Wafer evaluation method, device and readable storage medium

Abstract

Embodiments of the present application provide a wafer evaluation method, device and readable storage medium, comprising: acquiring a wafer image; dividing a plurality of regions in the wafer image; determining a plurality of region groups in the plurality of regions according to two adjacent regions as a group; calculating a particle density ratio of two regions in the region group; and determining a wafer corresponding to the wafer image as an abnormal product in a case that the calculated particle density ratio is greater than a preset threshold.

Description

Technical Field

[0001] The present invention relates to the field of wafer fabrication technology, and in particular to a wafer evaluation method, apparatus and readable storage medium. Background Technology

[0002] Crystal-originating particles (COPs) are octahedral voids formed by the aggregation of vacancies during crystal growth. The presence of COPs directly affects the quality of produced wafers, making COP monitoring crucial. Current monitoring methods primarily rely on manual, periodic monitoring of particle counter data. Specifically, wafers are randomly sampled from different carriers and blocks. Once a carrier is selected, an overlay map of all wafers within that carrier is created, and the presence of COPs is manually determined by observing the inspection map. However, manual inspection suffers from the inability to inspect all products, leading to missed defects. Furthermore, subjective judgment can result in inaccurate wafer evaluations. Summary of the Invention

[0003] This invention provides a wafer evaluation method, apparatus, and readable storage medium, which solves the problem that manual COP inspection cannot detect all products and that subjective judgment can lead to inaccurate wafer evaluation results.

[0004] According to a first aspect of the present invention, a wafer evaluation method is provided, comprising:

[0005] Acquire wafer images;

[0006] The wafer image is divided into multiple regions;

[0007] Multiple region groups are determined among the multiple regions by grouping two adjacent regions together.

[0008] Calculate the particle density ratio between the two regions in the group of regions;

[0009] If the calculated particle density ratio is greater than a preset threshold, the wafer corresponding to the wafer image is determined to be an abnormal product.

[0010] Optionally, dividing the wafer image into multiple regions includes:

[0011] The wafer image is divided into multiple regions from the inside out.

[0012] Among the two adjacent regions, the inner region is the first region, and the outer region is the second region.

[0013] Optionally, the wafer is divided into multiple regions from the inside out, including:

[0014] The wafer image is divided into multiple annular regions with the same center, arranged at equal intervals from the inside out.

[0015] Optionally, calculating the particle density ratio between two regions in the group of regions includes:

[0016] Calculate the particle density ratio between the second region and the first region in each region group in order from the outside to the inside.

[0017] Optionally, the number of the plurality of regions is 5 to 15.

[0018] Optionally, the preset threshold is 3.5 to 4.5.

[0019] According to a first aspect of the present invention, a wafer evaluation apparatus is provided, comprising:

[0020] The acquisition module is used to acquire wafer images;

[0021] A partitioning module is used to partition multiple regions in the wafer image;

[0022] The first determining module is used to determine multiple region groups in the multiple regions, grouping them into two adjacent regions;

[0023] The calculation module is used to calculate the particle density ratio between two regions in the region group;

[0024] The second determining module is used to determine that the wafer corresponding to the wafer image is an abnormal product if the calculated particle density ratio is greater than a preset threshold.

[0025] Optionally, the partitioning module is specifically used for:

[0026] The wafer image is divided into multiple regions from the inside out.

[0027] Among the two adjacent regions, the inner region is the first region, and the outer region is the second region.

[0028] Optionally, the partitioning module is specifically used for:

[0029] The wafer image is divided into multiple annular regions with the same center, arranged at equal intervals from the inside out.

[0030] Optionally, the computing module is specifically used for:

[0031] Calculate the particle density ratio between the second region and the first region in each region group in order from the outside to the inside.

[0032] Optionally, the number of the plurality of regions is 5 to 15.

[0033] Optionally, the preset threshold is 3.5 to 4.5.

