A boat-free supporting boat for horizontal polycrystalline silicon back sealing furnace and a back sealing processing method

Abstract

This invention relates to a trail-free support boat for a horizontal polycrystalline silicon back-sealing furnace and a back-sealing processing method. The support boat includes a main body and several support slots equidistantly arranged along the main body. The inner side of each support slot has a supporting edge extending towards the center. The contact area between the supporting edge and the silicon wafer is located within the wafer's surface, not at its outer edge. The silicon wafer is placed horizontally within the support slot. The supporting edge supports the weight of the wafer within its surface. The bottom diameter of the slot is larger than the wafer's diameter, creating a radial gap between the wafer's outer edge and the bottom of the slot. This radial gap is maintained by a wafer mounting limiter during loading and by the dimensional difference between the slot's bottom diameter and the wafer's diameter during deposition. The entire outer edge of the wafer is suspended in a non-pressure-bearing state under load. This invention eliminates back-sealing trail defects at the physical structural level, ensuring uniform deposition of the polycrystalline silicon thin film across the entire back of the wafer. Product yield is improved by more than 9% compared to traditional processes. It eliminates the need for post-processing steps such as edge grinding and polishing, and can be directly adapted to existing horizontal back-sealing furnace equipment.

Description

Technical Field

[0001] This invention relates to the field of tooling technology for LPCVD polycrystalline silicon back sealing processing of semiconductor silicon wafers, specifically to a trackless carrier boat for a horizontal polycrystalline silicon back sealing furnace and a back sealing processing method. Background Technology

[0002] Polysilicon back-sealing is a core process in the manufacturing of power devices and integrated circuit silicon wafers. It involves depositing a uniform polysilicon thin film on the back of the wafer to achieve external gettering, optimize electrical performance, and improve the wafer's mechanical strength. Currently, the industry commonly uses horizontal LPCVD back-sealing furnaces for polysilicon deposition, with horizontal quartz carrier boats used to load the wafers during the production process.

[0003] Existing traditional horizontal quartz boats rely on edge supports for load-bearing capacity. Figure 7 This is a schematic diagram of a traditional horizontal quartz boat and silicon wafer loading. See also... Figure 7 The silicon wafer is placed vertically in the slot, and its outer edge is fixed and supported by the sides and bottom of the slot. In the high-temperature deposition environment of 580℃-680℃, the outer edge of the silicon wafer is tightly adhered to the quartz boat. This adhesion area hinders the flow of reactive gases, resulting in a lower local deposition rate. Furthermore, the deposited polycrystalline silicon crystals adhere the silicon wafer to the quartz boat, causing boat-track defects such as chipping during wafer unloading, severely affecting wafer quality. Simultaneously, multiple edge contacts between the silicon wafer and the slot lead to stress concentration, increasing the risk of fragmentation at high temperatures.

[0004] Current industry improvement methods are mainly reactive and cannot fundamentally solve the boat track problem: First, grinding the card slot edge into an arc structure can only reduce the contact area and slightly weaken the boat track, but cannot achieve boat track-free production; Second, fine-tuning the deposition effect by optimizing process temperature and pressure and gas flow parameters has limited improvement effect and is very likely to cause other process fluctuations; Third, adding edge grinding, edge polishing, and secondary cleaning after back sealing to repair defective edges not only increases production costs and production cycle, but also easily causes silicon wafer edge breakage, dimensional deviation, secondary contamination and other adverse problems; Fourth, spraying a protective coating on the surface of the boat is prone to peeling off under long-term high temperature, resulting in particulate contamination of the silicon wafer.

[0005] Among known improvement solutions, one involves tilting the support rod to reduce markings by ensuring only one side of the silicon wafer is in contact. However, this still results in the outer edge of the silicon wafer remaining in contact with the slot wall, only reducing the contact area and not fundamentally changing the physical fact of edge contact. Existing horizontal back-sealing furnaces generally use a vertical silicon wafer support method with outer edge support. This method is deeply coupled with the batch loading structure of the horizontal furnace, the size of the silicon wafer loading basket, and the conveyor paddle transport conditions. To change the silicon wafer to be supported horizontally and have its outer edge suspended while maintaining equipment compatibility and loading efficiency, multiple constraints need to be addressed simultaneously, including wafer positioning, zero contact at the edge of the deposited state, and compatibility with the size of existing silicon wafer loading baskets. Currently, there is no support boat structure in the industry that simultaneously meets all of these constraints.

