JPS58158837A - Ion source - Google Patents

Abstract

PURPOSE:To take out negative ion beam by ionizing ionization substance through the electron shock. CONSTITUTION:The positive pole side of high voltage source 23 of an electron gun is grounded while the negative pole side is connected to a wenelt 22. A bias resistor 24 is connected to the negative pole side of said source 23 and the intermediate terminal of secondary winding of a transformer T. The positive pole side of first high voltage source 9 is grounded while the negative pole side is connected to an emitter 3. The ionization substance 20 fused in the emitter will flow out through minute gap between a container 1 and an emitter chip 2 to the surface of the chip 2. The potential of a filament 21 of the electron gun is maintained to negative level lower than that of a lead-out electrode 5, thereby the electron produced from the filament 21 will impinge through second opening 5b of the electrode 5 against the emitter 3. Consequently the ionization substance flowed out to the emitter chip 2 will evaporate and ionize then attracted to said electrode 5 and accelerated to produce an ion beam i' which will pass through the first opening 5a of said electrode 5a.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ion source that ionizes an ionized substance by electron bombardment to generate an ion beam, and more particularly relates to an ion source that can extract a negative ion beam.

The configuration of a conventional ion source of the type in which ions are excited by electron bombardment of an emitter is shown in FIG. In the figure, 1 is a container filled with an ionized substance, 2 is an emitter chip that is inserted into the opening at the tip of the emitter chip, and is attached to the container 1.
constitutes the emitter 3. 4 is a filament that generates electrons for electron impact, 5 is an extraction electrode, and 6 is a power source that supplies power for heating the filament 4 via a transformer T. Further, 7 is a shield, 8 is a ground electrode, 9 is a high voltage power source, and 10 is a voltage dividing resistor connected to both ends of the high voltage power source. Predetermined potentials are applied to intermediate terminals of the secondary windings of the power source 1 to the lance T, the shield 7 and the lead electrode 5 from a voltage dividing resistor 10, respectively. In detail), the filament 4 is at a higher potential than the shield 7, and the shield 7 is at a higher potential than the extraction electrode 5. Furthermore, emitter 3. The ground electrode 8 is connected to a positive electrode and a negative electrode of a high voltage power supply 9, respectively.

In the conventional ion source configured as described above, when the filament 4 is heated to cause electrons to die, the electron beam e advances in the direction shown in the figure and bombards the emitter tip 2. Here, since the potentials of the filament 4, extraction electrode 5, etc. are set lower than the potential of the emitter 3, the electric field surrounding the emitter 3 acts to extract positive ions. Therefore, only positive ions generated by the impact action of the electron beam e are extracted as an ion beam i as shown in the figure.

In this type of ion source, when attempting to extract negative ions by reversing the polarity of the high-voltage power supply 9 and applying a negative potential to the emitter 3 mentioned above, the filament 4 becomes at a positive potential with respect to the emitter 3. As a result, electrons cannot impact the emitter 3. For this reason, conventionally,
It was believed that it was impossible to generate a negative ion beam.

However, in the application of ions, not only positive ions but also negative ions are extremely important, and there has been a need to develop an ion source that extracts a negative ion beam.

The present invention has been made in view of these points, and includes an emitter configured so that the ionized substance inside flows out to the surface of the emitter chip, and an ion beam disposer disposed opposite to the emitter. an extraction electrode having a first aperture and a second aperture for electron beam implantation; an electron gun made of a filament, Wehnelt, etc., and configured to cause electrons to collide with the emitter through the second opening of the extraction electrode; An ion source capable of generating a negative ion beam by maintaining the emitter at a higher negative potential than the extraction electrode and maintaining the electron gun at a higher negative potential than the emitter. This has been achieved.

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

FIG. 2 is a configuration diagram showing an embodiment of the present invention. 1st
The same parts as those in the figures are given the same reference numerals, and the explanation thereof will be omitted. In the figure, 21 is a filament for generating thermionic electrons;
22 is a Wehnelt, and 23 is a second high voltage power supply. The positive side of the high voltage power supply 23 is grounded, and the negative side is connected to the Wehnelt 2
Connected to 2. A bias resistor 24 is connected to the negative electrode side of the high-voltage power supply 23 and the intermediate terminal of the secondary winding of the transformer T. The filament 21, the Wehnelt electrode 22, the electrode #i6, and the transformer T constitute an electron gun. Note that the polarity of the first high voltage power supply 9 is reversed from that shown in FIG. That is, the positive electrode side is grounded and the negative electrode side is connected to the emitter 3. The potential and operation of each part of the ion source configured as described above will be explained below.

First, the relationship between the dark potentials of the emitter 3, extraction electrode 5, and electron gun (particularly the filament 21) will be explained.

Let the negative potential applied to the emitter 3 be 1, and the negative potential of the extraction electrode 5 given by the voltage dividing resistor 10 be V2.
Then, as is clear from FIG. 2, V2 is maintained at a high negative value with respect to ■1. Further, a negative potential is applied to the filament 21 of the electron gun via a bias resistor 24 from a high-voltage power supply 23. If this potential is v3, this potential v3 is a negative potential lower than the potential V1 of the emitter 3. value is maintained. That is, the relationship between each potential can be expressed as the following equation.

lV3 l>lVt I>lV2 l-. It flows out to the surface of the chip 2 through a small amount of !l1lII provided.By the way, as described above, the potential v3 of the filament 21 of the electron gun is a negative value lower than the potential v2 of the extraction electrode 5. Therefore, the electrons generated in the filament 21 pass through the second opening 56 of the extraction electrode 5 and reach the emitter 3.The potential v1 of the emitter 3 is a negative potential lower than the potential v2 of the extraction electrode 5. Since the value is maintained at the value of , when the electrons reach the emitter 3, they go up the potential and decelerate.

However, as shown in equation (1), 1V31>1V
As long as the tl relationship is maintained, it will eventually collide with emitter 3. At this time, the impact energy of the electron is
1Vsl corresponds to lVt1. Due to this electron impact, the ionized substance that has flowed to the emitter tip 2 is evaporated and ionized. Since the relationship of IVI l>lV21 is maintained, the negative ions generated by this are attracted to the extraction electrode 5 and accelerated to become an ion beam i', and after passing through the first opening 5a of the extraction electrode 5, it is grounded. The energy when passing through the electrode 8 corresponds to 1 Vrl.

As described above in detail, according to the present invention, it is possible to realize an ion source that can extract a negative ion beam.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the configuration of a conventional ion source, and FIG. 2 is a configuration diagram showing an embodiment of the present invention. 1... Container 2... Emitter chip 3.
... Emitter 4.21 ... Filament 5 ... Extraction electrode 6 ... Power supply 7 ... Shield 8 ... Ground electrode 9.23 ... High voltage power supply 10 ... Voltage dividing resistor 20 ...・Ionized substance 22
...Wehnelt 24...Bias resistance T...
Power transformer patent applicant JEOL Co., Ltd. Representative Patent attorney Fujiji Ijima Reform Figure 1 Figure 2

Claims (1)

[Claims] An emitter configured to allow internal ionized substances to flow out onto the surface of the emitter chip, and a first aperture for ion beam extraction and a second aperture for electron beam implantation arranged opposite to the emitter. a second lead-out electrode consisting of a filament, Wehnelt, etc.
an electron gun for causing electrons to collide with the emitter through an opening, the emitter being maintained at a higher negative potential than the extraction electrode, and the electron gun being maintained at a higher negative potential than the emitter. An ion source characterized by: