JPH03214634A - Manufacture of compound semiconductor crystal and manufacture of optical detection element - 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] 3. Regarding a liquid phase epitaxial growth method and a method for manufacturing a photodetecting element using the growth method, an epitaxial crystal layer formed on an epitaxial growth substrate is uniform along the epitaxial growth direction. For the purpose of obtaining a liquid phase epitaxial growth method that allows a compositional distribution to be obtained and a photodetector element manufactured using this growth method, a support plate is placed between a fixing jig that holds an epitaxial growth substrate. The epitaxial growth substrate and the dummy substrate are held in a state where they are relatively shifted from the center axis of the fixing jig, and the epitaxial growth melt is accommodated in a position facing the epitaxial growth substrate, and the fixing jig is a step of sealing in a container, heating the container to melt the epitaxial growth melt, and then rotating the container to bring the epitaxial growth melt into contact with the epitaxial growth substrate to form an epitaxial crystal on the substrate; A step of rotating the container to bring the dummy substrate into contact with the bitaxial growth melt and dissolving the components of the dummy substrate into the melt, and then repeating the above two steps to form an epitaxial crystal on the substrate. It consists of things.

[Industrial application field]

The present invention relates to a method for liquid-phase epitaxial growth of compound semiconductor crystals of mercury, cadmium, and tellurium used as materials for forming photodetecting elements, and in particular to a method for obtaining an epitaxial crystal layer having a uniform composition distribution in the thickness direction of the grown layer. Regarding the method.

In recent years, in infrared sensors such as photodetecting elements, there has been a particular demand for uniformity of characteristics between pixels.

Therefore, if the composition of the compound semiconductor epitaxial crystal used in the infrared sensor changes in the thickness direction of the crystal layer, the spectral sensitivity characteristics will vary between pixels due to slight differences in the thickness of the epitaxial crystal Ji. It is necessary to obtain a grown layer with a uniform composition in the thickness direction.

5 [Prior Art] As shown in FIG. 5, an apparatus used in a conventional liquid phase epitaxial growth method has a groove 3 that holds a plate-shaped substrate support plate 2 that holds a substrate 1 for epitaxial growth. A fixing jig 6 made of a pair of cylindrical quartz members facing each other and having a space 5 for accommodating the epitaxial growth melt 4 when the apparatus is rotated; It consists of a container 7.

A case in which epitaxial crystals are formed on a substrate by a conventional method using such an apparatus will be described.

As shown in FIG. 5 and FIG. 6 (al), which is a sectional view taken along the line v-v' in FIG.
The board support plate 2 is installed in the groove 3 of the fixing jig 6 described above.
The fixing jig 6 on which the substrate 1 is installed is filled with a material for forming the epitaxial growth melt 4, which is obtained by melting mercury, cadmium, and tellurium and solidifying it at the opposite position facing the substrate. and seal it in the container 7.

6 Next, the container 7 is inserted into a furnace core tube (not shown) in a heating furnace, and the container 7 is heated to melt the solidified epitaxial growth material in the container 7 to form an epitaxial growth melt (solution). do.

Next, the container 7 is rotated 180 degrees along the direction of arrow A, and the substrate 1 is brought into contact with the epitaxial growth melt 4, as shown in FIG. Hold the Hg+ on the board for a while.
-x Cdx Te epitaxial crystal is grown.

Next, the container 7 is further rotated 180 degrees in the direction of arrow B, and the epitaxial growth is stopped by a wipe-off operation in which the epitaxial growth melt adhering to the substrate is dropped to the lower part, as shown in FIG. 6fcl.

[Problem to be solved by the invention]

When performing epitaxial growth using such a conventional method, Cd atoms in a melt for epitaxial growth of a solution of an alloy of mercury, cadmium, and tellurium have a large segregation coefficient compared to other constituent atoms of the melt. As the layer grows, Cd atoms are easily segregated and consumed in the solid phase, resulting in a decrease in the concentration of Cd atoms in the melt.

Figure 7 shows Hg+-x CdXTe formed by the conventional method.
This is a diagram showing the relationship between the X value of a crystal and the thickness of the crystal. As shown in the figure, the X value decreases as the thickness of the Hg+-x Cd*Te crystal increases.

