JP2001156582A - Piezoelectric resonator - Google Patents
Piezoelectric resonatorInfo
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- JP2001156582A JP2001156582A JP34067299A JP34067299A JP2001156582A JP 2001156582 A JP2001156582 A JP 2001156582A JP 34067299 A JP34067299 A JP 34067299A JP 34067299 A JP34067299 A JP 34067299A JP 2001156582 A JP2001156582 A JP 2001156582A
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- Prior art keywords
- film
- electrode
- piezoelectric
- thickness
- piezoelectric resonator
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、携帯電話、無線Ｌ
ＡＮ等に好適に用いられる圧電共振子に関するものであ
る。TECHNICAL FIELD The present invention relates to a portable telephone, a wireless L
The present invention relates to a piezoelectric resonator suitably used for AN and the like.
【０００２】[0002]
【従来技術】近年、情報通信において、国際標準化シス
テム（ＩＭＴ−２０００）が適応されようとしており、
伝送する情報量が飛躍的に増大する。これにともなっ
て、端末に使用される電子部品に対する要求もますます
高度化し、特に、通信機器のキーデバイスであるフィル
ターにおいては広帯域、低損失が要求されている。2. Description of the Related Art In recent years, the international standardization system (IMT-2000) has been adapted to information communication.
The amount of information to be transmitted increases dramatically. Along with this, requirements for electronic components used in terminals have become more and more advanced, and in particular, filters which are key devices of communication devices are required to have a wide band and low loss.
【０００３】また、無線通信や電気回路に用いられる周
波数の高周波数化がますます進んでおり、これに伴っ
て、これらの電気信号に対して用いられる電子部品も高
周波数に対応したものが要求され、開発が行われてい
る。[0003] In addition, as the frequency used for wireless communication and electric circuits is becoming higher and higher, electronic components used for these electric signals are required to be compatible with high frequencies. Has been developed.
【０００４】最近は、例えば、レゾネーターとしては、
特に、バルク・アコースティック・ウェーブ・レゾネータ
ー（ＢＡＷＲ）と呼ばれる薄膜圧電共振子の開発が進め
られている。これは、入力される高周波電気信号に対し
て、圧電薄膜の振動により薄膜の厚さ方向に共振を起こ
すことを用いた共振子であり、ＧＨｚ領域の高い共振周
波数を持つレゾネーターなどへの応用が期待されてい
る。Recently, for example, as a resonator,
In particular, a thin film piezoelectric resonator called a bulk acoustic wave resonator (BAWR) has been developed. This is a resonator that uses the vibration of the piezoelectric thin film to resonate the input high-frequency electric signal in the thickness direction of the thin film, and is applicable to resonators having a high resonance frequency in the GHz range. Expected.
【０００５】ＢＡＷＲの基本的な構造は、Japanese Jou
rnal of Applied Physics誌 Vol.36, pp.6069-6072
(1997)に示されており、図３に示すように、基体２１
と、該基体２１表面上に形成された支持膜２２と、該支
持膜２２上に形成された第１電極２４と、該第1電極２
４上に形成された圧電体２５と、該圧電体２５上に形成
された２つの第２電極２６とから構成されている。[0005] The basic structure of BAWR is Japanese Jou
rnal of Applied Physics Magazine Vol.36, pp.6069-6072
(1997), and as shown in FIG.
A support film 22 formed on the surface of the base 21; a first electrode 24 formed on the support film 22;
4 includes a piezoelectric body 25 formed on the piezoelectric body 25 and two second electrodes 26 formed on the piezoelectric body 25.
【０００６】この文献には、支持膜２２を、基体２１に
形成された空間Ａを被覆するように、基体２１上面に形
成することにより、支持膜２２の空間Ａに接する部分が
振動することになる。したがって、空間Ａに接する支持
膜２２と、その表面に形成され、第１電極２４、圧電体
２５、および第２電極２６からなる振動体２７とが一体
となって振動する。According to this document, by forming the support film 22 on the upper surface of the base 21 so as to cover the space A formed in the base 21, the portion of the support film 22 in contact with the space A vibrates. Become. Therefore, the supporting film 22 in contact with the space A and the vibrating body 27 formed on the surface thereof and composed of the first electrode 24, the piezoelectric body 25, and the second electrode 26 vibrate integrally.
【０００７】また、この文献には、基体２１にＳｉ、支
持膜２２にＳｉＯ2、第１電極２４にＴｉとＰｔとの積
層体、圧電体２５にＰＺＴ、第２電極２６にＡｌが用い
ている。このうち、第１電極２４は、支持膜２２の上に
Ｔｉ膜２３が形成され、このＴｉ膜上にＰｔが形成され
てなるＰｔ／Ｔｉ積層体を形成してなるものである。こ
のＴｉは下地である支持膜２２との密着性を考慮して用
いられており、Ｐｔは圧電体２５からのＰｂ拡散を防ぐ
バリヤーとしての役割をはたしている。In this document, Si is used for the substrate 21, SiO 2 is used for the support film 22, a laminate of Ti and Pt is used for the first electrode 24, PZT is used for the piezoelectric body 25, and Al is used for the second electrode 26. I have. Among them, the first electrode 24 is formed by forming a Pt / Ti laminate in which a Ti film 23 is formed on the support film 22 and Pt is formed on the Ti film. This Ti is used in consideration of the adhesion to the support film 22 serving as a base, and Pt serves as a barrier for preventing Pb diffusion from the piezoelectric body 25.
【０００８】[0008]
【発明が解決しようとする課題】しかしながら、上記文
献に開示された圧電共振子においては、Ｔｉの体積抵抗
が１０-6ΩｃｍとＰｔの体積抵抗値１０-8Ωｃｍに比べ
て非常に高いために、Ｐｔの膜厚が小さいとＴｉの不要
な抵抗が寄生抵抗として第１電極２４で発生し、Ｑ値を
著しく低下させる原因となり、圧電共振子の特性を低く
するという問題があった。However, in the piezoelectric resonator disclosed in the above document, the volume resistance of Ti is 10 −6 Ωcm, which is much higher than the volume resistance of Pt, 10 −8 Ωcm. If the film thickness of Pt is small, unnecessary resistance of Ti is generated as parasitic resistance in the first electrode 24, causing a significant decrease in the Q value, and causing a problem of lowering the characteristics of the piezoelectric resonator.
【０００９】この問題を解決するために、Ｐｔの膜厚を
大きくすることができるが、Ｐｔを厚くすると、第１電
極の抵抗値が低くなって寄生抵抗の影響を少なくし、Ｑ
値の低下を防ぐことができる。しかし、Ｐｔの膜厚を大
きくすると、Ｐｔは重元素であり、かつその膜厚が２０
０ｎｍと大きくなると、振動における質量負荷が大きく
なり、共振周波数が低下して、高周波数に対応すること
ができないという問題があった。To solve this problem, the thickness of Pt can be increased. However, when the thickness of Pt is increased, the resistance of the first electrode is reduced to reduce the influence of the parasitic resistance, and Q
The value can be prevented from lowering. However, when the thickness of Pt is increased, Pt is a heavy element,
When it is as large as 0 nm, there is a problem that the mass load in vibration increases, the resonance frequency decreases, and it is not possible to cope with high frequencies.
【００１０】したがって、圧電共振子が、ＧＨｚ帯およ
びそれに準じる高周波領域で使用されることを考える
と、圧電共振子を構成する電極材料に軽元素で、かつ導
電率の高い金属を用いるとともに、その金属膜の厚みを
薄くすることが、求められている。そこで、比重が小さ
く、また体積抵抗値が小さい為、質量負荷による共振周
波数の低下が小さく高周波対応の共振子用電極として好
ましいＡｌを第１電極として使うことが考えられる。Therefore, considering that the piezoelectric resonator is used in a GHz band and a high frequency region equivalent thereto, a light element and a metal having high conductivity are used for the electrode material constituting the piezoelectric resonator. It is required to reduce the thickness of the metal film. Therefore, since the specific gravity is small and the volume resistance value is small, the decrease in the resonance frequency due to the mass load is small, and it is conceivable to use Al, which is preferable as a resonator electrode for high frequency, as the first electrode.
【００１１】しかし、第１電極としてＡｌを用いると、
Ａｌは酸化しやすいため、圧電体の形成時にまた第１電
極と圧電体との界面に、非圧電体で誘電活性の小さいア
ルミナ（Ａｌ2Ｏ3）が生成する。アルミナは、圧電体と
非圧電体の直列接続となる為、電極と圧電体からなる振
動体の見かけ上の圧電性は急激に小さくなり、圧電振動
子としての特性を大きく損なってしまうという問題があ
った。However, when Al is used as the first electrode,
Since Al is easily oxidized, alumina (Al 2 O 3 ), which is a non-piezoelectric material and has low dielectric activity, is generated at the interface between the first electrode and the piezoelectric material during the formation of the piezoelectric material. Alumina is a series connection of a piezoelectric body and a non-piezoelectric body.Therefore, the apparent piezoelectricity of the vibrating body consisting of the electrodes and the piezoelectric body suddenly decreases, and the characteristics of the piezoelectric vibrator are greatly impaired. there were.
【００１２】さらに、バンドパスフィルターに要求され
る帯域幅を満足できないという問題があった。Furthermore, there is a problem that the bandwidth required for the band-pass filter cannot be satisfied.
【００１３】そこで、本発明は、広帯域で使用でき、Ｑ
値や共振周波数などの電子部品特性を高めた圧電共振子
を提供することを目的とする。Therefore, the present invention can be used in a wide band,
It is an object of the present invention to provide a piezoelectric resonator having improved electronic component characteristics such as a value and a resonance frequency.
【００１４】[0014]
【課題を解決するための手段】本発明の圧電共振子は、
基体上に第１電極、誘電体、第２電極と順次積層してな
る圧電共振子において、前記第１電極をＡｌ膜とＰｔ膜
との積層体で構成したことを特徴とする。According to the present invention, there is provided a piezoelectric resonator comprising:
In a piezoelectric resonator in which a first electrode, a dielectric, and a second electrode are sequentially laminated on a base, the first electrode is formed of a laminate of an Al film and a Pt film.
【００１５】この構成において、Ａｌは体積抵抗値が小
さく、寄生抵抗の影響を無視できるので、共振子のＱ値
を飛躍的に大きくすることができる。また、Ｐｔ膜を薄
く形成することができるため、Ａｌの比重が小さいこと
から、共振子における電極の質量負荷効果を小さくせし
め、共振周波数を高めることができる。In this configuration, since Al has a small volume resistance value and the effect of the parasitic resistance can be neglected, the Q value of the resonator can be greatly increased. Further, since the Pt film can be formed thin, the specific gravity of Al is small, so that the effect of mass loading of the electrodes in the resonator can be reduced and the resonance frequency can be increased.
【００１６】特に、圧電体が強誘電体からなることが好
ましく、これにより広帯域で使用でき、Ｑ値や共振周波
数などの電子部品特性を高めた圧電共振子として用いる
ことができる。In particular, the piezoelectric body is preferably made of a ferroelectric substance, whereby the piezoelectric body can be used in a wide band, and can be used as a piezoelectric resonator having improved electronic component characteristics such as a Q value and a resonance frequency.
【００１７】また、第１電極を、Ｐｔ膜がＡｌ膜を挟持
するように設けられた積層体とすることが好ましい。す
なわち、薄いＰｔ膜を第１層として形成し、その上にＡ
ｌ膜を第２層として形成し、その上にＰｔ膜を第３層と
して形成することにより、Ａｌ膜表面酸化で形成する非
圧電体による圧電体の圧電性低下を防ぐことができる。Further, it is preferable that the first electrode is a laminated body provided so that the Pt film sandwiches the Al film. That is, a thin Pt film is formed as a first layer, and A
By forming the l film as the second layer and forming the Pt film thereon as the third layer, it is possible to prevent a decrease in the piezoelectricity of the piezoelectric body due to the non-piezoelectric body formed by oxidation of the Al film surface.
【００１８】また、この構造によりＡｌ膜の表面状態が
改善されてより平滑な薄膜を形成することができ、この
Ａｌ膜上にＰｔ膜を形成するときに、Ｐｔ膜がＡｌ膜の
全面を覆いやすくなるため、Ｐｔ膜の厚みを薄くでき、
電極の軽量化による共振子特性の改善が実現できる。Further, the surface condition of the Al film is improved by this structure, and a smoother thin film can be formed. When a Pt film is formed on this Al film, the Pt film covers the entire surface of the Al film. The thickness of the Pt film can be reduced,
Resonator characteristics can be improved by reducing the weight of the electrodes.
【００１９】特に、Ｐｔ膜の厚みを１０〜３０ｎｍと薄
くすることが好適である。これにより、質量負荷効果を
極めて小さくして共振子のＱ値を大きくできる。また共
振周波数を大きくできる。In particular, it is preferable to reduce the thickness of the Pt film to 10 to 30 nm. As a result, the mass load effect can be extremely reduced, and the Q value of the resonator can be increased. Further, the resonance frequency can be increased.
【００２０】[0020]
【発明の実施の形態】本発明の圧電共振子は、図１に示
すように、基体１上に支持膜２が形成され、この支持膜
２の上面に、Ａｌ膜３ａとＰｔ膜３ｂからなる第１電極
３が形成され、さらにその上に圧電体４、第２電極５が
順次設けられており、第１電極３および第２電極５が圧
電体４を挟持して振動体６が形成されている。また、支
持膜２の振動体６形成面の反対側には、振動空間が設け
られている。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a piezoelectric resonator according to the present invention has a support film 2 formed on a base 1 and an Al film 3a and a Pt film 3b on the support film 2. A first electrode 3 is formed, and a piezoelectric body 4 and a second electrode 5 are further provided thereon. The first electrode 3 and the second electrode 5 sandwich the piezoelectric body 4 to form a vibrating body 6. ing. A vibration space is provided on the side of the support film 2 opposite to the surface on which the vibration body 6 is formed.
【００２１】第１電極３は、Ａｌ膜３ａとＰｔ膜３ｂの
積層体で構成されており、特に、第１電極３は、Ｐｔ膜
３ｂがＡｌ膜３ａを挟持するように設けられた積層体で
ある事が望ましい。すなわち、Ａｌは比重が小さく、ま
た体積抵抗値が小さい為、質量負荷による共振周波数の
低下が小さく高周波対応の共振子として望ましく、また
Ｐｔ膜は、耐酸化性に優れ、容易に酸化するＡｌ膜を酸
化から防ぎ、非圧電体であり誘電活性の小さいアルミナ
（Ａｌ2Ｏ3）の生成を抑制できる。The first electrode 3 is composed of a laminate of an Al film 3a and a Pt film 3b. In particular, the first electrode 3 is a laminate in which the Pt film 3b is provided so as to sandwich the Al film 3a. Is desirable. That is, since Al has a small specific gravity and a small volume resistance value, the reduction of the resonance frequency due to the mass load is small, so that it is desirable as a resonator corresponding to a high frequency. Can be prevented from being oxidized, and generation of alumina (Al 2 O 3 ) which is a non-piezoelectric substance and has a small dielectric activity can be suppressed.
【００２２】第１電極３を構成するＰｔ膜３ｂの膜厚
は、１０〜３０ｎｍが望ましい。膜厚が３０ｎｍを越え
ると、Q値が低下する傾向がある。これは、Ｐｔ膜の体
積抵抗率がＡｌに比べると大きいため、膜厚を大きくす
ると寄生抵抗の原因になるためである。また、膜厚が１
０ｎｍ未満では、Ａｌ膜３ａを完全に覆い難しくなり、
表面に露出している部位のＡｌ膜３ａが増え、Ａｌ膜３
ａと圧電体４の界面にアルミナの占める面積比率が大き
くなり、振動体６の実効的圧電性が小さくなる傾向があ
る。さらに、特に、振動体６の圧電性、質量負荷効果に
よる共振周波数の低下抑制の点から、１０〜２０ｎｍが
望ましい。The thickness of the Pt film 3b constituting the first electrode 3 is preferably 10 to 30 nm. If the film thickness exceeds 30 nm, the Q value tends to decrease. This is because the volume resistivity of the Pt film is larger than that of Al, so that increasing the film thickness causes parasitic resistance. In addition, when the film thickness is 1
If it is less than 0 nm, it becomes difficult to completely cover the Al film 3a,
The portion of the Al film 3a exposed on the surface increases, and the Al film 3a
The ratio of the area occupied by alumina at the interface between a and the piezoelectric body 4 increases, and the effective piezoelectricity of the vibrating body 6 tends to decrease. Further, from the viewpoint of suppressing the decrease in the resonance frequency due to the piezoelectricity of the vibrating body 6 and the mass load effect, the thickness is preferably 10 to 20 nm.
【００２３】第１電極３は、高周波スパッタ法、真空蒸
着法等気相成長法により形成される。第１電極３として
Ａｌ膜３ａの膜厚は５０〜３００ｎｍが望ましい。３０
０ｎｍを越える膜厚になると、軽元素であるＡｌを用い
ても質量負荷効果が無視できなくなるとともに、Ａｌ膜
３ａ中での内部摩擦により損失が増える傾向がある。ま
た５０ｎｍより薄くなると被覆率が低下する傾向があ
り、抵抗が上昇することがある。また、電気抵抗と質量
負荷効果を考慮すると、特に５０〜２００ｎｍが望まし
い。The first electrode 3 is formed by a vapor phase growth method such as a high frequency sputtering method and a vacuum evaporation method. The thickness of the Al film 3a as the first electrode 3 is desirably 50 to 300 nm. 30
If the thickness exceeds 0 nm, the mass loading effect cannot be ignored even when Al, which is a light element, is used, and the loss tends to increase due to internal friction in the Al film 3a. If the thickness is less than 50 nm, the coverage tends to decrease, and the resistance may increase. Further, in consideration of the electric resistance and the mass load effect, the thickness is particularly preferably 50 to 200 nm.
【００２４】圧電体４は、圧電性の大きい強誘電体から
なる。強誘電体としては、ＰＺＴ、ＰＴなどのペロブス
カイト構造を持つ酸化物、ＫＳｒ2Ｎｂ5Ｏ15等のタング
ステンブロンズ構造を持つ酸化物が使用されるが、特に
ＰＺＴ、ＰＴ系材料が圧電性の大きさ、絶縁性から望ま
しい。The piezoelectric body 4 is made of a ferroelectric substance having high piezoelectricity. As the ferroelectric, an oxide having a perovskite structure such as PZT or PT or an oxide having a tungsten bronze structure such as KSr 2 Nb 5 O 15 is used. It is desirable from the viewpoint of insulation.
【００２５】圧電体４は、高周波マグネトロンスパッタ
法等の気相成膜法やゾルゲル法等の溶液法で形成できる
が、低温でＰＺＴ膜を形成できる高周波スパッタ法が特
に好ましい。さらに、圧電体４の膜厚は、２μｍ以下が
望ましい。これは、厚み縦振動を用いるＢＡＷＲにおい
ては、使用周波数である共振周波数が膜厚に逆比例し、
１ＧＨｚ以上の周波数で使用する為に、２μｍ以下の膜
厚が必要な為である。The piezoelectric body 4 can be formed by a vapor phase film forming method such as a high frequency magnetron sputtering method or a solution method such as a sol-gel method, but a high frequency sputtering method capable of forming a PZT film at a low temperature is particularly preferable. Further, the thickness of the piezoelectric body 4 is desirably 2 μm or less. This is because, in a BAWR using thickness longitudinal vibration, the resonance frequency, which is the frequency used, is inversely proportional to the film thickness.
This is because a film thickness of 2 μm or less is required for use at a frequency of 1 GHz or more.
【００２６】基体１は、シリコンやサファイアなどであ
り、基体１表面に形成する圧電体４の表面が平滑になる
ために、十分な平坦度と表面粗さ、例えば５μｍ以下の
平坦度とＲａ０．１μｍ以下の表面粗さを保有していれ
ば、特に材料を限定するものではない。The substrate 1 is made of silicon, sapphire, or the like, and has a sufficient flatness and surface roughness, for example, a flatness of 5 μm or less and Ra0. The material is not particularly limited as long as it has a surface roughness of 1 μm or less.
【００２７】また、基体１は、ＫＯＨ等を用いた化学的
エッチング法や、反応性イオンエッチング法等を用いた
エッチングにより、振動空間Ａが形成されている。基体
１の振動空間Ａとは、振動体４の振動を基体１に伝達し
ないための空間を言い、基体１に貫通孔を形成したり、
基体１の支持膜２を形成する部分に凹状の窪みを形成し
たりすることにより作製される。The vibration space A is formed in the substrate 1 by a chemical etching method using KOH or the like, or an etching using a reactive ion etching method or the like. The vibration space A of the base 1 refers to a space for preventing the vibration of the vibrating body 4 from being transmitted to the base 1, such as forming a through hole in the base 1,
It is manufactured by forming a concave depression in a portion of the base 1 where the support film 2 is formed.
【００２８】支持膜２は、ＳｉＯ2、Ａｌ2Ｏ3、Ｓｉ3Ｎ
4、ダイヤモンドなどの高強度高硬質材料が好ましく、
スパッタ法やＣＶＤ法等の方法で形成される。膜厚は、
０．５〜５μｍの厚みが好ましく、特には、１〜３μｍ
が好ましい。０．５μｍ以下では、支持膜強度が不十分
で、膜が自立できずに破壊されやすい。また、５μｍ以
上では、共振周波数が低下して高周波化に対応できな
い。The support film 2 is made of SiO 2 , Al 2 O 3 , Si 3 N
4 , high strength and high hardness materials such as diamond are preferable,
It is formed by a method such as a sputtering method or a CVD method. The film thickness is
A thickness of 0.5 to 5 μm is preferable, and in particular,
Is preferred. If the thickness is 0.5 μm or less, the strength of the supporting film is insufficient, and the film cannot be self-supported and is easily broken. On the other hand, if it is 5 μm or more, the resonance frequency is lowered, and it is not possible to cope with a higher frequency.
【００２９】以上のように構成された本発明の圧電共振
子では、抵抗が小さく比重の小さいＡｌ膜３ａと耐酸化
性に優れたＰｔ膜３ｂとの積層体を第１電極３として用
いることで、質量負荷による共振周波数の低下を抑制で
き、電極の寄生抵抗に起因した共振子のＱ値の低下を抑
制する事ができ、Ｑ値の高い高周波対応の圧電共振子を
実現できる。In the piezoelectric resonator of the present invention configured as described above, a laminate of an Al film 3a having a small resistance and a small specific gravity and a Pt film 3b having excellent oxidation resistance is used as the first electrode 3. In addition, a decrease in the resonance frequency due to a mass load can be suppressed, and a decrease in the Q value of the resonator due to the parasitic resistance of the electrode can be suppressed. Thus, a high-frequency piezoelectric resonator having a high Q value can be realized.
【００３０】また、図２は本発明の他の例を示すもので
あり、基体１１上に、音響インピーダンスの異なる第１
層１２ａと第２層１２ｂとからなる積層構造を３回繰り
返し積層した。こうして音響反射層１２が設けられ、そ
の上に第１電極１３と圧電体１４と第２電極１５とによ
り振動体１６が構成されている。第１電極は、Ａｌ膜１
３ａとＰｔ膜１３ｂとの積層構造からなっている。FIG. 2 shows another example of the present invention.
The laminated structure including the layer 12a and the second layer 12b was repeatedly laminated three times. Thus, the acoustic reflection layer 12 is provided, on which the first electrode 13, the piezoelectric body 14, and the second electrode 15 form the vibrating body 16. The first electrode is an Al film 1
3a and a Pt film 13b.
【００３１】このような圧電共振子では、第１電極１３
と第２電極１５との間に高周波電界が印加されることに
より、振動体１６が振動して音響波が発生する。音響波
は基体１１方向に進み、音響反射層１２で反射され、振
動体へ戻っていく。In such a piezoelectric resonator, the first electrode 13
When a high-frequency electric field is applied between the first electrode 15 and the second electrode 15, the vibrating body 16 vibrates to generate an acoustic wave. The acoustic wave travels toward the base 11, is reflected by the acoustic reflection layer 12, and returns to the vibrator.
【００３２】このように構成された本発明の圧電共振子
では、第１電極として適した構造であり、Ｑ値の高い高
周波対応の圧電共振子を実現できる。The piezoelectric resonator according to the present invention having the above-described structure has a structure suitable for the first electrode, and can realize a high Q value high frequency piezoelectric resonator.
【００３３】[0033]
【実施例】図１に示す圧電共振子を作製した。まず、減
圧ＣＶＤ法により窒化珪素膜を両面に形成したＳｉ基板
の表面上に、ＥＣＲスパッタ法により膜厚約１μｍの窒
化珪素膜（以後ＳＮ膜という）を作製した。ＥＣＲスパ
ッタ法によるＳＮ膜は高硬度で、しかも内部残留応力が
小さく、支持膜に適している。このようなＳＮ膜を用い
ると、１μｍの膜厚でも、残留応力によって自己破壊す
ることなく自立膜を形成できる。EXAMPLE A piezoelectric resonator shown in FIG. 1 was manufactured. First, a silicon nitride film (hereinafter, referred to as an SN film) having a thickness of about 1 μm was formed by ECR sputtering on the surface of a Si substrate on which silicon nitride films were formed on both sides by low-pressure CVD. The SN film formed by the ECR sputtering method has a high hardness and a small internal residual stress, and is suitable for a support film. When such an SN film is used, a self-standing film can be formed even with a film thickness of 1 μm without self-destruction due to residual stress.
【００３４】ＳＮ膜を形成した面と反対の面に減圧ＣＶ
Ｄで形成した窒化珪素膜をフォトレジスト法とＲＩＥを
用いてパターニングし、ＫＯＨ溶液によりＳｉ基板をエ
ッチング除去し、基体にビアホールを形成した。The decompression CV is applied to the surface opposite to the surface on which the SN film is formed.
The silicon nitride film formed in D was patterned using a photoresist method and RIE, and the Si substrate was removed by etching with a KOH solution to form a via hole in the base.
【００３５】この基体上に、所望により第１電極３の第
１層を、ＲＦマグネトロンスパッタ法によりＰｔ膜をＥ
ＣＲスパッタ形成窒化珪素膜上に成膜した。ＲＦパワー
１００Ｗ、Ａｒをスパッタガスとして基板温度４００℃
で作製した。次に、第２層としてＲＦマグネトロンスパ
ッタ法によりＡｌ膜３ａまたはＴｉ膜を形成した。ＲＦ
パワー３００Ｗ、基板温度は３００℃である。さらに、
第３層として、ＲＦマグネトロンスパッタ法によりＰｔ
膜３ｂまたはＴｉ膜を作製した。ＲＦパワー１００Ｗ、
基板温度は３００℃である。なお、各膜厚は表１の通り
である。On this substrate, if necessary, a first layer of the first electrode 3 is coated with a Pt film by RF magnetron sputtering.
A film was formed on a CR sputter-formed silicon nitride film. RF power 100 W, substrate temperature 400 ° C. using Ar as sputtering gas
Prepared. Next, an Al film 3a or a Ti film was formed as a second layer by an RF magnetron sputtering method. RF
The power is 300 W and the substrate temperature is 300 ° C. further,
As the third layer, Pt was formed by RF magnetron sputtering.
The film 3b or the Ti film was formed. RF power 100W,
The substrate temperature is 300 ° C. In addition, each film thickness is as shown in Table 1.
【００３６】次に、作製したＡｌ膜３ａとＰｔ膜３ｂの
積層電極上に、ＲＦマグネトロンスパッタ法により、膜
厚４００ｎｍのＰＺＴ膜、ＡｌＮ膜またはＺｎＯ膜を形
成した。ＲＦパワー２００Ｗ、Ａｒをスパッタガスとし
て基板温度５３０℃で作製した。Next, a 400 nm-thick PZT film, an AlN film, or a ZnO film was formed on the laminated electrode of the Al film 3a and the Pt film 3b by RF magnetron sputtering. The substrate was manufactured at a substrate temperature of 530 ° C. using RF power of 200 W and Ar as a sputtering gas.
【００３７】低温合成の為、Ｐｔ膜３ｂによるＡｌ膜３
ａへのＰｂの拡散とＡｌ膜の酸化によるアルミナの生成
を抑制できている。非圧電体であるアルミナが電極と圧
電体の界面に形成されると、振動体の圧電性は急激に減
少してしまう為、アルミナの生成の抑制が重要である。For low-temperature synthesis, the Al film 3 made of the Pt film 3b
The formation of alumina due to the diffusion of Pb into a and the oxidation of the Al film can be suppressed. If alumina, which is a non-piezoelectric body, is formed at the interface between the electrode and the piezoelectric body, the piezoelectricity of the vibrating body rapidly decreases. Therefore, it is important to suppress the generation of alumina.
【００３８】最後に、作製したＰＺＴ膜、ＡｌＮ膜また
はＺｎＯ膜の上に、Ａｌ膜をＲＦマグネトロンスパッタ
法により形成した。ＲＦパワー３００Ｗ、Ａｒをスパッ
タガスとして基板温度１００℃で作製した。膜厚は１０
０ｎｍである。共振子構造を構成する為に、Ａｌ膜３ａ
の上部電極は、メタルマスクを用いてドット状の電極膜
とした。２つの上部電極間に高周波電界を印加する事に
より、直列に接続した２つの共振子と等価となる。Finally, an Al film was formed on the produced PZT film, AlN film or ZnO film by RF magnetron sputtering. The substrate was manufactured at a substrate temperature of 100 ° C. using RF power of 300 W and Ar as a sputtering gas. The film thickness is 10
0 nm. To form the resonator structure, the Al film 3a
The upper electrode was a dot-shaped electrode film using a metal mask. By applying a high-frequency electric field between the two upper electrodes, it becomes equivalent to two resonators connected in series.
【００３９】圧電共振特性は、共振子構造についてＳパ
ラメータＳ11の測定により行った。ＲＦネットワークア
ナライザＨＰ８７１９Ｃ（ヒューレットパッカード社
製）と、ＲＦマイクロプローブを用い、Ｓ11の周波数特
性を測定する事により、共振周波数と***振周波数（ｆ
ａ）を評価した。支持膜を含めた複合振動子の第一次の
ピークより評価した共振周波数と***振周波数の周波数
差より、電気機械結合係数Ｋｔ2を算出した。The piezoelectric resonance characteristics, the resonator structure was carried out by measuring the S-parameters S 11. The RF network analyzer HP8719C (manufactured by Hewlett Packard), using the RF microprobe, by measuring the frequency characteristics of S 11, the resonant frequency and the antiresonant frequency (f
a) was evaluated. The electromechanical coupling coefficient Kt 2 was calculated from the frequency difference between the resonance frequency and the antiresonance frequency evaluated from the primary peak of the composite vibrator including the support film.
【００４０】Ｑ値は、第一次の***振でのＱ値を測定し
た。***振周波数の前後において、***振周波数でのＳ
11値から３デシベル変わったところでの周波数幅を求
め、***振周波数を周波数幅で割る事により、Ｑ値を算
出した。表１に結果を示す。As the Q value, the Q value at the first-order antiresonance was measured. Before and after the anti-resonance frequency, S at the anti-resonance frequency
The Q width was calculated by finding the frequency width at the point where 3 dB was changed from the 11 value, and dividing the anti-resonance frequency by the frequency width. Table 1 shows the results.
【００４１】[0041]
【表１】 [Table 1]
【００４２】圧電体が非強誘電体のＺｎＯおよびＡｌＮ
である本発明の試料Ｎｏ．２および３は、それぞれＫｔ
2が３．８、３．２％、ｆａが２．３５、２．１ＧＨ
ｚ、Ｑ値が３１５、３４０であった。Non-ferroelectric piezoelectric materials of ZnO and AlN
Is the sample No. of the present invention. 2 and 3 are Kt
2 is 3.8, 3.2%, fa is 2.35, 2.1GH
The z and Q values were 315 and 340.
【００４３】また、圧電体が強誘電体のＰＺＴ膜からな
り、電極がＡｌ膜３ａとＰｔ膜３ｂとの２層構造である
本発明の試料Ｎｏ．４〜８は、Ｋｔ2が５．０％以上、
ｆａが２．０ＧＨｚ以上、Ｑ値が１２７以上であった。
特に、第３層の膜厚が１０〜３０ｎｍである試料Ｎｏ．
４および５は、Ｋｔ2が５．０％以上、ｆａが２．２Ｈ
ｚ以上、Ｑ値が１６２以上であった。The sample No. 1 of the present invention in which the piezoelectric body was formed of a ferroelectric PZT film and the electrodes had a two-layer structure of an Al film 3a and a Pt film 3b. 4 to 8, Kt 2 is 5.0% or more;
The fa was 2.0 GHz or more, and the Q value was 127 or more.
In particular, in Sample No. 3 in which the thickness of the third layer was 10 to 30 nm.
4 and 5 had a Kt 2 of 5.0% or more and a fa of 2.2H.
The z value was not less than z and the Q value was not less than 162.
【００４４】また、第１層および第３層がＰｔ膜３ｂ
で、第２層のＡｌ膜３ａを挟持してなる電極を有する本
発明の試料Ｎｏ．９〜１４は、Ｋｔ2が６．５％以上、
ｆａが１．９ＧＨｚ以上、Ｑ値が１７０以上であった。The first and third layers are made of a Pt film 3b.
In the sample No. of the present invention having an electrode sandwiching the second layer Al film 3a. 9-14, Kt 2 is 6.5% or more,
The fa was 1.9 GHz or more, and the Q value was 170 or more.
【００４５】一方、本発明の範囲外であるＰｔ膜３ｂを
含まない試料Ｎｏ．１は、評価を試みたが、測定が困難
であった。また、Ｔｉ膜上にＰｔ膜３ｂが形成されてお
り、従来と類似の構造である本発明の範囲外の試料Ｎ
ｏ．１５は、Ｋｔ2が９．０％、ｆａが１．７２ＧＨ
ｚ、Ｑ値が７５であった。さらに、第３層にＴｉ膜を用
いた試料．１６は、共振せず、測定が不可能であった。On the other hand, the sample No. which does not include the Pt film 3b is out of the scope of the present invention. In No. 1, the evaluation was attempted, but the measurement was difficult. In addition, a Pt film 3b is formed on the Ti film, and a sample N having a structure similar to the conventional one, which is outside the scope of the present invention.
o. No. 15 has Kt 2 of 9.0% and fa of 1.72 GH
The z and Q values were 75. Furthermore, a sample using a Ti film as the third layer. No. 16 did not resonate and measurement was impossible.
【００４６】[0046]
【発明の効果】本発明の圧電共振子は、第１電極をＡｌ
膜３ａとＰｔ膜３ｂとの積層体とすることにより、圧電
共振子のＱ値と共振周波数を向上し、広帯域での使用を
可能とするような圧電共振子を提供できる。According to the piezoelectric resonator of the present invention, the first electrode is made of Al.
By forming a laminate of the film 3a and the Pt film 3b, the Q value and the resonance frequency of the piezoelectric resonator can be improved, and a piezoelectric resonator that can be used in a wide band can be provided.
【図１】本発明の圧電共振子の構造を示す断面図であ
る。FIG. 1 is a cross-sectional view illustrating a structure of a piezoelectric resonator of the present invention.
【図２】本発明の他の圧電共振子の構造を示す断面図で
ある。FIG. 2 is a cross-sectional view illustrating a structure of another piezoelectric resonator of the present invention.
【図３】従来の圧電共振子の構造を示す断面図である。FIG. 3 is a cross-sectional view illustrating a structure of a conventional piezoelectric resonator.
１・・基体 ２・・支持膜 ３・・第１電極 ３ａ・・・Ａｌ膜 ３ｂ・・・Ｐｔ膜 ４・・圧電体 ５・・第２電極 ６・・振動体 DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Support film 3 ... 1st electrode 3a ... Al film 3b ... Pt film 4 ... Piezoelectric body 5 ... 2nd electrode 6 ... Vibration body
Claims (4)
次積層してなる圧電共振子において、前記第１電極をＡ
ｌ膜とＰｔ膜との積層体で構成したことを特徴とする圧
電共振子。1. A piezoelectric resonator in which a first electrode, a piezoelectric body, and a second electrode are sequentially laminated on a base, wherein the first electrode is an A
A piezoelectric resonator comprising a laminated body of an l film and a Pt film.
ることを特徴とする請求項１記載の圧電共振子。2. The piezoelectric resonator according to claim 1, wherein the first electrode has an Al film sandwiched between Pt films.
を特徴とする請求項１または２記載の圧電共振子。3. The piezoelectric resonator according to claim 1, wherein the thickness of the Pt film is 10 to 30 nm.
請求項１乃至３のうちいずれかに記載の圧電共振子。4. The piezoelectric resonator according to claim 1, wherein the piezoelectric body is a ferroelectric.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP34067299A JP2001156582A (en) | 1999-11-30 | 1999-11-30 | Piezoelectric resonator |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP34067299A JP2001156582A (en) | 1999-11-30 | 1999-11-30 | Piezoelectric resonator |
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| Publication Number | Publication Date |
|---|---|
| JP2001156582A true JP2001156582A (en) | 2001-06-08 |
Family
ID=18339218
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP34067299A Pending JP2001156582A (en) | 1999-11-30 | 1999-11-30 | Piezoelectric resonator |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2001156582A (en) |
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| US7554426B2 (en) | 2006-09-12 | 2009-06-30 | Samsung Electronics Co., Ltd. | Resonator, apparatus having the same and fabrication method of resonator |
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