Stacked tower base silicon wafer and method of making same

Abstract

The application discloses a size-stacked tower base silicon wafer and a preparation method thereof, and relates to the field of solar cells. The preparation method comprises the following steps: pre-alkali washing, first-alkali throwing, first water washing, post-alkali throwing, second water washing, ozone cleaning, acid washing, third water washing, water-removing treatment and drying. The application can solve the problem that a single-tower base silicon wafer cannot provide a good interface.

Description

Technical Field

[0001] This application belongs to the field of solar cells, specifically relating to a stacked silicon wafer of different sizes and its preparation method. Background Technology

[0002] With the depletion of fossil fuels and increasing environmental pollution, there is an urgent need for a clean, pollution-free, and sustainable green energy source. Solar cells, as the most promising sustainable clean energy source, are particularly important. Therefore, the industry has conducted extensive and continuous research on solar cells. Back-contact (BC) cells, due to their high conversion efficiency, have received even more attention from the industry. The core technology of BC cells lies in fabricating a high-performance PN junction on the back of the silicon wafer and covering it with an aluminum oxide or silicon oxide film. This improves the cell's on-state voltage, passivates the back surface, and enhances long-wavelength response, thereby increasing the cell's conversion efficiency. The silicon wafer is the main material of solar cells, and its quality directly affects the conversion efficiency of the solar cell.

[0003] In some related technologies, solar cells use alkaline polishing to remove the damaged layer on the silicon wafer surface during the silicon wafer fabrication process, producing a single-layer silicon wafer. Subsequent processing steps are then carried out on this basis to produce a solar cell with relatively high performance.

[0004] However, the aforementioned single-tower silicon wafers cannot provide a good interface for the growth of polycrystalline silicon, thus failing to produce PN junctions with superior performance, exhibiting high contact resistance with the paste, and having poor surface quality. Summary of the Invention

[0005] The purpose of this application is to provide a stacked silicon wafer of different sizes and its preparation method, which can at least solve the problem that a single silicon wafer cannot provide a good interface for the growth of polycrystalline silicon.

[0006] To solve the above-mentioned technical problems, this application is implemented as follows:

[0007] This application provides a method for preparing stacked silicon wafers of varying sizes, the method comprising:

[0008] Pre-alkali washing: The original silicon wafer is cleaned with a cleaning solution to obtain the first substrate silicon wafer;

[0009] Pre-alkaline polishing: The first substrate silicon wafer is subjected to a first alkaline polishing treatment using a first alkaline polishing solution to obtain a second substrate silicon wafer;

[0010] First water wash: The second substrate silicon wafer is cleaned with deionized water to obtain the third substrate silicon wafer;

[0011] Post-alkali polishing: The third substrate silicon wafer is subjected to a second alkaline polishing treatment using a second alkaline polishing solution to obtain a fourth substrate silicon wafer;

[0012] Secondary water washing: The fourth substrate silicon wafer is cleaned with deionized water to obtain the fifth substrate silicon wafer;

[0013] Ozone cleaning: The fifth substrate silicon wafer is cleaned with ozone liquid to obtain the sixth substrate silicon wafer;

[0014] Pickling: The sixth substrate silicon wafer is pickled with pickling solution to obtain the seventh substrate silicon wafer;

[0015] Three water washes: The seventh substrate silicon wafer is cleaned with deionized water to obtain the eighth substrate silicon wafer;

[0016] Dehydration treatment: The eighth substrate silicon wafer is subjected to slow pulling dehydration treatment to obtain the ninth substrate silicon wafer;

[0017] Drying: The ninth substrate silicon wafer is dried to obtain stacked tower-based silicon wafers of different sizes.

[0018] This application also provides a large and small stacked tower-based silicon wafer, which is prepared by the above-described method for preparing large and small stacked tower-based silicon wafers.

[0019] This application employs a method for fabricating silicon wafers with large and small stacked bases, which can produce stacked bases with excellent interfaces, facilitating the growth of polycrystalline silicon. Based on this, a PN junction with superior performance can be fabricated, increasing the contact area with the paste, thereby reducing contact resistance and improving the conversion efficiency and lifespan of the solar cell. Furthermore, the fabrication method in this application can also improve the surface quality of the silicon wafer, reduce defect density, better support the growth of polycrystalline silicon, and improve cell performance. In addition, the fabrication method in this application optimizes the alkaline polishing process, effectively shortening the alkaline polishing time, improving production efficiency, and reducing production costs. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a single tower base in related technologies;

[0021] Figure 2 This is a schematic diagram of the large and small stacked tower bases disclosed in the embodiments of this application;

[0022] Figure 3 This is a flowchart illustrating the method for preparing the large and small stacked tower-based silicon wafers disclosed in an embodiment of this application. Detailed Implementation

[0023] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and the number of objects is not limited; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0025] The embodiments of this application will be described in detail below with reference to the accompanying drawings and specific examples and application scenarios.

[0026] refer to Figure 2 and Figure 3 This application discloses a method for preparing stacked silicon wafers of varying sizes. The disclosed preparation method includes:

[0027] Pre-alkali washing: The original silicon wafer is cleaned with a cleaning solution to obtain the first substrate silicon wafer;

[0028] Pre-alkaline polishing: The first substrate silicon wafer is subjected to the first alkaline polishing solution to obtain the second substrate silicon wafer;

[0029] First water wash: The second substrate silicon wafer is cleaned with deionized water to obtain the third substrate silicon wafer;

[0030] Post-alkali polishing: The third substrate silicon wafer is also subjected to a second alkaline polishing process using a second alkaline polishing process to obtain the fourth substrate silicon wafer;

[0031] Secondary water washing: The fourth substrate silicon wafer is cleaned with deionized water to obtain the fifth substrate silicon wafer;

[0032] Ozone cleaning: The fifth substrate silicon wafer is cleaned with ozone liquid to obtain the sixth substrate silicon wafer;

[0033] Pickling: The sixth substrate silicon wafer is pickled with pickling solution to obtain the seventh substrate silicon wafer;

[0034] Three water washes: The seventh substrate silicon wafer is cleaned with deionized water to obtain the eighth substrate silicon wafer;

[0035] Dehydration treatment: The eighth substrate silicon wafer is subjected to slow pulling dehydration treatment to obtain the ninth substrate silicon wafer;

[0036] Drying: The ninth substrate silicon wafer is dried to obtain stacked tower-based silicon wafers of different sizes.

[0037] Based on the above steps, the embodiment of this application adopts a method for preparing large and small stacked tower-based silicon wafers, which can prepare large and small stacked tower-based wafers with excellent interfaces, which is beneficial to the growth of polycrystalline silicon. On this basis, a PN junction with better performance can be prepared, increasing the contact area with the paste, thereby reducing the contact resistance and improving the conversion efficiency and service life of the solar cell.

[0038] The preparation method described in this application embodiment can also help improve the surface quality of silicon wafers, reduce defect density, better support the growth of polycrystalline silicon, and improve battery performance.

[0039] The preparation method in this application embodiment also optimizes the alkaline polishing process, which can effectively shorten the alkaline polishing time, improve production efficiency, and reduce production costs.

[0040] Optionally, pre-alkali washing includes:

[0041] The cleaning time for the raw silicon wafer is 50s to 200s, for example, 50s, 100s, 150s, 200s, etc.; the temperature of the cleaning solution is 40℃ to 70℃, for example, 40℃, 50℃, 60℃, 70℃, etc.

[0042] The cleaning solution may include water (DI), sodium hydroxide (NaOH), and hydrogen peroxide (H2O2). Specifically, water comprises 90%–98% of the solution, for example, 90%, 93%, 95%, 98%, etc.; sodium hydroxide comprises 0.5%–2%, for example, 0.5%, 1%, 1.5%, 2%, etc.; and hydrogen peroxide comprises 2%–8%, for example, 2%, 4%, 6%, 8%, etc. It should be noted that the above percentages represent volume percentages.

[0043] Preferably, the volume ratio of water, sodium hydroxide, and hydrogen peroxide in the cleaning solution is 420L:8L:32L. Of course, other ratios are also possible, and no specific limitation is made here.

[0044] Optionally, the time for the first alkaline polishing treatment is 180s to 200s, for example, 180s, 185s, 190s, 195s, 200s, etc.; the temperature of the first alkaline polishing solution is 75℃ to 80℃, for example, 75℃, 76℃, 77℃, 78℃, 79℃, 80℃, etc.

[0045] The components of the first alkaline polishing solution may include: water (DI), sodium hydroxide (NaOH), and additives (ADD). The water content is 90%–95%, for example, 90%, 91%, 92%, 93%, 94%, 95%, etc.; the sodium hydroxide content is 4%–8%, for example, 4%, 5%, 6%, 7%, 8%, etc.; and the additive content is 0.5%–1.5%, for example, 0.5%, 0.75%, 1%, 1.25%, 1.5%, etc. It should be noted that the above proportions can represent volume percentages.

[0046] Preferably, in the first alkaline solution, the volume ratio of water, sodium hydroxide, and additives is 425L:30L:5.5L. Of course, other ratios are also possible, and no specific limitation is made here.

[0047] Optionally, the additives used in the pre-alkali polishing process may include water, reaction catalysts, surfactants, corrosion and scale inhibitors, and inorganic salts.

[0048] Optionally, the washing time for one wash is 60s to 200s, for example, 60s, 100s, 150s, 200s, etc.

[0049] Optionally, the time for the second alkaline polishing treatment is 80s to 120s, for example, 80s, 90s, 100s, 110s, 120s, etc.; the temperature of the second alkaline polishing solution is 78℃ to 84℃, for example, 78℃, 80℃, 82℃, 84℃, etc.

[0050] The components of the second alkaline polishing solution may include: water (DI), sodium hydroxide (NaOH), and additives (ADD). The water content is 80%–85%, for example, 80%, 81%, 82%, 83%, 84%, 85%, etc.; the sodium hydroxide content is 14%–18%, for example, 14%, 15%, 16%, 17%, 18%, etc.; and the additives content is 0.8%–1.2%, for example, 0.8%, 0.9%, 1%, 1.1%, 1.2%, etc. It should be noted that the above proportions can represent volume percentages.

[0051] Preferably, in the second alkaline polishing solution, the volume ratio of water, sodium hydroxide, and additives is 380L:75L:4.5L. Of course, other ratios are also possible, and no specific limitation is made here.

[0052] Optionally, the additives used in the post-alkali polishing process may include water, reaction catalysts, surfactants, corrosion and scale inhibitors, and inorganic salts.

[0053] Optionally, the second wash time is 60s to 200s, for example, 60s, 100s, 150s, 200s, etc.

[0054] Optionally, the ozone cleaning time is 200s to 800s, for example, 200s, 400s, 600s, 800s, etc.

[0055] The components of ozone solution may include water, ozone, and hydrochloric acid. Water accounts for 99.8% to 99.95%, for example, 99.8%, 99.85%, 99.9%, 99.95%, etc.; hydrochloric acid accounts for 0.05% to 0.2%, for example, 0.05%, 0.1%, 0.15%, 0.2%, etc.; and the ozone concentration can be 20 ppm to 60 ppm, for example, 20 ppm, 40 ppm, 50 ppm, 60 ppm, etc.

[0056] Preferably, the volume ratio of water to hydrochloric acid is 460L:0.5L, and the ozone concentration can be 45ppm. Of course, other ratios are also possible, and no specific limitation is made here.

[0057] Optionally, the pickling time is 100s to 250s, for example, 100s, 150s, 200s, 250s, etc.

