Heterogeneous waveguide resonator and processing method

Abstract

The invention belongs to the field of communication circuit elements, and particularly relates to a heterogeneous waveguide resonator and a processing method thereof, and the passband, the rectangularity and the out-of-band performance of a filter of the resonator are improved through an inclined electrode; the oxide layer and the piezoelectric film material layer are made of specific thickness and materials, so that the signal excitation bandwidth of the resonator is increased, the reliability is high, and the resonator is more suitable for 5G communication; the advantage film layer is arranged between the oxide layer and the piezoelectric film material layer, so that the bandwidth of signal excitation is further widened, and the production cost is effectively reduced by optimizing the material combination and the technological process.

Description

Technical Field

[0001] The invention belongs to the field of communication circuit elements, and in particular relates to a heterogeneous waveguide resonator and a processing method thereof. Background Art

[0002] Generally speaking, the communication quality between mobile communication devices and base stations is determined by the combined effect of RF front-end devices and antennas. RF front-end devices enable control signals to be transmitted and received between communication networks, and filter, amplify, detect and demodulate the transmitted signals. With the development of communication technology, the new 5G networking standard first released by the 3rd Generation Partnership Project (3GPP) in June 2018 has promoted the development trend of RF front-end devices towards high frequency, large bandwidth, high power, multi-integration and miniaturization. With the increasing tension of spectrum resources, higher requirements are placed on the performance of filters, such as higher frequency, lower loss, larger bandwidth and higher power capacity.

[0003] The newly added frequency bands N77 (3300MHz-4200MHz) and N79 (4400MHz-5000MHz) in the new 5G communication standard have unprecedented bandwidths of 900MHz and 600MHz. The existing piezoelectric surface acoustic wave technology and thin film bulk acoustic wave technology face great challenges in the design and application of 5G large-bandwidth filters. They have limitations in frequency, Q value, temperature stability, etc., and it is difficult to meet the needs of 5G communications. Piezoelectric surface acoustic wave technology has therefore been pushed towards the selection of piezoelectric thin film materials, multi-layer heterogeneous stacking structures, and the exploration of thin film material advantages. However, there are still many problems in actual application exploration, and there are also major limitations in the process, which seriously affect the stability and reliability of the equipment and are difficult to meet the needs of actual applications. Summary of the invention

[0004] The technical problem solved by the present invention is to provide a heterogeneous waveguide resonator and a processing method to solve the problem of poor stability and reliability of the resonator under the newly added frequency bands and ultra-large bandwidths of 5G.

[0005] The basic scheme provided by the present invention is: a heterogeneous waveguide resonator, comprising a substrate structure and an upper electrode structure, wherein the upper electrode structure is arranged on the substrate structure, the substrate structure comprises a substrate layer, the upper surface of the substrate layer is provided with an oxide layer with a thickness of 0.1 to 0.35 times the wavelength, the upper surface of the oxide layer is provided with a piezoelectric thin film material layer, the thickness of the piezoelectric thin film material layer is 0.1 to 0.4 times the wavelength, and the upper electrode structure is an inclined electrode with an inclination angle of 20° to 38°.

[0006] Preferably, the piezoelectric film material layer is made of lithium niobate film, the cut type of the lithium niobate film is a YX cut type, and the cut angle of the lithium niobate film is 15° to 40° YX cut.

[0007] Preferably, a passivation layer is provided on the upper electrode structure.

[0008] Further preferably, the passivation layer is made of silicon nitride or silicon dioxide.

[0009] Preferably, a dominant film layer is provided between the oxide layer and the piezoelectric film material layer.

[0010] Further preferably, the dominant thin film layer is made of polysilicon thin film or SiC thin film.

[0011] A method for processing the heterogeneous waveguide resonator according to claim 1, comprising the following steps:

[0012] S1: sputtering an oxide layer with a thickness of 0.1 to 0.35 times the wavelength on the surface of the substrate layer, and performing roughness treatment on the surface of the oxide layer to control the surface roughness Ra to be less than or equal to 10 nm;

[0013] S2: The piezoelectric material is processed by the smart stripping technology to bond with the oxide layer surface to form a piezoelectric thin film material layer, thereby obtaining a superior waveguide substrate structure;

[0014] S3: Using a lift-off stripping process to process an upper electrode structure on the piezoelectric film material layer.

[0015] Preferably, the specific steps of using the smart stripping technology to process the piezoelectric material and bond it to the surface of the oxide layer in step S2 are:

[0016] S2-1) injecting damaging ions at a preset depth of the piezoelectric material to form a damage layer there;

[0017] S2-2) bonding the treated piezoelectric material to the surface of the oxide layer, and peeling off the unbonded portion of the piezoelectric material from the damaged layer to form a piezoelectric thin film material layer;

[0018] S2-3) roughening the surface of the piezoelectric thin film material layer to obtain a dominant waveguide substrate structure.

[0019] Preferably, the method further comprises step S4: injecting a passivation layer into the upper electrode structure.

[0020] The principles and advantages of the present invention are:

[0021] 1. The use of inclined electrodes reduces the energy component in the u2 direction and weakens the bus edge reflection effect, thereby suppressing the lateral stray ripples in the bandgap region of the main resonance signal response of the resonator, improving the passband, rectangularity and out-of-band performance of the filter based on the resonator, and having better stability.

[0022] 2. The thickness of the oxide layer is 0.1 to 0.35 times the wavelength, which can form effective reflection or transmission conditions, which helps to reduce unnecessary signal reflections, improve signal transmission efficiency, and ensure that the optimal operating point is found; the thickness of the piezoelectric film material layer is 0.1 to 0.4 times the wavelength, which can provide sufficient capacitance effect to optimize circuit performance without being too thick to cause additional losses or too thin to achieve the required electrical properties; oxide layers and piezoelectric film material layers of this thickness can maintain good performance over a larger frequency range, with high stability and reliability, and effectively increase the bandwidth of signal excitation, with a bandwidth close to 5GHz, which meets the requirements of 5G communications.

[0023] 3. An advantageous thin film layer is set between the oxide layer and the piezoelectric thin film material layer. This structural design can further improve the bandwidth of the signal excitation, and maintain the characteristics of a larger bandwidth when using lower-cost materials for the substrate layer, effectively reducing production costs and to a certain extent compensating for the performance degradation that may be caused by the use of low-cost materials, making high-performance microwave devices more popular and economical. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A partial cross-sectional view of a resonator in Example 1 of the present invention;

[0025] Figure 2 is a side view of a resonator of Example 1 of the present invention;

[0026] Figure 3 is a schematic structural diagram of a conventional upper electrode structure of the present invention;

[0027] Figure 4 The resonator structure admittance response curve of the conventional upper electrode structure of the present invention;

[0028] Figure 5 It is a structural schematic diagram of the inclined upper electrode structure of the present invention;

[0029] Figure 6 A graph showing the admittance response curve of the resonator structure of the inclined upper electrode structure of the present invention;

[0030] Figure 7 is a side view of a resonator of embodiment 4 of the present invention;

[0031] Figure 8 It is a topological structure diagram of the present invention;

[0032] Fig. 9 is a scattering curve diagram of the ladder filter of the present invention;

[0033] Fig.10 is an admittance response curve diagram of Example 4 of the present invention;

[0034] Fig.11 It is a side view of the resonator of Embodiment 5 and Embodiment 6 of the present invention;

[0035] Fig.12 is an admittance response curve diagram of Example 5 of the present invention;

[0036] Fig.13 is an admittance response curve diagram of Example 6 of the present invention;

[0037] Fig.14 is a flow chart of the present invention;

[0038] Fig.15 A flow chart of bonding the piezoelectric material and the oxide layer of the present invention;

[0039] Fig.16 It is a schematic diagram of the resonator processing process of the present invention. DETAILED DESCRIPTION

[0040] The following is further described in detail through specific implementation methods:

[0041] The specific implementation process is as follows:

