JP2765014B2 - Ion source device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion source device for generating an ion beam in a plasma by sustaining a DC discharge by electrons ionized by plasma generation based on a microwave discharge. .

[Conventional technology]

Conventionally, bucket type used for ion beam sputtering, in-beam mixing, ion assist, etc.
The Kaufman-type ion source device has a microwave plasma cathode (hereinafter referred to as MP cathode) chamber that ionizes and forms electrons by plasma generation based on microwave discharge as an electron emission source. To extend the service life.

A conventional bucket-type device for introducing a microwave into a cathode chamber using a coaxial cable and an antenna to generate a high-current ion beam is shown in FIG. 4 and an enlarged view of a part of FIG. It is configured as shown in FIG.

In these drawings, (1) is a main housing made of a nonmagnetic metal such as stainless steel, (2) is a main plasma chamber formed by the main housing (1), and (3) is a main plasma chamber (2). (4) is an ion beam extraction electrode group, and includes a first electrode (5), a second electrode (6), and a third electrode (7).
It is composed of (8), (9) and (10) are the main housing (1), insulators provided between the electrodes (5), (6) and (7), and (11) is the main housing (1) And a plurality of annular permanent magnets provided outside of the main plasma chamber to form a caps magnetic field in the main plasma chamber (2).

(12) is an arc power supply, the anode of which is in the main housing (1),
A cathode is connected to the first electrode (5) and brings the main housing (1) to an anode potential. Reference numeral (13) denotes an acceleration power supply, whose anode is connected to the cathode of the anode power supply (12), and applies a positive acceleration voltage lower than the anode potential to the first electrode (5). (14) is a deceleration power supply for applying a negative voltage to the second electrode (6).

(15) is the MP formed by the non-magnetic sub-housing (16)
Cathode chamber, (17) and (18) cover plates made of magnetic or non-magnetic material on both sides of sub-housing (16), (19) Main housing (1)
(20) is a gas inlet to the cathode chamber (15), (21) is a permanent magnet or electromagnet provided outside the sub-housing (16) And generates a magnetic field exceeding the electron cyclotron resonance (ECR) condition in the cathode chamber (15).

(22) a plurality of microwave power supplies having a microwave adjuster such as a variable attenuator, (23) a microwave power monitoring device connected to the power supply (22) via a coaxial cable (24), Reference numeral 25 denotes an antenna connected to the monitor device (23) via a coaxial cable (26) and disposed in the cathode chamber (15).

The sub-housing (16) is held at the cathode potential of the cathode of the arc power supply (12), and the tip of each antenna (25) is placed on the wall of the cathode chamber (15) so as to easily cause microwave discharge. It is provided in close proximity.

Next, when gas is supplied from the inlet (20) and microwaves are introduced from the respective microwave power supplies (22) via the monitoring device (23) and the antenna (25), the cathode chamber (15) is opened. Even when the antenna is not formed under the condition of the microwave cavity, the microwave discharge is easily generated by the high electric field between the tip of each antenna (25) and the wall surface of the cathode chamber (15), and the inlet (20) is formed. ) Is ionized to generate microwave plasma.

Further, based on the DC bias of the arc power supply (12), the electrons e ionized by the generation of the microwave plasma pass through each opening of the cover plate (17) and enter the main plasma chamber (2). Released.

Then, in the main plasma chamber (2), DC discharge is continued by the supplied electrons e, and ionized gas such as a rare gas introduced from the inlet (3) is ionized to generate a main plasma (27).

Next, ions are extracted from the generated main plasma (27) as an ion beam to a sputter chamber or the like by the beam extracting action of the electrode group (4).

On the other hand, the input amount (power) of the microwave from each antenna (25) is measured and monitored by each monitor device (23),
Based on the result, the microwave regulator of each microwave power supply (22) is adjusted automatically or manually so as to prevent the unevenness of the density of the microwave plasma.

By this adjustment, the main plasma (27) is made uniform, and a large current uniform ion beam is obtained.

[Problems to be solved by the invention]

In the case of the above-mentioned conventional device, as in the case of general microwave power measurement, each monitor device (2
It is difficult to accurately measure and monitor 3).

