JPH0945255A - Microwave ion source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the leak of a microwave from an ion source, when the size of a plasma chamber is made larger than a critical value, by providing a specific member, in the ion source having constitution where sputter voltage is applied between the plasma chamber and an ion drawing part. SOLUTION: This ion source is provided with a conductive waveguide member 13 and a conductive choke groove member 16. The member 13 abuts on an ion drawing part 2 at one end part to be provided so as to surround the outer wall surface of a plasma chamber (P) 1 main body to transmit a microwave, passed through an insulating member 7, along the outer wall surface of the P:1 main body. The member 16 is provided on the outer surface of the P:1 main body to be connected to the member 13 at a given interval with the other end part of the member 13 in between to reflect the microwave, guided by the member 13 to be transmitted along the outer wall surface of the Pal main body, by a bottom surface 16a. The depth L1 of the groove of the member 16 is set so that the wave length λg can be (1/4+N/2) λg, (n: 0, an positive integer), where L1 : the depth of the groove of the member 16, λg: the frequency length of microwave to be transmitted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion source that is used, for example, in an ion implantation apparatus and that generates plasma by microwave discharge and extracts ions from the plasma.

[0002]

2. Description of the Related Art In recent years, ion sources for converting elements into plasma and extracting ions in the plasma as ion beams have been used in various fields including an ion implantation apparatus. This ion source is equipped with ECR (Electron Cyclotron R
There are many types such as microwave type such as esonance) ion source and PIG (Penning Ionization Gauge) type such as Freeman ion source. These various ion sources are required to have required ion species and energy, The most suitable model can be used according to the current.

For example, in the case of an ion source having a filament such as a Freeman ion source, the life of the ion source is relatively short due to the consumption of the filament, and frequent maintenance is required. On the other hand, an ECR ion source using microwaves has a characteristic that it has a relatively long life because it does not use a filament. The structure of the ECR ion source will be described below as an example.

As shown in FIG. 3, the ECR ion source described above outputs microwaves output from a magnetron (not shown) through a waveguide 50, a microwave introducing rod 53, and a window (microwave introducing window) 54. It is introduced into the plasma chamber 51 to generate microwave discharge in a magnetic field under electron cyclotron resonance (ECR) conditions,
A gaseous ion source material introduced inside through a gas feedthrough (not shown) is turned into plasma.

Further, in order to suppress the heat of the plasma chamber 51 from being transferred to the ion source chamber 61 housing the plasma chamber 51 by radiation, the periphery of the plasma chamber 51 is temporarily urged by a spring hook 59. Are covered with a heat shield member 58 attached to the plasma chamber 51 in a hooked state.

After the plasma is generated in the plasma chamber 51, a high voltage (extraction voltage) is applied between the plasma chamber 51 and the extraction electrode system 60 provided outside the plasma chamber 51 to generate an electric field. By doing so, ions are extracted from the plasma slit 52 of the plasma chamber 51, and an ion beam is formed. The ion beam thus formed is used for processing such as ion implantation.

The inner wall of the plasma chamber 51 is covered with a liner 55 made of a dielectric material such as BN. This is because if the inner wall of the conductive plasma chamber 51 is not covered with a dielectric material, the conductive material jumped out from the inner wall of the chamber due to the sputtering by the plasma-forming substance adheres to the window 54 and the microwave is reflected. This is because the microwave power cannot be supplied to the plasma chamber 51.

However, when a corrosive gas such as BF ₃ gas is used as an ion source material to generate plasma, the liner 55 forming the inner wall of the plasma chamber 51 is etched by the plasma forming material. However, the resulting substance adheres to the vicinity of the ion extraction hole 52a of the plasma slit 52 to cause clogging, which causes a problem that the beam cannot be extracted.

