CN117673191A - Boron diffusion method, solar cell and preparation method thereof - Google Patents
Boron diffusion method, solar cell and preparation method thereof Download PDFInfo
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- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 title claims abstract description 72
- 229910052796 boron Inorganic materials 0.000 title claims abstract description 72
- 238000009792 diffusion process Methods 0.000 title claims abstract description 54
- 238000002360 preparation method Methods 0.000 title abstract description 16
- 230000008021 deposition Effects 0.000 claims abstract description 67
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 65
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 65
- 239000010703 silicon Substances 0.000 claims abstract description 65
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 36
- 239000001301 oxygen Substances 0.000 claims abstract description 36
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 36
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 35
- 239000007789 gas Substances 0.000 claims abstract description 18
- 230000001681 protective effect Effects 0.000 claims abstract description 17
- 238000004140 cleaning Methods 0.000 claims abstract description 8
- 238000000151 deposition Methods 0.000 claims description 69
- 238000010926 purge Methods 0.000 claims description 49
- 238000000034 method Methods 0.000 claims description 9
- 238000010438 heat treatment Methods 0.000 claims description 8
- 238000004519 manufacturing process Methods 0.000 claims description 4
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 claims 1
- 229910001882 dioxygen Inorganic materials 0.000 claims 1
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 72
- 235000012431 wafers Nutrition 0.000 description 58
- 229910052757 nitrogen Inorganic materials 0.000 description 36
- 230000000052 comparative effect Effects 0.000 description 15
- 238000001816 cooling Methods 0.000 description 10
- 238000003825 pressing Methods 0.000 description 10
- 239000010453 quartz Substances 0.000 description 10
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 10
- 238000006243 chemical reaction Methods 0.000 description 9
- 239000007788 liquid Substances 0.000 description 8
- 230000007797 corrosion Effects 0.000 description 5
- 238000005260 corrosion Methods 0.000 description 5
- 230000015572 biosynthetic process Effects 0.000 description 3
- 239000011261 inert gas Substances 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 239000005388 borosilicate glass Substances 0.000 description 2
- 238000005137 deposition process Methods 0.000 description 2
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 239000013067 intermediate product Substances 0.000 description 1
- 229910052743 krypton Inorganic materials 0.000 description 1
- DNNSSWSSYDEUBZ-UHFFFAOYSA-N krypton atom Chemical compound [Kr] DNNSSWSSYDEUBZ-UHFFFAOYSA-N 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000002923 metal particle Substances 0.000 description 1
- 238000001465 metallisation Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052754 neon Inorganic materials 0.000 description 1
- GKAOGPIIYCISHV-UHFFFAOYSA-N neon atom Chemical compound [Ne] GKAOGPIIYCISHV-UHFFFAOYSA-N 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000002161 passivation Methods 0.000 description 1
- 229910052704 radon Inorganic materials 0.000 description 1
- SYUHGPGVQRZVTB-UHFFFAOYSA-N radon atom Chemical compound [Rn] SYUHGPGVQRZVTB-UHFFFAOYSA-N 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 239000000523 sample Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 229910052724 xenon Inorganic materials 0.000 description 1
- FHNFHKCVQCLJFQ-UHFFFAOYSA-N xenon atom Chemical compound [Xe] FHNFHKCVQCLJFQ-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- 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
Abstract
The invention relates to a boron diffusion method, a solar cell and a preparation method thereof. The boron diffusion method comprises the following steps: placing the silicon wafer subjected to texturing and cleaning in diffusion equipment; and (3) carrying out deposition on a through source in diffusion equipment under preset pressure and preset temperature, wherein the through source comprises a boron source, oxygen, water vapor and a first protective gas, the volume ratio of the boron source to the oxygen to the water vapor is 1.8:7.2:1-2.3:8.2:1, and the temperature is raised, and a second protective gas is adopted to sweep the deposited silicon wafer. The boron diffusion method can uniformly distribute B on the surface of the silicon wafer, so that the prepared silicon wafer after boron diffusion has excellent sheet resistance uniformity, and can be better applied to the preparation of solar cells.
Description
Technical Field
The invention relates to the technical field of solar cells, in particular to a boron diffusion method, a solar cell and a preparation method thereof.
Background
In the production process of an N-type battery, the preparation of PN junction through boron diffusion is a key step for determining the efficiency of the N-type battery, and the boron source mainly adopted by the current boron diffusion technology is BBr 3 ，BBr 3 With O 2 Reaction to give intermediate B 2 O 3 Intermediate B 2 O 3 And the boron is reacted with the silicon wafer to generate B, so that boron diffusion is further promoted and generated. However, intermediate B 2 O 3 The boiling point of the Boron-Rich Layer is above 1800 ℃, the Boron-Rich Layer is always in a liquid state in the process of Boron diffusion, is difficult to uniformly distribute on the surface of a silicon wafer, and forms a Boron-Rich Layer (BRL) in a region with more Boron doping amount, so that the performance of the battery is seriously affected; in addition, B 2 O 3 The corrosion to the quartz device carrying the silicon chip is serious, borosilicate glass formed at low temperature is more adhered to the quartz surface, and the borosilicate glass is adhered and damaged in the process of opening and closing the quartz furnace door.
In order to make B 2 O 3 The most direct way is to reduce the pressure to below 1Pa, thereby bringing B 2 O 3 For a quartz device of large capacity, however, it is difficult to reduce the pressure to below 1Pa using a conventional pump, and thus it is difficult to realize in industrial production.
Disclosure of Invention
Based on the above, it is necessary to provide a boron diffusion method, a solar cell and a preparation method thereof, wherein the boron-diffused silicon wafer prepared by the boron diffusion method has excellent sheet resistance uniformity and can be better applied to the preparation of the solar cell.
The invention provides a boron diffusion method, which mainly comprises the following steps:
placing the silicon wafer subjected to texturing and cleaning in diffusion equipment;
depositing a source in the diffusion device under a preset pressure and a preset temperature, wherein the source comprises a boron source, oxygen, water vapor and a first protective gas, and the volume ratio of the boron source, the oxygen and the water vapor is 1.8:7.2:1-2.3:8.2:1
Heating, and purging the deposited silicon wafer by adopting a second protective gas.
In one embodiment, in the step of passing the source, the boron source is selected from BBr 3 And/or BCl 3 。
In one embodiment, the volume flow rate of the boron source is 100sccm-500sccm, the volume flow rate of the oxygen is 350sccm-2220sccm, the volume flow rate of the water vapor is 50sccm-300sccm, and the volume flow rate of the first protective gas is 1000sccm-4000sccm.
In one embodiment, the preset pressure is 100mbar to 300mbar, the preset temperature is 800 ℃ to 1050 ℃, and the time for the through source is 80s to 500s.
In one embodiment, the deposition is performed in more than two times, and purging is performed after each deposition, wherein the deposition temperature is sequentially increased in each deposition, and the on-source time is kept unchanged or sequentially increased.
In one embodiment, the deposition temperature in the first deposition is 800-920 ℃ and the on-time is 60-200 s in the fractional deposition;
and/or the increment of the deposition temperature is 20-50 ℃, and the increment of the on-source time is less than or equal to 100s.
In one embodiment, the purge is performed after deposition, with each temperature increase ranging from 30 ℃ to 60 ℃.
In one embodiment, the volume flow rate of the second protective gas is 800sccm to 3500sccm and the purge time is 80s to 400s when the purge is performed.
A preparation method of the solar cell comprises the boron diffusion method.
A solar cell is prepared by the preparation method of the solar cell.