[0042] Example 1

[0043] See also Figures 1 to 6A heterogeneous waveguide resonator comprises a substrate structure and an upper electrode structure. An upper electrode structure is arranged on the substrate structure, and the upper electrode structure 14 is an interdigital transducer structure. The substrate structure comprises a substrate layer 11, and the material of the substrate layer 11 can be selected from silicon nitride, silicon carbide, silicon, SOI, etc. In this embodiment, the substrate layer 11 is made of silicon carbide. An oxide layer 12 having a thickness of 0.1 to 0.35 times the wavelength is provided on the upper surface of the substrate layer 11. In this embodiment, the oxide layer 12 is made of silicon dioxide, and the thickness is 0.14 times the wavelength, specifically 0.2 microns. The upper surface of the oxide layer 12 is provided with a piezoelectric film material layer 13, the piezoelectric film material layer is a lithium niobate film, the cut type of the lithium niobate film is a YX cut type, and the cut angle of the lithium niobate film is 15° to 40°YX cut. In this embodiment, the piezoelectric film material layer 13 is a 25°YX lithium niobate material. When the electromechanical coupling coefficient of the excited resonance signal within the cut angle range is greater than 25%, the electromechanical coupling coefficient of the 25° cut type reaches a maximum value of 30.8%, which effectively improves the stability of the resonator signal output; the thickness of the piezoelectric film material layer 13 is 0.1 to 0.4 times the wavelength. In this embodiment, the thickness of the piezoelectric film material layer 13 is 0.21 times the wavelength, specifically 0.3 microns. The upper electrode structure is an inclined electrode with an inclination angle of 20° to 38°. In this embodiment, the inclination angle is 29°. The use of an inclined electrode can effectively reduce stray ripples between main mode resonance responses. The thickness of the upper electrode structure 14 is less than 0.5 μm, and in this embodiment, it is 0.1 μm. The material of the upper electrode structure can be a single layer material such as aluminum, gold, titanium, platinum, copper, molybdenum, etc., or a double layer combination of metal materials. Fig.10 and 12 As shown, the upper electrode structure includes a bus bar structure 41 , a forked finger structure 42 , and a dummy finger structure 43 .

[0044] See also Figure 1 , is a side cross-sectional view of the resonator, wherein a is the width of the upper electrode finger, p is the sum of the finger width and the finger gap, and the wavelength is twice the length of p. In this embodiment, the wavelength is preferably 1.44 microns.

[0045] The upper electrode finger width and the duty cycle have the following relationship: a=p×MR, where a is the upper electrode finger width, p is the finger width plus the dummy finger gap, and MR is the duty cycle.

[0046] like Figure 3 As shown, it is a conventional upper electrode structure without a corner electrode, such as Figure 4 As shown, it is the resonator structure admittance response curve of the conventional upper electrode structure; Figure 5 As shown, it is an inclined upper electrode structure, such as Figure 6As shown, it is the admittance response curve of the resonator structure with an inclined upper electrode structure, and the inclination angle θ is 29°. It can be seen that in the admittance response curve of the resonator structure with a conventional upper electrode structure, there is a relatively obvious stray signal in the middle of the main mode signal, while there is less stray signal in the admittance response curve of the resonator structure with an inclined upper electrode structure. The tilting motor has a positive effect on reducing the stray ripples between the main mode resonance responses.

[0047] Example 2

[0048] The difference between Example 2 and Example 1 is that the thickness of the oxide layer 12 is 0.1 times the wavelength, the cutting angle of the lithium niobate film is 15°YX cutting, the thickness of the piezoelectric film material layer 13 is 0.1 times the wavelength, and the tilt angle of the upper electrode structure is 20°.

[0049] Example 3

[0050] The difference between Example 3 and Example 1 is that the thickness of the oxide layer 12 is 0.35 times the wavelength, the cutting angle of the lithium niobate film is 40°YX cutting, the thickness of the piezoelectric film material layer 13 is 0.4 times the wavelength, and the tilt angle of the upper electrode structure is 38°.

[0051] Example 4

[0052] See also Figure 7 The difference between Example 4 and Example 1 is that a passivation layer 15 is further provided on the upper electrode structure, and the passivation layer 15 is made of silicon nitride or silicon dioxide. The passivation layer 15 improves the temperature characteristics of the resonator and prevents the upper electrode structure from being oxidized and damp.

[0053] like Figure 8 As shown in the figure, it is a topological structure diagram of the ladder filter of the resonator of the present invention. Through simulation of the topological diagram, it is obtained Fig. 9 The figure shows the scattering curve of the ladder filter. In the figure, the out-of-band suppression is better than 25dB, the filter center frequency is 2.55GHz, the 3dB bandwidth is greater than 520MHz, the passband is relatively flat, and the passband ripple is not obvious. It can be seen that the 3dB fractional bandwidth of the device is greater than 20%, and the insertion loss in the band is better than 1.2dB, indicating that the structure has strong anti-interference ability and good performance. Fig.10 The figure shows the admittance response curve. It can be seen that the signal excitation bandwidth of the structure is relatively large, exceeding 3 GHz. The structure can be applied to communications with ultra-large bandwidth.

[0054] Example 5

[0055] See also Fig.11, the difference between Example 5 and Example 4 is that a superior film layer 12a is provided between the oxide layer 12 on the substrate layer and the piezoelectric film material layer 13, and the superior film layer 12a is made of polysilicon film or SiC film. In this embodiment, the superior film layer 12a is made of SiC film. By setting the superior film layer, the bandwidth of signal excitation can be effectively improved, which is more suitable for 5G communication. The superior film layer 12a has a low cost, and the signal bandwidth can be greatly improved through low-cost changes.

[0056] Furthermore, the advantageous thin film layer 12a can be matched with a substrate layer 11 using materials with lower cost, such as silicon, quartz or glass, to further reduce production costs. In this embodiment, the substrate layer 11 is made of silicon. Fig.12 As shown, it is the admittance response curve of this embodiment. It can be seen that the structure has good performance under large bandwidth and the frequency is close to 5 GHz, which is more suitable for high-frequency communication.

[0057] Example 6

[0058] See also Figures 11 to 13 The difference between Example 6 and Example 5 is that the substrate layer 11 is made of glass. Fig.13 As shown, it is the admittance response curve of this embodiment. It can be seen that the frequency of this structure is close to 5 GHz, which can achieve a good resonance effect; and the substrate layer and the advantageous thin film layer are made of low-cost materials, which can effectively save costs.

[0059] See also Figures 14 to 16 , a method for processing a heterogeneous waveguide resonator, specifically comprising the following steps:

[0060] S1: Sputter an oxide layer 12 with a thickness of 0.1 to 0.35 times the wavelength on the surface of the substrate layer 11, and perform roughness treatment on the surface of the oxide layer 12 to control the surface roughness Ra to be less than or equal to 10nm. In this embodiment, the surface roughness of the oxide layer 12 is Ra10nm. Better roughness facilitates bonding and increases adhesion, making it less likely to generate bubbles between material layers, thereby ensuring the quality of the finished product. In another embodiment of the present application, the surface roughness of the oxide layer 12 is Ra8nm.

[0061] S2: The piezoelectric material is processed by intelligent stripping technology to bond with the surface of the oxide layer 12 to form a piezoelectric thin film material layer 13, so as to obtain a superior waveguide substrate structure; the piezoelectric thin film material layer is made of lithium niobate thin film, and the cut type of the lithium niobate thin film is YX cut type. In this embodiment, the piezoelectric thin film material layer is made of 25° YX lithium niobate material;

[0062] The specific steps of using the smart stripping technology to process the piezoelectric material and bond it to the surface of the oxide layer in step S2 are:

[0063] S2-1) injecting damaging ions (H+, He+, etc.) at a preset depth of the piezoelectric material to form a damage layer there. In this embodiment, hydrogen ions are injected into a preset depth of a lithium niobate single crystal to form a damage layer.

[0064] S2-2) bonding the processed piezoelectric material to the surface of the oxide layer 12, i.e., silicon dioxide, and peeling off the unbonded portion 13a of the piezoelectric material from the damaged layer to form a piezoelectric thin film material layer 13;

[0065] S2-3) roughening the surface of the piezoelectric thin film material layer 13 to obtain a dominant waveguide substrate structure. The thickness of the piezoelectric thin film material layer is 0.1 to 0.4 times the wavelength.

[0066] The advantage of using intelligent stripping technology to process piezoelectric materials is that it can form a thinner piezoelectric film material layer, reduce the number of grinding times, improve process efficiency, and effectively control process costs.

[0067] S3: Using a lift-off stripping process to process an upper electrode structure on the piezoelectric film material layer.

[0068] S4: injecting a passivation layer into the upper electrode structure to protect the upper electrode structure, prevent it from being oxidized and damp, and improve the temperature characteristics of the resonator. The material of the passivation layer is silicon nitride or silicon dioxide.

[0069] The above are only embodiments of the present invention. Common knowledge such as the known specific structures and characteristics in the scheme is not described in detail here. Ordinary technicians in the relevant field know all the common technical knowledge in the technical field to which the invention belongs before the application date or priority date, can obtain all the existing technologies in the field, and have the ability to apply conventional experimental means before that date. Ordinary technicians in the relevant field can improve and implement this scheme in combination with their own abilities under the enlightenment given by this application. Some typical known structures or known methods should not become obstacles for ordinary technicians in the relevant field to implement this application. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A heterogeneous waveguide resonator, comprising a substrate structure and an upper electrode structure, wherein the upper electrode structure is disposed on the substrate structure, characterized in that: The substrate structure comprises a substrate layer (11), an oxide layer (12) having a thickness of 0.1 to 0.35 times the wavelength is provided on the upper surface of the substrate layer (11), a piezoelectric film material layer (13) is provided on the upper surface of the oxide layer (12), the piezoelectric film material layer (13) having a thickness of 0.1 to 0.4 times the wavelength, and the upper electrode structure is an inclined electrode with an inclination angle of 20° to 38°.

2. The heterogeneous waveguide resonator according to claim 1, characterized in that: The piezoelectric film material layer is made of lithium niobate film, the cut type of the lithium niobate film is a YX cut type, and the cut angle of the lithium niobate film is 15° to 40° YX cut.

3. The heterogeneous waveguide resonator according to claim 1, characterized in that: A passivation layer (15) is provided on the upper electrode structure.

4. The heterogeneous waveguide resonator according to claim 3, characterized in that: The passivation layer (15) is made of silicon nitride or silicon dioxide.

5. The heterogeneous waveguide resonator according to claim 1, characterized in that: A dominant film layer (12a) is provided between the oxide layer (12) and the piezoelectric film material layer (13).

6. The heterogeneous waveguide resonator according to claim 5, characterized in that: The advantageous thin film layer (12a) is made of polysilicon thin film or SiC thin film.

7. A method for processing the heterogeneous waveguide resonator according to claim 1, characterized in that: The specific steps include: S1: sputtering an oxide layer with a thickness of 0.1 to 0.35 times the wavelength on the surface of the substrate layer, and performing roughness treatment on the surface of the oxide layer to control the surface roughness Ra to be less than or equal to 10 nm; S2: The piezoelectric material is processed by the smart stripping technology to bond with the oxide layer surface to form a piezoelectric thin film material layer, thereby obtaining a superior waveguide substrate structure; S3: Using a lift-off stripping process to process an upper electrode structure on the piezoelectric film material layer.

8. The method for processing a heterogeneous waveguide resonator according to claim 7, characterized in that: The specific steps of using the smart stripping technology to process the piezoelectric material and bond it to the surface of the oxide layer in step S2 are: S2-1) injecting damaging ions at a preset depth of the piezoelectric material to form a damage layer there; S2-2) bonding the treated piezoelectric material to the surface of the oxide layer, and peeling off the unbonded portion of the piezoelectric material from the damaged layer to form a piezoelectric thin film material layer; S2-3) roughening the surface of the piezoelectric thin film material layer to obtain a dominant waveguide substrate structure.

9. The method for processing a heterogeneous waveguide resonator according to claim 7, characterized in that: The method further comprises step S4: injecting a passivation layer into the upper electrode structure.

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