JP3724391B2 - Manufacturing method of polymer waveguide - Google Patents

Description

【０１０１】
ただし、化１式中、Ｒ１からＲ１２は、炭素数１〜１０のハロゲンまたはグリシジルオキシ基で置換されていてもよい脂肪族炭化水素基、炭素数６〜１２の芳香族炭化水素基、炭素数１〜８のアルコキシ基からなる群から選択される基であり、同一でも異なっていてもよい。ａ、ｂ、ｃ及びｄは０を含む整数であり、ａ＋ｂ＋ｃ＋ｄ≧１を満たすものである。このシリコーン化合物が有する、脂肪族炭化水素基の具体例として、メチル基、プロピル基、ブチル基、ヘキシル基、オクチル基、デシル基、トリフルオロプロピル基、グリシジルオキシプロピル基等のような脂環式のものが挙げられる。またアルコキシ基の具体例としては、メトキシ基、エトキシ基、フェノキシ基、オクチルオキシ基、ｔｅｒ−ブトキシ基等が挙げられる。Ｒ１からＲ１２の種類及びａ、ｂ、ｃ、ｄの値は特に重要ではなく、ポリシラン及び有機溶媒と相溶し、膜が透明なものであれば特に限定されない。相溶性を考慮した場合には、使用するポリシランが有する炭化水素基と同じ基を有していることが好ましい。例えば、ポリシランとして、フェニルメチル系のものを使用する場合には、同じフェニルメチル系またはジフェニル系のシリコーン化合物を使用することが好ましい。またＲ１からＲ２のうち、少なくとも２つが炭素系〜８のアルコキシ系であるような、１分子中にアルコキシ基を２つ以上有するシリコーン化合物は、架橋材として利用可能である。そのようなものとしては、アルコキシ基を１５から３５重量％含んだメチルフェニルメトキシシリコーンやフェニルメトキシシリコーン等を挙げることができる。分子量としては、１００００以下、好ましくは３０００以下のものが好適である。
【０１０２】
なお、膜中のＣＨ基やＯＨ基による光吸収を低減するために、ポリシラン化合物やシリコーン化合物に重水素化、少なくとも一部がハロゲン化、特にフッ素化したものを用いれば、吸収基による光損失を大幅に低減することができる。これにより、波長依存性の少ない低光損失のポリマ材料及びそれを用いたポリマ膜を実現可能となり、光学用材料及び部品として幅広い範囲に用途を拡大することが可能となる。
【０１０３】
またシリコーン化合物に架橋性、あるいはアルコキシ基からなるものを用いることによって分岐型ポリシラン化合物の中に均一に添加することができ、しかもトルエンのような有機溶媒中に容易に可溶してナノメータレベルの超微粒子状溶液となり、上記ポリマ溶液を用いることによって光散乱中心のない均一な構造体や膜を形成することができる。
【０１０４】
以上のように、本発明は下記に示すような効果を有している。
【０１０５】
（１）高比屈折率差化を実現すると共に、その後でポリシラン化合物を無機化することによりＣＨ基をほとんどなくすことができるので、このＣＨ基による吸収損失を大幅に低減した超低損失導波路を実現することができる。
【０１０６】
（２）低温状態で紫外線照射によって屈折率変化を形成するので、より短時間にポリマ層の深さ方向に紫外線の照射、非照射界面の屈折率変化を付けることができ、またその界面の急峻な屈折率変化を実現することができる。これにより高比屈折率差でも散乱損失の小さい導波路を実現することができる。
【０１０７】
（３）本発明の導波路はＡｕ／Ｓｎ半田のリフロー温度に耐えることができ、かつ屈折率の温度変動も少ないので、安定した光学特性の導波路を実現することができる。また電子部品、電子回路、光部品、光回路等をハイブリッド実装した光・電気複合デバイス用の導波路及び導波路型光回路用として適用することができる。
【０１０８】
（４）ポリマ溶液の塗布、加熱による簡易プロセスであるので、超低コストで、かつ高性能光部品及び光デバイスを実現することが可能であり、光情報通信の更なる普及を促進させる起爆剤になる。
【０１０９】
（５）より短波長（２６０ｎｍ付近）の紫外線を用いることにより、フォトブリーチング膜に大きな屈折率変化パターンを直接描画することができ、更なる高比屈折率差化を実現することができる。
【０１１０】
（６）紫外線のレーザビームで直接描画することにより、高屈折率の光伝搬層とその両側面の低屈折率クラッド層との比屈折率差Δをさらに高く、かつ界面にシャープな屈折率の境界を作ることができる。
【０１１１】
【発明の効果】
以上要するに本発明によれば、次のような優れた効果を発揮する。
【０１１２】
ポリマ材料を出発材にした低損失で高比屈折率差のポリマ導波路の製造方法の提供を実現することができる。
【図面の簡単な説明】
【図１】本発明のポリマ導波路製造方法の一実施の形態を示す工程図である。
【図２】本発明のポリマ導波路製造方法の他の実施の形態を示す工程図である。
【図３】本発明のポリマ導波路製造方法の他の実施の形態を示す工程図である。
【図４】本発明のポリマ導波路製造方法の他の実施の形態を示す工程図である。
【図５】本発明のポリマ導波路製造方法の他の実施の形態を示す工程図である。
【図６】本発明のポリマ導波路の製造方法を適用したフォトブリーチング用ポリマ膜の紫外線照射による屈折率変化特性を示す図である。
【図７】本発明のポリマ導波路の製造方法を適用したポリマ導波路に用いられるポリマ膜の伝搬損失のポストベーク温度依存性を示したものである。
【図８】本発明のポリマ導波路の製造方法を適用したポリマ導波路の断面図である。
【図９】本発明のポリマ導波路の製造方法を適用したポリマ導波路の断面図である。
【図１０】（ａ）は本発明のポリマ導波路の製造方法を適用したポリマ導波路の断面図であり、（ｂ）は（ａ）の面方向の位置と屈折率との関係を示す図であり、（ｃ）は（ａ）の厚さ方向の位置と屈折率との関係を示す図である。
【図１１】本発明のポリマ導波路の製造方法を適用したポリマ導波路の断面図である。
【図１２】本発明のポリマ導波路の製造方法を適用したポリマ導波路の断面図である。
【図１３】本発明のポリマ導波路の製造方法を適用したポリマ導波路の断面図である。
【符号の説明】
１ 基板（低屈折率基板）
２−１、２−２、２−３、２ａ−１、２ａ−２ 側面の低屈折率クラッド層
３、３−１、３−２ 高屈折率コア層
４ 上部低屈折率クラッド層
６、６−１、６−２、６−３ 高屈折率化した領域
７ 紫外線カット層[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a polymer waveguide.
