JPH0574559B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid phase epitaxial growth method, particularly to a liquid phase epitaxial growth method that makes the grown film thickness uniform.

[Prior Art] Liquid phase epitaxial growth methods include, for example, a slide method in which a wafer (substrate) is brought into contact with a growth solution using a slide boat to grow crystals, and a dip method in which crystals are grown by dipping a wafer in a solution. Various methods are known.

FIG. 3 is an explanatory diagram of the dip type epitaxial growth method, and shows a sectional view of the growth apparatus.

In the figure, 1 is a substrate holding part, 2 is a wafer,
The wafer 2 is held by the substrate holder 1 in a vertical direction. 3 is a solution for growing CaAs (gallium arsenide), etc., 4 is a solution holder that stores solution 3, 5 is an upper shutter, 6 is a lower shutter, 7 is a solution 3
8 indicates a support stand that supports the entire apparatus.

When epitaxial growth is performed using this apparatus, a plurality of wafers 2 are set vertically in the substrate holder 1, a solution 3 is stored above the wafers, and at the start of growth, the upper shutter 5 is opened to release the solution 3. The solution 3 is dropped between the wafers 2 to grow to a predetermined thickness, and after the growth, the lower shutter 6 is opened to allow the solution 3 to fall into the solution collection reservoir 7, thereby completing the growth process.

[Problems to be Solved by the Invention] As mentioned above, there are various liquid phase epitaxial growth methods, but when using the sliding method, the grown film thickness is uniform, but it is difficult to mass-produce. Further, in the case of the dip method, although it is excellent in mass production, there is a risk that variations in film thickness may occur.

FIG. 4 shows the variation in the grown film when ten wafers are set in the growth apparatus shown in FIG. 3 and epitaxial growth is performed.

The horizontal axis NO indicates the wafer number, and the vertical axis indicates the film thickness t. The circles in the figure indicate the average value, and the vertical lines indicate the standard deviation.

The characteristics shown in the figure show that the film thickness of wafers set outside the center of the apparatus is thicker than that of wafers set inside, and the variation is larger toward the outside.

This phenomenon causes a non-uniform temperature distribution within the growth apparatus during slow cooling at the end of growth, and a temperature difference within the solution, resulting in a significant deterioration of product quality.

An object of the present invention is to provide a liquid phase epitaxial growth method that allows the grown film thickness to be uniform, with little variation, and to improve quality.

[Means for Solving the Problems] The present invention provides a method for growing an epitaxial layer on the surface of the substrate by supplying a solution of an element constituting the semiconductor substrate to a substrate holding portion made of graphite that holds the semiconductor substrate. In the liquid phase epitaxial growth method, the outer layer of the substrate holding part is surrounded by a material having a higher thermal conductivity than the graphite to form a soaking part, and the outer layer is further made of a material having a lower thermal conductivity than the graphite. The method is characterized in that the growth process is performed by surrounding the semiconductor substrate with a heat insulating part to make the temperature distribution uniform during the epitaxial growth of the semiconductor substrate, thereby achieving the objective by making the grown film thickness uniform and reducing variations. It was calculated by

[Function] In the liquid phase epitaxial growth method of the present invention, when growing a thin film of an epitaxial layer by supplying a growth solution to a wafer, the outside of the graphite substrate holder that holds the wafer is coated with graphite. By surrounding it with a material with a higher thermal conductivity to form a heat-uniforming part, and further surrounding it with a material having a lower thermal conductivity than graphite to form a heat-insulating part, each It becomes possible to make the temperature distribution in the wafer and the solution uniform, and it is possible to obtain a high-quality semiconductor wafer with a uniform grown film thickness and little variation.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing an embodiment of an apparatus using the solution epitaxial growth method of the present invention. The same parts as in FIG. 3 are given the same reference numerals.

In the figure, 9 indicates a heat soaking section, and 10 indicates a heat insulation section.

In this example, the epitaxial growth of GaAs was targeted, and the growth film thickness was targeted to be 25 μm. A titanium plate heat-uniforming material was used for the heat-uniforming part 9, and an alumina heat-insulating material was used for the heat-insulating part 10.

If you want to start the growing process, start with 50mm x 50
A GaAs wafer 2 with a diameter of 2 mm was set in the apparatus, 500 g of Ga and 30 g of GaAa polycrystal were placed in the solution holder 4, and in this state the temperature of the apparatus was raised to 800° C. by hydrogen gas replacement.

After holding the temperature at 800℃ for 3 hours, slow cooling is performed at a rate of 0.5℃/min, and at the same time the upper shutter 5
Pull the lower shutter 6 in the direction of the arrow to drop the solution 3 between the wafers 2, allow the growth to occur for 40 minutes, and then pull the lower shutter 6 in the direction of the arrow to drop the solution 3 into the solution collection tank 7 to allow growth. Finish the process.

FIG. 2 shows the film thickness distribution of the epitaxial layer grown in this manner, where the horizontal axis shows the wafer number and the vertical axis shows the film thickness t. Circles indicate average values, and vertical lines indicate standard deviation.

The figure is No. 1 to 10, that is, when 10 wafers are set and grown, as is clear from the figure, the variation in the average value of the film thickness t is within 25 μm ± 3 μm, and the standard deviation is small and excellent characteristics can be obtained. to show that

The reason for this is that two layers, the soaking section 9 and the heat insulating section 10, are arranged on the outer layer of the substrate holding section 1.
This is because the temperature distribution of the wafer and solution became uniform during the epitaxial growth process.

In this embodiment, a titanium plate was used as the material for the soaking part 9, but other metals such as tungsten plates, potassium, indium, tin, etc., which become liquid at the melting temperature, were confined in the graphite material. You can also use In general, any material can be used as long as it has a low thermal conductivity value but has a large thermal conductive effect.

Although alumina material is used as the material for the heat insulating section 10, other ceramics such as silica, magnesium oxide, and zirconia can also be used.

Further, similar effects can be obtained by using a graphite material in addition to these materials.

Although FIG. 1 shows a method in which the growth solution is dropped, a method in which the growth solution is pushed up or injected may also be used.

Further, the same effect as described above can be obtained even when the heat equalizing material and the heat insulating material are used in the shutter section and the solution storage section.

As described above, by using this embodiment, the following effects can be obtained.

(1) The thickness of the grown film on the wafer during epitaxial growth becomes uniform and can be significantly reduced.

(2) It is possible to obtain mass production effects and improve quality and yield.

[Effects of the Invention] According to the present invention, it is possible to improve the liquid phase epitaxial growth method in which the grown film thickness is uniform, the variation is small, and the quality is improved.

[Brief explanation of the drawing]

FIG. 1 shows an epitaxial growth apparatus showing an embodiment of the liquid phase epitaxial growth method of the present invention;
FIG. 2 is a graph for measuring the thickness of a grown film, FIG. 3 is a graph for measuring the thickness of a grown film using the conventional epitaxial growth apparatus, and FIG. 4 is a graph for measuring the thickness of a grown film using the apparatus shown in FIG. DESCRIPTION OF SYMBOLS 1... Substrate holding part, 2... Wafer, 3... Solution, 5, 6... Shutter, 9... Soaking part, 10
...Insulation section.

Claims (1)

[Claims] 1. In a liquid phase epitaxial growth method in which an epitaxial layer is grown on a surface of the substrate by supplying a solution of an element constituting the semiconductor substrate to a substrate holder made of graphite that holds a semiconductor substrate, the substrate holder Surrounding the outer layer of the graphite with a material having a higher thermal conductivity than the graphite to form a heat-uniforming part, further surrounding the outer layer with a material having a lower thermal conductivity than the graphite to form a heat insulating part,
A liquid phase epitaxial growth method, characterized in that the growth process is performed with a uniform temperature distribution during epitaxial growth of the semiconductor substrate.