Graphite boat sleeve and graphite boat

Abstract

The present invention discloses a graphite boat sleeve, comprising a sleeve body having a cylindrical cavity penetrating in the axial direction; the sleeve body has at least one groove-like structure on the outer circumference of the tube wall, and the groove-like structure is constructed to include a narrow groove opened on the outer surface of the tube wall and a wide groove opened in the tube wall; the narrow groove is connected to the outside, and the wide groove is connected to the narrow groove, so as to form at least one circle of hanging wall structure on the outer circumference of the tube wall for shielding the deposition of thin film at the groove wall of the wide groove. Further, a graphite boat having the above-mentioned graphite boat sleeve structure is disclosed. The present invention can avoid the thin film deposited on the graphite boat sleeve from connecting between adjacent boat sheets to form a dielectric layer as much as possible through the design of a special groove-like structure and a hanging wall structure for shielding the deposition of thin film on the groove wall, reduce the influence of the thin film on the electric field between the boat sheets, stabilize the coating process, improve the coating quality, and reduce the number of graphite boat cleaning times.

Description

Technical Field

[0001] The invention belongs to the technical field of auxiliary accessories for solar cell manufacturing equipment, and in particular relates to a graphite boat sleeve and a graphite boat for tubular PECVD. Background Art

[0002] PECVD (Plasma Enhanced Chemical Vapor Deposition) is a plasma enhanced chemical vapor deposition method, which uses microwaves or radio frequencies to ionize the gas containing the atoms of the film components, forming plasma locally. The plasma has strong chemical activity and is easy to react. The desired film is deposited on the surface of the substrate with good film quality. At present, in the industrialized crystalline silicon battery preparation process, PECVD is often used to deposit films with different characteristics on the substrate surface, such as common silicon nitride films, silicon oxynitride films, etc. In the industrial tubular PECVD coating process, a ceramic sleeve with good insulation and high dielectric strength is usually set on the ceramic rod of the graphite boat, placed between adjacent boat slices, and in close contact with the boat slices. The ceramic sleeve is used to achieve physical support and electrical isolation between adjacent boat slices, and an electric field is formed.

[0003] With the continuous development of battery processes and technologies, PECVD is used in the preparation of other high-efficiency solar cells, such as tunneling oxide passivation contact cells (Topcon) and amorphous silicon heterojunction cells (HIT). At this time, PECVD needs to be used in the deposition process of other thin film materials, including the deposition of amorphous silicon thin films, doped amorphous silicon thin films, etc. With the diversification of the application scenarios of the PECVD coating process, we found that the coating is uneven, the coating rate is reduced, and even the situation of being unable to continue coating begins to appear, which seriously affects the quality of the coating. Moreover, only thinner films can be deposited in one process, and thick film and other process requirements cannot be met. In addition, the cleaning frequency of the graphite boat also increases accordingly, so that the graphite boat needs to be offline for cleaning after one or several uses, resulting in low utilization of the graphite boat and increased use costs. Therefore, tubular PECVD has not yet been widely used in the industrial preparation of the above-mentioned high-efficiency batteries. Summary of the invention

[0004] To solve the above problems, the present invention proposes a new type of graphite boat sleeve, which reduces the influence of the thin film deposited on the graphite boat sleeve on the electric field between the boat sheets through the design of a special groove structure and a hanging wall structure for shielding the thin film deposition on the groove wall, so as to stabilize the coating process, improve the coating quality, and reduce the frequency of graphite boat cleaning.

[0005] The technical solution of the present invention is as follows:

[0006] Solution 1: The present invention discloses a graphite boat sleeve, comprising a sleeve body having a cylindrical cavity penetrating along the axial direction; the sleeve body has at least one groove-like structure on the outer circumference of the tube wall, and the groove-like structure is constructed to include a narrow groove opened on the outer surface of the tube wall and a wide groove opened in the tube wall; the narrow groove is connected to the outside, and the wide groove is connected to the narrow groove, so as to form at least one hanging wall structure on the outer circumference of the tube wall for shielding the deposition of thin films on the wall of the wide groove.

