Plasma confinement system, plasma processing apparatus, and etching method

Abstract

The application discloses a plasma confinement system, a plasma processing device and an etching method. The plasma confinement system is used in a plasma processing device and comprises a plasma confinement ring, which is provided with an exhaust passage, one end of the exhaust passage is communicated with an etching area, and the other end is communicated with an exhaust area; and an impedance matching element, the plasma confinement ring can be grounded through the impedance matching element. According to the application, the plasma confinement ring can have an adaptive ground capacitance according to process requirements, and the plasma confinement performance under large radio frequency power can be improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor equipment technology, and more specifically to a plasma confinement system, a plasma processing apparatus, and an etching method. Background Technology

[0002] Dry etching utilizes plasma to etch wafers. This process is carried out within the reaction chamber of a plasma processing apparatus. During processing, a process gas is introduced into the reaction chamber, and then radio frequency power is applied to the introduced process gas through upper and lower electrodes to generate plasma. The plasma contains a large number of active particles such as electrons, ions, excited-state atoms, molecules, and free radicals. These active particles can undergo various physical and chemical reactions with the wafer surface, altering the wafer's morphology and completing the etching process.

[0003] To increase the mean free path of the plasma and remove reaction byproducts from the reaction chamber, a high degree of vacuum is maintained within the chamber via a pumping unit located at its bottom. The plasma within the chamber diffuses along with the gas flow. While most of the plasma remains within the etched area between the upper and lower electrodes, some diffuses beyond the etched area and flows into the pumping lines, causing corrosion or erosion, reducing the lifespan of the plasma processing unit, increasing maintenance frequency, and impacting efficiency.

[0004] Currently, plasma is typically confined within the etching region by placing a plasma confinement ring below the etching area in the reaction chamber, thus preventing it from entering the downstream extraction pipeline. However, in existing technologies, plasma leakage is still possible. For example, when there is a need to increase the aspect ratio of the etching, it is necessary to increase the etching rate and etching depth by increasing the power. This leads to an increase in the velocity of the plasma bombarding the plasma confinement ring, making it ineffective in confining the plasma, and allowing the plasma to pass through the plasma confinement ring and enter the downstream region. Summary of the Invention

[0005] The purpose of this invention is to provide a plasma confinement system, a plasma processing device, and an etching method, which can make the plasma confinement ring have an appropriate ground capacitance according to the process requirements, thereby improving the plasma confinement performance.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] A plasma confinement system for a plasma processing apparatus, characterized in that it comprises:

[0008] A plasma confinement ring is provided with an exhaust channel, one end of which is connected to an etching region and the other end of which is connected to an exhaust region.

[0009] An impedance matching element is provided, through which the plasma confinement ring can be grounded.

[0010] Preferably, the plasma confinement system further includes a grounding ring, and the impedance matching element is connected between the plasma confinement ring and the grounding ring to enable the plasma confinement ring to be grounded.

[0011] Preferably, the impedance of the impedance matching element is adjustable.

[0012] Preferably, the impedance matching element includes a variable capacitor or a variable inductor, and the impedance is adjusted by the variable capacitor or the variable inductor.

[0013] Preferably, it further includes an insulating ring disposed between the plasma confinement ring and the grounding ring.

[0014] A plasma processing apparatus includes a reaction chamber and a base located within the reaction chamber for supporting a wafer, and further includes:

[0015] A plasma confinement ring is arranged around the base and is equipped with an exhaust channel. One end of the exhaust channel is connected to the etched area above the base, and the other end is connected to the exhaust area.

[0016] An impedance matching element is provided, through which the plasma confinement ring is grounded.

[0017] Preferably, the plasma processing apparatus further includes: a grounding ring configured to surround the base and be located below the plasma confinement ring for supporting the plasma confinement ring, and an insulating ring disposed between the plasma confinement ring and the grounding ring.

[0018] Preferably, the thickness of the insulating ring is 3mm-12mm.

[0019] Preferably, an insulating ring is provided between the plasma confinement ring and the grounding ring, the insulating ring comprising an inner insulating ring and an outer insulating ring adapted to the inner confinement ring and the outer confinement ring.

[0020] Preferably, the insulating ring has a channel that penetrates the ring body to accommodate the connecting wire of the impedance matching element.

