JPH03173047A - Ion source - Google Patents

Abstract

PURPOSE:To suppress the generation of damage due to spark discharges by forming at least one portion of corner portions of an ion source on an ion- taking-out-electrode side to a curved surface. CONSTITUTION:In an ion source 1 taking out ions with an ion-taking-out- electrode 18, at least one portion of corner portions 20b on the electrode 18 side is formed to a curved surface. By forming at least one portion of corner portions on outside of a chamber of the ion source 1 to a curved surface, the creeping distance on the corner portions of the ion source chamber to the ion- taking-out-electrode is elongated, and the potential gradient can be lowered to reduce the possibility of the generation of spark discharges. Thereby the generation of damages due to spark discharges can be suppressed.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to an ion source.

(Prior Art) In general, ion processing equipment that performs processing by applying predetermined ions to a workpiece, such as an ion implantation equipment that implants ions as impurities into a semiconductor substrate, etc., is equipped with a predetermined raw material gas ( An ion source is provided for generating desired ions from solid raw materials (or solid raw materials).

As such an ion source, a so-called Freeman type ion source is conventionally known, in which a rod-shaped filament is provided so as to pass through a cylindrical chamber. In this Freeman type ion source, a predetermined source gas is introduced into a chamber, and a voltage is applied between the chamber and the filament to turn the source gas into plasma and generate ions.

An ion extraction electrode is provided so as to face a slit opening provided in the chamber, and ions are extracted to the outside from the slit opening by applying a high voltage between the chamber and the ion extraction electrode.

In addition, in an electron beam excited ion source, a voltage is applied between a filament and an anode electrode, and a predetermined discharge 7 generates a first plasma from the gas, and electrons are extracted from this first plasma to generate ions. A second plasma (ions) is generated by irradiating a predetermined source gas introduced into the chamber.

An ion extraction electrode is provided so as to face the slit opening provided in the ion generation chamber, and ions are extracted to the outside from the slit opening by applying a high voltage between the ion generation chamber and the ion extraction electrode. has been done.

Such an electron beam-excited ion source is characterized by being able to obtain a high ion current density with low ion energy.

(Problem to be Solved by the Invention) As described above, in the ion processing apparatus, the ion extraction electrode is provided so as to face the slit opening provided in the chamber of the ion source, and the ion extraction electrode is connected to the chamber of the ion source. The ion source is configured to apply a high voltage between the ion sources to extract and accelerate ions from the ion source.

However, in such a single ion processing bag, there are, for example, three
Since a high voltage such as 2 kilovolts is applied, spark discharge may occur between the ion source and the ion extraction electrode, and there is a problem in that each component is damaged by this discharge.

The present invention has been made in response to such conventional circumstances, and aims to provide an ion source that can reduce the occurrence of spark discharge and suppress the occurrence of damage caused by spark discharge compared to the prior art. It is something to do.

[Structure of the Invention] (Means for Solving the Problems) That is, the ion source according to claim 1 irradiates a raw material gas with electrons to generate plasma, and extracts ions ff.
In the ion source that extracts ions by 1ti, at least a part of the corner on the ion extraction electrode side is configured to have a curved surface.

Further, the ion source according to the second aspect is characterized in that at least a part of the outside of the chamber on the side of the ion extraction electrode is configured to have a mirror surface.

(Function) In the ion source according to the first aspect, at least a part of the corner of the ion source on the ion extraction electrode side outside the chamber is configured in a curved shape.

Therefore, the creepage distance between the ion extraction electrode and the ion extraction electrode at the chamber corner of the ion source becomes longer, and the change in potential becomes gentler, so that the possibility of spark discharge occurring can be reduced.

Further, in the ion source according to the second aspect, at least a part of the outside of the chamber of the ion source on the ion extraction electrode side is configured to have a mirror surface.

Therefore, it is possible to prevent spark discharge from occurring due to undesirable irregularities on the surface of the chamber of the ion source, and it is possible to reduce the possibility of spark discharge occurring.

(Example) Hereinafter, embodiments of the method of the present invention will be described with reference to the drawings.

As shown in FIG. 1, at the top of the ion source 1, there is a first container shaped like a rectangular container with each side having a length of, for example, several centimeters.
A chamber, for example an electron generation chamber 2, is provided. The electron generating chamber 2 is made of a conductive high melting point material, such as molybdenum, and is provided with an insulating plate 3 so as to close an opening provided on the lower side thereof. A U-shaped filament 4 made of a conductive high melting point material such as tungsten is provided on the insulating plate 3 so as to project into the electron generation chamber 2 with its both ends supported.

Furthermore, a discharge gas inlet 5 is provided in the upper part of the electron generation chamber 2 to introduce a discharge gas such as argon (Ar) gas to generate plasma and generate electrons. On the other hand, in the lower part of the electron generation chamber 2, a circular hole 6 is provided for extracting electrons from the plasma generated within the electron generation chamber 2.

Further, a plate-shaped insulating member 8 is provided at the lower part of the electron generating chamber 2 so as to form a bottleneck 7 continuous with the circular hole 6. An electron extraction electrode 10 having a through hole 9 is provided.

An insulating member 11 is provided below the electron extraction electrode IO.
The ion generation chamber 12 is connected via the ion generation chamber 12. The ion generation chamber 12 is made of conductive material with a high melting point (4F4, for example, molybdenum) in the shape of a container, and the inside thereof has a cylindrical shape with both a diameter and a height of about several centimeters.

