JP2004294711A - Micromirror and optical waveguide element equipped with micromirror, and their manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a micromirror which can easily be formed at an arbitrary position and is excellent in operability in a forming process. <P>SOLUTION: The micromirror is composed of a base body formed of a resin layer which is formed on a substrate surface and becomes hydrophilic and soluble through light irradiation, a surface which is formed on the base body and has a specified angle based on the substrate, and a metal film which is formed on the surface. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００３０】
ただし、Ｒ^１、Ｒ^２、Ｒ^３はそれぞれ１価の炭化水素基、アルコキシ基、水素原子を、ｎ、ｍはそれぞれ０以上で、かつ、ｎ＋ｍは５以上の整数を表わす。
このようなポリシランは、一般に２５０ｎｍ以上の紫外領域に吸収を有し、酸素存在下で紫外光を照射するとそのケイ素−ケイ素（Ｓｉ−Ｓｉ）結合が一部切断され、シロキサン（Ｓｉ−Ｏ−Ｓｉ）結合やシラノール（Ｓｉ−ＯＨ）基に変換される。
これにより、ポリシランの紫外吸収が減少するとともに、親水性とアルカリ溶液に対する可溶性が発現される。
また、上記ポリシランは、紫外光を照射することにより、屈折率が低下するという特性もあり、光導波路を形成する上でも有用である。
【００３１】
次に、上述の実施例による光導波路素子の製造方法について図２〜図１５に基づいて説明する。図２〜図１５は、図１に示される光導波路素子の製造工程を示す工程図である。
【００３２】
まず、図２に示されるように、基板２上に下部クラッド層３を形成する。基板２には平滑性に優れるガラス基板、あるいは可撓性と耐熱性に優れるポリイミドフィルムを用いる。
下部クラッド層３は後で形成するコア層４（図３参照）より屈折率の低いものであればよいが、耐熱性（ガラス転移点約３５０℃）に優れる点とスピンコートが可能な点でポリシラン（日本ペイント株式会社製、品名：グラシアＷＧ、品番：ＷＧ−００４）を用いる。
耐熱性が約３００℃以上であれば、後のはんだ付け工程で変性可能性が小さくなり、実装する際に有利となる。
下部クラッド層３は、上記ポリシランを基板２上にスピンコートで塗布し、約３５０℃で焼成して化学的に安定な膜とすることにより形成される。
【００３３】
次に、図３に示されるように、下部クラッド層３の上にコア層４を形成する。コア層４には光照射により親水性と可溶性と屈折率変化を示すポリシラン（日本ペイント株式会社製、品名：グラシアＷＧ、品番：ＷＧ−００５）を用いる。
ポリシランは、光照射により分子の一部が切断されて親水性を示すようになると同時に、アルカリ溶液に可溶となり、さらに屈折率が低下する。また、耐熱性の点からも好ましい。
但し、下部クラッド層３との屈折率差を確保するため、下部クラッド層３を構成するポリシランとは組成の異なるものを用いている。
コア層４は、上記ポリシランを下部クラッド層３上にスピンコートで塗布し、約２５０℃に加熱して膜中の溶剤を揮発させることにより形成される。
【００３４】
次に、図４に示されるように、グレーマスク３０を介してコア層４に紫外光を照射する。グレーマスク３０は、図５に示されるように透明基体３１と遮光膜３２とからなり、遮光膜３２は傾斜面７ａ，７ｂと対応する箇所において光透過率を漸減させるために、膜厚が徐々に変化する光透過部３３が形成されている。また、遮光膜３２のうち、ミラー用凹部５ａ，５ｂと対応する箇所には光透過部３３と隣接して開口部３４がそれぞれ形成されている。
ここで、紫外光照射による親水性と可溶性は、照射強度に応じてコア層４の表層から順に発現する。
このため、図５に示すようなグレーマスク３０を介してコア層４に紫外光を照射すると、光透過部３３のうち膜厚の薄い部分を介して照射された部分ではコア層４の深くまで親水性および可溶性が発現する。
一方、光透過部３３のうち膜厚の厚い部分を介して照射された部分では、コア層４の表層部分あるいはその近傍にのみ親水性と可溶性が発現する。
この結果、ポリシランからなるコア層４に傾斜面７ａ，７ｂを備えるミラー用凹部５ａ，５ｂの立体的な潜像が形成される。
【００３５】
次に、図６に示されるように、得られた基板２をアルカリ溶液に浸漬して親水性と可溶性が発現した部分を溶解除去し、ミラー用凹部５ａ，５ｂを形成すると共に基板２となす内角が約４５度の傾斜面７ａ，７ｂを形成する。
ここで、下部クラッド層３の表面が部分的に露出するようにミラー用凹部５ａ，５ｂを形成するのは、後の光導波路６を形成するための露光工程において、マスク５０の位置合わせ精度を緩和するためである（図１１（ａ）参照））。
【００３６】
次に、図７（ａ）および図７（ｂ）に示されるように、得られた基板２を無電解めっき法でめっき浴する。この際、ミラー用凹部５ａ，５ｂの表面には先の工程での紫外光照射により生じた親水基が残存するので、ミラー用凹部５ａ，５ｂの内面にのみ金属めっきが施され、反射膜８が形成される。
この工程では微小ミラーとすべき傾斜面７ａ，７ｂと対向する面にも反射膜８が形成されるが、これは光の伝搬の妨げとなるのでこの部分の反射膜８を次以降の工程で除去する。
【００３７】
