JPH0752634B2 - Ion beam device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is directed to ion implantation into a material performed during a semiconductor manufacturing process, ion drawing, and emission of secondary ions from a sample to be introduced into a mass spectrometer to introduce a sample. An ion beam device having a function such as an ion microanalyzer for performing composition analysis, which has pores in the chamber wall, gas or metal vapor is turned into plasma in the chamber, and a positive potential is applied to the ground potential. A plasma chamber and a plate-shaped hole formed in the center of the plasma chamber. The plasma chamber is arranged outside the plasma chamber so as to face the hole of the plasma chamber coaxially and is charged with a negative potential with respect to the ground potential. And an ion extraction electrode for extracting ions from the plasma chamber, and a plate-shaped electrode having a small hole in the center thereof, coaxial with the ion extraction electrode and spaced apart from the electrode, A ground electrode which is at ground potential disposed in the chamber side, wherein the plasma chamber, to those with a metallic vacuum vessel is at ground potential surrounding the ion extraction electrode and the ground electrode.

[Conventional technology]

FIG. 6 shows an example of the configuration of a conventional ion beam device.
An enlarged view of the main part of this device is shown in the figure. Gas or metal vapor is introduced into the plasma chamber 1 having the pores 11 on the chamber wall, and a suitable method, for example, the hot cathode wire which is housed in the plasma chamber and is perpendicular to the paper surface is energized and heated to emit thermoelectrons, A magnetic field perpendicular to the plane of the paper is applied to the thermoelectrons from the direction toward the chamber wall of the plasma chamber, which is charged to the positive side of the hot cathode line, causing the thermoelectrons to make a rotational motion, and the molecules of the introduced gas or metal vapor. Ion extraction electrodes arranged coaxially with the pores 11 of the plate-like plasma chamber having a pore 21 in the center of the plasma, by colliding with and ionizing the plasma. A high direct current voltage of several tens kV to several tens kV is applied between the plasma chamber 2 and the plasma chamber 1 to extract ion groups, that is, ions having various charge / mass ratios. The extracted ion group is connected to the ion beam 3 passing through the pore 81 provided in the central portion of the plate-shaped ground electrode 8 arranged behind the ion extraction electrode 2 to form a gap between the magnetic poles of the mass analysis magnet 4. It is incident on the DC magnetic field formed in. Only ions having a specific charge / mass ratio are selected by the action of the direct-current magnetic field from the group of ions constituting the incident ion beam, and the sample substrate 6 is ejected as the ion beam 5 from the mass analysis magnet 4. Is injected into. In the figure, 7 is a vacuum chamber that is grounded and surrounds the plasma chamber 1, the ion extraction electrode 2, the ground electrode 8 and the like, and 9 is an insulating tube for introducing a high DC voltage into the plasma chamber 1.

[Problems to be solved by the invention]

The problems with the ion beam device configured as described above are as follows. That is, there is residual gas in the vacuum container, and the residual gas is ionized by the ion beam, so that electrons are generated. These electrons drift in the ion beam and are accelerated by the electric field between the ion extraction electrode and the plasma chamber, and collide with and damage the plasma chamber. A negative potential of several hundred volts is applied with reference to the potential of the vacuum container to block electrons from the downstream side of the ion beam toward the plasma chamber. However, when the apparatus is operated, an abnormal discharge frequently occurs between the plasma chamber and the vacuum container due to the extraction of the ion beam, and the metal near the plasma chamber is melted.

It is an object of the present invention to provide an ion beam device that prevents drift electrons generated on the downstream side of the ion extraction electrode from penetrating the plasma chamber side beyond the ion extraction electrode, thereby reducing abnormal discharge.

