JPH079887B2 - Liquid phase epitaxial growth method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a method for liquid phase growing an epitaxial growth film on a crystal substrate, and an object thereof is to provide a method with excellent reproducibility of the grown film thickness. .

(B) Conventional technology In order to satisfy the requirements for high performance, high frequency, and mass production of planar type Schottky barrier diodes, the melt held in the melt reservoir is used once for each of multiple substrates. It is necessary to form an epitaxially grown film with little variation in film thickness with good reproducibility. Conventionally, the temperature of the melt to be brought into contact with the substrate is controlled so that the temperature distribution becomes constant. In this case, however, the amount of solute in the melt must be adjusted in order to form the epitaxially grown film multiple times using this melt. It is said that it is necessary to make the solute saturation amount at the crystal growth start temperature 1.5 times or more. When an epitaxial growth film is formed on a substrate by using such a melt, it is difficult to control the film thickness, and it is difficult to form a growth film with little variation in film thickness with good reproducibility. The outline of the liquid phase epitaxial growth method is July 10, 1982.
It is introduced on pages 96-101 of the "Latest Compound Handbook" published by Science Forum.

(C) Problems to be solved by the invention The amount of solute in the melt is the saturation amount at the crystal growth start temperature 1.
In the conventional growth method in which the temperature in the melt is 5 times or more and the temperature in the melt is uniform, there is a large variation in the film thickness of the grown film within the substrate surface. In that case, there was a variation of about ± 500Å on average.

An object of the present invention is to provide a method for reproducibly growing an epitaxial growth film having a small variation in film thickness on a plurality of substrates by using a melt once stored in a melt reservoir.

(D) Means for Solving Problems The present invention is directed to a substrate holder for supporting a main substrate for forming an epitaxially grown film on the surface and a dummy substrate for correcting excess or deficiency of the saturation of melt, and a melt reservoir. A melt holder that is provided so as to be slidable relative to the substrate holder, and a melt supported by the melt reservoir, and brings the melt into contact with the dummy substrate to saturate the melt. In the liquid phase epitaxial growth method in which the melt is brought into contact with the main substrate at a predetermined temperature lower than the temperature at the time of correction to form an epitaxial growth film on the main substrate, the melt is The temperature of the melt is 0 from the substrate holder side upward.
It is characterized in that the solute is set so as to fall with a temperature gradient in the range of 5 to 3 ° C./cm and has a solute equal to the saturation amount at the crystal growth start temperature in the solvent.

(E) Action In the liquid phase epitaxial growth method of the present invention, the temperature of the melt is set to drop upward from the substrate holder side with a temperature gradient in the range of 0.5 to 3 ° C./cm. And the solubility of the solute in this lower part increases. Therefore, the solute concentration of the melt on the side in contact with the main substrate increases, and the epitaxial growth film can be stably formed. Furthermore, for example, in order to mix the solute in the solvent, the melt is prepared at a temperature sufficiently higher than the crystal growth temperature, but at that time, since the lower part of the melt is heated to a higher temperature than the upper part, the solute convection is sufficient. It is possible to prevent uneven mixing, so that there is no risk of defective film formation due to uneven mixing when the temperature is lowered and the crystal is grown.

(F) Example FIG. 1 to FIG. 5 are process explanatory views of the method of the present invention, and FIG. 6 is a temperature program diagram of the melt during this process. Regions A to E in FIG. 6 correspond to the steps in FIGS. 1 to 5, respectively.

In each figure, (1) is a substrate holder having recesses for accommodating a substrate (main substrate) (2) and a dummy substrate (3) for forming an epitaxial growth film on the surface, and (4) is a melt (5) A melt holder equipped with a melt reservoir (6) for supporting the substrate holder (1) so that it can slide relative to the substrate holder (1). ), And an operating rod (not shown) is associated with the substrate holder (1) for moving the substrate holder (1) from the outside of the reactor for the above sliding. (7) is a lid for applying the melt (5) contained in the melt reservoir (6). In the reaction furnace, the melt (5) moves from the substrate holder (1) to the lid (7) with a predetermined temperature gradient (0.5 to 3 ° C /
The temperature is controlled so that it will be lowered by holding (cm). This control is possible by vertically dividing the heater installed outside the reaction furnace into two parts to heat the inside of the reaction furnace, and controlling the temperature of each of the divided heaters individually. Between the reactor and the heater before and after the heating area,
A seal made of a heat insulating material (for example, glass wool) is provided. The melt (5) contains a solute in a saturated amount at the crystal growth start temperature.

