JPH06176725A - Ion source - Google Patents

Abstract

PURPOSE:To improve the reliability at the time of control by eliminating the flow-in of a large quantity of ions, of which polarity is opposite to that of the electron and control voltage, into a control power source. CONSTITUTION:An ion source, which has an extraction electrode system 7 for drawing the ion among the plasma generated inside of a plasma chamber 3 from the ion emitting surface to the outside through a slit 3a of an extraction slit part 8, controls the beam quantity of the ion beam at a predetermined value. The ion source has a control electrode 9 for making a desired control voltage exist outside of the slit 3a of the extraction slit part 8, and a control power source 14, and a debye length control means for positioning the ion emitting surface of the plasma inside of the plasma chamber 3. With this structure, since the ion emitting surface is positioned inside of the plasma chamber 3, the influence of the extraction electrode 10 to the ion and the electron become large together with the influence of the control voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion source for producing an ion beam used in an ion implanter or the like.

[0002]

2. Description of the Related Art Usually, among the ion sources for extracting metal ion beams such as As and B, those capable of extracting an ion beam having a relatively large current amount are solid vapor or compound gas (BF ₃ or BCl _3). Etc.) is used to generate a plasma by discharging an operating gas in the air. There are many types of ion sources of this system, such as an electron impact type, a high frequency type, and a PIG (Penning Ionization Gauge) type. These various ion sources are required to generate necessary ions and energy, The most suitable model is selected according to the beam current.

For example, a Freeman ion source, which is a kind of electron impact type ion source, has a structure in which a rod-shaped hot filament is arranged near a slit formed in the side wall of a plasma chamber. Is generated to generate a plasma, and ions in the plasma are extracted via an slit by an extraction electrode system to generate an ion beam. Then, conventionally, the control of the beam amount of the ion beam in this Freeman ion source is performed by controlling the saturated ion current density in plasma using control parameters such as filament current, arc voltage, gas flow rate, oven temperature and the like. It is like this.

Further, for example, an ECR (Electron Cyclotron Resonance) ion source, which is a type of high-frequency ion source, has a structure in which a microwave generator is connected to a plasma chamber to which a magnetic field is applied via a waveguide. The plasma is generated by the microwave and the magnetic field output from the microwave generator, and the ions in the plasma are extracted through the slit by the extraction electrode system to generate the ion beam. Conventionally, the control of the beam amount of the ion beam in this ECR ion source is performed by using the control parameters such as the high frequency power supplied to the microwave generator, the gas flow rate, the oven temperature, and the magnetic field, and the saturated ion current density in the plasma. It is designed to be performed by controlling.

[0005]

As described above, various conventional ion sources are designed to control the beam quantity of the ion beam by using the saturated ion current density in the plasma. However, there is a problem in that it is difficult to stabilize the beam amount within the accuracy required in recent years only by controlling by the saturated ion current density.

That is, when the ion source is used in, for example, an ion implantation apparatus, the beam amount of the ion beam has a great influence on the physical properties of the ion irradiation target, so that the beam amount can be maintained at a desired value with high precision. Is desired. Therefore, the beam amount is feedback-controlled by using, for example, the extraction current from the plasma chamber, and the conventional ion source operates a control parameter to detect saturated ion when a change in the extraction current is detected. By changing the current density, the beam amount is feedback-controlled to a desired value.

However, in the above-mentioned feedback control, since the predetermined time is required until the saturated ion current density corresponds to the change amount after the change in the extraction current is detected and the control parameter is manipulated, the followability is deteriorated. It has become a thing. As a result, in the conventional ion source, the followability of the feedback control is insufficient, and it is difficult to maintain the beam amount at a desired value with high accuracy.

Further, in the high frequency type ion source, since the range of the saturated ion current density for stably generating plasma is narrow, it is impossible to control the saturated ion current density in a wide range, and the Freeman ion source has a saturated ion current density. By controlling the density, a wide range (1 to 10 ^-5 ) can be controlled, whereas the beam amount can be controlled only in a narrow range of about 1 to 10 ^-2 .

Accordingly, the conventional high frequency type ion source is
When it is attempted to control the beam amount irradiated to the ion irradiation target (target) over a wide range, means for providing a current limiting slit in the beam transport system, or controlling the beam optical system to widen the divergence angle of the ion beam, etc. It is necessary to take. However, these means have a problem that the controllability is lowered and the amount of contamination generated in the beam transport system is increased.

