JPH1154431A - Manufacture of thin crystal film and device used for it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a excellent thin crystal film and a device used for it which is superior in control and capable of manufacturing a crystal uniform in a face direction by giving a uniform heat conduction to substrate. SOLUTION: A substrate 4 supported by a lower boat 1 from the back, the surface of the substrate 4 is contacted to a solvent metal 6 comprising an added and melted crystal material as a solute, and a liquefied metal 10 used for heat conduction is filled and held between the backside of the substrate 4 and the lower boat 1, when a thin crystal film is obtained by depositing the solute on the substrate 4 by lowering the temperature of the substrate 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a crystal thin film based on a liquid phase epitaxial growth method and an apparatus used for the method.

[0002]

2. Description of the Related Art As a method of obtaining a crystalline thin film used as a semiconductor material, conventionally, a solute material is saturated at a high temperature in a solvent of a low melting point metal, and then the saturated solution is cooled to obtain a supersaturated solute material. Liquid phase growth method (Liquid Phase) to obtain crystalline thin film by depositing as crystals on a substrate
Epitaxy (hereinafter abbreviated as “LPE”) is well known. As an apparatus used for the LPE, for example, a slide boat type apparatus as shown in FIG. 10 is widely used.

This apparatus is a combination of upper and lower slide boats 1 and 2, and the lower boat 1 is movable in the left and right directions as indicated by arrows. A plurality of recesses 3 (only one is shown in the figure) are formed at predetermined intervals on the upper surface of the lower boat 1, and the substrate 4 is fitted into each of the recesses 3. On the other hand, a plurality of through holes 5 (2
In the state where each through hole 5 is positioned so as not to overlap with each recess 3 of the lower boat 1,
Each of the through holes 5 is filled with a solvent metal 6. Note that a crystalline material is added and melted as a solute to the solvent metal 6. Reference numeral 7 denotes a moving arm for moving the lower boat 1.

In a state where the solvent metal is filled and held, the lower boat 1 is moved by operating the moving arm 7 so that the respective through holes 5 and the substrates 4 in the respective recesses 3 are positioned so as to overlap each other as shown in the figure. Then, by lowering the temperature and depositing a crystalline thin film material on the surface of the substrate 4, epitaxial growth is performed.

[0005] Since the crystal growth by LPE is a crystal growth from a quasi-equilibrium state between a solid phase and a liquid phase, there is an advantage that a crystal with high purity and few defects and high integrity can be obtained. Also, there is an advantage that handling such as taking in and out of the substrate 4 is easy. Therefore, the LPE is considered promising as a method for forming a crystalline silicon thin film used for a semiconductor material or a solar cell.

[0006]

However, in the conventional LPE apparatus, the temperature of the substrate 4 is controlled by heating a film forming jig (the lower boat 1 in FIG. 10) for holding the substrate 4 from the back side. However, it is difficult to finish each contact surface between the film forming jig and the substrate 3 to a perfect mirror surface, and the two cannot be completely adhered to each other. For this reason, the thermal contact between the substrate 4 and the jig becomes non-uniform and a temperature distribution is generated, so that there is a problem that the crystal growth is not performed uniformly and the quality of the crystal deteriorates. In addition, problems such as abnormal growth of crystals at the end of the substrate 4 also occur.

[0007] The present invention has been made in view of such circumstances, and by providing uniform heat conduction to a substrate,
It is an object of the present invention to provide an excellent method for producing a crystal thin film, which is excellent in controllability and can obtain a uniform crystal in a plane direction, and an apparatus used therefor.

[0008]

According to a first aspect of the present invention, a substrate is held from the back side by a film forming jig. When the crystal material is brought into contact with the solvent metal added and melted as a solute to precipitate a solute on the surface of the substrate by lowering the substrate temperature to obtain a crystalline thin film, the back surface of the substrate and a jig for film formation. In the meantime, a method of producing a crystal thin film in which a liquefied metal for heat conduction is filled and held during the process.