In the boron diffusion process provided by the invention, a boron source, oxygen and water vapor in a specific proportion are simultaneously introduced, so that the boron source reacts with the oxygen to generate B in the deposition process 2 O 3 After that, the water vapor can be timely mixed with B 2 O 3 Reaction to form gaseous HBO 2 Compared with liquid B 2 O 3 Gaseous HBO 2 The silicon wafer surface is distributed more uniformly, and can further react with the silicon wafer to generate B, thereby not only effectively consuming liquid B 2 O 3 Even avoid liquid B 2 O 3 Is avoided B 2 O 3 The corrosion to quartz devices, and the B is uniformly distributed on the surface of the silicon wafer, so that BRL formation is avoided, and the prepared boron-expanded silicon wafer has excellent sheet resistance uniformity and can be better applied to the preparation of solar cells.
Drawings
Fig. 1 is a flow chart of a boron diffusion process provided by the present invention.
Detailed Description
In order that the invention may be readily understood, a more particular description of the invention will be rendered by reference to specific embodiments that are illustrated in the appended drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, 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 herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.
The boron diffusion method provided by the invention comprises the following steps:
s10, placing the silicon wafer subjected to texturing cleaning in diffusion equipment;
s20, depositing through a source in diffusion equipment under preset pressure and preset temperature; and
s30, heating, and purging the deposited silicon wafer by adopting a second protective gas.
In the step S10, the texturing and cleaning can remove the mechanical damage layer on the surface of the silicon wafer, remove oil stains, impurity particles and metal particles on the surface of the silicon wafer, form uneven textured surfaces on the surface of the silicon wafer and increase the absorption of the silicon wafer to sunlight.
In the step S20, the source comprises a boron source, oxygen, water vapor and a first protective gas, wherein the volume ratio of the boron source to the oxygen to the water vapor is 1.8:7.2:1-2.3:8.2:1, including but not limited to a boron source, oxygen, and steam at a volume ratio of 1.8:7.2:1, 1.9:7.2:1, 2.0:7.2:1, 2.1:7.2:1, 2.2:7.2:1, 1.8:7.4:1, 1.9:7.4:1, 2.0:7.4:1, 2.1:7.4:1, 1.8:7.6:1, 1.9:7.6:1, 2.0:7.6:1, 2.1:7.6:1, 2.2:7.6:1, 1.8:7.8:1, 1.9:7.8:1, 2.0:7.8:1, 2.1:7.8:1, 1.8:1, 2.8:8:1, 1.9:7.1, 2:1.0:1, 2.1, 2.1:1, 2.8:1, 2.1, 2.1:1, 2.0:1, 2.1:1, 2.2:1, 2.1:1.
The boron source, oxygen and water vapor are simultaneously introduced in a specific proportion, so that the boron source reacts with the oxygen to generate B in the deposition process 2 O 3 After that, the water vapor can be timely mixed with B 2 O 3 Reaction to form gaseous HBO 2 Compared with liquid B 2 O 3 Gaseous HBO 2 The silicon wafer is more uniformly distributed on the surface of the silicon wafer, and can further react with the silicon wafer to generate B.
Furthermore, not only effectively consume the liquid B 2 O 3 Even avoid liquid B 2 O 3 Is avoided B 2 O 3 The corrosion to quartz devices, and the B is uniformly distributed on the surface of the silicon wafer, so that BRL formation is avoided, and the prepared boron-expanded silicon wafer has excellent sheet resistance uniformity and can be better applied to the preparation of solar cells.
In one embodiment, the boron source is selected from BBr 3 And/or BCl 3 。
With BBr 3 As an example of a boron source, the following reaction specifically occurs during deposition, first a portion of BBr 3 React with oxygen to generate an intermediate product B 2 O 3 The reaction equation was 4BBr 3 +3O 2 →2B 2 O 3 +6Br 2 The method comprises the steps of carrying out a first treatment on the surface of the Because the diffusion device is also filled with water vapor, the water vapor can be connected with B 2 O 3 Reaction to form gaseous HBO 2 The reaction equation is B 2 O 3 +H 2 O→2HBO 2 At the same time, another part of boron source reacts with water vapor to generate gaseous HBO 2 The reaction equation is BBr 3 +2H 2 O→HBO 2 ++3 HBr due to HBO 2 Is in a gaseous state and can further react with a silicon wafer to generate B, and the reaction equation is 2HBO 2 +2Si→2SiO 2 +2B+H 2 Thus, the B is uniformly distributed on the surface of the silicon wafer.
