JP3460241B2 - Negative ion implanter - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a negative ion implanting device for implanting negative ions into an ion irradiation target.

[0002]

2. Description of the Related Art An ion implanter ionizes impurities to be diffused, extracts ions by an electric field to form an ion beam, then forms a beam of desired ions by mass spectrometry using a magnetic field, By accelerating and irradiating the ion irradiation target with an ion beam, impurities are injected into the ion irradiation target.The impurities that determine the characteristics of the device in the semiconductor process can be adjusted to an arbitrary amount and depth. Since it can be injected with good controllability, it is an important device in the manufacture of present-day integrated circuits.

As the above-mentioned ion implanter, a positive ion implanter for extracting positive ions from a positive ion source to form a positive ion beam and implanting positive impurity ions into an ion irradiation target has been put into practical use.

[0004]

In the above-described positive ion implantation apparatus, when a positive impurity ion is irradiated onto a beam irradiation target made of, for example, a silicon substrate having a polysilicon film, the impurity beam irradiation target Along with the injection into the object, the polysilicon film of the beam irradiation target is positively charged. Further, with the irradiation of the beam irradiation target with the positive ion beam, secondary electrons fly out from the irradiation surface. Some of the secondary electrons that have jumped out return to the polysilicon film again, and the other secondary electrons are emitted from the beam irradiation target. The emitted secondary electrons further charge the polysilicon film in a positive polarity. When the charging voltage of the polysilicon film exceeds the withstand voltage, discharge occurs (charge-up phenomenon) and the device is destroyed.

As described above, in the positive ion implantation process using the positive ion implantation apparatus, the charge-up phenomenon is likely to occur, whereas in the negative ion implantation process in which the negative impurity ions are implanted, the charge-up phenomenon is less likely to occur. This is because in the case of the negative ion implantation process, at the negative ion irradiation site of the polysilicon film, negative charges are accumulated by the injected negative ions and at the same time secondary electrons are emitted from the ion irradiation surface.
As a result, charges are hardly accumulated in the polysilicon film. Therefore, the negative ion implantation process is
It is very effective in creating a device.

However, when performing the negative ion implantation process, the large-current negative ions generated by the negative ion source (that is, the negative ion beam) are efficiently transported to the implantation position where the beam irradiation target is arranged. Is much more difficult than transporting positive ions. This is for the following reason.

That is, although the beam passage path in the ion implantation apparatus is evacuated to a vacuum, some residual gas is present, and the residual gas molecules collide with the ions transported to cause residual gas molecules. Ionizes into positive ions and electrons. The positive ions generated by this ionization have a very low velocity, and immediately after being generated, they are absorbed by the side wall of the beam tube forming the beam passage path, and only the electrons generated by the ionization exist in the space (beam passage path). Will remain.

Here, when the above-mentioned transported ions are positive ions, the electrons generated by ionization enter the positive ion beam, and as a result, the electrical neutralization of the beam is maintained and the positive ion is maintained. The ion beam is transported without spreading.

On the other hand, when the transported ions are negative ions, there are no positively charged particles that neutralize the beam. In a charged particle beam in which charged particles (negative ions) of the same polarity are concentrated at high density, the Coulomb force acting between charged particles repels each other and the charged particles try to become a beam with a spread. Therefore, in the process of transporting the negative ion beam, the negative ion beam becomes a beam that spreads toward the downstream side of the beam, so that many negative ions are absorbed by the side wall of the beam tube and reach the implantation position. The amount of ions is extremely small.

Therefore, in transporting the negative ions, a method can be considered in which the beam is electrically neutralized (converted into plasma) by the positive ions to efficiently transport the beam to the implantation position without spreading the beam. If the method is used, a neutralized ion beam will be injected,
The beam current reaching the implantation position cannot be measured. Normally, in the ion implantation system, the beam current is measured at the implantation position, and the ion implantation amount is controlled based on this measurement value. There is a problem that control cannot be performed.

Therefore, at present, the negative ion implanting apparatus for performing the negative ion implanting process has not yet been put to practical use.

The present invention has been made in view of the above, and an object thereof is to realize a negative ion implanter which is less likely to cause a charge-up phenomenon than a positive ion implanter and which is effective in manufacturing a device.

