Plasma external deposition apparatus and method

Abstract

The application belongs to the technical field of optical communication, and discloses a kind of plasma external deposition equipment and method, plasma external deposition equipment includes box, pedestal and torch structure, torch structure includes sleeve assembly, radio frequency coil and SiCl4 material pipe, sleeve assembly includes first quartz tube, second quartz tube, third quartz tube and fourth quartz tube, which are sequentially sleeved from outside to inside, first annular channel is formed between first quartz tube and second quartz tube, second annular channel is formed between second quartz tube and third quartz tube, third annular channel is formed between third quartz tube and fourth quartz tube, and center gas pipeline is provided in fourth quartz tube, the upper end of second quartz tube protrudes from first quartz tube, third quartz tube and fourth quartz tube, SiCl4 material pipe is arranged at the top of second quartz tube, and radio frequency coil is sleeved on second quartz tube. Plasma external deposition method is completed using the above-mentioned plasma external deposition equipment. The application can improve deposition efficiency.

Description

Technical Field

[0001] This invention relates to the field of optical communication technology, and in particular to a plasma external deposition apparatus and method. Background Technology

[0002] With the large-scale development of all-optical computing networks, transoceanic high-speed communication, and high-end specialty optical fibers, the market has placed higher demands on the transmission performance, manufacturing efficiency, and cost control of optical fibers. Highly fluorine-doped silica cladding, as the core structure of ultra-low-loss optical fibers and high-power laser transmission fibers, directly determines the transmission attenuation, mechanical properties, and large-scale production potential of optical fibers due to its doping uniformity, fluorine doping concentration, and fabrication size. This represents a key technological bottleneck in high-end optical fiber manufacturing.

[0003] Currently, the mainstream fabrication process for highly fluorine-doped cladding of optical fiber preforms mostly adopts the plasma external deposition route. However, existing processes generally introduce the silicon source from the bottom of the torch into the plasma excited by the RF coil, which brings two fundamental technical problems that seriously restrict its industrial application and performance improvement: First, the deposition rate and deposition efficiency are low. The current conventional plasma fluorine-doped external deposition scheme has a deposition rate of only 0.3g / min-0.5g / min, which is difficult to meet the needs of mass production of large-size preforms, resulting in extended production cycles and high manufacturing costs. Second, the process is prone to powder accumulation in the torch tube. Powder accumulation will gradually block the torch tube channel and interfere with plasma stability, thus preventing the equipment from working stably for a long time. Generally, the outer wall torch tube needs to be cleaned or replaced after 10-20 hours of operation, which not only affects the consistency of preform products, but also increases equipment maintenance costs and downtime losses.

[0004] Therefore, there is an urgent need for an external plasma deposition device and method to solve the above-mentioned technical problems. Summary of the Invention

[0005] The purpose of this invention is to provide a plasma external deposition device and method, which aims to solve the problems of low deposition efficiency and easy dust accumulation in existing deposition equipment, thus reducing production efficiency. This plasma external deposition device and method can achieve high-concentration fluorine-doped silica glass deposition, improve deposition rate and deposition efficiency, and at the same time reduce dust accumulation.

[0006] To achieve this objective, the present invention adopts the following technical solution: Plasma external deposition equipment, including: The box contains a target rod. A base is located at the bottom of the housing. A blowtorch structure is mounted on the base. The blowtorch structure includes a sleeve assembly, an RF coil, and a SiCl4 material tube. The sleeve assembly includes a first quartz tube, a second quartz tube, a third quartz tube, and a fourth quartz tube, sequentially nested from the outside in. The first and second quartz tubes form a first annular channel for introducing nitrogen gas. The second and third quartz tubes form a second annular channel for introducing argon and nitrogen gas. The third and fourth quartz tubes form a third annular channel for introducing oxygen gas. The fourth quartz tube has a central gas pipe for introducing oxygen and C2F6. The upper end of the second quartz tube protrudes beyond the first, third, and fourth quartz tubes. The SiCl4 material tube is disposed on the top of the second quartz tube. The radio frequency coil is sleeved on the upper end of the second quartz tube. With the energy of the radio frequency coil, plasma flame can be excited and ejected from the second quartz tube. The target rod is disposed above the SiCl4 material tube.

[0007] In some possible implementations, the plasma external deposition apparatus further includes a cooling nitrogen laminar flow generator, which includes a first gas storage chamber. The outer peripheral surface of the first gas storage chamber has a plurality of laminar flow holes, which are connected to the first annular channel. The plurality of laminar flow holes are evenly distributed along the circumference of the first gas storage chamber, and the axis of the laminar flow holes is coplanar with the axis of the torch structure and is set at an angle.

[0008] In some possible implementations, the angle between the axis of the laminar flow orifice and the axis of the torch structure ranges from 30° to 60°; the diameter of the laminar flow orifice ranges from 2 mm to 6 mm.

[0009] In some possible implementations, the plasma external deposition apparatus further includes a first swirling gas generator and a second swirling gas generator. The first swirling gas generator includes a second gas storage chamber. The outer peripheral surface of the second gas storage chamber has a plurality of first swirling holes. The first swirling holes are connected to the second annular channel. The plurality of first swirling holes are evenly distributed along the circumference of the second gas storage chamber. The axis of the first swirling holes is arranged in a non-plane manner with respect to the axis of the torch structure, and the axis of the first swirling holes is arranged at an angle relative to the horizontal plane. The second swirling gas generator includes a third gas storage chamber. The outer peripheral surface of the third gas storage chamber has a plurality of second swirling holes. The second swirling holes are connected to the third annular channel. The plurality of second swirling holes are evenly distributed along the circumference of the second gas storage chamber. The axis of the second swirling holes is arranged on opposite sides to the axis of the torch structure, and the axis of the second swirling holes is arranged at an angle relative to the horizontal plane.

[0010] In some possible implementations, the angle between the axis of the first swirling orifice and the horizontal plane is in the range of 30°-60°; the angle between the axis of the second swirling orifice and the horizontal plane is in the range of 30°-60°.

[0011] In some possible embodiments, the plasma external deposition apparatus further includes an oxygen-fluorine gas mixing generator, which includes a flow divider plate having a plurality of flow divider holes penetrating the upper and lower end faces. The plurality of flow divider holes are evenly distributed along the circumference of the flow divider plate, and the axis of the flow divider plate and the axis of the flow divider holes are arranged in opposite directions, with the axis of the flow divider holes forming an angle with respect to the horizontal plane.

[0012] In some possible implementations, the angle between the axis of the diversion hole and the horizontal plane ranges from 30° to 60°.

[0013] In some possible implementations, the target rod is horizontally positioned, and the target rod and the SiCl4 feed tube are arranged parallel to each other.

[0014] In some possible implementations, the outer diameter of the first quartz tube is 70mm-80mm; the outer diameter of the second quartz tube is 60mm-70mm; the outer diameter of the third quartz tube is 35mm-45mm; and the outer diameter of the fourth quartz tube is 20mm-25mm. The inner diameter of the radio frequency coil is 65mm-75mm, the number of turns is 3 or 4, and the diameter of the copper tube of the radio frequency coil is 6mm-10mm. The radio frequency source frequency of the radio frequency coil is 2MHz-5MHz, and the radio frequency power is 50kW-150kW.

[0015] The plasma external deposition method, performed using the plasma external deposition equipment described in any of the above schemes, includes the following steps: S1. Equipment installation and program debugging: Install the target rod, write the corresponding deposition program, and turn on the cooling system to protect the oscillation cabinet; S2. Equipment alignment, mechanism adjustment and pre-ventilation: Adjust the position of the target rod and the torch structure, drive the ignition needle at the tip of the Tesla coil to the top of the torch structure, introduce nitrogen into the first annular channel and argon into the second annular channel, and preload to prepare for ignition. S3. Equipment preheating and plasma ignition: Start the oscillating cabinet, connect the filament power supply for preheating, after the filament preheating is completed, connect the anode high voltage and increase the voltage to the preset voltage. After the voltage stabilizes, start the Tesla coil igniter to complete the ignition. After the plasma flame is stabilized, return the igniter to its original position. S4. Process atmosphere switching and target rod preheating: After ignition, the argon gas in the second annular channel is gradually replaced with nitrogen gas, and oxygen gas is gradually introduced into the third annular channel. During the gas adjustment process, the power of the radio frequency source is gradually increased. During the preheating process, the moving speed of the target rod is gradually reduced, and the distance between the torch structure and the target rod is reduced in a stepwise manner. S5. Target rod polishing, fluorine doping, and silica deposition: After preheating, the target rod surface is polished. A mixture of oxygen and C2F6 is introduced into the central gas pipe to polish the target rod surface. After the polishing process is completed, SiCl4 raw material is introduced into the plasma flame through the SiCl4 feed tube. In the top region of the torch structure, SiCl4 and oxygen react to generate SiO2 particles. In the contact area between the plasma flame and the target rod, a non-equilibrium chemical reaction occurs. The highly active fluorine groups and SiO2 vapor particles in the plasma flame are rapidly cooled and deposited on the target rod surface, completing the glass transition deposition process. S6. Process Termination, Annealing and Cooling, and Finished Product Discharge: When the diameter gauge detects that the target rod diameter has reached the process-set standard value, the silicon material and oxygen-fluorine mixed gas are stopped in the turning zone to terminate the deposition reaction. The system automatically starts the annealing program to perform annealing and stabilization treatment on the deposited target rod to eliminate internal stress annealing. After the annealing process is completed, the equipment automatically completes the pressure reduction, arc extinguishing, and shutdown operations. After the equipment and the target rod cool naturally, a qualified fluorine-doped preform product can be obtained.

