Second harmonic characterization method, characterization optical system based thereon, and detection device

Abstract

The present invention provides a second harmonic characterization method, a characterization optical system based thereon, and a detection device. After selecting a scanning point on the surface of a sample to be detected, the second harmonic characterization method continuously tunes the wavelength of the fundamental frequency light from a first set wavelength to a second set wavelength by tuning the wavelength of the fundamental frequency light. After each tuning of the wavelength of the fundamental frequency light, the fundamental frequency light with the tuned wavelength is incident on the scanning point, and the second harmonic signal generated by the wavelength-tuned fundamental frequency light is collected; then, based on the collected second harmonic signal, a nonlinear spectrum of the second harmonic signal is plotted. Through the nonlinear spectrum of the second harmonic signal, the different defect types, the defect energy levels of different defect types, and the fundamental frequency light wavelengths corresponding to different defect types of the scanning point during this scanning process can be obtained. The second harmonic is used to effectively characterize lower defect densities, and the relevant parameters of the sample to be detected can be extracted in a targeted manner, shortening the time spent extracting relevant device parameters.

Description

Technical Field

[0001] The present invention relates to the field of characterizing semiconductor materials and devices using nonlinear optical effects between materials and lasers, and in particular to a second harmonic characterization method, a characterization optical system based thereon, and a detection device. Background Art

[0002] As the feature size of semiconductor devices continues to decrease, defects in microelectronic devices, especially those at the channel interface, have an increasingly serious negative impact on their performance and reliability. Therefore, characterizing defects at the channel interface is extremely important. Second harmonic generation (SHG) can exploit the nonlinear effect between high-energy lasers and semiconductor materials to perform non-contact, rapid, and non-destructive characterization of defects at interfaces. Device characteristic parameters can be extracted based on SHG variations with various parameters. The time constant extracted from the time-dependent SHG signal (TD-SHG) can be used to obtain information on the interface state density Dit. Electric-field-induced second harmonic generation (EFISH) can be used to non-destructively sample the electrical signal of a photodiode. The flatband voltage of a MOS capacitor (metal-oxide-semiconductor structure) can be directly extracted by using the relative phase parameter of the SHG signal as it varies with the sample azimuth angle under different bias voltages. However, SHG is a second-order nonlinear effect and is inherently relatively weak. Lower defect densities produce smaller SHG signal intensities, and capturing the instantaneous SHG signal after passing through a series of optical elements is difficult. A significant integration time is typically required to obtain an SHG signal suitable for observation. This makes SHG incapable of characterizing low defect densities, and extracting relevant device parameters is time-consuming. Furthermore, SHG signals can only be used to extract parameters such as defect density, but cannot characterize the sample's defect energy levels. Summary of the Invention

[0003] The present invention provides a second harmonic characterization method, a characterization optical system based on the method, and a detection device, which utilizes second harmonics to effectively characterize lower defect densities, shortens the time spent extracting device-related parameters, and can derive different defect types, defect energy levels of different defect types, and fundamental frequency light wavelengths corresponding to different defect types.

[0004] In a first aspect, the present invention provides a second harmonic characterization method, which includes: step 1: selecting a scanning point on the surface of a sample to be detected; step 2: incident fundamental frequency light of a first set wavelength onto the scanning point; after the fundamental frequency light is incident on the sample to be detected, it can generate a second harmonic signal carrying sample defect information, and the second harmonic signal is emitted along the direction of the light beam reflected from the surface of the sample to be detected; step 3: collecting the second harmonic signal; step 4: continuously tune the fundamental frequency light from the first set wavelength to the second set wavelength according to a preset step; and after each tuning of the wavelength of the fundamental frequency light, the fundamental frequency light with the tuned wavelength is incident on the scanning point, and the second harmonic signal generated by the fundamental frequency light with the tuned wavelength is collected; step 5: based on the collected second harmonic signal, a nonlinear spectrum of the second harmonic signal is drawn.

[0005] In the above scheme, after selecting a scanning point on the surface of the sample to be tested, the wavelength of the fundamental frequency light is continuously tuned from the first set wavelength to the second set wavelength by tuning, and after each tuning of the wavelength of the fundamental frequency light, the wavelength-tuned fundamental frequency light is incident on the scanning point, and the second harmonic signal generated by the wavelength-tuned fundamental frequency light is collected; then, based on the collected second harmonic signal, the nonlinear spectrum of the second harmonic signal is drawn. Through the nonlinear spectrum of the second harmonic signal, the different defect types, the defect energy levels of different defect types, and the wavelength of the fundamental frequency light corresponding to different defect types of the scanning point in this scanning process can be obtained. Subsequently, in other defect detection processes such as scanning the second harmonic signals of other scanning points on the same surface of the sample to be tested, or detecting the time-related second harmonic signals of the scanning point, the corresponding scanning wavelength, detection wavelength, etc. can be determined based on the nonlinear spectrum of the second harmonic signal, and by tuning the wavelength of the fundamental frequency light, the second harmonic can be used to effectively characterize the lower defect density. Furthermore, due to the targeted tuning of the wavelength of the fundamental frequency light, the relevant parameters of the sample to be tested can be extracted in a targeted manner, thus shortening the time consumption for extracting the relevant parameters of the device.

[0006] In a specific embodiment, the second harmonic characterization method further includes: sequentially selecting other scanning points on the surface of the sample to be tested, and after each scanning point is selected, plotting the nonlinear spectrum of the second harmonic signal at that scanning point in accordance with steps 2 to 5. By performing second harmonic characterization using the above characterization method at each other scanning point on the surface of the sample to be tested, the second harmonic characterization can be used to characterize the lower defect density across the entire surface of the sample to be tested. It can also be used to determine the different defect types present at different locations on the surface of the sample to be tested, the defect energy levels of different defect types, and the fundamental frequency wavelengths corresponding to different defect types.

[0007] In a specific embodiment, the second harmonic characterization method further includes: according to the nonlinear spectrum of the second harmonic signal, the wavelength corresponding to the second harmonic signal when the intensity exceeds a first preset threshold is used as a scanning wavelength; other scanning points are selected on the surface of the sample to be tested in sequence, and after each scanning point is selected, the fundamental frequency light of the scanning wavelength is used to be incident on the scanning point, and the second harmonic signal generated by the fundamental frequency light of the scanning wavelength is collected. By selecting the wavelength corresponding to the characteristic peak with a larger second harmonic signal intensity as the scanning wavelength according to the nonlinear spectrum of the second harmonic signal, when scanning other scanning points on the surface of the sample to be tested, the second harmonic signal intensity is increased by using resonance enhancement technology, and by tuning the wavelength of the fundamental frequency light, the second harmonic can be used to effectively characterize lower defect densities. And because the wavelength of the fundamental frequency light is tuned in a targeted manner, the relevant parameters of the sample to be tested can be extracted in a targeted manner, shortening the time spent extracting device-related parameters.

[0008] In a specific embodiment, the second harmonic characterization method further includes: selecting, based on the nonlinear spectrum of the second harmonic signal, the wavelength corresponding to the second harmonic signal when its intensity exceeds a second preset threshold as a detection wavelength in detecting the time-dependent second harmonic signal; and using the detection wavelength to detect the time-dependent second harmonic signal at the scanning point. By selecting, based on the nonlinear spectrum of the second harmonic signal, the wavelength corresponding to the characteristic peak with the largest second harmonic signal intensity as the detection wavelength in detecting the time-dependent second harmonic signal, the resonance enhancement technology can be used to increase the second harmonic signal intensity, thereby improving the quality of the detected time-dependent second harmonic signal, while also preventing damage to the surface of the sample to be detected due to excessively strong fundamental frequency light.

[0009] In a second aspect, the present invention further provides a second harmonic characterization optical system based on any of the above-described second harmonic characterization methods. The second harmonic characterization optical system includes a sample stage, an incident light path system, an exit light path system, and a nonlinear spectrum mapping module. The sample stage is used to hold the sample to be tested on it. The incident light path system is used to inject fundamental frequency light of a first predetermined wavelength into a scanning point selected on the surface of the sample to be tested. After the fundamental frequency light is injected into the sample to be tested, it can generate a second harmonic signal carrying sample defect information, and the second harmonic signal is emitted along the direction of the light beam reflected from the surface of the sample to be tested. The exit light path system includes a detector, which is used to collect the second harmonic signal within the detector. The incident light path system is also capable of continuously tuning the fundamental frequency light from a first predetermined wavelength to a second predetermined wavelength in preset steps. After each wavelength tuning of the fundamental frequency light, the incident light path system injects the wavelength-tuned fundamental frequency light into the scanning point, and the exit light path system collects the second harmonic signal generated by the wavelength-tuned fundamental frequency light. The nonlinear spectrum drawing module is used to draw the nonlinear spectrum of the second harmonic signal according to the collected second harmonic signal.

[0010] In the above scheme, by adopting an incident optical path system with a tunable fundamental frequency wavelength, after selecting a scanning point on the surface of the sample to be inspected, the wavelength of the fundamental frequency light is continuously tuned from a first set wavelength to a second set wavelength by tuning the wavelength of the fundamental frequency light. After each tuning of the wavelength of the fundamental frequency light, the wavelength-tuned fundamental frequency light is incident on the scanning point, and the second harmonic signal generated by the wavelength-tuned fundamental frequency light is collected; then, based on the collected second harmonic signal, a nonlinear spectrum of the second harmonic signal is plotted. Through the nonlinear spectrum of the second harmonic signal, the different defect types, defect energy levels of different defect types, and the fundamental frequency wavelength corresponding to different defect types of the scanning point can be obtained. Subsequently, in other defect detection processes such as scanning the second harmonic signal of other scanning points on the same surface of the sample to be inspected, or detecting the time-related second harmonic signal of the scanning point, the corresponding scanning wavelength, detection wavelength, etc. can be determined based on the nonlinear spectrum of the second harmonic signal. By tuning the wavelength of the fundamental frequency light, the second harmonic can be used to effectively characterize lower defect densities. Furthermore, due to the targeted tuning of the wavelength of the fundamental frequency light, the relevant parameters of the sample to be tested can be extracted in a targeted manner, thus shortening the time consumption for extracting the relevant parameters of the device.

[0011] In a specific embodiment, the incident light path system includes: a tunable laser, a coupler, a polarizer, and a first objective lens. The tunable laser is used to emit a laser beam. The coupler is connected to the tunable laser light guide via an optical fiber. The polarizer is positioned opposite to the coupler, and the polarizer is used to polarize the laser beam into polarized fundamental frequency light with a set polarization state. The first objective lens is positioned opposite to the polarizer, and the first objective lens is used to focus the polarized fundamental frequency light into fundamental frequency light that meets the test requirements, and to incident the fundamental frequency light onto a scanning point on the surface of the sample to be tested. This simplifies the structural setting of the incident light path system.

[0012] In a specific embodiment, the tunable laser is a tunable femtosecond laser, and the narrow pulse width characteristic of the tunable femtosecond laser is utilized to improve the time resolution of the second harmonic characterization.

[0013] In a specific embodiment, the incident light path system also includes: a nonlinear optical frequency conversion module connected to the optical path between the tunable femtosecond laser and the coupler to expand the wavelength range of the incident fundamental frequency light that can be tuned by the incident light path system, utilize resonance enhancement technology to enhance the second harmonic signal intensity, expand the lower limit of the second harmonic characterization defect density, and reduce the integration time during the characterization process.

[0014] In a specific embodiment, the nonlinear optical frequency conversion module includes: an optical parametric oscillator connected to the optical path between the tunable femtosecond laser and the coupler to expand the wavelength range of the incident fundamental frequency light that can be tuned by the incident optical path system, use resonance enhancement technology to enhance the second harmonic signal intensity, expand the lower limit of the second harmonic characterization defect density, and reduce the integration time during the characterization process.

[0015] In a specific embodiment, the nonlinear optical frequency conversion module also includes: an idler light module connected to the optical path between the optical parametric oscillator and the coupler to expand the wavelength range of the incident fundamental frequency light that can be tuned by the incident optical path system, utilize resonance enhancement technology to enhance the second harmonic signal intensity, expand the lower limit of the second harmonic characterization defect density, and reduce the integration time during the characterization process.

[0016] In a specific embodiment, the nonlinear optical frequency conversion module also includes: a difference frequency module connected to the optical path between the idle frequency light module and the coupler to expand the wavelength range of the incident fundamental frequency light that can be tuned by the incident optical path system, utilize resonance enhancement technology to enhance the second harmonic signal intensity, expand the lower limit of the second harmonic characterization defect density, and reduce the integration time during the characterization process.

[0017] In one specific embodiment, the sample stage can move along three mutually perpendicular axes relative to the circular guide rail. The second harmonic characterization optical system also includes a control module that is communicatively connected to the incident light path system, the output light path system, the sample stage, and the nonlinear spectrum drawing module. The control module is used to control the incident light path system to tune the wavelength of the fundamental frequency light. The control module is also used to control the sample stage to sequentially move the sample to be tested to other positions after completing the characterization of the scanning point, so that the fundamental frequency light is sequentially incident on other scanning points on the surface of the sample to be tested. The control module is also used to control the incident light path system and the output light path system to perform steps 2 to 4 after each scanning point is moved, and the nonlinear spectrum drawing module draws the nonlinear spectrum of the second harmonic signal at that scanning point. By using the above-mentioned characterization method to perform second harmonic characterization at each other scanning point on the surface of the sample to be tested, the second harmonic characterization can be used to characterize the lower defect density on the entire surface of the sample to be tested. It is also possible to determine the different defect types, defect energy levels of different defect types, and the fundamental frequency light wavelengths corresponding to different defect types at different locations on the surface of the sample to be tested.

[0018] In a specific embodiment, the sample stage can move on three mutually perpendicular motion axes relative to the circular arc guide. The second harmonic characterization optical system also includes: a scanning wavelength determination module and a control module. The scanning wavelength determination module is used to use the wavelength corresponding to the second harmonic signal when the intensity exceeds the first preset threshold as the scanning wavelength based on the nonlinear spectrum of the second harmonic signal. The control module is communicatively connected with the incident light path system, the output light path system, the sample stage and the nonlinear spectrum drawing module. The control module is used to control the incident light path system to tune the wavelength of the fundamental frequency light; the control module is also used to control the sample stage to move the sample to be tested to other positions in sequence after completing the characterization of the scanning point, so that the fundamental frequency light is incident on other scanning points on the surface of the sample to be tested in sequence; and the control module is also used to control the incident light path system to use the fundamental frequency light of the scanning wavelength to be incident on the scanning point after each scanning point is moved, and control the output light path system to collect the second harmonic signal generated by the fundamental frequency light of the scanning wavelength. By determining the scanning wavelength based on the nonlinear spectrum of the second harmonic signal, the wavelength of the fundamental frequency light can be tuned when scanning other scanning points on the surface of the sample to be inspected, effectively characterizing lower defect densities using the second harmonic. This targeted tuning of the fundamental frequency wavelength allows for the extraction of relevant parameters of the sample to be inspected, shortening the time required to extract relevant device parameters.

[0019] In a specific embodiment, the second harmonic characterization optical system also includes a detection wavelength determination module and a detection module. The detection wavelength determination module is used to use the wavelength corresponding to the second harmonic signal when the intensity exceeds the second preset threshold value as the detection wavelength in the process of detecting the time-dependent second harmonic signal based on the nonlinear spectrum of the second harmonic signal. The detection module is used to use the detection wavelength to detect the time-dependent second harmonic signal at the scanning point. By determining the detection wavelength in the process of detecting the time-dependent second harmonic signal based on the nonlinear spectrum of the second harmonic signal, the quality of the detected time-dependent second harmonic signal can be improved, while also avoiding damage to the surface of the sample to be detected due to the fundamental frequency light with excessive energy.

[0020] In a third aspect, the present invention also provides a detection device based on second harmonic characterization, which includes any of the above-mentioned second harmonic characterization optical systems. By adopting an incident light path system with a tunable fundamental frequency light wavelength, after selecting a scanning point on the surface of the sample to be detected, the wavelength of the fundamental frequency light is continuously tuned from a first set wavelength to a second set wavelength by tuning, and after each tuning of the wavelength of the fundamental frequency light, the fundamental frequency light with the tuned wavelength is incident on the scanning point, and the second harmonic signal generated by the wavelength-tuned fundamental frequency light is collected; then, based on the collected second harmonic signal, a nonlinear spectrum of the second harmonic signal is drawn. Through the nonlinear spectrum of the second harmonic signal, the different defect types of the scanning point during this scanning process, the defect energy levels of different defect types, and the fundamental frequency light wavelengths corresponding to different defect types can be obtained. In subsequent defect detection processes, such as scanning the second harmonic signal at other scanning points on the same sample surface, or detecting the time-correlated second harmonic signal at the same scanning point, the corresponding scanning wavelength and detection wavelength can be determined based on the nonlinear spectrum of the second harmonic signal. By tuning the wavelength of the fundamental light, the second harmonic can be used to effectively characterize lower defect densities. This targeted tuning of the fundamental light wavelength allows for the extraction of relevant parameters of the sample to be tested, shortening the time required to extract relevant device parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A flowchart of a second harmonic characterization method provided by an embodiment of the present invention;

[0022] Figure 2 A schematic structural diagram of a second harmonic characterization optical system provided by an embodiment of the present invention;

[0023] Figure 3 A nonlinear spectrum diagram of a second harmonic signal provided by an embodiment of the present invention;

[0024] Figure 4 A schematic diagram of the principle of improving the second harmonic signal strength by using resonance enhancement technology provided by an embodiment of the present invention.

[0025] Reference numerals:

[0026] 10-Support structure 11-Sample stage 12-Sample to be tested

[0027] 21-tunable laser 22-optical fiber 23-coupler

[0028] 24- polarizer 25- first objective lens 26- fundamental frequency light

[0029] 27-Nonlinear Optical Frequency Conversion Module 301-Second Harmonic Signal

[0030] 31- detector 32- second objective lens 33- polarizer

[0031] 34-Filter 41-Semiconductor conduction band 42-Defect energy level DETAILED DESCRIPTION

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0033] To facilitate understanding of the second harmonic generation optical system for characterization provided by embodiments of the present invention, the following first describes an application scenario for the second harmonic generation optical system. This system is used in the detection of parameters such as semiconductor surface defects based on second harmonic generation. The following describes this system in detail with reference to the accompanying drawings.

[0034] refer to Figure 1 、 Figure 2 、 Figure 3 and Figure 4 , the second harmonic characterization method provided by the embodiment of the present invention includes:

[0035] Step 10: Select scanning points on the surface of the sample 12 to be tested;

[0036] Step 20: A fundamental frequency light 26 of a first set wavelength is incident on the scanning point. After the fundamental frequency light 26 is incident on the sample 12 to be inspected, a second harmonic signal 301 carrying the sample defect information is generated. The second harmonic signal 301 is emitted along the direction of the light beam reflected from the surface of the sample 12 to be inspected.

[0037] Step 30: Collect the second harmonic signal 301;

[0038] Step 40: Continuously tune the fundamental frequency light 26 from the first set wavelength to the second set wavelength according to a preset step; after each wavelength tuning of the fundamental frequency light 26, the wavelength-tuned fundamental frequency light 26 is incident on the scanning point, and the second harmonic signal 301 generated by the wavelength-tuned fundamental frequency light 26 is collected;

[0039] Step 50: Based on the collected second harmonic signal 301 , draw a nonlinear spectrum of the second harmonic signal 301 .

[0040] In the above scheme, after selecting a scanning point on the surface of the sample 12 to be inspected, the wavelength of the fundamental frequency light 26 is continuously tuned from a first set wavelength to a second set wavelength. After each wavelength tuning of the fundamental frequency light 26, the wavelength-tuned fundamental frequency light 26 is incident on the scanning point, and the second harmonic signal 301 generated by the wavelength-tuned fundamental frequency light 26 is collected. Then, based on the collected second harmonic signal 301, a nonlinear spectrum of the second harmonic signal 301 is plotted. The nonlinear spectrum of the second harmonic signal 301 can be used to determine the different defect types at the scanning point during the scanning process, the defect energy levels 42 of the different defect types, and the wavelengths of the fundamental frequency light 26 corresponding to the different defect types. In subsequent defect detection processes, such as scanning the second harmonic signal 301 at other scanning points on the surface of the same sample 12 to be inspected, or detecting the time-dependent second harmonic signal 301 at the same scanning point, the corresponding scanning wavelength and detection wavelength can be determined based on the nonlinear spectrum of the second harmonic signal 301. By tuning the wavelength of the fundamental frequency light 26, the second harmonic can be used to effectively characterize lower defect densities. Furthermore, due to the targeted tuning of the wavelength of the fundamental frequency light 26, relevant parameters of the sample 12 to be inspected can be extracted in a targeted manner, shortening the time required to extract relevant device parameters. The above steps are described in detail below with reference to the accompanying figures.

[0041] refer to Figure 1 and Figure 2 First, a scanning point is selected on the surface of the sample 12 to be tested. Then, the sample 12 to be tested is placed on the sample stage 11, and the sample stage 11 is moved so that the fundamental frequency light 26 emitted by the incident light path system can be incident on the selected scanning point on the surface of the sample 12 to be tested.

[0042] Next, if Figure 1 and Figure 2 As shown, a fundamental frequency light 26 of a first set wavelength is incident on the scanning point. Specifically, a fundamental frequency light 26 is incident on the scanning point selected on the surface of the sample 12 to be detected through the incident light path system. The wavelength of the fundamental frequency light 26 is the first set wavelength. The first set wavelength can be, for example, but not limited to, 345 nm. That is, the specific value of the first set wavelength can be determined according to the type of the sample 12 to be detected, the incident laser system, etc. Figure 1 and Figure 2 As shown, after the fundamental frequency light 26 is incident on the sample to be inspected 12 , it can generate a second harmonic signal 301 carrying sample defect information, and the second harmonic signal 301 is emitted along the direction of the light beam reflected from the surface of the sample to be inspected 12 .

[0043] Next, refer to Figure 1 , collect the second harmonic signal 301. Reference Figure 2After the fundamental frequency light 26 emitted by the incident optical path system is incident on the sample to be detected 12, it can generate a second harmonic signal 301 carrying sample defect information. The second harmonic signal 301 enters the output optical path system along the direction of the light beam reflected by the sample to be detected 12 and is collected in the detector 31 that receives the second harmonic signal 301.

[0044] Next, refer to Figure 1 The fundamental frequency light 26 is continuously tuned from a first set wavelength to a second set wavelength according to a preset step. After each wavelength tuning of the fundamental frequency light 26, the wavelength-tuned fundamental frequency light 26 is incident on the scanning point, and the second harmonic signal 301 generated by the wavelength-tuned fundamental frequency light 26 is collected. Specifically, during scanning of the selected scanning point, the fundamental frequency light 26 of the first set wavelength is initially incident on the scanning point, and the corresponding second harmonic signal 301 is collected. Thereafter, the wavelength of the fundamental frequency light 26 is gradually tuned according to the preset step, gradually increasing the wavelength of the fundamental frequency light 26 to the second set wavelength. After each wavelength tuning of the fundamental frequency light 26, the tuned fundamental frequency light 26 is incident on the scanning point at least once, and the corresponding second harmonic signal 301 generated by the tuned fundamental frequency light 26 is collected. The second set wavelength can be, for example, 2500 nm, 10 μm, etc., and can also be determined based on the type of sample 12 to be tested, the incident laser system, and other factors. The preset step size can be 1 nm, 2 nm, 5 nm, etc., and can be adjusted according to the incident light path system.

