Plasma treatment apparatus and its confinement ring assembly

Abstract

A plasma treatment apparatus and its confinement ring assembly are disclosed. The reaction chamber of the plasma treatment apparatus has a confinement ring assembly for confining the plasma within its exhaust region. The confinement ring assembly comprises a first confinement ring and a second confinement ring in close contact with each other. The first confinement ring is made of silicon and has multiple first gas channels along its thickness direction. The second confinement ring is located downstream of the first confinement ring and has multiple second gas channels along its thickness direction. The first and second gas channels constitute the gas channels of the confinement ring assembly, and the aspect ratio of the gas channels is greater than or equal to 8:1. This invention overcomes the defects of insufficient aspect ratio and low gas flow resistance caused by the processing difficulties of gas channels in silicon confinement rings. By using the second confinement ring to effectively compensate for the aspect ratio of the gas channels in the silicon confinement ring, the overall confinement ring assembly achieves suitable gas flow resistance, thereby achieving a suitable pumping rate and thus obtaining reaction uniformity and stability.

Description

Plasma treatment apparatus and its confinement ring assembly Technical Field

[0001] This invention relates to the field of semiconductor manufacturing, and in particular to a plasma processing apparatus and its confinement ring assembly. Prior Technology

[0002] Plasma processing equipment processes wafers by dissociating reactive gases into plasma. Typically, a flow-equalizing ion shield ring (LEI) is placed in the exhaust area of ​​the reaction chamber to confine the plasma within the processing zone. The LIE is generally positioned between the wafer-supporting base and the sidewall of the reaction chamber, forming a plasma sheath to constrain the plasma. The LIE has multiple gas channels penetrating its upper and lower surfaces, allowing gas within the reaction chamber to exit. Typically, the LIE is made of aluminum. By appropriately setting the width and aspect ratio of the gas channels on the LIE, and matching the valve opening of the appropriate pump, the pumping rate can be controlled within an ideal range, achieving stable control of the gas pressure within the reaction chamber.

[0003] However, for high aspect ratio etching, due to the high etching energy and the introduction of corrosive gases, conventional aluminum plasma confinement rings are subjected to intense bombardment and corrosion by the plasma, leading to metal particle contamination and even unstable discharge. To solve this problem, the plasma confinement ring material can be replaced with silicon (monocrystalline or polycrystalline silicon). However, silicon is a brittle material, making it very difficult to process. In actual processing, the success rate of processing silicon plasma confinement rings with a groove width of less than 2 mm and a thickness of more than 8 mm is low, and the cost is high, which is not conducive to large-scale production and use. Due to the limitations of silicon material in processing, the aspect ratio of the gas guide groove in silicon plasma confinement rings is significantly smaller than that of aluminum plasma confinement rings. Consequently, the flow resistance of gas flowing through silicon plasma confinement rings is significantly lower, which adversely affects plasma confinement, exhaust uniformity, and stability.

[0004] The statements herein provide only background technology relevant to this work and do not necessarily constitute prior art. Summary of the Invention

[0005] The purpose of this invention is to provide a plasma treatment device and its confinement ring assembly, which compensates for the defects of insufficient aspect ratio and low gas flow resistance caused by the difficulty in processing the gas channel of the silicon confinement ring. It effectively compensates for the aspect ratio of the gas channel of the silicon confinement ring, so that the overall confinement ring assembly can obtain a suitable gas flow resistance, thereby obtaining a suitable pumping rate, and thus obtaining the uniformity and stability of the reaction.

[0006] To achieve the above objectives, this invention provides a confinement ring assembly for a plasma processing apparatus. The plasma processing apparatus includes a reaction chamber and a lower electrode disposed within the reaction chamber. A plasma processing region for processing a wafer is formed above the lower electrode, and an exhaust region is located outside the plasma processing region. A confinement ring assembly is disposed within the exhaust region for confining the plasma. The confinement ring assembly has multiple gas channels for discharging a portion of the plasma from the plasma processing region to the exhaust region downstream of the confinement ring assembly. The constraint ring assembly includes a first constraint ring and a second constraint ring that are in close contact with each other. The first constraint ring is made of silicon, and multiple first gas channels are provided in the thickness direction of the first constraint ring; The second constraint ring is disposed downstream of the first constraint ring, and the second constraint ring has multiple second gas channels in the thickness direction; Each of the gas channels includes a first gas channel and a second gas channel, wherein the aspect ratio of the gas channels is greater than or equal to 8:1.

