JPS6188700A - Piezoelectric element - Google Patents
Piezoelectric elementInfo
- Publication number
- JPS6188700A JPS6188700A JP20972584A JP20972584A JPS6188700A JP S6188700 A JPS6188700 A JP S6188700A JP 20972584 A JP20972584 A JP 20972584A JP 20972584 A JP20972584 A JP 20972584A JP S6188700 A JPS6188700 A JP S6188700A
- Authority
- JP
- Japan
- Prior art keywords
- voltage
- zinc oxide
- thin film
- specific resistance
- piezoelectric element
- 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.)
- Granted
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
- B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
- B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
- B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
- B06B1/06—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction
- B06B1/0644—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using a single piezoelectric element
- B06B1/0662—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using a single piezoelectric element with an electrode on the sensitive surface
- B06B1/0677—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using a single piezoelectric element with an electrode on the sensitive surface and a high impedance backing
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Piezo-Electric Transducers For Audible Bands (AREA)
- Transducers For Ultrasonic Waves (AREA)
Abstract
(57)【要約】本公報は電子出願前の出願データであるた
め要約のデータは記録されません。(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.
Description
【発明の詳細な説明】
〔発明の利用分野〕
本発明は酸化亜鉛ＺｎＯを用いた薄膜圧電素子に関する
ものである。DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a thin film piezoelectric element using zinc oxide ZnO.
酸化亜鉛（ＺｎＯ）は、厚み縦振動の電気機械結合係数
がバルク単結晶の場合で０．３０ と割合に大きく、比
較的簡単に薄膜化できるために、高周波超音波変換器と
して広く応用されている。酸化亜鉛薄膜の製造方法とし
ては、気相成長（ＣＶＤ）法スパッタ法等があるが、ス
パッタ法が主流である。スパッタ法にも直流スパッタ法
、高周波スパッタ法があり、また酸化亜鉛ＺｎＯ自体を
ターゲットとしてスパッタを行う方法、あるいは亜鉛板
をターゲットとして酸−雰囲気中でスパッタを行う反応
性スパッタ法等の種々の作成方法がある。Zinc oxide (ZnO) has a relatively large electromechanical coupling coefficient of thickness longitudinal vibration of 0.30 in the case of a bulk single crystal, and because it can be made into a thin film relatively easily, it is widely applied as a high-frequency ultrasonic transducer. There is. Methods for manufacturing zinc oxide thin films include vapor phase epitaxy (CVD), sputtering, and the like, but sputtering is the mainstream method. Sputtering methods include direct current sputtering and high-frequency sputtering, and there are various methods such as a method in which sputtering is performed using zinc oxide ZnO itself as a target, and a reactive sputtering method in which sputtering is performed in an acid atmosphere using a zinc plate as a target. There is a way.
しかしいずれの方法を用いても薄膜化したことによりバ
ルク単結晶の場合に比べて電気音響変換特性は劣下する
。したがって大きな音響出力を得るためには印加する電
圧を高くする必要があり、この印加電圧に対する耐圧の
高い薄膜を作成することが重要となる。酸化亜鉛は酸素
欠陥型半導体であるため、その比抵抗等の電気的特性は
スパッタ時の雰囲気、ガス圧等の作成条件に大きく依存
する。そのため、高比抵抗、高耐圧の酸化亜鉛薄膜の作
成条件の検討が従来より行なわれてきた。しかし、比抵
抗絶縁耐圧等の電気的特性は同一条件で作成した場合で
もばらつきが大きい。そのため、実際に作成した薄膜の
絶縁耐圧が低いことがあり寿命等の安定性の面で問題が
あった。したがって薄膜の絶縁耐圧を非破壊で評価する
必要がある。However, no matter which method is used, the electroacoustic conversion characteristics are degraded by making the film thinner than in the case of a bulk single crystal. Therefore, in order to obtain a large acoustic output, it is necessary to increase the applied voltage, and it is important to create a thin film that has a high withstand voltage against this applied voltage. Since zinc oxide is an oxygen-deficient semiconductor, its electrical properties such as specific resistance greatly depend on the production conditions such as the atmosphere and gas pressure during sputtering. For this reason, studies have been made on the conditions for creating zinc oxide thin films with high resistivity and high breakdown voltage. However, electrical characteristics such as resistivity and breakdown voltage vary widely even when they are made under the same conditions. Therefore, the dielectric strength of the actually produced thin film may be low, which poses problems in terms of stability such as life span. Therefore, it is necessary to non-destructively evaluate the dielectric strength of thin films.
絶縁耐圧を非破壊で評価する試みとしては、絶縁破壊電
圧とｔａｎδ との関係に着目した方法が、電子通信学
会論文誌、Ｊ ６５− Ａ 、 １２１７ （１９８２
年）におけるｆｆ’ Ｚ ｎ Ｏ圧電膜超音波トランス
デューザの励振周波数電圧に対する絶縁破壊特性」と題
する文献において論じられている。しかし、ｔａｎδは
誘電損失及び導電率という２つの情報を含んでおり、し
かも導電率は印加電圧に依存する量であるが、この点に
ついては詳しくふれられていない。As an attempt to non-destructively evaluate dielectric strength voltage, a method focusing on the relationship between dielectric breakdown voltage and tan δ was reported in Journal of the Institute of Electronics and Communication Engineers, J 65-A, 1217 (1982).
ff' Z n O piezoelectric membrane ultrasonic transducer in 2013). However, tan δ includes two pieces of information: dielectric loss and electrical conductivity, and the electrical conductivity is a quantity that depends on the applied voltage, but this point is not mentioned in detail.
そこで本発明の目的は、非破壊で酸化亜鉛薄膜の絶縁耐
圧を確実に評価し、その範囲を規定することにより絶縁
耐圧が高く実用上安定に使用できる圧電素子を提供する
ことにある。Therefore, an object of the present invention is to provide a piezoelectric element that has a high dielectric strength voltage and can be stably used in practical use by reliably evaluating the dielectric strength voltage of a zinc oxide thin film in a non-destructive manner and defining its range.
〔発明の概要〕
上記目的を達成するため酸化亜鉛薄膜の電気的特性を詳
細に調べた結果、特定の電界印加時の比抵抗と絶縁破壊
電圧との間に相関のあることが実験により明らかになっ
た。この相関関係を用いて絶縁耐圧を評価、選択するこ
とにより、耐圧の高い薄膜を用いた変換器を提供するこ
とが可能である。[Summary of the Invention] To achieve the above object, as a result of detailed investigation of the electrical properties of zinc oxide thin films, it was revealed through experiments that there is a correlation between specific resistance and dielectric breakdown voltage when a specific electric field is applied. became. By evaluating and selecting the dielectric strength using this correlation, it is possible to provide a converter using a thin film with high withstand voltage.
本発明になる圧電素子は、およそ３Ｖ／μｍの電界印加
時の比抵抗が１０５Ω・■以上であることに特徴がある
。The piezoelectric element according to the present invention is characterized in that its specific resistance when an electric field of about 3 V/μm is applied is 10 5 Ω·■ or more.
以下、本発明を実験例を参照しながら詳しく説明する。 Hereinafter, the present invention will be explained in detail with reference to experimental examples.
石英ガラス板１ （２０ｗｌＸ ２０ ｎｖｎ Ｘ ｉ
＋ｎｍ ｔ、 ）の端面を光学研磨し、電極としてク
ロム及び金２を蒸着した。この電極上に高周波マグネＩ
〜ロンスパッタリングにより膜厚約１μｍの酸化亜鉛薄
膜３を形成した。スパッタ条件は、基板温度を１４０〜
３００℃、ガス圧を１〜１０Ｐａの範囲で適宜変えた。Quartz glass plate 1 (20wlX 20nvnXi
The end face of +nm t, ) was optically polished, and chromium and gold 2 were vapor-deposited as electrodes. A high frequency magnet I is placed on this electrode.
~A zinc oxide thin film 3 having a thickness of about 1 μm was formed by Ron sputtering. The sputtering conditions are a substrate temperature of 140~
The temperature was 300° C., and the gas pressure was changed as appropriate in the range of 1 to 10 Pa.
さらに、２ｍ角の穴が２０ケあいたモリブデンＭｏマス
クを用いてクロム及び金５を蒸着し上部電極とした。Further, using a molybdenum Mo mask with 20 2 m square holes, chromium and gold 5 were vapor-deposited to form an upper electrode.
まず両電極間に上部電極４側を十にして０．ＩＶから絶
縁破壊を起すまで直流電圧を徐々に印加し、各電圧印加
時に流れる電流値を測定した。その結果第２図に示すよ
うなＶ−１特性が得られ、電流は電圧に対し非線型であ
ることがわかった。First, set the upper electrode 4 side between the two electrodes to 0. A DC voltage was gradually applied from IV until dielectric breakdown occurred, and the value of the current flowing at each voltage application was measured. As a result, a V-1 characteristic as shown in FIG. 2 was obtained, and it was found that the current was nonlinear with respect to the voltage.
同一基板上の多数の個所について同様の測定を行ったと
ころ、絶縁破壊電圧には３〜４ｖのばらつきがあった。When similar measurements were made at many locations on the same substrate, there was a variation of 3 to 4 volts in the dielectric breakdown voltage.
次に、条件を変えて作成した多数の試料に対して同様の
実験を行い、各々につい一’＜ｖ−ｒ特性を測定した。Next, similar experiments were conducted on a large number of samples prepared under different conditions, and the 1'<vr characteristic was measured for each sample.
その結果、絶縁破壊電圧は作成条件にも大きく依存する
ことが明らかになった。As a result, it became clear that the dielectric breakdown voltage greatly depends on the manufacturing conditions.
以上得られた結果から、各電界印加時の比抵抗と絶縁破
壊電圧の関係を調べてみたところ、第３図に示すように
、１■印加時では相関はあるもののかなりデータが分散
しているのに対し、４■印加時ではかなり強い相関があ
菖ことがわかった。Based on the results obtained above, we investigated the relationship between specific resistance and dielectric breakdown voltage when each electric field was applied, and found that, as shown in Figure 3, although there is a correlation when 1■ is applied, the data is quite scattered. On the other hand, it was found that there was a fairly strong correlation when 4■ was applied.
次に各電界印加時での比抵抗ρの対数Ｒｏｇρと絶縁破
壊電圧■との相関係数を計算φた。その結果を第４図に
示しているが、この図かられかるように比抵抗と絶縁破
壊電圧との相関は、比抵抗測定のための印加電圧を３Ｖ
／μｍ以上とすることにより非常に強くなっている。し
たがって、３Ｖ／μｍ以上の電界を印加して比抵抗を測
定することにより、絶縁破壊電圧が予測できることが明
らかになった。Next, the correlation coefficient φ between the logarithm Rogρ of the specific resistance ρ and the dielectric breakdown voltage φ when each electric field was applied was calculated. The results are shown in Figure 4, and as can be seen from this figure, the correlation between specific resistance and dielectric breakdown voltage is that the applied voltage for specific resistance measurement is 3V.
/μm or more, it becomes extremely strong. Therefore, it has become clear that the dielectric breakdown voltage can be predicted by applying an electric field of 3 V/μm or more and measuring the resistivity.
以上の実験は膜厚を１μｍ一定として実験を行った。そ
こで次に膜厚を３μｍとして同様の実験を行った。その
結果、同電界印加時の比抵抗と絶縁破壊電圧の間には１
μｍの場合と同様の相関関係があることが明らかになっ
た。The above experiments were conducted with the film thickness constant at 1 μm. Therefore, a similar experiment was conducted next with a film thickness of 3 μm. As a result, there is a difference of 1 between the specific resistance and the breakdown voltage when the same electric field is applied.
It became clear that there was a correlation similar to that in the case of μm.
そこで実際に比抵抗の異なる酸化亜鉛薄膜を用いた変換
器を多数作成し、超音波パルス発生実験を行った。Therefore, we actually created a number of transducers using zinc oxide thin films with different resistivities and conducted ultrasonic pulse generation experiments.
