Gas path system and gas source control method of silicon carbide epitaxial furnace

Abstract

The invention discloses a gas path system of a silicon carbide epitaxial furnace and a gas source control method, and the gas path system of the silicon carbide epitaxial furnace comprises a first operation pipe, a second operation pipe, a first bypass pipe, a second bypass pipe, a silicon source conveying pipe, a carbon source conveying pipe, a mixing unit, a first valve assembly, a doped gas source conveying pipe and a second valve assembly, the mixing unit mixes a silicon source and a carbon source to obtain a mixed growth gas source, the first valve assembly switches the mixing unit outlet to be communicated with the first bypass pipe or the mixing unit outlet to be communicated with the first operation pipe, and the second valve assembly switches the doping gas source conveying pipe to be communicated with the second operation pipe or the doping gas source conveying pipe to be communicated with the second bypass pipe. The gas path system can reduce the time deviation of the silicon source and the carbon source entering the epitaxial reaction chamber, and can reduce the defect density of an epitaxial layer; the doping gas source conveying pipe and the mixing unit are independently arranged, the doping gas source can be independently controlled, a complex doping structure can be manufactured, and the performance requirement of a special silicon carbide device can be met.

Description

Technical Field

[0001] This application relates to the field of semiconductor material growth equipment technology, and more specifically, to a gas path system and gas source control method for a silicon carbide epitaxial furnace. Background Technology

[0002] The mainstream method for silicon carbide epitaxy is chemical vapor deposition, which uses a silicon carbide epitaxial furnace. Gas flow enters the silicon carbide epitaxial furnace and flows over the surface of the silicon carbide substrate. The gas flow undergoes a chemical reaction on the surface of the silicon carbide substrate, resulting in deposition.

[0003] In a silicon carbide epitaxial furnace, the carbon source and silicon source enter the delivery tubes separately. The delivery tubes include the running tube and the bypass tube. Due to the different distances from the carbon source and silicon source to the running tube, and the different properties of the carbon source and silicon source, the carbon source and silicon source cannot enter the running tube synchronously. The silicon carbide substrate first comes into contact with a single gas source (carbon source or silicon source), resulting in a higher local defect density in the epitaxial layer. For example, high-density step lines and silicon droplets will appear, which will reduce the withstand voltage performance and service life of silicon carbide devices.

[0004] In summary, how to reduce the defect density of epitaxial layers is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the purpose of this application is to provide a gas path system and gas source control method for a silicon carbide epitaxial furnace to reduce the defect density of the epitaxial layer.

[0006] To achieve the above objectives, this application provides the following technical solution:

[0007] A gas path system for a silicon carbide epitaxial furnace includes:

[0008] The first operating tube and the second operating tube, the outlets of which are both used to communicate with the epitaxial reaction chamber;

[0009] A first bypass pipe and a second bypass pipe, both of which are used for venting air;

[0010] Silicon source delivery pipe, wherein the silicon source delivery pipe delivers silicon source.

[0011] Carbon source delivery pipe, wherein the carbon source delivery pipe delivers carbon source.

[0012] The mixing unit is connected to the inlet of both the silicon source delivery pipe and the carbon source delivery pipe. The mixing unit is used to mix the silicon source and the carbon source to obtain a mixed growth gas source.

[0013] A first valve assembly is used to switch the outlet of the mixing unit to be connected to the first bypass pipe, or the outlet of the mixing unit to be connected to the first operating pipe.

[0014] A doping gas source delivery pipe, wherein the doping gas source delivery pipe is used to deliver a doping gas source;

[0015] The second valve assembly is used to switch the doped gas source delivery pipe connected to the second operating pipe or the doped gas source delivery pipe connected to the second bypass pipe.

[0016] In some embodiments, the gas path system of the silicon carbide epitaxial furnace further includes a check valve connected in series in the pipeline of the mixing unit, the check valve being located between the outlet and the inlet of the mixing unit.

[0017] In some embodiments, the mixing unit includes a mixing tube, wherein the inlet and outlet of the mixing unit are both ports of the mixing tube.

[0018] In some embodiments, the mixing pipe includes a first mixing branch pipe, a second mixing branch pipe, and a mixing main pipe, wherein the outlets of the silicon source delivery pipe and the carbon source delivery pipe are both connected to the inlet of the mixing main pipe, and the inlets of the first mixing branch pipe and the second mixing branch pipe are both connected to the outlet of the mixing main pipe.

[0019] The outlet of the first mixing branch pipe is connected to the first operating pipe, and the outlet of the second mixing branch pipe is connected to the first bypass pipe.

[0020] In some embodiments, the first valve assembly includes a first three-way valve, and the inlets of the first mixing branch and the second mixing branch are connected to the outlet of the main mixing pipe through the first three-way valve.

[0021] In some embodiments, the first valve assembly includes a first valve and a second valve, the first valve being connected in series with the first mixing branch pipe and the second valve being connected in series with the second mixing branch pipe.

[0022] In some embodiments, the silicon source delivery pipe and the carbon source delivery pipe are connected to the inlet of the mixing unit via a second three-way valve, the second three-way valve being used to adjust the flow rate of the silicon source and the flow rate of the carbon source.

