CN115250109A - MEMS acoustic wave device, method for manufacturing bulk acoustic wave resonator, filter, and electronic apparatus - Google Patents
MEMS acoustic wave device, method for manufacturing bulk acoustic wave resonator, filter, and electronic apparatus Download PDFInfo
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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
- H03H9/171—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator implemented with thin-film techniques, i.e. of the film bulk acoustic resonator [FBAR] type
- H03H9/172—Means for mounting on a substrate, i.e. means constituting the material interface confining the waves to a volume
- H03H9/173—Air-gaps
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/02007—Details of bulk acoustic wave devices
- H03H9/02015—Characteristics of piezoelectric layers, e.g. cutting angles
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
- H03H9/05—Holders; Supports
- H03H9/09—Elastic or damping supports
Abstract
The invention relates to an MEMS (micro-electromechanical system) acoustic wave device which comprises a piezoelectric layer, wherein the piezoelectric layer is a lithium niobate single crystal piezoelectric layer, and the piezoelectric layer is a rotary Y-cut of (yxl) 158-171 degrees. The invention also relates to a filter and an electronic device.
Description
Technical Field
Embodiments of the present invention relate to the field of semiconductors, and in particular, to an MEMS acoustic wave device, a method of manufacturing a bulk acoustic wave resonator, a filter, and an electronic apparatus.
Background
In the 5G era with increasingly stringent frequency bands, MEMS acoustic wave devices with high bandwidths are required to meet various urgent needs of people. LiNbO 3 The (LN) single crystal (i.e., lithium niobate single crystal) has excellent properties such as large electromechanical coupling coefficient and small propagation loss, and thus can be used to manufacture Acoustic wave devices with high frequency band, large bandwidth and low loss, such as Film Bulk Acoustic Resonator (FBAR, also called as BAW) and filters. Film bulk acoustic resonators play an important role in the field of communications, and in particular, FBAR filters have an increasing market share in the field of radio frequency filtersThe larger.
The performance of a conventional acoustic wave device (LN thickness is more than 10 μm, i.e. thick film LN) made of a single crystal piezoelectric material is closely related to its cut and propagation direction, which requires that a proper cut is selected to obtain high quality performance when the acoustic wave device is manufactured; however, since a MEMS acoustic wave device (LN thickness 10 μm or less) uses a thin film LN, the relationship of its performance and its shear mode and propagation direction differs from that of a conventional acoustic wave device due to boundary conditions and the like, and it is therefore necessary to find optimum conditions for a MEMS acoustic wave device based on a thin film LN single crystal piezoelectric material
Disclosure of Invention
The present invention has been made to mitigate or solve at least one of the above-mentioned problems in the prior art.
According to an aspect of an embodiment of the present invention, there is provided an acoustic wave device including:
the piezoelectric layer is a lithium niobate single crystal piezoelectric layer, and the piezoelectric layer is a rotary Y-cut of (yxl) 158-171 degrees.
The embodiment of the invention also relates to a manufacturing method of the bulk acoustic wave resonator, which comprises the following steps:
providing a POI wafer comprising a substrate, a piezoelectric layer and an insulating layer arranged between a first side of the piezoelectric layer and the substrate, wherein the piezoelectric layer is a lithium niobate single crystal piezoelectric layer and forms the piezoelectric layer of the resonator, and the piezoelectric layer is a rotary Y-cut of (yxl) 158-171 °;
providing a bottom electrode of a resonator on a second side of the piezoelectric layer, the second side being opposite to the first side in a thickness direction of the piezoelectric layer;
removing the substrate and at least a part of the insulating layer, wherein the insulating layer is used as a barrier layer for protecting the piezoelectric layer in the process of removing the substrate, the at least a part of the insulating layer is removed to expose the first side of the piezoelectric layer, and the insulating layer of the piezoelectric layer corresponding to the effective area of the resonator is removed;
a top electrode of the resonator is disposed on a first side of the piezoelectric layer.
Embodiments of the present invention also relate to a filter including the acoustic wave device described above.
Embodiments of the present invention also relate to an electronic apparatus including the above-described filter or the above-described acoustic wave device.
