CN112928180B - Diffusion method suitable for LDSE technology - Google Patents
Diffusion method suitable for LDSE technology Download PDFInfo
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- CN112928180B CN112928180B CN201911236922.1A CN201911236922A CN112928180B CN 112928180 B CN112928180 B CN 112928180B CN 201911236922 A CN201911236922 A CN 201911236922A CN 112928180 B CN112928180 B CN 112928180B
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- 238000009792 diffusion process Methods 0.000 title claims abstract description 65
- 238000005516 engineering process Methods 0.000 title claims abstract description 9
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 32
- 238000000034 method Methods 0.000 claims abstract description 25
- 230000003647 oxidation Effects 0.000 claims abstract description 20
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims abstract description 15
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 15
- 239000011574 phosphorus Substances 0.000 claims abstract description 15
- 238000001816 cooling Methods 0.000 claims abstract description 14
- 230000008569 process Effects 0.000 claims abstract description 13
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 10
- 230000009467 reduction Effects 0.000 claims abstract description 9
- 235000012239 silicon dioxide Nutrition 0.000 claims abstract description 6
- 239000011521 glass Substances 0.000 claims abstract description 5
- 239000000377 silicon dioxide Substances 0.000 claims abstract description 4
- HIVGXUNKSAJJDN-UHFFFAOYSA-N [Si].[P] Chemical compound [Si].[P] HIVGXUNKSAJJDN-UHFFFAOYSA-N 0.000 claims abstract description 3
- 229910052710 silicon Inorganic materials 0.000 claims description 27
- 239000010703 silicon Substances 0.000 claims description 27
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 16
- 239000005360 phosphosilicate glass Substances 0.000 claims description 16
- 238000010438 heat treatment Methods 0.000 claims description 9
- 229910052757 nitrogen Inorganic materials 0.000 claims description 9
- 230000001590 oxidative effect Effects 0.000 claims description 9
- 239000012159 carrier gas Substances 0.000 claims description 8
- 238000000137 annealing Methods 0.000 claims description 6
- 238000011068 loading method Methods 0.000 claims description 2
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 claims description 2
- UHZYTMXLRWXGPK-UHFFFAOYSA-N phosphorus pentachloride Chemical compound ClP(Cl)(Cl)(Cl)Cl UHZYTMXLRWXGPK-UHFFFAOYSA-N 0.000 claims description 2
- BHEPBYXIRTUNPN-UHFFFAOYSA-N hydridophosphorus(.) (triplet) Chemical compound [PH] BHEPBYXIRTUNPN-UHFFFAOYSA-N 0.000 claims 1
- 230000000153 supplemental effect Effects 0.000 claims 1
- 229910052751 metal Inorganic materials 0.000 abstract description 8
- 239000002184 metal Substances 0.000 abstract description 8
- 238000005215 recombination Methods 0.000 abstract description 6
- 230000006798 recombination Effects 0.000 abstract description 6
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 26
- 239000007789 gas Substances 0.000 description 23
- 239000010410 layer Substances 0.000 description 18
- 230000000694 effects Effects 0.000 description 8
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 6
- 238000000151 deposition Methods 0.000 description 6
- 239000001301 oxygen Substances 0.000 description 6
- 229910052760 oxygen Inorganic materials 0.000 description 6
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 5
- 230000008021 deposition Effects 0.000 description 5
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- 239000004332 silver Substances 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 4
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- 229910052581 Si3N4 Inorganic materials 0.000 description 3
- 229910052782 aluminium Inorganic materials 0.000 description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 3
- 230000003247 decreasing effect Effects 0.000 description 3
- 238000002161 passivation Methods 0.000 description 3
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 3
- 239000013589 supplement Substances 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 2
- 229910021419 crystalline silicon Inorganic materials 0.000 description 2
- 238000005247 gettering Methods 0.000 description 2
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 2
- 238000000623 plasma-assisted chemical vapour deposition Methods 0.000 description 2
- 239000010453 quartz Substances 0.000 description 2
- 230000001502 supplementing effect Effects 0.000 description 2
- 239000002344 surface layer Substances 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
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- 230000004298 light response Effects 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 125000004437 phosphorous atom Chemical group 0.000 description 1
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- 210000002268 wool Anatomy 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
- H01L31/186—Particular post-treatment for the devices, e.g. annealing, impurity gettering, short-circuit elimination, recrystallisation
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/22—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
- H01L21/223—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 using diffusion into or out of a solid from or into a gaseous phase
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
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- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
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Abstract
The invention discloses a diffusion method suitable for a laser doping technology, which is characterized in that the atmosphere is controlled to be pure O in the temperature reduction oxidation process 2 Reacting silicon dioxide growing on the surface of the diffusion layer with a phosphorus source doped on the surface to generate phosphorus-silicon glass with the thickness of 40-50 nm in an atmosphere, performing a post-oxidation step after cooling oxidation, and controlling the atmosphere to be pure O in the post-oxidation process 2 An atmosphere. On one hand, the surface active doping concentration is reduced, minority carrier recombination is reduced, and therefore Voc and Isc are improved, on the other hand, the sheet resistance of a heavily doped region is reduced, and then metal contact is improved, so that on the basis of further improving the gains of Voc and Isc, the Rs and FF loss of the battery is reduced, and the Eff of the battery is improved to the maximum extent.
