TW202423274A - Piezoelectric components and electronic equipment - Google Patents
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Abstract
根據本發明的壓電元件，在支承基材上依次層疊具備第1電極、具有摻雜有金屬元素的壓電材料的壓電體層和第2電極，該壓電體層具有第1壓電體層和第2壓電體層，該第2壓電體層設置在該第1壓電體層的上表面及下表面的至少一方，具有比該第1壓電體層中所含的該金屬元素的濃度低的該金屬元素的濃度。According to the piezoelectric element of the present invention, a first electrode, a piezoelectric layer having a piezoelectric material doped with a metal element, and a second electrode are stacked in sequence on a supporting substrate, the piezoelectric layer having a first piezoelectric layer and a second piezoelectric layer, the second piezoelectric layer being arranged on at least one of the upper surface and the lower surface of the first piezoelectric layer, and having a concentration of the metal element lower than the concentration of the metal element contained in the first piezoelectric layer.
Description
本發明涉及一種壓電元件及電子設備。The present invention relates to a piezoelectric component and an electronic device.
壓電元件具有由壓電材料構成的壓電體層。壓電元件利用壓電體層的壓電效果，例如作為壓力感測器、加速度感測器、檢測彈性波的AE(聲發射)感測器等感測器、高頻濾波器、壓電致動器、高頻(RF：Radio Frequency)濾波器等電子部件而用於電子設備。Piezoelectric elements have a piezoelectric layer made of piezoelectric material. Piezoelectric elements utilize the piezoelectric effect of the piezoelectric layer and are used in electronic devices as electronic components such as pressure sensors, acceleration sensors, AE (acoustic emission) sensors that detect elastic waves, high-frequency filters, piezoelectric actuators, and high-frequency (RF: Radio Frequency) filters.
壓電元件有時要求耐電力性，藉由加厚膜厚來提高耐電力性。作為壓電元件，例如公開了一種體聲波(BAW)諧振器器件，其具有配置在基板上的單片(monolithic)壓電層，該單片壓電層在下部電極和上部電極之間包括具有正或負的極性的第1部分和具有與第1部分相反的極性的第2部分(例如，參照專利文獻1)。 [先前技術文獻] [專利文獻] Piezoelectric elements are sometimes required to have electrical resistance, and the electrical resistance is improved by increasing the film thickness. As a piezoelectric element, for example, a bulk acoustic wave (BAW) resonator device is disclosed, which has a monolithic piezoelectric layer arranged on a substrate, and the monolithic piezoelectric layer includes a first part having a positive or negative polarity and a second part having a polarity opposite to the first part between a lower electrode and an upper electrode (for example, refer to patent document 1). [Prior art document] [Patent document]
美國專利申請公開2017/0288121號U.S. Patent Application Publication No. 2017/0288121
[發明所欲解決問題][Invent the problem you want to solve]
但是，在專利文獻1的BAW諧振器器件中，由於單片壓電層的第1部分和第2部分具有相反的極性，所以第1部分和第2部分的膜應力的朝向相反，在第1部分和第2部分的介面容易產生剝離。因此，存在著單片壓電層的壓電特性降低的問題。However, in the BAW resonator device of Patent Document 1, since the first and second parts of the monolithic piezoelectric layer have opposite polarities, the film stresses of the first and second parts are directed in opposite directions, and peeling is easily generated at the interface between the first and second parts. Therefore, there is a problem that the piezoelectric characteristics of the monolithic piezoelectric layer are degraded.
本發明的一個方式的目的在於提供一種能夠加厚壓電體層的膜厚並且維持壓電特性的壓電元件。 [解決問題之手段] One aspect of the present invention is to provide a piezoelectric element capable of increasing the film thickness of a piezoelectric layer while maintaining piezoelectric characteristics. [Means for solving the problem]
根據本發明的壓電元件的一個方式， 在支承基材上依次層疊具備第1電極、具有摻雜有金屬元素的壓電材料的壓電體層和第2電極， 該壓電體層具有第1壓電體層和第2壓電體層， 該第2壓電體層設置在該第1壓電體層的上表面及下表面的至少一方，具有比該第1壓電體層中所含的該金屬元素的濃度低的該金屬元素的濃度。 [發明功效] According to one mode of the piezoelectric element of the present invention, a first electrode, a piezoelectric layer having a piezoelectric material doped with a metal element, and a second electrode are sequentially stacked on a supporting substrate, the piezoelectric layer has a first piezoelectric layer and a second piezoelectric layer, the second piezoelectric layer is provided on at least one of the upper surface and the lower surface of the first piezoelectric layer, and has a concentration of the metal element lower than the concentration of the metal element contained in the first piezoelectric layer. [Effect of the invention]
根據本發明的壓電元件的一個方式，能夠在加厚壓電層的膜厚的同時維持壓電特性。According to one embodiment of the piezoelectric element of the present invention, the piezoelectric characteristics can be maintained while increasing the film thickness of the piezoelectric layer.
以下，詳細說明本發明的實施方式。另外，為了容易理解說明，在各圖式中對相同的結構要素標注相同的符號，省略重複的說明。此外，圖式中的各構件的比例尺可能與實際不同。在本說明書中，表示數值範圍的“～”是指除非另有說明，否則其前後記載的數值包括下限值和上限值。The following is a detailed description of the implementation of the present invention. In addition, in order to facilitate the understanding of the description, the same symbols are marked on the same structural elements in each figure, and repeated descriptions are omitted. In addition, the scale of each component in the figure may be different from the actual one. In this specification, "~" indicating a numerical range means that unless otherwise specified, the numerical values recorded before and after it include the lower limit and the upper limit.
＜壓電元件＞ 圖1是表示根據本實施方式的壓電元件的結構的概略截面圖。如圖1所示，壓電元件1A依次層疊具備支承基材10、聲鏡層20、第1電極30、壓電體層40及第2電極50。 <Piezoelectric element> FIG. 1 is a schematic cross-sectional view showing the structure of a piezoelectric element according to the present embodiment. As shown in FIG. 1 , a piezoelectric element 1A includes a support substrate 10, an acoustic mirror layer 20, a first electrode 30, a piezoelectric layer 40, and a second electrode 50 stacked in sequence.
另外，在本說明書中，使用三軸方向(X、Y和Z軸方向)的三維正交坐標系，將壓電元件1A的寬度方向設為X軸方向，將長度方向設為Y軸方向，將高度(厚度)方向(垂直方向)設為Z軸方向。將Z軸方向的第2電極50側為+Z軸方向，將支承基材10側為-Z軸方向。在以下的說明中，為了便於說明，將+Z軸方向稱為上或上方，將-Z軸方向稱為下或下方，但並不表示普遍的上下關係。In addition, in this specification, a three-dimensional orthogonal coordinate system of three-axis directions (X, Y and Z axis directions) is used, and the width direction of the piezoelectric element 1A is set as the X axis direction, the length direction is set as the Y axis direction, and the height (thickness) direction (vertical direction) is set as the Z axis direction. The second electrode 50 side in the Z axis direction is the +Z axis direction, and the support substrate 10 side is the -Z axis direction. In the following description, for the convenience of explanation, the +Z axis direction is referred to as the upper or upper side, and the -Z axis direction is referred to as the lower or lower side, but it does not represent a general up-down relationship.
壓電元件1A藉由將壓電體層40由含有摻雜了金屬元素的壓電材料、且具有金屬元素的濃度不同的壓電材料的2種壓電體層(後述的第1壓電體層41及第2壓電體層42)構成，壓電體層40由同一材料構成，因此能夠在控制作為壓電體層40的壓電特性的指標的K值的同時，維持作為頻率特性的銳度(尖銳性)的指標的Q值。另外，壓電體層40能夠抑制在2種壓電體層40(後述的第1壓電體層41及第2壓電體層42)彼此之間產生介面剝離。由此，壓電體層40能夠加厚壓電體層40的厚度而提高壓電特性，並且能夠抑制壓電特性的劣化，因此能夠在加厚壓電體層40的膜厚的同時維持壓電特性。The piezoelectric element 1A is formed by forming a piezoelectric layer 40 of two piezoelectric layers (a first piezoelectric layer 41 and a second piezoelectric layer 42 described below) containing a piezoelectric material doped with a metal element and having different concentrations of the metal element. The piezoelectric layer 40 is formed of the same material, so that the K value, which is an indicator of the piezoelectric characteristics of the piezoelectric layer 40, can be controlled while maintaining the Q value, which is an indicator of the sharpness (sharpness) of the frequency characteristics. In addition, the piezoelectric layer 40 can suppress the interface peeling between the two piezoelectric layers 40 (the first piezoelectric layer 41 and the second piezoelectric layer 42 described later). As a result, the piezoelectric layer 40 can be thickened to improve the piezoelectric characteristics, and the degradation of the piezoelectric characteristics can be suppressed, so that the piezoelectric characteristics can be maintained while the film thickness of the piezoelectric layer 40 is thickened.
另外，K值是機電耦合常數K的值。包含在壓電體層40中的壓電材料的機電耦合常數K的平方值(K 2值)表示針對壓電材料確定的電能的能量轉換效率。電能的能量轉換效率越高，具備壓電體層40的壓電元件1A的動作效率越好，壓電元件1A具有優異的壓電特性。在同一材料·組成中，壓電體層40中所含的壓電材料的結晶取向性越高，壓電材料的K 2值越大，且逐漸變得固定。即，壓電材料的結晶取向性越高，壓電材料的能量轉換效率越高，同時逐漸變得固定，壓電性變得固定。因此，機電耦合常數K越大，K 2值越大，壓電材料的能量轉換效率越高，因此意味著壓電特性越高。 In addition, the K value is the value of the electromechanical coupling constant K. The square value ( K2 value) of the electromechanical coupling constant K of the piezoelectric material contained in the piezoelectric layer 40 represents the energy conversion efficiency of electric energy determined for the piezoelectric material. The higher the energy conversion efficiency of electric energy, the better the operating efficiency of the piezoelectric element 1A having the piezoelectric layer 40, and the piezoelectric element 1A has excellent piezoelectric characteristics. In the same material and composition, the higher the crystal orientation of the piezoelectric material contained in the piezoelectric layer 40, the larger the K2 value of the piezoelectric material, and it gradually becomes fixed. That is, the higher the crystal orientation of the piezoelectric material, the higher the energy conversion efficiency of the piezoelectric material, and at the same time it gradually becomes fixed, and the piezoelectric property becomes fixed. Therefore, the larger the electromechanical coupling constant K and the larger the K2 value, the higher the energy conversion efficiency of the piezoelectric material, which means the higher the piezoelectric properties.
所謂Q值是表示頻率特性的銳度(尖銳性)的值。Q值越大，意味著頻率特性表現得越尖銳。The so-called Q value is a value that indicates the sharpness of the frequency characteristics. The larger the Q value, the sharper the frequency characteristics.
在說明書中，壓電特性包括施加應力時的產生電壓量(正壓電效應)和施加電場時的機械位移比例(逆壓電效應)這兩者。In the specification, piezoelectric properties include the amount of voltage generated when stress is applied (direct piezoelectric effect) and the ratio of mechanical displacement when an electric field is applied (inverse piezoelectric effect).
[支承基材] 如圖1所示，支承基材10是設置有聲鏡層20、第1電極30、壓電體層40及第2電極50的層疊體的基板，為了賦予壓電元件1A彎曲性，可以具有撓性。 [Supporting substrate] As shown in FIG1 , the supporting substrate 10 is a substrate on which a laminate of an acoustic mirror layer 20, a first electrode 30, a piezoelectric layer 40, and a second electrode 50 is provided, and may have flexibility in order to impart bendability to the piezoelectric element 1A.
作為形成支承基材10的材料，只要能夠穩定地支承層疊體，就可以使用不限種類的任意材料，例如，也可以使用塑膠基材、金屬箔、金屬板、矽(Si)基板、無機電介質基材、玻璃基材等。As the material forming the supporting substrate 10, any material can be used as long as it can stably support the layer stack. For example, a plastic substrate, metal foil, metal plate, silicon (Si) substrate, inorganic dielectric substrate, glass substrate, etc. can also be used.
在使用塑膠基材的情況下，優選使用能夠對具有壓電體層40的壓電元件1A賦予彎曲性的具有撓性的材料。When a plastic substrate is used, it is preferable to use a flexible material that can impart bendability to the piezoelectric element 1A having the piezoelectric layer 40 .
