JPH10209804A - Surface acoustic wave resonator and surface acoustic wave filter - Google Patents
Surface acoustic wave resonator and surface acoustic wave filterInfo
- Publication number
- JPH10209804A JPH10209804A JP1236697A JP1236697A JPH10209804A JP H10209804 A JPH10209804 A JP H10209804A JP 1236697 A JP1236697 A JP 1236697A JP 1236697 A JP1236697 A JP 1236697A JP H10209804 A JPH10209804 A JP H10209804A
- Authority
- JP
- Japan
- Prior art keywords
- idt
- surface acoustic
- reflector
- saw
- acoustic 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.)
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- Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、自動車・携帯電話
器のアンテナ分波器等に用いられる弾性表面波（Surfac
e Acoustic Wave、以下「ＳＡＷ」という）共振子及び
これを用いて構成される帯域フィルタであるＳＡＷフィ
ルタに関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface acoustic wave (Surfac) used for an antenna duplexer of an automobile or a cellular phone.
e Acoustic Wave (hereinafter referred to as "SAW") and a SAW filter which is a bandpass filter using the same.
【０００２】[0002]
【従来の技術】従来、この種のＳＡＷ共振子とこれを用
いたＳＡＷフィルタに関する技術としては、例えば、次
のような文献に記載されるものがあった。 文献：電子情報通信学会誌、Ｊ７６−Ａ［２］（１９９
３−２） Ｐ．２４５−２５２図１４及び図１５は前記
文献に記載されたＳＡＷ共振子を用いた定Ｋ型フィルタ
の原理を示す図であり、このうち図１４は１段梯型ＳＡ
Ｗフィルタの構成図、及び図１５は図１４のＳＡＷフィ
ルタの周波数特性図である。図１４の１段梯型ＳＡＷフ
ィルタは、１端子対ＳＡＷ共振子を直列腕１及び並列腕
２に用い、これらを梯型に接続して帯域フィルタにした
ものである。直列腕１及び並列腕２を構成するＳＡＷ共
振子は、ＳＡＷを励振するための複数の電極指を有する
すだれ状トランスデューサ（Interdigital Transduce
r、以下「ＩＤＴ」という）と、このＩＤＴの両脇（即
ち、左側と右側）に配置され、ＳＡＷを該ＩＤＴ側へ反
射させるための金属ストリップによる複数の電極指を有
する左側及び右側のグレーティング反射器（以下、単に
「反射器」という）とで、構成されている。2. Description of the Related Art Conventionally, as a technique relating to a SAW resonator of this type and a SAW filter using the same, there are techniques described in the following documents, for example. Reference: IEICE Journal, J76-A [2] (199
3-2) P.I. FIGS. 14 and 15 are diagrams showing the principle of a constant K-type filter using a SAW resonator described in the above-mentioned document. FIG. 14 shows a one-stage ladder type SA.
FIG. 15 is a configuration diagram of the W filter, and FIG. 15 is a frequency characteristic diagram of the SAW filter of FIG. The one-stage ladder-type SAW filter of FIG. 14 uses a one-port SAW resonator for the series arm 1 and the parallel arm 2 and connects them in a ladder shape to form a bandpass filter. The SAW resonators forming the series arm 1 and the parallel arm 2 are interdigital transducers (Interdigital Transduce) having a plurality of electrode fingers for exciting the SAW.
r, hereinafter referred to as “IDT”), and left and right gratings disposed on both sides (ie, left and right sides) of the IDT and having a plurality of electrode fingers formed by metal strips for reflecting the SAW to the IDT side. And a reflector (hereinafter simply referred to as a “reflector”).
【０００３】図１４のＳＡＷフィルタは、図１５に示す
ように、定Ｋ型フィルタの理論から、直列腕１の共振周
波数と並列腕２の反共振周波数を一致させることによっ
て帯域フィルタを実現できる。図１６は図１４の直列腕
１及び並列腕２を構成する従来の１端子対ＳＡＷ共振子
の平面図、及び図１７は図１６のＡ部分の拡大図であ
る。このＳＡＷ共振子は、３６°Ｙ−ＸのＬｉＴａＯ３
単結晶基板（以下、「ＬＴ基板」という）１１を有して
いる。ＬＴ基板１１上には、複数の電極指を有するＩＤ
Ｔ１２と、このＤＴ１２を挟んで左側と右側に配置され
た複数の電極指をそれぞれ有する左側及び右側の反射器
１３，１４とが、形成されている。ＩＤＴ１２の上端に
は一方の端子１５が接続され、下端には他方の端子１６
が接続されている。この種のＳＡＷ共振子では、例え
ば、端子１５，１６間に高周波信号を印加すると、ＩＤ
Ｔ１２下のＬＴ基板１１の表面が歪み、入力された高周
波信号と同じ周波数のＳＡＷが放射される。ＩＤＴ１２
から放射されたＳＡＷは、一部が該ＩＤＴ１２内で反射
され、他が反射器１３，１４で反射される。この結果、
両反射器１３，１４間の領域にＳＡＷの定在波が生成さ
れ、共振特性を示す。The SAW filter shown in FIG. 14 can be realized as a bandpass filter by matching the resonance frequency of the series arm 1 and the antiresonance frequency of the parallel arm 2 based on the theory of a constant K filter as shown in FIG. FIG. 16 is a plan view of a conventional one-port SAW resonator constituting the series arm 1 and the parallel arm 2 of FIG. 14, and FIG. 17 is an enlarged view of a portion A of FIG. This SAW resonator has a LiTaO 3 of 36 ° YX.
A single crystal substrate (hereinafter, referred to as “LT substrate”) 11 is provided. An ID having a plurality of electrode fingers on the LT substrate 11
T12 and left and right reflectors 13 and 14 having a plurality of electrode fingers disposed on the left and right sides of the DT12, respectively, are formed. One terminal 15 is connected to the upper end of the IDT 12, and the other terminal 16 is connected to the lower end.
Is connected. In this type of SAW resonator, for example, when a high-frequency signal is applied between terminals 15 and 16,
The surface of the LT substrate 11 under T12 is distorted, and a SAW having the same frequency as the input high-frequency signal is emitted. IDT12
A part of the SAW emitted from is reflected in the IDT 12 and the other part is reflected by the reflectors 13 and 14. As a result,
A standing wave of the SAW is generated in a region between the two reflectors 13 and 14, and exhibits a resonance characteristic.
【０００４】ＩＤＴ１２及び反射器１３，１４は、Ａｌ
膜で形成されている。図１７に示すように、通常はマス
クの作りやすさ等から、ＩＤＴ１２部分の電極指幅をＩ
ｍｉ、ＩＤＴ１２部分の電極指のない部分をＩｇｉ、反
射器１３部分の電極指幅をＩｍｇ、反射器１３部分の電
極指のない部分をＩｇｇ、ＳＡＷ波長をλとすると、次
のように設定されている。[0004] The IDT 12 and the reflectors 13 and 14 are made of Al.
It is formed of a film. As shown in FIG. 17, the width of the electrode finger in the IDT12 portion is usually set to I due to the ease of making the mask.
mi, the electrode finger width of the reflector 13 is Img, the electrode finger width of the reflector 13 is Igg, and the SAW wavelength is λ. ing.
【０００５】 Ｉｍｉ＋Ｉｇｉ＝λ／２ ・・・（１） Ｉｍｇ＋Ｉｇｇ＝λ／２ ・・・（２） Ｉｍｉ＝Ｉｇｉ＝Ｉｍｇ＝Ｉｇｇ＝λ／４ ・・・（３） 図１８（１）〜（５）は、図１４のＳＡＷフィルタを構
成する図１６のＳＡＷ共振子の製造方法の一例を示す図
である。図１６のＳＡＷ共振子は、例えば次の（ａ）〜
（ｅ）のような工程によって製造される。Imi + Igi = λ / 2 (1) Img + Igg = λ / 2 (2) Imi = Igi = Img = Igg = λ / 4 (3) FIGS. 18 (1) to (5) 17) is a diagram illustrating an example of a method of manufacturing the SAW resonator of FIG. 16 that configures the SAW filter of FIG. 14. The SAW resonator shown in FIG.
It is manufactured by a process as shown in FIG.
【０００６】（ａ） 図１８（１）の工程 ＬＴ基板１１上のパターンを形成する面に、レジスト１
７をスピンコートする。 （ｂ） 図１８（２）の露光工程 ガラスマスク１８を用い、光１９によってフィルタのパ
ターンをレジスト１７上に転写する。 （ｃ） 図１８（３）のパターン形成工程 現像によって不要なレジスト１７を除去し、レジストパ
ターン１７ａを形成する。 （ｄ） 図１８（４）の工程 電極指となるＡｌ膜２０を全面に蒸着する。 （ｅ） 図１８（５）の工程 有機溶剤を用い、不要なＡｌ膜２０をレジストパターン
１７ａと一緒にリフトオフし、ＩＤＴ１２及び反射器１
３，１４の電極指２０ａを形成する。その後、端子１
５，１６等を接続すれば、図１６のＳＡＷ共振子の製造
が終了する。(A) Step of FIG. 18A A resist 1 is formed on the surface of the LT substrate 11 where a pattern is to be formed.
7 is spin-coated. (B) Exposure Step of FIG. 18B Using a glass mask 18, the pattern of the filter is transferred onto the resist 17 by light 19. (C) Pattern forming step of FIG. 18C The unnecessary resist 17 is removed by development to form a resist pattern 17a. (D) Step of FIG. 18D An Al film 20 to be an electrode finger is deposited on the entire surface. (E) Step of FIG. 18 (5) The unnecessary Al film 20 is lifted off together with the resist pattern 17a using an organic solvent, and the IDT 12 and the reflector 1 are removed.
3, 14 electrode fingers 20a are formed. Then, terminal 1
When 5, 5, and the like are connected, the manufacture of the SAW resonator shown in FIG. 16 is completed.
【０００７】[0007]
【発明が解決しようとする課題】しかしながら、従来の
ＳＡＷ共振子とこれを用いた梯型ＳＡＷフィルタでは、
次のような問題があり、これを解決することが困難であ
った。図１９（ａ），（ｂ）は図１６のＳＡＷ共振子の
周波数特性図であり、同図（ａ）はＩＤＴ１２の放射コ
ンダクタンスの周波数特性図、及び同図（ｂ）は反射器
１３，１４の反射率の周波数特性図である。図１９
（ａ），（ｂ）に示すように、梯型ＳＡＷフィルタを構
成するＳＡＷ共振子のＩＤＴ１２の放射特性（放射コン
ダクタンスの周波数特性）の中心周波数ｆＯＩと比較し
て、反射器１３，１４の周波数特性の中心周波数ｆＯｇ
が高い方にずれている。図２０、図２１及び図２２は実
際にＬＴ基板１１上にＩＤＴ１２−１，１２−２間に反
射器１３を置いてその通過特性を測定した例を示す図で
あり（線幅約１μｍの例）、このうち図２０は通過特性
の測定回路図、及び図２１、図２２は反射器１３のスト
ップバンド評価を示す図である。なお、図２０の測定回
路において、ＩＤＴ１２−１，１２−２は交差長１１０
μｍ、対数１５であり、反射器１３の電極指は８０本で
ある。However, in a conventional SAW resonator and a ladder SAW filter using the same,
There were the following problems, which were difficult to solve. 19 (a) and 19 (b) are frequency characteristic diagrams of the SAW resonator of FIG. 16, FIG. 19 (a) is a frequency characteristic diagram of the radiation conductance of the IDT 12, and FIG. 19 (b) is reflectors 13 and 14. FIG. 7 is a frequency characteristic diagram of the reflectance of FIG. FIG.