[0002]
[Prior art]
With the advancement of optical interconnection technology, parallel optical transmission between devices via optical fiber has entered the practical stage. As a next-generation method, a method of transmitting in parallel on a board or between LSI chips using an optical signal has been studied in earnest. In order to realize this parallel transmission system, a waveguide is used as a transmission line instead of an optical fiber. As this waveguide, one using a polymer material is considered promising.
[0003]
Since waveguides using polymer materials can be easily made by low-temperature processes, we believe that superiority can be expected in terms of cost reduction and large size compared to waveguides using glass materials. It has been. That is, a polymer solution dissolved in an organic solvent is applied onto various substrates by a spin coating method, an extrusion coating method, or the like, and then heated at a low temperature (≦ 300 ° C.) to form a polymer film.
[0004]
Next, after obtaining a high refractive index core polymer pattern having a substantially rectangular cross-section using photolithography or an etching process, a low refractive index polymer film is formed so as to cover the core pattern.
[0005]
As a method for creating a polymer waveguide by a simple method in the atmosphere, the present inventor previously formed a polymer film for photobleaching on a substrate on which a polymer film having a lower refractive index is formed, Next, a photomask on which a desired core pattern is drawn is placed on the photobleaching polymer film, irradiated with ultraviolet light, and the refractive index of the photobleaching polymer film irradiated with ultraviolet light is lowered to reduce the side cladding layer. A polymer waveguide is realized by forming a low refractive index clad polymer film so as to cover the photobleaching polymer film in the core layer where the refractive index is not lowered in the region not irradiated with ultraviolet light. Proposed method to do.
[0006]
[Problems to be solved by the invention]
However, the polymer waveguide described above has the following major problems, which is an obstacle to practical use.
[0007]
(1) There is an absorption loss depending on the absorption group (CH group, OH group) specific to the polymer material, and it is extremely difficult to reduce the loss to 0.1 dB / cm or less.
[0008]
(2) Solder is used to hybridly mount electronic components, electronic circuits, optical components, optical circuits, etc. on the front surface or back surface of the waveguide, and further inside, but at present some low loss characteristics (0.2 dB) A waveguide using a polymer material that can be expected to have a high temperature / cm) has poor heat resistance, and it is difficult to withstand the solder reflow temperature (reflow temperature of Au / Sn solder:> 280 ° C.). Also, if the above components are mounted and processed in a waveguide at a temperature of 280 ° C. or higher, the refractive index of the polymer used in the waveguide will change, and the optical characteristics of the waveguide will change significantly, making it unusable. End up. On the other hand, a waveguide using a polymer material that can be expected to have heat-resistant characteristics has a problem in practical use because of a large loss and polarization dependency.
[0009]
(3) A polymer waveguide using a photobleaching polymer material has a feature that it can be produced in a simple manner in the atmosphere, but it is difficult to reduce the loss due to the intrinsic absorption.
[0010]
(4) The polymer material has a lower refractive index stability due to temperature change than the glass material, and the optical characteristics are likely to change even when an optical circuit is configured, which has a practical problem.
[0011]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems and provide a method for producing a polymer waveguide having a low loss and a high relative refractive index difference using a polymer material as a starting material.
[0012]
[Means for Solving the Problems]
  According to the first aspect of the present invention, there is provided a polymer forming step of forming a polymer layer of a polysilane compound on a low refractive index layer formed on the surface of a substrate at a temperature lower than 250 ° C., and a desired light propagation layer pattern on the polymer layer. A pattern formation process in which a photomask on which is drawn is placed and ultraviolet rays are irradiated from above the photomask to form a pattern with a reduced refractive index on the polymer layer. Forming an upper cladding layer having a refractive index to form a waveguide,350It consists of a heat treatment step in which heat treatment is performed in a temperature range of from ℃ to 380 ℃.
[0013]
  The invention of claim 2 is a polymer forming step of forming a polymer layer of a polysilane compound on a low refractive index layer formed on the surface of a substrate at a temperature lower than 250 ° C., and a desired light propagation layer pattern on the polymer layer A pattern forming step of irradiating an ultraviolet laser beam on the polymer layer to form a pattern having a reduced refractive index, forming an upper clad layer having a refractive index comparable to that of the low refractive index layer on the polymer layer, and a waveguide; Upper cladding layer forming process, waveguide350It consists of a heat treatment step in which heat treatment is performed in a temperature range of from ℃ to 380 ℃.
[0014]
  According to a third aspect of the present invention, there is provided a polymer forming step of forming a polymer layer of a polysilane compound on the low refractive index layer formed on the surface of the substrate at a temperature lower than 250 ° C., and the same as the low refractive index layer on the polymer layer. A waveguide forming process for forming an upper clad layer having a refractive index of about a degree, and a photomask on which a desired light propagation layer pattern is drawn is arranged on the polymer layer, and ultraviolet rays are emitted from above the photomask. Irradiates and forms a pattern with a reduced refractive index on the polymer layer.350It consists of a heat treatment step in which heat treatment is performed in a temperature range of from ℃ to 380 ℃.
[0015]
  According to a fourth aspect of the present invention, there is provided a polymer forming step of forming a polymer layer of a polysilane compound on the low refractive index layer formed on the surface of the substrate at a temperature lower than 250 ° C., and the same as the low refractive index layer on the polymer layer. A waveguide formation process in which an upper clad layer having a refractive index is formed to form a waveguide, a pattern in which a polymer layer is irradiated with an ultraviolet laser beam in a desired light propagation layer pattern and a refractive index is lowered on the polymer layer Pattern forming process to form the waveguide350It consists of a heat treatment step in which heat treatment is performed in a temperature range of from ℃ to 380 ℃.
