JPH10189927A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device in which photovoltaic voltage can be increased upon irradiation with light. SOLUTION: This semiconductor device employs an SOI substrate comprising a semiconductor substrate, i.e., a support silicon substrate 1, and an active silicon layer 3 formed thereon through an insulation layer 2, e.g. a silicon oxide, and a plurality of silicon islands 5 comprising the electrically isolated active silicon layer 3 are formed by making grooves 4 reaching the insulation layer 2 from the surface of the active silicon layer 3. Light-receiving elements are formed on respective silicon islands 5 and are connected electrically in series through metal wirings.

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 receiving element having an SOI structure.

[0002]

2. Description of the Related Art FIG. 4 is a schematic sectional view showing an SOI structure type light receiving element according to a conventional example. The SOI structure type light receiving element according to the conventional example includes a support silicon substrate 1 and a p-type active silicon layer 3 formed on the support silicon substrate 1 via an insulating layer 2 such as a silicon oxide film. SOI
(Silicon On Insulator) An n-type impurity such as phosphorus (P) is ion-implanted into the active silicon layer 3 of the substrate so as to be exposed on the surface of the active silicon layer 3.
A p-type impurity such as boron (B) is ion-implanted into active silicon layer 3 so as to form a p-type impurity region, surround the n + -type impurity region, and expose the surface of active silicon layer 3. An impurity region is formed. This n +
Type impurity region operates as n + type cathode region 8, and
The + type impurity region operates as the p + type anode region 9. Then, a cathode electrode (not shown) is formed so as to be electrically connected to n + type cathode region 8, and an anode electrode (not shown) is formed so as to be electrically connected to p + type anode region 9. Have been.

[0003] Light receiving elements of the SOI structure type have attracted attention due to expectations for integration of light receiving elements with semiconductor elements such as power elements and control circuits, and to increase the breakdown voltage by reducing the thickness of the active silicon layer 3.

The open-circuit voltage that can be generated by the silicon light receiving element during light irradiation is about 0.6 V. This means, for example, that the light emitting element and the light receiving element are optically coupled, and the photoelectromotive force from the light receiving element is applied to the gate electrode of an insulated gate type power element such as a power MOS or IGBT, so that the power element is turned on / off. In a so-called solid-state relay using a semiconductor element that drives a semiconductor device, when only one light receiving element is used, the threshold voltage of the power element must be designed to be at least 0.5 V or less.

[0005]

However, it is not easy to design a power element having a low threshold voltage, and there has been a problem that a malfunction or a decrease in yield is caused.

The effective applied voltage to the gate of the power MOSFET during conduction is a value obtained by subtracting the threshold voltage value from the gate applied voltage value, and the effective voltage value is proportional to the on-resistance value. Therefore, in order to reduce the loss during conduction, a higher voltage is required as the voltage applied from the light receiving element.

The present invention has been made in view of the above points, and an object of the present invention is to provide a semiconductor device capable of increasing a photovoltaic voltage at the time of light irradiation.

[0008]

According to the first aspect of the present invention,
A groove is formed so as to reach the insulating layer from the surface of the semiconductor layer of the SOI substrate including the semiconductor substrate and the semiconductor layer formed on the semiconductor substrate via the insulating layer, and the groove and the insulating layer are formed. A semiconductor island composed of a plurality of the semiconductor layers which are insulated and separated from each other, a light receiving element is formed for each of the semiconductor islands, and the light receiving elements are electrically connected in series.

According to a second aspect of the present invention, in the semiconductor device according to the first aspect, the semiconductor island has a multilayer structure of an insulating layer and a semiconductor layer, and has a plurality of the semiconductor islands in a depth direction. It is characterized by comprising.

According to a third aspect of the present invention, in the semiconductor device according to the first or second aspect, the light receiving elements are electrically connected in series by metal wiring.

According to a fourth aspect of the present invention, in the semiconductor device according to the first or second aspect, the light receiving elements are electrically connected in series by being arranged on a metal wiring formed on a mounting substrate. It is characterized by having made it.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. In this embodiment, the first conductivity type is p-type and the second conductivity type is n for convenience of explanation.
Although described as a type, the present invention is also applied to a case where p-type and n-type are reversed.

FIG. 1 shows an SOI according to an embodiment of the present invention.
It is a schematic sectional drawing which shows a structural type light receiving element. The semiconductor device according to the present embodiment includes a support silicon substrate 1 as a semiconductor substrate and an active silicon layer 3 formed on the support silicon substrate 1 via an insulating layer 2 such as a silicon oxide film. By using a SOI substrate, a groove 4 reaching the insulating layer 2 from the surface of the active silicon layer 3 is formed.
A plurality of silicon islands 5 composed of active silicon layers 3 electrically insulated from each other are formed.