[0034] According to a first aspect of the present invention, a readable storage medium is provided, on which a program or instructions are stored, which, when executed by a processor, implement the steps of the wafer evaluation method as described in the first aspect.

[0035] In this embodiment of the invention, the wafer image is divided into multiple regions, and adjacent regions are grouped together. The particle density ratio between the two regions in a group is calculated. If the calculated particle density ratio is greater than a preset threshold, the wafer corresponding to the wafer image is determined to be an abnormal product. Thus, on the one hand, compared to existing methods of overlaying and observing wafers, the detection method of calculating the particle density ratio between two regions is easier to implement and can be applied to the inspection of all wafers, achieving full inspection of all products and avoiding missed detections. On the other hand, the unified rules can be applied to automated inspection, thereby eliminating manual inspection, avoiding subjective influence on inspection, and improving the accuracy of wafer evaluation results. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the wafer evaluation method provided in an embodiment of the present invention;

[0038] Figure 2 This is a schematic diagram illustrating an application scenario provided by an embodiment of the present invention;

[0039] Figure 3 This is a schematic diagram of the crystal boundary in crystal pulling.

[0040] Figure 4 This is a diagram illustrating the formation process of a toroidal COP.

[0041] Figure 5 This is a diagram showing the percentage of the radius of the annular COP ring.

[0042] Figure 6 A graph showing the average number of particles in different regions;

[0043] Figure 7 This is a graph showing the ratio of the COP area to the inner ring area.

[0044] Figure 8 This is a graph showing the ratio of the COP region to the outer ring region. Detailed Implementation

[0045] The technical solutions of the embodiments of the present invention 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 the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] See Figure 1 This application provides a wafer evaluation method, including the following steps:

[0047] Step 101: Obtain wafer image; the wafer image can be obtained by existing methods. Considering that microscopic images are required for the detection of COP, a microscope camera can be used to capture the image.

[0048] Step 102: Divide the wafer image into multiple regions;

[0049] Step 103: Determine multiple region groups by grouping adjacent regions into one group;

[0050] Step 104: Calculate the particle density ratio between the two regions in the region group;

[0051] Step 105: If the calculated particle density ratio is greater than a preset threshold, the wafer corresponding to the wafer image is determined to be an abnormal product. Regions on the wafer where COP exists will show significant changes in particle density; therefore, in this embodiment, the presence of COP can be determined based on the particle density ratio between two adjacent regions.

[0052] In this embodiment of the invention, the wafer image is divided into multiple regions, and adjacent regions are grouped together. The particle density ratio between the two regions in a group is calculated. If the calculated particle density ratio is greater than a preset threshold, the wafer corresponding to the wafer image is determined to be an abnormal product. Thus, on the one hand, compared to existing methods of overlaying and observing wafers, the detection method of calculating the particle density ratio between two regions is easier to implement and can be applied to the inspection of all wafers, achieving full inspection of all products and avoiding missed detections. On the other hand, the unified rules can be applied to automated inspection, thereby eliminating manual inspection, avoiding subjective influence on inspection, and improving the accuracy of wafer evaluation results.

[0053] In one possible implementation, the wafer image is divided into multiple regions, including:

[0054] The wafer image is divided into multiple regions from the inside out.

[0055] Among the two adjacent regions, the inner region is the first region, and the outer region is the second region.

[0056] In this embodiment, the region division in the wafer image is specifically based on an inside-outward division. For two adjacent regions, the inner region is the first region, and the outer region is the second region. It should be noted that the concepts of inside and outside in this embodiment are defined within the context of the wafer image itself; that is, the inside-outward division refers to the direction from the center of the wafer image towards its edge.

[0057] Furthermore, the wafer is divided into multiple regions from the inside out, including:

[0058] In the wafer image, multiple annular regions with the same center are divided at equal intervals from the inside out.

[0059] In this embodiment of the application, the region division in the wafer image is specifically to divide multiple annular regions with the same center from the inside out with equal spacing. Accordingly, the first region and the second region are the inner ring region and the outer ring region of two adjacent regions.

