JPH03142885A - Manufacture of infrared detection element - Google Patents

Abstract

PURPOSE:To minimize the generation of cross talk and facilitate manufacturing by forming semiconductor crystal formed on a substrate partially with a different thickness and the growing semiconductor crystal for component formation on the substrate by isothermal vapor phase growth process, halting growth work when it is converted into semiconductor crystal equalized in its thickness direction by mutual diffusion, and processing the surface so that its surface may be flat. CONSTITUTION:After the formation of CdTe (x=1.0) crystal 12 including a constitutive element for Hg1-xCdxTe crystal 13 for component formation on an insulation substrate 11, the crystal 12 is etched in such a manner that its thickness may differ partially. Then, the crystal 13 is formed based on an isothermal vapor phase growth process. At first, a thin region 12A of the CdTe crystal is converted into Hg1-xCdxTe by the mutual diffusion between the CdTe crystal and the Hg1-xCdxTe. Isothermal vapor phase growth work is halted when the thin region of the CdTe crystal has been converted into Hg1-xCdxTe whose composition value is equalized in its thickness direction. Due to this process, the value x of the Hg1-xCdxTe crystal 13B converted in a thicker region 12B of the CdTe crystal is greater than the value x of the Hg1-xCdxTe crystal 13A converted in a thin region 12A of the CdTe crystal.

Description

[Detailed Description of the Invention] [Summary] Regarding a method for manufacturing an infrared sensing element, the present invention aims at a method for manufacturing an infrared sensing element that causes less crosstalk between pixels, and a semiconductor crystal for forming the element to be formed on a substrate. Semiconductor crystals containing constituent elements are partially made with different thicknesses to form t! After that, the semiconductor crystal for forming an element is grown on the substrate by an isothermal vapor phase growth method, and the partially thin semiconductor crystal region of the semiconductor crystal is interdiffused to form an element with a uniform composition in the thickness direction. When converted into a semiconductor crystal for forming an element, after stopping the growth operation of the semiconductor crystal for forming an element, the surface of the semiconductor crystal for forming an element formed on the substrate by an isothermal vapor phase growth method is processed to be flat;
An element is formed by introducing impurity atoms for element formation into a semiconductor crystal for element formation into which the semiconductor crystal on the thinner side is converted.

[Industrial application field]

The present invention relates to a method of manufacturing an infrared sensing element, and more particularly to a method of manufacturing an infrared sensing element that does not cause crosstalk.

Infrared sensing elements are formed of compound semiconductor crystals such as mercury-cadmium-tellurium (HgI-x Cdx Te), which have a narrow energy bandgap. In order to improve resolution, it is advisable to form them at higher and higher densities.

[Conventional technology]

As shown in FIG. 5, the conventional infrared sensing element is made of P-type HgI-xCd, which is used to form the element by a liquid phase epitaxial growth method, on a CdTe base + JIl that transmits infrared rays.
After forming the epitaxial crystal 2 that is more stable than Te, boron (B) atoms of N-type conductivity are ion-implanted into predetermined regions of the epitaxial crystal 2 to form N-type layers 3A, 38.3C.
A P-N junction 4 is formed between the Hfh-x Cdx Te epitaxial crystal 2 and the N-type layers 3A, 3B, and 3C.
Photovoltaic infrared sensing elements 5^, 5B, 5C by
is formed.

[Problem to be solved by the invention]

Incidentally, such infrared detecting elements 5A, 5B, and 5C need to be arranged at high density with narrow intervals between the detecting elements to form an infrared image with high resolution.

Therefore, as shown in Figure 5, when infrared rays are incident from the CdTe substrate surface side along the directions of arrows A and B, the infrared rays incident between these detection elements 5A and 5B and between 5B and 5C are photoelectrically converted. Carrier that occurred 6^
is now introduced across both the infrared sensing elements 5^ and 5B, and the infrared sensing elements 5B and 5C, so that the infrared rays shown by arrow C incident from directly below the infrared sensing element 5B Carrier 6B is photoelectrically converted
The carrier 6A is superimposed on the sensor, causing crosstalk, resulting in a sensing element with poor resolution.

