JP2003303570A - Ion beam irradiation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for generating a large amount of electrons of low energy, reducing the charge-up of a base in accompany with the irradiation of ion beam, and free from the vacuum down of a beam line and the like. <P>SOLUTION: This ion beam irradiation device comprises a thermoelectronic emission source 20 for emitting the thermoelectrons 33 in the direction excluding a passage of the ion beam 2, and a thermoelectron transporting unit 50 for transporting the thermoelectrons 33 in a state of being bent by magnetic field to be guided toward the passage of the ion beam 2. The thermoelectron emission source 20 comprises a sheet cathode 32 of potential within a range of 0 V--6 V to a holder 6 holding the base 4, a filament for heating the cathode, and a lead-out electrode 36 for leading out the thermoelectrons 33 emitted from the cathode 32. The thermoelectron transporting unit 50 comprises a guide cylinder 52 which is bent and widened into the horn-shape toward an outlet 54 at the other side, and a coil 56 wound on an outer part of the guide cylinder 52 in particular with the circular arc-shape at a horn-shaped part 52b. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion beam irradiation apparatus for irradiating a substrate with an ion beam to perform processing such as ion implantation, and more specifically, to charge up a substrate surface during ion beam irradiation. The present invention relates to the improvement of the suppression means.

[0002]

2. Description of the Related Art In an ion implanter or the like, when an ion beam is applied to a substrate which is an object to be irradiated, positive charges of ions forming the ion beam are accumulated on the surface of the substrate to cause charge-up. If this is left as it is, for example, dielectric breakdown of a semiconductor device formed on the surface of the substrate is caused.

Therefore, conventionally, a technique has been proposed for suppressing (releasing) charge-up by utilizing electrons (see, for example, Japanese Patent Laid-Open No. 3-93141). This is roughly classified into (a) using secondary electrons,
(B) There is a method of generating plasma and utilizing electrons in the plasma.

In the technique (a) of utilizing secondary electrons, the thermoelectrons (primary electrons) emitted from the filament are accelerated by an electric field to collide with the opposing wall, and at this time, the low electron emitted from the opposing wall. The secondary electrons of energy are guided to the substrate,
The above-mentioned charge-up is suppressed by neutralizing the positive charge of the ions by the secondary electrons.

In the technique of utilizing plasma of (b), a small plasma source is installed in the vicinity of the substrate, low-energy electrons in the plasma generated by this plasma source are guided to the substrate together with the ion beam, and the electrons are used to generate ions. The charge-up is suppressed by neutralizing the positive charge of.

[0006]

In the case of the technique of utilizing secondary electrons of (a) above, primary electrons of high energy as well as secondary electrons of low energy (thermoelectrons emitted from a filament and accelerated by an electric field) are used. ) Jumps into the substrate, causing the substrate to negatively charge up. At this time, the charging voltage on the surface of the substrate rises to a voltage corresponding to the energy of electrons jumping into the substrate, and thus becomes a high voltage. It is very difficult to select the primary electron and the secondary electron.

In the case of the above-mentioned technique utilizing plasma (b), a gas is required for plasma generation, and this gas flows out from the plasma source to generate an ion beam path (beam line) or a vacuum in the substrate processing chamber. Worsen. When the degree of vacuum deteriorates, for example, (a) the cross-sectional shape of the ion beam is changed due to collision with gas molecules and the uniformity of implantation on the substrate is deteriorated, or (b) due to collision with gas molecules, a current is generated. The number of neutral particles that cannot be measured increases, and they enter the substrate and are injected, resulting in an error in the injection amount.

Further, in recent years, there has been a strong demand for further suppressing the charge-up of the substrate to lower the charging voltage on the surface of the substrate. For example, when manufacturing a semiconductor device by ion implantation by irradiating a semiconductor substrate with an ion beam, miniaturization of the semiconductor device has been advanced in recent years. Lower (eg ±
There is a demand to suppress it to about 6V or less). The technique (b) uses low-energy electrons in plasma, and the charge-up of the substrate can be suppressed to a small level as compared with the technique (a), but the technique as described above is still used. It is difficult to meet the recent demands.

