JP3075129B2 - Ion source - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to an ion beam apparatus such as an ion implantation apparatus, and converts an ion species gas introduced into a plasma generation chamber into plasma to generate ions. The present invention relates to an ion source for extracting and forming an ion beam.

[0002]

2. Description of the Related Art In recent years, ion sources for converting elements into plasma and extracting ions in the plasma as an ion beam have been used in various fields such as ion implantation, ion plating, crystal growth, and ion processing. I have. In the above-mentioned ion source, a cathode filament is provided inside the plasma generation chamber for electrical insulation from the chamber, and a current is applied to the filament to heat the filament, and between the filament and the plasma generation chamber. Freeman generates an arc by applying a voltage necessary for the arc discharge to emit anrmionic electrons from the filament, and converts the ion species gas introduced into the plasma generation chamber into plasma by the arc discharge to generate ions. There is a low-voltage arc discharge type ion source represented by a type ion source.

[0003] Among the low voltage arc discharge ion sources, the Bernas type ion source can generate plasma by lowering the arc voltage than the Freeman type, so that the life of the filament can be extended and the electron confinement efficiency can be improved. Since it is good, the amount of multiply-charged ions in the plasma is increased, and a large number of multiply-charged ion beams are obtained. The general configuration of this burner type ion source is shown in FIGS.
2 will be described below.

[0004] Inside a plasma generation chamber 51 made of a high melting point metal such as molybdenum, a filament 52 bent in a substantially U-shape is provided. This filament 5
2 is a filament feedthrough 53
It is supported on one wall surface of the plasma generation chamber 51 via an insulating support member called 53. A reflection electrode 55 supported on one wall of the plasma generation chamber 51 via an insulating support member 54 is provided at a position inside the plasma generation chamber 51 facing the filament 52. Further, outside the plasma generation chamber 51, a source magnet having a solenoid coil (not shown) for forming a magnetic field B in a direction connecting the filament 52 and the reflection electrode 55 is provided.

In the above configuration, the filament power supply 56
Is supplied to supply current to the filament 52 to heat the filament 52, and an arc power supply 57 is supplied to apply a voltage required for arc discharge between the filament 52 and the plasma generation chamber 51.
An arc discharge occurs due to the emission of thermionic electrons from 2. At this time, the thermoelectrons emitted from the filament 52 drift in the plasma generation chamber 51 along the direction of the magnetic field B while colliding with the introduced gas particles and ionizing (plasmatizing) the particles, and reach the reflection electrode 55. The reflection electrode 5 in the foreground
Turned back at 5. That is, the above-mentioned thermoelectrons are confined between the filament 52 and the reflective electrode 55, and the range of the thermoelectrons is increased, thereby increasing the plasma generation efficiency.

The filament 52 and the reflection electrode 55 are formed of an insulating member (filament feedthrough 53).
Or, it is electrically insulated from the plasma generation chamber 51 by the insulating support member 54), but if the surface of the insulating member is contaminated and insulation failure occurs, a desired arc voltage or a potential for repelling thermoelectrons can be secured. Disappears. The contamination of the insulating member is mainly caused by the metallic plasma generation chamber 5.
This is caused by the fact that the conductive particles released by the sputtering of charged particles 1 and filaments 52 in the plasma adhere to the surface of the insulating member. Therefore, shield plates 59 and 60 made of a high melting point metal such as molybdenum.
Some ion sources partition the interior of the plasma generation chamber 51 to prevent contamination of the insulating member (see Bernas Source Engineering Incereases Implanter).
Utilization '' SEMICONDUCTOR INTERNATIONAL JUNE 1992
, Pp. 106-108).

[0007] In the plasma generation chamber 51, a slit-like ion extraction port 58 extending along the direction of the magnetic field B is provided.
Are formed, and by a strong electric field formed between the plasma generation chamber 51 and an extraction electrode (not shown), ions are extracted from the ion extraction port 58 and an ion beam is formed. When the ion source is provided in the ion implantation apparatus, only the desired ion is selected from the ion beam extracted from the ion source by a mass analysis magnet arranged at the subsequent stage, and acceleration, convergence, scanning, and the like are further performed as necessary. And irradiates the target (silicon wafer or the like).

[0008]

When performing a desired impurity ion implantation process using an ion implantation apparatus using a filament type ion source, a large ion beam amount can be obtained in order to increase the processing speed and throughput. At the same time, an ion source that requires less maintenance (filament replacement) due to wear of the filament 52 is desired. Although the Bernas-type ion source is superior to other filament-type ion sources such as the Freeman type in this respect, an ion source having a higher function has been desired today.

Particularly, when the desired ion species is boron, it is difficult to obtain a beam amount. This is for the following reason. For example, when generating ions such as arsenic and phosphorus, a solid sample such as arsenic and phosphorus is heated in an oven to be vaporized and introduced into the plasma generation chamber 51. On the other hand, when boron ions are generated by the ion source, the BF ₃ gas is usually used as the operating gas, so that the ratio of the desired boron ion component in the plasma is low. In particular, in obtaining a polyvalent boron ion beam such as B ²⁺ , electron capture and recombination of polyvalent ions are likely to occur due to collision with neutral BF ₃ gas particles. In general, in the case of a boron ion beam, it is often the case that a beam amount smaller than that of an ion beam of arsenic, phosphorus, or the like can be obtained by an order of magnitude.

In order to increase the beam current of desired ions, it is necessary to increase the plasma density in the plasma generation chamber 51. To achieve this, the arc voltage between the plasma generation chamber 51 and the filament 52 must be increased. Then, the amount of the filament 52 sputtered by the ions in the plasma increases, and as a result, the number of maintenance operations due to the wear of the filament 52 increases.

As shown in FIG. 12, the plasma density in the plasma generation chamber 51 has a density distribution in which the distance between the filament 52 and the reflection electrode 55 is highest. Therefore, the position of the filament 52 is set as close as possible to the wall surface where the ion outlet 58 is formed, and the plasma density near the ion outlet 58 is locally increased, so that the arc voltage can be increased. It is believed that the beam current of the desired ions can be increased.
However, the filament 52 is supplied to the plasma generation chamber 51 by the filament feedthroughs 53.
The installation position of the filament 52 is restricted by the size of the filament feedthrough 53. Although the filament feedthrough 53 is protected by the shield plate 59, it does not mean that contamination does not occur at all. Therefore, the size of the filament feedthrough 53 cannot be reduced so much in consideration of the occurrence of contamination. Therefore,
The filament 52 cannot be brought very close to the wall surface on which the ion outlet 58 is formed, and this cannot sufficiently contribute to an increase in beam current.

The present invention has been made in view of the above, and an object of the present invention is to provide an ion source capable of increasing a desired ion beam current without increasing an arc voltage.

[0013]

According to the present invention, there is provided an ion source comprising: a magnetic field forming means for forming a magnetic field in a direction perpendicular to an ion extraction direction in a plasma generating chamber; The generation chamber is provided in the plasma generation chamber in a state of being electrically insulated by the insulating member, and includes a filament that emits thermoelectrons and a reflective electrode that reflects thermoelectrons, and a gas containing a desired ion species. While introducing the gas into the plasma generation chamber, the introduced gas is turned into plasma by arc discharge due to thermionic emission, and ions are extracted from an ion outlet formed in the plasma generation chamber to form an ion beam. In order to solve the problem, the following measures are taken.

That is, the filament is bent inside the plasma generation chamber toward the ion extraction surface where the ion extraction port is formed.

[0015]

According to the structure of the present invention, since the filament is bent in the direction of the ion extraction surface inside the plasma generation chamber, the filament and the ion can be separated without reducing the size of the insulating member for insulating and holding the filament. The distance from the drawing surface can be reduced. in this case,
The region where the plasma density is highest (the filament that emits thermoelectrons and the reflective electrode that reflects thermoelectrons are provided facing the direction of the magnetic field formed in the plasma generation chamber. Is generated between the ion extraction port) and the plasma density near the ion extraction port is locally increased. Therefore, even with the same arc discharge voltage as that of the related art, the beam current extracted from the ion outlet increases more than before, and as a result, the beam current of desired ions can be increased.