[0007] As a preferred embodiment, the groove-like structure is an internal groove located at any position between the two ends of the sleeve body; the internal groove is constructed as a single-sided groove or a double-sided groove; in the single-sided groove, the narrow groove is located on one side of the wide groove; in the double-sided groove, the narrow groove is located between the two side walls of the wide groove.

[0008] As a preferred solution, in the double-sided grooves, the narrow groove is located in the middle of the wide groove.

[0009] As a preferred solution, the sleeve body is a hollow cylindrical structure, the length of the sleeve body is L, and the thickness of the tube wall is D; the longest length of the hanging wall structure is S, the width of the narrow groove is w1, and the depth of the wide groove is h2; in the single-sided groove, 1 / 3L≤S<2 / 3L, 1 / 6S≤w1≤1 / 3S, h2≤1 / 2D; in the double-sided groove, 1 / 4L≤S≤1 / 2L, 1 / 6S≤w1≤1 / 2S, h2≤1 / 2D.

[0010] As a preferred solution, the groove-like structure is an end groove located at the end of the sleeve body; in the end groove, the narrow groove is located on one side of the wide groove, and both the narrow groove and the wide groove are connected to the outside.

[0011] As a preferred solution, the sleeve body is a hollow cylindrical structure, the length of the sleeve body is L, and the thickness of the tube wall is D; the longest length of the hanging wall structure is S, the width of the narrow groove is w1, and the depth of the wide groove is h2; wherein, 1 / 4L≤S≤1 / 2L, 1 / 6S≤w1≤1 / 2S, h2≤1 / 2D.

[0012] As a preferred solution, the groove-like structures include at least two groove-like structures distributed along the axial direction of the sleeve body, and the shape and size of each groove-like structure are not required to be completely consistent.

[0013] As a preferred solution, the groove wall of the wide groove located at the hanging wall has at least one circle of step structure, or the groove wall of the wide groove located at the hanging wall is a slope structure.

[0014] As a preferred solution, the step structures or slope structures are all facing away from the narrow groove.

[0015] As a preferred solution, the cross-sectional shape of the narrow groove and the wide groove along the axial direction of the sleeve body is rectangular or trapezoidal.

[0016] As a preferred solution, the sleeve body is made of ceramic material.

[0017] Option 2: The present invention also discloses a graphite boat, comprising a graphite boat sheet, a support rod and a graphite boat sleeve having the features of Option 1 and any one of its preferred options; wherein: the support rod is used to support the graphite boat sheet; the graphite boat sleeve is sleeved on the support rod and arranged between adjacent graphite boat sheets, and is used to support and fix the position of the graphite boat sheet so that the same distance is maintained between adjacent graphite boat sheets.

[0018] Beneficial effects:

[0019] (1) Through the specially designed groove structure and the hanging wall structure formed on the outer periphery of the tube wall for shielding the deposition at the groove wall of the groove structure, the formation of a continuous film between the boat sheets after coating is avoided as much as possible, and the influence of the film deposited on the graphite boat sleeve on the electric field between the boat sheets is reduced or eliminated.

[0020] (2) Since the thin film deposited on the graphite boat sleeve is discontinuous in the direction of adjacent boat sheets, there is no through plane between the two ends of the ceramic sleeve connecting the adjacent boat sheets, thereby reducing or eliminating the influence of the deposited film on the electric field between the boat sheets, thereby stabilizing the coating process, improving the coating quality (including thickness, uniformity, etc.), greatly reducing the number of times the graphite boat is cleaned, and reducing the process production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the structure of the tubular PECVD graphite boat described in Example 1;

[0022] Figure 2 for Figure 1 A partial enlarged view of

[0023] Figure 3 Schematic diagram of the structure of the existing ceramic sleeve: (a) stereogram, (b) side view, (c) front view;

[0024] Figure 4 Schematic diagram of the structure of the ceramic sleeve described in Example 2: (a) stereogram, (b) front view;

[0025] Figure 5 Schematic diagram of the structure of the ceramic sleeve described in Example 3: (a) stereogram, (b) front view;

[0026] Figure 6 Schematic diagram of the structure of the ceramic sleeve described in Example 4: (a) stereogram, (b) front view;

