JPS5856948B2 - field emission electron gun - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a field emission type electron gun, and particularly to a field emission type electron gun that has a simple structure and can be miniaturized.

Field emission electron guns have the characteristics of providing a high-intensity and minute light source, and are used in various electron beam devices.

As shown in FIG. 1, the most conventional field emission electron gun has an emitter E1, a first anode A1, a second anode A2, and a power source v1. An electron gun composed of V2 is known.

In such a conventional electron gun, the electrostatic field created by the anodes A1tA2 acts as a lens, so the anodes A1. A2 requires a high degree of precision both in design and manufacturing.

Also, emitter E, anode A1. A2 A high degree of precision is also required for mutual axis alignment between the three parts.

Furthermore, consideration must be given to the insulation not only between the emitter and the first anode but also between the first anode and the second anode, making the electron gun unavoidably larger and more sophisticated.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a field emission type electron gun that has a simple structure and can be downsized.

An embodiment of the present invention will be explained in detail below based on the drawings.

FIG. 2 is a block diagram showing one embodiment of the present invention, and in the figure, 1 is an emitter that emits electrons.

Electrons emitted from the emitter 1 are accelerated by an anode 3 to which a voltage vk is applied by an acceleration power source 2.

An annular control electrode 4 is provided around the emitter 1, and a voltage VW from a DC control power source 5 is applied to the control electrode 4.

At this time, the polarity of the voltage applied to the control electrode 4 can be reversed by operating the changeover switch 6.

With the configuration as described above, the electric current E applied to the control electrode 4
By changing the polarity and magnitude of Vw, the electric field strength near the emitter surface can be changed.

Now, let us consider a case where the accelerating voltage vA is about 5 KV, which is not that high.

Although it cannot be said definitively depending on the diameter of the emitter, the distance between the emitter anode, etc., in general, at this level of accelerating voltage, the electric field created near the surface of the emitter 10 by the accelerating voltage VA applied to the anode 3 alone will not cause field emission. Even if it occurs, the required emission current (for example, about 10 μA) cannot be obtained.

Therefore, the required emission current can be obtained by increasing the electric field strength near the emitter surface by applying a control type FE, vw, which has a positive potential with respect to the emitter 1 to the control electrode 4.

Next, consider the case where the acceleration voltage VA is switched to 10 KV.

Generally, with an accelerating voltage of this level, only the electric field created near the surface of the emitter 10 by the acceleration chamber EVA applied to the anode 3 is sufficient to cause field emission.

Therefore, if the electric field strength near the surface of the emitter 1 is appropriately attenuated by switching the changeover switch 6 and applying a control voltage vW to the control electrode 4 so as to have a negative potential with respect to the emitter 1, the required emission current can be obtained. can be obtained.

Further, when the acceleration chamber EVA is increased to 15 KV, the electric field strength near the surface of the emitter 1 increases due to the increase in the acceleration voltage, resulting in an extreme increase in the emission current.

Therefore, the required emission current can be obtained by further increasing the electric current EVW and attenuating the electric field strength near the emitter surface.

As described above, according to the present invention, the emitter, the anode, and the control □
□Since a field emission type electron gun can be obtained with only an electrode configuration, it is possible to downsize the electron gun.

Furthermore, in the conventional electron gun shown in FIG. 1, when vl or v2 is changed, anode A1. Since the lens action by A2 changes, the imaging position (virtual light source position) of the crossover light formed after passing through the second anode A2 changes greatly, especially in the time order used in a scanning electron microscope.

However, since the electron gun according to the present invention does not have a portion exhibiting a lens effect, the change in the light source position is small even when V A and V W are changed.

Furthermore, axis alignment only needs to be performed between the emitter and the anode, which is simpler than in the past.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing a conventional field emission type electron gun.
FIG. 2 is a configuration diagram showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1...Emitter, 2...Acceleration power supply, 3...Anode, 4...Control power supply, 6...Selector switch.

Claims (1)

[Claims] 1 an emitter, a single anode for accelerating electrons emitted from the emitter, a control electrode provided around the emitter, and a control for applying a voltage between the control electrode and the emitter. 1. A field emission electron gun, characterized in that it is equipped with a power source and is configured to be able to switch the potential of a control electrode relative to the emitter to either positive or negative.