JPH11307001A - High frequency ion source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily adjust a beam profile of an ion beam without disassembling an ion source. SOLUTION: A length of long sides of a rectangular high-frequency electrode 6 is set more than approximately half-wavelength of high-frequency power supplied from a high-frequency power supply 18, and a cover conductor 44 having electric potential equal to that of a plasma chamber container 4 is provided so as to cover at least the high-frequency electrode 6 and insulators 8 with interspace between them. Further, near the outside of the insulators 8 in the cover conductor 44, at least one movable conductive control plates 46 are provided along the insulators 8 such that the distance between them and the insulators 8 can be adjusted. Here, the length of each control plates 46 is set more than approximately the half-wavelength of the high-frequency power.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to, for example, ion implantation (impurity implantation) into a semiconductor substrate, a liquid crystal display substrate, or the like by directly irradiating an ion beam extracted from an ion source without mass separation onto an object to be implanted. More specifically, the present invention relates to a high-frequency ion source used for performing such operations, and more specifically to a means for adjusting a beam profile (in-plane beam current density distribution; the same applies hereinafter) of an ion beam extracted from the high-frequency ion source.

[0002]

2. Description of the Related Art Objects to be implanted, such as semiconductor substrates and substrates for liquid crystal displays, tend to have a large area, and high-frequency ion sources used therefor are required to extract a large-area ion beam with good uniformity. I have.

FIG. 13 shows an example of a conventional high-frequency ion source capable of extracting a large-area ion beam. This high-frequency ion source 2 uses a cusp magnetic field for confining plasma, and is also called a bucket type ion source. An example of a high frequency ion source having a similar structure is disclosed in
No. 88981.

The high-frequency ion source 2 has a cylindrical plasma chamber container 4 having openings at both ends and into which an ion source gas 12 is introduced, and one opening of the plasma chamber container 4 is provided with an annular insulating member. The plasma chamber 10 includes a plate-like high-frequency electrode 6 covered with an insulator 8 and an extraction electrode system 22 provided near the other opening of the plasma chamber container 4. doing. The plasma chamber 10 is evacuated to a vacuum during the operation of the high-frequency ion source 2.

In the high-frequency ion source 2, the plasma chamber container 4 also serves as one high-frequency electrode, and a high-frequency power supply 18 is provided between the plasma chamber container 4 and the high-frequency electrode 6 via a matching circuit 20. Power is supplied. As a result, a high-frequency discharge is generated between the high-frequency electrode 6 and the plasma chamber container 4, ionizing the ion source gas 12,
6 is made.

The extraction electrode system 22 extracts an ion beam 28 from the plasma 16 by the action of an electric field.
More than one, usually a plurality of electrodes. More specifically, in this example, the plasma electrode 23, the extraction electrode 24, and the suppression electrode 2 that are arranged from the most plasma side to the downstream side.
5 and a ground electrode 26. Each electrode 23 ~
26 is a porous electrode which usually has a plurality of holes.

The plasma electrode 23 is an electrode for determining the energy of the ion beam 28 to be extracted, and an acceleration power source 30
, A positive high voltage (acceleration voltage) is applied with reference to the ground potential. The extraction electrode 24 generates a potential difference between the extraction electrode 24 and the plasma electrode 23, and generates an electric field therefrom.
An electrode for extracting the ion beam 28 from the electrode 6, and a negative voltage (extraction voltage) is applied from an extraction power supply 32 with reference to the potential of the plasma electrode 23. The suppression electrode 25 is an electrode for suppressing backflow of electrons from the downstream side, and a negative voltage (suppression voltage) is applied from the suppression power supply 34 with reference to the ground potential. The ground electrode 26 is grounded.

On the outer peripheral portion of the plasma chamber container 4 and the outer surface of the high-frequency electrode,
A plurality of permanent magnets 14 for forming a cusp magnetic field (multi-pole magnetic field) for confining plasma are arranged inside, ie, in the peripheral part of the plasma chamber 10. by this,
The plasma 16 having a large area and high uniformity can be generated. The permanent magnet 14 may be embedded in the plasma chamber container 4 or the high-frequency electrode 6.

