Confinement ring and plasma processing device

Abstract

The present invention provides a confinement ring for a plasma processing device, wherein the plasma processing device includes a base, and the confinement ring is arranged around the base between the plasma reaction region and the exhaust region of the plasma processing device. The confinement ring includes a plurality of concentrically arranged ring plates, and the plurality of ring plates are arranged along the radial direction of the base, and the gap between two adjacent ring plates forms a gas channel; at least two ring plates are magnetic, and a magnetic field is formed between two adjacent magnetic ring plates, and the magnetic field restricts charged particles discharged from the plasma reaction region from flowing into the exhaust region through the gas channel. Accordingly, a plasma processing device including the above-mentioned confinement ring is also provided. The present invention can not only improve the pumping efficiency, but also ensure a sufficient electron and ion wall collision rate, thereby reducing the risk of plasma leakage.

Description

Technical Field

[0001] The present invention relates to the technical field of plasma etching, and in particular to a confinement ring and a plasma processing device. Background Art

[0002] In plasma etching, the plasma reaction area is filled with neutral gas molecules, dissociated electrons, ions, active free radicals, and by-products produced after reaction with the etched object. These by-products need to be removed in time to ensure the smooth progress of the etching reaction. Therefore, the plasma etching devices currently used all use a flowing gas reaction chamber, that is, the reaction gas is continuously injected from one end of the reaction chamber, and the by-products and other unreacted substances are continuously removed from the other end. The structure of the reaction chamber is as follows Figure 1 As shown, the showerhead at the top of the reaction chamber is connected to a gas supply device for delivering reaction gases to the reaction chamber. An exhaust pump is also located below the reaction chamber to remove reaction byproducts from the reaction chamber and maintain the vacuum environment. Because the extracted gas has been ionized into plasma, the plasma needs to be quenched during the extraction process to prevent plasma corrosion of the vacuum pump and pipelines, as well as possible plasma conductivity leading to radio frequency leakage. Plasma quenching is the process of electrically neutralizing the electrons and ions in the plasma. The most efficient method is to use wall impact loss for quenching.

[0003] The commonly used quenching device currently consists of a multi-layered, nested, annular plasma confinement ring (Confinement Ring), positioned around the lower electrode. This design neither restricts the plasma reaction space nor blocks the transmission port. The confinement ring relies on a narrow ring spacing and ring plate height to increase the probability of electrons and ions hitting the wall, causing most electrons and ions to be lost on the ring plates, thus achieving the goal of quenching the plasma. However, this design comes at the cost of the exhaust gas path being divided into numerous narrow gaps by a dozen to dozens of ring plates, significantly limiting the flow conductance of the exhaust gas path and preventing the realization of an atmospheric flow and low-pressure working environment.

[0004] Due to this limitation, the existing quenching device—the confinement ring—is unable to meet the high flow and low pressure requirements of processes at 10nm and below, necessitating increased conductance. Based on current processes, there are only two ways to increase conductance: reducing the ring plate height or increasing the ring plate spacing. Both methods reduce the electron and ion wall impact rate, creating the risk of plasma leakage. Summary of the Invention

[0005] The object of the present invention is to provide a confinement ring and a plasma processing device, which can not only improve the air conduction of the pumping gas, but also ensure a sufficient electron and ion wall collision rate and reduce the risk of plasma leakage.

[0006] In order to achieve the above objectives, the present invention is implemented through the following technical solutions:

[0007] A confinement ring for a plasma processing device, the plasma processing device comprising a susceptor. The confinement ring surrounds the susceptor and is disposed between a plasma reaction region and an exhaust region of the plasma processing device. The confinement ring comprises a plurality of concentrically arranged ring plates, the plurality of ring plates being arranged radially along the susceptor, with gaps between adjacent ring plates forming gas channels.

[0008] At least two of the ring plates are magnetic, and a magnetic field is formed between two adjacent magnetic ring plates, wherein the magnetic field restricts charged particles discharged from the plasma reaction region from flowing into the exhaust region through the gas channel;

[0009] A radio frequency shielding area is provided in the reaction chamber, and the confinement ring is arranged in the radio frequency shielding area.

[0010] Furthermore, the direction of the magnetic field is along the radial direction of the ring plate.

[0011] Furthermore, the widths of the gaps between two adjacent ring plates are the same or different.

[0012] Furthermore, the width of the gap within the magnetic field is greater than the width of the gap outside the magnetic field.

[0013] Furthermore, the innermost ring plate of the concentrically arranged ring plates and the outermost ring plate of the concentrically arranged ring plates are magnetic.

[0014] Furthermore, the magnetic ring plate and the non-magnetic ring plate are spaced apart.

[0015] Furthermore, all the ring plates are magnetic.

[0016] Furthermore, the magnetic ring plate is made of a permanent magnet.

[0017] Furthermore, the permanent magnet is a neodymium iron boron magnet.

[0018] Furthermore, the surface of the ring plate has an insulating coating.

[0019] Furthermore, the insulating coating is at least one of oxides or fluoride oxides of rare earth elements.

[0020] A plasma processing device includes a reaction chamber surrounded by a chamber wall, wherein the reaction chamber has a plasma reaction area and an exhaust area, and a base is arranged in the reaction chamber. The above-mentioned confinement ring is arranged between the plasma reaction area and the exhaust area, and is located between the outer periphery of the base and the inner wall of the reaction chamber.

[0021] Furthermore, a first grounding ring extending along the axial direction of the base and a second grounding ring extending along the radial direction of the base are provided on the periphery of the base, the first grounding ring is connected to the second grounding ring, the bottom of the first grounding ring is connected to the bottom wall of the reaction chamber, and the second grounding ring is connected to the side wall of the reaction chamber.

[0022] Furthermore, the radio frequency shielding area is an area located below the second grounding ring.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] The confinement ring provided by the present invention forms a magnetic field in the gas channel by using a magnetic ring plate. The magnetic field restricts the plasma from being discharged into the exhaust area through the gas channel. While ensuring the plasma confinement effect, the spacing between the ring plates can be increased, the pumping efficiency can be improved, and the process requirements of high flow and low gas pressure in the 10nm and below process can be met. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for the description. Obviously, the drawings described below are one embodiment of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort:

[0026] Figure 1 A structural diagram of a reaction chamber of a plasma processing device;

[0027] Figure 2 A structural diagram of a confinement ring provided in one embodiment of the present invention;

[0028] Figure 3 A structural diagram of a confinement ring provided in another embodiment of the present invention;

[0029] Figure 4 Schematic diagram of the placement environment of a non-magnetic confinement ring in a reaction chamber in the prior art;

[0030] Figure 5 Schematic diagram of the placement environment of the confinement ring of the present invention in the reaction chamber. DETAILED DESCRIPTION

[0031] The scheme proposed in the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. According to the following description, the advantages and features of the present invention will be clearer. It should be noted that the drawings are in a very simplified form and use non-precise proportions, which are only used to conveniently and clearly assist in explaining the purpose of the implementation methods of the present invention. In order to make the purposes, features and advantages of the present invention more obvious and easy to understand, please refer to the accompanying drawings. It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention, so they have no technical substantive significance. Any structural modification, change in proportional relationship or adjustment of size, without affecting the efficacy and purpose that can be achieved by the present invention, should still fall within the scope of the technical content disclosed by the present invention.

