JP3244883B2 - Ion implantation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion implantation method for irradiating, for example, a silicon substrate made of a semiconductor material with an ion beam to implant a predetermined element.

[0002]

2. Description of the Related Art Conventionally, high voltage, high frequency,
2. Description of the Related Art There is known an ion implantation method in which a plasma is generated by a microwave or the like, ions generated are focused, a specific energy is given to the surface of a sample as an object to be processed by using an ion accelerating tube or the like, and the beam is irradiated. .

For example, as a method of implanting boron (B) into the extreme surface of a silicon (Si) -based semiconductor,
In order to inject boron uniformly in a short time, the material gas (BF
₃ ) is made into plasma by high voltage, high frequency or microwave, etc., and BF ₂ and BF ion beam generated are irradiated and injected into the sample surface. In this case, fluorine (F) is also implanted into the material as an impurity at the same time as boron.
That would have a significant effect on its properties.

In order to overcome such a problem of impurities, the energy of implanted ions is reduced to several KeV so that only boron is implanted into the pole surface. In this case, it becomes difficult to uniformly implant the implanted ions into the implanted region on the surface of the sample, which results in inhomogeneous material characteristics in the plane. Further, in order to overcome the problem of impurities and non-uniformity in the plane, implantation of molecular ions such as B ₂ is performed using a usual ion implantation apparatus. In this case, since the absolute amount of generated ions is extremely small, the time required for implantation becomes extremely long, which is not practical.

[0005]

As described above, in the conventional implantation method, when ions are implanted into the extreme surface of the material to be implanted, unnecessary elements are contained and the implantation in the implantation region is not performed. Problems such as non-uniformity and long injection time could not be avoided.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is intended to prevent unnecessary elements from being mixed at the time of ion implantation into the extreme surface of a material to be implanted and to make the implantation uniform in the implantation region. It is another object of the present invention to provide an ion implantation method capable of shortening the implantation time.

[0007]

In order to achieve the above object, the present invention is to generate ions from an ion source, convert the ions into a beam, irradiate the object, and implant a predetermined element into the object. In the ion implantation method, the ion source includes a constituent element and a predetermined element included in a material forming the object to be processed as constituent elements.

[0008]

According to the ion implantation method of the present invention, the ion source is converted into an ion beam by converting the constituent elements of the ion source into the predetermined elements to be implanted with the constituent elements contained in the material forming the object to be processed. In addition, when the predetermined element is injected into the object, unnecessary elements can be prevented from being mixed.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an outline of the present invention will be described. That is,
The present invention relates to an ion implantation method in which an impurity is implanted into a material surface, for example, by using an ion source material having a main component element of the implantation target material and the implantation element as a constituent element, and converting the main component element and the implantation element of the implantation target material to It is characterized by irradiating a molecular beam as follows.

As the ion generation method, a sputter ion method and a gas ionization method of high frequency, microwave, high voltage or the like are used. In the sputter ion implantation method, the sputter ion energy is 2 sputter ions.
KeV to ₂₀ KeV O ₂ ⁺ ion, O ⁻ ion, Cs
⁺ Ions or F ₂ ⁺ ions are used. Various ionization methods are used in a gas ion source.

As the ion source, a material (gas) containing the main component element of the material to be implanted and the implanted element as a constituent element is used, and a molecular beam containing the main component element of the material to be implanted and the implanted element as a constituent element is used as the implanted ions. Used. The number of atoms of the molecular ions is preferably in the range of 1 to 150. Further, in order to increase the generation efficiency of the molecular ions depending on the molecular ions, the O ₂ concentration, the F ₂ concentration, and other gas concentrations in the atmosphere where the ion source material exists are set to 1 × 10 ⁻² Torr.
１1 × 10 ⁻⁹ Torr. The energy of the generated ions is 1 KeV to 530 KeV.

For example, as a sputter ion implantation method for implanting boron into the surface of a silicon substrate, the initial degree of vacuum is set to 1 × 10 ^-5 to 1 × 10 ^-12 Torr. O ₂ ⁺ sputter ion energy 1~20KeV the sputter ion, ^O -, Cs ^+, with other ions, sintering a powder consisting of silicon and boron ₄ such SiB the ion source,
Alternatively, using a solidified material by another method, the partial pressure of gas such as oxygen on the surface of the ion source is set to 1 × 10 ⁻² to 1 × 10 ^2
-9 Torr. In addition, a molecular ion consisting of silicon and boron, such as SiB ^{+, which is} generated, is ion-accelerated by 1 to 5 with an ion accelerator.
A voltage of 30 KeV is applied, the diameter of the ion beam is reduced to about 0.1 μm to 1000 mm by an electrostatic lens, rastering is performed, the surface of the sample is scanned, and the surface is injected.

