CN117856757A - Method for manufacturing bulk acoustic wave resonator - Google Patents
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Abstract
The invention provides a manufacturing method of a bulk acoustic wave resonator, which increases the deposition times of electrode metal layers, wherein the acoustic impedance of the metal layers which are in contact with a piezoelectric film layer in a first electrode and a second electrode is larger than that of the metal layers which are not in contact with the piezoelectric film layer, namely the ratio of the acoustic impedances of the metal layers to the piezoelectric film layer is increased, so that the sound intensity transmission coefficient can be reduced, more acoustic energy is forced to enter the piezoelectric film layer, thereby increasing the acoustic energy in a piezoelectric material, improving the effective electromechanical coupling coefficient and improving the performance of the bulk acoustic wave resonator. Compared with the prior art, the piezoelectric film layer AlN is doped with Sc and other elements to improve the piezoelectric strain constant of the piezoelectric material so as to improve the effective electromechanical coupling coefficient, the requirement on the process is high, the element segregation can also reduce the uniformity of the piezoelectric film, and the manufacturing method of the bulk acoustic wave resonator has the advantages of simple and reliable process.
Description
Technical Field
The invention belongs to the technical field of microelectronic devices, and relates to a manufacturing method of a bulk acoustic wave resonator.
Background
Currently, radio frequency filters are required to have an operating frequency of 5GHz or higher for wireless data transmission, and filters used in 5G communication are mainly bulk acoustic wave filters (Bulk Acoustic Wave, BAW for short) and surface acoustic wave filters (Surface Acoustic Wave, SAW for short). The BAW device has extremely high quality factor Q value (over 4000), the working frequency band is from 100MHz to 20 GHz, and the BAW device has the advantages of high working frequency, low insertion loss, high frequency selection characteristic, high power capacity, strong antistatic capability and the like, and is an optimal solution for the radio frequency front end in the future.
In the traditional single metal electrode resonator structure, the device performance depends on the acoustic and electrical characteristics of a single metal material, and the ideal electrode material has the characteristics of high acoustic impedance, low resistivity, low density and the like, so that the optimal values of the characteristics are different from those of a certain metal material, and the metal material Mo which is the most used as an electrode at present also has relatively moderate acoustic impedance, resistivity and density, so that the effective electromechanical coupling coefficient is relatively reduced, and the application of the electrode material in a 5G high-frequency broadband filter is limited. In the prior art, sc doping is mainly carried out in AlN of a piezoelectric film layer to obtain Sc x Al (1-x) N(x>0) So that the piezoelectric coefficient e of the piezoelectric film layer 33 And relative dielectric constant epsilon r Increase of rigidity coefficient c 33 Decrease and thereby increase the piezoelectric strain constant d of the piezoelectric thin film layer 33 And a piezoelectric coupling coefficient k t 2 The element doping reduces the Young modulus of the piezoelectric film, reduces the longitudinal sound velocity and the temperature stability of the piezoelectric film, increases the dielectric loss, and increases the manufacturing cost due to the doping of elements such as Sc and the like which are expensive rare earth elements, and the element segregation also reduces the uniformity of the piezoelectric film.
Therefore, providing a new method for manufacturing a bulk acoustic wave resonator is a technical problem to be solved by those skilled in the art.
Disclosure of Invention
In view of the above-mentioned drawbacks of the prior art, an object of the present invention is to provide a method for manufacturing a bulk acoustic wave resonator, which is used for solving the problems of complex manufacturing process and high cost of the bulk acoustic wave resonator in the prior art.
To achieve the above and other related objects, the present invention provides a method for manufacturing a bulk acoustic wave resonator, comprising the steps of:
providing a first substrate, and forming a piezoelectric film layer on the first substrate;
forming a first electrode on the piezoelectric thin film layer, wherein the first electrode comprises a plurality of laminated metal layers, and the acoustic impedance of the metal layer in contact with the piezoelectric thin film layer in the first electrode is larger than that of the metal layer not in contact with the piezoelectric thin film layer;
forming a support layer covering the first electrode on the piezoelectric film layer and the first electrode, and patterning the support layer to form an opening exposing the first electrode;
providing a second substrate, bonding one side of the support layer away from the piezoelectric film layer with the second substrate, and removing the first substrate;
Forming a second electrode on one side of the piezoelectric film layer far away from the second substrate, wherein the second electrode comprises a plurality of laminated metal layers, the layers of the second electrode and the first electrode are the same, and the material lamination sequence of the second electrode and the first electrode is in mirror symmetry;
and forming a first electrode pad and a second electrode pad on one side of the piezoelectric film layer far away from the second substrate, wherein the first electrode pad penetrates through the piezoelectric film layer to be electrically connected with the first electrode, and the second electrode pad is electrically connected with the second electrode.
Optionally, the material of the first electrode includes at least two of Au, ag, ru, W, mo, ir, al, pt, nb, hf.
Optionally, the first electrode includes a tungsten metal layer and a molybdenum metal layer stacked, and the tungsten metal layer is in contact with the piezoelectric thin film layer.
Optionally, the thickness of the first electrode is not more than 0.3um.
Optionally, the material of the piezoelectric film layer comprises Al x Ga (1-x) N(0<x<1)、Sc x Al (1-x) N(0<x<1)、AlN、PZT、LiNbO 3 、ZnO、PbTiO 3 At least one of them.
The invention also provides a manufacturing method of the bulk acoustic wave resonator, which comprises the following steps:
providing a first substrate, and forming a piezoelectric film layer on the first substrate;
Forming a first electrode on the piezoelectric thin film layer, wherein the first electrode comprises a plurality of laminated metal layers, and the acoustic impedance of the metal layer in contact with the piezoelectric thin film layer in the first electrode is larger than that of the metal layer not in contact with the piezoelectric thin film layer;
forming a barrier layer covering the first electrode on the piezoelectric film layer, forming a sacrificial layer on the barrier layer, and overlapping the sacrificial layer with the first electrode in the horizontal direction;
forming a supporting layer on the barrier layer, wherein the supporting layer covers the sacrificial layer;
providing a second substrate, bonding one side of the support layer away from the piezoelectric film layer with the second substrate, and removing the first substrate;
forming a second electrode on one side of the piezoelectric film layer far away from the second substrate, wherein the second electrode comprises a plurality of laminated metal layers, the layers of the second electrode and the first electrode are the same, and the material lamination sequence of the second electrode and the first electrode is in mirror symmetry;
forming a first electrode pad and a second electrode pad on one side of the piezoelectric film layer far away from the second substrate, wherein the first electrode pad penetrates through the piezoelectric film layer to be electrically connected with the first electrode, and the second electrode pad is electrically connected with the second electrode;
And removing the sacrificial layer to form a cavity.
Optionally, the material of the first electrode includes at least two of Au, ag, ru, W, mo, ir, al, pt, nb, hf.
Optionally, the first electrode includes a tungsten metal layer and a molybdenum metal layer stacked, and the tungsten metal layer is in contact with the piezoelectric thin film layer.
Optionally, the thickness of the first electrode is not more than 0.3um.
Optionally, the material of the piezoelectric film layer comprises Al x Ga (1-x) N(0<x<1)、Sc x Al (1-x) N(0<x<1)、AlN、PZT、LiNbO 3 、ZnO、PbTiO 3 At least one of them.
The invention also provides a manufacturing method of the bulk acoustic wave resonator, which comprises the following steps:
providing a first substrate, and forming a piezoelectric film layer on the first substrate;
forming a first electrode on the piezoelectric thin film layer, wherein the first electrode comprises a plurality of laminated metal layers, and the acoustic impedance of the metal layer in contact with the piezoelectric thin film layer in the first electrode is larger than that of the metal layer not in contact with the piezoelectric thin film layer;
forming a Bragg reflection layer covering the first electrode on the piezoelectric film layer and the first electrode;
forming a dielectric layer on the Bragg reflection layer, and flattening the dielectric layer;
providing a second substrate, bonding one side of the dielectric layer away from the piezoelectric film layer with the second substrate, and removing the first substrate;
Forming a second electrode on one side of the piezoelectric film layer far away from the second substrate, wherein the second electrode comprises a plurality of laminated metal layers, the layers of the second electrode and the first electrode are the same, and the material lamination sequence of the second electrode and the first electrode is in mirror symmetry;
and forming a first electrode pad and a second electrode pad on one side of the piezoelectric film layer far away from the second substrate, wherein the first electrode pad penetrates through the piezoelectric film layer to be electrically connected with the first electrode, and the second electrode pad is electrically connected with the second electrode.
Optionally, the material of the first electrode includes at least two of Au, ag, ru, W, mo, ir, al, pt, nb, hf.
Optionally, the first electrode includes a tungsten metal layer and a molybdenum metal layer stacked, and the tungsten metal layer is in contact with the piezoelectric thin film layer.
Optionally, the thickness of the first electrode is not more than 0.3um.
Optionally, the pressingThe material of the electric film layer comprises Al x Ga (1-x) N(0<x<1)、Sc x Al (1-x) N(0<x<1)、AlN、PZT、LiNbO 3 、ZnO、PbTiO 3 At least one of them.
Optionally, the bragg reflection layer includes alternately stacked low acoustic impedance material layers and high acoustic impedance material layers, the material of the low acoustic impedance material layers includes one or more of AlN, si3N4 or SiO2, and the material of the high acoustic impedance material layers includes one or more of W, mo, pt, au, ni or Ir.
As described above, the method for manufacturing the bulk acoustic wave resonator of the invention increases the deposition times of the electrode metal layers, and the acoustic impedance of the metal layers which are in contact with the piezoelectric film layers in the first electrode and the second electrode is larger than that of the metal layers which are not in contact with the piezoelectric film layers, namely, the acoustic impedance of the metal layers is larger than that of the metal layers which are not in contact with the piezoelectric film layers, so that the transmission coefficient of sound intensity can be reduced, more sound energy can be forced to enter the piezoelectric film layers, thereby increasing the acoustic energy in the piezoelectric materials, improving the effective electromechanical coupling coefficient, improving the performance of the bulk acoustic wave resonator, and having the advantages of simple and reliable process.
Drawings
Fig. 1 is a process flow chart of a method for manufacturing a bulk acoustic wave resonator according to a first embodiment of the present invention.
Fig. 2 is a schematic diagram illustrating a piezoelectric thin film layer formed on a first substrate according to an embodiment of the invention.
Fig. 3 is a schematic diagram illustrating formation of a first electrode on a piezoelectric thin film layer according to an embodiment of the invention.
Fig. 4 is a schematic diagram illustrating a support layer formed on a piezoelectric thin film layer according to an embodiment of the invention.
Fig. 5 is a schematic view illustrating forming an opening in a support layer according to a first embodiment of the invention.
Fig. 6 is a schematic diagram of bonding a support layer to a second substrate according to a first embodiment of the invention.
Fig. 7 is a schematic view of removing a first substrate according to a first embodiment of the invention.
Fig. 8 is a schematic diagram illustrating formation of a second electrode on a side of the piezoelectric thin film layer away from the second substrate according to an embodiment of the invention.
Fig. 9 is a schematic view illustrating formation of a first electrode via in accordance with a first embodiment of the present invention.
Fig. 10 is a schematic view showing the formation of a first electrode pad and a second electrode pad in the first embodiment of the present invention.
Fig. 11 shows a schematic diagram of the propagation of sound waves in three dielectric layers.
Fig. 12 is a graph showing the change in transmittance obtained by changing the impedance of the intermediate layer without changing the impedance of the dielectric layers defining both sides in fig. 11.
Fig. 13 shows an impedance spectrum obtained by simulation in the first embodiment of the present invention.
Fig. 14 shows an impedance spectrum obtained by simulation in the comparative example of the present invention.
Fig. 15 is a process flow chart of a method for manufacturing a bulk acoustic wave resonator according to a second embodiment of the present invention.
Fig. 16 is a schematic view showing a piezoelectric thin film layer formed on a first substrate according to a second embodiment of the invention.
Fig. 17 is a schematic diagram illustrating formation of a first electrode on a piezoelectric thin film layer according to a second embodiment of the invention.
Fig. 18 is a schematic view showing formation of a barrier layer and a sacrificial layer in a second embodiment of the present invention.
Fig. 19 is a schematic view showing formation of a supporting layer in a second embodiment of the invention.
Fig. 20 is a schematic diagram of bonding a support layer to a second substrate according to a second embodiment of the invention.
Fig. 21 is a schematic view illustrating removal of a first substrate in a second embodiment of the invention.
Fig. 22 is a schematic diagram illustrating formation of a second electrode on a side of the piezoelectric thin film layer away from the second substrate in the second embodiment of the present invention.
Fig. 23 is a schematic view showing formation of a first electrode pad and a second electrode pad in a second embodiment of the present invention.
Fig. 24 is a schematic diagram illustrating removal of a sacrificial layer according to a second embodiment of the invention.
Fig. 25 is a process flow chart of a method for manufacturing a bulk acoustic wave resonator according to a third embodiment of the present invention.
Fig. 26 is a schematic diagram illustrating formation of a piezoelectric thin film layer on a first substrate according to a third embodiment of the present invention.
Fig. 27 is a schematic diagram illustrating formation of a first electrode on a piezoelectric thin film layer according to a third embodiment of the invention.
Fig. 28 is a schematic view showing formation of a supporting layer in the third embodiment of the present invention.
Fig. 29 is a schematic view showing the formation of a bragg reflection layer in the third embodiment of the present invention.
Fig. 30 is a schematic diagram illustrating formation of a dielectric layer according to a third embodiment of the present invention.
Fig. 31 is a schematic diagram of bonding a dielectric layer to a second substrate in a third embodiment of the present invention.
Fig. 32 is a schematic diagram showing the removal of the first substrate and the formation of the second electrode on the side of the piezoelectric film layer away from the second substrate in the third embodiment of the present invention.
Fig. 33 is a schematic view showing the formation of a first electrode pad and a second electrode pad in the third embodiment of the present invention.
Description of element reference numerals
1. A first substrate
2. Piezoelectric thin film layer
200. Opening of piezoelectric film layer
3. First electrode
300. Tungsten metal layer
301. Molybdenum metal layer
302. First electrode through hole
303. First electrode pad
4. Support layer
400. An opening
5. A second substrate
6. Cavity cavity
7. Second electrode
700. Tungsten metal layer
701. Molybdenum metal layer
702. Second electrode pad
8. Barrier layer
9. Sacrificial layer
10. Bragg reflection layer
1000. High acoustic impedance material layer
1001. Low acoustic impedance material layer
11. Dielectric layer
S1-S8 steps
Detailed Description
Other advantages and effects of the present invention will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present invention with reference to specific examples. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention.