In addition, CdTe substrates are difficult to manufacture as single crystals with large areas, and therefore CdTe substrates are difficult to manufacture on insulating substrates such as sapphire.
Te crystal is epitaxially grown and Hg+-x is grown on top of it.
CdxTe crystal is formed, but the Hg,-,C
When forming a semiconductor device in which a dXTe crystal and a Si substrate on which a signal circuit element is formed are bonded together, the sapphire substrate needs to be removed.

Therefore, when forming a photodetector element using the conventional method, after forming a CdTe crystal on a sapphire substrate by MOCVD method, l{g+-x Cd)+T is formed on the CdTe crystal.
After forming the Hg+-x Cdx Te crystal and adhering the St substrate on which the signal processing circuit element was formed, a selective etching solution for the CdTe crystal was used to form the Hg+-x Cdx Te crystal and the photodetecting element. An attempt was made to separate the x Cdx Te crystal from the sapphire substrate.

However, CdTe was deposited on the sapphire substrate using the above MOCVD method.
It takes a long time to form a thick crystal, and if a thin CdTe crystal is formed on a sapphire substrate, the etching solution for the CdTe crystal will erode the side surfaces of the thin C+ITe crystal and will not penetrate sufficiently into the CdTe crystal. Selective etching of crystals is difficult.

The present invention aims to solve the above-mentioned problems and provide a method for producing an epitaxial crystal of Hg+-xC(]+Te with a small composition gradient in the thickness direction.

Another object of the present invention is to provide a method for manufacturing a photodetecting element using the above method.

[Means for Solving the Problems] The liquid phase epitaxial growth method of the present invention that achieves the above object is characterized in that the epitaxial growth substrate and the dummy substrate are mounted on a fixing jig that holds the epitaxial growth substrate with a support plate in between. Fixing jig 9: sandwiching the fixing jig in a state where they are mutually shifted from their central axes, enclosing the fixing jig in a container with the epitaxial growth melt contained in a position facing the epitaxial growth substrate, and heating the container. to melt the epitaxial growth melt, and then rotate the container to bring the epitaxial growth melt into contact with the epitaxial growth substrate to form an epitaxial crystal on the substrate; further rotate the container to melt the dummy substrate; A step of bringing the dummy substrate into contact with the epitaxial growth melt 1 and dissolving the components of the dummy substrate in the melt. The above two steps are repeated a predetermined number of times to form an epitaxial crystal on the epitaxial growth substrate.

[For production]

In the method of the present invention, after a tlg+-x CdXTe crystal is grown on a substrate using a liquid phase epitaxial growth method, the epitaxial growth container is further rotated, and epitaxial growth is performed on a dummy substrate having the same composition as the Hg+-x CdXTe melt. The components of the dummy substrate are dissolved in the epitaxial growth melt.

Then, the melt whose X value has reached a predetermined value is further brought into contact with a substrate on which epitaxial growth has been performed, and the temperature of the melt is lowered to form a llg+-X CdxTe crystal.

By repeating this operation, the precipitated tlg+-x Cdx
Since Cd atoms, which are easily segregated into 're crystals, are supplied to the melt, the composition of the melt does not change, and when the operations of growing epitaxial crystals from the melt and dissolving the dummy substrate into the melt are repeated, An epitaxial crystal of Hg+-x Cdx Te with stable composition, thickness, and large dimensions is formed.

In addition, a CdTe crystal is used for the dummy substrate, and a CdTe crystal is used for the substrate.
When a sapphire substrate with a crystal formed thereon is used and a CdTe crystal is used as the melt for epitaxial growth, a thick CdTe crystal is formed on the substrate, and on top of this, Hg+-xCdX
After forming a Te crystal and adhering an St substrate on which a signal circuit element is formed to the Hg+-x Cdx Te crystal, the C
Selective removal of d11-Te crystals results in a high-quality thin layer of Hg+
-x A highly sensitive photodetecting element in which the photodetecting element is formed on a CdXTe crystal can be obtained.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1(a) to FIG. 1(dl) are explanatory diagrams of the epitaxial growth method of the present invention. FIG. 1(a) shows the state before the start of epitaxial growth, and FIG. 1(d) shows the state after the start of epitaxial growth, and all are sectional views taken along the line 1-1' of FIG. 1 (al).

FIG. 2 is a temperature distribution diagram of a heating furnace for carrying out the method of the present invention.

As shown in FIG. 1(a), CdT is placed on the upper side of the support plate 12.
An epitaxial growth substrate 13 made of a sapphire substrate on which e-crystals are formed is placed, and Ilg+-x Cdx of x = 0.2, which has the same composition as the melt, is placed on the lower side of the support plate.
With the Te dummy substrate 14 installed, these Evita 12 axial growth substrates and dummy substrates are attached to the fixing jig 11.
0 in the groove 32 on the opposing surface.

Then, both substrates are installed with their positions shifted with respect to the central axis 31 of the fixing jig 11, and a melt l-15 for epitaxial growth of lIg+-x Cdx Te with x = 0.2 is placed below this dummy substrate 14. Container 1 containing
Enclose in 6.

In this state, introduce the above container into the heating furnace and
As shown in FIG. 3, the temperature of the heating furnace was set to 550° C. to melt the epitaxial growth melt 15 described above.

Next, as shown in Figure 2b, the temperature of the molten melt is
While lowering the temperature at a rate of 0.1 to 0.2°C per minute,
The container shown in figure (bl) is rotated 180 degrees in the direction of arrow D,
In the state shown in Figure 1 (C), the epitaxial growth substrate is brought into contact with the epitaxial growth melt, and the x
= 0.2 Hg+-x Cd) (Te crystal of 10 μm
Form to a certain thickness.

Next, the container shown in FIG. 1 TCI is rotated 270 degrees in the direction of arrow E to bring it into the state shown in FIG.
A dummy substrate 14 is brought into contact with the melt 5 for 3-layer growth, and the temperature of the melt 15 is set to 525° C. as shown in FIG. 2C to dissolve the components of the dummy substrate in the melt.

Next, the container shown in FIG. 1 (D) was rotated 270 degrees in the direction of arrow F to bring it into the state shown in FIG. .1 ~0.2℃/min
As shown in Fig. 2d, a 10 μm thick epitaxial crystal of ■g, ~XCdXTe is deposited on the substrate.
Form to a thickness of .

By repeating these epitaxial growth steps and the step of dissolving the components of the dummy substrate into melt a plurality of times, an epitaxial crystal in which the X value of the Hg+-xCdXTe crystal formed on the substrate does not vary can be obtained.

In this way, as shown in FIG. 3, an epitaxial crystal of Hg+-x Cdx Te with little variation in the X value in the thickness direction can be obtained.

Furthermore, a case will be described in which a photodetector element is formed using the method of the present invention.

14 As shown in FIG. 4(a), Cd is applied to the sapphire substrate 21.
A substrate on which a Te crystal 22 is formed to a thickness of about 3 μm by MOCVD is used as a substrate for epitaxial growth.

Next, using a CdTe substrate as a dummy substrate and a CdTe crystal as an epitaxial growth melt, the components of this dummy substrate are dissolved in the epitaxial growth melt, and the above-mentioned repeated growth is performed to form a layer on the substrate as shown in Fig. CdTe crystal 22A with a thickness of several 100 μm
Form to a thickness of .

Next, as shown in FIG. 4(C), the epitaxial growth container was replaced, and a thickly formed C
Hgl-x Cdx Te crystal 2 on dTe crystal 22Δ
3 to a thickness of 10 μm.

Next, as shown in FIG. 4(d), this Hg+-, +
5i formed with CdXTe crystal 23 and signal processing circuit element
The substrate 25 is bonded with an adhesive.

Next, the thickly formed CdTe crystal was selectively etched using Esotin 15 solution which dissolves only the CdTe crystal without dissolving the Hg+-xCd)(Te crystal and the sapphire substrate, thereby removing the sapphire substrate and the photodetecting element. Hg formed
+-X Cd+tTe crystal is separated.

4 This state is shown in Figure d (e). In this way, the etching solution comes into contact with the side surface of the thickly formed CdTe crystal, and the etching solution enters inside the CdTe crystal so as to peel it back, so that it can be easily separated in a short time.

Since the separated HgI-xCd)(Te crystal is a thin layer and obtained by liquid phase epitaxial growth, a high quality crystal can be obtained.

Then in FIG. 4 (as in fl, Hg+-XCdx Te
The crystal 23 is separated and the separated Hg+-x Cd)+
An electrode 26 is formed on the Te crystal 23 to form a photodetector element.

Next, using a wire, a bonding connection is made to a signal processing device temporarily formed on the St base.

In this way, in the conventional method, the CdTe crystal becomes M
With the OCVD method, it takes a long time to form a thick film, and when a thin film is formed, the above-mentioned selective etching solution for the CdTe crystal does not penetrate into the inside of the CdTe crystal from the side surface.This solves the problem at once, and the signal processing A photodetector element bonded to the substrate on which the device is formed can be easily obtained.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, lIg+-x Cdx Te which does not cause compositional variation in the thickness direction
Crystals are obtained. Furthermore, this method has the advantage that it is possible to easily form a photodetector element adhered to the Si substrate on which the body image processing device is formed.

[Brief explanation of drawings]

Figure 1 fal to Figure 1 Fdl are cross-sectional views showing the steps of the method of the present invention. Figure 2 is a temperature profile diagram of the heating furnace used in the method of the present invention. Figure 3 is a diagram showing the temperature profile of the heating furnace used in the method of the present invention. Hg+-x Cdx T
e Crystal composition distribution diagram, Figure 4 (from a+ to Figure 4 (fl) is a cross-sectional view showing the method of manufacturing a photodetector element by the method of the present invention, 17 Figure 5 is a cross-section of a conventional liquid phase epitaxial growth apparatus. Figure 6fa) to Figure 6(C) are process diagrams of the conventional liquid phase epitaxial growth method.
A composition distribution map of crystals is shown. In the figure, 11 is a fixture, 12 is a support plate, 13 is an epitaxial growth substrate, 14 is a dummy substrate, 15 is an epitaxial growth melt, 16 is a container, 21 is a sapphire substrate, 2
2.22A is (:dTe crystal, 23 is tlg+-*C
dx Te crystal, 25 is a Si substrate, 26 is an electrode, 3J is a central axis, and 32 is a groove. 1 8 Φ 1-gi VarJX 1YX

Claims (3)

[Claims] (1) Place the epitaxial growth substrate (13) and dummy substrate (14) in a fixing jig (11) that holds the epitaxial growth substrate (13) with the support plate (12) in between, at the center of the fixing jig. A melt for epitaxial growth (15
) is enclosed in the container (16), and the container is heated to release the epitaxial growth melt (
15) after melting, rotating the container to bring the epitaxial growth melt into contact with the epitaxial growth substrate (13) to form an epitaxial crystal on the substrate; rotating the container to bring the epitaxial growth melt into contact with the dummy substrate (14); is brought into contact with the epitaxial growth melt (15) to dissolve the components of the dummy substrate into the melt, and the above two steps are further repeated a predetermined number of times to form an epitaxial crystal on the epitaxial growth substrate. A method for manufacturing a compound semiconductor crystal. (2) The epitaxial growth substrate (13) is made of Cd
A Te wafer or a substrate with a CdTe crystal formed on the surface is used, and the dummy substrate (14) is a Hg_1_-_xCd
2. The method for manufacturing a compound semiconductor crystal according to claim 1, wherein the compound semiconductor crystal is made of _xTe crystal. (3) A substrate with a CdTe crystal (22) formed on its surface and a support plate (12) that holds a substrate for epitaxial growth sandwiched between a fixing jig (11) that holds the substrate, and a CdTe crystal (22) formed on the surface of the substrate.
An e-crystal dummy substrate (14) is held in a position shifted relative to the central axis (31) of the fixing jig, and a C-crystal dummy substrate (14) is held at a position facing the epitaxial growth substrate.
The fixing jig is sealed in a container while containing the melt for epitaxial growth of dTe crystal, and after heating the container to melt the melt for epitaxial growth, the container is rotated to perform epitaxial growth of the components of the dummy substrate. After repeating the step of dissolving the substrate in the melt for epitaxial growth and the step of rotating the container to bring the substrate for epitaxial growth into contact with the melt for epitaxial growth, a CdTe crystal (22A) is formed to a predetermined thickness on the CdTe crystal on the substrate. , a Hg_1_-_xCd_xTe crystal (23) with a predetermined x value is formed on the CdTe crystal, and the crystal (23) is adhered to a substrate (25) on which a signal processing circuit element is formed, and the CdTe crystal (22A) is selectively etched,
The epitaxial growth substrate (13) is Hg_1_-
A method for manufacturing a photodetecting element, which comprises separating from a _xCd_xTe crystal (23), forming a photodetecting element on the crystal, and then electrically connecting the photodetecting element and the signal circuit element.