Wafer Inspection Method and System Based on Second Harmonic Waves

Abstract

This invention relates to a wafer inspection method and system based on second harmonic detection. The method includes: acquiring a set of measured second harmonic detection signals at pre-selected measurement points in a sample to be tested. The set of measured second harmonic detection signals includes multiple second harmonic detection signals generated when the pre-selected measurement points are irradiated by light sources from different azimuth angles and excited; performing fitting processing on the multiple second harmonic detection signals in the set of measured second harmonic detection signals based on a preset fitting algorithm to obtain lattice characteristic detection curve data; and determining the state of the wafer at the pre-selected measurement points based on the obtained lattice characteristic detection curve data. Since all related operations are performed based on second harmonic detection signals, it has the characteristic of fast signal acquisition speed, which can meet the requirements of faster detection and realize online detection. The wafer inspection method and system based on second harmonic detection of this invention has the characteristics of high detection efficiency, fast response speed, good performance, and good adaptability.

Description

Technical Field

[0001] This invention relates to the field of testing, and more particularly to the field of semiconductor manufacturing testing, specifically to a wafer testing method and system based on second harmonics. Background Technology

[0002] As chip manufacturing processes advance to 7 nanometers, 5 nanometers, and even smaller, the precision requirements for wafer manufacturing are extremely high. Any tiny defect can lead to chip failure. Among these, the lattice quality of the wafer is crucial to the performance of semiconductor materials. Therefore, effectively detecting the lattice condition of the wafer during the production stage is particularly important.

[0003] In the semiconductor testing industry, X-ray diffraction (XRD) technology is commonly used to measure lattice quality. This technology is based on the interaction between X-rays and crystals to generate diffraction patterns. By analyzing the patterns, lattice parameters, crystal orientation, and defect information can be obtained. However, the related equipment has problems such as high cost, small detection range, and low detection efficiency.

[0004] While the existing technology of transmission electron microscopy (TEM) can obtain microscopic images of materials by penetrating the sample with an electron beam, and can directly observe the arrangement of atoms in the crystal lattice and identify atomic-level defects and lattice distortions, the preparation process of sliced ​​samples is complicated, the detection conditions are demanding, and it is a destructive detection method. At the same time, TEM also suffers from high equipment costs and low detection efficiency.

[0005] Meanwhile, the X-ray diffraction (XRD) and transmission electron microscopy (TEM) technologies mentioned above both require the sample to be removed from the production line and placed on specific equipment for inspection. Wafer production involves hundreds of processes, and deviations in any process can affect the quality of the final product. Therefore, the existing detection methods cannot effectively meet the needs of rapid detection. Summary of the Invention

[0006] In view of the above-mentioned deficiencies of the prior art, the present invention provides a wafer inspection method and system based on second harmonics that solves at least one of the above problems and effectively satisfies the requirements of high efficiency, convenience and adaptability in the wafer fabrication process.

[0007] To achieve the above objectives, the wafer inspection method and system based on second harmonics of the present invention are as follows:

[0008] Firstly, the wafer inspection method based on second harmonics is characterized in that the wafer inspection method includes:

[0009] The measured second harmonic detection signal set at the pre-selected measurement point in the sample to be tested is obtained. The measured second harmonic detection signal set includes: multiple second harmonic detection signals generated by the pre-selected measurement point after being irradiated by light sources from different azimuth angles and excited.

[0010] Based on a preset fitting algorithm, multiple second harmonic detection signals in the measured second harmonic detection signal set are fitted to obtain lattice characteristic detection curve data.

[0011] The state of the wafer at the pre-selected measurement point is determined based on the obtained lattice characteristic detection curve data.

[0012] In the aforementioned wafer inspection method based on second harmonics, when the lattice characteristic detection curve data is obtained by fitting P-polarized light from multiple second harmonic detection signals in the measured second harmonic detection signal set, the preset fitting algorithm includes the following formula 1:

[0013]

[0014] in, This represents the value of the second harmonic signal corresponding to P-polarized light in the lattice property detection curve data. The azimuth angle of the light source when it illuminates the preselected test point is the value of the second harmonic signal corresponding to the P-polarized light, n is a preset constant, A and B are coefficients used to reflect the state of the wafer at the preselected test point, and the lattice characteristic detection curve data obtained based on the above formula 1 constitutes the first test target characteristic curve.

[0015] In the above-mentioned wafer inspection method based on second harmonics, n = 4 when the surface at the pre-selected measurement point is the (001) plane in a cubic lattice.

[0016] The above-described wafer inspection method based on second harmonics, wherein when the lattice characteristic detection curve data is obtained based on Equation 1, the step of determining the state of the wafer at the pre-selected measurement point based on the obtained lattice characteristic detection curve data includes the following steps:

[0017] Obtain the value of variable A in the first test target feature curve obtained based on Equation 1;

[0018] Based on the value of variable A, determine the state of the wafer at the pre-selected measurement point, including: the interface roughness state at the pre-selected measurement point;

[0019] The step of determining the wafer state at the pre-selected measurement point based on the value of variable A includes the following steps: the interface roughness state at the pre-selected measurement point.

[0020] Determine the threshold range into which the value of variable A falls;

[0021] The interface roughness state at the pre-selected measurement point is determined based on the threshold range into which the value of variable A falls.

[0022] The above-described wafer inspection method based on second harmonics, wherein when the lattice characteristic detection curve data is obtained based on Equation 1, the step of determining the state of the wafer at the pre-selected measurement point based on the obtained lattice characteristic detection curve data includes the following steps:

[0023] Obtain the value of variable B in the first test target feature curve obtained based on Equation 1;

[0024] Based on the value of variable B, the differences between the production processes corresponding to the test samples are determined.

[0025] The above-described wafer inspection method based on second harmonics, wherein when the lattice characteristic detection curve data is obtained based on Equation 1, the step of determining the state of the wafer at the pre-selected measurement point based on the obtained lattice characteristic detection curve data includes the following steps:

[0026] Obtain the value of variable B in the first test target feature curve obtained based on Equation 1;

[0027] Based on the value of variable B, determine the state of the wafer at the pre-selected measurement point, including: the state of the lattice features at the pre-selected measurement point;

[0028] The step of determining the state of the wafer at the pre-selected measurement point based on the value of variable B includes the following steps: the state of the lattice features at the pre-selected measurement point.

[0029] Determine the threshold range into which the value of variable B falls;

[0030] Based on the threshold range into which the value of variable B falls, the state of the lattice features at the pre-selected measurement point is determined.

[0031] The above-mentioned wafer inspection method based on second harmonics further includes: determining, based on the goodness of fit between the first test target characteristic curve and the preset first reference lattice characteristic detection curve data, whether the state of the wafer at the pre-selected test point includes: whether the lattice distortion and / or stress influence at the pre-selected test point is within an acceptable range.

[0032] The first reference lattice characteristic detection curve data is: curve data obtained by fitting the P-polarized light from multiple reference second harmonic detection signals in the reference second harmonic detection signal set into Equation 1 above.

[0033] In the aforementioned wafer inspection method based on second harmonics, when the lattice characteristic detection curve data is obtained by fitting S-polarized light from multiple second harmonic detection signals in the measured second harmonic detection signal set, the preset fitting algorithm includes the following formula 2:

[0034]

[0035] in, This represents the value of the second harmonic signal corresponding to S-polarized light in the lattice property detection curve data. The azimuth angle of the light source when it illuminates the preselected test point is the value of the second harmonic signal corresponding to the S-polarized light, n is a preset constant, C is a coefficient used to reflect the state of the wafer at the preselected test point, and D is the DC offset. The second test target characteristic curve is formed by the lattice characteristic detection curve data obtained based on the above formula 2.

[0036] In the above-mentioned wafer inspection method based on second harmonics, n = 4 when the surface at the pre-selected measurement point is the (001) plane in a cubic lattice.

[0037] The above-described wafer inspection method based on second harmonics, wherein when the lattice characteristic detection curve data is obtained based on Equation 2, the step of determining the wafer state at the pre-selected measurement point based on the obtained lattice characteristic detection curve data includes the following steps:

[0038] Obtain the value of variable C in the second test target feature curve obtained based on Equation 2;

[0039] Based on the value of variable C, determine the state of the wafer at the pre-selected measurement point, including: the state of the lattice features at the pre-selected measurement point;

[0040] The determination of the wafer state at the pre-selected measurement point based on the value of variable C includes the state of the lattice features at the pre-selected measurement point, comprising the following steps:

[0041] Determine the threshold range into which the value of variable C falls;

[0042] Based on the threshold range into which the value of variable C falls, the state of the lattice features at the pre-selected measurement point is determined.

[0043] The above-described wafer inspection method based on second harmonics, wherein when the lattice characteristic detection curve data is obtained based on Equation 2, the step of determining the wafer state at the pre-selected measurement point based on the obtained lattice characteristic detection curve data includes the following steps:

[0044] Obtain the value of variable C in the second test target feature curve obtained based on Equation 2;

[0045] Based on the value of variable C, the differences between the production processes corresponding to the test samples are determined.

[0046] The aforementioned wafer inspection method based on second harmonics further includes:

[0047] Based on the goodness of fit between the second test target characteristic curve and the preset second reference lattice characteristic detection curve data, determine whether the state of the wafer at the pre-selected test point includes: whether the lattice distortion and / or stress influence at the pre-selected test point is within an acceptable range.

[0048] The second reference lattice characteristic detection curve data is obtained by fitting the curve data after substituting the S-polarized light from multiple reference second harmonic detection signals in the reference second harmonic detection signal set into Equation 2 above.

[0049] The aforementioned wafer inspection method based on second harmonics further includes:

[0050] The goodness-of-fit R at the pre-selected measurement points in the sample to be tested is obtained based on the following equation 3. 2 Value:

[0051]

[0052] Among them, Y actual Y is the measured value of the second harmonic detection signal corresponding to the first preset azimuth angle in the measured second harmonic detection signal set. predict Y is the fitted value of the second harmonic signal corresponding to the first preset azimuth angle in the lattice characteristic detection curve data. mean It is the average value of several measured values ​​of the second harmonic detection signals in the measured second harmonic detection signal set;

[0053] According to the goodness of fit R 2 The value determines whether the state of the wafer at the preselected measurement point includes: whether the lattice distortion and / or stress effects at the preselected measurement point are within acceptable limits.

[0054] In the above-described wafer inspection method based on second harmonics, the plurality of second harmonic detection signals in the measured second harmonic detection signal set are all the second harmonic detection signals in the measured second harmonic detection signal set.

[0055] The aforementioned wafer inspection method based on second harmonics further includes:

[0056] Based on the detected state of the wafer at each pre-selected test point in the sample to be tested, a wafer map is generated to characterize the overall performance level of the sample to be tested.

[0057] The aforementioned wafer inspection method based on second harmonics obtains the measured second harmonic detection signal set at the pre-selected measurement points through the following operations:

[0058] The light source capable of exciting the sample under test to generate second harmonics moves continuously relative to the sample under test along the direction surrounding the pre-selected test point within a preset rotation angle range. At the same time, the second harmonic signals generated by the sample under test after being irradiated by the light source at different azimuth angles are continuously collected to obtain multiple second harmonic detection signals generated by the pre-selected test point after being irradiated by the light source from different azimuth angles.

[0059] The aforementioned wafer inspection method based on second harmonics obtains the measured second harmonic detection signal set at the pre-selected measurement points through the following operations:

[0060] A light source capable of exciting the sample under test to generate second harmonics is directed at the pre-selected test point from multiple preset azimuth angles within a preset rotation angle range, along the direction surrounding the pre-selected test point. By collecting the second harmonic signals generated by the sample under test after being irradiated by the light source at different azimuth angles, multiple second harmonic detection signals generated by the pre-selected test point after being irradiated by the light source from different azimuth angles are obtained.

[0061] Secondly, the wafer inspection system based on second harmonics is characterized in that the wafer inspection system is used to perform the wafer inspection method based on second harmonics described in the first aspect above.

[0062] The beneficial effects of the wafer inspection method and system based on second harmonics of the present invention are as follows:

[0063] The wafer inspection method and system based on second harmonics of the present invention acquires a set of measured second harmonic detection signals at pre-selected measurement points in the sample under test, and performs fitting processing on multiple second harmonic detection signals in the set. Based on the acquired lattice characteristic detection curve data, the state of the wafer at the pre-selected measurement points can be determined. Since all related operations are performed based on second harmonic detection signals, and existing wafer inspection systems for detecting electrical characteristic parameters of wafers using second harmonic scanning can generally be directly installed on the wafer production line and have the characteristic of fast signal acquisition speed, using second harmonics to inspect wafers during production can determine the lattice characteristics of the wafer more quickly. Furthermore, since the inspection can be completed without moving the sample under test, it can meet the requirements for faster inspection and achieve online inspection. The wafer inspection method and system based on second harmonics of the present invention has the characteristics of high inspection efficiency, fast response speed, good performance, and good adaptability. Attached Figure Description

[0064] The following will further explain the concept, specific structure, and technical effects of the present invention in conjunction with the accompanying drawings, so as to fully understand the purpose, features, and effects of the present invention.

[0065] Figure 1 This is a schematic diagram of the rotation direction for second harmonic detection in an example.

[0066] Figure 2 This is a schematic diagram of a crystal structure.

[0067] Figure 3a , Figure 3b , Figure 3c and Figure 3d These are schematic diagrams showing the roughness test results of four wafers as reflected by variable A in Equation 1.

[0068] Figure 4a It is a logic diagram showing the correspondence between the components and their proportions in the crystal lattice and the value of variable B.

[0069] Figure 4b It is a logic diagram showing the correspondence between the components and their proportions in the crystal lattice and the value of the variable C.

[0070] Figure 5 This is a schematic diagram of the distribution of measurement points on the wafer under test.

[0071] Figure 6a , Figure 6b and Figure 6c This is a schematic diagram of the three test results generated by combining Equation 2.

[0072] Figure 7 This is another test result graph generated by combining Equation 2.

[0073] Figure 8a This is a schematic diagram of the fitting state when the fitting effect is good.

[0074] Figure 8b This is a schematic diagram of the fitting state when the fitting effect is poor.

[0075] Figure 9 This is a flowchart of a wafer inspection method based on second harmonics in one embodiment.

[0076] Figure Labels

[0077] 1. Measuring point A

[0078] 2. Measuring point B

[0079] 3. Measuring point C Detailed Implementation

[0080] To make the technical means, inventive features, objectives, and effects of the invention readily understandable, the invention is further illustrated below with reference to specific figures. However, the invention is not limited to the embodiments described below.

[0081] It should be noted that the structures, proportions, sizes, etc., illustrated in the accompanying drawings of this specification are only used to complement the content disclosed in the specification for those skilled in the art to understand and read, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0082] For some wafer manufacturing processes, certain parameters are directly related to the quality of the output wafer. Conventional metrology methods can detect these properties, but they are slow, inefficient, and require very demanding conditions (such as vacuum conditions), making online testing impossible.

[0083] When using an X-ray diffractometer (XRD) for detection in existing technologies, the following problems exist:

[0084] a. Insufficient sensitivity / limited resolution: For some crystal structures or types, XRD cannot detect minute changes in the crystal structure and internal stress.

[0085] b. The cost is too high – current technology cannot directly install it on the production line;

[0086] c. Low detection efficiency – long XRD detection time.

[0087] To address the aforementioned issues, this technical solution provides a wafer inspection method and system based on second harmonics, enabling non-contact, non-destructive second harmonic detection of substrates or thin films with a certain lattice structure, and related applications, thereby achieving the goal of rapid and effective wafer inspection.

[0088] This invention is mainly based on RA-SHG (full name: Rotational Anisotropy Second Harmonic Generation). The rotational anisotropy second harmonic is used to represent the change in the intensity of the second harmonic signal under different azimuth angles. According to research, its formation is closely related to the crystal structure.

[0089] Example 1:

[0090] This embodiment provides a wafer inspection method based on second harmonics, including:

[0091] The measured second harmonic detection signal set at the pre-selected measurement point in the sample to be tested is obtained. The measured second harmonic detection signal set includes: multiple second harmonic detection signals generated by the pre-selected measurement point after being irradiated by light sources from different azimuth angles and excited.

[0092] In practice, the measured second harmonic detection signal set at the pre-selected measurement point can be obtained through the following operations:

[0093] A light source capable of exciting the sample to generate second harmonics is continuously moved relative to the sample within a preset rotation angle range along a direction surrounding the pre-selected measurement point. Simultaneously, the second harmonic signals generated by the sample after being irradiated by the light source at different azimuth angles are continuously acquired. This yields multiple second harmonic detection signals generated by the pre-selected measurement point after being irradiated by the light source from different azimuth angles (i.e., multiple second harmonic detection signals are acquired through continuous scanning; for ease of reading, this application also refers to this operation as RA-scan second harmonic detection); or

[0094] A light source capable of exciting the sample under test (i.e., wafer) to generate second harmonics is directed at the pre-selected test point from multiple preset azimuth angles within a preset rotation angle range, along the direction surrounding the pre-selected test point. By collecting the second harmonic signals generated by the sample under test after being irradiated by the light source at different azimuth angles, multiple second harmonic detection signals generated by the pre-selected test point after being irradiated by the light source from different azimuth angles are obtained (i.e., multiple second harmonic detection signals are obtained by discrete scanning; for ease of reading, this application also refers to the relevant operation as RA second harmonic detection).

[0095] For the incident angle and rotation direction of the relevant light source, please refer to [reference needed]. Figure 1 As shown, the elliptical surface is used to indicate the sample to be tested, and it is marked as the (100) plane in the crystal lattice. The center of the elliptical surface is the pre-selected test point. E ω，p For incident light (i.e., light emitted from the light source), E 2ω，p To detect the second harmonic distortion signal generated after excitation light shines on the wafer, x, y, and z are the coordinate axes. This represents the azimuth angle of the light source, where is related to the azimuth angle. Adjacent arrows indicate the direction of rotation. Figure 1As shown, during testing, the polarization and incidence of the incident light can be fixed, and then the wafer can be rotated around the z-axis to change the angle between the wafer's (100) crystal orientation and the incident plane, thereby measuring the magnitude of the second harmonic signal at different azimuth angles. This figure is only to illustrate the relationship between the incident angle and the rotation direction of the light source in order to explain the operating principle of the technical solution of this invention. In actual applications, the direction of the light source illuminating the lattice is not limited to the example shown in the figure.

[0096] Of course, the second harmonic detection signal obtained from the relevant detection can also be acquired by other methods and stored in the system for use during detection and analysis.

[0097] Based on a preset fitting algorithm, multiple second harmonic detection signals in the measured second harmonic detection signal set are fitted to obtain lattice characteristic detection curve data.

[0098] The state of the wafer at the pre-selected measurement point is determined based on the obtained lattice characteristic detection curve data.

[0099] Because this scheme can analyze the wafer state at pre-selected measurement points based on lattice characteristic detection curve data fitted from the second harmonic detection signal, and because the second harmonic signal has a fast acquisition speed and low requirements for detection conditions, and because the value of the second harmonic can very sensitively reflect differences in lattice structure, the method of this embodiment can quickly and effectively determine the wafer state at pre-selected measurement points by using lattice characteristic detection curve data fitted from the second harmonic signal. It should be noted that determining the wafer state at the pre-selected measurement points mentioned here means judging the wafer's state characteristics based on the difference between the lattice characteristic detection curve data and the reference curve (e.g., when its matching degree with a certain reference curve is high, it can be determined that the lattice characteristics or other states of the relevant wafer are close to the target state; when its matching degree with a certain reference curve is low, it can be confirmed that the relevant measurement point is inconsistent with the expected state, thus prompting the operator). It does not mean that the type, degree, or other specific characteristics of defects can be directly qualitatively and quantitatively analyzed solely based on the lattice characteristic detection curve data.

[0100] The fitting algorithm can be designed by the user according to the detection target they want to analyze.

[0101] This wafer inspection method based on second harmonics can more quickly and effectively reflect the difference between the pre-selected test point and the target state, effectively improving the inspection and production efficiency of wafers.

[0102] In this embodiment, when the lattice characteristic detection curve data is obtained by fitting P-polarized light from multiple second harmonic detection signals in the measured second harmonic detection signal set, the preset fitting algorithm includes the following formula 1:

[0103]

[0104] in, This represents the value of the second harmonic signal corresponding to P-polarized light in the lattice property detection curve data. The azimuth angle of the light source when it illuminates the preselected test point is the value of the second harmonic signal corresponding to the P-polarized light, n is a preset constant, A and B are coefficients used to reflect the state of the wafer at the preselected test point, and the lattice characteristic detection curve data obtained based on the above formula 1 constitutes the first test target characteristic curve.

[0105] The specific value of n is related to the anisotropy coefficient of the crystal. When implementing this method, the specific value of n is preset in the system by the operator based on the actual orientation of the crystal plane of the sample to be tested.

[0106] This embodiment mainly focuses on testing and theoretical analysis when the surface of the sample to be tested is a (001) crystal plane (or mainly on the surface of the pre-selected test point being a (001) plane in a cubic lattice), in which case the value of n is 4. Since the specific value of n is related to the anisotropy coefficient of the crystal, those skilled in the art can extend the above Equation 1 to other samples to be tested, or other lattice planes of the sample to be tested, and select the specific value of n according to the anisotropy coefficient of the corresponding sample surface.

[0107] The following is a further explanation of crystal planes. A crystal plane is a plane in a crystal composed of lattice points of atoms, ions, or molecules. The orientation of a crystal plane is not expressed in angles but in crystal plane indices, with the general formulas (hkl) or {hkt}. The former represents a set of parallel crystal planes; the latter represents all crystal planes with identical atomic or molecular arrangements. In the same crystal, crystal planes with different crystal plane indices {hkl} have different atomic distributions and densities.

[0108] Taking a sample made of silicon as an example, the crystal structure of single-crystal silicon is the same as that of diamond, which is a typical face-centered cubic unit cell structure. Its smallest unit is a regular tetrahedron composed of five atoms. Each vertex atom of the regular tetrahedron is shared by the four adjacent tetrahedrons, thus forming a unit cell composed of many structural units. Due to the microscopic anisotropy of crystals, the distribution of atoms on different crystal faces in silicon crystals is not the same. Among them, the atomic density is the highest on the (111) face, followed by the (110) face, and the lowest on the (100) face. Schematic diagrams of the relevant faces can be found in [reference needed]. Figure 2 As shown, face (001) is located on the top surface of the cube (as indicated by the arrow), and faces (100) and (010) are located on the sides of the cube. It should be noted that... Figure 2 This is for illustrative purposes only and is not intended to represent the actual shape and size of the crystals on the surface.

[0109] The specific composition and material of the sample under test, as well as the specific method for determining the lattice planes of the surface at the pre-selected test points, are not the focus of this invention. Therefore, this application does not provide a specific description of these details. The test data in the various embodiments mentioned herein are illustrative examples based on the case where n is 4. The specific value of n and the basis for that value will not be elaborated upon further.

[0110] In specific implementation, when the lattice characteristic detection curve data is obtained based on Equation 1, the step of determining the state of the wafer at the pre-selected measurement point based on the obtained lattice characteristic detection curve data includes the following steps:

[0111] Obtain the value of variable A in the first test target feature curve obtained based on Equation 1;

[0112] Based on the value of variable A, determine the state of the wafer at the pre-selected measurement point, including: the interface roughness state at the pre-selected measurement point;

[0113] The step of determining the wafer state at the pre-selected measurement point based on the value of variable A includes the following steps: the interface roughness state at the pre-selected measurement point.

[0114] Determine the threshold range into which the value of variable A falls;

[0115] The interface roughness state at the pre-selected measurement point is determined based on the threshold range into which the value of variable A falls.

