JP2889925B2 - Electron beam excited ion source and ion extraction method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to an electron beam excited ion source and an ion extraction method.

(Prior Art) For example, in an ion implantation apparatus used for manufacturing a semiconductor device or the like, development of a large current and long life ion source is required in order to improve the productivity of IC.

An electron beam excitation ion source for ionizing a source gas with an electron beam is known.

In such an electron beam excited ion source, electrons are extracted from plasma formed by glow discharge or the like, accelerated, and introduced into an ion generation chamber which is a source gas atmosphere for generating predetermined ions. Are made to collide with the above-mentioned raw material gas molecules to form plasma. The ion extraction slit provided in the ion generation chamber is configured to extract ions from the plasma, and has a feature that a high ion current density can be obtained with low ion energy.

(Problems to be Solved by the Invention) However, in the electron beam excitation ion source described above, it is naturally required to further increase the ion current density, to shorten the processing time and to improve the throughput.

The present invention has been made in view of such conventional circumstances, and can extract ions relatively efficiently, and can obtain a high ion current density, thereby shortening the processing time and improving the throughput. An object of the present invention is to provide an electron beam excited ion source and an ion extraction method.

[Structure of the Invention] (Means for Solving the Problems) That is, according to the first aspect of the present invention, a source gas introduced into an ion generation chamber is irradiated with electrons accelerated by an electric field formed in the ion generation chamber. In an electron beam excited ion source configured to extract the ions from an ion extraction slit provided in the ion generation chamber, the inside of the ion generation chamber is insulated except for the vicinity of the ion extraction slit. It is characterized by being covered with a member.

According to a second aspect of the present invention, in the electron beam excitation ion source according to the first aspect, the inside of the ion generation chamber is formed in a bottomed cylindrical shape according to the inside shape of the ion generation chamber, and the ion extraction is performed. Characterized by being covered by an inner cylinder having an opening formed at a portion corresponding to the slit for use.

Further, according to the invention of claim 3, the source gas introduced into the ion generation chamber is irradiated with electrons accelerated by an electric field formed in the ion generation chamber to generate ions, and the ions are provided in the ion generation chamber. In the ion extraction method for extracting from the ion extraction slit, at least the inside of the ion generation chamber is formed of an insulating member except for the vicinity of the ion extraction slit, and at least the inside of the ion generation chamber is used for the ion extraction. The ion is extracted so that the conductive member is exposed only in the vicinity of the slit.

(Operation) In the electron beam excited ion source and the ion extraction method of the present invention, the inside of the ion generation chamber is covered with the insulating member except for the vicinity of the ion extraction slit, so that the ion extraction is performed outside the ion generation chamber. When an electrode is provided to extract ions from the ion extraction slit, plasma (discharge) can be generated only in the vicinity of the ion extraction slit in the ion generation chamber.

Therefore, the generated ions can be efficiently extracted and a high ion current density can be obtained, so that the processing time can be reduced and the throughput can be improved.

(Embodiment) Hereinafter, an embodiment of an electron beam excited ion source and an ion extraction method of the present invention will be described with reference to the drawings.

The electron generation chamber 1 is formed of a high melting point conductive material, for example, molybdenum, in a rectangular container shape whose length of each side is, for example, about several centimeters. Also, on one side of the electron generation chamber 1,
An opening is provided, so as to close this opening,
For example, a plate-shaped insulating member 2 made of, for example, Si ₃ N ₄ or BN is provided, and the electron generating chamber 1 is airtightly configured.

In addition, the insulating member 2 is provided with a filament 3 formed of a material, for example, tungsten, formed in a substantially U-shape so as to protrude into the electron generation chamber 1. further,
A discharge gas introduction hole 4 for introducing a gas for generating plasma to generate electrons, for example, a discharge gas such as an argon (Ar) gas, is provided in an upper portion of the electron generation chamber 1. A circular hole 5a having a diameter of, for example, about 1 mm for extracting electrons from the plasma generated in the electron generation chamber 1 is provided below the generation chamber 1.

In addition, an insulating member 7 is provided below the electron generating chamber 1 so as to form a bottleneck 5b continuous with the circular hole 5a, and a high melting point material such as tungsten is provided through the insulating member 7. The porous electrode 8 having a large number of through holes is connected.

The discharge gas introduction hole 4 and the electron extraction hole 5
Are arranged eccentrically from the center of the electron generation chamber 1 to the side of an ion extraction slit, which will be described later, and are configured to extract ions efficiently.

Further, an ion generation chamber 10 is connected to a lower portion of the porous electrode 8 via an insulating member 9. The ion generation chamber 10 is formed in a container shape from a conductive high melting point material, for example, molybdenum, and has a cylindrical shape having a diameter and a height of about several centimeters. A source gas inlet 11 for introducing a source gas for generating desired ions, for example, BF ₃ or the like, into the ion generation chamber 10 is provided on a side surface of the ion generation chamber 10. An ion extraction slit 12 is provided so as to face the source gas inlet 11. Also, as shown in FIG. 2, in the ion generation chamber 10, a bottomed cylindrical shape is formed from an insulating material such as Si ₃ N ₄ , BN, etc. in accordance with the internal shape of the ion generation chamber 10. An inner cylinder 13 is provided. This inner cylinder 13
Has a circular opening 13a corresponding to the source gas inlet 11 and a vertically long rectangular opening 13b corresponding to the ion extracting slit 12.
The rectangular opening 13b is formed in the inner wall 10 made of a high melting point material near the opening of the ion extracting slit 12.
The opening size is configured to be larger than the ion extraction slit 12 so that a is exposed. This is so that at the time of ion extraction, the exposed portion of the inner wall 10a made of the high melting point material acts as an electrode, electrons are collected on the exposed surface of the electrode, and a discharge accompanying ion extraction is mainly generated in this portion. It is composed.

In the electron beam-excited ion source of this embodiment having the above-described configuration, a desired magnetic field is applied by a magnetic field generating means (not shown) to guide electrons in the vertical direction as shown by the arrow B in the following manner. Generate.

That is, a filament voltage Vf is applied to the filament 3 to heat it, and a discharge voltage Vd is applied to the filament 3 to the electron generating chamber 1 via the resistor R, and a discharge voltage Vd is applied to the porous electrode 8. 8 and ion generation chamber
10 and an acceleration voltage Va is applied.

Then, from the discharge gas introduction hole 4 into the electron generation chamber 1,
A discharge gas, for example, an argon gas is introduced, a discharge is generated by a discharge voltage Vd, and plasma is generated. Then
The electrons in the plasma pass through the electron extraction port 5 and the through-hole of the porous electrode 8 by the acceleration voltage Va, and pass through
Pulled out within.

On the other hand, in the ion generating chamber 10, in advance from the source gas inlet 13 leave introducing a predetermined raw material gas for example BF _3, keep the ion generation chamber 10 to a predetermined pressure for example 0.001~0.02Torr feed gas atmosphere.

Therefore, the electrons flowed into the ion generation chamber 10 is accelerated by the acceleration electric field, collide with BF _3, to generate a dense plasma. Then, ions are extracted from the plasma by the ion extraction slit 14, and are emitted to, for example, a magnetic field (not shown) for mass analysis of an ion implantation apparatus.
An ion implantation operation using an ion implantation apparatus is performed.

At this time, as described above, the inside of the ion generation chamber 10 is mostly covered with the insulating inner cylinder 13, and only the inner wall 10a near the ion extraction slit 12 is exposed. Only the discharge accompanying ion extraction occurs,
It is possible to efficiently extract ions with a small discharge current. Therefore, a higher ion current density can be obtained as compared with the related art, and the processing time can be reduced and the throughput can be improved.

In the above embodiment, an example in which the inner cylinder 13 is disposed in the ion generation chamber 10 has been described. However, for example, as shown in FIG. A conductive plate-like member 21 made of a high melting point material or the like having 12 is provided, and a voltage is applied only to the plate-like member 21, so that discharge accompanying ion extraction occurs only in the vicinity of the ion extraction slit 12. It can also be configured as follows.

[Effects of the Invention] As described above, according to the electron beam excited ion source and the ion extraction method of the present invention, desired ions can be efficiently extracted with a smaller discharge current than in the past,
By obtaining a high ion current density, processing time can be reduced and throughput can be improved.

[Brief description of the drawings]

FIG. 1 is a cutaway perspective view showing the configuration of an embodiment of the electron beam excited ion source of the present invention, FIG. 2 is a cross-sectional view of the ion generation chamber of FIG. 1, and FIG. It is a cross section showing an example. DESCRIPTION OF SYMBOLS 1 ... Electron generation chamber, 2 ... Insulating member, 3 ... Filament, 4 ... Discharge gas introduction hole, 5 ... Electron outlet, 7 ... Insulating member, 8 ... Porous electrode, 9 ... ... Insulating member, 10 ... Ion generation chamber, 10a ... Inner wall, 11 ... Source gas inlet, 12 ... Slot for ion extraction, 13 ...
Inner cylinder, 13a: circular opening, 13b: rectangular opening.

Claims (3)

(57) [Claims] A source gas introduced into an ion generation chamber is irradiated with electrons accelerated by an electric field formed in the ion generation chamber to generate ions, and the ions are provided in the ion generation chamber. An electron beam excited ion source configured to be extracted from a slit, wherein the inside of the ion generation chamber is covered with an insulating member except for the vicinity of the ion extraction slit. 2. The ion beam excitation ion source according to claim 1, wherein the inside of the ion generation chamber is formed in a bottomed cylindrical shape according to the inside shape of the ion generation chamber, and corresponds to the ion extraction slit. An electron beam excited ion source characterized by being covered by an inner cylinder having an opening formed in a portion that has been formed. 3. A source gas introduced into the ion generation chamber is irradiated with electrons accelerated by an electric field formed in the ion generation chamber to generate ions, and the ions are provided in the ion generation chamber for ion extraction. In the method for extracting ions from the slit, at least the inside of the ion generation chamber is formed of an insulating member except for the vicinity of the slit for ion extraction, and only at the vicinity of the slit for ion extraction among at least the inside of the ion generation chamber. An ion extraction method, wherein the ions are extracted so that the conductive member is exposed.