In order to prevent the occurrence of such losstalk, the present applicant previously proposed in Japanese Patent Application No. 63-60778, as shown in FIG. After forming an epitaxial crystal of HgI-x Cdg Te as a buffer layer 7, a second HgI-x Cdx Te crystal layer 8 having a smaller X value than the buffer layer is formed.
and separating the second "g+-x Cdz Te crystal layer 8 with a "Hg+-x Cd, Te crystal layer 9 having a larger X value than the second HgI-x Cdx Te crystal layer 8,
The separated second HgI-x Cdz Te crystal layer 8
proposes an infrared detection device in which an N-type layer 10 is formed to form a detection element.

In this detection device, since WIHtJ with a large X value is interposed between the elements, infrared rays incident on this layer are transmitted, so carriers are not generated within this layer and no crosstalk occurs.

However, this method of separating the 11g, □Cd, Te crystal layer has the problem of a complicated process.

The present invention aims to solve the above-mentioned problems, and to provide a method for manufacturing an infrared sensing element that causes less crosstalk and is easy to manufacture.

[Means to solve the problem]

The method for manufacturing an infrared sensing element of the present invention that achieves the above object is as shown in FIG. 1(a) and FIG. 1(1)).
After forming the semiconductor crystal 12 containing the constituent elements of the element-forming semiconductor crystal 13 to be formed on the substrate ll with partially different thicknesses, the element-forming semiconductor crystal 13 is placed on the primordium t7i 11 under isothermal air. When the partially thin semiconductor crystal region 12A of the semiconductor crystal 12 grown by a phase growth method is converted into the element-forming semiconductor crystal 13A having a uniform composition in the thickness direction by interdiffusion, After stopping the semiconductor crystal growth operation, the surface of the element forming semiconductor crystal 13 formed on the substrate by the isothermal vapor phase growth method is processed to be flat, and then the semiconductor crystal 12A on the thinner side is converted. This is to form an element by introducing impurity atoms for element formation into the element-forming semiconductor crystal 13A.

[For production]

As shown in FIG. 1(a), Hg1-x Cdx T for element formation is placed on an insulating substrate 11 such as a sapphire substrate.
CdTe containing constituent elements of e-crystal 13 (x = 1.
0) After forming the crystal 12, the CdTe crystal is etched so that the thickness is partially different.

Alternatively, as shown in FIG. 1(b), after forming the recessed region 14 on the substrate 11 and forming the CdTe crystal 12 on the substrate, the surface of the CdTe crystal is processed to be flat and the thickness is form CdTe crystals with partially different values.

Next, this CdTe crystal 12 is coated with HgI-w CdXTe.
A semiconductor crystal 13 for forming an element is formed using an isothermal vapor phase growth method. In this isothermal vapor phase growth method, the substrate on which the CdTe crystal is formed and the Ilgt-x Cd
HgI-, HgI-, A CdxTe crystal is grown by isothermal vapor phase growth.

Then, this CdTe crystal and the H grown on the crystal
The thin region 12A of the CdTe crystal first becomes HgI-x due to interdiffusion with the gt-x cdXTe crystal.
The thin region of this CdTe crystal becomes HgI-x Cdx with uniform composition (x) value in the thickness direction.
Once converted to Te, the temperature of the ampoule is lowered and the isothermal vapor phase growth process is stopped.

In this way, in the thick region 12B of the CdTe crystal, the converted Ilgt-*Cdx
The value is converted from the thin region 12A of the CdTe crystal) I
g+-x Cdg It becomes larger than the X value for Te crystal 13.

This will be explained in more detail using FIG. 4.

Figure 4 Ta) shows l(g+-x Cdx
The relationship between the composition distribution in the depth direction and the thickness d when a Te crystal is grown in an isothermal vapor phase is shown for times t=o, t==t, t=t. The vertical axis is "g+-x Cd Te's X
The value, the horizontal axis is the thickness d.

As shown in the figure, when 1=0 before vapor phase growth, the thickness of the CdTe crystal is Do, and the X value is X=1, as indicated by the dashed line. The thickness changes with the isothermal vapor phase growth method t, and at time point 18 during growth, the thickness increases as shown by curve 31.

It has an m gradient. and the point at which growth ends, t
, the thickness becomes D2, and the composition of the Ilgt-x cdXTe crystal becomes uniform along the depth direction as shown by the dotted line.

In isothermal vapor phase growth, growth proceeds with a constant composition (determined by growth conditions) on the surface, and growth ends when the composition is uniform in the thickness direction. Thereafter, no matter how much time passes, the thickness and Mi do not change.

The point at which this growth ends is the point at which the composition in the thickness direction becomes uniform.

