A gas splitting source
By introducing a beam plate and a Venturi structure into the gas pyrolysis source and optimizing the beam aperture design, the problem of low efficiency of the gas pyrolysis source under high flux was solved, and efficient gas pyrolysis and coating uniformity were achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NORTHEASTERN UNIV CHINA
- Filing Date
- 2024-01-16
- Publication Date
- 2026-07-21
AI Technical Summary
Existing gas pyrolysis sources have low thermal pyrolysis efficiency and low pyrolysis rate under large molecular flux, making it difficult to achieve efficient pyrolysis under large flow rates.
A beam plate with beam holes is introduced into the gas pyrolysis source. By optimizing the number and tilt angle of the beam holes, the effective number of collisions between the molecular flow and the hot filament is increased, and the ineffective collisions with the wall are reduced. Combined with the Venturi structure, rectification is carried out to improve the pyrolysis efficiency and rate.
It improves the pyrolysis efficiency and rate of the gas pyrolysis source, ensures the uniformity of the coating, and is suitable for high-efficiency pyrolysis under large molecular flux.
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Figure CN117904600B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of semiconductor technology, and in particular relates to a gas pyrolysis source. Background Technology
[0002] Fracturing sources are key components in molecular beam epitaxy, atomic layer deposition, and vacuum surface treatment equipment and processes. In the field of semiconductor technology, especially thin film deposition, the growth processes of some materials can only be achieved using fracturing sources. High-performance gas fracturing sources are also crucial for solving the interface problems of compound semiconductors. Compared to decades of long-term research and development and product iteration abroad, China's compound semiconductor industry lags behind advanced foreign levels in the technology of complete equipment and core components such as fracturing sources, and has long relied on imports. To achieve a breakthrough in the compound semiconductor industry and break free from foreign restrictions, the localization of high-performance fracturing sources is a crucial hurdle that must be overcome.
[0003] Hot-wire pyrolysis of gas molecules is a superior method for obtaining pure atoms. Current hot-wire gas pyrolysis sources typically have a cylindrical cavity with a hot wire inserted in the center, or a hot wire encased in a very fine cylindrical cavity. The gas inside the cavity is thermally pyrolyzed to obtain an extremely pure atomic stream. Hot-wire pyrolysis of gas molecules does not generate ions during molecular pyrolysis, thus avoiding bombardment of the coating surface and preventing coating defects. Existing gas pyrolysis mainly takes two forms: the hot wire is located inside the pyrolysis source furnace cavity, and the hot wire is encased in a thin tube, such as... Figure 1 As shown. The first type of fragmentation is as follows: Figure 1 As shown in (a), the number of molecules entering the cavity is large, but due to structural limitations, the effective collisions between molecules and the hot filament are few, resulting in low thermal decomposition efficiency. The second type... Figure 1 As shown in (b), the thermal pyrolysis efficiency can reach 80-99%, but the cylindrical cavity is too thin, i.e., the middle pipe is extremely narrow. Although the pyrolysis efficiency is high, the overall pyrolysis rate is not high, resulting in a small total pyrolysis volume and failing to achieve thermal pyrolysis under high-flux gas flow. Optimization of the pyrolysis source furnace structure to achieve a higher gas pyrolysis rate under larger molecular flux is imperative. Summary of the Invention
[0004] To address the shortcomings of existing technologies and improve the thermal decomposition efficiency and rate of gases, this invention provides a gas decomposition source. Based on the existing hot filament decomposition source structure, the structure of the decomposition source with a hot filament inserted in a cylindrical cavity is optimized to achieve a higher gas decomposition rate under a larger molecular flux.
[0005] A gas pyrolysis source includes a housing, a pyrolysis source front end cover at the top of the housing, a support portion and a hot wire disposed inside the housing, the pyrolysis source front end cover and the support portion forming a slit gas passage; a beam plate is disposed at the top of the housing, and beam holes are opened on the beam plate; a Venturi structure is disposed at the bottom of the housing.
[0006] The area between the beam plate and the front cover of the pyrolysis source is the beam region.
[0007] The space formed by the beam plate and the shell is a reaction chamber.
[0008] The top of the shell has a stop opening, and the beam plate is disposed inside the stop opening.
[0009] The beam holes are evenly distributed around the circumference of the beam plate.
