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CN113130306A - Method for carrying out phosphorus diffusion on silicon wafer, product thereof and solar cell - Google Patents

Method for carrying out phosphorus diffusion on silicon wafer, product thereof and solar cell Download PDF

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Publication number
CN113130306A
CN113130306A CN202110379091.4A CN202110379091A CN113130306A CN 113130306 A CN113130306 A CN 113130306A CN 202110379091 A CN202110379091 A CN 202110379091A CN 113130306 A CN113130306 A CN 113130306A
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time
phosphorus
temperature
reactor
gas containing
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CN113130306B (en
Inventor
李跃
何悦
宋飞飞
贾松燕
赵颖
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Hengdian Group DMEGC Magnetics Co Ltd
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Hengdian Group DMEGC Magnetics Co Ltd
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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
    • 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
    • H01L31/0248—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 characterised by their semiconductor bodies
    • H01L31/0256—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 characterised by their semiconductor bodies characterised by the material
    • H01L31/0264—Inorganic materials
    • H01L31/028—Inorganic materials including, apart from doping material or other impurities, only elements of Group IV of the Periodic Table
    • 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
    • H01L31/1804—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof comprising only elements of Group IV of the Periodic Table
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/547—Monocrystalline silicon PV cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

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  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • Physics & Mathematics (AREA)
  • Power Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Electromagnetism (AREA)
  • Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Photovoltaic Devices (AREA)
  • Formation Of Insulating Films (AREA)

Abstract

The invention provides a method for carrying out phosphorus diffusion on a silicon wafer, a product and a solar cell thereof. The method comprises the following steps: 1) placing a silicon wafer in a container, placing the container in a reactor, introducing oxidizing atmosphere, and heating the reactor; 2) introducing gas containing a phosphorus source into the reactor for the first time, and then introducing gas containing the phosphorus source into the reactor for the second time; 3) raising the temperature of the reactor, performing a first push, and then performing a second push; 4) cooling the reactor, introducing gas containing a phosphorus source for the third time, cooling again, and introducing gas containing a phosphorus source for the fourth time; 5) and introducing an oxidizing atmosphere to obtain the silicon wafer diffused with phosphorus. The phosphorus diffusion method provided by the invention improves the diffusion sheet resistance and the uniformity thereof, thereby further improving the conversion efficiency of the large-size solar cell.

Description

Method for carrying out phosphorus diffusion on silicon wafer, product thereof and solar cell
Technical Field
The invention belongs to the technical field of solar cells, and relates to a method for carrying out phosphorus diffusion on a silicon wafer, a product and a solar cell thereof.
Background
The demand of the photovoltaic market is increasingly demanding on solar cells. Photovoltaic enterprises have competitiveness in the market, and efficiency improvement and cost reduction are targets which need to be achieved all the time. The driving force for increasing the silicon wafer size is to increase the premium, spread the cost, and expand the profit margin, and M10/G12 is more advantageous than the existing G1/M6 in these respects. The following two main points exist: 1) compared with an M6 silicon chip, the area gain is 40%/60%, and the power of the corresponding 60-type component is improved by about 80W/230W. In the construction of a power station, the cost of a bracket, a combiner box, a cable and the like can be reduced by using a large-size silicon wafer high-power assembly, so that the cost of a single-tile system is reduced, and the assembly is in a premium price. The M10/G12 silicon wafer can be superposed with a plurality of technologies, namely a multi-master grid (MBB), a half wafer, a double-sided battery technology and the like, so that the power/generated energy gain is obvious, and the power cost reduction contribution can reach 20 percent at most. The double-sided battery assembly technology obtains 5-30% of generated energy gain by back power generation; the half cell module reduces 75% of internal resistance loss to realize 5-10W of power gain; the electrode resistance and the electrode shielding of the multi-main-gate battery are synchronously reduced, the silver consumption is reduced, and meanwhile, the power is improved by 5-10W.
The production of large-size cell plates needs to use larger diffusion tube diameter and quartz boats. Therefore, the uniformity of temperature and airflow is inevitably affected. The non-uniformity of diffusion directly affects the normal distribution of the electrical performance parameters of the cell, resulting in an increase in the low efficiency ratio of the cell. For a cell with an emission-high sheet resistance diffusion process, the influence on the cell performance will be more serious. The good resistance uniformity after diffusion is beneficial to the matching of the subsequent process, and the whole electrical property is more stable.