[0021] Preferably, the insulating ring is made of any one or more of ceramic, Teflon, polyetherimide, polyetheretherketone, or glass fiber.

[0022] Preferably, the impedance matching element is connected between the plasma confinement ring and the grounding ring to ground the plasma confinement ring.

[0023] Preferably, the plasma confinement ring includes an inner confinement ring and an outer confinement ring, and an annular grid is provided between the inner confinement ring and the outer confinement ring. The gaps between the inner confinement ring, the outer confinement ring and the annular grid form an air extraction channel.

[0024] It also includes a grounding ring configured to surround the base and be located below the plasma confinement ring to support the plasma confinement ring. The grounding ring includes an inner grounding ring and an outer grounding ring adapted to the inner confinement ring and the outer confinement ring, and the inner grounding ring and the outer grounding ring are connected by spokes that are evenly distributed in the circumferential direction.

[0025] There are multiple impedance matching elements, and the connection points of each impedance matching element and the plasma confinement ring are evenly distributed in the corresponding circumferential positions.

[0026] Preferably, both the inner limiting ring and the outer limiting ring are connected to the impedance matching element.

[0027] Preferably, the impedance of the impedance matching element is adjustable.

[0028] Preferably, the impedance matching element includes a variable capacitor or a variable inductor, and the impedance is adjusted by the variable capacitor or the variable inductor.

[0029] Preferably, the plasma processing apparatus further includes a controller connected to the impedance matching element, the controller being capable of adjusting the impedance of the impedance matching element.

[0030] Preferably, the controller adjusts the impedance of the impedance matching element according to the radio frequency power of the ionized reactive gas.

[0031] An etching method, comprising:

[0032] The wafer is loaded onto the base of any of the aforementioned plasma processing devices;

[0033] The wafer is etched using the plasma processing device.

[0034] Compared with the prior art, the present invention has the following advantages:

[0035] 1. By grounding the plasma confinement ring through an impedance matching element, the plasma confinement ring can have an appropriate ground capacitance according to process requirements, thereby improving plasma confinement performance.

[0036] 2. Through the design of adjustable impedance matching components, it can better adapt to different process requirements and has better flexibility;

[0037] 3. By dynamically linking the impedance matching components with the radio frequency power, the impedance of each impedance matching component can be dynamically adjusted according to the radio frequency power. This allows for minimizing the bombardment intensity of the plasma on the plasma confinement ring while effectively confining the plasma, thus preventing premature damage to the plasma confinement ring and extending its service life.

[0038] 4. By setting an insulating ring of a certain thickness between the plasma confinement ring and the grounding ring, the breakdown resistance between the plasma confinement ring and the grounding ring is further improved, avoiding instability of the radio frequency circuit and affecting the process. Attached Figure Description

[0039] To more clearly illustrate the technical solutions of the embodiments of this invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is a schematic diagram of a plasma etching device in the prior art.

[0041] Figure 2 This is a partial cross-sectional schematic diagram of the plasma confinement ring and grounding ring in the prior art;

[0042] Figure 3 This is a schematic diagram of one embodiment of the plasma confinement system of the present invention;

[0043] Figure 4 This is a schematic diagram of one embodiment of the plasma confinement system of the present invention;

[0044] Figure 5 This is a top view of one embodiment of the plasma confinement ring of the present invention;

[0045] Figure 6 This is a top view of one embodiment of the grounding ring of the present invention;

[0046] Figure 7 This is a front cross-sectional view of the plasma confinement ring, insulating ring, and grounding ring of the present invention. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described below with reference to the accompanying drawings. The described embodiments should not be regarded as limitations on the invention. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0048] In the following description, references to "some embodiments" or "one or more embodiments" describe a subset of all possible embodiments. However, it is understood that "some embodiments" or "one or more embodiments" may be the same subset or different subsets of all possible embodiments and may be combined with each other without conflict.

[0049] In the following description, the terms "first, second, third" are used only to distinguish similar objects and do not represent a specific ordering of objects. It is understood that "first, second, third" may be interchanged in a specific order or sequence where permitted, so that the embodiments of the invention described herein can be implemented in an order other than that shown in the illustrations or description.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing embodiments of the invention only and is not intended to limit the scope of the invention.