[0023] In some embodiments, a pressure control valve is connected in series with the second bypass pipe. In some embodiments, during the buffer layer stage, the C / Si value of the mixed growth gas source in the first operating pipe ranges from 0.45 to 0.75; during the epitaxial layer stage, the C / Si value of the mixed growth gas source in the first operating pipe ranges from 0.75 to 1.05.

[0024] In some embodiments, the doping gas source includes ammonia;

[0025] And / or, the silicon source includes trichlorosilane;

[0026] And / or, the carbon source includes ethylene.

[0027] Based on the gas path system of the silicon carbide epitaxial furnace provided above, this application also provides a gas source control method for a silicon carbide epitaxial furnace. The gas source control method for the silicon carbide epitaxial furnace is applicable to the gas path system of the silicon carbide epitaxial furnace described in any of the above claims. The gas source control method for the silicon carbide epitaxial furnace includes:

[0028] A silicon source is introduced into the mixing unit through a silicon source delivery pipe, and a carbon source is introduced into the mixing unit through a carbon source delivery pipe to obtain a mixed growth gas source.

[0029] The mixed growth gas source is introduced into the first bypass pipe and the doping gas source is introduced into the second bypass pipe. After a first preset time, the mixed growth gas source is introduced into the first operating pipe and the doping gas source is introduced into the second operating pipe to perform silicon carbide epitaxial growth.

[0030] In some embodiments, the gas source control method for the silicon carbide epitaxial furnace further includes:

[0031] Adjust the flow rate of the silicon source and / or the flow rate of the carbon source so that the C / Si ratio of the mixed growth gas source in the first operating tube is 0.45-0.75 in the buffer layer stage and 0.75-1.05 in the epitaxial layer stage.

[0032] In some embodiments, the gas source control method for the silicon carbide epitaxial furnace between the buffer layer stage and the epitaxial layer stage further includes:

[0033] The mixed growth gas source is introduced into the first bypass pipe and the doping gas source is introduced into the second bypass pipe. After a second preset time, the mixed growth gas source is introduced into the first operating pipe and the doping gas source is introduced into the second operating pipe.

[0034] The first preset duration and the second preset duration may be equal or unequal.

[0035] In the gas path system of the silicon carbide epitaxial furnace provided in this application, the mixing unit enables the silicon source and carbon source to be mixed before entering the first bypass tube and the first running tube. This allows the silicon source and carbon source to be mixed before entering the epitaxial reaction chamber, thereby reducing the time deviation between the silicon source and carbon source entering the epitaxial reaction chamber and improving the instantaneous uniformity of the silicon source and carbon source entering the epitaxial reaction chamber. For example, it can enable the carbon source and silicon source to enter the epitaxial reaction chamber synchronously, thereby reducing the probability that the silicon carbide substrate will first contact a single gas source (carbon source or silicon source), which in turn reduces the defect density of the epitaxial layer and improves the withstand voltage performance and service life of silicon carbide devices.

[0036] In the gas path system of the silicon carbide epitaxial furnace provided in this application, the doping gas source delivery pipe and the mixing unit are set up separately. The mixed growth gas source does not include the doping gas source, which can reduce the impact of the mixed growth gas source on the control of the doping gas source. Moreover, the doping gas source delivery pipe and the mixing unit are connected to different bypass pipes and different operating pipes, respectively. This allows for independent control of the doping gas source and enables the fabrication of complex doping structures such as steep doping concentration steps, thereby meeting the performance requirements of special silicon carbide devices. Furthermore, when the doping gas source includes ammonia and the silicon source includes silane, dichlorosilane, trichlorosilane, or silicon tetrachloride, the doping source including ammonia is not pre-mixed with the growth gas source (silicon source). This reduces the degree and probability of ammonolysis reaction between ammonia and silicon source, thereby reducing the probability of solid particles appearing in the gas source and the probability of blockage and corrosion of components such as gas pipelines, valves, mass flow controllers, and nozzles. This further reduces the maintenance cost of the silicon carbide epitaxial furnace and also reduces unnecessary consumption of reactants, thus lowering the production cost of silicon carbide devices. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0038] Figure 1 A schematic diagram of the gas path system of a silicon carbide epitaxial furnace provided in an embodiment of this application;

[0039] Figure 2 This is a schematic diagram of the structure of the first valve assembly in the gas path system of the silicon carbide epitaxial furnace provided in the embodiments of this application.

[0040] Explanation of reference numerals in the attached figures:

[0041] 1-First operating pipe, 2-First bypass pipe, 3-Silicon source delivery pipe, 4-Carbon source delivery pipe, 5-Mixing unit, 5a-Mixing pipe, 501-First mixing branch pipe, 502-Second mixing branch pipe, 503-Mixing main pipe, 6-First valve assembly, 601-First three-way valve, 602-First valve, 603-Second valve, 7-Doping gas source delivery pipe, 701-First doping branch pipe, 702-Second doping branch pipe, 703-Doping main pipe, 8-Second valve assembly, 801-Third three-way valve, 802-Fourth three-way valve, 9-Check valve, 10-Second three-way valve, 11-Carrier gas delivery pipe, 12-Second operating pipe, 13-Second bypass pipe, 14-Drain pipe, 15-Epipolar reaction chamber, 16-Pressure control valve. Detailed Implementation

[0042] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0043] The terminology used in the following embodiments is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. As used in the specification and appended claims of this application, the singular expressions “a,” “an,” “the,” “the,” “the,” and “this” are intended to also include expressions such as “one or more,” unless the context clearly indicates otherwise. It should also be understood that in the embodiments of this application, “one or more” means one, two, or more; “and / or” describes the relationship between related objects, indicating that three relationships may exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. The character “ / ” generally indicates that the preceding and following related objects are in an “or” relationship.

[0044] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0045] The "multiple" mentioned in the embodiments of this application refers to two or more. It should be noted that in the description of the embodiments of this application, terms such as "first" and "second" are used only for the purpose of distinguishing descriptions and should not be construed as indicating or implying relative importance, nor should they be construed as indicating or implying order.

[0046] like Figure 1 As shown, the gas path system of the silicon carbide epitaxial furnace provided in this application embodiment includes: a first operating pipe 1, a second operating pipe 12, a first bypass pipe 2, a second bypass pipe 13, a silicon source delivery pipe 3, a carbon source delivery pipe 4, a mixing unit 5, a first valve assembly 6, a doped gas source delivery pipe 7, and a second valve assembly 8.

[0047] The silicon source delivery pipe 3 is used to deliver the silicon source. The silicon source may include TCS, which is trichlorosilane; or, the silicon source may include silane, dichlorosilane, or silicon tetrachloride. The inlet of the silicon source delivery pipe 3 is for the silicon source to enter.

[0048] Carbon source delivery pipe 4 is used to deliver a carbon source. The carbon source may include ethylene or propane. The inlet of carbon source delivery pipe 4 allows the carbon source to enter.

[0049] Both the silicon source delivery pipe 3 and the carbon source delivery pipe 4 are connected to the inlet of the mixing unit 5. The mixing unit 5 is used to mix the silicon source and the carbon source to obtain a mixed growth gas source. It is understood that the mixed growth gas source is discharged from the outlet of the mixing unit 5. The mixed growth gas source is formed by mixing the silicon source and the carbon source.

[0050] The outlets of the first operating pipe 1 and the second operating pipe 12 are both used to connect to the extensional reaction chamber 15. The first bypass pipe 2 and the second bypass pipe 13 are both used to vent air. For example, the first bypass pipe 2 can be connected to the venting pipe 14, and the second bypass pipe 13 can be connected to the venting pipe 14 to achieve air venting.

[0051] The first valve assembly 6 is used to switch the outlet of the mixing unit 5 to be connected to the first bypass pipe 2, or the outlet of the mixing unit 5 to be connected to the first operating pipe 1. It is understood that the first valve assembly 6 has a first state and a second state; the first valve assembly 6 can switch between the first state and the second state; when the first valve assembly 6 is in the first state, the outlet of the mixing unit 5 is connected to the first bypass pipe 2; when the first valve assembly 6 is in the second state, the outlet of the mixing unit 5 is connected to the first operating pipe 1.

[0052] The doping gas supply pipe 7 is used to supply the doping gas source. The doping gas source may include ammonia; or, the doping gas source may include nitrogen or other gases. The second valve assembly 8 is used to switch the doping gas supply pipe 7 to be connected to the second operating pipe 12, or to the second bypass pipe 13. The second valve assembly 8 can switch between a third state and a fourth state; when the second valve assembly 8 is in the third state, the doping gas supply pipe 7 is connected to the second bypass pipe 13; when the second valve assembly 8 is in the fourth state, the doping gas supply pipe 7 is connected to the second operating pipe 12.

[0053] In the gas path system of the silicon carbide epitaxial furnace provided in this application embodiment, the mixing unit 5 enables the silicon source and carbon source to be mixed before entering the first bypass pipe 2 and the first running pipe 1, thereby enabling the silicon source and carbon source to be mixed before entering the epitaxial reaction chamber 15. This reduces the time deviation between the silicon source and carbon source entering the epitaxial reaction chamber 15 and improves the instantaneous uniformity of the silicon source and carbon source entering the epitaxial reaction chamber 15. For example, it can enable the carbon source and silicon source to enter the epitaxial reaction chamber 15 synchronously, thereby reducing the probability that the silicon carbide substrate will contact a single gas source (carbon source or silicon source) first, which in turn reduces the defect density of the epitaxial layer and improves the withstand voltage performance and service life of silicon carbide devices.

[0054] In the gas path system of the silicon carbide epitaxial furnace provided in this application embodiment, the doping gas source delivery pipe 7 and the mixing unit 5 are set separately. The mixed growth gas source does not include the doping gas source, which can reduce the influence of the mixed growth gas source on the control of the doping gas source. Moreover, the doping gas source delivery pipe 7 and the mixing unit 5 are respectively connected to different bypass pipes and are respectively connected to different running pipes. The doping gas source can be controlled independently, and complex doping structures such as steep doping concentration steps can be made, thereby meeting the performance requirements of special silicon carbide devices.