As an example of a method for forming the groove portion 4,
There is a method in which anisotropic etching is performed using an alkaline etchant such as a KOH aqueous solution using a silicon oxide film patterned into a predetermined shape as a mask.

A light receiving element (not shown) is formed on each silicon island 5, and each light receiving element is electrically connected in series by a metal wiring.

Accordingly, in the present embodiment, a single silicon photodetector which can only be expected to generate an open voltage of about 0.6 V is insulated and separated into a plurality of active silicon layers 3 of the SOI substrate. Since the light receiving elements are formed on each of the silicon islands 5 and the light receiving elements are electrically connected in series, an open circuit voltage of several volts or more can be easily achieved.

As shown in FIG. 2, each of the silicon islands 5 insulated and separated by the groove 4 shown in FIG. 1 is further separated into a plurality of insulating islands 2 by interposing an insulating layer 2a in the depth direction. Forming isolated silicon islands 5,
If a light receiving element is formed on each silicon island 5 and each light receiving element is connected in series by a metal wiring, a higher value open circuit voltage can be achieved.

In this embodiment, the respective light receiving elements are electrically connected in series by metal wiring.
The present invention is not limited to this. For example, as shown in FIG.
Alternatively, the light receiving elements formed on the SOI substrate shown in FIG. 2 may be arranged to connect the respective light receiving elements in series.

[0019]

According to the first aspect of the present invention, a groove is formed so as to reach an insulating layer from a semiconductor layer surface of an SOI substrate including a semiconductor substrate and a semiconductor layer formed on the semiconductor substrate via an insulating layer. Is formed, a semiconductor island composed of a plurality of semiconductor layers insulated and separated by the trench and the insulating layer is formed,
Since a light receiving element is formed for each semiconductor island and the light receiving elements are electrically connected in series, an open circuit voltage of several volts or more can be easily achieved, and the photovoltaic voltage at the time of light irradiation can be increased. A semiconductor device that can be provided.

According to a second aspect of the present invention, in the semiconductor device according to the first aspect, the semiconductor island has a multilayer structure of an insulating layer and a semiconductor layer, and has a plurality of semiconductor islands in a depth direction. Therefore, more light receiving elements can be formed, and a higher value open circuit voltage can be achieved.

According to a third aspect of the present invention, in the semiconductor device according to the first or second aspect, the light receiving elements are electrically connected in series by metal wiring, so that the wiring of the semiconductor elements can be performed simultaneously. Wiring can be performed, and a high open-circuit voltage can be achieved without increasing the number of steps.

According to a fourth aspect of the present invention, in the semiconductor device according to the first or second aspect, the light receiving element is electrically connected in series by disposing the light receiving element on a metal wiring formed on the mounting substrate. Therefore, the light receiving elements can be electrically connected in series while being mounted on the mounting board, and a high open-circuit voltage can be easily achieved.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing an SOI structure type light receiving element according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing an SOI structure type light receiving element according to another embodiment of the present invention.

FIG. 3 is a schematic sectional view showing an SOI structure type light receiving element according to another embodiment of the present invention.

FIG. 4 is a schematic sectional view showing a SOI structure type light receiving element according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Supporting silicon substrate 2, 2a Insulating layer 3 Active silicon layer 4 Groove part 5 Silicon island 6 Mounting substrate 7 Metal wiring 8 n + type cathode region 9 p + type anode region

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[Procedure amendment]

[Submission date] July 2, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction contents]

The open-circuit voltage that can be generated by the silicon light receiving element during light irradiation is about 0.6 V. This means, for example, that the light emitting element and the light receiving element are optically coupled, and the photoelectromotive force from the light receiving element is applied to the gate electrode of an insulated gate type power element such as a power MOS or IGBT, so that the power element is turned on / off. In the case of a so-called semiconductor type relay using a semiconductor element for driving a semiconductor device, when only one light receiving element is used, the threshold voltage of the power element is at least 0.
It is necessary to design at 5V or less.

 ──────────────────────────────────────────────────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 (4)

[Claims] An SOI substrate including a semiconductor substrate and a semiconductor layer formed on the semiconductor substrate via an insulating layer, wherein a groove is formed from the surface of the semiconductor layer to reach the insulating layer; A semiconductor island comprising a plurality of the semiconductor layers insulated and separated by the groove and the insulating layer is formed, a light receiving element is formed for each semiconductor island, and the light receiving elements are electrically connected in series. Semiconductor device. 2. The semiconductor device according to claim 1, wherein said semiconductor island has a multilayer structure of an insulating layer and a semiconductor layer, and has a plurality of said semiconductor islands in a depth direction. . 3. The semiconductor device according to claim 1, wherein said light receiving elements are electrically connected in series by metal wiring. 4. The semiconductor device according to claim 1, wherein said light receiving elements are electrically connected in series by being arranged on a metal wiring formed on a mounting substrate.