TOPCon battery boron doping method and TOPCon battery

Abstract

The invention provides a boron doping method for a TOPCon battery and the TOPCon battery, and relates to the technical field of solar cells, and the method comprises the following steps: enabling TEOS, O2, B2H6 and H2 to be led to a silicon substrate for PECVD (plasma enhanced chemical vapor deposition) process, depositing on the surface of the silicon substrate to form a BSG layer, and then propelling a boron source in the BSG layer into the silicon substrate to form a doped region. The technical problems that in the prior art, due to the fact that a high-temperature boron diffusion process (the temperature exceeds 1000 DEG C) is adopted, the concentric circle EL of the high-oxygen-content silicon wafer is prone to being poor, the productivity is low, the energy consumption is large, and the production cost is high are solved. The technical effects of reducing the boron diffusion process temperature, reducing the concentric circle proportion, reducing the silicon wafer manufacturing cost, preventing high temperature from damaging hardware and remarkably shortening the process time are achieved.

Description

Technical Field

[0001] This invention relates to the technical field of solar cells, and in particular to a method for boron doping of TOPCon cells and TOPCon cells. Background Technology

[0002] In the production of silicon wafers and ingots, the oxygen content is relatively high at the head and tail of the ingot. After the high-temperature boron diffusion process (temperatures exceeding 1000℃), these parts of the wafer are prone to concentric circle EL defects, which affects the yield of the cells and increases production costs. Furthermore, with intensifying competition in the photovoltaic industry, production needs to reduce costs and increase efficiency, and the high-temperature process, being a high-energy-consuming process, urgently requires improvement and optimization.

[0003] Therefore, there is a need to develop a low-temperature boron diffusion method to replace the traditional high-temperature process, so as to make full use of silicon wafers with high oxygen content and achieve the goal of reducing costs and increasing efficiency.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] One of the objectives of this invention is to provide a method for boron doping in TOPCon batteries, which can not only reduce the boron expansion process temperature at the battery production end, but also significantly shorten the process time, thereby achieving the goal of cost reduction and efficiency improvement.

[0006] The second objective of this invention is to provide a TOPCon battery with good performance.

[0007] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0008] In a first aspect, a method for boron doping in TOPCon batteries includes the following steps:

[0009] TEOS, O2, B2H6 and H2 are introduced into the silicon substrate for PECVD process to deposit a BSG layer on the silicon substrate surface. Then, the boron source in the BSG layer is pushed into the silicon substrate to form a doped region.

[0010] Furthermore, the temperature conditions for the PECVD process are 300℃-400℃;

[0011] The duration of the PECVD process is 30-90 minutes.

[0012] Furthermore, the TEOS is supplied to the silicon substrate via an inert gas source carrier method;

[0013] The flow rate of the inert gas is 200 sccm-5000 sccm.

[0014] Furthermore, the flow rate ratio of O2 to inert gas is 1:(2-15).

[0015] Furthermore, the flow rate of H2 is 500 sccm-8000 sccm.

[0016] Furthermore, the thickness of the BSG layer is 60nm-200nm.

[0017] Furthermore, the silicon substrate includes an N-type silicon wafer with a pyramidal textured surface.

[0018] Furthermore, the temperature at which the boron source propels is 900℃-1100℃.

[0019] Furthermore, the sheet resistance of the doped region is 80Ω-500Ω.

[0020] Secondly, a TOPCon battery is prepared by any of the methods described above.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The boron doping method for TOPCon batteries provided by this invention uses PECVD (plasma-enhanced chemical vapor deposition) to deposit the BSG layer, thereby replacing the traditional high-temperature boron diffusion doping process. This not only reduces the boron diffusion process temperature and the proportion of concentric circles, but also broadens the range of available oxygen content in silicon ingots at the original silicon wafer manufacturing end, reducing silicon wafer manufacturing costs. It also avoids hardware damage caused by high temperatures, reducing equipment maintenance costs. More importantly, the use of TEOS (tetraethyl orthosilicate) and O2 instead of SiH4 and N2O can improve the oxide layer deposition rate. The oxide layer deposition rate using TEOS and O2 can reach 10nm / min-25nm / min, and the process time can be controlled at around 40min. At the same time, due to the lower process temperature, the subsequent cooling time can be reduced to 6min-8min. Therefore, the overall process time is significantly reduced compared to the high-temperature boron diffusion process.

