Remote plasma source system based on 172nm ultraviolet light-assisted ignition

Abstract

This application belongs to the field of remote plasma source technology and discloses a remote plasma source system based on 172nm ultraviolet light-assisted ignition, including a remote plasma source and an ultraviolet pre-ionization device at its gas inlet; the ultraviolet pre-ionization device includes: a shell having a gas flow channel and a sealed gas cavity separated by a light-transmitting partition, the sealed gas cavity being filled with xenon gas, the gas flow channel being connected to the gas inlet of the remote plasma source and used for the flow of process gas; a positive electrode plate and a negative electrode plate, disposed on opposite sides of the shell and used to excite the xenon gas to generate 172nm ultraviolet light when an AC voltage is applied; the ultraviolet light can pass through the light-transmitting partition and enter the gas flow channel; a mesh electrode, disposed in the gas flow channel and used to cooperate with the ultraviolet light to pre-ionize the process gas when energized; it has the advantages of efficiently realizing plasma ignition of high-resistivity gases, improving ignition success rate and process stability, while avoiding contamination.

Description

Technical Field

[0001] This application relates to the field of remote plasma source technology, and more specifically, to a remote plasma source system based on 172nm ultraviolet light-assisted ignition. Background Technology

[0002] 172nm excimer ultraviolet light, with its ultra-high photon energy, excellent monochromaticity, and mercury-free environmental friendliness, exhibits unique technological advantages in the field of pre-ionization of difficult-to-ionize gases. This technology can directly break the chemical bonds of strong bond-energy gas molecules, efficiently generating a variety of highly reactive particles, which has an urgent application demand in plasma processes in semiconductor chip manufacturing. In particular, 172nm excimer ultraviolet light sources based on Xe excitation not only avoid the energy dispersion problem of traditional broadband light sources but also eliminate the risk of metal electrode contamination, becoming an important development direction for high-precision, high-stability plasma sources.

[0003] Existing plasma ignition technologies, particularly those involving remote plasma sources, suffer from significant limitations. Single electromagnetic excitation ignition techniques struggle with high-ionization-energy gases, exhibiting high breakdown impedance and a large ignition energy threshold, frequently resulting in ignition failure or delayed ignition, severely impacting process stability. Furthermore, low energy coupling efficiency, coupled with traditional matching networks and cavity structures not optimized for high-impedance gases, leads to high reflected power and substantial effective power loss. While single auxiliary gas premixing ignition methods can promote main gas ionization by lowering the average ionization energy, gas purity is affected, and the introduced auxiliary gas may participate in the reaction or remain in the cavity, causing contamination. Additionally, these methods have a narrow process window, high parameter sensitivity, and poor reproducibility. Existing ultraviolet pre-ionization-electromagnetic excitation combination technologies mostly adopt a simple series mode, which fails to achieve substantial synergy between optical energy and electromagnetic energy. The spatial separation between pre-ionization and the main excitation region leads to severe decay of the initial carrier density. At the same time, the performance of key components is insufficient, with low reflection efficiency for 172nm ultraviolet light, poor light energy utilization, and a lack of integrated design between the optical window and the electrode / cavity, resulting in limited improvement in ignition success rate and plasma density.

[0004] To address the aforementioned technical bottlenecks, there is an urgent need to develop a remote plasma source system capable of achieving efficient coordination between ultraviolet pre-ionization and electromagnetic excitation. This system should possess an optimized optical window structure, high-reflectivity cavity walls, and tightly connected pre-ionization and main excitation regions to solve key problems such as difficulties in igniting high-impedance gas plasmas and poor process consistency.

[0005] To address the aforementioned issues, existing technologies urgently need improvement. Summary of the Invention

[0006] The purpose of this application is to provide a remote plasma source system based on 172nm ultraviolet light-assisted ignition, which has the advantages of efficiently realizing plasma ignition of high-resistivity gases, improving ignition success rate and process stability, while avoiding contamination.

[0007] This application provides a remote plasma source system based on 172nm ultraviolet light-assisted ignition, including a remote plasma source and an ultraviolet pre-ionization device disposed at the gas inlet of the remote plasma source.

[0008] The ultraviolet pre-ionization device includes:

[0009] The housing has a gas flow channel and a sealed gas cavity separated by a light-transmitting partition. The sealed gas cavity is filled with xenon gas. The gas flow channel is connected to the gas inlet of the remote plasma source and is used for the flow of process gas.

[0010] Positive and negative electrode plates are disposed on opposite sides of the housing, and the sealed gas cavity is located between the positive and negative electrode plates; the positive and negative electrode plates are used to excite the xenon gas to generate 172nm ultraviolet light when an AC voltage is applied; the 172nm ultraviolet light can pass through the light-transmitting partition and enter the gas flow channel;

[0011] A mesh electrode is disposed inside the gas flow channel and is used to pre-ionize the process gas in conjunction with the 172nm ultraviolet light when energized.

[0012] Preferably, the axial distance between the outlet of the gas flow channel and the gas inlet of the remote plasma source is no more than 50 mm.

[0013] Preferably, a connecting member is provided between the outlet of the gas flow channel and the gas inlet of the remote plasma source, the connecting member having a Venturi channel that connects the outlet of the gas flow channel and the gas inlet of the remote plasma source.

[0014] Preferably, the ratio of the lateral dimension of the throat of the Venturi channel to the lateral dimension of the gas inlet of the remote plasma source is 1:3 to 1:5.

[0015] Preferably, a reflective layer is provided on the inner wall of the sealed gas cavity, excluding the light-transmitting partition, and the reflective layer is used to reflect the 172nm ultraviolet light into the gas flow channel.

[0016] Preferably, the reflective layer is an alternating stacked reflective structure composed of multiple SiO2 layers and multiple Al2O3 layers, wherein the thickness of each SiO2 layer is 10nm-50nm, the thickness of each Al2O3 layer is 20nm-100nm, and the sum of the number of SiO2 layers and Al2O3 layers is 4-10 layers.

