JPH11329270A - Ion source, and regulating method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To regulate the conditions for extracting desirable ion by another means different from a means for magnetic field regulation, and to selectively and efficiently extract the desirable ions. SOLUTION: This ion source is provided with an insulator 44 for insulating electrically a space between a plasma chamber container 4 and a plasma electrode (the utmost plasma side electrode) 21, and a direct current source 46 for impressing a direct current voltage VB between the container 4 and the electrode 21. In this constitution, ion energy E, coming from plasma into a space distributed with a magnetic field in the vicinity of a surface of the utmost plasma side electrode 21, is expressed by an expression E=VP±VB, where the VP represents a plasma potential for the plasma chamber container 4, and the VB represents the direct current voltage impressed from the direct current source 46. The direct current voltage VB comes to +VB, when the voltage VB is impressed to make the utmost plasma side electrode side negative, and the voltage VB comes to -VB when impressed positively. Therefore the ion energy E is regulated by the regulating largeness and direction (polarity) of the voltage VB.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used, for example, in a non-mass separation type ion implantation apparatus and the like, and selectively (selects) desired ions by a magnetic field of a magnet provided in a plasma chamber vessel or the like. And) an ion source that can be extracted.

[0002]

2. Description of the Related Art For example, when ion implantation is performed on a large substrate (for example, a glass substrate for a liquid crystal display), the ion beam extracted from the ion source is not separated without mass separation of the ion beam extracted from the ion source. There is a method and an apparatus for performing ion implantation by irradiating a substrate. This is called a non-mass separation type ion implantation method or ion implantation apparatus.

In order to manufacture a semiconductor, for example, a thin film transistor (TFT) on a glass substrate for a liquid crystal display, ions (dopant ions) containing dopants such as phosphorus (P) and boron (B) are extracted from an ion source. And inject it into the substrate. In this case, a hydride gas of a dopant such as phosphine (PH ₃ ) or diborane (B ₂ H ₆ ) is used as an ion source gas introduced into the ion source for ion generation. Further, usually, a gas obtained by diluting such a hydride gas with a diluting gas of hydrogen or helium is used.

When such a hydride gas or a gas obtained by diluting it with hydrogen or helium is used as an ion source gas, necessary (desired) dopant ions, for example, PH
Decomposed from diluent gas ions (hydrogen ions and helium ions) and hydride gas molecules in addition to hydride ions of dopants such as _x ⁺ (x = 0 to 4) and B ₂ H _x ⁺ (x = 0 to 6). Unwanted (unwanted) ions of hydrogen ions are generated, and a mixed ion beam is extracted from the ion source. The unnecessary ions are hydrogen ions or helium ions, and can be called light ions. The necessary ions can be called heavy ions or polymer ions because they are heavier than the light ions.

[0005] When ions are implanted into a substrate using such an ion beam, even unnecessary ions are incident on the substrate, which increases the temperature of the substrate. Since the penetration depth (implantation range) of the light ions becomes deeper with respect to the existing resist, the same phenomenon as curing by exposure to light hardens and the resist cannot be peeled off.

In order to solve such a problem, an ion source has been proposed by the same applicant that can preferentially extract desired ions by a magnetic field of a permanent magnet provided in a plasma chamber container. (Japanese Unexamined Patent Publication No.
No. 128984). FIG. 5 shows the ion source.

The ion source 2 includes, for example, a plasma chamber container 4 into which the above-described ion source gas 8 is introduced from a gas inlet 6, and an ion source gas 8 in the plasma chamber container 4.
And a drawing electrode system 20 which is provided near the opening of the plasma chamber container 4 and draws out an ion beam 28 from the plasma 16 by the action of an electric field. Have. In this example, the extracted ion beam 28 is irradiated and injected into the substrate 36 without mass separation. That is, the apparatus shown in FIG. 5 is a non-mass separation type ion implantation apparatus (this is also called an ion doping apparatus).
(The same applies to the devices shown in FIGS. 1 and 3 described later).

