JP2003347234A - Method of manufacturing iii nitride film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a high-quality single-crystal III nitride film causing little dislocation. <P>SOLUTION: A method of manufacturing the III nitride film (gallium nitride film etc.), includes a step (1) of growing the III nitride film on a substrate composed of a material (sapphire etc.), having a different lattice constant than the nitride film has, a step (2) of implanting ions into the nitride film so that the degree of crystallization of the ion-implanted region of the nitride film becomes 25-75%, and a step (3) of heat-treating the nitride film after the ions are implanted. When the steps (1) to (3) are performed, a high-quality single- crystal film can be formed in the ion-implanted region 26 of the nitride film 22 shown in the figure. <P>COPYRIGHT: (C)2004,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing or treating a group III nitride, and a method for producing a semiconductor device using a group III nitride produced or treated by the method.

[0002]

2. Description of the Related Art A layer made of a first material is grown on a substrate made of a second material having a different lattice constant from that of the first material. In this case, dislocations (linear defects) occur in the stacked first material layers due to the mismatch of lattice constants. Such dislocations reduce the performance of the semiconductor device formed in the first material layer or the like, and therefore, it is desired to reduce the dislocations as much as possible. The group III nitride used as the first material described above is a material useful for forming a semiconductor device such as an electronic device or an optical device.
Gallium nitride, which is a typical group III nitride, can provide a crystal layer with a small thickness even when grown without an underlying substrate. Therefore, gallium nitride is generally heteroepitaxially grown on a sapphire substrate corresponding to the above-mentioned second material. However, since the lattice constant of the gallium nitride film is significantly different from that of the sapphire substrate, dislocation occurs in the gallium nitride film grown on the sapphire substrate, and the dislocation density may be 10 ⁹ cm ⁻² or more.

As a technique aimed at reducing such dislocations, there is a method described in Japanese Patent Application Laid-Open No. 10-294281. This method has the following steps (1) to (3). (1) A layer made of a first material is grown on a substrate made of a second material having a different lattice constant from that of the first material. (2) Ions are implanted into the grown layer made of the first material so that the implanted region becomes amorphous. (3) Heat-treat the layer made of the first material after the ion implantation.

[0004]

SUMMARY OF THE INVENTION
This method is used as a processing method when the material is silicon, but when the first material is a group III nitride,
It is not an appropriate method to reduce dislocations in group II nitrides. That is, when the first material is a group III nitride, even if the group III nitride film is ion-implanted so that the implanted region becomes amorphous and the group III nitride film after the ion implantation is heat-treated, There is a problem that the material is not crystallized and stays in a polycrystalline state. This is considered to be mainly because the group III nitride has a different crystal structure from silicon, and the group III nitride is less likely to move atoms when heated than the silicon. In the case where the group III nitride film is in a polycrystalline state, it is a previous problem whether dislocations can be reduced,
It is difficult to form a high-performance semiconductor device using the group III nitride film. In order to realize a high-performance semiconductor device, the group III nitride film is in a single crystal state,
In addition, it is required to be of high quality with few dislocations.

[0005] The present invention relates to a high-quality single crystal having few dislocations.
It is intended to realize a group III nitride film.

[0006]

Means for Solving the Problems, Functions and Effects A method embodying the present invention has the following steps (1) to (3). (1) A group III nitride film is grown on a substrate made of a material having a different lattice constant from the group III nitride film. (2) Ions are implanted into the grown group III nitride film so that the crystallization ratio of the implanted region is 25% or more and 75% or less. (3) A heat treatment is performed on the group III nitride film after the ion implantation.

In the method of the present invention, ions are implanted into the group III nitride film, but the ions are not implanted until the implanted region becomes amorphous, and the crystallization rate of the implanted region is 25% or more.
A major feature is that ion implantation is performed so as to be 5% or less. As a result of intensive studies conducted by the present inventors, the dislocation-induced III-nitride film stacked on a substrate made of a material having a different lattice constant from that of the III-nitride film was crystallized in the implantation region. By implanting ions so that the rate becomes 25% or more and 75% or less and heat-treating the III-nitride film after the ion implantation, the III-nitride film in the ion-implanted region can be monocrystallized, In addition, they have found that a group III nitride film in which dislocations are significantly reduced as compared to before the method of the present invention is performed can be realized.

The method of the present invention differs from the above-mentioned conventional method in the basic technical idea. In the conventional method, ions are implanted into the group III nitride film until the implantation region becomes amorphous. This is based on the idea that, as an image, the atomic arrangement of the implanted region is dissociated, and dislocations are dissociated and eliminated. In some cases, heat treatment is performed to recrystallize an amorphous region. However, in the case of a group III nitride film, even if heat treatment is performed, the amorphous region remains in the polycrystalline state as described above, and is not single-crystallized.

