JPH0763937A - Thin-film optical waveguide element and its production - Google Patents

Abstract

PURPOSE:To provide a thin-film optical waveguide element capable of coupling guided light with high efficiency even in coupling between different waveguides by forming tapered coupling parts by wet etching by a photolithography method and the process for production of such element. CONSTITUTION:This thin-film optical waveguide element is constituted by coupling a first optical waveguide part A having a first optical waveguide layer 8 on a substrate 6, a second optical waveguide part B having a second optical waveguide layer 9 of the equiv. refractive index larger than the equiv. refractive index of this first optical waveguide layer 8 and a third optical waveguide part C having a third optical waveguide layer 10 of the equiv. refractive index smaller than the equiv. refractive index of this second optical waveguide layer 9. The first coupling part (a) where the film thickness of the second optical waveguide layer 9 is increased in a taper shape in the progressing direction of the guided light 12, is formed on the lower layer of the first optical waveguide layer 8 so as to exist between the first optical waveguide part A and the second optical waveguide part B. The second coupling part (b) where the film thickness of the second optical waveguide layer 9 is gradually decreased in a taper shape in the progressing direction of the guided light 12 so as to exist between the second optical waveguide part B and the third optical waveguide part C is formed as well.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a T in an optical integrated circuit.
The present invention relates to an E / TM mode separation element, a thin film optical waveguide element used as an optical coupling element between optical waveguides having different film thickness and refractive index, and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, in a coupling element between optical waveguides having different film thickness and refractive index, a method of smoothly guiding guided light from one optical waveguide to the other optical waveguide with reduced loss is, for example, "tapering". As a "spot size converter using a waveguide of the type" disclosed in 6p-ZD-5 of the 49th Japan Society of Applied Physics, Autumn, 1988.
"Reducing loss of spot size converter (SST) by overlapping tapered waveguides", 1989, spring,
Some are disclosed in Proceedings of the 36th Japan Society of Applied Physics, 1a-PB-9. In these tapered waveguide structures, the tapered structure formed by the shadow mask method realizes guided optical coupling with low loss between optical waveguides having different film thickness and refractive index.

FIGS. 12A to 12C show a method of manufacturing a coupling element between optical waveguides which forms a tapered coupling portion by using a shadow mask method. First, in (a),
The shadow mask 2 is placed on the substrate 1 to form an optical waveguide layer 3 having one end formed in a tapered shape by film formation.
In (b), the optical waveguide layer 3 is provided with its tapered end aligned with the tapered end of the shadow mask 4, and the optical waveguide layer 5 having one end tapered by film formation is formed. Thereby, as shown in (c), it is possible to fabricate a tapered coupling portion in which the optical waveguide layer 3 and the optical waveguide layer 5 are overlapped with each other. Then, by setting the taper angle of the taper coupling portion to 1 deg or less, it is possible to realize a low-loss optical waveguide coupling element. In this case, as a film forming method for forming the tapered optical waveguide layers 3 and 5,
A film forming method with good step coverage such as a sputtering method or a CVD method is used. The taper shape at this time is formed by the reaction species wrapping around at the edge of the shadow mask.

[0004]

However, in the method of forming the tapered joint portion by the shadow mask method as described above, although the gentle tapered shape required for the low loss coupling can be obtained, the positioning of the tapered joint portion with respect to the substrate 1 is achieved. Since the accuracy depends on the installation location of the shadow masks 2 and 4 during film formation, there is a problem that accurate positioning is difficult. In other words, the taper joint is formed on the substrate 1.
It is difficult to perform positioning with respect to the reference position (for example, the light receiving element or other functional element formed in the substrate 1) with the accuracy of the photolithography method.

Further, the positioning with respect to the substrate 1 in which the tapered ends of the second optical waveguide layer 5 are aligned so as to face each other so as to face each other in accordance with the shape of the tapered end of the optical waveguide layer 3 formed first, is performed at the taper coupling portion. By accumulating the positioning error of (1) and changing the opposed overlapping state of the two optical waveguide layers 3 and 5 of the taper coupling portion depending on the part, the coupling efficiency (coupling loss) of the guided light at the taper coupling portion also changes. However, it is not possible to obtain a uniform bond over the entire area of the tapered joint.

Furthermore, when the shadow masks 2 and 4 are installed, the shadow masks 2 and 4 come into contact with the substrate 6 and the optical waveguide layers 3 and 5 so that the substrate 6 and the optical waveguide layers 3 and 5 are prevented from scattering guided light. There is a problem that scratches are caused, and a warp of the shadow masks 2 and 4 causes a gap between the shadow masks 2 and the substrate 6 and the optical waveguide layers 3 and 5, which changes the taper shape to form a taper coupling portion. However, there is a problem that a uniform bond cannot be obtained over the entire area of.

[0007]

According to a first aspect of the present invention, a first optical waveguide portion having a first optical waveguide layer formed on a substrate and an equivalent refractive index larger than that of the first optical waveguide layer are provided. A thin-film optical waveguide device comprising a combination of a second optical waveguide section having a second optical waveguide layer and a third optical waveguide section having a third optical waveguide layer having an equivalent refractive index smaller than that of the second optical waveguide layer. ,
The film thickness of the second optical waveguide layer, which is located between the first optical waveguide section and the second optical waveguide section, is below the first optical waveguide layer, and the thickness of the second optical waveguide layer gradually decreases from 0 in the traveling direction of the guided light. A first coupling portion that is tapered to increase the film thickness of the second optical waveguide layer, and is located between the second optical waveguide portion and the third optical waveguide portion. A second coupling part was formed in which the film thickness of the wave layer gradually decreased in the taper direction until the film thickness of the wave guide layer reached the film thickness of the third optical waveguide layer.

According to the second aspect of the present invention, the second optical waveguide layer is laminated on the substrate, and the etching rate of the same etchant on the second optical waveguide layer is higher than that of the second optical waveguide layer. A speed layer is stacked, a first mask layer corresponding to the planar shape of the first coupling portion is stacked on the first speed increasing layer, and the first speed increasing layer near the opening of the first mask layer is formed by an etchant. After etching the second optical waveguide layer and the second optical waveguide layer, the first mask layer and the remaining first speed increasing layer are removed to form a first coupling portion having a tapered end face on the second optical waveguide layer. And the etching rate by the same etchant on the second optical waveguide layer of the first coupling portion formed by the first coupling portion forming step is higher than that of the second optical waveguide layer. A second speed-up layer is laminated and a second bond is formed on the second speed-up layer. Laminating a second mask layer corresponding to the planar shape of, and etching with an etchant up to the middle of the film thickness of the second speed increasing layer and the second optical waveguide layer at the opening of the second mask layer. After the application, the film thickness of the second optical waveguide layer is gradually reduced to the film thickness of the third optical waveguide layer by removing the second mask layer and the remaining second acceleration layer. A second coupling portion forming step of forming a second coupling portion, and the first coupling portion, the second optical waveguide layer and the second coupling portion formed by these first and second coupling portion forming steps. And the first optical waveguide layer is laminated on the substrate including the third optical waveguide layer.

According to the third aspect of the present invention, the first thin film layer is laminated on the substrate, and the second thin film layer having a smaller refractive index than the thin film and a high etching rate by the same etchant is formed on the first thin film layer. A multilayer thin film forming step of stacking, and a first speed increasing layer having a higher etching rate by an etchant than the first thin film layer and the second thin film layer on the second thin film layer obtained by this multilayer thin film forming step. Stacked
A first mask layer corresponding to the planar shape of the first coupling portion is laminated on the first speed increasing layer, and the first speed increasing layer and the second thin film layer at the opening of the first mask layer are formed by an etchant. And the first thin film layer are removed by etching, and then the first mask layer and the remaining first acceleration layer are removed to remove the second optical layer including the first thin film layer and the second thin film layer. First coupling portion forming step of forming a first coupling portion having a tapered end surface of the wave layer, and the second optical waveguide including the tapered end surface of the first coupling portion formed by the first coupling portion forming step A second acceleration layer having a higher etching rate by the same etchant than the second thin film layer is laminated on the layer, and a second mask layer corresponding to the planar shape of the second coupling portion is formed on the second acceleration layer. Laminate and etch with an etchant at the opening of the second mask layer The second acceleration layer and the second thin film layer forming a part of the second optical waveguide layer are removed by etching, and then the second mask layer and the remaining second acceleration layer are removed to remove the second A second coupling part forming step of forming a second coupling part in which the film thickness of the two optical waveguide layers is gradually reduced to the film thickness of the third optical waveguide layer composed of the first thin film layer, First on a substrate including the first coupling portion and the second optical waveguide layer and the second coupling portion and the third optical waveguide layer formed by the multilayer thin film forming step and the first and second coupling portion forming step. An optical waveguide layer was laminated.

According to the invention of claim 4, claim 2 or 3
In the invention described, in the first bonding portion forming step, the treatment is performed without removing the first speed increasing layer, and the remaining first speed increasing layer is also used in the subsequent second bonding portion forming step and then removed. I decided to do it.

According to a fifth aspect of the present invention, a first thin film layer is laminated, and a first speed increasing layer having a higher etching rate by the same etchant than the thin film is laminated on the first thin film layer. A second mask layer corresponding to the planar shape of the second coupling portion is laminated on the speed increasing layer, and the first speed increasing layer and the first thin film layer at the opening of the second mask layer are removed by etching with an etchant. After that, the second mask layer and the remaining first acceleration layer are removed, and the first thin film layer and the second thin film layer are laminated by laminating a second thin film layer on a substrate including the first thin film layer. A second coupling portion forming step of forming a second coupling portion in which the thickness of the second optical waveguide layer formed of a thin film layer is gradually reduced to the thickness of the third optical waveguide layer formed of the second thin film layer. , The second bonding portion and the second light formed by the second bonding portion forming step. On the substrate including the wave layer and the third optical waveguide layer, a second speed increasing layer having a higher etching rate by the same etchant than the second optical wave guiding layer is laminated, and a first speed increasing layer is formed on the second speed increasing layer. After laminating a first mask layer corresponding to the planar shape of the coupling portion and etching away the second speed increasing layer and the second optical waveguide layer at the opening of the first mask layer with an etchant, the first mask layer is removed. A first coupling portion forming step of forming a first coupling portion having a tapered end face on the second optical waveguide layer by removing the one mask layer and the remaining second acceleration layer. First optical waveguide on a substrate including the first coupling portion and the second optical waveguide layer and the second coupling portion and the third optical waveguide layer formed by the one coupling portion forming step and the second coupling portion forming step. The layers were laminated.

According to a sixth aspect of the present invention, a first optical waveguide portion having a first optical waveguide layer formed on a substrate and a second optical waveguide layer having an equivalent refractive index larger than that of the first optical waveguide layer are provided. A second optical waveguide portion, a third optical waveguide portion having a third optical waveguide layer having an equivalent refractive index smaller than that of the second optical waveguide layer, and a fourth optical waveguide portion having an equivalent refractive index smaller than that of the third optical waveguide layer. In a thin film optical waveguide device formed by coupling a fourth optical waveguide portion having an optical waveguide layer, a lower layer of the first optical waveguide layer located between the first optical waveguide portion and the second optical waveguide portion. And forming a taper-shaped first coupling portion in which the film thickness of the second optical waveguide layer gradually increases from 0 in the traveling direction of the guided light to the film thickness of the second optical waveguide layer. Located between the two optical waveguide portions and the third optical waveguide portion, the film thickness of the second optical waveguide layer is directed toward the traveling direction of the guided light. The second coupling portion is formed in a tapered shape until the thickness of the third optical waveguide layer is reduced, and the second coupling portion is formed between the third optical waveguide portion and the fourth optical waveguide portion. A fourth coupling portion is formed below the optical waveguide layer so that the film thickness of the third optical waveguide layer gradually decreases to 0 in the traveling direction of the guided light.

According to a seventh aspect of the present invention, the first thin film layer is laminated on the substrate, and the first speed increasing layer having a higher etching rate by the same etchant than the thin film is laminated on the first thin film layer. A second mask layer corresponding to the planar shape of the second coupling portion is laminated on the first speed increasing layer, and the first speed increasing layer and the first thin film at the opening of the second mask layer are formed by an etchant. After removing the layer by etching, the second mask layer and the remaining first acceleration layer are removed, and the first thin film layer is formed by laminating a second thin film layer on a substrate including the first thin film layer. And forming a second coupling portion in which the film thickness of the second optical waveguide layer formed of the second thin film layer is gradually reduced to the film thickness of the third optical waveguide layer formed of the second thin film layer. Two bonding portion forming step and the second bonding portion formed by this second bonding portion forming step And a second speed increasing layer having a higher etching rate by the same etchant than the second optical waveguide layer and the third optical waveguide layer on a substrate including the second optical waveguide layer and the third optical waveguide layer. Then, a first mask layer corresponding to the planar shape of the first coupling portion is laminated on this second speed increasing layer,
After etching away the second enhancement layer and the second optical waveguide layer at the opening of the first mask layer with an etchant, the second optical waveguide layer is tapered by removing the first mask layer. A first coupling part forming step of forming a first coupling part having a curved end surface, and the first coupling part, the second optical waveguide layer and the second coupling formed by the first coupling part forming step. Section and a third mask layer corresponding to the planar shape of the third coupling portion on the second speed increasing layer remaining during the etching for forming the first coupling portion on the substrate including the third optical waveguide layer. Then, the second mask layer and the third optical waveguide layer in the opening of the third mask layer are removed by etching with an etchant, and then the third mask layer and the remaining second mask layer are removed. By removing it, the third optical waveguide layer has a tapered end face. A third bonding portion forming step of forming three bonding portions, wherein the first bonding portion and the second bonding portion forming step, the second bonding portion forming step, and the third bonding portion forming step are performed. A first optical waveguide layer and a fourth optical waveguide layer were laminated on a substrate including two optical waveguide layers, the second coupling portion, the third optical waveguide layer and the third coupling portion.

According to an eighth aspect of the present invention, the first thin film layer is laminated on the substrate, and the first speed increasing layer having a higher etching rate by the same etchant than the thin film is laminated on the first thin film layer. A second mask layer corresponding to the planar shape of the second coupling portion is laminated on the first speed increasing layer, and the first speed increasing layer and the first thin film at the opening of the second mask layer are formed by an etchant. After removing the layer by etching, the second mask layer and the remaining first thin film layer are removed, a second thin film layer is laminated on a substrate including the first thin film layer, and the first thin film layer and A second coupling that forms a second coupling portion in which the film thickness of the second optical waveguide layer formed of the second thin film layer is gradually reduced to the thickness of the third optical waveguide layer formed of the second thin film layer. Part formation step, and the second combination part and the second combination part formed in the second combination part formation step. A second acceleration layer having an etching rate higher than that of the second optical waveguide layer and the third optical waveguide layer by the same etchant is laminated on a substrate including the optical waveguide layer and the third optical waveguide layer, A first mask layer corresponding to the planar shapes of the first bonding portion and the third bonding portion is laminated on the speed increasing layer, and the opening and the third bonding portion of the first mask layer corresponding to the first bonding portion. By introducing an etchant from an opening corresponding to the second speed-increasing layer corresponding to the first coupling portion and the second optical waveguide layer, and the second speed-increasing layer corresponding to the third coupling portion and the After removing the third optical waveguide layer by etching, the first mask layer and the remaining second speed-up layer are removed to form a second coupling portion having a tapered end surface in the second optical waveguide layer and the first coupling portion. Simultaneous formation of a third coupling portion having a tapered end face on the third optical waveguide layer First / third coupling portion simultaneous forming step, and the second coupling portion forming step and the first / third coupling portion simultaneous forming step, the first coupling portion, the second optical waveguide layer, and the first optical coupling layer. The first optical waveguide layer and the fourth optical waveguide layer were laminated on a substrate including two coupling portions, the third optical waveguide layer, and the third coupling portion.

According to a ninth aspect of the present invention, in a thin film optical waveguide device in which a plurality of optical waveguide layers are formed on a substrate via coupling portions, each optical waveguide layer is sequentially subjected to equivalent refraction in the traveling direction of guided light. The coupling portion formed between the optical waveguide layers is formed to have a high rate, and the film thickness gradually decreases from 0 in the traveling direction of the guided light below the optical waveguide layer located on the front side of the coupling portion. The film thickness is tapered until the film thickness of the optical waveguide layer on the rear side is reached.

[0016]

According to the invention of claim 1, a second optical waveguide layer is separately provided between the first optical waveguide layer and the third optical waveguide layer for coupling the guided light, and the first optical waveguide layer and the second optical waveguide layer are provided. The tapered first coupling portion is formed between the wave layer and the tapered second coupling portion between the second optical waveguide layer and the third optical waveguide layer. Optimal taper coupling can be configured without being constrained by the structure of the optical waveguide layers that are significantly different in the film thickness and the refractive index located in front and back of the optical waveguide layer. It is possible to achieve efficient coupling of guided light.

According to the second aspect of the present invention, since the tapered first coupling portion and the second coupling portion are formed by wet etching by photolithography, the coupling portions are formed by shadow mask method such as CVD. The positioning accuracy and reproducibility are better than those in the case where it is possible to prevent damage to the substrate.

According to the third aspect of the present invention, the etching rate of the first thin film layer is smaller than that of the second thin film layer. It is possible to prevent over-etching.

According to the fourth aspect of the invention, the first speed-increasing layer used in the first step of forming the first bonding portion having a tapered shape is not peeled and removed, and the first speed-increasing layer is subjected to the next taper shape. Since it is also used in the step of forming the second joint portion, the manufacturing process can be simplified.

In the invention according to claim 5, the first thin film layer and the second thin film layer are formed by forming a tapered end face on the first thin film layer and then laminating the second thin film layer thereon. The tapered shape of the second coupling portion provided between the second optical waveguide layer and the third optical waveguide layer formed by the second thin film layer can be formed sufficiently gently, which allows the film thickness by etching. It is possible to stably control the thickness of the third optical waveguide layer, which is difficult to control.

According to a sixth aspect of the invention, the thin-film optical waveguide device according to the first aspect having a tapered first coupling portion and a second coupling portion is used, and a third optical waveguide layer having a tapered shape is used. By forming the three-coupling portion, guided light can be efficiently guided from the third optical waveguide layer to the fourth optical waveguide layer, whereby the performance of the optical functional element can be sufficiently obtained.

According to the invention of claim 7, the second speed-increasing layer used in the step of forming the first joint portion having the tapered end face is not removed and removed, and the following second end having the tapered end face is formed. Since it is also used in the step of forming the three-bonded portion, the manufacturing process can be simplified.

In the invention described in claim 8, it is possible to shorten the manufacturing process by simultaneously performing the step of forming the tapered first connecting portion and the third connecting portion.

According to a ninth aspect of the invention, an optical waveguide layer for coupling guided light having an equivalent refractive index between the optical waveguide layers is provided in the optical path between the optical waveguide layers having greatly different equivalent refractive indexes, and the optical waveguide layer is provided. Form a tapered joint at the wave layer end,
By sequentially coupling the guided light, it becomes possible to finally couple the guided light to the target optical waveguide layer with high efficiency.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the invention described in claim 1 will be described with reference to FIG. Generally, in a thin film optical waveguide device, the refractive index and the film thickness of the waveguide layer may be changed for each waveguide region in order to have different functions for each waveguide region. For example,
In order to couple light between the thin film optical waveguide element and the outside, in order to excite TE mode and TM mode as guided light in a certain waveguide region (first optical waveguide part in FIG. 1) at the same time by a prism coupler or the like. And the TE mode and the TM mode that are simultaneously guided,
The refractive index and the film thickness of the waveguide layer are different from those of the waveguide region (the third optical waveguide section in FIG. 1) having the optimal waveguide layer for separating the M mode. Therefore, in this embodiment, in order to efficiently couple guided light with low loss between such waveguide layers having different refractive indexes and film thicknesses, two-stage taper coupling (first coupling portion a, first coupling in FIG. The two coupling portions b) are used to couple the guided light from the first optical waveguide portion to the third optical waveguide portion.

The structure of the thin film optical waveguide device in this embodiment will be described with reference to FIG. The substrate 6 includes a semiconductor Si substrate 7a (hereinafter referred to as a Si substrate 7a) and this Si substrate 7a.
The buffer layer 7b is formed on a by thermal oxidation or the like. A first optical waveguide layer 8, a second optical waveguide layer 9 and a third optical waveguide layer 10 are formed on the substrate 6. A part of the first optical waveguide layer 8 is composed of the second optical waveguide layer 9 and the third optical waveguide layer 1.
It covers the entire top of 0. A cladding layer 11 is laminated on the first optical waveguide layer 8. in this case,
The first optical waveguide portion A is composed of a first optical waveguide layer 8 and a cladding layer 11 in this order from the substrate 6 side. The second optical waveguide B is
The second optical waveguide layer 9, the first optical waveguide layer 8 and the cladding layer 11 are arranged in this order from the substrate 6 side. The third optical waveguide portion C is composed of a third optical waveguide layer 10, a first optical waveguide layer 8 and a cladding layer 11 in this order from the substrate 6 side.

A first coupling portion a is formed between the first optical waveguide portion A and the second optical waveguide portion B. In the first coupling portion a, the first optical waveguide layer 8 is formed to be inclined, The film thickness of the second optical waveguide layer 9 below the first optical waveguide layer 8 is gradually increased in a taper shape from 0 in the traveling direction of the guided light. A second coupling section b is formed between the second optical waveguide section B and the third optical waveguide section C, and the first optical waveguide layer 8 is formed to be inclined in the second coupling section b. The film thickness of the second optical waveguide layer 9 below the layer 8 is tapered in the traveling direction of the guided light. In this case, the equivalent refractive index of the second optical waveguide layer 9 of the second optical waveguide portion B is larger than the equivalent refractive index of the first optical waveguide layer 8 of the first optical waveguide portion A, and the third optical waveguide portion C
The equivalent refractive index of the third optical waveguide layer 10 is smaller than the equivalent refractive index of the second optical waveguide layer 9 of the second optical waveguide portion B.

The operation of light that has entered such a thin film optical waveguide device in such a structure will be described. Guided light 12 guided in the first optical waveguide layer 8 of the first optical waveguide portion A
First reaches the first coupling portion a. In the first coupling portion a, the equivalent refractive index gradually increases from the value of the first optical waveguide layer 8 to the value of the second optical waveguide layer 9, so that the guided light 12 has an equivalent refractive index. Coupling to the large second optical waveguide layer 9 can be performed with low loss without causing scattering or the like because the equivalent refractive index changes slowly at that time. Further, in this case, in the first coupling portion a, the second optical waveguide layer 9
Of the second optical waveguide layer 9 in which the tapered end of the second optical waveguide layer 9 is arranged in the lower layer of the first optical waveguide layer 8 as compared with the case of being arranged in the upper layer.
The mode coupling efficiency to is good.

