Preparation method and device for improving flatness of epitaxial wafer

Abstract

The invention discloses a preparation method and device for improving the flatness of an epitaxial wafer, and relates to the technical field of epitaxial wafer production. The preparation device for improving the flatness of an epitaxial wafer comprises a reaction shell with open ends, a sealed air inlet flange, which is sealed and connected to one end of the reaction shell; a sealed exhaust member, which is sealed and connected to the other end of the reaction shell; an air inlet pipe, which penetrates the sealed air inlet flange and extends into the reaction shell at one end; the invention uses a trumpet-shaped notch, a sealing cover plate, etc. to cooperate with each other, and in the initial inflation stage, the piston cavity is evacuated through an exhaust system, so that a large flow of protective gas flows out of the trumpet-shaped notch into the reaction shell. The large flow of protective gas can prevent the mixed gas of the vapor deposition reaction from being deposited on the epitaxial wafer too early before the gas is evenly mixed, resulting in uneven thickness of the epitaxial wafer.

Description

Technical Field

[0001] The invention relates to the technical field of epitaxial wafer production, and in particular to a preparation method and a device for improving the flatness of an epitaxial wafer. Background Art

[0002] Epitaxial wafer is a material that plays an important role in semiconductor manufacturing. Epitaxial wafer is a semiconductor material film with specific crystal structure and electrical properties grown on the original semiconductor substrate material through a specific process.

[0003] For example, the patent with the publication number CN111636098A discloses a CVD reaction module of silicon carbide epitaxial equipment, including a quartz shell, an air inlet flange and a tail flange. A heating layer and a heat-insulating layer are arranged in the quartz shell. The heating layer has a plurality of replacement parts, and the curvature of the internal top surface of the replacement parts is different. A tray for holding wafers is also arranged in the working chamber. A liner is also arranged around the corresponding tray in the heating layer. A top plate for supporting the tray is arranged below the tray, and a lifting rod extends outward from the bottom of the top plate. In the above technical solution, when the thickness of the liner increases to the point that the tray cannot normally perform the CVD process, the position of the tray is slightly raised to ensure that the CVD process can continue, and finally the purpose of extending the service life of the liner is achieved. By replacing the heating layer with a top surface of different curvatures, the temperature field in the working chamber can be adjusted, so that the temperature in the working chamber is more uniform, and then the thickness of the film formed on the wafer is more uniform.

[0004] Although the above patent can enhance the uniformity of the film thickness, during the initial air intake, the protective gas is only introduced from the ventilation holes. Since there is non-reactive gas in the reaction chamber, only a small flow of air is used to blow it away. The non-reactive gas in the reaction chamber cannot be quickly blown out, and the problem of uneven film thickness still exists.

[0005] Therefore, it is necessary to propose a preparation method and device for improving the flatness of epitaxial wafers in the present invention to solve the above problems. Summary of the invention

[0006] The object of the present invention is to provide a preparation method and device for improving the flatness of an epitaxial wafer, so as to solve the problems raised in the above-mentioned background technology.

[0007] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a preparation device for improving the flatness of epitaxial wafers, comprising a reaction shell with open ends, and also comprising a sealed air inlet flange, which is sealed and connected to one end of the reaction shell; a sealed exhaust member, which is sealed and connected to the other end of the reaction shell; an air inlet pipe, which passes through the sealed air inlet flange and extends into the reaction shell at one end; a plurality of partitions, which are arranged in an array on the inner wall of the air inlet pipe to divide the cavity of the inner wall of the air inlet pipe into a plurality of channels; a trumpet-shaped notch, which is arranged at one end of the air inlet pipe located in the reaction shell; a sealing cover plate, which is arranged in the trumpet-shaped notch and has a shape that matches the trumpet-shaped notch, and a plurality of air inlet holes are arranged in an array on the sealing cover plate; a protective gas An air inlet duct, which is opened in the wall of the air inlet pipe and communicated with the trumpet-shaped notch; a guide rod, which is placed on the side of the sealing cover plate away from the reaction shell, extends to the outside of the air inlet pipe, and is sealingly and slidingly connected with the air inlet pipe; a sliding plate, which is slidably sleeved on the end of the guide rod located outside the air inlet pipe; an elastic reset component, which is sleeved on the end of the guide rod located outside the air inlet pipe, one end of which is connected to the sliding plate, and the other end of which is connected to the guide rod; a piston chamber, which is opened in the wall of the air inlet pipe, and the end of which is close to the reaction shell is respectively connected to the air inlet system and the air exhaust system through a conduit, and the end of which is away from the reaction shell is connected to the atmosphere; a piston, which is placed in the piston chamber; a push rod, one end of which is connected to the piston, and the other end of which is connected to the sliding plate.

