JP2007155426A - Parallel magnetic field type rutherford backscattering ion measuring instrument - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a parallel magnetic field type Rutherford backscattering ion measuring instrument equipped with an ion discrimination means (aperture) not causing pressure difference in a measuring chamber while ensuring the discrimination capacity of scattered ions for passing only specific scattered ions. <P>SOLUTION: A plurality of slits Zc extending along the radiation centering around the axis of an ion beam H are provided to the cutting-off part Zb of the scattered ions formed to the periphery of an ion passing opening part Za permitting the passage of the specific scattered ions. These slits Zc are formed to a plate-shaped cutting-off part Zb so that the sample side 20a of the measuring chamber 20 and an ion detector side 20b are allowed to communicate with each other in the direction R1 oblique to the axial direction of the ion beam H and have parts 51 and 52 mutually overlapped when viewed from the axial direction of the ion beam H to constitute the aperture Z1 in a state that a gap is not formed when viewed from the axial direction of the ion beam H. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a parallel magnetic field type Rutherford backscattered ion measuring apparatus for measuring scattered ions backscattered from a sample irradiated with an ion beam by focusing the scattered ions on a beam axis using a magnetic field parallel to the ion beam. .

Conventionally, for example, Patent Document 1 discloses a parallel magnetic field type Rutherford backscattered ion that converges a scattered ion backscattered by a sample on which a high and medium energy ion beam is incident on a beam axis using a magnetic field parallel to the ion beam. A measuring device (or a parallel field Rutherford backscattering analyzer) is shown.
FIG. 3 is a cross-sectional view of a general parallel magnetic field type Rutherford backscattered ion measuring apparatus X.
As shown in FIG. 3, the parallel magnetic field type Rutherford backscattered ion measuring device X (hereinafter referred to as scattered ion measuring device X) is roughly classified into an accelerator X1 that generates a measurement ion beam H, and a superconducting spectrometer unit ( (Hereinafter abbreviated as “spectrometer section”) X2.
Further, the accelerator X1 includes an ion source 11 that generates ions (primary ions) such as hydrogen or helium, an acceleration tube 12 that accelerates ions by applying a high voltage to the generated ions to form an ion beam H, and It has.
The ion beam H generated by the accelerator X1 passes through the beam duct 13 and through the quadrupole lens 14 and an objective collimator (not shown) toward the sample S arranged in the measurement chamber 20 of the spectrometer unit X2. Emitted.

On the other hand, the spectrometer unit X2 has a cylindrical measurement chamber 20 extending in the axial direction of the ion beam H and a uniform magnetic field (magnetic field) arranged on the side surface of the measurement chamber 20 and parallel to the axis of the ion beam H. An electromagnet 30 to be generated, a vacuum pump 38 for discharging the air in the measurement chamber 20 to the outside, and the like are provided. Here, the electromagnet 30 includes a superconducting solenoid coil (hereinafter referred to as a solenoid coil) 35, a correction coil 36, and a magnet yoke 37 that covers them. Further, the air in the measurement chamber 20 is sucked and discharged by a suction device (not shown) through the vacuum pump 38, whereby the inside of the measurement chamber 20 is maintained in a substantially vacuum state during the measurement.
Further, in the measurement chamber 20, there are a sample stage 22 on which the sample S is placed, an ion detector 21 that outputs a pulse current signal when scattered ions are incident, and the sample S and the ion detector 21. And an ion discrimination aperture 23 (an example of an ion discrimination means) disposed between them.
The aperture 23 allows the ion beam H incident on the sample S from the ion detector 21 side to pass, and ionizes scattered ions having specific energy and scattering angle converged on the axis of the ion beam H by the magnetic field of the solenoid coil 35. It is a plate-like member provided with an opening (ion opening for ion passage) for allowing the detector 21 to pass through. In general, the aperture 23 is constituted by a circular plate-like member having an opening for passing scattered ions substantially at the center. That is, the central opening of the CD-ROM is very small.

