JPH11204440A - Manufacture of crystalline thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To freely control crystal structure and plane orientation of a growth surface without depending on the underlying material, by radiating coherent synchrotron radiation or the like from a plurality of directions to form a specified two-dimensional interference image on the surface of an amorphous substrate, and at the same time, radiating molecules or atoms which are to be a crystal material. SOLUTION: Synchrotron radiation introduced into a reaction chamber 4 through a filter 6 from a synchrotron radiation light source 5 is split into a plurality of directions, for example, four directions, using half mirrors 13, 14, and 15, and is then radiated onto a substrate 7 through mirrors 16, 17, 18, and 19, thereby forming a two-dimensional interference image on the substrate 7. By changing the inclination of the synchrotron radiation in the four directions in a vertical plane, the spacing of the synchrotron radiation from the four directions reflected on the substrate 7 changes. In accordance with this change, the lattice spacing of the two-dimensional interference image changes. Thus, the inclination of the synchrotron radiation in the four directions in the vertical plane is set an a predetermined value in conformity to a desired lattice spacing of the two-dimensional interference image.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a crystalline thin film formed on an amorphous substrate or a crystalline substrate.

[0002]

2. Description of the Related Art The formation of a crystalline thin film having different physical properties on a crystalline base, the formation of a crystalline thin film on an amorphous base, especially the formation of an amorphous insulator. The realization of a so-called SOI technology for forming a thin film of a semiconductor crystal thereon has been achieved by optoelectronic devices, optoelectronic fusion circuits,
This is an indispensable issue in realizing an optoelectronic integrated circuit or a next-generation miniaturized electronic device and a three-dimensional integrated circuit.

Some luminescent materials and electronic materials have the same chemical composition but different crystal structures. It is known that a material having such a polymorph exhibits unique physical properties for each crystal structure. For example, gallium nitride, which is a blue light emitting material, has a hexagonal wurtzite structure or a cubic sphalerite structure, and each has different optical and electrical properties. It is very important to control the crystal structure of such materials.

[0004] There are a number of existing methods for growing crystalline thin films. These growth methods are classified into two methods from the viewpoint of how the crystal structure and the plane orientation of the growth plane are determined. The first method is to use a crystalline base as a seed. When a thin film is deposited on a crystalline underlying surface under suitable conditions, the deposited thin film becomes crystalline by inheriting the symmetry of the underlying crystal structure. If one part of the underlayer is crystalline and the other part is amorphous, perform selective lateral growth or perform melt recrystallization or solid phase growth after depositing an amorphous thin film. Thereby, a crystalline thin film can be formed on an amorphous base.

[0005] A second method is to use anisotropy of surface energy. When there is no seed crystal structure, that is, when the underlayer is amorphous or the symmetry of the underlying crystal structure is significantly different from the symmetry of the crystal structure of the deposited thin film, the undersubstrate and the overlying substrate are formed. The crystal structure and orientation of the crystalline thin film are determined by the anisotropy of the surface energy with the crystalline thin film. For example, to deposit crystalline silicon on a smooth amorphous SiO ₂ substrate, (100)
It is easy to precipitate in a state where the surface is in contact with the substrate.

However, when utilizing the anisotropy of the surface energy, the crystal orientation perpendicular to the substrate surface can be controlled, but the horizontal direction is not controlled. Therefore, graphoepitaxy has been proposed in which periodic irregularities are provided on the substrate surface, and the horizontal crystal orientation of the crystalline thin film is made uniform by utilizing the anisotropy of the surface energy of the side surfaces of the irregularities. Nevertheless, the crystal structure and orientation of the thin film often slightly depend on the deposition conditions of the thin film, and depending on the conditions, crystals having various structures and orientations are simultaneously formed.

[0007]

As described above, in the conventional crystal growth technique, the crystal structure of the crystalline thin film and the orientation of the growth plane depend on the structure and orientation of the seed crystal.
Alternatively, it is determined by the anisotropy of the surface energy with the base. However, in any case, the production of the crystalline thin film has various restrictions because it depends on the material of the base. When a seed crystal is used, the crystal structure and orientation of the seed crystal itself must be controlled. Therefore, the seed crystal is usually a crystalline substrate. Therefore, the crystalline thin film to be deposited must be in contact with the crystalline substrate.

In addition, it is not possible to deposit a crystalline thin film having a crystal structure that is significantly different from the underlayer on the seed crystal underlayer. Also when utilizing the anisotropy of surface energy, there are restrictions on the combination of the crystalline thin film and the underlayer and the crystal growth conditions. Therefore, it is difficult to form two or more types of crystalline thin films having significantly different crystal structures or growth plane orientations on the same base, regardless of whether the base is crystalline or amorphous.

Further, crystal grain boundaries and sub-grain boundaries are present inside the crystalline thin film formed on the amorphous base surface, and these degrade the electrical characteristics of the crystalline thin film. This degrades the characteristics of the device having the crystalline thin film. In order to avoid this problem, the size of the crystal grains must be made larger than the device size by controlling the growth conditions of the crystalline thin film, and special measures must be taken to control the position of the crystal grains. It is.

Accordingly, the present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to freely control the crystal structure and the plane orientation of a growth surface by a method that does not depend on the underlying material. It is an object of the present invention to provide a method for producing a crystalline thin film that can produce a thin film.

[0011]

In order to solve the above-mentioned problems, a method for producing a crystalline thin film according to claim 1 of the present invention is directed to a method for producing a coherent radiation, a laser beam, or a coherent electron beam (hereinafter referred to as a coherent electron beam). , Which may be referred to as a coherent beam) on a surface of an amorphous substrate from a plurality of directions to form a two-dimensional interference image having symmetry of a crystal plane having a specific plane orientation of a specific crystal structure on the substrate surface. Simultaneously irradiating a molecule or atom as a crystal raw material, thereby depositing a crystalline thin film having the specific crystal structure and a growth plane having the specific plane orientation on an amorphous substrate. It is.

That is, in the present invention, an interference image by coherent beams from a plurality of directions is used to control the crystal structure and the plane orientation of a growth plane. In this case, it is necessary to shorten the wavelength of the coherent beam to the level of the atomic size. Since a short-wavelength coherent beam, for example, radiation having a wavelength of 1 nanometer has an energy of about 1 keV, which is high enough to promote a chemical reaction, the raw material is located at a position where the two-dimensional interference image exists, that is, Reacts at a position corresponding to a lattice point of a desired crystal structure, and a crystalline thin film having a crystal structure and a growth surface determined by a two-dimensional interference image is deposited.

For a material having a polymorph, by forming a two-dimensional interference image having a symmetry of a growth plane of a desired crystal structure, it becomes possible to form different crystal structures. For example, a two-dimensional interference image having four-fold symmetry and a lattice spacing equal to the lattice constant on the crystal growth surface is formed by irradiating coherent beams from four directions at 90 ° intervals when viewed from above, By irradiating the atoms or molecules, the crystal can be grown while controlling the crystal structure to a four-fold symmetric structure.

Further, for example, a two-dimensional interference image having six-fold symmetry and a lattice spacing equal to the lattice constant on the crystal growth surface is formed by irradiating coherent beams from three directions at 120 ° intervals when viewed from above. At the same time, by irradiating atoms or molecules as a raw material, the crystal structure is changed to 6
Crystals can be grown while controlling to a symmetric structure. Note that, even in a material having no polymorph, a crystal can be grown in the same manner while controlling the plane orientation of the growth surface of the crystal structure in a desired direction.

According to a second aspect of the present invention, there is provided a method of manufacturing a crystalline thin film, wherein the substrate surface is irradiated with one of coherent radiation light, laser light, and a coherent electron beam from a plurality of directions. By forming a two-dimensional interference image having the symmetry of the crystal plane of the specific plane orientation of, and simultaneously irradiating the molecules or atoms as the raw material of the crystal,
Independently from the structure of the crystalline substrate, a crystalline thin film having the specific crystal structure and a growth plane having the specific plane orientation is deposited on the crystalline substrate.

Also in the second aspect, it is preferable that the wavelength of the coherent beam be shortened to the level of the atomic size. As in the case of the first aspect, in the case of a material having a polymorph, the crystal structure has a four-fold symmetry or a six-fold symmetry. Crystals can be grown while controlling the structure as described above. Further, even in a material having no polymorph, the crystal can be grown while controlling the plane orientation of the growth surface of the crystal structure.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an apparatus for manufacturing a crystalline thin film used in the present embodiment. This apparatus includes a coherent beam supply device 1, a gas supply device 2, a substrate exchange chamber 3, and a reaction chamber 4. The coherent beam supply device 1 is configured to monochromatize coherent radiation emitted from a radiation light source 5 such as a synchrotron radiation device with a filter 6 and then supply the monochromatic radiation to a reaction chamber 4.

