JPH065220A - Metallic ion source - Google Patents

Abstract

PURPOSE:To perform conformity adjustment between coaxial impedance and plasma and position adjustment for a sputter target, in a metallic ion source jointly using microwave discharge and sputtering. CONSTITUTION:A plasma chamber 2 is arranged at the tip part of a coaxial transmission path 3 extending in a straight line. A microwave supplied from a microwave source 10 is transmitted to the plasma chamber 2 through a coaxial microwave supply line 11, a capacitance coupling part 12, and the coaxial transmission path 3. A short-circuit plate 13, blocking a microwave transmitted to the opposite side to the plasma chamber 2 of the coaxial transmission path 3, is made movable in the axial line direction of the coaxial transmission path 3. A conductive member 5, composing the inner conductor 3a of the coaxial transmission path 3, is also made movable in the axial line direction. Negative voltage 19 for sputtering is made to be applied to a metallic target 18, fitted to the tip of the conductive member 5, through it.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal ion source used for obtaining an ion beam of a desired metal, and more particularly, to use a microwave discharge and sputtering together to generate metal ions. The present invention relates to a sputtering type metal ion source.

[0002]

2. Description of the Related Art For example, when a semiconductor element is manufactured by implanting impurities into a semiconductor, or when titanium is implanted into iron to increase its hardness, the metal as an impurity is ionized and the metal ion is ion beamed. As for irradiation injection. In that case, the metal ion beam is required to have high purity. In order to obtain such a metal ion beam, it is necessary to efficiently ionize the desired metal. As a metal ion source capable of producing ions of a desired metal with high purity in this way, a sputtering method disclosed in, for example, Japanese Patent Publication No. 58-51378 is known. A sputtering type metal ion source introduces a gas and a microwave into a plasma chamber in which a magnetic field exists to generate gas plasma, and the gas plasma causes sputtering on the surface of a metal target placed in the plasma chamber. This is to ionize the metal atoms that fly out of the metal target. Therefore, if a desired metal is placed as the target, ions of the metal can be efficiently generated.

By the way, in such a sputtering type metal ion source, a microwave is transmitted to the plasma chamber and a negative voltage is applied to the metal target arranged in the plasma chamber. Will be required. Usually, a coaxial transmission line is used for microwave transmission. The coaxial transmission line is arranged coaxially with the inner conductor and the outer conductor insulated from each other. When transmitting microwaves to the plasma chamber through such a coaxial transmission line, attach a microwave source that generates microwaves to the proximal end of the coaxial transmission line and provide the plasma chamber at the tip of the coaxial transmission line. To In that case, the tip of the inner conductor of the coaxial transmission line is exposed in the plasma chamber. Moreover, the inner conductor and the plasma chamber are kept in an insulating state. Therefore, in order to dispose the metal target in the plasma chamber in an insulated state with respect to the plasma chamber and to transmit the microwave to the plasma chamber and to apply the negative voltage to the metal target, It is conceivable that the tip end of the inner conductor of the coaxial transmission line that transmits the is used as the metal target and a negative voltage is applied to the inner conductor. However, it is necessary to prevent the direct-current voltage applied to the metal target from being applied to the microwave source that generates microwaves. That is, when a negative voltage is applied to the metal target through the inner conductor of the coaxial transmission line, the inner conductor must be galvanically isolated between the plasma chamber side and the microwave source side. Is required. Further, in order to efficiently transmit the microwave to the plasma chamber, it is necessary to prevent the microwave from leaking to the outside from the DC voltage applying section to the inner conductor.

Therefore, in the metal ion source described in the above publication, a DC voltage is applied to the inner conductor of the coaxial transmission line at the longitudinal intermediate portion of the microwave transmission line having a coaxial structure for transmitting microwaves from the microwave source to the plasma chamber. In addition to providing a coaxial branch line for applying a voltage, an insulating means is provided between the branch portion and the microwave source for allowing microwaves to pass therethrough but insulating in terms of direct current. That is, as shown in FIG.
In the microwave transmission path 03 having a coaxial structure for transmitting microwaves to the plasma chamber 02, a branch line 04 having a coaxial structure is provided at an intermediate portion in the longitudinal direction. A choke structure 05 for microwaves is provided at the terminal end of the coaxial branch line 04, whereby the inner conductor 04a and the outer conductor 04b of the branch line 04 are galvanically insulated, and the terminal end thereof is provided. Is a short-circuited end in the microwave. Moreover, the branch line 04 has a length corresponding to a quarter wavelength of the microwave. Therefore,
The propagation of microwaves in the branch direction is prevented. Then, the inner conductor 04a of the branch line 04
DC power source 06 is connected to the terminal of the
A negative voltage is applied to the inner conductor 03a of the coaxial transmission line 03 via the. Further, a choke structure 07 is provided on the inner conductor 03a of the coaxial transmission line 03 between the branch portion and the microwave source 01 to allow the microwave supplied from the microwave source 01 to pass, but for the direct current microwave source The 01 side and the plasma chamber 02 side are insulated from each other.

The tip of the inner conductor 03a of the coaxial transmission line 03 is supported by the insulating plate 08 that allows microwaves to pass therethrough while being insulated from the outer conductor 03b. The insulating plate 08 hermetically closes the space between the inner conductor 03a and the outer conductor 03b, whereby the plasma chamber 02 is held in a vacuum state. In this way, the tip of the inner conductor 03a of the coaxial transmission line 03 is projected into the plasma chamber 02. The tip is formed of the metal to be ionized. Plasma chamber 0
A magnetic field is formed inside 2 by a coil 09 for generating a magnetic field, and gas is introduced from a gas inlet 010. Furthermore, on the wall surface of the plasma chamber 02,
A positive potential is applied by the DC power supply 011. Then, the metal ions generated in the plasma chamber 02 are extracted to the outside from the ion extraction hole 012 formed in the front end surface of the plasma chamber 02 by the grounded extraction electrode 013 provided in the vicinity thereof. It is like this.

In the metal ion source configured as described above, a gas is introduced into the plasma chamber 02 while a magnetic field is formed in the plasma chamber 02, and the microwave source 01 is further introduced.
When a microwave is supplied from the gas chamber, gas plasma is generated in the plasma chamber 02. Therefore, the coaxial transmission line 03
If a negative voltage is applied to the inner conductor 03a, the tip portion of the inner conductor 03a exposed in the plasma chamber 02 is sputtered by the gas plasma, and the metal atoms forming the tip portion are sputtered from the tip portion. Jump out. Then, the metal atoms are ionized in the plasma, and the tip of the inner conductor 03a is further sputtered by the metal ions. In this way, highly concentrated metal ions are generated in the plasma chamber 02. The metal ions are extracted from the extraction hole 012 as an ion beam 014 by the extraction electrode 013. In that case, the coaxial transmission line 0 connected to the DC power source 06
Since the choke structure 07 is provided between the inner conductor 03a of 3 and the microwave source 01, there is no fear that a DC voltage is applied to the microwave source 01. Further, since the coaxial branch line 04 is neglected in terms of microwave, the microwave does not leak to the outside from the DC power supply connection portion. Therefore, the microwave power can be effectively used.

[0007]

However, in a metal ion source provided with such a coaxial branch line 04, the position of the inner conductor 03a of the coaxial microwave transmission line 03 can be adjusted for the branch line 04. It will be impossible,
We cannot solve the following problems. That is,
The microwave generated by the microwave source 01 is required to be efficiently supplied to the discharge plasma formed inside the plasma chamber 02, but the plasma is not necessarily a load matched with the impedance of the coaxial transmission path 03. Therefore, it is difficult to ensure that all of the input microwave power is supplied to the plasma. In order to increase the microwave supply efficiency, it is necessary to separately provide a variable matching device such as a stub tuner. Therefore, the entire device becomes expensive. Further, in the case of a sputtering type metal ion source in which sputtering is performed at the tip of the inner conductor 03a of the coaxial transmission line 03 in this way, wear of the tip of the inner conductor with the lapse of operating time is optimal for ion generation. The tip position of the inner conductor 03a changes. Moreover, its position also differs depending on the metal used. Therefore, it is required to be able to deal with it, but it is extremely difficult to do so because the inner conductor 03a is fixed. Further, the tip portion of the inner conductor 03a, which is the sputtering portion, is heated by ion bombardment, and the heat may deteriorate the vacuum seal portion of the insulating plate 08 that supports the tip portion of the inner conductor 03a. However, the inner conductor 04a of the coaxial branch line 04 connected to the tip of the inner conductor 03a and exposed to the outside is the inner conductor 03a of the coaxial transmission line 03.
Since it forms an angle with respect to, it is difficult to provide a cooling mechanism for removing the heat.

