PE-poly process method for variable phosphorane flow multi-layer in-situ doped amorphous silicon layer

Abstract

The invention discloses a PE-poly process method of a variable phosphorane flow multilayer in-situ doped amorphous silicon layer, and belongs to the technical field of photovoltaic solar cell preparation, and the PE-poly process method comprises the following steps: S1, pre-treating an N-type silicon substrate; s2, growing a tunneling oxide layer on the surface of the N-type silicon substrate: carrying out reaction on the back surface of the N-type silicon substrate by utilizing laughing gas through a PECVD (Plasma Enhanced Chemical Vapor Deposition) technology to generate the tunneling oxide layer; s3, adjusting and controlling the flow of phosphorane step by step to grow a phosphorus-doped amorphous silicon film on the tunneling oxide layer: respectively introducing the phosphorane with increasing flow and silane and hydrogen with equal flow in four stages, applying conditions such as corresponding pressure and radio frequency power supply frequency, and depositing to generate the phosphorus-doped amorphous silicon film; and S4, carrying out a post-treatment process. Compared with the prior art, the method has the advantages that the phosphorus doping concentration is increased without increasing the phosphorane consumption through multi-stage regulation and control of the phosphorane flow, the limitation that the phosphorus doping concentration is increased by directly increasing the phosphorane consumption is avoided, and the passivation effect of a polycrystalline silicon field is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of photovoltaic solar cell preparation, and in particular relates to a PE-poly process method for in-situ doping of amorphous silicon layers with variable phosphine flow rates. Background Art

[0002] PE-poly is a solar cell manufacturing process using PECVD technology. It is a key step in the preparation of TOPCon cells. Its main function is to prepare high-quality ultra-thin oxide layers and doped polysilicon to achieve full back-side efficiency of the cell. This process integrates oxide layers, poly layers, and polysilicon layers, which is conducive to improving the performance and stable control of the cell. Compared with traditional LPCVD (low-pressure vapor deposition), it has a more streamlined process and better yield, and lower production costs. This process also has advantages in solving winding plating and quartz tube losses.

[0003] However, the current phosphorus doping concentration of the polysilicon layer is not ideal. Although simply increasing the phosphine consumption can increase the doping concentration to a certain extent, this method will not only increase production costs, but will also cause damage to the oxide layer to a certain extent, thereby reducing the efficiency of solar cells.

[0004] Therefore, developing a process method that can effectively increase the phosphorus doping concentration of polysilicon, control production costs and stabilize battery performance is of great significance for promoting the improvement of TOPCon battery performance and mass production.

[0005] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0006] The object of the present invention is to provide a PE-poly process method for in-situ doping of amorphous silicon layers with multiple layers of variable phosphine flow, which can adjust the phosphine concentration from low to high in four stages, improve the phosphorus doping concentration without increasing the phosphine consumption and time, and at the same time achieve an improved polysilicon field passivation effect.

[0007] In order to achieve the above object, a technical solution provided by a specific embodiment of the present invention is as follows:

[0008] A PE-poly process method for in-situ doping of amorphous silicon layers with variable phosphine flow rate, comprising the following steps:

[0009] S1, N-type silicon substrate pretreatment;

[0010] S2. Growth of tunnel oxide layer on the surface of N-type silicon substrate: Using PECVD technology, nitrous oxide is used to react on the back of N-type silicon substrate to generate tunnel oxide layer;

[0011] S3, gradually regulating the flow rate of phosphine to grow a phosphorus-doped amorphous silicon film on the tunnel oxide layer: introducing phosphine with increasing flow rates and silane and hydrogen with equal flow rates in four stages, and then applying corresponding pressure, radio frequency power supply frequency and other conditions to deposit and generate a phosphorus-doped amorphous silicon film;

[0012] S4, post-processing process.

[0013] In one or more embodiments of the present invention, in S3, the flow rates of the phosphine introduced in four stages are 150 sccm, 200 sccm, 600 sccm and 750 sccm respectively.

[0014] In one or more embodiments of the present invention, in S3, the phosphorus doping concentration of the phosphorus doped amorphous silicon film is (6-8)*10 20 atoms / cm 3 The thickness of the phosphorus-doped amorphous silicon film is 70 to 90 nm.

