A non-destructive method for precise positioning in chip cross-section grinding

Abstract

The present invention provides a non-destructive method for precisely positioning chip cross-sectional structures during grinding, belonging to the field of semiconductor device analysis and sample preparation technology. The method utilizes a deposition coating method to symmetrically arrange raised identification icons on both sides of the target grinding position of the chip sample to be ground, thereby achieving precise positioning during the grinding of the chip cross-sectional structure. The non-destructive method of the present invention utilizes a raised film layer as the raised identification icon, which is non-destructive to the target electronic circuit throughout the process. The identification icon only uses a row of icons with gradually varying sizes, providing real-time reminders to the grinding staff about the grinding progress, improving grinding efficiency and achieving the target position for mechanical grinding quickly and accurately.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor device analysis and sample preparation, specifically relates to the technical field of chip cross-section structure grinding, and in particular relates to a non-destructive method for precise positioning in chip cross-section structure grinding. Background Art

[0002] In semiconductor chip failure analysis, chip cross-section structure analysis is often performed, and the quality of chip cross-section sample preparation is crucial. As semiconductor manufacturing processes become increasingly smaller, the corresponding semiconductor chips and devices are also becoming increasingly smaller and finer. Therefore, the grinding precision required for analyzing micro-nano chip structures is also becoming increasingly higher. Therefore, grinding specific locations, especially sub-micron areas, is very challenging.

[0003] For a chip that needs to be cross-sectioned and ground to a specified position, the operator uses manual grinding, which can generally only be observed through an optical microscope (OM). For specified positions less than 1 micron, there is no reference and only a rough estimate can be made, which makes it easy to not grind in place or over-grind.

[0004] CN 119734193 A discloses a system and method for positioning and grinding the cross-section of a semiconductor chip sample. The positioning and grinding system provides a plurality of grinding marks on the surface of the semiconductor chip sample to be ground, thereby providing real-time reminders to the operator of the grinding progress, thereby achieving precise positioning during mechanical grinding. However, the icon positioning method of this technical solution uses downward etching to form graphic marks, which is a lossy method and may damage the electronic circuits under the chip.

[0005] In summary, it is necessary to develop a non-destructive method for precise positioning during chip cross-sectional structure grinding. Summary of the Invention

[0006] In view of the problems existing in the prior art, the present invention provides a non-destructive method for precisely positioning chip cross-sectional structures during grinding. The method utilizes a deposition coating method to symmetrically place raised identification icons on both sides of the target grinding position of the chip sample to be ground, thereby achieving precise positioning during the grinding of the chip cross-sectional structure. The non-destructive method of the present invention utilizes a raised film layer as the raised identification icon, which is non-destructive to the target electronic circuit throughout the process. The identification icon only uses a row of icons with gradually varying sizes, providing real-time notifications to the grinding staff about the grinding progress, improving grinding efficiency and achieving the target position for mechanical grinding quickly and accurately.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] The object of the present invention is to provide a non-destructive method for precise positioning during chip cross-sectional structure grinding, the non-destructive method comprising the following steps:

[0009] (1) Prepare the chip sample to be ground and determine the target grinding position on its surface;

[0010] (2) A deposition coating method is used to symmetrically set raised identification icons on both sides of the target grinding position to achieve precise positioning during the grinding of the chip cross-sectional structure; wherein, parallel to the grinding direction, the bottom edge of the raised identification icon is kept on the same straight line as the target grinding position.

[0011] As a preferred technical solution of the present invention, the deposition coating method in step (2) includes: deposition coating using a focused ion beam device with a gas injection system.

[0012] As a preferred technical solution of the present invention, in step (2), at least three groups of raised identification icons of different sizes are symmetrically arranged on both sides of the target grinding position.

[0013] As a preferred technical solution of the present invention, 3-6 groups of raised identification icons of different sizes are symmetrically arranged on both sides of the target grinding position.

[0014] As a preferred technical solution of the present invention, the size of the raised identification icon decreases in a direction perpendicular to the grinding direction and close to the target grinding position.

[0015] As a preferred technical solution of the present invention, perpendicular to the grinding direction, the minimum distance between the target grinding position and the adjacent raised identification icon is ≥20 μm.

[0016] As a preferred technical solution of the present invention, on a certain side of the target grinding position, the minimum distance between adjacent raised identification icons of different sizes is 2-10 μm.

[0017] As a preferred technical solution of the present invention, the graphics of the raised identification icon include at least one of the following: a regular polygon, a rectangle with unequal length and width, a trapezoid, and a circle.

[0018] As a preferred technical solution of the present invention, the shortest side length or diameter of the raised identification icon is in the range of 5-100 μm.

[0019] As a preferred technical solution of the present invention, the shortest side length or diameter of the raised identification icon closest to the target grinding position is in the range of 5-10 μm.

[0020] Compared with the existing technical solutions, the present invention has at least the following beneficial effects:

[0021] This invention provides a non-destructive method for precisely positioning chip cross-sectional structures during grinding. The method utilizes a deposition coating method to symmetrically position raised identification icons on both sides of the target grinding position of the chip sample to be ground, achieving precise positioning during grinding of the chip cross-sectional structure. The non-destructive method utilizes a raised film layer as the raised identification icon, which is non-destructive to the target electronic circuitry. The identification icon utilizes only a row of gradually varying sizes, providing real-time notifications to the grinding staff regarding grinding progress, improving grinding efficiency and enabling rapid and accurate mechanical grinding to the target position. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic top view of a chip sample to be ground after deposition of a coating in a specific embodiment of the present invention.

[0023] In the figure, 1-target grinding position; 2-raised identification icon; 21-first raised identification icon; 22-second raised identification icon; 23-third raised identification icon; 24-fourth raised identification icon; 3-chip sample to be ground.

[0024] Figure 2 It is a top view of a chip sample to be ground after deposition of a coating in a specific embodiment of the present invention.

[0025] Figure 3 Shown Figure 2 Cross-sectional SEM image of the target area of ​​the chip sample to be ground when it is precisely ground to the target grinding position. DETAILED DESCRIPTION

[0026] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementation methods.

[0027] To better illustrate the present invention and facilitate understanding of the technical solutions of the present invention, typical but non-limiting embodiments of the present invention are as follows:

[0028] A specific embodiment of the present invention provides a non-destructive method for precise positioning during chip cross-sectional structure grinding, the non-destructive method comprising the following steps:

[0029] (1) Prepare the chip sample to be ground and determine the target grinding position on its surface;

[0030] (2) A deposition coating method is used to symmetrically set raised identification icons on both sides of the target grinding position to achieve precise positioning during the grinding of the chip cross-sectional structure; wherein, parallel to the grinding direction, the bottom edge of the raised identification icon is kept on the same straight line as the target grinding position.

[0031] The present invention adopts a deposition coating method to form a raised identification icon protruding from the surface. This method does not damage the internal structure near the fixed point position or the entire chip, and can be considered as a non-destructive icon production method.

[0032] Specifically, the deposition coating method in step (2) includes: deposition coating using a focused ion beam (FIB) device with a gas injection system (GIS), for example, introducing a GIS pre-compound injection system into the FIB device, introducing a gaseous precursor into the focused ion beam action area, bombarding the gaseous precursor with the focused ion beam and decomposing it, depositing non-volatile components (such as metals), and extracting volatile by-products (such as CO2, H2O), thereby forming a raised identification icon through deposition coating. This method can be directly deposited on the passivation layer (passivation) on the chip surface, or it can be first delayered to a specific film layer and then formed on it. This method is the only option for chips whose internal structures cannot be damaged.

[0033] Specifically, in step (2), at least three groups of raised identification icons of different sizes are symmetrically arranged on both sides of the target grinding position.

[0034] Specifically, 3-6 groups of raised identification icons of different sizes are symmetrically arranged on both sides of the target grinding position.

[0035] Specifically, in a direction perpendicular to the grinding direction and approaching the target grinding position, the size of the raised identification icon decreases.

[0036] The present invention adopts an icon positioning method. Through precise identification icon technology, such as FIB technology with GIS, aligned raised identification icons of varying sizes are generated on both sides of the position to be measured. For example, the icon size decreases from large to small as it approaches the position to be measured from far to near. One function of the raised identification icon is to be visible under OM, because engineers need to observe while grinding and need timely feedback. Another function of the raised identification icon is to avoid tilting during grinding. Because the raised identification icons are symmetrically set on both sides of the positioning position, it is easy for grinding engineers to identify, such as whether the largest icon on one side and the symmetrical large icon are ground close. If the difference is too large, timely adjustment is required to achieve the purpose of preventing tilting. The engineer can continue to advance to the designated position. The gradually smaller icons make the grinding position resolution higher. When advancing to the smallest icon, it is necessary to carefully observe the symmetry of the grinding of the icons on both sides, so that it can accurately stay at the designated position when grinding to the lower surface of the icon.

[0037] For example Figure 1The figure shows a top view of a chip sample to be ground after deposition coating in a specific embodiment. It can be seen that: on the surface of the chip sample 3 to be ground, a target grinding position 1 is determined, and a deposition coating method is adopted, specifically a FIB device with GIS is used for deposition coating. Raised identification icons 2 are symmetrically set on both sides of the target grinding position 1 to achieve precise positioning during the grinding of the chip cross-sectional structure; wherein, parallel to the grinding direction, the bottom edge of the raised identification icon 2 is kept on the same straight line as the target grinding position 1; and 4 groups of different The raised identification icons 2 are of different sizes, perpendicular to the grinding direction and close to the target grinding position, and the sizes of the raised identification icons decrease, which are the fourth raised identification icon 24, the third raised identification icon 23, the second raised identification icon 22, and the first raised identification icon 21; specifically, the first raised identification icon 21 is a 7μm×7μm square, the second raised identification icon 22 is a 10μm×10μm square, the third raised identification icon 23 is a 15μm×15μm square, and the fourth raised identification icon 24 is a 20μm×20μm square. Figure 2 The following figure shows a top view of a chip sample to be ground after deposition and coating in a specific embodiment of the present invention. Specifically, it is an optical microscope image, showing a top view of the icon positioning of a real chip sample to be ground after deposition and coating under a 50x lens. Because the FIB GIS always has an overflow space when forming the logo icon, about 100 nanometers, when the icon is basically disappeared in the OM observation plane, there is still a raised part in the FIB cross section. Therefore, Figure 3 Shown Figure 2 The cross-sectional SEM image of the target area of ​​the chip sample to be ground is precisely ground to the target grinding position. It can be clearly seen that the convex part corresponding to the convex identification icon 2 in the cross-sectional case, that is, four obvious convex parts can be seen in the red frame areas on the left and right sides of the target grinding position 1, corresponding to Figure 2 If the side of the flat icon close to the designated position is intact, it means that it has been ground in place according to the icon. The position in the middle of the icons on both sides is the designated grinding position.

[0038] Specifically, perpendicular to the grinding direction, the minimum distance between the target grinding position and the adjacent raised identification icon is ≥20 μm.

[0039] Specifically, on one side of the target grinding position, the minimum distance between adjacent raised identification icons of different sizes is 2-10 μm, such as 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm, etc., but is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0040] Specifically, the graphic of the raised identification icon includes at least one of the following: a regular polygon, a rectangle with unequal length and width, a trapezoid, and a circle.

[0041] Specifically, the shortest side length or diameter of the raised identification icon ranges from 5 to 100 μm, for example, 5 μm, 7 μm, 10 μm, 12 μm, 15 μm, 17 μm, 20 μm, 23 μm, 25 μm, 28 μm, 30 μm, 33 μm, 35 μm, 38 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm or 100 μm, etc., but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0042] Specifically, the shortest side length or diameter of the raised identification icon closest to the target grinding position is in the range of 5-10μm, such as 5μm, 6μm, 7μm, 8μm, 9μm or 10μm, etc., but is not limited to the listed values. Other unlisted values ​​within the above numerical range are also applicable.

[0043] It should be noted that in the present invention, small island-like protrusions are set as icons. When the defect size is about 1 micron, it is difficult to observe with the naked eye in OM. The size of the smallest icon can be set at 5 to 10 microns. In this way, the grinder has enough space to gradually grind from the top of the smallest icon to the bottom, that is, the designated position. This will make grinding positioning much easier, and it is also easier to find the largest icon under OM. This variable-size icon method combines the advantages of icon positioning.