[0009]

In the high-frequency ion source 2 as described above, in order to realize an ion beam 28 with good beam profile uniformity, the uniformity of the plasma 16 generated in the plasma chamber 10 has been conventionally known. For optimizing the arrangement (alignment) of the holes of the electrodes 23 to 26 constituting the extraction electrode system 22, optimizing the voltage applied to each of the electrodes 23 to 26 constituting the extraction electrode system 22, and the like. Has been adopted.

However, even if the uniformity of the beam profile is good at first, the operation of the high-frequency ion source 2 causes contamination of the plasma chamber container 4, the high-frequency electrode 6, and the extraction electrode system 22, and the contamination proceeds. Plasma 1
The electrode 23 is deformed due to thermal expansion or the like of the electrodes 23 to 26 constituting the extraction electrode system 22, which reduces the uniformity of the electrode 23.
Due to a change in the arrangement of the holes 26 to 26, the beam profile of the ion beam 28 changes, and the uniformity often decreases. In such a case, normally, the vacuum of the high-frequency ion source 2 is broken and the high-frequency ion source 2 is disassembled to clean the plasma chamber container 4, the high-frequency electrode 6 and the extraction electrode system 22, and to clean the electrodes 23 to 23. Optimization of the arrangement of the 26 holes and the like must be performed, which requires a great deal of labor and time.

Accordingly, it is a main object of the present invention to provide a high-frequency ion source capable of easily adjusting a beam profile of an ion beam without disassembling the ion source.

[0012]

One of the high-frequency ion sources according to the present invention has a cylindrical plasma chamber vessel having a rectangular cross section and a rectangular high-frequency electrode. The length is set to be approximately half a wavelength or more of the high-frequency power, and at least the high-frequency electrode and the insulator are covered with a space between them and a cover conductor having the same potential as the plasma chamber container is provided. In the cover conductor, near the outside of the insulator, one or more movable conductive control plates capable of adjusting the distance between the insulator and the insulator are provided along the insulator, and The length of each control plate is substantially equal to or longer than a half wavelength of the high frequency power (claim 1).

When the dimensions of the high-frequency electrode are set as described above and the above-described cover conductor is provided, the high frequency supplied to the high-frequency electrode from the high-frequency power source propagates as electromagnetic waves between the high-frequency electrode and the cover conductor. The plasma enters the plasma chamber through an insulator between the electrode and the plasma chamber. The electromagnetic wave that has entered the plasma chamber container cooperates with a cusp magnetic field formed by the permanent magnet to ionize the ion source gas and generate plasma. In that case, the plasma is generated mainly around the magnetic field strength that causes electron cyclotron resonance (ECR) and diffuses out therefrom.

The control plate provided near the outside of the insulator reflects or absorbs an electromagnetic wave that is going to enter the plasma chamber through the insulator. Therefore, by moving the control plate and adjusting the distance between the control plate and the insulator, the intensity of the electromagnetic wave entering the plasma chamber container from the portion of the control plate can be controlled. By controlling the density distribution of the plasma,
The beam profile of the ion beam extracted from the plasma can be controlled. Thus, the beam profile of the ion beam can be easily adjusted without disassembling the ion source.

The cross section of the plasma chamber container and the high-frequency electrode may be square. In this case, the length of one side of the high-frequency electrode is set to be approximately half a wavelength of the high-frequency power or more.

The cross section of the plasma chamber container and the high-frequency electrode may be circular. In this case, the diameter of the high-frequency electrode is set to be at least about half the wavelength of the high-frequency power.

If each control plate is made of metal, an electromagnetic wave that is going to enter the plasma chamber container is reflected by this control plate. If each control plate is composed of a resistor, a part of the electromagnetic wave which is going to enter the plasma chamber container is absorbed by the control plate and a part is reflected. In any case, as described above, by moving the control plate, the intensity of the electromagnetic wave entering the plasma chamber container can be controlled.

[0018]

FIG. 1 is a sectional view showing an example of a high-frequency ion source according to the present invention together with a power supply. FIG.
FIG. 2 is a front view around a high-frequency electrode of the high-frequency ion source of FIG. 1. FIG. 3 is an enlarged sectional view around a control plate of the high-frequency ion source of FIG. Parts that are the same as or correspond to those of the conventional example in FIG. 13 are denoted by the same reference numerals, and differences from the conventional example will be mainly described below. 2 to 12, illustration of the permanent magnet 14 shown in FIGS. 1 and 3 is omitted.

In the high-frequency ion source 2a, the above-described plasma chamber container 4 has a tubular shape (square tubular shape) having a rectangular cross section, and the insulator 8 has a rectangular annular shape. The high-frequency electrode 6 has a rectangular shape (see FIG. 2).

The length L of the long side of the high-frequency electrode 6
₁ (see FIG. 2) is changed to a half-wavelength or more of the high-frequency power supplied from the high-frequency power supply 18 (that is, substantially λ / 2 or more; λ
Is the wavelength of the high-frequency power). More specifically, in this example, the frequency of the high-frequency power supplied from the high-frequency power supply 18 is set to 500 MHz, in which case the half-wavelength is 0.3 m, and the length L _{1 of the} long side of the high-frequency electrode 6. About 600 mm larger than the half wavelength 0.3 m
I have to. The length L ₂ of the short side is about 300 mm.

Further, a cover conductor 44 is provided to cover at least the high-frequency electrode 6 and the insulator 8 with a space therebetween. The cover conductor 44 is made of a copper plate in this example. The cover conductor 44 is electrically connected to the plasma chamber container 4 to have the same potential as the plasma chamber container 4. The cover conductor 44 may cover only the high frequency electrode 6 and the insulator 8 as in the example shown in FIG. 3, or may cover the high frequency electrode 6, the insulator 8 and the plasma as in the example shown in FIG. What covers the whole circumference of the chamber container 4 may be sufficient.

In this example, a coaxial tube 36 is connected to a substantially central portion of the cover conductor 44, and the center conductor 38 is connected to a substantially central portion of the high-frequency electrode 6. The high-frequency power from the high-frequency power supply 18 is supplied between the high-frequency electrode 6 and the plasma chamber container 4. A stub tuner 42 is provided in the middle of the coaxial tube 36 so as to correspond to the matching circuit 20 of the conventional example so as to achieve matching.

In the cover conductor 44, near the outside of the insulator 8, near the outside of the insulator 8, a conductive material capable of adjusting the distance G (see FIG. 3) between the insulator 8 and the insulator 8. Or more control plates 46 are provided. Specifically, in this example, as shown in FIG. 2 and the like, a total of six high frequency electrodes 6 are provided, two each along the long side and one along each short side. Each control plate 46 is movable in the front-rear direction with respect to the insulator 8 as shown by the arrow A.

In order to realize this movement, in this example, a mechanism shown in FIG. 3 is employed as an example, but the present invention is not limited to this. In FIG. 3, a support shaft 48 is attached to each control plate 46, and a support 50 that supports and fixes each support shaft 48 movably back and forth is attached to the cover conductor 44. In this example, each control plate 46 is electrically connected to the cover conductor 44 via the support shaft 48 and the support portion 50 to have the same potential as the cover conductor 44, but it is essential to do so. Instead, each control plate 46
May be electrically floating. Even in such a case, each control plate 46 can reflect or absorb the electromagnetic wave.

Each control plate 46 may be made of a conductor, specifically, a metal, or may be made of a resistor. In this example, it is made of a copper plate. One example of the resistor is carbon.

The length L ₃ of each control plate 46 (see FIG. 2) is
The high-frequency power supplied from the high-frequency power supply 18 is set to be approximately half a wavelength or more (approximately λ / 2 or more). More specifically, since the half wavelength of the high-frequency power is 0.3 m as described above, in this example, the length L ₃ of each control plate 46 is set to about 300
mm. In this example, the length of the two control plates 46 along each short side of the high-frequency electrode 6 is slightly longer than 300 mm, but is approximately 30 as with the other control plates 46.
It may be 0 mm. The height M ₁ of each control plate 46 is shown in FIG.
As shown in, it is sufficient height of the insulator 8 (i.e. the gap between the high frequency electrode 6 and the plasma chamber container 4) M ₂ or more.
If so, the control plate 46 can cover the outside (the entrance) of the insulator 8.

