Hole opening method of passive film for solar cell and application of hole opening method
By coating and removing the patterned insulating layer formed by insulating slurry on the surface of the silicon wafer, the deposition of the PECVD passivation film is blocked, and the damage and safety hazards of the silicon wafer caused by the opening of the passivation film in the prior art are solved, thereby realizing the problem of silicon wafer damage and safety hazards caused by the opening of the passivation film in the prior art. Accurate and controllable passivation film openings.
Patent Information
- Application Number
- CN202310778436.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-06-28
- Publication Date
- 2024-12-31
AI Technical Summary
Existing passivation film pore opening methods, such as laser pore opening methods and corrosion slurry pore opening methods, will lead to damage to silicon wafers and safety hazards, and it is difficult to achieve precise control and controllable size openings.
The silicon wafer is coated with an insulating slurry that is easily removed by water, acid or alkaline solution, forming a patterned insulating layer to block the deposition of the PECVD passivation film, and then the insulating layer is removed by cleaning to achieve accurate opening of the passivation film. hole.
The precise opening of the passivation film is achieved, which avoids silicon wafer damage and safety hazards, and the size of the opening area is controllable, improving the accuracy and safety of the opening.
Smart Images
Figure CN119230645A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of solar cells, and in particular to a method for opening a hole in a passivation film for a solar cell and an application thereof. Background Art
[0002] In the field of solar cell technology, it is a common technique to make holes in a passivation film (such as a passivation film prepared by plasma enhanced chemical vapor deposition, i.e., a passivation film prepared by PECVD). After the passivation film is made, a metal electrode can be prepared by metallization at the opening, so that the metal electrode contacts the exposed silicon wafer or doped layer (such as P+ doped layer) at the opening, thereby achieving conductivity. The passivation film hole making technology is often used to make holes in the passivation film corresponding to the back field P+ doped area of solar cells such as PERC and P-TBC.
[0003] There are two commonly used methods for opening holes in the passivation film: laser opening method and etching slurry opening method. Among them, the laser opening method (as shown in CN114267742A) mainly involves: scanning a specific area of the passivation film with a laser, using the high energy of the laser to destroy the structure of the passivation film, thereby achieving laser opening of the passivation film. However, the main disadvantage of this laser opening method is that the high energy of the laser will not only destroy the structure of the passivation film, but also the structure of the exposed silicon wafer surface after the hole is opened, causing damage to the silicon wafer, thereby increasing the fragmentation rate.
[0004] The etching slurry hole opening method is: use screen printing to print the etching slurry on the local area of the passivation film surface. Since the etching slurry itself is highly corrosive, it can react chemically with the passivation film and corrode the passivation film, thereby opening the passivation film. The main disadvantages of this hole opening method are: the etching slurry will also damage the silicon wafer, and the etching slurry itself is highly corrosive, which poses a great safety hazard. Summary of the invention
[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a method for opening a hole in a passivation film for a solar cell and its application.
[0006] Based on this, the present invention discloses a method for opening a hole in a passivation film for a solar cell, comprising the following steps:
[0007] Step S1, pre-treating the surface of the silicon wafer;
[0008] Step S2, coating an insulating slurry on a local area of the pretreated silicon wafer surface; wherein the insulating slurry is a slurry with insulating properties that is easily removed by water or acid or alkali;
[0009] Step S3, drying the insulating slurry to solidify the insulating slurry to form a patterned insulating layer on the surface of the silicon wafer;
[0010] Step S4, depositing a passivation film on the surface of the silicon wafer treated in step S3 by plasma enhanced chemical vapor deposition; wherein the insulating layer blocks the deposition of the passivation film on its surface, and the passivation film is deposited on the area on the surface of the silicon wafer where the insulating layer is not formed;
[0011] Step S5, using water or acid solution or alkali solution to clean and remove the patterned insulating layer, so that the corresponding area where the patterned insulating layer is removed becomes the opening area of the passivation film.
[0012] Preferably, the insulating paste is the insulating paste of product model Sr-100 produced by Toray Industries, Inc.
[0013] Preferably, in step S2, the insulating slurry is applied by screen printing.
[0014] Further preferably, in step S3, the pattern of the insulating layer is determined by a screen-printed pattern; the pattern area of the insulating layer is the opening area of the passivation film in step S5.
[0015] Preferably, in step S3, the drying temperature is 180-250° C., the drying time is 8-15 min, and ventilation is provided throughout the drying process.
[0016] Preferably, in step S4, the conditions for depositing the passivation film by PECVD are: deposition temperature of 450-550°C, deposition time of 10-16 min, deposition pressure of 1600-1680 mTorr, deposition power of 8-9 KW, and special gas ratio of NH 3 :SiH 4 =6400sccm:780-850sccm.
[0017] Preferably, in step S5, when the alkali solution is used to clean and remove the patterned insulating layer, the alkali solution used is a NaOH solution with a volume ratio of NaOH of 1-3%, and the cleaning time is 5-10 minutes.
[0018] Preferably, before step S1, the method further comprises the step of selecting a P-type silicon wafer having a thickness of 130-180 um and a resistivity of 1-9 Ω·cm;
[0019] In step S1, the pretreatment is polishing, etching or texturing.
[0020] It should be noted that when the PECVD method is used to deposit the passivation film, under normal conditions, the voltage on the surface of the silicon wafer can ionize the special gas in the middle of the wafer (i.e., the silicon wafer) into plasma, and then deposit the plasma on the surface of the silicon wafer, thereby forming a passivation film.
[0021] The method for opening a hole in the passivation film of the present invention utilizes the insulating properties and high temperature resistance of the insulating layer formed by the insulating slurry after coating the insulating slurry, so that the insulating layer plays a better barrier role. Therefore, on the corresponding surface of the silicon wafer prepared with the insulating layer, the voltage cannot act on the special gas, plasma cannot be formed, and the passivation film cannot be deposited on the insulating layer; thereby providing a prerequisite for the formation of the opening area of the passivation film in the subsequent step S5.
[0022] The blocking effect of the patterned insulating layer is that the patterned insulating layer isolates PECVD plasma deposition; the area on the surface of the silicon wafer where no insulating layer is formed can be smoothly deposited with a uniform passivation film by the PECVD method, while the area on the surface of the silicon wafer where an insulating layer is formed will not be deposited to form a passivation film due to the blocking effect of the insulating layer.
[0023] According to the experimental results, it is found that no passivation film is deposited in the area where the insulating paste (such as the insulating paste Sr-100) is printed, which indirectly verifies that the insulating layer of this embodiment plays a good barrier role.
[0024] The present invention also discloses an application of a method for opening a hole in a passivation film for a solar cell. The method is applied to opening a hole in a passivation film corresponding to a back field P+ region of a PREC cell or a P-IBC cell, so that during the metallization process, a metal electrode prepared by a non-burn-through metallization slurry forms an ohmic contact with a silicon wafer through the opening.
[0025] Among them, the non-burn-through metallization paste is aluminum paste or low-temperature metallization paste below 700°C; these metallization pastes themselves do not have the ability to burn through the passivation film, so it is necessary to open holes in the passivation film in advance, so that in the subsequent metallization process, the metal electrode prepared by the non-burn-through metallization paste can form ohmic contact with the silicon wafer through the opening.
[0026] Compared with the prior art, the present invention has at least the following beneficial effects:
[0027] The present invention, before depositing the passivation film, coats the local area of the silicon wafer surface with an insulating slurry, and utilizes the characteristics of the insulating slurry (such as being easily removed by water or acid or alkali, and having insulating characteristics) to enable the patterned insulating layer formed by drying to play a blocking role in the deposition of the PECVD passivation film, and then combines the cleaning step of the patterned insulating layer to make the corresponding area where the patterned insulating layer is removed become the opening area of the passivation film, so as to achieve precise opening of the PECVD passivation film, and make the size of the opening area controllable. Moreover, the above-mentioned opening method of the present invention does not need to use a high-energy laser, and compared with the laser opening method, it will not cause damage to the silicon wafer, so it will not increase the fragmentation rate; and the insulating slurry, compared with the etching slurry, is not highly corrosive, and is safer and more reliable. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Figure 1 It is a schematic diagram of the cross-sectional structure of the silicon wafer after being processed in step S1 in the method for opening a hole in the passivation film of this embodiment.
[0029] Figure 2 It is a schematic diagram of the cross-sectional structure of the silicon wafer after being processed in step S3 in the method for opening holes in the passivation film of this embodiment.
[0030] Figure 3 It is a schematic diagram of the cross-sectional structure of the silicon wafer after being processed in step S4 in the method for opening holes in the passivation film of this embodiment.
[0031] Figure 4 It is a schematic diagram of the cross-sectional structure of the silicon wafer after being processed in step S5 in the method for opening holes in the passivation film of this embodiment.
[0032] Figure 5 This is a test image of the silicon wafer surface after being processed by the passivation film opening method of this embodiment.
[0033] Description of the accompanying drawings: silicon wafer 1; insulating layer 2; passivation film 3; opening area 4. DETAILED DESCRIPTION
[0034] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.
[0035] Example
[0036] A method for opening a hole in a passivation film for a solar cell according to the present embodiment includes the following steps performed in sequence:
[0037] Step S1, pre-treating the surface of the silicon wafer 1.
[0038] Before the pretreatment in step S1, a P-type silicon wafer with a thickness of 130-180 um and a resistivity of 1-9 Ω·cm is selected. For example, a P-type silicon wafer with a thickness of 150 um and a resistivity of 3 Ω·cm is used.
[0039] In one example of this embodiment, the pretreatment in step S1 is: polishing the surface of the silicon wafer 1, such as Figure 1 As shown, the surface of the polished silicon wafer 1 is flat and planar.
[0040] The polishing conditions are as follows: the polishing temperature is 75±15°C, the polishing time is 130±50s, and the polishing liquid is a NaOH solution with a volume fraction of 2.50-3.50%. For example, in step S1, the polishing temperature is 80°C, the polishing time is 135s, and the polishing liquid is a NaOH solution with a volume fraction of 3%.
[0041] In other examples of this embodiment, the pretreatment in step S1 may also be: etching or texturing the surface of the silicon wafer 1 so that the surface of the silicon wafer 1 after the treatment is in the shape of an inverted pyramid.
[0042] Step S2, coating an insulating paste on a local area of the surface of the pre-treated silicon wafer 1.
[0043] The insulating slurry is a slurry with insulating properties that is easily removed by water, acid or alkali.
[0044] In one example of this embodiment, the insulating paste is an insulating paste of product model Sr-100 produced by Toray Industries, Ltd. The insulating paste is easily removed by water or acid or alkali, has excellent insulating properties, is resistant to high temperatures, and is beneficial for subsequent operations.
[0045] Of course, in other examples of this embodiment, the insulating slurry may also be other slurries with insulating properties that are easily removed by water or acid or alkali.
[0046] The coating method of the insulating paste is preferably screen printing, so that the pattern of the subsequent opening area 4 of the passivation film 3 can be determined by the pattern of screen printing.
[0047] Specifically, the insulating paste is screen-printed on a local area of the surface of the pretreated silicon wafer 1 so that the insulating paste covers the local area of the surface of the silicon wafer 1, that is, the local area forms a pattern covered with the insulating paste; and the pattern area is the area where the subsequent passivation film 3 is to be opened.
[0048] Step S3 , drying the insulating paste to solidify the insulating paste, so as to form a patterned insulating layer 2 on the surface of the silicon wafer 1 .
[0049] After step S2, the silicon wafer 1 printed with the insulating paste needs to be dried to solidify the insulating paste on the surface of the silicon wafer 1, thereby forming a patterned insulating layer 2 on the surface of the silicon wafer 1. The structure of the silicon wafer 1 after step S3 is as follows: Figure 2 shown.
[0050] The drying process in step S3 is as follows: the drying temperature is 180-250°C, the drying time is 8-15 minutes, and ventilation is provided during the drying process. For example, the drying temperature in step S3 is 200°C, and the drying time is 10 minutes.
