WO2020209152A1 - Dispositif à ondes acoustiques et dispositif de filtrage le comprenant - Google Patents
Dispositif à ondes acoustiques et dispositif de filtrage le comprenant Download PDFInfo
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- WO2020209152A1 WO2020209152A1 PCT/JP2020/015004 JP2020015004W WO2020209152A1 WO 2020209152 A1 WO2020209152 A1 WO 2020209152A1 JP 2020015004 W JP2020015004 W JP 2020015004W WO 2020209152 A1 WO2020209152 A1 WO 2020209152A1
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- layer
- elastic wave
- wave device
- piezoelectric film
- intermediate layer
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Images
Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
- H03H9/17—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/25—Constructional features of resonators using surface acoustic waves
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/46—Filters
- H03H9/54—Filters comprising resonators of piezoelectric or electrostrictive material
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/46—Filters
- H03H9/64—Filters using surface acoustic waves
Definitions
- the present disclosure relates to an elastic wave device and a filter device including the elastic wave device, and more specifically, to a technique for suppressing deterioration of characteristics in the elastic wave device.
- Patent Document 1 discloses a thin film bulk acoustic resonator (elastic wave device) having a seed layer formed on a semiconductor support substrate.
- a material containing aluminum nitride (AlN) may be used.
- AlN aluminum nitride
- the aluminum nitride is formed on the support substrate by, for example, sputtering.
- the aluminum nitride formed by sputtering has a column-like structure and contains many grain boundaries. When grain boundaries are present, the grain boundaries serve as diffusion paths for aluminum atoms in the seed layer, and grain boundary diffusion is likely to occur.
- the present disclosure has been made to solve the above-mentioned problems, and an object thereof is to suppress deterioration of characteristics in an elastic wave device having a layer containing aluminum nitride.
- An elastic wave device includes a support substrate formed of a semiconductor material, a functional layer formed on the support substrate, and an intermediate layer formed between the support substrate and the functional layer.
- the functional layer includes a piezoelectric film and a transducer electrode formed on the piezoelectric film.
- the layer in contact with the intermediate layer in the functional layer is formed of a material containing an aluminum compound.
- the intermediate layer is formed of an insulator having a higher nitrogen atom concentration or oxygen atom concentration than the layer in contact with the intermediate layer.
- an intermediate layer is formed between a functional layer containing aluminum nitride and a semiconductor support substrate, and in the intermediate layer, nitrogen is more than a portion of the functional layer in contact with the intermediate layer.
- Atomic concentration or oxygen atom concentration is high.
- FIG. It is a figure which shows the equivalent circuit of the elastic wave device of the comparative example. It is sectional drawing of the elastic wave device according to Embodiment 2. It is sectional drawing of the elastic wave device according to Embodiment 3. It is sectional drawing of the elastic wave device according to Embodiment 4. It is sectional drawing of the elastic wave device according to Embodiment 5.
- FIG. 1 is a cross-sectional view of the elastic wave device 100 according to the first embodiment.
- the elastic wave device 100 is used, for example, as a filter device for passing or attenuating a high frequency signal in a specific frequency band.
- the thickness direction of the elastic wave device is defined as the Z-axis direction
- the plane perpendicular to the Z-axis direction is defined by the X-axis and the Y-axis.
- the positive direction of the Z axis in each figure may be referred to as an upward direction
- the negative direction may be referred to as a downward direction.
- the elastic wave device 100 includes a support substrate 110, a functional layer 115, and an intermediate layer 150.
- the functional layer 115 includes a piezoelectric film 120 and functional elements (transducer electrodes) 130 and 140.
- the elastic wave device 100 is an FBAR (Film Bulk Acoustic Resonator) type BAW resonator, and the functional layer 115 functions as a resonator.
- the support substrate 110 is a semiconductor substrate made of a material such as silicon (Si), gallium arsenide (GaAs), gallium nitride (GaN), or silicon carbide (SiC).
- the piezoelectric film 120 of the functional layer 115 is laminated on the support substrate 110 via the intermediate layer 150.
- the support substrate 110 is silicon.
- the piezoelectric film 120 is made of a material containing aluminum nitride (AlN). Further, the piezoelectric film 120 may be a material in which aluminum nitride is doped with a rare earth element such as indium (In), yttrium (Y), erbium (Er), or lanthanum (La).
- the piezoelectric film 120 includes an upper surface (first main surface) 121 and a lower surface (second main surface) 122 that face each other. Plate-shaped electrodes 130 and 140 are formed on the upper surface 121 and the lower surface 122, respectively.
- the electrodes 130 and 140 are formed by using an electrode material such as a single metal composed of at least one of aluminum, copper, silver, gold, titanium, tungsten, platinum, chromium, nickel and molybdenum, or an alloy containing these as main components. Will be done.
- the electrodes 130 and 140 are molybdenum (Mo).
- the "electrode 130" and “electrode 140" correspond to the "first electrode” and the "second electrode” in the present disclosure, respectively.
- a cavity 160 is formed between the portion of the functional layer 115 where the electrodes 130 and 140 are formed and the support substrate 110.
- the cavity 160 allows the piezoelectric film 120 to vibrate freely.
- the piezoelectric film 120 is supported by the support substrate 110 in the portion of the elastic wave device 100 where the cavity 160 is not formed. As described above, the intermediate layer 150 is formed between the piezoelectric film 120 and the support substrate 110.
- the intermediate layer 150 is, for example, an insulating film formed of a silicon oxide film, a silicon nitride film, silicon oxynitride, an aluminum oxide film, an aluminum nitride film, or the like.
- the intermediate layer 150 is made of a material having a higher nitrogen atom concentration or oxygen atom concentration than the piezoelectric film 120.
- the intermediate layer 150 is preferably an aluminum nitride film. In this case, since the crystal structures of the piezoelectric film 120 and the intermediate layer 150 are close to each other, grain boundaries are unlikely to occur. Therefore, the intergranular diffusion is reduced, unnecessary current is less likely to flow at the boundary portion with the seed layer in the semiconductor substrate, and the characteristics of the resonator are less likely to be deteriorated.
- the piezoelectric film 120 is generally formed by sputtering. It is known that aluminum nitride formed by sputtering has a column-like structure and contains many grain boundaries. When such a grain boundary is present, the grain boundary becomes a diffusion path for aluminum atoms in the piezoelectric film 120, and grain boundary diffusion is likely to occur toward the support substrate 110.
- the resistance of the surface layer portion of the support substrate 110 is lower than that of other portions of the support substrate 110 due to the diffused aluminum atoms.
- an unnecessary current tends to flow at the boundary portion of the support substrate 110 with the piezoelectric film 120, which may deteriorate the characteristics of the elastic wave device.
- Layer 150 is arranged. Nitrogen atoms and oxygen atoms have a relatively large binding energy with aluminum atoms. Therefore, the aluminum atoms diffused from the piezoelectric film 120 are trapped by the nitrogen atoms and oxygen atoms of the intermediate layer 150 and are difficult to reach the support substrate 110. That is, the intermediate layer 150 functions as an "anti-diffusion film" for aluminum atoms.
- FIG. 2 is a diagram showing an electrical equivalent circuit in an elastic wave device of a comparative example in which the intermediate layer 150 in FIG. 1 is not formed.
- a parallel circuit of the non-linear capacitance C2 forming the current path for generating the capacitance C1 and the leak current is formed between the input Pin and the output Pout. Therefore, a non-linear high frequency signal due to the leak current path is superimposed on the high frequency signal transmitted from the electrode 130 to the electrode 140, and intermodulation distortion (IMD) or harmonic distortion occurs.
- IMD intermodulation distortion
- an intermediate layer 150 of an insulating material having a higher nitrogen atom concentration or oxygen electron concentration than the piezoelectric film 120 is formed between the support substrate 110 and the piezoelectric film 120, so that the piezoelectric film
- the aluminum atoms diffused from 120 combine with nitrogen or oxygen in the intermediate layer 150 and are trapped in the intermediate layer 150.
- the aluminum atoms from the piezoelectric film 120 are suppressed from reaching the support substrate 110, so that a low resistance region is prevented from being formed on the surface layer portion of the support substrate 110.
- the non-linear high-frequency signal due to the leak current path is suppressed and the occurrence of IMD and harmonic distortion can be prevented, so that the deterioration of the characteristics of the elastic wave device is suppressed.
- the average length of the travel distance required for this coupling is referred to as "diffusion length". If the intermediate layer 150 is thinner than the diffusion length of the aluminum atoms in the intermediate layer 150, a part of the diffused aluminum atoms cannot be completely captured by the intermediate layer 150 and can reach the support substrate 110. Therefore, it is preferable that the thickness direction of the intermediate layer 150 is longer than the diffusion length of the aluminum atoms in the intermediate layer 150.
- the support substrate 110 is silicon
- silicon atoms in the support substrate 110 may diffuse into the piezoelectric film 120, and a low resistance region may be formed in a region of the piezoelectric film 120 in contact with the support substrate 110.
- the intermediate layer 150 by forming the intermediate layer 150, the silicon atoms diffused by the nitrogen atoms or oxygen atoms in the intermediate layer 150 are trapped, so that the deterioration of the characteristics of the elastic wave device due to the diffusion of the silicon atoms is suppressed. can do.
- FIG. 3 is a cross-sectional view of the elastic wave device 100A according to the second embodiment.
- the functional layer 115A in the elastic wave device 100A has a piezoelectric film 120 containing aluminum nitride and an IDT electrode 170 formed on the upper surface 121 of the piezoelectric film 120.
- a cavity 160 is formed between the region where the IDT electrode 170 is formed in the functional layer 115A and the support substrate 110.
- the "region in which the IDT electrode 170 is formed” is not limited to the case where all the IDT electrodes 170 are included in the region, and may be the case where a part of the IDT electrode 170 is included. That is, the “region in which the IDT electrode 170 is formed” means a region including at least a part of the IDT electrode 170.
- the thickness of the piezoelectric film 120 is set to a wavelength equal to or less than the wavelength defined by the pitch of the electrode fingers of the IDT electrode 170.
- the diffusion of aluminum atoms from the piezoelectric film 120 causes a leak current path as described in FIG. 2 between adjacent electrode fingers of the IDT electrode 170. Deterioration of the characteristics of elastic wave devices may occur.
- FIG. 4 is a cross-sectional view of the elastic wave device 100B according to the third embodiment.
- a seed layer 175 made of a material containing aluminum nitride is formed in the lowermost layer of the functional layer 115B.
- the seed layer 175 has a function of improving the crystallinity of the electrode or the piezoelectric film formed on the seed layer 175. Further, since aluminum nitride has a bulk wave sound velocity higher than the sound velocity (elastic wave sound velocity) in the elastic wave mode, the seed layer 175 also functions as a reflection layer.
- the functional layer 115B has such a seed layer 175 as the lowest layer, even if the piezoelectric film 120 is made of a material that does not contain aluminum atoms, if the functional layer 115B is directly arranged on the support substrate 110, , Aluminum atoms in the seed layer 175 may diffuse into the support substrate 110 to form a leak current path. Therefore, when the lowermost layer of the functional layer is formed of a material containing aluminum atoms, the leakage current path accompanying the diffusion of aluminum atoms is provided by providing the intermediate layer 150 between the support substrate 110 and the functional layer. Can be suppressed. As a result, deterioration of the characteristics of the elastic wave device can be suppressed.
- FIG. 5 is a cross-sectional view of the elastic wave device 100C according to the fourth embodiment.
- the functional layer 115C includes a piezoelectric film 180, an IDT electrode 170 which is a functional element (transducer electrode), a hypersonic film 191 and a low sound velocity film 192.
- the functional layer 115C is laminated on the support substrate 110 via the intermediate layer 150.
- the hypersonic film 191 and the low sound velocity film 192 and the piezoelectric film 180 are laminated in this order from the support substrate 110 side in the positive direction of the Z axis.
- lithium tantalate (LT) is used as the piezoelectric film 180, and the IDT electrode 170 is formed on the upper surface 181 of the piezoelectric film 180.
- a SAW resonator is formed by the piezoelectric film 180 and the IDT electrode 170.
- the piezoelectric film 180 lithium niobate (LN), aluminum nitride, zinc oxide, lead zirconate titanate (PZT), or the like may be used.
- the hypersonic film 191 is made of a material in which the bulk wave sound velocity propagating through the hypersonic film 191 is higher than the elastic wave sound velocity propagating through the piezoelectric film 180. In other words, the hypersonic film 191 is made of a material having a higher acoustic impedance than the piezoelectric film 180.
- the treble speed film 191 is formed of, for example, a material such as aluminum nitride, silicon nitride, aluminum oxide (alumina), silicon oxynitride, silicon carbide, diamond-like carbon (DLC), and diamond.
- the hypersonic film 191 is made of aluminum nitride (AlN).
- the bass velocity film 192 is made of a material in which the bulk wave sound velocity propagating through the bass velocity film 192 is lower than the bulk wave sound velocity propagating through the piezoelectric film 180.
- the bass velocity film 192 is made of a material having an acoustic impedance lower than that of the piezoelectric film 180.
- the bass velocity film 192 is formed of, for example, a dielectric such as silicon dioxide, glass, silicon oxynitride, or tantalum oxide, or a compound obtained by adding fluorine, carbon, boron, or the like to silicon dioxide.
- the bass velocity film 192 is made of silicon dioxide (SiO 2 ).
- the high sound velocity film 191 and the low sound velocity film 192 function as a reflective layer (mirror layer) 190.
- the reflective layer 190 is a so-called acoustic Bragg reflector.
- the surface acoustic wave leaking from the piezoelectric film 180 toward the support substrate 110 is reflected by the hypersonic film 191 due to the difference in the propagating sound velocity, and is confined as a standing wave in the hypersonic film 192.
- the loss of acoustic energy of the surface acoustic wave propagated by the piezoelectric film 180 is suppressed, so that the surface acoustic wave can be efficiently propagated.
- FIG. 5 an example in which the hypersonic film 191 and the low sound velocity film 192 are each a single layer as the reflective layer 190 has been described, but in the reflective layer 190, a plurality of high sound velocity films 191 and the low sound velocity film 192 alternate. It may be a configuration arranged in.
- the lowermost layer of the functional layer 115C is a layer formed of a material containing aluminum atoms.
- the "hypersonic film 191" and the “hypersonic film 192" correspond to the "first layer” and the “second layer” of the present disclosure, respectively. Further, the acoustic impedance of the "hypersonic film 191” corresponds to the "first acoustic impedance” of the present disclosure, and the acoustic impedance of the "hypersonic film 192" corresponds to the "second acoustic impedance" of the present disclosure.
- FIG. 6 is a cross-sectional view of the elastic wave device 100D according to the fifth embodiment.
- the functional layer 115D of the elastic wave device 100D includes a piezoelectric film 120 and electrodes 130 and 140 forming a BAW resonator, and a plurality of high sound velocity films 191A and low sound velocity films 192A forming a reflective layer 190A.
- the piezoelectric film 120 is made of aluminum nitride and the electrodes 130 and 140 are made of molybdenum, as in FIGS. 1 and 4.
- the hypersonic film 192A is made of silicon dioxide
- the hypersonic film 191A is made of aluminum nitride.
- the reflective layer 190A has a configuration in which a plurality of high-sound velocity films 191A and low-sound velocity films 192A are alternately laminated, and a BAW resonator is laminated on the reflective layer 190A.
- An intermediate layer 150 is formed between the functional layer 115D and the support substrate 110.
- the hypersonic film 191A containing aluminum nitride is arranged in the lowermost layer of the functional layer 115D. Therefore, by forming the intermediate layer 150 between the functional layer 115D and the support substrate 110, the aluminum atoms diffused from the high sound velocity film 191A are trapped by the nitrogen atoms or oxygen atoms in the intermediate layer 150. It is possible to suppress the occurrence of a low resistance region on the surface layer portion of the support substrate 110. Therefore, it is possible to suppress the generation of a leak current path due to the diffusion of aluminum atoms, and it is possible to suppress the deterioration of the characteristics of the elastic wave device.
- 100,100A-100D elastic wave device 110 support substrate, 115,115A-115D functional layer, 120,180 piezoelectric film, 121,181 upper surface, 122 lower surface, 130,140 electrode, 170 IDT electrode, 150 intermediate layer, 160 cavity 175 seed layer, 190, 190A reflective layer, 191, 191A hypersonic film, 192, 192A low sound film.
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- Acoustics & Sound (AREA)
- Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)
Abstract
La présente invention concerne un dispositif à ondes acoustiques (100) qui comprend un substrat de support (110) qui est formé à partir d'un matériau semi-conducteur, une couche fonctionnelle (115) qui est formée sur le substrat de support (110), et une couche intermédiaire (150) qui est formée entre le substrat de support (110) et la couche fonctionnelle (115). La couche fonctionnelle (115) comprend un film piézoélectrique (120) et des électrodes de transducteur (130, 140) qui sont formées sur le film piézoélectrique (120). La couche de la couche fonctionnelle (115) qui est en contact avec la couche intermédiaire (150) est formée à partir d'un matériau contenant un composé d'aluminium. La couche intermédiaire (150) est formée à partir d'un isolant qui a une concentration en atomes d'azote ou une concentration en atomes d'oxygène supérieure à celle de la couche qui est en contact avec la couche intermédiaire (150).
Applications Claiming Priority (2)
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CN113162579A (zh) * | 2021-03-15 | 2021-07-23 | 电子科技大学 | 一种固态反射型声表面波谐振器及其制备方法 |
WO2022085565A1 (fr) * | 2020-10-23 | 2022-04-28 | 株式会社村田製作所 | Dispositif à ondes élastiques |
WO2022118970A1 (fr) * | 2020-12-04 | 2022-06-09 | 株式会社村田製作所 | Appareil à ondes élastiques |
WO2022210293A1 (fr) * | 2021-03-31 | 2022-10-06 | 株式会社村田製作所 | Dispositif à ondes élastiques |
WO2022210683A1 (fr) * | 2021-03-31 | 2022-10-06 | 株式会社村田製作所 | Dispositif à ondes élastiques et son procédé de fabrication |
WO2022211055A1 (fr) * | 2021-03-31 | 2022-10-06 | 株式会社村田製作所 | Dispositif à ondes élastiques |
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