Drawings
These and other features and advantages of the various embodiments of the disclosed invention will be better understood from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate like parts throughout, and in which:
fig. 1A-1C are schematic top views, schematic cross-sectional views along line AA in fig. 1A, and schematic cross-sectional views along line BB in fig. 1A, respectively, of a bulk acoustic wave resonator according to an exemplary embodiment of the present invention;
2A-2C through 18A-18C are a series of diagrams illustrating exemplary fabrication processes of the bulk acoustic wave resonator shown in FIGS. 1A-1C, wherein A corresponds to a top view schematic, B corresponds to a schematic cross-sectional view of line AA, and C corresponds to a schematic cross-sectional view of line BB;
FIG. 19A is a schematic view of a Y-cut LN;
FIG. 19B is a schematic illustration of (yxl) 163 ° cut LN;
FIG. 20 is a schematic cross-sectional view of an LNOI structure where the piezoelectric layer is a (yxl) 163 ° cut LN piezoelectric layer;
FIG. 21 is a graph schematically illustrating the electromechanical coupling coefficient variation during a 90-270 degree counterclockwise rotation of the Y-cut LN about the X-crystal axis;
FIGS. 22A and 22B show a schematic deformation diagram for the shear wave mode and a schematic deformation diagram for the thickness extensional mode, respectively;
FIG. 23 is a simulated plot of the impedance log frequency response of (yxl) 163 ° cut LN;
FIG. 24 is a simulated plot of the log frequency response of the impedances for 158 ° cut LN (yxl) and 171 ° cut LN (yxl);
fig. 25A-25C are schematic top views, schematic cross-sectional views along line AA in fig. 25A, and schematic cross-sectional views along line BB in fig. 25A, respectively, of a bulk acoustic wave resonator according to an exemplary embodiment of the present invention, showing a remaining insulating layer between an electrode connection end of a top electrode and a piezoelectric layer.
Detailed Description
The technical scheme of the invention is further specifically described by the following embodiments and the accompanying drawings. In the specification, the same or similar reference numerals denote the same or similar components. The following description of the embodiments of the present invention with reference to the accompanying drawings is intended to explain the general inventive concept of the present invention and should not be construed as limiting the invention. Some, but not all embodiments of the invention are described. All other embodiments that can be derived by one of ordinary skill in the art from the embodiments given herein are intended to be within the scope of the present invention.
Fig. 1A to 1C are a schematic top view, a schematic cross-sectional view along line AA in fig. 1A, and a schematic cross-sectional view along line BB in fig. 1A, respectively, of a bulk acoustic wave resonator according to an exemplary embodiment of the present invention. In the present invention, bulk acoustic wave resonators are fabricated based on POI (single crystal piezoelectric layer on Insulator) wafers. The POI wafer includes an auxiliary substrate, a single crystal piezoelectric layer, and an insulating layer disposed between the single crystal piezoelectric layer and the auxiliary substrate.
As mentioned later, the insulating layer can better protect the single crystal piezoelectric film (i.e. the single crystal piezoelectric layer) during the transfer process of the resonator, so that the damage to the single crystal piezoelectric film during the subsequent process of removing the auxiliary substrate can be reduced or even avoided, and the surface damage to the piezoelectric film can be reduced or even avoided, so as to obtain the bulk acoustic wave resonator with excellent performance.
In addition, the existence of the insulating layer is also beneficial to diversification of an auxiliary substrate removing scheme, and the device processing technology is simplified.
In the invention, the POI wafer is an LNOI structure, and the corresponding bulk acoustic wave resonator is LiNbO 3 (LN) Single Crystal Acoustic wave resonator. LNOI structure LN is lithium niobate single crystal. In the present invention, bulk acoustic wave resonators or other acoustic devices are fabricated based on LNOI structures.
The common cutting patterns of the LN single crystal comprise Y cutting, X cutting and Z cutting, wherein the X, Y and Z are respectively designated X crystal axis, Y crystal axis and Z crystal axis of the LN single crystal, and the cutting planes of the several cutting patterns are perpendicular to a certain crystal axis. For example, the Y-cut of FIG. 19A below, whose cutting plane-M is perpendicular to the Y-crystal axis, is called Y-cut. The cut in this patent is a rotary Y cut, and the cut shown in fig. 19B below is (yxl) a 163 ° cut, which is a rotation of the Y crystal axis by 163 ° counterclockwise about the X crystal axis, and the cut plane-N is perpendicular to the Y +163 ° axis.
In order to operate the main mode of the LN bulk acoustic resonator in the 5G band, it is necessary to obtain a LN film with a thickness of the order of microns or even sub-micron, which requires a special process to bond the LN to the substrate, and fig. 20 is a schematic cross-sectional view of an LNOI structure in which the piezoelectric layer is (yxl) cut 158 ° -171 ° to the LN piezoelectric layer. In fig. 20, LN is a lithium niobate single crystal, silicon ("I") is used as the substrate, silicon dioxide ("O") is used as the bonding layer, and the piezoelectric layer is (yxl) a 163 ° cut LN piezoelectric layer. The LNOI structure in fig. 20 is a POI wafer structure comprising a substrate (I in fig. 20), a single crystal piezoelectric layer (LN in fig. 20), and an insulating layer (O in fig. 20) disposed between the single crystal piezoelectric layer and the substrate.
