JP2000030646A - Electron beam source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electron beam source capable of extremely increasing a discharge current in a plasma generating porous anode without causing the thermal damage to the plasma generating porous anode. SOLUTION: A discharge power supply 12 is connected between a plasma generating cathode 1 and a plasma generating porous anode 3 via a second switching element SW2, and plasma can be generated between the plasma generating cathode 1 and the plasma generating porous anode 3. The discharge power supply 12 is connected to an auxiliary anode 2 via a first switching element SW1, and plasma (pilot) can be held between the plasma generating cathode 1 and the auxiliary anode 2 in the standby state when no plasma process is under way. When the first switching element SW1 is turned on or off interlockingly as the second switching element SW2 is turned on or off, plasma can be held between the plasma generating cathode 1 and the plasma generating porous anode 3 or between the plasma generating cathode 1 and the auxiliary anode 2 in turn.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam source, and more particularly, to an electron beam source for generating plasma used for various plasma processes such as dry etching and film formation of semiconductors and plasma cleaning.

[0002]

2. Description of the Related Art As an electron beam source for generating plasma used in various plasma processes such as dry etching and film formation of semiconductors and plasma cleaning, for example, Japanese Patent Application Laid-Open No. Hei 6-30
An electron beam source described in Japanese Patent No. 2291 is known.

The electron beam source described in Japanese Patent Application Laid-Open No. 6-302291 generates a plasma between a cathode for plasma generation and a cathode for plasma generation and transmits electrons in the generated plasma. A plasma generating porous anode having a plurality of through holes, and between the plasma generating porous anode, for accelerating electrons extracted through each through hole of the plasma generating porous anode and transmitting the accelerated electrons. And a porous electrode for electron acceleration having a plurality of through holes.

[0004]

However, in the above-described conventional electron beam source, the thickness of the plasma-generating porous anode through which electrons pass is set to a predetermined size (about 0.5 to 1 mm).
), The cooling mechanism cannot be built into the plasma-generating porous anode, and the thermal conduction characteristics of the plasma-generating porous anode deteriorate. Cannot be cooled sufficiently. Therefore, when the discharge current flowing through the plasma-generating porous anode is set to a predetermined value (about 5 A) or more, an excessive heat load is applied to the plasma-generating porous anode, and the plasma-generating porous anode is thermally damaged. There is a problem that it is easy to occur.

The present invention has been made in view of the above points, and can increase the discharge current flowing through the plasma generating porous anode without causing thermal damage to the plasma generating porous anode. It is intended to provide an electron beam source.

[0006]

A first feature of the present invention is as follows.
A plasma generating cathode, a plasma generating porous anode having a plurality of through holes for generating plasma between the plasma generating cathode and transmitting electrons in the generated plasma, and the plasma generating porous anode A plurality of through holes for accelerating electrons extracted through the through holes and transmitting the accelerated electrons, a porous electrode for accelerating electrons, the cathode for plasma generation, and the plasma generation. An electric circuit having a voltage switching element for switching the magnitude of the voltage applied between the porous anode and the porous anode between the plasma generating cathode and the plasma generating porous anode by controlling the electric circuit. An electron beam source comprising: an electric circuit control device that intermittently changes a state of generated plasma.

According to a second aspect of the present invention, in the first aspect of the present invention, there is provided a through-hole for allowing the plasma to pass therethrough, which is disposed between the plasma generating cathode and the plasma generating porous anode. The electric circuit further includes an auxiliary anode having a hole, the electric circuit further includes an auxiliary voltage switching element for switching a voltage applied between the plasma generating cathode and the auxiliary anode, and the electric circuit control device includes: An electron beam, comprising: controlling an electric circuit to alternately maintain plasma between the plasma generating cathode and the plasma generating porous anode or between the plasma generating cathode and the auxiliary anode. Source.

According to a third aspect of the present invention, in the above-mentioned second aspect of the present invention, the auxiliary anode has a first auxiliary anode section having a first through hole for transmitting plasma, and the first auxiliary anode section has a first through-hole. A second auxiliary anode portion disposed adjacent to the anode portion and having a second through hole for transmitting plasma, wherein the first through hole and the second through hole have different opening areas from each other; An electron beam source characterized in that: In the third aspect of the present invention, the first through-hole has an opening area large enough to prevent gas from flowing from the plasma generating porous anode to the plasma generating cathode. The second through hole has an opening area sufficiently larger than the opening area of the first through hole so that the plasma can be stably held between the cathode for plasma generation and the second auxiliary anode portion. Is preferred.

