Upper electrode assembly

Abstract

To provide a lift bar-based upper electrode assembly that improves workability and maintains a constant fastening force when fastening and dismantling a plasma electrode plate to and from equipment.SOLUTION: A plasma electrode plate includes a bushing assembly fastened to the insertion hole of a plasma electrode plate, and a lift bar received in the receiving space of the electrode support plate to detachably connect the plasma electrode plate to the electrode support plate. The bushing assembly includes a bushing configured to be connected to the lift bar, and the lift bar includes a connecting portion configured to be connected to the bushing, the connecting portion including a bushing insertion groove into which the bushing is inserted, a first path configured to move the lift bar axially with the bushing inserted, and a second path configured to rotate the lift bar with the bushing positioned beyond the first path.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an upper electrode assembly, and more particularly to an upper electrode assembly that is configured to improve coupling strength when coupling a plasma electrode plate to an electrode support plate using a lift bar and to enable quick and convenient fastening. [Background technology]

[0002] Semiconductor devices can be manufactured through a variety of processes. For example, semiconductor devices are manufactured through photolithography, etching, deposition, etc., on wafers such as silicon. Plasma-like materials are used in each process for manufacturing semiconductor devices. In processes using plasma, electrodes are used to generate and control plasma within semiconductor manufacturing equipment. The electrodes for plasma are located at the bottom and top of a chamber. The electrodes for plasma are formed by combining multiple components.

[0003] Conventionally, a fixing structure that combines an electrode plate with an insertion groove, a bushing, a fastening member (bolt), etc. has been commonly used to connect a plasma electrode plate to equipment. However, such a fastening structure can have problems such as reduced workability when fastening and disassembling the plasma electrode plate, and the flatness and adhesion of the electrode plate can be reduced due to uneven fastening force. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2024-114595 A Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention addresses the above-mentioned problems by providing a lift bar-based upper electrode assembly that improves workability and maintains a constant fastening force when fastening and dismantling a plasma electrode plate to and from equipment. [Means for solving the problem]

[0006] An upper electrode assembly according to the present invention may include a bushing assembly fastened to an insertion hole of a plasma electrode plate, and a lift bar received in an accommodating space of an electrode support plate to detachably connect the plasma electrode plate to the electrode support plate. The bushing assembly may include a bushing configured to be connected to the lift bar, and the lift bar may include a connecting portion configured to be connected to the bushing, and the connecting portion may include a bushing insertion groove into which the bushing is inserted, a first path configured to move the lift bar axially when the bushing is inserted, and a second path configured to rotate the lift bar when the bushing is positioned beyond the first path. [Effects of the Invention]

[0007] The upper electrode assembly according to an embodiment of the present invention may include a lift bar having a lift-up function that can move axially and then rotate, thereby enabling quick and stable assembly and disassembly of the plasma electrode plate to the electrode support plate without the need for additional tools. Furthermore, by using the lift bar to fasten the plasma electrode plate to the electrode support plate, uniform fastening force can be ensured, and the adhesion and flatness of the plasma electrode plate can be maintained.

[0008] In the upper electrode assembly according to an embodiment of the present invention, the bushing assembly and the lift bar are fastened along their respective insertion grooves and paths, thereby minimizing assembly errors. Furthermore, the configuration of the fastening portion between the bushing assembly and the lift bar can improve mechanical stability by preventing movement of the lift bar after fastening. When a lift bar guide portion is included, the insertion direction and alignment position of the lift bar can be more precisely guided. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a partial exploded view of an upper electrode assembly according to an embodiment of the present invention. [Figure 2] 1 is an assembly view of an upper electrode assembly according to an embodiment of the present invention; [Figure 3a] 1 is a cross-sectional view of an assembled upper electrode assembly according to an embodiment of the present invention; [Figure 3b] 10 is a cross-sectional view of an assembled upper electrode assembly according to another embodiment of the present invention; [Figure 4a] 1A and 1B are perspective and enlarged views of a lift bar according to an embodiment of the present invention; [Figure 4b] FIG. 2 is a left perspective view of a lift bar according to an embodiment of the present invention. [Figure 4c] FIG. 1 is a bottom perspective view of a lift bar according to an embodiment of the present invention. [Figure 4d] FIG. 2 is a bottom view of a lift bar according to an embodiment of the present invention. [Figure 4e] FIG. 2 is a right side view of a lift bar according to an embodiment of the present invention. [Figure 4f] FIG. 2 is a top view of a lift bar according to an embodiment of the present invention. [Figure 4g] FIG. 2 is a left side view of a lift bar according to an embodiment of the present invention. [Figure 4h] FIG. 2 is a front view of a lift bar according to an embodiment of the present invention. [Figure 5a] 1 is an assembly view of a bushing assembly according to an embodiment of the present invention in an assembled state. [Figure 5b] 1 is a cross-sectional view of a bushing assembly according to an embodiment of the present invention in an assembled state; [Figure 5c] FIG. 2 is an exploded view of a bushing assembly according to an embodiment of the present invention. [Figure 5d] 1 is an assembly view of a bushing assembly according to an embodiment of the present invention in an assembled state. [Figure 6] 1 is a perspective view of an electrode support plate further including a rib insertion hole according to an embodiment of the present invention; [Figure 7] 1 is an assembly view of an upper electrode assembly including a lift bar guide unit according to an embodiment of the present invention; [Figure 8] 4 is a cross-sectional view of an assembled upper electrode assembly including a lift bar guide unit according to an embodiment of the present invention; [Figure 9a] FIG. 2 is a perspective view of a lift bar guide portion according to an embodiment of the present invention. [Figure 9b] FIG. 4 is a bottom view of the lift bar guide portion according to the embodiment of the present invention. [Figure 10a] 1 is a partially exploded perspective view of an upper electrode assembly according to an embodiment of the present invention; [Figure 10b] 10A to 10C are perspective views sequentially illustrating a fastening process according to an embodiment of the present invention. [Figure 10c] 10A to 10C are perspective views sequentially illustrating a fastening process according to an embodiment of the present invention. [Figure 10d] 10A to 10C are perspective views sequentially illustrating a fastening process according to an embodiment of the present invention. [Figure 10e] 10A to 10C are perspective views sequentially illustrating a fastening process according to an embodiment of the present invention. [Figure 10f] 10A to 10C are front views sequentially illustrating a fastening process according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] In order to fully understand the configuration and effects of the present invention, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, and may be embodied in various forms and may undergo various modifications. However, the description of the present embodiments is provided to ensure complete disclosure of the present invention and to fully convey the scope of the invention to those skilled in the art.

[0011] In this specification, when a component is referred to as being on top of another component, it means that it may be formed directly on the other component, or that a third component may be interposed between them. Also, in the drawings, the thickness of the components is exaggerated for the purpose of effectively explaining the technical content. Throughout the specification, parts designated with the same reference numerals refer to the same components.

[0012] The embodiments described herein are described with reference to cross-sectional views, plan views, and / or perspective views that are ideal exemplary views of the present invention. In various embodiments of the present specification, terms such as "first," "second," and "third" are used to describe various components, but these components should not be limited to such terms. These terms are merely used to distinguish one component from another. The embodiments described and illustrated herein also include complementary embodiments thereof.

[0013] The terms used in this specification are for the purpose of describing the embodiments and are not intended to limit the present invention. In this specification, the singular form includes the plural form unless otherwise specified in the phrase. When used in this specification, "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components to the referenced components.

[0014] 1 and 2, an upper electrode assembly 10 according to an embodiment of the present invention may include an electrode support plate 100, a plasma electrode plate 200, a lift bar 300, and a bushing assembly 400.

[0015] The upper electrode assembly 10 may be installed in a chamber for a process that utilizes plasma. For example, the upper electrode assembly 10 may be installed in a chamber for etching a semiconductor. More specifically, the upper electrode assembly 10 may be an electrode installed above a lower electrode (not shown) in an etching chamber.

[0016] The electrode support plate 100 is the upper structure of the equipment and may be formed in a disk-like structure. The electrode support plate 100 may have an opening 110 formed on a side thereof for inserting the lift bar 300, and a through-groove 120 formed on a bottom thereof for inserting the bushing assembly 400 that is inserted into and fastened to the plasma electrode plate 200. An accommodating space 130 formed inside the electrode support plate 100 may be formed to accommodate the lift bar 300, the bushing assembly 400, etc. The accommodating space 130 may have a three-dimensional shape such as a rectangular parallelepiped or a cylinder, but is not limited thereto.

[0017] The plasma electrode plate 200 may include ceramic materials such as silicon, silicon carbide, alumina, quartz, etc. The plasma electrode plate 200 may be formed in a disk-like structure. The upper surface of the plasma electrode plate 200 may be flat to closely contact the electrode support plate 100.

[0018] An insertion hole 210 may be formed on the plasma electrode plate 200, penetrating the upper surface of the plasma electrode plate 200. The bushing assembly 400 may be inserted into the insertion hole 210. The bushing assembly 400 may be inserted into the insertion hole 210 to mechanically connect the plasma electrode plate 200 to the upper electrode support plate 100. A plurality of insertion holes 210 may be provided. The plurality of insertion holes 210 may be spaced apart from each other in the circumferential direction. A plurality of bushing assemblies 400 may be provided. For example, the number of bushing assemblies 400 may be the same as the number of insertion holes 210. A plurality of bushing assemblies 400 may be inserted into the plurality of insertion holes 210, respectively.

[0019] The plasma electrode plate 200 may include a plurality of nozzles provided on its surface. The nozzles may be configured to supply process gas. For example, the plasma electrode plate 200 may be a showerhead. The plasma electrode plate 200 may also include micropores (not shown). The micropores may be holes through which process gas passes, but are not limited thereto. A plurality of micropores may be provided.

[0020] Figure 3a is a cross-sectional view taken along line A-A' of the assembled upper electrode assembly 10 according to the embodiment of the present invention shown in Figure 2. Figure 3b is a cross-sectional view taken along line A-A' of the assembled upper electrode assembly 10 according to another embodiment of the present invention. Figures 4a to 4h are perspective and plan views of the lift bar 300 viewed from various directions. Figures 5a to 5d are views showing the assembled and disassembled states of the bushing assembly 400. Referring to these drawings, the structural shapes and interconnection relationships of the lift bar 300 and the bushing assembly 400 can be more clearly understood.

[0021] 3a and 5a to 5c, a bushing assembly 400 according to an embodiment of the present invention may include a bushing 410, a washer 420, and a bushing fastener 430. The bushing 410 may include a bushing body 412, a bushing head 411, and a fastener 413.

[0022] The fastening portion 413 may be formed on the lower portion of the bushing body 412. The fastening portion 413 may be disposed in the insertion hole 210 of the plasma electrode plate 200. The fastening portion 413 may be fastened by a bushing fastening member 430 within the insertion hole 210. When fastening the bushing 410 and the plasma electrode plate 200, a washer 420 may be interposed between the fastening portion 413 and the bushing fastening member 430. The washer 420 is interposed between the fastening portion 413 and the bushing fastening member 430 and may play a role in maintaining the fastening height and fastening force, absorbing vibrations, etc. A plurality of washers 420 may be provided.

[0023] The bushing body 412 may be formed to extend upward from the fastening portion 413. The bushing body 412 may be inserted into the receiving space 130 by passing through the through-groove 120 of the electrode support plate 100. The bushing body 412 may be cylindrical, for example, and may be inserted into the bushing insertion hole 311 of the connecting portion 310 of the lift bar 300.

[0024] A bushing head 411 having a square or disc shape may be formed on the upper part of the bushing body 412, but is not limited thereto. The bushing head 411 may have a diameter larger than that of the bushing body 412 and may be inserted into the receiving space 130 by passing through the through-groove 120 of the electrode support plate 100. The bushing head 411 may also be inserted into the bushing insertion groove 311 of the coupling part 310 of the lift bar 300. When the plasma electrode plate 200 is fastened to the electrode support plate 100, the bushing head 411 may be located at the upper end of the bushing fixing part 340 of the lift bar 300.

[0025] 3b and 5d, the bushing 410 may further include a protrusion 415 protruding from the bushing body 412. The fastening portion 413 may further include a support piece 414. The support piece 414 may be formed at the bottom of the fastening portion 413 and may be in close contact with the bottom surface of the insertion hole 210. The protrusion 415 may have a shape of, but is not limited to, a disk or a sphere. The protrusion 415 may have a diameter larger than that of the bushing head 411 and smaller than that of the support piece 414 located at the bottom of the fastening portion 413. The protrusion 415 may be formed at the bottom of the bushing body 412. The protrusion 415 may interfere with other components, such as the lift bar 300 of the upper electrode assembly 10. Details of the protrusion 415 will be described later.

