Silicon wafer processing method, silicon wafer with textured surface formed on single side surface and solar cell

Abstract

The invention relates to the technical field of silicon wafer treatment processes, in particular to a silicon wafer treatment method, a silicon wafer with a textured surface formed on a single side surface and a solar cell. The silicon wafer processing method comprises the following steps: placing a silicon wafer in an ozone gas environment; performing ultraviolet irradiation on the single-side surface of the silicon wafer to form a silicon dioxide oxide layer; and performing texturing cleaning on the silicon wafer on which the silicon dioxide oxide layer is formed so as to form a textured surface on the surface of one side, back to the silicon dioxide oxide layer, of the silicon wafer. According to the silicon wafer processing method, a thick silicon dioxide oxide layer can be formed in a short time, defects in the silicon dioxide oxide layer can be effectively reduced, the quality of the silicon dioxide oxide layer is improved, the alkali resistance of silicon dioxide serving as a protective layer is effectively enhanced, and the quality of a textured surface obtained in the texturing step is improved.

Description

Technical Field

[0001] The invention relates to the technical field of silicon wafer processing technology, and in particular to a silicon wafer processing method and a solar cell. Background Art

[0002] Monocrystalline solar cells usually adopt a pyramid velvet structure, which can play a good role in trapping light and improve the absorption utilization rate of incident light in the cell. Conventional monocrystalline silicon wafer texturing and cleaning is to place the monocrystalline silicon wafer in an alkaline solution of a specific concentration, and through process control, use the anisotropic arrangement characteristics of monocrystalline silicon atoms to etch a fine and uniform pyramid appearance along a specific crystal direction. In order to improve the reflectivity of the back of the cell and the back passivation effect, the optimization direction of texturing of monocrystalline silicon solar cells in the existing technology is single-sided texturing, that is, the light-receiving side is a pyramid velvet surface, and the back is a polished surface structure. Monocrystalline silicon solar cells with a single-sided texturing structure can reduce interface recombination and increase the open circuit voltage of the cell; at the same time, it is more conducive to the formation of the back inversion layer and the improvement of the back conductivity, improving the long-wave utilization to further improve the short-circuit current of the cell.

[0003] In the prior art texturing process, the conventional method for preparing a silicon dioxide oxide layer on a single crystal silicon wafer is to grow a silicon dioxide layer by thermal oxygen. However, in the actual process, when the silicon dioxide layer is formed by the reaction of oxygen and silicon, the initial oxide layer will prevent the subsequent oxygen molecules from directly contacting the surface of the single silicon, and the oxygen molecules need to diffuse to the interface layer between silicon dioxide and silicon to make the silicon dioxide layer continue to thicken, resulting in a slow formation speed of the silicon dioxide layer, low oxidation efficiency, and small thickness. In order to speed up the oxidation efficiency and increase the thickness of silicon dioxide, a silicon dioxide layer is formed by reacting silicon with a mixture of water and oxygen. Since the substance involved in the oxidation is a mixture of water and oxygen, its oxidation rate is much faster than that of dry oxygen oxidation. However, the quality of the generated silicon dioxide layer is poor, and it is easy to introduce oxygen vacancy defects in the silicon wafer to form oxygen rings, resulting in the concentric circle phenomenon of the prepared battery electroluminescence, affecting the battery electrical performance, reducing the battery conversion efficiency, causing the photovoltaic module to be degraded, and reducing the yield rate of the photovoltaic module. At the same time, thermal oxygen will further cause dirt on the surface of the silicon wafer to diffuse into the interior of the silicon wafer due to high temperature, causing additional impurity contamination. Summary of the invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defects of low efficiency and poor quality of the silicon dioxide layer generated when the silicon dioxide layer is oxidized to form a silicon dioxide layer in the single crystal silicon wafer texturing process in the prior art, thereby providing a silicon wafer processing method and a solar cell.