Description
Technical Field
The invention belongs to the field of solar cells, and relates to a diffusion method suitable for an LDSE (laser direct current) technology.
Background
With the increased competition of the crystalline silicon market, various crystalline silicon battery manufacturers are adopting various ways to improve the photoelectric performance of the battery. It is a common way to increase the Voc and Isc of a battery by optimizing the diffusion process to increase the sheet resistance and superimposing the Laser doping technique (LDSE). The reason is that the high sheet resistance corresponds to lower surface active doping concentration, so that the surface minority carrier recombination can be effectively reduced, and the minority carrier lifetime is prolonged; meanwhile, the short-wave response of emitter is enhanced, and the Isc is improved. However, conventional LDSE diffusion simply raises sheet resistance to increase Voc and Isc, and the gain of Eff is limited, mainly due to poor Si/metal contact at the high-square stop band of the SE heavily doped region. An increase in Rs brings about FF loss.
CN 1101759A discloses a regional layered deposition diffusion process, which comprises 1) cleaning P-type original silicon waferAfter the wool making, putting the quartz boat into the furnace tube of the diffusion furnace; 2) heating the diffusion furnace to 680-720 ℃, introducing nitrogen and oxygen, and pre-oxidizing the textured silicon wafer; 3) introducing low-concentration POCl into a diffusion furnace 3 Nitrogen and oxygen, and performing low-temperature low-concentration phosphorus source deposition on the pre-oxidized silicon wafer; 4) heating the diffusion furnace to 730-820 ℃, and introducing medium-concentration POCl 3 Nitrogen and oxygen, and performing high-temperature medium-concentration phosphorus source deposition on the silicon wafer subjected to low-temperature low-concentration phosphorus source deposition; 5) heating the diffusion furnace to 850-920 ℃, introducing nitrogen, and forming a PN junction on the surface of the silicon wafer after the phosphorus source with high concentration is deposited at high temperature; 6) cooling the diffusion furnace to 680-720 ℃, and introducing high-concentration POCl 3 Nitrogen and oxygen, and performing low-temperature high-concentration phosphorus source deposition on the processed silicon wafer; 7) and cooling the diffusion furnace, pushing out the quartz boat, and taking out the processed silicon wafer. The method adopts regional layered diffusion control, so that the surface of a silicon wafer has an even phosphorosilicate glass layer, and laser SE heavy doping is facilitated, so that ohmic contact and good contact performance of a cell are improved; and the emitter region can have low doping concentration and high-quality PN junction, so that the cell has the characteristics of excellent blue light response and high minority carrier lifetime, and the conversion efficiency of the cell is finally improved. However, after the heavy doping, the metal contact region Rs is difficult to drop to a lower value, and the improvement of the battery performance is influenced.
Therefore, it is necessary to develop a new diffusion technology to reduce Rs and FF loss of the battery and maximize Eff of the battery on the basis of further increasing Voc and Isc gains.
