CN111463323A - P-type selective doping method - Google Patents
P-type selective doping method Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 70
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 claims abstract description 110
- 229910052796 boron Inorganic materials 0.000 claims abstract description 110
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 76
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 71
- 239000010703 silicon Substances 0.000 claims abstract description 71
- 239000003513 alkali Substances 0.000 claims abstract description 45
- 239000002019 doping agent Substances 0.000 claims abstract description 45
- 230000007797 corrosion Effects 0.000 claims abstract description 18
- 238000005260 corrosion Methods 0.000 claims abstract description 18
- 239000005388 borosilicate glass Substances 0.000 claims abstract description 14
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- 238000005530 etching Methods 0.000 claims description 14
- 238000003486 chemical etching Methods 0.000 claims description 13
- 229910052751 metal Inorganic materials 0.000 claims description 8
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- 238000007639 printing Methods 0.000 claims description 6
- 239000011863 silicon-based powder Substances 0.000 claims description 6
- 238000005520 cutting process Methods 0.000 claims description 5
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- 239000000243 solution Substances 0.000 abstract description 34
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- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 24
- 229910021419 crystalline silicon Inorganic materials 0.000 description 18
- 229910021421 monocrystalline silicon Inorganic materials 0.000 description 15
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- H01L21/22—Diffusion of impurity materials, e.g. doping materials, electrode materials, into or out of a semiconductor body, or between semiconductor regions; Interactions between two or more impurities; Redistribution of impurities
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Abstract
The invention discloses a p-type selective doping method, which provides a silicon wafer, wherein a boron dopant is partially covered on the surface of the silicon wafer, boron in the boron dopant is pushed into the silicon wafer through a high-temperature pushing process and is activated, and the surface concentration of the boron in the activated silicon wafer is not lower than 7E19cm‑3Removing borosilicate glass generated on the surface of the silicon wafer in the high-temperature propelling process, immersing the silicon wafer without the borosilicate glass into alkaline solution, and removing the p-type doping layer outside the local doping source region on the surface of the silicon wafer in a chemical corrosion mode. According to the method, a boron dopant is used as a local doping source on the surface of the silicon wafer to directly form a local heavily doped region, and an alkali solution is used for chemically corroding the silicon wafer after high-temperature advance to remove the region which does not need to be doped.
Description
Technical Field
The invention relates to the technical field of crystalline silicon semiconductors and silicon solar cells, in particular to a p-type selective doping method.
Background
In the field of crystalline silicon semiconductors and solar cells, doping is a core process for forming pn junctions. The formation of the high-quality doped layer on the surface of the device plays an important role in improving the performance of the crystalline silicon semiconductor device. In recent years, selective doping technology is used in the fabrication of crystalline silicon semiconductor devices and novel efficient solar cells, and the selective doping technology can form a heavily doped junction and a lightly doped junction of a partition with a specific pattern on the surface of the device, so as to obtain a required electrical structure. Research on selective doping has made effective progress in n-type doping, and particularly in the field of solar cells, the n-type semiconductor laser doping technology has been introduced into mass production by a large number of large-scale production enterprises.
The p-type selective doping technology has mainly focused on two directions of boron dopant doping and laser doping, but a mature technical scheme cannot be developed in time, and the reasons for limiting the progress of the p-type selective doping technology mainly include the following two aspects: 1) when laser doping is used, uniform boron doping is generally carried out on the whole surface, then laser heat treatment is carried out to further dope the local part, and the laser heat treatment acts on a uniform p-type doping layer containing borosilicate glass, so that the solid solubility of boron in the borosilicate glass is higher than that of boron in silicon, and the surface concentration of boron in the silicon after the laser heat treatment of the p-type doping layer is greatly reduced and is contrary to the purpose of heavy doping; 2) when the boron dopant is used for doping, although the boron dopant can partially cover the surface of the crystalline silicon semiconductor device to form heavy doping, the boron dopant doping needs to use higher propelling temperature (generally more than 800 ℃), boron element can be volatilized from the boron dopant and enter a region which does not need to be doped at high temperature, and the doping region formed in the mode belongs to light doping and extremely uneven doping concentration, so that the performance of the device can be greatly damaged.
Disclosure of Invention
In view of the above, the present invention provides a p-type selective doping method, in which a boron dopant is used as a local doping source on the surface of a silicon wafer to directly form a local heavily doped region, and after the silicon wafer is advanced at a high temperature, an alkali solution is used to chemically etch the silicon wafer to remove regions that do not need to be doped, so as to improve the device performance.
In order to achieve the purpose, the invention discloses a p-type selective doping method, which comprises the following steps:
providing a silicon wafer;
partially covering a boron dopant on the surface of the silicon wafer;
pushing boron in the boron dopant into a silicon wafer through a high-temperature pushing process, activating, covering a boron dopant region in the silicon wafer to form heavy doping, wherein the surface concentration of the boron in the heavy doping region is not lower than that of the boron in the silicon wafer7E19cm-3；
Removing borosilicate glass generated on the surface of the silicon wafer in the high-temperature propelling process;
and immersing the silicon wafer with the borosilicate glass removed in an alkali solution, and removing the p-type doping layer outside the heavily doped region on the surface of the silicon wafer in a chemical corrosion mode. Here, the surface topography formed after the chemical etching may determine the surface topography of the region outside the heavily doped region.
As a preferable scheme, the concentration of the alkali solution is 2-30%, and the temperature is 50-90 ℃.
Preferably, the chemical etching mode includes alkali polishing and alkali texturing.
As a preferable scheme, when the chemical corrosion mode is alkaline wool making, alkaline wool making liquid with the concentration of 2-5% and the temperature of 50-80 ℃ is adopted, and the corresponding wool making time is 5-10 min.
As a preferable scheme, when the chemical corrosion mode is polishing, 3-15% of alkali polishing solution with the temperature of 50-80 ℃ is adopted, and the corresponding polishing time is 3-8 min.
As a preferred scheme, the boron dopant includes but is not limited to boron-containing slurry, boron Ink (Ink), and boron-doped silicon powder.
Preferably, the boron dopant is locally printed on the surface of the silicon wafer by means of screen printing or printing.
Preferably, the areas overlying the boron dopant are patterned.
Preferably, after the high-temperature drive-in process, the surface concentration of the boron element in the heavily doped region is 7E19-1E22cm-3。
Preferably, after the high-temperature drive-in process, the surface concentration of the boron element in the heavily doped region is 1E20-5E21cm-3。
Preferably, after the chemical etching, the surface concentration of the boron element in the heavily doped region can be controlled to be 5E19-4E21 cm-3And the control can be specifically carried out according to the requirements.
As a preferable scheme, the process conditions of the high-temperature propulsion are as follows: the advancing temperature is 750-1100 ℃, and the advancing time is 30-120 min.
As a preferable scheme, before the surface of the silicon wafer is partially covered with the boron dopant, the method further comprises the following steps: and carrying out surface treatment on the silicon wafer to remove a cutting damage layer and metal impurities on the surface of the silicon wafer and form a specific appearance on the surface of the silicon wafer. The surface treatment mode comprises alkali polishing, alkali texturing, acid etching and acid texturing. The surface topography formed by the surface treatment herein may determine the surface topography of the heavily doped region.
As a preferred scheme, the borosilicate glass on the surface of the silicon wafer is removed by cleaning with hydrofluoric acid; the concentration of the hydrofluoric acid is 5-15%, and the cleaning time is 10-30 min.
In summary, according to the p-type selective doping method provided by the invention, boron dopants and the like are used as local doping sources on the surface of the silicon wafer, the silicon wafer is chemically etched by using alkali solution after the local doping sources are advanced at a high temperature, and a specific etching effect is realized by utilizing the reaction rate difference of crystalline silicon with different boron doping concentrations in the alkali solution. After the alkali etching, the partial heavily doped p-type region covered by the boron dopant is reserved due to the lower alkali etching rate, and the non-uniform lightly doped region which is not covered by the boron dopant but is formed due to the volatilization of boron element is completely removed, so that the ideal partial heavily doped effect is formed. In addition, the surface appearances of the heavily doped region and the region outside the heavily doped region can be controlled independently and respectively have corresponding appearances according to requirements. The selected silicon wafer can be a common monocrystalline silicon substrate or a common polycrystalline silicon substrate, and can also be an amorphous silicon substrate, a microcrystalline silicon substrate or a metallurgical silicon substrate. Because the concentration of boron is high enough after doping, the window of the corresponding alkali solution etching process parameters is also wide, for example, potassium hydroxide (KOH) or sodium hydroxide (NaOH) alkali solution with the concentration of 2-30% and the temperature of 20-80 ℃ can be adopted.
