Plasma processing apparatus and control method thereof

Abstract

The application discloses a kind of plasma processing equipment and its control method, for the problem that remote plasma source or ion trap is needed in existing free radical etching, leading to the complexity of equipment, low efficiency of gas inlet and outlet, independent controllable radio frequency coil structure is used in center and edge.In the first process based on free radical processing, the edge coil is controlled to run at high power, and the center coil can run at zero power, the plasma excitation is transferred to the edge of the reaction cavity, and the characteristics of long-life diffusion of free radicals and short-life annihilation of ions are used to remove ions in situ.The application does not need additional ion filtering device, greatly simplifies the structure of the equipment, reduces the gas flow resistance, improves the response speed of gas inlet and outlet and the process cycle efficiency;At the same time, the diffusion of ions to the substrate is effectively inhibited, the pure free radical reaction characteristics are maintained, the conversion to reactive ion etching is avoided, especially suitable for atomic layer etching process, significantly improves the production capacity and processing precision.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing technology, and in particular to a plasma processing apparatus and its control method for atomic layer etching processes. Background Technology

[0002] Radical etching is a dry etching technique that removes materials by relying on the chemical reaction between highly reactive neutral free radicals and the material surface. It has the advantages of no physical damage, ultra-high selectivity, and atomic-level precision.

[0003] Existing radical etching equipment generally employs remote plasma scanning (RPS) or grid / ion trap methods to filter ions from the plasma, retaining radicals for processing. However, such solutions are complex, have low air intake and exhaust efficiency, and result in slow processes. This bottleneck in process efficiency becomes particularly pronounced when radical reactions need to be combined with other processes in a cyclical manner.

[0004] Therefore, there is an urgent need for a new plasma processing equipment and its control method that can improve intake and exhaust efficiency and increase production capacity while suppressing the diffusion of ions in the plasma to the substrate. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a plasma processing device and its control method, which can effectively suppress the diffusion of ions into the substrate through differentiated control of radio frequency coils, while eliminating the need for RPS or ion shielding components, thereby improving intake and exhaust efficiency and helping to increase production capacity.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A plasma processing apparatus includes a reaction chamber, a gas inlet device, a vacuum pumping device, a source radio frequency (RF) generator, and an RF coil. The reaction chamber has a base to support a substrate. The gas inlet device supplies process gas to the reaction chamber. The vacuum pumping device operates the reaction chamber at the pressure required for the process. The reaction chamber has a dielectric window, the top of which is sealed. An RF coil is located outside the dielectric window. The source RF generator feeds radio frequency energy into the reaction chamber through the RF coil to excite plasma within the reaction chamber to process the substrate. The radio frequency coil includes an edge coil located outside the axial projection region of the base and away from the axis of the reaction chamber, and a center coil located at least partially within the axial projection region. There is no grid structure between the air intake device and the substrate, and the grid structure is used to reduce the flow of ions to the substrate; It also includes a controller, which is configured to: The reaction chamber is operated in a first process based on free radical treatment, and The edge coil is operated in a first power mode, and the center coil is operated in a second power mode; The average power output of the second power mode is less than the average power output of the first power mode.

[0007] For example, the radio frequency coil also includes an intermediate coil located between the center coil and the edge coil.

[0008] For example, the source radio frequency includes a first radio frequency and a second radio frequency, the first radio frequency supplying power to the center coil and the edge coil, and the second radio frequency supplying power to the intermediate coil.

[0009] For example, it also includes a power divider that adjusts the power distribution ratio between the center coil and the edge coils.

[0010] For example, the output frequencies of the first radio frequency and the second radio frequency are different.

[0011] For example, the edge coil is located on the top or side wall of the reaction chamber.

[0012] For example, the dielectric window includes a first dielectric window located at the top of the reaction chamber and a second dielectric window located on the side wall of the reaction chamber, the center coil is located outside the first dielectric window and the edge coil is located outside the second dielectric window.

[0013] For example, the air intake device further includes an edge air intake device disposed on the side wall of the reaction chamber, the edge air intake device being used to supply the first process gas for the first process.

[0014] For example, the second power mode includes a zero power mode or a pulse mode.

[0015] For example, the maximum distance from the top of the reaction chamber to the top surface of the base is less than 1 / 4 of the maximum inner diameter of the sidewall of the reaction chamber.

[0016] The present invention also provides a control method for the aforementioned plasma processing equipment, comprising: Step a: Provide a reaction chamber with a vacuum environment and generate plasma through a plasma source to process the substrate, wherein there is no grid structure between the plasma and the substrate, and the plasma source includes an edge coil located outside the axial projection area of ​​the base and a central coil located at least partially within the axial projection area; Step b: The reaction chamber is operated in a first process based on free radical processing, the edge coil operates in a first power mode, and the center coil operates in a second power mode; wherein the average power output of the second power mode is less than the average power output of the first power mode.

[0017] For example, the output power of the second power mode is zero.

[0018] For example, for at least half the duration of the first process, the first power mode output is in continuous wave mode and the second power mode output is in pulse mode.

[0019] For example, in the first process, the first power mode and the second power mode outputs are pulse modes, wherein, The power duty cycle of the second power mode is less than the power duty cycle of the first power mode, and / or The power pulse frequency of the second power mode is greater than the power pulse frequency of the first power mode, and / or The power pulse width of the second power mode is smaller than that of the first power mode.

[0020] For example, it also includes step c: running the reaction chamber in a second process based on ion bombardment, wherein the first process forms a modified layer on the substrate surface, and the second process removes the modified layer, and the first process and the second process are alternately cycled to perform atomic layer etching on the substrate, wherein the ratio of the average power output of the center coil to the edge coil in the second process is greater than the ratio of the average power output of the center coil to the edge coil in the first process.

