JPH09270234A - Chamber inserted ecr low energy ion gun - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a chamber inserted ion gun to irradiate ion beam onto a substrate by generating plasma by resonance excitation of a raw material gas with microwaves. SOLUTION: Ultra-high vacuum flange 6 is fixed in an installation flange of a chamber through an insulator. A long coaxial tube 8 is installed uprightly at right angles to the face in the flange 6. An ECR ion source 10, Einzel lens 11, E×B mass separator 13, a suppresser part 17, an analyzing slit 16, and electrode 18 for deflection are installed linearly in the tip of the coaxial tube 8. A linear antenna and a cylindrical permanent magnet are installed in an ion source, a gas is introduced to generate plasma and converted into ion beam by a taking out electrode. The ion beam is mass-separated by the E×B mass separator 13. Only ions in desiring mass are taken out as ion beam and radiated to a specimen.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chamber-insertion type ion gun for irradiating a substrate with an ion beam to generate a plasma by resonantly exciting a source gas by microwaves. Resonance absorption of microwaves by a magnetic field further increases efficiency. ECR (Electron Cyclotron)
Resonace). Further, the present invention is directed to low energy rather than high energy objects. When the energy is high, the ions penetrate deep into the target. Used for ion implantation. With low energy, it can be used for thin film growth and annealing of the thin film surface.

The chamber insertion type means that it is used by inserting it into the chamber of the thin film growth apparatus from the outside. This is one point. Since it is an insertion type, it is desirable that it can be inserted by a smaller flange. It is also preferable that the length of protrusion to the outside is short. Further, when used in a molecular beam epitaxial growth apparatus, it is preferable that the tip of the gun extends to the very vicinity of the sample. In this way, various conditions are imposed. Since the chamber-insertion type ion gun itself is new, the conditions imposed on it are also new.

[0003]

2. Description of the Related Art Ishikawa et al. Have proposed a device for generating a high-density plasma by generating a longitudinal magnetic field using a permanent magnet and causing an electron resonance with respect to a microwave introduced by a coil type antenna. Junzo Ishikawa, Yasuhiko Takeiri and Toshinori T
akagi, "Axial magnetic field extraction-type microwa
ve ion source with a permanent magnet ", Rev. Sci.
Instrum. 55 (4), April 1984, p449

FIG. 2 shows a schematic structure. This produces a longitudinal magnetic field in the chamber 21 by the permanent magnet 20. Raw material gas is introduced from the gas inlet 28 into the chamber 21.
Will be introduced. The microwave 30 transmitted through the waveguide 29 is guided to the chamber 21 by the antenna 22. The electrons contained in the gas are vibrated by the microwave. The electron moves cyclotron by the magnetic field and absorbs the microwave resonantly. The electrons excite gas molecules and convert them into plasma. Extraction electrodes 23 and 24 are provided in front of the chamber 21 to accelerate and extract ions as an ion beam 31.

The antenna 22 has a shape in which the tip of a straight line portion is wound one turn in a lateral coil shape 39. Since it is a coil antenna, the chamber expands laterally. In order to strengthen the magnetic field created by the permanent magnet 20, the magnetic extraction electrode 23 is used.
And the relay wheel 38 of ferromagnetic material is used. Since the chamber 21 side and the extraction electrode 23 side have different voltages, they are insulated by the insulator 25. The ferromagnetic relay wheel 38, the insulator 25, and the ferromagnetic lead electrode 24 are welded to each other.

A cooling medium 37 passes through the base flange 36. The intermediate flange 26 is also made of a ferromagnetic material. A magnetic circuit is formed by the permanent magnet 20, the extraction electrodes 23 and 24, and the intermediate flange 26. This is for strengthening the magnetic field lines in the chamber by the permanent magnets. The upper flange 27 is a non-magnetic material. A heater 34 for heating is wound around this. It is stated that an ion beam of a gas such as argon or nitrogen introduced from the gas inlet 28 can be extracted. Gives a small ion source.

Japanese Patent Application No. 6-183922 (July 1994)
Filed on Dec. 12, “ECR ion radical source” JP-A-8-3
(No. 1358) This was invented by the present inventor as a source of both an ion source and a radical source, inspired by the device.
An antenna bent for one turn is passed through a chamber, and microwaves are introduced by the antenna to turn gas into plasma and extract radicals or ions to the outside.
Since it is difficult to excite gas only with microwaves, a magnetic field is applied so that electrons resonate with cyclotron. A magnet is provided outside the plasma chamber to generate a vertical magnetic field.