In order to avoid the above inconvenience, conventionally, the plasma slit 52 is electrically insulated from the main body of the plasma chamber 51 by an insulating ring 56 made of a dielectric material, and the plasma slit 52 is supplied by a sputtering power source 57. 52
Is set to a negative potential higher than the ion source reference potential (potential of the plasma chamber 51), the ions in the plasma are positively collided with the plasma slit 52 to remove deposits on the plasma slit 52, and It is configured to ensure a long life.

[0010]

By the way, when plasma is generated in the plasma chamber 51, microwaves are propagated and absorbed in the plasma, but when plasma is not generated (for example, gas In the case where the microwaves are introduced when, for example, is not introduced), the microwaves propagate in the plasma chamber 51. In this case, in the above configuration, if the size (inner diameter) of the plasma chamber 51 is larger than the critical value determined by the cutoff wavelength of the microwaves, the microwaves propagating in the plasma chamber 51 travel from the insulating ring 56 to the outside of the chamber. It will leak out.

If the microwave leaking from the plasma chamber 51 leaks to the outside from the insulating insulator 62 provided in the ion source chamber 61, it becomes noise of the power supply / control system around the ion source. Furthermore, if the door of a shield cabinet (not shown) provided so as to surround the ion source chamber is opened, microwaves may leak to the outside.

Therefore, in the above-mentioned conventional ion source, in order to prevent the microwave from leaking from the plasma chamber 51, the size of the plasma chamber 51 needs to be equal to or less than a critical value determined by the cutoff wavelength of the microwave.

For example, in the case of a cylindrical plasma chamber 51, when a microwave of 2.45 GHz (which propagates in the TE ₁₁ mode) is used, the wavelength of the microwave is λ = 12.2 cm. The size of the chamber 51 is limited to an inner diameter of 7.16 cm or less.

As described above, in the above-mentioned conventional structure, the size of the plasma chamber 51 cannot be increased due to the above-mentioned limitation, and therefore the width of the slit-shaped ion extraction hole 52a in the longitudinal direction is naturally limited. There is a problem that the amount of the beam extracted from the plasma chamber 51 is limited due to the restriction of (1).

Further, in the above-mentioned conventional structure, the insulating ring 5 is used.
Since 6 is exposed to the outside, this portion is easily contaminated. This is because outside the plasma chamber 51, there are conductive particles generated by a part of the ions extracted from the plasma chamber 51 colliding with the extraction electrode system 60 and the like. If the surface of the insulating ring 56 is contaminated due to long-term use and the plasma slit 52 is short-circuited to another structure, a potential difference between the plasma slit 52 and the plasma chamber 51 main body cannot be secured, and cleaning by plasma sputtering is performed. The effect will be reduced.

The present invention has been made in view of the above, and an object thereof is to provide an ion having a plasma chamber configured to apply a sputtering voltage between the plasma chamber main body and the ion extracting portion (plasma slit 52). It is an object of the present invention to provide a microwave ion source capable of preventing microwaves from leaking from the ion source even when the size of the plasma chamber in the source is made larger than a critical value. Another object of the present invention is to provide a microwave ion source capable of preventing the surface of the insulating member (insulating ring 56) from being contaminated and providing a stable cleaning effect by plasma sputtering for a long period of time.

[0017]

A microwave type ion source according to the present invention has a conductive ion extraction portion having an ion extraction hole for extracting ions in plasma to the outside, and has an internal structure. In the plasma chamber, a plasma chamber for generating plasma by microwave discharge is provided, and the conductive plasma chamber main body whose inner wall surface is covered with a dielectric and the ion extracting portion are electrically insulated by an insulating member. A sputtering voltage is applied between the main body and the ion extracting portion, and the following means are taken to solve the above problems.

