JP2930701B2 - Field emission type electron gun - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a field emission electron gun, and more particularly, to a field emission electron gun having an axis alignment mechanism and a conditioning mechanism.

[Prior Art] In a field emission electron gun, the position of an emitter tip can be adjusted from the atmosphere side in order to align the position of the emitter with the optical axis. Therefore, the field emission electron gun has a shaft alignment rod for adjusting the position of the emitter tip from the atmosphere side, and the shaft alignment rod is inserted into a cylinder formed of an insulator. .

Further, the field emission type electron gun has a mechanism for performing conditioning. This conditioning mechanism is for applying a negative high voltage to the insulator tube to generate a discharge between the insulator tube and the case held at the ground potential, so that no discharge occurs when the electron gun is operated. is there.

When the discharge extends between the anode and the extraction electrode with this conditioning, the potential of the extraction electrode greatly changes, so that a large voltage is applied between the chip and the extraction electrode. Therefore, a large current flows between the chip and the extraction electrode, and the chip is damaged. Therefore, in order to prevent such damage to the chip, when conditioning is performed, the extraction electrode is brought into conduction with the anode to make them the same potential, and even if the discharge extends between the anode and the extraction electrode, A large current is prevented from flowing between the chip and the extraction electrode to protect the chip. Therefore, the conventional field emission type electron gun has an operation rod for switching conduction and non-conduction between the chip and the extraction electrode from the atmosphere side, and this operation rod is also inserted into the insulator tube.

[Problem to be Solved by the Invention] In such a conventional apparatus, since the shaft alignment rod and the operation rod are not particularly considered, they are formed of different materials, and The diameter was also different.

Therefore, in the related art, a minute discharge is generated between the rods or between the rod and the inner surface of the insulator, and as a result, the high voltage applied to the chip fluctuates due to the minute discharge. Therefore, when such an electron gun is used for a scanning electron microscope, for example, flickering of an image has occurred.

An object of the present invention is to solve such a conventional drawback and to provide a field emission type electron gun capable of suppressing generation of the above-mentioned minute discharge.

Means for Solving the Problems Therefore, the present invention provides an electron gun casing including an electron gun casing, an insulator cylinder fixed inside the electron gun casing, and a lead wire for applying a high voltage to an emitter chip. A coating layer disposed at the inner central portion, and an emitter chip which is disposed at substantially equal intervals on the same circumference substantially in the middle of the inner peripheral surface of the insulator cylinder and the coating layer and which is moved from the atmosphere side to emit light. A shaft alignment rod made of a plurality of insulators for adjusting to the center of the shaft, and an intermediate member between the inner shaft of the insulator cylinder and the coating layer and between the two shaft alignment rods and between the tip and the anode during conditioning. In the field emission type electron gun provided with an operation rod made of an insulator for conducting the electric field, the axis alignment rod and the operation rod are formed to have the same diameter.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a sectional view of an embodiment of the present invention, in which 1 is an electron gun casing, and 2 is an insulator cylinder.
A metal donut plate 3 is attached to the bottom of the insulator tube 2. A bellows 4 is attached to the metal donut plate 3, and an insulating material chip support plate 5 is attached to the bellows 4. An emitter chip 10 is mounted on the chip support plate 5. Reference numeral 6a denotes a first alignment rod, which is not shown, but is taken out to the atmosphere side while maintaining airtightness, and is rotatable around its axis from the atmosphere side. It has become. The tip of the shaft alignment rod is fitted into the recess of the adjustment screw 7a. The tip of the adjusting screw 7a is in contact with a contact member 8 fixed to the donut plate 3. This contact member 8 is formed of an insulator. An electrode support tube 13 is attached to the donut plate 3 via insulating members 11 and 12. The extraction electrode 14 is fixed to the electrode support cylinder 13 and a magnetic lens 15 is attached to the extraction electrode 14. 9 is tip 10 during conditioning
And an operating rod for conducting between the lead-out electrode 14. A metal contact 17 is fixed to the tip of the operating rod 9.
17 is connected to the chip 10 by a lead wire 16. contact
A metal member 18 is arranged opposite to 17. The metal member 18 is electrically connected to the extraction electrode 14 and is insulated from the chip 10 by the insulating member 12.
Although not shown, a potential that is slightly higher than the electron extraction chip 10 is applied to the extraction electrode 14 during operation. An anode 19 is attached to the insulator tube 2. A lead wire 2 is provided inside the insulator tube 2 for the purpose of applying a high pressure to the chip or the like.
1,22 (FIG. 1) have been inserted. These leads are molded with a coating layer 20 made of epoxy resin. The insulator cylinder 2 is sealed by the chip support plate 5, the bellows 4, and the donut plate 3, and a gas for enhancing insulation is sealed in the sealed space.