[0010] The beam aperture and the beam plate have an angle α, i.e., beam aperture tilt angle α, so that the direction of the rectified airflow minimizes the number of collisions with the inner wall of the shell and the supporting part, reaches the hot wire surface as soon as possible, and has an effective collision with it to generate catalytic thermal decomposition, thus shortening the time for the fluid to react with the hot wire after entering the cavity.
[0011] The length of the support portion extending into the reaction chamber, excluding the stop portion, is L1. The axial distance from the point where the molecular flow enters the reaction chamber through the beam orifice to the point of first collision with the inner wall of the shell is L4. The design principle of the beam orifice inclination angle α is to ensure that the first collision position of the molecular flow with the inner wall of the shell exceeds the junction of the support portion and the hot wire, and L4>L1.
[0012] The beam aperture tilt angle α satisfies formulas (2) and (3):
[0013] ;
[0014] ;
[0015] in,
[0016] The length of the support portion extending into the reaction chamber, excluding the stop portion, is L1; the length of the hot wire is L2; the axial length of the reaction chamber, excluding the stop portion, is L3; the axial distance from the point where the molecular flow enters the reaction chamber through the beam orifice to the point of first collision with the inner wall of the shell is L4; the diameter of the hot wire is D1; the diameter of the support portion is D2; the diameter of the reaction chamber is D4; the depth of the beam orifice is d; the closest distance of the beam orifice from the central axis is a1; and the farthest distance of the beam orifice from the central axis is a2.
[0017] There are two limiting forms of molecules passing through the beam aperture: the molecules enter from one side of the beam aperture and the inlet end and exit from the opposite side. The angle between the path in the beam aperture and the axis is the limiting value, namely the limiting angle β and the limiting angle γ. The size requirements of the two limiting angles are given in formula (2) and formula (3).
[0018] The sum of the areas of all the aforementioned beam apertures is greater than the cross-sectional area of the slit air passage.
[0019] The beneficial effects of this invention are:
[0020] 1. This invention provides a gas pyrolysis source structure with a beam plate. The beam plate is equipped with beam holes, and the number and tilt angle of the beam holes are set according to the specific structure of the pyrolysis source furnace, while ensuring that the sum of the areas of all beam holes is greater than the cross-sectional area of the slit gas path. The beam holes act as a guiding structure to increase the probability of collisions between molecules and the hot filament. The beam plate rectifies the molecular flow entering the pyrolysis furnace in all directions, allowing it to be guided more quickly to the surface of the hot filament after entering the pyrolysis chamber, and to achieve effective collisions, thus realizing the conversion of molecules into atoms and improving the efficiency and rate of pyrolysis.
[0021] 2. The beam aperture and the beam plate have an angle. The purpose of the beam aperture tilt angle is to reduce the number of ineffective collisions between molecules and the wall, so that after fewer collisions, they can have effective collisions with the hot wire to generate thermal decomposition, thereby improving the decomposition rate and decomposition efficiency inside the entire decomposition source furnace.
[0022] 3. The present invention provides a Venturi structure at the tail of the pyrolysis source shell, which rectifies the atomic flow after pyrolysis before it enters the coating area, thereby improving the uniformity of the coating.
[0023] 4. This invention serves as a reference for the forward design of gas pyrolysis source furnaces. Attached Figure Description
[0024] Figure 1 This is a schematic diagram of the hot filament pyrolysis method in the prior art;
[0025] Figure 2 This is a schematic diagram of the internal structure of a gas pyrolysis source in the prior art;
[0026] Figure 3 This is a schematic diagram of the internal structure of the gas pyrolysis source provided by the present invention;
[0027] Figure 4 This is a schematic diagram of the beam plate in the gas pyrolysis source provided by the present invention;
[0028] Figure 5 A partial cross-sectional view of the beam plate in the gas pyrolysis source provided by the present invention;
[0029] Figure 6 This is a schematic diagram of the internal flow direction and molecular fragmentation of the cavity in this invention;
[0030] Figure 7 Schematic diagram of the structural dimensions of the gas pyrolysis source provided by the present invention Figure 1 ;
[0031] Figure 8 Schematic diagram of the structural dimensions of the gas pyrolysis source provided by the present invention Figure 2 ;
[0032] Figure 9 A schematic diagram of the flow within the beam aperture of the gas pyrolysis source provided by the present invention;
[0033] in,
[0034] 1-Shell, 2-Pyrolysis source front end cap, 3-Supporting part, 4-Hot wire, 5-Slit gas passage, 6-Beam plate, 7-Beam hole, 8-Venturi structure. Detailed Implementation
[0035] To better explain and facilitate understanding of the present invention, the technical solution and effects of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.
[0036] Existing gas pyrolysis source structures such as Figure 2 As shown, gas enters the pyrolysis source cavity through the slit gas path. Under high vacuum, the sudden expansion of space causes the Knudsen gas to increase several times over, resulting in high-degree-of-freedom expansion of gas molecules inside the cavity. Intermolecular collisions are almost zero; collisions primarily occur between gas molecules and the wall. At this point, without any constraint or guidance on the direction of molecular flow, the collisions inside the cavity become chaotic, reducing the probability of molecules colliding with the hot filament 4 while increasing the time it takes for molecules to reach the surface of the hot filament 4. Some molecules may even return to the vicinity of the slit gas path after diffuse reflection, affecting the inflow of the front gas stream into the cavity.
[0037] This invention provides a gas pyrolysis source, such as... Figure 3 As shown, the device includes a housing 1, with a pyrolysis source front end cap 2 on the top of the housing 1. A support portion 3 and a hot wire 4 are disposed inside the housing 1, forming a slit gas passage 5 with the pyrolysis source front end cap 2 and the support portion 3. A stop is provided inside the top of the housing 1, and a beam plate 6 is disposed inside the stop to increase the probability of gas molecules colliding with the hot wire 4, thereby improving the overall pyrolysis efficiency. A beam hole 7 is provided on the beam plate 6. The area between the beam plate 6 and the pyrolysis source front end cap 2 is the beam region, and the space formed by the beam plate 6 and the housing 1 is the reaction chamber. A Venturi structure 8 is provided at the bottom of the housing 1. Its functions are twofold: first, to reflect some molecules that do not collide with the hot wire 4 back to the surface of the hot wire 4 for pyrolysis; and second, to guide and rectify the post-reaction flow, allowing it to expand in the corresponding direction after entering the coating area, thus ensuring the uniformity of the coating to a certain extent.
[0038] like Figures 4-5 As shown, the beam holes 7 on the beam plate 6 are evenly distributed circumferentially, and the beam holes 7 and the central axis of the beam plate 6 have an angle α, so that the direction of the rectified airflow minimizes the number of collisions with the inner wall of the shell 1 and the support part 3, and reaches the surface of the hot wire 4 as soon as possible to have an effective collision with it and generate catalytic thermal decomposition, thus shortening the time for the fluid to react with the hot wire 4 after entering the cavity.
[0039] The number of beam holes 7 and the angle between the beam holes 7 and the axis can be changed according to the diameter and length of the housing 1 to ensure that the sum of the areas of all beam holes 7 is greater than the cross-sectional area of the slit air passage 5, so as to avoid the reduction of the upstream and downstream areas of the flow direction, which would cause the pressure inside the rectification region to exceed the pressure at the slit air passage 5. Figure 7 and Figure 8 The diagram shows the structural dimensions of the gas pyrolysis source. The length of the support part 3 extending into the reaction chamber excluding the stop portion is L1, the length of the hot wire 4 is L2, the axial length of the reaction chamber excluding the stop portion is L3, the axial distance from the point where the molecular flow enters the reaction chamber through the beam hole 7 to the point of first collision with the inner wall of the shell 1 is L4, the diameter of the hot wire 4 is D1, the diameter of the support part 3 is D2, the diameter of the reaction chamber is D3, the depth of the beam hole 7 is d, the closest distance of the beam hole 7 from the central axis is a1, the farthest distance of the beam hole 7 from the central axis is a2, and the angle between the beam hole 7 and the axis, i.e., the tilt angle of the beam hole 7, is α. Figure 6 The middle arrow indicates the main intake pipe and each stream. Fluid enters the reaction chamber after passing through each stream aperture 7, achieving a transition from continuous flow to molecular flow. The main function of the stream aperture 7 is to constrain the direction of the molecular flow, ensuring it flows in a fixed direction and collides with the wall of the casing 1, where it undergoes specular or diffuse reflection, such as... Figure 8 As shown. The design principle of the beam hole 7 tilt angle α is to make the first collision position of the molecular flow with the inner wall of the shell 1 exceed the junction of the support part 3 and the hot wire 4, that is, L4>L1, and the included angle α satisfies formula (2) and formula (3).
[0040] Figure 9 The flow conditions inside the beam aperture are shown. For example... Figure 7 As shown, the left and right sides of the support portion 3 represent the collisional fragmentation at the limiting angles β and γ, respectively, i.e., the two limiting forms of molecules passing through the beam aperture 7, as shown in the figure. Figure 7 As shown in β and γ, the molecules enter from one side of the beam aperture 7 and the inlet end and exit from the opposite side. The angle between the path in the beam aperture 7 and the axis is the limit value. For the two limit forms of molecules passing through the beam aperture 7, the two limit angles β and γ of the molecules passing through the beam aperture 7, as long as the position of the first incident point of the molecules under the two limit angles is guaranteed, it can be guaranteed that the molecules under the other angles can collide with the hot wire 4 in the shortest time. The requirements for the size of the two limit angles are shown in formula (2) and formula (3).
[0041] (2);
[0042] (3);
[0043] Combination Figure 6As shown, the airflow enters the slit air passage 5 after passing through the flow valve and flows into the beam region. After being rectified by the beam aperture 7 on the beam plate 6, it enters the reaction chamber. After passing through the beam aperture 7, the molecular flow undergoes one or more collisions with the support part 3 and the inner wall surface of the shell 1 (i.e., specular reflection and diffuse reflection) to reach the surface of the hot filament 4, where thermal decomposition occurs, breaking the molecules into atoms. After being rectified by the Venturi structure 8, the molecules enter the coating chamber.
Claims
1. A gas pyrolysis source, characterized in that: The device includes a housing, with a pyrolysis source front end cap on the top of the housing, a support portion and a hot wire disposed inside the housing, and the pyrolysis source front end cap and the support portion forming a slit gas passage; a beam plate is disposed at the top of the housing, and beam holes are opened on the beam plate; a Venturi structure is disposed at the bottom of the housing. The beam aperture and the beam plate have an angle α, i.e., beam aperture tilt angle α, so that the direction of the rectified airflow minimizes the number of collisions with the inner wall of the shell and the supporting part, reaches the hot wire surface as soon as possible, and has an effective collision with it to generate catalytic thermal decomposition, thus shortening the time for the fluid to react with the hot wire after entering the cavity. The beam aperture tilt angle α satisfies the following formula: ； ； in, The length of the support portion extending into the reaction chamber, excluding the stop portion, is L1; the length of the hot wire is L2; the axial length of the reaction chamber, excluding the stop portion, is L3; the axial distance from the point where the molecular flow enters the reaction chamber through the beam orifice to the point of first collision with the inner wall of the shell is L4; the diameter of the hot wire is D1; the diameter of the support portion is D2; the diameter of the reaction chamber is D4; the depth of the beam orifice is d; the closest distance of the beam orifice from the central axis is a1; and the farthest distance of the beam orifice from the central axis is a2. There are two limiting forms for molecules passing through the beam aperture: molecules enter from one side of the beam aperture and the inlet end and exit from the opposite side. The angle between the path in the beam aperture and the axis is the limiting value, namely the limiting angle β and the limiting angle γ. The size requirements of the two limiting angles are given in the formula above.
2. The gas pyrolysis source according to claim 1, characterized in that: The area between the beam plate and the front cover of the pyrolysis source is the beam region.
3. The gas pyrolysis source according to claim 1, characterized in that: The space formed by the beam plate and the shell is a reaction chamber.
4. A gas pyrolysis source according to claim 1, characterized in that: The top of the shell has a stop opening, and the beam plate is disposed inside the stop opening.
5. A gas pyrolysis source according to claim 1, characterized in that: The beam holes are evenly distributed along the circumference of the beam plate.
6. A gas pyrolysis source according to claim 1, characterized in that: The length of the support portion extending into the reaction chamber, excluding the stop portion, is L1. The axial distance from the point where the molecular flow enters the reaction chamber through the beam orifice to the point of first collision with the inner wall of the shell is L4. The design principle of the beam orifice inclination angle α is to ensure that the first collision position of the molecular flow with the inner wall of the shell exceeds the junction of the support portion and the hot wire, and L4>L1.
7. A gas pyrolysis source according to claim 1, characterized in that: The sum of the areas of all the aforementioned beam apertures is greater than the cross-sectional area of the slit air passage.