[0016] The beneficial effects of this invention are: The plasma external deposition apparatus provided by this invention enhances gas convection between the second quartz tube and the radio frequency coil by introducing nitrogen gas into the first annular channel, reducing the problem of uneven temperature inside and outside the radio frequency coil caused by thermal radiation; by introducing nitrogen gas into the second annular channel, it protects the third quartz tube, maintains stable plasma flow, and isolates premature reaction of SiCl4, avoiding the accumulation of micropowder; by introducing oxygen into the third annular channel, oxygen can regulate the plasma morphology and help the plasma morphology shrink; by placing the SiCl4 feed tube at the top of the second quartz tube (i.e., the top of the torch structure), it is compatible with existing SiCl4 deposition apparatuses. Compared to SiCl4, which flows from bottom to top through the center of the plasma flame, SiCl4 does not. Therefore, the increased SiCl4 flux does not affect the stability of the plasma, thus removing the limitations of RF power and SiCl4 flux. C2F6, as a highly electronegative gas, can effectively obtain energy from the plasma when introduced from the bottom, generating a large number of high-energy active groups. These groups combine with SiO2 generated from the reaction of SiCl4 and O2 at the top of the torch structure, resulting in a non-equilibrium reaction that achieves high-concentration fluorine-doped silica glass deposition, thereby improving the deposition rate and efficiency.

[0017] The plasma external deposition method provided by this invention, since the SiCl4 feed tube is located at the top of the second quartz tube (i.e., the top of the torch structure), does not pass through the center of the plasma flame during deposition. Therefore, the plasma flame will not be affected by the increased SiCl4 flux, thus removing the limitations of radio frequency power and SiCl4 flux. As a strongly electronegative gas, C2F6, when introduced from the bottom, can effectively obtain energy from the plasma and generate a large number of high-energy active groups. These groups combine with SiO2 generated by the reaction of SiCl4 and O2 at the top of the torch structure to undergo a non-equilibrium reaction, achieving the deposition of highly concentrated fluorine-doped silica glass, thereby improving the deposition rate and deposition efficiency. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the plasma external deposition device provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of the plasma external deposition equipment (machine tool platform and housing not shown) provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the oxygen-fluorine gas mixing generator provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the structure of the first swirling gas generator and the second swirling gas generator provided in the embodiments of the present invention; Figure 5This is a schematic diagram of the structure of the cooling nitrogen laminar flow generator provided in an embodiment of the present invention.

[0019] In the picture: 10. Target rod; 100. Housing; 200. Base; 311. First quartz tube; 312. Second quartz tube; 313. Third quartz tube; 314. Fourth quartz tube; 320. Radio frequency coil; 330. SiCl4 feed tube; 400. Cooling nitrogen laminar flow generator; 410. First gas storage chamber; 411. Laminar flow orifice; 500. First swirling gas generator; 510. Second gas storage chamber; 511. First swirling orifice; 600. Second swirling gas generator; 610. Third gas storage chamber; 611. Second swirling orifice; 700. Oxy-fluorine gas mixing generator; 710. Flow divider; 711. Flow divider orifice; 800. Plasma flame; 900. Machine tool platform; 1000. Central fluorine-oxygen pipeline. Detailed Implementation

[0020] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar components or components having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0021] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection or a detachable connection; a mechanical connection or an electrical connection; a direct connection or an indirect connection through an intermediate medium; or the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0022] In the description of this invention, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0023] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0024] like Figures 1 to 5 As shown, this embodiment provides a plasma external deposition apparatus, including a housing 100, a base 200, and a torch structure. The base 200 is disposed at the bottom of the housing 100, and the torch structure is disposed on the base 200. A target rod 10 is also disposed inside the housing 100. In use, the housing 100 can be mounted on a machine tool platform 900. The torch structure includes a sleeve assembly, an RF coil 320, and a SiCl4 material tube 330. The sleeve assembly includes a first quartz tube 311, a second quartz tube 312, a third quartz tube 313, and a fourth quartz tube 314, which are sequentially sleeved from the outside to the inside. The first quartz tube 311 and the second quartz tube 312 form a first annular channel for introducing nitrogen gas. The second quartz tube 312 and the third quartz tube 313 form a second annular channel for introducing argon and nitrogen gas. The third quartz tube 313 and the fourth quartz tube 314 form a third annular channel. A shaped channel is used to introduce oxygen. The fourth quartz tube 314 has a central gas pipe for introducing oxygen and C2F6. The upper end of the second quartz tube 312 protrudes from the first quartz tube 311, the third quartz tube 313, and the fourth quartz tube 314. The SiCl4 material tube 330 is disposed on the top of the second quartz tube 312. The radio frequency coil 320 is sleeved on the upper end of the second quartz tube 312. With the energy of the radio frequency coil 320, the second quartz tube 312 can be excited and ejected with plasma flame 800. The target rod 10 is disposed above the SiCl4 material tube 330.

