JP3264074B2 - Laminated ferroelectric and bonding method thereof - Google Patents
Laminated ferroelectric and bonding method thereofInfo
- Publication number
- JP3264074B2 JP3264074B2 JP565494A JP565494A JP3264074B2 JP 3264074 B2 JP3264074 B2 JP 3264074B2 JP 565494 A JP565494 A JP 565494A JP 565494 A JP565494 A JP 565494A JP 3264074 B2 JP3264074 B2 JP 3264074B2
- Authority
- JP
- Japan
- Prior art keywords
- bonding
- ferroelectric
- joined
- piezoelectric ceramics
- mirror
- 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.)
- Expired - Fee Related
Links
- 238000000034 method Methods 0.000 title claims description 27
- 230000010287 polarization Effects 0.000 claims description 55
- 239000013078 crystal Substances 0.000 claims description 36
- 239000000919 ceramic Substances 0.000 claims description 31
- 239000000463 material Substances 0.000 claims description 20
- 229910052451 lead zirconate titanate Inorganic materials 0.000 claims description 18
- 238000010438 heat treatment Methods 0.000 claims description 16
- HFGPZNIAWCZYJU-UHFFFAOYSA-N lead zirconate titanate Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Ti+4].[Zr+4].[Pb+2] HFGPZNIAWCZYJU-UHFFFAOYSA-N 0.000 claims description 10
- WSMQKESQZFQMFW-UHFFFAOYSA-N 5-methyl-pyrazole-3-carboxylic acid Chemical compound CC1=CC(C(O)=O)=NN1 WSMQKESQZFQMFW-UHFFFAOYSA-N 0.000 claims description 4
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 claims description 4
- 238000005498 polishing Methods 0.000 claims description 3
- 239000007787 solid Substances 0.000 claims 2
- 238000004140 cleaning Methods 0.000 claims 1
- 230000000994 depressogenic effect Effects 0.000 claims 1
- 239000000758 substrate Substances 0.000 description 56
- 229910013641 LiNbO 3 Inorganic materials 0.000 description 10
- 239000000853 adhesive Substances 0.000 description 10
- 230000001070 adhesive effect Effects 0.000 description 10
- 239000010410 layer Substances 0.000 description 6
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 5
- 238000005452 bending Methods 0.000 description 4
- 230000005684 electric field Effects 0.000 description 4
- 230000005616 pyroelectricity Effects 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 230000005284 excitation Effects 0.000 description 3
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 239000012790 adhesive layer Substances 0.000 description 2
- 230000008878 coupling Effects 0.000 description 2
- 238000010168 coupling process Methods 0.000 description 2
- 238000005859 coupling reaction Methods 0.000 description 2
- 230000001747 exhibiting effect Effects 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- 238000005411 Van der Waals force Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000003486 chemical etching Methods 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 239000003989 dielectric material Substances 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 230000002269 spontaneous effect Effects 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Landscapes
- Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)
- Ceramic Products (AREA)
- Compositions Of Oxide Ceramics (AREA)
- Crystals, And After-Treatments Of Crystals (AREA)
- Inorganic Insulating Materials (AREA)
Description
【０００１】[0001]
【産業上の利用分野】本発明は単結晶強誘電体、例えば
ニオブ酸リチウム（ＬｉＮｂＯ3）基板あるいはタンタ
ル酸リチウム（ＬｉＴａＯ3）基板及び圧電セラミック
ス、例えばチタン酸ジルコン酸鉛（ＰＺＴ）あるいはラ
ンタン添加チタン酸ジルコン酸鉛（ＰＬＺＴ）を主成分
とするものを接着剤を用いずに強固に接合し、一体化し
た積層強誘電体及びその接合方法に関するものである。BACKGROUND OF THE INVENTION The present invention is a single crystal ferroelectrics, e.g. lithium niobate (LiNbO 3) substrate or lithium tantalate (LiTaO 3) substrate and a piezoelectric ceramic, e.g., lead zirconate titanate (PZT) or lanthanum-added The present invention relates to a laminated ferroelectric material in which a material mainly composed of lead zirconate titanate (PLZT) is firmly joined without using an adhesive and integrated, and a joining method thereof.
【０００２】[0002]
【従来の技術】強誘電体の中には圧電性を示すものが多
く、その特性を利用して圧電セラミックスや単結晶強誘
電体は各種フィルタや発振子に広く用いられている。Some of the prior art ferroelectric often show a piezoelectricity, a piezoelectric ceramic or a single crystal ferroelectric by utilizing the properties have been widely used for various filters and oscillators.
【０００３】しかし、単結晶引き上げ法によってえられ
た強誘電体単結晶インゴットや焼結後の圧電セラミック
スはそのままでは圧電性を示さず、高温下において直流
電界を印加して分極処理を行なうことが必要となる。こ
の分極処理により強誘電体内の自発分極が印加電界方向
に配向する。そして一旦配向した分極は電界を取り去っ
ても保存され、圧電体として機能させることができる。However, ferroelectric single crystal ingots obtained by the single crystal pulling method and piezoelectric ceramics after sintering do not exhibit piezoelectricity as they are, and polarization treatment can be performed by applying a DC electric field at a high temperature. Required. By this polarization processing, spontaneous polarization in the ferroelectric substance is oriented in the direction of the applied electric field. The polarization once oriented is preserved even when the electric field is removed, and can function as a piezoelectric body.
