Adjustable aperture supersonic nozzle, gas cluster ion source and polishing system

Abstract

The application relates to the technical field of supersonic nozzles, and provides a supersonic nozzle with adjustable aperture, which comprises a nozzle flow channel formed by a compression section, a throat section and an expansion section in sequence; the throat section is formed by a center-aperture elastic metal diaphragm, the center aperture of the elastic metal diaphragm constitutes the minimum flow passage section of the nozzle flow channel; an annular actuator is arranged around the outer periphery of the elastic metal diaphragm, the annular actuator is configured to generate a radial force along the center aperture in an excited state, the elastic metal diaphragm is elastically deformed, and the aperture size of the center aperture is continuously adjusted. The annular actuator is adopted to realize high-precision, linear and stepless adjustment of the throat aperture of the supersonic nozzle within a preset range, so that the mass number and distribution of gas clusters are dynamically controlled.

Description

Adjustable aperture supersonic nozzle, gas cluster ion source and polishing system Technical Field

[0001] This application relates to the field of supersonic nozzle technology, and more specifically, to a supersonic nozzle with adjustable aperture, a gas cluster ion source, and a polishing system. Background Technology

[0002] In advanced optical systems, ultra-smooth optical elements, due to their extremely low surface roughness and scattering loss, are a key foundation for achieving high-resolution imaging, high energy transfer efficiency, and stability in extreme environments. With the development of cutting-edge technologies such as extreme ultraviolet lithography, space exploration, and high-energy lasers, the requirements for the surface quality of optical elements have entered the sub-nanometer and even atomic scales. Traditional contact polishing methods are prone to introducing problems such as subsurface damage, edge collapse, and selective material removal, making it difficult to meet the ultra-smooth processing requirements of complex structures and special materials. Summary of the Invention

[0003] The purpose of this application is to provide an adjustable-aperture supersonic nozzle, a gas cluster ion source, and a polishing system, which can solve at least one of the aforementioned technical problems. The specific solution is as follows:

[0004] According to a specific embodiment disclosed in this application, this application provides a supersonic nozzle with adjustable aperture, comprising: a compression section, a throat section, and an expansion section, wherein the compression section, throat section, and expansion section are sequentially connected to form a nozzle flow channel; wherein, the throat section comprises: an elastic metal diaphragm having a central hole, the central hole constituting the minimum flow cross section of the nozzle flow channel; and an annular actuator disposed around the outer periphery of the elastic metal diaphragm, the annular actuator being configured to generate a radial force along the central hole under an excitation state, causing the elastic metal diaphragm to elastically deform, thereby continuously adjusting the aperture size of the central hole.

[0005] In some embodiments, the ring actuator is one of a piezoelectric ceramic actuator, a thermo-bimetallic actuator, a shape memory alloy actuator, or an electromagnetic actuator.

[0006] In some embodiments, the annular actuator is in the form of a closed ring or consists of a plurality of actuator units uniformly distributed circumferentially along the central hole, such that the radial force applied to the elastic metal diaphragm is axisymmetric.

[0007] In some embodiments, the elastic metal diaphragm is made of beryllium copper alloy, phosphor bronze, or stainless steel sheet, wherein the elastic metal diaphragm has a thickness of 20–300 μm and operates within the linear elastic deformation range during the intended adjustment stroke.

[0008] In some embodiments, the compression section includes a first conical channel, the expansion section includes a second conical channel, and the first conical channel, the central hole, and the second conical channel are sealed together.

[0009] In some embodiments, the supersonic nozzle is used as a gas cluster ion source. By adjusting the aperture of the central hole, the average mass number of the generated gas clusters is controlled, thereby optimizing the sputtering uniformity and surface roughness of the gas cluster ion beam in the ultra-smooth polishing process of the material to be processed.

[0010] In some embodiments, the average mass number of the gas clusters is controlled within a range corresponding to 500 to 2000 atoms / molecules per cluster.