[0017] Preferably, the housing is made of quartz, the light-transmitting partition is a quartz partition integrally formed with the housing, and the layer in the reflective layer connected to the inner wall of the sealed air cavity is a SiO2 layer.

[0018] Preferably, the remote plasma source includes a plasma cavity, an electromagnetic excitation mechanism sleeved on the plasma cavity, a radio frequency power supply, and an impedance matching network connected between the radio frequency power supply and the electromagnetic excitation mechanism.

[0019] Preferably, the volume of the integral chamber formed by the plasma chamber and the gas flow channel is 1L-3L.

[0020] Preferably, the process gas is pure nitrogen fluoride or a mixture of nitrogen fluoride and argon.

[0021] Beneficial effects: The remote plasma source system based on 172nm ultraviolet light-assisted ignition provided in this application uses an ultraviolet pre-ionization device to pre-ionize the process gas with 172nm ultraviolet light, thereby efficiently realizing plasma ignition of high-resistivity gas, improving the ignition success rate and process stability, and avoiding contamination. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a remote plasma source system provided in this application.

[0023] Figure 2 This is a schematic diagram of the ultraviolet pre-ionization device.

[0024] Labeling Explanation: 100, Remote Plasma Source; 200, Ultraviolet Pre-ionization Device; 300, Connecting Component; 400, Ionization Rate Monitoring Device; 1, Shell; 101, Transparent Partition; 102, Gas Flow Channel; 103, Sealed Gas Chamber; 2, Positive Electrode Plate; 3, Negative Electrode Plate; 4, Mesh Electrode; 5, Reflective Layer; 6, Plasma Chamber; 7, Electromagnetic Excitation Mechanism; 8, Radio Frequency Power Supply; 9, Impedance Matching Network. Detailed Implementation

[0025] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0026] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this application, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0027] Please refer to Figures 1-2 A remote plasma source system based on 172nm ultraviolet light-assisted ignition in some embodiments of this application includes a remote plasma source 100 and an ultraviolet pre-ionization device 200 disposed at the gas inlet of the remote plasma source 100.

[0028] The ultraviolet pre-ionization device 200 includes:

[0029] The housing 1 has a gas flow channel 102 and a sealed gas chamber 103 separated by a light-transmitting partition 101. The sealed gas chamber 103 is filled with xenon gas. The gas flow channel 102 is connected to the gas inlet of the remote plasma source 100 and is used to supply process gas flow.

[0030] Positive electrode plate 2 and negative electrode plate 3 are disposed on opposite sides of housing 1, and sealed gas cavity 103 is located between positive electrode plate 2 and negative electrode plate 3; positive electrode plate 2 and negative electrode plate 3 are used to excite xenon gas to generate 172nm ultraviolet light when AC voltage is applied; 172nm ultraviolet light can pass through light-transmitting partition 101 and enter gas flow channel 102.

[0031] The mesh electrode 4 is disposed inside the gas flow channel 102 and is used to pre-ionize the process gas in conjunction with 172nm ultraviolet light when energized.

[0032] The remote plasma source 100 is a device that separates the plasma generation area from the process reaction area. Its main function is to generate highly reactive plasma at a location far from the process chamber and transport it into the process chamber via gas flow, thereby avoiding direct damage to the sensitive substrate by the plasma and reducing chamber contamination. The remote plasma source 100 typically includes components such as a plasma chamber 6, an electromagnetic excitation mechanism 7, a radio frequency power supply 8, and an impedance matching network 9.

[0033] The ultraviolet pre-ionization device 200 includes a housing 1, which has a gas flow channel 102 and a sealed gas chamber 103 separated by a light-transmitting partition 101. The sealed gas chamber 103 is filled with xenon gas, and the gas flow channel 102 is connected to the gas inlet of a remote plasma source 100 and is used for the flow of process gas. As one embodiment, the housing 1 can be made of quartz glass to ensure good ultraviolet light transmittance and corrosion resistance. The light-transmitting partition 101 can be integrally formed with the housing 1 or fixed inside the housing 1 by a sealing method to effectively isolate the gas flow channel 102 from the sealed gas chamber 103. The gas flow channel 102 can be designed as a straight cylinder to allow smooth flow of process gas. The volume of the sealed gas chamber 103 can be designed according to the required xenon gas filling amount and ultraviolet light generation efficiency; for example, it can be designed as an annular cavity surrounding the gas flow channel 102.

[0034] Furthermore, the positive electrode plate 2 and the negative electrode plate 3 are disposed on opposite sides of the housing 1, and the sealed gas cavity 103 is located between the positive electrode plate 2 and the negative electrode plate 3. The positive electrode plate 2 and the negative electrode plate 3 are used to excite xenon gas to generate 172nm ultraviolet light when an AC voltage is applied. The 172nm ultraviolet light can pass through the light-transmitting partition 101 and enter the gas flow channel 102. As one embodiment, the electrode plates can be made of a metallic material, such as aluminum or stainless steel, and connected to an external power source. The frequency and amplitude of the AC voltage can be adjusted according to the optimal conditions for xenon gas excitation to ensure efficient generation of 172nm ultraviolet light. For example, a high-frequency, high-voltage power supply can be used to drive the electrode plates. The 172nm ultraviolet light has high photon energy and can effectively break down gas molecules with strong bond energy.

[0035] Furthermore, the mesh electrode 4 is disposed inside the gas flow channel 102 and is used to pre-ionize the process gas in conjunction with 172nm ultraviolet light when energized. As one embodiment, the mesh electrode 4 can be made of conductive metal wire mesh, such as stainless steel mesh or nickel-chromium alloy mesh, and fixed to the inner wall of the gas flow channel 102. The mesh electrode 4 can be connected to an independent DC or AC power supply to generate an auxiliary electric field. The mesh density and wire diameter of the mesh electrode 4 can be optimized according to the requirements of gas flow rate and pre-ionization effect. For example, the mesh electrode 4 can be designed with a sufficiently large porosity to avoid significant obstruction to gas flow while providing sufficient electric field strength.

[0036] This application presents a remote plasma source system based on 172nm ultraviolet light-assisted ignition. By incorporating an ultraviolet pre-ionization device 200 at the gas inlet of the remote plasma source 100, it achieves highly efficient pre-ionization of the process gas. Compared to traditional single electromagnetic excitation ignition technology, this application directly cleaves high-ionization-energy gas molecules using 172nm ultraviolet light, significantly reducing the ignition energy threshold and avoiding ignition failure or ignition delay, thereby improving process stability. Compared to single auxiliary gas premixing ignition technology, this application eliminates the need for auxiliary gas, avoiding the risks of gas purity degradation and wafer contamination, while also broadening the process window and reducing process debugging and maintenance costs. Furthermore, compared to existing ultraviolet pre-ionization-electromagnetic excitation combination technologies, this application places the ultraviolet pre-ionization device 200 at the gas inlet of the remote plasma source 100, ensuring close integration of pre-ionization with the main excitation region. This effectively reduces recombination losses of highly reactive particles during transport, maintains the initial carrier density, and thus more effectively lowers the main region ignition threshold. The synergistic effect of the mesh electrode 4 and ultraviolet light further enhances the pre-ionization effect, enabling efficient coupling between photoelectrons and the electric field, significantly improving the ignition success rate and plasma density. Therefore, this application provides a highly reliable and efficient plasma ignition solution for high-performance chip manufacturing.

[0037] Preferably, the axial distance between the outlet of the gas flow channel 102 and the gas inlet of the remote plasma source 100 is no more than 50 mm.

[0038] Specifically, the outlet of gas channel 102 refers to the end of the channel in the ultraviolet pre-ionization device 200 used for the flow of process gas, and is the physical interface at which the pre-ionized process gas leaves the pre-ionization region. The function of this outlet is to guide the pre-ionized process gas to the remote plasma source 100. This can be achieved through a simple pipe end opening or through a specially designed nozzle or diffuser to optimize gas flow. The gas inlet of the remote plasma source 100 is the port through which the remote plasma source 100 receives the process gas, and is the channel through which the pre-ionized gas enters the main plasma generation region. This inlet can be a standard flange connection or an integrated structure directly integrated with the pre-ionization device. An axial distance of no more than 50 mm refers to the maximum permissible space between the outlet of gas channel 102 and the gas inlet of the remote plasma source 100 along the main flow direction of the process gas. This distance limitation aims to ensure that the active particles generated by pre-ionization can be efficiently transported from the pre-ionization region to the main excitation region of the remote plasma source 100, reducing losses during the transport process. This distance can be achieved by directly and tightly connecting the ultraviolet preionization device 200 to the gas inlet of the remote plasma source 100, or by bridging the two using a short connecting member 300.

[0039] The solution in this application effectively optimizes the transport path of the pre-ionized gas to the main excitation region and reduces the loss of active particles by limiting the axial distance between the outlet of the gas channel 102 and the gas inlet of the remote plasma source 100 to no more than 50 mm. In the remote plasma source 100 system, the ultraviolet pre-ionization device 200 uses 172 nm ultraviolet light to pre-ionize the process gas, generating a large number of initial carriers and highly active particles. These particles are crucial for reducing the ignition threshold of the remote plasma source 100 and improving the ignition success rate and stability. However, these active particles typically have short lifetimes and are prone to recombination or deactivation during transport. By strictly controlling the axial distance between the outlet of the gas channel 102 and the gas inlet of the remote plasma source 100, it is ensured that the active particles generated by pre-ionization can enter the main excitation region of the remote plasma source 100 with the shortest path and the fastest speed. This tight connection minimizes the recombination loss of active particles during transport, thereby ensuring that the process gas entering the remote plasma source 100 has a sufficiently high initial carrier density. This enables the remote plasma source 100 to achieve plasma ignition more quickly and stably under subsequent electromagnetic excitation, especially for high ionization energy gases such as nitrogen fluoride, where its ignition efficiency and stability are significantly improved.

[0040] In some preferred embodiments, see Figure 1 A connecting member 300 is connected between the outlet of the gas flow channel 102 and the gas inlet of the remote plasma source 100. The connecting member 300 has a Venturi channel that connects the outlet of the gas flow channel 102 and the gas inlet of the remote plasma source 100.

[0041] The connecting member 300 is a structure used for physical connection and gas flow guidance. Its main function is to ensure a continuous and sealed gas transmission path between the gas channel 102 of the ultraviolet pre-ionization device 200 and the gas inlet of the remote plasma source 100. The connecting member 300 can be a standalone adapter or part of the ultraviolet pre-ionization device 200 or the remote plasma source 100, achieving a tight connection through welding, bolting, flange connection, or other methods. The connecting member 300 is designed to eliminate gaps in the gas transmission path, preventing external gas infiltration or pre-ionization gas leakage, thereby maintaining gas purity and reducing the loss of pre-ionized particles.

[0042] A Venturi channel is a fluid channel with a specific geometry, typically comprising a gradually narrowing inlet section, a throat with a minimum cross-sectional area, and a gradually expanding outlet section. This structure, according to Bernoulli's principle, increases the gas velocity while simultaneously reducing pressure as the gas flows through the throat. In this application, the Venturi channel optimizes the gas flow field, shortening the time it takes for pre-ionized particles to travel from the ultraviolet pre-ionization device 200 to the remote plasma source 100 by accelerating gas flow, thereby effectively suppressing recombination of highly reactive particles during transport. Furthermore, the design of its expanding section facilitates the smooth recovery of gas velocity, reduces turbulence, and ensures that the gas enters the remote plasma source 100 in a stable state.

[0043] The Venturi channel connects the outlet of the gas flow channel 102 with the gas inlet of the remote plasma source 100, meaning that the channel structurally achieves a seamless connection between the ultraviolet pre-ionization device 200 and the remote plasma source 100. This connection method ensures that the pre-ionized process gas can directly and efficiently enter the main excitation region of the remote plasma source 100 from the pre-ionization region, avoiding gas stagnation, diffusion, or excessive collision with the cavity wall in the transmission path, thereby maximizing the preservation of the activity of the pre-ionized particles.

