JPS6047342A - Liquid metal ion source - Google Patents

Abstract

PURPOSE:To reduce excessive current to a leading-out electrode and obtain a stable ion beam by decreasing the area of the leading-out electrode and providing an exhaust port around the leading-out electrode hole. CONSTITUTION:A leading-out electrode 25 consisting of a conical leading-out electrode 22 and a leading-out electrode 23 with an exhaust port is comprised in such structure that it can be proximate to a pin-shaped emitter 1 in the vicinity of the axis of the pin-shaped emitter 1 and the area of a pin-shaped emitter opposed surface 21 can be reduced. In addition, an exhaust port 24 is arranged around a leading-out electrode hole 10. As a result, the gas generated near the pin-shaped emitter 1 is exhausted quickly as much as possible and the degree of vacuum near the pin-shaped emitter 1 can be set in high vacuum during operation. Furthermore, leading-out electrode current is reduced and the fluctuation of ion beam current can sharply be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a field emission type liquid metal ion source that emits a highly stable ion beam.

(Prior Art) A field emission liquid metal ion source using a needle emitter is well known as a high mu ion source.

The applicant has developed a liquid metal ion source of this type that is equipped with two extractor electrodes that are arranged opposite to a reservoir part that stores liquid metal from which ions are to be emitted, and that draw out liquid metal ions from a nail-shaped emitter. A liquid metal ion source characterized in that the liquid metal is stored in the reservoir section on the side opposite to the ion emission direction with respect to the nail-shaped emitter was published in the special issue of the 3rd issue of Proposed.

The configuration of a liquid metal cap 1 source with such a reserve configuration is shown in FIGS. 1 and 2. In Figures 1 and 1, / is a needle-shaped emitter, ko is a liquid metal needle, gu is a heater placed around the liquid metal reservoir λ, y is a heating power source for this heater, and ot is an extraction electrode. , 7 is the power source for connecting the pull-out electrode B, and 7 is the support part of the pull-out electrode B. is the surface of the extraction electrode B facing the needle emitter / (needle emitter opposing surface), and /θ is the hole for extracting ions (extraction electrode hole). Furthermore, // is a voltage introduction terminal for device integration (q flange, 7.2 is a wire feeding board, /3 is a support part of the ion source main body, /l is a high voltage that supplies high voltage to the needle emitter / supply terminal, /, 9 is a support for heating the liquid metal storage part made of an insulating heat conductive material, /6 is a conductive liquid metal storage part fixing body,
/7 is a heat shield plate, and 7g is an exhaust port for exhaust. The nail-shaped emitter / protrudes from the liquid metal reservoir λ with a gap (approximately θ, /~(7 J'm)) from the hole provided at the tip of the liquid metal reservoir λ.

In such a configuration, gold m3 to be ionized is placed in the liquid metal reservoir, and the metal J in the liquid metal reservoir is melted using a heating power source, thereby melting it to the tip of the needle emitter L. metal is supplied. Here, by applying a high electric field between the nail-shaped emitter I and the extraction electrode B using the extraction power source 7, ions are emitted from the liquid metal at the tip of the needle-shaped emitter I.

In an ion source configured as shown in Figure 1 (1), when an ion beam is emitted using a high melting point metal such as Al or a high melting point metal such as Au, the ions emitted to the extraction electrode B. A current flow that seems to be unrelated to the beam is observed.In other words, when an extraction voltage is applied, a current is already flowing to the extraction electrode B before ions are ejected.If this current is large, generally There was a problem that the stability of the emitted ion beam was poor and it was difficult to obtain a focused ion beam with a small beam spot diameter.This phenomenon has not been made public, and the cause is unknown and can only be speculated. However, this phenomenon became noticeable at least as the temperature of the ion source itself increased.

(Purpose) Therefore, in order to eliminate these drawbacks, an object of the present invention is to suppress IE of currents other than the ion current flowing through the extraction electrode by improving the structure of the extraction electrode, thereby reducing the emitted ion beam. The object of the present invention is to provide a stabilized liquid gold ion source.

(Structure of the Invention) In order to achieve the above object, the present invention includes: (1) a reservoir section for storing liquid liquid to be emitted; a nail-shaped emitter disposed at the bottom of the reservoir section; Liquid gold from the reservoir to the sword-shaped emitter!・A supply section for supplying ((iL) is placed opposite the gold emitter,
It is equipped with an extraction electrode that draws out liquid gold E3 from the nail-shaped emitter, and in the reservoir section, the liquid metal is stored on the opposite side of the needle-shaped emitter from the ion emitting side. On the side where ions are emitted from the tip of the gold-shaped emitter, the extraction electrode is brought closest to the needle-shaped emitter in the part near the axis of the needle-shaped emitter, and the extraction electrode is placed closest to the needle-shaped emitter in the part far from the axis of the gold emitter. It is characterized by being located close to the side.

Here, it is preferable that the extraction electrode is provided with an exhaust port for exhaust on the side from which ions are emitted from the tip of the needle emitter.

Further, it is preferable to attach a water cooling pipe to the extraction electrode.

[For the output electrode, the shape of the portion facing the tip of the needle-like emitter can be made into a substantially truncated cone shape that first tapers toward the needle-like emitter.

(Example) The present invention will be explained in detail below with reference to the drawings.

Figure 3 and Figure 1/Figure 3 show the configuration of an embodiment of the liquid gold 6 ion source of the present invention, in which the same parts as in Figures 1 and 2 are given the same reference numerals. The details are omitted. In the figure, 1.2/ is the surface facing the needle emitter, and n is the drawer 1 in the center.
1! A truncated cone-shaped extraction electrode having a pole hole /θ and tapering toward the nail-shaped emitter, and U 3 are the extraction electrodes with an nTh air hole. The extraction electrode 3 is configured.

Furthermore, ``mu'' is an extraction electrode and a support part for ``2''. This ion source can also emit an ion beam in the same manner as the ion source shown in FIG.

The ion source according to the previous proposal shown in FIG. 1 and the ion source according to the invention shown in FIG. (FIG. 3) differs in structure as described below.

(1) The extraction voltage of the ion source, pole 6 (
As shown in Figure 1, Figure 1) is a flat plate installed perpendicularly to the axial direction of the nail-shaped emitter l, and a hole IO for extracting ions is drilled in this flat plate. something is being used. In contrast, in the present invention, as shown in FIG.
The extraction electrode 3 consisting of 3 is formed in a tII structure such that it is closest to the needle-shaped emitter 1 at a point near the axis 2, and moves away from the nail-shaped emitter 1 at a point away from the axis. That is, the structure is such that the area of the lead-out electrode 3 facing the needle emitter 1 and close to the needle emitter 1, that is, the area of the surface facing the nail emitter 1, is small.

For this purpose, as shown in Fig. 3, a conical extraction voltage tIl1 is required.
1.2.2, and the wall thickness can be made thinner, or the peripheral edge of the extraction electrode hole 10 can be made to have an acute angle within a range that prevents sputtering and does not affect emitted ions. .

(,2) In the ion source (Fig. 1) in the previous proposal,
Exhaust port/g beam is provided on the side of the electrode support part g, and the extraction power is $Ii! t is not provided with an exhaust port for exhaust. On the other hand, in the present invention, as shown in the third figure, the exhaust port 2/I is arranged around the extraction electrode hole 10, so that the structure is <14>. According to this, the gas generated in the vicinity of the gold emitter 1 can be exhausted as slowly as possible, and the degree of vacuum in the vicinity of the needle-shaped emitter 1 during operation can be made high vacuum.

Ion emission characteristics when this example is applied to an Al ion source are shown in FIGS. 5 and A. In addition, in this example, the pull υ
The total cross-sectional area of the exhaust port for 4 electrodes and 2 electrodes was approximately 30 mm.

Figure 9 shows the extraction electrode current just before ejecting Al ions (the state where the extraction voltage is applied just before emitting ions) when changing the surface 2/t of the needle-shaped emitter opposing surface.
The graph shows the change in the extraction electrode current, and the smaller the area of the needle-shaped emitter facing surface, the smaller the extraction electrode current.