[0021] This invention reduces the average ion concentration in the central region by operating the edge coil in a first power mode and the center coil in a second power mode in a first process based on free radical processing. The average power output of the second power mode is lower than that of the first power mode. This effectively suppresses the diffusion of high-energy ions into the substrate and avoids interference of ions with the pure free radical reaction.

[0022] In the first process, plasma excitation is primarily transferred to the edge region, with the edge coil providing most of the radio frequency energy to excite the process gas and generate active free radicals. These active free radicals reach the substrate surface through diffusion, ensuring a sufficient free radical reaction effect. Ions, due to their short lifetime and poor diffusion characteristics, are either annihilated by collisions or expelled through the vacuum direction after generation in the edge region, making it difficult for them to diffuse to the substrate processing area. Simultaneously, the lower radio frequency energy in the central region does not affect the chemical reaction between the active free radicals and the material to be treated, thus not reducing the efficiency and quality of the first process.

[0023] This invention eliminates the need for additional ion filtering devices such as remote plasma sources (RPS), grids, or ion traps, significantly simplifying the upstream structure of the reaction chamber, reducing gas flow resistance, and substantially improving intake and exhaust response speeds and process cycle efficiency. Simultaneously, it avoids the risk of particulate contamination associated with complex structures, enhancing the stability and reliability of equipment operation.

[0024] Therefore, this invention, while ensuring the quality of free radical processing, suppresses the ion flux and energy on the substrate surface, maintains the characteristics of pure free radical reaction, improves processing precision and selectivity, and significantly increases process throughput. It is particularly suitable for atomic layer etching processes that require frequent alternation between free radical reaction and ion bombardment. Attached Figure Description

[0025] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0026] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0027] Figure 1 This is a schematic diagram of the overall structure of a plasma processing device according to the present invention; Figure 2 This is a schematic diagram of a radio frequency supply structure according to the first embodiment of the present invention; Figure 3 This is a schematic diagram of another radio frequency supply structure according to the first embodiment of the present invention; Figure 4 This is a schematic diagram of a radio frequency coil structure according to a second embodiment of the present invention; Figure 5 This is a schematic diagram of a three-coil structure according to the third embodiment of the present invention; Figure 6 This is a flowchart of a control method for the plasma processing equipment of the present invention. Detailed Implementation

[0028] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and specific examples. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0029] As shown in Figure 1, the plasma processing equipment of the present invention mainly includes a reaction chamber 10, a base 20, an air inlet device 30, a vacuum pumping device 40, a dielectric window 50, a radio frequency coil 60, a source radio frequency device 70, and a controller 80.

[0030] For example, reaction chamber 10 is a vacuum chamber, typically made of a corrosion-resistant metal with a low outgassing rate, which defines the space for plasma processing. The inner walls of reaction chamber 10 are polished and coated to reduce particle generation and metal contamination during the process.

[0031] A base 20 is disposed within the reaction chamber 10 to support the substrate 90 to be processed. For example, the base 20 may integrate heating and cooling devices to precisely control the temperature of the substrate 90 within the range required by the process. The base 20 may also be connected to a bias radio frequency power supply (not shown) to apply a bias voltage to the substrate 90 to control the bombardment energy of ions in the plasma. In this invention, the bias radio frequency power supply is typically off or substantially positive in the first process based on the free radical treatment process to further reduce the bombardment energy of ions.

[0032] The gas inlet device 30 is used to supply various process gases into the reaction chamber 10. The gas inlet device 30 may include multiple independent gas pipelines, mass flow controllers and gas nozzles, which can precisely control the flow rate and ratio of various process gases.

[0033] The top of the reaction chamber 10 is sealed by a dielectric window 50. Typically, the dielectric window 50, located at the top of the reaction chamber 10, is made of a material with good dielectric properties, high-temperature resistance, and plasma corrosion resistance, such as high-purity quartz or alumina ceramic. The dielectric window 50 isolates the vacuum environment of the reaction chamber 10 from the external atmospheric environment while allowing radio frequency energy to pass through into the reaction chamber 10. The lower surface of the dielectric window 50 can be specially treated to reduce deposit adhesion during the process.

[0034] The radio frequency coil 60 is disposed outside the dielectric window 50 and electrically connected to the source radio frequency 70. The radio frequency energy generated by the source radio frequency 70 enters the reaction chamber 10 through the radio frequency coil 60 via inductive coupling, exciting the process gas to form plasma.

[0035] For example, the RF coil 60 can be a three-dimensional coil or a planar coil or a combination of both.

[0036] The radio frequency coil 60 includes at least two independently controllable coils, namely a center coil 61 and an edge coil 62. The center coil 61 is located close to the axis of the reaction chamber 10 and is mainly used to excite plasma in the central region of the reaction chamber 10; the edge coil 62 is located away from the axis of the reaction chamber 10 and is mainly used to excite plasma in the edge region of the reaction chamber 10.

[0037] In this embodiment, the edge coil 62 is located outside the axial projection region Z of the base 20, and the center coil 61 is at least partially located within the axial projection region Z. The edge coil 62 is located outside the axial projection region Z of the substrate 90. The axial projection region Z can be as follows: Figure 1 The dashed line represents the three-dimensional projection area along the axial direction of the base 20. In this way, the plasma generated by the edge coil 62 is mainly distributed on the outer edge of the substrate 90. The free radicals then diffuse to the surface of the substrate 90, avoiding the destructive effects of ions on the pure free radical reaction. This structural design avoids the edge coil 62 generating excessively strong plasma directly above the edge of the substrate 90, thereby further reducing the number of high-energy ions in the edge region and preventing the pure free radical reaction in the edge region from transforming into reactive ion etching.

