Gas content control device

Abstract

The invention provides a gas content control device which comprises a reaction cavity and a first uniform flow cavity, and the reaction cavity comprises an upper cavity body and a lower cavity body which are isolated from each other up and down; the first uniform flow cavity is used for introducing inert gas into the upper cavity; the first flow uniformizing cavity comprises a first air inlet cavity, an air inlet uniformizing plate, a second air inlet cavity and an air outlet panel which are sequentially arranged in the air inlet direction, the air inlet uniformizing plate is provided with a plurality of air inlet holes, the cross section area of the air inlet holes close to the air inlet connector is smaller than that of the air inlet holes away from the air inlet connector, and the air outlet panel is provided with a plurality of first air outlets. And each first air outlet is isolated from the inner wall of the upper cavity through the air outlet panel. By adopting the gas content control device provided by the invention, the problems of large gas consumption, non-uniform purging, high possibility of turbulent flow in the cavity and the like are solved.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor processing, and in particular to a gas content control device. Background Art

[0002] During the operation of the laser annealing equipment, the oxygen around the silicon wafer will affect the treatment effect of the film layer on the surface of the silicon wafer, causing oxidation of the silicon wafer. Therefore, before and after annealing, high requirements are placed on the oxygen content around the silicon wafer. In order to solve the above problems, a sealed chamber with a nitrogen purge device can be used to reduce the oxygen content to a certain value within a certain period of time. In actual situations, there are problems such as high oxygen concentration in the annealing chamber and uneven nitrogen purge at the annealing chamber inlet, resulting in unstable airflow. Summary of the invention

[0003] An object of the present invention is to provide a gas content control device to solve one or more problems existing in the prior art.

[0004] In order to solve the above technical problems, the present invention provides a gas content control device, comprising: a reaction chamber and a first uniform flow chamber, wherein the first uniform flow chamber is arranged at one side of the reaction chamber; the reaction chamber comprises an upper chamber body and a lower chamber body which are arranged to be isolated from each other; the first uniform flow chamber is used to connect with an air inlet interface to pass an inert gas into the upper chamber;

[0005] The first uniform flow chamber includes a first air inlet chamber, an air inlet homogenizing plate, a second air inlet chamber and an air outlet panel which are arranged in sequence along the air inlet direction; the air inlet homogenizing plate has a plurality of air inlet holes, and the cross-sectional area of ​​the air inlet holes close to the air inlet interface is smaller than the cross-sectional area of ​​the air inlet holes away from the air inlet interface; the air outlet panel has a plurality of first air outlets, and each of the first air outlets is spaced apart from the top wall of the upper chamber.

[0006] Optionally, in the gas content control device, the diameter of the air inlet hole closest to the air inlet interface is 1.5 to 2 mm, and the diameter of the air inlet hole farthest from the air inlet interface is 3 to 4 mm.

[0007] Optionally, in the gas content control device, the gas outlet panel is grid-shaped, and a plurality of the first gas outlets are arranged in sequence along the width direction of the gas outlet panel, and the distance between the top of each of the first gas outlets and the inner side of the top wall of the upper cavity is 0.5 to 1 mm, and the distance between the bottom of each of the first gas outlets and the inner side of the bottom wall of the upper cavity is 0.5 to 1 mm.

[0008] Optionally, in the gas content control device, the sweep width of the gas outlet panel is not less than 1.3 times the diameter of the protection area in the upper cavity.

[0009] Optionally, in the gas content control device, it is characterized in that it also includes a second uniform flow chamber, the first uniform flow chamber and the second uniform flow chamber are respectively arranged on both sides of the reaction chamber, and the second uniform flow chamber is used to connect with the gas outlet interface to discharge the inert gas in the upper chamber;

[0010] The second flow-homogenizing chamber comprises an exhaust homogenizing plate and a recovery chamber sequentially arranged along the exhaust direction, the exhaust homogenizing plate has a plurality of second air outlets, and the cross-sectional area of ​​the second air outlets is greater than the cross-sectional area of ​​the air inlet.

[0011] Optionally, in the gas content control device, the exhaust homogenization plate adopts the same hole shape as the intake homogenization plate, and the cross-sectional area of ​​the second gas outlet is more than twice the cross-sectional area of ​​the intake hole.

