JPH0369137B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an electron impact or field emission type ion source device that heats an ion source material to perform surface ionization or electric field ionization and extracts an ion beam through a high electric field. For example, it can be used for fabricating submicron structures in LSI (large scale integrated circuits) and submicron measurements in secondary ion mass spectrometry.

[Prior art]

Submicron measurement and processing using ion beams has come to be widely used in the field of microstructure fabrication technology, but conventional ion source devices used in such application fields have been based on electric discharge in a low-pressure gas atmosphere. There is a so-called plasma ion gun that generates plasma and applies an extraction electric field to the plasma space to extract ions.

However, the above-mentioned ion sources have (1) low brightness as an ion source, (2) large size of the light source as an ion source, (3) limitations on ion species, and (4) single metals. There were disadvantages such as difficulty in extracting ionic species.

In response to this, the present inventors have developed an ion source using an electron impact or field emission type, in which the ion source material is first heated by electron bombardment to cause surface ionization or electric field ionization, and an ion beam is extracted through a high electric field. proposed a device (see Japanese Patent Application No. 108338/1983). An example of this will be explained with reference to FIG. In FIG. 1, 1 is an ion source material, 2 is an emitter chip, and 3 is a crucible. The crucible 3 is made of a material with a high melting point and low reactivity, and coaxially holds an emitter chip 2 in the shape of a round bar with a pointed tip. The ion source material 1 is loaded into the lower part of the interior of the crucible and the outer periphery of the tip of the chip 2. The chip 2 is provided with a constriction (a narrow diameter part) for increasing thermal resistance, and one or more hollow discs 4 (only one is shown) are attached for axial alignment of the chip 2. These 1, 2, 3, and 4 constitute an ion source material holding section.

5 is a filament that emits an electron beam to bombard the chip 2 with electrons from below; 6 is a heating power source; 7 is arranged to surround the filament 5 and is electrically connected to one end of the filament 5; An auxiliary electrode 8 corrects the trajectory of the emitted electron beam from the auxiliary electrode 7 and the chip 2.
A voltage is applied between the filament 5 and the chip 2 to accelerate the electron beam 10 from the filament 5 to the chip 2.
An acceleration power source 12 is provided below the auxiliary electrode 7 to extract the ion beam 11 from the ion beam 11.
An ion beam accelerating electrode 9 is an ion beam accelerating power source that applies an ion beam accelerating voltage between the accelerating electrode 12 and the auxiliary electrode 7.

The conventional device shown in FIG. 1 having the above configuration operates as follows. First, the filament 5 is heated by the heating power source 6, and then a voltage is applied between the chip 2 and the auxiliary electrode 7 by the acceleration power source 8. As a result, the electron beam 10 emitted from the filament 5
is irradiated onto the tip of the tip 2, and the tip of the tip 2 is heated. When the tip of the tip 2 is heated, the ion source material 1 is heated and melted by thermal conduction, and the ion source material 1 is continuously supplied to the tip of the tip. On the other hand, the tip of the chip 2 is heated, and the ion source 1 is ionized.
This will be extracted as an ion beam 11.

By using such an electron impact or field emission type ion source, the aforementioned disadvantages of the plasma ion gun type ion source device can be overcome; however,
However, the following problems still remain with electron impact and field emission type ion source devices. That is, the problem is that the ion beam current fluctuates due to fluctuations in filament heating temperature, the influence of atmospheric gas in the crucible, and the like.

[Purpose of the invention]

The purpose of the present invention is to solve the above-mentioned problems in electron impact and field emission type ion source devices, and to provide an ion source that can stabilize the ion current against fluctuations in filament heating temperature and the effects of atmospheric gas. The objective is to provide a source device.

[Summary of the invention]

A feature of the present invention is that in an electron impact or field emission type ion source device, a control electrode is provided between an auxiliary electrode and an ion source section, and a semi-fixed bias power source is connected between the control electrode and the auxiliary electrode. A self-bias resistor is arranged in the middle of a connection line that is electrically connected and connects this connection point and the ion source via a heating power source.

[Embodiments of the invention]

An embodiment of the present invention will be explained with reference to FIG. This is a configuration in which the control electrode and the auxiliary electrode are electrically connected via a semi-fixed bias power supply, and a self-bias resistor is placed in the connection line that electrically connects this connection point and the chip. It's summery. That is, in FIG. 2, 13 is a control electrode additionally installed between the chip 2 and the auxiliary electrode 7, and this control electrode 13 is electrically connected to the auxiliary electrode 7 via the semi-fixed bias power supply 15. A self-bias resistor 14 is inserted in the middle of the connection line connecting this connection point and the acceleration power source 8. The same reference numerals are used for the other parts as in the conventional device shown in FIG.