すなわち、図８（ａ）および図８（ｂ）に示されるように、コア層４上にレジスト４０を塗布し、傾斜面７ａ，７ｂを覆いつつ傾斜面７ａ，７ｂと対向する面を露出させるようにフォトリソグラフィーにより開口４１を形成する。
次に、図９（ａ）および図９（ｂ）に示されるように、得られた基板２をエッチング液に浸漬し、不要な反射膜８（図８（ａ）および図８（ｂ）参照）を除去する。
次に、図１０（ａ）および図１０（ｂ）に示されるように、コア層４上に残るレジスト４０（図９（ａ）および図９（ｂ）参照）を有機溶剤で溶解除去する。
【００３８】
次に、図１１（ａ）および図１１（ｂ）に示されるように、コア層４内に光導波路６を形成するため、光導波路６に対応するパターンの遮光膜５２を備えたマスク５０を介して紫外光を照射する。
すなわち、コア層４を構成するポリシランは、紫外光を照射することにより屈折率が低下するので、コア層４のうち、光導波路６としない部分に紫外光を照射して屈折率を低下させ、光導波路６とすべき部分の屈折率を相対的に高め、光導波路６を形成するのである。
この際、上述の通り、ミラー用凹部５ａ，５ｂは、下部クラッド層３の表面が部分的に露出するように形成されているため、下部クラッド層３がミラー用凹部５ａ，５ｂ内に露出する幅Ｗ１分だけマスク５０の位置合わせ精度が緩和される。
【００３９】
次に、図１２に示されるように、コア層４を約３５０℃で焼成して化学的に安定させる。
この際、コア層４の屈折率は全体的に低下するが、先の工程で光導波路６を形成するためにつくりだした屈折率差はほぼそのまま維持され、また、コア層４全体の屈折率は、いずれの部分についても下部クラッド層３より高く維持される。
【００４０】
次に、図１３に示されるように、コア層４上に上部クラッド層９を形成する。上部クラッド層９は、コア層４を構成するポリシランと同じポリシランをスピンコートで塗布し、約２５０℃に加熱して膜中の溶剤を揮発させることにより形成される。
【００４１】
次に、図１４（ａ）および図１４（ｂ）に示されるように、傾斜面７ａ，７ｂの上方と対応する箇所にのみ遮光膜６２を備えたマスク６０を介して紫外光を上部クラッド層９に照射し、照射部分の屈折率を低下させて光導波路１０ａ，１０ｂとすべき部分の屈折率を相対的に高めることにより上部クラッド層９内に光導波路１０ａ，１０ｂを形成する。
次に、図１５（ａ）および図１５（ｂ）に示されるように、上部クラッド層９を約３５０℃で焼成して化学的に安定させる。
その後、面発光レーザ２０や光検出器２１を搭載するための電極パッド１１を上部クラッド層９上に形成し、面発光レーザ２０や光検出器２１をそれぞれ電極パッド１１にはんだ付けすることにより図１に示される光導波路素子１が完成する。
【００４２】
この化学変化は照射される紫外光強度が強いほど早く進む傾向がある。したがって、上記マスクを介して紫外光を照射すると、紫外光がよく通る部分では樹脂層の深くまで化学変化が生じ、紫外光が弱くしか通らない部分では化学変化が表層部分あるいはその近傍に限定される。
このような原理によってポリシランからなる樹脂層に３次元的な立体形状の潜像を形成することができる。
【００４３】
【発明の効果】
本発明による微小ミラー及びその形成方法ではミラーの基体が光照射により親水性と可溶性を示す樹脂からなるので、工程は基本的にグレーマスクによる露光、現像工程、めっき工程のわずか３工程で済む。しかも、全て大気中で処理可能、且つ、化学反応処理であるので処理能力を容易に拡大でき、コスト的に有利である。ミラーの位置や形状はグレーマスクの設計により任意に設定できるので、隣接する導波路を損傷することもない。さらに、形成された４５度面は基板の表面から加工できるので反射膜が形成し易く、塗布した光硬化性樹脂を未硬化半液状の状態で取り扱う必要もないので作業性が良い。
【００４４】
また、本発明による微小ミラー付き導波路素子及びその形成方法ではミラーの基体が光照射により親水性と可溶性と屈折率変化を示す樹脂からなるので、上記の効果に加えてミラー基体とチャネル導波路を同一の樹脂層を利用して形成でき、チャネル導波路を形成するための工程の一部が省略できる。また、ミラーとチャネル導波路が同一の樹脂層から形成されるので両者に厚み方向のずれが生じることがない。
【図面の簡単な説明】
【図１】この発明の実施例による光導波路素子の構成を概略的に示す説明図である。
【図２】図１に示される光導波路素子の製造工程を示す工程図である。
【図３】図１に示される光導波路素子の製造工程を示す工程図である。
【図４】図１に示される光導波路素子の製造工程を示す工程図である。
【図５】図１に示される光導波路素子の製造工程を示す工程図である。
【図６】図１に示される光導波路素子の製造工程を示す工程図である。
【図７】図１に示される光導波路素子の製造工程を示す工程図であり、同図において（ａ）と（ｂ）は同工程における断面と平面をそれぞれ示している。
【図８】図１に示される光導波路素子の製造工程を示す工程図であり、同図において（ａ）と（ｂ）は同工程における断面と平面をそれぞれ示している。
【図９】図１に示される光導波路素子の製造工程を示す工程図であり、同図において（ａ）と（ｂ）は同工程における断面と平面をそれぞれ示している。
【図１０】図１に示される光導波路素子の製造工程を示す工程図であり、同図において（ａ）と（ｂ）は同工程における断面と平面をそれぞれ示している。
【図１１】図１に示される光導波路素子の製造工程を示す工程図であり、同図において（ａ）と（ｂ）は同工程における断面と平面をそれぞれ示している。
【図１２】図１に示される光導波路素子の製造工程を示す工程図である。
【図１３】図１に示される光導波路素子の製造工程を示す工程図である。
【図１４】図１に示される光導波路素子の製造工程を示す工程図であり、同図において（ａ）と（ｂ）は同工程における断面と平面をそれぞれ示している。
【図１５】図１に示される光導波路素子の製造工程を示す工程図であり、同図において（ａ）と（ｂ）は同工程における断面と平面をそれぞれ示している。
【図１６】従来の微小ミラー付き導波路素子の構造を示す説明図である。
【図１７】従来の微小ミラー付き導波路素子の形成工程を示す説明図である。
【図１８】従来の４５度ミラーの形成方法を示す説明図である。
【図１９】従来の４５度ミラーの形成方法を示す説明図である。
【符号の説明】
１・・・光導波路素子
２・・・基板
３・・・下部クラッド層
４・・・コア層
５ａ，５ｂ・・・ミラー用凹部
６・・・光導波路
７ａ，７ｂ・・・傾斜面
８ａ，８ｂ・・・反射膜
９・・・上部クラッド層
１０ａ，１０ｂ・・・光導波路
１１・・・電極パッド
１２ａ，１２ａ・・・微小ミラー
２０・・・面発光レーザ
２１・・・光検出器
３０・・・グレーマスク
３１・・・透明基体
３２，５２，６２・・・遮光膜
３３・・・光透過部
３４・・・開口部
４０・・・レジスト
４１・・・開口
５０，６０・・・マスク[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a micromirror, an optical waveguide device having the micromirror, and a method for manufacturing the micromirror and the optical waveguide device.
[0002]
[Prior art]
In order to realize a computer that performs faster arithmetic processing, the number of clocks of the CPU tends to increase year by year, and a frequency of about GHz is now appearing. As a result, there is a portion where a high-frequency signal flows in electrical wiring made of copper on a printed circuit board in a computer, and a malfunction occurs due to generation of noise. In addition, it emits electromagnetic waves and affects surroundings.
[0003]
In order to solve such a problem, a method of replacing a part of the electric wiring made of copper on the printed circuit board with an optical wiring made of an optical waveguide and using an optical signal instead of an electric signal has been actively tried. . Since the optical signal does not cause so-called electromagnetic induction, there is little malfunction due to noise as described above.
[0004]
In the optical wiring using an optical waveguide, it is important to align the relative positions of the light emitting element and the optical waveguide with an accuracy of μm and to efficiently couple light to the optical waveguide. For example, the structure of the optical waveguide element as shown in FIG. It is known (for example, see Patent Document 1).
[0005]
In FIG. 16, a surface emitting laser 101 has a lead wire 102 connected to an electric wiring 109 on an optical waveguide element by solder 103. The optical waveguide device includes an upper cladding layer 105, a core layer 106, a lower cladding layer 107, a lens 104, and a mirror 110. Light emitted from the surface emitting laser 101 is condensed by the lens 104 and is incident on the mirror 110. The light is reflected and propagates through the core layer 106. Reference numeral 108 denotes a filler for filling a space generated when the mirror 110 is formed and forming the electric wiring 109. Since a surface emitting laser is usually used for the light source because of ease of mounting and arraying, the mirror 110 that bends the traveling direction of the emitted light by 90 degrees is an essential element in the optical waveguide element for optical wiring.
