JP2002009584A - Surface acoustic wave device - Google Patents
Surface acoustic wave deviceInfo
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- JP2002009584A JP2002009584A JP2000194887A JP2000194887A JP2002009584A JP 2002009584 A JP2002009584 A JP 2002009584A JP 2000194887 A JP2000194887 A JP 2000194887A JP 2000194887 A JP2000194887 A JP 2000194887A JP 2002009584 A JP2002009584 A JP 2002009584A
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- acoustic wave
- surface acoustic
- wave device
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は携帯電話等に用いら
れる弾性表面波を用いる素子およびその基板の製造方法
に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device using a surface acoustic wave used in a cellular phone and the like, and a method of manufacturing a substrate thereof.
【０００２】[0002]
【従来の技術】携帯電話等に用いられる弾性表面波素子
は、例えば、電子情報通信学会論文誌Ａ，Ｊ７６巻−
Ａ，２号、１８５−１９２頁（１９９３年２月）に示さ
れているように、タンタル酸リチウム基板、ニオブ酸リ
チウム基板および四ホウ酸リチウム基板などの単結晶圧
電基板上に金属薄膜の櫛形交差電極を形成して構成され
ている。2. Description of the Related Art A surface acoustic wave element used for a cellular phone or the like is disclosed in, for example, IEICE Transactions A, J76-
A, No. 2, pp. 185-192 (February 1993), a comb-like metal thin film formed on a single-crystal piezoelectric substrate such as a lithium tantalate substrate, a lithium niobate substrate, and a lithium tetraborate substrate. It is configured by forming cross electrodes.
【０００３】携帯電話等の高性能化に伴い、それらに用
いる弾性表面波素子用基板の遅延時間温度係数を改善さ
せた報告がなされている。例えば、特開平１１−５５０
７０号に示されているように単結晶圧電基板とガラス基
板を直接接合させた事例がある。さらに、第２０回超音
波シンポジウム予稿集５１頁（１９９９年１１月）に示
されているように単結晶圧電基板とマイナス膨張ガラス
を紫外線硬化型樹脂で接合させた事例がある。As the performance of mobile phones and the like has been improved, reports have been made on the improvement of the temperature coefficient of delay time of a substrate for a surface acoustic wave device used for them. For example, JP-A-11-550
As shown in No. 70, there is an example in which a single crystal piezoelectric substrate and a glass substrate are directly bonded. Further, as shown in the 20th Ultrasonic Symposium Proceedings, p. 51 (November 1999), there is a case where a single-crystal piezoelectric substrate and minus-expandable glass are joined by an ultraviolet curing resin.
【０００４】[0004]
【発明が解決しようとする課題】携帯電話等は、近年の
急速な市場拡大から、送受信の各周波数帯域がより拡大
される傾向にあり、送信帯域と受信帯域の周波数間隔が
非常に狭いシステムも存在している。このことから携帯
電話等に内蔵される各種デバイスに対しても、より一層
の高性能化が要求されている。特にタンタル酸リチウム
基板あるいはニオブ酸リチウム基板等の単結晶圧電基板
上に金属薄膜の櫛形交差電極を形成する従来の弾性表面
波素子では、遅延時間温度係数が大きい場合、帯域間減
衰量が十分に取れないため重大な課題となる。With the rapid market expansion in recent years, portable telephones and the like tend to have more and more frequency bands for transmission and reception, and there are also systems where the frequency interval between the transmission band and the reception band is very narrow. Existing. For this reason, various devices incorporated in mobile phones and the like are required to have higher performance. In particular, in the case of a conventional surface acoustic wave element in which a comb-shaped cross electrode of a metal thin film is formed on a single crystal piezoelectric substrate such as a lithium tantalate substrate or a lithium niobate substrate, if the delay time temperature coefficient is large, the inter-band attenuation is sufficient. It is a serious issue because it cannot be taken.
【０００５】弾性表面波素子の遅延時間温度係数は、単
結晶圧電基板の線熱膨張係数と弾性表面波伝搬速度の温
度係数との差によって決定される。これらの値は単結晶
圧電基板固有の値であり、線熱膨張係数に関して言え
ば、例えばＸ軸を中心にＹ軸からＺ軸方向に３６°〜４
６°の角度で回転された面方位を持つタンタル酸リチウ
ム基板のＸ軸、すなわち弾性表面波伝搬方向では約１
６．１ｐｐｍ／℃、またＸ軸を中心にＹ軸からＺ軸方向
に６４°の角度で回転された面方位を持つニオブ酸リチ
ウム基板のＸ軸すなわち弾性表面波伝搬方向では約１
５．４ｐｐｍ／℃と大きい。今後、弾性表面波素子の性
能向上を図る上でこの点が障害となっている。[0005] The temperature coefficient of the delay time of the surface acoustic wave element is determined by the difference between the linear thermal expansion coefficient of the single crystal piezoelectric substrate and the temperature coefficient of the surface acoustic wave propagation velocity. These values are specific to the single-crystal piezoelectric substrate, and in terms of the linear thermal expansion coefficient, for example, 36 ° to 4 ° from the Y axis to the Z axis around the X axis.
The X axis of the lithium tantalate substrate having a plane orientation rotated at an angle of 6 °, that is, about 1 in the surface acoustic wave propagation direction.
6.1 ppm / ° C., and about 1 in the X-axis of the lithium niobate substrate having a plane orientation rotated at an angle of 64 ° from the Y-axis to the Z-axis about the X-axis, that is, the surface acoustic wave propagation direction.
It is as large as 5.4 ppm / ° C. This will be an obstacle in improving the performance of the surface acoustic wave device in the future.
【０００６】上記の課題を解決する方法として、単結晶
圧電基板に線熱膨張係数が小さいガラス基板を直接接合
した複合圧電基板を用いる方法がある。しかし、上記複
合圧電基板は材質の異なる基板を接合しているため、特
に基板接合界面でのバルク波反射の影響が大きく、弾性
表面波素子の特性を劣化させる問題（フィルタでは例え
ば帯域内リップル、あるいは帯域外のスプリアス応答
等）がある。As a method for solving the above problem, there is a method using a composite piezoelectric substrate in which a glass substrate having a small linear thermal expansion coefficient is directly joined to a single crystal piezoelectric substrate. However, since the composite piezoelectric substrate is formed by bonding substrates made of different materials, the influence of bulk wave reflection is particularly large at the bonding interface of the substrates, thereby deteriorating the characteristics of the surface acoustic wave element. Or out-of-band spurious responses).
【０００７】また、基板接合方法に関しては、前記直接
接合以外に、接着剤等を用いる方法もあるが、適用でき
る接着剤に耐熱性がなく、デバイスを形成する過程での
加熱処理時に問題が生じるおそれがある。As for the method of bonding the substrates, there is a method using an adhesive or the like other than the direct bonding. However, the applicable adhesive has no heat resistance and causes a problem during the heat treatment in the process of forming the device. There is a risk.
【０００８】本発明は、上記のような問題を考慮し、弾
性表面波を励振伝搬させる単結晶圧電基板の線熱膨張係
数を改善することによって、遅延時間温度係数が向上で
きる弾性表面波素子用基板、およびその弾性表面波素子
用基板上に弾性表面波素子を実現することを目的とす
る。SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-described problems, and is intended to improve a temperature coefficient of delay time by improving a linear thermal expansion coefficient of a single crystal piezoelectric substrate for exciting propagation of a surface acoustic wave. It is an object to realize a surface acoustic wave device on a substrate and a substrate for the surface acoustic wave device.
【０００９】すなわち、単結晶圧電基板の接合法に関し
ては、直接接合法において基板接合界面でのバルク波反
射の影響を抑えた良好な弾性表面波伝搬特性を実現する
ことを目的とし、また接着層を介して基板接合を行う方
法において基板接合後の櫛形交差電極の製造プロセス工
程に対して十分な耐熱性および耐薬品性を示す基板接合
を実現することを目的とする。That is, with respect to the bonding method of a single crystal piezoelectric substrate, it is an object of the present invention to realize good surface acoustic wave propagation characteristics in which the influence of bulk wave reflection at the substrate bonding interface is suppressed in the direct bonding method. It is an object of the present invention to realize a substrate bonding exhibiting sufficient heat resistance and chemical resistance with respect to a process of manufacturing a comb-shaped crossed electrode after the substrate bonding in a method of performing substrate bonding via the substrate.
【００１０】[0010]
【課題を解決するための手段】上記目的を達成するため
に、本発明による弾性表面波素子は、単結晶圧電基板で
ある第１の基板と、第１の基板に接合された第２の基板
と、第１の基板の第２の基板との接合面と反対側の面上
に形成され弾性表面波を励振伝搬する櫛型交差電極とを
備えた構造において、第１の基板の弾性表面波伝搬方向
を第２の基板の接合面内で最も線熱膨張係数の小さい方
向と平行にすることを特徴とする。In order to achieve the above object, a surface acoustic wave device according to the present invention comprises a first substrate which is a single crystal piezoelectric substrate and a second substrate which is joined to the first substrate. And a comb-shaped crossing electrode formed on a surface of the first substrate opposite to a bonding surface with the second substrate and configured to excite and propagate a surface acoustic wave. The propagation direction is parallel to the direction having the smallest linear thermal expansion coefficient in the bonding surface of the second substrate.
【００１１】上記において、第１と第２の基板が実質的
に接合層を介さず、直接接合される構成の場合、上記第
１と第２の基板の材質は、同じ材質であることが好まし
い。また、本発明による上記第１と第２の基板が異種材
料を接合した構成であるときには、耐熱性および耐薬品
性の問題を解決した基板接合を可能とするために、基板
の接合界面に塗布ガラスを主成分とする接着層を介する
ことが好ましい。In the above structure, when the first and second substrates are directly bonded without substantially interposing a bonding layer, the materials of the first and second substrates are preferably the same. . Further, when the first and second substrates according to the present invention have a configuration in which dissimilar materials are bonded, the first and second substrates are coated on the bonding interface of the substrates in order to enable the bonding of the substrates to solve the problems of heat resistance and chemical resistance. It is preferable to use an adhesive layer mainly composed of glass.
