Wafer-level high-performance surface acoustic wave resonator and preparation method thereof

Abstract

The invention belongs to the technical field of microelectronic devices, and particularly relates to a wafer-level high-performance surface acoustic wave resonator and a preparation method thereof. The wafer-level high-performance surface acoustic wave resonator comprises a high-resistance silicon supporting substrate used for reducing radio frequency loss, the intrinsic silicon resistivity of the high-resistance silicon supporting substrate is larger than 5 kilohm.m, and a polycrystalline diamond layer, a piezoelectric layer and an interdigital electrode are sequentially stacked on the high-resistance silicon supporting substrate. According to the surface acoustic wave resonator, the polycrystalline diamond film is deposited on the high-resistance silicon to serve as the substrate of the surface acoustic wave device, the wafer-level, low-cost and high-performance surface acoustic wave device can be manufactured, the polycrystalline diamond film can restrain energy leakage of an existing surface acoustic wave resonator, the working frequency of the surface acoustic wave device is improved, and the surface acoustic wave resonator can be applied to the field of surface acoustic wave resonators. The high-resistance silicon is used as the supporting substrate, so that the performance of the surface acoustic wave device is improved, and meanwhile, the lower manufacturing cost is ensured.

Description

Technical Field

[0001] The invention belongs to the technical field of microelectronic devices, and in particular relates to a wafer-level high-performance surface acoustic wave resonator and a preparation method thereof. Background Art

[0002] Surface acoustic wave devices are solid devices that utilize the characteristics of acoustic-electric transducers to perform various processes on acoustic signals propagating on the surface of a piezoelectric material substrate and to accomplish various functions. They are mainly composed of a base material with piezoelectric properties and interlaced interdigital transducers composed of metal films made on the polished surface of the material. Surface acoustic wave devices have the characteristics of miniaturization, high reliability, multi-functions, and wafer-level high performance, and are widely used in radar, wireless communications, fiber-optic communications, and broadcasting and television systems.

[0003] Since the sound waves of SAW devices propagate on the surface of solids, the energy is mainly concentrated on the surface of solids, so when the surface is stimulated by external stimuli, the characteristics of the sound waves will change greatly. With the further development of wireless communication technology, higher requirements are placed on the performance of surface acoustic wave devices, such as higher operating frequency and higher quality factor. At present, an effective way to increase the operating frequency or higher quality factor of surface acoustic wave devices is to use a bonding method between piezoelectric single crystal film and non-piezoelectric substrate to improve the characteristics of the excited acoustic wave mode, such as horizontal shear surface acoustic wave mode or longitudinal leakage surface acoustic wave mode.

[0004] At present, the commonly used substrate materials for surface acoustic wave devices are silicon, sapphire, silicon carbide, quartz or polycrystalline diamond. Among them, polycrystalline diamond substrates have the highest sound velocity, so surface acoustic wave devices based on polycrystalline diamond substrates have attracted widespread attention. However, due to the process level limitations of polycrystalline diamond substrates, the growth of large-sized diamonds at the wafer level is still a big problem, and the preparation cost is high, which makes it difficult to meet the higher demands of the increasingly developed communication technology. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a wafer-level high-performance surface acoustic wave resonator and a preparation method thereof. By depositing a polycrystalline diamond film on high-resistance silicon as a substrate for a surface acoustic wave device, a wafer-level, low-cost wafer-level high-performance surface acoustic wave device can be manufactured. The high-resistance silicon support substrate suppresses the energy leakage of the current surface acoustic wave resonator, increases the operating frequency of the surface acoustic wave device, and ensures a low manufacturing cost while improving the performance of the surface acoustic wave device.

[0006] The present invention solves the above technical problems through the following technical solutions.

[0007] One of the purposes of the present invention is to provide a wafer-level high-performance surface acoustic wave resonator, which includes a high-resistance silicon support substrate for reducing radio frequency loss, wherein the intrinsic silicon resistivity of the high-resistance silicon support substrate is greater than 5kΩ·cm, and a polycrystalline diamond layer, a piezoelectric layer and interdigital electrodes are sequentially stacked on the high-resistance silicon support substrate.