[0038] For example, a vacuum pump 40 is connected to the region below the substrate 90 of the reaction chamber 10 to evacuate the pressure within the reaction chamber 10 to the vacuum level required for the process. The vacuum pump 40 typically includes a mechanical pump, a turbomolecular pump, and corresponding vacuum valves and pressure sensors. A controller 80 can adjust the opening of the vacuum valves based on feedback signals from the pressure sensors to stabilize the pressure within the reaction chamber 10 at the required process value.

[0039] For example, the gas inlet device 30 includes an edge gas inlet device surrounding the sidewall of the reaction chamber 10. The edge gas inlet, in conjunction with the edge radio frequency coil, excites plasma at the radially distal end of the substrate 90, increasing the distance ions diffuse towards the substrate 90 and improving the probability of charge neutralization and annihilation along the way. Considering the continuous suction effect of the vacuum device 40, using the edge gas inlet to supply the first process gas for the first process helps to excite the plasma upstream of the gas flow towards the substrate 90, thereby allowing free radicals to diffuse sufficiently to the surface of the substrate 90 under the action of the flow field, resulting in a complete and uniform free radical reaction.

[0040] However, by supplying the first process gas directly above the substrate 90, the plasma excitation is located on the edge side of the reaction chamber 10. The supply of gas from above causes the plasma to be excited on the downstream side of the substrate 90, which increases the resistance to the diffusion of free radicals to the substrate 90. This may lead to insufficient diffusion of free radicals and affect the consistency of the free radical reaction on the substrate 90.

[0041] The source RF 70 is used to generate RF energy, and its output frequency can be selected according to process requirements. For example, the source RF 70 can include multiple independent RF power supplies, each powering different coils, or a single RF power supply can distribute power to different coils, or a combination of both. Optionally, each RF power supply can be frequency-modulated and can output both continuous wave RF energy and pulsed RF energy, and its output power can be continuously adjusted within a predetermined range. Furthermore, each RF power supply can control parameters such as the duty cycle, frequency, and pulse width of the pulsed RF.

[0042] For example, controller 80 is electrically connected to various components of the plasma processing equipment to control the operation of the entire process. Controller 80 can be a general-purpose computer, a dedicated industrial controller, or an embedded system, internally storing preset process programs and control parameters. In this embodiment, controller 80 is configured to execute the plasma processing control method of the present invention, that is, in the first process based on free radical processing and the second process based on ion bombardment, different strategies are used to control the operating mode and average power output of the central coil 61 and the edge coil 62, respectively, to achieve the purpose of suppressing ion diffusion, facilitating free radical reactions, and improving substrate processing yield.

[0043] Specifically, there is no grid structure between the gas inlet device 30 and the substrate 90. Generally, grid structures are used to reduce ions flowing towards the substrate, acting as ion traps. However, they inevitably and significantly increase flow resistance, making the process gas inlet and outlet switching very slow and drastically reducing process throughput. Furthermore, because it is located upstream of the incoming gas from the substrate 90, it is highly susceptible to particulate contamination, reducing yield. This embodiment does not use structures such as grids, ion traps, or ion shielding devices that significantly increase resistance to filter ions from the substrate-side incoming gas. It also eliminates the need for a remote plasma source (RPS), instead achieving radical etching through the power distribution pattern between the edge and center coils.

[0044] In a first embodiment of the invention, the radio frequency coil 60 adopts a top-nested structure. For example, the center coil 61 and the edge coil 62 are annular and positioned above the dielectric window 50 at the top of the reaction chamber 10. The center coil 61 has a smaller diameter and is located in the central region of the dielectric window 50; the edge coil 62 has a larger diameter and surrounds the outside of the center coil 61. They can be coaxially or non-coaxially arranged.

[0045] In one embodiment, as shown in FIG2, the center coil 61 and the edge coil 62 are both connected to the source RF 70 and powered by a single RF power supply. Power is distributed through a power divider 74, which can be any known structure, such as adjusting the power ratio of the two coils through a variable capacitor. A controller 80 is electrically connected to both the source RF 70 and the power divider 74. The controller 80 controls the output power of the source RF 70 and controls the power distribution ratio between the center coil 61 and the edge coil 62 by controlling the power divider 74.

[0046] In one embodiment, the center coil 61 and the edge coil 62 are electrically connected to different radio frequency (RF) sources to independently control the output of continuous wave or pulsed RF energy. Preferably, parameters such as the RF frequency, power, pulse duty cycle, pulse frequency, and pulse width of the RF source output can be adjusted independently. The controller 80 is electrically connected to each of the different RF sources to precisely control their output.

[0047] As shown in Figure 3, in one embodiment, the center coil 61 is connected in series with a first high-frequency switch 75, and the controller 80 is electrically connected to the first high-frequency switch 75. The power output pulse duty cycle, pulse frequency and pulse width of the center coil 61 are controlled by the on and off state of the first high-frequency switch 75.

[0048] In one embodiment, the center coil 61 is connected in series with a first high-frequency switch 75, the edge coil 62 is connected in series with a second high-frequency switch 76, and the controller 80 is electrically connected to the first high-frequency switch 75 and the second high-frequency switch 76 respectively. The controller controls the duty cycle, pulse frequency and pulse width of the power output pulse of the center coil 61 and the edge coil 62 by switching the first high-frequency switch 75 and the second high-frequency switch 76 on and off.

[0049] It is understandable that there is no power output when the duty cycle is 0, and there is continuous wave output when the duty cycle is 1.

[0050] In the first process, the controller 80 controls the edge coil 62 to output radio frequency energy in a first power mode; simultaneously, it controls the first radio frequency source 71 to output radio frequency energy in a second power mode to the center coil 61. The average power output of the second power mode is lower than the average power output of the first power mode.