[0006] In view of this, this application provides a traceless carrier boat for a horizontal polycrystalline silicon back sealing furnace and a back sealing processing method. Summary of the Invention

[0007] This application provides a traceless support boat for a horizontal polycrystalline silicon back-sealing furnace and a back-sealing processing method, which at least solves the problems in the prior art of trace defects, low product yield, and cumbersome subsequent repair processes caused by the use of silicon wafer edge support for quartz boats in horizontal back-sealing furnaces.

[0008] In a first aspect, this application provides a trackless support boat for a horizontal polycrystalline silicon back-sealing furnace, comprising a boat body and a plurality of support slots equidistantly arranged along the height direction of the boat body, and further comprising: The supporting edge extends from the inside of the bearing slot toward the center of the boat body. The supporting contact area between the supporting edge and the silicon wafer is located in the area inside the silicon wafer surface. A suspension space is reserved between the supporting contact area and the outer edge of the silicon wafer. The silicon wafer is placed horizontally in the carrier slot. The supporting edge supports the weight of the silicon wafer in the area within the wafer surface. The entire outer edge of the silicon wafer is suspended in a non-pressure-bearing state and has no pressure contact with the carrier slot. The bottom diameter of each carrier slot is larger than the diameter of the silicon wafer, so that a radial gap is formed between the outer edge of the silicon wafer and the bottom of the carrier slot. The radial gap is maintained by the size difference between the bottom diameter of the slot and the diameter of the silicon wafer during the silicon wafer deposition state.

[0009] Optionally, the main body of the boat includes at least a number of support columns, at least two wafer mounting limiting members, and an upper annular plate and a lower annular plate. The support columns are fixed between the upper annular plate and the lower annular plate. The wafer mounting limiting members are inserted into positioning holes opened on the upper annular plate and the lower annular plate. In the wafer mounting state, the wafer mounting limiting members restrict the edge of the silicon wafer from contacting the bottom of the carrier slot to maintain the radial clearance. They are removed before thin film deposition to restore the outer edge of the silicon wafer to a non-pressure-bearing suspended state.

[0010] Optionally, the mounting limiting member is any one of a detachable positioning bar, an elastic claw, a retractable pin, or a magnetic stop.

[0011] Optionally, the support columns are arranged in a ring array with the center of the silicon wafer as the center, and each of the support edges cooperates to support the flat silicon wafer; the spacing between adjacent support slots is evenly distributed.

[0012] Optionally, the length of the support edge is 5 mm to 8 mm, the support slot is inverted V-shaped, the opening height of the support slot is less than its bottom height, the contact part between the silicon wafer and the support edge is at the front end of the support edge, and the upper surface of the support edge is a smooth arc contact surface.

[0013] Optionally, the contact point between the support edge and the silicon wafer is 1 mm to 8 mm from the outer edge of the silicon wafer; preferably, the contact point between the support edge and the silicon wafer is 3 mm to 5 mm from the outer edge of the silicon wafer.

[0014] Optionally, the mounting limiting member is a detachable round bar-shaped quartz strip with a diameter of 6 mm to 10 mm, which is installed in a ring array on the upper and lower ring plates.

[0015] Optionally, the upper and lower annular plates are 3 mm to 5 mm thick, and are welded together with the support column. They are provided with positioning holes for installing the plate limiting member.

[0016] Optionally, the main body of the boat is made of high-purity quartz or silicon carbide, and its surface is chemically polished.

[0017] Optionally, the mounting plate limiting member and the support column are arranged in concentric circles, and the diameter of the positioning circle formed by the mounting plate limiting member is 1 mm to 2 mm smaller than the bottom diameter of the slot.

[0018] Preferably, the height and spacing of the bearing slot are consistent with the size of the silicon wafer loading basket, and the bottom diameter of the slot is 2-3 mm larger than the diameter of the silicon wafer.

[0019] Secondly, this application provides a method for processing traceless polycrystalline silicon back sealing, using the traceless carrier boat for the horizontal polycrystalline silicon back sealing furnace provided in the first aspect above, including the following steps: S1. Boat pretreatment: The carrier boat is pickled, rinsed with ultrapure water, dried at high temperature, and then the loading limiter is installed for use. S2, Wafer loading: The silicon wafer to be back-sealed is placed horizontally in the carrier slot. The supporting edge supports the weight of the silicon wafer in the area within the wafer surface. The wafer loading limiting member restricts the edge of the silicon wafer from contacting the bottom of the carrier slot to maintain the radial gap. S3, Furnace loading: The carrier boat loaded with silicon wafers is transferred to the conveyor paddle and placed horizontally. Before thin film deposition, the constraint of the wafer mounting limiter on the radial position of the silicon wafer is released, so that the outer edge of the silicon wafer remains non-pressure-bearing and suspended throughout the deposition process. It is then fed into the horizontal back-sealed furnace cavity through the conveyor paddle. S4. Thin film deposition: Under preset process conditions, silicon source gas and carrier gas are introduced to deposit a polycrystalline silicon thin film on the back of the silicon wafer. S5. Cooling and unloading: Stop the introduction of reaction gas, purge with nitrogen to cool down, and remove the paddle after the furnace body has cooled down, completing the back sealing process without boat tracks.

[0020] Optionally, in S3, the method of releasing the wafer mounting limiting member from the radial position constraint of the silicon wafer is any one of: removing the wafer mounting limiting member from the positioning hole, retracting the elastic claw, retracting the retractable pin, or demagnetizing and disengaging the magnetic retaining edge.

[0021] Optionally, in S4, the thin film deposition process conditions are: deposition temperature 580℃-680℃, silicon source gas is silane or trichlorosilane, carrier gas is hydrogen or nitrogen, and deposition time is 30 minutes-120 minutes.

[0022] Optionally, in step S3, the loading limiters are released synchronously in batches by a robotic arm, or released one by one on the conveyor paddle.

[0023] Compared with related technologies, the horizontal polycrystalline silicon back-sealing furnace and back-sealing processing method provided in this application have at least the following technical advantages: This application relocates the silicon wafer support from the edge to the in-plane area, changing the industry's long-standing edge-support method. The support edge extends from the inside of the support slot towards the center, with the contact point located approximately 3.5 mm in-plane within the silicon wafer. The slot bottom diameter is 2-3 mm larger than the silicon wafer diameter. Combined with the wafer mounting limiter, this maintains a radial gap between the outer edge of the silicon wafer and the bottom of the slot during wafer mounting. The entire outer edge of the silicon wafer is suspended in a non-pressure-bearing state under load, completely eliminating contact between the wafer and the wafer edge from the physical structural perspective. The resulting silicon wafer exhibits a film thickness deviation of no more than 3% across the entire back surface, eliminating the need for post-processing steps such as edge grinding, edge polishing, and secondary cleaning. This shortens the production chain and improves product yield by more than 9% compared to traditional processes.

[0024] In summary, the overall dimensions of the support boat are compatible with existing horizontal back-sealing furnace equipment, allowing for direct batch replacement of traditional quartz boats without equipment modification or process adjustments. The support boat is constructed entirely of high-purity quartz through welding and undergoes chemical polishing, resulting in high-temperature resistance, excellent chemical stability, and no impurity precipitation. It is also resistant to deformation and chipping even after prolonged high-temperature use.

[0025] Details of one or more embodiments of this application are set forth in the following drawings and description to make other features, objects and advantages of this application more readily apparent. Attached Figure Description

[0026] Figure 1 This is one of the schematic diagrams of a three-dimensional structure of a boat without boat tracks, according to an exemplary embodiment.

[0027] Figure 2 This is the second schematic diagram of a three-dimensional structure of a boat without boat tracks, according to an exemplary embodiment.

[0028] Figure 3 This is a side view of a boat without boat tracks, as shown according to an exemplary embodiment.

[0029] Figure 4 This is a top view of a boat without boat tracks, according to an exemplary embodiment.

[0030] Figure 5 yes Figure 2 A schematic diagram of section AA.

[0031] Figure 6 yes Figure 2 Enlarged schematic diagram of the B-structure.

[0032] Figure 7 This is a schematic diagram of the loading of a traditional horizontal quartz boat and a silicon wafer.

[0033] Explanation of reference numerals in the attached drawings: support column 10; bearing slot 101; support edge 102; suspension space 103; wafer mounting limiter 20; positioning hole 201; upper ring plate 30; lower ring plate 40; silicon wafer 50. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this disclosure clearer, the technical solutions of the embodiments of this application are described clearly and completely below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0035] Unless otherwise defined, the technical or scientific terms used in this disclosure shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” and similar terms used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as “comprising” or “including” mean that an element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as “connected” or “linked” are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect.

[0036] Example 1 Embodiment 1 of this application provides a trackless support boat for a horizontal polycrystalline silicon back-sealing furnace. Figure 1 This is one of the schematic diagrams of a three-dimensional structure of a boat without boat tracks, according to an exemplary embodiment. Figure 2 This is the second schematic diagram of a three-dimensional structure of a boat without boat tracks, according to an exemplary embodiment. Figure 3 This is a side view of a boat without boat tracks, as shown according to an exemplary embodiment. Figure 4 This is a top view of a boat without hull tracks, according to an exemplary embodiment. (Refer to...) Figures 1-4 The boat without a track includes a boat body, which is composed of several support columns 10, at least two plate limiting members 20, an upper ring plate 30, and a lower ring plate 40. The support columns 10 have several bearing slots 101 equidistantly provided along their length, and the inner side of the bearing slots 101 is provided with a support edge 102 extending towards the center of the boat body.

[0037] Figure 5 yes Figure 2 A schematic diagram of section AA. Figure 6 yes Figure 2 Enlarged schematic diagram of structure B in the middle. (Refer to...) Figures 1-6 The support columns 10 are arranged in a ring array centered on the silicon wafer, with the spacing between adjacent carrier slots 101 being uniform. The height and spacing of the carrier slots 101 are consistent with the silicon wafer loading basket, and the overall dimensions are compatible with existing horizontal back-sealing furnace equipment. Each support column 10 has an opening on one radial side, allowing the silicon wafer to horizontally enter between the support columns 10 and fall into the carrier slot 101. The bottom diameter of the slot formed by each support column 10 is 2-3 mm larger than the diameter of the silicon wafer 50, so that there is a radial gap between the outer edge of the silicon wafer 50 and the bottom of the slot after it is loaded.

[0038] The length of the support edge 102 is 5 mm to 8 mm, and the support slot 101 has an inverted V-shaped shape, with the opening height of the slot being less than its bottom height. The support contact area between the support edge 102 and the silicon wafer 50 is located within the silicon wafer surface, with the contact point approximately 3.5 mm from the edge of the silicon wafer 50. The upper surface of the support edge 102 is a smooth, rounded contact surface without sharp edges. A suspension space 103 is reserved between the support contact area and the outer edge of the silicon wafer 50, ensuring that the entire outer edge of the silicon wafer 50 is completely suspended and has no contact with the support slot 101 under load.

[0039] In one possible design, continue to refer to Figures 1-6The wafer mounting limiting member 20 is a detachable round bar-shaped quartz strip with a diameter of 6 mm to 10 mm. The wafer mounting limiting members 20 are arranged in a ring array on the upper ring plate 30 and the lower ring plate 40. The thickness of the upper ring plate 30 and the lower ring plate 40 is 3 mm to 5 mm. They are welded to the support column 10 as a whole, and the upper ring plate 30 and the lower ring plate 40 are provided with positioning holes 201 for mounting the wafer mounting limiting members 20. The wafer mounting limiting members 20 and the support column 10 are arranged in concentric circles, and the diameter of the positioning circle formed by the wafer mounting limiting members 20 is 1 mm to 2 mm smaller than the bottom diameter of the slot. The wafer mounting limiting members 20 constitute one embodiment of the wafer mounting limiting member of this application, ensuring that the edge of the silicon wafer 50 maintains a preset radial gap with the bottom of the slot in the wafer mounting state. Before entering the furnace, the wafer mounting limiter 20 is removed from the positioning hole 201. It is understood that the limiter can also be released by means of elastic claw retraction, retractable pin retraction, or magnetic edge demagnetization, allowing the outer edge of the silicon wafer 50 to return to a non-pressure-bearing, suspended state. During deposition, the radial gap between the outer edge of the silicon wafer 50 and the bottom of the slot is maintained by the dimensional difference between the slot bottom diameter and the silicon wafer diameter, requiring no intervention of any limiting structure.

[0040] In one possible design, the wafer mounting stop 20 can also be an elastic claw. One end of the elastic claw is fixed to the upper annular plate 30 or the lower annular plate 40, and the other end elastically abuts against the outer edge of the silicon wafer 50 in the wafer mounting state. After the wafer mounting is completed, the claw retracts and disengages from the outer edge of the silicon wafer 50 by external force or temperature triggering. Alternatively, a retractable pin can be used, which passes through the positioning hole 201 and retracts by screwing or spring resetting. A magnetic retaining edge can also be used, which is embedded in the positioning hole 201 and is attracted and demagnetized by an external magnetic field. All of the above alternatives can release the constraint on the radial position of the silicon wafer 50 before thin film deposition.

[0041] In one possible design, continue to refer to Figures 1-6 The carrier boat is constructed entirely of high-purity quartz material, welded together, and its surface is chemically polished. It exhibits high temperature resistance, good chemical stability, and no impurity precipitation, making it suitable for high-temperature polycrystalline silicon deposition processes. Alternatively, silicon carbide can be used to meet even higher temperature resistance requirements.

[0042] In the above embodiment, the silicon wafer 50 is horizontally supported by the in-plane support edge 102, and its outer edge is suspended in a non-pressure-bearing state under load, without pressure contact with the support boat. In the subsequent back-sealing process, the wafer loading, furnace entry, deposition, and furnace exit steps are described in accordance with the method described in Embodiment 2. During wafer loading, the wafer loading limiting member 20 maintains a radial gap in the wafer loading state. Before entering the furnace, the wafer loading limiting member 20 is removed to restore the non-pressure-bearing suspended state of the edge of the silicon wafer 50.

[0043] Comparative experiments verified that, under the same horizontal back-sealing furnace equipment and the same deposition process parameters (deposition temperature 620℃, silane flow rate, deposition time 60 minutes), at least three batches of 6-inch silicon wafers were processed using the carrier boat of this embodiment and the traditional horizontal quartz boat, with at least 25 wafers per batch. The silicon wafers processed using the carrier boat of this embodiment showed no boat marks or thin film areas on the entire back surface. The thickness deviation between the edge and the in-plane area measured by ellipsometer did not exceed 3% (the statistical caliber is the difference between the maximum and minimum values ​​within a single batch divided by the average value). The thickness deviation between the in-plane support edge contact area and the in-plane non-contact area did not exceed 2%. The surface morphology was uniform, and the product yield was improved by more than 9% compared to the traditional process (the yield caliber is the number of qualified wafers / number of wafers processed). No post-processing edge trimming was required. In contrast, the silicon wafers processed using the traditional horizontal quartz boat under the same equipment and process parameters showed obvious boat mark defects at the edges, uneven film thickness in the contact area, and a thickness deviation exceeding 5%.

[0044] In summary, the trail-free support boat for the horizontal polycrystalline silicon back-sealing furnace provided in Embodiment 1 extends the support edge 102 from the inside of the support slot 101 towards the center, shifting the support contact point from the edge of the silicon wafer to the in-plane area. Combined with the structural design where the slot bottom diameter is 2-3 mm larger than the silicon wafer diameter and the limiting effect of the wafer mounting limiter, the entire outer edge of the silicon wafer is suspended in a non-pressure-bearing state under load, eliminating trail defects from the root of the physical structure. The overall dimensions of the support boat are compatible with existing equipment, allowing for direct batch replacement of traditional quartz boats without equipment modification.

[0045] Example 2 Embodiment 2 of this application provides a method for fabricating a boat-less polycrystalline silicon back seal. For example... Figures 1-6 As shown, this method uses the trackless carrier boat described in Embodiment 1 above and includes the following steps: S1. Boat pretreatment: The carrier boat is acid-washed to remove surface impurities and oxides, rinsed with ultrapure water multiple times to remove residual acid, and dried at high temperature to remove moisture. The loading limiter 20 is installed in the positioning holes 201 of the upper ring plate 30 and the lower ring plate 40 for later use.

[0046] S2. Wafer Loading: The operator or automated robotic arm uses a suction pen to place the silicon wafers 50 to be back-sealed horizontally through the openings into the respective support slots 101 one by one. The supporting edges 102 support the weight of the silicon wafers 50 within the wafer surface area. During the wafer loading process, the wafer loading limiter 20 restricts the edge of the silicon wafer 50 from contacting the bottom of the slot, ensuring that the radial outer edge of each silicon wafer 50 maintains a radial gap of 1 mm to 2 mm with the bottom of the slot.

[0047] S3. Furnace Loading: The carrier boat carrying silicon wafer 50 is transferred as a whole onto the conveyor paddle and placed horizontally on the paddle surface. Before thin film deposition, the constraint of the wafer mounting limiting device on the radial position of silicon wafer 50 is released. For example, the wafer mounting limiting device 20 can be removed from the positioning hole 201, or the elastic claw can be retracted, the retractable pin can be retracted, and the magnetic retaining edge can be demagnetized and disengaged, thereby restoring the outer edge of silicon wafer 50 to a non-pressure-bearing suspended state. At this time, silicon wafer 50 is only supported by the in-plane support edge 102, and the outer edge has no pressure contact with any structure of the carrier boat. The carrier boat is sent into the horizontal back-sealed furnace cavity by the movement of the conveyor paddle. The operation of releasing the wafer mounting limiting device is the key step that distinguishes this method from existing processes. It provides precise positioning guarantee during the wafer mounting stage and removes all edge limiting structures during the deposition stage, so that the outer edge of silicon wafer 50 remains non-pressure-bearing and suspended throughout the deposition process; the radial gap during the deposition process is maintained by the size difference between the bottom diameter of the slot and the diameter of the silicon wafer. During mass production, each piece-mounting limit component 20 can be simultaneously clamped by a robotic arm and withdrawn in batches, or a piece-by-piece release mechanism can be set on the conveyor paddle to automatically release each piece-mounting limit component during the process of placing the carrier boat on the paddle surface.

[0048] S4. Thin Film Deposition: Under preset process conditions, silicon source gas and carrier gas are introduced to complete the deposition of polycrystalline silicon thin film on the back side of silicon wafer 50. The outer edge of silicon wafer 50 remains unpressurized and suspended throughout the deposition process. The reactive gas flows uniformly throughout the entire back side of silicon wafer 50 without edge obstruction or local airflow stagnation, resulting in a uniform thickness of the deposited polycrystalline silicon thin film.

[0049] S5. Cooling and Unloading: Stop the flow of reaction gas and continuously purge the furnace cavity with nitrogen to cool it down. After the furnace body cools to the process temperature, the conveyor paddle moves out to remove the carrier boat, completing the boat-trace-free back sealing process. The processed silicon wafer 50 has no boat traces on the entire back surface, eliminating the need for subsequent repair processes such as edge grinding, edge polishing, and secondary cleaning.

[0050] In summary, the boat-trace-free polycrystalline silicon back-sealing processing method provided in this embodiment 2 precisely defines the radial position of the silicon wafer using a wafer mounting limiter during the wafer mounting stage. Before thin film deposition, the wafer mounting limiter is released to restore the non-pressure-bearing suspended edge of the silicon wafer 50, so that the silicon wafer 50 is not disturbed by any edge pressure contact during subsequent deposition. Under the premise that the back-sealing effect is consistent with the traditional process, the boat-trace defect is completely eliminated, the subsequent process is simplified and the product yield is improved.

[0051] The content disclosed above is only a preferred and feasible embodiment of the present invention, and is not intended to limit the scope of the patent application of the present invention. Therefore, all equivalent technical changes made based on the content of the present invention specification and drawings are included in the scope of the patent application of the present invention.

Claims

1. A trackless support boat for a horizontal polycrystalline silicon back-sealing furnace, comprising a boat body and a plurality of support slots equidistantly arranged along the height direction of the boat body, characterized in that, It also includes: The supporting edge extends from the inside of the bearing slot toward the center of the boat body. The supporting contact area between the supporting edge and the silicon wafer is located in the area inside the silicon wafer surface. A suspension space is reserved between the supporting contact area and the outer edge of the silicon wafer. The silicon wafer is placed horizontally in the carrier slot. The supporting edge supports the weight of the silicon wafer in the area within the wafer surface. The entire outer edge of the silicon wafer is suspended in a non-pressure-bearing state and has no pressure contact with the carrier slot. The bottom diameter of each carrier slot is larger than the diameter of the silicon wafer, so that a radial gap is formed between the outer edge of the silicon wafer and the bottom of the carrier slot. The radial gap is maintained by the size difference between the bottom diameter of the slot and the diameter of the silicon wafer during the silicon wafer deposition state.

2. The trackless carrying vessel as described in claim 1, characterized in that, The main body of the boat includes at least a number of support columns, at least two wafer mounting limiting members, and an upper annular plate and a lower annular plate. The support columns are fixed between the upper annular plate and the lower annular plate. The wafer mounting limiting members are inserted into positioning holes opened on the upper annular plate and the lower annular plate. In the wafer mounting state, the wafer mounting limiting members restrict the edge of the silicon wafer from contacting the bottom of the carrier slot to maintain the radial clearance. They are removed before thin film deposition so that the outer edge of the silicon wafer returns to a non-pressure-bearing suspended state.

3. The trackless carrying vessel as described in claim 2, characterized in that, The mounting limiting component is any one of a detachable positioning bar, an elastic claw, a retractable pin, or a magnetic stop.

4. The trackless carrying vessel as described in claim 2, characterized in that, The support columns are arranged in a ring array with the center of the silicon wafer as the center, and each support edge works together to support the flat silicon wafer; the spacing between adjacent support slots is evenly distributed.

5. The trackless carrying vessel as described in claim 4, characterized in that, The length of the support edge is 5 mm to 8 mm, the support slot is inverted V shape, the opening height of the support slot is less than its bottom height, the contact part between the silicon wafer and the support edge is at the front end of the support edge, and the upper surface of the support edge is a smooth arc contact surface.

6. The trackless carrying vessel as described in claim 5, characterized in that, The contact point between the support edge and the silicon wafer is 1 mm to 8 mm from the outer edge of the silicon wafer.

7. The trackless carrying vessel as described in claim 3, characterized in that, The mounting limiting component is a detachable round bar-shaped quartz strip with a diameter of 6 mm to 10 mm, which is installed in a ring array on the upper and lower ring plates.

8. The trackless carrying vessel as described in claim 2, characterized in that, The upper and lower annular plates are 3-5 mm thick and are welded together with the support column. They are provided with positioning holes for installing the plate limiting component.

9. The trackless carrying vessel as described in claim 1, characterized in that, The main body of the boat is made of high-purity quartz or silicon carbide, and its surface is chemically polished.

10. The trackless carrying vessel as described in claim 2, characterized in that, The mounting plate limiting member and the support column are arranged in concentric circles, and the diameter of the positioning circle formed by the mounting plate limiting member is 1 mm to 2 mm smaller than the bottom diameter of the slot.

11. A method for processing traceless polycrystalline silicon back sealing, using a traceless carrier boat for a horizontal polycrystalline silicon back sealing furnace as described in any one of claims 1-10, characterized in that, Includes the following steps: S1. Boat pretreatment: The carrier boat is pickled, rinsed with ultrapure water, dried at high temperature, and then the loading limiter is installed for use. S2, Wafer loading: The silicon wafer to be back-sealed is placed horizontally in the carrier slot. The supporting edge supports the weight of the silicon wafer in the area within the wafer surface. The wafer loading limiting member restricts the edge of the silicon wafer from contacting the bottom of the carrier slot to maintain the radial gap. S3, Furnace loading: The carrier boat loaded with silicon wafers is transferred to the conveyor paddle and placed horizontally. Before thin film deposition, the constraint of the wafer mounting limiter on the radial position of the silicon wafer is released, so that the outer edge of the silicon wafer remains non-pressure-bearing and suspended throughout the deposition process. It is then fed into the horizontal back-sealed furnace cavity through the conveyor paddle. S4. Thin film deposition: Under preset process conditions, silicon source gas and carrier gas are introduced to deposit a polycrystalline silicon thin film on the back of the silicon wafer. S5. Cooling and unloading: Stop the introduction of reaction gas, purge with nitrogen to cool down, and remove the paddle after the furnace body has cooled down, completing the back sealing process without boat tracks.

12. The method as described in claim 11, characterized in that, In step S3, the method to release the wafer mounting limiting member from the radial position constraint of the silicon wafer is any one of the following: removing the wafer mounting limiting member from the positioning hole, retracting the elastic claw, retracting the retractable pin, or demagnetizing and disengaging the magnetic retaining edge.

13. The method as described in claim 11, characterized in that, In S4, the thin film deposition process conditions are: deposition temperature 580℃-680℃, silicon source gas is silane or trichlorosilane, carrier gas is hydrogen or nitrogen, and deposition time is 30 minutes-120 minutes.

14. The method as described in claim 11, characterized in that, In step S3, the loading limiters are released in batches synchronously by a robotic arm, or one piece at a time on the conveyor paddle.

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