JPH0997571A - Ion beam generating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ion beam generating device capable of drawing an ion beam with lower density. SOLUTION: This ion beam generating device has an ion source 2 for emitting an ion beam 40 and a power source device 30b for applying an ion beam drawing voltage thereto. The ion source 2 has a plasma source part 4 for generating a plasma 14 and an drawing electrode system 20 for drawing the ion beam 40 therefrom, and a first electrode 21 constituting the drawing electrode system 20 is electrically insulated from the plasma source part 4 by an insulator 50. The power source device 30b has a DC bias power source 37 for applying a positive bias voltage VG to the first electrode 21 on the basis of the plasma source part 4, and a control power source 39 for applying a positive control voltage VS to the second power source 22 on the basis of the plasma source part 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion beam processing object such as an ion implantation apparatus, an ion doping apparatus (non-mass separation type ion implantation apparatus), and a thin film forming apparatus using both ion irradiation and vacuum deposition. The present invention relates to an ion beam generator used when irradiating an object for processing.

[0002]

2. Description of the Related Art FIG. 9 is a sectional view showing an example of an ion implantation apparatus using a conventional ion beam generator. In this ion implantation apparatus, an ion source 2 of an ion beam generator having an ion source 2 for ejecting an ion beam 40 and a power supply device 30 for applying a voltage for extracting the ion beam thereto is attached to an upper part of a processing chamber 42. It has a different structure.

A holder 44 for holding a substrate 46, which is an example of an object to be processed, is provided in the processing chamber 42. The processing chamber 42 is evacuated by a vacuum exhaust device (not shown).

The ion source 2 shown in the figure is a high frequency ion source, and a plasma source section 4 for generating a plasma 14 by ionizing the gas by a high frequency discharge and a vicinity of an outlet of the plasma source section 4 And an extraction electrode system 20 for extracting the ion beam 40 from the plasma 14 in the plasma source section 4 by the action of an electric field.

The plasma source part 4 is provided with a plasma generating container 6 having a side wall 6a and a back plate 6b attached to the side wall 6a with an insulator 8 interposed therebetween. Gas is introduced from the downstream side. Also, in this example, the side wall 6a and the back plate 6b
Also serve as electrodes (discharge electrodes), and a high frequency power supply 16 is connected between them via a matching circuit 18.
However, the gas may be directly introduced into the plasma generation container 6.

In this example, the extraction electrode system 20 has a first electrode 21, a second electrode 22, a third electrode 23 and a fourth electrode 24 arranged from the most plasma side toward the downstream side. Reference numeral 26 is an insulator. Each of these electrodes 21 to 2
Although 4 is a porous electrode in this example, it may have an ion extraction slit.

The first electrode 21 is used for extracting the ion beam 4
This is an electrode for determining the energy of 0, and in this example, a positive high voltage is applied from the first power supply 31 constituting the power supply device 30 with reference to the ground potential. The first electrode 21 and the plasma source portion 4 (more specifically, the plasma generation container 6 constituting the same) are connected to each other and have the same potential.

The second electrode 22 is an electrode that produces a potential difference between the second electrode 22 and the first electrode 21 and extracts the ion beam 40 from the plasma 14 by the electric field generated by the potential difference. From the first electrode 2
A negative voltage is applied with reference to the potential of 1.

The third electrode 23 is an electrode for suppressing backflow electrons from the downstream side, and in this example, a negative voltage is applied from the third power supply 33 constituting the power supply device 30 with reference to the ground potential. .

The fourth electrode 24 is grounded.

Explaining an operation example of the ion implantation apparatus of FIG. 9, while holding a desired substrate 46 on a holder 44 in the processing chamber 42 and evacuating the inside of the processing chamber 42, a plasma source part of the ion source 2 is provided. When a desired gas is introduced into the inside of 4 from the downstream side of the extraction electrode system 20 and a high frequency power of, for example, 13.56 MHz is supplied from the high frequency power supply 16 between the side wall 6a and the back plate 6b, the space between the side wall 6a and the back plate 6b is High-frequency discharge occurs in the plasma 14
Is made. Ions in the plasma 14 are extracted as an ion beam 40 by the extraction electrode system 20. The extracted ion beam 40 is directly applied to the substrate 46 without mass separation, and ion implantation (ion doping) is performed.

