JP3983956B2 - Multistage multipole lens system and electron energy analyzer using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a multistage multipole lens system used for an energy analyzer for an electron microscope and an electron energy analyzer using the same, and more particularly to an electron used in an analytical electron microscope for observing a micro part of a sample and performing elemental analysis. The present invention relates to a multistage multipole lens system suitable for improving the convergence characteristics of an energy analyzer and an electron energy analyzer using the same.
[0002]
[Prior art]
By attaching a sector magnetic field energy analyzer to a conventional electron microscope and analyzing the energy of electrons transmitted through the sample, the magnified image of the minute part of the sample becomes clearer, and elemental analysis and mapping images of specific elements are obtained. be able to. In this case, conventionally, in order to increase energy dispersion and improve resolution, a plurality of quadrupole lenses are installed before and after the sector magnetic field. Specific examples thereof are disclosed in, for example, US Pat. No. 4,743,756, PARALLEL DETECTION ELECTRON ENERGY-LOSS SPECTROMETER, (May, 10, 1988).
[0003]
In some cases, a hexapole lens is further connected to remove secondary aberration. As a specific example, a parallel detection type energy loss analyzer is disclosed in, for example, Japanese Patent Application Laid-Open No. 11-96955 (applications 97, 9, 19). The configuration is shown in FIGS. 6A and 6B. This is an electron optical system that combines a quadrupole magnetic lens and a hexapole magnetic lens before and after the sector magnetic field to expand and converge the dispersion and remove secondary aberrations. 10 is an electron beam, 11 is a crossover created by an electron microscope, 12 is a fan-shaped magnetic field, 13 is a quadrupole magnetic lens, 14 is a 6-pole magnetic lens, 15 is a 6-pole magnetic lens, 16 is a quadrupole magnetic pole A child lens, 17 is a double pole lens, and 18 is a diode array detector.
[0004]
The function of this configuration is not sufficient with the energy distribution of the sector magnetic field 12 alone, so the quadrupole lens (Q2) 16 installed after the magnetic field is emitted changes the dispersibility greatly, and the quadrupole at the sector magnetic field entrance. A magnetic pole lens (Q1) 13 converges the diode array detector. However, if the dispersion is expanded with Q2, the secondary aberration related to the beam divergence angle increases and the resolution also decreases. Therefore, the two-stage hexapole lens (H1) 14 and (H2) 15 must be operated properly. Thus, it is possible to remove these secondary aberrations and improve the energy resolution, but it is necessary that the center axes of the quadrupole magnetic lens and the hexapole magnetic lens coincide with each other.
[0005]
[Problems to be solved by the invention]
However, as the configuration becomes complicated, various problems occur in practical use. That is, conventionally, individual lenses are assembled and arranged along a vacuum container pipe provided at the center. In addition, each multiple magnetic pole element is structured to be incorporated in a separate yoke. Therefore, there were the following problems.
[0006]
{Circle around (1)} Due to an assembly error between the individual multiple magnetic pole lenses, a deviation occurs between the respective central axes, which causes an axial deviation aberration.
{Circle around (2)} Assembling errors due to asymmetry between individual magnetic poles incorporated in the yoke may occur, which may reduce convergence.
{Circle around (3)} When a mechanical axis adjustment mechanism is added, a mechanism for finely moving individual multipole lenses is required, and the number of adjustment points increases.
(4) The number of parts is large, not only assembly errors but also production costs are increased, and adjustment time is increased.
[0007]
An object of the present invention is to provide a multistage multipole lens system and an electron energy analyzer using the multistage multipole lens system that solve the above problems.
[0008]
[Means for Solving the Problems]
The present invention has a structure in which the magnetic path (yoke) of the multi-stage lens is shared by a single body in a lens system that improves the convergence characteristics of the charged particle beam by combining multi-stage multi-pole lenses in a straight line. It is characterized by.
Another feature of the present invention is that in the multistage multipole lens system in which the magnetic path (yoke) of the multistage lens is formed as a single body, a magnetic shield portion is integrated with the lens magnetic path between each multipole lens. It has a structure.
Another feature of the present invention is that in the multistage multipole lens system in which the magnetic path (yoke) of the multistage lens is formed as a single body, the multipole lens is a double pole element, a quadrupole pole element, a hexapole pole. It is a combination of any of the children.
[0009]
Another feature of the present invention resides in an electron energy analyzer with a multistage multipole lens in which the multistage multipole lens is installed on the incident side and the exit side of the fan-shaped magnetic pole of the energy analyzer below the electron microscope.
Another feature of the present invention is that the multistage multipole lens is a combination of a quadrupole magnetic lens and a hexapole magnetic pole lens installed on the incident side and the outgoing side of the fan-shaped magnetic pole of the energy analyzer below the electron microscope. Is in the electron energy analyzer.
[0010]
According to the present invention, a multi-stage multi-pole lens system and a multi-stage multi-pole lens system that solves each of the above problems by incorporating a plurality of multi-pole magnetic lens systems into one magnetic path and using a position fixing jig between the magnetic poles as an insulating material, and An electron energy analyzer using the same can be provided.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the multistage multipole lens system of the present invention will be described below.