[0008] Preferably, it also includes a lower pressure plate, which is placed in the channel and horizontally slidably connected to the channel, and its end close to the reaction shell is connected by a connecting part, and its thickness gradually increases from the end located in the tube wall to the end of the reaction shell; a "U"-shaped groove, which is opened in one of the vertical planes in the tube wall of the intake pipe; a sliding column, which is placed at the end of the lower pressure plate away from the reaction shell and extends into the "U"-shaped groove; an elastic reset member, one end of which is connected to the sliding column, and the other end is connected to the "U"-shaped groove; a ball, which is placed in the "U"-shaped groove; a push rod for pushing the ball is provided on the side wall of the push rod, and a push groove connected to the piston cavity for the push rod to be inserted into the side wall of the "U"-shaped groove.

[0009] Preferably, it also includes an induction coil, which is wound around the outside of the reaction shell; a thermal insulation layer, which is sleeved inside the reaction shell; a heating layer, which is sleeved inside the thermal insulation layer; and a lining layer, which is placed inside the heating layer and is used to protect the heating layer.

[0010] Preferably, it also includes a tray, which is placed in the inner cavity of the lining layer; a top plate, which is placed in the inner cavity of the lining layer and located at the bottom of the tray and is limitedly plugged with the tray; a lifting rod, which is placed at the bottom of the top plate and extends outside the reaction shell, and is sealed and movably connected to the reaction shell.

[0011] Preferably, it also includes a pneumatic rotary joint, which is transmission-connected to the lifting rod and connected to the air intake system.

[0012] Preferably, it also includes a height adjustment component, which is placed at the bottom of the pneumatic rotary joint.

[0013] Preferably, it also includes a soft start valve, which is placed between the pneumatic rotary joint and the air intake system and controls the gas flow and pressure entering the pneumatic rotary joint to gradually increase.

[0014] Preferably, it also includes a protective gas inlet, which is placed at one end of the air inlet pipe away from the reaction shell and is connected to the protective gas inlet duct.

[0015] Preferably, it also includes a plurality of mixed gas inlets, which are placed at one end of the intake pipe away from the reaction shell, each channel is connected to a mixed gas inlet, the number of which is the same as the number of channels, and is connected to the mixed gas intake system.

[0016] The present invention also provides a preparation method for improving the flatness of an epitaxial wafer, comprising the following steps:

[0017] Step 1: Control the exhaust system to exhaust air from the piston chamber, so that the piston slides and drives the sealing cover plate to slide toward the reaction shell through the push rod, the sliding plate and the guide rod, so that the trumpet-shaped notch is opened, thereby quickly blowing out the non-reactive gas in the reaction shell;

[0018] Step 2: Control the air intake system to inflate the piston cavity, so that the piston slides and drives the sealing cover plate to slide away from the reaction shell through the push rod, sliding plate and guide rod, so that the trumpet-shaped notch is closed, and the protective gas is blown out only from the air intake hole to form a uniform and stable airflow.

[0019] Technical effects and advantages of the present invention:

[0020] The present invention achieves mutual cooperation between the trumpet-shaped notch, the sealing cover plate, etc. In the initial inflation stage, the piston cavity is evacuated through the exhaust system to open the trumpet-shaped notch, thereby allowing a large flow of protective gas to flow out from the trumpet-shaped notch into the reaction shell. The large flow of protective gas can prevent the mixed gas of the vapor deposition reaction from being precipitated on the epitaxial wafer prematurely before the gas is evenly mixed, resulting in uneven thickness of the epitaxial wafer.

[0021] The present invention achieves mutual cooperation between the trumpet-shaped notch, the sealing cover plate, etc. In the initial inflation stage, the piston cavity is evacuated through the exhaust system to open the trumpet-shaped notch, thereby allowing a large flow of protective gas to flow out of the trumpet-shaped notch into the reaction shell, thereby preventing the mixed gas of the vapor deposition reaction from being deposited on the inner lining layer.

