JPH06102592B2 - Liquid phase epitaxial growth method and growth apparatus - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a liquid phase epitaxial growth method and a growth apparatus by a vertical dipping method.

[Prior Art] The liquid phase epitaxial growth method by the vertical dipping method has been conventionally known as a crystal growth method excellent in mass productivity.

FIG. 8 is a sectional view showing a conventional growth apparatus using the vertical dipping method. In FIG. 8, a raw material solution 5 is placed in the crucible 1. The raw material solution 5 is obtained by heating and melting a raw material for liquid phase epitaxial growth such as a solvent, a solute and a dopant. Wafer 3 is cassette 2
Multiple sheets are lined up and stored inside. FIG. 11 is a perspective view showing this cassette, and as shown in FIG. 11, a slit 4 is formed in the side surface of the cassette 2 in the vertical direction. The inside of the cassette 2 is open at the slit 4, and the raw material solution 5 can be introduced into the inside through the slit 4. FIG. 8 shows a state before the cassette 2 is immersed in the raw material solution 5.

FIG. 9 shows a state in which the cassette 2 is immersed in the raw material solution 5, and the raw material solution 5 is introduced into the cassette 2 through the slit 4. After the raw material solution 5 is introduced into the cassette 2 in this manner, the raw material solution 5 is gradually cooled to be epitaxially grown on the wafer 3. After the epitaxial growth is completed, the cassette 2 is pulled up again,
At this time, the raw material solution 5 is discharged from the cassette 2 into the crucible 1 through the slit 4.

FIG. 10 shows such a state, in which the cassette 2 is pulled up from the raw material solution 5.

[Problems to be Solved by the Invention] However, in such a conventional method, the raw material solution in the cassette moves through the slit during the epitaxial crystal growth, and due to the difference in specific gravity of elution and the dopant, the raw material solution in the cassette is increased. A concentration distribution of the solution resulted. FIG. 12 is an enlarged cross-sectional view showing movement of a raw material solution between wafers in a cassette in such a conventional growth apparatus. First
As shown in FIG. 12, the raw material solution 5 in the cassette 2 is
, But moved between the wafers 3 as indicated by an arrow, and a concentration distribution was generated in the raw material solution 5. Therefore, there is a problem in that the characteristics of the obtained epitaxial crystal layer greatly differ between the wafer stored above the cassette and the wafer stored below. Furthermore, there is also a problem that such movement of the raw material solution 5 causes unevenness in thickness in the vicinity of the slit on the surface of the wafer, resulting in a pattern.

It is an object of the present invention to provide a liquid phase epitaxial growth method and a growth apparatus which can solve such conventional problems and can uniformly perform epitaxial growth on each wafer in a cassette.

[Means for Solving Problems] In the liquid phase epitaxial growth method according to claim 1, a cassette containing a plurality of wafers is dipped in a raw material solution, and each cassette is separated from a slit formed in the cassette for each wafer. This is a method of introducing the raw material solution into the inside of the wafer and growing the epitaxial crystal layer on each wafer, then pulling up the cassette and discharging the raw material solution from the slit. It is characterized in that the slit is closed so that the raw material solution does not move between the wafers until the raw material solution is discharged from the slit after completion of the step.

The liquid phase epitaxial growth apparatus of claim 2 is an apparatus for carrying out the method of claim 1, wherein the raw material solution is placed inside a crucible in which the raw material solution is placed and a plurality of wafers. Equipped with a cassette formed with a slit for introducing, introducing the raw material solution into the cassette by immersing the cassette in the raw material solution in the crucible, after growing the epitaxial crystal layer on the wafer, the cassette A device that pulls up and discharges the raw material solution from the slit, and after introducing the raw material solution into the cassette from the slit,
It further comprises a slit opening / closing member for closing the slit so that the raw material solution does not move in each wafer until the raw material solution is discharged from the slit after the crystal growth is completed.

[Operation] In the liquid phase epitaxial growth method of the first aspect, the slit is closed during crystal growth so that the raw material solution does not move between wafers. For this reason, unlike the conventional case, the raw material solution does not move between the wafers through the slits, so that the concentration distribution due to the difference in specific gravity of elution and dopant does not occur. Also, because the slit is closed,
The raw material solution does not cause convection between the wafers.

