CN114497283A - Diffusion method for silicon wafer and photovoltaic silicon wafer - Google Patents

Diffusion method for silicon wafer and photovoltaic silicon wafer Download PDF

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CN114497283A
CN114497283A CN202210117046.6A CN202210117046A CN114497283A CN 114497283 A CN114497283 A CN 114497283A CN 202210117046 A CN202210117046 A CN 202210117046A CN 114497283 A CN114497283 A CN 114497283A
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silicon wafer
temperature
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李红飞
徐冠群
郑傲然
夏伟
吉克超
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Tongwei Solar Anhui Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
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    • C30B31/00—Diffusion or doping processes for single crystals or homogeneous polycrystalline material with defined structure; Apparatus therefor
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    • H01L21/02318—Forming insulating materials on a substrate characterised by the treatment performed before or after the formation of the layer post-treatment
    • H01L21/02321—Forming insulating materials on a substrate characterised by the treatment performed before or after the formation of the layer post-treatment introduction of substances into an already existing insulating layer

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Abstract

The embodiment of the application provides a diffusion method for a silicon wafer and a photovoltaic silicon wafer, and relates to the field of photovoltaic cells. The diffusion method for the silicon wafer comprises the following steps: firstly, performing primary deposition treatment on a pretreated silicon wafer at 700-780 ℃, and then performing secondary deposition treatment at 720-800 ℃, wherein the temperature of the secondary deposition treatment is higher than that of the primary deposition treatment; carrying out primary push-bonding treatment on the silicon wafer at the temperature of 800-840 ℃; then, carrying out secondary junction pushing treatment on the silicon wafer at the temperature of 840-880 ℃; the temperature of the primary knot pushing treatment is higher than that of the secondary deposition and lower than that of the secondary knot pushing treatment. The photovoltaic silicon wafer obtained by the diffusion method has low surface doping concentration, high and uniform internal doping concentration, small surface recombination effect and long minority carrier lifetime, and can obtain a solar cell with high light conversion efficiency when being used for the solar cell.

Description

Diffusion method for silicon wafer and photovoltaic silicon wafer
Technical Field
The application relates to the field of photovoltaic cells, in particular to a diffusion method for a silicon wafer and a photovoltaic silicon wafer.
Background
In the crystalline silicon solar cell, the silicon wafer needs to be subjected to diffusion treatment, so that the surface doping concentration of the silicon wafer is reduced, the internal doping concentration of the silicon wafer is increased, the light conversion efficiency of the cell is further increased, and the cell attenuation rate is reduced.
The current diffusion mode cannot well reduce the surface doping concentration of the silicon wafer, the internal doping concentration of the silicon wafer is difficult to further improve, the light conversion efficiency of the cell is still to be improved, and the attenuation rate of the cell efficiency is still to be reduced.
Disclosure of Invention
The embodiment of the application aims to provide a diffusion method for a silicon wafer and a photovoltaic silicon wafer, after the silicon wafer is processed by the diffusion method, the surface doping concentration of the silicon wafer can be reduced, and the internal doping concentration of the silicon wafer can be improved, so that the surface recombination of the silicon wafer is greatly reduced, the minority carrier lifetime in the silicon wafer is prolonged, and when the photovoltaic silicon wafer is used for preparing a photovoltaic cell, the energy conversion efficiency of the cell can be improved.
In a first aspect, an embodiment of the present application provides a diffusion method for a silicon wafer, which includes the following steps: firstly, performing primary deposition treatment on a pretreated silicon wafer, and then performing secondary deposition treatment, wherein the temperature of the secondary deposition treatment is higher than that of the primary deposition treatment; carrying out primary knot pushing treatment on the silicon wafer; then, carrying out secondary knot pushing treatment on the silicon wafer; the temperature of the primary knot pushing treatment is higher than that of the secondary deposition and lower than that of the secondary knot pushing treatment.
In the technical scheme, the silicon wafer is subjected to deposition treatment, so that the doping substances can be deposited on the surface of the silicon wafer, the subsequent junction pushing treatment is facilitated, the temperature of the two times of deposition treatment is increased in a stepped manner, and most of the doping substances on the surface of the silicon wafer can be well kept in an unactivated state during the deposition treatment.
