JPH0897671A - Surface acoustic wave device - Google Patents
Surface acoustic wave deviceInfo
- Publication number
- JPH0897671A JPH0897671A JP23152194A JP23152194A JPH0897671A JP H0897671 A JPH0897671 A JP H0897671A JP 23152194 A JP23152194 A JP 23152194A JP 23152194 A JP23152194 A JP 23152194A JP H0897671 A JPH0897671 A JP H0897671A
- Authority
- JP
- Japan
- Prior art keywords
- film
- acoustic wave
- surface acoustic
- protective film
- piezoelectric substrate
- 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]
【産業上の利用分野】この発明は、弾性表面波装置に関
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 device.
【０００２】[0002]
【従来の技術】弾性表面波装置は、圧電基板上に入力お
よび出力用の変換器（ＩＤＴ：Interdigital Transduce
r 、以下、ＩＤＴと称することがある。）が対をなして
配置されており、表面波を応用したデバイスである。こ
れらのＩＤＴにより電気信号と弾性表面波との相互変換
を行う。ＩＤＴは弾性表面波励振部および引き出し電極
で構成されている。2. Description of the Related Art A surface acoustic wave device is a transducer for input and output (IDT: Interdigital Transducer) on a piezoelectric substrate.
r, hereinafter may be referred to as IDT. ) Are arranged in pairs and are devices that apply surface waves. Mutual conversion between an electric signal and a surface acoustic wave is performed by these IDTs. The IDT is composed of a surface acoustic wave excitation unit and an extraction electrode.
【０００３】この弾性表面波装置の材料として、一般的
に以下のようなものが用いられている。例えば、圧電基
板には電気機械結合係数の比較的大きい、ニオブ酸リチ
ウムＬｉＮｂＯ3 やタンタル酸リチウムＬｉＴａＯ3 等
が用いられる。また、引き出し電極にはボンディングを
容易にするためＡｕが用いられる。弾性表面波励振部に
は圧電基板表面から伝わる振動に対する負荷を軽くし、
伝搬損失を少なくするため、比重の小さいＡｌや、銅ま
たはシリコンを１０％未満程度含んだＡｌ合金（以下、
単にＡｌ合金と称する。）等が用いられる。また、ＩＤ
Ｔ製造時の機械的損傷の防止や、入出力ＩＤＴおよび弾
性表面波伝搬路における塵埃による汚染を防止し、保護
する目的で、弾性表面波励振部の露出している部分と弾
性表面波の伝搬路とをＳｉＯ2 膜で覆う。Ａｌは湿度に
弱く、保護膜としてのＳｉＯ2 膜も耐湿性には乏しいの
で、弾性表面波装置は腐食防止のため、通常キャンパッ
ケージあるいはセラミックパッケージに１．０×１０-6
ａｔｍｃｃ／ｓｅｃ以下のオーダーで高気密封止されて
いる。The following materials are generally used as the material of this surface acoustic wave device. For example, lithium niobate LiNbO 3 or lithium tantalate LiTaO 3 having a relatively large electromechanical coupling coefficient is used for the piezoelectric substrate. Further, Au is used for the extraction electrode to facilitate bonding. The surface acoustic wave excitation section is lightly loaded against the vibration transmitted from the surface of the piezoelectric substrate,
In order to reduce the propagation loss, Al having a small specific gravity or an Al alloy containing less than 10% of copper or silicon (hereinafter,
It is simply called an Al alloy. ) Etc. are used. Also, ID
Propagation of surface acoustic waves and exposed parts of surface acoustic wave excitation parts for the purpose of preventing mechanical damage during manufacturing, and preventing and protecting the input / output IDT and the surface acoustic wave propagation path from contamination by dust. The channels are covered with a SiO 2 film. Since Al is weak to humidity and the SiO 2 film as a protective film also has poor moisture resistance, the surface acoustic wave device usually has 1.0 × 10 −6 in a can package or a ceramic package to prevent corrosion.
Highly airtightly sealed on the order of atmcc / sec or less.
【０００４】[0004]
【発明が解決しようとする課題】しかしながら、従来の
弾性表面波装置には、以下に示すような問題点があっ
た。However, the conventional surface acoustic wave device has the following problems.
【０００５】ＩＤＴを構成する弾性表面波励振部には上
述したように、ＡｌまたはＡｌ合金が用いられることが
多い。しかしＡｌまたはＡｌ合金は湿度に弱く、腐食す
る。一般にＡｌの腐食を防止するための保護膜として、
耐湿性に優れたＳｉ3 Ｎ4 膜が知られているが、弾性表
面波装置においてこのＳｉ3 Ｎ4 膜を適用しようとした
場合、次のような問題が生じる。弾性表面波装置に保護
膜を設けるにあたって、圧電基板と弾性表面波励振部と
の段差部分にクラックが発生するのを防ぐために、通
常、保護膜の膜厚は保護される電極金属の膜厚の１．５
〜２倍程度を必要とする。しかしＳｉ3 Ｎ4 の線膨張係
数は２．５〜４．３×１０-6／℃であるのに対し、圧電
基板として通常用いられるＬｉＮｂＯ3 、ＬｉＴａＯ3
の線膨張係数はそれぞれ１．６１×１０-5／℃、１．５
４×１０-5／℃であり、その値に１桁もの大きな差があ
る。このため、保護膜の膜厚が厚くなると温度変動によ
りＳｉ3 Ｎ4 膜にクラックが入る。たとえば自動車電話
などで使用される８００〜９００ＭＨｚ帯では、通常弾
性表面波励振部の膜厚が１００〜３００ｎｍ必要である
から、保護膜の厚さを１５０〜６００ｎｍにする必要が
あるが、Ｓｉ3 Ｎ4 膜を適用した場合、１００ｎｍ以上
の厚さにすると温度変動によりクラックが入るため、腐
食防止に対する信頼性に問題が生じてしまう。As described above, Al or Al alloy is often used for the surface acoustic wave excitation portion constituting the IDT. However, Al or Al alloy is sensitive to humidity and corrodes. Generally, as a protective film to prevent Al corrosion,
A Si 3 N 4 film having excellent moisture resistance is known, but when the Si 3 N 4 film is applied to a surface acoustic wave device, the following problems occur. When a protective film is provided on a surface acoustic wave device, the thickness of the protective film is usually the same as the thickness of the electrode metal to be protected in order to prevent cracks from occurring at the step between the piezoelectric substrate and the surface acoustic wave excitation part. 1.5
Approximately twice as much is required. However, while the coefficient of linear expansion of Si 3 N 4 is 2.5 to 4.3 × 10 −6 / ° C., LiNbO 3 and LiTaO 3 which are commonly used as piezoelectric substrates are used.
Coefficient of linear expansion of 1.61 × 10 -5 / ℃, 1.5
It is 4 × 10 −5 / ° C., and there is a large difference of one digit in the value. Therefore, if the protective film becomes thicker, the Si 3 N 4 film will be cracked due to temperature fluctuations. For example, in 800~900MHz band used in automobile telephones, because the thickness of the ordinary surface acoustic wave exciter is required 100 to 300 nm, although the thickness of the protective film it is necessary to 150 to 600 nm, Si 3 When the N 4 film is applied, if the thickness is 100 nm or more, cracks are generated due to temperature fluctuations, which causes a problem in reliability of corrosion prevention.
【０００６】しかし、圧電基板と比較的近い線膨張係数
といえる３．０〜５．０×１０-5／℃の線膨張係数を有
するＳｉＯ2 を保護膜に適用すると、このＳｉＯ2 は湿
度に弱いために腐食の防止をすることができず、機械的
損傷や塵埃による汚染等から保護する役目を果たすに過
ぎない。したがって、弾性表面波装置の腐食を防止する
ためには、キャンパッケージあるいはセラミックパッケ
ージに、高気密を保った状態で封止しなければならな
い。このため、高気密封止する工程が必要となり、歩留
の低下と、他の半導体デバイスとの一体化の困難とを招
くという問題が生じる。However, when SiO 2 having a linear expansion coefficient of 3.0 to 5.0 × 10 -5 / ° C., which is a linear expansion coefficient relatively close to that of the piezoelectric substrate, is applied to the protective film, the SiO 2 is exposed to humidity. Since it is weak, it cannot prevent corrosion, and only serves to protect it from mechanical damage and contamination by dust. Therefore, in order to prevent corrosion of the surface acoustic wave device, the can package or the ceramic package must be sealed in a highly airtight state. Therefore, a step of highly airtightly sealing is required, which causes a problem that yield is reduced and it is difficult to integrate with another semiconductor device.