[0025] During deposition, nitrogen is first introduced into the first annular channel, and argon is introduced into the second annular channel to prepare for ignition. After ignition, the gas supply is switched, with nitrogen gradually introduced into the second annular channel and oxygen gradually introduced into the third annular channel. After the target rod 10 is preheated, oxygen and C2F6 are introduced into the central gas pipe to polish the surface of the target rod 10, removing surface defects and impurities. At the same time, C2F6 generates active fluorine groups through plasma ionization. SiCl4 raw material is then introduced into the plasma flame 800 region through the SiCl4 feed tube 330. SiCl4 and oxygen react to generate SiO2 particles at the top of the torch structure. In the contact area between the plasma flame 800 and the target rod 10, a non-equilibrium chemical reaction occurs. The active fluorine groups and SiO2 vapor particles in the plasma flame 800 are rapidly deposited on the surface of the target rod 10, completing the vitrification deposition process.

[0026] By introducing nitrogen into the first annular channel, gas convection between the second quartz tube 312 and the radio frequency coil 320 is enhanced, reducing the problem of uneven temperature inside and outside the radio frequency coil 320 caused by thermal radiation. Introducing nitrogen into the second annular channel protects the third quartz tube 313, maintains the stability of the plasma flame 800, and prevents premature reaction of SiCl4, thus avoiding the accumulation of fine powder. Introducing oxygen into the third annular channel allows for the regulation of the plasma morphology, aiding in its contraction. By placing the SiCl4 feed tube 330 at the top of the second quartz tube 312 (i.e., the top of the torch structure), it is integrated with existing SiCl4 feed tubes. Compared to the plasma flow pattern where SiCl4 flows from bottom to top through the center of plasma flow 800, SiCl4 does not pass through the center of plasma flow 800. Therefore, the increased SiCl4 flux does not affect the stability of the plasma itself, removing the limitations of RF power and SiCl4 flux. C2F6, as a highly electronegative gas, can effectively obtain energy from the plasma when introduced from the bottom, generating a large number of high-energy active groups. These groups combine with SiO2 generated from the reaction of SiCl4 and oxygen at the top of the torch structure, undergoing a non-equilibrium reaction to achieve high-concentration fluorine-doped silica glass deposition, thus improving the deposition rate and efficiency. The external plasma deposition equipment provided in this embodiment can achieve a deposition rate of 1 g / min-2 g / min and an efficiency improvement of over 10% at the same fluorine doping concentration. Furthermore, it can meet the requirements for long-term stable operation, with an effective working life of 60-100 hours.

[0027] Optionally, the plasma external deposition apparatus further includes a cooling nitrogen laminar flow generator 400. The cooling nitrogen laminar flow generator 400 includes a first gas storage chamber 410. The outer peripheral surface of the first gas storage chamber 410 has multiple laminar flow holes 411, which communicate with a first annular channel. The multiple laminar flow holes 411 are uniformly distributed along the circumference of the first gas storage chamber 410. The axes of the laminar flow holes 411 are coplanar with the axis of the torch structure and are set at an angle. The cooling nitrogen gas ejected obliquely from the laminar flow holes 411 flows towards the axis of the torch structure. The airflow flows to the area near the radio frequency coil 320, enhancing convective heat transfer at the radio frequency coil 320 and effectively protecting the radio frequency coil 320, preventing localized overheating.

[0028] In some embodiments, the angle between the axis of the laminar flow orifice 411 and the axis of the torch structure ranges from 30° to 60°, preferably 30°. By setting the angle between the axis of the laminar flow orifice 411 and the axis of the torch structure to a range of 30° to 60°, the airflow of cooling nitrogen has sufficient convergence and stable flow. Optionally, the diameter of the laminar flow orifice 411 ranges from 2mm to 6mm, preferably 2mm. If the diameter of the laminar flow orifice 411 is too large, the consumption of cooling nitrogen will be too large, which will easily disrupt the laminar flow state and form turbulence; if the diameter of the laminar flow orifice 411 is too small, it will easily lead to insufficient flow of cooling nitrogen.

[0029] Optionally, the number of laminar flow holes 411 is 6 to 30, preferably 12. If the number of laminar flow holes 411 is too small, it will cause discontinuity of the air curtain and dead zones in cooling; if the number of laminar flow holes 411 is too large, it will be difficult to process and the manufacturing cost will be high.

[0030] In some embodiments, the plasma external deposition apparatus further includes a first swirling gas generator 500 and a second swirling gas generator 600. The first swirling gas generator 500 includes a second gas storage chamber 510. The outer peripheral surface of the second gas storage chamber 510 has a plurality of first swirling holes 511. The first swirling holes 511 communicate with a second annular channel. The plurality of first swirling holes 511 are uniformly distributed along the circumference of the second gas storage chamber 510. The axis of the first swirling holes 511 is out of plane from the axis of the torch structure, and the axis of the first swirling holes 511 is set at an angle relative to the horizontal plane. This arrangement ensures that the argon and nitrogen gas introduced into the first swirling holes 511 simultaneously possess tangential velocity components and axial velocity components, thereby expanding the homogenization range of the introduced gas within the second annular channel.

[0031] In some embodiments, the second swirling gas generator 600 includes a third gas storage chamber 610. The outer peripheral surface of the third gas storage chamber 610 has a plurality of second swirling holes 611. The second swirling holes 611 communicate with a third annular channel. The plurality of second swirling holes 611 are uniformly distributed circumferentially along the second gas storage chamber 610. The axes of the second swirling holes 611 are out of plane with respect to the axis of the torch structure, and the axes of the second swirling holes 611 are set at an angle relative to the horizontal plane. This arrangement ensures that the oxygen introduced into the second swirling holes 611 simultaneously possesses both tangential velocity components and axial velocity components, thereby expanding the homogenization range of the introduced gas within the third annular channel.

[0032] Optionally, the angle between the axis of the first swirling orifice 511 and the horizontal plane is in the range of 30°-60°; the angle between the axis of the second swirling orifice 611 and the horizontal plane is in the range of 30°-60°. If the angle is too large, the range of swirling gas formed will not cover the axial direction of the torch structure sufficiently; if the angle is too small, the stability of the swirling gas will be poor.

[0033] Optionally, the projection of the axis of the first swirling orifice 511 onto the horizontal plane forms an angle of 30°-60° with the radial axis of the blowtorch structure; the projection of the axis of the second swirling orifice 611 onto the horizontal plane forms an angle of 30°-60° with the radial axis of the blowtorch structure. This angle represents the tangential offset angle of the swirling orifice relative to the radial direction of the blowtorch structure, thus ensuring sufficient convergence and stability of the swirling gas.

[0034] In some embodiments, the number of first swirl holes 511 is 6 to 30; the number of second swirl holes 611 is 6 to 30. If the number is too large, the density of swirl holes will be too high, reducing the structural strength, the airflow of a single hole will be insufficient, and the swirl intensity will decrease; if the number is too small, the swirl torque will be insufficient, and there will be gaps in the circumferential swirl field.

[0035] Optionally, the diameter of the first swirl orifice 511 is in the range of 2mm-6mm, preferably 2mm; the diameter of the second swirl orifice 611 is in the range of 2mm-6mm, preferably 2mm. If the orifice diameter is too small, the airflow in a single orifice will be insufficient; if the orifice diameter is too large, turbulence will be easily induced, leading to uncontrolled air pressure.

[0036] In some embodiments, the plasma external deposition apparatus further includes an oxygen-fluorine gas mixer 700, which includes a flow divider 710. The flow divider 710 has a plurality of flow divider holes 711 penetrating the upper and lower end faces. The plurality of flow divider holes 711 are uniformly distributed circumferentially along the flow divider 710. The axis of the flow divider 710 and the axis of the flow divider holes 711 are arranged out of plane, and the axis of the flow divider holes 711 is arranged at an angle relative to the horizontal plane. This arrangement ensures that the gas introduced into the flow divider holes 711 simultaneously possesses tangential velocity components and axial velocity components, thereby improving mixing uniformity.

[0037] Optionally, the angle between the axis of the diversion orifice 711 and the horizontal plane is in the range of 30°-60°. If the angle is too small, the diverted gas is prone to backflow dead zone; if the angle is too large, the tangential component of the diverted gas is weakened, making it difficult to form a uniform diversion.

[0038] Optionally, the angle between the projection of the axis of the diversion orifice 711 onto the horizontal plane and the radial direction of the axis of the diversion plate 710 is 30°-60°. This angle represents the radial tangential offset angle of the diversion orifice 711 relative to the diversion plate 710, thus providing sufficient converging ability and stability for the diverted gas.

[0039] Optionally, the thickness of the flow divider 710 is 10mm-20mm, preferably 10mm. If the flow divider 710 is too thin, it will cause the airflow direction to become unstable; if the flow divider 710 is too thick, the gas flow resistance will be large, and the flow divider hole 711 will be difficult to process.

[0040] In some embodiments, the bottom of the diverter plate 710 is connected to a central fluorine-oxygen conduit 1000 for conveying a mixture of oxygen and C2F6.

[0041] In some embodiments, the outer diameter of the first quartz tube 311 is 70mm-80mm; the outer diameter of the second quartz tube 312 is 60mm-70mm; the outer diameter of the third quartz tube 313 is 35mm-45mm; and the outer diameter of the fourth quartz tube 314 is 20mm-25mm. This facilitates control over the stability and morphology of the plasma flame 800. For example, the dimensions of the first quartz tube 311 can be set to 75mm (outer diameter) × 70mm (inner diameter) × 150mm (length); the dimensions of the second quartz tube 312 can be set to 60mm (outer diameter) × 55mm (inner diameter) × 300mm (length); the dimensions of the third quartz tube 313 can be set to 40mm (outer diameter) × 36mm (inner diameter) × 120mm (length); and the dimensions of the fourth quartz tube 314 can be set to 20mm (outer diameter) × 16mm (inner diameter) × 40mm (length). In other embodiments, the dimensions of the first quartz tube 311, the second quartz tube 312, the third quartz tube 313, and the fourth quartz tube 314 can also be set to other values, as needed. Of course, the sleeve assembly can also be designed as a five-layer sleeve structure to meet the requirements.

[0042] Optionally, the inner diameter of the RF coil 320 is 65mm-75mm, preferably 70mm, with 3 or 4 turns, preferably 4 turns. The diameter of the copper tube of the RF coil 320 is 6mm-10mm, preferably 8mm. The RF coil 320 is connected to an external RF oscillation cabinet. The RF source frequency of the RF coil 320 is 2MHz-5MHz, preferably 5MHz, and the RF power is 50kW-150kW, preferably 100kW. If the inner diameter of the RF coil 320 is too small, the gap between the RF coil 320 and the outer wall of the second quartz tube 312 will be too small, resulting in excessive heat load on the RF coil 320. If the inner diameter of the RF coil 320 is too large, it will reduce the plasma coupling efficiency. By setting the RF source frequency to 2MHz-5MHz and the RF power to 50kW-150kW, a high-density and stable plasma is ensured to guarantee the deposition rate.

[0043] Optionally, the target rod 10 is horizontally positioned, and the target rod 10 and the SiCl4 feed tube 330 are arranged parallel to each other. This ensures that the SiCl4 material is supplied uniformly along the axial direction of the target rod 10, improving deposition uniformity. Of course, in other embodiments, the SiCl4 feed tube 330 may also be arranged at an angle to the target rod 10, or the SiCl4 feed tube 330 may be located at a suitable position between the torch structure and the target rod 10, as long as it is ensured that the SiCl4 does not pass through the center of the plasma flame 800 when it is introduced from the top of the torch structure.

[0044] This embodiment also provides a plasma external deposition method, which is performed using the aforementioned plasma external deposition equipment. The plasma external deposition method includes the following steps: S1. Equipment installation and program debugging: Install target rod 10, write the corresponding deposition program, and turn on the cooling system to protect the oscillation cabinet; For example, the diameter of the target rod 10 can be in the range of 40mm-60mm. After confirming the specific diameter of the target rod 10, the corresponding deposition program is written. Since different diameters of the target rod 10 will affect process parameters such as RF power, torch spacing, and target rod 10 moving speed, the specific deposition program needs to be determined according to the diameter of the target rod 10.

[0045] S2. Equipment alignment, mechanism adjustment and pre-ventilation: Adjust the position of the target rod 10 and the torch structure, drive the ignition needle at the tip of the Tesla coil to the top of the torch structure, introduce nitrogen into the first annular channel to enhance the convection of the radio frequency coil 320, introduce argon into the second annular channel, and preload to prepare for ignition. For example, the height of the target rod 10 is adjusted by a lifting motor, thereby adjusting the relative position between the torch structure and the target rod 10. During ignition, the sudden excitation of the plasma generates high temperatures, which may affect the target rod 10. The distance between the torch structure and the target rod 10 can be adjusted to 40mm-120mm, preferably 100mm. The ignition needle at the tip of the Tesla coil is driven to the upper end of the torch structure by a cylinder, and the distance between the ignition needle and the torch structure is within 10mm. Optionally, the nitrogen flow rate is 100SLM-200SLM, preferably 100SLM.

[0046] S3. Equipment preheating and plasma ignition: Start the oscillating cabinet, connect the filament power supply for preheating, and after the filament preheating is completed, connect the anode high voltage and increase the voltage to the preset voltage. After the voltage stabilizes, start the Tesla coil igniter to complete the ignition. After the plasma flame stabilizes at 800, return the igniter to its original position. For example, the preset voltage can be set to 5kV. After the plasma flame 800 stabilizes, the igniter is returned to its original position to prevent it from affecting the translation of the machine tool platform 900.

[0047] S4. Process atmosphere switching and target rod 10 preheating: After ignition, the argon gas in the second annular channel is gradually replaced with nitrogen gas, and oxygen gas is gradually introduced into the third annular channel. During the gas adjustment process, the power of the radio frequency source is gradually increased. During the preheating process, the moving speed of the target rod 10 is gradually reduced, and the distance between the torch structure and the target rod 10 is gradually reduced as the preheating process progresses. During the preheating process, the distance between the torch structure and the target rod 10 is reduced in a stepwise manner. For example, the flow rate of nitrogen is 50SLM-100SLM, preferably 50SLM; the flow rate of oxygen is 50SLM-100SLM, preferably 50SLM; the power of the radio frequency source is 50kW-150kW, and the preheating power of the target rod 10 is preferably 100kW; during the preheating process, the moving speed of the target rod 10 is 200mm / min-800mm / min; the distance between the top of the torch structure and the target rod 10 is 40mm-120mm; after preheating, the distance between the target rod 10 on the top of the torch structure is 60mm; after preheating, the temperature range of the plasma flame 800 contact area is maintained at 1650℃-1800℃.