By the way, for example, in the case of manufacturing a polycrystalline silicon thin film transistor, it is necessary to perform implantation with a low dose amount of 10 ¹¹ to 10 ¹² ions / cm ² .

In order to use the above ion beam generator for such a low dose implantation, the ion current density of the ion beam 40 extracted from the ion source 2 must be reduced, but the conventional ion beam generator described above is used. There was a limit in reducing the ion current density in the device.

This is because the plasma 14 generated in the plasma source section 4 has a much higher moving speed of the electrons forming the plasma 14 than that of the ions, so that a large number of electrons cause the plasma generation chamber 6 and the plasma generating chamber 6 to move. The first electrode 21 has a negative potential with respect to the plasma 14, and from a different perspective, the plasma 14 has a positive potential with respect to the plasma generation container 6 and the first electrode 21, so that the output voltage V2 of the second power supply 32 is changed. This is because even if it is set to 0, ions are extracted due to the above-mentioned potential difference existing between the plasma 14 and the first electrode 21, and the ion current density of the ion beam 40 cannot be set to 0. Therefore, conventionally, when the ion current density of the ion beam 40 is reduced, the density of the plasma 14 is also reduced. However, in order to reduce the density of the plasma 14, the power supplied to the plasma 14, that is, the high frequency power source is used. It is necessary to reduce the electric power supplied from 16 to the plasma 14. If this is done, the plasma 14 cannot be maintained, or even if it can be maintained, there is a lower limit that can be maintained, so that the ion current density of the ion beam 40 can be reduced. There was a limit.

FIG. 10 illustrates the above situation. When the power input to the plasma 14 is lowered below the lower limit for maintaining the plasma, the plasma disappears and the ion beam 40 cannot be extracted.

If the ion current density of the ion beam 40 cannot be made too small, when low dose implantation is performed,
The implantation time becomes, for example, several seconds or 1 second or less, and the controllability and reproducibility for performing the prescribed dose implantation deteriorate.

An ion beam generator capable of solving such problems of the prior art has been previously proposed by the same applicant (Japanese Patent Application No. 7-136003). One example is shown in FIG.

In this ion beam generator, between the first electrode 21 constituting the extraction electrode system 20 and the plasma source portion 4 (more specifically, the plasma generation container 6) in the ion source 2 described above. Insulator 50 is installed on
The first electrode 21 and the plasma source part 4 are electrically insulated from each other, and the first electrode 21 is positive or negative with respect to the plasma source part 4 in the power supply device 30a corresponding to the conventional power supply device 30. The DC bias power supply 38 for applying the bias voltage VB is provided.

By increasing the bias voltage VB positively or negatively, for example, as shown in FIG. 12, the ion current density can be made smaller than the conventional lower limit without lowering the power supplied to the plasma 14. You can This is because when the bias voltage VB is made positive and a positive potential is applied to the first electrode 21, the plasma 1 in the plasma source unit 4 is
4 are partially repelled by the first electrode 21 having a positive potential, and conversely, when the bias voltage VB is made negative and a negative potential is applied to the first electrode 21, the plasma source unit 4 Some of the ions that are about to be extracted from the plasma 14 inside the first electrode 21 of this negative potential.
It is considered that this is because the amount of ions that are absorbed by and are both extracted decreases. By the way, the bias voltage VB
The ion current density J ₁ or J ₂ when is 0 corresponds to the conventional lower limit.