The gas supply device 2 supplies a raw material gas to the reaction chamber 4. The substrate exchange chamber 3 is provided for introducing the substrate 7 into the reaction chamber 4 without breaking the vacuum of the reaction chamber 4, and the reaction chamber 4 and the substrate exchange chamber 3 are separated by a gate valve 8. The substrate exchange chamber 3 and the reaction chamber 4 are provided with independent vacuum exhaust devices 9 and 10, respectively.

The reaction chamber 4 is always kept in a vacuum by a vacuum exhaust device 10. The substrate 7 is mounted on the substrate holder 11 in the reaction chamber 4. A substrate heater 12 is mounted below the substrate holder 11, and heats the substrate 7 as necessary. Note that, instead of providing the substrate heater 12, heating may be performed by irradiating infrared rays or the like from a position away from the substrate holder 11.

The radiated light introduced into the reaction chamber 4 from the radiated light source 5 via the filter 6 is applied to the half mirrors 13 and 1.
The light is divided into a plurality of directions, for example, four directions using the light sources 4 and 15, and is further irradiated onto the substrate 7 from the four directions via mirrors 16, 17, 18, and 19. In addition, between the half mirrors 13 and 15, the half mirror 14 and the mirror 1
Mirrors 20, 21 and 22 are arranged between the mirrors 7 and between the half mirror 15 and the mirror 19, respectively. The half mirrors 13 to 15 and the mirrors 16 to 22 may be located outside the reaction chamber 4 as long as the direction of irradiating the substrate 7 with the radiated light is always constant.

On the substrate 7, for example, to form a two-dimensional interference image having a periodic structure of a square lattice,
When radiated light is irradiated from four directions A to D via four mirrors 16 to 19, these four directions are set to have an angular interval of 90 ° when viewed from above as shown in FIG. Have been. The inclination angles (θ in FIG. 3) of the emitted light in the four directions in the vertical plane are made equal to each other according to the lattice spacing in the growth plane of the crystal structure to be manufactured on the substrate 7. When the inclination angle θ changes, the interval at which the waves W of the radiated light from the four directions A to D appear on the substrate 7 changes, and accordingly, the lattice interval of the two-dimensional interference image also changes. According to the lattice spacing of the desired two-dimensional interference image,
It is necessary to set the inclination angle θ in the vertical plane to a predetermined value. As described above, for example, 90 ° when viewed from above
And the waves from the four directions A to D having the same inclination angle θ in the vertical plane mutually interfere with each other, so that a two-dimensional periodic interference image having a square lattice is formed. Is done.

FIG. 4 shows that, in order to form a two-dimensional interference image having a periodic structure of a hexagonal lattice, the substrate 7 is irradiated with the radiated light from three directions E to G, and each of them is 120 ° relative to each other. 3 shows a case where irradiation is performed from a direction having an angle of. The tilt angles of the three directions of radiation in the vertical plane are
These are made equal to each other in accordance with the lattice spacing in the growth plane of the crystal structure to be manufactured. In this case, the emitted lights from three directions interfere with each other to form a two-dimensionally periodic interference image having a hexagonal lattice.

In the present invention, the two-dimensional interference image formed on the substrate 7 is not limited to an image having a square lattice or an image having a hexagonal lattice. It is possible to form a two-dimensional interference image having an arbitrary periodic arrangement by changing the number of directions in which the emitted light is irradiated, the angle viewed from above, and the inclination angle in the vertical plane.

In FIG. 1, a source gas introduced into a reaction chamber 4 from a gas supply device 2 is irradiated onto a substrate 7 by a gas nozzle 23.

[0025]

Next, embodiments of the present invention will be described. For example, GaN has a hexagonal crystal structure and a cubic crystal structure, and is known to exhibit unique physical properties. Hexagonal and cubic GaN have lattice constants of 3.189 angstroms and 4.51 angstroms, respectively. Therefore, when growing hexagonal GaN, as shown in FIG. 4, by irradiating the substrate 7 with radiated light from three directions at intervals of 120 ° when viewed from above, as shown in FIG.
A two-dimensional interference image having a hexagonal lattice periodic structure having a lattice interval L1 of 3.189 angstroms is formed on the surface of the substrate 7, and at the same time, while maintaining the temperature of the substrate 7 at 900 ° C., trimethylgallium and ammonia are used as raw materials. If supplied, as shown in FIG. 6, hexagonal GaN
24 grow.

On the other hand, when cubic GaN is grown, as shown in FIG.
By irradiating radiation from four directions at intervals of °,
As shown in the figure, a two-dimensional interference image having a periodic structure of a square lattice having a lattice spacing L2 of 4.51 Å is formed on the substrate 7, and at the same time, the same trimethylgallium and ammonia are supplied at a substrate temperature of 900 ° C. Then, as shown in FIG. 8, cubic GaN 25 grows on substrate 7.

As another example, it is known that SiC also has hexagonal and cubic crystal structures.
Hexagonal and cubic crystals of C have lattice constants of 3.086 angstroms and 4.358 angstroms, respectively. Therefore, when growing hexagonal SiC, FIG.
As shown in FIG. 5, by irradiating the substrate 7 with radiation light at intervals of 120 ° when viewed from above, the substrate 7 has a lattice spacing L1 of 3.086 Å on the surface of the substrate 7 as shown in FIG. If a two-dimensional interference image having a hexagonal lattice periodic structure is formed and, at the same time, disilane and acetylene are supplied as raw materials while maintaining the temperature of the substrate 7 at 900 ° C., hexagonal SiC grows on the substrate 7.

On the other hand, when cubic SiC is grown, as shown in FIG.
By irradiating radiation from four directions at intervals of °,
As shown in FIG. 2, a substrate having a square lattice periodic structure having a lattice spacing L2 of 4.358 angstroms on the substrate 7
If a two-dimensional interference image is formed and simultaneously the same disilane and acetylene are supplied at a substrate temperature of 900 ° C., hexagonal SiC grows on the substrate 7.

Further, as another embodiment, a case where the orientation of the growth plane of the silicon crystal is controlled will be described. That is,
Even in silicon having a single diamond structure,
For example, when growing (100) silicon, as shown in FIG.
By irradiating the emitted light from the direction, as shown in FIG.
By forming a two-dimensional interference image having a periodic structure of a square lattice having a lattice spacing L3 of angstrom and simultaneously irradiating a raw material such as disilane or dichlorosilane, (10
The (0) plane becomes the growth plane, and (100) silicon 26 is deposited on the substrate 7 as shown in FIG.

On the other hand, when growing (111) silicon, as shown in FIG.
Irradiation light is irradiated from three directions at intervals of 0 °, and as shown in FIG. 11, the period of a hexagonal lattice having a lattice spacing L4 of 3.840 angstroms (1 / √2 of the lattice constant of silicon) is formed on the substrate 7. When a two-dimensional interference image having a structure is formed and simultaneously irradiated with a raw material such as disilane or dichlorosilane, the (111) plane becomes a growth plane, and (111) silicon 27 is deposited on the substrate 7 as shown in FIG. .

In each of the above embodiments, the substrate 7 may be either an amorphous substrate or a crystalline substrate. Specific examples of the amorphous substrate include quartz glass and the like.
Specific examples of the crystalline substrate include silicon, gallium arsenide, and the like. As described above, when an amorphous substrate is used, when a crystalline thin film is formed on an amorphous base such as an SOI structure, the crystal structure and the plane orientation of the growth surface can be freely changed. On the other hand, when a crystalline substrate is used, there is an advantage that a crystalline thin film having a symmetry significantly different from that of the crystal structure of the substrate can be formed on the substrate.

[0032]

As described above, according to the first aspect of the present invention,
According to the method for producing a crystalline thin film of (1), any one of coherent radiation, laser light, or coherent electron beam (coherent beam) is irradiated on the surface of the amorphous substrate from a plurality of directions, and a specific crystal is formed on the substrate surface. Forming a two-dimensional interference image having symmetry of a crystal plane having a specific plane orientation of the structure,
At the same time, by irradiating the molecules or atoms that are the raw materials of the crystal, the crystalline thin film having the specific crystal structure and the growth plane with the specific plane orientation is deposited on the amorphous substrate, so that the polymorphism When viewed from above, a coherent beam is irradiated from a plurality of directions at predetermined intervals, for example, 90 ° or 120 ° to obtain a material having four-fold symmetry or six-fold symmetry and a crystal growth surface. By forming a two-dimensional interference image having a lattice spacing equal to the lattice constant at the same time and simultaneously irradiating the atomic or molecular beam of the raw material, the crystal structure can be changed to a desired symmetry such as 4-fold or 6-fold symmetry. Crystals can be grown while controlling the structure. Further, even in a material having no polymorph, a crystal can be grown in a similar manner while controlling the growth plane of the crystal structure to a desired plane orientation. This makes it possible to freely control the crystal structure and the plane orientation of the growth surface when forming a crystalline thin film on an amorphous base, as in the SOI structure.

