JP2556206B2 - Method for manufacturing dielectric thin film - Google Patents
Method for manufacturing dielectric thin filmInfo
- Publication number
- JP2556206B2 JP2556206B2 JP3053511A JP5351191A JP2556206B2 JP 2556206 B2 JP2556206 B2 JP 2556206B2 JP 3053511 A JP3053511 A JP 3053511A JP 5351191 A JP5351191 A JP 5351191A JP 2556206 B2 JP2556206 B2 JP 2556206B2
- Authority
- JP
- Japan
- Prior art keywords
- thin film
- refractive index
- substrate
- waveguide
- dielectric thin
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Landscapes
- Inorganic Compounds Of Heavy Metals (AREA)
- Physical Vapour Deposition (AREA)
- Inorganic Insulating Materials (AREA)
- Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)
Description
【0001】[0001]
【産業上の利用分野】本発明は誘電体薄膜の製造方法に
関し、特に屈折率や誘電率を膜厚方向に自由に変化させ
ることのできる誘電体薄膜の製造方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a dielectric thin film, and more particularly to a method for producing a dielectric thin film whose refractive index and permittivity can be freely changed in the film thickness direction.
【0002】[0002]
【従来の技術】光ファイバ通信の発達とそのシングルモ
−ド化に伴って、光通信システムに必須となる光スイッ
チや光変調器などの光集積回路も一段と重要性を増して
きている。なかでも誘電体薄膜を光の導波層として用い
るハイブリッド型や、半導体基板にバッファ層を設け、
その上に誘電体薄膜の光導波路を作製する準ハイブリッ
ド型の光集積回路は、導波路材料を光源や検出器とは別
に自由に選択でき最適化できるという点で有利であり、
現在盛んに開発が行われている。従来の光導波路として
代表的なものは2種類あり、その1つは、基板にLiN
bO3単結晶を用い、表面にTiを拡散させたり、Li
をH+と交換することで導波路層としたグレ―デッド型
導波路で、別の1つは、ガラス基板や、あるいはSi基
板上にバッファ層としてSiO2層を設けた基板の上
に、ZnOなどの誘電体薄膜を形成したステップ型光導
波路である。LiNbO3単結晶を用いた導波路に関し
ては、ジャ−ナル・オブ・アメリカン・セラミクス・ソ
サイアティ( Journal of American Ceramics Society )
第72巻,8号,1311〜1321頁に開示されてい
る。 ステップ型導波路は基板上に薄膜を作製するだけ
で導波路を形成できるという点で作製が容易であり、導
波光を外部から制御するとき効率が高い等の利点を有す
るが、基板あるいはバッファ層などの導波路下層部の屈
折率が導波路部分よりも小さいことが必要で、導波路材
料に対して基板材料を選択するときに制限がある。ま
た、基板と導波路薄膜との界面がフラットでないと光の
散乱が生じ導波損失が増加するため、界面を厳密に制御
してフラットにすることが要求される。また、従来の技
術では、LiNbO3やSrTiO3などの誘電体の薄膜
において成膜時の基板温度を変化させることで誘電率を
変化させることができるという報告があるが、その誘電
率や屈折率は膜厚方向に一定である。一方、グレ−デッ
ド型導波路は不純物拡散やイオン交換によって導波路層
を形成するため、屈折率が徐々に変化し、したがって導
波光が界面の乱れによって散乱されることも少なく、導
波損失は抑えられるという利点を持つ。しかしながら、
高温での熱プロセスが必要なため、電子集積回路も含め
た集積化において熱処理温度に上限がある。また、材料
によっては不純物拡散やイオン交換により屈折率を増加
させることができないものもある点が問題である。2. Description of the Related Art With the development of optical fiber communication and its single mode, optical integrated circuits such as optical switches and optical modulators, which are indispensable for optical communication systems, are becoming more important. Above all, a hybrid type using a dielectric thin film as an optical waveguide layer or a buffer layer provided on a semiconductor substrate,
A quasi-hybrid type optical integrated circuit on which an optical waveguide of a dielectric thin film is formed is advantageous in that the waveguide material can be freely selected and optimized separately from the light source and the detector,
Development is currently underway. There are two typical types of conventional optical waveguides, one of which is LiN on the substrate.
Using a bO 3 single crystal, Ti is diffused on the surface and Li
Is a graded-type waveguide that is used as a waveguide layer by exchanging with H +, and another is a glass substrate or a substrate in which a SiO 2 layer is provided as a buffer layer on a Si substrate, It is a step type optical waveguide in which a dielectric thin film such as ZnO is formed. Regarding the waveguide using a LiNbO 3 single crystal, Journal of American Ceramics Society (Journal of American Ceramics Society)
Vol. 72, No. 8, pp. 1311 to 1321. The step-type waveguide is easy to manufacture in that the waveguide can be formed simply by forming a thin film on the substrate, and has advantages such as high efficiency when controlling the guided light from the outside, but the substrate or the buffer layer It is necessary that the refractive index of the lower layer portion of the waveguide is smaller than that of the waveguide portion, and there is a limitation when selecting the substrate material for the waveguide material. Also, if the interface between the substrate and the waveguide thin film is not flat, light scattering will occur and the waveguide loss will increase, so it is required to strictly control the interface to make it flat. In addition, with the conventional technology, there is a report that the dielectric constant can be changed by changing the substrate temperature at the time of film formation in a dielectric thin film such as LiNbO 3 or SrTiO 3. Is constant in the film thickness direction. On the other hand, in the graded-type waveguide, since the waveguide layer is formed by impurity diffusion or ion exchange, the refractive index gradually changes, and therefore the guided light is less likely to be scattered due to the disturbance of the interface, and the waveguide loss is It has the advantage of being suppressed. However,
Since a high temperature thermal process is required, there is an upper limit to the heat treatment temperature in integration including electronic integrated circuits. Another problem is that some materials cannot increase the refractive index due to impurity diffusion or ion exchange.
【0003】[0003]
【発明が解決しようとする課題】上記のような特徴を有
するグレ−デッド型導波路材料であるLiNbO3を薄
膜化する試みはこれまでもなされている。しかしなが
ら、導波路部分のLiNbO3の屈折率は膜厚方向に一
定であり、SiなどのLiNbO3より高い屈折率の基
板上にLiNbO3薄膜を作製すると導波は起こらな
い。このような場合、もし薄膜形成時に膜厚方向に誘電
率を変化させ、表面ほど屈折率が高くなるような誘電体
薄膜ができれば、任意の基板上に誘電体の光導波路を作
製できる。また屈折率のプロファイルも任意に制御でき
るので、光の閉じ込めに最も適した屈折率分布を得るこ
ともできる。しかしながら、従来は薄膜作製時の基板温
度を変化させて誘電率や屈折率を変化させていたので、
制御性に乏しく、ステップ状に変化させるといった高速
応答が期待できなかった。また、高い誘電率や屈折率を
得るためには高い基板温度が必要で、プロセスの低温化
が図れないという欠点があった。本発明の目的は、高温
での熱プロセスを必要とせずに、誘電体薄膜の屈折率や
誘電率を膜厚方向に自由に変化させることができ、従っ
て任意の基板上に光導波路を形成することの可能な誘電
体薄膜の製造方法を提供することにある。Attempts have been made to date to thin the graded-type waveguide material LiNbO 3 having the above characteristics. However, the refractive index of the LiNbO 3 waveguide portion is constant in the film thickness direction, the waveguide does not occur when making LiNbO 3 thin film on a substrate of higher refractive index than the LiNbO 3, such as Si. In such a case, if a dielectric thin film in which the dielectric constant is changed in the film thickness direction when the thin film is formed so that the refractive index becomes higher toward the surface, a dielectric optical waveguide can be manufactured on an arbitrary substrate. Further, since the profile of the refractive index can be controlled arbitrarily, the refractive index distribution most suitable for confining light can be obtained. However, conventionally, the dielectric constant and the refractive index were changed by changing the substrate temperature during thin film production,
The controllability was poor, and high-speed response such as stepwise changes could not be expected. In addition, a high substrate temperature is required to obtain a high dielectric constant and a high refractive index, and there is a drawback in that the process cannot be lowered in temperature. An object of the present invention is to freely change the refractive index and the dielectric constant of a dielectric thin film in the film thickness direction without requiring a high temperature thermal process, and thus to form an optical waveguide on an arbitrary substrate. Another object of the present invention is to provide a method of manufacturing a dielectric thin film capable of achieving the above.
【0004】[0004]
【課題を解決するための手段】本発明は、タ−ゲットに
化学式がABO3で表され、それぞれAとしてBa,S
r,Pb,La,Liの少なくとも1種以上、Bとして
Zr,Ti,Ta,Nbの少なくとも1種以上を含む材
料、あるいはBi4Ti3O12、あるいはZnOを用い、
イオンビ―ムスパッタ法でスパッタ粒子の加速電圧を変
化させることにより、誘電率あるいは屈折率が膜厚方向
に変化する誘電体薄膜を任意の基板上に形成する工程を
備えたことを特徴とする誘電体薄膜の製造方法である。According to the present invention, the target has a chemical formula represented by ABO 3 , and A and Ba and S are respectively represented.
Using at least one or more of r, Pb, La and Li, a material containing at least one or more of Zr, Ti, Ta and Nb as B, or Bi 4 Ti 3 O 12 or ZnO,
A dielectric material comprising a step of forming a dielectric thin film whose permittivity or refractive index changes in a film thickness direction on an arbitrary substrate by changing an acceleration voltage of sputtered particles by an ion beam sputtering method. It is a method of manufacturing a thin film.
【0005】[0005]
【作用】本発明は、誘電体薄膜を製造するのにイオンビ
―ムスパッタ法を用い、スパッタ粒子のエネルギ−を加
速電圧を変化させることで、粒子束の密度とは独立に変
化させる。この結果、低い基板温度で誘電体薄膜の屈折
率や誘電率を膜厚方向に自由に変化させ、任意の基板上
に光導波路を形成することができる。In the present invention, the ion beam sputtering method is used to manufacture a dielectric thin film, and the energy of sputtered particles is changed independently of the density of particle bundles by changing the acceleration voltage. As a result, the refractive index and the dielectric constant of the dielectric thin film can be freely changed in the film thickness direction at a low substrate temperature, and the optical waveguide can be formed on any substrate.
【0006】[0006]
【実施例】以下、本発明の実施例について図面を参照し
て説明する。 実施例1 図1は、タ−ゲットにSrTiO3焼結体を用い、イオ
ンビ―ムスパッタ法によりサファイア基板上に作製した
SrTiO3薄膜の、誘電率と屈折率のイオンビ―ムの
加速電圧に対する関係を示す。誘電率は10kHz、屈
折率は波長6328オングストロ―ムでの値である。基
板温度は430℃、SrTiO3の膜厚は約100n
m、イオンビ―ム電流は41mAで、O2ガスを5sc
cm流しながら、真空度2×10-4torrで成膜した
結果である。従来の方法では誘電率は薄膜作製時の基板
温度にのみ依存して変化するだけであって、同一基板温
度でこのように誘電率が変化するという報告はない。屈
折率も誘電率と同様に加速電圧に対してほぼ比例して増
加する。イオンビ―ムの加速電圧を変化させるのは非常
に簡単であり、成膜時間に対しステップ状に変化させた
り、徐々に変化させたりとプログラミングすることも可
能である。従って、SrTiO3薄膜の屈折率や誘電率
を膜厚方向に自由に制御性良く変化させることができ
る。また、低基板温度で従来得られなかった高い誘電率
も得られる。Embodiments of the present invention will be described below with reference to the drawings. Example 1 FIG. 1 shows the relationship between the dielectric constant and the refractive index of an SrTiO 3 thin film formed on a sapphire substrate by an ion beam sputtering method using a SrTiO 3 sintered body as a target and the acceleration voltage of the ion beam. Show. The dielectric constant is 10 kHz and the refractive index is a value at a wavelength of 6328 angstrom. The substrate temperature is 430 ° C. and the film thickness of SrTiO 3 is about 100 n.
m, ion beam current is 41 mA, O 2 gas is 5 sc
This is the result of film formation at a vacuum degree of 2 × 10 −4 torr while flowing a cm. In the conventional method, the dielectric constant only changes depending on the substrate temperature at the time of forming the thin film, and there is no report that the dielectric constant changes like this at the same substrate temperature. Like the dielectric constant, the refractive index also increases almost in proportion to the acceleration voltage. It is very easy to change the accelerating voltage of the ion beam, and it is possible to program the film forming time by changing it stepwise or gradually. Therefore, the refractive index and dielectric constant of the SrTiO 3 thin film can be freely changed in the film thickness direction with good controllability. In addition, a high dielectric constant, which has not been obtained conventionally, can be obtained at a low substrate temperature.
【0007】実施例2 図2は、Si基板上にSrTiO3薄膜を直接成膜した
光導波路の断面図と屈折率の説明図である。このSrT
iO3薄膜の屈折率は、同図に示すように膜厚方向に変
化しており、Si基板との界面では小さく、表面に近づ
くにしたがって大きくなっている。このような薄膜を形
成するには、成膜初期の加速電圧は小さくして、しだい
に大きくしてゆけば良い。その結果、SrTiO3薄膜
の表面で光の閉じ込めが生じ、基板として屈折率の高い
Siを用いているにも関わらず光導波が生じる。従っ
て、Siなどの半導体基板を用いたときの誘電体光導波
路にみられるSiO2等のバッファ層なしに導波路が形
成でき、構造が単純になった。また、導波損失もTE0
モ―ド、波長6328オングストロ―ムにおいて、1d
B/cm以下の十分小さな値となった。Example 2 FIG. 2 is a sectional view and an explanatory view of the refractive index of an optical waveguide in which a SrTiO 3 thin film is directly formed on a Si substrate. This SrT
The refractive index of the iO 3 thin film changes in the film thickness direction as shown in the figure, and is small at the interface with the Si substrate and increases as it approaches the surface. In order to form such a thin film, the accelerating voltage at the initial stage of film formation may be reduced and gradually increased. As a result, light is confined on the surface of the SrTiO 3 thin film, and optical waveguide is generated even though Si having a high refractive index is used as the substrate. Therefore, the waveguide can be formed without a buffer layer such as SiO 2 which is found in a dielectric optical waveguide when a semiconductor substrate such as Si is used, and the structure is simplified. Also, the waveguide loss is TE 0.
Mode, wavelength 6328 angstrom, 1d
It was a sufficiently small value of B / cm or less.
【0008】実施例3 図3は、Si基板上にLiNbO3薄膜を形成し、その
上部に櫛形のAl電極を形成した光変調器の断面図と屈
折率の説明図である。LiNbO3薄膜の屈折率は同図
に示すように膜の中央部が高く、基板やAl電極との界
面では小さくなっている。従って、LiNbO3薄膜内
に導入された光は、最も屈折率の高い層を伝搬する。従
来このような誘電体光変調器を作製するときには、上部
電極との間にもSiO2層などのバッファ層を用いなけ
ればいけない場合もあったが、本発明によりその必要は
なくなった。櫛形電極にDCパルスを印加した時、電極
直下を導波するTE0モ−ド、TM0モ−ドのいずれの導
波光も回折されることを確認した。Example 3 FIG. 3 is a sectional view and an explanatory view of the refractive index of an optical modulator in which a LiNbO 3 thin film is formed on a Si substrate and a comb-shaped Al electrode is formed on the LiNbO 3 thin film. As shown in the figure, the refractive index of the LiNbO 3 thin film is high in the central part of the film and small at the interface with the substrate or the Al electrode. Therefore, the light introduced into the LiNbO 3 thin film propagates through the layer having the highest refractive index. Conventionally, when manufacturing such a dielectric optical modulator, it was sometimes necessary to use a buffer layer such as a SiO 2 layer between the upper electrode and the upper electrode, but this is no longer necessary according to the present invention. It was confirmed that when a DC pulse was applied to the comb-shaped electrode, both the TE 0 mode and TM 0 mode guided light guided directly under the electrode were diffracted.
【0009】[0009]
【発明の効果】以上説明したように、本発明によれば誘
電体薄膜の屈折率や誘電率を膜厚方向に自由に変化させ
ることができるので、任意の基板上にバッファ層なしに
光導波路を形成でき、構造が単純化される。また、低基
板温度で形成できるので、プロセスの低温化が達成され
る。As described above, according to the present invention, since the refractive index and the dielectric constant of the dielectric thin film can be freely changed in the film thickness direction, the optical waveguide can be formed on any substrate without the buffer layer. Can be formed and the structure is simplified. Further, since the substrate can be formed at a low substrate temperature, the process temperature can be lowered.
