CN111294011B - Solid-state assembly resonator and preparation method thereof - Google Patents
Solid-state assembly resonator and preparation method thereof Download PDFInfo
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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
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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
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- 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 mounted resonator and a method of manufacturing the same, the solid state mounted resonator comprising: a piezoelectric structure, the piezoelectric structure comprising: upper electrode layer, lower electrode layer and piezoelectricity layer, lower electrode layer sets up corresponding to piezoelectricity structure's below, and lower electrode layer includes: a convex part which is arranged in a protruding way downwards corresponding to the lower surface of the lower electrode layer; the piezoelectric layer is arranged on the upper surface of the lower electrode layer; the upper electrode layer is disposed on the upper surface of the piezoelectric layer. The protrusions are formed on the lower surface of the lower electrode layer in correspondence to the upper surface of the lower electrode layer in contact with the piezoelectric layer, so that the upper surface of the lower electrode layer can form a planarized surface, and therefore, the piezoelectric layer is grown on the planarized surface, and a crystal structure with high c-axis orientation with good growth texture is more easily obtained, so that the piezoelectric performance of the piezoelectric layer is improved, and the performance (e.g., the Q value) of the resonator is improved.
Description
Technical Field
The disclosure relates to the technical field of resonators, in particular to a solid-state assembly type resonator and a preparation method thereof.
Background
A solid state assembled resonator (Solidly Mounted Resonator, SMR) is a device that includes a bragg reflector structure and a piezoelectric structure. In conventional solid state assembly resonator applications, a piezoelectric structure is formed on a Bragg reflector structure, the Bragg reflector is formed of alternating high and low acoustic impedance materials, the piezoelectric structure is formed of upper and lower electrode layers sandwiching piezoelectric material, and the piezoelectric material grows on the upper surface of the lower electrode to form a piezoelectric layer. Therefore, the prior art usually etches the bottom electrode pattern first and then deposits the piezoelectric layer, so that the piezoelectric layer can grow on the surface of the uneven bottom electrode, the lattice structure and the lattice orientation of the piezoelectric layer can be degraded at uneven places, and the piezoelectric effect of the piezoelectric layer is affected, thereby affecting the performance of the device.
Disclosure of Invention
First, the technical problem to be solved
In order to solve the problem that in the prior art, the lower electrode pattern is etched first and then the piezoelectric layer is deposited, so that the piezoelectric layer can grow on the surface of the uneven lower electrode to influence the performance of a device, the solid assembly type resonator and the preparation method thereof are provided.
(II) technical scheme
One aspect of the present disclosure provides a solid state assembled resonator comprising: a piezoelectric structure, the piezoelectric structure comprising: lower electrode layer and piezoelectricity layer, upper electrode layer, lower electrode layer set up corresponding to piezoelectricity structure's below, and lower electrode layer includes: a convex part which is arranged in a protruding way downwards corresponding to the lower surface of the lower electrode layer; the piezoelectric layer is arranged on the upper surface of the lower electrode layer; the upper electrode layer is disposed on the upper surface of the piezoelectric layer.
According to an embodiment of the present disclosure, the convex portion includes: the first convex part and the second convex part are arranged in a downward protruding way corresponding to the edge of the lower surface of the lower electrode layer; the second convex part is arranged in a way of protruding downwards corresponding to the middle part of the lower surface of the lower electrode layer.
According to the embodiment of the disclosure, the first protruding part is an annular closed structure; wherein the interval 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 protruding part relative to the lower surface of the lower electrode layer is a second distance b; the protruding distance of the second protruding 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 aluminum nitride AlN, zinc oxide ZnO or lead zirconate titanate PZT.
According to an embodiment of the present disclosure, a solid state assembly resonator includes: substrate layer and stromatolite structure, the substrate layer sets up under piezoelectric structure, and the stromatolite structure sets up between piezoelectric structure and substrate layer, and the stromatolite structure includes from bottom to top in proper order: the piezoelectric device 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 arranged below a piezoelectric layer of the piezoelectric structure.
According to an embodiment of the present disclosure, the third low acoustic impedance layer includes: the lower electrode groove, the upper surface of lower electrode groove relative third low acoustic impedance layer is sunken to set up downwards, and the lower electrode groove includes: the first groove and the second groove are arranged in a downward concave manner corresponding to the edge of the bottom surface of the lower electrode groove; and the second groove is arranged corresponding to the middle part of the bottom surface of the lower electrode groove and is recessed downwards.
