CN210326075U

CN210326075U - Split type easily-tuned microwave resonant cavity suitable for PCVD (plasma chemical vapor deposition) process

Info

Publication number: CN210326075U
Application number: CN201921368082.XU
Authority: CN
Inventors: 连海洲; 吴海华
Original assignee: PNC Process Systems Co Ltd
Current assignee: PNC Process Systems Co Ltd
Priority date: 2019-08-21
Filing date: 2019-08-21
Publication date: 2020-04-14
Anticipated expiration: 2029-08-21

Abstract

The utility model discloses a split type easy-tuning microwave resonant cavity suitable for PCVD process, which comprises a cavity body with an opening and a cavity cover which is detachably buckled on the opening of the cavity body and is used for forming a closed cavity between the cavity body and the cavity cover, wherein the side wall of the cavity body is provided with a waveguide inlet which is used for enabling microwave coupling to enter the closed cavity; the inner wall of the cavity is provided with a first coaxial ring which extends along the axial direction and is used for inserting one end of the glass base tube, the inner wall of the cavity cover is provided with a second coaxial ring which extends along the axial direction and is used for inserting the other end of the glass base tube, the end face of the tail end of the first coaxial ring is opposite to the end face of the tail end of the second coaxial ring, and a radiation slit for the resonant microwave to pass through is reserved between the first coaxial ring and the second coaxial ring. The utility model discloses a dismouting changes the axial length that the chamber lid of different inner wall surface thickness changes closed cavity on the cavity, realizes the resonant frequency tuning operation of microwave cavity, guarantees that the microwave can start smoothly in closed cavity to vibrate for resonant frequency keeps matching with the plasma load.

Description

Split type easily-tuned microwave resonant cavity suitable for PCVD (plasma chemical vapor deposition) process

Technical Field

The utility model relates to a PCVD technical field, in particular to split type easy harmonious microwave cavity suitable for PCVD technology.

Background

The PCVD (Plasma Chemical Vapor Deposition) process technology is the main process technology for manufacturing optical fiber preforms.

Among them, the microwave plasma system is a part unique to the process and different from other processes, and is a core part thereof. The microwave plasma system consists of a microwave generator, a waveguide device and a microwave resonant cavity, wherein the waveguide device transmits electromagnetic wave energy generated by the microwave generator to the microwave resonant cavity, the microwave resonant cavity resonates the input electromagnetic wave and transmits high-frequency microwave energy to a PCVD process deposition area so as to finish the deposition process of the PCVD process.

Currently, the microwave cavity used to perform the PCVD process generally employs a cylindrical or coaxial cavity to ensure uniformity of the deposited glass. The coaxial resonant cavity has the advantages of simple oscillation mode and stable field structure, is convenient to tune, easy to start oscillation, easy to process and manufacture, and is formed by a section of coaxial line with fixed length and two short-circuited ends, and the axial length of the coaxial resonant cavity is generally an integral multiple of half wavelength, such as lambda/2. The structural design of the resonant cavity is very important, and the unreasonable structural size not only can influence the coupling effect, cause the loss of microwave energy and influence the processing precision of the PCVD process, but also can easily damage microwave devices and influence the production process. Since the microwave resonant cavity for performing the PCVD process performs high-speed reciprocating motion in a high-temperature environment of about 1200 ℃, it is very difficult to install a reliable tuning device in the resonant cavity, and therefore, in the actual production of the PCVD process, the microwave resonant cavity is mostly non-tunable, the structural size of the cavity is fixed, which will have very high requirements on the resonant frequency and the processing precision of the resonant cavity.

