Cutting processing and treatment method for reducing surface roughness of monocrystalline silicon wafer

Abstract

The invention belongs to the technical field of monocrystalline silicon wafer processing, and provides a cutting processing and processing method for reducing the surface roughness of a monocrystalline silicon wafer, which comprises the following steps of: bonding and curing; preparing a cutting cooling liquid; arranging a wire net; setting cutting parameters; carrying out post-treatment; and laser repairing. Compared with a silicon wafer processed by a traditional electroplating diamond wire technology, the number of line marks of the monocrystalline silicon wafer obtained through processing is obviously reduced by adjusting cutting parameters and prolonging a bidirectional reciprocating cutting reversing period, and the number of the line marks on the surface of the monocrystalline silicon wafer can be controlled within three; according to the cutting processing method, by reducing the machine speed, the line mark depth of the monocrystalline silicon wafer can be reduced to be within 5 microns; according to the method, the processed silicon wafer is subjected to laser repairing, industrialization and automation of efficient laser repairing of the silicon wafer are expected to be achieved through the reconstruction mechanism of a monocrystalline silicon lattice structure in the laser irradiation process, line marks on the surface of the repaired silicon wafer can reach within 3 micrometers, and the surface roughness of the silicon wafer is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of monocrystalline silicon wafer processing, and particularly to a cutting processing and treatment method for reducing the surface roughness of monocrystalline silicon wafers. Background Art

[0002] Currently, crystalline silicon solar cells are the most common, have the largest installed capacity, and are the most mature photovoltaic cells. Among them, high-efficiency N-type monocrystalline cell technologies such as TOPCon, HJT, BC, etc. have increased the mass production efficiency to more than 26%, and the highest efficiency of commercially applied crystalline silicon solar cells has reached more than 26.8%, getting closer and closer to the theoretical efficiency limit (32%) of crystalline silicon solar cells. Continuing to improve the efficiency requires a large amount of technical and financial investment, with great difficulty in efficiency improvement and limited efficiency increase. As a single-junction solar cell, crystalline silicon cells only convert a part of the absorbed photon energy into electrical energy, and the rest is converted into heat loss.

[0003] In recent years, organic / inorganic hybrid perovskite solar cells (PSCs) have the advantages of high light absorption coefficient, long carrier diffusion length, adjustable bandgap, etc., and have been widely studied and commercialized. Although the materials and manufacturing costs of such cells are low, the efficiency of single perovskite cells is relatively low, lacking the support of large-scale ground power station application scenarios and not having a competitive advantage. Considering the advantages and disadvantages of crystalline silicon and perovskite cells, perovskite / crystalline silicon tandem cells have the advantages of fast efficiency improvement and low cost, and are the most commercially promising multi-junction tandem solar cell technology, gradually becoming a research hotspot and the next-stage technical route for crystalline silicon solar cells. How to deposit a perovskite structure on the surface of existing crystalline silicon solar cells is the key to this technology. In addition to the deposition process itself, the surface morphology of crystalline silicon is also a key factor affecting the deposition quality. Currently, most of the perovskite crystalline silicon tandem solar cells in experiments use small-sized silicon wafers, or intercept regions with better surface morphology on large-sized silicon wafers, and the silicon wafers need to be surface-treated to obtain better deposition effects. Therefore, the quality of the silicon wafer surface has become one of the core factors affecting the quality of perovskite / crystalline silicon tandem cells.

[0004] The existing mainstream silicon wafer processing technology is electroplated diamond wire slicing technology, which belongs to the category of fixed abrasive slicing processing. Although electroplated diamond wire slicing technology has many advantages such as high cutting efficiency, low cost, and environmental friendliness, limited by the technology itself, visible periodic structures called wire marks will appear on the surface of the processed silicon wafers, usually as ripples parallel to the running direction of the wire saw. The average depth of these wire marks is about 5 - 6 μm, significantly reducing the flatness and surface quality of the silicon wafers. Moreover, with the development of slicing technology towards large size and thinness, the impact of surface wire marks on the quality of silicon wafers is becoming more and more significant. In recent years, with the popularization of 150 μm and thinner silicon wafers, the standard control of the depth of surface wire marks has become more and more strict, and the wire mark depth requirement is less than or equal to 10 μm.

[0005] Generally, it is considered that after texturing the surface of these silicon wafers with slight line marks (less than or equal to 10 μm), the performance of crystalline silicon cells is not significantly affected. In actual production, silicon wafer processing enterprises generally use high-speed sorting machines to sort silicon wafers, pick out the silicon wafers with excessive line marks for downgrading treatment, and then send the silicon wafers that meet the quality requirements to battery manufacturers. This treatment method can meet the requirements of existing crystalline silicon cell manufacturers.