[0048] S5, Target Rod 10 Polishing, Fluorine Doping, and Silica Deposition: After preheating, the surface of the target rod 10 is polished. A mixture of oxygen and C2F6 is introduced into the central gas pipe to polish the surface of the target rod 10. After the polishing process is completed, SiCl4 raw material is introduced into the plasma flame 800 through the SiCl4 material pipe 330. In the top area of ​​the torch structure, SiCl4 and oxygen react to generate SiO2 particles. In the contact area between the plasma flame 800 and the target rod 10, a non-equilibrium chemical reaction occurs. The highly active fluorine groups and SiO2 vapor particles in the plasma flame 800 are rapidly cooled and deposited on the surface of the target rod 10, completing the glass deposition process. For example, the oxygen flow rate is 5-10 slm, preferably 10 slm, and the C2F6 flow rate is 200-2000 slm, preferably 500 slm. After the oxygen and C2F6 are introduced, the plasma flame 800 broadens, polishing the surface of the target rod 10 to remove surface defects and impurities. Optionally, the SiCl4 flow rate is 2-10 slm, preferably 5 slm. During the deposition process, the temperature range of the deposition zone is 1550℃-1650℃. Optionally, during the movement of the target rod 10, after each deposition, a diameter gauge records the diameter change of the target rod 10.

[0049] S6. Process Termination, Annealing and Cooling, and Finished Product Discharge: When the diameter of the target rod 10 is detected by the diameter gauge to reach the process set standard value, the silicon material (SiCl4) and oxygen-fluorine mixed gas (mixed oxygen and C2F6) are stopped in the turning area to terminate the deposition reaction. The system automatically starts the annealing program to perform annealing and stabilization treatment on the deposited target rod 10 to eliminate internal stress annealing. After the annealing process is completed, the equipment automatically completes the pressure reduction, arc extinguishing, and shutdown operations. After the equipment and target rod 10 are naturally cooled, qualified fluorine-doped preform finished products can be obtained.

[0050] For example, the temperature of the contact area between the plasma flame 800 and the target rod 10 is maintained at 1400℃-1600℃, and the annealing process is completed by multiple step annealing processes.

[0051] The plasma external deposition method provided in this embodiment, since the SiCl4 feed tube 330 is located at the top of the second quartz tube 312 (i.e., the top of the torch structure), and the SiCl4 does not pass through the center of the plasma flame 800, the plasma flame 800 will not be affected by the increased SiCl4 flux, thus removing the limitations of radio frequency power and SiCl4 flux. As a strongly electronegative gas, C2F6 can effectively obtain energy from the plasma and generate a large number of high-energy active groups when introduced from the bottom. These groups combine with SiO2 generated by the reaction of SiCl4 and O2 at the top of the torch structure to undergo a non-equilibrium reaction, thereby achieving the deposition of highly concentrated fluorine-doped silica glass and improving the deposition rate and deposition efficiency.

[0052] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A plasma external deposition apparatus, characterized in that, include: A housing (100) is provided inside the housing (100); A base (200) is disposed at the bottom of the housing (100). A blowtorch structure is disposed on the base (200). The blowtorch structure includes a sleeve assembly, an RF coil (320), and a SiCl4 tube (330). The sleeve assembly includes a first quartz tube (311), a second quartz tube (312), a third quartz tube (313), and a fourth quartz tube (314) sequentially sleeved from the outside to the inside. The first quartz tube (311) and the second quartz tube (312) form a first... An annular channel is formed, wherein the first annular channel is used to introduce nitrogen gas, the second quartz tube (312) and the third quartz tube (313) form a second annular channel for introducing argon and nitrogen gas, the third quartz tube (313) and the fourth quartz tube (314) form a third annular channel for introducing oxygen gas, and the fourth quartz tube (314) has a central gas pipe for introducing oxygen and C2F6; wherein, The upper end of the second quartz tube (312) protrudes from the first quartz tube (311), the third quartz tube (313), and the fourth quartz tube (314). The SiCl4 material tube (330) is disposed on the top of the second quartz tube (312). The radio frequency coil (320) is sleeved on the upper end of the second quartz tube (312). With the energy of the radio frequency coil (320), the second quartz tube (312) can be excited and ejected with plasma flame (800). The target rod (10) is disposed above the SiCl4 material tube (330).

2. The plasma external deposition apparatus according to claim 1, characterized in that, The plasma external deposition apparatus further includes a cooling nitrogen laminar flow generator (400), which includes a first gas storage chamber (410). The outer peripheral surface of the first gas storage chamber (410) has a plurality of laminar flow holes (411). The laminar flow holes (411) are connected to the first annular channel. The plurality of laminar flow holes (411) are evenly distributed along the circumference of the first gas storage chamber (410). The axis of the laminar flow holes (411) is coplanar with the axis of the torch structure and is set at an angle.

3. The plasma external deposition apparatus according to claim 2, characterized in that, The angle between the axis of the laminar flow orifice (411) and the axis of the torch structure is in the range of 30°-60°; the diameter of the laminar flow orifice (411) is in the range of 2mm-6mm.

4. The plasma external deposition apparatus according to claim 1, characterized in that, The plasma external deposition apparatus further includes a first swirling gas generator (500) and a second swirling gas generator (600). The first swirling gas generator (500) includes a second gas storage chamber (510). The outer peripheral surface of the second gas storage chamber (510) has a plurality of first swirling holes (511). The first swirling holes (511) are connected to the second annular channel. The plurality of first swirling holes (511) are evenly distributed along the circumference of the second gas storage chamber (510). The axis of the first swirling hole (511) and the axis of the torch structure are arranged on opposite sides, and the axis of the first swirling hole (511) is set at an angle relative to the horizontal plane. The second swirling gas generator (600) includes a third gas storage chamber (610). The outer peripheral surface of the third gas storage chamber (610) has a plurality of second swirling holes (611). The second swirling holes (611) are connected to the third annular channel. The plurality of second swirling holes (611) are evenly distributed along the circumference of the second gas storage chamber (510). The axis of the second swirling hole (611) is arranged opposite to the axis of the torch structure, and the axis of the second swirling hole (611) is arranged at an angle relative to the horizontal plane.

5. The plasma external deposition apparatus according to claim 4, characterized in that, The angle between the axis of the first swirling hole (511) and the horizontal plane is in the range of 30°-60°; the angle between the axis of the second swirling hole (611) and the horizontal plane is in the range of 30°-60°.

6. The plasma external deposition apparatus according to claim 1, characterized in that, The plasma external deposition equipment also includes an oxygen-fluorine gas mixing generator (700), which includes a flow divider plate (710). The flow divider plate (710) has a plurality of flow divider holes (711) penetrating the upper and lower end faces. The plurality of flow divider holes (711) are evenly distributed along the circumference of the flow divider plate (710). The axis of the flow divider plate (710) and the axis of the flow divider holes (711) are arranged on opposite sides, and the axis of the flow divider holes (711) is set at an angle relative to the horizontal plane.

7. The plasma external deposition apparatus according to claim 6, characterized in that, The angle between the axis of the diversion hole (711) and the horizontal plane is in the range of 30°-60°.

8. The plasma external deposition apparatus according to claim 1, characterized in that, The target rod (10) is horizontally arranged, and the target rod (10) and the SiCl4 material tube (330) are arranged parallel to each other.

9. The plasma external deposition apparatus according to claim 1, characterized in that, The outer diameter of the first quartz tube (311) is 70mm-80mm; the outer diameter of the second quartz tube (312) is 60mm-70mm; the outer diameter of the third quartz tube (313) is 35mm-45mm; and the outer diameter of the fourth quartz tube (314) is 20mm-25mm. The inner diameter of the radio frequency coil (320) is 65mm-75mm, and the number of turns is 3 or 4. The diameter of the copper tube of the radio frequency coil (320) is 6mm-10mm. The radio frequency source frequency of the radio frequency coil (320) is 2MHz-5MHz, and the radio frequency power is 50kW-150kW.

10. A plasma external deposition method, characterized in that, The plasma external deposition method is performed using the plasma external deposition apparatus as described in any one of claims 1-9, and includes the steps of: S1. Equipment installation and program debugging: Install the target rod (10), write the corresponding deposition program, and turn on the cooling system to protect the oscillation cabinet; S2. Equipment alignment, mechanism adjustment and pre-ventilation: Adjust the position of the target rod (10) and the torch structure, drive the Tesla coil tip ignition needle to the top of the torch structure, introduce nitrogen into the first annular channel, introduce argon into the second annular channel, and preload to prepare for ignition. S3. Equipment preheating and plasma ignition: Start the oscillating cabinet, connect the filament power supply for preheating, after the filament preheating is completed, connect the anode high voltage and increase the voltage to the preset voltage. After the voltage stabilizes, start the Tesla coil igniter to complete the ignition. After the plasma flame (800) stabilizes, return the igniter to its original position. S4. Process atmosphere switching and target rod (10) preheating: After ignition, argon in the second annular channel is gradually replaced with nitrogen, and oxygen is gradually introduced into the third annular channel. During the gas adjustment process, the power of the radio frequency source is gradually increased. During the preheating process, the moving speed of the target rod (10) is gradually reduced, and the distance between the torch structure and the target rod (10) is reduced stepwise. S5. Polishing, fluorine doping, and silica deposition of target rod (10): After preheating, the surface of the target rod (10) is polished. Mixed oxygen and C2F6 are introduced into the central gas pipe to polish the surface of the target rod (10). After the polishing process is completed, SiCl4 raw material is introduced into the plasma flame (800) through the SiCl4 material pipe (330). In the top area of ​​the torch structure, SiCl4 and oxygen react to generate SiO2 particles. In the contact area between the plasma flame (800) and the target rod (10), a non-equilibrium chemical reaction occurs. The highly active fluorine groups and SiO2 vapor particles in the plasma flame (800) are rapidly cooled and deposited on the surface of the target rod (10) to complete the glass deposition process. S6. Process termination, annealing and cooling and finished product discharge: When the diameter of the target rod (10) is detected by the diameter measuring instrument to reach the process set standard value, the silicon material and oxygen-fluorine mixed gas are stopped in the turning area to terminate the deposition reaction. The system automatically starts the annealing program to perform annealing and stabilization treatment on the deposited target rod (10) to eliminate internal stress annealing. After the annealing process is completed, the equipment automatically completes the pressure reduction, arc extinguishing and shutdown operations. After the equipment and the target rod (10) are naturally cooled, qualified fluorine-doped preform finished product can be obtained.

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