JPS5949132A - Ion source with high intensity - Google Patents

Abstract

PURPOSE:To obtain a fine ion source with high intensity capable of radiating the desired ion seed when heated and applied with an electric field by carbonizing a filament or a needle-like surface layer formed with a transition metal. CONSTITUTION:A transition metal and a compound made of Si only or two or more elements are alloyed to form a prototype of a filament or a sharp needle, and the prototype is carburized to carbonize its surface layer. For example, a filament bored with a diameter of 0.5mm. at its center by machining ribbon- like tantalum (with a width of 1.5mm., a thickness of 0.1mm., a length of 20mm.) is heated at 2,200 deg.C for 60sec for carburization by introducing several Torr of C2H4 in a vacuum furnace, then a likewise-carburized sharp needle 10 is inserted into the hole of the filament 11 to form an ion source comprised of a liquid metal reservoir 9. At this time, TaC is formed on the surface of the filament and sharp needle.

Description

[Detailed description of the invention] [Field of application of the invention] The present invention is an ion micro analyzer.

The present invention relates to a minute and high-intensity ion source that can be used in an ion beam lithography system, a microbeam IO7 implanter, etc. to improve its performance.

[Prior art]

Conventionally, both gas ion sources and liquid metal ion sources have used a pointed needle made by electrolytically polishing W as the ion source base material. In the case of a gas ion source, there are fewer problems because the ion source does not heat up the ion source, but rather cools it down. However, in a liquid metal ion source, the metal used as the ion species is in a liquid state and ions are emitted from the W needle, so for substances with high melting points, W
Due to the reactivity with the W-pointed needle, the lifespan of the W-pointed needle was short. For this reason, depending on the ion species, B, A,! et al. have devised a method of using glassy carbon as a point, and a method of using a carbide point for Si or the like.

However, improvements are needed in terms of wettability and operability.

[Purpose of the invention]

The object of the present invention is B+ AS+ P, ktg Sr.

Be, Zn, Te, Se, etc. (7) Io7'tAwo alone-
T::, or a combination of two or more of them, or making a compound or alloy with one or more of the above elements for the purpose of lowering the melting point, although it is not particularly desired as an ion heavy metal such as Ni. An alloy or compound with other metals that can be used as an ionizing substance is heated to create an electric field.
By doing so, the purpose is to provide an ion source capable of emitting the desired ion species.

[Summary of the invention]

There are few materials that have low reactivity with all substances. Carbon has relatively low reactivity with respect to the above ion species, and for example, carbon alone, like B, has a melting point of ~2000 tr.
By using NiB as the substance, the melting point is ~1000t
Lowered to Z'. However, in this case, a problem arises in that the reaction between Ni and carbon is relatively large. Currently, the lifespan of actual carbon meters is longer than that of W actual meters, but other means are required in order to achieve a longer life. Another problem is that carbon has poor wettability, as is the case with 9NiB.

It has been known that the material that can solve these two problems is a carbide material such as tungsten carbide, but when using normal carbide (including whiskers), gold@ A carbon filament that can be used must be used. A liquid metal ion source requires a reservoir part to replenish this liquid metal with the simplest possible structure, but since it can only replenish a small amount if it is in the actual measuring part, the filament part is kept wet. The first step is to create a reservoir. However, as described in 1'I above, when a carbon filament is used, there are problems similar to those of the actual carbon meter. Therefore, in addition to the above two problems and the structural problems as a 0/ion space, ■Low reactivity as a pointed needle ■Good wettability as a pointed needle ■Simple structure of the filament and 1 clasp, and the same requirements as ■■ , 03 points, and good practical operability. The structure that solves these problems is made of carbide (11V) to satisfy the defects on the surface of the filament and the filament, which is practically equivalent to gold, filament of tungsten, etc. This is a method of carbonizing a material equivalent to the conventional method, which can be formed by deformation, by carburizing.

[Embodiments of the invention]

Examples are shown below using figures. Figure 1 is similar to the conventionally used ■ Yahiki, in which a W + cross line with a diameter of about 0.15 mm is attached to a stem 1 held by a filament base 2 made of alumina etc. in a V-shape. The filament portion 3 formed in the shape of the filament is spot welded, and a W wire of the same diameter is spot welded to the bending center of the filament to form the actual measurement portion 4, and then electropolishing is performed. This integrated thing is CTl4. C2H
Hydrocarbon gas such as No. 4 is heated at approximately 2100 r in a vacuum with a partial pressure of several Torr or in an Ar inert gas at a temperature of 20 to 60
Carburize by heating for seconds to carbonize the surface layer. As a result of this treatment, the cross section of the filament 3 changes as shown in FIG.
tC) layer is formed. In the actual meter section 4, the value changes as shown in the figure 2. If the upper rudder is treated, approximately 1/1 of the wire diameter
Since the surface layer with a thickness of 10 mm is carbonized, in the case of this example,
A carbonized layer of approximately 15 μnl was formed. The large needle and filament thus made are heated (approximately 1000 tons) in a furnace 7 made of carbon in a vacuum (to a molten state) in NiB, as shown in Figure 3 (a). By pulling it up, a NiB reservoir 9 is formed around the junction between the filament portion 3' having a carbide surface and the tip 4'.

Although the actual measuring section is directly connected to the filament, it may be connected via an ionic material that becomes liquid metal when the filament is heated.