[0032] like Figure 1 As shown, a plasma processing apparatus comprises a reaction chamber 100 equipped with a gas showerhead 110 and a susceptor 120. The region between the gas showerhead 110 and the susceptor 120 is the plasma reaction region A. Within this region, the reactive gas injected from the gas showerhead 110 dissociates into a plasma. The plasma contains a large number of active species, such as electrons, ions, excited atoms, molecules, and free radicals. These active species can undergo various physical and chemical reactions with the surface of the wafer to be processed above the susceptor 120, changing the wafer surface morphology and completing the etching process. A confinement ring 130 surrounds the susceptor 120 and is disposed between the plasma reaction region A and the exhaust region B of the plasma processing apparatus. Reaction byproducts within the plasma reaction region A need to be evacuated from the reaction chamber. During evacuation, the reaction byproducts pass through the confinement ring 130 and enter the exhaust region B. Upon entering the confinement ring 130, the charged particles collide with the inner wall of the confinement ring 130 and are quenched, thereby preventing the plasma from entering the exhaust region B.

[0033] As described in the background technology, Figure 1 The confinement ring of the prior art shown is affected by two conditions: plasma confinement efficiency and pumping efficiency. It cannot guarantee high plasma confinement efficiency under high pumping efficiency, and cannot meet the process requirements of high gas flow and low gas pressure in processes below 10nm.

[0034] like Figure 2 、 Figure 3 As shown, the present invention provides a restriction ring 230 comprising a plurality of concentrically arranged ring plates 231. Figure 5The plurality of ring plates 231 are arranged radially along the base 220. The gaps between two adjacent ring plates 231 form a gas channel. The reaction byproducts in the plasma reaction region A flow into the exhaust region B through the gas channel. After the plasma enters the gas channel, it collides with the ring plates 231 and is quenched. In the present invention, the ring plates 231 are perpendicular to the supporting surface of the base 220 for supporting wafers. In some embodiments, the upper surface of the ring plates 231 does not exceed the supporting surface of the base 220. Therefore, the height of the ring plates 231 can be appropriately increased, and the gas channel can be longer. In this way, the plasma above the base 220 is more easily quenched after entering the confinement rings. The gaps between the ring plates 231 can be appropriately set larger. In addition, the confinement rings 230 will not block the wafer transfer port of the reaction chamber, thereby avoiding interference with wafer transfer.

[0035] The width of the gap between adjacent ring plates 231 affects the plasma confinement and pumping efficiency of confinement ring 230. A wider gap improves pumping efficiency, but reduces plasma confinement efficiency, potentially leading to plasma leakage into exhaust region B, damaging components in exhaust region B and causing RF leakage. To ensure plasma confinement efficiency despite a wide gap, the present invention employs the following approach: At least two of the multiple ring plates 231 in confinement ring 230 are magnetic. A magnetic field is formed between two adjacent magnetic ring plates 231, which restricts charged particles discharged from plasma reaction region A from flowing through the gas channel into exhaust region B.

[0036] Optionally, the direction of the magnetic field is radially along the annular plate 231. In this case, plasma entering the gas channel is subjected to the Lorentz force in the magnetic field, causing it to rotate along a helical trajectory and ultimately collide with the sidewall of the upper annular plate 231. Consequently, charged particles in the plasma can pass through the confinement ring relatively directly and more easily move toward the sidewall of the annular plate. Even if the spacing between adjacent annular plates is increased, the purpose of confining the plasma can still be achieved. In other embodiments, the direction of the magnetic field can also be other directions, as long as it can cause charged particles in the plasma to collide with the sidewall of the annular plate 231.

[0037] Furthermore, the widths of the gaps between two adjacent ring plates 231 can be the same or different, as long as the plasma confinement efficiency can be guaranteed. In order to improve the pumping efficiency of the confinement ring 230, the width of the gap within the magnetic field can be made larger than the width of the gap outside the magnetic field. Figure 2In the embodiment shown, the gaps on the left are close to the base, and the gaps on the right are far away from the base. The four gaps on the left are all in the magnetic field, and the two gaps on the right are not in the magnetic field. Therefore, the four gaps on the left have greater ability to confine plasma than the two gaps on the right. Therefore, the widths of the four gaps on the left can be appropriately increased to increase the air flow conduction at the four gaps, thereby improving the air extraction efficiency near the base, so that the by-products of the substrate reaction can be extracted faster to meet the process requirements of advanced processes.

[0038] In order to further improve the air extraction efficiency of the limiting ring 230, each gap in the limiting ring 230 can be made to have a larger air extraction flow guide, that is, the width of each gap can be increased. One way to achieve this is to make the innermost ring plate 231 of the multiple concentrically arranged ring plates 231 and the outermost ring plate 231 of the multiple concentrically arranged ring plates have magnetic properties. Figure 2 , the first ring plate 231 on the left and the first ring plate 231 on the right shown in the figure can be made magnetic. A magnetic field is formed between these two ring plates 231, thereby forming magnetic fields in the same direction at the six gaps shown in the figure. This magnetic field enhances the confinement efficiency of the plasma flowing into these six gaps, so the widths of these six gaps can be appropriately increased. Furthermore, the magnetic field increases at the gaps closer to the magnetic ring plate 231, thereby further increasing the gaps at these locations.

[0039] In another implementation, the magnetic ring plate 231 and the non-magnetic ring plate 231 may be spaced apart. Figure 2 , the first, third, fifth, and seventh ring plates 231 from the left in the figure can be made magnetic, while the second, fourth, and sixth ring plates 231 can be non-magnetic. Consequently, a magnetic field is formed between the first and third ring plates 231 from the left, and the first and second gaps from the left in the figure are located within this magnetic field. Similarly, the third and fifth ring plates 231 form magnetic fields at the third and fourth gaps, and the fifth and seventh ring plates 231 form magnetic fields at the fifth and sixth gaps. Because the distance between adjacent magnetic ring plates 231 is reduced, the magnetic induction intensity at each gap is stronger, resulting in a correspondingly higher plasma confinement efficiency at each gap. Therefore, the width of each gap can be appropriately increased to further improve the pumping efficiency of the confinement rings 230.

[0040] In yet another implementation, Figure 3 As shown, all the ring plates 231 can be made magnetic, so that there is a magnetic field in the gaps between adjacent ring plates 231, and the magnetic induction intensity at each gap is stronger, and the confinement efficiency of each gap on the plasma is higher. Therefore, the width of each gap can be further appropriately increased to further improve the pumping efficiency of the confinement ring 230.

[0041] The magnetic ring plate 231 can be made of a permanent magnet or an electromagnet. However, since electromagnets require electricity, the confinement ring 230 is placed in the reaction chamber, and the power supply circuit is prone to radio frequency leakage. Therefore, the magnetic ring plate 231 is preferably made of a permanent magnet. The permanent magnet is a strong neodymium iron boron magnet.

[0042] Furthermore, to prevent the confinement ring 230 from being corroded by the plasma, the surface of the ring plate 231 is provided with an insulating coating. Optionally, the insulating coating is at least one of an oxide or oxyfluoride of a rare earth element, such as Y2O3. Furthermore, since electrons in the plasma move more rapidly, they can reach the surface of the ring plate 231 earlier. Due to the insulating coating on the surface of the ring plate 231, the electrons form a negative electric field on the surface of the ring plate 231, exerting a force toward the ring plate while repelling electrons. This allows charged particles in the plasma to reach the sides of the ring plate more quickly, thereby improving quenching efficiency and further reducing the requirements for magnetic induction intensity.

[0043] The following Figure 3 Taking the restriction ring 230 as an example, the feasibility of the present invention is analyzed.

[0044] For the RF plasma used for etching, take argon (Ar) gas plasma as an example, where Ar + The thermal motion velocity of is about 500m / s, and the thermal motion velocity of electrons is about Ar + 100 times, that is, 5*10 4 m / s, the two perpendicular magnetic flux lines are incident into a uniform magnetic field with a magnetic induction intensity of B and then acted upon by the Lorentz force to produce circular motion. The motion radius is:

[0045]

[0046] For common permanent magnets, the magnetic induction intensity near the magnetic pole is 0.1~0.5T, and the magnetic induction intensity near the magnetic pole of stronger NdFeB magnets is 0.2~0.6T. Taking B=0.4T as the middle value, we can calculate: R[Ar + ]=0.52mm,R[e - ]=7E-4mm.

