A method for testing the recombination of a crystalline silicon surface

Abstract

This invention relates to the field of solar cell technology and discloses a testing method for surface recombination in crystalline silicon, comprising: preparing a silicon wafer sample including a calibration region and a test region; measuring the excess carrier concentration value Δn of the calibration region under different light intensities; measuring the spatially resolved photoluminescence (PL) brightness value of the entire silicon wafer sample under different light intensities; obtaining a calibration constant C based on the average Δn and average PL brightness value of the calibration region; obtaining the spatially resolved Δn of the entire silicon wafer sample under different light intensities based on C and the spatially resolved PL brightness value; and obtaining the spatially resolved minority carrier lifetime τ of the entire silicon wafer sample under different light intensities based on C and the spatially resolved Δn. eff Based on spatial resolution τ eff By using spatial resolution Δn, the spatially resolved surface recombination value J0 of the entire silicon wafer sample under different implantation concentrations is obtained. This method combines high spatial resolution and accuracy, accurately obtaining individual surface recombination values ​​under different implantation concentrations, and is time-efficient.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, and more specifically to a testing method for crystalline silicon surface composite. Background Technology

[0002] The surface recombination value of crystalline silicon (referred to as silicon wafer) is directly related to the open-circuit voltage of crystalline silicon solar cells. Therefore, to ensure a high open-circuit voltage, passivation antireflection films are usually deposited on the front and back surfaces of crystalline silicon solar cells to reduce surface recombination. Surface recombination of crystalline silicon is typically measured using the WCT-120 minority carrier lifetime test from Sinton Technologies, Inc. This test measures the change in photoconductivity within the silicon wafer using an oscillator circuit coil, thereby obtaining electrical parameters such as minority carrier lifetime and surface recombination under different injection concentrations (i.e., excess carrier concentrations under different light intensities). The oscillator circuit coil in the WCT-120 minority carrier lifetime test has a diameter of 4 cm. This not only means that the spatial resolution limit of the test is a circle with a diameter of 4 cm, and silicon wafer samples with a diameter smaller than 4 cm cannot be tested using the WCT-120 minority carrier lifetime test; it also means that the surface recombination value obtained using the WCT-120 minority carrier lifetime test is an average value and cannot reflect anomalies in local structures with a diameter smaller than 4 cm.

[0003] In previous years, commercially available crystalline silicon solar cells were relatively limited, including aluminum back surface field (ASF) cells and PERC cells. The conversion efficiency of crystalline silicon solar cells was also relatively low (<23%), and the emitter of crystalline silicon solar cells was uniformly doped across the entire surface. Therefore, the WCT-120 minority carrier lifetime test could be used to measure the surface recombination value of the silicon wafer. However, in recent years, with the application of new structures to crystalline silicon solar cells, such as selective emitter (SE) technology and localized passivation contact technology, the efficiency of commercially available crystalline silicon solar cells has gradually exceeded 24%. In these new commercially available crystalline silicon solar cells, the electrical performance of the local structure of the silicon wafer differs significantly from that of the rest of the wafer. The surface recombination value of this local structure also differs significantly from that of the rest of the wafer. The size of this local structure is typically on the micrometer scale. For example, the width of the heavily doped region in the SE structure is generally 80–120 μm, much smaller than the diameter of 4 cm, making it impossible to use the WCT-120 minority carrier lifetime test to measure the surface recombination value of this local structure. In such cases, the industry typically employs the following method: Prepare a large-area test region on the silicon wafer with the same performance as the localized structure, making the test region a circle with a diameter of 4cm. Then, use a WCT-120 minority carrier lifetime tester to measure the surface recombination value of the test region. However, using a large-area test region has several drawbacks: 1) It is difficult to ensure that the performance of a large-area test region is completely identical to that of a small-sized localized structure. That is, the surface recombination value obtained from a large-area test region cannot accurately represent the surface recombination value of a small-sized localized structure. Taking laser SE as an example, if a laser is used to continuously scan the silicon wafer for doping to form a test region with a side length of 4cm, the laser will undergo multiple acceleration, deceleration, and translational movements within the 4cm test region. This differs from the laser movement in actual laser SE cell fabrication, significantly affecting the accuracy of the surface recombination value of the small-sized localized structure on the silicon wafer. 2) The preparation time for a large-area test region is long. Taking laser SE as an example, the time required to form a test region with a side length of 4cm is 200 times or more than the time required in actual laser SE cell fabrication.

[0004] Besides the drawbacks of insufficient accuracy and long processing time, the limited number of large-area test areas that can be accommodated on a single silicon wafer makes process debugging on a single wafer extremely inefficient. Taking laser SE as an example, when debugging laser processes, if an M10 (side length 18.2cm, area 330.15cm²) is used... 2 A single silicon wafer can form a maximum of 16 square test areas with sides of 4cm, meaning a maximum of 16 laser processes can be adjusted. If the spatial resolution of the test surface can be reduced to 1cm, the area of ​​the test region can be reduced to 1cm. 2This allows for the formation of at least 300 square test areas with sides of 1 cm on a single silicon wafer, improving the efficiency of laser process debugging by at least 18 times. If the spatial resolution of the test surface can be further reduced, the corresponding process debugging efficiency will further increase.

[0005] Photoluminescence (PL) testing is a relatively new testing method that detects defects in silicon wafers by capturing images of the brightness of the photoluminescence emitted by the wafer. It offers advantages such as being non-contact, non-destructive, and having high spatial resolution, allowing for the simultaneous acquisition of millions of data points within seconds. Common PL equipment in the industry uses CCD or CMOS cameras with 1 million pixels and a resolution of 1024*1024. If the camera's field of view is focused on a 4cm*4cm square area, the spatial resolution can reach 39μm (4cm / 1024=39μm), which is far smaller than the size of local structures on the silicon wafer (e.g., the width of heavily doped regions in SE structures is typically 80–120μm). However, while PL testing offers high spatial resolution and allows calculation of the total recombination value of the silicon wafer (i.e., the sum of surface recombination and bulk recombination values), it cannot separate the surface recombination value from the bulk recombination value. Therefore, it cannot obtain the surface recombination value independently, affecting the accuracy of the surface recombination value of the silicon wafer.

[0006] CN113075172A discloses a method for testing the surface recombination current density distribution of a double-sided symmetrical passivated silicon wafer. This method tests the excess carrier concentration Δn and average luminous intensity PL of the test area of ​​the double-sided symmetrical passivated silicon wafer under a series of different illumination conditions. Then, based on the specific relationship between Δn and the implicit open-circuit voltage iVoc, a linear relationship between iVoc and ln(PL) is established. Furthermore, based on the correspondence between iVoc and the surface recombination current density (referred to as surface recombination) distribution J0 of the double-sided symmetrical passivated silicon wafer, a correspondence between ln(PL) and J0 is established. Thus, the surface recombination current density distribution J0 of the test area can be obtained. However, this method has the following three drawbacks: 1) The J0 value obtained by this method is the total recombination value, which includes the bulk recombination value; see paragraph

[0032] of the method specification. Because iVoc reflects the implicit open-circuit voltage of the silicon wafer as a whole in the test area, while the surface recombination current density can only reflect the recombination degree on the surface of the test area, this method cannot obtain a simple surface recombination value, affecting the accuracy of the surface recombination value of the silicon wafer. 2) Although this method preferably uses silicon wafers with high resistivity and low doping concentration as the substrate, because the bulk recombination of high resistivity silicon wafers is relatively small compared to its surface recombination, the influence of bulk recombination on the surface recombination current density test results can be ignored during the test (see paragraph

[0035] of the method specification). However, when the process treatment performed on the test area affects the bulk area, such as a deeper doping concentration or damage to the bulk area by laser SE process, even if a silicon wafer with high resistivity and low doping concentration is used, the influence of bulk recombination on the surface recombination current density test results cannot be ignored, affecting the accuracy of the surface recombination value of the silicon wafer. 3) This method can only obtain the recombination current density value under one solar intensity condition. It is a single value and cannot obtain the recombination current density value (referred to as recombination value) under different injection concentrations. In high-efficiency crystalline silicon solar cells, the surface recombination value will change with the injection concentration, and only the surface recombination value at the maximum power point is representative.

[0007] It is evident that existing methods for testing surface recombination in crystalline silicon still have many shortcomings: such as being time-consuming, lacking micron-level spatial resolution, being unable to accurately obtain individual surface recombination values, resulting in low accuracy, and being unable to obtain surface recombination values ​​under different implantation concentrations; in particular, they cannot simultaneously achieve high spatial resolution and accuracy. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a test method for surface recombination of crystalline silicon with micron-level spatial resolution. This test method has both high spatial resolution and accuracy, can accurately obtain individual surface recombination values, is time-efficient, and can obtain surface recombination values ​​under different implantation concentrations.

[0009] Based on this, the present invention discloses a test method for surface recombination of crystalline silicon, comprising the following test steps:

[0010] Step S1: Prepare a silicon wafer sample using a single-crystal silicon substrate. The silicon wafer sample includes a calibration area and a test area. The calibration area is a square area with a size of not less than 4cm*4cm, and the test area is a square area with a side length of micrometers. The passivation properties of the test area and the calibration area are different, and the passivation properties of each position in the calibration area are relatively uniform, so that the difference in surface recombination value of each position in the calibration area does not exceed 10%.

[0011] Step S2: Test the calibration area and obtain the excess carrier concentration value Δn under different light intensities;

[0012] Step S3: Test the entire silicon wafer sample to obtain the spatially resolved photoluminescence (PL) brightness values ​​of the entire silicon wafer sample under different light intensities;

[0013] Step S4: Obtain the calibration constant C based on the average excess carrier concentration value Δn and the average spatially resolved photoluminescence (PL) brightness value in the calibration area;

[0014] Step S5: Based on the calibration constant C and the spatially resolved photoluminescence (PL) brightness value, obtain the spatially resolved excess carrier concentration value Δn of the entire silicon wafer sample under different light intensities;

[0015] Step S6: Based on the calibration constant C and the spatially resolved excess carrier concentration value Δn, obtain the spatially resolved minority carrier lifetime τ of the entire silicon wafer sample under different light intensities. eff ;

[0016] Step S7: Spatially determine minority carrier lifetime τ eff By combining the spatially resolved excess carrier concentration value Δn, the spatially resolved surface recombination value J0 of the entire silicon wafer sample under different injection concentrations is obtained.

[0017] Preferably, in step S1, the conductivity type of the single-crystal silicon substrate is N-type or P-type;

[0018] The test area is a square region with a side length of not less than 1 μm;

[0019] The difference in passivation performance between the test area and the calibration area includes differences in doping, structure, and / or passivation antireflection film between the two areas.

[0020] More preferably, the silicon wafer sample includes a monocrystalline silicon substrate, and passivation antireflection films are provided on the front and back surfaces of the monocrystalline silicon substrate. A doped layer with a homojunction and passivation contact structure may be provided between the monocrystalline silicon substrate and the passivation antireflection film of the silicon wafer sample; alternatively, no doped layer may be provided between the monocrystalline silicon substrate and the passivation antireflection film of the silicon wafer sample.

[0021] Preferably, in step S2, the excess carrier concentration value Δn of the calibration region under different light intensities is measured using a WCT-120 minority carrier lifetime tester.

[0022] Preferably, step S3 specifically includes the following steps:

[0023] Step S31: Use a PL device to measure the spatially resolved photoluminescence PL brightness map of the entire silicon wafer sample under different light intensities;

[0024] Step S32: Based on the spatially resolved photoluminescence (PL) brightness map, obtain the spatially resolved photoluminescence (PL) brightness values ​​of the entire silicon wafer sample under different light intensities.

[0025] Preferably, step S4 specifically includes the following steps:

[0026] Step S41: Based on the excess carrier concentration values ​​Δn of the calibration area under different light intensities in Step S2, obtain the average excess carrier concentration value Δn0 of the calibration area under a specific light intensity; and based on the spatially resolved photoluminescence (PL) brightness values ​​of the entire silicon wafer sample under different light intensities in Step S3, obtain the average PL brightness value I of the calibration area under the same specific light intensity. PL,0 ;

[0027] Step S42: Based on Δn0 and I PL,0 The calibration constant C is calculated using the following formula:

[0028]

[0029] In the formula, I PL,0 Δn0 is the average PL brightness value of the calibration area under a specific light intensity, Δn0 is the average excess carrier concentration value of the calibration area under the same specific light intensity, C is the calibration constant, and N is the average excess carrier concentration value of the calibration area under the same specific light intensity. doped The doping concentration is the doping concentration of the single-crystal silicon substrate.

[0030] Preferably, step S5 specifically includes the following steps:

[0031] Step S51: When any point in the silicon wafer sample corresponds to a pixel with x-coordinate and y-coordinate in the pixel matrix of the PL device's camera, then under light intensity n suns, the spatially resolved photoluminescence PL brightness value of the point with coordinates (x,y) is I. PL_n (x,y);

[0032] Step S52: According to I PL_n Given (x,y) and the calibration constant C, the spatially resolved excess carrier concentration Δn at coordinates (x,y) in the silicon wafer sample under the same light intensity is obtained using the following formula. _n (x,y):

[0033]

[0034] In the formula, I PL_n (x,y) represents the spatially resolved photoluminescence (PL) value of the point at coordinates (x,y) in the silicon wafer sample under n solar intensities; Δn _n (x,y) represents the spatially resolved excess carrier concentration at coordinates (x,y) in the silicon wafer sample under the same light intensity; C is the calibration constant; N doped The doping concentration is the doping concentration of the single-crystal silicon substrate.

[0035] More preferably, in step S6, according to Δn _n Given (x,y) and the calibration constant C, the spatially resolved minority carrier lifetime τ of the point with coordinates (x,y) in the silicon wafer sample under the same light intensity is obtained using the following formula. eff (x,y):

[0036]

[0037] In the formula, Δn _n (x,y) represents the spatially resolved excess carrier concentration at coordinates (x,y) in a silicon wafer sample under n solar intensities; τ eff (x,y) represents the spatially resolved minority carrier lifetime of the point at coordinates (x,y) in the silicon wafer sample under the same light intensity; R is the reflectivity of the silicon wafer sample; W is the thickness of the single-crystal silicon substrate; Φ is the photon flux irradiated to the surface of the silicon wafer sample by the PL device, and the photon flux of 1 solar intensity is 2.5 × 10⁻⁶. 17 cm -2 s -1 .

[0038] More preferably, in step S7, the minority carrier lifetime τ is determined based on spatial resolution. eff The spatially resolved excess carrier concentration Δn is used to obtain the spatially resolved surface recombination value J0 of the entire silicon wafer sample under different implantation concentrations using the following formula:

[0039]

[0040] In the formula, J0 is the spatially resolved surface recombination value of the silicon wafer sample under different injection concentrations, Δn is the spatially resolved excess carrier concentration value of the silicon wafer sample under different light intensities, and q is the unit charge of the silicon wafer sample, with a value of 1.6 × 10⁻⁶. - 19 C; W is the thickness of the single-crystal silicon substrate; n i This represents the intrinsic carrier concentration of the silicon wafer sample, with a value of 8.6 × 10⁻⁶. 9 cm -3 ;

[0041] in,

[0042]

[0043] In the formula, τ cor For the corrected minority carrier lifetime, τ eff τ represents the minority carrier lifetime of the silicon wafer sample. Auger τ represents the Auger recombination lifetime of the silicon wafer sample. bulk,SRH For the bulk SRH recombination lifetime of the silicon wafer sample, when the implantation concentration is constant, 1 / τ bulk,SRH N is a constant; doped The doping concentration is the doping concentration of the single-crystal silicon substrate.

[0044] More preferably, in step S7, the spatially resolved surface recombination value J0(x,y) of the point with coordinates (x,y) in the silicon wafer sample at a specific implantation concentration is obtained by the following formula:

[0045]

[0046] In the formula, the solar intensity n is greater than the solar intensity m, and Δn _n (x,y) represents the spatially resolved excess carrier concentration at n solar irradiances, Δn _m (x,y) represents the spatially resolved excess carrier concentration at m solar irradiances, τ cor_n (x,y) represents the corrected minority carrier lifetime under n solar intensities, τ cor_m (x,y) represents the corrected minority carrier lifetime under m solar intensities; q represents the unit charge of the silicon wafer sample, with a value of 1.6 × 10⁻⁶. -19 C; W is the thickness of the single-crystal silicon substrate; n i This represents the intrinsic carrier concentration of the silicon wafer sample, with a value of 8.6 × 10⁻⁶. 9 cm -3 .