第５図に、形成した超音波変換器の構造を示した。まず
石英ガラスロッド１０ （１０ｎｗｎφ×１０■）の両
端面を鏡面研磨し、電極としてクロム及び金１１を蒸着
した。この電極上に高周波マグネトロンスパッタリング
により膜厚約４μｍの酸化亜鉛薄膜１２を形成した。ス
パッタ条件は、基板温度を２２０，３００℃としガス圧
を１．３，６Ｐａとして多数の試料を作成した。この薄
膜上に２■φの穴のあいたモリブデンＭｏマスクを用い
て上部電極１３を形成した。FIG. 5 shows the structure of the formed ultrasonic transducer. First, both end surfaces of a quartz glass rod 10 (10 nwnφ×10 mm) were mirror-polished, and chromium and gold 11 were vapor-deposited as electrodes. A zinc oxide thin film 12 having a thickness of approximately 4 μm was formed on this electrode by high frequency magnetron sputtering. As for the sputtering conditions, a large number of samples were prepared with a substrate temperature of 220,300° C. and a gas pressure of 1.3.6 Pa. An upper electrode 13 was formed on this thin film using a molybdenum Mo mask with a hole of 2 .phi.
これらの試料に対して３Ｖ／μｍの電界を印加し、その
時流れる電流値を測定して比抵抗を求めたところ、その
比抵抗は８×１０３〜Ｉ Ｘ １０７Ω・Ｃまで分散し
ていた。When an electric field of 3 V/μm was applied to these samples and the value of the current flowing at that time was measured to determine the specific resistance, the specific resistance was dispersed from 8×10 3 to I×10 7 Ω·C.
上記比抵抗の異なる変換器に対し、両電極間に０．２〜
１ 、２ Ｇ Ｈｚのパース１−波を印加して超音波パ
ルスを発生させる実験を行ったところ、比抵抗の低いも
のは測定を繰り返すうちに絶縁破壊を起した。For converters with different specific resistances, 0.2~
When we conducted an experiment in which ultrasonic pulses were generated by applying a pulse wave of 1 or 2 GHz, dielectric breakdown occurred in those with low resistivity as measurements were repeated.
そこで絶縁破壊を起した変換器の割合を調べた。Therefore, we investigated the percentage of converters that experienced dielectric breakdown.
３Ｖ／μｍ印加時の比抵抗がＩ Ｘ １０’Ω・印以上
の変換器では絶縁破壊を起したものはなく、５ｘ１０５
〜１０６では２％、１０５〜５ Ｘ １０５Ω・印の場
合でも７％と少ないのに対し、５ Ｘ １０’〜１０５
Ω・印では３０％と急激に絶縁破壊を起こすものの数が
増え、１０４〜５Ｘ１０’Ω・■では約５０％となりそ
れ以下では半数以上が絶縁破壊を起こした。したがって
、３Ｖ／μｍ印加時の比抵抗が１０５Ω・（７）以−ヒ
の酸化亜鉛薄膜髪有する変換器であれば、はぼ安定に使
用できることは明らかである。None of the converters with a specific resistance of I x 10' Ω or more when 3 V/μm was applied had dielectric breakdown, and 5 x 105
In the case of ~106, it is 2%, and even in the case of 105~5 × 105Ω・mark, it is as low as 7%, whereas in the case of 5 × 10'~105
For the Ω mark, the number of dielectric breakdowns rapidly increased to 30%, and for 104-5X10'Ω•■, it was about 50%, and below that, more than half of them caused dielectric breakdown. Therefore, it is clear that a transducer having a zinc oxide thin film having a specific resistance of 10 5 Ω·(7) or higher when 3 V/μm is applied can be used very stably.
さらに、３Ｖ／μｍ印加時の比抵抗が５Ｘ］ＯＳΩ・■
以上であればさらに安定性が向上し、Ｉ０６Ω・■以」
二であれば尚信頼性が高いことも明らかである。Furthermore, the specific resistance when applying 3V/μm is 5X]OSΩ・■
If it is above, the stability will be further improved, and I06Ω・■ or higher.
It is clear that the reliability is even higher if it is 2.
