JP4239506B2 - Method for manufacturing substrate for piezoelectric device - Google Patents

Description

【００１５】
次に、これらの原料を振動攪拌機で１時間混合させ、外径１００ｍｍ×６０ｍｍの寸法をもったペレットに成形する。次に、ペレットを電気炉で１２００℃の温度で、１時間空気中で焼成する。
結晶の育成は、高周波加熱育成炉において、図２に示すように、白金製のルツボ１を用いて行い、該ルツボ１の外側と上方にアルミナ及びジルコニアの断熱材２を設け、ホットゾーンを形成する。断熱材２の外側には、加熱用の高周波ワークコイル３を設置する。
【００１６】
なお、ルツボ１底部には、熱電対４が設置されている。また、引き上げ軸５には、結晶の重量を測定する重量センサ６が接続されている。さらに、この高周波加熱育成炉は、重量センサ６により計測された結晶の重量から融液組成のずれを推測し、適切な量のＧａ_２Ｏ_３及びＳｉＯ_２の少なくとも一方を連続的かつ自動的にルツボ１内に供給、補充する補充機構１０を備えている。該補充機構１０は、適量に調整された粉状又は粒状のＧａ_２Ｏ_３及びＳｉＯ_２の少なくとも一方をルツボ１内に投入する機構や、棒状に形成されたＧａ_２Ｏ_３及びＳｉＯ_２の少なくとも一方の下部を長さ調整して融液Ｌ内に浸ける機構等が採用される。
【００１７】
育成の際に、ルツボ１の中に焼成されたペレットをチャージし、加熱、融解させて所定温度の融液Ｌとする。そして、ランガサイト（Ｌａ_３Ｇａ_５ＳｉＯ_１４）の種結晶Ｓを引き上げ軸５に固定し、所定の回転数と引上速度で融液Ｌからランガサイト単結晶Ｃを育成する。自動直径制御は、引き上げ軸５につながる重量センサ６で検出した結晶の重量変化信号により行う。また、同時に、補充機構１０により、結晶の重量から融液組成のずれを推測し、適切な量でＧａ_２Ｏ_３及びＳｉＯ_２の少なくとも一方を自動的に補充する。
【００１８】
このようにして育成したランガサイト単結晶Ｃ（直径１０５ｍｍで直胴部の長さが２００ｍｍ）は、秤量時の組成範囲と同様の組成範囲内の単結晶となることに限らず、この組成範囲よりＬａ_２Ｏ_３を多く含み、またはＧａ_２Ｏ_３を少なく含む組成を持つ単結晶となる。この結晶の融点は１３００〜１４５０℃と従来技術で育成されたランガサイト単結晶より低い。
【００１９】
次に、このランガサイト単結晶Ｃは、スライスされて圧電デバイス用基板に加工される。さらに、この圧電デバイス用基板には、図３に示すように、その表面に励振電極（すだれ電極（櫛歯電極））７が形成されてＳＡＷフィルタ（表面弾性波デバイス）８が作製される。
【００２０】
本実施形態では、Ｌａ_２Ｏ_３、Ｇａ_２Ｏ_３及びＳｉＯ_２のそれぞれ組成範囲を上述した範囲内で秤量し、ルツボ１内で融解させ、該ルツボ１内からＬａ_３Ｇａ_５ＳｉＯ_１４単結晶Ｃを引き上げ育成するので、原料組成がランガサイトの初晶領域若しくはその近傍領域で混合されていると考えられ、後述する実施例の結果から、ランガサイト以外の相の析出を防ぎ、異相及びツイン成長を防ぐことができる。特に、原料の組成範囲がランガサイトの初晶領域の組成範囲内であれば、より良好な結晶性を得ることができる。
【００２１】
また、引き上げ育成時に、補充機構１０によってルツボ１内にＧａ_２Ｏ_３及びＳｉＯ_２の少なくとも一方を連続的に補充するので、育成中の融液組成のずれを修正することができる。
さらに、ランガサイトの初晶領域及びその近傍領域では融点が低いので、長寿命の白金製ルツボを使用することが可能になり、低コストの生産を実現することができる。
また、ルツボ１が白金で形成されているので、従来のイリジウム製ルツボの場合にあった酸素雰囲気中におけるルツボの酸化がほとんどなく、酸化によるルツボ１の減量が極めて少なくなる。したがって、ルツボ１の寿命が長くなり、より生産コストを低減させることができる。
【００２２】
【実施例】
次に、本発明に係る圧電デバイス基板及びその製造方法を、実施例により図１を参照して具体的に説明する。
【００２３】
上記本実施形態の製造方法において、実際に上記点Ａ、Ｂ、Ｃ、Ｄのそれぞれの組成で原料を混合し、４回に分けて単結晶を育成した結果、育成された単結晶は、いずれも異相成長もツイン成長もなく、良好な結晶であった。また、育成過程は順調であり、４回の育成は全部成功し、成功率は１００％であった。
【００２４】
また、上記本実施形態の製造方法において、Ｌａ_２Ｏ_３、Ｇａ_２Ｏ_３及びＳｉＯ_２の原料を、図１及び表２に示すように、上述した組成範囲内である点Ｅの組成で秤量し、結晶を育成した。この点Ｅの組成は、Ｌａ_２Ｏ_３が４１重量％、Ｇａ_２Ｏ_３が５３重量％、ＳｉＯ_２が６重量％である。
また、比較例として、Ｌａ_２Ｏ_３、Ｇａ_２Ｏ_３及びＳｉＯ_２の原料を、図１及び表２に示すように、上述した組成範囲外であり化学量論比組成に基づいた点Ｆの組成で秤量したもので、上記実施例と同様に、結晶を育成した。この点Ｆの組成は、Ｌａ_２Ｏ_３が４８重量％、Ｇａ_２Ｏ_３が４６重量％、ＳｉＯ_２が６重量％である。なお、ランガサイトの化学量論比では融点が高いため、ルツボにはイリジウム製を使用した。
