CN111245387A - Structure and manufacturing process of solid assembled resonator - Google Patents
Structure and manufacturing process of solid assembled resonator Download PDFInfo
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- H—ELECTRICITY
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- H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
- H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
- H03H3/02—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
- H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
- H03H3/02—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks
- H03H2003/023—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks the resonators or networks being of the membrane type
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
- H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
- H03H3/02—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks
- H03H2003/028—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks for obtaining desired values of other parameters
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Abstract
The invention discloses a solid assembled resonator and a manufacturing process thereof, wherein the solid assembled resonator comprises a substrate, a sound wave reflecting layer formed on the substrate and a resonance function layer formed on the sound wave reflecting layer, the resonance function layer comprises a bottom electrode layer, a piezoelectric layer and a top electrode layer which are sequentially stacked, a dielectric layer is formed around the bottom electrode layer, the bottom electrode layer and the dielectric layer form a flat surface on the sound wave reflecting layer, and the piezoelectric layer is arranged on the flat surface. In the manufacturing process, an absolutely flat seed layer can be grown on an absolutely flat Si substrate, so that a piezoelectric layer AlN film with a preferred orientation of a C axis can be better obtained, and the working performance of a resonator is improved; growing a piezoelectric layer on the absolutely flat seed layer to ensure that the piezoelectric layer has a very flat surface, thereby ensuring the stress consistency and the electromechanical coupling coefficient consistency; removing the piezoelectric layer AlN in the initial amorphous state can enable the piezoelectric layer AlN film to obtain excellent C-axis orientation, and therefore better device performance and product yield are obtained.
Description
Technical Field
The application relates to the field of communication devices, in particular to a structure and a manufacturing process of a solid-state assembled resonator.
Background
With the increasing crowding of electromagnetic spectrum and the increase of frequency bands and functions of wireless communication equipment, the electromagnetic spectrum used for wireless communication increases at a high speed from 500MHz to more than 5GHz, and the demand for a radio frequency front-end module with high performance, low cost, low power consumption and small size also increases increasingly. The filter is one of radio frequency front end modules, can improve transmitting and receiving signals and is mainly formed by connecting a plurality of resonators through a topological network structure. BAW (bulk Acoustic wave) is a bulk Acoustic wave resonator, and a filter formed by the BAW (bulk Acoustic wave) has the advantages of small volume, strong integration capability, high quality factor Q guarantee during high-frequency operation, strong power bearing capability and the like and is used as a core device of a radio frequency front end.
SMR (solid Mounted resonator) is one of BAW device types, and the basic structure is composed of an acoustic wave reflection layer, a top electrode, a bottom electrode and a piezoelectric layer. The sound wave reflecting layer is formed by alternately stacking metal and dielectric film layers with unmatched acoustic impedances, and the theoretical thickness of each layer is lambda/4. When high-frequency voltage is applied to the upper electrode of the SMR, the piezoelectric layer can realize the conversion of electric energy and mechanical energy, and the mechanical energy exists in the form of sound wave. The piezoelectric layer vibrates in piston mode, and longitudinal waves propagate in the effective area of the resonator and are reflected at the top electrode-air interface and the bottom electrode-reflective layer interface respectively. The top electrode, the piezoelectric layer and the bottom electrode in the effective area need to have good C-axis preferred orientation, so that the acoustic loss can be reduced, and the resonator is prompted to maintain a required vibration mode under the working frequency.
In the prior art, the piezoelectric layer of the solid assembled resonator needs to be manufactured through sputtering, photoetching and etching processes, because the edge of the bottom electrode has a certain angle, the piezoelectric layer can grow along the bottom electrode with the angle at the edge to be contacted with the reflecting layer (lambda/4 layer), so that the piezoelectric layer is uneven and cannot obtain good C-axis orientation under the influence of stress. In addition, the etching process may cause the sidewalls to be vulnerable.
The invention aims to design a solid assembled resonator structure, and a piezoelectric layer, a top electrode and a bottom electrode with good preferred C-axis orientation or a flat piezoelectric layer is obtained, so that the solid assembled resonator structure with high performance and high quality factor is obtained.
Disclosure of Invention
The piezoelectric layer of the solid-state assembled resonator is easily affected by stress, and good preferred orientation of the C axis is difficult to obtain. The present application proposes a solid state assembled resonator and fabrication process to solve the above existing problems.
In a first aspect, the present application provides a solid-state assembled resonator, including a substrate, an acoustic wave reflection layer formed on the substrate, and a resonance function layer formed on the acoustic wave reflection layer, the resonance function layer including a bottom electrode layer, a piezoelectric layer, and a top electrode layer stacked in this order, a dielectric layer being formed around the bottom electrode layer, and the bottom electrode layer and the dielectric layer forming a flat surface on the acoustic wave reflection layer, the piezoelectric layer being disposed on the flat surface. The piezoelectric layer on the solid-state assembled resonator has a very flat surface, and stress consistency and electromechanical coupling coefficient consistency can be guaranteed.
In some embodiments, the acoustic wave reflective layer comprises a combination of at least two sets of dielectric reflective layers and metal reflective layers that are alternately stacked. The resonance functional layer realizes the conversion of electric energy and mechanical energy through the piezoelectric layer, the mechanical energy exists in the form of sound wave, and the sound wave reflecting layer has the alternating characteristics of high sound impedance and low sound impedance, can effectively reflect the sound wave, avoids the loss of sound wave energy, and enables the sound wave to achieve the purpose of resonance in an effective resonance area.
In some embodiments, the substrate and the side of the bottom electrode layer adjacent to the acoustic wave reflective layer are provided with a dielectric reflective layer. In this case, the metal reflective layer is sandwiched between the dielectric reflective layers, thereby forming an acoustic wave reflective layer having a good reflection effect.
In some embodiments, a dielectric layer is disposed around the acoustic wave reflecting layer. The dielectric layer surrounds the bottom electrode layer and the sound wave reflecting layer and is used for protecting the bottom electrode layer and the sound wave reflecting layer.
In some embodiments, the material of the bottom electrode layer and the top electrode layer is a composite of one or more of Mo, W, Al, Pt, or Ru. On the premise that the piezoelectric layer has a flat surface, the bottom electrode layer and the top electrode layer can be made of other electrode materials except Mo, the selection limit of the electrode materials is relatively small, the selection range of the electrode materials can be expanded, and the cost is reduced.
In a second aspect, the present application also provides a process for manufacturing a solid-state assembled resonator, comprising the steps of:
s1, manufacturing a piezoelectric layer on the first substrate, and then manufacturing a bottom electrode layer on the piezoelectric layer;
s2, manufacturing a sound wave reflecting layer on the bottom electrode layer;
s3, bonding a second substrate on the acoustic wave reflective layer;
s4, removing the first substrate to expose a back surface of the piezoelectric layer opposite to the bottom electrode layer; and
and S5, manufacturing a top electrode layer on the back surface of the piezoelectric layer.
In some embodiments, step S2 specifically includes the following sub-steps:
s21, growing a medium reflecting layer on the layer formed in the previous step, and grinding the medium reflecting layer to be flat;
s22, manufacturing a metal reflecting layer on the medium reflecting layer;
s23, repeating the above steps S21-S22 to form at least two sets of dielectric reflection layers and metal reflection layers which are alternately stacked to form the acoustic wave reflection layer.
The resonance function layer realizes the conversion of electric energy and mechanical energy through the piezoelectric layer, and the mechanical energy exists in the form of sound waves. The sound wave reflecting layer has the characteristic of alternating high sound impedance and low sound impedance, can effectively reflect sound waves, avoids the loss of sound wave energy and enables the sound waves to achieve the purpose of resonance in an effective resonance area.
In some embodiments, step S3 specifically includes bonding a second substrate on the acoustic wave reflecting layer by a wafer bonding process. The wafer bonding process is mature and convenient for bonding the second substrate.
In some embodiments, step S1 further includes fabricating a seed layer between the first substrate and the piezoelectric layer. The presence of the seed layer facilitates the formation of a piezoelectric layer, a top electrode layer and a bottom electrode layer with good C-axis preferred orientation, reducing the selection constraints of the electrode materials.
