WO2021189964A1 - Résonateur acoustique de volume à film mince et son procédé de fabrication - Google Patents

Résonateur acoustique de volume à film mince et son procédé de fabrication Download PDF

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Publication number
WO2021189964A1
WO2021189964A1 PCT/CN2020/135656 CN2020135656W WO2021189964A1 WO 2021189964 A1 WO2021189964 A1 WO 2021189964A1 CN 2020135656 W CN2020135656 W CN 2020135656W WO 2021189964 A1 WO2021189964 A1 WO 2021189964A1
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Prior art keywords
electrode
layer
piezoelectric
substrate
bulk acoustic
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PCT/CN2020/135656
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English (en)
Chinese (zh)
Inventor
黄河
罗海龙
李伟
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中芯集成电路（宁波）有限公司
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Publication of WO2021189964A1 publication Critical patent/WO2021189964A1/fr

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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
    • H03H9/02—Details
    • 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

Definitions

  • the invention relates to the field of semiconductor device manufacturing, in particular to a thin-film bulk acoustic wave resonator and a manufacturing method thereof.
  • radio frequency front-end modules have gradually become the core components of communication equipment.
  • the filter has become the component with the strongest growth momentum and the greatest development prospects.
  • the performance of the filter is determined by the resonator unit that composes the filter.
  • the film bulk acoustic resonator (FBAR) has the characteristics of small size, low insertion loss, large out-of-band suppression, high quality factor, high operating frequency, large power capacity, and good resistance to electrostatic shock. Become one of the most suitable filters for 5G applications.
  • the thin film bulk acoustic wave resonator includes two thin film electrodes, and a piezoelectric thin film layer is arranged between the two thin film electrodes. Its working principle is to use the piezoelectric thin film layer to generate vibration under an alternating electric field.
  • the bulk acoustic wave propagating in the thickness direction of the electric film layer is transmitted to the interface between the upper and lower electrodes and the air to be reflected back, and then reflected back and forth inside the film to form an oscillation.
  • a standing wave oscillation is formed.
  • the crystal orientation of the piezoelectric layer is largely dependent on the electrode below it.
  • the electrode boundary needs to be made with a smaller inclination angle (generally 15-20 degrees), so that the quality factor (Q) of the resonator cannot be further improved, so it cannot meet the needs of high-performance radio frequency systems.
  • the purpose of the present invention is to provide a thin film bulk acoustic wave resonator and a manufacturing method thereof, which can improve the crystal orientation of the piezoelectric layer, reduce the transverse wave loss of the resonator, and improve the quality factor of the thin film bulk acoustic wave resonator.
  • the present invention provides a thin film bulk acoustic wave resonator, including: a first substrate; The first cavity; a piezoelectric laminate structure covering the first cavity, the piezoelectric laminate structure includes a first electrode, a piezoelectric layer, and a second electrode stacked in sequence from top to bottom, in the effective resonance region
  • the first electrode, the piezoelectric layer, and the second electrode overlap in a direction perpendicular to the piezoelectric layer;
  • the first electrode includes a first side surface and/or the second electrode includes a second side surface, the effective At least part of the boundary of the resonance region includes the first side surface and/or the second side surface, and the angle between the first side surface and/or the second side surface and the piezoelectric layer surface is 85-95 degrees .
  • the present invention also provides a method for manufacturing a thin-film bulk acoustic resonator, which includes: providing a second substrate; forming a piezoelectric laminate structure on the second substrate, the piezoelectric laminate structure including being sequentially formed on the second substrate; The first electrode, the piezoelectric layer and the second electrode on the second substrate; forming a support layer on the piezoelectric laminate structure; forming a first cavity in the support layer, the first cavity Penetrating the supporting layer; providing a first substrate, bonding the first substrate to the supporting layer, the first substrate covering the first cavity; removing the second substrate; And after forming the piezoelectric laminate structure, patterning the piezoelectric laminate structure to form an effective resonance region, the boundary of the effective resonance region includes the first side surface of the first electrode and/or the second side surface of the second electrode The angle between the first side surface of the first electrode and the piezoelectric layer is 85-95 degrees and/or the angle between the second side surface of the second electrode and the piezoelectric layer is 85
  • the beneficial effect of the present invention is that the piezoelectric layer of the thin film bulk acoustic resonator provided by the present invention is formed above the unetched electrode.
  • the upper surface of the electrode is flat, and the side surface of the electrode does not need to be formed. Therefore, the first side surface of the first electrode at the boundary of the effective resonance region and/or the second side surface of the second electrode at the boundary of the effective resonance region can be made into an angle with the surface of the piezoelectric layer.
  • the first cavity is formed by bonding, the second electrode and the piezoelectric layer have strong flatness, and the bonding method can be realized before bonding, the second groove is etched from the bonding surface to the second electrode surface.
  • the sidewalls of the two trenches are vertical or nearly vertical, thereby forming a second side surface with an angle of 85-95 degrees.
  • the second trench is connected to the first cavity.
  • the acoustic impedance of the gas medium is the same, which is beneficial to the surface of the second electrode and The formation of the acoustic impedance mismatch on the second side can well realize the reflection of the acoustic wave, prevent the acoustic wave from leaking, and improve the quality factor of the acoustic wave resonator.
  • the effective resonance region is located above the first cavity, which reduces longitudinal acoustic wave leakage and improves the quality factor of the resonator.
  • first groove and/or the second groove extend into the piezoelectric layer or penetrate through the piezoelectric layer, so that the leakage of the transverse acoustic wave of the piezoelectric layer is improved, and the quality factor of the resonator is improved.
  • the first electrode, the piezoelectric layer, and the second electrode are sequentially deposited on the second substrate, and the first electrode under the piezoelectric layer is not etched.
  • the upper surface of the first electrode is flat, so as to maintain the good crystal orientation of the piezoelectric layer.
  • the inclination angle at the electrode boundary can be sandwiched with the piezoelectric layer surface. The angle is 85-95 degrees, which improves the quality factor of the resonator.
  • FIG. 1 is a schematic structural diagram of a thin film bulk acoustic resonator according to Embodiment 1 of the present invention.
  • FIG. 1A shows the structure of the boundary of the effective resonance region in an embodiment.
  • FIG. 1B shows the structure of the boundary of the effective resonance region in an embodiment.
  • FIG. 1C shows the structure of the boundary of the effective resonance region in an embodiment.
  • FIG. 1D shows how the boundary of the effective resonance region is constructed in an embodiment.
  • Figure 2 is a diagram showing the relationship between the resonant impedance Zp and the quality factor Qp of the resonator.
  • Figure 3 is a simulation diagram of related parameters when the electrode inclination angle is 90 degrees.
  • Fig. 4 is a simulation diagram of related parameters when the inclination angle of the bottom electrode is 15 degrees.
  • Figure 5 is a simulation diagram of related parameters when the inclination angle of the bottom electrode is 87 degrees.
  • Fig. 6 is a simulation diagram of related parameters when the inclination angle of the bottom electrode is 110 degrees.
  • FIG. 7 is a schematic structural diagram of a thin film bulk acoustic resonator according to Embodiment 2 of the present invention.
  • FIG. 8 to FIG. 17 are schematic diagrams of corresponding structures in corresponding steps in a method for manufacturing a thin-film bulk acoustic resonator according to Embodiment 3 of the present invention.
  • the thin film bulk acoustic wave resonator and the manufacturing method of the thin film bulk acoustic wave resonator of the present invention will be further described in detail with reference to the accompanying drawings and specific embodiments. According to the following description and drawings, the advantages and features of the present invention will be clearer. However, it should be noted that the concept of the technical solution of the present invention can be implemented in many different forms and is not limited to the specific implementation set forth herein. example. The drawings all adopt a very simplified form and all use imprecise proportions, which are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.
  • Embodiment 1 of the present invention provides a thin-film bulk acoustic resonator.
  • FIG. 1 is a schematic structural diagram of the thin-film bulk acoustic resonator according to Embodiment 1 of the present invention. Please refer to FIG. 1.
  • the thin-film bulk acoustic resonator includes: a first substrate Bottom 100; a support layer 206 bonded to the first substrate 100, the support layer 206 is formed with a first cavity 230 penetrating the support layer 206; a piezoelectric laminate structure, covering the first A cavity 230, the piezoelectric laminated structure includes a first electrode 202, a piezoelectric layer 203, and a second electrode 204 that are sequentially stacked from top to bottom.
  • the electrode 202, the piezoelectric layer 203, and the second electrode 204 overlap in a direction perpendicular to the piezoelectric layer 203;
  • the first electrode 202 includes a first side surface 2021 and/or the second electrode 204 includes a second side surface 2041 (This embodiment includes the first side surface 2021 and the second side surface 2041), at least part of the boundary of the effective resonance region includes the first side surface 2021 and/or the second side surface 2041, and the first side surface
  • the angle between 2021 and/or the second side surface 2041 and the surface of the piezoelectric layer 203 is 85-95 degrees.
  • the boundary of the effective resonance region is formed by the first side surface 2021.