Disclosure of Invention
In view of the above problems in the prior art, an object of the present invention is to provide a diffusion method suitable for LDSE technology.
In order to achieve the purpose, the invention adopts the following technical scheme:
a diffusion method suitable for laser doping technology is characterized in that the atmosphere is controlled to be pure O in the temperature reduction oxidation process 2 Reacting the silicon dioxide growing on the surface of the diffusion layer with the phosphorus source doped on the surface to generate the phosphorosilicate glass with the thickness of 40-50 nm in the atmosphere, and cooling and oxidizing the phosphorosilicate glassA post-oxidation step is also carried out, and the atmosphere is controlled to be pure O in the post-oxidation process 2 An atmosphere.
The invention controls pure O in the cooling oxidation process 2 Atmosphere, specific thickness of the resulting phosphosilicate glass, and pure O in the step of temperature-reducing oxidation 2 The atmosphere reduces the surface active doping concentration to reduce minority carrier recombination and further improve the Voc and the Isc on the one hand, and reduces the sheet resistance of a heavily doped region and further improves/metal contact on the other hand, so that the Rs and FF loss of the battery is reduced and the Eff of the battery is maximally improved on the basis of further improving the gains of the Voc and the Isc.
The following is a preferred technical solution of the present invention, but not a limitation to the technical solution provided by the present invention, and the technical objects and advantageous effects of the present invention can be better achieved and achieved by the following preferred technical solution.
Preferably, the diffusion method comprises:
(1) and (3) heating: heating to T 1 750-810 ℃, providing a stable temperature environment for a ventilation source, and simultaneously vacuumizing;
(2) general source: at T 1 Loading a phosphorus source with carrier gas at 750-810 ℃;
(3) controlling the temperature at T 2 Propelling at 810-880 ℃, wherein the atmosphere is pure nitrogen;
(4) cooling and oxidizing: controlling the atmosphere to be pure O in the temperature-reducing oxidation process 2 Reacting silicon dioxide growing on the surface of the diffusion layer with a phosphorus source doped on the surface to generate phosphorus-silicon glass with the thickness of 40-50 nm under the atmosphere with the flow rate of 300-400 sccm;
(5) post-oxidation: in pure O 2 Under atmosphere T 3 Oxidizing at 700-760 deg.c to complete diffusion.
In this preferred embodiment, T 1 750 to 810 ℃, for example 750 ℃, 775 ℃, 785 ℃, 800 ℃, 805 ℃, or 810 ℃, etc. T is 1 ' 750 to 810 ℃, for example 750 ℃, 760 ℃, 770 ℃, 775 ℃, 785 ℃, 800 ℃, 805 ℃, 810 ℃, or the like. T is 2 810 to 880 ℃, for example 810 ℃, 820 ℃, 830 ℃, 840 ℃, 850 ℃, 860 ℃, 870 ℃, 880 ℃ or the like. Thickness of phosphosilicate glass40 to 50nm, such as 40nm, 43nm, 44nm, 45nm, 46nm, 48nm or 50 nm. T is 3 700 to 760 ℃, for example 700 ℃, 710 ℃, 715 ℃, 725 ℃, 735 ℃, 745 ℃, 760 ℃ or the like.
In this preferred embodiment, T 1 And T 1 ' the temperature intervals are the same, and the actual temperature values may be the same or different.
In the preferred embodiment, the purpose of step (3) is to gradually diffuse phosphorus atoms generated by the high-temperature reaction from the silicon surface into the silicon body in a substitutional doping manner.
In the preferred technical scheme, the purpose of the temperature reduction and oxidation in the step (4) is as follows: and reacting phosphorus pentachloride growing on the surface of the diffusion layer with silicon to generate a layer of phosphosilicate glass (PSG), wherein the thickness of the phosphosilicate glass is controlled to be 40-50 nm. Has the following advantages: firstly, in the process of secondary source application, a phosphorus source is redistributed in a PSG layer and then diffused into the surface of a silicon wafer, so that the diffusion effect is more uniform; secondly, higher-concentration P is accumulated in the PSG, the doping rear resistance obtained by the same laser power is lower during the subsequent laser doping, the metal/silicon contact at the battery end is better, and the FF of the battery is improved. The step is one of the innovation points of the patent, and the process requires that: the gas is pure O 2 The flow rate is 300-400 sccm. The flow rate is higher than that of the prior art O 2 Lower flow and pure O 2 The atmosphere, cell side, appears to have a lower Rs, FF is improved over prior art.