The substrate holder (1) and the melt holder (4) were inserted into the reaction furnace in the relative positional relationship shown in Fig. 1, and the temperature was 800 ° C in H ₂ gas.
The temperature is raised to (displayed as the temperature of the melted portion in contact with the substrate, the same applies below) and held at 800 ° C for 30 minutes. At this time, since the upper part of the melt is kept at a slightly low temperature, convection of the solute in the solvent is performed to prevent uneven mixing. After that, from 800 ℃ to 7
The temperature is lowered to around 60 ° C., and when it reaches 760 ° C., the relationship between the substrate holder (1) and the melt holder (4) is set to the state shown in FIG. 2, and the state is held for 30 minutes. At this time, as shown in the figure, the melt (5) is in contact with the dummy substrate (3) having a role of correcting the excess or deficiency of the saturation of the melt. afterwards,
As shown in Fig. 3, melt (5) is used as substrate (2) and dummy substrate (3).
In this state, the melt (5) is cooled at a constant cooling rate, and when the temperature drops by a predetermined temperature (ΔT), as shown in FIG. The melt (5) is brought into contact with the substrate (2). After a lapse of time for forming an epitaxial growth film having a required film thickness, the melt (5) is removed from the substrate (2) as shown in FIG.

In the same way as the above crystal growth example, ΔT = 1.5 ° C.
A melt (melt thickness 5 mm) in which a is a solvent and As is a solute is used. As the melt state, 1.5 times As of the saturation amount at the crystal growth start temperature is put, and the temperature is increased in the depth direction of the melt during crystal growth. One without a gradient (Sample 1, conventional technique) and one with As equal to the saturation amount at the crystal growth start temperature so as not to have a temperature gradient in the depth direction of the melt during crystal growth ( Sample 2), As, which is equal to the saturation amount at the crystal growth start temperature, was added and the temperature gradient during crystal growth was 1 ° C / c.
One with m (Sample 3) was set, and a thin film of about 3000 Å was grown on a 4 × 4 cm wafer (substrate). The melt was used 5 times and the variations in the film thickness of the 5 wafers were averaged. As a result, the epitaxial growth films of 3000Å ± 500Å, 3000Å ± 750Å and 3000Å ± 200Å were obtained for Samples 1, 2 and 3, respectively.

(G) Effect of the Invention The present invention has a substrate holder for supporting a substrate for forming an epitaxially grown film on the surface and a dummy substrate for correcting excess or deficiency of the saturation of melt, and a substrate holder having a melt reservoir. The melt holder is provided so as to be relatively slidable with respect to the melt, and the melt is supported by the melt reservoir. After the melt is brought into contact with the dummy substrate to correct the saturation of the melt, In the liquid phase epitaxial growth method of contacting a melt with a substrate at a predetermined temperature lower than the temperature at the time of correction to form an epitaxial growth film on the substrate, the melt has a temperature of the melt upward from the substrate holder side of 0.5. Since the solute is set to fall with a temperature gradient in the range of ~ 3 ° C / cm and the solute is equal to the saturation amount at the crystal growth start temperature in the solvent, The solute concentration of the melt is increased and the epitaxial growth film can be stably formed. Further, the convection of the solute in the melt is sufficiently carried out to prevent uneven mixing, and it is possible to eliminate the risk of defective film formation. As a result, epitaxial growth with a small variation in film thickness can be performed a plurality of times with good reproducibility.

[Brief description of drawings]

FIG. 1, FIG. 2, FIG. 3, FIG. 4, and FIG. 5 are process explanatory views of one embodiment of the method of the present invention, and FIG. 6 is a temperature program diagram of the melt during this process. (1) …… substrate holder, (2) …… substrate, (4) …… melt holder, (5) …… melt, (7) …… lid.

Claims (1)

[Claims] 1. A substrate holder for supporting a main substrate for forming an epitaxially grown film on a surface thereof and a dummy substrate for correcting excess or deficiency of the saturation of melt, and a holder having a melt reservoir and facing the substrate holder. A melt holder that is slidably installed, and a melt supported by the melt reservoir. After the melt is brought into contact with the dummy substrate to correct the saturation of the melt, In the liquid phase epitaxial growth method of forming the epitaxial growth film on the main substrate by bringing the melt into contact with the main substrate at a predetermined temperature lower than the temperature at the time of correction, the melt is
The temperature of the melt rises from the substrate holder side
A liquid phase epitaxial growth method, characterized in that a solute is set so as to fall at a temperature gradient in the range of 0.5 to 3 ° C./cm, and a solute equal to the saturation amount at the crystal growth start temperature is provided in the solvent.