[0026] 3, a lift bar 300 according to an embodiment of the present invention is inserted through the opening 110 of the electrode support plate 100 and accommodated in the accommodation space 130, and serves to detachably couple the plasma electrode plate 200 to the electrode support plate 100. The lift bar 300 may be disposed to contact the lower and upper surfaces of the accommodation space 130 to provide a uniform fastening force and ensure adhesion and flatness of the plasma electrode plate 200. The lift bar 300 may be formed in a cylindrical shape, for example.

[0027] 3 and 4, the lift bar 300 may include a connecting portion 310, an operating portion 320, a body portion 330, a bush fixing portion 340, and a lift portion 350. The operating portion 320 may be disposed adjacent to the opening 110 of the electrode support plate 100. The lift bar 300 may be moved and rotated axially within the receiving space 130 by the operating portion 320. The axial direction may refer to the direction in which the lift bar 300 moves from the opening 110 of the electrode support plate 100 toward the center of the electrode support plate 100, and this axial direction may be exemplarily expressed as the A-A' direction shown in FIG. 2. The body portion 330 may be formed in a bar shape extending in the axial direction of the lift bar 300. The body portion 330 may serve as a structural center supporting the axial movement and rotation of the lift bar 300. The body portion 330 may have a shape such as, but is not limited to, a cylinder. A plurality of body portions 330 may be provided.

[0028] The coupling portion 310 is a portion where the lift bar 300 and the bushing assembly 400 are coupled together, and may include a bushing insertion groove 311, a first passage 312, and a second passage 313. The coupling portion 310 may have a cylindrical shape, but is not limited thereto. A plurality of coupling portions 310 may be provided. The main body portion 330 may be disposed between the plurality of coupling portions 310.

[0029] 3A and 4, the lift portion 350 according to an embodiment of the present invention may be formed by protruding from a side of the coupling portion 310, but is not limited to this. The lift portion 350 may have a shape such as a semicircle, but is not limited to this. The lift portion 350 may come into contact with the lower part of the electrode supporting plate 100 when the lift bar 300 rotates. As the lift portion 350 comes into contact with the lower part of the electrode supporting plate 100, it may lift the lift bar 300 up from the lower part of the electrode supporting plate 100.

[0030] 4h is a front view of the lift bar 300 showing the lift portion 350 protruding from the connecting portion 310. The diameter L2 of the connecting portion 310 including the lift portion 350 may be larger than the diameter L1 of the body portion 330, and when the lift bar 300 rotates, the lift portion 350 may contact the lower part of the electrode support plate 100, thereby lifting the lift bar 300 upward. At this time, the height to which the lift bar 300 rises may be the difference (L2-L1) between the diameter L2 of the connecting portion 310 including the lift portion 350 and the diameter L1 of the body portion 330. As the lift bar 300 is lifted upward, the plasma electrode plate 200 may be tightly secured to the lower surface of the electrode support plate 100.

[0031] 3b, according to another embodiment of the present invention, the lift portion 350 may be formed to protrude from the side of the body portion 330. In this case, the height to which the lift bar 300 rises may be the difference L1-L2 between the diameter L1 of the body portion 330 including the lift portion 350 and the diameter L2 of the coupling portion 310. The protrusion 415 may be formed on the lower surface of the electrode support plate 100 or on the lower portion of the bushing body 412 at a height equal to or smaller than the height L1-L2 to which the lift bar 300 rises. Thus, the protrusion 415 may limit the height to which the lift portion 350 rises.

[0032] The bushing 410 of the bushing assembly 400 can be inserted into the bushing insertion groove 311. For example, the bushing body 412 and the bushing head 411 of the bushing 410 can be inserted into the bushing insertion groove 311.

[0033] The first passage 312 may function to allow the lift bar 300 to move in the axial direction when the bushing 410 is inserted into the bushing insertion groove 311. In addition, the first passage 312 formed in the coupling portion 310 may be formed to have a structure that allows it to pass through the bushing body 412. The first passage 312 may have an open or through-type structure that extends in the axial direction of the lift bar 300.

[0034] The second passage 313 may be formed continuously from the end of the first passage 312 and may have a structure such as a fan shape or a curve. The second passage 313 may also be formed to have a structure that can pass through the bushing body 412. The second passage 313 may allow the lift bar 300 to rotate with the bushing 410 positioned at the end of the first passage 312, and may serve to guide the bushing head 411 so that it can be positioned above the bushing fixing portion 340 when the lift bar 300 rotates.

