A mask layer, a method for growing the same, and an application thereof

Abstract

The present invention provides a mask layer, a growth method thereof and an application. The growth method includes: performing epitaxial growth using an oxygen source and a silicon source under low-pressure conditions to obtain a silicon oxide mask layer; the pressure of the low pressure is 15-25 Pa. By using the silicon source and the oxygen source to perform epitaxial growth under low-pressure conditions, the present invention prepares a high-quality silicon oxide mask layer, which has a fast growth rate of the silicon oxide mask layer, can shorten the process time; and deposits the silicon oxide mask layer by epitaxial growth, without reacting with the bottom structure, and can protect the performance of the passivation structure.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor manufacturing, and particularly relates to a mask layer, a growth method thereof and an application thereof. Background Art

[0002] Cost reduction and efficiency improvement are the eternal pursuits, and efficiency improvement is the long-term direction. The core driving force for the development of the photovoltaic industry is the continuous decline in the cost per kilowatt-hour of electricity, driving the continuous increase in the investment return rate. Cost reduction and efficiency improvement are the eternal pursuits of the industry development. At present, when the conversion efficiency and cost reduction space of passivated emitter and rear cell are approaching the limit, new battery technologies with higher conversion efficiency have ushered in a development window period. New generation battery technologies such as tunnel oxide passivated contact battery, photovoltaic heterojunction battery, full back electrode contact crystalline silicon solar cell or interdigitated back contact heterojunction are expected to rise rapidly.

[0003] With the rise of new generation technologies, the complexity of process steps increases, and mask protection needs to be added in some steps to ensure an efficient battery structure. Traditional masks are mainly phosphosilicate glass (PSG), borosilicate glass (BSG) and SiO2 grown by high-temperature oxygen. As a mask layer, the thickness of PSG is about 30-50 nm, the growth rate is relatively slow, and the corrosion rate of HF and alkaline solution used for cleaning on the PSG layer is very fast. Acid pickling needs to overcome the corrosion of acid gas and acid solution on PSG, and alkaline cleaning needs to develop additives for protecting the PSG layer for use together, so the protection window is relatively small; as a mask layer, the thickness of BSG is about 60-120 nm, the growth rate is relatively slow, the growth temperature is high, and the long-term high-temperature process will affect the performance of the passivation structure. Moreover, BSG will continue to dope P to form BPSG during subsequent phosphorus diffusion, and the corrosion resistance effect against HF will be significantly reduced; as a mask layer, SiO2 grown by high-temperature oxygen has good compactness, but due to the very slow growth rate of silicon oxide, a higher temperature is required to grow a thicker oxide layer, and during growth, thinning phenomena will occur to Si, amorphous silicon and polycrystalline silicon, and phenomena of promoting or precipitating doped atoms will also occur, resulting in a decline in passivation performance.

[0004] For example, CN110391317B discloses a method for preparing a textured surface of a single-crystalline silicon wafer, aiming to provide a new method for preparing an inverted pyramid-shaped textured structure using an SiO2 mask. The technical solution is as follows: (1) removing organic dirt on the surface of the single-crystalline silicon wafer; (2) subjecting the single-crystalline silicon wafer obtained in step (1) to surface oxidation to generate a silicon oxide mask layer; (3) annealing the single-crystalline silicon wafer obtained in step (2) at a high temperature; a high density of pinholes are generated in the silicon oxide mask after annealing, forming channels for direct contact reaction between the alkaline solution and the silicon wafer; (4) texturing the single-crystalline silicon wafer obtained in step (3); finally, an inverted pyramid-shaped structure is formed at the pinhole positions of the silicon oxide mask; (5) removing the silicon oxide mask layer from the single-crystalline silicon wafer obtained in step (4) to obtain the required inverted pyramid-shaped textured surface.

[0005] CN107785456A discloses a method for preparing a back-contact solar cell. The preparation method includes texturing; preparing a front surface thin mask; performing double-sided phosphorus diffusion to form an n+ lightly doped region and a PSG layer on the front surface, and an n+ heavily doped region and a PSG layer on the back surface; laser grooving, polishing, and boron diffusion on the back surface; cleaning the substrate and preparing a passivation and antireflection film; printing metal electrodes and sintering.

[0006] CN104485390A discloses a production method for a full-back electrode solar cell. The steps of the method are as follows: providing a pre-treated silicon wafer; performing boron diffusion treatment on both sides of the silicon wafer; etching off the BSG layer formed on the front surface, and using the BSG layer formed on the back surface as a texturing mask layer to texture the front surface of the silicon wafer; removing the BSG layer on the back surface, cleaning the silicon wafer, and preparing an etching mask layer on both sides; then depositing a SiN x passivation film layer on the back surface; and then depositing a SiN x antireflection film layer on the front surface; grooving the area on the back surface where a back surface field needs to be formed; etching the grooved area to etch off the boron-doped region, and the remaining boron-doped region is the emitter; performing phosphorus diffusion treatment on the grooved area to form a back surface field; removing the remaining PSG layer and the etching mask layer; then opening holes in the emitter region; printing corresponding metals to connect the back surface field and the emitter respectively, and sintering to form corresponding electrodes.

[0007] In summary, these mask layers grow slowly and affect the passivation performance of some film layer structures during the growth process, so the new technology cannot be stably mass-produced.

[0008] Therefore, how to increase the growth rate of the protective film without affecting the passivation performance and protective performance, and achieve high-quality mask layer growth in a short time is a technical problem to be solved urgently. Summary of the Invention

[0009] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a mask layer, a growth method thereof and an application. The present invention uses a silicon source and an oxygen source for epitaxial growth under a low pressure condition of 15 - 25 Pa, and a high-quality silicon oxide mask layer can be obtained in a short time. This method can improve the growth rate without reacting with the bottom structure, and can also protect the performance of the passivation structure.

[0010] To achieve the purpose of this invention, the following technical solutions are adopted in the present invention:

[0011] In the first aspect, the present invention provides a growth method of a mask layer, and the growth method includes:

[0012] Using an oxygen source and a silicon source for epitaxial growth under a low pressure condition to obtain a silicon oxide mask layer;

[0013] The pressure of the low pressure is 15 - 25 Pa, and for example, it can be 15 Pa, 16 Pa, 17 Pa, 18 Pa, 19 Pa, 20 Pa, 21 Pa, 22 Pa, 23 Pa, 24 Pa or 25 Pa, etc.

[0014] The present invention uses a silicon source and an oxygen source for epitaxial growth of a silicon oxide mask layer under a low pressure condition. Under a low pressure condition, the average free path of molecules increases, the gas distribution is more uniform, which is beneficial to the uniformity of decomposition and deposition; in addition, under a low pressure condition, the total amount of gas will decrease, the gas consumption can be reduced, the production cost can be lowered, and the evacuation speed of the gas under a low pressure increases, which is more conducive to the evacuation of by-products and increases the quality of the thin film formation. Therefore, a high-quality silicon oxide mask can be obtained in a short time, and the silicon oxide mask prepared by this method will not react with the bottom structure, and can also protect the performance of the passivation structure.

[0015] In the present invention, when the pressure during epitaxial growth is lower than 15 Pa, the growth rate will be slow, affecting the production efficiency, while when the pressure is higher than 25 Pa, the growth rate will be too fast, resulting in a large amount of dust, affecting the mask quality.

[0016] Preferably, the oxygen source is oxygen.

[0017] Preferably, the flow rate of the oxygen source is 500 - 1500 sccm, and for example, it can be 500 sccm, 600 sccm, 700 sccm, 800 sccm, 900 sccm, 1000 sccm, 1100 sccm, 1200 sccm, 1300 sccm, 1400 sccm or 1500 sccm, etc.

[0018] In the present invention, if the flow rate of the oxygen source is too large, it will increase the evacuation speed of the gas in the tube and reduce the concentration of the silicon source in the furnace tube, thereby reducing the deposition rate. When the flow rate of the oxygen source is too small, the deposition rate will also be reduced.