FIG. 4 shows another embodiment. Ribbon tantalum (width 1.
A filament with a diameter of 0.5 mm and a hole of 0.5 mm in diameter was processed into a vacuum furnace, and C and H4 were introduced into the vacuum furnace. A similarly carburized large needle 10 is passed through the hole of the filament 11 formed by heating and carburizing it at 2200C for 60 seconds to obtain an ion source consisting of a liquid metal reservoir 9, (a) is a cross-sectional view, and (b) is a floor plan. shows. In this case, the surface of the filament and large needle is T
aC is formed.

FIG. 5 also shows another embodiment. A reservoir 9 is created by melting NiB between a pipe-shaped electrode 13 made of glassy carbon or SiC with an inner diameter of about 0.5 mm and a large needle 10 made of a Ti wire, which is carburized to have a carbide surface. . The heating method is to energize the filament 12 made of W or the like and arranged in a circular shape around the filament 13 using a power source 16 to heat it and emit thermionic electrons. The filament 12 is heated by the power source 17 for electronic impact heating.
A potential is applied so that 13 is on the positive side, and electron impact heat is applied to 13. That is, the tip and the reservoir 9 are also heated at the same time. Reference numeral 14 denotes a control electrode, which controls the ion emission current emitted by the power source 18 based on the potential applied by the power source 19 applied between the cathode 15 and the ion source, that is, the anode. It is also possible for the power supplies 17 and 18 to serve as both power supplies. The ion beam thus ejected can be focused by an ion optical system to obtain a minute, high-intensity spot, although this differs depending on the purpose.

Another embodiment, although not particularly illustrated, is an application example in the case of silicon. A filament and a point (arrows are electrolytically polished) having a cross-sectional shape similar to that shown in FIG. 1 are made integrally by photo-etching from a wafer having a thickness of 0.1 to 0.2 mm, and then carbonized by carburizing treatment. In particular, alloys of silicon and other metals (A
t8i.

This is effective when using PdSi, Ni8i) as the ionic material.

In the above embodiment, as for the material of the filament 3- and the tip 4 immediately before carbonization, the simplest structure was to use only W, but in general, any transition metal can be used with RIJ. It is also possible for 3 and 4 to be made of different materials. As a criterion for selecting f, it is sufficient to consider that the melting point of the metal to be used as the ionic species is 1, and the material to be used is 1 so. In addition, the dripping properties may differ slightly depending on the silk combination. And as a way to further improve your accent,
For example, by using an alloy of W and Ni instead of W, wettability for many ion species is improved. As a result, this ion source can be used as a common ion source for many ion species. Especially Wr N'
*Cre Mn, Fe, and Co are preferred.

In addition, the heating in the carburizing or surface carbonizing treatment in this example may be performed by applying Fi'J'rl (to the filament) or may be performed in a furnace. The thickness can be monitored by the current applied, and if the current is attenuated by about 2%, it is considered that the thickness corresponding to the average diameter of 1710 mm has been carbonized.

〔Effect of the invention〕 According to the present invention, there are effects in the following points.

(1) It can be used as an ion source for high-melting-point ionic species materials without changing the filament or actual shape of the conventional wl, that is, the manufacturing method and structure are simple, and there is no need to increase the heating power.

(Depending on the electric crab structure, the minimum is 6 to 10 W, other means require at least IOW or more. Ionic material: i point 2
Possible up to about 5001r, impossible to achieve with other methods considering the backlash at the filament) (2)
It is possible to improve the wettability of materials of any ionic species, and therefore to stabilize the ionic current.

(3) Because the reactivity of the filament and tip with the ionic material is low, the lifespan is longer than that of ion sources using other materials (tungsten has a lifespan of several hours, but
0 hours or more).

[Brief explanation of the drawing]

Fig. 1 is a front cross-sectional view showing the structure of the ion ripple before carburizing in the conventional and the present invention, and Fig. 2 shows (a) and (b) the changes due to carburization on the r-plane inside the filament, and ρ1 is the actual value. FIG. 3 is an explanatory diagram of creating a reservoir in the ion source;
(B) is a front view after creating a reservoir in the ion source; FIG. 4 is another embodiment; (A) is a front sectional view; (B) is a sketch; FIG. 5 is another embodiment; FIG. 2 is a diagram showing both a front sectional view and a conceptual diagram of potential application. DESCRIPTION OF SYMBOLS 1... Stem, 2... Base, 3... Filament such as W, 4... Pointed hook such as W, 5... Cross section of filament such as W, 6... Carbide after carburizing treatment Layer, 3'...
・Filament after carburizing treatment, 4'... Out of balance after carburizing treatment, 7... Furnace made of carbon etc., 8... Ionic material such as NiB in molten state %9... NrB etc. ionic material reservoir part, 10... carburized pointed skein, 11...
・1-280 Higashikoigakubo, Kokubunji City, Hitachi, Ltd. Central Research Laboratory 08''''7-08, □, Engineering@280@ Hitachi, Ltd. Central Research Laboratory

Claims (1)

[Claims] 1. Form a prototype of at least one of the filament and the needle using a composite or alloy made of a transition metal and silicon or a combination of two or more thereof, and carburize the prototype to form the filament and the needle. A high-brightness ion source characterized in that at least one surface layer of the ion source is made of carbide.