In actual production, shape deviation, machining size deviation, inner surface conductivity coefficient of the inner surface of the resonant cavity, the depth of the coupling probe (antenna) inserted into the resonant cavity and the like all affect the resonant frequency of the resonant cavity, so that the electromagnetic wave is difficult to start oscillation in the cavity, or the microwave resonant frequency is not matched with the plasma load. Therefore, in practice, it is necessary to perform thermal testing of microwave transmission, and repeatedly modify and process the structural dimensions of the resonant cavity for many times to finally complete a qualified resonant cavity meeting the deposition requirements of the PCVD process. However, the microwave resonant cavities in the prior art are all of an integral mounting structure, which is difficult to easily adjust the structural size of the microwave resonant cavity, and the adjustment easily causes corresponding changes in the sizes of other structures with connection relations, and the adjustment process needs to be very careful, so that the whole thermal test process of microwave transmission is very complicated, the processing amount is very large, and the efficiency is very low.

Therefore, how to simply and conveniently realize the tuning operation of the microwave resonant cavity, ensure the smooth oscillation of the microwave in the resonant cavity, and keep the matching of the resonant frequency and the plasma load is a technical problem faced by those skilled in the art.

SUMMERY OF THE UTILITY MODEL

The utility model aims at providing a split type easy tuning microwave cavity suitable for PCVD technology can realize the tuning operation to the microwave cavity simply conveniently, guarantees that the microwave starts to vibrate smoothly in the cavity, and resonant frequency keeps matching with the plasma load.

In order to solve the technical problem, the utility model provides a split type easy-tuning microwave resonant cavity suitable for PCVD technology, which comprises a cavity body with an opening and a cavity cover detachably buckled on the opening of the cavity body and used for forming a closed cavity between the cavity body and the cavity cover, wherein the side wall of the cavity body is provided with a waveguide inlet used for enabling microwave coupling to enter the closed cavity;

the inner wall of the cavity is provided with a first coaxial ring which extends along the axial direction and is used for inserting one end of the glass base tube, the inner wall of the cavity cover is provided with a second coaxial ring which extends along the axial direction and is used for inserting the other end of the glass base tube, the end face of the tail end of the first coaxial ring is opposite to the end face of the tail end of the second coaxial ring, and a radiation slit for the resonant microwave to pass through is reserved between the first coaxial ring and the second coaxial ring.

Preferably, a plurality of cooling water cavities distributed annularly are formed in the side wall of the cavity along the axial direction of the cavity, and water inlets and water outlets communicated with the cooling water cavities to form a circulating water path are formed in the side wall of the cavity.

Preferably, water collecting circular channels communicated with the water inlet and the water outlet are formed in the end faces of the two ends of the cavity along the circumferential direction, pipe orifices of the two ends of each cooling water cavity are communicated with the corresponding water collecting circular channels respectively, and liquid sealing is achieved on each water collecting circular channel through a sealing ring installed on the end face of the cavity.

Preferably, a plurality of mounting holes are formed in the outer end face of each cavity cover along the circumferential direction of the cavity cover, and each cavity cover is detachably connected with the inner end face of the cavity through fasteners mounted in the mounting holes.

Preferably, the inner diameter and the outer diameter of the first coaxial ring and the second coaxial ring are equal, and the central axes of the first coaxial ring and the second coaxial ring are collinear.

Preferably, the inner diameter of the closed cavity is 80-120 mm, and the outer diameters of the first coaxial ring and the second coaxial ring are 40-60 mm; the extension length of the first coaxial ring is 30-33 mm, the extension length of the second coaxial ring is 18-22 mm, and the width of the radiation slit is 10-14 mm.

Preferably, the inner surface of the closed cavity is provided with a coating for reducing microwave loss.

