Method for cleaning preheating ring in epitaxial cavity and epitaxial device

Abstract

The invention provides a method for cleaning a preheating ring in an epitaxial cavity and an epitaxial device. A covering layer can be prevented from appearing at a corresponding turbulent flow position on the preheating ring. The method comprises a first cycle and a second cycle, each of the first circulation and the second circulation comprises a growth process and a cleaning process; in the first circulation, the base rotates clockwise and anticlockwise in an XY plane respectively in the growing process and the cleaning process; in the second circulation, the base rotates anticlockwise and clockwise in the XY plane in the growing process and the cleaning process respectively, and a covering layer of an epitaxial material can be prevented from being generated at the fixed position of the preheating ring in the mode. According to the technical scheme, the substrate directions are opposite in the epitaxial growth process and the cleaning process. Through repeated alternation of the forward rotation circulation and the reverse rotation circulation, an epitaxial material covering layer is prevented from being generated at the fixed position of the preheating ring.

Description

Technical Field

[0001] This invention relates to the field of semiconductor equipment, and more particularly to a method for cleaning a preheating ring inside an epitaxial cavity and an epitaxial apparatus. Background Technology

[0002] In semiconductor manufacturing, epitaxial wafers with silicon epitaxial layers are the fundamental material for manufacturing IC devices. During the epitaxial wafer manufacturing process, epitaxial growth equipment deposits an additional silicon epitaxial layer on the existing silicon substrate. This equipment places a single wafer inside a quartz cavity, heats it to provide sufficient growth temperature, and introduces a gaseous substance containing silicon to grow the epitaxial layer. The quality of the silicon epitaxial layer is crucial to the performance of subsequent IC devices; even minute particle contamination or metal contamination can cause subsequent device failures, thus affecting the yield during IC processing. With the development of semiconductor IC manufacturing processes, wafers with epitaxial layers have reached 300mm. To ensure the quality of epitaxial wafers, epitaxial production equipment needs to maintain a high level of cleanliness to avoid additional particle contamination.

[0003] A significant source of particulate contamination in epitaxial growth equipment is the silicon capping layer formed within the chamber after epitaxial growth. To achieve epitaxial growth, a 300mm wafer is placed on a substrate, and silicon is supplied via TCS gas. The TCS gas is first heated to a certain temperature through a preheating ring before flowing over the positive surface of the wafer to complete the growth. Therefore, the silicon capping layer is generated in the following areas within the chamber: inside the quartz chamber, on the surface of the graphite substrate, and on the surface of the preheating ring. This silicon capping layer is amorphous or polycrystalline silicon that grows from the decomposition of TCS within the quartz chamber, on the surface of the graphite substrate, and on the surface of the preheating ring. This silicon capping layer peels off during the epitaxial growth process, resulting in particulate contamination.

[0004] Currently, the industry uses a method to avoid silicon capping contamination by performing an HCl cleaning process after epitaxial growth to remove the silicon capping layer. Specifically, after the epitaxial growth step is completed, the wafer is transferred out of the cavity. Instead of directly transferring it to the next wafer for epitaxial growth, HCl gas is introduced, and the silicon capping layer inside the quartz cavity, on the surface of the graphite substrate, and on the surface of the preheating ring is etched by the high-temperature HCl gas. After the HCl cleaning step is completed, the next wafer growth step is performed. This alternating growth / cleaning cycle can effectively remove most of the silicon capping layer.

[0005] To ensure uniform growth during epitaxial growth and uniform removal of the silicon capping layer during cleaning, a rotating substrate is used to create localized non-uniformities. The rotating substrate causes the airflow to rotate in a corresponding direction. At certain points, this rotating airflow will collide with the incoming airflow, creating turbulence at these points. This turbulence negatively impacts epitaxial growth and silicon capping layer etching. Specifically, it increases the residence time of the TCS (Transient Controlled Space) at turbulent locations on the preheating ring during epitaxial growth, resulting in a thicker silicon capping layer at these locations. Simultaneously, during cleaning, the HCl etching effect at these turbulent locations on the preheating ring is weakened, leading to poorer silicon capping layer removal. Finally, as the cumulative thickness of the epitaxial growth increases, the silicon capping layer at the turbulent locations on the preheating ring thickens, resulting in particulate contamination. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method and device for cleaning a preheating ring in an epitaxial cavity, which can prevent the formation of a covering layer at the corresponding turbulent position on the preheating ring.

[0007] To address the aforementioned problems, this invention provides a method for cleaning a preheating ring within an epitaxial cavity, comprising a first cycle and a second cycle; each of the first and second cycles includes a growth process and a cleaning process; in the first cycle, the base rotates clockwise and counterclockwise in the XY plane during the growth and cleaning processes, respectively; in the second cycle, the base rotates counterclockwise and clockwise in the XY plane during the growth and cleaning processes, respectively. This method can prevent the formation of a covering layer of epitaxial material at the fixed position of the preheating ring.

[0008] Optionally, the growth process specifically includes the following steps: transferring the wafer to a substrate within the epitaxial cavity; controlling the substrate to rotate clockwise or counterclockwise in the XY plane; introducing TCS gas through the gas inlet of the epitaxial cavity, using the TCS gas to provide a silicon source, and performing epitaxial growth on the wafer; after the epitaxial growth is completed, stopping the substrate rotation and stopping the introduction of TCS gas, thus ending the growth process.

[0009] Optionally, the cleaning process is performed after the growth process is completed, and specifically includes the following steps: transferring the completed epitaxial wafer out of the epitaxial cavity; controlling the substrate to rotate counterclockwise or clockwise in the XY plane; introducing HCl etching gas through the gas inlet of the epitaxial cavity, and using HCl gas to etch and clean the epitaxial material covering layer, including the surface of the preheating ring, inside the cavity; after cleaning, stopping the rotation of the substrate and stopping the introduction of HCl etching gas, and the cleaning process ends.

[0010] Optionally, the base may be rotated at a speed of 10 to 100 rpm.

[0011] Optionally, the first loop and the second loop may be performed alternately multiple times.

[0012] Optionally, the growth process and the cleaning process in each cycle are alternated multiple times.

[0013] To address the aforementioned problems, this invention provides an epitaxial apparatus, comprising an epitaxial cavity, a substrate, an air intake assembly, and a control unit. The epitaxial cavity contains a substrate for supporting a wafer, and a preheating ring surrounds the substrate. The air intake assembly is connected to the epitaxial cavity and is used to introduce epitaxial source gas and etching gas for cleaning into the cavity. The control unit is electrically connected to both the substrate and the air intake assembly, and is used to control the apparatus to execute a first cycle and a second cycle, each of which includes a growth process and a cleaning process. In the first cycle, the control unit controls the substrate to rotate clockwise along the XY plane during the growth process and counterclockwise along the XY plane during the cleaning process. In the second cycle, the control unit controls the substrate to rotate counterclockwise along the XY plane during the growth process and clockwise along the XY plane during the cleaning process. Through the execution of the first and second cycles, the formation of a capping layer of epitaxial material at the fixed position of the preheating ring is avoided.

[0014] The aforementioned technique involves opposing base directions during the epitaxial growth and cleaning processes. This alternating forward and reverse rotation prevents the formation of an epitaxial material coating at the fixed position of the preheating ring.

[0015] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit the invention. Techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and apparatus should be considered part of the specification. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Appendix Figure 1 The diagram shows the implementation steps of a preheating ring cleaning method for an epitaxial cavity according to the present invention.

[0018] Appendix Figure 2 The diagram shown is a structural schematic of a specific embodiment of the epitaxial device described in this invention.

[0019] Appendix Figure 3 The diagram shown is a structural schematic of the base and preheating ring corresponding to a specific embodiment of the epitaxial device described in this invention.