Furthermore, Fig. 6 shows the dependence of the extraction Tf on the emitted ion beam current after AI ion emission, the polar current characteristic; The smaller the area of the opposing surface, 2/, the smaller the electrode current. Note that the area of the needle emitter's opposing surface is approximately θmI! Regarding the ion emission characteristics, the fluctuation of the ion beam current was significantly reduced compared to those with a larger area.Furthermore, those with an area of about g- (marked with .) have a surface area of about gOmd. Compared to (x mark), no fluctuation of the ion beam current was observed at all.

From these results, in order to obtain a stable ion beam in the low ion beam region where the ion beam current is less than μA, the area of the needle-shaped emitter opposing surface, 2/, must be approximately gO- or less, Furthermore, it has become clear that it is better to reduce the area as much as possible.

Figure 7 shows the mj product of the nail-shaped emitter opposing surface 2/about gIl.
d and the extraction voltage to 7. It shows the variation of the angular current density over time when jKV (constant) and the ion beam current is 20 μA, where the ion current variation rate is ±1%.
/ j hrs or less, resulting in a low ion beam current (2
It was very stable at θμA). 1 ion beam was obtained.

In addition, the total exhaust port cross-sectional area can be changed from about 1I30- to about iho 1
．． As a result of examining the changes in these characteristics for a similar AA ion source when the cross-sectional area is reduced to l, the ion source with a cross-sectional area of approximately 3°- is better in all respects than the one with a cross-sectional area of approximately / The results showed that Moreover, liquid metal A/temperature approximately A6
0~9θO℃, total operating time approx./! Even after more than Ohrs had elapsed, no deterioration of the liquid metal i at the tip of the needle emitter l was observed.

From the above, the area of the acicular emitter opposing surface, 2/, is set to be less than about It has become clear that an ion beam of high melting point metal can be obtained stably for a long time.

The reason why the ion beam can be stably emitted with such extraction ↑ n pole I, near + i is considered to be as follows.

(1) Drawer 111. Heating (temperature rise) of IJ4 causes heat 1 (1, 1) emission, and this thermoelectric p current is estimated to be one of the factors of instability. t1-;,, i・
It is thought that it is effective to reduce the thermionic emission area of iil11. In the real f+'ti example, only the small 11'i product ff:'+')J facing the needle emitter /! 'I moisten;
The temperature in other parts is 1 z [-thorn l]. Because it is also small,
It is thought that the instability factor was due to a decrease in the current of the four lead-out electrodes.

(,2) Furthermore, the ・r-on source is heated (boosted Wi'u )
When the ion 2 is released, conductive material is easily removed from the surface of the extraction electrode facing the gold emitter 1. This is not enough to increase the temperature, even more! ′J, it is thought that it becomes easier to emit electrons. Therefore, it is thought that by reducing the area on which deposits are deposited, the current flowing to the extraction electrode 3, which is a cause of instability, becomes less likely to flow due to the structure of the present invention, which is designed to be warmer. .

(3) If the space near the needle-shaped emitter is poor, deposits tend to adhere to the surface of the lead-out electrode, 2/, which faces the needle-shaped emitter. In this embodiment, the performance is considered to have been further improved because the structure is such that the air space near the nail-shaped emitter l is always kept at a high vacuum by one exhaust rogue.

FIGS. g and 9 show another implementation of the invention I! AJ is an exhaust port, and 3/I is a surface facing the nail-shaped emitter. This embodiment is a further improvement of the structure of the extraction electrode J shown in Fig. 3, and the extraction electrode hole/
The nrr difference of the extraction electrode 3/ other than the θ portion is made smaller. As shown in the figure, the area of the extraction electrode 3/
The number of lead-out electrodes 3 is reduced compared to the example shown in the figure.
) has a substantially band-like shape, and the total cross-sectional area of the air loss port, which is approximately defined by the remaining exhaust port portion, is increased, making it possible to emit the ion beam more stably.

FIG. 1θ shows yet another embodiment of the invention, where Q/ is the extraction electrode and Q is the extraction electrode l! / support part,
3 is a water cooling pipe attached to the extraction electrode plate, and 3 is an exhaust port. As mentioned above, the extraction power ff511/
Considering that preventing the temperature rise of the ion beam is a factor that guarantees stable emission of the ion beam, in this example, [
By providing a water-cooling vibrator 1/3 to the output electrode 4t/, the ion beam current is stabilized. 71 (It goes without saying that it is effective to arrange pipe 4/3 for i in a part of the extraction electrode lI/ where the temperature is likely to rise as much as possible without affecting the emitted ion beam. .

In the embodiments of the present invention described above, the present invention has been explained by taking a particularly highly reactive high melting point metal such as AA as an example, but a liquid metal ion source such as a high melting point metal such as Au or other alloys, etc. It goes without saying that the present invention can also be applied to. Furthermore, it goes without saying that the ion source having the extraction electrode configuration disclosed in the present invention can be applied to charged particle generators other than field emission type ions.

(Effects) As explained above, according to the present invention, for a field emission type liquid metal ion source, the area of the extraction electrode facing the needle emitter tip can be reduced, and the extraction electrode hole can be reduced. By providing an exhaust port around the electrode, it is possible to reduce the flow of excess current to the extraction electrode. It is extremely useful because it can achieve long-term and highly stable emission of ion beams. Thus, the present invention is useful as a liquid gold 5 ion source.

Since the liquid metal ion source of the present invention is capable of generating various ion species with high brightness, it can be used for various purposes such as battanning (FI light, etc.), ion implantation, micro etching, ion beam micro etching, and even ion beam micro etching. It has a wide range of applications as an ion source for analysis.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an example of a conventional field emission type liquid metal ion source, FIG. Figure 9 is a sectional view taken along the line B-B, Figures 1, 6, and 7 are diagrams showing various characteristics of the ion source of the present invention. Example? FIG. 10 is a sectional view taken along the line C--C, and FIG. 10 is a configuration diagram showing still another embodiment of the present invention. l...acicular emitter, c...liquid metal storage section, 3...liquid metal, ri...heater, S...power supply for heating, 6...electrode for extraction, 7... Output power source 1 g...Output electrode support part, F...needle emitter opposing surface, IO...Output electrode hole, /ka...Flange with voltage introduction terminal 1 7.2...Insulating substrate, /3...Extraction electrode support part 1 /ll...High voltage supply terminal, /S...Liquid metal storage part heating support body, //,...
Liquid metal storage unit fixing body, /7... Heat shield plate, 7g... Exhaust port, 2/... Needle emitter opposing surface 1. 2λ... truncated conical extraction electrode, 2.7... extraction electrode with exhaust port, J... exhaust port 1. 2S... Extracting electrode, U4... Extracting electrode support part 1 31... Extracting electrode, 32... Extracting electrode support part 1 33... Exhaust port, 3'l... Opposing needle-shaped emitter Surface 1 3S...Exhaust port part, Rooftop...Extractor electrode, Intrusion...Extractor electrode support part, Su...Water cooling pipe, qlI...Exhaust port. Patent applicant Yoshi Tani, patent attorney representing Nippon Telegraph and Telephone Public Corporation -: :1 い〉Heem Denyu ()IA) Figure 8 Figure 10

Claims (1)

[Scope of Claims] /) A reservoir section that stores liquid metal from which ions are to be emitted; a needle-like emitter disposed at a lower part of the reservoir section; and supplying the liquid metal from the reservoir section to the needle-like emitter. and an extraction electrode disposed opposite to the needle-shaped emitter to draw out the ions of the liquid metal from the nail-shaped emitter, and in the reservoir section, the ion-emitting direction and the extraction electrode are arranged to face the needle-shaped emitter. The liquid metal is stored on the opposite side, and the extraction electrode is connected to the side where ions are emitted from the tip of the needle-shaped emitter, and the extraction electrode is connected to the needle-shaped emitter at a portion closer to the axis of the needle-shaped emitter. A liquid metal ion source characterized in that the needle emitter is located at a position closest to the ion emitting side in a portion away from the axis of the needle emitter. 2) The liquid metal ion source according to claim 1, wherein the extraction electrode is provided with an exhaust port on the side from which ions are emitted from the tip of the needle emitter. , 7) A claim characterized in that the shape of the portion of the lead-out electrode facing the tip of the needle-like emitter is formed into a substantially truncated cone shape facing the needle-like emitter. The liquid metal ion source according to item 1. 2) The liquid metal ion source according to claim 1, wherein a water cooling vibrator 2 is attached to the extraction electrode. (hereinafter referred to as Kinpaku)