JPH01201971A - Infra-red ray detector - Google Patents

Abstract

PURPOSE:To reduce crosstalks by forming a crystal layer having an energy band gap greater than that of a crystal layer for forming an element as a buffer layer between a compound semiconductor crystal layer for forming an element and a substrate, and further by providing a light absorber in the bottom of a grove where elements are separated. CONSTITUTION:A compound semiconductor crystal having a higher energy band gap than that of a compound semiconductor crystal layer 13 for forming an element is provided as a buffer layer 12 between an insulating or semi-insulating substrate 11 and a compound semiconductor crystal layer 13 for forming an element. The compound semiconductor crystal layer 13 provided with a PN junction 17 for forming an element is provided with a groove 19 that reaches the buffer layer 12 from the surface of the crystal layer 13 or reaches the substrate 11 from the surface of the crystal layer 13 for forming an element. An infra-red ray detector is arranged by forming the crystal layer 13 for forming an element, or the crystal layer 13 for forming an element laminated in the buffer layer 12 to a mesa form and by providing a light absorber 20. This enables a detecting array having a high pixel density and causing a small number of crosstalks to be arranged. A high-quality detecting array which applies a uniform bias voltage to each photodiode can also be obtained.

Description

[Detailed Description of the Invention] [Summary] Regarding an infrared detection device, the purpose is to reduce the occurrence of crosstalk between detection elements and to prevent fluctuations in the bias voltage applied to each detection element. , or a device in which a photodiode array is formed by providing a P-N junction at a predetermined position of a compound semiconductor crystal layer formed on a semi-insulating substrate, wherein the photodiode array is formed between the substrate and the compound semiconductor crystal layer for element formation. , a compound semiconductor crystal having a larger energy hand gap than the element-forming compound semiconductor crystal is provided as a buffer layer, and the element-forming compound semiconductor crystal layer provided with the P-N junction is disposed in the buffer layer from the surface of the crystal layer. Alternatively, by providing a groove that reaches the substrate from the surface of the crystal layer for element formation, the crystal layer for element formation or the crystal layer for element formation laminated on the buffer layer is formed in a merry shape, and at the bottom of the groove. It is configured by providing a light absorber.

[Industrial Field of Application] The present invention relates to an infrared detection device, and more particularly to an infrared detection device that reduces the occurrence of crosstalk between detection elements formed in an array.

Semi-insulating substrates such as cadmium tellurium (CdTe),
Alternatively, on an insulating substrate such as Leefire, mercury, cadmira J, tellurium (with a narrow energy hand gap)
A compound semiconductor such as 1Lg+-1Cd, Te) is formed into a thin layer using an epitaxial method, and a predetermined pattern of PN junctions is formed in the compound semiconductor crystal layer to form an array of PoI diodes. An infrared detection device formed in the shape of
i) An infrared imaging device is formed by connecting and forming a signal processing device such as a multiplexer formed on a substrate using an indium (In) metal pillar.

[Conventional technology] The structure of a conventional infrared detection device is shown in FIG.

As shown in FIG. 6, the conventional infrared detection device uses Cd T
Semi-insulating substrate 1-[-1] type l+1-8 consisting of e
Cd.

A Te crystal 2 is formed using a vapor phase epitaxial growth method, etc., boron (Bo) atoms are introduced into a predetermined position of the crystal layer 2 using an ion implantation method using a resist v as a mask, and a N layer 3 is formed. 1)-N junction 4 is formed. Further, on the surface of the crystal layer 2, a photodiode 6 is formed as an anodic oxidation film of the crystal or an anodic sulfide 8W film 5. Further, the protective film 5 on the photoquat 6 is opened to allow the formed N
On the ``layer 3, a metal column 7 of In is formed by adhesion.

Then, infrared rays are incident on the back surface side of the substrate 1, and the incident infrared rays are directed to the substrate 1 and the compound semiconductor crystal layer.
The light passes through the crystal layer 2 and is photoelectrically converted into carriers, which are detected as photovoltaic force.

[Problems that inventions are unlikely to solve]

By the way, in the conventional device, as shown in FIG. 7(a), photoelectric conversion is performed either by the distance S between the tie-outs or by the infrared rays introduced into the compound semiconductor crystal 2 from the back surface of the CdTe 1 substrate. Diffusion length d of minority carriers formed by
, the minority carriers 8 generated between the diodes 1" 6A and 5B recombine and disappear at the position marked with an "X" in the crystal layer 2, and
, 6B will never be reached, and no near-stoke will occur.

However, in recent years, back-illuminated photodiode arrays have been required to be larger and more densely formed, and as a result, the distance S between diodes has become smaller than the minority carrier diffusion length d. , in this case Fig. 7(b)
As shown in FIG.
There is a problem that a crosstalk phenomenon occurs when A and 6B are reached.

It is an object of the present invention to provide an infrared detection device that eliminates the above-mentioned problems and reduces the occurrence of crosstalk.

(Means for Solving the Problems) The infrared detection device of the present invention that achieves the above-mentioned “Objective 1” has the following features:
As shown in FIG. 1, a compound semiconductor crystal having a larger energy hand gap than the compound semiconductor crystal layer 13 for forming an element is buffered between an insulating or semi-insulating substrate 11 and a compound semiconductor crystal layer 13 for forming an element. A compound semiconductor crystal layer 13 for forming an element provided as a layer 12 and provided with a P-N junction 17 is layered from the surface of the crystal layer 13 to the buffer layer 1.
2, or by providing a groove 19 reaching the substrate 11 from the surface of the element forming crystal layer 13, the element forming crystal layer 13 laminated on the element forming crystal layer 13 or the buffer layer 12 described in 01. A light absorber 20 is provided at the bottom of the groove 19.

[For production]

The infrared detection device of the present invention includes a compound semiconductor crystal layer 1 for forming an element forming a photodiode constituting the detection device.
By forming a crystal Jj'i having a larger energy hand gap than the element-forming crystal layer 13 between the buffer layer 12 and the substrate 11, and forming the above-mentioned hole diode in a diagonal shape, , ensure element isolation between the diodes.

A light absorber 20 is further provided at the bottom of the trench 19 where the elements are separated. In this way, as shown in FIG. 5, the infrared rays to be detected are absorbed by the crystal layer 13 for forming the element, and -1
-Even if it becomes Yaria, the minority carry 7 (
Since the energy band gap 21 of the buffer layer 12 is wide, the electrons a hit the wall Q of the conduction band 22 and move in the direction of arrow B, so that the carriers do not reach the buffer layer 12 side. The other minority carrier b is the valence band 2
4 and the conduction band 22 reaches the narrow region side of the element forming crystal layer 13 and the P-N junction 23
is detected as a photocurrent.

Further, since the crystal layer 13 for forming the element is separated into mesa rings, carriers do not flow into adjacent pixels, so that no cross-reflection occurs.

Furthermore, in the present invention, a light absorber 20 made of a layered layer of zinc sulfide (ZnS) and chromium (Cr) is provided at the bottom of the groove 19 separating the elements, so that light incident on the bottom of the CdTe plate 1, P, The light incident between the meridian-shaped detection elements having the -N junction is absorbed by the light absorber 20 described in +'+ii,
Therefore, such stray light that has entered between the elements will not reach the multiplexer, be reflected on the surface of the multiplexer, and be reintroduced into the PN junction, so that the crosstalk phenomenon can be further reliably eliminated.

Furthermore, a buffer layer 12 through which infrared rays having a wavelength to be detected is transmitted.
Since it is formed in a laminated state with the crystal layer 13 for element formation, the thickness of the entire crystal layer becomes thick, and the sheet resistance of the entire crystal layer decreases as the thickness increases. It is no longer necessary to vary the bias voltage applied to each photodiode in accordance with the position in the longitudinal direction of the crystal layer of each photodiode, and the bias voltage applied to each diode may have a uniform value.

[Example] Hereinafter, an example of the present invention will be described in detail using the drawings.

The second section is a cross-sectional view of an embodiment of the infrared detection device of the present invention, and is a detection device sensitive to a wavelength of 10 μm'jl). As shown in the figure, the device of the present invention uses a semi-insulating Cd
Energy key hand gap on Te4% plate 11 is 0.2
A crystal layer of l1g of 5 eV, -yCdyTe (y=0.3) with a thickness of 30 μm is formed as the buffer layer 12,
Above that is the energy hand camp, 0.11eV
A crystal layer 13 for element formation of Hg+-xCd, Te (x"0.2) is formed, and a N layer 14 is formed by implanting B' atomic ions into predetermined positions of the crystal layer 13. The crystal layer 13 in which the P-N junction is formed is etched into a mesa ring.The groove 1 forming this mesa structure is
A light absorber layer 20 formed by laminating a Zn3 layer 20A and a Cr layer 20B by vapor deposition is formed on the bottom of the mesa, and the anodic sulfide film of the crystal layer is formed on the surface of the side wall of the mesa as a protective film 15.
It is formed as. Further, an In metal plug 16 is formed on the top of the merry.

When infrared rays are introduced from the bottom of the substrate 11 of the device of the present invention, the crystal layer 12 absorbs light with a wavelength of 5 μm or less, but transmits light with a wavelength of 5 μm or more.
Light with a wavelength of μm or less is absorbed by the crystal layer 12 and photoelectrically converted into carriers.

On the other hand, light of 5 μm or more passes through the crystal layer 12 and reaches the crystal layer 13. Since the crystal layer 13 absorbs light shorter than the 10 μm band, light with a wavelength of 5 μm to 10 μm is absorbed by the crystal layer 1.
3, photoelectrically converted into carriers, and p-N junction 17
and is detected by the photodiode 18. The carriers photoelectrically converted in this crystal layer 13 are reliably separated into elements in the photodiode 1 in a mesa shape.
No crosstalk will occur. In addition, since a hunt barrier is formed between the crystal layer 1 and the buffer layer,
Minority carriers generated in step 3 do not flow into adjacent pixels via the buffer layer.

