JP2956412B2 - How to clean the 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 a non-mass separation type ion implantation apparatus which irradiates an ion beam extracted from an ion source onto a sample without performing mass separation and implants ions into the sample. Related to the cleaning method.

[0002]

2. Description of the Related Art FIG. 1 shows an example of a non-mass separation type ion implantation apparatus. This apparatus is also called an ion doping apparatus, and includes a processing chamber 34 and an ion source 2 attached thereto.

In a processing chamber 34, a sample 3 to be processed is placed.
6 are stored. The processing chamber 34 is evacuated by a not-shown evacuation device.

In this example, the ion source 2 is a so-called capacitively-coupled high-frequency ion source, and includes a plasma chamber 4 for generating and holding a plasma 8 by high-frequency discharge, and an electric field generated by the plasma 8 in the plasma chamber 4. And an extraction electrode system 10 for extracting the ion beam 22 by operation.

The plasma chamber 4 is surrounded by a side wall 4a, a back plate 4b and an extraction electrode 12 of an extraction electrode system 10. In this example, the side wall 4a and the back plate 4b also serve as electrodes (discharge electrodes). A high frequency power supply 24 is connected between the two.

The extraction electrode system 10 in this example is composed of four porous electrodes, namely, an extraction electrode 12, an acceleration electrode 13, a suppression electrode 14, and a ground electrode 15. The extraction electrode 12 has a positive voltage for extracting an ion beam from an extraction power supply 28, the acceleration electrode 13 has a positive voltage for ion beam acceleration from an acceleration power supply 30, and the suppression electrode 14 has a positive voltage for suppressing backflow electrons from a suppression power supply 32. Negative voltages are each supplied. The ground electrode 15 is grounded. 18 to 21 are insulators.

An operation example will be described. A desired gas 6 is introduced from a gas inlet 5 into a plasma chamber 4 of an ion source 2 while a sample 36 is accommodated in a processing chamber 34 and evacuated therefrom. When high-frequency power is supplied between the side wall 4a and the back plate 4b from the high-frequency power supply 24, a high-frequency discharge occurs between the side wall 4a and the back plate 4b, whereby the gas 6 is decomposed and the plasma 8 is produced. The ions in the plasma 8 are extracted as an ion beam 22 by the extraction electrode system 10 to which a high voltage is applied. The extracted ion beam 22 is
Irradiated on the sample 36 without mass separation,
Ion Note Nyusho management is carried out.

For example, PH ₃ / H ₂ (phosphine diluted with hydrogen) is introduced as the gas 6, an ion beam 22 containing phosphorus ions is extracted, and phosphorus is injected into the sample 36 as a dopant, or the same device is used. And gas 6
To B ₂ H ₆ / H ₂ (diborane diluted with hydrogen)
The ion beam 22 containing boron is extracted, and a sample 36 is extracted.
Or boron as a dopant.

[0009]

When the ion beam 22 is used for a long time as described above, the wall surface of the plasma chamber 4 (that is, the inner surface of the side wall 4a, the back plate 4b, the insulator 18, and the extraction electrode 12). Decomposed phosphorus, boron and the like adhere to and deposit on the same), which causes various troubles.

For example, the withstand voltage of the insulator 18 between the side wall 4a also serving as a discharge electrode and the back plate 4b is reduced, causing dielectric breakdown, and the apparatus cannot operate.

Further, the attached phosphorus and the like are re-evaporated by the heat of the plasma 8, and are mixed into the plasma 8. Then, the concentration of ions (for example, phosphorus ions) in the plasma 8 becomes equal to or higher than the concentration of a predetermined element (for example, phosphorus) in the gas 6, and the rate of the increase is uncertain. Worsen. This becomes a problem particularly in the case of low concentration implantation or the like.

Further, in an apparatus of the present invention that does not perform mass separation, unnecessary ions (for example, phosphorus ions during boron doping) are irradiated and implanted, which adversely affects the processing of the sample 36. For example, when a semiconductor element is formed on the sample 36, its characteristics deteriorate.

The above problem can be prevented by frequently disassembling and cleaning the ion source 2, but it requires a lot of time and labor. In addition, since the device is stopped for a long time, the operation rate of the device is also reduced.

SUMMARY OF THE INVENTION Accordingly, it is a primary object of the present invention to provide a method of cleaning an ion source which can easily remove deposits in a plasma chamber of the ion source.

[0015]

In order to achieve the above object, a cleaning method according to the present invention comprises introducing hydrogen gas into the ion source at times other than during ion implantation of a sample.
And generating hydrogen plasma in the ion source.