According to a second aspect of the present invention, in the method for producing a crystalline thin film, the temperature of the liquefied metal for heat conduction, which is filled and held, is directly controlled by temperature control means. According to a third aspect of the present invention, in the method for producing a crystalline thin film, the thickness of the liquefied metal for heat conduction filled and held is set to 0.1 to 20 mm. It is something to do.

Further, according to a fourth aspect of the present invention, in the above-mentioned method for producing a crystal thin film, a liquefied metal reservoir and a gas vent communicating with a space for filling and holding a liquefied metal for heat conduction in a film forming jig. A liquefied metal is automatically filled from the liquefied metal reservoir by providing a passage.

Further, according to the invention of claim 5 of the present invention, the substrate is held from the back side by a film forming jig, and in this state, the surface of the substrate is brought into contact with a solvent metal to which a crystalline material has been added and melted as a solute. An apparatus used to deposit a solute on the surface of the substrate by contacting and lowering the temperature of the substrate to obtain a crystalline thin film, and heat conduction is provided between the back surface of the substrate and a film forming jig. SUMMARY OF THE INVENTION An object of the present invention is to provide an apparatus for manufacturing a crystal thin film in which a liquefied metal is filled and held.

According to a sixth aspect of the present invention, in the above-described apparatus for producing a crystalline thin film, the temperature of the liquefied metal for heat conduction filled and held is directly controlled by temperature control means, and the temperature of the liquefied metal is reduced. The temperature of the substrate is controlled by the temperature of the substrate. The invention according to claim 7 of the present invention is directed to the apparatus for manufacturing a crystalline thin film, wherein the thickness of the liquefied metal for heat conduction filled and held is 0.1%. It is set to 20 mm.

Further, according to an eighth aspect of the present invention, in the above-described apparatus for manufacturing a crystal thin film, a liquefied metal reservoir and a gas which communicate with a space for filling and holding a liquefied metal for heat conduction in a film forming jig. A bleed path is provided, and liquefied metal is automatically filled from the liquefied metal reservoir.

[0014]

Next, embodiments of the present invention will be described in detail.

FIG. 1 shows an example of an LPE apparatus used in the present invention. That is, this apparatus is a slide boat type apparatus as in the apparatus of FIG. 10, but the recess 3 for board insertion of the lower boat 1 is separate from the board insertion space.
The space 3 is formed one step deeper,
A liquid metal 10 for heat conduction is filled and sealed in a. Other configurations are the same as those in FIG. 10, and the same portions are denoted by the same reference numerals.

A slight step is formed at the boundary between the space 3a filled with the liquefied metal 10 for heat conduction and the space (recess 3) into which the substrate is fitted. The substrate 4 is held at a certain height (the height at which the surface of the substrate 4 is flush with the sliding surface of the lower boat 1) by the step so as not to fall into the inside.

According to this apparatus, the back surface of the substrate 4 does not directly contact the lower boat 1, and the liquefied metal 10
Will intervene. Accordingly, when the lower boat 1 is heated by a heater or the like in order to bring the substrate 4 to a predetermined temperature, the heat conduction is performed uniformly and efficiently through the liquefied metal 10 and the temperature of the substrate 4 is reduced. In addition, control can be performed with excellent followability to a temperature change of the lower boat 1. In addition, due to the heat conduction effect of the liquefied metal 10 in the horizontal direction, an effect that the temperature of the substrate 4 becomes very uniform in the plane direction can be obtained.

Liquid metal 10 for heat conduction used in the present invention
Is a metal that is in a liquid state under the temperature conditions at the time of film formation by LPE (in the present invention, this is called "liquefied metal")
Examples of such a liquefied metal 10 include low melting point metals such as tin, indium, lead, aluminum, gallium, and copper. Among them, tin, indium, and lead having a melting point of 350 ° C. or less are preferable. That is,
If the melting point is high, the metal may change from a liquid to a solid when the temperature is lowered for crystal precipitation. Further, those having high thermal conductivity are preferable, and in that regard, tin is particularly preferable.

As the substrate 4 used in the present invention, for example, various inorganic and ceramic materials such as carbon, quartz, alumina, silicon carbide, graphite, glassy carbon, zirconia, and silicon nitride can be used. These are preferable because they can withstand high temperatures during liquid phase growth and do not dissolve in the solvent metal 6 and the liquefied metal 10 for heat conduction. It is particularly preferable to use quartz or glassy carbon from the viewpoint of semiconductor device fabrication.

When the inorganic and ceramic substrates 4 are used, the amount of the liquefied metal 10 for heat conduction brought into contact with the back surface thereof is preferably as small as possible from the viewpoint of thermal conductivity. In consideration of the surface tension of the metal 10, the size of the substrate 4, the surface roughness of the opposing surface of the substrate 4 and the lower boat 1, the filling thickness t (see FIG. 3) is usually 0.1 to 20 mm. It is preferable that the setting is made as follows.

Further, the types of the solvent metal 6 and the solute (crystal material) used in the present invention, the materials of the slide boats 1 and 2, and the temperature and pressure conditions are not particularly limited, and are appropriately determined according to general LPE. Selected / set.

The above example is given to the lower boat 1 by filling and holding the liquefied metal 10 for heat conduction between the back surface of the substrate 4 and the lower boat 1 in the slide boat type LPE apparatus. Although the temperature control is transmitted uniformly to the substrate 4 by the liquefied metal 10, for example, as shown in FIG.
An independent temperature control block 11 different from the lower boat 1 is provided below the filling section of
The temperature control may be directly applied to the liquefied metal 10 from the top surface of the liquefied metal 10. Reference numeral 12 denotes the temperature control block 1
1 is a pipe for introducing a heat medium (for example, helium gas) adjusted to a predetermined temperature.

According to the apparatus shown in FIG. 2, the temperature of the substrate 4 can be controlled independently of the lower boat 1 via the liquefied metal 10, whereby not only the temperature of the substrate 4 but also the substrate 4 can be controlled. Also, the magnitude of the temperature gradient formed in the solvent metal 6 (including the solute) can be controlled. As in the case of FIG. 1 described above, there is an advantage that the degree of freedom of the film forming process is remarkably increased in combination with the excellent uniformity of heat conduction in the plane direction of the substrate 4. In addition, the quality of the obtained crystal thin film is extremely good.

In the present invention, in addition to using the inorganic or ceramic substrate 4 as described above, a single crystal or polycrystalline semiconductor substrate can also be used. However, in that case, as shown in FIG. 3, it is necessary to set the liquefied metal 10 for heat conduction in contact with the back surface of the semiconductor substrate 4a to a minimum amount. That is, if the amount of the liquefied metal 10 is large, the back surface of the semiconductor substrate 4a may be partially dissolved in the liquefied metal 10 or a pinhole may be generated. The minimum amount of the liquefied metal is also as described above,
It depends on the surface tension of the liquefied metal, the size of the substrates 4 and 4a, the surface roughness of the opposing surfaces of the substrates 4 and 4a and the lower boat 1, and the like. Usually, the filling thickness t is 30 to 200 μm.
It is preferable to set such that: By the way, when a 1-inch square substrate 4a or a 1-inch diameter circular substrate 4a is used, the minimum thickness t of the liquefied metal 10
Is preferably set to about 100 μm. In addition,
If the thickness of the liquefied metal 10 is set to be very thin as described above, the effect of equalizing the temperature of the substrate 4a due to the lateral heat conduction cannot be expected so much. Etc.). Further, in the apparatus of FIG. 3, similarly to the case of FIG. 2, a structure in which the temperature control block 11 directly controls the temperature of the liquefied metal 10 can be employed. However, also in this case, for the same reason as described above, it is necessary to form the temperature control block 11 with a material having high thermal conductivity.

