JP2003346696A - Scattered ion analyzer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a scattered ion analyzer making it possible to analyze a sample with high resolution by generating a magnetic field parallel with an incident ion beam and equipped with a secondary electron detector capable of exactly detecting secondary electrons produced on the surface of the sample by incidence of the ion beam. <P>SOLUTION: In the scattered ion analyzer equipped with an ion beam generating means X irradiating a sample 2 with an accelerated ion beam 1, magnetic field generating means 8-11 generating a magnetic field parallel with the ion beam, an aperture 15 arranged within the parallel magnetic field for striking the ion beam and permeating scattered ions, and an ion detector arranged with a space of a prescribed distance on an upstream side rather than the aperture 15 in an incident direction of the ion beam 1, a secondary electron detector 13 is provided on an upstream side rather than the region of the parallel magnetic field in the incident direction of the ion beam 1. <P>COPYRIGHT: (C)2004,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the identification of sample constituent elements by irradiating a sample with ions of a single energy such as helium or hydrogen and analyzing the energy spectrum of scattered ions scattered from the sample surface. More specifically, the present invention relates to an ion scattering analyzer for performing composition analysis in the direction of depth and in the depth direction.
The present invention relates to an apparatus having a secondary electron detector.

[0002]

2. Description of the Related Art For example, in the field of semiconductor development and crystalline thin films, research and development of device materials by epitaxial film formation, MBE film formation, and the like have been conducted. Defects (for example, vacancies, impurity adsorption, abnormal growth, etc.) in the surface layer of these materials, specifically, one to several atomic layers, have a large effect on the characteristics. Therefore, in the development and production control of these materials, information on surface layer defects is extremely important. Also, the bonding state between atoms in the surface layer can be important information for understanding the material properties. For these reasons, it is extremely important to know the information on the surface layer in the development of device materials. As a method for analyzing the information of the surface layer of such a sample, Rutherford Backscattering (Rutheford Backs) is used.
catering Spectroscopy: RB
S). RBS analysis irradiates a sample with light ions (eg, hydrogen or helium) accelerated to about 1 million eV,
Among the scattered ions elastically scattered by the constituent atoms in the sample, the energy spectrum of the scattered ions scattered backward (scattering angle: 180 °) is measured to identify sample constituent elements and composition in the depth direction. The analysis can be performed nondestructively and with high accuracy. Furthermore, the above RBS
In the analysis, the ion beam irradiating the sample is
By converging with a converging lens or the like to form an ion beam that forms a beam spot on the surface of the sample, local analysis of the sample can be performed. Incidentally, in order to perform the local analysis, it is necessary to accurately irradiate the ion beam forming the beam spot to a predetermined position of the sample to be measured. Therefore, the conventional RB
The S analyzer detects the secondary electron intensity generated on the sample surface together with the scattered ions by the irradiation of the ion beam, thereby grasping information on the irregularities or composition of the sample surface, and irradiating the ion beam. It was common to determine the location. Here, FIG. 2 shows a typical configuration of a secondary electron detector for detecting a secondary electron intensity. As shown in the figure, the secondary electron detector Y includes a scintillator 5 made of plastic or the like covered with a mesh or an ultra-thin conductive electrode 4 to which a positive potential is applied by a power supply 7, and a photomultiplier tube 6. And has a structure similar to that of an electron microscope, for example. Thereby, the secondary electron detector Y can pull the secondary electrons 3 generated on the surface of the sample 2 by the ion beam 2 with the ultra-thin conductive electrode 4 having a positive potential. The secondary electrons 3 accelerated by the above strike the scintillator 5 to emit fluorescent light, and the light can be captured with high sensitivity by the photomultiplier 6. Therefore, the operator who performs the local analysis can grasp information on the sample surface by using the data (secondary electron intensity) obtained from the secondary electron detector Y, and can form a beam spot. The above-described ion beam can be accurately applied to a predetermined position of the sample to be measured.