[0008] It should be noted that the excellent thermal and acoustic properties of diamond are very attractive for surface acoustic wave devices. However, due to the limitation of the process level of polycrystalline diamond substrates, the growth of large-sized diamonds at the wafer level is still a big problem, and the preparation cost is high, which is difficult to meet the higher requirements of the increasingly developed communication technology. However, since the energy of the surface acoustic wave is usually concentrated within a few wavelengths on the surface of the substrate, when the surface acoustic wave propagates along the propagation direction, the energy will leak to the substrate. The use of a high-speed polycrystalline diamond film can suppress the leakage of acoustic energy and reduce the loss of acoustic energy. Therefore, for surface acoustic wave devices, the use of a diamond film can greatly improve the performance of the device. The present invention deposits a polycrystalline diamond film on high-resistance silicon as a substrate for a surface acoustic wave device. The polycrystalline diamond film can suppress the energy leakage of the surface acoustic wave resonator and improve the operating frequency of the surface acoustic wave device. The high-resistance silicon support substrate used has good insulation performance, radio frequency performance and chemical stability, can reduce the radio frequency loss of the device, and improve the performance of the surface acoustic wave device, so that a large-sized substrate at the wafer level can be provided, and a high-performance surface acoustic wave device made at the wafer level and low cost can be obtained.

[0009] In some embodiments, the thickness of the high-resistance silicon support substrate is 0.2 mm to 1 mm. It should be noted that the high-resistance silicon support substrate used in the present invention has good insulation performance, radio frequency performance and chemical stability, can reduce the radio frequency loss of the device, and improve the performance of the surface acoustic wave device. However, if the thickness of the high-resistance silicon support substrate is too large, the volume of the device will also increase, which is not conducive to miniaturization integration. If the thickness is too small, it will be fragile in subsequent processes.

[0010] In some embodiments, the thickness of the polycrystalline diamond layer is 0.1 μm to 100 μm. It should be noted that it is difficult to obtain a low-cost diamond substrate of large size at the wafer level due to the limitations of the microwave frequency of the synthetic diamond substrate equipment, the internal stress of the substrate, etc. The preparation of diamond film on silicon substrate can greatly reduce the preparation difficulty and preparation cost.

[0011] It should be noted that the polycrystalline diamond film layer has a high sound velocity, which can inhibit the leakage of energy to the substrate. The diamond can also be a single crystal diamond, but it is very difficult to grow a single crystal diamond of the thickness required by the present invention in terms of technology. If the thickness of the polycrystalline diamond film layer is too low, the effect of inhibiting energy leakage will be poor, but if the thickness is increased, the roughness inside the wafer will increase, the stress of the substrate will increase, and the substrate will be easily broken.

[0012] In some embodiments, the thickness of the piezoelectric layer is 0.1 μm to 2 μm, and the material of the piezoelectric layer is lithium tantalate or lithium niobate. The present invention controls the type, cut and thickness of the piezoelectric material to stimulate surface acoustic waves with different characteristics to meet different device requirements.

[0013] In some embodiments, the thickness of the interdigital electrodes is 0.05 μm-1 μm, and the material of the interdigital electrodes is titanium, aluminum, chromium, silver, gold or copper.

[0014] In some embodiments, a temperature compensation layer is further provided between the polycrystalline diamond layer and the piezoelectric layer, wherein the material of the temperature compensation layer is silicon dioxide, and the thickness of the temperature compensation layer is 0.05um~10μm. It should be noted that the present invention does not specifically limit the preparation method of the temperature compensation layer. Its purpose is to prepare the temperature compensation layer between the polycrystalline diamond layer and the piezoelectric layer by conventional preparation methods, such as the temperature compensation layer is prepared on the surface of the polycrystalline diamond layer by plasma enhanced chemical vapor deposition, dry oxidation or wet oxidation, and then the piezoelectric layer is bonded to the temperature compensation layer by a bonding process. On the one hand, the temperature compensation layer provides a better interface for the bonding of the piezoelectric layer, which is convenient for bonding; on the other hand, it can improve the frequency-temperature characteristics of the surface acoustic wave device.