Therefore, the high-frequency ion source has a structure in which a control electrode is added to the extraction electrode system for extracting an ion beam from the plasma chamber, and a control power supply capable of applying a positive or negative control voltage is connected to the control electrode (actually, Kaihei 3-607
No. 41), it is possible to easily control the beam amount of the ion beam extracted from the plasma chamber, and to turn on / off the ion beam by applying a reverse voltage of the charge of the ions. .

Further, in this case, since the time from the change in the extraction current is detected and the control power source is operated to the change in the beam amount is shortened, the followability of feedback control is improved, It is possible to maintain the quantity at the desired value with high accuracy. Incidentally, the improvement of the followability of the feedback control can be obtained similarly even when the above-mentioned configuration is adopted in various other ion sources.

As described above, the ion source adopting the above-mentioned structure can solve the conventional problems.
However, if only the beam amount is controlled by this configuration, for example, when extracting a positively charged ion beam, electrons in the plasma or negatively charged ions are attracted to the control electrode, and a large amount of current flows into the control power supply and May be short-circuited, and there is a problem of insufficient reliability. Therefore, it is an object of the present invention to provide an ion source capable of controlling the beam amount with a stable control voltage.

[0013]

In order to solve the above-mentioned problems, the ion source of the present invention has a first electrode to which an accelerating voltage is applied from the ion emission surface of the ions in the plasma generated in the plasma chamber. It has an extraction electrode system that is drawn out to the outside through the slit opening, and controls the beam amount of the ion beam composed of the ions to a predetermined value, and has the following features.

That is, the ion source is provided in the extraction electrode system, and is a control electrode and a control power source which are control voltage means for causing an arbitrary control voltage to exist outside the slit opening of the first electrode, and the ion emission of the plasma. Debye length control means for positioning the surface in the plasma chamber.

[0015]

According to the above arrangement, while the Debye length control means positions the plasma ion emitting surface in the plasma chamber, the control voltage means controls the first control voltage to generate an arbitrary control voltage.
It is designed to exist outside the slit opening of the electrode. Therefore, the beam quantity of the ion beam consisting of the ions emitted from the slit mouth can be controlled in a wide range by arbitrarily changing the control voltage in the extraction electrode system because the ions have electric charges. become.

At this time, the ion emitting surface is located in the plasma chamber, and the influence of the first electrode having the slit port on the ions and electrons is large together with the influence of the control voltage. Therefore, a large amount of electrons and ions having the opposite polarity to the control voltage do not flow into the control voltage means to cause a short circuit state, so that the reliability at the time of control is improved. This allows the ion source to control the beam amount to a predetermined value in a wide range with high reliability.

Further, when the control of the beam amount is feedback control, the time from when the change of the beam amount is detected and the control voltage means is operated until the control voltage corresponds to the change amount is completed in a short time. Therefore, the followability is improved, and as a result, the beam amount can be maintained at a predetermined value in a wide range and with high reliability with high reliability.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following will describe one embodiment of the present invention with reference to FIGS.

The ion source according to this embodiment is composed of BF ₃ and A
It is a high-frequency ion source for generating ions by converting working gas such as r and metal vapor into plasma by microwave discharge, and is mounted on an ion implanter as shown in FIG. 1, for example. This ion source is, for example, 2.45.
A magnetron 1 for outputting a microwave of GHz, a hollow waveguide 2 having an insulating portion, a plasma chamber 3 connected to the magnetron 1 via the waveguide 2,
It has a pair of source magnets 6 arranged around the plasma chamber 3. The microwave output from the magnetron 1 is introduced into the plasma chamber 3 via the waveguide 2, and the source magnets 6 generate an ECR magnetic field. ing.

Further, a working gas supply means (not shown) is connected to the plasma chamber 3, and the working gas supply means is filled with a working gas or a gas cylinder in which solid impurities are evaporated by a metal vapor generating furnace. The working gas composed of the gaseous impurities that has been used is supplied into the plasma chamber 3.