The utility model provides a split type easy harmonious microwave cavity suitable for PCVD technology mainly includes cavity and chamber lid. The cavity is a main structure of the microwave resonant cavity and is provided with an opening, the cavity cover is buckled on the opening of the cavity, and the cavity cover and the cavity are buckled to form a closed cavity in the middle to serve as a resonant cavity, namely a microwave resonant place. The side wall of the cavity is provided with a waveguide inlet which is used as a channel for microwave coupling to enter the closed cavity. Simultaneously, set up the first coaxial ring that extends along the axial on the inner wall of cavity, set up the second coaxial ring that extends along the axial on the inner wall of chamber lid, these two glass parent tubes that are used for cartridge PCVD technology jointly. And the first coaxial ring and the second coaxial ring are not in contact, the end faces of the two coaxial rings are opposite to each other, and a radiation slit is reserved for the microwave resonant in the closed cavity to pass through, and then the microwave is radiated into the glass substrate tube through the radiation slit to activate and ionize the gas mixture in the glass substrate tube to form non-equilibrium plasma, so that the PCVD process is realized. Importantly, the whole microwave resonant cavity is of a split structure, the cavity cover is detachably connected with the cavity, and the cavity cover can be conveniently installed and detached on the cavity, so that the corresponding cavity cover is selectively installed on the cavity, the axial length of the formed closed cavity is changed by replacing the cavity covers with different inner wall surface thicknesses, the axial length of the closed cavity is matched with the half-wave resonant wavelength of the microwave, and the resonant frequency tuning operation of the microwave resonant cavity is realized. To sum up, the utility model provides a split type easy harmonious microwave cavity suitable for PCVD technology changes the axial length of the closed cavity that forms between the two through the mode of the chamber lid of dismouting change different inner wall surface thickness on the cavity, realizes the resonant frequency tuning operation of microwave cavity, guarantees that the microwave can shake smoothly in closed cavity for resonant frequency and plasma load keep matching.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.

Fig. 1 is a schematic overall structure diagram of a specific embodiment of the present invention.

Fig. 2 is a cross-sectional view of the chamber shown in fig. 1.

Wherein, in fig. 1-2:

a cavity-1, a cavity cover-2, a waveguide inlet-3, a radiation slit-4 and a fastener-5;

the water cooling device comprises a first coaxial ring-101, a cooling water cavity-102, a water inlet and outlet-103, a water collecting ring channel-104, a sealing ring-105 and a second coaxial ring-201.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.

Referring to fig. 1, fig. 1 is a schematic diagram of an overall structure of an embodiment of the present invention.

In a specific embodiment provided by the present invention, the split type easily tunable microwave resonant cavity suitable for PCVD process mainly includes a cavity 1 and a cavity cover 2.

The cavity 1 is a main structure of the microwave resonant cavity and is provided with an opening, the cavity cover 2 is buckled on the opening of the cavity 1, and a closed cavity is formed in the middle after the cavity cover and the cavity are buckled to serve as a microwave resonant place. The side wall of the cavity 1 is provided with a waveguide inlet 3 which is used as a channel for microwave coupling to enter the closed cavity.

Meanwhile, the inner wall of the cavity 1 is provided with a first coaxial ring 101 extending along the axial direction, and the inner wall of the cavity cover 2 is provided with a second coaxial ring 201 extending along the axial direction, and the first coaxial ring and the second coaxial ring are used for being inserted into a glass base tube of a PCVD (plasma chemical vapor deposition) process. And the first coaxial ring 101 and the second coaxial ring 201 are not in contact, the end faces of the two coaxial rings are opposite to each other, and a radiation slit 4 is reserved for the microwave resonant in the closed cavity to pass through, and then the microwave is radiated into the glass substrate tube through the radiation slit 4, and the gas mixture in the glass substrate tube is activated and ionized to form non-equilibrium plasma, so that the PCVD process is realized.

Importantly, the whole microwave resonant cavity is of a split structure, the cavity cover 2 is detachably connected with the cavity 1, the cavity cover 2 can be conveniently installed and detached on the cavity 1, the corresponding cavity cover 2 is selectively installed on the cavity 1, the axial length of the formed closed cavity is changed by replacing the cavity covers 2 with different inner wall surface thicknesses, the axial length of the closed cavity is matched with the half-wave resonant length of the microwave, and the resonant frequency tuning operation of the microwave resonant cavity is further realized.

In summary, the split type easily tunable microwave resonant cavity suitable for the PCVD process provided by this embodiment changes the axial length of the closed cavity formed between the cavity 1 and the cover 2 by dismounting and replacing the cavity cover with different inner wall surface thicknesses, so as to realize the resonant frequency tuning operation of the microwave resonant cavity, ensure that the microwave can start to vibrate smoothly in the resonant cavity, and keep the resonant frequency matched with the plasma load.

As shown in fig. 1, the axial length L of the microwave resonant cavity is equal to a + b + t, where a is the extension length of the first coaxial ring 101, b is the extension length of the second coaxial ring 201, t is the width of the radiation slit 4, and the b dimension is related to the c dimension, which is the adjustable dimension, the c dimensions of the different cavity covers 2 are different, and the larger the surface thickness of the inner concave surface of the cavity cover 2, the smaller the c dimension, and vice versa. Generally, the a-dimension is in the range of 30 to 33mm, the b-dimension is in the range of 18 to 22mm, the t-dimension is in the range of 10 to 14mm, and the c-dimension is in the range of 0 to 4 mm. Meanwhile, the outer diameters of the first coaxial ring 101 and the second coaxial ring 201 are 40-60 mm, the central axes of the first coaxial ring and the second coaxial ring are collinear, and the inner diameter of the closed cavity can be 80-120 mm.

In a specific embodiment, in order to conveniently realize the thickness adjustment of the inner wall surface of the cavity cover 2, after the cavity cover 2 is detached from the cavity 1, the surface of the inner concave surface of the cavity cover 2 is subjected to simple surface treatment such as surface scraping or grinding, so that the surface thickness of the inner concave surface of the cavity cover 2 can be gradually reduced, and the c size value and the b size value are increased. Of course, this adjustment method can only adjust the thickness of the inner wall surface of the cavity cover 2 in one direction, so that the thickness of the inner wall surface is gradually reduced.

In addition, the microwave resonant cavity can generate heat in the operation process, and in order to ensure the long-term stable working condition of the microwave resonant cavity, a cooling structure is additionally arranged on the cavity 1 in the embodiment.

As shown in fig. 2, fig. 2 is a cross-sectional view of the chamber 1 shown in fig. 1.

Specifically, a plurality of cooling water cavities 102 are formed in the side wall of the cavity 1, and each cooling water cavity 102 is distributed along the axial direction of the cavity 1, and the cooling water cavities 102 are distributed in the side wall of the cavity 1 in an annular shape as a whole. Meanwhile, the embodiment further provides 2 water inlets and outlets 103 at the preset positions on the sidewall of the cavity 1, wherein one of the water inlets and outlets 103 is used as a water inlet, the other water inlet and outlet is used as a water outlet, and both the water inlets and outlets are communicated with the cooling water cavities 102. Thus, after being introduced from the outside, the cooling water can enter each cooling water cavity 102 through one of the water inlet/outlet 103, and after absorbing heat generated by the microwave resonant cavity in the process of flowing through, the cooling water flows out from the other water inlet/outlet 103, then is cooled to the outside, and flows back to the first water inlet/outlet 103 again, so that the circulating flow of the cooling water is realized. Of course, since the waveguide inlet 3 is further opened on the side wall of the cavity 1, the opening position of the cooling water cavity 102 needs to avoid the waveguide inlet 3.

Further, in order to improve the flowing efficiency of the cooling water in the cavity 1, the water collecting ring 104 is circumferentially provided on the end surfaces of the two ends of the cavity 1. The distribution area of the water collecting loop 104 is overlapped with the distribution area of the pipe orifice of each cooling water cavity 102, the pipe orifice of each cooling water cavity 102 is communicated with the corresponding water collecting loop 104, and the water collecting loop 104 is also communicated with the water inlet and outlet 103, so that the cooling water flows along the circumferential direction after entering from the water inlet and outlet 103, is filled with one water collecting loop 104 firstly, then enters into each cooling water cavity 102 respectively in the circumferential flow process, then is collected into the other water collecting loop 104, and flows out from the other water inlet and outlet 103.