The guided light 12 guided in the second optical waveguide layer 9 of the second optical waveguide section B reaches the second coupling section b. In the second coupling portion b, the equivalent refractive index gradually decreases from the value of the second optical waveguide layer 9 to the value of the third optical waveguide layer 10, and the change in the equivalent refractive index is gradual. Guided light 1
2 can be coupled to the third optical waveguide layer 10 with low loss without causing scattering or the like.

As described above, in order to couple the guided light 12 from the first optical waveguide A to the third optical waveguide C, the guided light 12 is directly fed from the first optical waveguide A to the third optical waveguide C. Instead of coupling, the guided light 12 is once coupled to the second optical waveguide B by taper coupling, and then the second optical waveguide B is again coupled.
From the third to the third optical waveguide portion C, the guided light beams 12 are coupled by taper coupling. Thus, by optimizing the waveguide configuration of the second optical waveguide B provided in the middle without being restricted by the waveguide configurations of the first optical waveguide A and the third optical waveguide C, It is possible to efficiently couple the guided light 12. That is, the film thickness of the first optical waveguide layer 8 is several times thicker than the film thickness of the third optical waveguide layer 10.
Even if the electric field intensity distribution size of the guided light 12 therein is several times larger than the electric field intensity distribution size of the guided light 12 in the third optical waveguide layer 10, the film thickness of the second optical waveguide layer 9 is set to the third value. By forming the optical waveguide layer 10 thicker than the film thickness of the optical waveguide layer 10, the thickness difference between the waveguide layers in the first coupling portion a is reduced, and the coupling length of the taper coupling portion is made long. The guided light 12 is more likely to be coupled than when the guided light 12 is directly coupled from the wave portion A to the third optical waveguide portion C. In addition, by gradually compressing the electric field intensity distribution size of the guided light 12 in the second optical waveguide layer 9 to the electric field intensity distribution size of the guided light 12 in the third optical waveguide layer 10 at the second coupling portion b, The guided light 12 can be coupled from the one optical waveguide portion A to the third optical waveguide portion C with high efficiency.

Next, an embodiment of the invention described in claim 2 will be described with reference to FIG. The description of the same parts as those in the first aspect of the present invention will be omitted, and the same reference numerals will be used for the same parts.

This example describes a method of manufacturing the thin film optical waveguide device (see FIG. 1) according to claim 1. First, in step (a), the substrate 6 is formed by stacking the buffer layer 7b on the Si substrate 7a by a thermal oxidation method or the like. On this substrate 6, plasma CV
The second optical waveguide layer 9 made of SiN (silicon nitride) is formed by the D method using SiH ₄ , NH ₃ , and an inert carrier gas. The film thickness of the second optical waveguide layer 9 is set to the film thickness of the embodiment described in claim 1 described above. On the second optical waveguide layer 9, S by the plasma CVD method is formed.
A first speed-increasing layer 13 made of iH ₄ , NH ₃ , N ₂ O, and SiON (silicon oxynitride) using an inert carrier gas is laminated, and a first bonding portion a is formed on the first speed-increasing layer 13. The first mask layer 14 corresponding to the planar shape of is laminated. The etching rate of the first acceleration layer 13 can be set higher than that of the second optical waveguide layer 9 for the hydrofluoric acid-based etchant.

Next, in the step (b), the first accelerating layer 13 and the second optical waveguide layer 9 in the opening of the first mask layer 14 are removed by etching with a hydrofluoric acid-based etchant to remove the first coupling portion a. To form. During this etching, the second optical waveguide layer 9
Since the etching rate of the first speed increasing layer 13 is higher than that of the first speed increasing layer 13, the etching end of the second optical waveguide layer 9 is processed into a taper shape, whereby a sufficiently gentle taper shape can be obtained.

Next, in the step (c), the first mask layer 14 is peeled and removed, and further the first speed increasing layer 13 is removed by a diluted dilute hydrofluoric acid etchant. At the time of this etching, the first speed increasing layer 13 has a much higher etching rate than the second optical waveguide layer 9, so that the first speed increasing layer 1
The change in shape of the taper end of the second optical waveguide layer 9 and the decrease in the film thickness of the buffer layer 7b after removing 3 are extremely slight and pose no problem. In addition, the steps (a) to (c) constitute a first bonding portion forming step of forming the first bonding portion a.

Next, in step (d), SiH ₄ , NH ₃ , N ₂ O and an inert carrier gas by plasma CVD are used on the second optical waveguide layer 9 on which the first coupling portion a is formed. The second speed increasing layer 15 made of SiON is laminated, and the second mask layer 16 corresponding to the planar shape of the second coupling portion b is laminated on the second speed increasing layer 15. In this case, the etching rate of the second acceleration layer 15 is set higher than that of the second optical waveguide layer 9 with respect to the hydrofluoric acid-based etchant.

Next, in step (e), the second speed-increasing layer 15 in the opening of the second mask layer 9 is removed by etching with a hydrofluoric acid-based etchant, and the second optical waveguide layer 9 is partially removed. Etching is performed to form the second coupling portion b. During this etching, the second speed increasing layer 1 is more than the second optical waveguide layer 9.
5 has a higher etching rate, the second optical waveguide layer 9
The end portion of is formed into a sufficiently gentle tapered shape by etching, whereby the second coupling portion b is formed. Then, this etching is performed so that the film thickness of the second optical waveguide layer 9 becomes the film thickness of the third optical waveguide layer 10 (see FIG. 1).

Next, in step (f), the second mask layer 16 is peeled and removed, and then the second speed increasing layer 15 is removed by etching with a diluted dilute hydrofluoric acid etchant.
In addition, the steps (d) to (f) constitute a second bonding portion forming step of forming the second bonding portion b.

Next, in the step (g), the first connecting portion a
SiH formed by the plasma CVD method on the substrate 6 on which the second optical waveguide layer 9, the second coupling portion b, and the third optical waveguide layer 10 are formed.
₄ , NH ₃ , N ₂ O, Si using an inert carrier gas
A first optical waveguide layer 8 made of ON is laminated, and SiH ₄ , NH ₃ , N by plasma CVD method is laminated on the first optical waveguide layer 8.
_A cladding layer 17 made of SiON using ₂ O ₂ and an inert carrier gas is laminated.

Here, a specific configuration example will be described.
Table 1 shows the relationship between the refractive index n and the film thickness t (wavelength 632.8 nm) of each layer in the thin film optical waveguide device of this example.

[0040]

[Table 1]

The equivalent refractive index of the second optical waveguide layer 9 is larger than that of the first optical waveguide layer 8, and the equivalent refractive index of the third optical waveguide layer 10 is larger than that of the second optical waveguide layer 9. Can be made smaller to form a thin-film optical waveguide device, and as a result, the first optical waveguide layer 8 and the third optical waveguide layer are coupled via the first coupling portion a and the second coupling portion b having a sufficiently gentle taper shape. The guided light 12 can be coupled to the layer 10 with high efficiency.

As described above, by forming the tapered first joint portion a and the second joint portion b by wet etching by photolithography, positioning accuracy and reproducibility are improved as compared with the shadow mask method by CVD or the like. The damage to the substrate 6 can be eliminated. Further, this makes it possible to manufacture a small-sized thin film optical waveguide device for optical coupling between waveguides.

In this embodiment, the second connecting portion b is formed after forming the first connecting portion a, but the first connecting portion a may be formed after forming the second connecting portion b. Good.
The method of etching the first bonding portion a, the second bonding portion b, the first speed increasing layer 13 and the second speed increasing layer 15 using a hydrofluoric acid-based etchant is disclosed in Japanese Patent Application No. 24-24768.
This is the same as the etching method disclosed in the patent application already filed in No. 8 as "taper forming method of thin film structure element".

Next, an embodiment of the invention described in claim 3 will be described with reference to FIG. The description of the same parts as those in the first and second aspects of the present invention is omitted, and the same parts are designated by the same reference numerals.

First, in step (a), on the substrate 6,
A first thin film layer 18 made of SiH ₄ , NH ₃ , and SiN using an inert carrier gas is formed by the plasma CVD method. The film thickness of the first thin film layer 18 is adjusted to be the film thickness of the third optical waveguide layer 10.

Next, in the step (b), the first thin film layer 1
The first thin film layer 1 is composed of SiH ₄ and NH ₃ by plasma CVD and SiN using an inert carrier gas
The second thin film layer 19 having a smaller refractive index and a higher etching rate than that of No. 8 is formed. On the second thin film layer 19, SiH ₄ , NH ₃ , N ₂ O by plasma CVD method,
A first speed-increasing layer 20 made of SiON using an inert carrier gas is laminated, and a first bonding portion a is formed on the first speed-increasing layer 20.
The first mask layer 21 corresponding to the planar shape of is laminated. The etching rate of each layer increases in the order of the first thin film layer 18, the second thin film layer 19, and the first speed increasing layer 20 with respect to the hydrofluoric acid-based etchant. The steps (a) and (b) constitute a multilayer thin film forming step.

Next, in step (c), the first acceleration layer 20, which corresponds to the opening of the first mask layer 21, the second thin film layer 19, and the first thin film layer 18 are etched with a hydrofluoric acid-based etchant. Then, the first joint portion a is formed. At the time of this etching, since the first acceleration layer 20 has the highest etching rate, the etching ends of the second thin film layer 19 and the first thin film layer 18 can have a sufficiently gentle tapered shape.
In this case, the taper end of the first thin film layer 18 has a steeper angle than that of the second thin film layer 19, but since it is still sufficiently gentle, there is almost no deterioration in the guided light coupling efficiency.

Next, in the step (d), the first mask layer 21 is peeled and removed, and the first speed increasing layer 20 is removed by a diluted dilute hydrofluoric acid etchant. At this time, since the first speed increasing layer 20 has a much higher etching rate than the first thin film layer 18 and the second thin film layer 19, the second thin film after the first speed increasing layer 20 is removed. The change in shape of the taper end of the layer 19 and the first thin film layer 18 and the decrease in the thickness of the buffer layer 7b are extremely slight and pose no problem. It should be noted that steps (c) to (d) constitute a first joint portion forming step.

Next, in the step (e), the second thin film layer 1
On top of 9 by plasma CVD method SiH ₄ , NH ₃ , N
_{A second} acceleration layer 22 using ₂ O ₂ and an inert carrier gas is laminated, and a second mask layer 23 corresponding to the planar shape of the second coupling portion is laminated on this second acceleration layer 22. Second speed increasing layer 22
The etching rate can be higher than the etching rate of the second thin film layer 19 with respect to the hydrofluoric acid-based etchant.

Next, in the step (f), the second acceleration layer 22 corresponding to the opening of the second mask layer 23 is removed by etching and the second thin film layer 19 is etched by a hydrofluoric acid-based etchant to obtain a second The joint b is formed. In this case, since the second accelerating layer 22 on the second thin film layer 19 has a higher etching rate, the end portion of the second thin film layer 19 is processed into a tapered shape, thereby obtaining a sufficiently gentle tapered shape. be able to. Further, since the etching rate of the first thin film layer 18 with respect to the hydrofluoric acid-based etchant is smaller than that of the second thin film layer 19, even if the etching time is slightly exceeded, the film loss of the first thin film layer 18 in this portion can be reduced. As a result, the film thickness corresponding to the third optical waveguide layer 10 (see FIG. 1) can be stably formed.

Next, in the step (g), the second mask layer 23 is peeled and removed, and the second speed increasing layer 22 is removed using a diluted dilute hydrofluoric acid etchant. It should be noted that steps (e) to (g) constitute a second joint portion forming step.

Next, in the step (h), the first connecting portion a
On the substrate 6 including the second optical waveguide layer 19 including the second thin film layer 19 and the first thin film layer 18, the second coupling portion b, and the third optical waveguide layer 10 including the first thin film layer 18. Plasma CVD
A first optical waveguide layer 8 made of SiH ₄ , NH ₃ , N ₂ O, and SiON using an inert carrier gas,
Further, a clad layer 24 made of SiH ₄ , NH ₃ , N ₂ O and SiON using an inert carrier gas is laminated on the first optical waveguide layer 8 by the plasma CVD method.

Here, a concrete configuration example will be described.
Table 2 shows the relationship between the refractive index n and the film thickness t (wavelength 632.8 nm) of each layer in the thin film optical waveguide device of this example.

[0054]

[Table 2]

The equivalent refractive index of the second optical waveguide layer 9 is larger than that of the first optical waveguide layer 8, and the equivalent refractive index of the third optical waveguide layer 10 is larger than that of the second optical waveguide layer 9. It is possible to form a thin film optical waveguide device by making the first optical waveguide layer 8 and the third optical waveguide layer 8 via the first coupling portion a and the second coupling portion b each having a sufficiently gentle taper shape. The guided light 12 can be coupled to the layer 10 with high efficiency.

As described above, since the etching rate of the first thin film layer 18 is smaller than that of the second thin film layer 19, the first thin film layer 18 is formed when the second bonding portion b is formed by wet etching. Can prevent over-etching of
Thereby, the film thickness of the third optical waveguide layer 10 including the first thin film layer 18 can be stably formed. When a tapered end face is further formed on the first thin film layer 18 in order to form a functional element in the third optical waveguide layer 10 including the first thin film layer 18, the taper shape of the tapered end face of the first thin film layer 18 is formed. The (taper ratio) can be changed as compared with the first joint portion a. Thereby, the taper shape of the functional element formed in the third optical waveguide layer 10 can be optimized separately from the taper shape of the first coupling portion a. In addition, in the present embodiment, the second joint portion b was formed after the first joint portion a was formed, but conversely, the first joint portion a is formed after the second joint portion b is formed. May be.

Next, an embodiment of the invention described in claim 4 will be described with reference to FIGS. 4 and 5. The description of the same parts as those in the first to third aspects of the present invention is omitted, and the same parts are designated by the same reference numerals.

The invention according to claim 2 and claim 3 described above.
In the described invention, after forming the first joint portion a, the first speed increasing layers 13 and 20 were also peeled and removed, whereas in the present embodiment, after forming the first joint portion a, First speed increasing layer 1
It is adapted to be used also in the subsequent step of forming the second joint portion b while leaving 3 and 20 without peeling and removing.

Specifically, the steps of FIGS. 4A to 4G correspond to the steps of FIGS. 2A to 2G. In this case, the first speed increasing layer 13 is not present in FIG. 2C, but the first speed increasing layer 13 is present in FIG. 4C. Also,
Similarly, the steps of FIGS. 5A to 5H are similar to those of FIG.
This corresponds to the steps (a) to (h). In this case, although there is no first speed increasing layer 20 in FIG.
In (d), the first speed increasing layer 20 is present.

As described above, the first speed-increasing layers 13 and 20 used in the first taper-shaped first joint forming step are not peeled and removed, and the first speed-increasing layers 13 and 20 are removed as follows. The manufacturing process can be simplified and the manufacturing cost can be reduced by using the same in the tapered second joint forming process.

Next, an embodiment of the invention described in claim 5 will be described with reference to FIGS. 6 and 7. The description of the same parts as those in the first to fourth aspects of the present invention is omitted, and the same parts are designated by the same reference numerals.

First, the first embodiment will be described with reference to FIG. 6A to 6I show an example of a method for manufacturing the thin film optical waveguide device according to claim 1 described above. First, in step (a), the substrate 6 is formed by stacking the buffer layer 7b on the Si substrate 7a by a thermal oxidation method or the like. On the substrate 6, SiH ₄ , NH ₃ and an inert carrier gas are used to form Si by plasma CVD.
A first thin film layer 25 made of N is formed.

Next, in step (b), SiH ₄ , NH by plasma CVD is formed on the first thin film layer 25.
₃ , N ₂ O, a first speed increasing layer 26 made of SiON using an inert carrier gas is laminated, and a second mask layer corresponding to the planar shape of the second coupling portion b is laminated on the first speed increasing layer 26. 27 is laminated. The etching rate of the first acceleration layer 26 can be higher than that of the first thin film layer 25 with respect to the hydrofluoric acid-based etchant.

Next, in the step (c), the first accelerating layer 26 and the first thin film layer 25 corresponding to the opening of the second mask layer 27 are etched with a hydrofluoric acid-based etchant to form the second bonding portion b. To form. At the time of this etching, the etching speed of the first speed increasing layer 26 is higher than that of the first thin film layer 25, so that the etching end of the first thin film layer 25 is processed into a taper shape, thereby forming a sufficiently gentle taper shape. Obtainable.

Next, in the step (d), the second mask layer 27 is peeled and removed, and further the first speed increasing layer 26 is removed by a diluted dilute hydrofluoric acid etchant. At the time of this etching, the first speed increasing layer 26 has a much higher etching rate than the first thin film layer 25.
The change in shape of the taper end of the first thin film layer 25 and the decrease in the film thickness of the buffer layer 7b after removing 6 are extremely slight and pose no problem. In addition, the steps (a) to (d) constitute a second bonding portion forming step of forming the second bonding portion b.

Next, in the step (e), the first thin film layer 2
Si on the substrate 6 on which the film 5 is formed by the plasma CVD method.
A second thin film layer 28 composed of H ₄ , NH ₃ and SiN using an inert carrier gas is laminated. In this case, the thickness of the second thin film layer 28 is set to the thickness of the third optical waveguide layer 10 (see FIG. 1). As a result, the third optical waveguide layer 10 including the second coupling portion b and the second thin film layer 28 is formed.

Next, in the step (f), the second joint b
And the plasma C on the substrate 6 on which the second thin film layer 28 is formed.
A second speed increasing layer 29 made of SiH ₄ , NH ₃ , N ₂ O by the VD method and SiON using an inert carrier gas is laminated, and the planar shape of the first coupling portion a is formed on the second speed increasing layer 29. The first mask layer 30 corresponding to is laminated. In this case, the etching rate of the second acceleration layer 29 can be set higher than the etching rates of the second thin film layer 28 and the first thin film layer 25 with respect to the hydrofluoric acid-based etchant.

Next, in the step (g), the second acceleration layer 29 corresponding to the opening of the first mask layer 30 is etched with a hydrofluoric acid type etchant, and the second thin film layer 28 and the first thin film layer 25 are etched. Etching is performed to form the first joint portion a. In this case, the second thin film layer 28 and the first thin film layer 25
The etching end of is processed into a taper shape,
A sufficiently gentle tapered end shape can be obtained.

Next, in the step (h), the first mask layer 30 is peeled and removed, and further the second speed increasing layer 29 is removed by a diluted diluted hydrofluoric acid etchant. It should be noted that the steps (e) to (h) constitute a first joint portion forming step of forming the first joint portion a.

Next, in the step (i), the first connecting portion a
On the substrate 6 including the second optical waveguide layer 9 including the second thin film layer 28 and the first thin film layer 25, the second coupling portion b, and the third optical waveguide layer 10 including the second thin film layer 28. , Plasma CVD
A first optical waveguide layer 8 made of SiH ₄ , NH ₃ , N ₂ O, and SiON using an inert carrier gas,
Further, a clad layer 31 made of SiH ₄ , NH ₃ , N ₂ O and SiON using an inert carrier gas is laminated on the first optical waveguide layer 8 by a plasma CVD method.

Here, a specific example will be described. Table 3 shows
It shows the relationship between the refractive index n and the film thickness t (wavelength 632.8 nm) of each layer in the thin film optical waveguide device.

[0072]

[Table 3]

In this case, the equivalent refractive index of the second optical waveguide layer 9 is larger than that of the first optical waveguide layer 8, and the equivalent refractive index of the third optical waveguide layer 10 is equivalent to that of the second optical waveguide layer 9. By manufacturing a thin film optical waveguide device having a refractive index smaller than that of the refractive index, the first optical waveguide layer 8 to the third optical waveguide layer 10 via the first coupling portion a and the second coupling portion b having a sufficiently gentle taper shape.
The guided light 12 can be coupled with high efficiency.

As a result, the tapered end of the first thin film layer 25 is first formed, and then the second thin film layer 28 is laminated on the upper end of the first thin film layer 25 so that the tapered thickness of the second coupling portion b is reduced. Therefore, the above-mentioned claims 2, 3 and 4 are adopted.
This is an effective means when it is difficult to control the film thickness of the third optical waveguide layer 10 at the same time when the second coupling portion b is formed by etching in the described embodiment.

Next, a second embodiment will be described with reference to FIG. 7 (a) to 7 (i) show another example of the method for manufacturing the thin film optical waveguide device according to claim 1 described above. This step is almost the same as the above-described steps of FIGS. 6A to 6I, but here, in particular, the etching rates of the first thin film layer 25 and the second thin film layer 28 for the hydrofluoric acid-based etchant are changed. ing. That is, specifically, the first thin film layer 2
5 is formed of SiH ₄ and NH ₃ by a plasma CVD method and SiN using an inert carrier gas, and the second thin film layer 28 is formed.
Is formed of SiN by the same plasma CVD method using SiH ₄ , NH ₃ , and an inert carrier gas, which has a smaller refractive index than the first thin film layer 25 and a high etching rate. In FIG. 7, it can be seen that the taper ratios are different as shown in (g) and (h).

As a result, when the tapered end face (second coupling portion b) is formed in the third optical waveguide layer 10 including the second thin film layer 28, the taper end face of the second thin film layer 28 (taper ratio) is formed. The taper shape of the functional element formed in the third optical waveguide layer 10 can be optimized by changing it as compared with the first coupling portion a.

As can be seen from the two embodiments described above,
The second optical waveguide layer 9 formed by the first thin film layer 25 and the second thin film layer 28 is formed by forming a tapered end face on the first thin film layer 25 and then stacking the second thin film layer 28 on the end face. And the third optical waveguide layer 10 formed by the second thin film layer 28.
The taper shape of the second coupling portion b provided between the first optical waveguide layer 10 and the second optical waveguide layer 10 can be formed to be sufficiently gentle, so that the thickness of the third optical waveguide layer 10, which is difficult to control by etching, can be stably controlled. be able to.

Next, an embodiment of the invention described in claim 6 will be described with reference to FIG. The description of the same parts as those in the first to fifth aspects of the present invention will be omitted, and the same reference numerals will be used for the same parts.

This embodiment uses the two-stage optical waveguide coupling of the first coupling portion a and the second coupling portion b in the thin film optical waveguide device according to claim 1 described above, and further the third optical waveguide layer 10 is used. The tapered end face formed in 1 has a function of totally reflecting or refracting the guided light 12.

The structure from the first optical waveguide portion A to the third optical waveguide portion C is the thin film optical waveguide device according to claim 1 (see FIG. 1).
Since it is the same as, the description here is omitted. The substrate 6 is obtained by laminating a buffer layer (SiO ₂ ) 7b formed by thermal oxidation or the like on a semiconductor Si substrate 7a, but the buffer layer 7b is not necessarily used when using a substrate that does not absorb light. There is no. The fourth optical waveguide portion D includes a fourth optical waveguide layer 32 (made of the same thin film as the first optical waveguide layer 8) from the substrate 6 side,
The clad layers 11 are laminated in this order. A tapered third coupling portion c is formed between the fourth optical waveguide portion D and the third optical waveguide portion C. This third joint c
Is the third optical waveguide layer 10, the first optical waveguide layer 8 and the cladding layer 1.
1 and the thickness of the third optical waveguide layer 10 is formed on the tapered end face which gradually decreases to 0 in the traveling direction of the guided light 12. Further, here, the equivalent refractive index of the fourth optical waveguide layer 32 is formed to be smaller than the equivalent refractive index of the third optical waveguide layer 10. In addition, the relationship of the equivalent refractive index from the first optical waveguide layer 8 to the third optical waveguide layer 10 is as follows:
Similar to the described embodiment.

In such a structure, the guided light 12 is
Similar to the above-described embodiment of claim 1, the first optical waveguide layer 8 is highly efficiently coupled to the third optical waveguide layer 10 via the tapered first coupling portion a and the second coupling portion b. . And
The guided light 12 guided in the third optical waveguide layer 10 reaches the third coupling portion c. At this time, compared with the equivalent refractive index of the fourth optical waveguide layer 32 (TE mode: N _E4 , TM mode: N _M4 ), the equivalent refractive index of the third optical waveguide layer 10 (TE mode: N _E3 ,
Since the TM mode: N _M3 ) is large, the incident angle α of the guided light 12 with respect to the planar shape of the third coupling portion c is α> ar.
The TE-mode guided light 12 with csin (N _E4 / N _E3 ) is totally reflected, and the TE-mode guided light 12 with α <arcsin (N _E4 / N _E3 ) is refracted. Similarly, α> arcs
The TM mode guided light 12 with in (N _M4 / N _M3 ) is totally reflected, and the TM mode guided light 12 with α <arcsin (N _M4 / N _M3 ) is refracted. Furthermore, since the third coupling portion c has a gentle teper shape, so-called Fresnel reflection does not occur during refraction, and efficient total reflection / total refraction can be achieved. Waveguide elements can be constructed.

Table 4 shows specific examples of the thin film optical waveguide device. Similar to the case of the examples described above (Tables 1 to 3), the relationship between the refractive index n of each layer and the film thickness t (wavelength 632.8 nm) is shown.

[0083]

[Table 4]

As described above, the thin film optical waveguide device according to claim 1 having the tapered first coupling portion a and the second coupling portion b is further provided with the tapered third coupling portion c. Since the guided light 12 is efficiently guided to the optical waveguide layer 32, it is possible to obtain a thin film optical waveguide device having high functional efficiency of total reflection / total refraction.

Next, an embodiment of the invention described in claim 7 will be described with reference to FIG. The description of the same parts as those in the first to sixth aspects of the present invention will be omitted, and the same reference numerals will be used for the same parts.

This embodiment describes a method of manufacturing the thin film optical waveguide device (see FIG. 8) described in claim 6. First, in step (a), a first thin film layer 33 made of SiH ₄ , NH ₃ and SiN using an inert carrier gas is formed on the substrate 6 by a plasma CVD method. On this first thin film layer 33, a first speed increasing layer 34 made of SiH ₄ , NH ₃ , N ₂ O, and SiON using an inert carrier gas by a plasma CVD method is laminated, and further, the first speed increasing layer 34. A second mask layer 35 corresponding to the planar shape of the second coupling portion b is laminated on top. The etching rate of the first acceleration layer 34 is set to be higher than that of the first thin film layer 33 with respect to the hydrofluoric acid-based etchant.

Next, in step (b), the first acceleration layer 34 corresponding to the opening of the second mask layer 35 and the first thin film layer 33 are etched with a hydrofluoric acid-based etchant to form a second bond. Form part b. At this time, since the etching rate of the first acceleration layer 34 is higher than that of the first thin film layer 33,
The etching end of the first thin film layer 33 is processed into a tapered shape, whereby a sufficiently gentle tapered shape can be obtained.

Next, in the step (c), the second mask layer 35 is peeled and removed, and the first speed increasing layer 34 is removed by using a diluted diluted hydrofluoric acid type etchant. At this time, since the first acceleration layer 34 has a much higher etching rate than the first thin film layer 33, the taper shape and the buffer of the first thin film layer 33 after the first acceleration layer 34 is removed. The film loss of the layer 7b is very slight and there is no problem.

Next, in the step (d), a second thin film made of SiH ₄ and NH ₃ by a plasma CVD method and SiN using an inert carrier gas is formed on the substrate 6 having the tapered first thin film layer 33. Layer 36 is laminated. The film thickness of the second thin film layer 36 at this time is controlled to be the film thickness of the third optical waveguide layer 10 described in claim 6. By performing such etching, the first thin film layer 33 having the same thickness is formed.
The third optical waveguide layer 10 including the second optical waveguide layer 9 including the second thin film layer 36, the tapered second coupling portion b, and the second thin film layer 36 is formed. It should be noted that the steps (a) to (d) constitute a second joint portion forming step. Further, in this case, the method of laminating the second thin film layer 36 after forming the tapered end on the first thin film layer 33 first is the same method as the embodiment (see FIGS. 6 and 7) described in claim 5 described above. Is.

Next, in step (e), on the substrate 6,
A second speed increasing layer 37 made of SiH ₄ , NH ₃ , N ₂ O by plasma CVD method and SiON using an inert carrier gas is laminated, and a plane of the first bonding portion a is formed on the second speed increasing layer 37. The first mask layer 38 corresponding to the shape is laminated. In this case, the etching rate of the second acceleration layer 37 is the same as that of the second thin film layer 36 and the first thin film layer 33 with respect to the hydrofluoric acid-based etchant.
Is higher than the etching rate of.

Next, in the step (f), the second accelerating layer 37 corresponding to the opening of the first mask layer 38 is etched with a hydrofluoric acid-based etchant and the second thin film layer 36 and the first thin film layer 33 are etched. By performing etching, the first joint portion a is formed. At this time, since the etching rate of the second acceleration layer 37 is higher than that of the first thin film layer 33 and the second thin film layer 36, the end portions of the first thin film layer 33 and the second thin film layer 36 are processed into a tapered shape. As a result, it is possible to obtain a sufficiently gentle tapered first coupling portion a.

Next, in step (g), only the first mask layer 38 is peeled and removed. At this time, the second speed increasing layer 37 is not peeled and removed, and is used in the subsequent step of forming the third joint portion c. It should be noted that the steps (e) to (g) constitute a first joint portion forming step.

Next, in the step (h), the second speed increasing layer 3
A third mask layer 39 corresponding to the planar shape of the third coupling portion c is laminated on the surface 7.

Next, in the step (i), the second speed increasing layer 37 corresponding to the opening of the third mask layer 39 and the second thin film layer 36 are etched with a hydrofluoric acid-based etchant. The third joint portion c is formed. At this time, since the second accelerating layer 37 on the second thin film layer 36 has a higher etching rate, the end portion of the second thin film layer 36 is processed into a taper shape, whereby a sufficiently gentle taper-shaped third portion is formed. The coupling part c can be formed.

Next, in the step (j), the third mask layer 39 is peeled and removed, and the second speed increasing layer 37 is removed by a diluted diluted hydrofluoric acid etchant. In addition, process (h)-
Up to the step (j), a third joint portion forming step is constituted.

Next, in the step (k), the first connecting portion a
A second optical waveguide layer 9 composed of the second thin film layer 36 and the first thin film layer 33, a second coupling part b, a third optical waveguide layer 10 composed of the second thin film layer 36, and a third coupling part c. SiH ₄ , NH ₃ , and N formed by plasma CVD on the substrate 6 on which
₂ O, a first optical waveguide layer 8 made of SiON using an inert carrier gas is laminated, and SiH ₄ , NH ₃ , N ₂ O, an inert carrier by a plasma CVD method is further laminated on the first optical waveguide layer 8. The cladding layer 11 made of SiON using gas is laminated. Thereby, the fourth optical waveguide layer 32 including the first optical waveguide layer 8 can be formed. In addition, in the process of the above-mentioned Example, although the 3rd joint part c was formed after forming the 1st joint part a, conversely, after forming the 3rd joint part c, the 1st joint part is formed. You may make it form a.

As described above, when the thin film optical waveguide device according to claim 6 (see FIG. 8) is manufactured, the second speed increasing layer 37 used in the first bonding portion forming step is replaced with the third bonding portion forming step. By also using it, it is possible to omit the step of forming a new speed-up layer for forming the tapered shape of the third coupling portion c, thereby improving the work efficiency and suppressing the production cost.

Next, an embodiment of the present invention will be described with reference to FIG. The description of the same parts as those in the first to seventh aspects of the invention is omitted, and the same parts are denoted by the same reference numerals.

This example describes a method of manufacturing the thin film optical waveguide device (see FIG. 8) according to claim 6 described above. First, in step (a), the first thin film layer 40 made of SiH ₄ , NH ₃ , and SiN using an inert carrier gas is formed on the substrate 6 by the plasma CVD method. On this first thin film layer 40, a first speed increasing layer 41 made of SiH ₄ , NH ₃ , N ₂ O, and SiON using an inert carrier gas is laminated by the plasma CVD method, and on this first speed increasing layer 41. Then, the second mask layer 42 corresponding to the planar shape of the second coupling portion b is laminated. In this case, the etching rate of the first acceleration layer 41 is higher than the etching rate of the first thin film layer 40 with respect to the hydrofluoric acid-based etchant.

Next, in step (b), the first accelerating layer 41 and the first thin film layer 40 are etched by a hydrofluoric acid-based etchant so as to correspond to the opening of the second mask layer 42, and the second bond is formed. Form part b. At this time, since the etching rate of the first acceleration layer 41 is higher than that of the first thin film layer 40, the end portion of the first thin film layer 40 is processed into a taper shape, thereby obtaining a sufficiently gentle taper shape. You can

Next, in the step (c), the second mask layer 42 is peeled and removed, and the first speed increasing layer 41 is removed by a diluted diluted hydrofluoric acid etchant. At this time, the first speed increasing layer 41
Has a much higher etching rate than the first thin film layer 40. Therefore, the taper shape change of the first thin film layer 40 and the film reduction degree of the buffer layer 7b after the removal of the first acceleration layer 41 are , Very few and no problem.

Next, in step (d), a second thin film layer 43 made of SiH ₄ , NH ₃ and SiN using an inert carrier gas is deposited on the substrate 6 by plasma CVD. In this case, the film thickness of the second thin film layer 43 is set to the film thickness of the third optical waveguide layer 10 in the thin film optical waveguide device according to the sixth aspect. Thus, the second optical waveguide layer 9 including the first thin film layer 40 and the second thin film layer 43, the tapered second coupling portion b, and the third optical waveguide layer 1 including the second thin film layer 43.
0 will be formed on the substrate 6. Further, here, after forming the tapered end on the first thin film layer 40 first,
By laminating the second thin film layer 43 on the upper portion of the second thin film layer 43, a tapered thickness reduction of the second coupling portion b is formed. It should be noted that the steps (a) to (d) constitute a second joint portion forming step.

Next, in the step (e), the second acceleration layer 4 made of SiH ₄ , NH ₃ , N ₂ O by the plasma CVD method and SiON using an inert carrier gas is formed on the substrate 6.
4 is formed, and the first mask layer 45 corresponding to the planar shapes of the first coupling portion a and the third coupling portion c is laminated on the second speed increasing layer 44. In this case, the etching rate of the second acceleration layer 44 can be made higher than the etching rates of the second thin film layer 43 and the first thin film layer 40 with respect to the hydrofluoric acid-based etchant.

Next, in the step (f), the second accelerating layer 44, the first thin film layer 40, and the second thin film layer 40 in the opening corresponding to the first bonding portion a of the first mask layer 45 are formed by a hydrofluoric acid-based etchant. By simultaneously etching both the thin film layer 43 and the second acceleration layer 44 and the second thin film layer 43 in the opening corresponding to the third bonding portion c of the first mask layer 45, the first bonding portion is formed. a and the third joint b are simultaneously formed. In this case, since the second acceleration layer 44 has a higher etching rate than the first thin film layer 40 and the second thin film layer 43, the left and right ends of the first thin film layer 40 and the second thin film layer 43 are It is formed in a sufficiently gentle taper shape. Further, in the simultaneous etching of both the first bonding portion a and the third bonding portion c, while the first thin film layer 40 of the first bonding portion a is being etched, the buffer is provided on the third bonding portion c side. Although the layer 7b is over-etched, the etching rate of the buffer layer 7b at this time is extremely smaller than the etching rates of the second thin film layer 43 and the second acceleration layer 44, so that the over-etched portion of the buffer layer 7b is Etched into a gentle taper. As a result, scattering of the guided light 12 due to the taper shape of the over-etched portion does not occur, and if the buffer layer 7b is made sufficiently thick, it will depend on the substrate 6 made of semiconductor Si as the underlying layer. No light absorption and no problem.

Next, in the step (g), the first mask layer 45 is peeled and removed, and the second speed increasing layer 44 is removed using a diluted dilute hydrofluoric acid type etchant. Thus, on the substrate 6, the first coupling portion a, the second optical waveguide layer 9 including the second thin film layer 43 and the first thin film layer 40, and the second coupling portion b,
The third optical waveguide layer 10 including the second thin film layer 43 and the third coupling portion c are formed. Note that the steps (e) to (g) constitute a first / third joint portion simultaneous forming step.

Next, in the step (h), the first optical waveguide layer 8 made of SiH ₄ , NH ₃ , N ₂ O and SiON using an inert carrier gas is laminated on the substrate 6 by the plasma CVD method, Further, a plasma C is formed on the first optical waveguide layer 8.
A clad layer 46 made of SiH ₄ , NH ₃ , N ₂ O by the VD method and SiON using an inert carrier gas is laminated. In this case, the first optical waveguide layer 8 is a portion corresponding to the fourth optical waveguide layer 32 in the thin film optical waveguide device according to claim 6. The refractive index n and the film thickness t (wavelength 632.8 nm) of each layer in this step are the same as the values in Table 4 in the embodiment of claim 6.

As described above, when the thin-film optical waveguide device according to claim 6 (see FIG. 8) is manufactured, the first coupling part a and the third coupling part c are simultaneously etched, so that the manufacturing process It is possible to shorten the manufacturing cost.

Next, an embodiment of the invention described in claim 9 will be described with reference to FIG. It should be noted that the description of the same parts as those in the first to eighth aspects of the present invention is omitted, and the same parts are designated by the same reference numerals.

In this embodiment, in a thin film optical waveguide device in which a plurality of optical waveguide layers are formed on a substrate 6 via coupling portions, each optical waveguide layer sequentially has an equivalent refractive index in the traveling direction of the guided light 12. Is formed such that the film thickness is gradually increased, and the film thickness gradually decreases from 0 in the traveling direction of the guided light 12 below the optical waveguide layer located on the front side of the optical waveguide layer. It is formed so as to taper up to the film thickness of the optical waveguide layer on the rear side.

A specific example will be described below. In FIG. 11, the substrate 6 is a buffer layer (Si
It is formed by stacking the O ₂ layer) 7b by a thermal oxidation method or the like. In this embodiment, guided light 1 is transmitted from the first optical waveguide layer 8 of the first optical waveguide portion A to the fourth optical waveguide layer 32 of the fourth optical waveguide portion D.
In order to couple the two, the second optical waveguide layer 9 and the third optical waveguide layer 10 having an equivalent refractive index between the first optical waveguide layer 8 and the fourth optical waveguide layer 32 are inserted in the optical path, and , The waveguide light intrusion end face of each optical waveguide layer is coupled to the lower layer of the optical waveguide layer located in front of the optical waveguide layer so that the film thickness increases in a tapered manner in the traveling direction of the waveguide light 12 (first coupling portion a, The second coupling part b,
It has a third coupling part c). Further, a clad layer 47 also serving as a protective film is laminated on the uppermost layer of the substrate 6 on which the respective optical waveguide layers and the respective coupling portions are formed. in this case,
Each of the fourth optical waveguide layer 32, the third optical waveguide layer 10, the second optical waveguide layer 9, the first optical waveguide layer 8 and the cladding layer 47 can be formed by a plasma CVD method or the like, and has a tapered shape. Each joint can be formed by the etching method as described above.

Table 5 shows specific examples of the thin film optical waveguide device. Similar to the case of the examples described above (Tables 1 to 4), the relationship between the refractive index n of each layer and the film thickness t (wavelength 632.8 nm) is shown.

[0112]

[Table 5]

With the above-described structure, the equivalent optical index from the first optical waveguide layer 8 to the fourth optical waveguide layer 32 is too large, and the guided light 12 can be completely generated by forming one taper coupling. Even when it is impossible to couple them, or when the tapered coupling portion between the waveguides where the equivalent refractive index difference is too large cannot form a sufficiently gentle tapered shape, the first optical waveguide layer 8 and the fourth optical waveguide layer 32 are formed. By forming a second optical waveguide layer 9 and a third optical waveguide layer 10 having an equivalent refractive index located in the middle between them and forming a taper coupling portion at the waveguide end. 12 is gradually coupled from the first optical waveguide layer 8 to the second optical waveguide layer 9 and the third optical waveguide layer 10 in this order, so that the finally guided fourth optical waveguide layer 32 is provided with the guided light 12. Can be efficiently combined. In this case, the equivalent refractive index difference between the optical waveguide layers on the way is not so large as the equivalent refractive index difference between the first optical waveguide layer 8 and the fourth optical waveguide layer 32, and therefore the taper coupling portion has a very gentle taper. It is possible to realize perfect optical coupling between waveguides without having a shape.

[0114]

According to the invention of claim 1, a first optical waveguide portion having a first optical waveguide layer formed on a substrate, and a second optical waveguide having an equivalent refractive index larger than that of the first optical waveguide layer are provided. A thin-film optical waveguide device comprising a second optical waveguide section having a layer and a third optical waveguide section having a third optical waveguide layer having an equivalent refractive index smaller than that of the second optical waveguide layer, The film thickness of the second optical waveguide layer, which is located between the optical waveguide section and the second optical waveguide section, is below the first optical waveguide layer, and the thickness of the second optical waveguide layer gradually decreases from 0 in the traveling direction of the guided light. Forming a first coupling portion that increases in a taper shape to the thickness of the two optical waveguide layers, and is located between the second optical waveguide portion and the third optical waveguide portion, and A second coupling portion is formed in which the film thickness gradually decreases in the traveling direction of the guided light until reaching the film thickness of the third optical waveguide layer. Therefore, it is possible to configure an optimum taper coupling without being constrained by the structure of the optical waveguide layer having the film thickness and the refractive index that are largely different from each other with respect to the traveling direction of the guided light. It is possible to obtain a thin film optical waveguide device capable of achieving highly efficient coupling of guided light between different optical waveguide layers.

According to the second aspect of the present invention, the second optical waveguide layer is laminated on the substrate, and the etching rate by the same etchant on the second optical waveguide layer is higher than that of the second optical waveguide layer. A speed layer is stacked, a first mask layer corresponding to the planar shape of the first coupling portion is stacked on the first speed increasing layer, and the first speed increasing layer near the opening of the first mask layer is formed by an etchant. And etching the second optical waveguide layer, and then removing the first mask layer and the remaining first speed-up layer to form a first coupling portion having a tapered end face on the second optical waveguide layer. And an etching rate of the same etchant on the second optical waveguide layer of the first coupling portion formed by the first coupling portion forming step is higher than that of the second optical waveguide layer. The second speed increasing layer is laminated, and the second connecting portion is formed on the second speed increasing layer. A second mask layer corresponding to the planar shape is laminated, and an etching process is performed by an etchant up to the middle of the film thickness of the second speed increasing layer and the second optical waveguide layer at the opening of the second mask layer. After that, by removing the second mask layer and the remaining second acceleration layer, the film thickness of the second optical waveguide layer is gradually reduced to the film thickness of the third optical waveguide layer. A second coupling portion forming step of forming two coupling portions, and the first coupling portion and the second optical waveguide layer and the second coupling portion formed by these first and second coupling portion forming steps. Since the first optical waveguide layer is laminated on the substrate including the third optical waveguide layer, the tapered first coupling portion and the second coupling portion are formed by wet etching by a photolithography method to form the coupling portions. CV
Positioning accuracy and reproducibility are better than in the case of forming by a shadow mask method using D or the like, and damage to the substrate can be eliminated, and thus a small-sized thin film optical waveguide device with high coupling efficiency can be manufactured. It is a thing.

According to the third aspect of the present invention, the first thin film layer is laminated on the substrate, and the second thin film layer having a smaller refractive index than the thin film and a high etching rate by the same etchant is formed on the first thin film layer. A multilayer thin film forming step of stacking, and a first speed increasing layer having a higher etching rate by an etchant than the first thin film layer and the second thin film layer on the second thin film layer obtained by this multilayer thin film forming step. A first mask layer corresponding to the planar shape of the first coupling portion is laminated on the first speed increasing layer, and the first speed increasing layer and the first speed increasing layer at the opening of the first mask layer are stacked by an etchant. After the two thin film layers and the first thin film layer are removed by etching, the first mask layer and the remaining first acceleration layer are removed to form the first thin film layer and the second thin film layer. The tapered end face of the second optical waveguide layer And a second thin film on the second optical waveguide layer including a tapered end face of the first coupling portion formed by the first coupling portion forming step. A second speed-up layer having a higher etching rate with the same etchant than that of the layer is stacked, a second mask layer corresponding to the planar shape of the second coupling portion is stacked on the second speed-up layer, and the first layer is formed by the etchant. After etching away the second acceleration layer and the second thin film layer forming a part of the second optical waveguide layer in the opening of the second mask layer, the second mask layer and the remaining second enhancement layer are removed. Forming a second coupling part in which the film thickness of the second optical waveguide layer is gradually reduced to a film thickness of the third optical waveguide layer formed of the first thin film layer by removing the fast layer. A connecting portion forming step, and the multilayer thin film forming step and the first and second Since the first optical waveguide layer is laminated on the substrate including the first coupling portion, the second optical waveguide layer, the second coupling portion and the third optical waveguide layer formed by the coupling portion forming step, By making the etching rate of the first thin film layer smaller than that of the thin film layer, it is possible to prevent overetching of the first thin film layer when forming the second bonding portion by wet etching. The third optical waveguide layer composed of layers can be stably formed.

According to a fourth aspect of the present invention, in the first bonding portion forming step, the treatment is performed without removing the first speed increasing layer, and the remaining first speed increasing layer is then subjected to the second bonding portion forming step. Since the first speed-up layer used in the first taper-shaped first bonding portion forming step is not peeled and removed, the first speed-up layer is removed to the next taper shape. The manufacturing process can be simplified by using it also in the second bonding portion forming process, and thus the manufacturing cost can be reduced.

According to a fifth aspect of the present invention, a first thin film layer is laminated, and a first speed increasing layer having a higher etching rate by the same etchant than the thin film is laminated on the first thin film layer,
A second mask layer corresponding to the planar shape of the second coupling portion is laminated on the first speed increasing layer, and the first speed increasing layer and the first thin film layer at the opening of the second mask layer are formed by an etchant. After etching away, the second mask layer and the remaining first acceleration layer are removed, and the first thin film layer and the second thin film layer by laminating a second thin film layer on the substrate including the first thin film layer and A second coupling part forming a second coupling part in which the film thickness of the second optical waveguide layer composed of the second thin film layer is gradually reduced to the film thickness of the third optical waveguide layer composed of the second thin film layer. The same etchant as the second optical waveguide layer on the substrate including the forming step and the second coupling portion, the second optical waveguide layer, and the third optical waveguide layer formed by the second coupling portion forming step. The second speed-increasing layer, which has a high etching rate by the A first mask layer corresponding to the planar shape of the first portion is laminated, and the second speed-increasing layer and the second optical waveguide layer in the opening of the first mask layer are removed by etching with an etchant, and then the first mask layer is removed. A first coupling portion forming step of forming a first coupling portion having a tapered end surface on the second optical waveguide layer by removing the mask layer and the remaining second speed increasing layer. A first optical waveguide layer on a substrate including the first coupling portion and the second optical waveguide layer and the second coupling portion and the third optical waveguide layer formed by the coupling portion forming step and the second coupling portion forming step. As described above, since the tapered end surface is formed on the first thin film layer and then the second thin film layer is stacked thereon, the second thin film layer formed by the first thin film layer and the second thin film layer is formed. It is provided between the optical waveguide layer and the third optical waveguide layer formed by the second thin film layer. It is possible to form the tapered shape of the second coupling portion to be sufficiently gentle, and thereby to stably control the film thickness of the third optical waveguide layer, which is difficult to control the film thickness by etching. ..

According to a sixth aspect of the present invention, a first optical waveguide portion having a first optical waveguide layer formed on a substrate and a second optical waveguide layer having an equivalent refractive index larger than that of the first optical waveguide layer are provided. A second optical waveguide portion, a third optical waveguide portion having a third optical waveguide layer having an equivalent refractive index smaller than that of the second optical waveguide layer, and a fourth optical waveguide portion having an equivalent refractive index smaller than that of the third optical waveguide layer. In a thin film optical waveguide device formed by coupling a fourth optical waveguide portion having an optical waveguide layer, a lower layer of the first optical waveguide layer located between the first optical waveguide portion and the second optical waveguide portion. And forming a taper-shaped first coupling portion in which the film thickness of the second optical waveguide layer gradually increases from 0 in the traveling direction of the guided light to the film thickness of the second optical waveguide layer. Located between the second optical waveguide portion and the third optical waveguide portion, the film thickness of the second optical waveguide layer is set in the forward direction of the guided light. A second coupling portion is formed in a tapered shape until the film thickness of the third optical waveguide layer is reached, and the second optical coupling portion is located between the third optical waveguide portion and the fourth optical waveguide portion. Since the third coupling portion in which the film thickness of the third optical waveguide layer gradually decreases to 0 in the traveling direction of the guided light is formed in the lower layer of the wave layer, the tapered first coupling portion and the third coupling portion are formed. The structure of the thin-film optical waveguide device according to claim 1, which has two coupling portions, is used to form a third coupling portion composed of a tapered third optical waveguide layer, so that the third optical waveguide layer to the fourth optical waveguide layer are formed. The guided light can be efficiently guided to the layer, whereby the performance of the optical functional element can be sufficiently brought out, and the thin film optical waveguide element with the highest coupling efficiency can be obtained.

According to a seventh aspect of the present invention, the first thin film layer is laminated on the substrate, and the first speed increasing layer having a higher etching rate by the same etchant than the thin film is laminated on the first thin film layer. A second mask layer corresponding to the planar shape of the second coupling portion is laminated on the first speed increasing layer, and the first speed increasing layer and the first thin film at the opening of the second mask layer are formed by an etchant. After removing the layer by etching, the second mask layer and the remaining first acceleration layer are removed, and the first thin film layer is formed by laminating a second thin film layer on a substrate including the first thin film layer. And forming a second coupling portion in which the film thickness of the second optical waveguide layer formed of the second thin film layer is gradually reduced to the film thickness of the third optical waveguide layer formed of the second thin film layer. Two bonding portion forming step, and the second bonding portion formed by this second bonding portion forming step And a second speed increasing layer having a higher etching rate by the same etchant than the second optical waveguide layer and the third optical waveguide layer on a substrate including the second optical waveguide layer and the third optical waveguide layer. Then, a first mask layer corresponding to the planar shape of the first coupling portion is laminated on the second speed increasing layer, and the second speed increasing layer and the second mask layer at the opening of the first mask layer are formed by an etchant. After etching and removing the optical waveguide layer, a first coupling portion forming step of forming a first coupling portion having a tapered end surface on the second optical waveguide layer by removing the first mask layer, Etching of forming the first coupling portion on the substrate including the first coupling portion, the second optical waveguide layer, the second coupling portion and the third optical waveguide layer formed by the first coupling portion forming step. In the plan view of the third joint on the second speed increasing layer that remained A corresponding third mask layer is laminated, and the second acceleration layer and the third optical waveguide layer in the opening of the third mask layer are removed by etching with an etchant. A third coupling portion forming step of forming a third coupling portion having a tapered end surface in the third optical waveguide layer by removing the second speed increasing layer, and the first coupling portion forming step and A substrate including the first coupling portion and the second optical waveguide layer, the second coupling portion, the third optical waveguide layer, and the third coupling portion, which are formed by the second coupling portion forming step and the third coupling portion forming step. Since the first optical waveguide layer and the fourth optical waveguide layer are laminated on the second optical waveguide layer, the second speed-increasing layer used in the step of forming the first coupling portion having the tapered end face is not peeled and removed, and the subsequent taper shape is formed. By using it for the formation process of the next third joint with the end face, the manufacturing process is It can be simplified, and thereby the manufacturing cost can be reduced.

According to an eighth aspect of the present invention, the first thin film layer is laminated on the substrate, and the first speed increasing layer having a higher etching rate by the same etchant than the thin film is laminated on the first thin film layer. A second mask layer corresponding to the planar shape of the second coupling portion is laminated on the first speed increasing layer, and the first speed increasing layer and the first thin film at the opening of the second mask layer are formed by an etchant. After removing the layer by etching, the second mask layer and the remaining first thin film layer are removed, a second thin film layer is laminated on a substrate including the first thin film layer, and the first thin film layer and A second coupling that forms a second coupling portion in which the thickness of the second optical waveguide layer formed of the second thin film layer is gradually reduced to the thickness of the third optical waveguide layer formed of the second thin film layer. Part formation step, and the second combination part and the second part formed by this second combination part formation step. On the substrate including the waveguide layer and the third optical waveguide layer, a second acceleration layer having a higher etching rate by the same etchant than the second optical waveguide layer and the third optical waveguide layer is laminated, A first mask layer corresponding to the planar shapes of the first bonding portion and the third bonding portion is laminated on the speed increasing layer, and the opening and the third bonding portion of the first mask layer corresponding to the first bonding portion. By introducing an etchant from an opening corresponding to the second speed-increasing layer corresponding to the first coupling portion and the second optical waveguide layer, and the second speed-increasing layer corresponding to the third coupling portion and the After the third optical waveguide layer is removed by etching, the first mask layer and the remaining second speed-up layer are removed to remove the first optical waveguide layer from the first coupling portion having a tapered end face and the second optical waveguide layer. Simultaneously forming a third coupling part with a tapered end face in the third optical waveguide layer First / third joint portion simultaneous forming step, and the second joint portion forming step and the first / third joint portion simultaneous forming step, the first joint portion, the second optical waveguide layer, and the second Since the first optical waveguide layer and the fourth optical waveguide layer are laminated on the substrate including the coupling portion, the third optical waveguide layer, and the third coupling portion, the tapered first coupling portion and the third coupling portion are formed. It is possible to shorten the manufacturing process by performing the forming process of
As a result, the manufacturing cost can be reduced.

According to a ninth aspect of the present invention, in a thin film optical waveguide device in which a plurality of optical waveguide layers are formed on a substrate via coupling portions, each optical waveguide layer sequentially has an equivalent refraction in the traveling direction of guided light. The coupling portion, which is formed so as to have a high refractive index and is disposed between the optical waveguide layers, has a film thickness of 0 in the traveling direction of the guided light below the optical waveguide layer located on the front side of the coupling portion.
Since the taper is gradually increased until the film thickness of the optical waveguide layer on the rear side of the optical waveguide layer, the equivalent refractive index between the optical waveguide layers is increased in the middle of the optical path between the optical waveguide layers where the equivalent refractive index greatly differs. By arranging an optical waveguide layer for coupling the guided light, and forming a tapered coupling portion at the end of this optical waveguide layer to sequentially couple the guided light, the waveguide light is finally guided to the target optical waveguide layer. Can be coupled with high efficiency, which makes it possible to completely couple guided light with one taper coupling due to the large difference in equivalent refractive index, or to form a sufficiently gentle tapered shape in the tapered coupling part between the optical waveguide layers. Even when it cannot be formed, perfect inter-waveguide coupling can be realized.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a thin film optical waveguide device according to an embodiment of the present invention.

FIG. 2 is a process drawing showing a method of manufacturing a thin film optical waveguide device according to an embodiment of the invention as set forth in claim 2.

FIG. 3 is a process drawing showing a method of manufacturing a thin film optical waveguide device according to an embodiment of the invention as set forth in claim 3.

FIG. 4 is a process drawing showing a method of manufacturing a thin film optical waveguide device according to an embodiment of the invention as set forth in claim 4.

FIG. 5 is a process drawing showing a method of manufacturing a thin film optical waveguide device which is another embodiment of the invention as set forth in claim 4.

FIG. 6 is a process drawing showing a method of manufacturing a thin film optical waveguide device which is a first embodiment of the invention as set forth in claim 5.

FIG. 7 is a process chart showing a method of manufacturing a thin film optical waveguide device according to a second embodiment of the invention as set forth in claim 5.

FIG. 8 is a sectional view showing a thin film optical waveguide device according to an embodiment of the present invention.

FIG. 9 is a process chart showing a method of manufacturing a thin film optical waveguide device according to an embodiment of the invention as set forth in claim 7.

FIG. 10 is a process drawing showing a method of manufacturing a thin film optical waveguide device according to an embodiment of the invention as set forth in claim 8.

FIG. 11 is a cross-sectional view showing a thin film optical waveguide device according to an embodiment of the present invention.

FIG. 12 is a process chart showing a conventional method of manufacturing an optical waveguide in which a tapered coupling portion is formed by using a shadow mask method.

[Explanation of symbols]

 6 substrate 8 1st optical waveguide layer 9 2nd optical waveguide layer 10 3rd optical waveguide layer 12 guided light 13 1st speedup layer 14 1st mask layer 15 2nd speedup layer 16 2nd mask layer 18 1st thin film layer 19 2nd thin film layer 20 1st speed increasing layer 21 1st mask layer 22 2nd speed increasing layer 23 2nd mask layer 25 1st thin film layer 26 1st speed increasing layer 27 2nd mask layer 28 2nd thin film layer 32th Four optical waveguide layer 34 1st speedup layer 35 2nd mask layer 36 2nd thin film layer 37 2nd speedup layer 38 1st mask layer 39 3rd mask layer 40 1st thin film layer 41 1st speedup layer 42 2nd Mask layer 43 Second thin film layer 44 Second speed-up layer 45 First mask layer A First optical waveguide part B Second optical waveguide part C Third optical waveguide part D Fourth optical waveguide part a First coupling part b Second Joining part c Third joining part

Claims (9)

[Claims] 1. A second optical waveguide portion having a first optical waveguide layer formed on a substrate and a second optical waveguide layer having an equivalent refractive index larger than that of the first optical waveguide layer. And a third optical waveguide portion having a third optical waveguide layer having an equivalent refractive index smaller than that of the second optical waveguide layer, wherein the first optical waveguide portion and the second optical waveguide element are combined. The film thickness of the second optical waveguide layer below the first optical waveguide layer located between the wave portion and the film thickness of the second optical waveguide layer gradually decreases from 0 in the traveling direction of the guided light. Forming a first coupling portion that increases in a taper shape until the film thickness of the second optical waveguide layer is between the second optical waveguide portion and the third optical waveguide portion. Thin film light, characterized by forming a second coupling portion tapering gradually toward the third optical waveguide layer. Waveguide device. 2. A second optical waveguide layer is laminated on a substrate, and a first speed increasing layer having an etching rate by the same etchant larger than that of the second optical waveguide layer is laminated on the second optical waveguide layer, A first mask layer corresponding to the planar shape of the first coupling portion is laminated on the first speed increasing layer, and the first speed increasing layer near the opening of the first mask layer and the second optical waveguide are stacked by an etchant. After etching the layer, the first mask layer and the remaining first speed-up layer are removed to form a first coupling part having a tapered end face in the second optical waveguide layer. And a second speed increasing layer having a higher etching rate by the same etchant than the second optical waveguide layer on the second optical waveguide layer of the first coupling portion formed by the first coupling portion forming step. Laminate the first speed-increasing layer on top of the After stacking two mask layers, etching with the etchant up to the middle of the film thickness of the second speed increasing layer and the second optical waveguide layer at the opening of the second mask layer, the second mask layer is formed. By removing the mask layer and the remaining second speed-up layer, a second coupling portion is formed in which the film thickness of the second optical waveguide layer gradually decreases to the film thickness of the third optical waveguide layer. A second coupling portion forming step, and the first coupling portion, the second optical waveguide layer, the second coupling portion and the third optical waveguide layer formed by the first and second coupling portion forming steps. A method of manufacturing a thin-film optical waveguide device, characterized in that a first optical waveguide layer is laminated on a substrate including. 3. A multi-layer thin film forming step of laminating a first thin film layer on a substrate, and laminating a second thin film layer having a smaller refractive index than this thin film and a high etching rate by the same etchant on the first thin film layer. And a first speed increasing layer having a higher etching rate by an etchant than the first thin film layer and the second thin film layer is laminated on the second thin film layer obtained by the multilayer thin film forming step. A first mask layer corresponding to the planar shape of the first coupling portion is laminated on the speed increasing layer, and the first speed increasing layer, the second thin film layer, and the first thin film layer at the opening of the first mask layer are formed by an etchant. After removing one thin film layer by etching, a second optical waveguide layer consisting of the first thin film layer and the second thin film layer by removing the first mask layer and the remaining first acceleration layer Form a first joint with a tapered end face And a second etch layer formed on the second optical waveguide layer including the tapered end surface of the first bond portion formed by the first bond portion forming step by the same etchant as compared with the second thin film layer. A second acceleration layer having a high etching rate is laminated, a second mask layer corresponding to the planar shape of the second bonding portion is laminated on the second acceleration layer, and an etchant is used to form an opening in the second mask layer. After removing the second acceleration layer and the second thin film layer forming a part of the second optical waveguide layer by etching, the second mask layer and the remaining second acceleration layer are removed. A second coupling part forming step of forming a second coupling part in which the thickness of the second optical waveguide layer is gradually reduced to the thickness of the third optical waveguide layer formed of the first thin film layer. The multilayer thin film forming process and the first and second joint forming processes A thin film optical waveguide device, wherein a first optical waveguide layer is laminated on a substrate including the formed first coupling portion, the second optical waveguide layer, the second coupling portion and the third optical waveguide layer. Manufacturing method. 4. The first bonding portion forming step is performed without removing the first speed increasing layer, and the remaining first speed increasing layer is also used after the second bonding portion forming step to be performed next. The method for producing a thin film optical waveguide device according to claim 2 or 3, characterized in that. 5. A first thin film layer is laminated, a first speed increasing layer having a higher etching rate by the same etchant than the thin film is stacked on the first thin film layer, and a first speed increasing layer is formed on the first speed increasing layer. Laminating a second mask layer corresponding to the planar shape of the two coupling portion,
After etching away the first speed increasing layer and the first thin film layer at the opening of the second mask layer with an etchant, the second mask layer and the remaining first speed increasing layer are removed, and By stacking a second thin film layer on a substrate including a first thin film layer, the thickness of the second optical waveguide layer formed of the first thin film layer and the second thin film layer is the third optical layer formed of the second thin film layer. A second coupling portion forming step of forming a second coupling portion that taperly decreases to the thickness of the wave layer, and the second coupling portion and the second optical waveguide formed by the second coupling portion forming step. A second acceleration layer having a higher etching rate by the same etchant than the second optical waveguide layer is stacked on the substrate including the layer and the third optical waveguide layer, and a first bond is formed on the second acceleration layer. The first mask layer corresponding to the planar shape of the part is laminated, and the first mask layer is After removing the second speed increasing layer and the second optical waveguide layer at the opening of the mask layer by etching, the second mask by removing the first mask layer and the remaining second speed increasing layer. A first coupling portion forming step of forming a first coupling portion having a tapered end face on the optical waveguide layer, and the first coupling portion formed by the first coupling portion forming step and the second coupling portion forming step. And a method of manufacturing a thin film optical waveguide device, characterized in that a first optical waveguide layer is laminated on a substrate including the second optical waveguide layer, the second coupling portion and the third optical waveguide layer. 6. A second optical waveguide section having a first optical waveguide layer formed on a substrate and a second optical waveguide layer having an equivalent refractive index larger than that of the first optical waveguide layer. A third optical waveguide having a third optical waveguide layer having an equivalent refractive index smaller than that of the second optical waveguide layer, and a fourth optical waveguide layer having a fourth optical waveguide layer having an equivalent refractive index smaller than that of the third optical waveguide layer. In a thin film optical waveguide device formed by coupling four optical waveguide portions, the second optical waveguide is located between the first optical waveguide portion and the second optical waveguide portion and is located below the first optical waveguide layer. A first coupling portion is formed in which the film thickness of the layer gradually increases from 0 in the traveling direction of the guided light to the film thickness of the second optical waveguide layer. The film thickness of the second optical waveguide layer located between the third optical waveguide portion and the third optical waveguide layer is the same as the film thickness of the third optical waveguide layer in the traveling direction of the guided light. Forming a second coupling portion that gradually decreases in taper shape, and is located between the third optical waveguide portion and the fourth optical waveguide portion, and the third optical waveguide is formed under the fourth optical waveguide layer. A thin-film optical waveguide device, characterized in that a third coupling portion is formed in which the film thickness of the wave layer gradually decreases to 0 in the traveling direction of the guided light. 7. A first thin film layer is laminated on a substrate, and a first acceleration layer having a higher etching rate by the same etchant than the thin film is laminated on the first thin film layer. A second mask layer corresponding to the planar shape of the second bonding portion is laminated on the layer, and the first speed increasing layer and the first thin film layer at the opening of the second mask layer are removed by etching with an etchant. After that, the second mask layer and the remaining first acceleration layer are removed, and the first thin film layer and the second thin film layer are laminated by laminating the second thin film layer on the substrate including the first thin film layer. A second coupling part forming step of forming a second coupling part in which the film thickness of the second optical waveguide layer consisting of is gradually reduced to the film thickness of the third optical waveguide layer consisting of the second thin film layer. , The second coupling portion and the second optical waveguide layer formed by the second coupling portion forming step. And a second speed increasing layer having an etching rate higher than that of the second light guiding layer and the third light guiding layer by the same etchant is laminated on the substrate including the third light guiding layer. A first mask layer corresponding to the planar shape of the first coupling portion is laminated on the layer, and the second speed increasing layer and the second optical waveguide layer at the opening of the first mask layer are removed by etching with an etchant. And a first coupling portion forming step of forming a first coupling portion having a tapered end surface on the second optical waveguide layer by removing the first mask layer. The second coupling portion and the second optical waveguide layer formed by the second coupling portion on the substrate including the second coupling portion and the third optical waveguide layer A third mask layer corresponding to the planar shape of the third joint is formed on the acceleration layer. And etching the second speed-up layer and the third optical waveguide layer at the opening of the third mask layer with an etchant, and then removing the third mask layer and the remaining second speed-up layer. And a third coupling part forming step of forming a third coupling part having a tapered end surface on the third optical waveguide layer by removing the first coupling part forming step and the second coupling part forming step. A first optical waveguide layer on a substrate including the first coupling portion, the second optical waveguide layer, the second coupling portion, the third optical waveguide layer, and the third coupling portion, which are formed by the third coupling portion forming step. And a method of manufacturing a thin-film optical waveguide device, which comprises laminating a fourth optical waveguide layer. 8. A first thin film layer is laminated on a substrate, and a first acceleration layer having an etching rate higher than that of this thin film by the same etchant is laminated on the first thin film layer, and the first acceleration layer is formed. A second mask layer corresponding to the planar shape of the second bonding portion is laminated on the layer, and the first speed increasing layer and the first thin film layer at the opening of the second mask layer are removed by etching with an etchant. After that, the second mask layer and the remaining first thin film layer are removed, a second thin film layer is laminated on a substrate including the first thin film layer, the first thin film layer and the second thin film layer. A second coupling portion forming step of forming a second coupling portion in which the film thickness of the second optical waveguide layer consisting of is gradually reduced to the thickness of the third optical waveguide layer consisting of the second thin film layer, The second coupling portion, the second optical waveguide layer, and the third optical waveguide formed in the second coupling portion forming step. A second acceleration layer having a higher etching rate by the same etchant than the second optical waveguide layer and the third optical waveguide layer is laminated on a substrate including a layer, and a first bond is formed on the second acceleration layer. Layer and a first mask layer corresponding to the planar shape of the third bonding portion are stacked, and an etchant is provided from the opening portion corresponding to the first bonding portion and the opening portion corresponding to the third bonding portion of the first mask layer. Etching the second speed increasing layer and the second optical waveguide layer corresponding to the first coupling portion and the second speed increasing layer and the third optical waveguide layer corresponding to the third coupling portion by introducing After the removal, the first mask layer and the remaining second speed-up layer are removed so that the first coupling portion having the tapered end face in the second optical waveguide layer and the tapered shape in the third optical waveguide layer. Simultaneous formation of the first and third joints that simultaneously form the third joint having an end face And a step of forming the second coupling portion and a step of simultaneously forming the first and third coupling portions, the first coupling portion and the second optical waveguide layer, the second coupling portion, and the third optical waveguide. A method of manufacturing a thin film optical waveguide device, characterized in that the first optical waveguide layer and the fourth optical waveguide layer are laminated on a substrate including a layer and the third coupling portion. 9. In a thin-film optical waveguide device having a plurality of optical waveguide layers formed on a substrate via coupling portions, each optical waveguide layer has an equivalent refractive index that sequentially increases in a traveling direction of guided light. The coupling portion formed and disposed between the optical waveguide layers has an optical waveguide layer having a film thickness gradually increasing from 0 in the traveling direction of the guided light below the optical waveguide layer located on the front side of the coupling portion. A thin-film optical waveguide device characterized by increasing in taper shape until the film thickness becomes