Method and device for testing minority carrier lifetime of semiconductor material

Abstract

The invention provides a method and device for testing minority carrier lifetime of a semiconductor material, and the method comprises the steps: fixing an incident laser parameter, enabling laser to vertically enter the surface of a sample, firstly testing the reflectivity of a to-be-tested sample to the incident laser when a zero magnetic field is tested, taking the reflectivity as a reference value, then applying an incremental magnetic field, and finally testing the minority carrier lifetime of the to-be-tested sample. And testing the change rate of the corresponding reflectivity relative to the reference value under a plurality of different magnetic field intensities to obtain a data set of the change rate of the reflectivity along with the change of the magnetic field, fitting to obtain a reflectivity change rate-magnetic field curve, and finally solving the minority carrier lifetime based on the curve. The detection device comprises a sample table, a magnetic field applying device and a light path assembly. Magnetic field-optical cooperative modulation is used, the sensitivity of carrier space distribution to minority carrier lifetime is enhanced by using a magnetic field, the signal-to-noise ratio limitation of a traditional optical method is overcome, a multi-parameter decoupling algorithm is used, and cross interference of mobility is eliminated through variable magnetic field measurement. And high-precision extraction of single-variable minority carrier lifetime can be realized.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor technology and relates to a method and apparatus for testing the minority carrier lifetime of semiconductor materials. Background Technology

[0002] In pure intrinsic semiconductors (such as intrinsic Si and Ge), electrons and holes are generated by intrinsic excitation (thermal excitation), and their concentrations are strictly equal. At this point, there is no majority / minority distinction, and the overall carrier concentration is extremely low, resulting in poor conductivity. In practical applications, semiconductors are doped (P-type or N-type) to change the carrier concentration. After doping, one type of carrier becomes absolutely dominant, while the other is generated only by thermal excitation, significantly improving the semiconductor's conductivity. Minority carriers, which have a lower concentration in the semiconductor, are the opposite of majority carriers. Their concentration is determined by the type and concentration of doping in the semiconductor, and they are the two main carriers of semiconductor conductivity.

[0003] For N-type doped semiconductors, such as doping intrinsic semiconductors (such as Si) with pentavalent impurities (such as phosphorus P and arsenic As), of the five valence electrons of the impurity atom, four form covalent bonds with the Si atom, and the remaining valence electron easily detaches from the impurity atom to become a free electron. Moreover, this process does not require thermal excitation (or only requires extremely low energy). Therefore, the majority carriers of N-type semiconductors are free electrons (directly provided by doping, with a concentration approximately equal to the doping concentration), and the minority carriers are holes (generated only by thermal excitation, with a concentration much lower than that of electrons).

[0004] For P-type doped semiconductors, such as doping intrinsic semiconductors with trivalent impurities (e.g., boron B, gallium Ga), the impurity atoms have only 3 valence electrons. When they form covalent bonds with Si atoms, they generate 1 hole. This hole can easily capture surrounding valence electrons, meaning that the hole can move freely. Similarly, it does not require high-energy excitation. Therefore, the majority carriers of P-type semiconductors are holes (directly provided by doping, concentration ≈ doping concentration), and the minority carriers are electrons.

[0005] The operation of a semiconductor device is essentially a non-equilibrium transport and recombination process of minority carriers. The mobility of minority carriers (describing how fast they move in an electric field) affects their transport speed, while the minority carrier lifetime (τ) describes the average time from their generation to recombination (disappearance), and is a core parameter determining the performance of semiconductor devices (such as switching speed and luminous efficiency). If the minority carrier lifetime is too long, recombination is slow, resulting in a low device switching speed; if the minority carrier lifetime is too short, recombination occurs before the carriers participate in device operation, leading to a significant decrease in luminous efficiency and current gain.

[0006] Traditional minority carrier lifetime testing methods, such as microwave photoconductivity attenuation (μ-PCD), require calibration and are sensitive to surfaces, while direct optical methods (such as transient reflection / transmission) are expensive and complex. Traditional detection methods, such as secondary ion mass spectrometry (SIMS) and deep-level transient spectroscopy (DLTS), have high accuracy but suffer from the following problems: (1) destructive: requiring sample pretreatment (such as etching and electrode preparation); (2) high cost: long detection cycle.

[0007] Therefore, how to provide a method and apparatus for testing the minority carrier lifetime of semiconductor materials to achieve non-contact, high-precision extraction of the single variable minority carrier lifetime τ has become an important technical problem that needs to be solved by those skilled in the art.

[0008] It should be noted that the above introduction to the technical background is only for the purpose of providing a clear and complete explanation of the technical solutions of this application and facilitating understanding by those skilled in the art. It should not be assumed that these technical solutions are known to those skilled in the art simply because they have been described in the background section of this application. Summary of the Invention

[0009] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a method and apparatus for testing the minority carrier lifetime of semiconductor materials, so as to solve the problems of high destructiveness and high cost of the detection methods in the prior art.

[0010] To achieve the above and other related objectives, the present invention provides a method for testing the minority carrier lifetime of semiconductor materials, comprising the following steps:

[0011] Provide a sample to be tested, the sample to be tested comprising a doped semiconductor layer;

[0012] With the parameters of the incident laser fixed, the laser is incident perpendicularly on the surface of the sample to be tested. The reflectivity of the sample to be tested to the incident laser is measured when there is zero magnetic field, and this is used as the reflectivity reference value.

[0013] An increasing magnetic field is applied, and the reflectivity of the sample to be tested for the incident laser is tested under multiple different magnetic field intensities. The rate of change of the reflectivity obtained each time relative to the reference reflectivity value is calculated to obtain a dataset of the rate of change of reflectivity with the magnetic field.

[0014] Based on the dataset, a reflectance change rate-magnetic field curve was obtained;

[0015] The minority carrier lifetime is determined based on the reflectivity change rate-magnetic field curve.

[0016] Optionally, when obtaining the reflectivity change rate-magnetic field curve based on the dataset, the reflectivity change rate-magnetic field curve is fitted to the theoretical model. , where ΔR is the reflectivity change, B is the magnetic field strength, ∝ is the proportional sign, μ is the carrier mobility, and τ is the minority carrier lifetime.

[0017] Optionally, the reflectivity change rate-magnetic field curve can be obtained by fitting using the least squares method.

[0018] Optionally, the doped semiconductor layer includes a p-type silicon layer, the minority carrier diffusion coefficient of which is 12 cm⁻¹. 2 / s.

[0019] Optionally, the increment of the increasing magnetic field does not exceed 0.2 T.

[0020] Optionally, the increasing magnetic field increases sequentially within the range of 0 T to NT, where N is no greater than 2.

[0021] The present invention also provides a detection device for performing the test method for minority carrier lifetime of semiconductor materials as described in any of the above embodiments, comprising:

[0022] The sample stage is used to hold the sample to be tested.

[0023] A magnetic field application device is disposed above the sample stage;

[0024] An optical path assembly is disposed between the sample stage and the magnetic field application device. The optical path assembly includes a laser, a polarizer, a focusing lens, a beam splitter, a reflector, and a photodetector arranged sequentially according to a preset path. The laser emitted by the laser passes sequentially through the polarizer and the focusing lens to the beam splitter, and is then reflected by the beam splitter to the surface of the sample to be tested. It is then reflected again by the sample to be tested to the beam splitter, and transmitted through the beam splitter to the reflector. The photodetector receives the laser reflected from the reflector and performs photoelectric conversion to obtain reflectivity data.

[0025] Optionally, the sample stage includes a non-magnetic ceramic base.

[0026] Optionally, the laser emits laser light with a wavelength of 830 nm.

[0027] Optionally, the extinction ratio of the polarizer is >1000:1, and the reflection-to-transmission ratio of the beam splitter is 1:1.