It took about 10 minutes to implant 1 × 10 ¹⁵ atoms / cm ² by this method. No elements other than silicon and boron were found. Other implanted ions include SiB ₂ ⁺ , Si ₂ B ⁺ , SiB ₃ ⁺ , and Si ₃ B
Molecular ions composed of silicon and boron such as ⁺ can be applied.

In the case of the sputter ion implantation method for implanting nitrogen into the surface of the stainless steel substrate, the initial vacuum degree is 1 × 1
0 ^-5 to 1 × 10 ^-12 Torr. O ₂ ⁺ having a sputter ion energy of 1 to 20 KeV and other ions are used as sputter ions, and a sintered material of Fe ₂ N powder is used as an ion source. The partial pressure of gas such as oxygen on the surface of the ion source is 1 ×.
10 ⁻² to 1 × 10 ⁻⁹ Torr. Generated Fe ₂ N
⁺ Molecular ions composed of iron (Fe) and nitrogen, such as applying a voltage of 1KeV~530KeV by ion accelerating tube, 0.1Myuemu～100 the diameter of the ion beam by an electrostatic lens
It is squeezed to about 0 mm, rastered and injected into the sample surface.
Other than the implanted ions, FeN ₂ ⁺ , Fe ₂ N ⁺ , Fe
N ₃ ⁺ , Fe ₃ N ⁺ , and other molecular ions can also be used.

In the ion implantation method of implanting Be into a GaAs substrate, the initial degree of vacuum is 1 × 10 ⁻⁵ to 1 ×.
10 ^-12 Torr. Be and G for sputter ion source
Acceleration voltage of 1 to 3
The gas partial pressure of fluorine or the like on the surface of the sputter ion source is set to 1 × 10 ⁻² to 1 × 10 ⁻⁹ Torr by using 20 KeV Cs ⁺ or the like.
And Ga such as Ga ₂ Be generated and As and Be
From 1 to 530K by ion accelerator
A voltage of eV is applied, the diameter of the ion beam is reduced to about 0.1 μm to 1000 mm by an electrostatic lens, rasterized and injected into the sample surface.

In order to implant boron into the extreme surface of the silicon substrate, the initial degree of vacuum is set to 1 × 10 ⁻⁵ by ion implantation.
１1 × 10 ⁻¹² Torr. Using a mixed gas of B ₂ H ₆ , SiH _4, and O _{2 as} an ion source, Si ₂ B ions and other molecular ions generated by ionization of various gas ions are applied to a voltage of 1 to 530 KeV by an ion accelerator. And the diameter of the ion beam is 1μ by the electrostatic lens.
The drawing raster is drawn to about m to 1000 mm, and it is injected into the sample surface.

The implanted molecular ions according to the present invention are several times to several tens times heavier than normal implanted ions, so that they are implanted to a depth of several tenths to several tenths at the same energy. For example, when boron is implanted into silicon, at an acceleration voltage of 20 KeV, ordinary boron ions and BSi ₂ ions are implanted to a depth of 66 nm from the surface, and BSi ions are implanted to a depth of 15 nm (see FIG. 11). ).

In addition, since there is no unnecessary element in the constituent elements of the molecular ion, excellent characteristics can be obtained. In addition, by controlling the partial pressure of gas such as O ₂ in the ion source, the amount of generated ions is dramatically increased, so that the ions can be implanted in a short time.
For example, when the O ₂ partial pressure on the surface of the sputter ion source is very low (vacuum degree 1 × 10 ⁻⁹ ) and when the oxygen partial pressure is appropriate (vacuum degree 1 × 10 ⁻⁶ ), the ion implantation time is ^short. It differs by about one digit (see FIG. 12).

An embodiment according to the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing the configuration of the ion implantation apparatus according to the present invention. In the present embodiment, a case where boron is implanted into the extreme surface of the silicon substrate will be described as an example. In addition, sputter ion energy of 15 Ke
It is assumed that O ₂ ⁺ ions of V are used.

First, the interior of the sputtering unit 11 is set to an initial degree of vacuum of 1 × 10 ⁻⁹ Torr. A sputter ion source 13 obtained by sintering SiB ₄ powder is disposed inside the sputter unit 11, and the oxygen concentration on the surface of the ion source is 5 × 10
^-4 Torr.

