WO2022170683A1 - Procédé de fabrication de résonateur à ondes acoustiques et résonateur à ondes acoustiques - Google Patents

Procédé de fabrication de résonateur à ondes acoustiques et résonateur à ondes acoustiques Download PDF

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WO2022170683A1
WO2022170683A1 PCT/CN2021/092048 CN2021092048W WO2022170683A1 WO 2022170683 A1 WO2022170683 A1 WO 2022170683A1 CN 2021092048 W CN2021092048 W CN 2021092048W WO 2022170683 A1 WO2022170683 A1 WO 2022170683A1
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layer
acoustic
stack
wafer substrate
piezoelectric wafer
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PCT/CN2021/092048
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English (en)
Chinese (zh)
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龚颂斌
维达尔-阿尔瓦雷斯·加布里埃尔
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偲百创(深圳)科技有限公司
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
    • H03H9/17—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
    • H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
    • H03H3/02—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks
    • 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

Definitions

  • the present application relates to the technical field of resonators, and in particular, to a method for manufacturing an acoustic wave resonator and an acoustic wave resonator.
  • acoustic devices are used to synthesize filtering with low loss and fast roll-off characteristics. These devices are micro-machined structures based on semiconductor technology that use acoustic vibration to synthesize and cascade inductors and capacitors. Equivalent resonator function. Often referred to as Surface Acoustic Wave (SAW) devices or Bulk Acoustic Wave (BAW) devices, these devices can achieve extremely high quality factor Q (directly related to low loss) in a very small form factor compatible with modern electronic components ), so it has become the mainstream solution for RF filtering of high-end front-end modules. In particular, since the performance of BAW devices is better than that of SAW devices at high frequency and low loss exceeding 2.5GHz, BAW devices are more widely used in high-frequency filtering technology of high-end front-end modules.
  • SAW Surface Acoustic Wave
  • BAW Bulk Acoustic Wave
  • BAW devices sandwich a piezoelectric thin-film layer between metal electrodes and some other thin-film layers to reduce the temperature sensitivity of the device.
  • the new 5G standard requires operation at higher frequencies (above 3GHz) and wider bandwidths. Achieving high frequency requirements presents new challenges for BAW devices, which need to utilize extremely thin layers or sacrifice bandwidth.
  • a method for making an acoustic wave resonator comprising the following steps:
  • a piezoelectric wafer substrate is provided, and a first stack is prepared on the piezoelectric wafer substrate; the first stack is used for transmitting electrical signals and confining acoustic wave signals;
  • a second stack is prepared on the side of the piezoelectric wafer substrate away from the first stack to form an acoustic resonator; the second stack is used to transmit electrical and acoustic signals.
  • a piezoelectric wafer substrate is first provided, a first stack is prepared on the piezoelectric wafer substrate, and the first stack is separated from one side of the piezoelectric wafer substrate.
  • a second stack is prepared on the side of the piezoelectric wafer substrate away from the first stack to form
  • the first stack is used to transmit electrical signals and bound acoustic signals
  • the second stack is used to transmit electrical signals and acoustic signals.
  • the second stack, the piezoelectric wafer substrate, the first stack and the carrier wafer are stacked and arranged, the carrier wafer plays a bearing role, and the piezoelectric wafer
  • the piezoelectric film formed by thinning the substrate can be excited to vibrate acoustically, and the first stack and the second stack can transmit electrical signals and bound acoustic signals, so that the resulting acoustic resonator can work at high frequencies.
  • Acoustic resonators fabricated by the method have specific stack combinations and piezoelectric films, which can excite and support high-performance acoustic vibration modes, so that the fabricated devices exhibit low loss, high quality factor, wide bandwidth, and low temperature sensitivity. , high reliability.
  • the first stack includes a bottom metal layer and a bottom acoustically reflective layer, the providing a piezoelectric wafer substrate on which the first stack is fabricated, including :
  • the bottom acoustic reflection layer is deposited on the side of the bottom metal layer away from the piezoelectric wafer substrate.
  • the bottom acoustic reflection layer includes a low acoustic impedance layer and a high acoustic impedance layer, and the bottom acoustic reflection layer is deposited on a side of the bottom metal layer away from the piezoelectric wafer substrate layers, including:
  • the low acoustic impedance layer is deposited on the side of the high acoustic impedance layer away from the bottom metal layer.
  • the low acoustic impedance layers and the high acoustic impedance layers are alternately arranged.
  • the bottom acoustic reflection layer further includes a filling reflection layer
  • the depositing the low acoustic impedance layer after the high acoustic impedance layer is away from the bottom metal layer further includes:
  • the fill reflective layer is deposited on the side of the low acoustic impedance layer away from the bottom metal layer.