【図1】SrTiO3薄膜の誘電率および屈折率に対す
るイオンビ―ム加速電圧依存性を示した図である。FIG. 1 is a diagram showing the ion beam accelerating voltage dependence on the dielectric constant and refractive index of a SrTiO 3 thin film.
【図2】本発明によるSi基板上のSrTiO3薄膜光
導波路の断面図と屈折率の説明図である。FIG. 2 is a cross-sectional view of a SrTiO 3 thin film optical waveguide on a Si substrate according to the present invention and an explanatory view of a refractive index.
【図3】本発明によるSi基板上のLiNbO3薄膜光
導波路を用いた光変調器の断面図と屈折率の説明図であ
る。3A and 3B are a sectional view and an explanatory view of a refractive index of an optical modulator using a LiNbO 3 thin film optical waveguide on a Si substrate according to the present invention.
フロントページの続き (51)Int.Cl.6 識別記号 庁内整理番号 FI 技術表示箇所 C01G 35/00 C01G 35/00 C23C 14/34 C23C 14/34 H03H 3/02 H03H 3/02 B // H01L 27/15 8832−4M H01L 27/15 Continuation of the front page (51) Int.Cl. 6 Identification number Office reference number FI Technical display location C01G 35/00 C01G 35/00 C23C 14/34 C23C 14/34 H03H 3/02 H03H 3/02 B // H01L 27/15 8832-4M H01L 27/15
Claims (1)
れ、それぞれAとしてBa,Sr,Pb,La,Liの
少なくとも1種以上、BとしてZr,Ti,Ta,Nb
の少なくとも1種以上を含む材料、あるいはBi4Ti3
O12、あるいはZnOを用い、イオンビ―ムスパッタ法
でスパッタ粒子の加速電圧を変化させることにより、誘
電率あるいは屈折率が膜厚方向に変化する誘電体薄膜を
任意の基板上に形成する工程を備えたことを特徴とする
誘電体薄膜の製造方法。1. The target has a chemical formula represented by ABO 3 , wherein A is at least one of Ba, Sr, Pb, La and Li, and B is Zr, Ti, Ta and Nb.
A material containing at least one or more of Bi 4 Ti 3
A step of forming a dielectric thin film whose permittivity or refractive index changes in the film thickness direction on an arbitrary substrate by changing the acceleration voltage of sputtered particles by ion beam sputtering using O 12 or ZnO A method for producing a dielectric thin film, comprising:
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP3053511A JP2556206B2 (en) | 1991-02-27 | 1991-02-27 | Method for manufacturing dielectric thin film |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP3053511A JP2556206B2 (en) | 1991-02-27 | 1991-02-27 | Method for manufacturing dielectric thin film |
Publications (2)
Publication Number | Publication Date |
---|---|
JPH04272608A JPH04272608A (en) | 1992-09-29 |
JP2556206B2 true JP2556206B2 (en) | 1996-11-20 |
Family
ID=12944843
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP3053511A Expired - Fee Related JP2556206B2 (en) | 1991-02-27 | 1991-02-27 | Method for manufacturing dielectric thin film |
Country Status (1)
Country | Link |
---|---|
JP (1) | JP2556206B2 (en) |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2642876B2 (en) * | 1994-08-11 | 1997-08-20 | 工業技術院長 | Lead titanate-based dielectric thin film |
JPH11236666A (en) * | 1998-02-25 | 1999-08-31 | Murata Mfg Co Ltd | Film forming device and production of dielectric film |
JP2009249689A (en) * | 2008-04-07 | 2009-10-29 | Toyota Motor Corp | Method for manufacturing lithium composite oxide thin film and method for manufacturing electrode body |
Family Cites Families (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS63266061A (en) * | 1987-04-23 | 1988-11-02 | Sumitomo Metal Mining Co Ltd | Producing of multielemental sputtering thin film and sputtering device |
-
1991
- 1991-02-27 JP JP3053511A patent/JP2556206B2/en not_active Expired - Fee Related
Also Published As
Publication number | Publication date |
---|---|
JPH04272608A (en) | 1992-09-29 |
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