Wafer detection method and system based on second harmonic

Abstract

The invention relates to a wafer detection method and system based on second harmonics, and the method comprises the steps: obtaining an actual measurement second harmonic detection signal set at a preselected detection point in a to-be-detected sample, the actually measured second harmonic detection signal set comprises a plurality of second harmonic detection signals generated by excitation after the preselected detection point is irradiated by light sources from different azimuth angles; performing fitting processing on a plurality of second harmonic detection signals in the actually measured second harmonic detection signal set based on a preset fitting algorithm to obtain lattice characteristic detection curve data; and determining the state of the wafer at the pre-selected measuring point according to the obtained lattice characteristic detection curve data. The related operation is executed based on the second harmonic detection signal, so that the method has the characteristic of high signal acquisition speed, can meet the requirement of quicker detection, and realizes online detection. The wafer detection method and system based on the second harmonic have the advantages of being high in detection efficiency, high in response speed, good in performance and good in adaptability.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of detection, in particular to the field of semiconductor production detection, and more particularly to a wafer detection method and system based on second harmonic. BACKGROUND

[0002] With the development of chip manufacturing process to 7nm, 5nm or even smaller, the precision requirement of wafer manufacturing is extremely high, and any tiny defect may cause chip failure. Among them, the lattice quality of wafer is crucial to the performance of semiconductor material, so it is particularly important to effectively detect the lattice condition of wafer in the production stage.

[0003] In the prior art, in the semiconductor detection industry, X-ray diffraction (XRD) technology is often used to measure the lattice quality. This technology is based on the diffraction pattern generated by the interaction of X-rays and crystals. By analyzing the pattern, lattice parameters, crystal orientation and defect information can be obtained. However, the related equipment has the problems of high cost, small detection range and low detection efficiency.

[0004] The technology of using the transmission electron microscope (TEM) in the prior art to get the micro image of the material by penetrating the sample with an electron beam can intuitively observe the arrangement of lattice atoms and identify atomic-level defects and lattice distortion. However, the preparation process of the slice sample is complex, the detection condition is high, and it is a destructive detection method. At the same time, TEM also has the problems of high equipment cost and low detection efficiency.

[0005] At the same time, the X-ray diffraction (XRD) technology and the transmission electron microscope (TEM) mentioned above both need to take the sample to be detected off the production line and then place it on a specific device for detection. Wafer production involves hundreds of processes, and any deviation in any process may affect the quality of the final product. Therefore, the detection method in the prior art cannot effectively meet the demand for rapid detection. SUMMARY

[0006] In view of the above defects of the prior art, the present application provides a wafer detection method and system based on second harmonic, which at least solves one of the above problems and effectively meets the needs of high efficiency, convenience and adaptability in wafer production process.

[0007] In order to achieve the above purpose, the wafer detection method and system based on second harmonic of the present application are as follows:

[0008] In a first aspect, the wafer detection method based on second harmonic mainly comprises:

[0009] acquire a set of measured second-harmonic detection signals at a preselected measurement point in a sample to be measured, the set of measured second-harmonic detection signals including a plurality of second-harmonic detection signals generated by excitation of the preselected measurement point by light sources from different azimuth angles;

[0010] fit process the plurality of 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;

[0011] determine a state of a wafer at the preselected measurement point according to the obtained lattice characteristic detection curve data.

[0012] The above-mentioned wafer detection method based on second-harmonic wave, wherein when the lattice characteristic detection curve data is obtained based on P-polarized light fitting of the plurality of second-harmonic detection signals in the set of measured second-harmonic detection signals, the preset fitting algorithm includes the following formula 1:

[0013]

[0014] wherein, is a value of a second-harmonic signal corresponding to P-polarized light in the lattice characteristic detection curve data, is an azimuth angle of the light source when the light source is directed to the preselected measurement point corresponding to the value of the second-harmonic signal corresponding to P-polarized light, n is a preset constant, A and B are coefficients for reflecting a state of a wafer at the preselected measurement point, and a first test target characteristic curve is constituted by the lattice characteristic detection curve data obtained based on the above-mentioned formula 1.

[0015] The above-mentioned wafer detection method based on second-harmonic wave, wherein when the surface at the preselected measurement point is a (001) surface in a cubic lattice, n = 4.

[0016] The above-mentioned wafer detection method based on second-harmonic wave, wherein when the lattice characteristic detection curve data is obtained based on the formula 1, the determination of the state of the wafer at the preselected measurement point according to the obtained lattice characteristic detection curve data includes the following steps:

[0017] acquire a value of variable A in the first test target characteristic curve obtained based on the formula 1;

[0018] determine, according to the value of the variable A, that the state of the wafer at the preselected measurement point includes an interface roughness state at the preselected measurement point.

[0019] The above-mentioned wafer detection method based on second-harmonic wave, wherein when the surface at the preselected measurement point is a (001) surface in a cubic lattice, n = 4.

[0020] determining a threshold interval into which the value of the variable A falls;

[0021] determining an interface roughness state at the preselected measurement point according to the threshold interval into which the value of the variable A falls.

[0022] The wafer detection method based on second harmonic wave as described above, wherein when the lattice characteristic detection curve data is obtained based on the formula 1, the determination of the state of the wafer at the preselected measurement point according to the obtained lattice characteristic detection curve data comprises the following steps:

[0023] obtaining a value of a variable B in the first test target characteristic curve based on the formula 1;

[0024] determining the difference between the production processes corresponding to the sample to be tested according to the value of the variable B.

[0025] The wafer detection method based on second harmonic wave as described above, wherein when the lattice characteristic detection curve data is obtained based on the formula 1, the determination of the state of the wafer at the preselected measurement point according to the obtained lattice characteristic detection curve data comprises the following steps:

[0026] obtaining a value of a variable B in the first test target characteristic curve based on the formula 1;

[0027] determining the state of the wafer at the preselected measurement point according to the value of the variable B, which comprises the state of the lattice characteristic at the preselected measurement point.

[0028] The determination of the state of the wafer at the preselected measurement point according to the value of the variable B, which comprises the state of the lattice characteristic at the preselected measurement point, comprises the following steps:

[0029] determining a threshold interval into which the value of the variable B falls;

[0030] determining the state of the lattice characteristic at the preselected measurement point according to the threshold interval into which the value of the variable B falls.

[0031] The wafer detection method based on second harmonic wave as described above, wherein the method further comprises: determining whether the lattice distortion and / or stress influence at the preselected measurement point is within an acceptable range according to the goodness of fit of the first test target characteristic curve and a preset first reference lattice characteristic detection curve data.

[0032] The first reference lattice characteristic detection curve data is curve data fitted by substituting P-polarized light in a plurality of reference second harmonic wave detection signals in a reference second harmonic wave detection signal set into the formula 1.

[0033] The wafer detection method based on second harmonic above, wherein, when the lattice characteristic detection curve data is fitted based on the S-polarized light in the plurality of second harmonic detection signals in the measured second harmonic detection signal set, the preset fitting algorithm includes the following formula 2:

[0034]

[0035] Wherein, is the value of the second harmonic signal corresponding to the S-polarized light in the lattice characteristic detection curve data, is the azimuth angle of the light source when the value of the second harmonic signal corresponding to the S-polarized light is illuminated to the preselected measurement point, n is a preset constant, C is a coefficient for reflecting the state of the wafer at the preselected measurement point, and D is a direct current offset. The lattice characteristic detection curve data obtained based on the above formula 2 constitutes a second test target characteristic curve.

[0036] The wafer detection method based on second harmonic above, wherein, when the surface at the preselected measurement point is (001) surface in cubic lattice, n=4.

[0037] The wafer detection method based on second harmonic above, wherein, when the lattice characteristic detection curve data is obtained based on the formula 2, the state of the wafer at the preselected measurement point is determined according to the obtained lattice characteristic detection curve data, comprising the following steps:

[0038] Obtaining the value of variable C in the second test target characteristic curve obtained based on the formula 2;

[0039] According to the value of the variable C, the state of the wafer at the preselected measurement point contains the state of the lattice characteristic at the preselected measurement point.

[0040] According to the value of the variable C, the state of the wafer at the preselected measurement point contains the state of the lattice characteristic at the preselected measurement point, comprising the following steps:

[0041] Judging the threshold interval in which the value of the variable C falls;

[0042] According to the threshold interval in which the value of the variable C falls, the state of the lattice characteristic at the preselected measurement point is determined.

[0043] The wafer detection method based on second harmonic above, wherein, when the lattice characteristic detection curve data is obtained based on the formula 2, the state of the wafer at the preselected measurement point is determined according to the obtained lattice characteristic detection curve data, comprising the following steps:

[0044] Obtaining the value of variable C in the second test target characteristic curve obtained based on the formula 2;

[0045] According to the value of the variable C, the difference between the production process corresponding to the sample to be tested is determined.

[0046] The wafer detection method based on second harmonic wave described above, wherein the method further comprises:

[0047] According to the goodness of fit of the second test target characteristic curve and the preset second reference lattice characteristic detection curve data, it is determined whether the state of the wafer at the preselected measurement point contains: the lattice distortion and / or stress effect at the preselected measurement point is within the acceptable range;

[0048] Wherein, the second reference lattice characteristic detection curve data is: the curve data fitted after the S-polarized light in the plurality of reference second harmonic wave detection signals in the reference second harmonic wave detection signal set is substituted into the above formula 2.

[0049] The wafer detection method based on second harmonic wave described above, wherein the method further comprises:

[0050] The goodness of fit R of the preselected measurement point in the sample to be tested is calculated based on the following formula 3: 2 The value of:

[0051]

[0052] Wherein, Y actual is the measured value of the second harmonic wave signal corresponding to the first preset azimuth angle in the measured second harmonic wave detection signal set, Y predict is the fitted value of the second harmonic wave signal corresponding to the first preset azimuth angle in the lattice characteristic detection curve data, Y mean is the average value of the measured values of a plurality of second harmonic wave detection signals in the measured second harmonic wave detection signal set.

[0053] According to the value of the goodness of fit R 2 of the preselected measurement point, it is determined whether the state of the wafer at the preselected measurement point contains: the lattice distortion and / or stress effect at the preselected measurement point is within the acceptable range.

[0054] The wafer detection method based on second harmonic wave described above, wherein the plurality of second harmonic wave detection signals in the measured second harmonic wave detection signal set are all the second harmonic wave detection signals in the measured second harmonic wave detection signal set.

[0055] The wafer detection method based on second harmonic wave described above, wherein the wafer detection method further comprises:

[0056] Based on the state of the wafer at each preselected measurement point in the sample to be tested, a wafer map is generated to represent the overall performance level of the sample to be tested.

[0057] The wafer detection method based on second harmonic wave, wherein the measured second harmonic wave detection signal set at the preselected measurement point is obtained by the following operation:

[0058] The light source capable of exciting the to-be-measured sample to generate second harmonic wave is continuously moved along the direction surrounding the preselected measurement point within a preset rotation angle range relative to the to-be-measured sample, and the second harmonic wave signal generated by the to-be-measured sample after being irradiated by the light source at different azimuth angles is continuously collected to obtain a plurality of the second harmonic wave detection signals generated by the preselected measurement point after being irradiated by the light source at different azimuth angles.

[0059] The wafer detection method based on second harmonic wave, wherein the measured second harmonic wave detection signal set at the preselected measurement point is obtained by the following operation:

[0060] The light source capable of exciting the to-be-measured sample to generate second harmonic wave is continuously moved along the direction surrounding the preselected measurement point within a preset rotation angle range relative to the to-be-measured sample, and the second harmonic wave signal generated by the to-be-measured sample after being irradiated by the light source at different azimuth angles is continuously collected to obtain a plurality of the second harmonic wave detection signals generated by the preselected measurement point after being irradiated by the light source at different azimuth angles.

[0061] The second aspect is the wafer detection system based on second harmonic wave, and the main feature is that the wafer detection system is used to execute the wafer detection method based on second harmonic wave in the first aspect.

[0062] The wafer detection method and system based on second harmonic wave have the following advantages:

[0063] The wafer detection method and system based on second harmonic wave obtain the measured second harmonic wave detection signal set at the preselected measurement point in the to-be-measured sample, and perform fitting processing on a plurality of the second harmonic wave detection signals in the measured second harmonic wave detection signal set, so that the state of the wafer at the preselected measurement point can be determined through the lattice characteristic detection curve data subsequently. Since the related operations are performed based on the second harmonic wave detection signal, and the wafer detection system based on second harmonic wave scanning for realizing the detection of the electrical characteristic parameters of the wafer in the prior art can be directly arranged on the production line of the wafer generation and has the characteristic of fast signal acquisition speed, the wafer can be detected by the second harmonic wave during production to determine the lattice characteristic of the wafer more quickly. Since the detection can be completed without moving the to-be-measured sample, the requirement for faster detection can be met, online detection is realized, and the wafer detection method and system based on second harmonic wave have the characteristics of high detection 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] In order to make the technical means, creative features, purposes and effects of the application easy to understand, the application is further described below in combination with specific drawings. However, the application is not limited to the following embodiments.

[0081] It should be understood that the structures, proportions, sizes, etc. shown in the drawings attached to the specification are only used to illustrate the content disclosed in the specification for understanding and reading by those skilled in the art, and do not define the limiting conditions for implementing the application, and therefore do not have technical substantive significance. Any modification of the structure, change of the proportion relationship or adjustment of the size, without affecting the effects and purposes that can be achieved by the application, should still fall within the scope of the disclosed technology.

[0082] For some wafer manufacturing processes, some parameters in the manufacturing process are directly related to the quality of the output wafer. Conventional detection methods can achieve related performance detection, but the detection speed is slow, the efficiency is low, and the detection conditions are very harsh (such as some need to be detected in a vacuum state), which cannot complete online detection.

[0083] When detecting by using an X-ray diffractometer (English name: X-ray Powder diffractometer, abbreviated as XRD) in the prior art, the following problems exist:

[0084] a. Insufficient sensitivity / limited resolution capability - for some lattice structures or types, when the lattice structure and internal stress change slightly, XRD cannot detect it well;

[0085] b. High cost - the prior art cannot be directly set on the production line;

[0086] c. Low detection efficiency - XRD detection time is long.

[0087] Based on the above problems, the technical solution provides a wafer detection method and system based on second harmonic, to realize a non-contact and lossless second harmonic detection method for substrates or thin films with certain lattice structures and related applications, so as to achieve the purpose of quickly and effectively detecting wafers.

[0088] The application is mainly implemented based on RA-SHG (full name: Rotational Anisotropy Second Harmonic Generation, i.e. Rotational Anisotropy Second Harmonic Generation), which is used to represent the change of second harmonic signal intensity at different azimuth angles, and research shows that its formation reason is closely related to the lattice structure.

[0089] Embodiment 1:

[0090] The embodiment provides a wafer detection method based on second harmonic, which comprises the following steps:

[0091] acquiring a measured second harmonic detection signal set at a preselected measurement point in a sample to be measured, wherein the measured second harmonic detection signal set comprises a plurality of second harmonic detection signals generated by the preselected measurement point after being irradiated by light sources from different azimuth angles;

[0092] In a specific implementation, the measured second harmonic detection signal set at the preselected measurement point can be obtained by the following operations:

[0093] continuously moving a light source capable of exciting the sample to be measured to generate second harmonic along a direction surrounding the preselected measurement point within a preset rotation angle range relative to the sample to be measured, and continuously collecting second harmonic signals generated by the sample to be measured after being irradiated by the light source at different azimuth angles, so as to acquire a plurality of second harmonic detection signals generated by the preselected measurement point after being irradiated by light sources from different azimuth angles (that is, a plurality of second harmonic detection signals are acquired by means of continuous scanning, for the convenience of reading, the related operation is also referred to as RA-scan second harmonic detection); or

[0094] continuously moving a light source capable of exciting the sample to be measured to generate second harmonic along a direction surrounding the preselected measurement point within a preset rotation angle range relative to the sample to be measured, and continuously collecting second harmonic signals generated by the sample to be measured after being irradiated by the light source at different azimuth angles, so as to acquire a plurality of second harmonic detection signals generated by the preselected measurement point after being irradiated by light sources from different azimuth angles (that is, a plurality of second harmonic detection signals are acquired by means of continuous scanning, for the convenience of reading, the related operation is also referred to as RA-scan second harmonic detection); or

[0095] The incident angle and rotation direction of the related light source can be referred to as shown in Figure 1 , wherein the elliptical surface is used to show the sample to be measured, and the surface is marked as a (100) surface in the lattice, wherein the center position of the elliptical surface is the preselected measurement point, wherein, E ω，p is incident light (that is, light emitted by the light source), E 2ω，p is a second harmonic detection signal generated after the excitation light irradiates the wafer, x, y and z are coordinate axes, represents the azimuth angle of the light source, wherein the arrow adjacent to the azimuth angle represents the rotation direction. Figure 1It is shown that the polarization of the incident light can be fixed during testing, and then the wafer is rotated around the z-axis to change the angle between the (100) crystal orientation of the wafer and the incident plane, so as to measure the size of the second harmonic signal at different azimuth angles. The figure only shows the relationship between the incident angle of the light source and the rotation direction in order to explain the operation principle of the technical solution of the present scheme. In actual application, the direction of the light source shining on the lattice is not limited to the example shown in the figure.

[0096] Of course, the second harmonic detection signal obtained by the relevant detection can also be collected in other ways and stored in the system for calling during detection and analysis.

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

[0098] According to the obtained lattice characteristic detection curve data, the state of the wafer at the preselected measurement point is determined.

[0099] Since the lattice characteristic detection curve data fitted based on the second harmonic detection signal in the scheme can be used to analyze the state of the wafer at the preselected measurement point, the collection speed of the second harmonic signal is relatively fast, and the detection condition is relatively low. At the same time, the value of the second harmonic can very sensitively reflect the difference of the lattice structure. Therefore, the method of the embodiment can realize fast and effective determination of the state of the wafer at the preselected measurement point according to the lattice characteristic detection curve data fitted based on the second harmonic signal. It should be noted that the determination of the state of the wafer at the preselected measurement point mentioned here means that the state characteristics of the wafer (such as when the matching degree with a certain reference curve is relatively high, it can be determined that the lattice characteristics or other states of the related wafer are close to the target state, and when the matching degree with a certain reference curve is relatively low, it can be confirmed that the related measurement point is inconsistent with the expected state, so as to prompt the operator) can be determined according to the difference between the lattice characteristic detection curve data and the reference curve, but it does not mean that the defect type, defect degree or other specific characteristics can be directly analyzed qualitatively and quantitatively according to the lattice characteristic detection curve data.

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

[0101] The wafer detection method based on the second harmonic can more quickly and effectively reflect the difference between the preselected measurement point and the target state, and effectively improve the detection and production efficiency of the wafer.

[0102] In the embodiment, when the lattice characteristic detection curve data is fitted based on the P-polarized light in the plurality of second harmonic detection signals in the measured second harmonic detection signal set, the preset fitting algorithm includes the following formula 1:

[0103]

[0104] wherein, is a value of a second harmonic signal corresponding to P-polarized light in the lattice characteristic detection curve data, is an azimuth angle of the light source when the light source is directed to the preselected measurement point corresponding to the value of the second harmonic signal corresponding to P-polarized light, n is a preset constant, and A and B are coefficients for reflecting a state of a wafer at the preselected measurement point, and the first test target characteristic curve is constituted by the lattice characteristic detection curve data obtained based on the above-mentioned formula 1.

[0105] wherein, the specific value of n is associated with the anisotropy coefficient of the crystal, and the specific value of n is preset in the system by the operator according to the actual measured crystal plane orientation of the sample to be measured when the method is implemented.

[0106] This embodiment mainly aims at testing and theoretically analyzing the case that the surface of the sample to be measured is a (001) crystal plane (or the surface at the preselected measurement point is a (001) plane in a cubic lattice), and the value of n is 4. Since the specific value of n is associated with the anisotropy coefficient of the crystal, those skilled in the art can generalize the above-mentioned formula 1 to other samples to be measured or other lattice planes of the sample to be measured, and select the specific value of n according to the anisotropy coefficient of the surface of the corresponding sample to be measured.

[0107] The crystal plane is further described below. The crystal plane is a plane composed of atomic, ionic or molecular points in a crystal, and the orientation of the crystal plane is not expressed by an angle but by a crystal plane index, which has a general form of (hkl) or {hkt}, the former representing a set of parallel crystal planes, and the latter representing a family of all crystal planes with completely identical atomic or molecular arrangement. In the same crystal, the atomic distribution and arrangement density of the crystal planes with different crystal plane indices {hkl} are different.

[0108] Taking a sample to be measured composed of silicon material 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, and the smallest unit is a regular tetrahedron composed of five atoms. Each apex atom of the regular tetrahedron is shared by four adjacent tetrahedrons, so that a unit cell is composed of many structural minimum units. Due to the microscopic anisotropy of the crystal, the distribution of atoms on different crystal planes in the silicon crystal is not the same. Among them, the atomic density of the (111) plane is the largest, the (110) plane is the second, and the (100) plane is the smallest. The schematic diagram of the related planes can be referred to in Figure 2 , wherein the (001) plane is located on the upper surface of the cube shown in the figure (i.e. the position marked by the arrow), and the (100) plane and the (010) plane are located on the side surface of the cube shown in the figure. It should be noted that Figure 2 is only a schematic diagram and is not used to represent the actual crystal shape and size of the surface.

[0109] The specific determination method of the specific component material of the to-be-tested sample and the specific lattice plane of the surface at the pre-selected measurement point is not the focus of the present application, and therefore, the related content is not specifically described in the present application. The related test data in each embodiment mentioned in the present application are based on the value of n being 4, and the specific value of n and the basis for the value will not be described in detail hereinafter.

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

[0111] Obtaining the value of the variable A in the first test target characteristic curve based on the formula 1;

[0112] According to the value of the variable A, determining the state of the wafer at the pre-selected measurement point includes determining the interface roughness state at the pre-selected measurement point.

[0113] According to the value of the variable A, determining the state of the wafer at the pre-selected measurement point includes determining the interface roughness state at the pre-selected measurement point.

[0114] Determining the threshold interval in which the value of the variable A falls;

[0115] According to the threshold interval in which the value of the variable A falls, determining the interface roughness state at the pre-selected measurement point.

[0116] In detection, a plurality of threshold intervals can be set, and then the interface roughness state at the pre-selected measurement point is determined by judging the threshold interval in which the value of the variable A falls. For example, the applicant found through actual detection that when different production processes are used to manufacture materials, the roughness of the obtained wafer will be obviously different, and accordingly, the value of the variable A detected will also have a large difference. Therefore, in detection, the production process used by the to-be-tested sample can be inferred according to the interval in which the value of the variable A falls, and whether the roughness of the to-be-tested sample meets the expected requirement can also be determined according to whether the value of the variable A falls into the target threshold interval. That is, the coefficient A in formula 1 can represent the interface roughness of the sample at the measurement point, and thus the characteristics of representing the type of the sample and / or the type of the manufacturing process can be embodied.

[0117] Based on the states of the wafers at each pre-selected measurement point in the to-be-tested sample, a wafer chart is generated to represent the overall performance level of the to-be-tested sample.

[0118] Therefore, through the operation, the test data of different regions of the wafer can be better compared and analyzed, so that the tester can more intuitively understand the states of different regions of the wafer, better and more conveniently understand the global state of the wafer, and provide a basis for subsequent process optimization design scheme.

[0119] In this embodiment, the detection target object reflected by formula 1 and the correlation coefficient in formula 1 is obtained by the applicant through analysis and research on a large amount of test data. The applicant also verifies the scheme through a large number of experiments to ensure the feasibility of the implementation of the related method.

[0120] Specifically, for different types of wafers, or the same type of wafer after different manufacturing processes, the interface quality and interface characteristics will have certain differences. For example, for a thin film of the same material, it can be formed by multiple processes. Due to the different formation principles and formation rates, especially the different interface roughnesses. For example, for thin films of different materials, the formation principles and formation rates are also different, so the interface roughness is also different.

[0121] The roughness here is not the roughness introduced by simple production processes in the traditional manufacturing industry, which is in the order of angstroms, so it is usually difficult to distinguish. Generally, in order to distinguish the roughness of the interface, the prior art usually uses AFM (atomic force microscope) and the like to observe, and the AFM detection speed is slow and the detection requirement is high, and sometimes it cannot meet the needs of online detection. The difference in interface roughness is a very important indicator in the wafer production process, and in each production process of the wafer, the interface roughness may change with different manufacturing processes. If AFM is used for observation, the wafer needs to be taken off the production line for detection, and the detection efficiency is very low, so it cannot meet the needs of timely and effective judgment of the interface roughness state of the wafer to be tested.

[0122] In the present application, the wafer is detected based on the second harmonic, and the detection efficiency of the related detection method is high. Based on the detection requirement of the electrical characteristics, the wafer production line in the prior art is provided with a second harmonic detection device, so the needs of online detection can be effectively met. As described above, after the RA second harmonic detection or the RA-scan second harmonic detection is completed, the coefficient A (i.e. the value of the variable A) of the fitted characteristic curve can be used to represent the interface roughness of the sample, so as to distinguish different samples to be tested.

[0123] According to the prior art, it can be understood that, microscopically, atoms (or ions) in the crystal are arranged and stacked in a certain way, and the packing density of the atoms is different in different directions, which is manifested in macroscopic anisotropy of many properties. The applicant of the present application takes advantage of this characteristic and thinks of analyzing the collected second harmonic detection signal, thereby analyzing the roughness of the interface to be measured, and further analyzing the interface roughness at the pre-selected measurement point by using the second harmonic. Specifically, according to the research, the variable A in formula 1 is a coefficient that can reflect the electric dipole contribution at the pre-selected measurement point, which is sensitive to the interface roughness, so it can be used as a detection basis for analyzing the interface roughness.

[0124] Figures 3a to 3d are four schematic diagrams of roughness test results of different wafers using the variable A in formula 1, and the dots in each diagram represent the measurement points (i.e. Test Points) on the wafer. The horizontal and vertical axes in each diagram represent the size in millimeters.

[0125] As shown in Figures 3a to 3d , the schematic diagram of the roughness test results of the wafer generated by the detection results obtained by using the variable A in formula 1 can reflect the roughness detection state of different measurement points of different wafers, i.e. Figures 3a to 3d belongs to a wafer map. Specifically, Figures 3a to 3d is a wafer map generated after detecting the pre-set 13 measurement points on four wafers to be measured according to the method in the present embodiment and obtaining the value of the coefficient A in the related RA-scan characteristic curve. Each diagram can be used to represent the roughness level of the corresponding wafer surface. It should be noted that the color scale of the wafer map should have the specific value of the coefficient A corresponding to the color in the wafer map as a reference in the actual detection process, but to avoid the specific value of the detected value affecting the understanding of the scheme by those skilled in the art, the specific value on the color scale in the current picture is removed. However, the difference between the detection results can still be seen directly by the color difference between the wafer maps.

[0126] According to the differences between Figure 3a , Figure 3b , Figure 3c and Figure 3d , it can be seen that there are obvious differences between the test data of the four wafers to be measured. Specifically, the roughness levels of wafer 1 and wafer 2 are close, and there are obvious differences compared with the roughness levels of wafer 3 and wafer 4, which is called wafer-to-wafer difference. The main reason for the related difference is that the manufacturing processes of the four wafers to be measured are different, which may come from chemical mechanical grinding, chemical mechanical polishing, wet etching and other production processes, so the roughness of the wafer surface is different. The production process of the wafer to be measured can be determined by the roughness during detection.

[0127] Further, according to Figure 3a , Figure 3b , Figure 3c and Figure 3d It can be observed that the roughness distribution of the surfaces of the four wafers to be tested is relatively uniform. For some production processes, the wafer map of the wafer to be tested can intuitively reflect the difference in the roughness distribution of different positions on the surface of the wafer to be tested, which is referred to as intra-wafer difference, and also has certain reference value.

[0128] Based on the above analysis, by Figure 3a , Figure 3b , Figure 3c and Figure 3d It can be effectively verified that the variable A in formula 1 can effectively reflect the roughness of the wafer surface. It should be noted that Figure 3a , Figure 3b , Figure 3c and Figure 3d Only a part of the test examples is shown for the convenience of understanding and observation of those skilled in the art. In actual research and development, the applicant has made more tests to verify the related conclusions, which will not be listed one by one here.

[0129] The wafer detection method based on second harmonic in the embodiment can quickly and effectively distinguish the wafer roughness at the preselected test points, so as to judge the difference between the manufacturing processes, effectively meet the detection requirements, and the whole test process is non-contact detection, so it will not cause damage to the wafer. The overall scheme has the characteristics of good adaptability and easy implementation.

[0130] Embodiment 2:

[0131] The embodiment provides a wafer detection method based on second harmonic, comprising:

[0132] Obtaining a set of measured second harmonic detection signals at preselected test points in a sample to be tested, the set of measured second harmonic detection signals comprising: a plurality of second harmonic detection signals generated by the preselected test points after being irradiated by light sources from different azimuth angles; wherein the specific collection method of the related second harmonic detection signals is the same as that of embodiment 1, so the embodiment will not be described in detail.

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

[0134] According to the obtained lattice characteristic detection curve data, the state of the wafer at the preselected test point is determined.

[0135] In the embodiment, when the lattice characteristic detection curve data is fitted based on the P-polarized light in the plurality of second harmonic detection signals in the measured second harmonic detection signal set, the preset fitting algorithm includes the following formula 1:

[0136]

[0137] wherein, is a value of the second harmonic signal corresponding to the P-polarized light in the lattice characteristic detection curve data, is an azimuth angle of the light source when the light source is directed to the preselected measurement point, n is a preset constant, A and B are parameters for reflecting the state of the wafer at the preselected measurement point, and the first test target characteristic curve is constituted by the lattice characteristic detection curve data obtained based on the above formula 1.

[0138] In specific implementation, in the embodiment, the value of n can also be preset in the system by an operator according to detection needs. For example, when silicon material is detected, n = 4 when the surface at the preselected measurement point is a (001) surface in a cubic lattice.

[0139] In specific implementation, when the lattice characteristic detection curve data is obtained based on the formula 1, the state of the wafer at the preselected measurement point is determined based on the obtained lattice characteristic detection curve data, including the following steps:

[0140] The value of variable B in the first test target characteristic curve obtained based on the formula 1 is obtained.

[0141] The value of variable B is used to determine the difference between the production processes corresponding to the sample to be detected.

[0142] Through the operation step, the user can better select a suitable production process. For example, in the wafer research and development process, different manufacturing processes (such as adjusting the doping concentration of different components, changing the production method, etc.) can be tried to produce wafers, and different manufacturing processes can cause differences in the lattice characteristics of wafers, greatly affecting the detected second harmonic detection signal, and thus causing the variable B in formula 1 fitted based on the second harmonic detection signal to change.

[0143] That is, according to the test confirmation, the value of variable B is related to the lattice constant of the measured target, and the lattice constant is related to the difference in the production process of the sample to be measured. Based on the relevant characteristics, the user can characterize the corresponding equivalent lattice constant by the obtained value of variable B, so as to judge whether there is a difference between the selected wafer production processes. The difference between the production processes mentioned here can include the difference between the selected processes during manufacturing, or the difference between different samples or different measurement points when the same production process is selected.

[0144] The application of specifically using the value of variable B to reflect the difference between the production processes corresponding to the sample to be measured can include the following examples:

[0145] For example, the user can determine the production process used to produce the measured point according to the threshold interval of the value of variable B; or

[0146] If the user determines that the wafer manufactured by a certain production process meets the requirements, when the detected value of variable B does not match the expected value, it can be understood that the currently used production process has changed. That is, the detection method plays a "monitoring" role. It should be noted that this embodiment mainly reflects whether the production process has changed, so that the operator can quickly trace back the relevant operation steps that caused the change. However, it is not intended to accurately detect the specific operation process or the influencing factors in the related process by the value of variable B.

[0147] In implementation, wafers processed by different production processes (the wafers mentioned in this paper can be wafers after production, or parts obtained in a certain processing step during wafer production) can be obtained respectively, and then the values of B corresponding to these wafer samples can be detected respectively to determine the values of variable B corresponding to different production processes. In addition, based on the known performance of the wafer, it can be determined that the value of variable B is within a certain threshold range, and the equivalent lattice constant and the wafer processed by the related production process meet the user's requirements. The related operation is mainly used to anchor the correspondence between the value of variable B and the wafer production process. The specific wafer performance detection can be determined by using other detection schemes in the prior art.

[0148] In implementation, when the lattice characteristic detection curve data is obtained based on the formula 1, the determination of the state of the wafer at the preselected measurement point based on the obtained lattice characteristic detection curve data can further include the following steps:

[0149] Obtaining the value of variable B in the first test target characteristic curve obtained based on the formula 1;

[0150] According to the value of the variable B, determining the state of the wafer at the pre-selected measurement point comprises determining the state of the lattice feature at the pre-selected measurement point.

[0151] According to the value of the variable B, determining the state of the wafer at the pre-selected measurement point comprises determining the state of the lattice feature at the pre-selected measurement point.

[0152] Determining the threshold interval into which the value of the variable B falls.

[0153] According to the threshold interval into which the value of the variable B falls, determining the state of the lattice feature at the pre-selected measurement point.

[0154] Based on the detected state of the wafer at each pre-selected measurement point in the sample to be measured, generating a wafer map to represent the overall performance level of the sample to be measured.

[0155] Specifically, during detection, whether the wafer meets the production requirements can be determined by determining the threshold interval into which the value of the variable B falls.

[0156] In actual applications, the proportion of elements in the production of wafers will affect the state of the lattice, which should be manifested as a change in the lattice constant d (which can also be regarded as an equivalent lattice constant d'), and the embodiment can reflect the equivalent lattice constant d' through the value of the variable B. Therefore, during actual testing, the proportion of X elements (i.e., a certain element that constitutes the wafer to be measured) can be indirectly reflected by analyzing the value of the variable B to determine whether the wafer is produced according to the predetermined doping ratio.

[0157] The related detection can be obtained by analyzing the lattice characteristic detection curve data, thereby having the characteristics of high detection efficiency.

[0158] The principles of the embodiment will be further analyzed below to demonstrate the feasibility of the scheme:

[0159] According to existing theoretical research, the lattice constant d can be used to represent some characteristics of the lattice, and according to existing literature, the second-order polarizability X 2 is related to the lattice constant d, and the second-harmonic signal intensity I(2ω) changes with the azimuth angle and the second-order polarizability X 2 are related. Therefore, the second-harmonic signal intensity I(2ω) changes with the azimuth angle of the curve (referred to as a characteristic curve, the same below) can be used to represent the second-order polarizability X 2, so as to indirectly compare the lattice constant d. For the convenience of expression, the indirect comparison of the lattice constant d can be regarded as obtaining an equivalent lattice constant d' according to the second harmonic detection result, the equivalent lattice constant d' is used to represent the overall influence of all lattices in the resolution range of the second harmonic detection (the lattice constant of each single lattice is not necessarily d', but the overall performance is equivalent to the performance when the lattice constant of all lattices is equal to d'), so it can reflect the overall lattice quality level of the point to a certain extent.

[0160] Based on the above principle, the applicant tries to use the lattice characteristic detection curve data fitted according to the second harmonic detection signal to reflect the transformation of the equivalent lattice constant, and then infer whether there is a difference in the process.

[0161] According to the verification by experiments and the like, the value of the variable B is proportional to the second-order susceptibility χ (2)Q of the wafer, that is, according to the value of the variable B, a reference value of the second-order susceptibility χ (2)Q of the wafer can be obtained.

[0162] Specifically, when the composition and its proportion in the wafer lattice change, the lattice constant d of the wafer will change. The relationship between the second-order susceptibility χ (2)Q (that is, χ (2) in the following formula) and the lattice constant d is as follows:

[0163]

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

[0165] Based on the above formula, when the composition and its proportion in the wafer lattice change, the lattice constant d changes, so that the second-order susceptibility χ (2)Q of the wafer changes.

[0166] Based on the related characteristics, the applicant tries to find a method that can quickly and effectively detect the lattice characteristics of the target to be measured by using the second harmonic detection signal. The applicant determines that the value of the variable B in formula 1 can effectively reflect the equivalent lattice constant, and then the value of the variable B can be used to reflect the lattice characteristics at the pre-selected measurement point. The relationship between the value of the variable B and the lattice constant d can be embodied by the following formula 5:

[0167] B∝1 / d 4 Formula 5;

[0168] That is, when the composition and its proportion in the wafer lattice change, the lattice constant d changes, so that the second-order susceptibility of the wafer changes, and finally the value of the variable B obtained by RA-SHG fitting changes, and the logical relationship can be referred to Figure 4aThe value of variable B can be used to monitor the composition in the wafer lattice according to the value of variable B. In particular, for a wafer composed of only two elements, the proportion can be determined according to the value of variable B, that is, the value of variable B can be used to determine whether the element doping ratio in the wafer production process meets the requirements.

[0169] Based on the difference in the selection of different composition elements and composition ratios, the value of variable B may still be the same, so sometimes the value of variable B cannot be used to determine whether the wafer meets the requirements, and sometimes a comprehensive judgment is made in combination with the goodness of fit. The value of variable B is used to represent the lattice itself parameter, that is, the lattice constant or the equivalent lattice constant, so as to assist the tester to calculate part of the key process parameters under the preset conditions.

[0170] Through this embodiment, the lattice characteristics of the sample to be tested can be analyzed to determine whether the related production process meets the expectation in time, thereby meeting the requirement of rapid detection.

[0171] Embodiment 3:

[0172] The embodiment provides a wafer detection method based on second harmonic, which comprises the following steps:

[0173] Obtaining a measured second harmonic detection signal set at a preselected measurement point in a sample to be tested, the measured second harmonic detection signal set comprising: a plurality of second harmonic detection signals generated by the preselected measurement point after being irradiated by light sources from different azimuth angles and being excited;

[0174] Based on a preset fitting algorithm, fitting processing is performed on a plurality of second harmonic detection signals in the measured second harmonic detection signal set, and lattice characteristic detection curve data is obtained;

[0175] According to the obtained lattice characteristic detection curve data, the state of the wafer at the preselected measurement point is determined;

[0176] When the lattice characteristic detection curve data is obtained based on P-polarized light in the plurality of second harmonic detection signals in the measured second harmonic detection signal set, the preset fitting algorithm comprises the following formula 1:

[0177] Formula 1:

[0178]

[0179] Wherein, is the value of the second harmonic signal corresponding to P-polarized light in the lattice characteristic 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 with 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 measuring 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 measuring 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] Assuming that the center points on the samples 1, 2, 3 and 4 are detected, according to experience, the acceptable interval of the goodness of fit R 2 is greater than or equal to 0.8, the reference range of the coefficient B (i.e. the value of the variable B) is 30-80, and the detection result is as follows according to the detection:

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

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

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

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

[0197] Among them, it can be known through analysis that the goodness of fit of sample 1 and sample 2 meets the acceptable interval, so it can be judged that the lattice defect level of sample 1 and sample 2 is low, which belongs to the acceptable range, while the goodness of fit of sample 3 and sample 4 does not fall into the acceptable interval, so it can be judged that the lattice defect level of sample 3 and sample 4 is high, which does not belong to the acceptable range, and the process needs to be improved;

[0198] The coefficient corresponding to the lattice property of sample 1 and sample 3 is in the normal interval; the coefficient value corresponding to the lattice property of sample 4 is abnormal and needs to be adjusted; the coefficient corresponding to the lattice property of sample 2 is at the critical value and needs to be further monitored.

[0199] Therefore, by comprehensively analyzing the lattice defect level and the lattice property, for sample 3, although the conclusion is that the coefficient is normal, after improving the process to reduce the defect level, it is unknown whether the value of the variable B can remain at the current level, so only sample 1 of the above four samples meets the detection standard and is considered qualified.

[0200] Here, it can be understood that the goodness of fit R 2 in the acceptable interval is a prerequisite for the value of the variable B to be reliable, if the goodness of fit R 2 does not meet the requirements, then even if the value of the variable B falls into the target interval, the wafer may have abnormal problems.

[0201] Among them, the order of obtaining the goodness of fit R 2 and the value of the variable B does not affect the detection result, therefore, the order of the detection of the state of the lattice characteristics and the detection of the influence of the lattice distortion and / or stress at the pre-selected detection point is not limited in the present application. That is, the embodiment utilizes the goodness of fit R 2For characterizing the defect level, the coefficient B can reflect the lattice symmetry, and the coefficient B can reflect the lattice parameter, i.e. the lattice constant or the equivalent lattice constant, so as to calculate some key process parameters under preset conditions.

[0202] It should be noted that the above examples are only for fitting goodness R 2 The value of the variable B is applied to the analysis example. In actual application, according to the detection requirement, it is not necessary to analyze the value of R 2 or B can also determine whether the lattice distortion and / or stress effect at the preselected measurement point is within the acceptable range, or when A or B is calculated separately to meet the detection requirement, it is not necessary to analyze the fitting goodness R 2 .

[0203] By using this embodiment, based on the second harmonic detection signal, more efficient and rapid detection can be realized to detect the lattice defect level as soon as possible.

[0204] Based on the state of the wafer at each preselected measurement point in the sample to be measured, a wafer chart is generated to represent the overall performance level of the sample to be measured.

[0205] Embodiment 4:

[0206] This embodiment provides a wafer detection method based on second harmonic, and the basic principle is similar to that of the method in embodiment 2. It can also be used to analyze the state of the lattice characteristics at the preselected measurement point. The main difference is that the implementation of the technical solution in this embodiment is mainly based on S-polarized light in the second harmonic detection signal.

[0207] Specifically, the wafer detection method of this embodiment comprises:

[0208] Obtaining a set of measured second harmonic detection signals at the preselected measurement point in the sample to be measured, the set of measured second harmonic detection signals comprising a plurality of second harmonic detection signals generated by the preselected measurement point after being irradiated by light sources from different azimuth angles; wherein, in specific implementation, the set of measured second harmonic detection signals at the preselected measurement point can be obtained by the operations mentioned in embodiments 1 and 2, and the corresponding signal collection method is not described in this embodiment.

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

[0210] When the lattice characteristic detection curve data is fitted based on S-polarized light in the plurality of second harmonic detection signals in the set of measured second harmonic detection signals, the preset fitting algorithm comprises the following formula 2:

[0211]

[0212] wherein, is a value of a second harmonic signal corresponding to S-polarized light in the lattice characteristic detection curve data, is an azimuth angle of the light source when the light source is directed to the preselected measurement point corresponding to the value of the second harmonic signal corresponding to S-polarized light, n is a preset constant, C is a coefficient for reflecting a state of the wafer at the preselected measurement point, D is a direct current offset, and a second test target characteristic curve is constituted by the lattice characteristic detection curve data obtained based on the above-mentioned formula 2; wherein the direct current offset D is a constant, the specific value of the direct current offset D is a variable generated by fitting based on the detection data, and generally the value of the direct current offset D is greater than or equal to 0, and under an ideal model, the direct current offset D is equal to 0.

[0213] In specific implementation, the value of n in this embodiment can also be preset in the system by an operator according to detection needs. For example, when silicon material is detected, n = 4 when the surface at the preselected measurement point is a (001) plane in a cubic lattice.

[0214] According to the obtained lattice characteristic detection curve data, the state of the wafer at the preselected measurement point is determined, wherein when the lattice characteristic detection curve data is obtained based on the formula 2, the state of the wafer at the preselected measurement point is determined according to the obtained lattice characteristic detection curve data, including the following steps:

[0215] The value of the variable C in the second test target characteristic curve obtained based on the formula 2 is obtained;

[0216] According to the value of the variable C, the difference between the production processes corresponding to the sample to be detected is determined.

[0217] Through this operation step, the user can better select a suitable production process, as in the wafer development process, different production processes (such as adjusting the doping concentration of different components, changing the production method, etc.) can be tried to produce wafers, and different production processes can cause great differences in the lattice characteristics of the produced wafers, and the related lattice differences will greatly affect the detected second harmonic detection signal, which will in turn cause the variable C in formula 2 to change based on the related characteristics. The user can obtain the value of the variable C to represent the corresponding equivalent lattice constant, so as to determine whether there is a difference between the selected wafer production processes, and the difference between the production processes mentioned here can include the difference between the processes selected during manufacturing, and can also include the difference between different samples or different measurement points when the same production process is selected.

[0218] Specifically, applications that use the value of variable C to reflect the differences between the production processes corresponding to the tested samples may 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] According to the verification by experiments and the like, the value of the variable C is proportional to the effective second-order polarizability of the block That is And B = f c C, wherein f c is the effective Fresnel coefficient of the sample to be measured. The value of the variable B can reflect the characteristics of the lattice at the preselected measurement point, and the control relationship between the value of the variable B and the value of the variable C can know that, during detection, the composition in the wafer lattice can be monitored according to the value of the variable C. Especially for wafers composed of only two elements, the proportion can even be judged according to the value of the variable C, that is, the value of the variable C can be used to judge whether the element doping ratio in the wafer production process meets the requirements, and effectively monitor the composition and its proportion change in the wafer lattice. Correspondingly, the logical relationship can be referred to as shown in Figure 4b

[0236] Similar to the variable B, sometimes the value of the variable C cannot directly determine whether the wafer meets the requirements, and sometimes a comprehensive judgment is also made in combination with the goodness of fit. The value of the variable C is used to represent the lattice itself parameter, that is, the lattice constant or the equivalent lattice constant, so as to assist the tester to calculate part of the key process parameters under the pre-set conditions. If necessary, in order to improve the reliability of the detection result, the values of the variables B and C can also be used to evaluate the level of the key process parameters.

[0237] Through the embodiment, the lattice characteristics of the sample to be measured can be analyzed, so as to determine whether the related production process meets the expectation in time. The requirement of rapid detection is met.

[0238] Meanwhile, the inventor also uses a large number of experiments to verify the related method, and confirms the feasibility of the scheme.

[0239] Through the embodiment, the lattice characteristics of the sample to be measured can also be analyzed, so as to determine whether the related production process meets the expectation in time. The requirement of rapid detection is met.

[0240] Embodiment 5:

[0241] The embodiment provides a wafer detection method based on second harmonic, comprising:

[0242] Obtaining a measured second harmonic detection signal set at a preselected measurement point in a sample to be measured, the measured second harmonic detection signal set comprising: a plurality of second harmonic detection signals generated by the preselected measurement point after being irradiated by light sources from different azimuth angles; each second harmonic detection signal can also be collected in the manner mentioned in the above embodiment 1;

[0243] Based on a pre-set fitting algorithm, a plurality of second harmonic detection signals in the measured second harmonic detection signal set are fitted and processed to obtain lattice characteristic detection curve data; ​

[0244] According to the obtained lattice characteristic detection curve data, the state of the wafer at the preselected measurement point is determined.

[0245] When the lattice characteristic detection curve data is fitted based on the S-polarized light in the plurality of second harmonic detection signals in the measured second harmonic detection signal set, the preset fitting algorithm includes the following formula 2:

[0246]

[0247] Wherein, is the value of the second harmonic signal corresponding to the S-polarized light in the lattice characteristic detection curve data, is the azimuth angle of the light source when the value of the second harmonic signal corresponding to the S-polarized light is illuminated to the preselected measurement point, n is a preset constant, C is a coefficient for reflecting the state of the wafer at the preselected measurement point, D is a direct current offset, which is a variable, and generally the value of the direct current offset D is greater than or equal to 0, and the lattice characteristic detection curve data obtained based on the above formula 2 constitutes a second test target characteristic curve.

[0248] According to the fitting degree of the second test target characteristic curve and the preset second reference lattice characteristic detection curve data, it is determined whether the lattice distortion and / or stress effect at the preselected measurement point is within an acceptable range.

[0249] Wherein, the second reference lattice characteristic detection curve data is curve data fitted by substituting the S-polarized light in the plurality of reference second harmonic detection signals in the reference second harmonic detection signal set into the above formula 2.

[0250] The judgment method of whether the lattice distortion and / or stress effect at the preselected measurement point in this embodiment is within an acceptable range can be implemented in combination with the lattice characteristic verification method in embodiment 4, so as to more comprehensively analyze the wafer.

[0251] In order to better illustrate, the following will be specifically described in combination with some experiments in the research and development process:

[0252] Figure 6a 、 Figure 6b 、 Figure 6c and Figure 7 are four test result diagrams generated in combination with formula 2. Figures 6a to 7 Respectively embody the relationship between the S-polarized second harmonic (SHG) signal and the RA-SHG azimuth angle under the P-polarized light incident condition (i.e. Figures 6a to 7 The horizontal axis of represents the azimuth angle, unit: degree; the vertical axis represents the value of the second harmonic signal). Among them, Figures 6a to 7The middle data points are actually collected data, and the curve is a curve fitted according to formula 2 based on the collected data points.

[0253] Wherein, the lattice quality can be reflected by the goodness of fit between the actually collected data and the fitted curve, and the value of the variable C obtained after fitting is related to part of the performance parameters of the sample to be measured.

[0254] In the example with low goodness of fit, the fitting degree between the actually collected data and the fitted curve will be poor, such as the first peak in each period may be low, the second peak may be high, and the symmetry degree may be poor, which can indicate that the lattice quality of the wafer in this example is poor, and the azimuth angles corresponding to the two peaks are about 45 degrees, which is guessed to be due to the existence of some defects in the crystal. Therefore, even if the value of the variable C meets the expectation, it does not mean that the related lattice state meets the requirements, that is, the reliability of the coefficient C is reduced.

[0255] And in the example with high goodness of fit, the fitting degree between the actually collected data and the fitted curve will be good, and the related example can refer to the example with high goodness of fit in the figure Figure 7 , Figure 7 The overall curve is more consistent with the theoretical curve, indicating that the lattice quality is good, and the value of the variable C can be used to represent the relative level of part of the performance parameters of the sample to be measured.

[0256] It should be noted that the second harmonic (SHG) signal of S polarization is obviously weaker than the second harmonic (SHG) signal of P polarization, and in some use scenarios, it is seriously disturbed by noise and has low signal-to-noise ratio, so it is more suitable for verifying other detection results.

[0257] Similarly, it should be noted that the process of judging the state of the lattice characteristics by the value of the variable C in this embodiment has no order requirement with the process of judging the defect condition by the goodness of fit. In some embodiments, only one of the detection processes can be performed.

[0258] In specific implementation, the state of the wafer at each preselected measurement point in the sample to be measured can also be detected to generate a wafer chart to represent the overall performance level of the sample to be measured.

[0259] Through this embodiment, the lattice characteristics of the sample to be measured can also be analyzed to determine whether the related production process meets the expectation in time, meeting the demand for rapid detection.

[0260] Embodiment 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 Equation 3 below. 2 Value:

[0265]

[0266] Among them, Y actual Y is the measured value of the second harmonic signal in the measured second harmonic detection signal set corresponding to the first preset azimuth angle. 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. 2Indirectly represent the matching degree of the detection result and the expected target, thereby indirectly reflecting the characteristics of the lattice, effectively achieving the purpose of detection,

[0271] The following will further analyze the fitting degree R of the characteristic curve in this scheme 2 The implementation and principle of characterizing the good or bad of the lattice quality at the measurement point (i.e., characterizing the degree of overall influence of stress and defects):

[0272] The theoretical characteristic curve is the curve obtained by detecting the perfect lattice (which can constitute the reference lattice characteristic detection curve), which is consistent with the theoretical derivation result. Assuming that the characteristic curve actually measured for the sample to be measured is completely coincident with the theoretical curve, the fitting degree calculated at this time is: R 2 =1, so it can be considered that the lattice structure of the measurement point is completely consistent with the ideal situation, which means that there is no defect or stress influence on the measurement point;

[0273] Through practice, it can be found that the sample produced in actual situation must have certain defects or stress influence, correspondingly, the greater the influence of defects or stress, the more the measured characteristic curve deviates from the theoretical curve, correspondingly, the lower the value of the fitting degree R 2 of the detection obtained, that is, the farther away from the theoretical curve.

[0274] In order to facilitate understanding, the following will combine Figure 8a and Figure 8b to embody the fitting state diagram under different conditions (the orange points in the figure are the actually detected measurement points, and the blue curve is the fitting curve). Among them, Figure 8a is the fitting state diagram when the fitting effect is good, the fitting degree of the detection result in this diagram state is: R 2 =1 (this diagram is designed for users to understand, and is not the actually detected diagram), as can be seen from the diagram, the actual detected measurement points in this example have a higher matching degree with the fitting result; and Figure 8b is the fitting state diagram when the fitting effect is poor, the fitting degree of the detection result in this diagram state is: R 2 =0.83, as can be seen from the diagram, the actual detected measurement points in this example have a lower matching degree with the fitting result, and it can be judged that Figure 8a corresponding wafer has better lattice quality than Figure 8b corresponding wafer.

[0275] In the actual data processing process, the change of the fitting degree R 2 is not completely linear, which needs to be judged according to the actual situation.

[0276] For the detection of actual samples, a fitting degree R 2a reference value, for example:

[0277] When the goodness of fit R 2 is greater than or equal to 0.9, it is considered that the lattice defects or stress effects are within an acceptable range, the detection is passed, and it is indicated that the process is not abnormal.

[0278] When the goodness of fit R 2 is less than 0.9, it is considered that the lattice defects or stress effects reach a certain degree, and further judgment of the specific type and cause of the defects is needed.

[0279] The value of 0.9 is not fixed and can be appropriately adjusted according to process conditions, yield requirements, and other factors.

[0280] In actual detection, for different samples to be tested, especially for samples to be tested after different processes, the properties such as lattice structure or element ratio may change (lattice defects, impurities, or stress distribution changes may be introduced to cause lattice distortion), thereby causing the lattice constant to change. Therefore, the characteristic curve may not be well matched with the theoretical formula. Based on the related characteristics, the goodness of fit R 2 of the characteristic curve in this application indirectly indicates the matching degree and can also reflect the characteristics of the lattice.

[0281] It should be noted that the detection application cannot directly qualitatively or quantitatively judge the real level of defects or stress, such as the specific defect type, the size of the stress, and the degree of lattice distortion, but can determine the relative level to judge whether the defect or stress level is within an acceptable range. The detection method of this embodiment can achieve the purpose of rapid detection.

[0282] Embodiment 7:

[0283] This embodiment provides a wafer detection method based on second harmonic, comprising:

[0284] Obtaining a set of measured second harmonic detection signals at a preselected measurement point in the sample to be tested, the set of measured second harmonic detection signals comprising a plurality of second harmonic detection signals generated by the preselected measurement point after being irradiated by light sources from different azimuth angles; The second harmonic detection signals can be obtained in the manner of embodiment 1, which will not be described herein.

[0285] Based on a predetermined fitting algorithm, the plurality of second harmonic detection signals in the set of measured second harmonic detection signals are fitted and processed to obtain lattice characteristic detection curve data.

[0286] According to the obtained lattice characteristic detection curve data, the state of the wafer at the preselected measurement point is determined.

[0287] When the lattice characteristic detection curve data is fitted based on the P-polarized light of a plurality of the second harmonic detection signals in the measured second harmonic detection signal set, the preset fitting algorithm includes the following formula 1:

[0288]

[0289] wherein, is a value of the second harmonic signal corresponding to the P-polarized light in the lattice characteristic detection curve data, is an azimuth angle of the light source when the light source is directed to the preselected measurement point corresponding to the value of the second harmonic signal corresponding to the P-polarized light, n is a preset constant, A and B are coefficients for reflecting the state of the wafer at the preselected measurement point, and the first test target characteristic curve is constituted by the lattice characteristic detection curve data obtained based on the above formula 1.

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

[0291] When the lattice characteristic detection curve data is obtained based on the formula 1, the state of the wafer at the preselected measurement point is determined according to the obtained lattice characteristic detection curve data, including the following steps:

[0292] Obtaining a value of variable A in the first test target characteristic curve obtained based on the formula 1;

[0293] According to the value of the variable A, the state of the wafer at the preselected measurement point includes the following steps:

[0294] According to the value of the variable A, the state of the wafer at the preselected measurement point includes the following steps:

[0295] Judging the threshold interval in which the value of the variable A falls;

[0296] According to the threshold interval in which the value of the variable A falls, the interface roughness state at the preselected measurement point is determined.

[0297] When the lattice characteristic detection curve data is obtained based on the formula 1, the state of the wafer at the preselected measurement point is determined according to the obtained lattice characteristic detection curve data, including the following steps:

[0298] Obtaining a value of variable B in the first test target characteristic curve obtained based on the formula 1;

[0299] According to the value of the variable B, the difference between the production processes corresponding to the sample to be measured is determined.

[0300] When the lattice characteristic detection curve data is obtained based on the formula 1, the step of determining the state of the wafer at the preselected measurement point according to the obtained lattice characteristic detection curve data comprises the following steps:

[0301] obtaining the value of the variable B in the first test target characteristic curve based on the formula 1;

[0302] According to the value of the variable B, determining the state of the wafer at the preselected measurement point comprises the state of the lattice characteristic at the preselected measurement point.

[0303] According to the value of the variable B, determining the state of the wafer at the preselected measurement point comprises the state of the lattice characteristic at the preselected measurement point.

[0304] determining the threshold interval to which the value of the variable B falls;

[0305] According to the threshold interval to which the value of the variable B falls, determining the state of the lattice characteristic at the preselected measurement point.

[0306] Based on the following formula 3, the value of the goodness of fit R 2 at the preselected measurement point in the sample to be measured is obtained:

[0307]

[0308] wherein Y actual is the measured value of the second harmonic signal corresponding to the first preset azimuth angle in the measured second harmonic detection signal set, Y predict is the fitted value of the second harmonic signal corresponding to the first preset azimuth angle in the lattice characteristic detection curve data, Y mean is the average value of the measured values of a plurality of second harmonic detection signals in the measured second harmonic detection signal set;

[0309] According to the value of the goodness of fit R 2 , it is determined whether the lattice distortion and / or stress influence at the preselected measurement point is within the acceptable range.

[0310] 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.

[0311] The wafer detection method further comprises:

[0312] Based on the detected state of the wafer at each preselected measurement point in the sample to be measured, a wafer map is generated to represent the overall performance level of the sample to be measured.

[0313] The values of variables A, B and the goodness of fit R are used in this embodiment to determine the state of the wafer at the preselected point, effectively satisfying the detection of wafer surface roughness, the state of lattice characteristics and the effects of lattice distortion and / or stress. 2 The values of variables A, B and the goodness of fit R are used in this embodiment to determine the state of the wafer at the preselected point, effectively satisfying the detection of wafer surface roughness, the state of lattice characteristics and the effects of lattice distortion and / or stress.

[0314] In particular implementation, the detection result of the state of the lattice characteristics can also be verified by the following steps:

[0315] When the S-polarized light is used to fit the plurality of second harmonic detection signals in the set of second harmonic detection signals to obtain the lattice characteristic detection curve data, the preset fitting algorithm includes the following formula 2:

[0316]

[0317] wherein, is the value of the second harmonic signal corresponding to the S-polarized light in the lattice characteristic detection curve data, is the azimuth angle of the light source when the light source is directed to the preselected point corresponding to the value of the second harmonic signal corresponding to the S-polarized light, n is a preset constant, C is a coefficient for reflecting the state of the wafer at the preselected point, and D is a direct current offset, and the second test target characteristic curve is constituted 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 the formula 2, the determination of the state of the wafer at the preselected point based on the obtained lattice characteristic detection curve data includes the following steps:

[0319] Obtaining the value of variable C in the second test target characteristic curve obtained based on the formula 2;

[0320] Determining the difference between the production processes corresponding to the sample to be tested according to the value of variable C;

[0321] Obtaining the value of variable C in the second test target characteristic curve obtained based on the formula 2;

[0322] Determining the state of the wafer at the preselected point according to the value of variable C, which includes the state of the lattice characteristics at the preselected point.

[0323] The determination of the state of the wafer at the preselected point according to the value of variable C, which includes the state of the lattice characteristics at the preselected point, includes the following steps:

[0324] Judging the threshold interval in which the value of variable C falls;

[0325] According to the value of the variable C falling into which threshold interval, the state of the lattice feature at the preselected measurement point is determined.

[0326] The detection result can be further verified through the related steps to improve the accuracy of the detection result.

[0327] The interface roughness state, the state of the lattice feature at the preselected measurement point, and the detection of the lattice distortion and / or stress influence at the preselected measurement point do not have a sequence requirement, and the user can design the detection sequence and detection items according to the detection requirements, and are not limited to the above writing sequence.

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

[0329] Based on the state of the wafer at each preselected measurement point in the to-be-detected sample obtained through detection, a wafer map is generated to represent the overall performance level of the to-be-detected sample.

[0330] In this embodiment, the wafer map is used to reflect the distribution rule of the overall performance of the wafer.

[0331] For a measurement point, the feature curve obtained through RA or RA-scan can reflect the detection results of the above applications, and for a to-be-detected wafer, according to the detection requirements, a plurality of measurement points are selected to reflect the overall performance level of the to-be-detected wafer.

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

[0333] In this embodiment, the detection method of the present application can be embodied in the wafer map, so that the above-mentioned phenomenon can be more intuitively observed by those skilled in the art, but the specific causes of the detection results and subsequent improvement means need to be analyzed by those skilled in the art in combination with the actual situation.

[0334] Meanwhile, for the above several detection items, one of them can be selected for special analysis during actual implementation, or a plurality of them can be comprehensively analyzed at the same time to realize online monitoring. The specific situation should be determined by the requirements of the to-be-detected sample or the to-be-monitored production process. For different to-be-detected samples or to-be-monitored production processes, those skilled in the art can obtain the most reasonable and perfect detection method (such as detection sequence, judgment condition, etc.) based on theoretical optimization, which is based on the application of the multiple RA or RA-scan second harmonic detection proposed in the present application.

[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 further analysis to determine the causes and 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 detection module is configured to receive the second harmonic signal generated after the light source irradiates the sample to be measured, and to perform the second harmonic-based wafer detection method according to any one of embodiments 1 to 7.

[0352] The operation flow of the second harmonic-based wafer detection system in this embodiment when performing the above method can refer to Figure 9 The operation flow of the second harmonic-based wafer detection system in this embodiment when performing the above method can refer to

[0353] Loading the sample to be measured;

[0354] Using the second harmonic detection method of RA second harmonic detection or RA-scan, a set of actual second harmonic detection signals of the measurement point on the sample to be measured is obtained;

[0355] Based on the preset fitting algorithm, a plurality of second harmonic detection signals in the set of actual second harmonic detection signals are fitted to obtain lattice characteristic detection curve data;

[0356] At least one key coefficient of the coefficients A / B / C and the goodness of fit R in the corresponding lattice characteristic detection curve data of the measurement point is obtained to detect the related state of the measurement point that needs to be detected; 2

[0357] Continue to detect other measurement points, and after completion, draw a wafer map (i.e., a wafer map) according to the different key coefficients to intuitively show the detection results.

[0358] Using the second harmonic-based wafer detection system in this embodiment, the detection of the wafer can be more quickly and effectively completed, and the detection of the lattice characteristics can be realized.

[0359] The second harmonic-based wafer detection method and system of the present application have the following advantages:

[0360] ​The wafer detection method and system based on second harmonic of the present application can obtain the measured second harmonic detection signal set at the preselected measurement point in the sample to be measured, and perform fitting processing on the plurality of second harmonic detection signals in the measured second harmonic detection signal set, so as to determine the state of the wafer at the preselected measurement point according to the obtained lattice characteristic detection curve data. Since the related operations are all performed based on the second harmonic detection signal, and the wafer detection system for realizing the second harmonic scanning for detecting the electrical characteristic parameters of the wafer in the prior art can be directly arranged on the production line of the wafer generation, and has the characteristics of fast signal acquisition speed, when the wafer is detected by the second harmonic during production, the lattice characteristics of the wafer can be determined more quickly, and since the detection can be completed without moving the sample to be measured, the requirement for faster detection can be met, and online detection can be realized. At the same time, when the related method is executed, no contact with the sample to be measured is generated, so the overall method is a non-destructive detection scheme, and the sample to be measured does not need to be transported, the complexity of repeatedly adjusting the detection position due to contact is avoided, and the operation process is more convenient. The wafer detection method and system based on second harmonic of the present application have the characteristics of high detection efficiency, fast response speed, good performance, and good adaptability.

[0361] The preferred embodiments of the present application are described in detail above. It should be understood that those skilled in the art can make many modifications and changes to the present application without creative labor based on the concept of the present application. Therefore, any technical solution obtained by logical analysis, reasoning or limited experiment based on the concept of the present application and the prior art should be within the protection scope determined 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.

2. The wafer inspection method based on second harmonics according to claim 1, characterized in that, 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: 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.

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

4. The wafer inspection method based on second harmonics according to claim 2, 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 value of variable A in the first test target feature curve obtained based on Equation 1; 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; 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. Determine the threshold range into which the value of variable A falls; 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.

5. The wafer inspection method based on second harmonics according to claim 2, 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 value of variable B in the first test target feature curve obtained based on Equation 1; Based on the value of variable B, the differences between the production processes corresponding to the test samples are determined.

6. The wafer inspection method based on second harmonics according to claim 2, 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 value of variable B in the first test target feature curve obtained based on Equation 1; 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; 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. Determine the threshold range into which the value of variable B falls; 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.

7. The wafer inspection method based on second harmonics according to claim 2, 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.

8. The wafer inspection method based on second harmonics according to claim 1, characterized in that, 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: 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.

9. The wafer inspection method based on second harmonics according to claim 8, characterized in that, When the surface at the pre-selected measurement point is the (001) plane in a cubic lattice, n = 4.

10. The wafer inspection method based on second harmonics according to claim 8, 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 value of variable C in the second test target feature curve obtained based on Equation 2; 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; 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: Determine the threshold range into which the value of variable C falls; 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.

11. The wafer inspection method based on second harmonics according to claim 8, 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 value of variable C in the second test target feature curve obtained based on Equation 2; Based on the value of variable C, the differences between the production processes corresponding to the test samples are determined.

12. The wafer inspection method based on second harmonics according to claim 8, 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.

13. The wafer inspection method based on second harmonics according to claim 1, characterized in that, The method further includes: 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: 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; 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.

14. The wafer inspection method based on second harmonics according to claim 13, 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.

15. The wafer inspection method based on second harmonics according to any one of claims 1 to 14, 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.

16. The wafer inspection method based on second harmonics according to any one of claims 1 to 14, 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.

17. The wafer inspection method based on second harmonics according to any one of claims 1 to 14, 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.

18. A wafer inspection system based on second harmonics, characterized in that, The wafer inspection system is used to perform the second harmonic-based wafer inspection method according to any one of claims 1 to 17.

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