[0011] In some embodiments, the diameter of the central hole can be adjusted from 0.05 mm to 0.2 mm.

[0012] This application provides a gas cluster ion source comprising a supersonic nozzle with adjustable aperture as described in any of the preceding claims.

[0013] This application provides a polishing system, including a gas cluster ion source as described above, as well as a vacuum chamber, an ion extraction electrode, and a workpiece stage. The system maintains the gas cluster ion beam parameters within a preset process window by adjusting the throat aperture of the supersonic nozzle in real time, so that the surface roughness of the material to be processed is less than 1 nm RMS.

[0014] Compared with the prior art, the above-disclosed solution in this application has at least one of the following beneficial effects:

[0015] This application employs a ring actuator to achieve high-precision, linear, and stepless adjustment of the throat aperture of a supersonic nozzle within a preset range, thereby dynamically controlling the mass number and distribution of gas clusters. By changing the aperture size in real time, the mass number corresponding to the peak cluster abundance can be precisely controlled, meeting the differentiated requirements for sputtering characteristics and surface smoothness under different material and process conditions. This application can be adapted to various GCIB processing scenarios without hardware replacement, significantly improving equipment flexibility and process robustness, and is particularly suitable for the ultra-smooth manufacturing of fragile structures such as gratings and special crystals. This application solves the core problems of existing technologies, such as cluster parameter adjustment relying on physical nozzle replacement, poor process flexibility, and insufficient thermal management, providing key equipment support for the efficient and controllable manufacturing of ultra-smooth optical components. Attached Figure Description

[0016] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the disclosure of this application and, together with the description, serve to explain the principles of the disclosure. It is obvious that the drawings described below are merely some embodiments disclosed in this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. In the drawings:

[0017] Figure 1 is an overall structural diagram of the adjustable aperture supersonic nozzle provided in an embodiment of this application;

[0018] Figure 2 is a cross-sectional view of the supersonic nozzle with adjustable orifice provided in an embodiment of this application;

[0019] Figure 3 is an exploded view of the orifice-adjustable supersonic nozzle provided in an embodiment of this application;

[0020] Figure 4 is a partial exploded view of the orifice-adjustable supersonic nozzle provided in an embodiment of this application.

[0021] Figure label:

[0022] Compression section 1, first conical channel 11, compression section body 12, mounting flange 13; throat section 2, center hole 21, elastic metal diaphragm 22, annular actuator 23; expansion section 3, second conical channel 31, expansion section body 32; temperature-controlled circulating water jacket 4; installation structure 5. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments disclosed in this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments disclosed in this application without creative effort are within the scope of protection of this application.

[0024] The terminology used in the embodiments disclosed in this application is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. The singular forms “a,” “said,” and “the” used in the embodiments disclosed in this application and the appended claims are also intended to include the plural forms, and “multiple” generally includes at least two unless the context clearly indicates otherwise.

[0025] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0026] It should be understood that although the terms first, second, third, etc., may be used to describe the embodiments disclosed in this application, these descriptions should not be limited to these terms. These terms are only used to distinguish the descriptions. For example, first may also be referred to as second without departing from the scope of the embodiments disclosed in this application, and similarly, second may also be referred to as first.

[0027] Depending on the context, the words “if” or “suppose” as used here can be interpreted as “when” or “in response to determination” or “in response to detection.” Similarly, depending on the context, the phrases “if determination” or “if detection (of the stated condition or event)” can be interpreted as “when determination” or “in response to determination” or “when detection (of the stated condition or event)” or “in response to detection (of the stated condition or event).”

[0028] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device that includes said element.

[0029] Gas cluster ion beam (GCIB) can be applied to the field of ultra-smooth polishing technology. As a non-contact precision machining method, it utilizes gas clusters formed by thousands of inert gas atoms bound together by van der Waals forces. These clusters are accelerated and bombard the workpiece surface, achieving atomically smooth surfaces without the introduction of mechanical stress through a uniform removal mechanism generated by lateral sputtering. This technology is particularly suitable for the ultra-smooth manufacturing of special crystal materials such as gratings, diffractive optical elements, and calcium fluoride, avoiding microcracks or phase transformation defects caused by localized stress concentration in traditional processes.