[0044] The solution of this application optimizes the transmission process of pre-ionized gas from the ultraviolet pre-ionization device 200 to the remote plasma source 100 by setting a connecting member 300 between the outlet of the gas flow channel 102 and the gas inlet of the remote plasma source 100, and by giving the connecting member 300 a Venturi channel. Specifically, the introduction of the connecting member 300 eliminates the potential gap between the two, ensuring the continuity and sealing of the gas transmission path and effectively preventing the loss of pre-ionized particles during transmission. At the same time, the Venturi channel design causes the pre-ionized gas to undergo an acceleration process before entering the remote plasma source 100, significantly shortening the residence time of highly reactive particles in the transmission path, thereby greatly reducing their recombination probability. This optimized gas transmission mechanism effectively complements the pre-ionization treatment of the process gas by the aforementioned ultraviolet pre-ionization device 200. Pre-ionization of the process gas using 172nm ultraviolet light generates a large number of initial charge carriers and highly reactive particles. A Venturi channel ensures that these highly reactive particles are transported to the main excitation region of the remote plasma source 100 with minimal loss and maximum speed. This tight connection and efficient transmission enable the remote plasma source 100 to receive a higher density of initial reactive particles during ignition, thereby significantly reducing the energy threshold required for ignition and improving the success rate and stability of ignition.

[0045] Preferably, the ratio of the lateral dimension of the throat of the Venturi channel to the lateral dimension of the gas inlet of the remote plasma source 100 is 1:3 to 1:5.

[0046] The lateral dimension of the throat of the Venturi channel refers to the lateral dimension of the narrowest part of the Venturi channel. Its function is to accelerate gas flow and reduce local pressure, thereby guiding the gas efficiently into subsequent cavities. This lateral dimension can refer to the diameter of the throat, or, for non-circular channels, its hydraulic diameter. The lateral dimension of the gas inlet of the remote plasma source 100 refers to the lateral dimension at the inlet where the remote plasma source 100 receives the process gas, which serves as the channel for the pre-ionized gas to enter the main plasma cavity. This lateral dimension can refer to the diameter of the inlet, or, for non-circular inlets, its hydraulic diameter. The ratio of the lateral dimension of the throat of the Venturi channel to the lateral dimension of the gas inlet of the remote plasma source 100 is set in the range of 1:3 to 1:5. This ratio defines the relative size relationship between the two, ensuring that the gas can be properly accelerated in the Venturi channel while avoiding excessive pressure drop or turbulence, thereby optimizing gas transport efficiency and stability. For gas entering the Venturi channel at a velocity of 5 m / s to 15 m / s in the gas flow channel, within this ratio range, it can be reliably guaranteed that the pre-ionized gas can be accelerated into the remote plasma source 100 in a laminar flow state. For example, this ratio can be 1:3, 1:4, or 1:5, or any ratio between these values.

[0047] The proposed solution involves conveying pre-ionized gas generated by the ultraviolet pre-ionization device 200 to the gas inlet of the remote plasma source 100 via a Venturi channel in the connecting member 300. The ratio of the lateral dimension of the throat of the Venturi channel to the lateral dimension of the gas inlet of the remote plasma source 100 is precisely defined within the range of 1:3 to 1:5. When the pre-ionized gas flows through the Venturi channel, it is accelerated at the throat, resulting in a local pressure reduction. This helps maintain the laminar flow of the gas and shortens the residence time of active particles in the transport path, thereby effectively reducing the loss of active particles due to recombination before entering the remote plasma source 100. This specific size ratio ensures a moderate gas acceleration effect, avoiding both excessive pressure drop and turbulence that may result from an excessively small throat, and insufficient acceleration and slowed flow rate that may result from an excessively large throat, thus maintaining the continuity and stability of the airflow. This optimized gas transport path enables high-density pre-ionized active particles to enter the remote plasma source 100 efficiently and stably, providing sufficient initial charge carriers for subsequent plasma ignition and significantly improving the success rate and stability of ignition.

[0048] In some preferred embodiments, see Figure 2The inner wall of the sealed gas cavity 103, except for the light-transmitting partition 101, is provided with a reflective layer 5, which is used to reflect 172nm ultraviolet light to the gas flow channel 102.

[0049] The reflective layer 5 is a thin film or coating capable of reflecting light of a specific wavelength back. Its function is to improve light energy utilization by redirecting ultraviolet light that might otherwise be absorbed or scattered back to the target area. The reflective layer 5 can be implemented in various ways. For example, a dielectric film reflective layer 5 can be used, which is composed of multiple layers of dielectric materials with different refractive indices stacked alternately, achieving high reflectivity through optical interference effects, such as multilayer film structures like titanium dioxide / silicon dioxide or tantalum pentoxide / silicon dioxide. Alternatively, a metal reflective layer 5 can be used, by depositing a layer of high-reflectivity metal, such as aluminum, silver, or gold, on its inner wall and covering its surface with a protective layer to prevent oxidation or corrosion. A composite reflective layer 5 can also be used, combining the advantages of dielectric and metal films; for example, a dielectric protective layer can be deposited on the metal reflective layer 5 to improve reflectivity and durability.

[0050] The working principle of this scheme is as follows: In the ultraviolet pre-ionization device 200, when an AC voltage is applied to the positive electrode plate 2 and the negative electrode plate 3 to excite the xenon gas in the sealed gas cavity 103 to generate 172nm ultraviolet light, this ultraviolet light is intended to pass through the light-transmitting partition 101 and enter the gas flow channel 102 to pre-ionize the process gas. However, some ultraviolet light inevitably irradiates the inner wall of the sealed gas cavity 103 other than the light-transmitting partition 101. By setting a reflective layer 5 on these inner walls, the ultraviolet light that would otherwise be absorbed or scattered by the inner walls is effectively reflected. This reflected ultraviolet light is then redirected so that it can enter the gas flow channel 102. This mechanism ensures that a larger proportion of the generated 172nm ultraviolet light can effectively act on the process gas in the gas flow channel 102, thereby significantly enhancing the irradiation intensity of the ultraviolet light on the process gas and improving the efficiency of the pre-ionization process. The reflective layer 5 maximizes the utilization rate of the ultraviolet light in the pre-ionization process by concentrating the ultraviolet light energy. This optimized pre-ionization process provides a higher initial carrier density for the subsequent electromagnetic excitation of the remote plasma source 100, thereby helping to achieve more stable and efficient plasma ignition, especially for process gases that are difficult to ionize.

[0051] In some possible implementations, the reflective layer 5 is an alternating stacked reflective structure composed of multiple SiO2 layers and multiple Al2O3 layers, with each SiO2 layer having a thickness of 10nm-50nm and each Al2O3 layer having a thickness of 20nm-100nm, and the sum of the number of SiO2 layers and Al2O3 layers being 4-10 layers.

[0052] The reflective layer 5 is an alternating stacked reflective structure composed of multiple SiO2 layers and multiple Al2O3 layers. This structure utilizes the multilayer stacking of materials with different refractive indices to achieve high reflectivity within a specific wavelength range through the interference effect of light waves. This alternating stacked reflective structure can be realized using various thin film deposition techniques. For example, the sol-gel method can be used to precisely control the thickness and uniformity of each layer; physical vapor deposition (PVD) techniques, such as magnetron sputtering or electron beam evaporation, can also be used to precisely control the thickness and uniformity of each layer; alternatively, chemical vapor deposition (CVD) techniques can be used to form a thin film on the substrate surface through chemical reactions, suitable for deposition on complex-shaped inner walls; or atomic layer deposition (ALD) techniques can be used to control the film thickness with atomic-level precision, ensuring film density and uniformity.

[0053] Each SiO2 layer has a thickness of 10 nm to 50 nm. As a low-refractive-index layer in an alternating stacked reflective structure, the thickness of the SiO2 layer is crucial to the interference reflection effect, directly affecting the position and intensity of the reflection peak. The thickness control can be precisely measured and adjusted during the deposition process using a real-time optical monitoring system (e.g., an ellipsometer); or it can be controlled by pre-calibrated deposition rate and deposition time to ensure that the desired thickness range is achieved.

[0054] Each Al2O3 layer has a thickness of 20nm-100nm. As a high-refractive-index layer in the alternating stacked reflective structure, the Al2O3 layer works synergistically with the SiO2 layer to jointly determine the reflection peak and bandwidth. The thickness control can be achieved similarly to that of the SiO2 layer, through optical monitoring or deposition rate control; alternatively, during the deposition process, a quartz crystal microbalance (QCM) can be used to monitor the deposition rate and film thickness in real time.

[0055] The total number of SiO2 and Al2O3 layers ranges from 4 to 10. The number of layers determines the reflectivity and bandwidth of the reflective structure; an appropriate number of layers ensures high reflectivity at a wavelength of 172 nm. The selection of the number of layers can be optimized based on the required reflectivity and process window. For example, increasing the number of layers can improve reflectivity but also increase manufacturing costs and complexity; alternatively, in practical applications, the optimal number of layers can be determined through simulation based on the specific requirements for 172 nm ultraviolet light reflection efficiency.

[0056] The solution presented in this application effectively solves the problems of insufficient reflection efficiency and low light energy utilization in the prior art through the aforementioned alternating stacked reflective structure. Specifically, the reflective layer 5 is composed of multiple SiO2 layers and multiple Al2O3 layers stacked alternately, and its working principle is based on the thin-film optical interference effect. When 172nm ultraviolet light generated in the sealed gas cavity 103 is incident on this multilayer dielectric film structure, multiple reflections and transmissions occur at the interfaces of SiO2 layers and Al2O3 layers with different refractive indices. By precisely controlling the thickness of each SiO2 layer within the range of 10nm-50nm and the thickness of each Al2O3 layer within the range of 20nm-100nm, the light waves reflected at these interfaces can constructively interfere in a phase-superimposed manner, thereby generating extremely high reflectivity at a wavelength of 172nm. The total number of SiO2 layers and Al2O3 layers is limited to 4-10 layers, and this range has been optimized to ensure that high reflectivity is achieved while also considering the feasibility and cost-effectiveness of the manufacturing process. This highly reflective, alternating layered reflective structure efficiently reflects most of the 172nm ultraviolet light generated within the sealed gas cavity 103 back to the gas flow channel 102. Combined with the technique in the ultraviolet pre-ionization device 200 where the reflective layer 5 is located on the inner wall of the sealed gas cavity 103 (excluding the light-transmitting partition 101) to reflect 172nm ultraviolet light to the gas flow channel 102, this significantly increases the flux of 172nm ultraviolet light entering the gas flow channel 102. Therefore, before entering the remote plasma source 100, the process gas can fully absorb high-energy 172nm ultraviolet light, thus being more effectively pre-ionized and generating a higher density of initial charge carriers. These high-density initial charge carriers significantly reduce the breakdown threshold and ignition difficulty during subsequent electromagnetic excitation of the remote plasma source 100. Especially for high-ionization-energy gases such as nitrogen fluoride, this effectively avoids ignition failure or delay, thereby improving the ignition success rate and process stability of the entire remote plasma source 100 system.

[0057] Furthermore, the shell 1 is made of quartz, the light-transmitting partition 101 is a quartz partition integrally formed with the shell 1, and the layer in the reflective layer 5 connected to the inner wall of the sealed air cavity 103 is a SiO2 layer.