[0047] Taking B = 0.05T as a conservative value, we can calculate: R[Ar + ]=4.1mm,R[e - ]=6E-3mm.

[0048] Therefore, for a gap with a magnetic induction intensity of 0.05 T, when ions are incident tangentially and perpendicularly to the magnetic flux lines, the gap height only needs to be greater than 2R[Ar+], or 8.2 mm, to ensure that the Ar+ returns to the plasma reaction region A after one rotation in the magnetic field and does not enter the exhaust region B below the confinement ring 230. When ions are not incident perpendicularly to the magnetic flux lines, they will perform solenoid motion along the direction of the magnetic flux lines, eventually reaching the side wall of the ring plate 231 and impacting it. In practice, due to the faster movement of electrons, they can reach the surface of the ring plate 231 earlier.

[0049] For a strong magnet, the magnetic induction intensity is strongest near its magnetic poles. Therefore, in a conservative embodiment, the ring plate spacing d is set to 5 mm, the ring plate height h is set to 10 mm, the magnetic induction intensity B is set to 0.05 T, and the ring plate diameter φ is set to 450 mm. At this time, the conductance of the gap between two adjacent ring plates 231 is:

[0050]

[0051] K is the shape correction coefficient. When the diameters of the two ring plates 231 are not much different (D1 / D2=1), K is set to 1.65. Substituting it into the equation, we can get

[0052] C m [Magnet] = 0.452m 3 / s

[0053] For the non-magnetic confinement ring 130 used in the prior art, the characteristic parameters of the two ring plates and the gap in the center are d = 1.5 mm, h = 17.4 mm, φ = 450 mm, and the calculation results are

[0054] C m [Al]=0.023m 3 / s

[0055] It can be seen that the conductance of the magnetic confinement ring calculated based on conservative data is 20 times greater than that of the non-magnetic confinement ring in the prior art, which is very beneficial for meeting the process requirements of high flow and low gas pressure.

[0056] In summary, the confinement ring provided by the present invention forms a magnetic field in the gas channel by adopting a magnetic ring plate. The magnetic field limits the plasma from being discharged into the exhaust area through the gas channel. While ensuring the plasma confinement effect, the spacing between the ring plates can be increased and the pumping efficiency can be improved.

[0057] Based on the same inventive concept, the present invention also provides a plasma processing device, including a reaction chamber surrounded by a chamber wall, wherein the reaction chamber has a plasma reaction area and an exhaust area, and a base is arranged in the reaction chamber. The above-mentioned confinement ring is arranged between the plasma reaction area and the exhaust area, and is located between the outer periphery of the base and the inner wall of the reaction chamber.

[0058] In the plasma processing device, the reaction chamber has a radio frequency shielding area. Figure 4 As shown, an upper grounding ring 140 is disposed between confinement ring 130 and base 120. A middle grounding ring 150 is disposed below confinement ring 130 to provide electric field shielding for confinement ring 130. A lower grounding ring 160 is disposed below middle grounding ring 150. Upper grounding ring 140, middle grounding ring 150, and lower grounding ring 160 are electrically connected to form a radio frequency grounding loop within reaction chamber 100. The area between middle grounding ring 150, lower grounding ring 160, and the chamber wall forms a radio frequency shielding zone. Existing confinement ring 130 is located above middle grounding ring 150.

[0059] Since the reaction chamber of the plasma processing device uses radio frequency as the power source of the plasma, the radio frequency electromagnetic field is distributed in most of the space in the reaction chamber, and the radio frequency current will also propagate along the metal surface of the inner wall of the etching chamber. Figure 4 When placed in the reaction chamber in the manner shown, these periodically varying electromagnetic fields and radio frequency currents will pass through the permanent magnet, affecting the direction of the magnetic domains in the permanent magnet, causing the permanent magnet to demagnetize in the radio frequency field, causing the confinement ring to lose its confinement effect on the plasma.