[0051] It is understandable that the first power mode and the second power mode include parameters such as output power, output waveform type (e.g., continuous wave and pulse), and duty cycle. The average power output is the overall average power in the first process. It can be understood that when the peak output power of the source RF 70 or multiple RF sources is consistent, the average power output of the pulse output is smaller than that of the continuous wave output, and the ratio is proportional to the pulse duty cycle. For example, if the stable peak power of both the first power mode and the second power mode is 500W, and the first power mode is a continuous wave mode, then its average power output is approximately 500W. The second power mode is a pulse mode with a 10% duty cycle, so the average power output of the second power mode is approximately 50W, much smaller than the average power output of the first power mode.

[0052] Therefore, in one embodiment, for at least half the duration of the first process, the first power mode output is a continuous wave mode, and the second power mode output is a pulse mode. By setting the second power mode to pulse mode, the power output of the second power mode can be flexibly adjusted by adjusting parameters such as the pulse duty cycle, so that the plasma of the central coil 61 is in a low-energy mode, reducing its ion generation and diffusion.

[0053] It is understood that in this invention, the radio frequency power pulse mode feeds in radio frequency energy to reduce ion concentration. Since ion generation and annihilation are rapid, compared with the continuous wave mode, the pulse power causes ions in the plasma to be repeatedly generated and annihilated, making it difficult to form an effective ion concentration accumulation. Furthermore, methods such as reducing the pulse duty cycle and increasing the pulse frequency can further highlight this effect and suppress the stable existence of ion quantity.

[0054] By setting the second power mode to pulse mode instead of zero output, the plasma of the central coil 61 can be in a low-energy mode, reducing its ion generation and diffusion, and supplementing the free radical generation in the central region, thus avoiding the problem of uneven diffusion at the edges.

[0055] Considering the plasma activation mode of the RF coil, whether it is inductively coupled plasma (ICP) or transformer-coupled plasma (TCP), the high-energy region of RF energy in the reaction cavity 10 is located directly below the coil, exhibiting high plasma density and a large number of excited active particles. Conversely, the center of the coil is generally a low-energy region, exhibiting low plasma density or even incomplete activation, with fewer active particles, resulting in a non-uniform distribution. Although the diffusion effect of active particles can mitigate the difference in non-uniform distribution to some extent, the overall trend remains unchanged. Furthermore, due to the continuous suction of the vacuum device 40, the overall gas movement direction within the cavity is towards the vacuum device 40. This, combined with the fact that the lifetime of free radicals is generally longer than that of ions, and ions annihilate after being neutralized by collisional charges, means that when the plasma excitation region is located at the edge region far from the axis of the reaction cavity 10, free radicals can reach the substrate 90 region through diffusion, while ions have difficulty reaching it. Based on this, through the above scheme, in the first process stage, plasma excitation is mainly accomplished by the edge coil 62. The edge coil 62 generates high-density plasma in the edge region of the reaction cavity 10, exciting the first process gas to produce a large number of active free radicals. These active free radicals move from the edge region to the center region through diffusion, reaching the entire surface of the substrate 90, and react chemically with the material to be treated, thus carrying out the first process based on free radical reaction.

[0056] Meanwhile, the central coil 61 operates at a lower average power, resulting in a lower plasma density in the central region of the reaction chamber 10. This lower plasma density in the central region reduces the average electron temperature and average ion concentration, suppressing ion bombardment of the substrate. This effectively avoids the problem of the substrate undergoing a transformation from pure free radical reaction to reactive ion etching (RIE), eliminating the need for complex ion shielding structures and reducing particulate contamination.

[0057] In one implementation, the output power of the second power mode is zero, meaning the central coil 61 is completely off in the first process. At this time, all radio frequency energy is supplied by the edge coil 62, and the plasma is generated entirely in the edge region of the reaction chamber 10. In this case, the ion concentration in the central region is lowest, while active free radicals can still diffuse uniformly to the entire substrate surface, ensuring the effectiveness of the first process.

[0058] In one embodiment, the power duty cycle of the center coil 61 is less than the power duty cycle of the edge coil 62. Specifically, when the duty cycle is 1, it is a continuous wave mode; when the duty cycle is less than 1, it is a pulse mode; and when the duty cycle is 0, it is a zero output.

[0059] In one embodiment, the center coil 61 and the edge coil 62 operate in pulse mode, with the power pulse frequency of the center coil 61 being greater than that of the edge coil 62, or the power pulse pulse width of the center coil 61 being smaller than that of the edge coil 62. This allows for a further reduction in the average ion concentration of the plasma while maintaining the ability to generate free radicals, thereby further reducing the possibility of ions diffusing to the substrate 90.

[0060] In the second process based on ion bombardment, the process is primarily dominated by ion bombardment. Therefore, in the second process, the operating modes and average power output of the center coil 61 and the edge coil 62 can be independently adjusted to optimize the ion bombardment effect.

[0061] For example, both the center coil 61 and the edge coil 62 can be operated in continuous wave mode, with the output power of the center coil 61 being greater than that of the edge coil 62. This allows for a suitable plasma distribution within the reaction chamber 10, improving the uniformity of ion bombardment. Alternatively, both coils can be operated in pulsed mode to achieve a lower average ion concentration and improve etching selectivity. Furthermore, depending on different process requirements, one coil can operate in continuous wave mode while the other operates in pulsed mode.

[0062] As shown in Figure 4, in the second embodiment of the present invention, the radio frequency coil 60 adopts a structure of a top center coil plus a sidewall edge coil. The center coil 61 is disposed above the first dielectric window 51 at the top of the reaction chamber 10, and the edge coil 62 is disposed outside the second dielectric window 52 on the sidewall of the reaction chamber 10.

