JPH0546707B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an infrared detection element using Hg _1-x Cd _x Te and a method for manufacturing the same.

(Prior art and its problems) Hg _1-x Cd _x Te is a semiconductor with a narrow energy band gap. For example, in a composition with x = 0.2, electron-hole pairs are generated by infrared rays with a wavelength of about 10 μm. It is known as an optimal material for highly sensitive infrared detection elements, as its electrical resistance changes when excited. These infrared detection elements basically depend on the thickness.
Electrode terminals are formed on a HgCdTe crystal with a diameter of about 10 μm, and changes in resistance between them are detected, and its sensitivity greatly depends on the quality of the HgCdTe crystal, especially the lifetime of excited minority carriers. Therefore, efforts are being made to develop HgCdTe crystals with longer minority carrier lifetimes in order to obtain more sensitive infrared detection elements. However, in actual devices, the lifetime of these minority carriers depends not on the value of the HgCdTe crystal itself but on its surface condition. That is, since defects existing on the surface of the crystal become recombination centers for excited carriers, the effective lifetime is significantly reduced. In order to improve this problem, a conventional method has been used to form an oxide film on the crystal surface and to move the excited minority carriers away from the surface into a so-called accumulation state, thereby escaping the influence of surface defects. Although this method has made it possible to effectively improve minority carrier life, it requires complicated processing to actually form oxide films on the top, bottom, and side surfaces of an HgCdTe crystal with a thickness of about 10 μm. It takes
Furthermore, since HgCdTe is originally a narrow energy gap semiconductor, it is difficult to form it with sufficient control of band bending and good reproducibility.
It is still not easy to obtain a highly sensitive infrared detection element.

(Objective of the Invention) An object of the present invention is to provide an infrared detection element that has higher sensitivity and can be easily manufactured with good reproducibility, and a method for manufacturing the same.

(Structure of the Invention) According to the present invention, Hg _1-x Cd _x
It has a current path made of a Te single crystal film and an electrode terminal for supplying current to this and detecting voltage.
An infrared detection element characterized in that the upper and side surfaces of the current path are covered with a CdTe film is obtained. Furthermore, according to the present invention, on a CdTe single crystal substrate,
a step of epitaxially growing a Hg _1-x Cd _x Te single crystal film; a step of etching away the Hg _1-x Cd _x Te single crystal film in other parts except for the region where a current path is formed and its surrounding area; a step of laminating an electrode material except for a portion to be a photosensitive area of the current path;
Includes a step of etching the Hg _1-x Cd _x Te single crystal film and electrode material into the shape of a current path and an electrode terminal, and a step of forming a CdTe film on the entire surface except for the electrode terminal portion. A method for manufacturing an infrared detection element is obtained.

(Example) Hereinafter, the infrared detecting element of the present invention and its manufacturing method will be explained using the drawings.

FIG. 1 is a diagram showing the energy band of the junction between HgCdTe and CdTe, and using this diagram, it will be explained that the effective minority carrier lifetime can be improved. Note that although the HgCdTe crystal will be explained below as being of N type, the same applies even if it is of P type.
Since the HgCdTe crystal and the CdTe crystal have the same crystal system and almost the same lattice spacing, they form a so-called heterojunction. At this time, the band gap of Hg _1-x Cd _x Te is, for example, about 0.1 eV at x = 0.2, whereas in CdTe it is large, about 1.6 eV, and the part of HgCdTe2 sandwiched between CdTe1 is surrounded by an energy barrier. A passageway is formed. For this reason, the majority carrier 3 and minority carrier 4 both have the original HgCdTe surface,
That is, it can be confined sufficiently inside the interface 5 with CdTe, and it can be improved to the minority carrier lifetime inherent to the HgCdTe single crystal without being affected by recombination centers 6 of surface defects. Moreover, unlike the conventional method of forming an oxide film to create an accumulation state, the band gap is as narrow as 0.1 eV, so the band cannot be bent sufficiently and the effects of surface defects cannot be completely removed. Also, there is no disadvantage of large manufacturing variations or fluctuations. Furthermore, the carrier concentration of CdTe itself is negligible compared to the carrier concentration of HgCdTe, and even if they are bonded together, no extra carriers will be produced, and they are also transparent to the infrared rays that are to be detected. There are no negative effects from doing so.

FIGS. 2a and 2b are a plan view and a cross-sectional view, respectively, showing an embodiment of the infrared detecting element of the present invention. The infrared detection element of this example is a CdTe single crystal substrate 1
Current path 12 made of Hg _1-x Cd _x Te single crystal on
and an electrode terminal 13 are formed, and this electrode terminal 13
A CdTe film 14 is further formed except for the upper part. The electrode terminal 13 supplies current to the current path 12, and detects a change in resistance depending on the infrared intensity of the current path therebetween as a voltage change.
The bottom surface of the current path 12 of the Hg _1-x Cd _x Te single crystal is
It is in contact with the CdTe single crystal substrate 11, and its top and side surfaces are covered with a CdTe film 14, and the entire periphery is covered with a CdTe film 14.
Bonded with CdTe. As a result, as mentioned above, the minority carriers excited in the current path 12 by infrared rays do not come close to the upper, lower, and side surfaces, and are removed from the interface, that is, the original surface of the Hg _1-x Cd _x Te single crystal. The structure is such that the carrier life does not decrease due to defects present in the carrier.