【０００４】代表的な単結晶強誘電体としては、ＬｉＮ
ｂＯ3、ＬｉＴａＯ3 があり、均一性の高い単結晶が市販
されている。さらに、その形状加工の容易性、低コスト
性などからＰＺＴ、ＰＬＺＴに代表される圧電セラミッ
クスも広く利用されている。A typical single crystal ferroelectric is LiN
There are bO 3 and LiTaO 3 , and single crystals with high uniformity are commercially available. Further, piezoelectric ceramics represented by PZT and PLZT are widely used because of their ease of shape processing and low cost.
【０００５】これらの材料は圧電性とその電気機械結合
定数の大きさなどにより、以前から実用化されており、
比帯域幅や中心周波数などの条件により最適なものが選
ばれ、多くの素子が考案されている。[0005] These materials have been practically used for a long time because of their piezoelectricity and their electromechanical coupling constant.
Optimum ones are selected according to conditions such as the fractional bandwidth and the center frequency, and many devices have been devised.
【０００６】ただし、分極処理を施された強誘電体の分
極は、単結晶内では全て同一方向を向いた単一分極状態
である。また、圧電セラミックスにおいては、個々の結
晶粒の分極の向きはバラバラであるが、結晶粒内では同
一の方向を向いており、セラミックス全体としての巨視
的な分極方向は一定方向を向いている。However, the polarization of the ferroelectric that has been subjected to the polarization treatment is a single polarization state in which all directions are in the same direction in the single crystal. In the piezoelectric ceramics, the directions of polarization of individual crystal grains are different, but they are in the same direction in the crystal grains, and the macroscopic polarization direction of the entire ceramic is in a fixed direction.
【０００７】近年、ＬｉＮｂＯ3、ＬｉＴａＯ3の焦電性
を利用した分極反転層の形成が可能となり、その応用範
囲が拡大しようとしている。In recent years, it has become possible to form a domain-inverted layer using the pyroelectricity of LiNbO 3 or LiTaO 3 , and the range of application is expanding.
【０００８】分極の反転を利用した従来の屈曲振動子の
概略図を図６に示す。図６において、１１はＬｉＮｂＯ
3基板であり、６１は接着剤、６２は励振電極である。FIG. 6 is a schematic view of a conventional bending oscillator utilizing the reversal of polarization. In FIG. 6, reference numeral 11 denotes LiNbO.
3 is a substrate, 61 is an adhesive, 62 is the excitation electrode.
【０００９】図に示すように、２枚のＬｉＮｂＯ3基板
１１が、基板内に示してある分極方向Ｐsが逆になるよ
うに接着剤６１を介して接着されている。この基板に励
振電極６２により電圧を印加すると、一方の基板におい
て板が伸びるとすると、もう一方は縮むことになり、屈
曲振動が励振される。 [0009] As shown, the two LiNbO 3 substrate 11, the polarization direction P s which is shown in the substrate are bonded via an adhesive 61 so that the opposite. When a voltage is applied to this substrate by the excitation electrode 62, if the plate expands on one substrate, the other contracts, and the bending vibration is excited .
【００１０】しかし、従来の屈曲振動子では、基板間の
接着剤６１の存在が、Ｑの低下や周波数のばらつきの主
原因となっていた。[0010] However, the conventional bending vibrator, the presence of the adhesive 61 between the substrates, has been a major cause of variations in the reduction and frequency of Q.
【００１１】そこで、先に述べたとおり、一枚の基板に
前処理及び熱処理を加えることで分極反転層が形成され
るという現象を利用して、接着剤による接着層のない分
極反転強誘電体基板が作製可能になり注目されている。Therefore, as described above, by utilizing the phenomenon that a domain-inverted layer is formed by applying pretreatment and heat treatment to one substrate, a domain-inverted ferroelectric material without an adhesive layer by an adhesive is used. Substrates can now be manufactured and are attracting attention.
【００１２】[0012]
【発明が解決しようとする課題】しかし、ＬｉＮｂ
Ｏ3、ＬｉＴａＯ3基板内の分極反転層の形成には、キュ
リー点近くの高温を要したり、より低温において行うた
めには、Ｔｉ拡散やプロトン交換などを行い、反転層と
なるべき部分の表面層の結晶の組成を変えてから熱処理
を加える必要があった。さらに、この分極反転層は、Ｌ
ｉＮｂＯ3においては＋ｚ面に、ＬｉＴａＯ3において
は、−ｚ面に形成されるという制約があり、その深さも
制御が困難であるという問題を有していた。 However, LiNb
The formation of the domain-inverted layer in the O 3 or LiTaO 3 substrate requires a high temperature near the Curie point, and in order to perform the process at a lower temperature, Ti diffusion or proton exchange is performed. It was necessary to perform heat treatment after changing the composition of the crystals in the surface layer. Further, this polarization inversion layer has
In iNbO 3 , there is a restriction that it is formed on the + z plane, and in LiTaO 3 , there is a restriction that it is formed on the −z plane .
【００１３】さらに、分極の向きは電界印可により１８
０#反転させることができるのみで、任意の方向をもっ
た分域を意図的に同一結晶内に形成することは不可能で
あった。[0013] In addition, the polarization of the orientation by the electric field applied 18
It was impossible to intentionally form a domain having an arbitrary direction in the same crystal only by being able to reverse 0 #.
【００１４】この点は、圧電セラミックスにおいては強
誘電体内の分極が単分域構造になっていないため、さら
に難しく、互いに反転した層を作製することは非常に困
難であった。This point is more difficult because the polarization in the ferroelectric is not a single domain structure in the piezoelectric ceramics, and it has been very difficult to produce layers that are mutually inverted.