[0019] Preferably, the silicon source is tetraethyl orthosilicate.

[0020] Preferably, the flow rate of the silicon source is 50 - 100 sccm, for example, it can be 50 sccm, 60 sccm, 70 sccm, 80 sccm, 90 sccm or 100 sccm, etc.

[0021] Preferably, the flow rate ratio of the silicon source to the oxygen source is 1:(5 - 30), for example, it can be 1:5, 1:10, 1:15, 1:20, 1:25 or 1:30, etc.

[0022] In the present invention, if the flow rate ratio of the silicon source to the oxygen source is too large, that is, the flow rate of the oxygen source is too small, it will reduce the evacuation speed of the gas in the tube and the reaction rate between the silicon source and the oxygen source. When the flow rate ratio of the silicon source to the oxygen source is too small, excessive oxygen source will increase the evacuation rate of the gas in the tube and reduce the concentration of the silicon source in the furnace tube, resulting in a decrease in the deposition rate.

[0023] Preferably, the epitaxial growth is carried out in a reaction chamber, and the silicon source is carried into the reaction chamber by a carrier gas.

[0024] Preferably, the carrier gas includes any one or a combination of at least two of nitrogen, argon or helium.

[0025] Preferably, the flow rate ratio of the silicon source to the carrier gas is 1:(0.5 - 3), for example, it can be 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5 or 1:3, etc.

[0026] As a preferred technical solution of the present invention, the way of epitaxial growth is to first introduce the oxygen source and then introduce the silicon source.

[0027] Preferably, the temperature of the epitaxial growth is 650 - 850 °C, for example, it can be 650 °C, 700 °C, 750 °C, 800 °C or 850 °C, etc.

[0028] In the present invention, if the temperature of the epitaxial growth is too low, it will reduce the growth rate of the silicon oxide mask and prolong the growth time of the mask. When the temperature of the epitaxial growth is too high, it is easy to cause too fast local decomposition rate, affecting the uniformity of deposition.

[0029] Preferably, the heating rate of the temperature of the epitaxial growth is 8 - 12 °C / min, for example, it can be 8 °C / min, 9 °C / min, 10 °C / min, 11 °C / min or 12 °C / min, etc.

[0030] In the present invention, if the heating rate of the temperature is too fast, it will affect the epitaxial growth of the silicon oxide mask, resulting in poor temperature uniformity inside the tube, thereby affecting the deposition uniformity. While if the heating rate of the temperature is too slow, it will increase the process time and cost.

[0031] Preferably, after the temperature of the epitaxial growth reaches the set value, it is kept at a constant temperature for 3 - 7 minutes, for example, it can be 3 minutes, 4 minutes, 5 minutes, 6 minutes or 7 minutes, etc.

[0032] In the present invention, increasing the constant temperature time after reaching the set reaction temperature can make the temperature on the inner wall and in the middle of the reaction chamber tend to be consistent, ensure the temperature uniformity in the furnace tube, and is conducive to more sufficient reaction.

[0033] Preferably, the time of the epitaxial growth is 8 - 12 minutes, for example, it can be 8 minutes, 9 minutes, 10 minutes, 11 minutes or 12 minutes, etc.

[0034] Preferably, the outer wall temperature of the reaction chamber is 80 - 100 °C, for example, it can be 80 °C, 85 °C, 90 °C, 95 °C or 100 °C, etc.

[0035] As a preferred technical solution, after the epitaxial growth, the reaction chamber is purged under low pressure.

[0036] Preferably, the gas used for the low - pressure purge includes any one or a combination of at least two of nitrogen, argon or helium.

[0037] Preferably, the flow rate of the gas used for the low - pressure purge is 1000 - 2000 sccm, for example, it can be 1000 sccm, 1200 sccm, 1400 sccm, 1600 sccm, 1800 sccm or 2000 sccm, etc.

[0038] Preferably, the pressure of the low - pressure purge is 3 - 7 Pa, for example, it can be 3 Pa, 4 Pa, 5 Pa, 6 Pa or 7 Pa, etc.

[0039] Preferably, the time of the low - pressure purge is 8 - 12 minutes, for example, it can be 8 minutes, 9 minutes, 10 minutes, 11 minutes or 12 minutes, etc.

[0040] As a preferred technical solution, the epitaxial growth is carried out on a substrate.

[0041] Preferably, before the epitaxial growth, the substrate is pre - doped in situ by LPCVD, PECVD, phosphorus diffusion or boron diffusion, preferably phosphorus diffusion or boron diffusion.

[0042] It should be noted that the PSG and BSG masks grown by phosphorus diffusion and boron diffusion themselves mainly depend on temperature and time. Increasing the thickness requires providing high temperature and sufficient time, which will lead to a reduction in the service life of quartz parts and seals. At the same time, increasing the process time will also affect the doping concentration of the battery itself, which is not conducive to battery performance. The present invention can generate a relatively thick mask layer in a short time, reduce the process time, do not affect the performance parameters of the battery, and has good industrial potential.

[0043] As a preferred technical solution, the growth method includes the following steps:

[0044] (1) Under a pressure of 15 - 25 Pa, introduce 500 - 1500 sccm of oxygen source into the reaction chamber, and control the temperature at 650 - 850 °C;

[0045] (2) Leak detection: The leak rate is lower than 1.3 Pa / min;

[0046] (3) Introduce carrier gas into the silicon source bottle, and then carry 50 - 100 sccm of silicon source into the reaction chamber to react with the oxygen source to achieve epitaxial growth, where the flow ratio of the silicon source to the oxygen source is 1:(5 - 30), the flow ratio of the silicon source to the carrier gas is 1:(0.5 - 3), the epitaxial growth time is 8 - 12 min, and the temperature of the outer wall of the reaction chamber is controlled at 80 - 100 °C;

[0047] (4) Under a pressure of 3 - 7 Pa, introduce 1000 - 2000 sccm of gas for purging into the reaction chamber, and the purging time is 8 - 12 min;

[0048] (5) Introduce nitrogen to normal pressure and take out the boat.

[0049] In a second aspect, the present invention provides a mask layer, and the mask layer is obtained by using the growth method described in the first aspect.

[0050] The mask layer is located on the surface of the substrate.

[0051] Among them, the thickness of the mask layer is 80 - 110 nm, for example, it can be 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, 105 nm or 110 nm, etc.

[0052] In a third aspect, the present invention provides a silicon-based battery, and the silicon-based battery includes the mask layer described in the second aspect.

[0053] The numerical ranges described in the present invention not only include the point values listed above, but also include any point values between the above numerical ranges not listed. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the ranges.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] (1) By using a silicon source and an oxygen source for epitaxial growth under low-pressure conditions, the present invention prepares a high-quality silicon oxide mask layer with a fast growth rate, which can shorten the process time;

[0056] (2) The present invention epitaxially grows and deposits a silicon oxide mask layer, which will not react with the underlying structure and can protect the performance of the passivation structure;

[0057] (3) The silicon oxide mask layer prepared by the present invention can be rapidly decomposed at a relatively low temperature, greatly reducing the process temperature and also protecting the performance of the passivation structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 It is a graph showing the relationship between the growth rate of the silicon oxide mask layer in the present invention and the pressure in the reaction chamber.

[0059] Figure 2 It is a graph showing the relationship between the growth rate of the silicon oxide mask layer in the present invention and the flow rate of tetraethyl orthosilicate (TEOS).

[0060] Figure 3 It is a graph showing the relationship between the growth rate of the silicon oxide mask layer in the present invention and the temperature of epitaxial growth.

[0061] Figure 4 It is a microscope test diagram of the substrate covered with the mask layer provided in Examples 1-4 of the present invention after etching and cleaning.

[0062] Figure 5 It is a microscopic test diagram of the substrate covered with the mask layer provided in Comparative Example 1 of the present invention after cleaning. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0063] The technical solution of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be construed as specific limitations on the present invention.

[0064] Example 1

[0065] This example provides a method for growing a mask layer, which specifically includes the following steps:

[0066] (1) Place the substrate pre-doped by LPCVD in situ in the reaction chamber. Under a pressure of 20 Pa, introduce 1000 sccm of oxygen into the reaction chamber, and raise the temperature to 750 °C at a heating rate of 10 °C / min and keep it constant for 5 minutes;

[0067] (2) Leak detection: The leak rate is lower than 1.3 Pa / min;

[0068] (3) Nitrogen is introduced into the TEOS bottle, and then 75 sccm of TEOS is carried into the reaction chamber to react with oxygen to achieve epitaxial growth. The flow rate ratio of TEOS to oxygen is 1:13, and the flow rate ratio of TEOS to nitrogen is 1:2. The epitaxial growth time is 10 min, and the temperature of the outer wall of the reaction chamber is controlled at 90 °C;

[0069] (5) Nitrogen is introduced into the reaction chamber at a pressure of 5 Pa at a flow rate of 1500 sccm and purged for 10 min;

[0070] (6) Nitrogen is introduced until normal pressure is reached, and the boat is taken out to obtain a silicon oxide mask layer with a thickness of 90 nm.

[0071] Example 2

[0072] The example provides a method for growing a mask layer, which specifically includes the following steps:

[0073] (1) Place the substrate pre-doped in-situ by PECVD in the reaction chamber. At a pressure of 15 Pa, introduce 1500 sccm of oxygen into the reaction chamber, and increase the temperature to 650 °C at a heating rate of 8 °C / min and keep it constant for 3 min;

[0074] (2) Leak detection: The leak rate is lower than 1.3 Pa / min;

[0075] (3) Argon is introduced into the TEOS bottle, and then 80 sccm of TEOS is carried into the reaction chamber to react with oxygen to achieve epitaxial growth. The flow rate ratio of TEOS to oxygen is 1:30, and the flow rate ratio of TEOS to argon is 1:1. The epitaxial growth time is 8 min, and the temperature of the outer wall of the reaction chamber is controlled at 80 °C;

[0076] (5) Helium is introduced into the reaction chamber at a pressure of 3 Pa at a flow rate of 1000 sccm and purged for 8 min;

[0077] (6) Nitrogen is introduced until normal pressure is reached, and the boat is taken out to obtain a silicon oxide mask layer with a thickness of 90 nm.

[0078] Example 3

[0079] The example provides a method for growing a mask layer, which specifically includes the following steps:

[0080] (1) Place the substrate pre-diffused with phosphorus in the reaction chamber. At a pressure of 25 Pa, introduce 500 sccm of oxygen into the reaction chamber, and increase the temperature to 850 °C at a heating rate of 12 °C / min and keep it constant for 7 min;

[0081] (2) Leak detection: The leak rate is lower than 1.3 Pa / min;

[0082] (3) Helium is introduced into the TEOS bottle, and then 100 sccm of TEOS is carried into the reaction chamber to react with oxygen to achieve epitaxial growth. The flow rate ratio of TEOS to oxygen is 1:5, the flow rate ratio of TEOS to helium is 1:3, the epitaxial growth time is 12 min, and the temperature of the outer wall of the reaction chamber is controlled at 100 °C;

[0083] (5) Argon at 2000 sccm is introduced into the reaction chamber at a pressure of 7 Pa and purged for 12 min;

[0084] (6) Nitrogen is introduced until normal pressure is reached, and the boat is taken out to obtain a silicon oxide mask layer with a thickness of 108 nm.

