CN114361291A - Heavily doped silicon wafer, crystalline silicon solar cell and preparation method thereof - Google Patents
Heavily doped silicon wafer, crystalline silicon solar cell and preparation method thereof Download PDFInfo
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- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 83
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims abstract description 82
- 238000002360 preparation method Methods 0.000 title claims abstract description 18
- 229910021419 crystalline silicon Inorganic materials 0.000 title claims abstract description 16
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- 238000006243 chemical reaction Methods 0.000 abstract description 5
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- 238000009751 slip forming Methods 0.000 description 2
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- 239000003513 alkali Substances 0.000 description 1
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- 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 at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic System or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/26—Bombardment with radiation
- H01L21/263—Bombardment with radiation with high-energy radiation
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- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Abstract
The invention relates to a heavily doped silicon wafer, a crystalline silicon solar cell and a preparation method thereof. The method comprises the following steps: sequentially performing texturing and diffusion treatment on the front side of the silicon wafer to obtain a silicon wafer to be doped; determining a metal grid line region on the front side of a silicon wafer to be doped and a mark region outside the metal grid line region; adopting laser to sequentially and continuously form a marking pattern in the marking area and carry out laser doping in the metal grid line area to form a heavily doped area; the marking speed of the laser when forming the marking pattern is less than the marking speed when forming the heavily doped region. The preparation method changes the marking sequence of the marking graph and the heavily doped region, well solves the problem of rapid energy change in the conversion process from higher marking speed to lower marking speed, also avoids the problem of unstable laser caused by the change of the marking speed, ensures that the formed marking graph is clear and complete, is convenient for accurate positioning of the metal grid line formed subsequently, greatly improves the problems of metal grid line deviation and failure, and improves the yield.
Description
Technical Field
The invention relates to the technical field of solar cells, in particular to a heavily doped silicon wafer, a crystalline silicon solar cell and a preparation method thereof.
Background
The laser doping technique is to heavily dope the contact portion of the silicon wafer with the metal gate line (i.e., electrode), while keeping the light doping (low concentration doping) in the region of the silicon wafer except the electrode. Generally, the light doping is formed by performing pre-diffusion on the surface of a silicon wafer by a thermal diffusion method. Meanwhile, PSG (phosphosilicate glass layer) on the surface of the silicon wafer is used as a local laser heavily-doped source, and phosphorus atoms in the PSG are rapidly diffused into the silicon wafer for the second time through the local laser heat effect to form a local heavily-doped region. Generally, the heavily doped region and a metal grid line of subsequent screen printing need to be completely overlapped; therefore, the laser high-precision patterning is matched, and the overprinting effect with subsequent screen printing can be realized. In addition, the laser doping technology has the advantages of simple process flow, capability of reducing the thermal damage of the silicon body caused by high temperature to the maximum extent due to local laser thermal effect, no need of chemical treatment, no pollution and the like.
In actual operation, a heavily doped region is formed in a corresponding region of a silicon wafer by adopting laser doping; in order to accurately position the heavily doped region by subsequent screen printing, a mark pattern (i.e. a mark pattern) for positioning needs to be formed on the silicon wafer by using a laser. Therefore, when the subsequent screen printing is carried out, the marking pattern can be grabbed by the screen printing camera, so that the screen-printed metal grid line and the heavy doping region are aligned accurately. However, the marking pattern formed by the traditional laser doping grooving method has the problem of being identified by a screen printing camera to be dark, and the dark marking pattern is not beneficial to the accurate point grabbing of the screen printing camera, so that the problems of large-batch offset and failure of the printed metal grid line are caused.
Disclosure of Invention
Based on the above, there is a need for a heavily doped silicon wafer, a crystalline silicon solar cell and a preparation method thereof, which can improve the darkening of the mark pattern.
The invention is realized by the following technical scheme.
In one aspect of the present invention, a method for preparing a heavily doped silicon wafer is provided, which comprises the following steps:
sequentially performing texturing and diffusion treatment on the front side of the silicon wafer to obtain a silicon wafer to be doped;
determining a metal grid line region on the front side of the silicon wafer to be doped and a marking region outside the metal grid line region;
adopting laser to sequentially and continuously form a marking pattern in the marking area and carry out laser doping in the metal grid line area to form a heavily doped area;
wherein a marking speed of the laser when forming the marking pattern is less than a marking speed when forming the heavily doped region.
