JP3222663B2 - Single crystal thin film forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a single crystal thin film on a polycrystalline substrate or an amorphous substrate.

[0002]

2. Description of the Related Art Plasma chemical vapor deposition (plasma CV)
D) is a chemical vapor phase that forms a thin film of a predetermined substance on a substrate at a relatively low temperature by causing a reactive gas to be in a plasma state, generating active radicals and ions, and causing a chemical reaction in an active environment. This is a type of growth method (CVD).
In plasma CVD, various types of films can be formed at a low temperature, so that crystallization can be prevented to form an amorphous film, a non-heat-resistant substrate such as plastic can be used, and reaction with the substrate can be prevented. There are advantages such as being able to. For this reason, plasma CVD is increasingly used mainly in the semiconductor industry.

[0003]

By performing plasma CVD at a temperature at which crystallization proceeds, a single-crystal thin film of a predetermined substance can be epitaxially formed on a single-crystal substrate. However, conventional plasma CV
D has a problem that a single-crystal thin film cannot be formed on a polycrystalline substrate or an amorphous substrate.

The present invention has been made to solve the problems of the conventional plasma CVD.
It is an object of the present invention to provide a single crystal thin film forming method for forming a single crystal thin film on a polycrystalline substrate or an amorphous substrate using VD.

[0005]

According to a first aspect of the present invention, there is provided a method for forming a single crystal thin film on a polycrystalline substrate or an amorphous substrate by using a single crystal of a predetermined substance by a plasma chemical vapor deposition method. A method for forming a thin film, wherein a reaction gas is supplied onto the substrate at a low temperature at which crystallization of the predetermined substance does not occur only by the plasma chemical vapor deposition method, and the single crystal to be formed is simultaneously formed. from a direction perpendicular to the plurality of close-packed crystal plane different from direction of the phase in the thin film, a beam of low energy gas which does not cause sputtering of the prescribed material, irradiated to the substrate, the gas
The body beam is divided into a single beam source and the beam source
A reflector disposed in the path from the source to the substrate.
It is characterized by obtaining .

According to a second aspect of the present invention, there is provided a method for forming a single-crystal thin film, wherein the gas is an inert gas.

According to a third aspect of the present invention, in the method for forming a single crystal thin film according to the second aspect, the atomic weight of the element constituting the inert gas is the same as the atomic weight of the element constituting the predetermined substance. It is characterized by having a lower atomic weight than the maximum.

According to a fourth aspect of the present invention, there is provided a method for forming a single crystal thin film according to the first aspect, wherein the predetermined substance includes an element constituting a gaseous substance which is a gas at normal temperature. The gas beam may be a beam of the gaseous substance.

According to a fifth aspect of the present invention, there is provided a method for forming a single crystal thin film according to the first aspect, wherein the reaction gas includes a reaction gas substance composed of an impurity element to be added to the predetermined substance. It is characterized by the following.

According to a sixth aspect of the present invention, there is provided a method of forming a single crystal thin film according to the fifth aspect, wherein the plurality of types of impurity elements are provided, and each of the plurality of types is one. A plurality of types of reactive gas substances are alternately supplied onto the substrate.

A thin single crystal according to claim 7 according to the present invention.
The film formation method uses plasma chemical vapor deposition
Of a specified substance on a crystalline substrate or amorphous substrate
A method for forming a crystalline thin film, comprising:
The growth method alone does not cause crystallization of the predetermined substance.
At the same time, the reaction gas is supplied onto the substrate under the temperature,
Pluralities with different directions in the single crystal thin film to be formed
From the direction perpendicular to the densest crystal plane of
Low energy gas bubbles that do not cause pattering
The substrate is irradiated onto the substrate, and the predetermined substance is
The gas is neon and the low energy
Is less than 27 eV . According to a eighth aspect of the present invention, in the method of the seventh aspect , the gas beam is arranged on a single beam source and a path from the beam source to the substrate. And a reflector provided.

According to a ninth aspect of the present invention, there is provided a method of forming a single crystal thin film according to the first or eighth aspect , wherein
The beam generation source is an ion generation source for generating the ion beam of the gas, and the reflection plate is a metal reflection plate substantially made of metal.

According to a tenth aspect of the present invention, in the method of the first or eighth aspect , the beam generating source is an electron cyclotron resonance type ion generating source.

[0014]

According to the method of the present invention, a thin film of a predetermined substance is formed on a substrate by plasma enhanced chemical vapor deposition, and a gas beam is simultaneously applied to the thin film from a plurality of directions. Irradiate. The energy of this gaseous beam is such that it does not cause sputtering of the irradiated material, so Bravais
The law of action works. That is, the thin film of the predetermined substance being formed is sequentially converted into a crystal having a crystal orientation such that the plane perpendicular to the beam irradiation direction becomes the closest dense crystal plane. Since a plurality of gas beams are irradiated from directions perpendicular to a plurality of densest crystal planes having different directions, the orientation of the formed crystal is uniquely determined. That is, a single crystal thin film having a uniform crystal orientation is formed. At a temperature at which the crystallization of a given substance proceeds only by plasma enhanced chemical vapor deposition without beam irradiation, the crystal orientation is an arbitrary direction independent of the beam irradiation direction, and the orientation cannot be regulated. In addition, a polycrystal is completed. For this reason, the temperature is adjusted to a low temperature such that crystallization does not proceed only by the plasma chemical vapor deposition method. Furthermore, this
In the method of the present invention, the gas beam irradiating the substrate is
Beam source and a reflector arranged in the path
Directional phase without the need for multiple beam sources.
A gaseous bead from a direction perpendicular to
It is possible to irradiate the system. That is, the present invention
In the method, one beam source with complicated structure is prepared
It suffices to use a single-crystal thin film with a simple device configuration.
Can be formed. Also, if the beam source is 1
It is possible to form a thin film under a high vacuum.
You.

According to the method of the present invention, since the gas to be irradiated is an inert gas, even if atoms or ions of the gas remain in the thin film after the irradiation, they remain in the thin film. There is little adverse effect as an impurity on the electronic properties of the single crystal thin film.

According to the method of the present invention, the atomic weight of the element constituting the inert gas is lower than the maximum atomic weight of the constituent element of the predetermined substance growing as a thin film. Most of the atoms or ions of the irradiated inert gas recoil back at or near the surface of the thin film and hardly remain in the thin film.

<Effect of the Invention According to Claim 4> In the method of the present invention, the irradiated gas contains a constituent element of a substance which grows as a thin film. Therefore, even if atoms or ions of the constituent elements remain in the thin film after irradiation, there is no possibility that these atoms or impurities will adversely affect the single crystal thin film as impurities.

According to the method of the present invention, since the reaction gas contains an impurity element to be added to a substance grown as a thin film, for example, when a semiconductor single crystal thin film is formed, It is possible to form a p-type or n-type semiconductor single crystal thin film. That is, a single crystal thin film to which a desired impurity is added can be formed.

<Operation of the invention according to claim 6> In the method of the present invention, a plurality of types of reactive gas substances each composed of one of a plurality of types of impurity elements are alternately supplied onto the substrate.
For example, in the case of forming a semiconductor single crystal thin film, a plurality of types of single crystals to which respective ones of a plurality of types of impurities are respectively added, such as forming an n type semiconductor single crystal layer on a p type semiconductor single crystal layer. It is possible to form a single crystal thin film having a layer.

<Effect of the Invention According to Claim 7> In the method of the present invention, plasma chemical vapor deposition is used.
While forming a thin film of the specified substance on the substrate,
A thin film is irradiated with a gas beam from a direction. This gaseous
The energy of the
Bravais is a size that does not wake up
The law of action works. That is, the predetermined object being formed
Quality thin film, the surface perpendicular to the beam irradiation direction is the densest crystal
Are sequentially converted into crystals having a crystal orientation
You. The multiple gas beams are combined into multiple beams in different directions.
Irradiation from the direction perpendicular to the dense crystal plane
Thus, the orientation of the formed crystal is uniquely determined. Sand
That is, a single crystal thin film having a uniform crystal orientation is formed. Bee
Predetermined only by plasma enhanced chemical vapor deposition without irradiation
At the temperature where crystallization of the substance proceeds, the crystal orientation is the beam
Any direction unrelated to the irradiation direction of
And polycrystals are completed. others
Therefore, crystallization does not proceed only by plasma-enhanced chemical vapor deposition.
Temperature adjustment to a low temperature is performed. Furthermore, this
In the method of the invention, the gas to be irradiated is an inert gas.
Gas atoms or ions remain in the thin film after irradiation
However, these do not contribute to the electronic properties of single-crystal thin films as impurities.
Less adverse effect. In addition, inert gas
The atomic weight of the forming element is
Irradiation because it is lower than the maximum atomic weight of the constituent elements of the substance
Most of the atoms or ions of the inert gas
Recoils at or near the surface of the film and remains in the thin film
Difficult to do. As a result, a single crystal thin film is easily formed. <Effect of Claim 8 > In the method of the present invention, the gas beam to be irradiated on the substrate is
Since it is obtained by a single beam source and a reflector disposed in the path, the gas is not required from a plurality of beam sources, and the gas is transmitted from a direction perpendicular to a plurality of dense crystal planes having different directions. It is possible to irradiate the beam. That is, in the method of the present invention, it is sufficient to prepare one beam source having a complicated structure, so that a single-crystal thin film can be formed with a simple apparatus configuration. In addition, since only one beam source is required, a thin film can be formed under a high vacuum.

<Operation of the invention according to claim 9 > In the method of the present invention, the beam generating source has an ion generating source for generating a gaseous ion beam, and the reflecting plate is substantially made of metal. It is a board. For this reason, when the gas ion beam generated by the ion source is reflected by the metal reflector, it becomes a neutral beam. Thus, the substrate is irradiated with a parallel beam having a uniform direction. It is also possible to use an electrically insulating insulating substrate as the substrate.

<Operation of the Invention According to Claim 10 > In the method of the present invention, the beam generation source is an electron cyclotron resonance type ion generation source. For this reason, in addition to the high directivity of the ion beam, a neutral beam of high intensity can be obtained at a predetermined distance or more from the ion source without using a means for neutralizing the ions. By reflecting the neutral beam on the reflector and irradiating the substrate with the neutral beam, it is possible to irradiate the substrate with a parallel beam from a plurality of predetermined directions. It is also possible to use an electrically insulating insulating substrate as the substrate.

[0023]

【Example】

<1. Overall Configuration of Apparatus> FIG. 1 is a front sectional view showing a configuration of a single crystal thin film forming apparatus for effectively realizing a single crystal thin film forming method according to an embodiment of the present invention. In this apparatus 100, an electron generator 2 of an electron cyclotron resonance type (ECR) is incorporated in an upper part of a reaction vessel 1. The ECR ion generator 2 includes a plasma container 3 that defines a plasma chamber 4 inside. A magnetic coil 5 for applying a high DC magnetic field to the plasma chamber 4 is provided around the plasma container 3. On an upper surface of the plasma container 3, a waveguide 6 for introducing a microwave into the plasma chamber 4 and an inert gas introducing tube 7 for introducing an inert gas such as Ne are provided.

The reaction vessel 1 defines a reaction chamber 8 therein. The bottom of the plasma container 3 defines, at the center thereof, an outlet 9 through which the plasma passes. The reaction chamber 8 and the plasma chamber 4 communicate with each other via the outlet 9. Inside the reaction chamber 8, the sample table 10 is located just below the outlet 9.
Is installed. A substrate 11 is placed on the sample stage 10, and a reflection plate 12 is installed above the substrate 11. The substrate 11 is a flat plate made of a material having a polycrystalline structure or an amorphous structure, and is one of the elements constituting a sample. A desired single crystal thin film is formed on substrate 11. The reflection plate 12 is preferably made of metal. The sample stage 10 is connected to a rotation drive mechanism (not shown), and is rotatable in a horizontal plane. The sample stage 10 has a structure in which the substrate 11 can be moved horizontally while the reflector 12 is fixed.

A reaction gas supply pipe 13 communicates with the reaction chamber 8. A reaction gas for forming a thin film of a predetermined substance on the substrate 11 by plasma CVD is supplied through the reaction gas supply pipe 13. In the example of FIG. 1, three reaction gas supply pipes 13a, 13b, and 13c are provided. The reaction chamber 8 further communicates with a vacuum exhaust pipe 14. A vacuum device (not shown) is connected to one end of the vacuum exhaust pipe 14, and the gas present in the reaction chamber 8 is exhausted through the vacuum exhaust pipe 14 so that the degree of vacuum in the reaction chamber 8 becomes a predetermined value. Held at the height of A vacuum gauge 15 for indicating the degree of vacuum in the reaction chamber 8 is provided in communication with the reaction chamber 8.

<2. Configuration of Reflector> FIG.
It is a perspective view in an example. The reflection plate 12a is an example of a reflection plate for forming a single crystal having a diamond structure, such as single crystal Si. The reflecting plate 12a defines an opening at the center of the flat base 21. Around this opening, three rectangular blocks 22 are fixedly installed, and inside each of them, a reflecting block 23 is fixed. As a result, an equilateral triangular opening 24 bordered by these reflection blocks 23 is formed at the center of the base 21. In the reflection block 23, the slope 25 facing the opening 24 functions as a reflection surface that reflects the gas beam. Therefore, the inclination angle of the slope 25 is set to an appropriate size in accordance with the direction of the crystal axis of the single crystal to be formed.

FIG. 3 shows a block 22 and a reflection block 2.
3 (a), 3 (b), and 3 (c) are a plan view, a side view, and a front view, respectively. FIG.
As shown in (b), the inclination angle of the slope 25 is 55
Set to ゜. Since the reflection plate 12a does not fix the substrate 11, the substrate 11 can move horizontally relative to the reflection plate 12a. For this reason, it is possible to form a single crystal thin film on the substrate 11 having a large area by moving the substrate 11 horizontally while the reflection plate 12a is fixed to the sample stage 10.

<3. Operation of ECR ion generator 2> FIG.
Returning to, the operation of the ECR ion generator 2 will be described. Ne, A from the inert gas introduction pipe 7 to the plasma chamber 4
Microwaves are simultaneously introduced from the waveguide 6 into the plasma chamber 4 while introducing an inert gas such as r. At the same time, a DC current is supplied to the magnetic coil 5, so that a DC magnetic field is formed in and around the plasma chamber 4. The supplied gas is kept in a plasma state by the action of the microwave and the DC magnetic field. This plasma is generated by high-energy electrons that spirally move according to the principle of a cyclotron by a microwave and a DC magnetic field.

Since these electrons have diamagnetic properties,
It moves to the weaker magnetic field and forms an electron flow along the lines of magnetic force. As a result, in order to maintain electrical neutrality, positive ions also form an ion current along the magnetic field lines along with the electron current. That is, an electron flow and an ion flow are generated from the outlet 9 to the reaction chamber 8 in a downward direction. Since the ion flow flows in parallel with the electron flow, after the deionization time has elapsed,
Recombination with each other results in a neutral atomic flow. Therefore, at a position separated from the outlet 9 by a predetermined distance or more, almost only a neutral atomic flow is formed.

FIG. 4 shows that the ECR ion generator 2
9 is a graph showing the results of actually measuring the relationship between the ion current density and the distance from the outlet 9 when 10 eV Ar ⁺ ions are extracted from the outlet 9. According to this graph,
The ion current density starts to decrease sharply from a distance of 4 to 5 cm from the outlet, and from 1/10 to 1/1 at a position of 14 cm.
It can be seen that the value attenuates to a magnitude of 2. The neutral atom flow is increased by the amount corresponding to the attenuation of the ion current. At a position separated from the outlet 9 by 14 cm or more, almost only the neutral atom current flows downward.

As described above, although the ECR ion generator 2 is an apparatus for generating ions, it forms an ion stream in parallel with the electron stream. There is an advantage that a high-density neutral atomic flow can be easily obtained without using other means for making the particles neutral. In addition, since the ion current is formed in parallel with the electron current, the ion current is not diverged so much, and an ion current similar to a parallel current having a uniform traveling direction can be obtained. In addition, since the parallel ion current is converted into a neutral atomic current, the atomic current also becomes close to a parallel current having a uniform traveling direction.

<4. Operation of Apparatus 100> Returning to FIG. 1, the operation of the apparatus 100 will be described. An example in which the reflecting plate 12a shown in FIGS. 2 and 3 is used as the reflecting plate 12, polycrystalline SiO ₂ (quartz) is used as the substrate 11, and a single-crystal Si thin film is formed on the quartz substrate 11 will be described. SiH ₄ (silane) gas for supplying Si, which is the main material of single crystal Si, B ₂ H ₃ (diborane) gas for doping p-type impurities from each of the reaction gas supply pipes 13a, 13b, and 13c; PH ₃ (phosphine) gas for doping n-type impurities is supplied.
As the inert gas introduced from the inert gas introduction pipe 7, a Ne gas having a smaller atomic weight than Si atoms is preferably selected.

By the operation of the ECR ion generator 2, a Ne ⁺ ion current and an electron current are formed downward from the outlet 9. The distance from the outlet 9 to the reflector 12a (12) is preferably set to be large enough to convert the Ne ⁺ ion stream to a nearly neutral Ne atom stream. Further, the reflection plate 12a (12) is a Ne
It is installed at the position where the atomic flow falls. Reaction gas supply pipe 1
The silane gas supplied from 3 is struck toward the SiO ₂ substrate 11 by the Ne ⁺ ion flow or the Ne atomic flow. As a result, the plasma CVD reaction proceeds on the upper surface of the SiO ₂ substrate 11, and a thin film containing Si supplied by the silane gas, that is, a Si thin film grows. In addition, by supplying diborane gas or phosphine gas while adjusting the flow rate thereof appropriately, the plasma CVD reaction using these gases simultaneously proceeds, and a Si thin film containing B (boron) or P (phosphorus) at a desired concentration. Is formed.

The SiO ₂ substrate 11 is not heated. For this reason, the SiO ₂ substrate 11 is maintained at a substantially normal temperature. Therefore, the Si thin film grows at approximately normal temperature. That is,
A plasma CVD forms a Si thin film at a temperature lower than the temperature at which crystallization proceeds. Therefore, the Si thin film is first formed as amorphous Si by plasma CVD.

A part of the downward flow of Ne atoms is reflected by the three slopes 25 formed on the reflection plate 12a, and further passes through the opening 24 to form the SiO ₂ substrate 1.
1 is incident on the upper surface. Another part of the Ne atom flow is
The light does not enter the slope 25 but passes through the opening 24 and directly enters the upper surface of the SiO ₂ substrate 11. That is, the Si thin film that is being formed on the upper surface of the SiO ₂ substrate 11 has a four-component Ne atom composed of a component traveling straight from the outlet 9 and three components reflected by the three slopes 25. The stream is irradiated. Since the inclination angle of the slope 25 is set to 55 °, the incident directions of these four component Ne atom flows are four independent close-packed crystal planes of the Si single crystal to be formed, that is, the (111) plane. Correspond to four directions perpendicular to.

By the way, the energy of the plasma formed by the ECR ion generator 2, SiO ₂ substrate 11
, So that the energy of the Ne atoms that reaches the surface of the Si thin film does not cause sputtering in the Si thin film.
That is, it is set to be lower than a value (= 27 eV) known as threshold energy in sputtering of Si by irradiation of Ne atoms. Therefore, the so-called Bravais law acts on the growing amorphous Si thin film. That is, the Si atoms in the amorphous Si are rearranged such that the plane perpendicular to the incident direction of the Ne atom flow irradiated on the amorphous Si becomes the densest crystal plane. The irradiated Ne atom stream has four components, and the incident direction of each component corresponds to the direction perpendicular to the densest surface of single-crystal Si having a single crystal orientation. The Si atoms are rearranged such that the planes perpendicular to the incident direction of the components are all the densest planes. A plurality of Nes having mutually independent incident directions
Since the direction of the (111) plane is regulated by the component of the atomic flow, the rearrangement of the Si atoms forms single-crystal Si having a single crystal orientation. That is, amorphous Si growing by plasma CVD
The thin film is sequentially converted to a single crystal Si thin film having a uniform crystal orientation.

By supplying a diborane gas or a phosphine gas simultaneously with the silane gas from the reaction gas supply pipe 13, a p-type or n-type single crystal Si thin film to which B or P is added is formed. Further, by alternately supplying these reaction gases containing the impurity element, for example, an equiaxial n-type single-crystal Si layer can be formed on a p-type single-crystal Si layer.

As described above, the SiO ₂ substrate 11 is not heated, and a Si thin film is formed by plasma CVD at a temperature lower than the temperature at which crystallization proceeds. This is because, under a high temperature at which crystallization of Si proceeds only by plasma CVD even without irradiation of the Ne atom flow, the crystal orientation becomes an arbitrary direction independent of the irradiation direction of the Ne atom flow, and the orientation is regulated. This is because polycrystals are formed.

As described above, it is desirable to select Ne, which is lighter than Si atoms, as an element constituting the atomic flow for irradiating the Si thin film. This is because, when the Ne atom stream is irradiated on the Si thin film, the relatively heavy Si atoms are converted into the relatively light N atoms.
This is because it is unlikely that Ne atoms penetrate into the Si thin film and remain because the probability of scattering e atoms backward is high. Further, the reason for selecting an inert element as an element constituting the atomic flow to be irradiated is that, even if the inert element remains in the Si thin film, the remaining inert element includes Si and doped impurities. In either case, no compound is formed, the electronic properties of the Si thin film are not significantly affected, and the single-crystal Si thin film can be easily removed to the outside by raising the temperature to some extent.

As described above, it is desirable that the reflection plate 12 be made of metal. This is because the Ne ⁺ ion current slightly mixed with the neutral Ne atom current is generated by the conductive reflector 12.
This is because the Ne ⁺ ions are converted into neutral atoms when reflected by the substrate 11, and the converted neutral Ne atom flow is irradiated on the substrate 11. Unlike the ion stream, the neutral atom stream is unlikely to diverge in the traveling direction.
1 has the advantage of being incident on

In the apparatus 100, S is formed by plasma CVD.
During the process of growing the i-thin film, the conversion to a single crystal proceeds at the same time. Therefore, a single-crystal Si thin film having a large thickness is
Moreover, it can be formed at a low temperature. Since a single crystal thin film can be formed at a low temperature, for example, a new single crystal thin film can be formed on a substrate on which a predetermined device has already been formed without changing the characteristics of the device. .

<5. Demonstration Data> Here, a test that demonstrates that a single-crystal thin film is formed by the above method will be described. FIG. 5 is experimental data showing an electron diffraction image of a sample in which a single-crystal Si thin film is formed on a polycrystalline SiO ₂ substrate 11 based on the above method. FIG. 5 (a)
FIG. 5B relates to a sample obtained by irradiating the substrate 11 with only a Ne atom flow component perpendicular to the substrate 11 without using the reflector 12, and FIG. It relates to the resulting sample irradiated with the four components of the stream. In the former sample obtained by irradiating the atomic flow from only one direction, one (111) plane of the Si crystal is oriented so as to be perpendicular to the incident direction of the atomic flow, but the orientation around the incident direction is arbitrary. And is not regulated in one direction. That is, this sample is formed as polycrystalline Si having only one crystal axis. The fact that the diffraction spots are continuously distributed along the circumference in FIG. 5A reflects this feature.

On the other hand, in the latter sample obtained by irradiating a four-component Ne atom stream, a diffraction spot having three-fold rotational symmetry is obtained as shown in FIG. 5B. This demonstrates that the obtained sample is formed as single crystal Si having all the crystal axes aligned. Since a single-crystal Si thin film could be formed on a SiO ₂ substrate 11 having a polycrystalline structure having a higher degree of atomic arrangement than an amorphous structure, a single-crystal Si film was formed on a substrate having an amorphous structure such as amorphous Si. It can be determined that it is naturally possible to form a thin film.

<6. Method for Forming Single Crystal Thin Film Other than Si>
In the above, the configuration and operation of the apparatus 100 have been described by taking the formation of a single-crystal Si thin film as an example.
It is also possible to form a single crystal thin film other than Si. As an example, Tables 1 to 5 show conditions for forming a semiconductor single-bonded thin film having a relatively high demand including Si already mentioned. Table 1 shows types of the supplied inert gas and reactive gas.

Table 2 shows the threshold energy values for sputtering in various combinations of the types of atoms or ions to be irradiated and the elements constituting the target thin film. In each combination, an ion or atomic stream of energy below the listed threshold energy must be irradiated. For a thin film composed of a compound, the threshold energy of the element having the largest atomic weight among the constituent elements may be referred to. It should be noted that the values listed in Table 2 were all obtained based on simulations, except for some values specifically indicated.

Tables 3 to 5 show the reaction gas flow rate, the inert gas flow rate, and other process control conditions when forming each semiconductor single crystal thin film.

[0047]

[Table 1]

[0048]

[Table 2]

[0049]

[Table 3]

[0050]

[Table 4]

[0051]

[Table 5]

<7. Another Example of Reflector 12> Here, another configuration example of the reflector 12 will be described. FIGS. 6 and 7 show (1) similar to the reflector 12a shown in FIG.
11) Another example of a reflector for forming a single-crystal thin film having a crystal structure of a diamond structure having a closest-packed surface will be described. FIG. 6 is a perspective view of the reflection plate 12b, and FIG. 7 is a three-view drawing. In the reflector 12b, a groove 31a for sliding the substrate 11 in and out is formed on the upper surface of a base 31 mounted on the sample stage 10,
The structure is such that the substrate 11 is incorporated into the base 31.
Therefore, unlike the reflection plate 12a, in the reflection plate 12b, the substrate 11 is fixed to the groove 31a when performing irradiation. The bottom surface of the reflection block 33 is set on the upper surface of the base 31 so that the reflection block 33 is located on the substrate 11. As shown in FIG.
The inclination angle of the slope 35 is set to 55 ° similarly to the reflection plate 12a.

It is also possible to form a single crystal thin film having a crystal structure other than the diamond structure. For this purpose, a reflector having a structure suitable for each crystal structure other than the reflectors 12a and 12b is used. It is good to prepare. Further, single crystal thin films having various crystal orientations can be formed even if the crystal structures are the same. For this purpose, a reflector suitable for each crystal orientation is prepared. An example is described below.

FIG. 8 shows that the crystal plane parallel to the substrate plane is (10).
An example of a reflector corresponding to a single crystal having a diamond structure, which is the 0) plane, is shown. FIG. 8A is a front sectional view taken along the line AA in the plan view shown in FIG. 8B. A groove 42 is formed on the upper surface of the flat base 41. This groove 4
The substrate 11 is inserted into 2. That is, the reflection plate 12c has a structure in which the substrate 11 is incorporated, and the substrate 11 cannot move horizontally relative to the reflection plate 12c when performing irradiation. This base 41 is used for the sample table 1
It is set on 0.

On the base 41, four reflection blocks 43 are disposed around the substrate 11 so as to be adjacent to each other at right angles. On the upper surface of the reflection block 43, a shielding plate 46 having an opening 47 only above the slope 45 of the reflection block 43 is installed. The atomic current or the ion current incident from above the shielding plate 46 to the downward direction is transmitted through the opening 47.
Only the light passes through the slope 45 by passing through only the slope 45. That is, only the four components of the reflected atomic stream or ion stream are incident on the substrate 11, and there is no component directly incident from above. The slope angle of the slope 45 is 62.6.
It is set to 3 ゜. For this reason, the incident directions of the four components correspond to four independent (1) directions in the crystal having the diamond structure.
11) coincides with the direction perpendicular to the plane.

FIG. 9 shows that the crystal plane parallel to the substrate surface is (11).
An example of a reflector corresponding to a single crystal having a diamond structure, which is the 0) plane, is shown. FIG. 9A is a front sectional view taken along line BB in the plan view shown in FIG. 9B. A groove 52 is formed on the upper surface of the base 51 having an inclination angle of 35 °. The substrate 11 is inserted into the groove 52. That is, the reflecting plate 12d has a structure in which the substrate 11 is incorporated.
cannot move horizontally relative to d. This base 5
1 is set on the sample stage 10.

On the base 51, one reflection block 53 is provided. Slope 55 of reflection block 53
Of the base 51 with respect to the upper surface of the base 51 is set to 90 °. For this reason, the atomic flow or ion flow incident from above is divided into two components: a component directly incident on the substrate 11 at an incident angle of 35 ° and a component reflected by the inclined surface 55 and incident on the opposite side at the same incident angle of 35 °. Divided into two components. The incident directions of these components correspond to the directions perpendicular to two independent two of the four independent (111) planes in the diamond-structured crystal. That is, since these two components define the directions of the two closest dense surfaces independent of each other, by using this reflector 12d, (11
It is possible to form a single crystal thin film having a diamond structure in which the crystal orientation is aligned so that the 0) plane is parallel to the substrate surface.

<8. Other Examples> (1) When the single crystal thin film to be formed is, for example, a GaN single crystal thin film, an N ₂ (nitrogen) gas or an NH ₃ (ammonia) gas containing N atoms is introduced with an inert gas. The GaN thin film may be irradiated with the molecular flow or the dissociated N atom flow introduced into the tube 7. Irradiated N is Ga
Even if it remains inside N, it is incorporated into a single crystal as a constituent element of GaN, so that there is no possibility of adversely affecting the characteristics of GaN.

(2) Instead of using the reflection plate 12, the number of the ECR ion generators 2 provided is equal to the number of the components of the atomic flow applied to the thin film, and the thin film is irradiated with the atomic flow directly from the ECR ion generator 2. Is also good. However, as compared with this method, the method of FIG. 1 using one ECR ion generator 2 and the reflector 12 requires a minimum number of expensive ECR ion generators 2, and the configuration of the apparatus is simple. In addition to the above, there is an advantage that it is easy to keep the degree of vacuum in the reaction chamber 8 high.

The ECR ion generator 2 also functions as an energy source necessary for applying energy to the reaction gas for performing the plasma CVD. That is,
The method of FIG. 1 using one ECR ion generator 2 and a reflector 12 can be performed by simply adding the reflector 12 to a configuration originally required for performing plasma CVD. It has a notable advantage.