The invention has the following beneficial effects:
(1) the invention forms 7E19cm by a partial boron dopant capping step in combination with a high temperature drive-in step-3The boron doping concentration above can be realized by most doping methods; and the corresponding alkali solution etching process parameters are obtained due to the fact that the boron concentration is high enoughThe window of the method is also wide, the local heavily doped region is easy to realize by reserving the local heavily doped region after the alkali corrosion in the chemical corrosion step, the peripheral unnecessary doped region is easy to completely remove, and the method has good feasibility.
(2) When p-type selective doping is carried out, the boron doping agent is directly covered on the surface of the silicon wafer locally, so that the problem of boron concentration reduction caused by laser doping is avoided, and the input cost of laser equipment is greatly reduced; the invention uses the alkali solution to corrode and remove the uneven lightly doped area formed by volatilization of boron element in the high-temperature propelling process, and can also corrode the dead layer on the surface of the boron dopant covering area while keeping the local p-type heavily doped area, thereby obviously reducing the electric leakage of devices (including a crystalline silicon solar cell and a crystalline silicon semiconductor device) on one hand, and greatly improving the device performance on the other hand, particularly for the crystalline silicon solar cell, the open-circuit voltage and the final efficiency of the solar cell are further improved by reducing Auger recombination generated by uneven doping formed by volatilization of boron element and reducing the surface dead layer of the heavily doped area. In addition, the invention can also realize that the surface appearances of the areas outside the local doped area and the heavily doped area can be independently and flexibly controlled, thereby facilitating diversified device application schemes.
(3) Compared with other local boron doping technologies in the industry, the method disclosed by the invention is compatible with the existing industrial equipment through a short process, so that a plurality of technical bottlenecks can be avoided, the operation method is simple, the cost is lower, the surface appearance states of the doped region and the non-doped region have various matching schemes, the method can be matched with the mainstream process route in the crystalline silicon semiconductor and solar cell industries, the industrial use is facilitated, and the method has a wide application prospect.
Drawings
FIG. 1 is a schematic view of the main process of the present invention;
FIG. 2 is a topographical elevation view of a silicon wafer formed by the method described in example 1;
FIG. 3 is a partial view of the topography of a silicon wafer formed by the method of example 1;
FIG. 4 is a topographical elevation view of a silicon wafer formed by the method described in example 2;
FIG. 5 is a partial view of the topography of a silicon wafer formed by the method described in example 2.
The attached drawings are marked as follows: 11-p type monocrystalline silicon piece, 12-local boron doping, 12-polished surface, 21-n type monocrystalline silicon piece, 22-local boron doping and 23-textured surface manufacturing.
Detailed Description
Referring to fig. 1, the p-type selective doping method disclosed by the present invention mainly includes the following steps:
s1, surface treatment: selecting a silicon wafer for surface treatment, and removing a cutting damage layer and metal impurities on the surface of the silicon wafer. Wherein, the surface treatment can be alkali polishing, alkali texturing, acid etching or acid texturing. For example, an alkaline solution may be selected for polishing, or a texturing solution may be used to form a textured structure, and the surface topography formed by the surface treatment may determine the surface topography of the heavily doped region.
S2, partially covering the boron dopant: and partially covering the surface of the silicon wafer after the surface treatment with boron dopant. The boron dopant can be selected from boron-containing slurry, boron ink or boron-doped silicon powder and other dopants which can contain high-concentration boron element and have low volatility in a high-temperature environment, and accordingly, the covering of the local boron dopant on the surface of the silicon wafer can be realized by using screen printing or printing and other modes. The high boron content is to make the boron surface concentration meet the requirement after promotion, and the boron surface concentration is reserved in the alkali corrosion process, and the low volatility is to prevent the doping concentration caused by volatilization from being too high and unclean in the alkali corrosion process. For example, "NanoGram" silicon slurry available from Diricho corporation may be used.
S3, high-temperature propulsion: and putting the silicon wafer partially covered with the boron dopant into high-temperature heat treatment equipment for propulsion so as to propel boron elements in the boron dopant into the silicon wafer and activate the boron elements to form local heavy doping. The propulsion process scheme is as follows: the propulsion temperature is 750-1100 ℃, the time is 30-120min, the nitrogen flow is 3000-20000sccm, and the oxygen flow is 0-20000 sccm. The surface concentration of boron element in the local heavily doped region in the activated crystalline silicon is 7E19cm-3The surface concentration of the lightly doped region formed by volatilization of boron element in the boron dopant is generally 5E19cm-3The following.
S4, borosilicate glass (BSG): and cleaning the silicon wafer treated in the step S3 by using hydrofluoric acid to remove borosilicate glass generated on the surface of the silicon wafer in the process of high-temperature propulsion so as to enable subsequent chemical corrosion to be smoothly carried out. The hydrofluoric acid cleaning conditions are as follows: the concentration of hydrofluoric acid is 5-15%, and the cleaning time is 10-30 min.
S5, chemical etching: the doped layer outside the local heavily doped region on the surface of the silicon wafer cleaned by hydrofluoric acid is removed in a chemical etching mode, meanwhile, a local heavily doped p-type region formed by a local doping source can be reserved, and the surface appearance formed after chemical etching can determine the surface appearance of the region outside the heavily doped region. Specifically, the following two methods can be selected for chemical etching according to the application scheme of the device:
(1) selecting an alkali polishing solution for alkali corrosion, wherein the alkali polishing solution comprises the following components: the solution temperature is 50-80 deg.C, polishing time is 3-8min, and KOH or NaOH concentration is 3-15%.
(2) Selecting an alkaline texturing solution for alkaline corrosion: the solution temperature is 50-80 deg.C, the texturing time is 5-10min, the concentration of KOH or NaOH is 2-5%, and the concentration of auxiliary chemical for texturing is 0.05-2%. The auxiliary chemical for making the wool is a wool making (alkali wool making) additive, generally refers to a mixture mainly containing isopropanol, can increase the anisotropic ratio of silicon corrosion in the alkali wool making process, and improves the wool making effect, wherein the wool making additive is a conventional wool making additive in the photovoltaic industry.
Of course, the invention is not limited to the structured treatment of both polished and textured silicon surfaces, and other chemical etching methods may be used as long as the etching is achieved.
In the method, the boron dopant used in step S2 and the high temperature advancing step of step S3 are used to form the p-type region with the local heavy doping on the surface of the silicon wafer, in the above process, the partially covered boron dopant may volatilize to other regions at high temperature, and the chemical etching in step S5 can remove the light doping formed by the volatilized boron doping in other regions.
The invention utilizes the reaction speed in alkaline solution under the condition that the crystal silicon surfaces have different boron doping concentrationsThe difference in rate achieves a specific etching effect, removes unnecessary volatile doping, and protects the locally heavily doped p-type region. The reaction rate of silicon and alkaline chemical solution is lower and lower along with the increase of the concentration of boron element in the crystalline silicon, and the reaction rate of the heavily boron-doped crystalline silicon in the alkaline solution is generally lower by more than 1 order of magnitude than that of undoped or lightly doped crystalline silicon in the alkaline solution. Since the doped region is heavily doped in step S3, when the boron concentration reaches 7E19cm-3After the above, the reaction speed of silicon with the alkali solution is extremely slow. After the chemical etching in step S5, only a thin layer of the surface of the local heavily doped region is etched away, and the boron concentration on the surface of the local heavily doped region will be reduced slightly after the etching away. In step S3, since the unnecessary doped region formed by volatilization of boron is lightly doped, the boron concentration is low and extremely non-uniform, which may greatly impair the device performance. After the alkali etching in step S5, the region is very easy to be etched in the alkali solution, wherein the lightly doped boron element is completely removed, thereby forming the desired local doping. It should be noted that, the doping with boron dopant (including boron-containing slurry, boron ink and boron-doped silicon powder) can easily achieve high-concentration local boron doping, which is beneficial to reduce electrical recombination in the metallized region and reduce contact resistance. On the other hand, however, since the boron dopant coverage region is aligned with the metallization region, and the area of the heavily doped region of local boron is generally slightly larger than that of the metallization region, in the heavily doped region of local boron without metal coverage, the higher the surface boron doping concentration is, the larger the auger recombination is, and the boron doped layer with too high concentration becomes a boron-rich layer, and further the auger recombination is aggravated. According to the invention, the corrosion rate of local high-concentration boron-doped silicon in the alkali solution is low, the alkali solution can completely remove the doping formed by volatilization, and simultaneously, the boron-rich layer on the surface of the boron dopant coverage area can be corroded, so that the Auger recombination is reduced while the lower metal area recombination and metal semiconductor contact resistance are ensured, and the performance of the device is further improved.
The invention can also select polishing solution to polish or use the texturing solution to form a textured structure in surface treatment before doping, and can select alkali polishing solution to carry out alkali corrosion or select alkali texturing solution to carry out alkali texturing when unnecessary volatile doping (a p-type doped layer outside a local heavily doped region) on the surface of the silicon wafer is removed after high-temperature propulsion, thereby forming a specific surface structure in the heavily doped region by adopting different treatment schemes to meet the manufacturing requirements of different devices.
Embodiments of the present invention will now be further described with reference to the accompanying drawings and specific examples, which are provided as a real-time application of the present invention and do not cover all applications of the present invention.
As shown in fig. 2 and 3, embodiment 1 is directed to a p-type selective doping method for forming a polished doped surface, comprising the steps of:
a1: and (3) carrying out surface polishing treatment on the selected p-type monocrystalline silicon wafer with the (100) crystal orientation by using KOH polishing solution, and removing a cutting damage layer and metal impurities on the surface of the silicon wafer. In the KOH polishing solution, the concentration of KOH is 5 percent, the temperature of the KOH solution is 60 ℃, and the polishing time is about 3 min.
A2, printing the boron-containing slurry on one side surface of the polished p-type monocrystalline silicon piece by using a screen printing mode to form a plurality of randomly distributed H-shaped patterns, wherein the patterns are covered with boron dopants.
A3, putting the p-type monocrystalline silicon piece partially covered with the boron-containing slurry into a high-temperature furnace for propulsion, wherein the propulsion temperature is 960 ℃, the propulsion time is 30min, the nitrogen flow in the high-temperature furnace is about 10000sccm, the oxygen flow is about 5000sccm, and after the propulsion process is finished, the boron concentration of a local heavily doped region in the crystalline silicon reaches 6E20cm-3。
A4, cleaning the p-type monocrystalline silicon wafer after high-temperature propelling by using hydrofluoric acid to remove BSG generated on the surface of the silicon wafer during high-temperature propelling. The hydrofluoric acid cleaning conditions are as follows: the concentration of hydrofluoric acid is 15%, and the cleaning time is 15 min.
And A5, performing alkali polishing on the cleaned p-type monocrystalline silicon piece by using KOH polishing solution, and removing the p-type doped layer outside the local heavily doped region on the surface of the cleaned p-type monocrystalline silicon piece. Wherein the KOH concentration is 5%, the temperature of the KOH solution is 60 ℃, and the polishing time is 3 min. Proper boron surface concentration in locally heavily doped regions after alkaline polishingGround is reduced to about 1.6E20cm-3。
With reference to fig. 4 and 5, in embodiment 2, the following p-type selective doping method for forming a doped surface with a random pyramid textured topography includes the following steps:
b1, using KOH texturing liquid to texture the selected n-type monocrystalline silicon wafer with the (100) crystal orientation, and removing the cutting damage layer and the metal impurities on the surface of the silicon wafer. In the KOH texturing solution, the concentration of KOH is 3 percent, the concentration of a texturing additive is 0.2 percent, the temperature of the KOH solution is 70 ℃, and the texturing time is about 5 min.
B2, covering the boron-doped silicon powder on one side surface of the textured n-type monocrystalline silicon piece by using a printing mode to form lines distributed at equal intervals, and covering the lines with the boron dopant.
B3, putting the n-type monocrystalline silicon piece partially covered with the boron-doped silicon powder into a high-temperature furnace for propelling at the propelling temperature of 980 ℃ for 40min, wherein the nitrogen flow is about 5000sccm, the oxygen flow is about 10000sccm, and after the propelling process is finished, the concentration of boron in a heavily doped region in the crystalline silicon reaches 5E20cm-3。
And B4, cleaning the n-type monocrystalline silicon wafer after high-temperature propelling by using hydrofluoric acid to remove BSG generated on the surface of the silicon wafer during high-temperature propelling. The hydrofluoric acid cleaning conditions are as follows: the concentration of hydrofluoric acid is 7%, and the cleaning time is 30 min.