FIG. 1 shows a cross section taken along the line AA in FIG. 2, and the same components as those in FIG. 1 are denoted by the same reference numerals.

As shown in FIG. 1, actually, in addition to the shaft alignment rod 6a, the shaft alignment rods 6b and 6c are arranged at substantially equal intervals on the same circumference substantially in the middle between the insulator tube 2 and the coating layer 20. Have been. The rods 6a, 6b, 6c for axial alignment are for moving the tip 10 in a direction connecting each of these rods to the center of the insulator tube 2. The diameters of the rods 6a, 6b, 6c for alignment and the operation rod 9 are the same, and these four rods are formed of the same material, epoxy.

In such a configuration, when the axis of the chip 10 is aligned, a necessary one of the axes 6a, 6b, and 6c is rotated. Now, for example, when the alignment rod 6a is rotated, the adjusting screw 7a is rotated, whereby the insulating material chip supporting plate 5 is inclined and the chip 10 moves.

When performing conditioning, the operating rod 9 is moved along the direction of its axis. As a result, the contact 17 comes into contact with the metal member 18, and the tip 10 and the extraction electrode 14 have the same potential. Thus, if a high voltage is applied between the insulator cylinder 2 and the casing 1, the above-described damage to the chip 10 can be prevented and conditioning can be performed.

 Next, effects will be described.

The state of the electric field inside the insulator tube 2 of the above-mentioned field emission type electron gun was compared with that of the conventional field emission type electron gun. The following points were considered in analyzing the electric field distribution for that purpose. That is, when the inside of the tube is composed of only a conductor, the effect of the electric field concentration becomes more remarkable if the diameter of the operation rod or the like is small, and it is expected that a large electric field exists locally. Since the elements to be arranged are insulators, the analysis of the electric field distribution is not simple. Therefore, the analysis of the electric field distribution in the pipe was performed by computer simulation.

As a result, in the case of the above-described embodiment, the result is as shown in FIG. 3B. On the other hand, when the material of each bar is the same epoxy and the diameter is different, the result is as shown in FIG. 3A. In FIG. 3, a portion indicated by a indicates a portion having a high electric field intensity, and the darker the hatching, the stronger the electric field intensity is.

As in the case of the electron gun barrel of the field emission type electron gun to which the present invention is directed, in order to suppress micro-discharge in a composite composed of members having different relative dielectric constants, a portion having an abnormally high electric field strength is required. Make the electric field strength relatively low, and make the electric field strength uniform throughout (reducing the electric field strength of a part,
Since the electric field strength in other parts increases, it is necessary to reduce the variation in electric field strength in consideration of the balance.

From such a viewpoint, in the present application, the shaft alignment rods 6a, 6b, 6c
The diameter of the control rod 6d is the same as that of the control rod 6d, which eliminates the part where the electric field strength is extremely strong and makes the electric field strength uniform overall. Discharge can be suppressed. Therefore, if such a field emission type electron gun is used in, for example, a scanning electron microscope, the stability of an image can be improved.

[Effects of the Invention] As is clear from the above description, according to the field emission type electron gun of the present invention, the minute discharge between each rod in the insulator cylinder and the minute discharge between each rod and the inner surface of the insulator cylinder are provided. Therefore, if such a field emission electron gun is used in a scanning electron microscope or the like, the stability of an image can be improved.

[Brief description of the drawings]

FIG. 1 is a view showing a cross section of one embodiment of the present invention, and FIG.
The figure is a view showing another cross section of the device of this embodiment, and FIG.
The figure is a diagram for explaining the operation and effect of the present invention. 1: Electron gun case, 2: Insulator tube 3: Metallic donut plate, 4: Bellows 5: Chip support plate 6a, 6b, 6c: Alignment rod 7a: Adjustment screw, 8: Contact member 9: Operation rod , 10: chip 11, 12: insulating member, 13: electrode support tube 14: extraction electrode, 15: magnetic lens 16: lead wire, 17: contact 18: metal member, 19: electrode 20: coating layer 21, 22: lead line

Claims (1)

(57) [Claims] 1. A coating layer including an electron gun casing, an insulator cylinder fixed inside the electron gun casing, and a lead wire for applying a high voltage to an emitter chip, and disposed at a central portion inside the insulator cylinder. And a plurality of insulators which are arranged at substantially equal intervals on the same circumference substantially in the middle of the inner peripheral surface of the insulator cylinder and the coating layer, and which are moved from the atmosphere side to move the emitter tip to align with the center of the optical axis. And an insulator disposed between the inner peripheral surface of the insulator tube and the coating layer and between the two shafts, and for conducting between the chip and the anode during conditioning. A field emission type electron gun having an operation rod, wherein the axis alignment rod and the operation rod have the same diameter.