JPH0265181A - Infrared detector - Google Patents

Abstract

PURPOSE:To simplify a structure by simultaneously forming short and long wavelength side infrared detectors on one board. CONSTITUTION:An infrared ray is incident from the rear face side of a CdTe board 11 through a lens. The position of a focal point determined by chromatic aberration due to variation in the refractive index value of the lens when a short wavelength band infrared ray is incident is brought into coincidence with a boundary 20 between the board 11 and a crystalline layer 12. Thus, after the short wavelength light passes the board 11, it is introduced to the boundary 20 to become carrier in the layer 12, which is photoelectrically converted by a photodiode array PD 18, thereby detecting the infrared ray image. The long wavelength band infrared ray is transmitted through the board 11 and the layer 12 to be introduced from the boundary 14 between the crystalline layers 12 and 13 into the layer 13 to be detected by a PD 19. The detection signals of the PDs 18, 19 are introduced to a charge coupled device 22 by an indium metal bump 21.

Description

[Detailed Description of the Invention] [Hand Skin Required] Regarding an infrared detection device, a detection element capable of detecting infrared rays in a short wavelength range and a long wavelength range is formed on a single substrate, and the infrared ray detection device has a simple structure. Intended as a detection device, a lens installed on the back side of an infrared transmitting substrate and a lens formed on the infrared transmitting substrate, having sensitivity to a short wavelength band of infrared rays, and having sensitivity to the short wavelength band of infrared rays and long wavelengths. a first photodiode array formed in a first crystal layer having a thickness approximately equal to the value of chromatic aberration determined by the wavelength of the infrared light in the band; and a first photodiode array sensitive to the long wavelength band of the infrared light to be detected. A second photodiode array is formed on the second crystal layer, and infrared rays in the short wavelength band and long wavelength band are incident from the back side of the substrate through the lens, and the chromatic aberration is determined by the infrared rays in the short wavelength band. The first focal point of the lens is made to coincide with the interface between the substrate and the first crystal layer, and the second focal point of the lens is determined by the chromatic aberration in the long wavelength band of the infrared rays. The infrared rays in the short wavelength band are detected by the first photodiode array, and the infrared rays in the long wavelength band are detected by the second photodiode array, respectively, so as to match the boundary surfaces of the second crystal layer.

[Industrial application field]

The present invention relates to an infrared detection device, and more particularly to an infrared detection device capable of detecting short wavelength infrared rays and long wavelength infrared rays.

Infrared rays mainly include infrared rays with short wavelengths of 3 to 5 μm and 1
There are two types of infrared rays: one with a long wavelength of 0 μm.

[Conventional technology]

Conventionally, infrared detection devices that detect these two types of infrared rays have separately prepared a compound semiconductor crystal that is sensitive to the short wavelength side and a compound semiconductor crystal that is sensitive to the long wavelength side. Infrared detection devices such as photodiodes are formed separately on each crystal prepared in the next step.

[Problem to be solved by the invention]

Therefore, an inspection system that combines these detection devices and signal processing devices, such as separately providing a signal processing device connected to this detection device, is required, which poses a problem of complicating and increasing the size of the infrared detection system.

The present invention solves the problems mentioned above, and has a structure in which an element for detecting infrared rays on the short wavelength side and an element for detecting infrared rays on the long wavelength side are collectively formed on one substrate J. The purpose is simply to provide an infrared detection device.

[Means to solve the problem]

FIG. 1 is a principle diagram of the infrared detecting device of the present invention. As shown in the figure, a lens 2 installed on the back side of an infrared transmitting substrate 1, and a lens 2 formed on the infrared transmitting substrate detecting the short wavelength band of infrared rays. A first infrared ray formed in the first crystal layer 3 that has sensitivity and has a thickness approximately equal to the value of chromatic aberration determined by the wavelength of the infrared ray in the short wavelength band and the wavelength of the infrared ray in the long wavelength band. It consists of a detection element 4 and a second infrared detection element 6 formed on a second crystal N5 sensitive to the long wavelength band of the infrared rays to be detected. Infrared rays in a short wavelength band and a long wavelength band are incident, and the first focal point 7 of the lens, which is determined by the chromatic aberration due to the infrared rays in the short wavelength band, is made to match the interface between the substrate and the first crystal layer, A second focal point 8 of the lens determined by the chromatic aberration in the long wavelength band of the infrared rays is made to coincide with the interface between the first and second crystal layers, respectively, so that the infrared rays in the short wavelength band are focused on the first infrared ray. The detection element 4 detects infrared rays in the long wavelength band using the second infrared detection element 6.