While the inside of the plasma chamber 4 is evacuated, for example, through an extraction electrode system 20, an ion source gas 8 is introduced into the plasma chamber 4, and the filament 10 is heated by a filament power supply 12 while the filament 10 is heated.
When a DC voltage is applied from a DC arc power supply 14 between the plasma chamber container 4 and the plasma chamber container 4, an arc discharge is generated between the filament 10 and the plasma chamber container 4, whereby the ion source gas 8 is ionized and the plasma 16 is generated. Generated.

In this example, a number of magnets (for example, permanent magnets) 18 are provided around the plasma chamber container 4.
A cusp magnetic field (multipole magnetic field) near the inner wall of the plasma chamber 4
Is formed, which contributes to confinement of the plasma 16. Such an ion source is also called a bucket type ion source.

The extraction electrode system 20 includes one or more electrodes, usually a plurality of electrodes. In this example, the plasma electrode 2 arranged from the most plasma side to the downstream side
1, extraction electrode 22, suppression electrode 23 and ground electrode 24
It is composed of 26 is an insulator. Each electrode 21
To 24 represent a large number of ion extraction holes 21a to 21a in this example.
4a are provided at corresponding positions.

The plasma electrode 21 is an electrode for determining the energy of the ion beam 28 to be extracted. A positive high voltage (acceleration voltage) is applied to this electrode and the plasma chamber container 4 from a DC acceleration power supply 30 with respect to the ground potential. Applied. The extraction electrode 22 is an electrode that causes a potential difference between the plasma electrode 21 and the ion beam 28 from the plasma 16 by an electric field caused by the electric field.
, A negative voltage (drawing voltage) is applied with reference to the potentials of the plasma electrode 21 and the plasma chamber container 4. The suppression electrode 23 is an electrode for suppressing backflow of electrons from the downstream side, and a negative voltage (suppression voltage) is applied from a DC suppression power supply 34 with reference to the ground potential. The ground electrode 24 is grounded. In this example, the plasma chamber container 4 and the plasma electrode 21 are electrically connected to each other to have the same potential.

Further, in the plasma chamber vessel 4 and near the upper portion of the plasma electrode 21, a magnetic field 40 (having a component parallel to the surface) along the surface of the plasma electrode 21 on the side of the plasma 16 (FIG. 6). The permanent magnets 38 that generate the magnetic flux are disposed so as to avoid the positions of the ion extraction holes 21a to 24a.

As shown in FIG. 6, ions extracted from the plasma 16 through the space where the magnetic field 40 is distributed have a curvature corresponding to the ion energy E and the mass m with respect to the set magnetic flux density B and distribution. Bend at. Specifically, the turning radius R of the ion is represented by the following equation. q is the charge of the ion.

[0014]

## EQU1 ## R ² = ² mE / qB ²

That is, in the case of the same energy E, the light ions 28 such as the hydrogen ions and the helium ions described above are replaced with the light ions 28 a such as the above-described heavy ions 28 a such as the dopant ions.
b has a smaller turning radius R and is more likely to be captured in the space where the magnetic field 40 is distributed. Therefore, the magnetic field 4 generated by the permanent magnet 38
By appropriately setting 0, unnecessary light ions 28b are prevented from being extracted through the extraction electrode system 20 (that is, the light ions 28b are removed), and the desired heavy ions 2
8a can be selectively (preferably) extracted.

[0016]

The energy E of ions entering from the plasma 16 into the space where the magnetic field 40 is distributed.
The plasma 16 is determined by the potential (plasma potential) V _P which has on the plasma chamber container 4 and therewith the same potential of the plasma electrode 21.

[0017] However, this plasma potential V _P will vary with the conditions of the plasma 16, not determined unconditionally.
That is, the plasma potential _VP is simply the plasma 1
6 is determined by the difference between the amount of electrons and the amount of ions incident on an object (in this example, the plasma chamber container 4 and the plasma electrode 21) surrounding the plasma 6;
Power supplied to large 6, containment performance is poor in ion density of the plasma 16 is high, in the case of equal, since towards the electron mobility electrons are many incident is high, the plasma potential V _P is Get higher. In the opposite case, the plasma potential V
_P becomes lower. This plasma potential _VP is usually, for example, in the range of about + several tens V to +100 V.

