JP2002352761A - Ion beam irradiation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce electric charges on the surface of a substrate accompanying ion beam irradiation, without deteriorating the vacuum level in a beam line or a substrate processing chamber, by generating a large number of low energy electrons and utilizing them for neutralization. SOLUTION: This ion beam irradiation device comprises a planar negative electrode 10, which is in the same potential with a holder 6 for holding a substrate 4 and emits thermal electrons 12 by being heated with an external source, a heating source 14 for heating the electrode 10, an extraction electrode 26 for extracting thermal electrons 12 emitted from the negative electrode 10, and an extraction power source 28 for applying an extraction voltage VE of not more than 6 V on the extraction electrode 26. Additionally, the ion beam irradiation device comprises a magnetic field generator 34 for deflecting the direction of extracted thermal electrons 12 to make them advance to an ion beam 2 and to the substrate 4 side, and an electron release port 32 for selectively getting through thermal electrons 12, which move on loci of a prescribed range.

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 and performing processes such as ion implantation, and more specifically, to charging a substrate surface during ion beam irradiation. Up).

[0002]

2. Description of the Related Art In the manufacture of semiconductor devices by ion implantation and the like, it is important to suppress the charging of the substrate surface during ion beam irradiation to a small extent. One of the means is disclosed in, for example, JP-A-3-93141. As described above, the plasma emitted from the plasma generator is supplied to the ion beam near the upstream side of the substrate, and the electrons in the plasma are used to neutralize the positive charges associated with the ion beam irradiation. Techniques have been proposed in the past.

[0003] This type of plasma generator is generally
The filament is heated in the plasma generation vessel to generate thermoelectrons, which are accelerated by the electric field, and the plasma generation gas (usually an inert gas) introduced from the gas inlet.
The gas is ionized to generate plasma by colliding with the gas, and this plasma is supplied to the vicinity of the ion beam and the substrate.

[0004] By the supply of the plasma, electrons in the plasma are attracted to the positively charged substrate surface by ion beam irradiation and neutralize the positive charge. Electrons in the plasma are taken into the ion beam forming the beam plasma, and when the substrate is charged, the electron moves in the beam plasma to the substrate side by the potential, thereby neutralizing the positive charge. In principle, if the positive charges on the substrate surface are neutralized, the attraction of electrons to the substrate automatically stops. In this manner, charging of the substrate surface due to ion beam irradiation can be suppressed.

[0005]

In the plasma generator as described above, since (a) about 10 V is used for heating the filament, the energy of thermoelectrons generated from the filament is about 0 to 10 eV, and (b) Energy of about 10 to 20 eV is required to cause the thermal electrons to collide with the plasma generation gas and ionize it, and the thermal electrons are accelerated at a voltage of about 15 to 20 V so that the energy becomes higher than the energy. The energy distribution of the electrons in the plasma used for the neutralization ranges from about 10 to 20 eV, and has a peak around that.

When such high-energy electrons are excessively supplied to the substrate, the electrons cause the substrate to be negatively charged, and the charged voltage on the substrate surface becomes a voltage (corresponding to the energy of the electrons). (For example, about 10 to 20 V). Therefore, conventionally, it has been difficult to suppress the charging voltage lower than this level of voltage.

[0007] However, in recent years, there has been a strong demand for suppressing the charging of the substrate surface to a lower level to lower the charging voltage on the substrate surface. For example, when a semiconductor device is manufactured by ion implantation by irradiating a semiconductor substrate with an ion beam, the semiconductor device has been miniaturized in recent years. However, there is a demand to lower the voltage (for example, to about ± 6 V or less), but this cannot be met by the conventional plasma generator.

Further, the above-mentioned plasma generator uses a gas for plasma generation, and this gas leaks out of a plasma discharge hole of a plasma generation container to reduce a path (beam line) of an ion beam and a degree of vacuum in a substrate processing chamber. There is also the problem of worsening. When the degree of vacuum deteriorates, for example, (a)
The cross-sectional shape of the ion beam changes due to collisions with gas molecules, and the uniformity of implantation into the substrate deteriorates. (B) Neutral particles that cannot be measured as current increase due to collisions with gas molecules, and these are deposited on the substrate. Injection / injection results in an injection amount error.

If the size of the plasma emission hole is reduced to reduce the above-mentioned gas leakage, it is difficult to discharge the plasma from the hole, and the amount of supplied electrons is insufficient. Will happen.

Accordingly, the present invention provides a method for generating a large amount of low-energy electrons and using them for neutralization without causing deterioration in the degree of vacuum in a beam line or a substrate processing chamber, thereby reducing the surface of a substrate caused by ion beam irradiation. The main object of the present invention is to make it possible to suppress the electrification of the toner.

[0011]

An ion beam irradiation apparatus according to the present invention is disposed upstream of a holder for holding a substrate and at a side of a path of an ion beam, and is heated from the other side to generate thermoelectrons. A planar cathode emitting toward the upstream side of the ion beam and having the same potential as the holder,
A heating source for heating the cathode from behind to emit thermoelectrons, a porous extraction electrode provided in front of the cathode and extracting thermoelectrons emitted from the cathode toward the upstream side of the ion beam; An extraction power supply for applying an extraction voltage of 6 V or less with the former being a positive electrode side between the extraction electrode and the cathode, and bending the thermoelectrons extracted from the extraction electrode toward a path side of the ion beam to form an ion beam. A magnetic field generator for generating a magnetic field directed to the substrate side,
An electron emission port is provided for selectively passing thermoelectrons bent by the magnetic field generator, which draw a trajectory in a predetermined range.

According to the above arrangement, the heating by the heating source emits thermoelectrons from the cathode, and the thermoelectrons are extracted toward the upstream side of the ion beam through the extraction electrode. Further, these thermoelectrons are bent toward the ion beam and the substrate side by the magnetic field generated by the magnetic field generator, and only those that trace a predetermined range of trajectories pass through the electron emission port and are close to the ion beam and the substrate. Supplied to The thermoelectrons can neutralize the positive charges associated with the irradiation of the ion beam and suppress the charging of the substrate surface.

In this case, since a planar cathode, a heating source and an extraction electrode are provided, a large amount of thermoelectrons can be emitted from the cathode and used for neutralization.

In addition, since the cathode has the same potential as the holder, the energy of thermoelectrons emitted from the cathode is distributed in the vicinity of 0 eV with respect to the holder. Since this is extracted with an extraction voltage of 6 V or less, the energy of the thermoelectrons extracted through the extraction electrode is as low as about 6 eV or less. Such a large amount of low-energy thermoelectrons can be used for neutralization.

Further, by combining the magnetic field generator and the electron emission port, of the thermoelectrons drawn from the extraction electrode, those having a predetermined range of trajectories, that is, those having a predetermined range of energy are selectively taken out. Therefore, only the low-energy thermoelectrons can be more reliably used for neutralization.

As described above, since a large amount of low-energy thermoelectrons of about 6 eV or less can be generated and used for neutralization, the charge on the substrate surface due to ion beam irradiation can be suppressed to a small level.

In addition, this apparatus uses thermoelectrons and does not use a gas for generating plasma, so that the degree of vacuum in the beam line and the substrate processing chamber does not deteriorate.

[0018]

FIG. 1 is a sectional view showing an example of an ion beam irradiation apparatus according to the present invention. FIG. 2 shows FIG.
FIG.

This ion beam irradiation apparatus irradiates a substrate (for example, a semiconductor substrate) 4 held by a holder 6 with an ion beam 2 and performs a process such as ion implantation on the substrate 4. Note that in the example of FIG.
Except for 2, 24, 28, 42 and 46, all are arranged in a vacuum vessel (not shown). However, the magnetic field generator 3
4 may be arranged outside the vacuum vessel. In the example of FIG. 4, the devices from the microwave oscillator 56 to the tuner 62 are:
It is located outside the vacuum vessel.

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 ion beam 2 and the holder 6 are respectively scanned in X and Y directions orthogonal to each other. The potential of the holder 6 is fixed to the ground potential in this example.

