Plasma etching apparatus and viewing window protection system

Abstract

The application discloses a kind of plasma etching equipment and observation window protection system, belong to semiconductor manufacturing equipment technical field.The system includes reaction cavity, gas inlet pipeline, optical observation window and uniform gas structure, by innovatively using uniform gas structure, with uniform flow and radio frequency suppression function, under the guarantee gas flow function, effectively block plasma into pipeline, and by optical observation window is set at the end of gas inlet pipeline, realize light gas same road, to directly utilize process gas and pass through the inner surface of window to form protection gas curtain, effectively prevent deposit to adhere to the inner surface of window.The application fundamentally protects observation window and upstream optical path component, completely solves the end point detection distortion problem caused by window pollution in traditional scheme, and in preventing process byproduct deposition on optical observation window, without introducing extraneous purge gas, avoids process formulation disturbance, significantly improves end point detection accuracy and equipment utilization.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor manufacturing equipment, in particular to a kind of observation window protection system for plasma process equipment (such as etching, CVD) and the equipment comprising the system. More specifically, it relates to an innovative scheme for realizing long-term anti-pollution of optical observation window and ensuring the accuracy of process endpoint detection by integrating "light gas same path" structure, module with gas distribution and radio frequency limiting function and airflow-driven self-cleaning mechanism. BACKGROUND

[0002] In the manufacturing process of semiconductor devices, plasma etching is a crucial process. In order to achieve precise process control, optical emission spectroscopy (OES) technology is usually used for in-situ, real-time endpoint detection. The OES system collects plasma emission signals through the observation window (usually sapphire or quartz window) installed on the wall of the reaction chamber, and determines whether the etching process is complete by analyzing the changes in the intensity of specific spectral lines.

[0003] In the prior art, the commonly used method is to open an observation port on the side wall of the chamber, and press the sapphire sheet as the window (see Figure 1 schematic). However, this structure has inherent drawbacks: the inner wall of the window is directly exposed to the plasma environment and active reaction by-products. During the process, these by-products (including incompletely reacted precursors and generated polymers) will gradually deposit on the inner surface of the window, forming a thin film (see Figure 2 schematic), which will severely attenuate the transmitted light signal intensity, causing the signal received by the OES system to be distorted, affecting the accurate judgment of the process endpoint, and even leading to misjudgment, resulting in product scrap.

[0004] To solve this problem, the industry has tried various solutions. One is to stop regularly, open the chamber and manually replace or clean the observation window. This method is time-consuming and labor-intensive, severely reducing equipment utilization, and when dealing with toxic process gases, long-term nitrogen purging is required, which poses safety risks and increases costs. The second is to introduce inert purge gas (such as argon), which is blown from the side or above the window to form a gas curtain to block deposition, but the inert gas blown in will dilute the process gas in the chamber, changing its chemical composition and concentration, interfering with the normal process reaction and affecting the consistency of the process result. The third is to abandon inert gas and directly use process gas itself for purging, referring to the prior art (publication number TW466546B), which introduces process gas from a gas inlet located beside the window, making the gas flow parallel to the window surface to blow away the deposits.

[0005] However, the above-mentioned prior art has its own inherent limitations and cannot effectively prevent the pollution of the observation window.

[0006] Therefore, there is an urgent need in this field for an innovative solution that can effectively prevent contamination of the observation window without interfering with the normal process atmosphere or introducing additional complexity, and ensure that OES endpoint detection can be performed in a long-term, stable and reliable manner. Summary of the Invention

[0007] The primary objective of this invention is to overcome the aforementioned deficiencies of the prior art and provide a plasma etching apparatus and observation window protection system that not only prevents deposition but also suppresses the uplink of radio frequency energy and prevents plasma from being excited in the inlet channel, thereby fundamentally protecting the observation window and upstream optical path components. Furthermore, in preventing the deposition of process byproducts on the optical observation window, there is no need to introduce external purge gas, thus avoiding interference with the process.

[0008] This invention provides a protection system for the observation window of a plasma etching apparatus. Its core concept lies in "phosphor-gas co-path, radio frequency suppression, and airflow self-cleaning." The system mainly includes:

[0009] Reaction chamber: A container used for plasma processing;

[0010] Inlet piping: Used to deliver the reaction gases required for the process to the reaction chamber;

[0011] Optical observation window: Located at the end of the inlet pipe, used to receive plasma emission signals; a section of the inlet pipe connected to the reaction chamber is cleverly used as a phosgene-gas co-path channel, through which reactant gas and light signals are transmitted simultaneously, and the gas can flow in a directional manner to continuously purge the window surface, blocking particulate matter and polymer precursors from migrating to the window. The optical observation window is used by the endpoint detection system to analyze the light signal with a spectrometer to determine the endpoint.

