Graphite boat assembly and solar cell for PECVD coating

Abstract

The present invention provides a graphite boat group and solar cell for PECVD coating, and relates to the technical field of photovoltaic cells. The graphite boat group includes a first graphite boat and a second graphite boat; wherein, the first graphite boat is provided with a plurality of card points for fixing one side of a substrate; the second graphite boat is provided with a plurality of card points for fixing the other side of a substrate; and the plurality of card points on the first graphite boat and the plurality of card points on the second graphite boat are staggered. The present application changes the original use of the same graphite boat for coating the front and back sides of the battery twice to using different graphite boats for the front and back sides through the setting of the above-mentioned graphite boats, so that the card point positions of the two coatings on the front and back sides have no chance to overlap at the same point on the side elevation of the silicon wafer, thereby making it possible to thicken the insulating film layer at the "card point mark" during the PECVD coating process, thereby alleviating the quality problem of solar cells caused by leakage at the "card point mark" in the subsequent electroplating process.

Description

Technical Field

[0001] The invention relates to the technical field of photovoltaic cells, and in particular to a graphite boat assembly and a solar cell for PECVD coating. Background Art

[0002] In recent years, solar metallization methods such as nickel and copper electroplating or light-induced electroplating have replaced silver paste screen printing, significantly reducing the demand for silver in solar cell manufacturing.

[0003] However, the silicon nitride insulating film layer on the surface of the crystalline silicon semi-finished battery before the metal electrode is electroplated is deposited by the tubular PECVD (plasma enhanced chemical vapor deposition) method. In the actual production process, the front and back sides (NP sides) of the silicon wafer to be processed need to be placed on the graphite boat facing outward twice, and then sent to the PECVD equipment for processing. Because there are several card points designed on the graphite boat for fixing the silicon wafer, after the above-mentioned coating process is completed, there is a small area of ​​card point shielding area at the card point position of the silicon wafer that is not coated or the coating is obviously thin, which is generally called "card point print". In the subsequent solar metallization process based on nickel, copper and other metal electroplating or light-induced electroplating, the "card point print" leaks electricity due to the exposed silicon substrate, or the coating is too thin to leak electricity, causing the "card point print" to be accidentally plated with nickel, copper and other metals used for grid line metallization, causing the photovoltaic cell to leak electricity at the card point print, resulting in product performance degradation or even failure.

[0004] Therefore, it is necessary and urgent to research and develop a graphite boat set for PECVD coating to optimize the coverage of the silicon nitride film layer during the PECVD coating process, thereby solving the quality problems of solar cells caused by leakage at the "stuck point print" in the subsequent electroplating process.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The purpose of the present invention is to provide a graphite boat group for PECVD coating and a method for depositing silicon nitride insulating film layers on the front and back of a solar cell using the graphite boat group. The graphite boat group changes the original use of the same graphite boat for coating the front and back of the battery twice to using different graphite boats on both sides, so that the card point positions of the two coatings on the front and back have no chance to overlap at the same point on the side elevation of the silicon wafer. Furthermore, the present invention can also dig holes at the position where a card point mark has or will be produced on another graphite boat corresponding to one of the graphite boats in the graphite boat group, so that the reaction gas enters the hole to produce a bypass plating phenomenon, thickens the coating at the card point mark, and thus alleviates the quality problem of the solar cell caused by leakage at the "card point mark" after electroplating.

[0007] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0008] The present invention provides a graphite boat set for PECVD coating, the graphite boat set comprising: a first graphite boat and a second graphite boat;

[0009] The first graphite boat is provided with a plurality of clamping points for fixing one side of the substrate;

[0010] The second graphite boat is provided with a plurality of clamping points for fixing the other side of the substrate;

[0011] The plurality of clamping points on the first graphite boat and the plurality of clamping points on the second graphite boat are arranged in a staggered manner.

[0012] Furthermore, a plurality of clamping points on the first graphite boat and a plurality of clamping points on the second graphite boat are sequentially staggered.

[0013] Furthermore, the offset distance between each card point on the first graphite boat and each card point on the second graphite boat is ≥5mm, and the front and back card point prints do not interfere with each other. After this condition is met, the card point position can be designed at any position according to the machine automation plan.

[0014] Furthermore, the plurality of clamping points arranged on the first graphite boat correspond to three for each battery cell;

[0015] The number of clamping points arranged on the second graphite boat is three for each battery cell.

[0016] Furthermore, a hole is dug at each position of a graphite boat in a group corresponding to the position where another graphite boat has or will have a stuck point mark, so that the reaction gas enters the hole to produce a plating phenomenon, and the coating at the stuck point mark is thickened. The dug hole is a blind hole or a through hole, preferably a blind hole, and the depth of the blind hole is ≥0.2mm.

[0017] Further, the first graphite boat and the second graphite boat are used together in a PECVD coating process, wherein:

[0018] The first graphite boat is used for coating the front side of the substrate, and the second graphite boat is used for coating the back side of the substrate;

[0019] Or, the second graphite boat is used for coating the front side of the substrate, and the first graphite boat is used for coating the back side of the substrate.

[0020] The present invention provides an application of the graphite boat group for PECVD coating in preparing a silicon nitride insulating film layer of a solar cell by chemical deposition.

[0021] The present invention provides a solar cell, wherein the silicon nitride insulating film layers on the front and back sides of the solar cell are mainly prepared by chemical deposition of the above-mentioned graphite boat group for PECVD coating.

[0022] The present invention provides a method for depositing a silicon nitride insulating film layer of a solar cell, the deposition method comprising: providing an intermediate silicon wafer to be deposited, and then using the above-mentioned graphite boat assembly to deposit a silicon nitride insulating film layer on the intermediate silicon wafer;

[0023] Among them: the battery intermediate silicon wafer is loaded on the first graphite boat for film deposition to obtain a battery intermediate silicon wafer with a silicon nitride insulating film layer deposited on one side; then the battery intermediate silicon wafer is loaded on the second graphite boat for film deposition, and a silicon nitride insulating film layer is deposited on the other side of the intermediate silicon wafer to obtain a battery intermediate silicon wafer with a silicon nitride insulating film layer deposited on both sides.

[0024] Furthermore, the method for depositing a silicon nitride insulating film layer of the solar cell includes:

[0025] (A) providing a battery intermediate silicon wafer on which a silicon nitride insulating film layer is to be deposited, marking the position of the first graphite boat on one side of the battery intermediate silicon wafer, which is recorded as the first silicon wafer side; the first silicon wafer side is the front side or the back side of the battery intermediate silicon wafer;

[0026] and, marking the position of the second graphite boat's clamping point on the other side of the battery intermediate silicon wafer, which is recorded as the second silicon wafer side; the second silicon wafer side is the front side or the back side of the battery intermediate silicon wafer;

[0027] (B) drilling a hole on the first graphite boat at the position of the stuck point marked on the second silicon wafer, then loading the battery intermediate silicon wafer on the first graphite boat, introducing it into the furnace tube of the PECVD vacuum coating machine, and depositing a silicon nitride insulating film layer on the first silicon wafer surface to obtain a battery intermediate silicon wafer with the first silicon wafer surface coated;

[0028] At this time, the solar cell is coated with a small area locally on the second silicon wafer surface at the card point print position corresponding to the second graphite boat due to wrap-around plating.

[0029] (C) Holes are dug on the second graphite boat at the locations of the card points marked on the surface of the first silicon wafer, and then the battery intermediate silicon wafer is loaded on the second graphite boat and introduced into the furnace tube of the PECVD vacuum coating machine, and a silicon nitride insulating film layer is deposited on the surface of the second silicon wafer to obtain a double-sided coated solar cell.

[0030] At this time, on the first silicon wafer surface of the battery cell, a small area of ​​coating is produced locally at the card point print position corresponding to the first graphite boat due to wrap-around plating, which makes up for the problem of thin coating at the card point print when coating with the first graphite boat.

[0031] Furthermore, the hole dug on the first graphite boat in step (B) is a blind hole or a through hole, preferably a blind hole;

[0032] Preferably, the holes dug on the second graphite boat in step (C) are blind holes or through holes, preferably blind holes.