  • the pattern formed by the area enclosed by the first side surface is provided with an opening, and the first electrode extends out of the effective resonance region through the opening for electrical connection of the first electrode. .
  • Figure 1A Refer to Figure 1A.
  • the boundary of the effective resonance area is formed by the first side surface 2021 and the third side surface 2031 (the third side surface is the side surface of the piezoelectric layer), and the projection of the first side surface and the third side surface on the piezoelectric layer constitutes a closed pattern,
  • the projection of the first side or the third side alone can be continuous or segmented, as long as the projections of the two complement each other to form a closed figure. Refer to Figure 1B.
  • the boundary of the effective resonance area is formed by the second side surface.
  • the pattern formed by the area enclosed by the second side surface is provided with an opening, and the second electrode extends out of the effective resonance area through the opening for electrical connection of the second electrode.
  • the boundary of the effective resonance zone is composed of the second side and the third side (the third side is the side of the piezoelectric layer).
  • the projection of the second side and the third side on the piezoelectric layer forms a closed pattern.
  • the individual projections of the side surface or the third side surface can be continuous or segmented, as long as the projections of the two complement each other to form a closed figure.
  • the boundary of the effective resonance area is composed of the first side surface 2021 and the second side surface 2041.
  • the projections of the second side surface and the first side surface on the piezoelectric layer form a closed pattern.
  • the second side surface or the first side surface can be projected separately. It can be continuous or segmented, as long as the projections of the two complement each other to form a closed figure. Refer to Figure 1C.
  • the boundary of the effective resonance area is composed of the first side surface 2021, the second side surface 2041, and the third side surface 2031.
  • the projections of the second side, the first side and the third side on the piezoelectric layer form a closed pattern, and the second side
  • the single projection of the first side or the third side can be continuous or segmented, as long as the three projections complement each other to form a closed figure. Refer to Figure 1D.
  • the first cavity is surrounded by the first substrate, the support layer on the first substrate, and the piezoelectric laminated structure, which avoids the existing solution of using the piezoelectric laminated structure as the cover plate of the closed cavity.
  • the piezoelectric laminate structure is not restricted by the cavity production, and is formed before the cavity is closed, so that a relatively flat piezoelectric laminate structure can be obtained, and the second electrode surface can be etched from the second electrode surface before the cavity is closed.
  • the trench defines part of the boundary of the effective resonance area.
  • the sidewall of the second trench is easier to achieve vertical or close to vertical, thus forming the first side with an angle of 85-95 degrees, which can achieve sound wave reflection and prevent sound wave leakage , Improve the quality factor of the acoustic wave resonator.
  • the pattern of the effective resonance area is an irregular polygon, and any two sides of the polygon are not parallel.
  • the position of the angle 301 between the first side surface 2021 of the first electrode 202 and the surface of the piezoelectric layer is shown by the arrow in the figure.
  • the first side surface of the first electrode 202 is a surface that cuts the thickness direction of the first electrode 202.
  • the second side surface 2041 of the second electrode 204 is a surface cutting the thickness direction of the second electrode 204, and the position of the angle 302 between the second side surface 2041 of the second electrode 204 and the piezoelectric layer surface is shown by the arrow in the figure.
  • the above-mentioned two included angles are hereinafter referred to as electrode inclination angles.
  • the material of the first substrate 100 may be at least one of the following materials: silicon (Si), germanium (Ge), silicon germanium (SiGe), silicon carbon (SiC), silicon germanium (SiGeC), Indium arsenide (InAs), gallium arsenide (GaAs), indium phosphide (InP) or other III/V compound semiconductors, including multilayer structures composed of these semiconductors, or silicon-on-insulator (SOI), on-insulator Stacked silicon (SSOI), stacked silicon germanium on insulator (S-SiGeOI), silicon germanium on insulator (SiGeOI), and germanium on insulator (GeOI), or double-sided polished silicon wafers (DoubleSidePolishedWafers, DSP), also It can be a ceramic substrate such as alumina, a quartz or glass substrate, and the like.
  • a support layer 206 is provided above the first substrate 100, and a first cavity 230 penetrating the support layer 206 is formed in the support layer 206.
  • the material of the support layer can be one or a combination of silicon dioxide (SiO2), silicon nitride (Si3N4), aluminum oxide (Al2O3) and aluminum nitride (AlN).
  • the depth of the first cavity 230 in the film bulk acoustic wave resonator is related to the resonant frequency. Therefore, the depth of the first cavity 230 can be set according to the resonant frequency required by the film bulk acoustic wave resonator, that is, the depth of the support layer 206 thickness.
  • the depth of the first cavity 230 may be 0.5 ⁇ m-4 ⁇ m, for example, 1 ⁇ m or 2 ⁇ m or 3 ⁇ m.
  • the shape of the bottom surface of the first cavity 230 may be a rectangle or a polygon other than a rectangle, such as a pentagon, a hexagon, an octagon, etc., and may also be a circle or an ellipse.
  • the sidewall of the first cavity 230 may be inclined or vertical.
  • the bottom surface of the first cavity 230 is rectangular, and the sidewall and the bottom surface form an obtuse angle (the shape of the longitudinal section of the first cavity 230 (the section along the thickness direction of the first substrate 100) is an inverted trapezoid).
  • the longitudinal cross-sectional shape of the first cavity 230 may also be a spherical cap with a wide top and a narrow bottom, that is, the longitudinal cross-section of the first cavity 230 is U-shaped.
  • the first substrate 100 is bonded to the support layer 106 by bonding.
  • the bonding method includes thermal compression bonding or dry film bonding.
  • thermal compression bonding is used, the first substrate 100 is bonded to the support layer 106.
  • a bonding layer (not shown in the figure) is provided between 106, and the bonding layer may be a silicon dioxide layer.
  • dry film bonding is used, a dry film layer (not shown in the figure) is provided between the first substrate 100 and the support layer 106.
  • the dry film is an organic cured film, which is commonly used in semiconductor processes. ⁇ The materials.
  • an etch stop layer 205 is provided between the second electrode 204 and the support layer 206.
  • the material of the etch stop layer 205 includes but is not limited to silicon nitride (Si3N4) and silicon oxynitride (SiON).
  • the etch stop layer 205 has a lower etch rate than the support layer 206.
  • the support layer 206 can be etched to form the first cavity 230 to prevent over-etching and protect the The surface of the second electrode 204 underneath is not damaged.
  • a first electrode 202, a piezoelectric layer 203, and a second electrode 204 are sequentially stacked from top to bottom.
  • the overlapping part of the first electrode 202, the piezoelectric layer 203 and the second electrode 204 in the direction perpendicular to the piezoelectric layer 203 constitutes an effective resonance region.
  • the shape of the effective resonance region is a polygon, and any two sides of the polygon are not parallel.
  • the boundary of the effective resonance region is formed by several different combinations of the piezoelectric layer 230 boundary, the first side surface 2021 of the first electrode 202, and the second side surface 2041 of the second electrode 204, which constitute the boundary of the effective resonance region.
  • the inclination angle of the electrode is 85-95 degrees.
  • the boundary of the effective resonance region is formed by the first side surface 2021 of the first electrode 202 and the second side surface 2041 of the second electrode 204 together. And the boundary of the effective resonance region is located in the area enclosed by the first cavity 230.
  • longitudinal sound waves vibrating up and down are formed in the piezoelectric layer. Part of the longitudinal sound waves propagate to the first electrode 202 and the second electrode 204 and leak from the surfaces of the first electrode 202 and the second electrode 204, causing the sound wave The energy loss.
  • the entire boundary of the effective resonance region is located above the area enclosed by the first cavity 230.
  • the acoustic impedance mismatch with the second electrode 204 causes the acoustic waves propagating to the interface to be reflected back into the piezoelectric layer 203, reducing the leakage of longitudinal acoustic waves and improving the quality factor of the resonator.
  • the size of the first cavity 230 can be smaller, so that the area enclosed by the first cavity 230 is located within the boundary of the effective resonance region, and the boundary of the effective resonance region is located above the support layer. This arrangement sacrifices a part of the quality factor, but improves the structural strength of the resonator and facilitates heat dissipation.
  • the second electrode 204 on the first cavity 230 is provided with a second groove 220, and the inner sidewall of the second groove 220 forms the second side surface 2041 of the second electrode 204.
  • a first trench 240 is provided in the first electrode 202, and the inner sidewall of the first trench 240 forms the first side surface 2021 of the first electrode 202.
  • the first electrode is also formed on the outer sidewall of the first trench 240, and the area where the first electrode is located outside the outer sidewall is the invalid region of the resonator. Therefore, in other embodiments, the first electrode The piezoelectric layer on the outer side opposite to the side wall 2021 may not have the first electrode.
  • the boundary of the lower electrode needs to be etched to a relatively oblique inclination angle, which is generally required to be less than 20 degrees. Even so, after the bottom electrode is patterned, the surface of the wafer is always uneven, and the crystal orientation of the piezoelectric layer on the entire surface is poor. In addition, the traditional process requires that the boundary of the upper electrode is also beveled.
  • the thin film piezoelectric acoustic resonator in the embodiment of the present invention is manufactured using a new process method, and the specific process steps will be described in detail in the third embodiment.
  • the piezoelectric layer can be formed on the unetched electrode.
  • the upper surface of the electrode is flat, and the side of the electrode does not need to make a small inclination angle, thus forming an effective resonance
  • the first side surface of the first electrode at the boundary of the zone and/or the second side surface of the second electrode at the boundary of the effective resonance zone can be made to have an angle of 85-95 degrees with the surface of the piezoelectric layer.
  • the quality factor of the resonator is the main parameter used to judge the performance of the resonator.
  • the quality factor of the resonator and the resonance impedance Zp have a highly linear relationship.
  • the above-mentioned relational expression can be obtained through the ‘MBVD model’ and the ‘particle swarm algorithm fitting’.
  • the ‘MBVD model’ and the ‘particle swarm algorithm fitting’ are common knowledge of those skilled in the art, and the derivation process for obtaining the result will not be described here.
  • the resonant impedance Zp of the resonator when the resonant impedance Zp of the resonator is higher, it means that the resonator has a higher quality factor Qp.
  • the data of the simulation diagram provided in this article uses the following model parameters: the material of the upper electrode and the lower electrode is molybdenum, the thickness is both 0.2-0.3 microns, the material of the piezoelectric layer is aluminum nitride, and the piezoelectric layer The thickness is 0.5-1.5 microns.
  • Figure 3 is a simulation diagram of related parameters when the inclination angle of the bottom electrode is 90 degrees.
  • Fig. 4 is a simulation diagram of related parameters when the inclination angle of the bottom electrode is 15 degrees.
  • Figure 5 is a simulation diagram of related parameters when the inclination angle of the bottom electrode is 87 degrees.
  • Figure 6 is a simulation diagram of related parameters when the inclination angle of the bottom electrode is 110 degrees. It can be seen from Fig. 3 that when the inclination angle of the bottom electrode is 90 degrees, the resonance impedance Zp is 4514.8 ohm. It can be seen from Fig.
  • the resonance impedance Zp when the inclination angle of the bottom electrode is 15 degrees, the resonance impedance Zp is 2112 ohm. It can be seen from Fig. 5 that when the inclination angle of the bottom electrode is 87 degrees, the resonance impedance Zp is 3836 ohm. It can be seen from FIG. 6 that when the inclination angle of the bottom electrode is 110 degrees, the resonance impedance Zp is 3593 ohm.
  • the inventor also conducted simulation experiments on other angles of the lower electrode and found that when the lower electrode is perpendicular or nearly perpendicular to the piezoelectric layer, the lower electrode and the piezoelectric layer have a small inclination angle, which significantly increases the resonance impedance Zp of the resonator. , Improve the quality factor of the resonator.
  • the inclination angle between the lower electrode and the piezoelectric layer is 90 degrees, the resonance impedance Zp is the largest and the quality factor is the highest.
  • the materials of the second electrode 204 and the first electrode 202 may be metallic materials with conductive properties, for example, made of molybdenum (Mo), aluminum (Al), copper (Cu), tungsten (W), tantalum (Ta), platinum (Pt), ruthenium (Ru), rhodium (Rh), iridium (Ir), chromium (Cr), titanium (Ti), gold (Au), osmium (Os), rhenium (Re), palladium (Pd) and other metals
  • Mo molybdenum
  • Al aluminum
  • Cu copper
  • platinum (Pt) platinum
  • Ru ruthenium
  • Ru rhodium
  • Ir iridium
  • Cr chromium
  • Ti titanium
  • gold Au
  • Re palladium
  • Pd palladium
  • the semiconductor material is made of one kind or a laminated layer formed of the above-mentioned
  • the material of the piezoelectric layer 203 can be aluminum nitride (AlN), zinc oxide (ZnO), lead zirconate titanate (PZT), lithium niobate (LiNbO3), quartz (Quartz), potassium niobate (KNbO3) or tantalic acid Piezoelectric materials with wurtzite crystal structure such as lithium (LiTaO3) and their combinations.
  • the piezoelectric layer 104 includes aluminum nitride (AlN)
  • the piezoelectric layer 203 may further include rare earth metals, such as at least one of scandium (Sc), erbium (Er), yttrium (Y), and lanthanum (La).
  • the piezoelectric layer 203 may further include a transition metal, such as at least one of zirconium (Zr), titanium (Ti), manganese (Mn), and hafnium (Hf). kind.
  • a transition metal such as at least one of zirconium (Zr), titanium (Ti), manganese (Mn), and hafnium (Hf). kind.
  • the first cavity 230 includes at least one through hole 250 penetrating the structure above the first cavity 230, and the through hole 250 is located outside the effective resonance region.
  • the through hole 250 communicates the first cavity 230 with the outside, prevents the piezoelectric laminated structure from being deformed due to the difference in pressure between the upper and lower pressures, and improves the yield of the resonator.
  • the number of through holes 250 can also be 3, 5, etc., which is not limited.
  • a passivation layer 207 is further included, and the passivation layer 207 covers the first electrode 206, the piezoelectric layer 203 and the second electrode 204.
  • the passivation layer can further cover the support layer.
  • the material of the passivation layer 207 may be silicon dioxide (SiO2), silicon nitride (Si3N4), silicon oxynitride (SiON), aluminum nitride (A1N), aluminum oxide (A12O3), and the like.
  • the passivation layer 207 is also provided with a first pad 110 and a second pad 120, the first pad 110 and the first electrode 202 are electrically connected, and the second pad 120 and the second electrode 204 are electrically connected.
  • Both the first pad 110 and the second pad are located outside the first cavity 230.
  • the material of the first pad 110 and the second pad 120 may be aluminum (A1), copper (Cu), gold (Au), titanium (Ti), nickel (Ni), silver (Ag) or tungsten (W) A composite structure formed by a combination of one or more of them.
  • FIG. 7 is a schematic structural diagram of a thin film bulk acoustic resonator according to Embodiment 2 of the present invention.
  • the difference between the second embodiment and the first embodiment is that the first groove 240 and/or the second groove 220 penetrate at least a part of the thickness of the piezoelectric layer 203. That is to say, the depth of the first trench 240 not only penetrates the first electrode 202, but also extends downward to the piezoelectric layer 203 (it can penetrate the entire thickness of the piezoelectric layer 203 or end at the set depth of the piezoelectric layer 203). The depth of the second trench 220 not only penetrates the second electrode 204, but also extends downward to the piezoelectric layer 203 (it can penetrate the entire thickness of the piezoelectric layer 203 or end at the set depth of the piezoelectric layer 203).
  • FIG. 7 only shows a structural diagram of the main part.
  • the transverse parasitic waves generated in the piezoelectric layer 203 due to the mismatch between the acoustic impedance of the air and the acoustic impedance of the piezoelectric layer, propagate to the boundary of the piezoelectric layer, the sound waves are reflected back into the piezoelectric layer 203, The loss of transverse sound waves is reduced, and the quality factor of the resonator is improved.
  • the effect of preventing lateral acoustic wave leakage is better; when the first groove 240 and/or the second groove penetrate the piezoelectric layer 203 At a part of the thickness, the structural strength of the resonator is better.
  • Embodiment 3 of the present invention provides a method for manufacturing a thin film bulk acoustic resonator.
  • the method includes: S01: providing a second substrate; S02: forming a piezoelectric laminate structure on the second substrate, and The piezoelectric laminate structure includes a first electrode, a piezoelectric layer, and a second electrode sequentially formed on the second substrate; S03: a support layer is formed on the piezoelectric laminate structure; in the support layer A first cavity is formed, and the first cavity penetrates the support layer; S04: a first substrate is provided, and the first substrate is bonded to the support layer, and the first substrate covers the support layer.
  • FIG. 8 to FIG. 17 are schematic diagrams of corresponding structures in corresponding steps in a method for manufacturing a thin-film bulk acoustic resonator according to Embodiment 3 of the present invention.
  • FIG. 7 to FIG. 16 the method of manufacturing the thin film bulk acoustic wave resonator of the embodiment will be described in detail.
  • step S01 is performed: a second substrate 200 is provided.
  • the material of the second substrate 200 refers to the material of the first substrate in Embodiment 1.
  • the release layer 201 further includes forming a release layer 201 on the second substrate 200.
  • the release layer 201 can prevent the piezoelectric laminate structure of the thin film bulk acoustic resonator formed subsequently from affecting the second substrate.
  • the release layer 201 can be etched to separate the second substrate 200 from the piezoelectric laminate structure formed subsequently, It is helpful to quickly remove the second substrate 200 and improve the manufacturing efficiency of the process.
  • the material of the release layer 201 includes but is not limited to at least one of silicon dioxide (SiO2), silicon nitride (Si3N4), aluminum oxide (Al2O3) and aluminum nitride (AlN).
  • the release layer 201 can be formed by chemical vapor deposition, magnetron sputtering, or evaporation.