In these apparatuses, the substrates 4, 4
The liquefied metal 10 for heat conduction, which is filled underneath a, is usually filled beforehand in the space 3a below the substrates 4, 4a before mounting the substrates 4, 4a in the recess 3 of the lower boat 1. However, in this case, the liquefied metal 10 protrudes outside due to the volume expansion of the liquefied metal 10 due to the temperature rise,
Due to a decrease in the volume of the liquefied metal 10 due to the temperature drop, a gap may be formed at the interface between the substrates 4 and 4a and the liquefied metal 10, and heat transfer may not be performed uniformly. Therefore, in order to avoid these problems, for example, FIGS.
As shown in FIG.
It is preferable that the liquefied metal reservoir 13 is communicated with the lower space 3a of the substrates 4 and 4a so that the liquefied metal 10 automatically flows into the space 3a. In this case, it is preferable to provide a gas venting path 14 for discharging residual gas inside the lower boat 1 on the side opposite to the side where the liquefied metal reservoir 13 is provided.

The present invention also relates to a slide boat type L
The present invention can be applied to devices other than the PE device. For example, in an apparatus of a tipping method (inclination method) as shown in FIG. 7, a raw material 22 to be a solute and a solvent metal 6 are put into a melting tank 21 in an inclined furnace tube 20, and the solvent metal 6 is biased. A substrate 24 is mounted via a clamp 23 in a melting tank 21 on the opposite side to the raw material 22 and the raw material 22 is heated at a high temperature.
Diffusion in and saturation. Then, the furnace tube 20 is inclined to the opposite side, and the solvent metal 6 saturated with the solute is transferred to the substrate 24.
And epitaxial growth is performed while lowering the temperature in that state. In this apparatus, as shown in FIG. 8, a concave portion is provided on the inner surface of the melting tank 21 with which the back side of the mounted substrate 24 contacts, and the liquefied metal 10 for heat conduction is filled and held in this portion. The same effect as the slide boat type device can be obtained. Needless to say, the liquefied metal 10 may be filled by automatically flowing from the liquefied metal 21 itself or a liquefied metal reservoir (not shown) provided outside the molten tank 21.

Further, for example, as shown in FIG.
In the single-sided dip type (immersion method) apparatus, a platinum crucible 31 containing a solvent metal 6 is arranged in a vertical furnace 30, and a raw material 32 to be a solute is put therein and melted at a high temperature.
Next, the substrate 33 is lowered from above and immersed in the solvent metal 6, and in that state, the temperature is reduced and epitaxial growth is performed. In this apparatus, as the jig 34 for holding the substrate 33, as shown in FIG. 9B, the jig 34 having a structure in which the back surface of the substrate 33 is filled with the liquefied metal 10 for heat conduction is used. The same effect as that of the boat type apparatus can be obtained. Also in this case, the liquefied metal 10 can be automatically flowed and filled from a liquefied metal reservoir (not shown) provided at the end of the jig 34 for holding the substrate or other portions.

[0028]

As described above, according to the first aspect of the present invention, the back side of the substrate does not come into direct contact with the film forming jig holding the substrate, and the heat conduction Since the liquefied metal is interposed, heat conduction is performed uniformly and efficiently through the liquefied metal. Therefore, the substrate temperature can be controlled with excellent followability to the ambient temperature change. In addition, due to the heat conduction effect of the liquefied metal in the horizontal direction, the effect that the substrate temperature becomes very uniform in the plane direction can be obtained.

According to the second aspect of the present invention, in addition to the above-mentioned effects, the substrate temperature can be controlled independently via the liquefied metal. Therefore, not only the substrate temperature but also the magnitude of the temperature gradient formed between the substrate and the solvent metal (including the solute) can be controlled, and there is an advantage that the degree of freedom of the film forming process is dramatically increased. In addition, the quality of the obtained crystal thin film is extremely good.

Further, according to the third aspect of the present invention, the above effect can be further improved by limiting the filling thickness of the liquefied metal.

According to the invention as set forth in claim 4 of the present invention, the liquefied metal can be automatically filled in accordance with the temperature conditions and the like, instead of being charged in advance, so that the liquefied metal is There is no gap between the substrate and the back surface of the substrate, and the liquefied metal does not protrude to the outside.

Further, according to the invention as set forth in claims 5 to 8 of the present invention, it is possible to provide an apparatus capable of satisfactorily implementing the invention as set forth in claims 1 to 4.

Next, an embodiment will be described.

