JPH06140662A - Photocoupling type semiconductor device - Google Patents

Abstract

PURPOSE:To provide a photocoupling type semiconductor device which is so constituted as to make the outputs of respective light receiving cells uniform by taking not only distances from a light emitting device but also a whole photocoupling structure, especially the reflection from light transmitting resin, into account. CONSTITUTION:Areas of light receiving cells 2a which are placed at a center part are largest and the areas of light receiving cells 2b and 2c placed in circumferential parts are getting smaller in accordance with the distance from the center part to lower the receiving sensitivity of a direct light from a light emitting device. When a current is applied to the light emitting device and a light is generated, the light is applied to a photodetector 10 and photovoltages are generated by a plurality of the respective light receiving cells 2a, 2b and 2c. A voltage generated by one light receiving cell is, if the light receiving cell is composed of a light receiving diode, about 0.5 to 0.6 V which corresponds to a junction potential difference. If a plurality of the light receiving cells are connected in series, the junction potential difference is multiplied by the number of connected cells.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optically coupled semiconductor device, and more particularly to an optically coupled semiconductor device including a light receiving element formed by connecting a plurality of light receiving cells in series.

[0002]

2. Description of the Related Art FIG. 3 is a sectional view showing the structure of an optically coupled semiconductor device. A light emitting element 20 is provided at a position facing the light receiving element 10, and the light receiving element 10 and the light emitting element 20 are fixed by a light transmitting resin 30 to perform optical coupling.
The light emitting element 20 is usually formed so as to be opposed to the central portion of the light receiving element 10.

FIG. 2 is a plan view showing an arrangement of light receiving cells of a conventional light receiving element. Generally, unlike a light emitting element, a light receiving element is rarely formed of a single light receiving cell, and a plurality of light receiving cells are connected in series to obtain a photovoltaic force. In the conventional light receiving element 10 shown in FIG. 2, a plurality of single crystal silicon islands are formed on the surface of a substrate 1 made of polysilicon or the like via an insulator such as an oxide film, and the single crystal silicon islands are provided with light receiving diodes or the like. A method of forming a light receiving cell is used.

As shown in FIG. 2, 16 light receiving cells 2a are provided.
a, 2bb, and 2cc are formed, these light receiving cells are connected in series, and a photoelectromotive force is generated when light is irradiated.
When a plurality of light receiving cells are connected in series, the more uniform the generated photocurrent, the better the photovoltaic efficiency. This is because the total photocurrent is rate-controlled by the smallest photocurrent in the plurality of light-receiving cells because they are connected in series.

In general, the intensity of light is inversely proportional to the square of the distance. Therefore, in the case of a semiconductor device having an optical coupling structure as shown in FIG. The current is made uniform. In the arrangement of the light receiving cells shown in FIG. 2, the light receiving cell 2a located at the central portion
When the light emitting element 20 is arranged at a position facing a, the light receiving cells 2bb located in the peripheral portion are the light receiving cells 2a in the central portion
A light receiving cell 2c which is larger than a and is located at the outermost periphery
c forms a large area.

[0006]

In the light receiving element used in the conventional optical coupling type semiconductor device, the outputs of the respective light receiving cells are made uniform by considering only the distance from the light emitting element. However, as shown in FIG. 3, since the light receiving element 10 and the light emitting element 20 are arranged to face each other with the light transmitting resin 30 in between, the light receiving cell array of the light receiving element is considered in consideration of the influence of the light transmitting resin 30. Had to do. In the conventional arrangement of light-receiving elements, the area of the light-receiving cells was determined only by considering only the distance between the light-emitting elements and the light-receiving cells without considering the influence of the light-transmitting resin, so the output of each light-receiving cell is not always uniform. However, there is a problem in that the emission photoelectromotive force is not reduced.

The present invention has been made in order to solve the above-mentioned conventional problems, and considers not only the distance from the light emitting element but also the entire optical coupling structure, and in particular, considering the reflection from the light transmitting resin. An object of the present invention is to provide an optical coupling type semiconductor device in which the outputs of the light receiving cells are made uniform.

[0008]

In order to solve the above problems in the prior art, the present invention provides a light receiving element formed by connecting a plurality of light receiving cells formed on the same substrate in series,
Light composed of a light-emitting element provided at a position facing the light-receiving element to optically couple with the light-receiving element to generate a photoelectromotive force in the light-receiving element, and a light-transmitting resin that fixes the light-receiving element and the light-emitting element in an optically coupleable manner. In the coupled semiconductor device, the light receiving cell area in the peripheral portion of the light receiving element facing the light emitting element is formed smaller than the light receiving cell area in the central portion of the light emitting element.