[0028] As described above, the method for testing the minority carrier lifetime of semiconductor materials according to the present invention, under fixed incident laser parameters, involves perpendicularly incidenting the laser onto the sample surface. First, the reflectivity of the sample to the incident laser is measured at zero magnetic field and used as a reference value. Then, an increasing magnetic field is applied, and the reflectivity of the sample to the incident laser is measured at multiple different magnetic field intensities. The rate of change of reflectivity relative to the reference value is calculated each time, resulting in a dataset of reflectivity change rate versus magnetic field. A reflectivity change rate-magnetic field curve is then fitted based on this dataset, and the minority carrier lifetime is calculated from this curve. The detection device of the present invention includes a sample stage, a magnetic field application device, and an optical path assembly for performing the above testing method. The present invention uses magnetic field-optical co-modulation, leveraging the magnetic field to enhance the sensitivity of carrier spatial distribution to minority carrier lifetime, overcoming the signal-to-noise ratio limitations of traditional optical methods. Furthermore, the present invention uses a multi-parameter decoupling algorithm to eliminate cross-interference of mobility through variable magnetic field measurement, enabling non-contact, high-precision extraction of the single variable minority carrier lifetime. Attached Figure Description

[0029] Figure 1 The flowchart shown is a test method for the minority carrier lifetime of semiconductor materials according to the present invention.

[0030] Figure 2 The diagram shows the test principle of the test method for testing the minority carrier lifetime of semiconductor materials according to the present invention.

[0031] Figure 3 The method for testing the minority carrier lifetime of semiconductor materials according to the present invention is shown in one embodiment based on a reflectivity change rate-magnetic field curve obtained by fitting a dataset.

[0032] Figure 4 The diagram shown is a structural schematic of the detection device of the present invention.

[0033] Explanation of reference numerals in the attached figures

[0034] S1~S5 step 1 Sample stage 2 Magnetic field application device 3 Optical path components 301 laser 302 polarizer 303 Focusing lens 304 Beam splitter 305 reflector 306 Photodetector 4 Sample to be tested Detailed Implementation

[0035] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0036] It should be emphasized that the term "including / comprises" as used herein refers to the presence of a feature, whole, step, or component, but does not exclude the presence or addition of one or more other features, wholes, steps, or components.

[0037] Features described and / or illustrated for one embodiment may be used in the same or similar manner in one or more other embodiments, combined with features in other embodiments, or substituted for features in other embodiments.

[0038] In the detailed description of embodiments of the present invention, for ease of explanation, the schematic diagrams illustrating the device structure may be partially enlarged without adhering to the general scale, and the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. Furthermore, in actual manufacturing, the three-dimensional spatial dimensions of length, width, and depth should be included.

[0039] For ease of description, spatial relation terms such as “below,” “under,” “lower than,” “below,” “above,” and “upper” may be used herein to describe the relationship between one element or feature shown in the accompanying drawings and other elements or features. It will be understood that these spatial relation terms are intended to include directions other than those depicted in the drawings for devices in use or operation. Furthermore, when a layer is referred to as being “between” two layers, it may be the only layer between the two layers, or there may be one or more layers in between.

[0040] In the context of this application, the structure described above the first feature may include embodiments in which the first and second features are in direct contact, or embodiments in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact.

[0041] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the illustrations only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0042] This invention provides a method for testing the minority carrier lifetime of semiconductor materials. This method uses magnetic field-optical co-modulation to enhance the sensitivity of the spatial distribution of carriers to the minority carrier lifetime by utilizing the magnetic field, thus overcoming the signal-to-noise ratio limitation of traditional optical methods. Furthermore, this invention uses a multi-parameter decoupling algorithm to eliminate cross-interference of mobility through variable magnetic field measurement, which can achieve non-contact and high-precision extraction of the minority carrier lifetime of a single variable.

[0043] For details, please refer to Figure 1 The flowchart shown is a test method for the minority carrier lifetime of semiconductor materials according to the present invention, including the following steps:

[0044] S1: Provide a sample to be tested, the sample to be tested including a doped semiconductor layer;

[0045] S2: Fix the parameters of the incident laser, make the laser perpendicularly incident on the surface of the sample to be tested, test the reflectivity of the sample to be tested to the incident laser when there is zero magnetic field, and use it as the reflectivity reference value.

[0046] S3: Apply an increasing magnetic field, test the reflectivity of the sample under test to the incident laser under multiple different magnetic field intensities, and calculate the rate of change of the reflectivity obtained each time relative to the reflectivity reference value, to obtain a dataset of the reflectivity change rate as a function of the magnetic field.

[0047] S4: Based on the dataset, obtain the reflectivity change rate-magnetic field curve;

[0048] S5: Calculate the minority carrier lifetime based on the reflectivity change rate-magnetic field curve.

