Side edge auxiliary grounding device and plasma processing device

Abstract

The application provides a side edge auxiliary grounding device and a plasma processing device, the side edge auxiliary grounding device is arranged in the periphery of a pedestal in a plasma reaction cavity, and comprises a bearing part fixedly connected with the pedestal, a support fixed on the bearing part, a balance weight rod arranged at the top end of the support through a rotating support point, the first end of the balance weight rod is heavier than the second end, and the balance weight rod can rotate around the rotating support point; when the pedestal moves to a processing position, the second end of the balance weight rod is in contact with a protruding part protruding inward from the side wall of the reaction cavity, so as to form a radio frequency return path. The application guarantees the stable grounding of the side edge of the pedestal, forms a stable radio frequency return path, and further improves the uniformity of the distribution of the plasma.

Description

Technical Field

[0001] This invention relates to the field of semiconductor equipment technology, and in particular to a side auxiliary grounding device and a plasma processing device. Background Technology

[0002] Plasma-enhanced chemical vapor deposition (PECVD), as a highly efficient thin-film deposition technology, has been widely used for surface treatment of various substrate materials, such as semiconductor substrates, solar panels, and liquid crystal display (LCD) and organic light-emitting diode (OLED) substrates used in display manufacturing. A PECVD apparatus typically includes a vacuum reaction chamber containing a base for supporting the substrate. A precursor gas is introduced into the reaction chamber through an inlet mechanism located at the top and is uniformly distributed within the chamber. By coupling one or more radio frequency (RF) sources to the reaction chamber and applying RF power, the precursor gas within the chamber is excited into plasma, thereby forming a thin film of material on the substrate surface. A gas distribution plate is typically connected to the RF power supply, while the base is connected to the reaction chamber, thus forming an RF current loop.

[0003] To improve the uniformity of plasma distribution during the process, a side auxiliary grounding device is provided around the base. Existing side auxiliary grounding devices are mostly spring structures, which are prone to particulate contaminants and poor contact after prolonged processing. Therefore, an improved side auxiliary grounding device is urgently needed to enhance the stability of side RF grounding or the formation of an RF return path. Summary of the Invention

[0004] The purpose of this invention is to provide a side auxiliary grounding device and a plasma processing device that include a counterweight structure to ensure stable grounding of the base side, thereby forming a stable radio frequency return path and improving the uniformity of plasma distribution. The side auxiliary grounding device has the advantages of simple structure and low particulate contaminant generation.

[0005] To achieve the above objectives, the present invention provides a side auxiliary grounding device, which is disposed circumferentially on a base within a plasma reaction chamber, comprising: a support portion fixedly connected to the base; a bracket fixed to the support portion; and a counterweight rod disposed at the top of the bracket via a pivot point. The first end of the counterweight rod has a greater counterweight than the second end and can rotate around the pivot point. When the base moves to the processing position, the second end of the counterweight rod contacts an inwardly protruding portion of the sidewall of the reaction chamber, forming a radio frequency return path.

[0006] Optionally, the distance from the pivot point to the first end of the counterweight rod is less than or equal to the distance from the pivot point to the second end of the counterweight rod.

[0007] Optionally, when the base is in a non-processing position, the first end of the counterweight bar is always in contact with the load-bearing part.

[0008] Optionally, the angle between the counterweight bar and the horizontal plane is not less than 5°.

[0009] Optionally, the bearing portion is located below the base, and the second end of the counterweight rod is not higher than the lower surface of the base.

[0010] Optionally, the supporting part is an "L"-shaped supporting plate; the vertical part of the supporting plate is connected to the base, and the horizontal part is used to support the bracket and the first end of the counterweight rod.

[0011] Optionally, the load-bearing part, the bracket, and the counterweight bar are all made of conductive materials.

[0012] The present invention also provides a plasma processing apparatus, comprising: a reaction chamber; a spray head assembly disposed at the top of the reaction chamber; a base disposed at the bottom of the reaction chamber, opposite to the spray head assembly, for supporting a substrate; the base being circumferentially provided with a side auxiliary grounding device as described above; and a driving device disposed at the bottom of the base for driving the base to move to a processing position or a cleaning position.

