JP2008140723A - Analyzer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electron detector using a micro channel plate (MCP) whose life becomes longer by preventing the deterioration of sensitivity. <P>SOLUTION: An analyzer 1 to analyze a specimen W by irradiating the specimen W with an electron beam EB and detecting a secondary electron SE emitted from the specimen W comprises a micro channel plate 151, a detector 152 to detect the electron SE amplified by the micro channel plate 151, and a secondary electron control means 2 for applying an electric field to the secondary electron SE emitted from the specimen W and controlling the orbit of the secondary electron SE. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  In the present invention, for example, a scanning electron microscope (SEM) or the like irradiates a sample with energy rays, and detects charged particles such as secondary electrons and reflected electrons emitted from the sample to analyze the sample. More particularly, the present invention relates to an analysis apparatus using a microchannel plate (MCP).

  Conventionally, for example, an analyzer such as a scanning electron microscope is desired to be small in size, high in sensitivity, and high in resolution. For this reason, there is a secondary electron detector using a microchannel plate (MCP) (Patent Document 1).

However, the trajectory of secondary electrons emitted from the sample is determined by the pull-in voltage of the microchannel plate and the electric field around the secondary electron detector, and it becomes a part (predetermined area) of the many MCP channels. Secondary electron incidence is concentrated. As a result, the channel in which the secondary electrons are concentrated and incidentally has a problem that the secondary electrons are saturated and burnt, and the sensitivity of the secondary electron detector is deteriorated.
JP 07-335172 A

  Accordingly, the present invention has been made to solve the above-mentioned problems all at once, and prevents the short-term deterioration of the microchannel plate (MCP) due to the concentration of charged particles such as electrons and ions, thereby extending the life. This is the main desired issue.

  That is, the analyzer according to the present invention is an analyzer that analyzes a sample by irradiating a sample with energy rays and detecting charged particles generated by the sample, and has a passage hole for allowing the energy rays to pass therethrough. An annular microchannel plate arranged with the charged particle incident surface facing the sample surface, a detection unit for detecting the charged particles amplified by the microchannel plate, and coaxial with the energy line. And an annular charged particle trajectory adjusting means for generating an electric field and / or a magnetic field to change an incident region of the charged particles with respect to the microchannel plate. Here, the “energy beam” is, for example, an X-ray, an electron beam, an ion beam, or the like.

  With such a configuration, deterioration due to concentration of charged particles such as secondary electrons and secondary ions incident on the microchannel plate can be prevented, so that a decrease in sensitivity of the microchannel plate can be prevented over a long period of time. As a result, it is possible to extend the life of the microchannel plate. At this time, since the charged particle trajectory adjusting means is provided coaxially with the energy beam, the trajectory of the charged particle emitted from the sample can be controlled without adverse effects such as bending the energy beam.

  As a specific control mode of the charged particle trajectory of the charged particle trajectory adjusting means, the charged particle trajectory adjusting means changes the electric field and / or magnetic field when the gain of the microchannel plate becomes less than a predetermined value. Thus, the incident area may be changed.

  The charged particle trajectory adjusting means may change the incident area by periodically changing the electric field and / or magnetic field.

  As a specific embodiment of the charged particle trajectory adjusting means, an electrode, a magnetic pole, or a combination of them can be considered. More specifically, from the viewpoint of miniaturization and simplification of the analyzer, the objective lens It is desirable to use a sample side electrode. And when using the sample side electrode, it is desirable to change the incident area by changing the voltage of the sample side electrode within a range not affecting the energy beam.

  According to the present invention configured as described above, it is possible to control only the trajectory of the charged particles generated by the sample without changing the trajectory of the energy beam. Therefore, it is possible to prevent the microchannel plate from being deteriorated in a short period of time and to prolong the life of the microchannel plate.

  An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a scanning electron microscope 1 according to the present embodiment, and FIG. 2 is a partially enlarged sectional view mainly showing an objective lens and an electron trajectory adjusting means.

  As shown in FIG. 1, the scanning electron microscope 1 according to the present embodiment includes an electron gun 11, a lens mechanism that converges an electron beam EB emitted from the electron gun 11 to a predetermined portion of the sample W, and an electron beam EB. An electron beam control means 12 comprising a scanning mechanism for scanning, a lens barrel 13 having an electron gun 11 and an electron beam control means 12 therein, and a lower end portion of the lens barrel 13 are provided from the electron gun 11. A sample chamber 14 containing a sample W irradiated with an electron beam EB, an electron detector (charged particle detector) 15 for detecting secondary electrons (charged particles) SE generated by the electron beam EB irradiation on the sample W, and And an information processing device 16 that displays a sample image in synchronization with two-dimensional scanning of the electron beam EB on the sample W based on a detection signal from the electron detector 15. The electron gun 11 is a hot filament type or a thermal field emission type.