[0020] Appendix Figure 4 The diagram shown is a specific embodiment of the epitaxial device of the present invention, corresponding to the turbulence generated by the rotating base causing the airflow to rotate in the corresponding direction. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Appendix Figure 1 The diagram illustrates the implementation steps of a preheating ring cleaning method within an epitaxial cavity according to the present invention. The method includes a first cycle S11 and a second cycle S12. Each of the first and second cycles includes a growth process and a cleaning process. In the first cycle S11, the base rotates clockwise and counterclockwise in the XY plane during the growth and cleaning processes, respectively; in the second cycle S12, the base rotates counterclockwise and clockwise in the XY plane during the growth and cleaning processes, respectively. This method avoids the formation of a covering layer of epitaxial material at the fixed position of the preheating ring.

[0023] In different specific embodiments described above, the first and second cycles can be alternated multiple times. For example, they can be set to alternate 3-10 times. Each time they alternate, the control unit automatically switches the rotation direction of the base during the growth and cleaning processes without manual intervention. Repeated growth and cleaning within a single cycle: To further improve the cleaning effect, the growth and cleaning processes can be alternated multiple times within a single cycle. That is, after completing one growth and cleaning cycle, the cycle type is not switched, and the growth and cleaning operations of that cycle are performed again, further reducing the residual epitaxial material on the surface of the preheated ring.

[0024] The method described in this specific embodiment can solve the technical problem of epitaxial material coating and particulate contamination that easily occurs at the fixed position of the preheating ring in existing epitaxial production. By alternately executing the first and second cycles, precise control of epitaxial growth and cleaning is achieved, avoiding localized epitaxial material accumulation in the preheating ring and ensuring the quality of epitaxial wafers.

[0025] Appendix Figure 2 The diagram shown is a structural schematic of a specific embodiment of an epitaxial device implementing the above steps. (Attached) Figure 3 This is a structural diagram of the corresponding base and preheating ring. (See attached reference.) Figure 2 and attached Figure 3 As shown, the epitaxial device includes: an epitaxial cavity 21, a base 22, an air intake assembly 23, and a control unit 24.

[0026] The epitaxial cavity 21 contains a base 22 for supporting the wafer, and a preheating ring 25 surrounds the base 22. In this specific embodiment, the epitaxial cavity 21 is made of quartz material, which has high temperature resistance and corrosion resistance. It forms a closed epitaxial growth and cleaning space. The inner wall of the cavity is polished to reduce the risk of initial contamination. A preheating ring is fixedly installed inside the cavity, surrounding the outside of the base, and is used to preheat the introduced epitaxial source gas (such as TCS gas) to the preset growth temperature. The base is made of graphite material with a SiC coating on the surface, and is used to support the wafer. The base can rotate around its central axis in the XY plane. The rotation direction can be switched by a control unit, and the rotation speed can be adjusted from 10 to 100 rpm, preferably 50 rpm, to balance growth uniformity and airflow stability.

[0027] The air intake assembly 23 is connected to the epitaxial cavity 21 and is used to introduce epitaxial source gas and etching gas for cleaning into the epitaxial cavity 21. In this specific embodiment, the epitaxial source gas is TCS and the etching gas for cleaning is HCl. The air intake assembly 21 includes a gas storage tank, a flow controller, a gas conduit, and an air inlet and an air outlet of the cavity. The air inlet is located on the side wall of the epitaxial cavity and can respectively introduce TCS gas (purity ≥99.999%, used as a silicon source) and HCl etching gas (purity ≥99.99%, used for cleaning the epitaxial material capping layer). The flow controller can precisely control the gas introduction rate (TCS gas rate is 5~30 SLM, HCl gas rate is 10-100 SLM).