[0015] The second object of the present invention is to provide a method for preparing the above-mentioned wafer-level high-performance surface acoustic wave resonator, comprising the following steps: S1. Provide a high-resistance silicon support substrate.

[0016] S2. Preparing a polycrystalline diamond layer on the high-resistance silicon support substrate.

[0017] S3. Bonding a piezoelectric layer on the polycrystalline diamond layer.

[0018] S4. preparing interdigital electrodes on the piezoelectric layer.

[0019] S5. Obtain a wafer-level high-performance surface acoustic wave resonator.

[0020] It should be noted that the present invention does not limit the preparation method of polycrystalline diamond and interdigital electrodes. Its purpose is to prepare a polycrystalline diamond layer on the surface of a high-resistance silicon support substrate or to prepare interdigital electrodes on a piezoelectric layer by conventional preparation methods. The polycrystalline diamond layer, piezoelectric layer and interdigital electrodes can be deposited on the surface of a high-resistance silicon support substrate by conventional deposition methods; and the bonding process is not specifically limited. Its purpose is to bond the piezoelectric layer to the polycrystalline diamond layer by conventional bonding processes to obtain a piezoelectric layer of corresponding thickness.

[0021] Compared with the prior art, the present invention has the following beneficial effects: The present invention arranges a polycrystalline diamond film on high-resistance silicon to serve as a substrate for a surface acoustic wave device, thereby providing a large-size substrate at the wafer level, and obtaining a wafer-level, low-cost, high-performance surface acoustic wave device at the wafer level. The polycrystalline diamond film suppresses energy leakage of the surface acoustic wave resonator and improves the operating frequency of the surface acoustic wave device. The adopted high-resistance silicon support substrate has good insulation performance, radio frequency performance and chemical stability, can reduce the radio frequency loss of the device, and improve the performance of the surface acoustic wave device. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the overall structure of a wafer-level high-performance surface acoustic wave resonator according to Example 1 of the present invention.

[0023] Figure 2 This is a schematic diagram of the overall structure of a wafer-level high-performance surface acoustic wave resonator according to Example 2 of the present invention.

[0024] Figure 3 Graphs showing the admittance characteristics of the wafer-level high-performance surface acoustic wave resonator of Example 1 of the present invention and the surface acoustic wave resonator of Comparative Example 1.

[0025] Figure 4 1 and 1 , which are displacement distribution diagrams of the wafer-level high-performance surface acoustic wave resonator of Example 2 of the present invention and the surface acoustic wave resonator of Comparative Example 2.

[0026] 1. High-resistance silicon support substrate, 2. Polycrystalline diamond layer, 3. Piezoelectric layer, 4. Interdigital electrodes, 5. Temperature compensation layer. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] It should be noted that the professional terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention. Certain words are used in the present invention to refer to specific components. Those skilled in the art should understand that technicians will use different nouns to refer to the same component. The present invention does not distinguish between components by the difference in nouns, but by the difference in the functions of the components. As mentioned throughout the specification and claims, "including" is an open term and should be understood as "including but not limited to".

[0029] The invention is further described below through specific examples.

[0030] Example 1 A wafer-level high-performance surface acoustic wave resonator, such as Figure 1 As shown, the wafer-level high-performance surface acoustic wave resonator includes a high-resistance silicon support substrate 1 for reducing radio frequency loss. The resistivity of the high-resistance silicon support substrate 1 is 10 kΩ·cm, and a polycrystalline diamond layer 2, a piezoelectric layer 3 and interdigital electrodes 4 are sequentially stacked on the high-resistance silicon support substrate 1.