[0051] Step S4, using plasma enhanced chemical vapor deposition to deposit a passivation film 3 on the surface of the silicon wafer 1 treated in step S3; wherein the insulating layer 2 blocks the deposition of the passivation film 3 on the surface of the insulating layer 2 itself by the PECVD method, and the passivation film 3 is only deposited on the surface of the silicon wafer 1 in the area where the insulating layer 2 is not formed.
[0052] After the drying process in step S3, a passivation film 3 is deposited on the entire surface of the silicon wafer 1 by plasma enhanced chemical vapor deposition (PECVD), and the deposition surface is the corresponding surface of the silicon wafer 1 formed with the insulating layer 2. The structure of the silicon wafer 1 after the treatment in step S4 is as follows: Figure 3 shown.
[0053] The deposition conditions of the passivation film 3 by PECVD are as follows: deposition temperature is 450-550°C, deposition time is 10-16min, deposition pressure is 1600-1680mTorr, deposition power is 8-9KW, and the special gas ratio is NH 3 :SiH 4 =6400sccm:780-850sccm. For example, in the process of PECVD deposition of the passivation film 3, the deposition temperature is 500°C, the deposition time is 12min, the deposition pressure is 1640mTorr, the deposition power is 8.6KW, and the special gas ratio is NH 3 :SiH 4 =6400sccm:800sccm.
[0054] In the process of depositing the passivation film 3 by the PECVD method in step S4, the area on the surface of the silicon wafer 1 where the insulating layer 2 is not formed can be smoothly and uniformly deposited with the passivation film 3 by the PECVD method; while the area on the surface of the silicon wafer 1 where the insulating layer 2 is formed will not be deposited and formed due to the blocking effect of the insulating layer 2, and the reasons are as follows:
[0055] When the passivation film 3 is deposited by the PECVD method, under normal conditions, the voltage on the surface of the silicon wafer 1 can ionize the special gas in the middle of the wafer into plasma, and then deposit the plasma on the surface of the silicon wafer 1, thereby forming the passivation film 3. In the method for opening holes in the passivation film 3 of this embodiment, after printing the insulating slurry, the insulating properties and high temperature resistance of the insulating layer 2 formed by the insulating slurry are utilized to make the insulating layer 2 play a better blocking role. Therefore, on the corresponding surface of the silicon wafer 1 where the insulating layer 2 is prepared, the voltage cannot act on the special gas, plasma cannot be formed, and the passivation film 3 cannot be deposited on the insulating layer 2; thus, the prerequisite for the formation of the opening area 4 of the passivation film 3 in the subsequent step S5 is provided.
[0056] According to the experimental results, it is found that no passivation film 3 is deposited in the area where the insulating paste (such as the insulating paste Sr-100) is printed, which indirectly proves that the insulating layer 2 of this embodiment plays a good barrier role.
[0057] Step S5 , using water or acid or alkali to clean and remove the patterned insulating layer 2 , so that the corresponding area where the patterned insulating layer 2 is removed becomes the opening area 4 of the passivation film 3 .
[0058] After step S4, the silicon wafer 1 on which the passivation film 3 is deposited needs to be cleaned with water or acid or alkali to remove the insulating layer 2, and the opening of the passivation film 3 is completed. The structure of the silicon wafer 1 after step S5 is as follows: Figure 4 shown.
[0059] The insulating layer 2 needs to be easily removable and can be removed cleanly using water or a dilute acid or alkali solution to form an opening area 4 of a precise size.
[0060] In step S5, the cleaning conditions of using alkali solution to clean the passivation film 3 are: the alkali solution is a NaOH solution with a volume ratio of 1-3% NaOH, and the cleaning time is 5-10 minutes. For example, the alkali solution for cleaning the passivation film 3 is a NaOH solution with a volume ratio of 2% NaOH, and the cleaning time is 6 minutes.
[0061] See also Figure 5 After the silicon wafer is processed by the hole-opening method of this embodiment, horizontal line-shaped holes visible after cleaning are formed at the upper left corner and lower right corner of the passivation film surface, and a circular hole visible after cleaning is formed at the upper right corner of the passivation film. It can be seen that the hole-opening method of this embodiment has the advantages of controllable size of the hole area and high hole-opening accuracy.