As shown in (a) and (b), the frequency of the reflectors 13 and 14 is compared with the center frequency fOI of the radiation characteristic (frequency characteristic of radiation conductance) of the IDT 12 of the SAW resonator constituting the ladder SAW filter. Characteristics center frequency fOg
Is shifted to the higher side. FIGS. 20, 21 and 22 are diagrams showing examples in which the reflector 13 is actually placed on the LT substrate 11 between the IDTs 12-1 and 12-2 and the transmission characteristics thereof are measured (an example in which the line width is about 1 μm). FIG. 20 is a circuit diagram for measuring the pass characteristic, and FIGS. 21 and 22 are diagrams showing the evaluation of the stop band of the reflector 13. In the measurement circuit of FIG. 20, the IDTs 12-1 and 12-2 have an intersection length of 110.
μm, logarithm 15 and the number of electrode fingers of the reflector 13 is 80.
【０００８】これらの図２０〜図２２においても、反射
器１３の反射特性の中心周波数ｆＯＩがＩＤＴ１２−
１，１２−２の放射コンダクタンスの周波数特性の中心
周波数ｆＯｇよりも高い方にずれている。そのため、Ｉ
ＤＴ１２−１，１２−２の中心周波数ｆＯｇよりも低い
周波数に対しては反射器１３の反射効率が悪く、この結
果、ＳＡＷ共振子のＱ値があまり上がらず、低損失化し
にくいという問題があった。特に、ＩＤＴ１２−１，１
２−２の電極指の本数が少ない場合、該ＩＤＴ１２−
１，１２−２の放射コンダクタンスは広帯域であるか
ら、反射器１３の反射特性の中心周波数ｆＯＩがずれて
いると、ＩＤＴ１２−１，１２−２から放射された表面
波は反射器１３で閉込められず、Ｑ値が思ったほど上が
らないという問題があった。本発明は、前記従来技術が
持っていた課題を解決し、ＳＡＷ共振子のＱ値を向上さ
せ、低損失のＳＡＷフィルタを実現することを目的とす
る。[0008] Also in FIGS. 20 to 22, the center frequency fOI of the reflection characteristic of the reflector 13 is equal to the IDT12-.
The frequency characteristics of the radiation conductance of 1, 12-2 are shifted to a higher frequency than the center frequency fOg. Therefore, I
At frequencies lower than the center frequency fOg of the DTs 12-1 and 12-2, the reflection efficiency of the reflector 13 is poor. As a result, the Q value of the SAW resonator does not increase so much, and it is difficult to reduce the loss. Was. In particular, IDT 12-1, 1
When the number of electrode fingers of 2-2 is small, the IDT 12-
Since the radiated conductance of the IDTs 12-1 and 12-2 is broad, if the center frequency fOI of the reflection characteristics of the reflector 13 is shifted, the surface waves radiated from the IDTs 12-1 and 12-2 are confined by the reflector 13. There was a problem that the Q value did not increase as expected. An object of the present invention is to solve the problems of the prior art, improve the Q value of the SAW resonator, and realize a low-loss SAW filter.
【０００９】[0009]
【課題を解決するための手段】前記課題を解決するため
に、本発明のうちの請求項１の発明では、ＳＡＷ共振子
において、ＬＴ基板上に形成され、ＳＡＷを励振するた
めの金属膜からなる複数の電極指を有するＩＤＴと、前
記基板上に前記ＩＤＴを挟んで左側と右側に形成され、
前記ＳＡＷを該ＩＤＴ側へ反射させるための前記金属膜
と同一の金属膜からなる複数の電極指をそれぞれ有する
左側及び右側の反射器とを備え、比重が２〜３、熱膨張
率が１０〜２０、及び前記金属膜に対する膜厚比が４０
％〜７０％の絶縁膜を、前記反射器上に被着している。
請求項２の発明では、請求項１のＩＤＴ及び反射器を備
え、前記反射器の電極指膜厚を前記ＩＤＴの電極指膜厚
よりも４０％〜６０％厚くしている。請求項３の発明で
は、請求項１のＩＤＴ及び反射器を備え、前記反射器の
電極指幅を前記ＩＤＴの電極指幅よりも１０％〜５０％
広くしている。請求項４の発明では、請求項１のＩＤＴ
及び反射器を備え、前記反射器を、前記ＩＤＴの金属膜
よりも比重の大きな金属膜で形成している。According to a first aspect of the present invention, there is provided a SAW resonator comprising a metal film formed on an LT substrate for exciting a SAW. An IDT having a plurality of electrode fingers, and formed on the substrate on the left and right sides with the IDT interposed therebetween;
A reflector having left and right electrodes each having a plurality of electrode fingers made of the same metal film as the metal film for reflecting the SAW to the IDT side, having a specific gravity of 2-3 and a thermal expansion coefficient of 10 20, and the film thickness ratio to the metal film is 40
% To 70% of the insulating film is deposited on the reflector.
According to a second aspect of the present invention, the IDT and the reflector according to the first aspect are provided, and the thickness of the electrode finger of the reflector is 40% to 60% larger than the thickness of the electrode finger of the IDT. According to the third aspect of the present invention, the IDT and the reflector of the first aspect are provided, and the electrode finger width of the reflector is 10% to 50% of the electrode finger width of the IDT.
Wide. In the invention of claim 4, the IDT of claim 1
And a reflector, wherein the reflector is formed of a metal film having a higher specific gravity than the metal film of the IDT.
【００１０】請求項５の発明では、請求項１のＩＤＴ及
び反射器を備え、前記ＩＤＴの電極指幅を前記反射器の
電極指幅よりも１０％〜５０％狭くしている。請求項６
の発明では、請求項１、２、３又は５のＳＡＷ共振子を
直列腕及び並列腕に用い、これらを梯型に接続して前記
基板上に形成し、かつ該直列腕の共振周波数と該並列腕
の反共振周波数を一致させて定Ｋ型構成のＳＡＷフィル
タを構成している。請求項７の発明では、請求項６のＳ
ＡＷフィルタにおいて、前記基板を３６°Ｙ−Ｘ、ＬＴ
基板で、前記ＩＤＴ及び反射器をＡｌ膜で、それぞれ形
成している。請求項８の発明では、請求項４のＳＡＷ共
振子を直列腕及び並列腕に用い、これらを梯型に接続し
て前記基板上に形成し、かつ該直列腕の共振周波数と該
並列腕の反共振周波数を一致させて定Ｋ型構成のＳＡＷ
フィルタを構成している。請求項９の発明では、請求項
８のＳＡＷフィルタにおいて、前記基板を３６°Ｙ−
Ｘ、ＬＴ基板で、前記ＩＤＴをＡｌ膜で、前記反射器を
Ｔｉ、Ｓｎ、Ｆｅ、Ｎｉ又はＣｕのいずれか１つの金属
膜で、それぞれ形成している。According to a fifth aspect of the present invention, the IDT and the reflector of the first aspect are provided, and the electrode finger width of the IDT is made 10% to 50% narrower than the electrode finger width of the reflector. Claim 6
In the invention, the SAW resonator according to claim 1, 2, 3 or 5 is used for a series arm and a parallel arm, these are connected in a ladder shape to be formed on the substrate, and the resonance frequency of the series arm and the The anti-resonance frequencies of the parallel arms are matched to form a constant K-type SAW filter. According to the seventh aspect of the present invention, the S
In the AW filter, the substrate is 36 ° YX, LT
On the substrate, the IDT and the reflector are each formed of an Al film. According to an eighth aspect of the present invention, the SAW resonator according to the fourth aspect is used for a series arm and a parallel arm, these are connected in a ladder shape to be formed on the substrate, and the resonance frequency of the series arm and the parallel arm are used. SAW of constant K type configuration by matching anti-resonance frequency
Make up the filter. According to a ninth aspect of the present invention, in the SAW filter according to the eighth aspect, the substrate is formed at 36 ° Y−
In the X and LT substrates, the IDT is formed of an Al film, and the reflector is formed of a metal film of any one of Ti, Sn, Fe, Ni, and Cu.
【００１１】以上のように、請求項１、６及び７の発明
によれば、ＩＤＴから放射されたＳＡＷは、一部が該Ｉ
ＤＴ内部で反射され、他が反射器で反射される。反射器
上に絶縁膜が形成されているので、該反射器部分の音速
が低下して反射特性の中心周波数が低い方にシフトす
る。請求項２、６及び７の発明によれば、ＩＤＴの電極
指膜厚が反射器の電極指膜厚よりも薄くなっているの
で、該ＩＤＴ部分の音速が上がり、ＩＤＴ部分の放射コ
ンダクタンスの周波数特性が高い方にシフトする。請求
項３、６及び７の発明によれば、反射器の電極指幅が広
がっているので、該反射器下のＳＡＷは電極指の下を通
るほど音速が低下し、見かけ上、反射器部分の反射特性
の中心周波数が低い方にシフトする。請求項４、８及び
９の発明によれば、比重の大きな金属膜で形成された反
射器は、該反射器下の音速を低下させ、ＩＤＴの放射コ
ンダクタンスの周波数特性を低い周波数にシフトする。
請求項５、６及び７の発明によれば、ＩＤＴの電極指の
幅が狭くなっているので、該ＩＤＴ部分の放射コンダク
タンスの中心周波数は変らないが、広帯域となる。As described above, according to the first, sixth and seventh aspects of the present invention, a part of the SAW radiated from the IDT is
The light is reflected inside the DT and the others are reflected by the reflector. Since the insulating film is formed on the reflector, the sound speed of the reflector decreases, and the center frequency of the reflection characteristic shifts to a lower one. According to the second, sixth and seventh aspects of the present invention, since the thickness of the electrode finger of the IDT is smaller than the thickness of the electrode finger of the reflector, the sound speed of the IDT portion increases, and the frequency of the radiation conductance of the IDT portion increases. The characteristics shift to higher ones. According to the third, sixth and seventh aspects of the present invention, since the width of the electrode finger of the reflector is widened, the sound velocity of the SAW under the reflector decreases as the electrode finger passes below the electrode finger. , The center frequency of the reflection characteristic shifts to the lower side. According to the fourth, eighth and ninth aspects of the present invention, the reflector formed of a metal film having a large specific gravity lowers the speed of sound under the reflector, and shifts the frequency characteristic of the radiation conductance of the IDT to a lower frequency.
According to the fifth, sixth and seventh aspects of the present invention, since the width of the electrode finger of the IDT is reduced, the center frequency of the radiation conductance of the IDT portion does not change, but the band becomes wider.