Firstly, carrying out primary knot pushing treatment on the silicon wafer subjected to the deposition treatment, wherein the temperature of the primary knot pushing treatment is higher than that of the deposition treatment, and the doping substances can be activated and enter the silicon wafer body; and raising the temperature again to carry out secondary junction pushing treatment, so that the activated doping substances can further extend into the silicon wafer, the doping degree in the silicon wafer can be effectively improved, the doping concentration on the surface of the silicon wafer is reduced, and the photoelectric conversion efficiency of the silicon wafer is favorably improved.
In one possible implementation mode, the temperature of the primary deposition treatment is 700-780 ℃; and/or the temperature of the secondary deposition treatment is 720-800 ℃; and/or the temperature of the primary pushing treatment is 800-840 ℃; and/or the temperature of the secondary knot pushing treatment is 840-880 ℃; and/or the temperature of the secondary deposition treatment is 10-30 ℃ higher than that of the primary deposition treatment; and/or the temperature of the secondary knot pushing treatment is 20-40 ℃ higher than that of the primary knot pushing treatment.
In the technical scheme, the temperature of the two deposition treatments is within 800 ℃, most of doping substances on the surface of the silicon wafer can be in an activated state, the temperature difference between the first deposition treatment and the second deposition treatment cannot be too large or too small during the deposition treatment, the temperature difference should be within the range of 10-30 ℃, if the temperature difference is too large, the time is not enough, the temperature rise rate cannot reach the temperature, if the temperature difference is too small, the total time of the deposition treatment is prolonged, and the improvement of the uniformity of the diffusion reaction is not facilitated; the temperature of the two times of pushing and knotting treatment is over 800 ℃, doping substances on the surface of the silicon wafer can be activated, the temperature difference between the first pushing and knotting and the second pushing can not be too large or too small, the temperature should be within the range of 20-40 ℃, if the temperature is too large, junction depth is not easy to control, effective doping concentration is low when the junction depth is too deep, uniformity is poor, if the temperature is too small, the doping substances may not particularly penetrate into the silicon wafer, and doping uniformity inside the silicon wafer may also be poor.
In a possible implementation manner, the time of the primary knot pushing processing is 360-700 s, the time of the secondary knot pushing processing is 200-500 s, and the time of the primary knot pushing processing is longer than that of the secondary knot pushing processing.
In the technical scheme, the time of the primary junction pushing treatment is longer than that of the secondary junction pushing treatment, so that the doped substances deposited on the surface of the silicon wafer can be activated and then can penetrate into the silicon wafer.
In one possible implementation, the step of depositing includes: the time of the primary deposition treatment is 200-500 s; and/or the time of the secondary deposition treatment is 200-500 s.
In the technical scheme, the deposition is carried out twice according to the temperature, so that the deposition time can be kept in a shorter range every time, and the processing time of the silicon wafer is conveniently shortened.
In one possible implementation mode, the small nitrogen flow rate of the primary deposition treatment is 500-1000 sccm; and/or the small nitrogen flow rate of the secondary deposition treatment is 500-1000 sccm.
In the technical scheme, the deposition treatment is carried out in two steps, so that the doping degree of the surface of the silicon wafer can be ensured not to be too high even if the flow of the small nitrogen is increased, and the flow of the small nitrogen can be controlled to be 500-1000 sccm, so that the uniformity in the silicon wafer is improved.
In one possible implementation, the diffusion method further includes the steps of: oxidizing the silicon wafer subjected to the primary deposition treatment for 100-240 s; the oxidation temperature is higher than the temperature of the primary deposition treatment and lower than the temperature of the secondary deposition treatment; optionally, the oxidation temperature is 720-800 ℃.
In the technical scheme, the silicon wafer is subjected to oxidation treatment between the primary deposition treatment and the secondary deposition treatment, so that the concentration of the diffusion surface is further reduced.
In one possible implementation, the step of pre-processing the silicon wafer includes: pre-oxidation treatment is carried out on the silicon wafer, wherein the temperature is 700-780 ℃, and the time is 200-400 s.
According to the technical scheme, the silicon wafer is subjected to oxidation treatment before primary deposition treatment, so that the surface concentration of the silicon wafer can be reduced, and the diffusion uniformity is improved.
