JP3421672B2 - Method for producing crystalline thin film - 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 producing a crystalline thin film formed on an amorphous substrate or a crystalline substrate.

[0002]

2. Description of the Related Art Forming a crystalline thin film having different physical properties on a crystalline underlayer, and forming a crystalline thin film on an amorphous underlayer, especially for an amorphous insulator. To realize a so-called SOI technology for forming a thin film of a semiconductor crystal on an optoelectronic device, an optoelectronic fusion circuit,
This is an indispensable issue for realizing an optoelectronic integrated circuit, a next-generation miniaturized electronic device, or a three-dimensional integrated circuit.

Some light emitting materials and electronic materials have the same chemical composition but different crystal structures. It is known that materials having such polymorphism have 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. Controlling the crystal structure of such materials is extremely important.

There are numerous methods of growing crystalline thin films that currently exist. These growth methods are classified into two methods from the viewpoint of how the crystal structure and the plane orientation of the growth surface are determined. The first method is to use a crystalline underlayer as the seed. When a thin film is deposited under appropriate conditions on the surface of a crystalline substrate, the deposited thin film becomes crystalline because the deposited thin film inherits the symmetry of the underlying crystal structure. If the underlying part 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. Thus, a crystalline thin film can be formed even on an amorphous base.

The second method is to utilize the anisotropy of surface energy. If there is no seed crystal structure, that is, if the underlayer is amorphous, or if the symmetry of the underlayer crystal structure is significantly different from the symmetry of the deposited thin film crystal structure, the underlayer is formed on the underlying substrate. The crystal structure and orientation of the crystalline thin film are determined by the anisotropy of the surface energy of the crystalline thin film. For example, when depositing crystalline silicon on a smooth amorphous SiO ₂ substrate, (100)
Precipitates easily when 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, there has been proposed graphoepitaxy in which the substrate surface is provided with periodic irregularities and the horizontal crystal orientation of the crystalline thin film is aligned by utilizing the anisotropy of the surface energy on the side faces of the irregularities. However, the crystal structure and orientation of the thin film often depend delicately on the deposition conditions of the thin film, and crystals having various structures and orientations are simultaneously formed depending on the conditions.

[0007]

As described above, in the conventional crystal growth technique, the crystal structure of the crystalline thin film and the orientation of the growth surface 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 underlying layer. When using a seed crystal, the seed crystal is usually a crystalline substrate because the crystal structure and orientation of the seed crystal itself must be controlled. Therefore, the deposited crystalline thin film must be in contact with the crystalline substrate.

Further, it is impossible to deposit a crystalline thin film having a crystal structure whose symmetry is remarkably different from that of the base on the seed crystal base. Even 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 underlayer regardless of whether the underlayer is crystalline or amorphous.

Further, although there are crystal grain boundaries and sub-grain boundaries inside the crystalline thin film formed on the surface of the amorphous underlayer, these deteriorate the electrical characteristics of the crystalline thin film. The characteristics of the device having this crystalline thin film are deteriorated. In order to avoid this problem, it is necessary to control the growth condition of the crystalline thin film to make the crystal grain size larger than the device size, and special measures for controlling the crystal grain position are required. Is.

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

[0011]

In order to solve the above-mentioned problems, the method for producing a crystalline thin film according to claim 1 of the present invention uses a wave
Coherent synchronism where the length is at the atomic size level
Substrates are obtained by irradiating the surface of an amorphous substrate with tron radiation or one of coherent electron beams whose wavelength is at the atomic size level (hereinafter sometimes referred to as coherent beam). Crystal symmetry of surface-specific crystal structure with specific plane orientation and lattice in crystal growth plane
Forming a two-dimensional interference image with a lattice spacing equal to a constant ,
At the same time, by irradiating a molecule or atom serving as a raw material of the crystal, the two-dimensional interference image is used to control the crystal structure or the plane orientation of the growth plane, and the growth of the particular crystal structure and the particular plane orientation. A crystalline thin film having a plane is deposited on an amorphous substrate.

That is, in the present invention, the interference image by coherent beams from a plurality of directions is used to control the crystal structure and the plane orientation of the growth surface. In this case, the wavelength of the coherent beam needs to be shortened to the atomic size level. A short-wavelength coherent beam, for example, a radiant light having a wavelength of 1 nanometer has a high energy of about 1 keV, which is high enough to promote a chemical reaction. Since it reacts at a position corresponding to a lattice point of a desired crystal structure, a crystalline thin film having a crystal structure and a growth surface determined by a two-dimensional interference image is deposited.