On the other hand, according to the method of the present invention, the crystallization ratio of the ion-implanted region is 25% or more and 75% or less in the group III nitride film.
Ion implantation is performed at the following dose. Then
The implanted region does not fall apart as compared with the amorphous state, and a state where atoms are arranged to some extent is maintained.
As a result, in the state after the ion implantation and before the heat treatment, most dislocations in the implantation region remain. In addition, as a result of the injected ions colliding with a group III element or nitrogen constituting the group III nitride film, vacancies of group III elements or vacancies of nitrogen (vacancy type defects) are successively formed. Of these holes,
The vacancies introduced near dislocations in the ion implantation region serve to terminate the dislocations in the implantation region. Specifically, these vacancies stick to unbonded hands of atoms located near the dislocation or enter between atoms located near the dislocation.

When heat treatment is performed on the group III nitride film after the ion implantation, the holes of the group III element or the holes of nitrogen are diffused by the heat. When the vacancy of the group III element or the vacancy of nitrogen near the dislocation in the ion implantation region diffuses, the atomic position near the dislocation is reconstructed, and many of the dislocation in the ion implantation region disappear. In this embodiment, the ions are implanted so that the crystallization ratio of the implantation region is 25% or more and 75% or less. That is, ions are implanted so that the implanted region is not made more discrete than the amorphous state, and a state in which atoms are aligned to some extent is maintained. Therefore, even if the constituent atoms of the group III nitride are hard to move even when heat is applied, the heat treatment performs the heat treatment, so that the implanted region does not remain in the polycrystalline state but becomes single-crystallized.

Therefore, according to the method of the present invention, a high-quality single-crystal group III nitride film having few dislocations can be realized.

According to the method for treating a group III nitride film according to the twelfth aspect, the same operation and effect as those of the manufacturing method according to the first aspect can be obtained. In addition, it is needless to say that the methods of claims 2 to 11, which are improvements of the manufacturing method of claim 1, can be similarly applied as an improvement (dependent claim) of the processing method of claim 12.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, Embodiment III of the present invention
A method (processing method) for forming a group nitride film will be described. First,
As shown in FIG. 1, a group III nitride film 22 is grown on a substrate 20 made of a material having a different lattice constant from that of the group III nitride film 22 (heteroepitaxial growth). Dislocations (linear defects) 24 occur in the group III nitride film 22 due to the mismatch of the lattice constants. Gallium nitride (GaN), boron nitride (B
N), aluminum nitride (AlN), indium nitride (InN), and the like. As a material of the substrate 20,
Sapphire (Al ₂ O ₃ ), silicon carbide (SiC),
A material such as NGO (NdGaO ₃ perovskite) capable of heteroepitaxially growing the group III nitride 22 is used. The growth of the group III nitride film 22 on the substrate 20
It may be performed by various known methods such as an OVPE (metal organic chemical vapor deposition) method and an MBE (molecular beam epitaxy) method.

Thereafter, as shown in FIG. 2, a predetermined element ion is implanted into the group III nitride film 22 grown on the substrate 20 so that the crystallization ratio of the ion-implanted region becomes 25% or more and 75% or less. The ions are implanted at a predetermined dose and with a predetermined dose. Then, the implanted region 26 does not fall apart as compared with the amorphous state, and a state where atoms are aligned to some extent is maintained. As a result, in the state after the ion implantation and before the heat treatment, most of the dislocations 24 in the implantation region 26 remain. Further, as a result of the implanted ions collided with a group III element or nitrogen constituting the group III nitride film,
One after another, a vacancy 28 of a group III element or a vacancy 30 of nitrogen (vacancy type defect) is formed. Of these holes 28 and 30, the holes introduced near the dislocations 24 in the ion implantation region 26 work to terminate the dislocations 24 in the implantation region 26.
Specifically, these holes 28, 30
It may stick to unbonded hands of atoms located in the vicinity or penetrate between atoms located in the vicinity of dislocation 24. In addition,
These holes 28 and 30 are also introduced near the dislocation 24 in a region deeper than the ion implantation region 26 in the group III nitride film 22.