Next, a method of manufacturing this infrared detection element will be explained. FIG. 3 is a plan view and a sectional view showing an embodiment of the manufacturing method of the present invention in the order of steps. First, Figure 3a
As shown in the cross-sectional view, a Hg _1-x Cd x Te single crystal 22 having a thickness of about 10 μm and a predetermined composition ratio x is epitaxially grown on a _CdTe single crystal substrate 21 . This epitaxial growth may be performed by a well-known vapor phase or liquid phase epitaxial growth method. For example, it can be formed by liquid phase epitaxial growth at 550° C. for several hours from an HgCdTe melt containing excess Te. Next, as shown in FIGS. 3b and 3c, the resist 23 is used as a mask to form the photosensitive area, which is the current path, and its surrounding area.
Leaving the HgCdTe single crystal 22, the other parts are removed by etching. At this time, the etching is performed by performing a well-known chemical etching method using a bromine methanol solution, etc., and if necessary, by etching the entire surface very slightly, the steps at the end portion 24 of the HgCdTe single crystal 22 are smoothed out. This makes it possible to improve step coverage during subsequent electrode formation. Next, as shown in FIGS. 3d and 3e, electrode material 26 is laminated using the resist pattern 25 formed in the area to be the photosensitive area as a mask, and the resist pattern 26 is laminated by the so-called lift-off method.
Remove unnecessary electrode material on 5. Suitable materials for this electrode include a laminate of Cr and Au, Al, and the like, and can be formed by, for example, vapor deposition or sputtering. Furthermore, as shown in FIGS. 3f and 3g, unnecessary portions of the electrode material 26 and the HgCdTe single crystal 22 are removed by etching all at once using the resist pattern 27 in the shape of a predetermined current path and electrode terminal as a mask. Ion milling and reverse sputtering are suitable for this etching. Finally, as shown in FIG. 3h and i, the CdTe film 28
is formed on the entire surface by a vapor deposition method or a sputtering method, and then the CdTe film on the electrode terminal 29 is removed to complete the manufacture of the infrared detection element.

(Effects of the invention) The minority carrier life of the infrared detection element manufactured in this way is more than 10 times improved compared to the one without forming a CdTe film, and is also equivalent to or better than that of the one formed with a conventional oxide film. The effect was obtained. Furthermore, it has been confirmed that the manufacturing method of the present invention can be manufactured relatively easily and with good reproducibility, unlike conventional methods that utilize unstable oxide films.
Note that the CdTe film formed on the top does not need to be single crystal, and a sufficient effect can be obtained by simply forming the film in a polycrystalline state.

As explained above, according to the infrared detecting element and its manufacturing method of the present invention, by covering the current path of HgCdTe with CdTe, it is not affected by surface defects, and therefore the life of minority carriers is shortened. A long, high-sensitivity infrared detection element can be manufactured relatively easily and with good reproducibility.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the energy band of the junction between HgCdTe and CdTe, Figures 2a and b are a plan view and cross-sectional view, respectively, showing an embodiment of the infrared detection element of the present invention, and Figures 3a to i are FIG. 1 is a cross-sectional view and a plan view of an element in main steps for explaining the manufacturing method of the present invention. In the figure, 1 is a CdTe region, 2 is a HgCdTe region, 3 is a majority carrier, 4 is a minority carrier, and 5 is a
Interface between CdTe and HgCdTe, 6 is surface defect, 7 is conduction band, 8 is valence band, 9 is Fermi level, 11
and 21 are CdTe single crystal substrates, 12 and 22 are
Hg _1-x Cd _x Te single crystal, 13 and 29 are electrode terminals,
14 and 28 are CdTe films, 23, 25 and 27 are resist patterns, and 26 is an electrode material.

Claims (1)

[Claims] 1. A current path made of Hg _1-x Cd _{x Te} single crystal on a CdTe single crystal substrate, supplying current to the current path,
1. An infrared detection element, comprising an electrode terminal for detecting voltage, and the upper and side surfaces of the current path are covered with a CdTe film. 2 Epitaxially growing a Hg _1-x Cd _x Te single crystal film on a CdTe single crystal substrate, and growing the Hg _1-x Cd _x Te single crystal film in other parts except for the area where a current path is formed and its surrounding area. a step of removing the crystal film by etching, a step of laminating an electrode material except for a portion to be a photosensitive region of the current path, and a step of depositing the Hg _1-x
A step of etching the Cd _x Te single crystal film and the electrode material together into the shape of the current path and electrode terminal, and a step of forming a CdTe film on the entire surface except for the electrode terminal portion. A method for manufacturing an infrared detection element characterized by: