Surface acoustic wave resonator device and method of forming the same

Abstract

A surface acoustic wave resonator device and a forming method thereof, relates to the field of semiconductor manufacturing technology, wherein the device comprises: a piezoelectric substrate; an electrode structure on the piezoelectric substrate, the electrode structure comprising a first metal layer, a second metal layer and a third metal layer, the material density of the first metal layer and the third metal layer being greater than that of the second metal layer. By adding a third metal layer with higher material density, the acoustic migration phenomenon of low material density metal can be effectively suppressed, and the power tolerance of the surface acoustic wave resonator device is improved. In addition, since the thickness of the electrode structure will affect the resonant frequency of the surface acoustic wave resonator device, the thickness of the metal with high material density has a more significant impact on the frequency than the metal with low material density. Therefore, by adding a third metal layer with higher material density, the thickness of the third metal layer can be adjusted, thereby achieving the effect of precisely controlling the resonant frequency of the surface acoustic wave resonator device, making the frequency adjustment mode more flexible and controllable.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing technology, and in particular to a surface acoustic wave resonator and its formation method. Background Technology

[0002] Radio frequency (RF) front-end chips in wireless communication devices include power amplifiers, antenna switches, RF filters, multiplexers, and low-noise amplifiers. Among these, RF filters include surface acoustic wave (SAW) filters, bulk acoustic wave (BAW) filters, micro-electro-mechanical system (MEMS) filters, and integrated passive device (IPD) filters.

[0003] SAW resonators have a high quality factor (Q value). SAW resonators are used to create low-insertion-loss, high-out-of-band rejection RF filters, which are currently the mainstream RF filters used in mobile phones, base stations, and other wireless communication equipment. The Q value is the quality factor of the resonator, defined as the center frequency divided by the resonator's 3dB bandwidth. SAW filters are typically used in frequencies ranging from 0.4GHz to 2.7GHz.

[0004] However, surface acoustic wave resonator devices still need improvement. Summary of the Invention

[0005] The technical problem solved by this invention is to provide a surface acoustic wave resonator and its formation method to improve the power tolerance of the device, as well as the flexibility and controllability of the frequency modulation method.

[0006] To address the aforementioned problems, the present invention provides a surface acoustic wave resonator, comprising: a piezoelectric substrate; an electrode structure located on the piezoelectric substrate, the electrode structure comprising a first metal layer, a second metal layer located on the first metal layer, and a third metal layer located on the second metal layer, wherein the material density of the first metal layer and the third metal layer is greater than the material density of the second metal layer; and a temperature compensation layer located on the piezoelectric substrate, the temperature compensation layer covering the electrode structure.

[0007] Optionally, the electrode structure further includes one or more of a first adhesive layer, a second adhesive layer, and a third adhesive layer, wherein the first adhesive layer is located between the first metal layer and the piezoelectric substrate, the second adhesive layer is located between the first metal layer and the second metal layer, and the third adhesive layer is located between the second metal layer and the third metal layer.

[0008] Optionally, the electrode structure includes: a plurality of first electrode strips and a first bus connecting the plurality of first electrode strips, a plurality of second electrode strips and a second bus connecting the plurality of second electrode strips, wherein the plurality of first electrode strips and the plurality of second electrode strips are located between the first bus and the second bus and are staggered.

[0009] Optionally, the material of the first metal layer includes one or more of molybdenum, tungsten, platinum, palladium, ruthenium, and tantalum.

[0010] Optionally, the material of the second metal layer includes one or more of aluminum, copper, and magnesium.

[0011] Optionally, the material of the third metal layer includes one or more of molybdenum, tungsten, platinum, palladium, ruthenium, and tantalum.

[0012] Optionally, the first metal layer and the third metal layer are made of the same material.

[0013] Optionally, the first metal layer and the third metal layer are made of different materials.

[0014] Optionally, the material of the first adhesive layer includes: titanium, chromium, titanium nitride, titanium-tungsten alloy or nickel-chromium alloy; the material of the second adhesive layer includes: titanium, chromium, titanium nitride, titanium-tungsten alloy or nickel-chromium alloy; and the material of the third adhesive layer includes: titanium, chromium, titanium nitride, titanium-tungsten alloy or nickel-chromium alloy.

[0015] Optionally, the thickness of the first metal layer is 50 nanometers to 300 nanometers; the thickness of the second metal layer is 50 nanometers to 500 nanometers; and the thickness of the third metal layer is 5 nanometers to 100 nanometers.

[0016] Optionally, the thickness of the first adhesive layer is 0 nm to 30 nm, the thickness of the second adhesive layer is 0 nm to 30 nm, and the thickness of the third adhesive layer is 0 nm to 30 nm.

[0017] Accordingly, the present invention also provides a method for forming a surface acoustic wave resonator, comprising: providing a piezoelectric substrate; forming an electrode structure on the piezoelectric substrate, the electrode structure comprising a first metal layer, a second metal layer located on the first metal layer, and a third metal layer located on the second metal layer, wherein the material density of the first metal layer and the third metal layer is greater than the material density of the second metal layer; and forming a temperature compensation layer on the piezoelectric substrate, the temperature compensation layer covering the electrode structure.