In the preferred technical scheme, the step (5) aims to further increase the P concentration in the PSG layer, reduce the surface active P concentration and reduce the surface carrier recombination; meanwhile, the Voc and Isc of the battery end are improved through the oxygen gettering effect.
In the method, gas enters from the gas path, the gas path is divided into two types, one type is a small-flow gas path, and the other type is a large-flow gas path, the measuring range of the small-flow gas path is less than that of the large-flow gas path, for example, the measuring range of the small-flow gas path is 1000sccm, and the measuring range of the large-flow gas path is 3000 sccm.
Note that the gas x introduced by the small flow gas path is Sx, and the gas x introduced by the large flow gas path is Bx.
As a preferred technical scheme of the method of the invention, the step (1) is vacuumized to 50-300mbar, such as 50mbar, 65mbar, 80mbar, 90mbar, 100mbar, 125mbar, 150mbar, 170mbar, 180mbar, 200mbar, 220mbar, 240mbar, 265mbar, 280mbar or 300mbar, etc.
Preferably, the method further comprises a pre-oxidation step after step (1) and before step (2), wherein the atmosphere is pure O 2 The purpose is to pre-grow an oxide layer to improve the diffusion uniformity.
Preferably, the pure O 2 The flow rate is 500-1000 sccm, such as 500sccm, 600sccm, 700sccm, 750sccm, 800sccm, 850sccm, 900sccm, or 1000 sccm.
Preferably, the temperature of the pre-oxidation process is 750-810 ℃, such as 750 ℃, 760 ℃, 775 ℃, 785 ℃, 800 ℃ or 810 ℃, and the like, and the time is 250-300 s, such as 250s, 260s, 270s, 280s, 290s or 300s, and the like.
Preferably, the carrier gas in step (2) is N 2 Said N is 2 The flow rate is 500-1000 sccm, such as 500sccm, 600sccm, 700sccm, 800sccm, 850sccm, 900sccm, or 1000sccm, wherein N is 2 :O 2 The flow ratio was 1: 1. In this preferred embodiment, N 2 And O 2 All are introduced by a small-flow gas circuit.
Preferably, the temperature of the source in step (2) is 750-810 ℃, such as 750 ℃, 765 ℃, 780 ℃, 790 ℃, 800 ℃ or 810 ℃, and the like, and the time is 600-700 s, such as 600s, 650s, 660s, 680s or 700s, and the like.
Preferably, the phosphorus source of step (2) comprises POCl 3 。
Step (3) said T 2 And T in the step (1) 1 Satisfies the following conditions: t is 2 -T 1 ＝30～60℃。
Preferably, said T of step (3) 2 830-860 deg.C, such as 830 deg.C, 840 deg.C, 845 deg.C, 850 deg.C or 860 deg.C.
Preferably, the advancing time in step (3) is 250-450s, such as 250s, 260s, 280s, 300s, 350s, 365s, 400s, 425s or 450 s.
Preferably, said pure O of step (4) 2 The flow rate is 300-400 sccm, such as 300sccm, 320sccm, 350sccm, 370sccm, 380sccm, 390sccm, or 400 sccm.
Preferably, the temperature reduction and oxidation in the step (4) are as follows: from T 2 Cooling to T 3 800 to 840 ℃, such as 800 ℃, 805 ℃, 810 ℃, 820 ℃, 825 ℃, 830 ℃, 835 ℃ or 840 ℃, preferably 825 to 840 ℃.
Preferably, the cooling rate is 1-3 ℃/min, if the cooling rate is too low, pure O at high temperature is caused 2 The duration under the atmosphere is too long, more P is pushed inwards, the surface active P concentration is increased, the surface recombination is increased, and the open-circuit voltage of the solar cell is influenced; if the cooling rate is too high, the surface P concentration is low and the contact is poor.