In some embodiments, step S4 specifically includes removing the first substrate by grinding, chemical mechanical polishing, and trimming processes, removing the seed layer, and thinning the piezoelectric layer. Growing the piezoelectric layer on the absolutely flat seed layer to enable the piezoelectric layer to have a very flat surface, removing the first substrate and the seed layer, and obtaining the piezoelectric layer with the flat surface after trimming the piezoelectric layer to ensure stress consistency.
In some embodiments, the material of the piezoelectric layer is AlN, and the initial amorphous state of AlN in the piezoelectric layer is removed when the piezoelectric layer is trimming. The amorphous piezoelectric layer AlN is removed in the step, so that the integral piezoelectric layer has better C-axis orientation and better piezoelectricity, and the working performance of the resonator is improved.
In some embodiments, the seed layer comprises two or more layers of material formed by sputtering or deposition. The seed layers prepared from different materials can obtain the piezoelectric layer with good C-axis preferred orientation, can improve the selectivity of the electrode material, and can reduce the production cost.
In some embodiments, the seed layer includes an AlN layer proximate the first substrate and a Mo layer located on the AlN layer. The Mo layer may enhance the preferred degree of orientation of the piezoelectric layer.
In some embodiments, the seed layer includes a layer of Cr or Ir, Pt proximate to the first substrate and a layer of Mo overlying the layer of Cr or Ir, Pt. Mo is a (1,1,0) crystal face, and can enhance the C-axis preferred orientation of a subsequent film layer.
In some embodiments, the seed layer includes a SiC layer proximate the first substrate and an AlN layer on the SiC layer. Also, the AlN layer may enhance C-axis preferred orientation of subsequent film layers.
In some embodiments, the AlN layer has C-axis oriented (0,0,0,2) crystal planes. A Mo layer with a (1,1,0) crystal plane can be obtained.
In some embodiments, the Mo layer has a body-centered cubic structure with (1,1,0) crystal planes. The Mo of the (1,1,0) crystal plane can enhance the preferred orientation degree of the (0,0,0,2) crystal plane of the AlN piezoelectric layer, reduce the acoustic loss and promote the resonator to maintain the required vibration mode at the working frequency.
In some embodiments, the bottom and top electrode layers are a composite of one or more of Mo, W, Al, Pt, or Ru. On the premise that the piezoelectric layer has a flat surface, the bottom electrode layer and the top electrode layer can be made of other electrode materials except Mo, the selection limit of the electrode materials is relatively small, the selection range of the electrode materials can be expanded, and the cost is reduced.
In some embodiments, the material of the first substrate and the second substrate is Si. The Si substrate is convenient for processing and manufacturing the resonator.
The application provides a solid-state assembled resonator and a manufacturing process, the solid-state assembled resonator comprises a substrate, a sound wave reflecting layer formed on the substrate and a resonance function layer formed on the sound wave reflecting layer, the resonance function layer comprises a bottom electrode layer, a piezoelectric layer and a top electrode layer which are sequentially stacked, a dielectric layer is formed around the bottom electrode layer, the bottom electrode layer and the dielectric layer form a flat surface on the sound wave reflecting layer, and the piezoelectric layer is arranged on the flat surface. In the manufacturing process, an absolutely flat seed layer can be grown on an absolutely flat Si substrate, so that a piezoelectric layer AlN film with a preferred orientation of a C axis can be better obtained, and the working performance of a resonator is improved; growing a piezoelectric layer on the absolutely flat seed layer to ensure that the piezoelectric layer has a very flat surface, thereby ensuring the stress consistency and the electromechanical coupling coefficient consistency; removing the piezoelectric layer AlN in the initial amorphous state can enable the piezoelectric layer AlN film to obtain excellent C-axis orientation, and therefore better device performance and device product yield can be obtained. In addition, the AlN in the most initial amorphous state can be removed by a trimming (plasma grinding) technology, and an AlN piezoelectric layer with the preferred orientation of the C axis can be obtained, so that the piezoelectric ceramic has better piezoelectric performance.