[0045] Next, refer to Figure 1 and Figure 3 , based on the collected second harmonic signal 301, a nonlinear spectrum of the second harmonic signal 301 is drawn. Figure 3 The nonlinear spectrum of the second harmonic signal 301 is plotted as shown, wherein the horizontal axis represents the wavelength of the fundamental frequency light 26, and the vertical axis represents the intensity of the generated second harmonic signal 301. It should be understood that the plotting method of the nonlinear spectrum of the second harmonic signal 301 is not limited to Figure 3In addition to the method shown, other drawing methods can also be used. Through the nonlinear spectrum of the second harmonic signal 301 shown above, the different defect types, the defect energy levels 42 of different defect types, and the wavelengths of the fundamental frequency light 26 corresponding to different defect types of the scanning point can be obtained. Subsequently, in other defect detection processes such as scanning the second harmonic signal 301 of other scanning points on the surface of the same sample 12 to be tested, or detecting the time-related second harmonic signal 301 of the scanning point, the corresponding scanning wavelength, detection wavelength, etc. can be determined based on the nonlinear spectrum of the second harmonic signal 301, and by tuning the wavelength of the fundamental frequency light 26, the second harmonic can be used to effectively characterize the lower defect density. And because the wavelength of the fundamental frequency light 26 is tuned in a targeted manner, the relevant parameters of the sample 12 to be tested can be extracted in a targeted manner, shortening the time consumption of extracting device-related parameters.

[0046] After completing the second harmonic characterization of the selected scanning point, the second harmonic characterization method can further include: selecting other scanning points on the surface of the sample 12 to be tested in sequence, and after each scanning point is selected, plotting the nonlinear spectrum of the second harmonic signal 301 of the scanning point in accordance with steps 2 to 5. That is, the sample 12 to be tested is moved to another other position by the sample stage 11, so that the fundamental frequency light 26 is incident on other scanning points on the surface of the sample 12 to be tested, and after each movement of the sample 12 to be tested to another scanning point, the second harmonic characterization test needs to be performed in the above manner to plot the nonlinear spectrum of the second harmonic signal 301 of the selected new scanning point. By adjusting the motion trajectory of the sample stage 11, the entire surface of the sample 12 to be tested can be scanned in sequence, and the corresponding nonlinear spectrum of the second harmonic signal 301 is plotted for each scanning point on the entire surface of the sample 12 to be tested. The above method, by using the above characterization method to perform second harmonic characterization at each other scanning point on the surface of the sample to be tested 12, can characterize the lower defect density on the entire surface of the sample to be tested 12 by second harmonic characterization, and can also obtain the different defect types existing at different positions on the surface of the sample to be tested 12, the defect energy levels 42 of different defect types, and the fundamental frequency light 26 wavelengths corresponding to different defect types.

[0047] In addition, after completing the second harmonic characterization of the selected scanning point, other methods can be used to perform second harmonic characterization on other scanning points on the surface of the sample 12 to be inspected. For example, the second harmonic characterization method can further include: based on the nonlinear spectrum of the second harmonic signal 301, selecting the wavelength corresponding to the second harmonic signal 301 when the intensity exceeds a first preset threshold as the scanning wavelength; sequentially selecting other scanning points on the surface of the sample 12 to be inspected, and after each scanning point is selected, using the fundamental frequency light 26 of the scanning wavelength to be incident on the scanning point, and collecting the second harmonic signal 301 generated by the fundamental frequency light 26 of the scanning wavelength. That is, after obtaining the nonlinear spectrum of the second harmonic signal 301 of the initially selected scanning point, the sample 12 to be inspected can be processed using the same process as a whole, so that the distribution of defect types formed on the surface of the sample 12 to be inspected at different scanning points has a high degree of similarity. Based on the nonlinear spectrum of the second harmonic signal 301 of the initially selected scanning point, the wavelength corresponding to the characteristic peak with a larger intensity of the second harmonic signal 301 is selected as the scanning wavelength for the other scanning points. When scanning other scanning points on the surface of the sample to be tested 12, the resonance enhancement technology is used to increase the intensity of the second harmonic signal 301. By tuning the wavelength of the fundamental frequency light 26, the second harmonic characterization of the defect type with low second harmonic intensity is prevented from being missed, and the second harmonic can be used to effectively characterize the lower defect density. And because the wavelength of the fundamental frequency light 26 is tuned in a targeted manner, the relevant parameters of the sample to be tested 12 can be extracted in a targeted manner, shortening the time consumption of extracting device-related parameters. When selecting the scanning wavelength, the size of the first preset threshold can be adjusted, and according to the nonlinear spectrum of the second harmonic signal 301, the multiple wavelengths corresponding to the multiple second harmonic signals 301 when the intensity exceeds the first preset threshold are used as scanning wavelengths. Each scanning wavelength is used as the scanning wavelength of the fundamental frequency light 26. Using the above scanning method, the other scanning points on the surface of the sample to be tested 12 are scanned in sequence to obtain the second harmonic signals 301 of the other scanning points.

[0048] It should be understood that the use of the nonlinear spectrum of the second harmonic signal 301 is not limited to the above-mentioned method. In addition, it can also be used in other defect parameter detection processes. For example, the nonlinear spectrum of the second harmonic signal 301 can also be used in the process of detecting the time-dependent second harmonic signal 301. It should be explained that the generation mechanism of the time-dependent second harmonic signal 301 is: the fundamental frequency light and the second harmonic polarization term Satisfaction relationship: Among them, χ () represents the second-order nonlinear coefficient. When the fundamental frequency light is irradiated on the sample 12 to be tested, photogenerated carriers are generated, and the defects capture the photogenerated carriers, resulting in χ ()Because the intensity of the second harmonic signal 301 changes over time, the intensity of the second harmonic signal 301 changes over time. The change process of the second harmonic signal 301 over time is the time-dependent second harmonic signal 301. The time-dependent second harmonic signal 301 can be used to obtain the rate of change of the second harmonic signal 301 over time, thereby reflecting the defect density.

[0049] When utilizing the nonlinear spectrum of the second harmonic signal 301 to detect the time-dependent second harmonic signal 301, the wavelength corresponding to the second harmonic signal 301 when its intensity exceeds a second preset threshold can be used as the detection wavelength for detecting the time-dependent second harmonic signal 301 based on the nonlinear spectrum of the second harmonic signal 301. Subsequently, the detection wavelength is used to detect the time-dependent second harmonic signal 301 at the scanning point. That is, during the detection of the time-dependent second harmonic signal 301 at the initially selected scanning point, one or more wavelengths corresponding to the second harmonic signal 301 when its intensity exceeds the second preset threshold can be selected based on the nonlinear spectrum of the second harmonic signal 301 plotted above by adjusting the second preset threshold, thereby obtaining multiple detection wavelengths. Each detection wavelength is used to fix the wavelength of the fundamental frequency light 26, and the time-dependent second harmonic signal 301 formed at the scanning point with time as the independent variable is detected, thereby facilitating the determination of the rate of change of the second harmonic signal 301 over time, and thereby determining the defect density at the scanning point. In the above method, by selecting the wavelength corresponding to the characteristic peak with a larger intensity of the second harmonic signal 301 according to the nonlinear spectrum of the second harmonic signal 301, as the detection wavelength in the process of detecting the time-dependent second harmonic signal 301, the resonance enhancement technology can be used to enhance the intensity of the second harmonic signal 301, thereby improving the quality of the detected time-dependent second harmonic signal 301, while also avoiding damage to the surface of the sample 12 to be detected due to the fundamental frequency light 26 with excessive energy.

[0050] In the various embodiments described above, after selecting a scanning point on the surface of the sample 12 to be inspected, the wavelength of the fundamental frequency light 26 is continuously tuned from a first set wavelength to a second set wavelength. After each wavelength tuning of the fundamental frequency light 26, the wavelength-tuned fundamental frequency light 26 is incident on the scanning point, and the second harmonic signal 301 generated by the wavelength-tuned fundamental frequency light 26 is collected. A nonlinear spectrum of the second harmonic signal 301 is then plotted based on the collected second harmonic signal 301. The nonlinear spectrum of the second harmonic signal 301 can be used to determine the different defect types at the scanning point during the scanning process, the defect energy levels 42 of the different defect types, and the wavelengths of the fundamental frequency light 26 corresponding to the different defect types. In subsequent defect detection processes, such as scanning second harmonic signals 301 at other scanning points on the surface of the same sample 12 to be inspected, or detecting time-dependent second harmonic signals 301 at the same scanning points, the corresponding scanning wavelength and detection wavelength can be determined based on the nonlinear spectrum of second harmonic signal 301. By tuning the wavelength of fundamental frequency light 26, the second harmonic can be used to effectively characterize lower defect densities. Furthermore, due to the targeted tuning of the wavelength of fundamental frequency light 26, relevant parameters of the sample 12 to be inspected can be specifically extracted, shortening the time required to extract relevant device parameters.

[0051] In addition, an embodiment of the present invention further provides a second harmonic characterization optical system based on any of the above second harmonic characterization methods, referring to Figure 1 、 Figure 2 、 Figure 3 and Figure 4 The second harmonic characterization optical system includes a sample stage 11, an incident light path system, an exit light path system and a nonlinear spectrum drawing module. The sample stage 11 is used to hold the sample 12 to be tested thereon. The incident light path system is used to inject fundamental frequency light 26 of a first set wavelength into a scanning point selected on the surface of the sample 12 to be tested. After the fundamental frequency light 26 is incident on the sample 12 to be tested, it can generate a second harmonic signal 301 carrying sample defect information, and the second harmonic signal 301 is emitted along the direction of the light beam reflected from the surface of the sample 12 to be tested. The exit light path system includes a detector 31, and the exit light path system is used to collect the second harmonic signal 301 in the detector 31. The incident optical path system is further capable of continuously tuning fundamental frequency light 26 from a first set wavelength to a second set wavelength in preset steps. After each wavelength tuning of fundamental frequency light 26, the incident optical path system injects the wavelength-tuned fundamental frequency light 26 into the scanning point, and the output optical path system collects the second harmonic signal 301 generated by the wavelength-tuned fundamental frequency light 26. The nonlinear spectrum plotting module is configured to plot a nonlinear spectrum of the second harmonic signal 301 based on the collected second harmonic signal 301.

[0052] In the above-described scheme, by adopting an incident optical path system with a tunable wavelength of fundamental frequency light 26, after selecting a scanning point on the surface of the sample 12 to be tested, the wavelength of the fundamental frequency light 26 is continuously tuned from a first set wavelength to a second set wavelength. After each wavelength tuning of the fundamental frequency light 26, the wavelength-tuned fundamental frequency light 26 is incident on the scanning point, and the second harmonic signal 301 generated by the wavelength-tuned fundamental frequency light 26 is collected. Then, based on the collected second harmonic signal 301, a nonlinear spectrum of the second harmonic signal 301 is plotted. The nonlinear spectrum of the second harmonic signal 301 can be used to determine the different defect types at the scanning point during the scanning process, the defect energy levels 42 of the different defect types, and the wavelengths of the fundamental frequency light 26 corresponding to the different defect types. In subsequent defect detection processes, such as scanning the second harmonic signal 301 at other scanning points on the surface of the same sample 12 to be inspected, or detecting the time-dependent second harmonic signal 301 at the same scanning point, the corresponding scanning wavelength and detection wavelength can be determined based on the nonlinear spectrum of the second harmonic signal 301. By tuning the wavelength of the fundamental frequency light 26, the second harmonic can be used to effectively characterize lower defect densities. Furthermore, due to the targeted tuning of the wavelength of the fundamental frequency light 26, relevant parameters of the sample 12 to be inspected can be extracted in a targeted manner, shortening the time required to extract relevant device parameters. The above-mentioned structures are described in detail below with reference to the accompanying drawings.

[0053] When setting up the sample stage 11, refer to Figure 2 The sample stage 11 serves as a supporting platform, capable of holding a sample 12 to be tested thereon. The sample 12 to be tested may specifically be a sample structure such as a wafer or a substrate. A supporting structure 10 may be provided, which serves as a carrier for setting the sample stage 11 and the like. Figure 2 , the support structure 10 may include an arc guide rail. The guide rail extension direction of the arc guide rail is in the shape of an arc. A sample stage 11 is provided at the center of the arc guide rail, and the sample stage 11 is used to place, support and fix the sample to be tested 12. In addition, the sample stage 11 can be made to move on three mutually perpendicular motion axes relative to the arc guide rail, so that the sample to be tested 12 held on the sample stage 11 can move relative to the arc guide rail, so that the fundamental frequency light 26 scans the entire surface of the sample to be tested 12, which is convenient for performing a second harmonic mapping scan on the surface of the sample to be tested 12, and obtaining the surface defect information of the entire sample to be tested 12. Specifically, a motion platform can be integrated into the sample stage 11, and the motion platform drives the sample stage 11 to move, and then drives the sample to be tested 12 to move on three mutually perpendicular motion axes, which is convenient for detecting different positions of the sample to be tested 12, and also convenient for performing a second harmonic mapping scan on the surface of the sample to be tested 12, and obtaining the surface defect information of the entire sample to be tested 12.

[0054] When setting up the incident light path system, Figure 2 As shown, the incident light path system can inject fundamental frequency light 26 of a first set wavelength into a selected scanning point on the surface of the sample 12 to be tested. During configuration, the incident light path system may include: a tunable laser 21, a coupler 23, a polarizer 24, and a first objective lens 25. The tunable laser 21 is configured to emit a laser beam. The minimum wavelength that the tunable laser 21 can be tuned to can be used as the first set wavelength, and the maximum wavelength that the tunable laser 21 can be tuned to can be used as the second set wavelength. The coupler 23 is optically connected to the tunable laser 21 via an optical fiber 22 for transmitting the laser beam. The polarizer 24 is positioned opposite the coupler 23 and is configured to polarize the laser beam into polarized fundamental frequency light 26 having a set polarization state. The first objective lens 25 is positioned opposite the polarizer 24 and is configured to focus the polarized fundamental frequency light 26 into fundamental frequency light 26 that meets the test requirements and inject the fundamental frequency light 26 into the scanning point on the surface of the sample 12 to be tested. This simplifies the structural setup of the incident light path system. Specifically, an incident arm can be slidably mounted on a circular guide rail, with the tunable laser 21, coupler 23, polarizer 24, and first objective lens 25 secured to the incident arm. The incident arm's sliding path on the circular guide rail is a circular arc, allowing it to consistently slide around the sample stage 11. This arrangement facilitates the installation of the support structure 10 and facilitates changing the incident angle of the fundamental frequency light 26.

[0055] refer to Figure 2 After the fundamental frequency light 26 emitted by the incident optical path system is incident on the sample to be detected 12, it can generate a second harmonic signal 301 carrying the sample defect information. The second harmonic signal 301 is emitted along the direction of the light beam reflected by the sample to be detected 12, and then enters the output optical path system and is collected in the detector 31 that receives the second harmonic signal 301.