【００１５】[0015]
【課題を解決するための手段】上記のような問題点を解
決するために、本発明は、２個以上の単分域化された強
誘電体の接合すべき表面を鏡面研磨し、前記接合すべき
面を清浄化、親水化し、鏡面同士を密着した後、加熱す
ることで互いに原子レベルで強固に直接接合するもので
ある。SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a method for mirror-polishing the surfaces of two or more single-domain ferroelectrics to be joined, and After the surfaces to be cleaned are made hydrophilic, the mirror surfaces are brought into close contact with each other, and then heated, they are firmly and directly joined to each other at the atomic level.
【００１６】なお、ここでいう直接接合とは、清浄な基
板間に親水化処理を施すことにより生成されたＯＨ基間
に働くファンデルワールス力により、基板を密着せし
め、これらの基板に熱処理を加えることで、ＯＨ基同士
のファンデルワールス結合を強誘電体の構成原子間の共
有結合やイオン結合などの原子レベルの結合に置換し、
化学的、物理的に安定な接合を得るものである。Here, the direct bonding means that the substrates are brought into close contact with each other by van der Waals force acting between OH groups generated by performing hydrophilic treatment between clean substrates, and these substrates are subjected to a heat treatment. By adding, van der Waals bonds between OH groups are replaced with atomic level bonds such as covalent bonds and ionic bonds between constituent atoms of the ferroelectric,
A chemically and physically stable bond is obtained.
【００１７】[0017]
【作用】上記手段により、接着剤を用いないで単結晶強
誘電体及び圧電セラミックスを強固に接合することがで
きる。By the above means, the single crystal ferroelectric and the piezoelectric ceramic can be firmly joined without using an adhesive.
【００１８】特に焦電性を示す強誘電体においては、分
極軸の分極方向を合わせて接合することで、熱処理時に
現れる表面電荷による静電引力が働き、より密着性が増
し、分極方向を合わせないときに比べてより低温で強固
な接合が得られる。In particular, in a ferroelectric substance exhibiting pyroelectricity, by joining the polarization directions of the polarization axes together, an electrostatic attraction is exerted by the surface charges appearing during the heat treatment, whereby the adhesion is further increased and the polarization directions are adjusted. Strong bonding can be obtained at a lower temperature than when no bonding is performed.
【００１９】また、単分域化されている強誘電体の分極
方向を互いに逆にして接合すれば、容易に分極反転構造
が形成でき、分極方向が隣合う分域同士で逆向きの関係
をもった分域壁構造を簡便に再現性よく得ることが可能
になる。Further, if the ferroelectrics in a single domain are joined with their polarization directions being opposite to each other, a domain-inverted structure can be easily formed. It becomes possible to easily obtain a domain wall structure having good reproducibility.
【００２０】さらに、分極軸に対してある角度をもって
カットされた強誘電体であれば、そのカット角を適当に
選ぶことにより、任意の方向に分極構造を持った積層強
誘電体を得ることができる。Further, if the ferroelectric material is cut at a certain angle with respect to the polarization axis, a laminated ferroelectric material having a polarization structure in an arbitrary direction can be obtained by appropriately selecting the cut angle. it can.
【００２１】また、上記構造を有し、圧電性を示す強誘
電体においては、直接接合する強誘電体の分極方向の相
互関係とその接合体に印可する電圧の方向を適当に選ぶ
ことにより、その振動モードを制御することができる。In the case of a ferroelectric material having the above structure and exhibiting piezoelectricity, the relationship between the polarization directions of the ferroelectric materials directly joined and the direction of the voltage applied to the joined material are appropriately selected. You can control the vibration mode.
【００２２】その上、接合面は物理的・化学的に非常に
安定な格子レベルの接合によってなされているため、そ
れぞれの分域を機械的研磨あるいは化学的エッチングの
手法を用いて所期の厚さに薄板化できる。そのため、積
層構造のそれぞれの厚さを正確に制御できる上、特性の
経時変化が少ない基板が得られる。In addition, since the bonding surface is formed by bonding at a lattice level which is physically and chemically very stable, the respective domains are formed by mechanical polishing or chemical etching. It can be made thinner. Therefore, it is possible to accurately control the thickness of each of the laminated structures and to obtain a substrate with little change in characteristics over time.
【００２３】以下に本発明の実施例を述べる。Hereinafter, embodiments of the present invention will be described.
【００２４】[0024]
（実施例１）図１（ａ）、（ｂ）は、本発明の接合体の
一実施例及びその接合方法を示す斜視図である。基板の
カット角は、１２８゜回転ｙｃｕｔであり、結晶のｙ軸
よりｚ軸方向に１２８゜回転した軸に垂直にカットされ
ている。なお、これらの単結晶は、単分域化されてお
り、分極はｚ軸に平行となっている。(Embodiment 1) FIGS. 1A and 1B are perspective views showing an embodiment of a joined body of the present invention and a joining method thereof. The cut angle of the substrate is 128 ° rotation ycut, and the substrate is cut perpendicular to the axis rotated 128 ° in the z-axis direction from the y-axis of the crystal. These single crystals are divided into single domains, and the polarization is parallel to the z-axis.
【００２５】以下、図内において分極の方向は矢印で示
し、結晶方位もあわせて示す。図１（ａ）に示すよう
に、接合面を鏡面に研磨し、接合面上に塵や埃が存在し
ないように洗浄した２枚のＬｉＮｂＯ3基板１１を結晶
方位を合わせ、分極方向は逆になるようにして、図１
（ｂ）に示すように密着する。接合するのに必要な清浄
な表面を得るための洗浄は、例えば硫酸過酸化水素混合
液を加熱した液に数分間浸した後、純水洗浄することで
得られる。この処理によって、基板表面は清浄化される
とともに親水化処理され、水酸基（ＯＨ基）が表面に水
素結合により吸着する。この状態で基板を重ね合わせる
ことにより接合される。また、両基板を密着する際に
は、接合界面に異物が入らないように注意する。In the following, the direction of polarization is indicated by an arrow in the drawing, and the crystal orientation is also indicated. As shown in FIG. 1A, two LiNbO 3 substrates 11, which have been polished to a mirror surface and cleaned so that no dust or dirt is present on the bonding surface, are aligned in crystal orientation, and the polarization directions are reversed. As shown in FIG.