[0016]

1 to 10 show an embodiment of the present invention.
This will be described below.

As shown in FIG. 2, the burner type ion source according to this embodiment includes a plasma generation chamber 1 made of a high melting point metal such as molybdenum. On the side wall 1a of the plasma generation chamber 1, two filament feedthroughs 3 are provided at a predetermined interval, and the filament 2 bent in a substantially U-shape is introduced into the chamber via these. .

As shown in FIG. 3, a general configuration of the filament feedthrough 3 is a feedthrough 31 made of a high melting point metal such as molybdenum or tantalum, an insulating ring 32 made of alumina, and a nut 33 made of alumina. Consists of The feed-through 31 has an insertion hole 31a for inserting the filament 2 in the axial direction thereof, and has a screw portion 3 screwed with the nut 33 at one end thereof.
1b, the other end is formed with a stopper for preventing the insulating ring 32 from dropping off. The insulating ring 32 covers a portion of the feedthrough 31 where the threaded portion 31b is not formed, and the outer diameter of the end is substantially the same as the diameter of the feedthrough hole formed in the side wall 1a of the plasma generation chamber 1. It has the same size, and this part is inserted into the feed-through hole. The other part of the insulating ring 32 gradually increases in outer diameter (tapered shape) halfway as the distance from the side wall 1a increases, and gradually decreases in the middle (reverse tapered shape). The filament feedthrough 3 is attached to the plasma generation chamber 1 by inserting the feedthrough 31 provided with the insulating ring 32 into a feedthrough hole formed in the side wall 1a of the plasma generation chamber 1 from the inside of the chamber. This is done by fastening the nut 33 from outside the chamber. The filament 2 introduced into the plasma generation chamber 1 through the insertion hole 31 a of the feedthrough 31 is electrically insulated from the plasma generation chamber 1 by the insulating ring 32 and the nut 33.

In the above configuration, in the filament feedthrough 3, the end face C of the insulating ring 32, the end face D of the nut 33, the shaft surface of the feedthrough 31, and the feedthrough hole formed in the side wall 1a. There is a space surrounded by the hole walls. Here, if the end face C or the end face D is contaminated, insulation failure between the side wall 1a and the feedthrough 31 results. Since the end face C of the insulating ring 32 and the end face D of the nut 33 are relatively small, they are weak to slight dirt, and are likely to cause creeping discharge. During operation of the ion source, the temperature of the feed-through 31 and the side wall 1a becomes high, so that gas (metal vapor) is emitted from the metal portion into the space, and adheres to the end face C or the end face D. The end face C and the end face D become dirty.

Therefore, in order to increase the insulation between the side wall 1a and the feedthrough 31, it is desirable that the end of the nut 33 'be overlapped with the end of the insulating ring 32 as shown in FIG. In this configuration, the side wall 1a and the feedthrough 3 must be inserted through a very narrow gap at the overlapped portion.
In order for the surface of the insulating ring 32 and the end of the nut 33 'to be contaminated in order for the surface of the insulating ring 32 and the nut 33' not to be spatially connected to each other and to cause creeping discharge therebetween. In particular, since the gap at the overlapped portion is very narrow, gas discharged from the metal portion such as the side wall 1a is hard to enter the overlapped portion, and the reliability of insulation is considerably higher than that of the configuration shown in FIG. Of course, as shown in FIG.
May be overlapped.

A filament power supply 6 for supplying a filament current to the filament 2 is connected between both ends of the filament 2. An arc power source 7 is connected between the plasma generation chamber 1 and the filament 2 so that the plasma generation chamber 1 has a higher potential than the filament 2. The filament power source 6 is turned on to supply a current of, for example, about 200 A to the filament 2 to heat the filament 2, and the arc power source 7 is turned on to turn on the filament 2 and the plasma generation chamber 1.
If a voltage (for example, about −60 V) required for arc discharge is applied between the two, an arc discharge due to emission of thermoelectrons from the filament 2 occurs.