【００２５】
【表２】

【００２６】
この実施例で得られた結晶は、ツイン成長もクラックも生じず、良質なものであり、育成中ＬＳ（Ｇ）の析出はなかったものと考えられる。また、原料の融点それから結晶を育成する温度は約１３００〜１４５０℃と低く、白金製ルツボを使用したので、ルツボ酸化による減量は無視できる程度であった。また、図４に示すように、ランガサイト単結晶の上部から下部までの長さ方向において、複数の測定点でＳＡＷ音速を測定した。この結果、表３及び図５に示すように、結晶上部から下部に亘ってＳＡＷ音速のバラツキは６６ｐｐｍと小さかった。
【００２７】
【表３】

【００２８】
これに対して、上記比較例で得られた結晶は、肩部の形成段階において二次相が発生した。この結晶は、弾性波素子の基板材料として使用できないものであった。また、イリジウム製ルツボを使用したため、ルツボは酸化され、酸化イリジウムの黒い粉になって飛散し、育成炉の内部に付着した。そして、一回の育成当たり、ルツボの重量は約２００ｇ減少し、２０回の育成後、ルツボに液漏れが起こり、使用不能になった。また、上記実施例と同様に、ランガサイト単結晶の上部から下部までの長さ方向において、複数の測定点でＳＡＷ音速を測定した。この結果、表４及び図５に示すように、結晶上部から下部に亘ってＳＡＷ音速のバラツキは２７８ｐｐｍと大きかった。
【００２９】
【表４】

【００３０】
なお、本発明の技術範囲は上記実施の形態に限定されるものではなく、本発明の趣旨を逸脱しない範囲において種々の変更を加えることが可能である。
【００３１】
【発明の効果】
本発明の圧電デバイス基板の製造方法及びこれによる圧電デバイス基板によれば、Ｌａ_３Ｇａ_５ＳｉＯ_１４の原料であるＬａ_２Ｏ_３、Ｇａ_２Ｏ_３及びＳｉＯ_２を上記範囲内で秤量し、ルツボ内で融解させ、該ルツボ内からＬａ_３Ｇａ_５ＳｉＯ_１４の単結晶を引き上げ育成するので、異相及びツイン成長を防ぎ、育成の成功率を向上させることができる。また、上記組成範囲内では融点が低いので、長寿命の白金製ルツボを使用することが可能になり、生産の低コスト化が可能になる。したがって、良質でＳＡＷフィルタに好適な基板を低コストで得ることができる。
【図面の簡単な説明】
【図１】 本発明に係る一実施形態における圧電デバイス基板及びその製造方法において、ランガサイト単結晶の組成範囲を示す状態図である。
【図２】 本発明に係る一実施形態における圧電デバイス基板の製造方法において、ＣＺ法による引き上げ育成を示す概略的な断面図である。
【図３】 本発明に係る一実施形態の表面弾性波デバイスを示す斜視図である。
【図４】 本発明に係る実施例及び比較例において、ランガサイト単結晶の長さ方向におけるＳＡＷ音速の測定点を示す説明図である。
【図５】 本発明に係る実施例において、ランガサイト単結晶の長さ方向におけるＳＡＷ音速を示すグラフである。
【図６】 本発明に係る比較例において、ランガサイト単結晶の長さ方向におけるＳＡＷ音速を示すグラフである。
【図７】 ランガサイトの包晶系において原料の出発組成（初晶領域内の組成）範囲を示す状態図である。
【符号の説明】
１ ルツボ
７ 励振電極
８ ＳＡＷ（表面弾性波）デバイス
１０ 補充機構
Ｃ ランガサイト単結晶
Ｌ 融液
Ｓ 種結晶[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a piezoelectric device substrate manufacturing method suitable for a SAW filter or the like, a piezoelectric device substrate, and a surface acoustic wave device using the same.
[0002]
[Prior art]
In recent years, La ₃ Ga ₅ SiO ₁₄ (Langasite) single crystals have a small elastic wave propagation velocity and frequency change rate due to temperature, and an electromechanical coupling coefficient representing the magnitude of piezoelectricity (the mutual relationship between electrical energy and mechanical energy). Since the coefficient indicating the conversion efficiency is large, research has been conducted on substrate materials for piezoelectric devices such as surface acoustic wave (SAW) filters (for example, H. Takeda, K. Shimamura, VIChani, T. Fukuda, Effect of starting melt composition on crystal growth of La ₃ Ga ₅ SiO ₁₄ , J. Crystal Growth 197 (1999) 204.). In other words, this Langasite single crystal has the same temperature characteristics as quartz, and has an electromechanical coupling coefficient of about three times that of quartz, so that the bandwidth and size of SAW filters widely used in mobile phones and the like can be reduced. Is possible. For example, JP-A-10-126209 describes a surface acoustic wave device using a langasite single crystal.
Conventionally, in order to grow this langasite single crystal, a single crystal was grown by melting raw material pellets based on the stoichiometric ratio and the composition in the vicinity thereof.
[0003]
[Problems to be solved by the invention]
However, according to the research results of the present inventors, as shown in FIG. 7, the langasite is a peritectic system, and the melt having the stoichiometric ratio and the composition in the vicinity thereof is solidified as the temperature decreases from a high temperature. In this case, a ternary crystal (hereinafter referred to as LS (G)) containing Ga (gallium) and having a crystal structure of La ₁₄ Si ₉ O ₃₉ is precipitated first. In the conventional stoichiometric ratio and the growth of the composition in the vicinity, Langasite grows due to supercooling in the melt near the seed crystal, but a small amount of melt adhering to the crucible surface, particularly the crucible surface. Is exposed to the high temperature of the crucible, and LS (G) precipitates. Since LS (G) has a high melting point, it does not melt at the temperature inside the crucible, and convects together with the melt. And if it adheres to a crystal | crystallization, a different phase or a twin growth will start. Such a crystal is easily cracked, and the cut wafer has a very large variation in the propagation characteristics of the surface acoustic wave, making it impossible to produce a SAW filter with high accuracy. In terms of production efficiency, there was a disadvantage that the success rate of crystal growth was low and production efficiency was poor.
