CN111294011A - Solid assembled resonator and preparation method thereof - Google Patents
Solid assembled resonator and preparation method thereof Download PDFInfo
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- CN111294011A CN111294011A CN202010191951.7A CN202010191951A CN111294011A CN 111294011 A CN111294011 A CN 111294011A CN 202010191951 A CN202010191951 A CN 202010191951A CN 111294011 A CN111294011 A CN 111294011A
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- 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
- H03H9/178—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator of a laminated structure of multiple piezoelectric layers with inner electrodes
-
- 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
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
- Y02D30/00—Reducing energy consumption in communication networks
- Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks
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Abstract
The present disclosure provides a solid-state assembly resonator and a method for manufacturing the same, the solid-state assembly resonator including: a piezoelectric structure, the piezoelectric structure comprising: go up electrode layer, bottom electrode layer and piezoelectric layer, the bottom electrode layer sets up corresponding to piezoelectric structure's below, and the bottom electrode layer includes: a convex part which is arranged corresponding to the lower surface of the lower electrode layer and protrudes downwards; the piezoelectric layer is arranged on the upper surface of the lower electrode layer; the upper electrode layer is disposed on an upper surface of the piezoelectric layer. The convex part is correspondingly formed on the lower surface of the lower electrode layer, so that the upper surface of the lower electrode layer in contact with the piezoelectric layer can form a flattened surface, and therefore, the piezoelectric layer grows on the flattened surface, and a high c-axis oriented crystal structure with better growth texture is easier to obtain, so that the piezoelectric performance of the piezoelectric layer is improved, and the performance (such as the improvement of a Q value) of the resonator is improved.
Description
Technical Field
The disclosure relates to the technical field of resonators, and particularly relates to a solid-state assembly type resonator and a preparation method thereof.
Background
A solid-State Mounted Resonator (SMR) is a device that includes a bragg reflector structure and a piezoelectric structure. In the application of the traditional solid assembled resonator, a piezoelectric structure is formed on a Bragg reflector structure, the Bragg reflector is formed by alternately forming high and low acoustic impedance materials, the piezoelectric structure is formed by clamping piezoelectric materials by upper and lower electrode layers, and the piezoelectric materials are grown on the upper surface of the lower electrode to form a piezoelectric layer. Therefore, in the prior art, the lower electrode pattern is usually etched and then the piezoelectric layer is deposited, so that the piezoelectric layer can grow on the surface of the uneven lower electrode, the lattice structure and the lattice orientation of the piezoelectric layer can be deteriorated in uneven places, the piezoelectric effect of the piezoelectric layer is affected, and the performance of the device is affected.
Disclosure of Invention
Technical problem to be solved
In order to solve the problem that in the prior art, a lower electrode pattern is etched first and then a piezoelectric layer is deposited, so that the piezoelectric layer can grow on the surface of an uneven lower electrode and the performance of a device is influenced, the disclosure provides a solid assembled resonator and a preparation method thereof.
(II) technical scheme
One aspect of the present disclosure provides a solid-state fabricated resonator, including: a piezoelectric structure, the piezoelectric structure comprising: lower electrode layer and piezoelectric layer, last electrode layer, the lower electrode layer sets up corresponding to piezoelectric structure's below, and the lower electrode layer includes: a convex part which is arranged corresponding to the lower surface of the lower electrode layer and protrudes downwards; the piezoelectric layer is arranged on the upper surface of the lower electrode layer; the upper electrode layer is disposed on an upper surface of the piezoelectric layer.
According to an embodiment of the present disclosure, the convex portion includes: the first convex part corresponds to the edge of the lower surface of the lower electrode layer and is arranged in a downward protruding mode; the second convex part is arranged corresponding to the middle part of the lower surface of the lower electrode layer and protrudes downwards.
According to an embodiment of the present disclosure, the first protrusion is an annular closed structure; the distance between the inner edge of the first convex part and the outer edge of the second convex part is a first distance a; the protruding distance of the first convex part relative to the lower surface of the lower electrode layer is a second distance b; the protruding distance of the second convex part relative to the lower surface of the lower electrode layer is a third distance c; wherein b > c.
According to an embodiment of the present disclosure, the upper surface of the lower electrode layer is a planarized surface; the upper electrode layer and the lower electrode layer are made of one or a combination of more of molybdenum Mo, titanium Ti, tungsten W, gold Au, aluminum Al and platinum Pt; the piezoelectric layer is made of AlN nitride, ZnO or PZT.
According to an embodiment of the present disclosure, a solid-state mount resonator includes: substrate layer and stromatolite, the substrate layer sets up under piezoelectric structure, and the stromatolite sets up between piezoelectric structure and substrate layer, and the stromatolite includes from bottom to top in proper order: the piezoelectric transducer comprises a first low-sound impedance layer, a first high-sound impedance layer, a second low-sound impedance layer, a second high-sound impedance layer and a third low-sound impedance layer, wherein the third low-sound impedance layer is arranged below a piezoelectric layer of the piezoelectric structure.
According to an embodiment of the present disclosure, the third low acoustic impedance layer includes: lower electrode groove, lower electrode groove relatively the upper surface undercut setting of third low acoustic impedance layer, lower electrode groove includes: the first groove corresponds to the edge of the bottom surface of the lower electrode groove and is arranged in a downward concave mode; and the second groove is concavely arranged downwards corresponding to the middle part of the bottom surface of the lower electrode groove.
According to an embodiment of the present disclosure, the first groove is a closed annular groove; the distance between the inner edge of the first groove and the outer edge of the second groove is a first distance a; the first groove is recessed by a second distance b relative to the bottom surface of the lower electrode groove; the concave distance of the second groove relative to the bottom surface of the lower electrode groove is a third distance c; wherein b > c.
According to the embodiment of the disclosure, the material of the substrate layer is one or a combination of more materials of silicon, glass, sapphire and ceramic; the first low-sound-impedance layer, the second low-sound-impedance layer and the third low-sound-impedance layer are made of siloxane or silicon dioxide; and the first high acoustic impedance layer and the second high acoustic impedance layer are made of tungsten or molybdenum.