Therefore, according to the present invention, a large amount of low-energy electrons are generated and utilized for neutralization, so that the charge-up of the substrate due to ion beam irradiation can be suppressed to a small level, and the beam line and the substrate processing chamber can be suppressed. The main object of the present invention is to provide an ion beam irradiation apparatus that does not cause deterioration of the degree of vacuum.

[0010]

An ion beam irradiation apparatus according to the present invention is arranged upstream of a holder for holding a substrate and on a side of a path of an ion beam, so that thermoelectrons can be applied to the ion beam. A thermoelectron emission source that emits in a direction other than the path, and a thermoelectron transport that bends the thermoelectrons emitted from the thermoelectron emission source by a magnetic field and transports the thermoelectrons to guide them toward the ion beam path. And the thermoelectron emission source is a surface-like one that emits thermoelectrons when heated from the other, and is 0 ° with respect to the holder.
A cathode kept at a potential within the range of V to -6V, a filament for heating the cathode from behind to emit the thermoelectrons, and a heat provided from the cathode in front of the cathode. The thermionic transporter has the same function as the extraction electrode of the thermionic emission source, and has an extraction electrode for extracting electrons, which is kept at a potential within a range of 0 V to 10 V with respect to the cathode. A horn-shaped part that is of a potential and is bent so that one end is located in front of the extraction electrode and the other end is located in the vicinity of the path of the ion beam, and the other end side expands like a horn toward the exit. And a coil that is wound outside the guide cylinder to generate the magnetic field and that is wound in an arc shape that widens toward the outlet in the horn-shaped portion. That It is a symptom (claim 1).

According to the above structure, the thermoelectrons emitted from the thermoelectron emission source are bent and transported by the magnetic field by the thermoelectron transporter, are guided toward the path of the ion beam, and are supplied to the vicinity of the ion beam. It The thermoelectrons thus supplied are taken into the ion beam forming the beam plasma, and if the substrate is positively charged, it is attracted to the potential thereof and moves to the substrate side together with the ion beam to move to the positive surface of the substrate. Neutralize the charge. If the positive charge on the substrate surface is neutralized,
The drawing of thermoelectrons into the substrate automatically stops. In this way, charge-up of the substrate due to ion beam irradiation can be suppressed (relaxed).

In this case, since the thermionic emission source has the above-described planar cathode, the filament for heating it and the extraction electrode, a large amount of thermions are emitted from the cathode to neutralize it. Can be used for.

Moreover, the cathode is 0 V to −6 relative to the holder.
Since the potential is kept at a potential within the range of V, the energy of thermoelectrons emitted from this cathode is 0 eV to the holder.
It is distributed within the range of 6 eV. Between the cathode and the extraction electrode, 0 V to 10 V depending on the relationship between the potentials of the two.
Although there is a potential difference within the range of, and thermoelectrons are efficiently extracted from the cathode by the energy corresponding to this potential difference, the guide tube of the thermoelectron transporter has the same potential as the extraction electrode, so the heat emitted from the guide tube is The electrons are decelerated by energy corresponding to the potential of the cathode while moving toward the holder. As a result, the energy of the thermoelectrons reaching the substrate is
It depends on the potential of the cathode, not on the potential of the extraction electrode, which is in the range of 0 eV to 6 eV. According to the present invention, a large amount of such low energy thermoelectrons can be emitted and used for neutralization.

As a result, not only the positive charge due to the ion beam can be sufficiently neutralized, but even if the above-mentioned thermoelectrons reach the substrate in excess, the energy thereof is 0 eV to 6 e.
Since the energy is low within the range of V, the negative charging voltage of the substrate can be suppressed to 6V or less. That is, the charge up of the substrate due to the ion beam irradiation can be suppressed to a very small level.

Moreover, in this apparatus, the thermoelectrons are used and the gas for plasma generation is not used, so that the degree of vacuum in the beam line and the substrate processing chamber is not deteriorated.
Therefore, it is possible to prevent the deterioration of the injection uniformity and the occurrence of the injection amount error due to the deterioration of the degree of vacuum.

In the thermoelectron transporter, the other end of the guide tube forms a horn-shaped portion that widens toward the outlet, and a coil is wound around the horn-shaped portion in an arc shape that widens toward the outlet. Therefore, a magnetic field spreading like a fan is formed near the exit of the thermionic transporter. Since the thermoelectrons are led out along the magnetic field while being wound around the magnetic field, the thermoelectrons can be led out by being distributed over a wide range. Therefore, it is possible to cope well with a large-area ion beam or a scanned ion beam.

Further, according to the present invention, thermionic electrons are once emitted from the thermionic emission source in a direction other than the ion beam path, and then the thermionic electrons are directed to the ion beam path by the magnetic field generated by the thermionic transporter. Since the structure for bending back is adopted, it is possible to prevent the surface of the cathode from facing the ion beam. As a result, vaporized particles (metal particles) generated from the cathode due to heating of the cathode are less likely to enter the ion beam, so that contamination of the substrate (metal contamination) due to the vaporized particles can be prevented.

When the ion beam is reciprocally scanned within a predetermined scanning range, a coil power supply capable of switching a current in both forward and reverse directions to the coil of the thermoelectron transporter and a current supplied from the coil power supply are It is preferable to further provide a control device for controlling the ion beam to flow in one direction when it is in one half of the scanning range and to flow in the opposite direction when it is in the other half of the scanning range. 2).

By doing so, a large number of thermoelectrons can be supplied from the thermionic transporter to the side on which the ion beam exists for the reciprocally scanned ion beam, that is, following the ion beam scanning. Since the thermoelectrons can be efficiently supplied to the ion beam, it is possible to suppress the charge-up of the substrate to be small all over the entire scanning range of the ion beam.

[0020]

1 is a sectional view showing an example of an ion beam irradiation apparatus according to the present invention. 2 is shown in FIG.
It is a figure which shows an example of the electric circuit which comprises the apparatus of FIG.

In this ion beam irradiation apparatus, a substrate (for example, a semiconductor substrate) 4 which is an irradiation target held by a holder 6 is used.
The substrate 4 is irradiated with the ion beam 2, and the substrate 4 is subjected to a process such as ion implantation. The path of the ion beam 2, the substrate 4, the holder 6, the inside of the thermoelectron emission source 20 described later, the inside of the thermoelectron transporter 50, and the like are in a vacuum atmosphere.

In order to uniformly irradiate the entire surface of the substrate 4 with the ion beam 2, at least one of the ion beam 2 and the holder 6 holding the substrate 4 may be scanned during the irradiation of the ion beam 2. In this example, the scanner 10 reciprocally scans the ion beam 2 in the X direction (for example, the horizontal direction) within a predetermined scanning range W (see FIG. 3). In addition, the holder 6 is moved in a Y direction (for example, a vertical direction) substantially orthogonal to the X direction by a scanning mechanism (not shown).
It is mechanically reciprocally scanned. The potential of the holder 6 is ground potential in this example.

In this example, the scanner 10 has an iron core 12 and a coil 14 wound around the iron core 12, and reciprocally scans the ion beam 2 in the X direction by a reversing magnetic field B. The scanner 10 (more specifically, its coil 14) is supplied from the scanning power supply 16 with a triangular-wave scanning current I _S as shown in FIG. 3C, for example. However,
A scanner that reciprocally scans the ion beam 2 in the X direction by an inverting electric field may be used.

To the side of the path of the ion beam 2 near the upstream side of the holder 6, the thermoelectrons 33 are directed in a direction other than the path of the ion beam 2, more specifically, in this example, A thermoelectron emission source 20 that emits in a direction opposite to the path is provided. This thermionic emission source 20
Is connected to one end of a thermoelectron transporter 50 that bends and transports the thermoelectrons 33 emitted therefrom by a magnetic field and guides the thermoelectrons 33 toward the path of the ion beam 2. In this example, the thermoelectron emission source 20 is attached to and held by a cylindrical holder 22 through which the ion beam 2 passes. The potential of the holding table 22 is set to the ground potential in this example.

The thermoelectron emission source 20 is, in this example, a rectangular parallelepiped container 24 having an opening on one surface (upper surface) and a semi-cylindrical reflector 28 provided via an insulator 26 therein.
And a U-shaped filament 30 provided above it, and an insulator 2 above it, that is, at the opening of the container 24.
6 is provided with a planar cathode 32, and a porous extraction electrode 36 provided above the cathode 32 with an insulator 34 interposed therebetween.

The cathode 32 is, for example, a thin plate.
The work function of the material of the cathode 32 is 3.5 to 4.5 V.
Degree, Richardson constant A is 60 to 7
It is preferable to use a material having a viscosity of about 0 A / cm ² K ² . Examples of such a material include SiC and Ta.

The extraction electrode 36 has a large number of holes 37 (however,
2 may be a perforated flat plate having one), a mesh-shaped flat plate, or the like.

Referring also to FIG. 2, the filament 30 is heated by a DC filament power source 40 to generate thermoelectrons 3.
Release 1. In this example, a resistor 38 is connected between the negative end of the filament power supply 40 and one end of the filament 30, and the reflector 28 is connected to the negative end of the filament power supply 40. A voltage drop ΔV is generated in the resistor 38 by energizing the filament 30. Therefore, the reflector 28 always has a negative potential with respect to the filament 30, and the thermoelectrons 31 from the filament 30 are reflected to the cathode 32 side. Thereby, the thermoelectrons 31 emitted from the filament 30 can be efficiently used by heating the cathode 32.

Between the other end of the filament 30 (the positive end of the filament power supply 40) and the cathode 32, a direct current bombard power supply 42 is connected with the latter on the positive side.
The output voltage is, for example, about 300 V to 500 V, which allows the thermoelectrons 31 to be accelerated and collide with the cathode 32.

In this way, the cathode 32 receives energy by both radiant heat from the filament 30 and electron impact and is heated over a wide area, and a large amount of thermoelectrons 33 can be emitted from the wide area. .

To the cathode 32, a potential setting power source 44 of variable output voltage with direct current is connected to apply a cathode voltage V _C to the cathode 32 with reference to the potential of the holder 6. This cathode voltage V _C is in the range of 0V to −6V, preferably 0V.
Within the range of -3V. Thereby, the cathode 32 is in the range of 0V to -6V, preferably 0V with respect to the holder 6.
It is kept at a potential within the range of -3V. As a result, the energy of the thermoelectrons 33 when reaching the substrate 4 on the holder 6 is the energy corresponding to the above potential, that is, 0 eV to 6
It is kept within the range of eV, preferably within the range of 0 eV to 3 eV.

The extraction electrode 36 is connected to a extraction power supply 46 of variable output voltage with direct current for applying the extraction voltage V _E to the extraction electrode 36 with reference to the potential of the cathode 32. The extraction voltage V _E is set within the range of 0V to 10V. As a result, the extraction electrode 36 is kept at a potential within the range of 0V to 10V with respect to the cathode 32.

One end of the thermoelectron transporter 50 is the extraction electrode 3
6 is located in front of 6 and the other end (exit 54 side) is the ion beam 2
In this example, the U-shape (J
A tubular guide tube 52 that is bent (also called a letter shape), and a coil 56 that is wound around the guide tube 52 and that generates the magnetic field.
It has and.