[0023] The TOPCon battery provided by this invention has good working performance. Attached Figure Description

[0024] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0025] Figure 1A process flow diagram of a boron doping method provided in one embodiment of the present invention;

[0026] Figure 2 This is a schematic diagram of a boron-doped structure provided for one embodiment of the present invention.

[0027] Icons: 1-BSG layer; 2-Doped region; 3-Silicon substrate. Detailed Implementation

[0028] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] In existing technologies, high-temperature boron diffusion processes, with temperatures exceeding 1000℃, easily lead to concentric circle EL defects in silicon wafers with high oxygen content. Furthermore, the conventional furnace tube process in high-temperature boron diffusion takes 90-120 minutes, requiring an additional 20-30 minutes of cooling after completion, resulting in low production capacity. In addition, the high-temperature equipment consumes a large amount of energy, increasing energy costs, and the quartz furnace tubes are prone to deformation and damage under prolonged high-temperature operation, leading to high production costs. To address these problems, this invention is proposed.

[0030] According to a first aspect of the present invention, a method for boron doping in TOPCon batteries is provided, comprising the following steps:

[0031] TEOS, O2, B2H6 and H2 are introduced into the silicon substrate for PECVD process to deposit a BSG layer on the silicon substrate surface. Then, the boron source in the BSG layer is pushed into the silicon substrate to form a doped region.

[0032] The boron doping method for TOPCon batteries provided by this invention uses PECVD to deposit a BSG layer, thereby replacing the traditional high-temperature boron diffusion doping process. This not only reduces the boron diffusion process temperature and the proportion of concentric circles, but also broadens the range of available oxygen content in silicon ingots at the original silicon wafer manufacturing end, reducing silicon wafer manufacturing costs. It also avoids hardware damage caused by high temperatures, reducing equipment maintenance costs. More importantly, the use of TEOS (tetraethyl orthosilicate) and O2 instead of SiH4 and N2O can improve the oxide layer deposition rate. The oxide layer deposition rate using TEOS and O2 can reach 10nm / min-25nm / min, and the process time can be controlled at around 40min. At the same time, due to the lower process temperature, the subsequent cooling time can be reduced to 6min-8min. Therefore, the overall process time is significantly reduced compared to the high-temperature boron diffusion process.

[0033] In a preferred embodiment, the temperature conditions of the PECVD process can be 300°C-400°C, and typical but non-limiting temperature conditions are, for example, 300°C, 320°C, 340°C, 360°C, 380°C, and 400°C; the duration of the PECVD process can be 30 min-90 min, and typical but non-limiting durations are, for example, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, and 90 min.

[0034] The temperature and duration of the PECVD process in this invention are coordinated to better facilitate the deposition and formation of a BSG layer on the silicon substrate surface.

[0035] In this invention, the deposition thickness of the BSG layer can be 60nm-200nm, and typical but non-limiting deposition thicknesses are, for example, 60nm, 70nm, 80nm, 90nm, 100nm, 120nm, 140nm, 160nm, 180nm, and 200nm.

[0036] In a preferred embodiment, the silicon substrate comprises an N-type silicon wafer with a pyramidal textured surface.

[0037] Texturing a silicon substrate can produce a silicon substrate with a textured surface.

[0038] In a preferred embodiment, TEOS can be introduced to the silicon substrate via an inert gas source carrier method. The flow rate of the inert gas can be 200 sccm-5000 sccm, with typical but non-limiting flow rates such as 200 sccm, 400 sccm, 600 sccm, 800 sccm, 1000 sccm, 1500 sccm, 2000 sccm, 2500 sccm, 3000 sccm, 3500 sccm, 4000 sccm, 4500 sccm, and 5000 sccm.