[0031] The thickness of the high-resistance silicon support substrate 1 is 0.25 mm; the thickness of the polycrystalline diamond layer 2 is 2 μm; the piezoelectric layer 3 is a 33° YX lithium niobate layer with a thickness of 1.3 μm; the material of the interdigital electrode is aluminum, and the thickness of the interdigital electrode 4 is 0.16 μm.

[0032] The method for preparing the wafer-level high-performance surface acoustic wave resonator comprises the following steps: S1. Provide a high-resistance silicon support substrate 1.

[0033] S2, preparing a polycrystalline diamond layer 2 on the high-resistance silicon support substrate 1 by using microwave plasma chemical vapor deposition.

[0034] S3 , bonding a piezoelectric layer 3 on the polycrystalline diamond layer 2 .

[0035] S4, preparing interdigital electrodes 4 on the piezoelectric layer 3 by using photolithography and lift-off processes.

[0036] S5. Obtain a wafer-level high-performance surface acoustic wave resonator.

[0037] Example 2 A wafer-level high-performance surface acoustic wave resonator, such as Figure 2 As shown, the wafer-level high-performance surface acoustic wave resonator includes a high-resistance silicon support substrate 1 for reducing radio frequency loss. The resistivity of the high-resistance silicon support substrate 1 is 10 kΩ·cm, and a polycrystalline diamond layer 2, a temperature compensation layer 5, a piezoelectric layer 3, and interdigital electrodes 4 are sequentially stacked on the high-resistance silicon support substrate 1.

[0038] The thickness of the high-resistance silicon support substrate 1 is 0.25 mm; the thickness of the polycrystalline diamond layer 2 is 2 μm; the temperature compensation layer 5 is a silicon dioxide layer with a thickness of 0.5 μm; the piezoelectric layer 3 is a 42° YX lithium tantalate layer with a thickness of 0.6 μm; the material of the interdigital electrode is aluminum, and the thickness of the interdigital electrode 4 is 0.16 μm.

[0039] The method for preparing the wafer-level high-performance surface acoustic wave resonator comprises the following steps: S1. Provide a high-resistance silicon support substrate 1.

[0040] S2, depositing a polycrystalline diamond layer 2 on the high-resistance silicon support substrate 1 by microwave plasma chemical vapor deposition.

[0041] S3, preparing a temperature compensation layer 5 on the polycrystalline diamond layer 2 by using plasma enhanced chemical vapor deposition.

[0042] S4, bonding the piezoelectric layer 3 on the temperature compensation layer 5.

[0043] S5 , preparing interdigital electrodes 4 on the piezoelectric layer 3 by using photolithography and lift-off processes.

[0044] S6. Obtain a wafer-level high-performance surface acoustic wave resonator.

[0045] Example 3 A wafer-level high-performance surface acoustic wave resonator, such as Figure 2 As shown, the wafer-level high-performance surface acoustic wave resonator includes a high-resistance silicon support substrate 1 for reducing radio frequency loss. The resistivity of the high-resistance silicon support substrate 1 is 6 kΩ·cm, and a polycrystalline diamond layer 2, a temperature compensation layer 5, a piezoelectric layer 3, and interdigital electrodes 4 are sequentially stacked on the high-resistance silicon support substrate 1.

[0046] The thickness of the high-resistance silicon support substrate 1 is 1 mm; the thickness of the polycrystalline diamond layer 2 is 0.1 μm; the temperature compensation layer 5 is a silicon dioxide layer with a thickness of 0.05 μm; the piezoelectric layer 3 is 42° YX lithium tantalate with a thickness of 2 μm; the material of the interdigital electrode is copper, and the thickness of the interdigital electrode 4 is 0.5 μm.

[0047] The method for preparing the wafer-level high-performance surface acoustic wave resonator comprises the following steps: S1. Provide a high-resistance silicon support substrate 1.

[0048] S2, depositing a polycrystalline diamond layer 2 on the high-resistance silicon support substrate 1 by microwave plasma chemical vapor deposition.

[0049] S3, preparing a temperature compensation layer 5 on the polycrystalline diamond layer 2 by using plasma enhanced chemical vapor deposition.