(3) Instead of the ECR ion generator 2,
Other ion sources such as a cage type and a Kauffman type may be used. However, the ion flow formed at this time has a problem that the flow is diffused by the repulsive force due to the static electricity between the ions and the directivity is weakened. When the substrate 11 is irradiated with the ion current as it is, an electrically insulating substrate cannot be used. This is because charge accumulates on the substrate 11 and irradiation does not proceed. For this reason, it is necessary to provide a means for neutralizing ions and converting them into an atomic flow in the path of the ion flow. Alternatively, the reflection of the ion stream and the conversion to the neutral atom stream may be performed at the same time by forming the reflector 12 from a conductive material such as a metal.

On the other hand, in the above-described method using the ECR ion generator 2, a neutral atomic flow can be easily obtained without using a means for neutralizing the ion flow, and can be obtained in a form close to a parallel flow. There is an advantage. For this reason, it is easy to irradiate the thin film with the atomic flow having high incident angle accuracy. In addition, since a neutral atomic flow is mainly incident on the thin film, an insulating substrate such as a SiO ₂ substrate can be used as the substrate 11.

[0063]

According to the method of the present invention, a thin film of a predetermined substance is formed on a substrate by a plasma enhanced chemical vapor deposition method, and gas is simultaneously discharged from a plurality of directions. Since the thin film is irradiated with the beam, a single crystal thin film having a uniform crystal orientation is formed. Further, in the method of the present invention, during the process of growing a thin film by the plasma enhanced chemical vapor deposition method, the conversion to a single crystal proceeds simultaneously and sequentially. Therefore, a single crystal thin film having a large thickness can be formed at a low temperature. Furthermore, the present invention
The method uses a single beam of gas to irradiate the substrate.
Source and reflectors in the path
Different directions without the need for multiple beam sources
A beam of gas is illuminated from a direction perpendicular to multiple
It is possible to shoot. That is, in the method of the present invention,
If one beam source with a complicated structure is prepared,
Sufficient, forming a single crystal thin film with a simple device configuration
There is an effect that can be done. Also, one beam source is enough
Therefore, a thin film can be formed under a high vacuum.

<Effect of the Invention According to Claim 2> In the method of the present invention, since the gas to be irradiated is an inert gas, even if atoms or ions of the gas remain in the thin film after the irradiation, they remain in the thin film. This has the effect that the electronic properties of the single crystal thin film are not adversely affected as impurities.

<Effect of the Invention According to Claim 3> In the method of the present invention, the atomic weight of the element constituting the inert gas is lower than the maximum atomic weight of the constituent element of the predetermined substance growing as a thin film. The effect is that most of the atoms or ions of the irradiated inert gas recoil back at or near the surface of the thin film and hardly remain in the thin film.

<Effect of the Invention According to Claim 4> In the method of the present invention, since the irradiated gas contains a constituent element of a substance which grows as a thin film, the atoms or ions of the constituent element after irradiation are converted to the thin film. Even if they remain inside, there is an effect that there is no possibility that these may adversely affect the single crystal thin film as impurities. It is also possible to supply this constituent element to the thin film only by irradiating the gas beam without including this constituent element in the reaction gas.

<Effect of the Invention According to Claim 5> In the method of the present invention, since the reaction gas contains an impurity element to be added to a substance grown as a thin film, a single crystal thin film to which a desired impurity is added is formed. It is possible to form.

<Effect of the Invention According to Claim 6> In the method of the present invention, a plurality of types of reactive gas substances each composed of one of a plurality of types of impurity elements are alternately supplied onto the substrate.
It is possible to form a single crystal thin film having a plurality of types of single crystal layers to which respective ones of a plurality of types of impurities are added.

<Effect of the Invention According to Claim 7> In the method of the present invention, a plasma enhanced chemical vapor deposition method is used.
While forming a thin film of the specified substance on the substrate,
Since a thin film is irradiated with a gas beam from multiple directions,
A single-crystal thin film having a uniform crystal orientation is formed. Also this
In the method of the invention, a thin film is formed by plasma enhanced chemical vapor deposition.
During the growth process, the conversion to single crystal proceeds simultaneously
You. Therefore, a single-crystal thin film having a large thickness can be formed at a low temperature.
It is possible to form below. Furthermore, the present invention
In the method, the irradiation gas is an inert gas.
If later gas atoms or ions remain in the film,
These adversely affect the electronic properties of the single crystal thin film as impurities.
It has the effect of little effect. In addition, inert
The atomic weight of the elements that make up the gas grows as a thin film
Lower than the maximum atomic weight of the constituent elements of a given substance
And the majority of the atoms or ions of the irradiated inert gas
Recoil backward at or near the surface of the thin film,
There is an effect that hardly remains in the inside. As a result, a single crystal
A thin film is easily formed. <Effect of the Invention According to Claim 8 > In the method of the present invention, the gas beam irradiated to the substrate is
Since it is obtained by a single beam source and a reflector disposed in the path, the gas is not required from a plurality of beam sources, and the gas is transmitted from a direction perpendicular to a plurality of dense crystal planes having different directions. It is possible to irradiate the beam. That is, in the method of the present invention, it is sufficient to prepare one beam source having a complicated structure, so that there is an effect that a single crystal thin film can be formed with a simple device configuration. Also, if the beam source is 1
Since it is enough, a thin film can be formed under a high vacuum.

<Effect of the Invention According to Claim 9 > In the method of the present invention, the beam generating source has an ion generating source for generating a gaseous ion beam, and the reflecting plate is substantially made of metal. Since it is a plate, the gas ion beam generated by the ion source becomes a neutral beam when reflected by the metal reflector. For this reason, there is an effect that a parallel beam having a uniform direction is irradiated on the substrate. It is also possible to use an electrically insulating insulating substrate as the substrate.

<Effect of the Invention According to Claim 10 > In the method of the present invention, the beam generation source is an electron cyclotron resonance type ion generation source. At a distance equal to or more than a predetermined distance from, a neutral beam of high intensity can be obtained without using a means for neutralizing ions. By reflecting the neutral beam on the reflector and irradiating the substrate with the neutral beam, there is an advantageous effect that the substrate can be irradiated with a parallel beam having a uniform direction from a plurality of predetermined directions. It is also possible to use an electrically insulating insulating substrate as the substrate.

[Brief description of the drawings]

FIG. 1 is a front sectional view showing a configuration of an apparatus suitable for performing a method according to an embodiment.

FIG. 2 is a perspective view of a reflector in the embodiment.

FIG. 3 is a three-view drawing of a reflection plate in the embodiment.

FIG. 4 is a graph showing characteristics of the ECR ion generator in the example.

FIG. 5 shows experimental data demonstrating the method of the example.

FIG. 6 is a perspective view of a reflector in the embodiment.

FIG. 7 is a three-view drawing of a reflecting plate in the embodiment.

FIG. 8 is a structural diagram of a reflection plate in the embodiment.

FIG. 9 is a structural diagram of a reflection plate in an example.

[Explanation of symbols]

 2 ECR ion generator 7 Inert gas introduction pipe 11 Substrate 12 Reflector 13 Reaction gas introduction pipe

──────────────────────────────────────────────────続 き Continuation of front page (58) Fields investigated (Int. Cl. ⁷ , DB name) C30B 1/00-35/00 CA (STN) EPAT (QUESTEL) JICST file (JOIS) WPI (DIALOG) Practical file (PATOLIS) Patent file (PATOLIS)

Claims (10)

(57) [Claims] 1. A method for forming a single crystal thin film of a predetermined material on a polycrystalline substrate or an amorphous substrate by using a plasma enhanced chemical vapor deposition method, wherein the plasma enhanced chemical vapor deposition method alone is used to form the single crystal thin film. At a low temperature where crystallization of the substance does not occur, a reaction gas is supplied onto the substrate at the same time,
From the direction perpendicular to the plurality of densest crystal planes having different directions in the single crystal thin film to be formed, a low-energy gas beam that does not cause sputtering of the predetermined substance is irradiated onto the substrate, and the gas is irradiated. Beam
A beam source and the beam source to the substrate
A method for forming a single crystal thin film, wherein the method is obtained by using a reflector disposed in a path leading to the single crystal thin film. 2. The method according to claim 1, wherein said gas is an inert gas. 3. The method according to claim 2, wherein the atomic weight of the element constituting the inert gas is lower than the maximum atomic weight among the atomic weights of the elements constituting the predetermined substance. Crystal thin film forming method. 4. The method according to claim 1, wherein the predetermined substance includes an element constituting a gaseous substance that is a gas at normal temperature, and the beam of the gaseous substance is a beam of the gaseous substance. A method for forming a single crystal thin film, characterized by the following. 5. The method according to claim 1, wherein the reaction gas includes a reaction gas substance composed of an impurity element to be added to the predetermined substance. 6. The method according to claim 5, wherein the impurity element is of a plurality of types, and a plurality of types of reactive gas substances each composed of one of the plurality of types of impurity elements are alternately supplied onto the substrate. A method for forming a single crystal thin film. 7. A method for forming a plurality of particles by using a plasma enhanced chemical vapor deposition method.
Of a specified substance on a crystalline substrate or amorphous substrate
A method for forming a crystalline thin film, comprising:
The growth method alone does not cause crystallization of the predetermined substance.
At the same time, the reaction gas is supplied onto the substrate under the temperature,
Pluralities with different directions in the single crystal thin film to be formed
From the direction perpendicular to the densest crystal plane of
Low energy gas bubbles that do not cause pattering
The substrate is irradiated onto the substrate, and the predetermined substance is
The gas is neon and the low energy
A single crystal thin film characterized by having a voltage of less than 27 eV
How . 8. The method of claim 7 , wherein said gas
Beam from a single beam source and the beam source
And a reflector disposed on the path from
A method for forming a single-crystal thin film, comprising: 9. The method according to claim 1 , wherein said beam source emits an ion beam of said gas.
The reflecting plate is substantially a metal.
A method for forming a single-crystal thin film, comprising: 10. The method according to claim 1 or 8, wherein
Wherein the beam source is an electron cyclotron resonance type
Single crystal thin film formation characterized by being an ion source
Method.