CN112831828A - Growth method of gallium-doped Czochralski monocrystalline silicon, gallium-doped monocrystalline silicon and application - Google Patents
Growth method of gallium-doped Czochralski monocrystalline silicon, gallium-doped monocrystalline silicon and application Download PDFInfo
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- 229910001392 phosphorus oxide Inorganic materials 0.000 claims description 2
- FAIAAWCVCHQXDN-UHFFFAOYSA-N phosphorus trichloride Chemical compound ClP(Cl)Cl FAIAAWCVCHQXDN-UHFFFAOYSA-N 0.000 claims description 2
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
- C30B15/02—Single-crystal growth by pulling from a melt, e.g. Czochralski method adding crystallising materials or reactants forming it in situ to the melt
- C30B15/04—Single-crystal growth by pulling from a melt, e.g. Czochralski method adding crystallising materials or reactants forming it in situ to the melt adding doping materials, e.g. for n-p-junction
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/02—Elements
- C30B29/06—Silicon
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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
- H01L31/0248—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 System
- H01L31/0288—Inorganic materials including, apart from doping material or other impurities, only elements of Group IV of the Periodic System characterised by the doping material
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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
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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
- 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
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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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
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- 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 discloses a growth method of gallium-doped czochralski monocrystalline silicon, the gallium-doped monocrystalline silicon and application, and relates to the technical field of monocrystalline silicon. The growth method comprises the steps of heating a polycrystalline silicon raw material and a gallium dopant to a silicon melt, growing a silicon crystal by utilizing a Czochralski single crystal growing method, and introducing a gaseous phosphorus dopant or an arsenic dopant as a donor dopant at the growth stage of the silicon crystal. The inventor creatively introduces the gaseous donor dopant, so that the solidification ratio can be remarkably increased, and a silicon crystal with larger quality can be grown in a silicon melt with the same quality, thereby obviously improving the production efficiency of the crystal. The gallium-doped monocrystalline silicon prepared by the method has narrower resistivity distribution and low preparation cost, and can be applied to solar cells.
Description
Technical Field
The invention relates to the technical field of monocrystalline silicon, in particular to a growth method of gallium-doped czochralski monocrystalline silicon, the gallium-doped monocrystalline silicon and application.
Background
Solar cells based on the semiconductor photovoltaic effect have been widely used, and the mainstream solar cells are based on silicon crystal materials, especially single crystal silicon crystal materials, and the silicon crystal materials must be doped to be used as the base materials of the solar cells. The boron doping is more common, the segregation coefficient of boron in silicon is 0.8, silicon crystals with more uniformly distributed axial resistivity are easy to grow, and the silicon crystal is suitable for application of solar cells. However, the solar cell has a phenomenon of efficiency attenuation, i.e., a light attenuation phenomenon, at the initial stage of service due to the interaction between boron and another inevitable impurity, namely oxygen, in the monocrystalline silicon. To solve this problem, the use of gallium doping is one of the possible solutions.
However, since the segregation coefficient of gallium in silicon is 0.008, an excessively small segregation coefficient results in a wide distribution range of resistivity of gallium-doped single crystal silicon, and thus the proportion of cells that can be suitably used in the crystal is reduced. If the technical problem is not solved, the use cost of the gallium-doped monocrystalline silicon is obviously higher than that of the boron-doped monocrystalline silicon, and the industrial application of the gallium-doped monocrystalline silicon is not facilitated.
Disclosure of Invention
The invention aims to provide a growth method of gallium-doped czochralski silicon, aiming at improving the resistivity distribution of the gallium-doped monocrystalline silicon, obviously improving the solidification ratio g, improving the crystal proportion of a suitable battery and further reducing the application cost of a gallium-doped silicon wafer.
Another objective of the present invention is to provide a gallium-doped single crystal silicon with narrower resistivity distribution and low manufacturing cost.
The third purpose of the invention is to provide the application of the gallium-doped monocrystalline silicon in the solar cell.
