probe, electrons will be absorbed by the metal wire in the component and exported to an amplifier through the nano-probe, thereby obtaining the absorption current at this position. Through signal processing, the position of the defect can be determined. The method for locating the defective area 1 in the device by the electron beam absorption current method in this embodiment belongs to the prior art, and the specific operation process of locating the defective area 1 in the device by the electron beam absorption current method will not be elaborated in this embodiment.

[0026] S102. Fabricate a first positioning mark adjacent to the defective area, and use a focused ion beam to thin in a first direction to obtain a first sample including the first positioning mark and the defective area; Specifically, the focused ion beam technology uses an electric lens to focus an ion beam into an ion beam with a very small size to bombard the surface of a material, realizing the peeling, deposition, implantation, cutting, and modification of the material. The focused ion beam technology takes a gallium ion source as the core, and through precise control of the interaction between the ion beam and the sample surface, realizes nano-scale fine operations. Figure 3 For the schematic diagram of the first positioning mark and the defective area on the first sample after thinning in the first direction provided by the embodiment of the present invention, please refer to Figure 3 After the defective area 1 in the device is located by the electron beam absorption current method in this embodiment, a first positioning mark 2 is fabricated at a position adjacent to the defective area 1 by using a focused ion beam, and a first sample including the defective area 1 and the first positioning mark 2 is fabricated by cutting and thinning along the first direction with the focused ion beam. The width of the first sample fabricated in this embodiment is generally greater than 200 nm. The first positioning mark 2 in this embodiment is a reference mark for positioning the second positioning mark 3, and no special limitation is imposed on the specific size of the first positioning mark 2 in this embodiment. Exemplarily, the size of the outer contour of the first positioning mark 2 is 0.7 μm in length and 0.04 μm in width.

[0027] S103. Obtain the distance between the first positioning mark and the defective area in a second direction, where the second direction is perpendicular to the first direction; Specifically, after the above-mentioned first sample is fabricated, it is transferred to a copper mesh and photographed with a transmission electron microscope. Please refer to Figure 3 In this embodiment, the distance from the defective area 1 to the first positioning mark 2 in the second direction is 1.83 μm.

[0028] S104. Fabricate a second positioning mark based on the positional relationship and the size of the defective area; Specifically, Figure 4Schematic diagram of the positional relationship between the second positioning mark, the first positioning mark and the defect area provided by the embodiment of the present invention. In this embodiment, please refer to Figure 4 , after the distance between the defect area 1 and the first positioning mark 2 in the second direction is determined, the second positioning mark 3 is made with reference to the distance between the defect area 1 and the first positioning mark 2 in the second direction and the size of the defect area 1. The width of the defect area 1 in this embodiment is D1, and the length is D2. The width of the second positioning mark 3 in this embodiment in the second direction is the width of the defect area 1. The length of the second positioning mark 3 in this embodiment in the direction perpendicular to the second direction is generally an empirical value. For example, the length of the second positioning mark 3 in the direction perpendicular to the second direction is 0.7um, 1um, to avoid the phenomenon that the second positioning mark 3 is not obvious due to the too short length of the second positioning mark 3. Exemplarily, the width D1 of the defect area 1 in this embodiment is 0.04um, the length of the second positioning mark 3 in this embodiment is 0.7um, and the width is 0.04um. In this embodiment, an electron energy loss spectrum sample is obtained with reference to the second positioning mark 3. Since the sample required for the electron energy loss spectrum is an ultra-thin sample, the second positioning mark 3 is prepared based on the width of the defect area 1, which can ensure that the obtained electron energy loss spectrum sample is thin enough.

[0029] S105. With the second positioning mark as a reference, use a focused ion beam to thin the first sample in the second direction to obtain a second sample containing the defect area.

[0030] Specifically, Figure 5 Schematic diagram of the second positioning mark after being cut front and back along the second direction provided by the embodiment of the present invention, Figure 6 Schematic diagram of the first sample thinned in the second direction provided by the embodiment of the present invention. Please refer to Figure 5 , Figure 6 , in this embodiment, with the second positioning mark 3 as a reference, since the width of the second positioning mark 3 in the second direction is the width of the defect area 1, that is, in the second direction, with the width of the defect area 1 as a reference based on the distance between the first positioning mark 2 and the defect area 1 in the second direction, using a focused ion beam to thin the first sample can obtain a second sample containing the defect area 1. When preparing an electron energy loss spectrum sample in this embodiment, the width of the finally obtained second sample in the second direction is D1, that is, the thickness of the second sample is the width of the defect area 1, that is, this embodiment can accurately prepare an electron energy loss spectrum thin sample with a small defect retained.

