JPH05325813A - Negative ion source - Google Patents

Abstract

PURPOSE:To shorten a time for switching an ion kind. CONSTITUTION:A sputter target of a plasma sputter type negative ion source is divided and constituted of a plurality of target materials 15a, 15b of, for instance, GaAs for an arsenic ion and GaP for a phosphorus ion contained with a different target element. By setting an operation parameter of the ion source, a required ion kind is generated in an optimum condition. Simultaneously generated unnecessary ion kinds are removed by a mass analyzing electromagnet.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a negative ion source capable of generating a beam of a plurality of ion species.

[0002]

2. Description of the Related Art FIG. 4 is a basic configuration diagram of an ion implanter using a tandem accelerator, in which negative ions from a negative ion source 1 are separated and extracted by a mass analysis electromagnet 2 so that only a desired ion species is separated and extracted. Introduced in 3. Negative ions are first accelerated in the low energy side accelerating tube 6 to which a positive voltage is applied from the high voltage power source 4 through the high voltage terminal unit 5, and are positively charged in the charge stripper 7 into which the stripper gas is introduced. Charge is converted to ions. The positive ions are accelerated again toward the ground potential in the high energy side acceleration tube 8,
A beam of positive ions having a desired valence is extracted by the energy analysis electromagnet 9 and injected into a sample (not shown) or a semiconductor wafer.

FIG. 5 is a plasma sputter type negative ion source 1 used as the negative ion source 1 of the above-mentioned ion implantation apparatus.
It is a block diagram of 0. Gas inlet 12 to vacuum chamber 11
Xenon gas is introduced from the above to collide with the thermoelectrons emitted from the filament 13 to generate xenon plasma,
It is confined in the vacuum chamber by the magnetic field of the permanent magnet 14. In the vacuum chamber 11, a sputter target 15 made of a material containing a desired element to be generated is supported and arranged by a cooling shaft body 17 via a backing plate 16, and the target 15 is placed in a negative direction with respect to the vacuum chamber 11. The sputter target is sputtered with xenon plasma by biasing it to a potential. At this time, in order to improve the generation efficiency of negative ions, cesium vapor is supplied from the cesium reservoir 18 to deposit cesium on the sputter target 15. The extraction electrode 19 is arranged at the ion outlet of the vacuum chamber 11, and the extraction electrode 19 has a positive high potential (up to several tens of k) with respect to the vacuum chamber.
V), and negative ions are extracted as a beam.

[0004]

In the plasma sputtering type negative ion source 10 described above, the sputter target 15 for determining the generated ion species is composed of a single body of one kind of target material, as shown in FIG. Has been done. That is, for a beam of boron negative ions B ⁻ , for example, B
An Al alloy target is used, and a dedicated target for each ion species is used for the P ⁻ beam of phosphorus, like a GaP compound target.

Therefore, when the ion species are switched, the sputter target 15 dedicated to the ion species must be used. For example, the sputter target 15 together with the support member.
Must be configured to be interchangeable. For example,
As shown in FIG. 5, an air lock chamber 21 for drawing in the sputter target portion, which is shut off from the vacuum chamber 11 by the gate valve 20, is provided, and the air lock chamber is closed by a removable closing flange plate 22. . The cooling shaft 17 of the sputter target 15 is the closed flange plate 2
The air lock chamber 21 is slidably supported by the air suction chamber 2 and is connected to the roughing vacuum passage 23.

When switching the ion species, the operation of the ion source 10 is stopped, the gate valve 20 is opened, and the sputter target portion is indicated by the alternate long and short dash line.
1, the gate valve 20 is closed, and the vacuum in the airlock chamber 21 is broken. The closing flange plate 22 is removed, and the closing flange plate 22 to which another new sputter target 15 is attached is fixed to the airlock chamber 21. The air lock chamber 21 is roughly vacuum-evacuated, and the gate valve 2
0 is opened, a new sputter target 15 is placed in the vacuum chamber 11, and the operation of the ion source 10 is restarted. It takes 1 to 3 hours to replace the sputter target 15, and the operation of the ion implantation device must be completely stopped during this period.

An object of the present invention is to provide a negative ion source capable of switching ion species without replacing the sputter target.

[0008]

The present invention is characterized in that, in a plasma sputter type negative ion source, a sputter target is divided by a plurality of target materials containing different target elements.

[0009]

Since the optimum operating parameters of the ion source differ depending on the target material containing each target element, the required ion species can be generated in the optimum state from the ion source by selecting the operating parameters. Unwanted ion species generated at the same time can be removed by a mass analysis electromagnet that is cascaded in the ion source.

[0010]

Embodiments of the present invention will be described with reference to the drawings. The same reference numerals as those in FIGS. 2 and 3 denote the same parts. Figure 1
(A), (b) is a perspective view and a top view showing composition of a two-sputtering target part in a plasma sputtering type negative ion source. The sputter target is divided into two parts, which are target materials 15a and 15b containing different target elements, for example, a GaAs portion 15a for arsenic and a Ga for phosphorus.
The P portion 15b constitutes a sputter target.

2 (a) and 2 (b) are a perspective view and a plan view showing the structure of the three-divided target portion. The sputter targets are target materials containing different target elements, for example, GaAs target materials. 15a,
It is composed of a target material 15b made of GaP and a portion 15c of LaB ₆ which is a target material for boron.

In the plasma sputter negative ion source, important operating parameters include the arc current flowing from the filament to the vacuum chamber, the sputter voltage, the xenon gas pressure, the cesium reservoir oven temperature, etc. For example, the arc current is 5 to 20 A, sputtering voltage 0.5 to 2 kV, xenon gas pressure 1 × 10 ⁻⁴ to 1 ×
Although the operating temperature is 10 ⁻⁵ Torr and the oven temperature is 130 to 200 ° C., the optimum value of each parameter is different for each ion species, that is, for each target material. Therefore,
For example, when it is desired to obtain boron negative ion B ⁻ , the operation is carried out with a combination of parameters suitable for it, and phosphorus negative ion P −
^- a If it is desired to obtain, to operate the ion source at its optimal parameters. In this case, although unnecessary negative ions are also generated to some extent from the ion source, it suffices to finally select the target ion species with the mass analysis electromagnets arranged in cascade in the ion source.

The area ratio of each target material in the above-mentioned embodiments may be equal or may be changed according to the beam amount required for each ion species. Further, the sputter target may be divided into four or more kinds of target materials, and each target material may be subdivided and the divided pieces may be symmetrically distributed.

[0014]

Since the present invention is configured as described above, the ion species can be switched only by switching the operating parameters of the ion source, and the ion species can be switched from the conventional time unit to the minute unit. can do.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a sputter target portion according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of another embodiment.

FIG. 3 is a configuration diagram of a conventional sputter target portion.

FIG. 4 is a basic configuration diagram of an ion implantation apparatus using a tandem accelerator.

FIG. 5 is a configuration diagram of a conventional plasma sputtering type negative ion source.

[Explanation of symbols]

 15a, 15b, 15c Sputter target 16 Backing plate 17 Cooling shaft

Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display area H01L 21/265

Claims (1)

[Claims] 1. A negative ion source in a plasma sputter type negative ion source, characterized in that a sputter target is divided by a plurality of target materials containing different target elements.