Method for preparing transmission electron microscopy grid oxide sample and structure thereof

Abstract

The present disclosure relates to a method for manufacturing a transmission electron microscope grid oxide sample and a structure thereof. The method comprises the following steps: providing a sample; selecting a detection area on the sample; exposing an active area; and exposing a single row of active areas. The present disclosure removes the peripheral part of the initial protective layer of the sample along the length direction of the detection area, removes part of the sample along the arrangement direction of the active area on the sample, and exposes the active area on the sample. By adjusting the angle of the sample relative to the electron beam emitted by the transmission electron microscope, for example, rotating the machine table of the transmission electron microscope to the same angle as the angle between the length direction of the detection area and the length direction of the wire on the sample, the electron beam can be perpendicular to the length direction of the wire on the sample or perpendicular to the arrangement direction of the active area on the sample. The purpose of having a cross section along the arrangement direction of the active area and a cross section along the length direction of the wire on the same sample is achieved, and different angle detection is realized by single sample preparation.

Description

Technical Field

[0001] This disclosure relates to the field of semiconductor technology, and more particularly to a method for fabricating a gate oxide sample for transmission electron microscopy and the structure thereof. Background Technology

[0002] Currently, when performing failure analysis on wafers, the transmission electron microscope stage needs to be rotated at a certain angle in order to obtain the failure status of the wafer's upper line length direction or active region arrangement direction through electron beam emission.

[0003] Existing sample preparation methods can only perform failure analysis in a single direction and cannot satisfy failure analysis in different directions with a single sample preparation. Summary of the Invention

[0004] The following is an overview of the subject matter described in detail in this disclosure. This overview is not intended to limit the scope of the claims.

[0005] To overcome the problems existing in related technologies, this disclosure provides a method for preparing a grating oxide sample for transmission electron microscopy and its structure.

[0006] This disclosure provides a method for preparing a grating oxide sample for transmission electron microscopy (TEM), the method comprising:

[0007] Provide a sample; select a region to be detected on the sample, with the length direction of the region to be detected forming an angle with the length direction of the bit line on the sample; remove a portion of the sample around the initial protective layer along the length direction of the region to be detected; remove a portion of the sample along the active region arrangement direction on the sample, exposing the active region on the remaining sample; remove a portion of the sample, exposing a single row of active regions on the remaining sample.

[0008] According to some embodiments of this disclosure, providing the sample includes: providing a carrier and a wafer, the wafer being fixed to the carrier with the patterned surface of the wafer facing the carrier; removing a portion of the wafer to expose the patterned outline of the wafer from its back side.

[0009] According to some embodiments of this disclosure, the removal of a portion of the wafer includes: initially polishing the back side of the wafer until the graphic outline of the wafer is revealed through the back side of the wafer; secondly polishing the back side of the wafer after the initial polishing until the rough polishing marks on the wafer disappear; and thirdly polishing the back side of the wafer after the second polishing until the graphic outline of the wafer is exposed from the back side of the wafer.

[0010] According to some embodiments of this disclosure, removing a portion of the sample and exposing a single row of active regions on the remaining sample includes: removing a portion of the active regions on the sample, with the remaining active regions distributed in a single row on the sample.

[0011] According to some embodiments of this disclosure, removing the sample with exposed active regions includes: trimming the sample with a focused ion beam to remove the exposed portion of the active regions on the sample.

[0012] According to some embodiments of this disclosure, selecting the area to be detected on the sample includes: covering the sample with an initial protective layer, wherein the length direction of the initial protective layer is set at an angle to the length of the upper line of the sample, and the length direction of the initial protective layer is set at an angle to the active region arrangement direction on the sample.

[0013] According to some embodiments of this disclosure, covering the sample with an initial protective layer includes: defining an observation area on the sample; covering the observation area with a first protective layer; covering the first protective layer with a second protective layer, wherein the length direction of the second protective layer is set at an angle to the length direction of the bit line on the sample, and the molecular weight of the material of the second protective layer is greater than the molecular weight of the material of the first protective layer; and covering the second protective layer with a third protective layer, wherein the length direction of the third protective layer is set along the length direction of the second protective layer, and the molecular weight of the material of the third protective layer is greater than the molecular weight of the material of the second protective layer.

[0014] According to some embodiments of this disclosure, determining the area to be observed on the sample includes: determining the location of the area to be observed on the sample; removing a portion of the sample to form a sunken area in the area to be observed.

[0015] According to some embodiments of this disclosure, the first protective layer is made of carbon, the second protective layer is made of platinum, and the third protective layer is made of platinum.

[0016] According to some embodiments of this disclosure, the angle between the active region arrangement direction and the bit line length direction on the wafer is obtained by the following steps: removing a portion of the sample from the area to be observed; energizing the sample and measuring the angle between the active region arrangement direction and the bit line length direction on the sample.

[0017] According to some embodiments of this disclosure, the angle between the length direction of the initial protective layer and the length direction of the bit line on the sample is a°, and the angle between the length direction of the bit line on the sample and the arrangement direction of the active region is n°, where n-2a=-1 or 0 or 1.

[0018] A second aspect of this disclosure provides a structure for a transmission electron microscope (TEM) gate oxide sample, the structure of which includes a wafer layer, a first protective layer, a second protective layer, and a third protective layer stacked sequentially.

[0019] According to some embodiments of this disclosure, the second protective layer covers the center of the first protective layer.

[0020] According to some embodiments of this disclosure, the third protective layer covers the second protective layer, and the third protective layer covers a portion of the first protective layer surrounding the second protective layer.

[0021] According to some embodiments of this disclosure, the top surface of the first protective layer is flush with the top surface of the wafer layer.

[0022] The technical solutions provided by the embodiments of this disclosure can include the following beneficial effects: by removing a portion of the sample around the initial protective layer along the length direction of the area to be detected, which is set at an angle with the length direction of the upper part of the sample, and removing a portion of the sample along the active region arrangement direction on the sample, the active region on the sample is exposed. By adjusting the angle of the sample relative to the electron beam emitted by the transmission electron microscope, for example, by rotating the stage of the transmission electron microscope to the same angle as the length direction of the area to be detected and the length direction of the upper part of the sample, the electron beam can be made perpendicular to the length direction of the bit line on the sample or perpendicular to the arrangement direction of the active region on the sample. This achieves the purpose of having a cross-section along the arrangement direction of the active region and a cross-section along the length direction of the bit line on a single sample, thereby enabling detection at different angles through a single sample preparation.

[0023] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Other aspects will become apparent upon reading and understanding the accompanying drawings and detailed description. Attached Figure Description

[0024] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0025] Figure 1 This is a flowchart illustrating a method for preparing a grating oxide sample for transmission electron microscopy according to an exemplary embodiment.

[0026] Figure 2 This is a schematic diagram illustrating the arrangement direction of the active region according to an exemplary embodiment.

[0027] Figure 3 This is a schematic diagram showing the location of the coarse-cut holes in a method for preparing a gate oxide sample for transmission electron microscopy, according to an exemplary embodiment.

[0028] Figure 4 This is a schematic diagram showing the location of the fine-cut holes in a method for preparing a gate oxide sample for transmission electron microscopy, according to an exemplary embodiment.

[0029] Figure 5 This is a flowchart illustrating a method for preparing a grating oxide sample for transmission electron microscopy according to an exemplary embodiment.

[0030] Figure 6 This is a schematic diagram of the wafer position in a method for fabricating a transmission electron microscope gate oxide sample according to an exemplary embodiment.

[0031] Figure 7 This is a flowchart illustrating a method for preparing a grating oxide sample for transmission electron microscopy according to an exemplary embodiment.

[0032] Figure 8 This is a schematic diagram of the active region contour overlap in a method for fabricating a transmission electron microscope grating oxide sample according to an exemplary embodiment.

[0033] Figure 9 This is a schematic diagram of the outline of a single row of active regions in a method for fabricating a grating oxide sample for transmission electron microscopy, according to an exemplary embodiment.

[0034] Figure 10 This is a schematic diagram showing the position of the initial protective layer in a method for fabricating a transmission electron microscope gate oxide sample according to an exemplary embodiment.

[0035] Figure 11 This is a flowchart illustrating a method for preparing a grating oxide sample for transmission electron microscopy according to an exemplary embodiment.

[0036] Figure 12 This is a schematic diagram illustrating the location of the region to be detected in a method for preparing a grating oxide sample for transmission electron microscopy, according to an exemplary embodiment.

[0037] Figure 13 This is a schematic diagram showing the position of the first protective layer in a method for preparing a transmission electron microscope gate oxide sample according to an exemplary embodiment.

[0038] Figure 14 This is a schematic diagram showing the position of the second protective layer in a method for fabricating a transmission electron microscope gate oxide sample according to an exemplary embodiment.

[0039] Figure 15 This is a schematic diagram showing the position of the third protective layer in a method for preparing a transmission electron microscope gate oxide sample according to an exemplary embodiment.

[0040] Figure 16 This is a schematic diagram of the structure of a transmission electron microscope grating oxide sample according to an exemplary embodiment.

[0041] Figure 17 This is a flowchart illustrating a method for preparing a grating oxide sample for transmission electron microscopy according to an exemplary embodiment.

[0042] Figure 18 This is a schematic diagram showing the location of the marked area in a method for preparing a grating oxide sample for transmission electron microscopy according to an exemplary embodiment.

[0043] Figure 19 This is a flowchart illustrating a method for preparing a grating oxide sample for transmission electron microscopy according to an exemplary embodiment.

[0044] Figure Labels

[0045] 1. Carrier; 11. Adhesive layer; 2. Wafer; 21. Patterned surface; 22. Active region; 3. Sample; 31. Detection area; 311. Marking area; 32. Coarse-cut sample; 33. Coarse-cut hole; 34. Fine-cut sample; 35. Fine-cut hole; 4. First protective layer; 5. Second protective layer; 6. Third protective layer; 7. Initial protective layer. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions in the disclosed embodiments will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the scope of protection of this disclosure. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this disclosure can be arbitrarily combined with each other.

[0047] As mentioned in the background section, currently, when performing failure analysis on wafers, the transmission electron microscope stage needs to be rotated at a certain angle in order to obtain the failure status of the wafer's upper line length direction or active region arrangement direction through electron beam emission.

[0048] Existing sample preparation methods can only perform failure analysis in a single direction and cannot satisfy failure analysis in different directions with a single sample preparation.

[0049] Based on this, this disclosure provides a method and structure for preparing a grating oxide sample for transmission electron microscopy. By sequentially removing a portion of the sample around the initial protective layer along the length of the area to be detected, which is set at an angle to the length of the upper part of the sample, and removing a portion of the sample along the arrangement direction of the active region on the sample, the active region on the sample is exposed. By adjusting the angle of the sample relative to the electron beam emitted by the transmission electron microscope, for example, by rotating the stage of the transmission electron microscope to the same angle as the length of the area to be detected and the length of the upper part of the sample, the electron beam can be made perpendicular to the length of the upper part of the sample or perpendicular to the arrangement direction of the active region on the sample. This achieves the purpose of having a cross-section along the arrangement direction of the active region on the sample and a cross-section along the length of the upper part of the sample on a single sample, thereby enabling detection at different angles through a single sample preparation.

