JPH0554805A - Magnetron - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a liquid cooling type magnetron which can be continuously used in a clean room suitable for a plasma etching apparatus for semiconductor manufacturing and which can be easily mass-produced. [Structure] The cathode in the center of the tube is surrounded by a group of cavity resonators formed by an anode cylinder and a plurality of vanes protruding from the inner wall of the anode cylinder, and both ends of the anode cylinder are in contact with a magnetic pole and a magnetic pole flange portion, respectively. In a magnetron equipped with a circularly arranged permanent magnet and a yoke that adheres to the outer surface of the permanent magnet in the axial direction of the tube to form an external magnetic circuit, the magnetron is cooled inside a solid body having high thermal conductivity. The cooling block in which the flow passage of the medium for use was formed was installed so as to be in close contact with almost the entire outer peripheral wall surface of the anode cylinder and to be in thermal contact with part of each of the permanent magnet and the yoke.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention cools not only an anode cylinder, which is a heat generating portion, but also a magnetic member such as a permanent magnet or a yoke by a cooling block in which a liquid refrigerant flows so as to suppress characteristic changes due to temperature rise. A magnetron plasma etching device for semiconductor processing that uses microwaves, which does not disturb air and scatters dust, and has little characteristic change, that is, a decrease in microwave output power, even when used continuously for a long time in a dust-free room of a factory. For example, the present invention relates to a liquid cooling type magnetron.

[0002]

2. Description of the Related Art When a magnetron operates, heat loss occurs in the anode. Therefore, the temperature rise of the anode due to the above heat loss must be suppressed to the extent that it can be actually used by forced air cooling or liquid cooling. I have to. In a magnetron for a microwave oven, which is very often used, a plurality of radiator fins are press-fitted into an anode cylinder as disclosed in, for example, JP-A-63-81734, and the radiator fins are fitted. A forced air cooling system in which air is cooled by a blower has been preferred and used. Figure 2
Is a cross-sectional view of a plane including the tube axis of a conventional magnetron of this type, in which 1 is a filament cathode in which a thoria-containing tungsten wire is wound in a helix shape, 2 is an anode cylinder, 3
Is a vane radially protruding from the inner wall of the anode cylinder, 4 is a magnetic pole made of a soft ferromagnetic material for forming a static magnetic field in the tube axial direction in the working space surrounded by the cathode and the end of the vane, 5 is a permanent magnet,
Reference numeral 6 is a yoke that connects the magnets arranged at both ends of the anode cylinder to form a magnetic circuit (a radiator fin is fitted to the anode cylinder of the magnetron body whose interior has been evacuated to a vacuum, and the magnetic poles at both ends of the anode cylinder are flat. For convenience of assembly work after mounting permanent magnets on the flanges respectively, they are separated into upper and lower parts. 7 is a radiator fin, 10 is a microwave power output part, and 11 is microwave power on a cathode heating conductor. A filter case 12 for housing a filter for preventing leakage to the external commercial AC power source side is connected to the commercial AC power source by a cathode heating lead wire. The magnetron adopts the forced air cooling system because the liquid cooling system is troublesome and troublesome for household use even if normal water is used as the cooling liquid.
The output of such a magnetron is less than 5 kW. On the other hand, high power magnetrons for industrial heating with output of 5 kW or more and radar magnetrons of the type used for ultra-high power for a very short period of time also use a liquid cooling method in which the anode is cooled with a liquid refrigerant. is there. In these liquid cooling type magnetrons, for example, as shown in FIG. 3, a cooling pipe 13 for flowing a cooling liquid is wound around the outer circumference of the anode cylinder,
By brazing, or as shown in FIG. 4, the cylindrical hollow member 14 is installed in place of the cooling tube by closely contacting with the outer periphery of the anode cylinder,
It has an inlet and outlet for the cooling liquid at appropriate positions and directions, and there is no pipe line inside, but it is easier to manufacture than when the cooling pipe is wound so that the cooling liquid appropriately circulates around the anode cylinder. There were things that were aimed at becoming. In the case of the high power output magnetron that has conventionally used the liquid cooling method, the anode, which is the main heat source during microwave oscillation operation, is usually liquid cooled with a cooling liquid, and an electromagnet for static magnetic field formation or A method of cooling the cathode filament terminal portion by forced air cooling has been adopted.

[0003]

In recent years, a plasma etching apparatus or a plasma asher apparatus, for example, which is suitable for semiconductor manufacturing, has been developed and utilized, in which plasma is generated by microwave and used as an ion source having a large mass. ing. The microwave power used in these devices is often about 1 kW to 3 kW, and an output located just between the microwave oven magnetron and the industrial heating magnetron is used. Previously, no output magnetron suitable for these devices was produced, and a 5 kW-class magnetron for microwave ovens and industrial heating was used.

However, the main products of semiconductor manufacturing are ULSI and VLS in which about 1 million extremely fine elements are integrated.
As the so-called minimum line width becomes about μm or less, it becomes difficult to cope with the wet etching.
The demand for dry-type magnetron plasma etching equipment has increased rapidly. On the other hand, the plasma etching equipment for semiconductor manufacturing is used in a clean room, but the forced air cooling type magnetron is not suitable for use in a clean room because the cooling air scatters minute foreign matter. However, the liquid cooling method is unavoidable. Further, in the case of industrial use such as semiconductor manufacturing, unlike the case of domestic use, there is no problem in liquid cooling itself. In order to meet such demand, for example, as Japanese Patent Application No. 3-49347, a magnetron for a microwave oven is diverted from the main body of a magnetron evacuated to a vacuum, and the cooling method is changed from forced air cooling to liquid cooling. A changed one is proposed. A side view of the magnetron according to this proposal is shown in FIG. 5A, in which 5 is a permanent magnet, 6 is a yoke,
10 is a microwave power output unit, 11 is a filter case,
Reference numeral 12 is a cathode heating lead wire, 15 is a cooling block according to the above proposal, and 15a and 15b are inlets and outlets of a cooling liquid to and from the cooling block. FIG. 5B is a perspective view showing the cooling block 15 used in this magnetron.
Is a blind plug for closing an unnecessary opening formed at the time of processing after forming the flow path of the cooling liquid inside the cooling block 15, and other symbols are the same as those in FIG. 5 (a). .. Such a cooling block 15 was provided at one position around the hole after the cooling hole bored in the center of the block was fitted into the anode cylinder of the magnetron as shown in FIG. 5B. Tighten the screws from both sides of the notch to bring the inner surface of the cooling hole into close contact with the outer surface of the anode cylinder. As shown, in this proposal, the cooling block 15 cools only the outer surface of the anode cylinder.

Although the magnetron according to the above proposal is suitable for use in a clean room and has fulfilled its intended purpose,
When used continuously for the manufacturing industry, the temperature of magnetic members such as permanent magnets during use also rises due to heat conduction from the anode, reducing the magnetic field strength of the static magnetic field in the working space,
It has been a problem to solve the problem of changing the electric characteristics of the magnetron and reducing the microwave output.

It is an object of the present invention to provide a magnetron which solves the above-mentioned conventional problems and has a simple structure and which can be easily mass-produced by a liquid cooling system.

[0007]

In order to solve the above-mentioned problems, according to the present invention, a cathode located in the center of a tube is radially projected from an anode cylinder and its inner wall with a cylindrical working space. Surrounded by a group of cavities formed by multiple vanes, a flat magnetic field is formed at both ends of the anode cylinder to form a static magnetic field in the tube axial direction in the working space. The magnetic pole is made of a soft ferromagnetic material and has a conical surface extending to the vicinity of the end, and the annular permanent magnet is disposed outside the magnetic pole in the tube axial direction and serves as a magnetomotive force source. In the magnetron equipped with a yoke made of a soft ferromagnetic material that adheres to the annular end face in the direction outer direction and surrounds the outside of the anode cylinder to form a magnetic circuit, a cooling liquid flow pipe inside a solid having high thermal conductivity. The cooling block that formed the path is In close contact with substantially the entire surface of the outer cylindrical wall, and was intended for installation in contact with the heat to a portion of each of the permanent magnets and the yoke.

[0008]

[Operation] During the operation of the magnetron, a large heat loss is generated in the anode, so that the temperature rise of the anode is large. However, even in portions other than the anode, the temperature of the permanent magnets and the yokes arranged close to the anode also rises due to heat conduction from the anode. Further, heating power of about 40 to 120 W is supplied also to the cathode filament, and in addition to the anode, a power supply line to the cathode, a cathode stem supporting the filament cathode heated to a high temperature, a filter and thus a filter case, etc. Even the temperature rises,
The temperature of the yoke in contact with these is raised. Ferrite magnets that are excellent in cost performance are used as permanent magnets for microwave ovens, but this magnet has a considerably large negative temperature coefficient, and in the case of a magnetron that cools only the conventional anode described above, During operation, the temperature of the magnet rises to 78 ° C, and the static magnetic field strength in the working space decreases,
When the anode voltage was 4.2 kV at the start of operation, when the magnetron operates and the magnet temperature rises, the anode operating voltage that keeps the anode current at the same proper value will decrease by 450 V, and accordingly the micro-voltage will decrease. Wave output decreases.
On the other hand, according to the present invention, by cooling not only the anode, which is the main heat source, but also the permanent magnet and the yoke, the decrease in the strength of the static magnetic field in the working space is reduced, and changes in the electrical characteristics of the magnetron are suppressed. it can.

