JPH0346431B2 - - Google Patents

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a single crystal film growing method for growing a single crystal film of a desired substance on a substrate, and particularly relates to a method for growing a single crystal film of a desired compound on a single crystal substrate. It was designed to allow the plants to grow without any problems.

(Prior Art) Conventionally, in order to grow a single crystal film on a substrate, a method of epitaxially growing a desired material on a single crystal substrate of the desired material has generally been used. Furthermore, recently, attempts have been made to use graphite epitaxy, in which a single crystal film is grown on a substrate surface with parallel grooves or lattice grooves with a fine pitch of micrometer order or less.

However, in the former method, the single crystal wafer used as the substrate is expensive, requires a considerable thickness of about 1 mm, and has the disadvantage of wasting expensive material as a margin for cutting the crystal. Economic,
There were resource shortcomings. Also, the latter method has
There was a drawback that the manufacturing cost and labor required to provide fine pitch grooves on the substrate could not be ignored.

(Objective) The object of the present invention is to eliminate the above-mentioned conventional drawbacks, eliminate the use of an expensive single crystal substrate, and
A desired compound can be formed using a substrate made of any material, such as a normal substrate such as a glass plate, metal plate, or ceramic plate, or even a plastic plate if temperature conditions permit, without any special processing of the substrate. An object of the present invention is to provide a method for growing a single crystal film, which allows a single crystal film to be grown.

(Summary of the Invention) That is, the method for growing a single crystal film of the present invention includes a process of forming a desired compound film on a desired substrate other than a single crystal substrate, and a process of forming a desired compound film on a desired substrate other than a single crystal substrate, and forming a film with the lowest melting point and A process of covering the compound film with a film of a component substance having a vapor pressure, and a process of heating the compound film covered by the film to a temperature at which the compound film changes into a melt and then cooling it, The method is characterized in that by single-crystallizing the compound film, a single-crystal film of a desired compound can be grown without using a single-crystal substrate.

(Example) The present invention will be described in detail below with reference to the drawings.

First, FIG. 1 shows the substrate structure of a single crystal film manufactured by the method of the present invention. In the figure, 1 is a substrate, 2 is a compound film, and 3 is a film made of a substance that is one of the components of the compound film. More specifically, the compound film 2
For example, InP, GaAs, InSb, GaSb, GaP,
It is made of InAs or the like, or it is made of a compound semiconductor such as GaAlAs, InAlAs, ternary or quaternary GaAlAsP, InAlAsP, etc., which is made of In, Ga, etc. as a base and Al is added thereto. For example, the compound film 2 may be InP,
When it is made of either InSb or InAs, it is referred to as In.
Alternatively, if the compound film 2 is one of GaP, GaSb, and GaAs, it is formed of a substance having the lowest melting point and vapor pressure among the constituent materials of the compound film 2, such as Ga. In other words, In and Ga have the respective melting points of 157°C and 30°C, which are the lowest among the constituent substances of the above-mentioned compound group, and
The temperatures required to achieve a vapor pressure of 10 ^-2 Torr are both quite high, 952°C and 1093°C, and therefore have the lowest vapor pressures among the constituent substances in the above-mentioned compound group.

In the illustrated configuration, for example, an InP film 2 is deposited to a thickness of approximately 3 μm on a glass substrate 1 having a thickness of approximately 1 mm by molecular beam evaporation (ultra-high vacuum deposition), and an InP film 2 is deposited on a glass substrate 1 having a thickness of approximately 1 mm.
The membrane 3 is coated to a thickness of approximately 18 μm.

In practice, these thicknesses are not exact values, and the values shown here may be slightly larger or smaller.

FIG. 2 shows a schematic configuration of a molecular beam evaporation apparatus used to form a compound film having the above-described configuration. In the diagram, 4
5 is a heater for heating the substrate, and 5 is a substrate. Also, 6
is the deposition source material for one of the compounds, e.g. indium
A crucible 7 containing In is a crucible containing the other vapor deposition source material, for example, phosphorus P. Furthermore, 8 is a cooling shroud filled with liquid nitrogen, 9 is a vacuum chamber, and 10 is an exhaust port to an ultra-high vacuum pump, such as a cryo pump or an ion pump.