In one possible implementation, it further comprises the steps of: and carrying out three times of deposition treatment on the silicon wafer subjected to the secondary knot pushing treatment, wherein the temperature is 760-780 ℃, and the flow of small nitrogen is 1200-2500 sccm.
In the technical scheme, the silicon wafer is subjected to deposition treatment for three times after the secondary knot pushing treatment is finished, and the silicon wafer can be further treated by matching with subsequent processes such as SE.
In one possible implementation, it further comprises the steps of: and after the third deposition treatment, performing post-oxidation treatment on the silicon wafer for 480-640 s at 760-780 ℃.
In a second aspect, embodiments of the present application provide a photovoltaic silicon wafer, which is obtained by processing a silicon wafer by the above-mentioned diffusion method.
In the technical scheme, the photovoltaic silicon wafer obtained by the method is low in surface doping concentration and high and uniform in internal doping concentration, the surface recombination effect of the silicon wafer can be reduced, and the minority carrier lifetime is prolonged. When the material is used for preparing the solar cell, the light conversion efficiency, the current density and the open-circuit voltage of the solar cell are obviously improved, and the series internal resistance and the parallel internal resistance of the solar cell can be effectively reduced.
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In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments of the present application will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and that those skilled in the art can also obtain other related drawings based on the drawings without inventive efforts.
FIG. 1 is a partial process flow diagram of a diffusion method in an embodiment of the present application;
FIG. 2 is a graph comparing the ECV curves of the photovoltaic silicon wafers in example 1 and comparative example 7 of the present application.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application 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 following describes a photovoltaic silicon wafer and a processing method thereof in detail.
The embodiment of the application provides a photovoltaic silicon wafer, which is obtained after the silicon wafer is treated by a diffusion method, and because a series of specific operations such as temperature rise, nitrogen introduction, oxygen introduction, phosphorus introduction and the like are required in the diffusion method, the silicon wafer is generally placed in a quartz boat and is placed in a diffusion furnace for preparation, and the diffusion method of the application is specifically as follows:
s110, checking whether the diffusion furnace leaks gas or not;
s120, sending the textured silicon wafer into a diffusion furnace, and then heating to 700-780 ℃;
s130, pre-oxidation: and introducing oxygen and big nitrogen (namely pure nitrogen) into a diffusion furnace at 700-780 ℃, wherein the flow of the oxygen is controlled at 500-1500sccm, the pressure is controlled at 50-150 mbar, the oxygen is introduced to oxidize the silicon wafer, the surface concentration of the silicon wafer can be reduced, the diffusion uniformity is improved, and the time is generally controlled at 1-5 min.
Fig. 1 shows a partial process flow diagram of a diffusion method in the embodiment of the present application, which mainly includes S140, deposition processing, and S141, junction pushing processing, where the two processing steps are:
s140, deposition treatment: and (3) raising the temperature in stages, carrying out two-layer deposition treatment on the silicon wafer, and oxidizing the silicon wafer in the two-layer deposition treatment process. The method comprises the following specific steps:
s141, primary deposition treatment: keeping the flow of the large nitrogen unchanged, controlling the flow of oxygen at 500-1000 sccm, heating, introducing small nitrogen at 500-1000 sccm, and performing primary deposition treatment on the silicon wafer subjected to the pre-oxidation treatment for 200-500 s; the temperature is controlled within 700-780 ℃, and the temperature of the primary deposition treatment is higher than that of the pre-oxidation treatment, specifically 760-780 ℃.
S142, heating and oxidizing: keeping the flow of the large nitrogen unchanged, controlling the flow of the oxygen at 500-1500sccm, heating, suspending the introduction of the small nitrogen, oxidizing the silicon wafer subjected to the primary deposition treatment for 100-240 s, wherein the temperature is generally controlled at 750-800 ℃, and specifically can be 780-800 ℃.
S143, secondary deposition treatment: continuously heating and continuously introducing small nitrogen, wherein the temperature is generally controlled to be 720-800 ℃, and specifically, 780-800 ℃; the flow rate of the small nitrogen is 500-1000 sccm, and the treatment time is generally 200-500 s.