[0012] Optionally, in the gas content control device, the volume of the recovery chamber is not greater than the volume of the first gas inlet chamber, and the bottom of the second uniform flow chamber is at the same level as the gas outlet interface.

[0013] Optionally, in the gas content control device, the gas content control device also includes a filling piece, which fills the area of ​​the lower cavity except the working area, and the gap between the top of the filling piece and the outer side of the bottom wall of the upper cavity is less than 1 mm.

[0014] Optionally, in the gas content control device, the lower cavity is connected to the first air inlet cavity.

[0015] In summary, the gas content control device provided by the present invention includes: a reaction chamber and a first uniform flow chamber, the first uniform flow chamber is arranged on one side of the reaction chamber; the reaction chamber includes an upper chamber and a lower chamber that are isolated from each other; the first uniform flow chamber is used to connect with the air inlet interface to pass the inert gas into the upper chamber; the first uniform flow chamber includes a first air inlet chamber, an air inlet homogenization plate, a second air inlet chamber and an air outlet panel arranged in sequence along the air inlet direction, the air inlet homogenization plate has a plurality of air inlet holes, and the cross-sectional area of ​​the air inlet holes close to the air inlet interface is smaller than the cross-sectional area of ​​the air inlet holes away from the air inlet interface, and the air outlet panel has a plurality of first air outlets, each of which is isolated from the inner wall of the upper chamber by the air outlet panel. The gas content control device provided by the present invention solves the problems of high oxygen concentration in the annealing chamber and uneven nitrogen purge at the air inlet of the annealing chamber, so that the oxygen index can be controlled below 10ppm within a specified time. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic diagram of the overall structure of a gas content control device provided in an embodiment of the present invention;

[0017] Figure 2 A schematic cross-sectional view of a gas content control device provided in Embodiment 1 of the present invention;

[0018] Figure 3 Schematic diagram of the structure of the first homogenization chamber in an embodiment of the present invention;

[0019] Figure 4 Another structural schematic diagram of the first homogenization chamber in an embodiment of the present invention;

[0020] Figure 5 This is a diagram of the gas flow trend of the gas content control device in the first embodiment of the present invention;

[0021] Figure 6 This is a gas flow diagram of the gas content control device in the second embodiment of the present invention;

[0022] The descriptions of the accompanying drawings are as follows:

[0023] 10-upper cavity; 20-lower cavity; 30-partition;

[0024] 401-first air inlet cavity; 402-air inlet homogenizing plate; 403-second air inlet cavity; 404-air outlet panel;

[0025] 60-air inlet interface;

[0026] 4041-first air outlet;

[0027] 501-exhaust homogenizing plate; 502-recovery chamber;

[0028] 80-filler;

[0029] 201-Air intake. DETAILED DESCRIPTION

[0030] In order to make the purpose, advantages and features of the present invention clearer, the present invention is described in detail in conjunction with the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are not drawn to scale, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. In addition, the structure shown in the drawings is often a part of the actual structure. In particular, the emphasis of each drawing is different, and sometimes different proportions are used. It should also be understood that, unless otherwise specified or indicated, the terms "first", "second", "third" and the like in the specification are only used to distinguish the various components, elements, steps, etc. in the specification, rather than to represent the logical relationship or sequential relationship between the various components, elements, steps, etc. Therefore, the features defined as "first", "second", and "third" may explicitly or implicitly include one or at least two of the features, and "one end" and "the other end" generally refer to two corresponding parts, which include not only the endpoints. In addition, as used in the present invention, "installed", "connected", "connected", and one element "set" on another element should be understood in a broad sense, usually only indicating that there is a connection, coupling, cooperation or transmission relationship between the two elements, and the connection, coupling, cooperation or transmission between the two elements can be direct or indirect through an intermediate element, and cannot be understood as indicating or implying the spatial position relationship between the two elements, that is, one element can be in any orientation such as inside, outside, above, below or one side of another element, unless the content clearly indicates otherwise. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. In addition, directional terms such as above, below, up, down, upward, downward, left, right, etc. are used relative to the exemplary embodiments as shown in the figures, with the upward or upper direction toward the top of the corresponding figure, and the downward or lower direction toward the bottom of the corresponding figure.