On the other hand, with the dramatic improvement in semiconductor technology in recent years, the sample to be measured is at the atomic layer level (〜１０10 to 10).
The thickness of the sample has been reduced to 1), and further improvements in the technology for measuring the film thickness of the sample and analyzing the composition are desired. Therefore, the RBS analyzer based on the conventional RBS analysis was improved, and its resolution was increased to the atomic layer level.
An S analyzer has been developed and disclosed in Japanese Patent Application Laid-Open No. Hei 7-190963. RB disclosed by the above publication
As shown in FIG. 3, the S analyzer B includes an ion beam generator X (corresponding to an ion beam generator) for irradiating an ion beam 1, a measurement chamber 21 for disposing a sample 2 to be analyzed, and a superconducting solenoid. A coil 8, a set of pole pieces 10 and 11, and a return yoke 9 are provided, and a strong magnetic field parallel to the ion beam 1 is applied from a vicinity of the sample 2 to a predetermined region on the upstream side in the incident direction of the ion beam 1. A magnetic field generator (corresponding to a magnetic field generating means) to be generated, and the ion beam 1 disposed in the measurement chamber 21 and incident thereon, and the scattered ions 20 converged by the parallel magnetic field incident on the ion beam 1 Aperture 15 having an opening at the center for passage in the opposite direction
And an ion detector 16 which is disposed in the parallel magnetic field at a predetermined distance upstream of the aperture 15 in the direction of incidence of the ion beam 1 and has an opening at the center for allowing the ion beam 1 to enter. And is schematically configured. The ion beam generator X uses an ion source 1 using a gas (for example, helium gas) supplied from a cylinder.
The light ions generated by 8 are irradiated after being accelerated to a constant energy in the acceleration tube 19 by the high voltage supplied from the Cockcroft type high voltage circuit 17. The ion beam 1 irradiated from the ion beam generator X
Passes through the apertures of the aperture 15 and the ion detector 16 and irradiates the surface of the sample 2 arranged in the measurement chamber 21. The scattered ions 20 scattered from the surface of the sample 2 by the irradiation of the ion beam 1
Is converged by the magnetic field of the magnetic field generator, and only the scattered ions 20 (having a specific energy) satisfying a specific condition pass through the opening of the aperture 15 and are detected by the scattered ion detector 16. . The RBS analyzer B changes the intensity of the magnetic field generated by the magnetic field generator or the distance between the aperture 15 and the sample 2 to change the scattered ions 20 scattered from the surface of the sample 2. Of the above, the scattered ions 20 that pass through the opening of the aperture 15 and are detected by the scattered ion detector 16 can be sorted for each energy, and the energy spectrum of the scattered ions 20 can be measured with high accuracy. can do. With such a configuration, the RBS analyzer B enables the analysis at the atomic layer level of the sample surface which could not be measured by the conventional RBS analyzer, and the surface of the ultra-thin sample described above. A high energy resolution that can be applied to the analysis of defects in layers and the like has been realized.

[0004]

Here, it is assumed that the above-mentioned RBS analyzer B desires to perform a local analysis using an ion beam forming a beam spot. In that case, similar to the case of the conventional RBS analyzer described above,
In order to accurately irradiate the irradiation position of the ion beam to a predetermined position, it is essential to detect the intensity of secondary electrons generated by the ion beam. However,
In the RBS analyzer B, a magnetic field parallel to the ion beam 1 is generated in a predetermined area in the measurement chamber 21. Therefore, the secondary electrons 3 generated on the surface of the sample 2 by the irradiation of the ion beam 1 irrespective of the scattering direction and the energy, are changed to the magnetic flux lines along the ion beam 2 in the region of the parallel magnetic field. Wrap around,
While moving spirally (cyclotron), the ion beam 1 goes back to the upstream side in the incident direction of the ion beam 1 (an example of the trajectory of the secondary electron 3 is indicated by an arrow in the figure). The radius of the spiral movement is generally called a Rama radius, and is estimated to be about 1 μm when the energy of the secondary electrons 3 is 100 eV and the intensity of the parallel magnetic field is 2 Tesla. Therefore, the above RBS
In the analyzer B, it is difficult to pull the secondary electrons spirally wrapped around the magnetic flux lines into the electrodes even if the known secondary electron detector Y shown in FIG. 2 is used. There is a possibility that accurate secondary electron intensity (information on the sample surface) cannot be grasped, so that accurate local analysis cannot be performed. Accordingly, the present invention has been made in view of the above circumstances, and an object of the present invention is to generate a magnetic field parallel to an incident ion beam, thereby enabling an ion scattering analyzer to analyze a sample with high resolution. In the above, an object of the present invention is to provide an ion scattering analyzer having a secondary electron detector capable of accurately detecting secondary electrons generated on the surface of the sample by the incidence of the ion beam.