Drawings
The accompanying drawings are included to provide a further understanding of the embodiments and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments and together with the description serve to explain the principles of the invention. Other embodiments and many of the intended advantages of embodiments will be readily appreciated as they become better understood by reference to the following detailed description. The elements of the drawings are not necessarily to scale relative to each other. Like reference numerals designate corresponding similar parts.
FIG. 1 shows a schematic structural diagram of a solid-state assembled resonator according to an embodiment of the present invention;
FIG. 2 shows a flow diagram of a process for fabricating a solid state assembled resonator according to an embodiment of the invention
FIGS. 3a-3m are schematic structural diagrams illustrating a process for fabricating a solid state assembled resonator according to an embodiment of the present invention;
fig. 4 shows a flowchart of step S2 of a process of fabricating a solid state assembled resonator according to an embodiment of the present invention.
Detailed Description
The present application will be described in further detail with reference to the following drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the relevant invention and not restrictive of the invention. It should be noted that, for convenience of description, only the portions related to the related invention are shown in the drawings. It should be noted that the dimensions and sizes of the elements in the figures are not to scale and the sizes of some of the elements may be highlighted for clarity of illustration.
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments with reference to the attached drawings.
The invention provides a solid-state assembled resonator, as shown in fig. 1, comprising a substrate 101, an acoustic wave reflecting layer 201 formed on the substrate 101, and a resonance function layer 301 formed on the acoustic wave reflecting layer 201. The resonance function layer 301 includes a bottom electrode layer 302, a piezoelectric layer 303, and a top electrode layer 304, which are sequentially stacked. The bottom electrode layer 302, the piezoelectric layer 303, and the top electrode layer 304 constitute an effective resonance region in a direction perpendicular to the substrate 101. The resonant functional layer 301 converts electrical energy into mechanical energy in the form of acoustic waves by means of the piezoelectric layer 303. The sound wave reflecting layer 201 has the characteristic that high sound impedance and low sound impedance are alternated, can effectively reflect sound waves, avoids the loss of sound wave energy, and enables the sound waves to achieve the resonance effect in an effective resonance area. A dielectric layer 401 is formed around the bottom electrode layer 302 and the piezoelectric layer 303 may have a very flat surface.
In a particular embodiment, the acoustic wave reflective layer 201 includes a combination of at least two sets of dielectric reflective layers 202 and metallic reflective layers 203 that are alternately stacked. In a preferred embodiment, the thickness of the dielectric reflective layer 202 and the metal reflective layer 203 is 1/4 the longitudinal wave wavelength of the resonator in at least the range of the projected area perpendicular to the bottom electrode layer 302. Under this condition, the acoustic wave reflecting layer 201 may constitute a reflection grating, concentrate energy in the resonator, and achieve an effect of reflecting the acoustic wave.
In a specific embodiment, the substrate 101 and the bottom electrode layer 302 are provided with a dielectric reflective layer 202 on a side close to the acoustic wave reflective layer 201, and a dielectric layer 401 is provided around the acoustic wave reflective layer 201. Therefore, the metal reflective layer 203 is surrounded by the dielectric reflective layer 202 and the dielectric layer 401, the metal reflective layer 203 can be protected from corrosion, and the dielectric reflective layer 202 and the metal reflective layer 203 can form the acoustic wave reflective layer 201 with good reflection effect. Meanwhile, the bottom electrode layer 302 is also surrounded by the dielectric reflective layer 202 and the dielectric layer 401, so that the bottom electrode layer 302 can be protected from corrosion. In a specific embodiment, the material of the bottom electrode layer 302 and the top electrode layer 304 is a composite of one or more of Mo, W, Al, Pt, or Ru. In the prior art, the C-direction piezoelectric layer is generally obtained by using Mo as the bottom electrode layer 302, so there is a great limitation on the selection of the material of the bottom electrode layer 302. According to the embodiment of the application, on the premise that the piezoelectric layer 303 has a flat surface, the bottom electrode layer 302 and the top electrode layer 304 can be made of other electrode materials except for Mo, the selection limit of the electrode materials is relatively small, the selection range of the electrode materials can be expanded, and the cost is reduced.
The piezoelectric layer 303 on the solid assembled resonator is arranged on the flat surface, so that the piezoelectric layer 303 is very flat, the stress consistency is ensured, the electromechanical coupling coefficient consistency is ensured, and better device performance and device product yield can be obtained.
The invention also provides a manufacturing process of the solid assembled resonator, as shown in fig. 2, comprising the following steps:
s1, manufacturing a piezoelectric layer on the first substrate, and then manufacturing a bottom electrode layer on the piezoelectric layer;
s2, manufacturing a sound wave reflecting layer on the bottom electrode layer;
s3, bonding a second substrate on the acoustic wave reflective layer;
s4, removing the first substrate to expose a back surface of the piezoelectric layer opposite to the bottom electrode layer; and
and S5, manufacturing a top electrode layer on the back surface of the piezoelectric layer.
The manufacturing process of steps S1-S5 is described in detail by the method of the structure diagram. This step can be done directly by fabricating the piezoelectric layer 303 on the first substrate 111 in step S1, or further processing can be done on the first substrate 111 to obtain the piezoelectric layer 303 with good C-axis preferred orientation. The bottom electrode layer 302 is formed on the piezoelectric layer 303, and the piezoelectric layer 303 does not grow along the bottom electrode layer 302 with an angle at the edge to contact with the acoustic wave reflection layer 201. Fig. 3a-3m are schematic structural diagrams illustrating a manufacturing process of a solid-state assembled resonator according to an embodiment of the present application, and in a specific embodiment, as shown in fig. 3a, step S1 further includes manufacturing a seed layer 501 between the first substrate 111 and the piezoelectric layer 303. In a preferred embodiment, seed layer 501 is composed of two or more layers of material formed by sputtering or deposition. A first layer of material in the seed layer 501 is formed by sputtering or deposition on the first substrate 111, a second layer of material in the seed layer 501 is formed by sputtering or deposition on the first layer of material, and so on. The material of the first substrate 111 is Si, the piezoelectric layer 303 with a good C-axis preferred orientation can be obtained by preparing the seed layer 501 on the first substrate 111 through different materials, the selectivity of the electrode material can be improved, and the production cost can be reduced. In one embodiment, the seed layer 501 includes an AlN layer adjacent to the first substrate 111 and a Mo layer on the AlN layer. The AlN layer has a thickness of about 50nm, and AlN has a (0,0,0,2) crystal plane oriented in the C-axis direction. The thickness of the Mo layer is about 50nm, Mo is a body-centered cubic structure with a (1,1,0) crystal plane, the material of the first substrate 111 is Si, and the (0,0,0,2) crystal plane of the AlN seed layer enhances the preferred orientation degree of the Mo with the (1,1,0) crystal plane.
In another embodiment, the seed layer 501 includes a layer of Cr or Ir, Pt adjacent to the first substrate 111 and a layer of Mo on the layer of Cr or Ir, Pt. By using an MOCVD process, a Cr/Ir and Pt layer grows on the first substrate 111, and then factors such as temperature, pressure, gas flow, airtightness and the like are controlled to obtain a single crystal or polycrystalline Mo layer, wherein Mo is a (1,1,0) crystal face, so that the preferred orientation of the C axis of a subsequent film layer is enhanced.
In another embodiment, seed layer 501 includes a layer of SiC adjacent first substrate 111 and a layer of AlN on the SiC layer. By adopting an MOCVD process, firstly growing a SiC layer on the first substrate 111, obtaining a monocrystalline or polycrystalline AlN layer by controlling factors such as temperature, pressure, gas flow, airtightness and the like, and enhancing the C-axis preferred orientation of a subsequent film layer, wherein AlN is a (0,0,0,2) crystal face.