Preferably, the step (4) is followed by the step (5) and is preceded by the steps of replenishing and advancing. The purpose of source supplement is to increase the concentration of P on the surface layer, reduce the metal/silicon contact at the battery end and reduce the series resistance.
Preferably, the supplementary source is carried with phosphorus source by using carrier gas, and the carrier gas is N 2 Wherein N is 2 :O 2 500-900: 360, e.g., 500:360, 600:360, 700:360, 800:360, 850:360, 900:360, etc., illustratively N 2 The flow rate was 820sccm, O 2 The flow rate was 360 ssm. In this preferred embodiment, N 2 And O 2 All are introduced by a small-flow gas circuit.
Preferably, the temperature of the source supplement is 810-825 deg.C, such as 810 deg.C, 815 deg.C, 817 deg.C, 820 deg.C or 825 deg.C, and the time is 250-450s, such as 250s, 260s, 280s, 300s, 330s, 350s, 375s, 400s, 420s or 450 s. In the temperature and time range, the effects of increasing the surface layer P concentration, reducing the metal/silicon contact at the battery end and reducing the series resistance can be better realized.
Preferably, the propelling atmosphere is nitrogen, the propelling temperature is 800-820 ℃, such as 800 ℃, 803 ℃, 805 ℃, 810 ℃, 815 ℃ or 820 ℃ and the like, and the propelling time is 250-450s, such as 250s, 300s, 325s, 350s, 380s, 400s, 420s, 430s or 450s and the like.
Preferably, the time of the post-oxidation in step (5) is 1500-. The post-oxidation is carried out at the temperature and controlled within the time range, whereby the effects of increasing the P concentration in the PSG layer, decreasing the surface active P concentration, and sufficiently exerting the oxygen gettering effect can be more effectively achieved.
Preferably, the oxidation in step (5) is carried out while breaking vacuum, that is, the pressure in the pipe gradually recovers to the normal pressure, and the pressure in the pipe gradually recovers to be increased, that is, O in the pipe is increased 2 The concentration, in terms of performance, is reflected in a further drop in the Rs of the battery terminal, while Voc rises. Whereas the pressure in this step of the prior art is 100mbar, the atmosphere is also pure O as defined in the present invention 2 The atmosphere is different, can't reach the effect of this application.
As a preferable technical scheme of the method, the method further comprises the step of annealing treatment after the step (5). The purpose of this step is to recover the lattice damage caused by the high temperature stage.
Preferably, the annealing treatment temperature is 600-760 ℃, such as 600 ℃, 620 ℃, 635 ℃, 650 ℃, 680 ℃, 700 ℃, 720 ℃, 735 ℃, 750 ℃ or 760 ℃, and the time is 500-1800s, such as 500s, 650s, 800s, 900s, 1000s, 1200s, 1350s, 1500s, 1600s or 1800 s. Within this temperature range, the purpose of restoring the lattice damage can be better achieved.
Compared with the prior art, the invention has the following beneficial effects:
the invention provides a novel diffusion process by controlling pure O in the cooling oxidation process 2 Atmosphere, specific thickness of the resulting phosphosilicate glass, and pure O in the step of temperature-reducing oxidation 2 The atmosphere reduces the surface active doping concentration to reduce minority carrier recombination and further improve the Voc and the Isc on the one hand, and reduces the sheet resistance of a heavily doped region and further improves/metal contact on the other hand, so that the Rs and FF loss of the battery is reduced and the Eff of the battery is maximally improved on the basis of further improving the gains of the Voc and the Isc.
Drawings
FIG. 1 is a temperature-time comparison graph of the diffusion process of example 1 of the present invention and a prior art diffusion process.
Detailed Description
The technical scheme of the invention is further explained by the specific implementation mode in combination with the attached drawings.
In the embodiments of the invention, the gas N introduced by the small-flow gas path 2 Is SN 2 Gas N introduced from a large-flow gas path 2 Is BN 2 Gas O introduced from a low-flow gas circuit 2 Is SO 2 Gas N introduced from a large-flow gas path 2 Is BO 2 . The measuring range of the small-flow gas circuit is 1000sccm, and the measuring range of the large-flow gas circuit is 3000 sccm.