Further, a side wall 1 b of the plasma generation chamber 1 is located at a position facing the filament 2 inside the plasma generation chamber 1 via an insulating support member 4.
The reflection electrode 5 supported by the support is provided. The reflective electrode 5 repels thermoelectrons emitted from the filament 2 to the filament side, and is usually set at the same potential as the filament 2 (or a floating potential).

A source magnet having a solenoid coil (not shown) is provided around the plasma generation chamber 1, and a direction connecting the filament 2 and the reflection electrode 5 inside the plasma generation chamber 1. A magnetic field B is formed at the center. Due to the magnetic field B formed by the source magnet, the filament 2
Are emitted from the filament 2 and the reflective electrode 5
Drift between. The thermoelectrons drifted along the magnetic field B are repelled before the filament 2 and the reflective electrode 5 at the filament potential, and are confined between the two, and the range (so-called lifetime) is increased. .

The plasma generation chamber 1 includes:
An oven (not shown) for heating and evaporating a solid sample such as P or As is connected via a gas introduction pipe, and is used for supplying a working gas such as BF ₃ or a cleaning gas such as Ar. A gas box (not shown) is connected via a gas inlet tube. The gas particles containing the desired ion species introduced into the plasma generation chamber 1 via the gas introduction pipe collide with thermionic electrons emitted from the filament 2 to be ionized and turned into plasma.

As shown in FIG. 1, a slit-like ion extraction port 8 extending in the direction of the magnetic field B is formed in the upper wall 1c of the plasma generation chamber 1. Further, outside the plasma generation chamber 1, the ion extraction port 8 is provided.
An extraction electrode (not shown) in which a beam passage hole is formed is provided so as to face the. An extraction power source (not shown) is connected between the extraction electrode and the plasma generation chamber 1 so that the plasma generation chamber 1 has a higher potential than the extraction electrode. As a result, a strong external electric field is formed between the plasma generation chamber 1 and the extraction electrode 7, and positive ions in the plasma generated in the plasma generation chamber 1 are extracted from the ion extraction port 8 by the external electric field. , An ion beam is formed.

On the installation side of the filament 2 inside the plasma generation chamber 1, there is provided a filament shield 9 which is a partition plate for isolating the filament feedthrough 3 from the plasma generation region. A hole 9a through which the filament 2 is inserted is formed in the filament shield 9, and a main part of the filament 2 is introduced into the plasma generation region. One of the functions of the filament shield 9 is to prevent the conductive particles generated during the plasma generation from adhering to the surface of the insulating member of the filament feedthrough 3 as much as possible. In this configuration example, this filament shield 9
It is made of a material containing at least B (boron), such as ₂ O ₃ or B alone. As will be described later, the ratio of a desired boron ion component in the generated plasma is increased, so that the beam current of boron ions is increased. It also has the function of increasing

On the installation side of the reflection electrode 5 inside the plasma generation chamber 1, a reflection electrode shield 10 which is a partition plate for isolating the insulating support member 4 supporting the reflection electrode 5 from the plasma generation region is provided. Is provided. The reflective electrode shield 10 is provided with a hole through which the support rod 5b of the reflective electrode 5 is inserted, and the electrode portion 5a of the reflective electrode 5 is introduced to the plasma generation region side. One of the functions of the reflective electrode shield 10 is to prevent the conductive particles generated during plasma generation from adhering to the surface of the insulating support member 4 as much as possible. In this configuration example, the reflective electrode shield 10
Is at least B, such as BN, B ₂ O ₃ or B alone.
It is made of a material containing (boron) and has a function of increasing the ratio of a desired boron ion component in the generated plasma to increase the beam current, similarly to the filament shield 9.

As shown in FIG. 1, the support position of the filament 2 by the filament feedthrough 3 is determined by the upper wall 1c (ie, the ion extraction outlet 8) formed as much as possible.
(Ion extraction surface). Then, the filament 2 is inserted into the hole 9 of the filament shield 9.
The part introduced into the plasma generation region through a
It is bent toward the upper wall 1c where the ion outlet 8 is formed.

In the above configuration, BF is used as the operating gas.
_When the ion source is operated using ₃ or BCl ₃ , the filament shield 9 and the reflective electrode shield 10 made of the boron-containing material are sputtered by highly reactive plasma generated in the plasma generation chamber 1, and as a result, The proportion of the boron component in the plasma increases.

In particular, in the Bernas type ion source, the plasma drifts in the direction connecting the filament 2 and the reflective electrode 5 along the magnetic field B due to the source magnet magnetic field B formed inside the plasma generation chamber 1. ,
The plasma particles of the high plasma density hit the filament shield 9 and the reflective electrode shield 10. That is, the filament shield 9 and the reflective electrode shield 10
Has a higher sputtering rate than the other wall surfaces of the plasma generation chamber 1, and by configuring this portion with a boron-containing material, it is possible to efficiently increase the boron component ratio in the plasma.

When the filament shield 9 is made of a boron-containing material, it is heated by the high-temperature filament 2 and the boron-containing material in the vicinity of the filament evaporates. The ratio of boron components in them increases.

For example, when BF ₃ gas is used as the operating gas, B ⁺ , F ⁺ , BF ⁺ , BF ₂ ⁺ ,
There are positive ions such as BF ₃ ⁺ . In this case, in order to generate B ⁺ , _three F elements must be taken from BF _3, and the concentration of B ^{+ in} the plasma does not easily increase. On the other hand, boron supplied from the filament shield 9 and the reflection electrode shield 10 by sputtering easily becomes B ⁺ . Also, the filament shield 9
Is composed of, for example, BN, B ⁺ can be generated relatively easily by removing one N element from BN supplied by evaporation. If the filament shield 9 is composed of B alone, it is even easier to generate B ⁺ . Thus, B
The boron-containing substance supplied from the filament shield 9 and the reflective electrode shield 10 is much easier to generate B ⁺ than that of generating B ⁺ from F ₃ , whereby the boron component ratio in the plasma is increased. Can be efficiently increased.

When the reflective electrode shield 10 is made of a boron-containing material as described above, the size of the electrode portion 5a of the reflective electrode 5 is determined by the width of the ion extraction port 8 (the width orthogonal to the slit length direction). It is desirable to form it smaller than usual depending on ()). That is, by making the size of the electrode portion 5a of the reflective electrode 5 smaller than usual, the amount of plasma directly hitting the reflective electrode shield 10 is increased, and the boron component ratio in the plasma is further increased. The extent to which the electrode portion 5a of the reflective electrode 5 can be reduced depends on the width of the ion extraction port 8. In order to increase the plasma density in the vicinity of the ion outlet 8, an effect of repelling electrons by the reflective electrode 5 is required at least in the vicinity of the ion outlet 8. For this purpose, the size of the electrode portion 5 a of the reflective electrode 5 is required. Must be set to several times the width of the ion extraction port 8. If the required size can be ensured, it is advantageous to increase the amount of plasma directly hitting the reflective electrode shield 10 without increasing the size of the electrode portion 5a further in order to increase the boron component ratio in the plasma. .

When the ion source is provided in the ion implantation apparatus, only the desired ions are selectively extracted from the ion beam extracted from the ion source by a mass spectrometer magnet arranged at the subsequent stage. Is irradiated. In this case, the amount of the beam that can be transported is limited by the shape of the electrodes and the like provided on the beam transport path until the desired ion beam reaches the target, and all the beams extracted from the ion source can reach the target. is not. In particular, if the beam current (extraction current) extracted from the ion extraction port 8 increases to some extent, the beam diameter (spread) also increases. In this case, the ratio of the target current to the extraction current is not very good. In this regard, increasing the desired ion component ratio in the plasma is very effective because the beam current of desired ions in the target can be increased with the same extraction current.

In this embodiment, since the filament 2 is bent in the direction of the ion extraction surface inside the plasma generation chamber 1 as shown in FIG. 1, it is not necessary to reduce the size of the filament feedthrough 3. The distance between the filament 2 and the ion extraction surface can be reduced. In this case, the region where the plasma density is highest (between the filament 2 and the reflective electrode 5) shifts toward the ion outlet 8, and the plasma density near the ion outlet 8 can be locally increased. Therefore, even with the same arc voltage (arc current) as the conventional one, the beam current (extraction current) extracted from the ion extraction port 8 increases more than the conventional one.