[0031] The preparation of the electron energy loss spectrum sample in this embodiment can be applied to the failure analysis after gate oxide layer leakage, The principle of electron energy loss spectroscopy is to study the physical and chemical properties of a sample by analyzing the energy lost by an incident electron beam during inelastic scattering in the sample. When an electron beam with a known kinetic energy is incident on the material to be measured, some electrons interact with atoms and undergo inelastic scattering, losing some energy and undergoing small deflections in their paths. These energy losses can be measured by an electron spectrometer and reflect information such as the chemical composition, chemical bonds, and electronic structure of the sample. When performing failure analysis after gate oxide layer leakage, when using electron energy loss spectroscopy to analyze the chemical composition and element valence states of defects, the sample needs to be as thin as possible. Otherwise, multiple scattering due to the too-thick sample will affect the analysis effect. The thickness of the second sample prepared by the method for preparing an electron energy loss spectroscopy sample in this embodiment is the same as the width of the defect region 1, which can meet the failure analysis after gate oxide layer leakage.

[0032] In the method for preparing an electron energy loss spectroscopy sample in this embodiment, after locating the defect region 1 in the device, a first sample containing the defect region 1 and the first positioning mark 2 is fabricated by thinning in the first direction using a focused ion beam, and a second positioning mark 3 is fabricated by observing the positional relationship between the first positioning mark 2 and the defect region 1 and the size of the defect region through a transmission electron microscope on the first sample. A second sample containing the defect region 1 is fabricated with reference to the second positioning mark 3, and the second sample is thinned in the second direction to obtain a final sample containing the defect region 1. The method for preparing an electron energy loss spectroscopy sample in this embodiment can accurately prepare a thin sample with minute defects when applied to gate oxide layer leakage failure analysis.

[0033] The method for preparing an electron energy loss spectroscopy sample according to an embodiment of the present invention includes locating a defect region in a device by an electron beam induced current method; fabricating a first positioning mark adjacent to the defect region, and obtaining a first sample containing the first positioning mark and the defect region by thinning in a first direction using a focused ion beam; obtaining the distance between the first positioning mark and the defect region in a second direction perpendicular to the first direction, and fabricating a second positioning mark based on the distance and the size of the defect region; and obtaining a second sample containing the defect region by thinning the first sample in the second direction with reference to the second positioning mark. After locating the defect region in the device, the method thins in the first direction to fabricate a first sample containing the defect region and the first positioning mark, fabricates a second positioning mark based on the positional relationship between the first positioning mark and the defect region and the size of the defect region on the first sample, and obtains a second sample containing the defect region by thinning the first sample in the second direction with reference to the second positioning mark. This method can accurately prepare a thin electron energy loss spectroscopy sample retaining minute defects.

[0034] Further, a first positioning mark 2 is fabricated adjacent to the defect region 1. Thinning the first sample containing the defect region 1 in a first direction using a focused ion beam includes: fabricating a first electron beam protection layer on the device, where the area of the first electron beam protection layer is larger than the area of the first positioning mark 2; fabricating the first positioning mark 2 on the first electron beam protection layer; and fabricating a first ion beam protection layer on the first electron beam protection layer.

[0035] Specifically, in this embodiment, a focused ion beam cutting is generally used to fabricate the first positioning mark 2. The functions of the first electron beam protection layer in this embodiment include the following points: First, to prevent irradiation damage. During the focused ion beam cutting process, high-energy gallium ions (Ga+) will bombard the surface of the sample, which may cause damage to the sample. By depositing a protection layer on the surface of the sample, this irradiation damage can be effectively prevented to ensure the integrity of the sample; Second, to improve the analysis accuracy. The presence of the protection layer can reduce the deformation or damage of the sample during subsequent processing, thereby ensuring the accuracy of the analysis results. In this embodiment, after the first positioning mark 2 is fabricated, a first ion beam protection layer is fabricated on the first electron beam protection layer. The first ion beam protection layer can improve the strength of the sample during the thinning process and prevent the sample from being damaged during the thinning process. The first electron beam protection layer in this embodiment is a protection layer deposited by an electron beam, and the low electron beam energy will not damage the sample. The first ion beam protection layer is a protection layer deposited by an ion beam. The high ion beam energy can better prevent the sample from being damaged during the thinning process, and moreover, the first ion beam protection layer is deposited on the first electron beam protection layer without damaging the sample.