With respect to a material having a polymorphism, it becomes possible to make different crystal structures by forming a two-dimensional interference image having a symmetry of the growth plane of a desired crystal structure. For example, a coherent beam is irradiated from four directions at 90 ° intervals when viewed from above to form a two-dimensional interference image having four-fold symmetry and a lattice spacing equal to the lattice constant on the crystal growth plane, and at the same time, as a raw material. By irradiating these atoms or molecules, the crystal can be grown while controlling the crystal structure to have a 4-fold symmetry structure.

Further, for example, a two-dimensional interference image having 6-fold symmetry and a lattice spacing equal to the lattice constant on the crystal growth plane is formed by irradiating a coherent beam from three directions having an interval of 120 ° when viewed from above. Then, at the same time, by irradiating the atoms or molecules that are the raw materials,
Crystals can be grown while controlling the structure to have a rotational symmetry. Even in a material having no polymorphism, crystals can be grown in the same manner while controlling the plane orientation of the growth surface of the crystal structure in a desired direction.

[0015] method for producing a crystalline thin film according to claim 2, wavelength
Is a coherent synchroto with atomic level
The surface of a crystalline substrate is irradiated with a synchrotron electron beam or a coherent electron beam whose wavelength is at the atomic size level from a plurality of directions so that the surface of the substrate has a specific plane orientation of a specific crystal structure. In the crystal plane symmetry and the crystal growth plane
In order to control the crystal structure and the plane orientation of the growth surface by forming a two-dimensional interference image having a lattice spacing equal to the lattice constant and simultaneously irradiating the molecule or atom which is a raw material of the crystal. It is characterized in that a crystalline thin film having the above-mentioned specific crystal structure and the growth plane of the above-mentioned specific plane orientation is deposited on the crystalline substrate by utilizing the structure independently of the structure of the crystalline substrate.

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

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an apparatus for producing a crystalline thin film used in this embodiment. This apparatus comprises 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 supplies the reaction light to the reaction chamber 4 after the coherent emission light emitted from the emission light source 5 such as a synchrotron radiation device is monochromatic by the filter 6.

The gas supply device 2 supplies the raw material gas to the reaction chamber 4. The substrate exchange chamber 3 is provided to introduce 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 constantly kept in vacuum by the vacuum exhaust device 10. The substrate 7 is mounted on the substrate holder 11 in the reaction chamber 4. A substrate heater 12 is attached to the bottom of the substrate holder 11 to heat the substrate 7 as needed. Instead of providing the substrate heater 12, infrared rays or the like may be irradiated from a position distant from the substrate holder 11 to heat the substrate.

The emitted light introduced into the reaction chamber 4 from the emitted light source 5 through the filter 6 is reflected by the half mirrors 13 and 1.
4, 15 are used to divide into a plurality of directions, for example, 4 directions, and the substrate 7 is irradiated with the mirrors 16, 17, 18, 19 from, for example, 4 directions. 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 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, in order to form a two-dimensional interference image having a periodic structure of a square lattice,
When radiating light from four directions A to D through the 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. Has been done. 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 in correspondence with the lattice spacing in the growth plane of the crystal structure to be manufactured on the substrate 7. When the tilt angle θ changes, the interval at which the wave W of the emitted light from the four directions A to D is reflected on the substrate 7 changes, and the grid interval of the two-dimensional interference image also changes accordingly. 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
The waves from the four directions A to D, which are set at an interval of 1 and have the same inclination angle θ in the vertical plane, interfere with each other to form a two-dimensional periodic array interference image having a square lattice. To be done.

In FIG. 4, in order to form a two-dimensional interference image having a hexagonal lattice periodic structure, irradiation of radiant light onto the substrate 7 is made from three directions E to G, and 120 ° to each other. It shows the case of irradiating from the direction forming the angle. The inclination angle of the emitted light in the three directions in the vertical plane is
They are made equal to each other corresponding to the lattice spacing in the growth plane of the crystal structure to be manufactured. In this case, the emitted lights from the three directions interfere with each other to form a two-dimensionally arranged interference image having a hexagonal lattice.