[0013]

Means for Solving the Problems Claims 1 and 2
The negative ion implanting apparatus according to the invention of claim 1 is one for injecting negative ions into an object to be ion-irradiated, and is characterized by taking the following means in order to solve the above problems.

That is, the negative ion implanting apparatus according to claim 1 is a negative ion beam forming means for forming a negative ion beam and a beam for electrically neutralizing the negative ion beam by supplying positive ions to the beam. The ionizing means is provided immediately before the ion irradiation target, forms a predetermined electric field in the passage path of the ion beam in an electrically neutralized state, and deflects the negative ions and positive ions forming the ion beam. Electrostatic deflection separation means for separating the beam, and the beam neutralization means is an ECR ion separation means.
Source .

The negative ion implanter according to a second aspect of the present invention is a negative ion beam forming means for forming a negative ion beam, and a beam for electrically neutralizing the beam by supplying positive ions to the negative ion beam. A activating means, which is provided immediately before the ion irradiation target, forms a predetermined magnetic field in the passage path of the ion beam in an electrically neutralized state, and deflects the negative ions and the positive ions forming the ion beam. A magnetic field deflection separating means for separating the beam, and the beam neutralizing means is an ECR ion separating means.
Source .

[0016]

According to the configurations of the above-mentioned claims 1 and 2,
Since the negative ion beam formed by the negative ion beam forming means is electrically neutralized by the positive ions supplied from the beam neutralizing means and is transported to immediately before the ion irradiation target, Ions can be efficiently transported to immediately before the ion irradiation target.

Further, in the structure of claim 1, the ion beam in an electrically neutralized state, which has been transported to immediately before the object to be ion-irradiated, is converted into negative ions and positive ions by the electric field formed by the electrostatic deflection separation means. Since it is polarized and separated into ions, only negative ions can be injected into the ion irradiation target, and as a result, the dose amount of only negative ions can be measured.

According to the second aspect of the invention, the ion beam in an electrically neutralized state, which has been transported to the position immediately before the object to be ion-irradiated, is negative ions and positive ions due to the magnetic field formed by the magnetic field deflection separation means. Since it is polarized and separated into and, only negative ions can be injected into the ion irradiation target, and as a result, the dose amount of only negative ions can be measured.

Therefore, the above-mentioned claim 1 and claim 2
With this configuration, it is possible to perform high-current negative ion implantation with a good controllability of the implantation amount, and it is possible to realize a negative ion implantation process that is less likely to cause a charge-up phenomenon than positive ion implantation and is effective for device fabrication.

[0020]

【Example】

[Embodiment 1] The following description will discuss one embodiment of the present invention with reference to FIGS. 1 to 3.

The negative ion implanter according to this embodiment is shown in FIG.
As shown in, basically, a negative ion beam forming unit (negative ion beam forming means) 1 for forming a negative ion beam,
An accelerating tube 2 that accelerates negative ions to a predetermined energy by an electric field, a neutralizing positive ion source (beam neutralizing means) 3 that generates positive ions for electrically neutralizing a negative ion beam, and a predetermined A mass spectrometric section 4 for selecting and extracting only implanted ions, a beam deflecting section (electrostatic deflection separating means) 5 for deflecting an ion beam by an electric field immediately before implantation, an end station section 6 for performing negative ion implantation, and positive ions It is composed of a positive ion absorption chamber 7 for absorption.

The negative ion beam forming unit 1 basically extracts a negative ion from the inside of the chamber into a vacuum by an electric field and a negative ion source 11 for generating plasma containing desired negative ions in the plasma chamber. The extraction electrode 12 forms a negative ion beam.

As the negative ion source 11, for example, PI
An ion source such as a G (Penning Ionization Gauge) type or a microwave type can be used, but the source is not limited to this, and any source capable of generating plasma containing desired negative ions can be used. It may be configured.

The neutralizing positive ion source 3 is provided after the accelerating tube 2. In this embodiment, as the neutralizing positive ion source 3, electron cyclotron resonance (ECR:
A microwave type ion source (ECR ion source) is used that generates plasma by generating microwave discharge in a magnetic field of Electron Cyclotron Resonance).

As shown in FIG. 2, the neutralizing positive ion source 3 has, for example, a magnetron 31 that outputs a microwave of 2.45 GHz, and a magnetron power supply 32 that operates the magnetron 31. . The magnetron 31 is connected to one end of a cylindrical wave guide 33 formed of a material having a high permittivity through which microwaves can pass, for example, a material such as alumina (Al ₂ O ₃ ). The other end of the wave guide 33 is connected to a plasma chamber 34 forming a plasma generation chamber 37, and the wave guide 33 conducts the microwave output from the magnetron 31 to the plasma generation chamber 37. ing.

A working gas introducing pipe 35 is connected to the plasma chamber 34 so that the working gas filled in the gas cylinder 36 is introduced into the plasma generating chamber 37. Further, on the inner wall surface of the plasma chamber 34,
For example, a liner 38 made of a material such as BN is provided.

Further, around the plasma chamber 34,
A source magnet 39 having a solenoid coil to which a source magnet current is supplied from a source magnet power source (not shown) is arranged.
9 forms a magnetic field in the plasma generation chamber 37 in parallel with the direction in which positive ions are extracted.

The side of the plasma chamber 34 facing the connection with the wave guide 33 is connected to the beam tube 10 forming a beam passage, and the plasma generation chamber 37 and the beam passage are connected to the ion extraction hole. 34a
Through the. Thereby, from the plasma generated in the plasma generation chamber 37 by the negative potential of the negative ion beam passing through the beam tube 10,
Positive ions are extracted into the beam tube 10 through the ion extraction hole 34a. Therefore, the negative ion beam is transported in a state of being electrically neutralized by the positive ions downstream of the neutralizing positive ion source 3 in the beam traveling direction.

The reason why the above ECR ion source is used as the neutralizing positive ion source 3 in this embodiment is as follows. That is, when the energy of the positive ions extracted from the plasma is high, the positive ions rush into the inner wall of the beam tube 10 and cause contamination, so that the energy of the plasma generated in the neutralizing positive ion source 3 is increased. Is preferably as small as possible. At this point, the energy of the plasma generated in the ECR ion source is several ev
The ECR ion source is suitable as the neutralizing positive ion source 3 because it is relatively small, about several tens of ev .

As shown in FIG. 1, the beam deflecting section 5 has a pair of deflecting electrodes 51 and 52 which are arranged to face each other across the passage of the ion beam in the beam tube 10. A predetermined positive voltage is applied to the deflection electrode 51 from a power source 53, and a predetermined negative voltage is applied to the deflection electrode 52 from a power source 54. As a result, when the electrically neutralized ion beam passes through the beam deflecting section 5, the negative ions and positive ions forming the ion beam are deflected in different directions by the electric field generated between the deflection electrodes 51 and 52. , Are to be separated.

In the traveling direction of the negative ions deflected by the beam deflecting section 5, the end station section 6 is provided.
However, the positive ion absorption chambers 7 are provided in the traveling directions of the positive ions deflected by the beam deflector 5.

The end station section 6 is provided with a holding member 62 for holding an ion irradiation target 61 such as a silicon wafer. The holding member 62 is made of a metal material such as an aluminum alloy having excellent thermal conductivity. The beam current measuring unit (not shown) is connected to the holding member 62.

A cylindrical Faraday cup 63 formed so as to surround the passage path of the negative ion beam is provided in front of the ion irradiation target 61 held by the holding member 62 (on the upstream side in the ion advancing direction). Has been.
The Faraday cup 63 collects secondary electrons and secondary ions emitted from the irradiation surface of the ion irradiation target 61 and the holding member 62 with the negative ion beam. The measurement unit is connected. The Faraday cup 63 enables accurate beam current measurement with little influence of secondary electrons and secondary ions.

Further, the negative ion implanter is an implantation controller (not shown) for controlling the amount of ion implantation based on the beam current measured by the beam current measuring section.
Is equipped with.

The operation of the negative ion implanter having the above structure will be described below.

First, a negative ion beam is formed in the negative ion beam forming unit 1, and the negative ion beam is accelerated to a desired energy by passing through the accelerating tube 2.

On the other hand, in the neutralizing positive ion source 3, plasma is generated in the plasma generating chamber 37. That is, the working gas with which the gas cylinder 36 is filled is introduced into the plasma generation chamber 37 which has been brought to a high vacuum state by a vacuum exhaust unit (not shown). Furthermore, the source magnet 36
By this, a magnetic field parallel to the direction in which positive ions are extracted is formed in the plasma generation chamber 37, and the microwave power output from the magnetron 31 is introduced into the plasma generation chamber 37 via the wave guide 33. Microwave discharge due to the ECR phenomenon occurs in the plasma generation chamber 37, and the working gas is turned into plasma.

Then, due to the negative potential of the negative ion beam passing through the beam tube 10, the positive ions forming the plasma generated in the plasma generating chamber 37 are transferred from the plasma generating chamber 37 to the beam tube 10. Be drawn to. Then, the positive ions are drawn into the negative ion beam, and the negative ion beam is neutralized by the positive ions. As a result, downstream of the neutralizing positive ion source 3 in the beam traveling direction, the negative ion beam is efficiently neutralized by the positive ions and is efficiently transported without spreading.

The positive ions generated in the neutralizing positive ion source 3 are preferably those that do not affect the ion irradiation target 61 and are easy to obtain plasma.
For example, when a silicon wafer is used as the ion irradiation target 61, hydrogen ions (H ⁺ ) can be used.

After that, the ion beam electrically neutralized as described above is subjected to mass analysis of the beam constituent ions by the magnetic field in the mass analyzer 4 having a beam passage path bent at about 90 °. Thus, an ion beam from which negative ions other than the desired negative ions are removed is obtained. Here, the positive ions are much slower than the negative ions, and therefore are not significantly affected by the magnetic field and are entangled with the negative ion beam having a high negative potential and pass through the mass spectrometric unit 4. . Therefore, the ion beam is maintained in the electrically neutralized state even after passing through the mass analysis unit 4.

After that, the ion beam is transported in an electrically neutralized state, and is separated into negative ions and positive ions in the beam deflecting section 5 provided immediately before the end station section 6. Become. That is, the negative ions in the ion beam in the electrically neutralized state are deflected by the deflection electrodes 51 and 52.
An electric field generated between them deflects to the side of the deflection electrode 51 to which a positive voltage is applied from the power source 53, while positive ions in the ion beam are deflected to the side of the deflection electrode 52 to which a negative voltage is applied from the power source 54. To be done.

A positive ion absorption chamber 7 is provided in the traveling direction of the positive ions deflected and separated by the beam deflector 5, and the positive ions collide with the positive ion absorption chamber 7 and are absorbed in the chamber 7. Will end up.

On the other hand, an end station unit 6 is provided in the traveling direction of the negative ions deflected and separated by the beam deflecting unit 5, and the negative ion implantation into the ion irradiation target 61 is performed by the end station unit 6. Done. That is, after the negative ions (negative ion beam) enter the Faraday cup 63 provided in the end station unit 6,
It is injected into the ion irradiation target 61 held by the holding member 62.

The current amount of the negative ion beam with which the ion irradiation target 61 is irradiated is measured by a beam current measuring unit (not shown) connected to the Faraday cup 63 and the holding member 62, and the measured value is obtained. Based on the control of the ion implantation amount, an implantation controller (not shown) is used.

As described above, the negative ion implanter of this embodiment produces the negative ion beam forming unit 1 for forming the negative ion beam and the positive ions for electrically neutralizing the negative ion beam. A neutralizing positive ion source 3 and a beam deflector 5 that deflects and separates negative ions and positive ions forming an ion beam by an electric field immediately before the implantation position are provided.

As a result, the negative ion beam formed in the negative ion beam forming unit 1 is electrically neutralized by the positive ions extracted from the plasma generation chamber 37 of the neutralizing positive ion source 3. The negative ions can be efficiently transported to immediately before the injection position. Since the ion beam in the electrically neutralized state is deflected and separated into negative ions and positive ions by the beam deflecting unit 5 immediately before the implantation position, only negative ions can be implanted into the ion irradiation target 61. It is possible to measure the dose amount of only negative ions. Therefore,
With the above structure, a large amount of negative ion implantation with a good controllability of the implantation amount is possible, and a negative ion implantation process that is less likely to cause a charge-up phenomenon than positive ion implantation and is effective for device fabrication can be realized.

[Embodiment 2] The following will describe one embodiment of the invention of claim 2 with reference to FIGS. 3 to 5.

In the negative ion implanter according to this embodiment, a beam deflector 5'for deflecting an ion beam by a magnetic field is used instead of the beam deflector 5 for deflecting an ion beam by an electric field in the first embodiment. Except for the above, the configuration is basically the same as that of the first embodiment shown in FIG.
The components other than the beam deflector 5'are given the same reference numerals as those in the first embodiment, and the description thereof is omitted.