【００１２】[0012]
【発明の実施の形態】図１は本発明による弾性表面波素
子の第１の実施例を示す斜視図である。図の１は単結晶
圧電基板、２は上記基板１に接合された第２の基板、３
は上記基板１の、基板２との接合面と反対側の面上に形
成された櫛型交差電極である。本実施例において、基板
２の材質は基板１と同じであるが、基板１の弾性表面波
の伝搬方向（矢印４）における基板２の線熱膨張係数
は、基板１の同方向の線熱膨張係数より小さくなるよう
に接合されている。FIG. 1 is a perspective view showing a first embodiment of a surface acoustic wave device according to the present invention. 1 is a single-crystal piezoelectric substrate, 2 is a second substrate bonded to the substrate 1, and 3 is a single-crystal piezoelectric substrate.
Is a comb-shaped crossing electrode formed on the surface of the substrate 1 opposite to the bonding surface with the substrate 2. In this embodiment, the material of the substrate 2 is the same as that of the substrate 1, but the linear thermal expansion coefficient of the substrate 1 in the direction of propagation of the surface acoustic wave (arrow 4) is the linear thermal expansion of the substrate 1 in the same direction. It is joined so as to be smaller than the coefficient.
【００１３】本実施例における弾性表面波素子では、基
板１と基板２とが直接接合によって接合され、接合した
基板を弾性表面波素子用基板５として用いる。基板１上
に形成された櫛型交差電極３により励振された弾性表面
波は基板１上を伝搬し、弾性表面波素子として機能して
いる。櫛形交差電極３の電極指は基板１のＸ軸に対して
垂直方向に形成されているため、弾性表面波は基板１の
Ｘ軸に対して平行な方向に伝搬する。In the surface acoustic wave device according to this embodiment, the substrate 1 and the substrate 2 are joined by direct joining, and the joined substrate is used as the substrate 5 for the surface acoustic wave device. The surface acoustic wave excited by the comb-shaped cross electrodes 3 formed on the substrate 1 propagates on the substrate 1 and functions as a surface acoustic wave element. Since the electrode fingers of the interdigital transducer 3 are formed in a direction perpendicular to the X axis of the substrate 1, the surface acoustic waves propagate in a direction parallel to the X axis of the substrate 1.
【００１４】基板１上に金属薄膜の櫛形交差電極３を形
成した弾性表面波素子において遅延時間温度係数は、基
板１の弾性表面波伝搬方向４の線熱膨張係数と弾性表面
波伝搬速度の温度係数との差によって決定する。これら
の値は単結晶圧電基板固有の値であり、例えば、Ｘ軸を
中心にＹ軸からＺ軸方向に３６°〜４６°の角度で回転
された面方位を持つタンタル酸リチウム基板の弾性表面
波伝搬方向４（Ｘ軸方向）の線熱膨張係数は約１６．１
ｐｐｍ／℃と良好な数値ではない。In a surface acoustic wave device in which a comb-shaped cross electrode 3 of a metal thin film is formed on a substrate 1, the delay time temperature coefficient is determined by the linear thermal expansion coefficient of the substrate 1 in the surface acoustic wave propagation direction 4 and the temperature of the surface acoustic wave propagation velocity. Determined by the difference with the coefficient. These values are specific to the single-crystal piezoelectric substrate, and include, for example, the elastic surface of a lithium tantalate substrate having a plane orientation rotated at an angle of 36 ° to 46 ° from the Y axis to the Z axis around the X axis. The linear thermal expansion coefficient in the wave propagation direction 4 (X-axis direction) is about 16.1
ppm / ° C is not a good value.
【００１５】現在、弾性表面波素子に使用されている単
結晶圧電基板において、遅延時間温度係数が良好なもの
としては水晶基板がある。水晶基板の場合、弾性表面波
伝搬方向４の線熱膨張係数は約１３．７１ｐｐｍ／℃
と、けして良好な値ではないが、弾性表面波伝搬速度の
温度係数がタンタル酸リチウム基板やニオブ酸リチウム
基板などとは逆に正の値となる性質を持っているため、
線熱膨張係数の値が弾性表面波伝搬速度の温度係数の値
によって相殺され、遅延時間温度係数が小さな値を示
す。しかしながら、水晶基板は電気機械結合係数が小さ
く、十分な周波数帯域幅を得ることができないという欠
点がある。電気機械結合係数と遅延時間温度係数の両方
がともに良好な単結晶圧電基板は、現在のところ発見さ
れていない。At present, among the single crystal piezoelectric substrates used for the surface acoustic wave element, there is a quartz substrate having a good delay time temperature coefficient. In the case of a quartz substrate, the coefficient of linear thermal expansion in the surface acoustic wave propagation direction 4 is about 13.71 ppm / ° C.
Although it is not a good value, the temperature coefficient of the surface acoustic wave propagation velocity has the property of being a positive value contrary to lithium tantalate substrate, lithium niobate substrate, etc.
The value of the linear thermal expansion coefficient is offset by the value of the temperature coefficient of the surface acoustic wave propagation velocity, and the delay time temperature coefficient shows a small value. However, the quartz substrate has a drawback that the electromechanical coupling coefficient is small and a sufficient frequency bandwidth cannot be obtained. A single crystal piezoelectric substrate having both good electromechanical coupling coefficient and good delay time temperature coefficient has not been found so far.
【００１６】本実施例では、電気機械結合係数が大きい
単結晶圧電基板を用いて、遅延時間温度係数が小さい弾
性表面波素子を実現するために、単結晶圧電基板である
基板１の弾性表面波伝搬方向４と第２の基板２の線熱膨
張係数の小さい方向とを平行にして接合する。これによ
り、基板２の線熱膨張係数によって基板１の線熱膨張係
数が抑制され、遅延時間温度係数が改善される。In this embodiment, a single crystal piezoelectric substrate having a large electromechanical coupling coefficient is used to realize a surface acoustic wave device having a small delay time temperature coefficient. The joining is performed with the propagation direction 4 and the direction in which the coefficient of linear thermal expansion of the second substrate 2 is small being parallel. Thereby, the linear thermal expansion coefficient of the substrate 1 is suppressed by the linear thermal expansion coefficient of the substrate 2, and the delay time temperature coefficient is improved.
【００１７】図２は本実施例による基板１の面方位の一
例を示したものであり、図３は本実施例による基板２の
面方位の一例を示したものである。図３の矢印６は、第
２の基板の熱膨張係数が最も小さい方向を示す。ここで
は基板１としてＸ軸を中心にＹ軸からＺ軸方向に３６°
〜４６°の角度で回転された面方位を持つタンタル酸リ
チウム基板を用い、基板１と同じ材質からなる基板２と
してＹ軸方向の面方位を持つタンタル酸リチウム基板を
用いる。FIG. 2 shows an example of the plane orientation of the substrate 1 according to the present embodiment, and FIG. 3 shows an example of the plane orientation of the substrate 2 according to the present embodiment. Arrow 6 in FIG. 3 indicates the direction in which the thermal expansion coefficient of the second substrate is the smallest. Here, the substrate 1 is 36 ° from the Y axis to the Z axis around the X axis.
A lithium tantalate substrate having a plane orientation rotated by an angle of up to 46 ° is used, and a lithium tantalate substrate having a plane orientation in the Y-axis direction is used as a substrate 2 made of the same material as the substrate 1.
【００１８】図４は、基板１と基板２を接合させる場合
の接合方向を示した図である。ここで、基板１および基
板２の線熱膨張係数を考える。基板１であるＸ軸を中心
にＹ軸からＺ軸方向に３６°〜４６°の角度で回転され
た面方位を持つタンタル酸リチウム基板では、弾性表面
波の伝搬方向４であるＸ軸方向の線熱膨張係数が約１
６．１ｐｐｍ／℃である。これに対して、基板２である
Ｙ軸方向の面方位を持つタンタル酸リチウム基板の熱膨
張係数が非常に小さい方向（矢印６で示す。ここでは弾
性表面波の伝搬方向であるＸ軸方向に対して直交するＺ
軸方向）の線熱膨張係数は約４．１ｐｐｍ／℃と、この
面内で最も小さい。FIG. 4 is a view showing a joining direction when the substrate 1 and the substrate 2 are joined. Here, the linear thermal expansion coefficients of the substrate 1 and the substrate 2 are considered. In a lithium tantalate substrate having a plane orientation rotated at an angle of 36 ° to 46 ° from the Y axis to the Z axis centering on the X axis as the substrate 1, the X axis direction, which is the propagation direction 4 of the surface acoustic wave, is used. Linear thermal expansion coefficient is about 1
6.1 ppm / ° C. On the other hand, in the direction in which the thermal expansion coefficient of the lithium tantalate substrate having the plane orientation in the Y-axis direction as the substrate 2 is very small (indicated by an arrow 6; here, in the X-axis direction which is the propagation direction of the surface acoustic wave). Z orthogonal to
The coefficient of linear thermal expansion (axial direction) is about 4.1 ppm / ° C., which is the smallest in this plane.
【００１９】本発明によると図４に示すように、基板１
の弾性表面波伝搬方向４であるＸ軸方向と、基板２の線
熱膨張係数が非常に小さいＺ軸方向６を平行にして接合
することにより、基板１の線熱膨張係数が基板２の線熱
膨張係数によって抑制されるため、弾性表面波伝搬方向
４の線熱膨張係数を改善することができる。ただし、基
板１の線熱膨張係数がそのまま基板２の線熱膨張係数と
なるわけではなく、基板１と基板２の熱膨張差によって
接合面に生じる熱応力に準じた数値となるため、基板１
と基板２の基板厚さが重要となる。検討した結果、基板
２の厚さが基板１の厚さの３倍以上となるように基板１
を薄板化することにより、接合した弾性表面波素子用基
板５において弾性表面波伝搬方向の線熱膨張係数をより
顕著に改善できることが分かった。According to the present invention, as shown in FIG.
The X-axis direction which is the surface acoustic wave propagation direction 4 of the substrate 2 and the Z-axis direction 6 where the linear thermal expansion coefficient of the substrate 2 is very small are joined in parallel, so that the linear thermal expansion coefficient of the substrate 1 is Since the coefficient of thermal expansion is suppressed by the coefficient of thermal expansion, the coefficient of linear thermal expansion in the surface acoustic wave propagation direction 4 can be improved. However, the coefficient of linear thermal expansion of the substrate 1 does not directly become the coefficient of linear thermal expansion of the substrate 2, but becomes a numerical value according to the thermal stress generated on the bonding surface due to the difference in thermal expansion between the substrate 1 and the substrate 2.
