JPH0772117B2 - Liquid phase epitaxial growth method and apparatus - Google Patents

Description

The present invention relates to a liquid phase epitaxial growth method for growing a mixed crystal epitaxial wafer of gallium arsenide, gallium aluminum arsenide, etc., which is suitable for manufacturing a high-power light emitting diode. Regarding the device.

[Conventional technology]

In a high-power light emitting diode using GaAlAs, GaAs is used as a substrate for crystal growth. Here, regarding the conventional liquid phase epitaxial growth method,
Take growth as an example.

FIG. 5 is a view showing a conventional liquid phase epitaxial growth apparatus by the slide boat method, in which 1 is a raw material solution reservoir, 2 is a cover, 3 is a slider, 4 is a GaAs substrate, and 5 is a thermocouple.

The boat has a slider that slides in the x direction in the figure, and a solution reservoir 1 for containing a Ga solution is provided on the upper side of the boat, the solution reservoir has no bottom, and the solution is in contact with the surface of the slider. . The slider is provided with a recess for receiving the substrate's CaAs wafer. Solution reservoir 1
It has become possible to continuously grow a multi-layer structure by making only the kinds of semiconductor crystal thin films to be grown.

In such a configuration, by sliding the slider 3 in the x direction in the figure, a Ga solution containing GaAs is placed on the GaAs substrate 4 and the solution is cooled, whereby GaAs is deposited and grows on the substrate.

[Problems to be solved by the invention]

By the way, in LED work, the substrate is ground by lapping or the like to adjust the total thickness to 200 to 250 μm. However, the liquid phase epitaxial growth method by the conventional cooling method as shown in FIG. On the other hand, in the method of placing the substrate on the lower side, the epitaxial layer forming the P / N junction is 50 to 100 μm.
It is so thin that the GaAs substrate must be left when trying to adjust the total thickness to 200 to 250 μm. However, since the forbidden band width of GaAs is smaller than that of GaAlAs, the light emitted from the GaAlAs layer is absorbed by the remaining GaAs substrate layer, and the external light emission efficiency is reduced.

When the GaAs substrate is completely removed by lapping in order to prevent the reduction of the external light emission efficiency, the mechanical strength is insufficient because the total thickness of the epitaxial layer is as thin as 50 to 100 μm in the conventional technology, and the yield of the chip formation process is extremely high. Had fallen to. In addition, an epitaxial layer thickness of around 200 μm can be achieved by performing epitaxial growth multiple times.
The time required for growth is long and the productivity is poor. In addition, a defective junction easily occurs at the epitaxial interface during the second and subsequent epitaxial growths, resulting in a significant decrease in yield.

The present invention is for solving the above-mentioned problems.
It is an object of the present invention to provide a liquid phase epitaxial growth method and apparatus capable of obtaining an epitaxial layer having a sufficient film thickness by a single slow cooling method, eliminating the need to leave a GaAs substrate, and preventing a decrease in external light emission efficiency.

[Means for solving problems]

The present invention relates to a liquid phase epitaxial growth method using a slide boat method, in which a solution tank is vertically divided into two parts and slid,
When the substrate is placed in the solution tank, the substrate accommodating portion is formed on the lower surface side of the slide plate in which the slit for injecting the growth solution from the upper solution tank to the lower solution tank is formed, and the substrate accommodating portion is formed in the sliding direction front side from the slit position Holding, and when the substrate is reached just before the solution tank by sliding the slide plate, the slit is located in the solution tank and the growth solution is injected from the upper solution tank to the lower solution tank, with respect to the growth solution. It is characterized in that the substrate is placed on the upper side and epitaxial growth is performed by a slow cooling method.

The present invention also provides one or more solution tanks and a slit for vertically sliding each solution tank into two parts, and a slit for injecting a growth solution from the upper solution tank to the lower solution tank when positioned in the solution tank. And a slide plate having a substrate housing portion on the lower surface side on the front side in the sliding direction from the slit position, the substrate is held in the substrate housing portion and sequentially slid in each solution tank. It is characterized by

[Action]

In the present invention, the position of the substrate is arranged above the growth solution, and convection generated due to the difference in specific gravity due to the difference in concentration of the solution is used to increase the growth rate to twice or more as compared with the conventional method by the slow cooling method. It becomes possible. As a result, the total thickness of the epitaxial layer can be increased to 200 μm or more in a short time, and even if the GaAs substrate is removed, the chip formation process is
It has sufficient mechanical strength and can withstand.

〔Example〕

 Embodiments will be described below with reference to the drawings.

FIG. 1 is a diagram for explaining a liquid phase epitaxial growth process according to the present invention using a slide boat, FIG. 2 is a diagram for explaining a growth state, and FIG. 3 is a diagram showing a growth layer on a substrate. In the figure, 10 is a slide plate, 11 is a substrate accommodating portion, 12 is a substrate, 13 is a slit, 14 is a lid that also serves as a weight, 15 is a groove, and 16 and 17 are solution layers. In this example, the number of solution tanks is two, but it goes without saying that the number can be increased or decreased depending on the number of epitaxial layers.

The slide plate 10 slides through each of the solution tanks 16 and 17 to divide them vertically into two parts. The heated growth solution is placed above the slide plate of each solution tank,
Each of the lids 14 also serves as a weight. Slide plate
The substrate housing portion 11 is provided in the substrate 10 to hold the substrate 12, and the slit 13 is provided so that the growth solution is dropped and injected from the upper solution tank to the lower solution tank in the solution tank in which the slit 13 is located. It has become.