[0033] Furthermore, the depth of the blind hole is ≥0.2 mm.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The present invention provides a graphite boat group for PECVD coating, the graphite boat group comprising: a first graphite boat and a second graphite boat; wherein: the first graphite boat is provided with a plurality of clamping points for fixing one side of a substrate; the second graphite boat is provided with a plurality of clamping points for fixing the other side of the substrate; the plurality of clamping points on the first graphite boat are staggered with the plurality of clamping points on the second graphite boat.

[0036] In view of the fact that after the PECVD coating of the existing solar cell substrate is completed, there is a small area of ​​card point blocking area at the card point position of the silicon wafer that is not coated or the coating is obviously thin, forming a "card point mark", the present application modifies the design of the card point position of the existing graphite boat, and changes the original use of the same graphite boat for coating the front and back sides of the battery twice to different graphite boats dedicated to the front and back sides, so that the card point positions of the front and back coatings have no chance to overlap at the same point on the side surface of the silicon wafer, and then in the PECVD coating process, the coverage of the silicon nitride film layer can be optimized, and the insulating film layer at the "card point mark" can be thickened, thereby solving the quality problem of solar cells caused by leakage at the "card point mark" in the subsequent electroplating process.

[0037] The graphite boat set for PECVD coating provided by the present invention can be widely used in the process of preparing a silicon nitride insulating film layer for a solar cell by chemical deposition.

[0038] The present invention provides a solar cell, wherein the silicon nitride insulating film layers on the front and back of the solar cell are mainly prepared by chemical deposition of the above-mentioned graphite boat group for PECVD coating. Since different graphite boats with non-overlapping card point positions are used on the front and back of the solar cell during the coating process of the present application, there is no chance that the card point positions of the two coatings on the front and back will overlap at the same point on the side elevation of the silicon wafer. Furthermore, the present invention can also dig holes at positions where a card point mark has or will be produced on another graphite boat corresponding to one of the graphite boats in the graphite boat group, so that the reaction gas enters the holes to produce a bypass plating phenomenon, thickens the coating at the card point mark, and then effectively thickens the insulating film layer at the "card point mark" during the PECVD coating process. Therefore, compared with the prior art, the solar cell of the present application effectively alleviates the quality problem of solar cells caused by leakage at the "card point mark" in the electroplating process. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] 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.

[0040] Figure 1 A schematic plan view of a first graphite boat provided in Example 1 of the present invention;

[0041] Figure 2 A schematic diagram of the positions of the stuck points on the solar cell silicon wafer after the double-sided coating is completed provided in Comparative Example 1 of the present invention;

[0042] Figure 3 A comparison diagram of the coating effect of the card point position with a thin coating produced by the comparative example 1 provided by the present invention and the coating effect of the card point position with a thick coating produced by the wrapping plating in the embodiment 4;

[0043] Figure 4 The relative positions of the through holes dug on the graphite boat and the clamping points and the silicon wafers after loading in Example 4 provided by the present invention. DETAILED DESCRIPTION

[0044] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than 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.

[0045] According to one aspect of the present invention, a graphite boat set for PECVD coating comprises: a first graphite boat and a second graphite boat;

[0046] The first graphite boat is provided with a plurality of clamping points for fixing one side of the substrate;

[0047] The second graphite boat is provided with a plurality of clamping points for fixing the other side of the substrate;

[0048] The plurality of clamping points on the first graphite boat and the plurality of clamping points on the second graphite boat are arranged in a staggered manner.

[0049] Furthermore, the present application digs holes on a group of graphite boats corresponding to the positions where another graphite boat has or will have a stuck point mark, so that the reaction gas enters the holes to produce a bypass plating phenomenon and thicken the coating at the stuck point mark. For example, a hole is dug on the first graphite boat at the position where the second graphite boat has or will have a stuck point mark on the battery cell.

[0050] Preferably, the hole is a blind hole or a through hole, preferably a blind hole, and the depth of the blind hole is ≥0.2 mm.

[0051] The present invention provides a graphite boat group for PECVD coating, the graphite boat group comprising: a first graphite boat and a second graphite boat; wherein: the first graphite boat is provided with a plurality of clamping points for fixing one side of a substrate; the second graphite boat is provided with a plurality of clamping points for fixing the other side of a substrate; the plurality of clamping points on the first graphite boat and the plurality of clamping points on the second graphite boat are staggered. Furthermore, the present application digs holes on a group of graphite boats at positions corresponding to positions where clamping point marks have or will be produced on another graphite boat, so that the reaction gas enters the holes to produce a bypass plating phenomenon, and the coating at the clamping point marks is thickened.