[0063] For example, the first dielectric window 51 is planar and is disposed at the top of the reaction chamber 10; the second dielectric window 52 is annular and is disposed around the upper part of the side wall of the reaction chamber 10. Optionally, the center coil 61 is an annular coil and is coaxially disposed with the first dielectric window 51; the edge coil 62 is an annular coil and is coaxially disposed with the second dielectric window 52, ​​or is formed as multiple sets of coils whose coil axes intersect with the axial direction of the reaction chamber 10 and are arranged at intervals around the axial direction of the second dielectric window 52. The center coil 61 and the edge coil 62 are connected to the same radio frequency source or to different radio frequency sources respectively.

[0064] Compared to the first embodiment, in this embodiment, the edge coil 62 is disposed on the sidewall of the reaction cavity 10, and the radio frequency energy generated therefrom is mainly coupled into the reaction cavity 10 from the sidewall direction. This structural form can further optimize the spatial distribution of plasma and is more conducive to suppressing the diffusion of ions into the substrate.

[0065] In the first process, controller 80 controls the output of radio frequency (RF) energy in a first power mode to the sidewall edge coil 62, and simultaneously controls the output of RF energy in a second power mode to the center coil 61. The plasma generated by the sidewall edge coil 62 diffuses from the sidewall towards the center, making it more difficult for ions to reach the central substrate region. Simultaneously, since the plasma is generated from the sidewall direction, the ion movement direction is primarily horizontal, rather than vertically downwards towards the substrate surface. This further reduces the number of high-energy ions incident vertically to the substrate surface, thereby more effectively suppressing ion diffusion into the substrate.

[0066] Furthermore, in this embodiment, the edge gas inlet device can be used in conjunction with the sidewall edge coil 62. The edge gas inlet device supplies the first process gas of the first process into the reaction chamber 10 from the sidewall. In this way, after the first process gas enters the reaction chamber 10, it is immediately excited by the sidewall edge coil 62 to form plasma, which can generate active free radicals more quickly and effectively. At the same time, the gas flow direction is consistent with the plasma diffusion direction, which can promote the transport of active free radicals to the central region and improve the first process efficiency of the entire substrate 90 surface.

[0067] In the second process, the power and operating mode of the two coils can also be adjusted independently to achieve better removal results. For example, the power of the top center coil 61 can be increased to enhance the plasma density and ion flux in the central region, thereby achieving uniform bombardment. The second process gas in the second process can be supplied from the top or edge of the reaction chamber 10 without special restrictions.

[0068] As shown in Figure 5, in the third embodiment of the present invention, the radio frequency coil 60 adopts a three-coil structure, including a central coil 61, an edge coil 62, and an intermediate coil 63. The intermediate coil 63 is located between the central coil 61 and the edge coil 62, nested above the dielectric window 50 at the top of the reaction chamber 10. The three coils can be arranged coaxially or non-coaxially.

[0069] The center coil 61 and the edge coil 62 are connected to the first RF source 71, and the intermediate coil 63 is connected to the second RF source 72. A power divider 74 is also provided between the first RF source 71 and the center coil 61 and the edge coil 62. The power divider 74 is used to adjust the distribution ratio of the RF energy output by the first RF source 71 between the center coil 61 and the edge coil 62.

[0070] The controller 80 is electrically connected to the first RF source 71, the second RF source 72, and the power divider 74. By controlling the power divider 74, the power distribution between the center coil 61 and the edge coil 62 can be continuously adjusted; by controlling the second RF source 72, the RF frequency, output power, and operating mode of the intermediate coil 63 can be independently adjusted.

[0071] The three-coil structure further enhances the freedom of plasma control, enabling finer control of ion concentration distribution. In the first process, in addition to increasing the power of the edge coil 62 and decreasing the power of the central coil 61, the power and operating mode of the middle coil 63 can be adjusted as needed, resulting in a smooth gradient distribution of plasma density and ion concentration from the edge to the center. This ensures both the uniformity of free radical reactions across the entire substrate surface and the control of ion concentration at a low level throughout the region, thereby comprehensively suppressing ion diffusion into the substrate.

[0072] For example, the edge coil 62 can operate in continuous wave mode, outputting a first power mode; the middle coil 63 can operate in pulse mode, outputting a third power level; and the center coil 61 can operate in pulse mode, outputting a second power mode. The average power output of the first power mode is higher than that of the third power level, and the average power output of the third power level is higher than that of the second power mode. In this way, the plasma density gradually decreases from the edge to the center, and the ion concentration also gradually decreases accordingly. Throughout the entire substrate surface, the ion concentration density is controlled at a level that does not degrade the pure free radical reaction, thus achieving comprehensive protection of the entire substrate.

[0073] In the second process, the plasma distribution can also be precisely controlled by adjusting the power and operating mode of the three coils to achieve better removal results. For example, the power of the central coil 61 can be set to the highest, the power of the middle coil 63 to the second highest, and the power of the edge coil 62 to the lowest, thereby forming a suitable plasma distribution. This mitigates the problem of low plasma density distribution at the center and high at the edges caused by the RF coils, and helps to improve processing consistency.

[0074] Furthermore, in this embodiment, the first radio frequency source 71 and the second radio frequency source 72 can employ different output frequencies. For example, the first radio frequency source 71 can employ a higher frequency, and the second radio frequency source 72 can employ a lower frequency. Different frequencies of radio frequency energy have different effects on the plasma. High-frequency radio frequency energy is mainly used to excite the plasma, generating high-density electrons and active free radicals; low-frequency radio frequency energy is mainly used to accelerate ions, increasing their energy. By using different frequency radio frequency power supplies to power different coils, the plasma density and ion concentration distribution can be controlled more flexibly.

