An FBAR filter and a method of manufacturing and using the same

Abstract

The application discloses an FBAR filter and a preparation method and application thereof. The FBAR filter comprises a polyhedral supporting substrate and at least two bulk acoustic wave filters arranged on at least two surfaces of the supporting substrate. The bulk acoustic wave filter comprises a supporting layer, a bottom electrode, a piezoelectric layer and a top electrode. The bottom electrode and the top electrode are both patterned electrodes and are arranged on two surfaces of the piezoelectric layer respectively. The supporting layer, the piezoelectric layer and the bottom electrode in the bulk acoustic wave filter and the supporting substrate jointly form an air cavity. The FBAR filter can integrate bulk acoustic wave filters of various frequency ranges on the same substrate, thereby reducing the area and volume of the FBAR filter, lowering the manufacturing cost of the FBAR filter and being suitable for large-scale popularization and application.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device technology, specifically to an FBAR filter, its fabrication method, and its application. Background Technology

[0002] The mainstream frequency bands for global mobile communication are mainly concentrated in the 0.9GHz to 5.5GHz range. Filters can be used to select the required frequencies, allowing specific frequency components of the signal to pass through while significantly attenuating other frequency components. With the advent of the 5G era, the operating frequencies required by smartphones and various mobile communication devices are constantly increasing, and the supported radio frequency bands are also expanding. At the same time, the requirements for antenna and transceiver sizes are becoming more stringent. Therefore, to avoid mutual interference between different frequency signals and dropped calls, a sufficient number of filters must be configured in each communication device to isolate the radio frequency bands and ensure accurate signal transmission and reception. However, with the widespread use of available spectrum, newly allocated frequency bands are getting closer and closer to existing bands, and guard bands are becoming narrower, making band isolation increasingly difficult.

[0003] Film Bulk Acoustic Resonators (FBARs) offer advantages such as high frequency, miniaturization, high performance, low power consumption, and high power capacity. Their manufacturing process is compatible with IC processes, allowing for integration and reducing device power consumption and size. They are currently the only integrable RF front-end filter and are considered the optimal solution for high-frequency bands above 3GHz. An FBAR filter mainly consists of three parts: a substrate, an acoustic wave reflector layer, and a sandwich piezoelectric resonator (composed of upper and lower electrodes and a piezoelectric thin film sandwiched between them). When an RF voltage is applied between the two electrodes, an alternating electric field is generated within the piezoelectric resonator. Through the inverse piezoelectric effect of the piezoelectric thin film, some of the electrical energy is converted into bulk acoustic waves propagating along the film thickness and reflecting back and forth between the two electrodes. Resonance occurs when the propagation of the bulk acoustic wave in the piezoelectric resonator is exactly half the wavelength or an odd multiple of half the wavelength; that is, the fundamental frequency wavelength of the resonance is approximately equal to twice the thickness of the piezoelectric resonator.

[0004] Currently, FBAR filters are used in both civilian and military applications, including mobile phones, tablets, micro base stations, low Earth orbit satellite communications, radar and electronic warfare IF receivers, beacons, and IFF transponders. These applications cover a wide range of frequencies and require multiple FBAR filters capable of receiving various frequency ranges. However, traditional FBAR filters are typically grown only on one side of the substrate, resulting in a substrate area utilization rate of less than 45%, which hinders the reduction of FBAR filter size and manufacturing costs.

[0005] Therefore, it is of great significance to develop an FBAR filter with high substrate area utilization, small size, and low manufacturing cost. Summary of the Invention

[0006] The purpose of this invention is to provide an FBAR filter, its fabrication method, and its application.

[0007] The technical solution adopted in this invention is:

[0008] An FBAR filter comprises a multifaceted support substrate and at least two bulk acoustic wave filters disposed on at least two surfaces of the support substrate; the bulk acoustic wave filters comprise a support layer, a bottom electrode, a piezoelectric layer, and a top electrode; the bottom electrode and the top electrode are both patterned electrodes and are respectively disposed on two sides of the piezoelectric layer; the cavity formed by the support layer, the piezoelectric layer, and the bottom electrode together with the support substrate in the bulk acoustic wave filter is an air cavity.

[0009] Preferably, the supporting substrate is selected from one of silicon substrate, sapphire substrate, LiGaO2 substrate, and metal elemental substrate.

[0010] Preferably, the support layer is selected from one of the following: gold-tin alloy layer, gold-silicon alloy layer, nickel-tin alloy layer, and aluminum-germanium alloy layer.

[0011] Preferably, the thickness of the support layer is 1μm to 2μm.

[0012] Preferably, the support layer is a graphical support layer.

[0013] Preferably, the composition of the bottom electrode is selected from at least one of Al, Mo, W, Pt, Ti, and Au.

