JP2013236277A - Lithium tantalate single crystal of stoichiometric composition for surface acoustic wave element, method for manufacturing the same and composite piezoelectric substrate for surface acoustic wave element - Google Patents
Lithium tantalate single crystal of stoichiometric composition for surface acoustic wave element, method for manufacturing the same and composite piezoelectric substrate for surface acoustic wave element Download PDFInfo
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本発明は、弾性表面波素子用化学量論組成タンタル酸リチウム単結晶、その製造方法及び弾性表面波素子用複合圧電基板に関する。 The present invention relates to a stoichiometric composition lithium tantalate single crystal for surface acoustic wave elements, a method for producing the same, and a composite piezoelectric substrate for surface acoustic wave elements.
近年、携帯電話の通信システムは複数の通信規格をサポートし、各々の通信規格は複数の周波数バンドから構成される形態へと進展している。携帯電話の周波数調整・選択用の部品として、例えば圧電基板上に弾性表面波を励起するための櫛形電極が形成された弾性表面波（Ｓｕｒｆａｃｅ Ａｃｏｕｓｔｉｃ Ｗａｖｅ、ＳＡＷ）素子が用いられる。 In recent years, a communication system for mobile phones supports a plurality of communication standards, and each communication standard has progressed to a form composed of a plurality of frequency bands. For example, a surface acoustic wave (SAW) element in which a comb-shaped electrode for exciting a surface acoustic wave is formed on a piezoelectric substrate is used as a component for frequency adjustment / selection of a cellular phone.
弾性表面波素子は小型で挿入損失が小さく、不要波を通さない性能が要求される。弾性表面波素子の材料としては、タンタル酸リチウム（ＬｉＴａＯ３）などの圧電材料が用いられるが、現状より大きな電気機械結合係数を持った材料であれば、挿入損失や帯域幅などが改善されるため好ましいとされる。 The surface acoustic wave element is required to have a small size, a small insertion loss, and a performance not to pass unnecessary waves. As a material for the surface acoustic wave element, a piezoelectric material such as lithium tantalate (LiTaO 3 ) is used. However, if the material has a larger electromechanical coupling coefficient than the current state, insertion loss, bandwidth, and the like are improved. Therefore, it is preferable.
非特許文献１では、２重ルツボによる引き上げ法により作製した定比組成の３８．５°回転ＹカットＬｉＴａＯ３（以下、化学量論組成ＬＴとも記す）は、通常の引き上げ法による一致溶融組成ＬｉＴａＯ３に比べ、２０％電気機械結合係数が高いため好ましいとされている。しかし、化学量論組成ＬｉＴａＯ３は引き上げ速度が、通常の引き上げ法に比べ１桁小さく、コスト高となり、このままでは化学量論組成ＬｉＴａＯ３を弾性表面波素子用途に用いることは難しいとされる。 In Non-Patent Document 1, a 38.5 ° rotated Y-cut LiTaO 3 (hereinafter also referred to as stoichiometric composition LT) having a stoichiometric composition prepared by a pulling method using a double crucible is a coincident molten composition LiTaO by a normal pulling method. Compared to 3 , the electromechanical coupling coefficient is 20% higher, which is preferable. However, the stoichiometric composition LiTaO 3 has a pulling speed one order of magnitude lower than that of a normal pulling method and is expensive, and it is difficult to use the stoichiometric composition LiTaO 3 for the surface acoustic wave device.
また気相法による化学量論組成ＬｉＴａＯ３ウェーハは、特許文献１に詳細な記載がある。しかし、この気相法による化学量論組成ＬｉＴａＯ３ウェーハは、その処理の際に１炉あたりの処理量が限られる為コストが掛かり、弾性表面波素子用途には向かないという問題がある。 A stoichiometric composition LiTaO 3 wafer by a vapor phase method is described in detail in Patent Document 1. However, the stoichiometric composition LiTaO 3 wafer by this vapor phase method has a problem that the processing amount per one furnace is limited at the time of the processing, so that the cost is high and it is not suitable for use as a surface acoustic wave device.
なお、弾性表面波素子の電気機械結合係数が大きいことは好ましいが、通信バンド毎に合わせ、適度な電気機械結合係数に調整できることが更に好ましいとされる。 Although it is preferable that the electromechanical coupling coefficient of the surface acoustic wave element is large, it is further preferable that the surface acoustic wave element can be adjusted to an appropriate electromechanical coupling coefficient for each communication band.
本発明は、上記問題点に鑑みてなされたものであって、弾性表面波素子用として使用可能でかつ所望の電気機械結合係数に調整ができるよう改善された熱伝導率のよいＬｉＴａＯ３単結晶を提供することを目的とする。 The present invention has been made in view of the above problems, and can be used for a surface acoustic wave device, and can be adjusted to a desired electromechanical coupling coefficient. LiTaO 3 single crystal having good thermal conductivity has been improved. The purpose is to provide.
上記目的を達成するために、本発明は、弾性表面波素子用化学量論組成タンタル酸リチウム単結晶であって、前記化学量論組成タンタル酸リチウム単結晶は、引き上げ法により得られた、Ｆｅ，Ｎｉ，Ｃｏの少なくとも１つ以上の元素を０以上０．５ｍｏｌ％以下含み、厚さが７ｍｍ以上である一致溶融組成タンタル酸リチウム単結晶が、気相平衡法により化学量論組成に改質されたものであることを特徴とする弾性表面波素子用化学量論組成タンタル酸リチウム単結晶を提供する。 In order to achieve the above object, the present invention provides a stoichiometric composition lithium tantalate single crystal for a surface acoustic wave device, wherein the stoichiometric composition lithium tantalate single crystal is obtained by a pulling method. , Ni, Co containing at least one element of 0 to 0.5 mol% and a thickness of 7 mm or more conforming melt composition lithium tantalate single crystal is modified to stoichiometric composition by vapor phase equilibrium method Provided is a lithium tantalate single crystal having a stoichiometric composition for a surface acoustic wave device.
このような化学量論組成タンタル酸リチウム単結晶であれば、一致溶融組成タンタル酸リチウム単結晶の電気機械結合係数を１００％としたとき、電気機械結合係数が１００％〜約１２０％の範囲で所望の値に調整され、同時に、安価で熱伝導率のよい弾性表面波素子用化学量論組成タンタル酸リチウム単結晶となる。また、上記のような厚い一致溶融組成タンタル酸リチウム単結晶を用いても、一様に化学量論組成に改質され、より安価な弾性表面波素子用化学量論組成タンタル酸リチウム単結晶となる。 In the case of such a stoichiometric composition lithium tantalate single crystal, the electromechanical coupling coefficient is in the range of 100% to about 120% when the electromechanical coupling coefficient of the coincidence melting composition lithium tantalate single crystal is 100%. It is adjusted to a desired value, and at the same time, a stoichiometric composition lithium tantalate single crystal for a surface acoustic wave device with low cost and good thermal conductivity is obtained. Further, even when using a thick coincidence melt composition lithium tantalate single crystal as described above, it is uniformly modified to a stoichiometric composition, and a cheaper stoichiometric composition lithium tantalate single crystal for surface acoustic wave devices and Become.
このとき、前記改質される一致溶融組成タンタル酸リチウム単結晶の結晶方位が、３０°〜５０°回転Ｙカットであることが好ましい。
これにより、より大きな電気機械結合係数を示す弾性表面波素子用化学量論組成タンタル酸リチウム単結晶となる。
At this time, it is preferable that the crystal orientation of the conformal melt composition lithium tantalate single crystal to be modified is 30 ° to 50 ° rotated Y-cut.
As a result, a stoichiometric composition lithium tantalate single crystal for a surface acoustic wave device exhibiting a larger electromechanical coupling coefficient is obtained.
また、本発明は、弾性表面波素子用複合圧電基板であって、前記複合圧電基板は、結晶方位が異なる２種類の本発明の弾性表面波素子用化学量論組成タンタル酸リチウム単結晶のウェーハ同士を接合してなるものであることを特徴とする弾性表面波素子用複合圧電基板を提供する。 The present invention also relates to a composite piezoelectric substrate for a surface acoustic wave device, wherein the composite piezoelectric substrate is a wafer of two types of stoichiometric lithium tantalate single crystals for surface acoustic wave devices of the present invention having different crystal orientations. Provided is a composite piezoelectric substrate for a surface acoustic wave element, which is formed by bonding together.
これにより、弾性表面波素子の耐電力性や電気機械結合係数が向上される弾性表面波素子用複合圧電基板となる。 As a result, a surface acoustic wave element composite piezoelectric substrate is provided in which the power durability and electromechanical coupling coefficient of the surface acoustic wave element are improved.
また、本発明は、弾性表面波素子用化学量論組成タンタル酸リチウム単結晶の製造方法であって、引き上げ法により、Ｆｅ，Ｎｉ，Ｃｏの少なくとも１つ以上の元素を０以上０．５ｍｏｌ％以下含む一致溶融組成タンタル酸リチウム単結晶を得て、該一致溶融組成タンタル酸リチウム単結晶の表面の粗さ指標Ｒｍａｘを１μｍ以上とし、該一致溶融組成タンタル酸リチウム単結晶を複数積層して積層体を形成し、該積層体を気相平衡法により化学量論組成に改質することで前記化学量論組成タンタル酸リチウム単結晶を製造することを特徴とする弾性表面波素子用化学量論組成タンタル酸リチウム単結晶の製造方法を提供する。 The present invention also relates to a method for producing a stoichiometric lithium tantalate single crystal for a surface acoustic wave device, wherein at least one element of Fe, Ni, Co is added by 0 to 0.5 mol% by a pulling method. A conformal melt composition lithium tantalate single crystal including the following is obtained, the surface roughness index Rmax of the conform melt composition lithium tantalate single crystal is set to 1 μm or more, and a plurality of conform melt composition lithium tantalate single crystals are stacked The stoichiometry for a surface acoustic wave device is characterized in that the stoichiometric composition lithium tantalate single crystal is produced by forming a body and modifying the laminate to a stoichiometric composition by a vapor phase equilibrium method. A method for producing a composition lithium tantalate single crystal is provided.
これにより、引き上げ速度を落とす必要がなく高い生産性で製造できるため、コストを低減でき、かつ、引き上げ法により単結晶製造時に、Ｆｅ，Ｎｉ，Ｃｏの量を調整するだけで簡単に電気機械結合係数を調整できる弾性表面波素子用化学量論組成タンタル酸リチウム単結晶を製造できる。また、ウェーハを積層しても気相平衡法による改質の際の気相反応に大きな支障が生じることを防ぐことができ、一括で改質できるため、より低コストで化学量論組成タンタル酸リチウム単結晶を製造できる。 As a result, it is possible to manufacture with high productivity without lowering the pulling speed, so that the cost can be reduced and the electromechanical coupling can be easily performed by adjusting the amount of Fe, Ni, Co during the single crystal manufacturing by the pulling method. A stoichiometric composition lithium tantalate single crystal for a surface acoustic wave device capable of adjusting the coefficient can be produced. In addition, even if the wafers are stacked, it is possible to prevent a large hindrance to the gas phase reaction during the reforming by the vapor phase equilibrium method, and it is possible to modify the batch, so that the stoichiometric composition tantalate can be reduced at a lower cost. A lithium single crystal can be produced.
このとき、前記改質される一致溶融組成タンタル酸リチウム単結晶を、厚さ７ｍｍ以上とすることが好ましい。
このような厚い一致溶融組成タンタル酸リチウム単結晶を用いても、一様に化学量論組成に改質でき、弾性表面波素子用化学量論組成タンタル酸リチウム単結晶を効率良く製造できる。
At this time, it is preferable that the conforming molten composition lithium tantalate single crystal to be modified has a thickness of 7 mm or more.
Even if such a thick coincidence composition lithium tantalate single crystal is used, it can be uniformly modified to a stoichiometric composition, and a stoichiometric composition lithium tantalate single crystal for a surface acoustic wave device can be efficiently produced.
このとき、前記改質される一致溶融組成タンタル酸リチウム単結晶を、塩化カリウム溶液又は塩化ナトリウム溶液に浸漬させた後、気相平衡法により化学量論組成に改質することが好ましい。
このように予め処理することで、気相平衡法による改質の処理速度が飛躍的に向上して、化学量論組成タンタル酸リチウム単結晶をより生産性良く製造できる。
At this time, it is preferable that the matched molten composition lithium tantalate single crystal to be modified is immersed in a potassium chloride solution or a sodium chloride solution and then modified to a stoichiometric composition by a vapor phase equilibrium method.
By processing in advance in this way, the processing speed of the reforming by the vapor phase equilibrium method is dramatically improved, and a stoichiometric composition lithium tantalate single crystal can be manufactured with higher productivity.
このとき、前記改質される一致溶融組成タンタル酸リチウム単結晶の結晶方位を、３０°〜５０°回転Ｙカットとすることが好ましい。
これにより、より大きな電気機械結合係数を示す弾性表面波素子用化学量論組成タンタル酸リチウム単結晶を製造できる。
At this time, it is preferable that the crystal orientation of the conformal melt composition lithium tantalate single crystal to be modified is a 30 ° to 50 ° rotated Y-cut.
Thereby, a stoichiometric composition lithium tantalate single crystal for a surface acoustic wave device having a larger electromechanical coupling coefficient can be produced.
以上のように、本発明によれば、電気機械結合係数を所望の値に調整することが出来、同時に、安価で熱伝導率のよい弾性表面波素子用化学量論組成タンタル酸リチウム単結晶を提供することができる。 As described above, according to the present invention, the electromechanical coupling coefficient can be adjusted to a desired value, and at the same time, an inexpensive and good thermal conductivity stoichiometric composition for lithium surface tantalate single crystal Can be provided.
以下、本発明について、実施態様の一例として、図を参照しながら詳細に説明するが、本発明はこれに限定されるものではない。 Hereinafter, the present invention will be described in detail as an example of an embodiment with reference to the drawings, but the present invention is not limited thereto.
本発明の弾性表面波素子用化学量論組成タンタル酸リチウム単結晶は、引き上げ法により得られた、Ｆｅ，Ｎｉ，Ｃｏの少なくとも１つ以上の元素を０以上０．５ｍｏｌ％以下含み、厚さが７ｍｍ以上である一致溶融組成タンタル酸リチウム単結晶が、気相平衡法により化学量論組成に改質されたものである。 The stoichiometric composition lithium tantalate single crystal for surface acoustic wave device of the present invention contains at least one element of Fe, Ni, Co, obtained by a pulling method, in a range of 0 to 0.5 mol%, and has a thickness. A conformal melt composition lithium tantalate single crystal having a thickness of 7 mm or more is modified to a stoichiometric composition by a vapor phase equilibrium method.
このような化学量論組成タンタル酸リチウム単結晶であれば、一致溶融組成タンタル酸リチウム単結晶の電気機械結合係数を１００％としたとき、電気機械結合係数を１００％〜約１２０％の範囲で所望の値に調整することが出来、同時に、安価で熱伝導率のよい弾性表面波素子用化学量論組成タンタル酸リチウム単結晶となる。更に、上記のように厚い、例えばブール形状のタンタル酸リチウム単結晶を、気相平衡法により一様に化学量論組成に改質できるので、生産性良く製造でき、安価な弾性表面波素子用化学量論組成タンタル酸リチウム単結晶となる。 In such a stoichiometric composition lithium tantalate single crystal, when the electromechanical coupling coefficient of the coincidence melt composition lithium tantalate single crystal is 100%, the electromechanical coupling coefficient is in the range of 100% to about 120%. It can be adjusted to a desired value, and at the same time, a stoichiometric composition lithium tantalate single crystal for a surface acoustic wave device with low cost and good thermal conductivity is obtained. Furthermore, as described above, a thick boule-shaped lithium tantalate single crystal, for example, can be uniformly modified to a stoichiometric composition by a vapor phase equilibrium method, so that it can be manufactured with high productivity and is inexpensive for surface acoustic wave devices. Stoichiometric composition of lithium tantalate single crystal.
気相平衡法による処理において、一致溶融組成タンタル酸リチウム単結晶は、Ｌｉを外部より拡散することによりＬｉの空位がＬｉで補完され化学量論組成タンタル酸リチウム単結晶に変化する。これにより、Ｌｉの空位により制限されていた電気機械結合係数を、本来タンタル酸リチウム単結晶で達しうる電気結合係数へと回復することが出来ると考えられる。更に、本発明のように、Ｌｉ空位をＦｅ，Ｎｉ，Ｃｏの元素で予め占めることで、電気機械結合係数の最大性能から所望の値に当該元素の含有量によって調整可能である。 In the treatment by the vapor phase equilibrium method, the coincidence melt composition lithium tantalate single crystal is transformed into a stoichiometric composition lithium tantalate single crystal by diffusing Li from the outside to supplement Li vacancies with Li. Thereby, it is considered that the electromechanical coupling coefficient limited by the vacancies in Li can be restored to the electrical coupling coefficient that can be originally achieved by the lithium tantalate single crystal. Furthermore, as in the present invention, the Li vacancies are preliminarily occupied by elements of Fe, Ni and Co, so that the maximum performance of the electromechanical coupling coefficient can be adjusted to a desired value by adjusting the content of the element.