[0058] Specifically, the housing 1 is made of quartz material because quartz has excellent ultraviolet light transmittance, especially at a wavelength of 172nm, where its light absorption rate is extremely low, minimizing energy loss during ultraviolet light transmission. Furthermore, quartz possesses good chemical inertness and high-temperature resistance, enabling it to withstand corrosive gas environments and high operating temperatures that may exist in plasma processes, ensuring long-term stable operation of the system. The light-transmitting partition 101 is designed as a quartz partition integrally formed with the housing 1, meaning there is no independent connection interface or seam between the light-transmitting partition 101 and the housing 1. This integrated structure effectively eliminates the risks of light scattering, light leakage, or sealing failure that may result from connections of different materials or mechanical connections. Simultaneously, since both its material and the housing 1 are quartz, material consistency is ensured throughout the optical path, further optimizing the transmission efficiency of 172nm ultraviolet light and enhancing the mechanical strength and airtightness of the entire ultraviolet pre-ionization device 200. The first layer in the reflective layer 5 connected to the inner wall of the sealed gas cavity 103 is designated as a SiO2 layer. This design is based on the excellent interfacial compatibility and chemical affinity between SiO2 and quartz. SiO2, as the starting layer of reflective layer 5, can form a stable and firm adhesion with the quartz substrate, effectively preventing problems such as detachment, delamination, or performance degradation of reflective layer 5 due to material incompatibility. Simultaneously, SiO2 itself has a suitable refractive index at a wavelength of 172nm, enabling it to serve as a component of the multilayer reflective structure, working in conjunction with other layers to achieve efficient reflection of ultraviolet light.

[0059] Specifically, the housing 1 is made of quartz, and the light-transmitting partition 101 is an integrally formed quartz partition with the housing 1. This design ensures a high degree of material consistency throughout the optical path of the entire ultraviolet pre-ionization device 200. Utilizing the extremely high transmittance and extremely low absorption of quartz for 172nm ultraviolet light, light energy loss is minimized. The integrated quartz partition structure further eliminates the interface defects, light scattering, or leakage risks that may exist in traditional separate partitions, significantly enhancing the overall airtightness and mechanical stability of the device. To further improve the utilization efficiency of ultraviolet light, the first layer of the reflective layer 5 connected to the inner wall of the sealed gas cavity 103 is designed as a SiO2 layer. Given that the inner wall of the sealed gas cavity 103 is made of quartz, the SiO2 layer has excellent chemical compatibility and physical adhesion to the quartz substrate. This good interface matching ensures that the reflective layer 5 can be firmly and stably attached to the inner wall of the housing 1, effectively avoiding the detachment, delamination, or performance degradation of the reflective layer 5 due to material incompatibility. Because both the housing 1 and the light-transmitting partition 101 are made of quartz, and form a highly compatible interface with the first layer of SiO2 in the reflective layer 5, the entire ultraviolet pre-ionization device 200 can work collaboratively as a whole with excellent optical performance. When the xenon gas in the sealed gas cavity 103 is excited to generate 172nm ultraviolet light, this ultraviolet light can efficiently pass through the integrated quartz light-transmitting partition 101 and enter the gas flow channel 102. At the same time, the ultraviolet light that does not directly penetrate can be efficiently reflected by the stably attached and optically excellent SiO2 / Al2O3 alternating stacked reflective structure when it encounters the inner wall of the sealed gas cavity 103, and then redirected to the gas flow channel 102. This integrated and highly compatible design ensures that the 172nm ultraviolet light can be utilized to the maximum extent, thereby providing sufficient pre-ionization energy for the process gas in the gas flow channel 102, significantly improving the reliability and effect of the pre-ionization process.

[0060] Specifically, see Figure 1 The remote plasma source 100 includes a plasma cavity 6, an electromagnetic excitation mechanism 7 mounted on the plasma cavity 6, a radio frequency power supply 8, and an impedance matching network 9 connecting the radio frequency power supply 8 and the electromagnetic excitation mechanism 7. Preferably, an ionization rate monitoring device 400 may also be provided at the plasma outlet of the plasma cavity 6.

[0061] Plasma cavity 6 is a core component of the remote plasma source 100. Its main function is to provide a controlled reaction space to contain process gases and generate plasma within this space. This cavity is typically made of high-temperature and corrosion-resistant materials, such as quartz, ceramics, or special alloys, to meet the stringent requirements of the plasma environment. Its structural design can be cylindrical, spherical, toroidal, or irregularly shaped to optimize the gas flow field and plasma distribution. The size and shape of plasma cavity 6 directly affect the volume, density, and uniformity of the plasma, forming the basis for achieving stable plasma generation.

[0062] The electromagnetic excitation mechanism 7 is responsible for converting external energy into an electromagnetic field, which in turn excites the process gas within the plasma cavity 6, causing it to ionize and form plasma. This mechanism can take various forms, such as inductive coupling coils, microwave resonant cavities, or capacitive coupling electrodes. Inductive coupling coils induce gas ionization by generating an alternating magnetic field, while microwave resonant cavities utilize high-frequency microwave energy to excite the gas. The configuration and operating parameters of the electromagnetic excitation mechanism 7 directly determine the energy coupling efficiency and plasma characteristics, and are crucial for achieving efficient ignition.

[0063] The radio frequency (RF) power supply 8 is a device that provides high-frequency electrical energy to the electromagnetic excitation mechanism 7. It converts mains power into high-frequency alternating current with a specific frequency (e.g., hundreds of kHz to tens of MHz) and power. The output power, frequency stability, and power regulation capability of the RF power supply 8 are crucial for the stable generation and precise control of plasma. Its design typically includes power amplifiers, oscillators, and control circuitry to ensure the accuracy and reliability of energy output.

[0064] Impedance matching network 9 is a key component connecting the RF power supply 8 and the electromagnetic excitation mechanism 7. Its function is to adjust the output impedance of the RF power supply 8 and the input impedance of the electromagnetic excitation mechanism 7 (as a load) to match them. Through impedance matching, reflection loss of RF energy during transmission can be minimized, ensuring that most of the energy output from the RF power supply 8 can be effectively coupled into the process gas within the plasma chamber 6. Common impedance matching networks 9 include L-type, π-type, or T-type topologies, which achieve precise impedance adjustment through adjustable capacitors and inductors.

[0065] The ionization rate monitoring device 400 is used to detect the ionization state or plasma parameters at the plasma outlet in real time. This device can employ various technologies, such as an optical emission spectroscopy (OES) sensor, a Langmuir probe, or a microwave interferometer. The OES sensor identifies the types and densities of active particles by analyzing the spectrum of plasma emission; the Langmuir probe directly measures the electron density and electron temperature of the plasma. The purpose of setting up the ionization rate monitoring device 400 is to provide real-time feedback on the plasma's ignition state and operational stability, thereby enabling precise monitoring and adjustment of the process.

[0066] The remote plasma source 100 operates by having a radio frequency (RF) power supply 8 generate high-frequency electrical energy, which is then efficiently transmitted to an electromagnetic excitation mechanism 7 via an impedance matching network 9. The impedance matching network 9 adjusts the impedance to ensure that the output impedance of the RF power supply 8 matches the input impedance of the electromagnetic excitation mechanism 7, thereby minimizing energy reflection and improving energy transmission efficiency. Upon receiving the high-frequency energy, the electromagnetic excitation mechanism 7 generates an alternating electromagnetic field outside the plasma cavity 6. This electromagnetic field penetrates the wall of the plasma cavity 6 and acts on the process gas inside. Under the influence of the electromagnetic field, the process gas molecules are excited and ionized, forming plasma. The plasma cavity 6, acting as a reaction vessel, provides a stable environment for the generation and maintenance of plasma. In this way, the RF power supply 8, the impedance matching network 9, and the electromagnetic excitation mechanism 7 work together to ensure that energy can be coupled into the process gas efficiently and stably, thus solving the problems of low energy coupling efficiency and poor stability during the ignition process. Furthermore, the remote plasma source 100 of this application also works in conjunction with an ultraviolet pre-ionization device 200. Before the process gas enters the plasma chamber 6, the ultraviolet pre-ionization device 200 pre-ionizes the gas using 172nm ultraviolet light, generating initial free electrons and active particles. Upon entering the plasma chamber 6, the increased initial carrier density significantly reduces the gas's breakdown threshold and ignition energy requirement under electromagnetic excitation. Therefore, the electromagnetic excitation mechanism 7 can achieve rapid and stable plasma ignition with relatively low energy input. This combination of ultraviolet pre-ionization and electromagnetic excitation enables the remote plasma source 100 to overcome the difficulties and delays associated with traditional single electromagnetic excitation ignition when processing high-ionization-energy gases (such as nitrogen fluoride), significantly improving the success rate and stability of ignition. By installing an ionization rate monitoring device 400 at the plasma outlet of the plasma chamber 6, the ionization state of the plasma can be monitored in real time, providing data support for precise process control and further ensuring the controllability and consistency of the ignition process.

[0067] Preferably, the volume of the integral chamber formed by the plasma chamber 6 and the gas flow channel 102 is 1L-3L.

[0068] The integrated chamber, consisting of the plasma cavity 6 and the gas flow channel 102, refers to the structural integration or tight connection between the plasma cavity 6 of the remote plasma source 100 and the gas flow channel 102 of the ultraviolet pre-ionization device 200, forming a continuous internal space. The volume of the integrated chamber is 1L-3L, an optimized range designed to balance the efficiency, stability, and energy utilization of plasma ignition. This volume can be achieved by adjusting the geometric dimensions (such as length and diameter) of the plasma cavity 6 and the gas flow channel 102. For example, the plasma cavity 6 can be designed as a cylinder or ellipsoid, and the gas flow channel 102 can be designed as a pipe. By precisely controlling the dimensions of these components, the total internal volume falls within this optimized range.

[0069] This scheme achieves a tight connection between the pre-ionization region and the main excitation region by connecting the plasma cavity 6 of the remote plasma source 100 and the gas flow channel 102 of the ultraviolet pre-ionization device 200 into a single integrated chamber, limiting its volume to the range of 1L-3L. The process gas first enters the gas flow channel 102 of the ultraviolet pre-ionization device 200. Within this channel, 172nm ultraviolet light, in conjunction with the mesh electrode 4, pre-ionizes the process gas, generating initial charge carriers such as free electrons and active ions. Because the gas flow channel 102 is integrated with the plasma cavity 6, these pre-ionized active particles can rapidly enter the plasma cavity 6 with minimal loss. Inside the plasma cavity 6, the electromagnetic excitation mechanism 7, the radio frequency power supply 8, and the impedance matching network 9 connected between the radio frequency power supply 8 and the electromagnetic excitation mechanism 7, all mounted on the plasma cavity 6, provide the main excitation for the pre-ionized gas, thereby achieving stable plasma generation. Optimizing the overall chamber volume to 1L-3L effectively avoids the significant decrease in density of active particles generated during pre-ionization due to diffusion and recombination before reaching the main excitation region when the volume is too large, leading to decreased ignition efficiency and increased energy loss. Simultaneously, it avoids the problems that excessively small volumes may result in excessively high gas flow rates, insufficient residence time for adequate pre-ionization, or limitations on plasma formation in the main excitation region, thereby increasing the ignition threshold. This optimized volume design ensures efficient synergy between photoinduced carrier injection and electromagnetic energy coupling, maximizing the synergistic effect of pre-ionization and main excitation, thus solving the problems of difficult ignition and poor stability in traditional schemes.

[0070] Specifically, the process gas can be pure nitrogen fluoride or a mixture of nitrogen fluoride and argon.

[0071] Process gases are the core mediums that need to be ionized to form plasma in semiconductor manufacturing. Their selection directly affects the plasma's characteristics, reaction efficiency, and the etching or cleaning effect on the wafer. Pure nitrogen fluoride (NF3) is a fluorine-containing gas widely used in semiconductor manufacturing, especially as a fluorine source in cleaning and etching processes. It is characterized by high chemical bond energies, making it difficult to effectively ionize using traditional methods, which can easily lead to ignition difficulties and poor process stability. A mixture of nitrogen fluoride and argon is a process gas prepared by mixing nitrogen fluoride with the inert gas argon (Ar) in a certain proportion. Argon, as a low-ionization-energy auxiliary gas, can lower the overall ionization threshold of the mixture, helping to promote the ionization of nitrogen fluoride, thereby improving the plasma's ignition performance and stability.

