Wafer and defect detection method therefor

Abstract

Provided in the present application are a wafer and a defect detection method therefor. The detection method can comprise: for a cleaved sample obtained after a wafer under test is cleaved in a diameter direction, at a junction between a cleaved surface and a main surface of the cleaved sample, measuring, by means of infrared laser scattering tomography, the crystal originated particle (COP) defect density of each detection interval according to a set distance interval; and when the COP defect densities of all detection intervals are less than or equal to a set density threshold, determining that the wafer under test is a wafer without COP defects.

Description

Wafer and method for detecting defects of the wafer

[0001] Cross-reference to Related Applications

[0002] This application claims priority to Chinese Patent Application No. 202410827324.6 filed on June 25, 2024 in China, the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0003] The present application relates to the technical field of semiconductor manufacturing, and in particular, to a wafer and a method for detecting defects of the wafer. BACKGROUND

[0004] A semiconductor wafer, particularly a single crystal silicon wafer for forming a semiconductor device, is usually manufactured from a single crystal silicon rod manufactured by a Czochralski method or a Czochralski method with a magnetic field applied. The single crystal silicon manufactured by the Czochralski method usually contains octahedral void defects formed by the loss of silicon (Si) atoms at lattice points, which can be referred to as Crystal Originated Particle (COP) defects in some cases.

[0005] Current related solutions usually use a particle counter to detect COP defects of a wafer. In the related solution, on the one hand, the particle counter can usually only detect COP defects on the surface of the wafer and within a depth of 0.3 microns from the surface of the wafer, and COP defects are bulk defects of the wafer. Therefore, the particle counter cannot accurately detect all COP defects existing in the interior of the wafer. On the other hand, the particle counter needs to clean the surface of the wafer to be detected during the detection process, otherwise, particles attached to the surface of the wafer will be misjudged as COP defects.

[0006] Therefore, the current related solution has low detection accuracy for COP defects, cannot accurately quantitatively evaluate COP defects, and needs an additional surface cleaning process, thereby increasing the detection cost. SUMMARY

[0007] In view of this, the present application aims to provide a wafer and a method for detecting defects of the wafer, which can improve the detection accuracy of COP defects, accurately quantitatively evaluate COP defects, and reduce the detection cost.

[0008] The technical solution of the present application is implemented as follows:

[0009] In a first aspect, the present application provides a method for detecting defects of a wafer, the detection method comprising:

[0010] For the cleaved sample of the wafer to be tested, the COP defect density of each detection interval is measured at the joint of the cleaved surface and the main surface of the cleaved sample by infrared laser scattering chromatography at a set distance interval; wherein the detection interval is distinguished at the joint according to the distance interval;

[0011] When the COP defect density of all detection intervals is less than or equal to the set density threshold, the wafer to be tested is determined to be a COP defect-free wafer.

[0012] In some examples, the method further comprises:

[0013] Obtaining a plurality of reference wafers of surface defect-free aggregated patterns;

[0014] For each reference wafer, a corresponding reference sample is obtained by cleaving along the diameter direction;

[0015] For each reference sample, the COP defect density of each detection interval is measured at the joint of the cleaved surface and the main surface of the reference sample by infrared laser scattering chromatography at a set distance interval; wherein the detection interval is distinguished at the joint according to the distance interval;

[0016] The COP defect density mean and the standard deviation of the COP defect density are obtained according to the COP defect densities of all reference samples;

[0017] The density threshold is determined according to the COP defect density mean and a set number of standard deviation ranges.

[0018] In some examples, the density threshold is determined according to the COP defect density mean and a set number of standard deviation ranges, comprising:

[0019] The density threshold is determined according to the 5 standard deviation ranges in the positive and negative directions of the COP defect density mean, respectively.

[0020] In some examples, the density threshold is between 5×10 6 and 8×10 6 cm 3 .

[0021] In some examples, the COP defect density of each detection interval is measured at the joint of the cleaved surface and the main surface of the cleaved sample by infrared laser scattering chromatography at a set distance interval, comprising:

[0022] At the joint of the cleaved surface and the main surface of the cleaved sample, a plurality of detection intervals are determined according to the distance interval from the center of the wafer to be tested where the cleaved sample is located to the edge along the radial direction of the wafer to be tested.

[0023] For each detection interval, the infrared laser is incident from the main surface of the wafer to be tested;

[0024] The scattered light from the cleaved surface of the corresponding detection interval is detected by the detector to obtain the COP defect number of each detection interval;

[0025] According to the area of each detection interval and the COP defect number of each detection interval, the COP defect density in each detection interval is obtained.

[0026] In some examples, the COP defect density of each detection interval is measured by infrared laser scattering tomography at a set distance interval at the junction of the cleaved surface and the main surface of the cleaved sample, comprising:

[0027] At the junction of the cleaved surface and the main surface of the cleaved sample, a plurality of sub-interval pairs are determined according to the distance interval from the center of the wafer to be tested where the cleaved sample is located to the two edges along the diameter direction of the wafer to be tested; wherein the two sub-intervals in each sub-interval pair are equal in distance from the center of the wafer to be tested, and each sub-interval pair corresponds to a detection interval according to the distance from the center of the wafer to be tested, respectively;

[0028] For each sub-interval in each sub-interval pair, the infrared laser is incident from the main surface of the wafer to be tested;

[0029] The scattered light from the cleaved surface of the corresponding detection interval is detected by the detector to obtain the COP defect number of each sub-interval in each sub-interval pair;

[0030] According to the area of each sub-interval and the COP defect number of each sub-interval, the COP defect density in each sub-interval is obtained.

[0031] According to the COP defect density of the two sub-intervals in each sub-interval pair, the COP defect density corresponding to each sub-interval pair is obtained to obtain the COP defect density of each detection interval.

[0032] In some examples, the distance interval is between 1 and 5 mm.

[0033] In a second aspect, the present application provides a wafer, which is determined to be a COP defect-free wafer according to the wafer defect detection method of any one of the first aspect and its examples.

[0034] In a third aspect, the application provides a wafer, wherein, after the wafer is cracked along a diameter direction, a crystal original particle (COP) defect density of each detection interval measured by an infrared laser scattering tomography method at a set distance interval at a junction of a crack surface and a main surface of the wafer to be detected is less than a set density threshold value; and the density threshold value is between 5×10 6 and 8×10 6 cm-2. 3

[0035] In some examples, the distance interval is between 1 mm and 5 mm.

[0036] The application provides a wafer and a method for detecting defects of the wafer. After the wafer to be detected is cracked, the COP defect density of each detection interval is measured by the LST method from the scattered light from the crack surface inside the wafer. Compared with the conventional scheme using a particle counter, the COP defect can be detected from a greater depth, the detection accuracy of the COP defect is improved, the COP defect can be accurately quantitatively evaluated, and the scattered light from the inside of the wafer is not affected by the impurities attached to the surface of the wafer. Therefore, an additional cleaning process is not required before the COP defect density is detected, and the detection cost is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0037] FIG. 1 is a schematic diagram of a particle counter detecting a COP defect according to the application.

[0038] FIG. 2 is a schematic diagram of a method for detecting defects of a wafer according to the application.

[0039] FIG. 3(A) is a schematic diagram of a wafer to be detected according to the application.

[0040] FIG. 3(B) is a schematic diagram of a cracked sample according to the application.

[0041] FIG. 4 is a schematic diagram of dividing detection intervals according to the application.

[0042] FIG. 5 is a schematic diagram of measuring the COP defect density of a detection interval by the LST method according to the application.

[0043] FIG. 6 is another schematic diagram of dividing detection intervals according to the application.

[0044] FIG. 7 is a schematic diagram of determining a density threshold value according to the application.

[0045] FIG. 8(A) is a schematic diagram of a detection result of a wafer A measured by the LST method according to the application.

[0046] FIG. 8(B) is a schematic diagram of a detection result of the wafer A using a particle counter according to the application. ​

[0047] FIG. 9(A) is a schematic diagram of a detection result of wafer B measured by LST provided in the present application.

[0048] FIG. 9(B) is a schematic diagram of a detection result of wafer B using a particle counter provided in the present application.

[0049] FIG. 10(A) is a schematic diagram of a detection result of wafer C measured by LST provided in the present application.