[0049] Before detailing each step of the method for testing the minority carrier lifetime of semiconductor materials according to the present invention, the testing principle of the method for testing the minority carrier lifetime of semiconductor materials according to the present invention will be explained first.

[0050] Specifically, under the influence of a magnetic field, charge carriers in a semiconductor are affected by the Lorentz force, causing their trajectories to deflect and altering their spatial distribution. The longer the minority carrier lifetime, the greater the range of magnetic field modulation the carriers undergo before recombination, resulting in a significant change in the complex refractive index at the material surface / interface. By measuring the rate of reflectivity change under different magnetic field strengths, a quantitative model of its relationship with diffusion length can be established. Combined with the relationship between minority carrier lifetime and diffusion length, a relationship between the rate of reflectivity change and minority carrier lifetime can be established.

[0051] For example, please refer to Figure 2 The diagram shows the test principle of the method for testing the minority carrier lifetime of semiconductor materials according to the present invention. In this method, the change of magnetic field B causes a change in carrier distribution, which in turn causes a change in refractive index and a change in reflectivity. The change in carrier distribution is related to the minority carrier lifetime.

[0052] The following details each step of the method for testing the minority carrier lifetime of semiconductor materials according to the present invention.

[0053] First, perform step S1: provide a sample to be tested, the sample to be tested including a doped semiconductor layer.

[0054] As an example, the doped semiconductor layer may include a silicon layer or other semiconductor material layer, and its doping type may be P-type or N-type.

[0055] In one embodiment, the doped semiconductor layer is a P-type silicon wafer with a known minority carrier diffusion coefficient of 12 cm⁻¹. 2 / s.

[0056] Next, perform step S2: fix the parameters of the incident laser, make the laser perpendicularly incident on the surface of the sample to be tested, test the reflectivity of the sample to be tested to the incident laser when there is zero magnetic field, and use it as the reflectivity reference value R0.

[0057] In some embodiments, an 830 nm wavelength laser is used as incident light, and a photodetector is used to receive the reflected laser light and perform photoelectric conversion to obtain reflectivity data.

[0058] Next, step S3 is performed: an increasing magnetic field is applied, and the reflectivity of the sample to be tested to the incident laser is tested under multiple different magnetic field intensities. The rate of change of the reflectivity obtained each time relative to the reflectivity reference value is calculated to obtain a dataset of the reflectivity change rate as a function of the magnetic field.

[0059] As an example, the increment of the increasing magnetic field does not exceed 0.2 T.

[0060] As an example, the increasing magnetic field increases sequentially within the range of 0 T to NT, where N is no greater than 2.

[0061] In one embodiment, the doped semiconductor layer is a P-type silicon wafer with a known minority carrier diffusion coefficient of 12 cm⁻¹. 2 / s. By varying the magnetic field from 0 T, 0.1 T, 0.3 T, ..., to 1 T, the reflectivity change was measured, and the dataset of reflectivity change rate as a function of magnetic field was obtained as shown in Table 1 below. Here, ΔR represents the reflectivity change, and ΔR / R0 (%) represents the reflectivity change rate.

[0062] Table 1: Data set of reflectivity change rate as a function of magnetic field

[0063] Magnetic field (B)(T) △R / R0(%) 0 0 0.1 -0.028 0.2 -0.133 0.3 -0.248 0.4 -0.418 0.5 -0.6 0.6 -0.766 0.7 -0.893 0.8 -0.97 0.9 -1.005 1 -1.02

[0064] Next, step S4 is performed: the reflectivity change rate-magnetic field curve is obtained by fitting the dataset.

[0065] For example, please refer to Figure 3 The result is displayed as the reflectance change rate-magnetic field curve, i.e., the ΔR / R0-B curve, obtained by fitting the dataset.

[0066] As an example, when obtaining the reflectivity change rate-magnetic field curve based on the dataset, the reflectivity change rate-magnetic field curve is fitted to the theoretical model. , where ΔR is the reflectivity change, B is the magnetic field strength, ∝ is the proportional sign, μ is the carrier mobility, and τ is the minority carrier lifetime.