The water vapor can consume B 2 O 3 Thereby avoiding B 2 O 3 The boron-expanded silicon wafer has uneven sheet resistance, BRL formation and corrosion to quartz devices, but the water vapor can also generate oxidation reaction with the silicon wafer to generate SiO 2 The deposition of boron is adversely affected, and therefore, the volume ratio of the boron source, oxygen and water vapor needs to satisfy the above conditions, and it is preferable that the volume ratio of the boron source, oxygen and water vapor is 1.9:7.9:1 to 2.1:8.1:1.
In order to better improve the sheet resistance uniformity of the boron-amplified silicon wafer and simultaneously control the surface concentration of the boron-amplified silicon wafer, in one embodiment, in the step of introducing the source, the volume flow of the boron source is 100sccm-500sccm, including but not limited to, 100sccm, 200sccm, 300sccm, 400sccm, 500sccm, the volume flow of the oxygen is 350sccm-2220sccm, including but not limited to, 350ccm, 550sccm, 850sccm, 1250sccm, 1750sccm, or 2220sccm, and in one embodiment, the volume flow of the water vapor is 50sccm-300sccm, including but not limited to, 50sccm, 100sccm, 200sccm, 300sccm.
It is understood that the first protective gas is selected from nitrogen and/or inert gas, and the inert gas is specifically selected from helium, neon, argon, krypton, xenon and radon, and the volume flow rate of the first protective gas is 1000sccm-4000sccm for better controlling the surface concentration of the silicon wafer after boron expansion.
In order to better improve the sheet resistance uniformity of the silicon wafer after boron expansion and simultaneously control the surface concentration of the silicon wafer after boron expansion, in one embodiment, the preset pressure is 100mbar to 300mbar, and the preset temperature is 800 ℃ to 1050 ℃; including, but not limited to, a preset pressure of 100mbar, 150mbar, 200mbar, 250 mbar, or 300mbar, a preset temperature of 800 ℃, 820 ℃, 840 ℃, 860 ℃, 880 ℃, 900 ℃, 920 ℃, 940 ℃, 960 ℃, 980 ℃, 1000 ℃, 1020 ℃, or 1050 ℃.
In one embodiment, the time for the on-state is 80s-500s.
In step S30, the purging step can remove not only residual substances in the diffusion device, such as residual water vapor and liquid B 2 O 3 The interference to the subsequent steps is avoided, and the temperature is raised to enable the B deposited on the surface of the silicon wafer in the step S20 to enter the silicon wafer, so that the junction pushing is realized.
To better achieve the push junction, in one embodiment, the step of purging is performed at an elevated temperature ranging from 30 ℃ to 60 ℃, including, but not limited to, 30 ℃, 40 ℃, 50 ℃, or 60 ℃.
In one embodiment, the volume flow of the second protective gas is 800sccm-3500sccm and the purge time is 80s-400s when the purge is performed; wherein the second protective gas is selected from nitrogen and/or inert gases.
It should be noted that, the preset order of magnitude requirement of the boron doping concentration of the silicon wafer is generally E20-E21, and in order to achieve the preset order of magnitude requirement, the deposition can be performed once or in two or more times, and purging is performed after each deposition, wherein the deposition temperature is sequentially increased in the deposition steps, and the on-source time is kept unchanged or sequentially increased in the deposition steps.
It can be understood that in the step of purging after each deposition, the deposition refers to the step of introducing a source into the diffusion apparatus for deposition in the step S20, and the purging refers to the step of heating up in the step S30, and purging the deposited silicon wafer with the second protective gas, that is, when the deposition is performed twice or more, after the step S30, the step S20 and the step S30 are repeated until the boron doping concentration of the silicon wafer reaches the preset requirement.