In some embodiments, the marking speed of the laser in forming the marking pattern is 300-500 mm/s, and the laser frequency is 50-170 KHz;
and/or the marking speed of the laser when the heavily doped region is formed is 20000-30000 mm/s, and the laser frequency is 160-320 kilohertz.
In some embodiments, the marking speed of the laser in forming the marking pattern is 300-450 mm/s, and the laser frequency is 70-170 kHz.
In some embodiments, the metal gate line region includes a sub-gate line corresponding region, the sub-gate line corresponding region includes a plurality of first linear regions arranged in parallel, and the mark pattern is located between two adjacent first linear regions.
In some embodiments, the metal gate line region further includes a break-proof gate corresponding region, where the break-proof gate corresponding region includes a plurality of second linear regions arranged in parallel, and the second linear regions intersect with the first linear regions.
In some embodiments, a marking pattern is sequentially and continuously formed in the marking region by using laser, and laser doping is performed on the corresponding region of the subline line and the corresponding region of the anti-breaking gate to form a heavily doped region.
In some of these embodiments, the shape of the pattern of marks is a ring, dot or + -shape.
In another aspect of the invention, a heavily doped silicon wafer is provided, which is prepared by any one of the preparation methods of the heavily doped silicon wafer.
In another aspect of the present invention, a method for preparing a crystalline silicon solar cell is provided, which comprises the following steps:
preparing a heavily doped silicon wafer by adopting the preparation method of any one of the above steps; and
and respectively forming metal electrodes on the heavily doped region and the back of the front surface of the heavily doped silicon wafer.
In another aspect of the invention, a crystalline silicon solar cell is provided, which is prepared by the above preparation method of the crystalline silicon solar cell.
Since the marking speed of the laser when forming the marking pattern is different from the marking speed when forming the heavily doped region, there is a transition of the marking speed of the laser when forming the marking pattern and when forming the heavily doped region, which is accompanied by a rapid change in the laser energy. The preparation method of the heavily doped silicon wafer changes the marking sequence of the marking pattern and the heavily doped region, leads the laser to form the marking pattern at a lower marking speed firstly and then form the heavily doped region at a higher marking speed, not only can well meet the marking energy requirements of the marking pattern and the heavily doped region, reduces the laser energy received by the silicon wafer when the marking pattern is formed, further can reduce the damage to the silicon wafer, but also can well solve the problem of rapid energy change in the conversion process from the higher marking speed to the lower marking speed, also avoids the problem of unstable laser caused by the change of the marking speed, simultaneously forms the marking pattern which is clear, complete and easy to identify, is convenient for accurate positioning of the metal grid line formed subsequently, greatly improves the problems of metal grid line deviation and failure, improves the yield, and also can effectively improve the marking speed of the heavily doped region, thereby improving the production efficiency.
Drawings
FIG. 1 is a schematic illustration of a laser doping sub-region of a silicon wafer to be doped according to an embodiment;
FIG. 2 is a photograph of a marking pattern formed in comparative example 1 under a screen printing camera;
FIG. 3 is a photograph of the mark pattern formed in example 1 under a screen printing camera.
Detailed Description
To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. It is to be understood that these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
In the description of the present invention, it is to be understood that the terms "first", "second" and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implying any number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
As described above, the laser PSG doping method is to perform laser scanning using a phosphosilicate glass layer formed during diffusion as a doping source to form a heavily doped region. Before laser doping, however, the position of a laser-doped region on a silicon wafer needs to be determined, the position of the laser-doped region on the silicon wafer is generally the position of a secondary grid line, and then the sheet resistance drop and the secondary grid pitch PT value (which is the distance between two secondary grid lines located at the outermost side) of a metal grid line region are tested to ensure that the metal grid line region can be completely matched with a screen plate for subsequent screen printing.