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

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

[0025]

EXAMPLES Next, examples of the present invention will be described. For example, GaN has a hexagonal crystal structure and a cubic crystal structure, and it is known that each exhibits unique physical properties. Hexagonal and cubic GaN have lattice constants of 3.189 and 4.51 angstroms, respectively. Therefore, when growing hexagonal GaN, as shown in FIG. 4, by irradiating the substrate 7 with radiant light from three directions at 120 ° intervals as seen from above, as shown in FIG.
A two-dimensional interference image having a hexagonal lattice periodic structure having a lattice spacing L1 of 3.189 angstrom 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. When supplied, as shown in FIG. 6, hexagonal GaN is formed on the substrate 7.
24 grows.

On the other hand, when growing cubic GaN, as shown in FIG.
By irradiating radiant light from 4 directions at intervals of °,
As shown in FIG. 2, a two-dimensional interference image having a square lattice periodic structure with a lattice spacing L2 of 4.51 angstrom is formed on the substrate 7, and at the same time, the same trimethylgallium and ammonia as above are supplied at a substrate temperature of 900 ° C. Then, as shown in FIG. 8, cubic GaN 25 grows on the substrate 7.

As another embodiment, it is known that SiC also has a hexagonal crystal structure and a cubic crystal structure.
The hexagonal and cubic crystals of C have lattice constants of 3.086 Å and 4.358 Å, respectively. Therefore, in the case of growing hexagonal SiC, as shown in FIG.
By irradiating the substrate 7 with radiant light from three directions at 120 ° intervals as viewed from above, the substrate 7 has a lattice spacing L1 of 3.086 angstroms as shown in FIG. When a two-dimensional interference image having a hexagonal lattice periodic structure is formed and disilane and acetylene are supplied as raw materials while the temperature of the substrate 7 is kept at 900 ° C. at the same time, hexagonal SiC grows on the substrate 7.

On the other hand, in the case of growing cubic SiC, as shown in FIG.
By irradiating radiant light from 4 directions at intervals of °,
2 has a square lattice periodic structure with a lattice spacing L2 of 4.358 angstroms on the substrate 7.
When a dimensional interference image is formed and at the same time the same disilane and acetylene as described above are supplied at a substrate temperature of 900 ° C., hexagonal SiC grows on the substrate 7.

Further, as another embodiment, the case of controlling the orientation of the growth surface of the silicon crystal will be described. That is,
Even in silicon with a single diamond structure,
For example, in the case of growing (100) silicon, as shown in FIG.
By irradiating the synchrotron radiation from the direction, as shown in FIG. 9, 5.431 which is equal to the lattice constant of silicon on the substrate 7.
If a two-dimensional interference image having a periodic structure of a square lattice having a lattice spacing L3 of angstrom is formed, and a raw material such as disilane or dichlorosilane is simultaneously irradiated, (10
The (0) plane becomes a 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.
By radiating radiant light from 3 directions at 0 ° intervals, 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) on the substrate 7. When a two-dimensional interference image having a structure is formed and a raw material such as disilane or dichlorosilane is simultaneously irradiated, the (111) plane becomes a growth surface, 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, and specific examples of the amorphous substrate include quartz glass and the like.
Specific examples of the crystalline substrate include silicon and gallium arsenide. Then, as described above, when an amorphous substrate is used, the crystal structure and the plane orientation of the growth surface can be freely set when a crystalline thin film is formed on an amorphous underlayer like an SOI structure. 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 the symmetry 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
A coherent synchrotron radiation at a level or a coherent electron beam at a wavelength at the atomic size level ( a coherent beam at a wavelength at the atomic size level ) is amorphous from multiple directions. By irradiating the substrate surface, the symmetry of the crystal plane of a specific plane orientation of a specific crystal structure on the substrate surface and the lattice constant in the crystal growth plane, etc.
By forming a two-dimensional interference image with a new lattice spacing and simultaneously irradiating the molecule or atom that is the raw material of the crystal,
The two-dimensional interference image is used to control the crystal structure and the plane orientation of the growth plane to deposit a crystalline thin film having the particular crystal structure and the growth plane of the particular plane orientation on an amorphous substrate. So, for polymorphic materials,
When viewed from above, for example, a lattice having a 4-fold symmetry or a 6-fold symmetry by irradiating a coherent beam from a plurality of directions having a predetermined interval of 90 ° or 120 ° and having a lattice constant equal to the lattice constant on the crystal growth surface By forming a two-dimensional interference image with intervals and simultaneously irradiating the atomic or molecular beam of the raw material, the crystal structure is controlled while controlling the crystal structure to a desired symmetry structure such as 4-fold symmetry or 6-fold symmetry. Can grow. Further, even in the material having no polymorphism, in the same manner, the growth surface of the crystal structure may be grown while controlling the crystal to a desired plane direction. As a result, when a crystalline thin film is formed on an amorphous underlayer like the SOI structure, the crystal structure and the plane orientation of the growth surface can be freely controlled.

