JPH01105447A - Electron beam device - Google Patents

Abstract

PURPOSE:To precisely focus an electron beam and prevent the damage of a target due to a minor discharge by providing an auxiliary electrode with nearly the same potential as the target between the target and a focusing lens. CONSTITUTION:An electric field mitigating electrode 14 and an auxiliary electrode 15 are arranged between an objective lens 5 and a target 10, the electric field mitigating electrode 14 is kept at the same potential (ground potential) as that of the outside electrode 6 of the objective lens 5, and the auxiliary electrode 15 is kept at the same potential as that of the target 10. The decelerating electric field of an electron beam is formed between the electric field mitigating electrode 14 and the auxiliary electrode 15, an equipotential space is kept between the auxiliary electrode 15 and the target 10, thus the decelerating electric field is not disturbed even if projections and recesses exist on the surface of the target 10. The electron beam is thereby prevented from being incorrectly deflected, a blur is prevented from occurring, a minor discharge is not generated, and the damage of the target is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electron beam device, and particularly to an electron beam device that irradiates a target with a decelerated electron beam.

[Prior Art] In an electron beam device, a target is irradiated with an electron beam and the irradiation position is moved to draw a desired figure, and secondary electrons generated due to the irradiation of the electron beam are etc., and the surface of the target is observed. By the way, when a target is irradiated with an electron beam accelerated at an acceleration voltage of 30 (3), the surface portion of the target is etched due to the high energy of the electron beam, changing the shape of the target surface. For this reason, the acceleration voltage of the electron beam is lowered,
It is possible to lower the energy of the electron beam irradiated to the target, but if the accelerating voltage is lowered, the electron beam cannot be narrowly focused by the focusing lens, and although etching of the target is avoided, it may cause damage to minute parts. It becomes impossible to perform high-precision electron irradiation.

For this reason, an electron beam device as shown in FIG. 3 has been considered. In the figure, 1 is a cathode, 2 is a Wehnelt electrode, and 3
is an accelerating electrode, and between the cathode 1 and the accelerating electrode 3,
An accelerating voltage is applied from an accelerating voltage power source 4. , 5 is an objective lens, which is an Einzel type electrostatic lens,
It consists of an outer electrode 6 at ground potential and a center electrode 8 to which a lens voltage is applied from a lens electrode 17. 9 is a deflection electrode, 10 is a target such as a target to be drawn or a sample to be observed, which is irradiated with an electron beam, and 11 is a deceleration electric field power supply.

In the above-described configuration, the energy is generated from the cathode 1 and the accelerating electrode 3
The electron beam accelerated by the power source 7 of the center electrode 8
The light is narrowly focused onto the target laser 1-10 by the objective lens 5 to which a lens voltage is applied. The electron beam is deflected by a voltage applied to the deflection electrode 9, and the irradiation position of the electron beam on the target 10 can be changed arbitrarily.As a result, the electron beam drawing device draws a desired figure. When observing a surface with an electron beam, the desired observation surface is scanned by the electron beam.

Now, an accelerating voltage of, for example, -30 kV is applied from the accelerating voltage power source 4 between the cathode 1 and the accelerating electrode 3, and the electron beam enters the objective lens 5 with relatively high energy. It is narrowly focused onto the target 10. Here, a deceleration voltage of -27 to ■, for example, is applied to the target 10 from the power supply 11, and as a result, electrons are generated between the outer electrode 6 of the objective lens 5 at the ground potential and the target 10. A beam deceleration electric field is formed, and the electron beam is lowered in energy and irradiated onto the target 10. That is, the acceleration voltage of the electron beam irradiated onto the target 10 is substantially -3 kV.

In this way, in this device, the electron beam enters the electrostatic lens in a high energy state and is narrowly focused, while the target 10 is irradiated with a low energy state, so that the etching of the surface of the target is achieved. is prevented. Therefore, the target can be continuously irradiated with the electron beam without changing the surface shape of the target.

The apparatus shown in FIG. 4 is a modification of the apparatus of FIG. 3, in which the target 10 is maintained at ground potential. In FIG. 4, a predetermined voltage is applied from a power source 12 to the accelerating electrode 3, and a voltage is also applied from a power source 13 to the outer electrode 6 of the objective lens 5, which is an Einzel lens. The voltages applied to each electrode are, for example, -3 kV from the power source 4 to @pole 1, +27 kV from the power source 12 to the accelerating electrode 3, +27 kV from the power source 13 to the outer electrode 6 of the lens 5, and +27 kV from the power source 7 to the outer electrode 6 of the lens 5. Electrode 8 has one
2kV is applied. In such a configuration, the electron beam is accelerated at an acceleration voltage of -30'V, enters the objective lens 5 with high energy, and is narrowly focused. The electron beam transmitted through the objective lens is +27k
The outer electrode 6 to which V is applied and the target 10 at ground potential
The target is irradiated with an accelerating voltage of substantially -3 kV.

Therefore, in the apparatus shown in FIG. 4, the electron beam enters the objective lens with high energy and is narrowly focused, while the target 10 is irradiated with low energy, so that the target surface is etched. is prevented. As a result, fine parts on the target 10 can be irradiated with electrons with high precision without changing the surface shape of the target.

[Problems to be Solved by the Invention] In the above-described configuration, the objective lens 5 and the target 10
A decelerating electric field is formed between the target 10 and
If the surface of the electron beam is uneven, the deceleration electric field will be disturbed and become non-uniform, making it difficult to focus the electron beam narrowly and accurately. Further, when the target 10 is exposed to the electric field of the deceleration electric field and a minute discharge occurs between the target and the side electrode of the objective lens, the target may be damaged. Furthermore, when a secondary electron detector is placed near the target and the secondary electrons are detected, the secondary electrons from the target are accelerated with a high energy of 27 kV and enter the jump detector. It deteriorates rapidly.

The present invention has been made in view of the above-mentioned points, and even in an electron beam device provided with a decelerating electric field, it is possible to focus an electron beam with high precision, and also prevent damage to a target due to micro discharges. The purpose of the present invention is to provide an electron beam device that can perform

[Means for Solving the Problems] An electron beam device based on the present invention includes a focusing lens for focusing an accelerated electron beam generated from an electron beam generation source, and a target to be irradiated with the electron beam. An electron beam device configured to form a deceleration electric field between the focusing lens and the target, further comprising an auxiliary electrode having approximately the same potential as the target between the target and the focusing lens. It is characterized by

[Example] An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

The embodiment shown in FIG. 1 is an improved version of the device shown in FIG. 3, and the same parts as those in FIG. 3 are given the same numbers and detailed explanation thereof will be omitted. In this embodiment, an electric field relaxation electrode 14 and an auxiliary electrode 15 are provided between the objective lens 5 and the target 10.
and are arranged.

The electric field relaxation electrode 14 is kept at the same potential as the outer electrode 6 of the objective lens 5, that is, the ground potential, and its surface is polished smoothly. The auxiliary electrode 15 is kept at the same potential as the target 10, and an equipotential space is formed between the auxiliary electrode 15 and the target. A secondary electron detector 18 consisting of a multichannel plate 16 and a detection electrode 17 is located between the auxiliary electrode 15 and the target 10.
is located. The microchannel plate 16
The secondary electron emission surface 16b of the microchannel plate is kept at the same potential as the detection electrode 17, and the secondary electron emission surface 16b and the microchannel plate
1 to 1 from the power supply 20 to the secondary electron incident surface 16a.
A voltage of 2 kV is applied. Moreover, between the target 10 and the secondary electron entrance surface 16a, there are power supplies 19 to 100
A voltage of about V is applied. The detection electrode 17 is amplified by a preamplifier 21 and fed to a light emitting diode 22 .

In the above-described configuration, secondary electrons generated when the target 10 is irradiated with an electron beam are attracted to the incident surface 16a of the microchannel plate 16, which has a positive potential of 1 to 1.2 kV higher than the potential of the target. The light is amplified by the microchannel plate 16, exits from the output surface 16b, and is detected by the detection electrode 17. The detection signal is amplified by an amplifier 21 and then supplied to a light emitting diode 22 . The diode 22 emits light in accordance with the intensity of the signal, and the light enters the light receiving element on the ground potential side via an optical fiber (not shown) and is detected.