The guide cylinder 52 has the same potential as the extraction electrode 36. The guide cylinder 52 is composed of a bent portion 52a located on the side of the extraction electrode 36 and a horn-shaped portion 52b connected to the tip thereof. The bent portion 52a has an oval cross section, and its size is constant in the longitudinal direction (direction in which the thermoelectrons 33 are guided). The horn-shaped portion 52b has an oval cross section, but gradually widens toward the outlet 54 (see FIG. 4 or 5). That is, the horn-shaped portion 52b extends toward the outlet 54 in a flat horn shape.

The coil 56 is a bent portion 52 of the guide cylinder 52.
A is wound in a spiral shape in the usual winding manner. That is, when viewed in cross section, it is wound in an oval shape. Coil 56
The horn-shaped portion 52b of the guide cylinder 52 has a structure shown in FIG.
As shown in FIG. 3, the coil is wound in an arc shape that widens toward the outlet 54. In other words, the coil 56 is wound around the horn-shaped portion 52b in a concentric shape with the radius increasing toward the outlet 54 side.

This coil 56 has a DC coil power source 5
A coil current I _C is supplied from 8 to generate the magnetic field in the guide cylinder 52 for guiding the thermoelectrons 33. A more specific example of this coil power supply 58 and its control device 60 will be described later.

If necessary, a cooling pipe for cooling the guide cylinder 52 and the coil 56 may be provided outside the guide cylinder 52.

In this ion beam irradiation apparatus, the thermoelectrons 33 emitted from the thermoelectron emission source 20 are bent and transported by the magnetic field generated by the thermoelectron transporter 50, and are guided toward the path of the ion beam 2. That is, the thermoelectrons 33 emitted from the thermoelectron emission source 20 enter the guide cylinder 52 of the thermoelectron transporter 50 and are wound around the coil 56.
The magnetic field is generated while being wound around the generated magnetic field, and is eventually led out from the exit 54 toward the path of the ion beam 2 and supplied to the vicinity of the ion beam 2.

The thermoelectrons 33 thus supplied are
If the substrate 4 is positively charged by the ion beam 2 that forms the beam plasma and the substrate 4 is positively charged, it is attracted to the potential and moves to the substrate 4 side together with the ion beam 2 to neutralize the positive charge on the substrate surface. Harmonize When the positive charges on the surface of the substrate are neutralized, the drawing of the thermoelectrons 33 to the substrate 4 automatically stops. In this way, charge-up of the substrate 4 due to ion beam irradiation can be suppressed (relaxed).

In this case, the thermionic emission source 20 is composed of the above-mentioned planar cathode 32 and the filament 30 for heating it.
Since the cathode 32 has the extraction electrode 36, a large amount of thermoelectrons 33 can be emitted from the cathode 32 and used for neutralization.

Moreover, since the cathode 32 is kept at the potential of the cathode voltage V _C (which is within the range of 0 V to -6 V, preferably within the range of 0 V to -3 V as described above) with respect to the holder 6, The energy of the thermoelectrons 33 emitted from the cathode 32 is distributed in the range of 0 eV to 6 eV (preferably 0 eV to 3 eV) with respect to the holder 6.

Due to the application of the extraction voltage V _E , there is a potential difference within the range of 0 V to 10 V between the cathode 32 and the extraction electrode 36, and the thermoelectron 33 from the cathode 32 is efficient with the energy corresponding to this potential difference. Well drawn out. However, the guide tube 52 of the thermoelectron transporter 50 is
The thermoelectrons 3 emitted from the guide cylinder 52 have the same potential as
In No. 3, since the surrounding area is at the ground potential, deceleration starts from the moment when it jumps out of the outlet 54, and the outlet 54 and the holder 6
Since there is a relatively long distance between and, the thermoelectrons 33 are decelerated by energy corresponding to the potential of the cathode 32 while moving toward the holder 6. As a result, the energy of the thermoelectrons 33 reaching the substrate 4 does not depend on the potential of the extraction electrode 36, that is, the magnitude of the extraction voltage V _E , and thus the cathode 32.
Of the cathode voltage V _C set by the potential setting power source 44, which is 0 eV to
It is in the range of 6 eV (preferably 0 eV to 3 eV).
According to the present invention, such low energy thermoelectrons 3
A large amount of 3 can be released and used for neutralization.