  • the second substrate 200 is a silicon wafer
  • the material of the release layer 201 is silicon dioxide (SiO2).
  • step S02 is performed: forming a piezoelectric laminate structure on the second substrate 200, the piezoelectric laminate structure including a first electrode 202 and a piezoelectric layer formed on the second substrate 200 in sequence.
  • the first electrode 202 may be used as an input electrode or an output electrode that receives or provides an electrical signal such as a radio frequency (RF) signal.
  • RF radio frequency
  • the first electrode 202 can be used as an output electrode
  • the piezoelectric layer 203 can be used as an input electrode.
  • the electrical signal input through the first electrode 202 or the second electrode 204 is converted into a bulk acoustic wave.
  • the piezoelectric layer 203 converts electrical signals into bulk acoustic waves through physical vibration.
  • the first electrode 202 and the second electrode 204 can be formed by physical vapor deposition or chemical vapor deposition methods such as magnetron sputtering, evaporation, or the like.
  • the material of the piezoelectric layer 203 can be formed by chemical vapor deposition, physical vapor deposition, or atomic layer deposition with reference to the related description in Embodiment 1.
  • the piezoelectric laminate structure after the piezoelectric laminate structure is formed, it further includes forming an etch stop layer 205 on the second electrode 204.
  • the material and function of the etch stop layer 205 refer to Embodiment 1.
  • the etch stop layer 205 can be deposited by a method of chemical vapor deposition, physical vapor deposition or atomic layer deposition.
  • the boundary of the effective resonance region is formed by the first side surface of the first electrode and the second side surface of the second electrode.
  • Patterning the piezoelectric laminate structure includes, after forming the second electrode 204, patterning the second electrode 204 so that the angle between the first side surface of the first electrode and the piezoelectric layer is 85-95 degrees.
  • the material of the second electrode 204 is molybdenum
  • the method of patterning the second electrode 204 includes: forming a photoresist material layer on the second electrode, and after exposure and development, the photoresist material layer Form a pattern.
  • the sidewall morphology of the groove formed in the photoresist material layer is required to be relatively vertical, preferably 90 degrees.
  • the second trench 220 is etched in the second electrode 204 using sulfur fluoride etching gas, and the inner sidewall of the second trench 220 constitutes the second electrode 204 side.
  • the second trench 220 may extend into the piezoelectric layer 203, may penetrate the entire piezoelectric layer 203, or the bottom surface of the second trench 220 may extend to a set thickness of the piezoelectric layer 203.
  • the etching process will not be repeated, and the corresponding parameters can be changed. Refer to the related description in Embodiment 2 for the advantages of this arrangement.
  • step S03 is performed: a support layer 206 is formed on the piezoelectric laminate structure; a first cavity 230 is formed in the support layer 206, and the first cavity 230 penetrates the support ⁇ 206.
  • the support layer 206 may be formed by a chemical deposition method.
  • the material of the support layer 206 and the thickness of the formed support layer refer to the related description in Embodiment 1.
  • the support layer 206 is etched by an etching process to form a first cavity 230, and the first cavity 230 penetrates the support layer 206.
  • the shape of the first cavity 230 refer to the related description in Embodiment 1.
  • the etching process can be a wet etching or a dry etching process, and a dry etching process is preferably used.
  • Dry etching includes but not limited to reactive ion etching (RIE), ion beam etching, and plasma etching. Body etching or laser cutting.
  • step S04 is performed: a first substrate 100 is provided, and the first substrate 100 is bonded to the support layer 206, and the first substrate 100 covers the first cavity 230.
  • the bonding of the first substrate 100 and the supporting layer 206 can be achieved by thermocompression bonding.
  • the The support layer 206 is provided with a bonding layer on the side where the thermal compression bonding is performed, and the bonding layer may be a silicon dioxide layer.
  • other bonding methods may also be used for bonding, for example, the first substrate 100 and the supporting layer 206 are bonded into one body by dry film bonding.
  • a dry film layer is provided on the side of the first substrate 100 where the dry film is bonded, and the first substrate 100 is bonded to the support layer 206 through the dry film layer.
  • step S05 is performed: removing the second substrate.
  • the first substrate 100 may be removed through a thinning process, a heat release process, and a lift-off process.
  • the material of the release layer 201 includes a dielectric material.
  • the release layer 201 and the first substrate 100 can be removed by a thinning process, such as mechanical grinding; the release layer 201 is a photocurable glue, which can be removed by chemical reagents.
  • the photocurable adhesive is removed to remove the first substrate 100; the release layer is a hot melt adhesive, and the hot melt adhesive may lose its viscosity through a heat release process to remove the first substrate 100.