[0056] When setting up the output light path system, Figure 2The output optical path system shown in FIG. 3 may further include, in addition to the detector 31, a second objective lens 32, an analyzer 33, a filter 34, and a coupler 23. The second objective lens 32, the analyzer 33, and the filter 34 are all located on the same transmission optical path, and the coupler 23 is connected to the detector 31 through an optical fiber 22. The second objective lens 32 is used to collimate the light beam reflected from the sample 12 to be detected. The analyzer 33 is positioned relative to the second objective lens 32, and is used to receive the light beam emitted from the second objective lens 32 and perform polarization analysis to obtain output light of a set polarization state. The filter 34 is positioned relative to the analyzer 33, and is used to filter out the fundamental frequency light 26 in the output light to obtain a second harmonic signal 301. The coupler 23, which is connected to the detector 31, is fixed at a position relative to the filter 34 to receive the second harmonic signal 301 and transmit the received second harmonic signal 301 to the detector 31. Similarly, an output arm can be slidably assembled on the arc guide rail, and the detector 31, the coupler 23 connected to the detector 31 for guiding light, the filter 34, the analyzer 33, and the second objective lens 32 can be fixed on the output arm. By adopting the output optical path system shown above, the configuration of the output optical path system can be simplified. In addition, it should be understood that the above is only an exemplary output optical path system. In addition, other output optical path systems having a detector 31 and capable of receiving the reflected second harmonic signal 301 can also be adopted.

[0057] Furthermore, the aforementioned incident optical path system is capable of continuously tuning the fundamental frequency light 26 from a first set wavelength to a second set wavelength in preset steps. After each wavelength tuning of the fundamental frequency light 26, the incident optical path system injects the wavelength-tuned fundamental frequency light 26 into the scanning point, and the output optical path system collects the second harmonic signal 301 generated by the wavelength-tuned fundamental frequency light 26. Specifically, during scanning of a selected scanning point, the fundamental frequency light 26 of the first set wavelength is initially injected into the scanning point, and the corresponding second harmonic signal 301 is collected. Thereafter, the wavelength of the fundamental frequency light 26 is gradually tuned in preset steps, gradually increasing to the second set wavelength. Furthermore, after each wavelength tuning of the fundamental frequency light 26, the tuned fundamental frequency light 26 is injected into the scanning point at least once, and the corresponding second harmonic signal 301 generated by the tuned fundamental frequency light 26 is collected. The first set wavelength may be, for example, but not limited to, 345 nm, and the second set wavelength may be, for example, 2500 nm, 10 μm, etc., which may also be determined based on the type of sample 12 to be detected, the incident laser system, etc. The preset step size may be, for example, 1 nm, 2 nm, 5 nm, etc., which may be adjusted based on the incident light path system.

[0058] When the nonlinear spectrum drawing module is set, it can receive the wavelength of each incident fundamental frequency light 26 and the corresponding second harmonic signal 301 from the incident light path system and the outgoing light path system, and can also draw the nonlinear spectrum of the second harmonic signal 301 based on the collected second harmonic signal 301. Figure 3 The nonlinear spectrum of the second harmonic signal 301 is plotted as shown, wherein the horizontal axis represents the wavelength of the fundamental frequency light 26, and the vertical axis represents the intensity of the generated second harmonic signal 301. It should be understood that the plotting method of the nonlinear spectrum of the second harmonic signal 301 is not limited to Figure 3 In addition to the method shown, other drawing methods can also be used. Through the nonlinear spectrum of the second harmonic signal 301 shown above, the different defect types, the defect energy levels 42 of different defect types, and the wavelengths of the fundamental frequency light 26 corresponding to different defect types of the scanning point can be obtained. Subsequently, in other defect detection processes such as scanning the second harmonic signal 301 of other scanning points on the surface of the same sample 12 to be tested, or detecting the time-related second harmonic signal 301 of the scanning point, the corresponding scanning wavelength, detection wavelength, etc. can be determined based on the nonlinear spectrum of the second harmonic signal 301, and by tuning the wavelength of the fundamental frequency light 26, the second harmonic can be used to effectively characterize the lower defect density. And because the wavelength of the fundamental frequency light 26 is tuned in a targeted manner, the relevant parameters of the sample 12 to be tested can be extracted in a targeted manner, shortening the time consumption of extracting device-related parameters.

[0059] When specifically realizing the tunable wavelength of the incident light path system, the tunable laser 21 can be a tunable femtosecond laser, and the narrow pulse width characteristic of the tunable femtosecond laser is utilized to improve the time resolution of the second harmonic characterization. Figure 2 The incident light path system may further include: a nonlinear optical frequency conversion module 27 connected to the optical path between the tunable femtosecond laser and the coupler 23, so as to expand the wavelength range of the incident fundamental frequency light that can be tuned by the incident light path system, enhance the intensity of the second harmonic signal 301 by using the resonance enhancement technology, expand the lower limit of the second harmonic characterization defect density, and reduce the integration time during the characterization process. When the above-mentioned nonlinear optical frequency conversion module 27 is set, the nonlinear optical frequency conversion module 27 may include: an optical parametric oscillator connected to the optical path between the tunable femtosecond laser and the coupler 23, so as to expand the wavelength range of the incident fundamental frequency light that can be tuned by the incident light path system, enhance the intensity of the second harmonic signal 301 by using the resonance enhancement technology, expand the lower limit of the second harmonic characterization defect density, and reduce the integration time during the characterization process. When used, the fundamental frequency light 26 emitted from the tunable femtosecond laser enters the optical parametric oscillator, and the wavelength tuning range of the incident fundamental frequency light 26 can be expanded to 345-2500nm. Reference Figure 2 and Figure 4 , the tuned fundamental frequency wave is incident on the surface of the sample to be tested 12, and the fundamental frequency light 26 also interacts with the defect to generate a second harmonic signal 301. In the process of adjusting the wavelength of the incident fundamental frequency light 26 using an optical parametric oscillator, at a certain wavelength of the fundamental frequency light 26, if the energy of the two incident fundamental frequency lights 26 with a frequency of ω is exactly equal to the energy difference between the semiconductor conduction band 41 and the defect energy level 42, then the electrons absorb the energy of the two incident lights with a frequency of ω and transition to the semiconductor conduction band 41. When the electrons transition back to the defect energy level 42, they emit a second harmonic signal 301 with a frequency of 2ω, and the second harmonic signal 301 is thereby resonantly enhanced. The detector 31 can obtain a second harmonic signal 301 suitable for observation without long-term integration, and can draw a graph based on the multiple second harmonic signals 301 obtained in the continuous tuning process. Figure 3 The nonlinear spectrum of the second harmonic signal 301 is shown, and the position of the defect energy level 42 can be inferred based on the nonlinear spectrum of the second harmonic signal 301 .

[0060] Of course, in a more preferred embodiment, the nonlinear optical frequency conversion module 27 may further include: an idler optical module connected to the optical path between the optical parametric oscillator and the coupler 23, thereby expanding the wavelength range of the incident fundamental frequency light that can be tuned by the incident optical path system, utilizing resonance enhancement technology to increase the intensity of the second harmonic signal 301, thereby expanding the lower limit of the second harmonic defect density, and reducing the integration time during the characterization process. Furthermore, the nonlinear optical frequency conversion module 27 may further include: a difference frequency module connected to the optical path between the idler optical module and the coupler 23, thereby expanding the wavelength range of the incident fundamental frequency light that can be tuned by the incident optical path system, utilizing resonance enhancement technology to increase the intensity of the second harmonic signal 301, thereby expanding the lower limit of the second harmonic defect density, and reducing the integration time during the characterization process.

[0061] It should be understood that the above merely exemplifies several configuration methods of the incident light path system, and other configuration methods may also be used.