In the vicinity of the upstream side of the holder 6, in this example,
A beam passage tube 44 for passing the ion beam 2 is provided. A negative voltage with respect to the ground potential is applied to the beam passage tube 44 from a DC power supply 46.

In the vicinity of the upstream side of the holder 6 and near the side of the path of the ion beam 2, the heating electrons 14 are used to heat the thermoelectrons 12 upstream of the ion beam 2 (the left side in FIG. 1; this direction). Is referred to as the front in this specification). This cathode 10
Is a thin plate, for example, and is formed of a high melting point material (for example, tantalum).

The reason that the cathode 10 itself is not electrically heated is
When a voltage is applied to the cathode 10 for the energization heating, an energy distribution is generated in the thermoelectrons 12 emitted from the cathode 10 corresponding to the voltage, which is an obstacle to the generation of the low energy thermoelectrons 12. This is to prevent it.

The cathode 10 has the same potential as the holder 6. That is, in this example, since the holder 6 is at ground potential, the cathode 10 is also at ground potential. Therefore, the energy of the thermoelectrons 12 generated from the cathode 10 is distributed in the vicinity of 0 eV with respect to the holder 6 and the substrate 4. More specifically, since the thermoelectrons 12 have only energy corresponding to the heating temperature of the cathode 10, the thermoelectrons 12 have a value of at most 0.2 to
It has only about 0.3 eV of energy.

Behind the cathode 10, a heating source 1 for heating the cathode 10 from behind to emit thermoelectrons 12
4 are provided.

The heating source 14 is, in this example, a holder 6
With respect to the cathode storage container 18 disposed so as to face backward (that is, so that the opening faces the opposite side of the holder 6), the sub-cathode 16 provided in the cathode storage container 18, and the sub-cathode 16 Heating power supply 20 for heating to emit thermoelectrons
An accelerating power supply 24 for accelerating and colliding thermoelectrons emitted from the sub-cathode 16 toward the cathode 10;
And a reflection power source 22 for pushing back the thermoelectrons emitted from the cathode and preventing the thermoelectrons from colliding with the cathode housing 18. The cathode 10 is attached to the opening of the cathode container 18 via an insulator 50.

The acceleration power supply 24 is connected between the cathode 10 and the sub-cathode 16 with the former being on the positive side. Reflection power supply 2
2 is connected between the sub-cathode 16 and the cathode storage container 18 with the former being the positive electrode side. The reason why the reflection power supply 22 is provided is that it is preferable to use the thermoelectrons generated from the sub-cathode 16 more efficiently by heating the cathode 10.

The sub-cathode 16 is preferably non-inductively wound, for example, as shown in FIG. A and b in FIG. 3 are power supply units. With the non-induction winding, the thermoelectrons generated from the sub-cathode 16 are less likely to be trapped (captured) by the magnetic field generated by the current flowing through the sub-cathode 16, and the thermoelectrons can be efficiently used by heating the cathode 10. Can be.

The planar shape of the sub-cathode 16 is not limited to a circular shape as in this example. In order to heat the entire cathode 10 more uniformly, a plurality of sub-cathodes 16 are connected to the cathode 1.
They may be arranged side by side along 0.

By heating the sub-cathode 16 with electric current,
Thermionic electrons are emitted from the sub-cathode 16 and this is
And is collided with the cathode 10 to heat the cathode 10 by the energy. The cathode 10 is also heated by the radiant heat from the sub-cathode 16. By both of these heatings, the cathode 10 emits thermoelectrons 12 from its surface.

In front of the cathode 10, a planar porous extraction electrode 2 for extracting thermoelectrons 12 emitted from the cathode 10 toward the upstream side of the ion beam 2 via an insulator 51.
6 are provided. The extraction electrode 26 is a mesh-shaped flat plate in this example, but may be a porous flat plate having a large number of small holes. By making the extraction electrode 26 planar, the distance from the cathode 10 can be kept constant,
Since a uniform extraction electric field can be generated, a large amount of thermoelectrons 12 can be extracted with high uniformity. The extraction electrode 26 is preferably made of a high melting point material (for example, carbon), and it is preferable to minimize deformation due to heat from the cathode 10.