According to the first feature of the present invention, the state of the plasma generated between the cathode for plasma generation and the porous anode for plasma generation is intermittently changed, so that the plasma processing is not performed. In this state, the discharge current can be prevented from continuing to flow through the plasma-generating porous anode, so that the heat load applied to the plasma-generating porous anode can be reduced, thereby causing thermal damage to the plasma-generating porous anode. The discharge current flowing through the plasma-generating porous anode can be increased without causing the generation.

According to the second feature of the present invention, since the plasma is held between the plasma generating cathode and the auxiliary anode in the standby state where the plasma processing is not performed, the standby state during the continuous operation is maintained. The transition from the state to the plasma processing state can be performed smoothly, so that the reproducibility of plasma in the plasma processing state can be improved.

According to a third feature of the present invention, an auxiliary anode is constituted by at least two auxiliary anode portions having through holes having different opening areas, and an auxiliary anode portion having a through hole having a large opening area and a plasma are formed. Since the plasma is held between the cathode for generation and the voltage between the cathode for plasma generation and the porous anode for plasma generation in the plasma processing state, the voltage for plasma generation in the standby state in which the plasma processing state is not performed. The voltage between the cathode and the auxiliary anode does not greatly fluctuate, so that the transition from the plasma processing state to the standby state during continuous operation can be smoothly performed.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment An embodiment of the present invention will be described below with reference to the drawings. 1 and 2 are views showing a first embodiment of an electron beam source according to the present invention. Here, FIG. 1 is a schematic diagram showing the overall configuration of an electron beam excited plasma generator provided with an electron beam source, and FIG. 2 is a sequence diagram for explaining the operation of the electron beam source shown in FIG.

First, an overall configuration of an electron beam excited plasma generator having an electron beam source will be described with reference to FIG.

As shown in FIG. 1, an electron beam excited plasma generator 10 includes a container 10a, in which a plasma generating cathode is provided as an electron beam source for emitting an electron beam toward a sample 7. 1, an auxiliary anode 2 having a through hole 2a for transmitting plasma, a plasma generating porous anode 3 having a plurality of through holes 3a for transmitting electrons in the plasma, and a plasma generating porous anode 3. An electron accelerating porous electrode 4 having a plurality of through holes 4a provided corresponding to each of the through holes 3a for transmitting electrons in the plasma is provided.

An electric circuit 5 is connected to the cathode 1 for plasma generation, the auxiliary anode 2, the porous anode 3 for plasma generation and the porous electrode 4 for electron acceleration. Electric circuit 5 is 3
Power supply 11, 12, 13; three switching elements SW1, SW2, SW3; and two resistors 14, 15, of which switching elements SW1, SW2, SW
Reference numeral 3 is controlled by the electric circuit control device 6.

Here, a heating power supply 11 is connected to the plasma generating cathode 1, and the plasma generating cathode 1 is heated by energization. A discharge power source 1 is provided between the plasma generating cathode 1 and the plasma generating porous anode 3 via a second switching element (voltage switching element) SW2.
2 is connected to generate plasma between the cathode 1 for plasma generation and the porous anode 3 for plasma generation. Further, a first switching element (auxiliary voltage switching element) SW1 and a resistor 1 are connected to the auxiliary anode 2 disposed between the plasma generating cathode 1 and the plasma generating porous anode 3.
5, a discharge power supply 12 is connected, so that a plasma (a pilot flame) can be held between the plasma generating cathode 1 and the auxiliary anode 2 in a standby state where plasma processing is not performed. . Furthermore, an acceleration power supply 13 is connected between the plasma generating porous anode 3 and the electron accelerating porous electrode 4 via a third switching element SW3,
Electrons drawn between the plasma generating porous anode 3 and the electron accelerating porous electrode 4 through the through holes 3a of the plasma generating porous anode 3 are accelerated.

The second switching element SW2 is for switching the magnitude of the voltage applied between the plasma generating cathode 1 and the plasma generating porous anode 3, and the second switching element SW2 is turned on. By turning on / off, plasma can be generated / disappeared between the cathode 1 for plasma generation and the porous anode 3 for plasma generation. Further, the first switching element SW1 is for switching the magnitude of the voltage applied between the plasma generating cathode 1 and the auxiliary anode 2, and is linked to ON / OFF of the second switching element SW2. (1) The plasma is alternately held between the plasma generating cathode 1 and the plasma generating porous anode 3 or between the plasma generating cathode 1 and the auxiliary anode 2 by turning off / on the switching element SW1. Can be.

The container 10a has supply ports 41a, 41a.
b and an outlet 41c are provided, an argon gas (Ar) is supplied to a region between the cathode 1 for plasma generation and the auxiliary anode 2 through a supply port 41a, and a porous electrode 4 for electron acceleration and a sample 7 are provided. Argon gas (Ar), oxygen gas (O ₂ ), methane gas (CH ₄ ), and the like are supplied to the region between them through the supply port 41b. In the case where oxygen gas (O ₂ ) is supplied through the supply port 41b, the plasma generating porous anode 3 is kept in a standby state where no discharge current flows through the plasma generating porous anode 3.
In addition, since the surface of the porous electrode for electron acceleration 4 is oxidized and an insulator is easily generated, in such a case, the surface of the porous anode for plasma generation 3 and the surface of the porous electrode for electron acceleration 4 are formed by nickel plating or gold plating. It is preferable to perform plating for preventing oxidation.

Further, an insulating member 40 is coated on the inner peripheral surface of the region between the auxiliary anode 2 and the sample 7 in the container 10a, so that most of the discharge current flows to the plasma generating porous anode 3. I have. An insulating member 40 is also inserted between the container 10a and the plasma generating cathode 1, the auxiliary anode 2, the plasma generating porous anode 3, and the electron accelerating porous electrode 4.

Further, a cooling mechanism (not shown) is provided in the wall surface of the container 10a and in the auxiliary anode 2 for water-cooling a portion heated by the plasma.

Next, the operation of the first embodiment of the present invention having such a configuration will be described with reference to FIGS.

First, the first switching element SW1 is set to O
N, with the second switching element SW2 turned on and the third switching element SW3 turned off, the heating power supply ( _Vf ) 11, the discharge power supply ( _Vd ) 12, and the acceleration power supply (V
_a ) Turn on all of 13 (time (A)). Thereby, the voltage V is applied to the cathode 1 for plasma generation by the heating power supply 11.
_f is given, and the plasma generating cathode 1 is heated. At the same time, a voltage _Vd is applied between the cathode 1 for plasma generation and the auxiliary anode 2 and between the cathode 1 for plasma generation and the porous anode 3 for plasma generation by the discharge power supply 12, and the discharge current causes the cathode Vd for plasma generation to be applied. The plasma of the argon gas (Ar) supplied from the supply port 41a is generated between the plasma anode 1 and the plasma generating porous anode 3. However, at this point, since the first switching element SW1 is ON, most of the discharge current from the plasma generating cathode 1 flows to the auxiliary anode 2 side, and the discharge current between the plasma generating cathode 1 and the plasma generating porous anode 3 is increased. Plasma is not generated stably between the two.

Thereafter, the first switching element SW1 is set to O
FF (time (B)). Thereby, most of the discharge current from the plasma generating cathode 1 flows to the plasma generating porous anode 3 side, and the plasma is stably generated between the plasma generating cathode 1 and the plasma generating porous anode 3. .

Next, the third switching element SW3 is turned on.
(Time (C)). Thus, the voltage V _a applied between the plasma generation porous anode 3 and electrons accelerating porous electrode 4 by the acceleration power supply 13, plasma generating porous anodic 3
The electrons drawn between the electrode and the electron accelerating porous electrode 4 through the through holes 3a of the plasma generating porous anode 3 are accelerated.