[0022] The present invention can quickly blow out the remaining mixed gas that does not undergo vapor deposition reaction in the reaction shell through the mutual cooperation between the trumpet-shaped notch, the sealing cover plate, etc., to avoid poor quality of epitaxial wafer products produced due to the remaining mixed gas that does not undergo vapor deposition reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0024] Figure 2 It is a three-dimensional cross-sectional view of the overall structure of the present invention.

[0025] Figure 3 It is a schematic diagram of the intake pipe structure in the present invention.

[0026] Figure 4 For the present invention Figure 3 Schematic diagram of the structure from another angle.

[0027] Figure 5 For the present invention Figure 3 3D cross-sectional view of the structure.

[0028] Figure 6 For the present invention Figure 3 Schematic diagram of the vertical cross-section of the structure along the "U"-shaped groove.

[0029] Figure 7 It is a schematic diagram of the structural connection between the guide rod, the piston, the push rod and the lower pressure plate in the present invention.

[0030] Figure 8 It is a schematic diagram of the trumpet-shaped notch, guide rod and sealing cover plate structure in the present invention.

[0031] Fig. 9 For the present invention Figure 2 A schematic diagram of the enlarged structure of part A.

[0032] In the figure: 1. reaction shell; 2. sealing air inlet flange; 3. sealing exhaust member; 4. air inlet pipe; 5. partition; 6. channel; 7. trumpet-shaped notch; 8. sealing cover plate; 801. air inlet hole; 9. protective gas inlet duct; 10. guide rod; 11. sliding plate; 12. elastic reset component; 13. piston chamber; 14. piston; 15. push rod; 16. lower pressure plate; 17. sliding column; 18. "U"-shaped groove; 19. elastic reset member; 20. ball; 21. push groove; 22. insulation layer; 24. heating layer; 25. lining layer; 26. push rod; 27. tray; 28. top plate; 29. ​​lifting rod; 30. pneumatic rotary joint; 31. height adjustment component; 32. protective gas inlet; 33. mixed gas inlet. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] The present invention provides Figures 1 to 9 The preparation device for improving the flatness of epitaxial wafers shown includes a reaction shell 1 with open ends, and also includes a sealed air inlet flange 2, which is sealed and connected to one end of the reaction shell 1; the sealed air inlet flange 2 of the present invention is used to seal the air inlet end of the reaction shell 1.

[0035] The sealed exhaust member 3 is sealed and connected to the other end of the reaction shell 1 ; it is used to exhaust the gas after the reaction.

[0036] The air inlet pipe 4 penetrates the sealed air inlet flange 2 and one end of the air inlet pipe extends into the reaction shell 1. The present invention provides the air inlet pipe 4 to charge the reaction shell 1 with a protective gas and a reaction mixed gas.

[0037] A plurality of partitions 5 are arranged in an array on the inner wall of the air intake pipe 4 , dividing the inner wall cavity of the air intake pipe 4 into a plurality of channels 6 .

[0038] The trumpet-shaped notch 7 is disposed at one end of the air inlet pipe 4 located in the reaction shell 1. By providing the trumpet-shaped notch 7, the present invention can, on the one hand, prevent the mixed gas of the vapor deposition reaction from being deposited on the epitaxial wafer prematurely before the gas is evenly mixed during the initial inflation stage, thereby causing uneven thickness of the epitaxial wafer; on the other hand, prevent the mixed gas of the vapor deposition reaction from being deposited on the inner lining layer 25; and on the third hand, quickly blow out the remaining mixed gas of the reaction shell 1 that is not undergoing the vapor deposition reaction, thereby preventing the poor quality of the epitaxial wafer products produced due to the remaining mixed gas of the non-vapor deposition reaction.

[0039] The sealing cover plate 8 is placed in the trumpet-shaped slot 7, and its shape is adapted to the trumpet-shaped slot 7. The sealing cover plate 8 is provided with a plurality of air inlet holes 801 in an array. The present invention blocks the trumpet-shaped slot 7 after initial inflation by providing the sealing cover plate 8 and providing the air inlet holes 801 in a uniform array on the sealing cover plate 8. Under the action of the air inlet holes 801, a small stable protective airflow is formed to prevent the mixed gas of the vapor deposition reaction from being deposited at the entrance of the lining layer 25 too early, and at the same time, the mixed gas of the vapor deposition reaction in the reaction shell 1 is mixed more evenly.

