JP2007234508A - Mass filter for ion beam and ion beam device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mass filter for ion beams with which a heavy ion containing a C60 cluster can be obtained, and provide an ion beam device for the heavy ion beams which is small and economical. <P>SOLUTION: The ion beam device is provided with a first deflection electrode 11 on a side of an iron source to create a rotating electric field having a predetermined deflection angle which rotates in a plane perpendicular to a light axis and a second deflection electrode 12 on a side of discharging an iron beam IB to create a rotating electric field having a predetermined angle in a same frequency with the rotating electric field of the first deflection electrode 11. Between the first and second deflection electrode 11, 12, there is provided a mass filter 10 of a rotating electric field type composed of a lens system 13 made of a plurality of cylindrical electrodes 14, 15, 16. Apertures 20 are arranged on the side of the ion source of the first deflection electrode 11 and on the side of discharging an ion beam of the second electrode 12. Furthermore, in a middle part of the lens system in an axial direction, there is a shielding means 17 to shield a middle part of the ion beam passage. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ion beam mass filter and an ion beam apparatus, and more particularly to an ion beam mass filter and an ion beam apparatus suitable for making the ion beam heavy ions mainly composed of C60 (carbon 60 cluster) ions.

  Recently, an organic material such as an organic thin film having a minute thickness of nm class has been used in various fields such as a display device, a semiconductor device, and life science (biotechnology). In order to utilize an organic material, it is necessary to analyze in detail the chemical structure such as the composition and form of the material surface and inside.

  For material analysis, if a sample of organic material is placed in a vacuum container in a vacuum atmosphere and the surface of the sample is etched with a rare gas ion source such as Ar ions, the surface of the sample is significantly damaged, and the chemical structure of the organic matter Could not be analyzed deep inside. Recently, it has been known that when a sample surface is processed using a heavy ion beam mainly composed of C60, etching is uniformly performed and the surface is hardly damaged, and is suitable for analysis of the composition and chemical state of the sample. Yes. For this reason, it has also been proposed that an ion beam device for accelerating an ion beam mainly composed of C60 with a predetermined acceleration voltage is attached to a vacuum vessel of an analyzer to make a low damage etching source of a sample (see Patent Document 1). .

  In general, an ion beam apparatus generally has a structure including an ion source, an electromagnetic lens, an objective lens, a deflection lens, and the like arranged in a cylinder. Then, a high DC voltage is applied between the electrodes with respect to the gas in the ion source, the supplied gas is ionized to generate a gas plasma, and the gas ions in the plasma are accelerated by the voltage between the electrodes, When gas ions are emitted as an ion beam, the ion beam is deflected or converged by a lens or the like to obtain an ion beam suitable for processing the surface of the sample (see, for example, Patent Document 2).

  By the way, although the conventional ion beam apparatus is called a C60 cluster ion beam, in this ion beam, in addition to the original C60, light ions such as hydrogen element H, carbon element C, oxygen element O, etc. , There are many neutral particles of C60 clusters. A device has been devised to remove light impurities, which are impurities, and neutral particle components of C60 clusters to obtain a C60 cluster ion beam with higher purity.

  In order to take out heavy ions with an ion beam device, for example, a quadrupole filter, a Wien filter, a sector magnet, or the like is used, and a separation mechanism generally called a mass filter is used. In addition, in the conventional ion beam apparatus, neutral particles are separated from ions by utilizing the property that neutral particles travel straight even in an electric field or magnetic field in order to remove neutral particles from the ion beam. Things have been done.

JP 2005-134170 A JP 2005-44570 A

  A quadrupole filter, which is one of the separation mechanisms, has four columns arranged at equal distances from each other, and puts a signal in which a high frequency is superimposed on a DC voltage in this column, so that ions fly in the center with respect to the traveling direction. This is a method of vibrating by applying a vertical force. And when the magnitude of the DC voltage and the amplitude of the high frequency are a certain value, only ions of the mass corresponding to that value can pass through the column, and ions of other mass diverge and cannot pass It is. However, since this method uses a high frequency of a relatively low frequency, it is mainly suitable for light ions. To apply to heavy ions, the mechanism and structure are complicated and the dimensions are large, and the equipment is economical. There is a problem that cannot be produced.

  In addition, the Wien filter uses a direct electric field and magnetic field to pass only ions having a desired charge and mass ratio, and requires very strong magnetic flux lines to separate heavy ions. Since the magnet becomes enormous, it cannot be used for a small ion beam apparatus, and the sector magnet has the same problem.

  In the above-mentioned mass filter using the movement of charged particles in a high-frequency electric field, an electrostatic field, or a static magnetic field, the mass resolution deteriorates as the ion mass increases in any method, so the necessary mass resolution is ensured. Therefore, the shape of the filter has to be increased corresponding to the mass of ions to be selected, which is disadvantageous in principle for heavy ions.

  On the other hand, in the filter of the time-of-flight (Time Of Flight, hereinafter abbreviated as “TOF”) method, as the mass of ions increases, the mass resolution improves and the flight time becomes longer. It is known that can be shortened, and therefore the overall size can be reduced as the ion mass increases. However, the conventional TOF type filter has a drawback that the ion beam needs to be pulsed and the use efficiency of the ions is extremely deteriorated.

  Further, in order to remove the neutral particle component from the ion beam by the ion beam apparatus, the ion source needs to be deflected between the ion source and the target sample to be processed. And the optical axis of the ion optical system and the sample cannot be arranged on a straight line. As a result, this is a major drawback in constructing a small ion beam apparatus, and also a problem from the viewpoint of miniaturizing the beam spot size for converging the ion beam.

  An object of the present invention is to provide a mass filter for an ion beam from which heavy ions containing high-purity C60 clusters can be obtained.

  Another object of the present invention is to make it possible to manufacture a heavy ion beam ion beam apparatus including a C60 cluster in a compact and economical manner.

  In the ion beam mass filter of the present invention, a first deflection electrode that creates a rotating electric field having a predetermined deflection angle that rotates in a plane perpendicular to the optical axis is disposed on the ion source side, and on the ion beam emission side. A second deflection electrode that creates a rotating electric field that rotates in a plane perpendicular to the optical axis of a predetermined deflection angle at the same frequency as the rotating electric field of the first deflection electrode; It is characterized in that a lens system comprising a plurality of cylindrical electrodes is provided between the deflection electrodes.

  In the ion beam mass filter of the present invention, the first deflection electrode for generating a rotating electric field having a predetermined deflection angle is disposed on the ion source side, and the first deflection electrode is disposed on the ion beam emission side. A second deflection electrode that creates a rotating electric field that rotates in a plane perpendicular to the optical axis of a predetermined deflection angle at the same frequency as the rotating electric field is disposed, and a plurality of cylinders are disposed between the first and second deflecting electrodes. The lens system is provided with a cylindrical electrode, and a shielding means for shielding the central portion of the ion beam passage is disposed at a substantially axial intermediate portion of the lens system.

  Preferably, apertures are arranged on the ion source side of the first deflection electrode and the ion beam emission side of the second deflection electrode, respectively.

  Preferably, the shielding means is held by a cylindrical electrode located in an intermediate portion in the axial direction of the lens system.

  Furthermore, an ion beam apparatus according to the present invention is an ion beam apparatus in which an ion source is disposed on one end side of a cylindrical container, and the ion beam is emitted from an emission part on the other end side of the cylindrical container, A first deflection electrode that creates a rotating electric field having a predetermined deflection angle that rotates in a plane perpendicular to the optical axis is disposed on the ion source side, and the first deflection electrode is disposed on the ion beam emission side. A second deflection electrode that creates a rotating electric field that rotates in a plane perpendicular to the optical axis of a predetermined deflection angle at the same frequency as the rotating electric field is disposed, and a plurality of cylinders are disposed between the first and second deflecting electrodes. The lens system is formed of a cylindrical electrode, and apertures are arranged on the ion source side of the first deflection electrode and the ion beam emission side of the second deflection electrode, respectively.

  Preferably, a shielding means for shielding a central portion of the ion beam passage is arranged in a substantially axial middle portion of the lens system.

  Since the ion beam mass filter is constructed in a time-of-flight method and a continuous beam type as in the present invention, heavy ions mainly composed of high-purity C60 clusters from which light ions and neutral particles of C60 are removed with a simple structure. Can get.