In the apparatus of the embodiment shown in FIG. 2, the ion source material 1 is loaded into the crucible 3, the filament 5 is heated by the heating power source 6, the electron acceleration voltage from the acceleration power source 8 is applied to the rear end of the chip 2, and the tip of the chip is heated. The operation of heating the ion source material 1 with the electron beam 10, heating and melting the ion source material 1 by heat conduction from the heated chip tip, and emitting a high-intensity ion beam from the chip tip is as follows. Figure 1 is the same as the conventional device.

The control electrode 13, self-bias resistor 14, and semi-fixed bias power supply 15 additionally installed in the embodiment of FIG. 2 function as follows. Now, assume that the chip 2 is being irradiated with an electron beam 10 and an ion beam 11 is being emitted. In this state, the temperature of the chip 2 changes due to the electron flow 10 from the filament, and as a result, the emitted ion current i increases ±Δi
When the current changes by i±Δi, this current flows through the bias resistor 14 having a resistance value r, and the potential of the control electrode 13 with respect to the chip 2 becomes controlled (negative) by the voltage change ±Δv=±Δi・r.・Bias) That is, when the ion current i changes, for example, in an increasing direction, the potential difference between the chip 2 and the control electrode 13 increases by Δv compared to when the current i flows, and as a result, the ion beam 11 is extracted. Stabilization of the ion current is achieved by reducing the current flowing to the source. In addition, by making the resistance value r variable and changing it, it becomes possible to arbitrarily adjust the effectiveness of the self-bias.
This also makes it possible to change the ion current value. Furthermore, by arranging the semi-fixed bias power supply 15, the level of the ion current i can be changed significantly, and moreover, the ion current can be stabilized by the bias resistor 14 at each current level. . In this case, as the semi-fixed bias power supply 15, for example, a variable voltage source connected to both ends of a fixed voltage battery with a potentiometer type resistor and taken out from the sliding contact of this potentiometer may be used. I can do it.

As described above, according to the embodiment shown in FIG. 2, the instability of the ion current, which was a problem with the conventional device, can be solved by simply adding the control electrode 13, bias resistor 14, and semi-fixed bias power supply 15 to the conventional device. Furthermore, the level of the ion current can be changed arbitrarily, and stabilization of the ion current can be achieved at each current level.

〔Effect of the invention〕

According to the present invention, in addition to the above-mentioned effects as an electron impact and field emission type ion source device, (1) the present invention has a simple configuration that only requires adding a few parts to the conventional configuration, resulting in low cost; (2) If a semi-fixed bias power supply is added, the ion current can be greatly varied, and the ion current can be stabilized at each current level. This has the effect of stabilizing the ionic current. To give an example of a specific effect, as a result of actually measuring the current of ions In + or Au ⁺ emitted in the embodiment configuration shown in Figure 2 using a single metal In or ^Au as the ion source material 1, we found that We were able to improve the stability by about an order of magnitude compared to the ion current at

[Brief explanation of drawings]

FIG. 1 is a layout diagram of a conventional device, and FIG. 2 is a layout diagram of an embodiment of the present invention. Explanation of symbols, 1... Ion source material, 2... Emitter chip, 3... Crucible, 4... Hollow disk, 5... Filament, 6... Heating power source, 7... Auxiliary electrode, 8... Electron acceleration power source, 9... Ion acceleration power source, 10...electron beam, 1
1... Ion beam, 12... Ion accelerating electrode, 13
...Control electrode, 14...Self bias resistance, 15...
Semi-fixed bias power supply.

Claims (1)

[Scope of Claims] 1. An ion source section that holds an ion source material together with an emitter chip in a crucible, a filament that emits an electron beam to heat the ion source section by electron bombardment, and a filament that surrounds the filament. an auxiliary electrode provided on the ion source to regulate the trajectory of the emitted electron beam; an acceleration power source that applies voltage between the auxiliary electrode and the ion source to accelerate the electron beam; and an electron impact and electric field for extracting the ion beam. In the emission type ion source, a control electrode is provided between the auxiliary electrode and the ion source section, and this control electrode and the auxiliary electrode are electrically connected via a semi-fixed bias power source, and this connection An electron impact and field emission type ion source characterized in that a self-bias resistor is disposed in the middle of a connecting line connecting a point and an ion source section via the acceleration power source.