A gas float tray for silicon carbide epitaxial furnace

Abstract

The utility model provides a kind of for silicon carbide epitaxial furnace's air floatation tray, air floatation tray includes: tray body and airflow channel, the projection of the first airflow section and the second airflow section of airflow channel on the plane of the disc face of tray body has included angle θ, so that the path that air flow passes is a broken line, so air flow will due to inertia in the extension direction of first airflow section Impact, then again turn to second airflow section, finally flow out;The force generated by impact acts on tray body, will make the tray body suspended rotation, the path of broken line state makes the component force that air flow acts to airflow channel inner wall when turning, i.e. Compared with existing airflow channel, the same air flow is entered, more effective air flow in airflow channel plays the role of promoting tray body rotation, tray body rotates faster, airflow channel utilization is higher, fewer channel quantity can be set to reduce cost;Also reduce the air blowing amount of air hole, and then reduce epitaxial wafer surface defect.

Description

Technical Field

[0001] This utility model relates to the field of semiconductor epitaxial equipment technology, and in particular to an air-floating tray for a silicon carbide epitaxial furnace. Background Technology

[0002] Silicon carbide epitaxial furnaces are used for homoepitaxial growth of silicon carbide substrates. Horizontal silicon carbide epitaxial furnaces require air-floating trays. These trays are positioned on a carrier plate, and air is blown onto the underside of the tray through vents in the carrier plate to suspend the tray and prevent mechanical contact. Figure 1 As shown, the air flotation tray also has a tangential airflow channel inside. The air inlet of the airflow channel is close to or located at the position where the air hole projection is on the lower plate surface of the air flotation tray, and the air outlet is far away from this position. Since the airflow channel is set at an angle, the air flotation tray can be rotated by introducing airflow into the airflow channel to improve the uniformity of epitaxial growth. However, the existing airflow channel has a very small effective airflow rate entering the airflow channel during the epitaxial process, which makes the air flotation tray rotate slowly and also makes the air channel utilization rate low. Therefore, it is necessary to design more airflow channels, usually eight, to increase the airflow. Sometimes it is also necessary to increase the air blowing volume of the air hole on the carrier plate to speed up the rotation of the air flotation tray. More airflow channels not only increase the processing cost, but also reduce the load-bearing capacity of the air flotation tray. Summary of the Invention

[0003] This invention provides an air-floating tray for silicon carbide epitaxial furnaces to solve the technical problems of low effective airflow into the airflow channel, slow rotation of the air-floating tray, and low utilization rate of the air channel.

[0004] This utility model provides an air-floating tray for a silicon carbide epitaxial furnace, comprising a tray body and an airflow channel. The lower surface of the tray body includes a windward area for receiving airflow and suspending the tray body. The airflow channel is disposed within the tray body and has an inlet and an outlet, both located on the lower surface. The inlet is close to the windward area, and the outlet is away from the windward area. The airflow channel includes a first airflow segment and a second airflow segment, the projections of the first and second airflow segments onto the plane of the tray body forming an angle θ.

[0005] In one embodiment of this utility model, the value of θ ranges from 50° to 150°.

[0006] In one embodiment of the present invention, one end of the first airflow section is connected to one end of the second airflow section, and the connection between the first airflow section and the second airflow section is at an angle.

[0007] In one embodiment of the present invention, the length of the first airflow section is less than the length of the second airflow section.

[0008] In one embodiment of the present invention, the air inlet is located in the middle of the lower side panel of the tray body, and the air outlet is located at the outer edge of the lower side panel of the tray body.

[0009] In one embodiment of the present invention, a protrusion supporting the pallet body is provided in the middle of the lower surface of the pallet body.

[0010] In one embodiment of this utility model, the protrusion is flat.

[0011] In one embodiment of the present invention, the upper surface of the tray body is provided with ridges.

[0012] In one embodiment of the present invention, the ridge is arranged in a ring around the levitation direction of the tray body.

[0013] In one embodiment of the present invention, the airflow channels are provided in fewer than eight circumferential directions around the suspension direction of the tray body.

[0014] The beneficial effects of this utility model are as follows: The air-floating tray for a novel silicon carbide epitaxial furnace proposed in this utility model has an angle between the projections of the first and second airflow sections of the airflow channel onto the plane of the tray body. This causes the airflow path from the first airflow section to the second airflow section to be a broken line. Therefore, the airflow will impact the extension direction of the first airflow section due to inertia, and then turn to the second airflow section before finally flowing out. The force generated by the impact acts on the tray body, causing the suspended tray body to rotate. The broken line path results in a larger component force acting on the inner wall of the airflow channel when the airflow turns. It can be understood that, compared with existing airflow channels, under the same airflow rate, there is more effective airflow in the airflow channel to propel the tray body to rotate, making the tray body rotate faster and increasing the utilization rate of the airflow channel. Fewer channels can be set to reduce costs and reduce the amount of air blown through the pores, thereby reducing surface defects of the epitaxial wafer. Attached Figure Description

[0015] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0016] In the attached diagram:

[0017] Figure 1This is a schematic diagram of an existing air flotation tray along the air blowing direction in the background art of this utility model;

[0018] Figure 2 This is a schematic diagram of the air flotation tray provided in one embodiment of the present invention along the air blowing direction;

[0019] Figure 3 This is a side view of an air-floating tray provided in one embodiment of the present invention;

[0020] Figure 4 This is a schematic diagram of the air-floating tray along the blowing direction when θ is 130°, provided in one embodiment of the present invention;

[0021] Figure 5 This is a schematic diagram of the air-floating tray along the blowing direction when θ is 90° in one embodiment of the present invention;

[0022] Figure 6 This is a schematic diagram of the air-floating tray along the blowing direction when θ is 70° in one embodiment of the present invention;

[0023] Figure 7 This is a schematic diagram of existing epitaxial wafer defects provided in one embodiment of the present invention;

[0024] Figure 8 This is a schematic diagram of an epitaxial wafer defect when θ is 130°, provided in one embodiment of the present invention;

[0025] Figure 9 This is a schematic diagram of epitaxial wafer defects when θ is 90°, provided in one embodiment of the present invention;

[0026] Figure 10 This is a schematic diagram of the epitaxial wafer defect when θ is 70° in one embodiment of the present invention.

[0027] The attached figures are labeled as follows:

[0028] 100, Tray body; 200, Airflow channel; 210, First airflow section; 220, Second airflow section; 230, Air inlet; 240, Air outlet; 300, Protrusion; 400, Ridge; 500, Carrier tray; 510, Air hole. Detailed Implementation

[0029] The following specific examples illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification. This utility model can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this utility model. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0030] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. The drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0031] In the following description, numerous details are explored to provide a more thorough explanation of embodiments of the present invention. However, it will be apparent to those skilled in the art that embodiments of the present invention may be practiced without these specific details. In other embodiments, well-known structures and devices are shown in block diagram form rather than in detail to avoid obscuring embodiments of the present invention.

[0032] To address the problems existing in the prior art, please refer to Figures 2 to 3 The present invention provides an air-floating tray for a novel silicon carbide epitaxial furnace, comprising a tray body 100 and an airflow channel 200 disposed within the tray body 100. The airflow channel 200 includes a first airflow section 210 and a second airflow section 220. The projections of the first airflow section 210 and the second airflow section 220 onto the plane of the tray body 100 have an included angle θ. The path of the airflow from the first airflow section 210 to the second airflow section 220 is a broken line. Therefore, the airflow will impact the extension direction of the first airflow section 210 due to inertia, and then turn to the second airflow section 220 before finally flowing out. The force generated by the impact acts on the tray body 100, causing the suspended tray body 100 to rotate. The broken line path makes the component force of the airflow acting on the inner wall of the airflow channel 200 when turning larger. It can be understood that, compared with the existing airflow channel 200, under the same airflow, the airflow channel 200 in this embodiment has more effective airflow to push the tray body 100 to rotate, making the tray body 100 rotate faster and the airflow channel 200 more efficient. It also makes the airflow channel 200 less efficient and allows for fewer channels to be set to reduce costs.

