JPH03194832A - Ion source - Google Patents

Abstract

PURPOSE:To improve quality, uniformity and efficiency in ion treatment by specifying the diameter of a bottleneck or the length thereof. CONSTITUTION:In an ion source 1 wherein a first chamber 2 for generating plasma, a second chamber 9 installed through a bottleneck 7 in the first chamber 2, a porous electrode 11 installed on the second chamber 9, and a third chamber 13 to generate an ion by irradiating an electron from the porous electrode 11 to a desired raw material gas are installed, the diameter of a bottleneck 7 is made to be from 2mm to 10mm, or the length of the bolltleneck 7 is made to be 6mm or more. It is thereby possible to make more effective and stably supply of ions and make good, uniform and effective treatment of ions.

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 causing predetermined ions to act on an object to be processed, such as an ion resident equipment that implants ions as impurities into semiconductor wafers, etc., is equipped with a predetermined raw material gas (or An ion source is provided for producing desired ions from solid raw materials.

As such an ion source, a so-called Freeman type ion source in which a rod-shaped filament is provided so as to pass through a cylindrical chamber has been known.

Further, as such an ion source, there is a so-called electron beam excitation ion source that generates ions by irradiating a predetermined raw material gas with electrons.

This electron beam-excited ion source generates plasma by discharging a filament in a predetermined discharge gas atmosphere. Then, the electrons in this plasma are extracted,
A predetermined raw material gas is accelerated and irradiated to turn it into plasma, and ions are generated from the raw material gas.

Such an ion source has the characteristic that a high ion current density can be obtained with low ion energy.

(Problem to be solved by the invention) However, in order to put the above-mentioned ion source into practical use, it is necessary to make it possible to output ions more efficiently and stably, improve the quality of ion processing, and make it more uniform. ,
Naturally, it is required to improve efficiency.

The present invention was made in response to such conventional circumstances, and aims to provide an ion source that can efficiently and stably supply ions and that can perform high-quality and uniform processing with high efficiency. It is something to do.

[Structure of the Invention] (Means for Solving the Problems) That is, the invention according to claim 1 includes a first chamber for generating plasma therein, and a first chamber provided through a bottleneck in the first chamber. a second chamber;
In an ion source equipped with a porous electrode provided in a chamber, and a third chamber in which electrons from the porous electrode are irradiated onto a desired source gas to generate ions, the diameter of the bottleneck is 2InI11 or more and 10mm. It is characterized by the following.

Further, the invention according to claim 2 includes: a first chamber provided with a filament for generating plasma by electric discharge; a second chamber provided through a bottleneck in the first chamber; A third chamber is provided in the second chamber via a porous electrode, and is used to extract electrons from the second chamber and irradiate a desired raw material gas to generate ions. The ion source is characterized in that the length of the bottleneck is 61 or more.

(Function) A detailed investigation by the present inventors revealed that, for example, in an ion source as shown in FIG. It has been found that the diameter and length of the bottleneck 7 provided in the tube have a significant effect on the generation state of plasma for generating electrons, and the ion supply state changes greatly.

In other words, although the reason is not clear, the diameter of bottleneck 7 is set to 2.
If it is smaller than mm1II11, it becomes difficult to generate plasma in the plasma cathode chamber 9, and unless the flow rate of the discharge gas (for example, argon gas) is increased (for example, 0.53 CCM or more) and a large amount of discharge gas is not supplied, the plasma will not be generated. become unable to maintain it.

However, when a large amount of discharge gas is supplied, a problem arises in that a large amount of discharge gas flows into the third chamber where ions are generated, reducing the efficiency of generating desired ions. Further, problems such as increased consumption of discharge gas arise. Therefore, in the ion source of the present invention, the diameter of the bottleneck 7 is set to 2o.
+m or more, for example, 3■, so that stable plasma can be generated with a small amount of raw material gas.

On the other hand, the length of the bottleneck 7 is mainly the plasma cathode chamber 9.
affect the stability of the plasma within.

The graphs in Figures 2 and 3 show the length of bottleneck 7 as II.
Im (solid line), 2+em (dashed line), 4ms
(dotted line) and 6 ms (-dotted chain line), the potential between the filament 4 and the porous electrode 11 was measured while changing the magnetic field Bz. In addition, the second
The figure shows the discharge gas (argon gas) flow rate at 0.43CC.
3 shows the case where this flow rate is O and (isccM), and the flow rate of the raw material gas (argon gas) is 0.98 CCM in both cases. For example, BF3 gas or the like is used, but in the above experiment, argon gas was used.

As shown in the above graph, the length of bottleneck 7 is 6-
With the above configuration, the change in potential between the filament 4 and the porous electrode 11 becomes small with respect to the change in the magnetic field. this is,
This means that there is little change in the current flowing between the filament 4 and the porous electrode 11, that is, a change in the plasma, and that the state of the plasma is stable. This is because by making the length of the bottleneck 7 greater than Gml1, the plasma is converged and the plasma density becomes higher! lj is done. Note that if the state of the plasma becomes unstable, the electron extraction mechanism changes and it becomes impossible to supply a stable amount of ions. Therefore, the ion source of the present invention is configured such that a more stable plasma can be generated by setting the length of the bottleneck 7 to 6n+m or more.

(Example) Hereinafter, an example in which the present invention is applied to an ion source will be described based on the drawings.

As shown in FIG. 1, an electron generation chamber (first chamber) 2 formed in the shape of a rectangular container with each side having a length of, for example, several centimeters is provided in the upper part of the ion source 1. 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 for introducing discharge gas, for example, argon (Ar) gas, is provided in the upper part of the electron generation chamber 2. On the other hand, in the lower part of the electron generation chamber 2, a hole, for example, 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, and a plasma cathode is provided at the lower part of the insulating member 8. A chamber (second chamber) 9 is provided. Furthermore, a porous electrode 11 having a plurality of through holes 10 is provided at the bottom of the plasma cathode chamber 9 .

The diameter of the bottleneck 7 is 2 In11 or more, for example, 3 mm. This is because, as described above, if the diameter of the bottleneck 7 is made smaller than 2I, it becomes difficult for plasma to be generated in the plasma cathode chamber 9.

Note that if the diameter is larger than 101, the plasma in the electron generation chamber 2 and the plasma in the plasma cathode chamber 9 will be connected, reducing the efficiency of extracting electrons from the porous electrode 11. Riha, 2~lo
It is preferable to set it as im.

Further, the length of the bottleneck 7 is 61 or more.

This is because, as described above, when the length of the bottleneck 7 is made larger than Gaun, the plasma in the plasma cathode chamber 9 becomes stable. Note that the length of the bottleneck 7 is limited by the height inside the plasma cathode chamber 9, so in this embodiment, the length of the bottleneck 7 is limited to a maximum of about 9 nV. Therefore, the length of the bottleneck 7 is substantially 6 to 9I.

An ion generation chamber (third chamber) 13 is connected to the lower part of the porous electrode 11 via an insulating member 12. The ion generation chamber 13 is made of a conductive high melting point material such as molybdenum and is shaped like a container, and the inside thereof is
It has a cylindrical shape with both diameter and height of several centimeters. A bottom plate 15 is fixed to the bottom of the ion generation chamber 13 via an insulating member 14.

Furthermore, a source gas inlet 16 is provided on the side surface of the ion generation chamber 13 for introducing a source gas such as BF3 into the ion generation chamber 13 to generate desired ions. An ion extraction slit opening 17 is provided at a position facing the introduction port 16.

Also, is filament 4 a filament? 1 [vr is connected, and the filament 4 is configured to be heated by electricity. Further, a discharge power source Vd is connected to the electron generation chamber 2 via a resistor R, a discharge power source Vd is directly connected to the porous electrode 11, and a discharge power source Vd is connected between the porous electrode 11 and the ion generation chamber 13. Acceleration power sources Va are connected so as to be arranged in series with. Note that the discharge power supply Vd is set to, for example, about 50 volts, and the acceleration power supply Va is set to, for example, about 100 volts.

The ion source having the above configuration generates desired ions as follows.

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 electrons in the electron extraction direction as shown in z, and a filament electric current riv is applied.
A predetermined voltage is applied to each part by r, a discharge power supply Vd, and an acceleration power supply V3.

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 to cause discharge and generate plasma. Then, the electrons in this plasma are accelerated by the electric field and are drawn out into the plasma cathode chamber 9 through the circular hole 6 and the bottleneck 7, forming plasma also in this plasma cathode chamber 9. At this time, as mentioned above, bottleneck 7
Since the diameter is 311II and the length is 61, the flow rate of the discharge gas, for example argon gas, is set to 0.0, for example.
Even at a low flow rate of 58 CCM or more, stable plasma can be generated in the plasma cathode chamber 9.

Then, the electrons in the plasma inside the plasma cathode chamber 9 are accelerated by the porous electrode 11, and the porous electrode 11
is drawn out into the ion generation chamber 13 through the through hole 10 .

On the other hand, a predetermined raw material gas, for example, BF3, is introduced into the ion generation chamber 13 from the raw material gas inlet 16 at a predetermined flow rate, for example, 0.
．． It is introduced at 153 CCM or more to create a predetermined raw material gas atmosphere. Therefore, the electrons flowing into the ion generation chamber 13 collide with the source gas molecules and generate dense plasma.

Then, these ions are extracted from the ion generation chamber 13 by an ion extraction electrode (not shown) and used for processing such as ion implantation into a semiconductor wafer.

That is, in the ion source of this embodiment, as mentioned above, the diameter of the bottleneck 7 is 2III1 or more and the length is 61m11 or more. Even at low flow rates,
Stable plasma can be generated in the plasma cathode chamber 9. Therefore, for example, a large amount of discharge gas flows into the third chamber where ions are generated, and the efficiency of generating desired ions does not decrease, and the consumption of discharge gas does not increase. can be supplied.

Therefore, high quality and uniform processing can be performed with high efficiency in processing using ions, such as ion implantation, etching, ashing, etc.

In the above embodiment, an example was explained in which the diameter of the bottleneck 7 is 2 m++ or more and the length of the bottleneck 7 is Bam or more, but the two factors of the diameter and length of the bottleneck 7 are , which act independently. Therefore, for example, the diameter of the bottleneck 7 is 2mo+ or more, and the length of the bottleneck 7 is 6+mo+.
If it is shorter than a+a, or the length of bottleneck 7 is 6■
- or more, and even if the diameter of the bottleneck 7 is smaller than 2 mm 111, each effect can be obtained.

In the above embodiment, an example in which the present invention is applied to an ion source of an ion implantation apparatus has been described, but any ion source may be used, such as ion etching, X-ray source, ion repair, etc.

[Effects of the Invention] As explained above, according to the ion source of the present invention, ions can be efficiently and stably supplied, and high-quality and uniform processing can be performed with high efficiency.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of an embodiment in which the present invention is applied to an ion source for an ion implanter, and FIGS. 2 and 3 are diagrams showing the strength of the magnetic field in the ion source shown in FIG. 1 and the distance between the filament and the porous electrode. FIG. 1...Ion source, 2...Electron generation chamber (
first chamber), 3...insulating plate, 4...
...Filament, 5...Discharge gas inlet,
6... circular hole, 7... defile, 8...
...Insulating member, 9...Plasma cathode chamber (
second chamber), 10... through hole, 11...
...Porous electrode, 12...Insulating member, 13.
...Ion generation chamber (third chamber), 14...
... Insulating member, 15 ... Bottom plate, 16 ...
... Raw material gas inlet, 17... Opening above the slot for extracting ions.

Claims (2)

[Claims] (1) a first chamber for generating plasma inside; a second chamber provided in the first chamber via a bottleneck; a porous electrode provided in the second chamber; An ion source comprising a third chamber for irradiating a desired source gas with electrons from a porous electrode to generate ions, characterized in that the diameter of the bottleneck is 2 mm or more and 10 mm or less. (2) a first chamber in which a filament for generating plasma by electric discharge is provided; a second chamber provided in the first chamber via a bottleneck; and a second chamber provided in the first chamber via a bottleneck; and a third chamber for extracting electrons from the second chamber by the porous electrode and irradiating them to a desired source gas to generate ions, the ion source comprising: An ion source characterized by having a length of 6 mm or more.