JPS58979Y2 - Surface wave thin film interdigital transducer - Google Patents
Surface wave thin film interdigital transducerInfo
- Publication number
- JPS58979Y2 JPS58979Y2 JP16216281U JP16216281U JPS58979Y2 JP S58979 Y2 JPS58979 Y2 JP S58979Y2 JP 16216281 U JP16216281 U JP 16216281U JP 16216281 U JP16216281 U JP 16216281U JP S58979 Y2 JPS58979 Y2 JP S58979Y2
- Authority
- JP
- Japan
- Prior art keywords
- thin film
- electrode
- piezoelectric
- interdigital
- surface wave
- 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
Links
Landscapes
- Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)
Description
【考案の詳細な説明】
本考案は弾性表面波（以後単に表面波と称す）の薄膜す
だれ状変換器に関するものである。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thin film interdigital transducer for surface acoustic waves (hereinafter simply referred to as surface waves).
従来、表面波を用いた素子は、ＶＨＦ−ＵＨＦ帯域で使
用可能な、低損失・超小型で優れた性能を有する電気通
信路素子（例えば遅延線・フィルタなど）として開発さ
れつつある。Conventionally, devices using surface waves are being developed as telecommunication path devices (for example, delay lines, filters, etc.) that can be used in the VHF-UHF band and have low loss, ultra-small size, and excellent performance.
表面波素子に必要な、送・受波用変換器の代表例として
は、構造の簡単さ、製作の容易さのため、圧電物質の表
面に、金属の蒸着によって形成されたすだれ状電極をも
つ変換器がしばしば用いられてきた。A typical example of a transmitting/receiving transducer required for a surface wave device is a transducer that has interdigital electrodes formed by vapor deposition of metal on the surface of a piezoelectric material due to its simple structure and ease of manufacture. Transducers have often been used.
しかし最近では、表面波の用途が拡大され、ガラスや半
導体などの非圧電物質基板上での表面波が利用されてい
る。However, recently, the applications of surface waves have been expanded to include surface waves on non-piezoelectric substrates such as glass and semiconductors.
この場合の変換器は、基板上に圧電薄膜を形成せしめ、
基板と薄膜の境界面もしくは薄膜表面の一方にすだれ状
電極會備え他方に短絡用平板電極を備えるか、又は前記
平板電極を用いない薄膜変換器が知られている。The transducer in this case has a piezoelectric thin film formed on the substrate,
Thin film transducers are known in which one of the interface between the substrate and the thin film or the surface of the thin film is provided with an interdigital interdigital electrode assembly and the other is provided with a flat plate electrode for shorting, or which does not use the flat plate electrode.
ところで、一般に圧電物質の音響インピーダンスは、物
質中での電気的又は音響的摂動状態により異なる。Incidentally, the acoustic impedance of a piezoelectric material generally varies depending on the state of electrical or acoustic perturbation within the material.
上述の変換器の場合、前記すだれ状電極の電極指領域の
音響インピーダンスは、電極指間隙領域のそれに比して
減少または増大する。In the case of the transducer described above, the acoustic impedance of the interdigital electrode finger region is reduced or increased compared to that of the interdigital gap region.
このときの両者の大小関係は膜の厚さおよび上記平板電
極の有無に依存する。The size relationship between the two at this time depends on the thickness of the film and the presence or absence of the flat electrode.
両者の場合このため表面波の伝搬面で、音響インピーダ
ンスが周期的に変動するため、表面波の反射がおこる。In both cases, the acoustic impedance fluctuates periodically on the surface wave propagation surface, causing reflection of the surface wave.
特に、狭帯域フィルタや、分散形遅延線、電極符号化遅
延線などのように、多数の櫛歯を要する変換器の場合は
、前記の反射表面波がフィルタ特性におよぼす影響は無
視できず、その振幅・位相特性にリップルを生ぜしめ、
極めて好ましくない。In particular, in the case of converters that require a large number of comb teeth, such as narrowband filters, distributed delay lines, and electrode-coded delay lines, the influence of the reflected surface waves on the filter characteristics cannot be ignored. It causes ripples in its amplitude and phase characteristics,
Extremely undesirable.
従って、上述の理由による音響インピーダンスの周期的
変動をなくすような構造・手段が望まれる。Therefore, a structure and means are desired that eliminate periodic fluctuations in acoustic impedance due to the above-mentioned reasons.
