JPH06208030A - Optical coupling structure - Google Patents

Abstract

PURPOSE:To easily couple the light emitting element and light receiving element formed on a substrate having a level difference and to decrease leakage of light to this substrate by forming a flattening layer to flatten the level difference formed by the light emitting element, the light receiving element and an electronic circuit and disposing a optical waveguide structure on this flattening layer. CONSTITUTION:The electronic circuit 2, the light emitting element 3 and the light receiving element 4 are mounted on the substrate 1. The level difference is generated between the electronic circuit and the light emitting element 3 and the light receiving element 4 and, therefore, the flattening layer 5 is formed to produce the optical waveguide 6 for the purpose of efficient coupling of the light emitting element 3 and the light receiving element 4; thereafter, the optical waveguide 6 is formed on the flattening layer 5. An ordinary patterning technique is usable for producing the optical waveguide 6 atop the flattening layer 5 in such a manner and the easy registration of the optical waveguide 6 and the light elements 3, 4 is possible. A material absorbing the light from the light emitting element 3 is used as the flattening layer 5, by which the influence of the leaking light from the optical waveguide 6 to the electronic circuit 2 is lessened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical coupling structure for coupling a light emitting element and a light receiving element formed on the same substrate.

[0002]

2. Description of the Related Art LSI to be Solved
In such integrated circuits, electric wiring is thinned for higher integration. Along with this, problems occur in wiring delay time and heat generation, and it is considered to use light for wiring. At this time, 1992 Proceedings of Solid State Conference 10
As shown on page -12, a substrate for an optical circuit provided separately from the LSI has been used for connecting the light emitting element and the light receiving element provided on the LSI.

However, in this structure, after the LSI and the substrate for the optical circuit have to be manufactured separately, it is necessary to perform further alignment, which complicates the process, and it is necessary to fix them after alignment. There was a problem with stability over the long term.

As a method for solving the above problems,
Although it is possible to install the optical circuit directly on the LSI,
When the LSI is gallium arsenide (GaAs) and the light emitting element and the light receiving element are made of a material whose main component is indium phosphide (InP), or when the LSI is silicon (Si), the light emitting element and the light receiving element Is made of a material containing GaAs or InP as a main component, the thickness of the light emitting element portion and the light receiving element portion is increased in order to obtain a good light emitting element and light receiving element.

For this reason, a step which is larger than the step in the electronic circuit of the LSI is generated, and the connection thereof is difficult. Further, leakage of light from the optical circuit to the electronic circuit is one of the major causes of malfunction.

In view of the above problems, the present invention easily couples a light emitting element and a light receiving element formed on a substrate having a step,
And it aims at providing the optical coupling structure which reduces the leak of the light to a board | substrate.

[0007]

An optical coupling structure according to the present invention that achieves the above-mentioned object is an optical coupling structure for connecting a light emitting element and a light receiving element on a semiconductor substrate having an electronic circuit, a light emitting element and a light receiving element. In the coupling structure, a flattening layer for flattening a step formed by one or both of the light emitting element and the light receiving element and the electronic circuit is formed, and an optical waveguide structure is provided on the flattening layer. It is characterized by

Further, in the above structure, at least a part of the flattening layer for flattening the step may be a light absorbing layer.

The contents of the present invention will be described below.

FIG. 1 is a diagram for explaining the configuration of the present invention. In the figure, 1 is a substrate, 2 is an electronic circuit, 3 is a light emitting element, 4
Is a light receiving element, 5 is a flattening layer, and 6 is an optical waveguide. An electronic circuit 2, a light emitting element 3, and a light receiving element 4 are mounted on the substrate 1. Since a step is generated between the electronic circuit 2 and the light emitting element 3 and the light receiving element 4, the flattening layer 5 is formed in order to produce the optical waveguide 6 for efficiently coupling the light emitting element 3 and the light receiving element 4. And then this flattening layer 5
The optical waveguide 6 is formed on the upper layer.

At this time, since the optical waveguide 6 is formed on the upper surface of the flattening layer 5, ordinary patterning techniques such as photolithography and dry etching can be used, and the optical waveguide and the optical element can be easily aligned.

In FIG. 1, the light-emitting element 3 and the light-receiving element 4 are shown in the form of emitting and receiving light in the horizontal direction, but they can be applied to those of the vertical direction.

The flattening layer 5 is made of a material that absorbs the light from the light emitting element 3, or the material that absorbs the light is dispersed, so that the light leaked from the optical waveguide 6 affects the electronic circuit 2. Can be reduced.

As described above, according to the present invention, the step formed by the light emitting element and / or the light receiving element and the electronic circuit is flattened to facilitate the coupling of light, and the flattened portion is provided with the light absorption layer to guide light. The light leaked from the waveguide is reduced.

[0015]

The preferred embodiments of the present invention will be described below. (Example 1) G is formed on a part of the Si substrate 1 having the electronic circuit 2.
A buffer layer made of aAs, strained superlattice and InP is grown, and a 1.5 μm band laser structure using InGaAs and InGaAsP multiple quantum wells (MQW) as active layers is grown on the buffer layer, and a part of the laser structure is grown. , Part of which is the light receiving element 4.

The step of the light emitting portion from the substrate was 15 μm. Polymethyl methacrylate is 5 μm for the flattening layer 5.
Was spin-coated to a thickness of. Next, a copolymer of deuterated methacrylate and deuterated fluorinated methacrylate,
A guide layer was formed by spin coating to a thickness of 8 μm.

Next, a copolymer having an increased proportion of deuterated methacrylate was spin-coated to a thickness of 4 μm, and a core for connecting the light emitting element 3 and the light receiving element 4 was produced by using photolithography and dry etching. Then, the same copolymer as the above guide was applied. The error rate of the electronic circuit 2 did not increase even when the optical element was driven.

(Example 2) GaAs having an electronic circuit 2
A buffer layer made of strained superlattice and InP is grown on a part of the substrate 1, and a 1.3 μm band laser structure using InGaAsP and InGaAsP multiple quantum wells (MQW) as active layers is grown on the buffer layer. A part is a light emitting element 3, and a part is a light receiving element 4.

The step of the light emitting portion from the substrate was 13 μm. Polymethyl methacrylate is 4 μm for the flattening layer 5.
Was spin-coated to a thickness of. Next, a copolymer of deuterated methacrylate and deuterated fluorinated methacrylate was added to 6
A guide layer was formed by spin coating to a thickness of μm.

Next, a copolymer having an increased proportion of deuterated methacrylate was spin-coated to a thickness of 4 μm, and a core for connecting the light-emitting element 3 and the light-receiving element 4 was produced by photolithography and dry etching. Then, the same copolymer as the above guide was applied. The error rate of the electronic circuit 2 did not increase even when the optical element was driven.

(Embodiment 3) A buffer layer made of GaAs, strained superlattice and GaAs is grown on a part of a Si substrate 1 having an electronic circuit 2, and GaAs and AlGaAs multiple quantum wells (MQW) are activated thereon. A 0.8 μm band laser structure as a layer was grown, and a part thereof was used as a light emitting element 3 and a part thereof was used as a light receiving element 4.

The step of the light emitting portion from the substrate was 7 μm. Polycarbonate was spin-coated on the flattening layer 5 and the guide layer to a thickness of 5 μm, and this was impregnated with a methacrylate monomer and heated to polymerize.

Next, polycarbonate was spin-coated to a thickness of 4 μm, and this was impregnated with a methacrylate monomer to polymerize a monomer other than the core connecting the light emitting element 3 and the light receiving element 4 using photolithography. ,
The residual monomer was removed. The error rate of the electronic circuit 2 did not increase even when the optical element was driven.

(Embodiment 4) GaAs, AlGaAs multiple quantum wells (M
A 0.8 μm band laser structure having a QW) as an active layer was adhered, and a part thereof was used as a light emitting element 3 and a part thereof was used as a light receiving element 4.
The step difference from the substrate of the light emitting portion was 15 μm.

Polyimide mixed with carbon powder was spin-coated on the flattening layer 5 to a thickness of 7 μm. Next, polymethacrylate was spin-coated to a thickness of 8 μm to form a guide layer.

Then, 3 μl of polybenzyl methacrylate was added.
A core for coupling the light emitting element 3 and the light receiving element 4 was produced by spin coating to a thickness of m using photolithography and dry etching, and then polymethacrylate was applied. The error rate of the electronic circuit 2 did not increase even when the optical element was driven.

[0027]

As described above, according to the optical coupling structure of the present invention, a method similar to the semiconductor process can be used, and the light emitting element and the light receiving element on the semiconductor can be easily coupled. Is.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a configuration of the present invention.

[Explanation of symbols]

 1 substrate 2 electronic circuit 3 light emitting element 4 light receiving element 5 planarization layer 6 optical waveguide

Claims (2)

[Claims] 1. An optical coupling structure for coupling a light emitting element and a light receiving element on a semiconductor substrate having an electronic circuit, a light emitting element and a light receiving element, and one or both of the light emitting element and the light receiving element and the above. An optical coupling structure comprising: forming a flattening layer for flattening a step formed by an electronic circuit and disposing an optical waveguide structure on the flattening layer. 2. The optical coupling structure according to claim 1, wherein at least a part of the flattening layer for flattening the step is a light absorbing layer.