[0028] The control unit 24 is electrically connected to the base 22 and the air intake assembly 23, respectively, and is used to control the device to execute a first cycle and a second cycle, each of which includes a growth process and a cleaning process. In the first cycle, the control unit controls the base to rotate clockwise along the XY plane during the growth process and counterclockwise along the XY plane during the cleaning process. In the second cycle, the control unit controls the base to rotate counterclockwise along the XY plane during the growth process and clockwise along the XY plane during the cleaning process. Through the execution of the above-mentioned first and second cycles, the formation of an epitaxial material covering layer at the fixed position of the preheating ring is avoided. In this specific embodiment, the control unit adopts a PLC controller, which is electrically connected to the drive motor of the base and the flow controller of the air intake assembly, respectively. It can preset the cycle program and automatically control the rotation direction, rotation start and stop, and the introduction and stop of TCS gas and HCl gas. Figure 2 The diagram shows a clockwise rotation. The structure for counter-clockwise rotation is similar and will be omitted here.

[0029] The base rotation speed is set in the range of 10-100 rpm because if the speed is too low, the airflow is prone to stagnation in some areas, resulting in uneven epitaxial growth and incomplete cleaning; if the speed is too high, it will cause airflow turbulence inside the cavity, which will affect the contact efficiency between the gas and the wafer surface. The optimal value of 50 rpm has been verified by multiple experiments and can ensure growth uniformity while avoiding excessive airflow turbulence.

[0030] A TCS gas rate of 5~30 SLM can meet the silicon source requirements for epitaxial growth of 300mm wafers, avoiding insufficient silicon source leading to slow growth rate or excessive silicon source causing waste; an HCl gas rate of 10~100 SLM can ensure that the etching of the epitaxial material capping layer is completed within a reasonable time.

[0031] Using the above-mentioned apparatus and method, the first and second cycles are executed alternately. Each cycle includes a growth process and a cleaning process, which enables precise control of epitaxial growth and cleaning, avoids local epitaxial material accumulation in the preheating ring, and ensures the quality of epitaxial wafers.

[0032] During the first cycle S11, the base rotates clockwise and counterclockwise in the XY plane during the growth and cleaning processes, respectively.

[0033] The growth process includes: transferring the wafer to be grown through a transfer gate onto a substrate within the epitaxial cavity, ensuring alignment between the wafer center and the substrate center. A command is sent from the control unit to start the substrate drive motor, controlling the substrate to rotate clockwise at 50 rpm in the XY plane, maintaining a horizontal position during rotation to prevent wafer misalignment. The control unit then controls the flow controller of the gas inlet assembly to open the valve of the TCS gas storage tank, allowing TCS gas to be introduced into the cavity through the inlet at a rate of 20 SLM. After preheating to 1150°C via a preheating ring, the TCS gas flows over the positive surface of the wafer, performing epitaxial growth on the silicon wafer. The growth time is set according to the required epitaxial layer thickness. After epitaxial growth is complete, the control unit first closes the TCS gas valve, stopping the TCS gas supply, and then stops the substrate drive motor, halting substrate rotation, thus ending the growth process.

[0034] The cleaning process includes: After the growth process is completed, the epitaxial wafer transfer door is opened, and the completed epitaxial wafer is transferred from the cavity to the wafer storage box. The wafer transfer mechanism then resets and the transfer door closes. The control unit sends a command to start the substrate drive motor, controlling the substrate to rotate counterclockwise in the XY plane at 50 rpm, in the opposite direction to the growth process, ensuring a change in airflow direction and covering different areas of the preheating ring. The control unit controls the flow controller of the air intake assembly to open the valve of the HCl etching gas storage tank, introducing HCl etching gas into the cavity through the air inlet at a rate of 50 SLM. The HCl gas flows inside the cavity, etching and cleaning the epitaxial material coating (amorphous silicon or polycrystalline silicon) on the inner wall of the cavity, the surface of the substrate, and the surface of the preheating ring. The cleaning time is set to 8 minutes. After cleaning, the control unit first closes the HCl etching gas valve, stopping the HCl gas supply, and then controls the substrate drive motor to stop working, the substrate stops rotating, and the cleaning process ends.

[0035] This completes the first cycle. In other implementations, the growth and cleaning processes can be repeated multiple times.

[0036] During the second cycle S12, the base rotates counterclockwise and clockwise in the XY plane during the growth and cleaning processes, respectively.

[0037] The growth process includes: transferring the wafer to be grown through a transfer gate onto a substrate within the epitaxial cavity, ensuring alignment between the wafer center and the substrate center. A command is sent from the control unit to start the substrate drive motor, controlling the substrate to rotate counter-clockwise at 50 rpm in the XY plane, maintaining a horizontal position during rotation to prevent wafer misalignment. The control unit controls the flow controller of the gas inlet assembly to open the valve of the TCS gas storage tank, allowing TCS gas to be introduced into the cavity through the inlet at a rate of 20 SLM. After preheating to 1150°C via a preheating ring, the TCS gas flows over the positive surface of the wafer, performing epitaxial growth on the silicon wafer. The growth time is set according to the required epitaxial layer thickness. After epitaxial growth is complete, the control unit first closes the TCS gas valve, stopping the TCS gas supply, and then controls the substrate drive motor to stop operating, halting substrate rotation, thus ending the growth process.

[0038] The cleaning process includes: After the growth process is completed, the epitaxial wafer transfer door is opened, and the completed epitaxial wafer is transferred from the cavity to the wafer storage box. The wafer transfer mechanism then resets and the transfer door closes. The control unit sends a command to start the substrate drive motor, controlling the substrate to rotate clockwise in the XY plane at 50 rpm, in the opposite direction to the growth process, ensuring a change in airflow direction and covering different areas of the preheating ring. The control unit controls the flow controller of the air intake assembly to open the valve of the HCl etching gas storage tank, introducing HCl etching gas into the cavity through the air inlet at a rate of 50 SLM. The HCl gas flows inside the cavity, etching and cleaning the epitaxial material coating (amorphous silicon or polycrystalline silicon) on the inner wall of the cavity, the surface of the substrate, and the surface of the preheating ring. The cleaning time is set to 8 minutes. After cleaning, the control unit first closes the HCl etching gas valve, stopping the introduction of HCl gas, and then controls the substrate drive motor to stop working, the substrate stops rotating, and the cleaning process ends.

[0039] This completes the second cycle. In other implementations, the growth and cleaning processes can be repeated multiple times.

[0040] Based on production needs, the first and second cycles can be alternated multiple times. For example, it can be set to alternate 3-10 times. During each alternation, the control unit automatically switches the rotation direction of the base during the growth and cleaning processes without manual intervention. Repeated growth and cleaning within a single cycle: To further improve the cleaning effect, the growth and cleaning processes can be alternated multiple times within a single cycle. That is, after completing one growth and cleaning cycle, the cycle type is not switched, and the growth and cleaning operations of that cycle are executed again, further reducing the residual epitaxial material on the surface of the preheating ring.

[0041] Appendix Figure 4The diagram illustrates the turbulence generated when a rotating base causes the airflow to rotate in a corresponding direction. At certain points, the rotating airflow driven by the base will collide with the intake airflow, creating turbulence at these points. This turbulence can negatively impact epitaxial growth and the etching of the epitaxial capping layer. Therefore, during the growth process, the base should be rotated clockwise / counterclockwise within the XY plane. Figure 4 The turbulent flow at the location creates a capping layer of epitaxial material. However, in the aforementioned technical solution, during the cleaning process, the base is rotated counterclockwise / counterclockwise in the XY plane. At this point, HCl etching at the turbulent location in the figure does not generate turbulence, and the HCl etching effect is not reduced, which helps to completely remove the capping layer of epitaxial material.