[0016]
5. The pattern according to claim 2, wherein the refractive index is lowered in the region irradiated with the laser beam by the relative movement of either the substrate or the laser beam while condensing and irradiating the laser beam on the polymer layer. May be directly drawn.
[0017]
In the invention of any one of claims 1 to 5, it is preferable that the wavelength of the ultraviolet light is selected from a range of 230 nm to 420 nm.
[0018]
  In the invention according to any one of claims 1 to 6, as the polysilane compoundSi In addition to atoms, bonded to hydrocarbon, alkoxy, or hydrogen atomsA thing may be used.
[0019]
  In the invention according to any one of claims 1 to 7, as the polysilane compoundAt least partially deuteratedA thing may be used.
[0020]
  In any one of Claims 1-8, as a polysilane compound,At least partially fluorinatedA thing may be used.
[0021]
  From claim 19In any of the inventions, as the polysilane compoundSilicone compound is added in desired ratioA thing may be used.
[0022]
  Claim10In the invention, a silicone compound having a crosslinkability or an alkoxy group may be used.
[0023]
  Claim10 or 11In the present invention, a silicone compound that is at least partially deuterated may be used.
[0024]
  Claim10 to 12In any one of the inventions, a silicone compound that is at least partially fluorinated may be used.
[0025]
  Claim10 to 13In any of the inventions, a polysilane compound having a photoacid generator added at a desired compounding ratio in addition to the silicone compound may be used.
[0026]
The invention according to any one of claims 1 to 14, wherein an ultrashort pulse laser beam having a pulse width of 1000 fs or less is condensed and irradiated on the surface or inside of a region which has not been irradiated with ultraviolet rays, either the substrate or the pulse laser beam. A pattern with a high refractive index may be directly drawn in the region irradiated with the pulse laser beam by such relative movement.
[0027]
The present inventor has studied a waveguide using a polysilane compound film formed by applying a solution of a polysilane compound dissolved in an organic solvent onto a substrate by a coating process. As a result, when the polysilane compound film is heated at a temperature of 350 ° C. or higher, mineralization proceeds and the film becomes a very uniform, crack-free film with a very low loss. Found.
[0028]
For example, in the case where phenylmethylpolysilane is used as the polysilane compound, heat treatment is usually performed at a temperature within 250 ° C. to form a polymer film, but by heating this at a temperature of 350 ° C. or higher, The phenyl group or methyl group in the side chain is eliminated and mineralization occurs. When the propagation loss of the film that caused such mineralization was evaluated, as will be described later, as the mineralization progresses, that is, as the heat treatment temperature becomes higher, the propagation loss of the conventional polymer film significantly increases. We found that low values can be realized. The present invention utilizes this phenomenon.
[0029]
By the way, when the conventional polymer film other than the polysilane compound is subjected to the above high-temperature heat treatment, the film is cracked or peeled off, so that the high-temperature treatment cannot be performed.
[0030]
On the other hand, the present inventor has found that cracks and film peeling do not occur even when high-temperature heat treatment is performed by using a polysilane compound, particularly a polysilane compound to which a silicone compound is added.
[0031]
However, when a photomask on which a desired light propagation layer pattern is drawn is placed on a polymer layer that has been heat-treated at a high temperature and irradiated with ultraviolet rays from above, a pattern having a reduced refractive index is formed on the polymer layer. The relative refractive index difference Δ between the unirradiated region and the ultraviolet irradiated region is very small, and it has been found that it is difficult to make a waveguide with a high relative refractive index difference.
[0032]
  Therefore, after forming a polymer layer of a polysilane compound at a temperature lower than 250 ° C., a photomask on which a desired light propagation layer pattern is drawn is placed on the polymer layer, and ultraviolet rays are irradiated from above to refract the polymer layer. When a pattern with a reduced index is formed, and then an upper cladding layer having a refractive index similar to that of the low refractive index layer is formed on the polymer layer to form a waveguide, a high relative refractive index difference is realized, After that, the waveguide350It has been found that if the heat treatment is carried out in the temperature range from 0 ° C. to 380 ° C., the relative refractive index difference is slightly reduced, but a higher relative refractive index difference can be realized and a low-loss waveguide can be realized than the above-described method. It was also found that the relative refractive index difference Δ can be easily controlled. In addition, by directly drawing with an ultraviolet laser beam, the interface between the irradiated region and the non-irradiated region could be made uniform.
[0033]
According to the present invention,
(1) While realizing a high relative refractive index difference and making the polysilane compound inorganic after that, CH groups can be almost eliminated. Therefore, an ultra-low loss waveguide in which absorption loss due to the CH groups is greatly reduced. Can be expected.
[0034]
(2) Since the refractive index change is formed by ultraviolet irradiation in a low temperature state, ultraviolet irradiation in the depth direction of the polymer layer can be applied in a shorter time, and the refractive index change of the non-irradiated interface can be applied, and the sharp refraction of the interface It becomes possible to realize a rate change. As a result, a waveguide with a small scattering loss can be realized even with a high relative refractive index difference.
[0035]
(3) Since it can withstand the reflow temperature of Au / Sn solder and the temperature variation of the refractive index is small, a waveguide with stable optical characteristics can be realized. Further, the present invention can be applied to a waveguide for an optical / electric composite device in which an electronic component, an electronic circuit, an optical component, an optical circuit, etc. are hybrid-mounted, and a waveguide type optical circuit.
[0036]
(4) It is a simple process that uses a polymer solution coating process, can realize ultra-low cost, high-performance optical components and optical devices, and is an initiating agent that promotes further spread of optical information communication. Become.
[0037]
(5) By directly drawing the refractive index change pattern on the photobleaching film with ultraviolet light having a shorter wavelength (near 260 nm), it is possible to realize a further higher relative refractive index difference.
