Graphite boat saturation method and application suitable for PECVD tunneling polycrystalline layer deposition process

Abstract

The present invention belongs to the technical field of back contact battery, and specifically relates to a graphite boat saturation method and application suitable for PECVD deposition tunneling polycrystalline layer process, the graphite boat saturation method includes: depositing silicon nitride film on the surface of graphite boat, then turning on the glow for hydrogen treatment, and then depositing silicon oxide film on the graphite boat obtained after the hydrogen treatment; wherein, the thickness of silicon nitride film is 50-100nm, and the thickness of silicon oxide film is 375-700nm; and the conditions of the hydrogen treatment include: controlling the flow rate of hydrogen introduced to be 10000-20000sccm, the power is 6000-10000W, and the reaction time is 600-1800s. The present invention can deposit high-quality tunneling polycrystalline layer, improve the passivation level, improve the conversion efficiency of the battery, solve the influence of graphite boat saturation on the first few rounds of coating, improve the production yield, and the graphite boat saturation method of the present invention can greatly shorten the pickling time of graphite boat.

Description

Technical Field

[0001] The invention belongs to the technical field of back contact batteries, and in particular relates to a graphite boat saturation method and application suitable for a PECVD tunneling polycrystalline layer deposition process. Background Art

[0002] Tubular PECVD is widely used in solar cells. The saturation effect of the graphite boat affects the coating effect of tubular PECVD to a considerable extent. If the saturation process of the graphite boat cannot be controlled well, the cell efficiency will be greatly affected.

[0003] At present, tubular PECVD is mainly used to deposit silicon nitride in the industry, so the traditional graphite boat saturation process mainly uses silicon nitride saturation. With the continuous improvement of PECVD technology, the industry currently uses more tubular PECVD to deposit tunneling polysilicon processes. Since the tunneling polycrystalline process requires the deposition of a high-quality tunneling oxide layer to ensure excellent interface passivation, when using the traditional graphite boat silicon nitride saturation method, when the tunneling oxide layer is grown by nitrous oxide plasma bombardment, the nitrous oxide will corrode the graphite boat and dope the nitrogen element in the silicon nitride into the oxide layer, resulting in a serious decrease in the passivation level, affecting the battery efficiency. With the increase in the number of coating times, this effect can be gradually reduced, and the pickling time is long.

[0004] It should be noted that this part of the present invention only provides background technology related to the present invention and does not necessarily constitute prior art or known technology. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects of the conventional graphite boat saturation method in the prior art that the passivation level is seriously reduced, affecting the battery efficiency, and to provide a graphite boat saturation method and application suitable for PECVD deposition of tunneling polycrystalline layers, which can deposit high-quality tunneling polycrystalline layers, improve the passivation level, improve the conversion efficiency of the battery, solve the influence of graphite boat saturation on the previous rounds of coating, and improve the production yield. At the same time, the graphite boat saturation method used in the present invention can greatly shorten the pickling time of the graphite boat compared to the existing silicon nitride saturation process.

[0006] In order to achieve the above-mentioned purpose, in the first aspect, the present invention provides a graphite boat saturation method suitable for PECVD deposition of tunneling polycrystalline layer process, comprising: depositing a silicon nitride film on the surface of the graphite boat, then turning on the glow for hydrogen treatment, and then depositing a silicon oxide film on the graphite boat obtained after the hydrogen treatment; wherein the thickness of the silicon nitride film is 50-100nm, and the thickness of the silicon oxide film is 375-700nm; and the conditions of the hydrogen treatment include: controlling the flow rate of the introduced hydrogen to be 10000-20000sccm, the power to be 6000-10000W, and the reaction time to be 600-1800s.

[0007] In some preferred embodiments of the present invention, the hydrogen treatment conditions further include: a hydrogen treatment temperature of 400-450° C. and a reaction pressure of 2000-4000 mtorr.

[0008] In some preferred embodiments of the present invention, the conditions for depositing the silicon nitride film include: a temperature of 430-530° C., a pressure of 2000-4000 mtorr, a power of 4000-6000 W, and a reaction time of 15-20 min.

[0009] In some preferred embodiments of the present invention, the conditions for depositing the silicon nitride film include: the reaction gases are ammonia gas and silane gas, the silane flow rate is 1200-2000 sccm, and the NH3 flow rate is 5000-8000 sccm.

[0010] In some preferred embodiments of the present invention, the conditions for depositing the silicon oxide film include: temperature of 430-530° C., pressure of 1000-1500 mtorr, power of 4000-6000 W, and reaction time of 90-180 min.

[0011] In some preferred embodiments of the present invention, the conditions for depositing the silicon oxide film include: the reaction gases are silane and nitrous oxide, the silane flow rate is 600-1000 sccm, and the nitrous oxide flow rate is 1600-3000 sccm.

[0012] In some preferred embodiments of the present invention, the graphite boat saturation method further comprises: first cleaning the graphite boat, then baking it in the presence of nitrogen, and then depositing the silicon nitride film.

[0013] In some preferred embodiments of the present invention, the baking conditions include: the temperature in the furnace tube is kept constant at 400-600° C., nitrogen is purged, the nitrogen flow rate is 8-10 slm, the chamber pressure is 2000-5000 mtorr, and the baking time is 90-360 min.

[0014] In some preferred embodiments of the present invention, the cleaning process includes: first pickling the graphite boat with a mixed solution containing hydrofluoric acid and nitric acid, and then overflow cleaning the graphite boat with pure water after pickling; wherein the mass concentration of hydrofluoric acid in the mixed solution is 2%-10%, the mass concentration of nitric acid is 0.1%-0.5%, the cleaning time of pickling is 200-360min, and the time of overflow cleaning is 180-360min.

[0015] In some preferred embodiments of the present invention, the thickness d of the silicon oxide film is adjusted according to the deposition temperature T of the tunneling polycrystalline layer and satisfies: d=(T / 2)×α, α is 1.3-3.5, the unit of d is nm, and the unit of T is °C.

[0016] In a second aspect, the present invention provides a saturated graphite boat suitable for PECVD tunneling polycrystalline layer deposition process, which is prepared by the graphite boat saturation method suitable for PECVD tunneling polycrystalline layer deposition process described in the first aspect.

[0017] In a third aspect, the present invention provides a saturated graphite boat suitable for PECVD tunneling polycrystalline layer deposition process, comprising a silicon nitride film and a silicon oxide film sequentially deposited on the surface of the graphite boat, and a clean layer is provided on the side of the silicon nitride film close to the silicon oxide film, and the hydrogen content of the clean layer is 1e17cm -3 -3e20cm -3 , and the thickness of the silicon nitride film is 50-100nm, and the thickness of the silicon oxide film is 375-700nm.

[0018] In some preferred embodiments of the present invention, the thickness ratio of the silicon nitride film to the silicon oxide film is 1:3.75-140.

[0019] In some preferred embodiments of the present invention, the thickness d of the silicon oxide film is adjusted according to the deposition temperature T of the tunneling polycrystalline layer and satisfies: d=(T / 2)×α, α is 1.3-3.5, the unit of d is nm, and the unit of T is °C.

[0020] In a fourth aspect, the present invention provides a method for preparing a solar cell, comprising: placing a silicon wafer on a saturated graphite boat suitable for the PECVD deposition of a tunneling polycrystalline layer process as described in the second aspect or the third aspect, and using tubular PECVD deposition to obtain a tunneling polycrystalline layer.

[0021] In some preferred embodiments of the present invention, the deposition temperature of the tunnel polycrystalline layer is between 300° C. and 600° C., and the thickness d of the silicon oxide film increases as the deposition temperature T of the tunnel polycrystalline layer increases.

[0022] In a fifth aspect, the present invention provides a solar cell, which is manufactured by the method for manufacturing a solar cell according to the fourth aspect.

[0023] Beneficial effects:

[0024] The present invention adopts the above technical scheme to first deposit a silicon nitride film of suitable thickness on the surface of the graphite boat, and then perform a suitable high-power hydrogen treatment after the deposition is completed to form a clean layer on the surface of the silicon nitride film to prevent nitrogen element overflow, and finally deposit a second film layer of silicon oxide film of suitable thickness to obtain a saturated graphite boat; when used in the PECVD deposition tunneling polycrystalline layer process, a high-quality tunneling oxide layer can be deposited to ensure excellent interface passivation.