[0030] Key parameters affecting the processing efficiency of gas clusters by ion beams include the energy, type, and mass number of the gas clusters—that is, the number of atoms contained in a single cluster. The cluster mass number directly determines its effective cross-section, momentum distribution, and energy density, thus affecting material removal rate, surface smoothness, and processing uniformity. The formation of gas clusters depends on the adiabatic expansion of high-pressure gas through a supersonic nozzle at low temperatures. During this process, the gas undergoes saturated condensation and aggregates. The supersonic nozzle, as the core component of the cluster source, determines the gas flow expansion characteristics, shock wave structure, and nucleation efficiency through its orifice size, convergent-divergent profile, and surface finish. This allows for precise control of the average mass, yield, and mass number distribution width of the generated clusters.

[0031] Therefore, for different materials and process objectives, it is necessary to optimize the nozzle geometry parameters to match the required cluster characteristics, and ensure that a cluster beam with high stability, narrow distribution and high throughput is obtained, so as to provide a physical basis for achieving repeatable and efficient ultra-smooth processing.

[0032] Based on this, this application provides a supersonic nozzle with adjustable aperture, comprising: a compression section, a throat section, and an expansion section, wherein the compression section, throat section, and expansion section are sequentially connected to form a nozzle flow channel; wherein, the throat section comprises: an elastic metal diaphragm having a central hole, the central hole constituting the minimum flow cross section of the nozzle flow channel; and an annular actuator disposed around the outer periphery of the elastic metal diaphragm, the annular actuator being configured to generate a radial force along the central hole under an excitation state, causing the elastic metal diaphragm to elastically deform, thereby continuously adjusting the aperture size of the central hole.

[0033] This application dynamically controls the nucleation rate and cluster growth conditions of high-pressure gas during supersonic expansion by adjusting the throat aperture in real time. This allows for customized control of the mass number and distribution width of the generated gas clusters, particularly enabling precise control of the mass number corresponding to the peak cluster abundance. Compared to supersonic nozzles with fixed apertures, this application achieves wide-range, highly repeatable adjustment of cluster parameters without hardware replacement, significantly improving the adaptability of the GCIB process to different materials (such as fused silica, silicon carbide, and calcium fluoride crystals) and surface conditions.

[0034] The optional embodiments disclosed in this application are described in detail below with reference to the accompanying drawings.

[0035] As shown in Figures 1 and 2, this application provides a supersonic nozzle with adjustable orifice diameter, comprising a compression section 1, a throat section 2, and an expansion section 3. The compression section 1 includes a first conical channel 11, the throat section 2 includes a central hole 21, and the expansion section 3 includes a second conical channel 31. The first conical channel 11, the central hole 21, and the second conical channel 31 are sequentially and sealed together to form a nozzle flow channel. The throat section 2 further includes an elastic metal diaphragm 22 with a central opening and an annular actuator 23. The central hole 21 of the elastic metal diaphragm 22 constitutes the minimum flow cross-section of the nozzle flow channel. The annular actuator 23 is arranged around the outer periphery of the elastic metal diaphragm 22 and is configured to generate a radially inward force along the central hole 21 under excitation, causing the elastic metal diaphragm 22 to elastically deform, thereby continuously adjusting the orifice diameter of the central hole.

[0036] The supersonic nozzle of this application is a fluid control element that accelerates compressed gas to supersonic speeds. It is a core component of a gas cluster generation system, its function being to force high-pressure inert gas (such as argon) through a sub-millimeter diameter nozzle, causing it to expand adiabatically and cool rapidly, thus promoting the aggregation of gas atoms or molecules into nanoscale clusters. The nozzle orifice diameter directly determines the gas flow rate, density distribution, and expansion free path, thereby affecting the average size, particle size distribution, and formation efficiency of the clusters. Smaller orifice diameters are beneficial for forming higher density, smaller clusters, but the risk of clogging and processing accuracy must be considered; larger orifice diameters may lead to uneven cluster size or decreased generation efficiency.

[0037] As shown in Figure 2, the compression section 1 includes a compression section body 12 and a first conical channel 11. The diameter of the first conical channel 11 gradually decreases along the axial direction of the compression section body 12 to compress gas. The compression section 1 serves as the front-end module for gas input and structural support, as well as the gas pre-compression and mechanical interface. The mounting flange 13 at the end of the compression section body 12 adopts a standard vacuum flange interface (such as CF or KF series), providing a high-vacuum compatible mechanical fixing surface and sealing reference to ensure reliable installation and airtightness of the entire nozzle in the ultra-high vacuum chamber; the first conical channel 11 is a tapered flow channel structure with an inlet diameter of typically 5–15 mm and an outlet that converges to match the inlet of the central hole 21 (approximately 0.3–0.4 mm). Through the adiabatic compression effect, it accelerates the input high-pressure working gas (such as Ar, N2, SF6, etc., with a pressure range of 1–10 bar) to near the speed of sound (Ma ≈ 1), providing initial momentum conditions for subsequent supersonic expansion; the inner surface of the first conical channel 11 is ultra-precision polished (Ra ≤ 0.3 μm) to suppress turbulence and boundary layer separation, ensure airflow uniformity, and avoid disturbance sources during the agglomeration process.

[0038] The outlet of the first conical channel 11 is smoothly and sealed at the connection with the central hole 21. When the diameter of the central hole 21 is adjusted, the diameter of the outlet of the first conical channel 11 at the connection with the central hole 21 remains basically unchanged, thus avoiding flow field distortion caused by diameter adjustment.

[0039] The throat segment 2 enables active control of the cluster mass number, and its aperture size directly determines the gas expansion ratio and nucleation kinetics path. The throat segment 2 includes an elastic metal diaphragm 22 with a central aperture 21 and an annular actuator 23 surrounding the outer periphery of the elastic metal diaphragm 22. In some embodiments, the elastic metal diaphragm 22 is made of beryllium copper alloy, phosphor bronze, or stainless steel sheet, wherein the thickness of the elastic metal diaphragm 22 is 20–300 μm, and it operates within the linear elastic deformation range within the expected adjustment stroke.

[0040] For example, the elastic metal diaphragm 22 is a microporous diaphragm with a thickness of about 20–50 μm and an initial inner diameter of 0.15 mm, made of an elastic metal material with high elastic modulus, low hysteresis, and resistance to low-temperature impact. For example, beryllium copper alloy (BeCu, C17200) or nickel-titanium shape memory alloy (NiTi, such as Nitinol 55).

[0041] Among them, BeCu has an elastic modulus of ≈128 GPa, high yield strength (≥1100 MPa), and fatigue life >10. 7 Secondly, it exhibits good thermal conductivity (65 W / m·K), making it suitable for high-frequency adjustment; NiTi can achieve a hyperelastic strain of up to 8%, but its response speed is relatively slow, making it more suitable for low-frequency, large-stroke adjustment. This application prefers BeCu because its linear elastic response better matches the micro-displacement output characteristics of piezoelectric ceramics.

[0042] The outer periphery of the elastic metal diaphragm 22 is fastened to the compression section 1 and expansion section 3 at both ends by laser welding or micro-threading to form an airtight cavity and achieve a leak-free connection with the compression section 1 and expansion section 3.

[0043] The outer ring of the elastic metal diaphragm 22 is coaxially wrapped by the annular actuator 23. The coaxial wrapping applies radial preload, and the continuous and linear shrinkage of the aperture is achieved by the elastic deformation of the elastic metal diaphragm 22 (e.g., the adjustment range is 0.15 mm-0.1 mm).

[0044] In some embodiments, the diameter of the central hole 21 can be adjusted from 0.05 mm to 0.2 mm.

[0045] In some embodiments, the annular actuator 23 is in the form of a closed ring or consists of a plurality of actuator units evenly distributed circumferentially along the central hole 21, such that the radial force applied to the elastic metal diaphragm 22 is axisymmetric.

[0046] In some embodiments, the annular actuator 23 is one of a piezoelectric ceramic actuator, a thermal bimetallic actuator, a shape memory alloy actuator, or an electromagnetic actuator.

[0047] The ring-shaped piezoelectric ceramic actuator employs a ring-shaped multilayer piezoelectric ceramic stacked structure (preferably made of modified lead zirconate titanate PZT-5H or lead-free piezoelectric ceramics such as KNN-LiSbO3), coaxially wrapped around the outer periphery of an elastic metal diaphragm 22. When a DC or low-frequency AC voltage (typically 0–150 V) is applied, the piezoelectric ceramic contracts / expands along its thickness direction, converting the displacement into a uniform radial pressure on the elastic metal diaphragm 22 through a rigid force transmission ring. The elastic metal diaphragm 22 undergoes linear scaling of its central aperture (e.g., 0.25 mm – 0.18 mm) due to elastic deformation, resulting in fast adjustment response (millisecond level), high repeatability, and no mechanical wear. A displacement sensor can be integrated to achieve closed-loop feedback control, ensuring the long-term stability of the aperture setpoint. The ring-shaped piezoelectric ceramic actuator offers high precision, fast response, and suitability for high-frequency adjustment, making it suitable for experimental scenarios requiring real-time tuning of cluster sizes.

[0048] The toroidal thermal bimetallic actuator consists of two layers of thin metal sheets with significantly different coefficients of thermal expansion (such as brass / Invar alloy) wound into a ring structure, tightly adhering to the outer wall of an elastic metal diaphragm 22. Under electrical heating or external heat source excitation, the bimetallic ring generates radial contraction force due to asymmetric thermal expansion, compressing the inner elastic metal diaphragm 22 to reduce the aperture. The aperture adjustment range can be controlled by the heating power, with typical response times ranging from hundreds of milliseconds to seconds. The toroidal thermal bimetallic actuator is simple in structure, low in cost, and requires no high-voltage power supply, making it suitable for steady-state experiments where high adjustment speed is not required. Applicable scenarios: low-cost systems, long-term stable operation, and applications where frequent switching of cluster parameters is not required.

[0049] A ring-shaped shape memory alloy (SMA) drive ring, made of nickel-titanium-based shape memory alloy (such as Nitinol) wire or strip, is machined into a closed ring and pre-tensioned and installed around an elastic metal diaphragm 22. When energized and Joule-heated to above the phase transition temperature (Af ≈ 70–90°C), the SMA ring contracts, generating a recovery strain of up to 4–6%, applying continuous pressure to the central elastic metal diaphragm 22. After cooling, it returns to its initial state, achieving aperture reset. The ring-shaped shape memory alloy (SMA) drive ring has a large output force and a compact structure, but its response speed is limited by the thermal cycling rate. It is suitable for high output force density and applications requiring large aperture changes (>100μm); it can be used in conjunction with a temperature-controlled water jacket for thermal management.

[0050] The ring-shaped electromagnetic actuator (micro-solenoid array) arranges multiple micro-electromagnetic units around the aperture section in a symmetrical ring arrangement. Each unit contains an iron core and a coil. When energized, it generates a strong magnetic field, which attracts a flexible pressure ring made of soft magnetic material (such as pure iron or permalloy) to move inward, thereby compressing the elastic metal diaphragm 22. The uniformity of pressure distribution can be controlled by adjusting the current of each unit to avoid eccentric deformation. It has a fast response speed (<10 ms) and the driving force can be continuously adjusted by the current. The ring-shaped electromagnetic actuator is suitable for advanced systems that require high-speed switching or multi-point independent control and can be expanded to two-dimensional deformation control.