When the frequency of the microwave is 2.45 GHz, when a magnetic field of 875 G is generated by the magnet, the frequency of the spiral motion of the electron matches the microwave frequency, and thus cyclotron resonance occurs. It can efficiently absorb energy from microwaves and excite gas molecules into neutral radicals. E because it uses the resonance absorption of microwaves
Called CR.

This allows the ion beam to be extracted by applying a voltage to the extraction electrode. Neutral radicals can be extracted by setting the electrode voltage to 0 and applying a differential pressure. It is called an ion radical source because it can selectively emit both ion beams and radicals.
It can be used for two purposes.

[0010]

An ion source for generating a plasma by a microwave and extracting it as an ion beam to the outside is disclosed. Can be used as both an ion source and a radical source. In any case, it is used alone. The present invention does not, however, relate to an ion source that can be used for thin film formation by inserting it into a chamber instead of a molecular beam cell in a molecular beam epitaxial growth apparatus (MBE). This request itself is new.

Since the object of the present invention relates to a novel component which is most suitable for an MBE apparatus, the molecular beam epitaxial growth method will be described first. The MBE apparatus is an apparatus for forming a thin film by irradiating a heated substrate with a molecular beam of a raw material in an ultrahigh vacuum to cause a gas phase reaction. A K cell or a molecular beam cell is used to make the raw material a molecular beam. It consists of a PBN crucible, a heater, a reflector, a column, a thermocouple, etc., and the column is fixed to an ultra-high vacuum flange. Such is a molecular beam cell. This is to evaporate what is solid at room temperature to form a molecular beam by heating. In many cases,
By heating and evaporating, a sufficiently reactive molecular beam can be obtained.

However, in the case of a certain limited material, it may not be possible to form a thin film by simply using a molecular beam because of its poor reactivity. For example, in the case of nitrogen gas, it is a gas from the beginning and is a stable gas. The reaction does not occur even with molecular beams. In such a case, it is better to use ion beams instead of molecular beams. It is also preferable to irradiate with low energy ion beams instead of high energy. The high energy ion beam penetrates deeply into the thin film. It must have low energy to be incorporated on the surface of the thin film. It is several eV, several tens eV, or at most several hundreds eV.

The above-mentioned is not suitable for insertion and attachment in a molecular beam epitaxial growth apparatus. The width is too large and the length is insufficient. It is not something that can be inserted from the outside instead of a conventional molecular beam cell. Since the coil antenna is used and a short cylindrical permanent magnet is used, the width is large and short. Morphologically, it is not suitable for an insertion type ion source such as a molecular beam epitaxy device. In order to be inserted into the chamber of the molecular beam epitaxy apparatus from the outside, it must have a thin and long shape. Why is thinness required? Molecular beam epitaxy equipment
It has cylindrical ports for multiple molecular beam cells on its outer wall.

In the molecular beam cell, a current introducing terminal and a support are attached to an ultra-high vacuum flange, and a crucible, a heater, and
A thermocouple and a reflector are attached. The chamber is not very large and the number of attached molecular beam cells is large. Therefore, the diameter of the attachment port of the molecular beam cell here is small. In the case of many molecular beam epitaxy devices, the ultra-high vacuum flange that mounts the molecular beam cell has a diameter of 70 mm (inner diameter 35 m
m).

The size of the flange is expressed by ICF. Abbreviation for International Conflat Flange. If it is attached to an existing molecular beam cell port, the flange diameter must be 70 mm (ICF70). There are also ICF114 and 152 flanges on it. A molecular beam epitaxy device can be newly designed in accordance with this. Then, the molecular beam epitaxy device itself must be large. If the outer diameter of the flange is 70 mm, the diameter of the member provided thereon is limited to 35 mm by the inner diameter of the pipe. It is necessary to put it together in an extremely thin shape. The above-mentioned stubby prior arts and the like cannot satisfy the demand very much.

Thus, a long and slender product is required. Because of its geometrical shape, it would be better to call it an ion gun rather than an ion source. Therefore, the target mechanism will be referred to as an ion gun hereinafter.

It is not enough to make the ports common. Ion guns have several differences from molecular beam cells. Gas must be introduced from the outside. It is different from the molecular beam cell that puts the material in the crucible. In addition, microwaves must be input from the outside and used for gas excitation. AEON Bee
It is necessary to apply an accelerating voltage in order to reduce the power consumption. Thus, unlike the molecular beam cell, it is necessary to introduce various things from the outside. Also, since there is a high voltage part, it is necessary to surround the protruding part for safety.