Moreover, since the melting point of the raw material and the crystal is high at the stoichiometric ratio and the composition in the vicinity thereof, a iridium crucible made of a noble metal is often used. However, since the growth is performed in an oxygen atmosphere in order to suppress evaporation of gallium, the iridium crucible is oxidized and partly evaporated. For this reason, not only does the production cost increase due to the reduction of the iridium crucible with each growth, but the life of the crucible is significantly shortened.
Therefore, with the conventional technology using the raw material pellet based on the stoichiometric ratio and the composition in the vicinity thereof, it is difficult to obtain a uniform langasite single crystal, the success rate of crystal growth is low, and the production cost is also high. There was an inconvenience.
[0004]
The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a method for manufacturing a substrate for a piezoelectric device that can achieve a high success rate of crystal growth with a uniform single crystal and a high production cost. And
[0005]
[Means for Solving the Problems]
The present invention employs the following configuration in order to solve the above problems. That is, the method for manufacturing a piezoelectric device substrate according to the present invention is a method for manufacturing a piezoelectric device substrate in which a La ₃ Ga ₅ SiO ₁₄ single crystal is grown and processed into a piezoelectric device substrate,
Point A shown in the attached drawing 1 (La ₂ O ₃ is 44 wt%, Ga ₂ O ₃ is 46 wt%, SiO ₂ is 10 wt%),
Point B (La ₂ O ₃ is 45 wt%, Ga ₂ O ₃ is 52 wt%, SiO ₂ is 3 wt%),
Point C (La ₂ O ₃ is 32 wt%, Ga ₂ O ₃ is 65 wt%, SiO ₂ is 3 wt%),
Weigh in a composition range surrounded by point D (37% by weight of La ₂ O ₃ , 53% by weight of Ga ₂ O _3, 10% by weight of SiO ₂ ) and melt in the crucible, and from within the crucible, the La It is characterized by pulling and growing a ₃ Ga ₅ SiO ₁₄ single crystal.
[0006]
In this method for manufacturing a piezoelectric device substrate, La ₂ O ₃ , Ga ₂ O ₃ and SiO ₂ which are raw materials of La ₃ Ga ₅ SiO ₁₄ are weighed within the above range, melted in the crucible, and from within the crucible. Since a single crystal of La ₃ Ga ₅ SiO ₁₄ is pulled and grown, precipitation of phases other than langasite can be prevented, and heterogeneous and twin growth can be prevented, as shown in the experimental results described later. The reason why such a good crystal can be obtained is considered that the composition range is the primary crystal region of langasite or a region near it. And since melting | fusing point is low in the primary crystal area | region or its vicinity area | region of a langasite, it becomes possible to use a long life platinum crucible, and it becomes possible to implement | achieve low-cost production.
[0007]
The manufacturing method of a substrate for the piezoelectric device of the present invention, the weighing is preferably carried out in the composition range primary phase area of La ₃ Ga ₅ SiO ₁₄ is present. That is, this piezoelectric device substrate manufacturing method can further prevent heterogeneous phase and twin growth by weighing the raw materials within the composition range in which the primary crystal region of La ₃ Ga ₅ SiO ₁₄ exists.
[0008]
In addition, the method for manufacturing a piezoelectric device substrate according to the present invention employs a technique in which at least one of Ga ₂ O ₃ and SiO ₂ is continuously replenished in the crucible during the pulling and growing. That is, in this method for manufacturing a piezoelectric device substrate, at the time of pulling and growing, at least one of Ga ₂ O ₃ and SiO ₂ is continuously replenished in the crucible, so that the deviation of the melt composition during growth can be corrected. it can.
Note that the meaning of “continuous” includes a case where replenishment is performed a plurality of times even during the growth.
[0009]
Moreover, the manufacturing method of the board | substrate for piezoelectric devices of this invention employ | adopts the technique in which the said crucible is formed with platinum. That is, in this method for manufacturing a substrate for piezoelectric devices, the crucible is formed of platinum, so that there is almost no oxidation of the crucible in an oxygen atmosphere as in the case of a conventional iridium crucible, and the weight loss of the crucible due to oxidation is extremely low. Less. Therefore, the life of the crucible can be extended and the production cost can be reduced.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EMBODIMENTS Hereinafter, a piezoelectric device substrate manufacturing method, a piezoelectric device substrate, and a surface acoustic wave device using the same according to an embodiment of the present invention will be described with reference to FIGS. 1 to 3.
[0013]
To manufacture the piezoelectric device substrate and the surface acoustic wave device of the present embodiment, first, the composition range shown in FIG. 1 and Table 1, that is,
Point A shown in FIG. 1 and Table 1 (La ₂ O ₃ is 44 wt%, Ga ₂ O ₃ is 46 wt%, SiO ₂ is 10 wt%),
Point B (La ₂ O ₃ is 45 wt%, Ga ₂ O ₃ is 52 wt%, SiO ₂ is 3 wt%),
Point C (La ₂ O ₃ is 32 wt%, Ga ₂ O ₃ is 65 wt%, SiO ₂ is 3 wt%),
Point D (La ₂ O ₃ is 37 wt%, Ga ₂ O ₃ is 53 wt%, SiO ₂ is 10 wt%)
The raw materials (La ₂ O ₃ , Ga ₂ O ₃ , SiO ₂ ) are weighed within the composition range surrounded by.
[0014]
[Table 1]

[0015]
Next, these raw materials are mixed with a vibration stirrer for 1 hour and formed into pellets having a size of an outer diameter of 100 mm × 60 mm. Next, the pellet is fired in air at a temperature of 1200 ° C. for 1 hour in an electric furnace.
Crystal growth is performed in a high-frequency heating growth furnace using a platinum crucible 1 as shown in FIG. 2, and an insulating material 2 of alumina and zirconia is provided outside and above the crucible 1 to form a hot zone. To do. A high-frequency work coil 3 for heating is installed outside the heat insulating material 2.
[0016]
A thermocouple 4 is installed at the bottom of the crucible 1. A weight sensor 6 for measuring the weight of the crystal is connected to the pulling shaft 5. Further, the high-frequency heating growth furnace estimates the deviation of the melt composition from the weight of the crystal measured by the weight sensor 6, and continuously and automatically adds an appropriate amount of at least one of Ga ₂ O ₃ and SiO _2. A replenishing mechanism 10 for supplying and replenishing the crucible 1 is provided. The replenishing mechanism 10, at least one of the adjusted powder or granular in the _Ga 2 _{O 3} and the SiO ₂ in an appropriate amount and mechanisms to be introduced into the crucible 1, at least in the _Ga 2 _{O 3} and the SiO ₂ formed into a rod A mechanism or the like in which the length of one lower part is adjusted and immersed in the melt L is adopted.
[0017]
During the growth, the baked pellets are charged in the crucible 1 and heated and melted to obtain a melt L at a predetermined temperature. Then, the seed crystal S of langasite (La ₃ Ga ₅ SiO ₁₄ ) is fixed to the pulling shaft 5, and the langasite single crystal C is grown from the melt L at a predetermined rotational speed and pulling speed. The automatic diameter control is performed based on a crystal weight change signal detected by a weight sensor 6 connected to the pulling shaft 5. At the same time, the replenishment mechanism 10 estimates the deviation of the melt composition from the crystal weight and automatically replenishes at least one of Ga ₂ O ₃ and SiO ₂ with an appropriate amount.
[0018]
The Langasite single crystal C (diameter 105 mm and straight body length 200 mm) grown in this way is not limited to a single crystal within the composition range similar to the composition range at the time of weighing, but this composition range. A single crystal having a composition containing more La ₂ O ₃ or less Ga ₂ O ₃ is obtained. The melting point of this crystal is 1300 to 1450 ° C., which is lower than the langasite single crystal grown by the prior art.
