JPH03222483A - Infrared ray detecting element - Google Patents

Abstract

PURPOSE:To improve the ratio of openings by connecting at least one of a pair of electrodes of a plurality of photoconductive cells to a wiring layer through openings formed at an insulating layer, thereby laying wirings under the cells. CONSTITUTION:An SiO2 film 11 is formed on a silicon substrate 10, and individual wirings 12 and a common wiring 13 are laid on the film 11. Here, the wirings 12 are so formed that individual contact pads 14 are formed under one ends of photoconductive cells 2, and the wiring 13 is so formed as to form a common contact pad 15 under the other end of the cells 2. The wirings 12, the wiring 13, the pads 14 and the pad 15 are buried in an SiO2 film 18. Accordingly, a wiring layer and the cells 2 are separated by an insulating film. Thus, the wirings are laid under the cells to obtain an infrared ray detecting element for improving the ratio of the openings.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a photoconductive type infrared detection element, and is particularly used for an element in which photoconductive cells are integrated in a matrix or array.

[Conventional technology]

Infrared detection elements using photoconductive cells such as PbS and PbSe are known. FIG. 5 shows a conventional example with a 4×4 matrix configuration. As shown, there are 4
X4-16 photoconductive cells 2 are arranged, and each photoconductive cell 2 is provided with a common electrode 3 on one side and an individual electrode 4 on the other side. Common electrode 3 is common wiring 5
The individual electrodes 4 are connected to individual wires 6, and a bias is applied to the photoconductive cell 2 via these.

[Problem to be solved by the invention]

However, when photoconductive cells are conventionally arranged in a matrix or array, as the number of photoconductive cells increases, the area occupied by the common wiring 5 and the individual wiring 6 increases. For example, in the example shown in Fig. 5, the individual wiring 6
is emitted to the outside from between the photoconductive cells 2, so that a wide dead area appears between the photoconductive cells 2 in the vertical direction. For this reason, there was a drawback that the aperture ratio as a detection element was greatly reduced.

On the other hand, when adopting the configuration shown in Fig. 5, the photoconductive material is deposited on the entire surface of the substrate and then separated into individual cells, and electrodes and wiring are formed thereon, or electrodes and wiring are formed on the substrate. After forming the wiring and the wiring, it is necessary to apply a photoconductive material thereon and separate each cell, or to adopt one of two methods. However, with the former method, it is difficult to form fine wiring patterns, and with the latter method, cells cannot be separated using methods such as ion etching (chemical etching is required), so deterioration of photoconductive properties is unavoidable. .

The present invention aims to solve the above-mentioned drawbacks.

[Means to solve the problem]

The infrared detecting element of the present invention includes a substrate having at least an insulating upper surface, a wiring layer laid on the upper surface of this substrate,
It comprises an insulating layer formed on this wiring layer, and a plurality of photoconductive cells arranged in a matrix or array on this insulating layer, and one of a pair of electrodes each of the plurality of photoconductive cells has. , at least one electrode is connected to a wiring layer through an opening formed in an insulating layer. Here, the substrate may be constructed by depositing an insulating film on the upper surface of the semiconductor substrate, and a circuit for processing the output signal of the photoconductive cell may be formed on the semiconductor substrate.

Further, one of the pair of electrodes each of the photoconductive cells has is commonly connected between the plurality of photoconductive cells, and at least a part of the wiring layer is laid below the photoconductive cells via an insulating layer. You can.

[Effect]

According to the configuration of the present invention, the wiring layer and the photoconductive cell are separated by the insulating layer. Therefore, wiring can be laid under the photoconductive cell to improve the aperture ratio.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows the configuration of an embodiment, with FIG. 1(a) being a plan view and FIG. 1(b) being a sectional view taken along the line A--A. A SiO2 film 11 is formed on the upper surface of the silicon substrate 10, and individual wirings 12 and a common wiring 13 are laid on the SsO2 film 11. Here, the individual wiring 12 is formed to form an individual contact pad 14 under one end of the photoconductive cell 2, and the common wiring 13 is formed to form a common contact pad 15 under the other end of the photoconductive cell 2. It is shaped like this.

Note that the individual wiring 12, the common wiring 13, the individual contact pads 14, and the common contact pad 15 are all integrally formed of aluminum or the like.

Above the individual contact pads 14 and common contact pads 15, individual electrodes 16 and common electrodes 17 are formed of, for example, gold.
Individual contact pads 14 and common contact pads 15 are embedded in 5102 film 18. A photoconductive cell 2 is provided in ohmic contact with the individual electrodes 16 and the common electrode 17, and a protective film 19 is deposited thereon.

In the above embodiment, the individual wiring 12 and the common wiring 13 are separated from the photoconductive cell 2 by the S102 film 18, and the individual wiring 12 and the common wiring 13 are laid under the photoconductive cell 2. Therefore, the space for forming the individual wiring 12 and the common wiring 13 is not limited to between the photoconductive cells 2, so that it becomes possible to integrate a plurality of photoconductive cells 2. Further, since the infrared detection element is formed on the silicon substrate 10, a signal processing circuit can be formed on this silicon substrate 10. Specifically, it is possible to provide a bias circuit that applies a constant bias to the photoconductive cell 2, and a circuit (amplifier circuit, A/D conversion circuit, multiplexer, etc.) that processes the output signal of the photoconductive cell 2 in analog and digital form. Become. The process of the example can be applied to a so-called silicon wafer process, and therefore a 100 μm
×100μm photoconductive cell 2, 120~130μm
Can be integrated with m pitch.

