JPS61258501A - Microwave variable reactance element - Google Patents

Abstract

PURPOSE:To ensure stable operation by forming a short-circuit face between a metallic rod and a waveguide so as to prevent a fault such as discharge. CONSTITUTION:A metallic net formed as a torus shape as an elastic member 4 forming the short-circuit face is inserted into an air gap provided between the waveguide 2 and a supporting member 3. The metallic net is in contact with the entire circumference of the metallic rod 1 and adhered closely to the waveguide 2. In constituting a 3-pillar matching device for a microwave plasma processing device with the titled element, when no matching is given, a system causing reflection of nearly 1.1kW to incident of 1.5kW is matched to the reflection of nearly 0.3kW against the incident wave of 1.5kW. Further, the operation for the readjustment is attained normally while being kept to room temperature and no damage is given to a screwed part.

Description

[Detailed Description of the Invention] [Summary] The present invention provides a microwave variable reactance element that is adjusted by the insertion length of a metal rod. By forming a short-circuit surface between the metal rod and the waveguide, This prevents problems such as electrical discharge and ensures stable operation.

[Industrial application field]

The present invention relates to improvements in variable reactance elements used in microwave three-dimensional circuits.

For example, in the manufacturing process of semiconductor devices, plasma processing has the effect of making the process dryer and cooler, or making the pattern finer. However, in order to generate a large amount of active species and increase the throughput, high power Excitation is performed using microwaves that can apply .

Increasingly, high output power is required in such microwave power application devices, and it is a matter of course that the microwave circuit elements used in these devices must be able to sufficiently withstand the power being handled and operate stably. .

[Conventional technology]

A schematic diagram of a microwave plasma processing apparatus is shown in FIG. 3 as an example of microwave power application.

Microwaves with a frequency of 2.45 GIIz, which are normally oscillated by a Macnetron in the micro-electrified Ig, 11, are guided to the isolator 12 by a waveguide. The isolator 12 allows almost complete transmission of incident waves due to its built-in ferrite, but reflected waves that return due to mismatch are deflected by 90 degrees and absorbed by the pseudo load. The microwaves guided in this manner are monitored by the directional coupler 13 for the power of the incident wave and the reflected wave.

A quartz tube is inserted as a plasma generation chamber 17 in the electric field direction of the TEo+ mode waveguide 15, and in this plasma generation chamber 17, for example, carbon tetrafluoride (cp) and oxygen (0□
) is introduced at a pressure of about 0.1 to 1 O Torr, and the plasma is excited by the microwave power. At this time, the three-pillar matching box 14 and the short-circuit plunger matching box 16
Microwave matching is performed by

The plasma generated in this manner is led to the plasma processing chamber 18, where, for example, etching processing of the semiconductor substrate 20 is performed. Note that the plasma generation chamber 17 is water-cooled by a cooler 19.

As mentioned above, in microwave power application devices, except for some simple devices such as microwave ovens, a matching box consisting of a G variable reactance element is inserted between the power source and the load in order to supply maximum power to the load. Ru.

Among the reactance element structures of microwave three-dimensional circuits,
In the structure in which a metal rod is inserted parallel to the electric field from the wide surface of the wind wave tube, the reactance changes from capacitive to inductive through series resonance depending on the insertion length, and the insertion length can be easily varied due to the structure. , often used as a variable reactance element. Note that this metal rod is called a stub.

Figure 2 (al and bl) are sectional views of conventional examples of variable reactance elements using the metal rods mentioned above.
The example shown in l is a basic structure, with a wind wave tube 2 of a metal rod 1.
The insertion length is variable due to the spring structure. In this structure, the inner wall surface of the waveguide 2 is considered to be the contact point between the waveguide 2 and the metal rod 1, but in reality, a large fouling may occur at this threaded portion 5, or an electric discharge may occur, causing a high temperature. This causes problems such as inability to adjust due to thermal expansion or fusion.

In order to deal with this problem, a choke flange structure is added to isolate the threaded portion 5 from the microwaves, as shown in FIG. 5(b). However, this structure still has problems such as discharge occurring near the opening when the microwave power is increased.

[Problem that the invention seeks to solve]

As explained above, a variable reactance element that adjusts the insertion length of a metal bar into a waveguide is most suitable for matching devices, etc., but conventional variable reactance elements with this structure are used when increasing microwave power, etc. There is a strong possibility that this will occur, and improvements are strongly desired.

[Means for solving problems]

The problem is that, for example, as in the embodiment shown in FIG. 1, the other end of the metal rod 1 screwed into the support member 3 near one end is inserted into the waveguide 2 parallel to the electric field, and the insertion length is The micro according to the present invention is adjustable by the rotation of the metal rod 1 and includes an elastic member 4 that goes around the metal rod 1 to form a short-circuit surface between the metal rod 1 and the waveguide 2. This is solved by a wave variable reactance element.

[For production]

The microwave variable reactance element according to the present invention provides a short circuit surface in the gap between the metal rod and the waveguide.
This prevents the generation of discharge and reflected waves, which were problems in the past.

Displacement in the direction perpendicular to the axis of the metal rod due to rotation for adjusting the insertion length is dealt with by forming this short circuit surface with an elastic member. Examples of conductive members having elasticity that can be used for this purpose include electrically conductive O-rings, molded metal nets, and the like.

〔Example〕

The present invention will be specifically explained below with reference to an embodiment whose cross-sectional view is shown in FIG.

In the same figure, ■ is a metal rod, 2 is a waveguide, and 3 is a metal rod 1.
The metal rod 1 is threaded near one end and is screwed into the support member 3, as in the conventional case.

In this embodiment, a metal mesh formed into an annular Q shape is inserted into a gap provided between the waveguide 2 and the support member 3 as the elastic member 4 forming the short circuit surface, and this metal mesh is made of metal. stick 1
is in contact with the entire circumference of the tube, and is in close contact with the 2-wave tube 2.

Note that when a three-wooden matching device of a microwave plasma processing apparatus similar to the apparatus described above with reference to FIG.
A system that produces a reflection of about 1 in 1.1 for kHz has an incidence of 1.1.
The reflection was matched to about 0.3kt+ for 5kW.

Furthermore, in a three-wooden matching device consisting of the elements shown in FIG. 2 (bl), the aforementioned arc discharge often occurs, for example,
The temperature at the end of the metal rod reaches about 170°C after a minute of operation, making adjustment impossible.In contrast, in this embodiment, the temperature is maintained at room temperature and readjustment operations are always possible. ,
There was no damage to the threaded parts.

〔Effect of the invention〕

As described above, the variable reactance element according to the present invention has a remarkable effect of preventing the occurrence of failures such as discharge in high-power microwave power application equipment, etc., and greatly contributes to the stable performance of the intended process.

[Brief explanation of the drawing]

Part 1 is a cross-sectional view showing an example of a variable reactance element according to the present invention, Fig. 2 is a cross-sectional view showing a conventional example of a variable reactance element, and Fig. 3 is a schematic diagram showing an example of a microwave plasma processing apparatus. . In the figure, 1 is a metal rod, 2 is a waveguide, 3 is a supporting member, and 4 is an elastic member forming a short-circuit surface. Variable 7 kunnu rare' + tf) Project 11〈νη'The drawing 1 Figure=,, (shi) The door is multiplied 2. Motoko Tsukasa's first orgasm cross-section
b k-diagram

Claims (1)

[Claims] A metal rod (
1) The other end is inserted into the waveguide (2) parallel to the electric field,
The insertion length can be adjusted by rotating the metal rod (1), and the metal rod (1) and the waveguide (
2) A microwave variable reactance element comprising an elastic member (4) forming a short-circuit surface between the element and the elastic member (4).