JP2703340B2 - Liquid phase epitaxial growth method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a liquid phase epitaxial growth method for eliminating the formation of groove-like concave portions due to the suppression of abnormal growth on the surface of an epitaxial growth layer in liquid phase epitaxial growth of a GaP compound semiconductor.

[Conventional technology]

The liquid phase epitaxial growth method uses a crystal precipitation from a solution based on thermodynamic phase equilibrium to grow a crystal on a main surface of a crystal substrate. Is often used when manufacturing optical devices such as laser diodes and light emitting diodes.

However, in the liquid phase epitaxial growth method, it is difficult to control the temperature of the single crystal substrate and the solution in contact with the single crystal substrate to a uniform temperature over the entire surface of the substrate during the epitaxial growth process, and furthermore, it is difficult to uniformly stir the solution. For this reason, the uniformity of the growth thickness of the epitaxial layer is likely to be impaired. Conventionally, the following proposals have been made to solve such problems.

For example, according to Japanese Patent Application Laid-Open No. 60-20594, the angle θ between the substrate surface and the crystallographic main surface is 0.5 to 2 ° in the direction parallel to the direction of the stripe-shaped mesas, or A technique for improving the in-plane distribution of the epitaxial layer thickness by using a substrate whose direction is 10 'in the vertical direction is disclosed. Further, JP-A-59-225518 discloses a technique in which a donut-shaped crystal substrate is provided in contact with a peripheral portion of a main surface of a substrate so as to prevent protrusions due to edge growth on the peripheral portion of the main surface. .

[Problems to be solved by the invention]

However, the crystallographic orientation of the main surface is close to {111}
Using aP compound semiconductor single crystal substrate, when performing a liquid phase epitaxial growth of GaP on this, if a growth of about 100 μm is performed, a narrow groove extending to a depth of 3 to 4 μm or sometimes 10 to 50 μm is often formed on the outer peripheral portion of the substrate. Is formed, and a complicated and winding surface formation is observed on the epitaxial growth surface like a plurality of earthworms (hereinafter referred to as earthworms). Since such earthworms are the narrow grooves as described above, the area containing the earthworms cannot be used for manufacturing the above-described optical device, and thus needs to be eliminated.

The present invention provides an epitaxial growth method in which no worms are generated on the growth surface when GaP liquid phase epitaxial growth is performed on a GaP compound semiconductor substrate whose main surface has a crystallographic orientation close to {111}, or the generation is significantly reduced. The aim is to provide a method.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a liquid phase epitaxial growth method for growing an epitaxial layer on a GaP compound semiconductor substrate, wherein a crystallographic orientation of a main surface of the substrate forms an angle with a {111} plane. 1 'to 8'.

In the initial stage of generation of earthworms (abnormal growth suppressing portions) on the epitaxial growth layer, the epitaxial growth is interrupted, and after dissolving and removing the earthworms (abnormal growth suppressing portions) by partially dissolving the epitaxial layer, It is preferable that the epitaxial growth be restarted.

Furthermore, after the epitaxial growth layer has grown to 30 to 60 μm, the epitaxial growth is interrupted, and after the earthworm (abnormal growth suppression portion) is dissolved and removed by partially dissolving the epitaxial layer, the epitaxial growth is restarted. Can also.

In the earthworm region, the epitaxial growth is suppressed, and therefore, when the depth of the narrow groove forming the earthworm increases, some defects occur in the pn junction of the epitaxial growth surface layer, and the light emission near the junction is insufficient. Become
Further, when an electrode is attached to an epitaxially grown surface layer during the manufacture of a light emitting diode, the ohmic property and the bondability are adversely affected. Therefore, it is necessary that no earthworms are completely present. However, since the light emitting area of the light emitting diode is extremely small with respect to the total surface area of the epitaxial growth layer, even if the earthworms are present on the epitaxial growth layer to a certain extent, the production cost is mainly reduced. Acceptable from the point.
According to the experience of the inventor of the present invention, it is considered that the allowable area where the earthworm is generated is about 5% of the total epitaxial layer surface area.

(Background of the Invention) The state of occurrence of earthworms generated on the surface of a GaP liquid phase epitaxial growth layer on a GaP compound semiconductor single crystal substrate whose principal surface is close to the crystallographic orientation {111} according to the conventional method will be described with reference to the accompanying drawings. Keep it. FIGS. 1 and 2 show the epitaxial layer L. The earthworm M is shown in FIGS.
It is considered that the growth proceeds through each of the steps (I) to (VI) in the figure. In (I), epitaxial growth stripes 1 are generated at an early stage of liquid phase epitaxial growth. (II)
In this case, the growth stripe 1 grows with the growth of the epitaxial layer, and the step becomes stronger. In (III), the growth stripe 1 becomes a double line m as the epitaxial layer grows. In (IV), the epitaxial layer further grows, and the double line m grows to a state called white earthworm M. This white earthworm M is not black because the light reflected at the bottom comes out to the top because the groove is still shallow. On the other hand, (V) and (VI) show that the white earthworm M further grew and became a state called black earthworm M.
Due to the deep groove, light does not come out at the top and looks black. FIG. 2 (V) shows a plan view of a normal black earthworm M, which is formed along the epitaxial growth stripes. FIG. 2 (VI) shows a plan view of a strong black earthworm M. The black earthworm M has grooves deeper and straightened, and is formed following one crystal orientation.