[0051] Appendix Figure 1 A capacitively coupled plasma processing device is shown, comprising a vacuum-ejectable reaction chamber 1. A spray head 2 for introducing reactive gas into the reaction chamber 1 is located at the top of the chamber, and a base 3 for supporting a wafer W is located below the spray head 2. An etching region A is located between the spray head 2 and the base 3. Typically, the spray head 2 serves as the upper electrode, and the base 3 as the lower electrode. At least one radio frequency (RF) power supply applies RF energy to at least one of the upper and lower electrodes through an impedance matching network, generating an RF electric field between the upper and lower electrodes. This ignites and dissociates the reactive gas in the etching region A into plasma. The plasma reaching the upper surface of the wafer W can perform etching and other processes on the wafer W. During the process, depending on the different etching aspect ratio requirements, the RF power of the ignited plasma needs to be adjusted to control the etching rate and etching depth; the higher the applied RF power, the greater the etching rate and etching depth. The lower part of the reaction chamber 1 is an exhaust region B connected to a vacuum pump 6, which extracts the process waste gas generated after the etching reaction from the reaction chamber 1.

[0052] Between the etching region A and the exhaust region B, a plasma confinement ring 04 is also provided around the base 3 to confine the plasma within the etching region A, preventing it from diffusing into the exhaust region B below and thus corroding the reaction chamber walls, pipes, etc., within the exhaust region B. Below the plasma confinement ring 04, an insulated grounding ring 05 is provided. This grounding ring 05 is grounded, serves to support the plasma confinement ring 04, and provides a radio frequency circuit for the radio frequency field within the reaction chamber 1. Figure 2As shown, in some embodiments, a gap exists between the plasma confinement ring 04 and the grounding ring 05, forming a capacitor structure between them during the process. Simultaneously, the plasma continuously bombards the plasma confinement ring 04 during the process, increasing its potential and creating a potential difference between it and the grounding ring 05. The greater the radio frequency power applied between the upper and lower electrodes, the more plasma is generated and the faster its velocity, resulting in stronger plasma bombardment of the plasma confinement ring 04 and a larger potential difference between it and the grounding ring 05. This leads to several problems: firstly, the possibility of plasma escaping and leaking from the plasma confinement ring 04 increases; secondly, the high-intensity plasma bombardment can easily cause the plasma confinement ring 04 to be consumed and damaged too quickly, and the excessively large potential difference between the plasma confinement ring 04 and the grounding ring 05 may further lead to breakdown between them, resulting in more serious consequences such as structural damage within the reaction chamber 1.

[0053] To address this technical problem, existing technologies reduce the distance between the opposing surfaces of the plasma confinement ring 04 and the grounding ring 05, thereby increasing the capacitance formed between them and reducing the potential difference. Because a larger capacitance between the plasma confinement ring 04 and the grounding ring 05 results in a smaller impedance to ground (hereinafter referred to as impedance) for the plasma confinement ring 04, a thicker plasma sheath above it, and greater difficulty for plasma to pass through the plasma confinement ring 04, leading to a better plasma confinement effect; however, a thicker plasma sheath also results in stronger plasma bombardment of the plasma confinement ring 04, making it more susceptible to damage. The existing methods are not ideal. On the one hand, the capacitance between the two is too small to produce a satisfactory plasma confinement effect. Furthermore, due to the rough surface caused by machining, the contact between the plasma confinement ring 04 and the grounding ring 05 is uneven. When the distance between them decreases, discharge is more likely to occur at some sharp points, breaking down the capacitance between them, causing instability in the RF circuit and affecting the manufacturing process. On the other hand, when the RF power is high, the impedance to ground of the plasma confinement ring 04 remains relatively low, which leads to continuous high-intensity bombardment of the plasma confinement ring 04 by the plasma, resulting in premature damage to the plasma confinement ring 04 and shortening its service life.

[0054] This invention addresses this technical problem by providing a plasma confinement system and a plasma processing apparatus. Its working principle involves grounding the plasma confinement ring through an impedance matching element. Furthermore, the impedance of the plasma confinement ring is adjusted according to process requirements to meet the requirements of the plasma confinement ring's capacitance to ground, thus achieving a satisfactory plasma confinement effect. Simultaneously, it avoids excessive capacitance to ground, which could lead to excessive bombardment of the plasma confinement ring by the plasma, thereby improving the lifespan of the plasma confinement ring. In addition, by placing a relatively thick insulating layer between the plasma confinement ring and the grounding ring, it further prevents discharge breakdown between the plasma confinement ring and the grounding ring.

[0055] Below, in conjunction with the appendix Figures 3-7 The plasma confinement system of the present invention will be described in detail below. (See attached diagram) Figure 3 , 4 As shown, the plasma confinement system includes:

[0056] A plasma confinement ring 4, surrounding the base 3, is disposed within the reaction chamber 1. It is equipped with an extraction channel, the two ends of which are connected to the etching region A and the exhaust region B, respectively. This channel confines the plasma within the etching region A, serving as a conduit for the discharge of process waste gas from the etching region A to the exhaust region B. (Appendix) Figure 5 A top view of a plasma confinement ring 4 in one embodiment is shown, which includes an inner confinement ring 41 surrounding the outer periphery of a base 3 and an outer confinement ring 42 surrounding the inner confinement ring 41, and an annular grid 43 located between the inner confinement ring 41 and the outer confinement ring 42. The annular grid 43 includes a set of concentrically arranged limiting single rings 431 with increasing radii between the limiting inner ring 41 and the limiting outer ring 42, and a number of limiting spokes 432 arranged radially along the limiting inner ring 41 to connect the limiting inner ring 41, the limiting outer ring 42 and each limiting single ring 431. Optionally, each limiting spoke 432 is evenly distributed circumferentially. The gaps between the limiting inner ring 41, the limiting outer ring 42 and the annular grid 43 form multiple exhaust channels. The top end of each exhaust channel is connected to the etching area A, and the bottom end is connected to the exhaust area B. The exhaust area B is connected to the vacuum pump 6. The vacuum pump 6 draws in the process waste gas generated after the etching reaction through the exhaust channels and discharges it outside the cavity. The plasma flowing with the process waste gas will collide with the annular grid 43 and be neutralized and annihilated when passing through the exhaust channels, thereby confining the plasma in the etching area A and avoiding the plasma bombarding the side wall of the chamber in the exhaust area B and corroding the exhaust pipeline.

[0057] A grounding ring 5, surrounding the base 3 and reaction chamber 1 and positioned below the plasma confinement ring 4, serves to support the plasma confinement ring 4 and provide a radio frequency (RF) loop for the RF field within the reaction chamber 1. (Appendix) Figure 6A top view of a grounding ring 5 in one embodiment is shown, which includes an inner grounding ring 51 surrounding the outer periphery of the base 3 and an outer grounding ring 52 surrounding the inner grounding ring 51, and a plurality of grounding spokes 53 connected at both ends to the inner grounding ring 51 and the outer grounding ring 52, respectively, with each grounding spoke 53 evenly distributed in the circumferential direction; wherein the inner grounding ring 51 and the outer grounding ring 52 are adapted to the shape and size of the inner limiting ring 41 and the outer limiting ring 42, respectively.

[0058] An impedance matching element 7 is connected to the plasma confinement ring 4, through which the plasma confinement ring 4 is grounded. This element 7 adjusts the impedance of the plasma confinement ring 4 to meet the process requirements for the plasma confinement ring 4's capacitance to ground, achieving good plasma confinement performance and preventing excessive plasma bombardment of the plasma confinement ring 4 due to excessive capacitance to ground, thus extending the lifespan of the plasma confinement ring. The impedance matching element 7 can be grounded in two ways: direct grounding and indirect grounding. Figure 3 An embodiment of direct grounding is shown, in which the plasma confinement ring 4 is directly grounded via impedance matching element 7; Appendix Figure 4 An embodiment of indirect grounding is shown, in which the plasma confinement ring 4 is connected to the grounding ring 5 via the impedance matching element 7, and then grounded via the grounding ring 5.

[0059] Preferably, in some embodiments, there are multiple impedance matching elements 7, and each impedance matching element 7 is uniformly distributed circumferentially with each connection point of the plasma confinement ring 4 or with each connection point of the plasma confinement ring 4 and the grounding ring 5, so that the circumferential impedance of the plasma confinement ring 4 is uniformly distributed.

