JPH03203146A - Ion source device - Google Patents

Abstract

PURPOSE:To prevent the negative charge-up in a bottom plate in a device for generating plasma by the high frequency discharge between a cylindrical side plate and the bottom plate by disposing a determined coil in parallel to the side plate and the bottom plate. CONSTITUTION:A cylindrical side plate 6 and a bottom plate 8 form electrodes, respectively, between which high frequency discharge is executed through a matching circuit 22 and a high frequency power source 30. The gas introduced into the cylinder is made into plasma, and drawn through a drawing electrode system 14. A coil 40 is connected in parallel between the bottom plate 8 and the side plate 6. The relation of wL>1/wC is satisfied among the inductance L of the coil 40, the total capacitance C on the ion source 2 side seen from the matching circuit 22, and the angle frequency (w) of the high frequency power from the high frequency power source 30. Hence, the negative charge-up in the bottom plate 8 is prevented, allowing the stable drawing of ion beams.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is an ion source that is used in, for example, an ion implantation device, a thin film forming device, etc., and is equipped with an ion source that generates plasma using high frequency waves. Regarding equipment.

(Conventional technology) A conventional example of this type of ion source device is shown in FIG.

This ion source device includes an ion source 2 having a plasma source section 4 that generates plasma 12 and an extraction electrode system 14 that extracts an ion beam 20 from the plasma source section 4 by the action of an electric field.

In the plasma source section 4, a plasma generation container is constituted by a cylindrical side plate 6 and a bottom plate 8 that covers one end with an insulator 10 sandwiched between them, and the side plate 6 and the bottom plate 8 are used for high frequency discharge. It also serves as a discharge electrode.

A high frequency power source 30 is connected between the side plate 6 and the bottom plate 8 via a matching circuit 22.

The matching circuit 22 used in this type of device usually consists of a series-parallel circuit of a coil 24 and capacitors 26, 28, as in this example. Capacitor 28 is normally a variable capacitor.

The extraction electrode system 14 is provided at the opening of the plasma source part 4, and in this example, both are porous electrodes, and a plasma electrode 15 and a suppression electrode to which a positive voltage is applied by an extraction power source (also called an acceleration power source) 32. The suppression electrode 16 to which a negative voltage is applied by the power source 34 and the ground electrode 17 that is grounded are used.

The plasma electrode 15 and the side plate 6 are usually electrically connected directly or through a resistor as shown in the illustrated example.

With the above configuration, the inside of the plasma source section 4 is evacuated, and the required gas is supplied thereto at a required pressure (for example, 10
-'Tor r) and supply high-frequency power from the high-frequency power supply 30 to the matching circuit 22 between the side plate 6 and the bottom plate 8, the high-frequency power between the side plate 6 and the bottom plate 8 is Plasma 12 is created within the plasma source section 4 by the discharge.

When a predetermined voltage as described above is applied to the extraction electrode system 14, the ion beam 20 is extracted from the plasma 12 via the extraction electrode system 14 due to the action of the electric field.

[Problems to be Solved by the Invention] In the ion source 2, in order to apply a positive voltage to the plasma electrode 15 in order to extract the ion beam 20 from the plasma 12, negative carriers (negative ions,
The electrons) 38 move toward the bottom plate 8 on the opposite side to the direction in which the ion beam 20 is extracted.

However, the capacitor 26 .
Conventionally, the bottom plate 8 is in a DC-floating state due to 28, etc., so there is no route for the negative carriers 38 gathered there to leak to the ground side, and therefore, the bottom plate 8 is negatively charged up by the negative carriers 38 at the bottom '+1i, 8. arise.

When such charge-up occurs, positive ions in the plasma 12 are pulled toward the bottom plate 8, making it difficult to extract a stable ion beam 20.

Therefore, the main object of the present invention is to provide an ion source device that prevents the charge-up on the bottom plate as described above, thereby making it possible to extract a stable ion beam.