[0035] The bushing fixing portion 340 may be configured to support the lower surface of the bushing head 411 when the lift bar 300 is rotated, thereby stably maintaining a fastened state between the lift bar 300 and the bushing assembly 40. The bushing fixing portion 340 may maintain a fixed state so that the lift bar 300 does not rotate in the reverse direction.

[0036] 6 to 9b, the upper electrode assembly 10 according to an embodiment of the present invention may further include a lift bar guide portion 500. The lift bar guide portion 500 may be disposed within the receiving space 130 of the electrode support plate 100. The lift bar guide portion 500 may guide the lift bar 300 so that it can be inserted into a predetermined position.

[0037] The lift bar guide unit 500 may include a lift bar guide 510, a bushing head inserting unit 520, and a bushing head fixing unit 530. The lift bar guide 510 may provide an insertion space that guides the lift bar 300 to be inserted at a predetermined position.

[0038] The lift bar guide 510 may guide the lift bar 300 so that its axial movement and rotational position are accurately aligned within the receiving space 130 of the electrode support plate 100. The lift bar guide 510 may be formed in the shape of a rectangular parallelepiped housing with an open bottom, but is not limited to this. The lift bar guide 510 may further include a rib 540 protruding from the outer side, and the rib 540 may be inserted into a rib insertion groove 140 formed on the side of the receiving space 130 of the electrode support plate 100, so that the entire lift bar guide unit 500 may be accurately fixed within the device.

[0039] The bush head inserting portion 520 and the bush head fixing portion 530 may be disposed on the upper surface of the lift bar guide 510. The bush head inserting portion 520 and the bush head fixing portion 530 may be formed in a shape such as, but not limited to, a circular shape. When the upper electrode assembly 10 further includes a lift bar guide portion 500, the bush head 411 may be located on the upper ends of the bush head inserting portion 520 and the bush head fixing portion 530.

[0040] 10a to 10f, the process of fastening the upper electrode assembly 10 according to an embodiment of the present invention can be understood in more detail. Fig. 10a is a partially exploded perspective view of the upper electrode assembly 10 according to an embodiment of the present invention. Figs. 10b to 10f are views sequentially illustrating the process of closely contacting and fastening the plasma electrode plate 200, into which the bushing assembly 400 is inserted, to the electrode support plate 100 by axially moving and rotating the lift bar 300.

[0041] Referring to FIG. 10a, in the upper electrode assembly 10 according to an embodiment of the present invention, when the lift bar 300 is inserted into the opening 110 of the electrode support plate 100 and accommodated in the accommodation space 130, the bushing assembly 400 inserted in the plasma electrode plate 200 can be inserted into the through groove 120 of the electrode support plate 100 and inserted into the bushing insertion groove 311 of the lift bar 300.

[0042] 10b, with the bushing assembly 400 inserted into the bushing insertion groove 311 of the lift bar 300, the lift bar 300 can be moved axially by operating the operating part 320. The first passage 312 formed in the coupling part 310 of the lift bar 300 can be configured as an open structure formed to allow the bushing 410 to pass through, and can guide the lift bar 300 to move axially.

[0043] 10c to 10f, when the lift bar 300 moves axially and the bushing 410 is positioned at the end of the first path 312, the lift bar 300 can be rotated by operating the operating unit 320. As the lift bar 300 rotates, the second path 313 can pass through the bushing 410, guiding the bushing 410 to be positioned at the bushing fixing portion 340. In addition, the bushing head 411 can be guided to be positioned at the top of the bushing fixing portion 340.

[0044] As the lift bar 300 rotates, the lift portion 350 protruding from the coupling portion 310 comes into contact with the lower portion of the electrode support plate 100, thereby lifting the lift bar 300 up from the lower portion of the electrode support plate 100. The lift bar 300 can be lifted up by a difference L2-L1 between the diameter L2 of the coupling portion 310 including the lift portion 350 and the diameter L1 of the body portion 330. As the lift bar 300 is lifted upward, the bushing 410 can be positioned in the bushing fixing portion 340, and when the rotation is completed, the bushing fixing portion 340 can be positioned below the bushing head 411 to support the bushing head 411, thereby allowing the plasma electrode plate 200 to be tightly fastened to the lower portion of the electrode support plate 100.