That is, the microwave ion source is
The one end is in contact with the ion extracting part, and is provided so as to surround the outer wall surface of the plasma chamber body,
Between the conductive waveguide member for propagating the microwave passing through the insulating member along the outer wall surface of the plasma chamber body and the other end portion of the waveguide member provided on the outer wall surface of the plasma chamber. A conductive choke groove member that is connected to the waveguide member at a predetermined interval, is guided by the waveguide member, and reflects microwaves propagating along the outer wall surface of the plasma chamber body at the bottom surface; The groove depth of the choke groove member is λg, which is the wavelength of the microwave guided by the waveguide member and propagating along the outer wall surface of the plasma chamber body.
Then, approximately (1/4 + n / 2) λg, where n is set to 0 or a positive integer.

Considering the case where the size of the plasma chamber is designed to be larger than the critical value determined by the cutoff wavelength of microwaves in the above configuration, if microwaves are introduced into the plasma chamber when plasma is not generated. , Microwaves propagate in the plasma chamber, pass through the insulating member, and go out of the chamber. The microwaves passing through the insulating member are guided to the waveguide member provided so as to contact the ion extracting portion and surround the outer wall surface of the plasma chamber body, and propagate along the outer wall surface of the plasma chamber body. . The microwave guided and propagated in the waveguide member is reflected by the bottom surface of the conductive choke groove member connected to the end of the waveguide member. Therefore, a standing wave is generated in the choke groove member and in the microwave waveguide between the outer peripheral wall of the plasma chamber and the waveguide member.

The above standing wave has a minimum current (current of 0 or a positive integer) at each point (n is 0 or a positive integer) distant from the bottom surface of the choke groove member by a reflection end by (1/4 + n / 2) λg. Section). The groove depth of the choke groove member is approximately (1 /
4 + n / 2) .lamda.g, and therefore the connection between the waveguide member and the choke groove member is provided near the point where the current is minimum (a predetermined interval is provided between both ends).
Therefore, it is possible to prevent the microwave from leaking to the outside from the gap of the connecting portion. That is, the connection between the waveguide member and the choke groove member can be considered as so-called choke coupling.

While the sputtering voltage is being applied, the waveguide member is in contact with the ion extracting portion and therefore has the same potential as the ion extracting portion. On the other hand, the choke groove member is provided in the plasma chamber main body and therefore the plasma chamber main body. It becomes the same potential.
Such a potential state can be ensured because a predetermined space is provided at the connecting portion between the waveguide member and the choke groove member.

Since the waveguide member is provided so as to abut the ion extracting portion and surround the outer wall surface of the plasma chamber body, the insulating member is not exposed to the outside. Therefore, since the surface of the insulating member can be prevented from being contaminated, the potential difference (sputtering voltage) between the plasma chamber main body and the ion extracting part can be reliably ensured, and the cleaning effect by stable plasma sputtering is expected for a long time. it can.

As described above, in the present ion source, microwaves can be prevented from leaking from the ion source even when the size of the plasma chamber is made larger than the critical value, and the plasma chamber main body and the ion extracting portion can be prevented. It is also possible to apply a sputter voltage between and.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the invention.
The following is a description with reference to FIG.

The microwave type ion source according to the present embodiment is an ECR ion source that generates a plasma by generating a microwave discharge in a magnetic field under the electron cyclotron resonance condition, and extracts ions from the plasma as a beam.
For example, it is applied to an ion beam application device such as an ion implantation device.

The above ion source has, for example, a magnetron that outputs a microwave of 2.45 GHz and a magnetron power supply that operates this magnetron. As shown in FIG. 1, the microwave generated by the magnetron is It is guided to the cylindrical plasma chamber 1 by the waveguide 6 and the microwave introducing rod 3 made of a dielectric material such as ceramics.

The inside of the plasma chamber 1 is a plasma generation chamber for converting the ion source substance into plasma, and a gas feedthrough (not shown) for introducing various ion source substances into the inside thereof. Are connected. A gas box for supplying a gaseous ion source substance such as BF ₃ or a solid oven for vaporizing a solid ion source substance such as metal is connected to the gas feedthrough.

A window 4 made of a dielectric material such as BN is provided on the wall surface of the plasma chamber 1 connected to the microwave introducing rod 3. This window 4
Is to introduce the microwave that has passed through the microwave introducing rod 3 into the plasma chamber 1.

The outer wall of the plasma chamber 1 is formed of a metal such as stainless steel or molybdenum, and the inside thereof is covered with a BN liner 5 made of BN having high electric insulation.

The wall surface of the plasma chamber 1 facing the window 4 is formed with a plasma slit 2 (ion extraction portion) having a slit-shaped ion extraction hole 2a formed therein. It is electrically insulated from the main body of the plasma chamber 1 by an insulating ring 7 (insulating member) including the above. Then, the positive electrode terminal of the sputtering power source 11 is in the main body of the plasma chamber 1 and the negative electrode terminals are both conductive spring hooks 12 and heat shield members so that the plasma slit 2 has a negative potential than the main body side of the plasma chamber 1. 13 (waveguide member)
Are connected to the plasma slits 2 respectively.

Voltage applied to the sputtering power source 11 (potential difference between the plasma slit 2 and the main body of the plasma chamber 1)
Is preferably set so that the speed at which the deposits are deposited on the plasma slit 2 and the speed at which the deposits are scraped off by sputtering are approximately in equilibrium.
It is about 2.0 kV.

The heat shield member 13 is made of a refractory metal and is formed in a cylindrical shape having a diameter larger than that of the plasma chamber 1. The heat of the plasma chamber 1 is covered with ions by covering the periphery of the plasma chamber 1. Source chamber 1
It has a heat retaining function of suppressing the transmission to the 5 side by radiation and keeping the temperature of the plasma chamber 1 at a high temperature. A locking portion 13a having an inner diameter smaller than that of the plasma chamber 1 and abutting against the end portion 2b of the plasma slit 2 is formed at one end of the cylindrical heat shield member 13. Further, on the outer wall surface on the other end side of the heat shield member 13,
A plurality of protrusions 13b ... With which the hook portion 12a of the spring hook 12 is locked are projected.

The heat shield member 13 has protrusions 13
are urged in the direction indicated by arrow X in the figure by a plurality of spring hooks 12 hooked on b ..., and the engaging portion 13a abuts against the end 2b of the plasma slit 2 and engages with it. And is mounted coaxially with the plasma chamber 1.

Since the heat shield member 13 also has the function of an introduction terminal for applying a sputtering voltage,
An end portion of the spring hook 12 opposite to the hook portion 12a is fixed by an insulating support portion 14 while being electrically insulated from the ion source chamber 15. However, one of the spring hooks 12 penetrates the insulating support portion 14 and is connected to the sputter power supply 11.

In the state where the heat shield member 13 is coaxially attached to the plasma chamber 1 as described above, the microwave leaking from the insulating ring 7 to the outside of the plasma chamber 1 is heated by the outer peripheral wall of the plasma chamber 1 and heat. It propagates between the inner peripheral wall of the shield member 13. this is,
As shown in FIG. 2, when the plasma chamber 1 is considered as a cylindrical waveguide, it can be regarded as a coaxial waveguide having a coaxial line formed on the outside thereof, and it is assumed that the coaxial waveguide is covered with a lid 20. can do.

Then, as shown in FIG. 1, on the outer peripheral wall of the plasma chamber 1, outside of the microwave propagated through the coaxial line between the outer peripheral wall of the plasma chamber 1 and the inner peripheral wall of the heat shield member 13. A choke groove member 16 is provided to prevent leakage to the. The choke groove member 16 has substantially the same outer diameter as the heat shield member 13, and one end of the choke groove member 16 is connected to the end portion of the heat shield member 13 with a predetermined gap (this connecting portion is a choke coupling connection). Therefore, although it is mechanically discontinuous, it is continuous as a microwave path), and the other end is closed to form a reflection end 16a.