In the measurement chamber 20, when the incident ion beam H is irradiated onto the sample S, the incident ions collide with the constituent elements on the sample surface and are scattered. The scattered ions are subjected to Lorentz force by the magnetic field generated by the solenoid coil 35, and move away from the sample S along the spiral orbit (cyclotron orbit) in the measurement chamber 20 (direction of the magnetic field), that is, the direction of the ion detector 21. Make a swivel flight toward Such swirling flight of scattered ions is generally called cyclotron motion.
An aperture 23 is arranged at a position where scattered ions having specific energy and scattering angle converge on the axis of the ion beam H or in the vicinity thereof, and only the specific scattered ions pass through the aperture 23 and the ion detector 21. Passes to the side and other scattered ions are blocked. Thereby, only the scattered ions having specific energy and scattering angle can be discriminated and detected by the two-dimensional ion detector 21 to obtain an energy spectrum. Based on the energy spectrum thus obtained, identification of the component elements of the sample S and composition analysis in the depth direction can be performed.
JP-A-7-190963

However, the conventional aperture 23 is configured by a plate-like member that is provided with a very small opening through which specific scattered ions pass so that other than specific ones of the scattered ions do not pass to the ion detector 21 side. Therefore, the conductance (air permeability) is small, and this acts like a partition plate that partitions the measurement chamber 20 into the ion detector 21 side and the sample S side. Therefore, when the vacuum pump 38 evacuates the measurement chamber 20, there is a difference in vacuum state (difference in vacuum level) between the space on the ion detector 21 side and the space on the sample S side in the measurement chamber 20. This has the problem of affecting measurement accuracy. In addition, since the vacuum pump 38 is generally provided on the sample S side (see FIG. 3), the ion detector 21 side is not in a sufficient vacuum state, which causes discharge of the ion detector 21, resulting in the ion detector. There was also a problem that 21 deteriorated.
Therefore, the present invention has been made in view of the above circumstances, and the object of the present invention is to ensure the discrimination performance of scattered ions that allows only specific scattered ions to pass through and reliably blocks other scattered ions. On the other hand, it is an object of the present invention to provide a parallel magnetic field type Rutherford backscattered ion measuring apparatus including an ion discriminating means that increases conductance (increases air permeability) and does not cause a pressure difference in a measurement chamber.

In order to achieve the above-described object, the present invention is a method in which scattered ions back-scattered from a sample on which an ion beam is incident are placed in a magnetic field parallel to the ion beam in a measurement chamber in a substantially vacuum (generally in a high vacuum state). It is used in a backscattered ion measuring device (that is, a parallel magnetic field type Rutherford backscattered ion measuring device) that is detected by an ion detector after flying, and is disposed between the sample and the ion detector, and the scattering Parallel magnetic field type Rutherford backscattered ion measurement provided with ion discriminating means provided with an ion passage opening for allowing a part of ions to pass toward the ion detector and a blocking portion for blocking the passage of other scattered ions It is applied to the device.
Here, the present invention provides a state in which no gap is formed when viewed from the axial direction of the ion beam by having portions that overlap each other when viewed from the axial direction of the ion beam in the blocking portion of the ion discriminating means. A communication mechanism for providing communication between the sample side and the ion detector side is provided.
With such a configuration, only specific scattered ions that have reached the position of the ion passage opening that is formed to be very small pass through this and reach the ion detector. On the other hand, since the communication mechanism in the blocking unit has no gap formed by overlapping portions when viewed from the axial direction of the ion beam, scattered ions other than the specific scattered ions are blocked by this blocking unit. Ion discrimination performance is secured. Furthermore, since the communication mechanism allows the sample side and the ion detector side to communicate with each other, an ion discriminating means that hardly causes a pressure difference in the measurement chamber can be configured.