During the deposition treatment, the temperature difference between the primary deposition treatment and the secondary deposition treatment is within the range of 10-30 ℃, so that the junction depth and the whole doping concentration can be controlled.
The big nitrogen is pure nitrogen; the small nitrogen is nitrogen with phosphorus oxychloride, and the small nitrogen is generally obtained by passing the nitrogen through phosphorus oxychloride liquid; the oxygen is pure oxygen; during the deposition treatment, small nitrogen is introduced to provide raw material phosphorus, so that the phosphorus can be deposited on the surface of the silicon wafer. The flow of small nitrogen cannot be too large, otherwise, the doping concentration of the surface of the silicon wafer is easily increased, and the surface recombination of the silicon wafer is improved, so that the conversion efficiency is reduced when a battery is subsequently prepared; but the flow of the small nitrogen cannot be too low, otherwise, the content of the phosphorus is low, and the phosphorus is not mixed enough in gas, so that the reaction is not sufficient, the uniformity of a subsequent silicon wafer is poor, and the conversion efficiency of the cell is also influenced; and too small a flow rate increases the processing time and increases the deposition temperature.
As can be seen from fig. 1, the temperature of the deposition process of the present application is increased in a stepwise manner, and different stages correspond to different temperatures. From the first deposition to the oxidation and then to the second deposition, the temperature is gradually increased, so that the flow of small nitrogen can be increased to 500-1000 sccm during deposition treatment, the doping degree of the surface of the silicon wafer is not improved, and the uniformity inside the silicon wafer is good. Specifically, the small nitrogen flow rate can be 500sccm, 600sccm, 700sccm, 800sccm, 900sccm, or 1000 sccm. And the step-type temperature rise can also ensure that the silicon wafer can finish the deposition step within 800 ℃, so that most of phosphorus sources on the surface of the silicon wafer are in an unactivated state, and the phosphorus sources can not be pushed into the silicon wafer during deposition treatment.
S150, knot pushing treatment: and (3) raising the temperature in stages, and carrying out two-layer junction pushing treatment on the silicon wafer, wherein the method specifically comprises the following steps:
s151, primary knot pushing processing: and stopping introducing the small nitrogen and the oxygen, adjusting the flow of the large nitrogen to be 1000-3000sccm, and heating to 800-840 ℃ to process the silicon wafer for 360-700 s.
S152, secondary knot pushing treatment: and heating to 840-880 ℃ to process the silicon wafer for 200-500 s, wherein the time of the secondary knot pushing processing is shorter than that of the primary knot pushing processing.
During the junction pushing treatment, the temperature difference between the primary junction pushing treatment and the secondary junction pushing treatment is within the range of 20-40 ℃, so that the heating rate and the junction depth of the silicon wafer can be better controlled.
As can be seen from FIG. 1, the temperature of the present application is also increased in a stepwise manner during the push-knot process, with different temperatures corresponding to different stages. When the primary junction pushing treatment is carried out, the temperature is 800-840 ℃, so that the phosphorus source can be activated, the phosphorus source on the surface can be diffused into the silicon chip, the activity of the phosphorus source can be ensured to be low, and the phosphorus source cannot particularly penetrate into the silicon chip; therefore, the uniformity of the silicon wafer is improved, the time of one-time knot pushing treatment is long, and the uniformity of the silicon wafer is also improved; and during secondary junction pushing treatment, the temperature is 840-880 ℃, the phosphorus source can be fully activated, the doped elements can penetrate into the silicon wafer, the effective doping concentration in the silicon wafer is further improved, and the improvement of the battery efficiency is facilitated.
The temperature is changed during the deposition treatment, two stepped deposition treatments are carried out, and two knot pushing treatments (see a process flow chart in figure 1) are carried out after the two deposition treatments are finished, so that the surface recombination phenomenon of the photovoltaic silicon wafer can be greatly reduced, the service life of minority carriers can be prolonged, and the light conversion efficiency of the solar cell can be improved. Surface recombination is a phenomenon that semiconductor minority carriers disappear on the surface, and can negatively affect the light conversion efficiency of the solar cell.
S160, cooling: and introducing oxygen, controlling the flow of the oxygen to be 300-1000 sccm, and cooling the temperature in the diffusion furnace to be below 800 ℃ within 800-1500 s.