[0047] Compared with the prior art, the present invention has at least the following beneficial effects:

[0048] The present invention provides a method for testing surface recombination in crystalline silicon that overcomes the size limitations of conventional surface recombination testing methods (such as WCT-120 minority carrier lifetime testing) on ​​silicon wafer samples. It combines the advantage of the conventional WCT-120 minority carrier lifetime testing method in obtaining surface recombination with the advantage of photoluminescence (PL) testing method in obtaining high spatial resolution. This method overcomes the dependence of the conventional WCT-120 minority carrier lifetime testing method on silicon wafer sample size, the disadvantage of the photoluminescence (PL) testing method in not being able to obtain surface recombination on its own, and the defect of existing crystalline silicon surface recombination testing methods in not being able to accurately obtain surface recombination values. It can accurately and quickly test the surface recombination value of uniformly doped layers in conventional silicon wafer samples, as well as the surface recombination value of small local structures in silicon wafer samples.

[0049] The technical advantages of the test method for surface recombination in crystalline silicon of this invention include: 1) The test method has high spatial resolution (up to 39 μm or even smaller), at the micrometer level, suitable for testing small local structures in silicon wafer samples; 2) The test method has high accuracy. This test method is based on the conventional WCT-120 minority carrier lifetime test method, is not affected by body recombination, and is not limited by the size of the silicon wafer sample, and can accurately obtain the individual surface recombination values ​​of small local structures in the silicon wafer sample; 3) The test range is wide, and surface recombination values ​​under different implantation concentrations can be obtained, not limited to a single implantation concentration value, and applicable to doped layers of isojunction and passivated contact structures; 4) It improves the efficiency of process debugging on silicon wafer samples, is not limited by the size of the area to be tested, is not limited by the resistivity of the silicon wafer, can accommodate more local structures on the same silicon wafer, and can try more process conditions at the same time. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of the test process for a test method of crystalline silicon surface composite according to the present invention.

[0051] Figure 2 This is a schematic diagram of the structure of the silicon wafer sample to be tested in Embodiment 1 of the present invention.

[0052] Figure 3 This is a graph showing the excess carrier concentration Δn of the calibration region under different light intensities obtained in step two of Embodiment 1 of the present invention.

[0053] Figure 4 This is a spatially resolved photoluminescence (PL) brightness diagram of the silicon wafer sample obtained in step three of Embodiment 1 of the present invention at 0.4 solar intensity.

[0054] Figure 5This is a two-dimensional distribution diagram of the surface composite value J0 of the silicon wafer sample obtained in step seven of Embodiment 1 of the present invention.

[0055] Figure 6 This is a two-dimensional distribution diagram of the surface composite value J0 of the silicon wafer sample obtained in step seven of Embodiment 2 of the present invention.

[0056] Figure 7 This is a two-dimensional distribution diagram of the surface composite value J0 of the silicon wafer sample obtained in step seven of embodiment 3 of the present invention.

[0057] Figure 8 This is a schematic diagram of the planar distribution of the test area of ​​the silicon wafer sample in Embodiment 4 of the present invention.

[0058] Figure 9 This is a schematic diagram of the structure of the silicon wafer sample to be tested in Example 4 of the present invention.

[0059] Figure 10 This is a graph showing the excess carrier concentration Δn of the calibration region obtained in step two of Embodiment 4 of the present invention under different light intensities.

[0060] Figure 11 This is a spatially resolved photoluminescence (PL) brightness diagram of the silicon wafer sample obtained in step three of Example 4 of the present invention at 0.4 solar intensity.

[0061] Figure 12 This is a two-dimensional distribution diagram of the surface composite value J0 of the silicon wafer sample obtained in step seven of embodiment 4 of the present invention.

[0062] Figure 13 This is a partially enlarged view of the two-dimensional distribution map of the surface composite value J0 of the silicon wafer sample obtained in step seven of Embodiment 4 of the present invention.

[0063] The following are the symbols in the attached diagram: 1 is a single-crystal silicon substrate, 2 is a tunneling silicon dioxide layer, 3 is a heavily doped polycrystalline silicon layer, 4 is a lightly doped boron emitter, 5 is a heavily doped boron emitter, and 6 is a passivation antireflection film. Detailed Implementation

[0064] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0065] Example 1

[0066] This embodiment provides a test method for surface recombination on crystalline silicon, see [link to relevant documentation]. Figure 1 Specifically, the test steps include the following:

[0067] Step 1: Prepare a silicon wafer sample, which includes a calibration area and a test area. This silicon wafer sample has the following characteristics:

[0068] 1) The silicon wafer sample is prepared using a single-crystal silicon substrate 1, which is of N-type or P-type conductivity; 2) The calibration area is a square area with a size of not less than 4cm*4cm, and the test area is a square area with a side length of micrometers (i.e., a side length greater than or equal to 1μm). In this embodiment, the test area is a square area with a size of not less than 40μm*40μm. The positions of the calibration area and the test area on the single-crystal silicon substrate 1 are not limited; 3) There are differences in passivation performance between the test area and the calibration area, including but not limited to differences in doping, structure and / or passivation antireflection film between the test area and the calibration area; 4) The passivation performance of each position in the calibration area is relatively uniform, and the difference in surface recombination value of each position in the calibration area does not exceed 10%.

[0069] The preparation of the silicon wafer sample in this embodiment includes the following preparation steps:

[0070] a) A damaged layer was removed and texturized from an N-type single-crystal silicon substrate 1 with a resistivity of 1.0 Ω·cm and a thickness of 160 μm. The texturized N-type single-crystal silicon substrate 1 was then polished to form a planar structure on its surface. Next, a tunneling silicon dioxide layer 2 (1.0–2.0 nm thick) and a heavily doped polycrystalline silicon layer 3 were sequentially deposited on the front surface of the N-type single-crystal silicon substrate 1, and the same layer was deposited on the rear surface. The substrate was then annealed at 875 °C for 60 min. The thickness of the heavily doped polycrystalline silicon layer 3 on both the front and rear surfaces of the N-type single-crystal silicon substrate 1 was 100–150 nm, and the doping concentration was 2.0–3.0 × 10⁻⁶. 20 cm -3 .

[0071] b) The robotic arm used for loading or unloading on the production line forms scratches of varying degrees at random positions on the surface of the N-type single crystal silicon substrate 1 after the treatment in step a). The size of the scratched area is not less than 40μm*40μm, and the scratched area serves as the test area of ​​this embodiment. The size of the area not scratched by the robotic arm is not less than 4cm*4cm, and the unscratched area serves as the calibration area of ​​this embodiment.

[0072] c) After completing step b), a passivation antireflection film 6 is deposited on both the front and back surfaces of the heavily doped polycrystalline silicon layer 3. The passivation antireflection film 6 is one or a combination of alumina, silicon dioxide, silicon nitride, and silicon oxynitride, and the total thickness of the passivation antireflection film 6 on both the front and back surfaces is 50–150 nm. Taking the front surface as an example, the preferred deposition process for the passivation antireflection film 6 is as follows: an alumina film with a thickness of 0.5–5.0 nm is deposited on the heavily doped polycrystalline silicon layer 3 using the ALD method, followed by the deposition of a SiN film with a thickness of 60–85 nm on the alumina film using the PECVD method.x Anti-reflection coating. After step c), the silicon wafer sample of this embodiment is obtained, and its structure is as follows. Figure 2 As shown.

[0073] Step 2: Test the calibration area and obtain the excess carrier concentration value Δn under different light intensities.

[0074] The silicon wafer sample to be tested is placed on the test platform of the Sinton WCT-120 minority carrier lifetime tester. The calibration area of ​​the silicon wafer sample is aligned with the center of the test coil of the WCT-120 minority carrier lifetime tester. The excess carrier concentration value Δn corresponding to different light intensities in the calibration area is obtained. For example, the average excess carrier concentration value of the calibration area under a specific light intensity is recorded as Δn0. It should be noted that the light intensity range of step two is 0.01 to 1.0 solar irradiance.