[0060] Based on this, in the plasma processing device of the present invention, the confinement ring is arranged in the radio frequency shielding area in the reaction chamber, thereby avoiding the adverse effect of the radio frequency field in the reaction chamber on the magnetism of the confinement ring. Figure 5 As shown, within the reaction chamber 200, a first grounding ring 250 extending axially of the base 220 and a second grounding ring 240 extending radially of the base 220 are provided on the periphery of the base 220. The first grounding ring 250 is connected to the second grounding ring 240. The bottom of the first grounding ring 250 is connected to the bottom wall of the reaction chamber 200, and the second grounding ring 240 is connected to the side wall of the reaction chamber 200. The RF shielding area is located below the second grounding ring 240. Therefore, the confinement ring 230 is installed below the second grounding ring 240. Within this RF shielding area, the effectiveness of the confinement ring can be ensured and its service life can be extended.

[0061] The plasma processing apparatus of the present invention may be a capacitively coupled plasma processor (CCP) or an inductively coupled plasma processor (ICP).

[0062] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply the existence of any such actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or device comprising the element.

[0063] Although the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description is not intended to limit the present invention. After reading the above description, various modifications and substitutions of the present invention will become apparent to those skilled in the art. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A confinement ring for a plasma processing device, wherein the plasma processing device includes a susceptor, and the confinement ring is disposed around the susceptor between a plasma reaction region and an exhaust region of the plasma processing device, wherein: It comprises a plurality of concentrically arranged ring plates, the plurality of ring plates being arranged along the radial direction of the base, and the gap between two adjacent ring plates forming a gas channel; At least two of the ring plates are magnetic, and a magnetic field is formed between two adjacent magnetic ring plates, wherein the magnetic field restricts charged particles discharged from the plasma reaction region from flowing into the exhaust region through the gas channel; The reaction chamber of the plasma processing device has a radio frequency shielding area, and the confinement ring is arranged in the radio frequency shielding area to prevent the radio frequency electromagnetic field in the reaction chamber from demagnetizing the ring plate; A first grounding ring extending along the axial direction of the base and a second grounding ring extending along the radial direction of the base are provided on the periphery of the base. The first grounding ring is connected to the second grounding ring. The bottom of the first grounding ring is connected to the bottom wall of the reaction chamber. The second grounding ring is connected to the side wall of the reaction chamber. The radio frequency shielding area is the area located below the second grounding ring.

2. The confinement ring according to claim 1, wherein The direction of the magnetic field is along the radial direction of the ring plate.

3. The confinement ring according to claim 1, wherein: The widths of the gaps between two adjacent ring plates are the same or different.

4. The confinement ring according to claim 3, wherein: The width of the gap within the magnetic field is greater than the width of the gap outside the magnetic field.

5. The confinement ring according to claim 1, wherein: The innermost ring plate of the concentrically arranged ring plates and the outermost ring plate of the concentrically arranged ring plates are magnetic.

6. The confinement ring according to claim 1, wherein: The magnetic ring plate and the non-magnetic ring plate are spaced apart from each other.

7. The confinement ring according to claim 1, wherein: All ring plates are magnetic.

8. The confinement ring of claim 1, wherein: The magnetic ring plate is made of permanent magnets.

9. The confinement ring of claim 8, wherein: The permanent magnet is a neodymium iron boron magnet.

10. The confinement ring of claim 1, wherein: The surface of the ring plate is provided with an insulating coating.

11. The confinement ring of claim 10, wherein: The insulating coating is at least one of oxides or fluoride oxides of rare earth elements.

12. A plasma processing device, comprising a reaction chamber surrounded by a chamber wall, wherein the reaction chamber has a plasma reaction area and an exhaust area, and a base is provided in the reaction chamber, characterized in that: The confinement ring described in any one of claims 1 to 11 is arranged between the plasma reaction region and the exhaust region, and is located between the outer periphery of the base and the inner wall of the reaction chamber.

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