[0045] The upper electrode assembly according to the embodiment of the present invention has the above-described configuration, which improves the operability of connecting and disconnecting the plasma electrode plate and the electrode support plate. It also ensures a uniform fastening force and maintains the adhesion and flatness of the plasma electrode plate. This increases the ease of replacing the plasma electrode plate in the upper electrode assembly and improves the structural stability of the upper electrode assembly, thereby ensuring product quality and cost-effectiveness.

[0046] Although the embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention may be embodied in other specific forms without changing the technical idea or essential features thereof. Therefore, it should be understood that the above-described embodiments are illustrative in all respects and are not limiting. [Explanation of symbols]

[0047] 10 Upper electrode assembly 100 Electrode support plate 110 Aperture 120 Through groove 130 Storage Space 140 Rib insertion groove 200 Plasma electrode plate 210 Insertion hole 300 Lift Bar 310 Joint 311 Bush insertion groove 312 Route 1 313 Route 2 320 Control unit 330 Main body 340 Bush fixing part 350 Lift section 400 Bush assembly 410 Bush 411 Bushhead 412 Bush body 413 Fastening part 414 Protrusion 415 Support piece 420 Washer 430 Bush fastening member 500 Lift bar guide part 510 Lift Bar Guide 520 Bush head insert 530 Bush head fixing part 540 Rib L1 Body diameter L2 Diameter of joint

Claims

1. a bushing assembly fastened to an insertion hole of the plasma electrode plate; a lift bar that is received in the receiving space of an electrode support plate and detachably connects the plasma electrode plate to the electrode support plate; the bushing assembly includes a bushing configured to couple to the lift bar; the lift bar includes a coupling portion configured to couple with the bushing; The coupling portion is a bushing insertion groove into which the bushing is inserted; a first path configured to axially move the lift bar with the bushing inserted; a second path along which the lift bar rotates with the bush positioned at the tip of the first path.

2. The bushing assembly includes: a bushing fastening member for fastening the bushing to the insertion hole of the plasma electrode plate; a washer interposed between the bush fastening member and the bush, The bushing is a fastening portion disposed in the insertion hole of the plasma electrode plate; a bushing body protruding from the fastening portion and configured to penetrate the lift bar; The upper electrode assembly according to claim 1 , further comprising: a bush head formed on an upper portion of the bush body and configured to be fixed to the lift bar.

3. The bushing further includes a protrusion formed protruding from the bushing body, The fastening portion further includes a support piece formed at a lowermost end thereof, 3. The upper electrode assembly according to claim 2, wherein the protrusion has a diameter larger than that of the bush head and smaller than that of the support piece.

4. The electrode support plate is an opening formed on a side surface of the electrode support plate, into which the lift bar is inserted; 3. The upper electrode assembly of claim 2, further comprising a through-groove formed in a lower portion of the electrode support plate, into which the bush body and the bush head are inserted.

5. The lift bar is an operating unit for operating the axial movement and rotation of the lift bar; 2. The upper electrode assembly according to claim 1, further comprising: a bar-shaped body portion extending in an axial direction.

6. the operating portion is disposed at a tip of the lift bar adjacent to the opening, the coupling portion includes a plurality of coupling portions; The upper electrode assembly of claim 5 , wherein the body portion is disposed between the plurality of coupling portions.

7. The lift bar further includes a lift portion formed on one of the coupling portion and the body portion, 6. The upper electrode assembly of claim 5, wherein the lifting portion lifts the lifting bar up from below the electrode support plate by rotating the lifting bar.

8. The lift bar further includes a bush fixing portion that fixes the bush head and the lift bar when the lift bar is rotated, 3. The upper electrode assembly of claim 2, wherein the bush fixing portion is disposed below the bush head to support the bush head.

9. The electrode support plate further includes a lift bar guide portion disposed in the receiving space of the electrode support plate, The upper electrode assembly of claim 2 , wherein the lift bar guide portion includes a lift bar guide configured to receive the lift bar.

10. The lift bar guide portion is a bush head insertion portion into which the bush head is inserted; The upper electrode assembly of claim 9 , further comprising: a bushing head fixing portion to which the bushing head is fixed.

11. The lift bar guide further includes a rib protruding from a side surface thereof, The upper electrode assembly of claim 10 , wherein the receiving space of the electrode support plate further includes a rib insertion groove into which the rib is inserted.

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