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

Abstract

The present invention relates to the technical field of silicon wafer processing processes, and particularly relates to a silicon wafer processing 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; subjecting a single side surface of the silicon wafer to ultraviolet irradiation, so as to form a silicon dioxide oxide layer; and subjecting the silicon wafer, on which the silicon dioxide oxide layer is formed, to texturing cleaning, so as to form a textured surface on the surface of the side, opposite to the silicon dioxide oxide layer, of the silicon wafer. By means of the silicon wafer processing method of the present invention, a relatively thick silicon dioxide oxide layer can be formed in a short time, and the generation of defects in the silicon dioxide oxide layer can be effectively reduced, thereby improving the quality of the silicon dioxide oxide layer, effectively enhancing the alkali resistance of silicon dioxide serving as a protective layer, and improving the quality of the textured surface obtained in the texturing step.

Description

Silicon wafer processing methods, silicon wafers with textured surfaces on one side, and solar cells

[0001] Cross-references to related applications

[0002] This disclosure claims priority to Chinese Patent Application No. 202411791681.8, filed on December 6, 2024, entitled "Method for processing silicon wafers, silicon wafers with a textured surface formed on one side and solar cells", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to the field of silicon wafer processing technology, specifically to a silicon wafer processing method and a solar cell. Background Technology

[0004] Monocrystalline solar cells typically employ a pyramidal textured structure, which effectively traps light, thereby improving the cell's incident light absorption and utilization rate. Conventional texturing and cleaning of monocrystalline silicon wafers involves immersing the wafer in an alkaline solution of a specific concentration. Through process control, the anisotropic arrangement of monocrystalline silicon atoms is utilized to etch a fine, uniform pyramidal appearance along specific crystal orientations. To improve the reflectivity and passivation effect of the back side of the cell, current optimizations in monocrystalline silicon solar cell texturing focus on single-sided texturing, where the light-receiving side has a pyramidal textured surface and the back side has a polished structure. Single-sided texturing reduces interfacial recombination, increasing the cell's open-circuit voltage; it also facilitates the formation of a back-side inversion layer and improves back-side conductivity, enhancing long-wavelength utilization and further improving the cell's short-circuit current.

[0005] In existing texturing processes, the conventional method for preparing a silicon dioxide oxide layer on a monocrystalline silicon wafer is thermal oxygen growth. However, in actual processes, when forming a silicon dioxide layer through the reaction of oxygen with silicon, the initial oxide layer prevents subsequent oxygen molecules from directly contacting the elemental silicon surface. Oxygen molecules need to diffuse to the silicon-silicon interface layer for the silicon dioxide layer to continue thickening, resulting in a slow formation rate, low oxidation efficiency, and small thickness. To accelerate oxidation efficiency and increase silicon dioxide thickness, a mixture of water and oxygen is used to react with silicon to form the silicon dioxide layer. Because the oxidizing substances are a mixture of water and oxygen, its oxidation rate is much faster than dry oxygen oxidation. However, the resulting silicon dioxide layer is of poor quality and easily introduces oxygen vacancy defects into the silicon wafer, forming oxygen rings. This causes concentric circles in the electroluminescence of the prepared battery, affecting the battery's electrical performance, reducing conversion efficiency, leading to degradation of the photovoltaic module, and lowering the yield rate. At the same time, heat and oxygen will further cause dirt on the surface of the silicon wafer to diffuse and penetrate into the interior of the silicon wafer due to high temperature, resulting in additional impurity contamination. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to overcome the defects of low efficiency and poor quality of silicon dioxide layer formation during oxidation to form silicon dioxide layer in the existing single crystal silicon wafer texturing process, thereby providing a silicon wafer processing method and a solar cell.