[0052] After the PECVD coating of the existing solar cell substrate is completed, there is a small area of ​​card point blocking area at the card point position of the silicon wafer that is not coated or the coating is obviously thin, forming a "card point mark". The present application modifies the design of the card point position of the existing graphite boat, and changes the original use of the same graphite boat for the two coatings on the front and back of the battery to using different graphite boats for the front and back, so that the card point positions of the two coatings on the front and back have no chance to overlap at the same point on the side elevation of the silicon wafer, and at the same time, the reaction gas enters the holes of the graphite boat to produce a wrap-around plating phenomenon, thickening the coating at the card point mark. Furthermore, in the process of PECVD coating, the coverage of the silicon nitride film layer can be optimized, and the insulating film layer at the "card point mark" can be thickened, thereby solving the quality problem of solar cells caused by leakage at the "card point mark" in the subsequent electroplating process.

[0053] In a preferred embodiment of the present invention, the plurality of clamping points on the first graphite boat and the plurality of clamping points on the second graphite boat are sequentially staggered.

[0054] As a preferred embodiment, in order to realize the digging of holes on the graphite boat, the plurality of clamping points on the first graphite boat and the plurality of clamping points on the second graphite boat are sequentially staggered. Because only the staggered setting will not dig out the clamping points, and then the plating can be realized at the digging holes, alleviating the problem that the existing PECVD coating is thin at the clamping points and easily causes leakage.

[0055] In the above preferred embodiment, the offset distance between each card point on the first graphite boat and each card point on the second graphite boat is ≥5mm, and the front and back card points do not interfere with each other. After this condition is met, the card point position can be designed at any position according to the machine automation plan.

[0056] As a preferred implementation method, the plurality of card points on the first graphite boat and the plurality of card points on the second graphite boat are sequentially staggered, and the staggered distance between each card point on the first graphite boat and each card point on the second graphite boat is ≥5mm. The sequential staggered arrangement of the plurality of card points on the first graphite boat and the second graphite boat can effectively maintain the stable loading of the substrate and the graphite boat during the electroplating deposition process; at the same time, in order to form effective wrap-around plating at the card points, a hole is dug on each of the graphite boats corresponding to the position where the card point mark has or will be produced on the other graphite boat, so that the reaction gas enters the hole to produce wrap-around plating.

[0057] In a preferred embodiment of the present invention, the plurality of clamping points arranged on the first graphite boat correspond to three for each battery cell;

[0058] The number of clamping points arranged on the second graphite boat is three for each battery cell.

[0059] In a preferred embodiment of the present invention, the first graphite boat and the second graphite boat are used together in a PECVD coating process, wherein:

[0060] The first graphite boat is used for coating the front side of the substrate, and the second graphite boat is used for coating the back side of the substrate;

[0061] Or, the second graphite boat is used for coating the front side of the substrate, and the first graphite boat is used for coating the back side of the substrate.

[0062] According to one aspect of the present invention, the above-mentioned graphite boat assembly for PECVD coating is used in preparing a silicon nitride insulating film layer of a solar cell by chemical deposition.

[0063] The graphite boat set for PECVD coating provided by the present invention can be widely used in the process of preparing a silicon nitride insulating film layer for a solar cell by chemical deposition.

[0064] According to one aspect of the present invention, a solar cell is provided, wherein the silicon nitride insulating film layers on the front and back sides of the solar cell are mainly prepared by chemical deposition of the above-mentioned graphite boat assembly for PECVD coating.

[0065] The present invention provides a solar cell, wherein the silicon nitride insulating film layers on the front and back of the solar cell are mainly prepared by chemical deposition of the above-mentioned graphite boat group for PECVD coating. Since different graphite boats with non-overlapping card points are used on the front and back of the solar cell during the coating process of the present application, the card points of the two coatings on the front and back have no chance to overlap at the same point on the side elevation of the silicon wafer, and at the same time, a hole is dug on the graphite boat at the position corresponding to the card point print, so that the reaction gas enters the hole to produce a bypass plating phenomenon, and then in the PECVD coating process, the insulating film layer at the "card point print" is effectively thickened. Therefore, compared with the prior art, the solar cell of the present application effectively alleviates the quality problem of solar cells caused by leakage at the "card point print" in the electroplating process.

[0066] According to one aspect of the present invention, a method for depositing a silicon nitride insulating film layer of a solar cell comprises: providing an intermediate silicon wafer to be deposited, and then using the above-mentioned graphite boat assembly to deposit a silicon nitride insulating film layer on the intermediate silicon wafer;

[0067] Among them: the battery intermediate silicon wafer is loaded on the first graphite boat for film deposition to obtain a battery intermediate silicon wafer with a silicon nitride insulating film layer deposited on one side; then the battery intermediate silicon wafer is loaded on the second graphite boat for film deposition, and a silicon nitride insulating film layer is deposited on the other side of the intermediate silicon wafer to obtain a battery intermediate silicon wafer with a silicon nitride insulating film layer deposited on both sides.

[0068] In a preferred embodiment of the present invention, the deposition method further comprises:

[0069] According to the positions of a plurality of card points corresponding to the card points of the second graphite boat after the silicon wafer to be processed is loaded on the first graphite boat, holes are dug on the first graphite boat;

[0070] and, according to the positions of a plurality of card points corresponding to the card points of the first graphite boat after the silicon wafer to be processed is loaded on the second graphite boat, holes are dug on the second graphite boat.

[0071] In the above preferred embodiment, the method for depositing a silicon nitride insulating film layer of a solar cell comprises:

[0072] (A) providing a battery intermediate silicon wafer on which a silicon nitride insulating film layer is to be deposited, recording one side of the battery intermediate silicon wafer as a first silicon wafer side; the first silicon wafer side is the front side or the back side of the battery intermediate silicon wafer; recording the other side of the battery intermediate silicon wafer as a second silicon wafer side; the second silicon wafer side is the back side or the front side of the battery intermediate silicon wafer;

[0073] (B) Subsequently, the battery intermediate silicon wafer is loaded onto a first graphite boat designed according to the present application, introduced into a furnace tube of a PECVD vacuum coating machine, and a silicon nitride insulating film layer is deposited on the surface of the first silicon wafer to obtain a battery intermediate silicon wafer with one side coated;

[0074] (C) The battery intermediate silicon wafer is then loaded onto a second graphite boat designed according to the present application, introduced into a furnace tube of a PECVD vacuum coating machine, and a silicon nitride insulating film layer is deposited on the surface of the second silicon wafer to obtain a double-sided coated solar cell.

[0075] As a preferred embodiment, the above-mentioned silicon nitride insulating film deposition method is designed by finding the card point mark position corresponding to the card point of the second graphite boat after the silicon wafer to be processed is loaded on the first graphite boat, and digging a hole at this position of the boat sheet of the first graphite boat; and, the card point mark position corresponding to the card point of the first graphite boat after the silicon wafer to be processed is loaded on the second graphite boat, and digging a hole at this position of the boat sheet of the second graphite boat; the diameter of the hole is designed to be consistent with the size of the "card point mark" commonly produced on the products produced by the PECVD vacuum coating machine and the graphite boat used.

[0076] Due to the existence of the above-mentioned blind holes, process gases will drill into the blind holes during processing to produce "around plating". The small-scale coating caused by "around plating" can just thicken the film layer of the "card point mark" when coating on the "other side" corresponding to this coating.

[0077] In a preferred embodiment of the present invention, the hole dug in step (B) is a blind hole or a through hole, preferably a blind hole.

[0078] Preferably, the depth of the blind hole is ≥0.2 mm.

[0079] As a preferred embodiment, the depth of the blind hole needs to be fine-tuned according to the process menu conditions of the PECVD equipment (mainly the furnace tube pressure), and can be gradually deepened from 0.2mm until the difference between the "card mark" at the blind hole and the coating color of the overall appearance of the silicon wafer after double-sided coating is minimized, so as to obtain a beautiful product appearance. Extremely, the blind hole processing reaches a certain depth to form a through hole, which can also achieve the effect of the present invention.

[0080] The technical solution of the present invention will be further described below in conjunction with embodiments.

[0081] Example 1

[0082] (a) A graphite boat assembly for PECVD coating, the graphite boat assembly comprising: a first graphite boat and a second graphite boat;

[0083] The first graphite boat is provided with a plurality of clamping points for fixing one side of the substrate;

[0084] The second graphite boat is provided with a plurality of clamping points for fixing the other side of the substrate;

[0085] The plurality of clamping points on the first graphite boat and the plurality of clamping points on the second graphite boat are arranged in a staggered manner.

[0086] The plurality of clamping points on the first graphite boat and the plurality of clamping points on the second graphite boat are sequentially staggered, and the staggered distance of each clamping point is 5 mm.

[0087] The number of the card points arranged on the first graphite boat corresponds to three for each battery cell, and the number of the card points arranged on the second graphite boat corresponds to three for each battery cell.

[0088] Figure 1 A schematic plan view of a first graphite boat provided in this embodiment; Figure 1 The "asterisk" in the middle indicates the position of the original stuck point on the first graphite boat after displacement; Figure 1 The "triangle" in the middle indicates the position of the hole on the first graphite boat (corresponding to the position of the card point print on the other boat). Since all products are loaded in a mirror image on both sides of the boat, there are 6 hole positions on a certain graphite boat.

[0089] (ii) Using the graphite boat assembly of this embodiment to perform PECVD deposition coating on the silicon nitride insulating film layer of the solar cell, the specific method includes:

[0090] 1. Provide a silicon wafer to be coated that has completed the processes of pre-diffusion, POLY deposition, etc., and then load the silicon wafer to be coated with its front side facing upward into a PECVD vacuum coating machine on a first graphite boat provided with a blind hole as described in the present application, perform a coating process, and complete the front side coating; the silicon wafer produced after the coating is completed has an overall coating on the front side but has a card point mark corresponding to the card point of the first graphite boat, and an uncoated back side but has 6 local circumferentially coated films of a similar size to the card point mark at the blind hole on the first graphite boat, and the positions of the 6 local circumferentially coated films correspond to the positions where the card point mark may be generated by the second graphite boat in the next step.

[0091] 2. Then, the back side of the silicon wafer to be coated is loaded upward into the PECVD vacuum coating machine on the second graphite boat with the blind holes described in the present application dug therein, and the coating process is performed to complete the back side coating. After the back side coating is completed, the back side of the silicon wafer is coated as a whole, and the card point prints on the back side corresponding to the card points of the second graphite boat have been partially circumvented in the previous step, so the card point prints corresponding to the card points of the second graphite boat will not have the problem of thin coating; at the same time, when the card point prints on the front side of the silicon wafer corresponding to the card point of the first graphite boat are coated on the second graphite, the card point prints corresponding to the card point of the first graphite boat will be thickened and repaired due to the existence of the blind holes on the second graphite, so the card point prints corresponding to the card points of the first graphite boat will not have the problem of thin coating.

[0092] Example 2

[0093] This embodiment is the same as Embodiment 1 except that in step (i), the misalignment distance between the plurality of clamping points on the first graphite boat and the plurality of clamping points on the second graphite boat is 3 mm.

[0094] Example 3

[0095] This embodiment is the same as Embodiment 1 except that in step (i), the misalignment distance between the plurality of clamping points on the first graphite boat and the plurality of clamping points on the second graphite boat is 8 mm.

[0096] Example 4

[0097] This embodiment is the same as Embodiment 1 except that in step (ii), the holes on the graphite boat are through holes.

[0098] Comparative Example 1

[0099] The intermediate silicon wafer to be coated is coated twice on the front and back sides on the industry's standard graphite boat. The order of the two coatings is not limited. Because the graphite boat is of standard design, the two coatings on the front and back sides are exactly the same. At the same time, the intermediate silicon wafer is loaded on the graphite boat with mirror symmetry on both sides. Therefore, after completing the two coating processes on the front and back sides, the intermediate silicon wafer has a 50% probability of having 3 card point prints that overlap on the front and back sides, and another 50% probability of having non-overlapping card point prints on the front and back sides, 3 on each side, for a total of 6 card point prints.

[0100] All the card point prints in the above two situations have the phenomenon of thin coating or exposed silicon substrate. Abnormal metal deposition occurs in the subsequent electroplating gate line process, causing leakage in the final product, affecting the product yield and reliability.

[0101] Figure 2 This is a schematic diagram of the locations of the card points on the solar cell silicon wafer after double-sided coating is completed in this comparative example. Figure 2 The circled part is the coating card point on the silicon wafer of comparative example 1.

[0102] Figure 3 This is a comparison chart of the coating effects of the card point marks with thin coating produced in comparative example 1 and the card point positions with thick coating produced in embodiment 4.

[0103] See also Figure 3 , Figure 3 A in the middle is the coating card point print of comparative example 1, which is thinner than the overall coating thickness. Figure 3 B in the middle is the location of the thickening point of the winding plating in Example 4, and the location of the thickening point is thicker than the overall coating thickness.

[0104] Figure 4 The relative positions of the through holes dug on the graphite boat and the clamping points and the silicon wafer after loading in Example 4. Figure 4 a is the stuck point of the graphite boat. Figure 4 In the middle, b is a hole dug on the graphite boat. Figure 4 In the middle, c is the loaded silicon wafer.

[0105] Test Example 1

[0106] To show that the graphite boat group used for PECVD coating in the present application can effectively thicken the insulating film layer at the "stuck point mark" during the PECVD coating process, compared with the prior art, it effectively alleviates the quality problem of solar cells caused by leakage at the "stuck point mark" in the electroplating process.

[0107] (1) The performance of the solar cells prepared by the PECVD deposition coating method of Examples 1 to 4 of the present application and Comparative Example 1 is tested.

[0108] The raw materials, specifications and performance parameters of the silicon wafers to be coated that have completed diffusion and POLY deposition and are used in the various embodiments and comparative examples of the present application are at the same level.

[0109] After preparing a solar cell with a silicon nitride insulating film layer coated on both the front and back sides, the present application uses conventional processing technology to carry out subsequent processes including electroplating metallization (the processes used in each embodiment and comparative example are the same) to prepare a solar cell.

[0110] (2) The performance of the solar cell prepared by the PECVD deposition coating method of Example 1 and Comparative Example 1 of the present application was tested. The specific testing method is as follows:

[0111] Use IV tester to test the parallel resistance and leakage parameters of ten pieces each;

[0112] The specific test results are shown in the following table:

[0113]

[0114] After using the present invention, the parallel resistance is increased from an average of 46 ohms in comparative example 1 to an average of 2625 ohms. The leakage current is reduced from an average of 1.79 amperes in comparative example 1 to an average of 0.04 amperes. This greatly improves the problem of excessive leakage current in the current standard process of coating intermediate cells after electroplating the grid line.

[0115] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A graphite boat assembly for PECVD coating, characterized in that: The graphite boat group includes: a first graphite boat and a second graphite boat; The first graphite boat is provided with a plurality of clamping points for fixing one side of the substrate; The second graphite boat is provided with a plurality of clamping points for fixing the other side of the substrate; The plurality of clamping points on the first graphite boat and the plurality of clamping points on the second graphite boat are arranged in a staggered manner; The first graphite boat and the second graphite boat are provided with holes, and the holes are: According to the positions of a plurality of card points corresponding to the card points of the second graphite boat after the silicon wafer to be processed is loaded on the first graphite boat, holes are dug on the first graphite boat; and, according to the positions of a plurality of card points corresponding to the card points of the first graphite boat after the silicon wafer to be processed is loaded on the second graphite boat, holes are dug on the second graphite boat.

2. The graphite boat assembly according to claim 1, characterized in that: The plurality of clamping points on the first graphite boat and the plurality of clamping points on the second graphite boat are sequentially staggered.

3. The graphite boat assembly according to claim 1, characterized in that: The offset distance between each card point on the first graphite boat and each card point on the second graphite boat is ≥5mm, and the front and back card points do not interfere with each other. After this condition is met, the card point position can be designed at any position according to the machine automation plan.

4. The graphite boat assembly according to claim 1, characterized in that: The plurality of clamping points arranged on the first graphite boat correspond to three for each battery cell; The number of clamping points arranged on the second graphite boat is three for each battery cell.

5. The graphite boat assembly according to claim 1, characterized in that: The first graphite boat and the second graphite boat are used together in a PECVD coating process, wherein: The first graphite boat is used for coating the front side of the substrate, and the second graphite boat is used for coating the back side of the substrate; Or, the second graphite boat is used for coating the front side of the substrate, and the first graphite boat is used for coating the back side of the substrate.

6. Use of the graphite boat assembly according to any one of claims 1 to 5 in preparing a silicon nitride insulating film layer of a solar cell by chemical deposition.

7. A solar cell, characterized in that: The silicon nitride insulating film layers on the front and back sides of the solar cell are mainly prepared by chemical deposition of the graphite boat assembly described in any one of claims 1 to 5.

8. A method for depositing a silicon nitride insulating film layer of a solar cell according to claim 7, characterized in that: The deposition method comprises: Providing an intermediate silicon wafer to be deposited, and then using the graphite boat assembly according to any one of claims 1 to 5 to deposit a silicon nitride insulating film layer on the intermediate silicon wafer; The battery intermediate silicon wafer is loaded on a first graphite boat for film deposition to obtain a battery intermediate silicon wafer with a silicon nitride insulating film layer deposited on one side; Subsequently, the battery intermediate silicon wafer is loaded onto a second graphite boat for film deposition, and a silicon nitride insulating film layer is deposited on the other side of the intermediate silicon wafer to obtain a battery intermediate silicon wafer with a double-sided silicon nitride insulating film layer deposited thereon.

9. The method for depositing a silicon nitride insulating film layer of a solar cell according to claim 8, characterized in that: The deposition method further comprises: According to the positions of a plurality of card points corresponding to the card points of the second graphite boat after the silicon wafer to be processed is loaded on the first graphite boat, holes are dug on the first graphite boat; and, according to the positions of a plurality of card points corresponding to the card points of the first graphite boat after the silicon wafer to be processed is loaded on the second graphite boat, holes are dug on the second graphite boat.

10. The method for depositing a silicon nitride insulating film layer of a solar cell according to claim 8, characterized in that: The silicon nitride insulating film deposition method comprises the following steps: (A) providing a battery intermediate silicon wafer on which a silicon nitride insulating film layer is to be deposited, marking the position of the first graphite boat on one side of the battery intermediate silicon wafer, which is recorded as the first silicon wafer side; the first silicon wafer side is the front side or the back side of the battery intermediate silicon wafer; and, marking the position of the second graphite boat's clamping point on the other side of the battery intermediate silicon wafer, which is recorded as the second silicon wafer side; the second silicon wafer side is the front side or the back side of the battery intermediate silicon wafer; (B) drilling a hole on the first graphite boat at the position of the stuck point marked on the second silicon wafer, then loading the battery intermediate silicon wafer on the first graphite boat, introducing it into the furnace tube of the PECVD vacuum coating machine, and depositing a silicon nitride insulating film layer on the first silicon wafer surface to obtain a battery intermediate silicon wafer with the first silicon wafer surface coated; At this time, a small area of ​​coating is produced locally on the second silicon wafer surface at the card point print position corresponding to the second graphite boat due to wrap-around plating; (C) A hole is dug on the second graphite boat according to the stuck point position marked on the surface of the first silicon wafer, and then the battery intermediate silicon wafer is loaded on the second graphite boat, introduced into the furnace tube of the PECVD vacuum coating machine, and a silicon nitride insulating film layer is deposited on the surface of the second silicon wafer to obtain a double-sided coated solar cell; At this time, on the first silicon wafer surface of the battery cell, a small area of ​​coating is produced locally at the card point printing position corresponding to the first graphite boat due to wrap-around plating.

11. The method for depositing a silicon nitride insulating film layer of a solar cell according to claim 10, characterized in that: The holes dug on the first graphite boat in the step (B) are blind holes or through holes.

12. The method for depositing a silicon nitride insulating film layer of a solar cell according to claim 11, characterized in that: The holes dug on the first graphite boat in the step (B) are blind holes.

13. The method for depositing a silicon nitride insulating film layer of a solar cell according to claim 10, characterized in that: The holes dug on the second graphite boat in the step (C) are blind holes or through holes.

14. The method for depositing a silicon nitride insulating film layer of a solar cell according to claim 13, characterized in that: The holes dug on the second graphite boat in the step (C) are blind holes, and the depth of the blind holes is ≥0.2 mm.

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