[0018] Optionally, the method for forming the electrode structure includes: forming a first metal material layer on the piezoelectric substrate; forming a second metal material layer on the first metal material layer; forming a third metal material layer on the second metal material layer; and performing patterning processing on the first metal material layer, the second metal material layer, and the third metal material layer to form the electrode structure.

[0019] Optionally, after forming the third metal material layer and before the patterning process, the method further includes: thinning the third metal material layer.

[0020] Optionally, after forming the electrode structure, the process further includes thinning the third metal layer.

[0021] Optionally, the method for forming the electrode structure includes: forming a patterned photoresist layer on the piezoelectric substrate; using the patterned photoresist layer as a mask, forming a first metal material layer on the piezoelectric substrate, the first metal material layer covering the exposed surface of the piezoelectric substrate and the top surface of the patterned photoresist layer; forming a second metal material layer on the first metal material layer; forming a third metal material layer on the second metal material layer; and removing the patterned photoresist layer and the first, second, and third metal material layers located on the patterned photoresist layer by a stripping process to form the electrode structure.

[0022] Optionally, after forming the third metal material layer and before the stripping process, the method further includes: thinning the third metal material layer.

[0023] Optionally, after forming the electrode structure, the process further includes thinning the third metal layer.

[0024] Optionally, the method for forming the electrode structure further includes: forming one or more of a first adhesive material layer, a second adhesive material layer, and a third adhesive material layer, wherein the first adhesive material layer is located between the first metal material layer and the piezoelectric substrate, the second adhesive material layer is located between the first metal material layer and the second metal material layer, and the third adhesive material layer is located between the second metal material layer and the third metal material layer; and forming one or more of the patterned first adhesive material layer, the second adhesive material layer, and the third adhesive material layer to form a corresponding first adhesive layer, second adhesive layer, and third adhesive layer.

[0025] Optionally, the method for forming the electrode structure further includes: forming a plurality of first electrode strips and a first bus connecting the plurality of first electrode strips, forming a plurality of second electrode strips and a second bus connecting the plurality of second electrode strips, wherein the plurality of first electrode strips and the plurality of second electrode strips are located between the first bus and the second bus and are staggered.

[0026] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0027] In the surface acoustic wave (SAW) resonator of this invention, the electrode structure includes a first metal layer, a second metal layer on the first metal layer, and a third metal layer on the second metal layer. The material density of the first and third metal layers is greater than that of the second metal layer. By adding the third metal layer with higher material density, the acoustic migration phenomenon of low-density metals can be effectively suppressed, improving the power tolerance of the SAW resonator. Furthermore, since the thickness of the electrode structure affects the resonant frequency of the SAW resonator, and the effect of high-density metal thickness on the resonant frequency is more significant than that of low-density metals, by adding the third metal layer with higher material density, the thickness of the third metal layer can be controlled by methods such as ion bombardment or etching, thereby achieving precise control of the resonant frequency of the SAW resonator and making the frequency modulation method more flexible and controllable.

[0028] Furthermore, the electrode structure further includes one or more of a first adhesive layer, a second adhesive layer, and a third adhesive layer, wherein the first adhesive layer is located between the first metal layer and the piezoelectric substrate, the second adhesive layer is located between the first metal layer and the second metal layer, and the third adhesive layer is located between the second metal layer and the third metal layer. Because the bonding between some metal materials or between some metal materials and the piezoelectric substrate is poor when selecting the metal materials for the first, second, and third metal layers, adding the first, second, or third adhesive layer can better improve the bonding between the metal layers or between the metal layer and the piezoelectric substrate, thereby improving the performance of the surface acoustic wave resonator.

[0029] In the method for forming a surface acoustic wave (SAW) resonator according to the present invention, the electrode structure includes a first metal layer, a second metal layer located on the first metal layer, and a third metal layer located on the second metal layer. The material density of the first metal layer and the third metal layer is greater than that of the second metal layer. By adding the third metal layer with higher material density, the acoustic migration phenomenon of low-density metals can be effectively suppressed, thereby improving the power tolerance of the SAW resonator. Furthermore, since the thickness of the electrode structure affects the resonant frequency of the SAW resonator, and the thickness of high-density metals has a more significant impact on the resonant frequency than low-density metals, by adding the third metal layer with higher material density, the thickness of the third metal layer can be controlled by methods such as ion bombardment or etching, thereby achieving precise control of the resonant frequency of the SAW resonator and making the frequency modulation method more flexible and controllable.

[0030] Furthermore, the method for forming the electrode structure further includes: forming one or more of a first adhesive material layer, a second adhesive material layer, and a third adhesive material layer, wherein the first adhesive material layer is located between the first metal material layer and the piezoelectric substrate, the second adhesive material layer is located between the first metal material layer and the second metal material layer, and the third adhesive material layer is located between the second metal material layer and the third metal material layer; and forming one or more of the patterned first adhesive material layer, the second adhesive material layer, and the third adhesive material layer to form corresponding first adhesive layer, second adhesive layer, and third adhesive layer. Because the bonding between some metal materials or between some metal materials and the piezoelectric substrate is poor when selecting the metal materials for the first, second, and third metal material layers, adding the first, second, or third adhesive material layer can better improve the bonding between the metal material layers or between the metal material layer and the piezoelectric substrate, thereby improving the performance of the surface acoustic wave resonator. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of a surface acoustic wave resonator.

[0032] Figures 2 to 9 This is a schematic diagram of the structure of each step of the surface acoustic wave resonator and its formation method in an embodiment of the present invention;

[0033] Figures 10 to 13 This is a schematic diagram of the structure of each step of the surface acoustic wave resonator and its formation method in another embodiment of the present invention;

[0034] Figures 14 to 19This is a schematic diagram of the structure of each step of the surface acoustic wave resonator and its formation method in another embodiment of the present invention;

[0035] Figures 20 to 21 This is a schematic diagram of the structure of the surface acoustic wave resonator and its formation method in another embodiment of the present invention. Detailed Implementation

[0036] As described in the background section, surface acoustic wave resonator devices still require improvement. Figure 1 This is a schematic diagram of the structure of a surface acoustic wave resonator.

[0037] Please refer to Figure 1 A surface acoustic wave resonator includes: a piezoelectric substrate 100; an electrode structure 101 located on the piezoelectric substrate 100, the electrode structure 101 including a first metal layer 101a and a second metal layer 101b located on the first metal layer 101a, the material density of the first metal layer 101a being greater than the material density of the second metal layer 101b; and a temperature compensation layer 102 located on the piezoelectric substrate 100, the temperature compensation layer 102 covering the electrode structure 101.

[0038] In this embodiment, when the surface acoustic wave resonator is operating under high power conditions, the second metal layer 101b, which is located on the upper layer and has a lower material density, will undergo severe acoustic migration, resulting in voids, mound defects and grain boundary rearrangement in the electrode structure 101. In severe cases, the electrode structure 101 may break, thereby causing the surface acoustic wave resonator to fail.

[0039] Based on this, the present invention provides a surface acoustic wave (SAW) resonator and its formation method. The electrode structure includes a first metal layer, a second metal layer on the first metal layer, and a third metal layer on the second metal layer. The material density of the first and third metal layers is greater than that of the second metal layer. By adding the third metal layer with higher material density, the acoustic migration phenomenon of low-density metals can be effectively suppressed, improving the power tolerance of the SAW resonator. Furthermore, since the thickness of the electrode structure affects the resonant frequency of the SAW resonator, and the effect of high-density metal thickness on the resonant frequency is more significant than that of low-density metals, by adding the third metal layer with higher material density, the thickness of the third metal layer can be controlled by methods such as ion bombardment or etching, thereby achieving precise control of the resonant frequency of the SAW resonator and making the frequency modulation method more flexible and controllable.

[0040] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0041] Figures 2 to 9 This is a schematic diagram of the structural steps of the method for forming a surface acoustic wave resonator in one embodiment of the present invention.

[0042] Please refer to Figure 2 Provides a piezoelectric substrate 200.

[0043] In this embodiment, the material of the piezoelectric substrate 200 includes: lithium tantalate, lithium niobate, lead zirconate titanate, lead magnesium niobate-lead titanate, aluminum nitride, aluminum nitride alloy, gallium nitride, or zinc oxide.

[0044] After providing the piezoelectric substrate 200, the method further includes: forming an electrode structure on the piezoelectric substrate 200, the electrode structure including a first metal layer, a second metal layer located on the first metal layer, and a third metal layer located on the second metal layer, wherein the material density of the first metal layer and the third metal layer is greater than the material density of the second metal layer. For the specific formation process of the electrode structure, please refer to [reference needed]. Figures 3 to 8 .

[0045] Please refer to Figure 3 A first metallic material layer 201 is formed on the piezoelectric substrate 200.

[0046] In this embodiment, the material of the first metal material layer 201 includes one or more of molybdenum, tungsten, platinum, palladium, ruthenium, and tantalum.

[0047] In this embodiment, the thickness of the first metal material layer 201 is 50 nanometers to 300 nanometers.

[0048] Please refer to Figure 4 A second metal material layer 202 is formed on the first metal material layer 201.

[0049] In this embodiment, the material of the second metal material layer 202 includes one or more of aluminum, copper, and magnesium.

[0050] In this embodiment, the thickness of the second metal material layer 202 is 50 nanometers to 500 nanometers.

[0051] Please refer to Figure 5 A third metal material layer 203 is formed on the second metal material layer 202.

[0052] In this embodiment, the material of the third metal material layer 203 includes one or more of molybdenum, tungsten, platinum, palladium, ruthenium, and tantalum.

[0053] Please refer to Figure 6 The third metal material layer 203 is thinned.

[0054] In this embodiment, the thickness of the third metal material layer 203 after thinning treatment is 5 nanometers to 100 nanometers.

[0055] In other embodiments, the third metal layer may be thinned after the electrode structure is formed.