Next, the manufacturing process of the infrared detection element according to the above example is as follows:
This will be explained with reference to a cross-sectional view of the element shown in FIG.

First, as shown in FIG. 2(a), a 5102 film 11 is formed on the upper surface of a silicon substrate 10 by a CVD method or the like, and an aluminum wiring is patterned by a lift-off method using a photomask (not shown). These are designated as individual wiring 12, common wiring 13, individual contact pad 14, and common contact pad 15. Note that nickel or the like may be used for the wiring material. In this step, since wiring is formed on the flat upper surface of the 5IO2 film 11, a sufficiently fine pattern can be obtained. Next, a SiO2 film 18 is deposited on the entire surface using a CVD method or the like, and the above wiring material is embedded (as shown in FIG. 2(b)).

Next, the 5102 film 18 is selectively etched using a photomask (not shown), and the individual contact pads 18 are etched.
4 and the upper surfaces of the common contact pad 15 are exposed (as shown in FIG. 4(c)). Next, the individual electrodes 16 and the common electrode 17 are buried in the upper surfaces of the individual contact pads 14 and the common contact pads 15 by gold plating, and a photoconductive material such as PB S or PB Se is deposited on the entire surface thereof.

Thereafter, this photoconductive material film is separated into individual cells by etching to form photoconductive cells 2 (as shown in FIG. 4(d)). In this process, the photoconductive material film is etched by
Since the individual wiring 12, the common wiring 13, etc. are buried in the 8102 film 18, it is possible to separate each photoconductive cell 2 using, for example, ion etching.
Therefore, the characteristics of the photoconductive cell 2 are not deteriorated by chemical etching. Finally, after activating the photoconductive cell 2, a protective film 19 is applied over the entire surface, thereby completing the infrared detecting element shown in FIG.

Next, a modification of the above embodiment will be explained with reference to FIGS. 3 and 4.

On the 5IO2 film 11 formed on the silicon substrate 10,
A plurality of horizontal wirings 21 extending in the horizontal direction are formed, and a photoconductive cell 2 is provided thereon, in which a horizontal electrode 22 and a vertical electrode 23 are formed on the lower side of one end and the upper side of the other end. A plurality of vertical wiring lines 24 extending in the vertical direction are disposed above it.
will be laid down.

Here, between the horizontal wiring 21 and the horizontal electrode 22, the vertical electrode 2
3 and the vertical wiring 24 are both electrically connected, and these are embedded in a 5102 film (not shown). and,
A protective film (not shown) is formed on the upper surface, and the modified infrared detection element is completed.

FIG. 4 shows the overall circuit configuration of the above modification.

As illustrated, the horizontal wiring 21 is connected to the scanning circuit 31,
Vertical wiring 24 is connected to readout circuit 32 . Here, the photoconductive cell 2 is connected in parallel with a capacitor 33 for charging signal charges, which can be obtained by forming, for example, a pn diode in the silicon substrate 10. According to this modification, the horizontal wiring 21 is
By scanning the lines one by one, the detection signal can be read out to the readout circuit 32 line by line.

〔Effect of the invention〕

As described above, according to the configuration of the present invention, the wiring layer and the photoconductive cell are separated by the insulating film.

Therefore, wiring can be laid under the photoconductive cell to improve the aperture ratio. Furthermore, since the infrared detecting element of the present invention can be sufficiently miniaturized in its overall size, it is possible to further improve the characteristics by adding, for example, a Peltier electronic cooler.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of an infrared detection element according to an embodiment of the present invention, Fig. 2 is a sectional view showing the manufacturing process of an infrared detection element according to an embodiment of the invention, and Fig. 3 is a modification of the embodiment. FIG. 4 is a perspective view of such an infrared detection element, FIG. 4 is a circuit configuration diagram thereof, and FIG. 5 is a configuration diagram of a conventional infrared detection element. 10... Silicon substrate, 11... 5102 film, 12
...Individual wiring, 13...Common wiring, 14...Individual contact pad, 15...Common contact pad,
16...Individual electrode, 17...Common electrode, 18...
5102 film, 19...protective film.

Claims (1)

[Claims] 1. A substrate having at least an insulating upper surface, a wiring layer laid on the upper surface of this substrate, an insulating layer formed on this wiring layer, and an insulating layer formed on this insulating layer. A plurality of photoconductive cells arranged in a matrix or an array, and among a pair of electrodes each of the plurality of photoconductive cells has,
An infrared detecting element, wherein at least one electrode is connected to the wiring layer through an opening formed in the insulating layer. 2. The infrared detecting element according to claim 1, wherein the substrate is constructed by depositing an insulating film on the upper surface of a semiconductor substrate, and a circuit for processing an output signal of the photoconductive cell is formed on the semiconductor substrate. 3. The infrared detecting element according to claim 1, wherein one of the pair of electrodes each of the photoconductive cells has is commonly connected between the plurality of photoconductive cells. 4. The infrared detecting element according to claim 1, wherein at least a portion of the wiring layer is laid below the photoconductive cell with the insulating layer interposed therebetween.