JPWO2004074890A1 - Optical waveguide device manufacturing method and optical waveguide device - Google Patents

Abstract

The present invention relates to a method of manufacturing an optical waveguide device and an optical waveguide device. A core layer (2) having a predetermined pattern is formed on a first cladding layer (1), and a part of the core layer (2) is formed. An etching mask (5) having a mask pattern for changing the etching rate in a specific direction of the part is formed in a region other than the part, and the core layer (2) is partially etched using the etching mask (5) as a mask. By a very simple manufacturing process, the core layer 2 can be provided in a vertical taper shape at low cost.

Description

  The present invention relates to a method of manufacturing an optical waveguide device and an optical waveguide device, and more particularly to a method of manufacturing a planar light-wave circuit used in the field of optical communication.

In recent years, the communication capacity has increased explosively, and in order to respond to this, construction of a large-capacity photonic network using WDM (Wavelength Division Multiplexing) has been promoted. In order to reduce the size and cost of this WDM transmission system, application of a planar light-wave circuit type functional integrated element that can be mass-produced using a batch process is considered promising.
In particular, even if the radius of curvature of the waveguide is large by increasing the relative refractive index difference between the core and the clad (refractive index difference = 0.8 to 4%) for high functionality and low cost by high density integration. A planar optical waveguide that can reduce the bending loss is promising.
However, in the optical waveguide having a high refractive index difference as described above, the core diameter for satisfying the single mode condition is small, and the spot size is also smaller than that of the optical fiber. There is a problem that becomes large.
Therefore, by gradually reducing the diameter of the line-shaped core (core diameter) in the longitudinal direction, the spot size is expanded to match the diameter of the optical fiber and the spot size, thereby reducing the connection loss. The method is known. As a technique related to such a spot size conversion waveguide, for example, it is proposed by Patent Document 1 (Japanese Patent Laid-Open No. 8-171020) and Patent Document 2 (Japanese Patent Laid-Open No. 2000-137129 (Japanese Patent No. 3279270)). There is something that has been.
Among these, for example, the technique disclosed in Patent Document 1 is a technique of reducing the core diameter in the longitudinal direction of the core stepwise (stepwise). However, in such a technique, the spot size changes abruptly at the connecting portion where the core diameter becomes small, so that there is a problem that radiation loss occurs at this portion and excessive loss at the time of spot size conversion increases. Moreover, there are many manufacturing processes and it is not suitable for cost reduction.
The technique disclosed in Patent Document 2 (hereinafter referred to as a known technique) is a technique for reducing the core diameter in a taper (slope) shape, and the core system is reduced in a staircase shape as described above. Compared to the case, excess loss at the time of spot size conversion can be reduced.
FIG. 14 is a schematic perspective view of an optical waveguide with a spot size conversion unit in the above-described known technology, FIGS. 15A to 15E are schematic cross-sectional views showing the manufacturing method of the optical waveguide shown in FIG. FIG. 15A is a schematic top view corresponding to each step shown in FIGS.
First, as shown in FIG. 14, an optical waveguide 100 with a spot size conversion unit in the known technique is an optical waveguide having a core 101 made of a quartz material and claddings 104 and 105 on a silicon substrate 103, and an end face of the optical waveguide. A part of the core 101 near 106 is processed (tapered) so as to have a tapered portion (spot size converting portion) 102 that gradually decreases in width and thickness as it approaches the end face 106.
And the optical waveguide 100 with such a spot size conversion part is manufactured as follows. That is, first, as shown in FIG. 15A, a quartz-based film is formed on the silicon substrate 103 as the lower clad 104 and the core layer 112. At this time, a metal film (metal mask) 107 is embedded in the core layer 112 in order to change the thickness of the core layer 112 in a step shape in a later process. The metal film 107 is formed 1.5 μm above the interface with the lower clad 104, and as shown in FIG. 15A, the metal film 107 is formed in a tapered shape whose width gradually decreases toward the tip.
Next, as shown in FIG. 15B and FIG. 16B, the core layer 112 is etched by reactive ion etching (RIE) under the metal film 107 and the mask 108, and the tapered portion 113 is formed at the tip. A stepped core 101 is formed. At this time, the metal film 107 becomes an etching stop layer, and a stepped step is formed in a part of the core 101.
Further, as shown in FIG. 15C and FIG. 16C, a metal film (metal mask) 109 is formed on the core 1 except for the portion 113 processed into a tapered shape, and as shown in FIG. 15D and FIG. A quartz-based film 111 having a film thickness of about 2 to 3 μm is formed on the entire surface by pressure chemical vapor deposition (APCVD: Atmospheric Pressure Chemical Vapor Deposition). Then, the quartz-based film 111 is reflowed by heat so that the step of the core 101 is smoothly filled, and a mask is formed on the quartz-based film 111 so as to include the taper region of the core 101. At this time, a good reflow shape can be obtained by annealing at a temperature of 800 ° C. or higher.
Finally, as shown in FIG. 15E and FIG. 16E, the taper portion 113 of the core 101 is masked, and unnecessary quartz-based films other than the taper portion 113 are removed by etching. Through the above steps, the spot size conversion unit 102 in which both the width and the thickness change smoothly in a tapered shape is obtained.
However, in such a manufacturing method, the following steps are increased as compared with the formation of the waveguide without the spot size conversion portion, so that it is difficult to reduce the cost.
(1) Two stages of film formation of the core layer 101 are required. (2) Film formation of a stop layer (metal mask 107) attached in the middle of the core layer 101 (including a photolithography process)
(3) Removal of stop layer (metal mask 107) after formation of core pattern (4) Formation of metal mask 109 in a portion other than taper portion 113 (including a photolithography process)
(5) Film formation and annealing of thin film layer (quartz diameter film) 111 for forming tapered portion 102 (6) Formation of etching mask on tapered portion 102 (including photolithography process)
(7) Etching for removing thin film layer 111 other than tapered portion 102 (8) Removal of etching mask The present invention was devised in view of such a problem, and the waveguide diameter (core) is formed in a tapered shape. It is an object of the present invention to make it possible to manufacture an optical waveguide with a spot size conversion unit that gradually reduces the diameter) and converts the spot size with low loss in a very simple and low cost process.
JP-A-8-171020 JP 2000-137129 A (Patent No. 3279270)

In order to achieve the above object, an optical waveguide device manufacturing method of the present invention is a method for manufacturing an optical waveguide device having a core layer and a cladding layer covering the periphery of the core layer, the first cladding layer A core layer having a predetermined pattern is formed thereon, and an etching mask having a mask pattern for changing an etching rate in a specific direction of the part is formed in a region excluding a part of the core layer, and the etching mask is masked. The core layer is partially etched.
Here, the etching mask is preferably formed after the core layer is formed. In addition, after the above etching, it is preferable to remove the etching mask and form a second cladding layer on the core layer and the first cladding layer.
Further, as the above etching mask, it is desired to form a tapered shape whose thickness changes in the specific direction in the core layer, and the opening degree is gradually increased in the width direction of the core layer gradually from the part along the pattern of the core layer. It is preferable to form a mask pattern.
The etching mask is preferably formed of a photosensitive resin, and the minimum value of the opening degree is preferably set to be equal to or lower than the resolution of photolithography. It is preferable to set it to be greater than the width. The thickness of the etching mask is preferably 10 μm or more.
Further, RIE using a predetermined etching gas is preferably used for etching the core layer, and more preferably, a gas containing C3F8 or C4F8 is used.
The core layer is preferably formed to have a taper shape in the width direction so as to have a square cross-sectional shape.
Further, in the photomask used when the above etching mask is formed by photolithography, the amount of light transmission gradually increases from the portion where the mask pattern starts to the opening toward the direction in which the opening becomes wider. A transparent portion may be provided, and this translucent portion is preferably configured to change the light transmittance by arranging a minute rectangular pattern having one side of 1 μm or less and changing its density. .