[0056] Please refer to Figure 7 and Figure 8 , Figure 8 yes Figure 7 A schematic diagram of a cross section along line AA shows that the first metal material layer 201, the second metal material layer 202, and the third metal material layer 203 are graphically processed to form the electrode structure 204.

[0057] In this embodiment, the patterning process includes: forming a patterned layer (not shown) on the third metal material layer 203, wherein the patterned layer exposes a portion of the top surface of the third metal material layer 203; etching the first metal material layer 201, the second metal material layer 202, and the third metal material layer 203 using the patterned layer as a mask until the surface of the piezoelectric substrate 200 is exposed, thereby forming the electrode structure 204.

[0058] It should be noted that, in this embodiment, after the patterning process, the first metal layer 204a is formed based on the first metal material layer 201. The material of the first metal layer 204a also includes one or more of molybdenum, tungsten, platinum, palladium, ruthenium, and tantalum, and the thickness of the first metal layer 204a is 50 nanometers to 300 nanometers. The second metal layer 204b is formed based on the second metal material layer 202. The material of the second metal layer 204b also includes one or more of aluminum, copper, and magnesium, and the thickness of the second metal layer 204b is 50 nanometers to 500 nanometers. The third metal layer 204c is formed based on the third metal material layer 203. The material of the third metal layer 204c also includes one or more of molybdenum, tungsten, platinum, palladium, ruthenium, and tantalum, and the thickness of the third metal layer 204c is 5 nanometers to 100 nanometers.

[0059] In this embodiment, the material of the first metal layer 204a is the same as the material of the third metal layer 204c.

[0060] In other embodiments, the materials of the first metal layer and the third metal layer may be different.

[0061] Please continue to refer to this. Figure 7In this embodiment, the method for forming the electrode structure 204 further includes: forming a plurality of first electrode strips 2041 and a first bus 2042 connecting the plurality of first electrode strips 2041, a plurality of second electrode strips 2043 and a second bus 2044 connecting the plurality of second electrode strips 2043, wherein the plurality of first electrode strips 2041 and the plurality of second electrode strips 2043 are located between the first bus 2042 and the second bus 2044 and are staggered.

[0062] In this embodiment, by adding the third metal layer 204c with a higher material density, the acoustic migration phenomenon of low-density metals can be effectively suppressed, improving the power tolerance of the surface acoustic wave resonator. Furthermore, since the thickness of the electrode structure 204 affects the resonant frequency of the surface acoustic wave resonator, and the thickness of a high-density metal has a more significant impact on the resonant frequency than a low-density metal, by adding the third metal layer 204c with a higher material density, the thickness of the third metal layer 204c can be adjusted by methods such as ion bombardment or etching, thereby achieving precise control of the resonant frequency of the surface acoustic wave resonator and making the frequency modulation method more flexible and controllable.

[0063] Please refer to Figure 9 , Figure 9 and Figure 8 With the view orientation consistent, a temperature compensation layer 205 is formed on the piezoelectric substrate 200, and the temperature compensation layer 205 covers the electrode structure 204.

[0064] It should be noted that the temperature compensation layer 205 has opposite temperature frequency shift characteristics to the piezoelectric substrate 200, and the temperature coefficient of frequency (TCF) can be adjusted to tend to 0 ppm / ℃, thereby improving the characteristics of the operating frequency of the surface acoustic wave resonator drifting with the operating temperature and having higher frequency-temperature stability.

[0065] In this embodiment, the material of the temperature compensation layer 205 includes silicon dioxide, silicon fluoride, or silicon carbide.

[0066] Accordingly, this invention also provides a surface acoustic wave resonator device; please refer to [link / reference needed]. Figure 9The device includes: a piezoelectric substrate 200; an electrode structure 204 located on the piezoelectric substrate 200, the electrode structure 204 including a first metal layer 204a, a second metal layer 204b located on the first metal layer 204a, and a third metal layer 204c located on the second metal layer 204b, wherein the material density of the first metal layer 204a and the third metal layer 204c is greater than the material density of the second metal layer 204b; and a temperature compensation layer 205 located on the piezoelectric substrate 200, the temperature compensation layer 205 covering the electrode structure 204.

[0067] In this embodiment, by adding the third metal layer 204c with a higher material density, the acoustic migration phenomenon of low-density metals can be effectively suppressed, improving the power tolerance of the surface acoustic wave resonator. Furthermore, since the thickness of the electrode structure 204 affects the resonant frequency of the surface acoustic wave resonator, and the thickness of a high-density metal has a more significant impact on the resonant frequency than a low-density metal, by adding the third metal layer 204c with a higher material density, the thickness of the third metal layer 204c can be adjusted by methods such as ion bombardment or etching, thereby achieving precise control of the resonant frequency of the surface acoustic wave resonator and making the frequency modulation method more flexible and controllable.

[0068] Please continue to refer to this. Figure 7 In this embodiment, the electrode structure 204 includes: a plurality of first electrode strips 2041 and a first bus 2042 connecting the plurality of first electrode strips 2041, a plurality of second electrode strips 2043 and a second bus 2044 connecting the plurality of second electrode strips 2043, wherein the plurality of first electrode strips 2041 and the plurality of second electrode strips 2043 are located between the first bus 2042 and the second bus 2044 and are staggered.

[0069] In this embodiment, the material of the first metal layer 204a includes one or more of molybdenum, tungsten, platinum, palladium, ruthenium, and tantalum.

[0070] In this embodiment, the material of the second metal layer 204b includes one or more of aluminum, copper, and magnesium.

[0071] In this embodiment, the material of the third metal layer 204c includes one or more of molybdenum, tungsten, platinum, palladium, ruthenium, and tantalum.

[0072] In this embodiment, the first metal layer 204a and the third metal layer 204c are made of the same material.

[0073] In other embodiments, the materials of the first metal layer and the third metal layer may also be different.

[0074] In this embodiment, the thickness of the first metal layer 204a is 50 nanometers to 300 nanometers; the thickness of the second metal layer 204b is 50 nanometers to 500 nanometers; and the thickness of the third metal layer 204c is 5 nanometers to 100 nanometers.

[0075] In this embodiment, the material of the temperature compensation layer 205 includes silicon dioxide, silicon oxycarbonate, or silicon oxyfluoride.

[0076] Figures 10 to 13 A schematic diagram of the steps in forming a surface acoustic wave resonator device according to another embodiment of the present invention is shown.

[0077] This embodiment is based on the surface acoustic wave resonator device in the above embodiment. Figure 5 Continuing with the description of the surface acoustic wave resonator, the difference between this embodiment and the previous embodiment lies in that the method for forming the electrode structure 204 further includes: forming one or more of a first adhesive material layer, a second adhesive material layer, and a third adhesive material layer, wherein the first adhesive material layer is located between the first metal material layer 201 and the piezoelectric substrate 200, the second adhesive material layer is located between the first metal material layer 201 and the second metal material layer 202, and the third adhesive material layer is located between the second metal material layer 202 and the third metal material layer 203; one or more of the patterned first adhesive material layer, second adhesive layer, and third adhesive layer form a corresponding first adhesive layer, second adhesive layer, and third adhesive layer. A detailed description will follow with reference to the accompanying drawings.

[0078] Please refer to Figure 10 This forms one or more of a first adhesive material layer 301, a second adhesive material layer 302, and a third adhesive material layer 303, wherein the first adhesive material layer 301 is located between the first metal material layer 201 and the piezoelectric substrate 200, the second adhesive material layer 302 is located between the first metal material layer 201 and the second metal material layer 202, and the third adhesive material layer 303 is located between the second metal material layer 202 and the third metal material layer 203.

[0079] In this embodiment, the material of the first adhesive layer 301 includes titanium, chromium, titanium nitride, titanium-tungsten alloy or nickel-chromium alloy, the material of the second adhesive layer 302 includes titanium, chromium, titanium nitride, titanium-tungsten alloy or nickel-chromium alloy, and the material of the third adhesive layer 303 includes titanium, chromium, titanium nitride, titanium-tungsten alloy or nickel-chromium alloy.

[0080] In this embodiment, the thickness of the first adhesive material layer 301 is 0 nanometers to 30 nanometers, the thickness of the second adhesive material layer 302 is 0 nanometers to 30 nanometers, and the thickness of the third adhesive material layer 303 is 0 nanometers to 30 nanometers.

[0081] In this embodiment, the first adhesive material layer 301, the second adhesive material layer 302, and the third adhesive material layer 303 are formed simultaneously.

[0082] In other embodiments, one or both of the first adhesive material layer 301, the second adhesive material layer 302, and the third adhesive material layer 303 may also be formed.

[0083] Please refer to Figure 11 The third metal material layer 203 is thinned.

[0084] In this embodiment, please refer to the following for details regarding the thickness of the third metal material layer undergoing the thinning process and the sequence of other processes involved in the thinning process. Figure 6 The relevant explanations have already been provided and will not be repeated here.

[0085] Please refer to Figure 12 The first metal material layer 201, the second metal material layer 202, and the third metal material layer 203 are patterned to form the electrode structure 204.

[0086] The process of graphical processing also includes: forming one or more of the first adhesive material layer 301, the second adhesive material layer 302 and the third adhesive material layer 303 formed by graphical processing to form one or more of the corresponding first adhesive layer, second adhesive layer and third adhesive layer.

[0087] In this embodiment, the first adhesive material layer 301, the second adhesive material layer 302, and the third adhesive material layer 303 are graphically formed.

[0088] In other embodiments, only one or both of the first adhesive material layer, the second adhesive material layer, and the third adhesive material layer may be graphically formed.

[0089] It should be noted that, in this embodiment, after the patterning process, the first adhesive layer 204d is formed based on the first adhesive material layer 301, the second adhesive layer 204e is formed based on the second adhesive material layer 302, and the third adhesive layer 204f is formed based on the third adhesive material layer 303. The material of the first adhesive layer 204d includes titanium, chromium, titanium nitride, titanium-tungsten alloy, or nickel-chromium alloy; the thickness of the first adhesive layer 204d is 0 nm to 30 nm. The material of the second adhesive layer 204e also includes titanium, chromium, titanium nitride, titanium-tungsten alloy, or nickel-chromium alloy; the thickness of the second adhesive layer 204e is 0 nm to 30 nm. The material of the third adhesive layer 204f also includes titanium, chromium, titanium nitride, titanium-tungsten alloy, or nickel-chromium alloy; the thickness of the third adhesive layer 204f is 0 nm to 30 nm.

[0090] In this embodiment, the method further includes: thinning the third metal material layer or the third metal layer. The sequence of the thinning steps is described in the following reference. Figure 6 The relevant explanations have already been provided and will not be repeated here.

[0091] In this embodiment, the first adhesive layer 204d is located between the first metal layer 204a and the piezoelectric substrate 200; the second adhesive layer 204e is located between the first metal layer 204a and the second metal layer 204b; and the third adhesive layer 204f is located between the second metal layer 204b and the third metal layer 204c.

[0092] In other embodiments, only one or both of the first adhesive layer, the second adhesive layer, and the third adhesive layer may be formed.

[0093] In this embodiment, due to the poor bonding between some metal materials or between some metal materials and the piezoelectric substrate 200 when selecting the metal materials for the first metal layer 204a, the second metal layer 204b, and the third metal layer 204c, the bonding between the metal layers or between the metal materials and the piezoelectric substrate 200 can be better improved by adding the first adhesive layer 204d, the second adhesive layer 204e, and the third adhesive layer 204f, thereby improving the performance of the surface acoustic wave resonator.

[0094] Please refer to Figure 13 A temperature compensation layer 205 is formed on the piezoelectric substrate 200, and the temperature compensation layer 205 covers the electrode structure 204.

[0095] In this embodiment, please refer to the following for details regarding the function and materials of the temperature compensation layer 205. Figure 9 The relevant explanations have already been provided and will not be repeated here.

[0096] Accordingly, this invention also provides a surface acoustic wave resonator device; please refer to [link / reference needed]. Figure 13 The electrode structure includes: a piezoelectric substrate 200; an electrode structure 204 located on the piezoelectric substrate 200, the electrode structure 204 including a first metal layer 204a, a second metal layer 204b located above the first metal layer 204a, and a third metal layer 204c located above the second metal layer 204b; the material density of the first metal layer 204a and the third metal layer 204c is greater than the material density of the second metal layer 204b; the electrode structure 204 further includes a first adhesive layer 204d between the first metal layer 204a and the piezoelectric substrate 200, a second adhesive layer 204e between the first metal layer 204a and the second metal layer 204b, and a third adhesive layer 204f between the second metal layer 204b and the third metal layer 204c; and a temperature compensation layer 205 located on the piezoelectric substrate 200, the temperature compensation layer 205 covering the electrode structure 204.

[0097] In this embodiment, by adding the third metal layer 204c with a higher material density, the acoustic migration phenomenon of low-density metals can be effectively suppressed, improving the power tolerance of the surface acoustic wave resonator. Furthermore, since the thickness of the electrode structure 204 affects the resonant frequency of the surface acoustic wave resonator, and the thickness of a high-density metal has a more significant impact on the resonant frequency than a low-density metal, by adding the third metal layer 204c with a higher material density, the thickness of the third metal layer 204c can be adjusted by methods such as ion bombardment or etching, thereby achieving precise control of the resonant frequency of the surface acoustic wave resonator and making the frequency modulation method more flexible and controllable.

[0098] In this embodiment, the electrode structure further includes: a first adhesive layer 204d located between the first metal layer 204a and the piezoelectric substrate 200; a second adhesive layer 204e located between the first metal layer 204a and the second metal layer 204b; and a third adhesive layer 204f located between the second metal layer 204b and the third metal layer 204c. Because the bonding between some metal materials or between some metal materials and the piezoelectric substrate 200 is poor when selecting the metal materials for the first metal layer 204a, the second metal layer 204b, and the third metal layer 204c, the addition of the first adhesive layer 204d, the second adhesive layer 204e, and the third adhesive layer 204f can better improve the bonding between the metal layers or between the metal layers and the piezoelectric substrate 200, thereby improving the performance of the surface acoustic wave resonator.

[0099] In other embodiments, only one or both of the first adhesive layer, the second adhesive layer, and the third adhesive layer may be formed.

[0100] Figures 14 to 19 A schematic diagram of the steps in forming a surface acoustic wave resonator device according to another embodiment of the present invention is shown.

[0101] This embodiment is based on the surface acoustic wave resonator device in the above embodiment. Figure 2 The surface acoustic wave resonator will continue to be described below. The difference between this embodiment and the previous embodiments is that the electrode structure is formed using a stripping process. A detailed description will follow with reference to the accompanying drawings.

[0102] Please refer to Figure 14 A patterned photoresist layer 401 is formed on the piezoelectric substrate 200.

[0103] In this embodiment, the method for forming the patterned photoresist layer 401 includes: forming a patterned photoresist material layer (not shown) on the piezoelectric substrate 200; and performing patterning processing on the patterned photoresist material layer to form the patterned photoresist layer 401.

[0104] Please refer to Figure 15 Using the patterned photoresist layer 401 as a mask, a first metal material layer 201 is formed on the piezoelectric substrate 200. The first metal material layer 201 covers the exposed surface of the piezoelectric substrate 200 and the top surface of the patterned photoresist layer 401.

[0105] In this embodiment, please refer to the specific details regarding the material and thickness of the first metal material layer 201. Figure 3 The relevant explanations have already been provided and will not be repeated here.

[0106] Please refer to Figure 16 A second metal material layer 202 is formed on the first metal material layer 201.

[0107] In this embodiment, please refer to the specific details regarding the material and thickness of the second metal material layer 202. Figure 4 The relevant explanations have already been provided and will not be repeated here.

[0108] Please refer to Figure 17 A third metal material layer 203 is formed on the second metal material layer 202.

[0109] In this embodiment, please refer to the specific details regarding the material and thickness of the third metal material layer 203. Figure 6 The relevant explanations have already been provided and will not be repeated here.

[0110] Please refer to Figure 18 The third metal material layer 203 is thinned.

[0111] In this embodiment, please refer to the following for details regarding the thickness of the third metal material layer undergoing the thinning process and the sequence of other processes involved in the thinning process. Figure 6 The relevant explanations have already been provided and will not be repeated here.

[0112] Please refer to Figure 19 The patterned photoresist layer 401, the first metal material layer 201, the second metal material layer 202 and the third metal material layer 203 located on the patterned photoresist layer 401 are removed by a stripping process to form the electrode structure 204.

[0113] In this embodiment, please refer to the specific structure and function of the electrode structure 204. Figure 7 and Figure 8 The relevant explanations have already been provided and will not be repeated here.

[0114] Figures 20 to 21 A schematic diagram of the steps in forming a surface acoustic wave resonator device according to another embodiment of the present invention is shown.

[0115] This embodiment is based on the surface acoustic wave resonator device in the above embodiment. Figure 17 The surface acoustic wave resonator device will continue to be described below. The difference between this embodiment and the previous embodiments is that the method for forming the electrode structure 204 further includes forming one or more of a first adhesive material layer, a second adhesive material layer, and a third adhesive material layer. The first adhesive material layer is located between the first metal material layer 201 and the piezoelectric substrate 200, the second adhesive layer is located between the first metal material layer 201 and the second metal material layer 202, and the third adhesive layer is located between the second metal material layer 202 and the third metal material layer 203. A detailed description will follow with reference to the accompanying drawings.

[0116] Please refer to Figure 20 This forms one or more of a first adhesive material layer 501, a second adhesive material layer 502, and a third adhesive material layer 503, wherein the first adhesive material layer 501 is located between the first metal material layer 201 and the piezoelectric substrate 200, the second adhesive material layer 502 is located between the first metal material layer 201 and the second metal material layer 202, and the third adhesive material layer 503 is located between the second metal material layer 202 and the third metal material layer 203.

[0117] In this embodiment, please refer to the specific details regarding the materials, thicknesses, and locations of the first adhesive layer 501, the second adhesive layer 502, and the third adhesive layer 503. Figure 10 The relevant explanations have already been provided and will not be repeated here.

[0118] Please refer to Figure 21 The first metal material layer 201, the second metal material layer 202, the third metal material layer 203, the first adhesive material layer 501, the second adhesive material layer 502, and the third adhesive material layer 503 located on the patterned photoresist layer are stripped to form the electrode structure 204.

[0119] In this embodiment, the specific structure and function of the electrode structure 204, as well as the positions and functions of the first adhesive layer 204d, the second adhesive layer 204e, and the third adhesive layer 204f formed by the first adhesive layer 501, the second adhesive layer 502, and the third adhesive layer 503, are detailed in the following reference: Figure 12 The relevant explanations will not be repeated here.

[0120] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A surface acoustic wave resonator, characterized in that, include: piezoelectric substrate; An electrode structure located on the piezoelectric substrate, the electrode structure including a first metal layer, a second metal layer located on the first metal layer, and a third metal layer located on the second metal layer, wherein the material density of the first metal layer and the third metal layer is greater than the material density of the second metal layer, and the thickness of the third metal layer is 5 nanometers to 100 nanometers; A temperature compensation layer is located on the piezoelectric substrate, and the temperature compensation layer covers the electrode structure.

2. The surface acoustic wave resonator as described in claim 1, characterized in that, The electrode structure further includes one or more of a first adhesive layer, a second adhesive layer, and a third adhesive layer, wherein the first adhesive layer is located between the first metal layer and the piezoelectric substrate, the second adhesive layer is located between the first metal layer and the second metal layer, and the third adhesive layer is located between the second metal layer and the third metal layer.

3. The surface acoustic wave resonator as described in claim 1, characterized in that, The electrode structure includes: a plurality of first electrode strips and a first bus connecting the plurality of first electrode strips, a plurality of second electrode strips and a second bus connecting the plurality of second electrode strips, wherein the plurality of first electrode strips and the plurality of second electrode strips are located between the first bus and the second bus and are staggered.

