Wafer for epitaxial aluminum nitride bulk acoustic wave filter device by thermal self-splitting process, method for manufacturing the same, and bulk acoustic wave filter device

Abstract

An embodiment of the present application provides a wafer for an epitaxial aluminum nitride bulk acoustic wave filter device by a thermal self-splitting process, comprising: a support substrate; a wafer bonding layer on the upper side of the support substrate; an acoustic mirror configured on the upper side of the wafer bonding layer; a lower electrode formed on the upper side of the acoustic mirror; a piezoelectric thin film configured on the upper side of the lower electrode and grown into a single crystal structure by an epitaxial growth method; and an upper electrode configured on the upper side of the piezoelectric thin film.

Description

Technical Field

[0001] This invention relates to a wafer for an epitaxial aluminum nitride bulk acoustic wave filter device using hot self-split technology and wafer bonding process, which minimizes the consumption of expensive seed substrates containing SiC while utilizing high-quality epitaxial AlN or AlScN piezoelectric thin films to simultaneously meet excellent physical properties and economy, as well as the manufacturing method of the wafer and the bulk acoustic wave filter device. Background Technology

[0002] As the current standard wireless communication technology, 5G requires high-performance filtering solutions due to its high data transmission speed, low latency, and the simultaneous access of numerous devices.

[0003] Representative filter types include LC filters, SAW filters, and BAW filters. The appropriate product is selected based on factors such as the frequency band used and the size of the components.

[0004] In 5G mobile communication systems, SAW (Surface Acoustic Wave Filter) and BAW (Bulk Acoustic Wave Filter) filters are mainly used.

[0005] BAW filters have a sandwich structure with electrodes positioned on the upper and lower parts of a piezoelectric film. Compared to SAW filters, they are more complex to manufacture and more expensive, but they feature high module receiving sensitivity and high transmission power efficiency.

[0006] On the other hand, in order to realize ultra-high-speed communication systems above 5G, it is necessary to improve product characteristics such as excellent high-frequency characteristics, maximize piezoelectric conversion efficiency and expand bandwidth. Therefore, the necessity of piezoelectric thin films of materials that alloy a second element (such as Sc, Y, etc.) to replace a portion of aluminum (Al) in order to increase the piezoelectric capability of epitaxial single crystal AlN or piezoelectric thin films is becoming increasingly clear.

[0007] Furthermore, the thickness uniformity of single-crystal AlN or AlScN piezoelectric films plays a role as a key performance index (KPI) for BAW filters.

[0008] To achieve a thickness uniformity of 0.1% to 1%, wafer warpage needs to be minimized when growing single-crystal AlN (or AlScN). Ideally, when growing single-crystal AlN (or AlScN) films, a growth substrate that minimizes the difference in lattice constants should be selected (e.g., SiC>Sapphire>Si), and wafer warpage should be compensated by increasing the thickness of the growth substrate (SiC).

[0009] Therefore, it is necessary to address the economic issues arising from the increase in the thickness of the growth substrate (SiC). Summary of the Invention

[0010] Technical problems to be solved The present invention aims to provide a wafer for epitaxial aluminum nitride bulk acoustic wave filter device, a method for manufacturing the wafer, and the bulk acoustic wave filter device thereof, which uses an expensive SiC substrate with a thickness that minimizes the warping phenomenon as a consumable material and also ensures economic efficiency through a thermal self-splitting process, in the high-temperature process necessary for high-quality epitaxial growth.

[0011] Technical solution An embodiment of the present invention provides a wafer for an epitaxial aluminum nitride bulk acoustic wave filter device produced by a thermal self-splitting process, comprising: a supporting substrate; a wafer bonding layer located on the upper side of the supporting substrate; an acoustic mirror disposed on the upper side of the wafer bonding layer; a lower electrode formed on the upper side of the acoustic mirror; a piezoelectric thin film disposed on the upper side of the lower electrode and grown into a single crystal structure by an epitaxial growth method; and an upper electrode disposed on the upper side of the piezoelectric thin film.