[0013] Optionally, the reaction chamber includes two opposing first sidewalls and two opposing second sidewalls; each first sidewall has an inwardly protruding first protrusion on its inner wall, the first length of which extends along the first sidewall is less than the length of the inner wall of the first sidewall; each second sidewall has an inwardly protruding second protrusion on its inner wall, the second length of which extends along the second sidewall is less than the length of the inner wall of the second sidewall.

[0014] Optionally, the base is rectangular in the circumference, including two opposite first sides and two opposite second sides; an edge covering frame is also provided around the circumference of the base.

[0015] Optionally, when the base is moved to the cleaning process position, the edge covering frame overlaps the first protrusion and the second protrusion, forming an air extraction channel between two adjacent first protrusions and second protrusions.

[0016] Optionally, the base is rectangular in circumference; the number of side auxiliary grounding devices provided on the first side of the base is not less than 8; the number of side auxiliary grounding devices provided on the second side of the base is not less than 4.

[0017] Compared with the prior art, the technical solution of the present invention has at least the following advantages: by setting the first counterweight at the first end of the balance counterweight rod to be greater than the second counterweight at the second end, the first end of the balance counterweight rod always provides a downward first force, and the torque is transmitted through the balance counterweight rod, so that the second end of the balance counterweight rod always generates an upward second force. In this way, the second end of the balance counterweight rod always maintains close contact with the protrusion during the processing, forming a stable radio frequency return path, thereby improving the uniformity of plasma distribution; at the same time, it also reduces the generation of particulate contaminants, improves the film uniformity of the substrate, and improves the product yield. Attached Figure Description

[0018] Figure 1 This is a cross-sectional schematic diagram of a plasma processing apparatus according to an embodiment of the present invention;

[0019] Figure 2 This is an enlarged schematic diagram of the structure of a side auxiliary grounding device according to an embodiment of the present invention;

[0020] Figure 3 This is an enlarged schematic diagram of the structure of the base located at the processing stage in a plasma processing apparatus according to an embodiment of the present invention.

[0021] Figure 4 This is an enlarged schematic diagram of the structure of the plasma treatment device according to an embodiment of the present invention, showing the base located at the cleaning process position.

[0022] Figure 5 This is a schematic cross-sectional top view of the reaction chamber of a plasma processing apparatus according to an embodiment of the present invention. Detailed Implementation

[0023] The technical solutions, structural features, achieved objectives, and effects of the present invention will be described in detail below with reference to the accompanying drawings in the embodiments of the present invention.

[0024] It should be noted that the accompanying drawings are in a very simplified form and use non-precise proportions. They are only used to facilitate and clarify the purpose of illustrating the embodiments of the present invention, and are not intended to limit the implementation conditions of the present invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportional relationship, or adjustments to the size should still fall within the scope of the technical content disclosed in the present invention, provided that they do not affect the effects and objectives that the present invention can produce.

[0025] It should be noted that, in this invention, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only the expressly listed elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0026] Research has found that in plasma processing equipment, especially plasma-enhanced chemical vapor deposition (PECVD) equipment, the radio frequency (RF) return path formed within the reaction chamber has a significant impact on the uniformity of plasma distribution. To improve the uniformity of plasma distribution during the processing, a side auxiliary grounding device is provided circumferentially on the base to form a uniformly distributed RF return path. However, existing side auxiliary grounding devices are mostly spring structures, which have the following drawbacks: Firstly, when the spring structure is compressed and deformed, deposition byproducts attached to the spring structure are easily detached, forming particulate contaminants that affect film quality. Secondly, after a long processing time, the elasticity of the spring structure decreases, leading to poor contact between the spring structure and the protrusions on the sidewall of the reaction chamber, thus failing to generate an effective RF return path. This results in an uneven distribution of the RF return path, reducing the uniformity of plasma distribution, causing uneven film deposition, and lowering product yield.

[0027] To address the aforementioned deficiencies, this invention discloses a side-mounted auxiliary grounding device including a counterweight structure. The side-mounted auxiliary grounding device is disposed circumferentially around a base within a plasma reaction chamber to form a stable radio frequency return path. It mainly includes: a support unit fixedly connected to the base for supporting the counterweight structure; the counterweight structure includes: a bracket fixed to the support unit; and a counterweight rod disposed at the top of the bracket via a rotation fulcrum. The first end of the counterweight rod is heavier than the second end and can rotate around the rotation fulcrum, forming a seesaw with the bracket. Structure: When the base moves to the processing position, the second end of the counterweight rod contacts the protrusion protruding inward from the side wall of the reaction chamber. Since the counterweight at the first end of the counterweight rod is greater than that at the second end, the first end of the counterweight rod always provides a downward first force. Through the torque transmitted by the counterweight rod, the second end of the counterweight rod always generates an upward second force. This ensures that the second end of the counterweight rod always maintains close contact with the protrusion during the processing, forming a stable radio frequency return path and avoiding the defect of not being able to generate a radio frequency return path due to poor contact.

[0028] like Figure 1 The diagram shows a cross-sectional view of a plasma processing device 100 according to an embodiment of the present invention. This plasma processing device 100 is suitable for processing large-area substrates W and includes: a reaction chamber 101, which includes four sidewalls 111 and a spray head assembly 102 disposed on the top of the sidewalls 111; the spray head assembly 102 is connected to a reaction gas source 121 for supplying reaction gas to the reaction chamber 101; at least one sidewall 111 of the vacuum reaction chamber 101 has a transfer port (not shown) penetrating through the sidewall 111, through which the substrate W can be picked up, thereby realizing the transfer of the substrate W; and a base 103 disposed at the bottom of the reaction chamber 101, adjacent to the spray head assembly 102. Yes, it is used to support the substrate W; the base 103 is circumferentially provided with a side auxiliary grounding device 104 including a counterweight structure provided by the present invention. Each side auxiliary grounding device 104 contacts an inwardly protruding portion 112 on the side wall 111 of the reaction chamber to form an RF return path between the side of the base 103 and the side wall 111 of the reaction chamber; the bottom of the base 103 is also connected to a driving device 105, which is used to move the base 103 to a processing position, a cleaning position, or a wafer transfer position, thereby adjusting the distance between the substrate W and the spray head assembly 102 to realize the picking and placing of the substrate W and the processing, as well as the cleaning of the reaction chamber. An exhaust port is also provided below the reaction chamber 101. The exhaust port is connected to a vacuum pump 106 to discharge the reaction byproducts from the reaction chamber and maintain the vacuum environment of the reaction chamber 101.

[0029] In this embodiment, as Figure 1 As shown, the spray head assembly 102 includes an upper cover plate 122 and a gas distribution plate 123. The gas distribution plate 123 is located below the upper cover plate 122 and is connected to the upper cover plate 122 to form a uniform gas chamber. The reaction gas source 121 is connected to the uniform gas chamber through an air inlet pipe 124 to deliver the reaction gas into the uniform gas chamber and diffuse the reaction gas into the reaction chamber 101 through the gas distribution plate 123. In another embodiment, a remote plasma source 125 is connected to the air inlet pipe 124 to supply plasma generated by the cleaning gas into the reaction chamber 101 through the gas distribution plate 123 to clean the cavity components of the reaction chamber 101.

[0030] Furthermore, such as Figure 1As shown, shielding plates 113 are also spaced above the upper cover plate 122. The lower edge of the shielding plate 113 is connected to the side wall 111 of the reaction chamber 101. The shielding plate 113 is used to prevent radio frequency energy leakage. The radio frequency power supply 107 is connected to the spray head assembly 102 through the radio frequency matching unit 108, and is used to apply radio frequency current into the reaction chamber 101 to generate a radio frequency electric field between the spray head assembly 102 and the base 103, so as to dissociate the reaction gas into plasma.

[0031] like Figure 2 The diagram shown is an enlarged view of the structure of a side auxiliary grounding device 104 according to an embodiment of the present invention. The side auxiliary grounding device 104 includes a supporting part 141, which is fixedly connected to the circumferential side wall of the base 103 and located below the base 103 for supporting a counterweight structure. In this embodiment, the counterweight structure includes: a bracket 142, which is vertically fixed on the supporting part 141; and a counterweight rod 143, which is disposed at the top of the bracket 142 through a rotation fulcrum 144. The first counterweight of the first end 1431 of the counterweight rod 143 is greater than the second counterweight of the second end 1432, so that the first end 1431 always provides a downward first force on the counterweight rod 143.