[0042] It should be noted that references to "an embodiment," "an embodiment," "an exemplary embodiment," "some embodiments," etc., in the specification indicate that the described embodiments may include specific features, structures, or characteristics, but each embodiment may not necessarily include that specific feature, structure, or characteristic. Furthermore, such phrases do not necessarily refer to the same embodiment. In addition, when a specific feature, structure, or characteristic is described in connection with an embodiment, whether explicitly described or not, implementing such a feature, structure, or characteristic in conjunction with other embodiments is within the knowledge of those skilled in the art.

[0043] It should be noted that the terms "comprising" and "having," and their variations, used in this invention document are intended to cover non-exclusive inclusion. The terms "first," "second," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence, unless explicitly indicated by the context. It should be understood that such data used interchangeably where appropriate. Furthermore, embodiments and features within embodiments of this invention can be combined with each other unless otherwise specified. In addition, descriptions of well-known components and technologies have been omitted in the above description to avoid unnecessarily obscuring the concepts of this invention. In the various embodiments described above, each embodiment focuses on its differences from other embodiments; similar or identical parts between embodiments can be referred to interchangeably.

[0044] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method of cleaning a preheating ring in an epitaxial chamber, the method comprising: providing a preheating ring having a plurality of holes; and providing a cleaning gas to the preheating ring through the plurality of holes. Including the first and second cycles; The first and second cycles each include a growth process and a cleaning process; During the first cycle, the base rotates clockwise and counterclockwise in the XY plane during the growth and cleaning processes, respectively. During the second cycle, the base rotates counterclockwise and clockwise in the XY plane during the growth and cleaning processes, respectively. The above method can avoid the formation of an epitaxial material covering layer at the fixed position of the preheating ring.

2. The method for cleaning the preheating ring inside the epitaxial cavity according to claim 1, characterized in that, The growth process specifically includes the following steps: The wafer is transferred to the base inside the epitaxial cavity; Control the base to rotate clockwise or counterclockwise in the XY plane; TCS gas is introduced through the gas inlet of the epitaxial cavity, and the silicon source is provided by the TCS gas to perform epitaxial growth on the wafer. After epitaxial growth is complete, stop rotating the base and stop supplying TCS gas; the growth process is then finished.

3. The method of claim 1, wherein the preheating ring is made of a material selected from the group consisting of: stainless steel, titanium, and aluminum. The cleaning process is performed after the growth process is completed, and specifically includes the following steps: The completed epitaxial wafer is transferred out of the epitaxial cavity; Control the base to rotate counterclockwise or clockwise in the XY plane; HCl etching gas is introduced through the air inlet of the epitaxial cavity to etch and clean the epitaxial material coating layer inside the cavity, including the surface of the preheating ring. After cleaning, stop rotating the base and stop supplying HCl etching gas; the cleaning process is now complete.

4. The epitaxial in-cavity preheating ring cleaning method of claim 2 or 3, wherein, The base is rotated at a speed of 10 to 100 rpm.

5. The method for cleaning the preheating ring inside the epitaxial cavity according to claim 1, characterized in that, The first and second cycles alternate multiple times.

6. The method for cleaning the preheating ring inside the epitaxial cavity according to claim 1, characterized in that, The growth and cleaning processes in each cycle are repeated multiple times.

7. An epitaxial device, characterized in that, Includes an extended cavity, base, intake assembly, and control unit; The epitaxial cavity is provided with a base for supporting the wafer, and a preheating ring is provided around the base; The air intake assembly is connected to the epitaxial cavity and is used to introduce epitaxial source material gas and etching gas for cleaning into the cavity. The control unit is electrically connected to the base and the air intake assembly, respectively, and is used to control the device to execute a first cycle and a second cycle. Each of the first and second cycles includes a growth process and a cleaning process. In the first cycle, the control unit controls the base to rotate clockwise along the XY plane during the growth process and counterclockwise along the XY plane during the cleaning process. In the second cycle, the control unit controls the base to rotate counterclockwise along the XY plane during the growth process and clockwise along the XY plane during the cleaning process. By executing the above-mentioned first and second cycles, the formation of an epitaxial material covering layer at the fixed position of the preheating ring is avoided.

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