The substrate thickness of the substrate 2 is important. As a result of the examination, the substrate 1 was set so that the thickness of the substrate 2 was three times or more the thickness of the substrate 1.
It has been found that by reducing the thickness of the substrate, the coefficient of linear thermal expansion in the surface acoustic wave propagation direction in the bonded surface acoustic wave element substrate 5 can be more remarkably improved.
【００２０】ここでは、基板１であるＸ軸を中心にＹ軸
からＺ軸方向に３６°〜４６°の角度で回転された面方
位を持つタンタル酸リチウム基板の板厚を９０μm、基
板２であるＹ軸方向の面方位を持つタンタル酸リチウム
基板の板厚を２７０μmとすることにより、Ｙ軸方向の
面方位を持つタンタル酸リチウム基板の線熱膨張係数が
支配的となり、線熱膨張係数が改善される。この場合の
遅延時間温度係数を測定した結果、２４ｐｐｍ／℃であ
った。基板接合を行わない従来の弾性表面波素子の遅延
時間温度係数は３３ｐｐｍ／℃であるから、本発明によ
り９ｐｐｍ／℃の改善効果があった。また、基板１の板
厚をより一層薄くすることで、より大きい効果が得られ
る。Here, the thickness of a lithium tantalate substrate having a plane orientation rotated at an angle of 36 ° to 46 ° from the Y axis to the Z axis around the X axis as the substrate 1 is 90 μm, By setting the thickness of the lithium tantalate substrate having a plane orientation in a certain Y-axis direction to 270 μm, the linear thermal expansion coefficient of the lithium tantalate substrate having a plane orientation in the Y-axis direction becomes dominant, and the linear thermal expansion coefficient becomes Be improved. As a result of measuring the delay time temperature coefficient in this case, it was 24 ppm / ° C. Since the delay time temperature coefficient of the conventional surface acoustic wave device without substrate bonding is 33 ppm / ° C., the present invention has an effect of improving 9 ppm / ° C. Further, by further reducing the thickness of the substrate 1, a greater effect can be obtained.
【００２１】また、本実施例によれば、接合された基板
１と基板２が同じ材質からなる構造、すなわち接合界面
における格子定数が同じとなる構造であるため、単結晶
圧電基板とガラス基板に代表されるような異種材料基板
の接合と比較して、より強力な接着力が実現できる。す
なわち、Ｘ軸を中心にＹ軸からＺ軸方向に３６°〜４６
°の角度で回転された面方位を持つタンタル酸リチウム
基板とＹ軸方向の面方位を持つタンタル酸リチウム基板
は同じ材質であることから、非常に強力な接着力の実現
が可能である。Further, according to the present embodiment, since the bonded substrate 1 and the substrate 2 have the same material, that is, the same lattice constant at the bonding interface, the single crystal piezoelectric substrate and the glass substrate have the same structure. Stronger adhesive strength can be realized as compared with the joining of dissimilar material substrates as represented. That is, from the Y axis to the Z axis in the direction of 36 ° to 46 ° around the X axis.
Since the lithium tantalate substrate having a plane orientation rotated by an angle of ° and the lithium tantalate substrate having a plane orientation in the Y-axis direction are made of the same material, it is possible to realize a very strong adhesive force.
【００２２】図５を用いて本実施例による基板接合界面
のバルク波反射の影響を説明する。基板２の厚さが基板
１の厚さの３倍以上となるように基板１の板厚を薄板化
すると、基板１の表面と基板接合界面とが接近するため
に（ａ）に示すようにバルク波７の基板接合界面からの
反射波８の影響がより大きくなる。しかしながら、本実
施例によれば（ｂ）に示すように、接合した基板１と基
板２が同じ材質からなる構造であるため、異種材料基板
を接合した場合と比較して、バルク波７の基板接合界面
からの反射波８の影響が小さくなる。The influence of the reflection of the bulk wave on the interface between the substrates according to the present embodiment will be described with reference to FIG. When the thickness of the substrate 1 is reduced so that the thickness of the substrate 2 becomes three times or more the thickness of the substrate 1, the surface of the substrate 1 and the substrate bonding interface come close to each other, as shown in FIG. The influence of the reflected wave 8 from the substrate bonding interface of the bulk wave 7 becomes larger. However, according to this embodiment, as shown in (b), the bonded substrate 1 and the substrate 2 have a structure made of the same material. The influence of the reflected wave 8 from the bonding interface is reduced.
【００２３】すなわち、Ｘ軸を中心にＹ軸からＺ軸方向
に３６°〜４６°の角度で回転された面方位を持つタン
タル酸リチウム基板とＹ軸方向の面方位を持つタンタル
酸リチウム基板は、同じ材質であることから接合界面で
の反射による影響が小さく、この構造を有する本実施例
の弾性表面波では接合界面からのバルク波反射による素
子特性の劣化を小さくすることができる。That is, a lithium tantalate substrate having a plane orientation rotated at an angle of 36 ° to 46 ° from the Y axis to a Z axis direction about the X axis and a lithium tantalate substrate having a plane orientation in the Y axis direction are: Since the same material is used, the influence of reflection at the bonding interface is small, and in the surface acoustic wave of this embodiment having this structure, deterioration of device characteristics due to bulk wave reflection from the bonding interface can be reduced.
【００２４】また、異種材料基板どうしを直接接合する
場合には、接合基板の線熱膨張係数の差やボイド部と接
合部との熱応力の不均一などにより、基板破損の問題が
生じやすいが、本実施例によれば、接合された基板１と
２が同じ材質であるため、異種材料基板の直接接合と比
較して基板破損の問題が生じにくい。When substrates of different materials are directly bonded to each other, a problem of substrate breakage is likely to occur due to a difference in linear thermal expansion coefficient of the bonded substrates or uneven thermal stress between the void portion and the bonded portion. According to the present embodiment, since the bonded substrates 1 and 2 are made of the same material, the problem of substrate breakage is less likely to occur as compared with the direct bonding of substrates of different materials.
【００２５】つぎに本発明の弾性表面波素子の製造方法
の一例を図６により説明する。例えば基板１として、Ｘ
軸を中心にＹ軸からＺ軸方向に３６°〜４６°の角度で
回転された面方位を持つ鏡面研磨されたタンタル酸リチ
ウム基板を用意する。また、基板２としてはＹ軸方向の
面方位を持つ鏡面研磨されたタンタル酸リチウム基板を
用意する。上記両者を接合する前処理として３００℃以
上の温度で１時間以上の熱処理を行う。これは基板１お
よび基板２の表面に付着しているガスや有機物を除去す
る目的で行う。この処理を怠ると基板接合後に接合界面
にボイドが発生する可能性がある。Next, an example of a method for manufacturing a surface acoustic wave device according to the present invention will be described with reference to FIG. For example, as the substrate 1, X
A mirror-polished lithium tantalate substrate having a plane orientation rotated at an angle of 36 ° to 46 ° from the Y axis to the Z axis around the axis is prepared. As the substrate 2, a mirror-polished lithium tantalate substrate having a plane orientation in the Y-axis direction is prepared. As a pretreatment for joining the two, a heat treatment is performed at a temperature of 300 ° C. or more for 1 hour or more. This is performed for the purpose of removing gases and organic substances attached to the surfaces of the substrate 1 and the substrate 2. If this treatment is neglected, voids may be generated at the bonding interface after bonding the substrates.
【００２６】次いで、接合する２枚のタンタル酸リチウ
ム基板を、過酸化水素（Ｈ2Ｏ2）とアンモニア水溶液
（ＮＨ4ＯＨ）と純水（Ｈ2Ｏ）を混合した溶液に約１０
分程度浸漬させた後、純水によるリンスを行う。これは
基板１および基板２の表面に親水性を持たせ、基板接合
時に基板表面に吸着されている水分子間に働くファンデ
ルワース力により結合させる効果がある。Next, the two lithium tantalate substrates to be joined are placed in a solution obtained by mixing hydrogen peroxide (H 2 O 2 ), an aqueous ammonia solution (NH 4 OH) and pure water (H 2 O).
After immersion for about a minute, rinsing with pure water is performed. This has the effect of imparting hydrophilicity to the surfaces of the substrate 1 and the substrate 2 and bonding them by the van der Waals force acting between the water molecules adsorbed on the substrate surface when the substrates are joined.
【００２７】その後、２枚のタンタル酸リチウム基板を
乾燥させた後、室温、空気雰囲気中で基板接合を行う。
ここではパーティクルフリーの接合界面を得ることが特
に重要であり、前記洗浄後、クラス１０以上のクリーン
度を持つクリーンルームで基板接合を行うことが望まし
い。また、接合直前に洗浄を行うことによりパーティク
ルフリーの界面と親水性を持った界面を両立させること
ができる。After drying the two lithium tantalate substrates, the substrates are joined at room temperature in an air atmosphere.
Here, it is particularly important to obtain a particle-free bonding interface, and it is desirable to bond the substrates in a clean room having a class 10 or higher cleanness after the above-mentioned cleaning. Further, by performing cleaning immediately before joining, both a particle-free interface and a hydrophilic interface can be achieved.
【００２８】その後、接合された２枚のタンタル酸リチ
ウム基板は基板２であるＹ軸方向の面方位を持つタンタ
ル酸リチウム基板の線熱膨張係数が支配的となるよう
に、基板１であるＸ軸を中心にＹ軸からＺ軸方向に３６
°〜４６°の角度で回転された面方位を持つタンタル酸
リチウム基板の薄板化を行う。基板研磨装置を用いて、
Ｘ軸を中心にＹ軸からＺ軸方向に３６°〜４６°の角度
で回転された面方位を持つタンタル酸リチウム基板の板
厚を、Ｙ軸方向の面方位を持つタンタル酸リチウム基板
の板厚に対して３分の１以下となるように研磨する。After that, the two lithium tantalate substrates joined together are made of the substrate 1 such that the linear thermal expansion coefficient of the lithium tantalate substrate having the plane orientation in the Y-axis direction becomes dominant. 36 from the Y axis to the Z axis around the axis
Thinning of a lithium tantalate substrate having a plane orientation rotated by an angle of ° to 46 ° is performed. Using a substrate polishing device,
The thickness of the lithium tantalate substrate having a plane orientation rotated at an angle of 36 ° to 46 ° in the Z axis direction from the Y axis about the X axis is determined by the thickness of the lithium tantalate substrate having the plane orientation in the Y axis direction. Polishing is performed so that the thickness is 1/3 or less.