[0012] Gas equalization structure: Located at the connection between the air inlet pipe and the reaction chamber, this structure is one of the key innovations of this invention. It is designed to have dual functions: (a) gas equalization function: to ensure uniform distribution of gas entering from the air inlet pipe and ensure process uniformity; (b) radio frequency limiting function: its structure (such as aperture, depth, and arrangement) is designed to form a barrier with high airflow impedance and high radio frequency impedance, effectively suppressing the conduction of radio frequency energy in the reaction chamber to the upstream air inlet pipe, thereby preventing plasma from forming in the pipe and protecting the observation window from plasma bombardment and deposition.

[0013] Preferably, the gas distribution structure is a porous plate or gas distribution groove, the aperture, number of holes, hole spacing and depth of which are designed based on the plasma impedance characteristics in the reaction chamber and the frequency of the radio frequency power source, so as to form the radio frequency limiting barrier to suppress the conduction of radio frequency energy in the reaction chamber to the air inlet pipe through the gas distribution structure.

[0014] Preferably, the perforation structure of the gas distribution structure is one or more combinations of conical holes, stepped holes, or blind holes, used to adjust airflow resistance and optimize radio frequency isolation performance.

[0015] Preferably, the observation window protection system further includes a cleaning mechanism disposed on the side of the optical observation window facing the air intake duct; the cleaning mechanism is configured to be driven by airflow flowing through the air intake duct to clean the surface of the optical observation window. In implementation, the cleaning mechanism is disposed inside the observation window and consists of a rotatable cleaning element (such as a brush or scraper). Its unique feature is that it is driven to rotate by airflow flowing through the air intake duct, achieving automatic cleaning without external power.

[0016] And / or, the observation window protection system further includes an airflow guiding device, disposed within the air intake duct or at one end of the air intake duct near the uniform air distribution structure; the airflow guiding device is configured to adjustably change the direction and / or velocity of part or all of the airflow to prevent it from directly impacting the central area of ​​the optical observation window. In implementation, the airflow guiding device is disposed within the air intake duct or near the uniform air distribution structure, such as an adjustable-angle guide vane. Its function is to optimize the airflow field, prevent the airflow from directly impacting the center of the window and causing turbulence, and selectively guide more airflow to the cleaning mechanism to enhance its driving force. In addition, the airflow guiding device can also be linked with the cleaning mechanism through a mechanical mechanism (such as gears, linkages). The airflow guiding device (such as an adjustable guide vane) enables intelligent airflow distribution, which can optimize the default flow field, avoid vibration, and enhance the airflow driving the cleaning mechanism when needed (such as periodically or according to signal attenuation), achieving on-demand enhanced cleaning and giving the system intelligent and adaptive capabilities.

[0017] Preferably, the cleaning mechanism includes a rotatable cleaning element, the rotation axis of which forms an angle with the airflow direction; and / or, the contact force between the cleaning mechanism and the optical observation window can be adjusted by a preload spring or a magnetic assembly.

[0018] And / or, the airflow guiding device includes one or more adjustable-angle guide vanes, the angle of which can be adjusted by a manual knob or motor driver outside the cavity;

[0019] And / or, the airflow guiding device is further configured to direct a portion of the airflow to a cleaning mechanism to drive its operation.

[0020] Preferably, the cleaning element is a brush bristles, a scraper, or an airflow turbine;

[0021] Preferably, the airflow guiding device is linked to the cleaning mechanism through a gear set or linkage mechanism to convert the kinetic energy of the airflow into the mechanical energy of the cleaning mechanism.

[0022] Preferably, the gas distribution structure is integrated with the upper electrode or cavity wall of the reaction chamber, or it is installed and connected to the reaction chamber as an independent, detachable module.

[0023] Preferably, the optical observation window is made of sapphire or quartz;

[0024] And / or, the inner wall of the air intake pipe is polished or coated with a high-reflectivity film to enhance the transmission efficiency of optical signals.

[0025] The present invention also provides a plasma etching apparatus, including a reaction chamber, a radio frequency power supply, a gas supply system and an endpoint detection system, wherein the endpoint detection system integrates an observation window protection system as described in any one of the present invention.

[0026] Compared with the prior art, the present invention has the following one or more significant beneficial effects:

[0027] Extremely high window cleanliness and long-lasting performance: Through the dual mechanisms of "gas-directed flow barrier" and "airflow-driven active cleaning", the formation of window deposits is almost completely avoided, extending the window life by several times or even dozens of times.

[0028] Significantly improved accuracy of endpoint detection: Due to the absence of optical signal attenuation, the signals collected by the OES system are real and stable, greatly improving the accuracy and reliability of endpoint judgment and reducing product scrap rate;

[0029] Zero process interference: The process gas itself is used for protection and cleaning, without the need to introduce any external purging gas, thus perfectly maintaining the purity and stability of the reaction atmosphere in the process chamber.

[0030] Radio frequency suppression protection: The uniform gas structure effectively prevents plasma excitation in the pipe, protecting not only the window but also upstream components such as optical fibers, thus improving the overall reliability of the system.

[0031] Maintenance costs and downtime are significantly reduced: There is no longer a need for frequent downtime due to window replacement or cleaning, the overall equipment efficiency (OEE) is significantly improved, and maintenance and consumable costs are significantly reduced;

[0032] Intelligent and adaptive: By linking with process formulation or light transmittance monitoring, it can intelligently trigger or adjust the cleaning intensity to achieve adaptive maintenance. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of a structure in the prior art where the observation window is located on the side wall;

[0034] Figure 2 This is a schematic diagram of contamination encountered when the observation window is located behind the side wall in existing technology;

[0035] Figure 3 This is a schematic diagram of the observation window protection system provided in an embodiment of the present invention;

[0036] Figure 4 This is a schematic diagram of various hole types in the gas uniform structure of one embodiment of the present invention ((a) cylindrical hole, (b) conical hole, (c) stepped hole, (d) blind hole).

[0037] Figure 5 This is a schematic diagram of a gas-uniform structure in one embodiment of the present invention, which simultaneously provides multiple hole types ((a) cylindrical hole, (b) conical hole, (c) stepped hole, (d) blind hole).

[0038] Figure 6 This is a schematic diagram of the cleaning mechanism (turbine-driven) in one embodiment of the present invention.

[0039] Figure 7 This is a schematic diagram of the cleaning mechanism (scraper type and contact force adjustment mechanism) in another embodiment of the present invention.

[0040] Figure 8 This is a cross-sectional structural diagram of an airflow guiding device installed on an intake pipe in one embodiment of the present invention;

[0041] Figure 9 This is a schematic diagram of the linkage between the airflow guiding device and the cleaning mechanism in one embodiment of the present invention;

[0042] Figure 10 This is a structural block diagram of the plasma etching apparatus using the present invention. Detailed Implementation

[0043] The implementation of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0044] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0045] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0046] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this invention, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number and aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0047] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. The drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0048] Additionally, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that practice can be carried out without these specific details.

[0049] As analyzed above, the observation window in the prior art is located either on the side wall (most solutions use the side wall setting method) or on the intake pipe (such as the prior art TW466546B).

[0050] Through in-depth analysis and practice, this invention has discovered that even existing technical solutions with observation windows installed in the intake manifold (i.e., prior art TW466546B) still have inherent and undisclosed limitations:

[0051] Defect 1: "Midway Interception" and Formulation Perturbation Risk: Before entering the main reaction chamber, the process gas is diverted for cleaning the window. This gas may undergo pre-reaction (e.g., reacting with deposits on the window surface) or dissipate energy near the window. When it finally merges with the gas entering from the main inlet, its chemical activity and state may differ slightly but critically. For advanced nanoscale processes, this inconsistency in the path and state of entry into the reaction zone is a potential source of deterioration in within-wafer uniformity.

[0052] Defect 2: Lack of radio frequency suppression mechanism, posing a safety hazard: Because the air inlet directly connects to the reaction chamber, a path for reverse conduction of radio frequency energy is formed. In a high-power radio frequency environment, energy may couple into the upstream gas pipeline through this path, exciting the generation of unnecessary "pipeline plasma." This will not only severely corrode and contaminate the air inlet pipeline and observation window, contrary to the design purpose, but may also change the load impedance of the main reaction chamber, interfering with process stability.

[0053] Defect 3: Passive cleaning with low efficiency: Its cleaning mechanism relies entirely on the physical purging force of the airflow, making it a passive protection method. For polymers with strong adhesion or processes with high deposition rates, its cleaning effect is clearly limited: since the airflow is mainly used to prevent new deposition, its ability to remove existing minor deposits is limited.

[0054] Based on this, the purpose of this invention is no longer to solve the problem of "what kind of gas to use" as in traditional solutions, but to better protect the observation window from contamination (including contamination by deposits, radio frequency plasma, etc.) from the source. In other words, even if there may be a small amount of deposit contamination before operation, the observation window can be cleaned automatically and promptly after operation starts without being contaminated by deposits, radio frequency plasma, etc.

[0055] To achieve the above objectives, this invention has made system-level architectural innovations. Its core concept is to construct an integrated functional channel that integrates "phosphor and gas", and to integrate the two core functions of "radio frequency suppression" and "energy capture-self-cleaning" in this channel.

[0056] On the one hand, there is the architectural concept of moving from "bypass purging" to "mainstream integration". To eliminate the "halfway interception" effect, it is necessary to ensure that the paths and states of all process gases are 100% consistent before entering the reaction chamber. Therefore, the observation window is moved from the side wall of the reaction chamber to the end of the pipeline that delivers the process gases to the reaction chamber, so that the "pipeline" that delivers the gases becomes the "channel" of light, and all gases must flow through the inner surface of the window.

[0057] refer to Figure 3 As illustrated, the inner cavity of the intake pipe 2 is designed to simultaneously transmit reactive gases and optical signals, and the optical observation window 3 is installed at the end of the pipe, achieving a revolutionary layout design. The technical objectives achieved are as follows:

[0058] First, the gas utilization efficiency is almost 100%: all gases participate in forming a protective gas curtain without any diversion.

[0059] Second, the process state is basically zero disturbance: after passing through the protective window, the gas directly and without damage enters the reaction chamber 1, and its state is not changed by any pre-reaction.

[0060] Third, it protects efficiency: the gas flow path naturally and maximizes the coverage of the entire window surface.

[0061] Secondly, this invention provides a fundamental concept for integrated "gas equalization-radio frequency limitation" to achieve protection from the root cause. As analyzed above, simple pipe connections can introduce new risks of radio frequency reverse coupling. Therefore, this invention sets a gas equalization structure 4 (i.e., a "barrier") at the gas inlet, which can both ensure smooth gas flow and effectively block radio frequency energy. In practice, this invention innovatively adds a gas equalization structure 4 at the interface between the gas inlet pipe 2 and the reaction chamber 1. The core function of this gas equalization structure 4 is to optimize the airflow of the reaction gas from the gas inlet pipe 2 into the reaction chamber 1 using its porous structure, so that the airflow can enter the reaction chamber evenly and smoothly, and to effectively suppress radio frequency using its porous structure, that is, to prevent radio frequency plasma in the reaction chamber 1 from entering the gas inlet pipe 2.

[0062] In practice, the working principle of the uniform gas structure 4-pair RF suppression is based on the waveguide cutoff frequency principle. When the wavelength of the RF wave is much larger than the lateral dimension of the waveguide (here referring to the holes in the uniform gas structure), its propagation will experience significant attenuation. Therefore, by precisely designing the aperture (D), aperture depth (L), and aspect ratio (L / D), the structure can exhibit extremely high impedance to RF waves at RF operating frequencies (such as 13.56MHz), forming a highly efficient RF filter.

[0063] Therefore, by adding the gas equalization structure 4, the problems of airflow and radio frequency suppression can be solved in one fell swoop, providing a key guarantee for process stability.

[0064] In three aspects, this invention represents a functional leap from "passive air blowing" to "active mechanical cleaning," achieving a comprehensive breakthrough in cleaning efficiency. To overcome the bottleneck of cleaning efficiency in passive air blowing, this invention actively introduces an automatic cleaning structure, the power source of which comes from the kinetic energy of the only available flowing gas within the system. In implementation, a cleaning mechanism 5 is installed at the bottom of the sapphire sheet. This cleaning mechanism 5 is designed to be driven during gas entry, thereby automatically cleaning the bottom of the sapphire sheet without requiring an additional power source and preventing obstruction of the upward contact of the reactive gas within the cavity with the observation window.

[0065] The present invention integrates a cleaning mechanism 5, the core of which is automatic energy capture and conversion: a cleaning element (such as a turbine or windmill) driven by airflow is set in the airflow channel. The flowing gas drives the element to rotate, directly converting the kinetic energy of the fluid into mechanical energy. This mechanical energy is then used to drive the bristles or scraper to mechanically clean the window.

[0066] The Cleaning System 5 solution requires no external power, achieving "zero-cost" active self-cleaning. Its cleaning efficiency is far superior to simple air blowing, especially in removing existing deposits, thus preventing deposits from adhering to the observation window at the source.

[0067] In summary, through the above-described technical concept, this invention achieves one or more of the following highly beneficial effects based on synergy:

[0068] First, the purity and stability of the process are maximized: the "interception halfway" effect is completely eliminated, ensuring process repeatability;

[0069] Secondly, the system reliability is significantly enhanced: the built-in radio frequency suppression mechanism eliminates the hidden dangers of pipeline plasma, which is a technological advantage that is not seen and completely absent in existing technologies.

[0070] Third, the window cleaning efficiency is fundamentally improved: the dual mechanism of "air curtain barrier" + "active mechanical cleaning" provides a cleaning capability far exceeding that of simple air blowing.

[0071] Fourth, intelligence and long-term effectiveness: The system has self-sensing, self-optimization and self-cleaning capabilities, which greatly reduces maintenance cycle and cost.

[0072] Example 1: Observation window protection system with dual functions of phosgene co-pathing and radio frequency suppression

[0073] like Figure 3 As shown, this embodiment provides a basic implementation example of an observation window protection system. The system includes a reaction chamber 1, an air inlet pipe 2, an optical observation window 3, and a gas distribution structure 4.

[0074] In practice, the reaction chamber 1 is typically made of aluminum alloy or stainless steel, with internal anodizing or ceramic coating for corrosion resistance. The inlet pipe 2 is preferably made of stainless steel with a very smooth inner wall; its inner diameter can be designed according to the process gas flow rate and optical path requirements, typically between 10mm and 50mm. The optical observation window 3 uses a high-purity, plasma-resistant sapphire sheet, which is press-fitted to the end flange of the connection between the inlet pipe 2 and the reaction chamber 1 using a metal sealing ring (such as a Cu gasket) to ensure vacuum sealing.

[0075] The lens serving as the observation window 3 can be fixed using a clamping plate 31. The clamping plate 31 can be of various shapes and materials, such as a ring-shaped or semi-circular metal sheet, or a snap-fit ​​structure made of plastic. The inner diameter of the clamping plate 31 is slightly smaller than the outer diameter of the lens to ensure effective positioning of the lens.

[0076] In some examples, fasteners 32 can be used to secure the pressure plate 31. The fasteners 32 can be corrosion-resistant bolts, clips, or other suitable fastening devices, and their number and distribution can be designed according to actual needs. For example, 3-6 fasteners 32 can be evenly distributed around the pressure plate 31 to ensure uniform pressure distribution.

[0077] In some embodiments, the interface for installing the observation window 3 can be a flange interface, and the pressure plate 31 can have four evenly distributed bolt holes for installing fixing bolts to connect to the flange interface. Additionally, an O-ring seal, made of fluororubber, can be added between the pressure plate 31 and the flange interface to further enhance the sealing effect.

[0078] The core of this embodiment lies in the gas-uniform structure 4: this structure is a detachable module, precisely machined from high-temperature resistant and insulating materials such as silicon, quartz, or alumina ceramics. Essentially a perforated plate, its design far surpasses that of ordinary screens.

[0079] Specifically, the design of the uniform gas structure 4 is based on the plasma load impedance (Z_plasma) within the reaction chamber 1 and the frequency (f) of the radio frequency power source (RF Source). Its design goal is to present the highest possible impedance to radio frequency energy at a specific radio frequency (e.g., 13.56MHz) while ensuring sufficient airflow.

[0080] Therefore, the four key design parameters for the uniform gas structure include:

[0081] Aperture (D): A smaller aperture helps increase RF impedance but reduces airflow. A balance needs to be struck between the two, typically between 0.5 mm and 3 mm.

[0082] Hole depth (L): The ratio of hole depth to hole diameter (L / D) is a key factor affecting RF impedance. The larger the L / D, the higher the RF impedance. Hole depth is typically between 3mm and 15mm.

[0083] Hole spacing (P): Affects airflow uniformity and mechanical strength.

[0084] Open area ratio: The ratio of the total cross-sectional area of ​​all holes to the area of ​​the uniform air structure, which directly affects the airflow velocity and stability.

[0085] refer to Figure 4 The schematic cross-sectional structure shows that the perforation shape of the uniform air structure 4 can be a simple straight cylindrical perforation (see...). Figure 4 (a) in the figure illustrates that the aperture D is set to the preset value L, i.e., D=L), or it can be other types of aperture.

[0086] For example: tapered hole (see...) Figure 4(b) illustrates this: the inlet aperture D1 is set to be larger, and the outlet aperture D2 is set to be smaller, i.e., D1 > D2. This reduces the pressure drop at the airflow inlet while maintaining a smaller effective aperture at the outlet to preserve high RF impedance. It should be noted that the tapered aperture here can generally be understood as an aperture shaped like a frustum of a cone.

[0087] For example: stepped hole (see...) Figure 4 (c) in the diagram): Different depth segments have different apertures. For example, the aperture of the first step segment is set to D1 and the aperture of the second step segment is set to D2. By setting D1≠D2, the stepped segments are formed to create stepped apertures, which can be used to adjust the flow resistance and RF impedance of different regions.

[0088] For example: blind hole (see...) Figure 4 (d) in the diagram: The hole is not drilled through; the bottom has a thin, closed wall, while the side walls have openings for gas flow. Blind via design can provide extremely high RF impedance because RF fields have difficulty passing through the capacitance at the bottom of the metal blind via.

[0089] It should be noted that one or more pore types can be provided in the gas uniform structure 4, such as Figure 5 The schematic cross-sectional structure shows that straight cylindrical holes are provided on the gas distribution structure 4 (see...). Figure 5 (a) schematic diagram), conical hole (see diagram) Figure 5 As shown in (b) in the diagram, there are also tapered holes that can be set as tapered holes with one end larger than the other, and stepped holes (see...). Figure 5 (c) illustration), blind hole (see Figure 5 (d) in the diagram) etc., which makes it convenient to use different aperture types to form different gas flow rates in different areas, so that the spatial distribution of plasma 100 above the wafer in the reaction chamber 1 is more in line with the actual use needs.

[0090] like Figure 3 As shown, the process gas required for system operation flows in from the inlet pipe 2, and after being homogenized and depressurized by the gas equalization structure 4, it smoothly enters the reaction chamber 1 to participate in the reaction. At the same time, the light signal emitted by the plasma 100 passes in the opposite direction through the holes of the gas equalization structure 4 and enters the inner cavity of the inlet pipe 2—the photogas co-path channel—and is finally detected by the endpoint detection device (such as the spectrometer 300 connected by the optical fiber 200) behind the optical observation window 3.

[0091] In this example, the radio frequency (RF) confinement function of the gas distribution structure 4 ensures that the RF energy is confined within the reaction chamber 1 and cannot be effectively coupled into the inlet pipe 2, thereby preventing the generation of pipe plasma and protecting the observation window 3. Simultaneously, because the observation window 3 is located at the end of a section of the inlet pipe 2 connecting to the reaction chamber 1, the observation window 3 and the upper inner wall of the inlet pipe 2 are at the same horizontal plane. This allows the continuously flowing process gas in the inlet pipe 2 to form a dynamic gas film on the surface of the observation window 3, effectively preventing contaminants in the chamber from migrating to the window.

[0092] Example 2: Integrated airflow-driven self-cleaning mechanism

[0093] Based on the above embodiments, this embodiment further integrates a self-cleaning function, wherein the cleaning mechanism is located inside the observation window.

[0094] In one example, such as Figure 6 As shown, the cleaning mechanism 5 includes a cleaning element 51 and a power coupling mechanism 52. Figure 6 This paper demonstrates a cleaning structure design based on a turbine-driven system and a cleaning brush. The cleaning element 51 is a soft-bristled disc with a power coupling mechanism 52 (such as a micro-turbine) mounted on its shaft. The turbine blades are aerodynamically designed so that their frontal surface is at an optimal angle (e.g., 30°-60°) to the airflow direction. When process gas flows through it, the airflow impacts the turbine blades, causing the entire cleaning element 51 to rotate at high speed, thereby continuously brushing the inner surface of the observation window 3. The working principle is illustrated as follows: airflow drives the turbine to rotate → driving the cleaning brush to clean the window surface.

[0095] Figure 7 Another example of a scraper-type cleaning structure design is shown. The cleaning element 51 is preferably a flexible scraper 53, whose axis of rotation is connected to a simple windmill-like drive wheel 54 via a set of gears or linkages. Airflow drives the windmill-like drive wheel 54 to rotate, and the gear set converts the rotational speed into torque more suitable for scraping, driving the scraper 53 to scrape the surface of the viewing window 3, which is particularly suitable for removing more stubborn deposits that have formed.