[0031] See also Figure 2 Combined with Figure 1 , this embodiment provides a gas content control device, the gas content control device includes: a reaction chamber, the reaction chamber includes an upper cavity 10 and a lower cavity 20 which are isolated from each other. Specifically, the reaction chamber can be divided into two upper and lower cavities by using a partition 30, the laser annealing operation is performed in the upper cavity 10, and the lower cavity 20 is used for other process operations. An elevator structure can be set in the lower cavity 20 for other operations on the wafer, which is not limited in this application. The upper cavity 10 and the lower cavity 20 are isolated from each other, which reduces the space of the cavity used for laser annealing, reduces the amount of inert gas used, reduces the time for the oxygen concentration in the upper cavity 10 to be less than 10ppm, and improves the efficiency of laser annealing. Wherein, the inert gas is, for example, nitrogen.

[0032] According to the theories related to fluid turbulence and multiphase flow, in order to achieve a stable and extremely low oxygen content inside the sealed cavity, in addition to avoiding the mixing of the fluids in the upper and lower cavities, the entrainment leading to an increase in the oxygen concentration in the upper cavity, and the large amount of nitrogen required, the air inlet must be purged evenly. Obviously, using only the partition 30 to separate the upper and lower cavities cannot solve such problems.

[0033] In view of this, the gas content control device provided in this embodiment also includes: a first uniform flow chamber, which is arranged on one side of the reaction chamber; the first uniform flow chamber is used to connect with the air inlet interface 60 to pass the inert gas into the upper chamber 10; the first uniform flow chamber includes a first air inlet chamber 401, an air inlet homogenizing plate 402, a second air inlet chamber 403 and an air outlet panel 404 arranged in sequence along the air inlet direction, the air inlet homogenizing plate 402 has a plurality of air inlet holes, and the cross-sectional area of ​​the air inlet holes close to the air inlet interface 60 is smaller than the cross-sectional area of ​​the air inlet holes away from the air inlet interface 60. In the gas content control device provided in this embodiment, the cross-sectional area of ​​the air inlet holes of the air inlet homogenizing plate 402 close to the air inlet interface 60 is smaller than the cross-sectional area of ​​the air inlet holes away from the air inlet interface 60, thereby ensuring the uniformity of air intake. In this way, the two uniform flow chambers, the air inlet homogenizing plate 402, and the air outlet panel 404 can be used together to perform two-stage homogenization on the air inlet to ensure that a good laminar flow is formed on the air outlet surface, so that the nitrogen gas at the air inlet of the upper cavity 10 serving as the annealing chamber is evenly purged.

[0034] See also Figure 3 , the gas outlet panel 404 has a plurality of first gas outlets 4041, and each of the first gas outlets 4041 is arranged at a distance from the inner wall of the upper cavity 10; that is, the first gas outlet 4041 does not extend to contact the top wall and the bottom wall of the upper cavity 10 in the height direction. The cavity wall is rough, and after contacting with the gas, turbulence will be generated due to viscosity. Each of the first gas outlets 4041 is separated from the inner wall of the upper cavity 10 by the gas outlet panel 404, avoiding the influence of the roughness of the wall of the upper cavity 10 and the existence of the surrounding gaps on the air flow speed and uniformity, and ensuring the uniformity of the flow in the whole domain. It can be seen that the gas content control device provided by this embodiment can be used to evenly purge the air inlet under the joint action of the air inlet homogenization plate 402 and the air outlet panel 404, and the cavity flows evenly without turbulence.

[0035] Specifically, the first air inlet cavity 401 and the second air inlet cavity 402 are arranged in sequence along the height direction of the reaction cavity (i.e., the vertical direction shown in the figure, which can also be understood as the Z direction), the air inlet interface 60 is connected to the first air inlet cavity 401, and the air inlet homogenizing plate 402 is arranged along the horizontal direction shown in the figure (which can also be understood as the plane formed by the X direction and the Y direction), and the air inlet hole on the air inlet homogenizing plate 402 enables the gas in the first air inlet cavity 401 to pass into the second air inlet cavity 402. Since the air inlet interface 60 is taken as the origin, as the (x, y) coordinate value increases, the gas density in the first air inlet cavity 401 gradually decreases. By design, the aperture of the air inlet hole gradually increases with the change of position, so that the gas density entering different positions in the second air inlet cavity 402 is consistent, so that the gas can be evenly blown into the upper cavity 10.