Further, the waveguide 2 of the plasma chamber 3
A window made of, for example, ceramics is provided on the inner wall surface on the side. The window separates the waveguide 2 from the inside of the plasma chamber 3, and the magnetron 1 to the waveguide 2 are separated from each other.
The microwave output through the plasma chamber 3
It is designed to be introduced inside. On the other hand, in addition to the inner wall of the plasma chamber 3, as shown in FIG. 2, BF ₃
Liners 5 having corrosion resistance to corrosive working gases such as the above are provided, and these liners 5 constitute the inner wall surface of the plasma chamber 3.

The partition wall of the plasma chamber 3 is
A slit port 3a is formed to release ions from the inside of the plasma chamber 3. This slit mouth 3a
Is formed in a rectangular shape having a long side distance b and a short side distance a, and the partition wall having the slit port 3a is used as the extraction slit portion 8 as the first electrode of the extraction electrode system 7. . The extraction electrode system 7 includes the extraction slit portion 8 that is the first electrode, the control electrode 9 that is the second electrode, and the third electrode.
Extraction electrode 10 that is an electrode and ground electrode 1 that is a fourth electrode
1 and the control electrode 9, the extraction electrode 10, and the ground electrode 11 have a passage port 9 for passing an ion beam.
a, 10a, 11a are formed respectively. Then, as shown in FIG. 1, the extraction slit portion 8, the control electrode 9, the extraction electrode 10, and the ground electrode 11 that form the extraction electrode system 7 are arranged in this order from the slit port 3a to the outside (ion emission direction). It is arranged.

A positive electrode side of a drawing power source 12 is connected to the plasma chamber 3 having the drawing slit portion 8 so that a drawing voltage is applied by the drawing power source 12. Further, a resistor 13 and a control power source 14 are also connected to the positive electrode side of the power source 12 for drawing power.
No. 4 can output the control voltage arbitrarily in the range from the positive voltage to the negative voltage. The control power supply 14 applies a control voltage to the control electrode 9.

On the other hand, the negative electrode side of the deceleration power supply 15 is connected to the extraction electrode 10, and the deceleration voltage is applied by the deceleration power supply 15. The positive electrode side of the deceleration power supply 15 is connected to the ground electrode 11 and the negative electrode side of the extraction power supply 12 and is also grounded to the analysis magnet housing. A ground voltage is applied to the ground electrode 11. ing. As a result, the potential distributions of the plasma chamber 3 and the extraction electrode system 7 are in the state shown in FIG. 2, for example.

Further, the ion source has a feedback control means and a Debye length control means which are not shown. The above feedback control means is used for the plasma chamber 3
The beam amount is controlled by operating the control power supply 14 or the like based on the extraction current I _ex detected from the beam current I _ex and the beam current I _b detected from the Faraday section 18. The control of the beam amount is not limited to the feedback control, and another control method may be adopted.

On the other hand, the Debye length control means is a source that determines the high frequency power of the magnetron 1 that determines the microwave power, the gas flow rate of the working gas that determines the gas pressure in the plasma chamber 3, and the ECR magnetic field strength and distribution. The Debye length control parameter consisting of the coil currents Coil1 and Coil2 of the magnets 6 and 6 can be controlled. The Debye length control means controls the Debye length control parameter under the following conditions to position the ion emitting surface 20a of the plasma 20 in the plasma chamber 3.

That is, the Debye length control means uses the extraction current I _ex.
The saturated ion current density j _s (mA / cm ² ) can be calculated by dividing by the opening area (a × b) of the slit mouth 3a, and the saturated ion current density j _s (mA / cm ² ) can be measured in advance by an electrostatic probe or the like, or The electron temperature kTe (eV) can be calculated by always installing the electric probe in the ion source, and the saturated ion current density j _s and the electron temperature k of these can be calculated.
Substituting Te into the following calculation formula (1), the Debye length λ _D (m
m) can be calculated.

The Debye length _{λ D = (ε 0 kTe /} n e e 2) 1/2 = (ε 0 / ej s) 1/2 · kTe 3/4 / m i 1/4 ... (1) However, ε ₀ is the dielectric constant in vacuum (8.85 × 10 ^-12 ), e
Is the amount of charge (1.6 × 10 ⁻¹⁹ ), m _i is the mass of the ion, n
_e is the electron density (plasma density).