[0055] When the doping gas source includes ammonia and the silicon source includes silane, dichlorosilane, trichlorosilane, or silicon tetrachloride, the chlorine atoms bonded to the silicon atoms in the silicon source are highly reactive. Ammonia is a weak base with strong nucleophilic properties. If ammonia and silicon source are premixed, a rapid and violent ammonolysis reaction will occur at room temperature or low temperature, generating solid ammonium chloride and silicon-nitride powder, etc. These products will quickly combine into solid particles in the gas phase, which will block and corrode gas pipelines, valves, mass flow controllers, and nozzles, leading to increased equipment maintenance costs. It will also consume reactants (doping source and silicon source), leading to increased production costs. In this embodiment, the doping gas source delivery pipe 7 and the mixing unit 5 are separately configured. The doping gas source delivery pipe 7 and the mixing unit 5 are respectively connected to different bypass pipes and to different operating pipes. This ensures that the doping source, including ammonia, is not pre-mixed with the growth gas source (silicon source), which reduces the degree and probability of ammonia and silicon source undergoing ammonolysis reaction. This reduces the probability of solid particles appearing in the gas source and the probability of blockage and corrosion of components such as gas pipelines, valves, mass flow controllers, and nozzles. Consequently, it reduces the maintenance cost of the silicon carbide epitaxial furnace. It also reduces unnecessary consumption of reactants and lowers the production cost of silicon carbide devices.

[0056] It should be noted that the silicon source delivery pipe 3, the carbon source delivery pipe 4, the doping gas source delivery pipe 7, and the carrier gas delivery pipe 11 mentioned later are all connected in series with a mass flow controller.

[0057] In this embodiment, the mixed growth gas source first enters the first bypass pipe 2 and then the first operating pipe 1. During the process of switching from the connection between the outlet of the first bypass pipe 2 and the mixing unit 5 to the connection between the outlet of the first operating pipe 1 and the mixing unit 5, that is, during the process of the first valve assembly 6 switching from the first state to the second state, a backflow phenomenon occurs, affecting the safety and reliability of the gas circuit system. To solve this problem, such as Figure 1 As shown, the gas path system of the silicon carbide epitaxial furnace also includes a check valve 9, which is connected in series in the pipeline of the mixing unit 5. The check valve 9 is located between the outlet and the inlet of the mixing unit 5. In this way, the check valve 9 can reduce the probability of backflow and mitigate the degree of backflow. At the same time, the carbon source and silicon source can be mixed upstream of the check valve 9, which helps to ensure that the carbon source and silicon source are uniformly mixed before reaching the epitaxial reaction chamber 15, which is beneficial to further reduce the defect density of the epitaxial layer.

[0058] In some embodiments, the mixing unit 5 may include a mixing container, the inlet of the mixing unit 5 being the inlet of the mixing container's inlet pipe, and the outlet of the mixing unit 5 being the outlet of the mixing container's outlet pipe.

[0059] like Figure 1As shown, in some other embodiments, the mixing unit 5 may include a mixing pipe 5a, with both the inlet and outlet of the mixing unit 5 being the openings of the mixing pipe 5a. This simplifies the structure of the mixing unit 5, thereby simplifying the structure of the gas path system of the silicon carbide epitaxial furnace.

[0060] To facilitate the mixing of silicon and carbon sources in the mixing pipe 5a, the mixing pipe 5a may include a first mixing branch pipe 501, a second mixing branch pipe 502, and a mixing main pipe 503. The outlets of the silicon source delivery pipe 3 and the carbon source delivery pipe 4 are both connected to the inlet of the mixing main pipe 503. The inlets of the first mixing branch pipe 501 and the second mixing branch pipe 502 are both connected to the outlet of the mixing main pipe 503. The outlet of the first mixing branch pipe 501 is connected to the first operating pipe 1, and the outlet of the second mixing branch pipe 502 is connected to the first bypass pipe 2.

[0061] It is understood that the inlet of the mixing main pipe 503 is the inlet of the mixing unit 5, and the outlets of the first mixing branch pipe 501 and the second mixing branch pipe 502 are both outlets of the mixing unit 5, meaning the mixing unit 5 has two outlets. In the first state, the first valve assembly 6 is in the first state, with the outlet of the second mixing branch pipe 502 connected to the first bypass pipe 2; in the second state, the first valve assembly 6 is in the second state, with the outlet of the first mixing branch pipe 501 connected to the first operating pipe 1. The aforementioned check valve 9 can be one, connected in series with the mixing main pipe 503; or, there can be two check valves 9, one connected in series with the first mixing branch pipe 501 and the other connected in series with the second mixing branch pipe 502.

[0062] In the above-mentioned mixing pipe 5a, the first mixing branch pipe 501 and the second mixing branch pipe 502 can be distributed in a U-shape; or, the first mixing branch pipe 501 and the second mixing branch pipe 502 can be distributed in other shapes.

[0063] like Figure 1 As shown, the first valve assembly 6 may include a first three-way valve 601, and the inlets of the first mixing branch pipe 501 and the second mixing branch pipe 502 are connected to the outlet of the mixing main pipe 503 through the first three-way valve 601.

[0064] It should be noted that the first three-way valve 601 has a first valve port, a second valve port, and a third valve port, and the first three-way valve 601 has a first valve position and a second valve position; when the first three-way valve 601 is in the first valve position, the first valve port and the third valve port are connected; when the first three-way valve 601 is in the second valve position, the second valve port and the third valve port are connected; wherein, the first valve port is connected to the first mixing branch pipe 501, the second valve port is connected to the second mixing branch pipe 502, and the third valve port is connected to the outlet of the mixing main pipe 503.

[0065] The first valve assembly 6 can also have other structures. For example... Figure 2As shown, the first valve assembly 6 includes a first valve 602 and a second valve 603. The first valve 602 is connected in series with the first mixing branch pipe 501, and the second valve 603 is connected in series with the second mixing branch pipe 502.

[0066] To reduce the number of valves, the first valve assembly 6 may include a first three-way valve 601.

[0067] In some embodiments, the silicon source delivery pipe 3 and the carbon source delivery pipe 4 may be arranged in a U-shape. It is understood that the silicon source delivery pipe 3 and the carbon source delivery pipe 4 cooperate to form a U-shaped structure.

[0068] In some other embodiments, the silicon source delivery pipe 3 and the carbon source delivery pipe 4 may be distributed in other shapes, and are not limited to U-shape.

[0069] In silicon carbide epitaxy, the C / Si ratio in the mixed growth gas source needs to be controlled within a set range. C / Si refers to the ratio of the molar flow rate of the carbon source gas to the molar flow rate of the silicon source gas.

[0070] To ensure a consistent C / Si ratio in the mixed growth gas source, both the silicon source and carbon source flow rates are adjustable. For example... Figure 1 As shown, in some embodiments, the silicon source delivery pipe 3 and the carbon source delivery pipe 4 are connected to the inlet of the mixing unit 5 via a second three-way valve 10, which is used to regulate the flow rates of the silicon source and the carbon source. This reduces the number of valves and facilitates the adjustment of the C / Si ratio in the mixed growth gas source.

[0071] like Figure 1 As shown, in some embodiments, in order to improve the pressure stability of the gas path system, a pressure control valve 16 is connected in series with the second bypass pipe 13. This ensures that the pressure of the gas path system is stable when the mixed growth gas source is switched from the first bypass pipe 2 to the first operating pipe 1, and when the doping gas source is introduced into the second operating pipe 12. This allows the gases (mixed growth gas source, doping gas source, and carrier gas mentioned later) to enter the corresponding operating pipes simultaneously for mixing at the moment of switching. After mixing, they enter the epitaxial reaction chamber 15, which is beneficial to improving the performance of silicon carbide devices.

[0072] In some embodiments, to improve the performance of the silicon carbide device, during the buffer layer stage, the C / Si ratio of the mixed growth gas source in the first operating tube 1 can range from 0.45 to 0.75; during the epitaxial layer stage, the C / Si ratio of the mixed growth gas source in the first operating tube 1 can range from 0.75 to 1.05. For example, during the drift layer stage of the epitaxial layer stage, the C / Si ratio of the mixed growth gas source in the first operating tube 1 ranges from 0.75 to 1.05.

[0073] It's important to note that in silicon carbide epitaxial processes, the buffer layer stage and the epitaxial layer stage are two distinct steps. The buffer layer stage refers to the formation of the buffer layer, which is the first high-quality homogeneous epitaxial layer (usually silicon carbide, but may have a different doping type or concentration than the substrate) to grow on the silicon carbide substrate. The epitaxial layer stage refers to the formation of the epitaxial layer, which is a silicon carbide epitaxial layer with a specific thickness, doping concentration, and type, built upon the high-quality buffer layer, according to the design requirements of the target device.

[0074] In other embodiments, the C / Si ratio of the mixed growth gas source can be in other ranges, and is not limited to the ranges described above.

[0075] In this embodiment, the second valve assembly 8 may include a third three-way valve 801, and the doped gas source delivery pipe 7 includes a doped main pipe 703, a first doped branch pipe 701 and a second doped branch pipe 702. The inlet of the first doped branch pipe 701 and the inlet of the second doped branch pipe 702 are connected to the outlet of the doped main pipe 703 through the third three-way valve 801. The outlet of the first doped branch pipe 701 is connected to the second running pipe 12, and the outlet of the second doped branch pipe 702 is connected to the second bypass pipe 13.

[0076] It should be noted that when the second valve assembly 8 is in the third state, the third three-way valve 801 is in the first valve position, and the second doped branch pipe 702 is connected to the second bypass pipe 13; when the second valve assembly 8 is in the fourth state, the third three-way valve 801 is in the second valve position, and the first doped branch pipe 701 is connected to the second operating pipe 12.

[0077] The aforementioned third three-way valve 801 can also be replaced by two two-way valves, one two-way valve connected in series with the first doped branch pipe 701 and the other two-way valve connected in series with the second doped branch pipe 702.

[0078] In the silicon carbide epitaxial process, a carrier gas is also required, which may include hydrogen. Therefore, the gas path system of the silicon carbide epitaxial furnace also includes a carrier gas delivery pipe 11, which is used to deliver the carrier gas.

[0079] The carrier gas also needs to be introduced into the second operating pipe 12 and the second bypass pipe 13. Based on this, the gas path system of the silicon carbide epitaxial furnace also includes a carrier gas delivery pipe 11, which can be connected to the second operating pipe 12 or the second bypass pipe 13.