The shape of the filament 2 is not limited to the U-shape (non-induction type) shown in FIG. 2, and for example, as shown in FIG. (The impedance of the portion is high, so that thermoelectrons are easily emitted from this portion.) As shown in FIG. 7, an inductive type called a pig-til type in which a tip portion is wound in a coil shape can be used.

When the filament 2 is of a pig-til type, a part of the filament 2 can be arranged near the ion extraction surface by increasing the winding radius. However, since the winding radius is large, the distribution of plasma is reduced. spread,
The purpose of increasing the plasma density near the ion extraction surface is not sufficiently achieved. Even in the case of the pig-til type, the plasma distribution is not significantly increased by bending the filament 2 from the root side (support portion side) and bringing the entire wound portion closer to the ion extraction surface without increasing the winding radius to about 3 mm to 4 mm. A non-spread, dense plasma can be generated near the ion outlet. Thereby, the ratio of the extraction current to the arc voltage is increased.

When the filament 2 is of a pig-tilt type, as shown in FIG. 8, the magnetic field b formed by the filament current is opposite to the direction of the magnetic field B applied from an external source magnet. It is desirable to connect the filament power supply 6 to the filament 2. Thereby, a region having the highest plasma density is formed at the center of the filament, and the sputtering of the filament shield 9 by the plasma can be strengthened. In this case, in order to increase the plasma density in the vicinity of the ion extraction port 8, the center of the winding portion of the filament 2 having the highest plasma density is made to coincide with the ion extraction direction in the ion extraction direction.

In the filament shield 9,
Sputtering and evaporation occur mainly in the vicinity of the filament 2 (particularly, the central portion of the filament 2 and the filament heating portion). Therefore, as shown in FIG.
Only the portion 9b of the filament shield 9 where spattering or evaporation is likely to occur is made of a material containing at least boron, such as BN, B ₂ O ₃ , or B alone, and the other portion 9c is of a high melting point such as Mo, Ta, Wa, etc. It may be made of metal.

Since the portion of the filament shield 9 near the filament 2 where spattering and evaporation are likely to occur is consumed faster than other portions, as shown in FIG. 10, the consumable portion 9e is made of a material containing at least boron. The main body 9f (which may be a material containing boron or a high melting point metal) may be detachably mounted and exchanged (supplied).

The plasma generation chamber 1 has a structure in which each chamber wall can be divided so that the inside of the plasma generation chamber 1 can be cleaned by a person. The replacement work of the reflection electrode shield 10 is possible. Also,
When the filament shield 9 and the reflective electrode shield 10 are attached to the side walls 1a and 1b, the chamber walls other than the side walls 1a and 1b in the plasma generation chamber 1 may be integrally formed, and only the side walls 1a and 1b may be divided. it can.

In the above embodiment, the desired ion species is described as boron. However, when another ion species is targeted, the filament shield 9 and the reflection electrode shield 10 are made of a material containing the other ion species. do it.

As described above, the ion source according to this configuration example includes a source magnet (magnetic field forming means) for forming a magnetic field B in a direction perpendicular to the ion extraction direction inside the plasma generation chamber 1, A filament 2 and a reflective electrode 5 provided in the plasma generation chamber 1 facing each other in the direction, and a filament feedthrough 3 (insulating member) for electrically insulating the filament 2 from the plasma generation chamber 1 are separated from the plasma forming region. A filament shield 9 (partition plate) provided in the plasma generation chamber 1 for isolation, and a gas containing a desired ion species is introduced into the plasma generation chamber 1 by arc discharge by thermionic emission while introducing the gas into the plasma generation chamber 1 At least a filament of the filament shield 9 Vicinity of 2, a configuration that is formed of a material containing the desired ion species, and the first feature of this.

