JP5316617B2 - Optical waveguide device and manufacturing method thereof - Google Patents

Description

  The present invention relates to an optical waveguide device and a manufacturing method thereof, and more particularly to an optical waveguide device in which a metal-loaded polarizer is disposed on a part of a substrate on which an optical waveguide is formed, and a manufacturing method thereof.

  In the optical communication field and the optical measurement field, an optical waveguide device in which an optical waveguide is formed on a substrate having an electrooptic effect, such as lithium niobate, is used as an optical modulator. In an optical waveguide device using a crystal substrate having an electro-optic effect, r33 having the largest electro-optic effect is generally used.

  For example, when X-cut lithium niobate is used, since r33 is in the horizontal direction of the crystal, the TM wave having a plane of polarization equal to the direction of r33 is selected as the light that acts on the electro-optic effect. For this reason, unnecessary TE waves are removed by a polarizer.

  The polarizer includes a rampole or polar core that is attached to the light incident / exit end face of a chip such as lithium niobate and inserted on the optical path as in Patent Document 1, or an optical crystal as in Patent Document 2. There is a metal loading type that absorbs a TE wave by loading a metal film such as aluminum on the optical waveguide formed in (1). In particular, the latter polarizer is suitable in terms of cost and workability because it can be implemented as part of the wafer process.

  FIG. 1 shows an example of a metal loaded polarizer 3 arranged on the surface of the substrate 1. In the metal loaded polarizer 3, a metal film 30 and oxygen deficient film bodies 32 and 31 are disposed on the front and back surfaces thereof. Such a film body has a function of preventing the metal film from being oxidized by coming into contact with the substrate 1 or coming into contact with outside air. Reference numeral 2 denotes an optical waveguide formed on the substrate 1.

A buffer layer such as a SiO ₂ film is often formed on the surface of the substrate 1. Such a buffer layer is disposed on the surface of the substrate 1 in proximity to the left and right of the metal loaded polarizer 3. When the buffer layer is disposed in the vicinity of the metal-loaded polarizer 3, the side surface of the metal film 30 is not exposed as in FIG. 1, but there is no buffer layer, or the metal-loaded polarizer 3 is not exposed. If they are arranged apart from each other, the side surfaces of the metal film are oxidized.

  In particular, in the optical waveguide device fabrication process, the metal film is etched by a cleaning process using an alkaline surfactant, which is a subsequent process, or by wet etching for removing the base metal after the gold electrode is formed. There was a problem that sufficient child functions could not be secured.

Japanese Patent Laid-Open No. 10-3064 JP-A-10-68830

  The problem to be solved by the present invention is to solve the above-described problems, suppress the oxidation of the metal film constituting the metal-loaded polarizer and the etching in the subsequent process of the manufacturing process, and the optical waveguide having excellent optical characteristics It is to provide a device and a manufacturing method thereof.

To solve the above problems, the invention according to claim 1 including a substrate having an electro-optic effect, an optical waveguide formed on the substrate so as to cover at least a portion of the optical waveguide, from the substrate-side low In an optical waveguide device having a refractive index material layer, a metal film, and a metal-loaded polarizer formed by sequentially laminating a low refractive index material layer, the low refractive index material layer is lower than the refractive index of the optical waveguide has a refractive index, with the said metal loaded type polarizer, a protective film so as to cover all the exposed portions of the metal film is formed, the protective film is a film of an oxygen-deficient state, film thickness and wherein the der Rukoto more than 200nm.

The invention according to claim 2, in the optical waveguide device according to claim 1, wherein the protective film is characterized in that a SiOx (However, x <2).

The invention according to claim 3 is the optical waveguide device according to claim 1 or 2, wherein the protective film is formed by a sputtering method.

The invention according to claim 4 is the optical waveguide device according to any one of claims 1 to 3, wherein there are two or more optical waveguides formed on the substrate, and the metal-loaded polarizer is formed of the optical waveguide. Of these, it is formed integrally so as to cover at least two or more optical waveguides.

The invention according to claim 5 is an optical waveguide having a substrate having an electro-optic effect, an optical waveguide formed on the substrate, and a metal loaded polarizer formed so as to cover at least a part of the optical waveguide. In the device manufacturing method, the metal-loaded polarizer is a film body in an oxygen-deficient state from the substrate side by disposing a masking material on the substrate, and having a refractive index lower than the refractive index of the optical waveguide. A low refractive index material layer having a refractive index, a metal film, and the low refractive index material layer are laminated in this order , and then the masking material is within a range of 0.3 to 2 mm from the position where the metal loaded polarizer is formed. Separated and rearranged on the substrate to form a protective film covering the entire metal-loaded polarizer and having a film thickness of 200 nm or more and the same oxygen deficient film as the low refractive index material layer It is characterized by doing.