A method of manufacturing a crystalline thin film according to claim 2 is characterized by a wavelength
Is a coherent synchroto with atomic level
The surface of a crystalline substrate is irradiated with a synchrotron electron beam or a coherent electron beam whose wavelength is at the atomic size level from a plurality of directions so that the surface of the substrate has a specific plane orientation of a specific crystal structure. In the crystal plane symmetry and the crystal growth plane
In order to control the crystal structure and the plane orientation of the growth surface by forming a two-dimensional interference image having a lattice spacing equal to the lattice constant and simultaneously irradiating the molecule or atom which is a raw material of the crystal. Since the crystalline thin film having the specific crystal structure and the growth plane of the specific plane orientation is deposited on the crystalline substrate independently of the structure of the crystalline substrate, the same as in claim 1. In a polymorphic material, a crystal can be grown while controlling the crystal structure to have a desired symmetry structure such as 4-fold symmetry or 6-fold symmetry. It is possible to grow a crystal while controlling the growth surface of (1) to a desired plane orientation. As a result, a crystalline thin film having a symmetry significantly different from the symmetry of the crystal structure of the substrate can be formed on the specific crystalline substrate.

[Brief description of drawings]

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

FIG. 2 is a plan view of the substrate when viewed from above in the embodiment 4;
The schematic plan view which shows the irradiation direction of light at the time of 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 a light irradiation direction when light is applied to the substrate from three directions.

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

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

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

8 is an explanatory view showing a state in which cubic GaN is deposited on the substrate of FIG.

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

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

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

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

[Explanation of symbols]

1 Coherent beam supply device 2 gas supply device 3 board exchange room 4 Reaction chamber 5 Synchrotron radiation source 6 filters 7 substrate 8 gate valves 9,10 Vacuum exhaust device 11 board holder 12 Substrate heater 13 to 15 half mirror 16 to 22 mirrors 23 Gas nozzle 24 GaN (Hexagonal) 25 GaN (cubic) 26 (100) Silicon 27 (111) Silicon

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 62-18709 (JP, A) JP 7-221027 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 21/205 C30B 29/06 504 C30B 29/38

Claims (2)

(57) [Claims] 1. A coherent synchrotron radiation in which the wavelength is at the atomic size level or the wavelength is at the atomic size.
Symmetry and forming one of the coherent electron beam is level from a plurality of directions of crystal planes of a particular plane orientation of a particular crystal structure on the substrate surface by irradiating an amorphous substrate surface
The two-dimensional interference image is formed by forming a two-dimensional interference image having a lattice spacing equal to the lattice constant on the growth surface of the crystal and simultaneously irradiating the molecules or atoms that are the raw material of the crystal to obtain the crystal structure and the plane orientation of the growth surface. A method for producing a crystalline thin film, characterized in that a crystalline thin film having the above-mentioned specific crystal structure and a growth plane with the above-mentioned specific plane orientation is deposited on an amorphous substrate by utilizing it for controlling the temperature. 2. Coherent synchrotron radiation in which the wavelength is at the atomic size level or the wavelength is at the atomic size
Of a coherent electron beam at different levels from several directions to irradiate the surface of the crystalline substrate, and the symmetry and bonding of the crystal planes of the specific plane orientation of the specific crystal structure on the substrate surface.
The two-dimensional interference image is formed by forming a two-dimensional interference image having a lattice spacing equal to the lattice constant on the growth surface of the crystal and simultaneously irradiating the molecules or atoms that are the raw material of the crystal to obtain the crystal structure and the plane orientation of the growth surface. A crystalline thin film having the above-mentioned specific crystal structure and the growth plane of the above-mentioned specific plane orientation independently of the structure of the crystalline substrate, and is deposited on the crystalline substrate. Method for forming a thin film.