[0025] The saturated graphite boat of the present invention can deposit a high-quality tunneling polycrystalline layer, improve the passivation level, improve the conversion efficiency of the battery, solve the influence of graphite boat saturation on the previous rounds of coating, and improve the production yield. At the same time, the graphite boat saturation method used in the present invention can greatly shorten the pickling time of the graphite boat. Conventional graphite boat saturation processes basically consider the cleaning of the graphite boat and the uniformity of coating. Because the PE-POLY process (i.e., the tunneling polycrystalline process) is a new process in recent years, there is no graphite boat saturation method specifically suitable for the tunneling polycrystalline process. The graphite boat saturation method of the present invention can completely isolate the influence of impurities on the tunneling polycrystalline layer and ensure the passivation level.

[0026] Further research has found that the thickness of the silicon oxide film is related to the deposition temperature used in the PE-POLY process (PECVD deposition tunneling polycrystalline layer process). Since the deposition temperature range of the PE-POLY process is relatively large, it can be deposited at 300-600°C. Different deposition temperatures directly affect the overflow of nitrogen. In this regard, in the preferred embodiment of the present invention, the thickness d of the silicon oxide film is controlled according to the deposition temperature T of the tunneling polycrystalline layer, and satisfies: d=(T / 2)×α, α is 1.3-3.5, d is in nm, and T is in °C. It can match the deposition temperature T with the appropriate thickness d, which is more conducive to effectively preventing the overflow of nitrogen in the silicon nitride film and increasing the service life of the graphite boat. DETAILED DESCRIPTION

[0027] In the present invention, unless otherwise stated, directional words such as "up, down, left, right" are generally understood in conjunction with the directions shown in actual applications.

[0028] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0029] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0030] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article. Among them, the terms "optional" and "optional" all mean that they may be included or not included (or may be present or not).

[0031] In the first aspect, the present invention provides a graphite boat saturation method suitable for PECVD deposition of tunneling polycrystalline layers, comprising: depositing a silicon nitride film on the surface of the graphite boat, then turning on the glow for hydrogen treatment, and then depositing a silicon oxide film on the graphite boat obtained after the hydrogen treatment; wherein the thickness of the silicon nitride film is 50-100nm, and the thickness of the silicon oxide film is 375-700nm; and the conditions for the hydrogen treatment include: controlling the flow rate of the hydrogen introduced to be 10000-20000sccm, the power to be 6000-10000W, and the reaction time to be 600-1800s, preferably 1200-1800s.

[0032] Among them, controlling the appropriate high hydrogen flow rate and high power and the appropriate hydrogen treatment time is conducive to forming a clean layer on the surface of the silicon nitride film while reducing the damage of the hydrogen treatment to the surface of the silicon nitride film.

[0033] In some preferred embodiments of the present invention, the hydrogen treatment conditions also include: a hydrogen treatment temperature of 400-450° C. and a reaction pressure of 2000-4000 mtorr. Using appropriate temperature and pressure for hydrogen treatment is more conducive to forming a uniform clean layer on the surface of the silicon nitride film.

[0034] In some preferred embodiments of the present invention, the conditions for depositing the silicon nitride film include: a temperature of 430-530° C., a pressure of 2000-4000 mtorr, a power of 4000-6000 W, and a reaction time of 15-20 min. Using appropriate deposition conditions to deposit the silicon nitride film is more conducive to forming a uniform silicon nitride film.

[0035] In some preferred embodiments of the present invention, the conditions for depositing the silicon nitride film include: the reaction gases are ammonia gas and silane gas, the silane flow rate is 1200-2000 sccm, and the NH3 flow rate is 5000-8000 sccm.

[0036] In some preferred embodiments of the present invention, the conditions for depositing the silicon oxide film include: a temperature of 430-530° C., a pressure of 1000-1500 mtorr, a power of 4000-6000 W, and a reaction time of 90-180 min. The use of suitable deposition conditions to deposit the silicon oxide film is more conducive to forming a uniform silicon oxide film, especially using a lower pressure, which is conducive to forming a denser silicon oxide film and better preventing nitrogen from overflowing.