Further, since the density distribution of the microwave plasma changes depending on the gas pressure and the like, even if the input amount of the microwave is adjusted based on the measurement and monitoring of each monitor device (23), the main plasma chamber ( The density of the electrons e emitted in 2) becomes uneven.

Therefore, there is a problem that the main plasma (27) is not generated at a uniform density and a uniform ion beam cannot be obtained.

In addition, since each monitor device (23) handling microwaves is extremely complicated and expensive, there is a problem that the device cannot be simplified and the price cannot be reduced.

It should be noted that a Kaufman-type device or the like also has substantially the same problems as described above.

SUMMARY OF THE INVENTION The present invention provides an ion source device which takes the above points into consideration, and makes the density of a main plasma uniform with a simple and inexpensive configuration for detecting and adjusting a DC cathode current, thereby obtaining a uniform ion beam with a large current. The purpose is to:

[Means for Solving the Problems]

In order to solve the above problems, an ion source device according to the present invention includes a plurality of microwave plasma cathode chambers to which a microwave of a microwave power supply is supplied and generates electrons by microwave discharge, A main plasma chamber which is DC-biased to a positive potential and generates an ion beam by a DC discharge based on electrons emitted from each of the cathode chambers; and between a casing of each of the cathode chambers and a casing of the plasma chamber. A plurality of current detectors provided in the cathode current path, and a current regulator such as a variable DC power supply or a variable resistor provided in series with each of the current detectors. Based on the value, the controller adjusts the cathode current of each of the cathode chambers to adjust the amount of electrons emitted from each of the cathode chambers.

(Operation)

In the ion source device of the present invention configured as described above, the density distribution of the main plasma is determined by the amount of electrons emitted from the plurality of independent MP cathode chambers to the main plasma chamber, and the amount of electrons in each cathode chamber is reduced. Since the cathode current is detected by each electric detector and the cathode current of each cathode chamber is adjusted by adjusting each regulator based on the detected value of each detector, the microwave input amount, gas pressure The amount of electrons in each cathode chamber is directly measured, and the amount of electrons in each cathode chamber is accurately adjusted by adjusting the cathode current in each cathode chamber based on the measurement results. The unevenness in the density of electrons is prevented, the density distribution of the main plasma is made uniform, and a uniform ion beam is obtained.

In addition, since the measurement, monitoring and adjustment of microwaves can be performed by detecting and adjusting the DC cathode current of each cathode chamber, the apparatus can be formed simply and inexpensively.

〔Example〕

An embodiment will be described with reference to FIG. 1 to FIG.

In these drawings, the same symbols as those in FIGS. 4 and 5 indicate the same components.

Example 1 FIGS. 1 and 2 showing Example 1 will be described.

In the same figure, (28) is a plurality of MP cathode chambers each accommodating an antenna (25), like the cathode chamber (15) in FIG. Is provided with a permanent magnet or an electromagnet.

(29) is an inlet for supplying gas to the cathode chamber (28),
(30) a current detector provided in the cathode current path between the main housing (1) and the sub-housing of each cathode chamber (28); (31)
Is a variable DC power supply connected in series to each current detector (31), and corresponds to the arc power supply (12) in FIG. (32) is a control device having a microcomputer configuration for automatically adjusting the variable DC power supply (31) based on the detection value of each detector (31).

(33) is a current limiting resistor provided between the main housing (1) and the first electrode (5), (34) is a microwave power source, and (35) is a microwave power source (34) for dividing the microwave. Branch circuit, (36)
Is a coaxial cable or waveguide between the microwave power supply (34) and the branch circuit (35), and (37) is a coaxial cable between the branch circuit (35) and each antenna (25).

Then, from the microwave power supply (34) via the branch circuit (35), the respective cathode chambers (2
Electrons e are individually emitted from each cathode chamber (28) to the main plasma chamber (2) by the microwave discharge based on the microwave introduced into 8).

At this time, the potential (cathode potential) of each cathode chamber (28) with respect to the potential (anode potential) of the main plasma chamber (2) is separately set by each variable DC power supply (31). Chamber (2) and each cathode chamber (2
8), the amount of electrons emitted from each cathode chamber (28) changes as shown in FIG.