According to an embodiment of the present disclosure, the first groove is a closed annular groove; the space between the inner edge of the first groove and the outer edge of the second groove is a first distance a; the concave distance of the first groove relative to the bottom surface of the lower electrode groove is a second distance b; 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 an embodiment of the present disclosure, the material of the substrate layer is a combination of one or more of silicon, glass, sapphire, ceramic; the first low acoustic impedance layer, the second low acoustic impedance layer and the third low acoustic impedance layer are made of siloxane or silicon dioxide; and the materials of the first high acoustic impedance layer and the second high acoustic impedance layer are tungsten or molybdenum.
Another aspect of the present disclosure provides a method for preparing the above solid-state assembly resonator, comprising: forming a laminated structure, and forming a lower electrode layer of the piezoelectric structure on the laminated structure; wherein the lower electrode layer includes: the convex part 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 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 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 recessed downward on an upper surface of the third low acoustic impedance layer; wherein, the edge corresponding to the bottom surface of the lower electrode groove forms a first groove which is concave downwards; a second groove recessed downward is formed corresponding to the middle portion of the bottom surface of the lower electrode trench.
According to an embodiment of the present disclosure, forming a lower electrode layer of a piezoelectric structure on a stacked structure includes: forming a lower electrode layer in the lower electrode groove based on the first groove and the second groove; wherein, first convex parts corresponding to the convex parts formed in the first grooves; and a second convex part corresponding to the convex part 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, and the flattened surface is leveled with the upper surface of the third low acoustic impedance layer.
According to an embodiment of the present disclosure, the preparation method 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 a piezoelectric structure is formed on an upper surface of the piezoelectric layer.
(III) beneficial effects
The present disclosure provides a solid state assembled resonator comprising: a piezoelectric structure, the piezoelectric structure comprising: upper electrode layer, lower electrode layer and piezoelectricity layer, lower electrode layer sets up corresponding to piezoelectricity structure's below, and lower electrode layer includes: a convex part which is arranged in a protruding way downwards corresponding to the lower surface of the lower electrode layer; the piezoelectric layer is arranged on the upper surface of the lower electrode layer; the upper electrode layer is disposed on the upper surface of the piezoelectric layer. The convex portion is correspondingly formed on the lower surface of the lower electrode layer, so that the upper surface of the lower electrode layer, which is in contact with the piezoelectric layer, can form a flattened surface, and therefore, the piezoelectric layer grows on the flattened surface, and a crystal structure with high c-axis orientation and good growth texture is easier to obtain, so that the piezoelectric performance of the piezoelectric layer is improved, and the performance (such as Q value improvement) 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 present disclosure;
fig. 2A schematically illustrates a structural cross-sectional view and a plan view of a lower electrode layer in an embodiment of the present disclosure;
FIG. 2B schematically illustrates a cross-sectional view of the structure of the lower electrode trench in an embodiment of the disclosure;
FIG. 3 schematically illustrates a flow chart of a method of manufacturing a solid state fabricated resonator in an embodiment of the present disclosure;
FIG. 4 schematically illustrates a cross-sectional view of a structure of a method of manufacturing a solid state assembled resonator in an embodiment of the present disclosure at a manufacturing stage;
FIG. 5A schematically illustrates a cross-sectional view of another fabrication stage of a method of fabricating a solid state fabricated resonator in accordance with an embodiment of the present disclosure;
FIG. 5B schematically illustrates a cross-sectional view of a structure of a further fabrication stage of a fabrication method of a solid state fabricated resonator in an embodiment of the present disclosure;
FIG. 5C schematically illustrates a cross-sectional view of a structure of a further fabrication stage of a fabrication method of a solid state fabricated resonator in an embodiment of the present disclosure;
FIG. 6 schematically illustrates a cross-sectional view of a structure of a further fabrication stage of a fabrication method of a solid state fabricated resonator in an embodiment of the present disclosure;
FIG. 7 schematically illustrates a cross-sectional view of a structure of a further fabrication stage of a fabrication method of a solid state fabricated resonator in an embodiment of the present disclosure;
FIG. 8 schematically illustrates a cross-sectional view of a structure of a further fabrication stage of a fabrication method of a solid state fabricated resonator in an embodiment of the present disclosure;
fig. 9 schematically illustrates a cross-sectional view of a structure of a further manufacturing stage of a method for manufacturing a solid-state assembled resonator in an embodiment of the present disclosure.
Detailed Description
For the purposes of promoting an understanding of the principles and advantages of the disclosure, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same.
In order to solve the problem that in the prior art, the lower electrode pattern is etched first and then the piezoelectric layer is deposited, so that the piezoelectric layer can grow on the surface of the uneven lower electrode to influence the performance of a device, the solid assembly type resonator and the preparation method thereof are provided.
One aspect of the present disclosure provides a solid state assembled resonator, as shown in fig. 1-2B, comprising: and the piezoelectric structure is used for playing a piezoelectric effect. The piezoelectric structure includes: the upper electrode layer 106, the lower electrode layer 104 and the piezoelectric layer 105, wherein the lower electrode layer 104 is disposed correspondingly to the lower portion of the piezoelectric structure, specifically, the lower electrode layer 104 may be a constituent structure of the lower portion of the piezoelectric structure, disposed below the piezoelectric layer 105, for use as a lower electrode of the piezoelectric structure. According to an embodiment of the present disclosure, the lower electrode layer 104 includes: the convex portion is provided to protrude downward corresponding to the lower surface of the lower electrode layer 104. The lower electrode layer 104 includes a convex portion and an electrode body 107 (as shown in fig. 2A), and the lower surface of the lower electrode layer 104 may be the lower surface of the electrode body 107, and at the same time, the convex portion protrudes downward with respect to the lower surface, so that a lower electrode pattern required for the piezoelectric structure may be formed on the lower surface of the lower electrode layer 104 for the generation of the piezoelectric effect of the piezoelectric structure.
According to an embodiment of the present disclosure, a piezoelectric layer 105 is disposed on an 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, and 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 perform a piezoelectric effect in cooperation with 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 functioning as an extraction electrode of the device.
In the solid-state assembly resonator of the present disclosure, the quality factor Q is determined by the material loss of the piezoelectric layer, and the smaller 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 made unnecessary to form the above convex structure 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) can be made flat, so that the piezoelectric layer 105 of the piezoelectric structure can be grown on the flat upper surface of the lower electrode layer 104, which is more advantageous in obtaining a crystal structure with a growth crystal phase more prone to c-axis orientation between the upper electrode layer 106 and the lower electrode layer 104, thereby improving the piezoelectric performance of the piezoelectric layer 105, and improving the performance (improvement in Q value) of the solid-state assembled resonator of the present disclosure.
Based on the above structure of the solid-state assembly resonator, the present disclosure produces an unexpected technical effect: the pattern formation convex 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 the conventional manner of forming on the upper surface of the lower electrode layer 104 or directly on the upper surface of the upper electrode 106 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 when the surface is etched, and in addition, due to the metal characteristics (for example, the metal etching selectivity is relatively poor) of the electrode layer, the metal over-etching phenomenon of the electrode layer of the metal is very easy to occur in the etching process of the bump structure pattern on the process, and the control of the etching depth is also difficult. Therefore, by adopting the structure of the solid assembly resonator, the problem of metal overetching can be prevented, the preparation yield of the device can be effectively improved, multiple times of etching can be avoided, the step of forming the protruding part of the electrode layer is reduced, and the thickness change of the electrode layer can be effectively controlled. The electrode layers described above may include the upper electrode layer 106 and/or the lower electrode layer 104, according to embodiments of the present disclosure.
Finally, through the structure of the solid-state assembly resonator disclosed by the invention, another technical effect which is not achieved by the intention is further produced: according to the embodiment of the disclosure, an electrode groove is formed in the laminated structure below the piezoelectric structure and is used for embedding the lower electrode layer in the electrode groove of the laminated structure, so that the thickness dimension of the device structure can be reduced on the basis of the effect, and the dimension of the device structure is further reduced.
According to an embodiment of the present disclosure, as shown in fig. 1 and 2A, the solid state assembled resonator of the present disclosure further includes an electrode body 107 that may be used to provide a set 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 corresponding piezoelectricity 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 convex portion 103 and a second convex portion 102, the first convex portion 103 being provided to protrude downward corresponding to an edge of a lower surface of the lower electrode layer 104; specifically, the first protrusion 103 protrudes downward from the lower surface of the electrode body 107 of the lower electrode layer 104, so as to generate impedance mismatch at the periphery of the resonator, so that bulk acoustic wave energy generated by the device is limited to the inside of the protrusion structure of the lower electrode layer 104 of the piezoelectric structure, so that the bulk acoustic wave energy is less prone to leak, energy loss is reduced, and the Q value of the device is improved.
The second protrusion 102 is disposed to protrude downward corresponding to the middle portion of the lower surface of the lower electrode layer 104, specifically, the second protrusion 102 is disposed to protrude downward with respect to the lower surface of the electrode body 107 of the lower electrode layer 104, and has a protruding height smaller than that of the first protrusion, so as to form a pit between the first protrusion and the second protrusion, which pit can effectively reduce the parasitic resonance of the lateral mode below the cut-off frequency and also helps to raise the Q value of the resonator. As shown in fig. 1 and 2A.
Based on the structures of the first protrusion 103 and the second protrusion 102, the present disclosure has another technical effect that is not expected: the energy loss of a solid state fabricated resonator is mainly due to the lateral modes of the device structure such that it is a leak of bulk acoustic wave energy that occurs at the edges of the structure. Since the surface needs to be etched during the formation of the lower electrode layer 104 or the formation of the convex structure on the upper surface of the lower electrode, the edges of the lower electrode layer and the convex of the pattern are repeatedly exposed to various dry and wet etching, resulting in deterioration of the edge quality and profile shape of the lower electrode layer and the convex of the pattern, and extremely easy leakage of the bulk acoustic wave energy. Compared with the traditional mode that the upper surface of the lower electrode layer 104 is directly formed 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 through a metal deposition method, so that the structure of the solid-state assembly resonator can effectively ensure that the edges of the lower electrode layer 104, the first convex part 103 and the second convex part 102 cannot be poor in edge quality and outline shape, further prevent leakage of bulk acoustic wave energy, play a more obvious acoustic impedance mismatch role, effectively prevent energy loss caused by a transverse mode of a device structure, enable the device to have a better piezoelectric effect, further improve Rp values, and improve negative effects on device performance caused by transverse mode parasitic resonance lower than a cut-off frequency. In addition, the metal electrode can also prevent the metal electrode from being excessively etched, simplify the process steps and the like, and the details are not repeated here.
According to the embodiment of the present disclosure, as shown in fig. 2A, the first protrusion 103 is an annular closed structure; wherein a distance between an inner edge of the first protrusion 103 and an outer edge of the second protrusion 102 is a first distance a; when the first protrusion 103 is an annular closed protrusion structure, the inner edge of the first protrusion 103 is opposite to the second protrusion 102 surrounding the lower surface of the electrode body 107 at the middle of the first protrusion 103, 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 second protrusion 102 is the outer edge. The protruding distance of the first protruding portion 103 relative to the lower surface of the lower electrode layer 104 is a second distance b, so that the side portion of the bulk acoustic wave energy of the device structure is prevented from being leaked, and the energy loss is reduced; the protruding distance of the second protruding portion 102 from the lower surface of the lower electrode layer 104 is a third distance c, where b > c, for forming a pit between the first protruding portion and the second protruding portion, 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 limited within the area enclosed by the first protruding portion 103 as much as possible. Here, the lower surface of the lower electrode layer 104, i.e., the lower surface of the electrode body 107, the piezoelectric effect region of the piezoelectric structure corresponds to the region 401 in fig. 1, and is located at a portion inside the inner edge of the first convex portion 103, on the lower surface of the lower electrode layer 104.
According to an embodiment of the present disclosure, the upper surface of the lower electrode layer 104 is a planarized surface. Specifically, the upper surface of the lower electrode layer 104 may be subjected to a planarization process, for example, the upper surface of the lower electrode layer 104 before the formation of the piezoelectric layer 105 may be planarized by using a chemical mechanical polishing (Chemical Mechanical Polishing, abbreviated as CMP) process, so that a planarized plane of the lower electrode layer may be formed, and therefore, the piezoelectric layer 105 of the piezoelectric structure may be grown on the upper surface of the planarized lower electrode layer 104, that is, the lower surface of the piezoelectric layer 105 corresponding to 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 high c-axis orientation 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 improvement) of the solid assembly resonator of the disclosure.
According to an embodiment of the present disclosure, the material of the upper electrode layer 106, the lower electrode layer 104 is one or more 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 finish the deposition preparation of the lower electrode layer at one time. When the material selection of the protruding portion is inconsistent with the material selection of the electrode 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 preparation material of the lower electrode layer 104 (including the first convex portion 103 and the second convex portion 102) or the upper electrode layer 106. Through the materials of the upper electrode layer 106 and the lower electrode layer 104, better bonding capability with the materials of the piezoelectric layer 105 described below can be achieved, and a crystal structure with high c-axis orientation and better growth texture is obtained between the piezoelectric layer 105 and the lower electrode layer 104 or the upper electrode layer 106, so that the piezoelectric performance of the piezoelectric layer 105 is further improved, and the performance (such as the improvement of the Q value) of the solid assembly resonator is improved.
The material of the piezoelectric layer 105 is aluminum nitride AlN, zinc oxide ZnO, lead zirconate titanate PZT, or the like, and the material of the piezoelectric layer 105 may be one or a combination of a plurality of aluminum nitride AlN, zinc oxide ZnO, lead zirconate titanate PZT, or the like, and the combination of the materials of the plurality of piezoelectric layers 105 may be a 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, which collectively constitute the three-layer structure. By the material of the piezoelectric layer 105, better bonding capability can be formed with the material of the upper electrode layer 106 and the lower electrode layer 104, so that a crystal structure with high c-axis orientation and 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 enhancing the performance (such as the improvement of the Q value) of the solid assembly resonator of the disclosure.
According to an embodiment of the present disclosure, as shown in fig. 1, a solid state assembly type 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 foundation for the piezoelectric structure to function as a substrate. The laminated structure 200 is disposed between the piezoelectric structure and the substrate layer 101, that is, the laminated structure 200 is disposed on the substrate layer 101, and the laminated structure 200 sequentially includes, 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 are formed as a bragg reflection layer structure (i.e., the laminated structure 200) shown in fig. 1, which is a sandwich-type sandwich structure formed by alternately forming low acoustic impedance material layers and high acoustic impedance material layers, so as to realize a bragg reflection effect on the generated bulk acoustic wave of 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 the bulk acoustic wave, and may also provide a forming location for forming the lower electrode layer 104, and simultaneously perform a supporting function or a substrate function for forming the piezoelectric structure.
According to embodiments of the present disclosure, the material of the substrate layer 101 is one or more of silicon, glass, sapphire, ceramic, etc., for example, glass may be used as the substrate layer 101 to facilitate better bonding 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 helpful for forming Bragg reflector structures with better performance; and the materials of the first high acoustic impedance layer 202 and the second high acoustic impedance layer 204 are tungsten W or molybdenum Mo to form better high acoustic impedance performance, which is helpful for forming the bragg reflector structure with better performance.
According to an embodiment of the present disclosure, as shown in fig. 1 and 2B, the third low acoustic impedance layer 205 includes: the lower electrode groove 301, the lower electrode groove 301 being disposed recessed downward with respect to the upper surface of the third low acoustic impedance layer 205, the lower electrode groove 301 comprising: the first groove 303, the second groove 302 and the main body groove 304, wherein the first groove 303 is arranged corresponding to the edge of the bottom surface of the lower electrode groove 301 and is recessed downwards, and the shape and the size of the first groove are matched with the shape and the size of the second protrusion 102, so that the first groove 303 is a closed annular groove for correspondingly accommodating the first protrusion 103. And the second recess 302 is provided corresponding to the middle part of the bottom surface of the lower electrode groove 301, recessed downward, and has a shape and size matching the shape and size of the first protrusion 103 for correspondingly accommodating the first protrusion 103. Wherein the space corresponds to the structure of the body groove 304 as shown in the annular closed dashed line of fig. 2B, 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 is configured to perform bragg reflection with respect to the bottom surface of the lower electrode trench 301 of the region 401 shown in fig. 1 and 2B, and the bottom surface of the lower electrode trench 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 of the present disclosure that actually functions as a Bragg reflection corresponds to the stacked structure 200 identified as 200 in FIG. 1 and FIGS. 4-9.
According to the embodiment of the disclosure, as shown in fig. 1 and 2B, the first groove 303 is configured to accommodate the first protrusion 103 in a matching manner, and then corresponds to the first protrusion 103 shown in fig. 2A, and the first groove 303 is a closed annular groove, that is, a closed annular groove; wherein, corresponding to the first convex portion 103 and the second convex portion 102 as shown in fig. 2A, a space between an inner edge of the first groove 303 and an outer edge of the second groove 302 is a first distance a; the first recess 303 is recessed a second distance b from the bottom surface of the lower electrode trench 301; the concave distance of the second groove 302 relative to the bottom surface of the lower electrode groove 301 is a third distance c; wherein b > c such that a groove protrusion 305 between the inner edge of the first groove 303 and the outer edge of the second groove 302 can be formed in the lower electrode groove 301 of the third low acoustic impedance layer 205, the groove protrusion 305 being a closed annular protrusion having a width dimension 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 is in contact with the top surface of the second convex portion 102, and the side wall surface of the second groove 302 is in contact with the side surface of the second convex portion 102; in addition, the lower surface of the electrode body 107 of the lower electrode layer 104 is in contact with the top surface of the trench protrusion 305.
According to an 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 laminate 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 grooves 303 and 302 and the body groove 304. The area of the present disclosure that acts as a bragg reflection actually corresponds to the laminate structure 200 identified as 200 in fig. 1 and 4-9, i.e., the actual effective functional layer (or area) 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 embedded in the laminated structure 200 by the matching and embedding arrangement of the lower electrode groove 301 and the lower electrode layer 104, so that 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 also serves to support and stabilize the piezoelectric structure as well as to help prevent leakage of bulk acoustic wave energy. Therefore, the structure of the solid-state assembly 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 and with good growth texture, so that the lower electrode layer is combined with the piezoelectric layer 105 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 structure detachment phenomenon is not easy to occur in the production and preparation process, and the improvement of the overall performance of the device is also very facilitated.
According to an embodiment of the present disclosure, the reserved thickness of the third low acoustic impedance layer 205 is the sum of the thickness of the convex portion of the lower electrode layer 104 (for example, the thickness of the second convex portion 102), the thickness of the electrode body 107 of the lower electrode layer 104, and the required thickness for performing 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 required frequency of the solid-state assembly resonator. Note that, since the effective area thereof is the area 401 shown in fig. 1 and 2B for both the piezoelectric structure and the bragg reflection structure, the predetermined thickness may not include the thickness of the power-down first protruding portion 103.
Another aspect of the present disclosure provides a method for preparing the above solid state assembled resonator, as shown in fig. 3, comprising:
s310, forming a laminated structure 200,
s320, forming a lower electrode layer 104 of the piezoelectric structure on the laminated structure 200; wherein the lower electrode layer 104 includes: the convex portion is provided to protrude downward corresponding to the lower surface of the lower electrode layer 104.
In the method for manufacturing the solid-state assembly 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 be simultaneously made not to need to form the pattern, 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 be made flat, so that the piezoelectric layer 105 of the piezoelectric structure may be grown on the flat upper surface of the lower electrode layer 104, and it is more advantageous to obtain a crystal structure with a high c-axis orientation 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 enhancing the performance (the improvement of Q-value) of the solid-state assembly resonator of the present disclosure.
Based on the preparation method, the method has the unexpected technical effect that: compared with the traditional mode that the upper surface of the lower electrode layer 104 or the upper surface of the upper electrode 106 is directly formed by a metal etching method, the pattern forming structure protruding part of the lower electrode layer 104 can not only prevent the metal over-etching problem in the preparation process, effectively improve the preparation yield of devices, but also avoid multiple etching, reduce the forming steps of the protruding 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.
Reference may be made to the solid state assembly type resonator shown in fig. 1-2B for the structure of the resonator, and the description thereof will be omitted.
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 in this order from bottom to top on the backing layer 101. Specifically, the stacked structure 200 is formed on the upper surface of the substrate layer 101 as a bragg reflection layer structure of the solid-state-assembled resonator of the present disclosure. Alternately depositing a low acoustic impedance layer and a high acoustic impedance layer on the upper surface of the substrate 101 to form a bragg reflection layer structure, specifically, a first low acoustic impedance layer 201 may be deposited first, a first high acoustic impedance layer 202 is deposited on the upper surface of the first low acoustic impedance layer 201, a second low acoustic impedance layer 203 is deposited on the first high acoustic impedance layer 202, a second high acoustic impedance layer 204 is deposited on the upper surface of the second low acoustic impedance layer 203, and a third low acoustic impedance layer 205 is deposited on the upper surface of the second high acoustic impedance layer 204, as shown in fig. 4. In the preparation of depositing the third low acoustic impedance layer 205, the thicknesses that need to be removed when the structures (e.g., the first groove 303, the second groove 302, the body groove 304) in the lower electrode groove 301 and the upper surface of the lower electrode layer 104 are subjected to the planarization process 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 recessed downward is formed on the upper surface of the third low acoustic impedance layer 205; wherein a first groove 303 recessed downward is formed corresponding to an edge of a bottom surface of the lower electrode groove 301; a second groove 302 recessed downward is formed corresponding to the middle 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 down 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 be a dry etching process, so that the main body groove 304 of the lower electrode groove 301 and the depths of the first groove 303 and the second groove 302 (as shown in fig. 2B) are preferably formed by controlling the etching rate. Wherein, the main body groove 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 first groove 303 is continuously etched down 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 formed corresponding to the position of the lower electrode layer 104 and the upper surface of the third low acoustic impedance layer 205 are subjected to photolithography to form a main body groove 304 embedded in the upper surface of the third low acoustic impedance layer 205, as shown in fig. 5A. Based on forming the inner surface of the body groove 304 and then forming the second photoresist layer, the second photoresist layer formed corresponding to the position of the second protrusion 102 and the middle of the bottom surface of the body groove 304 are subjected to photolithography, so as to form the second groove 302 embedded in the bottom surface of the body groove 304, as shown in fig. 5B. Based on the formation of the inner surface of the second recess 302, the formation of the third photoresist layer is continued, and the edges of the formed third photoresist layer corresponding to the position of the first protrusion 103 and the bottom surface of the body groove 304 are subjected to photolithography to form the first recess 303 embedded in the bottom surface of the body groove 304, as shown in fig. 5C.
Since the depth of the first groove 303 with respect to the upper surface of the third low acoustic impedance layer 205 is maximized, the above can also be adjusted such that the second groove 302 is formed first, then the body groove 304 is formed, and finally the first groove 303 is formed. The above photolithography process can well control the depth of etching the third low acoustic impedance layer 205 according to the etching rate and etching time. In addition, compared with the conventional method of forming the 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 the metal electrode with poor etching selectivity, so that the precise 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 of 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 includes: forming a 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 a first convex portion 103 is formed corresponding to the first concave portion 303; a second convex portion 102 corresponding to the convex portion formed in the second groove 302; corresponding to the electrode body 107 in which the lower electrode layer 104 is formed in the body groove 304. After forming the lower electrode trench 301, 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 beyond the opening of the main body trench 304, so as to ensure that the lower electrode trench 301 may be completely filled, and facilitate the next planarization of the upper surface of the lower electrode layer 104 without affecting the predetermined thicknesses of the lower electrode layer 104 and the third low acoustic impedance layer 205, as shown in fig. 6. The deposition process of the present disclosure may be a physical vapor deposition (Physical Vapour Deposition, PVD for short) or a chemical vapor deposition (Chemical Vapor Deposition, CVD for short), such as a deposition process for molybdenum Mo as the lower electrode layer material.
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, and the upper surface of the lower electrode layer 104 is a planarized surface, which 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 ensuring that the lower electrode groove 301 is completely filled. Therefore, it is necessary to perform planarization treatment. For example, the upper surface of the lower electrode layer 104 is planarized by a chemical mechanical polishing (Chemical Mechanical Polishing, CMP) process, so as to form a planarized surface of the lower electrode layer.
In embodiments of the present disclosure, the CMP process may not only polish the deposited metal material of the lower electrode layer 104, but may also polish the material of the third low acoustic impedance layer 205 (e.g., silicon dioxide) at the same time. In addition, the CMP process can 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 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 is level with the upper surface of the third low acoustic impedance layer 205. The thickness of the electrode material removed by the planarization process may be determined based on the thickness of the electrode material protruding outside the opening of the body groove 304 and the in-line measured value. Then, the planarization process is continued on the upper surface of the third low acoustic impedance layer 205 and the upper surface of the planarized lower electrode layer 104 until the upper surface of the entire structure is planarized (i.e., the planarized surface of the lower electrode layer 104 is obtained), and the thicknesses of the first protrusion 103, the second protrusion 102, and the electrode 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 preparation method further comprises: a piezoelectric layer forming a piezoelectric structure corresponding to the flattened 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 such that the 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, the central region of which is in contact with the upper surface of the lower electrode layer 104, as shown in fig. 8, by, for example, PVD process or CVD process.
Therefore, the piezoelectric layer 105 of the piezoelectric structure can be grown on the upper surface of the flat lower electrode layer 104, and a crystal structure with high c-axis orientation and good growth texture is more beneficial to be obtained 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 (the improvement of Q value) of the solid assembly resonator is improved. For example, the material used in the piezoelectric layer 105 may be AlN, where AlN is formed on a flat surface, and when it contacts the upper surface of the lower electrode layer 104, the C-axis crystal orientation thereof is better, which can significantly improve the piezoelectric effect, so as to further improve the overall performance of the device.
According to an embodiment of the present disclosure, the preparation method 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, PVD or CVD, 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 assembly resonator.