[0018] Thus, for the plasma potential V _P is not determined to be constant, not fixed to the energy E of the ions is constant, therefore, as can be seen from Equation 1, the magnetic flux for deriving selectively the desired ions It is difficult to determine the optimum density B. That is, the permanent magnet 38 is a magnetic flux density B is constant, it is impossible to respond to changes in the ion energy E due to the change in the plasma potential V _P, therefore when considering the change in the plasma potential V _P, the prior art Then, it is difficult to efficiently extract desired ions.

If an electromagnet is used in place of the permanent magnet 38, it is possible to adjust the magnetic flux density B to optimize it. However, in such a case, the structure around the electromagnet becomes complicated, Another problem arises in that a relatively large capacity magnetic field power supply is required for exciting the electromagnet.

Accordingly, the present invention provides an ion source and a method of adjusting the ion source capable of selectively and efficiently extracting desired ions by enabling adjustment of conditions for extracting desired ions by means different from the magnetic field adjustment. Its primary purpose is to provide.

[0021]

The ion source according to the present invention comprises:
An insulator that electrically insulates between the plasma chamber container and the electrode on the most plasma side, and a DC power supply that applies a DC voltage between the plasma chamber container and the electrode on the most plasma side are provided. .

According to the above configuration, when the plasma potential with respect to the plasma chamber container is V _P and the DC voltage applied from the DC power supply is V _B , the space where the magnetic field is distributed near the surface of the electrode on the most plasma side is provided. The energy E of the ions entering from the plasma can be expressed by the following equation. Here, the DC voltage V _B
When applying the in + V _B, when applying a DC voltage V _B in the positive polarity becomes -V _B.

[0023]

[Equation 2] E = V _P ± V _B

Therefore, by adjusting the DC voltage V _B , that is, by adjusting its magnitude and direction (polarity), the energy E of the ions can be adjusted, whereby the desired ions can be extracted. , Specifically, the radius of gyration R of the ions shown in the above equation (1) can be adjusted. As a result, even if the conditions on the plasma side change, desired ions can be selectively and efficiently extracted by means other than the magnetic field adjustment.

[0025]

FIG. 1 is a sectional view showing an example of an ion source according to the present invention together with a power supply. Parts that are the same as or correspond to those in the conventional example of FIG. 5 are denoted by the same reference numerals, and differences from the conventional example will be mainly described below.

In the ion source 2a of this embodiment, a support for supporting the plasma electrode 21 between the plasma chamber container 4 and the plasma electrode (electrode on the most plasma side) 21 described above, more specifically, in this embodiment. An annular insulator 44 is provided between the flange 42 and the plasma chamber container 4 to electrically insulate the plasma chamber container 4 from the plasma electrode 21. The support flange 42 is made of a conductor and is electrically connected to the plasma electrode 21.

Further, the plasma chamber container 4 and the support flange 4
2 thus connects the DC power source 46 between the plasma electrode 21, in this example between the plasma chamber container 4 and the plasma electrode 21 so as to apply a DC voltage V _B to the plasma electrode 21 side to the negative polarity ing. However, as described later, the above with the polarity reversed, may be applied a DC voltage V _B to the plasma electrode 21 side to the positive polarity.
The DC voltage V _B may also be referred to as a bias voltage. The DC power supply 46 preferably has a variable output voltage rather than a fixed output voltage. That is the DC voltage V _B
Adjustment becomes easy.

The above-described acceleration power supply 30 and drawer power supply 3
Reference numeral 2 denotes a positive electrode side of the plasma chamber container 4 in this example.
Connected to

As an example of the magnetic field generating means, in this example,
A magnetic field 50 having a component along the surface near the surface of the plasma electrode 21 on the plasma 16 side, that is, having a component parallel to the surface, is generated on the left and right sides near the end on the plasma electrode 21 side in the plasma chamber container 4. Two magnets 48 are attached and arranged. In this example, both magnets 48 are housed in a magnet container 52 made of a non-magnetic material for protection such as heat shielding.

The magnet 48 and the magnet container 52 may be mounted on the upper surface of the plasma electrode 21. Also,
The magnet 48 may be arranged outside the plasma chamber container 4. Plasma chamber container 4, support flange 42, plasma electrode 21
And the like do not disturb the magnetic field 50 from the magnet 48 because they are formed of a non-magnetic material in this example.

The function of bending ions entering from the plasma 16 into the space where the magnetic field 50 created by the magnet 48 is distributed, the turning radius R, and the like are basically the same as those described above with reference to FIG. Here, the overlapping description is omitted.

Extraction electrode system 20 including plasma electrode 21
In this example, the planar shape of the plasma chamber container 4 is quadrangular (square), more specifically, rectangular. Each of the magnets 48 has a straight rod shape in this example, as shown in FIG.
1a to 24a with different polarities (that is, N pole and S pole)
Poles) are arranged in two rows so as to face each other.

However, the plasma chamber container 4 and the extraction electrode system 2
The plane shape such as 0 is not limited to a square, but may be a circle or the like. In that case, each magnet 48 may be formed in a shape that matches the planar shape of the plasma chamber container 4 or the like. For example, when the planar shape of the plasma chamber container 4 or the like is circular, each magnet 48 may be formed in a semi-circular shape.

Although the two magnets 48 are constituted by permanent magnets in this example, they may be constituted by electromagnets. However, a permanent magnet is preferred because it has a simple structure and does not require a magnetic field power supply.

Since the extraction electrode system 20 and the like have a rectangular shape in this example as described above, in this example, the ion beam 28 having a rectangular cross section is extracted. The ion extraction holes 21a to 24a of the extraction electrode system 20 may be a plurality of elongated slit-shaped holes instead of a large number of small round holes as in the example shown in FIG. Each slit-shaped hole is provided with a magnet 48.
May be arranged in a direction along the axis, or may be arranged in a direction crossing the magnet 48.

In the ion source 2a, as described above, the plasma potential with respect to the plasma chamber container 4 is set to V _P ,
Assuming that the DC voltage applied from the DC power supply 46 is V _B , the energy E of the ions entering from the plasma 16 into the space where the magnetic field 50 is distributed can be expressed by the above-described equation (2).

Therefore, by adjusting the magnitude and direction (polarity) of the DC voltage V _P , the energy E of the ions can be adjusted, whereby the conditions for extracting desired ions, specifically, the conditions for extracting ions can be adjusted. The turning radius R of the ions shown in the above equation 1 can be adjusted. As a result, even if the conditions on the plasma 16 side change, desired ions, for example, the above-described dopant ions (PH _x ⁺ , B ₂ H _x ^+, etc.) can be selectively and efficiently used by means other than magnetic field adjustment. Can be withdrawn. That is, the ion beam 28
The ratio of unnecessary ions contained therein, for example, the above-described hydrogen ions and diluent gas ions can be reduced, and the ratio of desired ions can be increased. In this case, the magnetic field 5 generated by the magnet 48
The magnetic flux density B of 0 may be constant. Therefore, the magnet 48 may be a permanent magnet.

[0038] For example, if the plasma potential V _P plasma 16 side condition is changed as described above is increased, correspondingly, it may be reduced DC voltage V _B. If, after reducing the DC voltage V _B is not yet compensated may be contrary to the illustrated polarity of the DC voltage V _B. By doing so, since E = V _P -V _B is satisfied, the plasma potential V
The _P increase in the can be canceled by the DC voltage V _B. If the plasma potential V _P is reduced to the contrary, that amount may be increased DC voltage V _B. By doing so, it is possible to make the energy E of the ions close to a constant. Therefore, even if the magnetic flux density B of the magnetic field 50 is constant, the desired ions are preferentially extracted and the ratio of the desired ions contained in the ion beam 28 is reduced. Can be increased.

Further, even when the plasma potential V _P is not changed, if the magnetic flux density B of the magnetic field 50 is too strong relative to the drawer of the desired ions, increases the DC voltage V _B so can I increase the energy E of the ions Just do it.
Conversely, if the magnetic flux density B is too weak, so can we reduce the energy E of the ions may be reduced DC voltage V _B. If, after reducing the DC voltage V _B is not yet compensated may be contrary to the illustrated polarity of the DC voltage V _B. By doing so, since E = V _P -V _B is satisfied, it is possible to further reduce the energy E of the ions.

The variable range of the DC voltage V _B is, for example,
Considering that the ratio of hydrogen ions contained in the ion beam 28 may be minimized at around 70 to 80 V as in the example shown in FIG.
It is preferable to set it within the range of about 50V. Also, considering the case of reversing the polarity, -150 V to +150
It is preferable to be within the range of about V.

Since the arc power source 14 connected between the plasma chamber container 4 and the filament 10 is also a DC power source, instead of providing the DC power source 46, for example, as shown in FIG. filament 10 side of the arc power supply 14 (negative electrode in this example) connected to the support flange 42 and thus the plasma electrode 21 in conductor 54, the output voltage of the arc power supply 14, as the DC voltage V _B, the plasma chamber container 4 And the plasma electrode 21 may be applied. That is, the arc power supply 14 may also serve as the DC power supply 46. By doing so, the DC power supply 46 can be omitted, so that the configuration can be simplified.

The output voltage of the arc power supply 14 is usually, for example, about 40 V to 120 V.
4 can also serve as the DC power supply 46. In this case, if the output voltage itself of the arc power supply 14 is changed, the generation conditions of the plasma 16 are changed and the plasma potential _VP is changed, so that the DC voltage applied between the plasma chamber container 4 and the plasma electrode 21 is changed. When it is necessary to adjust the magnitude of V _B , the output voltage of the arc power supply 14 is fixed, and a voltage divider (for example, a voltage dividing resistor) is provided, for example, in the middle of the conducting wire 54. preferably, adjusting the voltage V _B.

The plasma chamber container 4 and the plasma electrode 2
Conventionally, there is an ion source electrically insulated from the ion source 1 and connected to each other by a resistor having a fixed value (however, there is no combination with the permanent magnet 38 or the magnet 48 as described above). A current flows through this resistor due to the difference in the amount of electrons and ions incident on the plasma electrode 21 from 16 and a potential difference is generated across the resistor, whereby a voltage is applied between the plasma chamber container 4 and the plasma electrode 21. However, the operation of this resistor is completely different from that of the DC power supply 46 or the dual-purpose arc power supply 14. That is, the voltage generated in the current turn both ends flows through the resistor, as in the case of the plasma potential V _P, since changes by the above-mentioned conditions of the plasma 16, the plasma potential V _P by the voltage across this resistor And thus the energy E of ions entering the region of the magnetic field 50 from the plasma 16 cannot be adjusted to the desired one. In order to make such adjustment, the DC power supply 46 or the arc power supply 1
As the 4, it does not depend on the conditions of the plasma 16 (i.e. independent of the conditions of the plasma 16) of the DC power source to output a DC voltage V _B is effective.

As the plasma generating means, instead of using the above-described filament 10, the plasma chamber 4
A high frequency or microwave is introduced into the plasma chamber vessel 4
The plasma 16 may be generated by generating a high-frequency discharge or a microwave discharge therein, thereby ionizing the ion source gas 8.

[0045]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In an ion source 2a having a filament 10 as shown in FIG.
(I.e., the width of the ion extraction holes 21a to 24a formation region) was set to 50 to 70 mm, and two rows of magnets 48 were arranged on both sides thereof with a distance L of 10 to 30 mm (see also FIG. 2). The magnetic flux density B of the magnetic field 50 formed between the two magnets 48 was distributed at 200 to 800 Gauss.

