JPS61228634A - Manufacture of semiconductor crystal - Google Patents

Abstract

PURPOSE:To prevent the epitaxial growth on the bask side of a semiconductor crystal substrate by bringing a crystal body of exactly the same material as that of the semiconductor crystal substrate in close contact to the back side of the substrate during the epitaxial growth. CONSTITUTION:The front and back surfaces of a CdTe substrate 14 subjected to epitaxial growth are mirror-polished and furthermore these are etched with a boron methanol solution. The dummy substrate 15 of CdTe which is attached closely to the back side of the CdTe substrate 14 is also subjected to the mirror polishing of the plane to be in contact with the substrate and the similar treatment to that for the CdTe substrate. The CdTe crystal substrate 14 and the dummy substrate 15 contained in a growth ampoule 11 are immersed in an HgCdTe solution by the similar method to the conventional method to effect the epitaxial growth. Even during the epitaxial growth, because both single crystal substrate and dummy substrate are mirror-polished, a contact property is good and if there is a slight gap, CdTe molecules are in a saturation state so that mercury can not enter and accordingly the HgCdTe layer is not formed.

Description

Detailed Description of the Invention [Summary] The present invention is a manufacturing method in which epitaxial growth is performed on the surface of a semiconductor crystal substrate in a liquid phase or gas phase, and during epitaxial growth, a semiconductor crystal is grown on the back side of the semiconductor crystal substrate. Epitaxial growth on the back surface of a semiconductor crystal substrate is prevented by closely adhering a crystal body made of the same material as the crystal substrate.

[Industrial Field of Application] The present invention relates to a method for growing semiconductor crystals, and in particular to epitaxial growth of mercury cadmium tellurium (HgCdTe) crystals on cadmium telluride (CdTe) crystal substrates used in infrared detectors and the like. Regarding.

For example, when growing an HgCdTe crystal on a CdTe crystal substrate by liquid phase epitaxial growth, generally
As a result of mutual diffusion of CdTe and HgTe occurring not only on the front surface of the dTe crystal substrate but also on the back surface, Hg Cd Te
A layer is formed.

When a crystal substrate with a Hg Cd Te layer formed on the back surface of the substrate is used, for example, in an infrared device, there are disadvantages such as a decrease in infrared transmittance due to the layer.

Therefore, complicated operations such as mechanical polishing are required to remove the formed film on the back surface of these substrates, and mechanical polishing of the surface of such a crystal substrate may distort the crystal arrangement on the crystal surface. This leads to a decrease in the quality of the crystal, so there is a need for improvement.

[Prior Art] FIG. 2 is a schematic sectional view of a main part of a conventional liquid phase epitaxial crystal growth apparatus.

There is a growth ampoule 1 made of quartz, and inside the growth ampoule there is a melt holder 2 made of quartz, and a Cd Te single crystal substrate 4 is held by grooves 3 on both end faces of this melt holder. Single-crystal HgCd is grown on a CdTe single-crystal substrate 4 by liquid phase epitaxial growth.
To grow Te, Hg Cd Te solution 5
is filled into the growth ampoule.

FIG. 3 is a perspective view showing an example of the melt holder 2, and the melt holder 2 held by the connecting bar 6 includes:
Grooves 3 for supporting the substrate are formed facing each other.

After inserting this growth ampoule into a heating furnace and melting the crystal material at a high temperature, the single crystal substrate 4 is immersed in the Hg Cd Te solution 5 by rotating the growth ampoule 180 degrees. Next, by slowly cooling the temperature of the solution for a predetermined period of time, HgCdT with a thickness of 30 μ- to 40 μ-
The e-layer is epitaxially grown.

In this way, the CdTe single crystal substrate 4 is replaced with HgCdTe.
Epitaxial growth is performed by immersing in solution 5, but C
Due to the difference in chemical potential of both materials, dTe and Hg Cd Te, Cd Te
Single-crystal substrates are relatively stable and slow to diffuse, but on the other hand, H
Since gCdTe diffuses quickly, a polycrystalline HgCdTe layer is formed on the back surface of the CdTe single crystal substrate.

The only way to remove the HgCdTe layer deposited on the back surface is by polishing, and this polishing process involves mixing fine powder such as alumina into a liquid and polishing the back surface of the substrate with the alumina mixed liquid. However, with this polishing method, H
This has the drawback of causing distortion in the crystal of the g Cd Ta substrate, resulting in deterioration of device characteristics.

[Problems to be Solved by the Invention] When a Hg Cd Te single crystal is liquid-phase epitaxially grown on a Cd Ta single crystal substrate, interdiffusion of CdTe and HgTe occurs on the back surface of the CdTe crystal substrate. The problem is that a polycrystalline Hg Cd Te layer is formed.

[Means for Solving the Problems] FIG. 1 is a sectional view of a liquid phase epitaxial growth apparatus according to the present invention for solving the above problems. on the surface of
When epitaxial growth is performed using a solution, mutual diffusion between the solution and the semiconductor single crystal substrate is prevented by closely contacting the back side of the semiconductor single crystal substrate with a substrate of the same type as the semiconductor single crystal substrate. This prevents a polycrystalline growth film from being formed on the back surface of a semiconductor single crystal substrate.

This method of preventing the formation of a polycrystalline growth film on the back surface of a semiconductor single crystal substrate is not limited to liquid phase epitaxial growth (it can also be adopted in the case of vapor phase epitaxial growth). .

[Function] The Hg Cd Te layer is formed on the back surface of the CdTe crystal substrate because mutual diffusion occurs because the chemical potentials of CdTe and HgCdTa are different. If the same CdTe crystals are placed in close contact with each other, the CdTo molecules in the microspace on the back surface of the CdTe substrate will be immediately saturated and will not evaporate from the CdTe crystal, resulting in a polycrystalline HgCdTe layer due to interdiffusion. Therefore, there is no need to polish the grown film in a post-process, and good epitaxial growth can be achieved.

[Example] A liquid phase epitaxial growth apparatus according to the present invention will be explained in detail with reference to a schematic cross-sectional view of main parts in FIG.

There is a growth ampoule 11 made of quartz, and inside thereof there is a melt holder 12 made of quartz which rotates within the growth ampoule and is supported by grooves 13 on both sides of the melt holder.
CdTe single crystal substrate 1 on which epitaxial growth is performed
4 and a dummy CdTe single crystal substrate 15 placed in close contact with the back side of this CdTe single crystal substrate 14 are held in the melt holder in a double manner.

Further, in the growth ampoule, HgCdTe is placed for liquid phase epitaxial growth on the surface of the CdTe crystal substrate 14.
The molten liquid 16 is dissolved.

Cd Te substrate 14 on which epitaxial growth is performed
The front and back surfaces of the CdTe substrate 14 are polished to a mirror surface, and then etched with a bromine-methanol solution. Perform mirror polishing and Cd
The same treatment as for the Te substrate is performed.

CdTe crystal substrate 1 housed in growth ampoule 11
4 and the dummy substrate 15 are coated with Hg using the same method as before.
Epitaxial growth is performed by immersing in a Cd Ta solution.

Even during epitaxial growth, both the single crystal substrate and the dummy substrate have good adhesion because they are mirror polished, and even if there is a slight gap, the CdTe molecules become saturated, so mercury does not get in. Therefore, HgCdT
No e-layer is formed.

According to this method, polycrystalline Hg is formed on the back surface of CdTe.
No CdTe layer is formed and there is no need for a post-growth polishing step.

[Effects of the Invention] As explained above in detail, by performing epitaxial growth according to the present invention, a high-quality substrate can be provided without forming a polycrystalline growth layer due to diffusion on the back surface of the growth substrate. It is very effective.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a liquid phase epitaxial growth apparatus of the present invention, FIG. 2 is a sectional view of main parts of a conventional liquid phase epitaxial growth apparatus, and FIG. 3 is a perspective view of a melt holder. , 12 is a melt holder, 13 is a groove, 14 is a single crystal substrate 15 on which epitaxial growth is performed, is a dummy single crystal substrate, and 16 is a solution. , V
1st(2)mt! A

Claims (1)

[Claims] A semiconductor single crystal substrate (14) and a solution (16) are placed in a growth ampoule (11) for performing liquid phase or vapor phase epitaxial growth.
), and when epitaxial growth is performed on the surface of the semiconductor single crystal substrate (14), a dummy single crystal substrate of the same type as the semiconductor single crystal substrate is placed on the back side of the semiconductor single crystal substrate (14). (15) A method for growing a semiconductor crystal, characterized in that epitaxial growth is performed with the crystals in close contact with each other.