JPH0798718B2 - Liquid phase epitaxial growth system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a liquid phase epitaxial growth apparatus.

(Prior Art) In a liquid phase epitaxial growth apparatus, a gradual cooling and cooling method has been generally used, but a temperature difference method has been proposed as a new method. Explaining this temperature difference method, a temperature difference is formed in the solution as shown in FIGS. 4 (a) and 4 (b),
Float the source crystal of the crystal to be grown on this high temperature side T1,
The substrate crystal is placed on the low temperature side T2. Then, the extra solute dissolved on the high temperature side is transported to the substrate on the low temperature side by the density diffusion due to the difference in density due to the temperature difference ΔT = T1−T2 and the thermal diffusion due to the temperature difference.

The amount of solute transported is determined by the temperature difference. Therefore, the temperature of the growth furnace is constant and the crystal growth proceeds, and the crystal growth is rate-limited by the solubility of the solute in the solvent as in the slow cooling temperature-falling method. Absent.

For this reason, crystal growth is possible if the solute has enough thermal energy to migrate on the substrate, so that there is an advantage that the growth can be performed at a lower temperature as compared with the slow cooling temperature decreasing method.

Here, when the temperature difference method is adopted, it is necessary to make a temperature difference between the upper and lower temperatures in the growth furnace.

(Problems to be Solved by the Invention) If the temperature difference method is carried out in the liquid phase epitaxial growth apparatus described above, it is necessary to make a temperature difference in the vertical direction within the reaction tube. Only a device that makes a difference is provided, and a liquid phase epitaxial growth apparatus that can preferably perform the temperature difference method has not been provided.

In recent years, there has been provided a furnace body in which half-split split heaters are arranged above and below the reaction tube, and the temperature of the upper and lower heaters can be controlled separately. However, a heat insulating material is arranged around these furnace bodies. Therefore, the heat diffusion was poor, and it was substantially difficult to make a temperature difference between the upper and lower parts inside the reaction tube even by the above control.

Therefore, an object of the present invention is to solve the above-mentioned conventional problems, and to make a temperature difference between upper and lower temperatures in a reaction tube easily, and to maintain the liquid by a temperature difference method. It is to provide a phase epitaxial growth apparatus.

[Structure of the Invention] (Means for Solving Problems) In the present invention, a substrate in which a solution in which a material to be grown is set to a supersaturation temperature is brought into contact with the upper surface of the substrate in a heated horizontal reaction tube A liquid phase epitaxial growth apparatus for growing a crystal of the above material, which comprises a first heating means and a first cooling means, an upper temperature setting means for setting an upper temperature in the reaction tube, and a second heating means. Means and a second cooling means, lower temperature setting means for setting the temperature of the lower side in the reaction tube, heat insulating material arranged around the upper and lower temperature setting means, the first Of the heating means and the first cooling means, and the heating temperature and the cooling temperature of each of the second heating means and the second cooling means are independently controlled to make the upper side in the reaction tube a high temperature and the lower side. The temperature that forms the temperature difference And having a control means.

(Operation) In the liquid phase epitaxial growth apparatus that implements the temperature difference method,
A solution containing the material to be grown in supersaturation is placed on the upper side in the reaction tube, and when this solution is in contact with the upper surface of the substrate, the solution side is set to a high temperature and the substrate side is set to a low temperature, and the difference in density due to this temperature difference is Due to the resulting density diffusion and the thermal diffusion due to the temperature difference, the solute excessively melted on the high temperature side is transported to the low temperature side substrate to perform crystal growth on the substrate.

Here, in the present invention, temperature setting means is provided above and below the reaction tube in order to form a temperature difference in which the upper side of the reaction tube is at a high temperature and the lower side is at a low temperature, and each temperature setting means is independently controlled by the temperature control means. A possible heating means and cooling means are provided, and the surroundings are covered with a heat insulating material.

With such a configuration, it is possible to prevent the temperature of the low temperature side from rising due to the heat of the high temperature side in the reaction tube which is surrounded by the heat insulating material and in which it is difficult to diffuse the heat. That is, since the cooling means provided above and below the reaction tube functions to diffuse heat, even in a reaction tube where it is difficult to diffuse heat from the surroundings, the temperature difference is surely formed in the reaction tube. be able to.

Further, if a so-called vapor pressure temperature control method is adopted for the cooling means, it is possible to improve the soaking property inside the reaction tube.

Further, if the temperature setting means is of a split type and can be opened and closed freely, maintenance of the device can be facilitated.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

This liquid phase epitaxial growth apparatus is a heating furnace 10 having a split type structure, a quartz reaction tube 20 disposed in the heating furnace 10 and having a hollow region in a cylindrical portion as a process region, and the periphery of the quartz reaction tube 20. And a cooling medium circulating portion 21 which is arranged so as to be vertically separable, accommodates a cooling medium in a wall surface in a circulatory manner, and has half-split portions 21a and 21b which are vertically divided into two parts are overlapped with each other, Cooling portions 30a, 30b, which are respectively connected to one end sides of the half-split portions 21a, 21b and cool the heat medium.
And the pressure control units 40a and 40b for controlling the vapor pressure of the heat medium in the cooling units 30a and 30b.

The heating furnace 10 is, for example, an electric resistance type heating furnace, and in the case of the present embodiment, as shown in FIG. 2, it has a split type furnace structure in which the reaction tube 20 is divided into upper and lower parts.

That is, the heater wires 11a and 11b having a semicircular cross section are connected to the reaction tube 20.
Are arranged above and below the perimeter of the above, and the heat insulating materials 12a and 12b that are further divided into the top and the bottom are arranged around the perimeter of the above. The upper heater wire 11a and the heat insulating material 12a and the lower heater wire 11b and the heat insulating material 12b are attached to the stainless covers 13a and 13b, respectively. It supports openably and closably with 14a and 14b as fulcrums.

Similarly, the half-split portions 21a and 21b of the cooling medium circulation portion 21 are also attached to the stainless steel covers 13a and 13b and can be opened and closed vertically.

In the reaction tube 20 arranged in the half-cracked portion 21a, 21b,
Crystal growth is performed by sliding the boats that are vertically separated. That is, as shown in FIG. 3, the boat 22 is vertically separated and is slidable in the x direction in the figure. On the upper side of the boat 22, for example, a raw material solution such as Ga (a solid state before being dissolved)
A solution reservoir 24 that accommodates 23 is provided.
There is no bottom 24 and the solution 23 is adapted to contact the surface of the lower part of the boat 22. A plurality of solution reservoirs 24 can be provided depending on the type of thin film to be grown semiconductor crystals. Also, the raw wafers are
A depression 27 is provided for receiving the wafer 25 and the wafer 26 of the substrate.

Next, the operation will be described.

First, the liquid phase epitaxial growth will be briefly described. First, the boat 22 is arranged in the reaction tube 20, and first, the solution reservoir 24
The lower side is set at a position where neither the raw material wafer 25 nor the substrate wafer 26 is in contact, and the inside of the reaction tube 20 is evacuated. next,
High-purity hydrogen is flown into the reaction tube 20, the temperature is raised by the heating furnace 10, and the raw material 23, which is a lump in the solution reservoir 24, is dissolved.

After that, the lower side of the solution reservoir 24 and the raw material wafer 25 are set by the rod operation so as to be in contact with each other, and set at that position until the raw material 25, for example, GaAs is saturated in the solution, for example, Ga. When the raw material 25 is saturated in the solution 23,
The cooling is started, and after a lapse of a predetermined time, the lower side of the solution reservoir 24 and the substrate 26 are set in contact with each other. Thus, a crystal such as GaAs grows on the substrate 26.

Here, in the present embodiment, the temperature difference method is adopted in place of the conventional slow cooling and cooling method. Therefore, during cooling by the above action,
The temperature is controlled so that there is a vertical temperature difference in the reaction tube 20.

That is, in this embodiment, since the heating furnace 10 employs a half-split heater divided into upper and lower parts, the upper and lower heater wires 11
By controlling the energization of a and 11b, the temperature of the heater is controlled to be different in the upper and lower directions.

However, as described above, it is difficult to make a temperature difference between the upper and lower sides of the reaction tube 20 only by controlling the upper and lower heaters.

Therefore, in this embodiment, the heat medium is housed in the wall surfaces of the half-split portions 21a and 21b of the cooling medium circulation portion 21 arranged around the reaction tube 20, and the vapor pressure of the heat medium is controlled.

That is, according to the thermodynamic principle, by controlling the pressure of the heat medium, it is possible to control the temperature of the cooling medium circulation unit 21 that circulates the heat medium. It is possible to control the temperature inside the reaction tube 20 provided in the above.

Moreover, in the present embodiment, the cooling medium circulation portion 21 is configured as upper and lower half-split portions 21a and 21b, and if this control is performed differently above and below the reaction tube 20, the upper region within the reaction tube 20 is It is possible to set the temperature difference such that the temperature is high and the lower region is low.

By adopting the vapor pressure temperature control method as the cooling means as in the above embodiment, the soaking property inside the reaction tube 20 can be improved and a high soaking property of ± 0.01 ° C. can be secured.

The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the present invention.

The present invention only needs to have a cooling means on the lower side in order to make a temperature difference in the vertical direction in the reaction tube 20, and does not necessarily have a cooling means in the vertical direction as in the above embodiment. May be.

By arranging a cooling unit as a cooling means by controlling vapor pressure in the upper region as in the above embodiment, it is possible to improve the thermal uniformity in the reaction tube 20.

Further, as the cooling means, it is preferable to use vapor pressure control from the viewpoint of ensuring uniform heating, but for example, cooling means may be used to cool the lower region of the reaction tube 20 by passing a refrigerant through a quartz tube. As for, various other methods can be adopted.

Further, although the above-described embodiment has been described with respect to the horizontal furnace, it can be similarly carried out in the case of a vertical furnace. In the case of a horizontal furnace, a tunnel system in which a boat is inserted from one end and taken out from the other end is possible, which has the effect of significantly improving throughput.

Furthermore, a cooling medium circulation unit that is an example of the above-described cooling unit.
21 is not necessarily provided separately from the reaction tube 20, and the wall surface of the reaction tube 20 itself may be configured as a cooling medium circulation unit.

Next, an example in which the above temperature control by vapor pressure is applied to a vapor phase epitaxial growth apparatus will be described.

In the vapor phase epitaxial growth apparatus, for example, a halide system,
In the hydride system, it is necessary to make a temperature difference in the axial direction of the reaction tube.

In this case, as shown in FIG. 5, a circulation part 51 containing a heat medium is arranged substantially in the center of the reaction tube 50, and heating furnaces 52 and 53 capable of independently controlling the temperature are provided on both sides of the circulation part 51. Place it around. Further, the cooling unit 54 for cooling the heat medium in the circulation unit 51 and the pressure control unit 55 for controlling the vapor pressure of the heat medium are provided in the same manner as in the above embodiment.

In such a vapor phase epitaxial growth apparatus, the reaction tube 50
Although it is necessary to make a temperature difference in the longitudinal direction of, the temperature on the low temperature side rises due to the heat effect on the higher temperature side than before, and in order to prevent this, it is necessary to set a distance that is not affected by heat. The device was upsized.

In the above example, the cooling means by vapor pressure control is provided between the high temperature side and the low temperature side, so the heat on the high temperature side can be diffused, and there is no need to take a large distance as in the conventional system, so a compact system. It is possible to create a furnace body having a large temperature difference.

[Effects of the Invention] As described above, according to the present invention, since a temperature difference can be surely made between the upper and lower sides of the inside of the reaction tube, liquid phase epitaxial growth by the temperature difference method can be easily realized.

If the vapor pressure temperature control method is adopted as the cooling means,
The soaking property inside the reaction tube can be improved.

Furthermore, by adopting the split mold temperature setting means that can be opened and closed above and below the reaction tube as the means for forming the temperature difference, the split mold temperature setting means and the reaction tube can be easily maintained.

[Brief description of drawings]

FIG. 1 is a schematic perspective view for explaining a liquid phase epitaxial growth apparatus to which the present invention is applied, FIG. 2 is a sectional view of a split type heater showing a heating means in FIG. 1, and FIG. FIG. 4 is a schematic explanatory view showing a slide boat inserted in a reaction tube, FIG. 4 is a schematic explanatory view for explaining a temperature difference method, and FIG. 5 is a schematic perspective view of a vapor phase epitaxial growth apparatus equipped with a cooling unit by vapor pressure control. It is a figure. 10 ... heating means, 20 ... reaction tube, 21a, 21b, 30a, 30b, 40a, 40b ... cooling means,

Claims (3)

[Claims] 1. A liquid phase epitaxial growth apparatus for growing a crystal of a material to be grown on a substrate by bringing a solution of the material to be grown, which is set at a supersaturation temperature, into contact with the upper surface of the substrate in a heated horizontal reaction tube. An upper temperature setting means for setting an upper temperature in the reaction tube, a first heating means and a first cooling means, and a second heating means and a second cooling means in the reaction tube Lower temperature setting means for setting the lower temperature, a heat insulating material arranged around the upper and lower temperature setting means, the first heating means and the first cooling means, the second Independently controlling the heating temperature and the cooling temperature of each of the heating means and the second cooling means, a temperature control means for forming a temperature difference in which the upper side in the reaction tube has a high temperature and the lower side has a low temperature, Liquid phase characterized by having Epitaxial growth apparatus. 2. The first and second cooling means are a cooling medium which is sealed and circulated around a reaction tube, a cooling section which cools the cooling medium, and a vapor pressure of the cooling medium to control the vapor pressure of the cooling medium. The liquid phase epitaxial growth apparatus according to claim 1, wherein the liquid phase epitaxial growth apparatus comprises: a pressure control unit that controls the temperature in the cooling unit. 3. A liquid phase epitaxial growth apparatus for growing a crystal of a material to be grown on a substrate by bringing a solution of the material to be grown, which is set to a supersaturation temperature, into contact with the upper surface of the substrate in a heated horizontal reaction tube. An upper temperature setting means for setting an upper temperature in the reaction tube, a first heating means and a first cooling means, and a second heating means and a second cooling means in the reaction tube Lower temperature setting means for setting the temperature of the lower side of the, and the first and second heat insulating material arranged around the upper and lower temperature setting means, and divided into upper and lower, the first The heating temperature and the cooling temperature of each of the heating means and the first cooling means and the second heating means and the second cooling means are independently controlled to make the upper side in the reaction tube a high temperature and the lower side to Temperature control hand that creates a temperature difference to be low A step, and an upper cover and a lower cover that can be opened and closed via a hinge, fixing the first heating means, the first cooling means, and the first heat insulating material to the upper cover, A liquid phase epitaxial growth apparatus, characterized in that a second heating means, a second cooling means and a second heat insulating material are fixed to the lower cover.