[0012] This invention provides a method for manufacturing a wafer for an epitaxial aluminum nitride bulk acoustic wave filter device using a thermal self-splitting process. The method includes: preparing a seed substrate for growing an epitaxial layer to form the device; epitaxially growing a piezoelectric thin film on the seed substrate; sequentially forming a resonant portion including a lower electrode and an acoustic mirror on the upper side of the piezoelectric thin film; performing a seed substrate modification step before or after the resonant portion formation step by irradiating the seed substrate with a stealth laser to form a reforming layer inside the seed substrate; performing a wafer bonding step by wafer bonding the upper surface of the acoustic mirror to a support substrate using a predetermined wafer bonding layer as a medium; a seed region separation step by separating the seed substrate on one side of the piezoelectric thin film with the reforming layer as a boundary to form a seed region; a seed region removal step by removing the seed region; and an upper electrode formation step by forming an upper electrode on the exposed lower surface of the acoustic mirror.

[0013] A manufacturing method according to another embodiment of the present invention includes: a step of preparing a seed substrate for growing an epitaxial layer for forming a device; a step of growing a piezoelectric thin film on the seed substrate by an epitaxial method; an upper electrode forming step of forming an upper electrode on the upper side of the piezoelectric thin film; a seed substrate modification step of irradiating the seed substrate with a stealth laser to form a reforming layer inside the seed substrate before or after performing the upper electrode forming step; a temporary substrate bonding step of bonding the upper surface of the upper electrode to a temporary substrate with an adhesive layer as a medium; a seed region separation step of separating the seed substrate on one side of the piezoelectric thin film with the reforming layer as a boundary to form a seed region; a seed region removal step of removing the seed region; a resonant portion forming step of forming a resonant portion including a lower electrode and an acoustic mirror on the lower surface of the piezoelectric thin film; and a wafer bonding step of wafer bonding a support substrate on the lower surface of the acoustic mirror with a wafer bonding layer as a medium after performing the resonant portion forming step.

[0014] In the manufacturing method according to an embodiment of the present invention, the seed crystal region separation step may be: the seed crystal substrates on both sides centered on the modified layer are separated without external force by means of thermal stress or mechanical stress formed in the modified layer, through structural asymmetry having quantitative differences or thickness differences in thermal properties including thermal expansion coefficient.

[0015] The present invention provides an epitaxial aluminum nitride bulk acoustic wave filter manufactured using a wafer of the above-mentioned epitaxial aluminum nitride bulk acoustic wave filter device through a thermal self-splitting process.

[0016] Invention Effects According to the present invention, by utilizing thermal self-splitting technology, the consumption of seed crystal substrates can be minimized while high-quality epitaxial piezoelectric thin film deposition can be achieved, thus enabling the fabrication of bulk acoustic wave filters that simultaneously satisfy excellent physical properties and cost-effectiveness.

[0017] According to the present invention, the wafer bonding process facilitates the execution of various processing techniques, thereby significantly improving the manufacturability of the bulk acoustic wave filter and the wafer used to manufacture it. Attached Figure Description

[0018] Figure 1 This diagram illustrates one embodiment of a wafer for an epitaxial aluminum nitride bulk acoustic filter device according to the present invention, produced by a thermal self-splitting process.

[0019] Figures 2 to 9This diagram illustrates one embodiment of the wafer manufacturing method for an epitaxial aluminum nitride bulk acoustic filter device according to the present invention via a thermal self-splitting process.

[0020] Figures 10 to 19 This diagram illustrates another embodiment of the wafer fabrication method for an epitaxial aluminum nitride bulk acoustic filter device according to the present invention via a thermal self-splitting process. Detailed Implementation

[0021] Hereinafter, with reference to the accompanying drawings, we will describe in detail the wafer for an epitaxial aluminum nitride bulk acoustic wave filter device according to the present invention, the manufacturing method thereof, and various embodiments of the bulk acoustic wave filter device.

[0022] The terminology used below is chosen for ease of explanation. Therefore, when grasping the intrinsic technical concept of this invention, it should not be limited to its dictionary meaning, but should be interpreted in the sense that conforms to the technical concept of this invention.

[0023] Reference Figure 1 The epitaxial aluminum nitride bulk acoustic wave filter device wafer according to this embodiment, which is produced by thermal self-splitting process, includes a support substrate (110), a wafer bonding layer (120), an acoustic mirror (131), a lower electrode (132), a piezoelectric film (140), and an upper electrode (150).

[0024] The support substrate (110) can be formed from any one of AlN polycrystalline, SiC polycrystalline, Si single crystal, or SiC single crystal.