The invention according to claim 6 is the method for manufacturing an optical waveguide device according to claim 5, wherein the protective film is formed by a sputtering method .

According to the invention of claim 1, an optical waveguide comprising a substrate having an electro-optic effect, an optical waveguide formed on the substrate, and a metal-loaded polarizer formed so as to cover at least a part of the optical waveguide in the device, the said metal loaded type polarizer, a protective film so as to cover all the exposed portions of the metal film is formed, the thickness of the protective film constituting the der because the metal loaded polarizer least 200nm It is possible to suppress the oxidation of the metal film and the etching in the subsequent process of the manufacturing process, and to provide an optical waveguide device having excellent optical characteristics.

Further , according to the first aspect of the present invention, the metal-loaded polarizer is laminated in the order of a low refractive index material layer, a metal film , and a low refractive index material layer from the substrate side, and the low refractive index material layer is a refractive index of the optical waveguide. Since the refractive index is lower than the refractive index, the low refractive index material layer on the substrate side suppresses the absorption of the TM wave of the light wave propagating through the optical waveguide by the metal layer (metal film), and the TE of the light wave Waves can be removed efficiently. Further, the deterioration of the metal layer (metal film) such as oxidation of the metal layer can be suppressed by the low refractive index material layer opposite to the substrate.

Further , according to the first aspect of the invention, since the protective film is a film body in an oxygen deficient state, the protective film is resistant to acid and alkali, oxidation and etching of the metal film are suppressed, and deterioration of optical characteristics can be prevented.

According to the invention of claim 2 , since the protective film is SiOx (x <2), the influence of the protective film on the light wave propagating through the optical waveguide is suppressed, and only the oxidation and etching of the metal film are prevented. In addition, an optical waveguide device having excellent optical characteristics can be provided. Further, when the film body sandwiching the metal film in the metal-loaded polarizer is composed of similar SiOx, the film body and the protective film can be integrated, and the entire surface of the metal film is coated with SiOx. Is possible.

According to the invention of claim 3, since the protective film is formed by sputtering, it is possible to obtain a protective film formed with high accuracy.

According to the invention of claim 4, there are two or more optical waveguides formed on the substrate, and the metal-loaded polarizer is integrally formed so as to cover at least two of the optical waveguides. Therefore, even for an optical waveguide device having a complicated waveguide structure such as DP-QPSK, the manufacturing process can be simplified as compared with the case where a polarizer is arranged on the incident end face of each optical waveguide. It becomes possible.

According to the invention of claim 5, an optical waveguide comprising a substrate having an electro-optic effect, an optical waveguide formed on the substrate, and a metal loaded polarizer formed to cover at least a part of the optical waveguide In the device manufacturing method, the metal-loaded polarizer is a film body in an oxygen-deficient state from the substrate side by disposing a masking material on the substrate, and having a refractive index lower than the refractive index of the optical waveguide. A low refractive index material layer having a refractive index, a metal film, and the low refractive index material layer are laminated in this order , and then the masking material is within a range of 0.3 to 2 mm from the position where the metal loaded polarizer is formed. Separated and rearranged on the substrate to form a protective film covering the entire metal-loaded polarizer and having a film thickness of 200 nm or more and the same oxygen deficient film as the low refractive index material layer After the metal film oxidation and manufacturing process Can be suppressed etching by degree, it is possible to manufacture an excellent optical waveguide device of the optical properties. In addition, it is not necessary to separately prepare a masking material for forming the protective film, and an increase in manufacturing cost can be suppressed.

Furthermore , the metal-loaded polarizer has an oxygen-deficient film body disposed so as to sandwich the metal film, and the protective film is made of the same oxygen-deficient film body. After forming the oxygen-deficient film body on the upper surface side of the metal film, especially the manufacturing process of the child, the protective film can be formed simply by changing the position of the masking material without changing the film-forming material Is possible. In addition, since the protective film is formed of the same material as the film body sandwiching the metal film, the film body and the protective film can be integrated, and problems such as the protective film being easily peeled off hardly occur.

According to the invention of claim 6, since the protective film is formed by sputtering, the protective film can be formed with high accuracy.

It is a figure explaining the conventional optical waveguide device. It is a figure explaining the optical waveguide device of this invention. It is a figure explaining the manufacturing method of the optical waveguide device of this invention. It is a figure explaining the masking material used for the manufacturing method of the optical waveguide device of this invention. It is a figure explaining the example which comprises a part of optical waveguide device by PLC and uses a metal loading type polarizer.

Hereinafter, the present invention will be described in detail using preferred examples. FIG. 2 shows an optical waveguide device of the present invention.
The present invention relates to an optical waveguide device having a substrate 1 having an electro-optic effect, an optical waveguide 2 formed on the substrate, and a metal loaded polarizer 3 formed so as to cover at least a part of the optical waveguide. The metal-loaded polarizer is characterized in that a protective film 33 is formed so as to cover all exposed portions of the metal film 30.

  In FIG. 2, in the metal-loaded polarizer, film bodies 31 and 32 in an oxygen deficient state are disposed so as to sandwich the metal film 30, thereby suppressing oxidation of the metal film 30. Furthermore, by covering with the protective film 33, it is possible to suppress the oxidation of the metal film constituting the metal-loaded polarizer and the etching in the subsequent process of the manufacturing process, and to provide an optical waveguide device having excellent optical characteristics. . An arrow L indicates the propagation direction of the light wave propagating through the optical waveguide 2.

As the substrate 1 having an electro-optic effect, any single crystal of LiNbO ₃ , LiTaO ₃ or PLZT (lead lanthanum zirconate titanate) can be suitably used. The optical waveguide 2 formed on the substrate is formed, for example, by thermally diffusing a high refractive index material such as titanium (Ti) on a LiNbO ₃ substrate (LN substrate). Further, a rib-type optical waveguide in which grooves are formed on both sides of a portion that becomes an optical waveguide can also be used.

The optical waveguide device can be provided with a modulation electrode for modulating a light wave propagating through the optical waveguide. For example, a signal electrode or a ground electrode can be provided as a modulation electrode, and a Ti / Au electrode pattern can be formed on the surface of the substrate 1 and formed by a gold plating method or the like. Furthermore, a buffer layer such as dielectric SiO ₂ can be provided on the substrate surface after the formation of the optical waveguide, if necessary, except where the metal-loaded polarizer is formed.

  In the optical waveguide device of the present invention, a metal loaded polarizer is disposed on a substrate on which an optical waveguide is formed. The width of the metal film 30 along the optical waveguide (lateral length in FIG. 2) is about 0.2 to 2 mm. Aluminum can be suitably used as the metal film. Further, as the film body sandwiching the metal film 30 from above and below, a film body in an oxygen deficient state of SiOx (x <2) can be used.

  The protective film 33 can be made of the same material as that of the film bodies (31, 32). In particular, SiOx (however, x <2) that is a film body in an oxygen deficient state is preferably used. In this case, if the film thickness is 200 nm or more, resistance to chemicals such as acid and alkali works, and oxidation and etching of the metal film can be prevented.

Next, the manufacturing method of the optical waveguide device of this invention is demonstrated.
In the manufacturing process, the substrate 1 is processed in a wafer state, and after incorporation of necessary components such as an optical waveguide and a metal-loaded polarizer is completed, the substrate 1 is cut and formed into individual chip-shaped optical waveguide devices. .

  First, as shown in FIG. 3A, an optical waveguide 2 is formed on a substrate 1 having an electro-optic effect by a Ti thermal diffusion method or the like. Next, in order to form a metal-loaded polarizer, a masking material (40, 41) is placed at a predetermined position on the substrate 1 (wafer substrate). As shown in FIG. 4, the masking materials (40, 41) are arranged so as to cover the substrate surface other than the region 4 where the metal-loaded polarizer is formed.

  As shown in FIG. 3 (2), an oxygen deficient film body 31 such as SiOx is disposed in a region not covered with a masking material, then a metal film 30 such as aluminum, and again an oxygen deficient film body. 32 are sequentially stacked.

  As shown in FIG. 3 (3), the masking material (40, 41) is shifted from the metal loaded polarizer 3 and rearranged. The distance between the masking materials 40 and 41 is set to a distance obtained by adding an arbitrary value in the range of 0.3 to 2 mm to the width (about 0.2 to 2 mm) of the metal film of the metal loaded polarizer. When the added distance is less than 0.3 mm, the film formation is hindered by the thickness of the masking material, and it becomes difficult to make the thickness of the protective film 200 nm or more. Further, when the added distance is larger than 2 mm, the area of the protective film is increased, and the protective film is easily peeled off from the metal-loaded polarizer and the substrate due to thermal expansion of the protective film, and the reliability of the optical waveguide device is lowered. .

  Next, as shown in FIG. 3D, a protective film 33 is formed, and the exposed portion of the metal layer 30 is completely covered with the protective film. The protective film is SiOx resistant to chemicals such as acid and alkali, and plays a role of effectively protecting the metal layer from oxidation and etching of the metal layer. By using the same oxygen-deficient state film body and the oxygen-deficient state film body (31, 32) arranged so as to sandwich the metal film constituting the metal-loaded polarizer, and the protective film 33, The complexity of the manufacturing process can be suppressed. In addition, since the protective film is formed of the same material as the film body sandwiching the metal film, the film body and the protective film can be integrated, and problems such as the protective film being easily peeled off hardly occur.

  Finally, the removal of the masking material (40, 41) completes the incorporation of the metal loaded polarizer having the protective layer into the optical waveguide device.

  As an optical waveguide device, an optical waveguide is formed on an X-cut lithium niobate substrate, masking is performed on portions other than those requiring a polarizer, and a SiOx (x <2) film body 31 is formed to a thickness of 10 nm by sputtering. Then, an aluminum metal film with a thickness of 100 nm and a SiOx (x <2) film body 32 with a thickness of 100 nm were sequentially formed by sputtering to constitute a polarizer.

  Thereafter, the masking material was further spread by 0.5 mm, and SiOx (x <2) was formed with a thickness of 200 nm or more by sputtering. The optical waveguide device thus obtained was not observed to be oxidized or etched in the metal film even after various chemical treatments in the subsequent steps, and the yield in the wafer process was improved. Evaluation of the optical characteristics of the individual optical waveguide devices made into chips revealed that there was little variation between the devices and the function of the polarizer was stable.

  As shown in FIG. 5, the optical waveguide device of the present invention can be suitably applied to an optical waveguide device having a complicated waveguide structure such as DP-QPSK. For example, a PLC (planar light wave circuit) 10 is used for the input / output branching portion, and a substrate 11 having an electro-optic effect such as lithium niobate is used for the light modulation unit. Both are joined at the joint 12. At the time of bonding, the optical waveguides (20, 21) formed on the respective substrates are bonded so as to reduce the optical coupling loss at the coupling portion. A metal-loaded polarizer 3 is disposed on the surface of the substrate 11. The manufacturing process can be simplified as compared with the case where a polarizer is arranged on the incident end face of each optical waveguide.

  As described above, according to the present invention, an optical waveguide device having excellent optical characteristics and a method for manufacturing the same are provided by suppressing oxidation of a metal film constituting a metal-loaded polarizer and etching in a subsequent process of the manufacturing process. It becomes possible.

DESCRIPTION OF SYMBOLS 1 Substrate 2 Optical waveguide 3 Metal loaded polarizer 30 Metal film 33 Protective films 40 and 41 Masking material

Claims (6)

A substrate having an electro-optic effect, an optical waveguide formed on the substrate, and a low refractive index material layer, a metal film, and a low refractive index material layer in this order from the substrate side so as to cover at least a part of the optical waveguide. In an optical waveguide device having a metal-loaded polarizer formed by stacking ,
The low refractive index material layer has a refractive index lower than the refractive index of the optical waveguide;
The said metal loaded type polarizer, and the protective film so as to cover all formed the exposed portion of the metal film,
The protective film is not only a film of oxygen-deficient state, the optical waveguide device having a thickness and wherein the der Rukoto than 200 nm. An optical waveguide device according to claim 1, wherein the protective film, an optical waveguide device, characterized in that the SiOx (However, x <2). 3. The optical waveguide device according to claim 1, wherein the protective film is formed by a sputtering method. The optical waveguide device according to any one of claims 1 to 3,
There are two or more optical waveguides formed on the substrate,
The metal-loaded polarizer is integrally formed so as to cover at least two of the optical waveguides. In a method of manufacturing an optical waveguide device having a substrate having an electro-optic effect, an optical waveguide formed on the substrate, and a metal-loaded polarizer formed so as to cover at least a part of the optical waveguide,
The metal-loaded polarizer has a low refractive index in which a masking material is disposed on the substrate and is a film body in an oxygen deficient state from the substrate side, and has a refractive index lower than the refractive index of the optical waveguide. After laminating the material layer, the metal film, and the low refractive index material layer in this order ,
The masking material is separated from the position where the metal-loaded polarizer is formed within a range of 0.3 to 2 mm, and is rearranged on the substrate to cover the entire metal-loaded polarizer. And forming a protective film which is a film body in the same oxygen deficiency state as the low refractive index material layer . 6. The method of manufacturing an optical waveguide device according to claim 5, wherein the protective film is formed by a sputtering method.

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