S170, deposition treatment for three times: and further cooling the temperature in the furnace to 760-780 ℃, adjusting the flow of the large nitrogen to 500-1500sccm, introducing small nitrogen with the flow of the oxygen of 500-1000 sccm and the flow of the small nitrogen of 1200-2500 sccm, and performing deposition treatment on the silicon wafer for 480-640 s for three times.
In the third deposition treatment, the flow rate of the small nitrogen is larger than that in the previous two deposition treatments, namely high-source low-temperature deposition. Therefore, the concentration of the unactivated reaction source on the surface of the silicon wafer can be increased, and the SE process after the diffusion process is favorably carried out. In the subsequent SE process, the screen printing region is heavily doped and the non-printing region is lightly doped through a laser experiment, so that the efficiency of the cell can be improved, which is not described herein.
S180, post-oxidation treatment: keeping the temperature and the flow of the large nitrogen unchanged, adjusting the flow of the oxygen to be 1000-3000sccm, stopping introducing the small nitrogen, performing oxidation treatment on the silicon wafer subjected to the three-time deposition treatment for 480-640 s, and protecting the silicon wafer subjected to the three-time deposition treatment.
S190, pressure regulating and boat discharging: and adjusting the pressure in the furnace to atmospheric pressure, opening the furnace door, and sending the silicon wafer out of the diffusion furnace. Specifically, the pressure regulating time is 60-180 s, the temperature is 760-780 ℃, the oxygen flow is 1000-3000sccm, and the large nitrogen flow is 500-1500 sccm; the boat-out time is 400-600 s, the temperature is 760-780 ℃, and the flow of the large nitrogen is 2000-4000 sccm.
The silicon wafer treated by the diffusion method can be used as a photovoltaic silicon wafer, is used in the field of solar cells, and can improve the light conversion efficiency of the cell.
The features and properties of the present application are described in further detail below with reference to examples.
Example 1
The embodiment provides a photovoltaic silicon wafer, which is obtained by placing a silicon wafer in a quartz boat and treating the silicon wafer in a diffusion furnace by a diffusion method, wherein the diffusion method comprises the following specific steps in sequence:
1. firstly, checking whether the diffusion furnace leaks gas or not;
2. sending the silicon wafer after texturing into a diffusion furnace, and then heating to 740 ℃;
3. pre-oxidation: maintaining the pressure in the furnace at 100mbar, and introducing oxygen and big nitrogen for treatment for 3 min; the oxygen flow rate was 1000sccm and the large nitrogen flow rate was 1000 sccm.
4. Deposition treatment: a. primary deposition treatment: raising the temperature to 760 ℃, introducing small nitrogen for treatment for 350s, wherein the flow rate of the small nitrogen is 750sccm, and the treatment time is 350 s.
b. Heating and oxidizing: the small nitrogen is stopped and the temperature is increased to 780 ℃ for treatment for 170 s.
c. Secondary deposition treatment: heating to 790 ℃, continuously introducing small nitrogen, maintaining the flow of the small nitrogen at 750sccm, and treating for 350 s.
5. Knot pushing treatment: a. primary knot pushing treatment: and (4) stopping introducing small nitrogen and oxygen, maintaining the flow of large nitrogen at 1000sccm, and heating to 820 ℃ for 530 s.
b. Secondary knot pushing treatment: the temperature is increased to 860 ℃ for 350s of treatment.
6. Cooling: introducing oxygen with the flow rate of 1000sccm, and cooling the temperature in the diffusion furnace to 780 ℃ within 1000 s.
7. And (3) deposition treatment for three times: and further reducing the temperature in the furnace to 760 ℃, introducing small nitrogen with the flow of 1900sccm, and performing deposition treatment on the silicon wafer for three times for 560 s.
8. Post-oxidation treatment: stopping introducing the small nitrogen, and carrying out oxidation treatment on the silicon wafer for 560 s.
9. Pressure regulating and discharging: adjusting the pressure in the furnace to atmospheric pressure within 120s, and controlling the temperature to be 760 ℃; then controlling the flow of the large nitrogen to be 2000sccm and maintaining the temperature to be 760 ℃ for 400s, and finally taking the silicon wafer out of the diffusion furnace.