[For production]

As shown in FIG. 1, the chromatic aberration of a lens is caused by the wavelength of infrared rays incident on the lens being λ1. When λ2 is different, the position where the image is generated, that is, the focal point (F), and the size of the image are different. This phenomenon occurs because the refractive index of the material forming the lens differs depending on the wavelength of the light.

The chromatic aberration Δf of the lens 2 is expressed by equation (1), where f is the focal length with respect to the average refractive index n of the lens.

Δr−rΔn/n−1・・・・・・・・・(1)
Furthermore, the wavelength of the light beam incident on the lens is set to λ0. When λ2 is assumed, Δn in 1 is expressed by equation (2).

Δn=n (λ,)−n(λ2)・・・・・・・・・(
2) Therefore, the lens receives two different wavelengths of infrared rays,
That is, when infrared rays in a short wavelength band with a wavelength λ of 3 to 5 μm and infrared rays in a long wavelength band with a wavelength λ of 10 μm are incident,
The focal point r+(λ
+), rz (λ2) are formed, and at these two different focal positions, two types of crystal layers are formed on the - substrate and are sensitive to each of the above two types of wavelengths. By arranging these photodiodes, - infrared sensors can detect infrared rays of two different wavelengths.

〔Example〕

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

FIG. 2 shows an embodiment of the infrared detection device of the present invention. As shown in the figure, a first layer of P-type Hg+-x Cdx Te (x = 0.
3) of the crystal layer 12 and the second layer of P-type I (gl-, CdX
Crystal layers 13 of Te (x = 0.2) are each formed by vapor phase epitaxial growth.

The first crystal layer 12 is in the infrared short wavelength band (λ).

= 3 to 5 μm), the second crystal layer 13 has high sensitivity to long wavelengths of infrared rays (λ2-10 μII+), and the thickness d of the first crystal layer 12 is: The thickness is made to be the same as the chromatic aberration value Δr shown in (1) 2 above.

What is the energy band gap Eg of this crystal layer 3? 1 is a blank constant (6,626X10-”Js), and C
If is the speed of light (2,9979X 108m/5ec), then Eg, = hc/λ, -1,24/λ,
Also, the energy band gap Eg2 of the crystal layer 5 = h
c/λ2=], 24/λ2.

By making the thickness d of the first crystal layer 3 the same as the chromatic aberration value Δf in this way, the long wavelength band light (10 μm) incident from the back surface of the substrate 11 is transmitted through the first crystal layer 3. 3rd and 2nd
The focal point (f2) coincides with the boundary surface of the crystal layer 5, and light in a long wavelength band can be detected efficiently.

For example, when using a Si lens with a focal length f of 30 mm, the refractive index of the lens at the short wavelength of infrared rays (5 μm) is 3.4221, and the refractive index of the lens at the long wavelength of infrared rays (10 μm) is 3. From .4177, according to equation (1),
Since the chromatic aberration Δf = 54.6 μm, the thickness of d is 54
．． The thickness will be 611m.

Furthermore, a mesa-like etching is performed from the surface of the second crystal layer 13 in the section H until reaching the boundary surface 14 of the first crystal layer 12, and the mesa-etched area is covered with an insulating film 15. The insulating film 15 is opened at the top 16 and bottom 17 of the mesa, and boron (B) atoms, which are N-type impurities, are ion-implanted to form an N-type layer, which increases sensitivity to the short wavelength side of infrared rays. A first photodiode array 18 having a photodiode array 18 and a second photodiode array 19 having a sensitivity on the long wavelength side of infrared rays are formed, respectively.

An In metal bump 21 is connected to each photodiode array 18 and photodiode array 19, and this metal bump 21 is connected to an input diode of a charge coupled device 22 formed on a Si substrate.

Infrared rays are incident on the back side of the CdTe substrate 11 of such an infrared detection device through the lens 2 described above. Then, the position of the first focal point 7 determined by the chromatic aberration caused by the variation in the refractive index value of the lens when infrared rays in the short wavelength band of 5 μm are incident is made to coincide with the boundary surface 20 between the substrate and the first crystal layer.