[0040] The protective gas inlet passage 9 is provided on the wall of the inlet pipe 4 and is connected to the trumpet-shaped notch 7 . The present invention provides the protective gas inlet passage 9 to supply gas to the trumpet-shaped notch 7 .

[0041] The guide rod 10 is placed on the side of the sealing cover plate 8 away from the reaction shell 1, extends to the outside of the air inlet pipe 4, and is sealed and slidably connected to the air inlet pipe 4; on the first hand, it is used to guide the sliding of the sealing cover plate 8, and on the second hand, it is used to push the sealing cover plate 8 to slide, thereby adjusting the position of the sealing cover plate 8 and then opening or closing the trumpet-shaped notch 7.

[0042] The sliding plate 11 is slidably sleeved on one end of the guide rod 10 located outside the air inlet pipe 4 .

[0043] The elastic reset component 12 is sleeved on one end of the guide rod 10 located outside the air inlet pipe 4, one end of which is connected to the sliding plate 11, and the other end of which is connected to the guide rod 10; further, the elastic reset component 12 is a spring.

[0044] The piston chamber 13 is opened on the wall of the air inlet pipe 4, and its end close to the reaction shell 1 is connected to the air inlet system and the air exhaust system through conduits, and its end away from the reaction shell 1 is connected to the atmosphere.

[0045] The piston 14 is disposed in the piston chamber 13 .

[0046] The push rod 15 has one end connected to the piston 14 and the other end connected to the sliding plate 11 .

[0047] The present invention is provided with a sliding plate 11, an elastic reset component 12, a piston chamber 13, a piston 14 and a push rod 15. In the initial inflation stage, the piston chamber 13 is evacuated by an exhaust system. As the exhaust system evacuates air, a negative pressure is generated on the side of the piston chamber 13 close to the reaction shell 1. Under the action of the negative pressure, the piston 14 slides toward the side of the reaction shell 1. The sliding of the piston 14 drives the push rod 15 to slide. The sliding of the push rod 15 drives the sliding plate 11 to slide. The sliding of the sliding plate 11 drives the elastic reset component 12 to slide. The sliding of the elastic reset component 12 drives the guide rod 10 to slide. The sliding of the guide rod 10 drives the sealing cover plate 8 to slide. , so that the trumpet-shaped notch 7 is opened, and then a large flow of protective gas flows out from the trumpet-shaped notch 7 into the reaction shell 1. The large flow of protective gas can, on the one hand, prevent the mixed gas of the vapor deposition reaction from being deposited on the epitaxial wafer too early before the gas is evenly mixed, resulting in uneven thickness of the epitaxial wafer; on the other hand, prevent the mixed gas of the vapor deposition reaction from being deposited on the lining layer 25; on the third hand, the remaining mixed gas that is not undergoing the vapor deposition reaction in the reaction shell 1 can be quickly blown out, so as to avoid the poor quality of the epitaxial wafer products produced due to the remaining mixed gas that is not undergoing the vapor deposition reaction.

[0048] In this embodiment, the lower pressure plate 16 is placed in the channel 6 and is horizontally slidably connected to the channel 6. Its end close to the reaction shell 1 is connected through a connecting portion, and its thickness gradually increases from the end located in the tube wall to the end of the reaction shell 1. The present invention arranges the lower pressure plate 16 in the above manner so that the lower surface of the lower pressure plate 16 presents an inclined surface, thereby guiding the mixed gas of the vapor deposition reaction to the epitaxial wafer, thereby improving the deposition efficiency.

[0049] The U-shaped groove 18 is formed in one of the vertical planes in the wall of the air inlet pipe 4 .

[0050] The slide post 17 is disposed at one end of the lower pressing plate 16 away from the reaction shell 1 and extends into the "U"-shaped groove 18; the present invention realizes sliding guidance and position limiting of the lower pressing plate 16 by arranging the slide post 17.

[0051] The elastic reset member 19 has one end connected to the sliding column 17 and the other end connected to the “U”-shaped groove 18 . The elastic reset member 19 is provided to realize the reset of the sliding column 17 .