[0116] During testing, multiple threshold intervals can be set. The interface roughness state at the pre-selected test point is determined by judging which threshold interval the value of variable A falls into. For example, the applicant may find through actual testing that the roughness of the obtained wafers varies significantly when different manufacturing processes are used to manufacture the material. Correspondingly, the detected values ​​of variable A will also vary considerably. Therefore, during testing, the manufacturing process used for the sample can be inferred from the interval in which the value of variable A falls. Furthermore, whether the roughness of the sample meets the expected requirements can be determined based on whether the value of variable A falls into the target threshold interval. Thus, the coefficient A in Equation 1 can characterize the interface roughness of the sample at that test point, thereby reflecting characteristics such as the type of sample and / or its manufacturing process.

[0117] Based on the detected state of the wafer at each pre-selected test point in the sample to be tested, a wafer map is generated to characterize the overall performance level of the sample to be tested.

[0118] Therefore, this operation allows for better comparison and analysis of test data from different areas of the wafer, enabling testers to more intuitively understand the state of different areas of the wafer, better and more conveniently understand the overall state of the wafer, and provide a basis for subsequent process optimization design schemes.

[0119] In this embodiment, the target object to be detected, as reflected by Equation 1 and the correlation coefficient in Equation 1, was obtained by the applicant after analyzing and studying a large amount of test data. The applicant also conducted extensive experiments to test and verify the scheme to ensure the feasibility of the relevant method.

[0120] Specifically, different types of wafers, or even the same type of wafer processed using different manufacturing processes, will exhibit variations in interface quality and characteristics. For example, thin films made of the same material can be formed using various processes, and due to differences in formation principles and rates, this will result in variations in interface roughness. Similarly, thin films made of different materials will have different formation principles and rates, thus leading to variations in interface roughness.

[0121] The roughness here is not the roughness introduced by simple manufacturing processes as understood in traditional manufacturing; it is on the order of angstroms, making it generally difficult to distinguish. Typically, to distinguish the roughness of an interface, current technologies use methods such as AFM (Atomic Force Microscopy). However, AFM is slow and has high requirements, sometimes failing to meet the needs of online inspection. Furthermore, the difference in interface roughness is a crucial indicator in wafer manufacturing, and it can change with each manufacturing step. Using AFM would require continuously removing wafers from the production line for inspection, resulting in extremely low efficiency and failing to meet the need for timely and effective determination of the interface roughness state of the wafer under test.

[0122] In this invention, the wafer is inspected using a second harmonic detection method, which offers high detection efficiency. Furthermore, existing wafer production lines already incorporate second harmonic detection equipment to meet the electrical characteristics required for inspection, effectively satisfying the need for online inspection. As described above, in practice, after completing RA second harmonic detection or RA-scan second harmonic detection, the coefficient A (i.e., the value of variable A) of the fitted characteristic curve can be used to characterize the sample interface roughness, thereby distinguishing different samples under test.

[0123] According to publicly available information in the prior art, at the microscopic level, atoms (or ions) are arranged and packed in a certain way inside a crystal. The packing density of atoms varies in different directions, which manifests as anisotropy in many properties at the macroscopic level. The applicant of this invention utilizes this characteristic to analyze the acquired second harmonic detection signal, thereby analyzing the roughness of the interface under test, and ultimately using second harmonic analysis to determine the interface roughness state at a pre-selected measurement point. Specifically, research has found that variable A in Equation 1 is a coefficient that reflects the contribution of the electric dipole at the pre-selected measurement point. It is sensitive to interface roughness and can therefore be used as a detection criterion for analyzing interface roughness.

[0124] Figures 3a to 3d Four diagrams are shown, each representing the roughness test results of different wafers using variable A in Equation 1. The dots in each diagram represent test points on the wafer. The horizontal and vertical axes in each diagram represent dimensions, in millimeters.

[0125] like Figures 3a to 3d As shown in the diagram, the roughness test results of the wafer generated by using the detection results obtained from variable A in Equation 1 can illustrate the roughness detection status at different measurement points on different wafers. Figures 3a to 3d It belongs to a type of wafer pattern. Specifically, Figures 3a to 3d In a test example, after detecting 13 preset measurement points on four wafers according to the method in this embodiment, the values ​​of coefficient A in the relevant RA-scan characteristic curves are obtained, and wafer images are generated. Each image can be used to characterize the roughness level of the corresponding wafer surface. It should be noted that in the actual detection process, the color scales of the wafer images should be marked with the specific values ​​of coefficient A corresponding to the colors in the wafer images for reference. However, to avoid the specific values ​​detected affecting the understanding of the scheme by those skilled in the art, the specific values ​​on the color scales in the current image have been removed. Nevertheless, the differences between the detection results can still be intuitively seen through the color differences between the wafer images.

[0126] according to Figure 3a , Figure 3b , Figure 3c and Figure 3d The differences between the four wafers show that there are significant differences in the test data. Specifically, the roughness levels of wafers 1 and 2 are similar, but they are significantly different from the roughness levels of wafers 3 and 4. This is called inter-wafer difference. The main reason for these differences is that the four wafers were manufactured using different processes, such as chemical mechanical polishing, chemical mechanical grinding, and wet etching. Therefore, the surface roughness of the wafers is different, and the manufacturing process of the wafer can be determined by the roughness during testing.

[0127] Furthermore, according to Figure 3a , Figure 3b , Figure 3c and Figure 3d It can be observed that the surface roughness distribution of the four wafers under test is relatively uniform. For some manufacturing processes, the wafer image of the wafer under test can intuitively reflect the differences in the roughness distribution at different locations on the surface of the wafer under test. This is called intra-wafer variation and has certain reference value.

[0128] Based on the above analysis, through Figure 3a , Figure 3b , Figure 3c and Figure 3d This can be effectively verified: Variable A in Equation 1 can effectively reflect the surface roughness of the wafer. It should be noted that... Figure 3a , Figure 3b , Figure 3c and Figure 3d The test examples shown are only for the convenience of those skilled in the art to understand and observe. In the actual research and development process, the applicant conducted more tests to verify the relevant conclusions, which will not be listed here.

[0129] The wafer inspection method based on second harmonics in this embodiment can quickly and effectively distinguish the wafer roughness at pre-selected test points, thereby determining the differences between manufacturing processes and effectively meeting inspection requirements. Furthermore, the entire testing process is non-contact, so it will not damage the wafer. The overall solution is highly adaptable and easy to implement.

[0130] Example 2:

[0131] This embodiment provides a wafer inspection method based on second harmonics, including:

[0132] The measured second harmonic detection signal set at the pre-selected measurement point in the sample to be tested is obtained. The measured second harmonic detection signal set includes multiple second harmonic detection signals generated by the pre-selected measurement point after being irradiated by light sources from different azimuth angles and excited. The specific acquisition method of the relevant second harmonic detection signals is the same as that in Example 1, so it will not be described again in this example.

[0133] Based on a preset fitting algorithm, multiple second harmonic detection signals in the measured second harmonic detection signal set are fitted to obtain lattice characteristic detection curve data.

[0134] The state of the wafer at the pre-selected measurement point is determined based on the obtained lattice characteristic detection curve data.

[0135] In this embodiment, when the lattice characteristic detection curve data is obtained by fitting P-polarized light from multiple second harmonic detection signals in the measured second harmonic detection signal set, the preset fitting algorithm includes the following formula 1:

[0136]

[0137] in, This represents the value of the second harmonic signal corresponding to P-polarized light in the lattice property detection curve data. The azimuth angle of the light source when it illuminates the preselected test point is the value of the second harmonic signal corresponding to the P-polarized light, n is a preset constant, A and B are parameters used to reflect the state of the wafer at the preselected test point, and the lattice characteristic detection curve data obtained based on the above formula 1 constitutes the first test target characteristic curve.

[0138] In practice, this embodiment can also allow the operator to preset the value of n in the system according to the detection needs. For example, when detecting silicon material, n = 4 when the surface at the pre-selected test point is the (001) plane in a cubic lattice.

[0139] In specific implementation, when the lattice characteristic detection curve data is obtained based on Equation 1, the step of determining the state of the wafer at the pre-selected measurement point based on the obtained lattice characteristic detection curve data includes the following steps:

[0140] Obtain the value of variable B in the first test target feature curve obtained based on Equation 1;

[0141] Based on the value of variable B, the differences between the production processes corresponding to the test samples are determined.

[0142] This operational procedure allows users to better select the appropriate manufacturing process. For example, during wafer development, different manufacturing processes may be tried to produce the wafer (such as adjusting the doping concentration of different components, changing the production method, etc.). Different manufacturing processes may lead to differences in the lattice characteristics of the wafer, which will greatly affect the detected second harmonic detection signal, and thus cause the variable B in Equation 1, which is fitted based on the second harmonic detection signal, to change.

[0143] According to experimental confirmation, the value of variable B is related to the lattice constant of the target being measured, and the lattice constant is related to the differences in the manufacturing process of the sample being measured. Based on these related characteristics, users can characterize the corresponding equivalent lattice constant by obtaining the value of variable B, thereby determining whether there are differences between the selected wafer manufacturing processes. The differences between the manufacturing processes mentioned here can include the differences between the processes selected during manufacturing, as well as the differences in the level of different samples or different measurement points when the same manufacturing process is used.

[0144] Specifically, applications that use the value of variable B to reflect the differences between the production processes corresponding to the samples being tested can include the following examples:

[0145] For example, users can determine the production process used to manufacture the test point based on the threshold range in which the value of variable B falls; or

[0146] If a user determines that the wafer manufactured using a certain production process meets the requirements, then when the detected value of variable B does not match the expected value, it indicates that the current production process has changed. In other words, this detection method plays a "monitoring" role. It should be noted that this embodiment mainly serves to indicate whether there has been a change in the production process, so that operators can quickly trace back the relevant operational steps that brought about the change. However, it is not intended to accurately detect the specific selected operating process or the influencing factors in the related process through the value of variable B.

[0147] In practice, wafers processed using different manufacturing processes can be acquired (the wafers mentioned in this article can refer to completed wafers or components obtained during a specific processing step in wafer manufacturing). The values ​​of B corresponding to these wafer samples are then measured to determine the values ​​of variable B for different manufacturing processes. Furthermore, based on the known performance of the wafers, it can be determined within what threshold range the value of variable B corresponds to the equivalent lattice constant and whether the wafers processed using the relevant manufacturing processes meet user requirements. These operations primarily serve to anchor the correspondence between the value of variable B and the relevant wafer manufacturing processes. Specific wafer performance testing can be performed using other existing testing methods.

[0148] In implementation, when the lattice characteristic detection curve data is obtained based on Equation 1, the step of determining the state of the wafer at the pre-selected measurement point based on the obtained lattice characteristic detection curve data may further include the following steps:

[0149] Obtain the value of variable B in the first test target feature curve obtained based on Equation 1;

[0150] Based on the value of variable B, determine the state of the wafer at the pre-selected measurement point, including: the state of the lattice features at the pre-selected measurement point;

[0151] The step of determining the state of the wafer at the pre-selected measurement point based on the value of variable B includes the following steps: the state of the lattice features at the pre-selected measurement point.

[0152] Determine the threshold range into which the value of variable B falls;

[0153] Based on the threshold range into which the value of variable B falls, the state of the lattice features at the pre-selected measurement point is determined.

[0154] Based on the detected state of the wafer at each pre-selected test point in the sample to be tested, a wafer map is generated to characterize the overall performance level of the sample to be tested.

[0155] Specifically, during testing, the threshold range into which the value of variable B falls can be used to determine whether the wafer meets production requirements.

[0156] In practical applications, the element ratios during wafer production affect the state of the lattice, specifically manifested as a change in the lattice constant d (which can also be considered as the equivalent lattice constant d'). This embodiment can reflect the equivalent lattice constant d' through the value of variable B. Therefore, in actual testing, the analysis of the value of variable B can be combined to determine whether the wafer is produced according to the predetermined doping ratio, indirectly reflecting the relative level of the proportion of element X (i.e., a certain element that makes up the wafer being tested).

[0157] The relevant detection can be obtained by analyzing the detection curve data based on lattice characteristics, thus possessing the characteristic of high detection efficiency.