Thereafter, when heat treatment is performed on the group III nitride film 22 at a predetermined temperature for a predetermined time, the state shown in FIG. 3 is obtained.
Note that reference numeral 34 in FIG. 3 denotes a cap layer 34 described later. The dislocations 24 in the ion implantation region 26 are generated by the heat of the heat treatment.
When the vacancies 28 of the group III element or the vacancies 30 of nitrogen in the vicinity diffuse, the atomic positions near the dislocations 24 are reconstructed, and many of the dislocations in the ion implantation region 26 disappear. In the present embodiment, the crystallization rate of the implantation region 26 is 25% or more and 75% or more.
Ion implantation is performed as follows. That is, the implantation region 26
Is implanted so as to maintain the state in which atoms are aligned to some extent without making the state of the atoms more discrete than the amorphous state. Therefore, even if the constituent atoms of the group III nitride are hard to move even when heat is applied, the heat treatment causes the implanted region 26 to be single crystallized without staying in the polycrystalline state. Therefore, according to the method of the present embodiment, a high-quality single-crystal group III nitride film with few dislocations can be realized in the ion implantation region 26.

Here, in the ion implantation step of FIG.
The type of element ions to be implanted is not limited, but is preferably an element ion that can be introduced into at least one of a group III element lattice site and a nitrogen lattice site. When a heat treatment is performed after the implantation of such element ions, the group III element or nitrogen vacancy, which constitutes a point defect existing before the ion implantation or a point defect (vacancy type defect) caused by the ion implantation, is removed. Ions can be introduced. As a result, since these point defects can be reduced, in addition to dislocations which are linear defects,
A high-quality single-crystal group III nitride film with reduced point defects can be realized.

More preferably, both ions of an element which can be introduced into a lattice site of a group III element and ions of an element which can be introduced into a lattice site of nitrogen are implanted (co-ion implantation). If heat treatment is performed after the implantation of both such element ions, the ions can be introduced into both the group III element and nitrogen vacancies. As a result, an extremely high-quality single-crystal group III nitride film in which point defects as well as dislocations as linear defects are further reduced can be realized.

In this case, the ratio of the dose of the ion of the element which can be introduced into the lattice site of the group III element to the ion of the element which can be introduced into the lattice site of nitrogen is the group III element constituting the group III nitride. It is preferable that the stoichiometric ratio of nitrogen and nitrogen is substantially equal. For example, if the group III nitride is gallium nitride (Ga
In the case of N), since the stoichiometric ratio of gallium to nitrogen is 1: 1, it is preferable that the ratio of the dose amounts of both element ions is also 1: 1. By setting the ratio of the dose amounts of both element ions as described above, element ions can be introduced into group III elements and nitrogen vacancies constituting a point defect at a high ratio, so that defects are further reduced. Thus, a high-quality single-crystal group III nitride film can be realized.

Here, the element ions that can be introduced into the lattice site of the group III element are p ions with respect to the group III element and the group III nitride.
-Type dopant elements (Be, Mg, Ca, etc.), n-type dopant elements (Si, Ge, etc.) for Group III nitrides,
It is preferably an ion of any of semi-insulating elements (Fe, Zn, Cr, P, etc.). The element ions that can be introduced into the nitrogen vacancies are nitrogen and oxygen (n group III nitrides).
It is preferably an ion such as an element of a type dopant). By implanting such element ions, a p-type region, an n-type region, an insulating region, and the like can be formed in the group III nitride film. For this reason, the group III nitride film can function as a semiconductor device having a desired function.

As described above, the dose of the ion implantation is set so that the crystallization ratio of the ion-implanted region becomes 25% or more and 75% or less. In particular, the dose is preferably such that the crystallization ratio of the ion-implanted region is 25% or more and 55% or less. When ions are implanted so that the crystallization ratio is 25% or more and 55% or less, a high-quality single-crystal Group III nitride film with very few dislocations can be realized. The dose for setting the crystallization ratio of the ion-implanted region to 25% or more and 75% or less depends on the type of elemental ions to be implanted and the like.

The acceleration energy for ion implantation is selected according to the depth of the ion implantation region to be formed from the surface of the group III nitride film. Here, it is preferable that the ion implantation be performed with different acceleration energies. For example, when ions are implanted into silicon, even if ions having a certain magnitude of acceleration energy are implanted, the ions diffuse widely into the silicon. However, the compound III
In the case of a group nitride film, implanted ions are unlikely to diffuse widely into the group III nitride film. Therefore, by implanting ions with different magnitudes of acceleration energy of ions as in the present embodiment, even in the case of a group III nitride film, implanted ions can be easily and widely distributed. In this case, a desired dose distribution can be obtained in a desired region by appropriately changing the dose of each ion implantation performed by changing the acceleration energy of the ion implantation.