As a result, not only the positive charge on the surface of the substrate due to the ion beam 2 can be sufficiently neutralized, but even if the thermoelectrons 33 reach the substrate 4 excessively, the energy thereof is 0 eV to 6 eV (preferably). Has a low energy in the range of 0 eV to 3 eV), so that the negative charging voltage of the substrate 4 can be suppressed to 6 V (preferably 3 V) or less. That is, the charge-up of the substrate 4 due to the ion beam irradiation can be suppressed to a very small level. Therefore, this ion beam irradiation apparatus can be sufficiently applied to the manufacture of semiconductor devices with advanced miniaturization.

Moreover, in this ion beam irradiation apparatus, since the thermoelectrons 33 are used and the gas for plasma generation is not used, the vacuum degree of the beam line and the substrate processing chamber is not deteriorated. Therefore, it is possible to prevent the deterioration of the injection uniformity and the occurrence of the injection amount error due to the deterioration of the degree of vacuum.

Further, in the thermoelectron transporter 50, the other end side of the guide cylinder 52 forms a horn-shaped portion 52b which widens toward the outlet 54, and the coil 56 extends in the horn-shaped portion 52b toward the outlet. Since it is wound in an arc shape, a magnetic field spreading like a fan is formed near the exit 54 of the thermoelectron transporter 50. Since the thermoelectrons 33 are led out along the magnetic field while being wound around the magnetic field, the thermoelectrons 33 can be led out by being distributed over a wide range. Therefore, it is possible to cope with a large-area ion beam 2 and a scanned ion beam 2 well. As a result, it is possible to sufficiently cope with an increase in the diameter of the substrate 4.

Further, in this ion beam irradiation device, thermionic emission source 20 once causes thermionic electrons 33 to be emitted in a direction other than the path of the ion beam 2, and thereafter the anionic beam 3 is emitted.
Since the structure in which 3 is bent back toward the path of the ion beam 2 by the magnetic field from the thermoelectron transporter 50 is adopted, it is possible to prevent the surface of the cathode 32 from facing the ion beam 2. As a result, vaporized particles (metal particles) generated from the cathode 32 due to the heating of the cathode 32 are less likely to enter the ion beam 2, so that contamination of the substrate 4 (metal contamination) due to the vaporized particles can be prevented. .
Since the vaporized particles generated from the cathode 32 do not have an electric charge, they are not bent by the magnetic field generated by the coil 56. Even if they have an electric field, they are much heavier than electrons, and therefore are bent much. This is because it is very small and collides with the inner wall of the guide cylinder 52 and cannot exit from the outlet 54.

By the way, in the ion beam irradiation apparatus of this example, the coil power supply 58 is a power supply capable of switching (reversing) the coil current I _{C in} both the forward and reverse directions to the coil 56 of the thermoelectron transporter 50. (See FIG. 2). Such a power supply is also called a bipolar power supply.

From this coil power source 58 to the coil 5
6, the direction of the coil current I _C flowing from the thermoelectron transporter 50 to the side where the ion beam 2 to be scanned exists.
Further, a control device 60 is provided to switch so that a large amount is supplied. The control device 60 refers to FIGS. 3 to 5, and the coil current I flowing from the coil power supply 58 to the coil 56 is used.
_When the ion beam 2 is in one half (left half from the center) W ₁ of the scanning range W, it flows in the positive direction (direction shown in FIG. 4) and the other half (right half from the center) W. When the value is ₂ , the control is performed so that the flow is switched in the reverse direction (direction shown in FIG. 5).

More specifically, as shown in FIG. 3, when the scanning power supply 16 supplies the scanning current I _S having a triangular waveform as shown in FIG. Correspondingly, as shown in FIG. 3B, the ion beam 2 is scanned from the point a on the center of the scanning range W to the maximum scanning point b of the half W ₁ on one side, and then the point c on the center is scanned. After being scanned via the other half of the one side W ₂ up to the maximum scanning point d, it returns to point e on the center, and thereafter, such reciprocal scanning is repeated.