Further, the optical waveguide device of the present invention is characterized in that a portion whose thickness changes in the specific direction is formed in both the core layer and the cladding layer by the above-described method for manufacturing an optical waveguide device.

1A to 1C, 2A to 2C, 3A to 3C, and 4A to 4C are schematic views for explaining a method of manufacturing a planar optical waveguide device according to the first embodiment of the present invention. .
FIGS. 5A to 5C, FIGS. 6A to 6C, FIGS. 7A to 7C, and FIGS. 8A to 8C are schematic views for explaining a method of manufacturing a planar optical waveguide according to the second embodiment of the present invention.
FIGS. 9A to 9C, FIGS. 10A to 10D, FIGS. 11A to 11C, FIGS. 12A to 12C, FIGS. 13A and 13B are respectively for explaining a method of manufacturing a planar optical waveguide according to the third embodiment of the present invention. FIG.
FIG. 14 is a schematic perspective view of a conventional optical waveguide with a spot size converter.
15A to 15E are schematic cross-sectional views showing the method of manufacturing the optical waveguide shown in FIG. 14 for each step.
16A to 16E are schematic top views corresponding to the steps shown in FIGS. 15A to 15E.

[A] Description of First Embodiment FIGS. 1A to 1C, FIGS. 2A to 2C, FIGS. 3A to 3C and FIGS. 4A to 4C are respectively methods for manufacturing a planar optical waveguide device according to the first embodiment of the present invention. It is a schematic diagram for demonstrating. 1A and 1B are side views of a planar optical waveguide device corresponding to the view of arrow D in FIG. 1C, respectively, and FIG. 1C is a top view in the middle of manufacturing the planar optical waveguide device. 2A, 2B, and 2C are an AA sectional view, a BB sectional view, and a CC sectional view, respectively, in FIG. 1C. 3A, 3B, and 3C are cross-sectional views corresponding to FIGS. 2A, 2B, and 2C, respectively, and FIGS. 4A, 4B, and 4C are cross-sectional views corresponding to FIGS. 2A, 2B, and 2C, respectively. FIG.
Hereinafter, based on these drawings, a method for manufacturing a planar optical waveguide device having a taper (slope) shape as a spot size conversion portion in the thickness direction of the core (hereinafter may be simply abbreviated as “planar optical waveguide”). explain.
First, as shown in FIG. 1A, an under-cladding layer (first cladding layer) 1 is formed on a substrate such as a silicon (Si) substrate with a quartz-based layer film, and a core layer is further formed thereon with a quartz-based layer film. 2 is formed. As a method for forming the under cladding layer 1 and the core layer 2, for example, CVD (Chemical Vapor Deposition), FHD (Frame Hydrolysis Deposition), sputtering, or the like can be used. The substrate may be a quartz substrate in order to match the thermal expansion coefficient with the optical waveguide manufactured on the substrate. In addition, when a quartz substrate is used, the quartz substrate may also serve as the under cladding layer 1.
Next, an optical waveguide structure is formed according to the following steps.
First, as shown in FIG. 1A, an etching mask 3 for forming a predetermined core pattern is formed on the core layer 2. As a method of manufacturing the pattern of the etching mask 3, a metal, polyimide, or the like is formed on the core layer 2, and a photoresist is applied on the core layer 2 for patterning. A two-layer mask method in which the metal, polyimide, or the like is formed by etching or a single-layer mask method in which a photoresist having high heat resistance is applied / patterned on the core layer 2 and the photoresist is used as the etching mask 3 can be applied. .
Next, as shown in FIG. 1B, using the etching mask 3 as a mask, a part of the core layer 2 and the under cladding layer 1 are etched by RIE using an etching gas, and then the remaining etching mask 3 is removed. . As a result, a core pattern 4 (a linear waveguide in FIG. 1C) corresponding to the pattern of the etching mask 3 is formed. As the etching gas, for example, a fluorine-based gas (CF4, C3F8, C4F8, etc.) is used.
Next, as shown in FIG. 1C and FIGS. 2A to 2C, a taper shape (hereinafter referred to as a vertical taper shape) is formed in a direction perpendicular to the substrate (or the under cladding layer 1) (the thickness direction of the core layer 2). Etching mask 5 having a shape in which the opening of the mask is gradually enlarged with a width equal to or larger than the width of core pattern 4 in a direction to be deeply carved as a vertical taper shape while masking core pattern 4 other than the desired portion. (Shaded part) is formed.
As the etching mask 5, for example, a photosensitive resin (photosensitive polyimide, photoresist, or the like) that can be easily formed by spin coating and photolithography is suitable. The thickness of the etching mask 5 is desirably 10 μm or more so that the etching rate difference due to the pattern effect is efficiently generated in the next etching process.
Next, etching is performed using the etching mask 5 as a mask, and the core layer 2 and the under cladding layer 1 are etched until the thickness of the core layer 2 reaches a desired thickness at a position where the opening degree of the etching mask 5 is the largest. This etching may be performed by any etching method in which the etching rate differs depending on the shape (opening degree) of the etching mask (hereinafter also simply referred to as “mask”) 5 (either wet etching or dry etching may be used).
As an optimum etching method, there is RIE. RIE has good controllability of etching in the depth (thickness) direction, and has a pattern effect called a microloading effect. The smaller the opening degree of the etching mask 5, the lower the etching rate at the bottom.
Therefore, when etching is performed using such an etching mask 5, due to the pattern effect of the mask 5, as shown in FIGS. 3A to 3C, the etching rate is slow in the narrow portion of the opening portion of the mask 5 due to the microloading effect. Since the microloading effect is reduced and the etching rate is increased as the opening becomes wider, the core layer 2 in the narrow portion of the opening of the etching mask 5 becomes thicker after RIE, and the opening of the etching mask 5 becomes wider. Accordingly, a vertical taper shape in which the core layer 2 becomes thin is formed.
At this time, as shown in FIGS. 3A to 3C, the under cladding layer 1 is etched together with the core layer 2 to the same extent as the core layer 2, so that the opening degree of the mask 5 also increases in the under cladding layer 1. It has a vertical taper shape. That is, in the planar optical waveguide device manufactured by this manufacturing method, a portion whose thickness changes in a specific direction (longitudinal direction of the core pattern 4) is formed in both the core layer 2 and the (under) clad layer 1. It is. The vertical taper shape of the clad layer 1 can be confirmed as a boundary between the clad layers 1 and 6 with a microscope or the like even if the over clad layer 6 is formed in a later step.
By the way, in general, a fluorine-based gas is used for RIE of a quartz-based film. However, in order to effectively bring out the microloading effect, a C / F ratio of C3F8, C4F8, etc. It is preferable to use a gas having a high ratio. Moreover, since the magnitude of the microloading effect can be adjusted by adding a small amount of oxygen, it is preferable to add a small amount of oxygen in order to obtain a desired shape.
After the etching is completed, the remaining etching mask 5 is removed by oxygen ashing or the like, and as shown in FIGS. 4A to 4C, an over clad layer 6 is formed and the core pattern 4 is embedded. Note that, for example, CVD, FHD, sputtering, or the like is also used for forming the over clad layer 6.
The planar optical waveguide which has the vertical taper-shaped core pattern 4 as a spot size conversion part by the above process is produced. The etching mask 5 may be formed before the core pattern 4 is formed. However, since the formation of the core pattern 4 after the etching mask 5 is formed becomes difficult in accuracy, the formation of the core pattern 4 is performed as described above. The latter is preferred.
As described above, according to the method of manufacturing the planar optical waveguide of the present embodiment, the etching mask 5 having the mask pattern in which the opening portion gradually increases from the portion of the core pattern 4 where the tapered shape is to be formed is formed. Using the mask as a mask, the core layer 2 can be formed in a very simple process using the difference in etching rate due to the microloading effect during RIE. .
Therefore, it is possible to realize and provide a planar optical waveguide having a vertical taper-shaped spot size conversion unit at a lower cost than conventional ones.
[B] Description of Second Embodiment FIGS. 5A to 5C, FIGS. 6A to 6C, FIGS. 7A to 7C, and FIGS. 8A to 8C each illustrate a method of manufacturing a planar optical waveguide according to the second embodiment of the present invention. It is a schematic diagram for demonstrating. 5A and 5B are side views of the planar optical waveguide corresponding to the view of arrow D in FIG. 5C, respectively, and FIG. 5C is a top view in the middle of manufacturing the planar optical waveguide. 6A, 6B, and 6C are an AA sectional view, a BB sectional view, and a CC sectional view, respectively, in FIG. 5C. 7A, 7B, and 7C are cross-sectional views corresponding to FIGS. 6A, 6B, and 6C, respectively, and FIGS. 8A, 8B, and 8C are also cross-sections corresponding to FIGS. 6A, 6B, and 6C, respectively. FIG.
Hereinafter, based on these drawings, a method of manufacturing a planar optical waveguide according to the second embodiment will be described.
First, in the present embodiment as well, as in the first embodiment, as shown in FIG. 5A, a quartz-based layer is formed on a substrate such as a silicon (Si) substrate by using a film forming method such as CVD, FHD, or sputtering. An under cladding layer 1 is formed with a film, and a core layer 2 is further formed with a quartz-based layer film thereon. In this case as well, a quartz substrate may be used for the substrate in order to match the thermal expansion coefficient with the optical waveguide manufactured on the substrate. When a quartz substrate is used, the quartz substrate is an underclad layer. In some cases, it also serves as one.
Next, as shown in FIG. 5A, an etching mask 3 a for forming a predetermined core pattern is formed on the core layer 2. Also for the pattern of the etching mask 3a, for example, a metal, polyimide, or the like is formed on the core layer 2, and a photoresist is applied thereon to perform patterning. A two-layer mask method in which metal, polyimide, or the like is formed by etching, a single layer mask method in which a photoresist having high heat resistance is applied and patterned on the core layer, and the photoresist is used as an etching mask 3a can be applied.
However, in the present embodiment, as shown in FIG. 5C, the etching mask 3 a is patterned so that a core pattern having a tapered shape in which the core pattern width gradually decreases toward the spot size conversion unit end surface 7. The ratio of thinning is matched with the finally formed vertical taper shape, and the core cross-sectional shape of the taper portion is adjusted to be almost square everywhere.
Then, as shown in FIG. 5B, using the etching mask 3a as a mask, a part of the core layer 2 and the under cladding layer 1 is etched by RIE using an etching gas, and then the remaining etching mask 3a is removed. As a result, a waveguide having a taper shape (hereinafter, referred to as a horizontal taper shape) whose width gradually narrows toward the end surface 7 of the spot size conversion portion in FIG. 5C is formed according to the pattern of the etching mask 3a. As the etching gas, for example, a fluorine-based gas (CF4, C3F8, C4F8, etc.) is used.
Next, as shown in FIGS. 5C and 6A to 6C, as in the first embodiment, the core pattern 4 a other than the portion where the vertical taper shape is desired to be masked, and the vertical taper shape is desired to be deeply engraved. An etching mask 5 (shaded portion) having a width larger than the width of the core pattern 4 and a shape in which the mask opening gradually increases is formed in the direction.