[0085] Example 4

[0086] The example provides a method for growing a mask layer, which specifically includes the following steps:

[0087] (1) Place the pre-diffused boron substrate in the reaction chamber. At a pressure of 20 Pa, introduce 1200 sccm of oxygen into the reaction chamber, and raise the temperature to 700 °C at a heating rate of 10 °C / min and hold for 5 min;

[0088] (2) Leak detection: The leak rate is lower than 1.3 Pa / min;

[0089] (3) Nitrogen is introduced into the TEOS bottle, and then 60 sccm of TEOS is carried into the reaction chamber to react with oxygen to achieve epitaxial growth. The flow rate ratio of TEOS to oxygen is 1:20, the flow rate ratio of TEOS to nitrogen is 1:0.5, the epitaxial growth time is 10 min, and the temperature of the outer wall of the reaction chamber is controlled at 90 °C;

[0090] (5) Nitrogen at 1500 sccm is introduced into the reaction chamber at a pressure of 5 Pa and purged for 10 min;

[0091] (6) Nitrogen is introduced until normal pressure is reached, and the boat is taken out to obtain a silicon oxide mask layer with a thickness of 82 nm.

[0092] Example 5

[0093] The difference between this example and Example 1 is that the pressure in the chamber in step (1) is 15 Pa.

[0094] The remaining preparation methods and parameters are the same as those in Example 1.

[0095] Example 6

[0096] The difference between this example and Example 1 is that the pressure in the chamber in step (1) is 23 Pa.

[0097] The remaining preparation methods and parameters are the same as those in Example 1.

[0098] Example 7

[0099] The difference between this example and Example 1 is that the flow rate of oxygen in step (1) is 400 sccm.

[0100] The remaining preparation methods and parameters are the same as those in Example 1.

[0101] Example 8

[0102] The difference between this example and Example 1 is that the flow rate of oxygen in step (1) is 1600 sccm.

[0103] The remaining preparation methods and parameters are the same as those in Example 1.

[0104] Example 9

[0105] The difference between this example and Example 1 is that the flow rate of TEOS in step (1) is 60 sccm, and the flow rate ratio of TEOS to oxygen is 1:17.

[0106] The remaining preparation methods and parameters are the same as those in Example 1.

[0107] Example 10

[0108] The difference between this example and Example 1 is that the flow rate of TEOS in step (1) is 90 sccm, and the flow rate ratio of TEOS to oxygen is 1:11.

[0109] The remaining preparation methods and parameters are the same as those in Example 1.

[0110] Example 11

[0111] The difference between this example and Example 1 is that the flow rate ratio of TEOS to oxygen in step (1) is 1:4.

[0112] The remaining preparation methods and parameters are the same as those in Example 1.

[0113] Example 12

[0114] The difference between this example and Example 1 is that the flow rate ratio of TEOS to oxygen in step (1) is 1:32.

[0115] The remaining preparation methods and parameters are the same as those in Example 1.

[0116] Example 13

[0117] The difference between this example and Example 1 is that the temperature in step (1) is 600 °C.

[0118] The remaining preparation methods and parameters are the same as those in Example 1.

[0119] Example 14

[0120] The difference between this example and Example 1 is that the temperature in step (1) is 900 °C.

[0121] The remaining preparation methods and parameters are the same as those in Example 1.

[0122] Example 15

[0123] The difference between this example and Example 1 is that the constant temperature time in step (1) is 2 min.

[0124] The remaining preparation methods and parameters are the same as those in Example 1.

[0125] Example 16

[0126] The difference between this example and Example 1 is that the constant temperature time in step (1) is 8 min.

[0127] The remaining preparation methods and parameters are the same as those in Example 1.

[0128] Example 17

[0129] The difference between this example and Example 1 is that oxygen and nitrogen carrying TEOS enter the reaction chamber simultaneously, rather than oxygen first and then nitrogen carrying TEOS.

[0130] The remaining preparation methods and parameters are the same as those in Example 1.

[0131] Comparative Example 1

[0132] The difference between this comparative example and Example 1 is that the pressure in the chamber in step (1) is 10 Pa.

[0133] The remaining preparation methods and parameters are the same as those in Example 1.

[0134] Comparative Example 2

[0135] The difference between this comparative example and Example 1 is that the pressure in the chamber in step (1) is 30 Pa.

