JPH10340696A - Ion implanter - Google Patents

Abstract

(57) Abstract: Provided is an ion implantation apparatus that reduces the amount of ion collision with the inner wall of a chamber for generating ions and derives an ion beam having a high ion density and a uniform ion density distribution. . SOLUTION: An ion source unit 40 of an ion implantation apparatus.
Are a first wall 42A and a second wall 42B facing each other.
And a chamber 42 composed of a cylindrical side wall 42C connecting the first and second walls. First wall 42A
Are configured as thermoelectron emission electrodes 42A that emit thermoelectrons, and the second wall 42B has an ion beam outlet 4
3 is formed so as to penetrate the second wall. Of the side wall 42C, the side wall portion facing the ion beam outlet 43 and sandwiching the ion beam outlet 43 is configured as an arc discharge electrode 42C1 for performing arc discharge with the thermionic emission electrode 42A. ing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion implantation apparatus, and more particularly, to an ion implantation apparatus for reducing the amount of ion collision with a chamber wall for generating ions and extracting an ion beam having a high ion density. It is about.

[0002]

2. Description of the Related Art In the manufacture of semiconductor devices, an ion implantation apparatus is often used to implant ions into an object to be implanted such as a wafer. FIG. 7 is a plan view showing a configuration of a conventional ion implantation apparatus. The conventional ion implantation apparatus 10 includes an ion source unit 12 for generating ions in a chamber, an extraction electrode 14 for extracting ions from the ion source unit 12 as an ion beam, and a mass spectrometer 1 for selecting an ion type.
6, an ion accelerating unit 18 for accelerating ions, and a sample chamber 20 for holding an object to be implanted such as a wafer for ion implantation.

FIGS. 8 and 9 both show an ion source 1
It is a perspective view which shows the component part of the 2nd chamber 22. The chamber 22 generally includes a filament 24 and a reflector electrode 26 provided in the chamber 22 so as to face each other, a gas inlet 28 provided between the filament 24 and the reflector electrode 26 to introduce a gas serving as an ion source, An ion beam outlet 30 is provided on the front side and guides ions as an ion beam. The chamber wall having the ion beam outlet 30 is shown in FIG.
As shown in FIG. Note that an ion source having a chamber having such a configuration may be referred to as a Bernas-type ion source.

FIG. 10 is a side view showing an electrical connection state of the ion source section 12. As shown in FIG. The ion source unit 12
A direct-current filament power supply 32 for applying voltage to the filament 24 to emit thermoelectrons is provided. The ion source unit 12 further includes a direct current type arc discharge power supply 34, and the positive electrode is electrically connected to the chamber wall, and the negative electrode is electrically connected to the positive terminal of the filament 24.
By these electrical connections, the potential of each electrode is made lower in the order of the chamber 22, the filament 24, and the lower potential side of the reflector electrode 26. Chamber 22
, A magnetic field B for confining thermoelectrons is applied from the filament 24 toward the reflector electrode 26.

In order to implant ions into a wafer (not shown) using the ion implantation apparatus 10, thermoelectrons are emitted from a filament power supply 32 while introducing a gas serving as an ion source from a gas inlet 28. The applied voltage of the filament power supply is
For example, 5 V, and the filament current is, for example, 200 A. FIG. 11 is a plan sectional view of a chamber showing a plasma zone by arc discharge. Thermions emitted from the filament 24 collide with the introduced gas molecules to generate ions, and the presence of the thermoelectrons and the generated ions creates a plasma zone 36 by arc discharge.
The voltage applied to the arc discharge electrode 34 is, for example, 100 V, and the arc discharge current is, for example, 5 A. Of the thermoelectrons emitted from the filament 24, those that draw a long trajectory move from the filament 24 toward the reflector electrode 26 under the action of Fleming's left hand rule, and then are inverted by the potential of the reflector electrode 26. Then, a trajectory 38 which proceeds toward the chamber wall and is collected by the DC power supply 34 is drawn. The ions generated by the arc discharge are led out from the ion beam outlet 30 and injected into the object.