[0072] When the process gas is pure nitrogen fluoride, the system utilizes the high photon energy of 172nm ultraviolet light to directly and efficiently break the strong chemical bonds of nitrogen fluoride molecules, generating a variety of highly reactive particles such as fluorine atoms, fluorine radicals, fluoride ions, and free electrons. This pre-ionization process injects sufficient initial charge carriers into the gas before it enters the remote plasma source 100, significantly reducing the breakdown impedance and ignition energy threshold of pure nitrogen fluoride. Since no auxiliary gas is introduced, this scheme fundamentally avoids problems such as gas purity degradation, wafer contamination, or film deterioration, ensuring the cleanliness of the plasma process. When the process gas is a mixture of nitrogen fluoride and argon, argon, as a low-ionization-energy auxiliary component, is more easily ionized under 172nm ultraviolet light, generating a large number of initial electrons and ions. These pre-ionized argon particles then transfer energy to nitrogen fluoride molecules through collisions, effectively promoting the ionization of nitrogen fluoride, thereby reducing the overall ionization threshold of the mixed gas and significantly improving the success rate and stability of ignition. Both of the aforementioned process gas selection schemes are closely integrated with the overall design of the ultraviolet pre-ionization device 200 and the remote plasma source 100. The reflective layer 5 in the ultraviolet pre-ionization device 200 (e.g., an alternating stacked reflective structure composed of multiple SiO2 layers and multiple Al2O3 layers) ensures efficient utilization of 172nm ultraviolet light, maximizing the pre-ionization effect. Simultaneously, the short axial distance (no more than 50mm) between the outlet of the gas channel 102 and the gas inlet of the remote plasma source 100, and the design of the connecting component 300 (e.g., with a Venturi channel), ensure that the highly reactive particles generated by pre-ionization can quickly and efficiently enter the main excitation region of the remote plasma source 100, minimizing recombination losses of reactive particles during transport. This synergistic effect enables stable and efficient plasma ignition for both pure nitrogen fluoride and a mixture of nitrogen fluoride and argon, overcoming the difficulties of high-bond-energy gas ignition and the introduction of contamination by auxiliary gases in traditional technologies.

[0073] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A remote plasma source system based on 172nm ultraviolet light-assisted ignition, characterized in that, It includes a remote plasma source (100) and an ultraviolet pre-ionization device (200) disposed at the gas inlet of the remote plasma source (100). The ultraviolet pre-ionization device (200) includes: The housing (1) has a gas flow channel (102) and a sealed gas chamber (103) separated by a light-transmitting partition (101), the sealed gas chamber (103) being filled with xenon gas, and the gas flow channel (102) being connected to the gas inlet of the remote plasma source (100) and used for the flow of process gas; Positive electrode plate (2) and negative electrode plate (3) are disposed on opposite sides of the housing (1), and the sealed gas cavity (103) is located between the positive electrode plate (2) and the negative electrode plate (3); the positive electrode plate (2) and the negative electrode plate (3) are used to excite the xenon gas to generate 172nm ultraviolet light when an AC voltage is applied; the 172nm ultraviolet light can pass through the light-transmitting partition (101) and enter the gas flow channel (102). A mesh electrode (4) is disposed inside the gas flow channel (102) and is used to pre-ionize the process gas in conjunction with the 172nm ultraviolet light when energized. The inner wall of the sealed gas cavity (103), except for the light-transmitting partition (101), is provided with a reflective layer (5), which is used to reflect the 172nm ultraviolet light to the gas flow channel (102). The reflective layer (5) is an alternating stacked reflective structure composed of multiple SiO2 layers and multiple Al2O3 layers. The thickness of each SiO2 layer is 10nm-50nm, the thickness of each Al2O3 layer is 20nm-100nm, and the sum of the number of SiO2 layers and Al2O3 layers is 4-10 layers. The housing (1) is made of quartz, the light-transmitting partition (101) is a quartz partition integrally formed with the housing (1), and the layer in the reflective layer (5) connected to the inner wall of the sealed air cavity (103) is a SiO2 layer.

2. The remote plasma source system based on 172nm ultraviolet light-assisted ignition as described in claim 1, characterized in that, The axial distance between the outlet of the gas channel (102) and the gas inlet of the remote plasma source (100) is no greater than 50 mm.

3. The remote plasma source system based on 172nm ultraviolet light-assisted ignition as described in claim 1, characterized in that, A connecting member (300) is provided between the outlet of the gas flow channel (102) and the gas inlet of the remote plasma source (100). The connecting member (300) has a Venturi channel that connects the outlet of the gas flow channel (102) and the gas inlet of the remote plasma source (100).

4. The remote plasma source system based on 172nm ultraviolet light-assisted ignition as described in claim 3, characterized in that, The ratio of the lateral dimension of the throat of the Venturi channel to the lateral dimension of the gas inlet of the remote plasma source (100) is 1:3 to 1:

5.

5. The remote plasma source system based on 172nm ultraviolet light-assisted ignition as described in claim 1, characterized in that, The remote plasma source (100) includes a plasma cavity (6), an electromagnetic excitation mechanism (7) sleeved on the plasma cavity (6), a radio frequency power supply (8), and an impedance matching network (9) connected between the radio frequency power supply (8) and the electromagnetic excitation mechanism (7).

6. The remote plasma source system based on 172nm ultraviolet light-assisted ignition as described in claim 5, characterized in that, The volume of the integral chamber formed by the plasma chamber (6) and the gas flow channel (102) is 1L-3L.

7. The remote plasma source system based on 172nm ultraviolet light-assisted ignition as described in claim 1, characterized in that, The process gas is pure nitrogen fluoride or a mixture of nitrogen fluoride and argon.

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