[0016]

According to the above method, the deposits in the plasma chamber are peeled off from the wall surface by the heat of the hydrogen plasma, sputtering or the like. The peeled deposits are discharged to the outside via a processing chamber which is evacuated by combining with hydrogen to form a hydrogen compound. Hydrogen is also discharged to the outside via the processing chamber without adhering to the wall of the plasma chamber. In this way, the deposits in the plasma chamber of the ion source can be easily removed.

[0017]

In this embodiment, in the apparatus shown in FIG.
The plasma was supplied to the plasma chamber 4 and a process of generating plasma 8 (hydrogen plasma) in the ion source 2 using the plasma was performed.

By doing so, the phosphorus adhering to the wall surface of the plasma chamber 4 is peeled off from the wall surface by the heat of hydrogen plasma, sputtering, etc., and combines with hydrogen to form a hydrogen compound, which is not shown. It is discharged to the outside via the processing chamber 34 which is evacuated by the evacuation device. Excess hydrogen is also discharged to the outside via the processing chamber 34 without adhering to the wall surface of the plasma chamber 4.

At this time, as an example, the flow rate of the hydrogen gas was 20 ccm, the high frequency power supplied from the high frequency power supply 24 was 100 W, and the processing time was 90 minutes. Before and after this treatment, a hydrogen ion beam was extracted as the ion beam 22 and the amount of phosphorus contained therein was measured. As a result, the amount after the treatment was reduced to about 1/20 of that before the treatment.

As another example, the flow rate of hydrogen gas is set to 5
0 ccm, the high frequency power supplied from the high frequency power supply 24 is 1
As a result of setting the power to 00 W and the processing time to 30 minutes, the amount of phosphorus in the hydrogen ion beam after the treatment was reduced to about 1/20 as compared to before the treatment as in the above example.

The reason why the processing time was shortened in the later example is that the density of the hydrogen plasma was increased by the increase in the flow rate of the hydrogen gas, and the cleaning action was thereby increased. The plasma density may be increased by increasing the high-frequency power in addition to the gas flow rate. In any case, by increasing the plasma density, more effective cleaning can be performed.

The above-described cleaning process is very simple and takes a long time because the ion source 2 does not need to be decomposed by merely introducing hydrogen gas into the plasma chamber 4 and generating hydrogen plasma. It does not take much effort.

In addition, since it is not necessary to return the inside of the ion source 2 to the atmospheric pressure, it is possible to stably apply a high voltage to the extraction electrode system 10 without causing a discharge for the time required for vacuum start-up or after the vacuum start-up. The time required for starting the high voltage until the voltage becomes the same can be omitted. As a result, it is possible to prevent a decrease in the operation rate of the device.

It should be noted that the ion source 2 is not limited to the high-frequency ion source as described above, but may be of another type, for example, a microwave ion source using a microwave, or a multi-pole magnetic source having a filament. Of course, a bucket type ion source or the like may be used.

[0025]

As described above, according to the present invention , hydrogen gas is supplied to the ion source at times other than during ion implantation of the sample.
By introducing and generating hydrogen plasma in the ion source, it is possible to remove deposits in the plasma chamber of the ion source and discharge them to the outside, and it is not necessary to disassemble the ion source. It takes less time and effort.

In addition, since it is not necessary to return the inside of the ion source to the atmospheric pressure, the time required for starting up the vacuum and the time required for starting up the high voltage can be omitted, and as a result, a reduction in the operation rate of the apparatus can be prevented. it can.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of a non-mass separation type ion implantation apparatus.

[Explanation of symbols]

 2 Ion source 4 Plasma chamber 6 Gas 8 Plasma 10 Extraction electrode system 22 Ion beam 24 High frequency power supply 34 Processing chamber 36 Sample

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiro Okute 47, Umezu Takaune-cho, Ukyo-ku, Kyoto-shi, Nissin Electric Co., Ltd. (56) References JP-A-3-64462 (JP, A) JP-A-2 -271621 (JP, A) JP-A-63-267430 (JP, A) JP-A-2-213039 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01J 37/317 C23C 14/48 H01J 27/00-27/26 H01J 37/08 H01J 21/265

Claims (1)

(57) [Claims] 1. A method for diluting a dopant-containing gas with hydrogen gas.
Gas is irradiated to the sample processing chamber without performing mass separation of ion beam extracted from an ion source to be introduced
In a non-mass separation type ion implantation apparatus for performing ion implantation , the ion
A method for cleaning an ion source, comprising introducing hydrogen gas into the source and generating hydrogen plasma in the ion source.