[0052] The ball 20 is placed in the “U” shaped groove 18 .

[0053] A push rod 26 for pushing the ball 20 is arranged on the side wall of the push rod 15, and a push groove 21 which is connected with the piston cavity 13 and for inserting the push rod 26 is opened on the side wall of the "U"-shaped groove 18.

[0054] The present invention provides a sliding column 17, a "U"-shaped groove 18, an elastic reset member 19, a ball 20 and a push rod 26. After the initial inflation stage is over, the sealing cover plate 8 is restored to a state of blocking the trumpet-shaped notch 7. The air intake system is controlled to inflate the piston chamber 13, so that air pressure is generated on the side of the piston chamber 13 close to the reaction shell 1. Under the action of the air pressure, the piston 14 is pushed to slide. The sliding of the piston 14 pushes the push rod 15 to slide. The sliding of the push rod 15 first pushes the sliding plate 11 to slide. The sliding of the sliding plate 11 further squeezes the elastic reset member 12, so that the sealing cover plate 8 is pushed forward. The push rod 15 is pressed tightly on the trumpet-shaped groove 7 to seal the trumpet-shaped groove 7; the push rod 15 slides on the second side to drive the push rod 26 to slide, and the push rod 26 slides into the "U"-shaped groove 18 and contacts the ball 20 in the "U"-shaped groove 18, and finally pushes the ball 20 to slide along the "U"-shaped groove 18, and squeezes the sliding column 17 to push the sliding column 17 to slide, and the sliding of the sliding column 17 will push the lower pressure plate 16 to slide, thereby adjusting the position of the lower pressure plate 16 to adjust the lower pressure position of the mixed gas of the vapor deposition reaction, so as to adapt to the production of epitaxial wafers of various sizes.

[0055] It also includes an induction coil, which is wound outside the reaction shell 1. The induction coil is a prior art and will not be described in detail here.

[0056] The heat-insulating layer 22 is sleeved inside the reaction shell 1 and is used to achieve heat insulation.

[0057] The heating layer 24 is sleeved in the heat-insulating layer 22 and is placed in the magnetic field generated by the induction coil being energized, so that the heating layer 24 generates heat due to the eddy current effect, thereby achieving heating.

[0058] The lining layer 25 is disposed inside the heating layer 24 and is used to protect the heating layer 24 .

[0059] In this embodiment, a tray 27 is also included, which is placed in the inner cavity of the lining layer 25; when replacing the vapor deposited epitaxial wafer, the present invention controls the height adjustment component 31 to extend, and the extension of the height adjustment component 31 will push the lifting rod 29 to move upward, and the upward movement of the lifting rod 29 will push the top plate 28 and the tray 27 to move upward, so that the robot arm can grab the tray 27 for removal, thereby facilitating the replacement of the epitaxial wafer.

[0060] The top plate 28 is placed in the inner cavity of the lining layer 25 and at the bottom of the tray 27 , and is inserted into the tray 27 in a limited position.

[0061] Specifically, the height adjustment assembly 31 is disposed at the bottom of the pneumatic rotary joint 30 .

[0062] The lifting rod 29 is placed at the bottom of the top plate 28 and extends to the outside of the reaction shell 1 , and is sealed and movably connected to the reaction shell 1 .

[0063] In this embodiment, a pneumatic rotary joint 30 is also included, which is transmission-connected to the lifting rod 29, and connected to the air intake system. By setting the pneumatic rotary joint 30, the airflow of the air intake system will drive the pneumatic rotary joint 30 to rotate, and the rotation of the pneumatic rotary joint 30 will drive the lifting rod 29, the top plate 28, the tray 27 and the epitaxial wafer to rotate, thereby making the flatness of the epitaxial wafer produced by vapor deposition more flat.

[0064] A soft start valve is also included, which is placed between the pneumatic rotary joint 30 and the air intake system, and controls the gas flow and pressure entering the pneumatic rotary joint 30 to gradually increase. The present invention sets a soft start valve, and when starting, controls the gas flow and pressure entering the pneumatic rotary joint 30 to gradually increase, so that the pneumatic rotary joint 30 starts slowly, thereby avoiding direct connection with the air intake system, resulting in sudden start, causing the tray 27 and the epitaxial wafer to shake, thereby affecting the flatness of the epitaxial wafer.