[0009]

In the present invention, since the light receiving cell is formed small in the peripheral portion, the sensitivity of the light receiving cell in the peripheral portion is smaller than that in the central portion. However, since the reflected light from the light-transmitting resin is sufficiently high in the peripheral cells, the light receiving sensitivity from the light emitting element becomes equal to that in the central portion in consideration of this reflection effect. Therefore, the receiving sensitivity becomes uniform over the entire area of the light receiving element.

[0010]

1 is a plan view showing an arrangement of light receiving cells of a light receiving element of the present invention. The method of forming the light receiving element 10 is the same as that of the conventional case shown in FIG. In the present invention, unlike the conventional arrangement of the light receiving cells, the area of the light receiving cell 2a located in the central portion is maximized, and the area of the light receiving cells 2b and 2c located in the peripheral portion is reduced as the distance from the central portion increases, and the light emitting element 2
The reception sensitivity of direct light from 0 is reduced.

When an electric current is applied to the light emitting element 20 to generate light, the light is applied to the light receiving element 10 through the light transmitting resin 30 so that the plurality of light receiving cells 2a, 2b, 2 on the light receiving element 10 are irradiated.
Each of c generates a photoelectromotive force. When a light receiving cell is formed by a light receiving diode, the voltage generated in one light receiving cell is about 0.5 to 0.6 V, which is the junction potential difference. However, when a plurality of cells are connected in series, the junction potential difference is multiplied by the number of connections. Is amplified.

In the case of the embodiment shown in FIG. 1, since 16 pieces are connected in series, a voltage of about 8 to 9.6V can be obtained. The current generated is determined by the intensity of the emitted light and the photosensitivity that depends on the area of each photocell, etc., but the overall output current of each photocell is the smallest because the photocells are connected in series. It is rate-controlled by photocurrent. When trying to obtain the output current most efficiently in a limited area, it is an effective means to make the output current of each light receiving cell uniform.

Generally, the intensity of light is inversely proportional to the square of the distance from the light source. Therefore, the light emitted from the light source directly to the light receiving diode becomes weaker in the peripheral portion.

However, as described above, in the case of the optical coupling type semiconductor device as shown in FIG. 3, the light receiving cells located in the peripheral portion are close to the wall 30a of the light transmitting resin 30, so that the reflected light from this wall 30a is generated. The direct light from the light emitting element 20 is added and irradiated. Therefore, when the reflected light from the wall 30a is taken into consideration, if the receiving sensitivity of the light receiving cells located in the peripheral portion is lowered, the output currents of the respective light receiving cells are made uniform and taken out. Therefore, as shown in FIG. 1, the area of the light receiving cell 2c at the corner farthest from the light emitting element is minimized, and then the area of the light receiving cell 2b located in the peripheral portion is made smaller than that of the light receiving cell 2a located in the central portion. . It should be noted that the extent to which the area of the light receiving cells in the peripheral portion is made smaller than the area of the light receiving cells belonging to the central portion depends on the material of the light transmitting resin 30 and the shape of the wall 30a and the light receiving cells belonging to the peripheral portion from the wall 30a. It depends on how far you are from each other, and it is better to determine the area experimentally.

[0015]

As described above in detail with reference to the embodiments, in the present invention, the light receiving sensitivity of the light receiving element in the peripheral portion is set in consideration of the light reflected from the wall of the light transmitting resin. The receiving sensitivity of each light receiving cell is made even lower by making it even lower. Therefore, it is possible to obtain an optically coupled semiconductor device that can efficiently maximize the output current.

[Brief description of drawings]

FIG. 1 is a plan view showing an arrangement of light receiving cells of a light receiving element of the present invention.

FIG. 2 is a plan view showing an arrangement of light receiving cells of a conventional light receiving element.

FIG. 3 is a cross-sectional view of an optically coupled semiconductor device.

[Explanation of symbols]

 1 substrate 2 single crystal islands 2a, 2b, 2c light receiving cell 10 light receiving element 20 light emitting element 30 light transmitting resin 30a light transmitting resin wall

Claims (1)

[Claims] 1. A light receiving element formed by connecting a plurality of light receiving cells formed on the same substrate in series, and a light receiving element provided at a position facing the light receiving element and optically coupled to the light receiving element. In a light-coupled semiconductor device including a light-emitting element that generates electric power, and a light-transmitting resin that fixes the light-receiving element and the light-emitting element so that they can be optically coupled, the peripheral portion of the light-receiving element facing the light-emitting element An optical coupling type semiconductor device characterized in that a light receiving cell area is formed smaller than the light receiving cell area in the central portion of the light emitting element.