When the deposition is performed twice, the boron diffusion method provided by the invention comprises the following steps: and (S10) performing first deposition and purging, then performing second deposition and purging, and finally cooling and back-pressing to obtain the boron-expanded silicon wafer.
When the deposition is performed three times, the boron diffusion method provided by the invention comprises the following steps: and after the step S10, performing first deposition and purging, performing second deposition and purging, performing third deposition and purging, and finally cooling and back-pressing to obtain the boron-expanded silicon wafer.
When the deposition is performed for four times, after step S10, performing the first deposition and the purging, then performing the second deposition and the purging, and then performing the third deposition and the purging, then performing the fourth deposition and the purging, and finally cooling and back pressing to obtain the boron-expanded silicon wafer.
In order to improve the controllability of boron diffusion, it is preferable to perform the deposition three times.
The temperature during the fractional deposition is controlled between 800 ℃ and 1050 ℃, in one embodiment, the deposition temperature during the first deposition is 800 ℃ to 920 ℃ and the on-source time is 60s to 200s.
To better achieve the push junction, in one embodiment, the deposition temperature is increased by 20-50 ℃ and the on-time is increased by less than or equal to 100s.
To better achieve the push junction, in one embodiment, the step of purging is performed at an amplitude of 30-60 ℃ per rise in temperature, including, but not limited to, 30 ℃, 40 ℃, 50 ℃ or 60 ℃.
In the case of fractional deposition, the source-through method in each deposition may be directly referred to the source-through method in step S20. The manner of purging in step S30 may be referred to as a purging manner.
Thus, the boron diffusion method of the invention not only avoids B 2 O 3 The corrosion to quartz devices also realizes the simple preparation of the boron-amplified silicon wafer with excellent sheet resistance uniformity, and avoids the boron amplificationBRL appears on the surface of the silicon wafer, so that the silicon wafer after boron expansion can be better applied to the preparation of solar cells.
The invention also provides a preparation method of the solar cell, which comprises the boron diffusion method.
In one embodiment, the method for manufacturing a solar cell further comprises the steps of passivation, metallization and the like.
The invention also provides a solar cell, which is prepared by the preparation method of the solar cell.
In the solar cell provided by the invention, the silicon wafer after the raw material boron is expanded has excellent sheet resistance uniformity, so that the solar cell has excellent efficiency.
Hereinafter, a boron diffusion method, a solar cell, and a method of manufacturing the same will be further described by the following specific examples.
Example 1
Placing the silicon wafer subjected to texturing and cleaning into a diffusion furnace, keeping the pressure in the furnace unchanged after reaching a preset pressure value of 200mbar, heating to a preset temperature of 860 ℃, enabling the source time to be 120s, and introducing nitrogen with a volume flow of 2500sccm and BBr 3 The first deposition was performed at a volume flow rate of 400sccm, an oxygen volume flow rate of 1600sccm, and a water vapor volume flow rate of 200 sccm.
After heating to 900 ℃, the purge time was 160s and the nitrogen volumetric flow was 2000sccm.
Maintaining the temperature in the furnace at 900 ℃, the source time at 160s, and introducing nitrogen with volume flow of 2500sccm and BBr 3 The second deposition was performed at a volume flow rate of 400sccm, a dry oxygen volume flow rate of 1600sccm, and a water vapor volume flow rate of 200 sccm.
The temperature was raised to 940℃and the purge time was 200s with a nitrogen volume flow of 2000sccm.
Maintaining the temperature in the furnace at 940 ℃, the source time at 200s, and introducing nitrogen with volume flow of 2500sccm and BBr 3 The third deposition was performed at a volume flow of 400sccm, a dry oxygen volume flow of 1600sccm, and a water vapor volume flow of 200 sccm.
The temperature was raised to 1000℃and the purge time was 240s, with a nitrogen volume flow of 2000sccm.
And cooling to 750 ℃, and back pressing to 1013mbar for 900s to obtain the boron-expanded silicon wafer.
Example 2
Example 2 was performed with reference to example 1, except that the textured and cleaned silicon wafer was placed in a diffusion furnace.
The preset temperature is 800 ℃, the source time is 60s, the volume flow of nitrogen is 1000sccm, and BBr 3 The volume flow rate was 100sccm, the volume flow rate of oxygen was 370sccm, and the volume flow rate of water vapor was 50sccm, and deposition was performed.
The temperature was raised to 830℃and the purge time was 80s, with a nitrogen volumetric flow of 800sccm.
The temperature in the furnace is kept at 830 ℃, the source time is 80s, and the volume flow of nitrogen is 1000sccm. BBr (BBr) 3 The volume flow rate was 100sccm, the volume flow rate of oxygen was 370sccm, and the volume flow rate of water vapor was 50sccm, and deposition was performed.
The temperature was raised to 860℃and the purge time was 100s, with a nitrogen volumetric flow of 800sccm.
Maintaining the temperature in the furnace at 860 ℃, the source time at 100s, the nitrogen volume flow at 1000sccm and BBr 3 The volume flow rate was 100sccm, the volume flow rate of oxygen was 370sccm, and the volume flow rate of water vapor was 50sccm, and deposition was performed.
The temperature was raised to 920℃and the purge time was 160s, with a nitrogen volumetric flow of 800sccm.
And cooling and back pressing to obtain the boron-expanded silicon wafer.
Example 3
Example 3 was performed with reference to example 1, except that the textured and cleaned silicon wafer was placed in a diffusion furnace.
Preset temperature is 920 ℃, the source-through time is 200s, the nitrogen-through volume flow is 4000sccm, and BBr 3 The deposition was performed at a volume flow rate of 500sccm, an oxygen volume flow rate of 2220sccm, and a water vapor volume flow rate of 300sccm.
The temperature was raised to 960℃and the purge time was 260s, with a nitrogen volumetric flow of 3500sccm.
Maintaining the temperature in the furnace at 960 ℃ and the on-source time at 26%0s, nitrogen flow volume of 4000sccm, BBr 3 The deposition was performed at a volume flow rate of 500sccm, an oxygen volume flow rate of 2220sccm, and a water vapor volume flow rate of 300sccm.
The temperature was raised to 1000℃and the purge time was 330s, with a nitrogen volumetric flow of 3500sccm.
Maintaining the temperature in the furnace at 1000 ℃, the source-through time at 350s, the nitrogen-through volume flow at 4000sccm and BBr 3 The deposition was performed at a volume flow rate of 500sccm, an oxygen volume flow rate of 2220sccm, and a water vapor volume flow rate of 300sccm.
The temperature was raised to 1060℃and the purge time was 400s, with a nitrogen volumetric flow of 3500sccm.
And cooling and back pressing to obtain the boron-expanded silicon wafer.
Example 4
Example 4 was performed with reference to example 1, except that the textured and cleaned silicon wafer was placed in a diffusion furnace.
The preset temperature is 960 ℃, the source time is 480s, the volume flow of the introduced nitrogen is 2500sccm, and the BBr 3 The deposition was performed at a volume flow rate of 400sccm, an oxygen volume flow rate of 1600sccm, and a water vapor volume flow rate of 200 sccm.
The temperature was raised to 1000℃and the purge time was 600s, with a nitrogen volume flow of 2000sccm.
And cooling and back pressing to obtain the boron-expanded silicon wafer.
Example 5
Example 5 was performed with reference to example 1, except that the textured and cleaned silicon wafer was placed in a diffusion furnace.
The preset temperature is 920 ℃, the source time is 240s, the volume flow of the introduced nitrogen is 2500sccm, and the BBr 3 The deposition was performed at a volume flow rate of 400sccm, an oxygen volume flow rate of 1600sccm, and a water vapor volume flow rate of 200 sccm.
The temperature was raised to 960℃and the purge time was 300s, with a nitrogen volume flow of 2000sccm.
The temperature in the furnace is 960 ℃, the source time is 240s, the volume flow of the introduced nitrogen is 2500sccm, and the BBr is 3 The volume flow is 400sccm, the oxygen volume flow is 1600sccm, and the water is steamedThe deposition was performed at a gas volume flow of 200 sccm.
The temperature was raised to 1000℃and the purge time was 300s, with a nitrogen volume flow of 2000sccm.
Example 6
Example 6 was performed with reference to example 1, except that BBr was used 3 Replaced by BCl 3 。
Comparative example 1
Placing the silicon wafer subjected to texturing and cleaning into a diffusion furnace, keeping the pressure in the furnace unchanged after reaching a preset pressure value of 200mbar, heating to a preset temperature of 860 ℃, enabling the source time to be 120s, and introducing nitrogen with a volume flow of 2500sccm and BBr 3 The first deposition was performed at a volume flow of 400sccm and an oxygen volume flow of 1600 sccm.
After heating to 900 ℃, the purge time was 160s and the nitrogen volumetric flow was 2000sccm.
Maintaining the temperature in the furnace at 900 ℃, the source time at 160s, and introducing nitrogen with volume flow of 2500sccm and BBr 3 The second deposition was performed at a volume flow rate of 400sccm and a dry oxygen volume flow rate of 1600 sccm.
The temperature was raised to 940℃and the purge time was 200s with a nitrogen volume flow of 2000sccm.
Maintaining the temperature in the furnace at 940 ℃, the source time at 200s, and introducing nitrogen with volume flow of 2500sccm and BBr 3 The third deposition was performed at a volume flow of 400sccm and a dry oxygen volume flow of 1600 sccm.
The temperature was raised to 1000℃and the purge time was 240s, with a nitrogen volume flow of 2000sccm.
And cooling to 750 ℃, and back pressing to 1013mbar for 900s to obtain the boron-expanded silicon wafer.
Comparative example 2
Comparative example 2 the procedure of example 1 was followed except that the silicon wafer after the texturing and cleaning was placed in a diffusion furnace.
The preset temperature is 960 ℃, the source time is 480s, the volume flow of the introduced nitrogen is 2500sccm, and the BBr 3 Deposition was performed at a volume flow rate of 400sccm and a dry oxygen volume flow rate of 1600 sccm.
The temperature was raised to 1000℃and the purge time was 600s, with a nitrogen volume flow of 2000sccm.
And cooling and back pressing to obtain the boron-expanded silicon wafer.
Comparative example 3
Comparative example 3 the procedure of example 1 was followed except that the textured and cleaned silicon wafer was placed in a diffusion furnace.
The preset temperature is 920 ℃, the source time is 240s, the volume flow of the introduced nitrogen is 2500sccm, and the BBr 3 Deposition was performed at a volume flow rate of 400sccm and a dry oxygen volume flow rate of 1600 sccm.
The temperature was raised to 960℃and the purge time was 300s, with a nitrogen volume flow of 2000sccm.
The temperature in the furnace is 960 ℃, the source time is 240s, the volume flow of the introduced nitrogen is 2500sccm, and the BBr is 3 The deposition was performed at a volume flow rate of 400sccm and an oxygen volume flow rate of 1600 sccm.
The temperature was raised to 1000℃and the purge time was 300s, with a nitrogen volume flow of 2000sccm.
And cooling and back pressing to obtain the boron-expanded silicon wafer.
Test example 1
After 3 batch experiments were performed on examples 1 to 6 and comparative examples 1 to 3, the surface sheet resistance and sheet resistance uniformity of the silicon wafer after boron expansion were measured by using a four-probe tester, and specific test results are shown in table 1.
TABLE 1
Test example 2
The boron-amplified silicon wafers of examples 1 to 9 and comparative examples 1 to 3 were fabricated into N-type solar cells, and the efficiency (Eta), short-circuit current (Isc), open-circuit voltage (Uoc) and Fill Factor (FF) of the N-type solar cells were measured using a halm tester, and the measurement results are shown in table 2.
TABLE 2
| Eta(％) | Isc(A) | Uoc(V) | FF(％) | |
| Example 1 | 23.53 | 0.6992 | 13.643 | 81.42 |
| Example 2 | 23.44 | 0.6974 | 13.641 | 81.34 |
| Example 3 | 23.50 | 0.6994 | 13.639 | 81.35 |
| Example 4 | 23.33 | 0.6971 | 13.642 | 80.98 |
| Example 5 | 23.47 | 0.6983 | 13.647 | 81.32 |
| Example 6 | 23.53 | 0.6993 | 13.642 | 81.44 |
| Comparative example 1 | 23.39 | 0.6964 | 13.635 | 81.32 |
| Comparative example 2 | 23.38 | 0.6961 | 13.636 | 81.31 |
| Comparative example 3 | 23.38 | 0.6962 | 13.635 | 81.30 |
By combining table 1 and table 2, the efficiency Eta of example 1 is improved by 0.14 compared with comparative example 1, the main improvement is Isc, uoc, FF, the surface sheet resistance uniformity is 3.5%, the surface sheet resistance uniformity of comparative example 1 is 6.3%, and the improvement is 2.8%; comparative example 1 has negligible Eta difference from comparative example 2, but the surface sheet resistance and uniformity are respectivelyAnd->6.3% and 7.8%, demonstrating positive benefits for small, step-wise boron expansion on the resistance and uniformity. The service life of the quartz device under the boron diffusion method is 7.5 months, and the service life of the quartz device under the dry boron diffusion of comparative examples 1-3 is improved by 3.5 months.
The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples illustrate only a few embodiments of the invention, which are described in detail and are not to be construed as limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.
Claims (10)
1. The boron diffusion method is characterized by mainly comprising the following steps of:
placing the silicon wafer subjected to texturing and cleaning in diffusion equipment;
depositing a source in the diffusion device under a preset pressure and a preset temperature, wherein the source comprises a boron source, oxygen, water vapor and a first protective gas, and the volume ratio of the boron source, the oxygen and the water vapor is 1.8:7.2:1-2.3:8.2:1
Heating, and purging the deposited silicon wafer by adopting a second protective gas.
2. The boron diffusion method of claim 1, whereinCharacterized in that in the step of the source, the boron source is selected from BBr 3 And/or BCl 3 。
3. The boron diffusion method of claim 1, wherein the boron source has a volume flow rate of 100sccm-500sccm, the oxygen gas has a volume flow rate of 350sccm-2220sccm, the water vapor has a volume flow rate of 50sccm-300sccm, and the first protective gas has a volume flow rate of 1000sccm-4000sccm.
4. The boron diffusion method according to claim 1, wherein the preset pressure is 100mbar to 300mbar, the preset temperature is 800 ℃ to 1050 ℃, and the time of the through source is 80s to 500s.
5. The boron diffusion method of any one of claims 1 to 4, wherein the deposition is performed in two or more times and the purging is performed after each deposition, wherein the deposition temperature is sequentially increased in the case of the deposition in the number of times, and the on-time is maintained or sequentially increased.
6. The boron diffusion method according to claim 5, wherein the deposition temperature at the time of the first deposition is 800 ℃ to 920 ℃ and the on-time is 60s to 200s in the case of the fractional deposition;
and/or the increment of the deposition temperature is 20-50 ℃, and the increment of the on-source time is less than or equal to 100s.
7. The boron diffusion method of claim 5, wherein the magnitude of each temperature rise is 30 ℃ to 60 ℃ when purging is performed after deposition.
8. The boron diffusion method according to claim 1, wherein the volume flow rate of the second protective gas is 800sccm to 3500sccm and the purge time is 80s to 400s when the purge is performed.
9. A method of manufacturing a solar cell comprising the boron diffusion method according to any one of claims 1 to 8.
10. A solar cell prepared by the method of claim 9.
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