[0036] Preferably, the aperture of the air inlet closest to the air inlet interface 60 is 1.5mm-2mm, and the aperture of the air inlet farthest from the air inlet interface 60 is 3mm-4mm. That is to say, as the setting position changes, the aperture of the air inlet changes in the range of 1.5mm-4mm. A too small aperture will lead to too large flow resistance and make it difficult to exhaust air from the air outlet. A too large aperture will lead to poor homogenization effect. When the air inlet gradually changes within 1.5mm-4mm, the airflow can be well homogenized.

[0037] In an optional embodiment, the air outlet panel 404 is grille-shaped, and preferably, multiple identical first air outlets 4041 are arranged in sequence along the width direction of the air outlet panel 404, that is, multiple first air outlets 4041 are evenly arranged in sequence along the width direction of the air outlet panel, and the distance between the top of each first air outlet 4041 and the inner side of the top wall of the upper cavity and the distance between the bottom of each first air outlet 4041 and the inner side of the bottom wall of the upper cavity are equal. Designing multiple first air outlets 4041 to have the same distance from the inner sides of the upper and lower walls of the upper cavity can improve the uniformity of the airflow of gas entering the upper cavity 10. Further preferably, the distance between the top of the first air outlet 4041 and the inner side of the top wall of the upper cavity 10 is 0.5 to 1 mm, and the distance between the bottom of the first air outlet 4041 and the inner side of the bottom wall of the upper cavity 10 is 0.5 to 3 mm. When the process permits, preferably, the distance between the bottom of the first air outlet 4041 and the inner side of the bottom wall of the upper cavity 10 is 0.5 to 1 mm. When there are process restrictions, the minimum distance between the bottom of each first air outlet and the inner side of the bottom wall of the upper cavity can be designed to be 3 mm. The first air outlet 4041 is positioned so that the gas does not contact the inner wall of the upper cavity 10, thereby avoiding the influence of the rough inner wall of the cavity on the uniformity of the air flow. At the same time, the bottom of the first air outlet 4041 should be as close as possible to the inner side of the top wall of the upper cavity 10, and the top of the first air outlet 4041 should be as close as possible to the inner side of the bottom wall of the upper cavity 10, so as to increase the purge area and avoid poor purge effect.

[0038] Further preferably, Figure 3 As shown, the first air outlet 4041 adopts a waist hole design. When the first air outlet 4041 adopts a waist hole design, the top of the first air outlet 4041 is a rounded structure, and the rounded structure can prevent the airflow from rushing up and causing turbulence in the cavity.

[0039] In another alternative embodiment, if Figure 4 As shown, the gas outlet panel 404 does not adopt a grille design, and a plurality of the first gas outlets 4041 are arranged in an array on the gas outlet panel 404, that is, a plurality of rows of the first gas outlets 4041 are arranged in sequence along the height direction of the gas outlet panel 404, but still meet the requirement that each of the first gas outlets 4041 is arranged at a distance from the inner wall of the upper cavity 10 to ensure that when the gas enters from the first gas outlet 4041, it does not contact the inner wall of the upper cavity 10. With this design, the uniformity of the airflow can also be ensured.

[0040] In this embodiment, the gas content control device also includes a second uniform flow chamber, and the first uniform flow chamber and the second uniform flow chamber are respectively arranged on both sides of the reaction chamber, and the second uniform flow chamber is used to connect with the gas outlet interface to discharge the inert gas in the upper cavity 10. Furthermore, the second uniform flow chamber includes an exhaust homogenization plate 501 and a recovery chamber 502 arranged in sequence along the exhaust direction, and the exhaust homogenization plate 501 has a plurality of second gas outlets. Preferably, the cross-sectional area of ​​the second gas outlet is larger than the cross-sectional area of ​​the gas inlet. The cross-sectional area of ​​the second gas outlet is larger than the cross-sectional area of ​​the gas inlet, which can reduce the resistance of fluid recovery, so that vortices are not easily generated at the exhaust homogenization plate 501.