Furthermore, since the &J light absorber 20 is formed at the bottom of the groove 19, stray light that enters from the back side of the CdTe substrate and does not reach the square infrared sensing element having the P-N junction 17 is Since it is absorbed by the light absorber 20, the stray light hits the multiplex filter installed in a part of the detection element and is reflected, and the light reaches the P-N junction and generates crosstalk. Accidents caused by accidents are prevented.

Furthermore, even if the crystal layer 12 is formed thick, light with a wavelength in the 10 μm band will pass through the crystal layer 12, so the sensitivity of the detection device will not decrease. Since the thickness of the compound semiconductor crystal layer 12.13 becomes thicker, the sheet resistance of the crystal layer 12.13 does not increase. Therefore, depending on the position of the crystal layer 13 in the longitudinal direction, the increase in sheet resistance causes a change in the photodiode. There is no need to vary the applied bias voltage.

In addition, as shown in FIG. 4 as another example of this example,
A groove 25 is formed that passes through the buffer layer 13 from the crystal layer 12 for element formation and reaches the substrate 11, and the above-mentioned light absorber 20 is provided on this groove 25, and the bottom layer 13 divided by the linear groove 25 is formed. With the element forming crystal layer 12 laminated thereon,
The element-forming crystal layer 12 may be formed in a mesa shape together with the buffer layer.

Regarding the manufacturing method of the first embodiment of such an infrared detection device, as shown in FIG. 3(a), CdTe base +
Energy hand gap is 0.25e on F1.11
V's Ilg l -y Cdy Te (y-O, J)
A buffer layer 12 having a thickness of 30 μm is formed by vapor phase epitaxial growth.

Next, as shown in FIG. 2(b), the energy hand gap is 0.11 eV of Hg, -1Cd,
A crystal layer 13 for element formation of Te(x-0,2) is formed by vapor phase epitaxial growth.

Next, as shown in 31F (C), B atoms are ion-implanted into the element-forming crystal layer 13 to form an N+ layer 14.

Further, as shown in FIG. 3(d), the element forming crystal layer 13 in which the 11'-N junction is formed is etched into a mesa shape using a photoresist film as a mask until it reaches the buffer layer 12. As shown in FIG. 1, a light absorber 20 in which a ZnS film 208 and a Cr layer 20B are laminated is provided at the bottom of the i-sapling 19, and one of the mesas of the element-forming crystal layer 12 is provided. ] The anode sulfide film of the crystal layer 12.13 is formed on the II wall using an anode sulfide film solution, and as shown in FIG. The absorber 20 is provided, the crystal layer 13 for element formation and the Hanwha 1i12 are processed, and the anodic sulfide film 15 of the crystal layer 12.13 is formed on the side wall of the chimed mesa as shown in FIG. 2(a). It may be formed by

〔Effect of the invention〕

As is clear from the above description, according to the present invention, it is possible to construct a detection array with high pixel density and less occurrence of cross 1-1, and also to provide high-quality infrared rays with uniform bias voltage applied to each photodiode. This has the effect of providing a detection device.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the basic structure of the infrared detection device of the present invention, FIG. 2 is a sectional view of the first embodiment of the infrared detection device of the present invention, and FIG. Fig. 4 is a cross-sectional view of an infrared detection device according to a second embodiment of the present invention, and Fig. 5 is a cross-sectional view showing a method of manufacturing the device of the first embodiment. Fig. 6 is a cross-sectional view of a conventional infrared detection device, Fig. 7(a)
FIG. 7(b) is an explanatory diagram of an inconvenient state of the conventional device. In the figure, 11 is a CdTe substrate, 12 is a buffer layer (Hgl-yC
dyTe crystal layer), 13 is a crystal layer for element formation (tlg
l-8CdXT (crystal layer of !), 14 is N layer, 15 is protective film, 16 is In metal column, 17.23 is P-N junction, 18 is BoI/diode, 19.25 is groove, 20 is a light absorber, 20A is a ZnS film, 20B is a Cr layer, 21 is an energy hand gap, 22 is a conduction band, and 24 is a valence band. Agent Patent Attorney Sada Igata −

Claims (1)

[Claims] A device in which a photodiode array is formed by providing a P-N junction at a predetermined position of a compound semiconductor crystal layer (13) formed on an insulating or semi-insulating substrate (11), The substrate (11) and a compound semiconductor crystal layer for element formation (
13), a compound semiconductor crystal layer (1
2) is provided as a buffer layer, and the compound semiconductor crystal layer (13) for forming an element provided with the P-N junction is transferred from the surface of the crystal layer (13) to the buffer layer (12), or the crystal for forming an element. By providing a groove (19) reaching the substrate (11) from the surface of the layer (13), the crystal layer (13) for forming an element is laminated on the crystal layer (13) for forming an element or the buffer layer (12). An infrared detection device characterized in that the groove is formed into a mesa shape, and a light absorber (20) is provided at the bottom of the groove.