According to the above configuration, the source magnet magnetic field B formed inside the plasma generation chamber 1 causes the plasma to drift in the direction connecting the filament 2 and the reflective electrode 5, and causes the plasma in a portion where the plasma density is high to be high. The particles concentrate on the portion of the filament shield 9 in the vicinity of the filament 2, and this portion is formed of a material containing a desired ion species, so that the desired ion species can be efficiently supplied by sputtering. Further, a gas containing a desired ion species is also supplied by evaporation of the filament 2 by heating. As a result, the component ratio of desired ions in the plasma can be increased, and as a result, the beam current of the desired ions can be increased without increasing the arc voltage. The test results are shown below.

This test was conducted by incorporating an ion source into an ion implantation apparatus. As a comparative example, a conventional burner type ion source whose material of the filament shield is Mo (see FIGS. 11 and 12) was used. In an example, the material of the filament shield in the ion source of the comparative example was changed to BN. Instead, an ion source (here, the filament 2 is not bent toward the ion extraction surface as shown in FIG. 1 and the reflective electrode shield 10 is not made of a boron-containing material) is used. Then, the operation of the ion implanter was performed for each under the following operating conditions.

Working gas: BF ₃ gas flow rate: 0.8 cc / m Filament current: 120 A Arc current (arc voltage): 4 A (60 V) Extraction current (extraction voltage): 10 mA (30 kV) Beam energy: 150 keV When using the Bernas type ion source of
B ⁺ ions with a beam current of 600 μA were obtained at the target. On the other hand, when the ion source of the example in which the material of the filament shield was changed to BN was used, B ⁺ ions with a beam current of 800 μA were obtained at the target.

Further, in the ion source of this configuration example, if the same beam current as that of the related art is obtained, the arc voltage can be made lower than that of the related art. Can be reduced.

In the ion source according to this configuration example, in the configuration of the first aspect, the insulating support member 4 for electrically insulating the reflection electrode 5 from the plasma generation chamber 1 is isolated from the plasma forming region. Plasma generation chamber 1
The reflective electrode shield 10 provided therein is formed of a material containing a desired ion species, which is a second feature. The reflective electrode shield 10 is arranged to face the filament 2, and the plasma particles of a relatively high plasma density hit the reflective electrode shield 10 by the source magnet magnetic field B in the same manner as described above. By this sputtering phenomenon, the component ratio of desired ions in the plasma can be increased. As a result, the beam current of the desired ions can be further increased without increasing the arc voltage. In this experiment, the ion implanter was operated under the same conditions as described above, except that the material of the filament shield and the reflective electrode shield in the conventional ion source used in the above test was changed to BN. As a result,
B ⁺ ions with a beam current of 1 mA were obtained at the target.

The ion source according to the present embodiment faces a source magnet (magnetic field forming means) for forming a magnetic field B in the direction perpendicular to the ion extraction direction inside the plasma generation chamber 1 in the direction of the magnetic field B. The plasma generation chamber 1 is provided with a filament 2 and a reflection electrode 5 provided in the plasma generation chamber 1, respectively, and the gas containing a desired ion species is introduced into the plasma generation chamber 1 while the introduced gas is plasma-generated by arc discharge by thermionic emission. The filament 2 is formed into an ion beam by extracting ions from the ion extraction port 8 formed in the plasma generation chamber 1. The filament 2 is formed inside the plasma generation chamber 1 by the ion extraction port 8. It is characterized in that you are bent in the direction of the pull-out surface.

Thus, the distance between the filament 2 and the ion extraction surface can be reduced without reducing the size of the filament feedthrough 3 for insulatingly holding the filament 2, and the plasma density near the ion extraction outlet 8 can be reduced. Can be locally increased. Therefore, the extraction current drawn from the ion extraction port 8 can be increased without increasing the arc voltage. Further, the plasma generation position (in other words, the plasma distribution in the plasma generation chamber 1) only by the bending amount of the filament 2
Can be changed, so that the optimum plasma generation position can be easily found.

In the ion source according to the present embodiment, the pigtail type filament 2 wound in a coil shape and a filament current is applied to the filament 2 as shown in FIG. magnetic field b, which is formed by the, is characterized also this connecting a filament power supply 6 so as to be opposite to the direction of the magnetic field B applied from an external source the magnet to the filament 2.
Thereby, a region having the highest plasma density is formed at the center of the filament, and the sputtering of the filament shield 9 by the plasma can be strengthened. Therefore, the desired ion component ratio in the plasma can be efficiently increased.

Further, as shown in FIG. 4 or FIG.
An insertion hole 31a for inserting the filament 2 (FIG. 3)
And an insulating ring 32 that covers a portion of the feedthrough 31 other than the threaded portion 31b (see FIG. 3).
(32 '), and an insulating nut 33 (33') to be screwed into the screw portion 31b.
The insulating ring 32 (3) is attached to a feed-through hole formed in the wall of the device to provide electrical insulation between the filament 2 and the plasma generation chamber 1.
And even this that the ends are overlapped in the 'end and the nut 33) (33' 2) is characterized. Thereby, the reliability of insulation between the filament 2 and the plasma generation chamber 1 is improved.

The above configuration examples are merely for clarifying the technical contents of the present invention, and should not be construed as being limited to such specific examples in a narrow sense. Various modifications can be made within the scope of the claims.

[0054]

As described above, in the ion source according to the present invention, the filament emitting thermoelectrons and the reflection electrode reflecting thermoelectrons face the direction of the magnetic field formed in the plasma generation chamber. Is provided to extract ions from an ion extraction port formed in the plasma generation chamber to form an ion beam, wherein the filament is:
The inside of the plasma generation chamber is bent in the direction of the ion extraction surface where the ion extraction port is formed.

Therefore, the distance between the filament and the ion extraction surface can be reduced without reducing the size of the insulating member for insulating and holding the filament, and the plasma density near the ion extraction outlet can be locally increased. can do. Therefore, even with the same arc discharge voltage as that of the related art, the beam current drawn from the ion outlet is increased as compared with the related art, and as a result, the beam current of desired ions can be increased.

[Brief description of the drawings]

FIG. 1, showing an embodiment of the present invention, is a schematic longitudinal sectional view of a Bernas-type ion source.

FIG. 2 is a schematic cross-sectional view of the ion source.

FIG. 3 is a schematic sectional view showing a configuration of a filament feedthrough of the ion source.

FIG. 4 is a schematic sectional view showing another configuration of a filament feedthrough of the ion source.

FIG. 5 is a schematic sectional view showing still another configuration of the filament feedthrough of the ion source.

FIG. 6 is an explanatory diagram showing an example of a filament shape applied to the ion source.

FIG. 7 is an explanatory diagram showing another example of a filament shape applied to the ion source.

FIG. 8 is a schematic cross-sectional view of a burner-type ion source according to another embodiment of the present invention.

FIG. 9 is a schematic cross-sectional view of a Bernas-type ion source according to still another embodiment of the present invention.

FIG. 10 is a schematic cross-sectional view showing a configuration around a filament of a burner-type ion source according to still another embodiment of the present invention.

FIG. 11 is a schematic cross-sectional view of a conventional Bernas-type ion source.

FIG. 12 is a schematic longitudinal sectional view of the conventional burner-type ion source.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 plasma generation chamber 2 filament 3 filament feedthrough (insulating member) 4 insulating support member 5 reflective electrode 6 filament power supply 7 arc power supply 8 ion extraction port 9 filament shield (partition plate) 10 reflective electrode shield

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01J 37/08 H01J 27/04

Claims (1)

(57) [Claims] 1. A magnetic field forming means for forming a magnetic field in a direction perpendicular to an ion extraction direction in a plasma generation chamber, and is electrically insulated from the plasma generation chamber by an insulating member in opposition to the direction of the magnetic field. Equipped with a filament that emits thermoelectrons and a reflective electrode that reflects thermoelectrons, respectively, provided in the plasma generation chamber in a heated state, and emits thermoelectrons while introducing a gas containing a desired ion species into the plasma generation chamber In an ion source for forming an ion beam by extracting ions from an ion extraction port formed in a plasma generation chamber by turning an introduced gas into plasma by arc discharge according to
An ion source characterized by being bent in the direction of an ion extraction surface in which an ion extraction port is formed.