JPH02303169A - Infrared detector - Google Patents

Abstract

PURPOSE:To obtain a high-sensitivity Schottky-type infrared detection device which uses an Si substrate by a method wherein metal layers or silicide layers and semiconductor layers are laminated and formed alternately on a semiconductor substrate so as to be a multilayer structure and Schottky junctions composed of the metal layers or the silicide layers and the semiconductor layers are formed so as to be a multilayer. CONSTITUTION:A first-layer platinum silicide (PtSi) layer 12A in a thickness of about 10Angstrom is formed, by a molecular beam epitaxial growth method, on a P-type Si substrate 11 whose acceptor concentration NA is 1X10<15>; in addition, a first-layer P-type silicon (Si) layer 13A in a thickness of about 200Angstrom is formed on it by said growth method. In addition, a second-layer platinum silicide layer 12B, a second-layer P-type Si layer 13B, a third-layer platinum silicide layer 12C and a third-layer P-type Si layer 13C in the same thickness are formed on it to be a multilayer structure by said growth method. When said growth method is used in this manner, the platinum silicide layers and the Si layers can be obtained to be a thin-layer structure in a state that their crystallinity is good. Thereby, hot carriers generated in a platinum silicide layer 12 are implanted in both direction of an arrow B and an arrow C; an increase in a sensitivity can be anticipated as compared with a structure in which only one layer of the platinum silicide layer is formed.

Description

[Detailed Description of the Invention] [Summary] Regarding an infrared detection device, the present invention aims at an infrared detection device with a large number of pixels, easy manufacture, and high sensitivity, in which metal layers or silicide layers and semiconductor layers are alternately arranged on a semiconductor substrate. The semiconductor layer is laminated in a multilayer structure, and a Schottky junction between the metal layer or silicide layer and the semiconductor layer is provided in the multilayer structure.

[Industrial application field]

The present invention relates to an infrared detection device, and particularly to an infrared detection device that has a large number of pixels and is easy to manufacture.

In recent years, Si substrates, for which large-area single crystals can be easily obtained and the manufacturing technology for semiconductor devices such as LSIs has been established, are used, and metal electrodes such as platinum are formed on the substrate in a predetermined pattern by vapor deposition or sputtering. A Schottky junction type infrared sensing element in which a Schottky junction is formed between Si and a metal electrode is attracting attention because it can easily produce a multi-pixel device with about 500 x 500 pixels, which is comparable to that of a television.

[Conventional technology]

Conventionally, as a Schottky-type infrared sensing element using such a Si substrate, an infrared imaging device that combines the sensing element and a signal processing element that processes a signal from the sensing element has been described in the literature (Kimata, M., etallssc
c DrGEST OF TECHNICAL
PAPER3, WPM 10.3"^512 X5
12 Element PtSi 5chottky-
Barrier Infrared, Tmage Se
m5or”, Feb. 1987).

A cross-sectional view of the main parts of this sensing element is shown in FIG.

As shown in the figure, an N-type layer 2 is formed at a predetermined position on the surface of a P-type Si substrate 1, and this N-type layer has a guard ring function to avoid electric field concentration around the sensing element. ing. Further, a thin platinum silicide layer 3 is formed on the surface of the substrate by sputtering or the like, a 5in2 film 4 is formed thereon, and an i-reflection film 5 is further formed thereon. This 5iOz film 4 reflects the infrared rays that are not absorbed by the thin platinum silicide layer among the infrared rays incident from the bottom of the substrate in the direction of the arrow, and reflects them by hitting the A2 reflective film 5, and reflects them again in the direction of the platinum silicide layer. It is designed to act as an optical resonator for re-injecting light into the detection element, thereby increasing the quantum efficiency and sensitivity of the detection element.

The operation of such a sensing element will be explained using the energy band diagram shown in FIG. A hot hole 7 is formed after
These hot holes 7 move randomly within the platinum silicide layer 3 until they recombine with electrons. During this movement, only the hot holes that have reached the interface 8 between the platinum silicide layer 3 and the P-type Si substrate 1 have an energy greater than the energy barrier of φ5 (corresponding to the momentum perpendicular to the interface). However, the P-type Si substrate 1 is smaller than the platinum silicide layer 3.
It is said that the photocurrent is injected in the direction of .

[Problem to be solved by the invention]

However, even in the Schottky junction type infrared detector structure described above, the optical resonance structure is not sufficient to capture the infrared rays transmitted through the platinum silicide layer, and the quantum efficiency of the detector is 1%. It has the following shortcomings.

For this reason, indium antimony (InSb), mercury, cadmium, tellurium (Hg + -x Cd) + Te)
Compared to an infrared detection device using a compound semiconductor substrate with a narrow energy bandgap, a Schottky junction type infrared detection element has a disadvantage of having poor quantum efficiency and resulting in a detection device with low sensitivity.

The present invention aims to eliminate the above-mentioned problems and provide a highly sensitive Schottky infrared detection device using a Si substrate.

[Means to solve the problem]

As shown in the principle diagram of FIG. 1, the infrared detecting device of the present invention that achieves the above object has a multilayer structure in which metal layers or silicide layers 12 and semiconductor layers 13 are alternately stacked on a semiconductor substrate 11. It is constructed by providing multiple Schottky junctions between the metal layer or silicide layer and the semiconductor layer.

[For production]

As shown in FIG. 1, the Schottky-type infrared detection device of the present invention includes a semiconductor substrate 11 made of Si that transmits infrared rays, a silicide layer 12 made of platinum silicide with a thickness of 50 Å or less, and a is 20
．． Semiconductor layers 13 made of P-type Si layers with zero nesting degree are alternately stacked in a multilayer structure.

In this way, the silicide layer 1 of the platinum silicide
Since the hot carriers generated in 2 are injected in both directions of arrows B and C, sensitivity can be expected to improve approximately twice as much as compared to the conventional structure in which only one platinum silicide layer is formed on a Si substrate. .

Furthermore, by forming the silicide layer 12 made of platinum silicide with good crystallinity thinly using a molecular beam epitaxial growth method, the thickness of the silicide layer becomes smaller than the value of the mean free path of hot holes in the silicide. Therefore,
The hot holes are injected into the Si layer in a state where they are difficult to recombine and are easily converted into photocurrent, improving quantum efficiency.

Furthermore, when the above-mentioned silicide layer 12 is formed thinly to improve quantum efficiency, infrared rays that are transmitted without being absorbed by this thin silicide layer 12 are absorbed by the Si semiconductor layer 13 above it, and are further absorbed by this Si semiconductor layer 13. Infrared rays that are not absorbed by the layer 13 are absorbed by the second silicide layer thereon, so that the quantum efficiency of the incident infrared rays does not decrease, and the detection sensitivity of the device improves.

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

FIG. 2 is a sectional view showing an embodiment of the infrared detection device of the present invention.

As illustrated in FIG. 2, the infrared detection device of the present invention includes:
P-type Si substrate 1 with acceptor concentration NA of l Xl015
1, the first layer of platinum silicide (P) is about 10 layers thick.
tSi) layer 128 is formed by the molecular beam epitaxial growth method, and on top of that, a layer 128 of about 200 layers is deposited.
A P-type silicon (S'i) layer 13A is formed by molecular beam epitaxial growth.

Furthermore, a second layer of platinum silicide layer 12B, a second layer of P-type Si layer 13B,
The aJi-th platinum silicide layer 12C1 and the third P-type Si layer 13C are sequentially formed into a multilayer structure by the above-described molecular beam epitaxial growth method.

As described above, when the molecular beam epitaxial growth method is used, the platinum silicide layer and the Si layer can be obtained in a thin layer structure with good crystallinity.

The platinum silicide layer and Si layer stacked in a multilayer structure in this way are mesa-etched, and the sides of the mesa are etched.
Eight for making contact with the platinum silicide layer! A metal electrode 14 is formed by vapor deposition or sputtering, and a P'Si layer 15 doped with P-type impurity atoms at a high concentration is formed by sputtering or the like on the side surface of the other mesa to make contact with the substrate. has been done.

Although not shown, an N'' layer 16 is formed on the P-type Si substrate 11 to form an input diode for injecting photoelectrically converted signal charges into the charge transfer element.

Infrared rays are incident from the bottom of the substrate 11 of the infrared detecting device thus formed along the direction of the arrow. Hot holes are formed by infrared light transmitted through the substrate and absorbed by the platinum silicide layer 12A. And this hot hole is Si
The photocurrent moves to both the substrate 11 and the Si layer 13A and becomes a photocurrent.

Specifically, compared to a conventional device in which a platinum silicide film is simply formed on a substrate, the quantum efficiency is improved because hot holes move to both the Si substrate and the Si layer.

Furthermore, since the platinum silicide layer 12A is thin, the infrared rays that penetrate through the platinum silicide layer 12A are transmitted through the platinum silicide layer 12A.
The hot carriers reaching the platinum silicide layer 12B of the third layer and generated in the silicide layer 12B are
13A and 13B are injected to form a photocurrent, and since such an operation can be repeated, an infrared detection device with improved quantum efficiency can be obtained.

In this example, a platinum silicide layer was used as the silicide layer, but other silicide layers such as iridium silicide (IrSi) and palladium silicide (PdS) were used.
i) may also be used.

Further, instead of the silicide layer, a metal layer such as a platinum (Pt) layer, an iridium (Ir) layer, a palladium (Pd) layer, etc. may be used.

Furthermore, as a semiconductor layer, in addition to Si, germanium (Ge
), silicon germanium (5iGe) may also be used.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, hot carriers generated in a thin metal or silicide layer are injected into the semiconductor layers on both sides of the metal or silicide layer to become a photocurrent, and the metal, Alternatively, infrared rays that are not absorbed by the silicide layer are further captured by the metal or silicide layer above the silicide layer, so a Schottky-type infrared detection device using a high-sensitivity multi-pixel Si substrate with improved quantum efficiency can be obtained. There is.

[Brief explanation of drawings]

Fig. 1 is a principle diagram of the infrared detection device of the present invention, Fig. 2 is a sectional view of an embodiment of the infrared detection device of the present invention, Fig. 3 is a sectional view showing the structure of a conventional detection device, and Fig. 4 is an explanatory diagram of energy bands of a Schottky-type infrared sensing element. In the figure, 11 is a semiconductor substrate (P-type Si substrate), 12 is a gold N layer (silicide layer), 12^, 12B, 12C is a platinum silicide layer, 13 is a semiconductor layer (Si layer), 13A, 13
B, 13C is a Si layer, 14 is a metal electrode, 15 is P″Si
Show layers. Principle Diagram 31 Figure 31 Figure 1 I71 Mefu External Removal Aya Chiki 1-Shioke What Shunmen Shokan 2 Diagram

Claims (1)

[Claims] A metal layer or a silicide layer (
12) and semiconductor layers (13) are alternately stacked in a multilayer structure, and a Schottky junction between the metal layer or silicide layer and the semiconductor layer is provided in the multilayer structure.