[0005] In order to solve the above technical problems, the present invention provides a silicon wafer processing method, comprising the following steps:

[0006] Place the silicon wafer in an ozone gas environment;

[0007] The single-side surface of the silicon wafer is irradiated with ultraviolet light to generate excited oxygen atoms from ozone, and the excited oxygen atoms react with silicon atoms on the surface of the silicon wafer to form a silicon dioxide oxide layer on the single-side surface of the silicon wafer;

[0008] The silicon wafer having the silicon dioxide oxide layer formed thereon is subjected to texturing and cleaning to form a textured surface on the surface of the silicon wafer facing away from the silicon dioxide oxide layer.

[0009] Optionally, the step of placing the silicon wafer in an ozone gas environment includes:

[0010] Placing a silicon wafer in a vacuum chamber;

[0011] A mixed gas of ozone and nitrogen is introduced into the vacuum chamber.

[0012] Optionally, the ratio of ozone to nitrogen in the mixed gas of ozone and nitrogen is 3:2-5:3.

[0013] Optionally, in the step of irradiating the single-side surface of the silicon wafer with ultraviolet light, the temperature of the silicon wafer is controlled to be 150° C.-200° C.

[0014] Optionally, in the step of irradiating the single-side surface of the silicon wafer with ultraviolet light, the wavelength of the ultraviolet light is 210nm-300nm.

[0015] Optionally, in the step of irradiating the single-side surface of the silicon wafer with ultraviolet light, the power of the ultraviolet light is 150W-250W, and the irradiation time of the ultraviolet light is 4min-10min.

[0016] Optionally, before placing the silicon wafer in an ozone gas environment, the method further comprises:

[0017] The surface of the silicon wafer is subjected to alkali polishing and RCA surface cleaning to remove the cutting damage layer on the surface of the silicon wafer and impurities on the surface of the silicon wafer.

[0018] Optionally, the method further comprises: after forming the suede surface, removing the silicon dioxide oxide layer by pickling to expose the polished surface.

[0019] The present invention also provides a silicon wafer with a velvet surface formed on one side thereof, which is prepared by the silicon wafer processing method of the present invention.

[0020] The present invention also provides a solar cell, comprising: a silicon wafer with a velvet surface formed on one side obtained by the silicon wafer processing method described in the present invention, and a passivation layer, a doping layer, a transparent conductive layer and a gate line electrode formed in sequence on at least one side of the silicon wafer with the velvet surface.

[0021] The technical solution of the present invention has the following advantages:

[0022] 1. The silicon wafer processing method provided by the present invention is to place the silicon wafer in an ozone environment and irradiate the surface of the silicon wafer with ultraviolet light, so that the ozone on the side of the silicon wafer irradiated by ultraviolet light is decomposed to generate oxygen and free oxygen atoms, and the free oxygen atoms react rapidly with silicon single substance with strong reducing property to generate a silicon dioxide oxide layer, and then perform a texturing operation. In this process, after oxygen contacts the surface of the silicon wafer, a silicon dioxide film is initially formed on the surface of the silicon wafer; since the free oxygen atoms generated by the decomposition of ozone are small in volume, they can smoothly move in the gaps of the silicon dioxide crystals, and the initially formed silicon dioxide oxide film has less restriction on the movement of the free oxygen atoms, so that the free oxygen atoms can quickly pass through the silicon dioxide oxide film, and the silicon single substance at the interface layer between silicon dioxide and silicon reacts to continue to form silicon dioxide, so that the initially formed silicon dioxide film continues to grow, and then forms the final silicon dioxide oxide layer. When a silicon dioxide layer is formed on the surface of a silicon wafer by reacting free oxygen atoms with the silicon wafer, the silicon dioxide layer is formed quickly and a thicker silicon dioxide layer can be formed in a short time. Under ultraviolet light conditions, a dense silicon dioxide layer of 3nm-4nm can be grown in 4min-6min, which greatly shortens the process time for growing a fixed thickness silicon dioxide anti-alkali protective layer. In addition, the silicon dioxide layer can block further penetration of impurities, and the free oxygen atoms are small in size and can move smoothly between the gaps of the silicon dioxide crystals, which can effectively reduce the generation of defects in the silicon dioxide layer, improve the quality of the silicon dioxide layer, effectively enhance the alkali resistance of silicon dioxide as a protective layer, and improve the quality of the velvet surface obtained in the velvet making step.