【００２９】研磨工程は粗研磨から仕上げ研磨を段階的
に行い、鏡面研磨を実現する。このとき、ここに示した
ように基板接合後の研磨工程によって薄板化するのでは
なく、あらかじめＹ軸方向の面方位を持つタンタル酸リ
チウム基板に対して３分の１以下の板厚となるＸ軸を中
心にＹ軸からＺ軸方向に３６°〜４６°の角度で回転さ
れた面方位を持つタンタル酸リチウム基板を用意してか
ら接合してもよく、基板１の板厚が基板２の板厚に対し
て３分の１以下の板厚であれば製法は特に問わない。In the polishing step, mirror polishing is realized by performing stepwise from rough polishing to finish polishing. At this time, instead of being thinned by the polishing process after the bonding of the substrates as shown here, the thickness becomes less than one-third that of the lithium tantalate substrate having the plane orientation in the Y-axis direction in advance. A lithium tantalate substrate having a plane orientation rotated at an angle of 36 ° to 46 ° from the Y axis to the Z axis around the axis may be prepared and then joined. The manufacturing method is not particularly limited as long as the thickness is 1/3 or less of the thickness.
【００３０】基板１を薄板化した後、２５０℃の温度で
約２時間の熱処理を行うことにより２枚のタンタル酸リ
チウム基板は完全に接合される。その後、図７に示すよ
うな櫛形交差電極３を、基板２に接合された基板１上に
通常の電極作製工程を行って作製する。このとき櫛形交
差電極３により励振伝搬される弾性表面波が基板１の弾
性表面波伝搬方向（Ｘ軸方向）と一致するように櫛形交
差電極３を配置する。After the substrate 1 is thinned, a heat treatment is performed at a temperature of 250 ° C. for about 2 hours, whereby the two lithium tantalate substrates are completely joined. Thereafter, a comb-shaped cross electrode 3 as shown in FIG. 7 is manufactured by performing a normal electrode manufacturing process on the substrate 1 bonded to the substrate 2. At this time, the comb-shaped cross electrodes 3 are arranged so that the surface acoustic waves excited and propagated by the comb-shaped cross electrodes 3 coincide with the surface acoustic wave propagation direction (X-axis direction) of the substrate 1.
【００３１】上記、第１の実施例においては、基板１と
してＸ軸を中心にＹ軸からＺ軸方向に３６°〜４６°の
角度で回転された面方位を持つタンタル酸リチウム基
板、同じ材質からなる基板２としてＹ軸方向の面方位を
持つタンタル酸リチウム基板を用いた例について説明し
たが、基板２としてＸ軸方向の面方位を持つタンタル酸
リチウム基板を用いた場合も同様の効果がある。In the first embodiment, as the substrate 1, a lithium tantalate substrate having a plane orientation rotated at an angle of 36 ° to 46 ° from the Y axis to the Z axis around the X axis, and the same material An example in which a lithium tantalate substrate having a plane orientation in the Y-axis direction is used as the substrate 2 made of the above has been described. However, a similar effect can be obtained when a lithium tantalate substrate having a plane orientation in the X-axis direction is used as the substrate 2. is there.
【００３２】同様に、基板１としてＸ軸を中心にＹ軸か
らＺ軸方向に３６°〜４６°の角度で回転された面方位
を持つタンタル酸リチウム基板を用い、同じ材質からな
る基板２として基板１と同じ面方位を持つタンタル酸リ
チウム基板を用い、基板１のＸ軸方向が基板２のＸ軸方
向と直交するように接合した場合も同様の効果がある。Similarly, as the substrate 1, a lithium tantalate substrate having a plane orientation rotated at an angle of 36 ° to 46 ° from the Y axis to the Z axis around the X axis is used. The same effect can be obtained when a lithium tantalate substrate having the same plane orientation as the substrate 1 is used and bonded so that the X-axis direction of the substrate 1 is orthogonal to the X-axis direction of the substrate 2.
【００３３】同様に、基板１としてＸ軸方向の面方位を
持つタンタル酸リチウム基板を用い、同じ材質からなる
基板２としてＹ軸方向もしくはＸ軸方向の面方位を持つ
タンタル酸リチウム基板を用い、基板１の弾性表面波伝
搬方向４であるＹ軸からＺ軸方向に１１２°の角度で回
転された方向が基板２のＺ軸方向と平行となるように接
合した場合も同様の効果がある。Similarly, a lithium tantalate substrate having a plane orientation in the X-axis direction is used as the substrate 1, and a lithium tantalate substrate having a plane orientation in the Y-axis direction or the X-axis direction is used as the substrate 2 made of the same material. The same effect can be obtained when the substrate 1 is joined so that the direction rotated at an angle of 112 ° from the Y axis, which is the surface acoustic wave propagation direction 4 of the substrate 1, to the Z axis is parallel to the Z axis direction of the substrate 2.
【００３４】同様に、基板１としてＸ軸を中心にＹ軸か
らＺ軸方向に４１°〜６４°の角度で回転された面方位
を持つニオブ酸リチウム基板を用い、同じ材質からなる
基板２としてＹ軸方向もしくはＸ軸方向の面方位を持つ
ニオブ酸リチウム基板を用い、基板１のＸ軸方向が基板
２のＺ軸方向と平行するように接合した場合も同様の効
果がある。Similarly, as the substrate 1, a lithium niobate substrate having a plane orientation rotated at an angle of 41 ° to 64 ° from the Y axis to the Z axis around the X axis is used. The same effect is obtained when a lithium niobate substrate having a plane orientation in the Y-axis direction or the X-axis direction is used and the substrate 1 is bonded so that the X-axis direction of the substrate 1 is parallel to the Z-axis direction of the substrate 2.
【００３５】同様に、基板１としてＸ軸を中心にＹ軸か
らＺ軸方向に４１°〜６４°の角度で回転された面方位
を持つニオブ酸リチウム基板を用い、同じ材質からなる
基板２として基板１と同じ面方位を持つニオブ酸リチウ
ム基板を用い、基板１のＸ軸方向が基板２のＸ軸方向と
直交するように接合した場合も同様の効果がある。Similarly, as the substrate 1, a lithium niobate substrate having a plane orientation rotated at an angle of 41 ° to 64 ° from the Y axis to the Z axis around the X axis is used. The same effect can be obtained when a lithium niobate substrate having the same plane orientation as the substrate 1 is used and bonded so that the X-axis direction of the substrate 1 is orthogonal to the X-axis direction of the substrate 2.
【００３６】また、基板１として四ホウ酸リチウム基板
を用い、同じ材質からなる基板２として接合面内にｃ軸
を有する四ホウ酸リチウム基板を用い、基板１の弾性表
面波伝搬方向４が基板２のｃ軸方向と平行となるように
接合した弾性表面波素子用基板５においても同様の効果
がある。Further, a lithium tetraborate substrate is used as the substrate 1, a lithium tetraborate substrate having a c-axis in the bonding surface is used as the substrate 2 made of the same material, and the surface acoustic wave propagation direction 4 of the substrate 1 is The same effect is obtained in the surface acoustic wave element substrate 5 joined so as to be parallel to the c-axis direction of FIG.
【００３７】この場合の基板１および基板２の線熱膨張
係数を考えると、基板１である四ホウ酸リチウム基板の
ａ軸方向の線熱膨張係数が約１３ｐｐｍ／℃であるのに
対して、基板２である四ホウ酸リチウム基板のｃ軸の線
熱膨張係数は約−１．５ｐｐｍ／℃と負の線熱膨張係数
となる。よって、四ホウ酸リチウム基板のａ軸方向と四
ホウ酸リチウム基板のｃ軸方向が平行となるように基板
接合することにより、ａ軸方向の線熱膨張係数の約１３
ｐｐｍ／℃がｃ軸方向の線熱膨張係数の約−１．５ｐｐ
ｍ／℃によって抑制され、接合した弾性表面波素子用基
板５において弾性表面波伝搬方向の線熱膨張係数が改善
できる。Considering the linear thermal expansion coefficients of the substrate 1 and the substrate 2 in this case, the linear thermal expansion coefficient in the a-axis direction of the lithium tetraborate substrate as the substrate 1 is about 13 ppm / ° C. The linear thermal expansion coefficient of the c-axis of the lithium tetraborate substrate as the substrate 2 is about -1.5 ppm / ° C., which is a negative linear thermal expansion coefficient. Therefore, by bonding the substrates so that the a-axis direction of the lithium tetraborate substrate and the c-axis direction of the lithium tetraborate substrate are parallel, a linear thermal expansion coefficient of about 13 in the a-axis direction is obtained.
ppm / ° C is approximately -1.5 pp of the linear thermal expansion coefficient in the c-axis direction.
m / ° C., the coefficient of linear thermal expansion in the surface acoustic wave propagation direction can be improved in the bonded surface acoustic wave element substrate 5.
【００３８】つぎに、本発明の別の実施例を説明する。
図８は本発明による弾性表面波素子の第２の実施例を示
す斜視図である。図８に示す弾性表面波素子は単結晶圧
電基板である基板１と、基板１に接合された基板２と、
基板１の基板２との接合面と反対側の面上に形成され弾
性表面波を励振する櫛型交差電極３とを備えた弾性表面
波素子であり、基板１と基板２の接合には基板１と基板
２の接合界面に塗布ガラス（ＳＯＧ：Spin On Gras
s）を主成分とする接着層９を有している。Next, another embodiment of the present invention will be described.
FIG. 8 is a perspective view showing a second embodiment of the surface acoustic wave device according to the present invention. The surface acoustic wave device shown in FIG. 8 includes a substrate 1 which is a single crystal piezoelectric substrate, a substrate 2 bonded to the substrate 1,
A surface acoustic wave element comprising a comb-shaped cross electrode 3 formed on a surface of the substrate 1 opposite to a surface to be joined to the substrate 2 and exciting a surface acoustic wave. Coating glass (SOG: Spin On Gras)
and s) as the main component.