4. The surface acoustic wave resonator as described in claim 1, characterized in that, The material of the first metal layer includes one or more of molybdenum, tungsten, platinum, palladium, ruthenium, and tantalum.

5. The surface acoustic wave resonator as described in claim 1, characterized in that, The material of the second metal layer includes one or more of aluminum, copper, and magnesium.

6. The surface acoustic wave resonator as described in claim 1, characterized in that, The material of the third metal layer includes one or more of molybdenum, tungsten, platinum, palladium, ruthenium, and tantalum.

7. The surface acoustic wave resonator as described in claim 1, characterized in that, The first metal layer and the third metal layer are made of the same material.

8. The surface acoustic wave resonator as described in claim 1, characterized in that, The first metal layer and the third metal layer are made of different materials.

9. The surface acoustic wave resonator as described in claim 2, characterized in that, The materials of the first adhesive layer include: titanium, chromium, titanium nitride, titanium-tungsten alloy or nickel-chromium alloy; the materials of the second adhesive layer include: titanium, chromium, titanium nitride, titanium-tungsten alloy or nickel-chromium alloy; and the materials of the third adhesive layer include: titanium, chromium, titanium nitride, titanium-tungsten alloy or nickel-chromium alloy.

10. The surface acoustic wave resonator as described in claim 1, characterized in that, The thickness of the first metal layer is 50 nanometers to 300 nanometers; the thickness of the second metal layer is 50 nanometers to 500 nanometers.

11. The surface acoustic wave resonator as described in claim 2, characterized in that, The thickness of the first adhesive layer is 0 nanometers to 30 nanometers, the thickness of the second adhesive layer is 0 nanometers to 30 nanometers, and the thickness of the third adhesive layer is 0 nanometers to 30 nanometers.

12. A method for forming a surface acoustic wave resonator, characterized in that, include: Provide a piezoelectric substrate; An electrode structure is formed on the piezoelectric substrate. The electrode structure includes a first metal layer, a second metal layer located on the first metal layer, and a third metal layer located on the second metal layer. The material density of the first metal layer and the third metal layer is greater than the material density of the second metal layer. The thickness of the third metal layer is 5 nanometers to 100 nanometers. A temperature compensation layer is formed on the piezoelectric substrate, and the temperature compensation layer covers the electrode structure.

13. The method for forming a surface acoustic wave resonator as described in claim 12, characterized in that, The method for forming the electrode structure includes: forming a first metal material layer on the piezoelectric substrate; forming a second metal material layer on the first metal material layer; forming a third metal material layer on the second metal material layer; and performing patterning processing on the first metal material layer, the second metal material layer, and the third metal material layer to form the electrode structure.

14. The method for forming a surface acoustic wave resonator as described in claim 13, characterized in that, After the formation of the third metal material layer and before the patterning process, the method further includes: thinning the third metal material layer.

15. The method for forming a surface acoustic wave resonator as described in claim 13, characterized in that, After forming the electrode structure, the process further includes thinning the third metal layer.

16. The method for forming a surface acoustic wave resonator as described in claim 12, characterized in that, The method for forming the electrode structure includes: forming a patterned photoresist layer on the piezoelectric substrate; using the patterned photoresist layer as a mask, forming a first metal material layer on the piezoelectric substrate, the first metal material layer covering the exposed surface of the piezoelectric substrate and the top surface of the patterned photoresist layer; forming a second metal material layer on the first metal material layer; forming a third metal material layer on the second metal material layer; and removing the patterned photoresist layer and the first, second, and third metal material layers located on the patterned photoresist layer by a stripping process to form the electrode structure.

17. The method for forming a surface acoustic wave resonator as described in claim 16, characterized in that, After the formation of the third metal material layer and before the stripping process, the method further includes: thinning the third metal material layer.

18. The method for forming a surface acoustic wave resonator as described in claim 16, characterized in that, After forming the electrode structure, the process further includes thinning the third metal layer.

19. The method for forming a surface acoustic wave resonator as described in claim 13 or 16, characterized in that, The method for forming the electrode structure further includes: forming one or more of a first adhesive material layer, a second adhesive material layer, and a third adhesive material layer, wherein the first adhesive material layer is located between the first metal material layer and the piezoelectric substrate, the second adhesive material layer is located between the first metal material layer and the second metal material layer, and the third adhesive material layer is located between the second metal material layer and the third metal material layer; and forming one or more of the patterned first adhesive material layer, the second adhesive material layer, and the third adhesive material layer to form a corresponding first adhesive layer, second adhesive layer, and third adhesive layer.

20. The method for forming a surface acoustic wave resonator as described in claim 12, characterized in that, The method for forming the electrode structure further includes: forming a plurality of first electrode strips and a first bus connecting the plurality of first electrode strips, forming a plurality of second electrode strips and a second bus connecting the plurality of second electrode strips, wherein the plurality of first electrode strips and the plurality of second electrode strips are located between the first bus and the second bus and are staggered.

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