[0036] In one embodiment, obtaining the distance between the first positioning mark 2 and the defect region 1 in a second direction includes: using a transmission electron microscope to obtain the distance between the first positioning mark 2 and the defect region 1 in the second direction.

[0037] In this embodiment, the first sample is observed using a transmission electron microscope. The transmission electron microscope can achieve a very high spatial resolution to provide high contrast of the microscopic image and improve the accuracy of marking the distance between the first positioning mark 2 and the defect region 1.

[0038] Specifically, the thickness of the first sample in the first direction is greater than or equal to 200 nm. The thickness of the first sample in this embodiment in the first direction is about 200 nm. The first sample in this embodiment is thinned and obtained by a focused ion beam technique under a scanning electron microscope system.

[0039] Specifically, based on the distance and the size of the defect area 1, fabricating the second positioning mark 3 includes: fabricating a second electron beam protection layer on the upper surface of the defect area, where the area of the second electron beam protection layer is larger than the area of the defect area; fabricating the second positioning mark on the second electron beam protection layer; and fabricating a second ion beam protection layer on the second electron beam protection layer.

[0040] Fabricate a second protection layer 4 on the upper surface of the defect area 1, where the area of the second protection layer 4 is larger than the area of the defect area 1; fabricate the second positioning mark 3 on the second protection layer 4.

[0041] Please refer to Figure 5 , in this embodiment, a second electron beam protection layer 4 is fabricated on the upper surface of the defect position before fabricating the second positioning mark 3, and the second positioning mark 3 is fabricated on the second electron beam protection layer 4. The second positioning mark 3 of this embodiment is fabricated using a focused ion beam. To prevent the sample from being irradiated and damaged by the gallium ion beam during the processing of the second positioning mark 3, the second positioning mark 3 of this embodiment is fabricated on the second electron beam protection layer 4, thereby ensuring the integrity of the sample and the accuracy of the analysis in the later stage. To better prevent damage to the sample when fabricating the second positioning mark 3, the area of the second electron beam protection layer 4 is larger than the area of the defect area 1. After the second positioning mark 3 is fabricated in this embodiment, a second ion beam protection layer 5 is fabricated on the second electron beam protection layer 4. The second ion beam protection layer 5 can improve the strength of the sample during the thinning process and prevent the sample from being damaged during the thinning process. The second electron beam protection layer 4 of this embodiment is a protection layer deposited using an electron beam, and the electron beam has a low energy and will not damage the sample. The second ion beam protection layer 5 is a protection layer deposited using an ion beam. The ion beam has a high energy and can better prevent the sample from being damaged during the thinning process. Moreover, the second ion beam protection layer 5 is deposited on the second electron beam protection layer 4 and will not damage the sample.

[0042] Specifically, based on the distance and the size of the defect area 1, fabricating the second positioning mark 3 includes: the width of the second positioning mark 3 in the second direction is equivalent to the width of the defect area 1.

[0043] Since the sample needs to be thin enough when fabricating an electron energy loss spectroscopy sample, the width of the second positioning mark 3 in the second direction is equivalent to the width of the defect area 1. When thinning the first sample in the second direction, using the width of the defect area 1 as a reference can ensure that a thin enough sample including the defect area 1 is obtained.

[0044] Specifically, taking the second positioning mark 3 as a reference, using a focused ion beam to thin the first sample in the second direction to obtain a second sample containing the defect area 1 includes: Thin the first sample in the second direction based on the width of the defect region 1 to obtain the second sample.