[0005]

In order to achieve the above object, the present invention irradiates a sample placed in a vacuum vessel with an accelerated ion beam to scatter scattered ions from the sample surface. An ion beam generating means, a magnetic field generating means for generating a magnetic field parallel to the ion beam from a vicinity of the sample to a predetermined region on the upstream side in the incident direction of the ion beam, and a magnetic field generating means arranged in the parallel magnetic field; An aperture having a central portion through which a beam is incident and through which the scattered ions converged by the parallel magnetic field pass in a direction opposite to the direction of incidence of the ion beam; and an incidence direction of the ion beam rather than the aperture. An ion detector arranged in the parallel magnetic field at a predetermined distance away from the upstream side and having an opening at the center for letting the ion beam enter. A scattered ion analyzer for analyzing the sample by measuring an energy spectrum of the scattered ions from the sample surface based on data from the ion detector. A secondary electron detector which has an opening at the center thereof for passing the ion beam on the upstream side in the direction of incidence of the ion beam and detects secondary electrons generated on the sample surface by irradiation of the ion beam. Is provided as a scattered ion analyzer. Here, it is preferable that the secondary electron detector is provided at a position where the magnetic flux of the magnetic field generating means is blocked. As a result, the secondary electrons generated on the sample surface by the incidence of the ion beam and wrapping around the magnetic flux lines along the ion beam and moving backward in the direction of incidence of the ion beam while spirally moving are converted into the secondary electrons. The detection can be performed accurately by the detector, and the information on the sample surface (such as unevenness / composition) can be accurately grasped. As a result, for example, when a user using the apparatus desires to perform a local analysis using an ion beam that forms a beam spot, the beam spot can be accurately guided to a predetermined position on the sample. In addition, by displacing the sample two-dimensionally, the two-dimensional intensity of the sample is two-dimensionally mapped, and the two-dimensional intensity of the sample is reconstructed.
It can be expressed as a next electronic image, and the beam spot can be guided to a predetermined position with better operability.

Further, it is preferable that the secondary electron detector is formed in a cylindrical shape or a cylindrical shape that diverges from an upstream side to a downstream side in the incident direction of the ion beam. Thus, the magnetic flux lines (magnetic fields) generated by the magnetic field generating means are radially away from the incident beam further upstream of the parallel magnetic field than the region of the parallel magnetic field, so that the secondary beam moves along the magnetic flux lines. Since electrons collide with the inner surface of the secondary electron detector at an angle close to perpendicular,
The secondary electrons efficiently flow into the secondary electron detection unit (flow as current).

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments and examples of the present invention will be described below with reference to the accompanying drawings to provide an understanding of the present invention. The following embodiments and examples are mere examples embodying the present invention, and do not limit the technical scope of the present invention. 1 is a diagram showing a schematic configuration of a scattered ion analyzer A according to an embodiment of the present invention, FIG. 2 is a configuration diagram of a conventionally known secondary electron detector Y, and FIG. FIG. 2 is a diagram illustrating a schematic configuration of an analyzer B.

First, the configuration of a scattered ion analyzer A according to an embodiment of the present invention will be described with reference to FIG.
The same elements as those of the conventionally known scattered ion analyzer B are denoted by the same reference numerals. The scattered ion analyzer A
Is a measuring chamber 21 which is a vacuum vessel, an ion beam generator X for emitting an ion beam 1 for irradiating a sample 2 to be analyzed in the measuring chamber 21, a superconducting solenoid coil 8 and a set of pole pieces ( Magnetic pole) 10,1
1 and a return yoke 9 and the measurement chamber 2
1. A magnetic field generator (corresponding to a magnetic field generating means) for generating a strong magnetic field parallel to the ion beam 1 in the apparatus 1; The converged scattered ions 2
An aperture 15 having a central portion through which an ion beam 1 passes through in the direction opposite to the direction of incidence of the ion beam 1, and the aperture 15 at a predetermined distance upstream of the aperture 15 in the direction of incidence of the ion beam 1. An ion detector 16 which is arranged in a magnetic field and has an opening at the center thereof for letting the ion beam 1 incident thereon, and a secondary electron detector such as an electrode for capturing secondary electrons 3 generated on the surface of the sample 2 And a secondary electron detector including a microammeter 14 for detecting a current due to the secondary electrons captured by the secondary electron detection unit 13. Here, the secondary electron detector uses a scintillator and a photomultiplier tube coated with a potential electrode drawn into the secondary electron detector 13 and detects an electric current due to the secondary electrons amplified by these with an ammeter. Or the like. The ion beam generator X converts the light ions generated by the ion source 18 using a gas (for example, helium gas) supplied from a cylinder into a high-voltage supplied from a Cockcroft-type high-voltage circuit 17 to the acceleration tube 1.
Irradiate after accelerating to a constant energy in 9. Also,
In the magnetic field generators 8 to 11, one of the pole pieces 10 constituting the magnetic field generators 8 faces the downstream side of the analysis chamber 21 in the direction of incidence of the ion beam 1, and the other pole piece 11 faces the upstream side. The sample 2 is irradiated with the ion beam 1 through an opening 11 a provided in the pole piece 11, and a magnetic field parallel to the ion beam 2 is applied between the pole pieces 10 to 11. It is configured to generate. This allows
A strong magnetic field (hereinafter, referred to as a parallel magnetic field) parallel to the ion beam 2 is generated in a region (hereinafter, referred to as a parallel magnetic field region) upstream of the sample 2 in the direction of incidence of the ion beam 1. (The generated magnetic flux is indicated by an arrow 12 in the figure.) The opening 11a provided in the pole piece 11 on the upstream side in the incident direction of the ion beam 1 is formed in a substantially conical shape with the opening as a vertex. At the same time, the secondary electron detector 13 formed in a tubular shape diverging from the upstream side to the downstream side in the incident direction of the ion beam 2 is provided in an insulated state.

Next, the operation of the scattered ion analyzer A will be described. The ion beam 1 radiated from the ion beam generator X is applied to the secondary electron detector 13.
Opening 1 and the ion detector 1 in the parallel magnetic field region
6 and the surface of the sample 2 is irradiated through the opening of the aperture 15. At this time, since the strong magnetic field generated by the magnetic field generator is parallel to the ion beam 1, the ion beam 1 travels straight without being affected by the magnetic field and reaches the surface of the sample 2. The scattered ions 20 scattered from the surface of the sample 2 by the ion beam 1 are converged by the parallel magnetic field, and only the scattered ions 20 having a specific condition (having a specific energy) meet the aperture 15.
And the scattered ion detector 16 detects it. On the other hand, the secondary electrons 3 generated on the surface of the sample 2 are helically wound around the magnetic flux lines along the ion beam 2 in the parallel magnetic field region regardless of the scattering direction and energy (about 100 eV). It moves back to the ion beam 1 upstream direction while moving. That is, all the secondary electrons 3 generated on the surface of the sample 2 move back along the parallel magnetic field while spirally moving toward the upstream side in the incident direction of the ion beam 1. Here, the secondary electron detector 13
Is provided at a position where it blocks the magnetic flux of the magnetic field generating means, so that the secondary electrons 3 that trace back along the magnetic flux can be captured at a capture rate of approximately 100%. by the way,
In the vicinity of the secondary electron detection unit 13 further upstream of the ion beam 1 in the parallel magnetic field region, a magnetic flux line (magnetic field) generated by the magnetic field generator is applied to the return yoke 10 provided outside the pole piece 9. Radially away from the ion beam 1 (see the magnetic flux lines shown in FIG. 1). Therefore, the secondary electrons 3 moving along the magnetic flux lines are almost perpendicular to the inner surface of the secondary electron detection unit 13 formed in a divergent cylindrical shape toward the downstream side of the ion beam 1. The secondary electrons 3
Efficiently flows into the secondary electron detection unit 13 (flows as a current). Of course, there is no particular problem in detecting the secondary electrons 3 even if the secondary electron detector 13 is formed in a cylindrical shape or a disk shape provided with an opening through which the ion beam 1 passes. In addition, if the secondary electron intensity obtained while displacing the sample 2 two-dimensionally in the direction of the arrow Z shown in FIG. It is also possible to express information on the surface of the sample 2 as a next electronic image.

[0010]

As described above, the present invention provides an ion beam generating means for irradiating a sample placed in a vacuum vessel with an accelerated ion beam and scattering scattered ions from the surface of the sample. Magnetic field generating means for generating a magnetic field parallel to the ion beam from a vicinity of the sample to a predetermined region on the upstream side in the direction of incidence of the ion beam; and a magnetic field generating means arranged in the parallel magnetic field for causing the ion beam to enter; An aperture having an opening at the center for passing the scattered ions converged by the parallel magnetic field in a direction opposite to the direction of incidence of the ion beam, and a predetermined distance upstream of the aperture in the direction of incidence of the ion beam; An ion detector which is located in the parallel magnetic field at a distance and has an opening at the center for letting the ion beam enter. In a scattered ion analyzer that analyzes the sample by measuring the energy spectrum of the scattered ions from the sample surface based on data from a detector, the scattered ion analyzer is configured to analyze the sample in such a manner that the ion beam is incident more than the parallel magnetic field region. A secondary electron detector having an opening for passing the ion beam in the center at the center in the direction upstream and detecting secondary electrons generated on the sample surface by irradiation of the ion beam is provided. It is configured as a scattered ion analyzer characterized by the following. Here, it is preferable that the secondary electron detector is provided at a position where the magnetic flux of the magnetic field generating means is blocked. As a result, the sample is generated on the sample surface by the incidence of the ion beam,
By the action of the parallel magnetic field, the secondary electrons that wind around the magnetic flux lines along the ion beam and return to the upstream side in the incident direction of the ion beam by spiral (cyclotron) motion can be accurately detected by the secondary electron detector. At the same time, it is possible to grasp the information (irregularity / composition) on the sample surface. As a result, for example, even when a user using the apparatus desires to perform a local analysis using an ion beam that forms a beam spot, the beam spot can be accurately guided to a predetermined position on the sample. Become. In addition, by displacing the sample two-dimensionally, the two-dimensional intensity of the sample can be two-dimensionally mapped and expressed as a secondary electron image like an electron microscope. Can be directed to the beam spot.