CN104979190A discloses a method for improving the distribution uniformity of phosphorus in phosphosilicate glass, which comprises the following steps: step 01: carrying out a first cleaning process on the electrostatic chuck; step 02: using process gas NF3Performing a second cleaning process on the electrostatic chuck to remove the process byproducts located at the edge of the electrostatic chuck; wherein the process gas NF3 is not processed by the remote plasma control system; step 03: and placing the wafer on the electrostatic chuck, and preparing the phosphorosilicate glass on the surface of the wafer.
CN108389933A discloses a high-concentration phosphosilicate glass and high-sheet resistance diffusion method, which comprises the following steps: step 1, first predeposition; step 2, heating for the first time; step 3, second predeposition; step 4, raising the temperature for the second time; step 5, propelling; step 6, cooling; and 7, carrying out third predeposition.
However, the above solutions have a problem that they are not suitable for large-sized silicon wafers for solar cells. The silicon wafer size gradually increases, the sheet resistance needs to be further improved, and the requirement on the uniformity of diffusion is higher. Therefore, a process capable of further improving the diffusion sheet resistance and simultaneously considering the diffusion uniformity needs to be developed to meet the requirement of improving the efficiency in the current situation.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a method for carrying out phosphorus diffusion on a silicon wafer, a product and a solar cell thereof. The method provided by the invention can improve the diffusion uniformity of the large-size solar cell.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a method for performing phosphorus diffusion on a silicon wafer, the method comprising the steps of:
(1) placing a silicon wafer in a container, placing the container in a reactor, introducing oxidizing atmosphere, and heating the reactor;
(2) introducing gas containing a phosphorus source into the reactor for the first time, and then introducing gas containing the phosphorus source into the reactor for the second time;
(3) raising the temperature of the reactor, performing a first push, and then performing a second push;
(4) cooling the reactor, introducing gas containing a phosphorus source for the third time, cooling again, and introducing gas containing a phosphorus source for the fourth time;
(5) and introducing an oxidizing atmosphere to obtain the silicon wafer diffused with phosphorus.
The phosphorus diffusion method provided by the invention improves the diffusion sheet resistance and the uniformity thereof, thereby further improving the conversion efficiency of the large-size solar cell.
Specifically, the oxidizing atmosphere is introduced in the step (1) to promote the phosphorus source (phosphorus oxychloride) to be fully decomposed and avoid the corrosion of phosphorus pentachloride on the surface of the silicon wafer in the subsequent steps. In addition, a layer of silicon dioxide is formed on the surface of the silicon, and the diffusion coefficient of the impurity phosphorus in the oxide layer is far smaller than that in the silicon, so that the oxide layer has the capability of blocking the impurity phosphorus from diffusing into the silicon, and the diffusion is more uniform.
The first-time source introduction in the step (2) aims to decompose a phosphorus source (phosphorus oxychloride) under the action of an oxidizing atmosphere (oxygen) to generate phosphorus pentoxide which is deposited on the surface of the silicon wafer. Phosphorus pentoxide reacts with surface silicon to generate silicon oxide and phosphorus atoms, phosphorus-silicon glass is formed on the surface of the silicon wafer, and phosphorus atom distribution with constant surface concentration is formed on the surface of the silicon wafer.
And (2) introducing a phosphorus source (phosphorus oxychloride) for the second time, so that the surface concentration of phosphorus in the silicon wafer can be further improved.
And (3) in the first pushing, raising the furnace temperature until the temperature zone in the diffusion tube is uniformly distributed, and realizing the diffusion of phosphorus into silicon under the action of the phosphorosilicate glass on the surface of the silicon wafer at the early high temperature. Because of one-time diffusion, more 'dead junctions' are easily formed on the surface of the silicon wafer. Due to the presence of a large number of interstitial atoms, dislocations and defects in the "dead layer", the minority carrier lifetime of the battery is severely affected.
And (3) in the second pushing, maintaining the temperature from the furnace mouth to the furnace temperature unchanged, and performing secondary diffusion of phosphorus to reduce a 'dead layer' on the surface of the silicon wafer. The concentration of phosphorus atoms on the surface is reduced, the uniformity of the diffusion sheet resistance is increased, and the dead layer is reduced.
And (4) cooling because the temperature-variable diffusion can form obvious phosphorus atom concentration gradient difference in the diffusion process. More concentration gradients will create an additional electric field that promotes more minority carriers to flow towards the junction boundary, thereby avoiding carrier recombination. In addition, the diffusion temperature is lowered to enhance the effect of phosphorus to absorb impurities. When impurities are absorbed, the impurities are required to be segregated to the impurity absorption region within a certain time and a low temperature range. And at a lower temperature, the segregation coefficients of the impurities in different areas are greatly different, so that the impurities are more favorably segregated to the impurity absorption area.
And (4) introducing gas containing a phosphorus source for the third time to form phosphorosilicate glass on the surface of the silicon wafer and form phosphorus atom distribution with constant surface concentration on the surface of the silicon wafer.
And (4) adopting a fourth-time ventilation source, wherein the purpose is to introduce gas containing a phosphorus source, and further increase the surface concentration of phosphorus atoms so as to ensure that the emission region has enough phosphorus source concentration.
And (5) introducing an oxidizing atmosphere (oxygen) to completely react the residual phosphorus pentachloride in the diffusion layer.
With the increase of the size of the silicon chip, the control of the uniformity of the diffusion sheet resistance is difficult to realize. The uniformity of diffusion is directly reflected in the difference of PN junction depths after the silicon wafer is diffused, and if the uniformity is good, the difference of the junction depths is small, and vice versa. The sintering temperatures for different junction depths are also different. In other words, the ohmic contact of the cell with good diffusion uniformity under the same sintering conditions is good, and electrical performance parameters such as short-circuit current and filling factor are stable. Therefore, the conversion efficiency of the battery piece is more stable. Moreover, the consistency of electrical performance parameters between the solar cells is good, and the stability and the attenuation resistance of the assembly are facilitated, so that the service life of the solar cell is prolonged.
In addition, the 'dead layer' on the surface of the silicon wafer can be further reduced to reduce the recombination loss of minority carriers, so that the minority carrier lifetime is prolonged. The resistance value of the front phosphorus diffusion rear side is higher, the selective emitter can be matched with the subsequent manufacture, the direct contact between metal and a semiconductor is increased, and the conversion efficiency of the P-type passivated contact battery is further improved. Therefore, the phosphorus diffusion method provided by the invention has important significance.
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.
AsAccording to the preferable technical scheme of the invention, the area of the silicon wafer in the step (1) is 251.99cm2Above, e.g. 251.99cm2、255cm2、260cm2、265cm2Or 270cm2And the like. The advantages of the method can be exerted more effectively by the large-area silicon wafer.
Preferably, the reactor in step (1) is a quartz boat.
Preferably, the reactor in the step (1) is a diffusion furnace.
Preferably, the oxidizing atmosphere of step (1) comprises oxygen.
Preferably, the flow rate of the oxidizing atmosphere in step (1) is 500sccm, such as 500sccm, 550sccm, 600sccm, 650sccm, or 700 sccm.
Preferably, the oxidizing atmosphere in step (1) is introduced for 5-7min, such as 5min, 5.5min, 6min, 6.5min or 7 min.
Preferably, the heating temperature in step (1) is 780-790 ℃, such as 780 ℃, 783 ℃, 785 ℃, 787 ℃ or 790 ℃, etc.
Preferably, before the oxidizing atmosphere is introduced in the step (1), the reactor with the container is vacuumized and leakage is detected.
As a preferable technical scheme of the invention, the gas containing the phosphorus source introduced for the first time in the step (2) is protective gas carrying phosphorus oxychloride.
Preferably, the protective gas comprises nitrogen and/or argon.
Preferably, the flow rate of the gas containing the phosphorus source introduced for the first time in step (2) is 600sccm and 800sccm, such as 600sccm, 650sccm, 700sccm, 750sccm, or 800 sccm.
Preferably, in the first introducing of the gas containing the phosphorus source in step (2), the temperature of the reactor is 780-790 ℃, for example 780 ℃, 783 ℃, 785 ℃, 787 ℃ or 790 ℃, etc.
Preferably, the first time of introducing the gas containing the phosphorus source in step (2) is 1-3min, such as 1min, 1.5min, 2min, 2.5min or 3 min.
Preferably, the gas containing the phosphorus source introduced for the second time in the step (2) is a protective gas carrying phosphorus oxychloride.
Preferably, the protective gas comprises nitrogen and/or argon.
Preferably, the flow rate of the gas containing the phosphorus source introduced for the second time in step (2) is 600sccm and 800sccm, such as 600sccm, 650sccm, 700sccm, 750sccm, or 800 sccm.
Preferably, in the second introducing of the gas containing the phosphorus source in the step (2), the temperature of the reactor is 780-790 ℃, for example 780 ℃, 783 ℃, 785 ℃, 787 ℃ or 790 ℃, etc.
Preferably, the second time of introducing the gas containing the phosphorus source in step (2) is 1-3min, such as 1min, 1.5min, 2min, 2.5min or 3 min.
As a preferred technical proposal of the invention, the temperature for the first propulsion in the step (3) is 850-.
Preferably, the time of the first propelling in step (3) is 6-10min, such as 6min, 7min, 8min, 9min or 10 min.
Preferably, the temperature of the second advancing in step (3) is 850-.
Preferably, the time of the second advancing in step (3) is 9-12min, such as 9min, 10min, 11min or 12 min.
As a preferred technical scheme of the invention, the temperature is reduced to 820 ℃ at step (4), such as 800 ℃, 805 ℃, 810 ℃, 815 ℃ or 820 ℃.
Preferably, the cooling time for cooling in step (4) is 12-16min, such as 12min, 13min, 14min, 15min or 16 min.
Preferably, the gas containing the phosphorus source introduced for the third time in the step (4) is a protective gas carrying phosphorus oxychloride.
Preferably, the protective gas comprises nitrogen and/or argon.
Preferably, the flow rate of the gas containing the phosphorus source introduced for the third time in step (4) is 600sccm and 800sccm, such as 600sccm, 650sccm, 700sccm, 750sccm, or 800 sccm.
Preferably, in the third introducing of the gas containing the phosphorus source in step (4), the temperature of the reactor is 800-820 ℃, for example, 800 ℃, 805 ℃, 810 ℃, 815 ℃ or 820 ℃.
Preferably, the third time of introducing the gas containing the phosphorus source in step (4) is 3-5min, such as 3min, 3.5min, 4min, 4.5min, or 5 min.
As a preferred technical scheme of the invention, the temperature is reduced to 780-810 ℃ in the step (4), for example, 780 ℃, 790 ℃, 800 ℃ or 810 ℃ and the like.
Preferably, the time for cooling again in step (4) is 7-10min, such as 7min, 8min, 9min or 10 min.
Preferably, the gas containing the phosphorus source introduced for the fourth time in the step (4) is a protective gas carrying phosphorus oxychloride.
Preferably, the protective gas comprises nitrogen and/or argon.
Preferably, the flow rate of the gas containing the phosphorus source introduced for the fourth time in step (4) is 800-1000sccm, such as 800sccm, 850sccm, 900sccm, 950sccm, or 1000 sccm.
Preferably, in the fourth introduction of the gas containing the phosphorus source in step (4), the temperature of the reactor is 800-840 ℃, such as 800 ℃, 810 ℃, 820 ℃, 830 ℃ or 840 ℃.
Preferably, the fourth time of introducing the gas containing the phosphorus source in the step (4) is 5-8min, such as 5min, 6min, 7min or 8 min.
In a preferred embodiment of the present invention, the oxidizing atmosphere in step (5) comprises oxygen.
Preferably, the flow rate of the oxidizing atmosphere in step (5) is 700-.
Preferably, the oxidizing atmosphere in step (5) is introduced for 1-3min, such as 1min, 1.5min, 2min, 2.5min or 3 min.
Preferably, in the process of introducing the oxidizing atmosphere in the step (5), the temperature of the reactor is 750-790 ℃, for example, 750 ℃, 760 ℃, 770 ℃, 780 ℃, 790 ℃ or the like.
As a further preferable technical scheme of the preparation method, the method comprises the following steps:
(1) placing a silicon wafer in a container, placing the container in a reactor, vacuumizing and detecting leakage, introducing oxygen with the flow rate of 500-;
(2) introducing gas containing a phosphorus source into the reactor for the first time at the temperature of 780-790 ℃ and at the flow rate of 600-800sccm for 1-3 min; then, gas containing a phosphorus source is introduced into the reactor for the second time at the temperature of 780-790 ℃ and the flow rate of 600-800sccm for 1-3 min;
(3) raising the temperature of the reactor, performing first pushing at the temperature of 850-860 ℃ for 6-10min, and then performing second pushing at the temperature of 850-860 ℃ for 9-12 min;
(4) cooling the reactor to 800-;
(5) introducing oxidizing atmosphere at 750-790 deg.C and 900sccm for 1-3min to obtain silicon wafer with diffused phosphorus.