[0023] 2. The silicon wafer processing method provided by the present invention introduces a mixed gas of ozone and nitrogen into a vacuum chamber, and uses nitrogen as a protective gas to prevent the silicon element in a certain area on the silicon wafer from being oxidized too quickly, so that the thickness of the silicon dioxide oxide layer generated on the surface of the silicon wafer remains uniform. At the same time, nitrogen can also be used as a carrier source of ozone, so that ozone is evenly distributed in the chamber, avoiding local aggregation of ozone in the chamber, thereby improving the uniformity of the silicon dioxide oxide layer generated on the surface of the silicon wafer and improving the preparation quality of the silicon dioxide oxide layer. In addition, nitrogen can also be used to adjust the gas pressure in the chamber so that ozone can react under a suitable pressure.

[0024] 3. The solar cell provided by the present invention is prepared with a velvet surface by the silicon wafer processing method provided by the present invention. The silicon dioxide oxide layer formed in the process is more compact, thereby improving the anti-alkali protection performance of the silicon dioxide oxide layer in the velvet making process, thereby improving the quality of the obtained velvet surface, thereby improving the photoelectric performance of the solar cell, and improving the average conversion efficiency of all the prepared solar cells, thereby improving the yield rate of the solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 This is a flow chart of the silicon wafer processing method in Example 1 of the present invention.

[0027] Figure 2 Schematic diagram of the alkali polishing and RCA surface cleaning steps in the silicon wafer processing method in Example 1 of the present invention.

[0028] Figure 3 Schematic diagram of the step of irradiating a single side surface of a silicon wafer with ultraviolet light in the silicon wafer processing method in Example 1 of the present invention.

[0029] Figure 4 Schematic diagram of the structure of a silicon wafer with a silicon dioxide oxide layer formed thereon obtained in the silicon wafer processing method in Example 1 of the present invention.

[0030] Figure 5 This is a schematic diagram of the texturing and cleaning steps in the silicon wafer processing method in Example 1 of the present invention.

[0031] Figure 6 Schematic diagram of the structure of a silicon wafer with a textured surface obtained in the silicon wafer processing method in Example 1 of the present invention.

[0032] Figure 7 Schematic diagram of the structure of the polished silicon wafer obtained in the silicon wafer processing method in Example 1 of the present invention.

[0033] Explanation of the reference numerals: 1. silicon wafer; 2. silicon dioxide oxide layer; 3. velvet surface; 4. chamber; 5. infrared heating plate; 6. quartz mercury lamp; 7. ozone pipeline; 8. nitrogen pipeline. DETAILED DESCRIPTION

[0034] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0036] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0037] Example 1

[0038] Figure 1 The present embodiment provides a silicon wafer processing method for forming a textured surface on a silicon wafer. The silicon wafer processing method includes the following steps:

[0039] S1: Place the silicon wafer in an ozone gas environment;

[0040] S2: irradiating a single side surface of the silicon wafer with ultraviolet light to generate excited oxygen atoms from ozone, and the excited oxygen atoms react with silicon atoms on the single side surface of the silicon wafer to form a silicon dioxide oxide layer on the surface of the silicon wafer;

[0041] S3: performing texturing and cleaning on the silicon wafer having the silicon dioxide oxide layer formed thereon, so as to form a textured surface on the surface of the silicon wafer facing away from the silicon dioxide oxide layer.