(Examples) Hereinafter, the present invention will be described with reference to examples, but it is needless to say that the present invention is not limited to these examples.

The liquid phase epitaxial growth apparatus used in the following examples is schematically illustrated in FIG. In the figure,
1 is a substrate and 2 is a quartz holder, which raises and lowers the substrate 1. Reference numeral 3 denotes a growth solution, 4 denotes a quartz container main body, 5 denotes a quartz hermetic lid, 6 denotes an inlet and an outlet for an atmospheric gas, and 7 denotes a heater.

Examples 1 to 5 and Comparative Examples 1 and 2 Experiments in which the crystallographic orientation of the main surface of the semiconductor substrate was slightly inclined from the {111} plane.
A GaP compound semiconductor substrate (about 2 inches in diameter, about 300 μm in thickness) with the following inclination (off angle) with respect to the surface is attached to a growth solution (GaP dissolved in Ga at a ratio of 3.3% by weight in Ga). It was immersed, and argon gas was used as an atmosphere gas. For this board, its off angle is
Three pieces each of 7 types of 1 ', 3', 4 ', 5', 7 ', 10', 13 'were used. The growth solution was heated and cooled by a temperature program as shown in FIG. In FIG. 4, the vertical axis shows temperature, and the horizontal axis shows time and the corresponding thickness of the grown layer. As shown in the figure, the growth solution temperature was 4 ° C from 1040 ° C to 850 ° C.
/ Min, and epitaxial growth was performed. The area including earthworms per substrate was measured on a magnifying projector screen, and the results are shown in FIG. As a result, when the off angle was 1 'to 8', the area including earthworms could be reduced to 5% or less of the total substrate area (1 cm ² or less in surface area).

In the method of the present invention, the crystallographic orientation of the main surface of the substrate is slightly inclined (1 ′ to 8 ′) from the {111} plane, and the epitaxial growth is carried out on the epitaxial growth layer at an early stage of earthworm generation. Interrupting, after dissolving and removing the earthworms by partially dissolving the epitaxial layer, a method of resuming the epitaxial growth, or after the epitaxially grown layer has grown 30 to 60 μm, interrupting the epitaxial growth, and partially removing the epitaxial layer. After dissolving and removing the earthworms by dissolution, a method of restarting the epitaxial growth may be synergistic. In this case, as the partial melting step of the epitaxial growth layer, the temperature program shown in FIG. 6 or 7 can be exemplified.

〔The invention's effect〕

As described above, according to the present invention, it is possible to eliminate the groove-like shape on the surface of the liquid phase epitaxial growth layer, that is, the growth of earthworms, thereby improving the yield and reducing the number of chamfering steps.

[Brief description of the drawings]

FIG. 1 is an explanatory side view showing a state of generation of earthworms generated on the surface of a liquid phase epitaxial growth layer, FIG. 2 is an explanatory top view of FIG. 1, and FIG. 3 is a schematic illustration of a growth apparatus used in Examples. FIG. 4 is a drawing showing a temperature program of the liquid phase epitaxial growth process of Examples 1 to 5 and Comparative Examples 1 and 2, and FIG. 5 is a graph showing the off angles and earthworms of Examples 1 to 5 and Comparative Examples 1 and 2. FIG. 6 is a drawing showing the correlation of the areas including the data, FIG. 6 is a drawing showing an example of a temperature program of a liquid phase epitaxial growth step used in carrying out the method of the present invention, and FIG. 6 is a drawing showing another example of the temperature program of FIG. M: earthworm, 1 ... semiconductor substrate, 2 ... quartz holder.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hitoshi Ikeda 2-13-1, Isobe, Annaka-shi, Gunma Shin-Etsu Semiconductor Co., Ltd. Isobe Plant (56) References JP-A-57-103314 (JP, A) JP 54-38599 (JP, B2)

Claims (3)

(57) [Claims] In a liquid phase epitaxial growth method for growing an epitaxial layer on a GaP compound semiconductor substrate,
An epitaxial growth method, wherein a crystallographic orientation of a main surface of the substrate is 1 'to 8' at an angle formed with a {111} plane. 2. The epitaxial growth is interrupted in an initial stage of generation of an abnormal growth suppressing portion on the epitaxial growth layer, and the abnormal growth suppressing portion is dissolved and removed by partially dissolving the epitaxial layer, and then the epitaxial growth is restarted. The epitaxial growth method according to claim 1, wherein 3. The method according to claim 3, wherein the epitaxial growth is interrupted after the epitaxial growth layer has grown by 30 to 60 μm, the abnormal growth suppression portion is dissolved and removed by partially dissolving the epitaxial layer, and then the epitaxial growth is restarted. The epitaxial growth method according to claim 1.