[0075] In the first process, a high-frequency radio frequency (RF) power supply can be used to power the edge and middle coils to generate a high density of active free radicals; simultaneously, a lower-frequency RF power supply is used to power the center coil, and its power is reduced to further decrease the ion concentration in the central region. This frequency-differentiated control method can further optimize the free radical treatment effect and the substrate protection effect.

[0076] In one embodiment, there may be four or more RF coils, which may be powered by a unified RF power supply or at least partially by different RF power supplies independently, as long as it is ensured that in the first process, the average power output of the coils near the center is less than the average power output of the coils near the edges, in order to achieve more precise plasma distribution control.

[0077] In the fourth embodiment of the present invention, the radio frequency coil 60 adopts a structure in which multiple sets are axially distributed. Specifically, multiple sets of edge coils 62 are arranged axially at intervals on the sidewall of the reaction chamber 10. Each set of edge coils 62 can share the same radio frequency power supply or be connected to an independent radio frequency power supply. The controller 80 can control the power and operating mode of each set of edge coils 62 respectively.

[0078] This structural design enables control over the axial distribution of plasma. By adjusting the power of the edge coils 62 at different axial positions, the axial distribution of plasma within the reaction chamber 10 can be altered, thereby optimizing the generation and transport of active free radicals while further suppressing ion diffusion into the substrate.

[0079] For example, in the first process, the power of the edge coil 62 farther from the substrate surface can be increased, while the power of the edge coil 62 closer to the substrate surface can be decreased. In this way, plasma is mainly generated in the upper part of the reaction chamber, and active free radicals reach the substrate surface by diffusing downwards. The plasma density and ion concentration are lower near the substrate surface, thereby reducing the number of high-energy ions incident vertically to the substrate surface.

[0080] In the second process, the power of the edge coils 62 at different axial positions can be adjusted as needed to obtain better ion concentration and etching rate distributions. For example, the power of the edge coils closer to the substrate surface can be increased to enhance the plasma density and ion flux near the substrate surface, thereby improving removal efficiency.

[0081] Furthermore, axially distributed edge coils can be combined with top central and intermediate coils to form a three-dimensional coil structure. This three-dimensional coil structure enables precise control of plasma in three-dimensional space, meeting the most complex process requirements and achieving better substrate protection and processing quality.

[0082] In one embodiment, the maximum distance from the top of the reaction chamber 10 to the top surface of the base 20 is less than 1 / 4 of the maximum inner diameter of the sidewall of the reaction chamber 10, making the plasma space above the substrate 90 flat. This flattened plasma space, superimposed on the plasma edge excitation in the first process, increases the probability of collisional annihilation of ions radially diffusing to the substrate 90, further reducing the possibility of ions diffusing to the substrate 90.

[0083] A control method for the aforementioned plasma processing equipment of the present invention mainly includes the following steps: Step a: Provide a reaction chamber with a vacuum environment, and generate plasma through a plasma source to process the substrate, wherein there is no grid structure between the plasma and the substrate, and the plasma source includes a central coil located near the axis of the reaction chamber and an edge coil located away from the axis of the reaction chamber. Step b: The reaction chamber is operated in a first process based on free radical processing, the edge coil operates in a first power mode, and the center coil operates in a second power mode; wherein the average power output of the second power mode is less than the average power output of the first power mode.

[0084] In radical etching processes, a large number of neutral radicals are required to react chemically with the material being treated. The presence of ions can disrupt the pure radical reaction characteristics, causing the process to transform into reactive ion etching. This invention addresses this by employing a differentiated control strategy in the first process—high power / continuous wave at the edge coils and low power / pulsed at the center coils—to achieve spatial separation of plasma excitation and radical reaction within the reaction chamber. This solves the problems of complex equipment and low air intake / exhaust efficiency caused by the need for additional ion filtering devices in traditional radical etching schemes. Furthermore, this invention eliminates the need for additional ion grids, shielding devices, and remote plasma sources (RPS), avoiding excessive flow resistance that leads to slow gas pressure response rates. Ion stripping is achieved simply by configuring the output power of different RF coils within the reaction chamber, preserving the radicals for further processing.

[0085] In one implementation, the output power of the second power mode is zero, meaning the central coil 61 is completely off in the first process. At this time, all radio frequency energy is supplied by the edge coil 62, and the plasma is generated entirely in the edge region of the reaction chamber 10. In this case, the ion concentration in the central region is lowest, while active free radicals can still diffuse uniformly to the entire substrate surface, ensuring the effectiveness of the first process.

[0086] In one implementation, for at least half the duration of the first process, the first power mode output is a continuous wave mode and the second power mode output is a pulse mode.

[0087] It is understood that in this invention, the radio frequency power pulse mode feeds in radio frequency energy to reduce ion concentration. Since ion generation and annihilation are rapid, compared with the continuous wave mode, the pulse power causes ions in the plasma to be repeatedly generated and annihilated, making it difficult to form an effective ion concentration accumulation. Furthermore, methods such as reducing the pulse duty cycle and increasing the pulse frequency can further highlight this effect and suppress the stable existence of ion quantity.

[0088] By setting the second power mode to pulse mode instead of zero output, the plasma of the central coil 61 can be in a low-energy mode, reducing its ion generation and diffusion, and supplementing the free radical generation in the central region, thus avoiding the problem of uneven diffusion at the edges.

[0089] In one embodiment, both the center coil 61 and the edge coil 62 operate in pulse mode, such that the power duty cycle of the center coil 61 is less than that of the edge coil 62, or the power pulse frequency of the center coil 61 is greater than that of the edge coil 62, or the power pulse pulse width of the center coil 61 is less than that of the edge coil 62. This allows for a further reduction in the average ion concentration of the plasma while maintaining the ability to generate free radicals, thereby further reducing the possibility of ions diffusing to the substrate 90.