As shown in FIG. Washing for obtaining a clean surface necessary for bonding can be obtained, for example, by immersing a mixed solution of sulfuric acid and hydrogen peroxide in a heated solution for several minutes and then washing with pure water. By this treatment, the surface of the substrate is cleaned and hydrophilized, and hydroxyl groups (OH groups) are adsorbed on the surface by hydrogen bonding. In this state, the substrates are joined by overlapping. When the two substrates are brought into close contact with each other, care should be taken so that foreign matter does not enter the bonding interface.
【００２６】常温において密着したＬｉＮｂＯ3基板１
１同士は、この時点でもかなり強力に接着しており、引
っ張り強度にして数十kg／cm2の値が得られる。しか
し、この時点での接合は原子間力と基板表面に存在する
ＯＨ基同士の水素結合によるものであると考えられる。
そのため、接合界面に水分や化学薬品が浸透すると簡単
に分離してしまう。そこで、より強力な接合状態を得る
ために熱処理を行う。熱処理は、ＬｉＮｂＯ3のキュリ
ー点を越えない温度で行う。この熱処理により、脱水反
応が生じ、接合界面の原子同士の結合が共有結合やイオ
ン結合などの原子レベルの結合となり、強固な接合が両
基板間で達成される。熱処理温度がキュリー点を越える
と、誘電体内の分極の配向がバラバラになってしまうた
め、必ずこの温度以下でなくてはならない。LiNbO 3 substrate 1 adhered at room temperature
Even at this point, the pieces 1 are strongly bonded to each other, and a value of several tens of kg / cm 2 can be obtained in terms of tensile strength. However, it is considered that the bonding at this time is due to an atomic force and a hydrogen bond between OH groups existing on the substrate surface.
Therefore, when moisture or a chemical penetrates into the joint interface, it is easily separated. Therefore, heat treatment is performed to obtain a stronger bonding state. The heat treatment is performed at a temperature not exceeding the Curie point of LiNbO 3 . By this heat treatment, a dehydration reaction occurs, and the bonds between the atoms at the bonding interface become atomic-level bonds such as covalent bonds and ionic bonds, so that a strong bonding is achieved between the two substrates. If the heat treatment temperature exceeds the Curie point, the orientation of the polarization in the dielectric material will vary, so the temperature must always be lower than this temperature.
【００２７】上に示したような手順により、分極方向が
反転した接合体が接着剤を用いずに得られる。According to the above-described procedure, a joined body having a reversed polarization direction can be obtained without using an adhesive.
【００２８】また、得られる接合体の分極方向は結晶の
カット角を選ぶことにより自由に選ぶことができるの
で、利用したい振動モードにより最適な組み合わせで設
計できる。さらに、接合される基板の厚みが同じであれ
ば、分極の境界が基板の中央にあるので振動子として用
いたときに面内振動はほとんど励振されないためスプリ
アス振動が抑制される。さらに、圧電アクチュエータと
して、振動子構造に直流電圧を印加する場合も、ヒステ
リシスの原因のひとつである接着剤がないので、良好な
線形性と大振幅が得られる。Further, since the polarization direction of the obtained joined body can be freely selected by selecting the cut angle of the crystal, it is possible to design an optimum combination according to the desired vibration mode. Furthermore, if the thicknesses of the substrates to be joined are the same, the boundary of polarization is at the center of the substrate, so that when used as a vibrator, in-plane vibration is hardly excited, and spurious vibration is suppressed. Furthermore, when a DC voltage is applied to the vibrator structure as a piezoelectric actuator, good linearity and large amplitude can be obtained because there is no adhesive which is one of the causes of hysteresis.
【００２９】基板がＬｉＴａＯ3基板である場合にも、
同様なことがいえる。次にその例を示す。When the substrate is a LiTaO 3 substrate,
The same can be said. The following is an example.
【００３０】（実施例２）図２は、本発明の第２の実施
例の接合体を示す側面図である。図２において、２１は
ＬｉＴａＯ3基板である。なお、基板のカット角はｚｃ
ｕｔである。(Embodiment 2) FIG. 2 is a side view showing a joined body according to a second embodiment of the present invention. In FIG. 2, reference numeral 21 denotes a LiTaO 3 substrate. The cut angle of the substrate is zc
ut.
【００３１】本実施例は実施例１とほぼ同じであるが、
異なる点はＬｉＴａＯ3がＬｉＮｂＯ3に比べて、キュリ
ー点が低い点である。This embodiment is almost the same as the first embodiment,
The difference is that LiTaO 3 has a lower Curie point than LiNbO 3 .
【００３２】そこで、ｚｃｕｔＬｉＴａＯ3基板同士を
接合する際には、前に述べたのと同じ理由で、熱処理温
度がＬｉＴａＯ3のキュリー点を越えないようにしなく
てはならない。Therefore, when the zcutLiTaO 3 substrates are joined together, the heat treatment temperature must not exceed the Curie point of LiTaO 3 for the same reason as described above.