Further, also in the liquid phase epitaxial growth apparatus of claim 2, since the slits are closed by the slit opening / closing member during the crystal growth, the raw material solution is prevented from moving between the wafers, and the difference in specific gravity or the like causes a difference between the wafers. Does not cause a concentration distribution, and does not cause convection of the raw material solution between the wafers.

[Operation] FIG. 1 is a sectional view showing an embodiment of the present invention. In FIG. 1, a raw material solution 15 is placed in a crucible 11. A plurality of wafers 13 are accommodated side by side in the cassette 12, and a slit 14 is formed in the vertical direction on the side surface of the cassette 12. FIG. 4 is a perspective view showing the cassette 12 of this embodiment. As shown in FIGS. 1 and 4, in this embodiment, a rod-shaped slit opening / closing member 16 having a size to be inserted into the slit 4 of the cassette 2 is provided. This slit opening / closing member 16 is slit from above.
By inserting into the cassette 14, the slit 14 can be closed and the inside of the cassette 12 can be sealed.

First, as shown in FIG. 1, the slit opening / closing member 16 is installed above the cassette 12. After the raw material solution 15 reaches a predetermined temperature, the cassette 12 is moved downward to
Soak in 15. The raw material solution 15 is passed through the slit 14,
The wafers 13 are introduced into a cassette 12 that is partitioned for each wafer 13.
After the raw material solution 15 is introduced into the cassette 12, the slit opening / closing member 16 is moved downward to insert the inside of the slit 14.
Close the slit 14.

This state is shown in FIG. Slit opening / closing member
Closing the slit 14 by 16 prevents movement of the raw material solution 15 between the wafers 13. After the epitaxial growth is completed, the slit opening / closing member 16 is pulled up again and removed from the slit 14. As a result, the slit 14 is opened again. Next, the cassette 12 is pulled up from the raw material solution 15, and the raw material solution 15 in the cassette 12 is discharged into the crucible 11 through the slit 14. This state is shown in FIG.

As described above, in this embodiment, the slit 14 is closed by the slit opening / closing member 16 during the epitaxial growth, which prevents the raw material solution 5 itself from convection between the upper and lower wafers 13. Further, it is possible to prevent the solute and the like from moving between the wafers 13 and diffusing due to the difference in specific gravity from the solvent. Therefore, the epitaxial growth layer obtained by this embodiment can be a uniform epitaxial crystal layer having almost the same characteristics from the upper side to the lower side of the cassette. Further, since the amount of the solution existing on each wafer is small, the influence of the convection is small, and the in-plane characteristics of the obtained epitaxial crystal layer are uniform and good.

A Zn-doped AlGaAs epitaxial crystal layer was grown on a GaAs wafer by using the apparatus of the embodiment shown in FIGS. As a GaAs wafer, the diameter is 2 inches (D =
A 50 mm) Zn-doped (100) GaAs wafer was used. Crucible 1
1, the cassette 12 and the slit opening / closing part 16 were made of high-purity carbon. First, six wafers 13 are set in the cassette 12, and the crucible 11 is made of GaAs500g and Al.
2530mg, GaAs polycrystalline 20g and Zn500 as dopant
mg was introduced. After the temperature is raised to 900 ° C, the cassette 12 is immersed in the raw material solution 15 and the slit opening / closing member 16 is used to slit 14
Was closed and the temperature was lowered to 600 ° C. at a cooling rate of 0.1 to 1.0 ° C./min to complete the epitaxial crystal growth. After completion of crystal growth, the slit opening / closing member 16 is pulled up, the slit 14 is opened, the cassette 12 is pulled up, and the raw material solution 15 therein is crucible.
Discharged during 11.

For comparison, under the same conditions as above, without using the slit opening / closing member, even during the epitaxial crystal growth, the epitaxial crystal was grown in the same manner as the conventional method without closing the slit 14 ( Comparative example).

In each of the experimental example and the comparative example according to the present invention, the obtained AlGa
The As epitaxial crystal layer has an Al mixed crystal ratio of x = 0.4 to 0.8.
Met. For each of the experimental example and the comparative example according to the present invention, the thickness of the epitaxial layer of each of the six wafers contained in the cassette was measured, and the results are shown in FIG. The comparative example according to the conventional method is the sixth example.
As shown in the figure, the thickness of the epitaxial layer gradually increases from the lower side to the upper side of the cassette. However, in the experimental example according to the present invention, every wafer in the cassette has a thickness of 202 ± 7 μm. It was found that the epitaxial layer was formed within the range and the thicknesses were almost equal.