[0062] A control module can also be provided, which is in communication with the incident light path system, the outgoing light path system, the sample stage 11, and the nonlinear spectrum drawing module to control the system or exchange information. For example, as shown in the aforementioned method, after completing the second harmonic characterization of a selected scanning point, other scanning points are sequentially selected on the surface of the sample 12 to be tested. After each scanning point is selected, the control module can control the incident light path system to tune the wavelength of the fundamental frequency light 26 in the process of drawing the nonlinear spectrum of the second harmonic signal 301 at that scanning point according to steps 2 to 5. The control module can also control the sample stage 11 to sequentially move the sample 12 to other positions after completing the characterization of the scanning points, so that the fundamental frequency light 26 is sequentially incident on the other scanning points on the surface of the sample 12 to be tested. The control module is also configured to control the incident light path system and the outgoing light path system to execute steps 2 to 4 after each scanning point is moved, so that the nonlinear spectrum drawing module draws the nonlinear spectrum of the second harmonic signal 301 at that scanning point. That is, the sample to be tested 12 is moved to another position by the sample stage 11, so that the fundamental frequency light 26 is incident on other scanning points on the surface of the sample to be tested 12, and after each movement of the sample to be tested 12 to another scanning point, the second harmonic characterization test needs to be performed in the above manner to draw the nonlinear spectrum of the second harmonic signal 301 of the selected new scanning point. By adjusting the motion trajectory of the sample stage 11, the entire surface of the sample to be tested 12 can be scanned in sequence, and for each scanning point on the entire surface of the sample to be tested 12, the corresponding nonlinear spectrum of the second harmonic signal 301 is drawn. In the above manner, by using the above characterization method to perform second harmonic characterization at each other scanning point on the surface of the sample to be tested 12, the lower defect density on the entire surface of the sample to be tested 12 can be characterized by second harmonics, and the different defect types existing at different positions on the surface of the sample to be tested 12, the defect energy levels 42 of different defect types, and the wavelengths of the fundamental frequency light 26 corresponding to different defect types can also be obtained.

[0063] In addition, the second harmonic characterization optical system can further include a scanning wavelength determination module, and of course, can also include the above-mentioned control module. As described in the above-mentioned method section, after completing the second harmonic characterization of a scanning point selected above, based on the nonlinear spectrum of the second harmonic signal 301, the wavelength corresponding to the second harmonic signal 301 when the intensity exceeds the first preset threshold is used as the scanning wavelength. Afterwards, other scanning points are selected on the surface of the sample 12 to be tested in turn, and after each scanning point is selected, the fundamental frequency light 26 of the scanning wavelength is used to be incident on the scanning point, and in the process of collecting the second harmonic signal 301 generated by the fundamental frequency light 26 of the scanning wavelength, the scanning wavelength determination module and the control module can perform the following operations. The scanning wavelength determination module uses the wavelength corresponding to the second harmonic signal 301 when the intensity exceeds the first preset threshold as the scanning wavelength based on the nonlinear spectrum of the second harmonic signal 301. Afterwards, the control module is used to control the incident optical path system to tune the wavelength of the fundamental frequency light 26; the control module is also used to control the sample stage 11 to move the sample to be tested 12 to other positions in sequence after completing the characterization of the scanning point, so that the fundamental frequency light 26 is incident on other scanning points on the surface of the sample to be tested 12 in sequence; and the control module is also used to control the incident optical path system to use the fundamental frequency light 26 of the scanning wavelength to be incident on the scanning point after each scanning point is moved, and control the output optical path system to collect the second harmonic signal 301 generated by the fundamental frequency light 26 according to the scanning wavelength.

[0064] That is, after obtaining the nonlinear spectrum of the second harmonic signal 301 of the initially selected scanning point, the same processing technology can be used as a whole for the sample 12 to be tested, so that the distribution of the defect types formed on the surface of the sample 12 to be tested at different scanning points has a high similarity. According to the nonlinear spectrum of the second harmonic signal 301 of the initially selected scanning point, the wavelength corresponding to the characteristic peak with a larger intensity of the second harmonic signal 301 is selected as the scanning wavelength of other scanning points. When scanning other scanning points on the surface of the sample 12 to be tested, the resonance enhancement technology is used to enhance the intensity of the second harmonic signal 301. By tuning the wavelength of the fundamental frequency light 26, the second harmonic characterization of the defect type with a lower second harmonic intensity is prevented from being missed, and the second harmonic can be used to effectively characterize the lower defect density. And because the wavelength of the fundamental frequency light 26 is tuned in a targeted manner, the relevant parameters of the sample 12 to be tested can be extracted in a targeted manner, shortening the time spent on extracting device-related parameters. When selecting a scanning wavelength, the first preset threshold can be adjusted. Based on the nonlinear spectrum of second harmonic signal 301, multiple wavelengths corresponding to multiple second harmonic signals 301 whose intensities exceed the first preset threshold are selected as scanning wavelengths. Each scanning wavelength serves as the scanning wavelength of fundamental frequency light 26. Using the above scanning method, other scanning points on the surface of the sample 12 to be tested are sequentially scanned to obtain second harmonic signals 301 at the other scanning points.

[0065] Furthermore, when applying the second harmonic characterization optical system to the process of detecting the time-dependent second harmonic signal 301 as described in the method described above, the second harmonic characterization optical system can further include a detection wavelength determination module and a detection module. The detection wavelength determination module can, based on the nonlinear spectrum of the second harmonic signal 301, select the wavelength corresponding to the second harmonic signal 301 when its intensity exceeds a second preset threshold as the detection wavelength for detecting the time-dependent second harmonic signal 301. The detection module is configured to use the detection wavelength to detect the time-dependent second harmonic signal 301 at the scanning point. That is, during the detection of the time-dependent second harmonic signal 301 at the initially selected scanning point, one or more wavelengths corresponding to the second harmonic signal 301 when its intensity exceeds the second preset threshold can be selected based on the nonlinear spectrum of the second harmonic signal 301 drawn above by adjusting the second preset threshold, thereby obtaining multiple detection wavelengths. Each detection wavelength is used to fix the wavelength of fundamental frequency light 26, and the time-dependent second harmonic signal 301 generated at the scanning point with time as the independent variable is detected, so as to obtain the rate of change of second harmonic signal 301 over time, and thus the defect density at the scanning point. The above method selects the wavelength corresponding to the characteristic peak with the largest intensity of second harmonic signal 301 based on the nonlinear spectrum of second harmonic signal 301 as the detection wavelength during the detection of time-dependent second harmonic signal 301. This can utilize resonance enhancement technology to increase the intensity of second harmonic signal 301, thereby improving the quality of the detected time-dependent second harmonic signal 301, while also preventing damage to the surface of the sample 12 to be tested due to the excessively strong fundamental frequency light 26.

[0066] In the various embodiments described above, by employing an incident optical path system with a tunable wavelength of the fundamental frequency light 26, after selecting a scanning point on the surface of the sample 12 to be inspected, the wavelength of the fundamental frequency light 26 is continuously tuned from a first set wavelength to a second set wavelength. After each wavelength tuning of the fundamental frequency light 26, the wavelength-tuned fundamental frequency light 26 is incident upon the scanning point, and the second harmonic signal 301 generated by the wavelength-tuned fundamental frequency light 26 is collected. A nonlinear spectrum of the second harmonic signal 301 is then plotted based on the collected second harmonic signal 301. The nonlinear spectrum of the second harmonic signal 301 can be used to determine the different defect types, defect energy levels 42 of the different defect types, and the wavelengths of the fundamental frequency light 26 corresponding to the different defect types at the scanning point during the scanning process. In subsequent defect detection processes, such as scanning second harmonic signals 301 at other scanning points on the surface of the same sample 12 to be inspected, or detecting time-dependent second harmonic signals 301 at the same scanning points, the corresponding scanning wavelength and detection wavelength can be determined based on the nonlinear spectrum of second harmonic signal 301. By tuning the wavelength of fundamental frequency light 26, the second harmonic can be used to effectively characterize lower defect densities. Furthermore, due to the targeted tuning of the wavelength of fundamental frequency light 26, relevant parameters of the sample 12 to be inspected can be specifically extracted, shortening the time required to extract relevant device parameters.