Example 1
The embodiment provides a diffusion method suitable for a laser doping technology, which comprises the following steps:
texturing is carried out on the silicon wafer to form a light trapping structure suede, the silicon wafer enters a diffusion furnace for single-side diffusion after texturing, the diffusion surface is an N-type emitter, the back surface is a P-type surface, and a PN junction is formed.
The diffusion process comprises the following steps:
(1) opening a furnace door: under atmospheric conditions of BN 2 (flow rate 3000sccm), SN 2 (flow 0), BO 2 (flow rate 3000sccm), SO 2 (flow 1000sccm), pressure (1060 mbar);
(2) entering a boat: under atmospheric conditions of BN 2 (flow rate 3000sccm), SN 2 (flow 0), BO 2 (flow 0), SO 2 (flow 0), pressure (1060 mbar);
(3) and (3) heating: BN 2 (flow 0), SN 2 (flow 0), BO 2 (flow 0), SO 2 (flow 0), pressure (100 mbar);
(4) pre-oxidation: BN 2 (flow 0), SN 2 (flow 0), BO 2 (flow 0), SO 2 (flow rate 740sccm), pressure (100 mbar);
(5) general source: under atmospheric conditions of BN 2 (flow 0), SN 2 (flow 740sccm), BO 2 (flow 0), SO 2 (flow rate 740sccm), pressure (100 mbar);
(6) and (3) heating: BN 2 (flow rate 1500sccm), SN 2 (flow 0), BO 2 (flow 0), SO 2 (flow 0), pressure (100 mbar);
(7) propelling: under atmospheric conditions of BN 2 (flow rate 1500sccm), SN 2 (flow 0), BO 2 (flow 0), SO 2 (flow 0), pressure (100 mbar);
(8) cooling and oxidizing: under atmospheric conditions of BN 2 (flow 0), SN 2 (flow 0), BO 2 (flow 0), SO 2 (flow rate 360sccm), pressure (100 mbar);
(9) source supplement: under atmospheric conditions of BN 2 (0)，SN 2 (flow 820sccm), BO 2 (flow 0), SO 2 (flow rate 360sccm), pressure (100 mbar);
(10) propelling: under atmospheric conditions of BN 2 (flow rate 1500sccm), SN 2 (flow 0), BO 2 (flow 0), SO 2 (flow 0), pressure (100 mbar);
(11) post-oxidation: under atmospheric conditions of BN 2 (flow 0), SN 2 (flow 0), BO 2 (flow rate 3000sccm), SO 2 (flow 1000sccm), pressure (1060 mbar);
(12) annealing: under atmospheric conditions of BN 2 (flow rate 3000sccm), SN 2 (flow 0), BO 2 (flow 0), SO 2 (flow 0), pressure (1060 mbar);
(13) taking out of the boat: under atmospheric conditions of BN 2 (flow rate 3000sccm), SN 2 (flow 0), BO 2 (flow 0), SO 2 (flow 0), pressure (1060 mbar);
examples 2 to 5
The temperature and time of each step was varied and is detailed in table 1.
Example 6
The procedure and conditions were the same as in example 1 except that the temperature decreasing rate was adjusted to 0.3 deg.C/min.
Example 7
The procedure and conditions were the same as in example 1 except that the temperature decreasing rate was adjusted to 8 deg.C/min.
Comparative example 1
The present comparative example provides a diffusion control, and the specific differences from this patent include: 1. step 8, the temperature reduction atmosphere is N 2 /O 2 The temperature reduction rate is slower when the atmosphere is mixed; 2. step 9, source supplementing temperature is constant temperature source supplementing; 3. the oxidizing atmosphere after the step 10 is N 2 /O 2 Mixing the atmosphere.
The products obtained in each example and comparative example were tested, and the thickness of the SG layer and the concentration of surface active P were measured on a single crystal polished wafer. The surface active P concentration is measured by an electrochemical capacitance voltage tester, and the thickness of the PSG layer is measured by a full-wavelength ellipse plate tester. The PSG layer thickness and surface active P concentration data are shown in table 1.
The invention also provides a method for continuously preparing the battery by adopting the product obtained in the embodiment and the product of the comparison group, which comprises the following steps:
(A) the diffused silicon wafer carries out laser doping on the emitter, the doping power is 41% of the power, and the purpose is to further dope P in the PSG layer formed after diffusion into silicon to form a local heavily doped region;
(B) etching the doped silicon wafer, removing the PSG layer on the surface of the N-type emitter and the N-type doped layers on the four sides of the silicon wafer, and polishing the P-type surface;
(C) depositing a layer of compact aluminum oxide on the P-shaped surface atomic layer of the etched silicon wafer for back passivation, wherein the thickness of the aluminum oxide is 10 nm; 6. and carrying out PECVD (plasma enhanced chemical vapor deposition) on two sides of the silicon wafer with the passivated back, and plating silicon nitride films, wherein the thickness and the refractive index of the silicon nitride on the front side and the back side are respectively 85 +/-5 nm, 2.05 +/-0.05 and 90 +/-5 nm, and 2.15 +/-0.1. The silicon nitride film can be used as an antireflection film of light to increase the light absorption and can also play a field passivation role on the silicon wafer;
(D) and carrying out laser grooving on the P-shaped surface, wherein the laser grooving pattern is matched with the back field screen pattern. The purpose is to make the printed aluminum paste better contact with the silicon wafer; 8. and screen printing is carried out according to the sequence of back silver, back aluminum and front silver, and an upper back silver electrode, an aluminum back field and a front silver electrode are sequentially printed. Wherein: the number of the front main grids is 9, the number of the auxiliary grids is 100, and the number of Pad points on each main grid is 9. The number of the back main grids is 9, the number of the auxiliary grids is 146, and the number of the silver electrodes on each main grid is 9.
(E) The printed battery piece passes through a high-temperature (800 ℃) sintering furnace, so that the slurry is in close contact with silicon, and the passivation effect is further improved.
(F) The cell is annealed for 24 hours at 105 ℃ and 3.5A, so that the purposes of reducing attenuation and further improving efficiency are achieved.
And (3) testing electrical properties: the performance of the front cell was tested using a hall solar simulator, and the test results are shown in table 2.
TABLE 1
TABLE 2 diffusion related parameters and PSG thickness
Example 1 compared to comparative example 1, Voc is increased by 2.2mV over SE baseline and the PSG layer is thicker in the cell electrical performance: 50nm, and the sheet resistance after LDSE doping is reduced by about 50%, which is shown in the electrical property of the battery, Rs is reduced by 0.2m omega, and Eff is improved by 0.16%. As shown in table 1.
The applicant states that the present invention is illustrated in detail by the above examples, but the present invention is not limited to the above detailed methods, i.e. it is not meant that the present invention must rely on the above detailed methods for its implementation. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.
Claims (24)
1. A diffusion method suitable for laser doping technology is characterized in that the atmosphere is controlled to be pure O in the process of temperature reduction and oxidation 2 Reacting silicon dioxide growing on the surface of the diffusion layer with a phosphorus source doped on the surface to generate phosphorus-silicon glass with the thickness of 40-50 nm in an atmosphere, performing a post-oxidation step after temperature reduction and oxidation, and controlling the atmosphere in the post-oxidation processIs pure O 2 An atmosphere.
2. The diffusion method according to claim 1, wherein the diffusion method comprises:
(1) and (3) heating: heating to T 1 = 750-810 ℃, and vacuuming;
(2) general source: at T 1 ' = 750-810 ℃, and loading a phosphorus source by using a carrier gas;
(3) controlling the temperature at T 2 The temperature is 810-860 ℃ and the process is carried out, and the atmosphere is pure nitrogen;
(4) cooling and oxidizing: controlling the atmosphere to be pure O in the temperature-reducing oxidation process 2 Reacting phosphorus pentachloride growing on the surface of the diffusion layer with silicon to generate phosphosilicate glass with the thickness of 40-50 nm in an atmosphere with the flow rate of 300-400 sccm;
(5) post-oxidation: in pure O 2 Under atmosphere T 3 And (c) = oxidation at 700-760 ℃ to complete diffusion.