[0090] In one embodiment, the control method further includes: Step c: The reaction chamber is operated in a second process based on ion bombardment, wherein the first process forms a modified layer on the substrate surface, and the second process removes the modified layer, and the first process and the second process are alternately cycled to perform atomic layer etching (ALE) on the substrate, wherein the ratio of the average power output of the center coil to the edge coil in the second process is greater than the ratio of the average power output of the center coil to the edge coil in the first process.

[0091] By introducing differentiated RF coil energy feeds during the modification and removal steps in the ALE process, the self-limiting nature of the modification is facilitated, preventing the process from transforming into reactive ion etching. Simultaneously, more uniform removal of the modified layer is achieved during the removal step.

[0092] For example, as shown in Figure 6, the atomic layer etching process may specifically include the following steps: Step S1: System initialization.

[0093] For example, the substrate 90 to be processed is transferred to the base 20 inside the reaction chamber 10 and firmly adsorbed onto the base 20 by electrostatic adsorption. Then, the door of the reaction chamber is closed, and the reaction chamber 10 is evacuated to a predetermined base vacuum pressure using the vacuum pump 40. Optionally, the temperature control system of the base 20 is activated to slowly adjust the temperature of the substrate 90 to the required process temperature and maintain it stable.

[0094] Step S2: Introduce the first process gas.

[0095] A first process gas, namely a free radical treatment gas, is introduced into the reaction chamber 10 through the gas inlet device 30. The flow rate of the first process gas is controlled at a predetermined value by a mass flow controller. At the same time, the pressure inside the reaction chamber 10 is stabilized at the pressure required for the first process by a vacuum device 40.

[0096] Step S3: Perform the first process.

[0097] The power source RF 70 is activated to excite the first process gas to form plasma. The controller 80 controls the power modes of the center coil 61 and the edge coil 62 according to preset control parameters.

[0098] In the first process, the edge coil 62 operates in a first power mode, and the center coil 61 operates in a second power mode. The average power output of the second power mode is lower than that of the first power mode. As previously described, this control strategy can primarily transfer plasma excitation to the edge region, reducing the ion concentration in the center region, thereby effectively suppressing ion diffusion into the substrate.

[0099] When both the center coil 61 and the edge coil 62 are operating in pulse mode, the controller 80 can also adjust their pulse duty cycle, pulse frequency, and pulse width, respectively. By optimizing these pulse parameters, the average ion concentration of the plasma can be further reduced while ensuring the effectiveness of free radical treatment, thereby improving the protection of the substrate.

[0100] After the first process has continued for a predetermined time, the controller 80 sends a command to shut down the source RF 70 and simultaneously stop the supply of the first process gas.

[0101] Step S4: Introduce the second process gas. The second process gas, also known as the removal gas, is introduced into the reaction chamber 10 through the gas inlet device 30. The flow rate of the second process gas is controlled at a predetermined value using a mass flow controller. Simultaneously, the pressure inside the reaction chamber 10 is stabilized to the pressure required for the second process using a vacuum pump 40.

[0102] Step S5: Execute the second process. Reactivate the source RF 70 to excite the second process gas to form plasma. The controller 80 independently adjusts the average power output of the center coil 61 and the edge coil 62 according to preset control parameters.

[0103] For example, in the second process, the RF power of the center coil 61 can be greater than that of the edge coil 62 to smooth out plasma distribution and ensure that the modified layer can be removed uniformly. Alternatively, both coils can be operated in pulsed mode to obtain a lower average ion concentration and improve etching selectivity.

[0104] After the second process has continued for a predetermined time, the controller 80 sends a command to shut down the source RF 70 and simultaneously stop the supply of the second process gas.

[0105] Step S6: Determine if etching is complete. If the atomic layer etching process has not reached the required number of cycles or the required etching depth, return to step S2 and repeat the first and second processes until the required etching depth is reached. If the required etching depth has been reached, proceed to step S7.

[0106] Step S7: Process complete. Inert gas, such as argon or nitrogen, is introduced into reaction chamber 10 to slowly restore the pressure inside reaction chamber 10 to atmospheric pressure. Then, the door of the reaction chamber is opened, and the processed substrate is transferred out of reaction chamber 10 and sent to subsequent process steps.

[0107] In one embodiment, the edge coil 62 may be located outside the axial projection region of the substrate 90. The axial projection region may be as follows: Figure 1The dashed line represents the axially projected three-dimensional region. Thus, the plasma generated by the edge coil 62 is primarily distributed on the outer edge of the substrate 90. Free radicals then diffuse to the surface of the substrate 90, avoiding the destructive effects of ions on pure free radical reactions. This structure prevents the edge coil 62 from generating excessively strong plasma directly above the edge of the substrate 90, further reducing the number of high-energy ions in the edge region and preventing the pure free radical reaction in the edge region from transforming into reactive ion etching.

[0108] In another embodiment, the air intake device 30 can employ a zoned air intake method. The air intake device is divided into multiple independent air intake zones, each corresponding to a radio frequency coil. By controlling the gas flow rate in each air intake zone separately, the gas distribution can be matched with the plasma distribution, further optimizing the generation and transport of active free radicals and improving the effectiveness of the first process.

[0109] In another embodiment, the plasma processing equipment may further include plasma diagnostic devices, such as emission spectrometers, Langmuir probes, and mass spectrometers. The plasma diagnostic devices are used to monitor plasma parameters within the reaction chamber 10 in real time, such as electron density, electron temperature, ion concentration distribution, and active free radical concentration. The controller 80 can dynamically adjust the power and operating mode of each RF coil based on the feedback signal from the plasma diagnostic devices, achieving feedback control. This feedback control method can further improve the stability and repeatability of the process, ensuring consistent substrate processing results under different process conditions.