As a more specific configuration of the communication mechanism, for example, the plate-shaped blocking portion is formed to communicate the sample side and the ion detector side in an oblique direction with respect to the axial direction of the ion beam. The thing comprised by the slit can be considered.
The slit in this case is formed so that the sample side and the ion detector side communicate with each other in a direction orthogonal or substantially orthogonal to the direction in which the scattered ions swirl and fly in the plate-shaped blocking unit. It is desirable to be.
As a result, unnecessary scattered ions other than the specific scattered ions that reach a position other than the ion passage opening in the ion discriminating means are reliably ensured by the slit wall perpendicular or nearly perpendicular to the flight direction (traveling direction). It is blocked and does not reach the ion detector side. That is, the discrimination performance of scattered ions is ensured. In addition, the slit can secure the air permeability between the space on the ion detector side and the space on the sample side, and can constitute an ion discriminating means that does not cause a pressure difference (a difference in vacuum state) as much as possible.
Further, as another specific example of the communication mechanism, for example, a plurality of plate-shaped blocking portions may be arranged in the axial direction of the ion beam in a state where a part thereof overlaps each other when viewed from the axial direction of the ion beam. It is possible to use a mechanism that is configured to hold at intervals.
As an example, the blocking portion includes a first plate-like member in which the ion passage opening is formed, and an outer edge larger than the first plate-like member, and the sample side and the ion detector side are disposed inside the first plate-like member. And one or a plurality of second plate-like members in which a communication opening serving as a communication path is formed, and the communication mechanism includes the first plate-like member and the second plate-like member. , When viewed from the axial direction of the ion beam, each of the communication opening portions of the second plate-like member is formed by the first plate-like member, or the first plate-like member and the other second A structure constituted by a mechanism that holds the ion beam at an interval in the axial direction in a state of being blocked by a plate-like member is conceivable.

  According to the present invention, the sample side and the ion detector are formed in a state where no gap is formed when viewed from the axial direction of the ion beam in the blocking portion (portion other than the ion passage opening) in the ion discriminating means. Since a communication mechanism is provided to communicate with the side of the ion detector, the ion detector side allows only specific scattered ions to pass through and blocks other unnecessary scattered ions, while ensuring the discrimination performance of scattered ions. It is possible to provide a parallel magnetic field type Rutherford backscattered ion measuring apparatus provided with an ion discriminating means which does not cause a pressure difference (difference in vacuum state) between both the detector side and the sample side. As a result, it is possible to avoid the occurrence of a measurement error due to the pressure difference in the measurement chamber. Furthermore, the high vacuum property around the ion detector can be maintained, and deterioration due to discharge of the ion detector can be prevented.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings for understanding of the present invention. In addition, the following embodiment is an example which actualized this invention, Comprising: The thing of the character which limits the technical scope of this invention is not.
FIG. 1 is a front view and a partial cross-sectional view of an ion discrimination aperture Z1 according to the first embodiment of the present invention. FIG. 2 is a front view and a side view of the ion discrimination aperture Z2 according to the second embodiment of the present invention. (Partial cross-sectional view), FIG. 3 is a cross-sectional view showing a schematic configuration of a parallel magnetic field type Rutherford backscattered ion measuring apparatus X to which the ion discrimination aperture according to the embodiment of the present invention is applied, and FIG. 4 is a parallel magnetic field type Rutherford. 4 is a cross-sectional view illustrating a schematic configuration of a measurement chamber in the backscattered ion measurement apparatus X. FIG.

The ion discriminating apertures Z1 and Z2 (hereinafter referred to as apertures Z1 and Z2), which are ion discriminating means according to the embodiment of the present invention, are represented by the general parallel magnetic field type Rutherford backscattered ion measuring apparatus X (hereinafter referred to as the following). This is applied to a scattered ion measurement device X).
In the backscattered ion measuring apparatus X shown in FIG. 3, the scattered ions backscattered from the sample S on which the ion beam H is incident in the vacuum measurement chamber 20 are made to fly after flying in a magnetic field parallel to the ion beam H. Although it is an apparatus which detects with the detector 21, since it already demonstrated, description is abbreviate | omitted here. Note that the aperture 23 shown in FIG. 3 is replaced with the aperture Z1 or Z2 (hereinafter collectively referred to as the aperture Z) according to the embodiment of the present invention.