  • the release layer 201 is a laser release material, and the release layer 201 can be ablated by laser to peel off the first substrate 100.
  • patterning the piezoelectric laminate structure further includes patterning the first electrode 202 so that the angle between the first side surface 2012 of the first electrode 202 and the piezoelectric layer is 85-95 degrees .
  • the boundary of the effective resonance region is located in the area enclosed by the first cavity 230.
  • the first electrode 202 is etched by a dry etching process to form a first trench 240, so that the inner sidewall of the first trench 240 constitutes the first side surface of the first electrode 202, and the first The angle between the side surface and the surface of the piezoelectric layer is 85-95 degrees.
  • the method for forming the electrode inclination angle of 85-95 degrees in the dry etching process refers to the foregoing description.
  • the second substrate after removing the second substrate, it further includes: forming a through hole 250 that penetrates the piezoelectric laminate structure above the first cavity 230 and outside the effective resonance region. .
  • the through hole 250 may be formed by a dry etching process or a punching process. Refer to the related description in Embodiment 1 for the number, position, and function of the through holes 250.
  • the step of patterning the second electrode to form the second side surface is after forming the second electrode 204 and before forming the supporting layer 206.
  • the step of patterning the second electrode to form the second side surface may be after forming the first cavity 230.
  • a support layer 206 is formed on the second electrode 204, a first cavity 230 is formed in the support layer 206, and the second electrode 204 exposed at the bottom of the first cavity 230 is dried by drying.
  • the second trench 220 is etched by the method etching process.
  • the inner side wall of the second trench 220 constitutes the second side surface of the second electrode 204.
  • the dry etching process method is the same as this embodiment.
  • the boundary of the effective resonance region includes the first side surface of the first electrode; patterning the piezoelectric laminate structure includes: after removing the second substrate, performing processing on the first electrode The first side surface is formed in a pattern.
  • the boundary of the effective resonance region includes the second side surface of the second electrode; patterning the piezoelectric laminate structure includes: forming the first cavity before bonding the second substrate After that, or before forming the support layer, pattern the second electrode to form the second side surface.
  • the boundary of the effective resonance region includes the second side surface of the second electrode and the third side surface of the piezoelectric layer; patterning the piezoelectric laminate structure includes: bonding the second liner Before the bottom, after forming the first cavity, or before forming the support layer, pattern the second electrode to form the second side surface; after patterning the second electrode, pattern the piezoelectric The layer forms the third side surface.
  • the boundary of the effective resonance region includes the first side surface of the first electrode and the second side surface of the second electrode; patterning the piezoelectric laminate structure includes: before bonding the second substrate After forming the first cavity, or before forming the support layer, pattern the second electrode to form the second side surface; after removing the second substrate, pattern the first electrode To form the first side surface.

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  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)

Abstract

La présente invention concerne un résonateur acoustique de volume à film mince et son procédé de fabrication, le résonateur acoustique de volume à film mince comprenant : un premier substrat ; une couche de support liée sur le premier substrat, une première cavité vide qui s'étend à travers la couche de support étant formée à l'intérieur de la couche de support ; une structure de couche de chevauchement piézoélectrique qui recouvre la première cavité vide, la structure de couche de chevauchement piézoélectrique, de haut en bas de manière à se chevaucher de manière séquentielle, comprenant une première électrode, une couche piézoélectrique et une seconde électrode, où dans une zone de résonance active, la première électrode, la couche piézoélectrique et la seconde électrode se chevauchent dans la direction orthogonale à la couche piézoélectrique ; la première électrode comprend une première face latérale et/ou la seconde électrode comprend une seconde face latérale, au moins une partie des bordures de la zone de résonance active comprenant la première face latérale et/ou la seconde face latérale, et l'angle inclus de la première face latérale et/ou de la seconde face latérale avec une surface de la couche piézoélectrique est de 85 à 95 degrés. La présente invention peut améliorer l'orientation cristalline de la couche piézoélectrique, réduire la perte d'onde transversale, et permettre l'amélioration du facteur Q de résonateurs acoustiques de volume à film mince.
PCT/CN2020/135656 2020-03-23 2020-12-11 Résonateur acoustique de volume à film mince et son procédé de fabrication WO2021189964A1 (fr)

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CN117015932A (zh) * 2021-02-10 2023-11-07 广东致能科技有限公司 一种体滤波器
CN114894229B (zh) * 2022-04-26 2024-05-03 武汉敏声新技术有限公司 一种薄膜体声波传感器及其制备方法

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