The technical problem to be solved by the invention is realized by adopting the following technical scheme.
The invention provides a growth method of gallium-doped czochralski silicon, which comprises the following steps:
heating a polycrystalline silicon raw material and a gallium dopant to a silicon melt in a growth container, growing a silicon crystal by utilizing a Czochralski single crystal growing method, and introducing a gaseous donor dopant in the growth stage of the silicon crystal;
stopping introducing donor gas when the solidification ratio g reaches 0.5-0.85, and finishing crystal growth;
wherein the solidification ratio g is the ratio of the mass of the crystal to the mass of the initial melt, and the donor dopant is a phosphorus dopant or an arsenic dopant.
The invention also provides gallium-doped monocrystalline silicon which is prepared by adopting the growth method of the gallium-doped czochralski monocrystalline silicon.
The invention also provides application of the gallium-doped monocrystalline silicon in a solar cell.
The embodiment of the invention provides a growth method of gallium-doped Czochralski silicon, which comprises the steps of heating a polycrystalline silicon raw material and a gallium dopant to a silicon melt, growing a silicon crystal by utilizing a Czochralski method, and introducing a gaseous phosphorus dopant or an arsenic dopant as a donor dopant in the growth stage of the silicon crystal. The inventor creatively introduces the gaseous donor dopant, so that the solidification ratio can be remarkably increased, and a silicon crystal with larger quality can be grown in a silicon melt with the same quality, thereby obviously improving the production efficiency of the crystal.
The embodiment of the invention also provides gallium-doped monocrystalline silicon which is prepared by the growth method, has narrower resistivity distribution and low preparation cost, and can be applied to solar cells.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
FIG. 1 is a graph comparing the resistivity profiles of gallium-doped single crystal silicon crystals conditioned with gaseous donors for example 1 and comparative example 1;
figure 2 is a graph comparing the resistivity profiles of gallium-doped single crystal silicon crystals conditioned with gaseous donors for example 2 and comparative example 1.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
The growth method, gallium-doped monocrystalline silicon and application of the gallium-doped czochralski silicon provided by the embodiment of the invention are specifically described below.
The embodiment of the invention provides a growth method of gallium-doped Czochralski silicon, which comprises the following steps:
s1 growth of first crystal
Heating a set amount of polysilicon raw material and a set amount of gallium dopant to a silicon melt in a growth container (such as a crucible), growing the silicon crystal by Czochralski method, introducing gaseous donor dopant in the growth stage of the silicon crystal, and controlling the doping rate VD(ii) a When the solidification ratio g reaches 0.5-0.85, the introduction of donor gas is stopped, and the crystal growth is finished. The donor dopant is phosphorus dopant or arsenic dopant, and the donor doping rate VDIs 1 × 10-7-1×10-5mol/min。
The inventor creatively introduces gaseous donor dopant in the crystal growth process and controls the doping rate of the species of the donor dopant, so that the solidification ratio can be expanded from 0.5-0.6 to 0.85 at most, and a silicon crystal with larger quality can be grown in a silicon melt with the same quality, thereby obviously improving the production efficiency of the crystal. The introduced gaseous donor dopant decomposes at high temperature, releasing donor atoms, which dissolve into the silicon melt. In the process of crystal growth, gallium as an acceptor atom and a donor atom enter the silicon crystal together, the doping rate of the donor atom in the silicon crystal and the segregation distribution of the gallium are matched, and the net carrier concentration in the silicon crystal can be adjusted through electron/hole compensation, so that the distribution of the crystal resistivity is controlled.
In addition, the gaseous donor dopant can better control the introduction rate and distribution of the gaseous donor dopant, so that the content of the donor dopant in each part of the crystal can be controlled, and the phenomenon that the content of the donor dopant is too high to influence the performance of the crystal is prevented. During the operation of the solar cell, the output current is generated by the movement of photogenerated carriers, so the mobility of the carriers is involved. Whereas minority carriers in the crystal are scattered by ionized impurities in the crystal, the mobility is related to the total concentration of the doped impurities. According to the mobility model analysis, the influence of the introduction of the donor on the solar cell efficiency is acceptable in the gallium and donor concentration range of the invention. Especially in the range of preferred conditions, the introduced donors have little adverse effect on the cell efficiency, and are rather advantageous for improving the cell performance due to the reasonable control of the resistivity.
Specifically, the set amount of the polycrystalline silicon raw material is determined according to the volume of the growth vessel, and the set amount of the gallium dopant is determined according to the resistivity of the resulting silicon crystal head and the set amount of the polycrystalline silicon raw material. The set amount of the gallium dopant directly affects the resistivity of the head of the silicon crystal, so the set amount of the gallium dopant is determined according to the resistivity of the head of the silicon crystal, the head resistivity is defined according to the usage formula, the head resistivity is generally 1-3 ohm cm according to the practical situation in the photovoltaic industry at present, and then the relationship between the resistivity and the doping concentration is converted according to the existing documents, such as GB/T13389-2014 'conversion procedure for resistivity and dopant concentration of boron-doped, phosphorus-doped, arsenic-doped silicon single crystal', and the like, which is the prior art and is not described herein in detail.
Further, the phosphorus dopant is selected from at least one of phosphorus, phosphine, phosphorus chloride, phosphorus oxide, phosphorus oxychloride and phosphorus organic matter; the arsenic dopant is selected from at least one of arsine, arsenic chloride and arsenic oxide. The phosphorus dopant and the arsenic dopant are suitable as donor dopants in the application, and can make the resistivity distribution of the crystal narrower after being introduced, and the solidification ratio g can be obviously increased.
In some embodiments, the donor dopant is diluted with an inert gas and then introduced, and the actual introduction rate of the donor dopant is determined according to the donor doping rate and the dilution factor to ensure that the effective introduction rate is 1 × 10-7-1×10- 5mol/min, the inert gas can be argon, etc.
S2, growth of second to Nth crystals
And after the crystal growth is finished, taking out the crystal, cooling, reloading the polycrystalline silicon raw material and the gallium dopant into the growth container, and growing the second to Nth crystals after the silicon melt is stabilized. When a plurality of crystals are grown in the same crucible, the advantage that the solidification ratio g is expanded to 0.6-0.85 is more obvious, which means that more polycrystalline silicon raw materials can be refilled after the growth of one crystal is finished, so that the unit yield of the crucible is improved, and the production cost is reduced.
Specifically, the polysilicon raw material is reloaded by complementing the polysilicon raw material to a set amount, in all the grown single crystal silicon crystals, the gallium concentration from the head part to the tail part is less than or equal to 10ppma, the donor concentration is less than or equal to 8ppma, the total range of the resistivity of each part is controlled to be 0.3-5 Ω cm, the set range of the resistivity of the tail part is 0.3-0.6 Ω cm, and the supplement amount and the donor doping rate of the gallium dopant are determined according to the standard. Preferably, the gallium concentration throughout the grown single crystal silicon crystal is 4ppma or less and the donor concentration is 2ppma or less from the head to the tail. The indexes are parameters for directly reacting the final crystallization product, and the excellent performance of the silicon crystal can be ensured in the range.
Note that, the parameters of the set ratio g and the tail resistivity ρ areeAnd donor doping rate VDAre interrelated and are limited by the specified maximum concentration of gallium and donors. In actual production, the head ρ can be confirmed by prioritytTail resistivity ρeThis is directly related to the specification of the silicon crystal, then the appropriate solidification ratio g in production is identified, and finally the optimum donor doping rate V is identifiedD。
Further, after taking out the crystal and cooling it, the resistivity of the head, middle and tail of the crystal was measured, and the replenishment amount of gallium dopant Δ m during the growth of the second to nth crystalsGaAnd calculating according to the resistivity of each part. Specifically, according to the resistivity of each part, the tail gallium concentration N is respectively determinedGaActual carrier concentration NpThen from NGaAnd NpThe difference determines the donor concentration ND，ΔmGaIs calculated as formula (1):
ΔmGa＝M0·ND/NGa (1)；
wherein M is0Represents the initial gallium dopant set-point reflecting the head resistivity of the crystal. During the growth of the subsequent Nth crystal, the same or similar gallium addition amount needs to be added during each reloading process.
Specifically, the gallium dopant concentration of the head can be determined according to the resistivity of the head, and then the tail gallium concentration N is obtained according to the growth curve of galliumGaDetermining the actual carrier concentration N from the tail resistivitypThen in the second step ofGaAnd NpThe difference determines the donor concentration ND. The formula (1) and the subsequent formulas (2) and (3) in the specification are theories summarized by the inventor, and the parameter indexes of the finally obtained crystal can be ensured to meet the requirements by calculating the supplement amount of the gallium dopant and the donor doping rate according to the method. The calculation method of each parameter in the formula belongs to the prior art, and can be converted by referring to the prior documents such as GB/T13389-2014 conversion specification of resistivity and concentration of dopant of boron-doped, phosphorus-doped, arsenic-doped silicon single crystal and the like.
Further, in order to more precisely control the content of the donor dopant in the first crystal, the donor doping rate V is set during the growth of the first crystalD(1) The calculation formula of (a) is as follows:
VD(1)＝ND·v/f(g)，
wherein v represents the rate of crystal growth in cm3/min；kDK for phosphorus dopant for effective segregation coefficient of donor in siliconD0.35, k corresponding to arsenic dopantDIs 0.30; a is a constant, the value of a corresponding to the phosphorus dopant is 0.54, the value of a corresponding to the arsenic dopant is 0.43, and g is the solidification ratio at the end of the isodiametric growth.
Further, in order to more precisely control the content of the donor dopant in the second to Nth crystals, segregation of gallium is further regulated, and the donor dopant is doped during the growth of the second to Nth crystalsVelocity VDThe calculation formula of (N) is as follows:
VD()＝VD(1)+(N-1)ΔVD，
wherein k isGaThe effective segregation coefficient of gallium in silicon is 0.008, and g is the solidification ratio at the end of the equal-diameter growth.
It should be noted that the donor doping rate is calculated according to donor atoms, if diluted by inert shielding gas such as argon, etc., the corresponding dilution factor needs to be calculated, and in the actual production process, the adjustment of the dilution factor and the flow rate is one of the ways of adjusting the doping rate.
It is added that in order to further optimize the actual resistivity profile in the gallium-doped crystal, it is possible to follow a variable doping rate while ensuring the total donor doping. In a preferred embodiment, the adjustment can be made in a linear even shift with slow forward and fast backward.
The embodiment of the invention also provides gallium-doped monocrystalline silicon which is prepared by adopting the growth method of the gallium-doped czochralski monocrystalline silicon, the conductive type is p type, and the total range of the resistivity of each part is controlled to be 0.3-5 omega. The gallium-doped monocrystalline silicon has narrow resistivity distribution, and the crystal proportion of a suitable battery is improved, so that the application cost of the gallium-doped silicon wafer is reduced, and the gallium-doped monocrystalline silicon can be applied to solar batteries.
The features and properties of the present invention are described in further detail below with reference to examples.
