JPH10149997A - Liquid phase epitaxial growth equipment - Google Patents

Abstract

(57) [Problem] To correct non-uniformity of a grown film thickness formed on a semiconductor substrate by devising a shape of a back plate and changing a melt thickness. SOLUTION: In a liquid phase epitaxial growth apparatus in which a plurality of semiconductor substrates 3, 3... Are set upright in an epitaxial growth chamber 27 and epitaxial growth is performed, one surface is set in close contact with the back surface of the semiconductor substrate 3. On the other surface of the rear plate 1 to be formed, a concave portion 2 concentric with the rear plate 1 is formed, and the concave portion 2 is formed shallower toward the outer peripheral portion and deeper toward the central portion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid phase epitaxial growth apparatus in which a plurality of semiconductor substrates are set upright in an epitaxial growth chamber to perform epitaxial growth, and more particularly, to a liquid phase epitaxial growth apparatus formed on a semiconductor substrate. The present invention relates to a liquid phase epitaxial growth apparatus for improving uniformity.

[0002]

2. Description of the Related Art In a liquid phase epitaxial growth method (cooling method), for example, a Ga-As group III-V compound is used as an example. The boat (liquid phase epitaxial growth apparatus) was placed in a growth furnace in a hydrogen atmosphere, and
After the temperature is raised from 00 ° C. to 1000 ° C., the saturated solution is brought into contact with the semiconductor substrate, and crystal growth is performed while lowering the temperature.

[0003] A boat in which semiconductor substrates are set upright is used in part because of the advantage that the substrate filling amount can be greatly increased as compared with a slide boat in which semiconductor substrates are set sideways.

FIGS. 8 and 9 show an example of the structure of an upright boat for setting such a semiconductor substrate in an upright position.

FIG. 8 shows a state in which the temperature is being raised, and FIG. 9 shows a state in which the growth is in progress. In the figure, reference numeral 21 is a solution reservoir, 22 is a slider, 23 is a solution, 24 is a bottom plate, and 25 is a back plate. ,
26 is a semiconductor substrate, 27 is a growth chamber.

Generally, graphite (graphite) subjected to a high-purity treatment is used as a boat material.

[0007]

In a liquid-phase epitaxial growth apparatus having a structure in which the semiconductor substrate 26 is set upright, the following two causes are considered as the main causes of variations in the epitaxial growth film thickness. .

The first cause is that when the semiconductor substrate 26 is set upright, the upper portion in the growth chamber 27 is more likely to grow than the lower portion. As a result, the growth film becomes non-uniform. That is, the grown film thickness on the upper side of the set semiconductor substrate 26 is large, and the grown film thickness on the lower side is small. This is because the solute (GaAs) in the solution 23 has a lower specific gravity than the solvent (Ga).

In the liquid phase epitaxial growth method, the process of determining the growth rate is roughly divided into two processes. One is a process in which a growth material is transported to a growth interface, and the other is a process in which a growth material is transported. This is the process in which the growing substance is deposited as crystals.

As one of the factors affecting the former growth process, a state of heat radiation when the temperature of the solution is lowered can be considered. That is, the difference between the shape of the growth chamber 27 and the properties of the material for heat and the properties of the solution 23 for heat (Ga as the solvent of the solution has a higher thermal conductivity than graphite of the boat). This is considered to be the second cause of the variation in the epitaxial growth film thickness.

In other words, the vicinity of the inner wall of the growth chamber 27 (portion close to graphite) is in a state in which the response to the cooling command is fast and easy to grow, while the vicinity of the center in the growth chamber 27 has a slow response to the cooling command and Since the growth is difficult, as a result, the grown film becomes uneven. That is, when the semiconductor substrate 26 is placed upright on such a boat, the grown film thickness at the peripheral portion of the set semiconductor substrate 26 is large, and the grown film thickness at the central portion is small.

From these two causes, the semiconductor substrate 2
6 is set upright, the growth room 2
7 has a large growth film thickness in the upper portion, and the growth chamber 2
The growth film thickness of the portion located near the center in 7 becomes thin.

The difference in the growth film thickness due to the difference in the position in the growth chamber 27 is as shown in FIG.
6 is rotated at a constant speed together with the back plate 27 (semiconductor substrate 26).
The rotation can be corrected to some extent by rotating the wheel around the center point of the rotation of the wheel). That is, by rotating, the outer peripheral portion of the semiconductor substrate 26 becomes
This is because the light passes through the upper side of 7 evenly.

However, such a semiconductor substrate 26
Due to this rotation, the non-uniformity of the grown film thickness such that the central part of the semiconductor substrate 26 is still thin and the outer peripheral part is thick remains.

Since the solution composition varies depending on the position in the growth chamber 27, a method of growing the solution while mechanically stirring the solution so that the solution composition in the growth chamber becomes uniform can be considered. However, specific methods are scarce and impractical.

The present invention has been made in order to solve such a problem, and the melt thickness (the distance between the substrate growth surface and the back plate opposed thereto) is one factor that influences the growth film thickness. While paying attention, in order to prevent crystal growth on the back surface of the semiconductor substrate, we focused on the back plate used in close contact with the back surface of the semiconductor substrate, and by changing the melt thickness by devising the shape of this back plate, It is an object of the present invention to provide a liquid phase epitaxial growth apparatus that improves the uniformity of a film thickness formed on a semiconductor substrate.

[0017]

According to a first aspect of the present invention, there is provided a liquid phase epitaxial growth apparatus for performing a epitaxial growth by setting a plurality of semiconductor substrates vertically in an epitaxial growth chamber. In an epitaxial growth apparatus, a concentric concave portion is formed on the other surface of a back plate on which one surface is set in close contact with the back surface of a semiconductor substrate.

In the liquid-phase epitaxial growth apparatus according to a second aspect of the present invention, in the first aspect, the recess is formed such that an outer peripheral portion is shallower and a deeper portion is formed toward a central portion.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of the shape of a back plate 1 which is a main part of the present invention.

That is, in the present invention, in order to prevent crystal growth on the back surface of the semiconductor substrate 3, the other surface (the semiconductor substrate 3) of the back plate 1 used in close contact with the back surface of the semiconductor substrate 3 is used.
(A surface on which is not set) is formed with a concave portion 2 concentric with the rear plate 1. The shape of the recess 2 is conical in the present embodiment.

As a result, the melt thickness (distance between the substrate growth surface and the opposite back plate) of the semiconductor substrate 3 facing the back plate 1 and facing the same is changed in the substrate plane.

The melt thickness is also a factor that affects the growth film thickness. This is because if the melt thickness is small, the solute is not sufficiently supplied to the substrate growth surface, and the grown film thickness becomes small. Further, in a boat having a structure in which semiconductor substrates are set upright and arranged at regular intervals, as described in the related art, the amount of solute supplied to the center of the semiconductor substrate is smaller than the amount of solute supplied to the outer peripheral portion of the set semiconductor substrate. Supply is not enough,
The difference in the grown film thickness becomes more remarkable.

Therefore, like the back plate 1 according to the present invention, by forming a concentric concave portion 2 on the other surface, the central portion of the substrate growth surface facing the back plate 1 has a large melt thickness. As a result, a sufficient source of solute is secured (in the direction of increasing the thickness of the grown film), and the outer peripheral portion is in a state where the melt thickness is reduced and the supply of solute is difficult (in the direction of decreasing the thickness of the grown film).

That is, by using the back plate 1 according to the present invention in a conventional liquid phase epitaxial growth apparatus, the growth thickness of the central portion of the semiconductor substrate 1 and the growth thickness of the peripheral portion of the semiconductor substrate 1 are increased. The characteristic and the characteristic of using the back plate 1 according to the present invention, in which the grown film thickness in the central portion of the semiconductor substrate 1 is large and the grown film thickness in the outer peripheral portion is small, cancel out the growth film. The unevenness of the thickness is corrected.

The epitaxial growth method after setting the semiconductor substrate 3 on the back plate 1 according to the present invention is the same as the conventional one as shown in FIGS. FIG. 2 shows a state in which the temperature is being raised, and FIG. 3 shows a state in which the growth is in progress. During the growth, the semiconductor substrate 3 and the back plate 1 are rotated at a constant speed. The same members as those shown in FIGS. 8 and 9 are denoted by the same reference numerals.

If the recess 2 formed in the back plate 1 is concentric with the back plate 1, the recess 2 may have any shape such as a bowl shape or a step shape as shown in FIGS. 4 (a) and 4 (b). Each of the growth film thicknesses and growth materials (GaP, GaAs)
Etc.), and may be appropriately designed according to the growth conditions and the like.