作為形成塑膠基材的材料，例如可以使用聚對苯二甲酸乙二醇酯(PET)、聚萘二甲酸乙二醇酯(PEN)、聚碳酸酯(PC)、丙烯酸系樹脂、環烯烴系聚合物、聚醯胺(PA)樹脂、聚醯亞胺(PI)樹脂、聚苯硫醚(PPS)、聚四氟乙烯(PTFE)、鄰苯二甲酸二烯丙酯樹脂(PDAP)等。As materials for forming the plastic substrate, for example, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC), acrylic resins, cycloolefin polymers, polyamide (PA) resins, polyimide (PI) resins, polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), diallyl phthalate resin (PDAP), etc. can be used.
支承基材10可以是透明的、半透明的或不透明的。另外，所謂透明，是指對可見光(波長380～780nm的光)具有從外側能夠看到支承基材10內部的透過性，可見光的光透射率為40%以上，優選為80%以上，更優選為90%以上。光透射率是使用JIS K 7375：2008規定的"塑膠-全光線透射率和全光線反射率的求法"來測定的。The support substrate 10 may be transparent, translucent or opaque. In addition, the so-called transparency means that the support substrate 10 has a transmittance to visible light (light with a wavelength of 380 to 780 nm) so that the inside of the support substrate 10 can be seen from the outside, and the light transmittance of visible light is 40% or more, preferably 80% or more, and more preferably 90% or more. The light transmittance is measured using the "Plastics - Method for determining total light transmittance and total light reflectance" specified in JIS K 7375:2008.
在壓電元件1A要求透光性的情況下，優選使用PET、PEN、PC、丙烯酸類樹脂及環烯烴類聚合物等。這些材料適用於將壓電元件1A應用於觸摸面板等透光性部件的情況。在壓電元件1A不要求透光性的情況下，例如在適用于脈搏計、心跳計等保健用品、車載壓力檢測片等的情況下，也可以使用半透明或不透明的塑膠材料。When the piezoelectric element 1A requires light transmittance, PET, PEN, PC, acrylic resin, cycloolefin polymer, etc. are preferably used. These materials are suitable for the case where the piezoelectric element 1A is applied to a light-transmitting component such as a touch panel. When the piezoelectric element 1A does not require light transmittance, for example, when it is applied to health products such as pulsometers and heart rate monitors, and vehicle-mounted pressure detection pieces, etc., a translucent or opaque plastic material may also be used.
作為形成金屬箔的材料，可以使用Au、Pt、Ag、Ti、Al、Mo、Ru、Cu等金屬。As a material forming the metal foil, metals such as Au, Pt, Ag, Ti, Al, Mo, Ru, and Cu can be used.
作為形成金屬板的材料，例如可以使用鋁、銅、不銹鋼、鉭等。As a material forming the metal plate, for example, aluminum, copper, stainless steel, tantalum, etc. can be used.
作為形成無機電介質基材的材料，例如可以使用MgO、藍寶石等。As a material forming the inorganic dielectric substrate, for example, MgO, sapphire, etc. can be used.
支承基材10的厚度沒有特別限定，可以根據壓電元件1A的用途、支承基材10的材料等適當地決定，例如也可以設為1μm～150μm。如果支承基材10的厚度為1μm～150μm，則能夠穩定地支承包含聲鏡層20、第1電極30、壓電體層40及第2電極50的層疊體。另外，支承基材10的翹曲被抑制，能夠減輕支承基材10的翹曲對壓電特性帶來的影響，因此壓電元件1A能夠具有所希望的壓電特性。The thickness of the support substrate 10 is not particularly limited and can be appropriately determined according to the purpose of the piezoelectric element 1A, the material of the support substrate 10, etc., and can be set to, for example, 1 μm to 150 μm. If the thickness of the support substrate 10 is 1 μm to 150 μm, the stack including the acoustic mirror layer 20, the first electrode 30, the piezoelectric layer 40, and the second electrode 50 can be stably supported. In addition, the warp of the support substrate 10 is suppressed, and the influence of the warp of the support substrate 10 on the piezoelectric characteristics can be reduced, so that the piezoelectric element 1A can have the desired piezoelectric characteristics.
在本說明書中，支承基材10的厚度是指垂直于支承基材10的表面的方向上的長度。對支承基材10的厚度的測定方法沒有特別限定，可以使用任意的測定方法。支承基材10的厚度例如可以是在支承基材10的截面中測定任意位置時的厚度，也可以是在任意的位置測定多處，作為這些測定值的平均值。以下，厚度的定義在其他構件中也同樣進行定義。In this specification, the thickness of the support substrate 10 refers to the length in the direction perpendicular to the surface of the support substrate 10. There is no particular limitation on the method for measuring the thickness of the support substrate 10, and any measurement method can be used. The thickness of the support substrate 10 can be, for example, the thickness when measuring any position in the cross section of the support substrate 10, or it can be the average value of the measured values measured at multiple positions at any position. The definition of thickness is also defined in the other components below.
[聲鏡層] 如圖1所示，聲鏡層20設置在支承基材10的上方的主面(上表面)101上。聲鏡層20可以由固有聲阻抗不同的聲學多層膜構成。聲鏡層20是將具有規定的固有聲阻抗的高聲阻抗層21和固有聲阻抗比高聲阻抗層21低的低聲阻抗層22交替層疊2組以上而成的多層膜。 [Acoustic mirror layer] As shown in FIG. 1 , the acoustic mirror layer 20 is provided on the main surface (upper surface) 101 above the supporting substrate 10. The acoustic mirror layer 20 can be composed of an acoustic multilayer film having different inherent acoustic impedances. The acoustic mirror layer 20 is a multilayer film in which two or more sets of high acoustic impedance layers 21 having a predetermined inherent acoustic impedance and low acoustic impedance layers 22 having lower inherent acoustic impedance than the high acoustic impedance layers 21 are alternately stacked.
如果諧振振動被傳遞到聲鏡層20中，則諧振的振動能量被聲鏡層20反射。振動的波(彈性波)在高聲阻抗層21中傳播的速度與在低聲阻抗層22中傳播的速度不同。藉由在構成聲鏡層20的各層的介面上設計膜厚以使反射波因干涉而相互增強，使諧振的振動能量不受支承基材10的影響而返回到彈性波的入射方向，同時使熱能向支承基材10的方向逸出。If the resonant vibration is transmitted to the acoustic mirror layer 20, the resonant vibration energy is reflected by the acoustic mirror layer 20. The propagation speed of the vibrating wave (elastic wave) in the high acoustic impedance layer 21 is different from the propagation speed in the low acoustic impedance layer 22. By designing the film thickness at the interface of each layer constituting the acoustic mirror layer 20 so that the reflected waves are mutually reinforced due to interference, the resonant vibration energy is not affected by the supporting substrate 10 and returns to the incident direction of the elastic wave, and at the same time, the heat energy is released in the direction of the supporting substrate 10.
高聲阻抗層21由W、Mo、Ta 2O 5、ZnO等密度或體積彈性模量高的材料形成。低聲阻抗層22由密度或體積彈性模量低於高聲阻抗層21的材料形成。 The high acoustic impedance layer 21 is formed of a material having a high density or a high volume modulus of elasticity, such as W, Mo, Ta 2 O 5 , or ZnO. The low acoustic impedance layer 22 is formed of a material having a lower density or a lower volume modulus of elasticity than the high acoustic impedance layer 21 .
低聲阻抗層22由SiO 2等密度或體積彈性模量低的材料形成。低聲阻抗層22可以是非晶層或非晶占主導地位的層。藉由使低聲阻抗層22為非晶占主導地位的層，能夠抑制高聲阻抗層21中的應力增大。 The low acoustic impedance layer 22 is formed of a material having a low density or volume modulus such as SiO 2. The low acoustic impedance layer 22 may be an amorphous layer or a layer dominated by amorphous. By making the low acoustic impedance layer 22 a layer dominated by amorphous, the stress increase in the high acoustic impedance layer 21 can be suppressed.
高聲阻抗層21和低聲阻抗層22藉由濺射等形成在支承基材10上。The high acoustic impedance layer 21 and the low acoustic impedance layer 22 are formed on the supporting substrate 10 by sputtering or the like.
[第1電極] 如圖1所示，第1電極30設置在聲鏡層20上方的主面(上表面)201上。第1電極30可以在聲鏡層20的一部分或整個面上形成薄膜狀，也可以條紋狀地平行設置複數個。 [First electrode] As shown in FIG1 , the first electrode 30 is provided on the main surface (upper surface) 201 above the acoustic mirror layer 20. The first electrode 30 may be formed in a thin film on a part or the entire surface of the acoustic mirror layer 20, or a plurality of the first electrodes 30 may be provided in parallel in a stripe shape.
第1電極30可以使用具有導電性的任何材料。作為上述材料，可以使用Pt、Au、Ag、Cu、Mg、Al、Si、Ti、Cr、Fe、Ni、Zn、Rb、Zr、Nb、Mo、Rh、Pd、Ru、Sn、Ir、Ta及W等金屬，氧化錫、ITO(Indium Tin Oxide)、IZO(Indium Zinc Oxide)、IZTO(Indium Zinc Tin Oxide)、IGZO(Indium Gallium Zinc Oxide)等金屬氧化物。Any conductive material can be used for the first electrode 30. As the above-mentioned material, metals such as Pt, Au, Ag, Cu, Mg, Al, Si, Ti, Cr, Fe, Ni, Zn, Rb, Zr, Nb, Mo, Rh, Pd, Ru, Sn, Ir, Ta and W, and metal oxides such as tin oxide, ITO (Indium Tin Oxide), IZO (Indium Zinc Oxide), IZTO (Indium Zinc Tin Oxide), and IGZO (Indium Gallium Zinc Oxide) can be used.
第1電極30可以是由對可見光透明的導電材料形成的透明電極。根據壓電元件1A的應用領域，第1電極30的透明性不是必須的，但在將壓電元件1A應用於觸摸面板等顯示器的情況下，要求具有對可見光的光透射性。在第1電極30要求透光性的情況下，作為上述材料，可以使用由ITO、IZO、IZTO、IGZO等透明的金屬氧化物構成的氧化物導電膜等。The first electrode 30 may be a transparent electrode formed of a conductive material that is transparent to visible light. Depending on the application field of the piezoelectric element 1A, the transparency of the first electrode 30 is not essential, but when the piezoelectric element 1A is applied to a display such as a touch panel, it is required to have light transmittance to visible light. When the first electrode 30 is required to have light transmittance, as the above-mentioned material, an oxide conductive film composed of a transparent metal oxide such as ITO, IZO, IZTO, IGZO, etc. can be used.
在第1電極30不需要透光性的情況下，作為上述材料，可以使用金屬等，也可以使用具有與纖鋅礦相同的晶格結構的六方晶系的金屬。作為六方晶系的金屬，可以組合使用Ti、Zr、Hf、Ru、Zn、Y、Sc等。When the first electrode 30 does not need to be light-transmissive, metal or the like can be used as the material, and a hexagonal metal having the same lattice structure as zirconite can be used. As the hexagonal metal, Ti, Zr, Hf, Ru, Zn, Y, Sc, etc. can be used in combination.
從抑制第1電極30與壓電體層40之間的介面的凹凸或晶界的觀點出發，第1電極30也可以是非晶質的膜。藉由形成非晶質的膜，能夠抑制第1電極30的表面的凹凸、或成為洩漏路徑的主要原因的晶界的生成。另外，上層的壓電體層40不受第1電極30的結晶取向的影響，能夠以良好的結晶取向性成長。From the viewpoint of suppressing the unevenness or grain boundaries at the interface between the first electrode 30 and the piezoelectric layer 40, the first electrode 30 may also be an amorphous film. By forming an amorphous film, the unevenness on the surface of the first electrode 30 or the generation of grain boundaries that are the main causes of the leakage path can be suppressed. In addition, the upper piezoelectric layer 40 is not affected by the crystal orientation of the first electrode 30 and can grow with good crystal orientation.
第1電極30的厚度可以適宜地設計，例如可以是3nm～300nm。如果第1電極30的厚度為3nm～300nm，則能夠顯示作為電極的功能，並且能夠實現壓電元件1A的薄膜化。The thickness of the first electrode 30 can be appropriately designed, and can be, for example, 3 nm to 300 nm. If the thickness of the first electrode 30 is 3 nm to 300 nm, the function as an electrode can be exhibited, and the piezoelectric element 1A can be made thinner.