[0007] The second constraint ring is made of insulating material.

[0008] Preferably, the second constraint ring is made of quartz or ceramic.

[0009] The number of the first gas channel and the number of the second gas channel are the same.

[0010] The first gas channel and the second gas channel have the same shape.

[0011] Optionally, the first gas channel and the second gas channel can be any one or more of the following: annular, grid-shaped, or perforated.

[0012] The thickness of the first constraint ring is 4mm to 8mm, and the thickness of the second constraint ring is 8mm to 12mm.

[0013] The first constraint ring includes a first mounting component made of radio frequency conductive material. The first mounting component connects the first constraint ring and the inner wall of the reaction chamber, and / or the first mounting component connects the first constraint ring and the lower electrode.

[0014] The second constraint ring includes a second mounting assembly made of insulating material. The second mounting assembly connects the second constraint ring and the inner wall of the reaction chamber, and / or connects the second constraint ring and the lower electrode.

[0015] This invention also provides a plasma treatment apparatus, comprising: reaction chamber; An upper electrode, disposed within the reaction chamber, is used to introduce reaction gas into the reaction chamber; The lower electrode is disposed within the reaction chamber, located below the upper electrode. The lower electrode includes a base for supporting the wafer. A plasma processing area for processing the wafer is formed above the lower electrode, and an exhaust area is located outside the plasma processing area. A radio frequency power supply, connected to the lower electrode, is used to generate an electric field to cause the reactive gas to form plasma; The constraint ring assembly is disposed within the exhaust region.

[0016] This invention utilizes a second constraint ring to adjust the flow resistance of the entire constraint ring assembly. The second constraint ring is positioned downstream of the first constraint ring made of silicon material and is close to the first constraint ring. The second gas channel on the second constraint ring extends the depth of the first gas channel on the first constraint ring, thus compensating for the defects of insufficient aspect ratio and low gas flow resistance caused by the processing difficulties of the gas channel in the silicon constraint ring.

[0017] The second constraint ring effectively compensates for the aspect ratio of the gas channel of the first constraint ring made of silicon, so that the overall gas channel has a sufficient aspect ratio to meet the requirements of semiconductor manufacturing process, and the overall constraint ring assembly has a suitable gas flow resistance, thereby obtaining a suitable pumping rate, and thus obtaining the uniformity and stability of the reaction.

[0018] The second constraint ring, made of insulating material, does not alter the radio frequency circuit in the reaction chamber, ensuring stable transmission of radio frequency power and avoiding plasma instability caused by fluctuations in the radio frequency circuit. This improves the stability of the etching rate and the yield of wafer production, avoids arc damage at the connection points caused by radio frequency circuit instability, and enhances the overall stability and reliability of the equipment.

[0019] The second constraint ring can be made of quartz or ceramic, neither of which will introduce additional pollution.

[0020] The second mounting component makes it easy to install the second constraint ring downstream of the first constraint ring, and also makes it easy to remove the second constraint ring for maintenance and replacement with a new one. The operation is simple and easy to maintain. Simple Explanation of the Diagram

[0021] Figure 1 is a structural diagram of a plasma processing device provided in this invention. Figure 2 is a structural schematic diagram of a constraint ring assembly provided in this invention. Implementation

[0022] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a further detailed explanation of the plasma treatment device and its constraint ring assembly proposed in this invention. The advantages and features of this invention will become clearer from the following description. It should be noted that the drawings are in a very simplified form and use non-precise proportions, intended only to facilitate and clearly illustrate the embodiments of this invention. Please refer to the drawings for a clearer understanding of the purpose, features, and advantages of this invention. It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are only for illustrative purposes and to aid those skilled in the art, and are not intended to limit the implementation conditions of this invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to the size, without affecting the effectiveness and purpose achieved by this invention, should still fall within the scope of the technical content disclosed in this invention.

