JPH11194222A - Production of optical waveguide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve smoothness of the upper face of a core layer and to decrease optical insertion loss of an optical waveguide. SOLUTION: This producing method includes a process to form a core layer 21 on a substrate 20, a process to form two layers of pattern mask layers 22, 23 having the pattern of an optical waveguide on the core layer, a process to apply a photoresist 24 on the pattern mask layers, a process to expose and develop the photoresist by photolithographic technique to remove the photoresist 24a except the optical waveguide pattern, a process to etch the mask layer 23a except the optical waveguide pattern, a process to etch the core layer 21a except the optical waveguide pattern, and a process to form a clad layer on the core layer obtd. by etching.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical waveguide, and more particularly to a method for manufacturing an optical waveguide with reduced optical insertion loss.

[0002]

2. Description of the Related Art Conventionally, a silica-based optical waveguide for guiding light has been manufactured by various steps shown in FIG. 1. Substrate cleaning The quartz substrate is cleaned.

[0003] 2. Core Layer Deposition P, B, and Ge core layers are formed on a quartz substrate to a thickness of 8 μm by a P-CVD apparatus / FHD apparatus. 3. Mask Si film formation A mask Si (or Ti) film (core layer patterning mask) is formed on the core layer by a sputtering apparatus. mask
The thickness of the Si film is about 1 μm.

[0004] 4. Resist application A photoresist is applied on the pattern mask layer by a spin coater. The thickness of the photoresist is about 0.5 μm. 5. Photolithography → prebaking → exposure → developing The photoresist is prebaked by photolithography technology, patterned and exposed by a mask aligner, and developed to remove the photoresist other than the core portion to obtain a desired pattern.

<Core processing step> Core Layer Mask Etching Using a patterned photoresist, the core layer mask is etched by an RIE (reactive ion etching) apparatus. 7. Core layer etching The core layer is etched by the RIE device.

[0006] 8. Mask removal The mask is etched by a wet etching device. 9. Cladding Layer Formation A 40 μm-thick cladding layer is formed on the core layer obtained by etching using a P-CVD apparatus / FHD apparatus. 10. Reinforced glass pasting A 1.5 mm thick reinforcing glass is pasted with a UV adhesive. 11. Chip forming process Cutting, polishing and assembling are performed.

In this method of manufacturing an optical waveguide, FIG.
As shown in Fig. 7, after the removal of the mask, parallel linear projections were formed on the upper side surface of the core. In order to obtain the knowledge of the cause of the formation of the protrusions, a core with a reduced RIE (reactive ion etching) time for mask removal was observed, and FIG.
Was obtained. From the results of FIG. 4, the process by which the mask disappears by etching is considered as follows.

1) The mask is uniformly etched from both the upper and side directions. 2) Reaction products during etching are deposited on the side of the mask, and the etching is stopped. 3) Etching is performed only from above the mask, and the mask disappears. 4) Deposits remaining on the side of the mask remain, and serve as a mask to form projections.

Therefore, as long as RIE (Reactive Ion Etching) is used, it is considered that the occurrence of the protrusions is difficult, although to a large extent, to completely eliminate them. Also,
In the mask material removing step, a mask material having a high selectivity is generally resistant to wet etching using an acid,
I can not use it.

[0010]

As described above, in the conventional method for manufacturing an optical waveguide, there is a problem that a convex portion parallel to the side surface is formed on the upper portion of the core after the metal mask is removed, so that the optical insertion loss increases.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of manufacturing an optical waveguide with reduced optical insertion loss.

[0012]

In order to achieve this object, a method of manufacturing an optical waveguide according to the present invention comprises forming a core layer on a substrate, and forming a two-layer pattern mask having an optical waveguide pattern on the core layer. Forming a layer, applying a photoresist on the pattern mask layer, exposing and developing the photoresist by photolithography technology to remove the photoresist other than the optical waveguide pattern, a mask layer other than the optical waveguide pattern , Etching a core layer other than the optical waveguide pattern, and forming a clad layer on the core layer obtained by the etching.

In this method for manufacturing an optical waveguide, the two pattern mask layers are an acid-soluble lower pattern mask layer formed on the core layer, and an upper pattern mask layer formed on the lower pattern mask layer. Consists of

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a method for manufacturing an optical waveguide according to the present invention will be described below with reference to the drawings. The production of the optical waveguide of the present invention is performed by the steps shown in FIG. 1. Substrate cleaning The quartz substrate 20 is cleaned.

2. Core Layer Formation A P, B, and Ge core layer 21 is formed on the quartz substrate 20 to a thickness of 8 μm by a P-CVD apparatus / FHD apparatus. 3. Metal mask Fe-Si two-layer film formation Two pattern mask layers 22 and 23 having an optical waveguide pattern are formed on the core layer 21. These two pattern mask layers 22 and 23 are composed of an acid-soluble lower pattern mask layer (mask for removing the upper pattern mask layer) 22 formed on the core layer and an upper layer formed on the lower pattern mask layer. Pattern mask layer (core layer patterning mask) 23
Consisting of As an example, iron is used for the lower pattern mask layer 22 and silicon is used for the upper pattern mask layer 23. As a film forming method, a vapor deposition method is used for iron Fe of the lower pattern mask layer 22, and a sputtering method is used for silicon Si of the upper pattern mask layer 23.
μm.

4. Photoresist 24 is applied on the pattern mask layer 23 by a spin coater. The thickness of the photoresist 24 is about 0.5 μm. 5. Photolithography → prebaking → exposure → development The photoresist 24 is prebaked by photolithography technology, patterned and exposed by a mask aligner and developed to remove the photoresist 24a other than the optical waveguide pattern to obtain a desired pattern.

<Core processing step> Core Layer Mask Etching Using a patterned photoresist, the core layer metal mask 23a other than the optical waveguide pattern is etched by an RIE (reactive ion etching) apparatus.

[7] Core Layer Etching The core layer 21a other than the optical waveguide pattern is etched by the RIE device. 8. Metal mask removal The metal mask 23b is removed by etching with a wet etching apparatus. In this metal mask removal, 1
When a 0% HCl solution was used, the metal mask was completely removed by immersion for 10 minutes.

9. Cladding layer formation A cladding layer 25 is formed on the core layer 21 obtained by etching.
A 40 μm film is formed by a P-CVD device / FHD device. 10. Reinforcing glass stuck A 1.5 mm thick reinforcing glass 26 is stuck with a UV adhesive 27. 11. Chip forming process Cutting, polishing and assembling are performed.

The metal mask Fe-Si two-layer films 22 and 23 formed by the above-described optical waveguide manufacturing method have the same resistance as the conventional method in the steps up to the etching of the core layer. According to this method of manufacturing an optical waveguide, a convex portion parallel to the side surface formed on the upper portion of the core after removing the metal mask is no longer generated, and the same smooth state as that at the time of forming the core layer is maintained. An optical waveguide with reduced loss was obtained.

The method of manufacturing such an optical waveguide can be applied to a group of products in which a core is formed by dry etching in a quartz, dielectric, or semiconductor optical waveguide device or the like.

[0022]

As is clear from the above description, according to the optical waveguide manufacturing method of the present invention, the smoothness of the upper surface of the core layer is improved by forming two metal masks on the core layer. As a result, the light insertion loss of the optical waveguide is reduced.

[Brief description of the drawings]

FIG. 1 is a process chart showing a method for manufacturing an optical waveguide of the present invention.

FIG. 2 is a process chart showing a conventional optical waveguide manufacturing method.

FIG. 3 is an enlarged view showing an upper part of a core obtained by a conventional optical waveguide manufacturing method.

FIG. 4 is a partially enlarged view showing an upper part of a core obtained by a conventional optical waveguide manufacturing method.

[Explanation of symbols]

 20... Substrate 21... Core layer 22, 23... Two pattern mask layers 24... Photoresist 21a... Core layer other than optical waveguide pattern 23a... Mask layer other than optical waveguide pattern 24a... Photoresist other than optical waveguide pattern 25... Cladding layer

Claims (2)

[Claims] 1. A method for forming a core layer on a substrate, forming two pattern mask layers having an optical waveguide pattern on the core layer, and applying a photoresist on the pattern mask layer. Exposing and developing the photoresist by photolithography to remove the photoresist other than the optical waveguide pattern; etching the mask layer other than the optical waveguide pattern; the core layer other than the optical waveguide pattern And forming a cladding layer on the core layer obtained by the etching. 2. The pattern mask layer according to claim 1, wherein the two pattern mask layers include an acid-soluble lower pattern mask layer formed on the core layer, and an upper pattern mask layer formed on the lower pattern mask layer. The method for manufacturing an optical waveguide according to claim 1, wherein: