JPH1092362A - Liquid metal ion source - Google Patents

Abstract

(57) [Problem] To provide a liquid metal ion source which is easy to use, stable and has a long life. A base (1) is an insulator such as porcelain and a support (5) is sealed thereto. A hairpin type heater 2 is connected to one end of the support by spot welding. A reservoir and an emitter are connected to the center of the heater. The reservoir spirals a tungsten wire, and an emitter is formed continuously at one end.
The ionized substance 6 is held in the portion of the reservoir 3 and is continuously held from this portion to the ion emitting portion 7 while being wet on the surface. The tip of the emitter has a convex shape, and an ion emitting portion 7 for emitting liquid metal ions is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid metal ion source used for a focused ion beam device or the like.

[0002]

2. Description of the Related Art Heretofore, a great number of liquid metal ion source structures are known. For example, structures related to the liquid metal ion source of the present invention include structures shown in FIGS. However, the structure shown in FIG. 6 has the following problems.

(1) Since the reservoir, the ionized substance, and the heater are integrated, depending on the consumption of the ionized substance,
Since the resistance value of the heater changes, the optimum heater power changes.

(2) When the heater is heated, the temperature decreases in a direction away from the ion emitting portion of the emitter, and the ionized substance moves in a low temperature direction.

(3) Since the emitter is needle-shaped and the reservoir is a cylinder (coil), the ionized substance held between them becomes less likely to flow from the reservoir to the emitter due to the difference in surface tension as it is consumed.

Similarly, the structure shown in FIG. 7 has the following problem.

(4) Since the heater is connected between the reservoir and the emitter, the flow of the ionized substance is deteriorated in this portion.

The above problem (1) is the same in the structure shown in FIG.

[0009]

According to the present invention, the above (1) to
(4) To provide a liquid metal ion source that is easy to use, stable, and has a long life by solving the problem (4).

[0010]

In order to solve the problem (1), a structure is adopted in which the ionized substance does not directly touch the heater so that the amount of the ionized substance does not change the heater characteristics. (2)
In contrast, the components were arranged in the order of heater, reservoir, and emitter. In contrast to (3), as in FIG. 7, the reservoir and the emitter are formed in an integrated structure to reduce the influence of surface tension.
In contrast to (4), factors that alienate the flow of ionized substances such as spot welding marks between the reservoir and the emitter have been eliminated. Furthermore, in order to provide a liquid metal ion source at a low price, the consumable part can be replaced.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIG. This liquid metal ion source is composed of a base 1, a heater 2, a reservoir 3, an emitter 4, a support 5, an ionized substance 6, and an ion emitting section 7. The base 1 is made of an insulating material such as porcelain, on which the columns 5 are sealed. A hairpin type heater 2 is connected to one end of the support by spot welding. A reservoir and an emitter are connected to the center of the heater. The reservoir spirals a tungsten wire, and an emitter is formed continuously at one end. The ionized substance 6 is held in the portion of the reservoir 3 and is continuously held from this portion to the ion emitting portion 7 while being wet on the surface. The tip of the emitter has a convex shape, and an ion emitting portion 7 for emitting liquid metal ions is formed.

Next, the operation of the present liquid metal ion source will be described with reference to FIG. When an ion extraction electrode 13 is arranged opposite to the ion emission portion 7 of the liquid metal ion source 9 and a voltage of 7 to 8 kV is applied between the emitter 4 and the extraction electrode by an ion accelerating power supply, Ga as an ionized substance causes this electric field to be generated. And become sharp at the ion emitting portion to emit ions by the strong electric field in that portion. Ga released as ions is supplied from the reservoir 3. The resistance of the flow path is designed to be uniform between the reservoir serving as the supply path, the emitter, and the ion emitting section. Therefore, the output current Ip can be obtained stably.

When the liquid metal ion source is operated for several tens of hours, Ga combines with the peripheral oxygen remaining in the vacuum to form an oxide. Since this oxide is not a liquid, the ion emission becomes unstable when the oxide flows through the flow path and reaches the ionized portion. In this case, the current Ih is caused to flow by the heater power supply 10 so that the reservoir section and the emitter section are set to about 800 degrees Celsius.
Each time it is heated, it is returned to the original state by decomposing and evaporating the oxide. This operation is called flushing. If the flushing temperature is low, the effect cannot be sufficiently obtained, and if it is too high, Ga is vaporized. For this reason, the flushing temperature must be properly controlled. Conventionally, Ga has a structure in which Ga accumulates in the heater portion, and since Ga decreases with use time, it is equivalent to a change in the resistance of the heater every moment. In the present invention, Ga that changes the resistance of the heater does not accumulate on the heater, so that the resistance of the heater is constant. Thus, the complexity in use is reduced.

When the temperature is increased during flushing, Ga has a property of flowing to a lower temperature. When the heater 2 is raised, the temperature rises from the heater part, so that it flows farther from the heater part, that is, flows in the direction of the ion emitting part 7, so that Ga
Will not be lost. Since Ga, which is an ionized substance, is continuously wet from the reservoir to the emitter and is separated from the heater, it is not subjected to an extra surface tension effect that prevents the flow of Ga. For this reason, once filled Ga can be operated until the entire amount is ionized.

FIG. 3 shows a second embodiment of the present invention. FIG.
The difference is that the heater 2 has a coil shape,
The point is that the emitter 4 is directly attached to the emitter holding bracket 8. The operation is the same as in FIG. 1, except that the reservoir,
The emitter can be removed alone. The emitter and the reservoir are the emitter holding bracket 8 fixed to the base.
Loosen the screw 14 and remove it.

FIG. 4 shows a third embodiment of the present invention. In this case, the heater 2 is arranged outside the base. The advantage is that since the heater is not affected by the back spatter or secondary electron impact accompanying the ion emission, its characteristics are not changed much and can be used stably. However, this structure requires a spatial device to remove the emitter.

FIG. 5 shows a fourth embodiment of the present invention. The configuration in this case is almost the same as that of FIG. 3, but the heater part overlaps the one-part reservoir part. Although they overlap, the arrangement maintains the relationship between the heater, the reservoir, and the ion emitting section. In the heating in this case, the ratio of the radiant heating is large.

[0018]

The liquid metal ion source of the present invention has the following effects.

(1) It is efficient because all of the charged ionized substance can be ionized.

(2) Since the flushing condition is always constant, it can be used stably and does not fail.

(3) Since only the emitter and the reservoir can be replaced, the operating cost can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of the operation of the liquid metal ion source of the present invention.

FIG. 3 is an explanatory view showing a second embodiment of the present invention.

FIG. 4 is an explanatory view showing a third embodiment of the present invention.

FIG. 5 is an explanatory view showing a fourth embodiment of the present invention.

FIG. 6 is an explanatory diagram of a first related art.

FIG. 7 is an explanatory diagram of a second related art.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Base, 2 ... Heater, 3 ... Reservoir, 4 ... Emitter, 5 ... Support, 6 ... Ionized substance, 7 ... Ion emission part,
8 ... Emitter holding bracket, 9 ... Liquid metal ion source, 10 ...
Heater power supply, 11 ... ion extraction power supply, 12 ... collector,
13 ... ion extraction electrode, 14 ... screw.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kazuto Hikichi 882 Momo, Oaza, Hitachinaka-shi, Ibaraki Pref.

Claims (4)

[Claims] 1. A liquid metal ion source, wherein a heater, a reservoir, and an emitter are arranged in this order, and the reservoir and the emitter have an integral structure. 2. The liquid metal ion source according to claim 1, wherein the reservoir and the emitter are made of a seamless wire. 3. The liquid metal ion source according to claim 1, wherein the heater section has a structure in which the ionized substance does not come into direct contact with the heater section. 4. The liquid metal ion source according to claim 1, wherein the emitter and the reservoir are replaceable.