[0006] However, for perovskite / crystalline silicon tandem cells, depositing a perovskite thin film with a uniform thickness on an uneven surface texture structure is a great challenge. These slight line marks under the existing crystalline silicon cell technology may be an insurmountable gap for future perovskite / crystalline silicon tandem cells. For example, when depositing a perovskite thin film with a thickness less than 1 μm using the solution method, the solution will accumulate in the deep valleys of valley-shaped line marks, and ridge-shaped line marks are an obstacle to the spreading of the perovskite solution on the surface of the silicon wafer, resulting in the perovskite thin film after film formation being unable to completely cover the entire crystalline silicon cell wafer, which will cause the battery circuit to short-circuit and significantly reduce the photoelectric conversion efficiency of the crystalline silicon / perovskite tandem.

[0007] It can be seen that the emergence of perovskite / crystalline silicon tandem cells poses new challenges to the existing electroplated diamond wire slicing technology. Therefore, developing a processing method to reduce the line mark depth and improve the surface quality of silicon wafers to meet the next-generation battery technology is an urgent problem that the existing electroplated diamond wire slicing technology needs to solve. Summary of the Invention

[0008] The purpose of the present invention is to provide a cutting processing and treatment method for reducing the surface roughness of single-crystalline silicon wafers. By re-designing the cutting processing parameters, the number and depth of line marks on the surface of the silicon wafers are significantly reduced, and the position of the line marks on the silicon wafer and the interval between the line marks are accurately positioned, and the line marks on the silicon wafer surface are laser-treated to repair the line marks. Compared with the traditional electroplated diamond wire cutting method, this cutting processing method can significantly reduce the number and depth of line marks on the surface of the silicon wafer, and then through laser treatment, the line mark depth on the silicon wafer surface is controlled within the required range.

[0009] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0010] The present invention provides a cutting processing and treatment method for reducing the surface roughness of single-crystalline silicon wafers, comprising the following steps:

[0011] (1) Bonding and curing: Bonding the surface-ground single-crystalline silicon rod to the base and curing it to obtain a silicon rod group;

[0012] (2) Preparing cutting coolant: Ultrasonically cleaning the coolant, then mixing and stirring it with water to adjust the surface tension to obtain the cutting coolant;

[0013] (3) Arranging the wire mesh: Install the silicon rod group in step (1) into the processing chamber of the diamond wire cutting machine, lead out the diamond wire from the wire pay-off chamber, arrange the diamond wire in the corresponding wire grooves on the main roller. After the diamond wire covers the entire main roller, lead out the wire end of the diamond wire to the wire take-up chamber to complete the wiring work of the wire mesh;

[0014] (4) Setting cutting parameters: Set the flow rate of the cutting coolant, set the diamond wire tension according to the wire diameter of the diamond wire, then perform a warm-up cycle. After the warm-up is completed, perform cutting, and set the process of the cutting stage according to the wire table ratio:

[0015] The table speed is set to 2.0 - 2.4 mm / min, the wire speed is set to 18 - 20 m / s, the forward wire feeding distance is set to 28000 - 32000 m, the reverse wire feeding distance is set to 23000 - 27000 m, and the time for one cutting cycle is set to 40 - 50 min;

[0016] (5) Post-treatment: After cutting, the silicon rod group is processed into silicon wafers, and the silicon wafers are sequentially degummed, cleaned and sorted to complete the processing of the silicon wafers;

[0017] (6) Laser repair: Perform laser scanning repair on the processed silicon wafers to obtain the monocrystalline silicon wafers.

[0018] Preferably, the curing temperature in step (1) is 20 - 30 °C;

[0019] The curing time is 8 - 12 h.

[0020] Preferably, the volume ratio of the coolant to water in step (2) is 1 - 1.5:350 - 400;

[0021] The surface tension of the cutting coolant in step (2) is 28 - 30 N / m.

[0022] Preferably, the flow rate of the cutting coolant in step (4) is 8000 - 10000 m 3 / h.

[0023] Preferably, the wire diameter of the diamond wire in step (4) is 24 - 28 μm;

[0024] The tension of the diamond wire in step (4) is 3 - 4.5 N.

[0025] Preferably, the exposed wire rate of the diamond wire in step (4) is 150 - 280, and the exposed wire height of the diamond wire is 3 - 6 μm.

[0026] Preferably, when the wire diameter of the diamond wire in step (4) is 24 - 26 μm, the diamond wire tension is set to 3 - 4 N;

[0027] When the wire diameter of the diamond wire in step (4) is 26 - 28 μm, the tension of the diamond wire is set to 3.5 - 4.5 N.

[0028] Preferably, the wire table ratio in step (4) is 8 - 10.

[0029] Preferably, the light source of the laser in step (6) comes from a sub - nanosecond pulsed laser;

[0030] In step (6), the wavelength of the laser is 532 nm, the pulse width of the laser is 652.1 ps, and the pulse repetition frequency of the laser is 56 kHz.