[0110] Furthermore, the technical solution of this invention is not only applicable to atomic layer etching processes, but can also be applied to any other plasma processing process that is sensitive to ion damage. For example, in the gate etching process of semiconductor devices, this invention can be used to suppress the diffusion of ions into the gate oxide layer and avoid damage to the gate oxide layer; in the thin film deposition process, this invention can be used to control the ion concentration of the plasma and reduce defects in the thin film.

[0111] In the second process, a modified layer has already been applied to the surface of the material to be treated, protecting the underlying substrate from ionic damage. Therefore, we can independently adjust the power and operating mode of each coil according to the removal requirements to achieve better removal results. This step-by-step optimization approach enables both high-quality radical treatment and efficient removal, thereby improving the overall quality and throughput of the atomic layer etching process.

[0112] This invention ensures the quality of free radical treatment while suppressing the ion flux and energy on the substrate surface, maintaining the characteristics of pure free radical reactions, improving processing precision and selectivity, and at the same time greatly simplifies the equipment structure, reduces gas flow resistance, improves inlet and outlet efficiency and process cycle speed, and significantly increases production capacity.

[0113] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A plasma processing apparatus, comprising a reaction chamber, a gas inlet device, a vacuum pumping device, a source radio frequency (RF) generator, and an RF coil, wherein a base is provided within the reaction chamber to support a substrate; the gas inlet device supplies process gas to the reaction chamber; the vacuum pumping device operates the reaction chamber at the pressure required for the process; the reaction chamber has a dielectric window, the top of the reaction chamber is sealed by the dielectric window, an RF coil is provided outside the dielectric window, and the source RF generator feeds RF energy into the reaction chamber through the RF coil to excite plasma within the reaction chamber to process the substrate; characterized in that... The radio frequency coil includes an edge coil located outside the axial projection area of ​​the base and a center coil located at least partially within the axial projection area; There is no grid structure between the air intake device and the substrate, and the grid structure is used to reduce the flow of ions to the substrate; It also includes a controller, which is configured to: The reaction chamber is operated in a first process based on free radical treatment, and The edge coil is operated in a first power mode, and the center coil is operated in a second power mode; The average power output of the second power mode is less than the average power output of the first power mode.

2. The plasma processing equipment as described in claim 1, characterized in that, The radio frequency coil also includes an intermediate coil, which is located between the center coil and the edge coil.

3. The plasma processing equipment as described in claim 2, characterized in that, The source radio frequency includes a first radio frequency and a second radio frequency, wherein the first radio frequency supplies power to the center coil and the edge coil, and the second radio frequency supplies power to the middle coil.

4. The plasma processing equipment as described in claim 3, characterized in that, It also includes a power divider that adjusts the power distribution ratio between the center coil and the edge coils.

5. The plasma processing apparatus as described in claim 3, characterized in that, The first radio frequency and the second radio frequency have different output frequencies.

6. The plasma processing apparatus as described in claim 1, characterized in that, The edge coil is located at the top or side wall of the reaction chamber.

7. The plasma processing apparatus as described in claim 6, characterized in that, The dielectric window includes a first dielectric window located at the top of the reaction chamber and a second dielectric window located on the side wall of the reaction chamber. The center coil is located outside the first dielectric window, and the edge coil is located outside the second dielectric window.

8. The plasma processing apparatus as described in claim 1, characterized in that, The air intake device further includes an edge air intake device disposed on the side wall of the reaction chamber, the edge air intake device being used to supply the first process gas for the first process.

9. The plasma processing apparatus as described in claim 1, characterized in that, The second power mode includes zero power mode or pulse mode.

10. The plasma processing apparatus as described in claim 1, characterized in that, The maximum distance from the top of the reaction chamber to the top surface of the base is less than 1 / 4 of the maximum inner diameter of the sidewall of the reaction chamber.

11. A control method for a plasma processing device, characterized in that, The control method, applied to the plasma processing apparatus as described in any one of claims 1 to 10, comprises: Step a: Provide a reaction chamber with a vacuum environment and generate plasma through a plasma source to process the substrate, wherein there is no grid structure between the plasma and the substrate, and the plasma source includes an edge coil located outside the axial projection area of ​​the base and a central coil located at least partially within the axial projection area; Step b: The reaction chamber is operated in a first process based on free radical processing, the edge coil operates in a first power mode, and the center coil operates in a second power mode; wherein the average power output of the second power mode is less than the average power output of the first power mode.

12. The control method as described in claim 11, characterized in that, The output power of the second power mode is zero.

13. The control method as described in claim 11, characterized in that, For at least half the duration of the first process, the first power mode output is in continuous wave mode, and the second power mode output is in pulse mode.

14. The control method as described in claim 11, characterized in that, In the first process, the first power mode and the second power mode outputs a pulse mode, wherein... The power duty cycle of the second power mode is less than the power duty cycle of the first power mode, and / or The power pulse frequency of the second power mode is greater than the power pulse frequency of the first power mode, and / or The power pulse width of the second power mode is smaller than that of the first power mode.

15. The control method as described in claim 11, characterized in that, Also includes Step c: The reaction chamber is operated in a second process based on ion bombardment, wherein the first process forms a modified layer on the substrate surface, and the second process removes the modified layer, and the first process and the second process are alternately cycled to perform atomic layer etching on the substrate, wherein the ratio of the average power output of the center coil to the edge coil in the second process is greater than the ratio of the average power output of the center coil to the edge coil in the first process.

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