【００３３】本実施例の基板は厚み振動子に適用する
と、従来の半波長共振に対して一波長での共振が可能に
なるため、板厚が半分の振動子と等価に働くことにな
る。そのため、これまで薄板化する際の加工精度で制限
されていた周波数の上限を２倍に拡大できるので、従来
の技術で、さらに高周波の厚み振動子が得られる。When the substrate of this embodiment is applied to a thickness vibrator, resonance at one wavelength becomes possible with respect to the conventional half-wavelength resonance, so that it works equivalently to a vibrator having a half plate thickness. For this reason, the upper limit of the frequency, which has been limited by the processing accuracy when thinning the sheet, can be doubled, so that a higher-frequency thickness oscillator can be obtained by the conventional technique.
【００３４】次に、接合する基板の分極の向きが同じで
ある場合の実施例を示す。 （実施例３） 図３は本発明の第３の実施例の接合体を示す側面図であ
る。本実施例において特徴的なことは、熱処理の際に基
板間に静電引力が働くことである。これはＬｉＮｂＯ3
が焦電性をもっていることが原因である。焦電性をもっ
た材料は熱を加え、温度を変化させることでその表面に
電荷が現れる。この電荷の極性は分極の方向により決ま
る。本実施例の場合、分極方向が両基板において合わせ
てあるため、基板間にはそれぞれの基板表面に逆極性の
電荷が生じ、静電的により強く密着する。加熱時の昇温
は速やかに行っても両基板の熱膨張率が全く等しいため
特に問題はない上、より大きな静電引力が働くので都合
がよい。しかし、実施例２のように、両基板の極性を合
わせていない場合には、それぞれの基板表面には同極性
の電荷が生じる。この電気的な反発力が基板間の接合強
度をこえると両基板ははがれてしまい、強固に接合する
ことができない。分極方向に垂直にカットされた焦電性
強誘電体基板を接合する際には、この点に注意する必要
がある。分極方向を逆に接合する場合には、加熱を緩や
かに行うか、基板間に圧力を加えておくなどの工夫をす
るとよい。なお、分極方向にある角度をもってカットさ
れた基板においても分極方向を合わせた方が逆にした場
合に比べて、同じ温度で処理した場合の接合強度が大き
いことがわかっている。Next, an embodiment in which the directions of polarization of the substrates to be joined are the same will be described. Embodiment 3 FIG. 3 is a side view showing a joined body according to a third embodiment of the present invention. What is characteristic in this embodiment is that electrostatic attraction acts between the substrates during the heat treatment. This is LiNbO 3
Is caused by pyroelectricity. Pyroelectric materials generate heat on their surface by applying heat and changing the temperature. The polarity of this charge is determined by the direction of polarization. In the case of the present embodiment, since the polarization directions are matched between the two substrates, charges of opposite polarities are generated between the substrates and the surfaces of the respective substrates are brought closer together electrostatically. Even if the temperature is raised quickly during heating, there is no particular problem since the thermal expansion coefficients of the two substrates are completely equal, and a greater electrostatic attraction acts, which is convenient. However, when the polarities of both substrates are not matched as in the second embodiment, charges of the same polarity are generated on the surfaces of the respective substrates. If the electric repulsion exceeds the bonding strength between the substrates, the two substrates are peeled off from each other and cannot be bonded firmly. It is necessary to pay attention to this point when joining a pyroelectric ferroelectric substrate cut perpendicularly to the polarization direction. In the case of joining in the reverse direction of the polarization, it is advisable to gently heat the device or to apply a pressure between the substrates. The polarization direction is cut at an angle.
When the polarization direction is reversed even if the substrate is
Higher joint strength when treated at the same temperature
I know that .
【００３５】次に、圧電セラミックスを接合する例を示
す。 （実施例４）図４（ａ）〜（ｅ）は、本発明の第４の実
施例の接合体を示す側面図である。図において、４１は
チタン酸ジルコン酸鉛あるいはランタン添加チタン酸ジ
ルコン酸鉛を主成分とするＰＺＴ、ＰＬＺＴ系の圧電セ
ラミックスである。Next, an example of joining piezoelectric ceramics will be described. (Embodiment 4) FIGS. 4 (a) to 4 (e) are side views showing a joined body according to a fourth embodiment of the present invention. In the figure, reference numeral 41 denotes a PZT or PLZT piezoelectric ceramic mainly composed of lead zirconate titanate or lanthanum-added lead zirconate titanate.
【００３６】ＰＺＴ、ＰＬＺＴ系の圧電セラミックス
は、電気機械結合係数が高く、成形が容易なため、現在
最も広く用いられている圧電材料である。特に、ＰＬＺ
Ｔ系の圧電セラミックスは緻密に焼結し、透明なものも
得られるため、本方法で接合するのに必要な鏡面の表面
状態が比較的容易に得られる材料である。PZT and PLZT piezoelectric ceramics are the most widely used piezoelectric materials at present because of their high electromechanical coupling coefficient and easy molding. In particular, PLZ
T-based piezoelectric ceramics are densely sintered and transparent ones can be obtained. Therefore, the surface condition of the mirror surface required for bonding by the present method can be relatively easily obtained.
【００３７】図に示すように、分極方向のそれぞれ異な
る圧電セラミックスがいくつかの組み合わせで接合され
ている。その方法は前に述べたとおりである。As shown in the figure, several combinations of piezoelectric ceramics having different polarization directions are joined. The method is as described above.