In the traditional laser doping method, after the position of a region (such as a metal grid line region) needing laser doping is determined, a laser grooving mode is firstly adopted to form a heavily doped region at the position of the region, so that the main body structure of a silicon wafer is determined, and then a marking pattern is formed on the region outside the metal grid line region on the silicon wafer. Meanwhile, the number of the secondary grid lines is large, and the time (also called marking time) required by the corresponding laser grooving is relatively long, so that enough time is provided for improving the marking speed of the laser to the required marking speed, and for the secondary grid lines, the marking energy and the marking speed are relatively large. However, when marking a mark pattern, the mark pattern generally has a small area, and in order to reduce damage to a silicon wafer and avoid the problem of hidden cracking or breaking of the silicon wafer when marking the mark pattern, the marking speed of the mark pattern needs to be reduced.
However, a lot of practices show that the mark pattern formed by the laser doping grooving method is identified by the screen printing camera to be dark, and the dark mark pattern is not beneficial to accurate point grabbing of the screen printing camera, so that the printed metal grid line has the problems of large-batch offset and failure. The skilled person of the present invention finds, through research, that this may be because the whole marking process of the finger lines and the marking patterns is relatively short (about 1 second), and the marking speed and the marking energy required for the finger lines and the marking patterns are different. Generally, the marking speed of the secondary grid line is higher than that of the marked graph, however, the energy is rapidly changed in the conversion process from the higher marking speed of the secondary grid line to the lower marking speed of the marked graph, so that laser is unstable, laser fluctuation is large, and finally the problem that the marked graph obtained through marking is dark under the recognition of a screen printing camera is caused. The dark marked graph is not beneficial to the accurate point grabbing of a screen printing camera, and further causes the problems of large-batch offset and failure of the printed metal grid line.
It is understood that the screen printing camera may be other cameras, here being just one example. The screen printing is only a specific optional way to realize the metal grid line, and the forming method of the metal grid line is not limited to this. However, in order to accurately position the heavily doped region so as to accurately form the metal gate line in the heavily doped region, a camera is required to identify and acquire the position of the mark pattern so as to accurately position the mark pattern.
Based on this, the technicians of the invention break the conventional process on the basis of a great deal of research, and provide a brand-new laser doping method for the silicon wafer, and the laser doping method also provides a new preparation method for the heavily doped silicon wafer.
One embodiment of the present invention provides a method for preparing a heavily doped silicon wafer, which includes the following steps S11 to S13.
And step S11, performing texturing and diffusion treatment on the front side of the silicon wafer in sequence to obtain the silicon wafer to be doped.
The purpose of texturing is to form a textured surface on the front surface of a silicon wafer firstly, so that the absorption of sunlight is increased, the reflection of the sunlight is reduced, the PN junction area is increased, the short-circuit current is increased, and the photoelectric conversion efficiency of the cell is improved.
The purpose of the diffusion is to create a PN junction for the cell, and the phosphosilicate glass (PSG) layer formed during the diffusion can be used as a doping source for laser doping in step S13.
And step S12, determining a metal grid line region on the front surface of the silicon wafer to be doped and a mark region outside the metal grid line region.
As shown in fig. 1, it shows a schematic diagram of laser doping partition of a silicon wafer to be doped; wherein x represents the central point of the silicon wafer to be doped, and the four-quadrant two-dimensional coordinate is established by taking the central point as the origin. The metal grid line region 11 of the silicon wafer to be doped comprises an auxiliary grid line corresponding region and an anti-breaking grid corresponding region. Further, the corresponding sub-gate line region includes a plurality of first linear regions 111 arranged in parallel, and the mark pattern is located between two adjacent first linear regions 111. The corresponding region of the anti-breaking gate includes a plurality of second linear regions 112 arranged in parallel, and the second linear regions 112 intersect with the first linear regions 111.
Further, the second linear region 112 perpendicularly intersects the first linear region 111.
It is understood that, in other embodiments, the metal gate line region 11 of the silicon wafer to be doped may not include the anti-breaking gate corresponding region.
Further, in the specific example shown in fig. 1, a mark region 12 is disposed in a region other than the metal gate line region 11 on the silicon wafer to be doped, and the mark region 12 is located between two adjacent first linear regions 111. Further, the mark region 12 is located between two adjacent second linear regions 112.
Further, there are 4 mark areas 12, the directions of the first straight area 111 and the second straight area 112 are XY axes, the center point is an origin, and the 4 mark areas 12 are respectively located in four quadrants of the formed two-dimensional coordinates. Further, the transverse and longitudinal distances from the origin of the 4 mark areas are the same.
And step S13, sequentially and continuously forming a mark pattern in the mark region and performing laser doping in the metal grid line region to form a heavily doped region by adopting laser.
Wherein, the marking speed of the laser when forming the marking pattern is less than the marking speed when forming the heavily doped region.
It is understood that the above "sequentially continuous" means that the subsequent steps are performed in a sequential order, and the laser corresponding to the laser in the two sequential steps is continuously operated. In other words, the formation of the marking pattern in the marking region and the formation of the heavily doped region by laser doping in the metal gate line region are performed sequentially, and the laser corresponding to the laser does not shut down within the time interval between the formation of the marking pattern and the heavily doped region.
Since the marking speed of the laser when forming the marking pattern is different from the marking speed when forming the heavily doped region, there is a transition of the marking speed of the laser when forming the marking pattern and when forming the heavily doped region, which is accompanied by a rapid change in the laser energy. The preparation method of the heavily doped silicon wafer changes the marking sequence of the marking pattern and the heavily doped region, leads the laser to form the marking pattern at a lower marking speed firstly and then form the heavily doped region at a higher marking speed, not only can well meet the marking energy requirements of the marking pattern and the heavily doped region, reduces the laser energy received by the silicon wafer when the marking pattern is formed, further can reduce the damage to the silicon wafer, but also can well solve the problem of rapid energy change in the conversion process from the higher marking speed to the lower marking speed, also avoids the problem of unstable laser caused by the change of the marking speed, simultaneously forms the marking pattern which is clear, complete and easy to identify, is convenient for accurate positioning of the metal grid line formed subsequently, greatly improves the problems of metal grid line deviation and failure, improves the yield, and also can effectively improve the marking speed of the heavily doped region, thereby improving the production efficiency.
In some embodiments, the marking speed of the laser in forming the marking pattern is 300-500 mm/s, such as 300 mm/s, 310 mm/s, 320 mm/s, 340 mm/s, 350 mm/s, 380 mm/s, 400 mm/s, 420 mm/s, 450 mm/s, 480 mm/s, 500 mm/s; the laser frequency is 50-170 KHz, such as 50 KHz, 60 KHz, 70 KHz, 80 KHz, 90 KHz, 100 KHz, 110 KHz, 120 KHz, 130 KHz, 140 KHz, 150 KHz, 160 KHz, 170 KHz.
Further, the marking speed of the laser when forming the marking pattern is 300-450 mm/s, and the laser frequency is 70-170 KHz. Furthermore, the marking speed of the laser in forming the marking pattern is 300-340 mm/s, and the laser frequency is 130-170 KHz.
In some embodiments, the marking speed of the laser in forming the heavily doped region is 20000-30000 mm/s, and the laser frequency is 160-320 kHz.
In some embodiments, the mark pattern is formed in the mark region. In a specific example, the metal gate line region includes a sub-gate line corresponding region, the sub-gate line corresponding region includes a plurality of first linear regions arranged in parallel, and the mark pattern is located between two adjacent first linear regions.
Further, the shape of the mark pattern is a ring, a dot or a + -shape, such as a circular ring. It is understood that the shape of the marking pattern includes, but is not limited to, this. Further, the outer diameter of the mark pattern was 0.5 mm.
Further, when the metal gate line region further includes a break-preventing gate corresponding region, step S13 is: and laser is adopted to sequentially and continuously form a marking pattern in the marking area, and laser doping is carried out in the area corresponding to the auxiliary grid line and the area corresponding to the anti-breaking grid to form a heavily doped area. Namely, after the mark pattern is formed in the mark region, a heavily doped region is formed in the corresponding region of the sub-gate line, and then a heavily doped region is formed in the corresponding region of the anti-breaking gate.
It is understood that, in another example, after the mark pattern is formed in the mark region, the heavily doped region may be formed in the anti-breaking gate corresponding region, and then the heavily doped region may be formed in the sub-gate line corresponding region.
In another embodiment of the present invention, a heavily doped silicon wafer is provided, which is manufactured by any one of the above methods for manufacturing a heavily doped silicon wafer.