[0096] To further optimize the cleaning effect, this embodiment may also include a contact force adjustment module. For example... Figure 7 As shown, this module can be a preloaded spring 55. By adjusting the preload of the spring 55, the contact pressure between the bristles or scraper and the window surface can be controlled, thus adapting to different levels of contamination. For example, a smaller pressure can be used in the early stages of contamination to prevent excessive wear, while the pressure can be increased to ensure cleaning effectiveness when the contamination is severe. In other examples, a magnetic component can also be used, allowing for stepless adjustment of the contact force by changing the magnitude of the magnetic force.

[0097] To further optimize the cleaning effect, this embodiment may also include an adjusting screw assembly 56, which is set on the air intake pipe 2. The air flow rate can be adjusted by adjusting the adjusting screw assembly 56, thereby controlling the scraping effect.

[0098] Example 3: Intelligent Airflow Guidance and Linkage Control

[0099] This embodiment, based on the above embodiments, introduces an airflow guiding device, which realizes precise control of airflow and functional reuse.

[0100] In some examples, the airflow guide device 6 (i.e., the airflow guide section, such as...) Figure 8 (Illustrative) The air inlet pipe 2 located upstream of the uniform air structure 4 is set in the shape of a funnel, and the airflow is better guided by the airflow guide device 6 through the funnel.

[0101] In some examples, the airflow guide device 6 (i.e., the airflow guide section, such as...) Figure 9 (Illustrative) The air intake pipe 2 located upstream of the uniform air structure 4 is composed of one or more adjustable angle guide vanes 61. The rotation shaft of the guide vane 61 extends to the outside of the cavity through a mechanical linkage mechanism. It can be coarsely adjusted by a manual knob or precisely controlled by a micro stepper motor 62.

[0102] This device has multiple operating modes:

[0103] Protection mode (default): The guide vane 61 is adjusted to angle α so that the mainstream airflow flows parallel to the pipe wall, forming a "wall jet" effect. This avoids the airflow directly impacting the center of the window, causing vibration or interference with the optical path, while effectively covering the entire window surface for air curtain protection.

[0104] Cleaning Mode: When the system determines that cleaning is needed based on a preset process cycle (e.g., every 5 wafers) or real-time feedback from a transmittance sensor (not shown in the figure), the control unit issues a command, and the stepper motor 62 drives the guide vane 61 to rotate to angle β. This angle directs a portion of the mainstream airflow to the drive turbine (or windmill) of the cleaning mechanism 5, significantly increasing its speed and torque, thereby initiating or enhancing the cleaning operation.

[0105] Linkage Mode: Reference Figure 9 The rotating mechanism of the guide vane 61 can also be linked to the lifting or biasing mechanism of the cleaning mechanism 5 via a linkage or cam mechanism. For example, when the guide vane 61 rotates to the cleaning angle β, the spring lever of the cleaning mechanism is pressed down synchronously through the linkage, increasing the contact force between the cleaning element and the window. Through mechanical linkage, the efficient and direct conversion of airflow energy into cleaning power is achieved, and the synchronous switching of cleaning modes can be realized without electronic control.

[0106] Example 4: Plasma Etching Equipment

[0107] refer to Figure 10 This embodiment illustrates a high-performance plasma etching apparatus. The apparatus includes components such as a reaction chamber module, an RF power supply module, a gas supply module, a vacuum system module, a main controller, a mass flow controller (MFC), and an endpoint detection system module. A key improvement of this invention is that the endpoint detection system module integrates the observation window protection system described in any of the above embodiments.

[0108] The process flow of this equipment includes: delivering precisely metered reaction gas to the inlet pipe 2 through the gas supply module; generating plasma in the reaction chamber 1 using the radio frequency power module to etch the wafer; simultaneously, the observation window protection system operates automatically: gas flow forms a protective gas curtain, the gas uniform structure 4 suppresses radio frequency uplink, and the cleaning mechanism 5 is activated as needed; the endpoint detection system collects stable light signals in real time through the photogas co-path channel, analyzes and processes them, accurately determines the etching endpoint, and stops the process.

[0109] The observation window protection system and method provided by this invention have an ingenious structural design and high reliability. They do not require changes to the existing main process route and can be directly integrated into various capacitively coupled plasma (CCP), inductively coupled plasma (ICP) etching equipment, plasma-enhanced chemical vapor deposition (PECVD) equipment, and other plasma process equipment that requires optical monitoring. They have extremely high industrial applicability and promotional value.

