A CVD pyrolytic graphite coating gas distribution system
Patent Information
- Application Number
- CN202522620942.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-10
- Publication Date
- 2026-10-30
- Estimated Expiration
- 2035-12-10
AI Technical Summary
然而，此种结构存在固有缺陷：气体在分气盒腔内沿内壁流动时，会受到流道阻力、局部涡流等因素的影响，形成自进气端至末端的显著压力梯度（通常进气口附近压力高，远端压力低）
1、本实用新型盒体内设置单向且上下气道均为环状，优化了气体流动路径，显著减少了气体在盒体内的流动阻力和产生紊流的可能性，为后续的均匀分配提供了基础。针对气体在环状气道内流动时必然存在的沿程压力损失（进气端压力高，末端压力低），通过增大下游出气孔的孔径（等效于减小该出气点的局部流阻），对下游较低的气道压力进行动态补偿，从而使得到达每个出气孔处的气体静压基本均衡，实现了气体从多路输出时流速一致性偏差≤5%，为反应区气体均匀供给奠定了物理基础。在马弗筒内设置带散气孔的散气板，对从分气盒均匀分配来的气体进行初次扩散，使其能更均匀地向上流动并覆盖放置在散气板上的工件，避免形成集中的气体射流。设置布气板对从马弗筒下端进入排气管区域的气流进行引导和整理，为气流均匀排出或进行二次分布创造条件。各部件技术特征相互协同，共同为热解石墨涂层的CVD沉积过程提供了一个气流高度均匀、温度场稳定、气氛可控的高效反应环境，有效提升了涂层产品的质量一致性、沉积效率及工艺重复性。
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Figure CN224917900U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of CVD deposition technology, specifically a CVD pyrolysis graphite coating gas distribution system. Background Technology
[0002] Pyrolytic graphite coatings possess irreplaceable application value in high-precision fields such as semiconductor manufacturing, aerospace, and nuclear industry due to their excellent high-temperature resistance, high chemical stability, good thermal and electrical conductivity, and low coefficient of friction. These coatings are typically prepared using chemical vapor deposition (CVD), which involves the decomposition of hydrocarbon gases at high temperatures (usually 1000℃ to 2000℃), resulting in the deposition of carbon atoms on the substrate surface to form a high-purity graphite structure.
[0003] In the CVD deposition process, the uniform distribution of reactive gases is crucial in determining the final coating thickness uniformity, microstructure consistency, and overall performance. Uneven gas distribution within the deposition furnace directly leads to differences in coating growth rates across different areas of the substrate, resulting in defective products with uneven thickness and inconsistent performance, severely impacting product reliability and yield.
[0004] Currently, common CVD furnace gas distribution devices typically employ a single gas distribution box structure. This box introduces process gas through an inlet pipe and connects to multiple outlet pipes of the same diameter to distribute the gas to the reaction zone. However, this structure has inherent drawbacks: as the gas flows along the inner wall of the distribution box, it is affected by factors such as flow channel resistance and local eddies, forming a significant pressure gradient from the inlet to the outlet (typically, the pressure is higher near the inlet and lower at the outlet). Since the outlet pipes have the same diameter, their flow resistance is essentially uniform, failing to compensate for the pressure difference between upstream and downstream, resulting in uneven gas flow rate and velocity from each outlet. This non-uniformity is directly transmitted to the deposition area, causing differences in coating thickness; measured thickness non-uniformity can reach 15% to 20%, severely restricting the quality and consistency of high-end pyrolytic graphite coating products.
[0005] In order to overcome the above-mentioned technical bottlenecks, it is urgent to develop a special gas distribution system that can achieve highly uniform gas distribution and ensure the uniformity of pyrolytic graphite coating deposition. Utility Model Content
[0006] This invention addresses the aforementioned shortcomings of existing technologies by providing a gas distribution system for CVD pyrolytic graphite coatings. This system offers a highly efficient reaction environment with highly uniform airflow, stable temperature field, and controllable atmosphere for the CVD deposition process of pyrolytic graphite coatings, effectively improving the quality consistency, deposition efficiency, and process repeatability of the coating products. To achieve the above objectives, this utility model provides the following technical solution: A CVD pyrolytic graphite coating gas distribution system includes a gas distribution box and a muffle cylinder. The gas distribution box includes a box body and a box cover. The box body has a one-way lower gas channel with an air inlet at the beginning of the lower gas channel and a lower air inlet pipe connected to the air inlet. The bottom of the box cover has a one-way upper gas channel corresponding to the position of the lower gas channel. The upper gas channel has air outlets with gradually increasing diameters evenly distributed along the airflow direction. The upper end of the air outlet is connected to an upper air inlet pipe, and the upper end of the upper air inlet pipe is connected to a support plate. The muffle cylinder is located above the support plate. The muffle cylinder has a gas dispersion plate for placing the workpiece, and gas dispersion holes are evenly distributed on the gas dispersion plate. The upper end of the muffle cylinder is connected to an exhaust pipe, and the bottom of the exhaust pipe is connected to a gas distribution plate.
[0007] Preferably, both the upper and lower airways are annular. Preferably, a graphite shaft is connected to the bottom of the air diffuser plate, and a motor is connected to the lower end of the graphite shaft. The motor is located below the support plate.
[0008] Preferably, the bottom of the exhaust pipe is a closed structure, and the lower end sidewall of the exhaust pipe is provided with air inlets evenly arranged along the circumference, with the air inlets located above the air distribution plate. Preferably, the air distribution plate is provided with air distribution holes, and the diameter of the air distribution holes gradually increases from the center of the air distribution plate to the surrounding area.
[0009] Preferably, the upper and lower air intake pipes are both connected to the air distribution box by threads.
[0010] Preferably, the number of upper air intake pipes is 6.
[0011] Preferably, a rotating component is connected to the output shaft of the motor, and the upper end of the rotating component is provided with a groove that cooperates with the graphite rotating shaft.
[0012] Compared with the prior art, the beneficial effects of this utility model are: 1. This utility model features a unidirectional, annular air passages inside the casing, optimizing the gas flow path and significantly reducing flow resistance and turbulence within the casing, thus providing a foundation for subsequent uniform distribution. Addressing the inevitable pressure loss along the flow path (high pressure at the inlet, low pressure at the outlet) when gas flows within the annular air passages, the lower downstream air passage pressure is dynamically compensated by increasing the diameter of the downstream outlet (equivalent to reducing the local flow resistance at that outlet point). This ensures a relatively uniform static pressure at each outlet, achieving a flow velocity consistency deviation of ≤5% when gas is output from multiple paths, laying the physical foundation for uniform gas supply to the reaction zone. A diffuser plate with diffuser holes is installed inside the muffle cylinder to initially diffuse the gas evenly distributed from the distribution box, allowing it to flow upwards more evenly and cover the workpiece placed on the diffuser plate, preventing the formation of concentrated gas jets. A distribution plate guides and organizes the airflow entering the exhaust pipe area from the lower end of the muffle cylinder, creating conditions for uniform airflow discharge or secondary distribution. The technical features of each component work together to provide a highly efficient reaction environment with highly uniform airflow, stable temperature field, and controllable atmosphere for the CVD deposition process of pyrolytic graphite coatings, effectively improving the quality consistency, deposition efficiency, and process repeatability of the coating products.
[0013] 2. The evenly distributed air diffuser holes on the diffuser plate of this invention can initially diffuse and distribute the airflow from the upper air inlet pipe, allowing the gas to enter the workpiece area more uniformly. The diffuser plate supporting the workpiece can rotate stably during the deposition process. The rotation causes the workpiece to continuously change its relative position with the airflow, achieving a "dynamic" uniform coverage of the workpiece surface by the gas, which can further "smooth out" microscopic airflow inhomogeneities and significantly improve the uniformity of the coating in the circumferential direction of the workpiece.
[0014] 3. High-purity isostatic graphite is used, leveraging its self-lubricating properties at high temperatures to effectively reduce friction and wear on rotating parts, ensuring smooth rotation. The hollow structure reduces weight, while rigid connections ensure effective power transmission. The rotating parts are made of forged molybdenum, which maintains a tensile strength of ≥100MPa at 1800-2000℃, providing excellent mechanical strength and creep resistance at high temperatures. This ensures reliable torque transmission and prevents power transmission failure or slippage due to softening at high temperatures, guaranteeing the long-term reliability of the air diffuser rotation.
[0015] 4. The aperture of the gas distribution holes gradually increases from the center outwards, guiding and secondary distributing the post-reaction exhaust gas rising and converging from around the muffle furnace. This gradual aperture design balances gas flow at different radial positions, allowing for more uniform gas discharge through the distribution plate. This prevents gas concentration at the center or edges, avoiding interference from localized eddies with the main reactive gas flow within the furnace, thus achieving a uniform secondary gas distribution. Simultaneously, this structure slightly increases the gas residence time in the reaction zone, which is beneficial for improving the utilization rate of the reactive gas and deposition efficiency.
[0016] 5. The exhaust pipe is sealed at the bottom, with an air inlet on its lower side wall. This forces all gas collected from the gas distribution plate to enter the exhaust pipe through the side wall inlet, completely preventing the possibility of process gas or tail gas being discharged directly from the center of the furnace bottom without sufficient mixing. This design, combined with the gas distribution plate, ensures uniform flow and renewal of the overall airflow within the furnace, maintaining the stability of the reaction atmosphere. Attached Figure Description
[0017] Figure 1 This is a schematic diagram of the structure of this utility model; Figure 2 This is a cross-sectional view of the present invention; Figure 3 This is a schematic diagram of the internal structure of the box; Figure 4 This is a schematic diagram of the bottom structure of the box lid; Figure 5 This is a schematic diagram of the exhaust pipe structure; Figure 6 This is a schematic diagram of the air distribution plate. Figure 7 This is a schematic diagram of the air diffuser plate. In the diagram: 1-Lower air intake pipe; 2-Air distribution box; 201-Box body; 202-Lower air passage; 203-Air inlet; 204-Box cover; 205-Upper air passage; 206-Air outlet; 3-Upper air intake pipe; 4-Support plate; 5-Muffler; 6-Exhaust pipe; 601-Air distribution plate; 602-Air distribution hole; 603-Air inlet; 7-Motor; 8-Graphite shaft; 801-Rotating component; 9-Air diffuser plate; 901-Air diffuser hole. Detailed Implementation
[0018] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.
[0019] like Figure 1 , Figure 2 As shown, a CVD pyrolysis graphite coating gas distribution system includes a gas distribution box 2 and a muffle cylinder 5 (including a muffle cover). The muffle cylinder 5 serves to insulate against heat and isolate the atmosphere, maintaining a stable temperature field inside the furnace and preventing external air intrusion from affecting the CVD reaction. The muffle cover is fitted onto the top of the muffle cylinder 5, forming a closed reaction space in conjunction with the muffle cylinder 5. Figure 3 , Figure 4 As shown, the gas separator 2 includes a body 201 and a cover 204. The gas separator 2 uses a high-purity graphite substrate made of pyrolytic graphite or a surface-deposited pyrolytic graphite coating. A 0.2-0.3 mm thick pyrolytic graphite coating with a roughness Ra ≤ 0.8 μm is deposited on the surface using a CVD process. This design gives the gas separator itself a coefficient of thermal expansion similar to that of the coating process, excellent high-temperature resistance and corrosion resistance, avoiding deformation, contamination or reaction with deposits under high-temperature reactive atmospheres, and ensuring the long-term stability and gas purity of the gas separation system.
[0020] The housing 201 contains a unidirectional lower air passage 202, with an air inlet 203 at its starting end. A lower air inlet pipe 1 is connected to the air inlet 203. The bottom of the housing cover 204 contains a unidirectional upper air passage 205 corresponding to the lower air passage 202. Both the upper and lower air passages 205 are annular to reduce gas flow resistance and improve gas distribution efficiency. The upper air passage 205 contains evenly spaced, gradually increasing diameter air outlets 206 along the airflow direction. An upper air inlet pipe 3 is connected to the upper end of the air outlets 206, and a support plate 4 is connected to the upper end of the upper air inlet pipe 3. The muffle cylinder 5 is located above the support plate 4, and a diffuser plate 9 for placing workpieces is provided inside the muffle cylinder 5. Figure 7 As shown, air diffuser 9 is evenly provided with air diffuser holes 901, the upper end of muffle 5 is connected to exhaust pipe 6, and the bottom of exhaust pipe 6 is connected to air distribution plate 601.
[0021] The upper air inlet pipe 3 and the lower air inlet pipe 1 are both connected to the air distribution box 2 by thread (with graphite sealing gaskets). The lower air inlet pipe 1 is connected to the air source to realize single-channel gas input.
[0022] The upper air inlet pipes 3 consist of six pipes, corresponding to the six air outlets 206 of the connecting cover 204. The pipe diameter matches the diameter of the connected air outlet 206, forming a "diameter-pipe diameter" collaborative compensation structure to ensure consistent gas flow velocity when output through the gas distribution pipes. The outlet pipe diameter ranges from 1 to 5 mm, with a flow velocity consistency deviation of ≤5%, effectively ensuring the uniformity of the pyrolytic graphite coating thickness. The layout design of the gas distribution box 2, with a single air inlet at the bottom and multiple air outlets at the top, reduces gas flow resistance and improves gas distribution efficiency.
[0023] The air diffuser plate 9 is integrally molded from high-density pyrolytic graphite, which has the dual functions of airflow dispersion and rotational stability. A graphite shaft 8 is connected to the bottom, and six support shafts supporting the air diffuser plate 9 are connected to the upper end of the graphite shaft 8 to ensure stability during rotation. The lower end of the graphite shaft 8 is driven by a motor 7.