The heavily doped silicon wafer prepared by the preparation method has clear, complete and easily-recognized mark patterns, is convenient for accurately positioning metal grid lines formed subsequently, greatly improves the problems of metal grid line deviation and failure, and improves the yield.
In another embodiment of the present invention, a crystalline silicon solar cell and a method for manufacturing the same are provided, the method for manufacturing the crystalline silicon solar cell including the following steps S10 to S20.
Step S10, preparing a heavily doped silicon wafer by adopting any one of the preparation methods; and
and step S20, forming metal electrodes on the heavily doped region and the back of the front surface of the heavily doped silicon wafer respectively.
According to the preparation method of the crystalline silicon solar cell, the marked graph formed by the heavily doped silicon wafer is clear, complete and easy to identify, the accurate positioning of the metal electrode formed on the front side is facilitated, the problems of deviation and failure of the metal electrode are greatly solved, and the yield of the crystalline silicon solar cell is improved.
It can be understood that the metal electrode formed on the heavily doped region on the front surface is a metal gate line to reduce the shielding of the metal electrode on the front surface, increase the absorption of sunlight by the front surface, and meet the requirement of effectively collecting carriers. The metal grid line may be a silver metal grid line. The back metal electrode may be a full-face electrode, such as a full-face silver electrode layer.
In some embodiments, the metal electrode formed on the front surface of the heavily doped silicon wafer includes a sub-gate line, and the sub-gate line is formed in the heavily doped region, specifically, in a corresponding region of the sub-gate line. Furthermore, the metal electrode formed on the front surface of the heavily doped silicon wafer comprises a breaking-proof grid line, and the breaking-proof grid line is formed in a breaking-proof grid corresponding region. Thus, a plurality of auxiliary grid lines which are parallel and arranged at intervals are formed, and the auxiliary grid line corresponding regions which are intersected with the auxiliary grid lines are formed. The material of the breakage-proof grid line can be the same as that of the auxiliary grid line, and the breakage-proof grid line is mainly connected with the auxiliary grid line, plays a certain role in supporting connection and preventing the auxiliary grid line from being broken.
Furthermore, the front auxiliary grid lines, the anti-breaking grid lines and other metal grid lines are formed in a screen printing mode, so that a screen printing camera can obtain clear and complete marking patterns, and accurate positioning of the metal grid lines is facilitated.
It can be understood that the front surface can be further provided with a main grid line for guiding out carriers collected by the auxiliary grid line.
It can be understood that the method for manufacturing the crystalline silicon solar cell further comprises, after step S10 and before step S20, the following steps:
carrying out thermal oxidation treatment on the heavily doped silicon wafer, removing a PSG layer on the surface of the heavily doped silicon wafer, alkali polishing treatment and annealing treatment, then forming an aluminum oxide passivation layer on the back surface of the heavily doped silicon wafer, forming antireflection films on the front surface and the back surface of the heavily doped silicon wafer, and then carrying out laser grooving treatment on the back surface.
Further, in step S20, silver paste is applied to both the front and back surfaces by screen printing, and sintered to form metal electrodes. After which the cell performance was tested.
In order to make the objects, technical solutions and advantages of the present invention more concise and clear, the present invention is described with the following specific embodiments, but the present invention is by no means limited to these embodiments. The following described examples are only preferred embodiments of the present invention, which can be used to describe the present invention and should not be construed as limiting the scope of the present invention. It should be understood that any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
In order to better illustrate the invention, the following examples are given to further illustrate the invention. The following are specific examples.
Comparative example 1
And (4) performing texturing and diffusion treatment on the front side of the silicon wafer in sequence to obtain the silicon wafer to be doped.
And designing a laser doping partition drawing for a silicon wafer to be doped, as shown in fig. 1. And x represents a central point of the silicon wafer to be doped, and a four-quadrant two-dimensional coordinate is established by taking the central point as an origin and the directions of the first linear area 111 and the second linear area 112 as XY axes.
According to the sub-grid pitch PT value and the number of the sub-grid lines on the screen printing plate, the distance between two adjacent sub-grid lines is calculated through the sub-grid pitch PT value/(the number of the sub-grid lines is-1), and the positions of all the sub-grid lines are equally marked, namely the first straight line region 111. The PT value is set to 157.195 micrometers, and the number of the sub-grid lines is 120, and the distance between two adjacent sub-grid lines is 1.3209 micrometers, namely the sub-grid pitch PT value/(the number of sub-grid lines-1).
And marking the positions of the anti-breaking grid lines, namely the second straight line regions 112 respectively according to the parameter position coordinates.
The position of the marking areas 12 is determined, 4 marking areas 12 are respectively positioned in four quadrants of the formed two-dimensional coordinate, and the transverse distances and the longitudinal distances of the 4 marking areas 12 from the origin are the same. The horizontal spacing of the 2 marker regions, which are the same on the ordinate, is 116.8 microns and the vertical spacing of the 2 marker regions, which are the same on the abscissa, is 134.745 microns.
According to the schematic diagram of the laser doping partition of fig. 1, laser doping is sequentially and continuously performed on the first linear region 111 and the second linear region 112 by using laser to form a heavily doped region, and a mark pattern is formed in the mark region 12.
Wherein, the marking speed of the laser when the first straight line region 111 and the second straight line region 112 form the heavily doped region is 25000 mm/s, and the laser frequency is 245 khz. The marking speed of the laser in forming the marking pattern was 350 mm/sec, and the laser frequency was 120 khz.
Example 1
Sequentially performing texturing and diffusion treatment on the front side of the silicon wafer to obtain a silicon wafer to be doped;
and designing a laser doping partition drawing for a silicon wafer to be doped, as shown in fig. 1. And x represents a central point of the silicon wafer to be doped, and a four-quadrant two-dimensional coordinate is established by taking the central point as an origin and the directions of the first linear area 111 and the second linear area 112 as XY axes.
The 4 marking areas 12 are respectively located in four quadrants of the formed two-dimensional coordinate, and the transverse distances and the longitudinal distances of the 4 marking areas from the origin are the same. The position of the mark area 12 is determined. The horizontal spacing of the 2 marker regions, which are the same on the ordinate, is 116.8 microns and the vertical spacing of the 2 marker regions, which are the same on the abscissa, is 134.745 microns.
According to the sub-grid pitch PT value and the number of the sub-grid lines on the screen printing plate, the distance between two adjacent sub-grid lines is calculated through the sub-grid pitch PT value/(the number of the sub-grid lines is-1), and the positions of all the sub-grid lines are equally marked, namely the first straight line region 111. The PT value is set to 157.195 micrometers, and the number of the sub-grid lines is 120, and the distance between two adjacent sub-grid lines is 1.3209 micrometers, namely the sub-grid pitch PT value/(the number of sub-grid lines-1).
And marking the positions of the anti-breaking grid lines, namely the second straight line regions 112 respectively according to the parameter position coordinates.
According to the schematic diagram of the laser doping partition of fig. 1, a marking pattern is sequentially and continuously formed in the marking region 12 by using laser, and laser doping is performed in the first linear region 111 and the second linear region 112 to form a heavily doped region.
Wherein, the marking speed of the laser when forming the marking pattern is 350 mm/s, and the laser frequency is 120 KHz. The marking speed of the laser when the first straight line region 111 and the second straight line region 112 form the heavily doped region is 25000 mm/sec, and the laser frequency is 245 khz.
Example 1 is essentially the same as comparative example 1, except that: the marking sequence of the marking pattern and the heavily doped region is different. The darker sheet of the marking pattern formed in comparative example 1 is shown in fig. 2. Statistically, there were 176 off-notes in a total of 55 million products per batch of comparative example 1. The mark pattern formed in example 1 was complete and clear in outline under the screen printing camera, as shown in fig. 3. Statistically, the number of dark spots in a total of 55 ten thousand of products per batch of example 1 was reduced to 30. The number of dark flakes in example 1 decreased by 83% compared to comparative example 1.
Example 2
Example 2 is essentially the same as example 1, except that: for the silicon wafer to be doped, the designed laser doping partition drawing does not contain a breaking-proof grid line, namely does not contain the second straight line region 112. And the horizontal spacing of 2 marker regions with the same ordinate is 96.45 microns and the vertical spacing of 2 marker regions with the same abscissa is 138 microns. The PT value is set to 157.185 micrometers, and the number of the finger lines is 134, and the distance between two adjacent finger lines is 1.181 micrometers (the finger pitch PT value/(finger number-1)).
Wherein, the marking speed of the laser when forming the marking pattern is 350 mm/s, and the laser frequency is 120 KHz. The marking speed of the laser when the first straight line region 111 and the second straight line region 112 form the heavily doped region is 25000 mm/sec, and the laser frequency is 245 khz.
Comparative example 2
Comparative example 2 is essentially the same as example 2, except that: the marking sequence of the marking pattern and the heavily doped region is different. The method comprises the following steps: laser doping is successively performed on the first linear region 111 to form a heavily doped region and a mark pattern is formed on the mark region 12 by using laser.
Statistically, there are 200 partial dark patches out of 55 ten thousand of the products per batch in comparative example 2. The number of dark spots in a total of 55 thousand of products per batch of example 2 decreased to 40. The number of dark flakes in example 2 decreased by 80% compared to comparative example 2.
Example 3
Example 3 is essentially the same as example 2, except that: the marking speed of the laser in forming the marking pattern was 300 mm/sec, and the laser frequency was 170 khz. Statistically, there are 35 partial dark films in a total of 55 ten thousand products per batch in example 3. This is probably because the marking speed is slower and the frequency is higher in example 3 than in example 2, and the circular mark pattern formed by marking is more uniform and brighter.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the patent of the present invention should be subject to the appended claims, and the description and the drawings can be used for explaining the contents of the claims.
Claims (10)
1. A preparation method of a heavily doped silicon wafer is characterized by comprising the following steps:
sequentially performing texturing and diffusion treatment on the front side of the silicon wafer to obtain a silicon wafer to be doped;
determining a metal grid line region on the front side of the silicon wafer to be doped and a marking region outside the metal grid line region;
adopting laser to sequentially and continuously form a marking pattern in the marking area and carry out laser doping in the metal grid line area to form a heavily doped area;
wherein a marking speed of the laser when forming the marking pattern is less than a marking speed when forming the heavily doped region.
2. The method for preparing a heavily doped silicon wafer according to claim 1, wherein the marking speed of the laser in forming the marking pattern is 300 to 500 mm/sec, and the laser frequency is 50 to 170 khz;
and/or the marking speed of the laser when the heavily doped region is formed is 20000-30000 mm/s, and the laser frequency is 160-320 kilohertz.
3. The method for preparing a heavily doped silicon wafer according to claim 1, wherein the marking speed of the laser in forming the marking pattern is 300 to 450 mm/sec, and the laser frequency is 70 to 170 khz.
4. The method according to any one of claims 1 to 3, wherein the metal gate line region includes a corresponding region of a gate line, the corresponding region of the gate line includes a plurality of first linear regions arranged in parallel, and the mark pattern is located between two adjacent first linear regions.
5. The method for preparing the heavily doped silicon wafer of claim 4, wherein the metal gate line region further comprises a break-preventing gate corresponding region, the break-preventing gate corresponding region comprises a plurality of second linear regions arranged in parallel, and the second linear regions intersect with the first linear regions.
6. The method for preparing the heavily doped silicon wafer as claimed in claim 5, wherein the heavily doped region is formed by sequentially and continuously forming a mark pattern in the mark region and performing laser doping in the corresponding region of the subline line and the corresponding region of the breakage-proof gate by using laser.
7. The method for preparing a heavily doped silicon wafer as claimed in any one of claims 1 to 3 and 5 to 6, wherein the shape of the mark pattern is a ring, a dot or a + shape.
8. A heavily doped silicon wafer produced by the method for producing a heavily doped silicon wafer according to any one of claims 1 to 7.
9. A preparation method of a crystalline silicon solar cell is characterized by comprising the following steps:
preparing a heavily doped silicon wafer by the preparation method according to any one of claims 1 to 7; and
and respectively forming metal electrodes on the heavily doped region and the back of the front surface of the heavily doped silicon wafer.
10. A crystalline silicon solar cell, characterized by being produced by the method for producing a crystalline silicon solar cell according to claim 9.
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