【００３８】圧電セラミックスは、熱膨張率の異方性を
ほとんどもたないため、分極方向をほぼ自由に選んでの
接合を容易に実現することができる。そのため、従来に
はない分極の構造を得ることができ、実際の素子に用い
る際にその振動モードに応じた自由な設計が可能にな
る。ここに示したのはあくまで一例に過ぎず、目的に応
じてその分極方向を変えることができ、ほぼ無限の組み
合わせが可能である。また、本実施例には圧電セラミッ
クスの場合を示したが、単結晶強誘電体によっても同様
な構造が達成できる。さらに、接合される材料が異種で
あっても問題はなく、材料の組み合わせにおいても、設
計の自由度は増大する。Since the piezoelectric ceramics have almost no anisotropy in the coefficient of thermal expansion, it is possible to easily realize the joining by selecting the polarization direction almost freely. Therefore, it is possible to obtain an unprecedented polarization structure, and it is possible to freely design according to the vibration mode when used in an actual device. This is merely an example, and the polarization direction can be changed according to the purpose, and almost infinite combinations are possible. In this embodiment, the case of piezoelectric ceramics is shown, but a similar structure can be achieved by using a single crystal ferroelectric. Further, there is no problem even if the materials to be joined are of different types, and the degree of freedom of design increases even in the combination of materials.
【００３９】ただし、異種材料の接合の場合には両者の
熱膨張率に注意する必要がある。次にその例を示す。However, in the case of joining different materials, it is necessary to pay attention to the coefficient of thermal expansion of both materials. The following is an example.
【００４０】図５に示すように、ｚｃｕｔＬｉＮｂＯ3
基板１１とｚｃｕｔＬｉＴａＯ3基板２１が接合されて
いる。一方のｚｃｕｔＬｉＮｂＯ3基板は平面方向（ｘ
軸方向）の熱膨張率が、１５４×１０-7／℃であり、も
う一方のｚｃｕｔＬｉＴａＯ3基板はその値が、１６１
×１０-7／℃である。実施例１、２とは異なり、接合さ
れる基板に熱膨張率差があるが、結晶形態がほぼ同じで
あるため相性がよく、ＬｉＴａＯ3のキュリー点までは
加熱しても熱膨張率差に起因する割れはなく異種材料で
あっても接合が可能である。 As shown in FIG. 5, zcutLiNbO 3
The substrate 11 and the zcutLiTaO 3 substrate 21 are joined. One zcutLiNbO 3 substrate has a planar direction (x
(Axial direction) is 154 × 10 −7 / ° C., and the other zcutLiTaO 3 substrate has a value of 161.
× 10 -7 / ° C. Unlike Examples 1 and 2, there is a difference in the coefficient of thermal expansion between the substrates to be joined. However, since the crystal morphologies are almost the same, they have good compatibility, and even if heated up to the Curie point of LiTaO 3 , the difference in the coefficient of thermal expansion is small. There are no cracks due to this, and joining is possible even with dissimilar materials .
【００４１】以上すべての実施例は、２個の基板を接合
する例のみを述べてきたが、３個以上の接合も当然可能
であり、その分極方向も自由に選択できることは当然で
ある。また、異種の材料でも可能である。本発明の主旨
は、基板の接合の際に、その分極方向が任意に選択でき
る積層強誘電体及びその接合方法にあり、上記条件を含
む接合体は全て含まれる。Although all of the embodiments have been described with respect to only an example in which two substrates are joined, it is naturally possible to join three or more substrates, and the polarization direction thereof can be freely selected. Further, different materials can be used. The gist of the present invention resides in a laminated ferroelectric substance whose polarization direction can be arbitrarily selected at the time of bonding substrates and a bonding method thereof, and includes all bonded bodies including the above conditions.
【００４２】ここでは、ＬｉＮｂＯ3、ＬｉＴａＯ3、Ｐ
ＺＴ、ＰＬＺＴの例を示したが、他の強誘電体でも原理
的には同様の処理が可能である。Here, LiNbO 3 , LiTaO 3 , P
Although examples of ZT and PLZT have been described, similar processing is possible in principle with other ferroelectrics.
【００４３】[0043]
【発明の効果】以上実施例で述べてきたように本発明に
よれば、上記手段により、接着剤を用いないで単結晶強
誘電体及び圧電セラミックスを強固に接合することがで
きる。その際、互いの分極方向を任意に設定できるた
め、従来にはない構造の積層強誘電体が容易に得られ
る。According to the present invention, as described in the embodiments above, the single crystal ferroelectric and the piezoelectric ceramic can be firmly joined by the above means without using an adhesive. At this time, since the polarization directions of the two layers can be set arbitrarily, a laminated ferroelectric having a structure that has not been conventionally obtained can be easily obtained.
【００４４】また、接合面はすべて化学的、物理的に安
定であるため、本発明の接合基板は加工が可能で、さら
に、本発明の積層強誘電体からなる圧電デバイスは、接
着剤の層が無いため特性が良く、経時変化の少ないもの
となる。特に焦電性を示す強誘電体においては、分極軸
の分極方向を合わせて接合することで、熱処理時に表面
電荷による静電引力が働き、より密着性が増し、分極方
向を合わせないときに比べてより低温で強固な接合が得
られる。Further, since all the bonding surfaces are chemically and physically stable, the bonding substrate of the present invention can be processed. Further, the piezoelectric device made of the laminated ferroelectric material of the present invention can be used as an adhesive layer. Because of the absence of the above, the characteristics are good and the change with time is small. In particular, in ferroelectrics that exhibit pyroelectricity, by joining together with the polarization direction of the polarization axis, electrostatic attraction due to the surface charge works during heat treatment, further increasing the adhesion and comparing with the case where the polarization direction is not matched. Thus, a strong bond can be obtained at a lower temperature.
【図１】本発明の第１の実施例の接合体及びその接合方
法を示す斜視図FIG. 1 is a perspective view showing a joined body and a joining method thereof according to a first embodiment of the present invention.
【図２】本発明の第２の実施例の接合体を示す側面図FIG. 2 is a side view showing a joined body according to a second embodiment of the present invention.
【図３】本発明の第３の実施例の接合体を示す側面図FIG. 3 is a side view showing a joined body according to a third embodiment of the present invention.
【図４】第４の実施例の接合体を示す側面図FIG. 4 is a side view showing a joined body of a fourth embodiment.
【図５】本発明の第５の実施例の接合体を示す側面図FIG. 5 is a side view showing a joined body according to a fifth embodiment of the present invention.
【図６】従来の屈曲振動子の概略を示す側面図FIG. 6 is a side view schematically showing a conventional bending oscillator.
１１ ＬｉＮｂＯ3基板 ２１ ＬｉＴａＯ3基盤 ４１ 圧電セラミックス ６１ 接着剤 ６２ 励振電極11 LiNbO 3 substrate 21 LiTaO 3 substrate 41 Piezoelectric ceramics 61 Adhesive 62 Excitation electrode
───────────────────────────────────────────────────── フロントページの続き (72)発明者 江田 和生 大阪府門真市大字門真1006番地 松下電 器産業株式会社内 (56)参考文献 特開 平７−45801（ＪＰ，Ａ) 特開 平５−178695（ＪＰ，Ａ) 特開 平５−178697（ＪＰ，Ａ) 特開 昭60−51700（ＪＰ，Ａ) (58)調査した分野(Int.Cl.7，ＤＢ名) C30B 1/00 - 35/00 H03H 9/00 - 9/76 ＣＡ（ＳＴＮ) ＪＩＣＳＴファイル（ＪＯＩＳ) ＷＰＩ（ＤＩＡＬＯＧ)────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Eda 1006 Kazuma Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. (56) References JP-A-7-45801 (JP, A) JP-A-5 -178695 (JP, A) JP-A-5-178697 (JP, A) JP-A-60-51700 (JP, A) (58) Fields investigated (Int. Cl. 7 , DB name) C30B 1/00- 35/00 H03H 9/00-9/76 CA (STN) JICST file (JOIS) WPI (DIALOG)
Claims (14)
切り出された２個以上の単分域化された単結晶強誘電体
を直接接合し、単一の固体内に互いに任意の分極方向を
もった分域が存在することを特徴とする積層強誘電体。1. A single solid-state ferroelectric material comprising two or more single-domain single-crystal ferroelectrics cut out at a certain angle with respect to the polarization direction of a crystal, and having any given polarization direction in a single solid. A laminated ferroelectric material characterized by the presence of a depressed domain.
クスを直接接合し、単一の固体内に互いに任意の分極方
向をもった分域が存在することを特徴とする積層強誘電
体。2. A laminated ferroelectric, wherein two or more piezoelectric ceramics subjected to a polarization treatment are directly bonded, and domains having arbitrary polarization directions are present in a single solid.
その接合すべき面を鏡面研磨し、前記接合すべき面を清
浄化、親水化し、前記鏡面同士を密着した後、前記単結
晶強誘電体のキュリー点以下で加熱し、前記接合面の接
合を原子レベルの接合に置換して互いに強固に直接接合
する工程を具備した積層強誘電体の接合方法。3. The method according to claim 2, wherein two or more single crystal ferroelectrics are divided into single domains.
The surface to be joined is mirror-polished, the surface to be joined is cleaned and hydrophilized, and the mirror surfaces are brought into close contact with each other, and then heated below the Curie point of the single crystal ferroelectric to join the joined surfaces. A method of joining laminated ferroelectrics, comprising a step of firmly directly joining each other by substituting for joining at the atomic level.
施し、その接合すべき面を鏡面研磨し、前記接合すべき
面を清浄化、親水化し、前記鏡面同士を密着した後、前
記圧電セラミックスのキュリー点以下で加熱し、前記接
合面の接合を原子レベルの接合に置換して互いに強固に
直接接合する工程を具備した積層強誘電体の接合方法。4. A method for subjecting two or more piezoelectric ceramics to polarization treatment, polishing the surfaces to be joined to a mirror surface, cleaning and hydrophilizing the surfaces to be joined, and bringing the mirror surfaces into close contact with each other. A method of heating at a temperature below the Curie point to replace the bonding at the bonding surface with bonding at the atomic level so as to make a direct and strong bonding to each other.
ＮｂＯ3）、タンタル酸リチウム（ＬｉＴａＯ3）のいず
れかより選ばれることを特徴とする請求項１記載の積層
強誘電体。5. The method according to claim 1, wherein the single crystal ferroelectric is lithium niobate (Li).
2. The laminated ferroelectric according to claim 1, wherein the ferroelectric is selected from the group consisting of NbO 3 ) and lithium tantalate (LiTaO 3 ).
（ＰＺＴ）、ランタン添加チタン酸ジルコン酸鉛（ＰＬ
ＺＴ）を主成分とする群より選ばれるいずれかであるこ
とを特徴とする請求項２記載の積層強誘電体。6. A piezoelectric ceramic comprising lead zirconate titanate (PZT) and lanthanum-added lead zirconate titanate (PL).
3. The laminated ferroelectric according to claim 2, wherein the ferroelectric is any one selected from the group consisting mainly of ZT).
ＮｂＯ3）、タンタル酸リチウム（ＬｉＴａＯ3）のいず
れかより選ばれることを特徴とする請求項３記載の積層
強誘電体の接合方法。7. A ferroelectric single crystal comprising lithium niobate (Li)
4. The method according to claim 3, wherein the method is selected from NbO 3 ) and lithium tantalate (LiTaO 3 ).
（ＰＺＴ）、ランタン添加チタン酸ジルコン酸鉛（ＰＬ
ＺＴ）を主成分とする群より選ばれるいずれかであるこ
とを特徴とする請求項４記載の積層強誘電体の接合方
法。8. A piezoelectric ceramic comprising lead zirconate titanate (PZT) and lanthanum-added lead zirconate titanate (PL).
5. The method according to claim 4, wherein the method is any one selected from the group consisting mainly of ZT).
の接合すべき面を鏡面研磨し、前記接合すべき面を清浄
化、親水化し、前記強誘電体の結晶方位を合わせて、分
極方向は逆になるように前記鏡面同士を密着した後、前
記単結晶強誘電体のキュリー点以下で加熱し、前記接合
面の接合を原子レベルの接合に置換して互いに強固に直
接接合する工程を具備した分極反転単結晶強誘電体の接
合方法。9. A mirror-polished surface of two or more single-domain single-crystal ferroelectrics to be joined, and the surface to be joined is cleaned and hydrophilized to change the crystal orientation of the ferroelectric. In addition, after the mirror surfaces are brought into close contact with each other so that the polarization directions are opposite to each other, heating is performed below the Curie point of the single crystal ferroelectric, and the bonding at the bonding surface is replaced with a bonding at an atomic level so that the bonding is firmly performed. A method of joining a domain-inverted single crystal ferroelectric, comprising a step of directly joining.
体の接合すべき面を鏡面研磨し、接合すべき面を清浄
化、親水化し、前記強誘電体の分極方向、結晶方位を全
て合わせて前記鏡面同士を密着した後、前記単結晶強誘
電体のキュリー点以下で加熱し、前記接合面の接合を原
子レベルの接合に置換して互いに強固に直接接合する工
程を具備した単結晶強誘電体の接合方法。10. The surface to be joined of two or more single-domain single-crystal ferroelectrics is mirror-polished, the surface to be joined is cleaned and hydrophilized, and the polarization direction of the ferroelectric and the crystal After the mirror surfaces are brought into close contact with each other in all directions, heating is performed below the Curie point of the single crystal ferroelectric, and the bonding at the bonding surface is replaced with bonding at the atomic level to directly bond each other firmly. Method of bonding single crystal ferroelectrics.
ミックスの接合すべき面を鏡面研磨し、前記接合すべき
面を清浄化、親水化し、前記圧電セラミックスの分極方
向を逆になるように前記鏡面同士を密着した後、前記圧
電セラミックスのキュリー点以下で加熱し、前記接合面
の接合を原子レベルの接合に置換して互いに強固に直接
接合する工程を具備した分極反転積層圧電セラミックス
の接合方法。11. A surface to be bonded of two or more piezoelectric ceramics subjected to a polarization treatment is mirror-polished to clean and hydrophilize the surface to be bonded so that the polarization direction of the piezoelectric ceramics is reversed. After the mirror surfaces are brought into close contact with each other, the piezoelectric ceramics are heated below the Curie point of the piezoelectric ceramics, and the bonding of the bonding surfaces is replaced with an atomic-level bonding to firmly directly bond each other. Joining method.
ミックスの接合すべき面を鏡面研磨し、前記接合すべき
面を清浄化、親水化し、前記圧電セラミックスの分極方
向を合わせて前記鏡面同士を密着した後、前記圧電セラ
ミックスのキュリー点以下で加熱し、前記接合面の接合
を原子レベルの接合に置換して互いに強固に直接接合す
る工程を具備した圧電セラミックスの接合方法。12. A mirror-polished surface of two or more piezoelectric ceramics which have been subjected to a polarization treatment is mirror-polished, and the surface to be bonded is cleaned and hydrophilized. A method for bonding piezoelectric ceramics, comprising the steps of: bonding the piezoelectric ceramics to each other, heating the same to a temperature below the Curie point of the piezoelectric ceramics, replacing the bonding at the bonding surface with atomic-level bonding, and firmly directly bonding each other.
ンタル酸リチウムのいずれかより選ばれることを特徴と
する請求項９または１０記載の単結晶強誘電体の接合方
法。13. The method for bonding a single crystal ferroelectric according to claim 9, wherein the single crystal ferroelectric is selected from lithium niobate and lithium tantalate.
鉛（ＰＺＴ）、ランタン添加チタン酸ジルコン酸鉛（Ｐ
ＬＺＴ）を主成分とする群より選ばれるいずれかである
ことを特徴とする請求項１１または１２記載の圧電セラ
ミックスの接合方法。14. A piezoelectric ceramic comprising lead zirconate titanate (PZT) and lanthanum-added lead zirconate titanate (PZT).
13. The method for bonding piezoelectric ceramics according to claim 11, wherein the method is any one selected from the group consisting mainly of (LZT).
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| JP565494A JP3264074B2 (en) | 1994-01-24 | 1994-01-24 | Laminated ferroelectric and bonding method thereof |
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|---|---|---|---|
| JP565494A JP3264074B2 (en) | 1994-01-24 | 1994-01-24 | Laminated ferroelectric and bonding method thereof |
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| JPH07206600A JPH07206600A (en) | 1995-08-08 |
| JP3264074B2 true JP3264074B2 (en) | 2002-03-11 |
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| JP565494A Expired - Fee Related JP3264074B2 (en) | 1994-01-24 | 1994-01-24 | Laminated ferroelectric and bonding method thereof |
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Cited By (1)
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| US8572825B2 (en) | 2008-12-10 | 2013-11-05 | Murata Manufacturing Co., Ltd. | Method for producing piezoelectric composite substrate and method for producing piezoelectric element |
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| JPH07206600A (en) | 1995-08-08 |
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