本考案の目的は、簡単な構造で上記の要請を満足できる
ような新しい薄膜すだれ状変換器を提供することにある
。An object of the present invention is to provide a new thin film interdigital transducer that can satisfy the above requirements with a simple structure.
本考案によれば、非圧電物質基板上に圧電物質から成る
薄膜が形成され、非圧電基板と圧電薄膜の境界面もしく
は圧電薄膜表面の一方にすだれ状電極を備える表面波変
換器において、前記非圧電基板表面の基板の表面層にお
ける、前記すだれ状電極の電極指間隙領域に、拡散法に
よる拡散層が形成され、前記電極指領域及び前記電極指
間隙領域の両音響インピーダンスの均一化が計られたこ
とを特徴とする表面波薄膜すだれ状変換器が得られる。According to the present invention, in a surface wave transducer, a thin film made of a piezoelectric material is formed on a non-piezoelectric material substrate, and an interdigital electrode is provided on one of the interface between the non-piezoelectric substrate and the piezoelectric thin film or the surface of the piezoelectric thin film. A diffusion layer is formed by a diffusion method in the electrode finger gap region of the interdigital electrode in the surface layer of the substrate on the surface of the piezoelectric substrate, and the acoustic impedance of both the electrode finger region and the electrode finger gap region is made uniform. A surface wave thin film interdigital transducer is obtained.
一般に、ガラスの表面近傍に含まれるある種の金属元素
を電界効果イオン変換法などの拡散法により、これより
重い元素で置換してやると、その領域の音響インピーダ
ンスは低下し、逆に軽い元素で置換すると、上昇するこ
とが知られている。In general, if a certain metal element contained near the surface of the glass is replaced with a heavier element using a diffusion method such as field effect ion conversion, the acoustic impedance of that region decreases, and conversely, it is replaced with a lighter element. It is known that it will increase.
しかもその置換領域のパターンは、フォトマスキングな
どの方法により、選択的に形成できる。Moreover, the pattern of the replacement region can be selectively formed by a method such as photomasking.
本考案はこの現象な利用するものである。The present invention takes advantage of this phenomenon.
即ち、従来の薄膜変換器において、すだれ状電極の電極
指領域の方が、電極指間隙領域よりも音響インピーダン
スが小さくなるように変換器の構造が設定されているも
のに対しては、予め電極指間隙領域の基板表面に、前述
の方法で拡散を施し、音響インピーダンスが周囲よりも
低下した領域を形成せしめておくことにより、変換器部
分の音響インピーダンスの均一化を計るものである。In other words, in conventional thin film transducers, the structure of the transducer is set so that the acoustic impedance is smaller in the electrode finger region of the interdigital electrode than in the electrode finger gap region. The acoustic impedance of the transducer portion is made uniform by applying diffusion to the substrate surface in the finger gap region using the method described above to form a region where the acoustic impedance is lower than the surrounding area.
逆に〜電極指領域の音響インピーダンスが、電極指間隙
領域のそれよりも大きいような構造の薄膜変換器に対し
ては、予め、電極指領域の基板表面に、前述の方法で拡
散を施すことにより、前記同様、音響インピーダンスの
均一化を計ることができる。Conversely, for a thin film transducer with a structure in which the acoustic impedance of the electrode finger region is larger than that of the electrode finger gap region, diffusion should be applied in advance to the substrate surface of the electrode finger region using the method described above. As described above, it is possible to equalize the acoustic impedance.
本発明の利点は、すだれ状電極の付着の有無による表面
波の反射が抑制され、従って変換器の振幅・位相特性の
りツプルが抑制されることにある。An advantage of the present invention is that the reflection of surface waves due to the presence or absence of interdigital electrodes is suppressed, and therefore the amplitude/phase characteristic ripple of the transducer is suppressed.
更に本考案の他の利点は、表面波伝搬面に機械停凹凸を
施すことなく、基板の表面近傍の物質定数のみを変化せ
しめるため表面波の減衰を増長させることなく、簡単な
構造でしかも短時間で作成できることにある。Furthermore, another advantage of the present invention is that only the material constant near the surface of the substrate is changed without adding mechanical irregularities to the surface wave propagation surface, so the attenuation of the surface wave is not increased, and the structure is simple and short. The reason lies in the fact that it can be created in a matter of time.
次に図面を用いて、本考案の詳細留説明する。Next, the present invention will be explained in detail with reference to the drawings.
図は、本考案の一実施例の構造断面図である。The figure is a structural sectional view of an embodiment of the present invention.