[0009]

FIG. 1A is a side view of an embodiment of the present invention.
Reference numeral 5 is a permanent magnet, 6 is a yoke, 9 is a cooling block according to the present invention, 9a and 9b are cooling liquid inlets and outlets of the cooling blocks, 10 is a microwave power output part, 11 is a filter case, and 12 is a cathode. It is a conducting wire for heating. As described above, the part hidden by the cooling block 9 and not visible is the same as the main part of the conventional magnetron shown in FIG. 2 (the part where the radiator is removed and the inside is evacuated to a vacuum). FIG. 1 (b) is a perspective view of the cooling block 9 according to the present invention, in which 9 is a cooling block, 9a and 9b are cooling liquid inlets and outlets of the cooling block, and 9c is an inside of the cooling block 9. It is a blind plug for closing an unnecessary opening generated during processing after forming a cooling liquid flow path in the inside. As shown in the drawing, the cooling hole formed in the center of the cooling block 9 according to the present invention has a diameter at both ends slightly larger than the outer diameter of the permanent magnet 5, and a diameter in the middle is equal to the outer diameter of the anode cylinder. , The length in the axial direction is the same as the height in the axial direction of the anode cylinder. The cooling block was made of aluminum, which has a high thermal conductivity and is easy to process.

Although the diameter of the intermediate portion of the cooling block 9 and the outer diameter of the anode cylinder are made equal, in reality, even if the notches are tightened from both sides due to an unavoidable error in working, they cannot be brought into close contact with each other. .. In addition, a small gap is usually formed between the magnet 5 or the yoke 6 and the cooling block 9. Therefore, a thermal conductive paste such as FS thermal diffusion compound manufactured by Fuji Polymer Co., Ltd. is applied to the outside of the anode cylinder, which is the cooled portion of the magnetron, to reduce the thermal resistance by preventing voids. Since the yoke 6 is in contact with the outer surface of the permanent magnet 5 in the tube axis direction, cooling the yoke 6 also serves to indirectly cool the permanent magnet 5.

According to the present invention, as shown in Table 1 below, the temperature rise of the magnet was reduced by 30 ° C., the anode operating voltage was lowered, and the microwave output reduction amount was also halved.

[0012]

[Table 1]

Since the microwave output of the magnetron is determined by the operating voltage when the anode current is constant, the output decrease of 0.45 / 4.2 = 10.7% occurs when only the conventional anode is cooled. On the other hand, in the embodiment of the present invention, 0.25 /
It was 4.2 = 6%, and the output reduction could be suppressed to about half.

[0014]

As described above, according to the present invention, a liquid-cooled magnetron that can be used in a clean room and that is suitable for a plasma etching apparatus for manufacturing semiconductors can be mass-produced extremely easily.

[Brief description of drawings]

1A is a side view of an embodiment of the present invention, FIG.
(B) is a perspective view of a cooling block according to the present invention.

FIG. 2 is a sectional view taken along a plane including a tube axis of a conventional magnetron.

FIG. 3 is a side view of a conventional high-power magnetron for industrial heating, in which a cooling tube for flowing a cooling liquid is wrapped around the outer periphery of an anode cylinder and brazed.

FIG. 4 is a side view of a conventional high-power magnetron in which a cooling liquid inlet / outlet is attached to a cylindrical tank instead of winding a cooling tube around an anode cylinder to facilitate manufacturing.

FIG. 5 (a) is a side view of a conventional magnetron for a semiconductor manufacturing apparatus in which a magnetron main body part for a conventional microwave oven is diverted, and only an anode is liquid-cooled, and FIG. 5 (b) is its cooling. It is a perspective view of a block.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Filament cathode in which thoria-containing tungsten wire is wound in a helix, 2 ... Anode cylinder, 3 ... Bain, 4
... magnetic pole, 5 ... permanent magnet, 6 ... yoke, 7 ... radiator fin, 9 ... cooling block according to the present invention, 10
… Microwave output part, 11… Filter case, 12
... Conductive wire for heating the cathode.

Claims (1)

[Claims] 1. A group of cavities formed by an anode cylinder and a plurality of vanes radially protruding from an inner wall of the cathode, which surrounds a cathode located in the center of the tube, is surrounded by a cylindrical working space. In order to form a static magnetic field in the working space in the axial direction of the tube, soft magnetic poles made of flat flanges on both ends of the anode cylinder and a conical surface extending inside the working space to the end of the working space. And an annular permanent magnet serving as a magnetomotive force source, which is arranged in contact with the outer side of the magnetic pole flange portion in the tube axis direction. In a magnetron provided with a soft ferromagnetic yoke that encloses a magnetic circuit, a cooling block in which a cooling liquid flow passage is formed inside a solid having high thermal conductivity Adheres to almost the entire surface of the Magnetron, characterized in that installed in contact with the thermally and permanent magnet and the yoke portion of each of the.