[0006]

Incidentally, in the conventional ion implantation apparatus, the amount of ions colliding with the chamber wall is large. Therefore, there is a first problem that a large amount of substances are released from the chamber wall due to the collision. This problem has caused various undesired situations, such as a decrease in the insulation due to the emission of substances adhering to the surface of the insulating material that is exposed around the filament and the electrical wiring of the reflector electrode and is exposed in the chamber. Was. In addition, there is a second problem that the ion density in the chamber may be non-uniform, and the ion density distribution of the derived ion beam may be non-uniform. Furthermore, there is a third problem that the amount of ions to be led out is small and therefore the amount of ions reaching the sample chamber is small. In view of the circumstances as described above, an object of the present invention is to reduce the amount of ion collision with a chamber wall for generating ions and to derive an ion beam having a high ion density and a uniform ion density distribution. It is to provide an ion implantation apparatus.

[0007]

The inventor measured the density distribution of the ion beam derived from the ion beam outlet 30. FIG. 12 is a diagram showing the measurement results. The horizontal axis X indicates the longitudinal position of the ion beam outlet, and the vertical axis Y indicates the ion density. As shown in FIG. 12, the derived ion beam had a large diameter and a low ion density. Therefore, the present inventors have studied to suppress the spread of the ion beam diameter and increase the ion density in the arc discharge zone in the chamber 22.

Further, the present inventor has studied a configuration of a chamber that generates a relatively large amount of thermoelectrons. Among the opposing walls of the chamber (hereinafter referred to as a first wall and a second wall), The first wall came up with a chamber wall configured as a thermionic emission electrode for emitting thermoelectrons. Then, among the side walls connecting the first wall and the second wall, the side wall portion close to the ion beam outlet is found to be an arc discharge electrode for generating an arc discharge between the first wall and the present invention. Was completed.

To achieve the above object, an ion implantation apparatus according to the present invention comprises a first wall and a second wall facing each other.
In a chamber composed of a wall and a cylindrical side wall connecting the first and second walls, ions are generated by arc discharge, extracted as an ion beam, and implanted into an object to be implanted. In the injection device, at least a part of the first wall is configured as a thermoelectron emission electrode that emits thermoelectrons, and the ion beam outlet is formed to penetrate the second wall and sandwich the ion beam outlet. It is characterized in that the side wall portion facing and near the ion beam outlet is configured as an arc discharge electrode for performing arc discharge with the thermionic emission electrode. The arc discharge electrode is electrically opposed to the thermionic emission electrode.

The gas serving as ion species to be introduced into the chamber is, for example, BF ₃ gas, PF ₃ gas, AsH ₃ gas or A
s vapor. By using the ion implantation apparatus according to the present invention, the plasma generation region is limited to a zone defined by the side wall near the ion beam outlet and the thermionic emission electrode, and the plasma density increases. Thereby, the ion density of the ion beam can be increased, and the reflector electrode is not required.

[0011] Preferably, the thermionic emission electrode comprises a thermionic emission metal and a heater for heating the metal. In a preferred embodiment of the present invention, the thermionic emission electrode is formed over the entire first wall.

[0012]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Example This example is a preferred embodiment of the present invention. The ion implantation apparatus according to the present embodiment includes an ion source unit 40 having the same size as the ion source unit 12 in place of the conventional ion source unit 12 as compared with the conventional ion implantation unit 10. 1 and 2 are perspective views showing components of a chamber of the ion source unit 40 of the ion implantation apparatus of the present embodiment. FIG. 3 is a perspective view of the ion source unit 40 of the ion implantation apparatus of the embodiment. FIG. 4 is a side view showing an electrical connection state of FIG. The ion source section 40 includes a box-shaped chamber 42 having a rectangular cross section, and a gas inlet 44 for introducing a gas serving as an ion species into the chamber. The chamber 42
A first wall 42A and a second wall 42B facing each other,
And a cylindrical side wall 42C connecting the first and second walls.

