Reaction chamber vacuum control system and method and pressure control valve used therein
The reaction chamber vacuum control system addresses asymmetric vacuum pumping in plasma etching machines by using a vertically arranged pressure control valve with rotating grid-shaped blades to achieve symmetrical exhaust, enhancing plasma uniformity and etching symmetry and reducing defects.
Patent Information
- Application Number
- CN201910694824.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2019-07-30
- Publication Date
- 2024-12-13
- Estimated Expiration
- 2039-07-30
AI Technical Summary
Current semiconductor equipment designs for plasma etching machines suffer from asymmetric vacuum pumping, leading to non-uniform plasma distribution and reduced wafer yield due to eccentric plasma direction, which affects etching uniformity and increases defects.
A reaction chamber vacuum control system with a vertically arranged pressure control valve featuring multiple grid-shaped blades that rotate in opposite directions to achieve symmetrical exhaust, improving plasma uniformity and etching symmetry.
The system enhances plasma uniformity and etching symmetry by aligning the plasma direction with the ideal path, reducing defects and improving wafer yield.
Smart Images
Figure CN110375076B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a semiconductor device, and in particular to a reaction chamber vacuum control system and method and a pressure control valve used therein. Background Art
[0002] In the field of semiconductor technology, semiconductor equipment has a huge impact on the yield of wafer manufacturing. As semiconductor wafers gradually increase from 4 inches and 5 inches to 12 inches or even 18 inches, the requirements for semiconductor equipment in wafer manufacturing are getting higher and higher. Among them, the vacuum chamber is a reaction chamber commonly used in the wafer manufacturing process, and the quality of its vacuum control directly affects the yield of the wafer.
[0003] Taking plasma etching as an example, plasma etching (Plasma Etching Technology) is used to etch by exciting the etching gas to form plasma. Generally speaking, in a plasma etching device, the plasma is generally formed by the etching gas discharged from the gas inlet unit at the top of the reaction chamber through radio frequency excitation. The plasma bombards the wafer on the chuck to achieve etching of the wafer. Please refer to Figure 1 , Figure 1 The following is a schematic diagram of a typical 8-inch wafer plasma etching machine. Figure 1 As shown, the plasma etching machine includes a reaction chamber 100, and the reaction chamber 100 includes a chuck 110, a wafer 120 located on the chuck, and an air intake unit 130 located at the top center of the reaction chamber 100. The air intake unit 130 is connected to a reaction gas source outside the reaction chamber for inputting the reaction gas into the reaction chamber. The reaction gas is ionized into plasma under the action of a radio frequency source to achieve etching of the wafer. The plasma etching machine also includes a pressure control valve 200 and a molecular pump 300. The molecular pump 300 extracts the used reaction gas from the reaction chamber 100 through the pressure control valve 200 and evacuates the reaction chamber 100. The wafer process has higher and higher requirements on the uniformity of the plasma plasma in the vacuum chamber of the reaction, and the exhaust direction of the vacuum control of the reaction chamber is more and more sensitive to the asymmetric influence of the plasma.
[0004] In the 8-inch and 12-inch equipment technology, suppliers have carried out multiple debugging and cavity structure updates to reduce the impact of vacuum pumping on plasma uniformity. However, to date, mass-produced machines have not yet truly achieved symmetrical settings for cavity vacuum pumping, and the asymmetry of the pumping direction has had an increasingly obvious impact on high-end processes.
[0005] like Figure 1As shown in the figure, in a typical 8-inch wafer plasma etching machine, a vacuum control valve 200 and a molecular pump 300 are horizontally placed on one side of the reaction chamber 100. This setting causes the airflow to pass through two 90-degree bends (as shown by the arrows in the figure), which seriously reduces the pumping speed. It also causes the pumping direction to be eccentric, as shown in Figure 2 , Figure 2 for Figure 1 Schematic diagram of the plasma direction in the reaction chamber of the plasma etching machine shown in FIG. Figure 2 As shown, the actual plasma direction 510 is significantly offset from the ideal plasma direction 520, which brings about the problem of asymmetric reaction of plasma to wafer, thereby reducing the wafer yield.
[0006] See also Figure 3 and Figure 4 , Figure 3 This is a schematic diagram of a typical 12-inch wafer plasma etching machine. Figure 4 is a schematic diagram of a pressure control valve, such as Figure 3 As shown, a pressure control valve 200 and a molecular pump 300 are vertically arranged below the reaction chamber 100. Figure 4 As shown, the pressure control valve 200 is a single fan-shaped valve, and its movement direction when opened is horizontal. Figure 1 The wafer plasma etching machine can improve the vacuum pumping rate, but due to the asymmetric disadvantage of the pressure control valve 200 when it is opened, it has no improvement in reducing the eccentricity defect of the pumping direction and improving the plasma uniformity, such as Figure 5 As shown, Figure 5 for Figure 3 Schematic diagram of the plasma direction in the reaction chamber of the plasma etching machine shown in FIG. Figure 5 As shown, the actual plasma direction 510 is significantly offset from the ideal plasma direction 520, which brings about the problem of asymmetric reaction of plasma to wafer, thereby reducing the wafer yield.
[0007] Therefore, in the current mainstream machines, due to inherent design defects, after the pressure control valve 200 is opened, the plasma is eccentrically asymmetric, which leads to a decrease in the uniformity of the etching rate of the reaction chamber 100, causing different reaction results of the wafer at different positions in the reaction chamber 100, causing interference to the online debugging and directly affecting the online measurement of the product; it even leads to an increase in online defects and electrical failure in areas where the uniformity deteriorates, resulting in a decrease in the yield. Summary of the invention
[0008] The object of the present invention is to provide a reaction chamber vacuum control system to achieve symmetry in the direction of exhaust gas, realize pressure control, improve the uniformity of plasma in the reaction chamber, and improve the uniformity and symmetry of chamber etching.
[0009] The reaction chamber vacuum control system provided by the present invention comprises: a reaction chamber, a pressure control valve and a molecular pump, wherein the reaction chamber comprises a chuck, a wafer located on the chuck and an air intake unit located at the top of the reaction chamber, the air intake unit is connected to a reaction gas source outside the reaction chamber and is used to input the reaction gas into the reaction chamber, the pressure control valve and the molecular pump are vertically arranged below the reaction chamber, and the pressure control valve is arranged between the reaction chamber and the molecular pump, the molecular pump is used to evacuate the reaction chamber into a vacuum through the pressure control valve, wherein the pressure control valve comprises a plurality of grid-shaped blades, and the rotation directions of every two adjacent grid-shaped blades are opposite.
[0010] Furthermore, the reaction chamber vacuum control system is a reaction chamber vacuum control system applied to a plasma etching machine.
[0011] Furthermore, the number of the grating blades is greater than or equal to 10.
[0012] Furthermore, the rotation angle of at least one of the cascade blades is 0 to 90 degrees, and the rotation angle of the adjacent cascade blade is 0 to -90 degrees.
[0013] Furthermore, each grid-shaped blade includes a rotating shaft, which is arranged in the middle position of the grid-shaped blade along the length direction of the grid-shaped blade, and each rotating shaft is connected to a motor, which drives the rotating shaft to rotate through motor control and then drives the grid-shaped blade to rotate.
[0014] Furthermore, the rotation directions of adjacent rotating shafts are opposite, so that the adjacent cascade blades rotate in the opposite direction, and the rotation angle of at least one of the cascade blades is 0 to 90 degrees, and the rotation angle of the adjacent cascade blade is 0 to -90 degrees.
[0015] The present invention also provides a reaction chamber vacuum control method, which is applicable to a reaction chamber vacuum control system. The reaction chamber vacuum control system includes a reaction chamber, a pressure control valve and a molecular pump. The reaction chamber includes a chuck, a wafer located on the chuck and an air intake unit located at the top of the reaction chamber. The air intake unit is connected to a reaction gas source outside the reaction chamber and is used to input the reaction gas into the reaction chamber. The pressure control valve and the molecular pump are vertically arranged below the reaction chamber, and the pressure control valve is arranged between the reaction chamber and the molecular pump. The molecular pump is used to evacuate the reaction chamber into a vacuum through the pressure control valve, wherein the pressure control valve includes a plurality of grid-shaped blades, and is characterized in that, in the process of evacuating the reaction chamber, the plurality of grid-shaped blades are controlled to rotate, and every two adjacent grid-shaped blades are controlled to rotate in the opposite direction.
[0016] Furthermore, the number of the grating blades is greater than or equal to 10.
[0017] Furthermore, the rotation angle of one of the grating blades is controlled to be 0 to 90 degrees, and the rotation angle of the adjacent grating blade is controlled to be 0 to -90 degrees.
[0018] Furthermore, each grid-shaped blade includes a rotating shaft, which is arranged in the middle position of the grid-shaped blade along the length direction of the grid-shaped blade, and each rotating shaft is connected to a motor, which drives the rotating shaft to rotate through motor control and then drives the grid-shaped blade to rotate.
[0019] Furthermore, the rotation directions of adjacent rotating shafts are opposite, so that the adjacent cascade blades rotate in the opposite direction, and the rotation angle of at least one of the cascade blades is 0 to 90 degrees, and the rotation angle of the adjacent cascade blade is 0 to -90 degrees.
[0020] The present invention also provides a pressure control valve, which is suitable for a reaction chamber vacuum control system. The reaction chamber vacuum control system also includes a reaction chamber and a molecular pump. The reaction chamber includes a chuck, a wafer located on the chuck, and an air intake unit located at the top of the reaction chamber. The air intake unit is connected to a reaction gas source outside the reaction chamber and is used to input the reaction gas into the reaction chamber. The pressure control valve and the molecular pump are vertically arranged below the reaction chamber, and the pressure control valve is arranged between the reaction chamber and the molecular pump. The molecular pump is used to evacuate the reaction chamber through the pressure control valve. The pressure control valve is characterized in that the pressure control valve includes a plurality of grid-shaped blades, and the rotation directions of every two adjacent grid-shaped blades are opposite.
[0021] Furthermore, the number of the grating blades is greater than or equal to 10.
[0022] Furthermore, the rotation angle of one of the cascade blades is 0 to 90 degrees, and the rotation angle of the adjacent cascade blade is 0 to -90 degrees.
[0023] Furthermore, each grid-shaped blade includes a rotating shaft, which is arranged in the middle position of the grid-shaped blade along the length direction of the grid-shaped blade, and each rotating shaft is connected to a motor, which drives the rotating shaft to rotate through motor control and then drives the grid-shaped blade to rotate.
[0024] Furthermore, the rotation directions of adjacent rotation axes are opposite, so that the adjacent cascade blades rotate in the opposite direction, and the rotation angle of at least one of the cascade blades is 0 to 90 degrees, and the rotation angle of the adjacent cascade blade is 0 to -90 degrees.
[0025] The reaction chamber vacuum control system and method provided by the present invention and the pressure control valve used therein are improved from a single fan-shaped opening valve to a design of multiple grid-shaped blades, and the movement direction is improved from horizontal opening to a mode in which every two adjacent grid-shaped blades rotate in opposite directions to open, thereby achieving symmetry in the direction of exhaust, realizing pressure control, improving the uniformity of plasma in the reaction chamber, and improving the uniformity and symmetry of chamber etching. BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Figure 1 This is a schematic diagram of a typical 8-inch wafer plasma etching machine.
[0027] Figure 2 for Figure 1 Schematic diagram of the plasma direction in the reaction chamber of a plasma etching machine.
[0028] Figure 3 This is a schematic diagram of a typical 12-inch wafer plasma etching machine.
[0029] Figure 4 Schematic diagram of a pressure control valve.
[0030] Figure 5 for Figure 3 Schematic diagram of the plasma direction in the reaction chamber of a plasma etching machine.
[0031] Figure 6 FIG. 1 is a detailed schematic diagram of a pressure control valve according to an embodiment of the present invention.
[0032] Figure 7 To adopt Figure 6 Schematic diagram of the plasma direction in the reaction chamber of a plasma etching machine with a pressure control valve shown.
[0033] The symbols used in the drawings are explained as follows:
[0034] 200. Pressure control valve; 210. Grid blades; 220. Rotating shaft; 300. Molecular pump. DETAILED DESCRIPTION
[0035] The following will be combined with the accompanying drawings to clearly and completely describe the technical solutions in the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.