An inner tube 13 made of a material such as ceramics is provided in the ion generation chamber 12 to protect the inner metal surface from plasma. Further, a bottom plate 15 is fixed to the bottom of the ion generation chamber 12 with an insulating member 14 interposed therebetween.

Further, a source gas inlet 16 is provided on the side surface of the ion generation chamber 12 for introducing a source gas such as BF3 into the ion generation chamber 12 to generate desired ions. An ion extraction slit opening 17 is provided at a position facing the introduction port 16.

Further, an ion extraction electrode 1 is provided on the outside of the ion generation chamber 12 so as to face the ion extraction slit opening 17.
8 is provided. This ion extraction electrode 18 is
It is made of conductive metal or ceramics in a plate shape, with a slit-shaped ion passage hole 1 in the center.
9 is provided. A high voltage of, for example, 32 kilovolts is applied between the ion extraction electrode 18 and the ion generation chamber 12, so that ions are extracted from the ion generation chamber 12, passed through the ion passage hole 19, and accelerated. ing.

As shown in FIGS. 2 and 3, the side surface 20
The corner portion 20a around the ion extraction slit opening 17 and the corner portion 20b around the ion extraction slit opening 17 are formed into a curved shape so as to be chamfered. This is to prevent undesired spark discharge from occurring at the corners 20a and 20b due to the high voltage applied to the ion extraction electrode 18 described above.

In addition, the ion extraction electrode 18 outside the ion generation chamber 12
The side surfaces 20 are polished to a mirror finish. This is because if undesirable irregularities are formed on the side surface 20, undesirable spark discharge is likely to occur at the convex part due to the high voltage between the ion extraction electrode 18 mentioned above. This is to prevent discharge.

In the ion processing apparatus having the above configuration, desired ions are generated in the following manner.

That is, by a magnetic field generating means (not shown), the arrow B shown in the drawing is
A magnetic field is applied to guide the electrons in the electron extraction direction as indicated by z. ), a filament voltage V' is applied to the filament 4 and heated by electricity, and a discharge voltage Vd is applied to the electron generation chamber 2 through the resistor R to discharge the electron extraction electrode 10. A voltage Vd is applied, and an accelerating voltage Va is applied between the electron extraction electrode 10 and the ion generation chamber 12.

Then, a discharge gas such as argon gas is introduced into the electron generation chamber 2 from the discharge gas inlet 5 at a predetermined flow rate of 0.05, for example.
It is introduced at 3 CCM or more, and a discharge is caused by a discharge voltage Vd to generate plasma. Then, the electrons in this plasma pass through the circular hole 6, the bottleneck 7, and the through hole 9 of the electron extraction electrode 10, and enter the ion generation chamber 1 due to the accelerated pressure Va.
It is pulled out within 2.

On the other hand, a predetermined raw material gas is supplied into the ion generation chamber 12 from the raw material gas inlet 16 at a predetermined flow rate of, for example, 0.158 CC.
The gas is introduced at M or more to create a predetermined raw material gas atmosphere. Therefore, the electrons flowing into the ion generation chamber 12 are accelerated by the accelerating electric field, collide with source gas molecules, and generate dense plasma.

Then, a high voltage ve of, for example, 32 kilovolts is applied between the ion generation chamber 12 and the ion extraction electrode 18, and ions are extracted from the ion generation chamber 12, passed through the ion passage hole 19, and accelerated. Then, this ion beam is sorted by, for example, a mass spectrometer magnet (not shown), further accelerated by an accelerator tube, and irradiated, for example, as a desired ion beam onto a semiconductor urchin or the like to perform a process such as ion implantation.

At this time, as described above, the side surface 20 of the ion generation chamber 12 on the ion extraction electrode 18 side is mirror-finished.
Furthermore, since the corner 20a around the side surface 20 and the corner 20b around the ion extraction slit opening 17 are formed into a curved shape as if chamfered, the high voltage Vc
Despite the application of , undesired spark discharge is less likely to occur between the ion extraction electrode 18 and the ion extraction electrode 18 than in the past, and damage caused by spark discharge can be suppressed.

[Effects of the Invention] As explained above, according to the ion source of the present invention, the occurrence of spark discharge can be reduced compared to the conventional one, and the occurrence of damage caused by sparks/IT electricity can be suppressed. Can be done.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an ion source according to an embodiment of the present invention;
2 and 3 are cross-sectional views of essential parts of the ion source of FIG. 1. FIG. 1... Ion source, 2... Electron generation chamber,
3... Insulating plate, 4... Filament,
5... Gas inlet for discharge, 6... Circular hole, 7... Bottle, 8... Insulating member, 9
......Through hole, 10...Electron extraction electrode, 11...Insulating member, 12...Ion generation chamber, 13...Inner Tube, 14...
... Insulating member, 15 ... Bottom plate, 16 ...
... Raw material gas inlet, 17... Slit opening for ion extraction, 18... Ion extraction electrode, 19... Ion passage hole.

Claims (2)

[Claims] (1) In an ion source in which a source gas is irradiated with electrons to generate plasma and ions are extracted by an ion extraction electrode, at least a part of the corner on the ion extraction electrode side is
An ion processing device characterized by having a curved surface configuration. (2) Claim 1 characterized in that at least a part of the outside of the chamber on the ion extraction electrode side is formed into a mirror surface.
Ion source as described.