Further, the Debye length control means compares the Debye length λ _D obtained from the above equation (1) with the short side distance a (slit length) of the slit port 3a, and debye length λ _D The side distance a and the following conditional expression (2) are satisfied,
By controlling the above-described Debye length control parameter, as shown in FIG.
0a is located in the plasma chamber 3. This is the Debye length λ _D that satisfies the conditional expression (2).
This is because the ion emitting surface 20a having the above is blocked by the acceleration voltage of the slit port 3a, so that the ion emitting surface 20a is prevented from leaking to the outside through the slit port 3a.

The _{λ D> a · k (1} > k ≧ 0.1) ... (2) In addition, k is used conditions (electron density n _e, the electron temperature kTe,
It is a value that varies depending on the operating gas, etc.).

When controlling the Debye length λ _D using the above Debye length control parameter, the coil current Coil1 to the source magnets 6 is changed so as to change the electron density n _e.
-It is desirable to operate Coil 2 to control the ECR magnetic field strength and distribution. This, by controlling the ECR field strength and distribution, the control range than the control of the electron temperature kTe about 1 eV ≦ kTe ≦ 20 eV, because the electron density n _e can be controlled in a wide range (2 orders of magnitude).
The control by the magnetic field intensity distribution can be reduced electron density n _e by approximating the magnetic field in the vicinity of the slit opening 3a to zero, the magnetic field is negative, the plasma 20
Ion beam 17 with a stable beam amount
Cannot be generated.

The operation of the ion source having the above structure will be described.

First, as shown in FIG. 1, after the beam amount set value is registered in the feedback control means so that the ion beam 17 having a desired beam amount is obtained, the inside of the plasma chamber 3 is evacuated (not shown). By means of the means, the pressure is reduced to a high vacuum state. After that, the working gas is introduced into the plasma chamber 3, and the magnetron 1 is operated by supplying the electric power to the magnetron 1.
It will be introduced into the plasma chamber 3 via. Also, the coil current Coil1 is applied to the source magnets 6 and 6.
When the coil 2 is energized, an ECR magnetic field is generated in the plasma chamber 3.

The microwave and the ECR magnetic field described above cause the electrons existing in the plasma chamber 3 to swirl around the magnetic field direction, and collide the electrons with the working gas to generate the plasma 20. After this,
Ions having a positive charge in the plasma 20 are attracted to the extraction electrode system 7 and emitted to the outside through the slit port 3a to be turned into the ion beam 17. Then, the ion beam 17 is mass-analyzed by the mass analyzer 19 into ions having a predetermined mass, and the ion beam 17 is irradiated onto the ion irradiation target 16 existing in the Faraday part 18. The ion beam 17 may be composed of negatively charged ions by operating the extraction electrode system 7.

When the ion beam 17 is emitted from the plasma chamber 3 to the outside, the ion beam 1
The extraction current I _ex corresponding to the beam amount of 7 is supplied from the plasma chamber 3 to the feedback control means. Further, when the ion beam 17 after the mass analysis is irradiated into the Faraday part 18, the beam current I _b is supplied to the feedback control means. Then, the feedback control means controls the control power supply 1 based on the extraction current I _{ex, the} beam current I _b, and the beam amount set value.
By operating 4 to apply a control voltage to the control electrode 9, the beam amount is feedback-controlled.

By the way, the Debye length control means divides the extraction current I _ex by the opening area (a × b) of the slit port 3a to obtain the saturated ion current density j _s (mA / cm ² ).
And the electron temperature kTe (eV). The Debye length λ _D (mm) is calculated by substituting the saturated ion current density j _s and the electron temperature kTe into the above-mentioned calculation formula (1), and further, the Debye length λ _D and the short length of the slit port 3a are calculated. The coil current Co of the source magnets 6 and 6 is set so that the side distance a satisfies the conditional expression (2) described above.
il1 and Coil2 are operated to control the ECR magnetic field strength and distribution. As a result, the ion emitting surface 20a of the plasma 20 is located in the plasma chamber 3 as shown in FIG. 3, and the reliability of the control of the beam amount is improved.

That is, for example, when the Debye length control means controls without satisfying the conditional expression (2), the plasma 20 leaks to the outside from the slit port 3a as shown in FIG. Become. When the ion emitting surface 20a and the control electrode 9 are close to each other, the influence of the potential of the control electrode 9 becomes larger than the influence of the potential of the extraction slit portion 8, so that electrons in the plasma 20 or ions of negative charge Are attracted to the control power supply 14, and a large amount of current flows into the control power supply 14 to cause a short circuit.

On the other hand, when the Debye length control means controls while satisfying the conditional expression (2), the ion emitting surface 20a of the plasma 20 is positioned in the plasma chamber 3 as shown in FIG. Will be done. In this case, since the acceleration voltage applied to the extraction slit portion 8 has a great influence on the ion emission surface 20a, most of the electrons or negatively charged ions emitted from the plasma 20 are transmitted to the control electrode 9. Before reaching, it will be pulled back toward the plasma chamber 3. Therefore, when the Debye length control means controls while satisfying the conditional expression (2), electrons or negatively charged ions in the plasma 20 are attracted to the extraction slit portion 8, and a large amount of current is generated by the control power supply 14. Therefore, the control power source 14 is not short-circuited to the control power source 14 to improve the reliability of the beam amount control.

After that, when the beam amount is reduced,
First, the saturated ion current density of the plasma 20 is lowered to a predetermined value, and thereafter, a desired beam amount is reset by the control voltage.

As described above, in the ion source of this embodiment, the ion emitting surface 20a of the plasma 20 is moved to the plasma chamber 3
While being positioned inside, the beam amount of the ion beam 17 is controlled by the control voltage applied to the control electrode 9. Therefore, the feedback control of the beam amount is
Since the time from detecting the changes in the extraction current I _ex and the beam current I _b to operating the control power supply 14 until the control voltage corresponds to the change amount is completed in a short time, the followability is improved. ing. Further, a large amount of electrons or negatively charged ions from the ion emitting surface 20a do not flow into the control power supply 14 via the control electrode 9, so that the reliability during feedback control is improved. This allows
The ion source of the present embodiment can maintain the beam amount at a desired value with high reliability and high accuracy.

Further, in the ion source of this embodiment, since the control electrode 9 is provided in the high frequency type ion source to control the beam amount, the control range of the beam amount is the conventional range (1-10 ^−). Wider range (1-10 ^-5 ) than ² ) and 1
It is possible to control the implantation amount in the range of 0 ¹¹ to 10 ¹⁶ P / cm ² , and it is possible to suppress the occurrence of contamination in the beam transport system, which has occurred when controlling the beam amount in the related art. There is.

Next, the ion source of this embodiment was subjected to the following condition 1
4 shows the measurement results when operated below.

First, as the condition 1, Ar gas was used as the working gas. Then, the Ar gas flow rate and the ECR magnetic field distribution are operated, the electron temperature kTe is +10 eV, and the coil currents Coil1 and Coil2 to the source magnets 6 and 6 are 69.7 A.
And 20.7 A, and M. W. By setting P (microwave power) to 141.3 Watt / 60.5 Watt, the Debye length λ _D is 10 λ _D to the short side distance a (1.
5 mm), so that the saturated ion current density j
_s was adjusted. After that, the control voltage of the control power supply 14 is set to 0V.
To 400 V, and the extraction current I _ex and the beam current I _b were measured to obtain the measurement results of FIG.

From the above measurement results, Ar gas was used as the working gas, and the Debye length λ _D was 10 λ _D
Under the condition that the short side distance a (1.5 mm) is present, by applying a control voltage of 0 V to 400 V to the control electrode 9, the extraction current I _ex is 800 μA to 20 μ.
It has been found that the range of A and the beam current I _b can be controlled within the range of 320 μA to 1 μA.

Then, under the condition 2, BF ₃ gas was used as the working gas. Then, the electron temperature kTe is + 10e
V, coil current to source magnets 6 and 6 Coil1 and Co
by setting il2 to 68.2A and 53.0A. W. By setting P to 241.7 watts / 20.9 watts and operating the Ar gas flow rate and the ECR magnetic field distribution, the Debye length λ _D is 10 λ _D to the short side distance a (1.
5 mm), so that the saturated ion current density j
_s was adjusted. After that, the control voltage of the control power supply 14 is set to 0V.
To 1,000 V, and the extraction current I _ex and the beam current I _b were measured to obtain the measurement results of FIG.

Thus, from the above measurement results, BF ₃
Using the gas as the working gas, the Debye length λ _D is 10 λ _D
-Under the condition of being present in the range of the short side distance a (1.5 mm), by applying a control voltage of 0 V to 1,000 V to the control electrode 9, the extraction current I _ex is 4 mA to 600 mA.
Range of μA, beam current I _b is 350 μA to 0.25 μA
It turned out that the range can be controlled.

Further, regarding the relationship between the extraction current I _ex and the beam current I _b when the control voltage is increased from 0 V to 1,000 V, the decrease in the extraction current I _ex is more remarkable than the decrease in the beam current I _b. . When the control voltage exceeds 400V,
It was also found that the extraction current I _ex was constant at 620 μA and the decrease rate of the beam current I _b was small.

Further, when the high frequency power from the magnetron 1 is increased so that the extraction current I _ex is increased above 4 mA, a short circuit occurs between the extraction slit portion 8 and the control electrode 9 and the control voltage is increased. Could not be raised. At this time, the electron temperature kTe is 10 eV and the extraction current I _ex
The Debye length λ _D calculated assuming that 4.4 mA / cm ² obtained from / (short side distance a × long side distance b) (slit size) is equal to the saturated ion current density j _s is 0.14 mm. Therefore, when the relationship of at least 10λ _D > short side distance a is established, the extraction slit portion 8 and the control electrode 9 are
It became clear that no short circuit with

Next, as condition 3, BF ₃ gas is used as an operating gas, the electron temperature kTe is +10 eV, and the coil currents Coil1 and Coil2 to the source magnets 6 and 6 are 67.2.
A. and 57.0 A. W. P
Was set to 241.9 watt / 3.0 watt, and the saturated ion current density j _s was adjusted so that the Debye length λ _D existed in the range of 10 λ _D to the short side distance a (1.5 mm).

After that, the control voltage of the control power supply 14 was increased from 0 V to 1,000 V, and the extraction current I _ex and the beam current I _b were measured to obtain the measurement result of FIG. 7. From this measurement result, BF ₃ gas was used as the working gas, and the Debye length λ _D was 10 λ _D to the short side distance a.
Under the condition of existing in the range of (1.5 mm), 0
By applying a control voltage of V to 1,000 V to the control electrode 9, the extraction current I _ex is in the range of 4 mA to 620 μA,
It has been found that the beam current I _b can be controlled in the range of 420 μA to 0.25 μA.

Also, regarding the relationship between the extraction current I _ex and the beam current I _b when the control voltage is increased from 0 V to 1,000 V, the decrease of the extraction current I _ex is similar to the case of the condition 2. It is more remarkable than the decrease of _b , and the control voltage is 400
It was also found that when V exceeds V, the extraction current I _ex becomes constant at 620 μA and the reduction rate of the beam current I _b decreases.

Next, as condition 4, BF ₃ gas is used as an operating gas, the electron temperature kTe is +10 eV, and the coil currents Coil1 and Coil2 to the source magnets 6 and 6 are 68.2.
A and M.38.8A. W. P
Was set to 107.7 watt / 8.3 watt, and the saturated ion current density j _s was adjusted so that the Debye length λ _D existed in the range of 10 λ _D to the short side distance a (1.5 mm).

After that, the control voltage of the control power supply 14 was increased from 0 V to 4,000 V, and the extraction current I _ex and the beam current I _b were measured to obtain the measurement result of FIG. From this measurement result, BF ₃ gas was used as the working gas, and the Debye length λ _D was 10 λ _D to the short side distance a.
Under the condition of existing in the range of (1.5 mm), 0
It was found that by applying a control voltage of V to 4,000 V to the control electrode 9, the extraction current I _ex can be controlled in the range of 160 μA to 10 μA and the beam current I _b can be controlled in the range of 3 μA to 0.03 μA.

Then, with the control voltage set to 0 V, the extraction current I _ex was controlled using the saturated ion current density j _s by the coil currents Coil1 and Coil2 so that the extraction current I _ex would be less than 160 μA. However, in this case, plasma could not be generated stably.
From this, it was revealed that the extraction current I _ex cannot be sufficiently controlled only by the control using the plasma generation condition, unlike the control using the control voltage. Incidentally, FIG.
And in FIG. 10, the beam current I _{b is set} to 0.
The stability when controlled to 35 μA and 35 nA is shown.

From the measurement results under the above conditions 2 and 6, the extraction current I _ex is 4 mA to 10 μA and the beam current I _b is 35 depending on the plasma generation conditions and the control voltage.
It became clear that stable control was possible from 0 μA to 0.03 μA. Furthermore, when the control voltage is set to a negative voltage, the extraction current I _ex is 30 mA and the beam current I _{b is}
Was also confirmed to increase to 3 mA, and the beam current I _b
It has been revealed that the control range of can be greatly increased.

In the present embodiment, the ion implantation apparatus is described using a high-frequency ion source mounted on a so-called high current ion implantation apparatus in which the beam energy is determined only by the extraction power source. It may be applied to a medium current type ion implantation apparatus having an accelerating tube. Further, it may be another type of ion source or may be mounted on a device other than the ion implantation device. Further, the control electrode 9 and the control power supply 14 may be used for controlling the increase / decrease of the beam amount and also used for emitting and stopping the ion beam 17. Further, as the slit length compared with the Debye length λ _D in the present embodiment, the short side distance a of the slit opening 3a is used, but the shape of the slit opening 3a is between two points of a straight line passing through the central portion. When there are multiple distances, the minimum distance is set.

[0057]

As described above, the ion source of the present invention has the extraction electrode system for extracting the ions in the plasma generated in the plasma chamber from the ion emission surface to the outside through the slit opening of the first electrode. However, the beam amount of the ion beam composed of the above ions is controlled to a predetermined value. The ion source is provided in the extraction electrode system, and the control voltage means for causing an arbitrary control voltage to exist outside the slit opening of the first electrode and the Debye length control for positioning the plasma ion emission surface in the plasma chamber. And means.

As a result, since the ion emitting surface is located in the plasma chamber, the influence of the first electrode on the ions and electrons is large together with the influence of the control voltage, so that a large amount of electrons and ions of the opposite polarity to the control voltage are produced. Since it does not flow into the control voltage means, the reliability at the time of control is improved, and the beam amount can be controlled to a predetermined value having a wide current amount control range with high reliability. .

[Brief description of drawings]

FIG. 1 illustrates the present invention and is an explanatory diagram showing a state of an ion source mounted on an ion implantation apparatus.

FIG. 2 is an explanatory diagram showing a potential distribution of an ion source.

FIG. 3 is an explanatory diagram showing a state of an ion emission surface of plasma.

FIG. 4 is an explanatory diagram showing a state of a plasma ion emitting surface.

FIG. 5 is a graph showing the relationship between the control voltage and the extraction current and beam current.

FIG. 6 is a graph showing a relationship between a control voltage and a drawing current and a beam current.

FIG. 7 is a graph showing a relationship between a control voltage and a drawing current and a beam current.

FIG. 8 is a graph showing a relationship between a control voltage and a drawing current and a beam current.

FIG. 9 is a graph showing a relationship between a beam current of 0.35 μA controlled by a control voltage and time.

FIG. 10 is a graph showing a relationship between a beam current of 35 nA controlled by a control voltage and time.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 magnetron 2 waveguide 3 plasma chamber 3a slit mouth 5 liner 6 source magnet (Debye length control means) 7 extraction electrode system 8 extraction slit part (first electrode) 9 control electrode (control voltage means) 10 extraction electrode 11 ground electrode 12 Extraction Power Supply 13 Resistor 14 Control Power Supply (Control Voltage Means) 15 Deceleration Power Supply 16 Ion Irradiation Target 17 Ion Beam 18 Faraday Part 19 Mass Spectrometer 20 Plasma 20a Ion Emission Surface

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yoshinori Saito, Yoshinori Saito, 47 Umezu Takaunecho, Ukyo-ku, Kyoto Prefecture, Nissin Electric Co., Ltd. Within the corporation

Claims (1)

[Claims] 1. An extraction electrode system for extracting ions in plasma generated in a plasma chamber from an ion emission surface to the outside through a slit opening of a first electrode, and a beam amount of an ion beam composed of the ions is provided. In an ion source controlled to a predetermined value, a control voltage means provided in the extraction electrode system for causing an arbitrary control voltage to exist outside the slit opening of the first electrode, and an ion emission surface of the plasma in the plasma chamber. An ion source having Debye length control means for positioning.