As shown in FIG. 4, the beam deflector 5'of the negative ion implanter of this embodiment has a pair of N and S poles opposed to each other with a beam tube 10 forming a beam passage path interposed therebetween. It is composed of magnets 55a and 55b of
The pair of magnets 55a and 55b form a magnetic field substantially perpendicular to the traveling direction of the ion beam electrically neutralized by the neutralizing positive ion source 3.
As a result, when the electrically neutralized ion beam passes through the beam deflecting section 5 ', the negative ions and the positive ions forming the ion beam move in different directions due to the magnetic field substantially perpendicular to the beam traveling direction. It is deflected and separated.

In the traveling direction of the negative ions deflected by the beam deflecting unit 5 ', the end station unit 6
Positive ion absorption chambers 7 are provided in the traveling directions of the positive ions deflected by the beam deflector 5 '.

The operation of the negative ion implanter having the above structure will be described below.

Until the ion beam reaches the beam deflecting section 5 ', it is the same as in the first embodiment, and the negative ion beam formed in the negative ion beam forming section 1 shown in FIG. The positive ions are transported while being electrically neutralized by the positive ions extracted from the plasma generation chamber 37 of the positive ion source 3.

Then, the ion beam in the electrically neutralized state is separated into negative ions and positive ions in the beam deflecting section 5'provided immediately before the end station section 6. That is, when the ion beam passes through the beam deflecting section 5 ', as shown in FIG. 5, the negative ions forming the ion beam are subjected to a force F ₁ F in the direction A ₁ shown in the following formula expressed by the following equation. ₁ = -q ₁ v ₁ × B acts. Here, q ₁ is the charge of negative ions, v ₁ is the velocity of negative ions, and B is the magnetic flux density. On the other hand, for the positive ions that make up the ion beam, A ₂
A directional force F ₂ F ₂ = q ₂ v ₂ × B acts. Here, q ₂ is the charge of positive ions, v ₂ is the velocity of positive ions, and B is the magnetic flux density.

A positive ion absorption chamber 7 is provided in the traveling direction of the positive ions deflected and separated by the beam deflector 5 ', and the positive ions collide with the positive ion absorption chamber 7 and are absorbed in the chamber 7. Will be done.

On the other hand, an end station unit 6 is provided in the traveling direction of the negative ions deflected and separated by the beam deflecting unit 5, and the negative ion implantation into the ion irradiation target 61 is performed by the end station unit 6. Done.

As described above, the negative ion implanter of this embodiment produces the negative ion beam forming unit 1 for forming the negative ion beam and the positive ions for electrically neutralizing the negative ion beam. A neutralizing positive ion source 3 and a beam deflecting unit 5'which deflects and separates negative ions and positive ions forming an ion beam by a magnetic field immediately before the implantation position are provided.

As a result, the negative ion beam formed in the negative ion beam forming unit 1 is electrically neutralized by the positive ions extracted from the plasma generation chamber 37 of the neutralizing positive ion source 3. The negative ions can be efficiently transported to immediately before the injection position. The ion beam in the electrically neutralized state is deflected and separated into negative ions and positive ions by the beam deflecting unit 5 ′ immediately before the implantation position. Therefore, only negative ions should be implanted into the ion irradiation target 61. Therefore, it becomes possible to measure the dose amount of only negative ions. Therefore, with the above-described configuration, it is possible to perform high-current negative ion implantation with a good controllability of the implantation amount, and it is possible to realize a negative ion implantation process that is less likely to cause a charge-up phenomenon than positive ion implantation and is effective for device fabrication.

Although the neutralizing positive ion source 3 is provided immediately after the accelerating tube 2 in the above-described first and second embodiments, its installation position is not limited to this. It may be provided immediately after the mass spectrometric section 4.

The above-described embodiments are intended to clarify the technical contents of the present invention, and should not be construed in a narrow sense by limiting to such specific examples. Various modifications can be made within the scope of the claims.