[Means for solving problems]

In order to achieve the above object, the inventors conducted detailed experiments and studies on the cause of the abnormal discharge between the plasma chamber and the vacuum vessel, and as a result, the abnormal discharge was caused by the electrons generated on the downstream side of the ion extraction electrode. Drift not only in the ion beam but in the entire vacuum chamber, and is caused by electrons passing between the ion extraction electrode and the vacuum chamber and reaching around the plasma chamber as shown by reference numeral 30 in FIG. And
It was found that the arriving electrons are accelerated toward the plasma chamber and collide with the metal in the vicinity of the plasma chamber to cause the melting phenomenon as described above. Therefore, according to the first aspect of the present invention, as means for achieving the above-mentioned object, according to the first aspect of the present invention, pores are provided in the chamber wall, and the gas or metal vapor is plasmatized in the chamber, and is positive potential with respect to the ground potential. A plasma chamber to be charged to the plate, and a hole formed in the central portion formed in a plate shape, and is arranged outside the plasma chamber so as to face the hole of the plasma chamber and coaxially, and to have a negative potential with respect to the ground potential. An ion extraction electrode that is charged and draws out ions from the plasma chamber, and an anti-plasma of the electrode that is formed in a plate shape and has a pore in the center thereof, is coaxial with the ion extraction electrode, and is spaced apart from the electrode. An ion beam apparatus comprising a ground electrode disposed on the chamber side and having a ground potential, the plasma chamber, an ion extraction electrode, and a metal vacuum container surrounding the ground electrode and having a ground potential, wherein the ion extraction electrode Or, in the ring-shaped space formed between the ground electrode and the vacuum container, a ring-shaped electrode arranged coaxially with the two electrodes and charged with a ground potential or a negative potential with respect to the ground potential is arranged. In this case, the ring-shaped electrode has an L-shaped cross section, and one side of the L-shape faces the inner wall surface of the vacuum container in parallel, and the other one side of the ring-shaped electrode surrounds the outer circumference of the ion extracting electrode. The electrode is tightly surrounded and integrated with the ion extracting electrode.

Further, according to the second invention of the present invention, a plasma chamber in which a chamber wall is provided with pores and gas or metal vapor is plasmatized in the chamber and is charged to a positive potential with respect to the ground potential, Is provided in the central portion of the plasma chamber, and is disposed outside the plasma chamber so as to be coaxially opposed to the pores of the plasma chamber and is charged to a negative potential with respect to the ground potential to remove ions from the plasma chamber. An ion-extracting electrode for extraction and a plate-shaped hole having a small hole in the central portion thereof, which is arranged coaxially with the ion-extracting electrode and at a distance from the electrode on the side opposite to the plasma chamber and at a ground potential An ion beam device comprising an electrode and a metal vacuum container surrounding the plasma chamber, the ion extracting electrode, and the ground electrode and having a ground potential, the ion beam device being formed between the ion extracting electrode or the ground electrode and the vacuum container. It In those negative ring electrode being Kaden to the potential was arranged against that in the ring-shaped space disposed in the both electrodes coaxially ground potential or a ground potential,
It is assumed that the ring-shaped electrode is a hollow disc-shaped electrode, the outer peripheral side of which is in close contact with the inner wall surface of the vacuum container and the inner peripheral side of which is in close contact with the outer peripheral surface of the ground electrode, and which are integrated with both.

Further, according to the third aspect of the present invention, a plasma chamber in which a chamber wall is provided with pores and gas or metal vapor is plasmatized in the chamber and is applied to a positive potential with respect to the ground potential, Is provided in the central portion of the plasma chamber, and is disposed outside the plasma chamber so as to be coaxially opposed to the pores of the plasma chamber and is charged to a negative potential with respect to the ground potential to remove ions from the plasma chamber. An ion-extracting electrode for extraction and a plate-shaped hole having a small hole in the central portion thereof, which is arranged coaxially with the ion-extracting electrode and at a distance from the electrode on the side opposite to the plasma chamber and at a ground potential An ion beam device comprising an electrode and a metal vacuum container surrounding the plasma chamber, the ion extracting electrode, and the ground electrode and having a ground potential, the ion beam device being formed between the ion extracting electrode or the ground electrode and the vacuum container. A ring-shaped electrode disposed coaxially with the both electrodes in the ring-shaped space to be applied with a ground potential or a negative potential with respect to the ground potential. A hollow disk-shaped electrode having a plurality of through holes in the plate surface, which is arranged between the vacuum container and the inner diameter side of the electrode for intimately contacting the outer peripheral surface of the ion extracting electrode, and which is integrated with the electrode, and a ground electrode. And an outer diameter side are in close contact with the inner wall surface of the vacuum vessel and an inner diameter side is in close contact with the outer peripheral surface of the ground electrode to be integrated.
A hollow disk-shaped electrode having a plurality of through holes on the plate surface.

[Action]

Thus, a ring-shaped electrode is arranged coaxially with both electrodes in the ring-shaped space between the ion extraction electrode or the ground electrode and the vacuum container, and the ring-shaped electrode is grounded or negative to the grounded potential. By applying an electric potential, a gap between the ring-shaped electrode and the ion extraction electrode, or between the ring-shaped electrode and the ground electrode and the vacuum container is formed between the conventional ion extraction electrode and the vacuum container. Since it is possible to form an electric field much stronger than the electric field that was generated, electrons that try to pass by this ring electrode flow into the ring electrode or the vacuum container or the ground electrode under the action of this strong electric field, Electrons are prevented from entering the plasma chamber side, and abnormal discharge between the plasma chamber and the vacuum container is drastically reduced.

Since the ring-shaped electrode has a width in the radial direction, the cross-sectional area of passage when electrons invade from the downstream side to the upstream side of the ion extraction electrode decreases, and the ring-shaped electrode has a small geometrical shape. Also, it has the effect of reducing the frequency of abnormal discharge.

〔Example〕

FIG. 1 shows a first reference example of the present invention. A ring-shaped electrode 10 having a circular cross section is arranged concentrically with the ground electrode 8 in a ring-shaped space between the ground electrode 8 and the vacuum container 7, and a negative potential almost equal to that of the ion extraction electrode 2 is applied to this electrode. ing. Therefore, an electric field much stronger than the electric field formed between the conventional ion extracting electrode 2 and the vacuum container 7 is formed between the lever electrode and the ground electrode 8 and between the vacuum container 7. The electrons that have drifted from the downstream side to the upstream side are attracted to the ground electrode or the vacuum container by this electric field. Therefore, the drift electrons are never accelerated toward the plasma chamber to high energy, and damage to the plasma chamber side is prevented.

FIG. 2 shows the first embodiment of the present invention in which the ring-shaped electrode has an L-shaped cross section and is applied with a negative potential equal to that of the ion extracting electrode with respect to the ground potential. In this case, in order to simplify the structure, the L-shaped 1
The ring-shaped electrode 11 and the ion-extracting electrode 2 are integrated so that their sides face each other in parallel to the inner surface of the vacuum container 7 and the ends of the other side closely surround the outer peripheral surface of the ion-extracting electrode 2. A strong electric field is formed in the facing gap between the ring electrode and the vacuum container. Therefore, the drift electrons that try to pass through the facing gap are subjected to the action of a strong electric field over the length of one side of the L-shaped facing, so that the number of electrons passing through the gap toward the plasma chamber is extremely small. Become. Further, the other one side of the L-shape plays a role of blocking the passage cross-sectional area of the drift electron toward the plasma chamber side, and therefore the electron whose path is blocked here is attracted to the ground electrode side and is no longer on the plasma chamber side. It cannot contribute to abnormal discharge.

FIG. 3 shows a second reference example of the present invention. In this embodiment, the ring-shaped electrode is configured as the electrode 12 having a flat rectangular cross section whose outer diameter is substantially equal to the inner diameter of the vacuum container 7, whereby the cross-sectional area of the drift electron passage is effectively narrowed and this electrode is Integrated with the vacuum container 7 to have the same potential,
A strong electric field is formed between the ion extracting electrode 2.

FIG. 4 shows the second embodiment of the present invention, and the third embodiment
The flat ring-shaped electrode in the figure is arranged between the ground electrode 8 and the vacuum container 7 and integrated with both to have the same potential. In this case, the passage of the drift electrons is only on the side of the fine hole of the ground electrode 8 as shown by the electron trajectory 34, the passage cross-sectional area is significantly narrowed, and the electrons passing through this fine hole are grounded to the ion extracting electrode 2 and the ground. The number of electrons that are attracted to the ground electrode side by the electric field formed between the electrodes 8 and pass through the facing gap between the two electrodes in the radial direction is extremely small.

FIG. 5 shows a third embodiment of the present invention. In this embodiment, a plurality of small holes are provided in the ring-shaped electrode 13 in the fourth embodiment to connect the upstream side and the downstream side, and the ring-shaped electrode 15 is arranged also between the ion extracting electrode and the vacuum container. Integrated with the ion extraction electrode to the same potential, and this electrode 15
It also has a plurality of small holes. The reason why the small hole is provided in the ring-shaped electrode to form the perforated plate is that the ring-shaped electrode 13 in the fourth embodiment completely closes the passage between the ground electrode and the vacuum container. Since the communication between the upstream side and the downstream side of the plasma chamber is performed only by the pores 81, the gas or metal vapor that is introduced into the plasma chamber and flows out from the pores of the plasma chamber without being largely ionized, or the ground electrode. It becomes easy to collect on the upstream side of. Therefore, when the vacuum exhaust system is located downstream of the ground electrode, its exhaust action extends to the upstream side of the ground electrode only through the thin high-temperature ion beam, so the exhaust effect on the upstream side is extremely small. , Therefore, the pressure on this upstream side rises,
When the insulation distance between the plasma chamber 1 and the vacuum vessel 7 is d and the pressure is p, the value of pd reaches the position of the valley portion of the V-shaped curve showing the relationship between pd and withstand voltage, Since the withstand voltage performance of the plasma chamber with respect to the vacuum vessel deteriorates, the pressure p is sufficiently reduced by exhausting through the small holes so that the value of pd gives a sufficiently high withstand voltage on the V-shaped curve. This is so that it will come to the position. Therefore, in this case, the electrons drifting from the downstream side pass through these small holes and try to proceed to the plasma chamber side, but they are integrated with the ion extracting electrode, the ground electrode, and both electrodes. Further, since a strong electric field is formed between the ring-shaped electrodes, electrons passing through the small hole on the ground electrode side are attracted again to the ground electrode side or the vacuum container side and cannot proceed to the plasma chamber side. Note that the total cross-sectional area of the small holes provided in the ring-shaped electrode is necessary as long as the pressure on the upstream side of the ground electrode is necessary and it is sufficient that the area is sufficient.
It is not necessary to make the area larger than the area of the entire ring-shaped electrode, so that the effect of narrowing the path of drift electrons does not become so small.

〔The invention's effect〕

As described above, according to the present invention, as a result of adopting the above configuration, electrons drifting from the downstream side of the ion extraction electrode to the plasma chamber side are ring-shaped electrodes and ground electrodes, vacuum containers or ions. The movement to the plasma chamber side is hindered by the action of a strong electric field formed with the extraction electrode, and the cross-sectional area of the electron passage is narrowed by the ring-shaped electrode. As a result, the discharge around the plasma chamber is drastically reduced. There is an effect.

[Brief description of drawings]

FIG. 1 is a diagram showing an electrode configuration of an ion beam device according to a first reference example of the present invention, FIG. 2 is a diagram showing an electrode configuration of an ion beam device according to the first invention of the present invention, and FIG. 3 is a diagram showing the present invention. Showing the electrode constitution of the ion beam device according to the second reference example, FIG. 4 is a diagram showing the electrode constitution of the ion beam device according to the second invention of the present invention, and FIG. 5 is the ion according to the third invention of the present invention. FIG. 6 is a diagram showing an electrode configuration of the beam device, FIG. 6 is an explanatory diagram showing a configuration example of a conventional ion beam device, and FIG. 7 is an enlarged view of a main part of the ion beam device of FIG. 1 ... Plasma chamber, 2 ... Ion extraction electrode, 3,5 ...
Ion beam, 7 ... vacuum container, 8 ... ground electrode, 10,1
1,12,13,14,15 …… Ring electrodes.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical indication H01L 21/265

Claims (3)

[Claims] 1. A plasma chamber in which a chamber wall is provided with pores and a gas or a metal vapor is plasmatized in the chamber and is applied to a positive potential with respect to a ground potential, and a central portion formed in a plate shape. An ion extraction electrode that is provided with pores outside the plasma chamber and is coaxially opposed to the pores of the plasma chamber, is negatively charged with respect to the ground potential, and extracts ions from the plasma chamber; A ground electrode that is formed in a shape and has a pore in the center thereof, is coaxial with the ion extraction electrode and is disposed on the side opposite to the plasma chamber of the electrode at a distance from the electrode and is at a ground potential, and the plasma chamber, An ion beam device comprising an ion extraction electrode and a metal vacuum container surrounding the ground electrode and having a ground potential, wherein a ring-shaped space formed between the ion extraction electrode or the ground electrode and the vacuum container. In which a ring-shaped electrode disposed coaxially with the both electrodes and charged with a ground potential or a negative potential with respect to the ground potential is disposed, the ring-shaped electrode is formed to have an L-shaped cross section, One side of the L-shape is parallel to the inner wall surface of the vacuum container, and the other one side end is an electrode that closely surrounds the outer circumference of the ion extraction electrode and is integrated with the ion extraction electrode. Characteristic ion beam device. 2. A plasma chamber in which pores are formed in a chamber wall, gas or metal vapor is turned into plasma in the chamber, and a positive potential is applied with respect to a ground potential, and a central portion formed in a plate shape. An ion extraction electrode that is provided with pores outside the plasma chamber and is coaxially opposed to the pores of the plasma chamber, is negatively charged with respect to the ground potential, and extracts ions from the plasma chamber; A ground electrode that is formed in a shape and has a pore in the center thereof, is coaxial with the ion extraction electrode and is disposed on the side opposite to the plasma chamber of the electrode at a distance from the electrode and is at a ground potential, and the plasma chamber, An ion beam device comprising an ion extraction electrode and a metal vacuum container surrounding the ground electrode and having a ground potential, wherein a ring-shaped space formed between the ion extraction electrode or the ground electrode and the vacuum container. In which a ring-shaped electrode which is arranged coaxially with the both electrodes and which is charged with a ground potential or a negative potential with respect to the ground potential is arranged, the ring-shaped electrode has an outer peripheral side closely packed with the inner wall surface of the vacuum container. The ion beam device is characterized in that it is a hollow disk-shaped electrode that is in contact with the inner peripheral side of the ground electrode and is in close contact with the outer peripheral surface of the ground electrode and is integrated with both of them. 3. A plasma chamber in which a chamber wall is provided with pores and gas or metal vapor is turned into plasma in the chamber and is applied to a positive potential with respect to a ground potential, and a central portion formed in a plate shape. An ion extraction electrode that is provided with pores outside the plasma chamber and is coaxially opposed to the pores of the plasma chamber, is negatively charged with respect to the ground potential, and extracts ions from the plasma chamber; A ground electrode that is formed in a shape and has a pore in the center thereof, is coaxial with the ion extraction electrode and is disposed on the side opposite to the plasma chamber of the electrode at a distance from the electrode and is at a ground potential, and the plasma chamber, An ion beam device comprising an ion extraction electrode and a metal vacuum container surrounding the ground electrode and having a ground potential, wherein a ring-shaped space formed between the ion extraction electrode or the ground electrode and the vacuum container. In which a ring-shaped electrode coaxially arranged with both electrodes and charged with a ground potential or a negative potential with respect to the ground potential is arranged, the ring-shaped electrode is provided between the ion extracting electrode and the vacuum container. A hollow disk-shaped electrode having a plurality of through-holes on its plate surface, the inner diameter side of which is in close contact with the outer peripheral surface of the ion extracting electrode and is integrated with the electrode; A hollow disk having a plurality of through holes on the plate surface, which are arranged between the outer diameter side and the inner wall surface of the vacuum container in close contact with each other and the inner diameter side closely contacts with the outer peripheral surface of the ground electrode. An ion beam device, which comprises an electrode.