According to a second aspect of the present invention, there is provided a method of manufacturing a crystalline thin film, wherein the surface of the crystalline substrate is irradiated with any one of a coherent radiation, a laser beam and a coherent electron beam from a plurality of directions. By forming a two-dimensional interference image having the symmetry of the crystal plane of the specific plane orientation of, and simultaneously irradiating the molecules or atoms that are the raw materials of the crystal,
Independently from the structure of the crystalline substrate, the crystalline thin film having the specific crystal structure and the growth plane having the specific plane orientation is deposited on the crystalline substrate. Crystals can be grown while controlling the crystal structure to a desired symmetry structure such as four-fold or six-fold symmetry in a material having the crystal structure. Can be grown while controlling the crystallographic orientation to a desired plane orientation. This makes it possible to form a crystalline thin film having a symmetry significantly different from that of the crystal structure of the substrate on a specific crystalline substrate.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an apparatus for manufacturing a crystalline thin film used in an embodiment of the present invention.

FIG. 2 is a plan view of the substrate according to the embodiment shown in FIG.
The schematic plan view which shows the irradiation direction of light when irradiating light from a direction.

FIG. 3 is a schematic vertical sectional view showing inclination angles of light in the four directions in a vertical plane.

FIG. 4 is a schematic plan view showing the irradiation direction of light when the substrate is irradiated with light from three directions.

FIG. 5 is an explanatory diagram showing a state where a two-dimensional interference image having a periodic structure of a hexagonal lattice corresponding to a growth surface of hexagonal GaN is formed on the substrate.

FIG. 6 is an explanatory view showing a state in which hexagonal GaN is deposited on the substrate of FIG. 6;

FIG. 7 is an explanatory diagram showing a state in which a two-dimensional interference image having a periodic structure of a square lattice corresponding to a growth surface of cubic GaN is formed on the substrate.

FIG. 8 is an explanatory view showing a state where cubic GaN is deposited on the substrate of FIG. 7;

FIG. 9 is an explanatory diagram showing a state in which a two-dimensional interference image having a periodic structure of a square lattice having a lattice spacing equal to the lattice constant of silicon is formed on the substrate.

FIG. 10 is an explanatory view showing a state where (100) silicon is deposited on the substrate of FIG. 9;

FIG. 11 shows 1 / √2 of the lattice constant of silicon on the substrate.
FIG. 5 is an explanatory diagram showing a state in which a two-dimensional interference image having a hexagonal lattice periodic structure with a lattice spacing equal to.

FIG. 12 is an explanatory view showing a state where (111) silicon is deposited on the substrate of FIG. 11;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Coherent beam supply device 2 Gas supply device 3 Substrate exchange room 4 Reaction chamber 5 Synchrotron radiation source 6 Filter 7 Substrate 8 Gate valve 9, 10 Vacuum exhaust device 11 Substrate holder 12 Substrate heater 13 to 15 Half mirror 16 to 22 Mirror 23 Gas nozzle 24 GaN (hexagonal) 25 GaN (cubic) 26 (100) silicon 27 (111) silicon

Claims (2)

[Claims] An amorphous substrate surface is irradiated with a coherent radiation light, a laser beam, or a coherent electron beam from a plurality of directions to form a crystal plane having a specific crystal orientation and a specific crystal orientation on a substrate surface. By forming a two-dimensional interference image having symmetry and simultaneously irradiating a molecule or atom serving as a crystal raw material, the crystalline thin film having the specific crystal structure and the growth plane having the specific plane orientation can be made amorphous. A method for producing a crystalline thin film, comprising: depositing a crystalline thin film on a substrate. 2. A method of irradiating a coherent radiation beam, a laser beam, or a coherent electron beam onto a surface of a crystalline substrate from a plurality of directions, and symmetrical crystal planes having a specific plane orientation of a specific crystal structure on the substrate surface. By forming a two-dimensional interference image having a characteristic and simultaneously irradiating a molecule or an atom serving as a crystal raw material, the growth surface of the specific crystal structure and the specific plane orientation can be formed independently of the structure of the crystalline substrate. A method for producing a crystalline thin film, comprising depositing a crystalline thin film on a crystalline substrate.