In a second aspect, the present invention provides a silicon wafer diffused with phosphorus, the silicon wafer diffused with phosphorus being prepared by the method according to the first aspect.
In a third aspect, the present invention provides a solar cell using the silicon wafer diffused with phosphorus according to the second aspect.
The solar cell manufacturing process flow comprises the steps of texturing, phosphorus diffusion, etching, back and front film coating, metallization, testing and sorting. The phosphorus diffusion method provided by the first aspect can be used for a phosphorus diffusion process in a solar cell manufacturing process flow.
Compared with the prior art, the invention has the following beneficial effects:
the method provided by the invention realizes uniform sheet resistance distribution in the silicon wafer by adjusting the phosphorus diffusion process, reduces 'dead layers' on the surface of the silicon wafer so as to reduce minority carrier recombination loss, prolongs the minority carrier service life and further improves the conversion efficiency of the P-type passivated contact battery. The phosphorus diffusion method provided by the invention can be used for producing large-size solar cells, the sheet resistance of the product can be maintained at 145 +/-10 omega, and the uniformity can also be maintained at less than or equal to 2.5 percent, so that the diffusion uniformity is met on the premise of realizing high sheet resistance, and the conversion efficiency of the large-size solar cells is further improved.
Detailed Description
In order to better illustrate the present invention and facilitate the understanding of the technical solutions of the present invention, the present invention is further described in detail below. The following examples are merely illustrative of the present invention and do not represent or limit the scope of the claims, which are defined by the claims.
The following are typical but non-limiting examples of the invention:
example 1
In this example, a silicon wafer was subjected to phosphorus diffusion as follows:
(1) the diffusion furnace tube firstly passes through a boat (the quartz boat filled with silicon wafers is arranged in a reactor, and the area of the silicon wafers is 252cm2) Vacuumizing and leakage detection, and keeping the precondition of cleanness, constant pressure and constant temperature in the furnace tube.
(2) Pre-oxidation, introducing oxygen at a flow rate of 600sccm for 6min, slowly increasing the furnace temperature, and maintaining the furnace temperature at 785 ℃.
(3) Introducing a source for the first time, introducing nitrogen carrying phosphorus oxychloride at a flow rate of 700sccm for 2min, and maintaining the preset temperature from the furnace mouth to the furnace tail at 785 ℃.
(4) Introducing nitrogen carrying phosphorus oxychloride for the second time at the flow rate of 700sccm for 2min, and maintaining the preset temperature from the furnace mouth to the furnace tail at 785 ℃.
(5) And (3) advancing for the first time, wherein the furnace temperature is increased to the preset temperature range from the furnace tail to the furnace mouth, the temperature range is kept at 855 ℃, the advancing of phosphorus is realized, and the advancing time is 8 min.
(6) And (4) carrying out secondary propulsion, wherein the temperature from the furnace tail to the furnace mouth is kept at 855 ℃, secondary propulsion of phosphorus is realized, and the propulsion time is 10 min.
(7) Cooling the furnace tube, slowly cooling, and finally maintaining at 810 ℃ for 14 min.
(8) And introducing a source for the third time, wherein the flow rate of nitrogen carrying phosphorus oxychloride is 700sccm, the time is 4min, and the preset temperature from the furnace mouth to the furnace tail is maintained at 810 ℃.
(9) And cooling the furnace tube again until the temperature is 795 ℃ and the cooling time is 9 min.
(10) Introducing a source for the fourth time, wherein the flow rate of nitrogen carrying phosphorus oxychloride is 900sccm, the time is 6min, and the temperature interval from the furnace mouth to the furnace tail is kept at 820 ℃.
(11) And (4) post-oxidizing, wherein the flow of the introduced oxygen is 800sccm, the time is 2min, and the preset temperature from the furnace mouth to the furnace tail is maintained at 770 ℃. And introducing oxygen to completely react the residual phosphorus pentachloride in the diffusion layer to obtain the silicon wafer diffused with phosphorus.
Example 2
In this example, a silicon wafer was subjected to phosphorus diffusion as follows:
(1) the diffusion furnace tube is firstly put into a boat (the quartz boat with silicon wafers is put into a reactor, and the area of the silicon wafers is 255cm2) Vacuumizing and leakage detection, and keeping the precondition of cleanness, constant pressure and constant temperature in the furnace tube.