[0067] In addition, the embodiment of the present invention also provides a detection device based on second harmonic characterization, referring to Figure 1 、 Figure 2 、 Figure 3 and Figure 4The detection device includes any of the above-mentioned second harmonic characterization optical systems. By adopting an incident optical path system with a tunable wavelength of the fundamental frequency light 26, after selecting a scanning point on the surface of the sample 12 to be detected, the wavelength of the fundamental frequency light 26 is continuously tuned from a first set wavelength to a second set wavelength by tuning. After each tuning of the wavelength of the fundamental frequency light 26, the wavelength-tuned fundamental frequency light 26 is incident on the scanning point, and the second harmonic signal 301 generated by the wavelength-tuned fundamental frequency light 26 is collected; then, based on the collected second harmonic signal 301, a nonlinear spectrum of the second harmonic signal 301 is plotted. Through the nonlinear spectrum of the second harmonic signal 301, the different defect types at the scanning point during this scanning process, the defect energy levels 42 of the different defect types, and the wavelengths of the fundamental frequency light 26 corresponding to the different defect types can be obtained. In subsequent defect detection processes, such as scanning second harmonic signals 301 at other scanning points on the surface of the same sample 12 to be inspected, or detecting time-dependent second harmonic signals 301 at the same scanning points, the corresponding scanning wavelength and detection wavelength can be determined based on the nonlinear spectrum of second harmonic signal 301. By tuning the wavelength of fundamental frequency light 26, the second harmonic can be used to effectively characterize lower defect densities. Furthermore, due to the targeted tuning of the wavelength of fundamental frequency light 26, relevant parameters of the sample 12 to be inspected can be specifically extracted, shortening the time required to extract relevant device parameters.

[0068] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A second harmonic characterization method, characterized in that: include: Step 1: Select scanning points on the surface of the sample to be tested; Step 2: injecting fundamental frequency light of a first set wavelength into the scanning point; After the fundamental frequency light is incident on the sample to be inspected, a second harmonic signal carrying sample defect information is generated, and the second harmonic signal is emitted along the direction of the light beam reflected from the surface of the sample to be inspected; Step 3: Collect the second harmonic signal; Step 4: continuously tuning the fundamental frequency light from the first set wavelength to the second set wavelength according to a preset step; After tuning the wavelength of the fundamental frequency light each time, the fundamental frequency light with the tuned wavelength is incident on the scanning point, and the second harmonic signal generated by the fundamental frequency light with the tuned wavelength is collected; Step 5: Drawing a nonlinear spectrum of the second harmonic signal based on the collected second harmonic signal; The method further comprises: According to the nonlinear spectrum of the second harmonic signal, the wavelength corresponding to the second harmonic signal when the intensity exceeds a first preset threshold is used as the scanning wavelength; Other scanning points are selected in sequence on the surface of the sample to be detected, and after each scanning point is selected, the fundamental frequency light of the scanning wavelength is incident on the scanning point, and the second harmonic signal generated by the fundamental frequency light of the scanning wavelength is collected.

2. The second harmonic characterization method according to claim 1, wherein: Also includes: Other scanning points are selected on the surface of the sample to be detected in sequence, and after each scanning point is selected, the nonlinear spectrum of the second harmonic signal of the scanning point is plotted according to steps 2 to 5.

3. The second harmonic characterization method according to claim 1, wherein: Also includes: According to the nonlinear spectrum of the second harmonic signal, the wavelength corresponding to the second harmonic signal when the intensity exceeds a second preset threshold is used as the detection wavelength in the process of detecting the time-dependent second harmonic signal; The time-correlated second harmonic signal at the scanning point is detected using the detection wavelength.

4. A second harmonic characterization optical system based on the second harmonic characterization method according to any one of claims 1 to 3, characterized in that: include: a sample stage for holding a sample to be tested thereon; An incident light path system is configured to inject fundamental frequency light of a first set wavelength into a scanning point selected on the surface of the sample to be inspected; after the fundamental frequency light is incident on the sample to be inspected, a second harmonic signal carrying sample defect information is generated, and the second harmonic signal is emitted along the direction of the light beam reflected from the surface of the sample to be inspected; An output optical path system including a detector, wherein the output optical path system is used to collect the second harmonic signal in the detector; The incident optical path system is further capable of continuously tuning the fundamental frequency light from the first set wavelength to the second set wavelength according to a preset step; and after each tuning of the wavelength of the fundamental frequency light, the incident optical path system injects the wavelength-tuned fundamental frequency light into the scanning point, and the outgoing optical path system collects the second harmonic signal generated by the wavelength-tuned fundamental frequency light; The invention also includes: a nonlinear spectrum drawing module, which is used to draw a nonlinear spectrum of the second harmonic signal according to the collected second harmonic signal; It also includes a support structure, the support structure includes an arc guide rail, the sample stage is arranged at the center of the arc guide rail, and the incident light path system and the output light path system are slidably assembled on the arc guide rail; The sample stage can move relative to the circular arc guide rail on three mutually perpendicular motion axes; The second harmonic characterization optical system further comprises: a scanning wavelength determination module, configured to determine, based on the nonlinear spectrum of the second harmonic signal, a wavelength corresponding to the second harmonic signal when the intensity exceeds a first preset threshold as a scanning wavelength; A control module that is communicatively connected to the incident light path system, the output light path system, the sample stage, and the nonlinear spectrum drawing module; The control module is used to control the incident light path system to tune the wavelength of the fundamental frequency light; The control module is further configured to control the sample stage to sequentially move the sample to be detected to other positions after completing the characterization of the scanning points, so that the fundamental frequency light is sequentially incident on other scanning points on the surface of the sample to be detected; The control module is also used to control the incident light path system to use the fundamental frequency light of the scanning wavelength to be incident on the scanning point after each movement of the scanning point, and control the output light path system to collect the second harmonic signal generated by the fundamental frequency light of the scanning wavelength.

5. The second harmonic characterization optical system according to claim 4, wherein: The incident light path system comprises: a tunable laser for emitting a laser beam; A coupler connected to the tunable laser through an optical fiber; a polarizer positioned opposite to the coupler, the polarizer being used to polarize the laser beam into polarized fundamental frequency light having a set polarization state; A first objective lens is located opposite to the polarizer, and is used to focus the polarized fundamental frequency light into the fundamental frequency light that meets the test requirements, and to make the fundamental frequency light incident on a scanning point on the surface of the sample to be tested.

6. The second harmonic characterization optical system according to claim 5, wherein: The tunable laser is a tunable femtosecond laser.

7. The second harmonic characterization optical system according to claim 6, wherein: The incident light path system also includes: A nonlinear optical frequency conversion module is connected to the optical path between the tunable femtosecond laser and the coupler.

8. The second harmonic characterization optical system according to claim 7, wherein: The nonlinear optical frequency conversion module includes: An optical parametric oscillator is connected to the optical path between the tunable femtosecond laser and the coupler.

9. The second harmonic characterization optical system according to claim 8, wherein: The nonlinear optical frequency conversion module further includes: An idler optical module is connected to the optical path between the optical parametric oscillator and the coupler.

10. The second harmonic characterization optical system according to claim 9, wherein: The nonlinear optical frequency conversion module further includes: A difference frequency module is connected to the optical path between the idler optical module and the coupler.

11. The second harmonic characterization optical system according to claim 4, wherein: The sample stage can move relative to the circular arc guide rail on three mutually perpendicular motion axes; The second harmonic characterization optical system further includes: a control module that is communicatively connected to the incident light path system, the output light path system, the sample stage, and the nonlinear spectrum drawing module; The control module is used to control the incident light path system to tune the wavelength of the fundamental frequency light; The control module is further configured to control the sample stage to sequentially move the sample to be detected to other positions after completing the characterization of the scanning points, so that the fundamental frequency light is sequentially incident on other scanning points on the surface of the sample to be detected; The control module is further configured to control the incident light path system and the output light path system to execute steps 2 to 4 after each scanning point is moved, and the nonlinear spectrum drawing module draws the second harmonic signal nonlinear spectrum of the scanning point.

12. The second harmonic characterization optical system according to claim 4, wherein: Also includes: a detection wavelength determination module, configured to use, based on the nonlinear spectrum of the second harmonic signal, the wavelength corresponding to the second harmonic signal when the intensity exceeds a second preset threshold as the detection wavelength in the process of detecting the time-dependent second harmonic signal; The detection module is configured to detect the time-correlated second harmonic signal at the scanning point using the detection wavelength.

13. A detection device based on second harmonic characterization, characterized in that: The optical system comprises the second harmonic characterization optical system according to any one of claims 4 to 12.

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