The present invention has been made in view of the above problems, and an object thereof is to make it possible to adjust the coaxial impedance, the sputtering position, etc. according to the operating state, and to reduce the sputtering portion. It is to obtain a metal ion source that is easy to cool.

[0009]

In order to achieve this object, in the present invention, the microwave transmission line having a coaxial structure for transmitting microwaves to the plasma chamber is made substantially linear, and the coaxial transmission line is The microwave is supplied from the side. That is, in the metal ion source according to the present invention, a plasma chamber is arranged at the tip of a coaxial transmission line that extends substantially linearly, and a coaxial chamber that supplies microwaves to the coaxial transmission line at an intermediate portion in the longitudinal direction of the coaxial transmission line. It is characterized by connecting the microwave supply line of the structure. The microwave supply line is designed to be insulated from the inner conductor of the coaxial transmission line in terms of direct current. On the side opposite to the plasma chamber as seen from the connection part of the microwave supply line, a short-circuit plate that short-circuits between the inner conductor and the outer conductor of the coaxial transmission line in a microwave manner but insulates from a direct current manner. Is provided. The metal target sputtered by the plasma in the plasma chamber is placed at the end of the inner conductor of the coaxial transmission line exposed in the plasma chamber.At the end of the inner conductor opposite to the plasma chamber, a negative voltage is applied to the metal target. A DC power supply for applying a voltage is connected. For supplying microwaves from the microwave supply line to the coaxial transmission line, for example, a capacitive coupling plate is attached to the tip of the inner conductor of the microwave supply line, and the capacitive coupling plate is placed close to the inner conductor of the coaxial transmission line. This is done by capacitive coupling of placement.

[0010]

With this configuration, the inner conductor of the microwave transmission line having the coaxial structure is galvanically isolated from the microwave source attached to the microwave supply line. A negative voltage for sputtering can be applied to the tip of the inner conductor exposed to the plasma through the conductor. Further, since the microwave supplied from the microwave supply line to the coaxial transmission line is blocked by the short-circuit plate on the side opposite to the plasma chamber, it does not leak to the outside and is efficiently guided to the plasma chamber side. Therefore, it is possible to generate metal ions with high efficiency by performing sputtering while applying microwave power to plasma. Since the inner conductor of the coaxial transmission line is substantially linear, it becomes possible to move the short-circuit plate provided on the outer periphery in the axial direction. It is possible to optimize impedance matching between the transmission line and the plasma formed in the plasma chamber. Therefore, the ion generation efficiency can be improved. In addition, the position of the metal target provided at the tip of the inner conductor of the coaxial transmission line can be adjusted, so when the optimal position for ion generation changes due to metal consumption in the sputter part, or when the type of metal used changes. When the optimum position changes due to, it is possible to respond to those changes. Furthermore, by making the inner conductor of the coaxial transmission line substantially linear, it becomes easy to provide a flow path inside the inner conductor for supplying and discharging the cooling medium to and from the tip portion thereof. Therefore,
It is possible to remove heat from the tip of the inner conductor where sputtering is performed, and it is possible to prevent deterioration of the vacuum seal member and the like and melting of the sputtered portion due to heat.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. In the drawings, FIG. 1 is a schematic vertical sectional view showing an embodiment of a metal ion source according to the present invention. As is clear from this figure, the plasma chamber 2 of the metal ion source 1 has the inner conductor 3a.
Microwave transmission line 3 having a coaxial structure composed of an outer conductor 3b and
Is located on the tip side (right side in the figure) of the. The inner conductor 3a of the coaxial transmission line 3 is formed by a cylindrical outer cylinder 4 which continuously extends linearly from the front end to the rear end, and a conductive member 5 which is fitted inside thereof to be slidable in the axial direction. It is configured. The conductive member 5 is longer than the outer cylinder 4, and both ends thereof are projected from both ends of the outer cylinder 4, respectively. The outer cylinder 4 of the inner conductor 3a is supported by the outer conductor 3b through the insulating plate 6 having a circular tip, and through the insulating spacer 7 at the rear end, whereby coaxial transmission is performed. The inner conductor 3a and the outer conductor 3b of the path 3 are coaxially held, and an insulating state is maintained between them. The plasma chamber 2 is a cylindrical chamber having an insulating plate 6 supporting the tip of the inner conductor 3a and a flange surface 2a as both bottom surfaces, and its outer peripheral wall 2b is directly coupled to the tip of the outer conductor 3b by a bolt or the like. , And electrically connected between them. Further, the electrically conductive member 5 and the outer cylinder 4 forming the inner conductor 3a are also kept electrically connected. The insulating plate 6 that supports the tip of the inner conductor 3a is formed of an airtight material, such as quartz glass, that allows microwaves to pass through but blocks the passage of gas. The fixed seal members 8a and 8b are used to hermetically seal between the inner peripheral portion of the insulating plate 6 and the tip of the inner conductor 3a, and between the outer peripheral portion of the insulating plate 6 and the outer peripheral wall 2b of the plasma chamber 2. It is sealed. The outer cylinder 4 of the inner conductor 3a and the conductive member 5 are vacuum-sealed by a slidable seal member 9. Thus, the inside of the plasma chamber 2 is kept vacuum.