The heat treatment temperature in the heat treatment step of FIG.
It is preferably at least 00 ° C. Heat treatment temperature 100
If the temperature is 0 degrees or more, diffusion of the vacancies 28 of the group III element and the vacancies 30 of nitrogen introduced near the dislocations 24 is activated. As a result, the reconstruction of the atomic positions near the dislocations 24 is promoted, and the dislocations 24 are likely to disappear. Therefore, dislocation 2
4 is easy to realize a high quality single crystal group III nitride film. Further, the heat treatment temperature is 1100 ° C. or higher and 1400 ° C.
It is more preferable that the temperature is not higher than ° C. Heat treatment temperature 110
When the angle is set to 0 degrees or more and 1400 degrees or less, the movement of the implanted ions is also activated. Therefore, the holes 2 forming the point defect
The introduction of implanted ions into 8, 30 and the like is promoted, and as a result, point defects can be reduced. Therefore, a high-quality single crystal II in which point defects are reduced in addition to the dislocations 24 which are linear defects.
It is easy to realize a group I nitride film.

When the heat treatment temperature is relatively low (about 1000 ° C. to 1100 ° C.), the heat treatment time in the heat treatment step may be about several tens of minutes, or may be longer than one hour. When the heat treatment temperature is higher than that (1100 ° C. or higher), it is preferably 10 minutes or less. When the heat treatment time is set to 10 minutes or less, damage to the group III nitride film is small, and in a short time, a high-quality single crystal can be obtained.
A group III nitride film can be realized. A particularly preferable combination of the heat treatment temperature and the heat treatment time is that the heat treatment temperature is 1250 ° C.
The heat treatment time is about 10 minutes or less, preferably about 5 minutes at about 1350 ° C. When heat treatment is performed under such conditions, a very high-quality single-crystal group III nitride film can be realized.

Further, as shown in FIG. 3, it is preferable to perform the heat treatment step in a state where the surface of the group III nitride film 22 is covered with the cap layer 34. The cap layer 34 is preferably formed of a material having low thermal conductivity. For example, the cap layer 34 is preferably formed of silicon oxide, silicon nitride, aluminum nitride, or the like. By performing the heat treatment step in the state of being covered with the cap layer 34 in this manner, the heat treatment is performed while suppressing the decomposition of the surface region of the group III nitride film 22 (such as nitrogen coming out of the group III nitride film 22). be able to.

Next, the superiority of the method of the present embodiment over the conventional method of treating a group III nitride film, which is different from the method described in [Prior Art], will be described. First, as a method of treating a group III nitride film different from the method described in [Prior Art], there is the following method. A group III nitride film is grown on a sapphire substrate. A mask such as a silicon oxide film is formed over the grown group III nitride film. Next, through a step of applying a resist and a photolithography step, the mask is partially etched to form openings. A new group III nitride film is regrown on the group III nitride film exposed from the opening of the mask. As a result, the regrown group III nitride film grows not only vertically but also horizontally so as to cover the mask. No dislocation basically occurs in the group III nitride film grown laterally on the mask. The above steps are repeated several times.

This conventional method comprises the steps of forming a mask, applying a resist, photolithography, etching,
A series of steps of regrowth of the group III nitride film must be performed. Moreover, these series of steps must be repeated several times. Therefore, the process is very complicated. In addition, in the conventional method, the lateral growth from the left and right sides on the mask toward the center of the mask has been performed.
The group nitride film collides near the center of the mask. As a result, a seam of the group III nitride film is formed near the center of the mask, and dislocation occurs near the seam. Therefore, according to the conventional method, it is difficult to reduce dislocations over the entire group III nitride film, and there are portions where dislocations are partially concentrated. As a result, it is difficult to form a semiconductor device in such a location where dislocations are concentrated, and it is necessary to select a location where dislocations are reduced and form a semiconductor device.

On the other hand, in the method of the present embodiment, the processes of ion implantation and heat treatment are basically performed, so that the process is much simpler than the conventional method. In addition, by reducing dislocations by the processes of ion implantation and heat treatment, dislocations can be reduced uniformly over the entire stacked group III nitride film. For this reason, there is no need to select a portion where dislocations are reduced as in the conventional method to form a semiconductor device, and the grown III-nitride film, or further grown on the III-nitride film, is used. It is possible to form a semiconductor device over the entire epitaxial layer. Therefore, there is obtained a useful effect that a semiconductor device, which has been difficult to form on a group III nitride film processed by a conventional method, can be formed.

Next, three methods for manufacturing a semiconductor device using the group III nitride film manufactured (processed) as described above will be described. In the first manufacturing method, as shown in FIG. 4, the group III nitride film 2 manufactured (processed) as described above is used.
The semiconductor device 36 is formed directly in the second ion implantation region 26.