[0031] Preferably, the output power of the laser repair in step (6) is 10 - 15 mW;

[0032] The scanning speed of the laser repair is 1.5 - 2.0 mm / s.

[0033] The present invention has the following beneficial effects:

[0034] 1. Compared with the silicon wafers processed by the traditional electroplated diamond wire process, by adjusting the cutting parameters and lengthening the bidirectional reciprocating cutting commutation period, the number of wire marks on the processed monocrystalline silicon wafers is significantly reduced, and the wire marks on the surface of the monocrystalline silicon wafers can be controlled within 3.

[0035] 2. By reducing the table speed in the cutting processing method of the present invention, the wire mark depth of the monocrystalline silicon wafer can be reduced to within 5 μm;

[0036] 3. The present invention performs laser repair on the processed silicon wafers. Through the reconstruction mechanism of the monocrystalline silicon lattice structure during the laser irradiation process, it is expected to realize industrialization and automation for the high - efficiency laser repair of silicon wafers. The wire marks on the surface of the repaired silicon wafers can reach within 3 μm, reducing the surface roughness of the silicon wafers. The silicon wafers processed by the present invention are more suitable for crystalline silicon / perovskite tandem cells and have broad market prospects. Specific embodiments

[0037] The present invention provides a cutting processing and treatment method for reducing the surface roughness of monocrystalline silicon wafers, including the following steps:

[0038] (1) Bonding and curing: Bonding the surface - polished monocrystalline silicon rod on the base and curing it to obtain a silicon rod group;

[0039] (2) Preparing cutting coolant: Ultrasonically cleaning the coolant, then mixing it with water and stirring to adjust the surface tension to obtain the cutting coolant;

[0040] (3) Arranging the wire mesh: Install the silicon rod group in step (1) into the processing chamber of the diamond wire cutting machine. Lead out the diamond wire from the wire feeding chamber, arrange the diamond wire in the corresponding wire grooves on the main roller. After the diamond wire covers the entire main roller, lead out the wire end of the diamond wire to the wire take-up chamber to complete the wiring work of the wire mesh;

[0041] (4) Setting cutting parameters: Set the flow rate of the cutting coolant, set the tension of the diamond wire according to the wire diameter of the diamond wire, then perform a warm-up cycle. After the warm-up is completed, perform cutting, and set the process of the cutting stage according to the wire table ratio:

[0042] The table speed is set to 2.0 - 2.4 mm / min, the wire speed is set to 18 - 20 m / s, the forward wire feeding distance is set to 28000 - 32000 m, the reverse wire feeding distance is set to 23000 - 27000 m, and the time used for one cutting cycle is set to 40 - 50 min;

[0043] (5) Post-treatment: After cutting, the silicon rod group is processed into silicon wafers. The silicon wafers are sequentially degummed, cleaned and sorted to complete the processing of the silicon wafers;

[0044] (6) Laser repair: Perform laser scanning repair on the processed silicon wafers to obtain the monocrystalline silicon wafers.

[0045] In the present invention, the curing temperature in step (1) is preferably 20 - 30 °C, further preferably 22 - 28 °C, and more preferably 24 - 26 °C.

[0046] In the present invention, the curing time is preferably 8 - 12 h, further preferably 8.5 - 11.5 h, and more preferably 9 - 11 h.

[0047] In the present invention, a two-component epoxy resin adhesive is used for bonding the silicon rods in step (1). The curing reaction is an exothermic reaction. If the surface temperature of the silicon rod is too low, on the one hand, it will affect the reaction effect, and on the other hand, too large a temperature difference will cause thermal stress concentration on the surface of the silicon rod, resulting in phenomena such as chipping and brittle crystal exfoliation on the adhesive surface of the cut silicon wafers. Therefore, before sticking the rods, the monocrystalline silicon rods need to be placed in a constant temperature zone for constant temperature. Especially in winter, the surface temperature of the silicon rods needs to be raised above 22 °C before curing.

[0048] In the present invention, in step (2), water is first injected into the coolant tank of the diamond wire cutting machine, and stirring and internal circulation are started; Measure the coolant and place it in the ultrasonic cleaner tank for ultrasonic treatment. After ultrasonic treatment, pour it into the coolant tank of the diamond wire cutting machine three times and mix it with water for stirring to adjust the surface tension of the solution to obtain the cutting coolant.

[0049] In the present invention, in the step (2), the volume ratio of the coolant to water is 1 to 1.5:350 to 400, further preferably 1.1 to 1.4:360 to 390, and more preferably 1.2 to 1.3:370 to 380.

[0050] In the present invention, in the step (2), the ultrasonic time is preferably 20 to 40 min, further preferably 22 to 38 min, and more preferably 25 to 35 min.

[0051] In the present invention, in the step (2), the mixing and stirring time is preferably 3 to 7 min, further preferably 3.5 to 6.5 min, and more preferably 4 to 6 min.

[0052] In the present invention, in the step (2), the surface tension of the cutting coolant is preferably 28 to 30 N / m, further preferably 28.2 to 29.8 N / m, and more preferably 28.5 to 29.5 N / m.

[0053] In the present invention, in the step (4), the flow rate of the cutting coolant is preferably 8000 to 10000 m 3 / h, further preferably 8200 to 9800 m 3 / h, and more preferably 8500 to 9500 m 3 / h.

[0054] In the present invention, in the step (4), the wire diameter of the diamond wire is preferably 24 to 28 μm, further preferably 24.5 to 27.5 μm, and more preferably 25 to 27 μm.

[0055] In the present invention, in the step (4), the tension of the diamond wire is preferably 3 to 4.5 N, further preferably 3.2 to 4.3 N, and more preferably 3.5 to 4 N.

[0056] In the present invention, in the step (4), the exposed edge rate of the diamond wire is preferably 150 to 280, further preferably 160 to 270, and more preferably 170 to 260.

[0057] In the present invention, the exposed edge height of the diamond wire is preferably 3 to 6 μm, further preferably 4 to 5 μm, and more preferably 5 μm.

[0058] In the present invention, when the wire diameter of the diamond wire in the step (4) is preferably 24 to 26 μm, the tension of the diamond wire is set to 3 to 4 N.

[0059] In the present invention, when the wire diameter of the diamond wire in the step (4) is preferably 26 to 28 μm, the tension of the diamond wire is set to 3.5 to 4.5 N.

[0060] In the present invention, the wire table ratio in step (4) is preferably 8 - 10, more preferably 8.2 - 9.8, and still more preferably 8.5 - 9.5.

[0061] In the present invention, the table speed in step (4) is set to 2.0 - 2.4 mm / min. In the cutting stage of the existing mainstream process, the table speed is set to 3.0 - 3.2 mm / min. The table speed in the present invention is reduced by about 30% compared with the existing mainstream process.

[0062] In the present invention, the wire speed in step (4) is set to 18 - 20 m / s. In the cutting stage of the existing mainstream process, the wire speed is set to 35 - 38 m / s. The wire speed in the present invention is reduced by about 50% compared with the existing mainstream process.

[0063] In the present invention, the forward wire feeding distance in step (4) is set to 28000 - 32000 m, the reverse wire feeding distance is set to 23000 - 27000 m, and the time taken for one cutting cycle is set to 40 - 50 min. In the cutting stage of the existing mainstream process, the forward wire feeding distance is set to 600 m, the reverse wire feeding distance is set to 550 m, and the time taken for one cutting cycle is set to 0.5 min. Therefore, in the existing mainstream process, a wire mark appears every 1.5 - 1.6 mm of feed, and the wire marks are relatively dense. In the present invention, a wire mark appears only after a feed of 90 - 99 mm. Due to the reduction of the table speed and wire marks, the cutting force of the electroplated diamond wire decreases, and the depth of its wire marks also decreases accordingly.

[0064] In the present invention, by adjusting the cutting parameters, the effects of controlling the number and depth of wire marks are achieved: in terms of the number, the reciprocating cutting commutation cycle of the existing traditional cutting parameters is lengthened. The periodic wire marks on the silicon wafer surface are mainly caused by periodic commutation. Lengthening the cycle can reduce the number of commutations, thereby achieving the purpose of reducing the number of wire marks; in terms of the depth: the depth of the wire marks is jointly determined by the table speed and the wire speed, and is more affected by the table speed. By appropriately sacrificing the cutting efficiency and reducing the table speed, the depth of the wire marks can be reduced.

[0065] In the present invention, the processed silicon wafer is placed in a sub - nanosecond pulsed laser for laser scanning repair.

[0066] In the present invention, in step (6), the wavelength of the laser is preferably 532 nm, the pulse width of the laser is preferably 652.1 ps, and the pulse repetition frequency of the laser is preferably 56 kHz.

[0067] In the present invention, in step (6), the output power of the laser repair is preferably 10 - 15 mW, more preferably 11 - 14 mW, and still more preferably 12 - 13 mW.

[0068] In the present invention, the scanning speed of the laser repair is preferably 1.5 - 2.0 mm / s, more preferably 1.6 - 1.9 mm / s, and still more preferably 1.7 - 1.8 mm / s.

[0069] In the present invention, a laser repair device is provided. By means of the reconstruction mechanism of the single-crystalline silicon lattice structure during the laser irradiation process, the surface wire marks are repaired, the depth of the wire marks is reduced, and the surface roughness of the silicon wafer is reduced.

[0070] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0071] The coolant used in the embodiments of the present application is a water-soluble coolant directly purchased from the market. The coolant manufacturer is Jiaxing Shengwang Technology Co., Ltd., and the coolant model is SW-DWS1524.

[0072] Embodiment 1

[0073] (1) Bonding and curing: The surface-ground single-crystalline silicon rod is bonded to the base and cured at 25 °C for 10 h to obtain a silicon rod group.

[0074] (2) Preparing the cutting coolant: Inject 370 L of water into the coolant tank of the diamond wire cutting machine, and turn on the stirring and internal circulation; measure 1.2 L of coolant and place it in the ultrasonic cleaning machine tank for ultrasonic treatment for 30 min. After ultrasonic treatment, pour it into the coolant tank of the diamond wire cutting machine in three times and mix it with water and stir for 5 min, and adjust the surface tension of the solution to 29 N / m by adding coolant or water to obtain the cutting coolant.

[0075] (3) Arranging the wire mesh: Install the silicon rod group in step (1) into the processing chamber of the diamond wire cutting machine. Lead out the diamond wire for cutting from the wire feeding chamber, and arrange the diamond wire in the corresponding wire grooves on the main roller through the small guide wheels. After the diamond wire covers the entire main roller, lead out the wire head of the diamond wire to the wire winding chamber to complete the wiring work of the wire mesh.

[0076] (4) Setting the cutting parameters: Set the flow rate of the cutting coolant to 9000 m 3 / h. For the diamond wire with a wire diameter of 25 μm, set the diamond wire tension to 3.3 N, and then perform a warm-up cycle. After the warm-up is completed, perform cutting, and set the process in the cutting stage according to the wire table ratio of 8.2 (the ratio of the wire speed to the table speed):

[0077] Set the table speed to 2.2 mm / min, the wire speed to 18 m / s, the forward wire feeding distance to 30000 m, the reverse wire feeding distance to 25000 m, and set the time for one cutting cycle to 45 min.

[0078] (5) Post-treatment: After cutting is completed, stop the machine and remove the silicon rod. The silicon rod group is processed into silicon wafers, and the silicon wafers are successively degummed, cleaned, and sorted to complete the processing of the silicon wafers;

[0079] (6) Laser repair: Place the processed silicon wafers in a sub-nanosecond pulsed laser for laser scanning repair. Set the wavelength of the laser to 532 nm, the pulse width to 652.1 ps, the pulse repetition frequency to 56 kHz, the output power to 12 mW, and the scanning speed to 1.8 mm / s to obtain the monocrystalline silicon wafers.

[0080] For the 210-mm monocrystalline silicon wafers obtained by the cutting method of this Example 1, the number of cutting line marks is within 3, the line mark depth of the processed monocrystalline silicon wafers is within 5 μm, and the line mark depth of the laser-repaired monocrystalline silicon wafers can reach within 3 μm.

[0081] Example 2

[0082] (1) Bonding and curing: Bond the surface-ground monocrystalline silicon rod to the base and cure it at 22 °C for 10 h to obtain a silicon rod group;

[0083] (2) Prepare cutting coolant: Inject 380 L of water into the coolant tank of the wire saw. Turn on the stirring and internal circulation; Measure 1.2 L of coolant and place it in the ultrasonic cleaner tank for 30 min of ultrasonic treatment. After ultrasonic treatment, pour it into the coolant tank of the wire saw in three times and mix it with water for 5 min, and adjust the surface tension of the solution to 30 N / m by adding coolant or water to obtain the cutting coolant;

[0084] (3) Arrange the wire mesh: Install the silicon rod group in step (1) into the processing chamber of the wire saw. Lead out the cutting wire from the wire feeding chamber, and arrange the wire on the corresponding wire grooves on the main roller through small guide wheels. After the wire covers the entire main roller, lead out the wire end to the wire take-up chamber to complete the wiring work of the wire mesh;

[0085] (4) Set cutting parameters: Set the flow rate of the cutting coolant to 8000 m 3 / h. For a wire saw with a wire diameter of 27 μm, set the wire tension to 4 N, then perform a warm-up cycle. After the warm-up is completed, perform cutting, and set the process of the cutting stage according to a wire table ratio of 9 (the ratio of wire speed to table speed):

[0086] Set the table speed to 2.0 mm / min, the wire speed to 18 m / s, the forward wire feeding distance to 30000 m, the reverse wire feeding distance to 25000 m, and the time for one cutting cycle to 45 min.

[0087] (5) Post-treatment: After cutting is completed, stop the machine and remove the silicon rod. The silicon rod group is processed into silicon wafers, and the silicon wafers are successively degummed, cleaned, and sorted to complete the processing of the silicon wafers;

[0088] (6) Laser repair: Place the processed silicon wafers in a sub-nanosecond pulse laser for laser scanning repair. Set the wavelength of the laser to 532 nm, the pulse width to 652.1 ps, the pulse repetition frequency to 56 kHz, the output power to 12 mW, and the scanning speed to 1.8 mm / s to obtain the monocrystalline silicon wafers.