The first wall 42A is configured as a thermionic emission electrode 42A for emitting thermoelectrons. The thermionic emission electrode 42A is an electrode in which an electric heater 41 (see FIG. 4) is provided in a hot plate 39 which is impregnated with lithium metal which easily emits thermoelectrons and is heated. In the second wall 42B, a slit-shaped ion beam outlet 43 for extracting ions as an ion beam is formed so as to penetrate the second wall 42B. Second wall 4
2B is grounded.

In the side wall 42C, the ion beam outlet 4
3 and the ion beam outlet 43
Is formed as an arc discharge electrode 42C1 for performing arc discharge with the thermionic emission electrode 42A. Between the side wall 42C and the thermionic emission electrode 42A,
A frame-shaped insulator 45A that is electrically insulated is provided, and a similar insulator 45B is provided between the side wall 42C and the second wall 42B. The arc discharge electrode 4
2C1 and the arc discharge electrode 42C1 of the side wall 42C.
Strip-shaped insulators 47 </ b> A to 47 </ b> D are provided between the other portions and the side wall portion 42 </ b> C <b> 2.

As shown in FIG. 3, the ion source section 40 further includes an arc discharge power supply 46 for arc discharge in the chamber 42 and a heating power supply 48 for heating the thermionic emission electrode 42A. The heating power supply 48 is
1 is electrically connected to the low potential side and the high potential side, and the arc discharge power supply 46 is electrically connected between the low potential side of the heater 41 and the arc discharge electrode 42C1. In addition, by these electrical connections, the arc discharge electrode 42C1, the second
The potential is reduced in the order of the wall 42B and the lower potential side of the thermionic emission electrode 42A. The side wall portion 42C2
Is electrically wired so as to have the same potential as that of the second wall 42B. Further, a magnetic field B ′ for confining thermoelectrons is formed in the chamber 42 from the low potential side of the heater 41 to the high potential side in the longitudinal direction of the chamber 42.

To use the ion implantation apparatus of this embodiment,
As in the conventional case, the wafer is held in the sample chamber in advance. Next, while introducing gas serving as an ion species into the chamber 42, the heater 41 is energized to emit thermoelectrons over the entire surface from the thermoelectron emission electrode 42 </ b> A to generate ions, and ions extracted from the ion beam outlet 43. Is injected into a body to be injected.

FIG. 5 is a plan sectional view of a chamber showing a plasma zone by arc discharge. Thermionic emission electrode 4
The thermoelectrons emitted from the entire surface of the 2A collide with the introduced gas molecules to generate ions, while the arc electrons are emitted from the arc discharge electrode 42.
Proceed toward C1. The arrows in FIG. 5 indicate the orbits of the thermoelectrons. As a result, due to thermionic electrons and generated ions,
The arc discharge is generated between the thermionic emission electrode 42A and the arc discharge electrode 42C1, and the zone where plasma is generated by the arc discharge is substantially limited to the zone 50 sandwiched between the arc discharge electrodes 42C1. Ions generated from the arc discharge are led out from the ion beam outlet 30 and injected into the body to be implanted.

In this embodiment, most of the ions are in zone 5
Since it is generated at 0 and hardly generated in other zones,
The ion density in the zone 50 is much higher than before and has a uniform distribution. Therefore, the ion beam outlet 4
The density distribution of the ion beam derived from No. 3 is uniform, and the ion density is much higher than before. Also, since the beam diameter does not expand, the amount of ions reaching the sample chamber is much larger than in the past. The thermionic emission electrode 42A is
Since it is formed over the entire surface of the first wall of the chamber, the area for emitting thermoelectrons is large, and therefore the arc discharge electrode 4 is formed.
The number of thermoelectrons traveling toward 2C is large, and the ion density in the zone 50 can be increased. Further, since the plasma zone is locally generated, the ion source can be configured without providing a reflector electrode as in the related art, and therefore, the configuration in the chamber can be simplified.

