JPH05135723A - Beam expander - Google Patents

Abstract

PURPOSE:To provide a high-energy ion implanter having a small beam expander, capable of being operated with a high-frequency power source having the power of about 1kW, and being utilized for the semiconductor industry at a low cost. CONSTITUTION:A pair of long electrodes 2, 2 and a pair of short electrodes 3, 3 are supported by the conducting first and second posts 5, 6 erected on a conducting base 4. When the preset high-frequency power is fed from a high- frequency power source, the quadruple electric field and the double electric field are generated in resonance. The length of the long electrodes 2, 2 is equal to the distance that charged particles advance in one cycle of the resonance frequency, and the length of the short electrodes 3, 3 is 1/2 of the length of the long electrodes 2, 2. A beam expander 1 is installed at the later stage of a bunching means, and a beam bunch is fed at every preset interval. When the beam expander 1 is operated synchronously with the feed of the beam bunch in response to the incidence timing of the beam bunch into the beam expander 1, the cross section of the beam bunch can be expanded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a beam expander for use in a high-energy ion implantation apparatus, which expands the cross-sectional area of a high-energy ion beam having a high power density to reduce the power density.

[0002]

2. Description of the Related Art An ion implantation apparatus ionizes impurities to be diffused, selectively extracts these impurity ions by mass spectrometry using a magnetic field, accelerates them by an electric field, and irradiates the ion irradiation target with the ions. Impurities are injected into the irradiation target. This ion implantation apparatus is an important apparatus for manufacturing integrated circuits at present because it can implant impurities that determine device characteristics in a semiconductor process to an arbitrary amount and depth with good controllability.

In recent years, semiconductor device manufacturers have been using CM
There is an increasing need for a MeV-class high-energy ion implanter having advantages such as formation of retrograde wells and post-ROM writing in the OS device manufacturing process.

One of the above high energy ion implanters is a high frequency linear accelerator (hereinafter referred to as R
There is one using an F accelerator) 27, an example of which is shown in FIG.

This high-energy ion implanter mass-analyzes the ions extracted from the ion source 21 by the extraction power source 22 by the mass analyzer 23 to selectively derive only ions of a predetermined mass, which are accelerated by a power supply 25. After being accelerated to an energy suitable for the RF linear accelerator 27 by the electrostatic accelerating tube 24 connected to the RF accelerating tube, and further subjected to beam shaping by the focusing system 26 such as a Q lens, the high frequency power from the high frequency power supply 28 is supplied to the RF. After being introduced into an accelerator 27, the above ions are accelerated to a predetermined high energy, and then the target 29 such as a wafer in an implantation chamber (not shown) is irradiated.

In the RF accelerator 27, a beam having a low emittance is preferred in order to improve the beam transmission, and also in consideration of acceleration efficiency. After passing through the accelerator, the beam has a substantially circular cross section with a diameter of 10 m.
It is generally around m. So, for example, RF
Beam current 1mA accelerated to 1MeV by accelerator 10
The target ion 29 is irradiated with the ion beam of the above with a power density of about 1 kW / cm ² .

[0007]

However, when the ion implantation is performed with the high power density as described above, the temperature of the target 29 is greatly increased and the charge-up easily occurs. Therefore, unless the power density at the time of ion implantation is lowered, it cannot be accepted in the current semiconductor industry.

At present, the ion implantation equipment used for manufacturing semiconductor devices has an acceleration energy of 10-80.
There is a so-called high-current ion implanter that can perform ion implantation under the conditions of about keV and a beam current of about 20 mA or less. In this case, a mechanical scan method is used, and a power density of about 40 W / cm ² on a silicon wafer. Ion implantation is now possible.

That is, even in the high energy ion implanter, the power density of the beam must be reduced to at least this level (about 40 W / cm ² ). For this purpose, the beam current must be extremely reduced, but this also results in an extremely small ion implantation amount (dose amount), which limits the use of the high energy ion implantation apparatus in the semiconductor industry. For the above reasons, the high energy ion implanter is still unaccepted in the semiconductor industry.

It is possible to use an electrostatic lens as one means for reducing the power density of the beam. That is, an electrostatic lens that functions as a diverging (concave) lens is provided on the downstream side of the RF accelerator 10 to enlarge the cross-sectional area of the beam with which the target 28 is irradiated. However,
In this case, one electrostatic lens diverges the beam only linearly, so in order to construct a divergent lens, electrostatic lenses must be combined in multiple stages (at least two stages). The device becomes very large. Further, in order to sufficiently expand the cross-sectional area of the beam in a short distance by using the electrostatic lens, a power supply with a very high voltage is required. From the above, the electrostatic lens is difficult to be practically used, and in reality, has not been industrially used.

The present invention has been made in view of the above, and an object thereof is to have a high power density so that a high energy ion implantation apparatus can be used in the semiconductor industry.
An object of the present invention is to provide a small beam expander capable of inexpensively expanding the cross-sectional area of a high-energy ion beam.

[0012]

In order to solve the above-mentioned problems, a beam expander of the present invention comprises a pair of long electrodes facing each other in a direction perpendicular to the traveling direction of a charged particle beam passing through a vacuum atmosphere. And has a length that is approximately half that of the long electrode, is arranged in parallel with one half of the long electrode divided at the center of the length, and faces each other in a direction orthogonal to the facing direction of the pair of long electrodes. A pair of short electrodes and a standing conductive base,
A conductive post that supports the pair of long electrodes and the pair of short electrodes, resonates when supplied with a predetermined high-frequency power from a high-frequency power supply, and collects the charged particle beams in a predetermined manner. It is characterized in that the lengths of the pair of long electrodes, which are installed in the latter stage of the bunch means that emits in the state of beam bunching at intervals, are approximately equal to the distance traveled by charged particles in one cycle of the resonance frequency.

[0013]

With the above arrangement, the beam expander is
It has a structure in which a pair of long electrodes and a pair of short electrodes are supported by conductive posts that are erected on a conductive base, and the short electrodes are approximately half the length of the long electrodes. It is arranged in parallel with one half of the one divided at the center.

This beam expander is a resonator coupled by a capacitance between electrodes and an inductance of a post. If a high frequency power of a predetermined frequency is supplied from the high frequency power supply to the resonator to resonate the beam expander, a beam of a charged particle beam is generated. A quadrupole electric field is generated in a portion where one half of a pair of long electrodes and a pair of short electrodes are arranged in parallel in a direction perpendicular to the traveling direction, and the other half of the pair of long electrodes is divided. An electric field (hereinafter, this is referred to as a dipole electric field) to which a polarity voltage having the same polarity with respect to the ground potential is applied is generated in each of the portions.

The length of the long electrode is substantially equal to the distance traveled by the charged particles in one cycle of the resonance frequency. Therefore, the charged particle beam incident on the beam expander has a quadrupole or two poles.
After passing through one of the electric fields of the heavy pole, it enters into the other electric field after a half cycle, and is emitted from the beam expander after this half cycle.

Further, the beam expander is installed after the bunch means for bundling the charged particle beam, and therefore,
The charged particle beam is incident on the beam expander in a state of a beam bunching at predetermined intervals. Therefore, the resonance frequency crosses the zero point at 0 ° or 18 ° in accordance with the timing of incidence of this beam group on the beam expander.
By adjusting the high-frequency power supply from the high-frequency power supply so that the phase becomes 0 °, the polarities of the electrodes can be maintained while the beam cluster passes through the electric field of either the quadrupole or the double pole. Does not change, and the polarity of the electrodes is reversed when the beam cluster enters the other electric field after half a period.

For example, when the charged particles are cations,
If the beam expander is operated in synchronism with the beam bunching so that the long electrode that generates the double pole electric field becomes the cathode while the beam bunching passes through the double pole electric field, the beam bunching will be performed. As it passes through the electric field, it is diverged in the opposing direction of the pair of long electrodes. In this case, when the beam cluster passes through the quadrupole electric field, the pair of long electrodes become the anode, and the pair of short electrodes become the cathode with a phase difference of 180 ° with the long electrode, and the beam cluster becomes The light is focused in the facing direction of the pair of long electrodes and diverged in the facing direction of the pair of short electrodes. As a result, the beam cluster exiting the beam expander is greatly expanded through an appropriate drift space, and the power density of the beam is reduced.

When the charged particles are negative ions, the cross section of the beam cluster can be expanded in the same manner as above by operating the beam expander with the phase of the resonance frequency being delayed by 180 ° compared to the case of the positive ions.

In the above beam expander, for example, if the charged particles are boron with an energy of 800 keV and the resonance frequency is 33 MHz, the length of the long electrode is 11c.
It can be about m. As described above, the beam expander is small, and by supplying high-frequency power of about 1 kW, the cross section of the charged particle beam can be sufficiently expanded, and the beam power density can be reduced at low cost.

[0020]

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

The beam expander 1 of this embodiment is shown in FIG.
As shown in FIG. 5, it is installed after the RF accelerator 27 in the beam transport section of the high energy ion implanter.

The high-energy ion implanter mass-analyzes ions as charged particles extracted from the ion source 21 by the extraction power source 22 by the mass analyzer 23 to selectively derive only ions of a predetermined mass. Is accelerated to an energy suitable for the RF accelerator 27 by the electrostatic accelerating tube 24 connected to the accelerating power source 25, and is further beam-shaped by the focusing system 26 such as a Q lens, and then high-frequency power is supplied from the high-frequency power source 28. RF accelerator 2
7 is used to accelerate the ions to a predetermined high energy, and then the beam expander 1 expands the beam cross section to reduce the power density and irradiates a target 29 such as a wafer in the implantation chamber. There is.

The RF accelerator 27 has a structure in which four rod-shaped electrodes having the same length are arranged around the center of the electrode at intervals of 90 °, and these electrodes are supported by conductive posts. , A so-called 4 Rod-RFQ type linear accelerator is used.

The RF accelerator 27 is a resonator coupled by a capacitance between electrodes and an inductance of a post, and when a high frequency power of a predetermined frequency is supplied from a high frequency power source 28 to resonate, the direction of the ion travels. A quadrupole electric field is formed in the orthogonal direction.

In the case of the RF accelerator 27, a modulation (wave) is formed on its electrode, an accelerating electric field is created in the direction of the central axis of the electrode, and the beam is converged and accelerated simultaneously.

Further, a bunch part for bunching the beam is formed at the beam entrance part of the RF accelerator 27 as the bunch means so that the beam can be easily accelerated. Therefore,
The incident beam of the RF accelerator 27 is first bunched at the bunch part, then accelerated while being converged, and is emitted in the state of a beam cluster having a substantially circular cross section (diameter is about 10 mm) as shown in FIG. The beams are sequentially incident on the beam expander 1 at regular intervals.

As shown in FIG. 1, the beam expander 1 is orthogonal to a pair of long electrodes 2 and 2 facing each other in the direction perpendicular to the ion traveling direction, and the facing direction of the long electrodes 2 and 2. It has a pair of short electrodes 3 facing each other in the direction.

The short electrodes 3 and 3 have a length L ₂ which is approximately half the length L ₁ of the long electrodes 2 and 2 and one half-divided portion 2a obtained by dividing the long electrode 2 at the center of the length. It is arranged in parallel with. Therefore, the beam expander 1 is composed of a quadrupole part A composed of one half-divided portion 2a of the long electrode 2.2 and the short electrode 3.3, and the other half-divided portion 2b of the long electrode 2.2. It is divided into two parts, the double pole part B.

The length L ₁ of the long electrodes 2 and 2 is designed to be substantially equal to the distance traveled by the ions in one cycle of the resonance frequency. That is, if the velocity of ions after passing through the RF accelerator 27 is v, the velocity of light in vacuum is c, and the wavelength of resonance is λ, then L ₁ = βλ (β = v / c). For example, when boron, which is a cation, is accelerated by the RF accelerator 27 at an acceleration voltage of 800 keV, if the resonance frequency is 33 MHz, the length L ₁ of the long electrode 2.2 is about 11 cm.

Further, the length L ₂ of the short electrode 3.3 is _{L 2 = L 1/2 =} βλ / 2, therefore, the length of the quadrupole unit A and the dipole section B, both It becomes βλ / 2.

