JPH07281000A - Charge convertor for measuring beam quantity - Google Patents

Abstract

PURPOSE:To measure a neutron quantity in addition to charge conversion by passing charged particles in a high speed gas fluid, converting electric charge into neutron particles, and immediately detecting ions produced in the gas fluid as electric current. CONSTITUTION:A pass hole 16 of beams 1, 2 is provided halfway of a gas divergent nozzle 5. Gas flow 3 which is made expansion and high speed with the nozzle 5 from a gas reservoir 4 becomes a supersonic jet and has directivity in a tank 6. After the gas flow 3 collides with the ion beam 1 and electric charge is converted, and exhausted. Gas 13 ionized in the gas flow 3 by bias voltage of a power source 9 is collected in the nozzle 5. When it is collected, electric current is allowed to flow to the ground, measured with an ammeter 10, and a charged quantity of the ionization gas 13 can be measured. Because the charged quantity is equal to the other charged quantity in which the gas flow 3 is charge-converted from the charged particle beam 1 into the neutron particle beam 2, the current of the ammeter 10 is proportional to charge- converted neutron particle quantity. Thereby, the measurement of the neutron particle quantity can be made possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a beam charge converter for converting a charge of a high-speed charged particle beam such as an ion beam into a neutral particle beam, which is used in the manufacture of semiconductors. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a beam amount measurement charge conversion device capable of measuring the amount of functional particles.

[0002]

2. Description of the Related Art Conventionally, a device called a gas cell shown in FIG. 4 has been used for this type of charge conversion device. In the gas cell, a gas container 6 having a hole 16 through which a particle beam passes is placed in a vacuum container, and the gas container 6 is passed through a charged particle beam 1 and brought into contact with a gas 3 introduced from a gas introduction pipe for charge conversion. It is a thing. Further, as a gas of a gas cell called a metal vapor cell, there is a gas in which an alkali metal vapor such as Li is used to bring charged particles and metal vapor into contact with each other through the charged particle beam 1 for charge conversion.

[0003]

However, since the gas 3 introduces the gas 3 into the gas container 6 located in the vacuum container, the hole 16 of the gas container 6 is provided for the purpose of preventing deterioration of the degree of vacuum due to pressure diffusion from the gas cell. Was small. Therefore, a large number of gas particles and charged particles in the gas cell cannot be obtained. Further, in the metal vapor cell, the beam amount is limited to maintain the degree of vacuum as in the gas cell, and since the alkali metal to be treated is chemically active, the container body must be damaged and it is necessary to be careful in handling.

Recently published Japanese Patent Laid-Open No. 5-12909
According to the charge neutralization method using a molecular beam of Japanese Patent Publication No. 6, in the case of a molecular beam, the charge conversion efficiency is poor because the number of molecules is small, and charge conversion of a large amount of beams is difficult.
Further, in the above method, when a large amount of ion beams are converted into neutral beams, the size of the device becomes large. The above-mentioned drawbacks exist in various conventional charge conversion devices.

Further, even if the charged particles are neutralized, there is no means for immediately measuring the amount of the neutral particles.

The present invention has been made in view of the above circumstances, and provides an apparatus capable of highly efficiently performing charge conversion on a beam having a high energy and a large beam amount and measuring the obtained neutral particle amount. The purpose is to do.

[0007]

A beam quantity measuring and charge converting apparatus of the present invention is an apparatus for converting charges of charged particles in a high-speed particle beam source such as an ion beam. Through which the charge is converted to form neutral particles, and at the same time, the amount of neutral particles to be converted in charge is monitored by detecting the ions generated in the high-speed gas fluid as a current.

[0008]

The ion particle beam is converted into the neutral particle beam by passing the charged particle beam through the high-speed gas fluid and converting the charge, so that the high-speed gas fluid diverges from the hole of the gas container to the outside of the gas container. That problem can be prevented. Therefore, for example, by increasing the contact area between the gas fluid and the charged particle beam by enlarging the hole of the gas container, it is possible to achieve high efficiency of charge conversion, and thus to achieve high energy of the beam. it can. Then, when the charged particle beam is passed through the high-speed gas fluid to be charge-converted to form a neutral particle beam, the high-speed gas granules are charged with excess charges that have been charged and converted. Therefore, the high-speed gas fluid is charged by the charge converted charge,
Ionize. The ionized amount in the gas fluid can be measured by collecting the ionized gas fluid in the ion collection electrode and measuring the current value. The amount of the functional particles can be measured.