A sputter ion gas box 15 and a sputter ion power supply 17 are connected to a sputter ion gun 19, and ions generated by the sputter ion gun 19 are
It is accelerated by the sputter ion acceleration unit 21 and
It is emitted toward the internal sputter ion source 13. Thus ions are generated from the sputtering ion source 13, Si ₂ separated according to their mass by the mass separation magnet 23 B ⁺
The ions are accelerated by an ion acceleration unit 25 to which 20 KeV is applied. Thereafter, a predetermined beam diameter is reduced by the electrostatic quadrupole lens 27, and in this embodiment, the diameter of the ion beam is reduced to about 10 mm, further deflected by the Y scan plate 29 and the X scan plate 31, and arranged in the vacuum transfer system 33. The surface of the sample S thus scanned is scanned, and ion implantation is performed.

It took about 10 minutes to implant 1 × 10 ¹⁵ atoms / cm ² by this method. This is about 80% of the time when a normal method is used, for example, when BF molecular ions are implanted. The sample S prepared by this method was analyzed by a secondary ion mass spectrometer (SIMS). This is shown in FIG. Referring to FIG. 2, the profile of boron shown by a solid line draws a Gaussian curve, and a peak position is obtained at a depth of about 50 nm. It can be seen that a large amount of boron exists at a depth of 50 nm. The peak observed at a depth of about 0 to 10 nm is caused by contamination of boron and fluorine on the surface. Also, fluorine does not exist at a depth of 10 nm or more,
Elements other than silicon and boron are not recognized.

When the BF ion implanted by the conventional method is analyzed by SIMS (see FIG. 3),
The profile of boron draws a Gaussian curve, but the peak position is about 80 nm. It can be seen that boron is present at a depth of 80 nm and fluorine is present at a location of 60 nm. The peak area of boron and fluorine is BF ₂ .

Next, a case where nitrogen is implanted into the surface of a stainless (SUS304) substrate in the same manner as the case where FeN ⁺ ions are implanted into stainless steel using the implantation apparatus shown in FIG. 1 will be described. O ₂ ⁺ ions having a sputter ion energy of 20 KeV are used as sputter ions, and a sputter ion source 13 obtained by sintering Fe ₂ N powder is used. First, the inside of the sputtering unit 11 is set to an initial degree of vacuum of 1 × 10 ⁻⁹ Torr. At this time, the oxygen concentration on the ion source surface is 7 × 10 ⁻⁴ Torr. The generated Fe ₂ N ⁺ ions are subjected to 40K by the ion accelerator 25.
The ion beam is accelerated by applying a voltage of eV, the diameter of the ion beam is reduced to about 30 mm by the electrostatic quadrupole lens 27, further deflected by the Y scan plate 29 and the X scan plate 31, and arranged in the vacuum transfer system 33. The surface of the sample S is scanned, and ion implantation is performed.

It took about one hour to implant 1 × 10 ¹⁷ atoms / cm ² by this method. This is about 40% of the time when a normal method is used, for example, when nitrogen ions are implanted. The sample prepared by this method was analyzed by a secondary ion mass spectrometer (SIMS). This is shown in FIG. Referring to FIG. 4, the profile of nitrogen shown by a solid line draws a Gaussian curve, and a peak position is obtained at a depth of about 5 nm. It can be seen that a large amount of nitrogen exists at a depth of 5 nm.

Further, when nitrogen ions are implanted by a conventional method and analyzed by SIMS (see FIG. 5),
Although the profile of nitrogen draws a Gaussian curve, the peak position is about 60 nm, and it can be seen that nitrogen exists a lot at a depth of 60 nm.

Next, GaAs is formed using the apparatus shown in FIG.
An example in which GaBe ⁺ ions are implanted therein will be described.
In addition, Cs ⁺ having an acceleration voltage of 15 KeV is used as sputter ions. First, the inside of the sputtering unit 11 is set to an initial vacuum degree of 2 ×
10 ^-9 Torr. In the inside of the sputtering unit 11, B
A sputter ion source 13, which is a sintered body of e and GaAs, is provided. At this time, the fluorine concentration on the surface of the sputter ion source is 1 × 10 ⁻⁶ Torr. The generated Ga ₂ Be ions are accelerated by applying a voltage of 30 KeV by the ion-ion accelerating unit 21, the diameter of the ion beam is reduced to about 40 mm by the electrostatic quadrupole lens 27, the sample is scanned with a raster, and the GaBe is scanned. ⁺ Ions are implanted. It took about 15 minutes to implant 1 × 10 ¹⁴ atoms / cm ² by this method.