When manufacturing a multi-pole lens system arranged in series relatively close to each other, a common yoke can be used. First, when a plurality of multiple magnetic pole lenses form different magnetic fields, a magnetic shield is required so that other fields do not overlap each other.
[0012]
FIG. 1 is a perspective view of a multi-stage multi-pole lens system of the present invention in which different multi-pole elements such as a quadrupole pole pole, a six-pole pole pole, and a magnetic shield are integrally combined with a common yoke. A longitudinal section thereof is shown in FIG. In the figure, 1 is a common yoke, 2 is a first stage multiple (quadrupole) pole, 3 is its exciting coil, 4 is a magnetic shield, 5 is a second stage multiple (sixfold) pole, 6 Is an exciting coil, 7 and 7 'are magnetic pole mounting screws, and 8 is a vacuum vessel pipe.
[0013]
The common yoke 1 has a cylindrical shape, and is a bamboo knot-like integral structure with a hole in the center of the magnetic shield 4. Each of the multiple magnetic poles 2 and 5 and each of the exciting coils 3 and 6 are assembled into holes that are accurately spaced at equal intervals on the side surface of the yoke, and fixed to the yoke by the mounting screws 7 and 7 'of the magnetic pole. Is done. A pipe 8 as a vacuum vessel is installed at the center of the lens and is connected to an evacuation system (omitted) so that a charged particle beam passes through it.
[0014]
According to the cross-sectional view of FIG. 2, the two-stage lens system yoke 1 and magnetic shield 4 have a single body structure, and screws 7, 7 ′ are formed in holes in which each magnetic pole is formed around the yoke 1. The structure attached is clearly indicated.
However, the assembly accuracy of each magnetic pole cannot always be obtained with the configuration of FIGS. 1 and 2 alone. Since mechanical accuracy is required in the vicinity where the beam passes, a jig for equalizing the magnetic poles is effective.
[0015]
In the multiple magnetic pole lens of the present invention, a position fixing jig for a non-magnetic material (for example, aluminum or phosphor bronze) obtained by incorporating a coil and a magnetic pole into a yoke and then scraping the shape of each magnetic pole with high accuracy Incorporate
[0016]
In some cases, the vacuum vessel pipe 8 has a function of applying an acceleration voltage to charged particles to select an energy by using a sector magnetic field and take a spectrum. In general, since multiple magnetic poles are used at a ground potential, it is necessary to electrically insulate between the vacuum pipe and the magnetic poles. In this case, an insulator (for example, hard resin) is used as the jig material in order to prevent discharge.
[0017]
【Example】
FIG. 3 shows a cross section of a quadrupole lens as an example of the multipole lens of the present invention. 9 is a position fixing jig between the magnetic poles, and 10 is the position of the charged particle beam. Since the conventional lens only attaches the magnetic pole 2 to the magnetic path 1, the assembly accuracy of the tip of the magnetic pole is not sufficient. The mounting accuracy is improved.
[0018]
FIG. 4 shows an example in which the present invention is implemented in a parallel detection type energy analyzer. 12 is a sector magnet, 19 is a sector magnetic field analysis tube, 20 is a multistage multipole lens system of the present invention installed on the entrance side, 21 is a multistage multipole lens system on the exit side, 22 is a beam stop mechanism, 23 is a terminal for applying an acceleration voltage to the vacuum vessel pipe, 24 and 25 are screws for adjusting the fine position of each lens system, 26 and 27 are lens storage cases, and 28 is a lens current terminal. It is possible to optimize the position of the lens system with a fine adjustment position adjusting screw attached to the case by leaving a space in the fine adjustment range between the multistage multi-pole lens system and the lens housing case.
[0019]
FIG. 5 shows an enlarged view of the fine adjustment position adjustment portion (exit side). A steel lens storage case 26 that functions as a vacuum container at the top and a lens storage container and a magnetic shield at the bottom, and the multistage multi-pole magnetic lens system 21 is beamed by eight adjusting screws 25 attached to the storage case. The position and angle relative to 10 are adjusted. Although the lens system is in the atmosphere, the inside 8 of the vacuum vessel pipe is vacuum sealed by the upper and lower flanges 29 and 30 via the O-ring.
[0020]
According to the parallel detection type energy analyzer of the embodiment of the present invention, the magnetic paths of the multiple magnetic poles arranged in a straight line are made common to improve machining accuracy and assembly accuracy, and the linear axis of the lens system is used as the beam axis. Since the mechanism for matching the lens is provided, the assembly accuracy between the lenses can be improved by incorporating the incorporation error of each lens into a common magnetic path.
[0021]
【The invention's effect】
According to the present invention, it is possible to obtain a multistage multipole lens system and an electron energy analyzer using the same having the following effects.
1) When a multi-stage multi-pole lens is incorporated in a common yoke integrally processed with the magnetic shield portion, the processing accuracy of the yoke is on the order of 10 microns, so that the mutual mounting accuracy is improved as compared with assembling individual lenses.