[0006]
FIG. 17 shows a method of forming the optical waveguide device of FIG. After a release film is formed on the support 112 that has been processed into a lens shape in advance, the upper clad layer 105 is formed. Next, after the core layer 106 is formed, the core layer is processed into a core pattern using sputtering, photolithography, or the like, and then the lower clad 107 is formed. Subsequently, the mirror 110 is formed by making a cut using a dicing saw 113 having a triangular cross section. Then, an optical waveguide element is obtained by peeling off from the support. The mirror may be left in the cut state, but a metal thin film is attached by vapor deposition or the like in order to prevent light from traveling straight and causing loss.
[0007]
Further, another method of forming a 45-degree mirror as shown in FIGS. 18 and 19 is also known (for example, see Patent Document 2). In FIG. 18, reference numeral 211 denotes a substrate, 212 denotes a photocurable resin layer, and 225 denotes a photomask. The photomask 225 includes a transparent substrate 223 and a light-shielding film 224. The light-shielding film 224 is a chromium film having a thickness of about 0.1 μm and has a shape as shown in FIG. The end 224b of the opening 224a of the light-shielding film 224 is gradually thinner and functions as a so-called gray mask. Therefore, when the photocurable resin 212 on the substrate 211 is irradiated with the light L through the photomask 225, all of the resin layer is cured at a place where the light intensity is strong, and only a surface near the mask is cured at a place where the light intensity is weak. Thus, after exposure, if the uncured portion is dissolved and removed with an organic solvent, an optical waveguide core layer 212c having 45 ° surfaces 212a and 212b at both ends as shown in FIG. 19 can be formed.
[0008]
As a method of forming a 45-degree mirror, other than the above, a method of exposing a photoresist to light whose intensity is modulated, or a method of softening at a high temperature to form a tapered shape, and transferring this to a waveguide layer by ion etching, There is a method of irradiating a high-energy excimer laser and shaping the waveguide surface three-dimensionally by erosion.
[0009]
Still another related art related to the present invention is a method for manufacturing an electric circuit board, comprising forming a polysilane film on a surface of a substrate, and having an opening corresponding to a circuit pattern in the polysilane film. The exposed portion is made hydrophilic by irradiating ultraviolet light through a mask, a palladium salt solution is attached to the exposed portion that has been made hydrophilic, a pattern composed of a palladium layer is formed on the exposed portion, and the pattern is subjected to metal plating. There is known a method for manufacturing an electric circuit board which is used as a conductive pattern (see, for example, Patent Document 3).
[0010]
Further, as still another related art related to the present invention, there is known a method of irradiating a polysilane compound with ultraviolet light to lower the refractive index of an irradiation portion in accordance with the irradiation amount (for example, Non-Patent Documents) 1).
[0011]
[Patent Document 1]
JP 2001-166167 A [Patent Document 2]
JP 2000-298221 A [Patent Document 3]
JP-A-10-326957 [Non-Patent Document 1]
Akihiro Hori, et al., "Investigation of Optical Waveguide Technology Using Photobleaching Polymer Material", Proceedings of the 12th Microelectronics Symposium, October 2002, pp. 223-226.
[Problems to be solved by the invention]
In the optical wiring as disclosed in Patent Document 1, since a surface emitting laser is used as a light source, a 45-degree mirror that bends the traveling direction of light by 90 degrees is essential. However, in the method using a dicing saw as shown in the above-described conventional example, since the dicing saw has a diameter of about 3 cm, mirrors can be formed in a line, but it is practically not possible to form individual mirrors at arbitrary positions. Have difficulty. Further, there is a possibility that the adjacent waveguide is damaged by the cut of the dicing saw.
[0013]
On the other hand, in the 45-degree surface forming method as disclosed in Patent Document 2, since the 45-degree surface is formed in a direction facing the substrate, it is difficult to perform processing such as forming a reflective film on the surface. Since the exposure operation is performed in an uncured state, that is, in a semi-liquid state, there are problems such as poor workability.
[0014]
Also, in the method of transferring a photoresist having a tapered shape by ion etching, since the etching process is a vacuum process, the apparatus is expensive, the substrate area that can be processed at one time is limited, and the evacuation time is required. In the case of manufacturing a large optical waveguide device of the order of cm required for optical wiring, the cost increases. The erosion by the excimer laser does not require a vacuum, but the apparatus and the rare gas as the raw material gas are expensive, and the mirrors are processed one by one, which is also disadvantageous in cost.
[0015]
In addition, in any of the above methods, vapor deposition or sputtering using a vacuum apparatus is used as a method of forming a metal film on a 45-degree surface, so that the same problem as in the above-described ion etching occurs in this step. Although it is possible to form a metal film by electroless plating, a processing step in which only the surface is partially chemically activated after forming the 45-degree surface is required.
[0016]
The present invention has been made in view of the above circumstances, and can be easily formed at an arbitrary position, and has a workability in a forming process, a micromirror and an optical waveguide device including a micromirror, and Is provided.
[0017]
[Means for Solving the Problems]
The micromirror according to the present invention is formed on a substrate surface and formed of a resin layer that exhibits hydrophilicity and solubility by light irradiation, a surface formed on the substrate and forming a predetermined angle with respect to the substrate, and a micromirror formed on the surface. And a metal film formed on the substrate.
[0018]
An optical waveguide device with a micromirror according to the present invention includes a resin layer formed on a substrate surface and exhibiting a change in refractive index, hydrophilicity and solubility by light irradiation, and forming a predetermined angle with respect to the substrate formed on the resin layer. It is characterized by comprising a micromirror having a metal film formed on its surface and an optical waveguide formed in the resin layer.
[0019]
The method for forming a micromirror according to the present invention includes a step of applying a resin exhibiting hydrophilicity and solubility to a substrate by light irradiation, and a step of applying light to the resin through a mask having a region in which light transmittance changes continuously. Irradiating, removing a portion of the resin irradiated with light by etching, and forming a metal film on the surface of the portion removed in the process by electroless plating.
[0020]
The method for forming an optical waveguide device with a micromirror according to the present invention includes a step of applying a resin exhibiting hydrophilicity, solubility, and a change in refractive index to a substrate by light irradiation, and a mask having a region in which light transmittance changes continuously. A step of irradiating the resin with light through, a step of removing the light-irradiated portion of the resin by etching, and a step of forming a metal film on the surface of the portion removed in the step by electroless plating, Forming a channel waveguide by irradiating the resin with light after forming the metal film.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail based on examples shown in the drawings.
[0022]
FIG. 1 is an explanatory view schematically showing a configuration of an optical waveguide device according to an embodiment of the present invention.
As shown in FIG. 1, an optical waveguide device 1 according to an embodiment of the present invention includes a substrate 2 and a core formed on the substrate 2 and made of a resin that exhibits hydrophilicity, solubility, and a change in refractive index by light irradiation. The core layer 4 is sandwiched between a lower cladding layer 3 and an upper cladding layer 9 provided on the core layer 4.
Inclined surfaces 7a and 7b are formed in the core layer 4 so that an inner angle with respect to the substrate 2 is about 45 degrees, and the inclined surfaces 7a and 7b rise vertically in the substrate and extend to the surface of the optical waveguide element 1. Optical waveguides 10a and 10b are provided, respectively. An optical waveguide 6 is formed in the core layer (resin layer) 4 using a change in the refractive index caused by light irradiation.
[0023]
Here, the micromirror 12a (or 12b) has a core layer (resin layer) 4 made of a resin that exhibits hydrophilicity, solubility, and a change in refractive index by light irradiation as a base, and an inclined surface 7a (or 12) formed on the surface thereof. 7b) and a reflective film 8a (or 8b) formed on the surface.
[0024]
An electrode pad 11 is provided on the surface of the optical waveguide element 1, and a surface emitting laser (light emitting element) 20 and a photodetector (light receiving element) 21 are mounted via the electrode pad 11.
[0025]
The surface emitting laser 20 emits a laser beam to the end of the optical waveguide 10a, and the laser beam incident on the optical waveguide 10a propagates in the optical waveguide 10a and reaches the reflection film 8a formed on the surface of the inclined surface 7a. I do.
The laser beam that has reached the reflection film 8a has its traveling direction bent by 90 degrees, enters the optical waveguide 6, propagates through the light waveguide 6, and reaches the reflection film 8b formed on the surface of the inclined surface 7b.
The laser light that has reached the reflection film 8b is turned 90 degrees again into the optical waveguide 10b, enters the optical waveguide 10b, propagates through the optical waveguide 10b, exits from the end of the optical waveguide 10b, and enters the photodetector 21. Converted to electrical signals.
[0026]
The micromirrors 12a and 12b according to the present invention are basically exposed by a gray mask (a mask having a region where light transmittance changes continuously) since the base of the mirror is made of a resin layer 4 that is hydrophilic and soluble by light irradiation. The mirror can be formed in only three steps of the development step and the plating step, and mass production can be performed at low cost. Further, by using a resin that changes its refractive index in addition to being hydrophilic and soluble by light irradiation, the optical waveguide 6 can be formed using the same resin layer, so that the inclined surfaces 7a of the micro mirrors 12a and 12b can be formed. , 7b and the optical waveguide 6 in the height direction, so that the optical loss can be reduced. Further, the step of forming the optical waveguide 6 is shortened, which contributes to cost reduction.
[0027]
Further, since the optical waveguide 10a is formed in the upper clad 9, the distance between the surface emitting laser 20 and the end face of the optical waveguide 10a becomes shorter than before, and the light radiated from the surface emitting laser 20 spreads. It is taken into the optical waveguide 10a in a small state. As a result, of the total light power emitted from the surface emitting laser 20, the ratio of light coupled into the optical waveguide 10a, that is, the coupling efficiency is improved, so that the quality of the transmitted signal can be kept high.
Further, since the optical waveguide 10b is formed in the upper clad 9, the distance between the photodetector 21 and the end face of the optical waveguide 10b becomes shorter than before, and the light emitted from the optical waveguide 10b has a smaller spread. In this state, the light enters the photodetector 21.
[0028]
Note that, as the resin, a resin that exhibits hydrophilicity and solubility in a predetermined solution by light irradiation can be used, and a resin generally called a photobleaching polymer material can be used.
Specific examples of the photobleaching polymer material include, for example, photobleachable polysilane (hereinafter simply referred to as polysilane).
Polysilane is an organosilicon polymer having a structure in which five or more silicon atoms are continuously connected, and specifically, a polymer having a structure as shown in the following Chemical Formula 1.
[0029]
Embedded image

[0030]
Here, R ¹ , R ² , and R ³ each represent a monovalent hydrocarbon group, an alkoxy group, or a hydrogen atom, n and m each represent an integer of 0 or more, and n + m represents an integer of 5 or more.
Such a polysilane generally has an absorption in an ultraviolet region of 250 nm or more, and when irradiated with ultraviolet light in the presence of oxygen, its silicon-silicon (Si-Si) bond is partially broken to form a siloxane (Si-O-Si). ) It is converted into a bond or a silanol (Si-OH) group.
As a result, ultraviolet absorption of polysilane is reduced, and hydrophilicity and solubility in an alkaline solution are exhibited.
In addition, the above polysilane has a property that the refractive index is reduced by irradiating ultraviolet light, and thus is useful for forming an optical waveguide.
[0031]
Next, a method of manufacturing the optical waveguide device according to the above-described embodiment will be described with reference to FIGS. 2 to 15 are process diagrams showing a process of manufacturing the optical waveguide device shown in FIG.
[0032]
First, as shown in FIG. 2, a lower cladding layer 3 is formed on a substrate 2. As the substrate 2, a glass substrate having excellent smoothness or a polyimide film having excellent flexibility and heat resistance is used.
The lower cladding layer 3 may have a lower refractive index than the core layer 4 (see FIG. 3) to be formed later. However, the lower cladding layer 3 has excellent heat resistance (glass transition point of about 350 ° C.) and can be spin-coated. Polysilane (manufactured by Nippon Paint Co., Ltd., product name: Gracia WG, product number: WG-004) is used.
If the heat resistance is about 300 ° C. or more, the possibility of denaturation in the subsequent soldering step is reduced, which is advantageous when mounting.
The lower cladding layer 3 is formed by applying the above polysilane on the substrate 2 by spin coating and baking it at about 350 ° C. to form a chemically stable film.
[0033]
Next, as shown in FIG. 3, a core layer 4 is formed on the lower cladding layer 3. Polysilane (manufactured by Nippon Paint Co., Ltd., product name: Gracia WG, product number: WG-005) showing hydrophilicity, solubility, and change in refractive index by light irradiation is used for the core layer 4.
At the same time, polysilane is partially broken by light irradiation to exhibit hydrophilicity, and at the same time becomes soluble in an alkaline solution, and further has a lower refractive index. It is also preferable from the viewpoint of heat resistance.
However, in order to ensure a difference in refractive index from the lower cladding layer 3, a material having a different composition from polysilane constituting the lower cladding layer 3 is used.
The core layer 4 is formed by applying the above polysilane on the lower cladding layer 3 by spin coating, and heating to about 250 ° C. to volatilize the solvent in the film.
[0034]
Next, as shown in FIG. 4, the core layer 4 is irradiated with ultraviolet light via the gray mask 30. As shown in FIG. 5, the gray mask 30 includes a transparent substrate 31 and a light-shielding film 32. The light-shielding film 32 has a thickness that is gradually reduced in order to gradually reduce light transmittance at portions corresponding to the inclined surfaces 7a and 7b. Is formed. In the light-shielding film 32, openings 34 are formed adjacent to the light transmitting portions 33 at locations corresponding to the mirror concave portions 5 a and 5 b.
Here, the hydrophilicity and the solubility by the ultraviolet light irradiation are sequentially developed from the surface layer of the core layer 4 according to the irradiation intensity.
For this reason, when the core layer 4 is irradiated with ultraviolet light through the gray mask 30 as shown in FIG. 5, the portion of the light transmitting portion 33 irradiated through the thinner portion has a depth as deep as the core layer 4. Expresses hydrophilicity and solubility.
On the other hand, in the portion of the light transmitting portion 33 irradiated through the thick portion, the hydrophilicity and solubility are expressed only in the surface portion of the core layer 4 or in the vicinity thereof.
As a result, a three-dimensional latent image of the mirror concave portions 5a and 5b having the inclined surfaces 7a and 7b is formed on the core layer 4 made of polysilane.
[0035]
Next, as shown in FIG. 6, the obtained substrate 2 is immersed in an alkaline solution to dissolve and remove the portions exhibiting hydrophilicity and solubility, thereby forming mirror recesses 5a and 5b and forming the substrate 2. The inclined surfaces 7a and 7b having an inner angle of about 45 degrees are formed.
Here, the reason why the concave portions 5a and 5b for mirrors are formed so that the surface of the lower clad layer 3 is partially exposed is that the positioning accuracy of the mask 50 is adjusted in an exposure process for forming the optical waveguide 6 later. This is for relaxation (see FIG. 11A).
[0036]
Next, as shown in FIGS. 7A and 7B, the obtained substrate 2 is subjected to a plating bath by an electroless plating method. At this time, since the hydrophilic groups generated by the ultraviolet light irradiation in the previous step remain on the surfaces of the mirror concave portions 5a and 5b, only the inner surfaces of the mirror concave portions 5a and 5b are plated with metal, and the reflection film 8 is formed. Is formed.
In this step, the reflection film 8 is also formed on the surface facing the inclined surfaces 7a and 7b, which are to be micromirrors. However, this hinders the propagation of light. Remove.
[0037]
That is, as shown in FIGS. 8A and 8B, a resist 40 is applied on the core layer 4 to expose the surfaces facing the inclined surfaces 7a and 7b while covering the inclined surfaces 7a and 7b. Opening 41 is formed by photolithography as described above.
Next, as shown in FIGS. 9A and 9B, the obtained substrate 2 is immersed in an etching solution, and unnecessary reflection films 8 (see FIGS. 8A and 8B). ).
Next, as shown in FIGS. 10A and 10B, the resist 40 remaining on the core layer 4 (see FIGS. 9A and 9B) is dissolved and removed with an organic solvent.
[0038]
Next, as shown in FIGS. 11A and 11B, in order to form the optical waveguide 6 in the core layer 4, a mask 50 having a light shielding film 52 having a pattern corresponding to the optical waveguide 6 is formed. Irradiate with ultraviolet light.
That is, since the refractive index of the polysilane constituting the core layer 4 is reduced by irradiating the ultraviolet light, the portion of the core layer 4 which is not the optical waveguide 6 is irradiated with the ultraviolet light to lower the refractive index, The refractive index of the portion to be the optical waveguide 6 is relatively increased, and the optical waveguide 6 is formed.
At this time, as described above, since the mirror concave portions 5a and 5b are formed so that the surface of the lower clad layer 3 is partially exposed, the lower clad layer 3 is exposed in the mirror concave portions 5a and 5b. The alignment accuracy of the mask 50 is reduced by the width W1.
[0039]
Next, as shown in FIG. 12, the core layer 4 is fired at about 350 ° C. to be chemically stabilized.
At this time, the refractive index of the core layer 4 is reduced as a whole, but the refractive index difference created for forming the optical waveguide 6 in the previous step is substantially maintained, and the refractive index of the entire core layer 4 is reduced. In each case, it is maintained higher than the lower cladding layer 3.
[0040]
Next, as shown in FIG. 13, the upper cladding layer 9 is formed on the core layer 4. The upper cladding layer 9 is formed by spin-coating the same polysilane as the polysilane constituting the core layer 4 and heating it to about 250 ° C. to volatilize the solvent in the film.
[0041]
Next, as shown in FIGS. 14A and 14B, ultraviolet light is applied to the upper cladding layer only through the mask 60 having the light shielding film 62 only at locations corresponding to the upper portions of the inclined surfaces 7a and 7b. By irradiating the upper clad layer 9, the optical waveguides 10a and 10b are formed in the upper clad layer 9 by lowering the refractive index of the irradiated portions and relatively increasing the refractive index of the portions to be the optical waveguides 10a and 10b.
Next, as shown in FIGS. 15A and 15B, the upper cladding layer 9 is fired at about 350 ° C. to be chemically stabilized.
Thereafter, an electrode pad 11 for mounting the surface emitting laser 20 and the photodetector 21 is formed on the upper cladding layer 9, and the surface emitting laser 20 and the photodetector 21 are soldered to the electrode pad 11, respectively. 1 is completed.
[0042]
This chemical change tends to progress faster as the intensity of the irradiated ultraviolet light is higher. Therefore, when ultraviolet light is irradiated through the mask, a chemical change occurs to a depth of the resin layer in a portion where ultraviolet light passes well, and a chemical change is limited to a surface layer portion or its vicinity in a portion where ultraviolet light passes only weakly. You.
According to such a principle, a three-dimensional three-dimensional latent image can be formed on the resin layer made of polysilane.
[0043]
【The invention's effect】
In the micromirror and the method of forming the micromirror according to the present invention, since the base of the mirror is made of a resin showing hydrophilicity and solubility when irradiated with light, basically, only three steps are required: exposure using a gray mask, development, and plating. In addition, since all the treatments can be performed in the atmosphere and the treatment is a chemical reaction treatment, the treatment capacity can be easily expanded, which is advantageous in cost. Since the position and shape of the mirror can be arbitrarily set by designing the gray mask, there is no damage to the adjacent waveguide. Further, the formed 45-degree surface can be processed from the surface of the substrate, so that a reflection film is easily formed, and it is not necessary to handle the applied photocurable resin in an uncured semi-liquid state, so that workability is good.
