JPH0251248B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field This invention relates to a liquid phase epitaxial growth method, more specifically, to controlling the layer thickness when epitaxially growing a layer on a substrate such as a semiconductor, and in particular, to controlling a thin layer. The present invention relates to a method and apparatus for controlling thickness.

Technical background Semiconductor electronic equipment, for example, Fig. 1 and Fig. 2
As shown in the figure, a semiconductor laser device 1 or 1'
In manufacturing, a liquid phase epitaxial growth method is used to form multiple layers such as an internal current confinement layer 3, a first cladding layer 4, an active layer 5, a second cladding layer 6, and a cap layer 7 on a semiconductor substrate 2. is used. By the way, the semiconductor laser device 1 or 1'
The active layer 5 normally requires a thin, uniform thickness of 0.1 .mu.m or less, and various proposals have been made regarding liquid phase epitaxial growth methods and devices for this purpose.

The methods proposed above include, for example, reducing the supersaturation degree ΔT of the growing melt, shortening the growth time to about a few seconds, reducing the amount of melt in the carbon board of this device, or increasing the growth rate depending on the crystal plane orientation. For example, a predetermined process is applied to a substrate on which a layer is to be grown by utilizing properties that depend on the .

However, the above-mentioned proposed method, in particular,
When growing multiple layers on a substrate, a thinning effect occurs on some unspecified layers, and it is very difficult to grow only a specific layer, for example, the active layer 5, thinly. difficult to implement.

Problems to be Solved This invention has been made in view of the above-mentioned problems, and provides a method for forming a space of a required volume at the top of a melt loading chamber for the layer material when epitaxially growing a layer on a substrate. It is an object of the present invention to provide a method and apparatus for liquid phase epitaxial growth in which layers of precise thickness, in particular thin layers, can be obtained by adjusting the heat capacity inside the melt loading chamber and controlling its cooling rate. purpose.

Structure In order to achieve the above object, the liquid phase epitaxial growth method of the present invention basically seals a melt loading chamber for epitaxial growth material and maintains the inside of the melt loading chamber at a predetermined temperature. and a step of forming a space at the top of the melt loading chamber and cooling the melt loading chamber while adjusting the volume of the space. The cooling rate inside the liquid loading chamber is adjusted to reduce the desired degree of supersaturation of the growth material in the melt, thereby growing a thin layer of precise thickness on the substrate.

Furthermore, the apparatus of the present invention is provided with means for forming a space of a desired volume at the top of the layer material melt loading chamber in the layer growth boat, and by controlling the volume of the space, the heat capacity inside the melt loading chamber is increased. to control the cooling rate inside the melt loading chamber, and thus,
The degree of supersaturation of the layer material in the melt is precisely controlled.

EXAMPLE The present invention will be described below with reference to FIG. 3, which shows an epitaxial growth apparatus or furnace of an example.

FIG. 3 shows the main components of a horizontal liquid phase epitaxial growth apparatus or furnace according to the present invention.

In the drawing, 20 is a boat for liquid phase epitaxial growth, for example, a carbon boat is used. This carbon boat 20 is composed of a band-shaped substrate holder 21 and a melt holder 22 formed by stacking two band-shaped plates 22-1 and 22-2 that are slidably placed on the substrate holder 21. be done. This melt holder 22 is movable to the left and right with respect to the substrate holder 21 via a known pushing or pulling rod (not shown).

The melt holder 22 is provided with a plurality of through holes 26 of a predetermined size. A lid support step 27 is formed at the upper end of each through hole 26, and a flange 27 is formed at one end.
9 is attached to the through hole 26 by insertion. In this case, the top surface 28a of the lid body 28
and the upper surface 22a-1 of the strip plate body 22-1 are flush with each other. In this way, each through hole 26 forms a sealed chamber 30 with the lid 28 and the upper surface 21a of the substrate holder 21. Each chamber 30 is charged with a melt of the material 31 of the layer to be grown on the substrate 23, for example a semiconductor material. This chamber 30 is hereinafter referred to as a melt loading chamber. A source crystal 32 having the same quality as the growth material is placed near the melt surface in each melt loading chamber 30 .

Of the melt loading chamber 30, a lid 28' having a large flange 29' is attached to the through hole 26, which corresponds to the melt loading chamber in which material for epitaxially growing a thin layer is loaded. Ru. This lid body 28' is adapted to be hung on the opening edge of the through hole 26, that is, on the upper surface 22a-1 of the strip body 22-1. Then, the wedge-shaped jig 35 having an inclined surface formed at the tip end is attached to the strip plate body 2 of the melt holder 22.
It is slidably mounted on 2-1. By inserting the tip of this wedge-shaped jig 35 into the lower part of the flange 29' of the lid 28', the lid 28' is moved upward so that a space is formed in the melt loading chamber 30. It's summery. The volume of this space is determined in accordance with the lifting distance of the lid 28' commensurate with the cooling rate inside the melt loading chamber 30, as will be described in detail later.

A heater (not shown) such as an electric resistance heating element is installed around the carbon boat 20.

Next, the operation of the liquid phase epitaxial growth apparatus having the above structure will be explained according to the manufacturing process of the semiconductor laser device 1 shown in FIG.