[0019]
Next, the langasite single crystal C is sliced and processed into a piezoelectric device substrate. Further, as shown in FIG. 3, the substrate for piezoelectric device has an excitation electrode (interdigital electrode (comb electrode)) 7 formed on the surface thereof, and a SAW filter (surface acoustic wave device) 8 is manufactured.
[0020]
In this embodiment, each composition range of La ₂ O ₃ , Ga ₂ O ₃ and SiO ₂ is weighed within the above-described range, melted in the crucible 1, and La ₃ Ga ₅ SiO ₁₄ single crystal from the crucible 1. Since C is pulled up and grown, it is considered that the raw material composition is mixed in the primary crystal region of langasite or in the vicinity thereof. From the results of the examples described later, precipitation of phases other than langasite is prevented, Growth can be prevented. In particular, if the composition range of the raw material is within the composition range of the primary crystal region of langasite, better crystallinity can be obtained.
[0021]
In addition, since at least one of Ga ₂ O ₃ and SiO ₂ is continuously replenished into the crucible 1 by the replenishment mechanism 10 during the pulling and growing, the deviation of the melt composition during the growth can be corrected.
Further, since the melting point is low in the primary crystal region of the langasite and the vicinity thereof, a long-life platinum crucible can be used, and low-cost production can be realized.
Further, since the crucible 1 is made of platinum, there is almost no oxidation of the crucible in an oxygen atmosphere, which is the case with conventional iridium crucibles, and the weight loss of the crucible 1 due to oxidation becomes extremely small. Therefore, the life of the crucible 1 is extended, and the production cost can be further reduced.
[0022]
【Example】
Next, the piezoelectric device substrate and the manufacturing method thereof according to the present invention will be specifically described with reference to FIG.
[0023]
In the manufacturing method of the present embodiment, as a result of actually mixing the raw materials with the respective compositions of the points A, B, C, and D and growing the single crystal in four times, the grown single crystal is There was no heterophasic growth or twin growth, and the crystals were good. Also, the training process was smooth, and all four trainings were successful, with a success rate of 100%.
[0024]
In the manufacturing method of the present embodiment, the raw materials of La ₂ O ₃ , Ga ₂ O ₃ and SiO ₂ are weighed with the composition of point E within the above-described composition range as shown in FIG. 1 and Table 2. The crystal was grown. The composition of this point E is La ₂ O ₃ 41% by weight, Ga ₂ O ₃ 53% by weight, and SiO ₂ 6% by weight.
Moreover, as a comparative example, the raw materials of La ₂ O ₃ , Ga ₂ O ₃ and SiO ₂ are outside the above-described composition range as shown in FIG. 1 and Table 2, and are based on the stoichiometric composition. The crystals were weighed according to the composition, and the crystals were grown in the same manner as in the above examples. The composition of this point F is 48% by weight of La ₂ O ₃ , 46% by weight of Ga ₂ O _{3 and} 6% by weight of SiO ₂ . Since the melting point is high in the stoichiometric ratio of langasite, iridium made crucible was used.
[0025]
[Table 2]

[0026]
The crystals obtained in this example are of high quality without twin growth or cracks, and it is considered that LS (G) did not precipitate during growth. Further, the melting point of the raw material and the temperature for growing crystals were as low as about 1300 to 1450 ° C. Since a platinum crucible was used, the weight loss due to crucible oxidation was negligible. In addition, as shown in FIG. 4, SAW sound velocity was measured at a plurality of measurement points in the length direction from the top to the bottom of the langasite single crystal. As a result, as shown in Table 3 and FIG. 5, the dispersion of the SAW sound velocity from the upper part of the crystal to the lower part was as small as 66 ppm.