[0014] Preferably, the piezoelectric layer is selected from one of the following: a single-crystal aluminum nitride layer, a polycrystalline aluminum nitride layer, a zinc oxide layer, and a lead zirconate titanate layer.

[0015] Preferably, the composition of the top electrode is selected from at least one of Al, Mo, W, Pt, Ti, and Au.

[0016] The above-mentioned method for fabricating the FBAR filter includes the following steps:

[0017] 1) Deposit piezoelectric layers on both sides of the substrate and pattern them;

[0018] 2) The bottom electrode is fabricated on the piezoelectric layer by photolithography, evaporation and lift-off, and then patterned;

[0019] 3) A support layer is prepared on the bottom electrode by photolithography, vapor deposition, and lift-off;

[0020] 4) The support layer is connected and fixed to the support substrate on two sides of the polyhedral support substrate using optical alignment technology, and then the substrate is peeled off to expose the piezoelectric layer.

[0021] 5) The top electrode was fabricated on the piezoelectric layer by photolithography, evaporation and lift-off, and patterned, that is, two PSA filters were fabricated on the two sides of the supporting substrate.

[0022] 6) Repeat steps 1) to 5) to continue fabricating bulk acoustic wave filters on other surfaces of the support substrate, thus obtaining FBAR filters.

[0023] Preferably, the substrate prepared in step 1) is selected from one of silicon substrate, sapphire substrate, LiGaO2 substrate, and metal elemental substrate.

[0024] Preferably, the deposition in step 1) is performed using metal-organic chemical vapor deposition (MOCVD) at a growth temperature of 850℃~950℃.

[0025] A communication device comprising the aforementioned FBAR filter.

[0026] The beneficial effects of this invention are: the FBAR filter of this invention integrates a bulk acoustic wave filter capable of receiving various frequency ranges on the same substrate, reducing the area and volume of the FBAR filter, lowering the manufacturing cost of the FBAR filter, and making it suitable for large-scale promotion and application.

[0027] The FBAR filter of this invention is fabricated by performing deposition, photoresist, etching and other processes on various surfaces of the same substrate, thereby integrating the bulk acoustic wave filter on the same substrate. This can effectively reduce the area and volume of the filter, as well as reduce the manufacturing cost of the filter. Moreover, the entire process is relatively simple (the CMP process is eliminated in the process of fabricating the cavity-type thin film bulk acoustic wave resonator using the stacked metal support method, and there is no need to introduce a sacrificial layer), with low equipment cost, high production efficiency and easy implementation. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the cross-section of the FBAR filter in the embodiment.

[0029] Figure 2 This is a schematic diagram of the device obtained in step 3) of the embodiment.

[0030] Figure 3 This is a schematic diagram of the device obtained in step 5) of the embodiment.

[0031] Explanation of the symbols in the attached figures: 1. Supporting substrate; 2. Supporting layer; 3. Bottom electrode; 4. Piezoelectric layer; 5. Top electrode; 6. Fabrication substrate; 7. Air cavity. Detailed Implementation

[0032] The present invention will be further explained and described below with reference to specific embodiments.

[0033] Example:

[0034] An FBAR filter (structural schematic shown) Figure 1 As shown, it comprises a cuboid support substrate 1 and six bulk acoustic wave filters disposed on six surfaces of the support substrate 1; the bulk acoustic wave filters comprise a support layer 2, a bottom electrode 3, a piezoelectric layer 4, and a top electrode 5; the bottom electrode 3 and the top electrode 5 are both patterned electrodes and are respectively disposed on two sides of the piezoelectric layer 4; the cavity formed by the support layer 2, the piezoelectric layer 4, and the bottom electrode 3 in the bulk acoustic wave filters together with the support substrate 1 is an air cavity 7.

[0035] The above-mentioned method for fabricating the FBAR filter includes the following steps:

[0036] 1) Single-crystal aluminum nitride layers (piezoelectric layers) with orientation (002) were deposited on both sides of a silicon substrate (preparation substrate) by MOCVD. The deposition conditions were: trimethylaluminum (TMA) flow rate of 50 sccm, NH3 flow rate of 3 slm, Ar flow rate of 1 slm, substrate temperature of 950℃, total pressure of reaction chamber of 40 Torr, and patterning was performed.

