CN111834211A - Pretreatment method of silicon wafer and preparation method of stitch welding solar module - Google Patents
Pretreatment method of silicon wafer and preparation method of stitch welding solar module Download PDFInfo
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims abstract description 188
- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 188
- 239000010703 silicon Substances 0.000 title claims abstract description 188
- 238000003466 welding Methods 0.000 title claims abstract description 30
- 238000002203 pretreatment Methods 0.000 title claims abstract description 16
- 238000002360 preparation method Methods 0.000 title abstract description 8
- 238000000034 method Methods 0.000 claims abstract description 53
- 238000001020 plasma etching Methods 0.000 claims abstract description 27
- 239000012530 fluid Substances 0.000 claims abstract description 22
- 230000009471 action Effects 0.000 claims abstract description 5
- 238000010438 heat treatment Methods 0.000 claims description 25
- 239000007789 gas Substances 0.000 claims description 17
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 12
- 238000001816 cooling Methods 0.000 claims description 12
- 239000007788 liquid Substances 0.000 claims description 12
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 11
- 238000005516 engineering process Methods 0.000 claims description 7
- 239000001569 carbon dioxide Substances 0.000 claims description 6
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 6
- 238000004519 manufacturing process Methods 0.000 claims description 4
- 229910052757 nitrogen Inorganic materials 0.000 claims description 4
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 3
- 229910001873 dinitrogen Inorganic materials 0.000 claims description 3
- 239000001257 hydrogen Substances 0.000 claims description 3
- 150000002431 hydrogen Chemical class 0.000 claims description 3
- 229910052739 hydrogen Inorganic materials 0.000 claims description 3
- 239000011261 inert gas Substances 0.000 claims description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 3
- 238000005336 cracking Methods 0.000 abstract description 20
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- 238000005401 electroluminescence Methods 0.000 description 3
- 230000006872 improvement Effects 0.000 description 3
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- 150000002500 ions Chemical class 0.000 description 2
- 238000003698 laser cutting Methods 0.000 description 2
- 238000001000 micrograph Methods 0.000 description 2
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- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
- H01L31/1804—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof comprising only elements of Group IV of the Periodic Table
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
- H01L21/302—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
- H01L21/306—Chemical or electrical treatment, e.g. electrolytic etching
- H01L21/3065—Plasma etching; Reactive-ion etching
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/547—Monocrystalline silicon PV cells
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
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Abstract
The invention belongs to the technical field of photovoltaics, and provides a silicon wafer pretreatment method and a stitch welding solar module preparation method, which comprise the following steps: the laser beam is adopted to rapidly heat the interior of the part of the silicon wafer to be cracked, and the fluid beam is adopted to rapidly cool the surface of the part of the silicon wafer to be cracked, so that the silicon wafer is cracked under the action of compressive stress and tensile stress, and plasma etching is carried out on at least one part of the surface of the silicon wafer. The method combines stress cracking and plasma etching to be applied to the pretreatment of the silicon wafer, can obviously improve the cutting damage to the silicon wafer, ensures that the section of the silicon wafer is uniform, has no burr or crack, obviously reduces the fragment rate of the silicon wafer, and obviously reduces the hidden crack number of the grains of the stitch-welded solar module.
Description
Technical Field
The invention belongs to the technical field of photovoltaics, and particularly relates to a pretreatment method of a silicon wafer and a preparation method of a stitch welding solar module.
Background
As a new battery welding process, the stitch welding technology realizes the superposition of battery pieces on the basis of the traditional welding strip welding process, reduces the space between the battery pieces, and maximizes the utilization area, thereby realizing high energy density.