Another aspect of the present disclosure provides a method of manufacturing the above solid state fabricated resonator, comprising: forming a laminated structure on which a lower electrode layer of a piezoelectric structure is formed; wherein the lower electrode layer includes: and a convex part which is arranged corresponding to the lower surface of the lower electrode layer and protrudes downwards.
According to an embodiment of the present disclosure, forming a stacked structure includes: a first low-sound impedance layer, a first high-sound impedance layer, a second low-sound impedance layer, a second high-sound impedance layer and a third low-sound impedance layer are sequentially formed on the substrate layer from bottom to top.
According to an embodiment of the present disclosure, forming a piezoelectric structure on a stacked structure includes: forming a lower electrode groove depressed downward on an upper surface of the third low acoustic impedance layer; wherein, a first groove which is sunken downwards is formed corresponding to the edge of the bottom surface of the lower electrode groove; a second groove depressed downward is formed corresponding to a middle portion of the bottom surface of the lower electrode tank.
According to an embodiment of the present disclosure, forming the lower electrode layer of the piezoelectric structure on the stacked structure includes: forming a lower electrode layer in the lower electrode groove based on the first groove and the second groove; wherein, form the first convex part of the convex part in the first recess correspondingly; a second protrusion corresponding to the protrusion formed in the second groove.
According to an embodiment of the present disclosure, forming the lower electrode layer of the piezoelectric structure on the stacked structure further includes: and flattening the lower electrode layer and the third low-acoustic-impedance layer, wherein the upper surface of the lower electrode layer is a flattened surface which is flush with the upper surface of the third low-acoustic-impedance layer.
According to an embodiment of the present disclosure, the method of preparing further comprises: forming a piezoelectric layer of a piezoelectric structure corresponding to the planarized surface of the lower electrode layer and the upper surface of the third low acoustic impedance layer; an upper electrode layer of the piezoelectric structure is formed on an upper surface of the piezoelectric layer.
(III) advantageous effects
The present disclosure provides a solid-state assembly type resonator, including: a piezoelectric structure, the piezoelectric structure comprising: go up electrode layer, bottom electrode layer and piezoelectric layer, the bottom electrode layer sets up corresponding to piezoelectric structure's below, and the bottom electrode layer includes: a convex part which is arranged corresponding to the lower surface of the lower electrode layer and protrudes downwards; the piezoelectric layer is arranged on the upper surface of the lower electrode layer; the upper electrode layer is disposed on an upper surface of the piezoelectric layer. The convex part is correspondingly formed on the lower surface of the lower electrode layer, so that the upper surface of the lower electrode layer in contact with the piezoelectric layer can form a flat surface, and therefore, the piezoelectric layer grows on the flat surface, and a high c-axis oriented crystal structure with better growth texture is easier to obtain, so that the piezoelectric performance of the piezoelectric layer is improved, and the performance (such as the Q value) of the resonator is improved.
Drawings
FIG. 1 schematically illustrates a cross-sectional view of a solid state fabricated resonator in an embodiment of the disclosure;
FIG. 2A schematically illustrates a cross-sectional view and a plan view of the structure of the lower electrode layer in an embodiment of the present disclosure;
FIG. 2B is a schematic sectional view showing the structure of the lower electrode tank in the embodiment of the present disclosure;
FIG. 3 schematically illustrates a flow chart of a method for fabricating a solid state fabricated resonator in an embodiment of the disclosure;
fig. 4 is a sectional view schematically showing a structure of a solid-state fabricated resonator in a first stage of a manufacturing method according to an embodiment of the present disclosure;
fig. 5A schematically illustrates a cross-sectional view of a solid-state fabricated resonator in an embodiment of the disclosure at another stage of fabrication;
FIG. 5B is a schematic cross-sectional view illustrating a further stage of fabrication of a solid-state fabricated resonator according to an embodiment of the present disclosure;
FIG. 5C is a schematic cross-sectional view illustrating a manufacturing process of a solid-state fabricated resonator according to an embodiment of the present disclosure in yet another stage of the structure;
fig. 6 schematically illustrates a cross-sectional view of a structure of a solid-state fabricated resonator in accordance with an embodiment of the present disclosure in a further stage of fabrication;
fig. 7 schematically illustrates a cross-sectional view of a structure of a solid-state fabricated resonator in accordance with an embodiment of the present disclosure in a further stage of fabrication;
fig. 8 schematically illustrates a cross-sectional view of a structure of a solid-state fabricated resonator in accordance with an embodiment of the present disclosure in a further stage of fabrication;
fig. 9 schematically shows a cross-sectional view of a structure of a solid-state fabricated resonator in a further manufacturing stage in an embodiment of the present disclosure.
Detailed Description
For the purpose of promoting a better understanding of the objects, aspects and advantages of the disclosure, reference should be made to the following detailed description taken in conjunction with the accompanying drawings.
In order to solve the problem that in the prior art, a lower electrode pattern is etched first and then a piezoelectric layer is deposited, so that the piezoelectric layer can grow on the surface of an uneven lower electrode and the performance of a device is influenced, the disclosure provides a solid assembled resonator and a preparation method thereof.
One aspect of the present disclosure provides a solid-state fabricated resonator, as shown in fig. 1-2B, comprising: and the piezoelectric structure is used for playing a piezoelectric effect. The piezoelectric structure includes: an upper electrode layer 106, a lower electrode layer 104 and a piezoelectric layer 105, wherein the lower electrode layer 104 is disposed below the piezoelectric structure, and specifically, the lower electrode layer 104 may be a constituent structure of a lower portion of the piezoelectric structure, and is disposed below the piezoelectric layer 105 to serve as a lower electrode of the piezoelectric structure. According to an embodiment of the present disclosure, the lower electrode layer 104 includes: and a convex portion provided to protrude downward corresponding to the lower surface of the lower electrode layer 104. The lower electrode layer 104 includes a protrusion and an electrode body 107 (as shown in fig. 2A), the lower surface of the lower electrode layer 104 may be the lower surface of the electrode body 107, and the protrusion protrudes downward relative to the lower surface, so that a lower electrode pattern required by the piezoelectric structure can be formed on the lower surface of the lower electrode layer 104 for generating the piezoelectric effect of the piezoelectric structure.