[0037] In some preferred embodiments of the present invention, the conditions for depositing the silicon oxide film include: the reaction gases are silane and nitrous oxide, the silane flow rate is 600-1000 sccm, and the nitrous oxide flow rate is 1600-3000 sccm.

[0038] In some preferred embodiments of the present invention, the graphite boat saturation method further includes: first cleaning the graphite boat, then baking it in the presence of nitrogen, and then depositing the silicon nitride film. The present invention has no restrictions on the baking equipment, for example, the graphite boat is placed in a furnace tube for baking. Baking after cleaning is conducive to volatilizing all the residual solution in the graphite boat, thereby preventing contamination during subsequent coating.

[0039] In some preferred embodiments of the present invention, the cleaning process includes: firstly pickling the graphite boat with a mixed solution containing hydrofluoric acid and nitric acid, and then overflow cleaning the graphite boat with pure water after pickling, which is more conducive to cleaning the film layer on the surface of the graphite boat.

[0040] Preferably, the mass concentration of hydrofluoric acid in the mixed solution is 2%-10%, and the mass concentration of nitric acid is 0.1%-0.5%.

[0041] More preferably, the cleaning time of pickling is 200-360 min, and the time of overflow cleaning is 180-360 min.

[0042] In some preferred embodiments of the present invention, the baking conditions include: controlling the ambient temperature to 400-600°C (for example, the temperature in the furnace tube is kept constant at 400-600°C), and the baking time is 90-360 minutes, preferably 180-360 minutes. Baking at an appropriate temperature and time is more conducive to the complete volatilization of the residual solution in the graphite boat and prevents the graphite boat from being deformed due to high temperature.

[0043] Preferably, the baking conditions include: using nitrogen purging, the nitrogen flow rate is 8-10slm, and the chamber pressure is 2000-5000mtorr. Controlling the appropriate nitrogen flow rate for purging and the appropriate chamber pressure is more conducive to the complete volatilization of the residual solution in the graphite boat.

[0044] In some preferred embodiments of the present invention, the thickness d of the silicon oxide film is adjusted according to the deposition temperature T of the tunneling polycrystalline layer, and satisfies: d=(T / 2)×α, α is 1.3-3.5, preferably 1.5-3, d is in nm, and T is in °C, which is more conducive to saving saturation time and improving equipment capacity while ensuring production yield.

[0045] In a second aspect, the present invention provides a saturated graphite boat suitable for PECVD tunneling polycrystalline layer deposition process, which is prepared by the graphite boat saturation method suitable for PECVD tunneling polycrystalline layer deposition process described in the first aspect.

[0046] In a third aspect, the present invention provides a saturated graphite boat suitable for PECVD tunneling polycrystalline layer deposition process, comprising a silicon nitride film and a silicon oxide film sequentially deposited on the surface of the graphite boat, and a clean layer is provided on the side of the silicon nitride film close to the silicon oxide film, and the hydrogen content of the clean layer is 1e17cm -3 -3e20cm -3 , preferably 1e18cm -3 -3e20cm -3 , and the thickness of the silicon nitride film is 50-100nm, and the thickness of the silicon oxide film is 375-700nm. The present invention sets a specific film layer on the graphite boat, and sets a clean layer with a suitable hydrogen content on the surface of the silicon nitride film, which can effectively reduce the impurity elements on the surface of the silicon nitride film, and controls the thickness of the silicon oxide film to be greater than the thickness of the silicon nitride film, which is more conducive to preventing nitrogen overflow and improving the equipment yield.

[0047] In some preferred embodiments of the present invention, the thickness ratio of the silicon nitride film and the silicon oxide film is 1:3.75-140, for example, it can be 1:3.75, 1:4, 1:5, 1:6, 1:7, 1:9, 1:10, 1:20, 1:30, 1:50, 1:70, 1:100, 1:120, 1:130, 1:140, etc., and the range between any two point values, for example, 1:4-40 can be preferred, and 1:4-20 can be further preferred, which is more conducive to saving saturation time and improving equipment production capacity while ensuring yield.

[0048] In some preferred embodiments of the present invention, the thickness d of the silicon oxide film is adjusted according to the deposition temperature T of the tunneling polycrystalline layer and satisfies: d=(T / 2)×α, α is 1.3-3.5, the unit of d is nm, and the unit of T is °C.