Here, the measurement chamber 20 provided in the backscattered ion measurement apparatus X will be described in more detail with reference to FIG.
The measurement chamber 20 is formed in a substantially cylindrical shape, is arranged so that the center axis of the cylinder coincides with the axis of the ion beam H, and the magnetic pole 31 that closes the entrance side of the ion beam H passes through the ion beam H. An opening 31a is provided. In the measurement chamber 20, a solenoid coil 35, a correction coil (see FIG. 3), and a magnet yoke (see FIG. 3) are arranged around, so that a magnetic field parallel to the axis of the ion beam H is generated.
In the measurement chamber 20, an ion detector 21, a scattered ion discrimination aperture Z, and a sample S are arranged in this order from the upstream side in the irradiation direction of the ion beam H (the magnetic pole 31 side). Here, an opening 21 a through which the ion beam H passes is provided in the approximate center of the ion detector 21.
On the other hand, an ion beam H is allowed to pass through substantially the center of the aperture Z disposed between the sample S and the ion detector 21 and a part of scattered ions flying from the sample S (specific scattered ions described later). ) An opening Za for passing e1 to the ion detector 21 side (hereinafter referred to as an ion passage opening) is provided, and a blocking portion Zb for blocking the passage of other scattered ions e2 is formed around the opening Za. .
The outer edge of the aperture Z has a shape substantially along the inner surface of the measurement chamber 20, and the measurement chamber 20 is partitioned by the aperture Z into a sample side 20a and an ion detector side 20b. .

In the measurement chamber 20 in a vacuum state, the sample beam S is irradiated with the ion beam H, and ions constituting the ion beam H strike the composition elements on the surface of the sample S and are scattered. The scattered ions receive a Lorentz force by a parallel magnetic field generated by the solenoid coil 35 and the like, and move away from the sample S (magnetic field direction) along the spiral orbit (cyclotron orbit) in the measurement chamber 20, that is, ion detection. A turn flight (cyclotron motion) is performed in the direction of the vessel 21.
The aperture Z is arranged such that the ion passing aperture Za is located at a position where scattered ions having specific energy and scattering angle (hereinafter referred to as specific scattered ions e1) are substantially converged on the axis of the ion beam H. Only the specific scattered ions e1 pass to the ion detector 21 side through the ion passage opening Za, and the other scattered ions e2 are blocked by the blocking unit Zb.

<First Embodiment>
Next, the scattered ion discrimination aperture Z1 according to the first embodiment of the present invention will be described with reference to FIG.
As shown in the front view of FIG. 1, the aperture Z <b> 1 is formed with a blocking portion Zb by a circular plate-like member so that the outer edge thereof is along the inner surface of the measurement chamber 20, and the ion passage opening Za is substantially at the center. Is provided. The aperture Z1 is arranged such that the ion beam H passes through the ion passage opening Za.
Further, the blocking portion Zb is provided with a plurality of slits Zc extending along radiation centering on the axis of the ion beam H.
As shown in the AA ′ cross-sectional view in FIG. 1, the slit Zc is formed in the measurement chamber 20 in a direction oblique to the axial direction of the ion beam H (direction R1 in FIG. 1) in the plate-shaped blocking portion Zb. The sample side 20a and the ion detector side 20b are formed so as to communicate with each other, and have portions 51 and 52 that overlap each other when viewed from the axial direction of the ion beam H, so that they can be viewed from the axial direction of the ion beam H. Thus, no gap is formed (an example of a communication mechanism).
By providing such a slit Zc in the blocking part Zb, the sample side 20a and the ion detection are detected in the measurement chamber 20 while ensuring the discrimination performance of allowing only the specific scattered ions e1 to pass (blocking other scattered ions e2). The conductance between the container side 20b can be increased and the pressure difference between the two spaces can be eliminated.

