JPH02237125A - Growth of epitaxial crystal - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] Regarding a method for growing an epitaxial crystal, the object is to prevent the substrate from warping after the epitaxial crystal growth and to obtain a flat surface of the epitaxial layer formed. In the epitaxial crystal growth process, the substrate for epitaxial crystal growth is heated to grow an epitaxial crystal having a coefficient of thermal expansion different from that of the substrate on the surface of the substrate, and then the substrate is cooled to a predetermined temperature. By forming in advance on the back side of the substrate a crystal layer having a coefficient of thermal expansion that applies stress to the substrate that counteracts the warping stress applied to the substrate due to the difference in thermal expansion coefficient between the epitaxial crystal and the epitaxial crystal. Configure.

[Industrial application field]

The present invention relates to a method for growing epitaxial crystals.

Compound semiconductor crystals with a narrow energy band gap, such as mercury-cadmium-tellurium (Hgl-x Cd. Te), are used as materials for forming infrared sensing elements.

[Conventional technology]

As a method for forming such a Hgl-x Cdx Te crystal in a large area and in a thin layer state conveniently for device formation, cadmium telluride (CdTe), which has a lattice constant close to that of the Hg+-x Cdx Te, is used. Il is grown using a liquid phase epitaxial growth method on a compound semiconductor substrate such as
An epitaxial crystal of g+-x cax Te is grown.

To explain the liquid phase epitaxial growth method in this way, as shown in FIG. Melt 3 for forming an epitaxial layer consisting of and tellurium
The epitaxial growth jig 2 is sealed in the ampoule 4 with the epitaxial growth jig 2 installed.

Next, the ampoule 4 is placed in a furnace core tube 5 installed in a heating furnace, and after heating and melting the epitaxial layer forming melt 3, the ampoule 4 is
After rotating the substrate 1 by 80 degrees and bringing the substrate 1 into contact with the molten epitaxial layer forming melt 3, the temperature of the melt is lowered at a predetermined temperature gradient to form Hg+-x Cd. T
is growing the evidential layer of e.

[Problem to be solved by the invention]

By the way, the thermal expansion coefficient of the epitaxial growth substrate 1 made of CdTe mentioned above is 5.5 xiO-'("c single layer"), whereas the epitaxial growth substrate 1 formed on it is
The thermal expansion coefficient of the epitaxial layer of 1g+-x Cdz Te is 4.3 After that, during the process of cooling the epitaxially grown substrate to room temperature before taking it out of the epitaxial growth jig, there is a problem in that the substrate warps upward in a convex shape as shown in FIG.

When the substrate warps upward in a convex manner, the epitaxial crystal 6 naturally tends to warp as well.

By the way, the epitaxial crystal needs to have a certain thickness in order to obtain the desired electrical characteristics as a sensing element.
In addition, if the surface is not flat, there is a problem in that masks cannot be aligned with high accuracy in a process such as mask alignment.

The present invention solves the above problems and prevents the substrate from warping during the process between heating the substrate to the epitaxial cell growth temperature and leaving it at room temperature in the epitaxial growth process, thereby preventing the epitaxial layer from warping. The purpose of the present invention is to provide a method for growing an epitaxial crystal that can obtain a flat surface.

[Means to solve the problem]

The method for growing an epitaxial crystal of the present invention which achieves the above object is based on the warping stress applied to the substrate 1 due to the difference in thermal expansion coefficient between the epitaxial growth substrate 1 and the epitaxial crystal 6 formed on the surface thereof, as shown in FIG. For,
This method includes the step of forming in advance on the back surface 1B side of the substrate 1 a crystal layer 11 having a coefficient of thermal expansion such that a stress that causes damage is applied to the substrate 1.

[For production]

The method of the present invention has a thermal expansion coefficient of 5.5
-') CdTe substrate surface has a coefficient of thermal expansion of 4.3
When an epitaxial layer of Hg.-x CdxTe with a coefficient of thermal expansion smaller than that of the CdTe substrate is formed at O-'["C-'], in the process of cooling the substrate from the epitaxial growth temperature to room temperature, as shown in FIG. Since the shrinkage rate of the substrate is larger than that of the epitaxial layer, the substrate tends to warp upward in a convex manner.Therefore, on the back side of the substrate, a layer with a coefficient of thermal expansion smaller than that of the substrate and of the epitaxial layer is formed. Hg+-x 4.7X, which is almost the same as the crystal of CdXTe
Silicon (with a coefficient of thermal expansion of IO-b ('C-')
By forming the Si crystal with approximately the same thickness as the epitaxial layer, stress is applied to the substrate to cancel out the warping stress that causes the epitaxial layer to curve upward in a convex state due to the difference in thermal expansion coefficient between the epitaxial layer and the substrate. Since it hangs on the back side, the substrate does not warp due to temperature fluctuations, and the substrate remains flat.

〔Example〕

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a cross-sectional view of an epitaxial growth substrate for carrying out the method of the present invention, and as shown in the figure, an epitaxial layer growth surface IA of an epitaxial growth substrate 1 made of CdTe is shown.
Hgl-X to be formed on the base 1 on the back side 1B
Hg+-x Cd to form Si crystal JWII having approximately the same coefficient of thermal expansion as the Cdx Te crystal on the substrate 1.
The thickness is approximately the same as that of the epitaxial layer of XTe, and is formed by vapor deposition or sputtering while heated to the temperature for epitaxial growth.

The CdTe substrate 1 thus prepared was placed in the epitaxial growth jig 2 as shown in FIG. The IA is brought into contact with the melt 3 of Hg+-x Cdx Te to form an epitaxial layer of Hg+-x Cd)I Te on the eviaxial layer growth surface IA of the substrate 1.

In this way, the St crystal layer 11 acts as a stress that reacts with the warping stress of the substrate 1 and is applied to the substrate, so that the substrate does not warp and an epitaxial layer is formed on it in a flat state. Therefore, the epitaxial layer can also be obtained in a flat state.

As shown in FIG. 1, the amount of warpage of the substrate before implementing this example was Hg+-x CdXTe with one side having 20 body angles.
When using a substrate, the distance from the center 0 of the substrate to the periphery of the substrate was 5 μm, but this was reduced to 1 μm according to this embodiment.

In this example, the Si crystal was formed on the back surface of the epitaxial growth surface of the substrate, but in short, the crystal that grows on the back surface of the epitaxial layer growth surface of the substrate depends on the thermal expansion coefficient of the substrate and the epitaxial layer formed thereon. In relation to the coefficient of thermal expansion, it is preferable that the crystal has a coefficient of thermal expansion such that stress is applied to the substrate in the direction in which the substrate warps. Further, although this embodiment has been explained using a liquid phase epitaxial growth method as an example, the present invention can also be applied to a vapor phase epitaxial growth method.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, the substrate does not warp during the process of cooling the epitaxial layer to the growth temperature and room temperature, so the epitaxial layer formed on the substrate can also be obtained in a flat state. .

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a substrate for epitaxial growth used in the method of the present invention, FIG. 2 is an explanatory view showing a liquid phase epitaxial growth method, and FIG. 3 is an explanatory view showing disadvantages in the conventional method. 1st Prisoner Said A Ding Pitaki Konrupe 1 vs. 3 E9 ■ View A Figure $ 2
In the figure, 1 indicates the substrate for epitaxial growth, IA indicates the epitaxial layer growth surface, 1B indicates the back surface, and 1 indicates the Si crystal layer.

Claims (1)

[Claims] After heating a substrate for epitaxial crystal growth (1) and growing an epitaxial crystal (6) having a coefficient of thermal expansion different from that of the substrate on the surface (1A) of the substrate, the substrate is heated to a predetermined temperature. During the growth of the epitaxial crystal, which is cooled until
A method for growing an epitaxial crystal, characterized in that a crystal layer (11) having a coefficient of thermal expansion such that a repulsive stress is applied to the substrate (1) is formed in advance on the back surface (1B) side of the substrate.