In the manufacturing process of the stitch welding solar module, after the silicon wafers are sorted, the silicon wafers need to be cut and preprocessed, and then the silicon wafers are mutually overlapped and welded by using a flexible welding strip and a customized tool based on a welding technology. The traditional silicon wafer cutting mode is as follows: a trench is scribed in a silicon wafer using a pulsed laser with high energy density and then mechanically broken. The cross section of the silicon wafer cut by the traditional mode is observed by a scanning electron microscope, and the cross section is extremely uneven, is obviously wavy and has more burrs and cracks, because the laser heat causes chemical change of the cut cross section of the battery, the melting phenomenon occurs, and the serious cutting damage is caused to the silicon wafer. Because the intersection point of the laser cutting and the mechanical breaking piece has stress, and the cutting part of the silicon chip is positioned at the rolling position of the welding strip, the quality of the stitch-welded solar module is finally influenced by the damage of the silicon chip caused in the cutting process, and the stitch-welded solar module has more hidden cracks of lines after lamination.
Disclosure of Invention
The invention aims to provide a pretreatment method of a silicon wafer and a preparation method of a stitch welding solar module aiming at the defects of the prior art.
In order to solve the above technical problems, a first aspect of the present invention provides a method for pre-processing a silicon wafer, which sequentially includes: rapidly heating the interior of a part to be cracked of the silicon wafer by adopting a laser beam so as to expand the interior of the part to be cracked of the silicon wafer to form compressive stress; rapidly cooling the surface of the part to be cracked of the silicon wafer by adopting a fluid beam so as to enable the surface of the part to be cracked of the silicon wafer to shrink to form tensile stress; the silicon wafer is cracked under the action of the compressive stress and the tensile stress; exposing at least one part of the surface of a silicon wafer to plasma, and carrying out plasma etching on at least one part of the surface of the silicon wafer, wherein at least one part of the surface of the silicon wafer comprises the surface of a part of the silicon wafer, which is cracked.
Compared with the prior art, the invention has at least the following beneficial effects:
the invention combines stress cracking and plasma etching to be applied to the pretreatment of the silicon wafer. Firstly, rapidly heating the interior of a part to be cracked of a silicon wafer by adopting a laser beam to ensure that the interior of the part to be cracked of the silicon wafer expands to form compressive stress; rapidly cooling the surface of the part to be cracked of the silicon wafer by adopting a fluid beam, so that the surface of the part to be cracked of the silicon wafer is contracted to form tensile stress; because the compressive rigidity of the brittle material is far greater than the tensile strength, when the tensile stress reaches the fracture strength of the silicon wafer, the silicon wafer can be naturally fractured, and the crack can stably expand along with the laser and cooling moving track. The method avoids the thermal damage and the mechanical damage to the silicon wafer in the traditional 'laser cutting and mechanical splitting' process, effectively improves the quality of the section of the silicon wafer, and simultaneously reduces the breaking rate in the splitting process. Secondly, after the silicon wafer is subjected to stress cracking, plasma etching is carried out on the silicon wafer, a diffusion layer on the surface of the silicon wafer and slight cracks or dust on the surface of a cracking part are removed, and the surface property of the silicon wafer is further improved.
The second aspect of the present invention also provides a method for manufacturing a stitch-welded solar module, including: according to the method of the first aspect of the invention, the silicon wafer is pretreated, and the pretreated silicon wafer is prepared into the solar module by adopting the stitch welding technology. The solar module prepared by the method provided by the second aspect of the invention has the advantage that the problem of hidden crack of grains is obviously improved.
Preferably, in the method for pretreating a silicon wafer provided by the present invention, the step of rapidly heating the interior of the portion of the silicon wafer to be cleaved with the laser beam sequentially comprises: rapidly heating the interior of the part to be cracked of the silicon wafer by adopting an ultraviolet laser beam with the wavelength of 320-400 nm and the power of 3-5W; and rapidly heating the interior of the part to be cracked of the silicon wafer by adopting an infrared laser beam with the wavelength of 1060-1100 nm and the power of 100-150W.
Preferably, in the silicon wafer pretreatment method provided by the invention, the distance between the interior of the part to be split of the silicon wafer and the surface of the part to be split of the silicon wafer is 1-3 mm. Within the distance range, the success rate of stress cracking and the cracking effect are the best.
Preferably, in the silicon wafer pretreatment method provided by the invention, in the step of rapidly cooling the surface of the to-be-cracked part of the silicon wafer by using the fluid beam, the fluid beam is selected from at least one of liquid water, liquid carbon dioxide, liquid hydrogen, liquid nitrogen, low-temperature inert gas, low-temperature carbon dioxide gas, low-temperature hydrogen gas and low-temperature nitrogen gas.
Preferably, in the silicon wafer pretreatment method provided by the invention, the temperature of the fluid beam is 20-30 ℃. In the method, the laser beam can enable the internal temperature of the part to be cracked of the silicon wafer to reach 150-200 ℃, and simultaneously, the stress cracking can be realized only by applying a fluid beam with the temperature of 20-30 ℃ on the surface of the part to be cracked of the silicon wafer for rapid cooling by matching with the laser parameters and the heating position of the method. The fluid beam at the temperature of 20-30 ℃ is easy to obtain and convenient to use, so that the method disclosed by the invention is good in operability and easy to apply industrially.
Preferably, in the method for pretreating a silicon wafer provided by the invention, the plasma etching step is performed in a plasma etcher.
Preferably, in the method for pretreating a silicon wafer according to the present invention, the gas for forming the plasma at least contains CF4And O2Said CF4The flow rate of (A) is 100 to 120sccm/min, and (B) is2The flow rate of the gas is 10 to 15 sccm/min.
Preferably, in the silicon wafer pretreatment method provided by the invention, the pressure for exciting the high-frequency glow of the plasma is 300-350 Pa, and the power is 100-120W.
Preferably, in the silicon wafer pretreatment method provided by the invention, the time for starting the high-frequency glow is 10-18 minutes, preferably 14 minutes.
Under the plasma gas flow range and the pressure and power condition of high-pressure glow provided by the invention, when the high-frequency glow is started and the plasma etching time for the surface of the silicon wafer is 14 minutes, the improvement effect of the subfissure of the stitch welding solar module can be optimal, and the subfissure number of the whole module can be controlled within 4.
Drawings
FIG. 1 is a scanning electron microscope photograph of the edge of a silicon wafer fragment pretreated in accordance with the method of the present invention in example 3;
FIG. 2 is a scanning electron microscope image of the cut edge of a silicon wafer after conventional laser dicing and plasma etching treatment in comparative example 1;
FIG. 3 is a scanning electron microscope photograph of a fragmented section of a silicon wafer pretreated in accordance with the method of the present invention in example 3;
FIG. 4 is a scanning electron microscope photograph of a cut section of a silicon wafer after conventional laser dicing and plasma etching treatment in comparative example 1;
fig. 5 is a schematic structural diagram of overlapping and connecting two adjacent silicon wafers in series in a stitch-bonded solar module according to an embodiment.
Detailed Description
In order that the objects, features and advantages of the present invention can be more clearly understood, embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The materials used are not indicated by the manufacturer, and are all conventional products available by commercial purchase. The description of the exemplary embodiments is for exemplary purposes only and is not intended to limit the invention or its applications.
According to a first aspect of the present invention, an embodiment of the present invention provides a silicon wafer pretreatment method, which sequentially includes: rapidly heating the interior of a part to be cracked of the silicon wafer by adopting a laser beam so as to expand the interior of the part to be cracked of the silicon wafer to form compressive stress; rapidly cooling the surface of the part to be cracked of the silicon wafer by adopting a fluid beam so as to enable the surface of the part to be cracked of the silicon wafer to shrink to form tensile stress; the silicon wafer is cracked under the action of the compressive stress and the tensile stress; exposing at least one part of the surface of a silicon wafer to plasma, and carrying out plasma etching on at least one part of the surface of the silicon wafer, wherein at least one part of the surface of the silicon wafer comprises the surface of a part of the silicon wafer, which is cracked.
In some embodiments of the present invention, the step of rapidly heating the interior of the to-be-cracked portion of the silicon wafer by using the laser beam sequentially comprises: firstly, rapidly heating the interior of a to-be-cracked part of the silicon wafer by adopting an ultraviolet laser beam with the wavelength of 320-400 nm and the power of 3-5W; and then, rapidly heating the interior of the part of the silicon wafer to be cracked by adopting an infrared laser beam with the wavelength of 1060-1100 nm and the power of 100-150W. As an example of some embodiments, an ultraviolet laser beam having a wavelength of 320nm and a power of 3W; an ultraviolet laser beam with the wavelength of 350nm and the power of 5W; an ultraviolet laser beam with the wavelength of 380nm and the power of 4W; ultraviolet laser beam with wavelength of 400nm and power of 4.5W, etc. Also, as an example of some embodiments, an infrared laser beam having a wavelength of 1060nm and a power of 100W; an infrared laser beam with the wavelength of 1070nm and the power of 110W; an infrared laser beam with the wavelength of 1080nm and the power of 120W; an infrared laser beam with a wavelength of 1090nm and a power of 130W; an infrared laser beam having a wavelength of 1100nm and a power of 150W, and the like.
In some embodiments of the present invention, a distance between an inside of the portion to be cleaved of the silicon wafer and a surface of the portion to be cleaved of the silicon wafer is 1 to 3 mm. As an example of some embodiments, the distance between the inside of the portion of the silicon wafer to be split and the surface of the portion of the silicon wafer to be split may be 1mm, 1.5mm, 2mm, 2.5mm, 3mm, or the like.
In some embodiments of the present invention, in the step of rapidly cooling the surface of the to-be-cracked portion of the silicon wafer by using the fluid beam, the fluid beam is selected from at least one of liquid water, liquid carbon dioxide, liquid hydrogen, liquid nitrogen, low-temperature inert gas, low-temperature carbon dioxide gas, low-temperature hydrogen gas, and low-temperature nitrogen gas.
In some embodiments of the present invention, the temperature of the fluid stream is 20 to 30 ℃. As examples of some embodiments, the temperature of the fluid beam may be 20 ℃, 24 ℃, 26 ℃, 28 ℃, or 30 ℃, and the like.
In some embodiments of the invention, the plasma etching step is performed in a plasma etcher. The embodiment of the invention has no special requirements on the brand and the model of the plasma etcher, and the plasma etcher can be applied as long as the plasma etcher can complete the following plasma etching processes: under low pressure, the reaction gas is excited by radio frequency power to generate ionization and form plasma, the plasma is composed of charged electrons and ions, and the gas in the reaction cavity can absorb energy and form a large amount of active reaction groups besides being converted into ions under the impact of the electrons; the active reaction group and the surface of the etched substance are subjected to chemical reaction to form a volatile reaction product; the reaction product is separated from the surface of the etched substance and is pumped out of the chamber by the vacuum system.
In some embodiments of the invention, the gas forming the plasma comprises at least CF4And O2Said CF4The flow rate of (A) is 100 to 120sccm/min, and (B) is2The flow rate of the gas is 10 to 15 sccm/min. As an example of some embodiments, CF4The flow rate can be 100sccm/min, 105sccm/min, 110sccm/min, 115sccm/min, 120sccm/min, etc.; o is2The flow rate can be 10sccm/min, 11sccm/min, 12sccm/min, 13sccm/min, 14sccm/min, 15sccm/min, etc.
In some embodiments of the present invention, the pressure for exciting the high-frequency glow of the plasma is 300 to 350Pa, and the power is 100 to 120W. As an example of some embodiments, the pressure of the high frequency glow that excites the plasma may be 300Pa, 310Pa, 320Pa, 340Pa, 350Pa, or the like; the power may be 100W, 105W, 110W, 115W, 120W, etc.
In some embodiments of the invention, the high-frequency glow is turned on for 10 to 18 minutes. For example, the time for turning on the high frequency glow may be 10 minutes, 12 minutes, 14 minutes, 16 minutes, 18 minutes, or the like.
According to a second aspect of the present invention, an embodiment of the present invention also provides a method for manufacturing a stitch-welded solar module, including: according to the method of the first aspect of the invention, the silicon wafer is pretreated, and the pretreated silicon wafer is prepared into the solar module by adopting the stitch welding technology.
The specific process steps for preparing the solar module by using the stitch welding technology are not particularly limited in the embodiment of the invention, and can be performed according to the conventional preparation method of the stitch welding solar module in the field.
In the stitch welding solar component provided by the embodiment of the invention, a plurality of pretreated silicon wafers are mutually overlapped and connected in series from front to back, and a welding strip is arranged between two adjacent silicon wafers. In the preparation process of the stitch welding solar module, the welding strip can be positioned between two adjacent silicon wafers for welding, and a plurality of silicon wafers are connected in series in a front-back lap joint manner; and then laminating, and heating and curing the glass substrate, the EVA film layer, the battery string, the back plate and the like into a rigid whole. Because the silicon wafer cracking part in the pretreatment process is in the position coinciding with the welding strip, the surface property and the stress resistance of the silicon wafer cracking part have higher requirements in the welding and laminating processes, and if the cracking part is subjected to heat influence or mechanical damage in the cracking process, or more microcracks or burrs are arranged on the surface of the cracking part, hidden crack of grains is easy to generate in the laminated assembly.
The advantages of the present application are further illustrated by the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present application. Unless otherwise specified, various parameters referred to in this specification have the common meaning known in the art and can be measured according to methods known in the art. For example, the test can be performed according to the method given in the examples of the present application. In addition, the preferred ranges and options for the various parameters given in the various preferred embodiments can be combined in any combination, and the various combinations thus obtained are considered to be within the scope of the disclosure of the present application.
Examples 1 to 12
1. Pretreatment of silicon wafers
After the silicon wafers are sorted, quickly heating the interior of the to-be-cracked part of the silicon wafer for 1-2 seconds by adopting an ultraviolet laser beam (continuous laser); and then, rapidly heating the interior of the part to be cracked of the silicon wafer for 1-2 seconds by adopting an infrared laser beam (continuous laser) so as to expand the interior of the part to be cracked of the silicon wafer to form compressive stress. And rapidly cooling the surface of the part to be cracked of the silicon wafer by adopting a fluid beam for 1-2 seconds so as to enable the surface of the part to be cracked of the silicon wafer to shrink to form tensile stress. The silicon chip is broken under the action of compressive stress and tensile stress, and the crack is stably expanded along with the moving tracks of the laser beam and the fluid beam.
Placing the silicon wafer in a plasma etching machine for plasma etching, wherein the gas for forming the plasma contains CF4And O2Control of CF4The flow rate of (A) is 100 to 120sccm/min, O2The flow rate of the gas is 10 to 15 sccm/min. The specific process flow of plasma etching is briefly described as follows: opening gas, electrifying the whole machine, preheating at high frequency, starting a pump, pre-pumping tail gas, closing the pre-pumping main pump, and sending process gas (CF)4And O2) Diluting, starting high-frequency glow discharge when the pressure is stabilized at a set value, closing high-frequency glow, closing process gas, feeding nitrogen, inflating to open a cover, and taking away the silicon wafer.
2. Preparation of stitch-welded solar module
The solar module is prepared by adopting a conventional stitch welding technology, and the specific process steps are briefly described as follows: taking a plurality of pretreated silicon wafers, respectively positioning the welding strips between two adjacent pretreated silicon wafers, and welding to obtain a battery string formed by mutually lapping and connecting the front and back of the pretreated silicon wafers in series; then laminating is carried out; and heating and curing the glass substrate, the EVA adhesive film layer, the cell string, the back plate and the like into a rigid whole to obtain the stitch-welded solar module.
Specific process parameters for examples 1-12 are shown in Table 1.
Comparative example 1
Comparative example 1 differs from example 3 in that: the wafers were laser grooved with a 100W uv laser using a conventional laser microtome and then mechanically broken. The subsequent steps of plasma etching the silicon wafer and preparing the stitch-welded solar module are the same as those in embodiment 3, and the specific process parameters are shown in table 1.