In such a configuration, the slit in FIG.
13 is located in the solution tank 16, and the P-GaAlAs layer growth solution is injected into the lower solution tank. Then, in FIG. 1 (b) in which the slide plate 10 is slid to the right side of the figure, the P-Ga into which the substrate 12 is injected is shown.
The slit 13 is located on the upper side of the AlAs layer growth solution, and the slit 13 is located in the solution tank 17, and the N-GaAlAs layer growth melt is injected therein. By gradually cooling in this state, the solute is precipitated from the P-GaAlAs layer growth solution and the P-GaAlAs layer grows on the substrate.
Next, when the slide plate 10 is slid to the right (FIG. 1 (c)), the substrate is positioned in the solution layer 17 into which the N-GaAlAs layer growth solution has been injected, and the N- The GaAlAs layer is grown and formed, and the whole process is completed.

In this embodiment, as the substrate, Zn-doped P-type Ga is used.
An As substrate was used, and the plane orientation of the surface was the (100) plane.

To grow the layer 1 shown in FIG. 3, 6 g of undoped GaAs polycrystal, 12.5 g of A, and 0.1 g of Zn were dissolved in 100 g of Ga. Third
Undoped GaAs in 100g Ga for growth of layer 2 shown
Polycrystalline 1.9 g, Al = 0.35 g, and Te = 0.001 g were dissolved.
These solutions were stored in the solution tank of the slide boat of FIG. 1, and the substrates were stored in the substrate storage portion of the boat of FIG.

After heating the boat to 900 ° C, the solutions for layer growth above were brought into contact with each other, and then cooled to 760 ° C, and the solute was removed from the solution as shown in Fig. 2 by utilizing the difference in specific gravity between the solution and the solute. Liquid phase epitaxial growth was performed by precipitation.

The thickness of the obtained epitaxial layer was as follows.

Layer 1: 170 μm Layer 2: 50 μm Furthermore, the GaAs substrate was polished and removed by etching to a total thickness of 20
An LED chip was prepared with a thickness of 0 μm.

The chip has a square shape with a side of 0.3 mm and has no epoxy coating. The current density is 8 A / cm ² , the brightness is 21 mcd, and the peak wavelength is 657 n.
m, LED yield was 97%.

[Comparative example]

Replace the slide boat with a conventional boat as shown in Fig. 5,
An epitaxial wafer was manufactured in exactly the same manner.

The thickness was as follows.

Layer 1: 70 μm Layer 2: 20 μm In the same manner as in the example, the total thickness was adjusted to 200 μm, and an LED was prepared with a substrate. Brightness 6.0 mcd, peak wavelength 662 nm
The LED yield was 95%.

On the other hand, when the substrate was completely removed and an LED was made with a total thickness of 80 μm, the brightness increased to 15.0 mcd and the peak wavelength was 662 m.
However, the LED yield was as low as 15% due to the large number of cracks.

FIG. 4 is a view showing the structure of the slide plate, in which FIG. 4 (a) is a sectional view and FIG. 4 (b) is a plan view.

The substrate accommodating portion 11 of the slide plate 10 is formed in accordance with the wafer shape as shown in FIG.
Although three pieces are formed orthogonally to the sliding direction, it is needless to say that the number is not limited to this.

〔The invention's effect〕

As described above, according to the present invention, since the following remarkable effects are obtained, the industrial utility value is extremely large.

An ordinary slow cooling method makes it possible to obtain an epitaxial wafer having a large film thickness in a relatively short time.

The manufactured epitaxial wafer can sufficiently withstand the mechanical strength in the chip forming process even if the substrate is removed.

The LED produced from the wafer with the substrate removed has a significantly higher output than the LED produced from the wafer with the substrate.

In addition, since the growth solution is dropped and injected from the upper solution tank to the lower solution tank immediately before the start of epitaxial growth, the solution is sufficiently agitated during epi growth and the concentration distribution of the solution becomes more uniform, so stable growth can be performed. it can.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a liquid phase epitaxial growth process according to the present invention using a slide boat, FIG. 2 is a diagram for explaining a growth state, and FIG. 3 is a diagram showing a growth layer on a substrate, FIG. 4 shows the structure of the slide plate, and FIG.
The figure shows a conventional liquid phase epitaxial growth apparatus using the slide boat method. 10 …… Slide plate, 11 …… Substrate housing, 12 …… Substrate, 13
…… Slits, 14 …… Lids and lids, 15 …… Grooves, 16, 17…
... solution tank.

Claims (4)

[Claims] 1. A liquid phase epitaxial growth method using a slide boat method, in which a solution tank is vertically slid into two parts and slid, and when positioned in the solution tank, a slit for injecting a growth solution from the upper solution tank to the lower solution tank. On the lower surface side of the slide plate on which the substrate is formed, a substrate accommodation portion is formed on the front side in the sliding direction from the slit position to hold the substrate, and the slide plate is slid to slit when the substrate reaches immediately before the solution tank. Is located in the solution tank, the growth solution is injected from the upper solution tank to the lower solution tank, and the substrate is positioned above the growth solution to perform epitaxial growth by slow cooling. 2. One or more solution tanks and slits for vertically sliding each solution tank into two parts, and a slit for injecting a growth solution from the upper solution tank to the lower solution tank when positioned in the solution tank. And a slide plate having a substrate housing portion on the lower surface side on the front side in the sliding direction from the slit position, the substrate is held in the substrate housing portion and sequentially slid in each solution tank. A liquid phase epitaxial growth apparatus characterized in that 3. The liquid phase epitaxial growth apparatus according to claim 2, wherein a groove for removing and containing an unnecessary solution adhering to the slide plate or the substrate is provided between the solution tanks. 4. The liquid phase epitaxial growth apparatus according to claim 2, wherein the substrate housing portion is provided in two or more rows in a direction orthogonal to the sliding direction.