[0051] The expansion section 3 completes the isentropic expansion of the gas from sonic speed to supersonic speed and controls the spatial divergence characteristics of the cluster beam. The expansion section 3 adopts the Laval Nozzle expansion section design, which includes the expansion section body 32 and the second conical channel 31. The half angle of the second conical channel 31 is usually 5°–15°, and the length is optimized according to the gas type and the target Mach number (Ma = 10–100). The adjustable range of the expansion ratio (exit area / center hole area) of the second conical channel 31 corresponds to the equivalent center hole size after the hole diameter is adjusted, ensuring that the expansion process is always in the supersaturated nucleation region. The inner wall of the second conical channel 31 is treated with ultra-smooth surface (Ra ≤ 0.3 μm) to suppress secondary collisions and cluster fragmentation.

[0052] Optionally, an electrostatic guiding electrode or a magnetic shielding structure can be integrated at the exit of expansion section 3 for subsequent beam collimation or docking with a mass spectrometer.

[0053] The effective expansion ratio of expansion section 3 changes dynamically with the central hole 21. The system achieves joint control of cluster size and spatial distribution through the coupling design of central hole 21 and second conical channel 31.

[0054] In some embodiments, the supersonic nozzle with adjustable aperture provided in this application further includes a temperature-controlled circulating water jacket 4, which is used to maintain the overall thermodynamic steady state of the nozzle, prevent local condensation or ice blockage caused by adiabatic expansion, and ensure the stability and repeatability of cluster formation.

[0055] The temperature-controlled circulating water jacket 4 surrounds the expansion section 3. The temperature-controlled circulating water jacket 4 adopts a dual-channel spiral flow structure, supporting cooling water circulation (for high repetition frequency operation) or electric heating compensation (for low temperature environments or start-up phases). The temperature-controlled circulating water jacket 4 has a built-in PT100 platinum resistance temperature sensor (accuracy ±0.1°C) and a thin-film electric heating element (power 5–20 W), which is dynamically adjusted by a PID controller. The operating temperature setting range is -50°C to +80°C, and the typical operating point is +20°C ± 1°C, ensuring stable gas expansion within the critical nucleation temperature window. The outer shell is insulated with a low thermal conductivity material (such as PEEK) to reduce environmental thermal disturbance.

[0056] Supersonic expansion can cause temperature drops of hundreds of Kelvin (e.g., Ar drops from 300 K to <50 K). Without an active temperature-controlled circulating water jacket, the nozzle surface is prone to frost formation or material embrittlement, which seriously affects lifespan and cluster consistency.

[0057] As shown in Figures 3 and 4, the supersonic nozzle of this application also includes an installation structure 5. The installation structure 5 has approximately symmetrical receiving portions on both sides for accommodating and fixing the compression section 1 and the expansion section 3, and ensuring a sealed and smooth connection between the first conical channel 11, the central hole 21 and the second conical channel 31.

[0058] This application's supersonic nozzle employs a piezoelectric ceramic-driven microthrottle structure, achieving high-precision, linear, and stepless adjustment of the nozzle throat orifice diameter within the range of 0.05 mm to 0.2 mm, thereby dynamically controlling the mass number and distribution of gas clusters. By changing the orifice size in real time, the mass number corresponding to the peak cluster abundance can be precisely controlled, meeting the differentiated requirements for sputtering characteristics and surface smoothness under different material and process conditions. A microchannel temperature-controlled flow path is set on the outer wall of the nozzle to effectively compensate for the Joule-Thomson cooling effect caused by supersonic gas expansion, maintaining stable nozzle temperature, avoiding condensation blockage and thermal deformation, and ensuring long-term consistency of cluster formation. It can be adapted to various GCIB processing scenarios without hardware replacement, significantly improving equipment flexibility and process robustness, and is particularly suitable for the ultra-smooth manufacturing of easily damaged structures such as gratings and special crystals.

[0059] In some embodiments, this application provides a gas cluster ion source comprising a supersonic nozzle with adjustable aperture as described in any of the preceding embodiments. The supersonic nozzle of this application is used as a gas cluster ion source, and by adjusting the aperture of the central aperture 21, the average mass number of the generated gas clusters is controlled, thereby optimizing the sputtering uniformity and surface roughness of the gas cluster ion beam in the ultra-smooth polishing process of the material to be processed.

[0060] In some embodiments, the average mass number of the gas clusters is controlled within a range corresponding to 500 to 2000 atoms / molecules per cluster.

[0061] Gas cluster ion beams utilize nanoscale clusters of thousands of gas atoms or molecules (such as argon) as bombardment particles, which are accelerated by ionization to perform low-damage finishing on material surfaces. Compared to single-atom ions, gas clusters have a significantly lower energy density per particle at the same energy level, enabling efficient material removal while suppressing subsurface damage and residual stress. This makes them particularly suitable for fields with extremely high surface integrity requirements, such as optical components and semiconductor devices. Gas cluster ion beams combine atomic-level removal precision with excellent surface roughness improvement capabilities, making them a key process for achieving picometer- to nanometer-level surface quality enhancement.

[0062] This application provides a polishing system, including a gas cluster ion source as described above, as well as a vacuum chamber, an ion extraction electrode, and a workpiece stage. The system maintains the gas cluster ion beam parameters within a preset process window by adjusting the throat aperture of the supersonic nozzle in real time, so that the surface roughness of the material to be processed is less than 1 nm RMS.

[0063] Ultrasmooth optical elements refer to high-precision optical elements with a surface roughness better than 0.5 nm rms, and are widely used in extreme ultraviolet lithography, high-energy laser systems, astronomical telescopes, and precision interferometry. These elements exhibit extremely low light scattering loss and sub-nanometer-level morphological uniformity, significantly improving the transmission efficiency and imaging quality of optical systems. The supersonic nozzle of this application can obtain a stable and controllable gas cluster beam, which is an important guarantee for achieving efficient and low-damage ion beam polishing.

[0064] This application proposes a supersonic nozzle structure with adjustable orifice size, enabling high-precision, rapid, and continuous adjustment of the throat orifice size. A microporous diaphragm made of an elastic metallic material (such as beryllium copper alloy) is introduced into the smallest cross-section (throat) of the supersonic nozzle, and an annular actuator is integrated around its periphery. By applying an external control signal, uniform radial pressure can be applied to the diaphragm, allowing for linear and reversible adjustment of the central orifice size within the micrometer range (e.g., continuously adjustable from 0.25 mm to 0.18 mm). This mechanism offers fast response (millisecond level) and good repeatability, avoiding interruptions and errors caused by mechanical nozzle replacement.

[0065] The distribution of cluster mass number is controlled by adjusting the orifice diameter, and the average mass number of gas clusters is highly sensitive to the geometry of the nozzle throat. This application directly adjusts the adiabatic expansion ratio and supersaturation of the gas within the nozzle through precise orifice diameter control, thereby effectively controlling the cluster growth scale during nucleation. This provides a reliable means for fine-tuning the output parameters of the ion source.

[0066] Ensuring the stability and consistency of the cluster ion beam is crucial for supporting ultra-smooth polishing processes. In gas cluster ion beam (GCIB) ultra-smooth polishing applications, cluster size distribution directly affects sputtering yield, surface damage depth, and roughness evolution. This application, by adjusting the aperture in real time, can stably control the cluster mass number within the process window (e.g., 500–2000), reducing localized oversputtering caused by large clusters or insufficient removal efficiency caused by small clusters, thereby improving polishing uniformity and final surface quality (typical surface roughness can be controlled at the sub-nanometer level).