Comparative example 2
Comparative example 1 differs from example 3 in that: firstly, rapidly heating the interior of a part to be cracked of a silicon wafer for 1-2 seconds by adopting an infrared laser beam (continuous laser); then, rapidly heating the interior of the part of the silicon wafer to be cracked for 1-2 seconds by adopting an ultraviolet laser beam (continuous laser); and then, rapidly cooling the surface of the part to be cracked of the silicon wafer by adopting a fluid beam, wherein the silicon wafer cannot be cracked by natural stress and is mechanically matched with the cracking. The subsequent steps of plasma etching the silicon wafer and preparing the stitch-welded solar module are the same as those in embodiment 3, and the specific process parameters are shown in table 1.
And respectively observing and detecting the cross section quality of the silicon wafer, the fragment rate of the silicon wafer and the hidden crack of the grain in the assembly on the pretreated silicon wafer and the stitch-welded solar module prepared in the examples 1-12 and the comparative examples 1-2.
The detection of the hidden crack of the lines in the module is carried out by using an EL (electro luminescence) tester (a full-automatic tester for detecting the defects of the solar cell module), the tester utilizes the electro luminescence principle of crystalline silicon, and a high-resolution CCD (charge coupled device) camera is adopted to shoot near-infrared images of the module to obtain and judge the hidden crack of the lines of the module.
FIG. 1 is a scanning electron microscope photograph of the edge of a silicon wafer fragment pretreated in accordance with the method of the present invention in example 3; FIG. 2 is a scanning electron microscope image of the cut edge of the silicon wafer after the conventional laser dicing and plasma etching treatment in comparative example 1.
FIG. 3 is a scanning electron microscope photograph of a fragmented section of a silicon wafer pretreated in accordance with the method of the present invention in example 3; FIG. 4 is a scanning electron microscope photograph of a cut cross-section of a silicon wafer after conventional laser dicing and plasma etching treatment in comparative example 1.
As can be seen from a comparison of FIGS. 1-4: the edge of the silicon wafer in the embodiment 3 of the invention has no heat affected zone, and on the cross section of the silicon wafer, micro cracks generated by laser processing do not exist in most zones (more than 92 percent), only few materials are removed, and the dust generation amount can be greatly reduced. The pretreatment method provided by the invention can effectively reduce the cutting damage of the cell, improve the mechanical strength of the silicon wafer and enable the silicon wafer to have better electrical performance. In contrast, the conventional laser dicing technique adopted in comparative example 1 leaves a significant heat affected zone at the edge of the silicon wafer, the depth of laser damage to the cross section of the silicon wafer almost reaches 50% of the material thickness, and there are many microcracks on the cross section of the silicon wafer, which can cause the mechanical strength of the silicon wafer to be reduced and inevitably accompanies the generation of a large amount of dust in the processing process.
Fig. 5 is a schematic structural view of overlapping and connecting two adjacent silicon wafers in a stitch-bonded solar module according to an embodiment of the invention. As shown in FIG. 5, two silicon wafers 1 pretreated by the method of the present invention are overlapped and connected in series from front to back, a solder strip 2 is connected to the lower surface of a first silicon wafer and the upper surface of a second silicon wafer in two adjacent silicon wafers, and the edge 3 of the silicon wafer 1 is overlapped with the solder strip 2, wherein the edge 3 of the silicon wafer 1 is a silicon wafer cracking part in the pretreatment process. The silicon wafer pretreated by the method provided by the invention has the advantages that the cracking part is not obviously affected by heat and mechanical damage, and has better surface property and higher mechanical strength, so that hidden cracking of grains is not easy to generate in the welding and laminating processes.
The remaining test results are shown in table 1.
TABLE 1
Comparative example 2 although the inside of the silicon wafer was heated by the laser beam and the surface of the silicon wafer was cooled by the fluid beam, it was heated by the infrared laser beam and then by the ultraviolet laser beam. After two-step laser internal heating, the silicon wafer can not realize natural stress cracking by combining with the surface cooling of the fluid beam, and the silicon wafer needs mechanical force to be matched with the cracking. As can be seen from the test results in Table 1, comparative example 2 has no significant improvement in the quality of the silicon wafer cross section, the chipping rate and the latent crack of the component grain.
