JPH0831357A - Ion beam generating device - Google Patents

Abstract

PURPOSE:To widen the variety of types of impurities which can be ion implanted, by ionizing even a substance having a high sublimating temp. in a high degree of vacuum, and emitting the generated ion beam. CONSTITUTION:A filament 3 for formation of plasma and an anode electrode 4 confronting the filament are installed in an arc chamber 1 where a carrier gas passes through. and there a magnetic field is generated so that a plasma is produced, and ions produced in the arc chamber 1 are drawn out by the electric field from a slit 2. In this ion beam generating device, an anode electrode 4a is made of a material including at least ion species to be used as an ion source so that the ion species is beaten out by sputtering from the surface of the anode electrode 4a. A surface unevenness is provided on the filament side of the anode electrode. The carrier gas should be of such a type as making chemical reaction with the anode electrode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion beam generator, and in particular, an arc chamber is provided with a filament for plasma formation and an anode electrode facing the filament, a carrier gas is passed through the arc chamber, The present invention relates to an ion beam generator which generates a plasma by the carrier gas by generating a magnetic field and draws out ions generated in the arc chamber to the outside by an electric field.

[0002]

2. Description of the Related Art In manufacturing a semiconductor device, impurities such as an impurity is injected into a surface of a semiconductor substrate for forming a semiconductor region and an impurity is injected into a polysilicon film on a surface of a semiconductor substrate for forming a conductor film. Implantation is indispensable, and this is mainly done by ion implantation. And
The ion implantation is performed by an ion beam generator. 3 (A) and 3 (B) show a conventional example of an ion beam generator, FIG. 3 (A) is a vertical sectional view, and FIG. 3 (B) is a sectional view taken along line BB. In the drawings, 1 is an arc chamber, and 2 is a slit formed in the center of the upper surface of the arc chamber 1, from which an ion beam is extracted. Reference numeral 3 denotes a filament, which is made of, for example, tungsten W and is supplied with an electric current to be heated to a high temperature by Joule heat and generate thermoelectrons. The filament 3 is attached to one inner surface of the arc chamber 1.

Reference numeral 4 denotes an anode electrode, which is attached to the inner side surface of the arc chamber 1 opposite to the inner side surface to which the filament 3 is attached so as to face the filament 3 and has a positive potential with respect to the filament 3. Has been given. The anode electrode 4 accelerates the thermoelectrons generated from the filament 3, and the accelerated thermoelectrons collide with the carrier gas such as the argon gas Ar supplied into the arc chamber 1 and ionize it. A strong magnetic field is formed in this arc chamber 1,
As a result, ionization is promoted and a plasma due to argon is formed. 5 is a high density plasma region having a particularly high plasma density in the plasma. Reference numeral 6 indicates magnetic lines of force. In a separate chamber (not shown) of the arc chamber 1, solid arsenic As is heated and sublimated, and this is used as an ion source.
The carrier gas is supplied into the arc chamber 1.

Arsenic As, which is an ion source supplied into the arc chamber 1, is ionized in the plasma 5 by argon. Then, the ionized arsenic As ⁺ is extracted from the slit 2 by the electric field created by an extraction electrode (not shown) provided outside to be an ion beam, which is deflected, accelerated, etc., and injected into the surface of the semiconductor wafer.

[0005]

However, the impurities that can be ion-implanted by the ion beam generator in the related art serve as ion sources in the form of gas with less danger, or under a vacuum degree of about 10 ^-6 Torr. 250 ~
It was limited to those that formed a solid that sublimated at 400 ° C. For example, phosphorus P, boron B, etc. can be supplied into the arc chamber 1 as an ion source in the form of gas. Moreover, antimony Sb and arsenic As can be used as an ion source in a solid form, and can be sublimated and supplied into the arc chamber 1 by a carrier gas. However, the degree of vacuum of indium In, gallium Ga, etc. is 10 ⁻⁶ Torr.
Since it is a metal-based substance whose sublimation temperature is higher than 400 ° C and becomes liquid at room temperature, it cannot be directly used as an ion source in the form of gas, or it can be sublimated and contained in a carrier gas. It cannot be used as an ion source.

Therefore, it has been unavoidable to use it in the form of an impregnated metal ion source. This is because it is necessary to impregnate the base material with impurities such as indium In and gallium Ga, which is not only very troublesome, but also causes a problem that ion species other than the intended impurities are easily mixed in the ion beam. Yes, it is very difficult to handle, and good ion implantation is difficult. As described above, the fact that the substances capable of producing impurities capable of favorable ion implantation are limited to specific ones is that impurities are implanted into a semiconductor wafer as impurities that are becoming stronger with the development of semiconductor technology, particularly compound semiconductor technology. This will prevent the demand for diversification of materials that should be used, and will limit the degree of freedom in device development, which is an issue that must be overcome.

The present invention has been made to solve the above problems, and a filament for plasma formation and an anode electrode facing the filament are provided in the arc chamber.
A carrier gas is passed through the arc chamber, a magnetic field is generated in the arc chamber, plasma is generated by the carrier gas, and ions generated in the arc chamber are extracted to the outside by an electric field. Enables ionization of a substance with a high sublimation temperature under vacuum to generate an ion beam, increasing the number of impurities that can be ion-implanted, that is, diversifying ion species The purpose is to

[0008]

An ion beam generator according to a first aspect of the invention is characterized in that the anode electrode is formed of a material containing at least ionic species. An ion beam generator according to a second aspect is the ion beam generator according to the first aspect, characterized in that unevenness is formed on a surface of the anode electrode on a filament side. An ion beam generator according to a third aspect is the ion beam generator according to the first or second aspect, wherein the carrier gas has chemical reactivity with the anode electrode.

[0009]

According to the ion beam generator of the present invention, the plasma performs cycloton motion and collides with the surface of the anode electrode to knock out its constituent substances, but the anode electrode is made of ionic species. Eventually, the ion species will be ejected, and the ion species ejected will be ionized in the plasma to be an ion beam, which will be extracted to the outside. Therefore, the anode electrode is used as it is as an ion source, and indium In and gallium Ga are used.
Even if the degree of vacuum is increased or the sublimation temperature is high, the ion species can be used without any trouble.

According to the second aspect of the ion beam generator, since the surface of the anode electrode on the filament side is uneven, the surface area of the anode electrode is increased.
Therefore, the ion generation efficiency is increased and the ion beam current can be increased. According to the ion beam generator of claim 3, since the carrier gas has chemical reactivity with the anode electrode, when the plasma of the carrier gas collides with the surface of the anode electrode made of the ion species, the ion species is physically generated. Not only is it knocked out, but it also causes a chemical reaction with the surface of the anode electrode to make it brittle. Therefore, the effect of ejecting ion species is strengthened, the synergy effect of physical collision and chemical reaction increases the ion generation efficiency, and the ion beam current can be increased.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The ion beam generator of the present invention will be described in detail below with reference to the illustrated embodiments. 1 (A) and 1 (B) show a conventional example of an ion beam generator, (A) is a vertical sectional view, (B) is a sectional view taken along line BB, and FIG.
(B) is a perspective view of an anode electrode which also functions as an ion source. The present ion beam generator differs greatly from the conventional ion beam generator shown in FIG. 3 in that the anode electrode is made of an ion species and that the carrier gas has a chemical reactivity with the anode electrode. However, since the other points are common and the common points have already been described, the description thereof will be omitted and only different points will be described. Further, common parts are denoted by common reference numerals throughout the drawings.

Although 4a is an anode electrode, it is also an ion source, for example, indium In or gallium Ga.
Etc. are formed by ion species to be implanted into the surface portion of the semiconductor wafer. The anode electrode 4a is given a positive potential with respect to the filament so as to function as the anode electrode, but since it also functions as an ion source, the filament 3 should be made more effective to fulfill its function. It is formed in the shape of a facing plate, and folds (concavities and convexities) are formed on the surface of the filament 3 side so that the surface area becomes wider. This is because it is possible to increase the ion generation efficiency and increase the ion beam current by increasing the surface area of the surface of the anode electrode 4a on the filament 3 side.

Needless to say, the carrier gas is supplied into the arc chamber 1 also in the present ion beam generator, but the carrier gas is not the argon gas Ar as in the conventional case but a chemically active gas. , For example, fluorine-based gas (for example, CF ₃ or BF ₃ , PF ₃
Etc.) are used. When the chemically active gas is used as the carrier gas, the plasma of the carrier gas not only physically ejects ionic species from the surface of the anode electrode 4a, but also the carrier gas chemically reacts with the surface of the anode electrode 4a. To make it brittle so that the ionic species can be more effectively ejected. The carrier gas does not necessarily have to have chemical reactivity with the anode electrode 4a, and an inert gas may be used, but in that case, the carrier gas causes the surface of the anode electrode 4a to change. We cannot expect the effect of attacking and making it brittle.