Then, the cathode current of each cathode chamber (28) flowing through each variable DC power supply (31) and each current detector (30) changes according to the voltage of each variable DC power supply (31), and each current detector (30)
The direct current detection directly measures the amount of electrons emitted from each cathode chamber (28), which varies depending on the amount of microwave input, gas pressure, etc., and is accurately detected.

Further, based on the detection value of each current detector (30), the control device (32) sets the cathode current of each cathode chamber (28) when the density distribution of the main plasma (27) becomes uniform, for example. The voltage of each variable DC power supply (31) is adjusted based on the value, and the cathode current of each cathode chamber (28) is automatically adjusted.

Therefore, the density unevenness of the electrons e emitted from each cathode chamber (28) to the main plasma chamber (2) is prevented, the density distribution of the main plasma (27) is made uniform, and a large current uniform ion beam is provided. Is obtained.

Furthermore, since the amount of microwave input to each cathode chamber (28) is not adjusted, it is not necessary to provide a microwave power supply (34) or the like with a conventional microwave regulator, and the microwave power supply (34) Are shared for supplying microwaves to each cathode chamber (28), so that the size of the apparatus can be reduced.

Second Embodiment FIG. 3 showing a second embodiment will be described.

1 differs from FIG. 1 in that an arc power supply (38) is provided between the main housing (1) and each of the current detectors (30), and instead of the variable DC power supply (31) in FIG. The difference is that a variable resistor (39) is provided as a current regulator.

Then, by adjusting each variable resistor (39) based on the detection value of each current detector (30), the cathode current of each cathode chamber (28) is automatically adjusted as in the case of FIG. The density distribution of the plasma (27) is made uniform, and a large current uniform ion beam can be obtained.

Further, the number of DC power supplies is smaller than that of the apparatus shown in FIG.

In each of the above embodiments, a coaxial cable and an antenna are used for supplying microwaves to each cathode chamber (28), but a waveguide may be used.

Further, the number of antennas (25) in each cathode chamber (28) is not limited to one, but may be plural.

Furthermore, each variable DC power supply (31) or each variable resistor (39) may be manually adjusted based on the detection value of each current detector (30).

 Further, the present invention can be applied to a Kauffman-type device or the like.

〔The invention's effect〕

Since the present invention is configured as described above,
The following effects are obtained.

The microwave plasma cathode chamber (28) is divided into a plurality of parts, and the amount of electrons emitted from each cathode chamber (28) to the main plasma chamber (2) is directly determined by detecting the cathode current by each current detector (30). Since it is measured and detected, the detection is accurate, and based on the detection value of each detector (30), each variable DC power supply (31) or each variable resistor (39) of each cathode current path The current controller adjusts the cathode current of each cathode chamber (28) and adjusts the amount of electrons emitted from each cathode chamber (28). Therefore, it is simple and inexpensive to detect and adjust the DC cathode current. With such a configuration, the density unevenness of the electrons emitted to the main plasma chamber (2) can be prevented, the main plasma (27) can be generated at a uniform density, and a large current uniform ion beam can be obtained.

[Brief description of the drawings]

1 and 2 are a configuration diagram and a characteristic diagram of the amount of emitted electrons of an ion source device according to a first embodiment of the present invention, FIG. 3 is a configuration diagram of a second embodiment of the present invention, and FIG. Fig. 5 shows the structure
It is a partially enlarged view of a figure. (2) Main plasma chamber, (28) Microwave plasma cathode chamber, (34) Microwave power supply, (30)
Current detector, (31)… Variable DC power supply, (39)… Variable resistor.

Claims (1)

(57) [Claims] 1. A microwave power supply is provided,
A plurality of microwave plasma cathode chambers for generating electrons by microwave discharge, and a DC bias to a positive potential with respect to each of the cathode chambers;
A main plasma chamber that generates an ion beam by a DC discharge based on electrons emitted from each of the cathode chambers; and a cathode current path between a housing of each of the cathode chambers and a housing of the plasma chamber. A plurality of current detectors, comprising a current regulator such as a variable DC power supply or a variable resistor provided in series with each of the current detectors, based on a detection value of each of the current detectors, An ion source device, wherein a cathode current of each of the cathode chambers is adjusted by each of the adjusters, and an amount of electrons emitted from each of the cathode chambers is adjusted.