[0007] To address the aforementioned technical problems, the first aspect of the present invention provides a silicon wafer processing method, comprising the following steps:

[0008] Place the silicon wafer in an ozone gas environment;

[0009] The silicon wafer is irradiated with ultraviolet light on one side to generate excited oxygen atoms from ozone. The excited oxygen atoms react with silicon atoms on the surface of the silicon wafer to form a silicon dioxide oxide layer on one side of the silicon wafer.

[0010] The silicon wafer on which the silicon dioxide oxide layer is formed is texturized and cleaned to form a textured surface on the side of the silicon wafer facing away from the silicon dioxide oxide layer.

[0011] Optionally, the step of placing the silicon wafer in an ozone gas environment includes:

[0012] The silicon wafer is placed inside a vacuum chamber;

[0013] A mixture of ozone and nitrogen is introduced into the vacuum chamber.

[0014] Optionally, the volumetric flow rate ratio of ozone to nitrogen in the ozone and nitrogen mixture is 3:2 to 5:3.

[0015] Optionally, in the step of irradiating one side of the silicon wafer with ultraviolet light, the temperature of the silicon wafer is controlled to be 150°C-200°C.

[0016] Optionally, in the step of irradiating one side of the silicon wafer with ultraviolet light, the wavelength of the ultraviolet light is 210nm-300nm, and the peak wavelength is 248nm-259nm.

[0017] Optionally, in the step of irradiating one side of the silicon wafer with ultraviolet light, the power of the ultraviolet light is 150W-250W, and the irradiation time is 4min-10min.

[0018] Optionally, before the step of placing the silicon wafer in an ozone gas environment, the method further includes:

[0019] The silicon wafer surface is subjected to alkaline polishing and RCA surface cleaning to remove the cutting damage layer and impurities on the silicon wafer surface.

[0020] Optionally, it further includes: after forming the textured surface, removing the silicon dioxide oxide layer by acid washing to expose the polished surface.

[0021] The second aspect of the present invention provides a silicon wafer with a textured surface formed on one side, which is prepared by the silicon wafer processing method provided in the first aspect of the present invention.

[0022] A third aspect of the present invention provides a solar cell, comprising:

[0023] Silicon wafers with a textured surface formed on one side;

[0024] Along the direction away from the textured side of the silicon wafer, at least on the surface of the silicon wafer on the side where the textured surface is formed, a passivation layer, a doped layer, and a transparent conductive layer are sequentially stacked.

[0025] The silicon wafer with a textured surface formed on one side is obtained using the silicon wafer processing method provided in the first aspect of this disclosure; or...

[0026] The silicon wafer with a textured surface on one side is the silicon wafer with a textured surface on one side provided in the second aspect of this disclosure.

[0027] The technical solution of this invention has the following advantages:

[0028] 1. The silicon wafer processing method provided by this invention involves placing the silicon wafer in an ozone environment and irradiating its surface with ultraviolet light. This causes the ozone on the irradiated side of the silicon wafer to decompose, generating oxygen and free oxygen atoms. The free oxygen atoms rapidly react with the highly reducing silicon to form a silicon dioxide oxide layer, followed by texturing. In this process, oxygen initially forms a silicon dioxide film upon contact with the silicon wafer surface. Because the free oxygen atoms generated by ozone decomposition are small, they can move easily through the gaps between silicon dioxide crystals. The initially formed silicon dioxide oxide film has minimal restriction on the movement of free oxygen atoms, allowing them to quickly penetrate the film and react with the silicon at the silicon-dioxide interface to further form silicon dioxide. This allows the initially formed silicon dioxide film to continuously grow, ultimately forming the final silicon dioxide oxide layer. When a silicon dioxide oxide layer is formed on the surface of a silicon wafer by reacting with free oxygen atoms, the silicon dioxide oxide layer forms rapidly and can be formed in a short time. A dense silicon dioxide oxide layer of 3nm-4nm can be grown by irradiating with ultraviolet light for 4-6 minutes, which greatly shortens the process time for growing a silicon dioxide anti-alkali protective layer of fixed thickness. Moreover, the silicon dioxide oxide layer can block the further penetration of impurities, and the small size of free oxygen atoms allows them to move smoothly in the gaps between 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, effectively enhance the anti-alkali performance of silicon dioxide as a protective layer, and improve the quality of the textured surface obtained in the texturing step.

[0029] 2. The silicon wafer processing method provided by this invention introduces a mixture of ozone and nitrogen into a vacuum chamber. Using nitrogen as a protective gas, the oxidation rate of elemental silicon in a specific area of ​​the silicon wafer is prevented from being too rapid, thus ensuring a uniform thickness of the silicon dioxide oxide layer formed on the wafer surface. Simultaneously, nitrogen acts as a carrier gas for ozone, ensuring its uniform distribution within the chamber and preventing localized ozone accumulation. This further improves the uniformity of the silicon dioxide oxide layer formed on the wafer surface and enhances its preparation quality. Furthermore, nitrogen can be used to regulate the gas pressure within the chamber, allowing ozone to react and generate excited-state oxygen atoms under suitable pressure.

[0030] 3. The silicon wafer processing method provided by the present invention involves the decomposition of ozone on the side of the silicon wafer exposed to ultraviolet light to generate oxygen and free oxygen atoms. The free oxygen atoms react rapidly with silicon, which has strong reducing properties, to generate a silicon dioxide oxide layer. This process is mainly a thermochemical oxidation process. The thermochemical oxidation process is relatively mild, which is conducive to maintaining low defects and low damage on the surface of the treated silicon wafer and promoting the formation of a good passivation layer in the subsequent passivation process.

[0031] 4. The solar cell provided by the present invention uses the silicon wafer processing method provided by the present invention to prepare a textured surface. The silicon dioxide oxide layer formed in this process is more dense and has better alkali resistance protection performance for the silicon wafer during the texturing process, which is conducive to improving the quality of the obtained textured surface, thereby improving the photoelectric performance, average conversion efficiency and yield of the solar cell. Attached Figure Description

[0032] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0033] Figure 1 is a flowchart of the silicon wafer processing method in Embodiment 1 of the present invention.

[0034] Figure 2 is a schematic diagram of the alkaline polishing and RCA surface cleaning steps in the silicon wafer processing method of Embodiment 1 of the present invention.

[0035] Figure 3 is a schematic diagram of the step of irradiating one side of the silicon wafer with ultraviolet light in the silicon wafer processing method of Embodiment 1 of the present invention.

[0036] Figure 4 is a schematic diagram of the structure of the silicon wafer with a silicon dioxide oxide layer obtained in the silicon wafer processing method of Embodiment 1 of the present invention.

[0037] Figure 5 is a schematic diagram of the texturing and cleaning step in the silicon wafer processing method of Embodiment 1 of the present invention.

[0038] Figure 6 is a schematic diagram of the structure of the textured silicon wafer obtained by the silicon wafer processing method in Embodiment 1 of the present invention.

[0039] Figure 7 is a schematic diagram of the structure of the polished silicon wafer obtained in the silicon wafer processing method of Embodiment 1 of the present invention.

[0040] Explanation of reference numerals in the attached diagram: 1. Silicon wafer; 2. Silicon dioxide oxide layer; 3. Textured surface; 4. Chamber; 5. Infrared heating plate; 6. Quartz mercury lamp; 7. Ozone pipeline; 8. Nitrogen pipeline. Detailed Implementation

[0041] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0043] Furthermore, 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.

[0044] Example 1

[0045] Figure 1 illustrates a silicon wafer processing method provided in this embodiment for forming a textured surface on a silicon wafer. The silicon wafer processing method includes the following steps:

[0046] S1: Place the silicon wafer in an ozone gas environment;

[0047] S2: Irradiate one side of the silicon wafer with ultraviolet light to generate excited oxygen atoms from ozone. The excited oxygen atoms react with silicon atoms on one side of the silicon wafer to form a silicon dioxide oxide layer on the silicon wafer surface.