[0058] The pickling solution may include water and hydrofluoric acid. Water comprises 90%–95%, for example, 90%, 92%, 94%, 95%, etc.; hydrofluoric acid comprises 5%–10%, for example, 5%, 7%, 8%, 10%, etc. It should be noted that the above percentages can represent volume percentages.

[0059] Preferably, the volume ratio of water to hydrofluoric acid is 420L:40L. Of course, other ratios are also possible, and no specific limitation is made here.

[0060] Optionally, the time for the three washes is 60s to 200s, for example, 60s, 100s, 150s, 200s, etc.

[0061] Optionally, the slow-lift dewatering treatment time is 20s to 60s, for example, 20s, 40s, 50s, 60s, etc.; the slow-lift dewatering treatment temperature is 15℃ to 30℃, for example, 15℃, 20℃, 25℃, 30℃, etc.

[0062] Specifically, the eighth silicon substrate wafer is placed in a slow-lift tank equipped with a robotic arm. The robotic arm and the slow-lift tank work together to remove water stains from the surface of the eighth silicon substrate wafer. The cleaning time for the slow-lift tank and robotic arm is 20-60 seconds, and the temperature is 15-30°C. After dehydration, the ninth silicon substrate wafer is obtained. It should be noted that the specific principles and steps of the slow-lift dehydration process can be found in relevant technologies and will not be elaborated here.

[0063] Optionally, the drying temperature is 80℃~100℃, for example, 80℃, 85℃, 90℃, 95℃, 100℃, etc.; the drying time is 600s~1200s, for example, 600℃, 800℃, 1000℃, 1200℃, etc.

[0064] Specifically, the ninth substrate silicon wafer is placed in a drying tank for drying treatment to remove water stains from the surface of the ninth substrate silicon wafer.

[0065] This application also discloses a stacked tower-based silicon wafer of varying sizes, see reference. Figure 2 and Figure 3 The disclosed large and small stacked tower-based silicon wafers are prepared using the above-mentioned method for preparing large and small stacked tower-based silicon wafers.

[0066] This application also discloses a solar cell made using the aforementioned stacked silicon wafers of different sizes.

[0067] In summary, the embodiments of this application improve the tower base structure of the silicon wafer, forming a stacked tower base with excellent interface, which is beneficial for polycrystalline silicon growth, facilitating the fabrication of PN junctions with superior performance and improving the conversion efficiency of solar cells. The stacked tower base structure increases the contact area between the silicon wafer and the paste, improving the contact interface and reducing contact resistance, thus enhancing the performance of the solar cell. Optimizing the cleaning process ensures precise time and temperature control for each step, allowing for more thorough removal of impurities and damage from the silicon wafer surface, improving wafer quality, performance, and lifespan, and reducing defect density. Furthermore, optimizing the alkaline polishing process shortens the polishing time, increasing production efficiency and reducing production costs.

[0068] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A method for preparing stacked silicon wafers of varying sizes, characterized in that, The preparation method includes: Pre-alkali washing: The original silicon wafer is cleaned with a cleaning solution to obtain the first substrate silicon wafer; Pre-alkaline polishing: The first substrate silicon wafer is subjected to a first alkaline polishing treatment using a first alkaline polishing solution to obtain a second substrate silicon wafer; First water wash: The second substrate silicon wafer is cleaned with deionized water to obtain the third substrate silicon wafer; Post-alkaline polishing: The third substrate silicon wafer is subjected to a second alkaline polishing treatment using a second alkaline polishing solution to obtain a fourth substrate silicon wafer; wherein, the components of the second alkaline polishing solution include water, sodium hydroxide and additives, wherein the water accounts for 80% to 85%, the sodium hydroxide accounts for 14% to 18%, and the additives account for 0.8% to 1.2%; Secondary water washing: The fourth substrate silicon wafer is cleaned with deionized water to obtain the fifth substrate silicon wafer; Ozone cleaning: The fifth substrate silicon wafer is cleaned with ozone liquid to obtain the sixth substrate silicon wafer; Pickling: The sixth substrate silicon wafer is pickled with pickling solution to obtain the seventh substrate silicon wafer; Three water washes: The seventh substrate silicon wafer is cleaned with deionized water to obtain the eighth substrate silicon wafer; Dehydration treatment: The eighth substrate silicon wafer is subjected to slow pulling dehydration treatment to obtain the ninth substrate silicon wafer; Drying: The ninth substrate silicon wafer is dried to obtain stacked tower-based silicon wafers of different sizes.