[0033] Furthermore, since the effective airflow rate entering the airflow channel 200 during the existing epitaxial process is very low, while designing multiple airflow channels to increase the airflow, it is sometimes necessary to increase the airflow rate of the air holes 510 on the carrier disk 500. However, increasing the airflow rate will blow more carbon powder generated on the surface of the graphite materials in the epitaxial furnace onto the surface of the epitaxial wafer, thereby increasing the surface defects of the epitaxial wafer, such as... Figure 7 As shown, the number of defects on the surface of the epitaxial wafer can typically reach 96. However, the angle θ design of the airflow channel 200 in this application allows for more effective airflow, which reduces the amount of air blown through the vents 510, thereby reducing the defects on the surface of the epitaxial wafer.

[0034] The lower surface of the tray body 100 includes a windward area for receiving airflow and suspending the tray body 100. The shape of the tray body 100 is not limited, as long as it can be suspended by airflow blowing towards the lower surface; it can be circular, square, or elliptical. This embodiment uses a circular shape, as a circular tray body 100 is more stable during rotation and reduces the concentration of circumferential stress. The lower surface of the tray body 100 is generally flat to facilitate suspending. Figure 3 As shown, since the tray body 100 is usually located on the carrier tray 500, the function of the windward area is to receive the wind blown out from the carrier tray 500. The carrier tray 500 is usually provided with air holes 510 to blow air into the windward area. Therefore, the windward area is generally set to correspond to the projection position of the air holes 510 on the lower tray surface. By blowing air into the lower tray surface of the tray body 100 through the air holes 510, the tray body 100 can be lifted and suspended by the wind force. Considering that the suspension of the tray body 100 is usually to overcome gravity, the lower tray surface in this embodiment is the tray surface of the tray body 100 that is lower along the direction of gravity.

[0035] The airflow channel 200 has an air inlet 230 and an air outlet 240, both of which are located on the lower side panel. The shape of the airflow channel 200 is not limited, as long as it can accommodate gas flow. Its cross-sectional shape can be circular, square, or elliptical. This embodiment uses a circular shape, which allows for smoother gas flow and reduces noise. The shapes of the air inlet 230 and the air outlet 240 are also circular to match the shape of the airflow channel 200. It should be noted that the air inlet 230 and the air outlet 240 can also be different shapes, and their shapes do not need to be identical. Figure 2 As shown, most of the airflow channel 200 is located in a single plane, which is parallel to the surface of the tray body 100. Except for the first airflow section 210 and the second airflow section 220, which need to form an angle θ between their projections on the plane where the tray surface is located, the direction of the airflow channel 200 within the tray body 100 should be as gentle and smooth as possible to reduce airflow resistance. The air inlet 230 is close to the windward area to receive the wind blown from the air hole 510 into the windward area, introduce the wind into the airflow channel 200, and form an airflow in the airflow channel 200. The air outlet 240 is far away from the windward area to avoid interference between the wind coming out of the air outlet 240 and the wind blown from the air hole 510 into the windward area, which would affect the intake air volume of the air inlet 230.

[0036] By setting the included angle between the first airflow section 210 and the second airflow section 220, the airflow utilization rate in the airflow channel 200 is improved, and the number of airflow channels 200 arranged circumferentially around the suspension direction of the pallet body 100 is less than the eight commonly used in the prior art. In practical applications, it is reduced to four, which reduces processing costs and improves the strength of the pallet body 100.

[0037] In this embodiment, as Figure 3 As shown, except for the part of the airflow channel 200 that needs to bend to connect with the air inlet 230 and the air outlet 240, most of the other part is in a plane parallel to the tray surface of the tray body 100, and this part is divided into two sections: the first airflow section 210 and the second airflow section 220, as shown in the figure. Figure 2 As shown, one end of the first airflow section 210 is connected to one end of the second airflow section 220. Both the first airflow section 210 and the second airflow section 220 are straight segments. The connection between the first airflow section 210 and the second airflow section 220 forms an angle, which is the angle θ. This makes the layout of the airflow channel 200 clear, with only the two straight segments of the first airflow section 210 and the second airflow section 220 forming an angle, reducing the processing difficulty and ensuring that the airflow experiences less resistance except at the angle, so that it impacts the angle with the greatest force and improves the rotation effect of the tray body 100. At the same time, it also makes the angle θ easier to measure and confirm.

[0038] The length of the first airflow section 210 is less than the length of the second airflow section 220. When the airflow passes through the inlet 230 to the first airflow section 210, it can take a shorter path to reach the impact position at the bend, which can reduce the resistance during the flow process. At the same time, the length of the first airflow section 210 should not be too short, so that the first airflow section 210 can also play the role of a general channel for guiding the airflow.

[0039] In this embodiment, θ ranges from 50° to 150°. The length of the portion of the airflow channel 200 within a plane parallel to the tray surface of the tray body 100 is L. Since the diameter of the air-bearing tray varies depending on different extension requirements, typically six inches and eight inches, this embodiment uses a six-inch air-bearing tray as an example. Therefore, the corresponding value of L ranges from 50mm to 100mm. Because the positions of the air inlet 230 and the air outlet 240 are relatively fixed, a smaller value of θ necessitates a larger value of L to meet design requirements. The length of the first airflow section 210 is defined as L1, and the length of the second airflow section 220 is defined as L2, where L1 + L2 = L.

[0040] like Figure 4 As shown, θ is first designed to be 130°, corresponding to a design L value of 60mm. Then, after epitaxial growth using this air-floating tray, as shown... Figure 8As shown, there are 59 surface defects on the epitaxial wafer, and most of them are located at the edges.

[0041] like Figure 5 As shown, θ is then designed to be 90°, corresponding to a design L value of 80mm. After epitaxial growth using this air-floating tray, as shown... Figure 9 As shown, there are 28 surface defects on the epitaxial wafer, and most of them are located at the edges.

[0042] like Figure 6 As shown, θ is finally designed to be 70°, corresponding to a design L value of 90mm. After epitaxial growth using this air-floating tray, as shown... Figure 10 As shown, there are 13 surface defects on the epitaxial wafer, and most of them are located at the edges.

[0043] As can be seen from the three examples above, within a certain range, the smaller the value of θ, the larger the length of the airflow channel 200, and the fewer defects generated on the epitaxial wafer. This is because a smaller θ value results in a better impact effect of the airflow between the first airflow section 210 and the second airflow section 220, generating a greater force on the pallet body 100, leading to a better rotational effect on the pallet body 100 and higher airflow utilization. Of course, since the pallet body 100 is in a suspended state, faster rotation has a greater impact on its stability, placing requirements on the working environment and pallet precision. Conversely, a larger θ value results in a worse effect.

[0044] However, if the value of θ is too small, the airflow in the first airflow section 210 will hit the corner position and will not easily flow out from the second airflow section 220. It will then react back and hinder the effect of the subsequent airflow. Furthermore, the smaller the value of θ, the longer the length of the airflow channel 200 needs to be designed. This not only makes it difficult to process and increases costs, but also results in more material being removed from the pallet body 100 after processing, affecting the strength of the pallet body 100.

[0045] Therefore, in this embodiment, the value of θ is in the range of 50°-150°. It will not be difficult to process due to the angle being too small. At the same time, considering that the faster the rotation, the greater the impact on its stability, a reasonable value can be selected within the range for different working conditions and pallet precision.

[0046] In this embodiment, the air inlet 230 is located in the middle of the lower side of the tray body 100, and the air outlet 240 is located at the outer edge of the lower side of the tray body 100. With four airflow channels 200, the air inlet 230 is concentrated in the middle position, and the windward area is smaller, which makes it easier for the air holes 510 on the tray 500 to blow air into the windward area.

[0047] In this embodiment, a flattened protrusion 300 supporting the tray body 100 is provided in the middle of the lower surface of the tray body 100. When the air hole 510 is not blowing air, the tray body 100 is first placed on the carrier tray 500. The air hole 510 starts blowing air, generating airflow in the airflow channel 200, and the tray body 100 also begins to levitate. Since it takes a certain amount of time to overcome gravity, although it is short, the airflow generated in the airflow channel 200 has already begun to act on the tray body 100 to make it rotate before levitation begins. In this way, the tray body 100 will rub against the carrier tray 500. Wear occurs during the friction process with the tray body 100. Since the carrier tray 500 is usually made of graphite, some carbon powder will be worn away. Since the epitaxial wafer is to be placed on the tray body 100, this carbon powder will be carried to the epitaxial wafer by the air blown out of the carrier tray 500, which increases the surface defects of the epitaxial wafer and reduces the surface defect yield of the epitaxial wafer. Therefore, the protrusion 300 is set to increase the distance between the epitaxial sheet and the carrier 500, and greatly reduce the contact area between the tray body 100 and the carrier 500, thereby reducing the diffusion of toner.

[0048] In this embodiment, the upper surface of the tray body 100 is provided with a ridge 400. The ridge 400 is arranged in a ring around the circumference of the tray body 100 in the suspension direction. During the epitaxial growth process, a rotating disk that follows the rotation is placed on the tray body 100 to carry the epitaxial wafer. The ring-shaped ridge 400 can better support the rotating disk.

[0049] The above embodiments are merely illustrative of the principles and effects of this utility model and are not intended to limit the scope of this utility model. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this utility model. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this utility model should still be covered by the claims of this utility model.

Claims

1. An air-floating tray for a silicon carbide epitaxial furnace, characterized in that, include: The tray body (100) has a lower side surface that includes a windward area for receiving airflow and suspending the tray body (100). An airflow channel (200) is provided inside the tray body (100), and the airflow channel (200) has an air inlet (230) and an air outlet (240). The air inlet (230) and the air outlet (240) are both opened on the lower side of the tray surface. The air inlet (230) is close to the windward area, and the air outlet (240) is far away from the windward area. The airflow channel (200) includes a first airflow section (210) and a second airflow section (220), and the projections of the first airflow section (210) and the second airflow section (220) onto the plane of the tray body (100) have an included angle θ.

2. The air-floating pallet according to claim 1, characterized in that, The value of θ ranges from 50° to 150°.

3. The air-floating pallet according to claim 1, characterized in that, One end of the first airflow section (210) is connected to one end of the second airflow section (220), and the connection between the first airflow section (210) and the second airflow section (220) is at an angle.

4. The air-floating pallet according to claim 3, characterized in that, The length of the first airflow section (210) is less than the length of the second airflow section (220).

5. The air-floating pallet according to claim 1, characterized in that, The air inlet (230) is located in the middle of the lower side of the tray body (100), and the air outlet (240) is located at the outer edge of the lower side of the tray body (100).

6. The air-floating pallet according to claim 1, characterized in that, The lower surface of the tray body (100) is provided with a protrusion (300) in the middle to support the tray body (100).

7. The air-floating pallet according to claim 6, characterized in that, The protrusion (300) is flat.

8. The air-floating pallet according to claim 1, characterized in that, The upper surface of the tray body (100) is provided with ridges (400).

9. The air-floating pallet according to claim 8, characterized in that, The ridge (400) is arranged in a ring around the circumference of the tray body (100) in the levitation direction.

10. The air-floating pallet according to claim 1, characterized in that, The airflow channels (200) are provided in fewer than 8 circumferentially around the suspension direction of the tray body (100).

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