In the embodiment shown in FIG. 20, 163 ° cut LN was chosen (yxl) as the single crystal piezoelectric layer material. The reason for this is explained as follows:
for designing LN bulk acoustic wave resonator with 5GHz frequency band, according to elastic stiffness matrix, piezoelectric stress constant matrix and relative dielectric constant matrix data of LN single crystal, the electromechanical coupling coefficient caused by applying alternating electric field in thickness direction can be drawn
Graph of the change of the rotation angle theta counterclockwise with respect to the X-axis. FIG. 21 is a graph schematically illustrating the electromechanical coupling coefficient change during a 90-270 degree counterclockwise rotation of the Y-cut LN about the X-crystal axis. Due to consideration of
And
is 0, and d 31 And d 32 Corresponding to
And
although not 0, the resonance frequency is substantially 1GHz or lower. Therefore, figure 21 only shows
(d 33 Thickness expansion mode) and
(d 34 y-z shear mode).
Fig. 22A shows a deformation diagram of the shear wave mode, i.e. (yxl) 163 ° cut LN resonator's main vibration mode. Fig. 22B shows a schematic diagram of a deformation of the thickness expansion mode, which should be suppressed as much as possible. The thickness t of the LN film is a main factor that determines the frequencies of the y-z shear wave mode and the thickness extensional mode, and since these two modes may occur simultaneously when designing a device in the 5G band, it is troublesome to design the device later, and it is necessary to avoid the occurrence of the thickness extensional mode.
As can be seen from fig. 21, when the wafer is rotated 253 degrees counterclockwise around the X-crystal axis,
near the peak while
At 0, this profile is called (yxl) 163 ° cut. Due to the fact that
The magnitude of (A) represents the intensity of the shear mode, and
the magnitude of (b) represents the strength of the thickness stretching mode, so that the film bulk acoustic resonator is manufactured by using (yxl) 163 ° cut LN single crystal, so that the resonator can obtain the optimal acoustic wave characteristics.
Considering slicingIn the process, certain errors exist, the cut type of the shear bulk acoustic wave resonator can be widened to a certain angle, as can be seen from fig. 21, the electromechanical coupling coefficient of the shear wave is reduced relatively fast on the left side of (yxl) 163 degrees, and when the shear wave reaches (yxl) 158 degrees, the shear wave mode is realized
The drop was 45%. And when the right side reaches (yxl) about 171 DEG, the shear wave mode is obtained
A peak value of 59.1% is reached, and in this case the thickness is in the telescopic mode
Only 1.8% is about 3% of the shear wave mode. Therefore, the LN film bulk acoustic resonator can be designed by selecting the cutting form of (yxl) 158-171 degrees.
FIG. 23 is a simulated plot of the log frequency response of the impedance at 163 ° cut LN of (yxl) and FIG. 24 is a simulated plot of the log frequency response of the impedance at 158 ° cut LN of (yxl) and at 171 ° cut LN of (yxl). It can be seen that although the thickness extensional mode (spurious) occurs with the (yxl) 158 ° cut and the (yxl) 171 ° cut curves compared to the 163 ° cut curves, the strength of the thickness extensional mode is much smaller (5% or less) than that of the shear mode (master mode), and therefore, selecting LN between the (yxl) 158 ° cut and the (yxl) 171 ° cut can suppress the spurious mode while maximizing the master mode.
The following describes in detail the manufacturing process of the bulk acoustic wave resonator shown in fig. 1A to 1C with reference to fig. 2A to 2C through fig. 18A to 18C.
In fig. 1A-1C to 18A-18C, reference numerals are exemplarily illustrated as follows:
100: the auxiliary substrate is made of silicon, silicon carbide, sapphire, silicon dioxide or other silicon-based materials.
101: a release hole penetrating the substrate 100.
110: the insulating layer or the bonding layer is, for example, silicon dioxide, silicon nitride, silicon carbide, sapphire, or the like, or the material of the insulating layer has a thermal conductivity of not less than 0.2W/cm · K.
111: an insulating layer, which functions to protect the piezoelectric layer or to separate the electrode connection terminal from the piezoelectric layer, such as silicon dioxide, silicon nitride, silicon carbide, sapphire, etc., may be a part of the insulating layer 110.
120: a single crystal lithium niobate piezoelectric layer or an LN single crystal piezoelectric layer.
121: and the release hole is used for releasing the sacrificial layer material in the acoustic mirror cavity.
122: vias or electrical connection holes, in particular embodiments, are used to deposit conductive material to bring the bottom electrode 131 out to be coplanar with the top electrode 181.