[壓電體層] 如圖1所示，壓電體層40被設置在第1電極30的上方的主面(上表面)301上。壓電體層40具有以規定的範圍的比例摻雜了金屬元素的壓電材料，也可以由摻雜了金屬元素的壓電材料構成。 [Piezoelectric layer] As shown in FIG. 1 , the piezoelectric layer 40 is provided on the main surface (upper surface) 301 above the first electrode 30. The piezoelectric layer 40 has a piezoelectric material doped with a metal element at a ratio within a predetermined range, and may also be composed of a piezoelectric material doped with a metal element.
壓電體層40優選包含壓電材料作為主要成分。另外，主成分是指壓電材料的含量為95atom%以上，優選為98atom%以上，更優選為99atom%以上。The piezoelectric layer 40 preferably contains a piezoelectric material as a main component. The main component means that the content of the piezoelectric material is 95 atom % or more, preferably 98 atom % or more, and more preferably 99 atom % or more.
作為壓電材料，可以使用具有鈣鈦礦型結晶結構的壓電材料(鈣鈦礦型結晶材料)或具有纖鋅礦型結晶結構的壓電材料(纖鋅礦型結晶材料)等。As the piezoelectric material, a piezoelectric material having a calcite-titanate type crystal structure (calcite-titanate type crystal material) or a piezoelectric material having a fibrous zincite type crystal structure (fibrous zincite type crystal material) or the like can be used.
纖鋅礦型的結晶結構用通式AB(A是陽性元素，B是陰性元素)表示。纖鋅礦型結晶材料具有六方晶的單位晶格，在平行於c軸的方向上具有極化向量。The crystalline structure of zirconia is represented by the general formula AB (A is a positive element and B is a negative element). The zirconia crystalline material has a hexagonal unit lattice and has a polarization vector in the direction parallel to the c-axis.
作為纖鋅礦型結晶材料，優選使用顯示一定值以上的壓電特性、能夠在200℃以下的低溫工藝中結晶化的材料。纖鋅礦型結晶材料作為用通式AB表示的陽性元素A，包含Zn、Al、Ga、Cd及Si等。作為纖鋅礦型結晶材料，例如可以使用氧化鋅(ZnO)、硫化鋅(ZnS)、硒化鋅(ZnSe)、碲化鋅(ZnTe)、氮化鋁(AlN)、氮化鎵(GaN)、硒化鎘(CdSe)、碲化鎘(CdTe)、碳化矽(SiC)等。其中，作為纖鋅礦型結晶材料，從即使在低溫工藝中也容易比較良好地進行c軸取向的方面考慮，優選ZnO。這些既可以單獨使用1種，也可以並用2種以上。在並用2種以上的纖鋅礦型結晶材料的情況下，也可以是含有其中的1種以上的成分作為主要成分，含有其他的成分作為任意成分。另外，可以將各個材料層疊，也可以使用複數個靶材形成為一個層。As a fibrous zincite type crystal material, it is preferred to use a material that shows piezoelectric properties above a certain value and can be crystallized in a low temperature process below 200°C. The fibrous zincite type crystal material is a positive element A represented by the general formula AB, including Zn, Al, Ga, Cd and Si. As a fibrous zincite type crystal material, for example, zinc oxide (ZnO), zinc sulfide (ZnS), zinc selenide (ZnSe), zinc telluride (ZnTe), aluminum nitride (AlN), gallium nitride (GaN), cadmium selenide (CdSe), cadmium telluride (CdTe), silicon carbide (SiC), etc. can be used. Among them, ZnO is preferred as a fibrous zincite type crystal material from the perspective of being easy to perform c-axis orientation relatively well even in a low-temperature process. These can be used alone or in combination of two or more. When two or more fibrous zincite type crystal materials are used in combination, one or more of the components can be contained as the main component, and other components can be contained as arbitrary components. In addition, each material can be stacked, or a plurality of target materials can be used to form a layer.
纖鋅礦型結晶材料優選含有ZnO，更優選實質上由ZnO構成，進一步優選僅由ZnO構成。“實質上”是指除了ZnO以外，還可以含有在製造過程中不可避免地含有的不可避免的雜質。The fibrous zinc mineral-type crystal material preferably contains ZnO, more preferably consists essentially of ZnO, and further preferably consists only of ZnO. "Essentially" means that in addition to ZnO, it may also contain inevitable impurities that are inevitably contained in the manufacturing process.
作為在壓電材料中摻雜的金屬元素，可以舉出Mg、Ca、Sr等堿土類金屬，或者V、Ti、Zr、Si、Sr、Li等。這些成分既可以以元素的狀態含有，也可以以氧化物的狀態含有。其中，從一邊控制壓電體層40的K值一邊維持Q值，發揮優異的壓電特性的觀點出發，作為摻雜的金屬元素，優選Mg。即，作為摻雜有金屬元素的壓電材料，優選使用在ZnO中摻雜有Mg的MgZnO。As metal elements doped in the piezoelectric material, alkaline earth metals such as Mg, Ca, and Sr, or V, Ti, Zr, Si, Sr, and Li can be cited. These components can be contained in the form of elements or in the form of oxides. Among them, Mg is preferably used as the doped metal element from the viewpoint of controlling the K value of the piezoelectric layer 40 while maintaining the Q value and exerting excellent piezoelectric characteristics. That is, as the piezoelectric material doped with metal elements, MgZnO in which Mg is doped in ZnO is preferably used.
壓電體層40作為摻雜的金屬元素的濃度不同的2種壓電體層，具有第1壓電體層41、和金屬元素的濃度比第1壓電體層41中含有的金屬元素的濃度低的第2壓電體層42。以下，有時將第1壓電體層41及第2壓電體層42合併，稱為壓電體層40。The piezoelectric layer 40 includes two types of piezoelectric layers having different concentrations of metal elements doped therein, namely, a first piezoelectric layer 41 and a second piezoelectric layer 42 having a lower concentration of metal elements than the first piezoelectric layer 41. Hereinafter, the first piezoelectric layer 41 and the second piezoelectric layer 42 may be collectively referred to as the piezoelectric layer 40.
第1壓電體層41配置在2個第2壓電體層42彼此之間。The first piezoelectric layer 41 is disposed between two second piezoelectric layers 42 .
第2壓電體層42設置在第1壓電體層41的上表面411及下表面412上。即，第2壓電體層42設置在第1電極30與第1壓電體層41之間、以及第1壓電體層41與第2電極50之間。The second piezoelectric layer 42 is provided on the upper surface 411 and the lower surface 412 of the first piezoelectric layer 41 . That is, the second piezoelectric layer 42 is provided between the first electrode 30 and the first piezoelectric layer 41 , and between the first piezoelectric layer 41 and the second electrode 50 .
包含在第1壓電體層41中的金屬元素的濃度優選為5atom%～30atom%。金屬元素的濃度的下限值更優選為10atom以上，進一步優選為15atom以上。The concentration of the metal element contained in the first piezoelectric layer 41 is preferably 5 atom % to 30 atom %. The lower limit of the concentration of the metal element is more preferably 10 atom % or more, and further preferably 15 atom % or more.
第2壓電體層42是金屬元素的濃度比第1壓電體層41低的層。The second piezoelectric layer 42 is a layer having a lower metal element concentration than the first piezoelectric layer 41 .
包含在第2壓電體層42中的金屬元素的濃度優選為超過0atom%且為10atom以下，更優選為1atom%～8atom%，進一步優選為3atom%～5atom%。The concentration of the metal element contained in the second piezoelectric layer 42 is preferably more than 0 atom % and less than 10 atom %, more preferably 1 atom % to 8 atom %, and further preferably 3 atom % to 5 atom %.
在並用2種以上的第1壓電體層41或第2壓電體層42的情況下，由各個壓電材料構成的第1壓電體層41及第2壓電體層42，也可以層疊複數個。When two or more first piezoelectric layers 41 or second piezoelectric layers 42 are used in combination, a plurality of first piezoelectric layers 41 and second piezoelectric layers 42 made of the respective piezoelectric materials may be stacked.
對壓電體層40中的添加元素的含量沒有特別限定，只要在壓電體層40能夠具有纖鋅礦型的結晶結構的範圍內即可。另外，壓電體層40中所含的添加元素的含量的測定方法，只要是能夠進行測定的方法即可，沒有特別限定。壓電體層40中所含的添加元素的含量，例如可以藉由盧瑟福背向散射分析法(RBS)，使用Pelletron 3SDH(NEC公司制)作為測定裝置來測定，也可以藉由二次離子品質分析法，使用動態SIMS(D-SIMS)等來測定。There is no particular limitation on the content of the additive element in the piezoelectric layer 40, as long as it is within the range in which the piezoelectric layer 40 can have a crystalline structure of a fibrous zinc mineral type. In addition, there is no particular limitation on the method for measuring the content of the additive element contained in the piezoelectric layer 40, as long as it is a method that can be measured. The content of the additive element contained in the piezoelectric layer 40 can be measured, for example, by Rutherford backscattering analysis (RBS) using Pelletron 3SDH (manufactured by NEC Corporation) as a measuring device, or by secondary ion mass spectrometry using dynamic SIMS (D-SIMS) or the like.
壓電體層40的厚度沒有特別限定，只要是具有充分的壓電特性、即與壓力成比例的極化特性、並且能夠降低在壓電體層40中產生裂紋等、穩定地發揮壓電特性的厚度即可。例如，壓電體層40的厚度可以為50nm～5μm。如果壓電體層40的厚度為50nm～5μm，則能夠發揮充分的壓電特性。The thickness of the piezoelectric layer 40 is not particularly limited, as long as it has sufficient piezoelectric characteristics, that is, polarization characteristics proportional to pressure, and can reduce the generation of cracks in the piezoelectric layer 40 and stably exert the piezoelectric characteristics. For example, the thickness of the piezoelectric layer 40 can be 50nm to 5μm. If the thickness of the piezoelectric layer 40 is 50nm to 5μm, sufficient piezoelectric characteristics can be exerted.
作為第1壓電體層41的厚度，例如只要是10nm～5μm即可，優選為100nm～1μm，更優選為150nm～700nm，進一步優選為250nm～500nμm。如果第1壓電體層41的厚度為10nm～5μm，則能夠發揮充分的壓電特性。The thickness of the first piezoelectric layer 41 may be, for example, 10 nm to 5 μm, preferably 100 nm to 1 μm, more preferably 150 nm to 700 nm, and further preferably 250 nm to 500 nm. If the thickness of the first piezoelectric layer 41 is 10 nm to 5 μm, sufficient piezoelectric characteristics can be exhibited.
作為第2壓電體層42的厚度，例如，只要是5nm～300nm即可，優選為10nm～200nm，更優選為30nm～150nm，進一步優選為50nm～100nμm。如果第2壓電體層42的厚度為5nm～300nm，則能夠發揮充分的壓電特性。The thickness of the second piezoelectric layer 42 may be, for example, 5 nm to 300 nm, preferably 10 nm to 200 nm, more preferably 30 nm to 150 nm, and further preferably 50 nm to 100 nm. If the thickness of the second piezoelectric layer 42 is 5 nm to 300 nm, sufficient piezoelectric characteristics can be exhibited.
壓電體層40的結晶取向性優選為5°以下。如果結晶取向性為5°以下，則壓電體層40中所含的壓電材料的往c軸方向的結晶取向性(c軸取向性)良好，能夠提高能量轉換效率，因此能夠提高壓電體層40的往厚度方向的壓電特性。在壓電體層40包含ZnO作為壓電材料的情況下，ZnO具有纖鋅礦型的結晶結構，與具有其他結晶結構的壓電材料相比，結晶取向性和壓電特性的相關性高。如果ZnO的結晶取向性為5°以下，則能量轉換效率容易進一步提高，因此能夠提高壓電元件1A的壓電特性。The crystal orientation of the piezoelectric layer 40 is preferably 5° or less. If the crystal orientation is 5° or less, the crystal orientation of the piezoelectric material contained in the piezoelectric layer 40 in the c-axis direction (c-axis orientation) is good, which can improve the energy conversion efficiency, and thus the piezoelectric properties of the piezoelectric layer 40 in the thickness direction can be improved. In the case where the piezoelectric layer 40 includes ZnO as the piezoelectric material, ZnO has a fibrous zincite-type crystal structure, and the correlation between the crystal orientation and the piezoelectric properties is high compared to piezoelectric materials having other crystal structures. If the crystal orientation of ZnO is 5° or less, the energy conversion efficiency can be easily further improved, and thus the piezoelectric properties of the piezoelectric element 1A can be improved.
壓電體層40的結晶取向可以用當藉由X射線鎖定曲線(XRC：X-ray Rocking Curve)法測量壓電體層40的表面時獲得的半值全寬(FWHM：Full Width at Half Maximum)來評估。即，壓電體層40的結晶取向性用藉由XRC法對作為主要成分包含在壓電體層40中的壓電材料的結晶的(0002)面的衍射進行測定時得到的鎖定曲線的峰值波形的FWHM來表示。在壓電體層40中包含的壓電材料具有ZnO等的纖鋅礦型結晶結構的情況下，FWHM表示構成壓電材料的結晶之間的c軸方向的排列的平行程度。因此，藉由XRC法得到的鎖定曲線的峰值波形的FWHM可以作為壓電體層40的c軸取向性的指標。因此，鎖定曲線的FWHM越小，可以評價為壓電體層40的c軸方向的結晶取向性越好。The crystal orientation of the piezoelectric layer 40 can be evaluated by the full width at half maximum (FWHM) obtained when the surface of the piezoelectric layer 40 is measured by the X-ray rocking curve (XRC) method. That is, the crystal orientation of the piezoelectric layer 40 is represented by the FWHM of the peak waveform of the rocking curve obtained when the diffraction of the (0002) plane of the crystal of the piezoelectric material as the main component contained in the piezoelectric layer 40 is measured by the XRC method. In the case where the piezoelectric material contained in the piezoelectric layer 40 has a fibrous zincite crystal structure such as ZnO, the FWHM represents the degree of parallelism of the arrangement of the c-axis direction between the crystals constituting the piezoelectric material. Therefore, the FWHM of the peak waveform of the locking curve obtained by the XRC method can be used as an index of the c-axis orientation of the piezoelectric layer 40. Therefore, the smaller the FWHM of the locking curve, the better the crystal orientation of the piezoelectric layer 40 in the c-axis direction.
另外，對於壓電體層40的結晶取向性，除了藉由XRC法在壓電體層40上測定來自壓電材料的特定結晶面(例如，ZnO結晶的(0002)面)的衍射而得到的鎖定曲線的FWHM之外，還可以包含峰強度來進行評價。即，壓電體層40的結晶取向性也可以使用峰值強度的積分值除以FWHM得到的值作為評價值來評價。例如，峰值強度的積分值除以FWHM得到的評價值越大，能夠評價為壓電體層40的結晶取向性越好。In addition, the crystal orientation of the piezoelectric layer 40 can be evaluated by including the peak intensity in addition to the FWHM of the locking curve obtained by measuring the diffraction from a specific crystal plane of the piezoelectric material (for example, the (0002) plane of the ZnO crystal) on the piezoelectric layer 40 by the XRC method. That is, the crystal orientation of the piezoelectric layer 40 can also be evaluated using the value obtained by dividing the integral value of the peak intensity by the FWHM as an evaluation value. For example, the larger the evaluation value obtained by dividing the integral value of the peak intensity by the FWHM, the better the crystal orientation of the piezoelectric layer 40 can be evaluated.
[第2電極] 如圖1所示，第2電極50設置在壓電體層40上方的主面(上表面)401上。第2電極50可以由具有導電性的任何材料形成，並且可以使用與第1電極30同樣的材料。 [Second electrode] As shown in FIG. 1 , the second electrode 50 is provided on the main surface (upper surface) 401 above the piezoelectric layer 40. The second electrode 50 can be formed of any material having conductivity, and the same material as the first electrode 30 can be used.
第2電極50與第1電極30同樣，可以在壓電體層40的上表面401的一部分或整個面上形成為薄膜狀，也可以適當地形成為任意的形狀。例如，在條紋狀平行設置複數個第1電極30的情況下，也可以是在俯視時，在與第1電極30的條紋狀延伸設置的方向正交的方向上，條紋狀平行設置複數個第2電極50。The second electrode 50, like the first electrode 30, can be formed as a thin film on a part or the entire surface of the upper surface 401 of the piezoelectric layer 40, or can be formed into any shape as appropriate. For example, when a plurality of first electrodes 30 are arranged in parallel in a stripe shape, a plurality of second electrodes 50 can be arranged in parallel in a stripe shape in a direction orthogonal to the direction in which the stripes of the first electrode 30 are extended when viewed from above.
第2電極50的厚度可以適當地進行設計，例如優選為20nm～300nm。如果第2電極50的厚度在上述優選的範圍內，則能夠顯現作為電極的功能，並且能夠實現壓電元件1A的薄膜化。The thickness of the second electrode 50 can be appropriately designed, and is preferably 20 nm to 300 nm, for example. When the thickness of the second electrode 50 is within the above-mentioned preferred range, the function as an electrode can be exhibited, and the piezoelectric element 1A can be made thinner.
壓電元件1A的製造方法沒有特別限定，可以適當地使用任意的製造方法。對壓電元件1A的製造方法的一例進行說明。The method for manufacturing the piezoelectric element 1A is not particularly limited, and any manufacturing method can be appropriately used. An example of a method for manufacturing the piezoelectric element 1A will be described.
首先，在形成為規定大小的支承基材10的上表面101上，將高聲阻抗層21和低聲阻抗層22作為一組，交替層疊高聲阻抗層21和低聲阻抗層22而形成聲鏡層20。First, on the upper surface 101 of the support base 10 formed into a predetermined size, the high acoustic impedance layer 21 and the low acoustic impedance layer 22 are alternately stacked as a set to form the acoustic mirror layer 20 .
高聲阻抗層21和低聲阻抗層22的形成方法沒有特別限定，可以是幹法工藝和濕法工藝中的任一種。作為高聲阻抗層21和低聲阻抗層22的形成方法，如果使用幹法工藝，則能夠容易地形成薄的高聲阻抗層21和低聲阻抗層22。The method for forming the high acoustic impedance layer 21 and the low acoustic impedance layer 22 is not particularly limited, and may be either a dry process or a wet process. As the method for forming the high acoustic impedance layer 21 and the low acoustic impedance layer 22, if a dry process is used, thin high acoustic impedance layer 21 and low acoustic impedance layer 22 can be easily formed.
作為幹法工藝，例如可以舉出濺射、蒸鍍等，作為濕法工藝，例如可以舉出電鍍等。Examples of dry processes include sputtering and evaporation, and examples of wet processes include electroplating.
作為濺射，例如可以使用DC(直流)或RF(高頻)的磁控濺射法等濺射法。As the sputtering, for example, a sputtering method such as a DC (direct current) or RF (high frequency) magnetron sputtering method can be used.
藉由使用濺射作為高聲阻抗層21和低聲阻抗層22的形成方法，可以容易地形成密度高、且薄的高聲阻抗層21和低聲阻抗層22。因此，作為高聲阻抗層21和低聲阻抗層22的形成方法，優選濺射。By using sputtering as a method for forming the high acoustic impedance layer 21 and the low acoustic impedance layer 22, it is possible to easily form the high acoustic impedance layer 21 and the low acoustic impedance layer 22 with high density and in a thin layer. Therefore, as a method for forming the high acoustic impedance layer 21 and the low acoustic impedance layer 22, sputtering is preferred.
作為高聲阻抗層21可以使用例如藉由DC或RF的磁控濺射法成膜的、由W、Mo、Ta 2O 5及ZnO等密度或體積彈性模量高的材料形成的薄膜等。 As the high acoustic impedance layer 21, for example, a thin film formed by a material having a high density or a high volume modulus such as W, Mo , Ta2O5 , or ZnO, which is formed by a DC or RF magnetron sputtering method, can be used.
作為低聲阻抗層22可以使用例如藉由DC或RF的磁控濺射法成膜的SiO 2膜等無機氧化物。 As the low acoustic impedance layer 22, for example, an inorganic oxide such as a SiO2 film formed by a DC or RF magnetron sputtering method can be used.
接著，在聲鏡層20的上表面201上形成(成膜)第1電極30。第1電極30的形成方法沒有特別限定，與高聲阻抗層21和低聲阻抗層22的形成方法相同，可以使用幹法工藝和濕法工藝中的任一種。幹法工藝和濕法工藝的細節與高聲阻抗層21和低聲阻抗層22的形成方法相同，因此省略細節。Next, the first electrode 30 is formed (film-formed) on the upper surface 201 of the acoustic mirror layer 20. The method for forming the first electrode 30 is not particularly limited, and the same as the method for forming the high acoustic impedance layer 21 and the low acoustic impedance layer 22, either a dry process or a wet process can be used. The details of the dry process and the wet process are the same as the method for forming the high acoustic impedance layer 21 and the low acoustic impedance layer 22, so the details are omitted.
第1電極30可以形成在聲鏡層20的上表面201的整個表面上。另外，第1電極30也可以藉由蝕刻等加工成具有規定形狀的圖案，從而適當地形成為任意的形狀。例如，第1電極30也可以圖案形成為條紋狀，並以條紋狀配置複數個。The first electrode 30 may be formed on the entire surface of the upper surface 201 of the acoustic mirror layer 20. In addition, the first electrode 30 may be processed into a pattern having a predetermined shape by etching or the like, thereby being appropriately formed into any shape. For example, the first electrode 30 may be patterned into a stripe shape, and a plurality of the first electrodes 30 may be arranged in the stripe shape.
接著，在第1電極30的上表面301上層疊第2壓電體層42、第1壓電體層41以及第2壓電體層42，從而形成壓電體層40。Next, the second piezoelectric layer 42 , the first piezoelectric layer 41 , and the second piezoelectric layer 42 are stacked on the upper surface 301 of the first electrode 30 , thereby forming the piezoelectric layer 40 .
對第2壓電體層42的形成方法進行說明。首先，在第1電極30的上表面301上形成第2壓電體層42。The method for forming the second piezoelectric layer 42 is described. First, the second piezoelectric layer 42 is formed on the upper surface 301 of the first electrode 30 .
例如，可以使用含有金屬元素和構成壓電材料的元素的靶材，在含有Ar等惰性氣體和微量氧的混合氣體氣氛中，藉由DC或RF的磁控濺射法等濺射法，形成金屬元素和壓電材料。藉由在第1電極30上濺射金屬元素和壓電材料，形成包含摻雜有金屬元素的壓電材料的第2壓電體層42。For example, a target containing a metal element and an element constituting a piezoelectric material can be used to form the metal element and the piezoelectric material by a sputtering method such as DC or RF magnetron sputtering in a mixed gas atmosphere containing an inert gas such as Ar and a trace amount of oxygen. By sputtering the metal element and the piezoelectric material on the first electrode 30, a second piezoelectric layer 42 containing a piezoelectric material doped with the metal element is formed.
由支承基材10、聲鏡層20以及第1電極30構成的層疊體，可以配置在濺射裝置的成膜室的成為陽極的成膜板上。例如，成膜板可以是可旋轉的。如果將由支承基材10、聲鏡層20以及第1電極30構成的層疊體配置在成膜板上，則能夠在第1電極30上以批量式形成第2壓電體層42。The stack composed of the support substrate 10, the acoustic mirror layer 20 and the first electrode 30 can be arranged on a film forming plate that serves as an anode in a film forming chamber of a sputtering device. For example, the film forming plate can be rotatable. If the stack composed of the support substrate 10, the acoustic mirror layer 20 and the first electrode 30 is arranged on the film forming plate, the second piezoelectric layer 42 can be formed on the first electrode 30 in a batch manner.
另外，也可以將由支承基材10、聲鏡層20及第1電極30構成的層疊體作為陽極，代替成膜板而捲繞在作為成膜輥的輥筒上。藉由將輥筒配置在成膜室中，能夠一邊以輥對輥方式輸送由支承基材10、聲鏡層20及第1電極30構成的層疊體，一邊在第1電極30上連續地成膜第2壓電體層42。Alternatively, a stack of the support substrate 10, the acoustic mirror layer 20, and the first electrode 30 may be used as an anode and wound around a roll as a film-forming roll instead of a film-forming plate. By placing the roll in the film-forming chamber, the second piezoelectric layer 42 can be continuously formed on the first electrode 30 while the stack of the support substrate 10, the acoustic mirror layer 20, and the first electrode 30 are transported in a roll-to-roll manner.
含有金屬元素和構成壓電材料的元素的靶材用作陰極。靶材以與濺射裝置內的成膜板隔開間隔相對的方式配置。A target containing a metal element and an element constituting a piezoelectric material is used as a cathode. The target is arranged to face a film-forming plate in a sputtering device with a gap therebetween.
在摻雜有金屬元素的壓電材料例如含有纖鋅礦型結晶材料的情況下，靶材可以使用含有金屬元素和構成第2壓電體層42中作為主成分含有的纖鋅礦型結晶材料的材料的單個或複數個靶材。藉由在使用複數個靶材作為陰極的情況下使用多元濺射法，在使用單個靶材作為陰極的情況下使用一維濺射法，能夠在第1電極30上形成含有摻雜了金屬元素的纖鋅礦型結晶材料的第2壓電體層42。In the case of a piezoelectric material doped with a metal element, for example, containing a fibrous zincite-type crystalline material, a target material may use a single or multiple targets containing a metal element and a material that constitutes the fibrous zincite-type crystalline material as a main component in the second piezoelectric layer 42. By using a multi-dimensional sputtering method when using multiple targets as cathodes and a one-dimensional sputtering method when using a single target as cathode, the second piezoelectric layer 42 containing the fibrous zincite-type crystalline material doped with a metal element can be formed on the first electrode 30.
在使用複數個靶材作為陰極的情況下，對於各個靶材，包括金屬元素和構成在第2壓電體層42中作為主成分包含的纖鋅礦型結晶材料的材料。作為複數個靶材，例如可以使用含有Mg等金屬元素的靶材、含有Zn的靶材、含有Si或Sn的靶材、含有Al的靶材，也可以使用由金屬元素構成的靶材和由纖鋅礦型結晶材料構成的靶材。另外，各個靶材可以使用含有氧的金屬氧化物的靶材。複數個靶材可以彼此間隔地佈置在成膜室中。在濺射時，可以根據第2壓電體層42中所含的金屬元素及纖鋅礦型結晶材料的種類等，調整對各個靶材施加的電力，調整構成摻雜有金屬元素的第2壓電體層42的各個材料彼此的原子比例。When a plurality of targets are used as cathodes, each target includes a metal element and a material constituting a fibrous zincite type crystal material contained as a main component in the second piezoelectric layer 42. As the plurality of targets, for example, a target containing a metal element such as Mg, a target containing Zn, a target containing Si or Sn, a target containing Al, a target composed of a metal element, and a target composed of a fibrous zincite type crystal material can be used. In addition, each target can use a target of a metal oxide containing oxygen. A plurality of targets can be arranged in a film forming chamber at intervals from each other. During sputtering, the electric force applied to each target material can be adjusted according to the metal element and the type of zirconia-type crystal material contained in the second piezoelectric layer 42, thereby adjusting the atomic ratio of each material constituting the second piezoelectric layer 42 doped with the metal element.
在使用單個靶材作為陰極的情況下，單個靶材含有金屬元素和包含在第2壓電體層42中的纖鋅礦型結晶材料。作為使用單個靶材的情況，可以使用調整了金屬元素和構成第2壓電體層42中含有的纖鋅礦型結晶材料的材料彼此的原子比例的合金靶材，可以使用含有預先以規定的比例添加了金屬元素的纖鋅礦型結晶材料的合金靶材。作為單個靶材，例如可以使用含有Mg等金屬元素、Zn、Si或Sn、Al的合金靶材。合金靶材可以使用金屬氧化物靶材，其包括金屬元素、纖鋅礦型結晶材料和氧。In the case of using a single target as a cathode, the single target contains a metal element and a fibrous zincite type crystalline material contained in the second piezoelectric layer 42. In the case of using a single target, an alloy target in which the atomic ratio of the metal element and the material constituting the fibrous zincite type crystalline material contained in the second piezoelectric layer 42 is adjusted can be used, and an alloy target containing a fibrous zincite type crystalline material to which a metal element is pre-added at a prescribed ratio can be used. As a single target, for example, an alloy target containing a metal element such as Mg, Zn, Si or Sn, and Al can be used. The alloy target can use a metal oxide target, which includes a metal element, a fibrous zincite type crystalline material, and oxygen.
摻雜有金屬元素的壓電材料例如為以規定的品質比含有作為金屬元素的MgO和作為纖鋅礦型結晶材料的ZnO的MgZnO時，可以使用：使用由MgO燒結體構成的靶材和由ZnO燒結體構成的靶材的多元濺射法。另外，作為其他方法，也可以使用：使用預先以規定比例添加了MgO的ZnO燒結體的靶材等含有ZnO和MgO的合金靶材的一維濺射法。When the piezoelectric material doped with a metal element is, for example, MgZnO containing MgO as a metal element and ZnO as a fibrous zinc mineral crystal material at a predetermined quality ratio, a multi-element sputtering method using a target composed of a sintered MgO body and a target composed of a sintered ZnO body can be used. In addition, as another method, a one-dimensional sputtering method using an alloy target containing ZnO and MgO, such as a target composed of a sintered ZnO body to which MgO is pre-added at a predetermined ratio, can also be used.
在使用多元濺射法的情況下，使用多元濺射裝置作為濺射裝置，將例如Ar等含有惰性氣體和氧的混合氣體供給到多元濺射裝置內，形成含有惰性氣體和氧的混合氣體氣氛。在混合氣體氣氛下，藉由使用MgO燒結體的靶材和ZnO燒結體的靶材同時且獨立地濺射到第1電極30上，能夠在第1電極30上形成由MgZnO構成的第2壓電體層42。When the multi-element sputtering method is used, a multi-element sputtering device is used as a sputtering device, and a mixed gas containing an inert gas such as Ar and oxygen is supplied into the multi-element sputtering device to form a mixed gas atmosphere containing an inert gas and oxygen. In the mixed gas atmosphere, a target material of a sintered MgO body and a target material of a sintered ZnO body are simultaneously and independently sputtered onto the first electrode 30, so that a second piezoelectric layer 42 composed of MgZnO can be formed on the first electrode 30.
在使用一維濺射法的情況下，使用濺射裝置，在含有Ar等惰性氣體和氧的混合氣體氣氛下，例如使用預先以規定的比例添加了MgO的ZnO燒結體的靶材進行濺射，由此能夠在第1電極30上形成由MgZnO薄膜構成的第2壓電體層42。When using a one-dimensional sputtering method, a sputtering device is used to perform sputtering in a mixed gas atmosphere containing an inert gas such as Ar and oxygen, for example, using a target material of a ZnO sintered body to which MgO has been pre-added in a specified proportion, thereby forming a second piezoelectric layer 42 composed of a MgZnO thin film on the first electrode 30.
濺射時的氣體氣氛不限於含有惰性氣體和氧的混合氣體氣氛，也可以是惰性氣體氣氛。The gas atmosphere during sputtering is not limited to a mixed gas atmosphere containing an inert gas and oxygen, but may be an inert gas atmosphere.
濺射時的氣體氣氛內的壓力可以根據金屬元素和壓電材料的種類、濺射法等適當決定，例如可以是0.1Pa～2.0Pa。The pressure in the gas atmosphere during sputtering can be appropriately determined according to the type of metal element and piezoelectric material, sputtering method, etc., and can be, for example, 0.1 Pa to 2.0 Pa.
第2壓電體層42的成膜溫度沒有特別限定，可以根據壓電元件1A的層結構等適當選擇，例如，也可以在150℃以下對第2壓電體層42進行成膜。The film-forming temperature of the second piezoelectric layer 42 is not particularly limited and can be appropriately selected according to the layer structure of the piezoelectric element 1A, etc. For example, the second piezoelectric layer 42 can be formed at 150° C. or lower.
藉由在第2壓電體層42的成膜中使用濺射法，能夠在大致保持化合物的靶材的組成比的狀態下形成附著力強的均勻的膜。另外，僅藉由時間的控制，就能夠高精度地形成所希望的厚度的第2壓電體層42。By using the sputtering method to form the second piezoelectric layer 42, a uniform film with strong adhesion can be formed while roughly maintaining the composition ratio of the target compound. In addition, the second piezoelectric layer 42 can be formed with high precision to a desired thickness simply by controlling the time.
第2壓電體層42也可以藉由層疊複數個摻雜有金屬元素的壓電材料的薄膜而構成。The second piezoelectric layer 42 may also be formed by stacking a plurality of thin films of piezoelectric material doped with a metal element.
接著，在第2壓電體層42的上表面421形成第1壓電體層41。第1壓電體層41的形成方法沒有特別限定，與第2壓電體層42的形成方法相同，可以使用幹法工藝和濕法工藝中的任何一種。幹法工藝和濕法工藝的細節與第2壓電體層42的形成方法相同，因此省略其細節。Next, the first piezoelectric layer 41 is formed on the upper surface 421 of the second piezoelectric layer 42. The method for forming the first piezoelectric layer 41 is not particularly limited, and the same as the method for forming the second piezoelectric layer 42, either a dry process or a wet process can be used. The details of the dry process and the wet process are the same as the method for forming the second piezoelectric layer 42, so the details are omitted.
接著，在第1壓電體層41的上表面411上形成第2壓電體層42。第2壓電體層42的形成方法與上述的在第1電極30的上表面301上形成第2壓電體層42的方法同樣，可以使用幹法工藝和濕法工藝中的任一種。幹法工藝和濕法工藝的細節與形成在第1電極30的上表面301上的第2壓電體層42的形成方法相同，因此省略其細節。Next, the second piezoelectric layer 42 is formed on the upper surface 411 of the first piezoelectric layer 41. The method for forming the second piezoelectric layer 42 is the same as the method for forming the second piezoelectric layer 42 on the upper surface 301 of the first electrode 30 described above, and either a dry process or a wet process can be used. The details of the dry process and the wet process are the same as the method for forming the second piezoelectric layer 42 on the upper surface 301 of the first electrode 30, so the details are omitted.
由此，藉由在第1電極30的上表面301上層疊第2壓電體層42、第1壓電體層41以及第2壓電體層42而形成按照第2壓電體層42、第1壓電體層41以及第2壓電體層42的順序層疊的壓電體層40。Thus, by stacking the second piezoelectric layer 42 , the first piezoelectric layer 41 , and the second piezoelectric layer 42 on the upper surface 301 of the first electrode 30 , the piezoelectric layer 40 in which the second piezoelectric layer 42 , the first piezoelectric layer 41 , and the second piezoelectric layer 42 are stacked in this order is formed.
接著，在壓電體層40的上表面401上形成具有規定形狀的第2電極50。第2電極50可以使用與第1電極30相同的形成方法來形成。Next, a second electrode 50 having a predetermined shape is formed on the upper surface 401 of the piezoelectric layer 40. The second electrode 50 can be formed using the same formation method as the first electrode 30.
第2電極50的厚度可以適當地設計，例如可以是20nm～300nm。The thickness of the second electrode 50 can be appropriately designed, and may be, for example, 20 nm to 300 nm.
第2電極50可以形成在壓電體層40的上表面401的整個面上，也可以適當地形成為任意的形狀。例如，在第1電極30形成為條紋狀的情況下，在俯視壓電元件1A時，第2電極50也可以在與第1電極30的條紋延伸設置的方向正交的方向上條紋狀地形成複數個。The second electrode 50 may be formed on the entire surface of the upper surface 401 of the piezoelectric layer 40, or may be appropriately formed in any shape. For example, when the first electrode 30 is formed in a stripe shape, when the piezoelectric element 1A is viewed from above, a plurality of second electrodes 50 may be formed in a stripe shape in a direction perpendicular to the direction in which the stripes of the first electrode 30 extend.
藉由在壓電體層40的上表面401上形成第2電極50來形成壓電元件1A。The piezoelectric element 1A is formed by forming the second electrode 50 on the upper surface 401 of the piezoelectric layer 40.
另外，在形成第2電極50後，也可以在比支承基材10的熔點或玻璃化轉變點低的溫度(例如，130℃)下，對壓電元件1A的整體進行加熱處理。藉由該加熱處理，能夠使第1電極30及第2電極50結晶化，並使其低電阻化。加熱處理不是必須的，在支承基材10由不具有耐熱性的材料形成的情況等下，也可以不在壓電元件1A的形成後進行。In addition, after forming the second electrode 50, the entire piezoelectric element 1A may be heat treated at a temperature (e.g., 130°C) lower than the melting point or glass transition point of the support substrate 10. By this heat treatment, the first electrode 30 and the second electrode 50 can be crystallized and their resistance can be reduced. The heat treatment is not essential, and in the case where the support substrate 10 is formed of a material that does not have heat resistance, the heat treatment may not be performed after the piezoelectric element 1A is formed.
這樣，根據本實施方式的壓電元件1A，具備支承基材10、聲鏡層20、第1電極30、壓電體層40及第2電極50。壓電體層40具有第1壓電體層41和設置在第1壓電體層41的上表面411及下表面412上的2個第2壓電體層42。壓電體層40由於將第1壓電體層41及第2壓電體層42由同一材料構成，因此能夠在維持Q值的同時控制壓電體層40的整體K值。另外，壓電體層40能夠抑制在第1壓電體層41與第2壓電體層42之間產生介面剝離。由此，壓電體層40能夠加厚壓電體層40的厚度而提高壓電特性，並且能夠抑制壓電特性的劣化。因此，壓電元件1A能夠在加厚壓電體層40的膜厚的同時維持壓電特性。Thus, the piezoelectric element 1A according to the present embodiment includes the supporting substrate 10, the acoustic mirror layer 20, the first electrode 30, the piezoelectric layer 40, and the second electrode 50. The piezoelectric layer 40 includes the first piezoelectric layer 41 and two second piezoelectric layers 42 provided on the upper surface 411 and the lower surface 412 of the first piezoelectric layer 41. Since the first piezoelectric layer 41 and the second piezoelectric layer 42 of the piezoelectric layer 40 are formed of the same material, the overall K value of the piezoelectric layer 40 can be controlled while maintaining the Q value. In addition, the piezoelectric layer 40 can suppress the occurrence of interface peeling between the first piezoelectric layer 41 and the second piezoelectric layer 42. As a result, the piezoelectric layer 40 can be thickened to improve the piezoelectric characteristics and suppress the degradation of the piezoelectric characteristics. Therefore, the piezoelectric element 1A can maintain the piezoelectric characteristics while increasing the thickness of the piezoelectric layer 40.
另外，壓電元件1A的壓電特性可以藉由測定壓電元件1A的壓電常數d 33(單位：pC/N)來進行評價。壓電常數d 33是表示往極化方向的伸縮模式的值，由向極化方向施加的每單位壓力的極化電荷量表示。壓電常數d 33表示壓電元件1A的膜厚方向、即c軸方向的伸縮模式。 In addition, the piezoelectric characteristics of the piezoelectric element 1A can be evaluated by measuring the piezoelectric constant d 33 (unit: pC/N) of the piezoelectric element 1A. The piezoelectric constant d 33 is a value indicating the expansion and contraction mode in the polarization direction, and is expressed by the polarization charge amount per unit pressure applied in the polarization direction. The piezoelectric constant d 33 indicates the expansion and contraction mode in the film thickness direction, i.e., the c-axis direction, of the piezoelectric element 1A.
壓電常數d 33按照以下的順序進行評價。在載物臺上以第1電極30為下側載置壓電元件1A，從壓電元件1A的上表面用壓頭施加規定的壓力，測定由c軸(膜厚)方向的極化產生的電荷。將施加負荷變化為5N～6N時的產生電荷量除以作為負荷差的1N得到的值設為壓電常數d 33值。 The piezoelectric constant d33 is evaluated in the following procedure. The piezoelectric element 1A is placed on a stage with the first electrode 30 at the bottom. A predetermined pressure is applied from the top surface of the piezoelectric element 1A with a pressing head, and the charge generated by polarization in the c-axis (film thickness) direction is measured. The value obtained by dividing the amount of charge generated when the applied load changes from 5N to 6N by 1N as the load difference is set as the piezoelectric constant d33 value.
壓電元件1A在壓電體層40中可以含有ZnO作為壓電材料，含有Mg作為金屬元素。通常，在壓電材料中摻雜其他金屬元素而形成的壓電體層的K值和Q值具有權衡的關係，如果將壓電元件用於例如僅取出5G帶等高頻帶的頻率的信號、除去除此之外的頻帶的信號的高頻濾波器等，則在高頻帶中如果得到必要的K值，則Q值有降低的傾向。在壓電體層40包含MgZnO作為壓電材料的情況下，MgZnO相對於Mg濃度沒有K值和Q值的權衡，即使在高頻區域也能夠一邊控制K值一邊維持Q值。壓電體層40可包含MgZnO作為壓電材料。因此，壓電元件1A能夠在壓電體層40中包含MgZnO作為壓電材料，因此能夠在高頻濾波器等的高頻區域中發揮壓電特性。The piezoelectric element 1A may contain ZnO as a piezoelectric material and Mg as a metal element in the piezoelectric layer 40. Generally, the K value and Q value of the piezoelectric layer formed by doping other metal elements in the piezoelectric material have a trade-off relationship. If the piezoelectric element is used, for example, as a high-frequency filter that only extracts signals of high-frequency bands such as the 5G band or removes signals of other frequency bands, the Q value tends to decrease if the necessary K value is obtained in the high-frequency band. In the case where the piezoelectric layer 40 contains MgZnO as a piezoelectric material, there is no trade-off between the K value and the Q value of MgZnO relative to the Mg concentration, and the Q value can be maintained while controlling the K value even in the high-frequency region. The piezoelectric layer 40 may include MgZnO as a piezoelectric material. Therefore, the piezoelectric element 1A can include MgZnO as a piezoelectric material in the piezoelectric layer 40, and thus can exhibit piezoelectric characteristics in a high-frequency region such as a high-frequency filter.
壓電元件1A可以使第1壓電體層41的Mg濃度為5atom%～30atom%。由此，第1壓電體層41容易形成Mg濃度比第2壓電體層42高的層，因此，壓電體層40容易包含壓電特性比第2壓電體層42高的第1壓電體層41。其結果，壓電體層40能夠可靠地提高第1壓電體層41的K值。因此，壓電元件1A能夠在高頻濾波器等的高頻區域中發揮高的壓電特性。The piezoelectric element 1A can make the Mg concentration of the first piezoelectric layer 41 be 5atom% to 30atom%. As a result, the first piezoelectric layer 41 is easily formed into a layer having a higher Mg concentration than the second piezoelectric layer 42, and therefore, the piezoelectric layer 40 is easy to include the first piezoelectric layer 41 having higher piezoelectric characteristics than the second piezoelectric layer 42. As a result, the piezoelectric layer 40 can reliably improve the K value of the first piezoelectric layer 41. Therefore, the piezoelectric element 1A can exert high piezoelectric characteristics in a high-frequency region such as a high-frequency filter.
壓電元件1A能夠使第2壓電體層42的Mg濃度超過0atom%而為10atom%以下。由此，第2壓電體層42容易形成Mg濃度比第1壓電體層41低的層，因此，壓電體層40容易包含壓電特性比第1壓電體層41低的第2壓電體層42。其結果，壓電體層40能夠在使第2壓電體層42的K值下降的同時可靠地維持Q值。因此，壓電元件1A能夠在高頻濾波器等的高頻區域中發揮優異的壓電特性。 The piezoelectric element 1A can make the Mg concentration of the second piezoelectric layer 42 exceed 0 atom% and be less than 10 atom%. As a result, the second piezoelectric layer 42 is easy to form a layer with a lower Mg concentration than the first piezoelectric layer 41, so the piezoelectric layer 40 is easy to include the second piezoelectric layer 42 with lower piezoelectric characteristics than the first piezoelectric layer 41. As a result, the piezoelectric layer 40 can reliably maintain the Q value while reducing the K value of the second piezoelectric layer 42. Therefore, the piezoelectric element 1A can exert excellent piezoelectric characteristics in the high-frequency region such as high-frequency filters.
壓電元件1A可以使第1壓電體層41和第2壓電體層42的厚度之比為0.3～1.0。由此，壓電體層40能夠在可靠地維持Q值的同時控制K值，因此壓電元件1A能夠在高頻濾波器等的高頻區域進一步可靠地發揮優異的壓電特性。The piezoelectric element 1A can have a thickness ratio of 0.3 to 1.0 between the first piezoelectric layer 41 and the second piezoelectric layer 42. This allows the piezoelectric layer 40 to control the K value while reliably maintaining the Q value, so that the piezoelectric element 1A can more reliably exhibit excellent piezoelectric characteristics in high-frequency regions such as high-frequency filters.
壓電元件1A可以使第2壓電體層42的厚度為5nm～300nm。由此，第2壓電體層42能夠在降低K值的同時可靠地維持Q值，並且能夠抑制對壓電體層40的諧振特性造成影響。因此，壓電元件1A能夠在高頻濾波器等的高頻區域中發揮優異的壓電特性，並且能夠可靠地維持壓電特性。The piezoelectric element 1A can make the thickness of the second piezoelectric layer 42 5nm to 300nm. As a result, the second piezoelectric layer 42 can reliably maintain the Q value while reducing the K value, and can suppress the influence on the resonance characteristics of the piezoelectric layer 40. Therefore, the piezoelectric element 1A can exert excellent piezoelectric characteristics in the high-frequency region such as a high-frequency filter, and can reliably maintain the piezoelectric characteristics.
壓電元件1A能夠長時間地具有優異的壓電特性，因此，作為在電子設備中利用正壓電效果或逆壓電效果的電子部件，能夠用於各種用途的電子設備。The piezoelectric element 1A can have excellent piezoelectric characteristics for a long period of time, and therefore can be used in electronic devices for various purposes as an electronic component that utilizes the forward piezoelectric effect or the reverse piezoelectric effect in electronic devices.
壓電元件1A作為利用了正壓電效應的電子部件，例如可以用在觸摸面板用力感測器、壓力感測器、加速度感測器、角速度感測器、聲發射(AE)感測器、防盜感測器、看護/照護感測器、衝擊感測器、可穿戴感測器、生物體信號感測器、車輛用防止夾入感測器、車輛用保險杠碰撞感測器、車輛用空氣流量感測器、氣象檢測感測器、火災檢測感測器、水中音響感測器、觸覺感測器以及壓力分佈感測器等各種感測器中。The piezoelectric element 1A is an electronic component that utilizes the positive piezoelectric effect. For example, it can be used in various sensors such as touch panel force sensors, pressure sensors, acceleration sensors, angular velocity sensors, acoustic emission (AE) sensors, anti-theft sensors, nursing/care sensors, impact sensors, wearable sensors, biological signal sensors, vehicle anti-pinch sensors, vehicle bumper collision sensors, vehicle air flow sensors, weather detection sensors, fire detection sensors, underwater sound sensors, tactile sensors, and pressure distribution sensors.
壓電元件1A作為利用了逆壓電效果的電子部件，例如可以用於揚聲器、蜂鳴器以及麥克風等壓電聲響部件、換能器、高頻濾波器、致動器、光掃描器、噴墨印表機用的頭、掃描器用的MEMS鏡、超聲波電動機、壓電電動機等。其中，壓電元件1A也可以用於特別是在高頻區域中要求高的壓電特性的用途，因此例如可以適合用於高頻濾波器。在高頻濾波器中，有利用表面彈性波(SAW：Surface Acoustic Wave)的SAW濾波器、利用體彈性波(BAW：Bulk Acoustic Wave)的濾波器等。特別是，在高頻濾波器中使用的壓電元件中，需要使壓電體層的厚度較薄。即使在存在壓電體層的厚度的制約的情況下，由於壓電元件1A在高頻帶中能夠長時間地維持高的壓電特性，所以能夠有效地用作BAW濾波器。The piezoelectric element 1A is an electronic component that utilizes the reverse piezoelectric effect, and can be used in piezoelectric acoustic components such as speakers, buzzers, and microphones, transducers, high-frequency filters, actuators, optical scanners, heads for inkjet printers, MEMS mirrors for scanners, ultrasonic motors, piezoelectric motors, and the like. Among them, the piezoelectric element 1A can also be used for applications that require high piezoelectric characteristics, especially in the high-frequency region, and is therefore suitable for use in high-frequency filters, for example. Among high-frequency filters, there are SAW filters that utilize surface acoustic waves (SAW), filters that utilize bulk acoustic waves (BAW), and the like. In particular, in piezoelectric elements used in high-frequency filters, the thickness of the piezoelectric layer needs to be thin. Even under the constraints of the thickness of the piezoelectric layer, the piezoelectric element 1A can maintain high piezoelectric characteristics for a long time in a high-frequency band, so it can be effectively used as a BAW filter.