図において゛予めタリウムイオン（Ｔｌ＋） を多く含
むガラス基板１２０表面に、アルミニウム（ＡＩ）およ
びチタン（Ｔｉ）からなるすだれ状電極１３が蒸着され
、該電極のない領域１５中に含まれるＴ１＋の一部が、
電界効果イオン交換法によりナトリウムやカリウムイオ
ン（Ｎａ＋・Ｋ＋）で置換されている。In the figure, an interdigital electrode 13 made of aluminum (AI) and titanium (Ti) is deposited in advance on the surface of a glass substrate 120 containing a large amount of thallium ions (Tl+). The department is
Sodium and potassium ions (Na+/K+) are substituted by field effect ion exchange method.
これら電極領域な覆うように硫化亜鉛（ＺｎＳ）膜１１
がスパッタリングにより形成されている。A zinc sulfide (ZnS) film 11 is placed to cover these electrode areas.
is formed by sputtering.
ＺｎＳの厚みは約４μ・電極１３の幅および間隙は１０
μである。The thickness of ZnS is approximately 4 μ, the width and gap of electrode 13 is 10
μ.
またイオン交換部１５の深さは約５μである。Further, the depth of the ion exchange section 15 is approximately 5μ.
本実施例では、前述のような櫛歯電極の有無による音響
インピーダンスの差に基く表面波伝搬速度の差△Ｖ／Ｖ
＝４％がガラス基板のイオン交換部１５で相殺されて、
音響インピーダンスの均一化が計られている。In this example, the difference in surface wave propagation velocity △V/V based on the difference in acoustic impedance due to the presence or absence of the comb-teeth electrode as described above.
=4% is offset by the ion exchange part 15 of the glass substrate,
The acoustic impedance is made uniform.
この場合、前述のように、前記伝搬速度差ＡＶ／′ｖは
、薄膜の厚みおよび短絡用平板電極の有無に依存して変
動するが、その変動量は、イオン交換部１５の深さおよ
びイオンの置換量を調整することにより相殺できる。In this case, as described above, the propagation velocity difference AV/'v varies depending on the thickness of the thin film and the presence or absence of the short-circuiting plate electrode, but the amount of variation varies depending on the depth of the ion exchange section 15 and the ion This can be offset by adjusting the amount of substitution.
図は、本考案の一実施例の構造断面図である。
図において、１１はＺｎＳ圧電薄膜、 １２はガラス基
板、１３はすだれ状電極、１５はガラス基板上のイオン
交換部である。The figure is a structural sectional view of an embodiment of the present invention. In the figure, 11 is a ZnS piezoelectric thin film, 12 is a glass substrate, 13 is an interdigital electrode, and 15 is an ion exchange section on the glass substrate.
Claims (1)
前記非圧電基板と前記圧電薄膜の境界面、もしくは前記
圧電薄膜表面のいづれか一方にすだれ状電極を備える表
面波変換器において、前記非圧電基板の表面層におれる
、前記すだれ状電極の電極指間隙領域に、拡散法による
拡散層が形成され、前記電極指領域及び前記電極指間隙
領域の両音響インピーダンスの均一化が計られたことヲ
特徴とする表面波薄膜すだれ状変換器。A thin film of piezoelectric material is formed on a non-piezoelectric material substrate,
In a surface wave transducer comprising an interdigital electrode on either the interface between the non-piezoelectric substrate and the piezoelectric thin film or the surface of the piezoelectric thin film, electrode fingers of the interdigital electrode placed on the surface layer of the non-piezoelectric substrate; 1. A surface acoustic wave thin film interdigital transducer characterized in that a diffusion layer is formed in the gap region by a diffusion method, and the acoustic impedance of both the electrode finger region and the electrode finger gap region is made uniform.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP16216281U JPS58979Y2 (en) | 1981-10-29 | 1981-10-29 | Surface wave thin film interdigital transducer |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP16216281U JPS58979Y2 (en) | 1981-10-29 | 1981-10-29 | Surface wave thin film interdigital transducer |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS5796518U JPS5796518U (en) | 1982-06-14 |
| JPS58979Y2 true JPS58979Y2 (en) | 1983-01-08 |
Family
ID=29521049
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP16216281U Expired JPS58979Y2 (en) | 1981-10-29 | 1981-10-29 | Surface wave thin film interdigital transducer |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS58979Y2 (en) |
-
1981
- 1981-10-29 JP JP16216281U patent/JPS58979Y2/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5796518U (en) | 1982-06-14 |
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