A dotted line 32 in FIG. 4(b) indicates a thin CdTe crystal of d (in FIG.
a, At the end of growth (t
= h) in the thickness direction m* distribution, and the thickness after growth is d,
It is.

Curve 33 in FIG. 4(C) has a thickness of dz (dz > d,)
Hgt-x on the CdTe crystal (region 12B in FIG. 1(a)) of FIG.
When Cd+tTe is grown in an isothermal vapor phase, the formed (Ig+-xCd,l) at time t=t3 during the growth
The thickness d4, which shows the composition distribution in the thickness direction of the Te crystal, is greater than d.

Comparing the dotted line 32 in FIG. 4(b) and the curve 33 in FIG. 4(C), it can be seen that a predetermined time t has elapsed since the isothermal vapor phase growth was started.

After (at the end of thin layer growth) HgI-YoCd
.

The X value of Te is the same as when the original CdTe crystal is thin (d
I), the composition in the thickness direction is uniform, but the original CdT
When the thickness of e-crystal is thick (when dX), the Φχ value of the HgI-x Cdx Te layer is larger than that of a thin layer except for the top part of the surface.

The larger the X value, the larger the energy bandgap of the HgI-x Cdg Te crystal, and the higher the sensitivity to short wavelength infrared rays.

Therefore, as shown in Fig. 1(a) and (bl), C
A thin region 12A of CdTe crystal having a predetermined shape is selectively formed at a predetermined position of the dTe crystal 12, and Hg
When an I-xCdXTe crystal is formed by isothermal vapor phase growth and the growth is stopped at the end of the growth of a thin layer, l1g, -, Cd, ↑ formed in the thin region 12A of the CdTe crystal.
The X value of the e-crystal 13A is uniform along the thickness direction, and the HgI-, which is formed in the region 12B other than the region 12A,
The layers excluding the uppermost surface of the CdxTe crystal 13B are f1g+-xCd,Te crystals having a small X value.

Small HgI-x Cdx T of Tekono X4'fi
B atoms are ion-implanted into a predetermined region of crystal 13A of e, and N
A mold layer 15 is formed to form an infrared sensing element 16.

In this way, the infrared rays in the detection wavelength range that are incident between the infrared detecting elements 16 are transmitted to the HgI-x Cdg Te crystal 13 with a large X value and a large energy band gap.
Since the light passes through B and no carriers are generated in this region, the occurrence of crosstalk is reduced.

〔Example〕

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

As shown in FIG. 2(a), a CdTe crystal 12 of 6 μm is deposited by MOCVD on a sapphire substrate 11 that transmits infrared rays.
After forming a resist film with a predetermined pattern (not shown) on the CdTe crystal, the CdTe crystal 12 is etched to a thickness of 3 μm using the resist film as a mask and selected in a predetermined area. A recessed portion 14 is formed in a specific manner.

Next, as shown in FIG. 2(b), the CdTe crystal 12
(Top) Igt-x Cdg Te crystal 13 is formed by isothermal vapor phase growth.

In this isothermal vapor phase growth method, the substrate on which the CdTe crystal described above is formed and the I1g+-x Cdg Te melt, which is made by melting and solidifying an alloy of mercury, cadmium, and tellurium, are sealed in an ampoule, and the ampoule is heated. Therefore, due to the three-phase equilibrium of the CdTe crystal, the melt of Hgr-x Cdx Te, and the vapor formed by melting the melt, 8g+-x
The method is to form Cd and Te crystals on a substrate. In the process of this isothermal vapor phase growth, CdTe crystal and Hg1
-x CdTe through interdiffusion with Cd and Te crystals
Since the crystal is converted to Hlh-x Cdx Te, C
The isothermal vapor phase growth operation is stopped when the thin region 12A of the dTe crystal is converted into HgI-CdXTe having a uniform composition in the thickness direction.

In this way, as shown in Figure 2 (C1), CdTe
The thin region 12A of the crystal is transformed into l(g+-x Cd
The X value of xTe crystal 13A is constant in the thickness direction,
The thick region 12B of the CdTe crystal was converted) Igt-
Values except for the top surface of yt Cdg Te crystal 13B (
(variation in the thickness direction) is larger than the value of the region 12A. Note that the HgI-xCdXTe crystal is grown to a thickness of about 20μ.

Next, as shown in FIG. 2(d), the Igl-g Cdx Te crystal 13 (formed on the substrate) is polished to make it flat. Then, B atoms are ion-implanted into a predetermined region of the HgI-x Cdx Te crystal 13A into which the thin region 12A of the CdTe crystal has been converted to form an N-type layer 15, thereby forming an infrared sensing element 16.

In this way, the carriers formed by the infrared rays incident between the detection elements 16 are Hlh-xCd, Te, which has a high X value and a large energy band gap.
Since the light passes through the crystal 13B, a high-resolution sensing element without crosstalk can be obtained.

A second embodiment of the method for manufacturing an infrared sensing element of the present invention will be described.

As shown in FIG. 3(a), a predetermined pattern of concave portions 14 having a depth of 3 μm is formed on the sapphire substrate 11 using the ion milling method, and then carbon dioxide is formed on the substrate using the MOCVD method.
After forming the dTe crystal 12 to a thickness of 6 μm, the surface of the CdTe crystal is polished flat.

Next, as shown in FIG. 3 (bl), HgI-x Cdg
A Te crystal 13 is formed. In this way, the thin region 12A of the CdTe crystal is converted and formed HgI-x
The X value of the Cdx Te crystal 13A is constant in the thickness direction, and the X value (varies in the thickness direction) except for the uppermost surface of the HgI-x CdxTe crystal 13B, which is formed by converting the thick region 12B of the CdTe crystal, is the same in the region 12A. becomes larger.

Then, as shown in FIG. 3(C), the formed Hg
The surface of the r-x Cdx Te crystal 13 is polished to make it flat.

Next, as shown in FIG. 3(dl), B atoms are selectively ion-implanted into the region of the formed HgI-8CdXTe crystal 13A having a small X value to form an N-type 1815 to form an infrared sensing element 16.

Note that, in addition to this embodiment, a GaAs substrate or a Si substrate may be used as the substrate.

Further, the present invention is applicable to both one-dimensional and two-dimensional sensors.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, the Hg1-jlCd, Te crystal in the formation region of the infrared sensing element is a Hg1-jlCd, Te crystal with a large energy band gap and a high X value.
+-x Since it is surrounded by CdllTe crystals, the infrared rays of the detection wavelength incident between the detection elements are transmitted, making it easy to obtain a high-resolution, high-sensitivity infrared detection element that does not cause crosstalk. It has the effect of

[Brief explanation of the drawing]

FIG. 1 is a principle diagram showing the method of the present invention. FIGS. figure(
From a) to FIG. 3(d) are cross-sectional views showing the steps of the second embodiment of the method for manufacturing an infrared sensing element of the present invention, FIG. 4(a), FIG. 4(b), and FIG. (C) is Hg
A diagram showing the composition distribution in the thickness direction of +-x CdxTe crystal,
FIG. 5 is a schematic diagram showing a conventional infrared detection element and its disadvantages, and FIG. 6 is a sectional view of the conventional infrared detection element. In the figure, 11 is the substrate (sapphire substrate), 12.12A, 12
B is the original CdTe crystal, 13.13A, 13B is Hg
+-x Cdx TI3 crystal, 14 is a concave portion, 15 is an N-type layer, 16 is an infrared sensing element, 31.32° 33 is an X value variation curve. (Q) (b) Half-invention / 7T is π0 Fig. 1 (Q) (C) (d) Sweat Bf4 revision; (C) Shave □ Correction 2 Sei 2 Moto ``Jtr + Ii Ojomo Fig. 3 Fig.

Claims (1)

[Claims] A semiconductor crystal for forming an element to be formed on a substrate (11) (
After forming a semiconductor crystal (12) containing the constituent elements (13) with partially different thicknesses, the semiconductor crystal (13) for forming an element is placed on the substrate (11).
is grown by an isothermal vapor phase growth method, and the partially thin semiconductor crystal region (12A) of the semiconductor crystal (12) is converted into a semiconductor crystal (13A) for device formation that is uniform in the thickness direction by interdiffusion. At this time, after stopping the growth operation of the semiconductor crystal (13) for forming an element, the surface of the semiconductor crystal for forming an element (13) formed on the substrate by isothermal vapor phase growth is processed to be flat and the thin layer is formed. A method for manufacturing an infrared sensing element, characterized in that an element is formed by introducing impurity atoms for element formation into a semiconductor crystal for element formation (13A) into which the side semiconductor crystal (12A) has been converted.