[0060] The use of ring-shaped region partitioning takes into account the shape of the wafer itself and the manufacturing process. Dividing the region into rings results in a more uniform particle density within the region, leading to a more accurate particle density ratio calculation. Furthermore, ring-shaped region partitioning facilitates the detection of ring-shaped COPs.

[0061] For example Figure 2 As shown, the wafer image is divided into annular regions from the inside out; Figure 2 The wafer image shown clearly shows a circle of dense dots, indicating a ring-shaped COP. Accordingly, dividing the wafer image into ring-shaped regions makes it easier to identify ring-shaped COPs.

[0062] In one possible implementation, calculating the particle density ratio between two regions in the group of regions includes:

[0063] Calculate the particle density ratio of the second region to the first region in each region group in order from the outside to the inside.

[0064] In this embodiment of the application, the particle density ratio is calculated sequentially for multiple region groups. Specifically, the particle density ratio of the outer ring region (i.e., the second region) to the inner ring region (i.e., the first region) in each region group is calculated. Since it is the outer ring to the inner ring, the particle density ratio in each region group is calculated sequentially from the outside to the inside within the entire wafer image range.

[0065] In one possible implementation, the number of regions is 5 to 15. An alternative number of regions is 10, such as... Figure 2 As shown.

[0066] The number of the aforementioned regions is based on considerations of the COP formation process. In existing processes, such as... Figure 3 As shown, single-crystal silicon prepared by the Magnetic Field Applied Czochralski Method (MCZ) exhibits crystal defects, such as crystal native defects (COP), flow pattern defects (FPD), oxidation-induced stacking faults (OiSF), and direct surface oxidation defects (DSOD). The accumulation of these defects not only leads to poor withstand voltage of the silicon substrate oxide film but also causes problems such as PN junction leakage, short circuits in slotted capacitors, or insulation failure, reducing the yield of integrated circuits. Therefore, it is necessary to control the crystal quality within the point defect region by adjusting the temperature and crystal growth rate within the crystal pulling furnace. Based on the type and aggregation mode of the defects, the following crystal regions are distinguished: vacancy defect aggregation region (v-rich), boundary (P-band), vacancy point defect region (Pv), gap point defect region (Pi), and gap defect aggregation region (i-rich). Due to the large number of different crystal defects, at least five partitions must be defined when defining the regions.

[0067] like Figure 4 As shown, the formation of cyclic COPs originates from the boundary between liquid and solid during the crystal production process, and the widest radius of the distributed rings is statistically no more than 10 mm. Figure 5 As shown, a total of 5000 annular COP samples were counted. Therefore, to cover all cases, for a 300mm wafer, the maximum number of annular partitions can be set to 15, ensuring that the minimum radius of the partitioned annular ring is 10mm.

[0068] In one possible implementation, the preset threshold is 3.5 to 4.5. An optional preset threshold is 4.0.

[0069] Regarding the aforementioned preset threshold setting, the same sample used in the above statistical analysis of the proportion of annular radii was selected, and the region was divided into 10 partitions, labeled from the inside out as region 1 to 10. The number of particles in the annular COP region and its preceding and following regions was statistically analyzed, and it was found that their quantity did not exhibit any obvious characteristics, such as... Figure 6 As shown. Next, a ratio analysis was performed, revealing that when a ring-shaped COP exists, its ratio with adjacent regions is mostly above 4.0. Therefore, the recommended preset threshold value is 3.5–4.5, as follows: Figure 7 , 8 As shown. To more accurately distinguish the cyclic COP, statistics were compiled on the ratio of the COP region to the inner ring and the ratio to the outer ring. It was found that a value of around 4.0 is more accurate, with more than 95% of values ​​being greater than 4.0. This shows that a preset threshold of 4.0 is more accurate.

[0070] This application also provides a wafer evaluation device, which can be a standalone device or an additional functional device in an existing system. This application does not specifically limit the device in this regard.

[0071] The device includes:

[0072] The acquisition module is used to acquire wafer images;

[0073] The partitioning module is used to divide the wafer image into multiple regions;

[0074] The first determining module is used to determine multiple region groups from multiple regions by grouping two adjacent regions together.

[0075] The calculation module is used to calculate the particle density ratio between two regions in the region group;

[0076] The second determining module is used to determine that the wafer corresponding to the wafer image is an abnormal product if the calculated particle density ratio is greater than a preset threshold.

[0077] Optionally, modules can be divided, specifically for:

[0078] The wafer image is divided into multiple regions from the inside out.

[0079] Among the two adjacent regions, the inner region is the first region, and the outer region is the second region.

[0080] Optionally, modules can be divided, specifically for:

[0081] In the wafer image, multiple annular regions with the same center are divided at equal intervals from the inside out.

[0082] Optionally, the calculation module is specifically used for:

[0083] Calculate the particle density ratio of the second region to the first region in each region group in order from the outside to the inside.

[0084] Optionally, the number of multiple zones can be 5 to 15.

[0085] Optionally, the preset threshold is 3.5 to 4.5.

[0086] It should be noted that the above-mentioned module divisions can be specific, independently configured hardware modules, or they can be integrated virtual modules. This application embodiment does not specifically limit this.

[0087] This application also provides a readable storage medium storing a program or instructions. When the program or instructions are executed by a processor, they implement the various processes of the above-described wafer evaluation method embodiments and achieve the same technical effect. To avoid repetition, they will not be described again here.

[0088] The processor is the processor in the terminal described in the above embodiments. The readable storage medium includes computer-readable storage media, such as computer read-only memory (ROM), random access memory (RAM), magnetic disk, or optical disk.

[0089] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of the present invention.

Claims

1. A wafer evaluation method, characterized in that, include: Acquire wafer images; The wafer image is divided into multiple regions; Multiple region groups are determined among the multiple regions by grouping two adjacent regions together. Calculate the particle density ratio between the two regions in the group of regions; If the calculated particle density ratio is greater than a preset threshold, the wafer corresponding to the wafer image is determined to be an abnormal product. The process of dividing the wafer image into multiple regions includes: The wafer image is divided into multiple annular regions with the same center, arranged at equal intervals from the inside out. Calculating the particle density ratio between two regions in the region group includes: Calculate the particle density ratio of the second region to the first region in each region group in order from the outside to the inside. The second region is the outer ring region in each region group, and the first region is the inner ring region in each region group.

2. The method according to claim 1, characterized in that, The number of the multiple regions is between 5 and 15.

3. The method according to claim 1, characterized in that, The preset threshold is 3.5 to 4.

5.

4. A wafer evaluation device, characterized in that, include: The acquisition module is used to acquire wafer images; A partitioning module is used to partition multiple regions in the wafer image; The first determining module is used to determine multiple region groups in the multiple regions, grouping them into two adjacent regions; The calculation module is used to calculate the particle density ratio between two regions in the region group; The second determining module is used to determine that the wafer corresponding to the wafer image is an abnormal product when the calculated particle density ratio is greater than a preset threshold. Specifically, the partitioning module is used for: The wafer image is divided into multiple annular regions with the same center, arranged at equal intervals from the inside out. Specifically, the calculation module is used for: Calculate the particle density ratio of the second region to the first region in each region group in order from the outside to the inside. The second region is the outer ring region in each region group, and the first region is the inner ring region in each region group.

5. The apparatus according to claim 4, characterized in that, The number of the multiple regions is between 5 and 15.

6. The apparatus according to claim 4, characterized in that, The preset threshold is 3.5 to 4.

5.

7. A readable storage medium, characterized in that, The readable storage medium stores a program or instructions that, when executed by a processor, implement the steps of the wafer evaluation method as described in any one of claims 1-3.

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