[0032] Between the lead-out electrode 26 and the cathode 10 is between them, the extraction electrode 26 6V or less (or 0V) to the positive electrode side extraction voltage V _E by extraction power source 28 is connected to apply the I have. The thermoelectrons 12 generated from the cathode 10 by the extraction voltage V _E are generated by the extraction electrode 2.
6 and is extracted toward the upstream side of the ion beam 2. The drawn hot electrons 12 are will have an energy corresponding to the drawer conductive V _E. For example, the extraction voltage V _E may at about 2-3 V, if so, the energy of thermal electrons 12 drawn from the lead-out electrode 26 is very low at most about 2~3eV the holder 6 and the substrate 4 Become energy.

A cylindrical deflection container 30 is provided in front of the extraction electrode 26 with an insulator 52 interposed therebetween. The deflection container 30 is electrically grounded, and is provided with an insulator 53.
Is attached to the upper part of the beam passage tube 44 through the through hole. Outside the deflection container 30, an extraction electrode 26 is provided.
There is provided a magnetic field generator 34 that generates a magnetic field 36 that bends the thermoelectrons 12 extracted from the substrate toward the path of the ion beam 2 and directs them toward the ion beam 2 and the substrate 4.

In this example, the magnetic field generator 34 includes a U-shaped yoke 38 sandwiching the deflection container 30, a coil 40 wound around the yoke 38, and a coil power supply 42 for energizing the coil 40. By adjusting the current output from the coil power supply 42, the strength of the magnetic field 36 can be adjusted. The direction of the magnetic field 36 is a direction perpendicular to the direction in which the thermoelectrons 12 are extracted from the extraction electrode 26, as shown in FIGS.

Thermionic electrons 1 extracted from the extraction electrode 26
2 draws a circular orbit by receiving the Lorentz force downward in the figure, that is, toward the ion beam 2 side by the magnetic field 36. The trajectory in FIG. 1 shows one example. As is well known, the radius R of the circular orbit can be approximately expressed by the following equation. Here, B is the strength of the magnetic field 36, m is the electron mass, e is the electron charge, V _E is the extraction voltage described above.

[0036]

## EQU1 ## R = B ^-1 ＝ (2 mV _E / e)

At the lower part of the deflecting container 30 and facing the holder 6, one of the thermoelectrons 12 bent as described above, which draws a predetermined range of trajectories, that is, one having a predetermined range of energy is selected. An elongated (e.g., slit-shaped) electron emission port 32 for selectively (ie, selectively) passing is provided.

As can be seen from the above equation (1), thermoelectrons 12
Be smaller the extraction voltage V _E in order to reduce energy, by reducing the intensity B of the magnetic field 36 in response thereto, it is possible to draw a predetermined trajectory thermionic 12. In other words, how much energy the thermoelectrons 12 have from the electron emission port 32 can be selected depending on the strength of the magnetic field 36 and the position of the electron emission port 32. Specifically, since the position of the electron emission port 32 is fixed, by adjusting the intensity of the magnetic field 36, more specifically, by adjusting the output of the coil power supply 42, the heat having the target energy can be obtained. Only the electrons 12 can be extracted from the electron emission port 32. However, since the electron emission port 32 has the width W (see FIG. 2), the energy of the thermoelectrons 12 extracted through the electron emission port 32 has a certain width. In this example, the aforementioned 2
The thermoelectrons 12 having an energy of about 3 eV are selectively extracted.

The thermoelectrons 12 passing through the electron emission port 32 are
It is supplied to the vicinity of the ion beam 2 and the substrate 4. As described above, the thermoelectrons 12 are attracted to the positively charged substrate 4 by ion beam irradiation and neutralize the positive charges. The thermoelectrons 12 are taken into the ion beam 2 forming the beam plasma, and when the substrate 4 is charged, move in the beam plasma toward the substrate 4 by the potential thereof to neutralize the positive charge. There is also. When the positive charges on the substrate surface are neutralized, the attraction of electrons to the substrate 4 automatically stops. In this manner, charging of the substrate surface due to ion beam irradiation can be suppressed.