[0089] Example 3

[0090] (1) Bonding and curing: Bond the surface-ground monocrystalline silicon rod to the base and cure it at 30 °C for 8 h to obtain a silicon rod group;

[0091] (2) Prepare cutting coolant: Pour 380 L of water into the coolant tank of the wire saw, and turn on the stirring and internal circulation; Measure 1.2 L of coolant and place it in the ultrasonic cleaner tank for 30 min of ultrasonic treatment. After ultrasonic treatment, pour it into the coolant tank of the wire saw in three times and mix it with water and stir for 5 min, and adjust the surface tension of the solution to 30 N / m by adding coolant or water to obtain the cutting coolant;

[0092] (3) Arrange the wire mesh: Install the silicon rod group in step (1) into the processing chamber of the wire saw. Lead out the diamond wire for cutting from the wire feeding chamber, and arrange the diamond wire in the corresponding wire grooves on the main roller through the small guide wheels. After the diamond wire covers the entire main roller, lead out the wire head of the diamond wire to the wire take-up chamber to complete the wiring work of the wire mesh;

[0093] (4) Set cutting parameters: Set the flow rate of the cutting coolant to 8500 m 3 / h. For a diamond wire with a wire diameter of 26 μm, set the diamond wire tension to 3.5 N, then perform a warm-up cycle. After the warm-up is completed, perform cutting, and set the process in the cutting stage according to a wire table ratio of 10 (the ratio of wire speed to table speed):

[0094] Set the table speed to 2.0 mm / min, the wire speed to 20 m / s, the forward wire feeding distance to 30000 m, the reverse wire feeding distance to 25000 m, and set the time for one cutting cycle to 45 min.

[0095] (5) Post-treatment: After cutting is completed, stop the machine and remove the silicon rod. The silicon rod group is processed into silicon wafers, and the silicon wafers are successively degummed, cleaned, and sorted to complete the processing of the silicon wafers;

[0096] (6) Laser repair: Place the processed silicon wafer in a sub-nanosecond pulsed laser for laser scanning repair. Set the wavelength of the laser to 532 nm, the pulse width to 652.1 ps, the pulse repetition frequency to 56 kHz, the output power to 12 mW, and the scanning speed to 1.8 mm / s to obtain the single-crystalline silicon wafer.

[0097] Example 4

[0098] (1) Bonding and curing: Bond the surface-ground single-crystalline silicon rod to the base and cure it at 20 °C for 12 h to obtain a group of silicon rods.

[0099] (2) Prepare cutting coolant: Pour 350 L of water into the coolant tank of the wire saw, and turn on the stirring and internal circulation. Measure 1.0 L of coolant and place it in the ultrasonic cleaner tank for 30 min of ultrasonic treatment. After ultrasonic treatment, pour it into the coolant tank of the wire saw in three times and mix it with water for 5 min, and adjust the surface tension of the solution to 28 N / m by adding coolant or water to obtain the cutting coolant.

[0100] (3) Arrange the wire mesh: Install the group of silicon rods in step (1) into the processing chamber of the wire saw. Lead out the diamond wire for cutting from the wire feeding chamber, and arrange the diamond wire in the corresponding wire grooves on the main roller through small guide wheels. After the diamond wire covers the entire main roller, lead out the wire head of the diamond wire to the wire collecting chamber to complete the wiring work of the wire mesh.

[0101] (4) Set cutting parameters: Set the flow rate of the cutting coolant to 8000 m 3 / h. For a diamond wire with a wire diameter of 24 μm, set the diamond wire tension to 3 N, then perform a warm-up cycle. After the warm-up is completed, perform cutting, and set the process in the cutting stage according to a wire table ratio of 9 (the ratio of wire speed to table speed):

[0102] Set the table speed to 2.0 mm / min, the wire speed to 18 m / s, the forward wire feeding distance to 28000 m, the reverse wire feeding distance to 23000 m, and the time for one cutting cycle to 40 min.

[0103] (5) Post-treatment: After cutting, stop the machine and remove the silicon rod. The group of silicon rods is processed into silicon wafers, and the silicon wafers are sequentially degummed, cleaned, and sorted to complete the processing of the silicon wafers.

[0104] (6) Laser repair: Place the processed silicon wafer in a sub-nanosecond pulsed laser for laser scanning repair. Set the wavelength of the laser to 532 nm, the pulse width to 652.1 ps, the pulse repetition frequency to 56 kHz, the output power to 10 mW, and the scanning speed to 1.5 mm / s to obtain the single-crystalline silicon wafer.

[0105] Example 5

[0106] (1) Bonding and curing: Bond the polished single-crystalline silicon rod on the base and cure it at 25 °C for 10 h to obtain a silicon rod group;

[0107] (2) Prepare cutting coolant: Inject 400 L of water into the coolant tank of the wire saw, and turn on the stirring and internal circulation; Measure 1.5 L of coolant and place it in the ultrasonic cleaner tank for 30 min of ultrasonic treatment. After the ultrasonic treatment, pour it into the coolant tank of the wire saw in three times and mix it with water for 5 min, and adjust the surface tension of the solution to 30 N / m by adding coolant or water to obtain the cutting coolant;

[0108] (3) Arrange the wire mesh: Install the silicon rod group in step (1) into the processing chamber of the wire saw, lead out the diamond wire for cutting from the wire feeding chamber, and arrange the diamond wire in the corresponding wire grooves on the main roller through small guide wheels. After the diamond wire covers the entire main roller, lead out the wire head of the diamond wire to the wire take-up chamber to complete the wiring work of the wire mesh;

[0109] (4) Set cutting parameters: Set the flow rate of the cutting coolant to 10000 m 3 / h. For the diamond wire with a wire diameter of 28 μm, set the diamond wire tension to 4.5 N, then perform a warm-up cycle. After the warm-up is completed, perform cutting, and set the process in the cutting stage according to the wire table ratio of 8.3 (the ratio of wire speed to table speed):

[0110] Set the table speed to 2.4 mm / min, the wire speed to 20 m / s, the forward wire feeding distance to 32000 m, the reverse wire feeding distance to 27000 m, and set the time for one cutting cycle to 50 min.

[0111] (5) Post-treatment: After cutting, stop the machine and remove the silicon rod. The silicon rod group is processed into silicon wafers, and the silicon wafers are sequentially degummed, cleaned and sorted to complete the processing of the silicon wafers;

[0112] (6) Laser repair: Place the processed silicon wafers in a sub-nanosecond pulsed laser for laser scanning repair. Set the wavelength of the laser to 532 nm, the pulse width to 652.1 ps, the pulse repetition frequency to 56 kHz, the output power to 15 mW, and the scanning speed to 2.0 mm / s to obtain the single-crystalline silicon wafers.

[0113] Comparative Example 1

[0114] (1) Bonding and curing: Bond the polished single-crystalline silicon rod on the base and cure it at 25 °C for 10 h to obtain a silicon rod group;

[0115] (2) Configure the cutting coolant: Pour 370 L of water into the coolant tank of the wire saw, and turn on the stirring and internal circulation; Measure 1.2 L of coolant and place it in the ultrasonic cleaner tank for ultrasonic treatment for 30 min. After the ultrasonic treatment, pour it into the coolant tank of the wire saw in three times and mix it with water and stir for 5 min, and adjust the surface tension of the solution to 29 N / m by adding coolant or water to obtain the cutting coolant;

[0116] (3) Arrange the wire mesh: Install the silicon rod group in step (1) into the processing chamber of the wire saw, lead out the diamond wire for cutting from the wire feeding chamber, and arrange the diamond wire in the corresponding wire grooves on the main roller through the small guide wheels. After the diamond wire covers the entire main roller, lead out the wire end of the diamond wire to the wire take-up chamber to complete the wiring work of the wire mesh;

[0117] (4) Set the cutting parameters: Set the flow rate of the cutting coolant to 9000 m 3 / h. For the diamond wire with a wire diameter of 25 μm, set the diamond wire tension to 3.3 N, and then perform a warm-up cycle. After the warm-up is completed, perform cutting, and set the process in the cutting stage:

[0118] The table speed is set to 3.0 mm / min, the wire speed is set to 35 m / s, the forward wire feeding distance is set to 600 m, the reverse wire feeding distance is set to 550 m, and the time used for one cutting cycle is set to 0.5 min.

[0119] (5) Post-treatment: After cutting is completed, stop the machine and remove the silicon rod. The silicon rod group is processed into silicon wafers, and the silicon wafers are sequentially degummed, cleaned and sorted to complete the processing of the silicon wafers and obtain monocrystalline silicon wafers.

[0120] For the 210 mm monocrystalline silicon wafers obtained in this comparative example, the number of cutting wire marks is 88, and the wire mark depth reaches 12 μm.

[0121] Compared with the monocrystalline silicon wafers obtained in Comparative Example 1, the number of wire marks on the monocrystalline silicon wafers of the present invention is much less than that of the comparative example, and the wire mark depth is also much lower than that of the comparative example, effectively reducing the surface roughness of the silicon wafers.