B5, alkali texturing is carried out on the cleaned n-type monocrystalline silicon piece by using KOH texturing liquid, and the p-type doped layer outside the local heavily doped region on the surface of the n-type monocrystalline silicon piece is removed. Wherein, the KOH concentration is 3 percent, the temperature of the KOH solution is 70 ℃, the concentration of the texturing additive is 0.2 percent, and the texturing time is about 3 min. The boron surface concentration of the locally heavily doped region after alkali texturing is about 1E20cm-3。
Based on the above description, the p-type selective doping method disclosed by the invention has the following characteristics:
the feasibility is high: 7E19cm formation by partial blanket boron dopant step in combination with high temperature drive-in step-3The above boron doping concentration can be achieved for most doping methods; the method is easy to realize by reserving a local heavily doped region after alkali corrosion in the chemical corrosion stepThe edge non-essential doped regions are easily and completely removed.
The cost is low: compared with other p-type selective doping technologies in the industry, the method can avoid a plurality of technical bottlenecks through a short process and short equipment without excessive processing procedures.
Can be compatible with the existing industrialized equipment: the method can be realized by using the existing equipment in the industry without special modification of the equipment.
The application prospect is wide: the surface states of the doped region and the non-doped region prepared by the method have various matching schemes and are suitable for different designs and preparation schemes of crystalline silicon semiconductor devices or crystalline silicon batteries. Whether the p-type battery or the n-type battery is adopted, the method can be put into application only by simply adjusting and combining with the subsequent battery flow.
Finally, it should be noted that while the above describes exemplifying embodiments of the invention with reference to the accompanying drawings, the invention is not limited to the embodiments and applications described above, which are intended to be illustrative and instructive only, and not limiting. Those skilled in the art, having the benefit of this disclosure, may effect numerous modifications thereto without departing from the scope of the invention as defined by the appended claims.
Claims (10)
1. A p-type selective doping method, comprising the steps of:
providing a silicon wafer;
partially covering a boron dopant on the surface of the silicon wafer;
pushing boron elements in the boron dopant into a silicon wafer through a high-temperature pushing process, activating, covering a boron dopant region in the silicon wafer to form heavy doping, wherein the surface concentration of the boron elements in the heavy doping region is not lower than 7E19cm-3；
Removing borosilicate glass generated on the surface of the silicon wafer in the high-temperature propelling process;
and immersing the silicon wafer with the borosilicate glass removed in an alkali solution, and removing the p-type doping layer outside the heavily doped region on the surface of the silicon wafer in a chemical corrosion mode.
2. The method of claim 1, wherein the alkali solution has a concentration of 2 to 30% and a temperature of 50 to 90 ℃.
3. The method of claim 1, wherein the chemical etching is alkali polishing or alkali texturing.
4. The method as claimed in claim 3, wherein when the chemical etching manner is alkaline etching, an alkaline etching solution with a concentration of 2-5% and a temperature of 50-80 ℃ is used, and the corresponding etching time is 5-10 min; when the chemical corrosion mode is polishing, 3-15% of alkali polishing solution with the temperature of 50-80 ℃ is adopted, and the corresponding polishing time is 3-8 min.
5. The method of claim 1, wherein the boron dopant includes, but is not limited to, boron-containing slurries, boron inks, boron-doped silicon powders; and locally printing boron doping agent on the surface of the silicon wafer by a screen printing or printing mode.
6. The method of claim 1, wherein the region overlying the boron dopant is patterned.
7. The method of claim 1, wherein the heavily doped region has a boron surface concentration of 7E19-1E22cm after the high temperature drive-in process-3。
8. The method of claim 7, wherein the heavily doped region has a boron surface concentration of 1E20-5E21cm after the high temperature drive-in process-3。
9. The method of claim 1, wherein the high temperature drive-in process conditions are: the advancing temperature is 750-1100 ℃, and the advancing time is 30-120 min.
10. The method of claim 1, further comprising, prior to partially covering the surface of the silicon wafer with the boron dopant: and carrying out surface chemical etching treatment on the silicon wafer to remove a cutting damage layer and metal impurities on the surface of the silicon wafer and form a specific appearance on the surface of the silicon wafer.
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