[0024] Graphite shaft 8: Made of high-purity isostatic graphite, the shaft has a hollow structure, with an external thread at one end (fitting with the internal thread of the air diffuser plate 9), and the other end connected to the rotating part 801 via a keyway structure. Utilizing the self-lubricating properties of graphite, rotational friction at high temperatures is reduced, while power is transmitted to the air diffuser plate 9 through a rigid connection, causing it to rotate synchronously with the shaft (the speed can be adjusted by an external drive, typically 5-30 rpm).
[0025] Rotating component 801: Made of forged molybdenum, with a groove at the upper end to mate with the graphite shaft, and the other end connected to the output shaft of motor 7 via an internal thread. The molybdenum material maintains a tensile strength of ≥100MPa even at high temperatures of 1800-2000℃, effectively resisting torque stress during rotation and ensuring slip-free power transmission.
[0026] like Figure 6 As shown, the surface of the gas distribution plate 601 has an array of gas distribution holes 602. The diameter of the gas distribution holes 602 gradually increases from the center of the gas distribution plate 601 to the surrounding area, so that the gas in the furnace is evenly collected and discharged through the gas distribution holes 602. At the same time, it can play a secondary role in uniformly distributing the airflow, avoiding the impact of local airflow on the coating quality; it can also increase the reaction time and improve the product quality.
[0027] like Figure 5 As shown, the bottom of the exhaust pipe 6 is a closed structure, and the lower end sidewall of the exhaust pipe 6 is uniformly provided with air inlets 603 along the circumference, with the air inlets 603 located above the gas distribution plate 601. The use of graphite material and the side opening structure prevents process gases from being directly discharged from the deposition furnace from bottom to top, further ensuring uniform airflow distribution.
[0028] The gas distribution box 2 enables precise distribution of the reactant gases, the muffle cylinder 5 maintains a stable high-temperature reaction environment, and the inlet pipe and diffuser plate 9 ensure uniform delivery and diffusion of the reactant gases. Combined with the rotating structure, the workpiece to be coated rotates stably at high temperatures. The synergistic effect of these components provides a stable and efficient internal environment for the CVD deposition process of pyrolytic graphite coatings, effectively improving the quality and deposition efficiency of the pyrolytic graphite coatings, demonstrating good practicality and promotional value.
[0029] Obviously, those skilled in the art can make various modifications and variations to this utility model without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this utility model and their equivalents, this utility model also intends to include these modifications and variations.
Claims
1. A CVD pyrolytic graphite coating gas distribution system, comprising a gas distribution box and a muffle cylinder, characterized in that: The air distribution box includes a box body and a box cover. The box body has a one-way lower air passage with an air inlet at the beginning and a lower air inlet pipe connected to the air inlet. The bottom of the box cover has a one-way upper air passage corresponding to the position of the lower air passage. The upper air passage has air outlets with gradually increasing diameters evenly distributed along the airflow direction. The upper end of the air outlet is connected to an upper air inlet pipe, and the upper end of the upper air inlet pipe is connected to a support plate. The muffle cylinder is located above the support plate. The muffle cylinder has a diffuser plate for placing workpieces inside. The diffuser plate has diffuser holes evenly distributed. The upper end of the muffle cylinder is connected to an exhaust pipe, and the bottom of the exhaust pipe is connected to an air distribution plate.
2. The CVD pyrolytic graphite coating gas separation system as described in claim 1, characterized in that: Both the upper and lower airways are annular.
3. The CVD pyrolytic graphite coating gas separation system as described in claim 1, characterized in that: The bottom of the air diffuser is connected to a graphite shaft, and the lower end of the graphite shaft is connected to a motor, which is located below the support plate.
4. The CVD pyrolytic graphite coating gas separation system as described in claim 1, characterized in that: The bottom of the exhaust pipe is a closed structure, and the lower end sidewall of the exhaust pipe is evenly provided with air inlets along the circumference, with the air inlets located above the air distribution plate.
5. A CVD pyrolytic graphite coating gas separation system as described in claim 4, characterized in that: The air distribution plate is provided with air distribution holes, and the diameter of the air distribution holes gradually increases from the center of the air distribution plate to the surrounding area.
6. A CVD pyrolytic graphite coating gas distribution system as described in claim 1, characterized in that: Both the upper and lower air intake pipes are connected to the air distribution box by threads.
7. A CVD pyrolytic graphite coating gas separation system as described in claim 1, characterized in that: The number of upper air intake pipes is 6.
8. A CVD pyrolytic graphite coating gas separation system as described in claim 3, characterized in that: A rotating component is connected to the output shaft of the motor, and the upper end of the rotating component is provided with a groove that mates with the graphite shaft.