[0065] This embodiment further includes a protective gas inlet 32, which is disposed at one end of the inlet pipe 4 away from the reaction housing 1 and communicates with the protective gas inlet passage 9. The present invention provides the protective gas inlet 32 ​​to charge the reaction housing 1 with protective gas.

[0066] This embodiment further includes a plurality of mixed gas inlets 33, which are disposed at one end of the intake pipe 4 away from the reaction housing 1, and each channel 6 is connected to a mixed gas inlet 33, the number of which is the same as the number of channels 6, which is connected to the mixed gas intake system. The present invention is provided with the mixed gas inlet 33 to realize charging the reaction housing 1 with mixed gas.

[0067] The present invention also provides a preparation method for improving the flatness of an epitaxial wafer, comprising the following steps:

[0068] Step 1: Control the exhaust system to exhaust air from the piston chamber 13, so that the piston 14 slides and drives the sealing cover plate 8 to slide toward the reaction shell 1 through the push rod 15, the sliding plate 11 and the guide rod 10, so that the trumpet-shaped notch 7 is opened, and the non-reactive gas in the reaction shell 1 is quickly blown out;

[0069] Step 2: Control the air intake system to inflate the piston chamber 13, so that the piston 14 slides and drives the sealing cover plate 8 to slide away from the reaction shell 1 through the push rod 15, the sliding plate 11 and the guide rod 10, so that the trumpet-shaped notch 7 is closed, and the protective gas is blown out only from the air inlet 801, forming a uniform and stable airflow.

[0070] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A preparation device for improving the flatness of an epitaxial wafer, comprising a reaction shell (1) with two ends open, characterized in that: It also includes a sealed air inlet flange (2) which is sealedly connected to one end of the reaction shell (1); A sealed exhaust member (3) which is sealingly connected to the other end of the reaction shell (1); An air inlet pipe (4), which passes through the sealed air inlet flange (2) and has one end extending into the reaction housing (1); A plurality of partitions (5) are arranged in an array on the inner wall of the air intake pipe (4) to divide the inner wall cavity of the air intake pipe (4) into a plurality of channels (6); A trumpet-shaped notch (7) disposed at one end of the air inlet pipe (4) located inside the reaction housing (1); A sealing cover plate (8) is placed in the trumpet-shaped notch (7) and has a shape that matches the trumpet-shaped notch (7). The sealing cover plate (8) is provided with a plurality of air inlet holes (801) in an array; A protective gas inlet passage (9), which is formed on the wall of the inlet pipe (4) and communicates with the trumpet-shaped notch (7); A guide rod (10) is disposed on a side of the sealing cover plate (8) facing away from the reaction housing (1), extends to the outside of the air inlet pipe (4), and is sealingly and slidably connected to the air inlet pipe (4); A sliding plate (11) which is slidably sleeved on one end of the guide rod (10) located outside the air inlet pipe (4); An elastic reset component (12) is sleeved on one end of the guide rod (10) located outside the air inlet pipe (4), one end of the elastic reset component is connected to the sliding plate (11), and the other end of the elastic reset component is connected to the guide rod (10); A piston chamber (13) is provided on the wall of the air inlet pipe (4), an end of which is close to the reaction housing (1) and is connected to the air inlet system and the air exhaust system respectively through a conduit, and an end of which is far from the reaction housing (1) and is connected to the atmosphere; A piston (14) disposed in the piston chamber (13); A push rod (15), one end of which is connected to the piston (14) and the other end of which is connected to the sliding plate (11); In the initial inflation stage, the piston chamber (13) is evacuated by the exhaust system, so that a negative pressure is generated on the side of the piston chamber (13) close to the reaction shell (1). Under the action of the negative pressure, the piston (14) will slide toward the side of the reaction shell (1). The sliding of the piston (14) will drive the push rod (15) to slide. The sliding of the push rod (15) will drive the sliding plate (11) to slide. The sliding of the sliding plate (11) will drive the elastic reset component (12) to slide. The sliding of the elastic reset component (12) will drive the guide rod (10) to slide. The sliding of the guide rod (10) will drive the sealing cover plate (8) to slide, thereby opening the trumpet-shaped notch (7), thereby allowing a large flow of protective gas to flow out of the trumpet-shaped notch (7) into the reaction shell (1).

2. The device for preparing an epitaxial wafer with improved flatness according to claim 1, characterized in that: It also includes a lower pressure plate (16), which is disposed in the channel (6) and is horizontally slidably connected to the channel (6), and one end of the lower pressure plate close to the reaction shell (1) is connected via a connecting portion, and the thickness of the lower pressure plate gradually increases from the end located in the tube wall to the end of the reaction shell (1); A "U"-shaped groove (18) is formed in one of the vertical planes in the wall of the air inlet pipe (4); A sliding column (17) is disposed at one end of the lower pressure plate (16) away from the reaction housing (1) and extends into the U-shaped groove (18); An elastic return member (19), one end of which is connected to the slide column (17) and the other end of which is connected to the U-shaped groove (18); A spherical ball (20) is placed in the "U"-shaped groove (18); A push rod (26) for pushing the ball (20) is provided on the peripheral side wall of the push rod (15), and a push groove (21) connected to the piston cavity (13) and for inserting the push rod (26) is provided on the side wall of the "U"-shaped groove (18).

3. The device for preparing an epitaxial wafer with improved flatness according to claim 1, characterized in that: It also includes an induction coil, which is wound around the outside of the reaction shell (1); A heat-insulating layer (22) is sleeved inside the reaction shell (1); A heating layer (24) is sleeved inside the thermal insulation layer (22); The lining layer (25) is disposed inside the heating layer (24) and is used to protect the heating layer (24).

4. The device for preparing an epitaxial wafer with improved flatness according to claim 3, characterized in that: It also includes a tray (27) placed in the inner cavity of the lining layer (25); A top plate (28) is placed in the inner cavity of the lining layer (25), is located at the bottom of the tray (27), and is inserted into the tray (27) in a limited position; A lifting rod (29) is placed at the bottom of the top plate (28) and extends outside the reaction shell (1), and is sealed and movably connected to the reaction shell (1).

5. The device for preparing an epitaxial wafer with improved flatness according to claim 1, characterized in that: It also includes a pneumatic rotary joint (30), which is transmission-connected to the lifting rod (29) and connected to the air intake system.

6. The device for preparing an epitaxial wafer with improved flatness according to claim 5, characterized in that: It also includes a height adjustment component (31) which is placed at the bottom of the pneumatic rotary joint (30).

7. The device for preparing an epitaxial wafer with improved flatness according to claim 5, characterized in that: It also includes a soft start valve, which is placed between the pneumatic rotary joint (30) and the air intake system and controls the gas flow and pressure entering the pneumatic rotary joint (30) to gradually increase.

8. The device for preparing an epitaxial wafer with improved flatness according to claim 1, characterized in that: It also includes a protective gas inlet (32), which is disposed at one end of the gas inlet pipe (4) away from the reaction housing (1) and is connected to the protective gas inlet duct (9).

9. The device for preparing an epitaxial wafer with improved flatness according to claim 1, characterized in that: It also includes a plurality of mixed gas inlets (33), which are disposed at one end of the intake pipe (4) away from the reaction housing (1), and each channel (6) is connected to a mixed gas inlet (33), the number of which is the same as the number of channels (6), and is connected to the mixed gas intake system.

10. A method for improving the flatness of an epitaxial wafer, wherein the method uses the device for improving the flatness of an epitaxial wafer as claimed in any one of claims 1 to 9 to prepare an epitaxial wafer, characterized in that: The following steps are involved: Step 1: Control the exhaust system to exhaust air from the piston chamber (13), so that the piston (14) slides and drives the sealing cover plate (8) to slide toward the reaction shell (1) through the push rod (15), the sliding plate (11) and the guide rod (10), so that the trumpet-shaped notch (7) opens, thereby quickly blowing out the non-reactive gas in the reaction shell (1); Step 2: Control the air intake system to inflate the piston chamber (13), so that the piston (14) slides and drives the sealing cover plate (8) to slide away from the reaction shell (1) through the push rod (15), the sliding plate (11) and the guide rod (10), so that the trumpet-shaped notch (7) is closed, and the protective gas is blown out only from the air intake hole (801), forming a uniform and stable airflow.

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