[0042] In this embodiment, the silicon wafer is placed in an ozone environment and the surface of the silicon wafer is irradiated with ultraviolet light, so that the ozone on the side of the silicon wafer irradiated with ultraviolet light is decomposed to generate oxygen and free oxygen atoms, and the free oxygen atoms react rapidly with silicon single substance with strong reducing property to generate silicon dioxide oxide layer, and then the texturing operation is performed. In this process, after oxygen contacts the surface of the silicon wafer, a silicon dioxide film is initially formed on the surface of the silicon wafer; since the free oxygen atoms generated by the decomposition of ozone are small in volume, they can smoothly move in the gaps of silicon dioxide crystals, and the initially formed silicon dioxide oxide film has less restriction on the movement of free oxygen atoms, so that the free oxygen atoms can quickly pass through the silicon dioxide oxide film, and the silicon single substance at the interface layer between silicon dioxide and silicon reacts to continue to form silicon dioxide, so that the initially formed silicon dioxide film continues to grow, and then forms the final silicon dioxide oxide layer. The silicon dioxide layer is grown on the silicon wafer using the existing British tube thermal oxidation process. The growth of the silicon dioxide anti-alkali protective layer takes about one and a half hours. When the silicon wafer is processed by the silicon wafer processing equipment provided in this embodiment, the silicon dioxide oxide layer is formed on the surface of the silicon wafer by reacting with free oxygen atoms and the silicon wafer. The silicon dioxide oxide layer is formed quickly. From placing the silicon wafer in an ozone environment to taking out the silicon wafer with the silicon dioxide oxide layer, the entire process of growing the silicon dioxide layer only takes about 10 minutes. A thicker silicon dioxide oxide layer can be formed in a short time, which greatly shortens the process time for growing a fixed thickness silicon dioxide anti-alkali protective layer. In addition, the free oxygen atoms can move smoothly between the gaps of the silicon dioxide oxide crystals, which can effectively reduce the generation of defects in the silicon dioxide oxide layer, improve the quality of the silicon dioxide oxide layer, and effectively enhance the alkali resistance of silicon dioxide as a protective layer.

[0043] The silicon wafer processing method provided in this embodiment also includes: before placing the silicon wafer in an ozone gas environment, performing alkali polishing and industrial standard wet process (RCA) surface cleaning on the surface of the silicon wafer to remove the cutting damage layer and impurities on the surface of the silicon wafer. After forming the velvet surface, the silicon dioxide oxide layer is removed by acid washing to expose the polished surface.

[0044] Refer to the following Figures 2 to 7 The process of forming a velvet surface on the surface of a silicon wafer by using a silicon wafer processing method is described in detail. The silicon wafer in this embodiment is a single crystal silicon wafer, and the velvet surface formed is a pyramid velvet surface. In other embodiments, the silicon wafer can also be a polycrystalline silicon wafer, and the velvet surface formed is a pit-shaped velvet surface.

[0045] First, if Figure 2 As shown, the surface of the silicon wafer 1 is subjected to conventional alkali polishing and RCA surface cleaning to remove the cutting damage layer on the surface of the silicon wafer, the metal or dust impurities on the surface of the silicon wafer, and the natural oxide layer on the surface of the silicon wafer.

[0046] Then, if Figure 3As shown, the cleaned single crystal silicon wafer 1 is placed in an ozone gas environment. Specifically, the silicon wafer 1 processing process is carried out in a closed chamber 4. Before the silicon wafer 1 enters the chamber 4, the silicon wafer is located in the upstream loading chamber. At this time, the loading chamber and the chamber 4 must be evacuated to form a vacuum environment. The clean single crystal silicon wafer is then transported to the vacuum chamber 4 through a conveyor roller. Then ozone and nitrogen are introduced into the vacuum chamber at the same time to form an ozone gas environment under a nitrogen background in the chamber. In the chamber 4, the silicon wafer 1 is placed on an infrared heating plate 5, and the side of the silicon wafer 1 to be oxidized is set up, and the ozone pipe 7 introduces ozone into the chamber from the top of the chamber, and the nitrogen pipe 8 introduces nitrogen from the bottom of the chamber. During the ventilation process, the molecular mass of ozone is larger, and the molecular mass of nitrogen is smaller. During the diffusion of ozone and nitrogen in the chamber 4, ozone tends to move downward and nitrogen tends to move upward, so that ozone and nitrogen can be fully mixed, and driven by nitrogen, ozone can evenly fill the entire chamber. The ratio of ozone to nitrogen in the mixed gas of ozone and nitrogen in the chamber is: 3:2-5:3, for example, 3:2, 19:12 or 5:3. When the ratio of ozone to nitrogen is between 3:2-5:3, the obtained oxide layer has moderate thickness, optimal density, and best protection effect. When the ratio of ozone to nitrogen is lower than 3:2, the obtained oxide layer is thinner, and when the ratio of ozone to nitrogen is higher than 5:3, the obtained oxide layer has poor density.

[0047] In some other embodiments, the directions and positions of ozone and oxygen introduction may also be set in other ways, with the priority being to ensure the ratio between the two.

[0048] Furthermore, the surface of the silicon wafer 1 is irradiated with ultraviolet light to cause ozone to generate excited oxygen atoms, which react with silicon atoms on the surface of the silicon wafer to prepare a silicon dioxide oxide layer on the surface of the silicon wafer 1. Specifically, in the chamber, the ultraviolet light source is a quartz mercury lamp 6, and the light emitted by the mercury lamp source is filtered by quartz to form pure ultraviolet light. Under the condition of heating by an infrared heating plate, ultraviolet light is used to irradiate the single-side surface of the silicon wafer. Under the irradiation of ultraviolet rays, the ozone in the chamber decomposes into oxygen and free oxygen atoms. The free oxygen atoms have extremely strong oxidizing properties, and silicon has strong reducing properties. The free oxygen atoms can quickly react with the silicon atoms on the surface of the silicon wafer to form a silicon dioxide oxide layer 2, such as Figure 4As shown. In the step of irradiating the single-side surface of the silicon wafer with ultraviolet light, the temperature of the silicon wafer is controlled to be 150°C-200°C, for example, 150°C, 160°C, 170°C, 180°C, 190°C or 200°C. When the temperature of the silicon wafer is lower than 150°C, the reaction rate of the silicon wafer is slow. When the temperature of the silicon wafer is higher than 200°C, the energy consumption of the equipment will be too high, and the cooling time after the oxidation is completed will be greatly increased, affecting the processing efficiency of the silicon wafer. The wavelength of the ultraviolet light emitted by the quartz mercury lamp 6 is controlled to be 210nm-300nm, for example, 210nm, 230nm, 250nm, 270nm, 290nm or 300nm. The energy of ultraviolet light of other wavelengths cannot be absorbed by ozone and cannot excite ozone to react. The power of the ultraviolet light emitted by the quartz mercury lamp 6 is controlled to be 150W-250W, for example, 150W, 170W, 190W, 210W, 230W or 250W, so as to ensure that the wavelength of the ultraviolet light is within the range of 210nm-300nm. The quartz mercury lamp 6 is controlled to emit ultraviolet light to irradiate the silicon wafer for 4min-10min, for example, 4min, 5min, 6min, 7min, 8min, 9min or 10min.

[0049] Then, if Figure 5 As shown, the silicon wafer 1 formed with the silicon dioxide oxide layer 2 is subjected to conventional texturing and cleaning to form a pyramid texture surface 3 on the surface of the silicon wafer 1 facing away from the silicon dioxide oxide layer 2, as shown in FIG. Figure 6 During the texturing and cleaning process, the silicon dioxide oxide layer 2 will be partially corroded, making the silicon dioxide oxide layer 2 thinner.

[0050] Finally, the silicon wafer 1 is pickled with hydrofluoric acid to remove the remaining silicon dioxide oxide layer 2 after the texturing cleaning and expose the polished surface. Figure 7 As shown, a single crystal silicon wafer after texturing is obtained.

[0051] The existing British tube thermal oxidation process is used to grow a silicon dioxide layer on the silicon wafer. The growth of the silicon dioxide anti-alkali protective layer takes about one and a half hours. The silicon dioxide oxide layer generated by ultraviolet light assisted ozone is denser than the silicon dioxide oxide layer generated by traditional thermal oxidation technology. Generally, under the conditions of 200°C temperature and 150W ultraviolet light, a 3nm-8nm dense silicon dioxide oxide layer can be grown in 4min-10min. This can greatly shorten the process time for growing a fixed thickness silicon dioxide oxide layer, meeting the large-scale mass production requirements of the photovoltaic industry.

[0052] In order to make ozone excited by ultraviolet light to generate excited oxygen atoms, a high-pressure mercury lamp must be used to generate ultraviolet light of a specific wavelength (wavelength 200-300nm) to directly irradiate the single crystal silicon substrate sample. The UV lamp has a wide and continuous light emission interval within a wavelength range longer than 210nm. Only ultraviolet light with a wavelength of 200-300nm contributes to ozone photodecomposition. In actual tests, wavelengths above 300nm are considered to have no contribution to the ozone excitation reaction.

[0053] The ozone generator is used to generate the process gas source. During the process of preparing the silicon dioxide oxide layer on the single side of the silicon wafer, the main reaction is that the strongly oxidizing ozone molecules excited by ultraviolet light react with silicon to generate silicon dioxide and ozone hexacyclic rings. This includes the ozone-oxygen-ozone cyclic chain reaction. The specific reaction process is as follows: a part of the ozone that has not reacted with silicon decomposes under ultraviolet light to generate oxygen and free oxygen atoms, and the obtained free oxygen atoms react with silicon elements to generate silicon dioxide; oxygen decomposes and oxidizes under ultraviolet light to generate ozone with stronger oxidizing properties, and then the above cycle is repeated. Through the above reactions, free oxygen atoms and ozone are continuously generated. In addition, the ozone source introduced by the ozone generator makes the single-crystal silicon substrate exposed to a relatively high-pressure and high-concentration oxidizing atmosphere on one side, thereby obtaining a fast and efficient oxidation reaction, so that a sufficiently thick and dense silicon dioxide layer can be generated in a short time.

[0054] By increasing the flow rate of ozone gas introduced through the ozone generator and controlling the temperature of the silicon wafer substrate, a higher oxidation rate can be obtained. Compared with the thermal oxidation process which only relies on a single oxidation reaction in a high temperature environment of more than 800°C by introducing oxygen, it is obvious that the oxidation method provided in this embodiment is more diverse and efficient and controllable.

[0055] After the silicon dioxide oxide layer is formed, the silicon wafer with the silicon dioxide oxide layer is cleaned by texturing. In terms of the technical route selection for preparing the silicon oxide layer, compared with the tubular thermal oxygen double-sided oxidation: by using ultraviolet lamps in an ozone atmosphere, large-area one-time single-sided rapid processing of single-crystal planar silicon can be performed to meet the requirements of all specifications of single-crystal silicon wafers in the current photovoltaic market. Compared with the existing tubular thermal oxygen double-sided oxidation process, it has significant advantages in convenience, especially in production cycle, production efficiency and production cost.

[0056] In the tubular hot oxygen texturing process, long-term heating at over 800°C is required. Long-term high-temperature heating will inevitably cause thermal damage and defects inside the single-crystal silicon wafer. In this embodiment, ozone is excited by ultraviolet light to generate excited oxygen atoms to oxidize the silicon wafer. The process temperature does not exceed 200°C, and the ultraviolet light energy during the oxidation process is less than the chemical bond energy between silicon atoms, so it will not cause any damage to the inside of the single-crystal silicon wafer and will not increase the number of defects inside the single-crystal silicon wafer.

