JPH10223925A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a light receiving element to receive incident light without lowering its photovoltaic force by forming porous silicon on a single-crystal silicon substrate with an insulating film in between and respectively forming the light receiving element and a light emitting element on the substrate and porous silicon so that the elements may be faced oppositely to each other. SOLUTION: Porous silicon 3 is formed on one main surface of a single- crystal silicon substrate 1 with a silicon oxide film 2 formed as an insulating film in between and a light receiving element 4 and a light emitting element 5 are respectively formed on the substrate 1 and porous silicon 3. In order to obtain the optical coupling between the elements 4 and 5, the porous silicon 3 is formed by anodically oxidizing one single-crystal silicon substrate of an SOI substrate and the elements 4 and 5 are respectively formed on the other single-crystal silicon substrate of the SOI substrate and the porous silicon 3 so that the elements 4 and 5 may be faced oppositely to each other. Therefore, the chip area of a semiconductor device can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly to a light emitting / receiving element having an SOI structure.

[0002]

2. Description of the Related Art FIG. 2 is a schematic sectional view showing an SOI structure type light receiving / emitting integrated device according to a conventional example. In the conventional light receiving and emitting integrated device, silicon islands 6a and 6b made of single crystal silicon are formed on one main surface of a single crystal silicon substrate 1 with a silicon oxide film 2 interposed therebetween. Here, an SOI (Silicon On Insulator) substrate is constituted by the single crystal silicon substrate 1, the silicon oxide film 2 and the single crystal silicon, and the silicon islands 6a and 6b are insulated from each other.

A light emitting element and a light receiving element are formed on the silicon islands 6a and 6b, respectively.
It is composed of a transistor, and the light receiving element is composed of a PN junction diode.

Light emitted from the base-collector junction of the PNP transistor is received by a light receiving element. The details are described in JP-A-6-69489.

[0005]

However, in the light receiving / emitting integrated device having the above structure, the light emitting device and the light receiving device are formed on the same surface of the SOI substrate.
Particularly, when a plurality of optical coupling pairs are integrated, a chip size is increased, which is not preferable.

Also, for example, a light emitting element and a light receiving element are optically coupled, and the photoelectromotive force from the light receiving element is converted into a power MOS or IGB.
In a so-called semiconductor type relay using a semiconductor element which drives the power element in a conductive / interrupted state by applying a voltage to the gate electrode of an insulated gate type power element such as T, the gate voltage applied to the insulated gate is at least several volts. The above is required, and therefore, it is necessary to electrically connect the light receiving elements in series.

In this case, the element area of the light receiving element becomes large, and in order to receive the incident light without reducing the photovoltaic power in this large light receiving element area, a plurality of light emitting elements are required in the structure shown in FIG. This is necessary and further results in an increase in chip area.

The present invention has been made in view of the above points, and an object of the present invention is to receive incident light without reducing the photovoltaic power without increasing the chip area. It is to provide a semiconductor device which can be realized.

[0009]

According to the first aspect of the present invention,
A single-crystal silicon substrate on which a light-receiving element is formed, and porous silicon formed with a light-emitting element formed on one main surface of the semiconductor substrate via an insulating film; The device is characterized in that the device and the device are opposed to each other with the insulating film interposed therebetween.

According to a second aspect of the present invention, in the semiconductor device of the first aspect, the porous silicon is formed by altering a single crystal silicon substrate by anodic oxidation. It is.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic sectional view showing a light emitting and receiving integrated device according to an embodiment of the present invention. The integrated light receiving / emitting element according to this embodiment is a single crystal silicon substrate 1
A porous silicon 3 is formed on one main surface of the substrate through a silicon oxide film 2 as an insulating film, a light receiving element 4 is formed on the single crystal silicon substrate 1, and a light emitting element 5 is formed on the porous silicon 3. Are formed.

In general, a light receiving element can be formed on a single crystal silicon substrate, but it is difficult to form a light emitting element.
Therefore, in the present embodiment, the porous silicon 3 is used for forming the light emitting element 5.

In this embodiment, a single-crystal silicon substrate 1 and a single-crystal silicon substrate (not shown) formed on one main surface of the single-crystal silicon substrate 1 with a silicon oxide film 2 interposed therebetween are used. SOI (Silicon On Insulat)
or) The single-crystal silicon substrate is anodized to be transformed to form porous silicon 3.

Therefore, in the present embodiment, the optical coupling between the light receiving element and the light emitting element, which has been conventionally performed by the mounting technology, is performed by using the SOI substrate to anodize one of the single crystal silicon substrates of the SOI substrate. With porous silicon 3
Is formed, the light receiving element 4 is formed on the other single crystal silicon substrate 1, the light emitting element 5 is formed on the porous silicon 3, and the light receiving element 4 and the light emitting element 5 are arranged to face each other.
The chip area can be reduced.

Further, since the light emitting element 5 is formed at the position facing the light receiving element 4 with the silicon oxide film 2 interposed therebetween, the light receiving efficiency to the light receiving element 4 can be improved.

[0016]

According to the first or second aspect of the present invention,
Porous silicon is formed on a single crystal silicon substrate via an insulating film, a light receiving element is formed on the single crystal silicon substrate, a light emitting element is formed on the porous silicon, and the light emitting element and the light receiving element are arranged facing each other. Therefore, it is possible to increase the light receiving efficiency to the light receiving element, without increasing the chip area,
A semiconductor device capable of receiving incident light without reducing the photovoltaic power can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a light emitting and receiving integrated device according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing a light emitting and receiving integrated device according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Single crystal silicon substrate 2 Silicon oxide film 3 Porous silicon 4 Light receiving element 5 Light emitting element 6a, 6b Silicon island

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshifumi Shirai 1048 Kadoma Kadoma, Kadoma City, Osaka Prefecture Inside Matsushita Electric Works, Ltd. (72) Inventor Yuji Suzuki 1048 Kazuma Kadoma, Kadoma City, Osaka Inside Matsushita Electric Works, Ltd.

Claims (2)

[Claims] 1. A semiconductor device comprising: a single-crystal silicon substrate on which a light-receiving element is formed; and porous silicon, on which a light-emitting element is formed, and which is formed on one main surface of the semiconductor substrate via an insulating film. A semiconductor device, wherein a light emitting element and the light receiving element are arranged to face each other with the insulating film interposed therebetween. 2. The semiconductor device according to claim 1, wherein said porous silicon is formed by altering a single crystal silicon substrate by anodic oxidation.