In a specific embodiment, as shown in fig. 3b, the piezoelectric layer 303 is sputtered on the seed layer 501, wherein the material of the piezoelectric layer 303 comprises AlN with a (0,0,0,2) crystal plane preferred orientation. The piezoelectric layer 303 is fabricated on the seed layer 501 having a flat surface so that the piezoelectric layer 303 has a good C-axis preferred orientation. As shown in fig. 3c, the bottom electrode layer 302 is formed on the piezoelectric layer 303 by photolithography, sputtering and etching processes, and in a preferred embodiment, the material of the bottom electrode layer 302 is Mo, and may be a single or composite electrode of tungsten, aluminum, molybdenum, platinum, ruthenium, etc. In the prior art, the C-direction piezoelectric layer 303 is generally obtained by taking Mo as the material of the bottom electrode layer 302, so there is a great limitation on the selection of the bottom electrode layer 302. In the embodiment of the present application, the AlN piezoelectric layer 303 with a height C direction is directly implemented by growing the AlN piezoelectric layer 303 on the composite seed layer 501, and thus the selection limitation on the electrode material is relatively small.
In a specific embodiment, as shown in fig. 4, step S2 specifically includes the following sub-steps:
s21, growing a medium reflecting layer on the layer formed in the previous step, and grinding the medium reflecting layer to be flat;
s22, manufacturing a metal reflecting layer on the medium reflecting layer;
s23, repeating the above steps S21-S22 to form at least two sets of dielectric reflection layers and metal reflection layers which are alternately stacked to form the acoustic wave reflection layer.
Step S2 is a process of manufacturing the acoustic wave reflective layer 201, and the acoustic wave reflective layer 201 includes a combination of at least two sets of dielectric reflective layers 202 and metal reflective layers 203 that are alternately laminated. In a preferred embodiment, the thickness of the dielectric reflective layer 202 and the metal reflective layer 203 is 1/4 the longitudinal wave wavelength of the resonator in at least the range of the projected area perpendicular to the bottom electrode layer 302. Under this condition, the acoustic wave reflecting layer 201 may constitute a reflection grating, concentrate energy in the resonator, and achieve an effect of reflecting the acoustic wave.
In a specific embodiment, the dielectric reflective layer 202 is grown by a CVD process, as shown in fig. 3 d. Wherein, the material of the dielectric reflective layer 202 is SiO2Or is SiO2And other dielectric materials such as SiOF, etc. As shown in fig. 3e, the upper surface of the dielectric reflective layer 202 is polished by a CMP (chemical mechanical polishing) process, wherein the thickness of the dielectric reflective layer 202 remaining on the bottom electrode layer 302 is 1/4 times the longitudinal wave wavelength λ of the resonator. The thickness can also be adjusted according to different effects brought by the materials of the dielectric reflective layer 202 and the metal reflective layer 203.
In a specific embodiment, as shown in fig. 3f, a metal reflective layer 203 is fabricated on the dielectric reflective layer 202 by photolithography, sputtering and etching processes, wherein the thickness of the metal reflective layer 203 is 1/4 times of the longitudinal wave wavelength λ of the resonator, and the material of the metal reflective layer 203 may include tungsten, aluminum, molybdenum, platinum, ruthenium, etc.
In a specific embodiment, as shown in fig. 3g-3j, the acoustic wave reflective layer 201 composed of multiple sets of the dielectric reflective layer 202 and the metal reflective layer 203 is fabricated by repeating steps S21-S22. In the acoustic wave reflective layer 201. The sound wave reflecting layer 201 can effectively reflect sound waves, so that the resonance function layer achieves a resonance effect. In a specific embodiment, as shown in fig. 3k, step S3 specifically includes bonding the second substrate 112 on the acoustic wave reflecting layer 201 by a wafer bonding process. Wherein the material of the second substrate 112 includes Si, the second substrate 112 may be processed by evaporation of gold, and the purpose of wafer evaporation of gold is to ensure the bonding force after bonding. The wafer bonding process is to combine two mirror polished homogeneous or heterogeneous wafers tightly by chemical and physical action, and after the wafers are combined, the atoms of the interface are acted by external force to react to form covalent bonds to combine into a whole, and the combined interface reaches a specific bonding strength. The wafer bonding process is widely applied to the preparation process of semiconductor devices, and the wafer bonding process technology is mature. The bonded second substrate 112 will remain on the device as a base or support.