【００１２】[0012]
【発明の実施の形態】第１の実施形態 本発明の第１の実施形態であるＳＡＷ共振子とこれを用
いて構成した梯型ＳＡＷフィルタの（１）構成、（２）
動作、及び（３）利点を説明する。 （１）構成 図１（ａ），（ｂ）は本発明の第１の実施形態である梯
型ＳＡＷフィルタを構成するＳＡＷ共振子の構成図であ
り、同図（ａ）は平面図、及び同図（ｂ）は断面図であ
る。このＳＡＷ共振子は、図１４に示す梯型ＳＡＷフィ
ルタの直列腕１及び並列腕２を構成するものであり、Ｌ
Ｔ基板（例えば、３６°Ｙ−ＸのＬＴ基板）２１を有し
ている。ＬＴ基板２１上には、ＳＡＷを励振するための
薄い金属膜（例えば、膜厚５０００ÅのＡｌ膜）からな
る複数の電極指を有するＩＤＴ２２と、このＤＴ２２を
挟んで左側と右側に配置され、ＳＡＷを該ＩＤＴ２２側
へ反射させるための薄い金属膜（例えば、膜厚５０００
ÅのＡｌ膜）からなる複数の電極指をそれぞれ有する左
側及び右側の反射器２３，２４とが、形成されている。
ＩＤＴ２２の上端には一方の端子２５が接続され、下端
には他方の端子２６が接続されている。左側及び右側の
反射器２３，２４上には、絶縁膜（例えば、ＳｉＯ２膜
の誘電体薄膜）２７が形成されている。ＳｉＯ２膜２７
は、比重が約２．４、熱膨張率が約１５であり、反射器
２３，２４上に膜厚が約２３００Å（これはＡｌ膜に対
する膜厚比で４６％に相当）形成されている。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment A SAW resonator according to a first embodiment of the present invention and a (1) configuration of a ladder type SAW filter using the same, and (2)
The operation and (3) advantages will be described. (1) Configuration FIGS. 1A and 1B are configuration diagrams of a SAW resonator constituting a ladder-type SAW filter according to a first embodiment of the present invention. FIG. 1A is a plan view, and FIG. FIG. 2B is a cross-sectional view. This SAW resonator constitutes the series arm 1 and the parallel arm 2 of the ladder-type SAW filter shown in FIG.
A T substrate (for example, a 36 ° YX LT substrate) 21 is provided. On the LT substrate 21, an IDT 22 having a plurality of electrode fingers made of a thin metal film (for example, an Al film having a thickness of 5000 °) for exciting a SAW is disposed on the left and right sides with the DT 22 interposed therebetween. A thin metal film (for example, a film thickness of 5000) for reflecting light to the IDT 22 side.
Left and right reflectors 23 and 24 each having a plurality of electrode fingers made of (Ａｌ Al film) are formed.
One terminal 25 is connected to the upper end of the IDT 22, and the other terminal 26 is connected to the lower end. An insulating film (for example, a dielectric thin film of SiO 2 ) 27 is formed on the left and right reflectors 23 and 24. SiO 2 film 27
Has a specific gravity of about 2.4, a thermal expansion coefficient of about 15, and a film thickness of about 2300 ° (corresponding to a film thickness ratio of 46% to the Al film) on the reflectors 23 and 24.
【００１３】本実施形態の特徴は、図１４の梯型ＳＡＷ
フィルタの直列腕１及び並列腕２を構成するＳＡＷ共振
子の反射器２３，２４上に、ＳｉＯ２膜２７を蒸着等に
よって形成している。これにより、反射器２３，２４の
反射周波数特性の中心周波数をＩＤＴ２２の放射コンダ
クタンスの周波数特性に合わせ、ＳＡＷ共振子のＱ値を
向上させ、ＳＡＷフィルタの低損失化を図っている。図
２（１）〜（９）は、図１４のＳＡＷフィルタを構成す
る図１のＳＡＷ共振子の製造方法の一例を示す図であ
る。このＳＡＷ共振子は、例えば、次の（ａ）〜（ｉ）
のような工程によって製造される。The feature of this embodiment is that the trapezoidal SAW shown in FIG.
An SiO 2 film 27 is formed on the reflectors 23 and 24 of the SAW resonator constituting the series arm 1 and the parallel arm 2 of the filter by vapor deposition or the like. Thereby, the center frequency of the reflection frequency characteristics of the reflectors 23 and 24 is matched with the frequency characteristic of the radiation conductance of the IDT 22, the Q value of the SAW resonator is improved, and the loss of the SAW filter is reduced. 2 (1) to 2 (9) are diagrams illustrating an example of a method of manufacturing the SAW resonator of FIG. 1 which constitutes the SAW filter of FIG. This SAW resonator has, for example, the following (a) to (i)
It is manufactured by such a process.
【００１４】（ａ） 図２（１）の工程 ＬＴ基板２１のパターンを形成する面に、スピンコート
法等によってレジスト２８を塗布する。 （ｂ） 図２（２）の露光工程 光学マスク２９を用い、光３０によってＳＡＷフィルタ
のパターンをレジスト２８上に転写する。 （ｃ） 図２（３）のパターン形成工程 現像によって不要なレジスト２８を除去し、レシストパ
ターン２８ａを形成する。 （ｄ） 図２（４）の工程 ＩＤＴ２２の電極指及び反射器２３，２４の電極指とな
るＡｌ膜３１を、蒸着等によって全面に形成する。 （ｅ） 図２（５）の工程 有機溶剤等を用い、不要なＡｌ膜３１をレジストパター
ン２８ａと一緒に除去し、ＩＤＴ２２及び反射器２３，
２４のＡｌ電極指３１ａを形成する。(A) Step of FIG. 2 (1) A resist 28 is applied to the surface of the LT substrate 21 on which a pattern is to be formed by a spin coating method or the like. (B) Exposure Step of FIG. 2B The pattern of the SAW filter is transferred onto the resist 28 by the light 30 using the optical mask 29. (C) Pattern forming step of FIG. 2C The unnecessary resist 28 is removed by development to form a resist pattern 28a. (D) Step of FIG. 2D An Al film 31 serving as an electrode finger of the IDT 22 and an electrode finger of the reflectors 23 and 24 is formed on the entire surface by vapor deposition or the like. (E) Step of FIG. 2 (5) Using an organic solvent or the like, the unnecessary Al film 31 is removed together with the resist pattern 28a, and the IDT 22 and the reflector 23 are removed.
24 Al electrode fingers 31a are formed.
【００１５】（ｆ） 図２（６）の工程 Ａｌ電極指３１ａ上に、スピンコート法等によってレジ
スト３２を塗布する。 （ｇ） 図２（７）の露光・パターン形成工程 光学マスクを用い、ＳｉＯ２膜２７のパターンをレジス
ト３２上に転写する（露光工程）。次に、現像によって
不要なレジスト３２を除去し、レジストパターン３２ａ
を形成する（パターン形成工程）。 （ｈ） 図２（８）の工程 スパッタ法等により、反射器２３，２４上にＳｉＯ２膜
２７を蒸着等で形成する。 （ｉ） 図２（９）のリフトオフ工程 有機溶剤等を用い、反射器２３，２４上以外の不要なＳ
ｉＯ２膜２７をレジストパターン３２ａと一緒に除去す
る。その後、端子２５，２６等を接続すれば、製造が終
了する。(F) Step of FIG. 2 (6) A resist 32 is applied on the Al electrode fingers 31a by a spin coating method or the like. (G) Exposure / Pattern Forming Step of FIG. 2 (7) The pattern of the SiO 2 film 27 is transferred onto the resist 32 using an optical mask (exposure step). Next, the unnecessary resist 32 is removed by development, and the resist pattern 32a is removed.
Is formed (pattern forming step). (H) Step of FIG. 2 (8) An SiO 2 film 27 is formed on the reflectors 23 and 24 by sputtering or the like by a sputtering method or the like. (I) Lift-off step of FIG. 2 (9) Unnecessary S other than on reflectors 23 and 24 using an organic solvent or the like
The iO 2 film 27 is removed together with the resist pattern 32a. Thereafter, if the terminals 25 and 26 are connected, the production is completed.
【００１６】（２）動作 高周波信号を端子２５，２６間に印加すると、ＩＤＴ２
２の電極指下のＬＴ基板２１の表面が歪み、印加された
高周波信号と同じ周波数のＳＡＷが放射される。ＩＤＴ
２２から放射されたＳＡＷは、一部は該ＩＤＴ２２内部
で反射され、他が反射器２３，２４で反射される。反射
器２３，２４上には、ＳｉＯ２膜２７が形成されている
ので、該反射器２３，２４部分の音速が低下し、反射特
性の中心周波数が低い方にシフトする。つまり、反射器
２３，２４のＡｌ電極指の膜厚が５０００Åで、この反
射器２３，２４上にＳｉＯ２膜２７が約２３００Å形成
されているので、該反射器２３，２４の反射特性とＩＤ
Ｔ２２の放射コンダクタンスの中心周波数が一致し、見
かけ上特性が一致したため、従来反射器２３，２４の外
に逃げていた表面波まで閉込められ、ＳＡＷ共振子のＱ
値が向上する。ＳｉＯ２膜２７の膜厚は、Ａｌ電極指に
対する膜厚比で４６％に相当し、４０％〜７０％の膜厚
比であると、特性が最も良い。(2) Operation When a high-frequency signal is applied between terminals 25 and 26, IDT2
The surface of the LT substrate 21 under the second electrode finger is distorted, and a SAW having the same frequency as the applied high-frequency signal is emitted. IDT
A part of the SAW radiated from the 22 is reflected inside the IDT 22, and the other is reflected by the reflectors 23 and 24. Since the SiO 2 film 27 is formed on the reflectors 23 and 24, the sound speed of the reflectors 23 and 24 decreases, and the center frequency of the reflection characteristic shifts to a lower one. That is, since the thickness of the Al electrode fingers of the reflectors 23 and 24 is 5000 Å and the SiO 2 film 27 is formed on the reflectors 23 and 24 at about 2300 、, the reflection characteristics of the reflectors 23 and 24 and the ID
Since the center frequency of the radiation conductance of T22 coincides with the apparent characteristic, the surface wave that has escaped outside the reflectors 23 and 24 is confined, and the Q of the SAW resonator is reduced.
The value improves. The film thickness of the SiO 2 film 27 corresponds to 46% in film thickness ratio with respect to the Al electrode finger, and the characteristics are best when the film thickness ratio is 40% to 70%.
【００１７】（３）利点 本実施形態では、梯型ＳＡＷフィルタを構成するＳＡＷ
共振子において、反射器２３，２４上にＳｉＯ２膜２７
を形成したので、該反射器２３，２４部分の音速が低下
し、ＩＤＴ２２の放射特性と反射器２３，２４の反射特
性が一致する。これにより、従来反射器２３，２４の外
に逃げていた表面波まで閉込められ、ＳＡＷ共振子のＱ
値が向上し、低損失のＳＡＷフィルタの実現が可能とな
る。なお、本実施形態では、絶縁膜としてＳｉＯ２膜２
７の誘電体薄膜について説明したが、比重が２〜３（Ｓ
ｉＯ２膜は約２．４）で、熱膨張率が１０〜２０（Ｓｉ
Ｏ２膜は約１５）である他の誘電体材料でも、同様の特
性を得ることができる。また、ＳＡＷフィルタのパター
ニングにおいて、リフトオフに代えて、エッチング等を
用いてもよい。(3) Advantages In this embodiment, the SAW constituting the ladder-type SAW filter is
In the resonator, the SiO 2 film 27 is formed on the reflectors 23 and 24.
