JP3409881B2 - RF discharge ion source - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an RF discharge type ion source used for ion plating, ion assisted vapor deposition and the like.

[0002]

2. Description of the Related Art Conventionally, there are various kinds of ion sources depending on their uses and purposes. Among them, an RF discharge type ion source suitable for extracting gas ions has a discharge gas inlet a as shown in FIG. A cathode d of a tungsten filament connected to an RF power source c is provided inside the provided discharge tube b, and ions of the discharge gas generated by the RF discharge between the cathode d and the discharge tube b constituting the anode are supplied to the discharge tube b. In general, the extraction electrode g is used to extract from the ion beam extraction port f on one side. In the figure, h is an insulator, i is a collector,
j is a flange.

[0003] The ion source of Figure 1 is mounted so as to be connected to the vacuum chamber via a flange j, within the ion source 10 in an exhaust system connected to the vacuum tank ^- was evacuated to ⁷ Torr ^{- 5} to 10 After that, an inert gas such as argon gas is introduced from the discharge gas introduction port a into the discharge cylinder b to move the inside of the discharge cylinder b to 1
0 ^{- 2-10 -} held to ³ Torr pressure. When electric power is supplied to the cathode d from the RF power source c in this state, plasma of an inert gas is generated in the discharge tube b. Ions in the generated plasma sputter the cathode d to emit electrons and neutrons from the cathode d, thereby increasing the density of the plasma. Ions in the plasma in the discharge tube b are collected in the collector i via the extraction electrode g and become an ion beam to irradiate the substrate prepared in the vacuum chamber. On the other hand, in the discharge tube b, ions continuously sputter the cathode d to emit electrons from the cathode d, collide with an inert gas and ionize the same, thereby increasing the plasma density in the discharge tube b. .

[0004]

In the above-mentioned conventional RF discharge type ion source, the generated electrons are trapped by the anode, and the electron density is lowered. Moreover, since the electric field of the high frequency itself is low, the plasma discharge can be maintained at 10 ^−.
It was difficult at a pressure of ⁴ Torr or less, and the plasma density was as low as 10 ⁸ to 10 ¹⁰ / cm ³ . Further, since tungsten is used as the material of the cathode d, the life of the cathode d is short and the cathode d has only a few hours in the O ₂ atmosphere.

An object of the present invention is to solve the above problems and to provide an RF discharge ion source capable of discharging in a high vacuum and continuously usable for a long time.

[0006]

DISCLOSURE OF THE INVENTION In the present invention, a discharge connected to an RF power source is provided inside a discharge tube having a discharge gas inlet, and a discharge generated by RF discharge between the cathode and the discharge tube of the anode. In an ion source in which gas ions are extracted from an ion beam outlet on one side of the discharge tube by an extraction electrode, the cathode is composed of a LaB ₆ rod material, and a direct current is supplied to the discharge tube of the cathode and the anode. A DC power supply was connected to form a field, and a magnet was provided around the discharge tube of the anode to achieve the above object.

[0007]

When the inside of the discharge tube is evacuated to a vacuum and a high frequency power source is connected to the cathode, plasma discharge is generated between the cathode and the anode. In addition to the high frequency electric field, a DC electric field from the DC power source is applied to the cathode. Since the electric field of the discharge tube is increased and the discharge tube of the anode has a DC electric field by the DC power source and a magnetic field by the magnets provided around it, electrons generated in the discharge tube are not captured by the anode. while maintaining a trochoid orbital to motion along the anode, therefore the electron density is increased, 10 ^{- 5} Torr at a high vacuum of regions to maintain a stable discharge can be extracted ion beam. Further, since the plasma density becomes high, the extraction electrode can be controlled to selectively extract the ion beam and the neutral beam. Since the cathode is made of LaB ₆ , the time is several ten times longer than that of tungsten. Can be used over

[0008]

EXAMPLE An example of the present invention will be described with reference to FIG.
Reference numeral 1 in the figure shows an RF discharge type ion source, and the ion source 1 is a discharge cylinder 3 made of SUS having a discharge gas introduction port 2.
And a cathode 5 mounted inside with a cathode holder 4 made of Mo, and the cathode 5 was connected to an RF power source 8 via an insulator 7 provided on a flange 6. An ion beam outlet 9 is provided on one side of the discharge tube 3, and an extraction electrode 1 is provided outside thereof.
By setting 0, the ions of the discharge gas generated in the discharge tube 3 are extracted. The ion source 1 is provided in a vacuum chamber 11 by a flange 6, and the ions extracted from the ion source 1 are used to deposit a film on a substrate (not shown) prepared in the vacuum chamber 1.