また、改質される一致溶融組成タンタル酸リチウム単結晶の結晶方位が、３０°〜５０°回転Ｙカットであることが好ましい。
これにより、より大きな電気機械結合係数が得られる弾性表面波素子用化学量論組成タンタル酸リチウム単結晶となる。
Moreover, it is preferable that the crystal orientation of the conformal fusion composition lithium tantalate single crystal to be modified is 30 ° to 50 ° rotated Y-cut.
As a result, a stoichiometric composition lithium tantalate single crystal for a surface acoustic wave device capable of obtaining a larger electromechanical coupling coefficient is obtained.
図１は、Ｆｅを０．５ｍｏｌ％以下含む一致溶融組成タンタル酸リチウム単結晶を改質した弾性表面波素子用化学量論組成タンタル酸リチウム単結晶と、Ｆｅを含まない（Ｆｅが０ｍｏｌ％）一致溶融組成タンタル酸リチウム単結晶を改質した化学量論組成タンタル酸リチウム単結晶の規格化した電気機械結合係数のＹカット角依存性を示している。ここで、図１の縦軸は一致溶融組成タンタル酸リチウム単結晶の各Ｙカット角における電気機械結合係数と化学量論組成タンタル酸リチウム単結晶の電気機械結合係数との比を表している。一方、図１の横軸は化学量論組成に改質される一致溶融組成タンタル酸リチウム単結晶のＹカット角を表している。 FIG. 1 shows a stoichiometric composition lithium tantalate single crystal for surface acoustic wave devices, which is modified from a conformal fusion composition lithium tantalate single crystal containing 0.5 mol% or less of Fe, and no Fe (Fe is 0 mol%). The Y-cut angle dependence of the normalized electromechanical coupling coefficient of a stoichiometric composition lithium tantalate single crystal obtained by modifying a conformal melt composition lithium tantalate single crystal is shown. Here, the vertical axis in FIG. 1 represents the ratio between the electromechanical coupling coefficient at each Y cut angle of the coincidence molten composition lithium tantalate single crystal and the electromechanical coupling coefficient of the stoichiometric lithium tantalate single crystal. On the other hand, the horizontal axis of FIG. 1 represents the Y-cut angle of a coincidence melt composition lithium tantalate single crystal that is modified to a stoichiometric composition.
図１に示すように、Ｆｅを含まない場合の化学量論組成タンタル酸リチウム単結晶の電気機械結合係数は、一致溶融組成タンタル酸リチウム単結晶の電気機械結合係数に比べ、最大１．２倍近くとなっている。
また、Ｆｅを０．５ｍｏｌ％含む場合の化学量論組成タンタル酸リチウム単結晶の電気機械結合係数は、一致溶融組成タンタル酸リチウム単結晶の電気機械結合係数に比べ、１．０５倍程度となっている。図１に示すように、Ｆｅの含有量によって電気機械結合係数が変化していることがわかる。また、Ｆｅの含有量が０．５ｍｏｌ％を超えると、電気機械結合係数が一致溶融組成タンタル酸リチウム単結晶の電気機械結合係数以下となってしまう場合があるため、Ｆｅの含有量は０．５ｍｏｌ％以下とする必要がある。尚、Ｎｉ，Ｃｏにおいても、上記Ｆｅと同じ傾向を示す。また、Ｆｅを含まない場合には、電気機械結合係数は一致溶融組成タンタル酸リチウム単結晶の１．２倍程度となっており、最も大きな値を示している。
As shown in FIG. 1, the electromechanical coupling coefficient of the stoichiometric composition lithium tantalate single crystal in the case of not containing Fe is up to 1.2 times the electromechanical coupling coefficient of the coincidence melt composition lithium tantalate single crystal. It is close.
In addition, the electromechanical coupling coefficient of the stoichiometric composition lithium tantalate single crystal in the case of containing 0.5 mol% of Fe is about 1.05 times the electromechanical coupling coefficient of the coincidence melting composition lithium tantalate single crystal. ing. As shown in FIG. 1, it can be seen that the electromechanical coupling coefficient varies depending on the Fe content. Further, if the Fe content exceeds 0.5 mol%, the electromechanical coupling coefficient may be less than or equal to the electromechanical coupling coefficient of the coincidence melt composition lithium tantalate single crystal. It is necessary to make it 5 mol% or less. Ni and Co also show the same tendency as Fe. Moreover, when Fe is not included, the electromechanical coupling coefficient is about 1.2 times that of the coincidence melt composition lithium tantalate single crystal, which is the largest value.
従って、これらより、Ｆｅ，Ｎｉ，Ｃｏの少なくとも１つ以上の元素を一致溶融組成タンタル酸リチウム単結晶に０以上０．５ｍｏｌ％以下含ませることにより、改質された化学量論組成タンタル酸リチウム単結晶の電気機械結合係数を、一致溶融組成タンタル酸リチウム単結晶の電気機械結合係数の１．０５倍程度から１．２倍近い値まで調整可能であることがわかる。また、一致溶融組成タンタル酸リチウム単結晶の回転Ｙカット角が３０°〜５０°の範囲において、電気機械結合係数が最大となっていることもわかる。 Therefore, the stoichiometric composition of lithium tantalate modified by adding at least one element of Fe, Ni, and Co into the coincidence melt composition lithium tantalate single crystal from 0 to 0.5 mol%. It can be seen that the electromechanical coupling coefficient of the single crystal can be adjusted from about 1.05 times to about 1.2 times the electromechanical coupling coefficient of the coincidence melt composition lithium tantalate single crystal. It can also be seen that the electromechanical coupling coefficient is maximum when the rotational Y-cut angle of the coincidence molten composition lithium tantalate single crystal is in the range of 30 ° to 50 °.
また、本発明は、結晶方位が異なる２種類の本発明の弾性表面波素子用化学量論組成タンタル酸リチウム単結晶のウェーハ同士を接合してなる弾性表面波素子用複合圧電基板を提供する。
このような弾性表面波素子用複合圧電基板であれば、電気機械結合係数が優れるとともに、結晶の放熱性が向上しているため、弾性表面波素子の耐電力性が向上する。更に、複合圧電基板であるが故に周波数温度特性が向上した安価な複合基板となる。
The present invention also provides a composite piezoelectric substrate for a surface acoustic wave device obtained by bonding two types of wafers of the stoichiometric composition lithium tantalate single crystal for the surface acoustic wave device of the present invention having different crystal orientations.
With such a composite piezoelectric substrate for a surface acoustic wave element, the electromechanical coupling coefficient is excellent and the heat dissipation of the crystal is improved, so that the power durability of the surface acoustic wave element is improved. Furthermore, since it is a composite piezoelectric substrate, it becomes an inexpensive composite substrate with improved frequency temperature characteristics.
そして、上記のような本発明の弾性表面波素子用化学量論組成タンタル酸リチウム単結晶を製造する本発明の製造方法は、引き上げ法により、Ｆｅ，Ｎｉ，Ｃｏの少なくとも１つ以上の元素を０以上０．５ｍｏｌ％以下含む一致溶融組成タンタル酸リチウム単結晶を得て、該一致溶融組成タンタル酸リチウム単結晶の表面の粗さ指標Ｒｍａｘを１μｍ以上とし、該一致溶融組成タンタル酸リチウム単結晶を複数積層して積層体を形成し、該積層体を気相平衡法により化学量論組成に改質することで前記化学量論組成タンタル酸リチウム単結晶を製造する。 And the manufacturing method of this invention which manufactures the stoichiometric composition lithium tantalate single crystal for surface acoustic wave elements of the present invention as described above is a method of pulling at least one element of Fe, Ni, Co. A conformal melt composition lithium tantalate single crystal containing 0 to 0.5 mol% is obtained, and the conformity melt composition lithium tantalate single crystal has a surface roughness index Rmax of 1 μm or more. A plurality of layers are stacked to form a laminate, and the laminate is modified to a stoichiometric composition by a vapor phase equilibrium method to produce the stoichiometric composition lithium tantalate single crystal.
すなわち、一旦通常の引き上げ法で一致溶融組成タンタル酸リチウム単結晶を得るので、引き上げ速度を落とす必要がなく高い生産性で製造できるため、コストを低減できる。また、引き上げ法により単結晶製造時に、Ｆｅ，Ｎｉ，Ｃｏの量を調整するだけで簡単に、電気機械結合係数を調整できる。
これにより、電気機械結合係数を所望の値に調整することが出来、同時に、安価で熱伝導率のよい弾性表面波素子用化学量論組成タンタル酸リチウム単結晶を提供できる。
That is, once a coincidence-melting composition lithium tantalate single crystal is obtained by a normal pulling method, it is not necessary to reduce the pulling rate, and it can be manufactured with high productivity, so that the cost can be reduced. In addition, the electromechanical coupling coefficient can be adjusted simply by adjusting the amounts of Fe, Ni, and Co during single crystal production by the pulling method.
As a result, the electromechanical coupling coefficient can be adjusted to a desired value, and at the same time, a low-cost stoichiometric composition lithium tantalate single crystal for surface acoustic wave elements with good thermal conductivity can be provided.
また、改質される一致溶融組成タンタル酸リチウム単結晶の表面の粗さ指標Ｒｍａｘを１μｍ以上、好ましくは５μｍ以上とし、この一致溶融組成タンタル酸リチウム単結晶を複数積層して積層体を形成し、その積層体を気相平衡法により一括で化学量論組成に改質することで、改質の際の気相反応に大きな支障が生じない。
このため、一括で多数のウェーハを気相平衡法により一様に化学量論組成タンタル酸リチウム単結晶に改質できる為、より安価な弾性表面波素子用化学量論組成タンタル酸リチウム単結晶を提供することができる。
In addition, the surface roughness index Rmax of the conforming molten composition lithium tantalate single crystal to be modified is set to 1 μm or more, preferably 5 μm or more, and a plurality of conforming melting composition lithium tantalate single crystals are stacked to form a laminate. The laminated body is reformed to a stoichiometric composition all at once by the vapor phase equilibrium method, so that no great hindrance occurs in the gas phase reaction during the reforming.
For this reason, since a large number of wafers can be uniformly modified to a stoichiometric composition lithium tantalate single crystal by vapor phase equilibrium method, a cheaper stoichiometric composition lithium tantalate single crystal for surface acoustic wave devices can be obtained. Can be provided.
更に、改質される一致溶融組成タンタル酸リチウム単結晶を、厚さ７ｍｍ以上とすることで、例えばブール形状の厚いタンタル酸リチウム単結晶を、気相平衡法により一様に化学量論組成に改質できるので、生産性良く製造でき、安価な弾性表面波素子用化学量論組成タンタル酸リチウム単結晶を提供できる。 Furthermore, the conformal melt composition lithium tantalate single crystal to be modified is made to have a thickness of 7 mm or more, so that, for example, a boule-shaped thick lithium tantalate single crystal has a uniform stoichiometric composition by a vapor phase equilibrium method. Since it can be modified, it can be produced with high productivity, and an inexpensive stoichiometric composition lithium tantalate single crystal for surface acoustic wave devices can be provided.
また、改質される一致溶融組成タンタル酸リチウム単結晶を、予め塩化カリウム溶液又は塩化ナトリウム溶液に浸漬させた後、気相平衡法により化学量論組成に改質することが好ましい。
これにより、表面を活性化することができ、気相平衡法における処理速度が飛躍的に向上するため、より生産性良く弾性表面波素子用化学量論組成タンタル酸リチウム単結晶を製造できる。
Moreover, it is preferable that the conformal melt composition lithium tantalate single crystal to be modified is previously immersed in a potassium chloride solution or a sodium chloride solution and then modified to a stoichiometric composition by a vapor phase equilibrium method.
As a result, the surface can be activated and the processing speed in the vapor phase equilibrium method can be dramatically improved, so that a stoichiometric composition lithium tantalate single crystal for a surface acoustic wave device can be produced with higher productivity.
更に、改質される一致溶融組成タンタル酸リチウム単結晶の結晶方位を、３０°〜５０°回転Ｙカットとすることが好ましい。
これにより、より大きな電気機械結合係数が得られる弾性表面波素子用化学量論組成タンタル酸リチウム単結晶を製造できる。
Furthermore, it is preferable that the crystal orientation of the conformal melt composition lithium tantalate single crystal to be modified is a 30 ° -50 ° rotated Y-cut.
Thereby, a stoichiometric composition lithium tantalate single crystal for a surface acoustic wave device capable of obtaining a larger electromechanical coupling coefficient can be produced.
以下、実施例を示して本発明をより具体的に説明するが、本発明はこれらに限定されるものではない。 EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated more concretely, this invention is not limited to these.
（実施例１）
引き上げ法によりＦｅを含まない一致溶融組成の４インチ（１０．１６ｃｍ）径３６°回転ＹカットＬｉＴａＯ３単結晶を作製し、これをスライスにより３０ｍｍｔの厚さのブール形状に仕上げ、塩化ナトリウム溶液に浸漬させた。そして、塩化ナトリウム溶液に浸漬させたＬｉＴａＯ３単結晶ブールを白金製の皿の上に載せ、Ｌｉ２ＣＯ３粉とＴａ２Ｏ５粉を６：４のモル比で混合した気相平衡処理原料と混在させ、両者を白金の容器に入れ、当該容器を電気炉に入れ、常圧、１４０２℃±１℃で１００時間加熱した（気相平衡処理）。
Example 1
A 4-inch (10.16 cm) diameter 36 ° -rotated Y-cut LiTaO 3 single crystal with a consistent melt composition not containing Fe was prepared by a pulling method, and this was sliced into a boule shape with a thickness of 30 mmt to form a sodium chloride solution. Soaked. Then, a LiTaO 3 single crystal boule immersed in a sodium chloride solution is placed on a platinum dish, and a Li 2 CO 3 powder and a Ta 2 O 5 powder are mixed at a molar ratio of 6: 4. Both were placed in a platinum container, the container was placed in an electric furnace, and heated at normal pressure at 1402 ° C. ± 1 ° C. for 100 hours (gas phase equilibrium treatment).
次に、前記３０ｍｍｔの厚さのＬｉＴａＯ３単結晶板を２００℃、１ｋｖ、５時間の印加電圧により、概略結晶のＺ軸方向に電界を掛け単一分極化する処理を行った（分極処理）。 Next, the LiTaO 3 single crystal plate having a thickness of 30 mm was subjected to a single polarization by applying an electric field in the Z-axis direction of the crystal with an applied voltage of 200 ° C., 1 kv, 5 hours (polarization treatment). .
次に、前記３６°回転ＹカットＬｉＴａＯ３単結晶ブールをスライス加工して、０．２ｍｍｔの厚さの板状に仕上げた。この板状に仕上げたＬｉＴａＯ３単結晶板の表面粗さを評価した所、Ｒｍａｘは３μｍであった。これを２０ｍｍ角に切断し、レーザフラッシュ法により熱伝導率を測定した所、その値は８．６５Ｗ／（ｍ・Ｋ）であった。 Next, the 36 ° rotated Y-cut LiTaO 3 single crystal boule was sliced and finished into a plate having a thickness of 0.2 mmt. When the surface roughness of the LiTaO 3 single crystal plate finished in this plate shape was evaluated, Rmax was 3 μm. When this was cut into 20 mm square and the thermal conductivity was measured by the laser flash method, the value was 8.65 W / (m · K).
一方、前記気相平衡処理前の、一致溶融組成の４インチ（１０．１６ｃｍ）径３６°回転ＹカットＬｉＴａＯ３単結晶からなる前記２０ｍｍ角に切断したＬｉＴａＯ３単結晶板と同一形状の試料の熱伝導率を測定した所、その値は４．５１Ｗ／（ｍ・Ｋ）であった。即ち、気相平衡処理により試料の熱伝導率が向上していた。 On the other hand, a sample having the same shape as the LiTaO 3 single crystal plate cut into the 20 mm square made of a 4 inch (10.16 cm) diameter 36 ° rotated Y-cut LiTaO 3 single crystal having a congruent melt composition before the vapor phase equilibration treatment. When the thermal conductivity was measured, the value was 4.51 W / (m · K). That is, the thermal conductivity of the sample was improved by the vapor phase equilibrium treatment.
次に、前記気相平衡処理と分極処理を施した３６°回転ＹカットＬｉＴａＯ３単結晶板をスライス、研磨してウェーハ形状に仕上げ、該ウェーハのＸ軸方向を伝播方向とする中心周波数１ＧＨｚの１ポートＳＡＷ共振子を作製し、電気機械結合係数を共振周波数と反共振周波数より求めた所、８．４％であった。 Next, the 36 ° rotated Y-cut LiTaO 3 single crystal plate subjected to the vapor phase equilibration process and the polarization process is sliced and polished into a wafer shape, and the center frequency is 1 GHz with the X-axis direction of the wafer as the propagation direction. A 1-port SAW resonator was fabricated, and the electromechanical coupling coefficient was obtained from the resonance frequency and the antiresonance frequency, and found to be 8.4%.
比較の為、前記気相平衡処理を施していない３６°回転ＹカットＬｉＴａＯ３単結晶板を上記と同様にウェーハ形状に仕上げ、上記と同様の１ポートＳＡＷ共振子を作製し、電気機械結合係数を上記と同様に求めた所、７．１％であった。 For comparison, the 36 ° rotated Y-cut LiTaO 3 single crystal plate not subjected to the vapor phase equilibration treatment is finished into a wafer shape in the same manner as described above to produce a 1-port SAW resonator similar to the above, and an electromechanical coupling coefficient Was determined in the same manner as above, and it was 7.1%.
（実施例２）
引き上げ法により、Ｆｅを０．５ｍｏｌ％含有する一致溶融組成の４インチ（１０．１６ｃｍ）径３６°回転ＹカットＬｉＴａＯ３単結晶を作製し、これをスライスにより３０ｍｍｔの厚さのブール形状に仕上げ、塩化ナトリウム溶液に浸漬させた。そして、塩化ナトリウム溶液に浸漬させたＬｉＴａＯ３単結晶ブールを白金製の皿の上に載せ、Ｌｉ２ＣＯ３粉とＴａ２Ｏ５粉を６：４のモル比で混合した気相平衡処理原料と混在させ、両者を白金の容器に入れ、当該容器を電気炉に入れ、常圧、１４０２℃±１℃で１００時間加熱した（気相平衡処理）。
(Example 2)
A 4-inch (10.16 cm) diameter 36 ° rotated Y-cut LiTaO 3 single crystal containing 0.5 mol% Fe and containing 0.5 mol% Fe was produced by a pulling method, and this was finished into a boule shape with a thickness of 30 mm by slicing. And soaked in a sodium chloride solution. Then, a LiTaO 3 single crystal boule immersed in a sodium chloride solution is placed on a platinum dish, and a Li 2 CO 3 powder and a Ta 2 O 5 powder are mixed at a molar ratio of 6: 4. Both were placed in a platinum container, the container was placed in an electric furnace, and heated at normal pressure at 1402 ° C. ± 1 ° C. for 100 hours (gas phase equilibrium treatment).
次に、前記３０ｍｍｔの厚さのＬｉＴａＯ３単結晶板を２００℃、１ｋｖ、５時間の印加電圧により、概略結晶のＺ軸方向に電界を掛け単一分極化する処理を行った（分極処理）。 Next, the LiTaO 3 single crystal plate having a thickness of 30 mm was subjected to a single polarization by applying an electric field in the Z-axis direction of the crystal with an applied voltage of 200 ° C., 1 kv, 5 hours (polarization treatment). .
この気相平衡処理済のＦｅを０．５ｍｏｌ％含有する３６°回転ＹカットＬｉＴａＯ３単結晶ブールをスライス加工して０．２ｍｍｔの厚さの板状に仕上げた。その表面粗さＲｍａｘは、３μｍであった。その後、２０ｍｍ角に切断し、レーザフラッシュ法により熱伝導率を測定した所、その値は６．３Ｗ／（ｍ・Ｋ）であった。 This 36 ° rotated Y-cut LiTaO 3 single crystal boule containing 0.5 mol% of Fe after the vapor phase equilibration treatment was sliced and finished into a plate having a thickness of 0.2 mmt. Its surface roughness Rmax was 3 μm. Then, when it cut | disconnected to 20 mm square and measured the thermal conductivity by the laser flash method, the value was 6.3 W / (m * K).
一方、前記気相平衡処理前の、Ｆｅを０．５ｍｏｌ％含有する一致溶融組成の４インチ（１０．１６ｃｍ）径３６°回転ＹカットＬｉＴａＯ３単結晶からなる前記２０ｍｍ角に切断したＬｉＴａＯ３単結晶ブールと同一形状の試料の熱伝導率を測定した所、その値は４．５１Ｗ／（ｍ・Ｋ）であった。即ち、気相平衡処理により試料の熱伝導率が向上していた。 On the other hand, before the vapor phase equilibration treatment, a LiTaO 3 single piece cut into the 20 mm square made of a 4 inch (10.16 cm) diameter 36 ° rotated Y-cut LiTaO 3 single crystal containing 0.5 mol% of Fe and having a congruent melting composition. When the thermal conductivity of the sample having the same shape as the crystal boule was measured, the value was 4.51 W / (m · K). That is, the thermal conductivity of the sample was improved by the vapor phase equilibrium treatment.
次に、前記気相平衡処理と分極処理を施したＦｅを０．５ｍｏｌ％含有する３６°回転ＹカットＬｉＴａＯ３単結晶を研磨してウェーハ形状に仕上げ、該ウェーハのＸ軸方向を伝播方向とする中心周波数１ＧＨｚの１ポートＳＡＷ共振子を作製し、電気機械結合係数を共振周波数と反共振周波数より求めた所、７．５％であった。 Next, the 36 ° rotated Y-cut LiTaO 3 single crystal containing 0.5 mol% of Fe subjected to the vapor phase equilibrium treatment and the polarization treatment is polished and finished into a wafer shape, and the X-axis direction of the wafer is defined as the propagation direction. A 1-port SAW resonator having a center frequency of 1 GHz was manufactured, and the electromechanical coupling coefficient was obtained from the resonance frequency and the anti-resonance frequency, which was 7.5%.
比較の為、前記気相平衡処理前のＦｅを０．５ｍｏｌ％含有する３６°回転ＹカットＬｉＴａＯ３単結晶板を上記と同様にウェーハ形状に仕上げ、上記と同様の１ポートＳＡＷ共振子を作製し、電気機械結合係数を上記と同様に求めた所、７．１％であった。 For comparison, a 36 ° rotated Y-cut LiTaO 3 single crystal plate containing 0.5 mol% of Fe before the vapor phase equilibration treatment is finished into a wafer shape in the same manner as described above to produce a 1-port SAW resonator similar to the above. And when the electromechanical coupling coefficient was determined in the same manner as described above, it was 7.1%.
（実施例３）
引き上げ法により、Ｆｅを含まない一致溶融組成の４インチ（１０．１６ｃｍ）径３６°回転ＹカットＬｉＴａＯ３単結晶を作製し、これをスライスにより０．１９ｍｍｔの厚さの板形状に仕上げた。この板形状のＬｉＴａＯ３単結晶の表面粗さを評価した所、Ｒｍａｘは３μｍであった。前記０．１９ｍｍｔの厚さの板形状のＬｉＴａＯ３単結晶を塩化ナトリウム溶液に浸漬させた後に、それを１００枚積層して積層体を形成した。そして、該積層体を白金製の皿の上に載せ、ＬｉＯ３粉とＴａ２Ｏ５粉を６：４のモル比で混合した気相平衡処理原料と混在させ、両者を白金の容器に入れ、当該容器を電気炉に入れ、常圧、１４０２℃±１℃で３０時間加熱して一括処理した（気相平衡処理）。
(Example 3)
A 4-inch (10.16 cm) diameter 36 ° -rotated Y-cut LiTaO 3 single crystal having a coincidence melting composition not containing Fe was produced by a pulling method, and finished into a plate shape having a thickness of 0.19 mmt by slicing. When the surface roughness of this plate-shaped LiTaO 3 single crystal was evaluated, Rmax was 3 μm. After the plate-shaped LiTaO 3 single crystal having a thickness of 0.19 mmt was immersed in a sodium chloride solution, 100 sheets thereof were laminated to form a laminate. Then, the laminate is placed on a platinum dish, mixed with a vapor phase equilibration raw material in which LiO 3 powder and Ta 2 O 5 powder are mixed at a molar ratio of 6: 4, and both are put in a platinum container. The container was placed in an electric furnace and heated at normal pressure and 1402 ° C. ± 1 ° C. for 30 hours for batch treatment (vapor phase equilibration treatment).
次に、前記積層体を２００℃、１ｋｖ、５時間の印加電圧により、概略結晶のＺ軸方向に電界を掛け一括して単一分極化する処理を行った（分極処理）。その後、前記３６°回転ＹカットＬｉＴａＯ３単結晶板を２０ｍｍ角に切断し、レーザフラッシュ法によりその熱伝導率を測定した所、その値は８．６５Ｗ／（ｍ・Ｋ）であった。この測定は前記積層体の上部、中央部、下部について評価したが、全て同じ結果が得られた。 Next, the laminated body was subjected to a single polarization process by applying an electric field in the Z-axis direction of the crystal roughly at an applied voltage of 200 ° C., 1 kv, and 5 hours (polarization process). Thereafter, the 36 ° rotated Y-cut LiTaO 3 single crystal plate was cut into a 20 mm square, and its thermal conductivity was measured by a laser flash method. The value was 8.65 W / (m · K). Although this measurement evaluated the upper part of the said laminated body, the center part, and the lower part, all obtained the same result.
一方、前記平衡処理前の、一致溶融組成の４インチ（１０．１６ｃｍ）径３６°回転ＹカットＬｉＴａＯ３単結晶からなる前記２０ｍｍ角に切断したＬｉＴａＯ３単結晶板と同一形状の試料の熱伝導率を測定した所、その値は４．５１Ｗ／（ｍ・Ｋ）であった。即ち、気相平衡処理により試料の熱伝導率が向上していた。 On the other hand, the heat conduction of the sample having the same shape as that of the LiTaO 3 single crystal plate cut into 20 mm square and made of a 4 inch (10.16 cm) diameter 36 ° rotated Y-cut LiTaO 3 single crystal having a congruent melting composition before the equilibration treatment. When the rate was measured, the value was 4.51 W / (m · K). That is, the thermal conductivity of the sample was improved by the vapor phase equilibrium treatment.
また、前記気相平衡処理と分極処理を施した３６°回転ＹカットＬｉＴａＯ３単結晶板を研磨してウェーハ形状に仕上げ、該ウェーハのＸ軸方向を伝播方向とする中心周波数１ＧＨｚの１ポートＳＡＷ共振子を作製し、電気機械結合係数を共振周波数と反共振周波数より求めた所、８．４％であった。 Further, the 36 ° rotated Y-cut LiTaO 3 single crystal plate subjected to the vapor phase equilibration process and the polarization process is polished into a wafer shape, and a 1-port SAW having a center frequency of 1 GHz with the X-axis direction of the wafer as a propagation direction. A resonator was fabricated, and the electromechanical coupling coefficient was obtained from the resonance frequency and the antiresonance frequency, and found to be 8.4%.
比較の為、前記気相平衡処理前の３６°回転ＹカットＬｉＴａＯ３単結晶板を同様にウェーハ形状に仕上げ、上記と同様の１ポートＳＡＷ共振子を作製し、電気機械結合係数を上記と同様に求めた所、７．１％であった。 For comparison, the 36 ° rotated Y-cut LiTaO 3 single crystal plate before the vapor phase equilibration treatment is similarly finished into a wafer shape, a 1-port SAW resonator similar to the above is fabricated, and the electromechanical coupling coefficient is the same as above. The result was 7.1%.
なお、前記気相平衡処理原料として、Ｔａ２Ｏ５粉の替わりにＺｒＯ２粉を用い、Ｌｉ２ＣＯ３粉とＺｒＯ２粉を７：３の割合で混合した気相平衡処理原料と、前記積層体と同様の一致溶融組成の４インチ（１０．１６ｃｍ）径３６°回転Ｙカットタンタル酸リチウム単結晶板を積層したものとを混在させ、両者を白金の容器に入れ、当該容器を電気炉に入れ、常圧、１２９０℃±１℃で１００時間加熱した場合についても、上記と同様に、熱伝導率と電気機械結合係数が上昇する結果が得られた。 In addition, as the gas phase equilibrium treatment raw material, ZrO 2 powder is used instead of Ta 2 O 5 powder, and the gas phase equilibrium treatment raw material in which Li 2 CO 3 powder and ZrO 2 powder are mixed at a ratio of 7: 3, A laminate of 4 inch (10.16 cm) diameter 36 ° rotated Y-cut lithium tantalate single crystal plates with a congruent melt composition similar to the laminate is mixed, and both are placed in a platinum container, and the container is placed in an electric furnace. In the case of heating to 100 ° C. at normal pressure and 1290 ° C. ± 1 ° C., the results of increasing the thermal conductivity and the electromechanical coupling coefficient were obtained as described above.
（実施例４）
引き上げ法によりＦｅを０．３ｍｏｌ％含有する一致溶融組成の４インチ（１０．１６ｃｍ）径３６°回転ＹカットＬｉＴａＯ３単結晶を作製し、これをスライスにより０．１９ｍｍｔの厚さの板形状に仕上げた。この板形状のＬｉＴａＯ３単結晶の表面粗さを評価した所、Ｒｍａｘは３μｍであった。
Example 4
A 4 inch (10.16 cm) diameter 36 ° rotated Y-cut LiTaO 3 single crystal containing 0.3 mol% Fe containing 0.3 mol% Fe was produced by a pulling method, and this was sliced into a plate shape having a thickness of 0.19 mm t. Finished. When the surface roughness of this plate-shaped LiTaO 3 single crystal was evaluated, Rmax was 3 μm.
前記０．１９ｍｍｔの厚さの板形状のＬｉＴａＯ３単結晶を塩化ナトリウム溶液に浸漬させた後に、それを１００枚積層して積層体を形成した。そして、該積層体を白金製の皿の上に載せ、ＬｉＯ３粉とＴａ２Ｏ５粉を６：４のモル比で混合した気相平衡処理原料と混在させ、両者を白金の容器に入れ、当該容器を電気炉に入れ、常圧、１４０２℃±１℃で３０時間加熱して一括処理した（気相平衡処理）。 After the plate-shaped LiTaO 3 single crystal having a thickness of 0.19 mmt was immersed in a sodium chloride solution, 100 sheets thereof were laminated to form a laminate. Then, the laminate is placed on a platinum dish, mixed with a vapor phase equilibration raw material in which LiO 3 powder and Ta 2 O 5 powder are mixed at a molar ratio of 6: 4, and both are put in a platinum container. The container was placed in an electric furnace and heated at normal pressure and 1402 ° C. ± 1 ° C. for 30 hours for batch treatment (vapor phase equilibration treatment).
次に、前記積層体を、２００℃、１ｋｖ、５時間の印加電圧により概略結晶のＺ軸方向に電界を掛け、一括して単一分極化する処理を行った（分極処理）。
このＦｅを０．３ｍｏｌ％含有する３６°回転ＹカットＬｉＴａＯ３単結晶板を２０ｍｍ角に切断し、レーザフラッシュ法により熱伝導率を測定した所、その値は７．３２Ｗ／（ｍ・Ｋ）であった。
Next, the laminate was subjected to a process of applying a single electric field in the Z-axis direction of the crystal by applying an applied voltage of 200 ° C., 1 kv, and 5 hours to collectively single polarization (polarization process).
A 36 ° rotated Y-cut LiTaO 3 single crystal plate containing 0.3 mol% of Fe was cut into 20 mm square, and the thermal conductivity was measured by a laser flash method. The value was 7.32 W / (m · K). Met.
一方、前記気相平衡処理前の、Ｆｅを０．３ｍｏｌ％含有する一致溶融組成の４インチ（１０．１６ｃｍ）径３６°回転ＹカットＬｉＴａＯ３単結晶からなる前記２０ｍｍ角に切断したＬｉＴａＯ３単結晶板と同一形状の試料の熱伝導率を測定した所、その値は４．５１Ｗ／（ｍ・Ｋ）であった。即ち、気相平衡処理により試料の熱伝導率が向上していた。 On the other hand, before the vapor phase equilibration treatment, the LiTaO 3 single piece cut into the 20 mm square composed of a 4 inch (10.16 cm) diameter 36 ° rotated Y-cut LiTaO 3 single crystal containing 0.3 mol% Fe and having a coincidence melting composition. When the thermal conductivity of the sample having the same shape as the crystal plate was measured, the value was 4.51 W / (m · K). That is, the thermal conductivity of the sample was improved by the vapor phase equilibrium treatment.
次に、前記気相平衡処理と分極処理を施したＦｅを０．３ｍｏｌ％含有する３６°回転ＹカットＬｉＴａＯ３単結晶板を研磨してウェーハ形状に仕上げ、前記ウェーハのＸ軸方向を伝播方向とする中心周波数１ＧＨｚの１ポートＳＡＷ共振子を作製し、電気機械結合係数を共振周波数と反共振周波数より求めた所、７．９％であった。 Next, a 36 ° rotated Y-cut LiTaO 3 single crystal plate containing 0.3 mol% of Fe subjected to the vapor phase equilibration treatment and polarization treatment is polished and finished into a wafer shape, and the X-axis direction of the wafer is propagated in the propagation direction. A 1-port SAW resonator having a center frequency of 1 GHz was manufactured, and the electromechanical coupling coefficient was obtained from the resonance frequency and the anti-resonance frequency, which was 7.9%.
比較の為、前記気相平衡処理前のＦｅを０．３ｍｏｌ％含有する３６°回転ＹカットＬｉＴａＯ３単結晶板を上記と同様にウェーハ形状に仕上げ、上記と同様の１ポートＳＡＷ共振子を作製し、電気機械結合係数を上記と同様に求めた所、７．１％であった。 For comparison, a 36 ° rotated Y-cut LiTaO 3 single crystal plate containing 0.3 mol% of Fe before the vapor phase equilibration treatment is finished into a wafer shape in the same manner as described above to produce a 1-port SAW resonator similar to the above. And when the electromechanical coupling coefficient was determined in the same manner as described above, it was 7.1%.
（実施例５）
実施例３と同様にして得られた、引き上げ法による一致溶融組成の４インチ（１０．１６ｃｍ）径３６°回転ＹカットＬｉＴａＯ３単結晶に、実施例３と同様の気相平衡処理と分極処理を施して化学量論組成ＬｉＴａＯ３単結晶を得た。そして、得られた化学量論組成ＬｉＴａＯ３単結晶をウェーハ形状にし、その裏面を鏡面研磨して０．１９ｍｍｔの厚さのウェーハとした。
(Example 5)
A vapor phase equilibration treatment and a polarization treatment similar to those in Example 3 were applied to a 4 inch (10.16 cm) diameter 36 ° rotated Y-cut LiTaO 3 single crystal obtained by the pulling method in the same manner as in Example 3. The stoichiometric composition LiTaO 3 single crystal was obtained. Then, the obtained stoichiometric composition LiTaO 3 single crystal was formed into a wafer shape, and the back surface thereof was mirror-polished to obtain a wafer having a thickness of 0.19 mmt.
また、引き上げ法による一致溶融組成の４インチ（１０．１６ｃｍ）径０°回転ＹカットＬｉＴａＯ３単結晶を、実施例３と同様にして気相平衡処理する一方、分極処理は施さずに片面を鏡面とするウェーハ形状に仕上げた。
Further, a 4 inch (10.16 cm)
前記の２種類の単結晶ウェーハを鏡面同士が重なるように、前記４インチ（１０．１６ｃｍ）径３６°回転ＹカットＬｉＴａＯ３単結晶のＸ軸と、前記の４インチ（１０．１６ｃｍ）径０°回転ＹカットＬｉＴａＯ３単結晶のＺ軸が一致するように、常温接合法により貼り合わせた。
The 4 inch (10.16 cm) diameter 36 ° rotated Y-cut LiTaO 3 single crystal X axis and the 4 inch (10.16 cm)
前記の接合体の３６°回転ＹカットＬｉＴａＯ３単結晶の表面を研磨して、該３６°回転ＹカットＬｉＴａＯ３単結晶の厚みが３０μｍの厚さとなるように仕上げた。
前記接合基板に中心周波数１ＧＨｚの１ポートＳＡＷ共振子を作製して周波数温度特性を評価した所、共振周波数の温度係数は−１２ｐｐｍ／℃、反共振周波数の温度係数は−２４ｐｐｍ／℃であった。また、前記接合基板の熱伝導率を測定した所、８．６５Ｗ／（ｍ・Ｋ）であった。
The surface of the 36 ° rotated Y-cut LiTaO 3 single crystal of the joined body was polished so that the thickness of the 36 ° rotated Y-cut LiTaO 3 single crystal was 30 μm.
When a 1-port SAW resonator having a center frequency of 1 GHz was fabricated on the bonding substrate and frequency temperature characteristics were evaluated, the temperature coefficient of the resonance frequency was −12 ppm / ° C., and the temperature coefficient of the anti-resonance frequency was −24 ppm / ° C. . Moreover, it was 8.65 W / (m * K) when the heat conductivity of the said bonded substrate was measured.
比較の為、一致溶融組成の４インチ（１０．１６ｃｍ）径３６°回転ＹカットＬｉＴａＯ３単結晶をウェーハ加工したもの単体に、上記と同様の中心周波数１ＧＨｚの１ポートＳＡＷ共振子を作製して周波数温度特性を評価した所、共振周波数の温度係数は−３２ｐｐｍ／℃、反共振周波数の温度係数は−４５ｐｐｍ／℃であった。また、熱伝導率を測定した所、４．５１Ｗ／（ｍ・Ｋ）であった。 For comparison, a 1-port SAW resonator having a center frequency of 1 GHz similar to the above was fabricated on a single wafer processed from a 4 inch (10.16 cm) diameter 36 ° rotated Y-cut LiTaO 3 single crystal having a congruent melt composition. When the frequency-temperature characteristics were evaluated, the temperature coefficient of the resonance frequency was −32 ppm / ° C., and the temperature coefficient of the anti-resonance frequency was −45 ppm / ° C. Moreover, it was 4.51 W / (m * K) when the heat conductivity was measured.
（比較例１）
引き上げ法により、Ｆｅを含まない一致溶融組成の４インチ（１０．１６ｃｍ）径３６°回転ＹカットＬｉＴａＯ３単結晶を作製し、これをスライス及び両面研磨により０．１９ｍｍｔの厚さの板形状に仕上げた。この板形状のＬｉＴａＯ３単結晶の表面粗さを評価した所、Ｒｍａｘが０．００１μｍの鏡面であった。前記０．１９ｍｍｔの厚さの板形状のＬｉＴａＯ３単結晶を塩化ナトリウム溶液に浸漬させた後、１００枚積層して積層体を形成した。そして、該積層体を白金製の皿の上に載せ、Ｌｉ２ＣＯ３粉とＴａ２Ｏ５粉を６：４のモル比で混合した気相平衡処理原料と混在させ、両者を白金の容器に入れ、当該容器を電気炉に入れ、常圧、１４０２℃±１℃で３０時間加熱して一括処理した（気相平衡処理）。
(Comparative Example 1)
A 4-inch (10.16 cm) diameter 36 ° -rotated Y-cut LiTaO 3 single crystal having a congruent melting composition not containing Fe was produced by the pulling method, and this was sliced and double-side polished into a plate shape having a thickness of 0.19 mmt. Finished. When the surface roughness of this plate-shaped LiTaO 3 single crystal was evaluated, it was a mirror surface with an Rmax of 0.001 μm. After the plate-shaped LiTaO 3 single crystal having a thickness of 0.19 mmt was immersed in a sodium chloride solution, 100 sheets were laminated to form a laminate. Then, the laminate is placed on a platinum dish, mixed with a vapor phase equilibration raw material in which Li 2 CO 3 powder and Ta 2 O 5 powder are mixed at a molar ratio of 6: 4, and both are mixed in a platinum container. The container was placed in an electric furnace and heated at normal pressure and 1402 ° C. ± 1 ° C. for 30 hours for batch treatment (vapor phase equilibration treatment).
次に、前記積層体を、２００℃、１ｋｖ、５時間の印加電圧により概略結晶のＺ軸方向に電界を掛け、一括して単一分極化する処理を行った（分極処理）。
その後、前記３６°回転ＹカットＬｉＴａＯ３単結晶板を２０ｍｍ角に切断し、レーザフラッシュ法によりその熱伝導率を測定した所、前記積層体の上部及び下部に位置する単結晶板では、８．６５Ｗ／（ｍ・Ｋ）であった。しかし、該積層体の中央部に位置する単結晶板の熱伝導率を測定した所、その値は４．５１Ｗ／（ｍ・Ｋ）であった。
Next, the laminate was subjected to a process of applying a single electric field in the Z-axis direction of the crystal by applying an applied voltage of 200 ° C., 1 kv, and 5 hours to collectively single polarization (polarization process).
Thereafter, the 36 ° rotated Y-cut LiTaO 3 single crystal plate was cut into a 20 mm square and its thermal conductivity was measured by a laser flash method. As a result, it was found that the single crystal plate located above and below the laminate was 8. It was 65 W / (m · K). However, when the thermal conductivity of the single crystal plate located at the center of the laminate was measured, the value was 4.51 W / (m · K).
また、前記気相平衡処理前の、一致溶融組成の４インチ（１０．１６ｃｍ）径３６°回転ＹカットＬｉＴａＯ３単結晶からなる前記２０ｍｍ角に切断したＬｉＴａＯ３単結晶と同一形状の試料の熱伝導率を測定した所、その値は４．５１Ｗ／（ｍ・Ｋ）であった。 Further, before the vapor phase equilibration treatment, the heat of the sample having the same shape as the LiTaO 3 single crystal cut into 20 mm square, which is made of a 4 inch (10.16 cm) diameter 36 ° -rotated Y-cut LiTaO 3 single crystal having a congruent melting composition When the conductivity was measured, the value was 4.51 W / (m · K).
次に、前記気相平衡処理と分極処理を施した３６°回転ＹカットＬｉＴａＯ３単結晶板を研磨してウェーハ形状に仕上げ、前記ウェーハのＸ軸方向を伝播方向とする中心周波数１ＧＨｚの１ポートＳＡＷ共振子を作製し、電気機械結合係数を共振周波数と反共振周波数より求めた所、上記積層体の上部及び下部に位置する単結晶ウェーハについては８．４％であった。しかし、上記積層体の中央部に位置する単結晶ウェーハの電気機械結合係数は７．１％であった。
以上のように、鏡面の場合は、一括処理は困難であることがわかった。
Next, the 36 ° rotated Y-cut LiTaO 3 single crystal plate that has been subjected to the vapor phase equilibration process and the polarization process is polished into a wafer shape, and 1 port at a center frequency of 1 GHz with the X-axis direction of the wafer as the propagation direction A SAW resonator was fabricated, and the electromechanical coupling coefficient was obtained from the resonance frequency and the antiresonance frequency. As a result, it was 8.4% for the single crystal wafers located above and below the laminate. However, the electromechanical coupling coefficient of the single crystal wafer located at the center of the laminate was 7.1%.
As described above, it was found that batch processing is difficult in the case of a mirror surface.
このように、実施例１〜５について、実施例４でＦｅを０．３ｍｏｌ％含有させた一致溶融組成ＬｉＴａＯ３単結晶を用いた以外は、実施例３では実施例４と同様の処理を行った。また、実施例２でＦｅを０．５ｍｏｌ％含有させた一致溶融組成ＬｉＴａＯ３単結晶を用いた以外は、実施例１では実施例２と同様の処理を行った。 As described above, for Examples 1 to 5, the same treatment as that of Example 4 was performed in Example 3 except that the coincident composition LiTaO 3 single crystal containing 0.3 mol% of Fe in Example 4 was used. It was. Further, the same treatment as in Example 2 was performed in Example 1 except that the coincident melt composition LiTaO 3 single crystal containing 0.5 mol% Fe in Example 2 was used.
その結果、実施例４ではＦｅを一致溶融組成ＬｉＴａＯ３単結晶に含有させて化学量論組成ＬｉＴａＯ３単結晶に改質したことで、電気機械結合係数が７．９％となり、実施例３の場合の８．４％に比べて低い数値となった。同様の理由で、実施例２では電気機械結合係数が７．５％となり、実施例１の場合の８．４％に比べて低い数値となった。 As a result, it was modified into stoichiometric LiTaO 3 single crystal by containing Fe in Example 4 in congruent LiTaO 3 single crystal, next electromechanical coupling coefficient of 7.9% of Example 3 The value was lower than 8.4% of cases. For the same reason, in Example 2, the electromechanical coupling coefficient was 7.5%, which was a lower value than 8.4% in Example 1.
従って、実施例１，２及び実施例３，４より、Ｆｅを一致溶融組成ＬｉＴａＯ３単結晶に含有させて化学量論組成ＬｉＴａＯ３単結晶に改質することで、改質後のＬｉＴａＯ３単結晶の電気機械結合係数が、改質前のＦｅを含まない一致溶融組成ＬｉＴａＯ３単結晶の電気機械結合係数に対して調整できることがわかった。また、実施例３，４より、Ｒｍａｘが１μｍ以上の一致溶融組成ＬｉＴａＯ３単結晶を積層しても、一括で改質可能でコストを削減できることがわかった。更に、実施例５では、本発明の化学量論組成ＬｉＴａＯ３単結晶を接合して得られた複合圧電基板が、良好な特性を示すことがわかった。 Accordingly, from Examples 1 and 2 and Examples 3 and 4, contain a Fe in congruent LiTaO 3 single crystal by modifying the stoichiometric LiTaO 3 single crystal, after reforming LiTaO 3 single It was found that the electromechanical coupling coefficient of the crystal can be adjusted with respect to the electromechanical coupling coefficient of the coincident melt composition LiTaO 3 single crystal containing no Fe before modification. In addition, from Examples 3 and 4, it was found that even when a coincidence melt composition LiTaO 3 single crystal having an Rmax of 1 μm or more is laminated, it can be reformed all at once and cost can be reduced. Furthermore, in Example 5, stoichiometric LiTaO 3 piezoelectric composite substrate obtained by bonding a single crystal of the present invention was found to exhibit excellent properties.
なお、本発明は、上記実施形態に限定されるものではない。上記実施形態は、例示であり、本発明の特許請求の範囲に記載された技術的思想と実質的に同一な構成を有し、同様な作用効果を奏するものは、いかなるものであっても本発明の技術的範囲に包含される。 The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.
Claims (7)
前記化学量論組成タンタル酸リチウム単結晶は、引き上げ法により得られた、Ｆｅ，Ｎｉ，Ｃｏの少なくとも１つ以上の元素を０以上０．５ｍｏｌ％以下含み、厚さが７ｍｍ以上である一致溶融組成タンタル酸リチウム単結晶が、気相平衡法により化学量論組成に改質されたものであることを特徴とする弾性表面波素子用化学量論組成タンタル酸リチウム単結晶。 A stoichiometric composition lithium tantalate single crystal for a surface acoustic wave device,
The stoichiometric lithium tantalate single crystal is obtained by a pulling method, contains at least one element of Fe, Ni, and Co and has a thickness of 7 mm or more containing 0 to 0.5 mol%. A stoichiometric composition lithium tantalate single crystal for a surface acoustic wave device, wherein the composition lithium tantalate single crystal is modified to a stoichiometric composition by a vapor phase equilibrium method.
前記複合圧電基板は、結晶方位が異なる２種類の請求項１又は請求項２に記載の弾性表面波素子用化学量論組成タンタル酸リチウム単結晶のウェーハ同士を接合してなるものであることを特徴とする弾性表面波素子用複合圧電基板。 A composite piezoelectric substrate for a surface acoustic wave device,
The composite piezoelectric substrate is formed by bonding two kinds of wafers of the stoichiometric composition lithium tantalate single crystal for surface acoustic wave elements according to claim 1 or 2 having different crystal orientations. A composite piezoelectric substrate for a surface acoustic wave device.
引き上げ法により、Ｆｅ，Ｎｉ，Ｃｏの少なくとも１つ以上の元素を０以上０．５ｍｏｌ％以下含む一致溶融組成タンタル酸リチウム単結晶を得て、該一致溶融組成タンタル酸リチウム単結晶の表面の粗さ指標Ｒｍａｘを１μｍ以上とし、該一致溶融組成タンタル酸リチウム単結晶を複数積層して積層体を形成し、該積層体を気相平衡法により化学量論組成に改質することで前記化学量論組成タンタル酸リチウム単結晶を製造することを特徴とする弾性表面波素子用化学量論組成タンタル酸リチウム単結晶の製造方法。 A method for producing a stoichiometric lithium tantalate single crystal for a surface acoustic wave device, comprising:
By a pulling method, a conformal molten composition lithium tantalate single crystal containing at least one element of Fe, Ni, Co and 0 to 0.5 mol% is obtained, and the surface of the conformal melt composition lithium tantalate single crystal is roughened. A thickness index Rmax is set to 1 μm or more, a plurality of the coincidence melt composition lithium tantalate single crystals are stacked to form a stack, and the stack is modified to a stoichiometric composition by a vapor phase equilibrium method. A method for producing a stoichiometric lithium tantalate single crystal for a surface acoustic wave device, comprising producing a stoichiometric lithium tantalate single crystal.
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| WO2015170656A1 (en) * | 2014-05-09 | 2015-11-12 | 信越化学工業株式会社 | Piezoelectric oxide single crystal substrate |
| WO2016167165A1 (en) * | 2015-04-16 | 2016-10-20 | 信越化学工業株式会社 | Lithium tantalate single-crystal substrate and joined substrate thereof, method for manufacturing same, and elastic surface wave device using joined substrate |
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