Examples 1 to 8 and examples 9 and 10 differ in that: in the step of rapidly heating the interior of the part to be cracked of the silicon wafer by adopting the laser beam, the distances between the heating part inside the silicon wafer and the surface of the silicon wafer are different. The distances in examples 1 to 8 were 1 to 3mm, while those in examples 9 and 10 were 0.5mm and 4mm, respectively. From the detection results in table 1, in the step of rapidly heating the interior of the portion to be cracked of the silicon wafer by using the laser beam, when the distance between the heating portion inside the silicon wafer and the surface of the silicon wafer is within the range of 1-3 mm, the breakage rate of the silicon wafer is the lowest, and the cutting damage to the silicon wafer is the smallest in the cracking process.
Examples 1 to 8 and examples 11 to 12 differ in that: in the step of carrying out plasma etching on the silicon wafer, the high-frequency glow is started for different time, namely the time for carrying out plasma etching is different. The plasma etching time in examples 1 to 8 was within a range of 10 to 18min, while the plasma etching time in examples 11 and 12 was 7min and 23min, respectively. The detection results in table 1 show that the plasma etching time is within the range of 10-18 min, and the improvement effect on the hidden crack of the component grain is most obvious.
The above examples are only for illustrating the technical idea and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the content of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.
Claims (10)
1. A silicon wafer pretreatment method is characterized by sequentially comprising the following steps:
rapidly heating the interior of a part to be cracked of the silicon wafer by adopting a laser beam so as to expand the interior of the part to be cracked of the silicon wafer to form compressive stress;
rapidly cooling the surface of the part to be cracked of the silicon wafer by adopting a fluid beam so as to enable the surface of the part to be cracked of the silicon wafer to shrink to form tensile stress;
the silicon wafer is cracked under the action of the compressive stress and the tensile stress;
exposing at least one part of the surface of a silicon wafer to plasma, and carrying out plasma etching on at least one part of the surface of the silicon wafer, wherein at least one part of the surface of the silicon wafer comprises the surface of a part of the silicon wafer, which is cracked.
2. The method for pretreating a silicon wafer according to claim 1, wherein the step of rapidly heating the interior of the portion of the silicon wafer to be cleaved with the laser beam sequentially comprises:
rapidly heating the interior of the part to be cracked of the silicon wafer by adopting an ultraviolet laser beam with the wavelength of 320-400 nm and the power of 3-5W;
and rapidly heating the interior of the part to be cracked of the silicon wafer by adopting an infrared laser beam with the wavelength of 1060-1100 nm and the power of 100-150W.
3. The method for pretreating a silicon wafer according to claim 1, wherein the distance between the inside of the portion of the silicon wafer to be cleaved and the surface of the portion of the silicon wafer to be cleaved is 1 to 3 mm.
4. The method for pretreating a silicon wafer according to claim 1, wherein in the step of rapidly cooling the surface of the portion of the silicon wafer to be cleaved with a fluid beam, the fluid beam is selected from at least one of liquid water, liquid carbon dioxide, liquid hydrogen, liquid nitrogen, low-temperature inert gas, low-temperature carbon dioxide gas, low-temperature hydrogen gas, and low-temperature nitrogen gas.
5. The method for pretreating a silicon wafer according to claim 1, wherein the temperature of the fluid jet is 20 to 30 ℃.
6. The method for pretreating a silicon wafer according to claim 1, wherein the plasma etching step is performed in a plasma etcher.
7. The method of claim 6, wherein the gas forming the plasma comprises at least CF4And O2Said CF4The flow rate of (A) is 100 to 120sccm/min, and (B) is2The flow rate of the gas is 10 to 15 sccm/min.
8. The method for pretreating a silicon wafer according to claim 7, wherein the pressure for exciting the high-frequency glow of the plasma is 300 to 350Pa, and the power is 100 to 120W.
9. The silicon wafer pretreatment method according to claim 8, wherein the time for turning on the high-frequency glow is 10 to 18 minutes, preferably 14 minutes.
10. A method for manufacturing a stitch-welded solar module is characterized by comprising the following steps:
the method according to any one of claims 1 to 9, wherein the silicon wafer is pretreated, and the pretreated silicon wafer is prepared into a solar module by adopting a stitch welding technology.
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