JPH0221671A - Photocoupling element - Google Patents

Abstract

PURPOSE:To reduce the delay in signals while correcting the noise margin for enhancing the performances of an IC by a method wherein photodetecting element comprising amorphous silicon is laminated to be three-dimensionally constituted on a light emitting element comprising a compound semiconductor through the intermediary of a transparent insulating film. CONSTITUTION:A light emitting element 10 as well as the whole surface extending over a substrate is coated with a transparent insulating film comprising an SiO2 film 22. A photodetecting element 30 to be arranged on the SiO2 film 20 is lamination composed of a lower electrode 31 comprising Al provided on the position not to disturb the light emission from the light emitting element 10, a p-aSi layer 32, an intrinsic aSi layer 33, an n-aSi layer 34 and an upper electrode 35 comprising Al.

Description

[Detailed Description of the Invention] [(Already Required)] Regarding a new configuration of an optical coupling device, for the purpose of high-density configuration, a light-transmitting insulating film is placed on a light-emitting device made of a compound semiconductor,
A three-dimensional structure is formed by stacking light-receiving elements made of amorphous silicon.

[Industrial application field]

The present invention relates to a novel configuration of an optical coupling device.

photocoupler (photocoupler)
er) is a combination of a light-emitting element and a light-receiving element, and is a circuit element that has rapidly grown as an opto-isolator, which transmits optical signals between circuits and provides electrical isolation.

In order to incorporate such an optical coupling element into an IC, a structure with as high density as possible is desired.

[Problems to be solved by conventional techniques and inventions] Recently, I
As C becomes highly integrated and miniaturized, the wiring within the device becomes finer and the wiring resistance increases, and signal delay due to this is becoming a problem. Furthermore, as the amount of signals has become smaller due to higher integration and miniaturization, the margin for noise introduced from the input and output ends of the element has also become smaller.

That is, although voltage and current signals become smaller due to miniaturization, the magnitude of thermal noise remains unchanged, and therefore the margin becomes smaller.

Therefore, in order to alleviate these problems, it is necessary to form optical coupling elements with high density, but in conventional optical coupling elements, the light emitting part and the light receiving part are made separately and assembled in a hybrid manner. method was adopted. In addition, in the monolithic formation method, the light emitting part and the light receiving part are arranged two-dimensionally within the same plane (Japanese Patent Application No. 58-101,
No. 176 and Japanese Patent Application No. 182779/1982). Therefore, a large volume and area are required, and there is a problem in that it is difficult to integrate them into an IC at a high density.

The present invention proposes an optical coupling element that is intended to alleviate such problems and to be configured with high density.

[Issues to solve problems]

As shown in the principle diagram shown in FIG. 1, the problem is to construct a three-dimensional structure in which a light-receiving element 30 made of amorphous silicon is laminated on a light-emitting element 10 made of a compound semiconductor with a light-transmitting insulating film 20 interposed therebetween. This problem is solved by a photocoupler.

[For production]

That is, the present invention transmits optical signals in the vertical direction on an IC substrate, uses a compound semiconductor heterojunction with high light-emitting efficiency for the light-emitting element, and uses amorphous silicon with high light-receiving efficiency for the light-receiving element. Use.

By doing so, the resistance of the signal line within the IC is reduced by increasing the density of the optical coupling element, the transmission of optical signals within the optical coupling element is improved, and the noise margin is also improved.

〔Example〕

Hereinafter, embodiments will be described in detail with reference to the drawings.

FIG. 2 shows an equivalent circuit diagram of the optical coupling device according to the present invention, where L is a light emitting device and P is a light receiving device.

R,, R2 are resistors, In is an input signal, and Out is an output signal, and these symbols are also shown in the principle diagram of FIG.

FIG. 3 shows a cross-sectional view of an embodiment according to the present invention,
10 is a light emitting element, 30 is a light receiving element, and 5i02 is in between.
Although a light-transmitting insulating film 20 made of (silicon oxide) film is interposed, the light emitting element 10 is
．． n-AlxGa+-xAs layer 12 (x=0.3
．． film thickness 0.5 μm), p-AlxGa+-x^S
Layer 13 (x=0.3, film thickness 0.5 μm).

p-GaAs layer 14 (thickness 0.25 μm)
, AuCr electrode 15 (upper electrode), and this light emitting element 10 is a MOC on an n-GaAs substrate 11.
After each layer was grown by the VD method and further patterned, an upper electrode was formed, and the n-GaAs substrate 11 served as the lower electrode.

A 5i02 film 20 is formed over the entire surface of the substrate on this light emitting element 10.
(film thickness: 1 μm) is coated with a light-transmitting insulating film.

The light-receiving element 30 placed thereon has a lower electrode 3L made of AI (aluminum) provided at a position that does not interfere with the light emission from the light-emitting element.
m) + intrinsic aSi layer 33 (film thickness 1 μm), na
It is constructed by stacking an Si layer 34 (film J!J, 0.1 μm) and an upper electrode 35 consisting of ^l, and each of these layers is formed by plasma CVD.

By vertically stacking the light-emitting and light-receiving pixel elements very closely together in this way, the transmission characteristics of optical signals are greatly improved. Moreover, if such high-density optical coupling elements are incorporated into an IC, the resistance of the signal line will also be reduced, and signal delay will also be reduced.

Although the above embodiment is an example in which the light emitting element is formed with a junction made of AIGaAsJiff, it may also be formed with other ■-■ group compound semiconductors, such as a GaAs layer, or ■-V
Even if a light emitting element is formed of a group I compound semiconductor such as Zn5e or ZnS, an element with high luminous efficiency can be obtained.

In addition, amorphous silicon (aSi) has an absorption coefficient for visible light that is approximately 1 loss larger than that of single crystal silicon.
In addition, the optical band gap is 1.7 to 1°8 eV,
It has an absorption peak in the visible light region, has an extremely high photoelectric conversion efficiency, and the hydrogenated amorphous silicon (aSi; H) film has a small localized level density.
-Layer Recently, this hydrogenated amorphous silicon film has been mainly used due to its property of exhibiting good photoconductivity, and the above aSi layer 32, 33, 34 is also made of such aS
i: It is composed of a H film.

By combining these, an optical coupling element with high density and good transmission characteristics of optical signals can be obtained.

〔Effect of the invention〕

As is clear from the above description, the optical coupling device according to the present invention is a three-dimensionally configured high-density device, and if such an optical coupling device is incorporated into an IC, signal delay can be reduced.
The noise margin is also improved, which greatly contributes to improving the performance of the IC.

I2 is n-8 IXGIII-XAS layer, 13 bap
-8 1xGal-xAs layers, 14 p-G
aAs layer, 15 uCr electrode (upper electrode), 31 lower electrode 1, 32 p-asi layer, 33
is the intrinsic aSi layer, 34 is the n-asi layer, 35 is the A
I shows the upper electrode.

[Brief explanation of the drawing]

Figure 1 is a principle diagram, Figure 2 is an equivalent circuit diagram, FIG. 3 is an example diagram. In the figure, 10 is a light emitting element; 20 is a transparent insulating film (Si02 film); 30 is a light receiving element; 11 is an n-GaAs substrate (lower electrode), Fig. 1 Equivalent circuit diagram Figure 2

Claims (1)

[Claims] Through a light-transmitting insulating film on a light-emitting element made of a compound semiconductor,
An optical coupling device characterized by having a three-dimensional structure by stacking photodetectors made of amorphous silicon.