[0080] In this embodiment, the carrier gas and doping gas source can be mixed, and therefore, the carrier gas and doping gas source can share a portion of the pipeline. In some embodiments, the second valve assembly 8 further includes a fourth three-way valve 802, through which the carrier gas delivery pipe 11 can be connected in series to the doping main pipe 703. In this way, the carrier gas can be introduced into the second operating pipe 12 through the first doping branch pipe 701, and the carrier gas can be introduced into the second bypass pipe 13 through the second doping branch pipe 702, which simplifies the entire gas path system.

[0081] It should be noted that the fourth three-way valve 802 is connected in series to the doping main pipe 703 through two valve ports, and the other valve port of the fourth three-way valve 802 is connected to the carrier gas delivery pipe 11. The fourth three-way valve 802 has a first valve position and a second valve position. When the fourth three-way valve 802 is in the first valve position, the doping main pipe 703 is connected through the fourth three-way valve 802, and the carrier gas delivery pipe 11 and the doping main pipe 703 are not connected. When the fourth three-way valve 802 is in the second valve position, the doping main pipe 703 is connected through the fourth three-way valve 802, and the carrier gas delivery pipe 11 and the doping main pipe 703 are connected through the fourth three-way valve 802. When the fourth three-way valve 802 is in the third valve position, the doping main pipe 703 is not connected, and the carrier gas delivery pipe 11 and the doping main pipe 703 are connected through the fourth three-way valve 802.

[0082] Based on the gas path system of the silicon carbide epitaxial furnace provided in the above embodiments, this application embodiment also provides a gas source control method for the silicon carbide epitaxial furnace. The gas source control method for the silicon carbide epitaxial furnace is applicable to the gas path system of the silicon carbide epitaxial furnace provided in the above embodiments.

[0083] In this embodiment of the application, the gas source control method for the silicon carbide epitaxial furnace includes:

[0084] S1: Silicon source is introduced into mixing unit 5 through silicon source delivery pipe 3 and carbon source is introduced into mixing unit 5 through carbon source delivery pipe 4 to obtain mixed growth gas source;

[0085] S2: The mixed growth gas source is introduced into the first bypass pipe 2 and the doping gas source is introduced into the second bypass pipe 13. After a first preset time, the mixed growth gas source is introduced into the first operating pipe 1 and the doping gas source is introduced into the second operating pipe 12 to carry out silicon carbide epitaxial growth.

[0086] In the above S2, the first valve assembly 6 is switched to the first state and the second valve assembly 8 is switched to the third state to allow the mixed growth gas source to be introduced into the first bypass pipe 2 and the doping gas source to be introduced into the second bypass pipe 13; the first valve assembly 6 is switched to the second state and the second valve assembly 8 is switched to the fourth state to allow the mixed growth gas source to be introduced into the first operating pipe 1 and the doping gas source to be introduced into the second operating pipe 12.

[0087] The first preset duration can be 1.5 min, 2 min, 2.5 min or 3 min, etc. The specific value of the first preset duration is not limited in the embodiments of this application.

[0088] In the gas source control method of the silicon carbide epitaxial furnace provided in this application embodiment, the mixing unit 5 can realize the mixing of silicon source and carbon source before entering the first bypass pipe 2 and the first running pipe 1, thereby realizing the mixing of silicon source and carbon source before entering the epitaxial reaction chamber 15. This can reduce the time deviation of silicon source and carbon source entering the epitaxial reaction chamber 15, and improve the instantaneous uniformity of silicon source and carbon source entering the epitaxial reaction chamber 15. For example, it can realize the synchronous entry of carbon source and silicon source into epitaxial reaction chamber 15, thereby reducing the probability that silicon carbide substrate comes into contact with a single gas source (carbon source or silicon source) first, thereby reducing the defect density of epitaxial layer, and improving the withstand voltage performance and service life of silicon carbide device.

[0089] In the gas source control method of the silicon carbide epitaxial furnace, the mixed gas source can be introduced into the first bypass pipe 2 and the first operating pipe 1, and the doping gas source can be introduced into the second bypass pipe 13 and the second operating pipe 12. This ensures that the mixed growth gas source does not include the doping gas source, which reduces the influence of the mixed growth gas source on the control of the doping gas source. It also allows for the independent control of the doping gas source, enabling the fabrication of complex doped structures such as steep doping concentration steps, thereby meeting the performance requirements of special silicon carbide devices. Furthermore, when the doping gas source includes ammonia and the silicon source includes silane, dichlorosilane, trichlorosilane, or silicon tetrachloride, the doping source, including ammonia, is not pre-mixed with the growth gas source (silicon source). This reduces the degree and probability of ammonolysis reaction between ammonia and silicon source, thereby reducing the probability of solid particles appearing in the gas source. It also reduces the probability of blockage and corrosion of components such as gas pipelines, valves, mass flow controllers, and nozzles, thus reducing the maintenance cost of the silicon carbide epitaxial furnace. Additionally, it reduces unnecessary consumption of reactants, thereby lowering the production cost of silicon carbide devices.

