JPH06267468A - Electron gun for electrificatyion neutralization - Google Patents

Abstract

PURPOSE:To reduce the leakage of light and to reduce a size in a device by providing a curved electron guiding pipe and a solenoid coil wound around the pipe. CONSTITUTION:An electron gun for electrification neutralization consists of a hot cathode filament 201, a grid electrode 202, a deriving electrode 203, a curved pipe 204 for an electron, a solenoid coil 205 wound around the pipe 204, a focusing lens 206, and a deflecting device 207. In this way, a thermion emitted from the filament 201 is accelerated by the grid electrode 202 and the deriving electrode 203 to be led to an inlet of the electron guiding pipe 204. An electron orbit inside the pipe 204 is led to an outlet of the pipe 204 by a magnetic path formed by the coil 205 wound around the pipe 204. As the pipe is bent emitted light from the filament 201 does not reach the straight line and only an extremely weak light, which is scattered for multiple times inside the pipe and has little light leakage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a focused ion beam (FIB for short) or the like for fine elements such as semiconductors and magnetic recording, and performs processing such as cross-section processing, etching, and deposition without masking. The present invention relates to an electron gun for charge neutralization of an insulator sample in a beam device for pattern correction.

[0002]

2. Description of the Related Art One example of a conventional FIB device equipped with a neutralizing electron beam generator is disclosed in Japanese Patent Laid-Open No. 61-248346. This device uses a channeltron or channel plate as a detector for secondary electrons and secondary ions that are secondary particles emitted from the sample surface. Further, a normal thermionic gun is adopted as the electron gun for neutralizing the charge. The acceleration voltage of the electron beam is as low as 1000 V or less,
Also, the electron beam diameter does not have to be narrowed down as sharply as FIB.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a small and simple electron gun for neutralizing charge on an insulator sample in a FIB device for processing or the like. For the secondary electron detector of the FIB device, in addition to the above-mentioned conventional channeltron or channel plate,
A combination detector of an ordinary scintillator and a photomultiplier (hereinafter abbreviated as SP detector) is often used. In the latter FIB device equipped with the SP detector, the electron gun for charge neutralization needs to be a type that does not leak light in order to prevent generation of noise light to the photomultiplier tube. Further, the electron gun for neutralizing the charge needs to be small.

[0004]

In order to solve the above problems, the electron gun is composed of a filament, an anode, a bent electron guide pipe, and a solenoid coil, and the solenoid coil is formed by winding the electron guide pipe.

[0005]

By the above means, the thermoelectrons emitted from the filament are accelerated by the anode and guided to the entrance of the bent electron guide pipe. The electron orbit in the pipe is entangled with the magnetic path formed by the solenoid coil wound around the pipe. As a result, the electrons are guided to the pipe exit despite the bent pipe. At the pipe exit,
Since the pipe is bent, the light emitted from the filament does not reach directly, only the extremely weak light scattered many times in the pipe arrives.

[0006]

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 is a schematic diagram of the electron gun for neutralizing charge used in the embodiment. It consists of a hot cathode filament 201, a grid electrode 202, an extraction electrode 203, a bent electron guide pipe 204, a solenoid coil 205, a focusing lens 206, and a deflector 207. The electronic guide pipe 204 is made of a thin copper pipe having an inner diameter of 4 mm, and is bent 90 degrees with a radius of curvature of 15 mm. The inner surface is coated with carbon paint to reduce the light reflectance. The focusing lens 206 and the deflector 207 are for respectively focusing the electron beam on the sample and adjusting the irradiation position. The focusing lens 206 is an electrostatic lens having a three-electrode configuration. The electrodes on both ends are grounded, and the intermediate electrode is applied with a focusing potential.
When the sample is set to earth potential, the respective electrode potentials are
Although depending on the material of the sample and the intensity of the irradiation FIB, the filament potential is approximately −50 to −500 V, the grid electrode potential is −several tens V with respect to the filament, and the extraction electrode and the electron guide pipe are always at the ground potential.
The magnetic flux density of the magnetic field generated by the solenoid coil 205 is several mWb / m ² . As a result, among the electrons emitted from the hot filament, several tenths to ones
One-hundredths of electrons, that is, several nA to several tens of nA of electrons pass through the solenoid coil and can be used for sample irradiation. The electron beam diameter is estimated to be about 1 mm or less. The overall length of this electron gun was as small as about 10 cm, and the configuration was simple and inexpensive to make.