[0038]
(6) By directly drawing with an ultraviolet laser beam, the relative refractive index difference Δ between the high refractive index light propagation layer and the low refractive index cladding layers on both sides thereof is further increased and a sharp refractive index boundary is formed. Can be made.
[0039]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0040]
FIG. 1 is a process diagram showing an embodiment of a polymer waveguide manufacturing method of the present invention.
[0041]
This manufacturing method includes steps P11 to P16 shown in FIG.
[0042]
First, as shown in step P11, a polymer solution made of a polysilane compound dissolved in an organic solvent is applied on the low refractive index layer formed on the substrate surface. Examples of the substrate used here include substrates of glass, ceramics, plastics, semiconductors, ferroelectrics, or composite materials thereof. The polymer solution is applied by spin coating using a spinner, extrusion coating, or the like.
[0043]
For the low refractive index layer, SiO₂, SiO₂Or a polymer layer (for example, a polymer layer of a polysilane compound obtained by adding 80 to 130 wt% of a silicone compound to a polysilane compound, or a polysilane compound) For example, a polymer layer whose refractive index is lowered by irradiating with UV light in advance. That is, when a silicone compound is added to a polysilane compound, the refractive index decreases as the amount added increases, so a polymer layer with an increased amount of silicone compound is used as the low refractive index layer.
[0044]
Further, if the solution or polymer layer of the polysilane compound is irradiated with ultraviolet rays in advance, the refractive index can be lowered, so that it can be used as a low refractive index layer. As a specific example, the following is used for the low refractive index layer.
[0045]
A polymer obtained by adding 50 wt% of a silicone compound to a branched polymethylphenylsilane compound having a branching degree of 20% is dissolved in toluene as an organic solvent to obtain a polymer solution for photobleaching. Is output by propagating through an image fiber bundle having a diameter of 20 mm, and is emitted at a distance of about 10 cm, and the output is about 1200 mw / cm.²It is. ) For 135 minutes (reducing the refractive index at a wavelength of 632.8 nm from 1.645 to 1.62 before UV irradiation), and applying this solution onto, for example, a Si substrate And pre-baking at 150 ° C. for 30 minutes.
[0046]
Next, as the polymer layer of the polysilane compound shown in Step P11, a material obtained by adding a silicone compound to 20 wt% to 80 wt% to the branched polysilane compound is used as will be described later. As an example, a polymer obtained by adding 50 wt% of a silicone compound to the branched polymethylphenylsilane compound having a branching degree of 20% shown above is dissolved in toluene, and a polymer solution for photobleaching is used. This solution is applied on a low refractive index substrate and pre-baked in the range of 100 ° C. to 250 ° C. for 30 minutes (step P12).
[0047]
Next, a polymer solution having a low refractive index is applied on the polymer film of the polysilane compound (Step P13).
[0048]
Thereafter, the polymer solution having a low refractive index is formed into a polymer film having a low refractive index under the same pre-baking conditions as above (Step P14).
[0049]
Next, a photomask on which a desired core pattern is drawn is placed on the low refractive index polymer layer, and an ultraviolet ray is irradiated on the photomask to form a refractive index change pattern in the polymer layer of the polysilane compound (process) P15).
[0050]
  Finally, the waveguide is realized by post-baking at a practical temperature at which a desired relative refractive index difference waveguide can be realized. The post-bake temperature range is350C. to 380.degree. C., and baking conditions are performed by programming the temperature rise, temperature retention and temperature drop characteristics. In particular, when baking at a temperature higher than 350 ° C., it is possible to prevent the occurrence of microcracks by lowering the temperature gradient with a slow temperature gradient of about 1 ° C./min to 3 ° C./min while removing the temperature when the temperature is lowered. It is effective. When it becomes higher than 5 ° C./min, microcracks are generated (process P16).
[0051]
As described above, it is possible to provide a method of manufacturing a polymer waveguide having a low loss and a high relative refractive index difference using a polymer material as a starting material.
[0052]
FIG. 2 is a process diagram showing another embodiment of the polymer waveguide manufacturing method of the present invention.
[0053]
This manufacturing method includes steps P21 to P26, as shown in FIG.
[0054]
The difference from the embodiment shown in FIG. 1 is that a process (process P23) corresponding to process P15 in FIG. 1 is provided after a process (process P22) corresponding to process P12 in FIG. That is, a light propagation layer pattern having a high dimensional accuracy is previously formed on a polymer film of a polysilane compound, and then a low refractive index polymer layer is coated thereon. The process P21 corresponds to the process P11 in FIG. 1, the process P24 corresponds to the process P13 in FIG. 1, and the process P26 corresponds to the process P16 in FIG.
[0055]
Also in this embodiment, the same effect as that of the embodiment shown in FIG. 1 can be obtained.
[0056]
FIG. 3 is a process diagram showing another embodiment of the polymer waveguide manufacturing method of the present invention.
[0057]
In this embodiment, a polysilane compound is used for the low refractive index layer.
[0058]
First, in Step P31, a desired amount of ultraviolet light is irradiated to a solution of a polysilane compound dissolved in an organic solvent to lower the refractive index. As a specific example, a polymer obtained by adding 50 wt% of a silicone compound to a branched polymethylphenylsilane compound having a branching degree of 20% is dissolved in toluene as an organic solvent to prepare a polymer solution for photobleaching. Light from a lamp propagates through an image fiber bundle having a diameter of 20 mm and is output, and is emitted at a distance of about 10 cm, and the output is about 1200 mw / cm.²It is. ) For 135 minutes, the refractive index is lowered (the refractive index at a wavelength of 632.8 nm is lowered from 1.645 to 1.62 before ultraviolet irradiation).
[0059]
Next, as shown in step P32, this solution is applied onto the substrate.
[0060]
Thereafter, as shown in Step P33, the polysilane compound solution is subjected to a first pre-baking at 100 to 150 ° C. for 20 minutes and a second pre-baking at 200 to 250 ° C. for 30 minutes to reduce the refractive index to 1.62. A refractive index layer is formed.
[0061]
Hereinafter, steps P34 to P39 are the same as steps P11 to P16 in FIG.