[0025] The wafer bonding layer (120) can be made of SiO2, SiN x SOG (Spin-on-Glass), AlN, and Al2O3 are used as bonding materials.

[0026] An acoustic reflector (131) is a structure consisting of at least two or more layers with different physical properties, disposed on the upper side of the wafer bonding layer (120).

[0027] The lower electrode (132) is formed on the upper side of the acoustic mirror (131).

[0028] The piezoelectric thin film (140) is disposed on the upper side of the lower electrode (132) and has a single crystal structure grown by epitaxial growth method, ideally formed using AlN or AlScN as the material.

[0029] In this embodiment, a piezoelectric thin film (140) is epitaxially grown on a SiC seed substrate (growth substrate). With a lower electrode (132) and an acoustic reflector (131) sequentially stacked on the piezoelectric thin film (140), a support substrate (110) is bonded together by means of a wafer bonding layer (120).

[0030] The SiC material seed substrate (growth substrate) is separated after bonding with the support substrate (110), and the upper electrode (150) is disposed on the upper side of the piezoelectric thin film (140). On the other hand, the separated SiC material seed substrate (growth substrate) is provided as a growth substrate for another piezoelectric thin film (140).

[0031] Typically, AlN piezoelectric thin films are formed on the upper part of a molybdenum (Mo) lower electrode by physical vapor deposition (PVD) methods such as sputtering. In this case, the (0001) crystal peak with a half-width (FWHM) of 0.5~1.5° is observed in the X-ray diffraction (XRD) spectrum.

[0032] The piezoelectric thin film (140) of this embodiment has film quality formed by epitaxial growth on a SiC material seed substrate (growth substrate) with a thickness of 300 μm or more, and has a (0001) crystal peak with a half width at half maximum (FWHM) of 0.01 to 0.05°.

[0033] Because the XRD full width at half maximum (FWHM) is significantly improved, it has the advantage of being able to extend the bandwidth of the filter.

[0034] Furthermore, due to the excellent quality and thickness uniformity of the piezoelectric film (140), it has certain acoustic properties independent of thickness, and can be expected to have excellent high-frequency characteristics. Moreover, by adjusting the single polarity (Al or Sc surface polarity, N surface polarity) of the AlN or AlScN surface on the upper and lower surfaces of the piezoelectric film (140), the piezoelectric conversion efficiency can be maximized and the energy loss minimized.

[0035] Next, refer to Figures 2 to 9 According to this embodiment, the wafer manufacturing method for an epitaxial aluminum nitride bulk acoustic wave filter device using a thermal self-splitting process includes a seed substrate preparation step (S100), a piezoelectric thin film growth step (S200), a seed substrate modification step (S300), a resonant part formation step (S400), a wafer bonding step (S450), a seed region separation step (S500), a seed region removal step (S600), and an upper electrode formation step (S700).

[0036] Seed substrate preparation step (S100): Prepare a seed substrate (10) for growing the specified epitaxial layer for forming the device.

[0037] The seed crystal substrate (10) is ideally a 4H-SiC single crystal material with an initial thickness of more than 1000 μm.

[0038] The piezoelectric thin film growth step (S200) involves epitaxially growing a piezoelectric thin film (140) on a seed substrate (10), which may have a single-crystal AlN or AlScN structure.

[0039] In the seed substrate modification step (S300), a stealth laser (L) is irradiated onto the seed substrate (10) to form a modification layer (11) inside the seed substrate (10).

[0040] The modified layer (11) is formed as a surface parallel to the growth surface of the seed substrate (10).

[0041] When the focal point of the photons of the stealth laser (L) moves along a specific plane to form a scanning plane, a modified layer (11) is formed along the scanning plane.

[0042] In the resonant part forming step (S400), a resonant part (130) including a lower electrode (132) and an acoustic reflector (131) is sequentially formed on the upper side of the piezoelectric film (140).

[0043] The seed substrate modification step (S300) can be performed before or after the resonant part formation step (S400).

[0044] If the process is performed before the resonant part formation step (S400), the stealth laser (L) can be projected from the upper side of the seed substrate (10) downward or from the lower side upward.

[0045] Conversely, if the process is performed after the resonant part formation step (S400), the projection direction of the stealth laser (L) is upward from the lower side of the seed substrate (10).

[0046] After the resonant part formation step (S400) is performed, the upper surface of the acoustic reflector (131) is bonded to the support substrate (110) using a specified wafer bonding layer (120) as the medium.

[0047] With the aid of the wafer bonding step (S450), the exposed upper surface of the acoustic reflector (131) and the surface of the supporting substrate (110) are fused together to form an irreversible and permanent bonding interface.

[0048] This is because: even if high-temperature heating processes may be performed in subsequent processes, the bonding characteristics can be maintained as is, thus enabling the application of a wide range of process conditions in the epitaxial device-package process.

[0049] The wafer bonding step (S450) is ideally performed at a bonding temperature above 250°C.

[0050] The wafer bonding layer (120) can be made of SiO2, SiN x It is composed of SOG (Spin-on-Glass), AlN, and Al2O3 dielectric ceramic bonding materials.

[0051] The wafer bonding layer (120) can form bonding materials on the exposed upper surface of the acoustic reflector (131) and the surface of the support substrate (110), respectively. After plasma or solution surface treatment, a pre-bonding process is first performed at room temperature (~25℃).

[0052] Ideally, for a surface roughness of less than 1 nm, surface planarization processes such as mechanical polishing or chemical mechanical polishing (CMP) should be preferentially adopted.

[0053] After performing the pre-bonding process, in order to strengthen the bonding force, it is ideal to perform a heat treatment step at a bonding temperature above 250°C, preferably at 1,200°C.

[0054] The wafer bonding step (S450) may further include a step of removing bubble gas components such as OH and H2 from the dielectric ceramic bonding (bonding) material.

[0055] The supporting substrate (110) is ideally AlN polycrystalline, SiC polycrystalline, Si single crystal, or SiC single crystal.

[0056] In the seed crystal region separation step (S500), the seed crystal substrate (10) on one side of the piezoelectric thin film (140) is separated with the modified layer (11) as the boundary to form a seed crystal region.

[0057] The seed crystal region separation step (S500) employs a hot self-split process, namely: the two sides of the modified layer (11) are separated by a structural asymmetry with quantitative differences or thickness differences in thermal properties including thermal expansion coefficient, thereby generating thermal stress or mechanical stress in the modified layer (11), so that the modified layer (11) can be separated without mechanical external force.

[0058] The thermal self-splitting process is performed during the cooling process of the heat supplied in the wafer bonding step (S450). In this respect, this embodiment includes the case where the formation of the modified layer (11) is performed after the wafer bonding step (S450).

[0059] Specifically, on both sides of the modified layer (11) as the boundary, due to the thickness, the structure formed by the permanent bonding of different materials and the physical properties of the different materials bonded together, the effective thermal expansion coefficient and effective thermal conductivity that can be applied to the physical interaction between them are different.

[0060] This is the factor that causes the seed crystal region (20) and the seed crystal substrate (10) to have different degrees of thermal expansion with the modified layer (11) as the boundary. It plays the role of the first factor that enables the seed crystal region (20) and the seed crystal substrate (10) to be "separated without external force" with the modified layer (11) as the center.

[0061] On the other hand, with the modified layer (11) as the boundary, the seed crystal region (20) and the seed crystal substrate (10) have the same lattice constant, but the seed crystal region (20) with the piezoelectric thin film (140) and the resonant part (130) has a different lattice constant based on its physical properties.

[0062] This generates mechanical stress in the modified layer (11), which is another factor that enables the seed crystal region (20) and the seed crystal substrate (10) to "separate without external force" centered on the modified layer (11).

[0063] In summary, the thermal self-splitting process has the following characteristics: by breaking the quantitative-qualitative identity of the physical properties of the seed crystal region (20) and the seed crystal substrate (10) with the modified layer (11) as the boundary, stress is generated along the modified layer (11), thereby separating them without the need for external mechanical force.

[0064] Therefore, the thermal self-splitting process can obtain a high-quality thin film structure by epitaxially growing a piezoelectric thin film (140) as the core structure of a bulk acoustic wave filter on a thick seed substrate (10). In addition, the consumption of the seed substrate is minimized to improve economic efficiency.

[0065] The seed substrate (10) ideally has an initial thickness of more than 1000 μm, is consumed by repeated use through a thermal self-splitting process, and is provided for the growth of piezoelectric films with a thickness of more than 300 μm.