[0039] In this invention, the inert gas can be Ar, but is not limited to it; TEOS is introduced into the furnace tube by Ar carrying source method, and the heating temperature of TEOS source bottle can be 100-200℃, for example, 100℃, 120℃, 140℃, 160℃, 180℃, 200℃, but is not limited to it, which is more conducive to further improving the deposition effect of BSG layer.

[0040] In a preferred embodiment, the flow ratio of O2 to inert gas can be 1:(2-15), which is more conducive to further improving the deposition effect of the BSG layer.

[0041] In a preferred embodiment, the flow rate of H2 can be 500 sccm-8000 sccm, with typical but non-limiting flow rates such as 500 sccm, 600 sccm, 800 sccm, 1000 sccm, 1500 sccm, 2000 sccm, 2500 sccm, 3000 sccm, 3500 sccm, 4000 sccm, 4500 sccm, 5000 sccm, 5500 sccm, 6000 sccm, 6500 sccm, 7000 sccm, 7500 sccm, and 8000 sccm, which is more conducive to further improving the deposition effect of the BSG layer.

[0042] This invention uses PECVD process to deposit a BSG layer on the surface of a silicon substrate. Through the synergistic effect of TEOS, O2, B2H6 and H2 and their specific parameters, it can not only reduce the temperature of the boron diffusion process at the battery production end, but also significantly shorten the process time, thus achieving the goal of cost reduction and efficiency improvement.

[0043] In this invention, a high-temperature propulsion method is used to propel the boron source in the BSG layer into the silicon substrate to form a doped region.

[0044] In a preferred embodiment, the temperature for high-temperature propulsion can be 900°C-1100°C.

[0045] In a preferred embodiment, the sheet resistance of the doped region can be 80Ω-500Ω, with typical but non-limiting sheet resistances such as 80Ω, 100Ω, 150Ω, 200Ω, 250Ω, 300Ω, 350Ω, 400Ω, 450Ω, and 500Ω.

[0046] In this invention, after the boron source is pushed into the silicon substrate to form a doped region, the edge of the silicon substrate can be cut by a laser SE process to remove the edge BSG layer.

[0047] A typical method for boron doping in TOPCon batteries is shown in the flowchart. Figure 1 This includes the following steps:

[0048] Step 1: Select an N-type silicon wafer as the silicon substrate, clean the silicon wafer with an alkaline solution, and then perform texturing on the front and back sides to form a pyramid textured surface, thus obtaining an N-type silicon wafer with a pyramid textured surface.

[0049] Step 2: Deposit a BSG layer (borosilicate glass layer) on the textured silicon wafer using PECVD;

[0050] The deposition method for the BSG layer is as follows:

[0051] TEOS, O2, B2H6 and H2 are introduced into the furnace tube, and a BSG layer is deposited on the front side of the silicon substrate by PECVD process. The thickness of the BSG layer is 60nm-200nm.

[0052] Among them, TEOS is introduced into the furnace tube through Ar source carrying method, the heating temperature of TEOS source bottle is 100℃-200℃, and the flow rate of Ar is 200sccm-5000sccm.

[0053] The flow rate ratio of O2 to Ar is 1:(2-15); the flow rate of H2 is 500 sccm-8000 sccm;

[0054] The deposition temperature of PECVD is 300℃-400℃, and the deposition time of PECVD is 30min-90min;

[0055] Step 3: A high-temperature propulsion method is used to form doped regions in the silicon substrate;

[0056] See the schematic diagram of the boron-doped structure. Figure 2 The boron source in BSG layer 1 is pushed into the silicon substrate 3 to form doped region 2;

[0057] The temperature for boron source propulsion is 900℃-1100℃; the sheet resistance of the doped region is 80Ω-500Ω.

[0058] In summary, with the synergistic effect of each step and its process parameters, the boron doping method of the present invention not only reduces the boron diffusion process temperature and the proportion of concentric circles, but also broadens the range of available oxygen content in silicon ingots at the original silicon wafer manufacturing end. At the same time, it can improve the oxide layer deposition rate and reduce the subsequent cooling time, thus significantly shortening the overall process time, which is significantly better than the traditional high-temperature boron diffusion process.

[0059] According to a third aspect of the present invention, a TOPCon battery is provided, which is prepared by the method described in any of the preceding claims.

[0060] The TOPCon battery provided by this invention has good working performance.

[0061] The present invention will be further illustrated by the following examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or purchased directly from the market.

[0062] Example 1

[0063] A method for boron doping in TOPCon batteries includes the following steps:

[0064] Step 1: Select an N-type silicon wafer as the silicon substrate, clean the silicon wafer with an alkaline solution, and then perform texturing on the front and back sides to form a pyramid textured surface, thus obtaining an N-type silicon wafer with a pyramid textured surface.

[0065] Step 2: Deposit a BSG layer (borosilicate glass layer) on the textured silicon wafer using PECVD;

[0066] The deposition method for the BSG layer is as follows:

[0067] TEOS, O2, B2H6 and H2 are introduced into the furnace tube, and a BSG layer is deposited on the front side of the silicon substrate by PECVD process. The thickness of the BSG layer is 100nm.

[0068] Among them, TEOS is introduced into the furnace tube through Ar source, the heating temperature of the TEOS source bottle is 150℃, and the flow rate of Ar is 2600sccm;

[0069] The flow rate ratio of O2 to Ar is 1:8; the flow rate of B2H6 is 3000 sccm, and the flow rate of H2 is 4200 sccm.

[0070] The PECVD deposition temperature was 350℃, and the PECVD deposition time was 60 min.

[0071] Step 3: Using a high-temperature propulsion method, the boron source in the BSG layer is pushed into the silicon substrate to form a doped region;

[0072] The boron source propulsion temperature is 1000℃; the sheet resistance of the doped region is 290Ω.

[0073] Subsequently, the edges of the silicon substrate are cut using a laser SE process to remove edge BSG.

[0074] Example 2

[0075] This embodiment provides a method for boron doping of TOPCon batteries. The difference from Embodiment 1 is that in step 2, the Ar flow rate is 200 sccm.

[0076] The remaining steps and their process parameters are the same as in Example 1.

[0077] Example 3

[0078] This embodiment provides a method for boron doping of TOPCon batteries. The difference from Embodiment 1 is that in step 2, the Ar flow rate is 5000 sccm.

[0079] The remaining steps and their process parameters are the same as in Example 1.

[0080] Example 4

[0081] This embodiment provides a method for boron doping of TOPCon batteries. The difference from Embodiment 1 is that in step 2, the flow rate ratio of O2 to Ar is 1:2.

[0082] The remaining steps and their process parameters are the same as in Example 1.

[0083] Example 5

[0084] This embodiment provides a method for boron doping of TOPCon batteries. The difference from Embodiment 1 is that in step 2, the flow rate ratio of O2 to Ar is 1:15.

[0085] The remaining steps and their process parameters are the same as in Example 1.

[0086] Example 6

[0087] This embodiment provides a method for boron doping of TOPCon batteries. The difference from Embodiment 1 is that in step 2, the H2 flow rate is 500 sccm.

[0088] The remaining steps and their process parameters are the same as in Example 1.

[0089] Example 7

[0090] This embodiment provides a method for boron doping of TOPCon batteries. The difference from Embodiment 1 is that in step 2, the H2 flow rate is 8000 sccm.

[0091] The remaining steps and their process parameters are the same as in Example 1.

[0092] Example 8

[0093] This embodiment provides a method for boron doping of TOPCon batteries. The difference from Embodiment 1 is that in step 2, the deposition temperature of PECVD is 300°C.

[0094] The remaining steps and their process parameters are the same as in Example 1.

[0095] Example 9

[0096] This embodiment provides a method for boron doping of TOPCon batteries. The difference from Embodiment 1 is that in step 2, the deposition temperature of PECVD is 400°C.

[0097] The remaining steps and their process parameters are the same as in Example 1.

[0098] Comparative Example 1

[0099] This comparative example provides a method for boron doping of TOPCon batteries. The difference from Example 1 is that in step 2, the deposition temperature of PECVD is 250°C.