[0062]
Also in this embodiment, the same effect as that of the embodiment shown in FIG. 1 can be obtained.
[0063]
FIG. 4 is a process diagram showing another embodiment of the polymer waveguide manufacturing method of the present invention.
[0064]
In the low refractive index layer forming steps P41 to P43, as in the embodiment shown in FIG. 3, a solution of a polysilane compound dissolved in an organic solvent is irradiated with ultraviolet rays. Subsequent steps P44 to P49 are the same as steps P21 to P26 shown in FIG.
[0065]
Also in this embodiment, the same effect as that of the embodiment shown in FIG. 1 can be obtained.
[0066]
FIG. 5 is a process diagram showing another embodiment of the polymer waveguide manufacturing method of the present invention.
[0067]
This is obtained by adding the process of P57 after the process of P16 of FIG.
[0068]
In the process of P57, the light propagation in which the refractive index of the irradiated region is increased while condensing and irradiating the ultrashort pulse laser beam having a pulse width of 1000 fs or less on the surface of the region not irradiated with ultraviolet rays or inside thereof. It is a process of changing to a layer. The light propagation layer is formed by relatively moving either the substrate or the pulsed laser beam.
[0069]
Also in this embodiment, the same effect as that of the embodiment shown in FIG. 1 can be obtained.
[0070]
FIG. 6 is a graph showing the refractive index change characteristic of a photobleaching polymer film to which the polymer waveguide manufacturing method of the present invention is applied, by ultraviolet irradiation, the horizontal axis indicates the post-bake temperature, and the vertical axis indicates the relative refractive index. The difference Δb is shown.
[0071]
First, a polymer obtained by adding 50 wt% of a silicone compound to a branched polymethylphenylsilane compound having a branching degree of 20% is dissolved in toluene as an organic solvent to obtain a polymer solution for photobleaching.
[0072]
Next, this polymer solution was spin-coated on a plurality of Si substrates with a spinner to form films.
[0073]
These films were set at various pre-baking temperatures of 150 ° C., 200 ° C., 250 ° C., 275 ° C., and 300 ° C. to prepare polymer films that were heat-treated at the respective pre-baking temperatures, and then the refractive index (nb) at a wavelength of 632.8 nm. ) Was measured.
[0074]
Next, the polymer film was irradiated with ultraviolet rays having an energy of 18000 mJ, and the refractive index was lowered (refractive index na).
[0075]
The relative refractive index difference Δb was determined from the refractive index nb and the refractive index na.
[0076]
Next, each polymer film was heat-treated at various post-baking temperatures to determine how much the refractive index was reduced, and the relative refractive index difference Δb after post-baking was determined from these refractive index values. The horizontal axis indicates the post bake temperature, and the vertical axis indicates Δb. As can be seen from this figure, Δb has a value of 0.1% or more even when the post-baking temperature is increased to about 380 ° C. at a low pre-baking temperature of 250 ° C. or lower. That is, this means that a waveguide structure can be obtained even when the temperature is raised to about 380 ° C. by this photobleaching method.
[0077]
On the contrary, when the pre-bake temperature is 275 ° C. or higher, a waveguide structure can be obtained until the post-bake temperature is about 350 ° C., but this means that the waveguide has a low relative refractive index difference Δ.
[0078]
FIG. 7 shows the post-baking temperature dependence of the propagation loss of the polymer film used in the polymer waveguide to which the polymer waveguide manufacturing method of the present invention is applied. In the figure, the horizontal axis indicates the post-bake temperature, and the vertical axis indicates the propagation loss of the polymer film.
[0079]
It can be seen from the figure that the higher the post-bake temperature, the lower the loss characteristics. This polymer film is coated on a Vycor glass substrate with a polymer solution for photobleaching made by dissolving a polymer containing 50% by weight of a silicone compound in a branched polymethylphenylsilane compound having a branching degree of 20% in an organic solvent toluene. The propagation loss was evaluated for a layer prepared by changing the post-baking temperature after pre-baking at 150 ° C. for 20 minutes.
[0080]
The higher the post-baking temperature, the lower the loss, and the higher the temperature of 350 ° C. or higher, that is, when the mineralization of the polymer layer proceeds, a further lower loss value is obtained, and no cracks are generated. It was found that it became even more uniform. This high temperature heat treatment shows that the polymer waveguide of the present invention can sufficiently withstand the Au / Sn solder reflow temperature and realize further low loss characteristics. That is, it has been found that by making the polysilane compound inorganic, it is possible to eliminate almost all CH groups, thereby realizing an ultra-low loss value. Even when heat treatment was performed at 500 ° C., there was no film peeling or cracking.
[0081]
8, FIG. 9, FIG. 10 (a), FIG. 11, FIG. 12 and FIG. 13 are cross-sectional views of polymer waveguides to which the polymer waveguide manufacturing method of the present invention is applied, and FIG. 10 (b) is FIG. It is a figure which shows the relationship between the position of the surface direction of (a), and a refractive index, and FIG.10 (c) is a figure which shows the relationship between the position of the thickness direction of FIG.10 (a), and a refractive index. In FIG. 10B, the horizontal axis indicates the position in the surface direction, and the vertical axis indicates the refractive index. In FIG. 10C, the horizontal axis indicates the refractive index, and the vertical axis indicates the position in the thickness direction.
[0082]
First, the polymer waveguide shown in FIG. 8 includes a core layer 3 (an unirradiated portion of ultraviolet rays) made of a high refractive index polysilane compound on a low refractive index substrate 1 and a low refractive index side cladding made of a polysilane compound on both side surfaces thereof. It has a structure having layers 2-1 and 2-2 (ultraviolet irradiation portion) and having an upper cladding layer 4 having a low refractive index on the core layer 3 and the side cladding layers 2-1 and 2-2.
[0083]
FIG. 9 shows a structure in which a low refractive index polymer layer 5 is provided between the low refractive index substrate 1, the polymer core layers 3-1, 3-2, and the side cladding layers 2-1, 2-2. That is, the polymer waveguide shown in FIG. 9 is a waveguide that can be manufactured by the manufacturing method shown in FIG. 3 or FIG.
