JPH0131657B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ion source used in an ion implanter or the like.

Conventionally, this type of ion source is one in which ions are generated by accelerating electrons emitted from a filament and colliding the energetic electrons with an introduced gas. Some methods apply a magnetic field using a magnetic coil to increase the ion beam, others use the internal magnetic field generated by the current flowing through the filament without using an external magnetic field, and some methods apply a magnetic field near the extraction electrode to effectively control the ion beam. In addition, there are widely used types of ion beams, such as ion beams that are focused on ion beams, and dual plasma type ion beams that form extremely dense plasma in order to obtain high-density, large-current ion beams.

By the way, in ion implantation technology, active gas containing arsenic, phosphorus, boron, etc. is turned into plasma and ions are extracted. Therefore, an ion source having a filament as described above has a short lifespan due to breakage of the filament due to the active plasma, dielectric breakdown of the insulator, etc., and therefore requires periodic replacement. In other words, the normal lifespan is about 50 to 60 mAHr with ¹¹ B ⁺ beam (10 mA at 5 mA) when using a high current type ion source.
~12 hours).

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a new ion source that eliminates the drawbacks of the conventional ion source having a filament as described above.

That is, the ion source according to the present invention is a hollow cathode type application, in which a cathode is formed on most of the wall of a cylindrical or rectangular parallelepiped ion generation chamber, and an anode is formed on the remaining part, and insulation is provided between the cathode and the anode. It is characterized by having a gas inlet and an ion extraction opening parallel to the axis of the cathode in the cathode forming wall.

Further, according to the present invention, there is provided an ion source in which an intermediate electrode is provided near the ion extraction opening to reduce conductance.

In this way, in the ion source according to the present invention, by forming plasma by hollow cathode discharge, ions are ejected from the ion extraction opening with kinetic energy close to the discharge voltage. In this case, the shape of the ion beam can be made into any shape by changing the shape of the ion extraction opening in the cathode forming wall portion.

Preferably, an accelerating electrode can be provided near the ion extraction opening to increase the energy of the ions to a desired level.

Furthermore, in order to keep the external pressure low, the inner diameter of the hollow cathode, that is, the reciprocating distance of the electrons can be increased.

Furthermore, in order to prevent dielectric breakdown due to contamination of the insulator between the cathode and the anode, the surface of the insulator facing the inside of the ion generation chamber may preferably be formed with a bend.

According to the ion source of the present invention configured in this manner, it is possible to form an ion beam that is uniform in space and time, and since there is no filament, various gases can be used and the life is long.
Furthermore, since the ion source of the present invention does not use a magnetic field, the discharge is quiet, and the discharge power is relatively small, making it energy-saving and versatile. Furthermore, as described above, by selecting the shape of the ion extraction port, there is great flexibility in the shape of the ion beam.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an ion source according to the present invention configured in a cylindrical shape, where 1 is a cylindrical member forming a cathode, and 2 is fixed to both ends of the cylindrical member 1 through annular insulators 3 made of ceramics. This is an end plate forming an anode, and these members constitute an ion generation chamber. As shown in the figure, the cylindrical member 1 forming the cathode is provided with a gas inlet 4 and a slit 5 for extracting ions, and the slit 5 for extracting ions is positioned parallel to the axis of the cylindrical member 1 forming the cathode. Ru. The insulator 3 inserted between the cathode member 1 and each anode end plate 2 is simply shown as an annular body in the drawing for the sake of simplicity, but in reality it is shown as an annular body to prevent contamination and to eliminate the risk of dielectric breakdown. At least the portion facing the inside of the ion generation chamber may be designed in various shapes to achieve this. Further, dimensions such as the inner diameter and length of the cathode member 1 are appropriately designed depending on the ion beam to be generated, the operating pressure, etc.

The cathode member 1 and each anode member 2 are connected to a power source 6 as shown. Also, in Fig. 1, 7 is an intermediate electrode for reducing conductance.
It can be positioned near the ion extraction slit 5.

FIG. 2 shows a modified embodiment of the cylindrical ion source shown in FIG.
It consists of 0. These three parts are preferably constructed integrally and form the cathode. On the other hand, in this embodiment, the anode 11 is formed by cutting out a part of the central cylindrical part 8 constituting the cathode, attaching it to an insulator frame 13 along its peripheral edge 12, and covering the cutout part on the insulator frame 13. It is installed like this. Further, 14 is a slit for extracting ions, and 15 is a gas inlet. The other configurations can be the same as in the case of FIG. 1.

FIG. 3 shows a further embodiment of the ion source according to the invention, in which the ion source has a rectangular parallelepiped shape, namely two rectangular parallelepiped sections 16, 17 forming the cathode; and a band-shaped body 18 that forms an anode provided in between. As shown in the figure, this strip 18 has an insulator frame 1 attached to one end of each of the two rectangular parallelepiped parts 16 and 17.
It is fixed via 9 and 20. A gas inlet 21 is provided at one end of the ion generation chamber thus formed, and an ion extraction slit 22 is provided at the opposite end. In this example, the overall shape is a rectangular parallelepiped, but it can also be constructed with a circular cross section as in the case of FIG.

Next, an example of an experiment using the ion source shown in FIG. 1 will be described.

The ion source is constructed with the cathode member 1 having an inner diameter of 47 mm and a length of 100 mm, and the ion extraction slit 5 having a width of 0.5 mm and a length of ¹⁴ mm. 8×
When the voltage was set to 10 ^-4 Torr, Ar was introduced from the gas inlet 4, and a discharge current of 400 V and 30 to 50 mA was applied, an ion current of 15 μA was obtained. The results of measurements made using the ion source according to the present invention are shown in FIGS. 4 and 5.

FIG. 4 shows the relationship between the voltage applied to the ion collecting electrode and the ion current, and FIG. 5 shows the relationship between the discharge current and the ion current.

Considering the results of the measurements carried out in this way, it is recognized that the ion source according to the present invention can be sufficiently applied to ion implantation apparatuses and the like in place of conventional ion sources having filaments.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view schematically showing one embodiment of an ion source according to the present invention, FIG. 2 is a partially sectional front view showing another embodiment, and FIG. 3 is a longitudinal cross-sectional view showing still another embodiment. 4 and 5 are graphs showing the characteristics of the ion source according to the present invention. In the figure, 1, 8, 9, 10, 16, 17: cathode,
2, 11, 18: Anode, 4, 15, 21: Gas inlet, 5, 14, 22: Ion extraction opening.

Claims (1)

[Scope of Claims] 1 A cathode is formed on most of the wall of a cylindrical or rectangular parallelepiped ion generation chamber, and an anode is formed on the remaining part, the cathode and the anode are insulated with an insulator, and the cathode forming wall is An ion source characterized by having a gas inlet and an ion extraction opening parallel to the axis of the cathode. 2 A cathode is formed on most of the wall of the cylindrical or rectangular parallelepiped ion generation chamber, and an anode is formed on the remaining part, the cathode and the anode are insulated with an insulator, and a gas inlet is formed on the wall where the cathode is formed. An ion source characterized in that an ion extraction opening is provided parallel to the axis of the cathode, and an intermediate electrode is further arranged near the ion extraction opening. 3. The ion source according to claim 1 or 2, wherein the surface of the insulator interposed between the cathode and the anode, which faces the inside of the ion generation chamber, forms a curved surface.