[0158] The principles of this embodiment will be further analyzed below to verify the feasibility of the solution:

[0159] According to existing theoretical research, some characteristics of the lattice can be characterized by the lattice constant d, and according to existing literature, the second-order polarizability X 2 It is related to the lattice constant d, while the second harmonic signal intensity I(2ω) varies with the azimuth angle. The relationship between the variation and the second-order polarizability X 2 Related. Therefore, the intensity of the second harmonic signal I(2ω) can be correlated with the azimuth angle. The curve representing the change in the second-order polarizability X (called the characteristic curve, hereinafter the same) is used to characterize the second-order polarizability X. 2This allows for an indirect comparison of the lattice constant d. For ease of expression, the indirect comparison of the lattice constant d can be considered as obtaining a corresponding equivalent lattice constant d' based on the second harmonic detection results. The equivalent lattice constant d' is used to represent the overall influence of all lattices within the resolution range of the second harmonic detection (the lattice constant of each individual lattice is not necessarily d', but the overall performance is equivalent to the performance when the lattice constants of all lattices are equal to d'). Therefore, it can reflect the overall lattice quality level at that point to a certain extent.

[0160] Based on the above principle, the applicant attempted to use the lattice characteristic detection curve data obtained by fitting the second harmonic detection signal to reflect the transformation of the equivalent lattice constant, and then infer whether there are differences in the process.

[0161] Experiments and other methods have verified that the value of variable B is proportional to the second-order polarizability χ of the wafer. (2)Q That is, the second-order polarizability χ of the wafer can be obtained based on the value of variable B. (2)Q Reference values.

[0162] Specifically, when the composition and proportions within a wafer lattice change, its lattice constant d transforms. Meanwhile, the second-order polarizability χ... (2)Q (i.e., χ in the following formula) (2) The relationship between ) and the lattice constant d is as follows:

[0163]

[0164] Where e is the elementary charge, ∈0 is the vacuum permittivity, m is the electron mass, and ω0 is the single resonant frequency.

[0165] Based on the above equation, it can be seen that when the composition and proportions in the wafer lattice change, the lattice constant d changes accordingly, causing the second-order polarizability χ of the wafer to change. (2)Q Things have changed.

[0166] Based on relevant characteristics, the applicant sought a method to rapidly and effectively detect the lattice features of a target object using a second harmonic detection signal. The applicant determined that the value of variable B in Equation 1 effectively reflects the equivalent lattice constant, and therefore the value of variable B can be used to reflect the lattice features at a pre-selected measurement point. The relationship between the value of variable B and the lattice constant d can be expressed by Equation 5:

[0167] B∝1 / d 4 Formula 5;

[0168] That is, when the composition and proportions in the wafer lattice change, the lattice constant d changes accordingly, causing a change in the second-order polarizability of the wafer, and ultimately changing the value of variable B obtained by RA-SHG fitting. The logical relationship can be found in [reference needed]. Figure 4aAs shown, this allows for effective monitoring of the composition within the wafer lattice based on the value of variable B. Particularly for wafers composed of only two elements, the ratio can even be determined based on the value of variable B; that is, the value of variable B can be used to determine whether the element doping ratio during wafer manufacturing meets the requirements.

[0169] Due to differences in the selection of different constituent elements and their proportions, the value of variable B may still be the same. Therefore, sometimes it is not possible to determine whether a wafer meets the requirements solely based on the value of variable B; sometimes, a comprehensive judgment is made in conjunction with the goodness-of-fit. The value of variable B is used to characterize the parameters of the crystal lattice itself, namely the lattice constant or equivalent lattice constant, thereby assisting testers in calculating some key process parameters under preset conditions.

[0170] This embodiment allows for the analysis of the lattice characteristics of the sample under test, enabling timely determination of whether the relevant production process meets expectations, thus satisfying the need for rapid detection.

[0171] Example 3:

[0172] This embodiment provides a wafer inspection method based on second harmonics, including:

[0173] The measured second harmonic detection signal set at the pre-selected measurement point in the sample to be tested is obtained. The measured second harmonic detection signal set includes multiple second harmonic detection signals generated by the pre-selected measurement point after being irradiated by light sources from different azimuth angles and excited. The specific acquisition method of the relevant second harmonic detection signals is the same as that in Example 1, so it will not be described again in this example.

[0174] Based on a preset fitting algorithm, multiple second harmonic detection signals in the measured second harmonic detection signal set are fitted to obtain lattice characteristic detection curve data.

[0175] The state of the wafer at the pre-selected measurement point is determined based on the obtained lattice characteristic detection curve data.

[0176] Wherein, when the lattice characteristic detection curve data is obtained by fitting P-polarized light from multiple second harmonic detection signals in the measured second harmonic detection signal set, the preset fitting algorithm includes the following:

[0177] Formula 1:

[0178]

[0179] in, This represents the value of the second harmonic signal corresponding to P-polarized light in the lattice property detection curve data. The azimuth angle of the light source when it illuminates the preselected test point is the value of the second harmonic signal corresponding to the P-polarized light, n is a preset constant, A and B are coefficients used to reflect the state of the wafer at the preselected test point, and the first test target feature curve is formed by the lattice characteristic detection curve data obtained based on the above formula 1.

[0180] Based on the goodness of fit between the first test target characteristic curve and the preset first reference lattice characteristic detection curve data, determine whether the state of the wafer at the pre-selected test point includes: whether the lattice distortion and / or stress influence at the pre-selected test point is within an acceptable range.

[0181] The first reference lattice characteristic detection curve data is: curve data obtained by fitting the P-polarized light from multiple reference second harmonic detection signals in the reference second harmonic detection signal set into Equation 1 above.

[0182] If the goodness of fit is poor, anomalies can be quickly identified at the corresponding measurement points.

[0183] In practice, the goodness of fit R at the pre-selected measurement points in the sample to be tested can be obtained using the following formula 3. 2 Value:

[0184]

[0185] Among them, Y actual Y is the measured value of the second harmonic detection signal corresponding to the first preset azimuth angle in the measured second harmonic detection signal set. predict Y is the fitted value of the second harmonic signal corresponding to the first preset azimuth angle in the lattice characteristic detection curve data. mean It is the average value of several measured values ​​of the second harmonic detection signals in the measured second harmonic detection signal set;

[0186] According to the goodness of fit R 2 The value determines whether the state of the wafer at the preselected measurement point includes: whether the lattice distortion and / or stress effects at the preselected measurement point are within acceptable limits.

[0187] In other embodiments, the goodness-of-fit R can also be obtained in other ways. 2 However, this is not limited to the method provided in this example. The goodness of fit R... 2 ≤1. R 2 The closer a value is to 1, the better the lattice quality (symmetry); conversely, the smaller the value is, the worse the lattice quality (symmetry) is considered to be.

[0188] The following is combined Figure 5 , Figure 6a , Figure 6b and Figure 6c Further analysis is needed. Figure 5 This is a schematic diagram of the measurement point distribution on the wafer under test, showing the distribution of measurement points on the wafer in one embodiment. Figure 6a , Figure 6b and Figure 6c This is a schematic diagram of the three test results generated by combining Equation 2, which respectively show... Figure 5 The test results corresponding to measuring points A1, B2, and C3 are shown. Figure 5 The outer circle represents the outer contour of the wafer, and the 13 "×" marks represent the locations of 13 measurement points. Figure 6a , Figure 6b and Figure 6c They are respectively with Figure 5 The diagram shows three schematic images of second harmonic detection signals corresponding to measurement points A1, B2, and C3. In each diagram, the blue dots (i.e., test data) represent the second harmonic detection signals of the pre-selected measurement points obtained from actual detection, while the red lines (i.e., fitted data) represent the characteristic curves fitted based on the blue dots. The horizontal axis represents the azimuth angle in degrees, and the vertical axis represents the value of the second harmonic signal. During analysis, the goodness-of-fit R-value corresponding to each fitted characteristic curve can be evaluated. 2 And perform comparative analysis on variable B.

[0189] for Figure 5 The goodness-of-fit data for the three measurement points shown are provided by the applicant as follows: Figure 5 The goodness of fit R of the characteristic curve at the midpoint A1 2 The goodness-of-fit R-value of the characteristic curve at measurement point B2 is 0.99. 2 The goodness-of-fit R-value for the characteristic curve at measurement point C3 is 0.98. 2 The value is 0.93. Generally speaking, for a goodness-of-fit R-value... 2 Measurement points with a value greater than 0.95 are considered to have good lattice quality (specific evaluation criteria can be set according to user requirements). The goodness-of-fit R obtained using Equation 3 in this embodiment can be reflected in the relevant experimental data. 2 It can effectively reflect the lattice quality.

[0190] In some specific embodiments, the goodness-of-fit R can also be utilized. 2 When analyzing the test results in conjunction with the value of variable B, it is important to note that the value of variable B is mainly used to reflect the state of the lattice characteristics at the measurement point. Therefore, the analysis should focus on its proximity to the target range, rather than using the magnitude of the value of B as the basis for judgment.

[0191] To facilitate understanding, the following analysis will be conducted using a specific numerical example:

[0192] Suppose we are detecting the center points of samples 1, 2, 3, and 4 in a batch. Based on experience, the goodness of fit R... 2 The acceptable range is greater than or equal to 0.8, and the reference range for coefficient B (i.e., the value of variable B) is 30-80. The results obtained from the test are as follows:

[0193] Sample 1: Goodness of fit R 2 =0.95, coefficient B = 60;

[0194] Sample 2: Goodness of fit R 2 =0.9, coefficient B=30;

[0195] Sample 3: Goodness of fit R 2 =0.7, coefficient B = 60;

[0196] Sample 4: Goodness of fit R 2 =0.6, coefficient B = 20;

[0197] Analysis shows that the goodness of fit of samples 1 and 2 is within the acceptable range, so it can be judged that the lattice defect level of samples 1 and 2 is low and within the acceptable range. However, the goodness of fit of samples 3 and 4 does not fall into the acceptable range, so it can be judged that the lattice defect level of samples 3 and 4 is high and not within the acceptable range, and the process needs to be improved.

[0198] The coefficients corresponding to the lattice properties of samples 1 and 3 are within the normal range; the coefficients corresponding to the lattice properties of sample 4 are abnormal and need to be adjusted; the coefficients corresponding to the lattice properties of sample 2 are at the critical value and need further monitoring.

[0199] Therefore, based on the analysis of both the lattice defect level and lattice properties, although the conclusion on the surface is that the coefficients of sample 3 are normal, it is unknown whether the value of variable B can still maintain its current level after the actual process is improved to reduce the defect level. Therefore, among the four samples, only sample 1 meets the test standard and is considered qualified.

[0200] This can be understood as the goodness of fit R. 2 The fact that the value of variable B is within an acceptable range is a prerequisite for its reliability. If the goodness of fit R0 is within this range... 2 If the requirements are not met, even if the value of variable B falls within the target range, the wafer may still have abnormal issues.

[0201] Among them, the goodness of fit R 2 The order in which the values ​​of variable B are obtained does not affect the detection results. Therefore, this application does not limit the order of detecting the state of lattice features and the influence of lattice distortion and / or stress at pre-selected measurement points. That is, this embodiment utilizes the goodness-of-fit R... 2It is used to characterize the defect level and can reflect the quality of lattice symmetry, while the coefficient B is used to characterize the lattice parameters themselves, namely the lattice constant or equivalent lattice constant, so as to calculate some key process parameters under preset conditions.

[0202] It should be noted that the above example is only for illustration of the goodness-of-fit R. 2 An example of applying the value of variable B in conjunction with the analysis. In practical applications, depending on the detection requirements, it may not necessarily be necessary to combine R with the value of variable B. 2 Analyzing the value of A or B can also determine whether the lattice distortion and / or stress influence at the pre-selected measurement point is within an acceptable range. Alternatively, when calculating the values ​​of A or B alone to meet the detection requirements, it is not necessarily necessary to consider the goodness-of-fit R. 2 Perform the analysis.

[0203] Using this embodiment, based on the second harmonic detection signal, more efficient and faster detection can be achieved, and the level of lattice defects and other conditions can be detected as soon as possible.

[0204] Based on the detected state of the wafer at each pre-selected test point in the sample to be tested, a wafer map is generated to characterize the overall performance level of the sample to be tested.