Then, after the light with a wavelength of 5 μm passes through the CdTe substrate 11, it is introduced into the boundary surface 20 and becomes carriers in the first crystal layer 12, and the carriers are photoelectrically converted in the first photodiode array 18. An infrared image is detected.

Furthermore, among the infrared rays, infrared rays in the long wavelength band pass through the substrate 11 and the first crystal layer 12 and pass through the interface 14 between the first crystal layer 12 and the second crystal layer 13 to the second crystal layer. After entering the layer 13 and being photoelectrically converted within the crystal layer 13, it is detected by the second photodiode array 19. The signals detected by the photodiode array in this way are introduced into the input diode of the charge-coupled device 22 using the indium metal bump 21, and the signals in the long wavelength band and the signals in the short wavelength band are transferred in time series by the transfer electrode. Transfer and process signals.

In this way, infrared rays in the short wavelength band and infrared rays in the long wavelength band are detected by one infrared detection device formed on a single substrate, eliminating the need for two infrared detection devices as in the past. The infrared detection system has a simple device configuration.

Further, the signal processed by the signal processing device may be subjected to AD conversion by an AD conversion circuit, and an infrared image may be formed on a CRT.

[Effects of the Invention] As is clear from the explanations given below, according to the present invention, an inspection system that detects infrared rays in a two-liquid long band of a short wavelength band and a long wavelength band uses a lens that condenses the infrared rays. Since it consists of one infrared detection sensor and one signal processing device that processes the signal obtained by the detection sensor, a simple infrared detection system does not require a complex optical system and can detect two-liquid long band infrared rays. It has a detectable effect.

FIG. 1 is a principle diagram of an infrared detection device of the present invention, and FIG. 2 is a sectional view showing an embodiment of the infrared detection device of the present invention.

In the figure, 1 is an infrared transmitting substrate, 2 is a lens, 3 is a first crystal layer,
4 is a first infrared sensing element, 5 is a second crystal layer, 6 is a second infrared sensing element, 7 is a first focal point, 8 is a second focal point, 11 is a CdTe substrate, 12 is a first scrap P type 11g+-+
t CdX Te crystal (x = 0.3), 13 is the second slaughter P
Type 11g+-x CdXTe crystal (x=0.2), 14
．． 20 is a boundary surface, 15 is an insulating film, 16 is a mesa top, 17
is the bottom of the mesa, 18 is the first photodiode array, 19
21 is a second photodiode array, 21 is an In metal hump, and 22 is a charge-coupled device.

[Brief explanation of the drawing]

$4”) 1 /l f', 7#?'A Keio vhil
/l/l KGri 1st) fl11? Tsuki-brown gaff Lr-shaped fujitsu ro-mei! Fig.2

Claims (2)

[Claims] (1) A lens (2) installed on the back side of the infrared transmitting substrate (1) and a lens (2) formed on the infrared transmitting substrate, having sensitivity to a short wavelength band of infrared rays, and having a wavelength of infrared rays in the short wavelength band. a first infrared sensing element (4) formed in a first crystal layer (3) having a thickness approximately equal to the value of chromatic aberration of the lens determined by and a second one having sensitivity to the long wavelength band of the infrared rays to be detected.
A second infrared sensing element (6) formed in the crystal layer (5) of
), the infrared rays in the short wavelength band and the long wavelength band are incident from the back side of the substrate (1) through the lens (2), and the infrared rays in the short wavelength band are determined by the chromatic aberration due to the infrared rays in the short wavelength band. The first focal point (7) of the lens is aligned with the interface between the substrate and the first crystal layer, and the second focal point (8) of the lens is determined by the chromatic aberration in the long wavelength band of the infrared rays. match the boundary surfaces of the second crystal layer, respectively,
The short wavelength band infrared rays are detected by the first infrared detection element (4
), the infrared rays in the long wavelength band are detected by a second infrared detection element (
6) An infrared detection device characterized by detecting. (2) a second crystal layer (5) formed on the substrate (1);
) to reach the first crystal layer (3) and mesa-etch into a predetermined pattern, and the surface of the second crystal layer (5) at the top of the mesa and the first crystal layer (3) at the bottom of the mesa are etched. 2. The infrared detection device according to claim 1, wherein impurity atoms are introduced into the bottom portion to form a PN junction.