[0084]
The polymer waveguide shown in FIG. 10A is a waveguide having a structure in which a region 6 that is further increased in refractive index by irradiation with an ultrashort pulse laser beam is provided in a polymer core layer 3 having a high refractive index. . Reference numerals 2a-1 and 2a-2 denote side cladding layers.
[0085]
FIG. 11 shows a structure in which an upper clad layer having a low refractive index is provided on the waveguide shown in FIG.
[0086]
FIG. 12 shows a structure in which a low refractive index polymer layer 5 is provided between the substrate 1, the core layer 3, and the side cladding layers 2-1 and 2-2.
[0087]
FIG. 13 shows a structure in which an ultraviolet cut layer 7 is provided on the upper cladding layer 4.
[0088]
Here, as a modified example of the present invention, a waveguide was produced using a polymer layer in which the branching degree of the polysilane compound was changed from 2% to 48%, and the loss was evaluated. As a result, the higher the branching degree, the longer the wavelength band. An ultra-low loss value (0.06 dB / cm) could be realized in (1300 nm band, 1550 nm band).
[0089]
As still another modification, a waveguide is formed using a polymer layer in which a photoacid generator (paramethoxytrizylazine having a maximum absorption wavelength of 177 nm and a melting point of 192 ° C.) is added to 2% to 5% to a polysilane compound to which a silicone compound is added. It was investigated. Although the loss tended to increase somewhat, the uniformity of the core layer pattern in the depth direction by ultraviolet irradiation was improved, and a rectangular core layer with higher dimensional accuracy could be realized. It has been found that a triazine-based photoacid generator is good.
[0090]
In addition, as a result of direct writing without using a photomask using a He—Cd laser having a wavelength of 325 nm as ultraviolet rays, the refractive index changes perpendicular to the depth direction with respect to the thickness of the photobleaching polymer layer of 8 μm. Was able to be realized. The laser output is a continuous wave laser of 20 mw. As a result of drawing with a beam spot diameter of about 1 μm and a moving speed of 100 μm / sec to 1000 μm / sec, the refractive index change perpendicular to the depth direction of the polymer layer and the laser A uniform pattern could also be formed on the side of the beam drawing width. In addition, a YAG third harmonic laser having a wavelength of 355 nm, a semiconductor laser having a wavelength of 400 nm, a He-Cd laser having a wavelength of 442 nm, an excimer laser having a wavelength of 255 nm, a deep UV laser having a wavelength of 266 nm can be used as the ultraviolet laser. In particular, a Deep UV laser of 266 nm is preferable in that a large refractive index change can be realized in the polymer layer and a high output of 200 mw or more can be output, so that high-speed drawing can be performed.
[0091]
As a method for increasing the refractive index by irradiating an ultra-short pulse laser beam to a region that has not been irradiated with ultraviolet rays, the wavelength is 800 nm, the pulse width is hundreds of fs to 1000 fs, the repetition frequency is 10 kHz to 300 kHz, and the average output is Use 50mw or more. The laser energy in the case of this laser irradiation is preferably in the range of several μJ to several tens μJ. If it is more than that, there will be holes in the polymer layer, which is not preferable.
[0092]
Various materials can be applied to the polysilane compound, silicone compound, triazine compound, photoacid generator, and the like used in the present embodiment. For example, the polysilane compound is preferably a branched polysilane compound having a branching degree of 2% or more from the viewpoint of light transparency. The photoacid generator is preferably a triazine, and among them, those having high light transparency at a long wavelength and those having a high melting point are preferred. A silicone compound having a high light transparency and a high melting point is also preferable.
[0093]
Examples of the organic solvent used in this embodiment include hydrocarbons having 5 to 12 carbon atoms, halogenated hydrocarbons, and ethers. Examples of the hydrocarbon include pentane, hexane, heptane, cyclohexane, n-decane, n-dodecane, benzene, toluene, xylene, methoxybenzene, and the like. As examples of halogenated hydrocarbons, carbon tetrachloride, chloroform, 1,2-dichloroethane, dichloromethane, chlorobenzene, and the like can be used. Examples of ethers that can be used include diethyl ether, dibutyl ether, tetrahydrofuran and the like. Further, as described above, pegemia may be used as the organic solvent for the silicone compound containing the nitrone compound as the polymer material for photobleaching.
[0094]
The polymer material for photobleaching must be a material that is soluble in the organic solvent. As the polysilane compound used in this embodiment, a linear type and a branched type can be used. The branched type and the straight type are distinguished by the bonding state of Si atoms contained in the polysilane. That is, the branched polysilane is a polysilane containing Si atoms having 3 or 4 bonds to adjacent Si atoms (number of bonds). On the other hand, in the linear polysilane, the number of bonds between Si atoms and adjacent Si atoms is two. Usually, it is bonded to a hydrocarbon group, an alkoxy group or a hydrogen atom in addition to the Si atom. As such a hydrocarbon group, an aliphatic hydrocarbon group which may be substituted with a halogen having 1 to 10 carbon atoms and an aromatic hydrocarbon group having 61 to 14 carbon atoms are preferable. Specific examples of the aliphatic hydrocarbon group include a chain group such as a methyl group, a propyl group, a butyl group, a hexyl group, an octyl group, a decyl group, a trifluoropropyl group, and a nonafluorohexyl group, a cyclohexyl group, and a methylcyclohexyl group. Examples include alicyclic groups such as groups. Specific examples of the aromatic hydrocarbon group include a phenyl group, a p-tolyl group, a biphenyl group, and an anthracyl group. Examples of the alkoxy group include those having 1 to 8 carbon atoms. Specific examples include methoxy group, ethoxy group, phenoxy group, octyloxy group and the like. Among these, a methyl group and a phenyl group are particularly preferable in view of ease of synthesis.
[0095]
In the case of a branched polysilane, the number of Si atoms having 3 or 4 bonds with adjacent Si atoms is preferably 2% or more of the total number of Si atoms in the branched polysilane. Less than 2% or linear polysilane has high crystallinity, and microcrystals are easily generated in the film, thereby causing light scattering, and light transparency is likely to be lowered.
[0096]
The polysilane used in this embodiment is produced by a polycondensation reaction by heating a halogenated silane compound to 80 ° C. or higher in an organic solvent such as n-decane or toluene in the presence of an alkali metal such as sodium. Can do. It can also be synthesized by an electrolytic polymerization method or a method using metal magnesium and metal chloride.
[0097]
In the case of branched polysilane, a halosilane mixture comprising an organotrihalosilane compound, a tetrahalosilane compound, and a diorganodihalosilane compound, wherein the organotrihalosilane compound and the tetrahalosilane compound are 2 mol% or more of the total amount. The target branched polysilane is obtained by polycondensation by heating. Here, the organotrihalosilane compound is a Si atom source having a bond number of 3 with an adjacent Si atom, and one tetrahalosilane compound is an Si atom source having a bond number of 4 with an adjacent Si atom. Become. The network structure can be confirmed by measuring an ultraviolet absorption spectrum or Si nuclear magnetic resonance spectrum.
[0098]
It is preferable that the halogen atom which each of the organotrihalosilane compound, the tetrahalosilane compound, and the diorganodihalosilane compound used as the raw material for polysilane has is a chlorine atom. Examples of the substituent other than the halogen atom that the organotrihalosilane compound and the diorganohalosilane compound have include a hydrocarbon group, an alkoxy group, and a hydrogen atom.
[0099]
As the silicone compound added to the polysilane compound of the present invention, those represented by the formula 1 are used.
[0100]
[Chemical 1]

[0101]
However, in Chemical Formula 1, R1 to R12 are an aliphatic hydrocarbon group optionally substituted with a halogen having 1 to 10 carbon atoms or a glycidyloxy group, an aromatic hydrocarbon group having 6 to 12 carbon atoms, or a carbon number. These are groups selected from the group consisting of 1 to 8 alkoxy groups, which may be the same or different. a, b, c, and d are integers including 0 and satisfy a + b + c + d ≧ 1. Specific examples of the aliphatic hydrocarbon group possessed by this silicone compound include alicyclic groups such as methyl group, propyl group, butyl group, hexyl group, octyl group, decyl group, trifluoropropyl group, glycidyloxypropyl group, etc. Can be mentioned. Specific examples of the alkoxy group include a methoxy group, an ethoxy group, a phenoxy group, an octyloxy group, and a ter-butoxy group. The types of R1 to R12 and the values of a, b, c, and d are not particularly important as long as they are compatible with polysilane and an organic solvent and the film is transparent. In consideration of compatibility, it is preferable that the polysilane used has the same group as the hydrocarbon group. For example, when a phenylmethyl type polysilane is used, it is preferable to use the same phenylmethyl type or diphenyl type silicone compound. In addition, a silicone compound having two or more alkoxy groups in one molecule such that at least two of R1 to R2 are carbon-based to alkoxy-based can be used as a crosslinking material. Examples thereof include methylphenylmethoxysilicone and phenylmethoxysilicone containing 15 to 35% by weight of alkoxy groups. The molecular weight is 10,000 or less, preferably 3000 or less.
[0102]
In order to reduce light absorption due to CH groups and OH groups in the film, if polysilane compound or silicone compound is deuterated, at least partially halogenated, especially fluorinated, light loss due to absorbing group Can be greatly reduced. As a result, it is possible to realize a low optical loss polymer material with little wavelength dependence and a polymer film using the same, and it is possible to expand the application to a wide range as optical materials and components.
[0103]
In addition, by using a silicone compound having a crosslinkable or alkoxy group, it can be uniformly added to the branched polysilane compound, and it can be easily dissolved in an organic solvent such as toluene and can be nanometer level. By using the polymer solution, a uniform structure or film having no light scattering center can be formed.
[0104]
As described above, the present invention has the following effects.
[0105]
(1) While realizing a high relative refractive index difference and making the polysilane compound inorganic after that, CH groups can be almost eliminated. Therefore, an ultra-low loss waveguide in which absorption loss due to the CH groups is greatly reduced. Can be realized.
[0106]
(2) Since the refractive index change is formed by ultraviolet irradiation in a low temperature state, the refractive index change of the non-irradiated interface can be applied in the depth direction of the polymer layer in a shorter time, and the interface is steep. Can be realized. As a result, a waveguide with a small scattering loss can be realized even with a high relative refractive index difference.
[0107]
(3) Since the waveguide of the present invention can withstand the reflow temperature of Au / Sn solder and the temperature variation of the refractive index is small, a waveguide having stable optical characteristics can be realized. Further, the present invention can be applied to a waveguide for an optical / electric composite device in which an electronic component, an electronic circuit, an optical component, an optical circuit, etc. are hybrid-mounted, and a waveguide type optical circuit.
[0108]
(4) Since it is a simple process by application and heating of a polymer solution, it is possible to realize ultra-low cost and high-performance optical components and optical devices, and to promote further spread of optical information communication. become.
[0109]
(5) By using ultraviolet rays having a shorter wavelength (near 260 nm), a large refractive index change pattern can be directly drawn on the photobleaching film, and a further higher relative refractive index difference can be realized.
[0110]
(6) By directly drawing with an ultraviolet laser beam, the relative refractive index difference Δ between the high-refractive-index light propagation layer and the low-refractive-index clad layers on both sides thereof is further increased, and the refractive index is sharp at the interface. You can make a boundary.
[0111]
【The invention's effect】
In short, according to the present invention, the following excellent effects are exhibited.
[0112]
It is possible to provide a method for manufacturing a polymer waveguide having a low loss and a high relative refractive index difference using a polymer material as a starting material.
[Brief description of the drawings]
FIG. 1 is a process diagram showing one embodiment of a polymer waveguide manufacturing method of the present invention.
FIG. 2 is a process diagram showing another embodiment of the polymer waveguide manufacturing method of the present invention.
FIG. 3 is a process diagram showing another embodiment of the polymer waveguide manufacturing method of the present invention.
FIG. 4 is a process diagram showing another embodiment of the polymer waveguide manufacturing method of the present invention.