FIG. 6 is a view showing the result of measurement of the ion beam derived from the ion beam outlet 43. 6 is the same as FIG. The beam diameter of the ion beam was small and did not expand as in the prior art, and the ion density was much higher than in the prior art.

[0020]

According to the present invention, the first wall and the second wall facing each other have at least a part of the first wall configured as a thermionic emission electrode for emitting thermoelectrons, and But,
It has an ion beam outlet. Further, of the side walls of the chamber, the side wall portion facing the ion beam outlet and sandwiching the ion beam outlet is formed as an arc discharge electrode for performing an arc discharge between the chamber and the thermionic emission electrode. I have. Thus, the zone where ions are generated in the chamber is limited to the vicinity of the ion beam outlet. Therefore, the number of ions colliding with the chamber wall is much lower than before, and the ion density of the derived ion beam is much higher than before. Further, since the reflector electrode need not be provided, the structure is simple.

[Brief description of the drawings]

FIG. 1 is a perspective view showing components of a chamber of an ion source unit according to an embodiment.

FIG. 2 is a perspective view showing components of a chamber of an ion source unit according to the embodiment.

FIG. 3 is a side view showing an electrical connection state of an ion source of the ion implantation apparatus according to the embodiment.

FIG. 4 is a view showing the configuration of a thermionic emission electrode of the chamber of the embodiment, as viewed from the direction of arrows II.

FIG. 5 is a plan sectional view of a chamber showing a plasma zone by arc discharge in the embodiment.

FIG. 6 is a diagram showing a measurement result of a density distribution of an ion beam derived from an ion beam outlet in the example.

FIG. 7 is a plan view showing a configuration of a conventional ion implantation apparatus.

FIG. 8 is a perspective view showing components of a chamber of an ion source section of a conventional ion implantation apparatus.

FIG. 9 is a perspective view showing components of a chamber of an ion source section of a conventional ion implantation apparatus.

FIG. 10 is a side view showing an electrical connection state of an ion source of a conventional ion implantation apparatus.

FIG. 11 is a plan cross-sectional view of a chamber showing a plasma zone by arc discharge in the related art.

FIG. 12 is a diagram showing a measurement result of a density distribution of an ion beam derived from an ion beam outlet according to the related art.

[Explanation of symbols]

10 ... Ion implantation apparatus, 12 ... Ion source part, 1
4 ... extraction electrode, 16 ... mass spectrometry section, 18 ... ion acceleration section, 20 ... sample chamber, 22 ... chamber, 24
... filament, 26 ... reflector electrode, 28 ...
Gas inlet, 30 ... Ion beam outlet, 32 ... Filament power supply, 34 ... Power supply for arc discharge, 36 ...
Plasma zone, 39 hot plate, 40 ion source section, 41 heater, 42 chamber, 4
2A: thermoelectron emission electrode (first wall), 42B: second
Wall, 42C ... Side wall, 42C1 ... Arc discharge electrode, 4
2C2 ... side wall part, 43 ... ion beam outlet, 4
4 ... Gas inlet, 45A, B ... Insulator, 46 ...
Power supply for arc discharge, 47A-D ... insulator, 48 ...
Power supply for heating, 50 zone.

Claims (3)

[Claims] An ion is generated by an arc discharge in a chamber including a first wall and a second wall facing each other, and a cylindrical side wall connecting the first and second walls. In an ion implantation apparatus which is derived as an ion beam and is injected into an object to be implanted, at least a part of the first wall is configured as a thermoelectron emission electrode for emitting thermoelectrons, The side wall portion formed so as to penetrate the wall, face the ion beam outlet, and is close to the ion beam outlet is configured as an arc discharge electrode for performing an arc discharge between the thermoelectron emission electrode and the ion beam outlet. An ion implantation apparatus characterized in that: 2. The ion implantation apparatus according to claim 1, wherein the thermoelectron emission electrode includes a thermoelectron-emitting metal and a heater for heating the metal. 3. The ion implantation apparatus according to claim 1, wherein the thermoelectron emission electrode is formed over the entire first wall.