Note that if the electric field relaxation electrode 15 is not provided, there is a potential difference of several tens of kV between the objective lens side and the target, so the electric field will concentrate on the uneven parts of the objective lens 5 and the deflection system 9, causing dielectric breakdown. This was established because there is a possibility that this may occur.

That is, the surface of this electrode 15, especially the target 10
Since the facing surface is polished smoothly, the electric field is relaxed and dielectric breakdown can be prevented.

In the embodiment shown in FIG. 1 described above, a detector using a microchannel plate was placed in the equipotential space between the auxiliary electrode 15 and the target 10, but instead, a scintillator and a photomultiplier were used. A secondary electron detector may also be provided.

Further, the voltage applied to the auxiliary electrode 15 does not need to be strictly equal to the voltage applied to the target.

Furthermore, although the embodiment shown in FIG. 1 is an improvement on the device shown in FIG.
When the present invention is applied to the apparatus shown in FIG. 4, the potential of the auxiliary electrode may be set to the same ground potential as that of the target.

As mentioned above, the decelerating electric field of the electron beam is
It is formed between the electric field relaxation electrode 14 and the auxiliary electrode 15, and there is an equipotential space between the auxiliary electrode 15 and the target, so even if there are irregularities on the surface of the target 10, the deceleration electric field is disturbed. This prevents the electron beam from being improperly deflected or blurred. or,
Since the target 10 is not exposed to the deceleration electric field, no micro discharge occurs between the target and other parts, and damage to the target is prevented. Furthermore, the secondary electrons generated when the target is irradiated with the electron beam are not accelerated with high energy because there is no decelerating electric field near the target surface, and the secondary electron detector deteriorates rapidly. Never.

Although FIG. 2 shows another embodiment of the present invention, parts that are the same or similar to this embodiment and the embodiment of FIG.

In this embodiment, a magnetic field type lens 30 is used as the objective lens, and the magnetic pole of the objective lens 3o is set at ground potential. 31, 32, and 33 are deflection coils and alignment coils, and 34 is several kV from the target 10.
High potential scintillator 35, light pipe 36. This is a secondary electron detector consisting of a photomultiplier 37 at ground potential.

This embodiment also achieves the same effect as in FIG. 1.

Note that, as in the apparatus shown in FIG. 4, in order to bring the target 10 to the ground potential, a high voltage for electron beam deceleration may be applied to the magnetic pole of the objective lens 30.

[Effects] As detailed above, in the present invention, an electrode having approximately the same potential as the target to be irradiated with the electron beam is arranged, and an equipotential space is formed between the target and the electrode. It is possible to focus with high precision and prevent damage to the target and secondary electron detector.

[Brief explanation of the drawing]

FIGS. 1 and 2 are diagrams showing one embodiment of the present invention, and FIGS. 3 and 4 are diagrams showing an apparatus for decelerating an electron beam and irradiating it onto a target. 1... Emitter 2... Extraction electrode 3... Accelerating electrode 5... Objective lens 6... Outer electrode
8... Center electrode 9... Deflection electrode 10... Target 4.7.11.12.13... Power source 14... Electric field relaxation electrode 16... Auxiliary electrode

Claims (6)

[Claims] (1) Equipped with a focusing lens for focusing an accelerated electron beam generated from an electron beam generation source and a target to which the electron beam is irradiated, and forming a deceleration electric field between the focusing lens and the target. An electron beam device configured to do so, further comprising an auxiliary electrode having substantially the same potential as the target between the target and the focusing lens. (2) The electron beam device according to claim 1, wherein a secondary electron detector is disposed between the auxiliary electrode and the target. (3) The electron beam device according to claim 1, wherein a voltage for forming a deceleration electric field is applied to the target. (4) The electron beam according to claim 1, wherein the focusing lens is an Einzel-type electrostatic lens, a voltage for forming a decelerating electric field is applied to the outer electrode of the lens, and the target is kept at ground potential. Beam device. (5) The electron beam device according to claim 1, wherein the focusing lens is a magnetic field type lens, a voltage for forming a deceleration electric field is applied to the magnetic pole of the lens, and the target is maintained at a ground potential. (6) The electron beam device according to claim 1, wherein an electrode to which a voltage for forming a deceleration electric field is applied is disposed below the focusing lens, and the target is maintained at a ground potential.