Here, the scattered ions e2 make a cyclotron motion and swirl, but as shown in the AA ′ cross-sectional view of FIG. 1, the scattered ions e2 swirl and fly in the slit Zc at the plate-shaped blocking portion Zb. The sample side 20a and the ion detector side 20b in the measurement chamber 20 are formed to communicate with each other in a direction R1 substantially orthogonal to the direction.
With such a configuration, it is possible to reliably block the scattered ions e2 while ensuring a high conductance by relatively reducing the width (overlapping range) of the overlapping portions 51 and 52 as viewed from the axial direction of the ion beam H.
Further, since the scattered ions e2 swirl around the axis of the ion beam H, the slit Zc in a direction substantially orthogonal to the direction of the swirl flight of the scattered ions e2 has the axis of the ion beam H as described above. If it is formed extending in the direction along the central radiation, the angle condition is almost the same with respect to the flight direction of the scattered ions e2 at any position. As a result, unnecessary scattered ions e2 are surely blocked by the wall forming the slit Zc, and can be reliably prevented from passing to the ion detector 21 side through the slit Zc.

Second Embodiment
Next, an aperture Z2 for scattered ion discrimination according to a second embodiment of the present invention will be described with reference to FIG.
As shown in FIG. 2, the aperture Z2 includes a plurality of (three in FIG. 2) plate-like blocking portions Zb1 to Zb3, and the plurality of blocking portions Zb1 to Zb3 are formed by columnar spacers Ze (posts). As seen from the axial direction of the ion beam H, the portions 61, 62a, 62b, 63 are held in the axial direction of the ion beam H with a gap Zd1, Zc2 therebetween.
In the example shown in FIG. 2, one blocking portion Zb1 is a circular plate-shaped member (an example of a first plate-shaped member) in which the ion passing opening Za is formed, and the other two sheets Each of the blocking portions Zb2 and Zb3 has a larger outer edge than the blocking portion Zb1, and communication openings Zc2 and Zc3 are formed inside the blocking portion Zb1 and serve as a communication path between the sample side 20a and the ion detector side 20b in the measurement chamber 20. This is a donut plate-like plate member (an example of a second plate member). Here, the communication opening Zc2 of the blocking part Zb2 is formed smaller than the outer edge of the blocking part Zb1, the communication opening Zc3 of the blocking part Zb3 is larger than the outer edge of the blocking part Zb1, and the blocking part Zb2 It is formed smaller than the outer edge. In addition, the largest blocking portion Zb3 is formed in a circular shape so that the outer edge thereof is along the inner surface of the measurement chamber 20.
The three plate-like blocking portions Zb1 are arranged substantially parallel to the axial direction of the ion beam H with intervals Zd1 and Zd2, and are connected and held by columnar spacers Ze provided at the intervals. Has been.
The aperture Z2 is arranged such that the ion beam H passes through the ion passage opening Za.

As shown in FIG. 2, the aperture Z <b> 2 also includes portions 61, 62 a, 62 b, and 63 that overlap each other when the blocking portions Zb <b> 1 to Zb <b> 3 are viewed from the axial direction of the ion beam H. As a result, no gap is formed. Further, the communication openings Zc2 and Zc3 and the distances Zd1 and Zd2 (gap) between the blocking portions Zb1 to Zb3 are communication paths between the sample side 20a and the ion detector side 20b in the measurement chamber 20. (An example of a communication mechanism).
In the example shown in FIG. 2, when viewed from the axial direction of the ion beam H, the communication opening Zc2 of the blocking portion Zb2 (an example of the second plate member) is the blocking portion Zb1 (an example of the first plate member). In the axial direction of the ion beam H in a state where the opening Zc3 for communication of the blocking part Zb3 (an example of the second plate member) is blocked by the blocking part Zb1 and the blocking part Zb2. The spacers Ze hold the gaps Zd1 and Zd2.
By having such a structure, unnecessary scattered ions e2 other than the specific scattered ions that reach the ion passage opening Za are reliably blocked by the wall surfaces of the respective blocking portions Zb1 to Zb3. Passing to the ion detector 21 side through the parts Zc1 to Zc3 can be reliably prevented. That is, the pressure difference between the space on the sample side 20a and the space on the ion detector side 20b in the measurement chamber 20 while ensuring the discrimination performance of allowing only the specific scattered ions e1 to pass (blocking other scattered ions e2). (Difference in vacuum state) can be eliminated.
Further, by sufficiently securing the intervals Zd1 and Zd2 between the plurality of blocking portions Zb1 to Zb3, the pressure loss can be further suppressed as compared with the case where the slit Zc in the aperture Z1 described above is provided. Further, it is not necessary to process the blocking portion in an oblique direction, and it can be manufactured relatively easily.