The third example shows the relationship between the temperature change of the substrate 5 and the elapsed time in a series of steps of compound film deposition, component substance film deposition, and single crystallization treatment using the above-mentioned deposition apparatus.
As shown in the figure. First, while maintaining the temperature of the substrate 5 at 270°C, molecular beam evaporation, that is, ultra-high vacuum evaporation, is performed on the substrate 5 from the evaporation source crucibles 6 and 7, each containing indium In and red phosphorus P with a purity of 6 nines. conduct. The degree of vacuum before deposition is 5.5×10 ^-9 Torr, and the degree of vacuum during deposition is 1.5× due to the vapor pressure of phosphorus P.
It was around 10 ^-7 Torr. In addition, indium In is
700-800°C, and phosphorus P evaporated at about 300°C.
After synthetically depositing the InP compound film 2 with a thickness of 3 μm in this manner, the temperature of the crucible 7 is lowered to stop the evaporation of phosphorus P, and the evaporation of only indium In from the crucible 6 is continued. Then, an In film 3 having a thickness of about 18 μm is laminated on the compound film 2. Such laminations 2, 3
The formation is performed while the temperature of the substrate 5 is maintained at 270 DEG C. in the period b-c in the time chart shown in FIG. Subsequently, the temperature of the substrate 5 is once lowered sequentially in sections c to f, and then the temperature of the substrate 5 is rapidly raised to about 1000° C. in sections fh, and then natural radiation cooling is performed. Let the temperature drop to room temperature. Since the melting point of the compound InP is 1060°C, the compound InP recrystallizes during the temperature rise to 1000°C, its crystal grains enlarge, and all crystal grains become parallel to the plane of the substrate 5 ( 111) plane becomes the dominant orientation. During recrystallization, if the impurities in the pre-deposited InP compound are extremely low, the impurities that form grain boundaries will also be extremely low, and grain boundaries will either be almost absent or only slightly present.

However, the phosphorus P, which has a high vapor pressure and exists in the InP compound, tries to dissociate and escape, but the surface
Since it is covered by the film, it cannot escape, and some of the phosphorus P dissolves into the indium In. Then,
As described above, after the substrate temperature reaches the recrystallization temperature of about 1000° C., it is immediately lowered to room temperature by natural heat radiation. What should be noted here is that if the recrystallization temperature
If kept at 1000℃ for a long time, InP compound 2 and
The In coating 3 will diffuse and fuse with each other, making it impossible to form a desired film. Now, as mentioned above, if the recrystallization temperature is immediately allowed to cool after reaching 1000°C, in the process of temperature drop, the recrystallized crystal is in a state of single crystal or (111) plane preferential orientation close to a single crystal. On the underlying InP compound film 2, indium In in which phosphorus P is dissolved as described above is applied.
(At this time, the temperature of the In layer containing P is below the melting point of the underlying InP recrystallized film, which is about 1000°C, and the melting point of In is about 1000°C or lower.) Considering that the temperature is 150° C. or higher, the In melt containing P comes into contact with the solid-phase InP recrystallized film.) In this way, a single crystal film is grown.

In addition, in the above natural cooling process, if the heater 4 is attached to only one side of the substrate 5 as shown in FIG. Zone melting is performed with the film surface perpendicular to the film deposition.
Therefore, the InP compound film 2 is purified.

In short, in the process of growing a single-crystal film according to the present invention, the film is in a single-crystal or near-single-crystal state due to recrystallization, and moreover, the (111)
It is considered that the InP compound film having plane-preferential orientation serves as a seed single crystal film, and liquid phase epitaxial growth of the InP compound is performed thereon, thereby promoting improvement in single crystallization. Furthermore, if the heater is mounted only on one side of the substrate as described above, a temperature gradient perpendicular to the film surface will be generated through the cooling process to room temperature during recrystallization and subsequent liquid phase epitaxial growth, resulting in zone melting. It is also conceivable that this simultaneously occurs in the film growth direction to purify the film, that is, to promote improvement in single crystallization.

In short, the present invention provides vacuum evaporation, recrystallization,
It is believed that a single crystal film is produced based on a combined phenomenon with liquid phase epitaxial growth. However, the interaction effect between recrystallization and the liquid-phase epitaxial growth formed by the seed single crystal film and the overlying compound component film is greater than the contribution from zone melting. This is considered to be an important factor promoting the

formed on a glass substrate as described above.
Figure 4 shows an example of a reflected X-ray Laue photograph of an InP single crystal film. In creating the reflected X-ray Laue photograph shown in the figure, the irradiated X-ray beam passes through a collimator with a diameter of 1 mm, and therefore the irradiated area is equivalent to a circle with a diameter of 1 mm, but it covers the entire surface of a membrane approximately 1 cm square. A spot pattern as shown was shown. As can be seen from the photograph, the film produced by the method of the present invention is a single crystal film having a (111) plane parallel to the substrate, as can be seen from the 3-fold symmetrical arrangement of the spots. In addition, the third
During the temperature change process shown in the figure, the sequential cooling process c-
In d-e-f, unless rapid interdiffusion fusion occurs between the InP compound film 2 and the In coating 3, this cooling process is omitted and the recrystallization temperature is directly reached from the heat retention process b-c to 1000°C. It is also possible to increase the substrate temperature.

In addition, when the component element distribution in the stacking direction in an example of manufacturing a single crystal film by the method of the present invention was confirmed by line analysis using an X-ray microanalyzer, first of all,
There is an InP compound film with a stoichiometric composition about 2.5 μm thick on the glass substrate surface, and on top of that there is an InP compound film about 7.5 μm thick.
There is a layer of phosphorus P in excess of In, that is, a layer of indium In in which phosphorus P is dissolved, and the amount of indium In gradually increases until finally a surface layer with a thickness of about
It had a structure in which 18 μm In films were laminated.
In addition, the lattice constant of the produced film by bond method measurement for single crystals was measured to be 5.889 Å in the cubic system, and ASTM,
The lattice constant of the InP single crystal shown on the card is 5.869
It showed good agreement with Å.

InP on the InP single crystal film fabricated as described above
Depending on the structure of the electronic device manufactured using the single crystal film, the film can be left as it is, or a part can be left and the remaining part can be removed by etching. In addition, in order to remove this In film, for example, the substrate temperature must be adjusted so that the InP single crystal film 2 does not melt and change in quality, and the In film is in a molten state (since the melting point of In is approximately 150°C). The In coating was mechanically removed by increasing the temperature to approximately 200°C.
Alternatively, an appropriate removal method can be used, such as removing only the In coating 3 by sputter etching. As a result of removing the In film 3 in this way, the exposed InP single crystal film 2 can be further epitaxially grown undoped on the single crystal film, or impurities can be evaporated from the crucible. Films are formed on the InP single crystal film 2 according to the purpose of use, such as by epitaxially growing InP while doping, to produce a single crystal film of good quality. It is possible to manufacture electronic devices, optical devices, etc. using this method.

In addition, when removing the In film 3 mentioned above, when InP epitaxial growth is subsequently carried out using the exposed InP single crystal film 2 as a seed single crystal substrate, the surface of the seed single crystal substrate is exposed to carbon C and oxygen contained in the air. O
In order to avoid contamination, it is extremely important to subsequently remove the In film 3 in an ultra-high vacuum without breaking the vacuum, and to subsequently grow epitaxially thereon. In other words, in conventional epitaxial growth, the surface of a single-crystal bulk substrate is polished, washed and etched, then placed in an ultra-high vacuum molecular beam epitaxy device, raised to the desired substrate temperature, and irradiated with As and P molecules. However, according to the present invention, a clean crystal surface can be obtained from the single crystal film stage instead of the substrate crystal, and acceptors and donors can be removed while maintaining the cleanliness of the crystal. This method has an extremely large advantage in that impurity doping is performed by evaporation in the same vacuum chamber, allowing consistent device fabrication (so-called in situ).

Further, although the compound film 2 has been described as an example of forming a film using a three-temperature method, other film forming methods such as flash vapor deposition, sputtering, and ion beam vapor deposition may also be used. Furthermore, as is clear from the principle, it is possible to fabricate a large-area single crystal film.

(Effects) As is clear from the above explanation, according to the present invention, a single crystal film can be formed on a normal amorphous substrate such as glass or a metal or semiconductor polycrystalline substrate, which was previously considered impossible or extremely difficult. This means that an innovative and breakthrough semiconductor technology has been developed. Therefore, according to the method for growing a single crystal film of the present invention, it is possible to significantly reduce the manufacturing cost of a single crystal film, and it is also possible to realize a large area single crystal film. It has become possible to reduce the costs of solar cells, various electronic devices, and optical devices, which has greatly contributed to the dramatic development of the electronics industry, and is expected to have a significant economic ripple effect on the electronics industry.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the basic structure of a single crystal film produced by the method of the present invention, FIG. 2 is a sectional view showing the schematic structure of a molecular beam evaporation apparatus by the method of the present invention,
The figure is a time chart showing an example of the process of substrate temperature change according to the method of the present invention, and FIG. 4 is a transfer diagram of a reflection X-ray Laue photograph of a single crystal film produced by the method of the present invention. 1...Substrate, 2...Compound film, 3...Coating, 4
...Substrate heating heater, 5...Substrate, 6,7...
Vapor deposition source and crucible, 8... cooling shroud, 9... vacuum chamber, 10... vacuum exhaust port.

Claims (1)

[Claims] 1. A process of producing a desired compound film on a desired substrate other than a single crystal substrate, and a coating of a component material having the lowest melting point and vapor pressure among the component materials constituting the compound film. a step of covering the compound film; and a step of heating the compound film covered by the coating to a temperature at which the compound film changes into a melt;
After heating, the compound film and the recrystallized compound film formed by cooling the film first come into contact with the film melt containing the compound film components as a seed crystal film, and further cooling causes liquid phase epitaxial growth. and growing a single crystal of the desired compound on the desired substrate without using a single crystal substrate. Single crystal film growth method. 2. In the method for growing a single crystal film according to claim 1, when the melt of the compound film is cooled, a temperature gradient is applied to the compound film grown by liquid phase epitaxial growth in a direction perpendicular to the plane of the film. A single crystal film growth method characterized by performing zone melting by giving