Example 2
The embodiment provides a photovoltaic silicon wafer, which is obtained by processing a silicon wafer by a diffusion method, and the specific steps of the diffusion method are mainly different from those of embodiment 1 in that:
during the deposition treatment, the temperature of the first deposition treatment is 760 ℃, the temperature of the second deposition treatment is 775 ℃, and the temperature difference between the two is 15 ℃.
Example 3
The embodiment provides a photovoltaic silicon wafer, which is obtained by processing a silicon wafer by a diffusion method, and the specific steps of the diffusion method are mainly different from those of embodiment 1 in that:
when the knot is pushed, the temperature of the primary knot pushing treatment is 830 ℃, the temperature of the secondary knot pushing treatment is 840 ℃, and the temperature difference between the two is 10 ℃.
Comparative example 1
The comparative example provides a photovoltaic silicon wafer, which is obtained by processing a silicon wafer by a diffusion method, and the specific steps of the diffusion method are mainly different from those of example 1 in that:
in the deposition treatment, the temperature of the secondary deposition treatment was 810 ℃.
Comparative example 2
The comparative example provides a photovoltaic silicon wafer, which is obtained by processing a silicon wafer by a diffusion method, and the specific steps of the diffusion method are mainly different from those of example 1 in that:
deposition treatment: the temperature in the furnace was gradually raised from 760 ℃ to 790 ℃ within 870s with a small nitrogen flow of 750 sccm.
Comparative example 3
The comparative example provides a photovoltaic silicon wafer, which is obtained by processing a silicon wafer by a diffusion method, and the specific steps of the diffusion method are mainly different from those of example 1 in that:
deposition treatment: a. deposition: raising the temperature to 760 ℃, introducing small nitrogen for treatment for 350s, wherein the flow rate of the small nitrogen is 750sccm, and the treatment time is 350 s. b. Heating and oxidizing: the small nitrogen is stopped and the temperature is increased to 780 ℃ for treatment for 170 s.
Comparative example 4
The comparative example provides a photovoltaic silicon wafer, which is obtained by processing a silicon wafer by a diffusion method, and the specific steps of the diffusion method are mainly different from those of example 1 in that:
deposition treatment: a. heating and oxidizing: the temperature is increased to 780 ℃ for treatment for 170 s. b. Deposition: heating to 790 ℃, introducing small nitrogen for treatment for 350s, wherein the flow rate of the small nitrogen is 750 sccm.
Comparative example 5
The comparative example provides a photovoltaic silicon wafer, which is obtained by processing a silicon wafer by a diffusion method, and the specific steps of the diffusion method are mainly different from those of example 1 in that:
knot pushing treatment: and (4) stopping introducing the small nitrogen and the oxygen, maintaining the flow rate of the large nitrogen at 1000sccm, and heating the diffusion furnace from 790 ℃ to 860 ℃ for 880 s.
Comparative example 6
The comparative example provides a photovoltaic silicon wafer, which is obtained by processing a silicon wafer by a diffusion method, and the specific steps of the diffusion method are mainly different from those of example 1 in that:
knot pushing treatment: the small nitrogen and oxygen gas are stopped to be introduced, the flow rate of the large nitrogen is maintained to be 1000sccm, and the temperature of the diffusion furnace is kept at 820 ℃ for treatment for 530 s.
Comparative example 7
The comparative example provides a photovoltaic silicon wafer, which is obtained by processing a silicon wafer by a diffusion method, and the specific steps of the diffusion method are mainly different from those of example 1 in that:
knot pushing treatment: a. primary knot pushing treatment: the small nitrogen and oxygen are stopped to be introduced, the flow of the large nitrogen is maintained to be 1000sccm, and the temperature is 790 ℃ for processing for 530 s. b. Secondary knot pushing treatment: the temperature is increased to 860 ℃ for 350s of treatment.
In summary, the preparation conditions of the deposition treatment and the push-to-tie treatment of examples 1 to 3 and comparative examples 1 to 7 are as shown in table 1:
TABLE 1 preparation conditions for deposition treatment and knot-pushing treatment in examples 1 to 3 and comparative examples 1 to 7
Figure BDA0003496814200000101
Figure BDA0003496814200000111
Application example
The ECV curves of the photovoltaic silicon wafers in example 2 and comparative example 5 were measured and compared using an ECV (Electrochemical capacitance-voltage) tester, as shown in fig. 2. In fig. 2, the abscissa represents junction depth and the ordinate represents doping concentration, and it can be seen from fig. 2 that the surface doping concentration of the photovoltaic silicon wafer in example 2 is lower and the effective doping concentration in the silicon wafer is higher.
When the photovoltaic silicon chips in the embodiments 1 to 3 and the comparative examples 1 to 7 are used for preparing the solar cell, the parameter performance of the cell is shown in the table 2 after being tested by a Halm tester:
TABLE 2 average Performance parameters of the photovoltaic silicon wafers of examples 1-3 and comparative examples 1-7 when fabricated into cells
Figure BDA0003496814200000121
In summary, the silicon wafer of the embodiment of the present application can well increase the light conversion efficiency through two deposition steps and two junction pushing steps during the preparation.
The above description is only an example of the present application and is not intended to limit the scope of the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims (10)

1. A diffusion method for a silicon wafer, comprising the steps of:
firstly, carrying out primary deposition treatment on a pretreated silicon wafer, and then carrying out secondary deposition treatment, wherein the temperature of the secondary deposition treatment is higher than that of the primary deposition treatment;
carrying out primary knot pushing treatment on the silicon wafer; then carrying out secondary knot pushing treatment on the silicon wafer;
the temperature of the primary knot pushing treatment is higher than that of the secondary deposition and lower than that of the secondary knot pushing treatment.
2. The diffusion method for silicon wafers as claimed in claim 1, wherein the temperature of the primary deposition treatment is 700 to 780 ℃; and/or the temperature of the secondary deposition treatment is 720-800 ℃; and/or the temperature of the primary push-knot treatment is 800-840 ℃; and/or the temperature of the secondary knot pushing treatment is 840-880 ℃; and/or the temperature of the secondary deposition treatment is 10-30 ℃ higher than that of the primary deposition treatment; and/or the temperature of the secondary knot pushing treatment is 20-40 ℃ higher than that of the primary knot pushing treatment.
3. The diffusion method for the silicon wafer as claimed in claim 1, wherein the time of the primary junction-pushing treatment is 360-700 s, the time of the secondary junction-pushing treatment is 200-500 s, and the time of the primary junction-pushing treatment is longer than that of the secondary junction-pushing treatment.
4. The diffusion method for silicon wafers according to claim 1, wherein the step of deposition treatment comprises:
the time of the primary deposition treatment is 200-500 s; and/or the time of the secondary deposition treatment is 200-500 s.
5. The diffusion method for silicon wafers as claimed in claim 4, wherein the small nitrogen flow rate of the primary deposition treatment is 500 to 1000 sccm; and/or the small nitrogen flow rate of the secondary deposition treatment is 500-1000 sccm.
6. The diffusion process for silicon wafers according to claim 4 further comprising the steps of:
oxidizing the silicon wafer subjected to the primary deposition treatment for 100-240 s; the oxidation temperature is higher than the temperature of the primary deposition treatment and lower than the temperature of the secondary deposition treatment; optionally, the oxidation temperature is 720-800 ℃.
7. The diffusion method for silicon wafers according to claim 1, wherein the pretreatment step of the silicon wafer comprises: pre-oxidation treatment is carried out on the silicon wafer, wherein the temperature is 700-780 ℃, and the time is 200-400 s.
8. The diffusion method for silicon wafers according to claim 1, further comprising the steps of:
and carrying out three times of deposition treatment on the silicon wafer subjected to the secondary knot pushing treatment, wherein the temperature is 760-780 ℃, and the small nitrogen flow is 1200-2500 sccm.
9. The diffusion method for silicon wafers according to claim 8, further comprising the steps of: and after the third deposition treatment, performing post-oxidation treatment on the silicon wafer for 480-640 s at 760-780 ℃.
10. A photovoltaic silicon wafer, which is obtained by subjecting a silicon wafer to the diffusion method for silicon wafers according to any one of claims 1 to 8.
CN202210117046.6A 2022-02-07 2022-02-07 Diffusion method for silicon wafer and photovoltaic silicon wafer Pending CN114497283A (en)

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