Is formed, the sound speed at the reflectors 23 and 24 decreases, and the radiation characteristics of the IDT 22 and the reflection characteristics of the reflectors 23 and 24 match. As a result, the surface wave that has escaped outside the reflectors 23 and 24 is confined, and the Q of the SAW resonator is reduced.
The value is improved, and a low-loss SAW filter can be realized. In this embodiment, the SiO 2 film 2 is used as the insulating film.
7, the specific gravity is 2-3 (S
The iO 2 film is about 2.4) and has a coefficient of thermal expansion of 10 to 20 (Si
Similar characteristics can be obtained with other dielectric materials whose O 2 film is about 15). In the patterning of the SAW filter, etching or the like may be used instead of lift-off.
【００１８】第２の実施形態 本発明の第２の実施形態であるＳＡＷ共振子とこれを用
いて構成した梯型ＳＡＷフィルタの（１）構成、（２）
動作、及び（３）利点について説明する。 （１）構成 図３（ａ），（ｂ）は本発明の第２の実施形態である梯
型ＳＡＷフィルタを構成するＳＡＷ共振子の構成図であ
り、同図（ａ）は平面図、及び同図（ｂ）は断面図であ
る。このＳＡＷ共振子では、第１の実施形態と同様に、
ＬＴ基板２１上に、複数のＡｌ電極指を有するＩＤＴ２
２Ａと、このＩＤＴ２２Ａを挟んで左側と右側に配置さ
れ、複数のＡｌ電極指をそれぞれ有する左側及び右側の
反射器２３Ａ，２４Ａとが、形成されている。本実施形
態では、ＩＤＴ２２ＡのＡｌ電極指をエッチングで削る
等して薄くすることにより（例えば、５０００Å）、該
ＩＤＴ２２Ａの周波数特性を反射器２３Ａ，２４Ａ（例
えば、膜厚が７５００Å）の周波数特性に合わせ、ＳＡ
Ｗ共振子のＱ値を向上させ、ＳＡＷフィルタの低損失化
を図っている。図４（１）〜（９）は、図１４のＳＡＷ
フィルタを構成する図３のＳＡＷ共振子の製造方法の一
例を示す図である。このＳＡＷ共振子は、例えば、次の
（ａ）〜（ｉ）のような工程によって製造される。Second Embodiment A SAW resonator according to a second embodiment of the present invention and a (1) configuration of a ladder-type SAW filter using the same, and (2)
The operation and (3) advantages will be described. (1) Configuration FIGS. 3A and 3B are configuration diagrams of a SAW resonator constituting a ladder-type SAW filter according to a second embodiment of the present invention. FIG. 3A is a plan view, and FIG. FIG. 2B is a cross-sectional view. In this SAW resonator, as in the first embodiment,
IDT 2 having a plurality of Al electrode fingers on LT substrate 21
2A and left and right reflectors 23A and 24A which are arranged on the left and right sides of the IDT 22A and have a plurality of Al electrode fingers, respectively. In the present embodiment, the frequency characteristics of the IDT 22A are changed to the frequency characteristics of the reflectors 23A and 24A (for example, the film thickness is 7500 °) by making the Al electrode finger of the IDT 22A thinner by etching or the like (for example, 5000 °). Together, SA
The Q value of the W resonator is improved to reduce the loss of the SAW filter. FIGS. 4 (1) to (9) show the SAW of FIG.
FIG. 4 is a diagram illustrating an example of a method of manufacturing the SAW resonator of FIG. 3 that configures a filter. This SAW resonator is manufactured, for example, by the following steps (a) to (i).
【００１９】（ａ） 図４（１）の工程 ＬＴ基板２１上のパターンを形成する面に、スピンコー
ト法等によってレジスト２８を塗布する。 （ｂ） 図４（２）の露光工程 光学マスク２９を用い、光３０によってＳＡＷフィルタ
のパターンをレジスト２８上に転写する。 （ｃ） 図４（３）のパターン形成工程 現像によって不要なレジスト２８を除去し、レジストパ
ターン２８ａを形成する。 （ｄ） 図４（４）の工程 ＩＤＴ２２Ａ及び反射器２３Ａ，２４Ａの電極指となる
Ａｌ膜３１を、蒸着等によって全面に形成する。 （ｅ） 図４（５）の工程 有機溶剤等により、不要なＡｌ膜３１をレジストパター
ン２８ａと一緒に除去し、Ａｌ電極指３１ａを形成す
る。(A) Step of FIG. 4A A resist 28 is applied to the surface of the LT substrate 21 on which a pattern is to be formed by a spin coating method or the like. (B) Exposure Step of FIG. 4B The pattern of the SAW filter is transferred onto the resist 28 by the light 30 using the optical mask 29. (C) Pattern forming step of FIG. 4C The unnecessary resist 28 is removed by development to form a resist pattern 28a. (D) Step of FIG. 4 (4) An Al film 31 serving as an electrode finger of the IDT 22A and the reflectors 23A and 24A is formed on the entire surface by vapor deposition or the like. (E) Step of FIG. 4 (5) The unnecessary Al film 31 is removed together with the resist pattern 28a using an organic solvent or the like to form an Al electrode finger 31a.
【００２０】（ｆ） 図４（６）の工程 スピンコート法等により、Ａｌ電極指３１ａ上にレジス
ト３３を塗布する。 （ｇ） 図４（７）の工程 光学マスクを用い、レジスト３３上にＩＤＴ２２Ａのパ
ターンを転写する。次に、現像によって不要なレジスト
３３を除去し、レジストパターン３３ａを形成する。こ
れにより、ＩＤＴ２２Ａ部分のＡｌ電極指３１ａがレジ
ストパターン３３ａから露出する。 （ｈ） 図４（８）の工程 レジストパターン３３ａをマスクにし、ドライエッチン
グ等によってＩＤＴ２２Ａ部分のＡｌ電極指３１ａを若
干削る。削られたＩＤＴ２２ＡのＡｌ電極指３１ｂは、
反射器２３Ａ，２４ＡのＡｌ電極指３１ａよりも膜厚が
薄くなっている。 （ｉ） 図４（９）の工程 不要なレジストパターン３３ａを除去した後、入力端子
２５及び出力端子２６等を接続すれば、製造が終了す
る。(F) Step of FIG. 4 (6) A resist 33 is applied on the Al electrode fingers 31a by spin coating or the like. (G) Step of FIG. 4 (7) The pattern of the IDT 22A is transferred onto the resist 33 using an optical mask. Next, unnecessary resist 33 is removed by development to form a resist pattern 33a. Thereby, the Al electrode finger 31a in the IDT 22A portion is exposed from the resist pattern 33a. (H) Step of FIG. 4 (8) Using the resist pattern 33a as a mask, the Al electrode finger 31a in the IDT 22A portion is slightly cut off by dry etching or the like. The Al electrode finger 31b of the shaved IDT 22A is
The film thickness is smaller than that of the Al electrode fingers 31a of the reflectors 23A and 24A. (I) Step of FIG. 4 (9) After removing the unnecessary resist pattern 33a, if the input terminal 25 and the output terminal 26 are connected, the production is completed.
【００２１】（２）動作 高周波信号を端子２５，２６間に印加すると、ＩＤＴ２
２ＡからＳＡＷが放射される。ＩＤＴ２２Ａで放射され
たＳＡＷは、一部が該ＩＤＴ２２Ａ内部で反射され、他
が反射器２３Ａ，２４Ａで反射される。ＩＤＴ２２Ａ部
分のＡｌ電極指３１ｂは、ドライエッチング等で若干削
られているので、該ＩＤＴ２２Ａ部分の音速が上がり、
ＩＤＴ２２Ａ部分の放射コンダクタンスの周波数特性が
高い方にシフトする。これにより、ＩＤＴ２２Ａの放射
コンダクタンスの周波数特性と反射器２３Ａ，２４Ａの
反射特性が一致し、ＳＡＷ共振子のＱ値が向上する。実
験結果より、Ａｌ電極指の膜厚２５００Åで、ＩＤＴ２
２Ａの放射抵抗の周波数が約２０ＭＨＺ変化する。例え
ば、本実施形態のように反射器２３Ａ，２４Ａを７５０
０Åとし、ドライエッチング等で２５００Å削ってＩＤ
Ｔ２２Ａを５０００Åとすると丁度良い。これは、反射
器２３Ａ，２４Ａの膜厚を５０％厚くしたことに相当す
る。(2) Operation When a high-frequency signal is applied between the terminals 25 and 26, the IDT 2
SAW is emitted from 2A. A part of the SAW emitted by the IDT 22A is reflected inside the IDT 22A, and the other is reflected by the reflectors 23A and 24A. Since the Al electrode finger 31b in the IDT 22A portion is slightly shaved by dry etching or the like, the sound speed in the IDT 22A portion increases,
The frequency characteristic of the radiation conductance of the IDT 22A shifts to a higher one. As a result, the frequency characteristic of the radiation conductance of the IDT 22A matches the reflection characteristic of the reflectors 23A and 24A, and the Q value of the SAW resonator is improved. According to the experimental results, the IDT2
Frequency of the radiation resistance of the 2A varies approximately 20MH Z. For example, as in the present embodiment, the reflectors 23A and 24A are 750
Set to 0Å, cut 2500Å by dry etching etc. and ID
It is just right to set T22A to 5000Å. This is equivalent to increasing the film thickness of the reflectors 23A and 24A by 50%.
【００２２】（３）利点 本実施形態では、梯型ＳＡＷフィルタを構成するＳＡＷ
共振子のＩＤＴ２２Ａ部分のＡｌ電極指３１ｂを削って
薄くしたので、該ＩＤＴ２２Ａの放射コンダクタンスの
周波数特性が高周波側にシフトし、ＩＤＴ２２Ａの放射
特性と反射器２３Ａ，２４Ａの反射特性が一致する。こ
れにより、ＳＡＷ共振子のＱ値が向上し、低損失のＳＡ
Ｗフィルタの実現が可能となる。また、ＩＤＴ２２Ａの
Ａｌ電極指３１ｂの膜厚は、反射器２３Ａ，２４ＡのＡ
ｌ電極指３１ａの４０％〜６０％であっても、同様の特
性が得られる。なお、ＳＡＷフィルタのパターニングに
おいて、リフトオフに代えて、エッチング等を用いても
よい。(3) Advantages In this embodiment, the SAW constituting the ladder SAW filter is
Since the Al electrode finger 31b of the IDT 22A portion of the resonator is shaved and thinned, the frequency characteristic of the radiation conductance of the IDT 22A shifts to the high frequency side, and the radiation characteristic of the IDT 22A matches the reflection characteristics of the reflectors 23A and 24A. As a result, the Q value of the SAW resonator is improved, and a low-loss SA
It is possible to realize a W filter. The film thickness of the Al electrode finger 31b of the IDT 22A is the same as that of the reflectors 23A and 24A.
Similar characteristics can be obtained even when the electrode finger 31a is 40% to 60%. In the patterning of the SAW filter, etching or the like may be used instead of lift-off.