2. The preparation method according to claim 1, characterized in that, The pre-alkali washing includes: The original silicon wafer is cleaned with the cleaning solution for 50s to 200s, and the temperature of the cleaning solution is 40℃ to 70℃.

3. The preparation method according to claim 1 or 2, characterized in that, The cleaning solution comprises water, sodium hydroxide, and hydrogen peroxide, wherein the water accounts for 90% to 98%, the sodium hydroxide accounts for 0.5% to 2%, and the hydrogen peroxide accounts for 2% to 8%.

4. The preparation method according to claim 3, characterized in that, In the cleaning solution, the volume ratio of water, sodium hydroxide, and hydrogen peroxide is 420L:8L:32L.

5. The preparation method according to claim 1, characterized in that, The first alkaline polishing treatment lasts for 180s to 200s, and the temperature of the first alkaline polishing solution is 75℃ to 80℃.

6. The preparation method according to claim 1 or 5, characterized in that, The first alkaline polishing solution comprises water, sodium hydroxide, and additives, wherein the water accounts for 90% to 95%, the sodium hydroxide accounts for 4% to 8%, and the additives account for 0.5% to 1.5%.

7. The preparation method according to claim 6, characterized in that, The volume ratio of water, sodium hydroxide, and additive in the first alkaline solution is 425L:30L:5.5L.

8. The preparation method according to claim 6, characterized in that, The duration of each water wash is 60s to 200s; And / or, the duration of the secondary water wash is 60s to 200s; And / or, the duration of the three water washes is 60s to 200s.

9. The preparation method according to claim 1, characterized in that, The second alkaline polishing treatment lasts for 80 to 120 seconds, and the temperature of the second alkaline polishing solution is 78°C to 84°C.

10. The preparation method according to claim 1 or 9, characterized in that, The volume ratio of water, sodium hydroxide, and additive in the second alkaline solution is 380L:75L:4.5L.

11. The preparation method according to claim 6, characterized in that, The additives in the first and second alkaline polishing solutions each comprise water, a reaction catalyst, a surfactant, a corrosion and scale inhibitor, and an inorganic salt.

12. The preparation method according to claim 1, characterized in that, The ozone cleaning time is 200s to 800s; And / or, the ozone solution comprises water, ozone and hydrochloric acid, wherein the water accounts for 99.8% to 99.95%, the hydrochloric acid accounts for 0.05% to 0.2%, and the ozone concentration is 20 ppm to 60 ppm.

13. The preparation method according to claim 12, characterized in that, The volume ratio of the water to the hydrochloric acid is 460L:0.5L.

14. The preparation method according to claim 1, characterized in that, The pickling time is 100s to 250s; And / or, the pickling solution comprises water and hydrofluoric acid, wherein the water accounts for 90% to 95% and the hydrofluoric acid accounts for 5% to 10%.

15. The preparation method according to claim 14, characterized in that, The volume ratio of the water to the hydrofluoric acid is 420L:40L.

16. The preparation method according to claim 1, characterized in that, The slow lifting dewatering treatment time is 20s to 60s, and the slow lifting dewatering treatment temperature is 15℃ to 30℃.

17. The preparation method according to claim 1, characterized in that, The drying temperature is 80℃~100℃, and the drying time is 600s~1200s.

18. A stacked silicon wafer of various sizes, characterized in that, It is prepared by the method for preparing stacked tower-based silicon wafers according to any one of claims 1 to 17.

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