【００３９】基板１の弾性表面波の伝搬方向４における
基板２の線熱膨張係数は、基板１の同方向の線熱膨張係
数より小さくなるように接合されている。また、基板２
の厚さが基板１の厚さの３倍以上となるように基板１の
板厚が薄板化されている。接着層９として塗布ガラスを
用いて基板１と基板２を接合させた基板を弾性表面波素
子用基板５として用いる。基板１上に形成された櫛型交
差電極３により励振された弾性表面波は基板１上を伝搬
し、弾性表面波素子として機能する。The substrates 2 are joined so that the linear thermal expansion coefficient of the substrate 2 in the surface acoustic wave propagation direction 4 is smaller than the linear thermal expansion coefficient of the substrate 1 in the same direction. Also, the substrate 2
The thickness of the substrate 1 is reduced so that the thickness of the substrate 1 is three times or more the thickness of the substrate 1. A substrate in which the substrate 1 and the substrate 2 are bonded to each other using coated glass as the adhesive layer 9 is used as the substrate 5 for a surface acoustic wave device. The surface acoustic wave excited by the comb-shaped cross electrodes 3 formed on the substrate 1 propagates on the substrate 1 and functions as a surface acoustic wave element.
【００４０】接着層９として用いる塗布ガラスは酸化珪
素を主成分とする被膜を塗布・焼成法で形成することが
できるもので、珪素化合物を有機溶剤に溶解させたもの
である。ここでは基板１としてＸ軸を中心にＹ軸からＺ
軸方向に３６°〜４６°の角度で回転された面方位を持
つタンタル酸リチウム基板を用い、基板２として酸化珪
素基板を用いる。The coated glass used as the adhesive layer 9 can be formed by coating and baking a film containing silicon oxide as a main component, and is obtained by dissolving a silicon compound in an organic solvent. Here, the substrate 1 is Z-axis from the Y-axis around the X-axis.
A lithium tantalate substrate having a plane orientation rotated at an angle of 36 ° to 46 ° in the axial direction is used, and a silicon oxide substrate is used as the substrate 2.
【００４１】本実施例によれば、基板１と基板２の接合
において、接着層９として主成分が酸化珪素からなる塗
布ガラスを用いることにより、接着層９自体の遅延時間
温度係数が小さいことから、例えば紫外線硬化型樹脂等
を接着剤として用いた場合との比較において、接着層９
による遅延時間温度係数の悪化がないため、接合した弾
性表面波素子用基板５の弾性表面波伝搬方向４に対する
遅延時間温度係数がより改善される。また、塗布ガラス
は主成分が酸化珪素からなるため非常に硬度が高く、基
板１の熱膨張による応力が発生した場合にも、例えば紫
外線硬化型樹脂等と比べて圧電基板１の伸びを抑制する
ことができ、線熱膨張係数の改善にも効果的である。According to the present embodiment, when the substrate 1 and the substrate 2 are joined together, the adhesive layer 9 is made of coated glass whose main component is silicon oxide, so that the delay time temperature coefficient of the adhesive layer 9 itself is small. For example, in comparison with the case where an ultraviolet curable resin or the like is used as the adhesive, the adhesive layer 9
Therefore, the delay time temperature coefficient of the bonded surface acoustic wave element substrate 5 with respect to the surface acoustic wave propagation direction 4 is further improved. Further, since the main component of the coated glass is silicon oxide, the coated glass has a very high hardness and suppresses the elongation of the piezoelectric substrate 1 as compared with, for example, an ultraviolet curable resin or the like even when a stress occurs due to the thermal expansion of the substrate 1. It is also effective in improving the coefficient of linear thermal expansion.
【００４２】基板１と基板２を接合した弾性表面波素子
用基板５は基板接合後に弾性表面波素子を作製する製造
プロセスとして、前工程においては金属薄膜被着工程、
ホトリソグラフィー工程、エッチング工程、さらに後工
程においては半田リフロー工程などの熱処理を伴う工程
を有するため、耐熱性が重要となる。また、各工程にお
いて、有機および無機薬品なども使用されるため耐薬品
性も重要となる。よって、接着層９を用いて基板１と基
板２を接合させる場合には接着層９に耐熱性および耐薬
品性が必須となる。The surface acoustic wave element substrate 5 in which the substrate 1 and the substrate 2 are joined is a manufacturing process for fabricating the surface acoustic wave element after joining the substrates.
Since the photolithography process, the etching process, and the subsequent process include a process involving a heat treatment such as a solder reflow process, heat resistance is important. In each step, organic and inorganic chemicals are used, so that chemical resistance is also important. Therefore, when bonding the substrate 1 and the substrate 2 using the adhesive layer 9, the adhesive layer 9 must have heat resistance and chemical resistance.
【００４３】一例として、接着層９に紫外線硬化型樹脂
を用いた場合について説明する。基板２の接合面に紫外
線硬化型樹脂を塗布し基板接合を行った後、紫外線を照
射するだけで紫外線硬化型樹脂が硬化して基板接合が完
了するため、熱処理も不要な非常に簡便な基板接合法で
ある。しかし、紫外線硬化型樹脂の特性として耐薬品性
は十分であるが、耐熱性が１２０℃程度と低いため接着
層９としての適用は難しい。As an example, a case where an ultraviolet curable resin is used for the adhesive layer 9 will be described. After applying an ultraviolet-curing resin to the bonding surface of the substrate 2 and bonding the substrates, the ultraviolet-curing resin is cured only by irradiating ultraviolet rays to complete the bonding of the substrates. It is a joining method. However, the UV-curable resin has sufficient chemical resistance as a characteristic, but is difficult to apply as the adhesive layer 9 because its heat resistance is as low as about 120 ° C.
【００４４】別の例として、接着層９に熱硬化型樹脂を
用いた場合について説明する。基板２の接合面に熱硬化
型樹脂を塗布し、熱処理により溶剤を揮発させ硬化させ
た後、熱硬化型樹脂が塗布された基板２を再び加熱し、
熱硬化型樹脂を軟化させた状態で基板１を接合し、基板
接合後に冷却することにより熱硬化型樹脂を硬化させ、
接合が完了する。しかし、熱硬化型樹脂の特性としては
耐薬品性が脆弱で、さらに基板接合後の再加熱により軟
化することもあるため接着層９としての適用は難しい。As another example, a case where a thermosetting resin is used for the adhesive layer 9 will be described. A thermosetting resin is applied to the bonding surface of the substrate 2, the solvent is volatilized by heat treatment and cured, and then the substrate 2 on which the thermosetting resin is applied is heated again,
The substrate 1 is joined in a state where the thermosetting resin is softened, and the thermosetting resin is cured by cooling after joining the substrates,
Joining is completed. However, it is difficult to apply the thermosetting resin as the adhesive layer 9 because the thermosetting resin has weak chemical resistance and may be softened by reheating after joining the substrates.
【００４５】さらに別の例として、接着層９に接着用ワ
ックスを用いた場合について説明する。ホットプレート
などで加熱した基板２の接合面に接着用ワックスを塗
り、接着用ワックスが溶けた状態で基板１を接合した
後、冷却することにより接着用ワックスを硬化させ、接
合が完了するという非常に簡便な基板接合方法である。
しかしながら、接着用ワックスの特性としては耐熱性が
低いことにくわえて、アルコールでも溶けるほど耐薬品
性がないため接着層９としての適用は難しい。As another example, a case where an adhesive wax is used for the adhesive layer 9 will be described. An adhesive wax is applied to the bonding surface of the substrate 2 heated by a hot plate or the like, and the substrate 1 is bonded in a state where the bonding wax is melted. Then, the bonding wax is cured by cooling, and the bonding is completed. This is a simple and easy substrate bonding method.
However, in addition to the low heat resistance of the adhesive wax, it is difficult to apply it as the adhesive layer 9 because it does not have chemical resistance enough to dissolve in alcohol.
【００４６】本実施例において、基板１と基板２を接合
する際に接着層９として用いる主成分が酸化珪素からな
る塗布ガラスは、４００℃以上の熱処理においても十分
な耐熱性を示し、また耐薬品性に関しても酸化珪素に準
じた高い耐性を示すため、前記紫外線硬化型樹脂、熱硬
化型樹脂、接着用ワックス等を接着層に使用した場合と
比較するまでもなく、櫛形交差電極３の製造プロセス工
程、半田リフロー工程等に対しても十分な耐熱性、耐薬
品性を示し、強力な接着力が維持できる。In this embodiment, the coated glass mainly composed of silicon oxide used as the adhesive layer 9 when joining the substrate 1 and the substrate 2 shows sufficient heat resistance even at a heat treatment of 400 ° C. or more. In view of the chemical resistance, which is as high as silicon oxide, the comb-shaped crossed electrode 3 can be manufactured without being compared with the case where the ultraviolet curing resin, the thermosetting resin, the bonding wax, or the like is used for the bonding layer. Shows sufficient heat resistance and chemical resistance even in process steps, solder reflow steps, etc., and can maintain strong adhesive strength.
【００４７】弾性表面波素子の遅延時間温度係数は、前
述のとおり単結晶圧電基板の弾性表面波伝搬方向４の線
熱膨張係数と弾性表面波伝搬速度の温度係数との差によ
って決定する。ここで弾性表面波伝搬速度の温度係数に
着目すると、タンタル酸リチウム基板やニオブ酸リチウ
ム基板等では負の値となる性質を持っているため、線熱
膨張係数との差により決まる遅延時間温度係数はより悪
化する。As described above, the delay time temperature coefficient of the surface acoustic wave element is determined by the difference between the linear thermal expansion coefficient of the single crystal piezoelectric substrate in the surface acoustic wave propagation direction 4 and the temperature coefficient of the surface acoustic wave propagation velocity. Focusing on the temperature coefficient of the surface acoustic wave propagation velocity, since the lithium tantalate substrate, lithium niobate substrate, and the like have a negative value, the delay time temperature coefficient determined by the difference from the linear thermal expansion coefficient Is worse.
【００４８】これに対して、本実施例において接着層９
として用いる塗布ガラスは主成分が酸化珪素からなるた
め、弾性表面波伝搬速度の温度係数が正の値となり、線
熱膨張係数との差により決まる遅延時間温度係数は向上
する。塗布ガラスが有するこの性質を利用することによ
り、基板１の線熱膨張係数の値を接着層９の塗布ガラス
が有する弾性表面波伝搬速度の温度係数の値によって相
殺することが可能である。On the other hand, in the present embodiment, the adhesive layer 9
Since the main component of the coated glass used is silicon oxide, the temperature coefficient of the surface acoustic wave propagation velocity becomes a positive value, and the delay time temperature coefficient determined by the difference from the linear thermal expansion coefficient is improved. By utilizing this property of the applied glass, the value of the linear thermal expansion coefficient of the substrate 1 can be offset by the value of the temperature coefficient of the surface acoustic wave propagation velocity of the applied glass of the adhesive layer 9.
【００４９】つまり、塗布ガラスを主成分とする接着層
９が有する弾性波伝搬速度の温度係数が、基板１の弾性
波表面波伝搬方向４の熱膨張係数を相殺する値となるよ
うに、接着層９の膜厚を最適化することにより、接合し
た弾性表面波素子用基板５の弾性表面波伝搬方向４の遅
延時間温度係数が改善できることになる。That is, the adhesive layer 9 mainly composed of coated glass has an adhesive layer 9 so that the temperature coefficient of the elastic wave propagation velocity has a value that offsets the thermal expansion coefficient of the substrate 1 in the acoustic wave surface wave propagation direction 4. By optimizing the film thickness of the layer 9, the delay time temperature coefficient of the bonded surface acoustic wave element substrate 5 in the surface acoustic wave propagation direction 4 can be improved.
【００５０】また本実施例として、基板１と基板２の接
合界面に塗布ガラスを主成分とする接着層９を有する弾
性表面波素子用基板５において、基板２として接合面内
にｃ軸を有する四ホウ酸リチウム基板を用い、基板１の
弾性表面波伝搬方向４が基板２のｃ軸と平行となるよう
に接合することにより、接合した弾性表面波素子用基板
５において弾性表面波伝搬方向４の線熱膨張係数が改善
できる。In this embodiment, a substrate 5 for a surface acoustic wave device having an adhesive layer 9 mainly composed of coated glass at a bonding interface between the substrate 1 and the substrate 2 has a c-axis in the bonding surface as the substrate 2. By using a lithium tetraborate substrate and joining the surface acoustic wave propagation direction 4 of the substrate 1 so as to be parallel to the c-axis of the substrate 2, the surface acoustic wave propagation direction 4 Can have an improved linear thermal expansion coefficient.
【００５１】四ホウ酸リチウム基板のｃ軸の線熱膨張係
数は前述のように約−１．５ｐｐｍ／℃と負の線熱膨張
係数を示すため、基板１の線熱膨張係数がより大きく改
善できるためである。Since the linear thermal expansion coefficient of the c-axis of the lithium tetraborate substrate is a negative linear thermal expansion coefficient of about -1.5 ppm / ° C. as described above, the linear thermal expansion coefficient of the substrate 1 is further improved. This is because it can be done.
【００５２】また本実施例の別の実施形態として、単結
晶圧電基板である基板１と、基板１に塗布ガラスを主成
分とする接着層９により接合された基板２と、基板１の
基板２との接合面と反対側の面上に形成され弾性表面波
を励振する櫛型交差電極３とを備えた弾性表面波素子に
おいて、基板２として弾性表面波伝搬速度が非常に高速
であるダイアモンド基板を用いると、接合した基板１上
に形成された弾性表面波素子において励振伝搬される弾
性表面波の伝搬速度が速くなるため、高周波化に対して
効果がある。さらに、基板２に用いたダイアモンド基板
には熱伝導性が非常に高いという性質もあるため、弾性
表面波素子の熱伝導率が高くなり、櫛形交差電極３の耐
電力性も向上できる。As another embodiment of the present embodiment, a substrate 1 which is a single crystal piezoelectric substrate, a substrate 2 joined to the substrate 1 by an adhesive layer 9 mainly composed of coated glass, and a substrate 2 of the substrate 1 A surface acoustic wave element having a comb-shaped cross electrode 3 formed on a surface opposite to a bonding surface with the substrate and having a comb-shaped cross electrode 3 for exciting a surface acoustic wave, wherein the substrate 2 has a very high surface acoustic wave propagation speed. When the surface acoustic wave element formed on the bonded substrate 1 is used, the propagation speed of the surface acoustic wave excited and propagated in the surface acoustic wave element formed on the bonded substrate 1 is increased, which is effective in increasing the frequency. Further, the diamond substrate used as the substrate 2 has a property that the thermal conductivity is very high, so that the thermal conductivity of the surface acoustic wave element is increased, and the power durability of the interdigital transducer 3 can be improved.
【００５３】つぎに本実施例の弾性表面波素子の製造方
法の一例を図９により説明する。例えば基板１として用
いる鏡面研磨されたＸ軸を中心にＹ軸からＺ軸方向に３
６°〜４６°の角度で回転された面方位を持つタンタル
酸リチウム基板と、基板２として用いる鏡面研磨された
ダイアモンド基板を、接合の前処理として３００℃以上
の温度で１時間以上の熱処理を行う。Next, an example of a method for manufacturing the surface acoustic wave device of this embodiment will be described with reference to FIG. For example, the center of the mirror-polished X-axis used as the substrate 1 is shifted from the Y-axis to the Z-axis by 3
A lithium tantalate substrate having a plane orientation rotated at an angle of 6 ° to 46 ° and a mirror-polished diamond substrate used as the substrate 2 are subjected to a heat treatment at a temperature of 300 ° C. or more for 1 hour or more as a pretreatment for bonding. Do.
【００５４】次いで、接合するタンタル酸リチウム基板
とダイアモンド基板を過酸化水素（Ｈ2Ｏ2）とアンモニ
ア水溶液（ＮＨ4ＯＨ）と純水（Ｈ2Ｏ）を混合した溶液
に約１０分程度浸漬させた後、純水によるリンスを行
う。２枚の基板を乾燥させた後、接着層９として塗布ガ
ラスを介して基板接合する工程を行う。まずダイアモン
ド基板の接合面に塗布ガラスを回転塗布する。Next, the lithium tantalate substrate and the diamond substrate to be bonded are immersed in a solution obtained by mixing hydrogen peroxide (H 2 O 2 ), an aqueous ammonia solution (NH 4 OH) and pure water (H 2 O) for about 10 minutes. After that, rinsing with pure water is performed. After the two substrates are dried, a step of bonding the substrates as a bonding layer 9 via a coating glass is performed. First, a coating glass is spin-coated on the bonding surface of the diamond substrate.
【００５５】その後、塗布ガラスを塗布したダイアモン
ド基板を８０℃程度に加熱したホットプレート上で５分
程度加熱する。これは塗布ガラスの溶媒である有機溶剤
を蒸発させるために行なう。５分間程度加熱した後、ホ
ットプレート上でタンタル酸リチウム基板の接合面とダ
イアモンド基板の塗布ガラス塗布面とを接合させる。こ
こではパーティクルフリーの接合界面を得ることが特に
重要であり、クラス１０以上のクリーン度を持つクリー
ンルームで基板接合を行うことが望ましい。Thereafter, the diamond substrate coated with the coated glass is heated on a hot plate heated to about 80 ° C. for about 5 minutes. This is performed in order to evaporate the organic solvent which is the solvent of the coated glass. After heating for about 5 minutes, the bonding surface of the lithium tantalate substrate and the coated glass-coated surface of the diamond substrate are bonded on a hot plate. Here, it is particularly important to obtain a particle-free bonding interface, and it is desirable to bond the substrates in a clean room having a class 10 or higher cleanness.
【００５６】基板接合後、タンタル酸リチウム基板とダ
イアモンド基板に圧力をかけることで基板接合界面の気
泡を完全に除去する。その後、接合された弾性表面波素
子用基板５は、ダイアモンド基板の線熱膨張係数が支配
的となるようにタンタル酸リチウム基板１の薄板化を行
う。基板研磨装置（図示せず）を用いて、タンタル酸リ
チウム基板１の板厚をダイアモンド基板２の板厚に対し
て３分の１以下となるように研磨する。上記研磨工程
は、粗研磨から仕上げ研磨を段階的に行い、鏡面研磨を
実現する。なお、基板の薄膜化に関しては前記の方法に
こだわるものではなく、基板１の板厚が基板２の板厚に
対して３分の１以下の板厚であれば製法は特に問わな
い。After bonding the substrates, pressure is applied to the lithium tantalate substrate and the diamond substrate to completely remove bubbles at the interface between the substrates. Thereafter, in the surface acoustic wave element substrate 5 bonded, the lithium tantalate substrate 1 is thinned so that the linear thermal expansion coefficient of the diamond substrate becomes dominant. Polishing is performed using a substrate polishing apparatus (not shown) so that the thickness of the lithium tantalate substrate 1 is one third or less of the thickness of the diamond substrate 2. In the polishing step, mirror polishing is realized by performing rough polishing to finish polishing stepwise. The method of thinning the substrate is not limited to the above-described method, and the manufacturing method is not particularly limited as long as the thickness of the substrate 1 is one third or less of the thickness of the substrate 2.
【００５７】タンタル酸リチウム基板を薄板化した後、
１５０℃の温度で２０分の熱処理を行い、さらに２００
℃の温度で約１時間程度の熱処理を行なうことにより、
２枚の基板は完全に接合される。After thinning the lithium tantalate substrate,
A heat treatment at a temperature of 150 ° C. for 20 minutes is performed,
By performing a heat treatment at a temperature of about 1 hour for about 1 hour,
The two substrates are completely bonded.
【００５８】その後、図１０に示すような櫛形交差電極
３を、塗布ガラスによる接着層９を介してダイアモンド
基板２に接合されたタンタル酸リチウム基板１上に、通
常の電極作製工程を行って作製する。このとき櫛形交差
電極３により励振伝搬される弾性表面波が基板１の弾性
表面波伝搬方向４（Ｘ軸方向）と一致するように櫛形交
差電極３を配置する。Thereafter, a comb-shaped cross electrode 3 as shown in FIG. 10 is formed on the lithium tantalate substrate 1 bonded to the diamond substrate 2 via the adhesive layer 9 made of coated glass by performing a normal electrode forming process. I do. At this time, the interdigital transducer 3 is arranged such that the surface acoustic wave excited and propagated by the interdigital transducer 3 coincides with the surface acoustic wave propagation direction 4 (X-axis direction) of the substrate 1.
【００５９】上記第２の実施例は、基板１としてＸ軸を
中心にＹ軸からＺ軸方向に３６°〜４６°の角度で回転
された面方位を持つタンタル酸リチウム基板について説
明したが、基板１としてＸ軸を面方位とするタンタル酸
リチウム、もしくはＸ軸を中心にＹ軸からＺ軸方向に４
１〜６４°の範囲の角度で回転された面方位を有するニ
オブ酸リチウム基板を用いた場合も同様の効果がある。In the second embodiment, a lithium tantalate substrate having a plane orientation rotated at an angle of 36 ° to 46 ° from the Y axis to the Z axis around the X axis as the substrate 1 has been described. Lithium tantalate having a plane orientation of the X axis as the substrate 1, or 4 from the Y axis to the Z axis around the X axis.
The same effect is obtained when a lithium niobate substrate having a plane orientation rotated at an angle in the range of 1 to 64 ° is used.
【００６０】また上記第２の実施例は、基板２として酸
化珪素基板、ダイアモンド基板および四ホウ酸リチウム
基板について説明したが、窒化アルミニウム、珪素、窒
化珪素、硼素、酸化硼素、窒化硼素、タンタル酸リチウ
ム、ニオブ酸リチウム、またはそれらの複合材料による
基板においても同様な効果がある。In the second embodiment, a silicon oxide substrate, a diamond substrate and a lithium tetraborate substrate have been described as the substrate 2. However, aluminum nitride, silicon, silicon nitride, boron, boron oxide, boron nitride, tantalum acid Similar effects are obtained with a substrate made of lithium, lithium niobate, or a composite material thereof.
【００６１】[0061]
【発明の効果】以上に説明したように、本発明において
弾性表面波を励振伝搬させる第１の基板の弾性波表面波
伝搬方向と、第１の基板と同じ材料からなる第２の基板
の接合面内で最も熱膨張係数の小さい方向とを平行にし
て接合する構造を提案した。これにより、線熱膨張係数
が改善され、遅延時間温度係数が小さい弾性表面波素子
の作製が可能となる。As described above, in the present invention, the direction of propagation of the surface acoustic wave of the first substrate for exciting and propagating the surface acoustic wave is joined to the bonding of the second substrate made of the same material as the first substrate. A structure in which the direction in which the coefficient of thermal expansion is the smallest in the plane is parallel to each other is proposed. As a result, the coefficient of linear thermal expansion is improved, and a surface acoustic wave device having a small delay time temperature coefficient can be manufactured.
【００６２】また、接合した第１の基板と第２の基板が
同じ材質からなる構造であることから、非常に強力な接
着力の実現でき、さらには接合界面でのバルク波反射の
影響が小さい弾性表面波素子の作製が可能となる。ま
た、同種材料基板どうしを直接接合することにより、異
種材料基板を直接接合する場合と比較して基板破損の発
生が減少するという効果もある。Further, since the bonded first substrate and second substrate are made of the same material, a very strong adhesive force can be realized, and the influence of bulk wave reflection at the bonding interface is small. It is possible to manufacture a surface acoustic wave device. Further, by directly bonding substrates of the same material, there is also an effect that occurrence of substrate damage is reduced as compared with a case of directly bonding substrates of different materials.
【００６３】また、本発明において、第１の基板と第２
の基板の接合に、塗布ガラスを接着層として用いる方法
を提案した。塗布ガラスを用いることにより、耐熱性、
耐薬品性を有する基板接合が簡便かつ安価な方法により
実現が可能となり、線熱膨張係数の小さい基板、弾性表
面波伝搬速度の速い基板、および熱伝導率が高い基板な
ど、あらゆる特性を持つ基板を第２の基板として用いる
ことができるため弾性表面波素子の特性改善が可能とな
る。In the present invention, the first substrate and the second substrate
A method using a coated glass as an adhesive layer was proposed for bonding substrates. By using coated glass, heat resistance,
Substrate with all characteristics, such as a substrate with low linear thermal expansion coefficient, a substrate with high surface acoustic wave propagation speed, and a substrate with high thermal conductivity. Can be used as the second substrate, so that the characteristics of the surface acoustic wave element can be improved.
【図１】本発明の第１の実施例による弾性表面波素子の
斜視図。FIG. 1 is a perspective view of a surface acoustic wave device according to a first embodiment of the present invention.
【図２】本発明の第１の実施例による第１の基板の面方
位の一例を示す説明図。FIG. 2 is an explanatory diagram showing an example of a plane orientation of a first substrate according to the first embodiment of the present invention.
【図３】本発明の第１の実施例による第２の基板の面方
位の一例を示す説明図。FIG. 3 is an explanatory diagram showing an example of a plane orientation of a second substrate according to the first embodiment of the present invention.
【図４】本発明の第１の実施例による弾性表面波素子用
基板の接合方向を示す説明図。FIG. 4 is an explanatory view showing a bonding direction of the surface acoustic wave element substrate according to the first embodiment of the present invention.
【図５】弾性表面波素子用基板の接合界面でのバルク波
反射を示す説明図。FIG. 5 is an explanatory view showing bulk wave reflection at a bonding interface of a surface acoustic wave element substrate.
【図６】本発明の第１の実施例による弾性表面波素子用
基板の製造工程を示す断面図。FIG. 6 is a sectional view showing a manufacturing process of the surface acoustic wave element substrate according to the first embodiment of the present invention.
【図７】本発明の第１の実施例による弾性表面波素子の
断面図。FIG. 7 is a sectional view of the surface acoustic wave device according to the first embodiment of the present invention.
【図８】本発明の第２の実施例による弾性表面波素子の
斜視図。FIG. 8 is a perspective view of a surface acoustic wave device according to a second embodiment of the present invention.
【図９】本発明の第２の実施例による弾性表面波素子用
基板の製造工程を示す断面図。FIG. 9 is a sectional view showing a manufacturing process of the surface acoustic wave element substrate according to the second embodiment of the present invention.
【図１０】本発明の第２の実施例による弾性表面波素子
の断面図。FIG. 10 is a sectional view of a surface acoustic wave device according to a second embodiment of the present invention.
１…第１の基板、２…第２の基板、３…櫛形交差電極、
４…第１の基板の弾性表面波伝搬方向、５…弾性表面波
素子用基板、６…第２の基板の熱膨張係数が最も小さい
方向、７…バルク波、８…反射波、９…接着層。DESCRIPTION OF SYMBOLS 1 ... 1st board | substrate, 2 ... 2nd board | substrate, 3 ... comb-shaped crossing electrode,
4: the direction of propagation of the surface acoustic wave of the first substrate, 5: the substrate for the surface acoustic wave element, 6: the direction of the smallest thermal expansion coefficient of the second substrate, 7: bulk wave, 8: reflected wave, 9: adhesion layer.
フロントページの続き (72)発明者 礒部 敦 東京都国分寺市東恋ケ窪一丁目280番地 株式会社日立製作所中央研究所内 Ｆターム(参考） 5J097 AA16 AA22 EE08 FF01 GG01 GG03 GG04 GG05 HA03 KK09 KK10 Continuation of the front page (72) Inventor Atsushi Isobe 1-280 Higashi Koigakubo, Kokubunji-shi, Tokyo F-term in Central Research Laboratory, Hitachi, Ltd. 5J097 AA16 AA22 EE08 FF01 GG01 GG03 GG04 GG05 HA03 KK09 KK10
Claims (16)
第１の基板に接合された第２の基板と、前記第１の基板
の前記第２の基板との接合面と反対側の面上に形成され
弾性波を励振する櫛型交差電極とを備えた弾性表面波素
子において、前記第２の基板は前記第１の基板と同一材
質の基板であり、前記第１の基板の前記弾性波の伝搬方
向における前記第２の基板の熱膨張係数は、前記第１の
基板の同方向の熱膨張係数より小さいことを特徴とする
弾性表面波素子。1. A first substrate which is a single crystal piezoelectric substrate, a second substrate bonded to the first substrate, and a side opposite to a bonding surface of the first substrate with the second substrate. And a comb-shaped cross electrode that excites an acoustic wave and is formed on the surface of the first substrate, wherein the second substrate is a substrate of the same material as the first substrate, The surface acoustic wave element according to claim 1, wherein a thermal expansion coefficient of the second substrate in a propagation direction of the elastic wave is smaller than a thermal expansion coefficient of the first substrate in the same direction.
前記第２の基板の厚さは前記第１の基板の厚さの３倍以
上であることを特徴とする弾性表面波素子。2. The surface acoustic wave device according to claim 1, wherein
The thickness of the second substrate is at least three times the thickness of the first substrate.
おいて、前記第１および第２の基板はタンタル酸リチウ
ムであり、前記第２の基板のＺ軸は前記第２の基板の接
合面内に存在し、前記第１の基板の前記弾性波の伝搬方
向は前記第２の基板のＺ軸と平行であることを特徴とす
る弾性表面波素子。3. The surface acoustic wave device according to claim 1, wherein the first and second substrates are made of lithium tantalate, and a Z-axis of the second substrate is a bonding surface of the second substrate. Wherein the direction of propagation of the acoustic wave on the first substrate is parallel to the Z-axis of the second substrate.
おいて、前記第１および第２の基板はタンタル酸リチウ
ムであり、前記第１の基板の面方位はＸ軸を中心にＹ軸
からＺ軸方向に３６°〜４６°の範囲の角度で回転され
た方向であり、前記第２の基板の面方位はＹ軸方向もし
くはＸ軸方向であり、前記第１の基板の前記弾性波の伝
搬方向は前記第１の基板のＸ軸方向であり、前記第１の
基板のＸ軸は前記第２の基板のＺ軸と平行であることを
特徴とする弾性表面波素子。4. The surface acoustic wave device according to claim 1, wherein the first and second substrates are made of lithium tantalate, and the plane orientation of the first substrate is from the Y axis around the X axis. A direction rotated by an angle in the range of 36 ° to 46 ° in the Z-axis direction, the plane orientation of the second substrate is the Y-axis direction or the X-axis direction, and the direction of the elastic wave of the first substrate is A surface acoustic wave element wherein a propagation direction is an X-axis direction of the first substrate, and an X-axis of the first substrate is parallel to a Z-axis of the second substrate.
おいて、前記第１および第２の基板はタンタル酸リチウ
ムであり、前記第１および第２の基板の面方位はＸ軸を
中心にＹ軸からＺ軸方向に３６°〜４６°の範囲の角度
で回転された方向であり、前記第１の基板の前記弾性波
の伝搬方向は前記第１の基板のＸ軸方向であり、前記第
１の基板のＸ軸は前記第２の基板のＸ軸と直交すること
を特徴とする弾性表面波素子。5. The surface acoustic wave device according to claim 1, wherein said first and second substrates are made of lithium tantalate, and said first and second substrates have a plane orientation centered on an X axis. A direction rotated by an angle in a range of 36 ° to 46 ° from a Y axis to a Z axis direction, a propagation direction of the elastic wave of the first substrate is an X axis direction of the first substrate, A surface acoustic wave device wherein the X axis of the first substrate is orthogonal to the X axis of the second substrate.
おいて、前記第１および前記第２の基板はタンタル酸リ
チウムであり、前記第１の基板の面方位はＸ軸方向であ
り、前記第２の基板の面方位はＹ軸方向もしくはＸ軸方
向であり、前記第１の基板の前記弾性波の伝搬方向は前
記第１の基板のＹ軸からＺ軸方向に１１２°の角度で回
転された方向であり、前記第１の基板のＹ軸からＺ軸方
向に１１２°の角度で回転された方向は前記第２の基板
のＺ軸と平行であることを特徴とする弾性表面波素子。6. The surface acoustic wave device according to claim 1, wherein the first and second substrates are made of lithium tantalate, and the plane orientation of the first substrate is an X-axis direction. The plane orientation of the second substrate is the Y-axis direction or the X-axis direction, and the propagation direction of the elastic wave of the first substrate is rotated at an angle of 112 ° in the Z-axis direction from the Y-axis of the first substrate. A surface acoustic wave element, wherein a direction rotated by 112 ° from the Y axis of the first substrate to the Z axis is parallel to the Z axis of the second substrate. .
おいて、前記第１および前記第２の基板はニオブ酸リチ
ウムであり、前記第２の基板のＺ軸は前記第２の基板の
接合面内に存在し、前記第１の基板の前記弾性波の伝搬
方向は前記第２の基板のＺ軸と平行であることを特徴と
する弾性表面波素子。7. The surface acoustic wave device according to claim 1, wherein the first and second substrates are made of lithium niobate, and a Z axis of the second substrate is a junction of the second substrate. A surface acoustic wave device which is present in a plane, wherein a propagation direction of the acoustic wave of the first substrate is parallel to a Z axis of the second substrate.
おいて、前記第１および前記第２の基板はニオブ酸リチ
ウムであり、前記第１の基板の面方位はＸ軸を中心にＹ
軸からＺ軸方向に４１〜６４°の範囲の角度で回転され
た方向であり、前記第２の基板の面方位はＹ軸方向もし
くはＸ軸方向であり、前記第１の基板の前記弾性波の伝
搬方向は前記第１の基板のＸ軸方向であり、前記第１の
基板のＸ軸は前記第２の基板のＺ軸と平行であることを
特徴とする弾性表面波素子。8. The surface acoustic wave device according to claim 1, wherein the first and second substrates are made of lithium niobate, and a plane orientation of the first substrate is Y around an X axis.
A direction rotated by an angle in the range of 41 to 64 ° in the Z-axis direction from the axis, the plane orientation of the second substrate is the Y-axis direction or the X-axis direction, and the elastic wave of the first substrate is Is a direction of the X-axis of the first substrate, and the X-axis of the first substrate is parallel to the Z-axis of the second substrate.
おいて、前記第１および前記第２の基板はニオブ酸リチ
ウムであり、前記第１および前記第２の基板の面方位は
Ｘ軸を中心にＹ軸からＺ軸方向に４１〜６４°の範囲の
角度で回転された方向であり、前記第１の基板の前記弾
性波の伝搬方向は前記第１の基板のＸ軸方向であり、前
記第１の基板のＸ軸は前記第２の基板のＸ軸と直交する
ことを特徴とする弾性表面波素子。9. The surface acoustic wave device according to claim 1, wherein said first and second substrates are made of lithium niobate, and said first and second substrates have an X-axis plane orientation. A direction rotated from the Y axis to the Z axis at an angle in the range of 41 to 64 ° from the center, and the propagation direction of the elastic wave of the first substrate is the X axis direction of the first substrate; A surface acoustic wave device wherein an X axis of the first substrate is orthogonal to an X axis of the second substrate.
において、前記第２の基板は四ホウ酸リチウム単結晶で
あり、前記第２の基板の四ホウ酸リチウム単結晶のｃ軸
は前記第２の基板の接合面内に存在し、前記第１の基板
の前記弾性波の伝搬方向は前記第２の基板の四ホウ酸リ
チウム単結晶のｃ軸と平行であることを特徴とする弾性
表面波素子。10. The surface acoustic wave device according to claim 1, wherein the second substrate is a lithium tetraborate single crystal, and the c-axis of the lithium tetraborate single crystal of the second substrate is The elastic wave is present in a bonding surface of the second substrate, and a propagation direction of the elastic wave of the first substrate is parallel to a c-axis of the lithium tetraborate single crystal of the second substrate. Surface wave element.
性表面波素子において、前記第１の基板と前記第２の基
板の接合は、前記第１の基板と前記第２の基板の接合界
面に塗布ガラスを主成分とする接着層を有することを特
徴とする弾性表面波素子。11. The surface acoustic wave device according to claim 1, wherein the first substrate and the second substrate are bonded at a bonding interface between the first substrate and the second substrate. A surface acoustic wave element comprising an adhesive layer mainly composed of coated glass.
記第１の基板に接合された第２の基板と、前記第１の基
板の前記第２の基板との接合面と反対側の面上に形成さ
れ弾性波を励振する櫛型交差電極とを備えた弾性表面波
素子において、塗布ガラスを主成分とする接着層を接合
界面に有し、前記第２の基板の厚さは前記第１の基板の
厚さの３倍以上であることを特徴とする弾性表面波素
子。12. A first substrate which is a single crystal piezoelectric substrate, a second substrate bonded to the first substrate, and a side opposite to a bonding surface of the first substrate with the second substrate. A surface acoustic wave element having a comb-shaped cross electrode that excites an acoustic wave and is formed on the surface of A surface acoustic wave device having a thickness of at least three times the thickness of the first substrate.
いて、前記塗布ガラスを主成分とする接着層が有する弾
性波伝搬速度の温度係数が、前記第１の基板の前記弾性
波の伝搬方向の熱膨張係数を相殺する値となるように、
塗布ガラス層の膜厚を最適化したことを特徴とする弾性
表面波素子。13. The surface acoustic wave element according to claim 12, wherein the temperature coefficient of the propagation speed of the elastic wave of the adhesive layer containing the coated glass as a main component is the propagation direction of the elastic wave on the first substrate. So as to have a value that offsets the coefficient of thermal expansion of
A surface acoustic wave device characterized in that the thickness of a coating glass layer is optimized.
素子用の基板を製造する方法であって、前記第１および
前記第２の基板を熱処理した後に洗浄する第１工程と、
前記第１もしくは前記第２の基板の接合面に塗布ガラス
膜を塗布した後、加熱により塗布ガラス膜の溶剤を蒸発
させる第２工程と、前記第１の基板と前記第２の基板を
接合させる第３工程と、基板接合後に加熱処理を行う第
４工程により、前記第１の基板と前記第２の基板を塗布
ガラス層を介して接合することを特徴とする弾性表面波
素子用基板の製造方法。14. A method for manufacturing a substrate for a surface acoustic wave device according to claim 11, wherein a first step of cleaning the first and second substrates after heat-treating the first and second substrates.
A second step of applying a coating glass film to the bonding surface of the first or second substrate and then evaporating a solvent of the coating glass film by heating; and bonding the first substrate and the second substrate. Manufacturing a substrate for a surface acoustic wave device, wherein the first substrate and the second substrate are joined via a coating glass layer by a third step and a fourth step of performing a heat treatment after the substrate is joined. Method.
素子において、前記第１の基板は、Ｘ軸を中心にＹ軸か
らＺ軸方向に３６°〜４６°の範囲の角度で回転された
面方位を有するタンタル酸リチウム、Ｘ軸を面方位とす
るタンタル酸リチウム、またはＸ軸を中心にＹ軸からＺ
軸方向に４１〜６４°の範囲の角度で回転された面方位
を有するニオブ酸リチウムであることを特徴とする弾性
表面波素子。15. The surface acoustic wave device according to claim 12, wherein the first substrate is rotated at an angle in the range of 36 ° to 46 ° from the Y axis to the Z axis around the X axis. Lithium tantalate having a plane orientation, lithium tantalate having a plane orientation along the X axis, or Z around the X axis from the Y axis
A surface acoustic wave device comprising lithium niobate having a plane orientation rotated in the axial direction at an angle in the range of 41 to 64 °.
素子において、前記第２の基板は、ダイヤモンド、窒化
アルミニウム、珪素、酸化珪素、窒化珪素、硼素、酸化
硼素、窒化硼素、タンタル酸リチウム、ニオブ酸リチウ
ム、四ホウ酸リチウムのいずれかまたはそれらの複合材
料からなることを特徴とする弾性表面波素子。16. A surface acoustic wave device according to claim 12, wherein said second substrate comprises diamond, aluminum nitride, silicon, silicon oxide, silicon nitride, boron, boron oxide, boron nitride, lithium tantalate, A surface acoustic wave device comprising any one of lithium niobate and lithium tetraborate or a composite material thereof.
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| US11979132B2 (en) | 2018-03-29 | 2024-05-07 | Soitec | Method for manufacturing a substrate for a radiofrequency filter |
| WO2021177341A1 (en) * | 2020-03-03 | 2021-09-10 | 株式会社村田製作所 | Acoustic wave device |
| WO2021177340A1 (en) * | 2020-03-03 | 2021-09-10 | 株式会社村田製作所 | Acoustic wave device |
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