  • the bottom acoustic reflection layer further includes a bonding layer
  • the depositing the filling reflection layer on the side of the low acoustic impedance layer away from the bottom metal layer further includes:
  • the bonding layer is deposited on the side of the filled reflective layer away from the low acoustic impedance layer.
  • the thinning of the side of the piezoelectric wafer substrate away from the first stack comprises:
  • the side of the piezoelectric wafer substrate away from the first stack is ground and then polished.
  • the second stack includes a top metal layer and a top acoustic reflective layer, and after thinning the side of the piezoelectric wafer substrate away from the first stack, the A second stack is prepared on the side of the piezoelectric wafer substrate away from the first stack, including:
  • the top acoustically reflective layer is deposited on the side of the top metal layer away from the piezoelectric wafer substrate.
  • the method further includes:
  • top acoustic reflection layer and the piezoelectric wafer substrate are etched so that the top metal layer and the bottom metal layer are accessible to electrode lines.
  • Fig. 1 is the flow chart of the manufacturing method of acoustic wave resonator in one embodiment
  • Fig. 2 is the flow chart of the manufacturing method of acoustic wave resonator in another embodiment
  • FIG. 3 is a flowchart of a method for making an acoustic resonator in yet another embodiment
  • FIG. 4 is a schematic structural diagram of an acoustic resonator in one embodiment
  • FIG. 5 is a schematic structural diagram of an acoustic resonator in another embodiment
  • FIG. 7 is a graphical result diagram of a high acoustic impedance layer and a low acoustic impedance layer in one embodiment
  • FIG. 8 is a schematic diagram of the deposition result of filling the reflective layer in one embodiment
  • FIG. 9 is a schematic diagram of the results of depositing a silicon dioxide layer in one embodiment
  • Figure 10 is a schematic diagram of the results of polishing and thinning of a silicon dioxide bonding layer in one embodiment
  • FIG. 11 is a schematic diagram of the results of bonding to a carrier wafer substrate in one embodiment
  • Figure 12 is a schematic diagram of the results of polishing and thinning of piezoelectric wafer substrates in one embodiment
  • FIG. 13 is a schematic diagram of the patterning results of the top metal layer in one embodiment
  • FIG. 14 is a schematic diagram of the results of deposition of the top acoustic reflective layer material after the top metal layer is patterned in one embodiment
  • 15 is a schematic diagram of two methods for obtaining frequency-shifted resonators on the same technology platform in one embodiment
  • 16 is a schematic diagram of an etching result in one embodiment
  • Figure 17 is a schematic diagram of a resonator pair in which all electrical connections are made using only the top metal layer in one embodiment.
  • a method for fabricating an acoustic wave resonator is provided, see FIG. 1 , and the method includes the following steps:
  • Step S200 a piezoelectric wafer substrate is provided, and a first stack is prepared on the piezoelectric wafer substrate.
  • the piezoelectric wafer substrate 10 has any axis symmetry, which is convenient for subsequent processing.
  • the type of the piezoelectric wafer substrate 10 is not unique.
  • the piezoelectric wafer substrate 10 is a single crystal piezoelectric wafer substrate.
  • the structure of the piezoelectric wafer substrate 10 is also not unique, and can be lithium niobate, lithium tantalate, aluminum nitride or quartz, or doped forms of these structures.
  • the piezoelectric wafer substrate 10 and the first stack 20 are both layered structures, and preparing the first stack 20 on the piezoelectric wafer substrate 10 may be the process of depositing the first stack 20 on the piezoelectric wafer substrate 10
  • the first stack 20 may also be patterned, so that the shape and size of the first stack 20 meet different requirements.
  • the structure of the first stack 20 is not unique as long as it can transmit electrical signals and bound acoustic signals.
  • the first stack 20 includes at least two different types of layer structures, and the two different types of layer structures can be used for transmitting electrical signals and confining acoustic wave signals, respectively, so as to improve the quality of the transmitted signals. It can be understood that, in other embodiments, the first stack 20 may also have other structures, as long as those skilled in the art consider that they can be implemented.
  • Step S400 bonding the side of the first stack away from the piezoelectric wafer substrate to the carrier wafer.
  • the piezoelectric wafer substrate 10 and the first stack 20 are bonded to the carrier wafer 40. Since the first stack 20 and the pressure The electro-wafer substrates 10 are arranged on top of each other, so it is only necessary to bond the side of the first stack 20 away from the piezoelectric wafer substrate 10 to the carrier wafer 40. The piezoelectric wafer substrate 10 can be bonded to the carrier wafer 40. Direct contact with the carrier wafer 40 is not necessary.