[0048] S3: Texturing and cleaning the silicon wafer with the silicon dioxide oxide layer to form a textured surface on the side of the silicon wafer facing away from the silicon dioxide oxide layer.

[0049] In this embodiment, a silicon wafer is placed in an ozone environment and its surface is irradiated with ultraviolet light. This causes the ozone on the irradiated side of the wafer to decompose, generating oxygen and free oxygen atoms. The free oxygen atoms react rapidly with the highly reducing silicon to form a silicon dioxide oxide layer, which is then texturing performed. During this process, oxygen initially forms a silicon dioxide film upon contact with the silicon wafer surface. Because the free oxygen atoms generated by ozone decomposition are small, they can move easily through the gaps between silicon dioxide crystals. The initially formed silicon dioxide oxide film has minimal restriction on the movement of free oxygen atoms, allowing them to quickly penetrate the film and react with the silicon at the silicon-dioxide interface to further form silicon dioxide. This allows the initially formed silicon dioxide film to continue growing, eventually forming the final silicon dioxide oxide layer. In existing technologies for growing silicon dioxide layers on silicon wafers using the thermo-oxidative process, the growth of the alkali-resistant silicon dioxide protective layer takes about one and a half hours. However, when processing silicon wafers using the silicon wafer processing equipment provided in this embodiment, a silicon dioxide oxide layer is formed on the silicon wafer surface by reacting with free oxygen atoms. The silicon dioxide oxide layer forms quickly; from placing the silicon wafer in the ozone environment to removing the silicon wafer with the silicon dioxide oxide layer, the entire process takes only about 10 minutes. A thicker silicon dioxide oxide layer can be formed in a short time, greatly shortening the process time for growing a silicon dioxide alkali-resistant protective layer of a fixed thickness. Moreover, free oxygen atoms can move smoothly in the gaps between silicon dioxide oxide crystals, effectively reducing the generation of defects in the silicon dioxide oxide layer, improving the quality of the silicon dioxide oxide layer, and effectively strengthening the alkali resistance of silicon dioxide as a protective layer.

[0050] The silicon wafer processing method provided in this embodiment further includes: before placing the silicon wafer in an ozone gas environment, performing alkaline polishing and industrial standard wet (RCA) surface cleaning on the silicon wafer surface to remove the cutting damage layer and impurities on the silicon wafer surface. After forming a textured surface, the silicon dioxide oxide layer is removed by acid washing to expose the polished surface.

[0051] The process of forming a textured surface on a silicon wafer using a silicon wafer processing method is described in detail below with reference to Figures 2 to 7. In this embodiment, the silicon wafer is a monocrystalline silicon wafer, and the formed texture is a pyramidal texture. In other embodiments, the silicon wafer can also be a polycrystalline silicon wafer, and the formed texture is a pitted texture.

[0052] First, as shown in Figure 2, the surface of silicon wafer 1 is subjected to conventional alkaline polishing and RCA surface cleaning to remove the cutting damage layer, metal or dust contaminants, and natural oxide layer on the silicon wafer surface.

[0053] Then, as shown in Figure 3, the cleaned monocrystalline silicon wafer 1 is placed in an ozone gas environment. Specifically, the silicon wafer 1 processing is carried out in a closed chamber 4. Before the silicon wafer 1 enters the chamber 4, it is located in the upstream loading chamber. At this time, the loading chamber and chamber 4 are evacuated to form a vacuum environment. Then, the clean monocrystalline silicon wafer is conveyed into the vacuum chamber 4 by a transfer roller. Ozone and nitrogen are then simultaneously introduced into the vacuum chamber to form an ozone gas environment under a nitrogen background. Inside the chamber 4, the silicon wafer 1 is placed on the infrared heating plate 5 with the side of the silicon wafer 1 to be oxidized facing upwards. Ozone is introduced into the chamber from the top of the chamber through the ozone pipe 7, and nitrogen is introduced into the chamber from the bottom of the chamber through the nitrogen pipe 8. During ventilation, ozone has a larger molecular weight, while nitrogen has a smaller molecular weight. As ozone and nitrogen diffuse within chamber 4, ozone tends to move downwards, while nitrogen tends to move upwards. This allows for thorough mixing of ozone and nitrogen, and the nitrogen's effect ensures that the ozone uniformly fills the entire chamber. In this invention, nitrogen effectively quenches excessively high local reactivity, preventing rapid oxidation that could lead to a porous silica oxide film structure. This ensures the uniformity of the silica oxide layer's thickness and density. The volumetric flow rate ratio of ozone to nitrogen in the mixed gas within the chamber is 3:2-5:3, for example, 3:2, 19:12, or 5:3. When the volumetric flow rate ratio of ozone to nitrogen is between 3:2 and 5:3, the synergistic effect of ozone and nitrogen results in a silica oxide layer with moderate thickness, optimal density, and the best protective effect. When the volume flow ratio of ozone to nitrogen is less than 3:2, the resulting oxide layer is thinner; when the volume flow ratio of ozone to nitrogen is greater than 5:3, the resulting oxide layer has poor density.

[0054] In other embodiments, the direction and location of ozone and oxygen introduction can also be set in other ways, with priority given to ensuring the ratio of the two.

[0055] Furthermore, the surface of silicon wafer 1 is irradiated with ultraviolet light, causing ozone to generate excited-state oxygen atoms. These excited-state oxygen atoms are mainly generated in large quantities in the gas phase region above the silicon wafer. They then diffuse to the silicon wafer surface and react with the silicon atoms on the surface to form a silicon dioxide oxide layer. This process does not rely on the surface adsorption process in traditional thermal oxidation and is completely different from the laser dissociation oxidation process involving high-energy ion bombardment. This effectively avoids the bombardment damage to the silicon wafer surface by high-energy ions from laser dissociation, resulting in a silicon dioxide layer with a higher interface state density. Specifically, within the chamber, the ultraviolet light source is a quartz mercury lamp 6. The light emitted by the quartz mercury lamp is filtered through quartz to form pure ultraviolet light. Under the heating condition of an infrared heating plate, ultraviolet light is used to irradiate one side of the silicon wafer surface. Under ultraviolet (UV) irradiation, ozone in the chamber decomposes into oxygen and free oxygen atoms. Free oxygen atoms possess strong oxidizing properties, while the silicon on the silicon wafer surface has strong reducing properties. The free oxygen atoms can rapidly react with the silicon atoms on the wafer surface to form a silicon dioxide oxide layer 2, as shown in Figure 4. In the step of irradiating one side of the silicon wafer with UV light, the wafer temperature is controlled between 150℃ and 200℃, for example, 150℃, 160℃, 170℃, 180℃, 190℃, or 200℃. When the wafer temperature is below 150℃, the reaction rate is slow; when the wafer temperature is above 200℃, the equipment's energy consumption becomes excessive, and the cooling time after oxidation is significantly increased, affecting the wafer processing efficiency. 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, to ensure that the wavelength of the ultraviolet light is within the range of 210nm-300nm. The irradiation time of the silicon wafer by the ultraviolet light emitted by the quartz mercury lamp 6 is controlled to be 4min-10min, for example, 4min, 5min, 6min, 7min, 8min, 9min, or 10min. When the silicon wafer temperature is within the aforementioned lower temperature range, and the ultraviolet light power (150-250W) and ozone concentration (60-62.5% by volume) are controlled, an oxidation rate of 0.5nm / s-1.0nm / s can be achieved to generate a denser, oxygen-vacancy-free, high-quality silicon dioxide oxide layer. 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, and the peak wavelength is 248nm-259nm, for example, 248nm, 249nm, 250nm, 251nm, 252nm, 253nm, 254nm, 255nm, 256nm, 257nm, 258nm or 259nm.Ultraviolet light of other wavelengths cannot be absorbed by ozone and therefore cannot excite ozone to react. Furthermore, the peak wavelength of ultraviolet light, between 248nm and 259nm, corresponds to the wavelength of ozone's strongest absorption peak, enabling the most efficient ozone decomposition and excited-state oxygen atom generation. Ultraviolet light with these wavelengths and peak wavelengths has high energy utilization efficiency, allowing for rapid oxidation of silicon wafer surfaces with lower power consumption and avoiding irreversible damage to the silicon lattice caused by high-energy ultraviolet lasers.

[0056] Next, as shown in Figure 5, the silicon wafer 1 with the silicon dioxide oxide layer 2 is subjected to conventional texturing and cleaning to form a pyramidal textured surface 3 on the surface of the silicon wafer 1 facing away from the silicon dioxide oxide layer 2, as shown in Figure 6. During the texturing and cleaning process, the silicon dioxide oxide layer 2 is partially etched, making the silicon dioxide oxide layer 2 thinner.

[0057] Finally, the silicon wafer 1 is acid-washed with hydrofluoric acid to remove the remaining silicon dioxide oxide layer 2 after texturing and cleaning, thus exposing the polished surface, as shown in Figure 7, thereby obtaining the texturized monocrystalline silicon wafer.

[0058] Using the existing thermo-oxidation process, a silicon dioxide layer can be grown on a silicon wafer. The growth of the silicon dioxide alkali-resistant 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 the traditional thermo-oxidation technology. Generally, a dense silicon dioxide oxide layer of 3nm-8nm can be grown in 4-10 minutes under 200℃ and 150W ultraviolet light conditions. This can greatly shorten the process time for growing a silicon dioxide oxide layer of fixed thickness, which meets the requirements of large-scale mass production in the photovoltaic industry.

[0059] To excite ozone to form excited-state oxygen atoms by ultraviolet light, a high-pressure mercury lamp must be used to generate ultraviolet light of a specific wavelength (200nm-300nm) which must be directly irradiated onto a single-crystal silicon wafer sample. UV lamps exhibit a broad and continuous emission spectrum in the long-wavelength region greater than 210nm. Only ultraviolet light with wavelengths of 200nm-300nm contributes to the photodecomposition of ozone; wavelengths above 300nm are considered to have no contribution to the ozone excitation reaction in practical tests.

[0060] Using an ozone generator as the ozone source, the main reaction during the formation of a silicon dioxide oxide layer on a single-sided surface of a silicon wafer involves ozone photolysis upon excitation by ultraviolet light, generating excited-state oxygen atoms and oxygen molecules. These oxygen atoms then react with silicon to form silicon dioxide. This includes a cyclic chain reaction of ozone-oxygen-ozone, specifically: some unreacted ozone decomposes under ultraviolet irradiation to generate oxygen and free oxygen atoms, which then react with silicon to form silicon dioxide. The oxygen formed from ozone decomposition is then decomposed and oxidized under ultraviolet irradiation to generate more potent ozone, and the cycle repeats. This continuous generation of free oxygen atoms and ozone, combined with the ozone source supplied by the ozone generator, exposes one side of the monocrystalline silicon wafer to a relatively high-pressure, high-concentration oxidizing atmosphere, promoting a rapid and efficient oxidation reaction. This allows for the formation of a sufficiently thick and dense silicon dioxide layer on the silicon wafer surface in a short time.

[0061] A higher oxidation rate can be achieved by increasing the flow rate of ozone gas introduced through the ozone generator and controlling the silicon wafer temperature. Compared to the thermo-oxidation process, which relies solely on oxygen introduction in a high-temperature environment exceeding 800°C for a single oxidation reaction, the oxidation method provided in this embodiment is clearly more diverse, efficient, and controllable.

[0062] After the formation of the silicon dioxide oxide layer, the silicon wafer with the silicon dioxide oxide layer is texturized and cleaned. Regarding the choice of technology for preparing the silicon dioxide oxide layer, compared to tubular thermal oxidative oxidation (TEO): using ultraviolet lamps in an ozone atmosphere allows for large-area, one-time, rapid processing of monocrystalline planar silicon wafers, meeting the needs of all current photovoltaic wafer sizes. Compared to existing tubular thermal oxidative oxidation processes, it has significant advantages in terms of convenience, especially in production cycle time, production efficiency, and production cost.

[0063] In tubular thermal texturing, prolonged heating at temperatures exceeding 800°C is required. This prolonged high-temperature heating inevitably causes thermal damage and defects to the interior of the monocrystalline silicon wafer. In this embodiment, ozone is excited by ultraviolet light to generate excited-state oxygen atoms to oxidize the silicon wafer. The process temperature does not exceed 200°C, and the energy of the ultraviolet light during oxidation is less than the energy of the chemical bonds between silicon atoms. Therefore, it does not cause any damage to the interior of the monocrystalline silicon wafer and does not increase the number of defects inside the wafer.

[0064] Because the oxidation rate of silicon wafers in tubular thermo-oxidative texturing is affected by the crystal orientation during oxidation, the oxidation rate is slow and the resulting oxide layer film thickness distribution is uneven. The method of texturing single-crystal silicon wafers irradiated with ultraviolet-assisted ozone provided in this embodiment overcomes the influence of differences in silicon oxide crystal orientation due to the strong oxidizing properties of ozone combined with the auxiliary decomposition of specific wavelength ultraviolet light. This results in a rapid and uniform reaction to form the silicon dioxide oxide layer. The silicon dioxide oxide layer prepared under these process conditions exhibits better uniformity and thickness, and better density. Consequently, the silicon dioxide mask protective layer obtained in the subsequent single-sided texturing process is more effective in resisting the alkali in the texturing solution.

[0065] To verify the compactness of the silicon dioxide oxide layer prepared in this embodiment, three sets of control experiments were conducted below.

[0066] In the first experiment, a clean elemental silicon wafer was placed in a 2% (v / v) alkaline sodium hydroxide solution.

[0067] In the second group of experiments, silicon wafers with a silica oxide layer prepared by a tubular thermal oxidation process were placed in a 2% (v / v) alkaline sodium hydroxide solution. In the tubular thermal oxidation process, clean monocrystalline silicon wafers were first loaded into a furnace boat within a tube furnace. The furnace boat then carried the silicon wafers into the tube furnace. The furnace was then sealed, oxygen was introduced, and the temperature was increased. After oxidation was complete, the furnace cooled down, and the furnace boat was removed to unload the silicon wafers, resulting in silicon wafers with a silica oxide layer. The oxidation time for the silicon wafers in the tube furnace was 30 minutes.

[0068] In the third group of experiments, a silicon wafer with a silicon dioxide oxide layer formed after being irradiated with ultraviolet light for 10 minutes in this embodiment was placed in a 2% (v / v) alkaline sodium hydroxide solution.

[0069] The experimental temperature for all three groups of experiments was controlled at 60℃, and the changes in the silicon wafers were observed in each group of experiments.

[0070] In the first group 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 limit of alkaline resistance time was recorded as 0 seconds.

[0071] In the second experiment, after the silicon wafer was placed in the alkaline solution for 282 seconds, the silicon dioxide oxide layer at the edge of the oxide surface began to peel off. Subsequently, the alkaline solution began to gradually spread and bubble towards the middle area of ​​the silicon wafer. The maximum alkaline resistance time was recorded as 282 seconds.

[0072] In the third group of experiments, after the silicon wafer was placed in the alkaline solution for 402 seconds, the silicon dioxide oxide layer in a local area of ​​the oxide surface began to peel off, followed by a bubbling reaction. The limit of alkaline resistance time was recorded as 402 seconds.

[0073] Based on the above three sets of comparative experiments, it can be seen that the silicon dioxide oxide layer generated on the silicon wafer in this embodiment can play a better protective role for the silicon element in the inner layer of the silicon wafer, effectively enhance the alkali resistance of the silicon dioxide oxide layer as a protective layer in the subsequent texturing step, and improve the quality of the pyramid textured surface obtained in the texturing step.

[0074] Example 2

[0075] This embodiment provides a solar cell, comprising: a silicon wafer with a pyramidal textured surface on one side obtained by the silicon wafer processing method of Embodiment 1; and, along the direction away from the textured surface of the silicon wafer, at least on the surface of the silicon wafer on which the textured surface is formed, a passivation layer, a doped layer, a transparent conductive layer, and a gate electrode are sequentially stacked. The passivation layer is formed on the pyramidal textured surface by a deposition process; the doped layer is formed on the surface of the passivation layer facing away from the silicon wafer by a deposition process; the transparent conductive layer is formed on the surface of the doped layer facing away from the silicon wafer by a coating process, an electroplating process, a vapor deposition process, or a spin coating process; and the gate electrode is formed on the surface of the transparent conductive layer facing away from the silicon wafer.

[0076] When the solar cell is a heterojunction cell, it further includes: along the direction away from the polished surface of the silicon wafer, a passivation layer, a doped layer, a transparent conductive layer and a grid electrode are disposed sequentially on the polished surface of the silicon wafer.

[0077] The solar cell provided in this embodiment uses the silicon wafer processing method provided in Example 1 to prepare a single-sided textured surface. The silicon dioxide oxide layer formed in the process is more dense, which improves the alkali resistance of the silicon dioxide oxide layer during the texturing process, improves the quality of the obtained textured surface, and thus improves the photoelectric performance of the solar cell.

[0078] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A silicon wafer processing method, characterized in that, Includes the following steps: Place the silicon wafer in an ozone gas environment; One side surface of the silicon wafer is irradiated with ultraviolet light to generate excited oxygen atoms from ozone. The excited oxygen atoms react with silicon atoms on one side surface of the silicon wafer to form a silicon dioxide oxide layer on one side surface of the silicon wafer. The silicon wafer on which the silicon dioxide oxide layer is formed is texturized and cleaned to form a textured surface on the side of the silicon wafer facing away from 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 includes: The silicon wafer is placed inside the vacuum chamber; A mixture of ozone and nitrogen is introduced into the vacuum chamber.

3. The preparation method according to claim 2, characterized in that, The volumetric flow rate ratio of ozone to nitrogen in the ozone and nitrogen mixture is 3:2 to 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 one side of the silicon wafer with ultraviolet light, the temperature of the silicon wafer is controlled at 150℃-200℃.

5. The silicon wafer processing method according to any one of claims 1 to 3, characterized in that, In the step of irradiating one side of the silicon wafer with ultraviolet light, the wavelength of the ultraviolet light is 210nm-300nm, and the peak wavelength is 248nm-259nm.

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

7. The silicon wafer processing method according to any one of claims 1 to 3, characterized in that, Prior to the step of placing the silicon wafer in an ozone gas environment, the method further includes: The surface of the silicon wafer is subjected to alkaline 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 silica oxide layer is removed by acid washing to expose the polished surface.

9. A silicon wafer with a textured surface formed on one side, characterized in that, It 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: Silicon wafers with a textured surface formed on one side; Along the direction away from the textured side of the silicon wafer, at least on the surface of the silicon wafer on the side where the textured surface is formed, a passivation layer, a doped layer, and a transparent conductive layer are sequentially stacked. The silicon wafer with a textured surface on one side is obtained using the silicon wafer processing method according to any one of claims 1 to 8; or... The silicon wafer with a textured surface on one side is the silicon wafer with a textured surface on one side as described in claim 9.

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