[0205] Example 4:

[0206] This embodiment provides a wafer inspection method based on second harmonics. Its basic principle is similar to that of the method in Embodiment 2. It can also be used to analyze the state of lattice features at pre-selected measurement points. The main difference is that the implementation of the technical solution in this embodiment is mainly based on the S-polarized light in the second harmonic detection signal.

[0207] Specifically, the wafer inspection method of this embodiment includes:

[0208] The measured second harmonic detection signal set at a pre-selected measurement point in the sample to be tested is obtained. The measured second harmonic detection signal set includes multiple second harmonic detection signals generated by the pre-selected measurement point after being irradiated by light sources from different azimuth angles and excited. In specific implementation, the measured second harmonic detection signal set at the pre-selected measurement point can be obtained through the operations mentioned in Examples 1 and 2 above. The corresponding signal acquisition method will not be described in detail in this example.

[0209] Based on a preset fitting algorithm, multiple second harmonic detection signals in the measured second harmonic detection signal set are fitted to obtain lattice characteristic detection curve data.

[0210] When the lattice characteristic detection curve data is obtained by fitting S-polarized light from multiple second harmonic detection signals in the measured second harmonic detection signal set, the preset fitting algorithm includes the following formula 2:

[0211]

[0212] in, This represents the value of the second harmonic signal corresponding to S-polarized light in the lattice property detection curve data. The azimuth angle of the light source when it illuminates the pre-selected test point, corresponding to the value of the second harmonic signal corresponding to the S-polarized light, is given by n, which is a preset constant. C is a coefficient used to reflect the state of the wafer at the pre-selected test point, and D is the DC offset. The second test target feature curve is constructed from the lattice characteristic detection curve data obtained based on the above formula 2. Wherein, the DC offset D is a constant, and the specific value of the DC offset D is a variable generated by fitting the detection data. Generally speaking, the value of the DC offset D is greater than or equal to 0. Under the ideal model, the DC offset D is equal to 0.

[0213] In practice, this embodiment can also allow the operator to preset the value of n in the system according to the detection needs. For example, when detecting silicon material, n = 4 when the surface at the pre-selected test point is the (001) plane in a cubic lattice.

[0214] Based on the acquired lattice characteristic detection curve data, the state of the wafer at the pre-selected measurement point is determined. When the lattice characteristic detection curve data is obtained based on Equation 2, determining the state of the wafer at the pre-selected measurement point based on the acquired lattice characteristic detection curve data includes the following steps:

[0215] Obtain the value of variable C in the second test target feature curve obtained based on Equation 2;

[0216] Based on the value of variable C, the differences between the production processes corresponding to the test samples are determined.

[0217] This operational procedure, similar to Example 2, allows users to better select a suitable manufacturing process. For instance, during wafer development, different manufacturing processes may be attempted (e.g., adjusting doping concentrations of different components, changing production methods, etc.). Different manufacturing processes can lead to significant differences in the lattice characteristics of the produced wafers, and these lattice differences will greatly affect the detected second harmonic detection signal, thus causing changes in variable C in Equation 2 derived from the second harmonic detection signal. Based on these characteristics, users can characterize the corresponding equivalent lattice constant through the obtained value of variable C, thereby determining whether there are differences between the selected wafer manufacturing processes. These differences can include variations in the processes used during manufacturing, as well as variations in the level of the same manufacturing process at different samples or measurement points.

[0218] Specifically, applications that use the value of variable C to reflect the differences between the production processes corresponding to the samples under test can include the following examples:

[0219] For example, users can determine the production process used to manufacture the point under test based on the threshold range in which the value of variable C falls; or

[0220] If a user determines that the wafer produced using a certain manufacturing process meets the requirements, then when the detected value of variable C does not match the expected value, it indicates that the current manufacturing process has changed. In other words, this detection method plays a "monitoring" role. It should be noted that this embodiment mainly serves to indicate whether there has been a change in the manufacturing process, so that operators can quickly trace back the relevant operational steps that brought about the change. However, it is not intended to accurately detect the specific operating process selected or the influencing factors in the related process through the value of variable C.

[0221] In practice, wafers processed using different manufacturing processes can be acquired (the wafers mentioned in this article can refer to completed wafers or components obtained during a specific processing step in wafer manufacturing). The C values ​​corresponding to these wafer samples are then measured to determine the values ​​of variable C for different manufacturing processes. Furthermore, based on the known performance of the wafers, it can be determined within what threshold range the equivalent lattice constant and related manufacturing processes meet user requirements. These operations primarily anchor the correspondence between the value of variable C and the relevant wafer manufacturing processes. Specific wafer performance testing can be performed using other existing testing methods.

[0222] In implementation, when the lattice characteristic detection curve data is obtained based on Equation 2, the step of determining the state of the wafer at the pre-selected measurement point based on the obtained lattice characteristic detection curve data may further include the following steps:

[0223] Obtain the value of variable C in the second test target feature curve obtained based on Equation 2;

[0224] Based on the value of variable C, determine the state of the wafer at the pre-selected measurement point, including: the state of the lattice features at the pre-selected measurement point;

[0225] The determination of the wafer state at the pre-selected measurement point based on the value of variable C includes the state of the lattice features at the pre-selected measurement point, comprising the following steps:

[0226] Determine the threshold range into which the value of variable C falls;

[0227] Based on the threshold range into which the value of variable C falls, the state of the lattice features at the pre-selected measurement point is determined.

[0228] Based on the detected state of the wafer at each pre-selected test point in the sample to be tested, a wafer map is generated to characterize the overall performance level of the sample to be tested.

[0229] Specifically, during testing, the threshold range into which the value of variable C falls can be used to determine whether the wafer meets production requirements.

[0230] Similarly, in practical applications, the element ratio during wafer production will affect the state of the lattice, which will manifest as a change in the lattice constant d (which can also be regarded as the equivalent lattice constant d'). In this embodiment, the equivalent lattice constant d' can be reflected by the value of variable C. Therefore, in the actual testing process, the analysis of the value of variable C can be combined to determine whether the wafer is produced according to the predetermined doping ratio, which indirectly reflects the relative level of the proportion of element X (i.e., a certain element that makes up the wafer being tested).

[0231] The relevant detection can be obtained by analyzing the detection curve data based on lattice characteristics, thus possessing the characteristic of high detection efficiency.

[0232] The principles of this embodiment will be further analyzed below to verify the feasibility of the solution:

[0233] As described in Example 2 above, according to the prior art, the characteristics of a crystal lattice can be characterized by the lattice constant d, and according to existing literature, the second-order polarizability X 2 It is related to the lattice constant d, while the second harmonic signal intensity I(2ω) varies with the azimuth angle. The relationship between the variation and the second-order polarizability X 2 Related. Therefore, the intensity of the second harmonic signal I(2ω) can be correlated with the azimuth angle. The curve representing the change in the second-order polarizability X (called the characteristic curve, hereinafter the same) is used to characterize the second-order polarizability X. 2 This allows for an indirect comparison of the lattice constant d. For ease of recording and expression, the indirect comparison of the lattice constant d can also be considered as measuring the equivalent lattice constant d'. The equivalent lattice constant d' is used to represent the overall influence of all lattices within the resolution range of second harmonic detection (the lattice constant of each individual lattice is not necessarily d', but the overall performance is equivalent to the performance when the lattice constants of all lattices are equal to d'). Therefore, it can reflect the overall lattice quality level at that point to a certain extent.

[0234] Based on the above principle, the applicant attempted to use the lattice characteristic detection curve data obtained by fitting the second harmonic detection signal to reflect the transformation of the equivalent lattice constant, and then infer whether there are differences in the process.

[0235] Experiments and other methods have verified that the value of variable C is proportional to the effective bulk second-order polarizability. Right now And B = f c C, where f c The effective Fresnel coefficient of the sample under test is given. The value of variable B reflects the characteristics of the lattice at the pre-selected measurement point. The relationship between the values ​​of variable B and variable C indicates that the composition of the wafer lattice can be monitored based on the value of variable C. Especially for wafers composed of only two elements, the ratio can even be determined based on the value of variable C. That is, the value of variable C can be used to determine whether the elemental doping ratio during wafer manufacturing meets the requirements, effectively monitoring the composition and its ratio changes in the wafer lattice. The corresponding logical relationship can be found in [reference needed]. Figure 4b As shown.

[0236] Similar to variable B, sometimes the value of variable C alone is insufficient to directly determine whether a wafer meets requirements; therefore, a comprehensive judgment is sometimes made by combining the goodness-of-fit value. The value of variable C characterizes the lattice parameters themselves, namely the lattice constant or equivalent lattice constant, thereby assisting testers in calculating some key process parameters under preset conditions. When necessary, to improve the reliability of test results, the values ​​of variables B and C can be combined to evaluate the level of key process parameters.

[0237] This embodiment allows for the analysis of the lattice characteristics of the sample under test, enabling timely determination of whether the relevant production process meets expectations, thus satisfying the need for rapid detection.

[0238] Meanwhile, the inventors also conducted numerous experiments to verify the relevant methods, confirming the feasibility of the scheme.

[0239] This embodiment also allows for the analysis of the lattice characteristics of the sample under test, enabling timely determination of whether the relevant production process meets expectations, thus satisfying the need for rapid detection.

[0240] Example 5:

[0241] This embodiment provides a wafer inspection method based on second harmonics, including:

[0242] The measured second harmonic detection signal set at the pre-selected measurement point in the sample to be tested is obtained. The measured second harmonic detection signal set includes: multiple second harmonic detection signals generated by the pre-selected measurement point after being irradiated by light sources from different azimuth angles and excited; each second harmonic detection signal can also be collected in the manner mentioned in Example 1 above.

[0243] Based on a preset fitting algorithm, multiple second harmonic detection signals in the measured second harmonic detection signal set are fitted to obtain lattice characteristic detection curve data.

[0244] The state of the wafer at the pre-selected measurement point is determined based on the obtained lattice characteristic detection curve data.

[0245] When the lattice characteristic detection curve data is obtained by fitting S-polarized light from multiple second harmonic detection signals in the measured second harmonic detection signal set, the preset fitting algorithm includes the following formula 2:

[0246]

[0247] in, This represents the value of the second harmonic signal corresponding to S-polarized light in the lattice property detection curve data. The azimuth angle of the light source when it illuminates the pre-selected test point is the value of the second harmonic signal corresponding to the S-polarized light, n is a preset constant, C is a coefficient used to reflect the state of the wafer at the pre-selected test point, and D is the DC offset, which is a variable. Generally, the value of the DC offset D is greater than or equal to 0. The lattice characteristic detection curve data obtained based on the above formula 2 constitutes the second test target characteristic curve.

[0248] Based on the goodness of fit between the second test target characteristic curve and the preset second reference lattice characteristic detection curve data, determine whether the state of the wafer at the pre-selected test point includes: whether the lattice distortion and / or stress influence at the pre-selected test point is within an acceptable range.

[0249] The second reference lattice characteristic detection curve data is obtained by fitting the curve data after substituting the S-polarized light from multiple reference second harmonic detection signals in the reference second harmonic detection signal set into Equation 2 above.

[0250] The method for determining whether the lattice distortion and / or stress influence at the pre-selected measurement points in this embodiment is within an acceptable range can be combined with the lattice feature verification method in Embodiment 4 to achieve a more comprehensive analysis of the wafer.

[0251] To better illustrate this, the following explanation will be based on some experiments conducted during the research and development process:

[0252] Figure 6a , Figure 6b , Figure 6c and Figure 7 These are schematic diagrams of the four test results generated by the four combined formulas. Figures 6a to 7 These examples illustrate the relationship between the S-polarized second harmonic (SHG) signal emitted under P-polarized light incident conditions and the RA-SHG azimuth angle in multiple embodiments (i.e., Figures 6a to 7 The horizontal axis represents the azimuth angle, in degrees; the vertical axis represents the value of the second harmonic signal. Figures 6a to 7The data points are the actual collected data, and the curve is the curve obtained by fitting the collected data points according to Equation 2.

[0253] The lattice quality can be reflected by the goodness of fit between the actual collected data and the fitted curve, and the value of variable C obtained after fitting is related to some performance parameters of the sample under test.

[0254] In examples with low goodness of fit, the actual collected data and the fitted curve will have a poor fit. For example, the first peak in each period may be lower than the second peak, indicating poor symmetry. This suggests that the wafer in this example has poor lattice quality. The azimuth angles corresponding to the two peaks differ by approximately 45 degrees, which is speculated to be due to some kind of defect inside the crystal. Therefore, even if the value of variable C meets expectations, it does not mean that the relevant lattice state meets the requirements; that is, the reliability of coefficient C decreases in this case.

[0255] In examples with high goodness of fit, the actual collected data and the fitted curve show a better fit. See relevant examples. Figure 7 As shown, Figure 7 The goodness of fit in the example is high, and the overall fit is relatively consistent with the theoretical curve, indicating that the lattice quality is good. In this case, the value of variable C can be used to characterize the relative level of some performance parameters of the sample under test.

[0256] It should be noted that the S-polarized second harmonic (SHG) signal is significantly weaker than the P-polarized second harmonic (SHG) signal. In some application scenarios, it is severely affected by noise interference and has a low signal-to-noise ratio. Therefore, it is more suitable for verifying other detection results.

[0257] Similarly, it should be noted that in this embodiment, the process of judging the state of lattice features by the value of variable C and the process of judging the defect situation by goodness of fit are not required to be in any particular order. In some embodiments, only one of the detection processes may be performed.

[0258] In practice, a wafer diagram can be generated based on the state of the wafer at each pre-selected test point in the sample to be tested to characterize the overall performance level of the sample to be tested.

[0259] This embodiment also allows for the analysis of the lattice characteristics of the sample under test, enabling timely determination of whether the relevant production process meets expectations, thus satisfying the need for rapid detection.

[0260] Example 6:

[0261] The measured second harmonic detection signal set at the pre-selected measurement point in the sample to be tested is obtained. The measured second harmonic detection signal set includes: multiple second harmonic detection signals generated by the pre-selected measurement point after being irradiated by light sources from different azimuth angles and excited. The second harmonic detection signals can be obtained in the manner described in Example 1, which will not be repeated here.

[0262] Based on a preset fitting algorithm, multiple second harmonic detection signals in the measured second harmonic detection signal set are fitted to obtain lattice characteristic detection curve data; in addition to the fitting method using Equation 1 or Equation 2 mentioned above, other methods can also be used to fit the second harmonic detection signals in specific implementations.

[0263] Based on the acquired lattice characteristic detection curve data, the state of the wafer at the pre-selected measurement point is determined, including:

[0264] The goodness-of-fit R at the pre-selected measurement points in the sample to be tested is obtained based on the following equation 3. 2 Value:

[0265]

[0266] Among them, Y actual Y is the measured value of the second harmonic detection signal corresponding to the first preset azimuth angle in the measured second harmonic detection signal set. predict Y is the fitted value of the second harmonic signal corresponding to the first preset azimuth angle in the lattice characteristic detection curve data. mean It is the average value of several measured values ​​of the second harmonic detection signals in the measured second harmonic detection signal set;

[0267] According to the goodness of fit R 2 The value determines whether the wafer state at the pre-selected measurement point includes: whether the lattice distortion and / or stress effects at the pre-selected measurement point are within acceptable limits. Wherein, the goodness of fit R... 2 ≤1. R 2 The closer a value is to 1, the better the lattice quality (symmetry); conversely, the smaller the value is, the worse the lattice quality (symmetry) is considered to be.

[0268] The several second harmonic detection signals in the measured second harmonic detection signal set are all the second harmonic detection signals in the measured second harmonic detection signal set.

[0269] Based on the detected state of the wafer at each pre-selected test point in the sample to be tested, a wafer map is generated to characterize the overall performance level of the sample to be tested.

[0270] In this embodiment, for the sample to be tested, the goodness of fit R of the characteristic curve is used. 2It indirectly indicates the degree of matching between the detection results and the expected target, thus reflecting the characteristics of the crystal lattice from the side and effectively achieving the purpose of detection.

[0271] The following section will further analyze the goodness-of-fit R-value of the characteristic curve in this scheme. 2 The method and principle for characterizing the lattice quality at this measurement point (i.e., the degree to which stress and defects have an overall influence):

[0272] The theoretical characteristic curve is obtained by second harmonic detection of a perfect lattice (which can constitute a reference lattice characteristic detection curve), and it is consistent with the theoretical derivation. Assuming that the measured characteristic curve of the sample under test completely coincides with the theoretical curve, the calculated goodness of fit is: R 2 =1, therefore it can be considered that the crystal structure of the test point is completely consistent with the ideal situation, which means that there are no defects or stresses affecting the test point.

[0273] Practice has shown that samples produced in real-world conditions inevitably have certain defects or stress effects. Correspondingly, the greater the influence of defects or stress, the greater the deviation between the measured characteristic curve and the theoretical curve, and the lower the goodness of fit R obtained from the test. 2 The lower the value, the further it deviates from the theoretical curve.

[0274] To facilitate understanding, the following combination Figure 8a and Figure 8b The diagram illustrates the fitting state under different conditions (the orange dots represent the actual detected measurement points, and the blue curve represents the fitting curve). Among them, Figure 8a This diagram illustrates the fitting state when the fit is good. The goodness of fit of the detection results in this state is: R 2 =1 (This diagram is for user understanding and is not a representation of actual detection results). The diagram shows a high degree of matching between the actual detection points and the fitting results in this example; while Figure 8b This diagram illustrates the fitting state when the fit is poor. The goodness of fit of the detection results in this state is: R 2 =0.83. The graph shows a low match between the actual measured points and the fitted results in this example, thus indicating... Figure 8a The corresponding wafer and Figure 8b Compared to the corresponding wafers, the lattice quality is better.

[0275] In actual data processing, the goodness of fit R 2 The changes are not entirely linear and need to be judged based on the actual situation.

[0276] For the detection of actual samples, a goodness-of-fit R can be preset. 2Reference values, for example:

[0277] When the goodness of fit R 2 A value greater than or equal to 0.9 is considered to indicate that the lattice defect or stress effect is within an acceptable range, and the test is passed, indicating that no abnormality has occurred in this process;

[0278] When the goodness of fit R 2 If the value is less than 0.9, it is considered that the lattice defect or stress influence has reached a certain level, and further determination of the specific type and cause of the defect is required;

[0279] The value of 0.9 is not fixed and can be adjusted appropriately based on factors such as process conditions and yield requirements.

[0280] In actual testing, the crystal structure or elemental ratios of different samples, especially those processed after different steps, may change (potentially introducing lattice defects, impurities, or stress distribution leading to lattice distortion), thus altering the lattice constant. Therefore, the characteristic curve may not match the theoretical formula well. Based on these characteristics, this application uses the goodness-of-fit R of the characteristic curve... 2 It indirectly indicates the degree of matching and can also reflect the characteristics of the crystal lattice.

[0281] It should be noted that this detection application cannot directly determine the true level of defects or stress, such as the specific type of defect, the magnitude of stress, or the degree of lattice distortion, but it can determine whether the defect or stress level is within an acceptable range by determining the relative level. The detection method of this embodiment can achieve the purpose of rapid detection.

[0282] Example 7:

[0283] This embodiment provides a wafer inspection method based on second harmonics, including:

[0284] The measured second harmonic detection signal set at the pre-selected measurement point in the sample to be tested is obtained. The measured second harmonic detection signal set includes multiple second harmonic detection signals generated by the pre-selected measurement point after being irradiated by light sources from different azimuth angles and excited. Specifically, the second harmonic detection signals can be obtained in the manner described in Example 1, which will not be elaborated in this example.

[0285] Based on a preset fitting algorithm, multiple second harmonic detection signals in the measured second harmonic detection signal set are fitted to obtain lattice characteristic detection curve data.

[0286] The state of the wafer at the pre-selected measurement point is determined based on the obtained lattice characteristic detection curve data.

[0287] When the lattice characteristic detection curve data is obtained by fitting P-polarized light from multiple second harmonic detection signals in the measured second harmonic detection signal set, the preset fitting algorithm includes the following formula 1:

[0288]

[0289] in, This represents the value of the second harmonic signal corresponding to P-polarized light in the lattice property detection curve data. The azimuth angle of the light source when it illuminates the preselected test point is the value of the second harmonic signal corresponding to the P-polarized light, n is a preset constant, A and B are coefficients used to reflect the state of the wafer at the preselected test point, and the lattice characteristic detection curve data obtained based on the above formula 1 constitutes the first test target characteristic curve.

[0290] When the surface at the pre-selected measurement point is the (001) plane in a cubic lattice, n = 4.

[0291] When the lattice characteristic detection curve data is obtained based on Equation 1, the step of determining the state of the wafer at the pre-selected measurement point based on the obtained lattice characteristic detection curve data includes the following steps:

[0292] Obtain the value of variable A in the first test target feature curve obtained based on Equation 1;

[0293] Based on the value of variable A, determine the state of the wafer at the pre-selected measurement point, including: the interface roughness state at the pre-selected measurement point;

[0294] The step of determining the wafer state at the pre-selected measurement point based on the value of variable A includes the following steps: the interface roughness state at the pre-selected measurement point.

[0295] Determine the threshold range into which the value of variable A falls;

[0296] The interface roughness state at the pre-selected measurement point is determined based on the threshold range into which the value of variable A falls.

[0297] When the lattice characteristic detection curve data is obtained based on Equation 1, the step of determining the state of the wafer at the pre-selected measurement point based on the obtained lattice characteristic detection curve data includes the following steps:

[0298] Obtain the value of variable B in the first test target feature curve obtained based on Equation 1;

[0299] Based on the value of variable B, the differences between the production processes corresponding to the test samples are determined;

[0300] When the lattice characteristic detection curve data is obtained based on Equation 1, the step of determining the state of the wafer at the pre-selected measurement point based on the obtained lattice characteristic detection curve data includes the following steps:

[0301] Obtain the value of variable B in the first test target feature curve obtained based on Equation 1;

[0302] Based on the value of variable B, determine the state of the wafer at the pre-selected measurement point, including: the state of the lattice features at the pre-selected measurement point;

[0303] The step of determining the state of the wafer at the pre-selected measurement point based on the value of variable B includes the following steps: the state of the lattice features at the pre-selected measurement point.

[0304] Determine the threshold range into which the value of variable B falls;

[0305] Based on the threshold range into which the value of variable B falls, the state of the lattice features at the pre-selected measurement point is determined.

[0306] The goodness-of-fit R at the pre-selected measurement points in the sample to be tested is obtained based on the following equation 3. 2 Value:

[0307]

[0308] Among them, Y actual Y is the measured value of the second harmonic detection signal corresponding to the first preset azimuth angle in the measured second harmonic detection signal set. predict Y is the fitted value of the second harmonic signal corresponding to the first preset azimuth angle in the lattice characteristic detection curve data. mean It is the average value of several measured values ​​of the second harmonic detection signals in the measured second harmonic detection signal set;

[0309] According to the goodness of fit R 2 The value determines whether the state of the wafer at the preselected measurement point includes: whether the lattice distortion and / or stress effects at the preselected measurement point are within acceptable limits.

[0310] The several second harmonic detection signals in the measured second harmonic detection signal set are all the second harmonic detection signals in the measured second harmonic detection signal set.

[0311] The wafer inspection method further includes:

[0312] Based on the detected state of the wafer at each pre-selected test point in the sample to be tested, a wafer map is generated to characterize the overall performance level of the sample to be tested.

[0313] In this embodiment, the values ​​of variable A, variable B, and goodness of fit R are used simultaneously. 2 The value is used to determine the state of the wafer at the pre-selected measurement point, effectively satisfying the detection of wafer surface roughness, lattice characteristics, lattice distortion and / or stress effects.

[0314] In practice, the detection results of the lattice feature state can also be verified using the following steps:

[0315] When the lattice characteristic detection curve data is obtained by fitting S-polarized light from multiple second harmonic detection signals in the measured second harmonic detection signal set, the preset fitting algorithm includes the following formula 2:

[0316]

[0317] in, This represents the value of the second harmonic signal corresponding to S-polarized light in the lattice property detection curve data. The azimuth angle of the light source when it illuminates the preselected test point is the value of the second harmonic signal corresponding to the S-polarized light, n is a preset constant, C is a coefficient used to reflect the state of the wafer at the preselected test point, and D is the DC offset. The second test target characteristic curve is formed by the lattice characteristic detection curve data obtained based on the above formula 2.

[0318] When the lattice characteristic detection curve data is obtained based on Equation 2, the step of determining the state of the wafer at the pre-selected measurement point based on the obtained lattice characteristic detection curve data includes the following steps:

[0319] Obtain the value of variable C in the second test target feature curve obtained based on Equation 2;

[0320] Based on the value of variable C, the differences between the production processes corresponding to the test samples are determined.

[0321] Obtain the value of variable C in the second test target feature curve obtained based on Equation 2;

[0322] Based on the value of variable C, determine the state of the wafer at the pre-selected measurement point, including: the state of the lattice features at the pre-selected measurement point;

[0323] The determination of the wafer state at the pre-selected measurement point based on the value of variable C includes the state of the lattice features at the pre-selected measurement point, comprising the following steps:

[0324] Determine the threshold range into which the value of variable C falls;

[0325] Based on the threshold range into which the value of variable C falls, the state of the lattice features at the pre-selected measurement point is determined.

[0326] The test results can be further verified through relevant steps, thereby improving their accuracy.

[0327] There is no requirement for the order of the detection of the interface roughness state, the state of lattice characteristics at the pre-selected measurement points, and the lattice distortion and / or stress influence at the pre-selected measurement points. Users can design the detection order and detection items according to their detection needs, and are not limited to the above writing order.

[0328] In addition, the following steps can also be performed during the detection:

[0329] Based on the detected state of the wafer at each pre-selected test point in the sample to be tested, a wafer map is generated to characterize the overall performance level of the sample to be tested.

[0330] Here, the wafer map refers to the distribution pattern of the overall performance of the wafer in this embodiment.

[0331] For a specific measurement point, the characteristic curve obtained by RA or RA-scan can reflect the detection results of the above applications. For the wafer under test, several measurement points will be selected to reflect the overall performance level of the wafer under test, depending on the testing requirements.

[0332] Specifically, in some testing applications, it can be observed that the lattice quality of the test point is related to the distance of that point from the center of the wafer. This result may be due to the characteristics of the manufacturing process (normal phenomenon), or it may be due to interference from certain influencing factors in the process (abnormal phenomenon).

[0333] In this embodiment, the detection method of the present invention can reflect the phenomenon in the wafer map, allowing those skilled in the art to observe the phenomenon more intuitively. However, the specific causes of the detection results and subsequent improvement methods need to be analyzed by those skilled in the art in combination with the actual situation.

[0334] Meanwhile, regarding the aforementioned testing items, in actual implementation, one can choose to conduct a specific analysis on one of them, or multiple items can be analyzed comprehensively simultaneously to achieve online monitoring. The specific approach should be determined by the requirements of the sample to be tested or the production process to be monitored. For different samples to be tested or production processes to be monitored, those skilled in the art can derive the most reasonable and complete testing methods (e.g., testing sequence, judgment conditions, etc.) based on theoretical optimization. This is based on the application of various RA or RA-scan second harmonic detection methods proposed in this invention.

[0335] Since the objects that variable C can detect are basically the same as those that variable B can detect, and the relevant analysis has already been performed above, this analysis will only focus on the values ​​of variable A, the values ​​of variable B, and the goodness of fit R. 2 The following example illustrates the detection results corresponding to the value.

[0336] like Figure 5 As shown, this is a schematic diagram of the measurement point locations on a sample to be tested. During the relevant testing process, the detection results of the 13 measurement points in the diagram can be used to fit a characteristic curve, obtaining the values ​​of variable A, variable B, and the goodness of fit R. 2 The value of is determined, and a comprehensive analysis of the wafer under test is performed. For example, by using the goodness-of-fit R... 2 The value can be used to analyze the goodness of fit R for each measurement point. 2 The differences between the detected values ​​can be used to infer the differences in lattice quality between each measuring point. The value of variable A can be used to determine the differences in roughness between measuring points, and the value of variable B can be used to characterize the differences in the state of lattice features at each measuring point on the wafer under test, thereby inferring the intra-wafer differences of the wafer under test in this production process.

[0337]

[0338] Table 1

[0339] As shown in Table 1 above, the following explanation uses a set of actual test data: Table 1 presents the fitting results of second harmonic detection corresponding to a total of 16 measurement points on four wafers. The fitting results include the values ​​of variable A, variable B, and the goodness of fit R. 2 The value of . Based on observation and analysis, the following conclusions can be drawn:

[0340] 1. Looking at the values ​​of the fitted variable A: The A values ​​at various measuring points within the same wafer are relatively close, generally indicating that after undergoing the same manufacturing process, the overall surface roughness of the same wafer is consistent, with no significant intra-wafer differences. However, the A values ​​of different wafers differ significantly. This could be due to variations in surface roughness resulting from different manufacturing processes, or it could be due to differences in the microstructure of different wafers, leading to inter-wafer differences even after undergoing the same manufacturing process. After obtaining the above test results, those skilled in the art should attempt to further analyze the causes to improve the production process or other aspects.

[0341] 2. From the fitted variable B, we can see that there is no consistent pattern among the wafers, and it is difficult to make further judgments under unknown conditions. However, for wafers of the same type and with the same manufacturing process, those skilled in the art can use the value of variable B to characterize the relevant parameters. For details, please refer to the relevant description in Example 2.

[0342] 3. From the fitted R... 2 To see the value: R of wafer 4 2 The lattice quality of wafer 4 is significantly lower than that of the other three wafers, and can be directly used to characterize the poor lattice quality of wafer 4. Based on this conclusion, those skilled in the art should inspect the production process corresponding to wafer 4 and explore the causes of the poor lattice quality of wafer 4, so that this second harmonic detection can play an auxiliary role in improving the yield.

[0343] 4. Specifically, the data at test point 1 on wafer 3 showed significant differences from other test points and other wafers. This could be due to a special defect at or near that point, or it could be due to other factors affecting the test results, such as changes in external conditions or fluctuations in the equipment status. Those skilled in the art should investigate all possibilities before determining the reliability of the data at that point.

[0344] The above test examples further confirm that:

[0345] The method described in this embodiment allows for a more systematic, comprehensive, effective, and rapid detection of wafer conditions, better meeting user needs. Furthermore, this method effectively avoids the problems of existing technologies for lattice composition detection. In the semiconductor testing industry, XPS and XRD are commonly used for measurements. X-ray diffraction has high requirements for sample crystallinity and limited ability to detect trace components and determine elemental chemical states. XPS has a fixed detection depth, requiring the thickness of the material to be measured to be at least 10 nm; otherwise, it will be affected by background materials, leading to inaccurate measurement results. The technical solution of this application better addresses the increasingly smaller size requirements of current integrated circuits, effectively meeting the need for online, rapid, and non-destructive detection of lattice composition, and solving a pressing problem in the semiconductor testing industry.

[0346] Example 8:

[0347] This embodiment also provides a wafer inspection system based on second harmonics, used to execute the wafer inspection method based on second harmonics as described in any one of embodiments 1 to 7 of the present invention.

[0348] In specific implementation, the wafer inspection system may include:

[0349] The stage includes a movable detection plane, which is used to carry the sample to be tested and selectively moves the sample to be tested.

[0350] A light source module is used to generate a light source capable of exciting the sample under test to produce a second harmonic.

[0351] An optical inspection module is used to receive the second harmonic signal generated after the light source illuminates the sample to be tested, and to execute the wafer inspection method based on second harmonics as described in any one of Embodiments 1 to 7 of the present invention.

[0352] The operation flow of the wafer inspection system based on second harmonics in this embodiment when performing the above method can be found in [reference needed]. Figure 9 As shown, the general process is as follows:

[0353] Load the sample to be tested;

[0354] The measured second harmonic detection signal set of the measurement point on the sample under test is obtained by using the second harmonic detection method of RA or RA-scan.

[0355] Based on a preset fitting algorithm, multiple second harmonic detection signals in the measured second harmonic detection signal set are fitted to obtain lattice characteristic detection curve data.

[0356] The coefficients A / B / C and the goodness of fit R are obtained from the lattice property detection curve data corresponding to this measurement point. 2 At least one key coefficient in the data is used to detect the relevant state that needs to be detected at the measurement point;

[0357] Continue testing other test points. Once completed, draw a wafer map based on the different key coefficients mentioned above to visually represent the test results.

[0358] The wafer inspection system based on second harmonics in this embodiment can be used to inspect wafers more quickly and effectively, especially to detect lattice characteristics.

[0359] The beneficial effects of the wafer inspection method and system based on second harmonics of the present invention are as follows:

[0360] The wafer inspection method and system based on second harmonics of the present invention acquires a set of measured second harmonic detection signals at pre-selected measurement points in the sample under test, and performs fitting processing on multiple second harmonic detection signals in the measured second harmonic detection signal set. Based on the acquired lattice characteristic detection curve data, the state of the wafer at the pre-selected measurement points can be determined subsequently through the lattice characteristic detection curve data. Since all related operations are performed based on second harmonic detection signals, and existing wafer inspection systems for detecting electrical characteristic parameters of wafers using second harmonic scanning can generally be directly set up on the wafer production line and have the characteristics of fast signal acquisition speed, using second harmonics to inspect wafers during production can determine the lattice characteristics of the wafer more quickly. Furthermore, since the inspection can be completed without moving the sample under test, it can meet the requirements of faster inspection and realize online inspection. Simultaneously, the method does not come into contact with the test item during execution, thus making it a non-destructive testing solution. Furthermore, it eliminates the need for sample transport, avoiding the complexity of repeatedly adjusting the testing position due to contact, and making the operation process more convenient. The wafer inspection method and system based on second harmonics of this invention features high detection efficiency, fast response speed, good performance, and excellent adaptability.

[0361] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A wafer inspection method based on second harmonic distortion, characterized in that, The wafer inspection method includes: The measured second harmonic detection signal set at the pre-selected measurement point in the sample to be tested is obtained. The measured second harmonic detection signal set includes: multiple second harmonic detection signals generated by the pre-selected measurement point after being irradiated by light sources from different azimuth angles and excited. Based on a preset fitting algorithm, multiple second harmonic detection signals in the measured second harmonic detection signal set are fitted to obtain lattice characteristic detection curve data. The state of the wafer at the pre-selected measurement point is determined based on the obtained lattice characteristic detection curve data. When the lattice characteristic detection curve data is obtained by fitting P-polarized light from multiple second harmonic detection signals in the measured second harmonic detection signal set, the preset fitting algorithm includes the following formula 1: Formula 1; in, This represents the value of the second harmonic signal corresponding to P-polarized light in the lattice property detection curve data. The azimuth angle of the light source when it illuminates the pre-selected measurement point, corresponding to the value of the second harmonic signal corresponding to the P-polarized light. As a preset constant, and The coefficient used to reflect the state of the wafer at the pre-selected test point is used to construct the first test target characteristic curve from the lattice characteristic detection curve data obtained based on Equation 1 above.

2. The wafer inspection method based on second harmonics according to claim 1, characterized in that, When the surface at the pre-selected measurement point is the (001) plane in a cubic lattice =4.

3. The wafer inspection method based on second harmonics according to claim 1, characterized in that, When the lattice characteristic detection curve data is obtained based on Equation 1, the step of determining the state of the wafer at the pre-selected measurement point based on the obtained lattice characteristic detection curve data includes the following steps: Obtain the variables in the first test target feature curve obtained based on Equation 1. The value; According to the variable The value determines the state of the wafer at the preselected measurement point, including: the interface roughness state at the preselected measurement point; Wherein, according to the variable The value of is used to determine the state of the wafer at the pre-selected measurement point, including the interface roughness state at the pre-selected measurement point, comprising the following steps: Determine the variable The threshold range into which the value falls; According to the variable The threshold range into which the value falls determines the interface roughness state at the pre-selected measurement point.

4. The wafer inspection method based on second harmonics according to claim 1, characterized in that, When the lattice characteristic detection curve data is obtained based on Equation 1, the step of determining the state of the wafer at the pre-selected measurement point based on the obtained lattice characteristic detection curve data includes the following steps: Obtain the variables in the first test target feature curve obtained based on Equation 1. The value; According to the variable The value is used to determine the differences between the production processes corresponding to the test sample.

5. The wafer inspection method based on second harmonics according to claim 1, characterized in that, When the lattice characteristic detection curve data is obtained based on Equation 1, the step of determining the state of the wafer at the pre-selected measurement point based on the obtained lattice characteristic detection curve data includes the following steps: Obtain the variables in the first test target feature curve obtained based on Equation 1. The value; According to the variable The value determines the state of the wafer at the preselected measurement point, including the state of the lattice features at the preselected measurement point; Wherein, according to the variable The value of is used to determine the state of the wafer at the pre-selected measurement point, which includes the state of the lattice features at the pre-selected measurement point, comprising the following steps: Determine the variable The threshold range into which the value falls; According to the variable The threshold range into which the value falls determines the state of the lattice features at the pre-selected measurement point.

6. The wafer inspection method based on second harmonics according to claim 1, characterized in that, The method further includes: determining, based on the goodness of fit between the first test target feature curve and the preset first reference lattice characteristic detection curve data, whether the lattice distortion and / or stress influence at the pre-selected test point, which is included in the state of the wafer at the pre-selected test point, is within an acceptable range. The first reference lattice characteristic detection curve data is: curve data obtained by fitting the P-polarized light from multiple reference second harmonic detection signals in the reference second harmonic detection signal set into Equation 1 above.

7. The wafer inspection method based on second harmonics according to claim 1, characterized in that, The method further includes: The goodness of fit at the pre-selected measurement points in the sample to be tested is obtained based on Equation 3 below. Value: Formula 3; in, The measured value of the second harmonic detection signal corresponding to the first preset azimuth angle is the actual value of the measured second harmonic detection signal set. The fitted value of the second harmonic signal corresponding to the first preset azimuth angle in the lattice characteristic detection curve data is [value missing]. It is the average value of several measured values ​​of the second harmonic detection signals in the measured second harmonic detection signal set; According to the goodness of fit The value determines whether the state of the wafer at the preselected measurement point includes: whether the lattice distortion and / or stress effects at the preselected measurement point are within acceptable limits.

8. The wafer inspection method based on second harmonics according to claim 7, characterized in that, The several second harmonic detection signals in the measured second harmonic detection signal set are all the second harmonic detection signals in the measured second harmonic detection signal set.

9. The wafer inspection method based on second harmonics according to any one of claims 1 to 8, characterized in that, The wafer inspection method further includes: Based on the detected state of the wafer at each pre-selected test point in the sample to be tested, a wafer map is generated to characterize the overall performance level of the sample to be tested.

10. The wafer inspection method based on second harmonics according to any one of claims 1 to 8, characterized in that, The measured second harmonic detection signal set at the pre-selected measurement point is obtained through the following operations: The light source capable of exciting the sample under test to generate second harmonics moves continuously relative to the sample under test along the direction surrounding the pre-selected test point within a preset rotation angle range. At the same time, the second harmonic signals generated by the sample under test after being irradiated by the light source at different azimuth angles are continuously collected to obtain multiple second harmonic detection signals generated by the pre-selected test point after being irradiated by the light source from different azimuth angles.

11. The wafer inspection method based on second harmonics according to any one of claims 1 to 8, characterized in that, The measured second harmonic detection signal set at the pre-selected measurement point is obtained through the following operations: A light source capable of exciting the sample under test to generate second harmonics is directed at the pre-selected test point from multiple preset azimuth angles within a preset rotation angle range, along the direction surrounding the pre-selected test point. By collecting the second harmonic signals generated by the sample under test after being irradiated by the light source at different azimuth angles, multiple second harmonic detection signals generated by the pre-selected test point after being irradiated by the light source from different azimuth angles are obtained.

12. A wafer inspection method based on second harmonics, characterized in that, The wafer inspection method includes: The measured second harmonic detection signal set at the pre-selected measurement point in the sample to be tested is obtained. The measured second harmonic detection signal set includes: multiple second harmonic detection signals generated by the pre-selected measurement point after being irradiated by light sources from different azimuth angles and excited. Based on a preset fitting algorithm, multiple second harmonic detection signals in the measured second harmonic detection signal set are fitted to obtain lattice characteristic detection curve data. The state of the wafer at the pre-selected measurement point is determined based on the obtained lattice characteristic detection curve data. When the lattice characteristic detection curve data is obtained by fitting S-polarized light from multiple second harmonic detection signals in the measured second harmonic detection signal set, the preset fitting algorithm includes the following formula 2: Formula 2; in, This represents the value of the second harmonic signal corresponding to S-polarized light in the lattice property detection curve data. The azimuth angle of the light source when it illuminates the pre-selected measurement point, corresponding to the value of the second harmonic signal corresponding to the S-polarized light. As a preset constant, This is a coefficient used to reflect the state of the wafer at the pre-selected measurement point. The DC offset is used to construct the second test target characteristic curve from the lattice characteristic detection curve data obtained based on Equation 2 above.

13. The wafer inspection method based on second harmonics according to claim 12, characterized in that, When the surface at the pre-selected measurement point is the (001) plane in a cubic lattice =4.

14. The wafer inspection method based on second harmonics according to claim 12, characterized in that, When the lattice characteristic detection curve data is obtained based on Equation 2, the step of determining the state of the wafer at the pre-selected measurement point based on the obtained lattice characteristic detection curve data includes the following steps: Obtain the variables in the second test target feature curve obtained based on Equation 2. The value; According to the variable The value determines the state of the wafer at the preselected measurement point, including the state of the lattice features at the preselected measurement point; According to the variable The value of is used to determine the state of the wafer at the pre-selected measurement point, which includes the state of the lattice features at the pre-selected measurement point, comprising the following steps: Determine the variable The threshold range into which the value falls; According to the variable The threshold range into which the value falls determines the state of the lattice features at the pre-selected measurement point.

15. The wafer inspection method based on second harmonics according to claim 12, characterized in that, When the lattice characteristic detection curve data is obtained based on Equation 2, the step of determining the state of the wafer at the pre-selected measurement point based on the obtained lattice characteristic detection curve data includes the following steps: Obtain the variables in the second test target feature curve obtained based on Equation 2. The value; According to the variable The value is used to determine the differences between the production processes corresponding to the test sample.

16. The wafer inspection method based on second harmonics according to claim 12, characterized in that, The method further includes: Based on the goodness of fit between the second test target characteristic curve and the preset second reference lattice characteristic detection curve data, determine whether the state of the wafer at the pre-selected test point includes: whether the lattice distortion and / or stress influence at the pre-selected test point is within an acceptable range. The second reference lattice characteristic detection curve data is obtained by fitting the curve data after substituting the S-polarized light from multiple reference second harmonic detection signals in the reference second harmonic detection signal set into Equation 2 above.

17. The wafer inspection method based on second harmonics according to claim 12, characterized in that, The method further includes: The goodness of fit at the pre-selected measurement points in the sample to be tested is obtained based on Equation 3 below. Value: Formula 3; in, The measured value of the second harmonic detection signal corresponding to the first preset azimuth angle is the actual value of the measured second harmonic detection signal set. The fitted value of the second harmonic signal corresponding to the first preset azimuth angle in the lattice characteristic detection curve data is [value missing]. It is the average value of several measured values ​​of the second harmonic detection signals in the measured second harmonic detection signal set; According to the goodness of fit The value determines whether the state of the wafer at the preselected measurement point includes: whether the lattice distortion and / or stress effects at the preselected measurement point are within acceptable limits.

18. The wafer inspection method based on second harmonics according to claim 17, characterized in that, The several second harmonic detection signals in the measured second harmonic detection signal set are all the second harmonic detection signals in the measured second harmonic detection signal set.

19. The wafer inspection method based on second harmonics according to any one of claims 12 to 18, characterized in that, The wafer inspection method further includes: Based on the detected state of the wafer at each pre-selected test point in the sample to be tested, a wafer map is generated to characterize the overall performance level of the sample to be tested.

20. The wafer inspection method based on second harmonics according to any one of claims 12 to 18, characterized in that, The measured second harmonic detection signal set at the pre-selected measurement point is obtained through the following operations: The light source capable of exciting the sample under test to generate second harmonics moves continuously relative to the sample under test along the direction surrounding the pre-selected test point within a preset rotation angle range. At the same time, the second harmonic signals generated by the sample under test after being irradiated by the light source at different azimuth angles are continuously collected to obtain multiple second harmonic detection signals generated by the pre-selected test point after being irradiated by the light source from different azimuth angles.

21. The wafer inspection method based on second harmonics according to any one of claims 12 to 18, characterized in that, The measured second harmonic detection signal set at the pre-selected measurement point is obtained through the following operations: A light source capable of exciting the sample under test to generate second harmonics is directed at the pre-selected test point from multiple preset azimuth angles within a preset rotation angle range, along the direction surrounding the pre-selected test point. By collecting the second harmonic signals generated by the sample under test after being irradiated by the light source at different azimuth angles, multiple second harmonic detection signals generated by the pre-selected test point after being irradiated by the light source from different azimuth angles are obtained.

22. A wafer inspection method based on second harmonics, characterized in that, The wafer inspection method includes: The measured second harmonic detection signal set at the pre-selected measurement point in the sample to be tested is obtained. The measured second harmonic detection signal set includes: multiple second harmonic detection signals generated by the pre-selected measurement point after being irradiated by light sources from different azimuth angles and excited. Based on a preset fitting algorithm, multiple second harmonic detection signals in the measured second harmonic detection signal set are fitted to obtain lattice characteristic detection curve data. The state of the wafer at the pre-selected measurement point is determined based on the obtained lattice characteristic detection curve data. The method further includes: The goodness of fit at the pre-selected measurement points in the sample to be tested is obtained based on Equation 3 below. Value: Formula 3; in, The measured value of the second harmonic detection signal corresponding to the first preset azimuth angle is the actual value of the measured second harmonic detection signal set. The fitted value of the second harmonic signal corresponding to the first preset azimuth angle in the lattice characteristic detection curve data is [value missing]. It is the average value of several measured values ​​of the second harmonic detection signals in the measured second harmonic detection signal set; According to the goodness of fit The value determines whether the state of the wafer at the preselected measurement point includes: whether the lattice distortion and / or stress effects at the preselected measurement point are within acceptable limits.

23. The wafer inspection method based on second harmonics according to claim 22, characterized in that, The several second harmonic detection signals in the measured second harmonic detection signal set are all the second harmonic detection signals in the measured second harmonic detection signal set.

24. The wafer inspection method based on second harmonics according to claim 22 or 23, characterized in that, The wafer inspection method further includes: Based on the detected state of the wafer at each pre-selected test point in the sample to be tested, a wafer map is generated to characterize the overall performance level of the sample to be tested.

25. The wafer inspection method based on second harmonics according to claim 22 or 23, characterized in that, The measured second harmonic detection signal set at the pre-selected measurement point is obtained through the following operations: The light source capable of exciting the sample under test to generate second harmonics moves continuously relative to the sample under test along the direction surrounding the pre-selected test point within a preset rotation angle range. At the same time, the second harmonic signals generated by the sample under test after being irradiated by the light source at different azimuth angles are continuously collected to obtain multiple second harmonic detection signals generated by the pre-selected test point after being irradiated by the light source from different azimuth angles.

26. The wafer inspection method based on second harmonics according to any one of claims 22 or 23, characterized in that, The measured second harmonic detection signal set at the pre-selected measurement point is obtained through the following operations: A light source capable of exciting the sample under test to generate second harmonics is directed at the pre-selected test point from multiple preset azimuth angles within a preset rotation angle range, along the direction surrounding the pre-selected test point. By collecting the second harmonic signals generated by the sample under test after being irradiated by the light source at different azimuth angles, multiple second harmonic detection signals generated by the pre-selected test point after being irradiated by the light source from different azimuth angles are obtained.

27. A wafer inspection system based on second harmonics, characterized in that, The wafer inspection system is used to perform the wafer inspection method based on second harmonics as described in any one of claims 1 to 26.

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