[0020]

In the ion beam generator of the above-mentioned prior art example, when the positive or negative bias voltage VB is applied to the first electrode 21, the ion current density can surely be reduced, but the ion current is reduced. The lower density of
As can be seen from FIG. 12, even when a more effective positive bias voltage VB is applied, the ion current density is at most about one-third compared with the case of 0 bias, and the lower limit is 5
It was about 0 to 60 nA / cm ² . This may not always be sufficient to ensure controllability and reproducibility for low dose implantation, for example, for implanting 10 ¹¹ ions / cm ² .

Therefore, the main object of the present invention is to provide an ion beam generator capable of extracting an ion beam having a lower density by further improving the above-mentioned prior art device.

[0022]

In the ion beam generator of the present invention, an insulator is provided between the first electrode on the most plasma side of the electrodes constituting the extraction electrode system of the ion source and the plasma source portion. Is provided to electrically insulate the two from each other, and the power supply device applies a positive bias voltage to the first electrode with a positive bias voltage based on the plasma source portion; and the first electrode. It is characterized in that it has a direct current control power supply for applying a positive control voltage based on the plasma source part to the second electrode immediately downstream thereof.

According to the above structure, the potential of the second electrode serves as a barrier for extracting the ions from the plasma in the plasma source portion, and the potential of the second electrode is fixed between them by the bias voltage. Since there is one electrode, it does not affect the plasma potential. Therefore, by increasing the potential of the second electrode by the control voltage,
It becomes possible to extract a lower density ion beam.

[0024]

1 is a sectional view showing an example of an ion implantation apparatus using an ion beam generator according to the present invention. The same or corresponding portions as those of the conventional example of FIG. 9 and the preceding example of FIG. 11 are denoted by the same reference numerals, and the differences from the preceding example will be mainly described below.

Also in this embodiment, in the above-mentioned ion source 2, the first electrode 21 constituting the extraction electrode system 20 and the plasma source portion 4 (more specifically, the plasma generation container 6; the same applies hereafter). An insulator 50 is provided in between to electrically insulate the first electrode 21 and the plasma source portion 4 from each other.

Further, in this embodiment, the power supply device 3 of the preceding example is used.
0a, which is equipped with a power supply device 30b having the following configuration that constitutes an ion beam generator together with the ion source 2.

That is, the power supply device 30b includes a DC bias power supply 37 for applying a positive bias voltage VB to the first electrode 21 with respect to the plasma source portion 4, and a downstream side of the first electrode 21. The second electrode 22 has a direct-current control power supply 39 for applying a positive control voltage VS based on the plasma source unit 4. This power supply device 30b
Further, as in the case of the prior example, the first power supply 3 for applying a positive high voltage to the plasma source section 4 with reference to the ground potential.
1 and a third power supply 33 that applies a negative voltage to the third electrode 23 with reference to the ground potential.

The bias power source 37 and the control power source 39 are
Variable output voltage is preferable because it has better controllability. It is arbitrary whether the output voltages V1 to V3 of the first power supply 31 and the third power supply 33 are variable or fixed.

To illustrate the magnitude of each of the above voltages, the output voltage V1 is, for example, about 30 kV to 100 kV and the output voltage V
3 is, for example, about 500 V to 1 kV, the bias voltage VB is, for example, about 0 to 200 V, and the control voltage VS is, for example, 0 to 2
It is about 00V.

FIG. 2 shows an example of the potential distribution in the ion source 2 when such a power supply device 30b is used. The potential of the plasma source unit 4 is determined by the output voltage V1 of the first power supply 31, and the first electrode 2 is located at a position higher than the output voltage of the bias power supply 37 (that is, the bias voltage VB).
There is a potential of 1, the potential of the second electrode 22 is higher than the output voltage of the control power supply 39 (that is, the control voltage VS) from the plasma source unit 4, and the potential of the third electrode 23 is the third.
It is determined by the output voltage V3 of the power supply 33. As described above, the plasma 14 has a positive potential with respect to the plasma generation container 6 including the back plate 6b and the side wall 6a.

In the ion beam generator of the prior art shown in FIG. 11, even if a positive bias voltage VB is applied to the first electrode 21, the ion current density is 1/3 of that in the 0 bias.
The reason why it could be lowered only to a certain degree is considered to be due to the following reasons.