Although such a structure is also equipped with a conventional RF discharge type ion source, in the present invention, the cathode 5 is a rod of LaB _{6 in} order to maintain a discharge in a high vacuum and extract a stable ion beam for a long time. And a DC power supply 12 is connected to the cathode 5 to superimpose a DC electric field on a high frequency electric field at the cathode 5, and a DC power supply 13 is also connected to the discharge tube 3 of the anode to form a DC electric field. Then, a permanent magnet or electromagnet 14 is provided around the discharge tube 3.
Cooling water was circulated through the pipe 15 inside the magnet 14.

In this embodiment, the RF power source 8 is 1 kw.
Use a 13.65MHz power supply and set the DC power supply 12 to 0 to 1
A power source of 5 kv and a DC power source 13 of 0 to 200 v was used. Further, a ferrite-based permanent magnet was used as the magnet 14. The operation of the ion source of this embodiment is as follows.

[0011] The exhaust system provided in the vacuum chamber 1 to discharge cylinder 3 10 ^- After evacuated to ⁶ Torr or less pressure, introducing an inert gas such as argon gas from the discharge gas inlet port 2 to the discharge tube 3 and, the electric discharge tube 3 10 ^- adjusted to ⁵ Torr pressure ^{- 4} -10. In this state, 1 kw of high frequency power and 15 kv maximum DC power are supplied to the cathode 5 from the RF power supply 8 and the DC power supply 12, and a maximum 200 v DC power is supplied to the discharge tube 3 of the anode. Inert gas plasma is generated in the cylinder 3. The electrons generated in this plasma are the DC electric field of the discharge tube 3 of the anode and the magnet 14 around it.
Due to the magnetic field generated by the discharge tube, the particles move along the inner surface while taking a trochoid orbit without being trapped by the discharge tube, so that the electron density increases and many ions in the plasma having a high electron density sputter the cathode 5. Electrons and neutral particles are emitted from the cathode 5, and the plasma density is further increased. Ions in the plasma are extracted in a beam shape from the discharge cylinder 3 into the vacuum chamber 1 by the extraction electrode 10 to irradiate the substrate. In this case, the beam of neutral particles can be extracted by controlling the potential of the extraction electrode 10.

[0012]

As described above, according to the present invention, the cathode connected to the RF power source of the RF discharge type ion source is made of the LaB ₆ rod material, and the DC power source is connected to the discharge cylinders of the cathode and the anode. Then, a DC electric field is formed in these, and a magnet is provided around the discharge tube of the anode, so that stable and high-density plasma can be generated in a high vacuum and an ion beam can be taken out for a long time. And so on.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a conventional RF discharge type ion source.

FIG. 2 is a cutaway side view of the embodiment of the present invention.

[Explanation of symbols]

1 RF discharge type ion source 2 Discharge gas inlet 3
Discharge cylinder 5 Cathode 8 RF power supply 9
Ion beam outlet 10 Extraction electrodes 12, 13 DC power supply 14
magnet

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshio Kojima 2-27-2 Onodai, Sagamihara City, Kanagawa Prefecture Showa vacuum (72) Inventor Takayasu Yamashiro 2-27-2 Onodai, Sagamihara City, Kanagawa Prefecture Showa vacuum (72) Inventor Toru Ii 2-27-2 Onodai, Sagamihara City, Kanagawa Prefecture Showa vacuum (56) Reference JP 62-93836 (JP, A) JP 5-47338 (JP) , A) JP-A-5-94796 (JP, A) JP-A-5-174721 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01J 37/08 H01J 27/18

Claims (2)

(57) [Claims] 1. A cathode connected to an RF power source is provided inside a discharge tube having a discharge gas introduction port, and ions of the discharge gas generated by RF discharge between the cathode and the discharge tube of the anode are provided in the discharge tube. In an ion source adapted to be extracted from an ion beam extraction port on one side by an extraction electrode, the cathode is composed of a LaB ₆ rod material, and a DC power source is used to form a DC electric field in the discharge tube of the cathode and the anode. And a magnet is provided around the discharge tube of the anode. 2. The RF discharge type ion source according to claim 1, wherein a negative voltage is applied to the cathode and anode discharge cylinders and the absolute value of the negative voltage is larger in the cathode than in the discharge cylinder.