【０００７】このため、従来より、ＩＤＴ製造時の機械
的損傷の防止や、入出力ＩＤＴおよび弾性表面波伝搬路
における塵埃による汚染の防止をすると同時に、高気密
封止パッケージングによらずに腐食を防止できるような
保護膜を有する弾性表面波装置の出現が望まれていた。Therefore, conventionally, the mechanical damage at the time of manufacturing the IDT is prevented, the contamination of the input / output IDT and the surface acoustic wave propagation path by the dust is prevented, and at the same time, the corrosion is achieved without using the highly hermetically sealed packaging. It has been desired to develop a surface acoustic wave device having a protective film capable of preventing the above-mentioned problems.
【０００８】[0008]
【課題を解決するための手段】このため、この発明によ
れば、圧電基板上に入力変換器および出力変換器と、こ
れら入力変換器および出力変換器のそれぞれの弾性表面
波励振部およびこれら入力変換器および出力変換器間の
弾性表面波伝搬路を少なくとも覆う保護膜とを具えた弾
性表面波装置において、保護膜が、圧電基板の線膨張係
数に近い線膨張係数を有する絶縁性の内側保護膜と、耐
湿性および絶縁性を有する外側保護膜との二層で構成さ
れていることを特徴とする。Therefore, according to the present invention, an input converter and an output converter, a surface acoustic wave excitation section of each of the input converter and the output converter, and their inputs are provided on the piezoelectric substrate. In a surface acoustic wave device including a protective film covering at least a surface acoustic wave propagation path between a converter and an output converter, the protective film has an insulating inner protective layer having a linear expansion coefficient close to that of the piezoelectric substrate. It is characterized by being constituted by two layers of a film and an outer protective film having a moisture resistance and an insulating property.
【０００９】[0009]
【作用】上述したこの発明の弾性表面波装置によれば、
保護膜が、圧電基板側に設けた内側保護膜と、表面側に
設けた外側保護膜の二層構造となっている。このとき、
内側保護膜は圧電基板の線膨張係数に近い線膨張係数を
有する絶縁性の膜であり、外側保護膜は耐湿性および絶
縁性を有する膜である。このため、温度変動があって
も、圧電基板と内側保護膜との線膨張係数が互いに近い
値となっているので、圧電基板に生じた歪みは内側保護
膜で緩和され、したがって、内側保護膜にクラックが生
じるおそれが実質的になくなる。また、外側保護膜は耐
湿性および絶縁性を有するので、ＩＤＴ製造時の機械的
損傷や、入出力ＩＤＴおよび弾性表面波伝搬路における
塵埃による汚染防止をすると同時に、高気密封止パッケ
ージングによらずに腐食の防止をすることができる。According to the surface acoustic wave device of the present invention described above,
The protective film has a two-layer structure of an inner protective film provided on the piezoelectric substrate side and an outer protective film provided on the front surface side. At this time,
The inner protective film is an insulating film having a linear expansion coefficient close to that of the piezoelectric substrate, and the outer protective film is a film having moisture resistance and insulating properties. Therefore, even if there is a temperature change, the linear expansion coefficients of the piezoelectric substrate and the inner protective film are close to each other, so that the strain generated in the piezoelectric substrate is relaxed by the inner protective film, and therefore the inner protective film is reduced. There is virtually no risk of cracks occurring in the. In addition, since the outer protective film has moisture resistance and insulation, it prevents mechanical damage during IDT manufacturing and prevents contamination of the input / output IDT and the surface acoustic wave propagation path by dust, and at the same time, the high airtight sealing packaging is used. Without being able to prevent corrosion.