[0037] 2) Coat the surface of the single crystal aluminum nitride layer with epoxy resin, then spin-coat the photoresist AZ1500 from American Anzhi, pre-bake to remove moisture, expose to ultraviolet light for 5s, immerse in developer for 50s, then evaporate and deposit a 100nm thick layer of metallic platinum using a pure platinum crucible through an electron beam evaporation system, then immerse in acetone for 3min, peel off the metal on the photoresist to form a patterned bottom electrode;

[0038] 3) On the bottom electrode, a gold layer with a thickness of 300 nm, a tin layer with a thickness of 400 nm, a gold layer with a thickness of 300 nm, and a tin-tungsten boat are sequentially deposited using an electron beam evaporation system in a pure gold crucible and a tin-tungsten boat. The electrode is then immersed in acetone for 3 minutes to remove the metal from the photoresist, forming a patterned support layer (see schematic diagram of the device structure). Figure 2 (as shown);

[0039] 4) The two devices prepared in step 3) are bonded to two faces of a cuboid silicon substrate (support substrate) using optical alignment technology. The support layer in the device is bonded to the face of the cuboid silicon substrate (support substrate), fixed with mechanical clamps, and then transferred to a bonding machine chamber that can be heated and pressurized. The clamps are released and the chamber is evacuated to a pressure of 1000 mBar. A pressure of 8500 mBar is applied, the temperature is raised to 300℃, held for 10 min, and then allowed to cool naturally to room temperature. Then, the silicon substrate (preparation substrate) in the device prepared in step 3) is peeled off by chemical etching (the mass ratio of HNO3, HF and CH3COOH in the etching solution is 1:1:3) to expose the piezoelectric layer.

[0040] 5) A 100 nm thick layer of metallic platinum was deposited on the piezoelectric layer surface using an electron beam evaporation system in a pure platinum crucible. The platinum was then immersed in acetone for 3 minutes, and the metal on the photoresist was peeled off to form a patterned top electrode. This resulted in the fabrication of two PSA filters on two sides of a silicon substrate (see schematic diagram of the device). Figure 3 (as shown);

[0041] 6) Repeat steps 1) to 5) to continue fabricating the bulk acoustic wave filter on the remaining surface of the silicon substrate, thus obtaining the FBAR filter.

[0042] The FBAR filter in this embodiment integrates six PSA filters on six faces of a cuboid silicon substrate, achieving a substrate area utilization rate of over 90% (traditional filters are generally grown on only one side of the substrate, with a substrate area utilization rate of less than 45%), and reducing substrate material consumption by more than 50%.

[0043] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. An FBAR filter, characterized in that, The device comprises a cuboid support substrate and six bulk acoustic wave filters disposed on the six sides of the support substrate. Each bulk acoustic wave filter comprises a support layer, a bottom electrode, a piezoelectric layer, and a top electrode. The bottom electrode and the top electrode are both patterned electrodes and are disposed on opposite sides of the piezoelectric layer. The cavity formed by the support layer, the piezoelectric layer, the bottom electrode, and the support substrate in the bulk acoustic wave filter is an air cavity.

2. The FBAR filter according to claim 1, characterized in that: The supporting substrate is selected from one of the following: silicon substrate, sapphire substrate, LiGaO2 substrate, and metal elemental substrate.

3. The FBAR filter according to claim 1, characterized in that: The support layer is selected from one of the following: gold-tin alloy layer, gold-silicon alloy layer, nickel-tin alloy layer, and aluminum-germanium alloy layer.

4. The FBAR filter according to any one of claims 1 to 3, characterized in that: The composition of the bottom electrode is selected from at least one of Al, Mo, W, Pt, Ti, and Au.

5. The FBAR filter according to any one of claims 1 to 3, characterized in that: The piezoelectric layer is selected from one of the following: monocrystalline aluminum nitride layer, polycrystalline aluminum nitride layer, zinc oxide layer, and lead zirconate titanate layer.

6. The FBAR filter according to any one of claims 1 to 3, characterized in that: The top electrode is composed of at least one of Al, Mo, W, Pt, Ti, and Au.

7. The method for fabricating the FBAR filter according to any one of claims 1 to 6, characterized in that, Includes the following steps: 1) Deposit piezoelectric layers on both sides of the substrate and pattern them; 2) The bottom electrode is fabricated on the piezoelectric layer by photolithography, evaporation and lift-off, and then patterned; 3) A support layer is prepared on the bottom electrode by photolithography, vapor deposition, and lift-off; 4) The support layer is connected and fixed to the support substrate on two sides of the polyhedral support substrate using optical alignment technology. The substrate is then peeled off to expose the piezoelectric layer. 5) The top electrode was fabricated on the piezoelectric layer by photolithography, evaporation and lift-off, and patterned, that is, two PSA filters were fabricated on the two sides of the supporting substrate. 6) Repeat steps 1) to 5) to continue fabricating bulk acoustic wave filters on other surfaces of the support substrate, thus obtaining FBAR filters.

8. The method for fabricating an FBAR filter according to claim 7, characterized in that: Step 1) The substrate to be prepared is selected from one of the following: silicon substrate, sapphire substrate, LiGaO2 substrate, and metal elemental substrate.

9. The method for fabricating an FBAR filter according to claim 7 or 8, characterized in that: Step 1) The deposition is performed using metal-organic chemical vapor deposition (MOCVD) at a growth temperature of 850℃~950℃.

10. A communication device, characterized in that, The composition includes the FBAR filter described in any one of claims 1 to 6.

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