[0050] S4, bonding the piezoelectric layer 3 on the temperature compensation layer 5.

[0051] S5 , preparing interdigital electrodes 4 on the piezoelectric layer 3 by using photolithography and lift-off processes.

[0052] S6. Obtain a wafer-level high-performance surface acoustic wave resonator.

[0053] Example 4 A wafer-level high-performance surface acoustic wave resonator, such as Figure 2As shown, the wafer-level high-performance surface acoustic wave resonator includes a high-resistance silicon support substrate 1 for reducing radio frequency loss. The resistivity of the high-resistance silicon support substrate 1 is 10 kΩ·cm, and a polycrystalline diamond layer 2, a temperature compensation layer 5, a piezoelectric layer 3, and interdigital electrodes 4 are sequentially stacked on the high-resistance silicon support substrate 1.

[0054] The thickness of the high-resistance silicon support substrate 1 is 0.2 mm; the thickness of the polycrystalline diamond layer 2 is 100 μm; the temperature compensation layer 5 is a silicon dioxide layer with a thickness of 5 μm; the piezoelectric layer 3 is 42° YX lithium tantalate with a thickness of 2 μm; the material of the interdigital electrode is copper, and the thickness of the interdigital electrode 4 is 0.05 μm.

[0055] The method for preparing the wafer-level high-performance surface acoustic wave resonator comprises the following steps: S1. Provide a high-resistance silicon support substrate 1.

[0056] S2, depositing a polycrystalline diamond layer 2 on the high-resistance silicon support substrate 1 by microwave plasma chemical vapor deposition.

[0057] S3, preparing a temperature compensation layer 5 on the polycrystalline diamond layer 2 by using plasma enhanced chemical vapor deposition.

[0058] S4, bonding the piezoelectric layer 3 on the temperature compensation layer 5.

[0059] S5 , preparing interdigital electrodes 4 on the piezoelectric layer 3 by using photolithography and lift-off processes.

[0060] S6. Obtain a wafer-level high-performance surface acoustic wave resonator.

[0061] Comparative Example 1 A surface acoustic wave resonator comprises a diamond substrate, on which a piezoelectric layer and interdigital electrodes are sequentially stacked.

[0062] The thickness of the diamond substrate is 0.25 mm; the piezoelectric layer is a 33° YX lithium tantalate layer with a thickness of 1.3 μm; the material of the interdigital electrode is aluminum, and the thickness of the interdigital electrode is 0.16 μm.

[0063] The method for preparing the surface acoustic wave resonator comprises the following steps: S1. Provide a diamond substrate.

[0064] S2. Bonding a piezoelectric layer on the diamond substrate.

[0065] S4. Prepare interdigital electrodes on the piezoelectric layer using photolithography and lift-off processes.

[0066] S5. Obtain a surface acoustic wave resonator.

[0067] Comparative Example 2 A surface acoustic wave resonator comprises a high-resistance silicon support substrate for reducing radio frequency loss. The resistivity of the high-resistance silicon support substrate is 10 kΩ·cm. A temperature compensation layer, a piezoelectric layer and interdigital electrodes are sequentially stacked on the high-resistance silicon support substrate.

[0068] The thickness of the high-resistance silicon support substrate is 0.25 mm; the temperature compensation layer is a silicon dioxide layer with a thickness of 0.5 μm; the piezoelectric layer is a 42°YX lithium tantalate layer with a thickness of 0.6 μm; the material of the interdigital electrode is aluminum, and the thickness of the interdigital electrode is 0.16 μm.

[0069] The method for preparing the surface acoustic wave resonator comprises the following steps: S1. Provide a high-resistance silicon support substrate.

[0070] S2. Prepare a temperature compensation layer 5 on the high-resistance silicon support substrate using plasma enhanced chemical vapor deposition.

[0071] S3. Bonding a piezoelectric layer on the temperature compensation layer.

[0072] S4. Prepare interdigital electrodes on the piezoelectric layer using photolithography and lift-off processes.

[0073] S5. Obtain a wafer-level high-performance surface acoustic wave resonator.

[0074] The wafer-level high-performance surface acoustic wave resonators prepared in Examples 2 to 4 have similar structures and similar effects, and the performance of the wafer-level high-performance surface acoustic wave resonators prepared in Examples 1 and 2 are taken as examples for further explanation.

[0075] Figure 3 The following is a graph showing the admittance characteristics of the surface acoustic wave resonator of Example 1 of the present invention and the surface acoustic wave resonator of Comparative Example 1. The horizontal axis is the frequency and the vertical axis is the admittance. Figure 3 It can be seen that the use of high-resistivity silicon-based diamond films achieves performance consistent with that of bulk diamond substrates.

[0076] Figure 4 The displacement distribution diagram of the wafer-level high-performance surface acoustic wave resonator of Example 2 of the present invention and the surface acoustic wave resonator of Comparative Example 2 is shown in FIG. 1 , wherein the horizontal axis is the distance from the substrate surface, and the vertical axis is the normalized displacement value. Figure 4 It can be seen that by using a substrate with a diamond film, the leakage of surface acoustic wave energy into the substrate is greatly suppressed due to the high acoustic velocity of the diamond film.

[0077] It should be noted that when the present invention involves a numerical range, it should be understood that the two endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as those in the embodiments, in order to avoid redundancy, the present invention describes a preferred embodiment. Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the attached claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0078] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A wafer-level high-performance surface acoustic wave resonator, characterized in that: The wafer-level high-performance surface acoustic wave resonator comprises a high-resistance silicon support substrate (1) for reducing radio frequency loss, wherein the intrinsic silicon resistivity of the high-resistance silicon support substrate (1) is greater than 5 kΩ·m, and a polycrystalline diamond layer (2), a piezoelectric layer (3) and interdigital electrodes (4) are sequentially stacked on the high-resistance silicon support substrate (1).

2. The wafer-level high-performance surface acoustic wave resonator according to claim 1, characterized in that: The thickness of the high-resistance silicon support substrate (1) is 0.2 mm to 1 mm.

3. The wafer-level high-performance surface acoustic wave resonator according to claim 1, characterized in that: The thickness of the polycrystalline diamond layer (2) is 0.1 μm to 100 μm.

4. The wafer-level high-performance surface acoustic wave resonator according to claim 1, characterized in that: The thickness of the piezoelectric layer (3) is 0.1 μm to 2 μm.

5. The wafer-level high-performance surface acoustic wave resonator according to claim 4, characterized in that: The material of the piezoelectric layer (3) is lithium tantalate or lithium niobate.

6. The wafer-level high-performance surface acoustic wave resonator according to claim 1, characterized in that: The thickness of the interdigital electrode (4) is 0.05 μm to 1 μm.

7. The wafer-level high-performance surface acoustic wave resonator according to claim 6, characterized in that: The material of the interdigital electrodes (4) is titanium, aluminum, chromium, silver, gold or copper.

8. The wafer-level high-performance surface acoustic wave resonator according to claim 1, characterized in that: A temperature compensation layer (5) is also provided between the polycrystalline diamond layer (2) and the piezoelectric layer (3), and the material of the temperature compensation layer (5) is silicon dioxide.

9. The wafer-level high-performance surface acoustic wave resonator according to claim 8, characterized in that: The thickness of the temperature compensation layer (5) is 0.05 μm to 10 μm.

10. A method for preparing a wafer-level high-performance surface acoustic wave resonator according to any one of claims 1 to 9, characterized in that: The following steps are involved: Providing a high-resistance silicon support substrate (1); Depositing a polycrystalline diamond layer (2) on the high-resistance silicon support substrate (1); Bonding a piezoelectric layer (3) on the polycrystalline diamond layer (2); Depositing interdigital electrodes (4) on the piezoelectric layer (3); A wafer-level high-performance surface acoustic wave resonator is obtained.

Images