In a specific embodiment, as shown in fig. 3l, step S4 specifically includes removing the first substrate 111 by grinding, chemical mechanical polishing and trimming, removing the seed layer 501, and thinning the piezoelectric layer 303 by trimming, in a preferred embodiment, the material of the piezoelectric layer is AlN, and the AlN in the initial amorphous state in the piezoelectric layer 303 is removed during trimming of the piezoelectric layer. Preferably, the piezoelectric layer 303 can be thinned by 30-50 nm. The existence of the seed layer 501 is beneficial to the piezoelectric layer 303 to form the piezoelectric layer 303, the bottom electrode layer 302 and the top electrode layer 304 with good C-axis preferred orientation, the selection limitation of electrode materials is reduced, and 30-50nm amorphous AlN on the piezoelectric layer 303 is removed, so that the piezoelectric layer is more kept in the crystal plane orientation of (0,0,0,2), the device has better piezoelectricity, and the working performance of the resonator is improved. When the AlN piezoelectric layer 303 is grown on the bottom electrode layer 302 (for example, the AlN piezoelectric layer is 1000nm thick), the most initial 30-50nm is amorphous AlN, and the performance of the piezoelectric layer is influenced by the amorphous AlN, so that the most initial 30-50nm amorphous AlN can be removed by a trimming process, and finally, the excellent C-axis oriented AlN piezoelectric layer is obtained, and the solid-state assembled resonator has better piezoelectric performance.
In a specific embodiment, as shown in fig. 3m, the device structure obtained in step S5 is obtained by fabricating a top electrode layer 304 on the back surface of the piezoelectric layer 303 through photolithography, sputtering and etching processes, wherein the material of the top electrode layer 304 is Mo, and may also be a single or composite electrode of tungsten, aluminum, molybdenum, platinum, ruthenium, and the like. In a preferred embodiment, the bottom electrode layer 302 and the top electrode layer 304 are a composite of one or more of Mo, W, Al, Pt, or Ru. On the premise that the piezoelectric layer 303 has a flat surface, the bottom electrode layer 302 and the top electrode layer 304 may be made of other electrode materials except Mo, so that the selection limitation on the electrode materials is relatively small, the selection range of the electrode materials can be expanded, and the cost can be reduced. The bottom electrode layer 302, the piezoelectric layer 303, and the top electrode layer 304 constitute an effective resonance region in a direction perpendicular to the second substrate 112. The resonant functional layer 301 converts electrical energy into mechanical energy in the form of acoustic waves by means of the piezoelectric layer 303. The sound wave reflecting layer 201 has the characteristic that high sound impedance and low sound impedance are alternated, can effectively reflect sound waves, avoids the loss of sound wave energy, and enables the sound waves to achieve the resonance effect in an effective resonance area.
The application provides a solid assembled resonator and a manufacturing process, the solid assembled resonator comprises a substrate, a sound wave reflecting layer formed on the substrate and a resonance function layer formed on the sound wave reflecting layer, the resonance function layer comprises a bottom electrode layer, a piezoelectric layer and a top electrode layer which are sequentially stacked, a dielectric layer is formed around the bottom electrode layer, the bottom electrode layer and the dielectric layer form a flat surface on the sound wave reflecting layer, and the piezoelectric layer is arranged on the flat surface. In the manufacturing process, an absolutely flat seed layer can be grown on an absolutely flat Si substrate, so that a piezoelectric layer AlN film with a preferred orientation of a C axis can be better obtained, and the working performance of a resonator is improved; growing a piezoelectric layer on the absolutely flat seed layer to ensure that the piezoelectric layer has a very flat surface, thereby ensuring the stress consistency and the electromechanical coupling coefficient consistency; removing the piezoelectric layer AlN in the initial amorphous state can enable the piezoelectric layer AlN film to obtain excellent C-axis orientation, and therefore better device performance and device product yield can be obtained. In addition, the AlN piezoelectric layer with the preferred C-axis orientation can be obtained by removing the most initial amorphous state AlN through a trimming (plasma grinding) technology, and the AlN piezoelectric layer has better piezoelectric performance.
While the present invention has been described with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.
In the description of the present application, it is to be understood that the terms "upper", "lower", "inner", "outer", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are only for convenience in describing the present application and simplifying the description, and do not indicate or imply that the referred devices or elements must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present application. The word 'comprising' does not exclude the presence of elements or steps not listed in a claim. The word 'a' or 'an' preceding an element does not exclude the presence of a plurality of such elements. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims shall not be construed as limiting the scope.
Claims (19)
1. A solid assembled resonator comprising a substrate, an acoustic wave reflecting layer formed on the substrate, and a resonance function layer formed on the acoustic wave reflecting layer, the resonance function layer comprising a bottom electrode layer, a piezoelectric layer and a top electrode layer which are laminated in this order, characterized in that a dielectric layer is formed around the bottom electrode layer, and the bottom electrode layer and the dielectric layer form a flat surface on the acoustic wave reflecting layer, the piezoelectric layer being provided on the flat surface.
2. The solid state assembled resonator of claim 1, wherein the acoustic wave reflecting layer comprises a combination of at least two sets of dielectric reflecting layers and metal reflecting layers alternately stacked.
3. The solid state assembled resonator of claim 2, wherein the substrate and the bottom electrode layer are provided with the dielectric reflective layer on a side thereof adjacent to the acoustic wave reflective layer.
4. The solid state assembled resonator of any of claims 1-3, wherein the dielectric layer is disposed around the acoustic wave reflective layer.
5. The solid state assembled resonator of any of claims 1-3, wherein the material of the bottom electrode layer and the top electrode layer is a composite of one or more of Mo, W, Al, Pt, or Ru.
6. A process for fabricating a solid state assembled resonator, comprising the steps of:
s1, manufacturing a piezoelectric layer on the first substrate, and then manufacturing a bottom electrode layer on the piezoelectric layer;
s2, manufacturing a sound wave reflecting layer on the bottom electrode layer;
s3, bonding a second substrate on the acoustic wave reflecting layer;
s4, removing the first substrate to expose the back surface of the piezoelectric layer opposite to the bottom electrode layer; and
s5, manufacturing a top electrode layer on the back surface of the piezoelectric layer.
7. The manufacturing process of claim 6, wherein the step S2 specifically comprises the following sub-steps:
s21, growing a medium reflecting layer on the layer formed in the previous step, and grinding the medium reflecting layer to be flat;
s22, manufacturing a metal reflecting layer on the medium reflecting layer;
s23, repeating the above steps S21-S22 to form at least two sets of dielectric reflection layers and metal reflection layers which are alternately stacked to form the acoustic wave reflection layer.
8. The process of claim 6, wherein the step S3 specifically includes bonding the second substrate on the acoustic wave reflecting layer by a wafer bonding process.
9. The process of claim 6, wherein the step S1 further includes forming a seed layer between the first substrate and the piezoelectric layer.
10. The manufacturing process of claim 6, wherein the step S4 specifically includes removing the first substrate by grinding, chemical mechanical polishing and trimming processes, removing the seed layer, and thinning the piezoelectric layer.
11. The process of claim 10, wherein the material of the piezoelectric layer is AlN, and the initial amorphous state of AlN in the piezoelectric layer is removed during trimming of the piezoelectric layer.
12. The process of claim 9, wherein the seed layer comprises two or more layers of material formed by sputtering or deposition.
13. The fabrication process of claim 12, wherein the seed layer comprises an AlN layer proximate the first substrate and a Mo layer on the AlN layer.
14. The process of claim 12, wherein the seed layer comprises a Cr or Ir, Pt layer adjacent to the first substrate and a Mo layer on the Cr or Ir, Pt layer.
15. The fabrication process of claim 12, wherein the seed layer comprises a SiC layer proximate to the first substrate and an AlN layer on the SiC layer.
16. The production process according to claim 13 or 15, wherein the AlN layer has a C-axis oriented (0,0,0,2) crystal plane.
17. The production process according to claim 13 or 14, wherein the Mo layer has a body-centered cubic structure with (1,1,0) crystal planes.
18. The manufacturing process according to any one of claims 6 to 15, wherein the bottom electrode layer and the top electrode layer are compounded by one or more materials of Mo, W, Al, Pt or Ru.
19. The manufacturing process according to any one of claims 6 to 15, wherein a material of the first substrate and the second substrate is Si.
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