FIG. 2 is a basic configuration diagram of the FIB device equipped with the electron gun for neutralizing the charge used in the above embodiment. The ion beam emitted from the liquid metal ion source 100 is sampled by the condenser lens 101 and the objective lens 106.
Focus on top. An aperture 102, an aligner / stigma 103, a blanker 104, and a deflector 105 are arranged between the lenses. The sample 112 has two axes (X,
It is fixed on a stage 111 movable in the Y direction. The gas generated from the deposition gas source 110 is guided to the vicinity of the FIB irradiation unit by the gas nozzle 108. F
An electron gun 109 for charge neutralization is located near the IB irradiation part.
Is installed. Sample 112 on stage 111 to F
Secondary electrons in the charged particles generated by the IB irradiation are S
It is detected by the P detector 107. On the other hand, the secondary ions (positive polarity) in the charged particles have a negative number kV in the ion-electron conversion electrode (not shown) placed near the FIB irradiation point.
The potential of is applied and secondary ions are collided there to be converted into electrons. Then, this electron is detected by the SP detector 107 as a substitute for the secondary ion. The detection modes of the secondary electrons and the secondary ions are selected by switching the polarities, and at the same time, the voltages applied to the scintillator and the ion-electron conversion electrode are also switched and controlled.

Next, the FI of ceramic, which is an insulator sample,
An example of B processing will be described. In the case of this sample, an electron gun for charge neutralization is activated. FIB is 30 keV G
a-FIB, beam diameter is about 0.3 μm, beam current is about 2 nA, and the electron beam for neutralization at this time has an acceleration voltage of 200 V and a current of about 4 nA. Computer C
The scanning ion (SIM) image is displayed on the CRT by synchronizing the XY position signal on the RT with the deflection control of the ion beam 1 and taking the intensity signal of the charged particles emitted from the sample as the brightness (Z signal) of the CRT. . When there is a neutralizing electron shower, the amount of secondary electron emission from the sample due to electron shower irradiation is usually larger than the amount of secondary electron emission due to ion irradiation, so the secondary electron mode for obtaining a SIM image is obtained. Cannot be used. Therefore, the detection mode of charged particles is set to the secondary ion (positive polarity) mode. Stable images could be obtained without significant charge-up due to electron irradiation.
In addition, since the light leakage from the end surface of the electron guide pipe on the sample side is small, the influence of the SP detector on the photomultiplier tube is small, and the increase in the background intensity can be ignored. The SIM image in the secondary ion mode was used for positioning the processing region.

[0010]

According to the present invention, it is possible to provide a compact electron gun of the type that does not leak strong light. Furthermore, if an FIB device equipped with this is used, it is possible to neutralize the charge in the insulator sample and to perform FIB cross-section processing and the like. The FIB device at this time may be an SP detector combined with an ion-electron conversion electrode as a charged particle detector.

[Brief description of drawings]

FIG. 1 is a diagram showing an electron gun for charge neutralization according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a focused ion beam device according to an embodiment of the present invention.

[Explanation of symbols]

100 ... Liquid metal ion source, 101 ... Condenser lens, 102 ... Aperture (diaphragm), 103 ... Aligner stigma, 104 ... Blanker, 105 ... Deflector, 106 ... Objective lens, 107 ... Secondary electron detector, 108 ... Gas nozzle, 109 ... Electron gun for charge neutralization,
110 ... Gas source, 111 ... Sample stage, 112 ... Sample, 201 ... Cathode filament, 202 ... Grid electrode, 203 ... Extraction electrode, 204 ... Electronic guide pipe, 205 ... Solenoid coil, 206 ... Focusing lens,
207 ... A deflector.

Claims (3)

[Claims] 1. An electron gun for charge neutralization comprising a cathode filament, an anode, an electron guide pipe, and a solenoid coil, the solenoid coil being wound around the electron guide pipe. 2. Irradiation of ions from an ion source is focused by a plurality of stages of electrostatic lenses to form a focused ion beam, and the focused ion beam is scanned on a sample surface by a deflector to irradiate the beam from the sample. In a focused ion beam device composed of a detector for detecting charged particles emitted by the above, and a charge neutralizing electron gun, the charge neutralizing electron gun comprises a filament, an anode, an electron guide pipe, and a solenoid coil, The focused ion beam device, wherein the solenoid coil is an electron gun wound around the electron guide pipe. 3. The focused ion beam apparatus according to claim 2, wherein the electron detector has a combination structure of a scintillator and a photomultiplier tube.