[0066] The thicker the seed substrate (10), the more the warping phenomenon in the high-temperature process is minimized, thus increasing the growth temperature of the piezoelectric film formed on the upper side, which can form a high-quality piezoelectric film.

[0067] Seed region removal step (S600) removes the seed region (20) separated from the seed substrate (10).

[0068] The upper electrode forming step (S700) forms an upper electrode (150) on the lower surface of the exposed acoustic reflector (131).

[0069] The above-described embodiment has the following technical features: after permanently fusing the seed substrate (10), the resonant part (130) and the piezoelectric thin film (140) to the support substrate using wafer bonding technology, the step of separating the seed substrate (10) into the seed region (20) and the seed substrate (10) outside the seed region (20) with the modified layer (11) as the center is performed.

[0070] Furthermore, since the piezoelectric film (140) and the resonant part (130) are already stably bonded to the support substrate (110) before being separated from the seed substrate (10), the piezoelectric film (140) and the resonant part (130), which are the basic structures of the bulk acoustic wave filter, are very easy to operate.

[0071] That is, it has the advantage of smooth process execution from the additional device manufacturing process of the bulk acoustic wave filter device layer to the final package process. In addition, since it is completely separated from the seed substrate (10) while firmly bonded to the support substrate (110), the possibility of defects such as breakage during separation and microcracks that are very difficult to inspect and test is greatly reduced.

[0072] On the other hand, the oscillation frequency of the bulk acoustic wave filter is determined by the thickness of the piezoelectric film. For 5G and above mobile wireless communication applications, the thickness uniformity of single-crystal AlN or AlScN is a key performance indicator.

[0073] In this embodiment, a piezoelectric film planarization step may be further included, which planarizes the surface of the exposed piezoelectric film (140) after the piezoelectric film growth step (S200) or the seed crystal region removal step (S600).

[0074] The piezoelectric thin film planarization step can be constituted by a process of digital dry etching of AlN (or AlScN) single crystal thin films at the nanoscale to achieve a thickness uniformity of 0.1% to less than 1%.

[0075] On the other hand, in this embodiment, for the SiC seed substrate, the polarity of the growth surface can be Si polar (Si-polar) or C polar (C-polar).

[0076] However, in the case of C-polarity, the upper surface of the AlN piezoelectric film has N-polarity, and its surface roughness is much greater than that of Al-polarity. Therefore, it has the disadvantage of requiring a CMP (one-time) process on the surface after growth (described later). Figures 10 to 19 The implementation requires both primary and secondary CMP processes. Therefore, the growth surface of the seed substrate is ideally Si-polar. In this case, the upper surface (surface) of the AlN piezoelectric film is Al-polar.

[0077] Next, refer to Figures 10 to 19 This embodiment includes a seed substrate preparation step (S1100), a piezoelectric thin film growth step (S1200), a seed substrate modification step (S1300), an upper electrode formation step (S1400), a temporary substrate bonding step (S1450), a seed region separation step (S1500), a seed region removal step (S1600), a resonant part formation step (S1700), and a wafer bonding step (S1750).

[0078] The steps are: seed substrate preparation (S1100), piezoelectric thin film growth (S1200), seed substrate modification (S1300), upper electrode formation (S1400), and resonator formation (S1700). Due to the... Figures 2 to 9 The implementation form is the same, so the above description is used instead.

[0079] This embodiment differs from others in that it involves two wafer bonding steps (temporary substrate bonding step (S1450) and wafer bonding step (S1750)). Figures 2 to 9 The implementation forms are different.

[0080] Thus, the AlN polarities on the upper and lower surfaces of the piezoelectric film can be made to be opposite to each other.

[0081] By adjusting the AlN polarity on the upper and lower surfaces of the piezoelectric film (140), the piezoelectric conversion efficiency can be maximized, thereby minimizing energy loss.

[0082] For example, if the prepared seed substrate (10) is a SiC substrate and its upper surface (growth surface) has a C-polar face, then the upper surface (grown surface) of the AlN or AlScN piezoelectric film (140) epitaxially grown on its upper side has an N-polar face.

[0083] Surfaces with an N-polar face are not only softer than those with an Al-polar face, but they are also more reactive with other substances, which may cause various problems in subsequent processes.

[0084] In this case, according to this embodiment, it is possible to form the upper surface of a piezoelectric thin film (140) having an Al-polar face.