[0041] In addition, preferably, the exhaust homogenizing plate 501 adopts the same hole shape design as the air outlet panel 404, that is, when the air inlet panel adopts a grille design, the exhaust homogenizing plate 501 also adopts a grille design, and accordingly, the second air outlet also adopts a waist hole design, and a plurality of the second air outlets are arranged in sequence along the width direction of the exhaust homogenizing plate 501. As mentioned above, the cross-sectional area of ​​the second air outlet is larger than the cross-sectional area of ​​the air inlet. In order to facilitate the setting and ensure the uniformity of the air flow, the longitudinal width of the second air outlet can be designed to be the same as the longitudinal width of the air inlet, and the transverse width of the second air outlet is larger than the transverse width of the air inlet. Preferably, the transverse width of the air outlet can be set to be more than twice the transverse width of the air inlet, so as to achieve a better effect of reducing the flow resistance at the exhaust homogenizing plate 501.

[0042] When the air intake panel does not adopt a grille design and the multiple air intake holes are arranged in an array, the multiple second air outlets are also arranged in an array, and the aperture of the second air outlet is designed to be larger than the aperture of the air intake hole, so that the final cross-sectional area of ​​the second air outlet is more than twice the cross-sectional area of ​​the air intake hole.

[0043] The upper cavity 10 is provided with a wafer carrying area for carrying wafers. After the wafer is placed in the carrying area, the annealing process is performed on the wafer. The wafer carrying area is also called a protection area. Preferably, the purge width of the gas outlet panel 404 is not less than 1.3 times the diameter of the protection area in the upper cavity 10, so that the airflow is better distributed symmetrically in the center.

[0044] Preferably, the volume of the recovery chamber 502 is not larger than the volume of the first air inlet chamber, and the bottom of the recovery chamber 502 is at the same level as the air outlet interface 70 to avoid a dead angle of flow at the bottom of the recovery chamber 502, thereby avoiding vortexes in the chamber.

[0045] Preferably, the gas content control device provided in this embodiment also includes a filling piece 80, and the filling piece 80 fills the area of ​​the lower cavity 20 except the working area (for example, the area provided with the lifting mechanism as described above). By filling the filling piece 80, the problem of large amount of inert gas can be further solved. In addition, preferably, the gap between the top of the filling piece 80 and the outer side of the bottom wall of the upper cavity 10 is less than 1 mm, so as to avoid the problems of cross-flow, mixing, and suction of the fluids in the upper and lower cavities 20 as much as possible.

[0046] [Example 2]

[0047] Different from the first embodiment, in this embodiment, the lower cavity 20 is connected with the first air inlet cavity 401, and the introduced gas not only purges the upper cavity 10, but also fills the space of the lower cavity 20. Specifically, the lower cavity 20 can be provided with an air inlet 201, and the lower cavity 20 is connected with the first air inlet cavity 401 through the air inlet 201, and the air inlet 201 is arranged on the side wall of the lower cavity 20.

[0048] The arrangement of the air inlet 201 can alleviate the airflow mixing and vortex phenomenon caused by the fluid in the upper cavity 10 entering the lower cavity 20. Specifically, Figure 5 As shown, when the lower cavity 20 is not connected to the first air inlet cavity 401, the airflow of the upper cavity 10 enters the lower cavity 20, flows to the air outlet interface 70 through the gap between the filling piece 80 and the lower cavity 20, and causes mixing with the airflow of the lower cavity 20 and generates vortexes. Figure 6 As shown, by setting the air inlet 201 to connect the lower cavity 20 and not the first air inlet cavity 401, when the air flows to the upper cavity 10, it will also flow to the lower cavity 20, and because the lower cavity 20 is filled with the filling piece 80, the internal space is reduced, so the internal airflow can be saturated quickly, so that the airflow in the lower cavity 20 will not cause airflow mixing or vortex phenomenon due to flowing into the lower cavity 20.

[0049] In summary, the gas content control device provided by the embodiment of the present invention includes: a reaction chamber and a first uniform flow chamber, the first uniform flow chamber is arranged on one side of the reaction chamber; the reaction chamber includes an upper chamber and a lower chamber that are isolated from each other; the first uniform flow chamber is used to connect with the air inlet interface to pass the inert gas into the upper chamber; the first uniform flow chamber includes a first air inlet chamber, an air inlet homogenization plate, a second air inlet chamber and an air outlet panel arranged in sequence along the air inlet direction, the air inlet homogenization plate has a plurality of air inlet holes, and the cross-sectional area of ​​the air inlet hole close to the air inlet interface is smaller than the cross-sectional area of ​​the air inlet hole away from the air inlet interface, and the air outlet panel has a plurality of first air outlets, each of which is isolated from the inner wall of the upper chamber by the air outlet panel. The gas content control device provided by the present invention solves the problems of large amount of inert gas, uneven nitrogen purge at the air inlet, and easy turbulence inside the chamber, so that the oxygen index can be controlled below 10ppm within a specified time.

[0050] It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other. In addition, the different parts between the various embodiments can also be used in combination with each other, and the present invention is not limited to this.

[0051] In addition, it should be recognized that although the present invention has been disclosed as a preferred embodiment, the above embodiment is not intended to limit the present invention. For any technician familiar with the art, without departing from the scope of the technical solution of the present invention, the technical content disclosed above can be used to make many possible changes and modifications to the technical solution of the present invention, or modified into equivalent embodiments of equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still belongs to the scope of protection of the technical solution of the present invention.

Claims

1. A gas content control device, characterized in that: include: A reaction chamber and a first uniform flow chamber, wherein the first uniform flow chamber is arranged at one side of the reaction chamber; the reaction chamber comprises an upper chamber body and a lower chamber body which are arranged in isolation from each other; the first uniform flow chamber is used to connect with an air inlet interface to pass an inert gas into the upper chamber; The first uniform flow chamber includes a first air inlet chamber, an air inlet homogenizing plate, a second air inlet chamber and an air outlet panel which are arranged in sequence along the air inlet direction; the air inlet homogenizing plate has a plurality of air inlet holes, and the cross-sectional area of ​​the air inlet holes close to the air inlet interface is smaller than the cross-sectional area of ​​the air inlet holes away from the air inlet interface; the air outlet panel has a plurality of first air outlets, and each of the first air outlets is spaced apart from the top wall of the upper chamber.

2. The gas content control device according to claim 1, characterized in that: The diameter of the air inlet hole closest to the air inlet interface is 1.5 to 2 mm, and the diameter of the air inlet hole farthest from the air inlet interface is 3 to 4 mm.

3. The gas content control device according to claim 1, characterized in that: The air outlet panel is in a grid shape, and multiple first air outlets are evenly arranged in sequence along the width direction of the air outlet panel. The distance between the top of each first air outlet and the inner side of the top wall of the upper cavity and the distance between the bottom of each first air outlet and the inner side of the bottom wall of the upper cavity are equal.

4. The gas content control device according to claim 3, characterized in that: The distance between the top of each first air outlet and the inner side of the top wall of the upper cavity is 0.5-1 mm, and the distance between the bottom of each first air outlet and the inner side of the bottom wall of the upper cavity is 0.5-1 mm.

5. The gas content control device according to claim 3, characterized in that: The sweeping width of the air outlet panel is not less than 1.3 times the diameter of the protection area in the upper cavity.

6. The gas content control device according to any one of claims 1 to 5, characterized in that: It also includes a second uniform flow chamber, wherein the first uniform flow chamber and the second uniform flow chamber are respectively arranged on both sides of the reaction chamber, and the second uniform flow chamber is used to connect with the gas outlet interface to discharge the inert gas in the upper chamber; The second flow-homogenizing chamber comprises an exhaust homogenizing plate and a recovery chamber sequentially arranged along the exhaust direction, the exhaust homogenizing plate has a plurality of second air outlets, and the cross-sectional area of ​​the second air outlets is greater than the cross-sectional area of ​​the air inlet.

7. The gas content control device according to claim 6, characterized in that: The exhaust homogenizing plate adopts the same hole shape as the intake homogenizing plate, and the cross-sectional area of ​​the second air outlet is more than twice the cross-sectional area of ​​the intake hole.

8. The gas content control device according to claim 6, characterized in that: The volume of the recovery cavity is not greater than the volume of the first air inlet cavity, and the bottom of the second flow-uniform cavity is located at the same level as the air outlet interface.

9. The gas content control device according to claim 1, characterized in that: The gas content control device further comprises a filling piece, which fills the area of ​​the lower cavity except the working area, and the gap between the top of the filling piece and the outer side of the bottom wall of the upper cavity is less than 1 mm.

10. The gas content control device according to claim 9, characterized in that: The lower cavity is communicated with the first air inlet cavity.

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