[0075] In this embodiment, the excess carrier concentration values ​​of the calibration area of ​​the silicon wafer sample under different light intensities are as follows: Figure 3 As shown. From Figure 3 The excess carrier concentration value Δn in the calibration region can be seen from the data; for example, when the light intensity is 0.4 solar hours, the excess carrier concentration value Δn in the calibration region is 5.0 × 10⁻⁶. 15 cm- 3 .

[0076] Step 3: Test the entire silicon wafer sample to obtain the spatially resolved photoluminescence (PL) brightness values ​​of the entire silicon wafer sample under different light intensities.

[0077] a) Place the silicon wafer sample on the test platform of the PL device with the side containing the test area facing down and the side not containing the test area facing up (i.e., towards the light-receiving surface). Adjust the photon flux irradiated onto the surface of the silicon wafer sample by the PL device to achieve different light intensities. Test the spatially resolved photoluminescence PL brightness map of the entire silicon wafer sample under different light intensities.

[0078] In this embodiment, with a light intensity of 0.4 solar hours, the spatially resolved photoluminescence (PL) brightness map (hereinafter referred to as PL brightness map) of the silicon wafer sample is as follows. Figure 4 As shown.

[0079] b) Based on the PL brightness map of the entire silicon wafer sample, obtain the average PL brightness value of the calibration area under different light intensities. For example, the average PL brightness value of the calibration area under a specific light intensity is denoted as I. PL,0 .

[0080] In this embodiment, with a light intensity of 0.4 solar hours, the average PL brightness value of the calibration area in the silicon wafer sample is 5545.

[0081] Step 4: Calculate the calibration constant C using the average Δn (i.e., the average excess carrier concentration) and the average PL brightness value of the calibration area.

[0082] Combining the average excess carrier concentration value Δn0 of the calibration region under a specific light intensity in step two with the average PL brightness value I of the calibration region under the same specific light intensity in step three... PL,0 The calibration constant C is calculated using the following formula (2).

[0083] Where Δn0 and I PL,0 The relationship is shown in the following formula (1):

[0084] I PL,0 =C*Δn0*(N doped +Δn0) (1)

[0085] Formula (1) can be transformed into the following formula (2):

[0086]

[0087] In formulas (1) and (2), I PL,0 Δn0 is the average PL brightness value of the calibration area under a specific light intensity, Δn0 is the average excess carrier concentration value of the calibration area under the same specific light intensity, C is the calibration constant, and N is the average excess carrier concentration value of the calibration area under the same specific light intensity. doped The doping concentration of the single-crystal silicon substrate 1 is given. It should be noted that the calibration constant C is related to the structure of the PL device and the silicon wafer sample, but almost unrelated to the magnitude of the light intensity. Therefore, the calculation of the calibration constant C does not specifically limit the light intensity.

[0088] In this embodiment, the doping concentration N of the N-type single-crystal silicon substrate 1 in the silicon wafer sample is... doped 4.95×10 15 cm -3 With a light intensity of 0.4 solar hours, the excess carrier concentration Δn in the calibration region is 5.0 × 10⁻⁶. 15 cm -3 The average PL luminance value of the calibration area is 5545, and the calibration constant C can be calculated as 1.08 × 10⁻⁶ according to the above formula (2). -28 cm 6 .

[0089] Step 5: By calibrating the constant C, obtain the spatially resolved excess carrier concentration value Δn (i.e., spatial resolution Δn) of the entire silicon wafer sample under different light intensities.

[0090] Combining the spatially resolved photoluminescence (PL) brightness values ​​of the whole silicon wafer sample under different light intensities in step three with the calibration constant C in step four, the spatially resolved excess carrier concentration value Δn of the whole silicon wafer sample under different light intensities is obtained by the following formula (3).

[0091] To further explain, in this embodiment, the camera in the PL device has a pixel size of 1024*1024 (1 million pixels), and its field of view is 165mm*165mm. Therefore, the spatially resolved photoluminescence (PL) brightness values ​​of the silicon wafer sample within the field of view are stored in the camera of the PL device in the form of a 1024*1024 matrix. If a point in the silicon wafer sample corresponds to a pixel with an x-coordinate and a y-coordinate, then under light intensity n times that of the sun, the spatially resolved PL brightness value of this point is denoted as I. PL_n (x,y). Combining the calibration constant C from step four, the spatially resolved excess carrier concentration Δn at the point with coordinates (x,y) under the same light intensity is obtained using the following formula (3). _n (x,y). Formula (3) is:

[0092]

[0093] In formula (3), I PL_n (x,y) represents the spatially resolved PL brightness value of the point at coordinates (x,y) in the silicon wafer sample under n solar intensities; Δn _n (x,y) represents the spatially resolved excess carrier concentration at coordinates (x,y) in the silicon wafer sample under the same light intensity; C is a calibration constant, and in this embodiment, the value of the calibration constant C is 1.08 × 10⁻⁶. - 28 cm 6 N doped The doping concentration of the single-crystal silicon substrate 1 in the silicon wafer sample is given.

[0094] In this embodiment, the injection concentration of 5.0 × 10⁻⁶ is mainly described. 15 cm -3 The method for testing the two-dimensional distribution of the surface recombination value J0 of a silicon wafer sample. See [link to relevant documentation]. Figure 3 In the calibration area of ​​the silicon wafer sample in this embodiment, the excess carrier concentration corresponding to a light intensity of 0.28 solar hours is 4.0 × 10⁻⁶. 15 cm -3 The excess carrier concentration corresponding to a light intensity of 0.54 solar hours is 6.0 × 10⁻⁶. 15 cm -3 Then, according to the description in step five, the spatial resolution Δn of the point with coordinates (x, y) under a specific light intensity is calculated using the above formula (3). _0.28 (x,y) and spatially resolved Δn _0.54 (x,y).

[0095] Step Six: By using the calibration constant C and the spatially resolved excess carrier concentration value Δn, the spatially resolved minority carrier lifetime τ of the entire silicon wafer sample under different light intensities is obtained.eff (i.e., spatial resolution τ) eff ).

[0096] Combining the calibration constant C from step four with the spatially resolved excess carrier concentration Δn under different light intensities from step five, the spatially resolved minority carrier lifetime τ of the entire silicon wafer sample under different light intensities can be obtained using the following formula (4). eff .

[0097] To further explain, if a point in the silicon wafer sample corresponds to a pixel with x-coordinate and y-coordinate, then under light intensity n times that of the sun, step five can be used to obtain the spatially resolved excess carrier concentration at this point as Δn. _n (x,y), combined with the calibration constant C from step four, the spatially resolved minority carrier lifetime τ of the point with coordinates (x,y) under the same light intensity can be obtained using the following formula (4). eff (x,y). Formula (4) is:

[0098]

[0099] In formula (4), Δn _n (x,y) represents the spatially resolved excess carrier concentration at coordinates (x,y) in a silicon wafer sample under n solar intensities; τ eff (x,y) represents the spatially resolved minority carrier lifetime at coordinates (x,y) on the silicon wafer sample under the same light intensity; R represents the reflectivity of the silicon wafer sample; W represents the thickness of the single-crystal silicon substrate 1; Φ represents the photon flux irradiated onto the surface of the silicon wafer sample by the PL device, with a photon flux of 2.5 × 10⁻⁶ for one solar intensity. 17 cm -2 s -1 .