2) The number of yoke parts is reduced to 1/3.
3) Since each lens field can be set independently by changing the current of the coil wound around the multi-pole, a lens function that is not different from the conventional lens function is selected.
4) The mounting accuracy between the multiple magnetic poles can be improved by adding a precision-processed position fixing jig 9.
5) In particular, when applying a voltage to the vacuum vessel pipe 8 in the multi-pole lens and accelerating the beam, the position fixing jig is made of an insulating material (hard resin, etc.) so that the gap between the pipe and the pole piece is increased. Discharge can be prevented.
6) When the entire lens system of the integral structure is finely moved with respect to the vacuum pipe, fine adjustment is conventionally performed individually, but the lens system can be finely adjusted with one mechanism.
[Brief description of the drawings]
FIG. 1 is an external perspective view of a multistage multipole lens system to which the present invention is applied.
FIG. 2 is a longitudinal sectional view of a multistage multi-pole lens system to which the present invention is applied.
FIG. 3 is a cross-sectional view of an embodiment of a quadrupole lens according to an embodiment of the present invention.
FIG. 4 is a longitudinal sectional view of an energy analyzer according to one embodiment of the present invention.
5 is an enlarged view of the fine adjustment mechanism of the embodiment of FIG.
FIG. 6 is a diagram showing an example of an energy analyzer in which a conventional two-stage quadrupole lens and a six-pole magnetic lens are combined.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Common yoke, 2 ... First stage multiple pole lens, 3 ... Excitation coil, 4 ... Magnetic shield part, 5 ... Second stage multiple pole lens, 6 ... Excitation coil, 7 ... Magnetic pole 8 ... Vacuum vessel pipe, 9 ... Position fixing jig between magnetic poles, 10 ... Beam position, 11 ... Beam crossover, 12 ... Fan magnetic field, 13 ... Quadrupole magnetic pole on the entrance side of the fan magnetic field Child lens, 14... Magnetic pole lens at the entrance side, 15... Hexapole lens at the exit side, 16. Quadrupole lens at the exit side, 17. Array detector, 19 ... Analytical tube for sector magnetic field, 20 ... Multi-stage multi-pole lens system on the entrance side, 21 ... Multi-stage multi-pole lens system on the exit side, 22 ... Beam stop, 23 ... Acceleration voltage application terminal, 24 ... Lens axis fine adjustment screw on the entrance side, 25 ... on the exit side Lens system axis fine adjustment screw, 26 ... entrance-side lens storage case, 27 ... exit lens storage case, 28 ... lens system current terminal, 29, 30 ... vacuum seal flange.

Claims (9)

  In a lens system that improves the convergence characteristics of a charged particle beam by combining multi-stage multi-pole lenses in a straight line, the multi-stage multi-pole lens has a structure that shares a single yoke. A multistage multi-pole lens system characterized in that a magnetic shield portion is provided in the yoke as an integral structure. 2. The multistage multipole lens system according to claim 1 , wherein the combination of the multistage multipole lenses is any one of a double pole pole, a quadrupole pole pole, and a six pole pole pole. Multi-stage multipole lens system. 2. The multistage multipole lens system according to claim 1 , wherein the multistage multipole elements of the multipole lens are fixed at equal intervals by a non-magnetic material. 4. The multistage multipole lens system according to claim 3 , further comprising: a vacuum container for allowing charged particles to pass through a central portion of the multistage multipole lens, wherein the non-magnetic substance is an electrical insulator. A multi-stage multi-pole lens system characterized in that each multi-pole element of the multi-pole pole and the vacuum vessel have a structure sandwiching an insulator. 5. The multistage multipole lens system according to claim 4 , further comprising a mechanism for applying a positive voltage to the vacuum vessel and accelerating charged particles within the lens. The multistage multipole lens system according to claim 4 or 5 , wherein the multistage multipole lens has a gap with the vacuum vessel and is parallel to a two-dimensional direction perpendicular to the axis of the charged particle beam. A multistage multi-pole lens system comprising a mechanism capable of fine tilting. The multistage multipole lens according to any one of claims 1 to 5 , wherein the multistage multipole lens is installed on an incident side and an exit side of a sector magnetic pole of an energy analyzer below an electron microscope. Electronic energy analyzer. The multistage multipole lens according to any one of claims 1 to 5, wherein a quadrupole magnetic pole lens and a hexapole magnetic pole lens are provided on an incident side and an outgoing side of a sector magnetic pole of an energy analyzer below an electron microscope. An electron energy analyzer characterized by being a combination of the above. Multistage multi Jikyokuko lenses double Jikyokuko lens on the incident side of the fan-shaped magnetic poles of energy analyzer bottom of the electron microscope according to any one of claims 1 to 5, the quadruple Jikyokuko lenses and hexapole Jikyokuko lens An electron energy analyzer, characterized in that it is installed in a combination of a three-stage lens and a two-stage lens of a quadrupole magnetic lens and a six-pole magnetic lens on the output side.

Images