  • the carrier wafer 40 is also generally a layered structure, is a carrier device of the acoustic wave resonator, and serves as a carrier for other structures in the acoustic wave resonator, and plays a role of bearing and fixing. Bonding the side of the first stack 20 away from the piezoelectric wafer substrate 10 to the carrier wafer 40 by bonding is beneficial to keep the position of the first stack 20 fixed and ensure the working performance of the acoustic wave resonator .
  • Step S600 after thinning the side of the piezoelectric wafer substrate away from the first stack, a second stack is prepared on the side of the piezoelectric wafer substrate away from the first stack to form an acoustic wave resonator.
  • the piezoelectric wafer substrate 10 Thinning is performed to achieve the desired thickness of the piezoelectric wafer.
  • a second stack 30 is deposited on the side of the thinned piezoelectric wafer substrate 10 away from the first stack 20 to form an acoustic wave resonator, which will not make the thickness of the acoustic wave resonator too large, which is beneficial to improve the sound wave The performance of the resonator.
  • the acoustic resonator includes a second stack 30 , a piezoelectric wafer substrate 10 , a first stack 20 and a carrier wafer 40 arranged in sequence.
  • the position where the second stack 30 is located is referred to as an acoustic resonator.
  • the top of the carrier wafer 40 is referred to as the bottom of the acoustic wave resonator, the second stack 30, the piezoelectric wafer substrate 10, the first stack 20 and the carrier wafer 40 are arranged from top to bottom. , which are stacked in order from top to bottom.
  • the second stack 30 is also generally a layered structure, and the second stack 30 can be prepared on the side of the piezoelectric wafer substrate 10 away from the first stack 20 , and the second stack 30 can be prepared on the piezoelectric wafer substrate 10 away from the first stack.
  • a second stack 30 is deposited on one side of 20 . After the second stack 30 is deposited, the second stack 30 may also be patterned so that the shape and size of the second stack 30 meet different requirements. For example, in some embodiments, the second stack 30 may be Aligned with the first stack 20 .
  • the structure of the second stack 30 is not unique, as long as electrical signals and acoustic wave signals can be transmitted.
  • the second stack 30 includes at least two different types of layer structures, and the two different types of layer structures can be used to transmit electrical signals and acoustic signals, respectively, so as to improve the quality of the transmitted signals. It can be understood that, in other embodiments, the second stack 30 may also have other structures, as long as those skilled in the art consider that they can be implemented.
  • the first stack 20 includes a bottom metal layer 21 and a bottom acoustic reflection layer 22
  • step S200 includes steps S220 and S240 .
  • Step S220 A piezoelectric wafer substrate is provided, and a bottom metal layer is deposited on the piezoelectric wafer substrate.
  • the first stack 20 includes a bottom metal layer 21 and a bottom acoustic reflection layer 22, the bottom metal layer 21 is used for transmitting electrical signals, and the bottom acoustic reflection layer 22 is used for transmitting acoustic wave signals.
  • the bottom metal layer 21 is also a layered structure, and the bottom metal layer 21 is deposited on the piezoelectric wafer substrate 10 to form the bottom electrode of the acoustic wave resonator. After the bottom metal layer 21 is deposited on the piezoelectric wafer substrate 10 , the bottom metal layer 21 can also be patterned, and the shape, area and thickness of the bottom metal can be adjusted to meet specific requirements.
  • the shape of the bottom metal layer 21 is not unique and can be any geometry extracted from a square, rectangle, trapezoid or any polygon with n sides, where n is from 4 to infinity to resemble a circle or an ellipse.
  • the structure of the bottom metal layer 21 is not unique, and can be a metal layer made of Al, AlCu, AlSiCu, Pt, Mo, Ru, W or Cu, or a metal layer made of alloys of these metals, etc. The actual demand is determined, as long as those skilled in the art think that it can be realized.
  • Step S240 depositing a bottom acoustic reflection layer on the side of the bottom metal layer away from the piezoelectric wafer substrate.
  • the bottom acoustic reflection layer 22 is generally a layered structure and is disposed on the other side of the bottom metal layer 21 to reflect sound waves.
  • the type of the bottom acoustic reflection layer 22 is not unique, and the material of the bottom acoustic reflection layer 22 can be selected according to specific requirements.
  • the acoustic reflection layer can also be patterned to make the shape and size of the bottom acoustic reflection layer 22 meet the requirements.
  • the bottom acoustic reflection layer 22 includes a low acoustic impedance layer 222 and a high acoustic impedance layer 221 , please refer to FIG. 3 , and step S240 includes steps S242 and S244 .
  • Step S242 depositing a high acoustic impedance layer on the side of the bottom metal layer away from the piezoelectric wafer substrate.