A substrate 23 corresponding to the substrate 2 of the semiconductor laser device 1 is fixed in a recess 24 of a substrate holder 21 in a boat 20 of the apparatus shown in FIG. Note that the layer 3 has already been formed on this base 23 by liquid phase epitaxial growth. On the other hand, the melt holder 22
The materials for forming the layers 4, 5, 6, and 7 and the source crystal 32 corresponding to the materials are sequentially charged into the four melt loading chambers 30 starting from the leftmost chamber. A lid 28' having a large flange 29' is attached to the melt loading chamber 30 in which the material 31 forming the active layer 5 is accommodated.

The carbon boat 20 is heated by a known method via a heater (not shown), and the ambient temperature of the carbon boat 20 is maintained at a constant temperature of about 850° C. for a predetermined period of time. This situation is shown in the period t ₀ to t ₁ in FIG. 4. In this way, it is ensured that the melt components of the material enclosed within each melt loading chamber 30 are uniformly mixed.

Next, at time _t1 , cooling of the atmosphere is started, and the melt holder 22 is slid onto the substrate holder 21 in the direction shown by the white arrow in FIG. 3 via a push or pull rod (not shown). The melt loading chamber 30 for the material forming the internal current confinement layer 3 is positioned directly above the substrate 23. In this way, the internal current confinement layer 3 of about several μm is epitaxially grown on the substrate 23.

Further, at time _t1 , the tip of the wedge-shaped jig 35 is pushed into the lower part of the flange 29' of the lid body 28', as shown in FIG. A space with a required volume is formed at the top. By forming this space, the heat capacity inside the melt loading chamber 30 is made smaller than that in other melt loading chambers 30 that do not have a space,
Therefore, the temperature within the chamber 30 is rapidly reduced. Therefore, the material components in the melt in the chamber 30 rapidly re-precipitate on the source crystal 32 disposed near the liquid surface, and the degree of supersaturation of the semiconductor material in the melt of the active layer material in the other chamber increases. 30. As a result, about 0.05 μm is formed on the substrate 23.
A very thin active layer can be grown epitaxially. The volume of the space thus formed is appropriately determined depending on the thickness of the layer to be epitaxially grown, the material of the layer, the capacity of the melt loading chamber 30, etc. Note that the volume of the space may be changed at an appropriate rate of change during epitaxial growth instead of being held constant during epitaxial growth in the above-described embodiment. In this way, the layer thickness of the grown layer can be adjusted more precisely.

Thereafter, as shown in FIG. 4, the melt holder 22 is moved in the direction of the outlined arrow at predetermined timings t ₂ , t _{3 ,} . 6 is grown epitaxially. These epitaxial growth operations are well known in the art and will not be described here.

In the above embodiment, the case of manufacturing the semiconductor laser device 1 has been described, but it goes without saying that the present invention can be used to manufacture other semiconductor electronic devices by the liquid phase epitaxial growth method.

Effects As has become clear from the above explanation, according to the present invention, a space is formed at the top of the melt loading chamber for the layer material to be epitaxially grown, and by adjusting the volume of the space, the melt is The heat capacity inside the loading chamber is reduced at a desired rate of change, and the degree of supersaturation of the growth material in the melt is adjusted as desired, making it possible to control the thickness of the growth layer very easily and accurately. can be controlled. In particular, when forming multiple semiconductor layers on a substrate, such as in the manufacture of semiconductor laser devices, it is difficult to form a very thin active layer of approximately 0.1 μm or less using conventional liquid phase epitaxial growth equipment. By simply adding means for forming a space of a required volume at the top of the material melt loading chamber, only a predetermined layer among a plurality of semiconductor layers can be epitaxially grown to a desired thin thickness.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional VSIS type semiconductor laser device, FIG. 2 is a sectional view of a conventional TRS type semiconductor laser device, and FIG. 3 is a main configuration of a liquid phase epitaxial growth apparatus according to an embodiment of the present invention. diagram showing the parts,
FIG. 4 is a graph showing an operating characteristic diagram when the semiconductor laser device 1 is manufactured using the liquid phase epitaxial growth apparatus. 1... Semiconductor laser element, 2... Substrate, 3...
Internal current confinement layer, 4... first cladding layer, 5...
Active layer, 6... Second cladding layer, 7... Cap layer, 8... V-shaped groove, 20... Epitaxial growth boat (carbon boat), 21... Substrate holder, 22... Melt holder, 22-1, 22-2
... Strip body, 23 ... Substrate, 24 ... Recess, 26
...Through hole, 27...Lid support step, 28,2
8'...Lid body, 29, 29'...Flange, 30...
... Growth material melt loading chamber, 31, 32... Source crystal, 35... Wedge-shaped jig.

Claims (1)

[Claims] 1. In epitaxially growing a layer on a substrate, a step of sealing a layer material melt loading chamber and maintaining the inside of the melt loading chamber at a predetermined temperature; A liquid phase epitaxial growth method comprising the steps of forming a space at the top and cooling the melt loading chamber while adjusting the volume of the space. 2. In an apparatus for growing a layer on a substrate by a liquid phase epitaxial growth method, a means for forming a space of a desired volume is provided at the top of a layer material melt loading chamber in a layer growth boat, and the volume of the space is controlled. A liquid phase epitaxial growth apparatus characterized in that the heat capacity in a melt loading chamber is adjusted by adjusting the heat capacity in a melt loading chamber.