(變形例) 另外，在本實施方式中，壓電元件1A不限於上述結構，只要能夠維持壓電體層40的壓電特性，也可以是其他結構。壓電元件1A的其他結構的一例如下所示。 (Variation) In addition, in the present embodiment, the piezoelectric element 1A is not limited to the above-mentioned structure, and may be other structures as long as the piezoelectric characteristics of the piezoelectric layer 40 can be maintained. An example of other structures of the piezoelectric element 1A is shown below.
如圖2所示，在壓電元件1B中，壓電體層40也可以僅在第1壓電體層41的上表面411具有第2壓電體層42。即，壓電體層40可僅在第1壓電體層41與第2電極50之間具有第2壓電體層42。即使在該情況下，由於壓電元件1B在第1壓電體層41的上表面411具備第2壓電體層42，所以能夠在維持Q值的同時控制壓電體層40的整體的K值。另外，能夠抑制在構成壓電體層40的2種第1壓電體層41與第2壓電體層42之間產生介面剝離。由此，壓電體層40能夠加厚壓電體層40的厚度而提高壓電特性，並且能夠抑制壓電特性的劣化。因此，即使在壓電元件1B中，也能夠在加厚壓電體層40的膜厚的同時維持壓電特性。As shown in FIG2 , in the piezoelectric element 1B, the piezoelectric layer 40 may include the second piezoelectric layer 42 only on the upper surface 411 of the first piezoelectric layer 41. That is, the piezoelectric layer 40 may include the second piezoelectric layer 42 only between the first piezoelectric layer 41 and the second electrode 50. Even in this case, since the piezoelectric element 1B includes the second piezoelectric layer 42 on the upper surface 411 of the first piezoelectric layer 41, the overall K value of the piezoelectric layer 40 can be controlled while maintaining the Q value. In addition, it is possible to suppress the occurrence of interface peeling between the two types of first piezoelectric layers 41 and second piezoelectric layers 42 constituting the piezoelectric layer 40. As a result, the thickness of the piezoelectric layer 40 can be increased to improve the piezoelectric characteristics, and the degradation of the piezoelectric characteristics can be suppressed. Therefore, even in the piezoelectric element 1B, the piezoelectric characteristics can be maintained while the film thickness of the piezoelectric layer 40 is increased.
如圖3所示，在壓電元件1C中，壓電體層40也可以僅在第1壓電體層41的下表面412上具有第2壓電體層42。即，壓電體層40可以僅在第1電極30和第1壓電體層41之間具有第2壓電體層42。即使在該情況下，由於壓電元件1C在第1壓電體層41的下表面412具備第2壓電體層42，所以能夠在維持Q值的同時控制壓電體層40的整體的K值。另外，能夠抑制在構成壓電體層40的2種第1壓電體層41與第2壓電體層42之間產生介面剝離。由此，壓電體層40能夠加厚壓電體層40的厚度而提高壓電特性，並且能夠抑制壓電特性的劣化。因此，即使在壓電元件1B中，也能夠在加厚壓電體層40的膜厚的同時維持壓電特性。As shown in FIG3 , in the piezoelectric element 1C, the piezoelectric layer 40 may include the second piezoelectric layer 42 only on the lower surface 412 of the first piezoelectric layer 41. That is, the piezoelectric layer 40 may include the second piezoelectric layer 42 only between the first electrode 30 and the first piezoelectric layer 41. Even in this case, since the piezoelectric element 1C includes the second piezoelectric layer 42 on the lower surface 412 of the first piezoelectric layer 41, the overall K value of the piezoelectric layer 40 can be controlled while maintaining the Q value. In addition, it is possible to suppress the occurrence of interface peeling between the two types of first piezoelectric layers 41 and second piezoelectric layers 42 constituting the piezoelectric layer 40. As a result, the thickness of the piezoelectric layer 40 can be increased to improve the piezoelectric characteristics, and the degradation of the piezoelectric characteristics can be suppressed. Therefore, even in the piezoelectric element 1B, the piezoelectric characteristics can be maintained while the film thickness of the piezoelectric layer 40 is increased.
在本實施方式中，對於壓電元件1A，由聲學多層膜構成聲鏡層20，但是，聲鏡層20也可以由空間構成。例如，如圖4所示，壓電元件1D也可以在支承基材10的上表面101設置凹陷部11，而使在支承基材10的凹陷部11和第1電極30之間形成的空間S發揮作為聲鏡層20的功能。壓電元件1D能夠使空間S作為聲鏡層20發揮功能，因此能夠在支承基材10的上表面101直接設置第1電極30。由此，壓電元件1E能夠減小整體的厚度，因此能夠實現小型化。In the present embodiment, the acoustic mirror layer 20 of the piezoelectric element 1A is constituted by an acoustic multilayer film, but the acoustic mirror layer 20 may also be constituted by a space. For example, as shown in FIG. 4 , the piezoelectric element 1D may also be provided with a recessed portion 11 on the upper surface 101 of the supporting substrate 10, and the space S formed between the recessed portion 11 of the supporting substrate 10 and the first electrode 30 may function as the acoustic mirror layer 20. The piezoelectric element 1D can make the space S function as the acoustic mirror layer 20, and thus the first electrode 30 may be directly provided on the upper surface 101 of the supporting substrate 10. As a result, the piezoelectric element 1E can reduce the overall thickness, and thus can be miniaturized.
在本實施方式中，壓電元件1A也可以不具備聲鏡層20。如圖5所示，壓電元件1E可以從支承基材10側依次層疊支承基材10、第1電極30、壓電體層40及第2電極50。In this embodiment, the piezoelectric element 1A may not include the acoustic mirror layer 20. As shown in FIG5 , the piezoelectric element 1E may include a support substrate 10, a first electrode 30, a piezoelectric layer 40, and a second electrode 50 stacked in this order from the support substrate 10 side.
在這種情況下，支承基材10可以是具有導電性的基板。在支承基材10是具有導電性的基板的情況下，由於支承基材10也能夠作為第1電極發揮功能，所以壓電元件1A也可以不具備第1電極30。例如，如圖6所示，壓電元件1F可以從支承基材10側依次層疊具備支承基材10、壓電體層40及第2電極50。支承基材10可以是金屬板，也可以是ITO、IZO、IZTO、IGZO等導電性透明基板。在支承基材10為金屬板的情況下，也可以使用Al箔、Cu箔、Al-Ti合金箔、Cu-Ti合金箔、不銹鋼箔等金屬膜。在金屬膜的厚度薄的情況下，由於支承基材10的撓性變高，所以也可以在支承基材10與壓電體層40之間***Ti、Ni等的金屬密接膜。如圖6所示，壓電元件1F能夠減少第1電極30的量的厚度。由此，壓電元件1F能夠減小整體的厚度，因此能夠實現小型化。In this case, the supporting substrate 10 may be a substrate having conductivity. In the case where the supporting substrate 10 is a substrate having conductivity, since the supporting substrate 10 can also function as the first electrode, the piezoelectric element 1A may not have the first electrode 30. For example, as shown in FIG6 , the piezoelectric element 1F may have a supporting substrate 10, a piezoelectric layer 40, and a second electrode 50 stacked in sequence from the supporting substrate 10 side. The supporting substrate 10 may be a metal plate, or a conductive transparent substrate such as ITO, IZO, IZTO, or IGZO. In the case where the supporting substrate 10 is a metal plate, a metal film such as Al foil, Cu foil, Al-Ti alloy foil, Cu-Ti alloy foil, or stainless steel foil may also be used. When the thickness of the metal film is thin, the flexibility of the support substrate 10 increases, so a metal adhesion film such as Ti or Ni may be inserted between the support substrate 10 and the piezoelectric layer 40. As shown in FIG6 , the thickness of the piezoelectric element 1F can be reduced by the first electrode 30. Thus, the piezoelectric element 1F can be reduced in overall thickness, and thus can be miniaturized.
如上所述，對實施方式進行了說明，但上述實施方式是作為例子進行提示的，本發明並不受上述實施方式的限制。上述實施方式可以以其他各種方式實施，在不脫離發明主旨的範圍內，可以進行各種組合、省略、置換、變更等。這些實施方式及其變形包含在發明的範圍和要旨中，並且包含在發明專利申請範圍所記載的發明及其等同的範圍中。As described above, the embodiments are described, but the embodiments are presented as examples, and the present invention is not limited to the embodiments. The embodiments can be implemented in various other ways, and various combinations, omissions, substitutions, changes, etc. can be made without departing from the scope of the invention. These embodiments and their variations are included in the scope and gist of the invention, and are included in the invention described in the scope of the invention patent application and its equivalent scope.
[實施例] 以下，藉由表示實施例和比較例對實施方式進行更具體的說明，但實施方式不限於這些實施例和比較例。 [Example] The following will describe the embodiment in more detail by showing examples and comparative examples, but the embodiment is not limited to these examples and comparative examples.
＜BAW諧振器＞ 作為壓電元件，製作了BAW諧振器。 [實施例1] (聲鏡層的製作) 在基材(Si基板)上，形成由高聲阻抗層和低聲阻抗層構成的聲鏡層。 1.高聲阻抗層的製作 在Si基板上，在Ar氣氛中利用DC磁控濺射法，使用鎢濺射靶材，將鎢(W)膜作為高聲阻抗層進行成膜。高聲阻抗層的聲阻抗為1.0×10 8N/m 2,高聲阻抗層的厚度為218nm。 2.低聲阻抗層的製作 在高聲阻抗層上，在Ar和O 2的混合氣體(Ar氣體：O 2氣體=90：10)氣氛中，藉由RF磁控濺射法，使用矽濺射靶材，將SiO 2膜作為低聲阻抗層進行成膜。低聲阻抗層的聲阻抗為1.3×10 7N/m 2，低聲阻抗層的厚度為242nm。 (第1電極的製作) 在聲鏡層上，在Ar氣氛中藉由DC磁控濺射法，使用鋁濺射靶材，將Al膜作為第1電極進行成膜。第3電極的聲阻抗為1.7×10 7N/m 2，第1電極的厚度為160nm。 (壓電體層的製作) 在第1電極上形成有由第1壓電體層及第2壓電體層構成的壓電體層。 1.第1壓電體層的製作 在聲鏡層上，在Ar和O 2的混合氣體(Ar氣體：O 2氣體=91：9)氣氛中，藉由RF磁控濺射法，使用ZnO和MgO以品質比被調整為80wt%：20wt%的濺射靶材，將被調整為第1壓電體層所含的Mg的濃度為20atom%的、具有六方晶系的纖鋅礦型結構的添加Mg的ZnO薄膜作為壓電體層來形成。添加Mg的ZnO薄膜的厚度為270nm。 2.第2壓電體層的製作 在第1壓電體層之上，在Ar和O 2的混合氣體(Ar氣體：O 2氣體=91：9)氣氛中，藉由RF磁控濺射法，使用ZnO和MgO以品質比被調整為95wt%：5wt%的濺射靶材，將被調整為第2壓電體層中所含的Mg的濃度為5atom%的、具有六方晶系的纖鋅礦型結構的添加Mg的ZnO薄膜形成為壓電體層。添加Mg的ZnO薄膜的厚度為335nm。 (第2電極的製作) 在壓電體層上，在Ar氣氛中，利用DC磁控濺射法，使用鉬濺射靶材，將鉬膜(Mo膜)作為第2電極進行成膜。Mo膜的厚度為89nm。 <BAW resonator> A BAW resonator was fabricated as a piezoelectric element. [Example 1] (Fabrication of an acoustic mirror layer) An acoustic mirror layer consisting of a high acoustic impedance layer and a low acoustic impedance layer was formed on a base material (Si substrate). 1. Fabrication of a high acoustic impedance layer A tungsten (W) film was formed as a high acoustic impedance layer on a Si substrate by DC magnetron sputtering in an Ar atmosphere using a tungsten sputtering target. The acoustic impedance of the high acoustic impedance layer was 1.0×10 8 N/m 2 , and the thickness of the high acoustic impedance layer was 218 nm. 2. Fabrication of low acoustic impedance layer On the high acoustic impedance layer, a SiO 2 film was formed as a low acoustic impedance layer by RF magnetron sputtering in an atmosphere of a mixed gas of Ar and O 2 (Ar gas:O 2 gas = 90:10) using a silicon sputtering target. The acoustic impedance of the low acoustic impedance layer was 1.3×10 7 N/m 2 and the thickness of the low acoustic impedance layer was 242nm. (Fabrication of the first electrode) On the acoustic mirror layer, an Al film was formed as a first electrode by DC magnetron sputtering in an Ar atmosphere using an aluminum sputtering target. The acoustic impedance of the third electrode was 1.7×10 7 N/m 2 and the thickness of the first electrode was 160nm. (Fabrication of piezoelectric layer) A piezoelectric layer consisting of a first piezoelectric layer and a second piezoelectric layer is formed on the first electrode. 1. Fabrication of the first piezoelectric layer On the acoustic mirror layer, in an atmosphere of a mixed gas of Ar and O 2 (Ar gas:O 2 gas=91:9), a Mg-added ZnO thin film having a hexagonal fibrous zincite structure and adjusted to a Mg concentration of 20 atom% in the first piezoelectric layer is formed as a piezoelectric layer by RF magnetron sputtering using a sputtering target material in which the quality ratio of ZnO and MgO is adjusted to 80wt%:20wt%. The thickness of the Mg-added ZnO thin film is 270nm. 2. Fabrication of the second piezoelectric layer On the first piezoelectric layer, in an atmosphere of a mixed gas of Ar and O2 (Ar gas: O2 gas = 91:9), a Mg-added ZnO thin film having a hexagonal fibrous zincite structure and adjusted to a Mg concentration of 5atom% in the second piezoelectric layer was formed as a piezoelectric layer by RF magnetron sputtering using a sputtering target material in which ZnO and MgO were adjusted to a quality ratio of 95wt%:5wt%. The thickness of the Mg-added ZnO thin film was 335nm. (Fabrication of Second Electrode) A molybdenum film (Mo film) was formed as the second electrode on the piezoelectric layer by DC magnetron sputtering in an Ar atmosphere using a molybdenum sputtering target. The thickness of the Mo film was 89 nm.