  Further, if the ion beam apparatus is configured using the ion beam mass filter as in the present invention, the apparatus for emitting a heavy ion beam can be made small and economical.

  In the ion beam mass filter of the present invention, the first deflection electrode that creates a rotating electric field that rotates in a plane perpendicular to the optical axis is arranged on the ion source side, and the ion beam emission side is perpendicular to the optical axis. A second deflection electrode is provided that creates a rotating electric field that rotates in the plane. The rotating electric fields of the first and second deflection electrodes are rotated at a predetermined deflection angle and the same frequency, and a lens system comprising a plurality of cylindrical electrodes is interposed between the first and second deflection electrodes. Provide and configure.

  In the ion beam apparatus of the present invention, the above-described mass filter is arranged in a cylindrical container, and apertures are arranged on the ion source side of the first deflection electrode and the ion beam emission side of the second deflection electrode, respectively. And configure.

  The ion beam mass filter and ion beam apparatus of the present invention will be described below with reference to embodiments shown in the drawings. In general, an ion beam apparatus called an ion gun is provided with an ion source 2 at one end of a cylindrical container 1 as shown in FIG. 1, and linearly emits an ion beam from an emission part 3 on the other end side of the cylindrical container 1. It is composed. Between the ion source 2 and the emission part 3, an extraction electrode 4 for accelerating and extracting the ion beam IB from the ion source 2, a condenser lens 5 for converging the ion beam IB, and an aligner electrode 6 centering on the ion beam IB axis. Further, an aligner movable diaphragm 7, an objective lens 8 of the ion beam IB, and a deflection electrode 9 for deflecting the ion beam IB to the object to be processed are disposed in order, and the ion beam IB is emitted from the emitting unit 3 to the object to be processed. It has a linear structure.

  In addition, a mass filter (RFMF) of a rotating electric field using the continuous TOF method using the rotating electric field of the present invention is provided between the ion source 2 and the emitting portion 3, that is, between the aligner electrode 6 and the aligner movable diaphragm 7 in the example of FIG. : Rotating Field Mass Filter (hereinafter abbreviated as “RFMF”) 10, the ion beam IB is once deflected by the RFMF 10 and then returned to the original state. Thereby, in the ion beam apparatus of the present invention, the ion source 2, the optical axis of the optical system of the ion beam IB, and a small structure in which a sample to be processed can be arranged on a straight line can be obtained. Neutral particles of ions can be efficiently removed, and the ion beam can be converged to reduce the beam spot size.

  As shown in FIG. 2, the RFMF 10 of the continuous TOF method of the present invention includes a plurality of static electrodes called Einzel lenses arranged between the first and second deflecting electrodes 11 and 12 and between them. The lens system 13 is composed of an electric cylindrical electrode.

  As the first and second deflecting electrodes 11 and 12 constituting the RFMF 10, various deflecting types can be used. In the example of FIG. 2, for generating a rotating electric field in a plane perpendicular to the optical axis, respectively. In addition, two pairs of parallel plate electrodes orthogonal to the x-axis and y-axis directions are used. For example, by applying an alternating voltage of a sine wave in the x direction and a cosine wave in the y direction, an in-plane perpendicular to the optical axis is used. A rotating electric field is generated at In this example, the lens system 13 uses three electrostatic cylindrical electrodes 14, 15 and 16 made of a nonmagnetic material such as copper or stainless steel.

  The lens system 13 composed of the electrostatic cylindrical electrodes 14, 15 and 16 has a spatial cross section of the cylindrical electrode 15 serving as an ion beam passage in a portion of the cylindrical electrode 15 at a position substantially in the middle of the axial dimension. The shielding means 17 is disposed so as to shield the central portion of the ion beam IB, that is, the central portion of the traveling axis of the ion beam IB, thereby blocking neutral components of 60 cluster ions.

  In order to attach the shielding means 17, for example, the central cylindrical electrode 15 is divided into two parts and fixed by being sandwiched between these divided parts, or the path of the ion beam IB on the cylindrical electrode 15 as shown in FIG. It fixes to the end surface using fixing members 22, such as a bolt.

  The shielding means 17 uses a non-magnetic material such as stainless steel, and has a circular shielding plate having a size of about 20% of the space cross-sectional area of the ion beam passage of the cylindrical electrode 15 as shown in FIG. And the annular support member 18 is positioned in the central portion so that the ion beam path can be secured by the support means 19 such as a wire or wire of the same material, or is cut from a nonmagnetic material in the same shape as this. By using it, it is manufactured and used as a unit.

  Further, the RFMF 10 includes an aperture 20 having a small hole 21 formed in the center portion thereof using a high melting point material such as tungsten, in the example of FIG. 2, the ion source side of the first deflection electrode 11 and the second deflection electrode. Twelve ion beam emission sides, that is, positions on the entrance side and exit side of the ion beam IB, respectively. Both of these apertures 20 shield unnecessary hydrogen elements and the like, and the ion beam IB can be made heavy ions mainly composed of 60 cluster ions.

  In this continuous TOF method RFMF 10, as shown in FIG. 3, the first and second deflection electrodes 11 and 12 at both ends of the lens system 13 are composed of, for example, two sets of parallel plate electrodes that are orthogonal to each other. Rotating electric fields A and B formed by these are arranged, the rotating electric field A is at a deflection angle θ, and the rotating electric field B rotates in the plane perpendicular to the optical axis at the same frequency as the rotating electric field A.

  Therefore, when the ion beam IB accelerated and extracted from the ion source 2 enters the rotating electric field A created by the first first deflection electrode 11 as shown in FIGS. 1 and 2, the optical axis is the center. Diverges into a cone with apex angle θ and enters the lens system. At this time, it is assumed that one ion is focused and bent in the positive direction of the y-axis at a deflection angle θ as indicated by an arrow. The C60 cluster ions converged again by the lens system 13 disposed in the middle are incident on the second deflection electrode 12 in the negative y-axis direction at a deflection angle of −θ. At this time, if the phase of the rotating electric field in the rotating electric field B happens to be the same as that of the rotating electric field A, the ions are turned back on the optical axis again in the same direction as the ion beam IB when coming out of the ion source 2. It becomes a component and can be discharged from the discharge portion to the workpiece in this state.

  The RFMF 10 will be described in more detail with reference to FIGS. 2 and 3. When the ion beam IB is incident along the z axis from the left side of the drawing, for example, the first and the second configured with two sets of parallel plate electrodes orthogonal to each other. For example, a sine wave in the x-axis direction and a cosine wave in the y-axis direction are applied to the second deflection electrodes 11 and 12, and a rotating electric field A having a predetermined deflection angle that rotates in a plane perpendicular to the optical axis. , B are generated. When the ion beam IB enters the first deflection electrode 11 and the electric field happens to be in the positive direction of the y-axis, the ion beam IB has a deflection angle θ in the y-axis direction as shown in FIG. Change direction and enter the lens system 13.

  The ion beam IB changes its trajectory by the converging action of each cylindrical electrode 14 to 16 of the lens system 13 and is incident on the second deflection electrode 12 in the negative y-axis direction with a deflection angle −θ. If the direction of the electric field at the second deflection electrode 12 at this time is the y-axis direction, the ion beam IB is deflected by an angle θ, the trajectory returns to the original central optical axis, and the aperture disposed on the ion beam exit side. 20 can be passed. The conditions for the ion beam to pass through the aperture 20 are determined by the ion energy and mass, the frequency of the rotating electric field, and the phase difference between the two rotating electric fields.

  The direction of the electric field when the ion beam IB is incident may be any direction, not the y-axis direction. The electric field at the first deflection electrode 11 when the ion beam IB is incident on the RFMF 10 is acceptable. If the direction and the direction of the electric field at the second deflection electrode 12 when the ion beam IB exits the RFMF 10 coincide with each other, the ion beam IB can pass through the RFMF 10. The above is true at any rotation angle, and the ion beam is a continuous beam.

The time t during which the ion beam IB flies between the first and second deflection electrodes 11 and 12 is determined by the ion acceleration voltage V, the ion mass M, the ion charge e, and the interelectrode distance L. 1) It is obtained by the formula.