[0067] Specifically, theoretical models The derivation process is as follows:

[0068] (1) Referring to "Solid State Physics" (Ashcroft & Mermin), the effect of the Lorentz force on carrier motion and the diffusion-drift equilibrium, the change in carrier concentration distribution caused by the magnetic field is as follows: ,in, For carrier concentration changes, For diffusion length, For carrier mobility, denoted as , where is the magnetic field strength.

[0069] (2) Refer to Moss, TS "Optical Properties of Semiconductors" (Butterworths, 1959), Chapter 3,

[0070] A linear approximation of carrier concentration and refractive index is obtained. .

[0071] (3) Referring to Fresnel's formula, for perpendicularly incident light, the relationship between reflectivity and refractive index is: Where R is reflectivity, For refractive index, for a small change in refractive index The changes in reflectivity and refractive index can be approximated as follows: Simplify the relationship to .

[0072] (4) Combining the relationship between minority carrier lifetime and diffusion length , and thus .

[0073] As an example, the reflectivity change rate-magnetic field curve is obtained by fitting using the least squares method.

[0074] Next, perform step S5: calculate the minority carrier lifetime based on the reflectivity change rate-magnetic field curve.

[0075] As an example, in the above embodiment, the minority carrier lifetime τ = 5.02 microseconds is obtained based on the reflectivity change rate-magnetic field curve.

[0076] Thus, by using magnetic field-optical co-modulation, the sensitivity of the spatial distribution of charge carriers to minority carrier lifetime is enhanced by the magnetic field, overcoming the signal-to-noise ratio limitation of traditional optical methods. Furthermore, by using a multi-parameter decoupling algorithm, cross-interference of mobility is eliminated through variable magnetic field measurement, ultimately achieving non-contact, high-precision detection of minority carrier lifetime in semiconductor materials.

[0077] The present invention also provides a detection device that can be used to perform the test method for minority carrier lifetime of semiconductor materials as described in any of the above embodiments.

[0078] For example, please refer to Figure 4 The diagram shows the structure of the detection device, which includes a sample stage 1, a magnetic field application device 2, and an optical path assembly 3. The sample stage 1 is used to hold the sample 4 to be tested. The magnetic field application device 2 is disposed above the sample stage. The optical path assembly 3 is disposed between the sample stage 1 and the magnetic field application device 2. The optical path assembly 3 includes a laser 301, a polarizer 302, a focusing lens 303, a beam splitter 304, a reflector 305, and a photodetector 306 arranged in sequence according to a preset path. The laser emitted by the laser 301 passes through the polarizer 302 and the focusing lens 303 to reach the beam splitter 304, and is then reflected by the beam splitter 304 to the surface of the sample 4 to be tested. It is then reflected again by the sample 4 to reach the beam splitter 304 and transmitted through the beam splitter 304 to the reflector 305. The photodetector 306 receives the laser reflected from the reflector 305 and performs photoelectric conversion to obtain reflectivity data.

[0079] In some embodiments, the sample stage 1 includes a non-magnetic ceramic base.

[0080] In some embodiments, the magnetic field applying device 2 includes an array of electromagnets / permanent magnets arranged parallel to the surface of the sample stage 1, and the magnetic field range is continuously adjustable from 0.1 T to 2 T.

[0081] In some embodiments, the laser 301 is an 830 nm laser that can emit laser light with a wavelength of 830 nm.

[0082] In some embodiments, the extinction ratio of the polarizer 302 is >1000:1 (s / p polarization separation), and the reflection-to-transmission ratio of the beam splitter 304 is 1:1.

[0083] In some embodiments, the focusing distance of the focusing lens 303 is 50 nm, and the spot diameter is <100 nm.

[0084] In some embodiments, the photodetector 306 includes an avalanche photodiode (APD) with a sensitivity of up to 10 nW.

[0085] The detection device of the present invention is easy to build and can achieve non-destructive, high-sensitivity detection of minority carrier lifetime of semiconductor materials based on magnetic field modulation of reflectivity.