[0049] In a fourth aspect, the present invention provides a method for preparing a solar cell, comprising: placing a silicon wafer on a saturated graphite boat suitable for the PECVD deposition of a tunneling polycrystalline layer process as described in the second aspect or the third aspect, and using tubular PECVD deposition to obtain a tunneling polycrystalline layer.

[0050] In some preferred embodiments of the present invention, the deposition temperature of the tunnel polycrystalline layer is between 300° C. and 600° C., and the thickness d of the silicon oxide film increases as the deposition temperature T of the tunnel polycrystalline layer increases.

[0051] In a fifth aspect, the present invention provides a solar cell, which is manufactured by the method for manufacturing a solar cell according to the fourth aspect.

[0052] The embodiments of the present invention are described in detail below, which are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0053] Example 1

[0054] A saturated graphite boat is prepared by the following method:

[0055] S1. First, clean the graphite boat. The cleaning process is as follows: pickle the graphite boat with a mixed solution containing hydrofluoric acid and nitric acid, wherein the mass concentration of hydrofluoric acid is 10% and the mass concentration of nitric acid is 0.5%. After pickling for 200 minutes, overflow with pure water for 240 minutes. Put the cleaned graphite boat into the furnace tube for baking; the baking conditions are: the furnace tube is kept at a constant temperature of 500°C, nitrogen is used for purging, the nitrogen flow rate is 9slm, the chamber pressure is 3000mtorr, and the baking time is 220 minutes;

[0056] S2, depositing a silicon nitride film on the baked graphite boat, the reaction gases are ammonia and silane gas, the silane flow rate is 1600sccm, the NH3 flow rate is 6000sccm, the temperature is 450°C, the pressure is 3000 mtorr, the reaction time is 18min, the power is 5000W, and the silicon nitride film thickness is 60nm;

[0057] S3, hydrogen treatment is performed on the graphite boat after the silicon nitride film is deposited, hydrogen is introduced, and the glow is turned on for hydrogen treatment. The hydrogen treatment temperature is 420°C, the hydrogen flow rate is 10000sccm, the reaction time is 1400s, the reaction pressure is 3000mtorr, and the power is 7000W; after the hydrogen treatment, a clean layer is formed on the surface of the silicon nitride film, and the hydrogen content of the clean layer is 1e19cm -3 .

[0058] S4. Depositing a silicon oxide film on the hydrogen-treated graphite boat, the reaction gases are silane and nitrous oxide, the silane flow rate is 700 sccm, the nitrous oxide flow rate is 2000 sccm, the temperature is 430°C, the pressure is 1200 mtorr, the reaction time is 110 min, the power is 4000 W, and the silicon oxide film thickness is 400 nm; a saturated graphite boat is obtained, and experimental production can be carried out after the coating is completed.

[0059] Example 2

[0060] The method of Example 1 is referred to, except that the thickness of the silicon nitride film is 80 nm. To meet this condition, the corresponding preparation process needs to be adjusted: the silane flow rate is 2000 sccm.

[0061] Example 3

[0062] The method of Example 1 is referred to, except that the thickness of the silicon oxide film is 700 nm. To meet this condition, the corresponding preparation process needs to be adjusted: the reaction time is 180 min.

[0063] Example 4

[0064] The method of Example 1 is referred to, except that the baking time is 90 minutes. The baking time is shortened, and the water vapor is not completely removed, so when the silicon nitride film and the silicon oxide film are plated, the water vapor will enter the silicon nitride film and the silicon oxide film, affecting the saturation quality.

[0065] Example 5

[0066] The method of Example 1 is followed, except that no baking is performed.

[0067] Example 6

[0068] The method of Example 1 was followed, except that the hydrogen treatment time was 600 s. The hydrogen content of the clean layer was 1e17 cm -3 .

[0069] Comparative Example 1

[0070] The same method as in Example 1 was used except that the silicon oxide film was not deposited.

[0071] Comparative Example 2

[0072] The method of Example 1 is referred to, except that the hydrogen treatment is not performed, and the silicon oxide film is deposited directly after the silicon nitride film is deposited.

[0073] Comparative Example 3

[0074] The method of Example 1 is followed, except that the power of hydrogen treatment is lower, 5000W.

[0075] Comparative Example 4

[0076] The method of Example 1 is referred to, except that the hydrogen flow rate of hydrogen treatment is lower, 7000 sccm. The corresponding hydrogen content in the clean layer is 1e16 cm 3 .

[0077] Comparative Example 5

[0078] The method of Example 1 is referred to, except that the thickness of the silicon oxide film is 100 nm. To meet this condition, the corresponding preparation process needs to be adjusted: the reaction time is 30 min.

[0079] Application Example 1

[0080] The saturated graphite boats of the above-mentioned embodiments and comparative examples are respectively used for the preparation of existing combined passivated back-contact solar cells. The preparation process of the combined passivated back-contact solar cells is the same and specifically as follows: a silicon wafer is placed on the corresponding saturated graphite boat, and a tunneling polycrystalline layer is obtained by tubular PECVD deposition on the back of the silicon wafer. The deposition temperature T of the tunneling polycrystalline layer is 400°C. The tunneling polycrystalline layer includes a tunneling oxide layer with a thickness of 1.5nm and an N-type doped polycrystalline silicon layer with a thickness of 120nm, forming a first semiconductor layer; then a second semiconductor opening area is formed; and then a texturing and cleaning process is performed to form a texturing layer on the light-receiving surface of the silicon wafer and the second semiconductor opening area. The silicon wafer is formed on the back surface; a passivation layer and an anti-reflection layer are then deposited on the light-receiving surface of the silicon wafer, and then a second semiconductor layer (including intrinsic amorphous silicon with a thickness of 10nm and P-type doped amorphous silicon with a thickness of 15nm) is deposited on the back surface, and then a first semiconductor opening area arranged in an interval with the second semiconductor opening area is formed on part of the second semiconductor layer; a conductive film layer is deposited on the obtained back surface, and an isolation groove is formed on part of the conductive film layer located between the first semiconductor opening area and the second semiconductor opening area; then metal electrodes are formed on the outer surfaces of the corresponding conductive film layers in the areas where the first semiconductor opening area and the second semiconductor opening area are located, respectively, to obtain a combined passivation back contact battery. The obtained combined passivation back contact battery is subjected to performance testing.

[0081] Application Example 2

[0082] The method for the combined passivation back contact solar cell of Application Example 1 is carried out according to Example 1, except that the deposition temperature of the tunneling polycrystalline layer is 600°C.

[0083] Test Case

[0084] The solar cells obtained from the above application examples were subjected to performance tests, and the results are shown in Table 1. The production yield refers to the value of the number of cells that meet the standards of cell efficiency above 26.5% and have no obvious color difference, broken corners, or scratches visible to the naked eye in a production batch (100 cells) / the total number of cells produced.

[0085] Table 1

[0086]

[0087] It can be seen from the above results that, compared with the comparative example, the embodiment scheme of the present invention can improve the passivation level, improve the conversion efficiency of the battery, solve the influence of graphite boat saturation on the previous rounds of coating, and improve the production yield. At the same time, the graphite boat saturation method used in the present invention can greatly shorten the pickling time of the graphite boat.

[0088] Furthermore, according to Example 1 and Examples 2-5, it can be seen that the adoption of the preferred solution of the present invention is more conducive to improving the passivation level, improving the conversion efficiency of the battery, and improving the production yield.

[0089] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A graphite boat saturation method suitable for PECVD tunneling polycrystalline layer deposition process, characterized in that: include: A silicon nitride film is deposited on the surface of a graphite boat, and then a glow light is turned on for hydrogen treatment to form a clean layer on the surface of the silicon nitride film, and then a silicon oxide film is deposited on the graphite boat obtained after the hydrogen treatment; wherein the thickness of the silicon nitride film is 50-100nm, and the thickness of the silicon oxide film is 375-700nm; and the conditions of the hydrogen treatment include: controlling the flow rate of the hydrogen gas to be 10000-20000sccm, the power to be 6000-10000W, the reaction time to be 600-1800s, and controlling the hydrogen content of the clean layer to be 1e17cm -3 -3e20cm -3 .

2. The graphite boat saturation method for PECVD tunneling polycrystalline layer deposition process according to claim 1, characterized in that: The conditions of the hydrogen treatment also include: a hydrogen treatment temperature of 400-450° C. and a reaction pressure of 2000-4000 mTorr.

3. The graphite boat saturation method suitable for PECVD tunneling polycrystalline layer deposition process according to claim 1, characterized in that: The conditions for depositing silicon nitride films include: The temperature is 430-530°C, the pressure is 2000-4000 mTorr, the power is 4000-6000W, and the reaction time is 15-20min; and / or, The reaction gases are ammonia and silane gases, the silane flow rate is 1200-2000sccm, and the NH3 flow rate is 5000-8000sccm.

4. The graphite boat saturation method for PECVD tunneling polycrystalline layer deposition process according to claim 1, characterized in that: The conditions for depositing silicon oxide films include: The temperature is 430-530°C, the pressure is 1000-1500 mTorr, the power is 4000-6000W, and the reaction time is 90-180min; and / or, The reaction gases are silane and nitrous oxide, the silane flow rate is 600-1000sccm, and the nitrous oxide flow rate is 1600-3000sccm.

5. The graphite boat saturation method suitable for PECVD tunneling polycrystalline layer deposition process according to any one of claims 1 to 4, characterized in that: The graphite boat saturation method further includes: first cleaning the graphite boat, then baking it in the presence of nitrogen, and then depositing the silicon nitride film.

6. The graphite boat saturation method for PECVD tunneling polycrystalline layer deposition process according to claim 5, characterized in that: The baking conditions include: the temperature in the furnace tube is kept constant at 400-600° C., nitrogen is purged, the nitrogen flow rate is 8-10 slm, the chamber pressure is 2000-5000 mTorr, and the baking time is 90-360 min; And / or, the cleaning process includes: first pickling the graphite boat with a mixed solution containing hydrofluoric acid and nitric acid, and then overflow cleaning the graphite boat with pure water after pickling; wherein the mass concentration of hydrofluoric acid in the mixed solution is 2%-10%, the mass concentration of nitric acid is 0.1%-0.5%, the cleaning time of pickling is 200-360 minutes, and the time of overflow cleaning is 180-360 minutes.

7. The graphite boat saturation method for PECVD tunneling polycrystalline layer deposition process according to claim 1, characterized in that: The thickness d of the silicon oxide film is adjusted according to the deposition temperature T of the tunneling polycrystalline layer and satisfies: d=(T / 2)×α, α is 1.3-3.5, the unit of d is nm, and the unit of T is °C.

8. A saturated graphite boat suitable for PECVD tunneling polycrystalline layer deposition process, characterized in that: The method is prepared by a graphite boat saturation method suitable for a PECVD tunneling polycrystalline layer deposition process as described in any one of claims 1 to 7.

9. A saturated graphite boat suitable for PECVD tunneling polycrystalline layer deposition process, characterized in that: The invention comprises a silicon nitride film and a silicon oxide film deposited on the surface of a graphite boat in sequence, and the surface of the silicon nitride film close to the silicon oxide film has a clean layer, and the hydrogen content of the clean layer is 1e17cm -3 -3e20cm -3 , and the thickness of the silicon nitride film is 50-100nm, and the thickness of the silicon oxide film is 375-700nm.

10. The saturated graphite boat suitable for PECVD tunneling polycrystalline layer deposition process according to claim 9, characterized in that: The thickness ratio of silicon nitride film to silicon oxide film is 1:3.75-10; And / or, the thickness d of the silicon oxide film is adjusted according to the deposition temperature T of the tunneling polycrystalline layer and satisfies: d=(T / 2)×α, α is 1.3-3.5, the unit of d is nm, and the unit of T is °C.

11. A method for preparing a solar cell, characterized in that: include: The silicon wafer is placed on a saturated graphite boat suitable for a PECVD tunneling polycrystalline layer deposition process as described in any one of claims 8 to 10, and a tunneling polycrystalline layer is obtained by using tubular PECVD deposition.

12. The method for preparing a solar cell according to claim 11, characterized in that: The deposition temperature of the tunnel polycrystalline layer is between 300° C. and 600° C., and the thickness d of the silicon oxide film increases as the deposition temperature T of the tunnel polycrystalline layer increases.

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