[0050] This disclosure provides an exemplary embodiment of a method for preparing a grating oxide sample for transmission electron microscopy and its structure, such as... Figure 1 As shown, Figure 1 This is a flowchart illustrating a method for preparing a grating oxide sample for transmission electron microscopy according to an exemplary embodiment; Figure 2 This is a schematic diagram illustrating the arrangement direction of the active regions according to an exemplary embodiment; Figure 3 This is a schematic diagram illustrating the location of the coarse-cut hole in a method for preparing a gate oxide sample for transmission electron microscopy according to an exemplary embodiment. Figure 4 This is a schematic diagram illustrating the location of the fine-cut holes in a method for fabricating a gate oxide sample for transmission electron microscopy according to an exemplary embodiment. Figure 5 This is a flowchart illustrating a method for preparing a grating oxide sample for transmission electron microscopy according to an exemplary embodiment; Figure 6 This is a schematic diagram of the wafer position in a method for fabricating a gate oxide sample for transmission electron microscopy according to an exemplary embodiment. Figure 7 This is a flowchart illustrating a method for preparing a grating oxide sample for transmission electron microscopy according to an exemplary embodiment; Figure 8 This is a schematic diagram of the active region contour overlap in a method for fabricating a grating oxide sample for transmission electron microscopy according to an exemplary embodiment. Figure 9 This is a schematic diagram of the outline of a single row of active regions in a method for fabricating a grating oxide sample for transmission electron microscopy, according to an exemplary embodiment. Figure 10 This is a schematic diagram showing the position of the initial protective layer in a method for fabricating a gate oxide sample for transmission electron microscopy according to an exemplary embodiment. Figure 11 This is a flowchart illustrating a method for preparing a grating oxide sample for transmission electron microscopy according to an exemplary embodiment; Figure 12 This is a schematic diagram showing the location of the region to be detected in a method for preparing a grating oxide sample for transmission electron microscopy according to an exemplary embodiment. Figure 13This is a schematic diagram showing the position of the first protective layer in a method for preparing a gate oxide sample for transmission electron microscopy according to an exemplary embodiment. Figure 14 This is a schematic diagram showing the position of the second protective layer in a method for preparing a grating oxide sample for transmission electron microscopy according to an exemplary embodiment. Figure 15 This is a schematic diagram showing the position of the third protective layer in a method for preparing a gate oxide sample for transmission electron microscopy according to an exemplary embodiment. Figure 16 This is a schematic diagram of the structure of a transmission electron microscope grating oxide sample according to an exemplary embodiment; Figure 17 This is a flowchart illustrating a method for preparing a grating oxide sample for transmission electron microscopy according to an exemplary embodiment; Figure 18 This is a schematic diagram illustrating the location of the marked area in a method for preparing a grating oxide sample for transmission electron microscopy according to an exemplary embodiment. Figure 19 This is a flowchart illustrating a method for preparing a grating oxide sample for transmission electron microscopy according to an exemplary embodiment. The following is in conjunction with... Figures 1 to 19 To explain.

[0051] The specific embodiments described below are intended to help those skilled in the art understand this embodiment, but this embodiment is not limited to the specific embodiments described below.

[0052] Reference Figure 1 This disclosure provides an exemplary embodiment of a method for preparing a transmission electron microscope (TEM) grating oxide sample, the method comprising:

[0053] S100, Provide samples.

[0054] For example, refer to Figure 2 and Figure 3 Sample 3 includes a wafer 2, which has regularly arranged active regions 22. There are multiple active regions 22 on the wafer 2, and they are arranged in rows. The active regions 22 in the same row are evenly distributed along a straight line (the arrangement direction of the active regions 22 on the wafer 2 mentioned below refers to the straight line along which the active regions 22 in the same row are arranged). The wafer 2 also has a bit line (not shown in the figure), and the length direction of the bit line is set at an angle to the arrangement direction of the active regions 22 in the same row.

[0055] S200. Select the area to be tested on the sample. Set the angle between the length direction of the area to be tested and the length direction of the bit line on the sample. Remove part of the sample around the initial protective layer along the length direction of the area to be tested.

[0056] For example, refer to Figure 2 and Figure 3The detection area 31 is located on the top surface of the sample 3. Below the detection area 31 is the detection area of ​​the predetermined transmission electron microscope. The detection area 31 is rectangular, and the length direction of the detection area 31 is set at an angle with the arrangement direction of the active area 22 on the wafer 2.

[0057] In this embodiment, a portion of the sample 3 around the edge of the area to be tested 31 is removed by a drilling process, forming coarse-cut holes 33 around the area to be tested 31 to retain the sample 3 entity in the area to be tested 31, forming a coarse-cut sample 32 and exposing the cross-section of the sample 3 entity in the area to be tested 31. There are two coarse-cut holes 33 around the area to be tested 31, located on opposite sides of the sample 3 entity in the testing area, thus retaining a portion of the sample 3 entity around the edge of the area to be tested 31 to achieve connection between the sample 3 entity in the area to be tested 31 and the sample 3 entity outside the edge of the area to be tested 31.

[0058] The sample 3 entity in the test area 31 is drilled and etched, and the sample 3 entity in the test area 31 is coarsely cut along a specific direction set at an angle with the length direction of the upper line of the sample 3. This can form a coarse cutting hole 33 for exposing the side profile of the coarsely cut sample 32. That is, by adjusting a certain angle, the purpose of observation and failure analysis can be achieved from the cross-section of the sample 3 along the length direction of the upper line.

[0059] S300: Remove part of the initial protective layer and part of the sample along the active region arrangement direction on the sample, exposing the active region on the remaining sample.

[0060] For example, refer to Figure 2 and Figure 4 A portion of the coarsely cut sample 32, positioned at an angle to the length direction of the bit line on the sample 3, is removed along the arrangement direction of the active region 22 on the sample 3 using a drilling and etching process. This forms a finely cut sample 34, whose length direction is aligned with the arrangement direction of the active region 22 on the sample 3. Finely cut holes 35, communicating with the coarsely cut holes 33, are formed around the finely cut sample 34. There are two finely cut holes 35 located on opposite sides of the finely cut sample 34, simultaneously exposing the cross-section of the finely cut sample 34. Similarly, a portion of the sample 3 entity surrounding the finely cut sample 34 is retained to establish a connection between the finely cut sample 34 entity and the sample 3 entity outside the edge of the detection area 31.

[0061] In this embodiment, the coarse-cut sample 32 is drilled and then finely cut along the arrangement direction of the active region 22 on the sample 3, forming a fine-cut hole 35 for exposing the side profile of the fine-cut sample 34. This fine-cut hole 35 exposes the side profile of the fine-cut sample 34, allowing for observation and failure analysis of the cross-section along the arrangement direction of the active region 22 on the sample 3. Combined with the aforementioned steps, observation and failure analysis of the cross-section along the bit line length direction of the sample 3 through the coarse-cut hole 33 are performed, achieving the goal of having both a cross-section along the arrangement direction of the active region 22 and a cross-section along the bit line length direction on a single sample 3. This allows for detection at different angles with a single sample preparation.

[0062] S400: Remove part of the sample, exposing a single row of active regions on the remaining sample.

[0063] For example, refer to Figure 2 and Figure 4 The side profile of the finely cut sample 34, formed after the coarsely cut sample 32 is drilled and finely cut, contains multiple rows of active regions 22. The outlines of the active regions 22 on the wafer 2 are revealed from the side profile of the finely cut sample 34 and overlap. By removing part of the finely cut sample 34, the overlapping and intersecting outlines of the multiple rows of active regions 22 revealed on the side profile of the finely cut sample 34 can be made regular, forming a single row of active region 22 outlines consistent with the regularly arranged active regions 22 on the wafer 2. This makes the images for failure analysis formed after transmission electron microscopy clear and complete, reduces the error of the test results, and improves the stability of the test process.

[0064] In an exemplary embodiment of this disclosure, reference is made to Figure 5 Step S100, providing samples, specifically includes:

[0065] S110. A carrier and a wafer are provided, with the wafer fixed on the carrier and the patterned surface of the wafer facing the carrier.

[0066] For example, refer to Figure 5 and Figure 6 Sample 3 also includes a carrier 1, which serves as a support base for fixing and supporting the wafer 2. The wafer 2 has a patterned surface 21 that shows the outline and arrangement of the active region 22 and a back surface opposite to the patterned surface 21. The wafer 2 is bonded to the carrier 1 with the patterned surface 21 facing the carrier 1, and an adhesive layer 11 is formed between the wafer 2 and the carrier 1.

[0067] In this embodiment, the carrier 1 can be a silicon substrate or another wafer 2. When another wafer 2 is selected as the carrier 1, the wafer 2 can be split into two wafers 2 by splitting, and the two wafers 2 are arranged opposite each other by the patterned surfaces 21 and fixed by adhesive. The dual wafer 2 configuration can provide higher fault tolerance and selectivity for the sample preparation process of the sample 3. For example, if the processing of one wafer 2 fails, another wafer 2 as the carrier 1 can be selected, and the failed wafer 2 can be used as a new carrier 1. Alternatively, if the active region 22 contour on the side profile of one wafer 2 does not meet expectations, the contour of the active region 22 on the zero-first wafer 2 as the carrier 1 can be observed, which improves the fault tolerance of the sample preparation process of the sample 3 and makes the test results more accurate.

[0068] S120: Remove part of the wafer to expose the wafer's pattern outline from the back side of the wafer.

[0069] For example, refer to Figure 5 and Figure 6 The back side of the wafer 2 is removed by a planarization process (Chemical Mechanical Planarization, CMP) to expose the outline of the patterned surface 21 on the wafer 2.

[0070] In this embodiment, since the wafer 2 has a certain degree of light transmittance when its thickness reaches a certain level, the outline of the patterned surface 21 on the wafer 2 can be directly exposed from the back side, or a portion of the back side structure can be retained to the extent that the clear outline of the patterned surface 21 on the wafer 2 can be found.

[0071] It should be understood that the above-described planarization process for removing part of the solid on the back side of wafer 2 is only one specific implementation. In other embodiments, other processes, such as patterning, can be used to remove part of the solid on the back side of wafer 2, or mechanical polishing can be used to expose the outline of the patterned surface 21 on wafer 2 from the back side.

[0072] In an exemplary embodiment of this disclosure, reference is made to Figure 7 Step S120, removing part of the wafer, specifically includes:

[0073] S121. The back side of the wafer is initially polished until the graphic outline of the wafer is revealed through the back side of the wafer.

[0074] For example, the back surface of wafer 2 is polished in stages by mechanical polishing process, using coarse sandpaper to rub back and forth on the back surface of wafer 2.

[0075] By removing a large portion of the back surface material through the initial polishing, the outline of the patterned surface 21 of the wafer 2 is revealed through the back surface of the wafer 2, reducing the amount of polishing required in subsequent steps and enabling fine finishing in subsequent steps.

[0076] S122. Polish the back of the wafer a second time after the initial polishing until the rough polishing marks on the wafer disappear.

[0077] For example, a diamond film is used to rub the back side of the wafer 2 after the initial polishing back and forth until the visible scratches on the back side of the wafer 2 are removed.