A microwave supply line 11 having a coaxial structure, which is composed of an inner conductor 11a and an outer conductor 11b, to which a microwave source 10 for generating a microwave is attached, is connected to an intermediate portion in the longitudinal direction of the coaxial transmission line 3. There is. The inner conductor 11
A capacitive coupling plate 12 is attached to the tip of a, and the capacitive coupling plate 12 is positioned on the inner conductor 3a of the coaxial transmission line 3 with a small space therebetween. Therefore, the inner conductors 3a and 11a are galvanically insulated. On the other hand, the outer conductor 11b of the microwave supply line 11 is joined to the outer conductor 3b of the coaxial transmission line 3. In this way, the microwave supplied from the microwave source 10 is transmitted to the coaxial transmission line 3 by capacitive coupling between the microwave supply line 11 and the coaxial transmission line 3. In the coaxial transmission path 3 on the side opposite to the plasma chamber 2 when viewed from the connection portion of the microwave supply line 11, a short-circuit plate 13 for microwaves is provided at a position separated by about 1/4 of the wavelength of the microwave. Has been. The short-circuit board 1
3 is slidable in the axial direction, and its position is adjusted by operating the operation member 14 protruding to the outside. The short-circuit plate 13 contacts the inner peripheral surface of the outer conductor 3b of the coaxial transmission line 3, and the inner conductor 3a is the inner conductor 3b.
The outer peripheral surface of a is contacted via an insulating film 15 as a thin insulating layer. And
A choke structure 16 is provided on a portion of the short-circuit plate 13 facing the inner conductor 3a. Therefore, the coaxial transmission line 3
The inner conductor 3a and the outer conductor 3b are short-circuited by microwaves by the short-circuiting plate 13 but are insulated by direct current. Thus, the microwaves supplied from the microwave source 10 to the coaxial transmission line 3 are transmitted to the plasma chamber 2
On the opposite side, the plasma chamber 2 is blocked by the short-circuit plate 13.
It is designed to be transmitted to the plasma chamber 2 from the coaxial transmission path 3 through the insulating plate 6 toward the side. Coaxial transmission line 3
In the outer conductor 3b, two conductor rods 1 projecting into the space between the inner conductor 3a and the outer conductor 3b at a position closer to the plasma chamber 2 from the connection portion of the microwave supply line 11 are formed.
7, 17 are slidably inserted. Therefore, the tip position of the conductor rod 17 is variable in the radial direction of the coaxial transmission line 3.

A sputter target 18 made of a metal to be ionized is attached to the tip of the conductive member 5 constituting the inner conductor 3a of the coaxial transmission line 3. Therefore, the metal target 18 is moved in the axial direction in the plasma chamber 2 by moving the conductive member 5 forward and backward. A DC power supply 19 for applying a negative voltage to the outer conductor 3b of the coaxial transmission line 3 is provided at the rear end of the conductive member 5, that is, the end projecting to the outside opposite to the plasma chamber 2. It is connected. Then, a positive potential is applied to the outer conductor 3b by the DC power supply 20. In this way, the plasma chamber 2 is maintained at a positive potential, and a negative voltage is applied to the metal target 18 with respect to the plasma chamber 2. Conductive member 5
Is hollow up to near its tip, that is, up to a portion close to the metal target 18. Then, a small-diameter pipe 21 having a rear end protruding to the outside and a front end reaching the vicinity of the front end of the conductive member 5 is inserted therein.
A cooling medium discharge port 22 that communicates with the internal space is provided at the rear end of the conductive member 5. In this way, the flow path 23 for the cooling medium is formed inside the inner conductor 3a of the coaxial transmission path 3, and the front end portion is cooled by supplying the cooling medium from the rear end of the pipe 21.

A permanent magnet 2 as a magnetic field generating means for forming a magnetic field in the plasma chamber 2 is provided on the outer periphery of the plasma chamber 2.
4 are provided. In addition, the outer peripheral wall 2b of the plasma chamber 2
Is provided with a gas inlet 25, and an inert gas such as argon is introduced into the plasma chamber 2 through the gas inlet 25. Further, the flange surface 2 a of the plasma chamber 2 is provided with an ion extraction hole 26, and outside the plasma chamber 2, in the vicinity of the ion extraction hole 26,
Extraction electrode 2 for extracting ions generated in plasma chamber 2
7 is provided. The extraction electrode 27 is grounded. Then, of the surface of the metal target 18 exposed in the plasma chamber 2, the side surface portion of the insulating plate 6 which faces the surface 6 a on the plasma chamber 2 side is a non-conductive cylindrical shield 28 protruding from the insulating plate 6. It is supposed to be covered by.

Next, the operation of the metal ion source 1 thus constructed will be described. When an ion beam of a desired metal is to be obtained by the metal ion source 1, the sputter target 18 made of the metal is attached to the coaxial transmission line 3
Is attached to the tip of the inner conductor 3a, that is, the tip of the conductive member 5. Then, the inside of the plasma chamber 2 is evacuated in advance, and, for example, argon gas is introduced into the plasma chamber 2 through the gas introduction port 25. In addition, the microwave source 10
Microwave is injected into the plasma chamber 2 through the coaxial microwave supply line 11, the capacitive coupling section, and the coaxial transmission line 3. A magnetic field is formed in the plasma chamber 2 by the magnet 24. Therefore, gas plasma is formed in the plasma chamber 2 by the magnetic field and the microwave. On the other hand, since the DC power source 19 is connected between the conductive member 5 and the outer conductor 3b of the coaxial transmission line 3, the metal target 18 arranged in the plasma chamber 2 has a negative potential with respect to the plasma chamber 2. A voltage is applied. The metal target 18
Are exposed to the plasma in the plasma chamber 2. As a result, sputtering occurs on the surface of the metal target 18, and metal atoms fly out from the surface. The metal atoms are ionized in the plasma. Then, the metal ions further sputter the metal target 18.
In this way, mixed ions of argon ions and metal ions are generated in the plasma chamber 2. The ion is
Due to the potential difference between the positive potential applied to the plasma chamber 2 from the DC power source 20 and the ground potential of the extraction electrode 27,
An ion beam 29 is extracted from the ion extraction hole 26 to the outside. The ion beam 29 is sent to a mass analyzer (not shown) provided outside, and is separated into argon ions and metal ions. Thus
A highly pure metal ion beam consisting of only desired metal ions can be obtained.