[0110] In this specification, the same or similar parts between the various embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the descriptions of the embodiments described later are relatively simple, and relevant parts can be referred to the descriptions of the foregoing embodiments.

[0111] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A protection system for the observation window of a plasma etching apparatus, characterized in that, include: The reaction chamber (1) is used for plasma etching processes; The L-shaped air inlet pipe (2) is connected to the reaction chamber (1) and is used to supply reaction gas to the reaction chamber (1); An optical observation window (3) is set at the end of the corner of the L-shaped air intake pipe (2) to receive the light signal from the reaction chamber (1), so that a section of the inner cavity connecting the air intake pipe (2) and the reaction chamber (1) can be used as a light-gas co-path channel to simultaneously transmit the reaction gas and the light signal from the reaction chamber (1). A gas equalization structure (4) is provided at the connection between the air inlet pipe (2) and the reaction chamber (1); the gas equalization structure (4) is configured to: make the reaction gas entering from the air inlet pipe (2) evenly distributed, and form a radio frequency limiting barrier to suppress the radio frequency energy in the reaction chamber (1) from being conducted to the air inlet pipe (2) via the gas equalization structure (4) to prevent plasma from entering the air inlet pipe (2).

2. The observation window protection system as described in claim 1, characterized in that, The gas equalization structure (4) is a porous plate or gas equalization groove. Its aperture, number of holes, hole spacing and depth are based on the plasma impedance characteristics in the reaction chamber (1) and the frequency design of the radio frequency power source, so as to form the radio frequency limiting barrier to suppress the conduction of radio frequency energy in the reaction chamber (1) to the air inlet pipe (2) through the gas equalization structure (4).

3. The observation window protection system as described in claim 2, characterized in that, The perforation structure of the gas distribution structure (4) is one or more combinations of conical holes, stepped holes or blind holes, used to adjust airflow resistance and optimize radio frequency isolation performance.

4. The observation window protection system as described in claim 1, characterized in that, The observation window protection system also includes a cleaning mechanism (5) disposed on the side of the optical observation window (3) facing the air intake pipe (2); the cleaning mechanism (5) is configured to be driven by the airflow flowing through the air intake pipe (2) to clean the surface of the optical observation window (3); And / or, the observation window protection system further includes an airflow guide device (6) disposed in the air intake pipe (2) or at one end of the air intake pipe (2) near the uniform air structure (4); the airflow guide device (6) is configured to adjustably change the direction and / or velocity of part or all of the airflow so as to avoid directly impacting the central area of ​​the optical observation window (3).

5. The observation window protection system as described in claim 4, characterized in that, The cleaning mechanism (5) includes a rotatable cleaning element (51), the rotation axis of which forms an angle with the airflow direction; and / or, the contact force between the cleaning mechanism (5) and the optical observation window (3) can be adjusted by a preload spring or a magnetic assembly. And / or, the airflow guiding device (6) includes one or more adjustable angle guide vanes (61), the angle of which can be adjusted by a manual knob or motor driver outside the cavity; And / or, the airflow guiding device (6) is further configured to guide a portion of the airflow to a cleaning mechanism (5) to drive its operation.

6. The observation window protection system as described in claim 5, characterized in that, The cleaning element (51) is a brush, a scraper, or an airflow turbine.

7. The observation window protection system as described in claim 5, characterized in that, The airflow guiding device (6) and the cleaning mechanism (5) are linked by a gear set or linkage mechanism to convert the kinetic energy of the airflow into the mechanical energy of the cleaning mechanism (5).

8. The observation window protection system as described in claim 1, characterized in that, The gas distribution structure (4) is manufactured in an integrated manner with the upper electrode or cavity wall of the reaction chamber (1), or is installed and connected to the reaction chamber (1) as an independent and detachable module.

9. The observation window protection system as described in any one of claims 1-8, characterized in that, The optical observation window (3) is made of sapphire or quartz; And / or, the inner wall of the air intake pipe (2) is polished or coated with a high reflectivity film to enhance the transmission efficiency of light signals.

10. A plasma etching apparatus, comprising a reaction chamber, a radio frequency power supply, a gas supply system, and an endpoint detection system, characterized in that, The endpoint detection system integrates an observation window protection system as described in any one of claims 1 to 9.

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