[0100] In this embodiment, the injection concentration of 5.0 × 10⁻⁶ is mainly described. 15 cm -3 The method for testing the two-dimensional distribution map of the surface recombination value J0 of a silicon wafer sample. In this embodiment, the reflectivity R of the silicon wafer sample is 3%, and the thickness W of the N-type single-crystal silicon substrate 1 is 160 μm; see [link to relevant documentation]. Figure 3 In the calibration area of ​​the silicon wafer sample in this embodiment, the excess carrier concentration corresponding to a light intensity of 0.28 solar hours is 4.0 × 10⁻⁶. 15 cm -3 The photon flux Φ of 0.28 solar masses is 7.0 × 10⁻⁶. 16 cm -2 s -1 The spatially resolved excess carrier concentration at coordinates (x, y) in the silicon wafer sample is Δn. _0.28(x, y); In the calibration area of ​​the silicon wafer sample in this embodiment, the excess carrier concentration corresponding to a light intensity of 0.54 solar hours is 6.0 × 10⁻⁶. 15 cm -3 The photon flux Φ of 0.54 solar masses is 1.35 × 10⁻⁶. 17 cm -2 s -1 The spatially resolved excess carrier concentration at coordinates (x, y) in the silicon wafer sample is Δn. _0.54 (x,y); According to the description in step six, the spatial resolution τ of the point with coordinates (x,y) under a specific light intensity is calculated using the above formula (4). eff_0.28 (x,y) and spatial resolution τ eff_0.54 (x,y).

[0101] Step 7: Spatially determine minority carrier lifetime τ eff By combining the spatially resolved excess carrier concentration value Δn, the spatially resolved surface recombination value J0 of the entire silicon wafer sample under different injection concentrations is obtained.

[0102] Combining the spatially resolved excess carrier concentration Δn of the whole silicon wafer sample under different light intensities in step five with the spatially resolved minority carrier lifetime τ of the whole silicon wafer sample under different light intensities in step six... eff The spatially resolved surface recombination value J0 of the whole silicon wafer sample under different injection concentrations is obtained by using the following formula (8).

[0103] The formula for calculating the surface composite value J0 is shown in formula (5) below:

[0104]

[0105] In formula (5), τ eff τ represents the minority carrier lifetime of the silicon wafer sample. rad τ represents the bulk radiative recombination lifetime of the silicon wafer sample. Auger τ represents the Auger recombination lifetime of the silicon wafer sample. bulk,SRH J0 represents the bulk SRH recombination lifetime of the silicon wafer sample, J0 represents the surface recombination value of the silicon wafer sample, and q represents the unit charge of the silicon wafer sample, with a value of 1.6 × 10⁻⁶. -19 C; W is the thickness of the single-crystal silicon substrate 1; n i This represents the intrinsic carrier concentration of the silicon wafer sample, with a value of 8.6 × 10⁻⁶. 9 cm -3 N doped The doping concentration of the single-crystal silicon substrate 1 is given.

[0106] Crystalline silicon is an indirect bandgap semiconductor with very small bulk radiative recombination and a very high bulk radiative recombination lifetime. Therefore, in formula (5), 1 / τ radThe term can be ignored; when the implantation concentration reaches a certain value, the SRH recombination in the bulk region of the silicon wafer sample is a constant, and can be regarded as a constant. Therefore, 1 / τ in formula (5) bulk,SRH The term can be considered a constant; the lifetime of Auger radiative recombination is directly related to the spatial resolution Δn, as shown in the following equation:

[0107]

[0108] In formula (6), C A The Auger radiative recombination coefficient of the silicon wafer sample is 1.66 × 10⁻⁶. -30 cm 6 s -1 Δn represents the spatially resolved excess carrier concentration of the silicon wafer sample under different light intensities. For a known Δn, the Auger recombination lifetime τ of the silicon wafer sample... Auger It can be calculated directly using formula (6).

[0109] Based on this, the formula for calculating the surface composite value J0 can be transformed into the following formula (7):

[0110]

[0111] In formula (7), τ cor The minority carrier lifetime of a silicon wafer sample, excluding Auger recombination, is called the modified minority carrier lifetime.

[0112] As can be seen from the above formula (7), if Δn is regarded as the independent variable, 1 / τ cor The doping concentration N of the single-crystal silicon substrate 1 is considered as the dependent variable. doped The lifetime τ of SRH recombination in the bulk region of the silicon wafer sample bulk,SRH If we consider it as a constant, then 2J0 / (qWn) i ^2 The slope is given by the equation (8), and the surface composite value J0 can be obtained by differential calculation.

[0113]

[0114] To further explain, in this embodiment, a point in the silicon wafer sample corresponds to a pixel with an abscissa of x and an ordinate of y. Therefore, when the light intensity is 0.28 solar volts and 0.54 solar volts respectively, the excess carrier concentration is 4.0 × 10⁻⁶. 15 cm -3 and 6.0×10 15 cm -3 Step five yields the spatially resolved excess carrier concentration at this point in the silicon wafer sample under a specific light intensity, Δn. _0.28 (x,y) and Δn _0.54(x,y), combined with step six, we can obtain the spatially resolved minority carrier lifetimes τ at this point in the silicon wafer sample under a specific light intensity. eff_0.28 (x,y) and τ eff_0.54 (x,y), by subtracting the Auger recombination lifetime at this point in the silicon wafer sample from formula (7), the corrected minority carrier lifetimes are obtained as τ. cor_0.28 (x,y) and τ cor_0.54 (x,y), the injection concentration at point (x,y) in the silicon wafer sample [4.0×10] 15 +6.0×10 15 ] / 2=5.0×10 15 cm -3 The spatially resolved surface composite value J0(x,y) can be calculated according to the following formula (9):

[0115]

[0116] Using the same testing method, the spatially resolved surface composite value J0 of other points in the pixel matrix can be obtained through steps two to seven above. For example, if the pixel matrix is ​​1024*1024 (1 million pixels), the spatially resolved surface composite value J0 of 1 million points in the silicon wafer sample can be calculated simultaneously, and then a two-dimensional distribution map of the surface composite value J0 of the entire surface of the silicon wafer sample can be obtained.

[0117] In this embodiment, the PL device has a pixel size of 1024*1024 (1 million pixels), the camera's field of view is 165mm*165mm, and the spatial resolution is 161μm. In this embodiment, the two-dimensional distribution map of the surface recombination value J0 of the entire silicon wafer sample obtained from the test is as follows: Figure 5 As shown, from Figure 5 As can be seen from the data, in the silicon wafer sample of this embodiment, the composite 2*J0 value (i.e., twice the spatially resolved surface composite value J0) of the unscratched calibration area is 14.2 fA / cm. 2 The composite 2*J0 value of the test area with minor scratches was 24.2 fA / cm. 2 The composite 2*J0 value of the test area with moderate scratches was 49.9 fA / cm. 2 The composite 2*J0 value of the severely scratched test area was 78.2 fA / cm. 2 .

[0118] Example 2

[0119] This embodiment provides a test method for surface recombination of crystalline silicon. The specific test steps are the same as in Embodiment 1, but the difference between Embodiment 1 and Embodiment 1 is as follows:

[0120] In step five, this embodiment mainly describes the injection concentration of 3.0 × 10⁻⁶. 15 cm-3 The method for testing the two-dimensional distribution of the surface recombination value J0 of a silicon wafer sample. See [link to relevant documentation]. Figure 3 In the calibration area of ​​the silicon wafer sample in this embodiment, the excess carrier concentration corresponding to a light intensity of 0.20 solar hours is 2.0 × 10⁻⁶. 15 cm -3 The excess carrier concentration corresponding to a light intensity of 0.28 solar hours is 4.0 × 10⁻⁶. 15 cm -3 Referring again to the description of step five in Example 1, the spatial resolution Δn of the point with coordinates (x,y) under a specific light intensity is calculated using formula (3). _0.20 (x,y) and spatially resolved Δn _0.28 (x,y).

[0121] In step six, this embodiment mainly describes the injection concentration of 3.0 × 10⁻⁶. 15 cm -3 The method for testing the two-dimensional distribution map of the surface recombination value J0 of a silicon wafer sample. In this embodiment, the reflectivity R of the silicon wafer sample is 3%, and the thickness W of the N-type single-crystal silicon substrate 1 is 160 μm; see [link to relevant documentation]. Figure 3 The excess carrier concentration corresponding to a light intensity of 0.20 solar hours is 2.0 × 10⁻⁶. 15 cm -3 The photon flux Φ of 0.20 solar masses is 5.0 × 10⁻⁶. 16 cm -2 s -1 The spatially resolved excess carrier concentration at coordinates (x, y) in the silicon wafer sample is Δn. _0.20 (x, y); In the calibration area of ​​the silicon wafer sample in this embodiment, the excess carrier concentration corresponding to a light intensity of 0.28 solar hours is 4.0 × 10⁻⁶. 15 cm -3 The photon flux Φ of 0.28 solar masses is 7.0 × 10⁻⁶. 16 cm -2 s -1 The spatially resolved excess carrier concentration at coordinates (x, y) in the silicon wafer sample is Δn. _0.28 (x,y); Refer to the description of step six in Example 1, and calculate the spatial resolution τ of the point with coordinates (x,y) under a specific light intensity using formula (4). eff_0.20 (x,y) and spatial resolution τ eff_0.28 (x,y).

[0122] In step seven, further explanation is provided. In this embodiment, a point in the silicon wafer sample corresponds to a pixel with an abscissa of x and an ordinate of y. Therefore, when the light intensity is 0.20 solar volts and 0.28 solar volts respectively, the excess carrier concentration is 2.0 × 10⁻⁶.15 cm -3 and 4.0×10 15 cm -3 Step five yields the spatially resolved excess carrier concentration at this point in the silicon wafer sample under a specific light intensity, Δn. _0.20 (x,y) and Δn _0.28 (x,y), combined with step six, we can obtain the spatially resolved minority carrier lifetimes τ at this point in the silicon wafer sample under a specific light intensity. eff_0.20 (x,y) and τ eff_0.28 (x,y), by subtracting the Auger recombination lifetime at this point in the silicon wafer sample from formula (7), the corrected minority carrier lifetimes are obtained as τ. cor_0.20 (x,y) and τ cor_0.28 (x,y), the point with coordinates (x,y) in the silicon wafer sample has an implantation concentration of [2.0×10]. 15 +4.0×10 15 ] / 2 = 3.0 × 10 15 cm -3 The spatially resolved surface composite value J0(x,y) can be calculated according to the following formula (10).

[0123]

[0124] In this embodiment, the PL (Plastic Photon Display) has a pixel size of 1024*1024 (1 million pixels), the camera's field of view in the PL device is 165mm*165mm, and the spatial resolution is 161μm. In this embodiment, the two-dimensional distribution map of the surface recombination value J0 of the entire silicon wafer sample obtained from the test is as follows: Figure 6 As shown, from Figure 6 As can be seen from the diagram, the two-dimensional distribution of the surface recombination value J0 of the silicon wafer sample in this embodiment is similar to that in Example 1. Figure 5 The two-dimensional distribution of surface composite values ​​J0 on the entire surface of the silicon wafer samples showed significant differences, which was due to the different implantation concentrations. Figure 6 In this embodiment, the composite 2*J0 value of the unscratched calibration area in the silicon wafer sample is 11.8 fA / cm. 2 The composite 2*J0 value of the severely scratched test area was 73.4 fA / cm. 2 .

[0125] Example 3

[0126] This embodiment provides a test method for surface recombination of crystalline silicon. The specific test steps are the same as in Embodiment 1, but the difference between Embodiment 1 and Embodiment 1 is as follows:

[0127] In step five, this embodiment mainly describes the injection concentration of 7.0 × 10⁻⁶. 15 cm -3The method for testing the two-dimensional distribution of the surface recombination value J0 of a silicon wafer sample. See [link to relevant documentation]. Figure 3 In the calibration area of ​​the silicon wafer sample in this embodiment, the excess carrier concentration corresponding to a light intensity of 0.54 solar hours is 6.0 × 10⁻⁶. 15 cm -3 The excess carrier concentration corresponding to a light intensity of 0.88 solar hours is 8.0 × 10⁻⁶. 15 cm -3 Referring again to the description of step five in Example 1, the spatial resolution Δn of the point with coordinates (x,y) under a specific light intensity is calculated using formula (3). _0.54 (x,y) and spatially resolved Δn _0.88 (x,y).

[0128] In step six, this embodiment mainly describes the injection concentration of 7.0 × 10⁻⁶. 15 cm -3 The method for testing the two-dimensional distribution map of the surface recombination value J0 of a silicon wafer sample. In this embodiment, the reflectivity R of the silicon wafer sample is 3%, and the thickness W of the N-type single-crystal silicon substrate 1 is 160 μm; see [link to relevant documentation]. Figure 3 The excess carrier concentration corresponding to a light intensity of 0.54 solar hours is 6.0 × 10⁻⁶. 15 cm -3 The photon flux Φ of 0.54 solar masses is 1.35 × 10⁻⁶. 17 cm -2 s -1 The spatially resolved excess carrier concentration at coordinates (x, y) in the silicon wafer sample is Δn. _0.54 (x, y); In the calibration area of ​​the silicon wafer sample in this embodiment, the excess carrier concentration corresponding to a light intensity of 0.88 solar hours is 8.0 × 10⁻⁶. 15 cm -3 The photon flux Φ of 0.88 solar masses is 2.2 × 10⁸. 17 cm -2 s -1 The spatially resolved excess carrier concentration at coordinates (x, y) in the silicon wafer sample is Δn. _0.88 (x,y); Refer to the description of step six in Example 1, and calculate the spatial resolution τ of the point with coordinates (x,y) under a specific light intensity using formula (4). eff_0.54 (x,y) and spatial resolution τ eff_0.88 (x,y).

[0129] In step seven, further explanation is provided. In this embodiment, a point in the silicon wafer sample corresponds to a pixel with an abscissa of x and an ordinate of y. Therefore, when the light intensity is 0.54 solar volts and 0.88 solar volts respectively, the excess carrier concentration is 6.0 × 10⁻⁶. 15 cm-3 and 8.0×10 15 cm -3 Step five yields the spatially resolved excess carrier concentration at this point in the silicon wafer sample under a specific light intensity, Δn. _0.54 (x,y) and Δn _0.88 (x,y), combined with step six, we can obtain the spatially resolved minority carrier lifetimes τ at this point in the silicon wafer sample under a specific light intensity. eff_0.54 (x,y) and τ eff_0.88 (x,y), by subtracting the Auger recombination lifetime at this point in the silicon wafer sample from formula (7), the corrected minority carrier lifetimes are obtained as τ. cor_0.54 (x,y) and τ cor_0.88 (x,y), the point with coordinates (x,y) in the silicon wafer sample has an implantation concentration of [6.0×10]. 15 +8.0×10 15 ] / 2]=7.0×10 15 cm -3 The spatially resolved surface composite value J0(x,y) can be calculated according to the following formula (11).

[0130]

[0131] In this embodiment, the PL (Plastic Photon Display) has a pixel size of 1024*1024 (1 million pixels), the camera's field of view in the PL device is 165mm*165mm, and the spatial resolution is 161μm. In this embodiment, the two-dimensional distribution map of the surface recombination value J0 of the entire silicon wafer sample obtained from the test is as follows: Figure 7 As shown, from Figure 7 As can be seen from the diagram, the two-dimensional distribution of the surface recombination value J0 of the silicon wafer sample in this embodiment is similar to that in Example 1. Figure 5 and in Example 2 Figure 6 The two-dimensional distribution maps of the surface composite values ​​J0 of the silicon wafer samples all showed significant differences, which was caused by different implantation concentrations. Figure 7 In this embodiment, the composite 2*J0 value of the unscratched calibration area in the silicon wafer sample is 14.1 fA / cm. 2 The composite 2*J0 value of the severely scratched test area was 75.0 fA / cm. 2 .

[0132] Example 4

[0133] This embodiment provides a test method for surface recombination of crystalline silicon. The specific test steps are the same as in Embodiment 1, but the difference between Embodiment 1 and Embodiment 1 is as follows:

[0134] In step one, the preparation of the silicon wafer sample in this embodiment includes the following preparation steps:

[0135] a) A damaged layer is removed and texturing is performed on an N-type single-crystal silicon substrate 1 with a resistivity of 1.0 Ω·cm and a thickness of 160 μm. Then, the texturized N-type single-crystal silicon substrate 1 is placed in a boron diffusion furnace for high-temperature diffusion to form front-to-back symmetrical boron light-doped emitters 4 on the front and back surfaces of the N-type single-crystal silicon substrate 1. The sheet resistance of the boron light-doped emitters 4 on the front and back surfaces is 100-150 Ω / sq and the junction depth is 0.9-1.0 μm.

[0136] b) A patterned scanning process is performed on one side (e.g., the front surface) of the N-type single-crystal silicon substrate 1 after step a) using an ultraviolet laser. Boron atoms in the lightly boron-doped emitter 4 in the scanned area will further propagate into the N-type single-crystal silicon substrate 1 due to the absorption of ultraviolet laser energy, forming a heavily boron-doped emitter 5; Figure 8 As shown, the area processed by ultraviolet laser patterning scanning is used as the test area in this embodiment. Eight different ultraviolet laser patterning scanning processing conditions correspond to eight different test areas. The test area is a square area with a size of 2.25cm*2.25cm. The area that has not been processed by ultraviolet laser patterning scanning is used as the calibration area in this embodiment. The calibration area is a square area with a size of 4cm*4cm.

[0137] c) A passivation antireflection film 6 is deposited on both the front and back surfaces of the N-type single-crystal silicon substrate 1 after step a). The passivation antireflection film 6 is one or a combination of aluminum oxide, silicon dioxide, silicon nitride, and silicon oxynitride, and the total thickness of the passivation antireflection film 6 on both the front and back surfaces is 50–150 nm. Taking the front surface as an example, the preferred deposition process for the passivation antireflection film 6 is as follows: an aluminum oxide film with a thickness of 0.5–5.0 nm is deposited on the lightly boron-doped emitter 4 and the heavily boron-doped emitter 5 using the ALD method, followed by the deposition of a SiN film with a thickness of 60–85 nm on the aluminum oxide film using the PECVD method. x Anti-reflection coating. After step c), the silicon wafer sample of this embodiment is obtained, and its structure is as follows. Figure 9 As shown.

[0138] In step two, in this embodiment, the excess carrier concentration values ​​of the calibration area of ​​the silicon wafer sample under different light intensities are as follows: Figure 10 As shown. From Figure 10 The excess carrier concentration value Δn in the calibration region can be seen from the data; for example, when the light intensity is 0.54 solar hours, the excess carrier concentration value Δn in the calibration region is 5.0 × 10⁻⁶. 15 cm -3 .

[0139] In step three, in this embodiment, with a light intensity of 0.54 solar hours, the spatially resolved photoluminescence (PL) brightness map (hereinafter referred to as PL brightness map) of the silicon wafer sample is as follows. Figure 11 As shown ( Figure 11 The image only shows a key portion of the PL brightness map, which includes eight test areas.

[0140] In this embodiment, with a light intensity of 0.54 solar hours, the average PL brightness value of the calibration area in the silicon wafer sample is 6927. In step four, in this embodiment, the doping concentration N of the N-type single-crystal silicon substrate 1 in the silicon wafer sample is... doped 4.95×10 15 cm -3 With a light intensity of 0.54 solar hours, the excess carrier concentration Δn in the calibration region is 5.0 × 10⁻⁶. 15 cm -3 The average PL luminance value of the calibration area is 6927, and the calibration constant C can be calculated as 1.14 × 10⁻⁶ according to formula (2) in Example 1. -28 cm 6 .

[0141] In step five, this embodiment mainly describes the injection concentration of 5.0 × 10⁻⁶. 15 cm -3 The method for testing the two-dimensional distribution of the surface recombination value J0 of a silicon wafer sample. See [link to relevant documentation]. Figure 10 In the calibration area of ​​the silicon wafer sample in this embodiment, the excess carrier concentration corresponding to a light intensity of 0.39 solar hours is 4.0 × 10⁻⁶. 15 cm -3 The excess carrier concentration corresponding to a light intensity of 0.72 solar hours is 6.0 × 10⁻⁶. 15 cm -3 Referring again to step five of Example 1, the spatial resolution Δn of the point with coordinates (x, y) under a specific light intensity is calculated using formula (3). _0.39 (x,y) and spatially resolved Δn _0.72 (x,y).

[0142] In step six, this embodiment mainly describes the injection concentration of 5.0 × 10⁻⁶. 15 cm -3 The method for testing the two-dimensional distribution map of the surface recombination value J0 of a silicon wafer sample. In this embodiment, the reflectivity R of the silicon wafer sample is 1.5%, and the thickness W of the N-type single-crystal silicon substrate 1 is 160 μm; see [link to relevant documentation]. Figure 10 In the calibration area of ​​the silicon wafer sample in this embodiment, the excess carrier concentration corresponding to a light intensity of 0.39 solar hours is 4.0 × 10⁻⁶. 15 cm -3 The photon flux Φ of 0.39 solar masses is 9.75 × 10⁻⁶. 16 cm -2 s -1The spatially resolved excess carrier concentration at coordinates (x, y) in the silicon wafer sample is Δn. _0.39 (x, y); In the calibration area of ​​the silicon wafer sample in this embodiment, the excess carrier concentration corresponding to a light intensity of 0.72 solar hours is 6.0 × 10⁻⁶. 15 cm -3 The photon flux Φ of 0.72 solar masses is 1.8 × 10⁻⁶. 17 cm -2 s -1 The spatially resolved excess carrier concentration at coordinates (x, y) in the silicon wafer sample is Δn. _0.72 (x,y); Referring to the description of step six in Example 1, the spatial resolution τ of the point with coordinates (x,y) under a specific light intensity is calculated using formula (4). eff_0.39 (x,y) and spatial resolution τ eff_0.72 (x,y).

[0143] In step seven, further explanation is provided. In this embodiment, a point in the silicon wafer sample corresponds to a pixel with an abscissa of x and an ordinate of y. Therefore, when the light intensity is 0.39 solar volts and 0.72 solar volts respectively, the excess carrier concentration is 4.0 × 10⁻⁶. 15 cm -3 and 6.0×10 15 cm -3 Step five yields the spatially resolved excess carrier concentration at this point in the silicon wafer sample under a specific light intensity, Δn. _0.39 (x,y) and Δn _0.72 (x,y), combined with step six, we can obtain the spatially resolved minority carrier lifetimes τ at this point in the silicon wafer sample under a specific light intensity. eff_0.39 (x,y) and τ eff_0.72 (x,y), referring to formula (7) of Example 1, subtract the Auger recombination lifetime at this point in the silicon wafer sample to obtain the corrected minority carrier lifetimes τ. cor_0.39 (x,y) and τ cor_0.72 (x,y), the point with coordinates (x,y) in the silicon wafer sample has an excess carrier concentration of [4.0×10⁻⁶]. 15 +6.0×10 15 ] / 2=5.0×10 15 cm -3 The spatially resolved surface composite value J0(x,y) can be calculated according to the following formula (12).

[0144]

[0145] In this embodiment, the PL device has a pixel size of 1024*1024 (1 million pixels), the camera's field of view is 165mm*165mm, and the spatial resolution is 161μm. In this embodiment, the two-dimensional distribution map of the surface recombination value J0 of the entire silicon wafer sample obtained from the test is as follows: Figure 12 As shown, from Figure 12 As can be seen from the data, in the silicon wafer sample of this embodiment, the composite 2*J0 value of the calibration area that has not undergone ultraviolet laser patterning scanning is 25.2 fA / cm. 2 The test areas treated under eight different ultraviolet laser patterning scanning conditions exhibited different composite 2*J0 values.

[0146] from Figure 12 It can be clearly seen that in the test area of ​​the silicon wafer sample in this embodiment, the composite 2*J0 value of the two sides after ultraviolet laser patterning scanning is significantly higher than that of the middle area. This is mainly because the ultraviolet laser spot has a low speed when it starts up and decelerates when it stops. The ultraviolet laser patterning scanning is more intense in the two sides, so the surface composite value of the two sides is higher.

[0147] In this embodiment, Figure 8 , 11 The positions of the eight test areas are the same as those of the 12 silicon wafer samples. Figure 13 for Figure 12 The magnified view of the 7th test area shows that, upon magnification, the surface composite values ​​of the two sides of the 7th test area are significantly higher, with a composite 2*J0 value as high as 580 fA / cm². 2 The composite 2*J0 value in the middle region is 325 fA / cm. 2 This also illustrates that when conventionally using the WCT-120 minority carrier lifetime test laser scanning to measure the surface recombination value of the doped region, if continuous laser scanning is used to form a test area with a side length of 4 cm, the laser will undergo multiple acceleration, deceleration, and translation movements within the 4 cm test area. This results in poor uniformity of the surface recombination value within the 4 cm test area, which differs from the laser scanning doping motion in the actual SE structure fabrication of crystalline silicon solar cells, leading to inaccurate results. This also highlights the advantages of the crystalline silicon surface recombination testing method of this invention in terms of both high spatial resolution and accuracy, which is of great significance for the performance testing and process optimization of crystalline silicon solar cells.

[0148] Although preferred embodiments of the present invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the present invention.

[0149] The technical solution provided by the present invention has been described in detail above. Specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A test method for surface recombination of crystalline silicon, characterized in that, The following test steps are included: Step S1: Prepare a silicon wafer sample using a single-crystal silicon substrate. The silicon wafer sample includes a calibration area and a test area. The calibration area is a square region with a size of not less than 4cm*4cm, and the test area is a square region with a side length in the micrometer range. The passivation properties of the test area and the calibration area are different, and the passivation properties of each position in the calibration area are relatively uniform, so that the difference in surface recombination value at each position in the calibration area does not exceed 10%. Step S2: Test the calibration area and obtain the excess carrier concentration value Δn under different light intensities; Step S3: Test the entire silicon wafer sample to obtain the spatially resolved photoluminescence (PL) brightness values ​​of the entire silicon wafer sample under different light intensities; Step S4: Obtain the calibration constant C based on the average excess carrier concentration value Δn and the average spatially resolved photoluminescence (PL) brightness value in the calibration area; Step S5: Based on the calibration constant C and the spatially resolved photoluminescence (PL) brightness value, obtain the spatially resolved excess carrier concentration value Δn of the entire silicon wafer sample under different light intensities; Step S6: Based on the calibration constant C and the spatially resolved excess carrier concentration value Δn, obtain the spatially resolved minority carrier lifetime τ of the entire silicon wafer sample under different light intensities. eff ; Step S7: Spatially determine minority carrier lifetime τ eff By combining the spatially resolved excess carrier concentration value Δn, the spatially resolved surface recombination value J0 of the entire silicon wafer sample under different injection concentrations is obtained; In step S7, the minority carrier lifetime τ is determined based on spatial resolution. eff The spatially resolved excess carrier concentration Δn is used to obtain the spatially resolved surface recombination value J0 of the entire silicon wafer sample under different implantation concentrations using the following formula: In the formula, J0 is the spatially resolved surface recombination value of the silicon wafer sample under different injection concentrations, Δn is the spatially resolved excess carrier concentration value of the silicon wafer sample under different light intensities, and q is the unit charge of the silicon wafer sample, with a value of 1.6 × 10⁻⁶. -19 C; W is the thickness of the single-crystal silicon substrate; n i This represents the intrinsic carrier concentration of the silicon wafer sample, with a value of 8.6 × 10⁻⁶. 9 cm -3 ; in, In the formula, τ cor For the corrected minority carrier lifetime, τ eff τ represents the minority carrier lifetime of the silicon wafer sample. Auger τ represents the Auger recombination lifetime of the silicon wafer sample. bulk,SRH For the bulk SRH recombination lifetime of the silicon wafer sample, when the implantation concentration is constant, 1 / τ bulk,SRH N is a constant; doped The doping concentration is the doping concentration of the single-crystal silicon substrate.

2. The test method for surface composite of crystalline silicon according to claim 1, characterized in that, In step S1, the conductivity type of the single-crystal silicon substrate is N-type or P-type. The test area is a square region with a side length of not less than 1 μm; The difference in passivation performance between the test area and the calibration area includes differences in doping, structure, and / or passivation antireflection film between the two areas.

3. A test method for surface composite of crystalline silicon according to claim 1 or 2, characterized in that, The silicon wafer sample includes a monocrystalline silicon substrate, and the front and back surfaces of the monocrystalline silicon substrate are provided with passivation antireflection films.

4. The test method for surface composite of crystalline silicon according to claim 1, characterized in that, In step S2, the excess carrier concentration Δn of the calibration region under different light intensities is measured using a WCT-120 minority carrier lifetime tester.

5. The test method for surface composite of crystalline silicon according to claim 1, characterized in that, Step S3 specifically includes the following steps: Step S31: Use a PL device to measure the spatially resolved photoluminescence PL brightness map of the entire silicon wafer sample under different light intensities; Step S32: Based on the spatially resolved photoluminescence (PL) brightness map, obtain the spatially resolved photoluminescence (PL) brightness values ​​of the entire silicon wafer sample under different light intensities.

6. The test method for surface composite of crystalline silicon according to claim 1, characterized in that, Step S4 specifically includes the following steps: Step S41: Based on the excess carrier concentration values ​​Δn of the calibration area under different light intensities in Step S2, obtain the average excess carrier concentration value Δn0 of the calibration area under a specific light intensity; and based on the spatially resolved photoluminescence (PL) brightness values ​​of the entire silicon wafer sample under different light intensities in Step S3, obtain the average PL brightness value I of the calibration area under the same specific light intensity. PL ,0; Step S42: Based on Δn0 and I PL The calibration constant C is calculated using the following formula: ,0. In the formula, I PL,0 Δn0 is the average PL brightness value of the calibration area under a specific light intensity, Δn0 is the average excess carrier concentration value of the calibration area under the same specific light intensity, C is the calibration constant, and N is the average excess carrier concentration value of the calibration area under the same specific light intensity. doped The doping concentration is the doping concentration of the single-crystal silicon substrate.

7. The test method for surface composite of crystalline silicon according to claim 1, characterized in that, Step S5 specifically includes the following steps: Step S51: When any point in the silicon wafer sample corresponds to a pixel with x-coordinate and y-coordinate in the pixel matrix of the PL device's camera, then under light intensity n suns, the spatially resolved photoluminescence PL brightness value of the point with coordinates (x,y) is I. PL_n (x,y); Step S52: According to I PL_n Given (x,y) and the calibration constant C, the spatially resolved excess carrier concentration Δn at coordinates (x,y) in the silicon wafer sample under the same light intensity is obtained using the following formula. _n (x,y): In the formula, I PL_n (x,y) represents the spatially resolved photoluminescence (PL) value of the point at coordinates (x,y) in the silicon wafer sample under n solar intensities; Δn _n (x,y) represents the spatially resolved excess carrier concentration at coordinates (x,y) in the silicon wafer sample under the same light intensity; C is the calibration constant; N doped The doping concentration is the doping concentration of the single-crystal silicon substrate.

8. The test method for surface composite of crystalline silicon according to claim 7, characterized in that, In step S6, according to Δn _n Given (x,y) and the calibration constant C, the spatially resolved minority carrier lifetime τ of the point with coordinates (x,y) in the silicon wafer sample under the same light intensity is obtained using the following formula. eff (x,y): In the formula, Δn _n (x,y) represents the spatially resolved excess carrier concentration at coordinates (x,y) in a silicon wafer sample under n solar intensities; τ eff (x,y) represents the spatially resolved minority carrier lifetime of the point at coordinates (x,y) in the silicon wafer sample under the same light intensity; R is the reflectivity of the silicon wafer sample; W is the thickness of the single-crystal silicon substrate; Φ is the photon flux irradiated to the surface of the silicon wafer sample by the PL device, and the photon flux of 1 solar intensity is 2.5 × 10⁻⁶. 17 cm -2 s -1 .

9. The test method for surface recombination of crystalline silicon according to claim 8, characterized in that, In step S7, the spatially resolved surface recombination value J0(x,y) of the point with coordinates (x,y) in the silicon wafer sample at a specific implantation concentration is obtained by the following formula: In the formula, the solar intensity n is greater than the solar intensity m, and Δn _n (x,y) represents the spatially resolved excess carrier concentration at n solar irradiances, Δn _m (x,y) represents the spatially resolved excess carrier concentration at m solar irradiances, τ cor_n (x,y) represents the corrected minority carrier lifetime under n solar intensities, τ cor_m (x,y) represents the corrected minority carrier lifetime under m solar intensities; q represents the unit charge of the silicon wafer sample, with a value of 1.6 × 10⁻⁶. -19 C; W is the thickness of the single-crystal silicon substrate; n i This represents the intrinsic carrier concentration of the silicon wafer sample, with a value of 8.6 × 10⁻⁶. 9 cm -3 .

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