In the meantime, as described above, the short-circuit plate 13 is positioned at a distance of about 1/4 of the wavelength of the microwave from the connection portion of the coaxial transmission line 3 with the microwave supply line 11. Therefore, the coaxial transmission line 3 on the side opposite to the plasma chamber 2 when viewed from the connecting portion is considered to have almost no microwave. However, if the position of the short-circuit plate 13 is changed, the impedance of the coaxial transmission line 3 changes. Therefore, the position of the short-circuit plate 13 is adjusted in order to match the coaxial impedance with the plasma load and efficiently transmit the microwave power to the plasma to improve the efficiency of ion generation.
Further, the conductor rods 17, 17 inserted into the outer conductor 3b of the coaxial transmission line 3 function as stub tuners, and the coaxial impedance changes even if the insertion length is changed. Therefore,
The insertion length of the conductor rod 17 is adjusted for the same purpose. On the other hand, when the optimum position of the metal target 18 in the plasma chamber 2 differs depending on the type of metal used, or when the surface of the metal target 18 deviates from the optimum position due to consumption of the metal target 18 due to sputtering, the conductive member 5 is used. The position of the metal target 18 is adjusted by pushing and pulling the rear end portion that protrudes to the outside. In that case, since the conductive member 5 and the outer cylinder 4 are vacuum-sealed by the slidable seal member 9, there is no possibility that the vacuum of the plasma chamber 2 is damaged by the adjustment. The position adjustment of the metal target 18 attached to the tip of the short-circuit plate 13 or the conductive member 5 is performed by adjusting the inner conductor 3 of the coaxial transmission line 3.
This is possible when a is a continuous straight line.

Further, by making the inner conductor 3a of the coaxial transmission line 3 continuous and straight, the pipe 21 is inserted into the conductive member 5 constituting the inner conductor 3a to double the conductive member 5. It becomes easy to make it a tubular structure. Then, by flowing the cooling medium through the flow path 23 formed thereby, it is possible to remove heat from the tip portion of the conductive member 5,
It is possible to prevent the deterioration of the vacuum seal member 9 and the melting of the metal target 18 due to the heat of sputtering. Further, by covering the side surface of the metal target 18 arranged in the plasma chamber 2 with the insulating shield 28, metal atoms derived from spattering generated on the side surface may be attached and deposited on the surface of the insulating plate 6. To be prevented. Since the insulating plate 6 transmits microwaves, if metal atoms are deposited on the insulating plate 6, the microwave transmission efficiency of the insulating plate 6 will be impaired. However, in the case of this metal ion source 1, the deposition of metal atoms on the insulating plate 6 is prevented as described above, so that microwaves that are injected into the plasma in the plasma chamber 2 through the coaxial transmission path 3 are prevented. The transmission efficiency can be kept high. Then, by supplying the microwave from the coaxial microwave supply line 11 to the coaxial microwave transmission line 3 by capacitive coupling, the configuration of the connecting portion is simplified, and
It is possible to easily secure direct current insulation during that time.
Further, by making the metal target 18 attached to the tip of the conductive member 5 detachable, the workability of exchanging the metal target 18 when the metal target 18 is consumed or when the type of metal to be used is changed. Can be improved. As described above, according to the metal ion source 1, it is possible to generate metal ions with high efficiency and to provide a metal ion source having high durability and a simple structure.

In the above embodiment, the inner conductor 3a of the coaxial transmission line 3 is composed of the outer cylinder 4 and the conductive member 5 slidably supported by the outer cylinder 4. If the cylinder 4 is slidably supported by the insulating plate 6 and the insulating spacer 7, the outer cylinder 4 and the conductive member 5 can be integrated to form the inner conductor 3a as a single component. In addition, the metal target 18 is connected to the conductive member 5
Although it is separate from the above, it is also possible to make them entirely of a metal to be ionized. Further, it is possible to employ a choke structure or the like for the connection between the coaxial microwave supply line 11 and the coaxial microwave transmission line 3.

[0019]

As is clear from the above description, according to the present invention, the inner conductor of the coaxial transmission line for transmitting microwaves to the plasma chamber extends substantially linearly.
The short-circuiting plate for microwaves that insulates the inner conductor and the outer conductor of the coaxial transmission line from a direct current can be movable in the axial direction of the coaxial transmission line. Then, by making the short-circuit plate movable, it is possible to adjust the impedance of the coaxial transmission line and the plasma in the plasma chamber,
The efficiency of inputting microwave power to plasma can be improved. Further, since the inner conductor is continuous from the tip exposed to the plasma chamber to the rear exposed to the outside, the metal target provided at the tip of the inner conductor can be moved. it can. And by doing so, it becomes possible to position the metal target at the optimum position for ion generation,
The ion generation efficiency can be increased. Furthermore, since it becomes easy to provide a flow path for the cooling medium inside the inner conductor, it is possible to remove heat from the metal target portion that receives sputtering at the tip of the inner conductor, and the vacuum caused by the heat generation at that portion can be performed. By avoiding deterioration of the seal member and melting of the metal target, it is possible to extend the life and improve the reliability.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view showing an embodiment of a metal ion source according to the present invention.