In the second manufacturing method, first, as shown in FIG. 5, the group III nitride film 2 manufactured (processed) as described above is used.
A group III nitride film is grown again on the second ion-implanted region 26 to form an epitaxial layer 38. Then, FIG.
A semiconductor device 36 is formed on the epitaxial layer 38 as shown in FIG.

In the third manufacturing method, first, similarly to the second method, as shown in FIG.
An epitaxial layer 38 is grown on the ion-implanted region 26 of the group III nitride film 22 thus formed. However, the epitaxial layer 38 is formed thicker than the second method. Then, FIG.
The substrate 20 is removed as shown in FIG. As a result, a freestanding substrate of the group III nitride film 22 is formed. Thereafter, as shown in FIG. 8, a semiconductor device 36 is formed on the epitaxial layer 38 constituting the self-standing substrate of the group III nitride film 22. The reason why the epitaxial layer 38 is formed thick in the third manufacturing method is that, when the substrate 20 is removed as shown in FIG. This is because it is difficult to form the device 36.

As in the first to third manufacturing methods, the semiconductor device 38 is manufactured using the high-quality single-crystal group III nitride film 22 having a small number of dislocations according to the present embodiment, thereby providing a high-performance semiconductor device. A semiconductor device can be realized. Here, the “semiconductor device” includes an electronic device and an optical device. When an electronic device (FET, LSI, etc.) is formed using the group III nitride film of the present embodiment, it is possible to realize a device having good FET characteristics, a high breakdown voltage and a low on-resistance. When an optical device (such as a light emitting diode or a semiconductor laser) is formed using the group III nitride film of the present embodiment, it is possible to realize a device having good emission characteristics and lifetime characteristics or a wide variation range thereof.

[0032]

[Example] MOVP on a sapphire (Al ₂ O ₃ ) substrate
An undoped gallium nitride (GaN) film was grown to a thickness of 4 μm by E (metal organic chemical vapor deposition). The sample in this state is referred to as Sample 1. FIG. 9 shows a TEM (transmission electron microscope) image of Sample 1. It can be seen that the gallium nitride film of FIG. 9 has a large number of dislocations (linear defects) unique to Group III nitrides. The residual dislocation density in this state is about 1 × 10 ⁹ cm ⁻² .

Thereafter, with respect to the sample 1, the dose is 1 at an acceleration energy such that the range (peak position of the implanted ion concentration) becomes 50 nm from the surface of the gallium nitride film.
Germanium ions of × 10 ¹⁵ cm ⁻² were implanted into the gallium nitride film. In this case, the crystallization ratio of the ion implantation region is about 30%. The sample in this state is referred to as Sample 2.

Thereafter, for Sample 2, a cap layer made of a silicon oxide film (SiO ₂ ) was formed to a thickness of 500 nm on the gallium nitride film and capped. Then 130
Heat treatment was performed at 0 ° C. for 5 minutes. The sample in this state is referred to as Sample 4. FIG. 10 shows a TEM image of Sample 4. As shown in FIG. 10, it can be seen that the threading dislocations observed in Sample 1 almost disappeared in the ion-implanted region near the surface of the gallium nitride film. Thus, it can be seen that in Sample 4, a high-quality single crystal layer was obtained.

Further, for another sample 1, germanium ions and nitrogen ions having doses of 1 × 10 ¹⁵ cm ⁻² and gallium nitride film were deposited at an acceleration energy such that the range was 50 nm from the surface of the gallium nitride film. Was injected. In this case, the crystallization rate of the ion implantation region is about 28
%. Note that the mass of nitrogen ions is smaller than the mass of germanium ions. Therefore, the crystallization rate does not change so much as compared with the case where only germanium ions are implanted. Sample 3 in this state
And

Then, for Sample 3, a cap layer made of a silicon oxide film was formed on the gallium nitride film by 500 n.
m and capped. Thereafter, heat treatment was performed at 1300 ° C. for 5 minutes. The sample in this state is referred to as Sample 5.
FIG. 11 shows an overall TEM image of Sample 5, and FIG. 12 shows an enlarged view of the vicinity of the surface. As shown in FIGS. 11 and 12, it can be seen that threading dislocations observed in sample 1 almost disappeared in the ion-implanted region. Sample 5
It can be seen that the contrast of sample No. 4 is smaller than that of sample 4 due to defects. in this way,
It can be seen that Sample 5 into which germanium ions and nitrogen ions were co-ion-implanted had a higher quality single crystal layer than Sample 4.

FIG. 13 shows SIMs for samples 2 to 5.
1 shows the concentration distribution of germanium (Ge) ions obtained by S analysis (secondary ion mass spectrometry) (hereinafter referred to as “germanium distribution”). The vertical axis in FIG. 13 is the concentration of germanium ions or nitrogen ions, and the horizontal axis is the depth from the surface of the gallium nitride film. The upper part of FIG.
4 shows the distribution of germanium. The white square point in the upper part of FIG. 13 is the germanium distribution of Sample 2 (after ion implantation), and the black dot is the germanium distribution of Sample 3 (after heat treatment). In addition, the point which looks like a black square is the point where the above-mentioned white square point and the black circle point overlap. Both the germanium distributions of Samples 2 and 4 show the TRI shown by the solid line.
The distribution substantially matches the germanium distribution calculated by simulation using M (software for calculating the distribution of implanted ions). The lower part of FIG. 13 shows the germanium distribution of Samples 3 and 5. In the nitrogen (N) distribution, only the simulation value by TRIM is shown by a dotted line. The white square in the lower part of FIG. 13 is the germanium distribution of Sample 3 (after the ion implantation), and the black circle is the germanium distribution of Sample 5 (after the heat treatment). Both the germanium distributions of Samples 3 and 5 substantially match the germanium distribution calculated by the simulation using TRIM indicated by the solid line.

FIG. 14 shows positron spectra of Samples 1 to 3. Sample 1 is in a state before ion implantation,
Samples 2 and 3 are in a state after ion implantation. The S parameter shown on the vertical axis has a correlation with the number or size of defects such as gallium vacancies. The larger the S parameter, the larger the number of defects such as gallium vacancies or the larger the size of the defects. The potential energy shown on the horizontal axis has a correlation with the depth of the gallium nitride film and its underlying substrate. The larger the potential energy on the horizontal axis, the closer to the bottom surface of the substrate. The position where the potential energy on the horizontal axis is small (Fig. 1
A region surrounded by a dotted line shown on the left side of the graph of FIG. 4) indicates an ion-implanted region near the surface of gallium nitride.

FIG. 14 shows that the positron spectra of Samples 2 and 3 in the state after the ion implantation are in a range of potential energy of 30 keV or less, that is, approximately equal to those of Sample 1 in the state before the ion implantation. It can be seen that the S parameter is large and the number of vacancy-type defects such as gallium vacancies is large in the entire region of the gallium film. That is, it can be seen that after the ion implantation, the gallium vacancies are introduced not only in the ion implantation region surrounded by the dotted line on the left side of FIG. 14 but also in the entire gallium nitride film.

FIG. 15 shows positron spectra of Samples 1, 4, and 5. Sample 1 is in a state before ion implantation, and samples 4 and 5 are in a state after heat treatment. The contents of the vertical and horizontal axes are the same as in FIG. The region surrounded by the dotted line on the left side of the graph in FIG. 15 is also an ion implantation region, as in FIG.

The positron spectra of Samples 4 and 5 in the state after the heat treatment are shown in the ion-implanted region surrounded by the dotted line on the left side of the graph in FIG. It can be seen that the S parameter has a large and steep distribution as compared with the positron spectrum of No. 3 and No. 3. This indicates that germanium ions were activated by the heat treatment, and a composite defect (large defect) of gallium vacancies and germanium occurred in the ion-implanted region. Also, it can be seen that the S parameter as a whole is larger in a region deeper than the ion-implanted region (region on the right side of the region surrounded by the dotted line in FIG. 15). This indicates that in a region deeper than the ion-implanted region, a large vacancy-type defect in which vacancies such as gallium vacancies are attached to each other occurs.

However, the above is an increase in the S parameter due to the occurrence of a large defect due to the heat treatment, and does not mean that the number of defects has increased due to the heat treatment. That is, the S parameter does not indicate the degree of high quality of the group III nitride film. Rather, when heat treatment is performed, the number of defects such as dislocations and point defects is greatly reduced, and a high-quality single crystal gallium nitride film is realized.

A gallium nitride film can be epitaxially grown again on the gallium nitride films of Samples 4 and 5 after the heat treatment in which dislocations have been significantly reduced to form an epitaxial layer. In addition, by forming the epitaxial growth layer sufficiently thick and then removing the sapphire substrate on which the gallium nitride film is laminated, a freestanding gallium nitride substrate can be manufactured. Dislocations propagated to the epitaxial layer thus formed are very small. Therefore, when a semiconductor device is formed on this epitaxial layer, a high-performance semiconductor device can be realized. In particular, a very high-quality sample 5 having very few dislocations and point defects in the ion-implanted region.
Is very suitable for forming a semiconductor device directly in an ion implantation region. Also in this case, a high-performance semiconductor device can be realized.

FIG. 16 shows the dose of each ion when both germanium ions and nitrogen ions were implanted into the gallium nitride film (co-ion implantation), the crystallization ratio before the heat treatment after the ion implantation, and the crystallization rate after the heat treatment. The measurement results of dislocation density and carrier mobility after heat treatment are shown. The acceleration energy was set to 150 KeV. The heat treatment temperature was 1300 ° C., and the heat treatment time was 5 minutes. The crystallization ratio was measured by the RBS (Rutherford backscattering) method. Dislocation density is TEM
(Transmission electron microscope). The mobility was measured by the Hall measurement method. The hatched portions in FIG. 16 are unmeasured portions. The places where "about" is described in the crystallization ratio are values calculated based on the measurement results and the like.

First, regarding the dislocation density after the heat treatment, when the crystallization ratio after the ion implantation and before the heat treatment is 75% (the dose of each ion is 1 × 10 ¹² cm ⁻² ), the dislocation density is 1 × 10 12 ⁹ cm ^-2 or less, and good results were obtained. The crystallization rate is 52% (dose amount 1 × 10 ¹³ cm)
^-2 ), the dislocation density was 1 × 10 ⁷ cm ⁻² or less, and very good results were obtained. Crystallization rate 28%
Also when the dose was 1 × 10 ¹⁵ cm ⁻² , the dislocation density was 1 × 10 ⁷ cm ⁻² or less, and very good results were obtained. Crystallization rate is 8% (dose amount 1 × 10 ¹⁶ c
It can be said that the case of m ⁻² ) substantially corresponds to the case where ions are implanted so as to make the implanted region amorphous in the method described in [Prior Art]. When the crystallization rate is 8%, the gallium nitride film is in a polycrystalline state even after the heat treatment, and the dislocations are in a state where the dislocations are so many that the dislocations are attached to each other. could not.

The mobility of carriers (electrons in this case) after the heat treatment is an index indicating the degree of high quality of the gallium nitride film. If the mobility is high, it can be said that the number of defects in the gallium nitride film including not only dislocations but also point defects is small. Looking at this carrier mobility in FIG.
Crystallization rate is about 48% (dose amount 2 × 10 ¹³ cm ⁻² )
At 166.6 cm ² / V · S and the crystallization rate is about 40
% (Dose amount 1 × 10 ¹⁴ cm ⁻² )
cm ² / V · S, crystallization rate about 36% (dose amount 3 ×
10 ¹⁴ 78.5cm ² / V · S when the cm ^-2),
Crystallization rate is 28% (dose is 1 × 10 ¹⁵ cm ⁻² )
At that time, it was 57.5 cm ² / V · S, and good results were obtained. This indicates that a very high-quality gallium nitride single crystal film having few point defects in addition to dislocations, which are linear defects, is realized.

FIG. 17 shows the relationship between silicon ions and nitrogen ions.
When both are co-ion implanted into a gallium nitride film,
ON dose and crystallization rate before heat treatment after ion implantation
And the measurement results of the mobility after the heat treatment. Note that acceleration
The energy was 150 KeV. Heat treatment temperature is 1300
° C and the heat treatment time was 5 minutes. The blank in Fig. 18 is not measured
It is a fixed part. The crystallization rate is about 75% (dose 1 × 1
0¹³cm^-2) For 224cm²/ VS, crystal
Conversion rate is about 60% (dose amount 1 × 10¹⁴cm^-2) And
129cm²/ V · S, the crystallization rate is about 40%
1 × 10^Fifteencm^-298.5cm²/
VS, crystallization rate about 30% (dose amount 3 × 10^Fifteenc
m ^-271.1cm²/ V · S, good
Results were obtained. In particular, the crystallization rate is about 40% (dose
Quantity 1 × 10^Fifteencm^-298.5cm mobility when)
²/ V · S, which is a very good result. This
As a result, a very high quality gallium nitride single crystal film has been realized.
You can see that it is.

In FIGS. 16 and 17, the mobility is higher in FIG. 17 even at substantially the same crystallization ratio. This is because the implanted ions are germanium ions in FIG.
In FIG. 7, a capping layer made of a silicon oxide film that covers the gallium nitride film is one of the factors.
Another difference is that it is formed by the n) method, and in FIG. 17 it is formed by the sputtering method. If the silicon oxide film constituting the cap layer is manufactured by the same method, FIG.
It is considered that the difference between the mobility of FIG. 6 and that of FIG. 17 becomes small.

The specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples illustrated above. In addition, the technical elements described in the present specification or the drawings,
The present invention exerts its technical utility alone or in various combinations, and is not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in the present specification or the drawings can simultaneously achieve a plurality of objects, and has technical utility by achieving one of the objects.

[Brief description of the drawings]

FIG. 1 shows a part of a group III nitride manufacturing step (processing step) (1).