  The electron beam control means 12 includes a gun lens for extracting electrons from the electron gun 11, an aperture for controlling the electron dose monitor and the opening angle of the electron beam EB, and astigmatism correction for correcting astigmatism of the electron beam EB. A stigmator, a scanning deflector (scanning deflector) for scanning the electron beam EB, and an objective lens for converging the electron beam EB on the surface of the sample W. These are formed in this order from the top. Yes. In this embodiment, the distance (working distance) between the lower end of the objective lens and the sample is 4 mm, for example.

  The sample chamber 14 includes a sample stage having a sample moving mechanism and a vacuum exhaust mechanism (not shown) for evacuating the sample chamber 14.

  As shown in FIG. 2, the electron detector 15 is arranged between the objective lens and the sample W, detects the secondary electrons SE from the sample W, and is a micro that amplifies the secondary electrons SE. A channel plate 151 and a detection unit 152 that detects amplified electrons amplified by the microchannel plate 151 are provided. The electron detector of this embodiment is embedded in the lower end portion of the lens barrel 13 in order to make the working distance as small as possible.

  The microchannel plate 151 has a passage hole 151a for allowing the electron beam EB to pass therethrough, and has a ring shape in which an electron incident surface faces the sample surface, and is a so-called center hole type. The electron incident surface is connected to the ground, and the electron emission surface has a potential of +2 kV when a high voltage is applied by a power source (not shown).

  The detection unit 152 detects electrons amplified by the microchannel plate 151 and outputs an electrical output signal corresponding to the detected amount of electrons to the information processing device 16. The detection unit 152 of this embodiment includes an anode 1521 for reading signals.

  The anode 1521 has substantially the same shape as the microchannel plate 151 in plan view, has a passage hole 1521a for allowing energy to pass through, and is a circle disposed facing the electron emission surface of the microchannel plate 151. Annular. The anode 1521 has a potential of +2.2 kV when a high voltage is applied by a power source (not shown). The microchannel plate 151 and the anode 1521 are provided coaxially with the central axis of the electron beam EB.

  The information processing apparatus 16 is a general-purpose or dedicated computer including, for example, a CPU, a memory, an input / output interface, an AD converter, an input unit, and the like. The information processing device 5 receives the electrical output signal from the electron detector 15 by operating the CPU and its peripheral devices based on the program stored in the predetermined area of the memory, and The next electron image is displayed.

  Therefore, as shown in FIG. 2, the scanning electron microscope 1 of the present embodiment generates an electric field, applies an electric field to the secondary electrons SE emitted from the sample W, and micro-magnetizes the secondary electrons SE. An annular electron trajectory adjusting means (charged particle trajectory adjusting means) 2 for changing the incident region with respect to the channel plate 151, a control unit 3 for controlling a voltage applied to the electron trajectory adjusting means 2, and an electron trajectory adjusting power source 4 And.

  The electron trajectory adjusting means 2 is a ring-shaped electrode (hereinafter also referred to as “electron trajectory adjusting electrode 2”) that is arranged coaxially with the electron beam EB, and a microchannel plate by a holding member (not shown). It is fixed below 151 (for example, near the electron incident surface). More specifically, the electron trajectory adjusting means 2 is arranged so that the central axis of the electron beam EB between the microchannel plate 151 and the sample W and the rotation axis of the electron trajectory adjusting electrode 2 substantially coincide. Thereby, the electric field generated by the electron trajectory control electrode 2 is axisymmetric with respect to the central axis of the electron beam EB. The lead wire is connected to the electronic orbit adjusting power source 4.

  The control unit 3 functions when the CPU and its peripheral devices operate based on a voltage control program stored in a predetermined area of the memory of the information processing device 16. By controlling the voltage, the electric field to be generated is controlled by adjusting the voltage applied to the electron trajectory control electrode 2.

  As a specific control method, the control unit 3 determines the gain of the microchannel plate 151 based on the electrical output signal acquired from the detection unit 152, and when the gain becomes less than a predetermined value, the electronic orbit By controlling the power supply 4 for adjustment and adjusting the voltage applied to the electron trajectory adjusting electrode 2, an electric field is generated and changed.

  For example, the control unit 3 controls the electronic orbit adjusting power source 4 so as not to apply a voltage to the electronic orbit adjusting electrode 2 in a normal state (see FIG. 3A).

  When the gain of the microchannel plate 151 becomes less than a predetermined value, the control unit 3 makes the voltage applied to the electron trajectory adjusting electrode 2 negative, for example, −20 V, so that the electronic trajectory adjusting power source 4 is set to −20V. To control. At this time, the secondary electrons SE are repelled by the electric field generated by the electron trajectory adjusting electrode 2. As a result, the incident region of the secondary electrons SE with respect to the microchannel plate 151 is changed to the outside as compared with the normal state (see FIG. 3B).

  Alternatively, the control unit 3 controls the electronic orbit adjustment power supply 4 so that the voltage applied to the electronic orbit adjustment electrode 2 becomes positive, for example, 50V. At this time, the secondary electrons SE receive a tensile force from the electric field generated by the electron trajectory adjusting electrode 2. As a result, the incident region of the secondary electrons SE with respect to the microchannel plate 151 is changed to the inner side as compared with the normal state (see FIG. 3C).

  According to the scanning electron microscope 1 according to the present embodiment configured as described above, deterioration due to concentration of the secondary electrons SE incident on the microchannel plate 151 can be prevented, so that a decrease in sensitivity of the microchannel plate 151 is prevented. be able to. In addition, the life of the microchannel plate 151 can be extended. At this time, since the electron trajectory adjusting means 2 and the electron detector 15 are provided coaxially with the electron beam EB, only the secondary electrons EB emitted from the sample W are obtained without adverse effects such as bending the electron beam EB. The trajectory can be controlled. Furthermore, since the microchannel plate 151 is used, the scanning electron microscope 1 can be reduced in size, sensitivity, and resolution.

  The present invention is not limited to the above embodiment. In the following description, the same reference numerals are given to members corresponding to the above-described embodiment.

  For example, in the above embodiment, the electron trajectory adjusting means 2 is an electrode, but it may be one that generates a magnetic field with magnetic poles, or one that uses both electrodes and magnetic poles.

  Further, regarding the electronic trajectory adjusting means 2, the electronic trajectory adjusting means 2 may also serve as a part of the electrode of the objective lens. At this time, for example, the voltage of the sample side electrode of the objective lens is changed. That is, the control unit 3 changes the voltage applied to the electron trajectory adjusting electrode 2 within a range that does not affect the electron beam EB (for example, ± several V).

  In addition, as a control method of the electron trajectory adjusting means 2, for example, it is conceivable to change the voltage to be applied periodically.

  The order of changing the incident region of the secondary electrons SE with respect to the microchannel plate 151 may be changed gradually from the central portion of the microchannel plate to the outside, or gradually changed from the outer portion to the central portion. You may make it change.

  Moreover, in the said embodiment, although the control part 3 and the information processing apparatus 16 were integrated, you may separate.

  In the above embodiment, the electron detector 15 is embedded in the lower end portion of the lens barrel 13, but it may be not embedded.

  In addition, in the above-described embodiment, the secondary electrons SE are detected. However, electrons such as Auger electrons and reflected electrons may be detected.

  In addition, the analysis apparatus 1 of the above embodiment is a scanning electron microscope. In addition, reflected electron and / or secondary electron detection in an electron beam microanalyzer (EPMA), Auger electron spectrometer (AES) ), A transmission electron microscope (TEM), a scanning ion microscope (SIM), and not only electrons but also secondary ions may be detected.

  In addition, some or all of the above-described embodiments and modified embodiments may be combined as appropriate, and the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. .

1 is a schematic configuration diagram of a scanning electron microscope according to an embodiment of the present invention. Sectional drawing which mainly shows the objective lens and electronic trajectory control means of the embodiment. The figure which shows the electronic trajectory control in the embodiment.

Explanation of symbols

EB ... Electron beam W ... Sample SE ... Secondary electron 1 ... Analytical device (scanning electron microscope)
15 ・ ・ ・ Electron detector 151 ・ ・ ・ Micro channel plate (MCP)
151a ... Passing hole 152 ... Detector 16 ... Information processing device 2 ... Electronic trajectory adjusting means (electronic trajectory adjusting electrode)
3 ... Control section

Claims (4)

An analyzer for analyzing the sample by irradiating the sample with energy rays and detecting charged particles generated by the sample,
An annular microchannel plate having a passage hole for allowing the energy beam to pass therethrough and having a charged particle incident surface facing the sample surface;
A detection unit for detecting the charged particles amplified by the microchannel plate;
And an annular charged particle trajectory adjusting means that is arranged coaxially with the energy line and generates an electric field and / or a magnetic field to change an incident region of the charged particles with respect to the microchannel plate. Analyzing device.   The charged particle trajectory adjusting means changes the incident region by changing the electric field and / or magnetic field when the gain of the microchannel plate becomes less than a predetermined value. The analyzer according to 1.   The analyzer according to claim 1, wherein the charged particle trajectory adjusting means changes the incident region by periodically changing the electric field and / or magnetic field. The electron trajectory adjusting means is a sample side electrode of an objective lens,
4. The analyzer according to claim 1, wherein the incident region is changed by changing a voltage of the sample side electrode within a range not affecting the irradiation of the energy beam.