[Means to solve the problem]

In order to achieve the above object, the ion source device of the present invention includes:
A coil is connected in parallel to a side plate and a bottom plate of the ion source,
The inductance of this coil is L1. The total capacitance on the ion source side as seen from the matching circuit is C1. When the angular frequency of the high-frequency power from the high-frequency power source is ω, the following relationship is satisfied: ωL〉1/ωC It is characterized by

[Effect]

According to the above configuration, since the side plate and the bottom plate of the ion source are short-circuited in terms of direct current by the coil, negative carriers that reach the bottom plate leak to the ground side via the coil. As a result, charge-up of the bottom plate is prevented, and stable extraction of the ion beam becomes possible.

Moreover, since the inductive reactance ωL of the above coil is larger than the capacitive reactance 1/ωC of the ion source side, even if the above coil is provided, it is difficult to supply high frequency power from the high frequency power supply to the ion source side. There are no particular problems.

〔Example〕

FIG. 1 is a schematic diagram showing an ion source device according to an embodiment of the present invention. The same reference numerals are given to the same or corresponding parts as in the conventional example shown in FIG. 2, and the differences from the conventional example will be mainly explained below.

In this embodiment, a coil 40 is connected in parallel between the side plate 6 and bottom plate 8 of the ion source 2 as described above.

In addition, let the inductance of this coil 40 be C, the total capacitance on the ion source 2 side seen from the matching circuit 22 described above be C, and the angular frequency of the high frequency power from the high frequency power source 30 described above be ω (=2πf, where f is, for example, 13. 56 MHz), the following relationship is satisfied: at least ωL>1/ωC, preferably ωL>1/ωC.

According to the above configuration, the side plate 6 and the bottom plate 8 of the ion source 2 are short-circuited by the coil 40, so that as the ion beam 20 is projected, the bottom plate 8
The above-mentioned negative carrier 38 that reaches , is leaked to the ground side via the same coil 40, for example, along the route shown by the arrow. As a result, charge-up of the bottom plate 8 is prevented, and stable extraction of the ion beam 20 becomes possible.

Moreover, as mentioned above, the inductive reactance ω of the coil 40
Since L is made larger than the capacitive reactance 1/ωC on the ion source 2 side, even if the coil 40 is provided, there is no particular problem in supplying high frequency power from the high frequency power supply 30 to the ion source 2 side. .

In this case, from the viewpoint of further reducing power loss in the coil 40, it is preferable to make the inductive reactance ωL in the coil 40 sufficiently large as described above.

Note that the above-described electrode configuration in the extraction electrode system 14 of the ion source 2 is merely an example, and other electrode configurations may also be adopted. For example, the extraction electrode system 14 may be configured by the plasma electrode 15 alone or by the plasma electrode 15 and the ground electrode 17.

(Effects of the Invention) As described above, according to the present invention, it is possible to prevent charge-up due to negative carriers on the bottom plate of the ion source, thereby making it possible to extract a stable ion beam.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an ion source device according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing an example of a conventional ion source device. 2... Ion source, 4... Plasma source section, 6...
・Side plate, 8... Bottom plate, 14... Extraction electrode system, 20
...Ion beam, 22...Matching circuit, 30...
High frequency power supply, 40...coil. Dimension 1=1

Claims (1)

[Claims] (1) A plasma generation container is constructed using cylindrical side plates and a bottom plate that are insulated from each other and also serve as discharge electrodes, and there is a plasma source section that generates plasma inside the container, and an extraction electrode that draws out the ion beam from this plasma source section. In the ion source device configured to supply high frequency power from a high frequency power supply between the side plate and the bottom plate of the ion source through a matching circuit, the ion source has a coil connected in parallel to the side plate and the bottom plate of the ion source. and the inductance of this coil is L, the total capacitance on the ion source side seen from the matching circuit is C, and the angular frequency of the high-frequency power from the high-frequency power source is ω, then ωL>1/ωC. An ion source device characterized in that it satisfies the following.