[0078] The secondary polishing removes the obvious scratches formed on the wafer 2 during the initial polishing process, and removes the uneven scratches formed on the back of the wafer 2 by the coarse sandpaper used in the initial polishing. This makes the back of the wafer 2 more flat after the secondary polishing, which facilitates further planarization processing of the back of the wafer 2. The outline of the pattern surface 21 of the wafer 2 can be more clearly displayed, and the wear of the grinding wheel in the subsequent planarization steps is also reduced.

[0079] S123. Polish the back side of the wafer a third time after the second polishing until the pattern outline of the wafer is exposed from the back side of the wafer.

[0080] For example, a grinding machine is used to grind the back side of the wafer 2 after secondary grinding until the outline of the patterned surface 21 of the wafer 2 is clearly and completely revealed from the back side of the wafer 2.

[0081] In this embodiment, the polishing machine serves as the final step in removing and planarizing the back side of wafer 2. This reduces unnecessary solid structures remaining on the back side of wafer 2, providing a high-quality substrate for the subsequent sample preparation process of sample 3. Furthermore, polishing reduces the surface roughness of the back side of wafer 2, further improving the clarity of the outline of the patterned surface 21 exposed from the back side of wafer 2. This reduces the possibility of damage to the patterned surface 21 of wafer 2 due to excessive polishing of the solid structures on the back side. The segmented polishing process improves the regularity of the substrate required for sample 3 preparation, reduces the possibility of defects in the substrate, reduces the deviation of transmission electron microscopy test results, and improves the stability of the sample preparation and failure analysis process of sample 3.

[0082] In an exemplary embodiment of this disclosure, reference is made to Figure 8 and Figure 9 Step S400, removing part of the sample and exposing a single row of active regions on the remaining sample, specifically includes:

[0083] The active region on the sample is removed, and the remaining active region is distributed in a single row on the sample.

[0084] For example, refer to Figure 8 and Figure 9 The active region 22 is exposed from the side profile of sample 3. When a non-wafer material is used as carrier 1, such as a silicon substrate, the outline of the active region 22 in the side profile of sample 3 is one-sidedly overlapping, as shown below. Figure 8The dashed line shows the outline of the overlapping and obscured active region 22. When the wafer 2 is used as the carrier 1, that is, when a wafer 2 is split into two wafers 2 by splitting, and the two wafers 2 are set opposite to each other by adhesive to form a sample 3, the outline of the active region 22 on the side section of the sample 3 is in the form of single-sided overlap and vertical overlap.

[0085] Regardless of the situation described above, the side profile of sample 3 will form multiple overlapping and interlaced active region 22 outlines. By removing some of the active regions 22 on the side profile of sample 3, so that only a single row of active regions 22 exists on the side profile of sample 3, the subsequent transmission electron microscopy imaging results can show a clearer and more complete active region 22 outline, reducing the impact of unclear imaging results or overlapping on the failure analysis results.

[0086] In an exemplary embodiment of this disclosure, reference is made to Figure 8 and Figure 9 Step S400, removing part of the active region on the sample, specifically includes:

[0087] The sample is trimmed using a focused ion beam to remove the exposed active region on the sample.

[0088] For example, the active region 22 on sample 3 is a multiple repeating structure. By bombarding the side profile of sample 3 with a focused ion beam, the overlapping and intersecting redundant active regions 22 can be removed, so that only one row of active regions 22 is retained on the side profile of sample 3. This forms a regular and clear row of active regions 22 outlines on the side profile of sample 3, reducing the impact of unclear imaging results or overlapping on failure analysis results.

[0089] In an exemplary embodiment of this disclosure, reference is made to Figure 10 Step S200, selecting the area to be detected on the sample, specifically includes:

[0090] An initial protective layer is applied to the sample. The length of the initial protective layer is set at an angle to the length of the upper line of the sample, and the length of the initial protective layer is set at an angle to the active region arrangement direction on the sample.

[0091] For example, refer to Figure 10 The test area 31 on sample 3 is deposited with an initial protective material by chemical vapor deposition (CVD) to form an initial protective layer 7 covering part of the test area 31. The initial protective layer 7 is located within the boundary surrounding the test area. The angle between the length direction of the initial protective layer 7 and the length direction of the upper line of sample 3 is a, and the angle between the length direction of the initial protective layer 7 and the arrangement direction of the active region 22 on sample 3 is b.

[0092] In this embodiment, the initial protective layer 7 is used to cover the area to be tested 31 and to protect the structure of the sample 3 below the initial protective layer 7 when the area to be tested 31 is subjected to the aforementioned coarse and fine cutting. For example, a focused ion beam is used to cut the area to be tested 31 on both sides to achieve the aforementioned coarse and fine cutting purpose. The initial protective layer 7 can reduce the damage to the structure below the initial protective layer 7 caused by the ions emitted during focused ion beam cutting, so as to protect the structural integrity of the area to be tested 31 and ensure the accuracy of subsequent transmission electron microscopy imaging.

[0093] In an exemplary embodiment of this disclosure, reference is made to Figure 2 and Figure 10 The angle between the length direction of the initial protective layer and the length direction of the bit line on the sample is a°, and the angle between the length direction of the bit line on the sample and the arrangement direction of the active region is n°, where n-2a=-1 or 0 or 1.

[0094] For example, refer to Figure 2 and Figure 10 , Figure 2 In the diagram, the x-direction represents the bit line length direction, and the y-direction represents the arrangement direction of the active region 22. The sample 3 entity below the initial protective layer 7 is the part to be photographed by the transmission electron microscope in subsequent steps. By setting the deflection angles α and b of the initial protective layer 7, it is possible to achieve the purpose of observation and failure analysis from the cross-section along the bit line length direction of the sample 3 by adjusting a certain angle. The angle between the length direction of the initial protective layer 7 and the bit line length direction of the sample 3 is determined according to the angle between the bit line length direction on the sample 3 and the arrangement direction of the active region 22. This ensures that the angle adjustment amount when the transmission electron microscope changes the observation direction is similar or close to the same, reducing the possibility of the transmission electron microscope stage deflection angle being too large, causing an alarm and affecting the failure analysis.

[0095] It should be understood that the above-described method of forming the initial protective layer 7 through chemical vapor deposition is only one specific embodiment. In other embodiments, the initial protective layer 7 can also be formed by means of, for example, physical vapor deposition (PVD), and this is not a limitation.

[0096] In an exemplary embodiment of this disclosure, reference is made to Figure 11 Step S200, covering the sample with an initial protective layer, specifically includes:

[0097] S210. Determine the area to be observed on the sample.

[0098] For example, refer to Figure 12 A region is selected on the top surface of sample 3 and designated as the observation area. In this embodiment, the observation area is the same as the detection area 31 mentioned above (the same applies below).

[0099] S220, cover the observation area with the first protective layer.

[0100] For example, refer to Figure 13 A first protective material is deposited in the area to be tested 31 (the area to be observed) using a chemical vapor deposition (CVD) process, forming a first protective layer 4 covering the area to be tested 31. The first protective layer 4 has the same rectangular outline as the area to be tested 31, and the boundary of the first protective layer 4 is located inside the boundary of the area to be tested 31.

[0101] The first protective layer 4 is attached to the top surface of the sample 3 and is used to reduce the damage to the structure of the region to be detected 31 caused by ions emitted by the focused ion beam during the subsequent coarse and fine cutting steps, so as to protect the structural integrity of the region to be detected 31 and ensure the accuracy of subsequent transmission electron microscopy imaging.

[0102] Similarly, the formation of the first protective layer 4 is not limited to the contents described in this disclosure. Other processes that can form a layer structure and can be known without creative effort are all part of the inventive concept of this disclosure. The same applies to the subsequent second protective layer 5 and third protective layer 6, which will not be described in detail here.

[0103] S230. A second protective layer is applied over the first protective layer. The length direction of the second protective layer is set at an angle to the length direction of the bit line on the sample. The molecular mass of the material of the second protective layer is greater than that of the material of the first protective layer.

[0104] For example, refer to Figure 13 and Figure 14 A second protective material is deposited on the first protective layer 4 to form a second protective layer 5 covering a portion of the first protective layer 4. The second protective layer 5 has the same rectangular outline as the first protective layer 4. The boundary of the second protective layer 5 is located inside the area surrounded by the boundary of the first protective layer 4, and the second protective layer 5 is offset relative to the first protective layer 4.

[0105] Since the molecular weight of the second protective material used to form the second protective layer 5 is greater than that of the first protective material used to form the first protective layer 4, the second protective material would damage the structure of the sample 3 in the detection area 31 without the obstruction of the first protective layer 4 during deposition, affecting the accuracy of subsequent transmission electron microscopy imaging. However, the structure of the sample 3 in the detection area 31 needs to be protected to prevent damage during subsequent coarse and fine cutting steps. Therefore, the first protective material with a lower molecular weight is selected to form the first protective layer 4 to protect the structure of the sample 3 in the detection area 31 during the deposition process of the second protective layer 5. The second protective layer 5 provides protection for the structure of the sample 3 in the detection area 31 during the coarse and fine cutting processes.

[0106] S240. A third protective layer is covered on the second protective layer, the length direction of the third protective layer is set along the length direction of the second protective layer, and the molecular mass of the material of the third protective layer is greater than the molecular mass of the material of the second protective layer.

[0107] For example, refer to Figure 15 and Figure 16 A third protective material is deposited on the second protective layer 5 to form a third protective layer 6 covering the second protective layer 5. The third protective layer 6 and the second protective layer 5 have the same rectangular outline. The third protective layer 6 covers the second protective layer 5 in the vertical direction, and the length direction of the third protective layer 6 is set along the length direction of the second protective layer 5.

[0108] Since the molecular weight of the third protective material used to form the third protective layer 6 is greater than that of the second protective material used to form the second protective layer 5, the third protective material would damage the sample 3 structure in the detection area 31 without the obstruction of the second protective layer 5 during deposition, affecting the accuracy of subsequent transmission electron microscopy imaging. However, the sample 3 structure in the detection area 31 needs to be protected from damage during subsequent coarse and fine cutting steps. Therefore, the second protective material with a lower molecular weight is selected to form the second protective layer 5 to protect the sample 3 structure in the detection area 31 during the deposition process of the third protective layer 6. The third protective layer 6 provides protection for the sample 3 structure in the detection area 31 during the coarse and fine cutting processes.

[0109] In this embodiment, the boundary of the third protective layer 6 intersects and overlaps with the boundary of the first protective layer 4. The third protective layer 6 directly faces the impact of the focused ion beam from the coarse and fine cutting steps, and is the first and most effective layer of protection for the sample 3 structure in the detection area 31. Furthermore, the third protective layer 6 has an area that overlaps with both the second protective layer 5 and the first protective layer 4. Therefore, even if the third protective layer 6 extends beyond the boundary of the second protective layer 5, or even beyond the boundary of the first protective layer 4, the potential damage to the sample 3 structure in the detection area 31 during the deposition of the third protective layer 6 can still be disregarded. When the sample 3 structure below the third protective layer 6, which extends beyond the boundary of the first protective layer 4, is not damaged by the deposition process of the third protective layer 6, the transmission electron microscope detection process will benefit from the larger size of the third protective layer 6, thus obtaining a larger imageable area and improving the fault tolerance of the failure analysis process.

[0110] In an exemplary embodiment of this disclosure, reference is made to Figure 17 Step S210, determining the area to be observed on the sample, specifically includes:

[0111] S211. Determine the location of the area to be observed on the sample.

[0112] S212. Remove part of the sample to form a sunken area in the area to be observed.

[0113] For example, refer to Figure 18 After selecting the detection area 31 (observation area) on the top surface of sample 3, the excess film layer on the top surface of sample 3 is removed by focused ion beam bombardment. In this embodiment, the excess film layer is, for example, the residual back solid structure on wafer 2 mentioned above. After removing the excess film layer, a recessed marking area 311 is formed on the top surface of sample 3. The boundary of the marking area 311 does not exceed the boundary of the detection area 31. In this embodiment, the boundary of the marking area 311 is located within the boundary of the detection area 31. The first protective layer 4 is deposited in the marking area 311 and fills the inner bottom surface of the marking area 311.

[0114] The recessed marking area 311 can provide space for the first protective layer 4 and provide positional guidance for the formation process of the first protective layer 4, so that the first protective layer 4 can be accurately formed in the predetermined position, and the subsequent second protective layer 5 and third protective layer 6 can stably and accurately cover the first protective layer 4, thereby improving the stability of the sample preparation process.

[0115] In an exemplary embodiment of this disclosure, the first protective layer is made of carbon, the second protective layer is made of platinum, and the third protective layer is made of platinum.

[0116] For example, the second protective layer 5 is made of platinum, and the third protective layer 6 is made of platinum.

[0117] In an exemplary embodiment of this disclosure, reference is made to Figure 19 The angle between the active region arrangement direction and the bit line length direction on the wafer is obtained through the following steps:

[0118] S100, Remove part of the sample from the area to be observed.

[0119] S200. Power on the sample and measure the angle between the active region arrangement direction and the bit line length direction on the sample.

[0120] A second aspect of this disclosure provides a structure of a grating oxide sample for transmission electron microscopy, with reference to... Figure 16 The structure of the gate oxide sample under transmission electron microscopy includes a stacked wafer layer, a first protective layer 4, a second protective layer 5, and a third protective layer 6. The molecular weight of the material in the third protective layer 6 is greater than that in the second protective layer 5, and the molecular weight of the material in the second protective layer is greater than that in the first protective layer 4.

[0121] For example, the first protective layer 4, the second protective layer 5, and the third protective layer 6 are all rectangular, and the first protective layer 4 covers the top surface of the wafer layer, the second protective layer 5 covers the top surface of the first protective layer 4, the third protective layer 6 covers the top surface of the second protective layer 5, and the area below the overlapping area of ​​the first protective layer 4, the second protective layer 5, and the third protective layer 6 is the sample 3 area for transmission electron microscopy imaging.

[0122] In this embodiment, since the molecular weight of the third protective material used to form the third protective layer 6 is greater than that of the second protective material used to form the second protective layer 5, the third protective material would damage the sample 3 structure in the detection area 31 without the obstruction of the second protective layer 5 during deposition, affecting the accuracy of subsequent transmission electron microscopy imaging. However, the sample 3 structure in the detection area 31 needs to be protected to prevent damage during subsequent coarse and fine cutting steps. Therefore, the second protective material with a lower molecular weight is selected to form the second protective layer 5 to protect the sample 3 structure in the detection area 31 during the deposition process of the third protective layer 6. The third protective layer 6 provides protection for the sample 3 structure in the detection area 31 during the coarse and fine cutting processes.

[0123] In an exemplary embodiment of this disclosure, reference is made to Figure 14 and Figure 16 The second protective layer 5 covers the center of the first protective layer 4.

[0124] For example, the second protective layer 5 has the same rectangular outline as the first protective layer 4, and the boundary of the second protective layer 5 is located inside the area surrounded by the boundary of the first protective layer 4.

[0125] In this embodiment, since the molecular weight of the second protective material used to form the second protective layer 5 is greater than that of the first protective material used to form the first protective layer 4, the second protective material would damage the sample 3 structure in the detection area 31 without the obstruction of the first protective layer 4 during deposition, affecting the accuracy of subsequent transmission electron microscopy imaging. However, the sample 3 structure in the detection area 31 needs to be protected to prevent damage during subsequent coarse and fine cutting steps. Therefore, the first protective material with a lower molecular weight is selected to form the first protective layer 4 to protect the sample 3 structure in the detection area 31 during the deposition process of the second protective layer 5. The second protective layer 5 provides protection for the sample 3 structure in the detection area 31 during the coarse and fine cutting processes.

[0126] In an exemplary embodiment of this disclosure, reference is made to Figure 15 and 16 The third protective layer 6 covers the second protective layer 5, and the third protective layer 6 also covers a portion of the first protective layer 4 surrounding the second protective layer 5.

[0127] For example, refer to Figure 14 and Figure 15 The third protective layer 6 covers the second protective layer 5 in the vertical direction, and the length direction of the third protective layer 6 is set along the length direction of the second protective layer 5.

[0128] In this embodiment, the boundary of the third protective layer 6 intersects and overlaps with the boundary of the first protective layer 4. The third protective layer 6 directly faces the impact of the focused ion beam from the coarse and fine cutting steps in the sample preparation process. It is the first and most effective layer of protection for the sample 3 structure. Moreover, the third protective layer 6 has a region that overlaps with both the second protective layer 5 and the first protective layer 4. Therefore, even if the third protective layer 6 extends beyond the boundary of the second protective layer 5, or even beyond the boundary of the first protective layer 4, the potential damage to the sample 3 structure during the formation of the third protective layer 6 can still be disregarded. When the sample 3 structure below the third protective layer 6, which extends beyond the boundary of the first protective layer 4, is not damaged by the formation process of the third protective layer 6, the transmission electron microscope detection process will benefit from the larger size of the third protective layer 6, thus obtaining a larger imageable area and improving the fault tolerance and sample preparation tolerance of the failure analysis process.

[0129] In an exemplary embodiment of this disclosure, reference is made to Figure 16 and Figure 18 The top surface of the first protective layer 4 is flush with the top surface of the wafer 2 layer.

[0130] For example, a recessed marking area 311 is formed on the top surface of sample 3, and a first protective layer 4 is deposited in the marking area 311 and fills the interior of the marking area 311.

[0131] In this embodiment, the recessed marking area 311 can provide a space for the first protective layer 4 and provide positional guidance for the formation process of the first protective layer 4, so that the first protective layer 4 can be accurately formed in the predetermined position, and the subsequent second protective layer 5 and third protective layer 6 can stably and accurately cover the first protective layer 4, thereby improving the stability of the sample preparation process.

[0132] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This disclosure is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the following claims.

[0133] It should be understood that this disclosure is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this disclosure is limited only by the appended claims.

Claims

1. A method for preparing a grating oxide sample for transmission electron microscopy, characterized in that, The method for preparing the transmission electron microscope grating oxide sample includes: Provide a sample and cover the sample with an initial protective layer; A region to be tested is selected on the sample, and the length direction of the region to be tested is set at an angle with the length direction of the bit line on the sample. The portion of the sample surrounding the initial protective layer is removed along the length direction of the region to be tested. A portion of the sample is removed along the active region arrangement direction on the sample, leaving the active region exposed on the remaining sample; After removing part of the sample, a single row of active regions is exposed on the remaining sample.

2. The method for preparing a transmission electron microscope grating oxide sample according to claim 1, characterized in that, The provided samples include: A carrier and a wafer are provided, the wafer being fixed to the carrier with the patterned surface of the wafer facing the carrier; A portion of the wafer is removed to expose the patterned outline of the wafer from its back side.

3. The method for preparing a transmission electron microscope grating oxide sample according to claim 2, characterized in that, The removed portion of the wafer includes: The back side of the wafer is initially polished until the graphic outline of the wafer is revealed through the back side of the wafer; The back of the wafer after the initial polishing is polished a second time until the rough polishing marks on the wafer disappear; The back side of the wafer, after the second polishing, is polished a third time until the graphic outline of the wafer is exposed from the back side of the wafer.

4. The method for preparing a transmission electron microscope grating oxide sample according to claim 1, characterized in that, The removal of a portion of the sample, leaving a single row of active regions exposed on the remaining sample, includes: A portion of the active region on the sample is removed, and the remaining active region is distributed in a single row on the sample.

5. The method for preparing a transmission electron microscope grating oxide sample according to claim 4, characterized in that, The removal of a portion of the active region from the sample includes: The sample is trimmed using a focused ion beam to remove the exposed portion of the active region on the sample.

6. The method for preparing a transmission electron microscope grating oxide sample according to claim 1, characterized in that, Selecting the area to be detected on the sample includes: The length direction of the initial protective layer is set at an angle to the length of the upper line of the sample, and the length direction of the initial protective layer is set at an angle to the active region arrangement direction of the sample.

7. The method for preparing a transmission electron microscope grating oxide sample according to claim 6, characterized in that, The process of covering the sample with an initial protective layer includes: The area to be observed was determined on the sample; A first protective layer is applied to the area to be observed. A second protective layer is covered on the first protective layer, the length direction of the second protective layer is set at an angle to the length direction of the bit line on the sample, and the molecular mass of the material of the second protective layer is greater than the molecular mass of the material of the first protective layer. A third protective layer is covered on the second protective layer, the length direction of the third protective layer is along the length direction of the second protective layer, and the molecular mass of the material of the third protective layer is greater than the molecular mass of the material of the second protective layer.

8. The method for preparing a transmission electron microscope grating oxide sample according to claim 7, characterized in that, Determining the region to be observed on the sample includes: The location of the area to be observed is determined on the sample; A portion of the sample is removed, creating a sunken area in the region to be observed.

9. The method for preparing a transmission electron microscope grating oxide sample according to claim 7, characterized in that, The active region arrangement direction on the sample forms an angle with the bit line length direction. This angle is obtained through the following steps: Remove a portion of the sample from the area to be observed; The sample is energized, and the angle between the active region arrangement direction and the bit line length direction is measured.

10. The method for preparing a transmission electron microscope grating oxide sample according to claim 1, characterized in that, The angle between the length direction of the initial protective layer and the length direction of the bit line on the sample is a°, and the angle between the length direction of the bit line on the sample and the arrangement direction of the active region is n°, where n-2a=-1 or 0 or 1.

11. A transmission electron microscope grating oxide sample prepared by the method according to any one of claims 1-10, characterized in that, The structure of the transmission electron microscope gate oxide sample includes a wafer layer, a first protective layer, a second protective layer, and a third protective layer stacked sequentially.

12. The transmission electron microscope grating oxide sample according to claim 11, characterized in that, The second protective layer covers the center of the first protective layer.

13. The transmission electron microscope grating oxide sample according to claim 11, characterized in that, The third protective layer covers the second protective layer, and the third protective layer also covers a portion of the first protective layer surrounding the second protective layer.

14. The transmission electron microscope grating oxide sample according to claim 11, characterized in that, The top surface of the first protective layer is flush with the top surface of the wafer layer.

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