As described above, since there is a gap (a gap greater than the dielectric breakdown distance) between the connection portion between the heat shield member 13 and the choke groove member 16, the heat shield member 1 is provided.
3 can be set to the potential of the plasma slit 2, and the choke groove member 16 can be set to the potential of the main body of the plasma chamber 1 different from the potential.

Since the choke coupling structure is employed, the depth (length in the microwave propagation direction) L ₁ of the choke groove member 16 is determined by the outer peripheral wall of the plasma chamber 1, the heat shield member 13 and the choke groove member. Let λg be the wavelength (in-tube wavelength) of the microwave propagating through the coaxial line formed by 16 and L ₁ = (1/4 + n / 2) λg (1) where n is 0 or a positive integer The dimensions are set to 1, 2, ...

As shown in FIG. 1, the heat shield member (58) is provided with a through hole at the end thereof and a spring hook (59) is not hooked therein, unlike the conventional structure shown in FIG. The reason why the projection 13b is provided on the outer wall surface of the shield member 13 and the spring hook 12 is hooked on the projection 13b is that the spring hook 12 does not have the function of the antenna (if the spring hook 12 is inside the heat shield member 13, the spring hook 12 does not function as an antenna). If the tip of 12 projects, the spring hook 12 acts as an antenna).

Outside the plasma chamber 1, the extraction electrode system 1 is provided at a position facing the plasma slit 2.
0 is provided. The extraction electrode system 10 is composed of a extraction electrode 8 and a ground electrode 9 each having beam passage holes 8a and 9a formed in the center thereof. The ground electrode 9 is set to the ground potential, and the extraction electrode 8 provided closer to the plasma chamber 1 than the ground electrode 9 is set to the negative potential than the ground electrode 9. When a high voltage such that the extraction electrode system 10 has a negative potential than that of the plasma chamber 1 side is applied from a power source (not shown), a strong external electric field is formed around the plasma slit 2, and the external electric field causes the plasma chamber Ions in 1 are extracted and an ion beam is formed. As described above, by setting the extraction electrode 8 to have a lower potential than the ground electrode 9, it is possible to prevent the backflow of electrons generated downstream of the extraction electrode 8.

The plasma chamber 1 is maintained in a high vacuum state by a vacuum exhaust means (not shown). Further, the plasma chamber 1 is housed in the ion source chamber 15 together with the extraction electrode system 10, and the inside of the ion source chamber 15 is also kept in a high vacuum state by a vacuum evacuation unit (not shown). The ion source chamber 15 has a high potential side in which the plasma chamber 1 is housed,
An insulating insulator 18 is provided to electrically isolate the low potential side.

A source magnet 17 provided with a solenoid coil is arranged around the plasma chamber 1. The source magnet 17 has an electron cyclotron resonance in the plasma chamber 1, which is substantially parallel to the beam extraction direction. It is designed to generate a magnetic field of conditions.

The operation of the ion source in the above structure will be described. The plasma chamber 1 is designed to have a size larger than a critical value determined by the cutoff wavelength of microwaves.

First, in a state where the plasma chamber 1 and the ion source chamber are kept in a high vacuum by the vacuum exhaust means, a magnetic field of electron cyclotron resonance condition is formed in the plasma chamber 1 by the source magnet 17 and output from the magnetron. The microwave that has passed through the waveguide 6 is introduced into the plasma chamber 1 through the microwave introduction rod 3 and the window 4, and a gaseous ion source material is introduced into the plasma chamber 1. With this, EC
Microwave discharge due to the R phenomenon occurs, and the ion source material introduced into the plasma chamber 1 is turned into plasma to generate ions. After the plasma is turned on, the microwave introduced into the plasma chamber 1 is absorbed by the plasma,
The plasma is maintained. Then, an electric field is applied to the plasma chamber 1 from the ion extraction hole 2a of the plasma slit 2.
Ions are extracted to form an ion beam.

During operation of this ion source, the temperature of the plasma chamber 1 becomes high, but the heat shield member 13 and the choke groove member 16 cover the periphery of the plasma chamber 1, and the heat of the plasma chamber 1 is heated by the ion source chamber 15. Radiation to the body is suppressed.

Here, when a plasma is generated using a corrosive gas such as BF ₃ as the ion source material, the BN liner 5 on the inner wall of the chamber is etched by the plasma forming material, resulting in a high B or BN content. The melting point substance is
It will adhere to the inner part of the plasma slit 2.
Therefore, when operating the ion source using a corrosive gas such as BF ₃ , the sputtering power supply 11 is turned on after confirming that the plasma is turned on. The confirmation of the plasma lighting can be confirmed by the fact that the current of the beam extracted from the plasma chamber 1 (extraction current) has become a predetermined value or more.

When the sputtering power source 11 is turned on, the plasma slit 2 has a negative potential more than that of the plasma chamber 1,
Ions in the plasma positively collide with the plasma slit 2. As a result, the deposits deposited on the plasma slit 2 are removed.

On the other hand, when plasma is not generated,
The microwave propagating in the plasma chamber 1 travels inside the insulating ring 7 and wraps between the outer peripheral wall of the plasma chamber 1 and the heat shield member 13. The microwaves that have passed around propagate along the outer peripheral wall of the plasma chamber 1 and are reflected by the bottom surface (reflection end 16a) of the choke groove formed by the choke groove member 16. As a result, a standing wave stands on the coaxial line between the outer peripheral wall of the plasma chamber 1 and the heat shield member 13 and the choke groove member 16.

This standing wave has a wavelength of λg /
4, 3λg / 4, ..., (1/4 + n / 2) λg at each point, the current becomes minimum (current node) (so-called open end state).

The depth (length in the propagation direction of microwaves) L ₁ of the choke groove of the choke groove member 16 is expressed by the above equation (1).
Is set to (1/4 + n / 2) λg,
Therefore, since the connection portion (gap portion) between the heat shield member 13 and the choke groove member 16 is located near the point where the current is minimized, it is possible to prevent the microwave from leaking to the outside from the gap of the connection portion. it can.

As an example, the outer diameter 2 of the plasma chamber 1
a = 9 cm, inner diameter of heat shield member 13 2 b = 10 cm
Consider the case (the inner diameter of the plasma chamber 1 is larger than the critical value).

When a microwave of 2.45 GHz (which propagates in the TE ₁₁ mode) is used, the wavelength of the microwave is λ = 12.2 cm. Further, the in-tube wavelength λg of the microwave propagating between the outer peripheral wall of the plasma chamber 1 and the heat shield member 13 and the choke groove member 16 is expressed by the following equation (2).

Λg = λ / [1- {λ / π (a + b)} ² ] ^1/2 ... (2) From λ = 12.2 cm, a = 4.5 cm, b = 5 cm, the above equation (2 The in-tube wavelength λg is about 13.4 cm.

In the above equation (1), n = 0, that is, L ₁
= Λg / 4, the depth L ₁ of the choke groove is about 3.3c
m.

The length L ₂ of the heat shield member 13 in the microwave propagation direction does not affect the choke coupling structure and is arbitrary. Here, as an example, L ₂ = 3λg / 4 and L ₂ is set to about 10.0 cm.

By setting L ₁ and L ₂ as described above, L ₁ + L ₂ becomes about 13.3 cm, and the plasma chamber 1 is composed of the heat shield member 13 and the choke groove member 16.
The heat of the plasma chamber 1 is prevented from radiating to the ion source chamber 15 by covering substantially the entire axial direction of the.

Further, since the sputtering voltage can be applied between the main body of the plasma chamber 1 and the plasma slit 2 as in the conventional case, even if a corrosive gas such as BF ₃ gas is used, the BN can be separated from the ion extraction hole 2a. It did not accumulate in the vicinity and block it, and the maintenance life was not shortened.

In the ion source designed as described above,
For example, in the plasma chamber 1, 2.45 GHz, 300
W microwave is introduced and BF ₃ gas is added at 1 cc /
If the plasma is introduced for a minimum of time, plasma can be turned on.
In this ion source, only a microwave of 2.45 GHz and 300 W was introduced without introducing a gas into the plasma chamber 1, and the amount of microwave leakage outside the insulating insulator 18 was measured to be 0.5 mW / cm. It was less than ² .

In order to compare with this, using a plasma chamber of the same size as the above with an ion source of the conventional configuration shown in FIG. 3, the amount of microwave leakage was measured under the same conditions as above, and the outside of the insulating insulator was measured. The microwave leakage of about 10 mW / cm ² was detected.

From these results, it can be seen that the ion source of this embodiment has a high effect of suppressing microwave leakage.

In the conventional configuration, if the size (inner diameter) of the plasma chamber is designed to be larger than the critical value, a large amount of microwave leaks as described above. Therefore, as shown in the section of the prior art, Plasma chamber size is inner diameter
The size is limited to 7.16 cm or less, and in this case, the slit size of the ion extraction hole is limited to 3 mm × 55 mm. Therefore, when this conventional ion source is applied to, for example, an ion implanter, the maximum beam current when implanting a 10 keV B ⁺ beam into a target wafer is about 7 mA.

On the other hand, in the ion source of this embodiment shown in FIG. 1, since the size of the plasma chamber 1 can be designed to be larger than the critical value, for example, the outer diameter of the plasma chamber 1 is set as described above. When designed to be 9 cm,
The ion extraction hole 2a has a slit size of 3 mm x 75 m
m. Therefore, when the ion source is applied to an ion implanter, a 10 keV B ⁺ beam 1
0 mA can be injected into the target wafer.

As described above, the microwave ion source of this embodiment is provided so that one end thereof abuts on the plasma slit 2 and surrounds the outer wall surface of the main body of the plasma chamber 1, and passes through the insulating ring 7. And a heat shield member 13 as a conductive wave guide member for propagating microwaves along the outer wall surface of the main body of the plasma chamber 1 and the other end of the heat shield member 13 with a predetermined gap therebetween. And a conductive choke groove member 16 that is connected in a coupled manner and reflects microwaves on the bottom surface, and the depth of the choke groove is approximately (1/4 + n / 2) λg (where n is 0 or a positive value). It is configured so that it becomes an integer).

As a result, even when the size of the plasma chamber 1 is made larger than the critical value, it is possible to prevent microwaves from leaking from the ion source. Therefore, the degree of freedom in designing the size of the plasma chamber 1 is higher than in the conventional case, and the size of the plasma chamber 1 can be designed to be large. As a result, the ion extraction hole 2a is enlarged to increase the extraction amount of the ion beam. be able to. Further, noise generation due to microwave leakage can be suppressed, and the operation of the power supply / control system around the ion source is not hindered.
In addition, since the shielding effect against microwaves is high, even if the door of the shield cabinet (not shown) provided so as to surround the ion source chamber is inadvertently opened,
The amount of microwaves leaking out to the outside is extremely small, and high safety is achieved even without various interlock mechanisms. Therefore, the reliability of safety is further improved by using the interlock mechanism together.

Furthermore, since the heat shield member 13 is provided so as to abut the plasma slit 2 and surround the outer wall surface of the plasma chamber 1 main body, the insulating ring 7 is not exposed to the outside. Therefore, the outer surface of the insulating ring 7 is not contaminated, the potential difference (sputtering voltage) between the plasma chamber 1 main body and the plasma slit 2 can be reliably secured, and the cleaning effect by stable plasma sputtering for a long time can be obtained. Can be expected.

Further, since the microwave ion source of this embodiment uses the heat shield member 13 as a waveguide member, the number of parts does not increase.

In the microwave type ion source of this embodiment, since the conductive waveguide member (heat shield member 13) can be used as the introduction terminal for applying the sputtering voltage, the conventional structure shown in FIG. The wiring structure for applying the sputtering voltage becomes easier than that. Further, by using the waveguide member (heat shield member 13) as the introduction terminal, it is not necessary to use a dedicated introduction terminal as in the conventional case, and therefore the distance between the introduction terminal and the extraction electrode system 10 is also larger than in the conventional case. It becomes longer and the possibility of discharge between them becomes smaller.

In the above embodiment, the plasma chamber 1 is described as a cylindrical shape, but it may have another shape such as a square shape. Of course, the microwave propagation mode is not limited to the TE ₁₁ mode. Further, the present invention is applicable to all ion sources using microwaves other than the ECR ion source. The above-described embodiment is merely to clarify the technical contents of the present invention, and should not be construed in a narrow sense by limiting only to such specific examples. The spirit of the present invention and the claims Various modifications can be made within the range.

[0069]

As described above, the microwave type ion source of the present invention is provided such that one end thereof abuts on the ion extracting portion and surrounds the outer wall surface of the plasma chamber body, and passes through the insulating member. A conductive waveguide member for propagating microwaves along the outer wall surface of the plasma chamber body, and provided on the outer wall surface of the plasma chamber,
A microwave that is connected to the other end of the above-mentioned waveguide member with a predetermined gap and is guided by the waveguide member and propagates along the outer wall surface of the plasma chamber body is reflected on the bottom surface. And a conductive choke groove member, the depth of the groove of the choke groove member is approximately when the wavelength of the microwave guided by the waveguide member and propagating along the outer wall surface of the plasma chamber body is λg. , (1/4 + n / 2) λg where n is set to 0 or a positive integer.

Therefore, even when the size of the plasma chamber is made larger than the critical value, it is possible to prevent microwaves from leaking from the ion source. As a result, the size of the plasma chamber (size of the ion extraction hole) can be designed larger than before, the amount of beam extraction can be increased, and noise generation due to microwave leakage can be suppressed. It has effects such as high reliability. Further, it also has an effect of preventing contamination of the outer surface of the insulating member and obtaining a cleaning effect by stable plasma sputtering for a long time.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention and is a schematic cross-sectional view of a microwave ion source.

FIG. 2 is an explanatory view schematically showing the plasma chamber of the microwave ion source as a coaxial waveguide.

FIG. 3 is a schematic cross-sectional view of a conventional microwave ion source.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plasma chamber 2 Plasma slit (ion extraction part) 2a Ion extraction hole 3 Microwave introduction rod 5 BN liner 6 Waveguide 7 Insulation ring (insulation member) 10 Extraction electrode system 11 Sputter power supply 12 Spring hook 13 Heat shield member (waveguide) Member) 15 ion source chamber 16 choke groove member 16a reflection end (bottom surface of choke groove member)

Claims (1)

[Claims] 1. A plasma chamber for producing a plasma by microwave discharge, comprising a conductive ion extracting portion having an ion extracting hole for extracting ions in plasma to the outside. The conductive plasma chamber body whose inner wall surface is covered with a dielectric is electrically insulated from the ion extracting portion by an insulating member, and a sputtering voltage is applied between the plasma chamber body and the ion extracting portion. In the microwave ion source, one end of the microwave ion source is in contact with the ion extracting portion and is provided so as to surround the outer wall surface of the plasma chamber body,
Between the conductive waveguide member for propagating the microwave passing through the insulating member along the outer wall surface of the plasma chamber body, and the other end portion of the waveguide member provided on the outer wall surface of the plasma chamber. A conductive choke groove member that is connected to the waveguide member at a predetermined interval, is guided by the waveguide member, and reflects the microwave propagating along the outer wall surface of the plasma chamber body at the bottom surface thereof; The depth of the groove of the choke groove member is approximately (1/4 + n / 2) λg, where n is the wavelength of the microwave guided by the waveguide member and propagating along the outer wall surface of the plasma chamber body. Is set to 0 or a positive integer, a microwave type ion source.