JPS638633B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an infrared detection device, and particularly to an infrared detection device in which a charge transfer element and an infrared photoelectric conversion element assembly are integrated.

Charge transfer devices (hereinafter abbreviated as CTD) using silicon (Si) as a substrate material are already well known and are expected to be used in various applications such as imaging, signal processing, and memory. However, the CTD of Si has a wavelength of approximately 1 μm.
The development of a CTD that operates in the infrared region is desired because only the following light is sensed, and the present inventor has already made several proposals regarding signal processing in such a CTD.

On the other hand, an infrared CTD is constructed by bonding and integrating an infrared sensing element assembly in which a large number of photovoltaic infrared elements are arranged on the surface of a single multi-component semiconductor substrate and a CTD made of Si. Attempts to do so have already been proposed (for example,
Publication No. 54-30787 [filed date August 12, 1952]).

Conventionally known infrared CTDs are classified into two types depending on the method of infrared incidence. That is, one makes the light incident from the infrared detecting element side, and the other makes the light incident from the Si substrate side of the CTD.

However, in order to avoid infrared absorption by a multi-component semiconductor substrate, the former uses a material with a relatively wide energy gap (and thus has low infrared absorption) as the substrate, and then uses epitaxial growth to coat the surface of the material with high sensitivity to infrared rays. Since a heterojunction must be formed by growing a semiconductor layer in an energy gap, the manufacturing process is difficult and the yield is low.

On the other hand, in the latter case, that is, the type in which infrared rays are incident from the back surface of the CTD, there is no need to use an infrared sensing element with a heterojunction, but on the other hand,
Since infrared rays are absorbed by the electrodes of both the CTD and the infrared sensing element, it is necessary to use a part of the light-receiving surface of the infrared sensing element assembly as the electrode attachment point, and use the remaining area as the light-receiving area. There are disadvantages such as lower integration density on the element side and difficulty in improving resolution.

The present invention fundamentally solves the above-mentioned problems and provides a new infrared detection device that is easy to manufacture and does not require special consideration for the method of infrared radiation incidence.

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a cross-sectional view of an embodiment of the present invention, in which an infrared sensing element D consists of a thin plate 1 made of indium antimonide (InSb) and having a thickness of about 20 μm.
is used as a substrate, and a mesa-shaped light receiving section 10 is provided on one surface of the substrate.
1, 102, 103, . . . are formed aggregates. Inside each mesa, there are Pn junction surfaces J ₁ , J ₂ , J _{3 . .} . , which convert the incident infrared energy into electrical signals. The upper surface of the InSb thin plate 1 is covered with an anodic oxide film 2, except for the top of each mesa. The anodic oxide film 2 is formed for the purpose of protecting the surface of the thin plate 1, particularly the exposed portion of the Pn junction surface on the side surface of the mesa.

A grid-shaped non-rectifying electrode 200 (described later) is formed on the back surface of the infrared sensing element D, and the back surface is fixed to a support plate 4 made of a transparent material such as sapphire via an infrared transparent adhesive 3. ing. From the above structure, infrared rays are transmitted to each mesa 101,
It is immediately understood that the absorption received until reaching the joint surfaces J ₁ , J ₂ , J ₃ , . . . of 102, 103, etc. is very small. The upper CTD20 is the Si substrate 2
A silicon dioxide (SiO ₂ ) film 22 and a reverse conductivity type diffusion layer 30 that will become the input diode (input part of the CTD) are formed on one surface of the substrate 1 (the surface facing the InSb thin plate).
1,302,303...

In order to make it easier to understand the bonding mode between the infrared sensing element D and the CTD 20 and the electrode arrangement of the CTD 20, the vicinity of the mesa 101 of the infrared sensing element is shown in an enlarged manner in FIG. 401 in Figure 2
501 is a transfer gate electrode, and 501 is a transfer electrode.
Mesa 101 is connected to input diode 301 by welding electrodes together.