[0034]

(Film forming conditions)

 Substrate Material: Glassy carbon 寸 法 Dimensions: Length 25 mm x width 25 mm x thickness 1 mm Solvent metal type Tin (90%) + aluminum (10%) alloy Solute (crystal material) type Silicon Solute concentration To the above solvent metal at 1200 ° C Saturation amount of liquefied metal Type: Tin 充填 Fill thickness: 5 mm Pressure 1 atm Initial temperature 1200 ° C Crystal growth temperature 1200-700 ° C (temperature gradient 1 ° C / min)

The silicon crystal thin film obtained as described above was superior in uniformity in the crystal plane direction and higher in quality than that obtained by the conventional apparatus shown in FIG.

[Brief description of the drawings]

FIG. 1 is a partial longitudinal sectional view showing one embodiment of an LPE apparatus used in the present invention.

FIG. 2 is a partial vertical sectional view showing another embodiment of the LPE apparatus used in the present invention.

FIG. 3 is a partial longitudinal sectional view showing still another embodiment of the LPE apparatus used in the present invention.

FIG. 4 is a partial plan view showing another embodiment of the LPE apparatus used in the present invention.

FIG. 5 is a sectional view taken along line AA ′ of FIG. 4;

FIG. 6 is a sectional view taken along line BB ′ of FIG. 4;

FIG. 7 is an explanatory diagram of another LPE device.

FIG. 8 is an explanatory diagram of a configuration in which the present invention is applied to the device of FIG. 7;

FIG. 9A is an explanatory view of still another LPE apparatus,
(B) is an explanatory diagram of a configuration in which the present invention is applied to the device of (a).

FIG. 10 is a partial vertical sectional view showing an example of a conventional LPE apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lower boat 2 Upper boat 4 Substrate 6 Solvent metal 10 Liquefied metal

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Keishi Yokoyama 2-6-6 Chikko Shinmachi, Sakai City, Osaka Daido Hokusan Co., Ltd. Sakai Plant

Claims (8)

[Claims] 1. A substrate is held from the back side by a film forming jig. In this state, the substrate surface is brought into contact with a solvent metal in which a crystalline material is added and melted as a solute to lower the substrate temperature. When depositing a solute on the surface of the substrate to obtain a crystal thin film, between the back surface of the substrate and the jig for film formation, a liquefied metal for heat conduction is filled and held. Manufacturing method of thin film. 2. The crystal thin film according to claim 1, wherein the temperature of the liquefied metal for heat conduction filled and held is directly controlled by temperature control means, and the temperature of the substrate is controlled by the temperature of the liquefied metal. Manufacturing method. 3. The method for producing a crystalline thin film according to claim 1, wherein the thickness of the liquefied metal for heat conduction filled and held is set to 0.1 to 20 mm. 4. A film forming jig is provided with a liquefied metal reservoir and a gas venting passage communicating with a space in which liquefied metal for heat conduction is to be filled and held, so that the liquefied metal is automatically filled from the liquefied metal reservoir. The method for producing a crystalline thin film according to claim 1. 5. A substrate is held from the back side by a film forming jig, and in this state, the substrate surface is brought into contact with a solvent metal to which a crystalline material is added and melted as a solute to lower the substrate temperature. An apparatus used to obtain a crystalline thin film by depositing a solute on the surface of the substrate, wherein between the back surface of the substrate and a jig for film formation, liquefied metal for heat conduction is filled and held. An apparatus for producing a crystalline thin film, comprising: 6. The temperature of the liquefied metal for heat conduction filled and held is directly controlled by temperature control means, and the temperature of the substrate is controlled by the temperature of the liquefied metal. Crystal thin film manufacturing equipment. 7. The apparatus for producing a crystalline thin film according to claim 5, wherein the thickness of the liquefied metal for heat conduction filled and held is set to 0.1 to 20 mm. 8. A film forming jig is provided with a liquefied metal reservoir and a gas venting passage communicating with a space for filling and holding a liquefied metal for heat conduction, and the liquefied metal is automatically filled from the liquefied metal reservoir. The apparatus for producing a crystal thin film according to claim 5, wherein