【００１０】[0010]
【実施例】以下、図面を参照して、この発明の実施例に
つき説明をする。なお、各図は、発明が理解できる程度
に概略的に示してあるにすぎず、断面を表すハッチング
等は一部を除き省略してある。また、以下の説明におい
て特定の材料および条件等を用いるが、これらは好適例
の一つにすぎず、したがって、この発明では何らこれに
限定されるものではない。Embodiments of the present invention will be described below with reference to the drawings. It should be noted that each of the drawings is only schematically illustrated to the extent that the invention can be understood, and hatching and the like showing cross sections are omitted except for a part. Further, although specific materials, conditions and the like are used in the following description, these are merely preferred examples, and therefore the present invention is not limited thereto.
【００１１】図１は、この発明の実施例の弾性表面波装
置の要部の構成を示す概略的平面図である。なお、この
実施例の弾性表面波装置として、弾性表面波フィルタを
適用した。以下、この発明の弾性表面波フィルタの製造
方法を簡単に説明しながら、構造の説明をする。FIG. 1 is a schematic plan view showing the structure of the main part of a surface acoustic wave device according to an embodiment of the present invention. A surface acoustic wave filter was applied as the surface acoustic wave device of this example. The structure will be described below while briefly explaining the method of manufacturing the surface acoustic wave filter of the present invention.
【００１２】まず、圧電基板１０上にＥＢ蒸着法により
Ａｌ膜を設ける。この膜厚は、自動車電話等で使用され
る８００〜９００ＭＨｚ帯に対応できるように、１００
〜３００ｎｍにする。次に、フォトリソグラフィを行う
ことによりパターン化し、弾性表面波励振部１２および
３２を形成する。この弾性表面波励振部１２、３４は、
周知の通り、一対の櫛型電極（すだれ状ともいう。）を
組み合わせて構成してある。各電極は一方向に延在する
基部と、その延在方向と直行する方向に突出した櫛歯部
とからなっている。この組み合わせ構造の一例として、
電極の基部を平行にし、一方の電極の櫛歯部を他方の電
極の櫛歯部間に、互いに接触しないように、挿入した構
造となっている。First, an Al film is provided on the piezoelectric substrate 10 by the EB vapor deposition method. This film thickness is 100 so that it can be used in the 800 to 900 MHz band used in automobile phones and the like.
˜300 nm. Next, patterning is performed by performing photolithography to form the surface acoustic wave excitation portions 12 and 32. The surface acoustic wave excitation units 12 and 34 are
As is well known, it is configured by combining a pair of comb-shaped electrodes (also called comb-shaped electrodes). Each electrode includes a base portion extending in one direction and a comb tooth portion protruding in a direction orthogonal to the extending direction. As an example of this combination structure,
The base portions of the electrodes are parallel to each other, and the comb-teeth portions of one electrode are inserted between the comb-teeth portions of the other electrode so as not to come into contact with each other.
【００１３】その後、各電極の基部の、櫛歯部とは反対
側の部分に、この基部に部分的に重なるようにして、圧
電基板１０上に、Ａｕを用いて引き出し電極１４および
３４を、２００〜５００ｎｍの膜厚で設ける。その後、
これら圧電基板１０と、弾性表面波励振部１２および３
２と、引き出し電極１４および３４との上全面を覆うよ
うにネガレジストを塗布する。その後、フォトリソグラ
フィによる露光・現像工程を経て、弾性表面波励振部１
２および３２と、引き出し電極１４および３４の一部分
とを含む、圧電基板１０の表面の一部分の領域、つまり
内側保護膜を設けたい部分を露出させる。圧電基板１０
の表面の一部分には、入力ＩＤＴおよび出力ＩＤＴ間
の、弾性表面波伝搬路も含まれている。After that, the lead electrodes 14 and 34 are formed on the piezoelectric substrate 10 by using Au so as to partially overlap the base of each electrode on the side opposite to the comb teeth so as to partially overlap the base. It is provided with a film thickness of 200 to 500 nm. afterwards,
The piezoelectric substrate 10 and the surface acoustic wave excitation units 12 and 3
2 is coated with a negative resist so as to cover the entire upper surfaces of 2 and the extraction electrodes 14 and 34. After that, through the exposure and development process by photolithography, the surface acoustic wave excitation unit 1
A region of a part of the surface of the piezoelectric substrate 10, including 2 and 32 and a part of the extraction electrodes 14 and 34, that is, a part where the inner protective film is to be provided is exposed. Piezoelectric substrate 10
The surface acoustic wave propagation path between the input IDT and the output IDT is also included in a part of the surface of the.
【００１４】次に、スパッタリング法により、例えばＳ
ｉＯ2 膜を堆積させる。この膜厚は、１５０〜６００ｎ
ｍの範囲（電極金属の１．５〜２倍程度）であれば、す
でに述べた８００〜９００ＭＨｚ帯に対応できる。次
に、これらを溶剤中に入れて、現像後に残ったネガレジ
ストを除去して、リフトオフ法によりＳｉＯ2 膜を内側
保護膜１８として残存形成する。Next, by a sputtering method, for example, S
Deposit an iO 2 film. This film thickness is 150 to 600 n
If it is in the range of m (about 1.5 to 2 times that of the electrode metal), it can correspond to the 800 to 900 MHz band already described. Next, these are put in a solvent to remove the negative resist remaining after the development, and the SiO 2 film is left as the inner protective film 18 by the lift-off method.
【００１５】次に、再度ネガレジストを、ＳｉＯ2 膜１
８が形成された構造体の、ＳｉＯ2膜１８側の全面を覆
うように塗布する。次にフォトリソグラフィによる露光
・現像を経て、内側保護膜（ＳｉＯ2 膜）１８とその周
囲の部分を露出させ、スパッタリング法によりＳｉＯ2
膜の上を覆うように、例えばＳｉ3 Ｎ4 膜を堆積させ
る。この膜厚は、温度変動によるクラックが生じない程
度に非常に薄く（約１０〜５０ｎｍ程度）堆積させる。
その後、現像後に残ったネガレジストを除去してリフト
オフ法によりＳｉ3 Ｎ4 膜を外側保護膜２０として残存
形成し、図１に示されるような二層の保護膜２２を有す
る弾性表面波フィルタが形成される。Next, the negative resist is again used to form the SiO 2 film 1.
Application is performed so as to cover the entire surface of the structure in which 8 is formed on the SiO 2 film 18 side. Next, through exposure / development by photolithography, the inner protective film (SiO 2 film) 18 and its peripheral portion are exposed, and SiO 2 is formed by a sputtering method.
For example, a Si 3 N 4 film is deposited so as to cover the film. This film is deposited very thin (about 10 to 50 nm) so that cracks due to temperature fluctuations do not occur.
After that, the negative resist remaining after the development is removed, and the Si 3 N 4 film is left as the outer protective film 20 by the lift-off method to form a surface acoustic wave filter having a two-layer protective film 22 as shown in FIG. It is formed.
【００１６】図１に示す平面図の、ＸＹ方向に切って矢
印の方向に見た断面図を図２に示す。図２のように、弾
性表面波励振部１２および３２のうち、引き出し電極１
４および３４が覆わずに露出している部分をすべて、内
側保護膜１８と外側保護膜２０とからなる二層の保護膜
２２が覆っている。FIG. 2 is a sectional view of the plan view shown in FIG. 1 cut in the XY directions and viewed in the direction of the arrow. As shown in FIG. 2, of the surface acoustic wave excitation units 12 and 32, the extraction electrode 1
All of the exposed portions of 4 and 34 which are not covered are covered with a two-layer protective film 22 including an inner protective film 18 and an outer protective film 20.
【００１７】この二層の保護膜２２を有する弾性表面波
装置の特性を、従来のＳｉＯ2 一層のみで覆われた保護
膜を有する弾性表面波装置と比較し、表１に示した。The characteristics of the surface acoustic wave device having the two-layer protective film 22 are shown in Table 1 in comparison with those of the conventional surface acoustic wave device having the protective film covered with only one SiO 2 layer.
【００１８】[0018]
【表１】 [Table 1]
【００１９】表１からも明らかなように、実施例の弾性
表面波装置は耐湿性に優れた外側保護膜であるＳｉ3 Ｎ
4 膜２０、および圧電基板１０（ＬｉＮｂＯ3 ）の線膨
張係数に近い、３．０〜５．０×１０-5／℃という線膨
張係数を持つ内側保護膜であるＳｉＯ2 膜１８とからな
る二層の保護膜２２を有する。このため、温度の変動が
起こっても、圧電基板１０に生じた歪みを、保護膜とし
て十分な厚み（１５０〜６００μｍ）をとった内側保護
膜であるＳｉＯ2 膜が緩和するため、クラックが発生す
る心配がない。また、外側保護膜としては、上述したよ
うに耐湿性に優れたＳｉ3 Ｎ4 を温度変動による影響が
出ない程度に薄く用いているので、従来通りＩＤＴ製造
時の機械的損傷の防止や、入出力ＩＤＴおよび弾性表面
波伝搬路における塵埃による汚染を防止し、保護すると
同時に、温度変動によるクラックの発生の心配もなく、
腐食防止にも優れている。このため、高気密に保って封
止する必要がなくなり、他の半導体デバイスと組み込ん
で一体化させることが可能となった。As is clear from Table 1, the surface acoustic wave devices of the examples are Si 3 N which is an outer protective film excellent in moisture resistance.
4 film 20 and SiO 2 film 18 which is an inner protective film having a linear expansion coefficient of 3.0 to 5.0 × 10 −5 / ° C., which is close to the linear expansion coefficient of the piezoelectric substrate 10 (LiNbO 3 ). The protective film 22 has two layers. Therefore, even if the temperature fluctuates, the strain generated in the piezoelectric substrate 10 is relaxed by the SiO 2 film, which is an inner protective film having a sufficient thickness (150 to 600 μm) as a protective film, and thus cracks occur. I don't have to worry. Further, as the outer protective film, Si 3 N 4 having excellent moisture resistance is used thinly as described above so as not to be affected by temperature fluctuations, and thus mechanical damage at the time of manufacturing the IDT is prevented as usual. Prevents and protects contamination by dust in the input / output IDT and the surface acoustic wave propagation path, and at the same time, does not worry about cracks due to temperature fluctuations.
It also has excellent corrosion protection. For this reason, it is not necessary to keep airtightness and sealing, and it becomes possible to incorporate and integrate with other semiconductor devices.
【００２０】この発明は、上述した実施例にのみ限定さ
れるものではないことが明らかである。例えば、実施例
においては、圧電基板１０にＬｉＮｂＯ3 を用いたが、
ＬｉＴａＯ3 あるいは水晶を用いても同様の効果があ
る。また、実施例では保護膜の形成にリフトオフ法を適
用しているが、エッチング法を適用しても良い。エッチ
ング法を適用した場合は、レジストとしてポジレジスト
を使用する。また、実施例では弾性表面波装置に弾性表
面波フィルタを適用したが、弾性表面波を利用した共振
器やコンボルバ等、弾性表面波装置全般にわたり適用可
能である。また、弾性表面波装置の耐湿性を向上させる
外側保護膜２０の好適材料としてＳｉ3 Ｎ4 膜を用いた
が、絶縁性と耐湿性とをあわせもつ材料であれば同様の
効果が得られる。また、内側保護膜のとしてＳｉＯ2 膜
を用いたが、圧電基板１０の線膨張係数に比較的近い線
膨張係数（圧電基板の線膨張係数と同程度から大体４〜
５倍程度までの範囲内）をもち、かつ絶縁性の材料であ
れば、同様の効果が得られる。It will be clear that the invention is not limited to the embodiments described above. For example, in the embodiment, LiNbO 3 is used for the piezoelectric substrate 10,
The same effect can be obtained by using LiTaO 3 or quartz. Further, although the lift-off method is applied to the formation of the protective film in the embodiment, the etching method may be applied. When the etching method is applied, a positive resist is used as the resist. Further, although the surface acoustic wave filter is applied to the surface acoustic wave device in the embodiments, the present invention can be applied to all surface acoustic wave devices such as resonators and convolvers using surface acoustic waves. Further, the Si 3 N 4 film is used as a suitable material for the outer protective film 20 for improving the moisture resistance of the surface acoustic wave device, but the same effect can be obtained as long as the material has both insulation and moisture resistance. Further, although the SiO 2 film is used as the inner protective film, the linear expansion coefficient relatively close to the linear expansion coefficient of the piezoelectric substrate 10 (from the linear expansion coefficient of the piezoelectric substrate is approximately 4 to 4).
The same effect can be obtained as long as the material has an insulating property (in the range of up to about 5 times).
【００２１】[0021]
【発明の効果】上述した説明からも明らかなように、こ
の発明の弾性表面波装置によれば、保護膜が、圧電基板
側に設けた内側保護膜と、表面側に設けた外側保護膜の
二層構造となっている。このとき、内側保護膜は圧電基
板の線膨張係数に近い線膨張係数を有する絶縁性の膜で
あり、外側保護膜は耐湿性および絶縁性を有する膜であ
る。このため、温度変動があっても、圧電基板と内側保
護膜との線膨張係数が互いに近い値となっているので、
圧電基板に生じた歪みは内側保護膜で緩和され、したが
って、内側保護膜にクラックが生じるおそれが実質的に
なくなる。また、外側保護膜は耐湿性および絶縁性を有
するので、ＩＤＴ製造時にの機械的損傷や、圧電基板上
の入出力ＩＤＴおよびそれらの間の弾性表面波伝搬路に
あたる部分における、塵埃による汚染防止をすると同時
に、高気密封止パッケージングによらずに腐食を防止す
ることができる。As is apparent from the above description, according to the surface acoustic wave device of the present invention, the protective film includes the inner protective film provided on the piezoelectric substrate side and the outer protective film provided on the front surface side. It has a two-layer structure. At this time, the inner protective film is an insulating film having a linear expansion coefficient close to that of the piezoelectric substrate, and the outer protective film is a film having moisture resistance and insulating properties. Therefore, even if the temperature changes, the linear expansion coefficients of the piezoelectric substrate and the inner protective film are close to each other.
The strain generated in the piezoelectric substrate is relaxed by the inner protective film, and therefore, the risk of cracks in the inner protective film is substantially eliminated. Further, since the outer protective film has moisture resistance and insulation properties, it is possible to prevent mechanical damage at the time of manufacturing the IDT, and to prevent contamination of the input / output IDT on the piezoelectric substrate and a portion corresponding to the surface acoustic wave propagation path between them with dust. At the same time, corrosion can be prevented without relying on highly hermetically sealed packaging.
【００２２】したがって高気密封止パッケージング工程
は不要となり、歩留が向上し、他の半導体デバイスとの
一体化も可能になる。Therefore, the highly hermetically sealed packaging step is not required, the yield is improved, and it can be integrated with other semiconductor devices.
【図１】この発明の実施例の弾性表面波装置の構成を示
す概略的平面図である。FIG. 1 is a schematic plan view showing the configuration of a surface acoustic wave device according to an embodiment of the present invention.
【図２】図１においてＸＹ部分で切った断面を矢印の方
向に見たときの断面図である。FIG. 2 is a cross-sectional view of the cross section cut along the XY portion in FIG. 1 as seen in the direction of the arrow.
１０：圧電基板 １２、３２：弾性表面波励振部 １４、３４：引き出し電極 １６：入力変換器（入力ＩＤＴ） １８：内側保護膜（ＳｉＯ2 膜） ２０：外側保護膜（Ｓｉ3 Ｎ4 膜） ３６：出力変換器（出力ＩＤＴ）10: Piezoelectric substrate 12, 32: Surface acoustic wave excitation part 14, 34: Extraction electrode 16: Input converter (input IDT) 18: Inner protective film (SiO 2 film) 20: Outer protective film (Si 3 N 4 film) 36: Output converter (output IDT)
───────────────────────────────────────────────────── フロントページの続き (72)発明者 坂本 信義 東京都港区虎ノ門１丁目７番12号 沖電気 工業株式会社内 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuyoshi Sakamoto 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd.
Claims (2)
器と、これら入力変換器および出力変換器のそれぞれの
弾性表面波励振部およびこれら入力変換器および出力変
換器間の弾性表面波伝搬路を少なくとも覆う保護膜とを
具えた弾性表面波装置において、 前記保護膜が、前記圧電基板の線膨張係数に近い線膨張
係数を有する絶縁性の内側保護膜と、耐湿性および絶縁
性を有する外側保護膜との二層で構成されていることを
特徴とする弾性表面波装置。1. An input converter and an output converter on a piezoelectric substrate, surface acoustic wave excitation units of the input converter and the output converter, and a surface acoustic wave propagation path between the input converter and the output converter. In a surface acoustic wave device including a protective film that covers at least the protective film, the protective film has an insulating inner protective film having a linear expansion coefficient close to that of the piezoelectric substrate, and a moisture resistant and insulating outer surface. A surface acoustic wave device comprising two layers including a protective film.
て、前記内側保護膜をＳｉＯ2 膜とし、および外側保護
膜をＳｉ3 Ｎ4 膜としたことを特徴とする弾性表面波装
置。2. The surface acoustic wave device according to claim 1, wherein the inner protective film is a SiO 2 film and the outer protective film is a Si 3 N 4 film.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP23152194A JPH0897671A (en) | 1994-09-27 | 1994-09-27 | Surface acoustic wave device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP23152194A JPH0897671A (en) | 1994-09-27 | 1994-09-27 | Surface acoustic wave device |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH0897671A true JPH0897671A (en) | 1996-04-12 |
Family
ID=16924794
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP23152194A Withdrawn JPH0897671A (en) | 1994-09-27 | 1994-09-27 | Surface acoustic wave device |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0897671A (en) |
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| JP2006279874A (en) * | 2005-03-30 | 2006-10-12 | Seiko Epson Corp | Acoustic wave element and electronic equipment |
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1994
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|---|---|---|---|---|
| US6909341B2 (en) * | 2000-10-23 | 2005-06-21 | Matsushita Electric Industrial Co., Ltd. | Surface acoustic wave filter utilizing a layer for preventing grain boundary diffusion |
| US7282835B2 (en) | 2003-06-26 | 2007-10-16 | Murata Manufacturing Co., Ltd. | Surface acoustic wave element |
| WO2005083881A1 (en) * | 2004-03-02 | 2005-09-09 | Murata Manufacturing Co., Ltd. | Surface acoustic wave device |
| US7327071B2 (en) | 2004-03-02 | 2008-02-05 | Murata Manufacturing Co., Ltd. | Surface acoustic wave device |
| JP2006279874A (en) * | 2005-03-30 | 2006-10-12 | Seiko Epson Corp | Acoustic wave element and electronic equipment |
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| US20120279795A1 (en) * | 2010-01-20 | 2012-11-08 | Panasonic Corporation | Acoustic wave device |
| WO2011142183A1 (en) * | 2010-05-10 | 2011-11-17 | 株式会社村田製作所 | Surface acoustic wave device |
| JP5083469B2 (en) * | 2010-05-10 | 2012-11-28 | 株式会社村田製作所 | Surface acoustic wave device |
| JP2012004613A (en) * | 2010-06-14 | 2012-01-05 | Murata Mfg Co Ltd | Surface acoustic wave device |
| JP2010246167A (en) * | 2010-07-22 | 2010-10-28 | Panasonic Corp | Saw device and manufacturing method thereof |
| WO2012132238A1 (en) * | 2011-03-25 | 2012-10-04 | Panasonic Corporation | Acoustic wave device with reduced higher order transverse modes |
| US9065424B2 (en) | 2011-03-25 | 2015-06-23 | Skyworks Panasonic Filter Solutions Japan Co., Ltd | Acoustic wave device with reduced higher order transverse modes |
| JP2015111923A (en) * | 2011-03-25 | 2015-06-18 | スカイワークス・パナソニック フィルターソリューションズ ジャパン株式会社 | Acoustic wave device suppressing higher-order transverse mode wave |
| JP2016184951A (en) * | 2011-03-25 | 2016-10-20 | スカイワークスフィルターソリューションズジャパン株式会社 | Acoustic wave device with suppressed higher order transverse mode |
| JP2017028543A (en) * | 2015-07-23 | 2017-02-02 | 株式会社デンソー | Elastic surface wave element |
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