FIG. 2 is a vertical sectional view showing a conventional metal ion source.

[Explanation of symbols]

 1 Metal Ion Source 2 Plasma Chamber 3 Coaxial Microwave Transmission Line 3a Inner Conductor 3b Outer Conductor 4 Outer Cylinder 5 Conductive Member 6 Insulating Plate 9 Sealing Member 10 Microwave Source 11 Coaxial Microwave Supply Line 12 Capacitive Coupling Plate 13 Short Circuit Plate 15 Insulating Film (Insulating layer) 16 Choke structure 17 Conductor rod 18 Metal target 19 DC power source for sputtering 23 Cooling medium flow path 24 Permanent magnet (magnetic field generating means) 25 Gas inlet port 28 Shield 29 Ion beam

Claims (8)

[Claims] 1. A metal target, to which a negative voltage is applied to the plasma chamber, is disposed in the plasma chamber where a gas magnetic field is generated and gas and microwave are introduced to generate gas plasma. In a metal ion source adapted to cause sputtering on the surface of the metal target by gas plasma and to ionize metal atoms emitted from the metal target so as to be extracted as metal ions; It is provided at the tip of a microwave transmission line having a coaxial structure composed of an inner conductor that extends linearly and an outer conductor that is coaxially arranged while being insulated from the inner conductor. A microwave supply line having a coaxial structure for supplying microwaves to the coaxial transmission line is provided in the middle portion in the longitudinal direction by the coaxial transmission. Is connected so as to be insulated from the inner conductor, and the inner conductor and the outer conductor of the coaxial transmission line are short-circuited in a microwave manner on the side opposite to the plasma chamber when viewed from the connecting portion. However, with a short circuit plate that is insulated in terms of direct current, the metal target is arranged at the tip of the inner conductor of the coaxial transmission line exposed in the plasma chamber, and the negative voltage is applied to the metal target. A metal ion source, wherein a direct current power source to be applied is connected to an end of the inner conductor of the coaxial transmission path opposite to the plasma chamber. 2. A capacitive coupling plate disposed near the inner conductor of the coaxial transmission line is attached to the tip of the inner conductor of the microwave supply line, and the capacitive coupling plate and the coaxial transmission line are connected to each other. The metal ion source according to claim 1, wherein the microwave supply line and the coaxial transmission line are microwave-coupled by capacitive coupling with the inner conductor. 3. The metal ion source according to claim 1, wherein the metal target is movable in the axial direction of the inner conductor of the coaxial transmission line. 4. The metal ion source according to claim 1, wherein the short-circuit plate is movable in the axial direction of the inner conductor of the coaxial transmission line. 5. The short-circuit plate is in contact with the outer conductor of the coaxial transmission line and is in contact with the inner conductor of the coaxial transmission line via a thin insulating layer, and faces the inner conductor of the short-circuit plate. The metal ion source according to claim 1, wherein a choke structure for microwaves is provided on the side. 6. A conductor rod that penetrates the outer conductor and projects into a space between the outer conductor of the coaxial transmission line and the inner conductor of the coaxial transmission line is variably inserted in the radial direction. Item 7. A metal ion source according to any one of items 1 to 5. 7. The inner conductor of the coaxial transmission line is hollow, and a flow path for a cooling medium from a rear end portion to a front end portion is formed inside the inner conductor. The metal ion source according to any one of 1. 8. The end portion of the inner conductor of the coaxial transmission line is supported by the outer conductor of the coaxial transmission line while being insulated from the outer conductor of the coaxial transmission line by an insulating plate that holds the vacuum of the plasma chamber but transmits microwaves. The metal ion according to any one of claims 1 to 7, wherein a side surface portion of the surface of the metal target that faces the surface of the insulating plate on the plasma chamber side is covered with a non-conductive shield. source.