Further, in the comparative wafer according to the conventional method, as shown in FIG. 5, a pattern due to uneven growth appeared on the surface of the wafer. On the other hand, in the experimental wafer according to the present invention,
No such pattern was observed.

For the third wafer from the bottom of the cassette,
The thickness of the epitaxial layer within the wafer surface was measured. FIG. 7 shows the result of measurement at 5 points on the wafer surface. As shown in FIG. 7, in the comparative example according to the conventional method, the thickness tends to be thin at the slit side portion, but in the experimental example according to the present invention, as a whole,
The thickness was 207 ± 4 μm, and it was confirmed that the in-plane thickness was almost uniform.

As described above, in the experimental example according to the present invention, uniform epitaxial crystal growth could be performed between each wafer and in the plane of the wafer.

Needless to say, in the growth apparatus of the present invention, the shape of the cassette, the slit formed in the cassette, and the slit opening / closing member is not limited to the shapes of the above-described embodiments.

[Effects of the Invention] As described above, according to the present invention, epitaxial growth can be performed uniformly on each wafer and in the wafer plane, and a large number of epitaxial wafers having substantially the same characteristics can be produced with good productivity. be able to.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, showing a state before the cassette is immersed in the raw material solution.
FIG. 2 is also a sectional view showing an embodiment of the present invention, showing a state in which the cassette is immersed in the raw material solution. FIG. 3 is also a sectional view showing one embodiment of the present invention, showing a state in which the cassette is pulled up from the raw material solution. FIG. 4 is a perspective view showing a cassette and a slit opening / closing member used in an embodiment of the present invention. FIG. 5 is a plan view showing a surface state of an epitaxial crystal layer grown on a wafer by a conventional method.
FIG. 6 is a diagram showing variations in the thickness of the epitaxial crystal layer between wafers. FIG. 7 is a diagram showing variations in the thickness of the epitaxial crystal layer within the wafer surface. FIG. 8 is a sectional view showing an example of a conventional growth apparatus, showing a state before the cassette is immersed in the raw material solution. FIG. 9 is a sectional view showing an example of a conventional growth apparatus, showing a state in which a cassette is immersed in a raw material solution. FIG. 10 is a sectional view showing an example of the conventional growth apparatus, showing a state in which the cassette is pulled up from the raw material solution. FIG. 11 is a perspective view showing a cassette in an example of a conventional growth apparatus. FIG. 12 is an enlarged cross-sectional view showing movement of a raw material solution between wafers in a cassette of a conventional growth apparatus. In the figure, 11 is a crucible, 12 is a cassette, 13 is a wafer,
Reference numeral 14 is a slit, 15 is a raw material solution, and 16 is a slit opening / closing member.

Claims (2)

[Claims] 1. A cassette containing a plurality of wafers is dipped in a raw material solution, and the raw material solution is introduced into a cassette partitioned for each wafer through a slit formed in the cassette, and the cassette is placed on each wafer. After growing the epitaxial crystal layer, in the liquid phase epitaxial growth method of pulling up the cassette and discharging the raw material solution from the slit, after introducing the raw material solution from the slit into the cassette,
A liquid phase epitaxial growth method, characterized in that the slit is closed so that the raw material solution does not move between the wafers until the raw material solution is discharged from the slit after the crystal growth is completed. 2. A crucible provided with a crucible for containing a raw material solution, and a cassette for accommodating a plurality of wafers and having a slit formed therein for introducing the raw material solution inside each of the wafers. A liquid that introduces the raw material solution into the cassette by immersing the cassette in the raw material solution, grows an epitaxial crystal layer on the wafer, and then pulls up the cassette to discharge the raw material solution from the slit. In the phase epitaxial growth apparatus, after introducing the raw material solution into the cassette from the slit, until the crystal growth is completed and the raw material solution is discharged from the slit, the raw material solution is not moved between the wafers. The liquid phase epitaxial growth apparatus further comprising a slit opening / closing member for keeping the slit closed.