Example 1
The embodiment provides a growth method of gallium-doped czochralski silicon, which specifically comprises the following steps:
580kg of high purity polysilicon raw material was charged into a crucible, and 48g of high purity gallium metal was added. The crucible is put into a crystal growth furnace, heated and melted into silicon melt, and growth of the gallium-doped Czochralski silicon is carried out according to the Czochralski czochralski method. Complete necking, shouldering, entering and the likeSetting the diameter to 228mm in the diameter growth stage, and stably growing the crystal at the rate of 2mm/min per minute, wherein the growth rate v of the crystal is 81.7cm3And/min. Preparing gaseous donor doping agent, and selecting high-purity phosphine gas to be diluted by 100 times by using high-purity argon gas, wherein the concentration is 1% volume ratio. Setting an initial doping rate VD(1) Is 2.4X 10-6mol/min, converted to an effective donor gas flow of 5.4mL/min (standard condition), was passed at a constant rate. The released phosphorus atoms dissolve into the silicon melt and enter the silicon crystal together with the gallium atoms. When the crystal grows to the length of about 4.5 m and the solidification ratio g is 0.75, the introduction of the donor gas is stopped, and then the ending and subsequent procedures are started.
The head resistivity is about 1.1 omega cm and the tail is about 0.48 omega cm through testing. At the moment, the mass of the residual melt in the crucible is about 145kg, 435kg of high-purity polycrystalline silicon raw material is refilled and is recovered to 580kg, and the mass of the high-purity gallium to be supplemented is 14g according to the calculation of the formula (1). And heating the silicon raw material again to obtain a stable melt, growing a second crystal according to a normal procedure, and introducing the gaseous donor dopant again after entering a stable equal-diameter growth stage. According to the formula (3), the doping rate increase obtained when the second crystal is grown should be 0.36VD(1) The required effective flow rate is 7.3 mL/min. Keeping the crystal to continue growing, similarly growing until the length of the equal-diameter part of the crystal is about 4.5 m, stopping introducing donor gas when the solidification ratio g is about 0.75, and starting to enter a final and subsequent procedure to finish the growth of a second crystal. According to production requirements, third, fourth, fifth or even more gallium-doped monocrystalline silicon crystals can be grown according to the method.
Example 2
The embodiment provides a growing method of gallium-doped czochralski silicon crystal, which grows gallium-doped monocrystalline silicon crystal according to the same parameters as embodiment 1, and mainly comprises the following steps: the use of gaseous donor dopants was adjusted as follows:
setting the doping rate VD(1)＝2.0×10-6mol/min, converted to an effective flow of 4.4 mL/min. The flow rate is controlled by a program, so that the flow rate is uniformly accelerated and changed along with time. Setting a time functionq (t) ═ t/300min, t (min), the gaseous donor dopant was introduced at an operating flow rate q (t) ═ t/300 × 4.4 mL/min. When the crystal grows to the length of about 4.5 m and the solidification ratio g is 0.75, the introduction of the donor gas is stopped, and then the ending and subsequent procedures are started.
The head resistivity is about 1.1 omega cm and the tail is about 0.5 omega cm through testing. The high-purity polysilicon raw material is refilled according to the method to produce the second crystal and the third crystal. The high-purity gallium is added 16g each time. Calculating according to formula (3): at the time of second crystal growth, doping rate VD(2)＝2.7×10-6mol/min, operating flow q (t) ═ t/300 × 6.0 mL/min; while growing the third crystal, the doping rate VD(3)＝3.4×10-6mol/min, operating flow q (t) ═ t/300 × 7.6 mL/min. And keeping the crystal to stably grow when gas is introduced. When the length of the equal-diameter part of the crystal is about 4.5 m and the solidification ratio g is about 0.75, stopping introducing donor gas, and entering a terminating procedure to finish crystal growth. The growth may continue with a fourth, fifth or even more crystals as described above.
Comparative example 1
The comparative example provides a growth method of gallium-doped czochralski silicon, which adopts the existing growth method and specifically comprises the following steps:
580kg of high purity polysilicon raw material was charged into a crucible, and 48g of high purity gallium metal was added. The crucible is put into a crystal growth furnace, heated and melted into silicon melt, and growth of the gallium-doped Czochralski silicon is carried out according to the Czochralski czochralski method. And (4) completing necking and shouldering, entering an isodiametric growth stage, setting the diameter to 228mm, and stably growing the crystal at the rate of 2mm/min per minute. And (3) introducing no gaseous donor dopant in the process of the isometric growth, and entering a final procedure when the crystal grows for 3.9 meters in the isometric growth (the solidification ratio g is about 0.64) to finish the first crystal growth.