(2) For pre-oxidation, oxygen was introduced at a flow rate of 500sccm for 7min, and the furnace temperature was slowly increased and maintained at 780 ℃.
(3) Introducing a source for the first time, introducing a nitrogen gas carrying phosphorus oxychloride at a flow rate of 600sccm for 3min, and maintaining the preset temperature from the furnace mouth to the furnace tail at 780 ℃.
(4) Introducing a source for the second time, wherein the flow rate of nitrogen carrying phosphorus oxychloride is 600sccm, the time is 3min, and the preset temperature from the furnace mouth to the furnace tail is maintained at 780 ℃.
(5) And (3) advancing for the first time, wherein the furnace temperature is increased to 850 ℃ from the furnace tail to the furnace mouth preset temperature, the advancing of phosphorus is realized, and the advancing time is 10 min.
(6) And (5) carrying out secondary propelling, wherein the temperature from the furnace tail to the furnace mouth is maintained at 850 ℃, the secondary propelling of phosphorus is realized, and the propelling time is 12 min.
(7) Cooling the furnace tube, slowly cooling, and finally maintaining at 800 ℃ for 16 min.
(8) Introducing a source for the third time, introducing a nitrogen gas carrying phosphorus oxychloride with the flow rate of 600sccm for 5min, and slowly cooling the furnace temperature to 780 ℃.
(9) Introducing a source for the fourth time, wherein the flow rate of nitrogen carrying phosphorus oxychloride is 800sccm, the time is 8min, and the temperature interval from the furnace mouth to the furnace tail is maintained at 800 ℃.
(10) And (4) post-oxidizing, wherein the flow of the introduced oxygen is 700sccm, the time is 3min, the preset temperature from the furnace mouth to the furnace tail is maintained at 750 ℃, and the silicon wafer diffused with phosphorus is obtained.
Example 3
In this example, a silicon wafer was subjected to phosphorus diffusion as follows:
(1) the diffusion furnace tube is firstly put into a boat (the quartz boat with silicon wafers is arranged in a reactor, and the area of the silicon wafers is 252cm2The steps are carried out, and the preparation steps of vacuumizing and leakage detection are carried out, so that the precondition of cleanness, constant pressure and constant temperature in the furnace pipe is kept.
(2) Pre-oxidation, introducing oxygen at a flow rate of 700sccm for 5min, slowly increasing the furnace temperature, and maintaining the furnace temperature at 790 ℃.
(3) Introducing a source for the first time, introducing a nitrogen gas carrying phosphorus oxychloride at a flow rate of 800sccm for 1min, and maintaining the preset temperature from the furnace mouth to the furnace tail at 790 ℃.
(4) Introducing a source for the second time, wherein the flow rate of nitrogen carrying phosphorus oxychloride is 800sccm, the time is 1min, and the preset temperature from the furnace mouth to the furnace tail is maintained at 790 ℃.
(5) And (3) advancing for the first time, wherein the furnace temperature is increased to the furnace tail to the furnace mouth preset temperature, the temperature interval is maintained at 860 ℃, the advancing of phosphorus is realized, and the advancing time is 6 min.
(6) And (4) carrying out secondary propelling, wherein the temperature from the furnace tail to the furnace mouth is maintained at 860 ℃, secondary propelling of phosphorus is realized, and propelling time is 9 min.
(7) Cooling the furnace tube, slowly cooling, and finally maintaining at 820 deg.C for 12 min.
(8) Introducing a source for the third time, introducing a nitrogen gas carrying phosphorus oxychloride at a flow rate of 800sccm for 3min, and slowly cooling the furnace temperature to 810 ℃.
(9) Introducing a source for the fourth time, wherein the flow rate of nitrogen carrying phosphorus oxychloride is 900sccm, the time is 6-9min, and the temperature interval from the furnace mouth to the furnace tail is kept at 840 ℃.
(10) And (4) post-oxidizing, wherein the flow of the introduced oxygen is 900sccm, the time is 1min, and the temperature from the furnace mouth to the furnace tail is reduced to 790 ℃. And introducing oxygen to completely react the residual phosphorus pentachloride in the diffusion layer to obtain the silicon wafer diffused with phosphorus.
Comparative example 1
The difference between the method for phosphorus diffusion provided in this comparative example and example 1 is that this comparative example does not perform the first source-through operation in step (3), and directly performs the operations of the subsequent steps (4) to (11).
Comparative example 2
The method for phosphorus diffusion provided in this comparative example differs from example 1 in that this comparative example does not perform the second energizing operation in step (4), and directly performs the operations of the subsequent steps (5) to (11).
Comparative example 3
The method for phosphorus diffusion provided in this comparative example differs from example 1 in that this comparative example does not perform the third energizing operation in step (8), and directly performs the operations of the subsequent steps (9) to (11).
Comparative example 4
The difference between the method for diffusing phosphorus provided in this comparative example and example 1 is that this comparative example does not perform the fourth round of source switching operation in step (10), and directly performs the subsequent step (11).
Test method
Using a napson sheet resistance tester at a temperature of 20 +/-5 ℃, relative humidity: the sheet resistances of the phosphorus-diffused silicon wafers obtained in the above examples and comparative examples were measured under the condition of 65% or less.
Using a napson sheet resistance tester at a temperature of 20 +/-5 ℃, relative humidity: the silicon wafers diffused with phosphorus obtained in the above examples and comparative examples were tested for uniformity of phosphorus diffusion at 65% or less.
The test results are given in the following table:
TABLE 1
Square resistance (omega) Uniformity (%)
Example 1 136 2.08
Example 2 143.2 2.26
Example 3 142.6 2.14
Comparative example 1 133.4 3.42
Comparative example 2 142 4.38
Comparative example 3 141 4.52
Comparative example 4 145 5.2
It can be known from the above embodiments and comparative examples that the method provided by the embodiments realizes more uniform sheet resistance distribution in the silicon wafer by adjusting the phosphorus diffusion process, and improves the diffusion sheet resistance and uniformity thereof.
Comparative example 1 because the first source-through is not carried out, the constant source in the furnace tube is unstable, the reaction is violent, the uniformity is poor, the diffusion temperature of the step is low, the diffusion time is short, and the diffusion depth of the impurity atoms on the surface of the silicon wafer is very shallow, which is equivalent to the deposition on the surface.
Comparative example 2 because the second source-through is not carried out, the constant source in the furnace tube is unstable, the reaction is violent, the uniformity is poor, the diffusion temperature of the step is low, the diffusion time is short, and the diffusion depth of the impurity atoms on the surface of the silicon wafer is very shallow, which is equivalent to the deposition on the surface.
In comparative example 3, since the third source-through was not performed, a junction having a low surface concentration could not be obtained, and the diffusion of impurities into the silicon wafer could not be performed, resulting in a non-dense uniformity of diffusion.
Comparative example 4 no fourth-pass source was performed, resulting in no redistribution diffusion, no high-temperature diffusion, and no effective control of surface concentration and diffusion depth, and a PN junction with strong uniformity as expected could be obtained.
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 (10)

1. A method of phosphorus diffusion in a silicon wafer, comprising the steps of:
(1) placing a silicon wafer in a container, placing the container in a reactor, introducing oxidizing atmosphere, and heating the reactor;
(2) introducing gas containing a phosphorus source into the reactor for the first time, and then introducing gas containing the phosphorus source into the reactor for the second time;
(3) raising the temperature of the reactor, performing a first push, and then performing a second push;
(4) cooling the reactor, introducing gas containing a phosphorus source for the third time, cooling again, and introducing gas containing a phosphorus source for the fourth time;
(5) and introducing an oxidizing atmosphere to obtain the silicon wafer diffused with phosphorus.
2. The method of claim 1, wherein the silicon wafer of step (1) has an area of 251.99cm2The above;
preferably, the reactor in the step (1) is a quartz boat;
preferably, the reactor of step (1) is a diffusion furnace;
preferably, the oxidizing atmosphere of step (1) comprises oxygen;
preferably, the flow rate of the oxidizing atmosphere in the step (1) is 500-700 sccm;
preferably, the introducing time of the oxidizing atmosphere in the step (1) is 5-7 min;
preferably, the temperature of the heating in the step (1) is 780-790 ℃;
preferably, before the oxidizing atmosphere is introduced in the step (1), the reactor with the container is vacuumized and leakage is detected.
3. The method according to claim 1 or 2, wherein the gas containing the phosphorus source introduced for the first time in step (2) is a protective gas carrying phosphorus oxychloride;
preferably, the protective gas comprises nitrogen;
preferably, the flow rate of the gas containing the phosphorus source, which is introduced for the first time in the step (2), is 600-800 sccm;
preferably, during the first introduction of the gas containing the phosphorus source in the step (2), the temperature of the reactor is 780-790 ℃;
preferably, the time for introducing the gas containing the phosphorus source for the first time in the step (2) is 1-3 min;
preferably, the gas containing the phosphorus source introduced for the second time in the step (2) is a protective gas carrying phosphorus oxychloride;
preferably, the protective gas comprises nitrogen and/or argon;
preferably, the flow rate of the gas containing the phosphorus source introduced for the second time in the step (2) is 600-800 sccm;
preferably, during the second introduction of the gas containing the phosphorus source in the step (2), the temperature of the reactor is 780-790 ℃;
preferably, the time for introducing the gas containing the phosphorus source for the second time in the step (2) is 1-3 min.
4. The method as claimed in any one of claims 1 to 3, wherein the temperature of the first advancing in step (3) is 850-;
preferably, the time of the first propelling in the step (3) is 6-10 min;
preferably, the temperature of the second advancing in the step (3) is 850-;
preferably, the temperature of the second advance of step (3) is the same as the temperature of the first advance;
preferably, the time of the second propelling in the step (3) is 9-12 min.
5. The method as claimed in any one of claims 1 to 4, wherein the temperature reduction in step (4) is carried out to reduce the temperature to 800-820 ℃;
preferably, the cooling time for cooling in the step (4) is 12-16 min;
preferably, the gas containing the phosphorus source introduced for the third time in the step (4) is a protective gas carrying phosphorus oxychloride;
preferably, the protective gas comprises nitrogen and/or argon;
preferably, the flow rate of the gas containing the phosphorus source introduced for the third time in the step (4) is 600-800 sccm;
preferably, in the third introducing of the gas containing the phosphorus source in the step (4), the temperature of the reactor is 800-820 ℃;
preferably, the time for introducing the gas containing the phosphorus source for the third time in the step (4) is 3-5 min.
6. The method as claimed in any one of claims 1 to 5, wherein the temperature reduction of step (4) is carried out again to reduce the temperature to 780-810 ℃;
preferably, the time for cooling again in the step (4) is 7-10 min;
preferably, the gas containing the phosphorus source introduced for the fourth time in the step (4) is protective gas carrying phosphorus oxychloride;
preferably, the protective gas comprises nitrogen and/or argon;
preferably, the flow rate of the gas containing the phosphorus source introduced for the fourth time in the step (4) is 800-;
preferably, in the step (4), during the fourth time of introducing the gas containing the phosphorus source, the temperature of the reactor is 800-840 ℃;
preferably, the fourth time of introducing the gas containing the phosphorus source in the step (4) is 5-8 min.
7. The method of any one of claims 1-6, wherein the oxidizing atmosphere of step (5) comprises oxygen;
preferably, the flow rate of the oxidizing atmosphere in the step (5) is 700-900 sccm;
preferably, the introducing time of the oxidizing atmosphere in the step (5) is 1-3 min;
preferably, the temperature of the reactor during the introduction of the oxidizing atmosphere in the step (5) is 750-790 ℃.
8. Method according to any of claims 1-7, characterized in that the method comprises the steps of:
(1) placing a silicon wafer in a container, placing the container in a reactor, vacuumizing and detecting leakage, introducing oxygen with the flow rate of 500-;
(2) introducing gas containing a phosphorus source into the reactor for the first time at the temperature of 780-790 ℃ and at the flow rate of 600-800sccm for 1-3 min; then, gas containing a phosphorus source is introduced into the reactor for the second time at the temperature of 780-790 ℃ and the flow rate of 600-800sccm for 1-3 min;
(3) raising the temperature of the reactor, performing first pushing at the temperature of 850-860 ℃ for 6-10min, and then performing second pushing at the temperature of 850-860 ℃ for 9-12 min;
(4) cooling the reactor to 800-;
(5) introducing oxidizing atmosphere at 750-790 deg.C and 900sccm for 1-3min to obtain silicon wafer with diffused phosphorus.
9. A phosphorus-diffused silicon wafer, which is produced by the method according to any one of claims 1 to 8.
10. A solar cell using the silicon wafer diffused with phosphorus according to claim 9.
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CN102820383A (en) * 2012-09-11 2012-12-12 江阴鑫辉太阳能有限公司 Spread method of polycrystalline silicon solar cell
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Denomination of invention: A method for phosphorus diffusion on silicon wafers and its product and solar cells

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