[0023] As shown in Figure 1, this invention provides a plasma processing apparatus, which includes a reaction chamber 1. A gas spray head 2 is disposed at the top of the reaction chamber 1, serving as the upper electrode of the reaction chamber 1. The gas spray head 2 is connected to a gas supply device 3 for introducing reactive gas from the gas supply device into the reaction chamber 1. A base 4 is disposed within the reaction chamber 1, opposite to the gas spray head 2. The base 4 supports the wafer W to be processed and serves as the lower electrode of the reaction chamber 1. An radio frequency power supply 5 is applied to the upper electrode or the lower electrode, generating a radio frequency electric field between the upper and lower electrodes to dissociate the reactive gas into plasma, forming a plasma processing region 6 between the upper and lower electrodes. The plasma contains a large number of active particles such as electrons, ions, excited-state atoms, molecules, and free radicals. These active particles can react with the surface of the wafer W to be processed, completing the etching process. An exhaust device 7 is also provided below the reaction chamber 1 to discharge reaction byproducts from the reaction chamber 1 and maintain a vacuum environment in the reaction chamber 1. The area outside the plasma treatment area 6 is an exhaust area 8. A constraint ring 9 is provided in the exhaust area 8. The constraint ring 9 is arranged around the periphery of the base 4 and between the side wall 101 of the reaction chamber 1 to at least partially constrain the boundary of the plasma in the plasma treatment area 6.

[0024] The confinement ring 9 has multiple gas channels 901 penetrating its upper and lower surfaces. Plasma and reaction byproduct gases from the plasma treatment region 6 enter the confinement ring 9 along the exhaust path upstream of the confinement ring 9. The confinement ring 9 extinguishes charged particles in the plasma, preventing plasma from being generated on the inner wall of the reaction chamber and the exhaust region 8 below the confinement ring 9, thus preventing sidewall erosion or arc discharge. The confinement ring 9 not only allows the reaction gases to exit the reaction chamber 1 but also confines the plasma within the plasma treatment region 6.

[0025] By reasonably setting the ratio between the length and width of the gas channel 901 of the confinement ring 9, so that the flow resistance of the gas channel 901 reaches a predetermined value, it can be ensured that when the plasma from the plasma treatment area 6 flows through the confinement ring 9, the charged particles, especially the high-energy active electrons, are extinguished or blocked, and the neutral or low-energy gas flows downward and is discharged through the gas channel 901 in the confinement ring 9 to the exhaust area 8 on the downstream side of the confinement ring 9, and is finally discharged from the reaction chamber 1 by the exhaust device 7.

[0026] For high aspect ratio etching processes, the depth-to-width ratio of the gas channel 901 typically needs to be set to 8:1 or greater to ensure that the flow conductance of the gas channel 901 meets the above requirements. Because the plasma etching energy in the reaction chamber of a high aspect ratio etching process is high and corrosive gases are introduced, silicon material (e.g., monocrystalline or polycrystalline silicon) is used to fabricate the confinement ring 9 to better resist the strong bombardment and corrosion from the plasma, preventing metal particle contamination and unstable discharge. However, there are significant limitations in the processing of silicon materials. Existing processing techniques make it difficult to achieve the required aspect ratio of the gas channel 901 on the silicon confinement ring 9 for high aspect ratio etching processes. Only gas channels with a smaller aspect ratio can be obtained, resulting in significantly lower flow resistance when the gas flows through the silicon confinement ring 9. This leads to a higher pumping rate, which adversely affects the uniformity and stability of the reaction. Furthermore, the gas channel 901, with its relatively small depth-to-width ratio, cannot extinguish all high-energy charged particles. Some plasma will enter the exhaust region 8 downstream of the gas channel 901, reducing the confinement ability of the confinement ring 9 on the plasma, causing a decrease in the plasma density of the plasma processing region 6, resulting in unstable fluctuations.