In order to ensure the liquid tightness of the chamber 1, the sealing rings 105 are mounted on the inner and outer end surfaces of the chamber 1. Specifically, the sealing ring 105 is welded on the end face of the cavity 1 and is pressed on the opening of the water collecting ring 104, so that the cooling water in the water collecting ring 104 is prevented from leaking when flowing in the circumferential direction, and the liquid tightness is ensured.

In addition, in order to conveniently realize the dismounting and replacement of the cavity cover 2 on the cavity 1, in the embodiment, a plurality of mounting holes are formed on the outer end face of each cavity cover 2 along the circumferential direction of the cavity cover, so that the cavity cover 2 and the cavity 1 are tensioned and fixed under the action of the fastening piece 5. Generally, the fastener 5 can adopt standard parts such as bolts and the like, and is convenient to disassemble and assemble.

In addition, in order to reduce the microwave loss of the microwave resonant cavity in the operation process, the inner surface of the closed cavity is provided with a coating layer. Specifically, the coating is a silver coating.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. The split type easily-tuned microwave resonant cavity suitable for the PCVD process is characterized by comprising a cavity body (1) with an opening and a cavity cover (2) which is detachably buckled on the opening of the cavity body (1) and is used for forming a closed cavity between the cavity body and the cavity cover, wherein a waveguide inlet (3) used for coupling microwaves into the closed cavity is formed in the side wall of the cavity body (1);

the inner wall of the cavity body (1) is provided with a first coaxial ring (101) which extends along the axial direction and is used for inserting one end of the glass base tube, the inner wall of the cavity cover (2) is provided with a second coaxial ring (201) which extends along the axial direction and is used for inserting the other end of the glass base tube, the end face of the tail end of the first coaxial ring (101) is opposite to the end face of the tail end of the second coaxial ring (201), and a radiation slit (4) for the resonant microwave to pass through is reserved between the first coaxial ring and the second coaxial ring.

2. The split type easy-tuning microwave resonant cavity suitable for the PCVD process according to claim 1, characterized in that a plurality of cooling water cavities (102) distributed annularly are opened in the side wall of the cavity (1) along the axial direction thereof, and a water inlet and a water outlet (103) communicated with each cooling water cavity (102) to form a circulating water path are opened on the side wall of the cavity (1).

3. The split type easy-tuning microwave resonant cavity suitable for the PCVD process according to claim 2, characterized in that the end surfaces of the two ends of the cavity (1) are respectively provided with a water collecting loop (104) communicated with the water inlet and outlet (103) along the circumferential direction, the pipe orifices of the two ends of each cooling water cavity (102) are respectively communicated with the corresponding water collecting loops (104), and the water collecting loops (104) are respectively sealed by a sealing ring (105) arranged on the end surface of the cavity (1).

4. The split type easy-tuning microwave resonant cavity suitable for the PCVD process according to claim 1, characterized in that a plurality of mounting holes are opened on the outer end surface of each cavity cover (2) along the circumferential direction thereof, and each cavity cover (2) is detachably connected with the inner end surface of the cavity (1) through fasteners (5) installed in the mounting holes.

5. The split type tunable microwave resonator suitable for a PCVD process according to claim 1, wherein the inner and outer diameters of the first coaxial ring (101) and the second coaxial ring (201) are equal, and the central axes thereof are collinear.

6. The split type easy-tuning microwave resonant cavity suitable for the PCVD process in accordance with claim 5, wherein the inner diameter of the closed cavity is 80-120 mm, and the outer diameters of the first coaxial ring (101) and the second coaxial ring (201) are both 40-60 mm; the extension length of the first coaxial ring (101) is 30-33 mm, the extension length of the second coaxial ring (201) is 18-22 mm, and the width of the radiation slit (4) is 10-14 mm.

7. The split, easy-tuning microwave resonator suitable for PCVD processes according to claim 1, wherein the inner surface of the closed cavity is provided with a coating for reducing microwave loss.