3. Diffusion process according to claim 2, characterized in that step (1) is evacuated to 50-300 mbar.
4. The diffusion method according to claim 2, further comprising a pre-oxidation step after step (1) and before step (2), wherein the atmosphere is pure O 2 。
5. The diffusion method of claim 4, wherein the pure O 2 The flow rate is 500-1000 sccm.
6. The diffusion method according to claim 4, wherein the pre-oxidation step is performed at a temperature of 750 to 810 ℃ for 250 to 300 seconds.
7. The diffusion method according to claim 2, wherein the carrier gas of step (2) is N 2 Said N is 2 The flow rate of (1) is 500 to 1000sccm, wherein N is 2 : O 2 Flow ratioIs 1:2 to 2: 1.
8. The diffusion method according to claim 2, wherein the temperature of the source in the step (2) is 750-810 ℃ for 600-700 s.
9. The diffusion method of claim 2, wherein the phosphorous source of step (2) comprises poci 3 。
10. The diffusion method according to claim 2, wherein said T of step (3) 2 And T in the step (1) 1 Satisfies the following conditions: t is 2 -T 1 =30~60℃。
11. The diffusion method according to claim 2, wherein said T of step (3) 2 =830~860℃。
12. The diffusion method according to claim 2, wherein the advancing time in step (3) is 250-450 s.
13. The diffusion method according to claim 2, wherein the pure O of step (4) 2 The flow rate of (2) is 300 to 400 sccm.
14. The diffusion method according to claim 2, wherein the step (4) of reducing the temperature and oxidizing into: from T 2 Cooling to T 3 =800~840℃。
15. The diffusion method of claim 14, wherein T is 3 =825~840℃。
16. The diffusion method according to claim 14, wherein the temperature reduction rate is 1 to 3 ℃/min.
17. The diffusion method according to claim 2, wherein the step (4) is followed by the step (5) and is preceded by the steps of replenishing the source and advancing.
18. The diffusion method of claim 17 wherein the supplemental source is a phosphorus source loaded with a carrier gas, the carrier gas being N 2 Wherein N is 2 :O 2 =(500~900):360。
19. The diffusion method as claimed in claim 17, wherein the temperature of the source is 810-825 ℃ and the time is 250-450 s.
20. The diffusion method as claimed in claim 17, wherein the propelling atmosphere is nitrogen, and the propelling temperature is 800-820 ℃ for 250-450 s.
21. The diffusion method as claimed in claim 2, wherein the post-oxidation time in step (5) is 1500-2200 s.
22. The diffusion method according to claim 2, wherein the step (5) is performed by breaking vacuum while oxidizing, and the pressure in the tube gradually increases.
23. The diffusion method of claim 2, further comprising annealing after step (5).
24. The diffusion method as claimed in claim 23, wherein the annealing temperature is 600-760 ℃, and the annealing time is 500-1800 s.
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| CN103066156A (en) * | 2013-01-06 | 2013-04-24 | 奥特斯维能源（太仓）有限公司 | Diffusion technology of emitter preparation applied to crystalline silicon solar cell |
| CN109411341A (en) * | 2018-09-29 | 2019-03-01 | 平煤隆基新能源科技有限公司 | A method of improving SE battery diffused sheet resistance uniformity |
| CN110164759A (en) * | 2019-04-25 | 2019-08-23 | 横店集团东磁股份有限公司 | A kind of regionality stratified sedimentation diffusion technique |
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| CN103066156A (en) * | 2013-01-06 | 2013-04-24 | 奥特斯维能源（太仓）有限公司 | Diffusion technology of emitter preparation applied to crystalline silicon solar cell |
| CN109411341A (en) * | 2018-09-29 | 2019-03-01 | 平煤隆基新能源科技有限公司 | A method of improving SE battery diffused sheet resistance uniformity |
| CN110164759A (en) * | 2019-04-25 | 2019-08-23 | 横店集团东磁股份有限公司 | A kind of regionality stratified sedimentation diffusion technique |
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