One end of each of the long electrodes 2 and 2 is supported by a conductive first post 5 standing on one end of a conductive flat plate-shaped base 4, and one end of each of the short electrodes 3 and 3 is It is supported by a conductive second post 6 provided upright on the other end of the base 4. Long electrode 2.2 and short electrode 3
Since the electrode length of 3 is relatively short, there is no problem even with the above cantilever structure.

The beam expander 1 is a resonator coupled by a capacitance between electrodes and an inductance of a post. The beam expander 1 is supplied with high frequency power of a predetermined frequency from a high frequency power source 28 to cause resonance. Then, in the direction perpendicular to the ion traveling direction, a quadrupole electric field is applied in the quadrupole part A, and a polar voltage of the same polarity with respect to the ground potential is applied in the double pole part B (hereinafter, It is called a dipole electric field). There is no modulation (wave) formed on the electrodes of the RF accelerator 27 in the long electrodes 2.2 and the short electrodes 3.3, and an accelerating electric field cannot be generated in the central axis direction of the electrodes.

In this embodiment, the beam expander 1 described above is used.
4 is arranged in the beam transvoting section so that the beam group is made incident from the quadrupole section A and is emitted from the double pole section B, as shown in FIG. The beam expander 1 may be arranged such that the beam cluster is made incident from the double pole portion B and emitted from the quadrupole portion A.

Since the lengths of the quadrupole part A and the double pole part B of the beam expander 1 are both βλ / 2, the quadrupole after the beam cluster is incident on the beam expander 1. The phase of the resonance frequency advances 180 ° while passing through the section A, and then the phase advances by another 180 ° while the beam cluster passes through the double pole section B.

The beam expander 1 is operated in synchronization with the RF accelerator 27 so that the phase of the resonance frequency when the beam group is incident on the quadrupole part A becomes 0 °. Specifically, the phase is adjusted by extracting monitor signals from the cavities of both the RF accelerator 27 and the beam expander 1 and synchronizing them.

Therefore, while the beam cluster passes through the quadrupole part A, the polarities of the quadrupole part A are as shown in FIG. While 3 becomes a cathode, while the beam cluster passes through the double pole portion B, the long electrode 2.2 of the double pole portion B becomes a cathode.

For this reason, when a beam cluster of positive ions such as boron passes through the beam expander 1, as shown in FIG. It is focused in the Y direction in the drawing and diverges in the facing direction of the short electrodes 3 and 3 (X direction in the drawing), and in the double pole portion B, the facing direction of the long electrodes 2 and 2 (Y direction). Direction).

In the above structure, as shown in FIG.
Positive ions such as boron extracted from the ion source 21 (FIG. 2) are accelerated by the RF accelerator 27 and are incident on the beam expander 1 in a beam cluster state. The beam expander 1 receives high-frequency power of a predetermined frequency from the high-frequency power supply 28, and generates a quadrupole electric field in the quadrupole part A.
In the double pole portion B, a double pole electric field is generated.

In this case, the beam expander 1 is phase-adjusted so that the phase of the resonance frequency when the beam group is incident on the quadrupole A is 0 °.
As a result, the beam cluster that has entered the beam expander 1 is focused in the Y direction and diverged in the X direction at the quadrupole portion A as shown in FIG. B enters and diverges in the Y direction at the double pole portion B.

As described above, if the length L 1 of the long electrodes 2 and 2 of the beam expander ₁ is about 11 cm, the high frequency power source 28 has a power of about 1 kW and the distance between the long electrode 2 and the short electrode 3 is large. A voltage of about 50 kV can be applied. In this case, for example, if the energy of the ions incident on the beam expander 1 is 500 keV, in the case of monovalent cations such as boron, the divergence angle α (r
ad) is α≈v _T / v _L = (50/500) ^1/2 ≈0.
It is 3 (rad), which means that a relatively large divergence angle is given. In the above equation, v _L is the velocity of the ion in the advancing direction, v _T is the velocity of the ion in the Y or X direction, and if the mass of the ion is m, then 500 = mv _L ²
/ 2,50 = is the mv _T ^2/2.

As a result, the beam cluster emitted from the beam expander 1 is moved to the target 2 as shown in FIG.
The target 29 is greatly expanded in a suitable drift space until reaching 9 and the power density is reduced.
Is irradiated.