In this case, as in this example, the DC power supply 46
Is provided, a low-energy thermoelectron 12 emitted from the electron emission port 32 escapes to the opposite side of the substrate 4, that is, to the upstream side of the ion beam 2. Since the thermoelectrons 12 emitted from the electron emission port 32 can be suppressed by the negative voltage,
Can be used more effectively by neutralization.

The beam passage tube 44 is formed of a ferromagnetic material such as iron and has a magnetic shielding function so that the magnetic field generated by the magnetic field generator 34 does not affect the ion beam 2 as much as possible. Is preferred.

According to this ion beam irradiation apparatus, since the planar cathode 10, the heating source 14 and the extraction electrode 26 are provided, a large amount of thermionic electrons 12 are emitted from the cathode 10 to neutralize the same. Can be used for

Further, since the cathode 10 has the same potential as the holder 6, the energy of the thermoelectrons 12 emitted from the cathode 10 is distributed to the holder 6 in the vicinity of 0 eV. Since draw this in the following extraction voltage V _E 6V, energy thermionic 12 drawn through the lead-out electrode 26 is very low energy of about 6eV below. A large amount of such low energy thermoelectrons 12 can be used for neutralization.

Further, the combination of the magnetic field generator 34 and the electron emission port 32 allows the thermoelectrons 12 drawn from the extraction electrode 26 to draw a predetermined range of trajectories, that is, those having a predetermined range of energy. Since it is selectively extracted and used for neutralization, only the low-energy thermoelectrons 12 can be more reliably used for neutralization. Even if the thermoelectrons 12 having an energy larger than the predetermined range are extracted from the extraction electrode 26 for some reason, they cannot pass through the electron emission port 32,
It is removed by colliding with the deflection container 30 or the like.

As described above, since a large amount of thermionic electrons 12 having a low energy of about 6 eV or less can be generated and used for neutralization, charging of the substrate 4 due to ion beam irradiation can be suppressed to a small level. . Even if such low-energy thermoelectrons 12 are excessively supplied to the substrate 4 in order to sufficiently neutralize the positive charges associated with the ion beam irradiation, the negative charging voltage of the substrate 4 is reduced by the energy of the thermoelectrons 12. Since the voltage does not rise above the corresponding voltage, the charging voltage can be suppressed to about 6V. Therefore, the ion beam irradiation apparatus can be applied to the manufacture of a semiconductor device with further miniaturization.

In addition, in this apparatus, since the thermoelectrons 12 are used and the gas for generating plasma is not used, the degree of vacuum in the beam line and the substrate processing chamber does not deteriorate. As a result, it is possible to prevent the above-described deterioration in the uniformity of implantation into the substrate 4 and the occurrence of an error in the amount of implantation into the substrate 4.

Further, in this example, the thermoelectrons 1
2 is first emitted toward the upstream side of the ion beam 2, and then the thermoelectrons 12 are bent back to the ion beam 2 and the substrate 4 side by the magnetic field 36 by the magnetic field generator 34. It is possible to avoid that the surface faces the ion beam 2 and the substrate 4. As a result, evaporated particles (metal particles) generated from the cathode 10 due to the heating of the cathode 10 are less likely to enter the ion beam 2 and the substrate 4, thereby preventing contamination of the substrate 4 (metal contamination) due to the evaporated particles. be able to. This is also advantageous for the manufacture of semiconductor devices with advanced miniaturization.

The magnetic field generator 34 is preferably of an electromagnet type as in this example, since the intensity of the magnetic field 36 can be easily adjusted, but a permanent magnet may be used. In that case, when the adjustment of the trajectory of the thermionic 12 is necessary, it can also be carried out by the extraction voltage V _E.

FIG. 4 is a diagram showing another example of the heating source.
Explaining mainly the differences from the examples shown in FIGS. 1 and 2, in this example, the dielectric 66 is heated by the microwave 58, and the cathode 10 attached to the dielectric 66 is heated by this heating. Thus, a structure in which thermoelectrons 12 are generated from the cathode 10 is employed.