FIG. 2 shows a part of a group III nitride manufacturing step (processing step) (2).

FIG. 3 shows a part of a group III nitride manufacturing step (processing step) (3).

FIG. 4 shows a part of a manufacturing step (processing step) in a first manufacturing method of a semiconductor device.

FIG. 5 shows a part of a manufacturing step (processing step) in a second method for manufacturing a semiconductor device (1).

FIG. 6 shows a part of a manufacturing step (processing step) in a second method for manufacturing a semiconductor device (2).

FIG. 7 shows a part of a manufacturing step (processing step) in a third method for manufacturing a semiconductor device (1).

FIG. 8 shows a part of a manufacturing step (processing step) in a third method for manufacturing a semiconductor device (2).

9 shows a TEM (transmission electron microscope) image of Sample 1. FIG.

FIG. 10 shows a TEM image of Sample 4.

11 shows a TEM image of Sample 5. FIG.

FIG. 12 shows an enlarged view of a TEM image of Sample 5.

FIG. 13 shows germanium distributions obtained by SIMS analysis (secondary ion mass spectrometry) of Samples 2 to 5.

FIG. 14 shows positron spectra of Samples 1 to 3.

FIG. 15 shows positron spectra of Samples 1, 4, and 5.

FIG. 16 shows the dose of each ion, the crystallization rate before heat treatment after ion implantation, the dislocation density after heat treatment, and the carrier after heat treatment when both germanium ions and nitrogen ions are implanted into the gallium nitride film. 4 shows the measurement results of mobility.

FIG. 17 shows the dose of each ion when both silicon ions and nitrogen ions are implanted into a gallium nitride film;
The measurement results of the crystallization ratio before the heat treatment after the ion implantation and the carrier mobility after the heat treatment are shown.

[Explanation of symbols]

20: Substrate 22: Group III nitride film 24: Dislocation 26: ion implantation area 28: Group III element vacancy 30: Nitrogen vacancy

   ────────────────────────────────────────────────── ─── Continuation of front page    F term (reference) 4G077 AA04 BE15 CA04 EF01 JA03                       JB07                 5F041 AA40 CA22 CA40 CA46 CA65                       CA71 CA73 CA77                 5F052 AA11 CA04 DA04 DB01 DB06                       EA01 EA15 HA03 HA06 HA08                       JA01 JA07 KA01 KA05

Claims (12)

[Claims] A step of growing a group III nitride film on a substrate made of a material having a different lattice constant from that of the group III nitride film; Rate 2
A method for producing a group III nitride film, comprising: a step of implanting ions so as to have a concentration of 5% or more and 75% or less; and a step of heat-treating the group III nitride film after the ion implantation. 2. The method according to claim 1, wherein the crystallization ratio is 2 in the step of ion implantation.
2. The method for producing a group III nitride film according to claim 1, wherein ions are implanted so as to have a concentration of 5% or more and 55% or less. 3. The method according to claim 1, wherein in the step of implanting ions, ions of an element which can be introduced into at least one of a lattice site of a group III element and a lattice site of nitrogen are implanted. A method for producing a group III nitride film. 4. The step of implanting ions includes implanting both ions of an element which can be introduced into a lattice site of a group III element and ions of an element which can be introduced into a lattice site of nitrogen. 3. The method for producing a group III nitride film according to item 1. 5. The method for producing a group III nitride film according to claim 1, wherein in the step of implanting ions, the ions are implanted with different acceleration energies. 6. The method for producing a group III nitride film according to claim 1, wherein a heat treatment temperature in the heat treatment step is 1000 ° C. or higher. 7. The method for producing a group III nitride film according to claim 6, wherein the heat treatment temperature in the heat treatment step is 1100 ° C. or more and 1400 ° C. or less. 8. The method for producing a group III nitride film according to claim 7, wherein the heat treatment time in the heat treatment step is 10 minutes or less. 9. The heat treatment step is performed with the surface of the group III nitride covered with a cap layer.
9. The method for producing a group III nitride film according to any one of items 1 to 8. 10. A method for manufacturing a semiconductor device, comprising the step of forming a semiconductor device on the group III nitride manufactured by the method according to claim 1. 11. A method for manufacturing a semiconductor device, comprising the steps of: growing an epitaxial layer on a group III nitride manufactured by the method of claim 1; and forming a semiconductor device on the epitaxial layer. . 12. A method for treating a group III nitride film having dislocations, wherein ions are implanted into the group III nitride film so that the crystallization ratio of an implantation region is 25% or more and 75% or less. A method of treating a group III nitride film, comprising: a step of heat-treating the group III nitride film after ion implantation.