130: the bottom electrode film layer is made of molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or their composite or their alloy.
131: the bottom electrode is formed by patterning a bottom electrode film layer, for example.
140: the sacrificial material film may be polysilicon, amorphous silicon, silicon dioxide, phosphorus doped silicon dioxide (PSG), zinc oxide, magnesium oxide, polymer, and the like.
141: the sacrificial material layer includes a cavity region 142 corresponding to the cavity of the acoustic mirror formed upon release and a channel region for the release of the sacrificial material formed upon release.
142: the release of the sacrificial material layer 141 forms the cavity region of the acoustic mirror cavity.
143: the acoustic mirror can be a cavity, and a Bragg reflection layer and other equivalent forms can also be adopted. The embodiment of the invention shown uses a cavity.
150: the material of the supporting material layer can be aluminum nitride, silicon nitride, polysilicon, silicon dioxide, amorphous silicon, boron-doped silicon dioxide, other silicon-based materials and the like.
151: and the support layer is formed by flattening the support material layer.
160. A bonding layer, which may be silicon dioxide or other silicon-based material, may be used to bond the support layer to the transfer substrate, and this material may be omitted. The bonding layer may also be an adhesive tape or the like.
170: the substrate is made of silicon, silicon carbide, sapphire, silicon dioxide or other silicon-based materials.
180: the top electrode film layer is made of molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or their composite or their alloy. The material of the top electrode film layer may be the same as or different from the material of the bottom electrode film layer.
181: the top electrode is formed by patterning a top electrode film layer, for example.
182: the material of the bottom electrode electric connection part can be selected from molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or the compound of the above metals or the alloy thereof, and the like. The material of the bottom electrode electrical connection portion 182 may be the same as or different from the top electrode film layer.
Fig. 2A-2C show a POI wafer. The POI wafer comprises auxiliary substrate 100, insulator layer 110 and LN single crystal piezoelectric layer 120, piezoelectric layer 120 being a (yxl) 163 ° cut LN piezoelectric layer.
FIGS. 2A-2C correspond to step 1: a POI wafer is provided that includes an auxiliary substrate 100, a single crystal piezoelectric layer 120, and an insulating layer 110 disposed between a first side of the single crystal piezoelectric layer and the substrate.
Fig. 3A to 3C and fig. 4A to 4C exemplarily show a process of depositing an electrode film layer on a surface of a piezoelectric single crystal thin film and forming a pattern of a bottom electrode.
A uniform electrode film 130 can be first deposited on the piezoelectric layer 120, as shown in fig. 3A-3C; the patterned bottom electrode 131 is then formed by means of wet or dry etching, as shown in fig. 4A-4C.
Alternatively, the pattern of the bottom electrode may be directly formed by a lift-off process (lift-off) or a printing process.
FIGS. 3A-3C and FIGS. 4A-4C correspond to step 2: a bottom electrode 131 is formed on a second side of the piezoelectric layer 120 of the POI wafer opposite the first side.
Fig. 5A-5C and 6A-6D illustrate the process of depositing a film 140 of sacrificial material and patterning a layer 141 of sacrificial material on the bottom electrode 131 and single crystal piezoelectric layer 120.
The patterned sacrificial material layer 141 may be formed by first depositing a uniform sacrificial material film 140 on the bottom electrode 131 and the piezoelectric single crystal thin film, as shown in fig. 5A-5C, and then forming the patterned sacrificial material layer 141 by wet or dry etching, as shown in fig. 6A-6D.
In fig. 6A to 6D, the sacrificial material layer 141 (corresponding to the acoustic mirror cavity) covers only a part of the bottom electrode 131 (at this time, as shown in fig. 18B, the non-electrode connecting end of the bottom electrode 131 is caused to be covered by the support layer 151 mentioned later), but the present invention is not limited thereto, and the sacrificial material layer 141 may cover both a part of the bottom electrode 131 and a part of the piezoelectric layer at the non-electrode connecting end of the bottom electrode 131 (at this time, although not shown, the non-electrode connecting end of the bottom electrode 131 is caused to be within the acoustic mirror cavity and not covered by the support layer 151).
The sacrificial material layer 141 of fig. 6C and 6D includes a cavity region 142 corresponding to the cavity of the acoustic mirror formed after release and a channel region for the release channel of the sacrificial material formed after release.
Fig. 7A-7C and 8A-8C illustrate the process of depositing and planarizing a layer of support material on the single crystal piezoelectric layer 120, the bottom electrode 131, and the layer of sacrificial material 141. The thickness of the support material layer 150 is greater than the thickness of the bottom electrode 131. The polished support layer 151 is formed by a polishing process such as CMP (chemical mechanical polishing).
FIGS. 5A-5C, FIGS. 6A-6D, FIGS. 7A-7C, and FIGS. 8A-8D correspond to step 3: an intermediate layer consisting of an acoustic mirror layer (i.e., a layer for forming an acoustic mirror) and a support layer 151 is provided, the intermediate layer covering the second side of the piezoelectric layer 120 and the bottom electrode 131, and the side of the intermediate layer remote from the auxiliary substrate 100 being a flat surface. More specifically, in fig. 5A-5C, 6A-6D, 7A-7C, and 8A-8D, step 3 includes: step 3A: forming a sacrificial material layer 141, the sacrificial material layer 141 covering only a portion of the bottom electrode 131 or a portion of the non-electrode connecting end of the bottom electrode 131 and a portion of the piezoelectric layer 120; and step 3B: a support material layer 150 is provided covering the sacrificial material layer 141, the bottom electrode 131 and the piezoelectric layer 120 such that the support material layer 150 is planarized to form the support layer 151.
More specifically, in step 3B described above, the side of the support layer 151 away from the substrate 100 is made to constitute the flat surface. However, the present invention is not limited thereto, and the support material layer 150 may be ground and polished until the side of the support layer 151 away from the substrate 100 is flush with the side of the sacrificial material layer 141 away from the substrate 100 to collectively constitute the flat surface.
Fig. 9A to 9C and fig. 10A to 10C illustrate a process of bonding the support layer 151 with the substrate 170.
As shown in fig. 9A to 9C, the flat surface of the support layer 151 is provided with a bonding layer 160, and as shown in fig. 10A to 10C, a substrate 170 is bonded to the support layer 151 via the bonding layer 160.
The substrate 170 and the support layer 151 may be physically or chemically bonded, and the material of the bonding layer 160 may be on the substrate 170 or the support layer 151, or on both surfaces.
The base 170 and the support layer 151 may not be directly bonded via a bonding layer, but a chemical bond may be formed between the base 170 and the support layer 151, or a physical bond may be formed by intermolecular force when the surface is polished to have extremely low surface roughness.
Fig. 9A to 9C and fig. 10A to 10C correspond to step 4: the substrate 170 is bonded to the intermediate layer (containing the support layer and the sacrificial material layer) at its planar side.
Fig. 11A-11D to 13A-13C are processes of device inversion, removal of the substrate 100 and the insulating layer 110.
The etching processes of the auxiliary substrate 100 and the insulating layer 110 (barrier layer) are different, for example, the auxiliary substrate 100 is silicon, the insulating layer 110 is silicon dioxide, the insulating layer 110 can function as a stop layer or a barrier layer in the process of removing the auxiliary substrate 100, the removing process of the insulating layer 110 is mild, and damage to the other surface of the piezoelectric single crystal thin film in the process of removing the auxiliary substrate 100 is reduced or even avoided.
The piezoelectric single crystal thin film surface release process may be implemented by removing the substrate 100 entirely and removing the insulating layer 110 entirely, for example, see fig. 11b,12b, and 13B.
In an alternative embodiment, as shown in fig. 11D, due to the existence of the insulating layer 110 as a barrier layer, the piezoelectric single crystal thin film surface release process may employ first forming release holes 101 on the substrate 100, and then releasing the insulating layer 110 material through the release holes. If the process of forming the release holes 101 on the substrate 100 does not cause any damage to the insulating layer 110 and the single crystal piezoelectric layer 120, the release holes can be arranged in any region; if the insulating layer 110 and the single crystal piezoelectric layer 120 are damaged, a release hole can be formed in an out-of-band area (such as a scribe lane) of the resonator or a filter formed by the resonator, so that the device processing process is simple.
The process of removing the entire substrate 100 or forming the release hole may be grinding, lapping, polishing, wet or dry etching, laser ablation, or the like, or a combination thereof.
The overall removal process of the insulating layer 110 may use grinding, lapping, polishing, wet or dry etching, laser ablation, or other related processes or a combination of these processes.
After the insulating layer 110 is removed, if the surface of the piezoelectric single crystal thin film has partial damage, especially damage to the effective region of the resonator or the filter formed of the resonator, the surface of the piezoelectric thin film may be polished by a polishing process.
The insulating layer 110 may also be removed only partially, leaving a portion outside the active area of the resonator, see for example fig. 25A-25C, where the portion shown corresponding to reference numeral 111 may be a portion of the insulating layer 110 that remains.
Fig. 11A to 11D to fig. 13A to 13C correspond to step 5: the substrate and the insulating layer are removed, at least a portion of the insulating layer is removed to expose the first side of the piezoelectric layer, and the insulating layer of the first side of the piezoelectric layer corresponding to the active area of the resonator is removed.
Fig. 14A to 14C and fig. 15A to 15C show a process of depositing a top electrode film on the release surface of the piezoelectric single crystal film or piezoelectric layer 120 and patterning the top electrode.
The top electrode may be formed by first depositing a uniform electrode film layer 180 (as shown in fig. 14A-14C) and then forming a patterned top electrode 181 (as shown in fig. 15A-15C) by means of wet or dry etching. The top electrode may be directly patterned by a lift-off process (lift-off) or a printing process.
Fig. 16A to 16C and fig. 17A to 17C show a process of forming a release hole of a sacrificial material layer, a connection hole of a bottom electrode connection part on a piezoelectric layer, and forming an electrical connection pattern.
The release holes 121 (shown in fig. 16A-16C) and the electrical connection holes 122 (shown in fig. 16A-16C) for forming the sacrificial material layer may be implemented by a related process such as wet or dry etching, laser ablation, or a combination thereof.
Forming the electrical connection pattern or bottom electrode electrical connection 182 can be done by first depositing a uniform conductive film layer and then forming a patterned bottom electrode electrical connection by wet or dry etching, or by lift-off or printing, etc. (as shown in fig. 17A-17C).
The process of forming the release hole 121 of the sacrificial material layer, the electrical connection hole 122 of the bottom electrode (fig. 16A-16C and fig. 17A-17C), and the bottom electrode electrical connection 182 and the top electrode (fig. 14A-14C and fig. 15A-15C) can be interchanged.
Fig. 18A-18C illustrate the process of releasing the sacrificial material layer 143 to form the acoustic mirror cavity 143. Fig. 18A to 18C are respectively a schematic top view, a schematic cross-sectional view along the line AA in fig. 18A, and a schematic cross-sectional view along the line BB in fig. 18A of a bulk acoustic wave resonator.
The sacrificial material layer 141 may be removed by wet or dry methods to form the acoustic mirror cavity 143, thereby obtaining the resonator structure shown in fig. 1A-1C.
In the above embodiment, after the bottom electrode 131 is formed, the sacrificial material layer 141 is formed first, and then the support layer 151 is formed, but the present invention is not limited thereto, and the sacrificial material layer 141 may be formed after the support material layer is formed.
Based on the above, the invention provides a method for manufacturing a bulk acoustic wave resonator, which comprises the following steps:
providing a POI wafer comprising a substrate 100, a piezoelectric layer 120, and an insulating layer 110 disposed between a first side of the piezoelectric layer 120 and the substrate, the piezoelectric layer 120 being a lithium niobate single crystal piezoelectric layer and constituting the piezoelectric layer of the resonator, the piezoelectric layer being a rotated Y-cut of (yxl) 158 ° -171 °;
providing a bottom electrode 131 of the resonator on a second side of the piezoelectric layer 120, the second side being opposite to the first side in a thickness direction of the piezoelectric layer;
removing the substrate 100 and at least a portion of the insulating layer 110, the insulating layer 110 acting as a barrier layer protecting the piezoelectric layer during the removal of the substrate 100, the at least a portion of the insulating layer being removed to expose a first side of the piezoelectric layer 120, and the insulating layer of the piezoelectric layer 120 corresponding to the active area of the resonator being removed;
a top electrode 181 of the resonator is arranged on a first side of the piezoelectric layer 120.
It is to be noted that, in the present invention, each numerical range, except when explicitly indicated as not including the end points, can be either the end points or the median of each numerical range, and all fall within the scope of the present invention.
In the present invention, the upper and lower are with respect to the bottom surface of the base of the resonator, and with respect to one component, the side thereof close to the bottom surface is the lower side, and the side thereof far from the bottom surface is the upper side.
In the present invention, the inner and outer are in the lateral direction or the radial direction with respect to the center of the effective area (i.e., the effective area center) of the resonator (the overlapping area of the piezoelectric layer, the top electrode, the bottom electrode, and the acoustic mirror in the thickness direction of the resonator constitutes the effective area), the side or end of a member close to the effective area center is the inner side or the inner end, and the side or end of the member away from the effective area center is the outer side or the outer end. For a reference position, being inside of the position means being between the position and the center of the effective area in the lateral or radial direction, and being outside of the position means being further away from the center of the effective area than the position in the lateral or radial direction.
As can be appreciated by those skilled in the art, the bulk acoustic wave resonator according to the present invention may be used to form a filter or an electronic device.
Based on the above, the invention provides the following technical scheme:
1. a MEMS acoustic wave device comprising:
the piezoelectric layer is a lithium niobate single crystal piezoelectric layer, and the piezoelectric layer is a rotary Y-cut of (yxl) 158-171 degrees.
2. The device of 1, wherein:
the piezoelectric layer is a 163 ° rotated Y-cut of (yxl).
3. The device of claim 1 or 2, wherein:
the acoustic wave device is a bulk acoustic wave resonator, the resonator comprises a substrate, an acoustic mirror, a bottom electrode and a top electrode, the piezoelectric layer is arranged between the bottom electrode and the top electrode, and further optionally, the piezoelectric layer is made of a thin film material and has a thickness ranging from 0.1 micrometer to 10 micrometers.
4. The device of claim 3, wherein:
the superposition area of the acoustic mirror, the bottom electrode, the piezoelectric layer and the top electrode in the thickness direction of the resonator forms the effective area of the resonator;
outside the active area, at least a portion of an upper surface of the piezoelectric layer is provided with an insulating layer.
5. The device of 4, wherein:
the insulating layer is at least arranged between the lower surface of the top electrode and the upper surface of the piezoelectric layer in an area corresponding to the part of the top electrode outside the effective area;
the material of the insulating layer is selected from one of silicon dioxide, silicon nitride, silicon carbide and sapphire, or the thermal conductivity coefficient of the material of the insulating layer is not less than 0.2W/cm K.
6. The device of claim 3, wherein:
a supporting structure is arranged between the lower surface of the piezoelectric layer and the upper surface of the substrate, the material of the supporting structure is selected from one of aluminum nitride, silicon carbide, polycrystalline silicon, monocrystalline silicon, silicon dioxide, amorphous silicon and doped silicon dioxide, or the thermal conductivity coefficient of the material of the supporting structure is not less than 0.2W/cm-K.
7. The device of claim 3, wherein:
the acoustic mirror is an acoustic mirror cavity.
8. The device of claim 7, wherein:
the acoustic mirror cavity is shaped to be recessed into the support layer, and a lower boundary of the acoustic mirror cavity is defined by the support layer; or
A lower boundary of the acoustic mirror cavity is defined by the substrate.
9. The device of claim 3, wherein:
the superposition area of the acoustic mirror, the bottom electrode, the piezoelectric layer and the top electrode in the thickness direction of the resonator forms an effective area of the resonator;
outside the active area, at least a portion of an upper surface of the piezoelectric layer is provided with an insulating layer.
10. The device of claim 9, wherein:
the insulating layer is at least arranged between the lower surface of the top electrode and the upper surface of the piezoelectric layer in an area corresponding to the part of the top electrode outside the effective area;
the material of the insulating layer is selected from one of silicon dioxide, silicon nitride, silicon carbide and sapphire, or the thermal conductivity coefficient of the material of the insulating layer is not less than 0.2W/cm K.
11. A method for manufacturing a bulk acoustic wave resonator comprises the following steps:
providing a POI wafer, wherein the POI wafer comprises a substrate, a piezoelectric layer and an insulating layer arranged between a first side of the piezoelectric layer and the substrate, the piezoelectric layer is a lithium niobate single crystal piezoelectric layer and forms the piezoelectric layer of the resonator, and the piezoelectric layer is a rotary Y-cut shape of (yxl) 158-171 degrees;
providing a bottom electrode of a resonator on a second side of the piezoelectric layer, the second side being opposite to the first side in a thickness direction of the piezoelectric layer;
removing the substrate and at least a part of the insulating layer, wherein the insulating layer is used as a barrier layer for protecting the piezoelectric layer in the process of removing the substrate, the at least a part of the insulating layer is removed to expose the first side of the piezoelectric layer, and the insulating layer of the piezoelectric layer corresponding to the effective area of the resonator is removed;
a top electrode of the resonator is arranged at the first side of the piezoelectric layer.
12. The method of claim 11, wherein:
all of the insulating layer is removed.
13. The method of claim 11, wherein:
such that the insulating layer remains between the top electrode and the piezoelectric layer in a region corresponding to a portion of the top electrode of the resonator outside the active area.
14. The method of claim 11, wherein:
the piezoelectric layer is a 163 ° rotated Y-cut of (yxl).
15. The method of claim 11, wherein:
the piezoelectric layer is a thin film material with a thickness ranging from 0.1 micron to 10 microns.
16. A filter comprising an acoustic wave device according to any of claims 1-10.
17. An electronic device comprising the filter according to 16 or the acoustic wave device according to any of claims 1-10.
The electronic device includes, but is not limited to, intermediate products such as a radio frequency front end and a filtering and amplifying module, and terminal products such as a mobile phone, WIFI and an unmanned aerial vehicle.