[0015] In one or more embodiments of the present invention, the phosphorus-doped amorphous silicon film sequentially includes a low-doped poly layer, a medium-doped poly layer, a first high-doped poly layer, and a second high-doped poly layer;

[0016] The doping concentration of the low-doped poly layer is (1.5-2)*10 20 cm 3 ;

[0017] The doping concentration of the middle doped poly layer is (3-4)*10 20 cm 3 ;

[0018] The phosphorus doping concentration of the first highly doped poly layer and the second highly doped poly layer is (5-6)*10 20 cm 3 .

[0019] In one or more embodiments of the present invention, the thickness of the low-doped poly layer is 5 to 10 nm;

[0020] The thickness of the doped poly layer is 15 to 25 nm;

[0021] The thickness of the first highly doped poly layer is 40-50 nm;

[0022] The thickness of the second highly doped poly layer is 10-20 nm.

[0023] In one or more embodiments of the present invention, in S3, the silane flow rate is 2000-3000 sccm, and the hydrogen flow rate is 10000-12000 sccm;

[0024] The deposition temperature is 400-500° C., the deposition time is 700s-800s, the deposition pressure is 2500-3500Pa, the radio frequency power supply power is 12000W-16000W, and the switch ratio is 1:13.

[0025] In one or more embodiments of the present invention, in S2, the laughing gas flow rate is 8000-10000 sccm;

[0026] The reaction temperature is 400-500° C., the reaction time is 70-90 s, the reaction pressure is 1500-2000 Pa, the radio frequency power supply power is 15000-20000 W, and the switch ratio is 1:80.

[0027] In one or more embodiments of the present invention, in S2, the tunneling oxide layer is a silicon dioxide layer, and the thickness of the tunneling oxide layer is 2 nm.

[0028] In one or more embodiments of the present invention, the N-type silicon substrate pretreatment includes texturing, boron diffusion, and alkali polishing in sequence.

[0029] In one or more embodiments of the present invention, the post-treatment process includes annealing, alkali polishing, front aluminum oxide passivation, front silicon nitride passivation, back silicon nitride passivation, and double-sided metallization in sequence.

[0030] Compared with the prior art, the present invention uses PECVD technology to first generate a silicon dioxide oxide layer on the back of an N-type silicon substrate using laughing gas, and then introduces silane with equal flow rates and phosphine with different flow rates in four stages, wherein the flow rate of phosphine increases with the progress of the stages, and corresponding pressure, radio frequency power supply frequency and other conditions are applied to achieve multi-layer in-situ doped phosphorus amorphous silicon layers;

[0031] By multi-stage regulation of the phosphine flow rate, the phosphorus doping concentration can be increased without increasing the phosphine consumption, thus avoiding the limitation of directly increasing the phosphine consumption to increase the phosphorus doping concentration and improving the field passivation effect of polysilicon. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 This is a flow chart of a PE-poly process method for in-situ doping of amorphous silicon layers with variable phosphine flow rates in one embodiment of the present invention;

[0034] Figure 2 It is a schematic diagram of the film layer structure on the back side of a TOPCon cell in a PE-poly process method of a multi-layer in-situ doping of an amorphous silicon layer with a variable phosphine flow rate in one embodiment of the present invention;

[0035] Figure 3 This is a batch-cut phosphine gradient experiment efficiency trend diagram of a PE-poly process method for in-situ doping of amorphous silicon layers with a variable phosphine flow rate in one embodiment of the present invention.

[0036] Description of main reference numerals:

[0037] 10. N-type silicon substrate; 20. tunneling oxide layer; 30. phosphorus-doped amorphous silicon film; 31. low-doped poly layer; 32. medium-doped poly layer; 33. first high-doped poly layer; 34. second high-doped poly layer. DETAILED DESCRIPTION

[0038] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0039] like Figure 1 and Figure 2 As shown, the purpose of the present invention is to improve the problems of low polysilicon phosphorus active doping concentration and deviation in polysilicon field passivation effect when polysilicon is doped with phosphorus using plasma enhanced chemical vapor deposition (PECVD) technology.

[0040] A PE-poly process method for in-situ doping of an amorphous silicon layer with a variable phosphine flow rate in one embodiment of the present invention comprises the following steps:

[0041] S1 . Pretreatment of the N-type silicon substrate 10 .

[0042] Specifically, the pretreatment of the N-type silicon substrate 10 includes texturing, boron diffusion, and alkaline polishing in sequence.

[0043] S2. Growth of a tunneling oxide layer 20 on the surface of the N-type silicon substrate 10: The tunneling oxide layer 20 is generated by reacting nitrous oxide (N2O) on the back side of the N-type silicon substrate 10 using PECVD technology.

[0044] Specifically, the parameters for growing the tunnel oxide layer 20 by the PECVD process are: nitrous oxide flow rate is 9600 sccm; reaction temperature is 430° C., reaction time is 82 s, reaction pressure is 1900 Pa, RF power is 16000 W, and switch ratio is 1:80.

[0045] The tunnel oxide layer 20 is a silicon dioxide layer, and the thickness of the tunnel oxide layer 20 is 2 nm.

[0046] S3. Regulating the flow rate of phosphine step by step to grow a phosphorus-doped amorphous silicon film 30 on the tunnel oxide layer 20: introducing phosphine with increasing flow rates and silane and hydrogen with equal flow rates in four stages, and then applying corresponding pressure, RF power frequency and other conditions to deposit and generate the phosphorus-doped amorphous silicon film 30.

[0047] Specifically, the parameters of the PECVD process for depositing the phosphorus-doped amorphous silicon film 30 are: silane flow rate is 2400sccm, hydrogen flow rate is 10000sccm; deposition temperature is 430°C, deposition time is 700s~800s, deposition pressure is 3100Pa, RF power is 12000W~16000W, and the switching ratio is 1:13.

[0048] In S3, the phosphorus doping concentration of the phosphorus doped amorphous silicon film 30 is 6.77*10 20 atoms / cm 3 , the thickness of the phosphorus-doped amorphous silicon film 30 is 86 nm.

[0049] The phosphorus-doped amorphous silicon film 30 includes a low-doped poly layer 31 , a medium-doped poly layer 32 , a first high-doped poly layer 33 and a second high-doped poly layer 34 in sequence.

[0050] The phosphine flow rates introduced in four stages are 150 sccm, 200 sccm, 600 sccm and 750 sccm, respectively, forming a low-doped poly layer 31, a medium-doped poly layer 32, a first highly-doped poly layer 33 and a second highly-doped poly layer 34.

[0051] The doping concentration of the low-doped poly layer 31 is 1.98*10 20 cm 3 The doping concentration of the doped poly layer 32 is 3.54*10 20 cm 3 The phosphorus doping concentration of the first highly doped poly layer 33 and the second highly doped poly layer 34 is 5.18*10 20 cm 3 .

[0052] The thickness of the low-doped poly layer 31 is 8 nm; the thickness of the medium-doped poly layer 32 is 20 nm; the thickness of the first high-doped poly layer 33 is 42 nm; and the thickness of the second high-doped poly layer 34 is 15 nm.

[0053] S4, post-processing process.

[0054] The post-processing process includes annealing, alkali polishing, front aluminum oxide passivation, front silicon nitride passivation, back silicon nitride passivation, and double-sided metallization.

[0055] The specific embodiments are as follows:

[0056] Provide an N-type silicon substrate 10 that has been processed through all previous steps and has been in normal production line operation. Now, a tunnel oxide layer 20 and a phosphorus-doped amorphous silicon film 30 need to be prepared. The steps are as follows:

[0057] 1 A tunneling oxide layer 20 is grown on the back of an N-type silicon substrate 10 by PECVD, wherein the process parameters are: temperature 430°C, reaction pressure 1900Pa, reaction time 82s, nitrous oxide flow 9600sccm, power 16000W, and switch ratio 1:80. In this step, the oxide layer prepared is silicon dioxide with a thickness of 2nm.

[0058] 2 After the growth of the silicon dioxide oxide layer is completed, stop introducing nitrous oxide, and introduce phosphine in four stages with flow rates of 150sccm, 200sccm, 600sccm and 750sccm, respectively. Other process parameters are: hydrogen flow rate 10000sccm; deposition temperature 430℃, deposition time 700s~800s, deposition pressure 3100Pa, RF power 12000W~16000W, and switch ratio 1:13. In this step, the phosphorus doping concentration of the prepared phosphorus-doped amorphous silicon film 30 is 6.77*10 20 atoms / cm 3 , thickness is 86nm.

[0059] like Figure 3 Combined with the table below, it can be obtained that the electrical performance data of the solar cells tested after the normal circulation is completed according to the production line process, the battery efficiency reaches 26.035%, and the short-circuit current is increased by 25mA, with obvious improvement effects.

[0060]

[0061] Compared with the prior art, the present invention uses PECVD technology to first generate a silicon dioxide oxide layer on the back of an N-type silicon substrate (10) using laughing gas, and then introduces silane with equal flow rates and phosphine with different flow rates in four stages, wherein the flow rate of phosphine increases as the stages proceed, and corresponding pressure, radio frequency power supply frequency and other conditions are applied to achieve multi-layer in-situ doped phosphorus amorphous silicon layers;

[0062] By multi-stage regulation of the phosphine flow rate, the phosphorus doping concentration can be increased without increasing the phosphine consumption, thus avoiding the limitation of directly increasing the phosphine consumption to increase the phosphorus doping concentration and improving the field passivation effect of polysilicon.

[0063] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0064] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A PE-poly process for in-situ doping of amorphous silicon layers with variable phosphine flow, characterized in that: The following steps are involved: S1, N-type silicon substrate pretreatment; S2. Growth of tunnel oxide layer on the surface of N-type silicon substrate: Using PECVD technology, nitrous oxide is used to react on the back of N-type silicon substrate to generate tunnel oxide layer; S3, gradually regulating the flow rate of phosphine to grow a phosphorus-doped amorphous silicon film on the tunnel oxide layer: introducing phosphine with increasing flow rates and silane and hydrogen with equal flow rates in four stages, and then applying corresponding pressure, radio frequency power supply frequency and other conditions to deposit and generate a phosphorus-doped amorphous silicon film; S4, post-processing process.

2. The PE-poly process of variable phosphine flow multilayer in-situ doping amorphous silicon layer according to claim 1, characterized in that: In S3, the flow rates of the phosphine introduced in four stages are 150 sccm, 200 sccm, 600 sccm and 750 sccm respectively.

3. The PE-poly process of variable phosphine flow multilayer in-situ doping amorphous silicon layer according to claim 1, characterized in that: In S3, the phosphorus doping concentration of the phosphorus doped amorphous silicon film is (6-8)*10 20 atoms / cm 3 The thickness of the phosphorus-doped amorphous silicon film is 70 to 90 nm.

4. The PE-poly process of variable phosphine flow multilayer in-situ doping amorphous silicon layer according to claim 3, characterized in that: The phosphorus-doped amorphous silicon film sequentially comprises a low-doped poly layer, a medium-doped poly layer, a first high-doped poly layer and a second high-doped poly layer; The doping concentration of the low-doped poly layer is (1.5-2)*10 20 atoms / cm 3 ; The doping concentration of the middle doped poly layer is (3-4)*10 20 atoms / cm 3 ; The doping concentration of the first highly doped poly layer and the second highly doped poly layer is (5-6)*10 20 atoms / cm 3 .

5. The PE-poly process of variable phosphine flow multilayer in-situ doping amorphous silicon layer according to claim 4, characterized in that: The thickness of the low-doped poly layer is 5 to 10 nm; The thickness of the doped poly layer is 15 to 25 nm; The thickness of the first highly doped poly layer is 40-50 nm; The thickness of the second highly doped poly layer is 10-20 nm.

6. The PE-poly process of variable phosphine flow multilayer in-situ doping amorphous silicon layer according to claim 1, characterized in that: In S3, the silane flow rate is 2000-3000 sccm, and the hydrogen flow rate is 10000-12000 sccm; The deposition temperature is 400-500° C., the deposition time is 700s-800s, the deposition pressure is 2500-3500Pa, the radio frequency power supply power is 12000W-16000W, and the switch ratio is 1:

13.

7. The PE-poly process of variable phosphine flow multilayer in-situ doping amorphous silicon layer according to claim 1, characterized in that: In S2, the laughing gas flow rate is 8000-10000 sccm; The reaction temperature is 400-500° C., the reaction time is 70-90 s, the reaction pressure is 1500-2000 Pa, the radio frequency power supply power is 15000-20000 W, and the switch ratio is 1:

80.

8. The PE-poly process of variable phosphine flow multi-layer in-situ doping amorphous silicon layer according to claim 1, characterized in that: In S2, the tunneling oxide layer is a silicon dioxide layer, and the thickness of the tunneling oxide layer is 2 nm.

9. The PE-poly process of variable phosphine flow multi-layer in-situ doping amorphous silicon layer according to claim 1, characterized in that: The N-type silicon substrate pretreatment includes texturing, boron diffusion, and alkaline polishing in sequence.

10. The PE-poly process of variable phosphine flow multi-layer in-situ doping amorphous silicon layer according to claim 1, characterized in that: The post-treatment process includes annealing, alkali polishing, front aluminum oxide passivation, front silicon nitride passivation, back silicon nitride passivation, and double-sided metallization in sequence.

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