[0100] The remaining steps and their process parameters are the same as in Example 1.

[0101] Compared with Example 1, the drawback of this comparative example is that the expansion and diffusion rate of B2H6 is slower, the gas does not diffuse sufficiently, the BSG deposition uniformity is poor, and there are uncoated areas.

[0102] Comparative Example 2

[0103] This comparative example provides a method for boron doping of TOPCon batteries. The difference from Example 1 is that in step 2, the deposition temperature of PECVD is 450°C.

[0104] The remaining steps and their process parameters are the same as in Example 1.

[0105] Compared with Example 1, the drawback of this comparative example is that the thermal decomposition of B2H6 at high temperature results in a low ionization decomposition ratio and a low BSG doping concentration.

[0106] Comparative Example 3

[0107] This comparative example provides a method for boron doping in TOPCon batteries, which employs a traditional high-temperature boron doping process, as follows:

[0108] 1. The texturized silicon wafer is placed in a plasma-enhanced chemical vapor deposition (PECVD) apparatus, and then SiH4, NO2, trimethyl borate (as a boron source) and H2 are introduced into the silicon substrate to deposit a borosilicate glass layer on the front side of the silicon substrate.

[0109] Wherein: the flow rate of SiH4 is 1000 sccm, the flow rate of N2O is 8000 sccm, and the flow rate ratio of SiH4 to N2O is 1:8;

[0110] The flow rate of H2 is 8000 sccm, and the flow rate of trimethyl borate is 10000 sccm.

[0111] The deposition process parameters for plasma-enhanced chemical vapor deposition are: deposition temperature 400℃, radio frequency power 25000W, deposition pressure 5000mbar, and deposition time 30min.

[0112] Compared with Example 1, the drawback of this comparative example is that the process temperature exceeds 1000°C, which makes silicon wafers with high oxygen content prone to concentric circle EL defects; at the same time, the production capacity is low, the energy consumption is high, resulting in high production costs.

[0113] Test case

[0114] The concentric circle ratio and overall process time of the boron-doped silicon wafers in Examples 1-9 and Comparative Examples 1-3 are shown in Table 1.

[0115] Table 1

[0116]

[0117] Therefore, the boron doping method for TOPCon batteries provided by this invention uses PECVD process to deposit BSG layer. Compared with the traditional high-temperature boron expansion process, it not only reduces the boron expansion process temperature and the proportion of concentric circles, but also broadens the range of available oxygen content in silicon ingots at the original silicon wafer manufacturing end. At the same time, it can improve the oxide layer deposition rate and reduce the subsequent cooling time, thus significantly shortening the overall process time.

[0118] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for boron doping in TOPCon batteries, characterized in that, Includes the following steps: TEOS, O2, B2H6 and H2 are introduced into the silicon substrate for PECVD process to deposit a BSG layer on the silicon substrate surface. Then, the boron source in the BSG layer is pushed into the silicon substrate to form a doped region.

2. The method according to claim 1, characterized in that, The temperature conditions for the PECVD process are 300℃-400℃; The duration of the PECVD process is 30-90 minutes.

3. The method according to claim 1, characterized in that, The TEOS is supplied to the silicon substrate via an inert gas source carrier method; The flow rate of the inert gas is 200 sccm-5000 sccm.

4. The method according to claim 3, characterized in that, The flow rate ratio of O2 to inert gas is 1:(2-15).

5. The method according to claim 1, characterized in that, The flow rate of H2 is 500 sccm-8000 sccm.

6. The method according to any one of claims 1-5, characterized in that, The thickness of the BSG layer is 60nm-200nm.

7. The method according to claim 6, characterized in that, The silicon substrate includes an N-type silicon wafer with a pyramidal textured surface.

8. The method according to claim 1, characterized in that, The temperature for propulsion by the boron source is 900℃-1100℃.

9. The method according to claim 8, characterized in that, The sheet resistance of the doped region is 80Ω-500Ω.

10. A TOPCon battery, characterized in that, It is prepared by the method described in any one of claims 1-9.

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