As described above, by using the present beam expander 1, it becomes possible to perform ion implantation under conditions of low power density (for example, about 40 W / cm ² ) which cannot be achieved by the conventional high-energy ion implantation apparatus. Therefore, the high-energy ion implanter can be sufficiently used in the semiconductor industry.

In particular, the present beam expander 1 has a small length L ₁ (that is, device length) of the long electrodes 2 and 2 of about 11 cm. The size of the injection device is slightly increased.

The beam expander 1 is 1 kW.
It can be put into practical use by using a high frequency power source 28 having a power of about the same level.
Can be shared with F accelerator 27. Therefore, by using the present beam expander 1, it is possible to realize a high-energy ion implanter that can be used in the semiconductor industry at low cost.

In this embodiment, it is explained that the beam cross section of cations such as boron is enlarged.
When enlarging the beam cross section of the negative ions, the phase of the resonance frequency when the beam cluster of the negative ions is incident on the quadrupole portion A is 180 ° (that is, the phase is 180 degrees more than that in the above embodiment). Delay)) and operate in synchronization with the beam bunch of the RF accelerator 27.

[0046]

As described above, the beam expander of the present invention has a pair of long electrodes facing each other in a direction perpendicular to the traveling direction of a charged particle beam passing through a vacuum atmosphere, and approximately half of the long electrodes. And a long electrode, which is arranged in parallel with one half of the long electrode divided at the center of the length, and has a pair of short electrodes facing each other in a direction orthogonal to the facing direction of the pair of long electrodes, and a conductive member. A beam expander that is erected on a flexible base and has a conductive post that supports the pair of long electrodes and the pair of short electrodes and that resonates when supplied with a predetermined high frequency power from a high frequency power supply. The pair of long electrodes are installed at a stage subsequent to the bunch means for collecting the charged particle beams and emitting them in a beam collecting state at a predetermined interval.
The configuration is such that the distance traveled by the charged particles in a cycle is approximately equal.

Therefore, if the beam expander is operated in synchronization with the incidence of the beam bunches, the cross section of the beam bunches can be enlarged. This beam expander is small and
It can be operated by using a high-frequency power source with a power of about kW, and for example, the cross-sectional area of a high-energy ion beam with high power density, which is accelerated and converged by an RF accelerator of a high-energy ion implanter, can be inexpensively expanded. .. Therefore, it is possible to realize a high-energy ion implanter that can be used in the semiconductor industry at low cost.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention and is a schematic perspective view of a beam expander.

FIG. 2 is a main part configuration diagram showing a high-energy ion implantation apparatus using the beam expander.

FIG. 3 is an explanatory diagram showing a group of beams before and after passing through the beam expander.

FIG. 4 is an explanatory view showing a cross section of a beam group passing through the beam expander and electrode polarities of the beam expander.

FIG. 5 is an explanatory diagram showing a divergence angle of a beam cluster passing through the beam expander.

FIG. 6 is a main part configuration diagram showing a conventional high-energy ion implanter.

[Explanation of symbols]

 1 Beam Expander 2 Long Electrode 3 Short Electrode 4 Base 5 1st Post (Post) 6 2nd Post (Post) 27 RF Accelerator (Bunch Means) 28 High Frequency Power Supply

Claims (1)

[Claims] 1. A pair of long electrodes facing each other in a direction perpendicular to a traveling direction of a charged particle beam passing through a vacuum atmosphere, and having a length which is about half of the length of the long electrodes, and the long electrode has a length of A pair of short electrodes, which are arranged in parallel with one half-divided portion divided at the center and face each other in a direction orthogonal to the facing direction of the pair of long electrodes,
A beam expander that is erected on a conductive base, has a conductive post that supports the pair of long electrodes and a pair of short electrodes, and resonates when supplied with a predetermined high-frequency power from a high-frequency power supply. The bunch means for collecting the charged particle beam and emitting the beam in a beam collecting state at a predetermined interval is installed at a stage subsequent to the bunch means. The length of the pair of long electrodes is the distance traveled by the charged particle in one cycle of the resonance frequency. A beam expander characterized by being approximately equal.