[0050] FIG. 10(B) is a schematic diagram of a detection result of wafer C using a particle counter provided in the present application.

[0051] FIG. 11(A) is a schematic diagram of a detection result of wafer D measured by LST provided in the present application.

[0052] FIG. 11(B) is a schematic diagram of a detection result of wafer D using a particle counter provided in the present application.

[0053] FIG. 11(C) is a schematic diagram of a detection result of wafer D using a SEM provided in the present application. DETAILED DESCRIPTION

[0054] The technical solutions in the present application will be described in detail below with reference to the accompanying drawings in the present application.

[0055] For the related solution of detecting COP defects of a wafer by using a particle counter, the present application briefly describes as follows in combination with FIG. 1: the particle counter irradiates incident light IL1 on a silicon wafer 1, receives scattered light SL1, and detects COP defects 3 according to light point defects (LPD) formed by the scattered light SL1. The related solution can detect COP defects 3 on the surface and within a depth of 0.3 μm from the surface, but cannot detect defects 2 within the wafer, for example, within a depth of 2 μm from the surface. In addition, in addition to the COP defects 3, impurities and the like attached to the surface of the silicon wafer 1 can also form LPD to misjudge the detection of the COP defects 3, and therefore, an additional cleaning process needs to be performed on the surface of the wafer 1 before the related solution is performed, so as to reduce the probability of misjudgment and increase the detection cost.

[0056] In view of the above, the present application aims to improve the accuracy of COP defect detection and reduce the detection cost without an additional process before detection.

[0057] Therefore, referring to FIG. 2, a detection method of wafer defects provided in the present application is shown. As shown in FIG. 2, the detection method can include steps S210 to S220.

[0058] In step S210, for the cleaved sample of the wafer to be tested after being cleaved along the diameter direction, at the joint of the cleaved surface and the main surface of the cleaved sample, the COP defect density of each detection interval is measured by the laser scattering tomography (LST) method at a set distance interval.

[0059] In step S220, when the COP defect density of all detection intervals is less than or equal to the set density threshold, it is determined that the wafer to be tested is a wafer without COP defects.

[0060] The steps in the technical solution shown in FIG. 2 are described in further detail below.

[0061] [Step S210]

[0062] In the present application, taking the wafer to be tested 30 shown in FIG. 3(A) as an example, after being cleaved along the diameter direction shown by the dashed line, the cleaved sample 31 shown in FIG. 3(B) is obtained. In the cleaved sample, in addition to the upper surface 32 and the lower surface 33 of the original wafer to be tested 30, it also includes the cleaved surface 34 formed by the cleaving operation. It should be noted that in FIG. 3(B), the upper surface 32 is the main surface, the cleaved surface 34 is combined with the upper surface 32 at the edge 35, which is the joint of the cleaved surface and the main surface of the cleaved sample in step S210. For this joint, the present application distinguishes the detection intervals according to the set distance interval to perform LST measurement.

[0063] In some examples, as shown in FIG. 4, the center of the wafer to be tested 30 is marked as O, and at the joint of the cleaved surface 34 and the main surface 32, based on the radius direction of the wafer to be tested 30 shown by the arrow to the edge E from the center O, the detection intervals shown by the dash-dot line can be distinguished according to the distance interval D at the cleaved surface 34, which are respectively marked as 41-1, 41-2, …, 41-N, N represents the number of detection intervals. In the present application, the distance interval D can be any value between 1mm and 5mm, such as D can be 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 4mm, 5mm, etc., which can also be determined flexibly according to the actual situation.

[0064] For each detection interval shown in FIG. 4, i.e. each of the detection intervals 41-1, 41-2, …, 41-N, the COP defect density of each detection interval is measured by LST method. Specifically, as shown in FIG. 5, taking the ith detection interval 41-i as an example, the infrared laser 51 is incident from the main surface 32; the scattered light 53 (Rayleigh scattering light) from the cleavage surface of the corresponding detection interval 41-i is detected by the detector 52 to obtain the COP defect number of the ith detection interval 41-i. In this application, the detector 52 can be a Charge Coupled Device (CCD) camera, a Complementary Metal-Oxide-Semiconductor (CMOS) image sensor, etc.

[0065] After obtaining the COP defect number of each detection interval according to the scheme shown in FIG. 5, the COP defect density in each detection interval can be obtained according to the area of each detection interval and the COP defect number of each detection interval. In this application, the unit of COP defect density is pieces / cm2. 3 .

[0066] It should be noted that, since the single crystal silicon rod is always slowly rotated and moved upward during the Czochralski process, it can be considered that the COP defect density at the same position from the center of the wafer is consistent. In the above example shown in FIG. 4, the detection intervals are only divided along the radial direction, so the COP defect density at the position symmetrical to the detection interval in the part without dividing the detection interval can be considered to be consistent with the COP defect density in the symmetrical detection interval.

[0067] In some examples, as shown in FIG. 6, the center of the wafer 30 to be measured is marked as O, and based on the diameter direction of the wafer 30 to be measured to the two edges E and E', the cleavage surface 34 is divided into N pairs of sub-intervals shown by the dotted line at a distance interval D from the center O, respectively marked as 61-1, 61-2, …, 61-N, each pair of sub-intervals can be correspondingly regarded as a detection interval in this application.

[0068] Each sub-interval pair contains two sub-intervals, for example, the sub-interval pair 61-1 contains the sub-intervals 61-1a and 61-1b, the sub-interval pair 61-2 contains the sub-intervals 61-2a and 61-2b, and so on, and the sub-interval pair 61-N contains the sub-intervals 61-Na and 61-Nb. In addition, in each sub-interval pair, the two sub-intervals contained therein are equal in distance from the center O, such as the sub-interval pair 61-2 shown in FIG. 6, which contains the sub-intervals 61-2a and 61-2b equal in distance from the center O.

[0069] For each sub-interval in each sub-interval pair, such as the sub-intervals 61-1a and 61-1b in the sub-interval pair 61-1, the COP defect density of each sub-interval can be measured using the same measurement scheme as described above with respect to FIG. 5. For example, for the sub-interval 61-1a, infrared laser light can be incident from the main surface 32; scattered light from the cleaved surface corresponding to the sub-interval 61-1a can be detected using the detector 52 to obtain the number of COP defects of the sub-interval 61-1a.

[0070] After obtaining the number of COP defects of the sub-interval 61-1a in the same scheme as shown in FIG. 5, the COP defect density of the sub-interval 61-1a can be obtained from the area of the sub-interval 61-1a and the number of COP defects. Understandably, the COP defect density of the sub-interval 61-1b can also be obtained in the same manner.

[0071] After obtaining the COP defect densities of the sub-intervals 61-1a and 61-1b, the COP defect density of the sub-interval pair 61-1, i.e., the COP defect density of the detection interval 61-1, can be calculated by averaging.

[0072] It should be noted that for each sub-interval pair in FIG. 6, the COP defect density of the corresponding detection interval can be obtained in the above-described manner, and the present application will not be described in detail.

[0073] As described above, after the wafer to be measured is cleaved, the COP defect density of each detection interval is measured by receiving scattered light from the cleaved surface inside the wafer by LST, which can detect COP defects from a greater depth compared to the conventional scheme using a particle counter, improves the detection accuracy of COP defects, and accurately quantifies and evaluates COP defects. In addition, the scattered light from the inside of the wafer is not affected by impurities attached to the surface of the wafer, and there is no need for an additional cleaning process on the surface of the wafer before COP defect density detection, thereby reducing the detection cost.

[0074] [Step 220]

[0075] After measuring the COP defect density of each detection zone in the cleaved sample, a correspondence between the detection zone and the COP defect density value can be formed. In the present application, the COP defect density corresponding to each detection zone is compared with a density threshold value for evaluating whether it is a COP free defect, to determine whether the wafer under test is COP free. It should be noted that "COP free" means that the COP defect density of the wafer is less than a specific index value, and in the present application, the density threshold value is a form of the index value. If the COP defect density of all detection zones is less than or equal to the density threshold value, it can be determined that the wafer under test 30 is a COP free wafer. If there is at least one detection zone whose COP defect density is greater than the density threshold value among all detection zones, it can be determined that the wafer under test 30 is a COP unfree wafer.

[0076] The density threshold value is an index for evaluating whether it is a COP free wafer. In some examples, the wafer defect detection method proposed in the present application can further include a process of determining the density threshold value. As shown in FIG. 7, the process of determining the density threshold value can include steps S201 to S205.

[0077] In step S201, a plurality of reference wafers of surface defect-free aggregation patterns are obtained.

[0078] In this step, the reference wafer can be a wafer whose surface particles are detected by a particle counter without native defect aggregation. Specifically, after detecting the surface particles of a wafer by a particle counter, if no ring aggregation pattern or circular aggregation pattern with the wafer center as the center can be found by visual inspection in the detection result, the wafer is detected by a scanning electron microscope (SEM). When the SEM detection result also indicates that the wafer has no COP defect, the wafer can be selected as a reference wafer. Otherwise, it cannot be selected as a reference wafer. In the present application, the number of reference wafers can be 5, 10, 15, 20, etc., and can also be flexibly set according to actual conditions.

[0079] In step S202, for each reference wafer, a corresponding reference sample is obtained by cleaving along the diameter direction.

[0080] In step S203, for each reference sample, the COP defect density of each detection zone is measured by LST at a set distance interval at the junction of the cleaved surface and the main surface of the reference sample.

[0081] In the present application, the implementation details of the above steps S202 and S203 are the same as the content about FIG. 3 to FIG. 5 in the foregoing detailed description of step S210, i.e., the COP defect density of each detection interval of each reference wafer is measured by using LST, which will not be repeated here. It should be noted that each detection interval of each reference wafer can be measured multiple times to accurately obtain statistical values.

[0082] For example, it is assumed that the reference wafers are 12-inch (diameter of 300 mm) single crystal wafers, the number of reference wafers is 5, and the distance interval is 2 mm. For each reference sample obtained by cleaving each reference wafer, according to the foregoing example of division of detection intervals shown in FIG. 4, the number of detection intervals of each reference sample is 75, and for each detection interval, 3 measurements are taken by using LST, so that a total of 75*3*5 = 1125 COP defect density values can be obtained.

[0083] In step S204, the COP defect density mean value and the COP defect density standard deviation are obtained according to the COP defect densities of all reference samples.

[0084] In the present application, in combination with the foregoing example, for the 1125 COP defect density values, the COP defect density mean value mean can be calculated. After obtaining the mean value mean, the COP defect density standard deviation σ can be calculated in combination with the mean value and the 1125 COP defect density values, and the standard deviation is used to measure the distribution dispersion degree of the COP defect density of the reference wafers.

[0085] In step S205, the density threshold is determined according to the COP defect density mean value and the set number of standard deviation ranges.

[0086] For step S205, most of the data points are concentrated in the range of 1 or 2 standard deviations in the positive and negative directions of the mean value, and the present application can be set to 5 standard deviation ranges, i.e., 99.99943% of the values in the data set will fall within the range of ±5 standard deviations (σ) of the mean value. In some examples, the density threshold can be determined according to the 5 standard deviation ranges in the positive and negative directions of the COP defect density mean value. Specifically, the density threshold baseline = mean + 5σ. In some examples, the density threshold is between 5*10 6 and 8*10 6 . 3 .

[0087] In the present application, since the wafer to be tested needs to be cleaved in the defect detection process according to the foregoing technical solution, even if the wafer to be tested is determined to be a COP defect-free wafer by the foregoing technical solution, the wafer to be tested cannot flow into the next process due to damage. Based on this, in some examples, the method further comprises: after determining that the wafer to be tested is a COP defect-free wafer, determining that other wafers in the same batch as the wafer to be tested are COP defect-free wafers.

[0088] For the above example, specifically, at least one wafer to be tested can be selected from the same batch, such as 25 wafers, and if the wafer to be tested is determined to be a COP defect-free wafer by the foregoing technical solution, then the other wafers in the batch can be determined to be COP defect-free wafers.

[0089] The following embodiments using four wafers to be tested respectively identified as A, B, C, and D will more specifically illustrate the technical solutions of the present application. It can be understood that the present application is not limited to the following embodiments. In the present application, the four wafers A, B, C, and D are all 12-inch (diameter 300mm) wafers.

[0090] [Embodiment 1]

[0091] Taking wafer A as an example, the detection intervals are divided according to a distance interval of 2mm from the center to the edge of wafer A in the radial direction, the COP defect density of the detection intervals is measured by LST, and the detection result is shown in FIG. 8(A). In FIG. 8(A), the abscissa represents the distance of the detection interval from the center of wafer A, the ordinate represents the COP defect density, and the horizontal line represents the density threshold baseline. As can be seen from FIG. 8(A), the COP defect density of all detection intervals is less than the baseline, so wafer A can be determined to be a COP defect-free wafer.

[0092] Before measuring the COP defect density of the detection intervals of wafer A by LST, the surface particles of wafer A are detected by a particle counter, and the detection result (map) is shown in FIG. 8(B). As can be seen from FIG. 8(B), the surface particles of wafer A are distributed dispersedly and in small quantities. Thus, the same conclusion as shown in FIG. 8(A) can be obtained, i.e., wafer A is a COP defect-free wafer.

[0093] [Embodiment 2]

[0094] Take wafer B as an example, based on the radial direction from the center of wafer B to the edge, the detection interval is divided according to the distance interval of 2mm, the COP defect density of the detection interval is measured by LST, and the detection result is shown in FIG. 9(A). As can be seen from FIG. 9(A), there are many detection intervals with COP defect density greater than baseline from the center of wafer B to the edge, and the number of detection intervals is large, so it can be determined that wafer B is a wafer with COP defects.

[0095] Before measuring the COP defect density of the detection interval of wafer A by LST, the surface particles of wafer B are detected by a particle counter (Particle counter), and the detection result (map) is shown in FIG. 9(B). As can be seen from FIG. 9(B), the surface particles of wafer B are densely distributed and the number is large. Therefore, the same conclusion as shown in FIG. 9(A) can be obtained, that is, wafer B is a wafer with COP defects.

[0096] [Example 3]

[0097] Take wafer C as an example, based on the radial direction from the center of wafer C to the edge, the detection interval is divided according to the distance interval of 2mm, the COP defect density of the detection interval is measured by LST, and the detection result is shown in FIG. 10(A). As can be seen from FIG. 10(A), the COP defect density from the center of wafer C to the region at a radius of 96mm is greater than baseline, and the COP defect density from 96mm to the edge is less than baseline, so it can be determined that wafer C is a wafer with COP defects.

[0098] Before measuring the COP defect density of the detection interval of wafer A by LST, the surface particles of wafer C are detected by a particle counter (Particle counter), and the detection result (map) is shown in FIG. 10(B). In FIG. 10(B), the number of particles from the center of wafer C to 96mm is large, and it presents a circular aggregation pattern with the wafer center as the center, so the same conclusion as shown in FIG. 10(A) can be obtained, that is, wafer C is a wafer with COP defects.

[0099] [Example 4]

[0100] Take wafer D as an example, based on the radial direction from the center of wafer D to the edge, the detection interval is divided according to the distance interval of 2mm, the COP defect density of the detection interval is measured by LST, and the detection result is shown in FIG. 11(A). As can be seen from FIG. 11(A), in all detection intervals, the COP defect density of the area from the center of wafer D to 24mm is greater than the baseline, and the COP defect density from 24mm to the edge is less than the baseline, it can be determined that wafer D is a wafer with COP defects (COP unfree).

[0101] Before measuring the COP defect density of the detection interval of wafer A by LST, the surface particles of wafer D are detected by a particle counter, and the detection result (map) is shown in FIG. 11(B). In FIG. 11(B), the surface particles of wafer D do not show a circular aggregation pattern, based on the results shown in FIG. 11(B), wafer D is a wafer without COP defects.

[0102] For the different defect judgment conclusions obtained in FIG. 11(A) and FIG. 11(B), respectively, in this embodiment, wafer D can be detected by a scanning electron microscope (SEM) before performing LST measurement, and the detection result is shown in FIG. 11(C). As can be seen from the scanning image on the left side of FIG. 11(C) and the composition analysis diagram on the right side of FIG. 11(C), wafer D is a wafer with COP defects (COP unfree), which is consistent with the conclusion obtained by LST measurement. It can be seen that the wafer defect detection method provided by the present application has higher detection accuracy of COP defects compared with the conventional scheme using a particle counter.

[0103] It should be noted that the technical solutions disclosed in the present application can be combined arbitrarily without conflict.

[0104] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical scope disclosed in the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for detecting wafer defects, the method comprising: For the fractured sample of the wafer under test after fracture along the diameter direction, the COP defect density of the crystal native particles in each detection interval is measured by infrared laser scattering tomography at a set distance interval at the junction of the fractured surface and the main surface of the fractured sample; wherein, the detection interval is distinguished at the junction according to the distance interval. When the COP defect density in all detection intervals is less than or equal to the set density threshold, the wafer under test is determined to be a wafer without COP defects.

2. The detection method according to claim 1, wherein, The method further includes: Obtain a reference wafer with multiple defect-free aggregated patterns on its surface; For each reference wafer, the corresponding reference sample is obtained by splitting along the diameter direction; For each reference sample, at the junction of the fracture surface and the main surface of the reference sample, the COP defect density of the native crystal particles in each detection interval is measured by infrared laser scattering tomography at a set distance interval; wherein, the detection interval is distinguished at the junction according to the distance interval. The mean COP defect density and the standard deviation of COP defect density are obtained based on the COP defect density of all benchmark samples. The density threshold is determined based on the mean COP defect density and the standard deviation range of the set number.

3. The detection method according to claim 2, wherein, Determining the density threshold based on the mean COP defect density and a set range of standard deviations includes: The density threshold is determined based on the mean COP defect density within five standard deviations in both the positive and negative directions.

4. The detection method according to claim 1, wherein, The density threshold is 5 × 10 6 Up to 8×10 6 pcs / cm 3 between.

5. The detection method according to claim 1, wherein, The method of measuring the COP defect density of the primary crystal particles at the junction of the fracture surface and the main surface of the fractured sample using infrared laser scattering tomography at predetermined intervals includes: At the junction of the fractured surface and the main surface of the fractured sample, multiple detection intervals are determined from the center of the wafer to be tested where the fractured sample is located to the edge along the radius direction of the wafer to be tested, according to the distance intervals. For each detection interval, infrared laser light is incident from the main surface of the wafer under test; The scattered light from the fracture surface of the corresponding detection interval is detected by a detector to obtain the number of COP defects in each detection interval; The COP defect density within each detection interval is obtained based on the area of ​​each detection interval and the number of COP defects in each detection interval.

6. The detection method according to claim 4, wherein, The method of measuring the COP defect density of the primary crystal particles at the junction of the fracture surface and the main surface of the fractured sample using infrared laser scattering tomography at predetermined intervals includes: At the junction of the fractured surface and the main surface of the fractured sample, multiple sub-interval pairs are determined from the center of the wafer to be tested where the fractured sample is located to the two edges along the diameter direction of the wafer to be tested, according to the distance interval; wherein, the two sub-intervals in each sub-interval pair are equidistant from the center of the wafer to be tested, and each sub-interval pair corresponds to a detection interval according to its distance from the center of the wafer to be tested; For each sub-interval in each sub-interval pair, infrared laser light is incident from the main surface of the wafer under test; The scattered light from the fracture surface of the corresponding detection interval is detected by a detector to obtain the number of COP defects in each sub-interval in each sub-interval pair. The COP defect density within each sub-interval is obtained based on the area of ​​each sub-interval and the number of COP defects in each sub-interval. The COP defect density of each detection interval is obtained by obtaining the COP defect density of each sub-interval pair corresponding to the two sub-intervals in each sub-interval pair.

7. The detection method according to any one of claims 1 to 6, wherein, The distance interval is between 1 and 5 mm.

8. A wafer, wherein the wafer is determined to be free of COP defects by the wafer defect detection method according to any one of claims 1 to 7.

9. A wafer, wherein after the wafer is fractured along its diameter, the density of crystal native grain COP defects in each detection interval at the junction of the fracture surface and the main surface of the wafer under test, measured by infrared laser scattering tomography at predetermined distance intervals, is less than a predetermined density threshold; wherein, The density threshold is 5 × 10 6 Up to 8×10 6 pcs / cm 3 between.

10. The wafer according to claim 9, wherein the distance interval is between 1 and 5 mm.

Images