  • the bottom acoustic reflection layer 22 includes a low acoustic impedance layer 222 and a high acoustic impedance layer 221 , and the high acoustic impedance layer 221 is in contact with the bottom metal layer 21 .
  • the high acoustic impedance layer 221 may be patterned so that the high acoustic impedance layer 221 has a generally higher acoustic impedance than the bottom metal layer 21 . Dimensions wide dimensions.
  • the shape of the high acoustic impedance layer 221 may follow the shape of the bottom metal layer 21 , or may be another geometric shape surrounding the shape of the bottom metal layer 21 .
  • the size and shape of the layers placed below the first layer in the acoustic resonator will include the layers above, and each layer will have a smaller projection on the piezoelectric wafer substrate 10 than the layer below it on the piezoelectric crystal.
  • the projection on the circular substrate 10 forms an arrangement from the top to the bottom of the acoustic wave resonator from small to large and from narrow to wide.
  • all layers in the acoustic wave resonator can also have the same size, with good structural consistency.
  • the type of the high acoustic impedance layer 221 is not unique, for example, it can be a layered structure made of aluminum nitride, tungsten, platinum, molybdenum, ruthenium and the oxidized form of the same material, and can also be made of other types of materials, as long as the Those skilled in the art can think that it can be realized.
  • Step S244 depositing the low acoustic impedance layer on the side of the high acoustic impedance layer away from the bottom metal layer.
  • the low acoustic impedance layer 222 is deposited on the side of the high acoustic impedance layer 221 away from the bottom metal layer 21 .
  • the low acoustic impedance layer 222 may be patterned so that the low acoustic impedance layer 222 has a generally higher acoustic impedance than the bottom metal layer 221. 21 size wide size.
  • the shape of the low acoustic impedance layer 222 may follow the shape of the high acoustic impedance layer 221 , or may be another geometric shape surrounding the shape of the high acoustic impedance layer 221 .
  • layers placed below the first layer in the acoustic resonator may be shaped and sized to include the layers above, with each layer having a smaller projection on the piezoelectric wafer substrate 10 than the layer below it on the piezoelectric crystal.
  • the projection on the circular substrate 10 forms an arrangement from the top to the bottom of the acoustic wave resonator from small to large and from narrow to wide.
  • all layers in the acoustic wave resonator can also have the same size, with good structural consistency.
  • the type of the low acoustic impedance layer 222 is not unique, for example, it can be a layered structure made of silicon dioxide, spin glass, tellurium oxide and other oxides containing other materials, and can also be made of other types of materials, As long as those skilled in the art think it can be realized.
  • both the low acoustic impedance layer 222 and the high acoustic impedance layer 221 may be patterned, or only the high acoustic impedance layer 221 may be patterned, or neither the low acoustic impedance layer 222 nor the high acoustic impedance layer 221 may be patterned. change.
  • Both the low acoustic impedance layer 222 and the high acoustic impedance layer 221 may be polished and thinned, or only the low acoustic impedance layer 222 may be polished and thinned, or neither the low acoustic impedance layer 222 nor the high acoustic impedance layer 221 may be polished and thinning.
  • the low acoustic impedance layers 222 and the high acoustic impedance layers 221 are alternately arranged.
  • the low acoustic impedance layer 222 and the high acoustic impedance layer 221 appear in pairs, the low acoustic impedance layer 222 and the high acoustic impedance layer 221 are alternately arranged, and the structure close to the bottom metal layer 21 is the high acoustic impedance layer 221, and the second stack 30 is formed.
  • the position at the top of the acoustic resonator is called the top of the acoustic resonator, and the position of the carrier wafer 40 is called the bottom of the acoustic resonator as an example.
  • the thickness of each bottom acoustic reflection layer 22 may be inconsistent, for example, the bottom acoustic reflection layer 22 closer to the piezoelectric wafer substrate 10 is thicker and farther away from the piezoelectric wafer substrate 10.
  • the bottom acoustically reflective layer 22 of the electrical wafer substrate 10 is thinner.
  • This design can provide more complete reflection, and can reduce the sensitivity of the design to unevenness in the process, and the different thickness of the bottom acoustic reflection layer 22 can provide better yield, and also has the effect of suppressing stray modes. It can be understood that, in other embodiments, the thickness of the bottom acoustic reflection layer 22 may also be other, as long as those skilled in the art consider it achievable.
  • the bottom acoustic reflection layer 22 further includes a filling reflection layer 223.
  • step S244 please refer to FIG. 3, and step S240 further includes step S246.
  • Step S246 depositing the filling reflective layer on the side of the low acoustic impedance layer away from the bottom metal layer.
  • the filling reflection layer 223 can be regarded as a part of the bottom acoustic reflection layer 22 . At this time, the filling reflection layer 223 is deposited on the side of the low acoustic impedance layer 222 away from the bottom metal layer 21 to fill the area around the low acoustic impedance layer 222 . Alternatively, the filling reflection layer 223 can also be regarded as a part of the acoustic wave resonator. In this case, the filling reflection layer 223 is deposited on the side of the bottom acoustic reflection layer 22 away from the bottom metal layer 21.
  • the filling reflective layer 223 is deposited on the side of the low acoustic impedance layer 222 away from the bottom metal layer 21 .
  • the type of filling reflection layer 223 is not unique, for example, it can be the same as the material used in the high acoustic impedance layer 221 or the material used in the low acoustic impedance layer 222, such as silicon dioxide, silicon nitride or spin glass filling reflection Layer 223.
  • the filling reflective layer 223 after depositing the filling reflective layer 223 on the side of the low acoustic impedance layer 222 away from the bottom metal layer 21, the filling reflective layer 223 can be polished and thinned to a desired thickness to meet more needs, or it can be It remains unchanged as long as those skilled in the art think it can be achieved.
  • the bottom acoustic reflection layer 22 further includes a bonding layer 224. Please refer to FIG. 3. After step S246, step S240 further includes step S248.
  • Step S248 depositing the bonding layer on the side of the filling reflective layer away from the low acoustic impedance layer.
  • the bonding layer 224 is located on the side of the filling reflection layer 223 away from the low acoustic impedance layer 222 , and the side of the bonding layer 224 away from the filling reflection layer 223 is the carrier wafer 40 .
  • the bonding layer 224 enables the thin film stack placed on the piezoelectric wafer substrate 10 to be bonded to the carrier wafer 40, in this embodiment, even though the fill reflective layer 223 is better bonded to the carrier wafer 40 superior.
  • the type of the bonding layer 224 is not unique.
  • the bonding layer 224 may be a silicon dioxide bonding layer 224.
  • the bonding layer 224 may also be a part of the bottom acoustic reflection layer 22 to transmit acoustic wave signals.
  • the thickness of the bonding layer 224 is not limited, and is generally relatively thin, so that the thickness of the acoustic wave resonator is not too large. Further, after the bonding layer 224 is deposited on the side of the filling reflective layer 223 away from the low acoustic impedance layer 222, the bonding layer 224 can also be thinned and polished to a desired thickness to facilitate bonding to the carrier crystal. Round 40.
  • thinning the side of the piezoelectric wafer substrate 10 away from the first stack 20 includes: grinding the side of the piezoelectric wafer substrate 10 away from the first stack 20 first, and then grinding the side of the piezoelectric wafer substrate 10 away from the first stack 20. Polish.
  • the thinning method is not unique.
  • the side of the piezoelectric wafer substrate 10 away from the first stack 20 is thinned first, so that the thickness of the piezoelectric wafer substrate 10 is reduced. Then, the piezoelectric wafer substrate is polished, so that the piezoelectric wafer substrate 10 can be better combined with the structures of other layers.
  • the degree of thinning of the piezoelectric wafer substrate 10 is not unique, and can be selected according to actual needs, and generally can be reduced from 500 um to several um.
  • the second stack 30 includes a top metal layer 31 and a top acoustic reflection layer 32 , please refer to FIG. 3 , and step S600 includes steps S640 and S660 .
  • Step S640 after thinning the side of the piezoelectric wafer substrate away from the first stack, a top metal layer is deposited on the side of the piezoelectric wafer substrate away from the first stack.
  • the second stack 30 includes a top metal layer 31 and a top acoustic reflection layer 32, the top metal layer 31 is used for transmitting electrical signals, and the top acoustic reflection layer 32 is used for transmitting acoustic wave signals.
  • the top metal layer 31 is also a layered structure. After thinning the side of the piezoelectric wafer substrate 10 away from the first stack 20, the top metal layer 31 is deposited on the piezoelectric wafer substrate 10. Forms the top electrode of the acoustic resonator.
  • the top metal layer 31 can also be patterned, and the shape, area and thickness of the top metal can be adjusted to meet specific requirements, for example, to match the bottom metal Layer 21 is properly aligned.
  • the shape of the top metal layer 31 is not unique and can be any geometry extracted from a square, rectangle, trapezoid or any polygon with n sides, where n is from 4 to infinity to resemble a circle or an ellipse.
  • the structure of the top metal layer 31 is not unique, and can be a metal layer made of aluminum, aluminum copper, aluminum silicon copper, Pt, Mo, Ru, W or Cu, or a metal layer made of alloys of these metals, etc. , which can be determined according to actual needs, as long as those skilled in the art think it can be realized.
  • Step S660 depositing the top acoustic reflection layer on the side of the top metal layer away from the piezoelectric wafer substrate.
  • the top acoustic reflection layer 32 is generally a layered structure and is disposed on the other side of the top metal layer 31 to reflect acoustic waves.
  • the type of the top acoustic reflection layer 32 is not unique, it can be a low acoustic impedance reflection layer, such as silicon dioxide, deposited on top of the top metal layer 31 forming the top electrode, and the material of the top acoustic reflection layer 32 can also be selected according to specific needs .
  • the top acoustic reflection layer 32 can also be patterned, so that the shape and size of the top acoustic reflection layer 32 can meet the requirements. .
  • the method for fabricating an acoustic wave resonator further includes step S700.
  • Step S700 Etch the top acoustic reflection layer and the piezoelectric wafer substrate, so that the top metal layer and the bottom metal layer can access electrode lines.
  • the top acoustic reflection layer 32 is regarded as the upper layer of the top metal layer 31
  • the lower layer of the top metal layer 31 is the piezoelectric wafer substrate 10
  • the lower layer of the piezoelectric wafer substrate 10 is the bottom metal layer 21 .
  • the top acoustic reflection layer 32 is disposed on top of the top metal layer 31. After the top acoustic reflection layer 32 is etched, the top metal layer 31 in the lower layer can be exposed and the electrode lines can be connected. In addition, after the piezoelectric wafer substrate 10 is etched, the bottom metal layer 21 located under the piezoelectric wafer substrate 10 can be exposed, and electrode lines can be connected to the bottom metal layer 21 .
  • the etching of the top acoustic reflection layer 32 and the etching of the piezoelectric wafer substrate 10 are both etching the entire thickness of the corresponding layer, so that the lower layer located in the layer is exposed, which is convenient for accessing the electrode lines, The entire thickness is etched in specific areas, preserving most of the original structure.
  • the acoustic wave resonator is a longitudinal acoustic wave resonator with n-th order thickness extension, please refer to FIG. 4 and FIG.
  • the manufacturing method of the acoustic wave resonator includes the following main steps: 1) on the piezoelectric wafer substrate 10 2) Bonding the stack (the first stack 20 ) and the piezoelectric wafer substrate 10 to the carrier wafer 40 3) thinning and polishing the piezoelectric wafer substrate 10 to the desired thickness; 4) depositing and patterning stacked layers on the top surface of the thinned piezoelectric wafer substrate 10, where the stacking The layers correspond to the second stack 30 above.
  • the piezoelectric wafer substrate 10 is the piezoelectric wafer substrate 10, and the detailed steps are as follows: first, deposit a metal layer (bottom metal layer 21) on the piezoelectric wafer substrate 10 and pattern it to form n Bottom electrode of a longitudinal acoustic wave resonator with order thickness extension (see Figure 6).
  • the thin metal layer can be any of the following materials and alloys thereof: Al, AlCu, AlSiCu, Pt, Mo, Ru, W and Cu.
  • the piezoelectric wafer substrate 10 may be any of the following materials and doped forms thereof: lithium niobate, lithium tantalate, aluminum nitride, and quartz.
  • a stack of low acoustic impedance layers 222 and high acoustic impedance layers 221 is then deposited and patterned on top of the metal layer (bottom metal layer 21) to form a set of acoustically reflective layers (bottom acoustically reflective layer 22), which may have Any number of layers ( Figure 7).
  • both layers forming the set of acoustically reflective layers can be patterned, or only the high acoustic impedance layer is patterned (Fig. 7a), b), c) and d)), possibly two of them
  • An embodiment in which none of the layers are patterned (Fig. 7e)).
  • Both layers forming the acoustic reflecting layer group may be polished and thinned, or only the low acoustic impedance layer 222 may be polished and thinned, or both layers may be polished and thinned.
  • the low acoustic impedance layer 222 may be formed of any of the following materials: silicon dioxide, spin glass, tellurium oxide, and other oxide families including other materials.
  • the high acoustic impedance layer 221 may be formed of any of the following materials: aluminum nitride, tungsten, platinum, molybdenum, ruthenium, and oxidized versions of the same.
  • a filling reflection layer 223 is deposited on the side of the low acoustic impedance layer 222 away from the bottom metal layer 21, and the material filling the reflection layer 223 can be any high or low acoustic impedance material (FIG. 5).
  • the material filling the reflection layer 223 can be any high or low acoustic impedance material (FIG. 5).
  • it may be silicon dioxide, silicon nitride, or spin glass or the like.
  • the fill reflective layer 223 may also be part of the acoustic reflective layer set itself.
  • the filled reflective layer 223 may be polished and thinned to a desired thickness, or may remain unchanged.
  • the final layer of the acoustically reflective layer set needs to be a thin layer of silicon dioxide to ensure that the thin film stack placed on the piezoelectric wafer substrate 10 can be bonded to the carrier wafer 40 (FIG. 6), this layer is also Can be part of the acoustic reflective layer set itself.
  • the final silicon dioxide bonding layer 224 is thinned and polished to the desired thickness to facilitate bonding to the carrier substrate (carrier wafer 40) (FIG. 10).
  • the piezoelectric wafer substrate 10 is bonded to the carrier wafer 40 by bonding of silicon dioxide (FIG. 11).
  • the piezoelectric wafer substrate 10 is thinned and polished to the desired thickness (FIG. 12).
  • top metal layer 31 is deposited on the top surface of the piezoelectric layer (piezo wafer substrate 10) and patterned to ensure proper alignment with the top metal layer 31 forming the bottom electrode (Fig. 13), other metal layers can also be deposited and patterned.
  • These metals can be any of the following materials and alloys: aluminum, aluminum copper, aluminum silicon copper, Pt, Mo, Ru, W, and Cu.
  • Another layer of low acoustic impedance material such as silicon dioxide, is deposited on top of the top metal layer 31 forming the top electrode (FIG. 14).
  • the low acoustic impedance layer 222 is etched and trimmed in specific areas (FIG. 15a).
  • additional layers 50 of other materials can also be deposited in specific regions of the resonator (Fig. 15b).
  • This material can be a metal or a dielectric.
  • Contact is made with the top electrode by etching through the low acoustic impedance layer 222 deposited on the top electrode (FIG. 13a).
  • Contact to the bottom electrode is obtained by a low acoustic impedance layer 222 (FIG. 13b) deposited on the top electrode and piezoelectric layer.
  • two or more (average) resonators can simply be arranged without making contact with the bottom electrode.
  • FIG 4 the top view (a) and cross-section (b)) of the active region show different patterns of a longitudinal acoustic wave resonator (nT-LAW resonator) with n-th order thickness extension layer.
  • the example shown uses two pairs of low-resistance and high-resistance layers (where only the high-resistance layer is patterned).
  • Cross-sections AA', BB' and CC' are also used in the latter figures to show the fabrication process flow of the nT-LAW resonator.
  • the fill pattern used for the plane pattern in the figure corresponds to the fill pattern of the applied layer in the subsequent fabrication process.
  • top view (a) and cross-sections (b) and c) of the active area showing frequency shifted nT-LAW oscillators and different graphic layers with additional steps (top etch of b) and deposition of additional layers 50 .
  • the example shown uses two pairs of low-resistance and high-resistance layers (where only the high-resistance layer is patterned).
  • Cross-sections A2A2', BB' and CC' are used in the following figures to show the manufacturing process flow of the nT-LAW vibrator.
  • FIG. 6 is a graphical result of the bottom electrode.
  • Figure 7 shows a graphic representation of a pair of low and high acoustic impedance layers 221.
  • a) is that only the high acoustic impedance layer 221 is patterned when each layer is deposited.
  • c) is the patterning of the low and high acoustic impedance layers 221 .
  • the high acoustic impedance layer 221 is patterned as each layer is deposited, and the low acoustic impedance layer 222 will be patterned together after the last high acoustic impedance layer 221 array.
  • d) is the patterning of the low and high acoustic impedance layers 221 .
  • the low acoustic impedance layer 222 and the high acoustic impedance layer 221 are both together.
  • e) is that neither the low acoustic impedance layer 222 nor the high acoustic impedance layer 221 is patterned.
  • FIG. 8 shows the deposition of the fill reflective layer 223.
  • FIG. 9 shows the deposition of a silicon dioxide layer (if the previous layer is of a different material) for bonding the thin film stack to the carrier wafer 40 .
  • FIG. 10 is the polishing and thinning of the silicon dioxide bonding layer 224 .
  • FIG. 11 is bonding to the carrier wafer 40 substrate.
  • FIG. 12 illustrates polishing and thinning of piezoelectric wafer substrate 10 .
  • FIG. 13 is the patterning of the top metal layer 31 .
  • FIG. 14 shows top acoustic reflective layer 32 material deposition after top metal layer 31 is patterned.
  • Figure 15 shows two methods of obtaining frequency shifted resonators on the same technology platform, where a) etching of low acoustic impedance material at certain locations and b) deposition of additional layers 50 at certain locations.
  • a) is etching the low acoustic impedance top material (top acoustic reflection layer 32) to access the top electrode
  • b) is etching the low acoustic impedance top material and piezoelectric layer (piezoelectric wafer substrate 10) to access the bottom electrode.
  • piezoelectric layer piezoelectric wafer substrate
  • a) is etching the material of the top acoustic reflection layer 32 to access the top electrode
  • b) is etching the material of the top acoustic reflection layer 32 and the piezoelectric wafer substrate 10 to access the bottom electrode.
  • Figure 17 shows a resonator pair with all electrical connections made with only the top metal layer 31. Including the opening of the electrode lead wire and the passivation layer, the opening is used to expose the electrode lead wire for electrical connection.
  • a piezoelectric wafer substrate 10 is provided, a first stack 20 is prepared on the piezoelectric wafer substrate 10, and the first stack 20 is away from the side of the piezoelectric wafer substrate 10. Bonding to the carrier wafer 40 , and then thinning the side of the piezoelectric wafer substrate 10 away from the first stack 20 , and then preparing on the side of the piezoelectric wafer substrate 10 away from the first stack 20
  • the second stack forms an acoustic resonator, the first stack 20 is used to transmit electrical signals and bound acoustic signals, and the second stack 30 is used to transmit electrical signals and acoustic signals.
  • the second stack 30, the piezoelectric wafer substrate 10, the first stack 20 and the carrier wafer 40 are stacked and arranged, and the carrier wafer 40 plays a bearing role.
  • the piezoelectric thin film formed by thinning the piezoelectric wafer substrate 10 can be excited to vibrate acoustically, and the first stack 20 and the second stack 30 can transmit electrical signals and bound acoustic wave signals, so that the resulting acoustic wave resonator can Working at high frequencies, because the acoustic wave resonator made by this method has a specific stack combination and piezoelectric film, it can excite and support high-performance acoustic vibration modes, so that the fabricated device exhibits low loss, high Quality factor, wide bandwidth and low temperature sensitivity, high reliability.
  • an acoustic resonator made according to the method described above.
  • the piezoelectric wafer substrate 10 is first provided, the first stack 20 is prepared on the piezoelectric wafer substrate 10, and the side of the first stack 20 away from the piezoelectric wafer substrate 10 is bonded onto the carrier wafer 40 , and after thinning the side of the piezoelectric wafer substrate 10 away from the first stack 20 , a second The layers are stacked to form an acoustic resonator, the first stack 20 is used to transmit electrical signals and bound acoustic signals, and the second stack 30 is used to transmit electrical signals and acoustic signals.
  • the second stack 30, the piezoelectric wafer substrate 10, the first stack 20 and the carrier wafer 40 are stacked and arranged, and the carrier wafer 40 plays a bearing role.
  • the piezoelectric thin film formed by thinning the piezoelectric wafer substrate 10 can be excited to vibrate acoustically, and the first stack 20 and the second stack 30 can transmit electrical signals and bound acoustic wave signals, so that the resulting acoustic wave resonator can Working at high frequencies, because the acoustic wave resonator made by this method has a specific stack combination and piezoelectric film, it can excite and support high-performance acoustic vibration modes, so that the fabricated device exhibits low loss, high Quality factor, wide bandwidth and low temperature sensitivity, high reliability.

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  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)

Abstract

La présente demande concerne un procédé de fabrication de résonateur à ondes acoustiques et un résonateur à ondes acoustiques. Le procédé comprend : préparer une première couche stratifiée sur un substrat de tranche piézoélectrique, lier le côté de la première couche stratifiée à l'opposé du substrat de tranche piézoélectrique à une tranche de support, et prépare une deuxième couche stratifiée après amincissement du côté du substrat de tranche piézoélectrique à l'opposé de la première couche stratifiée, et former le résonateur à ondes acoustiques. Dans le résonateur à ondes acoustiques fabriqué par le procédé, la deuxième couche stratifiée, le substrat de tranche piézoélectrique, la première couche stratifiée, et la tranche de support sont disposés dans un mode stratifié, la tranche de support joue un rôle de support, un film mince piézoélectrique formé par amincissement du substrat de tranche piézoélectrique peut être excité pour vibrer acoustiquement, et la première couche stratifiée et la deuxième couche stratifiée peuvent transmettre des signaux électriques et des signaux acoustiques liés, de telle sorte que le résonateur à ondes acoustiques obtenu peut fonctionner à haute fréquence, et le résonateur à ondes acoustiques a une combinaison de stratification spécifique et un film mince piézoélectrique, peut exciter et supporter un mode de vibration acoustique haute performance, et présente une faible perte, un facteur de qualité élevé, une large bande passante, une faible sensibilité à la température et une fiabilité d'utilisation élevée.
PCT/CN2021/092048 2021-02-09 2021-05-07 Procédé de fabrication de résonateur à ondes acoustiques et résonateur à ondes acoustiques WO2022170683A1 (fr)

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