[0044]
Further, in the waveguide device with a micro mirror and the method of forming the same according to the present invention, since the base of the mirror is made of a resin exhibiting hydrophilicity, solubility, and a change in the refractive index by light irradiation, the mirror base and the channel waveguide are added in addition to the above-mentioned effects. Can be formed using the same resin layer, and a part of the process for forming the channel waveguide can be omitted. In addition, since the mirror and the channel waveguide are formed from the same resin layer, there is no shift between them in the thickness direction.
[Brief description of the drawings]
FIG. 1 is an explanatory view schematically showing a configuration of an optical waveguide device according to an embodiment of the present invention.
FIG. 2 is a process chart showing a manufacturing process of the optical waveguide device shown in FIG.
FIG. 3 is a process chart showing a manufacturing process of the optical waveguide device shown in FIG. 1;
FIG. 4 is a process chart showing a manufacturing process of the optical waveguide device shown in FIG. 1;
FIG. 5 is a process chart showing a manufacturing process of the optical waveguide device shown in FIG. 1;
FIG. 6 is a process chart showing a manufacturing process of the optical waveguide element shown in FIG. 1;
FIGS. 7A and 7B are process diagrams showing a manufacturing process of the optical waveguide device shown in FIG. 1, wherein FIGS. 7A and 7B show a cross section and a plane in the process, respectively.
FIGS. 8A and 8B are process diagrams showing a manufacturing process of the optical waveguide device shown in FIG. 1, wherein FIGS. 8A and 8B show a cross section and a plane in the process, respectively.
9 is a process chart showing a manufacturing process of the optical waveguide device shown in FIG. 1, wherein (a) and (b) show a cross section and a plane in the process, respectively.
10 is a process diagram showing a manufacturing process of the optical waveguide device shown in FIG. 1, wherein (a) and (b) show a cross section and a plane in the process, respectively.
11 is a process chart showing a manufacturing process of the optical waveguide device shown in FIG. 1, in which (a) and (b) show a cross section and a plane in the same process, respectively.
FIG. 12 is a process chart showing a manufacturing process of the optical waveguide element shown in FIG. 1;
FIG. 13 is a process chart showing a manufacturing process of the optical waveguide element shown in FIG. 1;
14 is a process chart showing a manufacturing process of the optical waveguide device shown in FIG. 1, wherein (a) and (b) show a cross section and a plane in the process, respectively.
15 is a process diagram showing a manufacturing process of the optical waveguide device shown in FIG. 1, wherein (a) and (b) show a cross section and a plane in the process, respectively.
FIG. 16 is an explanatory view showing the structure of a conventional waveguide device with a micromirror.
FIG. 17 is an explanatory view showing a step of forming a conventional waveguide element with a micromirror.
FIG. 18 is an explanatory view showing a conventional method for forming a 45-degree mirror.
FIG. 19 is an explanatory diagram showing a conventional method of forming a 45-degree mirror.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Optical waveguide element 2 ... Substrate 3 ... Lower clad layer 4 ... Core layer 5a, 5b ... Mirror concave part 6 ... Optical waveguide 7a, 7b ... Inclined surface 8a, 8b Reflective film 9 Upper clad layers 10a and 10b Optical waveguide 11 Electrode pads 12a and 12a Micromirror 20 Surface emitting laser 21 Photodetector 30 ··· Gray mask 31 ··· Transparent bases 32, 52 and 62 ··· Shielding film 33 ··· Light transmitting portion 34 ··· Opening 40 ··· Resist 41 ··· Openings 50 and 60 ··· mask

Claims (4)

A base made of a resin layer formed on the substrate surface and expressing hydrophilicity and solubility by light irradiation,
A surface formed on the base and forming a predetermined angle with respect to the substrate,
A micro mirror comprising a metal film formed on the surface. A resin layer formed on the substrate surface and expressing a change in refractive index and hydrophilicity and solubility by light irradiation,
A micromirror formed on the resin layer and having a metal film formed on a surface forming a predetermined angle with respect to the substrate;
An optical waveguide device with a micro mirror, comprising an optical waveguide formed in the resin layer. A step of applying a resin expressing hydrophilicity and solubility to the substrate by light irradiation,
Irradiating the resin with light through a mask having a region where light transmittance changes continuously,
Removing a portion of the resin irradiated with light by etching;
A method for forming a micro mirror, comprising a step of forming a metal film on a surface of a portion removed in the step by electroless plating. A step of applying a resin that expresses hydrophilicity, solubility, and refractive index change by light irradiation to the substrate,
Irradiating the resin with light through a mask having a region where light transmittance changes continuously,
Removing a portion of the resin irradiated with light by etching;
Forming a metal film on the surface of the portion removed in the above step by electroless plating,
Forming a channel waveguide by irradiating the resin with light after forming the metal film.

Images