[0032] During the process of the base 103 being moved to the processing position by the driving device 105, the side auxiliary grounding device 104 moves upward in the vertical direction along with the base 103. The second end 1432 of the balance weight rod 143 contacts the protrusion 112 on the side wall 111 of the reaction chamber. The second end 1432 of the balance weight rod 143 is subjected to downward resistance provided by the protrusion 112. The balance weight rod 143 rotates around the rotation fulcrum 144 to a near-horizontal position (e.g., Figure 1 As shown in the figure, the angle between the counterweight rod 143 and the horizontal plane is not less than 5°, and the position of the base 103 at this time is the processing position. Further, if the angle between the counterweight rod 143 and the horizontal plane is less than 5°, it may cause the first end 1431 of the counterweight rod 143 (i.e. the end with the larger counterweight) to contact the protrusion 112. However, since the end with the larger counterweight may swing up and down due to slight shaking, it may cause the RF return path to be interrupted. Therefore, in this embodiment, by setting the angle between the counterweight rod 143 and the horizontal plane to be no less than 5°, the first end 1431 of the counterweight rod 143 always provides a downward first force. Through the torque transmitted by the counterweight rod 143, the second end 1432 of the counterweight rod 143 always generates an upward second force. This ensures that the second end 1432 of the counterweight rod 143 always maintains close contact with the protrusion 112 in the processing device, forming a stable radio frequency return path and ensuring the uniform distribution of plasma in the reaction chamber 101.

[0033] Furthermore, such as Figure 2 and Figure 4 As shown, in this embodiment, the supporting part 141 is an "L"-shaped supporting plate. The supporting plate includes a vertical part 1411 and a horizontal part 1412 that are perpendicularly connected to each other. The top end of the vertical part 1411 is connected to the base 103, and the bottom end is connected to the horizontal part 1412. The horizontal part 1412 serves as a supporting plane to support the bracket 142 and the first end 1431 of the counterweight rod 143. When the base 103 is in a non-processing position, the first end 1431 of the counterweight rod 143 is always in contact with the horizontal part 1412 of the supporting part 141 to reduce the rotation or vibration of the counterweight rod 143 during the up-and-down movement of the base 103 and improve the stability of the counterweight rod 143.

[0034] In this embodiment, such as Figure 2 As shown, the rotation fulcrum 144 is a rotation axis set at the top of the bracket 142. The counterweight rod 142 is hinged to the bracket 142 through the rotation axis, allowing the counterweight rod 142 to rotate around the rotation axis. The distance from the rotation fulcrum 144 to the first end 1431 of the counterweight rod 143 is less than the distance from the rotation fulcrum 144 to the second end 1432 of the counterweight rod 143. This is because the first counterweight of the first end 1431 of the counterweight rod 143 is greater than the second counterweight of the second end 1432. In order for the counterweight rod 143 to rotate to a near-horizontal position, the distance from the rotation fulcrum 144 to the first end 1431 of the counterweight rod 143 is set to be less than the distance from the rotation fulcrum 144 to the second end 1432 of the counterweight rod 143, so that the vertical movement distance of the second end 1432 of the counterweight rod 143 is as large as possible, thereby ensuring the movement range of the base 103.

[0035] In another embodiment, such as Figure 3 As shown, when the counterweight rod 143 is in the processing position, the counterweight rod 143 is in an inclined state, that is, the height of the first end 1431 is lower than the height of the second end 1432, and there is a certain angle between the counterweight rod 143 and the bracket 142, so that the second end 1432 always remains tilted upward, thereby ensuring that the second end 1432 is in close contact with the protrusion 112 and forming a stable radio frequency return path. At this time, the distance between the second end 1432 of the counterweight rod 143 and the protrusion 112 can be adjusted by adjusting the height of the bearing part 141 to the base 103, so as to meet the displacement requirements of the base 103 moving to the processing position.

[0036] The supporting part 141, the bracket 142 and the counterweight bar 143 are all made of conductive material (e.g., aluminum) and can be electrically connected to each other.

[0037] Figure 1 The arrows in the diagram schematically illustrate one implementation of the RF return path during the processing. The RF power supply 107 provides RF current to the RF matching unit 108, which is transmitted via the RF matching unit 108 to the upper surface of the upper cover plate 122 and the lower surface of the gas distribution plate 123. The RF current then reaches the upper surface of the base 103 or substrate W (e.g., ...) via plasma between the gas distribution plate 123 and the base 103. Figure 1 (As shown by the solid arrow in the middle), then the radio frequency current is transmitted to the second end 1432 of the balance counterweight rod 143 through the bearing part 141 and the bracket 142, and then the radio frequency current is transmitted to the side wall of the reaction chamber 101 through the protrusion 112 that contacts the second end 1432, and flows along the inner surface of the side wall of the reaction chamber 101 to the upper cover plate 122 and then flows back to the radio frequency matching unit 108 (as shown by the solid arrow in the middle). Figure 1 (As indicated by the dashed arrow). During the processing, because the second end 1432 of the counterweight 143 always maintains close contact with the protrusion 112, a stable RF return path is formed, avoiding the defect of not being able to generate an RF return path due to poor contact. At the same time, since both the counterweight 143 and the bracket 142 are made of rigid materials, when the second end 1432 of the counterweight 143 contacts the protrusion 112, the counterweight 143 will not undergo significant deformation, thereby reducing the generation of particulate contaminants, improving the film uniformity of the substrate W, and improving product yield.

[0038] Figure 5 This is a schematic cross-sectional top view of the reaction chamber 101 according to an embodiment of the present invention, showing a top plan view of the base 103. Wherein, as... Figure 5 As shown, the reaction chamber 101 includes two opposing first sidewalls 111a and two opposing second sidewalls 111b. In some embodiments, the length of the first sidewall 111a is greater than the length of the second sidewall 111b. Each first sidewall 111a has an inwardly protruding first protrusion 112a on its inner wall. The first length of the first protrusion 112a extending along the first sidewall 111a is less than the length of the inner wall of the first sidewall 111a. Each second sidewall 111b has an inwardly protruding second protrusion 112b on its inner wall. The second length of the second protrusion 112b extending along the second sidewall 111b is less than the length of the inner wall of the second sidewall 111b. The first protrusion 112a and the second protrusion 112b are electrically connected to the corresponding sidewall auxiliary grounding device 104 to provide an RF return path for the applied RF current.

[0039] Furthermore, such as Figure 5 As shown, the base 103 is rectangular in circumference, comprising two opposing first sides 131 and two opposing second sides 132. In some embodiments, the length of the first side 131 is greater than the length of the second side 132. An edge covering frame 133 is also provided around the circumference of the base. When the base 103 moves to the cleaning process position, as... Figure 4 and Figure 5 As shown, the edge covering frame 133 overlaps the first protrusion 112a and the second protrusion 112b. The second end 1432 of the counterweight rod 143 does not contact the first protrusion 112a and the second protrusion 112b, and forms an air extraction channel 114 between two adjacent first protrusions 112a and second protrusions 112b to guide the flow of clean gas. The clean gas can be NF3, SF6, C2F6, HCl or a combination thereof, but is not limited to these gases.

[0040] Specifically, in one embodiment, the cleaning gas NF3 is remotely ignited into cleaning plasma and delivered to the reaction chamber 101 via the spray head assembly 102 to etch away thin film byproducts deposited on the base 103, the edge covering frame 133, and the inner surface of the sidewall 111 of the reaction chamber 101. The cleaning plasma is then drawn away by the vacuum pump 106 through the extraction channel 114, ensuring that the cleaning plasma is uniformly guided to all corners of the reaction chamber 101, thus guaranteeing the uniformity of the cleaning gas flow and improving the cleaning efficiency of the corners of the reaction chamber 101.

[0041] To improve the uniformity of the RF return path distribution, in one embodiment, side auxiliary grounding devices 104 are evenly spaced on the first side 131 and the second side 132 of the base 103, making the side auxiliary grounding devices 104 symmetrically arranged to improve the uniformity of plasma distribution and the deposition uniformity on the substrate W. In this embodiment, since one sidewall 111 of the reaction cavity 101 is provided with a transfer port, the length of the first RF return path flowing through this sidewall is inconsistent with the length of the second RF return path flowing through other sidewalls. Therefore, the spacing between the side auxiliary grounding devices 104 on the base side corresponding to the sidewall with the transfer port can be adjusted to improve the distribution of RF current in the reaction cavity 101. Optionally, the number of side auxiliary grounding devices 104 provided on the first side 131 of the base 103 is not less than 8 (e.g., ...). Figure 1 As shown, in this embodiment, eight side auxiliary grounding devices 104 are provided on the first side 131 of the base 103; the number of side auxiliary grounding devices 104 provided on the second side 132 of the base 103 is not less than four, so as to reduce the non-uniformity of radio frequency current distribution and improve the uniformity of plasma distribution.

[0042] In summary, the side auxiliary grounding device and plasma processing device provided by the present invention, by setting the first counterweight of the first end 1431 of the balance counterweight rod 143 to be greater than the second counterweight of the second end 1432, ensures that the first end 1431 of the balance counterweight rod 143 always provides a downward first force, and transmits torque through the balance counterweight rod 143, ensuring that the second end 1432 of the balance counterweight rod 143 always generates an upward second force. This ensures that the second end 1432 of the balance counterweight rod 143 always maintains close contact with the protrusion 112 during the processing, forming a stable radio frequency return path and improving the uniformity of plasma distribution. It also reduces the generation of particulate contaminants, improves the film uniformity of the substrate W, and increases product yield.

[0043] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A side-assisted grounding device, which is disposed circumferentially on a base within a plasma reaction chamber, characterized in that, include: The supporting part is fixedly connected to the base; A bracket, which is fixed to the bearing portion; A counterweight bar is mounted at the top of the bracket via a pivot point. The first end of the counterweight rod is heavier than the second end, and it can rotate around the pivot point. When the base moves to the processing position, the second end of the counterweight rod contacts the protrusion protruding inward from the side wall of the reaction chamber, forming an RF return path.

2. The side auxiliary grounding device as described in claim 1, characterized in that, The distance from the pivot point to the first end of the counterweight rod is less than or equal to the distance from the pivot point to the second end of the counterweight rod.

3. The side auxiliary grounding device as described in claim 1, characterized in that, When the base is in a non-processing position, the first end of the counterweight bar is always in contact with the load-bearing part.

4. The side auxiliary grounding device as described in claim 1, characterized in that, The angle between the counterweight rod and the horizontal plane is not less than 5°.

5. The side auxiliary grounding device as described in claim 1, characterized in that, The load-bearing part is located below the base, and the second end of the counterweight rod is not higher than the lower surface of the base.

6. The side auxiliary grounding device as described in claim 5, characterized in that, The supporting part is an "L"-shaped supporting plate; the vertical part of the supporting plate is connected to the base, and the horizontal part is used to support the bracket and the first end of the counterweight rod.

7. The side auxiliary grounding device as described in claim 1, characterized in that, The load-bearing part, bracket, and counterweight bar are all made of conductive materials.

8. A plasma processing apparatus, characterized in that, include: reaction chamber; A spray head assembly is located at the top of the reaction chamber; A base, disposed at the bottom of the reaction chamber and opposite to the spray head assembly, is used to support the substrate; The base is circumferentially provided with a side auxiliary grounding device as described in any one of claims 1 to 7; A drive unit, which is located at the bottom of the base, drives the base to move to the processing position or the cleaning position.

9. The plasma processing apparatus as described in claim 8, characterized in that, The reaction chamber includes two opposing first sidewalls and two opposing second sidewalls; Each of the first sidewalls has an inwardly protruding first protrusion on its inner wall, the first length of which extends along the first sidewall is less than the length of the inner wall of the first sidewall; each of the second sidewalls has an inwardly protruding second protrusion on its inner wall, the second length of which extends along the second sidewall is less than the length of the inner wall of the second sidewall.

10. The plasma processing apparatus as described in claim 9, characterized in that, The base is rectangular in circumference, including two opposite first sides and two opposite second sides; an edge covering frame is also provided around the base in circumference.

11. The plasma processing apparatus as claimed in claim 10, characterized in that, When the base is moved to the cleaning process position, the edge covering frame overlaps the first protrusion and the second protrusion, forming an air extraction channel between two adjacent first protrusions and second protrusions.

12. The plasma processing apparatus as described in claim 8, characterized in that, The base is rectangular in circumference; the number of side auxiliary grounding devices provided on the first side of the base is not less than 8; the number of side auxiliary grounding devices provided on the second side of the base is not less than 4.

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