FIG. 5 shows the dimensions (conditions) of the back plate 1 when the recess 2 is formed in a conical shape, and the dimensions (conditions) of the set position with the semiconductor substrate 3, and FIG. FIG. 7 shows the dimensions (conditions) of the back plate 25 and the dimensions (conditions) of the set position with the semiconductor substrate 26. FIG. 7 shows the growth film thickness when epitaxial growth is performed under the conditions as shown in FIGS. The difference is shown.

FIG. 5A shows the size of the back plate 1 and the size of the set position at both right and left ends of the growth chamber.
(B) shows the size of the back plate 1 and the size of the set position at the center of the growth chamber.

The size of the back plate 1 at both left and right ends of the growth chamber is a disk shape having a radius of 30 mm and a thickness of 3 mm, and the depth of the center of the conical recess 2 is 2.3 mm. . The distance between the adjacent back plates 1 and 1 (more precisely, the distance between the semiconductor substrates 3 and 3) is 68 mm, the melt thickness is 5.8 mm at the center, and the radius is 20 mm from the center.
At the position of 4.2 mm.

On the other hand, the size of the back plate 1 at the center of the growth chamber is a disk shape having a radius of 30 mm and a thickness of 2.4 mm, and the depth of the center of the conical recess 2 is 1.4 mm. Has become. The distance between the adjacent back plates 1 and 1 (more precisely, the distance between the semiconductor substrates 3 and 3) is 68 mm, the melt thickness is 5.5 mm at the center, and the radius is 2 mm from the center.
It is 4.5 mm at the position of 0 mm.

The size of the conventional back plate 25 shown in FIG. 6 is a disk having a radius of 30 mm and a thickness of 1.5 mm. The distance between the adjacent rear plates 25 (more precisely, the distance between the semiconductor substrates 26, 26) is 68 mm.

As a result of performing epitaxial growth under such conditions, as shown in FIG. 7, both the semiconductor substrate 3 set at the left and right ends of the growth chamber and the semiconductor substrate 3 set at the center of the growth chamber have It can be seen that the grown film thickness is more uniform.

[0034]

According to the liquid phase epitaxial growth apparatus of the present invention, in a liquid phase epitaxial growth apparatus in which a plurality of semiconductor substrates are set upright in an epitaxial growth chamber to perform epitaxial growth, one surface is brought into close contact with the back surface of the semiconductor substrate. On the other surface of the back plate to be set, a concave portion is formed concentrically with the rear plate, and the shape of the concave portion is formed so that the outer peripheral portion is shallower and deeper toward the center. As a result, the characteristics of the conventional device that the growth thickness of the central portion of the semiconductor substrate is small and the growth thickness of the peripheral portion is large, and the growth thickness of the central portion of the semiconductor substrate is large and the growth thickness of the peripheral portion is small. The feature of using the back plate according to the present invention, such as thinning, cancels out the feature and makes the grown film thickness more uniform.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of a shape of a back plate which is a main part of the present invention.

FIG. 2 is a cross-sectional view showing a state during a temperature rise in which epitaxial growth is performed using a back plate according to the present invention.

FIG. 3 is a cross-sectional view showing a state during the epitaxial growth using the back plate according to the present invention.

FIG. 4 is a cross-sectional view showing another example of the shape of the back plate which is a main part of the present invention.

FIG. 5 is a diagram illustrating dimensions (conditions) of a back plate and dimensions (conditions) of a set position with a semiconductor substrate when a concave portion has a conical shape.

FIG. 6 is a diagram showing the dimensions (conditions) of a conventional back plate and the dimensions (conditions) of a set position with a semiconductor substrate.

FIG. 7 is a graph showing a difference in a grown film thickness when epitaxial growth is performed under the conditions shown in FIGS. 5 and 6;

FIG. 8 is a cross-sectional view showing a state in which a temperature is being raised during epitaxial growth by a conventional liquid phase epitaxial growth apparatus.

FIG. 9 is a cross-sectional view showing a state in the middle of a growth in which a conventional liquid phase epitaxial growth apparatus performs epitaxial growth.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Back plate 2 Depression 3 Semiconductor substrate

Claims (2)

[Claims] 1. A liquid phase epitaxial growth apparatus in which a plurality of semiconductor substrates are set upright in an epitaxial growth chamber to perform epitaxial growth, wherein the other surface of a back plate, one surface of which is set in close contact with the back surface of the semiconductor substrate. A liquid phase epitaxial growth apparatus, wherein a concentric concave portion is formed with the back plate. 2. The liquid phase epitaxial growth apparatus according to claim 1, wherein the concave portion is formed so that the outer peripheral portion is shallower and deeper toward the center.