As shown in FIG. 1, a DC voltage V _B is applied from the DC power supply 46 with the plasma electrode 21 side as a negative electrode, and an ion beam is applied to the ion source gas 8 using hydrogen diluted 20% PH ₃ (phosphine). 28 was pulled out. At this time, the output voltage of the arc power supply 14 is 50 V, the arc current flowing therethrough is 10 A, the output voltage of the acceleration power supply 30 is 50 kV, the output voltage of the extraction power supply 32 is 2.5 kV, and the output voltage of the suppression power supply 34 is 0.9 kV. Fixed.

FIG. 4 shows the result of measuring the ratio of hydrogen ions contained in the ion beam 28 by changing the magnitude of the DC voltage V _B. By adjusting the DC voltage V _B (set to about 70 V in this example),
It can be seen that the ratio of hydrogen ions in the ion beam 28 can be minimized, in other words, the ratio of ions other than hydrogen ions can be maximized.

[0048]

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

According to the first aspect of the present invention, the energy of ions entering the magnetic field created by the magnet from the plasma is changed by the DC voltage applied between the plasma chamber container and the electrode on the most plasma side from the DC power supply. Since the adjustment can be performed, the condition for extracting the desired ions can be adjusted by means different from the magnetic field adjustment, whereby the desired ions can be extracted selectively and efficiently.

According to the second aspect of the present invention, since the arc power supply also serves as the DC power supply, it is possible to achieve a further effect that the configuration can be simplified.

According to the third aspect of the present invention, since the magnet is constituted by a permanent magnet, the structure is simplified, and a magnetic field power supply is not required. Can be increased in the ratio of the desired ions contained in the.

[Brief description of the drawings]

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

FIG. 2 is an enlarged plan view showing an example around a magnet in FIG. 1;

FIG. 3 is a sectional view showing another example of the ion source according to the present invention together with a power supply.

FIG. 4 is a diagram showing an example of a measurement result of a hydrogen ion ratio in an ion beam when a magnitude of a DC voltage applied between a plasma chamber container and a plasma electrode is changed.

FIG. 5 is a cross-sectional view showing an example of a conventional ion source together with a power supply.

FIG. 6 is a diagram schematically showing a state in which ions are bent by a magnetic field of a magnet in FIG. 1, FIG. 3 or FIG. 5;

[Explanation of symbols]

 2a Ion source 4 Plasma chamber container 10 Filament 14 Arc power supply 16 Plasma 20 Extraction electrode system 21 Plasma electrode (electrode on the most plasma side) 28 Ion beam 44 Insulator 46 DC power supply 48 Magnet

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasunori Ando 47-47 Umezu Takaune-cho, Ukyo-ku, Kyoto, Kyoto Nissin Electric Co., Ltd.

Claims (3)

[Claims] 1. A plasma chamber container into which an ion source gas is introduced, plasma generating means for generating plasma by ionizing the ion source gas in the plasma chamber container, and a plasma chamber provided near an opening of the plasma chamber container. An extraction electrode system for extracting an ion beam from the plasma, and a magnet that generates a magnetic field along the surface near the plasma side surface of the most plasma side electrode constituting the extraction electrode system. An ion insulator comprising: an insulator that electrically insulates between the plasma chamber container and the electrode on the most plasma side; and a DC power supply that applies a DC voltage between the plasma chamber container and the electrode on the most plasma side. source. 2. The plasma generating means includes: a filament provided in the plasma chamber; a filament power supply for heating the filament; and a DC arc for generating an arc discharge between the filament and the plasma chamber. The ion source according to claim 1, further comprising a power supply, wherein the arc power supply also functions as the DC power supply. 3. The ion source according to claim 1, wherein the magnet is constituted by a permanent magnet, and a DC voltage applied between the plasma chamber container and an electrode on the most plasma side is adjusted. And adjusting the ratio of desired ions contained in the ion beam.