Please refer to fig. 1 to 33. It should be noted that, the illustrations provided in the present embodiment are merely schematic illustrations of the basic concepts of the present invention, and only the components related to the present invention are shown in the illustrations, rather than being drawn according to the number, shape and size of the components in actual implementation, and the form, number and proportion of each component in actual implementation may be arbitrarily changed, and the layout of the components may be more complex.
Example 1
The embodiment provides a method for manufacturing a bulk acoustic wave resonator, please refer to fig. 1, which shows a process flow chart of the method for manufacturing the bulk acoustic wave resonator, comprising the following steps:
providing a first substrate, and forming a piezoelectric film layer on the first substrate:
forming a first electrode on the piezoelectric thin film layer, wherein the first electrode comprises a plurality of laminated metal layers, and the acoustic impedance of the metal layer in contact with the piezoelectric thin film layer in the first electrode is larger than that of the metal layer not in contact with the piezoelectric thin film layer;
forming a support layer covering the first electrode on the piezoelectric film layer and the first electrode, and patterning the support layer to form an opening exposing the first electrode;
Providing a second substrate, bonding one side of the support layer away from the piezoelectric film layer with the second substrate, and removing the first substrate;
forming a second electrode on one side of the piezoelectric film layer far away from the second substrate, wherein the second electrode comprises a plurality of laminated metal layers, the layers of the second electrode and the first electrode are the same, and the material lamination sequence of the second electrode and the first electrode is in mirror symmetry;
and forming a first electrode pad and a second electrode pad on one side of the piezoelectric film layer far away from the second substrate, wherein the first electrode pad penetrates through the piezoelectric film layer to be electrically connected with the first electrode, and the second electrode pad is electrically connected with the second electrode.
First, referring to fig. 2, step S1 is performed: a first substrate 1 is provided, and a piezoelectric thin film layer 2 is formed on the first substrate 1.
As an example, the material of the first substrate 1 includes, but is not limited to, single crystal silicon, SOI substrate, silicon carbide, sapphire, gallium nitride, or the like; in this embodiment, the first substrate 1 is preferably a monocrystalline silicon substrate.
By way of example, the piezoelectric thin film layer 2 is formed on the first substrate 1 by physical vapor deposition, chemical vapor deposition, spin coating, or other suitable method, and the material of the piezoelectric thin film layer 2 includes AlN, al x Ga (1-x) N(0<x<1)、Sc x Al (1-x) N(0<x<1)、PZT、LiNbO 3 、ZnO、PbTiO 3 The thickness of the single layer is not less than 0.1um, and the total thickness is not more than 2um; in this embodiment, the piezoelectric thin film layer 2 is preferably a single crystal AlN layer.
Next, referring to fig. 3, step S2 is performed: a first electrode 3 is formed on the piezoelectric thin film layer 2, the first electrode 3 includes a plurality of stacked metal layers, and the acoustic impedance of the metal layer in contact with the piezoelectric thin film layer 2 in the first electrode 3 is larger than that of the metal layer not in contact with the piezoelectric thin film layer 2.
As an example, a stacked metal material layer is formed on the piezoelectric thin film layer 2 by a chemical vapor deposition method or a physical vapor deposition method, and patterned to obtain the first electrode 3, where the number of metal layers in the first electrode 3 is not less than two, and the first electrode 3 includes at least two of Au (gold), ag (silver), ru (ruthenium), W (tungsten), mo (molybdenum), ir (iridium), al (aluminum), pt (platinum), nb (niobium), and Hf (hafnium), and may be other suitable materials; the thickness of the first electrode 3 is not more than 0.3um, for example, may be 0.1um, 0.15um, 0.2um, 0.25um, 0.3um, etc., and in the case of satisfying the performance of the bulk acoustic wave resonator, the thickness thereof may be selected according to practical situations, wherein the thickness of each metal layer in the first electrode 3 is not more than 100nm.
Specifically, in the present embodiment, the first electrode 3 includes a tungsten metal layer 300 and a molybdenum metal layer 301 stacked, wherein the tungsten metal layer 300 is in contact with the piezoelectric thin film layer 2.
Next, referring to fig. 4 to 5, step S3 is performed: a support layer 4 is formed on the piezoelectric thin film layer 2 and the first electrode 3 to cover the first electrode 3, and the support layer 4 is patterned to form an opening 400 exposing the first electrode 3.
As an example, as shown in fig. 4, the support layer 4 is formed by deposition, and the support layer 4 material includes, but is not limited to, siO 2 After forming the support layer 4, the method further comprises a step of flattening the surface of the support layer 4 by adopting a chemical mechanical polishing method or a bonding layer deposition method.
As an example, as shown in fig. 5, the support layer 4 is patterned using an etching method or other suitable method to form the opening 400.
Next, referring to fig. 6 to 7, step S4 is performed: a second substrate 5 is provided, a side of the support layer 4 remote from the piezoelectric thin film layer 2 is bonded to the second substrate 5, and the first substrate 1 is removed.
As an example, the material of the second substrate 5 includes, but is not limited to, single crystal silicon, SOI substrate, silicon carbide, sapphire, gallium nitride, or the like; preferably, in order to increase the bonding power, bonding can be performed on the second substrate 5 Depositing a bonding layer consisting of, but not limited to Si, siN, PSG or SiO 2 And the like.
As an example, the method of removing the first substrate 1 includes, but is not limited to, ion implantation delamination, wet etching, dry etching, etc., and the selected method cannot cause loss to the crystal lattice of the piezoelectric thin film layer 2 or can be repaired by high temperature annealing after the occurrence of doping damage.
As an example, the second substrate 5 and the opening 400 enclose a cavity 6.
Next, referring to fig. 8, step S5 is performed: a second electrode 7 is formed on a side of the piezoelectric thin film layer 2 away from the second substrate 5, where the second electrode 7 includes a plurality of stacked metal layers, the number of layers of the second electrode 7 is the same as that of the first electrode 3, and the material stacking sequence of the second electrode 7 and the first electrode 3 is mirror symmetry.
As an example, the acoustic impedance of the metal layer of the second electrode 7 that is in contact with the piezoelectric thin film layer 2 is larger than that of the metal layer that is not in contact with the piezoelectric thin film layer 2, and the second electrode 7 includes at least two of Au (gold), ag (silver), ru (ruthenium), W (tungsten), mo (molybdenum), ir (iridium), al (aluminum), pt (platinum), nb (niobium), hf (hafnium), and may be other suitable materials; the thickness of the second electrode 7 is not more than 0.3um, for example, may be 0.1um, 0.15um, 0.2um, 0.25um, 0.3um, etc., and in the case of satisfying the performance of the bulk acoustic wave resonator, the thickness thereof may be selected according to practical situations.
Specifically, the material, thickness and lamination sequence of the second electrode 7 and the first electrode 3 are mirror symmetrical with respect to the piezoelectric thin film layer 2, and in this embodiment, the second electrode 7 includes a laminated tungsten metal layer 700 and a molybdenum metal layer 701, where the tungsten metal layer 700 is in contact with the piezoelectric thin film layer 2.
Next, referring to fig. 9 to 10, step S6 is performed: a first electrode pad 303 and a second electrode pad 702 are formed on a side of the piezoelectric thin film layer 2 away from the second substrate 5, the first electrode pad 303 penetrates through the piezoelectric thin film layer 2 to be electrically connected with the first electrode 3, and the second electrode pad 702 is electrically connected with the second electrode 7.
As an example, as shown in fig. 9, before forming the first electrode pad 303 and the second electrode pad 702, a step of forming a first electrode via 302 in the piezoelectric thin film layer 2 is further included, where the first electrode via 302 is used for electrically connecting the first electrode pad 303 with the first electrode 3 through the piezoelectric thin film layer 2, and a method of forming the first electrode via 302 includes, but is not limited to, dry etching or wet etching.
As an example, as shown in fig. 10, the process of forming the first electrode pad 303 and the second electrode pad 702 includes a thin film deposition and patterning process, and the first electrode pad 303 and the second electrode pad 702 should be formed of a material selected to have high adhesion, high conductivity, and oxidation resistance, and one or a combination of several metals or metalloids including, but not limited to, ti, al, au, cu or TiN, preferably a combination of Ti and Au may be used.
As an example, compared with a conventional single molybdenum electrode resonator, the first electrode 3 adopts a single molybdenum metal layer, the second electrode 7 adopts a single molybdenum metal layer, the acoustic reflection interface includes an interface between a piezoelectric thin film layer and an electrode and an interface between an electrode and air, in this application, the first electrode 3 and the second electrode 7 adopt a mode of stacking multiple metal layers, and the acoustic reflection interface includes an interface between a piezoelectric thin film layer and an electrode, an interface between an electrode and air, and an interface between adjacent metal layers in the electrode, and by adjusting acoustic impedances of different metal layers, distribution of acoustic energy in a resonance region is changed, thereby effectively adjusting electromechanical coupling efficiency.
Specifically, as shown in fig. 11, a propagation schematic diagram of sound waves incident into three dielectric layers is shown, a plane wave in the medium 1 is normally incident on the interface, and according to the generalized ray method and impedance transmission, the transmission coefficient of the sound intensity can be obtained as follows:
wherein z is 1 、z 2 、z 3 Characteristic impedance (acoustic impedance), k, of medium 1, medium 2 and medium 3, respectively 2 ＝w/c 2 Is the beam of the intermediate layer (medium 2) and d is the thickness of the intermediate layer (medium 2), it can be seen that the transmission coefficient is related to the frequency and the thickness of the intermediate layer. Thickness, k, of wavelength normalization for intermediate layer 2 d/2π＝d/λ 2 Consider the case where the characteristic impedances of medium 1 and medium 3 differ significantly:
(1) When z 2 ＝z 3 Or z 2 ＝z 1 The transmission coefficient of sound intensity corresponds to d=0 (single interface), which is:
i.e. the transmission coefficient does not vary with thickness and frequency;
(2) When z 2 In z 1 And z 3 When the thickness is not equal to integral multiple of half wavelength, the transmission coefficient of the intermediate layer is increasedWhen the transmission coefficient is maximum;
(3) When z 2 Not at z 1 And z 3 In the case of the intermediate layer, the transmission coefficient is reduced by the intermediate layer as long as the thickness is not equal to an integer multiple of half wavelength.
Specifically, take z 1 ＝1，z 3 ＝10，z 2 The change patterns of the sound intensity transmission coefficients obtained by taking 0.2, 0.5, 1, 2, 3.16, 5, 10, 20 and 50 respectively are shown in figure 12, when z 2 When 1 or 10 is taken, i.e. z 2 ＝z 3 Or z 2 ＝z 1 The transmission coefficient does not change; when z 2 When 2, 3.16 or 5 is taken, i.e. z 2 In z 1 And z 3 Between, the transmission coefficient increases; when z 2 When 0.2, 0.5, 20 or 50 is taken, i.e. z 2 Not at z 1 And z 3 And the transmission coefficient decreases. In the present invention, the piezoelectric thin film layer 1 is an AlN layer, the first electrode 3 is a tungsten metal layer 300 and a molybdenum metal layer 301 which are laminated, and the second electrode 7 is a layerA stack of tungsten metal layer 700 and molybdenum metal layer 701, wherein z AlN ＝33.7，z w ＝105.6，z Mo = 66.42, i.e. by disposing the tungsten metal layer 300 between the piezoelectric thin film layer 2 and the molybdenum metal layer 301 in the first electrode 3, and by disposing the tungsten metal layer 600 between the piezoelectric thin film layer 2 and the molybdenum metal layer 701 in the second electrode 7, the transmittance is reduced as long as the thicknesses of the tungsten metal layer 300 and the tungsten metal layer 700 are not equal to an integer multiple of half wavelength, since the characteristic impedance (acoustic impedance) of W is not between AlN and Mo; for the piezoelectric resonator, the sound intensity partially resides outside the piezoelectric material in the form of a stress field, so that the electromechanical coupling is reduced, therefore, on the basis of a Mo single electrode, the W is inserted between AlN and Mo to reduce the sound intensity transmission coefficient, so that more sound energy is forced to enter the piezoelectric film layer, thereby increasing the acoustic energy in the piezoelectric material, increasing the electromechanical coupling and improving the working passband width of the filter.
Specifically, in the present embodiment, a 300nm thick AlN layer is used for the piezoelectric thin film layer 2, a 60nm thick tungsten metal layer 300 and a 61.1nm thick molybdenum metal layer 301 are used for the first electrode 3, a 60nm thick tungsten metal layer 700 and a 61.1nm thick molybdenum metal layer 701 are used for the second electrode 7, and the impedance spectrum obtained by simulation is shown in FIG. 13, and the series resonance frequency f s At a parallel resonance frequency f of 5.001GHZ p 5.175GHZ; in the prior art, a single-layer molybdenum metal electrode is taken as a comparative example, a 300 nm-thick AlN layer is adopted for the piezoelectric film layer 1, a 160.4 nm-thick molybdenum metal layer is adopted for the first electrode 3, a 160.4 nm-thick molybdenum metal layer is adopted for the second electrode 7, and an impedance spectrum obtained by simulation is shown in figure 14, and the series resonance frequency f is shown in the figure s At a parallel resonance frequency f of 5.001GHZ p For 5.154GHZ, according to the calculation formula of the effective electromechanical coupling coefficient:
it can be obtained that the effective electromechanical coupling coefficient of the bulk acoustic wave resonator of the inventionAn effective electromechanical coupling coefficient of the bulk acoustic wave resonator in the comparative example +.>The mechanical-electrical coupling property can be increased and the performance can be improved by inserting W between AlN and Mo at 7.1%.
In addition, the thickness of the fixed electrode is that the first electrode 3 adopts a tungsten metal layer 300 with the thickness of 60nm and a molybdenum metal layer 301 with the thickness of 60nm, and the second electrode 7 adopts a tungsten metal layer 700 with the thickness of 60nm and a molybdenum metal layer 701 with the thickness of 60nm, and the simulation is carried out to obtain the series resonance frequency f s For 5.017GHZ, parallel resonance frequency f p For 5.191GHZ, effective electromechanical coupling coefficient7.99%; in the comparative example, the first electrode 3 was a 120nm thick molybdenum metal layer, and the second electrode 7 was a 120nm thick molybdenum metal layer, and the series resonance frequency f was obtained by simulation s For 5.869GHZ, parallel resonance frequency f p An effective electromechanical coupling coefficient of 6.062GHZ +.>It was found that the insertion of W between AlN and Mo was 7.57%, and the electromechanical coupling was increased to improve the performance.
As an example, the existence of the cavity 6 exposes the lower surface of the first electrode 3 to the cavity 6, that is, the lower area of the effective working area of the resonator is exposed to the cavity 6, so that the dissipation of acoustic wave energy during the operation of the resonator is reduced, and key indexes such as the effective electromechanical coupling coefficient and the quality factor Q value of the bulk acoustic wave resonator are further improved, so that the operation passband width or the out-of-band rejection capability of the filter are improved.
As described above, in the method for manufacturing a bulk acoustic wave resonator according to this embodiment, by increasing the number of times of depositing the metal layers of the electrodes, the acoustic impedance of the metal layer in contact with the piezoelectric thin film layer in the first electrode and the second electrode is larger than that of the metal layer not in contact with the piezoelectric thin film layer, that is, the acoustic impedance of the metal layer is larger than that of the piezoelectric thin film layer, so that the transmission coefficient of sound intensity can be reduced, more acoustic energy can be forced to enter the piezoelectric thin film layer, thereby increasing the acoustic energy in the piezoelectric material, improving the effective electromechanical coupling coefficient, and improving the performance of the bulk acoustic wave resonator.
Example two
The embodiment provides a method for manufacturing a bulk acoustic wave resonator, please refer to fig. 15, which shows a process flow chart of the method for manufacturing the bulk acoustic wave resonator, comprising the following steps:
s1: providing a first substrate, and forming a piezoelectric film layer on the first substrate;
s2: forming a first electrode on the piezoelectric thin film layer, wherein the first electrode comprises a plurality of laminated metal layers, and the acoustic impedance of the metal layer in contact with the piezoelectric thin film layer in the first electrode is larger than that of the metal layer not in contact with the piezoelectric thin film layer;
s3: forming a barrier layer covering the first electrode on the piezoelectric film layer, forming a sacrificial layer on the barrier layer, and overlapping the barrier layer with the first electrode in the horizontal direction;
s4: forming a supporting layer on the barrier layer, wherein the supporting layer covers the sacrificial layer;
s5: providing a second substrate, bonding one side of the support layer away from the piezoelectric film layer with the second substrate, and removing the first substrate;
s6: forming a second electrode on one side of the piezoelectric film layer far away from the second substrate, wherein the second electrode comprises a plurality of laminated metal layers, the layers of the second electrode and the first electrode are the same, and the material lamination sequence of the second electrode and the first electrode is in mirror symmetry;
S7: forming a first electrode pad and a second electrode pad on one side of the piezoelectric film layer far away from the second substrate, wherein the first electrode pad penetrates through the piezoelectric film layer to be electrically connected with the first electrode, and the second electrode pad is electrically connected with the second electrode;
s8: and removing the sacrificial layer to form a cavity.
First, referring to fig. 16, step S1 is performed: a first substrate 1 is provided, and a piezoelectric thin film layer 2 is formed on the first substrate 1.
As an example, the material of the first substrate 1 includes, but is not limited to, single crystal silicon, SOI substrate, silicon carbide, sapphire, gallium nitride, or the like; in this embodiment, the first substrate 1 is preferably a monocrystalline silicon substrate.
By way of example, the piezoelectric thin film layer 2 is formed on the first substrate 1 by physical vapor deposition, chemical vapor deposition, spin coating, or other suitable method, and the material of the piezoelectric thin film layer 1 includes AlN, al x Ga (1-x) N(0<x<1)、Sc x Al (1-x) N(0<x<1)、PZT、LiNbO 3 、ZnO、PbTiO 3 The thickness of the single layer is not less than 0.1um, and the total thickness is not more than 2um; in this embodiment, the piezoelectric thin film layer 2 is preferably a single crystal AlN layer.
Next, referring to fig. 17, step S2 is performed: a first electrode 3 is formed on the piezoelectric thin film layer 2, the first electrode 3 includes a plurality of stacked metal layers, and the acoustic impedance of the metal layer in contact with the piezoelectric thin film layer 2 in the first electrode 3 is larger than that of the metal layer not in contact with the piezoelectric thin film layer 2.
As an example, a stacked metal material layer is formed on the piezoelectric thin film layer 2 by a chemical vapor deposition method or a physical vapor deposition method, and patterned to obtain the first electrode 3, where the number of metal layers in the first electrode 3 is not less than two, and the first electrode 3 includes at least two of Au (gold), ag (silver), ru (ruthenium), W (tungsten), mo (molybdenum), ir (iridium), al (aluminum), pt (platinum), nb (niobium), and Hf (hafnium), and may be other suitable materials; the thickness of the first electrode 3 is not more than 0.3um, for example, may be 0.1um, 0.15um, 0.2um, 0.25um, 0.3um, etc., and in the case of satisfying the performance of the bulk acoustic wave resonator, the thickness thereof may be selected according to practical situations, wherein the thickness of each metal layer in the first electrode 3 is not more than 100nm.
Specifically, in the present embodiment, the first electrode 3 includes a tungsten metal layer 300 and a molybdenum metal layer 301 stacked, wherein the tungsten metal layer 300 is in contact with the piezoelectric thin film layer 2.
Next, referring to fig. 18, step S3 is performed: a barrier layer 8 is formed on the piezoelectric thin film layer 2 to cover the first electrode 3, a sacrificial layer 9 is formed on the barrier layer 8, and the sacrificial layer 9 overlaps the first electrode 3 in the horizontal direction.
As an example, the barrier layer 8 is formed by a deposition process, the barrier layer 8 also covers the exposed upper surface of the piezoelectric film layer 2, the material of the barrier layer 8 includes SiN, and the barrier layer 8 is used for protecting the first electrode 3 and the piezoelectric film layer 2 when the sacrificial layer 9 is removed by subsequent release.
As an example, the sacrificial layer 9 is formed by a deposition process and an etching process, and the material of the sacrificial layer 9 includes Si or SiO 2 Wherein at least a portion of the sacrificial layer 9 is located directly above the first electrode 3.
Next, referring to fig. 19, step S4 is performed: a support layer 4 is formed on the barrier layer 8, the support layer 4 covering the sacrificial layer 9.
As an example, the material of the supporting layer 4 is Si 3 N 4 The material of SiN or amorphous AlN, etc. having a large difference in performance from the sacrificial layer 9, makes the sacrificial layer 9 not react with the support layer 4 when the sacrificial layer 9 is removed by subsequent release with a release liquid or release gas.
As an example, after forming the support layer 4, the method further includes a step of planarizing the upper surface of the support layer 4 by using a chemical mechanical polishing process.
Next, referring to fig. 20 to 21, step S5 is performed: a second substrate 5 is provided, a side of the support layer 4 remote from the piezoelectric thin film layer 2 is bonded to the second substrate 5, and the first substrate 1 is removed.
As an example, the material of the second substrate 5 includes, but is not limited to, single crystal silicon, SOI substrate, silicon carbide, sapphire, gallium nitride, or the like; preferably, in order to increase the bonding power, a bonding layer may be deposited on the bonding surface of the second substrate 5, and the bonding layer is formed of a material including, but not limited to, si, siN, or PSG.
As an example, the method of removing the first substrate 1 includes, but is not limited to, ion implantation delamination, wet etching, dry etching, etc., and the selected method cannot cause loss to the crystal lattice of the piezoelectric thin film layer 2 or can be repaired by high temperature annealing after the occurrence of doping damage.
Next, referring to fig. 22, step S6 is performed: a second electrode 7 is formed on a side of the piezoelectric thin film layer 2 away from the second substrate 5, where the second electrode 7 includes a plurality of stacked metal layers, the number of layers of the second electrode 7 is the same as that of the first electrode 3, and the material stacking sequence of the second electrode 7 and the first electrode 3 is mirror symmetry.
As an example, the acoustic impedance of the metal layer of the second electrode 7 that is in contact with the piezoelectric thin film layer 2 is larger than that of the metal layer that is not in contact with the piezoelectric thin film layer 2, and the second electrode 7 includes at least two of Au (gold), ag (silver), ru (ruthenium), W (tungsten), mo (molybdenum), ir (iridium), al (aluminum), pt (platinum), nb (niobium), hf (hafnium), and may be other suitable materials; the thickness of the second electrode 7 is not more than 0.3um, for example, may be 0.1um, 0.15um, 0.2um, 0.25um, 0.3um, etc., and in the case of satisfying the performance of the bulk acoustic wave resonator, the thickness thereof may be selected according to practical situations.
Specifically, the material, thickness and lamination sequence of the second electrode 7 and the first electrode 3 are mirror symmetrical with respect to the piezoelectric thin film layer 2, and in this embodiment, the second electrode 7 includes a laminated tungsten metal layer 700 and a molybdenum metal layer 701, where the tungsten metal layer 700 is in contact with the piezoelectric thin film layer 2.
Next, referring to fig. 23, step S7 is performed: a first electrode pad 303 and a second electrode pad 702 are formed on a side of the piezoelectric thin film layer 2 away from the second substrate 5, the first electrode pad 303 penetrates through the piezoelectric thin film layer 2 to be electrically connected with the first electrode 3, and the second electrode pad 702 is electrically connected with the second electrode 7.
As an example, before forming the first electrode pad 303 and the second electrode pad 702, a step of forming a first electrode via in the piezoelectric thin film layer 2, the first electrode via being used for the first electrode pad 303 to be electrically connected with the first electrode 3 through the piezoelectric thin film layer 2, a method of forming the first electrode via including, but not limited to, dry etching or wet etching; the process of forming the first electrode pad 303 and the second electrode pad 702 includes a thin film deposition and patterning process, and the first electrode pad 303 and the second electrode pad 702 should be formed of a material having high adhesion, high conductivity, and oxidation resistance, and may be formed using one or a combination of several metals or metalloids including, but not limited to, ti, al, au, cu or TiN, preferably a combination of Ti and Au.
Next, referring to fig. 24, step S8 is performed: the sacrificial layer 9 is removed to form the cavity 6.
As an example, before removing the sacrificial layer 9, a release hole (not shown) for forming the sacrificial layer 9 is further included, and the etching solution etches the sacrificial layer 9 through the release hole to form the cavity 6.
As described above, in the method for manufacturing a bulk acoustic wave resonator according to this embodiment, by increasing the number of times of depositing the metal layers of the electrodes, the acoustic impedance of the metal layer in contact with the piezoelectric thin film layer in the first electrode and the second electrode is larger than that of the metal layer not in contact with the piezoelectric thin film layer, that is, the acoustic impedance of the metal layer is larger than that of the piezoelectric thin film layer, so that the transmission coefficient of sound intensity can be reduced, more acoustic energy can be forced to enter the piezoelectric thin film layer, thereby increasing the acoustic energy in the piezoelectric material, improving the effective electromechanical coupling coefficient, and improving the performance of the bulk acoustic wave resonator.
Example III
The embodiment provides a method for manufacturing a bulk acoustic wave resonator, please refer to fig. 25, which shows a process flow chart of the method for manufacturing the bulk acoustic wave resonator, comprising the following steps:
s1: providing a first substrate, and forming a piezoelectric film layer on the first substrate;
S2: forming a first electrode on the piezoelectric thin film layer, wherein the first electrode comprises a plurality of laminated metal layers, and the acoustic impedance of the metal layer in contact with the piezoelectric thin film layer in the first electrode is larger than that of the metal layer not in contact with the piezoelectric thin film layer;
s3: forming a Bragg reflection layer covering the first electrode on the piezoelectric film layer and the first electrode;
s4: forming a dielectric layer on the Bragg reflection layer, and flattening the dielectric layer;
s5: providing a second substrate, bonding one side of the dielectric layer away from the piezoelectric film layer with the second substrate, and removing the first substrate;
s6: forming a second electrode on one side of the piezoelectric film layer far away from the second substrate, wherein the second electrode comprises a plurality of laminated metal layers, the layers of the second electrode and the first electrode are the same, and the material lamination sequence of the second electrode and the first electrode is in mirror symmetry;
s7: and forming a first electrode pad and a second electrode pad on one side of the piezoelectric film layer far away from the second substrate, wherein the first electrode pad penetrates through the piezoelectric film layer to be electrically connected with the first electrode, and the second electrode pad is electrically connected with the second electrode.
First, referring to fig. 26, step S1 is performed: a first substrate 1 is provided, and a piezoelectric thin film layer 2 is formed on the first substrate 1.
As an example, the material of the first substrate 1 includes, but is not limited to, single crystal silicon, SOI substrate, silicon carbide, sapphire, gallium nitride, or the like; in this embodiment, the first substrate 1 is preferably a monocrystalline silicon substrate.
By way of example, the piezoelectric thin film layer 2 is formed on the first substrate 1 by physical vapor deposition, chemical vapor deposition, spin coating, or other suitable method, and the material of the piezoelectric thin film layer 2 includes AlN, al x Ga (1-x) N(0<x<1)、Sc x Al (1-x) N(0<x<1)、PZT、LiNbO 3 、ZnO、PbTiO 3 The thickness of the single layer is not less than 0.1um, and the total thickness is not more than 2um; in this embodiment, the piezoelectric thin film layer 2 is preferably a single crystal AlN layer.
Next, referring to fig. 27, step S2 is performed: a first electrode 3 is formed on the piezoelectric thin film layer 2, the first electrode 3 includes a plurality of stacked metal layers, and the acoustic impedance of the metal layer in contact with the piezoelectric thin film layer 2 in the first electrode 3 is larger than that of the metal layer not in contact with the piezoelectric thin film layer 2.
As an example, a stacked metal material layer is formed on the piezoelectric thin film layer 2 by a chemical vapor deposition method or a physical vapor deposition method, and patterned to obtain the first electrode 3, where the number of metal layers in the first electrode 3 is not less than two, and the first electrode 3 includes at least two of Au (gold), ag (silver), ru (ruthenium), W (tungsten), mo (molybdenum), ir (iridium), al (aluminum), pt (platinum), nb (niobium), and Hf (hafnium), and may be other suitable materials; the thickness of the first electrode 3 is not more than 0.3um, for example, may be 0.1um, 0.15um, 0.2um, 0.25um, 0.3um, etc., and in the case of satisfying the performance of the bulk acoustic wave resonator, the thickness thereof may be selected according to practical situations, wherein the thickness of each metal layer in the first electrode 3 is not more than 100nm.
Specifically, in the present embodiment, the first electrode 3 includes a tungsten metal layer 300 and a molybdenum metal layer 301 stacked, wherein the tungsten metal layer 300 is in contact with the piezoelectric thin film layer 2.
As an example, the step of patterning the piezoelectric film layer 2 to form the piezoelectric film layer opening 200 is further included to facilitate the release of stress in the piezoelectric film layer 2 and avoid cracking of the piezoelectric film layer 2.
Next, referring to fig. 28 to 29, step S3 is performed: a bragg reflection layer 10 covering the first electrode 3 is formed on the piezoelectric thin film layer 2 and the first electrode 3.
As an example, as shown in fig. 28, before forming the bragg reflection layer 10, a step of forming a supporting layer 4 is further included, and after forming the supporting layer 4, a planarization process is performed to form a surface of the supporting layer 4The surface is flat, which is beneficial to the subsequent formation of the Bragg reflection layer 10. Specifically, the material of the supporting layer 4 is a low acoustic impedance material including AlN, si 3 N 4 Or SiO 2 Etc.
As an example, as shown in fig. 29, the bragg reflection layer 10 is formed on the supporting layer 4, the bragg reflection layer 10 includes a stack of alternating high acoustic impedance material layers 1000 and low acoustic impedance material layers 1001, the material of the high acoustic impedance material layers 1000 includes one or more of metals such as W, mo, pt, au, ni, ir, etc., and the method of forming the high acoustic impedance material layers 1000 includes a method such as magnetron sputtering or evaporation, preferably magnetron sputtering; the material of the low acoustic impedance material layer 1001 includes AlN, si 3 N 4 ，SiO 2 One or more of these materials, the method of forming the low acoustic impedance material layer 1001 includes PECVD, ICPCVD, ALD, MBE, PLD and the like, preferably ICPCVD; the thickness of each layer in the Bragg reflection layer 10 is 1/4 or 3/4 of the resonant frequency of the resonator corresponding to the wavelength of the sound wave.
Next, referring to fig. 30, step S4 is performed: a dielectric layer 11 is formed on the bragg reflection layer 10, and the dielectric layer 11 is planarized.
As an example, the dielectric layer 11 includes, but is not limited to, si, siN, PSG, or the like, and the dielectric layer 11 can protect the outermost high acoustic impedance material layer 1000 from oxidation and can protect the bragg reflection layer 10 from damage when bonded to the second substrate 5 later (see fig. 31 later). In addition, the dielectric layer 11 is subjected to planarization treatment, so that the surface of the dielectric layer 11 is flat, and the bonding power with the second substrate 5 is improved.
Next, referring to fig. 31, step S5 is performed: a second substrate 5 is provided, a side of the dielectric layer 11 remote from the piezoelectric thin film layer 2 is bonded to the second substrate 5, and the first substrate 1 is removed.
As an example, the material of the second substrate 5 includes, but is not limited to, single crystal silicon, SOI substrate, silicon carbide, sapphire, gallium nitride, or the like.
As an example, the method of removing the first substrate 1 includes, but is not limited to, ion implantation delamination, wet etching, dry etching, etc., and the selected method cannot cause loss to the crystal lattice of the piezoelectric thin film layer 2 or can be repaired by high temperature annealing after the occurrence of doping damage.
Next, referring to fig. 32, step S6 is performed: a second electrode 7 is formed on a side of the piezoelectric thin film layer 2 away from the second substrate 5, where the second electrode 7 includes a plurality of stacked metal layers, the number of layers of the second electrode 7 is the same as that of the first electrode 3, and the material stacking sequence of the second electrode 7 and the first electrode 3 is mirror symmetry.
As an example, the acoustic impedance of the metal layer of the second electrode 7 that is in contact with the piezoelectric thin film layer 2 is larger than that of the metal layer that is not in contact with the piezoelectric thin film layer 2, and the second electrode 7 includes at least two of Au (gold), ag (silver), ru (ruthenium), W (tungsten), mo (molybdenum), ir (iridium), al (aluminum), pt (platinum), nb (niobium), hf (hafnium), and may be other suitable materials; the thickness of the second electrode 7 is not more than 0.3um, for example, may be 0.1um, 0.15um, 0.2um, 0.25um, 0.3um, etc., and in the case of satisfying the performance of the bulk acoustic wave resonator, the thickness thereof may be selected according to practical situations.
Specifically, the material, thickness and lamination sequence of the second electrode 7 and the first electrode 3 are mirror symmetrical with respect to the piezoelectric thin film layer 2, and in this embodiment, the second electrode 7 includes a laminated tungsten metal layer 700 and a molybdenum metal layer 701, where the tungsten metal layer 700 is in contact with the piezoelectric thin film layer 2.
Next, referring to fig. 33, step S7 is performed: a first electrode pad 303 and a second electrode pad 702 are formed on a side of the piezoelectric thin film layer 2 away from the second substrate 5, the first electrode pad 303 penetrates through the piezoelectric thin film layer 2 to be electrically connected with the first electrode 3, and the second electrode pad 702 is electrically connected with the second electrode 7.
As an example, before forming the first electrode pad 303 and the second electrode pad 702, a step of forming a first electrode through hole in the piezoelectric thin film layer 2, the first electrode through hole being used for the first electrode pad 303 to be electrically connected with the first electrode 3 through the piezoelectric thin film layer 2, and a method of forming the first electrode through hole including, but not limited to, dry etching or wet etching; the process of forming the first electrode pad 303 and the second electrode pad 702 includes a thin film deposition and patterning process, and the first electrode pad 303 and the second electrode pad 702 should be formed of a material having high adhesion, high conductivity, and oxidation resistance, and may be formed using one or a combination of several metals or metalloids including, but not limited to, ti, al, au, cu or TiN, preferably a combination of Ti and Au.
By way of example, in the method for manufacturing the bulk acoustic wave resonator according to the embodiment, by increasing the deposition times of the metal layers of the electrodes, the acoustic impedance of the metal layer in contact with the piezoelectric thin film layer in the first electrode and the second electrode is larger than that of the metal layer not in contact with the piezoelectric thin film layer, so that the transmission coefficient of sound intensity can be reduced, more sound energy is forced to enter the piezoelectric thin film layer, thereby increasing the acoustic energy in the piezoelectric material, improving the effective electromechanical coupling coefficient, and improving the performance of the bulk acoustic wave resonator.
As an example, the bragg reflection layer 10 includes the high acoustic impedance material layer 1000 and the bottom acoustic impedance material layer 1001 which are alternately stacked, and by designing the high acoustic impedance material layer 1000 and the low acoustic impedance material layer 1001 which are alternately stacked, the mechanical acoustic wave generated by the piezoelectric thin film layer 2 can be reflected back to the piezoelectric thin film layer 2, thereby reducing the electromechanical loss and further improving the effective electromechanical coupling coefficient and the Q value of the quality factor.
In summary, in the method for manufacturing the bulk acoustic wave resonator of the present invention, by increasing the deposition times of the electrode metal layers, the acoustic impedance of the metal layer contacting the piezoelectric thin film layer in the first electrode and the second electrode is larger than that of the metal layer not contacting the piezoelectric thin film layer, that is, the acoustic impedance of the metal layer contacting the piezoelectric thin film layer is larger, so that the transmission coefficient of sound intensity can be reduced, more sound energy can be forced to enter the piezoelectric thin film layer, thereby increasing the acoustic energy in the piezoelectric material, improving the effective electromechanical coupling coefficient, and improving the performance of the bulk acoustic wave resonator. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.