FIG. 5 is a process diagram showing another embodiment of the polymer waveguide manufacturing method of the present invention.
FIG. 6 is a diagram showing a refractive index change characteristic of a photobleaching polymer film to which the polymer waveguide manufacturing method of the present invention is applied by ultraviolet irradiation.
FIG. 7 shows the post-bake temperature dependence of the propagation loss of a polymer film used in a polymer waveguide to which the polymer waveguide manufacturing method of the present invention is applied.
FIG. 8 is a cross-sectional view of a polymer waveguide to which the polymer waveguide manufacturing method of the present invention is applied.
FIG. 9 is a cross-sectional view of a polymer waveguide to which the polymer waveguide manufacturing method of the present invention is applied.
10A is a cross-sectional view of a polymer waveguide to which the method for producing a polymer waveguide of the present invention is applied, and FIG. 10B is a diagram showing the relationship between the position in the plane direction of FIG. (C) is a figure which shows the relationship between the position of the thickness direction of (a), and a refractive index.
FIG. 11 is a cross-sectional view of a polymer waveguide to which the polymer waveguide manufacturing method of the present invention is applied.
FIG. 12 is a cross-sectional view of a polymer waveguide to which the polymer waveguide manufacturing method of the present invention is applied.
FIG. 13 is a cross-sectional view of a polymer waveguide to which the polymer waveguide manufacturing method of the present invention is applied.
[Explanation of symbols]
1 Substrate (Low refractive index substrate)
2-1, 2-2, 2-3, 2a-1, 2a-2 Low refractive index cladding layer on the side surface
3, 3-1, 3-2 High refractive index core layer
4 Upper low refractive index cladding layer
6, 6-1, 6-2, 6-3 High refractive index region
7 UV protection layer

Claims (15)

  A polymer forming step of forming a polymer layer of a polysilane compound on a low refractive index layer formed on the surface of the substrate at a temperature lower than 250 ° C., and a photomask on which a desired light propagation layer pattern is drawn on the polymer layer A pattern forming step of forming a pattern having a reduced refractive index on the polymer layer by irradiating ultraviolet rays from above the photomask, and an upper portion having a refractive index comparable to that of the low refractive index layer on the polymer layer A method of manufacturing a polymer waveguide, comprising: an upper clad layer forming step of forming a clad layer to form a waveguide; and a heat treatment step of heat-treating the waveguide in a temperature range of 350 ° C. to 380 ° C.   A polymer forming step for forming a polymer layer of a polysilane compound on a low refractive index layer formed on the surface of the substrate at a temperature lower than 250 ° C., and irradiating the polymer layer with an ultraviolet laser beam in a desired light propagation layer pattern Forming a pattern having a reduced refractive index on the polymer layer, and forming an upper cladding layer having a refractive index comparable to that of the low refractive index layer on the polymer layer to form a waveguide. A polymer waveguide manufacturing method comprising a layer forming step and a heat treatment step of heat-treating the waveguide in a temperature range of 350 ° C. to 380 ° C.   A polymer forming step of forming a polymer layer of a polysilane compound on the low refractive index layer formed on the surface of the substrate at a temperature lower than 250 ° C., and having a refractive index comparable to that of the low refractive index layer on the polymer layer A waveguide forming step of forming an upper clad layer to form a waveguide, a photomask on which a desired light propagation layer pattern is drawn is placed on the polymer layer, and ultraviolet rays are irradiated from above the photomask. A polymer waveguide manufacturing method comprising: a pattern forming step of forming a pattern having a reduced refractive index on a layer; and a heat treatment step of heat-treating the waveguide in a temperature range of 350 ° C. to 380 ° C.   A polymer forming step of forming a polymer layer of a polysilane compound on the low refractive index layer formed on the surface of the substrate at a temperature lower than 250 ° C., and having a refractive index comparable to that of the low refractive index layer on the polymer layer A waveguide forming step of forming an upper clad layer as a waveguide, and a pattern in which an ultraviolet laser beam is irradiated onto the polymer layer in a desired light propagation layer pattern to form a pattern with a reduced refractive index on the polymer layer A polymer waveguide manufacturing method comprising: a forming step, and a heat treatment step of heat-treating the waveguide in a temperature range of 350 ° C. to 380 ° C.   5. The refractive index of the region irradiated with the laser beam is lowered by the relative movement of either the substrate or the laser beam while condensing and irradiating the laser beam on the polymer layer. A method of manufacturing a polymer waveguide, wherein a pattern is directly drawn.   6. The method of manufacturing a polymer waveguide according to claim 1, wherein the wavelength of the ultraviolet ray is selected from a range of 230 nm to 420 nm. 7. The method for producing a polymer waveguide according to claim 1, wherein the polysilane compound is bonded to a hydrocarbon group, an alkoxy group, or a hydrogen atom in addition to the Si atom . 8. The method for producing a polymer waveguide according to claim 1, wherein at least a part of the polysilane compound is deuterated . 9. The method of manufacturing a polymer waveguide according to claim 1, wherein at least a part of the polysilane compound is fluorinated . In any of claims 1 to 9, the manufacturing method of the polymer optical waveguide, characterized in that used as the silicone compound is added in the desired mixing ratio as a polysilane compound. 11. The method for producing a polymer waveguide according to claim 10, wherein a silicone compound comprising a crosslinkable or alkoxy group is used. 12. The method for producing a polymer waveguide according to claim 10, wherein at least a part of the silicone compound is deuterated. 13. The method for producing a polymer waveguide according to claim 10 , wherein at least a part of the silicone compound is fluorinated. The method for producing a polymer waveguide according to any one of claims 10 to 13 , wherein a polysilane compound having a photoacid generator added at a desired mixing ratio in addition to the silicone compound is used.   15. The method according to claim 1, wherein an ultrashort pulse laser beam having a pulse width of 1000 fs or less is condensed and irradiated on the surface or inside of a region which has not been irradiated with ultraviolet rays. A method of manufacturing a polymer waveguide, wherein a pattern with a refractive index changed to be high is directly drawn in a region irradiated with the pulse laser beam by the relative movement.

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