According to an embodiment of the present disclosure, the piezoelectric layer 105 is disposed on the upper surface of the lower electrode layer 104 for generating a piezoelectric effect; the piezoelectric layer 105 is disposed on the upper surface of the lower electrode layer 104, the lower surface of the piezoelectric layer 105 is in contact with the upper surface of the lower electrode layer 104 (i.e. the upper surface of the electrode body 107, as shown in fig. 2A), and the piezoelectric layer 105 is configured to exert a piezoelectric effect under the cooperation of the upper electrode layer 106 and the lower electrode layer 104. An upper electrode layer 106 is provided on the upper surface of the piezoelectric layer 105 for serving as an extraction electrode of the device.
In the solid-state fabricated resonator of the present disclosure, the magnitude of the quality factor Q is determined by the material loss of the piezoelectric layer, and the lower the energy loss, the higher the Q value. By forming the convex structure on the lower surface of the lower electrode layer 104, the upper surface of the lower electrode layer 104 or the upper surface of the upper electrode 106 can be simultaneously made without forming the above convex structure, so that the upper surface of the lower electrode layer 104 (i.e. the upper surface of the electrode body 107, as shown in fig. 2A) can be formed into a flat surface, the piezoelectric layer 105 of the piezoelectric structure can be grown on the flat upper surface of the lower electrode layer 104, and a crystal structure with a growth crystal phase more tending to the c-axis orientation can be obtained between the upper electrode layer 106 and the lower electrode layer 104, so that the piezoelectric performance of the piezoelectric layer 105 is improved, and the performance (improvement of the Q value) of the solid-state fabricated resonator of the present disclosure is improved.
Based on the structure of the solid-state assembly resonator described above, the present disclosure produces an unexpected technical effect: the pattern-forming protrusion structure of the lower electrode layer 104 of the present disclosure may be formed on the lower surface of the lower electrode via a metal deposition method, which is simpler than a conventional method of forming the protrusion structure on the upper surface of the lower electrode layer 104 or the upper surface of the upper electrode 106 directly by a metal etching method. Specifically, since the conventional bump structure is formed on the upper surface of the upper electrode layer 106 or the lower electrode layer 104, at least two steps of etching are required to etch the surface, and due to the metal characteristics of the electrode layer (for example, the metal etching selectivity is poor), during the etching process of the bump structure pattern in the process, the metal over-etching phenomenon of the metal electrode layer is very easy to occur, and the control of the etching depth is also difficult. Therefore, by adopting the structure of the solid assembly type resonator, the problem of metal over-etching can be prevented, the preparation yield of the device can be effectively improved, multiple times of etching can be avoided, the formation steps of the convex part of the electrode layer can be reduced, and the thickness change of the electrode layer can be effectively controlled. According to an embodiment of the present disclosure, the electrode layer may include the upper electrode layer 106 and/or the lower electrode layer 104.
Finally, another unexpected technical effect is further generated by the structure of the solid-state assembly type resonator of the present disclosure: according to the embodiment of the disclosure, an electrode groove can be formed in the stacked structure below the piezoelectric structure, and the lower electrode layer is embedded in the electrode groove of the stacked structure, so that the thickness of the device structure can be reduced on the basis of the above effects, and the size of the device structure can be further reduced.
According to an embodiment of the present disclosure, as shown in fig. 1 and 2A, the solid-state mount resonator of the present disclosure further includes an electrode body 107 that can be used to provide a setting position for the above-described convex portions (e.g., the first convex portion 103 and the second convex portion 102 described below) in addition to functioning as respective piezoelectrics in the piezoelectric structure.
According to an embodiment of the present disclosure, as shown in fig. 1 and 2A, the convex portion includes: a first protrusion 103 and a second protrusion 102, wherein the first protrusion 103 protrudes downward corresponding to the edge of the lower surface of the lower electrode layer 104; specifically, the first protrusion 103 protrudes downward from the lower surface of the electrode main body 107 of the lower electrode layer 104, and is configured to generate impedance mismatch at the periphery of the resonator, so that the bulk acoustic wave energy generated by the device is limited inside the protrusion structure of the lower electrode layer 104 of the piezoelectric structure, and the bulk acoustic wave energy is less prone to leakage, so that the energy loss is reduced, and the Q value of the device is improved.
The second protrusion 102 protrudes downward from the middle of the lower surface of the lower electrode layer 104, and specifically, the second protrusion 102 protrudes downward from the lower surface of the electrode main body 107 of the lower electrode layer 104, and the protruding height of the second protrusion is smaller than that of the first protrusion, so as to form a pit between the first protrusion and the second protrusion, which can effectively reduce the lateral mode parasitic resonance below the cut-off frequency and also help to improve the Q value of the resonator. As shown in fig. 1 and 2A.
Based on the above-described structure of the first convex portion 103 and the second convex portion 102, the present disclosure produces another unexpected technical effect: the energy loss of solid state fabricated resonators is mainly due to the leakage of bulk acoustic wave energy from the lateral modes of the device structure such that it occurs at the structure edges. Since the lower electrode layer 104 is formed or the protruding portion structure is formed on the upper surface of the lower electrode, the surface needs to be etched, so that the lower electrode layer and the edge of the protruding portion of the pattern are repeatedly exposed to various dry and wet etching processes, which causes the deterioration of the edge quality and the contour shape of the protruding portion of the lower electrode layer and the pattern, and the leakage of bulk acoustic wave energy is easily caused. Compared with the traditional mode of directly forming the upper surface of the lower electrode layer 104 by etching, the first convex part 103 and the second convex part 102 of the lower electrode layer 104 can be formed in one step by a metal deposition method, so that by adopting the structure of the solid assembly type resonator, the edges of the lower electrode layer 104, the first convex part 103 and the second convex part 102 can be effectively prevented from deteriorating in edge quality and outline shape, the leakage of bulk acoustic wave energy is further prevented, a more obvious acoustic impedance mismatching effect is achieved, the energy loss caused by the transverse mode of the device structure is effectively prevented, the device has a better piezoelectric effect, the Rp value is further improved, and meanwhile, the negative influence of the transverse mode parasitic resonance lower than the cut-off frequency on the device performance can be improved. In addition, the metal electrode can be prevented from being over-etched, the process steps can be simplified, and the like, and the details are not repeated herein.
According to the embodiment of the present disclosure, as shown in fig. 2A, the first protrusion 103 is an annular closed structure; wherein, the distance between the inner edge of the first convex part 103 and the outer edge of the second convex part 102 is a first distance a; when the first protrusion 103 is a ring-shaped closed protrusion structure, the inner edge of the first protrusion 103 is relative to the second protrusion 102, where the first protrusion 103 surrounds the middle of the lower surface of the electrode body 107, that is, the edge of the first protrusion 103 facing the second protrusion 102 is the inner edge, and the edge facing away from the pair of second protrusions 102 is the outer edge. The protruding distance of the first convex part 103 relative to the lower surface of the lower electrode layer 104 is a second distance b, which is used for preventing the lateral leakage of the bulk acoustic wave energy of the device structure and reducing the energy loss; the protruding distance of the second protrusion 102 relative to the lower surface of the lower electrode layer 104 is a third distance c, where b > c, and is used to form a pit between the first protrusion and the second protrusion, where the pit can effectively reduce the lateral mode parasitic resonance below the cut-off frequency, so as to further ensure that the bulk acoustic wave energy can be confined within the region surrounded by the first protrusion 103 as much as possible. Here, the lower surface of the lower electrode layer 104, i.e., the lower surface of the electrode main body 107, and the piezoelectric effect region of the piezoelectric structure correspond to the region 401 in fig. 1, and are located at the lower surface of the lower electrode layer 104 and the portion inside the inner edge of the first convex portion 103.
According to an embodiment of the present disclosure, the upper surface of the lower electrode layer 104 is a planarized surface. Specifically, a planarization process may be performed on the upper surface of the lower electrode layer 104, for example, a Chemical Mechanical Polishing (CMP) process is used to planarize the upper surface of the lower electrode layer 104 before the piezoelectric layer 105 is formed, that is, a planarized plane of the lower electrode layer may be formed, so that the piezoelectric layer 105 of the piezoelectric structure may grow on the planarized upper surface of the lower electrode layer 104, that is, the lower surface of the piezoelectric layer 105, which is in contact with the upper surface of the lower electrode layer 104, is also a planarized surface, which is more beneficial to obtaining a crystal structure with a good growth texture and a high c-axis orientation between the piezoelectric layer 105 and the lower electrode layer 104, thereby improving the piezoelectric performance of the piezoelectric layer 105 and improving the performance (Q value improvement) of the solid-state assembly resonator of the present disclosure.
According to the embodiment of the present disclosure, the material of the upper electrode layer 106 and the lower electrode layer 104 is one or a combination of molybdenum Mo, titanium Ti, tungsten W, gold Au, aluminum Al, platinum Pt, and the like; wherein, the materials of the first convex part 103 and the second convex part 102 of the convex part can be consistent with the material of the lower electrode layer 104, so as to complete the deposition preparation of the lower electrode layer at one time. When the material selection of the convex portion is not consistent with the material selection of the electrode main body 107 of the lower electrode layer 104, the preparation process of the lower electrode layer 104 needs to be adjusted accordingly. For example, molybdenum Mo may be selected as a material for preparing the lower electrode layer 104 (including the first protrusion 103 and the second protrusion 102) or the upper electrode layer 106. By the above materials of the upper electrode layer 106 and the lower electrode layer 104, a better bonding capability can be formed with the material of the piezoelectric layer 105 described below, so that a high c-axis oriented crystal structure with better growth texture is obtained between the piezoelectric layer 105 and the lower electrode layer 104 or the upper electrode layer 106, thereby further improving the piezoelectric performance of the piezoelectric layer 105 and improving the performance (e.g., the Q value) of the solid assembled resonator of the present disclosure.
The material of the piezoelectric layer 105 may be aluminum nitride AlN, zinc oxide ZnO, or lead zirconate titanate PZT, and the material of the piezoelectric layer 105 may also be one or a combination of more than one of aluminum nitride AlN, zinc oxide ZnO, lead zirconate titanate PZT, and the combination of the materials of the above-mentioned multiple piezoelectric layers 105 may be for the piezoelectric layer 105 having a multilayer structure, for example, AlN as a first layer, ZnO as a second layer, and PZT as a third layer collectively constitute the piezoelectric layer 105 having a three-layer structure. Through the material of the piezoelectric layer 105, a better bonding capability can be formed with the material of the upper electrode layer 106 and the lower electrode layer 104, so that a high c-axis oriented crystal structure with better growth texture is obtained between the piezoelectric layer 105 and the lower electrode layer 104 or the upper electrode layer 106, thereby further improving the piezoelectric performance of the piezoelectric layer 105 and improving the performance (for example, the Q value) of the solid assembled resonator of the present disclosure.