[0027] To address the aforementioned problems with silicon-based constraint rings, as shown in Figure 2, this invention provides a constraint ring assembly 10. The constraint ring assembly 10 has multiple gas channels 01 penetrating its upper and lower surfaces. The constraint ring assembly 10 consists of a first constraint ring 11 and a second constraint ring 12. The first constraint ring 11 is made of silicon (monocrystalline or polycrystalline silicon). The second constraint ring 12 is located downstream of the first constraint ring 11, and the first and second constraint rings are in close contact with each other. Multiple first gas channels 1101 are provided along the thickness direction of the first constraint ring 11, and multiple second gas channels 1201 are provided along the thickness direction of the second constraint ring 12. The first gas channels 1101 and the second gas channels 1201 together form the gas channel 01. The width of the second gas channel 1201 is the same as the width of the first gas channel 1101, while the depth of the second gas channel 1201 is flexibly adjusted according to the depth of the first gas channel 1101, ultimately ensuring that the aspect ratio of the gas channel 01 is greater than or equal to 8:1.

[0028] This invention utilizes a second constraint ring 12 to adjust the flow resistance of the entire constraint ring assembly 10. The second constraint ring 12 is positioned downstream of and closely attached to the first constraint ring 11 made of silicon. The second gas channel 1201 on the second constraint ring 12 extends the depth of the first gas channel 1101 on the first constraint ring 11, compensating for the insufficient aspect ratio and low gas flow resistance caused by the processing difficulties of the gas channel in the silicon constraint ring. By using the second constraint ring 12 to effectively compensate for the aspect ratio of the gas channel in the first constraint ring 11 made of silicon, the overall gas channel 01 achieves a sufficient aspect ratio to meet the requirements of semiconductor manufacturing processes, resulting in appropriate gas flow resistance for the entire constraint ring assembly 10, and consequently, an appropriate pumping rate, thereby achieving uniformity and stability of the reaction.

[0029] The number of the second gas channels 1201 is consistent with the number of the first gas channels 1101. Each second gas channel 1201 corresponds to one first gas channel 1101. That is, each gas channel 01 can only be composed of one first gas channel 1101 and one second gas channel 1201. The first gas channel 1101 and the second gas channel 1201 in the gas channel 01 must be strictly corresponding and cannot be misplaced to prevent gas turbulence from causing unstable discharge.

[0030] Furthermore, the shape of the second gas channel 1201 must also be consistent with the shape of the first gas channel 1101 to ensure that the gas channel 01 formed by the first gas channel 1101 and the second gas channel 1201 has a uniform width, avoiding uneven fluctuations in the flow resistance of the gas channel 01, thereby ensuring that the gas flow resistance of the overall constraint ring assembly 10 remains stable. The first gas channel 1101 and the second gas channel 1201 can be annular channels, grid-shaped channels, or perforated channels, or any combination of the above shapes.

[0031] In practical applications, the width of the gas channel in the constraint ring is typically 2mm through processing. This size is relatively easy to manufacture and ensures structural strength while reducing direct plasma impact on the channel sidewalls, thus extending service life. Due to the aforementioned processing limitations, it is difficult to obtain a silicon material first constraint ring 11 with a thickness exceeding 8mm. Therefore, the thickness of the first constraint ring 11 is usually 4mm to 8mm. In this case, the thickness of the second constraint ring 12 needs to be appropriately set to effectively compensate for the thickness of the first constraint ring 11. Typically, the thickness of the second constraint ring 12 is set to 8mm to 12mm to ensure that the depth of the gas channel 01 in the overall constraint ring assembly 10 reaches a predetermined value, resulting in a depth-to-width ratio greater than or equal to 8:1. For example, when the thickness of the first constraint ring 11 is 4mm, the corresponding thickness of the second constraint ring 12 is set to 12mm. In this case, the depth of the gas channel 01 reaches 16mm, and the depth-to-width ratio of the gas channel 01 is 8:1, which meets the requirements. When the thickness of the first constraint ring 11 is 8mm, the thickness of the second constraint ring 12 can be reduced accordingly. However, the thickness of the second constraint ring 12 must still be at least 8mm. In this case, the depth of the gas channel 01 can also reach 16mm, and the aspect ratio of the gas channel 01 is also 8:1, which meets the requirements. The second constraint ring 12 effectively compensates for the aspect ratio of the gas channel of the silicon-based first constraint ring 11, so that the overall gas channel 01 has a sufficient aspect ratio to meet the requirements of the semiconductor process. This allows the overall constraint ring assembly 10 to obtain suitable gas flow resistance, thereby obtaining a suitable pumping rate, and thus achieving uniformity and stability of the reaction.

[0032] As shown in Figure 2, the first constraint ring 11 is fixedly disposed within the exhaust region 8 using the first mounting assembly 1102. The first constraint ring 11 is also fixed to the side wall 101 of the reaction chamber 1, or to the side wall of the base 4, using the first mounting assembly 1102. To improve the stability of the connection, one side of the first constraint ring 11 can be simultaneously fixed to the side wall 101 of the reaction chamber 1 via the first mounting assembly 1102, and the other side can be fixed to the side wall of the base 4 via the first mounting assembly 1102. The first mounting assembly 1102 is made of radio frequency conductive material to ground the first constraint ring 11 and form a complete radio frequency circuit in the reaction chamber 1. As shown in Figure 2, the solid black arrows represent the radio frequency (RF) transmission path. The RF power supply 5 applies RF voltage to the base 4, generating an RF electric field in the plasma processing area 6. The dashed black arrows represent the RF return path. The RF passes through the inner wall of the reaction chamber 1, enters the first constraint ring 11 along the first mounting component 1102, then enters the base 4 along the first mounting component 1102, and finally returns to the RF power supply 5. Thus, a complete RF loop is formed in the reaction chamber 1. The RF loop continuously provides RF energy, maintaining the stable existence of the plasma and ensuring the continuity and stability of the plasma processing process.

[0033] During plasma processing, maintaining the stability of the radio frequency (RF) circuit is crucial. Changes to the RF circuit can lead to unstable RF signals, an unstable RF environment, variations in etching rates, and uneven film thickness on the wafer surface, all of which negatively impact the plasma processing effect and product quality. The second constraint ring 12 is made of an insulating material. Since RF signals cannot conduct through insulating materials, the insulating material of the second constraint ring 12 does not alter the RF circuit in the reaction chamber 1, ensuring stable RF power transmission and preventing plasma instability caused by RF circuit fluctuations. This improves the stability of the etching rate and the yield rate of wafer production, avoids arc damage at connections caused by RF circuit instability, and enhances the overall stability and reliability of the equipment.

[0034] The second constraint ring 12 can be made of quartz or ceramic, as neither introduces additional contamination. Quartz has extremely high purity and chemical stability, and will not release impurities or react chemically with other substances under high temperature and high vacuum conditions. Quartz's low coefficient of thermal expansion allows it to maintain structural stability during temperature changes, further reducing the possibility of material decomposition or contamination due to thermal stress. Ceramic materials also possess high purity and chemical stability; in environments such as plasma processing, ceramic materials will not react chemically with reactive gases to produce contaminants, unlike some metals.

[0035] As shown in Figure 2, the second constraint ring 12 is fixedly disposed downstream of the first constraint ring 11 using the second mounting assembly 1202, ensuring close contact between the second constraint ring 12 and the first constraint ring 11. The second constraint ring 12 is also fixed to the side wall 101 of the reaction chamber 1 using the second mounting assembly 1202, or to the side wall of the base 4. To improve the stability of the connection, one side of the second constraint ring 12 can be simultaneously fixed to the side wall 101 of the reaction chamber 1 using the second mounting assembly 1202, and the other side can be fixed to the side wall of the base 4 using the second mounting assembly 1202.

[0036] The second mounting component 1202 is made of insulating material. Radio frequency signals cannot be conducted in the insulating material, so the radio frequency signals will not be introduced into the second constraint ring 12, and the radio frequency circuit in the reaction chamber 1 will not be changed. This ensures the stable transmission of radio frequency power, avoids plasma instability caused by radio frequency circuit fluctuations, thereby improving the stability of the etching rate and the yield of wafer production, avoiding arc damage at the connection caused by radio frequency circuit instability, and improving the overall stability and reliability of the equipment.

[0037] The second mounting component 1202 uses common connectors or fasteners, which makes it easy to install the second constraint ring 12 to the downstream side of the first constraint ring 11, and also makes it easy to remove the second constraint ring 12 for maintenance and replacement with a new second constraint ring 12. The operation is simple and easy to maintain.

[0038] Although the present invention has been described in detail through the preferred embodiments described above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above content. Therefore, the scope of protection of the present invention should be defined by the appended claims.

[0039] 1: Reaction Chamber 10: Constraint ring assembly 101: Sidewall 01: Gas Channel 11: First constraint loop 1101: First gas passage 1102: First installation component 12: Second constraint loop 1201: Second gas passage 1202: Second installation component 2: Gas spray head 3: Gas supply device 4: Base 5: RF power supply 6: Plasma treatment area 7: Exhaust device 8: Exhaust area 9: Constraint ring 901: Gas Channel W: Wafer to be processed

Claims

1. A confinement ring assembly for a plasma processing apparatus, the plasma processing apparatus comprising a reaction chamber and a lower electrode disposed within the reaction chamber, a plasma processing region for processing a wafer formed above the lower electrode, and an exhaust region located outside the plasma processing region, the confinement ring assembly being disposed within the exhaust region for confining plasma, characterized in that the confinement ring assembly has multiple gas channels for discharging a portion of the plasma from the plasma processing region to the exhaust region downstream of the confinement ring assembly; the confinement ring assembly comprises a first confinement ring and a second confinement ring in close contact with each other; the first confinement ring is made of silicon and has multiple first gas channels along its thickness direction; the second confinement ring is disposed downstream of the first confinement ring and has multiple second gas channels along its thickness direction; each gas channel comprises one first gas channel and one second gas channel, the aspect ratio of the gas channels being greater than or equal to 8:

1.

2. The constraint ring assembly as described in claim 1, wherein, The second constraint ring is made of insulating material.

3. The constraint ring assembly as described in claim 2, wherein, The second constraint ring is made of quartz or ceramic.

4. The constraint ring assembly as described in claim 1, wherein, The number of the first gas channel and the number of the second gas channel are the same.

5. The constraint ring assembly as described in claim 1, wherein, The first gas channel and the second gas channel have the same shape.

6. The constraint ring assembly as described in claim 5, wherein, The first gas channel and the second gas channel are any one or more of the following: annular, grid-shaped, and perforated.

7. The constraint ring assembly as described in claim 1, wherein, The thickness of the first constraint ring is 4mm to 8mm, and the thickness of the second constraint ring is 8mm to 12mm.

8. The constraint ring assembly as described in claim 1, wherein, The first constraint ring includes a first mounting component made of radio frequency conductive material. The first mounting component connects the first constraint ring and the inner wall of the reaction chamber, and / or the first mounting component connects the first constraint ring and the lower electrode.

9. The constraint ring assembly as described in claim 1, wherein, The second constraint ring includes a second mounting assembly made of insulating material. The second mounting assembly connects the second constraint ring to the inner wall of the reaction chamber, and / or connects the second constraint ring to the lower electrode.

10. A plasma processing apparatus, characterized in that it comprises: a reaction chamber; an upper electrode disposed within the reaction chamber for introducing reactive gases into the reaction chamber; a lower electrode disposed within the reaction chamber, located below the upper electrode, the lower electrode including a base for supporting a wafer, a plasma processing region for processing the wafer being formed above the lower electrode, and an exhaust region outside the plasma processing region; a radio frequency power supply connected to the lower electrode for generating an electric field to cause the reactive gases to form plasma; and a constraint ring assembly as described in any one of claims 1 to 9, the constraint ring assembly being disposed within the exhaust region.

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