JPH04124875A - Infra-red ray image pick-up device - Google Patents

Abstract

PURPOSE:To make it possible to enlarge the area of an effect sensitive section by a method wherein a Schottky junction is configured on the central part of sensitive section by using a metal whose barrier potential is lower with respect to a silicon substrate, and the shot-key Schottky junction is configured on the circumferential part of the sensitive section by using a metal whose barrier potential is higher with respect to the silicon substrate. CONSTITUTION:A reflection protective film 21 is provided on one side of the p-type silicon substrate where light enters, and a platinum(Pt) layer 22 is provided on the other side. On the circumference of the platinum layer 22, an aluminum(Al) layer 23 whose barrier potential is lower with respect to the p-type silicon. Moreover, the barrier potential of the Pt layer 22 is lower with respect to the p-type silicon.

Description

[Detailed Description of the Invention] [Summary] Regarding an infrared imaging device in which a photosensitive portion is configured with a Schottky junction, the purpose of this invention is to expand the effective area of the photosensitive portion. In an infrared imaging device that performs photoelectric conversion, a Schottky junction is formed in the center of the photosensitive part using a metal that has a low barrier potential with respect to the silicon substrate, and a Schottky junction is formed in the peripheral part of the photosensitive part with a metal that has a low barrier potential with respect to the silicon substrate. Construct a Schottky junction with high metal.

[Industrial application field]

The present invention relates to an infrared imaging device, and more particularly, to an infrared imaging device in which a photosensitive portion is formed by a Schottky junction.

In recent years, infrared imaging devices using Schottky junctions in photosensitive parts have been developed, and there is a demand for higher sensitivity and higher density of the devices.

[Conventional technology]

FIG. 2 shows a cross-sectional structure of an example of a conventional infrared imaging device.

In the figure, an antireflection film 1 is formed on one surface of a p-type silicon substrate 10.
1 is provided, and the other side is coated with platinum silicide (PtSi).
) layer 12 is provided. Pt5 of silicon substrate 10
A guard ring 13 of an n-type diffusion layer is provided near the periphery of the i-layer 12 to suppress leakage current.

[Problem to be solved by the invention]

The size of the barrier between Pt5il12 and the silicon substrate 10 is about 0.25 eV, and the size of the barrier between the PtSi layer 12 and the n-type silicon guard ring 13 is 0.87 eV.
becomes. Therefore, the barrier potential becomes high at the peripheral portion of the PtSi layer 120, and the leakage current decreases.

In this image sensor, the effective infrared light sensitive area is within the radius d inside the guard link 13. The guard ring 13 is a nu diffusion layer, and in order to perform heat diffusion, the radius d widens to some extent, and there is a problem in that the radius d1 of the photosensitive area becomes narrower by that amount.

The present invention has been made in view of the above points, and an object of the present invention is to provide an infrared imaging device that enlarges the effective area of a photosensitive portion.

[Means to solve the problem]

The infrared imaging device of the present invention is an infrared imaging device that performs photoelectric conversion of infrared light with a photosensitive portion configured with a Schottky junction, in which a Schottky junction is configured in the center of the photosensitive portion with a metal having a low barrier potential with respect to a silicon substrate. A Schottky junction is formed at the peripheral edge of the photosensitive area using a metal having a high barrier potential with respect to the silicon substrate.

[Effect]

In the present invention, since a Schottky junction is constructed using a metal with a high barrier potential at the peripheral portion of the photosensitive section, it is not necessary to provide a guard ring for n-type diffusion, and the effective area of the photosensitive section can be expanded.

〔Example〕

FIG. 1 shows a cross-sectional structural diagram of an embodiment of the device of the present invention.

In the figure, an anti-reflection film 21 is provided on one surface of the p-type silicon substrate 20 on the side where light enters, and the other surface is provided with a platinum (P)
t) layer 22 is provided. Further, on the outer periphery of the platinum layer 22, an aluminum (Al) layer 23, which is a metal having a high barrier potential with respect to p-type silicon, that is, a small work function, is provided.

Furthermore, on the silicon substrate 20 there is provided an n"
Mold area 24. p-type region 25, which serves as a transport channel. An n-type region 26 serving as a transfer channel is provided, and a p-type region 25 and an n-type region 26 are provided.
A transfer electrode 27 is provided above the mold region 26 and connected to the pass line.

The Pt layer 22 has a low barrier of 0.25 to p-type silicon.
eV, and is sensitive to infrared rays with a wavelength of 1.1 to 5 μm. Further, the barrier of the Af layer 23 to p-type silicon is high <0.58 eV, and it is sensitive to infrared rays having a wavelength of 1.1 to 21 μm. In other words, the A1 layer 23 has a large barrier potential, which reduces leakage current, and has sensitivity to infrared rays, which improves sensitivity particularly at wavelengths around 2 μm compared to conventional elements.

In addition, the width of the A1 layer 23 has become narrower to about 2 μm, which is about 1/2 of the radius d2 of the conventional n-type diffusion guard ring 13, and since the Af layer 23 is also sensitive to infrared rays, the photosensitive area The width d is larger than before, and the area of the photosensitive portion increases.

Note that as a metal with a small barrier potential, iridium (Ir) or the like may be used in addition to Pt, and as a metal with a large barrier potential, palladium or the like may be used in addition to AI, and the present invention is not limited to the above embodiments.

〔Effect of the invention〕

As described above, according to the infrared imaging device of the present invention, the effective area of the photosensitive portion can be expanded, and the sensitivity can be increased accordingly.
It is extremely useful in practice.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional structural diagram of an embodiment of the device of the present invention, and FIG. 2 is a cross-sectional structural diagram of an example of a conventional device. In the figure, 20 is a silicon substrate, 21 is an antireflection film, 22 is a platinum layer, 23 is an aluminum layer, 24 is an n" type region, 25 is an n type region, 26 is an n type region, and 27 is a transfer electrode. Figure 2

Claims (1)

[Scope of Claims] In an infrared imaging device that performs photoelectric conversion of infrared light with a photosensitive portion configured with a Schottky junction, a metal (
22) constitutes a Schottky junction, and the Schottky junction is constituted by a metal (23) having a high barrier potential with respect to the silicon substrate (20) at a peripheral portion of the photosensitive portion.