According to an embodiment of the present disclosure, as shown in fig. 1, a solid-state mount resonator includes: the substrate layer 101 and the laminated structure 200, the substrate layer 101 is disposed under the piezoelectric structure, and is used for providing a forming foundation for the piezoelectric structure, and functioning as a substrate. The laminated structure 200 is arranged between the piezoelectric structure and the substrate layer 101, namely the laminated structure 200 is arranged on the substrate layer 101, and the laminated structure 200 sequentially comprises from bottom to top: the first low acoustic impedance layer 201, the first high acoustic impedance layer 202, the second low acoustic impedance layer 203, the second high acoustic impedance layer 204, and the third low acoustic impedance layer 205, so as to form a bragg reflection layer structure (i.e. a stacked structure 200) as shown in fig. 1, where the bragg reflection layer structure is a sandwich-type sandwich structure formed by alternately forming a low acoustic impedance material layer and a high acoustic impedance material layer, so as to implement a bragg reflection effect on a bulk acoustic wave generated by the piezoelectric structure. The third low acoustic impedance layer 205 is disposed below the piezoelectric layer 105 of the piezoelectric structure, and is configured to directly perform a bragg reflection function on a bulk acoustic wave, and meanwhile, a forming position may be provided for forming the lower electrode layer 104, and a supporting function or a substrate function may be performed for forming the piezoelectric structure.
According to an embodiment of the present disclosure, the material of the substrate layer 101 is one or a combination of materials of silicon, glass, sapphire, ceramic, etc., for example, glass may be used as the substrate layer 101 to facilitate better bonding capability with the first low acoustic impedance layer 201 formed on the upper surface of the substrate layer 101. The materials of the first low acoustic impedance layer 201, the second low acoustic impedance layer 203 and the third low acoustic impedance layer 205 are siloxane or silicon dioxide, etc., so as to form better low acoustic impedance performance, which is beneficial to forming a bragg reflector structure with better performance; and the first high acoustic impedance layer 202 and the second high acoustic impedance layer 204 are made of tungsten W or molybdenum Mo, so as to form better high acoustic impedance performance, which facilitates the formation of better bragg reflector structure.
According to an embodiment of the present disclosure, as shown in fig. 1 and 2B, the third low acoustic impedance layer 205 includes: lower electrode groove 301, lower electrode groove 301 sets up with the upper surface undercut of third low acoustic impedance layer 205 relatively, and lower electrode groove 301 includes: a first groove 303, a second groove 302 and a main body groove 304, wherein the first groove 303 is recessed downwards corresponding to the edge of the bottom surface of the lower electrode groove 301, has a shape and size matching the shape and size of the second protrusion 102, and is a closed annular groove for correspondingly accommodating the first protrusion 103. And a second groove 302 is concavely provided corresponding to the middle of the bottom surface of the lower electrode tank 301, and has a shape and size matching the shape and size of the first protrusion 103, for correspondingly receiving the first protrusion 103. Wherein, as shown by the annular closed dotted line in fig. 2B, the space corresponds to the structure of the body groove 304, and the bottom surface of the lower electrode groove 301 may be the bottom surface of the body groove 304, which corresponds to the top surface of the groove protrusion 305. The third low acoustic impedance layer 205 serves to function as bragg reflection and corresponds to the bottom surface of the lower electrode groove 301 of the region 401 shown in fig. 1 and 2B, and the bottom surface of the lower electrode groove 301 corresponding to the region 401 may include the bottom surface of the first groove 303 and the top surface of the groove protrusion 305. Thus, the region that actually functions as a bragg reflector in this disclosure corresponds to the stack 200 identified as 200 in fig. 1 and 4-9.
According to the embodiment of the present disclosure, as shown in fig. 1 and fig. 2B, the first groove 303 is used for matching and accommodating the first protrusion 103, and then the first groove 303 is a closed annular groove corresponding to the first protrusion 103 shown in fig. 2A, i.e. a closed annular groove; wherein, corresponding to the first protrusion 103 and the second protrusion 102 shown in fig. 2A, the distance between the inner edge of the first groove 303 and the outer edge of the second groove 302 is a first distance a; the first groove 303 is recessed by a second distance b relative to the bottom surface of the lower electrode groove 301; the second groove 302 is recessed a third distance c with respect to the bottom surface of the lower electrode tank 301; where b > c, so that a groove protrusion 305 between the inner edge of the first groove 303 and the outer edge of the second groove 302 may be formed in the lower electrode groove 301 of the third low acoustic impedance layer 205, the groove protrusion 305 being a closed-type annular protrusion having a width dimension of a. Wherein the bottom surface of the first groove 303 is in contact with the top surface of the first protrusion 103, and the side wall surface of the first groove 303 is in contact with the side surface of the first protrusion 103; accordingly, the bottom surface of the second groove 302 contacts the top surface of the second protrusion 102, and the side wall surface of the second groove 302 contacts the side surface of the second protrusion 102; in addition, the lower surface of the electrode main body 107 of the lower electrode layer 104 is in contact with the top surface of the groove protrusion 305.
According to the embodiment of the present disclosure, as shown in fig. 1 and 2B, the third low acoustic impedance layer 205 needs to maintain a certain thickness dimension to form the lower electrode groove 301 (including the first and second grooves 303 and 302 and the main body groove 304) so that the lower electrode layer 104 (including the corresponding first and second protrusions 103 and 102 and the electrode main body 107) can be accommodated therein in a matching manner. Thus, a certain excess thickness may be pre-deposited when depositing the uppermost structure of the stacked structure 200 (e.g., the third low acoustic impedance layer in the present disclosure). So that the film thickness of the structural layer can be used to assist in etching the first and second recesses 303 and 302 and the body groove 304. The region of the present disclosure that functions as bragg reflection actually corresponds to the stacked-layer structure 200 identified as 200 in fig. 1 and fig. 4 to 9, i.e., the actual effective functional layer (or region) of the third low acoustic impedance layer 205 is located between the upper surface of the second high acoustic impedance layer 204 and the lower surface of the lower electrode layer 103. Therefore, the third low acoustic impedance layer 205 is actually disposed by matching and embedding the lower electrode groove 301 and the lower electrode layer 104, so that the piezoelectric structure is embedded in the stacked structure 200, and the upper surface of the third low acoustic impedance layer 205 outside the lower electrode groove 301 is actually in direct contact with the piezoelectric layer 105, which plays a role of protecting and sealing the lower electrode layer 104, and at the same time, is also used for supporting and stabilizing the above piezoelectric structure, and also helps to prevent leakage of bulk acoustic wave energy. Therefore, the structure of the solid-state fabricated resonator of the present disclosure can directly omit the thickness of the lower electrode layer 104 in the conventional structure to reduce the device size; in addition, another unexpected effect occurs: because the upper surface of the lower electrode layer 104 is a planarized surface, the contact between the lower electrode layer and the piezoelectric layer 105 can be a crystal contact with high c-axis orientation with good growth texture, so that the piezoelectric layer 105 and the piezoelectric layer are combined more stably, and therefore, under the limitation of the lower electrode groove 301, the piezoelectric structure can be combined with the laminated structure more stably, the phenomenon of structure separation is not easy to occur in the production and preparation process, and the improvement of the overall performance of the device is facilitated.
According to the embodiment of the present disclosure, the reserved thickness of the third low acoustic impedance layer 205 is the sum of the thickness of the protruding portion of the lower electrode layer 104 (e.g., the thickness of the second protruding portion 102), the thickness of the electrode body 107 of the lower electrode layer 104, and the required thickness for the planarization process after the deposition of the lower electrode layer 104 in the lower electrode groove 301, and in particular, the specific thickness may be calculated according to the frequency of the required solid-state mount resonator. Note that, since the effective region is the region 401 shown in fig. 1 and 2B for both the piezoelectric structure and the bragg reflection structure, the reserved thickness may not include the thickness of the lower electric first protrusion 103.
Another aspect of the present disclosure provides a method of manufacturing the above solid state fabricated resonator, as shown in fig. 3, including:
s310, forming the stacked structure 200,
s320, forming a lower electrode layer 104 of a piezoelectric structure on the laminated structure 200; wherein the lower electrode layer 104 includes: and a convex portion protruding downward corresponding to the lower surface of the lower electrode layer 104.
In the method for manufacturing the solid assembled resonator of the present disclosure, by forming the lower electrode pattern (corresponding to the convex portion) on the lower surface of the lower electrode layer 104, the upper surface of the lower electrode layer 104 may not need to form the above pattern at the same time, so that the upper surface of the lower electrode layer 104 (i.e., the upper surface of the electrode body 107, as shown in fig. 2A) may form a flat surface, so that the piezoelectric layer 105 of the piezoelectric structure can grow on the flat upper surface of the lower electrode layer 104, and it is more favorable for obtaining a high c-axis oriented crystal structure with a better growth texture between the piezoelectric layer 105 and the lower electrode layer 104, thereby improving the piezoelectric performance of the piezoelectric layer 105, and improving the performance (Q value) of the solid assembled resonator of the present disclosure.
Based on the preparation method, the method has the following unexpected technical effects: the disclosed convex part of the pattern forming structure of the lower electrode layer 104 can be formed by a metal deposition method, compared with the traditional mode of directly forming the convex part on the upper surface of the lower electrode layer 104 or the upper surface of the upper electrode 106 by a metal etching method, the convex part can prevent the problem of metal over-etching in the preparation process, effectively improve the preparation yield of a device, avoid multiple times of etching, reduce the forming steps of the convex part of the lower electrode layer, simplify the preparation process, and effectively control the thickness change of the lower electrode layer in the preparation process.
As for the structure of the resonator, reference may be made to a solid state mount type resonator as shown in fig. 1 to 2B, which will not be described herein.
According to an embodiment of the present disclosure, forming the stacked structure 200 includes: a first low acoustic impedance layer 201, a first high acoustic impedance layer 202, a second low acoustic impedance layer 203, a second high acoustic impedance layer 204, and a third low acoustic impedance layer 205 are formed on the substrate layer 101 in this order from the bottom. Specifically, the stacked-layer structure 200 is formed on the upper surface of the substrate layer 101 as a bragg reflection layer structure of the solid-state package resonator of the present disclosure. The bragg reflector structure is formed by alternately depositing low acoustic impedance layers and high acoustic impedance layers on the upper surface of the substrate 101, and specifically, a first low acoustic impedance layer 201 may be deposited first, a first high acoustic impedance layer 202 may be deposited on the upper surface of the first low acoustic impedance layer 201, a second low acoustic impedance layer 203 may be deposited on the first high acoustic impedance layer 202, a second high low acoustic impedance layer 204 may be deposited on the upper surface of the second low acoustic impedance layer 203, and a third low acoustic impedance layer 205 may be deposited on the upper surface of the second high acoustic impedance layer 204, as shown in fig. 4. In the preparation and deposition of the third low acoustic impedance layer 205, a thickness that needs to be removed when the planarization process is performed on the upper surfaces of the structures (e.g., the first groove 303, the second groove 302, the body groove 304) and the lower electrode layer 104 in the lower electrode groove 301 as shown in fig. 1 and 2B may be reserved.
According to an embodiment of the present disclosure, forming a piezoelectric structure on the stacked structure 200 includes: a lower electrode groove 301 depressed downward is formed on the upper surface of the third low acoustic impedance layer 205; wherein, a first groove 303 depressed downward is formed corresponding to an edge of the bottom surface of the lower electrode bath 301; a second recess 302 depressed downward is formed corresponding to a central portion of the bottom surface of the lower electrode groove 301, as shown in fig. 5A to 5C. Specifically, the lower electrode groove 301 may be etched downward on the upper surface of the third low acoustic impedance layer 205 by dry etching or wet etching. For example, the etching process may specifically adopt a dry etching process to form a desired depth of the body groove 304 and the first and second grooves 303 and 302 of the lower electrode groove 301 by better controlling the etching rate (as shown in fig. 2B). Wherein, the body trench 304 needs to be etched first, as shown in fig. 5A; then etching down the middle of the inner surface of the body groove 304 to form a second groove 302, as shown in fig. 5B; the etching process continues to form the first groove 303 at the edge of the inner surface of the body groove 304, and the groove protrusion 305 shown in fig. 2B can be formed at the same time, as shown in fig. 5C. Specifically, a first Photoresist (PR) layer is formed on the upper surface of the third low acoustic impedance layer 205, and the first photoresist layer corresponding to the position of the lower electrode layer 104 and the upper surface of the third low acoustic impedance layer 205 are formed by photolithography to form a body groove 304 recessed in the upper surface of the third low acoustic impedance layer 205, as shown in fig. 5A. A second photoresist layer is formed based on the inner surface of the body groove 304, and the second photoresist layer formed corresponding to the position of the second protrusion 102 and the middle portion of the bottom surface of the body groove 304 are subjected to photolithography to form a second groove 302 recessed into the bottom surface of the body groove 304, as shown in fig. 5B. The third photoresist layer is continuously formed on the basis of the inner surface where the second groove 302 is formed, and the third photoresist layer formed corresponding to the position of the first protrusion 103 and the edge of the bottom surface of the body groove 304 are subjected to photolithography to form a first groove 303 recessed in the bottom surface of the body groove 304, as shown in fig. 5C.
Since the depth of the first groove 303 is the largest relative to the upper surface of the third low acoustic impedance layer 205, the above may also be adjusted to form the second groove 302 first, then form the body groove 304, and finally form the first groove 303. The above-mentioned photolithography process can control the depth of etching the third low acoustic impedance layer 205 according to the etching rate and the etching time. In addition, compared with the conventional method of forming an electrical electrode pattern on the upper surface of the lower electrode layer, the method of etching the third low acoustic impedance layer 205 (the preparation material is siloxane or silicon dioxide, etc.) to form the lower electrode groove 301 can avoid etching a metal electrode with poor etching selectivity, so that the accurate control of the etching rate can be easily realized, and the situation that the metal electrode is over-etched can be further avoided in the etching process, so that the process for forming the lower electrode layer 104 is very simple.
According to an embodiment of the present disclosure, forming the lower electrode layer 104 corresponding to the lower side of the piezoelectric structure based on the stacked structure includes: forming the lower electrode layer 104 in the lower electrode groove 301 based on the first groove 303, the second groove 302, and the body groove 304; wherein, the first protrusion 103 corresponding to the protrusion formed in the first groove 303; a second projection 102 corresponding to the projection formed in the second groove 302; the electrode body 107 of the lower electrode layer 104 is formed in the body groove 304. After the lower electrode trench 301 is formed, an electrode material may be deposited therein to form the lower electrode layer 104, wherein it should be noted that the thickness of the deposited electrode material is significantly higher than the depth of the lower electrode trench 301, and may significantly protrude out of the opening of the main body trench 304, so as to ensure that the lower electrode trench 301 can be completely filled, and thus, the predetermined thickness of the lower electrode layer 104 and the third low acoustic impedance layer 205 is not affected when the upper surface of the lower electrode layer 104 is planarized in the next step, as shown in fig. 6. The Deposition process of the present disclosure may be a Physical Vapor Deposition (PVD) method or a Chemical Vapor Deposition (CVD) method, such as a Deposition process of Mo — Mo as a material of the bottom electrode layer.
According to an embodiment of the present disclosure, forming a piezoelectric structure on the stacked structure 200 includes:
the lower electrode layer 104 and the third low acoustic impedance layer 205 are planarized, the upper surface of the lower electrode layer 104 is a planarized surface, and the planarized surface is flush with the upper surface of the third low acoustic impedance layer 205. Specifically, as shown in fig. 6, the upper surface of the structure is actually uneven with the lower electrode groove 301 being ensured to be completely filled. Therefore, it is required to perform a planarization process. For example, a planarization plane of the lower electrode layer can be formed by planarizing the upper surface of the lower electrode layer 104 by a Chemical Mechanical Polishing (CMP) process.
In the embodiment of the present disclosure, the CMP process may polish and grind not only the deposited metal material of the lower electrode layer 104, but also the material (e.g., silicon dioxide) of the third low acoustic impedance layer 205 at the same time. In addition, the CMP process may achieve precise control of the polishing thickness by controlling the polishing rate, thereby precisely controlling the thicknesses of the first protrusion 103, the second protrusion 102, and the electrode body 107 corresponding to the lower electrode layer 104. Specifically, the planarization process first removes the excess electrode material from the upper surface of the deposited lower electrode layer 104, so that the upper surface of the lower electrode layer 104 can be leveled with the upper surface of the third low acoustic impedance layer 205. Wherein, through the planarization process, the specific thickness of the removed electrode material can be determined according to the thickness of the electrode material protruding out of the opening of the main body groove 304 and the value measured on the line. Then, the planarization process is continued on the upper surface of the third low acoustic impedance layer 205 and the polished upper surface of the lower electrode layer 104 until the upper surface of the whole structure is planarized (i.e. a planarized surface of the lower electrode layer 104 is obtained), and the thicknesses of the first convex portion 103, the second convex portion 102 and the electrode main body 107 corresponding to the lower electrode layer 104 are ensured, as shown in fig. 7.
According to an embodiment of the present disclosure, the method of preparing further comprises: a piezoelectric layer forming a piezoelectric structure corresponding to the planarized surface of the lower electrode layer 104 and the upper surface of the third low acoustic impedance layer 205; on the upper surface of the lower electrode layer 104 and the upper surface of the third low acoustic impedance layer 205 on which the planarization process has been performed, the piezoelectric layer 105 may be deposited by, for example, a PVD process or a CVD process, so that a peripheral region of the lower surface of the piezoelectric layer 105 is in contact with the upper surface of the third low acoustic impedance layer 205, and a central region thereof is in contact with the upper surface of the lower electrode layer 104, as shown in fig. 8.
Therefore, the piezoelectric layer 105 of the piezoelectric structure can grow on the flat upper surface of the lower electrode layer 104, which is more beneficial to obtain a crystal structure with a high c-axis orientation and a good growth texture between the piezoelectric layer 105 and the lower electrode layer 104, so that the piezoelectric performance of the piezoelectric layer 105 is improved, and the performance (improvement of the Q value) of the solid-state assembly resonator of the present disclosure is improved. For example, when the material used for the piezoelectric layer 105 is AlN formed on a flat surface and contacting the upper surface of the lower electrode layer 104, the C-axis crystal orientation is good, which can significantly improve the piezoelectric effect to further improve the overall performance of the device.