[0062] The application of a method for opening a hole in a passivation film for a solar cell in the present embodiment is specifically: the method is applied to the opening of a passivation film 3 corresponding to the back field P+ region of a PREC cell or a P-IBC cell, so that in the subsequent metallization process, a metal electrode prepared by a non-burn-through metallization paste forms an ohmic contact with the silicon wafer 1 through the opening.
[0063] Among them, the non-burn-through metallization paste is aluminum paste or low-temperature metallization paste below 700°C; these metallization pastes themselves do not have the ability to burn through the passivation film 3, so it is necessary to open holes in the passivation film 3 in advance, so that in the subsequent metallization process, the metal electrode prepared by the non-burn-through metallization paste can form an ohmic contact with the silicon wafer 1 through the opening.
[0064] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present invention.
[0065] The technical solution provided by the present invention is introduced in detail above. Specific examples are used in this article to illustrate the principle and implementation mode of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of the present invention, there will be changes in the specific implementation mode and application scope. In summary, the content of this specification should not be understood as limiting the present invention.
Claims
1. A method for opening a hole in a passivation film for a solar cell, characterized in that: The steps include: Step S1, pre-treating the surface of the silicon wafer; Step S2, coating an insulating slurry on a local area of the pretreated silicon wafer surface; wherein the insulating slurry is a slurry with insulating properties that is easily removed by water or acid or alkali; Step S3, drying the insulating slurry to solidify the insulating slurry to form a patterned insulating layer on the surface of the silicon wafer; Step S4, depositing a passivation film on the surface of the silicon wafer treated in step S3 by plasma enhanced chemical vapor deposition; wherein the insulating layer blocks the deposition of the passivation film on its surface, and the passivation film is deposited on the area on the surface of the silicon wafer where the insulating layer is not formed; Step S5, using water or acid or alkali to clean and remove the patterned insulating layer, so that the corresponding area where the patterned insulating layer is removed becomes the opening area of the passivation film.
2. The method for drilling holes in a passivation film for a solar cell according to claim 1, characterized in that: The insulating paste is the insulating paste of product model Sr-100 produced by Toray Industries, Inc.
3. The method for drilling holes in a passivation film for a solar cell according to claim 1, characterized in that: In step S2, the insulating paste is applied by screen printing.
4. The method for drilling holes in a passivation film for a solar cell according to claim 3, characterized in that: In step S3, the pattern of the insulating layer is determined by the pattern of screen printing; the pattern area of the insulating layer is the opening area of the passivation film in step S5.
5. The method for drilling holes in a passivation film for a solar cell according to claim 1, characterized in that: In step S3, the drying temperature is 180-250° C., the drying time is 8-15 min, and ventilation is provided throughout the drying process.
6. The method for drilling holes in a passivation film for a solar cell according to claim 1, characterized in that: In step S4, the conditions for depositing the passivation film by PECVD are: deposition temperature of 450-550°C, deposition time of 10-16min, deposition pressure of 1600-1680mTorr, deposition power of 8-9KW, and special gas ratio of NH3:SiH4=6400sccm:780-850sccm.
7. The method for drilling holes in a passivation film for a solar cell according to claim 1, characterized in that: In step S5, when the alkali solution is used to clean and remove the patterned insulating layer, the alkali solution used is a NaOH solution with a volume ratio of NaOH of 1-3%, and the cleaning time is 5-10 minutes.
8. The method for drilling holes in a passivation film for a solar cell according to claim 1, characterized in that: Before step S1, the method further includes the step of selecting a P-type silicon wafer having a thickness of 130-180 um and a resistivity of 1-9 Ω·cm.
9. The method for drilling holes in a passivation film for a solar cell according to claim 1, characterized in that: In step S1, the pretreatment is polishing, etching or texturing.
10. Application of the method for opening holes in a passivation film for solar cells according to any one of claims 1 to 9, characterized in that: The hole opening method is applied to the hole opening of the passivation film corresponding to the back field P+ region of the PREC cell or the P-IBC cell, so that during the metallization process, the metal electrode prepared by the non-burn-through metallization slurry forms an ohmic contact with the silicon wafer through the hole opening.