Further, it is preferable that the secondary electron detector is formed in a cylindrical shape or a cylindrical shape that diverges from an upstream side to a downstream side in the incident direction of the ion beam. Thus, the magnetic flux lines (magnetic fields) generated by the magnetic field generating means are radially away from the incident beam further upstream of the parallel magnetic field than the region of the parallel magnetic field, so that the secondary beam moves along the magnetic flux lines. Since electrons collide with the inner surface of the secondary electron detector at an angle close to perpendicular,
The secondary electrons efficiently flow into the secondary electron detection unit (flow as current).

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a scattered ion analyzer A according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a conventionally known secondary electron detector Y.

FIG. 3 is a diagram showing a schematic configuration of a conventionally known scattered ion analyzer B.

[Explanation of symbols]

1 ... Ion beam 2 ... sample 3 Secondary electrons 4. Ultra-thin conductive electrode 5… Scintillator 6 Photomultiplier tube 7 Power supply 8 ... superconducting solenoid coil 9 ... return yoke 10,11 ... Pole piece (magnetic pole) 11a: Opening of the pole piece on the upstream side of the ion beam 12 ... magnetic flux lines 13 Secondary electron detector 14… Micro ammeter 15 ... Aperture 16 ... Ion detector 17 ... Cockcroft type high voltage circuit 18 ... Ion source 19 ... Accelerator tube 20: Scattered ions 21 ... Measuring chamber

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Ichihara main tax             1-5-5 Takatsukadai, Nishi-ku, Kobe City, Hyogo Prefecture             Kobe Steel, Ltd.Kobe Research Institute (72) Inventor Satoru Yamaguchi             1-5-5 Takatsukadai, Nishi-ku, Kobe City, Hyogo Prefecture             Kobe Steel, Ltd.Kobe Research Institute (72) Inventor Yasuhiro Wasa             1-5-5 Takatsukadai, Nishi-ku, Kobe City, Hyogo Prefecture             Kobe Steel, Ltd.Kobe Research Institute (72) Inventor Mamoru Hamada             1-5-5 Takatsukadai, Nishi-ku, Kobe City, Hyogo Prefecture             Kobe Steel, Ltd.Kobe Research Institute F term (reference) 5C033 NN01 NP01 QQ15

Claims (3)

[Claims] An ion beam generating means for irradiating a sample placed in a vacuum vessel with an accelerated ion beam to scatter scattered ions from a surface of the sample, and an incident direction of the ion beam from near the sample. A magnetic field generating means for generating a magnetic field parallel to the ion beam over a predetermined region on the upstream side; and the scattering converged by the parallel magnetic field while being placed in the parallel magnetic field and allowing the ion beam to enter. An aperture having a central portion through which an ion passes in the direction opposite to the direction of incidence of the ion beam, and an aperture located at a predetermined distance upstream of the aperture in the direction of incidence of the ion beam and arranged in the parallel magnetic field; An ion detector having an opening through which the ion beam is incident at the center thereof, based on the data from the ion detector. In a scattered ion analyzer that analyzes the sample by measuring the energy spectrum of the scattered ions from the sample surface, the center of the ion beam is located on the upstream side of the parallel magnetic field region in the incident direction of the ion beam. A scattered ion analyzer having an opening through which the ion beam passes and a secondary electron detector for detecting secondary electrons generated on the surface of the sample by irradiation of the ion beam; . 2. The scattered ion analyzer according to claim 1, wherein the secondary electron detector is provided at a position where a magnetic flux of the magnetic field generating means is blocked. 3. The scattered ion analyzer according to claim 1, wherein the secondary electron detector is formed in a cylindrical shape or a tubular shape diverging from an upstream side to a downstream side in the incident direction of the ion beam.