  The apertures Z1 and Z2 described above are examples embodying the present invention, and have a portion that overlaps each other when viewed from the axial direction of the ion beam H in a blocking portion that blocks scattered ions other than specific scattered ions. Thus, the communication path between the sample side 20a and the ion detector side 20b in the measurement chamber 20 is formed while the gap is not generated when viewed from the axial direction of the ion beam H. If there is, it is an embodiment of the present invention even if it is realized by another configuration.

The front view and partial sectional view of the ion discrimination aperture Z1 according to the first embodiment of the present invention. The front view and side view (partial sectional view) of an ion discrimination aperture Z2 according to a second embodiment of the present invention. Sectional drawing showing schematic structure of the parallel magnetic field type | mold Rutherford backscattering ion measuring apparatus X used as the application object of the ion discrimination aperture which concerns on embodiment of this invention. FIG. 4 is a cross-sectional view illustrating a schematic configuration of a measurement chamber in the parallel magnetic field type Rutherford backscattered ion measurement apparatus X.

Explanation of symbols

X ... Parallel field type Rutherford backscattered ion measuring device X1 ... Accelerator X2 ... Superconducting spectrometer part Z1, Z2, Z ... Aperture Za ... Ion passage opening Zb, Zb1, Zb2, Zb3 ... Blocking part Zc ... Slit Ze ... Spacer S ... Sample 11 ... Ion source 12 ... Accelerator tube 20 ... Measurement chamber 21 ... Ion detector 22 ... Sample stand 30 ... Electromagnet 35 ... Superconducting solenoid coil 36 ... Correction coil

Claims (5)

This is a parallel magnetic field type Rutherford backscattered ion measuring device that detects scattered ions backscattered from a sample in which an ion beam is incident in a substantially vacuum measurement chamber by flying in a magnetic field parallel to the ion beam and then detecting the ions with an ion detector. And
An ion passage opening that is disposed between the sample and the ion detector and allows a part of the scattered ions to pass to the ion detector, and a blocking portion that blocks passage of the other scattered ions. Is provided, and the blocking portion has portions overlapping each other when viewed from the axial direction of the ion beam, so that no gap is formed when viewed from the axial direction of the ion beam and the ion side is detected. A parallel magnetic field type Rutherford backscattered ion measuring apparatus, comprising ion discriminating means provided with a communication mechanism for communicating with the vessel side.   2. The communication mechanism is configured by a slit formed to communicate the sample side and the ion detector side in an oblique direction with respect to the axial direction of the ion beam to the plate-shaped blocking portion. 2. A parallel magnetic field type Rutherford backscattered ion measuring apparatus described in 1.   The said slit is formed so that the said sample side and the said ion detector side may be connected in the direction substantially orthogonal to the direction in which the said scattered ion turns in the plate-shaped said interruption | blocking part. Parallel magnetic field type Rutherford backscattered ion measuring device.   The communication mechanism is configured by a mechanism that holds the plurality of plate-shaped blocking portions at intervals in the axial direction of the ion beam in a state where a part thereof overlaps each other when viewed from the axial direction of the ion beam. The parallel magnetic field type Rutherford backscattered ion measuring apparatus according to claim 1. The blocking portion includes a first plate-like member in which the ion passage opening is formed, an outer edge larger than the first plate-like member, and the sample side and the ion detector side inside the first plate-like member. And one or a plurality of second plate-like members in which a communication opening serving as a communication path is formed,
The communication mechanism is
When the first plate member and the second plate member are viewed from the axial direction of the ion beam, each of the communicating openings of the second plate member is formed by the first plate member. Alternatively, the parallel structure according to claim 4, comprising a mechanism that holds the ion beam at an interval in the axial direction while being closed by the first plate-like member and the other second plate-like member. Magnetic field type Rutherford backscattered ion measuring device.

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