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
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- JP
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- Prior art keywords
- idt
- surface acoustic
- reflector
- saw
- acoustic wave
- Prior art date
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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 |
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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 |
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Publication Number | Publication Date |
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Family
ID=11803282
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JP1236697A Withdrawn JPH10209804A (en) | 1997-01-27 | 1997-01-27 | Surface acoustic wave resonator and surface acoustic wave filter |
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