Subsequently, as shown in FIGS. 7A to 7C, etching is performed by RIE or the like using the etching mask 5 as a mask, and the thickness of the core layer 2 becomes a desired thickness at a location where the opening degree of the etching mask 5 is the largest. The core layer 2 and the undercladding layer 1 are etched up to. Then, also in this case, due to the pattern effect of the mask 5, the etching rate is slowed by the microloading effect in the narrow part of the opening of the mask 5, and the microloading effect is reduced and the etching rate is increased as the opening is widened. Therefore, after RIE, the core layer 2 in the narrow portion of the opening of the etching mask 5 is thick, and a vertical taper shape is formed in which the core layer 2 becomes thinner as the opening of the etching mask 5 becomes wider.
Therefore, the core layer 2 has a taper shape in which both the thickness and the width are gradually reduced toward the spot size conversion portion end surface 7, that is, the core cross-sectional shape of the taper portion is almost square everywhere. Will have the shape In this case as well, as shown in FIGS. 7A to 7C, the under cladding layer 1 is etched together with the core layer 2 to the same extent as the core layer 2. It will have a vertical taper shape in the direction.
That is, in the planar optical waveguide device manufactured by this manufacturing method, the core layer 2 has a portion whose width changes in the longitudinal direction, and the core layer 2 and the (under) clad layer 1 have a core. A portion where the thickness changes in the longitudinal direction of the pattern 4 is formed. The vertical taper shape of the cladding layer 1 can also be confirmed with a microscope or the like after the device is manufactured, as in the first embodiment.
Also in this embodiment, it is preferable to use a gas having a high C / F ratio (ratio of carbon to fluorine) such as C3F8 or C4F8 as the etching gas, and the desired micro-loading effect is adjusted. In order to obtain this shape, a small amount of oxygen (about 1-2%) may be added.
After the etching is completed, the remaining etching mask 5 is removed by oxygen ashing or the like, and an over clad layer 6 is formed and the core pattern 4 is embedded as shown in FIGS. 8A to 8C. Note that, for example, CVD, FHD, sputtering, or the like is also used for forming the over clad layer 6.
As described above, a planar optical waveguide having both vertical and horizontal tapered spot size conversion portions is manufactured. In such a planar optical waveguide, since the cross-sectional shape of the core layer 2 is reduced toward the end face 7 while maintaining a substantially square shape, a loss difference due to a difference in modes (TM and TE modes) of light propagating through the core layer 2. (Polarization dependence of loss) can be reduced, and a planar optical waveguide having a spot size conversion unit having a lower loss than that in the first embodiment can be realized by a simple process.
If such a spot size conversion part is used for a connection part between a planar optical waveguide device having a high refractive index difference and an optical fiber, the connection loss with the optical fiber can be reduced.
[C] Description of Third Embodiment FIGS. 9A to 9C, 10A to 10D, 11A to 11C, 12A to 12C, 13A, and 13B are planes according to the third embodiment of the present invention. It is a schematic diagram for demonstrating the manufacturing method of an optical waveguide. 9A and 9B are side views of the planar optical waveguide corresponding to the view of arrow E in FIG. 9C, respectively, and FIG. 9C is a top view in the middle of manufacturing the planar optical waveguide. 10A, 10B, and 10C are an AA sectional view, a BB sectional view, and a CC sectional view, respectively, in FIG. 9C. FIG. 10D is a DD section of a portion surrounded by the frame 8 in FIG. 9C. It is a figure which expands and shows. 11A, 11B, and 11C are cross-sectional views corresponding to FIGS. 10A, 10B, and 10C, respectively, and FIGS. 12A, 12B, and 12C are cross-sectional views corresponding to FIGS. 10A, 10B, and 10C, respectively. is there. 13A is a schematic top view of a photomask used when forming the etching mask shown in FIG. 9C, and FIG. 13B is an enlarged view of a portion surrounded by a frame 8 in FIG. 13A.
Hereinafter, a method for manufacturing a planar optical waveguide according to the third embodiment will be described with reference to these drawings.
First, as in the second embodiment, in this embodiment, as shown in FIG. 9A, a quartz-based layer is formed on a substrate such as a silicon (Si) substrate by using a film forming method such as CVD, FHD, or sputtering. An under cladding layer 1 is formed with a film, and a core layer 2 is further formed with a quartz-based layer film thereon. In this case as well, a quartz substrate may be used for the substrate in order to match the thermal expansion coefficient with the optical waveguide manufactured on the substrate. When a quartz substrate is used, the quartz substrate is an underclad layer. In some cases, it also serves as one.
Next, as shown in FIG. 9A, an etching mask 3 a for forming a predetermined core pattern is formed on the core layer 2. Also for the pattern of the etching mask 3a, for example, a metal, polyimide, or the like is formed on the core layer 2, and a photoresist is applied thereon to perform patterning. A two-layer mask method in which metal, polyimide, or the like is formed by etching, a single layer mask method in which a photoresist having high heat resistance is applied and patterned on the core layer, and the photoresist is used as an etching mask 3a can be applied.
Then, as shown in FIG. 9B, using the etching mask 3a as a mask, a part of the core layer 2 and the under cladding layer 1 are etched by RIE using an etching gas, and then the remaining etching mask 3a is removed. As a result, a core pattern 4a (horizontal taper shape in FIG. 9C) corresponding to the pattern of the etching mask 3a is formed. As the etching gas, for example, a fluorine-based gas (CF4, C3F8, C4F8, etc.) is used.
Next, as shown in FIG. 9C and FIGS. 10A to 10C, as in the second embodiment, the core pattern 4 a other than the portion where the vertical taper shape is desired to be masked and deeply carved as the vertical taper shape. An etching mask 5 (shaded portion) is formed in a shape that increases the opening of the mask in the direction.
However, in the present embodiment, as shown in FIG. 13A, in the photomask 9 for patterning the etching mask 5, the amount of light transmission gradually increases from the portion where the mask pattern starts to open toward the direction in which the opening becomes wider. A semi-transparent portion (a semi-transparent mask; a portion surrounded by a frame 8) is formed. Specifically, for example, as shown in FIG. 13B, the translucent portion 8 is configured to change the light transmittance by arranging minute rectangular patterns each having a side of 1 μm or less and changing the density thereof. ing.
When a photomask 9 having such a semi-transparent portion 8 is used, as shown in FIG. 10D, the photoresist remains in a slope shape according to the amount of transmitted light, and the etching mask 5 corresponding to at least the semi-transparent mask has a slope. Shape 5a is obtained. When the etching mask 5 having the slope shape 5a is formed in the opening surrounded by the frame 8, the core layer 2 at the boundary between the opening and the non-opening of the etching mask 5 is further smoothed by the following etching process. It is possible to form a vertical taper shape at an appropriate angle, and to reduce radiation loss at the time of spot size conversion.
Thereafter, as in the second embodiment, as shown in FIGS. 11A to 11C, etching is performed by RIE or the like using the etching mask 5 (5a) as a mask, and the core layer is formed at a place where the opening degree of the etching mask 5 is the largest. After etching the core layer 2 and the under-cladding layer 1 until the thickness of 2 becomes a desired thickness, the remaining etching mask 5 (5a) is removed by oxygen ashing or the like, as shown in FIGS. The overcladding layer 6 is formed and the core pattern 4 is embedded.
As a result, as in the second embodiment, the core layer 2 has both a vertical and horizontal taper shape in which the cross-sectional shape of the core layer 2 is reduced toward the end surface 7 while maintaining a substantially square shape, and the opening of the etching mask 5. A planar optical waveguide having a spot size conversion part in which the core layer 2 at the boundary between the part and the non-opening part is formed into a vertical taper shape at a smoother angle is manufactured in a very simple process.
Therefore, it is possible to realize and provide a planar optical waveguide having a spot size conversion unit with a smaller loss than the second embodiment at a low cost.
In the above-described example, the boundary between the opening and the non-opening is connected by the translucent mask 8, but by causing the opening degree of this part to be narrower than the resolution of photolithography, a photolithography defect is intentionally caused. By leaving the photoresist in a vertical taper shape, the same effect as described above can be obtained.
Further, in each of the above-described embodiments, as the core layer 2 and the cladding layers 1 and 6, a case where a quartz-based material is applied has been described. It is not limited to the materials. Furthermore, the mask pattern for changing the etching rate described above is not limited to the example described above, and may be appropriately changed according to the shape to be provided in the thickness direction of the core layer 2.
And this invention is not limited to each embodiment mentioned above, It cannot be overemphasized that various deformation | transformation can be implemented in the range which does not deviate from the meaning of this invention.

  As described above, according to the present invention, the vertical taper-shaped core pattern can be formed in a very simple process by using the difference in etching rate, so that the vertical taper can be formed at a lower cost than in the past. An optical waveguide device having a shape spot size converter can be realized and provided. Therefore, the present invention is considered extremely useful in the field of optical communication.

Claims (15)

In the method of manufacturing an optical waveguide device having a core layer (2) and a cladding layer (1, 6) covering the periphery of the core layer (2),
A mask for forming a core layer (2) having a predetermined pattern on the first cladding layer (1) and changing an etching rate in a specific direction of the part in a region excluding a part of the core layer (2). Forming an etching mask (5) having a pattern;
A method of manufacturing an optical waveguide device, wherein the core layer (2) is partially etched using the etching mask (5) as a mask. The method for manufacturing an optical waveguide device according to claim 1, wherein the etching mask (5) is formed after the core layer (2) is formed. After the etching, the etching mask (5) is removed,
The optical waveguide according to claim 1 or 2, characterized in that a second clad layer (6) is formed on the core layer (2) and the first clad layer (1). A method for manufacturing a waveguide device. As the etching mask (5), the core layer (2) is gradually formed along the pattern of the core layer (2) from the portion where the core layer (2) is desired to have a taper shape whose thickness changes in the specific direction. The method of manufacturing an optical waveguide device according to any one of claims 1 to 3, wherein a mask pattern having a large opening degree is formed in a width direction of the optical waveguide device. The method for manufacturing an optical waveguide device according to any one of claims 1 to 3, wherein the etching mask (5) is formed of a photosensitive resin. The method for manufacturing an optical waveguide device according to claim 4, wherein the etching mask (5) is formed of a photosensitive resin. 7. The method of manufacturing an optical waveguide device according to claim 6, wherein the width of the opening degree is set to be equal to or lower than a resolution of photolithography. The width of the opening degree is set to be equal to or larger than the width of the core layer (2), The manufacture of an optical waveguide device according to any one of claims 4, 6, and 7 Method. The core layer (2) according to any one of claims 4, 6 to 8, characterized in that the core layer (2) has a tapered shape in the width direction so as to have a square cross-sectional shape. The manufacturing method of the optical waveguide device of description. In the photomask used when the etching mask (5) is formed by photolithography, the amount of light transmission gradually increases from the portion where the mask pattern starts to the opening toward the direction in which the opening becomes wider. The method for manufacturing an optical waveguide device according to any one of claims 4 to 9, wherein a transparent portion (8) is present. The translucent portion (8) is configured to change the light transmittance by arranging a minute rectangular pattern having one side of 1 μm or less and changing its density. A method for manufacturing an optical waveguide device according to claim 10. The method for manufacturing an optical waveguide device according to any one of claims 1 to 11, wherein the etching mask (5) has a thickness of 10 µm or more. The method for manufacturing an optical waveguide device according to any one of claims 1 to 12, wherein RIE using a predetermined etching gas is used for etching the core layer (2). The method for manufacturing an optical waveguide device according to claim 13, wherein a gas containing C3F8 or C4F8 is used as the etching gas. According to the method for manufacturing an optical waveguide device according to any one of claims 1 to 14, both the core layer (2) and the clad layer (1, 6) have portions whose thickness changes in the specific direction. An optical waveguide device characterized by being formed.

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