[0122] As can be seen from the above embodiments, the present invention provides a cutting process and treatment method for reducing the surface roughness of monocrystalline silicon wafers, including the following steps: bonding and curing; preparing cutting coolant; arranging wire meshes; setting cutting parameters; post-treatment; and laser repair. Compared with the silicon wafers processed by the traditional electroplated diamond wire process, the present invention adjusts the cutting parameters and lengthens the bidirectional reciprocating cutting commutation period, so that the number of wire marks on the processed monocrystalline silicon wafers is significantly reduced, and the wire marks on the surface of the monocrystalline silicon wafers can be controlled within 3; by reducing the table speed, the wire mark depth of the monocrystalline silicon wafers can be reduced to within 5μm; the present invention performs laser repair on the processed silicon wafers. Through the reconstruction mechanism of the monocrystalline silicon lattice structure during the laser irradiation process, it is expected to realize industrialization and automation of laser high-efficiency repair of silicon wafers. The wire marks on the surface of the repaired silicon wafers can reach within 3μm, reducing the surface roughness of the silicon wafers. The processed silicon wafers of the present invention are more suitable for crystalline silicon / perovskite tandem cells and have broad market prospects.

[0123] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A cutting process and treatment method for reducing the surface roughness of single crystal silicon wafers, characterized in that, It includes the following steps: (1) Bonding and curing: Bond the surface-ground single-crystal silicon rod to the base and cure it to obtain a silicon rod group; (2) Preparing cutting coolant: Ultrasonically clean the coolant, then mix and stir it with water to adjust the surface tension to obtain the cutting coolant; (3) Arranging the wire mesh: Install the silicon rod group in step (1) into the processing chamber of the diamond wire cutting machine, lead out the diamond wire from the wire feeding chamber, arrange the diamond wire in the corresponding wire grooves on the main roller. After the diamond wire covers the entire main roller, lead out the wire head of the diamond wire to the wire winding chamber to complete the wiring work of the wire mesh; (4) Setting cutting parameters: Set the flow rate of the cutting coolant, set the diamond wire tension according to the wire diameter of the diamond wire, then perform a warm-up cycle. After the warm-up is completed, perform cutting and set the process of the cutting stage according to the wire table ratio: The table speed is set to 2.0 - 2.4 mm / min, the wire speed is set to 18 - 20 m / s, the forward wire feeding distance is set to 28000 - 32000 m, the reverse wire feeding distance is set to 23000 - 27000 m, and the time taken for one cutting cycle is set to 40 - 50 min; (5) Post-treatment: After cutting, the silicon rod group is processed into silicon wafers, and the silicon wafers are sequentially degummed, cleaned, and sorted to complete the processing of the silicon wafers; (6) Laser repair: Perform laser scanning repair on the processed silicon wafers to obtain the single-crystal silicon wafers.

2. A cutting process and treatment method for reducing the surface roughness of a single-crystal silicon wafer according to claim 1, characterized in that, The curing temperature in step (1) is 20 - 30 °C; The curing time is 8 - 12 h.

3. A cutting process and treatment method for reducing the surface roughness of a single-crystal silicon wafer according to claim 1, characterized in that, In step (2), the volume ratio of the coolant to water is 1 - 1.5:350 - 400; In step (2), the surface tension of the cutting coolant is 28 - 30 N / m.

4. A cutting process and treatment method for reducing the surface roughness of monocrystalline silicon wafers according to claim 1, characterized in that, The flow rate of the cutting coolant in step (4) is 8000 - 10000 m 3 / h.

5. A cutting process and treatment method for reducing the surface roughness of a single-crystal silicon wafer according to claim 1, characterized in that, In step (4), the wire diameter of the diamond wire is 24 - 28 μm; In step (4), the tension of the diamond wire is 3 - 4.5 N.

6. A cutting process and treatment method for reducing the surface roughness of monocrystalline silicon wafers according to claim 1, characterized in that, In step (4), the exposed blade rate of the diamond wire is 150 - 280, and the exposed blade height of the diamond wire is 3 - 6 μm.

7. A cutting process and treatment method for reducing the surface roughness of a single-crystalline silicon wafer according to claim 6, characterized in that, When the wire diameter of the diamond wire in step (4) is 24 - 26 μm, the diamond wire tension is set to 3 - 4 N; When the wire diameter of the diamond wire in step (4) is 26 - 28 μm, the diamond wire tension is set to 3.5 - 4.5 N.

8. A cutting process and treatment method for reducing the surface roughness of a single-crystal silicon wafer according to claim 1, characterized in that In step (4), the wire table ratio is 8 - 10.

9. A cutting process and treatment method for reducing the surface roughness of a single-crystal silicon wafer according to claim 1, characterized in that, In step (6), the light source of the laser comes from a sub-nanosecond pulsed laser; In step (6), the wavelength of the laser is 532 nm, the pulse width of the laser is 652.1 ps, and the pulse repetition frequency of the laser is 56 kHz.

10. A cutting process and treatment method for reducing the surface roughness of monocrystalline silicon wafers according to claim 1, characterized in that, In step (6), the output power of the laser repair is 10 - 15 mW; The scanning speed of the laser repair is 1.5 - 2.0 mm / s.