JPS60112235A - Cesium ion source - Google Patents

Abstract

PURPOSE:To obtain a cesium ion beam that can finely be stopped down by heating a heater, melting a cesium compound, and emitting a cesium ion from the small hole of a lead-out electrode. CONSTITUTION:An ion source consists of a reservoir 1, heater 2, emitter needle 3, and lead-out electrode 4. The needle 3 is protruded from a small hole 1a provided at the tip of the reservoir and the tip of the needle 3 is for a tapered pin form by electrolytic abrasion and such. A cesium compound powder 5 is packed inside of the reservoir 1 and an ion source is mounted on a secondary ion mass spectrometer and such. The reservoir 1 is vacuum exhausted, and then a heater 2 is electrified. The melted cesium compound reaches the tip of the needle 3 and is evaporated and ionized by an electric field applied between the needle 3 and the electrode 4, and a primary ion 7 is emitted from a small hole 6 provided at the electrode 4. As a result, a cesium ion beam that can finely be stopped down can be generated.

Description

Detailed Description of the Invention The present invention relates to a cesium ion source used in secondary ion mass spectrometers (hereinafter referred to as BIMS), etc., which uses a cesium compound that is stable and safe in the atmosphere, and This invention relates to a cesium ion source used for the purpose of focusing a fine ion beam (1 μm or less).

The S Engineering MS is a device that performs elemental analysis of a sample by irradiating the sample with a -order ion beam and performing total mass analysis of the secondary ions emitted from the sample.In order to improve the accuracy of this analysis, , - It is desired that the emission intensity of secondary ions per irradiation amount of secondary ions be high. - It is known that when cesium ions are used as secondary ions, the amount of negative secondary ions released increases. Therefore, cesium ion traces are essential in order to fully generate cesium ions as the primary ion species in the S engineering MS.

Furthermore, in recent years, the need for local D analysis in minute areas has increased, and for this reason it has become essential to focus the primary ion beam used in the S-engine M8.

Conventional cesium ion sources are generally of the surface ionization type, in which metallic cesium vapor permeates a porous tungsten electrode 11M, and an electric field between this electrode and an extraction electrode ionizes the cesium and extracts the cesium ion sound. In addition, in recent years, fEHD ion sources (electro-hytrodynamic ion sources) have been devised, in which liquid cesium metal is supplied to a capillary-type emitter or a needle-type emitter, and the cesium ions are extracted by an electric field applied to the tip of the emitter. It's been done.

However, both of them use metal cesium, which is highly reactive and reacts violently when it comes into contact with air, making it extremely difficult to handle, so care must be taken to avoid contact with air when loading the ion source. This required complicated work and special ingenuity.

In addition, these complications can be removed by using cesium compounds that are stable in the atmosphere, but currently, cesium ion sources using cesium compounds are limited to surface ionization type or electron GK bombardment type. Even if used, it is difficult to obtain a sufficient beam current density, and it is not suitable for application to focused beams.

The present invention uses a cesium compound that is stable in the atmosphere, especially a halogen compound (CsC!, Cs, etc.) in the FiHD ion source, thereby creating a cesium ion source that has a large beam current density and is easy to handle. The purpose is to provide

Conventionally, in BHD ion sources, the range of substances to be ionized was limited to liquid metals, but the present invention
, l, By applying it to insulators such as AS, J,
This will expand the uses of ft1HD Aeon Kaya.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

The drawing is a schematic cross-sectional view of an EHD ion source filled with a cesium compound. Ion source, reservoir II heater 2.
Emitter needle 3', pull-out electrode 4 and p-formation
1 needle 3 protrudes from a small hole 1α provided at the tip of the reservoir, and the tip of the needle 3 is shaped like a pointed needle with a radius of several μηL. The reservoir 1 is filled with 5'ft of powdered cesium compound such as KC8, installed in a device (not shown) such as an ion source MB, and evacuated, and then the heater 2 is energized. This heater heating melts the cesium compound in the reservoir. For example, as a cesium compound, CB(4,C8I
When using the like, the melting point is about 600 to 700°C, so it is easily melted by heating with a heater.

The cesium compound thus melted flows through the emitter needle 3 and reaches its tip.

The molten CgJ,C,9I has low viscosity and can easily flow and reach the tip. The cesium compound that has reached the tip in this way is connected to the needle 3 and the extraction electrode 4.
The primary ions 7 are evaporated and ionized by the electric field applied during this period, and are emitted from the small hole 6 provided in the portion of the extraction electrode 4 facing the needle 3 . Needle 3. An electric field between the electrodes 4 is applied so that positive ions are drawn out. Therefore, when a compound of cesium and halogen such as C8 or cBx is used, a large amount of cesium is extracted as a positive ion due to the difference in electron affinity between cesium and halogen. However, in order to obtain a highly pure cesium ion beam, it is necessary to use a beam that has been subjected to mass separation using a Wien filter or a sector type magnetic field.

In addition, the EHD ion source has a small ion generation region, the energy of the generated ions is spread out quickly, and an ion beam with a large angular current density can be obtained.
A finely focused ion beam with a submicron beam diameter can be formed.

As described above, according to the present invention, it is possible to obtain an ion source that generates a cesium ion beam that is safe, easy to operate, and can be narrowed down to a minute extent.

[Brief explanation of the drawing]

The drawing is a schematic cross-sectional view of an InHD ion source completely filled with powdered cesium compound.

Claims (1)

[Claims] A reservoir having a generally cylindrical shape as a whole, a heater provided on the outer periphery of this reservoir, a small hole formed at the lower end of this reservoir, and a needle provided inside the reservoir with its tip protruding from the opening. , an extraction electrode provided at a lower position of this reservoir and having a small hole at a position corresponding to the front Ne needle, and a cesium compound built in this reservoir, and by heating the heater,
A cesium ion source characterized in that the cesium compound is melted and cesium ions are emitted from the small hole of the extraction electrode.