以上説明したように、本発明によれは、酸化亜鉛薄膜を
用いる圧電素子において、およそ３Ｖ／μｍ印加時の比
抵抗が１０’Ω・■以上の酸化亜鉛薄膜を有するものを
選択したので、絶縁耐圧が亮く印加電圧に対する安定性
に優れた圧電素子を実現することが可能である。As explained above, according to the present invention, in the piezoelectric element using a zinc oxide thin film, a piezoelectric element having a specific resistance of 10'Ω·■ or more when approximately 3V/μm is applied is selected. It is possible to realize a piezoelectric element with high withstand voltage and excellent stability against applied voltage.
第１図は比抵抗、絶縁耐圧を評価するために作成した試
料の断面図、第２図は印加電圧と流オｂる電流の関係を
示す図、□第３図は比抵抗と絶縁破壊電圧の関係を示す
図、第４図は比抵抗の対数と絶縁破壊電圧との相関係数
を、比抵抗を評価するための印加電界に対して示した図
、第５図は超音波パルスを発生させるために作成した試
料の断面図。
第１図において、１・・・石英ガラス板、２・・・クロ
ム及び金電極、３・・・酸化亜鉛薄膜、４・・・上部電
極。
第５図において、１０・・・石英ガラスロッド、１１・
・・クロム及び金電極、１２・・・酸化亜鉛薄膜、１３
・・・上部電極。
￥−２図
０・Ｉ ＋ １０ ｔｏＤｔｐ １
）ｏ電圧ｔ、ｖ）
茅３目
茅５図
聾４図Figure 1 is a cross-sectional view of a sample prepared to evaluate resistivity and dielectric strength, Figure 2 is a diagram showing the relationship between applied voltage and flowing current, and Figure 3 is resistivity and dielectric breakdown voltage. Figure 4 is a diagram showing the correlation coefficient between the logarithm of resistivity and dielectric breakdown voltage with respect to the applied electric field for evaluating resistivity. Figure 5 is a diagram showing the relationship between A cross-sectional view of the sample prepared for this purpose. In FIG. 1, 1... quartz glass plate, 2... chromium and gold electrode, 3... zinc oxide thin film, 4... upper electrode. In FIG. 5, 10... quartz glass rod, 11...
...Chromium and gold electrode, 12...Zinc oxide thin film, 13
...Top electrode. ¥-2Figure 0・I + 10 toDtp 1
) o voltage t, v) 3 eyes, 5 figures, 4 figures
Claims (1)
た酸化亜鉛薄膜、および該薄膜上に形成された上部電極
を有する圧電素子において、およそ３Ｖ／μｍの直流電
圧を印加したときの上記酸化亜鉛薄膜の比抵抗が１０＾
５Ω・ｃｍ以上であることを特徴とする圧電素子。1. When a DC voltage of approximately 3 V/μm is applied to a piezoelectric element having an electrode film formed on a substrate, a zinc oxide thin film formed on the electrode film, and an upper electrode formed on the thin film. The specific resistance of the above zinc oxide thin film is 10^
A piezoelectric element characterized by having a resistance of 5Ω·cm or more.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP20972584A JPS6188700A (en) | 1984-10-08 | 1984-10-08 | Piezoelectric element |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP20972584A JPS6188700A (en) | 1984-10-08 | 1984-10-08 | Piezoelectric element |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS6188700A true JPS6188700A (en) | 1986-05-06 |
| JPH0481398B2 JPH0481398B2 (en) | 1992-12-22 |
Family
ID=16577607
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP20972584A Granted JPS6188700A (en) | 1984-10-08 | 1984-10-08 | Piezoelectric element |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS6188700A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0478471A (en) * | 1990-07-19 | 1992-03-12 | Shimada Phys & Chem Ind Co Ltd | Ultrasonic oscillator and production thereof |
-
1984
- 1984-10-08 JP JP20972584A patent/JPS6188700A/en active Granted
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0478471A (en) * | 1990-07-19 | 1992-03-12 | Shimada Phys & Chem Ind Co Ltd | Ultrasonic oscillator and production thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0481398B2 (en) | 1992-12-22 |
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