When the length L ₁ of the long side of the high-frequency electrode 6 is set to be approximately half a wavelength of the high-frequency power and the cover conductor 44 is provided as described above, the high-frequency electric field supplied from the high-frequency power supply 18 to the high-frequency electrode 6 Does not spread evenly over the high-frequency electrode 6 but has a distribution on the high-frequency electrode 6. FIG. 4 shows an example of the distribution of the electric field E at that moment in that case.
Is shown schematically in FIG. FIG. 4 shows the control plate 4 described above.
6 is not provided. When the electric field E changes over time on the high-frequency electrode 6, a change in the magnetic field H occurs according to the following Maxwell equation. ε is the dielectric constant of the space, and t is time. That is, the high frequency propagates between the high-frequency electrode 6 and the cover conductor 44 as an electromagnetic wave.

[0028]

[Equation 1] rotH = ε · ∂E / ∂t

The electromagnetic wave propagating between the high-frequency electrode 6 and the cover conductor 44 in this manner passes through the insulator 8 between the high-frequency electrode 6 and the plasma chamber container 4 and enters the plasma chamber container 4, that is, the plasma chamber 10. Get in. At this time, the cover conductor 44 also has a function of distributing the electromagnetic wave widely and evenly on the high-frequency electrode 6 and a function of preventing the electromagnetic wave from leaking to the outside. Even if the height M _{2 of the} insulator 8 is small (for example, about 10 mm), the length L
_As described above, the length of the insulator 8 in the portion located inside the control plate 46 also becomes about half the wavelength of the high-frequency power or more by making the length of 3 larger than about half the wavelength of the high-frequency power as described above.
With such a length, the electromagnetic wave can enter the plasma chamber container 4 from the insulator 8.

The electromagnetic wave that has entered the plasma chamber container 4 as described above cooperates with the cusp magnetic field formed by the permanent magnet 14 to ionize the ion source gas 12 and generate a plasma 16. In this case, the plasma 16 mainly generates a magnetic field strength that causes electron cyclotron resonance (ECR) (for example, 15 mT at a high frequency of 500 MHz).
(150 gauss)) and diffuses out from there.

Therefore, as in the high-frequency ion source 2a,
If a control plate 46 having a length of approximately half a wavelength or more of high-frequency power is provided near the outside of the insulator 8 serving as an entrance of the electromagnetic wave, the electromagnetic wave that is going to enter the plasma chamber container 4 through the insulator 8 is The light is reflected or absorbed by the control plate 46. When the control plate 46 is made of a metal plate as described above, the electromagnetic waves that try to enter the plasma chamber container 4 are reflected by the control plate 46. If the control plate 46 is made of a resistor as described above, the plasma chamber container 4
The electromagnetic waves that try to enter the inside are partially absorbed by the control plate 46 and partially reflected. Therefore, by moving each control plate 46 and adjusting the distance G between the control plate 46 and the insulator 8, the intensity of the electromagnetic wave that enters the plasma chamber container 4 from the control plate 46 can be controlled. The density distribution of the plasma 16 generated in the plasma chamber container 4 can be controlled. As a result, the plasma 16
The beam profile of the ion beam 28 extracted from can be adjusted. If the length L ₃ of each control plate 46 is smaller than approximately half the wavelength of the high-frequency power, the effect of reflecting or absorbing the electromagnetic wave by the control plate 46 is weakened, and the controllability of the beam profile is undesirably reduced.

Thus, the high-frequency ion source 2a
According to the method, the beam profile of the ion beam 28 can be easily adjusted without disassembling the ion source as in the conventional example. That is, since it is not necessary to disassemble the ion source, the adjustment of the beam profile can be performed easily and in a short time at any time without much trouble.

The adjustment of the beam profile by the control plate 46 is of course possible with only one control plate 46. However, the more the number of control plates 46 is increased, the finer the adjustment becomes. Become.

The sectional shape of the plasma chamber container 4, the planar shape of the insulator 8 and the high-frequency electrode 6
May have a square shape. In that case, the length of one side of the high-frequency electrode 6 may be set to be substantially equal to or longer than half the wavelength of the high-frequency power. Further, the cross-sectional shape of the plasma chamber container 4 and the planar shape of the insulator 8 and the planar shape of the high-frequency electrode 6 corresponding thereto may be circular as in the example shown in FIG. In that case, the diameter D of the high-frequency electrode 6 may be set to be approximately half or more of the high-frequency power. In any case, for the same reason as in the rectangular case, the high frequency supplied to the high-frequency electrode 6 propagates as an electromagnetic wave between the high-frequency electrode 6 and the cover conductor 44 and passes through the insulator 8 into the plasma chamber container 4. And can be controlled by the control plate 46.

[0035]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A high-frequency ion source 2 having the structure shown in FIGS.
By using a, the above-described distance G of only one of the left and right (the left and right in the drawing; the same applies hereinafter) of the six control plates 46 is opened to 5 mm, and the rest is closed, and the inside of the plasma chamber container 4 is closed. 5 to 8 show measurement results of a beam profile of an ion beam obtained when an electromagnetic wave is introduced into the substrate.

FIGS. 5A to 8A show each control plate 46. FIG.
(B) shows the beam profile of the ion beam obtained at that time in the form of a contour line. In each drawing, a region 27 indicated by a broken line is the extraction electrode system 2 described above.
2 shows an ion extraction region, from which an ion beam 28 is extracted. The beam profile was measured with a Faraday cup placed 700 mm downstream of the extraction electrode system 22. Table 1 shows the operating conditions of the ion source.

[0037]

[Table 1] Frequency of high-frequency power: 500 MHz Input high-frequency power: 150 W Ion source gas: PH ₃ (10%) / H ₂ ion source gas flow rate: 50 ccm Ion beam energy: 10 keV

As can be seen from FIGS. 5 to 8, when the upper control plate 46 is opened, the upper side has a dark beam profile, and when the lower control plate 46 is opened, the lower side has a dark beam profile. I have. From this, it is understood that the beam profile of the ion beam 28 can be adjusted by opening and closing the control plates 46. It should be noted that there is no significant difference in the beam profile regardless of which of the left and right control plates 46 is opened, because the effect of uniformizing the beam profile by plasma diffusion in the plasma chamber container 4 is as follows.
This is considered to be because a large contribution was made in the short side direction where the distance was short.

Next, the distance G of the lower left control plate 46 is fixed to 5 mm, the distance G of the upper left control plate 46 is set to 0 mm,
FIGS. 9 to 1 show the measurement results of the beam profile of the ion beam obtained when the distance was changed to 5 mm and 10 mm.
It is shown in FIG. How to read these figures and measurement conditions are the same as those in FIGS.

When the distance G of the upper left control plate 46 is 0 mm, the lower side has a dark beam profile (FIG. 9), whereas when the distance G of the upper left control plate 46 is 5 mm, the beam profile becomes uniform. It can be seen that when the distance G of the upper left control plate 46 is 10 mm, the upper beam intensity is excessively increased (FIG. 11). This also indicates that the beam profile of the ion beam 28 can be adjusted by adjusting the distance G between the control plates 46.

[0041]

As described above, according to the present invention, by moving the control plate and adjusting the distance between the control plate and the insulator, the electromagnetic wave that enters the plasma chamber container from the portion of the control plate through the insulator is obtained. Of the plasma generated in the plasma chamber vessel, thereby controlling the beam profile of the ion beam extracted from the plasma. Thus, the beam profile of the ion beam can be easily adjusted without disassembling the ion source.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a high-frequency ion source according to the present invention together with a power supply.

FIG. 2 is a front view around a high-frequency electrode of the high-frequency ion source of FIG. 1;

FIG. 3 is an enlarged sectional view around a control plate of the high-frequency ion source of FIG. 1;

FIG. 4 is a diagram illustrating a schematic example of a state of an electric field around a high-frequency electrode when a control plate is not provided in the high-frequency ion source of FIG. 1;

FIG. 5 is a diagram showing a state (A) of a control plate and a beam profile (B) obtained at that time.

FIG. 6 is a diagram showing a state (A) of a control plate and a beam profile (B) obtained at that time.

FIG. 7 is a diagram showing a state (A) of a control plate and a beam profile (B) obtained at that time.

FIG. 8 is a diagram showing a state (A) of a control plate and a beam profile (B) obtained at that time.

FIG. 9 is a diagram showing a state (A) of a control plate and a beam profile (B) obtained at that time.

FIG. 10 is a diagram showing a state (A) of a control plate and a beam profile (B) obtained at that time.

FIG. 11 is a diagram showing a state (A) of a control plate and a beam profile (B) obtained at that time.

FIG. 12 is a front view showing an example in which a high-frequency electrode and the like are circular, and corresponds to FIG.

FIG. 13 is a sectional view showing an example of a conventional high-frequency ion source together with a power supply.

[Explanation of symbols]

 2a High frequency ion source 4 Plasma chamber 6 High frequency electrode 8 Insulator 14 Permanent magnet 16 Plasma 18 High frequency power supply 22 Extraction electrode system 28 Ion beam 44 Cover conductor 46 Control plate

Claims (3)

[Claims] 1. A cylindrical plasma chamber container into which an ion source gas is introduced and having openings at both ends and having a rectangular cross section, and one opening of the plasma chamber container is formed into an annular shape. A high-frequency power is supplied between the high-frequency electrode and the plasma chamber container with a rectangular high-frequency electrode covered with an insulator, and the ion source gas is ionized by high-frequency discharge to generate plasma. A high frequency power supply,
An extraction electrode system provided near the other opening of the plasma chamber container to extract an ion beam from the plasma; and a cusp magnetic field formed inside the plasma chamber container and the high-frequency electrode to be provided inside the plasma chamber container and the high-frequency electrode. In a high-frequency ion source including a plurality of permanent magnets, a length of a long side of the high-frequency electrode is set to be approximately half a wavelength or more of the high-frequency power, and a space is formed between the high-frequency electrode and the insulator at least around the high-frequency electrode and the insulator. A cover conductor having the same potential as that of the plasma chamber container is provided, and the cover conductor is provided in the cover conductor, in the vicinity of the outside of the insulator, along the insulator, and between the insulator and the insulator. One or more movable conductive control plates capable of adjusting the distance are provided, and the length of each control plate is set to be at least about half the wavelength of the high-frequency power. High-frequency ion source. 2. A cylindrical plasma chamber container into which an ion source gas is introduced and having openings at both ends and having a square cross section, and one opening of the plasma chamber container is formed into an annular shape. A square high-frequency electrode covered with an insulator and a high-frequency power is supplied between the high-frequency electrode and the plasma chamber container to generate plasma by ionizing the ion source gas by high-frequency discharge. A high frequency power supply,
An extraction electrode system provided near the other opening of the plasma chamber container to extract an ion beam from the plasma; and a cusp magnetic field formed inside the plasma chamber container and the high-frequency electrode to be provided inside the plasma chamber container and the high-frequency electrode. In a high-frequency ion source including a plurality of permanent magnets, the length of one side of the high-frequency electrode is set to approximately half a wavelength or more of the high-frequency power, and a space is provided between the high-frequency electrode and the insulator at least around the high-frequency electrode and the insulator. A cover conductor having the same potential as that of the plasma chamber container is provided, and a distance between the insulator and the insulator along the insulator within the cover conductor and near the outside of the insulator. One or more movable conductive control plates capable of adjusting the power are provided, and the length of each control plate is set to be at least about half the wavelength of the high-frequency power. High-frequency ion source. 3. A cylindrical plasma chamber container into which an ion source gas is introduced and having openings at both ends, and one opening of the plasma chamber container is provided with an annular insulator interposed therebetween. A circular high-frequency electrode having a lid, a high-frequency power supply that supplies high-frequency power between the high-frequency electrode and the plasma chamber container to ionize the ion source gas by high-frequency discharge to generate plasma, and An extraction electrode system that is provided near the other opening of the chamber and extracts an ion beam from the plasma; and a plurality of extraction electrodes that are provided on the plasma chamber and the high-frequency electrode and form a cusp magnetic field inside them. In a high-frequency ion source comprising a permanent magnet, the diameter of the high-frequency electrode is set to be approximately half a wavelength or more of the high-frequency power, and A cover conductor having the same potential as that of the plasma chamber container is provided so as to cover the periphery of the insulator with a space therebetween, and the insulation is provided in the cover conductor and near the outside of the insulator. Along the insulator,
One or more movable conductive control plates capable of adjusting the distance to the insulator are provided, and the length of each of the control plates is set to be approximately half a wavelength or more of the high-frequency power. High frequency ion source.