The crucible was refilled with 371kg of the high purity polycrystalline silicon raw material, and the newly added raw material was heated to melt, and a second crystal was grown according to the growth program of the first crystal. In this manner, a third, or even more, crystal can be repeatedly grown.
Test example 1
The second crystal in example 1 was tested for gallium content and donor phosphorus concentration, and the resistivity profile of the gallium-doped single crystal silicon crystal adjusted using gaseous donors was tested and compared with the product obtained in comparative example 1.
Through the test, the following results are obtained: the second crystal tail has a gallium content of about 1.29ppma and a donor phosphorus concentration of about 0.58ppma, which is much lower than the control standard in the present invention, and thus the degradation of carrier mobility due to donor compensation has little effect on the solar cell performance. FIG. 1 is a graph of resistivity profile of a gallium-doped single crystal silicon crystal, adjusted using gaseous donors, with comparable head-to-tail resistivity compared to conventional gallium-doped crystal growth methods. However, the crystal of example 1 can grow to 4.5 m, while the crystal of comparative example 1 has a length of 3.9 m, and the productivity is remarkably improved. Meanwhile, from the aspect of resistivity distribution, the proportion biased to the 1 Ω cm level in the embodiment 1 is higher. Therefore, the method in the embodiment of the invention can obtain crystals with larger quality and meeting the specification, and is expected to reduce the cost of applying the gallium-doped monocrystalline silicon crystals to solar cells.
Test example 2
The third crystal in example 2 was tested for gallium content and donor phosphorus concentration, and the resistivity profile of the gallium-doped single crystal silicon crystal adjusted using gaseous donors was tested and compared with the product obtained in comparative example 1.
The test shows that: the doped atomic gallium content of the tail part of the third crystal is 1.64ppma, the donor content is about 0.97ppma, the control standard of gallium and donor concentration specified in the invention is also lower, and the influence of the reduction of the carrier mobility in the crystal on the performance of the solar cell is slight. FIG. 2 is a graph showing the resistivity distribution of the obtained gallium-doped single-crystal silicon crystal, which is adjusted by introducing gaseous donors in a uniformly variable speed manner, and which is more optimized than the resistivity distribution of the obtained gallium-doped single-crystal silicon crystal in the conventional gallium-doped crystal growth method. According to the studies of PERC solar cells, the optimum conversion efficiency corresponds to a matrix resistivity in the range of 0.5-1.1. Therefore, the invention is expected to become a potential gallium-doped crystal growth method, and the obtained compensated gallium-doped monocrystalline silicon is also completely suitable for manufacturing solar cells and can reduce the cost.
In summary, the growing method of the gallium-doped Czochralski silicon provided by the invention comprises the steps of heating the polysilicon raw material and the gallium dopant to the silicon melt, growing the silicon crystal by utilizing the Czochralski method, introducing the gaseous phosphorus dopant or arsenic dopant as the donor dopant in the growth stage of the silicon crystal, and controlling the doping rate VD. The inventor creatively introduces the gaseous donor dopant, so that the solidification ratio can be remarkably increased, and a silicon crystal with larger quality can be grown in a silicon melt with the same quality, thereby obviously improving the production efficiency of the crystal.
The embodiment of the invention also provides gallium-doped monocrystalline silicon which is prepared by the growth method, has narrower resistivity distribution, can be applied to solar cells and reduces the preparation cost.
The embodiments described above are some, but not all embodiments of the invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Claims (10)
1. A growth method of gallium-doped Czochralski silicon is characterized by comprising the following steps:
heating a polycrystalline silicon raw material and a gallium dopant to a silicon melt in a growth container, growing a silicon crystal by utilizing a Czochralski single crystal growing method, and introducing a gaseous donor dopant in the growth stage of the silicon crystal;
stopping introducing the donor dopant when the solidification ratio g reaches 0.5-0.85, and finishing crystal growth;
wherein the donor dopant is a phosphorus dopant or an arsenic dopant, and the solidification ratio g is the ratio of the crystal mass to the initial melt mass.
2. The method of growing gallium-doped Czochralski single crystal silicon of claim 1, whereinCharacterised in that the doping quantity of said gallium dopant is determined on the basis of the resistivity of the head of the silicon crystal obtained, the doping rate V of the donor dopantDIs 1 × 10-7-1×10-5mol/min。
3. The growth process of gallium-doped Czochralski silicon as claimed in claim 1 or 2, wherein after the crystal growth is completed, the crystal is taken out and cooled, the polycrystalline silicon raw material and the gallium dopant are newly charged into the growth vessel, and the second to Nth crystal growth is carried out after the silicon melt is stabilized;
the step of reloading the polycrystalline silicon raw material is that the polycrystalline silicon raw material is complemented to the initial amount, in all the grown monocrystalline silicon crystals, the gallium concentration from the head part to the tail part is less than or equal to 10ppma, the donor concentration is less than or equal to 8ppma, the total range of the resistivity of each part is controlled to be 0.3-5 omega cm, the set range of the resistivity of the tail part is 0.3-0.6 omega cm, and the supplement amount and the donor doping rate of the gallium dopant are determined according to the standard;
preferably, the gallium concentration throughout the grown single crystal silicon crystal is 4ppma or less and the donor concentration is 2ppma or less from the head to the tail.
4. The method of growing gallium-doped Czochralski silicon as claimed in claim 3, wherein the resistivity of the head, middle and tail portions of the crystal is measured after the crystal is taken out and cooled, and the supplementary amount Δ m of the gallium dopant is added during the growth of the second to Nth crystalsGaCalculating according to the resistivity of each part;
according to the resistivity of each part, determining the concentration N of the tail galliumGaActual carrier concentration NpThen from NGaAnd NpThe difference determines the donor concentration ND，ΔmGaThe calculation formula of (a) is as follows:
ΔmGa＝M0·ND/NGa；
wherein M is0Indicating the initial gallium dopant loading.
5. Root of herbaceous plantThe method for growing gallium-doped Czochralski single crystal silicon as claimed in claim 4, wherein the donor doping rate V is set during the growth of the first crystalD(1) The calculation formula of (a) is as follows:
VD(1)＝ND·v/f(g)，
wherein v represents the rate of crystal growth in cm3/min；kDK corresponding to the phosphorus dopant for effective segregation coefficient of donor in siliconDIs 0.35, k corresponding to the arsenic dopantDIs 0.30; a is a constant, the value of the phosphorus dopant corresponding to a is 0.54, and the value of the arsenic dopant corresponding to a is 0.43.
6. The method for growing gallium-doped Czochralski silicon as claimed in claim 5, wherein the donor doping rate V is set during the second to Nth crystal growthsDThe calculation formula of (N) is as follows:
VD(N)＝VD(1)+(N-1)ΔVD，
wherein k isGaThe value of the effective segregation coefficient of gallium in silicon is 0.008.
7. The method for growing gallium-doped Czochralski silicon as claimed in claim 5 or 6, wherein the donor dopant is introduced in the form of a mixed gas composed of an inert gas and the dopant;
preferably, the inert gas is argon.
8. The growth method of gallium-doped Czochralski single crystal silicon as claimed in claim 1, wherein the phosphorus dopant is selected from at least one of phosphorus, phosphane, phosphorus chloride, phosphorus oxide, phosphorus oxychloride and phosphorus organics;
preferably, the arsenic dopant is selected from at least one of arsine, arsenic chloride and arsenic oxide.
9. A gallium-doped single crystal silicon, which is prepared by the growth method of the gallium-doped Czochralski single crystal silicon as described in any one of claims 1 to 8.
10. Use of the gallium-doped single crystal silicon of claim 9 in a solar cell.
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