[0027] Figure 7 It is a schematic diagram of the three-dimensional structure of the ceramic sleeve described in Example 5;

[0028] Figure 8 :(a), (b), (c) are schematic diagrams of the structures of three other ceramic sleeves;

[0029] Fig. 9 Schematic diagram of dimension marking of the ceramic sleeve described in Example 3: (a) side view, (b) front view;

[0030] Fig.10 : (a) is a schematic diagram of the use status of the ceramic sleeve described in Example 3; (b) is a schematic diagram of the use status of another ceramic sleeve. DETAILED DESCRIPTION

[0031] Combination Figure 1 and Figure 2 As shown, Example 1 discloses a relatively common graphite boat for tubular PECVD process, mainly comprising a graphite boat sheet 1 (referred to as boat sheet 1), a ceramic sleeve 2, a nut 3, a clamping point 4, a ceramic rod 5, an electrode hole 6 and a graphite block 7, wherein: the graphite boat sheet 1 comprises a plurality of sheets arranged in parallel at equal intervals, and the graphite boat sheet 1 is provided with a uniformly arranged silicon wafer placement area 8 and a clamping point 4 for fixing the silicon wafer; the ceramic rod 5 comprises a plurality of rods penetrating the graphite boat sheet 1, for supporting the graphite boat sheet 1, and fastening the graphite boat sheet 1 through nuts 3 at both ends; the ceramic sleeve 2 is sleeved on the ceramic rod 3 and arranged between adjacent boat sheets 1, and is used to support and fix the position of the graphite boat sheet so that the adjacent boat sheets maintain the same distance, and on the other hand, to keep the adjacent boat sheets insulated to form an electric field. The graphite blocks 7 include two groups symmetrically arranged at both ends of the boat sheets 1, which are used to conduct the spaced boat sheets 1 with the same electrical properties. Each graphite block 7 is provided with an electrode hole 6, which is connected to the positive and negative electrodes through the graphite blocks 7, so that an electric field is formed between adjacent boat sheets 1 and plasma is excited.

[0032] Figure 3 The figure shows the ceramic sleeve structure commonly used in tubular PECVD. The ceramic sleeve is a hollow cylindrical structure made of ceramic material. After analysis and investigation, we found that films with different characteristics deposited on the surface of silicon wafers will also be deposited on the surface of other materials in the furnace tube, such as the ceramic sleeve. After the ceramic sleeve has been used for a period of time and a certain thickness of film has been deposited on the surface, the insulation and dielectric strength between adjacent boats may be affected by the deposited film.

[0033] In the coating process, a continuous film is usually deposited on the surface of the ceramic sleeve. When depositing films with certain conductivity or high dielectric constant such as amorphous silicon and doped amorphous silicon films, the continuous film will weaken or even conduct the electric field between adjacent boats, resulting in poor coating effect. After depositing amorphous silicon and doped amorphous silicon films, since the films themselves have certain conductivity and relatively high dielectric constant, after the ceramic sleeve deposits a continuous film of a certain thickness, the adjacent boats are connected to form a conductive dielectric layer during the process, and the electric field between adjacent boats is weakened, resulting in uneven coating, reduced coating rate, and even the inability to continue coating. At the same time, there will be a situation where only a thin film can be deposited in one process, and the process requirements such as thick film cannot be met. To this end, the present invention improves the existing structure, so that the film is deposited on the ceramic sleeve and the graphite boat without changing the electric field strength before the boat. Several specific embodiments and corresponding drawings are given below to illustrate.

[0034] like Figure 4 As shown, Example 2 provides a new type of ceramic sleeve, which can be used for the graphite boat described in Example 1. The ceramic sleeve is a hollow cylindrical structure with an inner diameter of The length L matches the outer diameter of the ceramic rod to be penetrated, and the wall thickness D of the ceramic sleeve is adapted to the interval between adjacent boat sheets. The wall surface of the ceramic sleeve has a circle of groove-like structures arranged in the circumferential direction, specifically composed of narrow grooves 21 and wide grooves 22.

[0035] During film coating, in order to make the film deposited on the ceramic sleeve discontinuous in the direction of the adjacent boats, a structure for shielding the deposition can be designed on the ceramic sleeve to avoid forming a continuous film between the boats as much as possible. To this end, the relevant dimensions of the narrow groove 21 and the wide groove 22 can be appropriately selected so that during tubular PECVD film coating, after the plasma enters the wide groove 22 from the narrow groove 21, during the process of depositing the film, the amount of film deposition in the direction extending from the opening of the narrow groove to both sides becomes less and less, and the thickness of the film deposited on the groove wall (the groove walls on both sides) of the wide groove away from the narrow groove in one process is almost zero. In other words, based on the structural design of the narrow groove 21 and the wide groove 22, at least one circle of suspension wall structure 23 similar to a cantilever beam structure for shielding deposition is formed on the ceramic sleeve. Due to the shielding of the suspension wall structure 23, the deposited film cannot completely cover the entire groove wall of the wide groove, and it is difficult to form a continuous film on the surface of the narrow groove and the wide groove, thereby reducing or even eliminating the influence of the deposited film on the electric field between the adjacent boats.

[0036] In Example 2, the narrow groove 21 is opened on the surface of the tube wall and communicates with the outside, and its width is w1 and its depth is h1; the wide groove 22 is opened inside the tube wall and communicates with the bottom of the narrow groove 2, and its width is w2 and its depth is h2; the length of the narrow groove 21 and the wide groove 22 is approximately the circumference of the groove. The narrow groove 21 is located in the middle of the wide groove 22, and the distance between the groove walls on the left and right sides of the narrow groove 21 is the groove width w1; the distance between the groove wall on one side of the narrow groove 21 and the groove wall of the wide groove 22 on the same side is the length S of the hanging wall structure 23, and the width w2 of the wide groove 22 is obtained as w1+2*S; w1>0, w2>0.

[0037] In order to meet the above requirements, usually under the premise that the manufacturing process of the ceramic sleeve allows and the strength of the ceramic sleeve itself is satisfied, w1 / S is as small as possible, h1 / w1 and h2 / S are also as small as possible. In this way, after the plasma enters the narrow groove, due to the shielding of the hanging wall structure 23, the proportion of plasma moving toward the side wall of the wide groove will decrease with the decrease of the above ratio, and accordingly, the probability of deposition will also decrease, thereby avoiding the formation of a continuous film between adjacent boat sheets. In the scheme of Example 2, it can be designed as follows: 1 / 4L≤S≤1 / 2L, 1 / 6S≤w1≤1 / 2S, h2≤1 / 2D. For example, in a ceramic sleeve with an overall length L of 12mm and a wall thickness D of 1.9mm, S can be designed to be 3mm-6mm, w1 to be 0.5mm-2mm, and h2 to be 0.3mm-0.7mm. Specifically, it can be designed as follows: S is 6mm, w1 is 1mm, and h2 is 0.6mm. Of course, in other embodiments, the narrow groove 21 is not required to be located in the middle of the wide groove 22. In this case, the lengths of the left and right hanging wall structures 23 are not equal, and usually only the longer hanging wall structure 23 needs to be paid attention to. In other words, the S mentioned above refers to the length of the longer hanging wall structure 23.

[0038] In addition, it should be noted that the embodiment 2 is a preferred embodiment, the groove-like structure is located in the middle of the tube wall, the narrow groove 21 is located in the middle of the wide groove 22, and it is a symmetrical structure as a whole. However, in actual use, it is not required that the groove-like structure is located in the middle of the tube wall, nor is it required to be a symmetrical structure as a whole. The groove-like structure can be called an internal groove as long as it is located between the left and right ports of the tube wall. The wide groove 22 of the internal groove must be connected to the outside through the narrow groove 21; and the narrow groove 21 is not required to be located in the middle of the wide groove 22, as long as it is located between the groove walls on both sides, it can be called a double-sided groove. On the contrary, if the narrow groove 21 is located on one side of the wide groove 22, it is called a single-sided groove.

[0039] like Figure 5As shown, Embodiment 3 provides another novel ceramic sleeve, which is different from Embodiment 1 in that the groove structure is located at the end of the ceramic sleeve, the narrow groove 21 and the wide groove 22 are both opened from one end of the tube wall in the axial direction, one side of the narrow groove 21 is flush with one side of the wide groove 22, that is, the narrow groove 21 is located on one side of the wide groove 22, and one side of the wide groove 22 can be directly connected to the outside, and the groove structure can be called an end groove, which is also a single-sided groove with only one hanging wall structure 23, and the width of the wide groove 22 is w2=w1+S. The end groove is easier to make and clean than the internal groove.

[0040] In the scheme of Example 3, it can be designed as follows: 1 / 3L≤S<2 / 3L, 1 / 6S≤w1≤1 / 2S, h2≤1 / 2D. For example, in a ceramic sleeve with an overall length L of 12mm and a wall thickness D of 1.9mm, S can be designed to be 4mm-8mm, w1 to be 0.7mm-2.6mm, and h2 to be 0.3mm-0.7mm. Specifically, it can be designed as follows: S is 6mm, w1 is 1mm, and h2 is 0.6mm.

[0041] like Figure 6 As shown, Example 4 provides another new type of ceramic sleeve, which also adopts an internal groove design, that is, the groove structure is located at one end of the ceramic sleeve between the left and right ports of the tube wall. The difference from Example 1 is that the narrow groove 21 is located on one side of the wide groove 22, forming a single-sided groove structure.

[0042] It can be seen from the above embodiments that the internal groove and the end groove are mainly restrictions on the position of the groove-like structure, and the single-sided groove and double-sided groove are mainly descriptions of the shape of the groove-like structure, among which the end groove can only be a single-sided groove, but the internal groove is not limited to being a single-sided groove or a double-sided groove.

[0043] like Figure 7 As shown, Example 5 provides another new type of ceramic sleeve, which adopts an internal groove design. The difference from Example 1 is that the tube wall includes two or more groove structures, and the shapes of each groove structure are not required to be completely consistent. It can be a double-sided groove or a single-sided groove, and the size parameters of the narrow groove and the wide groove in the single-sided groove and the double-sided groove are not required to be completely consistent. Similarly, the end groove can also be designed with two or more groove structures. However, it should be noted that since the distance between adjacent boat sheets of the existing graphite boat is not wide, and considering the production cost, whether the internal groove or the end groove is selected, generally 1 to 2 groove structures are designed.

[0044] It should also be noted that in the above embodiments, whether it is a narrow groove or a wide groove, its cross section is a rectangle when viewed from the front, but in actual application, whether it is a narrow groove or a wide groove, its cross section shape is not limited to a rectangle, and can be a trapezoid or other shapes. Figure 8The ceramic sleeve shown in (a) has an irregular cross-section of the long groove, and a circle of steps 24 is provided on the wall of the long groove. With this design, after the plasma enters the groove structure, since the step 24 is facing away from the direction of plasma entry, it is difficult for the plasma to deposit and form a thin film at the step 24. The continuous use time is relatively longer, the continuous use times are more, and the cleaning frequency is lower. Figure 8 (b) shows a ceramic sleeve, the cross section of which is also irregular, and has a slope 25 facing the inside of the wide groove (backwards from the narrow groove), which has similar advantages to Figure 8 (a). Figure 8 The ceramic sleeve shown in (c) has a long groove with a cross-section of an isosceles trapezoid and a slope 26 facing the outside of the wide groove. This structure makes the groove depth near the inside of the wide groove narrower, which can reduce the probability of plasma entering the inside of the wide groove and also achieve the purpose of extending the service life. Compared with the first two structures, it has stronger mechanical strength.

[0045] like Fig. 9 As shown, taking the end groove (single-side groove) shown in Example 3 as an example, a specific size parameter design reference is given. From the data in the figure, it can be seen that the inner diameter of the ceramic sleeve is outer diameter Length L = 11mm, tube wall thickness w1=4mm,w2=w1+S=8mm,h1=0.5mm,h2=0.4mm. The dimension tolerance range of mechanical manufacturing is ±0.05mm. The operating temperature of the ceramic sleeve is ≤600℃.

[0046] Further, combined with Fig.10 As shown in (a), during tubular PECVD coating, plasma deposits on the surface of the ceramic sleeve and enters the wide groove 22 through the narrow groove 21, moves toward the side wall of the wide groove 22 and deposits. However, due to the shielding of the hanging wall structure 23, it is difficult for the plasma to reach and deposit on the side wall of the wide groove 22, so that the film deposited on the ceramic sleeve is discontinuous in the direction of adjacent boats, avoiding the electric field between adjacent boats caused by the deposited film. Fig.10 As shown in (b), since the step 24 faces away from the plasma entry direction, it is also difficult to deposit a thin film at the step 24.

[0047] Finally, it should be noted that although the embodiments of the present invention are described above in conjunction with the accompanying drawings, the present invention is not limited to the above-mentioned specific embodiments and application fields, and the above-mentioned specific embodiments are only illustrative and instructive, rather than restrictive. Under the guidance of this specification, a person of ordinary skill in the art can also make many forms without departing from the scope of protection of the claims of the present invention, all of which belong to the scope of protection of the present invention.

Claims

1. A graphite boat casing, characterized in that: The invention comprises a sleeve body having a cylindrical cavity penetrating in the axial direction; the sleeve body has at least one circle of groove-like structure on the outer circumference of the tube wall, and the groove-like structure is constructed to include a narrow groove opened on the outer surface of the tube wall and a wide groove opened in the tube wall; the narrow groove is connected to the outside, and the wide groove is connected to the narrow groove, so as to form at least one circle of hanging wall structure on the outer circumference of the tube wall for shielding the thin film deposition at the groove wall of the wide groove; The groove-like structure is an internal groove located at any position between the two ends of the sleeve body; the internal groove is constructed as a single-sided groove or a double-sided groove; in the single-sided groove, the narrow groove is located on one side of the wide groove; in the double-sided groove, the narrow groove is located between the two side walls of the wide groove; the sleeve body is a hollow cylindrical structure made of ceramic material; the length of the sleeve body is L, and the thickness of the tube wall is D; the longest length of the hanging wall structure is S, the width of the narrow groove is w1, and the depth of the wide groove is h2; in the single-sided groove, 1 / 3L≤S<2 / 3L, 1 / 6S≤w1≤1 / 3S, h2≤1 / 2D; In the groove, 1 / 4L≤S≤1 / 2L, 1 / 6S≤w1≤1 / 2S, h2≤1 / 2D; or, the sleeve body is a hollow cylindrical structure made of ceramic material; the length of the sleeve body is L, and the tube wall thickness is D; the longest length in the hanging wall structure is S, the width of the narrow groove is w1, and the depth of the wide groove is h2; wherein, 1 / 4L≤S≤1 / 2L, 1 / 6S≤w1≤1 / 2S, h2≤1 / 2D; the groove-like structure is an end groove located at the end of the sleeve body; in the end groove, the narrow groove is located on one side of the wide groove, and both the narrow groove and the wide groove are connected to the outside.

2. The graphite boat sleeve according to claim 1, characterized in that: When the inner groove is configured as a double-sided groove, the narrow groove is located in the middle of the wide groove.

3. The graphite boat sleeve according to claim 1, characterized in that: The groove-like structures include at least two groove-like structures distributed along the axial direction of the sleeve body, and the shape and size of each groove-like structure are not required to be completely consistent.

4. The graphite boat sleeve according to claim 1, characterized in that: The groove wall of the wide groove located at the hanging wall has at least one circle of step structure, or the groove wall of the wide groove located at the hanging wall is a slope structure.

5. The graphite boat sleeve according to claim 4, characterized in that: The step structures or slope structures are arranged facing away from the narrow groove.

6. A graphite boat, characterized in that: It comprises a graphite boat sheet, a support rod, and the graphite boat sleeve according to any one of claims 1 to 5; the support rod is used to support the graphite boat sheet; the graphite boat sleeve is sleeved on the support rod and arranged between adjacent graphite boat sheets, and is used to support and fix the graphite boat sheets so that the same distance is maintained between adjacent graphite boat sheets.

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