More specifically, a microwave resonance cavity 64 is provided in the above-described vacuum vessel (not shown), and a dielectric 66 is placed therein. The above-mentioned planar cathode 10 is attached (for example, attached) to the surface of the dielectric 66 facing the extraction electrode 26. The microwave 58 generated by the microwave oscillator 56 is supplied to the microwave resonance cavity 64 via the waveguide 60 and the tuner 62. The tuner 62 is for matching so that the energy of the microwave 58 is sufficiently absorbed by the dielectric 66.

The microwave 58 supplied to the microwave resonance cavity 64 is absorbed by the dielectric 66, whereby
The frictional heat generated by the molecular movement in the dielectric 66 causes the dielectric 6 to move.
6 generates heat. In such microwave heating, the larger the dielectric constant and the dielectric loss tangent of the dielectric, the larger the amount of heat generated. Therefore, it is preferable to use a material for the dielectric 66 that has a large value. For example, it is preferable to use ceramics such as boron nitride.

The heat generated by the dielectric 66 also heats the cathode 10 attached to the dielectric 66 to generate heat.
Occurs. The potential of the cathode 10 is set to the same potential as the holder 6 (the ground potential in this example) as described above. Therefore, the energy of the thermoelectrons 12 generated from the cathode 10 is applied to the holder 6 and the substrate 4 as in the previous example.
It is distributed approximately in the vicinity of 0 eV. Derived by extraction voltage V _E of the thermionic 12 through the extraction electrode 26.
After that, it is the same as the previous example.

[0053]

As described above, according to the present invention, a large amount of thermoelectrons having an energy corresponding to the set voltage of the extraction voltage are generated in a large amount, and only such low-energy electrons are selectively produced. Can be used for neutralization, so that charging of the substrate surface due to ion beam irradiation can be suppressed to a small level. In addition, according to the present invention, since the thermoelectrons are used and the gas for plasma generation is not used, the degree of vacuum in the beam line and the substrate processing chamber does not deteriorate.

Further, the present invention employs a structure in which thermoelectrons are temporarily emitted from the cathode toward the upstream side of the ion beam, and then the thermoelectrons are bent back to the ion beam and the substrate by a magnetic field. Thus, there is also an effect that evaporation particles generated from the cathode due to the heating become difficult to enter the ion beam or the substrate, and contamination of the substrate by the evaporation particles can be prevented.

[Brief description of the 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 P view of FIG.

FIG. 3 is a front view showing an example of a sub-cathode.

FIG. 4 is a diagram showing another example of a heating source.

[Explanation of symbols]

 2 Ion beam 4 Substrate 6 Holder 10 Cathode 12 Thermoelectron 14 Heat source 16 Sub-cathode 26 Extraction electrode 28 Extraction power supply 32 Electron emission port 34 Magnetic field generator 36 Magnetic field

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01J 37/317 H01J 37/317 Z H01L 21/265 H01L 21/265 N

Claims (1)

[Claims] An ion beam irradiation apparatus for irradiating a substrate held by a holder with an ion beam to perform processing.
A planar cathode that is arranged on the upstream side of the holder and on the side of the path of the ion beam and that is heated from the other and emits thermoelectrons toward the upstream side of the ion beam. One having the same potential, a heating source for heating the cathode from behind to emit thermoelectrons, and a thermoelectron provided in front of the cathode and directing the thermoelectrons emitted from the cathode toward the upstream side of the ion beam. A porous extraction electrode to be extracted, an extraction power supply for applying an extraction voltage of 6 V or less with the former being a positive electrode side between the extraction electrode and the cathode, and a thermoelectron extracted from the extraction electrode being a path side of an ion beam. A magnetic field generator that generates an ion beam and a magnetic field that is directed toward the substrate side, and selectively allows a thermoelectron bent by the magnetic field generator to draw a trajectory within a predetermined range. Ion beam irradiation apparatus, characterized in that it comprises a child outlet.