A positive direction is applied to the coil 56 of the thermoelectron transporter 50.
Coil current I_C(In the orientation shown in FIG. 4, the size is, for example, 1
0A) and the coil current I in the reverse direction_C(Orientation shown in Figure 5
And, when the size is -10A, for example, thermionic
Orbit of the thermoelectrons 33 derived from the outlet 54 of the transporter 50
Figures 4 and 5 show the simulation results of
Show each. Coil current I_CIs positive, the gauge of the thermoelectron 33 is
The road is half W on the left side of the scanning range W of the ion beam 2.
₁Toward the right side, and if it is negative, half W on the right side ₂Direction
Suitable for Coil current I_CIf you make it positive, the exit 54
The magnetic field is emitted from the coil, and conversely the coil current I_CNegative
Then, the magnetic field is directed to enter the outlet 54. Thermoelectric like this
Reverse the direction of the magnetic field at the outlet 54 of the child transporter 50
Then, the Larmor motion of the thermoelectrons 33 wrapped around the magnetic field
This also reverses the direction so that
The drift direction of the thermoelectrons 33 when moving is left as described above.
It is thought to be flipped to the right.

In other words, the direction in which the coil current I _C flows is the direction in which the magnetic field at the outlet 54 of the thermoelectron transporter 50 is directed (as described above, the magnetic field is emitted in the example of FIG. 4, and in the example of FIG. 5). The coil current I _{C is made} to flow so that the ion beam 2 exists on the right side when viewed in the direction in which the magnetic field enters. By doing so, it has been confirmed by simulation that the thermoelectrons 33 are directed to the side where the ion beam 2 exists.

The coil current I as described above_CTo control
For this reason, the control device 60 of this example, as shown in FIG.
Scanning current I output from the scanning power supply 16_SThe polarity of
The determination circuit 62 that determines the
Coil current I output from the power supply 58_CDirection (pole
And a control circuit 64 for performing control to invert
It Specifically, as shown in FIG. 3, the ion beam 2
Left half W of scanning range W ₁Scan current I_SIs
Positive, right half W₂Scan current I _SIs negative
Therefore, this scanning current I_SThe polarity of
The coil current I having the same polarity as the determined polarity is determined._C
Flow, that is, the scanning current I_SIs positive when the coil current
Flow I_CPositive, and the scanning current I_SCoil current when is negative
I_CControl circuit 64 causes coil power supply 58 to be negative.
To control.

By controlling the coil current I _C flowing through the coil 56 of the thermoelectron transporter 50 as described above, the thermoelectron transporter 50 is supplied to the ion beam 2 which is reciprocally scanned.
Therefore, since many thermoelectrons 33 can be supplied to the side where the ion beam 2 exists, that is, the thermoelectrons 33 can be efficiently supplied to the ion beam 2 following the scanning of the ion beam 2. It is possible to suppress the charge-up of the substrate 4 to be small throughout the entire scanning range of the ion beam 2. Therefore, even when the ion beam 2 is scanned to correspond to the large-diameter substrate 4 or the like, the charge-up of the substrate 4 can be effectively suppressed to be small over the entire surface thereof.

[0054]

Since the present invention is configured as described above, it has the following effects.

According to the invention of claim 1, 0 eV to 6
A large amount of low-energy thermionic electrons in the eV range can be emitted and used for neutralization. as a result,
Not only can the positive charge due to the ion beam be sufficiently neutralized, but even if the above thermoelectrons reach the substrate excessively,
Since the energy is low energy in the range of 0 eV to 6 eV, the negative charging voltage of the substrate can be suppressed to 6 V or less. That is, the charge up of the substrate due to the ion beam irradiation can be suppressed to a very small level.

Moreover, in this apparatus, the thermoelectrons are used and the gas for plasma generation is not used, so that the degree of vacuum in the beam line and the substrate processing chamber is not deteriorated.

In the thermoelectron transporter, a magnetic field spreading like a fan is formed near the exit of the thermoelectron transporter, and the thermoelectrons are guided along the magnetic field while being wound around the magnetic field. Can be derived. Therefore, it is possible to cope well with a large-area ion beam or a scanned ion beam.

Further, in the present invention, thermionic electrons are once emitted from the thermionic emission source in a direction other than the ion beam path, and then the thermionic electrons are directed to the ion beam path by the magnetic field generated by the thermionic transporter. Since the structure for bending back is adopted, vaporized particles generated from the cathode due to heating of the cathode are less likely to enter the ion beam, and contamination of the substrate by the vaporized particles can be prevented.

According to the second aspect of the present invention, a large number of thermoelectrons can be supplied to the side where the ion beam exists from the thermoelectron transporter with respect to the reciprocally scanned ion beam, that is, the ion beam. Since it is possible to efficiently supply thermoelectrons to the ion beam following the scanning of
The further effect is that the charge-up of the substrate can be suppressed to be small all over the ion beam scanning range.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of an ion beam irradiation apparatus according to the present invention.

FIG. 2 is a diagram showing an example of an electric circuit constituting the device of FIG.

3 is a diagram showing an example of the relationship between the movement of an ion beam and the coil current in the apparatus of FIG.

FIG. 4 is a diagram showing a schematic example of a trajectory of thermoelectrons derived from a thermoelectron transporter when a coil current is passed in a positive direction.

FIG. 5 is a diagram showing a schematic example of trajectories of thermoelectrons derived from a thermoelectron transporter when a coil current flows in the opposite direction.

[Explanation of symbols]

2 ion beam 4 substrates 6 holder 10 Scanner 20 Thermionic emission source 30 filament 32 cathode 33 thermoelectrons 36 Extraction electrode 44 potential setting power supply 46 Drawer power supply 50 thermionic transporter 52 Guide tube 52b Horn-shaped part 56 coils 58 coil power supply 60 control device

Claims (2)

[Claims] 1. An ion beam irradiation apparatus for irradiating a substrate held by a holder with an ion beam for processing, wherein the ion beam irradiation apparatus is arranged on the upstream side of the holder and laterally of the path of the ion beam, A thermionic emission source that emits electrons in a direction other than the ion beam path, and a thermoelectron emitted from this thermionic emission source is bent by a magnetic field and transported to direct the thermoelectron to the ion beam path. A thermoelectron transporter for leading the thermoelectron transporter, and the thermoelectron emission source is a surface-shaped one that emits thermoelectrons when heated by another, and is 0 V to the holder.
A cathode kept at a potential within the range of −6 V, a filament for heating the cathode from behind to emit the thermoelectrons, and a thermoelectron provided in front of the cathode for the thermoelectrons emitted from the cathode. 0 for the cathode
An extraction electrode kept at a potential within the range of V to 10V, and the thermionic transporter has the same potential as the extraction electrode of the thermionic emission source, and one end thereof is the extraction electrode. And a guide tube that is bent forward so that the other end is located in the vicinity of the path of the ion beam and that the other end forms a horn-shaped portion that widens in a horn shape toward the exit. Ion beam irradiation characterized in that it is wound outside the cylinder to generate the magnetic field, and the horn-shaped portion has a coil wound in an arc shape expanding toward the exit. apparatus. 2. The ion beam is reciprocally scanned in a predetermined scanning range in a predetermined direction by an electric field or a magnetic field, and a coil capable of switching a current in both forward and reverse directions to a coil of the thermionic transporter. A power supply and a current flowing from this coil power supply are caused to flow in one direction when the ion beam is in one half of one side of the scanning range,
The ion beam irradiation apparatus according to claim 1, further comprising: a control device that performs control to switch to flow in the opposite direction when it is on the other half.