According to an embodiment of the present disclosure, the method of preparing further comprises: an upper electrode layer 106 of a piezoelectric structure is formed on the upper surface of the piezoelectric layer 105, as shown in fig. 9. The upper electrode layer 106 may be formed by, for example, a PVD process or a CVD process, and the material of the upper electrode layer 106 may be the same as that of the lower electrode layer 104. Finally, the upper electrode layer 106 is subjected to photolithography to form a predetermined upper electrode layer 106 pattern, i.e., an external pattern structure of the solid-state mount resonator.
The above-mentioned embodiments are intended to illustrate the objects, aspects and advantages of the present disclosure in further detail, and it should be understood that the above-mentioned embodiments are only examples of the present disclosure and are not intended to limit the present disclosure, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present disclosure should be included in the scope of the present disclosure.
Claims (10)
1. A solid state fabricated resonator, comprising: the structure of the piezoelectric material is such that,
the piezoelectric structure includes:
a lower electrode layer disposed corresponding to a lower side of the piezoelectric structure, the lower electrode layer including:
a convex part which is arranged corresponding to the lower surface of the lower electrode layer and protrudes downwards;
a piezoelectric layer disposed on an upper surface of the lower electrode layer;
an upper electrode layer disposed on an upper surface of the piezoelectric layer.
2. The solid state mount resonator of claim 1, wherein the boss comprises:
the first convex part is arranged corresponding to the edge of the lower surface of the lower electrode layer and protrudes downwards;
the second convex part is arranged in a downward protruding mode and corresponds to the middle of the lower surface of the lower electrode layer;
wherein, the first convex part is an annular closed structure; the distance between the inner edge of the first convex part and the outer edge of the second convex part is a first distance a; the protruding distance of the first convex part relative to the lower surface of the lower electrode layer is a second distance b; the protruding distance of the second convex part relative to the lower surface of the lower electrode layer is a third distance c; wherein b > c.
3. The solid state fabricated resonator of claim 1,
the upper surface of the lower electrode layer is a flattened surface;
the upper electrode layer and the lower electrode layer are made of one or a combination of more of molybdenum Mo, titanium Ti, tungsten W, gold Au, aluminum Al and platinum Pt;
the piezoelectric layer is made of AlN, ZnO or PZT.
4. The solid state mounted resonator of claim 1, further comprising:
a substrate layer disposed under the piezoelectric structure, an
The laminated structure is arranged between the piezoelectric structure and the substrate layer, and the laminated structure sequentially comprises from bottom to top: the piezoelectric transducer comprises a first low acoustic impedance layer, a first high acoustic impedance layer, a second low acoustic impedance layer, a second high acoustic impedance layer, and a third low acoustic impedance layer, wherein the third low acoustic impedance layer is disposed below a piezoelectric layer of the piezoelectric structure.
5. The solid state fabricated resonator of claim 4, wherein the third low acoustic impedance layer comprises:
lower electrode tank, it is relative the upper surface undercut setting of third low acoustic impedance layer, lower electrode tank includes:
the first groove is arranged corresponding to the edge of the bottom surface of the lower electrode groove and is downwards sunken; and
the second groove is arranged corresponding to the middle part of the bottom surface of the lower electrode groove and is sunken downwards;
wherein the first groove is a closed annular groove; the distance between the inner edge of the first groove and the outer edge of the second groove is a first distance a; the first groove is recessed by a second distance b relative to the bottom surface of the lower electrode groove; the concave distance of the second groove relative to the bottom surface of the lower electrode groove is a third distance c; wherein b > c.
6. The solid state fabricated resonator of claim 4,
the substrate layer is made of one or a combination of more of silicon, glass, sapphire and ceramic;
the first low-sound-impedance layer, the second low-sound-impedance layer and the third low-sound-impedance layer are made of siloxane or silicon dioxide; and
the first high acoustic impedance layer and the second high acoustic impedance layer are made of tungsten or molybdenum.
7. A method of manufacturing a solid-state mount resonator according to any of claims 1-6, comprising:
a laminated structure is formed, and a laminated structure is formed,
forming a lower electrode layer of a piezoelectric structure on the stacked structure;
wherein the lower electrode layer includes: and a convex part which is arranged corresponding to the lower surface of the lower electrode layer and protrudes downwards.
8. The production method according to claim 7,
the forming a stacked structure includes:
a first low-sound impedance layer, a first high-sound impedance layer, a second low-sound impedance layer, a second high-sound impedance layer and a third low-sound impedance layer are sequentially formed on the substrate layer from bottom to top;
forming a lower electrode groove depressed downward on an upper surface of the third low acoustic impedance layer;
wherein, a first groove which is concave downwards is formed corresponding to the edge of the bottom surface of the lower electrode groove; a second recess depressed downward is formed corresponding to a middle portion of the bottom surface of the lower electrode bath.
9. The method of claim 8, wherein the forming the lower electrode layer of the piezoelectric structure on the stacked structure comprises:
forming the lower electrode layer in a lower electrode groove based on the first groove and the second groove; wherein a first protrusion corresponding to the protrusion formed in the first groove; a second protrusion corresponding to the protrusion formed in the second groove;
and flattening the lower electrode layer and the third low-acoustic-impedance layer, wherein the upper surface of the lower electrode layer is a flattened surface, and the flattened surface is flush with the upper surface of the third low-acoustic-impedance layer.
10. The method of manufacturing according to claim 9, further comprising:
forming a piezoelectric layer of a piezoelectric structure corresponding to the planarized surface of the lower electrode layer and the upper surface of the third low acoustic impedance layer;
an upper electrode layer of the piezoelectric structure is formed on an upper surface of the piezoelectric layer.
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