[0060] Preferably, in some embodiments, both the inner limiting ring 41 and the outer limiting ring 42 are connected to the impedance matching element 7, which enables the radial impedance of the plasma confinement ring 4 to be uniformly distributed.

[0061] In some embodiments, the impedance matching element 7 is a passive impedance matching element, such as a circuit composed of a fixed capacitor and an inductor, whose impedance is not adjustable during use, but can be configured according to specific process requirements. Preferably, in some embodiments, the impedance of the impedance matching element 7 is adjustable, which can better adapt to the needs of different processes in the same equipment. That is, the impedance matching element 7 can be adjusted to adapt when different processes are performed in the same equipment, providing better flexibility. Further, in some embodiments, the impedance matching element 7 includes a variable capacitor or a variable inductor, which adjusts the impedance. More preferably, in some embodiments, the impedance matching element 7 is connected to a controller (not shown), which can adjust the impedance of the impedance matching element 7 according to specific processes or process parameters, such as the radio frequency power of the ignited plasma. Optionally, the radio frequency power is inversely proportional to the impedance of the impedance matching element 7. The principle is as follows: when the radio frequency power is higher, more plasma is generated in the reaction chamber 1 and the plasma movement speed is faster. The possibility of plasma escaping and leaking from the plasma confinement ring 4 is greater. At this time, the controller adjusts and reduces the impedance of the impedance matching element 7, so that the thickness of the plasma sheath layer on the surface of each component of the plasma confinement ring 4 increases and the plasma confinement performance is enhanced. When the radio frequency power is reduced, the plasma generated in the reaction chamber 1 is relatively reduced and the plasma movement speed is slower. Therefore, it is no longer necessary to maintain the previous strength of plasma confinement performance. At this time, the controller adjusts and increases the impedance of the impedance matching element 7, so that the thickness of the plasma sheath layer above the plasma confinement ring 4 decreases and the plasma bombardment of the plasma confinement ring 4 weakens. Thus, under the premise of effectively confining the plasma, the intensity of plasma bombardment of the plasma confinement ring 4 is reduced to the maximum extent, avoiding premature damage to the plasma confinement ring 4 and extending its service life.

[0062] Preferably, in order to improve the breakdown resistance between the plasma confinement ring 4 and the grounding ring 5, in some embodiments, such as Figure 7As shown, an insulating ring 8 is further provided between the plasma confinement ring 4 and the grounding ring 5. The shape of the insulating ring 8 is adapted to the plasma confinement ring 4 and the grounding ring 5. It includes an insulating inner ring (not shown) and an insulating outer ring (not shown) adapted to the inner confinement ring 41 and the outer confinement ring 42. It is readily understood that the insulating ring is provided with an opening that matches the exhaust channel of the confinement ring to avoid obstructing the exhaust. In some embodiments, the insulating ring 8 is made of any one or more of ceramic, Teflon, polyetherimide, polyetheretherketone, or glass fiber. Further, in some embodiments, the thickness of the insulating ring 8 is 3mm-12mm, which has good breakdown resistance and does not affect the device layout design in the reaction chamber 1. Preferably, its thickness is 6mm. In some embodiments, the insulating ring 8 is provided with a channel 81 for accommodating the connecting wire of the impedance matching element 7; the grounding ring 5 is also provided with a corresponding channel 54 for accommodating the connecting wire of the impedance matching element 7 to avoid affecting the electromagnetic environment inside the chamber.

[0063] In addition, the present invention also provides a plasma processing apparatus, comprising:

[0064] reaction chamber;

[0065] A base located within the reaction chamber for supporting the wafer;

[0066] Any of the aforementioned plasma confinement systems;

[0067] Preferably, in some embodiments, a controller as described above is also included, which is associated with the radio frequency power of the ignition plasma. The controller is connected to each impedance matching element 7 of the plasma confinement system and is capable of dynamically adjusting the impedance of each impedance matching element 7 according to the radio frequency power.

[0068] In addition, the present invention also provides an etching method, which includes:

[0069] The wafer is loaded onto the base of any of the aforementioned plasma processing devices;

[0070] The wafer is etched using a plasma processing device.

[0071] It is readily understood that the present invention is also applicable to other plasma processing apparatuses that require plasma confinement.

[0072] The above description is merely an embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and scope of the present invention are included within the scope of protection of the present invention.

Claims

1. A plasma confinement system for a plasma processing apparatus, characterized in that, include: A plasma confinement ring is provided with an exhaust channel, one end of which is connected to an etching region and the other end of which is connected to an exhaust region. An impedance matching element is provided, through which the plasma confinement ring can be grounded; The grounding ring is positioned below the plasma confinement ring.

2. The plasma confinement system as described in claim 1, characterized in that, The impedance matching element is connected between the plasma confinement ring and the grounding ring to enable the plasma confinement ring to be grounded.

3. The plasma confinement system as described in claim 1 or 2, characterized in that, The impedance of the impedance matching element is adjustable.

4. The plasma confinement system as described in claim 3, characterized in that, The impedance matching element includes a variable capacitor or a variable inductor, and the impedance is adjusted by the variable capacitor or the variable inductor.

5. The plasma confinement system as described in claim 2, characterized in that, It also includes insulating rings, The insulating ring is disposed between the plasma confinement ring and the grounding ring.

6. A plasma processing apparatus, comprising a reaction chamber and a base located within the reaction chamber for supporting a wafer, characterized in that, Also includes: A plasma confinement ring is arranged around the base and is equipped with an exhaust channel. One end of the exhaust channel is connected to the etched area above the base, and the other end is connected to the exhaust area. An impedance matching element is provided, through which the plasma confinement ring is grounded; A grounding ring, configured to surround the base and be located below the plasma confinement ring, is used to support the plasma confinement ring.

7. The plasma processing apparatus as described in claim 6, characterized in that, An insulating ring is provided between the plasma confinement ring and the grounding ring.

8. The plasma processing apparatus as described in claim 7, characterized in that, The thickness of the insulating ring is 3mm-12mm.

9. The plasma processing apparatus as described in claim 8, characterized in that, The insulating ring has a channel that penetrates the ring body to accommodate the connecting wires of the impedance matching element.

10. The plasma processing apparatus as described in claim 9, characterized in that, The insulating ring is made of any one or more of the following materials: ceramic, Teflon, polyetherimide, polyetheretherketone, or glass fiber.

11. The plasma processing apparatus as claimed in claim 10, characterized in that, The impedance matching element is connected between the plasma confinement ring and the grounding ring to ground the plasma confinement ring.

12. The plasma processing apparatus according to any one of claims 6-11, characterized in that, The plasma confinement ring includes an inner confinement ring and an outer confinement ring. An annular grid is provided between the inner confinement ring and the outer confinement ring. The gaps between the inner confinement ring, the outer confinement ring and the annular grid form an air extraction channel. The grounding ring includes an inner grounding ring and an outer grounding ring adapted to the inner limiting ring and the outer limiting ring, and the inner grounding ring and the outer grounding ring are connected by spokes that are evenly distributed in the circumferential direction; There are multiple impedance matching elements, and the connection points of each impedance matching element and the plasma confinement ring are evenly distributed in the corresponding circumferential positions.

13. The plasma processing apparatus as described in claim 12, characterized in that, Both the inner and outer limiting rings are connected to the impedance matching element.

14. The plasma processing apparatus as described in claim 6 or 7, characterized in that, The impedance of the impedance matching element is adjustable.

15. The plasma processing apparatus as described in claim 14, characterized in that, The impedance matching element includes a variable capacitor or a variable inductor, and the impedance is adjusted by the variable capacitor or the variable inductor.

16. The plasma processing apparatus as claimed in claim 15, characterized in that, It also includes a controller connected to the impedance matching element, the controller being able to adjust the impedance of the impedance matching element.

17. The plasma processing apparatus as claimed in claim 16, characterized in that, The controller adjusts the impedance of the impedance matching element according to the radio frequency power of the ionized gas.

18. An etching method, characterized in that, include: The wafer is loaded onto the base of the plasma processing apparatus as described in any one of claims 6 to 17; The wafer is etched using the plasma processing device.

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