[0067] Employing a fully solid-state, non-slip seal actuation structure, it is adaptable to ultra-high vacuum environments. The orifice adjustment mechanism has no moving parts or dynamic seals; it relies on the overall deformation of the elastic diaphragm to achieve orifice change, fundamentally avoiding the limitations of traditional mechanical control valves in ultra-high vacuum (<10⁻⁻⁶). 5This improves the reliability of the system's long-term operation by eliminating potential air leakage, particulate contamination, or jamming issues that may occur in the Pa environment.

[0068] Multiple toroidal actuation solutions are offered to enhance the flexibility of technical implementation. In addition to the primary piezoelectric ceramic actuation, alternative solutions such as thermo-bimetallic, shape memory alloy, and electromagnetic actuation have been designed, all based on the principle of toroidal symmetrical loading to ensure the axisymmetry of aperture deformation. Different solutions can be adapted to different requirements for response speed, adjustment range, or system complexity, providing technical redundancy and selection space for practical engineering applications.

[0069] This application achieves effective control of the mass number of gas clusters by integrating a high-response, high-precision aperture adjustment mechanism into the throat of a supersonic nozzle, thereby improving the process stability and controllability of the gas cluster ion source in precision surface processing (especially ultra-smooth polishing), and has clear technical value and application relevance.

[0070] Finally, it should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems or apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple, and relevant parts can be referred to the method section.

[0071] The above embodiments are only used to illustrate the technical solutions disclosed in this application, and are not intended to limit them. Although the disclosure of this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments disclosed in this application.

Claims

1. A supersonic nozzle with adjustable orifice diameter, characterized in that, include: The nozzle consists of a compression section, a throat section, and an expansion section, which are sequentially connected to form a nozzle flow channel. The throat section includes: an elastic metal diaphragm with a central hole, the central hole constituting the minimum flow cross-section of the nozzle flow channel; and an annular actuator surrounding the outer periphery of the elastic metal diaphragm, configured to generate a radial force along the central hole under excitation, causing elastic deformation of the elastic metal diaphragm and thereby continuously adjusting the aperture size of the central hole. The supersonic nozzle serves as a gas cluster ion source, and by adjusting the aperture of the central hole, the average mass number of the generated gas clusters is controlled, thereby optimizing the sputtering uniformity and surface roughness of the gas cluster ion beam in the ultra-smooth polishing process of the material to be processed.

2. The supersonic nozzle as described in claim 1, characterized in that, The ring actuator is one of a piezoelectric ceramic actuator, a thermo-bimetallic actuator, a shape memory alloy actuator, or an electromagnetic actuator.

3. The supersonic nozzle as described in claim 1 or 2, characterized in that, The annular actuator is in the form of a closed ring or consists of multiple actuation units evenly distributed around the central hole, so that the radial force applied to the elastic metal diaphragm is axisymmetric.

4. The supersonic nozzle as described in claim 1, characterized in that, The elastic metal diaphragm is made of beryllium copper alloy, phosphor bronze or stainless steel sheet, wherein the thickness of the elastic metal diaphragm is 20–300 μm and it operates in the linear elastic deformation range within the expected adjustment stroke.

5. The supersonic nozzle as described in claim 1, characterized in that, The compression section includes a first conical channel, and the expansion section includes a second conical channel. The first conical channel, the central hole, and the second conical channel are smoothly and sealed together.

6. The supersonic nozzle as described in claim 1, characterized in that, The average mass number of the gas clusters is controlled within a range of 500 to 2000 atoms / molecules per cluster.

7. The supersonic nozzle as described in claim 1, characterized in that, The diameter of the central hole can be adjusted from 0.05 mm to 0.2 mm.

8. A gas cluster ion source, characterized in that, It includes a supersonic nozzle with adjustable orifice as described in any one of claims 1–7.

9. A polishing system, characterized in that, The system includes the gas cluster ion source as described in claim 8, as well as a vacuum chamber, ion extraction electrodes, and a workpiece stage. The system maintains the gas cluster ion beam parameters within a preset process window by adjusting the throat aperture of the supersonic nozzle in real time, so that the surface roughness of the material to be processed is less than 1 nm RMS.

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