Various types of ion sources have already been manufactured and used. Excite the gas into plasma,
The beam is then extracted by the extraction electrode. Further, it is decelerated into a low energy beam. If this is applied to a part of the molecular beam epitaxy device, an exhaust device for drawing the ion source itself to an ultrahigh vacuum is required. A large number of parts such as an acceleration tube, a deceleration tube, a voltage terminal therefor, and an insulator are required, which cannot be fit in the flange of the ICF 70.

The first object of the present invention is to propose an elongated ion gun which can be used instead of a molecular beam cell in an MBE apparatus. A second object is to provide an ion gun for a molecular beam epitaxy apparatus which does not require a complicated combination of electrodes and power supplies for acceleration / deceleration and can be reduced in size. It is a third object of the present invention to provide an ion gun having a mass separation action capable of eliminating unnecessary ion beams. A fourth object is to provide an ion gun capable of irradiating a relatively wide range of objects with an ion beam.

[0020]

The ion gun of the present invention comprises an ultra-high vacuum flange fixed to a mounting port of a chamber of a molecular beam epitaxy apparatus through an insulator, and a coaxial tube fixed at a right angle to the surface of the flange. And an ion source fixed at the end of the coaxial tube to turn the gas into plasma by the action of the microwave and the magnetic field of the permanent magnet and drawing it out as an ion beam, and the desired mass by the action of the orthogonal electric and magnetic fields provided in front of the ion source. Gas mass separator that allows only the ions of XY to pass through, an XY deflection electrode that is provided in front of the E × B mass separator, and a gas that is provided from the ultra-high vacuum flange through the coaxial tube to the ion source. A gas tube to be introduced, a coaxial tube cable that penetrates the coaxial tube from the ultra-high vacuum flange to guide microwaves to the ion source, and a coaxial tube that penetrates the coaxial tube from the ultra-high vacuum flange to cool the coaxial tube Cooling tube for flowing a cooling medium for cooling, an electric wire for penetrating the coaxial tube from the ultra-high vacuum flange to give extraction voltage, E × B mass separation electrode voltage, XY deflection voltage, and inside of ion source The antenna includes an axially arranged antenna and a permanent magnet provided inside the ion source to generate a longitudinal magnetic field.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The ion gun of the present invention is characterized in that it can be first inserted into a chamber and attached, and then it can be extracted. For this purpose, the parts are arranged in a straight line on the ultra-high vacuum flange. The coaxial tube is set up on the ultra-high vacuum flange, and the ion source, E × B
A mass separator, an analysis slit, a deflection device, etc. are arranged in series. The whole is elongated and can be inserted into the cylindrical part of the attachment port of the molecular beam cell.

Gas and microwaves are introduced into the ion source through a gas pipe and a cable. Further, the ion source is cooled by flowing pure water cooling water, compressed air, or an insulating refrigerant into the cooling water pipe. The gas pipe, cable, and cooling water pipe are passed inside the coaxial pipe. In the ion source provided at the tip of the coaxial tube, the permanent magnet forms a longitudinal magnetic field. In the ion source, ECR resonance of electrons is caused by microwaves and gas becomes plasma. The ion source has an extraction electrode, and a voltage is applied between the extraction electrode and the ion source to extract the ion beam. Only those ions of the ion beam having the desired mass pass through the ExB mass separator. The mass-separated desired ions are further scanned to irradiate the target substrate. There is a voltage on the ion source. It is necessary to apply a voltage to the extraction electrode, the E × B mass separator, the deflection electrode and the like. Therefore, there is a current introduction terminal from which a voltage is applied to these electrodes.

It is necessary to apply a voltage corresponding to the acceleration energy to the ion source. The ion source has the same potential as the coaxial tube. The ultra-high vacuum flange cannot be set to ground potential. Therefore, the ultra-high vacuum flange is insulated from the chamber by an insulator. The insulator has the function of insulating the ultra-high vacuum flange from the molecular beam epitaxy device and the function of mechanically holding the ultra-high vacuum flange and the ion gun. The high pressure area around the ultra high vacuum flange can be avoided by surrounding it with a cover.

The portion protruding from the molecular beam epitaxy apparatus chamber to the outside is short. Further, since the ion source, the E × B mass separation device, and the XY deflection device are provided in series at the upper linear position of the flange, the whole can be made thin and long. Can be inserted into the port instead of the molecular beam cell.

A lens may be provided in the middle of the linear beam optical system to give the beam convergence. E × B
Mass separation is performed by mass separation. By making the electrodes elongated and the permanent magnets elongated, a thin and long mass separator can be obtained. Since the mass separation is performed, unnecessary ion beams do not hit the object. For example, even if a large number of hydrogen ions and the like are contained in the ion beam, they are mass-separated and removed.
The ExB device can be sized smaller than a sector magnet.

Since the XY deflecting device only needs to have two pairs of electrodes opposed to each other, it is possible to manufacture a device having a small size. In fact, the entire mechanism can be mounted on an ultra-high vacuum flange with a diameter of 70 mm. The diameter of these series bodies can be suppressed to 32 mm or less.

[0027]

Embodiment An embodiment of the present invention will be described with reference to FIG. On the outer wall of the molecular beam epitaxy apparatus chamber 1 indicated by broken lines, there are ports for mounting a plurality of molecular beam cells.
Here, one of the mounting ports 2 is shown. ICF7
A flange with an outer diameter of 0 can be fixed. This mounting port 2
Further, the cylindrical ground flange 3 at ground potential is fixed by bolts. It is integral with the annular insulator 4 and the ring 5. An ultra-high vacuum flange 6 is attached to the ring 5 by bolts. These parts are outside the molecular beam epitaxy system. The ultra-high vacuum flange 6 supports all parts of the ion gun of the present invention.

Gas connector 7, microwave introduction terminal 2
8. A cooling water connector 27 is provided through the ultra high vacuum flange 6. From the gas connector 7, raw material gas to be turned into plasma is introduced from an external gas bottle. The microwave introduction terminal 28 is an external microwave oscillator (not shown).
This is a terminal for introducing the microwave generated in the inside by a coaxial cable. Heat is generated due to generation of plasma by microwaves, and a cooling medium is introduced to cool the heat. A coaxial tube 8 is vertically installed inside the ultra-high vacuum flange 6.

A cylindrical insulator 9 is fixed to the tip of the coaxial tube 8. In the insulator 9, an extraction electrode 30, an einchel lens 11, an analysis slit 12, a mass separation unit 13, and
An analysis slit 16, a suppressor unit 17, and an XY deflection electrode 18 are provided. Although not shown in detail here, the ECR ion source 10 includes a gas introducing part, an antenna, a permanent magnet, and an ion source electrode. Microwave and gas coaxial tube 8
It is transmitted to the ion source 10 through a cable and a gas pipe inside.

The permanent magnet produces a longitudinal magnetic field. The microwave frequency is 2.45 GHz. The permanent magnet produces a longitudinal magnetic field of 875 Gauss near the antenna. Electrons cyclotron in a magnetic field and absorb microwaves. This excites the gas into plasma. Ions contained in the plasma are extracted from the ion source by the action of the extraction electrode. Cables are drawn to energize the ion source and electrode tube. The ion beam is narrowed down by the einchel lens 11. It passes through an analysis slit 12 having a thinner hole.

The mass separation unit 13 is for moving only an ion beam of a desired mass in a straight line by an electric field × a magnetic field. Also called the Wien filter. There are elongated permanent magnets 14, 14 with opposite poles facing each other. This permanent magnet is different from the permanent magnet in the ion source. Opposing permanent magnet 14,
There are electrodes 15 and 15 on both sides of 14 and an electric field E is generated in a direction orthogonal to the magnetic field. If the velocity in the axial direction is w, only ion beams having a velocity satisfying wB = E can go straight through this filter.

Other ions cannot go straight on this. It strikes the electrode 15 and the analysis slit 16 and loses its charge. These return to neutral molecules. The suppressor section 17 is for preventing secondary electrons emitted from the sample from returning to the ion source, and for preventing electrons in the thin plasma generated on the ion beam path from flowing into the sample. Further ahead, there is an XY deflection electrode 18, which is an object which scans the beam in the x and y directions by applying an AC voltage in the x and y directions. This causes the straight beam to swing left and right. A beam oscillating from side to side exits from the outlet 19 and can widely scan the sample surface (not shown). It also doubles as a deceleration tube that transports the ion beam close to the sample.

A voltage necessary for the extraction electrode, the mass separation electrode, and the XY deflection electrode is applied from the current introduction terminal 21. It is connected by wires 20 to the intended electrode.
The electric wires 20 are insulated from each other by a large number of small insulators. Several wire sets are required for the extraction electrode of the ion source, the electrode of the E × B mass separator 13, and the XY deflection electrode 18.

The coaxial tube 8 and the ECR ion source 10 are coaxial and elongated. Mounting port 2 is ICF 70mm
It is. The coaxial tube 8 and the ECR ion source 10 are insulated from the chamber 1 of the molecular beam epitaxy apparatus by the insulator 4. How can you make it thinner? One is that the shape of the ion source is made thin. The antenna is linear and the space is long and narrow. This also has the effect of reducing the load on the vacuum exhaust device. Another reason is that the mass separator itself is thin. Mass separation using an ordinary fan-shaped magnet cannot be made compact because the magnet is large. Since it is a Wien filter and the magnets and electrodes are elongated, the size can be reduced. Although it can be made thin and long, the beam itself can be scanned left and right, and irradiation can be performed so that the entire surface of the sample is covered.

Further, a feature of the present invention is that the length of protrusion to the outside is short. Only the part to the left of the ground flange 3 is outside. Only the insulator 4, the flange 6, the microwave introduction terminal 8, the gas connector 7, the cooling water connector 9, and the like. The protruding part is short, so it does not get in the way too much. Further, since this portion is covered with the high voltage cover 29, the high voltage portion is not exposed and it is safe.

[0036]

Since the mechanism can be elongated, it can be attached to the molecular beam cell port of the molecular beam epitaxy apparatus. It is thin and lightweight and easy to handle. This is an extremely effective material supply means in the case of a material that does not become an excited state suitable as a material for thin film growth as it is. It is not necessary to design and manufacture a new molecular beam epitaxy device, and the existing device can be effectively used.

Since the portion protruding to the outside is small, it does not disturb the operator. Does not require extra space.
High voltage is applied to the part protruding to the outside, but it is safe because it is covered by the cover. The cover is not too bulky because the protrusion is small.

Scanning in the XY directions is also effective for substrates having a large area. Since the flange is fixed to the port of the molecular beam epitaxy device through the insulator,
The potential of the ion gun becomes free from the chamber potential (ground potential) of the molecular beam epitaxy device. Although it is a small ion gun, mass separation is performed, so unnecessary ions do not enter the sample.

Since the gas space is narrow, the volume to be evacuated is small. Therefore, the inside of the ion gun can be simultaneously drawn by the exhaust system of the molecular beam epitaxy device. No special differential pumping system is required. The gas space is narrow and the extraction of the ion beam depends on the voltage of the extraction electrode. Due to the ECR discharge, the gas flow rate can be suppressed to an extremely low level. This is convenient for a molecular beam epitaxy apparatus that originally requires an ultrahigh vacuum. By squeezing the ion source electrode hole, the vacuum degree of 5 × 10 ⁻⁶ Torr can be maintained in the state where the gas is flown.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an ion gun according to an embodiment of the present invention.

[Figure 2] J. Ishikawa, Y. Takeiri and T. Takagi, "Axial m
agnetic field extracton-type microwave ion source w
ith a permanent magnet ", Rev. Sci. Instrum. 55 (4), A
Cross section of the ion source proposed in pril 1984, p449 (1984).

[Explanation of symbols]

 1 Chamber 2 Mounting Port 3 Grounding Flange 4 Insulator 5 Ring 6 Ultra High Vacuum Flange 7 Gas Connector 8 Coaxial Tube 9 Gaishi 10 ECR Ion Source 11 Einchellens 12 Analysis Slit 13 E × B Mass Separation 14 E × B Magnet 15 E × B electrode 16 Analysis slit 17 Suppressor section 18 XY deflection electrode 19 Beam exit 20 Electric wire 21 Current introduction terminal 27 Cooling water connector 28 Microwave introduction terminal 29 High voltage cover 30 Extraction electrode

Claims (1)

[Claims] 1. An ultra-high vacuum flange fixed to an attachment port of a chamber of a molecular beam epitaxy apparatus via an insulator, a coaxial tube fixed at a right angle to a surface of the flange, and a microwave fixed to an end of the coaxial tube. And an ion source for turning a gas into plasma by the action of a magnetic field of a permanent magnet and extracting it as an ion beam, and for passing only ions of a desired mass by the action of an electric field and a magnetic field orthogonal to each other provided in front of the ion source. From the mass separator, the XY deflection electrode provided in front of the E × B mass separator, the gas tube that penetrates the coaxial tube from the ultra-high vacuum flange to introduce gas into the ion source, and the ultra-high vacuum flange A coaxial tube cable that penetrates the coaxial tube and guides microwaves to the ion source; and a cooling tube that penetrates the coaxial tube from the ultra-high vacuum flange and that flows a cooling medium for cooling the coaxial tube. An electric wire provided through the coaxial tube from the ultra-high vacuum flange to give extraction voltage, E × B mass separation electrode voltage, and XY deflection voltage, an antenna provided inside the ion source in the axial direction, and an ion source A chamber-insertion type ECR low energy ion gun, which comprises a permanent magnet provided inside to generate a longitudinal magnetic field.