[0090] In the gas source control method of the silicon carbide epitaxial furnace provided in this application embodiment, the mixed growth gas source is first introduced into the first bypass pipe 2 and the doping gas source is introduced into the second bypass pipe 13. After a first preset time, the mixed growth gas source is then introduced into the first operating pipe 1 and the doping gas source is introduced into the second operating pipe 12. In this way, the C / Si ratio of the mixed growth gas source can be adjusted during the process of the mixed growth gas source being introduced into the first bypass pipe 2, so as to ensure that the C / Si ratio of the mixed growth gas source in the first operating pipe 1 meets the requirements, thereby improving the performance of the silicon carbide device.

[0091] In some embodiments, the gas source control method for silicon carbide epitaxial furnace further includes:

[0092] S2´: Adjust the flow rate of the silicon source and / or the flow rate of the carbon source so that the C / Si ratio of the mixed growth gas source in the first operating tube 1 is 0.45-0.75 in the buffer layer stage and 0.75-1.05 in the epitaxial layer stage.

[0093] For example, the flow rate of the silicon source is adjusted so that the C / Si ratio of the mixed growth gas source in the first operating tube 1 ranges from 0.45 to 0.75 in the buffer layer stage and from 0.75 to 1.05 in the epitaxial layer stage; or, the flow rate of the carbon source is adjusted so that the C / Si ratio of the mixed growth gas source in the first operating tube 1 ranges from 0.45 to 0.75 in the buffer layer stage and from 0.75 to 1.05 in the epitaxial layer stage; or, the flow rates of the silicon source and the carbon source are adjusted so that the C / Si ratio of the mixed growth gas source in the first operating tube 1 ranges from 0.45 to 0.75 in the buffer layer stage and from 0.75 to 1.05 in the epitaxial layer stage.

[0094] It should be noted that S2 above includes S2' above.

[0095] In the above embodiments, by controlling the C / Si ratio of the mixed growth gas source in the first operating tube 1 within the above-mentioned value range, the performance of the silicon carbide device can be improved.

[0096] In some embodiments, the gas source control method for the silicon carbide epitaxial furnace between the buffer layer stage and the epitaxial layer stage further includes:

[0097] S2´´: The mixed growth gas source is introduced into the first bypass pipe 2 and the doping gas source is introduced into the second bypass pipe 13. After a second preset time, the mixed growth gas source is introduced into the first operating pipe 1 and the doping gas source is introduced into the second operating pipe 12.

[0098] The specific value of the second preset duration can be referenced to the first preset duration. The first preset duration and the second preset duration can be equal or unequal, and this application embodiment does not limit this. For the sake of simplifying the control method, the first preset duration and the second preset duration are equal.

[0099] In the above embodiment, after the buffer layer stage is completed, the mixed growth gas source is introduced into the first bypass tube 2 and the doping gas source is introduced into the second bypass tube 13. After a second preset time, the mixed growth gas source is introduced into the first operating tube 1 and the doping gas source is introduced into the second operating tube 12 to start the epitaxial layer stage. In this way, the C / Si ratio of the mixed growth gas source can be adjusted during the process of the mixed growth gas source being introduced into the first bypass tube 2, so as to ensure that the C / Si ratio of the mixed growth gas source in the first operating tube 1 meets the requirements, thereby improving the performance of the silicon carbide device. At the same time, the second preset time can also provide a reserved time for the doping gas source to be introduced into the second bypass tube 13.

[0100] It should be noted that the flow rates of the silicon source and / or carbon source are adjusted so that the C / Si ratio of the mixed growth gas source in the first operating tube 1 is in the range of 0.45-0.75 during the buffer layer stage. This adjustment is performed before the buffer layer stage and before the mixed growth gas source and doping gas source are introduced into the first operating tube 1. For example, the flow rates of the silicon source and / or carbon source are adjusted so that the C / Si ratio of the mixed growth gas source in the first operating tube 1 is in the range of 0.45-0.75 during the buffer layer stage, and this is performed during the process of introducing the mixed growth gas source and doping gas source into the first bypass tube 2.

[0101] It should be noted that the flow rates of the silicon source and / or carbon source are adjusted so that the C / Si ratio of the mixed growth gas source in the first operating tube 1 ranges from 0.75 to 1.05 during the epitaxial layer stage, and this is performed after the buffer layer stage and before the mixed growth gas source and doping gas source are introduced into the first operating tube 1. For example, the flow rates of the silicon source and / or carbon source are adjusted so that the C / Si ratio of the mixed growth gas source in the first operating tube 1 ranges from 0.75 to 1.05 during the epitaxial layer stage, and this is performed after the buffer layer stage and during the process of introducing the mixed growth gas source and doping gas source into the first bypass tube 2.

[0102] The technical features mentioned above, as well as those shown individually in the accompanying drawings, can be combined arbitrarily, provided that the combined technical features are not contradictory. All feasible combinations of features are the technical content explicitly described herein. Any one of the multiple sub-features contained in the same statement can be applied independently, without necessarily being applied together with other sub-features.

[0103] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A gas path system for a silicon carbide epitaxial furnace, characterized in that, include: The first operating tube (1) and the second operating tube (12) are connected to the epitaxial reaction chamber (15) by their respective outlets. The first bypass pipe (2) and the second bypass pipe (13) are both used for venting air. Silicon source delivery pipe (3), the silicon source delivery pipe (3) is used to deliver silicon source, Carbon source delivery pipe (4), the carbon source delivery pipe (4) is used to deliver carbon source; The mixing unit (5) is connected to the inlet of the mixing unit (5) by both the silicon source delivery pipe (3) and the carbon source delivery pipe (4). The mixing unit (5) is used to mix silicon source and carbon source to obtain mixed growth gas source. First valve assembly (6), the first valve assembly (6) is used to switch the outlet of the mixing unit (5) to be connected to the first bypass pipe (2) or the outlet of the mixing unit (5) to be connected to the first operating pipe (1). Doping gas source delivery pipe (7), the doping gas source delivery pipe (7) is used to deliver doping gas source; The second valve assembly (8) is used to switch the doped gas source delivery pipe (7) to the second operating pipe (12) or the doped gas source delivery pipe (7) to the second bypass pipe (13).

2. The gas path system of the silicon carbide epitaxial furnace according to claim 1, characterized in that, It also includes a check valve (9), which is connected in series in the pipeline of the mixing unit (5) and is located between the outlet of the mixing unit (5) and the inlet of the mixing unit (5).

3. The gas path system of the silicon carbide epitaxial furnace according to claim 1, characterized in that, The mixing unit (5) includes a mixing pipe (5a), and the inlet and outlet of the mixing unit (5) are both the openings of the mixing pipe (5a).

4. The gas path system of the silicon carbide epitaxial furnace according to claim 3, characterized in that, The mixing pipe (5a) includes a first mixing branch pipe (501), a second mixing branch pipe (502), and a mixing main pipe (503). The outlets of the silicon source delivery pipe (3) and the carbon source delivery pipe (4) are connected to the inlet of the mixing main pipe (503), and the inlets of the first mixing branch pipe (501) and the second mixing branch pipe (502) are connected to the outlet of the mixing main pipe (503). The outlet of the first mixing branch pipe (501) is connected to the first operating pipe (1), and the outlet of the second mixing branch pipe (502) is connected to the first bypass pipe (2).

5. The gas path system of the silicon carbide epitaxial furnace according to claim 4, characterized in that, The first valve assembly (6) includes a first three-way valve (601), and the inlets of the first mixing branch (501) and the second mixing branch (502) are connected to the outlet of the mixing main pipe (503) through the first three-way valve (601).

6. The gas path system of the silicon carbide epitaxial furnace according to claim 4, characterized in that, The first valve assembly (6) includes a first valve (602) and a second valve (603), the first valve (602) being connected in series with the first mixing branch pipe (501), and the second valve (603) being connected in series with the second mixing branch pipe (502).

7. The gas path system of the silicon carbide epitaxial furnace according to claim 1, characterized in that, The silicon source delivery pipe (3) and the carbon source delivery pipe (4) are connected to the inlet of the mixing unit (5) through a second three-way valve (10), which is used to adjust the flow rate of the silicon source and the flow rate of the carbon source.

8. The gas path system of the silicon carbide epitaxial furnace according to claim 1, characterized in that, The second bypass pipe (13) is connected in series with a pressure control valve (16).

9. The gas path system of the silicon carbide epitaxial furnace according to claim 1, characterized in that, In the buffer layer stage, the C / Si value of the mixed growth gas source in the first operating tube (1) ranges from 0.45 to 0.75; in the epitaxial layer stage, the C / Si value of the mixed growth gas source in the first operating tube (1) ranges from 0.75 to 1.

05.

10. The gas path system of the silicon carbide epitaxial furnace according to any one of claims 1-9, characterized in that, The doping gas source includes ammonia; And / or, the silicon source includes trichlorosilane; And / or, the carbon source includes ethylene.

11. A gas source control method for a silicon carbide epitaxial furnace, characterized in that, The gas source control method for the silicon carbide epitaxial furnace is applicable to the gas path system of the silicon carbide epitaxial furnace as described in any one of claims 1-10, and the gas source control method for the silicon carbide epitaxial furnace includes: A silicon source is introduced into the mixing unit (5) through a silicon source delivery pipe (3), and a carbon source is introduced into the mixing unit (5) through a carbon source delivery pipe (4) to obtain a mixed growth gas source; The mixed growth gas source is introduced into the first bypass pipe (2), and the doping gas source is introduced into the second bypass pipe (13). After a first preset time, the mixed growth gas source is introduced into the first operating pipe (1), and the doping gas source is introduced into the second operating pipe (12) to carry out silicon carbide epitaxial growth.

12. The gas source control method for a silicon carbide epitaxial furnace according to claim 11, characterized in that, The gas source control method for the silicon carbide epitaxial furnace also includes: Adjust the flow rate of the silicon source and / or the flow rate of the carbon source so that the C / Si ratio of the mixed growth gas source in the first operating tube (1) is 0.45-0.75 in the buffer layer stage and 0.75-1.05 in the epitaxial layer stage.

13. The gas source control method for a silicon carbide epitaxial furnace according to claim 12, characterized in that, Between the buffer layer stage and the epitaxial layer stage, the gas source control method for the silicon carbide epitaxial furnace further includes: The mixed growth gas source is introduced into the first bypass pipe (2), and the doping gas source is introduced into the second bypass pipe (13). After a second preset time, the mixed growth gas source is introduced into the first operating pipe (1), and the doping gas source is introduced into the second operating pipe (12). The first preset duration and the second preset duration may be equal or unequal.

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