[0009]

1 to 3 show the first to third embodiments of the beam charge conversion device according to the present invention. Reference numeral 1 in each figure
Is an ion beam before charge conversion, reference numeral 2 is a neutral particle beam after charge conversion, reference numeral 3 is a high-speed fluid such as a gas that contacts the beam 1 before charge conversion to perform charge conversion, and reference numeral 4 is a reservoir tank for the gas 3. Is. Reference numeral 5 indicates that the gas 3 is a supersonic flow,
A divergent nozzle for making the velocity component of the gas 3 into a direction component perpendicular to the beam 1, reference numeral 6 is a vacuum container of the beam charge conversion device, and reference numeral 7 is a vacuum pump for exhausting the gas 3 emitted from the nozzle 5. . If the shape of the nozzle 5 and the gas pressure in the reservoir tank 4 are selected to be appropriate values, the gas 3 that comes out of the nozzle 5
Becomes a supersonic velocity, and it is less likely that the beams 1 and 2 passing through the container 6 will pass through the holes 16 for passage, and a large pressure difference with the outside of the container 6 can be secured. Reference numeral 8 is an insulator made of ceramic or the like for making the potential of the nozzle 5 independent of the vacuum container 6, and reference numeral 9 is a potential for electrostatically capturing the ionized gas 13 in the ion collecting electrode of the Suehiro nozzle 5 or the like. A bias power source to be applied, reference numeral 10 is an ammeter for measuring an ion current flowing into the divergent nozzle 5, and reference numeral 11 is a shield plate for preventing the charged particle beam 1 before charge conversion from irradiating the nozzle 5 to measure an erroneous current. . Reference numeral 12 is normally grounded and is connected to the vacuum container 6.

In FIG. 1, a hole 16 for passing the beams 1 and 2 is provided in the middle of the gas divergent nozzle 5. With such a structure, the charged particle (ion) beam 1 is passed through the gas fluid which is expanded at a high speed by the gas nozzle 5 from the gas reservoir tank 4.
Can be passed through to convert the charge to form the neutral particle beam 2.

FIG. 2 shows the nozzle 5 of the gas reservoir tank 4.
From B, the gas fluid is a free jet in the vacuum container 6. Reference numeral 14 is an electrode for collecting the ionized gas other than the nozzle 5. Holes 16 for passing beams 1 and 2
Are provided on the upper and lower surfaces of the container 6 and the electrode 14. With such a structure, the high-speed gas fluid that has become a free jet from the nozzle 4B of the gas reservoir tank 4 is filled with the holes 16 of the container 6.
The charged particle (ion) beam 1 can be passed through to convert the charge to form the neutral particle beam 2.

FIG. 3 shows a gas divergent nozzle 5 inside a container 6.
Is provided, and the charged particle beam 1 entering through the hole 16 of the container 6 and the expanded and high-speed gas are converted into a neutral particle beam 2 and emitted from the hole 16. Reference numeral 15 is an electrode electrically insulated from the gas nozzle 5, which collects the ionized gas 13 by applying a potential from the power supply 9. Here, the ion collecting electrode 15 has a rod shape.

For example, if the cross-sectional area of the throttle portion of the nozzle 5 is S1,
Assuming that the nozzle enlarged area is S2, S2 / S1 = 30, the pressure of the reservoir tank 4 is 1300 Pa, and the gas is Ar, the Ar gas discharged from the nozzle 5 has a pressure of 0.74 Pa.
Is a supersonic jet with a Mach number of about 7 and has directivity inside the container 6. The high-speed gas fluid 3 collides with the ion beam 1 and undergoes charge conversion, and is then exhausted by the vacuum pump 7. As an effect of this structure, it is possible to achieve a high rate of collision between the ion beam and the high-speed gas fluid inside the container 6 while keeping the outside of the container 6 in a high vacuum. Therefore, a large amount of neutral particle beams can be obtained.

High-speed gas fluid 3 made of Ar gas, for example
Removes the electric charge of the ion beam (charged particle) 1 and converts the charge into a neutral particle beam 2. At that time, a part of Ar particles of the high-speed gas fluid 3 itself is charged (ionized) to generate Ar ⁺ It becomes gas 13. 1 to 3, the ionized Ar ⁺ gas 13 has an electron energy (e
In terms of V) unit, it is about 0.06 eV in the present embodiment, so the nozzle 5 or the ion collecting electrodes 14, 15 are used.
A bias voltage of about -1 V is sufficient to trap the ionized gas 13. However, considering that the energy that the ionized gas has when it is separated is about several eV and the energy of the electron that is generated when the gas and the ion collide is about 5 to 30 eV, the nozzle 5 or the ion collection electrode 14, The voltage applied to 15 may be 50 V or higher.

Due to the bias voltage of the power supply 9, the ionized gas 13 in the high-speed gas fluid 3 is applied to the divergent nozzle electrode 5 in the embodiment of FIG. 1, to the collection electrode 14 in the embodiment of FIG. In the third embodiment, the collection electrode 15
To be collected by. When the ionized gas 13 is collected by the electrodes 5, 14 and 15, a current flows to the ground 12,
This current is measured by the ammeter 10 and the charge amount of the ionized gas 13 can be measured. Since the amount of charge of the ionized gas 13 is equal to the amount of charge of the beam in which the high-speed gas fluid 3 is charge-converted from the charged particle beam 1 to the neutral particle beam 2, the current measured by the ammeter 10 is converted into the charged one. It is proportional to the amount of the functional particles. Therefore, since the neutral particle beam is electrically neutral, it has not been possible to electrically measure the amount of neutral particles in the past. In addition, the amount of neutral particles can be measured.

Next, the high speed gas fluid 3 will be described.
The molecular velocity of a high-speed gas fluid is supersonic (5 at Mach number M).
>M> 1.2) or hypersonic speed (Mach number M, M> 5)
Is preferred. The gas flow rate a is a = (KRT) ^1/2 where K: specific heat ratio, R: gas constant, T: temperature In the case of Ar gas, K = 1.658, R = 208.15, T = 20 ( K
°) is required to have a flow velocity of about 100 to 415 m / s for supersonic velocity> 415 m / s for hypersonic velocity. The shape of the nozzle as described above,
By selecting gas pressure etc. appropriately, supersonic nozzle,
Hypersonic nozzles can be manufactured. By preparing a nozzle having a wide range of flow velocities, it becomes possible to select a gas fluid velocity matching the energy (velocity) of various charged particle beams to be subjected to charge conversion. Thereby, the controllability of the probability of charge conversion of high-energy particles can be improved, and the conversion efficiency can be increased.

The free molecular flow state of a high-speed gas fluid is defined as the mean free path of gas (λ) / representative dimension of nozzle (L)> 1. λ / L is called the Knudsen number, and it is preferable for charge conversion that a high-speed gas fluid having a Knudsen number of 1 or more is in a free molecular flow state. Mean free path λ = 2.3 × 10 ⁻²⁰ T / Pa ² (c
m) where T: temperature (° K), P: pressure (Torr), a:
Since the molecular diameter (cm) is Ar gas, T = 20 (° K), P = 1 × 10 ⁻⁵ (Torr) a =
When 3.67 × 10 ⁻⁸ (cm) and λ> 34 (cm), a free molecular flow state is established.

The beam charge conversion apparatus of this embodiment differs from the usual gas introduction method of a charge conversion gas cell in that the use of a nozzle allows the passage of charged particles without deteriorating the vacuum degree outside the gas container as compared with the conventional one. The holes to be formed can be enlarged, and the neutral particle beam can be obtained in high efficiency and in a large amount as compared with the conventional one. This is achieved by selecting the nozzle size to an appropriate value so that the velocity of the fluid exiting the nozzle has almost no velocity component in the beam passage hole direction.

Further, since the high-speed flow from the nozzle undergoes adiabatic expansion, a high-speed fluid having a higher density than that in the gas cell container at the same pressure, that is, a high-speed fluid having a large number of particles can be achieved, so that the charge conversion probability is improved. . By using a high-speed fluid, the pressure difference between the gas container and the vacuum container can be made sufficiently large. That is, a large amount of gas can be introduced into the gas container without deteriorating the degree of vacuum outside the container. The gas in the gas container that has passed through the vicinity of the charge conversion hole is exhausted by a vacuum pump for the gas container or is circulated and reused to prevent the gas from diffusing into the entire vacuum system.

In the conventional charge conversion device, the gas and metal vapor in the gas container have a random velocity with respect to the beam passage hole of the container, and therefore diffuse and deteriorate the pressure in the vacuum container. The apparatus of this embodiment can perform charge conversion with high efficiency and can obtain a large amount of beams. In particular, it is effective for the conversion of high-energy charged particles and is difficult to achieve by several Me
It is also possible to neutralize the beam of about V. Also, the size of the nozzle can be reduced, and the charge conversion device can be downsized accordingly.

In the above description, a high-speed gas fluid using Ar gas or the like has been explained, but as a high-speed gas fluid, N is used.
A metal vapor such as a, Ka or Cs, or a liquid such as liquid nitrogen may be used. By using various kinds of high-speed fluids, it is possible to cope with charge conversion of charged particles beams of various elements and various energies. As described above, various modifications can be made without departing from the spirit of the present invention. Further, the same reference numerals in the respective drawings indicate the same or corresponding parts.

[0022]

As described above, according to the present invention,
It is possible to prevent the deterioration of the degree of vacuum outside the charge conversion device, achieve a large amount of highly efficient beam charge conversion with a small device, and monitor the amount of neutral particles that have undergone charge conversion. According to the charge conversion device of the present invention, a large amount of electrically neutral particle beams can be obtained, and the amount of neutral particles can be measured.
Therefore, for example, a predetermined amount of neutral particles can be implanted instead of the ions of the ion implantation technique of implanting impurities into the semiconductor. This eliminates the problem of charge-up that occurs when impurities are ion-implanted on an insulating film, not by using neutral particles, and also achieves precise dose control, which is an advantage of ion-implantation devices, which is a major industry concern. You can expect an effect.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a beam amount measurement charge conversion device according to a first embodiment of the present invention, in which a beam passage hole is provided in the middle of a divergent nozzle.

FIG. 2 is an explanatory diagram of a beam amount measuring / charge converting device according to a second embodiment of the present invention, in which a gas fluid is made into a free jet from a nozzle of a reservoir tank.

FIG. 3 is an explanatory view of a beam amount measuring charge conversion device according to a third embodiment of the present invention, in which a divergent nozzle is provided inside the container.

FIG. 4 is an explanatory diagram of a conventional beam charge conversion device.

[Explanation of symbols]

 1 Beam before charge conversion 2 Beam after charge conversion 3 High-speed gas fluid 4 Reservoir tank 5 Suehiro nozzle 6 Container 7 Vacuum pump 8 Insulator 9 Bias voltage source 10 Ammeter 11 Ion beam shield plate 12 Grounding 13 Ionized gas 14 , 15 Ion collector electrode 16 holes

Claims (7)

[Claims] 1. A high-speed particle beam source such as an ion beam, which is an apparatus for converting the electric charge of charged particles, wherein the charged particles are passed through a high-speed gas fluid to convert the electric charges into neutral particles. A beam amount measurement charge conversion device, wherein the amount of neutral particles for charge conversion is monitored by detecting ions generated in the high-speed gas fluid as a current. 2. The beam amount measurement charge conversion device according to claim 1, wherein the charged particles are passed through a high-speed gas fluid ejected from a nozzle to convert charges to be neutral particles. 3. The beam amount measuring charge converting apparatus according to claim 1, wherein the charged particles are passed through a supersonic gas fluid by a nozzle to convert charges to be neutral particles. 4. The beam amount measurement charge conversion apparatus according to claim 1, wherein the charged particles are passed through a hypersonic gas fluid by a nozzle to convert charges to be neutral particles. 5. The charged particles are made into a high-speed gas fluid accelerated or expanded by a nozzle or a free jet in a free molecular flow state, and passed through the free molecular fluid to convert charges to become neutral particles. The beam amount measurement charge conversion device according to claim 1, wherein 6. The energy value of the charged particles is 1 keV.
A beam application apparatus using the beam amount measurement charge conversion apparatus according to claim 1 to a beam of about several to several MeV. 7. The beam application apparatus using a beam amount measurement charge conversion apparatus according to claim 1, wherein a gas containing a liquid or a metal vapor is used as a high-speed gas fluid accelerated by the nozzle.