[0057] Since the oxidation rate of silicon wafers in the tubular hot oxygen texturing process is affected by the crystal orientation during oxidation, the oxidation rate is slow during the process time and the thickness distribution of the generated oxide layer film will be uneven. The method of ultraviolet-assisted ozone irradiation of single-crystal silicon wafers provided in this embodiment is used for oxidation texturing. Due to the dual effects of the strong oxidizing property of ozone itself and the auxiliary decomposition of ultraviolet light of a specific wavelength, it is sufficient to overcome the influence of the difference in the crystal orientation of silicon oxide, so that the reaction of generating the silicon dioxide oxide layer is rapid and uniform. The silicon dioxide oxide layer prepared under this process condition performs better in uniformity and thickness, and has better compactness. The corresponding silicon dioxide mask protective layer obtained in the subsequent single-sided texturing process is more effective in the tolerance limit of alkali in the texturing solution.

[0058] In order to verify the compactness of the silicon dioxide oxide layer prepared in this example, three groups of control experiments were used for verification.

[0059] In the first set of experiments, clean silicon wafers were placed in an alkaline solution of sodium hydroxide with a volume fraction of 2%.

[0060] In the second group of experiments, the silicon wafers with silicon dioxide oxide layer prepared by the tubular thermal oxidation process were placed in a sodium hydroxide alkaline solution with a volume fraction of 2%. In the tubular thermal oxidation process, the clean single-crystal silicon wafers are first loaded into the furnace boat of the tubular furnace, and then the furnace boat is used to carry the single-crystal silicon wafers into the tubular furnace. Then the furnace body is sealed, oxygen is introduced and the temperature is increased. After the oxidation is completed, the furnace body is cooled down, and the furnace boat is taken out to unload the silicon wafers to obtain silicon wafers with silicon dioxide oxide layer. The time for the silicon wafer to heat up and oxidize in the tubular furnace is 30 minutes.

[0061] In the third group of experiments, the silicon wafer with the silicon dioxide oxide layer formed thereon, which was irradiated with ultraviolet rays for 10 minutes in this embodiment, was placed in an alkaline solution of sodium hydroxide with a volume fraction of 2%.

[0062] The experimental temperature of the three groups of experiments was controlled to be 60°C, and the changes of the silicon wafers in the three groups of experiments were observed respectively.

[0063] In the first set of experiments, as a control experiment without an oxide layer, the silicon wafer began to bubble violently when placed in the alkaline solution, and the maximum alkali resistance time was recorded as 0s.

[0064] In the second set of experiments, 282 seconds after the silicon wafer was placed in the alkaline solution, the silicon dioxide oxide layer on the edge of the oxidation surface began to fall off, and then the alkaline solution began to gradually spread and bubble to the middle area of ​​the silicon wafer. The maximum alkali resistance time was recorded as 282 seconds.

[0065] In the third set of experiments, 402 seconds after the silicon wafer was placed in the alkaline solution, the silicon dioxide oxide layer in the local area of ​​the oxidation surface began to fall off, followed by a bubbling reaction, and the maximum alkali resistance time was recorded as 402 seconds.

[0066] According to the above three groups of control experiments, it can be seen that the silicon dioxide oxide layer generated on the silicon wafer in this embodiment can better protect the silicon element in the inner layer of the silicon wafer, and can effectively enhance the alkali resistance of the silicon dioxide oxide layer as a protective layer in the subsequent texturing step, thereby improving the quality of the pyramid velvet surface obtained in the texturing step.

[0067] Example 2

[0068] This embodiment provides a solar cell, comprising: a silicon wafer with a pyramid velvet surface formed on one side of the surface obtained by the silicon wafer processing method described in Embodiment 1, and a passivation layer, a doping layer, a transparent conductive layer and a gate electrode formed in sequence on at least the side of the silicon wafer on which the velvet surface is formed. The passivation layer is formed on the surface of the pyramid velvet surface by a deposition process, the doping layer is formed on the surface of the passivation layer on the side facing away from the silicon wafer by a deposition process, the transparent conductive layer is formed on the surface of the doping layer on the side facing away from the silicon wafer by a coating process, an electroplating process, an evaporation process or a spin coating process, and the gate electrode is formed on the surface of the transparent conductive layer on the side facing away from the silicon wafer.

[0069] When the solar cell is a heterojunction cell, it also includes: a passivation layer, a doping layer, a transparent conductive layer and a grid line electrode which are sequentially formed on the polished surface of the silicon wafer.

[0070] The solar cell provided in this embodiment is prepared with a single-sided velvet surface by the silicon wafer processing method provided in Example 1. The silicon dioxide oxide layer formed in the process is more compact, thereby improving the anti-alkali protection performance of the silicon dioxide oxide layer during the velvet preparation process, thereby improving the quality of the obtained velvet surface, thereby improving the photoelectric performance of the solar cell.

[0071] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A silicon wafer processing method, characterized in that: The following steps are involved: Place the silicon wafer in an ozone gas environment; Irradiating the single-side surface of the silicon wafer with ultraviolet light to generate excited oxygen atoms from ozone, and the excited oxygen atoms react with silicon atoms on the single-side surface of the silicon wafer to form a silicon dioxide oxide layer on the single-side surface of the silicon wafer; The silicon wafer with the silicon dioxide oxide layer formed thereon is subjected to texturing and cleaning to form a textured surface on the surface of the silicon wafer which is opposite to the silicon dioxide oxide layer.

2. The silicon wafer processing method according to claim 1, characterized in that: The step of placing the silicon wafer in an ozone gas environment comprises: Placing a silicon wafer in a vacuum chamber; A mixed gas of ozone and nitrogen is introduced into the vacuum chamber.

3. The silicon wafer processing method according to claim 2, characterized in that: The ratio of ozone to nitrogen in the mixed gas of ozone and nitrogen is 3:2-5:

3.

4. The silicon wafer processing method according to any one of claims 1 to 3, characterized in that: In the step of irradiating the single-side surface of the silicon wafer with ultraviolet light, the temperature of the silicon wafer is controlled to be 150°C-200°C.

5. The silicon wafer processing method according to any one of claims 1 to 3, characterized in that: In the step of irradiating the single-side surface of the silicon wafer with ultraviolet light, the wavelength of the ultraviolet light is 210nm-300nm.

6. The silicon wafer processing method according to any one of claims 1 to 3, characterized in that: In the step of irradiating the single-side surface of the silicon wafer with ultraviolet light, the power of the ultraviolet light is 150W-250W, and the irradiation time of the ultraviolet light is 4min-10min.

7. The silicon wafer processing method according to any one of claims 1 to 3, characterized in that: Before the step of placing the silicon wafer in an ozone gas environment, the method further comprises: The surface of the silicon wafer is subjected to alkali polishing and RCA surface cleaning.

8. The silicon wafer processing method according to any one of claims 1 to 3, characterized in that: Also includes: After the textured surface is formed, the silicon dioxide oxide layer is removed by acid washing to expose the polished surface.

9. A silicon wafer with a velvet surface formed on one side, characterized in that: The silicon wafer is prepared by the silicon wafer processing method according to any one of claims 1 to 8.

10. A solar cell, characterized in that: include: A silicon wafer with a velvet surface formed on one side obtained by the silicon wafer processing method according to any one of claims 1 to 8 or a silicon wafer with a velvet surface formed on one side according to claim 9, and a passivation layer, a doping layer, and a transparent conductive layer formed in sequence on at least the surface of the silicon wafer on which the velvet is formed.

Images