The electrons accelerated in this manner are drawn out through the through holes 4a of the porous electrode 4 for electron acceleration, and the accelerated electrons cause the electrons between the porous electrode 4 for electron acceleration and the sample 7 to move. Plasma of argon gas (Ar), oxygen gas (O ₂ ), and methane gas (CH ₄ ) supplied from the supply port 41b is generated, and predetermined plasma processing is performed on the sample 7 (time (C) to (C). D)). Specifically, for example, a sample 7 such as a semiconductor, a mechanical component, a magnetic recording component, or the like is arranged, and an oxygen gas (O ₂ ) is supplied to a region between the sample 7 and the electron accelerating porous electrode 4 to generate plasma. Is generated, the surface of the sample 7 can be plasma-cleaned. In addition, a gas containing carbon and hydrogen (for example, methane gas (C
H ₄ ), ethylene gas (C ₂ H ₄ ), toluene gas (C ₇ H
By supplying ₈ )) to generate plasma, a thin film of diamond-like carbon (DLC) can be formed on the surface of the sample 7.

Thereafter, when the plasma processing on the sample 7 is completed, the third switching element SW3 is turned off (time point (D)), and the sample 7 is replaced by a load lock or the like until the next plasma processing is started. . The time of plasma processing such as plasma cleaning and film formation (time (C)
To (D)) and the time for exchanging the sample 7 by the load lock or the like (time points (D) to (A)) are about 10 to 20 seconds.

When only the third switching element SW3 is turned off, plasma is held between the plasma generating cathode 1 and the plasma generating porous anode 3, so that the discharge current is applied to the plasma generating porous anode 3. Continues to flow,
The plasma generating porous anode 3 is in a state where thermal damage is likely to occur. Here, the third switching element SW3 is turned off.
(Time (D)), the first switching element SW1
Is turned on (time (E)), and then the second switching element SW2 is turned off (time (F)) until the next plasma processing is started (time (F)).
(A)), a plasma (a pilot flame) is held between the plasma generating cathode 1 and the auxiliary anode 2. Here, since a cooling mechanism (not shown) is provided in the auxiliary anode 2, thermal damage of the auxiliary anode 2 in a standby state where plasma processing is not performed is minimized. The through hole 2a of the auxiliary anode 2 has an opening area (about 3 mm in diameter) that can prevent gas from flowing from the plasma generating porous anode 3 side to the plasma generating cathode 1 side. In the standby state in which the plasma processing is not performed, the plasma processing cathode 1 functions as an anode for maintaining plasma between itself and the plasma generating cathode 1 in the plasma processing state, and the plasma generating cathode 1 is separated from oxygen gas (O ₂ ) in the plasma processing state. Acts as a barrier for protection.

As described above, according to the first embodiment of the present invention, the state of the plasma generated between the cathode for plasma generation 1 and the porous anode for plasma generation 3 is intermittently changed, whereby the plasma is generated. Since the discharge current can be prevented from continuing to flow through the plasma-generating porous anode 3 in the standby state where the processing is not performed, the heat load applied to the plasma-generating porous anode 3 can be reduced, and therefore, Even when oxygen gas (O ₂ ) is supplied via the supply port 41b, the discharge current flowing through the plasma generating porous anode 3 is increased without causing thermal damage to the plasma generating porous anode 3. be able to. Further, since the heat load applied to the plasma generating porous anode 3 is small, it is not necessary to use a high melting point metal such as molybdenum or tantalum as an electrode material. Can be manufactured.

According to the first embodiment of the present invention,
In the standby state in which the plasma processing is not performed, the plasma (seed flame) between the plasma generating cathode 1 and the auxiliary anode 2
Is maintained, the transition from the standby state to the plasma processing state during continuous operation can be smoothly performed, and therefore, the reproducibility of plasma in the plasma processing state can be improved.

In the first embodiment, the plasma generating cathode 1 and the plasma generating porous anode 3 are used.
And the voltage applied between the cathode and the plasma generating cathode 1
Although a switching element is used as a voltage switching element for switching a voltage applied between the voltage and the auxiliary anode 2, the present invention is not limited to this, and a variable resistor or the like that continuously changes the voltage may be used. .

Second Embodiment Next, a second embodiment of the electron beam source according to the present invention will be described with reference to FIG. The second embodiment of the present invention is the same as the first embodiment shown in FIGS. 1 and 2 except that the auxiliary anode is constituted by at least two auxiliary anode portions having through holes having different opening areas. It is almost the same as the form. In the second embodiment of the present invention, the same parts as those in the first embodiment shown in FIGS. 1 and 2 are denoted by the same reference numerals, and detailed description is omitted.

As shown in FIG. 3, in an electron beam excited plasma generator 10 provided with an electron beam source, a first through-hole 21a having a first through hole 21a for transmitting plasma is provided.
The auxiliary anode 2 is composed of the auxiliary anode part 21 and the second auxiliary anode part 22 which is arranged adjacent to the first auxiliary anode part 21 and has a second through-hole 22a for transmitting plasma.

Here, the first through-hole 21a of the first auxiliary anode portion 21 has an opening area (diameter) such that gas can be prevented from flowing from the plasma generating porous anode 3 side to the plasma generating cathode 1 side. (About 3 mm). Also,
The second through-hole 22a of the second auxiliary anode section 22 has a larger opening area than the first through-hole 21a so that the plasma can be stably held between the cathode 1 for plasma generation and the second auxiliary anode section 22. Large enough opening area (about 30mm in diameter)
have.

The first auxiliary anode section 21 is connected to a discharge power supply 12 via a resistor 15, and the second auxiliary anode section 2
2 is a first switching element (auxiliary voltage switching element) SW
A discharge power supply 12 is connected via a resistor 1 and a resistor 16 so that a plasma (seed flame) is held between the plasma generating cathode 1 and the second auxiliary anode section 22 in a standby state where plasma processing is not performed. Has become.

As described above, according to the second embodiment of the present invention, at least two auxiliary anode portions 21 and 22 having through holes 21a and 22a having different opening areas are connected to the auxiliary anode 2
And a second through-hole 22a having a large opening area.
Between the plasma generating cathode 1 and the plasma generating porous anode 3 in the plasma processing state because the plasma (seed flame) is held between the second auxiliary anode portion 22 having The voltage and the voltage between the cathode for plasma generation 1 and the auxiliary anode 2 (second auxiliary anode section 22) in the standby state in which the plasma processing is not performed do not fluctuate greatly, and therefore, the state changes from the plasma processing state in the continuous operation. The transition to the standby state can be performed smoothly. In addition, the first through hole 2 of the first auxiliary anode portion 21
Since the opening area of 1a is kept small similarly to the through-hole 2a of the auxiliary anode 2 shown in FIG. 1, the gas from the plasma generating porous anode 3 side to the plasma generating cathode 1 side by the first auxiliary anode section 21. Can be prevented, and the cathode 1 for plasma generation can be effectively protected from oxygen gas (O ₂ ) and the like.

[0036]

Next, a specific embodiment of an electron beam excited plasma generator equipped with an electron beam source shown in FIG. 3 will be described.

(Embodiment 1) First, as a first embodiment,
Argon gas (Ar) is supplied to a region between the electron accelerating porous electrode 4 and the sample 7 through the supply port 41b, and O 3 of the third switching element SW3 is supplied according to the sequence shown in FIG.
An operation test was performed with the N time set to 10 seconds and the OFF time set to 10 seconds. The voltage V _f of the heating power source 11 is 8V, the voltage V _d of the discharge power supply 12 is 60V, the voltage V _a of the acceleration power supply 13 is set to 100 V, the resistor 14 2～5Omu, the resistance 15 and 16 was set to 200 [Omega. The pressure in the region between the cathode 1 for plasma generation and the auxiliary anode 2 (first auxiliary anode portion 21) is set to 0.1.
The pressure in the region between the auxiliary anode 2 (second auxiliary anode portion 22) and the sample 7 was set to 2 × 10 ⁻³ Torr at 2 Torr. Further, the plasma generating porous anode 3 has a diameter of 10
cm, a disk made of carbon with a thickness of 1 mm and a diameter of about 1-2
A hole having about 1200 mm through holes 4a was used.

As a result, even if such an operation test is continued for one hour or more in a continuous operation, a plasma of argon gas (Ar) can be generated with good reproducibility, and even if the discharge current is 10 A, the plasma generation pores can be generated. It was confirmed that the anode 3 did not glow.

The voltage between the plasma generating cathode 1 and the plasma generating porous anode 3 in the plasma processing state is 45 V, and the voltage between the plasma generating cathode 1 and the second auxiliary anode section 22 in the standby state is 44 V. The transition from the processing state to the standby state could be performed smoothly.

(Embodiment 2) Next, as a second embodiment,
Oxygen gas (O ₂ ) is supplied to the region between the electron accelerating porous electrode 4 and the sample 7 through the supply port 41b, and the ON time of the third switching element is set to 1 according to the sequence shown in FIG.
An operation test was performed with 0 second and 0 FF time set to 10 seconds.

As a result, even if such an operation test is continued for 5 hours or more in a continuous operation, a plasma of oxygen gas (O ₂ ) can be generated with good reproducibility, and even if the discharge current is 10 A, the plasma for oxygen generation can be obtained. It was confirmed that the porous anode 3 did not glow red.

The porous anode 3 for plasma generation is
The same operation test as in the first and second embodiments was performed using a disk having the same shape and using copper instead of copper. Similar good results were obtained.

[0043]

As described above, according to the present invention, the discharge current flowing through the plasma generating porous anode can be increased without causing thermal damage to the plasma generating porous anode.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an overall configuration of an electron beam excited plasma generator including an electron beam source according to a first embodiment of the present invention.

FIG. 2 is a sequence diagram for explaining the operation of the electron beam source shown in FIG.

FIG. 3 is a schematic diagram showing an overall configuration of an electron beam excited plasma generator including an electron beam source according to a second embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 cathode for plasma generation 2 auxiliary anode 2a through hole 21 first auxiliary anode part 21a first through hole 22 second auxiliary anode part 22a second through hole 3 plasma generation porous anode 3a through hole 4 electron acceleration porous electrode 4a penetration Hole 5 Electric circuit 6 Electric circuit controller 7 Sample 10 Electron beam excited plasma generator 11 Heating power supply 12 Discharge power supply 13 Acceleration power supply SW1, SW2, SW3 Switching element

Claims (7)

[Claims] A plasma generating cathode; a plasma generating porous anode having a plurality of through holes for generating plasma between the plasma generating cathode and transmitting electrons in the generated plasma; An electron accelerating porous electrode having a plurality of through holes for transmitting electrons accelerated through the respective through holes between the plasma generating porous anode and the accelerated electrons; and An electric circuit having a voltage switching element for switching the magnitude of the voltage applied between the cathode and the plasma generating porous anode; and controlling the electric circuit to control the plasma generating cathode and the plasma generating porous. An electron beam source, comprising: an electric circuit control device that intermittently changes a state of plasma generated between the anode and the anode. 2. The electron beam source according to claim 1, wherein said voltage switching element of said electric circuit is a switching element. 3. The plasma generating cathode according to claim 1, further comprising an auxiliary anode disposed between the plasma generating cathode and the plasma generating porous anode and having a through hole for transmitting plasma. And an auxiliary voltage switching element for switching a voltage applied between the auxiliary anode and the auxiliary anode, wherein the electric circuit controller controls the electric circuit to control the plasma generation cathode and the plasma generation porous anode. 2. The electron beam source according to claim 1, wherein plasma is alternately held between the anode and between the plasma generating cathode and the auxiliary anode. 4. The electron beam source according to claim 3, wherein said auxiliary voltage switching element of said electric circuit is a switching element. 5. An auxiliary anode having a first through-hole for transmitting plasma and a second auxiliary anode disposed adjacent to said first auxiliary anode and for transmitting plasma. 4. The electron beam source according to claim 3, comprising a second auxiliary anode portion having a through hole, wherein the first through hole and the second through hole have different opening areas. 6. The first through hole has an opening area large enough to prevent gas from flowing from the plasma generating porous anode side to the plasma generating cathode side.
The through-hole has an opening area sufficiently larger than the opening area of the first through-hole so that plasma can be stably held between the cathode for plasma generation and the second auxiliary anode portion. The electron beam source according to claim 5, wherein 7. The electron beam source according to claim 1, wherein the surface of the plasma generating porous anode is plated to prevent oxidation.