【００２３】第３の実施形態 本発明の第３の実施形態であるＳＡＷ共振子とこれを用
いて構成した梯型ＳＡＷフィルタの（１）構成、（２）
動作、及び（３）利点を説明する。 （１）構成 図５（ａ），（ｂ）は本発明の第３の実施形態である梯
型ＳＡＷフィルタを構成するＳＡＷ共振子の構成図であ
り、同図（ａ）は平面図、及び同図（ｂ）は断面図であ
る。図６は、図５（ｂ）のＢ部分の拡大図である。この
ＳＡＷ共振子では、図１の実施形態と同様に、ＬＴ基板
２１上に、複数のＡｌ電極指を有するＩＤＴ２２Ｂと、
このＩＤＴ２２Ｂを挟んで左側と右側に配置され、複数
のＡｌ電極指をそれぞれ有する左側及び右側の反射器２
３Ｂ，２４Ｂとが、形成されている。本実施形態では、
反射器２３Ｂ，２４ＢのＡｌ電極指をＩＤＴ２２ＢのＡ
ｌ電極指よりも太くすることにより（例えば、幅１７％
広くする）、該反射器２３Ｂ，２４Ｂの周波数特性をＩ
ＤＴ２２Ｂの周波数特性に合わせ、ＳＡＷ共振子のＱ値
を向上させ、ＳＡＷフィルタの低損失化を図っている。Third Embodiment A SAW resonator according to a third embodiment of the present invention and a (1) configuration of a ladder-type SAW filter using the same, and (2)
The operation and (3) advantages will be described. (1) Configuration FIGS. 5A and 5B are configuration diagrams of a SAW resonator constituting a ladder-type SAW filter according to a third embodiment of the present invention. FIG. 5A is a plan view and FIG. FIG. 2B is a cross-sectional view. FIG. 6 is an enlarged view of a portion B in FIG. In this SAW resonator, similarly to the embodiment of FIG. 1, an IDT 22B having a plurality of Al electrode fingers on an LT substrate 21;
Left and right reflectors 2 arranged on the left and right sides of the IDT 22B and having a plurality of Al electrode fingers, respectively.
3B and 24B are formed. In this embodiment,
The Al electrode fingers of the reflectors 23B and 24B are connected to A of the IDT 22B.
l By making the electrode finger thicker (for example, 17% in width)
The frequency characteristics of the reflectors 23B and 24B are
The Q value of the SAW resonator is improved in accordance with the frequency characteristics of the DT22B to reduce the loss of the SAW filter.
【００２４】図７（１）〜（５）は、図１４のＳＡＷフ
ィルタを構成する図５のＳＡＷ共振子の製造方法の一例
を示す図である。このＳＡＷ共振子は、例えば、次の
（ａ）〜（ｅ）のような工程によって製造される。 （ａ） 図７（１）の工程 ＬＴ基板２１上のパターンを形成する面に、スピンコー
ト法等によってレジスト２８を塗布する。 （ｂ） 図７（２）の露光工程 光学マスク３４を用い、光３０によってＳＡＷフィルタ
のパターンをレジスト２８上に転写する。 （ｃ） 図７（３）のパターン形成工程 現像によって不要なレジスト２８を除去し、レジストパ
ターン２８ｂを形成する。 （ｄ） 図７（４）の工程 ＩＤＴ２２Ｂ及び反射器２３Ｂ，２４Ｂの電極指となる
Ａｌ膜３５を、蒸着等によって全面に形成する。 （ｅ） 図７（５）の工程 有機溶剤等を用い、リフトオフによって不要なＡｌ膜３
５をレジストパターン２８ｂと一緒に除去し、ＩＤＴ２
２Ｂ及び反射器２３Ｂ，２４ＢのＡｌ電極指３５ａを形
成する。その後、端子２５，２６等を接続すれば、製造
が終了する。FIGS. 7 (1) to 7 (5) are views showing an example of a method of manufacturing the SAW resonator of FIG. 5 which constitutes the SAW filter of FIG. This SAW resonator is manufactured by, for example, the following steps (a) to (e). (A) Step of FIG. 7A A resist 28 is applied to the surface of the LT substrate 21 on which a pattern is to be formed, by spin coating or the like. (B) Exposure Step of FIG. 7B The pattern of the SAW filter is transferred onto the resist 28 by the light 30 using the optical mask 34. (C) Pattern forming step of FIG. 7C The unnecessary resist 28 is removed by development to form a resist pattern 28b. (D) Step of FIG. 7D An Al film 35 serving as an electrode finger of the IDT 22B and the reflectors 23B and 24B is formed on the entire surface by vapor deposition or the like. (E) Step of FIG. 7 (5) Unnecessary Al film 3 by lift-off using an organic solvent or the like
5 is removed together with the resist pattern 28b, and the IDT2 is removed.
The Al electrode fingers 35a of the 2B and the reflectors 23B and 24B are formed. Thereafter, if the terminals 25 and 26 are connected, the production is completed.
【００２５】（２）動作 高周波信号を端子２５，２６間に印加すると、ＩＤＴ２
２ＢからＳＡＷが放射される。ＩＤＴ２２Ｂから放射さ
れたＳＡＷは、一部が該ＩＤＴ２２Ｂ内部で反射され、
他が反射器２３Ｂ，２４Ｂで反射される。図６に示すよ
うに、ＩＤＴ２２Ｂ部分のＡｌ電極指幅をＩｍｉ、ＩＤ
Ｔ２２Ｂ部分のＡｌ電極指３５ａのない部分をＩｇｉ、
反射器２３Ｂ，２４Ｂ部分のＡｌ電極指幅をＩｍｇ、反
射器２３Ｂ，２４Ｂ部分のＡｌ電極指３５ａのない部分
をＩｇｇとする。通常は、マスクの作りやすさ等から、
幅Ｉｍｉ，Ｉｇｉ，Ｉｍｇ，Ｉｇｇが、前記（１）、
（２）、（３）式のように設定される。これに対し、本
実施形態では、次のように設定される。 Ｉｍｉ＋Ｉｇｉ＝λ／２、Ｉｍｉ＋Ｉｇｉ＝λ／４ Ｉｍｇ＋Ｉｇｇ＝λ／２、Ｉｍｇ＞Ｉｇｇ すなわち、反射器２３Ｂ，２４ＢのＡｌ電極指３５ａの
幅Ｉｍｇが広がったため、該反射器２３Ｂ，２４Ｂ下の
ＳＡＷは、Ａｌ電極指３５ａの下を通るほど音速が低下
する。このために見かけ上、反射器２３Ｂ，２４Ｂ部分
の反射特性の中心周波数が低い方にシフトし、ＩＤＴ２
２Ｂの放射特性と反射器２３Ｂ，２４Ｂの反射特性が一
致し、ＳＡＷ共振子のＱ値が向上する。実験結果より、
反射器２３Ｂ，２４ＢのＡｌ電極指３５ａの幅Ｉｍｇを
１７％広くした場合、Ｑ値が約３０％向上した。(2) Operation When a high-frequency signal is applied between the terminals 25 and 26, the IDT2
SAW is emitted from 2B. A part of the SAW radiated from the IDT 22B is reflected inside the IDT 22B,
Others are reflected by the reflectors 23B and 24B. As shown in FIG. 6, the finger width of the Al electrode in the IDT 22B portion is Imi, ID
The portion of the T22B portion without the Al electrode finger 35a is Igi,
The width of the Al electrode fingers at the reflectors 23B and 24B is Img, and the portion of the reflectors 23B and 24B without the Al electrode fingers 35a is Igg. Usually, because of the ease of making the mask,
The widths Imi, Igi, Img, Igg are as described in the above (1),
(2) and (3) are set. On the other hand, in the present embodiment, the following settings are made. Imi + Igi = λ / 2, Imi + Igi = λ / 4 Img + Igg = λ / 2, Img> Igg That is, since the width Img of the Al electrode finger 35a of the reflectors 23B and 24B is widened, the SAW below the reflectors 23B and 24B is: The sound speed decreases as the sound passes below the Al electrode finger 35a. For this reason, apparently, the center frequency of the reflection characteristics of the reflectors 23B and 24B shifts to the lower side, and the IDT2
The radiation characteristic of 2B matches the reflection characteristic of reflectors 23B and 24B, and the Q value of the SAW resonator is improved. From the experimental results,
When the width Img of the Al electrode fingers 35a of the reflectors 23B and 24B was increased by 17%, the Q value was improved by about 30%.
【００２６】（３）利点 本実施形態では、梯型ＳＡＷフィルタを構成するＳＡＷ
共振子の反射器２３Ｂ，２４Ｂ部分のＡｌ電極指３５ａ
を太くしたので、該反射器２３Ｂ，２４Ｂ部分の音速が
下がり、ＩＤＴ２２Ｂの放射特性と反射器２３Ｂ，２４
Ｂの反射特性が一致する。これにより、ＳＡＷ共振子の
Ｑ値が向上し、低損失のＳＡＷフィルタの実現が可能と
なる。反射器２３Ｂ，２４ＢのＡｌ電極指３５ａの幅Ｉ
ｍｇは、１０％〜５０％広いとＱ値の向上が見られ、特
に１０％〜２５％広いとＱ値の向上が著しい。なお、Ｓ
ＡＷフィルタのパターニングにおいて、リフトオフに代
えて、エッチング等を用いてもよい。(3) Advantage In this embodiment, the SAW constituting the ladder-type SAW filter is
Al electrode finger 35a on reflectors 23B and 24B of resonator
, The sound speed of the reflectors 23B and 24B is reduced, and the radiation characteristics of the IDT 22B and the reflectors 23B and 24B are reduced.
The reflection characteristics of B match. Thereby, the Q value of the SAW resonator is improved, and a low-loss SAW filter can be realized. Width I of Al electrode finger 35a of reflectors 23B and 24B
When the mg is 10% to 50% wider, the Q value is improved, and when the mg is 10% to 25% wider, the Q value is significantly improved. Note that S
In patterning the AW filter, etching or the like may be used instead of lift-off.
【００２７】第４の実施形態 本発明の第４の実施形態であるＳＡＷ共振子とこれを用
いて構成した梯型ＳＡＷフィルタの（１）構成、（２）
動作、及び（３）利点を説明する。 （１）構成 図８（ａ），（ｂ）は本発明の第４の実施形態である梯
型ＳＡＷフィルタを構成するＳＡＷ共振子の構成図であ
り、同図（ａ）は平面図、及び同図（ｂ）は断面図であ
る。このＳＡＷ共振子では、第１の実施形態と同様に、
ＬＴ基板２１上に、複数の電極指を有するＩＤＴ２２Ｃ
と、該ＩＤＴ２２Ｃを挟んで左側と右側に配置され、複
数の電極指をそれぞれ有する左側及び右側の反射器２３
Ｃ，２４Ｃとが、形成されている。本実施形態では、反
射器２３Ｃ，２４Ｃの電極指を、ＩＤＴ２２Ｃの電極指
を形成する金属膜（例えば、比重２．６９のＡｌ膜）よ
りも比重の重い金属膜（例えば、比重４．５８のＴｉ
膜）で形成することにより、該反射器２３Ｃ，２４Ｃの
周波数特性をＩＤＴ２２Ｃの周波数特性に合わせること
により、ＳＡＷ共振子のＱ値を向上させ、ＳＡＷフィル
タの低損失化を図っている。Fourth Embodiment A SAW resonator according to a fourth embodiment of the present invention and a (1) configuration of a ladder-type SAW filter using the same, and (2)
The operation and (3) advantages will be described. (1) Configuration FIGS. 8A and 8B are configuration diagrams of a SAW resonator constituting a ladder-type SAW filter according to a fourth embodiment of the present invention, and FIG. 8A is a plan view and FIG. FIG. 2B is a cross-sectional view. In this SAW resonator, as in the first embodiment,
IDT 22C having a plurality of electrode fingers on LT substrate 21
And left and right reflectors 23 disposed on the left and right sides of the IDT 22C and having a plurality of electrode fingers, respectively.
C and 24C are formed. In the present embodiment, the electrode fingers of the reflectors 23C and 24C are formed of a metal film (for example, having a specific gravity of 4.58) having a higher specific gravity than a metal film (for example, an Al film having a specific gravity of 2.69) forming the electrode fingers of the IDT 22C. Ti
By forming the reflectors 23C and 24C with the frequency characteristics of the IDT 22C, the Q value of the SAW resonator is improved and the loss of the SAW filter is reduced.
【００２８】図９（１）〜（９）は、図１４のＳＡＷフ
ィルタを構成する図８のＳＡＷ共振子の製造方法の一例
を示す図である。このＳＡＷ共振子は、例えば、次の
（ａ）〜（ｉ）のような工程によって製造される。 （ａ） 図９（１）の工程 ＬＴ基板２１上のパターンを形成する面に、スピンコー
ト法等によってレジスト２８を塗布する。 （ｂ） 図９（２）の露光工程 光学マスク３６を用い、光３０によってＳＡＷフィルタ
のパターンをレジスト２８上に転写する。 （ｃ） 図９（３）のパターン形成工程 現像によって不要なレジスト２８を除去し、レジストパ
ターン２８ｃを形成する。 （ｄ） 図９（４）の工程 ＩＤＴ２２Ｃの電極指となるＡｌ膜３７を、蒸着等によ
って全面に形成する。 （ｅ） 図９（５）の工程 有機溶剤等を用い、リフトオフによって不要なＡｌ膜３
７をレジストパターン２８ｃと一緒に除去し、ＩＤＴ２
２ＣのＡｌ電極指３７ａを形成する。FIGS. 9 (1) to 9 (9) are views showing an example of a method of manufacturing the SAW resonator of FIG. 8 which constitutes the SAW filter of FIG. This SAW resonator is manufactured, for example, by the following steps (a) to (i). (A) Step of FIG. 9A A resist 28 is applied to the surface of the LT substrate 21 on which a pattern is to be formed by a spin coating method or the like. (B) Exposure Step of FIG. 9B The pattern of the SAW filter is transferred onto the resist 28 by the light 30 using the optical mask 36. (C) Pattern forming step in FIG. 9C The unnecessary resist 28 is removed by development to form a resist pattern 28c. (D) Step of FIG. 9D An Al film 37 serving as an electrode finger of the IDT 22C is formed on the entire surface by vapor deposition or the like. (E) Step of FIG. 9 (5) Unnecessary Al film 3 by lift-off using an organic solvent or the like
7 is removed together with the resist pattern 28c, and the IDT2 is removed.
A 2C Al electrode finger 37a is formed.
【００２９】（ｆ） 図９（６）の工程 スピンコート法等により、Ａｌ電極指３７ａ上にレジス
ト３８を塗布する。 （ｇ） 図９（７）の工程 光学マスクを用い、反射器２３Ｃ，２４Ｃのパターンを
レジスト３８上に転写した後、現像によって不要なレジ
スト３８を除去してレジストパターン３８ａを形成す
る。 （ｈ） 図９（８）の反射器形成工程 反射器２３Ｃ，２４Ｃの電極指となるＴｉ膜３９を、蒸
着等によって全面に形成する。 （ｉ） 図９（９）のリフトオフ工程 有機溶剤等により、不要なＴｉ膜３９をレジストパター
ン３８ａと一緒に除去し、反射器２３Ｃ，２４ＣのＴｉ
電極指３９ａを形成する。その後、端子２５，２６等を
接続すれば、製造が終了する。(F) Step of FIG. 9 (6) A resist 38 is applied on the Al electrode fingers 37a by spin coating or the like. (G) Step of FIG. 9 (7) After transferring the patterns of the reflectors 23C and 24C onto the resist 38 using an optical mask, the unnecessary resist 38 is removed by development to form a resist pattern 38a. (H) Reflector forming step of FIG. 9 (8) A Ti film 39 to be an electrode finger of the reflectors 23C and 24C is formed on the entire surface by vapor deposition or the like. (I) Lift-off step of FIG. 9 (9) The unnecessary Ti film 39 is removed together with the resist pattern 38a by using an organic solvent or the like, and the Ti of the reflectors 23C and 24C is removed.
An electrode finger 39a is formed. Thereafter, if the terminals 25 and 26 are connected, the production is completed.
【００３０】（２）動作 高周波信号を端子２５，２６間に印加すると、ＩＤＴ２
２ＣからＳＡＷが放射される。ＩＤＴ２２Ｃから放射さ
れたＳＡＷは、一部が該ＩＤＴ２２Ｃ内部で反射され、
他が反射器２３Ｃ，２４Ｃで反射される。本実施形態で
は、反射器２３Ｃ，２４Ｃの電極指３９ａを、Ａｌ膜
（比重２．６９）よりも比重の重いＴｉ膜（比重４．５
８）で形成したため、該反射器２３Ｃ，２４Ｃ下の音速
が低下し、ＩＤＴ２２Ｃの放射コンダクタンスの周波数
特性が低い周波数にシフトする。これにより、反射器２
３Ｃ，２４Ｃの反射特性が一致し、ＳＡＷ共振子のＱ値
が向上する。実験結果より、例えば、膜厚が５０００Å
であると、Ａｌ膜は周波数が約３８ＭＨＺ変化し、Ｔｉ
膜の場合は約６３ＭＨＺ変化する。図２０〜図２２で
は、反射器１３の中心周波数が約２５ＭＨＺ低下し、丁
度良い。(2) Operation When a high-frequency signal is applied between terminals 25 and 26, IDT2
SAW is emitted from 2C. Part of the SAW emitted from the IDT 22C is reflected inside the IDT 22C,
Others are reflected by the reflectors 23C and 24C. In the present embodiment, the electrode fingers 39a of the reflectors 23C and 24C are provided with a Ti film (specific gravity 4.5) which is heavier than the Al film (specific gravity 2.69).
8), the sound velocity below the reflectors 23C and 24C decreases, and the frequency characteristic of the radiation conductance of the IDT 22C shifts to a lower frequency. Thereby, the reflector 2
The reflection characteristics of 3C and 24C match, and the Q value of the SAW resonator is improved. From the experimental results, for example, the film thickness is 5000
If it is, Al film frequency changes approximately 38MH Z, Ti
Film varies approximately 63MH Z in the case of. In FIGS. 20 22, the reflector center frequency of 13 is reduced to about 25MH Z, just right.
【００３１】（３）利点 本実施形態では、梯型ＳＡＷフィルタを構成するＳＡＷ
共振子の反射器２３Ｃ，２４Ｃの電極指３９ａを、Ａｌ
膜よりも比重の重いＴｉ膜で形成したので、該反射器２
３Ｃ，２４Ｃ下の音速が低下し、ＩＤＴ２２Ｃの放射コ
ンダクタンスの周波数特性が低い周波数にシフトする。
これにより、反射器２３Ｃ，２４Ｃの反射特性が一致
し、従来反射器２３Ｃ，２４Ｃの外に逃げていた表面波
まで閉込められ、ＳＡＷ共振子のＱ値が向上し、低損失
のＳＡＷフィルタの実現が可能となる。なお、反射器２
３Ｃ，２４Ｃの電極指３９ａを形成する金属膜として、
Ｔｉ以外の金属（例えば、Ｓｎ、Ｆｅ、Ｎｉ、Ｃｕ）で
も、同様の効果を得ることができる。この場合は、比重
をＴｉと比較して周波数変化を計算し、膜厚を調整すれ
ばよい。また、ＳＡＷフィルタのパターニングにおい
て、リフトオフに代えて、エッチング等を用いてもよ
い。(3) Advantages In this embodiment, the SAW constituting the ladder SAW filter is
The electrode fingers 39a of the reflectors 23C and 24C of the resonator are
Since the reflector 2 was formed of a Ti film having a higher specific gravity than the film,
The sound speed below 3C and 24C decreases, and the frequency characteristic of the radiation conductance of the IDT 22C shifts to a lower frequency.
As a result, the reflection characteristics of the reflectors 23C and 24C match, the surface wave which has escaped from the conventional reflectors 23C and 24C is confined, the Q value of the SAW resonator is improved, and a low-loss SAW filter is provided. Realization becomes possible. The reflector 2
As a metal film forming the electrode fingers 39a of 3C and 24C,
Similar effects can be obtained with metals other than Ti (for example, Sn, Fe, Ni, Cu). In this case, the specific gravity may be compared with Ti to calculate the frequency change, and the film thickness may be adjusted. In the patterning of the SAW filter, etching or the like may be used instead of lift-off.
【００３２】第５の実施形態 本発明の第５の実施形態であるＳＡＷ共振子とこれを用
いて構成した梯型ＳＡＷフィルタの（１）構成、（２）
動作、及び（３）利点を説明する。 （１）構成 図１０（ａ），（ｂ）は本発明の第５の実施形態である
梯型ＳＡＷフィルタを構成するＳＡＷ共振子の構成図で
あり、同図（ａ）は平面図、及び同図（ｂ）は断面図で
ある。図１１は、図１０（ｂ）のＣ部分の拡大図であ
る。このＳＡＷ共振子では、第１の実施形態と同様に、
ＬＴ基板２１上に、複数のＡｌ電極指を有するＩＤＴ２
２Ｄと、該ＩＤＴ２２Ｄを挟んで左側と右側に配置さ
れ、複数のＡｌ電極指をそれぞれ有する左側及び右側の
反射器２３Ｄ，２４Ｄとが、形成されている。本実施形
態では、ＩＤＴ２２ＤのＡｌ電極指の幅を細くし、該Ｉ
ＤＴ２２Ｄの周波数特性を反射器２３Ｄ，２４Ｄの周波
数特性に合わせることにより、ＳＡＷ共振子のＱ値を向
上させ、ＳＡＷフィルタの低損失化を図っている。図１
２（１）〜（５）は、図１０のＳＡＷ共振子の製造方法
の一例を示す図である。Fifth Embodiment A SAW resonator according to a fifth embodiment of the present invention and a (1) configuration of a ladder-type SAW filter using the same, and (2)
The operation and (3) advantages will be described. (1) Configuration FIGS. 10A and 10B are configuration diagrams of a SAW resonator constituting a ladder-type SAW filter according to a fifth embodiment of the present invention. FIG. 10A is a plan view and FIG. FIG. 2B is a cross-sectional view. FIG. 11 is an enlarged view of a portion C in FIG. In this SAW resonator, as in the first embodiment,
IDT 2 having a plurality of Al electrode fingers on LT substrate 21
2D and left and right reflectors 23D and 24D which are arranged on the left and right sides of the IDT 22D and have a plurality of Al electrode fingers, respectively, are formed. In this embodiment, the width of the Al electrode finger of the IDT 22D is reduced,
By matching the frequency characteristics of the DT 22D with the frequency characteristics of the reflectors 23D and 24D, the Q value of the SAW resonator is improved, and the loss of the SAW filter is reduced. FIG.