[0045] Specifically, in this embodiment, after thinning the initial sample in the second direction based on the width of the second positioning mark 3 to obtain the final sample, it can ensure that the defect position is on the final sample, and can ensure that the final sample is thin enough to meet the requirements for making a thin sample for electron energy loss spectroscopy. That is, it can ensure that the parts outside the defect region 1 are cut off before and after making the electron energy loss spectroscopy sample, avoiding the influence of multiple scattering on the analysis effect caused by the sample being too thick. In this embodiment, when making the second sample, focused ion beam thinning is used.

[0046] In a specific embodiment, based on the distance and the size of the defect region 1 in the second direction, after making the second positioning mark 3, it further includes: in the second direction, make third positioning marks 6 on both sides of the second positioning mark 3, and the third positioning marks 6 are used to identify the thinning order.

[0047] Exemplarily, in the second direction, make two parallel third positioning marks 6 on one side of the second positioning mark 3, and make one third positioning mark 6 on the other side of the second positioning mark 3. The three third positioning marks 6 are parallel. When thinning the first sample in the second direction by focused ion beam to obtain the second sample containing the defect region 1, the front and back of the defect region 1 can be determined by observing the third positioning marks 6. Exemplarily, when observing the two third positioning marks 6 on one side of the second positioning mark 3, it can be determined that the current thinning order is in front of the defect region 1, and when observing the one third positioning mark 6 on one side of the second positioning mark 3, it can be determined that the current thinning order is behind the defect region 1.

[0048] In a specific embodiment, thinning the first sample in the second direction based on the width of the defect region 1 to obtain the second sample includes: thinning with a first ion beam until the second positioning mark is initially revealed; performing fine thinning with a second ion beam until the second positioning mark is completely exposed and then terminating. The power of the first ion beam is greater than the power of the second ion beam.

[0049] Specifically, in this embodiment, when thinning the initial sample in the first direction based on the width of the second positioning mark 3, first perform rough machining on the first sample with a first ion beam current. The rough machining speed is relatively fast, which can reduce the difficulty of fine machining, improve the machining efficiency, and also reduce the machining cost.

[0050] Perform fine cleaning and thinning using a second ion beam current until the second positioning mark 3 is completely exposed and then terminate. In this embodiment, thinning is first performed using a first ion beam current until the shape is initially formed, and then a second ion beam current is used for finish machining. This can better control the precision of sample processing and ensure higher precision of the finally processed sample.

[0051] Exemplarily, the first ion beam in this embodiment uses an ion beam current with a voltage of 30 kV and a current of 0.26 nA, and the second ion beam uses an ion beam current with a voltage of 5 kV and a current of 17 pA.

[0052] Figure 7 It is a schematic diagram of the electron energy loss spectrum characterizing the chemical composition of defects provided by an embodiment of the present invention. Figure 8 It is a schematic diagram of the electron energy loss spectrum characterizing the chemical composition of defects provided by an embodiment of the present invention. Please refer to Figure 7 and Figure 8 , the method for preparing an electron energy loss spectrum sample in the above embodiment further includes: Obtain the electron energy loss spectrum of the second sample, and obtain the chemical composition and element valence state of the defect region 1.

[0053] The principle of the electron energy loss spectrum is to study the physical and chemical properties of a sample by analyzing the energy lost by an incident electron beam during inelastic scattering in the sample. When an electron beam with a known kinetic energy is incident on the material to be measured, some electrons interact with atoms and undergo inelastic scattering, losing part of their energy and undergoing a small deflection in their path. These energy losses can be measured by an electron energy spectrometer and reflect information such as the chemical composition, chemical bonds, and electronic structure of the sample.

[0054] Exemplarily, please refer to Figure 6 , the second sample formed by thinning the first sample in the second direction in this embodiment has a thickness thinned from 200 nm to 46 nm, which is close to the size of the defect region 1 and is suitable for making an electron energy loss spectrum. The chemical composition of the defect region 1 can be clearly characterized as the Fe element by the electron energy loss spectrum, and the signal-to-noise ratio is relatively high. It can be known through measurement and analysis by an electron energy spectrometer that the Fe contained in the defect is mainly Fe3+.

[0055] The method for preparing an electron energy loss spectroscopy sample provided by an embodiment of the present invention includes locating a defect area in a device by an electron beam absorption current method; fabricating a first positioning mark adjacent to the defect area, and thinning in a first direction by using a focused ion beam to obtain a first sample including the first positioning mark and the defect area; obtaining a distance between the first positioning mark and the defect area in a second direction perpendicular to the first direction; fabricating a second positioning mark based on the distance and the size of the defect area; and using the second positioning mark as a reference, thinning the first sample in the second direction by using a focused ion beam to obtain a second sample including the defect area. After locating the defect area in the device, the method thins in the first direction to fabricate the first sample including the defect area and the first positioning mark, fabricates the second positioning mark according to the positional relationship between the first positioning mark and the defect area on the first sample and the size of the defect area, and uses the second positioning mark as a reference to thin the first sample in the second direction to obtain the second sample including the defect area. This method can accurately prepare an electron energy loss spectroscopy thin sample with minute defects retained.

[0056] In the above description, the descriptions referring to terms such as "one embodiment", "some embodiments", "example", "specific example", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms are not necessarily directed to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0057] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a sample for electron energy loss spectroscopy, characterized in that, The method includes: Locating a defective area in a device by an electron beam absorption current method; Fabricating a first positioning mark adjacent to the defective area, and thinning in a first direction by a focused ion beam to obtain a first sample including the first positioning mark and the defective area; Obtaining the distance between the first positioning mark and the defective area in a second direction, where the second direction is perpendicular to the first direction; Fabricating a second positioning mark based on the distance and the size of the defective area; Taking the second positioning mark as a reference, and thinning the first sample in the second direction by a focused ion beam to obtain a second sample including the defective area.

2. The method for preparing an electron energy loss spectroscopy sample according to claim 1, wherein Fabricating a first positioning mark adjacent to the defective area, and thinning in a first direction by a focused ion beam to obtain a first sample including the defective area includes: Fabricating a first electron beam protection layer on the device, where the area of the first electron beam protection layer is larger than the area of the first positioning mark; Fabricating the first positioning mark on the first electron beam protection layer; Fabricating a first ion beam protection layer on the first electron beam protection layer.

3. The method for preparing an electron energy loss spectroscopy sample according to claim 1, wherein The obtaining the distance between the first positioning mark and the defective area in a second direction includes: Obtaining the distance between the first positioning mark and the defective area in a second direction by a transmission electron microscope.

4. The method for preparing an electron energy loss spectroscopy sample according to claim 1, wherein The thickness of the first sample in the first direction is greater than or equal to 200 nm.

5. The method for preparing an electron energy loss spectroscopy sample according to claim 1, wherein Fabricating a second positioning mark based on the distance and the size of the defective area includes: fabricating a second electron beam protection layer on the upper surface of the defective area, where the area of the second electron beam protection layer is larger than the area of the defective area; Fabricating the second positioning mark on the second electron beam protection layer; Fabricating a second ion beam protection layer on the second electron beam protection layer.

6. The method for preparing an electron energy loss spectroscopy sample according to claim 5, wherein Fabricating a second positioning mark based on the distance and the size of the defective area includes: the width of the second positioning mark in the second direction is equivalent to the width of the defective area.

7. The method for preparing an electron energy loss spectroscopy sample according to claim 6, wherein Taking the second positioning mark as a reference, and thinning the first sample in the second direction by a focused ion beam to obtain a second sample including the defective area includes: Thinning the first sample in the second direction based on the width of the defective area to obtain the second sample.

8. The method for preparing an electron energy loss spectroscopy sample according to claim 7, wherein After fabricating the second positioning mark based on the distance and the size of the defective area in the second direction, it further includes: Fabricating third positioning marks on both sides of the second positioning mark in the second direction, where the third positioning marks are used to identify the thinning sequence.

9. The method for preparing an electron energy loss spectroscopy sample according to claim 8, wherein Thinning the first sample in the second direction based on the width of the defective area to obtain the second sample includes: Thinning is performed using a first ion beam until the second positioning mark is initially revealed; Fine thinning is performed using a second ion beam until the second positioning mark is completely exposed and then terminated, the power of the first ion beam being greater than the power of the second ion beam.

10. The method for preparing an electron energy loss spectroscopy sample according to any one of claims 1-9, characterized in that, It further includes: Obtaining an electron energy loss spectrum of the second sample to obtain the chemical composition and element valence states of the defect region.

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