[0060]

As described above, the negative ion implanting apparatus according to the invention of claim 1 uses the negative ion beam forming means for forming the negative ion beam, and the positive ion is supplied to the negative ion beam to generate the beam. Beam neutralizing means for electrically neutralizing the ion beam, and forming the ion beam by providing a predetermined electric field in the passage path of the ion beam in the electrically neutralized state, which is provided immediately before the ion irradiation target. and a electrostatic deflection separating means for deflecting separating the negative ions and positive ions, the beam
The neutralization means is an ECR ion source .

Therefore, the negative ions can be efficiently transported, and only the negative ions can be injected into the ion irradiation target, and as a result, the dose amount of only the negative ions can be measured. Therefore, it is possible to perform high-current negative ion implantation with a good controllability of the implantation amount, and it is possible to realize a negative ion implantation process that is less likely to cause a charge-up phenomenon than positive ion implantation and is effective in device fabrication. .

As described above, the negative ion implanting apparatus according to the second aspect of the present invention uses the negative ion beam forming means for forming the negative ion beam and the negative ion beam by supplying positive ions to the beam electrically. Beam neutralizing means for neutralizing, and negative ions that are provided immediately before the ion irradiation target and that form a predetermined magnetic field in the passage path of the ion beam in the electrically neutralized state to form the ion beam. and the positive ions and a magnetic deflection separating means for deflecting separated, the beam
The neutralization means is an ECR ion source .

Therefore, the negative ions can be efficiently transported, and only the negative ions can be injected into the ion irradiation target, and as a result, the dose amount of only the negative ions can be measured. Therefore, it is possible to perform high-current negative ion implantation with a good controllability of the implantation amount, and it is possible to realize a negative ion implantation process that is less likely to cause a charge-up phenomenon than positive ion implantation and is effective in device fabrication. .

[Brief description of drawings]

FIG. 1 is an explanatory view showing a beam deflecting unit, an end station unit, and a positive ion absorbing chamber of a negative ion implanting apparatus according to the invention of claim 1, and explaining how a neutralized ion beam is deflected and separated. .

FIG. 2 is an explanatory view showing a neutralizing positive ion source for a negative ion implanting apparatus according to the first and second aspects of the present invention and explaining how a negative ion beam is electrically neutralized.

FIG. 3 is a schematic configuration diagram showing an overall configuration of the negative ion implantation apparatus.

FIG. 4 is an explanatory view showing a beam deflecting unit of the negative ion implanter according to the invention of claim 2;

FIG. 5 is an explanatory view showing a beam deflecting unit, an end station unit and a positive ion absorbing chamber of the negative ion implanting apparatus, and explaining how the neutralized ion beam is deflected and separated.

[Explanation of symbols]

1 Negative Ion Beam Forming Unit (Negative Ion Beam Forming Means) 2 Accelerator Tube 3 Neutralizing Positive Ion Source (Beam Neutralizing Means) 4 Mass Spectrometer 5 Beam Deflection Unit (Electrostatic Deflection Separation Means) 5'Beam Deflection Part (magnetic field deflection separation means) 6 End station part 7 Positive ion absorption chamber 10 Beam tube 11 Negative ion source 51 Deflection electrode 52 Deflection electrode 53 Power source 54 Power source 55a Magnet 55b Magnet 61 Ion irradiation target

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-52-147074 (JP, A) JP-B-56-7292 (JP, B1) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01J 37/317

Claims (2)

(57) [Claims] 1. A negative ion implanter for implanting negative ions into an object to be irradiated with ions, comprising: a negative ion beam forming means for forming a negative ion beam; and supplying positive ions to the negative ion beam to form a beam. Beam neutralizing means for electrically neutralizing, provided immediately before the ion irradiation target, to form a predetermined electric field in the passage path of the ion beam in the electrically neutralized state,
And a electrostatic deflection separating means for negative ions and deflecting the positive ion separation constituting the ion beam, a negative ion implanter, wherein said beam neutralization means is a ECR ion source. 2. A negative ion implanter for implanting negative ions into an object to be irradiated with ions, comprising: a negative ion beam forming means for forming a negative ion beam; and supplying positive ions to the negative ion beam to form a beam. Beam neutralizing means for electrically neutralizing, provided immediately before the ion irradiation target, to form a predetermined magnetic field in the passage path of the ion beam in the electrically neutralized state,
And a magnetic deflection separating means for deflecting separating the negative ions and positive ions constituting the ion beam, a negative ion implanter, wherein said beam neutralization means is a ECR ion source.