[0044] It should be noted that, parallel to the grinding direction, the bottom edges of all raised identification icons are kept in the same straight line as the target grinding position, that is, the bottom edges of all raised identification icons are aligned with the target grinding position, perpendicular to the grinding direction and close to the target grinding position, the size of the raised identification icons is reduced, the minimum icon size is selected to be 2-5 times the target size (this ratio is not limited), and the maximum icon is based on the size that can be easily seen under OM, such as 100 microns. The icons are symmetrically distributed on both sides of the target area, with the same spacing between icons, and the specified position can be accurately distinguished. This method of aligned variable-size icons can accurately locate the depth and angle of grinding, so that grinding personnel can quickly and accurately grind to the specified position, especially for positioning grinding of advanced chip processes.

[0045] It should be noted that the present invention uses identification icons for positioning grinding, which improves the accuracy from being unable to perform fixed-point grinding to being able to perform fixed-point grinding. It further utilizes the method of generating raised identification icons, that is, depositing a coating on the chip surface. Its characteristic is that it does not destroy the internal structure of the chip. It is a non-destructive positioning method for the chip and does not damage the internal structure near the fixed position or the entire chip.

[0046] In summary, the present invention provides a non-destructive method for precise positioning of chip cross-sectional structures during grinding. The key point is to use a deposition coating method to symmetrically set raised identification icons on both sides of the target grinding position of the chip sample to be ground, so as to achieve precise positioning of the chip cross-sectional structure during grinding. The non-destructive method described in the present invention uses a raised film layer as a raised identification icon, which is non-destructive to the target electronic circuit throughout the process. The identification icon only uses a row of icons with gradually changing sizes, which reminds the grinding staff of the grinding progress in real time, improves grinding efficiency, and reaches the target position of mechanical grinding quickly and accurately.

[0047] While the present invention is described through the above-described embodiments to illustrate the detailed structural features of the present invention, the present invention is not limited to these detailed structural features, nor does it necessarily rely on these detailed structural features for implementation. Those skilled in the art should understand that any improvements to the present invention, equivalent replacements for selected components, additions of auxiliary components, and selection of specific embodiments, etc., fall within the scope of protection and disclosure of the present invention.

[0048] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0049] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0050] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A non-destructive method for precise positioning of chip cross-section structure during grinding, characterized in that: The lossless method comprises the following steps: (1) Prepare the chip sample to be ground and determine the target grinding position on its surface; (2) A deposition coating method is used to symmetrically set raised identification icons on both sides of the target grinding position to achieve precise positioning during the grinding of the chip cross-sectional structure; wherein, parallel to the grinding direction, the bottom edge of the raised identification icon is kept on the same straight line as the target grinding position; at least three groups of raised identification icons of different sizes are symmetrically set on both sides of the target grinding position; perpendicular to the grinding direction and close to the target grinding position, the size of the raised identification icon decreases.

2. The non-destructive method for precise positioning of chip cross-sectional structure during grinding according to claim 1, characterized in that: The deposition coating method in step (2) includes: deposition coating using a focused ion beam device with a gas injection system.

3. The non-destructive method for precise positioning of chip cross-sectional structure during grinding according to claim 1, characterized in that: 3-6 groups of raised identification icons of different sizes are symmetrically arranged on both sides of the target grinding position.

4. The non-destructive method for precise positioning of chip cross-sectional structure during grinding according to claim 1, characterized in that: Perpendicular to the grinding direction, the minimum distance between the target grinding position and the adjacent raised identification icon is greater than or equal to 20 μm.

5. The non-destructive method for precise positioning during chip cross-sectional structure grinding according to claim 4, characterized in that: On one side of the target grinding position, the minimum distance between adjacent raised identification icons of different sizes is 2-10 μm.

6. The non-destructive method for precise positioning of chip cross-section structure during grinding according to any one of claims 1 to 5, characterized in that: The graphic of the raised identification icon includes at least one of the following: a regular polygon, a rectangle with unequal length and width, a trapezoid, and a circle.

7. The non-destructive method for precise positioning during chip cross-sectional structure grinding according to claim 6, characterized in that: The shortest side length or diameter of the raised identification icon is in the range of 5-100 μm.

8. The non-destructive method for precise positioning during chip cross-sectional structure grinding according to claim 7, characterized in that: The shortest side length or diameter of the raised identification icon closest to the target grinding position is in the range of 5-10 μm.

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