[0085] That is, given that the crystal polarity of the prepared seed substrate (10) surface is determined, the upper surface polarity of the piezoelectric thin film (140) can be selected.

[0086] In this embodiment, after the upper electrode formation step (S1400) is performed, the upper surface of the upper electrode (150) is bonded to the temporary substrate (30) using a specified adhesive layer (31) as the medium.

[0087] After the resonant part formation step (S1700) is performed, the wafer bonding step (S1750) involves bonding the support substrate (110) to the lower surface of the acoustic reflector (131) using a specified wafer bonding layer (120) as a medium.

[0088] The temporary substrate removal step (S1800) removes the temporary substrate (30) after the wafer bonding step (S1750) is performed.

[0089] According to this embodiment, by employing a temporary substrate (30) and a support substrate (110), more stable high workability is achieved in the manufacturing process of the manufactured bulk acoustic wave filter, thereby not only reducing manufacturing costs but also improving yield.

[0090] The temporary substrate (30) is bonded to the piezoelectric film (140) on which the upper electrode (150) is formed before the seed substrate (10) (excluding the seed region (20) is separated.

[0091] The seed crystal region separation step (S1500) employs a hot self-split process, namely: the two sides of the modified layer (11) are separated by a structural asymmetry with quantitative differences or thickness differences in thermal properties including thermal expansion coefficient, thereby generating thermal or mechanical stress in the modified layer (11), thus separating the modified layer (11) without the need for external mechanical force.

[0092] The thermal self-splitting process is performed during the cooling process of the heat supplied in the temporary substrate bonding step (S1450). In this respect, this embodiment includes the case where the formation of the modified layer (11) is performed after the temporary substrate bonding step (S1450).

[0093] The temporary substrate (30) can greatly mitigate the increased probability of breakage and cracking in the subsequent resonant formation step (S1700) and even the numerous processes of chip process and package process, which are carried out with only a thin piezoelectric film (140).

[0094] The support substrate (110) not only provides an appropriate vertical volume that makes the completed device easy to operate, but also provides rigidity on the underside of the thin resonant portion (130) and the piezoelectric film (140), thus enabling stable process execution in packaging processes such as die bonding and wire bonding.

[0095] The temporary substrate (30) can be made of Sapphire, SiC single crystal, or Si, ideally selected as a material with thermal properties similar to or the same as those of the supporting substrate (110), including its coefficient of thermal expansion and thermal conductivity.

[0096] This aims to ensure normal and excellent bonding characteristics between the support substrate (110) and the resonant part (130) in the wafer bonding step (S1750).

[0097] Wafer bonding is performed after heating the substrate and bonding layer to a specified temperature, which is one of the usual process conditions.

[0098] Therefore, if there is a large difference in the thermal properties between the temporary substrate (30) and the support substrate (110), the shrinkage characteristics of the interface between the support substrate (110) and the acoustic mirror (131) will differ during the bonding process, and thus stable bonding (joining) characteristics cannot be expected.

[0099] For the adhesive layer (31), preferred materials include organic materials such as resin, epoxy, SU-8, and BCB, and metallic materials such as Sn, In, Zn, Ga, Au, Ni, Ag, and Cu. However, depending on the circumstances, SiO2 and SiN may also be used. x Dielectric ceramic materials such as SOG (Spin-on-Glass), AlN, Al2O3, ITO, GaN, InGaN, AlGaN, AlGaInN, ZnO, and ZITO can also be used.

[0100] However, since the wafer bonding process between the support substrate (110) and the acoustic reflector (131) is based on SiO2 and SiN x Wafer bonding is performed using dielectric ceramic materials such as SOG (Spin-on-Glass), AlN, and Al2O3 as the medium. Therefore, it is ideal to have a smooth surface with a possible surface roughness of less than 1 nm before bonding, and to maintain the state of surface treatment such as plasma or solution to improve surface energy. This is one of the most important factors to obtain excellent bonding properties.

Claims

1. A wafer for epitaxial aluminum nitride bulk acoustic wave filter devices by a thermal self-splitting process, characterized in that, include: Support substrate; The wafer bonding layer located on the upper side of the supporting substrate; An acoustic reflector disposed on the upper side of the wafer bonding layer; The lower electrode is formed on the upper side of the acoustic reflector; A piezoelectric thin film disposed on the upper side of the lower electrode and grown as a single crystal structure by epitaxial growth method; and The upper electrode is disposed on the upper side of the piezoelectric film.

2. The wafer for an epitaxial aluminum nitride bulk acoustic wave filter device using a thermal self-splitting process according to claim 1, characterized in that, The piezoelectric film is formed of AlN or AlScN.

3. The wafer for an epitaxial aluminum nitride bulk acoustic wave filter device using a thermal self-splitting process according to claim 1, characterized in that, The supporting substrate is formed from any one of AlN polycrystalline, SiC polycrystalline, Si single crystal, and SiC single crystal as the material.

4. A method of manufacturing a wafer for an epitaxial aluminum nitride bulk acoustic wave filter device by a thermal self-splitting process, characterized by, include: The step of preparing a seed substrate for growing an epitaxial layer to form a device; The step of epitaxially growing a piezoelectric thin film on the seed substrate; A resonant section forming step in which a resonant section including a lower electrode and an acoustic reflector is sequentially formed on the upper side of the piezoelectric film; A seed substrate modification step is performed before or after the resonant part formation step, in which a stealth laser is irradiated onto the seed substrate to form a reforming layer inside the seed substrate. The wafer bonding step involves bonding the upper surface of the acoustic reflector to the supporting substrate using a wafer bonding layer as the medium. The seed crystal region separation step involves separating the seed crystal substrate on one side of the piezoelectric film using the modified layer as the boundary to form the seed crystal region. The seed crystal region removal step involves removing the seed crystal region. and The upper electrode forming step involves forming an upper electrode on the exposed lower surface of the acoustic reflector.

5. The method for manufacturing a wafer for an epitaxial aluminum nitride bulk acoustic wave filter device using a thermal self-splitting process according to claim 4, characterized in that, The seed crystal region separation step is as follows: the seed crystal substrates on both sides of the modified layer are separated without external force by means of the thermal stress or mechanical stress formed in the modified layer, through structural asymmetry with quantitative differences or thickness differences in thermal properties including thermal expansion coefficient.

6. The method for manufacturing a wafer for an epitaxial aluminum nitride bulk acoustic wave filter device using a thermal self-splitting process according to claim 4, characterized in that, After performing the piezoelectric film forming step, a piezoelectric film planarization step is also included to planarize the surface of the piezoelectric film.

7. A method of manufacturing a wafer for an epitaxial aluminum nitride bulk acoustic wave filter device by a thermal self-splitting process, characterized by, include: The step of preparing a seed substrate for growing an epitaxial layer to form a device; The step of growing a piezoelectric thin film on the seed substrate by epitaxy; The upper electrode forming step of forming an upper electrode on the upper side of the piezoelectric film; A seed substrate modification step is performed before or after the upper electrode formation step, in which a stealth laser is irradiated onto the seed substrate to form a reforming layer inside the seed substrate. The temporary substrate bonding step involves bonding the upper surface of the upper electrode to the temporary substrate using an adhesive layer as a medium. The seed crystal region separation step involves separating the seed crystal substrate on one side of the piezoelectric film using the modified layer as the boundary to form the seed crystal region. The seed crystal region removal step involves removing the seed crystal region. A resonant portion forming step, which includes a lower electrode and an acoustic reflector, is formed on the lower surface of the piezoelectric film; and After performing the resonant part formation step, a wafer bonding step is performed on the lower surface of the acoustic reflector to bond the support substrate with a wafer bonding layer as a medium.

8. The method for manufacturing a wafer for an epitaxial aluminum nitride bulk acoustic wave filter device using a thermal self-splitting process according to claim 7, characterized in that, After performing the wafer bonding step, a temporary substrate removal step is also included to remove the temporary substrate.

9. The method for manufacturing a wafer for an epitaxial aluminum nitride bulk acoustic wave filter device using a thermal self-splitting process according to claim 7, characterized in that, The seed crystal region separation step is as follows: the seed crystal substrates on both sides of the modified layer are separated without external force due to the quantitative difference in thermal properties including the thermal expansion coefficient or the structural asymmetry of thickness difference.

10. A bulk acoustic wave filter device, characterized in that, It is manufactured using a wafer of the epitaxial aluminum nitride bulk acoustic filter device according to any one of claims 1 to 3.

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