JPH01274349A - High voltage power source for electron gun - Google Patents

Abstract

PURPOSE:To easily obtain a drawing voltage by installing a Zener diode and a high voltage power source switchably between a filament and a drawing electrode. CONSTITUTION:When an electron gun is used at a high accelerating voltage, a switch 13 is changed so as to generate a voltage between a filament 8 and a drawing electrode 4 with a voltage drop of a Zener diode, and this voltage is utilized as the drawing voltage. When it is used at a low accelerating voltage, a drawing voltage having the electrode 4 as the positive electrode can easily be obtained in a simple structure not requiring the setting of the drawing power source on high voltage by a high voltage power source 12 similarly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a high voltage power supply used in an electron gun of a scanning electron microscope.

[Conventional technology]

A thermionic electron gun consists of three poles: a filament that is heated to emit thermionic electrons, a Wehnelt that focuses and controls the electrons that are about to diverge, and an anode that accelerates the focused electron beam. An accelerating voltage is applied between the anode and the filament, and a bias voltage is applied between Wehnelt and the filament using a bias resistor. Also, with this configuration, the thermoelectrons emitted from the filament are
It is focused by the Wehnelt electrode and further accelerated toward the anode by the electric field formed by the accelerating voltage. When accelerating voltages are used in the range of several hundred volts to tens of kilovolts, the electric field strength near the filament is insufficient at low accelerating voltages, and electron emission is suppressed due to the effect of space charge, reducing the brightness of the electron source. do. In order to prevent this reduction in the brightness of the electron source, a four-pole type electron gun has been proposed ("Electron Microscope JVo1.16, No. 1, p. 32
(1981)), Figure 2 shows the circuit diagram of this four-pole type electron gun.
is Wehnelt, 4 is an extraction electrode, 5 is an anode, 6
7 is a detection resistor, 7 is a heating power source, 8 is a filament, 9 is an electron beam, and 14 is an extraction power source.

This four-pole type electron gun includes an acceleration power source 1 for accelerating an electron beam 9 between a filament 8 and an anode 5, a bias resistor 2 for applying a bias between Wehnelt 3 and the filament 8, and a bias resistor 2 for applying a bias between the filament 8 and the filament 8. It is composed of an extraction electrode 4 and an anode 5 that are provided facing each other, a detection resistor 6, a heating power source 7 for heating the filament, and an extraction power source 14 that applies an extraction voltage between the extraction electrode 4 and the filament 8. In other words, when using only a low accelerating voltage, the extraction power source 14 can be generated from the low voltage side, but if you try to use even a high accelerating voltage, the extraction voltage must also be high. It is more efficient to generate the extraction voltage by floating it on a high voltage using an accelerating power source instead of from the low voltage side.

[Problem to be solved by the invention]

However, arranging the extraction power source 14 in the electron gun has the problem that an insulating structure is required to float it at a high voltage, and the cost for arranging the electric power source 114 is also high.

Therefore, an object of the present invention is to provide a high-voltage power supply that can easily obtain the accelerating voltage and extraction voltage for a quadrupole electron gun.

[Means to solve the problem]

The high voltage power source for an electron gun of the present invention includes an accelerating power source that applies an accelerating potential between the filament and the anode, and
The device is characterized in that a Zener diode and a high-voltage power source are switchably installed between the filament and the extraction electrode.

[Effect]

When using an electron gun at a high accelerating voltage, an accelerating power source that applies an accelerating potential is placed between the filament and the anode, and a Zener diode and a high voltage power source are switchably installed between the filament and the extraction electrode. By using the voltage drop effect of the Zener diode, a voltage can be generated between the filament and the extraction electrode and used as the extraction voltage. Since it is not possible to generate a voltage, a voltage can be applied to the extraction electrode with the extraction electrode set as positive using a separately prepared high voltage source that generates a voltage from the low voltage side.

Examples will be described below with reference to the drawings.

〔Example〕

FIG. 1 is a high-voltage power supply circuit diagram of the present invention, in which 1 is an acceleration power supply, 2 is a bias resistor, 3 is Wehnelt, 4 is an extraction electrode, 5 is an anode, 6 is a detection resistor, 7 is a heating power supply, 8 9 is a filament, 9 is an electron beam, 10 is a Zener diode, 11 is a resistor, 12 is a high-voltage power source, 13 is a switch, and 14 is an extraction power source.

As shown in FIG. 1, in place of the extraction power source 14 in the conventional four-pole electron gun, a Zener diode 10 and a high resistance 11 or a high voltage power source 12 are arranged so as to be switchable by a switch 13.

With this arrangement, when the electron gun is used at a high acceleration voltage, the switch 13 connects the extraction electrode 4 to the Zener diode l〇-resistor 11 side, so that when the acceleration voltage is -120KVO, the extraction voltage is set to -17KV. If it is set as follows, an extraction voltage of +3 KV can be supplied to the extraction electrode 4.

On the other hand, in the case of a low acceleration voltage, the extraction electrode becomes a positive voltage with respect to the ground, so the Zener diode cannot generate a voltage, and in this case, the switch 13
The extraction electrode 4 is connected to a high-voltage power supply 12 prepared separately, and a voltage is generated from the low voltage side to supply the voltage to the extraction electrode.

〔Effect of the invention〕

The voltage of the extraction electrode in an electron microscope is generated by a Zener diode when the electron gun is used at a high accelerating voltage, and by using a high voltage power source generated from the low voltage side when used at a low accelerating voltage. Compared to the case of using a conventional draw-out power source, the same effect can be achieved by simply installing a small number of simple parts, and there is no need to float it to high voltage as with a conventional draw-out power source, so it is possible to achieve a similar effect using a quadrupole electron gun. The manufacturing process can be simplified.

[Brief explanation of the drawing]

FIG. 1 shows a high-voltage power supply circuit diagram of the present invention, and FIG. 2 shows a conventional high-voltage power supply circuit diagram. In the figure, 1 is an acceleration power source, 2 is a bias resistor, 3 is a Wehnelt, 4 is an extraction electrode, 5 is an anode, 6 is a detection resistor, 7 is a heating power source, 8 is a filament, 9 is an electron beam, 10
is a Zener diode, 11 is a resistor, 12 is a high voltage power supply,
13 is a switch, and 14 is a power supply. Applicant: JEOL Co., Ltd. Agent Patent Attorney: 1) Nobuhiko (4 others) Figure 1 Figure 2

Claims (1)

[Claims] (1) A high-voltage electron gun characterized in that an accelerating power source that applies an accelerating potential is arranged between the filament and the anode, and a Zener diode and a high-voltage power source are switchably attached between the filament and the extraction electrode. power supply.