[0027]
[Table 3]

[0028]
On the other hand, in the crystal obtained in the comparative example, a secondary phase was generated in the shoulder formation stage. This crystal cannot be used as a substrate material for an acoustic wave device. In addition, since an iridium crucible was used, the crucible was oxidized and scattered as black powder of iridium oxide and adhered to the inside of the growth furnace. Then, the weight of the crucible decreased by about 200 g per one growth, and after the 20th growth, liquid leakage occurred in the crucible, making it unusable. Similarly to the above example, the SAW sound velocity was measured at a plurality of measurement points in the length direction from the top to the bottom of the langasite single crystal. As a result, as shown in Table 4 and FIG. 5, the dispersion of the SAW sound velocity was as large as 278 ppm from the top to the bottom of the crystal.
[0029]
[Table 4]

[0030]
The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.
[0031]
【The invention's effect】
According to the method for manufacturing a piezoelectric device substrate and the piezoelectric device substrate according to the present invention, La ₂ O ₃ , Ga ₂ O ₃ and SiO ₂ which are raw materials of La ₃ Ga ₅ SiO ₁₄ are weighed within the above range, and the crucible is measured. Since the single crystal of La ₃ Ga ₅ SiO ₁₄ is pulled up and grown from the inside of the crucible, heterophase and twin growth can be prevented and the success rate of the growth can be improved. In addition, since the melting point is low within the above composition range, it is possible to use a platinum crucible having a long life, and the production cost can be reduced. Therefore, a high-quality substrate suitable for a SAW filter can be obtained at low cost.
[Brief description of the drawings]
FIG. 1 is a state diagram showing a composition range of a langasite single crystal in a piezoelectric device substrate and a manufacturing method thereof according to an embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view showing pulling growth by a CZ method in a method for manufacturing a piezoelectric device substrate according to an embodiment of the present invention.
FIG. 3 is a perspective view showing a surface acoustic wave device according to an embodiment of the present invention.
FIG. 4 is an explanatory diagram showing measurement points of SAW sound velocity in the length direction of a langasite single crystal in Examples and Comparative Examples according to the present invention.
FIG. 5 is a graph showing SAW sound velocity in the length direction of a langasite single crystal in an example according to the present invention.
FIG. 6 is a graph showing SAW sound velocity in the length direction of a langasite single crystal in a comparative example according to the present invention.
FIG. 7 is a state diagram showing the starting composition range (composition in the primary crystal region) of the raw material in the peritectic system of langasite.
[Explanation of symbols]
1 Crucible 7 Excitation electrode 8 SAW (surface acoustic wave) device 10 Replenishment mechanism C Langasite single crystal L Melt S Seed crystal

Claims (4)

A method for manufacturing a piezoelectric device substrate in which a La ₃ Ga ₅ SiO ₁₄ single crystal is grown and processed into a piezoelectric device substrate,
Point A shown in the attached drawing 1 (La ₂ O ₃ is 44 wt%, Ga ₂ O ₃ is 46 wt%, SiO ₂ is 10 wt%),
Point B (La ₂ O ₃ is 45 wt%, Ga ₂ O ₃ is 52 wt%, SiO ₂ is 3 wt%),
Point C (La ₂ O ₃ is 32 wt%, Ga ₂ O ₃ is 65 wt%, SiO ₂ is 3 wt%),
Weigh in a composition range surrounded by point D (37% by weight of La ₂ O ₃ , 53% by weight of Ga ₂ O _3, 10% by weight of SiO ₂ ) and melt in the crucible, and from within the crucible, the La _A method for producing a substrate for a piezoelectric device, comprising raising and growing a ₃ Ga ₅ SiO ₁₄ single crystal. In the manufacturing method of the board | substrate for piezoelectric devices of Claim 1,
The method for producing a substrate for a piezoelectric device, wherein the weighing is performed within a composition range in which a primary crystal region of La ₃ Ga ₅ SiO ₁₄ is present. In the manufacturing method of the board | substrate for piezoelectric devices of Claim 1 or 2,
A method for manufacturing a substrate for a piezoelectric device, wherein at least one of Ga ₂ O ₃ and SiO ₂ is continuously replenished into the crucible during the pulling and growing. In the manufacturing method of the board | substrate for piezoelectric devices in any one of Claim 1 to 3,
The method of manufacturing a substrate for a piezoelectric device, wherein the crucible is made of platinum.

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