That is, a positive bias voltage V is applied to the first electrode 21.
The ion current density when B is applied depends on the potential difference ΔV between the potential of the plasma 14 and the potential of the first electrode 21,
If it is small, the ion current density also becomes small. FIG. 13 shows the potential distribution when the bias voltage VB is small in the device of the prior art, and FIG. 14 shows the potential distribution when the bias voltage VB is large, but even if the bias voltage VB is increased, as shown in FIG. In addition, since the potential of the plasma 14 facing the first electrode 21 is also dragged by the potential of the first electrode 21 and rises, the potential difference ΔV is not so small, which is the reason why the ion current density cannot be lowered so much. Is considered to be.

On the other hand, in this embodiment, as described above, the positive control voltage VS is applied to the second electrode 22 with the plasma source portion 4 as a reference. The potential of 22 does not affect the potential of the plasma 14 because the first electrode 21 whose potential is fixed by the bias voltage VB exists between them. Therefore, the potential of the second electrode 22 can be brought closer to the potential of the plasma 14 or higher than the potential of the plasma 14 by the control voltage VS. In the example of FIG. 2, the plasma 14 and the second electrode 22
The potential difference .DELTA.V 'between and is almost zero. This second electrode 2
Since the electric potential of 2 becomes a barrier for extracting ions from the plasma 14, the ion beam 4 extracted from the ion source 2 is increased by increasing the electric potential of the second electrode 22 as described above.
The lower limit of the ion current density of 0 can be made smaller than in the case of the preceding example, and the ion beam 40 having a lower density can be extracted.

FIG. 3 shows an example of the actual measurement result of the relationship between the control voltage VS and the ion current density. The high frequency power applied to the ion source 2 is 10 W and the output voltage V1 is 1.
This is when 0 kV and the output voltage V3 is 0.2 kV. From this figure, it is possible to control the ion current density by the control voltage VS. For example, if the control voltage VS is set to about 80 V or more, the ion current density can be made smaller than in the case of the preceding example and can be reduced to 0. I understand.

It is also understood from FIG. 3 that the bias voltage VB is increased so that the slope of the curve becomes gentler, and thus the control of the ion current density by the control voltage VS is easier.

As described above, the ion current density of the ion beam 40 extracted from the ion source 2 can be made smaller than the lower limit of the prior example, and as a result, the implantation is performed when the low dose implantation is performed on the substrate 46. Since the time can be made longer, the controllability and reproducibility when performing a predetermined dose injection is further improved.

FIGS. 4 to 7 are views showing other examples of the power supply unit constituting the ion beam generator according to the present invention. In either case, the bias power source 3
7, a positive bias voltage VB is applied to the first electrode 21 with reference to the plasma source section 4, and the control power supply 39 applies a positive control voltage VS to the second electrode 22 with reference to the plasma source section 4. Since the ion beam 40 can be extracted in this state, the ion current density of the ion beam 40 can be made smaller than the lower limit of the preceding example, as in the case of the example shown in FIG. Of these,
In the examples of FIGS. 5 to 7, since the potential of the second electrode 22 with respect to the plasma source unit 4 is the sum of the bias voltage VB and the control voltage VS, the output voltage of the control power supply 39 itself is the same as that of FIG. It can be smaller than in the case of the example of FIG.

The output voltage of the control power supply 39, that is, the control voltage VS may be switched between positive and negative to be output. By doing so, the ion current density can be reduced to a low level. Both dose implantation and high dose implantation with increased ion current density can be supported. The former case is as described above, and the latter case will be described here. When the control voltage VS is made negative, the potential distribution in the ion source 2 becomes as shown in FIG.
Since the potential difference ΔV ′ between the plasma 14 and the second electrode 22 becomes large, the ion beam 4 extracted from the ion source 2
The ionic current density of 0 is large and therefore applicable to high dose implants. In this case, the bias voltage VB may be set to 0, for example.