According to such an ion beam generator, since the anode electrode 4a is formed by the ion species to be implanted, it also functions as a sputtering target. That is, the carrier gas flowing into the arc chamber 1 collides with the thermoelectrons accelerated by the electric field generated from the filament 3 and applied to the anode electrode 4a to be ionized. Further, the ionization thereof is promoted by the magnetic field to generate carrier gas plasma, and the plasma causes cycloton motion to fly around in a random direction with strong force, and a part of the plasma collides with the surface of the anode electrode 4a. Then, the anode electrode 4
Ion species are knocked out by the plasma on the surface of a. The knocked out ion species are plasmatized in the arc chamber 1, and the ions, that is, the cations of the ion species are extracted from the slit 2 by an extraction electrode (not shown) provided outside the arc chamber 1. It becomes an ion beam.

Further, the plasma that has collided with the surface of the anode electrode 4a does not merely physically eject the ionic species on the surface of the anode electrode 4a, but chemically reacts with the ionic species to attack the anode electrode 4a. Since it becomes brittle, the hitting out will be performed more effectively. That is, the synergistic effect of the physical collision and the chemical reaction increases the ion generation efficiency, and the ion beam current can be increased.

The anode electrode 4a is formed in a dish shape facing the filament 3 side, and the filament 3
Since the folds (irregularities) are formed on the side surface and the surface area on the side of the filament 3 is made wider, the ion generation efficiency can be increased and the ion beam current can be increased. Incidentally, FIG. 2B shows another example 4b of the anode electrode forming the ion source. This example 4b is different from the anode electrode 4a shown in FIG. 2B in which the vertical cross-sectional shape of the inner peripheral surface is a straight line, which is a concave curve.

[0017]

The ion beam generator according to the present invention is characterized in that the anode electrode is formed of a material containing at least ionic species. Therefore, according to the ion beam generator of claim 1, the plasma performs cycloton motion and collides with the surface of the anode electrode to knock out the constituent substance from the anode electrode. However, since the anode electrode is made of ionic species, Eventually, the ion species will be ejected, and the ejected ion species will be ionized in the plasma and become an ion beam, which will be extracted to the outside. Therefore,
The anode electrode can be used as an ion source as it is, and even if the sublimation temperature such as indium In and gallium Ga is at a high vacuum degree, a substance having a considerably high sublimation temperature can be used as an ion species without any trouble, and the degree of freedom in device development can be increased. You can

The ion beam generator according to a second aspect of the invention is characterized in that unevenness is formed on the surface of the anode electrode on the filament side. Therefore, according to the ion beam generator of the second aspect, since the surface of the anode electrode on the filament side is uneven, the surface area of the anode electrode is increased. Therefore, the ion generation efficiency is increased and the ion beam current can be increased.

The ion beam generator of claim 3 is characterized in that the carrier gas has chemical reactivity with the anode electrode. Therefore, according to the ion beam generator of the third aspect, since the carrier gas has a chemical reactivity with the anode electrode, when the plasma of the carrier gas collides with the surface of the anode electrode made of the ion species, the carrier gas physically appears. In addition to knocking out ionic species, it causes a chemical reaction with the anode electrode surface and makes it brittle, so the ionic species hammering out effect becomes stronger, and the ion generation efficiency is high due to the synergistic effect of physical collision and chemical reaction. And, by extension,
The ion beam current can be increased.

[Brief description of drawings]

1A and 1B show a conventional example of an ion beam generator, wherein FIG. 1A is a vertical sectional view and FIG. 1B is a sectional view taken along line BB.

FIGS. 2A and 2B are perspective views of an anode electrode that also functions as an ion source.

3A and 3B show a conventional example of an ion beam generator, FIG. 3A is a vertical sectional view, and FIG. 3B is a sectional view taken along line BB.

[Explanation of symbols]

 1 arc chamber 2 slit 3 filament 4a, 4b anode electrode 5 high plasma region 6 magnetic field

Claims (3)

[Claims] 1. A filament for plasma formation and an anode electrode facing the filament are provided in an arc chamber, a carrier gas is passed through the arc chamber, and a magnetic field is generated in the arc chamber to generate plasma by the carrier gas. An ion beam generator for generating and extracting ions generated in an arc chamber to the outside by an electric field, wherein the anode electrode is made of a material containing at least an ion species. 2. The ion beam generator according to claim 1, wherein irregularities are formed on the surface of the anode electrode on the filament side. 3. The ion beam generator according to claim 1, wherein the carrier gas has chemical reactivity with the anode electrode.