[0136] The remaining preparation methods and parameters are the same as those in Example 1.

[0137] Comparative Example 3

[0138] The difference between this comparative example and Example 1 is that no oxygen is introduced.

[0139] The remaining preparation methods and parameters are the same as those in Example 1.

[0140] Figure 1It shows that the growth rate of the silicon oxide mask layer in Example 1, Example 5, and Example 6 shows an increasing trend as the pressure in the reaction chamber increases, and the increasing amplitude gradually decreases. Eventually, the growth rate tends to be stable.

[0141] Figure 2 It shows that the growth rate of the silicon oxide mask layer in Example 1, Example 9, and Example 10 shows an increasing trend as the flow rate ratio of TEOS to oxygen increases, and the increasing amplitude gradually decreases. Eventually, the growth rate tends to be stable.

[0142] Figure 3 It shows that the growth rate of the silicon oxide mask layer in Examples 1-4 shows a trend of first increasing and then decreasing as the temperature of epitaxial growth increases. The inflection point is about 730 °C. Therefore, the mask layer prepared by the present invention can be rapidly decomposed at a lower temperature.

[0143] Performance test

[0144] The substrates for growing mask layers provided in Examples 1-17 and Comparative Examples 1-3 are subjected to the following test steps, and the process is as follows: (1) The front side of the substrate (the side without the mask layer grown on the entire surface) is facing down and passes through a chain single-sided HF device to remove the plating-around mask on this side; (2) The silicon wafer is immersed in a trough-type alkaline texturing trough for 3 minutes. At this time, texturing is performed on the front side, and the back side is protected by a mask and not textured; (3) It is washed with pure water to remove the residual liquid medicine on the surface of the silicon wafer; (4) The back side mask layer of the silicon wafer is observed with a microscope to check whether there are perforations and whether the film layer is damaged, and the etching effect is tested.

[0145] The test results are as Figure 4 - 5 and shown in Table 1.

[0146] Figure 4 It shows the micrographs of the substrate surface after etching and cleaning of the mask layers provided in Examples 1-4. It can be seen from the figures that after the above test process, there are no perforations and no damage to the mask on the surfaces of the LPCVD, phosphorus diffusion, boron diffusion, and PECVD samples, indicating that the mask layer has good density and the ability to resist alkaline etching.

[0147] Figure 5 It shows the micrograph of the mask protection effect of the mask layer provided in Comparative Example 1 after cleaning. It can be seen from the figure that the morphology is abnormal, indicating that the mask protection effect is poor, resulting in holes being etched on the surface of the silicon wafer.

[0148] Table 1

[0149]

[0150]

[0151] Analysis:

[0152] It can be seen from the test results that the amount of oxygen passed before deposition affects the deposition rate. Within a certain range, increasing the oxygen flow rate can increase the deposition rate of the mask; passing oxygen during deposition will reduce the gas proportion of TEOS in the tube, resulting in a decrease in the overall reaction rate; when the mask thickness is greater than 80 nm, it can effectively resist the etching of the alkaline solution. If the film thickness is too low, abnormal morphology will occur; if the temperature of epitaxial growth is too low, the growth rate of the silicon oxide mask will be reduced and the growth time of the mask will be prolonged. When the temperature of epitaxial growth is too high, it is easy to cause too fast local decomposition rate, affecting the deposition uniformity; under the conditions of low pressure and high temperature, too fast decomposition rate will lead to poor intra-wafer uniformity; the constant temperature time affects the temperature uniformity in the furnace tube. A certain constant temperature time can make the temperature on the inner wall and in the middle of the reaction chamber tend to be consistent, ensuring the temperature uniformity in the furnace tube and facilitating more complete reaction; too low pressure during epitaxial growth will lead to slow growth rate, while too high pressure will lead to too fast growth rate, reducing the film thickness uniformity of the mask.

[0153] The applicant declares that the present invention illustrates the process method of the present invention through the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent substitution of the raw materials selected for the present invention, the addition of auxiliary components, the selection of specific methods, etc. all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for growing a mask layer, characterized in that The growth method includes: Performing epitaxial growth using an oxygen source and a silicon source under low-pressure conditions to obtain a silicon oxide mask layer; The pressure of the low pressure is 15 - 25 Pa; the temperature of the epitaxial growth is 650 - 850 °C; The oxygen source is oxygen; the silicon source is tetraethyl orthosilicate; The way of the epitaxial growth is to first introduce the oxygen source and then introduce the silicon source; The flow rate of the oxygen source is 500 - 1500 sccm; the flow rate of the silicon source is 50 - 100 sccm; the flow rate ratio of the silicon source to the oxygen source is 1:(5 - 30); After the temperature of the epitaxial growth reaches the set value, keep it at a constant temperature for 3 - 7 min; the time of the epitaxial growth is 8 - 12 min; The thickness of the mask layer is 80 - 110 nm.

2. The growth method according to claim 1, characterized in that The epitaxial growth is carried out in a reaction chamber, and the silicon source is carried into the reaction chamber by a carrier gas.

3. The growth method according to claim 2, wherein The carrier gas includes any one or a combination of at least two of nitrogen, argon or helium.

4. The growth method according to claim 2, characterized in that, The flow rate ratio of the silicon source to the carrier gas is 1:(0.5 - 3).

5. The growth method according to claim 1, characterized in that The heating rate of the temperature of the epitaxial growth is 8 - 12 °C / min.

6. The growth method according to claim 2, wherein, The outer wall temperature of the reaction chamber is 80 - 100 °C.

7. The growth method according to claim 1, wherein After the epitaxial growth, perform low-pressure purging on the reaction chamber.

8. The growth method according to claim 7, wherein The gas used for the low-pressure purging includes any one or a combination of at least two of nitrogen, argon or helium.

9. The growth method according to claim 7, characterized in that, The flow rate of the gas used for the low-pressure purging is 1000 - 2000 sccm.

10. The growth method according to claim 7, characterized in that, The pressure of the low-pressure purging is 3 - 7 Pa.

11. The growth method according to claim 7, characterized in that, The time of the low-pressure purging is 8 - 12 min.

12. The growth method according to claim 1, characterized in that, The epitaxial growth is carried out on a substrate.

13. The growth method according to claim 12, characterized in that, Before the epitaxial growth, the substrate is pre-treated by any one of LPCVD in-situ doping, PECVD in-situ doping, phosphorus diffusion or boron diffusion.

14. The growth method according to claim 13, characterized in that, Before the epitaxial growth, the substrate is pre-treated by phosphorus diffusion or boron diffusion.

15. The growth method according to claim 1, characterized in that, The growth method includes the following steps: (1) Under a pressure of 15 - 25 Pa, introduce 500 - 1500 sccm of the oxygen source into the reaction chamber, and control the temperature at 650 - 850 °C; the oxygen source is oxygen; (2) Leak detection: the leak rate is lower than 1.3 Pa / min; (3) Introduce the carrier gas into the silicon source bottle, and then carry 50 - 100 sccm of the silicon source into the reaction chamber to react with the oxygen source to achieve epitaxial growth, where the flow rate ratio of the silicon source to the oxygen source is 1:(5 - 30), the flow rate ratio of the silicon source to the carrier gas is 1:(0.5 - 3), the time of the epitaxial growth is 8 - 12 min, and the temperature of the outer wall of the reaction chamber is controlled at 80 - 100 °C; (4) Under a pressure of 3 - 7 Pa, introduce 1000 - 2000 sccm of the gas used for purging into the reaction chamber, and the purging time is 8 - 12 min; (5) Introduce nitrogen to normal pressure and take out the boat.

16. A mask layer, characterized in that, The mask layer is obtained by the growth method according to any one of claims 1 - 15; The mask layer is located on the surface of the substrate; Wherein, the thickness of the mask layer is 80 - 110 nm.

17. A silicon-based battery, characterized in that, The silicon-based battery includes the mask layer as described in claim 16.

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