This is about 60% of the time when a normal method is used, for example, when Be ions are implanted. The sample prepared by this method was analyzed by a secondary ion mass spectrometer (SIMS). This is shown in FIG. Beryllium (Be)
Shows a Gaussian curve, a peak position is obtained at a depth of about 15 nm, and it can be seen that a large amount of beryllium exists at a depth of 15 nm.

When a Be ion-implanted sample is analyzed by SIMS according to the conventional method (see FIG. 7), the profile of Be draws a Gaussian curve, but the peak position is 120.
nm, and it can be seen that beryllium is often present at a depth of 120 nm.

Next, an ion implantation apparatus having the structure shown in FIG. 8 will be described as an example. A sputter ion source 43, a sputter ion gas box 45, a sputter ion power supply 47, and a mass separation magnet 53 are provided inside the sputter section 41, and the inside thereof is set to an initial degree of vacuum of 2 × 10 ⁻⁹ Torr. The sputter ion gas box 45 contains a mixed gas of B ₂ H ₄ , SiH ₄ and O ₂ .

The mixed gas is led to a sputter ion source 43, and gas ionization is performed by a high voltage by a sputter ion power supply 47 which is a high voltage power supply. The generated ions are separated into Si ₂ B ions by the mass separation magnet 53. The separated Si ₂ B ions are accelerated by an ion acceleration unit 55 to which 20 KeV is applied. Subsequently, the accelerated ion beam is narrowed by an electrostatic quadrupole lens 57 to a predetermined beam diameter, here about 10 mm, and then deflected by a Y scan plate 59 and an X scan plate 61, and the vacuum transfer system 63. , A predetermined position of a silicon wafer, for example, a silicon wafer, is scanned and injected into the surface of the sample.

It took about 10 minutes to implant 1 × 10 ¹⁴ atoms / cm ² by this method. This is about 70% of the time in a usual method, for example, boron ion implantation. The sample S prepared by this method was analyzed by a secondary ion mass spectrometer (SIMS). This is shown in FIG. Referring to FIG. 9, the profile of boron shown by a solid line draws a Gaussian curve, and a peak position is obtained at a depth of about 50 nm.

When the BF ₂ ions implanted by the conventional method were analyzed by SIMS (see FIG. 10), the profile of boron showed a Gaussian curve, but the peak position was about 80 nm. Fluorine was also detected as an impurity.

[0034]

As described above, according to the ion implantation method of the present invention, unnecessary elements can be prevented from being mixed at the time of ion implantation into the extremely surface of the object to be processed, and the implantation time can be shortened.

[Brief description of the drawings]

FIG. 1 is a configuration diagram for explaining a configuration of an ion implantation apparatus for implanting ions into silicon.

FIG. 2 is a diagram showing a SIMS profile at the time of Si ₂ B ⁺ ion implantation.

FIG. 3 is a diagram showing a SIMS profile at the time of BF ⁺ ion implantation.

FIG. 4 is a diagram showing a SIMS profile during FeN ⁺ ion implantation.

FIG. 5 is a diagram showing a SIMS profile at the time of N ⁺ ion implantation.

FIG. 6 is a diagram showing a SIMS profile at the time of Ga ₂ Be ⁺ ion implantation.

FIG. 7 is a diagram showing a SIMS profile at the time of Be ⁺ ion implantation.

FIG. 8 is a configuration diagram showing a configuration of an ion implantation apparatus for implanting ions into silicon.

FIG. 9 is a diagram showing a SIMS profile at the time of Si ₂ B ⁺ ion implantation.

FIG. 10 is a diagram showing a SIMS profile at the time of BF ₂ ⁺ ion implantation.

FIG. 11 is a diagram showing a boron profile.

FIG. 12 is a diagram showing the relationship between the partial pressure of O ₂ and the injection time.

[Explanation of symbols]

 11, 41 Sputter section 13, 43 Sputter ion source 15, 45 Sputter ion gas box 17, 47 Sputter ion power supply 19 Sputter ion gun 21 Sputter ion accelerating section 23, 53 Mass separation magnet 25, 55 Ion accelerating section 27, 57 Static Electric quadrupole lens 29,59 Y scan plate 31,61 X scan plate 33,63 Vacuum transfer system S sample

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-163431 (JP, A) JP-A-4-358074 (JP, A) JP-A-62-1100933 (JP, A) JP-A-59-1988 149643 (JP, A) JP-A-3-209721 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/265 H01L 21/265 603

Claims (1)

(57) [Claims] In an ion implantation method in which ions are generated from an ion source, the ions are formed into a beam, and irradiating the object to be processed, and a predetermined element is implanted into the object to be processed, An ion implantation method, wherein a component element contained in a constituent material and the predetermined element are set as constituent elements.