[0086] In summary, the method for testing the minority carrier lifetime of semiconductor materials according to the present invention, under fixed incident laser parameters, involves perpendicularly incidenting the laser onto the sample surface. First, the reflectivity of the sample to the incident laser is measured at zero magnetic field and used as a reference value. Then, an increasing magnetic field is applied, and the reflectivity of the sample to the incident laser is measured at multiple different magnetic field intensities. The rate of change of reflectivity relative to the reference value is calculated each time, resulting in a dataset of reflectivity change rate versus magnetic field. Based on this dataset, a reflectivity change rate-magnetic field curve is fitted, and the minority carrier lifetime is calculated from this curve. The detection device of the present invention includes a sample stage, a magnetic field application device, and an optical path assembly for executing the above testing method. The present invention uses magnetic field-optical co-modulation, leveraging the magnetic field to enhance the sensitivity of carrier spatial distribution to minority carrier lifetime, overcoming the signal-to-noise ratio limitations of traditional optical methods. Furthermore, the present invention uses a multi-parameter decoupling algorithm to eliminate cross-interference of mobility through variable magnetic field measurement, achieving high-precision extraction of the single-variable minority carrier lifetime. Therefore, the present invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0087] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for testing the minority carrier lifetime of a semiconductor material, characterized in that, Includes the following steps: Provide a sample to be tested, the sample to be tested comprising a doped semiconductor layer; With the parameters of the incident laser fixed, the laser is incident perpendicularly on the surface of the sample to be tested. The reflectivity of the sample to be tested to the incident laser is measured when there is zero magnetic field, and this is used as the reflectivity reference value. An increasing magnetic field is applied, and the reflectivity of the sample to be tested for the incident laser is tested under multiple different magnetic field intensities. The rate of change of the reflectivity obtained each time relative to the reference reflectivity value is calculated to obtain a dataset of the rate of change of reflectivity with the magnetic field. Based on the dataset, a reflectance change rate-magnetic field curve was obtained; The minority carrier lifetime is determined based on the reflectivity change rate-magnetic field curve.

2. The method for testing the minority carrier lifetime of semiconductor materials according to claim 1, characterized in that: When obtaining the reflectivity change rate-magnetic field curve based on the dataset, the reflectivity change rate-magnetic field curve is fitted to the theoretical model. , where ΔR is the reflectivity change, B is the magnetic field strength, ∝ is the proportional sign, μ is the carrier mobility, and τ is the minority carrier lifetime.

3. The method for testing the minority carrier lifetime of semiconductor materials according to claim 1, characterized in that: The reflectivity change rate-magnetic field curve was obtained by fitting using the least squares method.

4. The method for testing the minority carrier lifetime of semiconductor materials according to claim 1, characterized in that: The doped semiconductor layer includes a p-type silicon layer, and the minority carrier diffusion coefficient of the p-type silicon layer is 12 cm⁻¹. 2 / s.

5. The method for testing the minority carrier lifetime of semiconductor materials according to claim 1, characterized in that: The increment of the increasing magnetic field does not exceed 0.2 T.

6. The method for testing the minority carrier lifetime of semiconductor materials according to claim 5, characterized in that: The increasing magnetic field increases sequentially within the range of 0 T to NT, where N is no greater than 2.

7. A detection apparatus for performing the test method for minority carrier lifetime of semiconductor materials as described in any one of claims 1 to 6, characterized in that, include: The sample stage is used to hold the sample to be tested. A magnetic field application device is disposed above the sample stage; An optical path assembly is disposed between the sample stage and the magnetic field application device. The optical path assembly includes a laser, a polarizer, a focusing lens, a beam splitter, a reflector, and a photodetector arranged sequentially according to a preset path. The laser emitted by the laser passes sequentially through the polarizer and the focusing lens to the beam splitter, and is then reflected by the beam splitter to the surface of the sample to be tested. It is then reflected again by the sample to be tested to the beam splitter, and transmitted through the beam splitter to the reflector. The photodetector receives the laser reflected from the reflector and performs photoelectric conversion to obtain reflectivity data.

8. The detection device according to claim 7, characterized in that: The sample stage includes a non-magnetic ceramic base.

9. The detection device according to claim 7, characterized in that: The laser emits laser light with a wavelength of 830 nm.

10. The detection device according to claim 7, characterized in that: The extinction ratio of the polarizer is >1000:1, and the reflection-to-transmission ratio of the beam splitter is 1:1.

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