Further, the plasma source portion 4 of the ion source 2
Is not limited to the method of ionizing gas by high frequency discharge to generate plasma 14 as in the above example, but other methods, for example, plasma 14 by ionizing gas by microwave discharge. A method of generating plasma or a method of generating plasma 14 by ionizing gas by DC arc discharge may be used.

Further, the number of electrodes constituting the extraction electrode system 20 of the ion source 2 is not limited to four as in the above example, and a plurality of other electrodes, for example, two, three,
5 or the like may be used.

[0041]

As described above, according to the present invention, the potential of the second electrode is brought closer to or higher than the potential of the plasma in the plasma source section by the positive control voltage output from the control power source. Therefore, the lower limit of the ion current density of the ion beam extracted from the ion source can be made smaller than in the case of the preceding example, and the ion beam of lower density can be extracted.

Therefore, if such an ion beam generator is used for ion implantation, for example, it is possible to prolong the implantation time when performing low dose implantation on a substrate, and thus when performing a predetermined dose implantation. The controllability and reproducibility of is further improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of an ion implantation apparatus using an ion beam generator according to the present invention.

FIG. 2 is a diagram showing an example of potential distribution in the ion source in FIG.

FIG. 3 is a diagram showing an example of an actual measurement result of the relationship between the control voltage applied to the ion source in FIG. 1 and the ion current density.

FIG. 4 is a diagram showing another example of a power supply device that constitutes the ion beam generator according to the present invention.

FIG. 5 is a diagram showing another example of a power supply device constituting the ion beam generator according to the present invention.

FIG. 6 is a diagram showing another example of a power supply device that constitutes the ion beam generator according to the present invention.

FIG. 7 is a diagram showing another example of a power supply device that constitutes the ion beam generator according to the present invention.

8 is a diagram showing an example of a potential distribution in the ion source in FIG. 1 when high dose implantation is performed.

FIG. 9 is a cross-sectional view showing an example of an ion implanter using a conventional ion beam generator.

10 is a schematic diagram showing an example of a relationship between input power and ion current density in the ion source in FIG.

FIG. 11 is a cross-sectional view showing an example of an ion implantation apparatus using the ion beam generator of the preceding example.

FIG. 12 is a diagram showing an example of an actual measurement result of the relationship between the bias voltage applied to the ion source in FIG. 11 and the ion current density.

FIG. 13 is a diagram showing an example of potential distribution when the bias voltage is small in the ion source in FIG.

FIG. 14 is a diagram showing an example of potential distribution when the bias voltage is increased in the ion source in FIG.

[Explanation of symbols]

 2 Ion Source 4 Plasma Source Section 6 Plasma Generation Container 14 Plasma 16 High Frequency Power Supply 20 Extraction Electrode System 21 First Electrode 22 Second Electrode 23 Third Electrode 24 Fourth Electrode 30b Power Supply 31 First Power Supply 33 Third Power Supply 37 Bias Power Supply 39 Control power supply 40 Ion beam 42 Processing chamber 46 Substrate 50 Insulator

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location H01L 21/203 H01L 21/203 Z 21/22 21/22 E 21/265 21/265 FD

Claims (1)

[Claims] 1. A plasma source part for introducing a gas and ionizing it by discharge to generate plasma, and an ion beam for extracting the ion beam from the plasma in the plasma source part by the action of an electric field, the extractor having a plurality of electrodes. In an ion beam generator including an ion source having an electrode system and a power supply device for applying a voltage for extracting an ion beam to an electrode forming an extraction electrode system of the ion source, the extraction electrode system is configured in the ion source. An insulating material is provided between the first electrode on the most plasma side of the electrodes and the plasma source portion to electrically insulate them from each other, and the power supply device supplies the plasma source to the first electrode. A DC bias power source for applying a positive bias voltage with reference to the second portion, and a second power supply immediately downstream of the first electrode.
An ion beam generator comprising: an electrode; and a direct current control power supply for applying a positive control voltage based on the plasma source portion.