由此，製作了在基材上依次層疊具備聲鏡層、第1電極、壓電體層、第2電極的BAW諧振器。In this way, a BAW resonator was manufactured in which an acoustic mirror layer, a first electrode, a piezoelectric layer, and a second electrode were stacked in sequence on a substrate.
[實施例2～5、比較例1和2] 在實施例1中，除了將第1壓電體層和第2壓電體層中含有的Mg元素的摻雜量、和第1壓電體層和第2壓電體層的厚度中的任意者變更為表1所示的Mg元素的摻雜量和厚度以外，與實施例1同樣地進行，製作BAW諧振器。 [Examples 2 to 5, Comparative Examples 1 and 2] In Example 1, except that the doping amount of the Mg element contained in the first piezoelectric layer and the second piezoelectric layer and the thickness of the first piezoelectric layer and the second piezoelectric layer are changed to the doping amount and thickness of the Mg element shown in Table 1, the same procedure as in Example 1 is followed to produce a BAW resonator.
構成各實施例及比較例的BAW諧振器的第1壓電體層及第2壓電體層中所含的Mg元素的摻雜量、以及第1壓電體層及第2壓電體層的厚度如表1所示。Table 1 shows the doping amounts of the Mg element contained in the first piezoelectric layer and the second piezoelectric layer constituting the BAW resonator of each embodiment and the comparative example, and the thicknesses of the first piezoelectric layer and the second piezoelectric layer.
[表1] [Table 1]
＜測量濾波器特性＞ 作為各實施例及比較例的BAW諧振器的濾波器特性，測量了藉由網路分析器的雙埠測量得到的透過信號中的通帶的衰減量。測量結果如圖7所示。如圖7所示，在比較例1中，與各實施例相比，通帶中的***損耗小，濾波器特性低。這可以說是因為比較例1與各實施例相比，第1壓電體層中含有的Mg元素的摻雜量(Mg元素的濃度)少的緣故。另外，對於比較例1，由於第1壓電體層的厚度比各實施例的第1壓電體層和第2壓電體層的總厚度薄，所以可以說耐電力性低。另外，在比較例2中，第1壓電體層中所含的Mg元素的摻雜量與各實施例相同，因此通帶中的***損耗與各實施例相同，但比較例2的第1壓電體層的厚度比各實施例的第1壓電體層和第2壓電體層的總厚度小，因此與比較例1相同，耐電力性可以說較低。與此相對，在各實施例中，通帶的衰減量大，濾波器特性提高，並且第1壓電體層和第2壓電體層的總厚度厚，因此耐電力性可以說較高。 <Measurement of filter characteristics> As the filter characteristics of the BAW resonator of each embodiment and comparative example, the attenuation of the passband in the transmitted signal obtained by two-port measurement of a network analyzer was measured. The measurement results are shown in FIG7. As shown in FIG7, in comparative example 1, the insertion loss in the passband is small compared with each embodiment, and the filter characteristics are low. This can be said to be because the doping amount of the Mg element (the concentration of the Mg element) contained in the first piezoelectric layer of comparative example 1 is less than that of each embodiment. In addition, for comparative example 1, since the thickness of the first piezoelectric layer is thinner than the total thickness of the first piezoelectric layer and the second piezoelectric layer of each embodiment, it can be said that the power resistance is low. In addition, in Comparative Example 2, the doping amount of the Mg element contained in the first piezoelectric layer is the same as that of each embodiment, so the insertion loss in the passband is the same as that of each embodiment, but the thickness of the first piezoelectric layer of Comparative Example 2 is smaller than the total thickness of the first piezoelectric layer and the second piezoelectric layer of each embodiment, so the power resistance can be said to be low, as in Comparative Example 1. In contrast, in each embodiment, the attenuation of the passband is large, the filter characteristics are improved, and the total thickness of the first piezoelectric layer and the second piezoelectric layer is thick, so the power resistance can be said to be high.
因此，各實施例的BAW濾波器藉由使用Mg元素的摻雜量高的第1壓電體層，能夠維持壓電特性，並且藉由層疊第1壓電體層和第2壓電體層使總厚度變厚，實現厚膜化，能夠提高耐電力性。因此，可以說各實施例的BAW濾波器能夠有效地用作高頻濾波器。Therefore, the BAW filter of each embodiment can maintain the piezoelectric characteristics by using the first piezoelectric layer with a high Mg doping amount, and can improve the power resistance by stacking the first piezoelectric layer and the second piezoelectric layer to make the total thickness thicker and realize thick film. Therefore, it can be said that the BAW filter of each embodiment can be effectively used as a high-frequency filter.
另外，本發明的實施方式的方式，例如如下。 ＜1＞一種壓電元件，在支承基材上依次層疊具備第1電極、具有摻雜有金屬元素的壓電材料的壓電體層和第2電極，其中， 該壓電體層具有第1壓電體層和第2壓電體層， 該第2壓電體層設置在該第1壓電體層的上表面及下表面的至少一方，具有比該第1壓電體層中所含的該金屬元素的濃度低的該金屬元素的濃度。 ＜2＞根據＜1＞所述的壓電元件，其中， 該壓電體層包含ZnO作為該壓電材料， 該金屬元素包括Mg。 ＜3＞根據＜2＞所述的壓電元件，其中， 該第1壓電體層的Mg濃度為5atom%～30atom%。 ＜4＞根據＜2＞或＜3＞所述的壓電元件，其中， 該第2壓電體層的Mg濃度超過0atom%且為10atom%以下。 ＜5＞根據＜1＞～＜4＞中任一項所述的壓電元件，其中， 該第1壓電體層與該第2壓電體層的厚度之比為0.3～1.0。 ＜6＞根據＜1＞～＜5＞中任一項所述的壓電元件，其中， 該第2壓電體層的厚度為5nm～300nm。 ＜7＞根據＜1＞～＜6＞中任一項所述的壓電元件，其中， 該支承基材與該第1電極之間具有聲鏡層， 該聲鏡層是高聲阻抗層和低聲阻抗層交替層疊一對以上而成的層疊體、或者是形成在該支承基材和該第1電極之間的空隙。 ＜8＞一種電子設備，具備根據＜1＞～＜7＞中任一項所述的壓電元件。 In addition, the implementation method of the present invention is as follows, for example. ＜1＞ A piezoelectric element having a first electrode, a piezoelectric layer having a piezoelectric material doped with a metal element, and a second electrode are sequentially stacked on a supporting substrate, wherein, the piezoelectric layer has a first piezoelectric layer and a second piezoelectric layer, the second piezoelectric layer is provided on at least one of the upper surface and the lower surface of the first piezoelectric layer, and has a concentration of the metal element lower than the concentration of the metal element contained in the first piezoelectric layer. ＜2＞ The piezoelectric element according to ＜1＞, wherein, the piezoelectric layer contains ZnO as the piezoelectric material, the metal element includes Mg. <3> The piezoelectric element according to <2>, wherein the Mg concentration of the first piezoelectric layer is 5atom% to 30atom%. <4> The piezoelectric element according to <2> or <3>, wherein the Mg concentration of the second piezoelectric layer exceeds 0atom% and is 10atom% or less. <5> The piezoelectric element according to any one of <1> to <4>, wherein the ratio of the thickness of the first piezoelectric layer to the thickness of the second piezoelectric layer is 0.3 to 1.0. <6> The piezoelectric element according to any one of <1> to <5>, wherein the thickness of the second piezoelectric layer is 5nm to 300nm. <7> A piezoelectric element according to any one of <1> to <6>, wherein, an acoustic mirror layer is provided between the support substrate and the first electrode, the acoustic mirror layer is a stack of one or more pairs of high acoustic impedance layers and low acoustic impedance layers alternately stacked, or a gap formed between the support substrate and the first electrode. <8> An electronic device having a piezoelectric element according to any one of <1> to <7>.
本申請基於2022年9月30日提交至日本特許廳的特願2022-157637號主張優先權，並引用上述申請中所述的全部內容。This application claims priority based on Tokugawa Pharmacopoeia No. 2022-157637 filed with the Japan Patent Office on September 30, 2022, and all the contents described in the aforementioned application are incorporated herein by reference.
1A~1F:壓電元件 10:支承基材 20:聲鏡層 21:高聲阻抗層 22:低聲阻抗層 30:第1電極 40:壓電體層 41:第1壓電體層 42:第2壓電體層 50:第2電極 101:上表面 201:上表面 301:上表面 401:上表面 411:上表面 412:下表面 421:上表面 S:空間 1A~1F: Piezoelectric element 10: Support substrate 20: Acoustic mirror layer 21: High acoustic impedance layer 22: Low acoustic impedance layer 30: First electrode 40: Piezoelectric layer 41: First piezoelectric layer 42: Second piezoelectric layer 50: Second electrode 101: Upper surface 201: Upper surface 301: Upper surface 401: Upper surface 411: Upper surface 412: Lower surface 421: Upper surface S: Space
圖1是表示根據本發明的實施方式的壓電元件的結構的概略截面圖。 圖2是表示壓電元件的另一結構的示例的概略截面圖。 圖3是表示壓電元件的另一結構的示例的概略截面圖。 圖4是表示壓電元件的另一結構的示例的概略截面圖。 圖5是表示壓電元件的另一結構的示例的概略截面圖。 圖6是表示壓電元件的另一結構的示例的概略截面圖。 圖7是表示實施例和比較例的濾波器特性的計算結果的圖。 FIG. 1 is a schematic cross-sectional view showing the structure of a piezoelectric element according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing an example of another structure of a piezoelectric element. FIG. 3 is a schematic cross-sectional view showing an example of another structure of a piezoelectric element. FIG. 4 is a schematic cross-sectional view showing an example of another structure of a piezoelectric element. FIG. 5 is a schematic cross-sectional view showing an example of another structure of a piezoelectric element. FIG. 6 is a schematic cross-sectional view showing an example of another structure of a piezoelectric element. FIG. 7 is a diagram showing the calculation results of the filter characteristics of the embodiment and the comparative example.
1A:壓電元件 1A: Piezoelectric components
10:支承基材 10: Supporting substrate
20:聲鏡層 20: Acoustic mirror layer
21:高聲阻抗層 21: High acoustic impedance layer
22:低聲阻抗層 22: Low acoustic impedance layer
30:第1電極 30: 1st electrode
40:壓電體層 40: Piezoelectric layer
41:第1壓電體層 41: 1st piezoelectric layer
42:第2壓電體層 42: Second piezoelectric layer
50:第2電極 50: Second electrode
101:上表面 101: Upper surface
201:上表面 201: Upper surface
301:上表面 301: Upper surface
401:上表面 401: Upper surface
411:上表面 411: Upper surface
412:下表面 412: Lower surface
421:上表面 421: Upper surface
Claims (8)
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2022-157637 | 2022-09-30 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| TW202423274A true TW202423274A (en) | 2024-06-01 |
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