2 (1) to 2 (5) are diagrams showing an example of a method for manufacturing the SAW resonator shown in FIG.
【００３３】このＳＡＷ共振子は、例えば、次の（ａ）
〜（ｅ）のような工程によって製造される。 （ａ） 図１２（１）の工程 ＬＴ基板２１上のパタンを形成する面に、スピンコート
法等によってレジスト２８を塗布する。 （ｂ） 図１２（２）の露光工程 光学マスク４０を用い、光３０によってＳＡＷフィルタ
のパターンをレジスト２８上に転写させる。 （ｃ） 図１２（３）のパターン形成工程 現像によって不要なレジスト２８を除去し、レシストパ
ターン２８ｄを形成する。 （ｄ） 図１２（４）の工程 ＩＤＴ２２Ｄ及び反射器２３Ｄ，２４Ｄの電極指となる
Ａｌ膜４１を、蒸着等によって全面に形成する。 （ｅ） 図１２（５）の工程 有機溶剤等により、リフトオフによって不要なＡｌ膜４
１をレジストパターン２８ｄと一緒に除去し、ＩＤＴ２
２Ｄ及び反射器２３Ｄ，２４ＤのＡｌ電極指４１ａを形
成する。その後、端子２５，２６等を接続すれば、製造
が終了する。This SAW resonator has, for example, the following (a)
(E). (A) Step of FIG. 12 (1) A resist 28 is applied on the surface of the LT substrate 21 on which a pattern is to be formed by a spin coating method or the like. (B) Exposure Step of FIG. 12B The pattern of the SAW filter is transferred onto the resist 28 by the light 30 using the optical mask 40. (C) Pattern forming step of FIG. 12 (3) The unnecessary resist 28 is removed by development to form a resist pattern 28d. (D) Step of FIG. 12 (4) An Al film 41 serving as an electrode finger of the IDT 22D and the reflectors 23D and 24D is formed on the entire surface by vapor deposition or the like. (E) Step of FIG. 12 (5) Al film 4 unnecessary by lift-off using an organic solvent or the like
1 is removed together with the resist pattern 28d, and IDT2 is removed.
The 2D and Al electrode fingers 41a of the reflectors 23D and 24D are formed. Thereafter, if the terminals 25 and 26 are connected, the production is completed.
【００３４】（２）動作 高周波信号を端子２５，２６間に印加すると、ＩＤＴ２
２ＤからＳＡＷが放射される。ＩＤＴ２２Ｄから放射さ
れたＳＡＷは、一部が該ＩＤＴ２２Ｄ内部で反射され、
他が反射器２３Ｄ，２４Ｄで反射される。図１１に示す
ように、ＩＤＴ２２Ｄ部分のＡｌ電極指幅をＩｍｉ、Ｉ
ＤＴ２２Ｄ部分のＡｌ電極指４１ａのない部分をＩｇ
ｉ、反射器２３Ｄ，２４Ｄ部分のＡｌ電極指幅をＩｍ
ｇ、及び反射器２３Ｄ，２４Ｄ部分のＡｌ電極指４１ａ
のない部分をＩｇｇとする。通常は、マスクの作りやす
さ等から、電極指の幅Ｉｍｉ，Ｉｇｉ，Ｉｍｇ，Ｉｇｇ
が、前記（１）、（２）、（３）式のように設定され
る。これに対し、本実施形態では、次のように設定され
る。 Ｉｍｉ＋Ｉｇｉ＝λ／２、Ｉｍｉ＜Ｉｇｉ Ｉｍｇ＋Ｉｇｇ＝λ／２、Ｉｍｇ＝Ｉｇｇ＝λ／４ すなわち、ＩＤＴ２２ＤのＡｌ電極指４１ａの幅Ｉｍｉ
を反射器２３Ｄ，２４ＤのＡｌ電極指４１ａの幅よりも
狭くしたため（例えば、１０％〜５０％狭くする）、該
ＩＤＴ２２Ｄの放射コンダクタンスの中心周波数は変ら
ないが、広帯域となる。(2) Operation When a high-frequency signal is applied between the terminals 25 and 26, the IDT2
SAW is emitted from 2D. A part of the SAW emitted from the IDT 22D is reflected inside the IDT 22D,
Others are reflected by the reflectors 23D and 24D. As shown in FIG. 11, the finger width of the Al electrode in the IDT 22D portion is Imi, I
The part of the DT22D part without the Al electrode finger 41a is Ig
i, the finger width of the Al electrode at the reflectors 23D and 24D is Im
g and the Al electrode fingers 41a of the reflectors 23D and 24D
The part without the mark is defined as Igg. Usually, the widths Imi, Igi, Img, Igg of the electrode fingers are taken into consideration for ease of making the mask.
Is set as in the equations (1), (2), and (3). On the other hand, in the present embodiment, the following settings are made. Imi + Igi = λ / 2, Imi <Igi Img + Igg = λ / 2, Img = Igg = λ / 4 That is, the width Imi of the Al electrode finger 41a of the IDT 22D.
Is made smaller than the width of the Al electrode fingers 41a of the reflectors 23D and 24D (for example, made narrower by 10% to 50%), so that the center frequency of the radiation conductance of the IDT 22D does not change, but becomes wider.
【００３５】図１３（ａ），（ｂ）は図１０のＳＡＷ共
振子の周波数特性図であり、同図（ａ）はＩＤＴ２２Ｄ
の放射コンダクタンスの周波数特性図、及び同図（ｂ）
は反射器２３Ｄ，２４Ｄの反射率の周波数特性図であ
る。この図１３（ａ），（ｂ）に示すように、ＩＤＴ２
２ＤのＡｌ電極指４１ａの幅Ｉｍｉを狭くすると、高周
波の部分まで放射コンダクタンスが広がり、該ＩＤＴ２
２Ｄの放射コンダクタンスと反射器２３Ｄ，２４Ｄの反
射特性の重なる部分が増え、ＳＡＷ共振子のＱ値が向上
する。FIGS. 13A and 13B are frequency characteristic diagrams of the SAW resonator shown in FIG. 10, and FIG. 13A shows the IDT 22D.
Of radiated conductance in Fig. 4 (b)
Is a frequency characteristic diagram of the reflectance of the reflectors 23D and 24D. As shown in FIGS. 13A and 13B, the IDT2
When the width Imi of the 2D Al electrode finger 41a is reduced, the radiation conductance is increased to a high frequency portion, and the IDT2 is increased.
The overlap between the 2D radiation conductance and the reflection characteristics of the reflectors 23D and 24D increases, and the Q value of the SAW resonator improves.
【００３６】（３）利点 本実施形態では、梯型ＳＡＷフィルタを構成するＳＡＷ
共振子のＩＤＴ２２ＤのＡｌ電極指４１ａを細くしたの
で、ＩＤＴ２２Ｄ部分の放射コンダクタンスの周波数特
性が広帯域になり、該ＩＤＴ２２Ｄの放射特性と反射器
２３Ｄ，２４Ｄの反射特性の重なる部分が広がる。これ
により、ＳＡＷ共振子のＱ値が向上し、低損失のＳＡＷ
フィルタの実現が可能となる。なお、ＳＡＷフィルタの
パターンニングにおいて、リフトオフに代えて、エッチ
ング等を用いてもよい。本発明は、上記実施形態に限定
されず、種々の変形が可能である。例えば、ＬＴ基板２
１は、３６°Ｙ−ＸのＬＴ基板以外のＬＴ基板を用いて
もよい。Ａｌ電極指は、他の金属膜を用いて形成しても
よい。また、図１４では、１段の梯型ＳＡＷフィルタに
ついて説明したが、これを複数段の梯型ＳＡＷフィルタ
で構成しても、上記実施形態とほぼ同様の利点が得られ
る。(3) Advantage In this embodiment, the SAW constituting the ladder-type SAW filter is
Since the Al electrode finger 41a of the IDT 22D of the resonator is made thinner, the frequency characteristic of the radiation conductance of the IDT 22D portion becomes broader, and the overlapping portion of the radiation characteristic of the IDT 22D and the reflection characteristics of the reflectors 23D and 24D becomes wider. As a result, the Q value of the SAW resonator is improved, and a low-loss SAW
A filter can be realized. In the patterning of the SAW filter, etching or the like may be used instead of lift-off. The present invention is not limited to the above embodiment, and various modifications are possible. For example, LT substrate 2
1 may use an LT substrate other than the 36 ° YX LT substrate. The Al electrode finger may be formed using another metal film. In FIG. 14, a single-stage ladder-type SAW filter has been described. However, even when the ladder-type SAW filter is constituted by a plurality of ladder-type SAW filters, substantially the same advantages as in the above-described embodiment can be obtained.
【００３７】[0037]
【発明の効果】以上詳細に説明したように、本発明のう
ちの請求項１、６及び７の発明によれば、反射器上に絶
縁膜を被着したので、該反射器部分の音速が低下し、Ｉ
ＤＴの放射特性と反射器の反射特性が一致する。これに
より、ＳＡＷ共振子のＱ値が向上し、低損失のＳＡＷフ
ィルタの実現が可能となる。請求項２、６及び７の発明
によれば、反射器の電極指の膜厚をＩＤＴ部分の電極指
の膜厚よりも４０％〜６０％厚くしたので、該ＩＤＴの
放射コンダクタンスの周波数特性が高周波側にシフト
し、ＩＤＴの放射特性と反射器の反射特性が一致する。
これにより、ＳＡＷ共振子のＱ値が向上し、低損失のＳ
ＡＷフィルタの実現が可能となる。請求項３、６及び７
の発明によれば、反射器の電極指の幅をＩＤＴの電極指
の幅よりも１０％〜５０％広くしたので、該反射器部分
の音速が下がり、ＩＤＴの放射特性と反射器の反射特性
が一致する。これにより、ＳＡＷ共振子のＱ値が向上
し、低損失のＳＡＷフィルタの実現が可能となる。As described above in detail, according to the first, sixth and seventh aspects of the present invention, since the insulating film is provided on the reflector, the sound speed of the reflector is reduced. Drops, I
The radiation characteristic of the DT matches the reflection characteristic of the reflector. Thereby, the Q value of the SAW resonator is improved, and a low-loss SAW filter can be realized. According to the second, sixth and seventh aspects of the present invention, the thickness of the electrode finger of the reflector is made 40% to 60% thicker than the thickness of the electrode finger of the IDT portion, so that the frequency characteristic of the radiation conductance of the IDT is reduced. The frequency shifts to the high frequency side, and the radiation characteristic of the IDT matches the reflection characteristic of the reflector.
As a result, the Q value of the SAW resonator is improved, and the low-loss S
An AW filter can be realized. Claims 3, 6, and 7
According to the invention, since the width of the electrode finger of the reflector is made 10% to 50% wider than the width of the electrode finger of the IDT, the sound speed of the reflector portion is reduced, and the radiation characteristics of the IDT and the reflection characteristics of the reflector are reduced. Matches. Thereby, the Q value of the SAW resonator is improved, and a low-loss SAW filter can be realized.
【００３８】請求項４、８及び９の発明によれば、反射
器の金属膜をＩＤＴの金属膜よりも比重の重い金属を用
いて形成したので、該反射器下の音速が低下し、ＩＤＴ
の放射コンダクタンスの周波数特性が低い周波数にシフ
トし、反射器の反射特性が一致する。これにより、ＳＡ
Ｗ共振子のＱ値が向上し、低損失のＳＡＷフィルタの実
現が可能となる。請求項５、６及び７の発明によれば、
ＩＤＴの電極指の幅を反射器の電極指の幅よりも１０％
〜５０％狭くしたので、該ＩＤＴ部分の放射コンダクタ
ンスの周波数特性が広帯域になり、ＩＤＴの放射特性と
反射器の反射特性の重なる部分が広がる。これにより、
ＳＡＷ共振子のＱ値が向上し、低損失のＳＡＷフィルタ
の実現が可能となる。According to the fourth, eighth and ninth aspects of the present invention, since the metal film of the reflector is formed by using a metal having a higher specific gravity than the metal film of the IDT, the sound speed below the reflector is reduced, and
The frequency characteristic of the radiated conductance shifts to a lower frequency, and the reflection characteristic of the reflector matches. Thereby, SA
The Q value of the W resonator is improved, and a low-loss SAW filter can be realized. According to the invention of claims 5, 6 and 7,
The width of the electrode finger of the IDT is 10% of the width of the electrode finger of the reflector.
Since the width is reduced by about 50%, the frequency characteristic of the radiation conductance of the IDT portion is broadened, and the overlapping portion of the radiation characteristic of the IDT and the reflection characteristic of the reflector is widened. This allows
The Q value of the SAW resonator is improved, and a low-loss SAW filter can be realized.
【図１】本発明の第１の実施形態を示すＳＡＷ共振子の
構成図である。FIG. 1 is a configuration diagram of a SAW resonator according to a first embodiment of the present invention.
【図２】図１の製造方法を示す図である。FIG. 2 is a view showing a manufacturing method of FIG. 1;
【図３】本発明の第２の実施形態を示すＳＡＷ共振子の
構成図である。FIG. 3 is a configuration diagram of a SAW resonator according to a second embodiment of the present invention.
【図４】図３の製造方法を示す図である。FIG. 4 is a view showing a manufacturing method of FIG. 3;
【図５】本発明の第３の実施形態を示すＳＡＷ共振子の
構成図である。FIG. 5 is a configuration diagram of a SAW resonator according to a third embodiment of the present invention.
【図６】図５（ｂ）のＢ部分の拡大図である。FIG. 6 is an enlarged view of a portion B in FIG. 5 (b).
【図７】図５の製造方法を示す図である。FIG. 7 is a view showing the manufacturing method of FIG. 5;
【図８】本発明の第４の実施形態を示すＳＡＷ共振子の
構成図である。FIG. 8 is a configuration diagram of a SAW resonator according to a fourth embodiment of the present invention.
【図９】図８の製造方法を示す図である。FIG. 9 is a view showing the manufacturing method of FIG. 8;
【図１０】本発明の第５の実施形態を示すＳＡＷ共振子
の構成図である。FIG. 10 is a configuration diagram of a SAW resonator according to a fifth embodiment of the present invention.
【図１１】図１０（ｂ）のＣ部分の拡大図である。FIG. 11 is an enlarged view of a portion C in FIG. 10 (b).
【図１２】図１０の製造方法を示す図である。FIG. 12 is a view showing the manufacturing method of FIG. 10;
【図１３】図１０の周波数特性図である。FIG. 13 is a frequency characteristic diagram of FIG.
【図１４】梯型ＳＡＷフィルタの構成図である。FIG. 14 is a configuration diagram of a ladder-type SAW filter.
【図１５】図１４の周波数特性図である。15 is a frequency characteristic diagram of FIG.
【図１６】従来の１端子対ＳＡＷ共振子の平面図であ
る。FIG. 16 is a plan view of a conventional one-port SAW resonator.
【図１７】図１６のＡ部分の拡大図である。FIG. 17 is an enlarged view of a portion A in FIG.
【図１８】図１６の製造方法を示す図である。FIG. 18 is a diagram illustrating the manufacturing method of FIG. 16;
【図１９】図１６の周波数特性図である。19 is a frequency characteristic diagram of FIG.
【図２０】反射器のストップバンド評価のための通過特
性の測定回路図である。FIG. 20 is a circuit diagram for measuring a pass characteristic for evaluating a stop band of a reflector.
【図２１】反射器のストップバンド評価を示す図であ
る。FIG. 21 is a diagram showing a stop band evaluation of a reflector.
【図２２】反射器のストップバンド評価を示す図であ
る。FIG. 22 is a diagram showing stop band evaluation of a reflector.
１ 直列腕 ２ 並列腕 ２１ ＬＴ基板 ２２，２２Ａ，２２Ｂ，２２Ｃ，２２Ｄ ＩＤＴ ２３，２３Ａ，２３Ｂ，２３Ｃ，２３Ｄ，２４，２４
Ａ，２４Ｂ，２４Ｃ，２４Ｄ
反射器Reference Signs List 1 serial arm 2 parallel arm 21 LT board 22, 22A, 22B, 22C, 22D IDT 23, 23A, 23B, 23C, 23D, 24, 24
A, 24B, 24C, 24D
Reflector
Claims (9)
弾性表面波を励振するための金属膜からなる複数の電極
指を有するすだれ状トランスデューサと、 前記基板上に前記トランスデューサを挟んで左側と右側
に形成され、前記弾性表面波を該トランスデューサ側へ
反射させるための前記金属膜と同一の金属膜からなる複
数の電極指をそれぞれ有する左側及び右側の反射器とを
備え、 比重が２〜３、熱膨張率が１０〜２０、及び前記金属膜
に対する膜厚比が４０％〜７０％の絶縁膜を、前記反射
器上に被着したことを特徴とする弾性表面波共振子。1. A method comprising: forming on a LiTaO 3 single crystal substrate;
An interdigital transducer having a plurality of electrode fingers made of a metal film for exciting a surface acoustic wave, and formed on the substrate on the left and right sides with the transducer interposed therebetween, and reflecting the surface acoustic wave to the transducer side The left and right reflectors respectively having a plurality of electrode fingers made of the same metal film as the metal film for specific gravity, the specific gravity is 2-3, the coefficient of thermal expansion is 10-20, and the film thickness for the metal film A surface acoustic wave resonator characterized in that an insulating film having a ratio of 40% to 70% is applied on said reflector.
を備え、 前記反射器の電極指膜厚を前記トランスデューサの電極
指膜厚よりも４０％〜６０％厚くしたことを特徴とする
弾性表面波共振子。2. A surface acoustic wave resonance comprising the transducer and the reflector according to claim 1, wherein the electrode finger thickness of the reflector is 40% to 60% thicker than the electrode finger thickness of the transducer. Child.
を備え、 前記反射器の電極指幅を前記トランスデューサの電極指
幅よりも１０％〜５０％広くしたことを特徴とする弾性
表面波共振子。3. A surface acoustic wave resonator comprising the transducer and the reflector according to claim 1, wherein an electrode finger width of the reflector is wider by 10% to 50% than an electrode finger width of the transducer.
を備え、 前記反射器を、前記トランスデューサの金属膜よりも比
重の大きな金属膜で形成したことを特徴とする弾性表面
波共振子。4. A surface acoustic wave resonator comprising the transducer and the reflector according to claim 1, wherein the reflector is formed of a metal film having a higher specific gravity than a metal film of the transducer.
を備え、 前記トランスデューサの電極指幅を前記反射器の電極指
幅よりも１０％〜５０％狭くしたことを特徴とする弾性
表面波共振子。5. A surface acoustic wave resonator comprising the transducer and the reflector according to claim 1, wherein the electrode finger width of the transducer is narrower by 10% to 50% than the electrode finger width of the reflector.
振子を直列腕及び並列腕に用い、これらを梯型に接続し
て前記基板上に形成し、かつ該直列腕の共振周波数と該
並列腕の反共振周波数を一致させて構成したことを特徴
とする弾性表面波フィルタ。6. The surface acoustic wave resonator according to claim 1, 2, 3, or 5 is used as a series arm and a parallel arm, and these are connected in a ladder shape to be formed on the substrate, and the resonance of the series arm is performed. A surface acoustic wave filter characterized in that the frequency and the anti-resonance frequency of the parallel arm are matched.
いて、 前記基板は３６°Ｙ−Ｘ、ＬｉＴａＯ３単結晶基板で、
前記トランスデューサ及び反射器はＡｌ膜で、それぞれ
形成したことを特徴とする弾性表面波フィルタ。7. The surface acoustic wave filter according to claim 6, wherein the substrate is a 36 ° YX, LiTaO 3 single crystal substrate,
A surface acoustic wave filter, wherein the transducer and the reflector are each formed of an Al film.
び並列腕に用い、これらを梯型に接続して前記基板上に
形成し、かつ該直列腕の共振周波数と該並列腕の反共振
周波数を一致させて構成したことを特徴とする弾性表面
波フィルタ。8. The surface acoustic wave resonator according to claim 4 is used for a series arm and a parallel arm, these are connected in a ladder shape to be formed on the substrate, and the resonance frequency of the series arm and the parallel arm A surface acoustic wave filter characterized in that anti-resonance frequencies are matched.
いて、 前記基板は３６°Ｙ−Ｘ、ＬｉＴａＯ３単結晶基板で、
前記トランスデューサはＡｌ膜で、前記反射器はＴｉ、
Ｓｎ、Ｆｅ、Ｎｉ又はＣｕのいずれか１つの金属膜で、
それぞれ形成したことを特徴とする弾性表面波フィル
タ。9. The surface acoustic wave filter according to claim 8, wherein the substrate is a 36 ° YX, LiTaO 3 single crystal substrate,
The transducer is an Al film, the reflector is Ti,
A metal film of any one of Sn, Fe, Ni or Cu,
A surface acoustic wave filter characterized by being formed respectively.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1236697A JPH10209804A (en) | 1997-01-27 | 1997-01-27 | Surface acoustic wave resonator and surface acoustic wave filter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1236697A JPH10209804A (en) | 1997-01-27 | 1997-01-27 | Surface acoustic wave resonator and surface acoustic wave filter |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH10209804A true JPH10209804A (en) | 1998-08-07 |
Family
ID=11803282
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP1236697A Withdrawn JPH10209804A (en) | 1997-01-27 | 1997-01-27 | Surface acoustic wave resonator and surface acoustic wave filter |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH10209804A (en) |
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|---|---|---|---|
| A300 | Withdrawal of application because of no request for examination |
Free format text: JAPANESE INTERMEDIATE CODE: A300 Effective date: 20040406 |