While the foregoing is directed to embodiments of the present disclosure, other and further details of the invention may be had by the foregoing description, it should be understood that the foregoing description is merely illustrative of the embodiments of the present disclosure and that any and all modifications, equivalents, improvements and/or other changes which may be made without departing from the spirit and principles of the present disclosure are intended to be included within the scope of the present disclosure.
Claims (9)
1. A solid state assembled resonator comprising: the piezoelectric structure of the piezoelectric ceramic comprises a piezoelectric layer,
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 protruding downward corresponding to the lower surface of the lower electrode layer;
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;
wherein the convex portion includes:
the first convex part is arranged in a downward protruding way corresponding to the edge of the lower surface of the lower electrode layer;
the second convex part is arranged in a protruding way downwards corresponding to the middle part of the lower surface of the lower electrode layer;
wherein the first convex part is an annular closed structure; the interval 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 protruding part relative to the lower surface of the lower electrode layer is a second distance b; the protruding distance of the second protruding part relative to the lower surface of the lower electrode layer is a third distance c; wherein b > c.
2. The solid state assembled resonator of claim 1, wherein,
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 more of molybdenum Mo, titanium Ti, tungsten W, gold Au, aluminum Al and platinum Pt;
the piezoelectric layer is made of aluminum nitride AlN, zinc oxide ZnO or lead zirconate titanate PZT.
3. The solid state assembled 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 comprises the following components from bottom to top in sequence: the piezoelectric structure 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 arranged below a piezoelectric layer of the piezoelectric structure.
4. The solid state assembled resonator of claim 3 wherein the third low acoustic impedance layer comprises:
the lower electrode groove is arranged in a downward concave manner relative to the upper surface of the third low acoustic impedance layer, and the lower electrode groove comprises:
the first groove is arranged in a downward concave manner corresponding to the edge of the bottom surface of the lower electrode groove; and
the second groove is arranged in a downward concave manner corresponding to the middle part of the bottom surface of the lower electrode groove;
wherein the first groove is a closed annular groove; the space between the inner edge of the first groove and the outer edge of the second groove is a first distance a; the concave distance of the first groove relative to the bottom surface of the lower electrode groove is a second distance b; 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.
5. A solid state assembled resonator as claimed in claim 3, wherein,
the material of the substrate layer is one or a combination of more materials of silicon, glass, sapphire and ceramic;
the materials of the first low acoustic impedance layer, the second low acoustic impedance layer and the third low acoustic impedance layer are siloxane or silicon dioxide; and
the materials of the first high acoustic impedance layer and the second high acoustic impedance layer are tungsten or molybdenum.
6. A method of making a solid state assembled resonator of any one of claims 1-5, comprising:
a laminated structure is formed and a plurality of layers of the laminated structure are formed,
forming a lower electrode layer of a piezoelectric structure on the laminated structure;
wherein the lower electrode layer includes: a convex part protruding downward corresponding to the lower surface of the lower electrode layer;
wherein the convex portion includes:
the first convex part is arranged in a downward protruding way corresponding to the edge of the lower surface of the lower electrode layer;
the second convex part is arranged in a protruding way downwards corresponding to the middle part of the lower surface of the lower electrode layer;
wherein the first convex part is an annular closed structure; the interval 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 protruding part relative to the lower surface of the lower electrode layer is a second distance b; the protruding distance of the second protruding part relative to the lower surface of the lower electrode layer is a third distance c; wherein b > c.
7. The method according to claim 6, wherein,
the forming of the laminated structure includes:
sequentially forming 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 on the substrate layer from bottom to top;
forming a lower electrode groove recessed downward on an upper surface of the third low acoustic impedance layer;
wherein, a first groove recessed downwards is formed corresponding to the edge of the bottom surface of the lower electrode groove; a second groove recessed downward is formed corresponding to the middle of the bottom surface of the lower electrode groove.
8. The method of manufacturing according to claim 7, wherein forming the lower electrode layer of the piezoelectric structure on the laminated 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 convex portion corresponding to the convex portion formed in the second groove;
and carrying out planarization treatment on the lower electrode layer and the third low acoustic impedance layer, wherein the upper surface of the lower electrode layer is a planarization surface, and the planarization surface is leveled with the upper surface of the third low acoustic impedance layer.
9. The method of manufacturing according to claim 8, further comprising:
a piezoelectric layer forming 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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| CN106209001A (en) * | 2016-06-29 | 2016-12-07 | 电子科技大学 | FBAR of based single crystal Lithium metaniobate thin slice and preparation method thereof |
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