Although embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.
Claims (18)
1. A MEMS acoustic wave device comprising:
the piezoelectric layer is a lithium niobate single crystal piezoelectric layer, and the piezoelectric layer is a rotary Y-cut of (yxl) 158-171 degrees.
2. The device of claim 1, wherein:
the piezoelectric layer is a 163 ° rotated Y-cut (yxl).
3. The device of claim 1 or 2, wherein:
the acoustic wave device is a bulk acoustic wave resonator, the resonator comprises a substrate, an acoustic mirror, a bottom electrode and a top electrode, and the piezoelectric layer is arranged between the bottom electrode and the top electrode.
4. The device of claim 3, wherein:
the superposition area of the acoustic mirror, the bottom electrode, the piezoelectric layer and the top electrode in the thickness direction of the resonator forms the effective area of the resonator;
outside the active area, at least a portion of an upper surface of the piezoelectric layer is provided with an insulating layer.
5. The device of claim 4, wherein:
the insulating layer is at least arranged between the lower surface of the top electrode and the upper surface of the piezoelectric layer in an area corresponding to the part of the top electrode outside the effective area;
the material of the insulating layer is selected from one of silicon dioxide, silicon nitride, silicon carbide and sapphire, or the thermal conductivity coefficient of the material of the insulating layer is not less than 0.2W/cm K.
6. The device of claim 3, wherein:
a supporting structure is arranged between the lower surface of the piezoelectric layer and the upper surface of the substrate, the material of the supporting structure is selected from one of aluminum nitride, silicon carbide, polycrystalline silicon, monocrystalline silicon, silicon dioxide, amorphous silicon and doped silicon dioxide, or the thermal conductivity coefficient of the material of the supporting structure is not less than 0.2W/cm-K.
7. The device of claim 3, wherein:
the acoustic mirror is an acoustic mirror cavity.
8. The device of claim 7, wherein:
the acoustic mirror cavity is shaped to be recessed into the support layer, and a lower boundary of the acoustic mirror cavity is defined by the support layer; or
A lower boundary of the acoustic mirror cavity is defined by the substrate.
9. The device of claim 3, wherein:
the superposition area of the acoustic mirror, the bottom electrode, the piezoelectric layer and the top electrode in the thickness direction of the resonator forms the effective area of the resonator;
outside the active area, at least a portion of an upper surface of the piezoelectric layer is provided with an insulating layer.
10. The device of claim 9, wherein:
the insulating layer is at least arranged between the lower surface of the top electrode and the upper surface of the piezoelectric layer in an area corresponding to the part of the top electrode outside the effective area;
the material of the insulating layer is selected from one of silicon dioxide, silicon nitride, silicon carbide and sapphire, or the thermal conductivity coefficient of the material of the insulating layer is not less than 0.2W/cm-K.
11. The device of claim 3, wherein:
the piezoelectric layer is a thin film material with a thickness ranging from 0.1 micron to 10 microns.
12. A method for manufacturing a bulk acoustic wave resonator comprises the following steps:
providing a POI wafer, wherein the POI wafer comprises a substrate, a piezoelectric layer and an insulating layer arranged between a first side of the piezoelectric layer and the substrate, the piezoelectric layer is a lithium niobate single crystal piezoelectric layer and forms the piezoelectric layer of the resonator, and the piezoelectric layer is a rotary Y-cut shape of (yxl) 158-171 degrees;
providing a bottom electrode of a resonator on a second side of the piezoelectric layer, the second side being opposite to the first side in a thickness direction of the piezoelectric layer;
removing the substrate and at least a part of the insulating layer, wherein the insulating layer is used as a barrier layer for protecting the piezoelectric layer in the process of removing the substrate, the at least a part of the insulating layer is removed to expose the first side of the piezoelectric layer, and the insulating layer of the piezoelectric layer corresponding to the effective area of the resonator is removed;
a top electrode of the resonator is disposed on a first side of the piezoelectric layer.
13. The method of claim 12, wherein:
all of the insulating layer is removed.
14. The method of claim 12, wherein:
such that the insulating layer remains between the top electrode and the piezoelectric layer in a region corresponding to a portion of the top electrode of the resonator outside the active area.
15. The method of claim 12, wherein:
the piezoelectric layer is a 163 ° rotated Y-cut of (yxl).
16. The method of claim 12, wherein:
the piezoelectric layer is a thin film material with a thickness ranging from 0.1 micron to 10 microns.
17. A filter comprising an acoustic wave device according to any of claims 1-11.
18. An electronic device comprising a filter according to claim 17, or an acoustic wave device according to any of claims 1-11.
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