The above embodiments are merely illustrative of the principles of the present invention and its effectiveness, and are not intended to limit the invention. Modifications and variations may be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the invention. Accordingly, it is intended that all equivalent modifications and variations of the invention be covered by the claims, which are within the ordinary skill of the art, be within the spirit and scope of the present disclosure.
Claims (16)
1. A method of fabricating a bulk acoustic wave resonator, comprising the steps of:
providing a first substrate, and forming a piezoelectric film layer on the first substrate;
forming a first electrode on the piezoelectric thin film layer, wherein the first electrode comprises a plurality of laminated metal layers, and the acoustic impedance of the metal layer in contact with the piezoelectric thin film layer in the first electrode is larger than that of the metal layer not in contact with the piezoelectric thin film layer;
forming a support layer covering the first electrode on the piezoelectric film layer and the first electrode, and patterning the support layer to form an opening exposing the first electrode;
providing a second substrate, bonding one side of the support layer away from the piezoelectric film layer with the second substrate, and removing the first substrate;
Forming a second electrode on one side of the piezoelectric film layer far away from the second substrate, wherein the second electrode comprises a plurality of laminated metal layers, the layers of the second electrode and the first electrode are the same, and the material lamination sequence of the second electrode and the first electrode is in mirror symmetry;
and forming a first electrode pad and a second electrode pad on one side of the piezoelectric film layer far away from the second substrate, wherein the first electrode pad penetrates through the piezoelectric film layer to be electrically connected with the first electrode, and the second electrode pad is electrically connected with the second electrode.
2. The method for manufacturing a bulk acoustic wave resonator according to claim 1, characterized in that: the material of the first electrode comprises at least two of Au, ag, ru, W, mo, ir, al, pt, nb, hf.
3. The method for manufacturing a bulk acoustic wave resonator according to claim 1, characterized in that: the first electrode includes a tungsten metal layer and a molybdenum metal layer stacked, the tungsten metal layer being in contact with the piezoelectric thin film layer.
4. The method for manufacturing a bulk acoustic wave resonator according to claim 1, characterized in that: the thickness of the first electrode is not more than 0.3um.
5. The method for manufacturing a bulk acoustic wave resonator according to claim 1, characterized in that: the material of the piezoelectric film layer comprises Al x Ga (1-x) N(0<x<1)、Sc x Al (1-x) N(0<x<1)、AlN、PZT、LiNbO 3 、ZnO、PbTiO 3 At least one of them.
6. A method of fabricating a bulk acoustic wave resonator, comprising the steps of:
providing a first substrate, and forming a piezoelectric film layer on the first substrate;
forming a first electrode on the piezoelectric thin film layer, wherein the first electrode comprises a plurality of laminated metal layers, and the acoustic impedance of the metal layer in contact with the piezoelectric thin film layer in the first electrode is larger than that of the metal layer not in contact with the piezoelectric thin film layer;
forming a barrier layer covering the first electrode on the piezoelectric film layer, forming a sacrificial layer on the barrier layer, and overlapping the sacrificial layer with the first electrode in the horizontal direction;
forming a supporting layer on the barrier layer, wherein the supporting layer covers the sacrificial layer;
providing a second substrate, bonding one side of the support layer away from the piezoelectric film layer with the second substrate, and removing the first substrate;
forming a second electrode on one side of the piezoelectric film layer far away from the second substrate, wherein the second electrode comprises a plurality of laminated metal layers, the layers of the second electrode and the first electrode are the same, and the material lamination sequence of the second electrode and the first electrode is in mirror symmetry;
Forming a first electrode pad and a second electrode pad on one side of the piezoelectric film layer far away from the second substrate, wherein the first electrode pad penetrates through the piezoelectric film layer to be electrically connected with the first electrode, and the second electrode pad is electrically connected with the second electrode;
and removing the sacrificial layer to form a cavity.
7. The method of manufacturing a bulk acoustic wave resonator according to claim 6, characterized in that: the material of the first electrode comprises at least two of Au, ag, ru, W, mo, ir, al, pt, nb, hf.
8. The method of manufacturing a bulk acoustic wave resonator according to claim 6, characterized in that: the first electrode includes a tungsten metal layer and a molybdenum metal layer stacked, the tungsten metal layer being in contact with the piezoelectric thin film layer.
9. The method of manufacturing a bulk acoustic wave resonator according to claim 6, characterized in that: the thickness of the first electrode is not more than 0.3um.
10. The method of manufacturing a bulk acoustic wave resonator according to claim 6, characterized in that: the material of the piezoelectric film layer comprises Al x Ga (1-x) N(0<x<1)、Sc x Al (1-x) N(0<x<1)、AlN、PZT、LiNbO 3 、ZnO、PbTiO 3 At least one of them.
11. A method of fabricating a bulk acoustic wave resonator, comprising the steps of:
Providing a first substrate, and forming a piezoelectric film layer on the first substrate;
forming a first electrode on the piezoelectric thin film layer, wherein the first electrode comprises a plurality of laminated metal layers, and the acoustic impedance of the metal layer in contact with the piezoelectric thin film layer in the first electrode is larger than that of the metal layer not in contact with the piezoelectric thin film layer;
forming a Bragg reflection layer covering the first electrode on the piezoelectric film layer and the first electrode;
forming a dielectric layer on the Bragg reflection layer, and flattening the dielectric layer;
providing a second substrate, bonding one side of the dielectric layer away from the piezoelectric film layer with the second substrate, and removing the first substrate;
forming a second electrode on one side of the piezoelectric film layer far away from the second substrate, wherein the second electrode comprises a plurality of laminated metal layers, the layers of the second electrode and the first electrode are the same, and the material lamination sequence of the second electrode and the first electrode is in mirror symmetry;
and forming a first electrode pad and a second electrode pad on one side of the piezoelectric film layer far away from the second substrate, wherein the first electrode pad penetrates through the piezoelectric film layer to be electrically connected with the first electrode, and the second electrode pad is electrically connected with the second electrode.
12. The method of manufacturing a bulk acoustic wave resonator according to claim 11, characterized in that: the material of the first electrode comprises at least two of Au, ag, ru, W, mo, ir, al, pt, nb, hf.
13. The method of manufacturing a bulk acoustic wave resonator according to claim 11, characterized in that: the first electrode includes a tungsten metal layer and a molybdenum metal layer stacked, the tungsten metal layer being in contact with the piezoelectric thin film layer.
14. The method of manufacturing a bulk acoustic wave resonator according to claim 11, characterized in that: the thickness of the first electrode is not more than 0.3um.
15. The method of manufacturing a bulk acoustic wave resonator according to claim 11, characterized in that: the material of the piezoelectric film layer comprises Al x Ga (1-x) N(0<x<1)、Sc x Al (1-x) N(0<x<1)、AlN、PZT、LiNbO 3 、ZnO、PbTiO 3 At least one of them.
16. The method of manufacturing a bulk acoustic wave resonator according to claim 11, characterized in that: the Bragg reflection layer comprises alternately laminated low acoustic impedance material layers and high acoustic impedance material layers, wherein the materials of the low acoustic impedance material layers comprise AlN and Si 3 N 4 Or SiO 2 The material of the high acoustic impedance material layer comprises one or more of W, mo, pt, au, ni or Ir.
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