[0036] In one embodiment of the present invention, a reaction chamber vacuum control system is provided. Figure 3 , and see Figure 6 , Figure 6 FIG. 1 is a detailed schematic diagram of a pressure control valve according to an embodiment of the present invention. Figure 3 and Figure 6 As shown, the reaction chamber vacuum control system includes: a reaction chamber 100, a pressure control valve 200 and a molecular pump 300. The reaction chamber 100 includes a chuck 110, a wafer 120 located on the chuck and an air intake unit 130 located at the top of the reaction chamber 100. The air intake unit 130 is connected to a reaction gas source outside the reaction chamber 100 and is used to input the reaction gas into the reaction chamber 100. The pressure control valve 200 and the molecular pump 300 are vertically arranged below the reaction chamber 100, and the pressure control valve 200 is arranged between the reaction chamber 100 and the molecular pump 300. The molecular pump 300 is used to evacuate the reaction chamber 100 through the pressure control valve 200, wherein the pressure control valve 200 includes a plurality of grid blades 210, and the rotation directions of every two adjacent grid blades 210 are opposite.
[0037] In one embodiment of the present invention, the reaction chamber vacuum control system is a reaction chamber vacuum control system applied to a plasma etching machine. Figure 7 , Figure 7 To adopt Figure 6 Schematic diagram of the plasma direction in the reaction chamber of a plasma etching machine with a pressure control valve as shown. Figure 7 As shown, the actual plasma direction 510 is close to the ideal plasma direction 520, which reduces the eccentricity defect of the pumping method, realizes pressure control, and improves the symmetry of the pumping direction; thereby improving the symmetry and uniformity of the plasma. In this way, by improving the pressure control valve from a single fan-shaped opening valve to a design of multiple grid-shaped blades 210, the movement direction is improved from horizontal opening to a method in which every two adjacent grid-shaped blades 210 rotate in opposite directions to open, thereby achieving the purpose of symmetry in the pumping direction and improving the uniformity and symmetry of the cavity etching. Of course, the above-mentioned reaction chamber vacuum control system can also be a reaction chamber vacuum control system applied to non-etching machines.
[0038] Furthermore, in one embodiment of the present invention, the number of the grating blades 210 is greater than or equal to 10, that is, the pressure control valve 200 is designed to be in a form similar to a shutter, thereby further improving the symmetry and uniformity of the exhaust direction.
[0039] Furthermore, in one embodiment of the present invention, the rotation angle of at least one of the cascade blades 210 is 0 to 90 degrees, and the rotation angle of the adjacent cascade blade is 0 to -90 degrees, that is, the rotation directions are opposite, and the angles are within 90 degrees, so as to improve the symmetry and uniformity of the exhaust direction.
[0040] Furthermore, in one embodiment of the present invention, each cascade blade 210 includes a rotating shaft 220, which is disposed in the middle of the cascade blade 210 along the length direction of the cascade blade 210, and each rotating shaft 220 is connected to a motor, and the rotating shaft 220 is driven to rotate by the motor control, thereby driving the cascade blade 210 to rotate. Furthermore, the rotation directions of adjacent rotating shafts 220 are opposite, so that the adjacent cascade blades rotate in the opposite direction, and the rotation angle of at least one of the cascade blades 210 is 0 to 90 degrees, and the rotation angle of the adjacent cascade blade is 0 to -90 degrees.
[0041] In one embodiment of the present invention, a reaction chamber vacuum control method is further provided, which is applicable to a reaction chamber vacuum control system. The reaction chamber vacuum control system is as described above, comprising: a reaction chamber 100, a pressure control valve 200 and a molecular pump 300. The reaction chamber 100 comprises a chuck 110, a wafer 120 located on the chuck and an air intake unit 130 located at the top of the reaction chamber 100. The air intake unit 130 is connected to a reaction gas source outside the reaction chamber 100 and is used to input the reaction gas into the reaction chamber 100. The pressure control valve 200 and the molecular pump 300 are vertically arranged below the reaction chamber 100, and the pressure control valve 200 is arranged between the reaction chamber 100 and the molecular pump 300. The molecular pump 300 is used to evacuate the reaction chamber 100 through the pressure control valve 200, wherein the pressure control valve 200 comprises a plurality of grid-shaped blades 210. In the process of evacuating the reaction chamber 100, the plurality of grid-shaped blades 210 are controlled to rotate, and every two adjacent grid-shaped blades 210 are controlled to rotate in the opposite direction.
[0042] Furthermore, in one embodiment of the present invention, the number of the grating blades 210 is greater than or equal to 10, that is, the pressure control valve 200 is designed to be in a form similar to a shutter, thereby further improving the symmetry and uniformity of the exhaust direction.
[0043] Furthermore, in one embodiment of the present invention, the rotation angle of one of the grating blades 210 is controlled to be 0 to 90 degrees, and the rotation angle of the adjacent grating blade is 0 to -90 degrees, that is, the rotation directions are opposite, and the angles are within 90 degrees, so as to improve the symmetry and uniformity of the exhaust direction.
[0044] Furthermore, in one embodiment of the present invention, each cascade blade 210 includes a rotating shaft 220, which is disposed in the middle of the cascade blade 210 along the length direction of the cascade blade 210, and each rotating shaft 220 is connected to a motor, and the rotating shaft 220 is driven to rotate by the motor control, thereby driving the cascade blade 210 to rotate. Furthermore, the rotation directions of adjacent rotating shafts 220 are opposite, so that the adjacent cascade blades rotate in the opposite direction, and the rotation angle of at least one of the cascade blades 210 is 0 to 90 degrees, and the rotation angle of the adjacent cascade blade is 0 to -90 degrees.
[0045] In one embodiment of the present invention, a pressure control valve is further provided. The pressure control valve is suitable for a reaction chamber vacuum control system. The reaction chamber vacuum control system is as described above, and further includes: a reaction chamber 100 and a molecular pump 300. The reaction chamber 100 includes a chuck 110, a wafer 120 located on the chuck, and an air intake unit 130 located at the top of the reaction chamber 100. The air intake unit 130 is connected to a reaction gas source outside the reaction chamber 100 and is used to input the reaction gas into the reaction chamber 100. The pressure control valve 200 and the molecular pump 300 are vertically arranged below the reaction chamber 100, and the pressure control valve 200 is arranged between the reaction chamber 100 and the molecular pump 300. The molecular pump 300 is used to evacuate the reaction chamber 100 through the pressure control valve 200, wherein the pressure control valve 200 includes a plurality of grid-shaped blades 210, and the rotation directions of every two adjacent grid-shaped blades 210 are opposite.
[0046] Furthermore, in one embodiment of the present invention, the number of the grating blades 210 is greater than or equal to 10, that is, the pressure control valve 200 is designed to be in a form similar to a shutter, thereby further improving the symmetry and uniformity of the exhaust direction.
[0047] Furthermore, in one embodiment of the present invention, the rotation angle of at least one of the cascade blades 210 is 0 to 90 degrees, and the rotation angle of the adjacent cascade blade is 0 to -90 degrees, that is, the rotation directions are opposite, and the angles are within 90 degrees, so as to improve the symmetry and uniformity of the exhaust direction.
[0048] Furthermore, in one embodiment of the present invention, each cascade blade 210 includes a rotating shaft 220, which is disposed in the middle of the cascade blade 210 along the length direction of the cascade blade 210, and each rotating shaft 220 is connected to a motor, and the rotating shaft 220 is driven to rotate by the motor control, thereby driving the cascade blade 210 to rotate. Furthermore, the rotation directions of adjacent rotating shafts 220 are opposite, so that the adjacent cascade blades rotate in the opposite direction, and the rotation angle of at least one of the cascade blades 210 is 0 to 90 degrees, and the rotation angle of the adjacent cascade blade is 0 to -90 degrees.
[0049] In summary, by improving the pressure control valve from a single fan-shaped opening valve to a design with multiple grating blades, the movement direction is improved from horizontal opening to a method in which every two adjacent grating blades rotate in opposite directions to open, thereby achieving symmetry in the direction of exhaust gas, realizing pressure control, improving the plasma uniformity of the reaction chamber, and improving the uniformity and symmetry of chamber etching.
[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A reaction chamber vacuum control system, characterized in that: include: A reaction chamber, a pressure control valve and a molecular pump, wherein the reaction chamber comprises a chuck, a wafer on the chuck and an air intake unit at the top of the reaction chamber, the air intake unit being connected to a reaction gas source outside the reaction chamber and being used to input the reaction gas into the reaction chamber, the pressure control valve and the molecular pump being vertically arranged below the reaction chamber, and the pressure control valve being arranged between the reaction chamber and the molecular pump, the molecular pump being used to evacuate the reaction chamber into a vacuum through the pressure control valve, wherein the pressure control valve comprises 10 or more grid-shaped blades, and the rotation directions of every two adjacent grid-shaped blades are opposite, each grid-shaped blade comprises a rotating shaft, the rotating shaft is arranged at the middle position of the grid-shaped blade along the length direction of the grid-shaped blade, and each rotating shaft is connected to a motor, and the rotating shaft is driven to rotate by the motor control and then the grid-shaped blade is driven to rotate, the rotation directions of adjacent rotating shafts are opposite, so that adjacent grid-shaped blades rotate in the opposite direction, and the rotation angle of at least one of the grid-shaped blades is 0 to 90 degrees, and the rotation angle of the grid-shaped blade adjacent to it is 0 to -90 degrees.
2. The reaction chamber vacuum control system according to claim 1, characterized in that: The reaction chamber vacuum control system is a reaction chamber vacuum control system applied to a plasma etching machine.
3. A reaction chamber vacuum control method, applicable to a reaction chamber vacuum control system, the reaction chamber vacuum control system comprising a reaction chamber, a pressure control valve and a molecular pump, the reaction chamber comprising a chuck, a wafer on the chuck and an air intake unit at the top of the reaction chamber, the air intake unit being connected to a reaction gas source outside the reaction chamber for inputting the reaction gas into the reaction chamber, the pressure control valve and the molecular pump being vertically arranged below the reaction chamber, and the pressure control valve being arranged between the reaction chamber and the molecular pump, the molecular pump being used for evacuating the reaction chamber into a vacuum through the pressure control valve, wherein the pressure control valve comprises more than or equal to 10 grid-shaped blades, each grid-shaped blade comprising a rotating shaft, the rotating shaft being arranged in the middle of the grid-shaped blade along the length direction of the grid-shaped blade, and each rotating shaft being connected to a motor, the rotating shaft being driven to rotate by the motor control and then the grid-shaped blade being driven to rotate, characterized in that During the process of evacuating the reaction chamber, a plurality of grid blades are controlled to rotate, and every two adjacent grid blades are controlled to rotate in the opposite direction. The rotation directions of adjacent rotation axes are opposite, so that the adjacent grid blades rotate in the opposite direction, and the rotation angle of at least one of the grid blades is 0 to 90 degrees, and the rotation angle of the grid blade adjacent to it is 0 to -90 degrees.
4. A pressure control valve, which is suitable for a reaction chamber vacuum control system, the reaction chamber vacuum control system also includes a reaction chamber and a molecular pump, the reaction chamber includes a chuck, a wafer on the chuck and an air intake unit located at the top of the reaction chamber, the air intake unit is connected to a reaction gas source outside the reaction chamber, and is used to input the reaction gas into the reaction chamber, the pressure control valve and the molecular pump are vertically arranged below the reaction chamber, and the pressure control valve is arranged between the reaction chamber and the molecular pump, the molecular pump is used to evacuate the reaction chamber through the pressure control valve, and is characterized in that The pressure control valve includes more than or equal to 10 grid-shaped blades, and the rotation directions of every two adjacent grid-shaped blades are opposite. Each grid-shaped blade includes a rotating shaft, which is arranged in the middle position of the grid-shaped blade along the length direction of the grid-shaped blade, and each rotating shaft is connected to a motor. The rotating shaft is driven to rotate by the motor control and then the grid-shaped blade is driven to rotate. The rotation directions of adjacent rotating shafts are opposite, so that the adjacent grid-shaped blades rotate in the opposite direction, and the rotation angle of at least one of the grid-shaped blades is 0 to 90 degrees, and the rotation angle of the grid-shaped blade adjacent to it is 0 to -90 degrees.