Assuming that the frequency f of the rotating electric field and the rotating electric field B at the deflection electrode 12 are delayed by the phase φ from the first rotating electric field A, only ions having a mass satisfying the following equation (2) can pass through.

  For this reason, by adjusting the frequency f or the phase φ, the mass of ions passing therethrough can be selected. The heavier ions can reduce the interelectrode distance L, and the ion beam IB becomes a continuous beam.

  Further, in the vicinity of the central portion of the axial dimension of the lens system 13, the equipotential surface is perpendicular to the central optical axis. Therefore, the shielding means 17 is disposed at the central position where an ion beam path can be secured, and the lens If the potential is the same as that of the cylindrical electrode 15 located in the central portion of the system in the axial direction, neutral particles of 60 cluster ions can be removed without affecting the trajectory of the ion beam, and the entire apparatus has a central optical axis. It is symmetric with respect to, and it is small and can be advantageous to the convergence of the ion beam.

It is a schematic block diagram which shows one Example of the ion beam apparatus to which this invention is applied. It is a principal part enlarged view which shows the mass filter for ion beams of this invention. It is a schematic diagram which shows the principle of the mass filter for ion beams of this invention. It is a principal part figure which shows an example of the lens system in the mass filter for ion beams of FIG. It is the front view and side view which show an example of the neutral particle shielding means used for the mass filter for ion beams.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Cylindrical container, 2 ... Ion source, 3 ... Emitter, 10 ... Rotating electric field type mass filter, 11 ... 1st deflection electrode, 12 ... 2nd deflection electrode, 13 ... Lens system, 14, 15 16 ... cylindrical electrode, 17 ... shielding means, 20 ... aperture, IB ... ion beam.

Claims (6)

  A first deflection electrode that creates a rotating electric field having a predetermined deflection angle that rotates in a plane perpendicular to the optical axis is disposed on the ion source side, and the rotating electric field of the first deflection electrode is disposed on the ion beam emission side. A second deflection electrode that creates a rotating electric field that rotates in a plane perpendicular to the optical axis at a predetermined deflection angle at the same frequency, and a plurality of cylindrical electrodes are disposed between the first and second deflection electrodes. A mass filter for an ion beam comprising a lens system comprising:   A first deflection electrode that creates a rotating electric field having a predetermined deflection angle that rotates in a plane perpendicular to the optical axis is disposed on the ion source side, and the rotating electric field of the first deflection electrode is disposed on the ion beam emission side. A second deflection electrode that creates a rotating electric field that rotates in a plane perpendicular to the optical axis at a predetermined deflection angle at the same frequency, and a plurality of cylindrical electrodes are disposed between the first and second deflection electrodes. An ion beam mass filter comprising: a lens system comprising: a shielding unit configured to shield a central portion of the ion beam passage at a substantially axial intermediate portion of the lens system.   3. The ion beam mass according to claim 1, wherein apertures are arranged respectively on the ion source side of the first deflection electrode and on the ion beam emission side of the second deflection electrode. filter.   3. The ion beam mass filter according to claim 2, wherein the shielding means is held by a cylindrical electrode located at an axially intermediate portion of the lens system.   An ion beam device that disposes an ion source on one end side of a cylindrical container and emits an ion beam from an emitting part on the other end side of the cylindrical container, the ion source side in the cylindrical container on the optical axis A first deflection electrode that creates a rotating electric field having a predetermined deflection angle that rotates in a vertical plane is disposed, and a predetermined deflection is performed at the same frequency as the rotating electric field of the first deflection electrode on the ion beam emission side. A second deflecting electrode that creates a rotating electric field that rotates in a plane perpendicular to the optical axis of the corner, and the rotating electric field of the first and second deflecting electrodes is between the first and second deflecting electrodes; The ion system is characterized in that a lens system comprising a plurality of cylindrical electrodes is provided, and apertures are arranged on the ion source side of the first deflection electrode and the ion beam emission side of the second deflection electrode, respectively. Beam device. 6. The ion beam apparatus according to claim 5, wherein shielding means for shielding a central portion of the ion beam passage is arranged at a substantially axial intermediate portion of the lens system.

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