Next, the operation of this embodiment will be briefly explained with reference to FIG. The infrared rays L incident on the back surface of the infrared detection element D (the adhesive surface with the support plate 4 made of saphire) through the support plate 4 are detected by Pn in the mesa 101.
Free carriers are generated near junction _J1 .

This free carrier enters the input diode 301 of the CTD 20 through the fused portion M between the electrodes, and the transfer gate electrode 401 is opened by applying a voltage.
When the state is reached, the light enters the depletion layer under the transfer electrode 501 and is transferred within the channel of the CTD 20 in a direction perpendicular to the plane of the paper. Note that B ₁ and B ₂ are busbars for supplying transfer voltage to the transfer electrode 501.

FIG. 3 shows a metal electrode 20 formed on the back side of the infrared sensing element D, that is, the side that is fixed to the support plate 4 made of sapphire in the previous two figures.
0 pattern, the metal electrode 200
As is clear from the figure, the mesa portions 101 and 10 on the opposing surface side are shown in a grid shape, and
2, etc. are positioned so that their projections are at the center of the rectangular area surrounded by metal electrodes. Therefore, as long as the infrared rays incident from the side on which the metal electrode 200 is attached are almost parallel light,
inside each mesa without being obstructed by the metal electrode 200.
It reaches the Pn junction and contributes to the generation of free carriers.

In order to form an infrared sensing element with such a structure, for example, a thick wafer of n-type InSb is used.
A P-type layer having a thickness of about 10 μm is formed, and after forming a grid-like electrode 200 on the surface of the P-type layer, it is fixed to a support plate such as sapphire, and a desired shape is formed by polishing and mesa etching.

As described in detail above, according to the present invention, the substrate electrodes of the multi-component semiconductor thin plate are formed in a grid pattern.
Electrically, the substrate resistance becomes uniform between each light receiving section, and the substrate resistance is lower than that in a case where the substrate electrode is provided at one location on the substrate. In addition, optically, the gap between the light receiving parts is shielded from light by the grid-like electrode and has separate openings.
This has the effect of reducing optical crosstalk.

Therefore, the infrared detection device according to the present invention can convert incident infrared rays into electrical signals with high efficiency based on its structure, and since it is integrated with the CTD, signal processing can be performed immediately. Moreover, since there are no difficulties in the manufacturing process, it is especially advantageous when it is necessary not only to take an image using infrared rays, but also to immediately apply processing such as filtering to a video signal obtained by photoelectric conversion, correction of non-uniform sensitivity of each light receiving part, etc. It is.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a main part showing the structure of an embodiment of an infrared detection device according to the present invention, Fig. 2 is a partially enlarged view of the previous figure, and Fig. 3 shows a metal electrode formed on the back side of the infrared detection element. FIG. 3 is a plan view showing a pattern. D: infrared sensing element, 1: InSb thin plate, 2: anodized film, 3: adhesive layer, 4: support plate, 101,
102, 103, ...: mesa-shaped light receiving section, 20:
Grid metal electrodes, 301, 302, 303,...
...: CTD input diode, 20: CTD, 2
1: Si substrate, 22: SiO ₂ film, 401: Transfer gate electrode, 501: Transfer electrode, B ₁ and B ₂ :
Generatrix, M: fused part.

Claims (1)

[Claims] 1. A plurality of light receiving sections 101, 10 each consisting of a Pn junction.
2, 103, . . . are formed on the surface thereof, and a support plate 4 made of an infrared transmitting material is fixed to the back surface thereof. A multi-component semiconductor thin plate 1, and a substrate 21 on which a charge transfer element is formed.
In a configuration in which the light receiving section and the input sections 301, 302, 303, . A metal electrode 200 in a lattice pattern is provided on the back surface of the light-receiving section, and the projection position of the incident light on the back surface of the light-receiving section is within each region surrounded by the lattice-shaped metal electrode. Device.