CN114785315A - Switchable acoustic wave filter, module and manufacturing method - Google Patents
Switchable acoustic wave filter, module and manufacturing method Download PDFInfo
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- H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
- H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
- H03H3/08—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of resonators or networks using surface acoustic waves
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- H—ELECTRICITY
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Abstract
The invention discloses a switchable acoustic wave filter, a module and a manufacturing method thereof, wherein the switchable acoustic wave filter comprises a series branch, a parallel branch and two high-mobility transistor switching tubes, the two high-mobility transistor switching tubes are arranged at two ends of the series branch, the high-mobility transistor switching tubes, the series branch and the parallel branch are integrated on the same chip, and the switchable acoustic wave filter module can be integrated by a plurality of switchable acoustic wave filters with different frequency bands and different types, so that the reconfigurable filtering function of multiple frequency bands can be realized. The invention realizes the fusion and integration of the acoustic wave filter and the radio frequency switch in the traditional radio frequency front end, improves the overall performance of the radio frequency front end and reduces the size.
Description
Technical Field
The invention relates to the field of radio frequency micro-electromechanical devices, in particular to a switchable acoustic wave filter, a switchable acoustic wave module and a manufacturing method.
Background
With the advance of the 5G era, the development of miniaturization, microminiaturization and integration of the radio frequency front end and the opening and use of a higher communication frequency band lead the market to continuously increase the demand on the bulk acoustic wave filtering technology. According to the expectation of Skyworks corporation, the number of radio frequency front-end filters of the novel wireless communication device in the 5G maturity stage can be increased to more than 100, and the number of switches can exceed more than 30, which means higher requirements of a radio frequency system on a switch filter bank. The traditional cavity filter and dielectric filter cannot be used in the 5G frequency band, and the acoustic wave filter is widely applied to the frequency band below 6G (sub-6G) due to its advantages of high quality factor (Q), high frequency, micro volume and suitability for mass production, so the requirement of the switch acoustic wave filter group is increased.
A common switch filter module consists of two switch circuits and multiple filter channels. The switch driving circuit controls the switching of the single-pole multi-throw switch circuits connected with the two ends of the filter, so that a filter channel needing to be used is opened, and a filter channel not needing to be used is closed, and a required frequency band is selected. The switch circuit has a complex structure, more processing steps and large use volume. In recent years, many studies have been made on the circuits of the switched acoustic wave filter bank in which the acoustic wave filter and the integrated circuit are integrated in a heterogeneous manner, such as guo pine, li, and the like, "FBAR switched filter bank chip based on heterogeneous integration technology" [ semiconductor technology ], 2020,45(04): 263-) -267. Although the structure saves part of the chip area, the processing steps and the manufacturing difficulty are not really simplified.
Disclosure of Invention
In order to overcome the disadvantages and shortcomings of the prior art, a first object of the present invention is to provide a switchable acoustic wave filter;
the second objective of the present invention is to provide a switchable acoustic wave filter module;
a third objective of the present invention is to provide a method for manufacturing a switchable acoustic wave filter.
The invention adopts the following technical means:
a switchable acoustic wave filter comprises a series branch, a parallel branch and two high mobility transistor switching tubes, wherein the two high mobility transistor switching tubes are arranged at two ends of the series branch, and the high mobility transistor switching tubes, the series branch and the parallel branch are integrated on the same chip;
the series branch comprises a plurality of first sound wave resonators connected in series, the parallel branch comprises a plurality of second sound wave resonators connected in parallel, the first sound wave resonators are non-switchable bulk acoustic wave resonators, and the second sound wave resonators are switchable bulk acoustic wave resonators.
Further, the first acoustic wave resonator and the second acoustic wave resonator at least comprise a first metal layer and a piezoelectric layer, the piezoelectric layer of the first acoustic wave resonator is a single layer, the piezoelectric layer of the second acoustic wave resonator comprises a first piezoelectric semiconductor material layer and a second piezoelectric semiconductor material layer, the forbidden bandwidth of the first piezoelectric semiconductor material layer is different from that of the second piezoelectric semiconductor material layer, the thickness of the second piezoelectric semiconductor material layer is larger than that of the first piezoelectric semiconductor material layer, the second piezoelectric semiconductor material layer is located below the first piezoelectric semiconductor material layer and forms a heterojunction with the first piezoelectric semiconductor material layer, and two-dimensional electron gas (2 DEG) or two-dimensional hole gas (2DHG) is generated.
Further, the first piezoelectric semiconductor material layer is composed of AlGaN, the second piezoelectric semiconductor material layer is composed of GaN, and a heterojunction formed at this time generates a two-dimensional electron gas; the first piezoelectric semiconductor material layer is composed of GaN, and the second piezoelectric semiconductor material layer is composed of AlN or AlGaN, and a heterojunction formed at this time generates two-dimensional hole gas.
Further, the low voltage is adopted to control the opening and closing of the second acoustic resonator, specifically:
when the heterojunction generates two-dimensional electron gas, the first metal layer of the second acoustic wave resonator applies negative voltage to control the opening of the resonator;
when the heterojunction generates two-dimensional hole gas, a first metal layer of the second acoustic wave resonator applies positive voltage to control the opening of the resonator;
when the first metal layer of the second acoustic wave resonator has no bias voltage, the second acoustic wave resonator is closed, and the second acoustic wave resonator is equivalent to a capacitor at the moment.
Further, the on and off of the switchable acoustic wave filter is controlled by applying a voltage to the gate of the high mobility transistor switching transistor, specifically:
when a positive voltage is applied to the grid electrode of the high-mobility transistor switch, the high-mobility transistor switch is turned off, and the high-mobility transistor switch is equivalent to a resistor, so that signal isolation is realized;
when the grid electrode of the high mobility transistor switching tube has no bias voltage, the high mobility transistor switching tube forms a signal path.
Further, the position of the resonance point of the series branch is changed by etching the thickness of the piezoelectric layer.
A switchable acoustic filter module includes a plurality of switchable acoustic filters connected in parallel, each switchable acoustic filter forming an independent channel, and an additional driving signal controlling the channel switch.
A method of making a switchable acoustic wave filter, comprising:
preparing a piezoelectric layer on a silicon wafer, specifically growing a first semiconductor material layer and a second piezoelectric semiconductor material layer by adopting an MOCVD (metal organic chemical vapor deposition) or MBE (molecular beam epitaxy) method;
etching the piezoelectric layer, and removing the first piezoelectric semiconductor material layer and part of the second piezoelectric semiconductor material layer in a graphical mode to enable the first acoustic wave resonators connected in series to have no switching characteristics, and meanwhile reducing the thickness of the second piezoelectric semiconductor material layer to enable resonance points of the first acoustic wave resonators connected in series to move towards high frequency and form a filter channel with the second acoustic wave resonators connected in parallel;
preparing a source electrode and a drain electrode of the high-mobility transistor switching tube;
simultaneously preparing a first metal layer and a grid electrode of a high-mobility transistor;
and preparing a metal bonding pad layer and releasing the back to obtain the switchable acoustic wave filter.
Further, the partial acoustic wave resonator needs to add a step of preparing a second metal layer after the back release.
Furthermore, a plurality of switchable acoustic wave filters with different frequency bands can be synchronously processed and manufactured on the same substrate.
The invention has the beneficial effects that:
(1) the high mobility transistor switching tube and the acoustic wave resonator are integrated on the same chip, namely, the switch and the filter at the front end of the radio frequency are integrated on a single chip, so that the circuit complexity is reduced, and the use area and the packaging cost are reduced;
(2) the invention can use low voltage driving signal to realize switch effect, and control the on and off of the high mobility transistor switch tube and the switchable acoustic wave resonator when the control signal applies low DC bias; the invention can realize good isolation by using very low direct current bias, and has wide research and development and commercial significance.
(3) The invention has high integration and improves the performance of the filter, integrates the control switch and the filter on the same chip, reduces the transmission loss of signals between the filter and the switch, and improves the passband performance of the filter. The switchable filter module provided by the invention can be composed of a plurality of acoustic wave filters with larger central frequency difference, can be further monolithically integrated with other devices at the radio frequency front end to realize the integral preparation of the radio frequency front end part module, and has very high applicability.
(4) The piezoelectric semiconductor material layer can adopt GaN, AlN or AlGaN to form a heterojunction, and can generate two-dimensional electron gas or two-dimensional hole gas, so that the material of the resonator structure is more diversified, and the piezoelectric semiconductor material layer can be applied to the manufacture of various acoustic wave filters. The application of the two-dimensional cavity gas enables the AlN having the advantages of high sound velocity, high mechanical quality factor (Q), high coupling coefficient and the like to be selected as the piezoelectric material for the acoustic wave filter.
(5) In the manufacturing method, the switching tube and the resonator are simultaneously prepared, the semiconductor material layer of the switching tube is shared with the piezoelectric layer of the resonator, and the semiconductor material layer is deposited simultaneously; the grid electrode of the switch tube is shared with the first metal layer, and the electron beam evaporation deposition metal and the metal stripping are carried out simultaneously. Meanwhile, the preparation process can save a photoetching plate and save photoetching and repeated process machine use, material consumption and the like.
Drawings
Fig. 1 is a schematic block diagram of a switchable acoustic wave filter bank according to embodiment 3 of the present invention;
fig. 2 is a structural diagram of a switchable acoustic wave filter according to embodiment 1 of the present invention;
fig. 3 is a structural diagram of a switchable bulk acoustic wave resonator in embodiment 1 of the present invention;
FIG. 4 is a comparison graph of S parameters of a single channel filter in ON and OFF states in accordance with embodiment 1 of the present invention;
fig. 5(a) -5 (h) are process flow diagrams of switchable bulk acoustic wave filter banks according to embodiment 2 of the present invention;
fig. 6(a) -6 (d) are S parameter diagrams of the multi-channel filter bank in the on state of each channel according to embodiment 3 of the present invention.
Detailed Description
The present invention will be described in further detail with reference to examples and drawings, but the embodiments of the present invention are not limited thereto.
Example 1
As shown in fig. 2, a switchable acoustic wave filter includes two high mobility transistor switches, a series branch and a parallel branch, where the two high mobility transistor switches, the series branch and the parallel branch are integrated on the same chip.
Further, the series branch comprises a plurality of first acoustic wave resonators 1 connected in series, the parallel branch comprises a plurality of second acoustic wave resonators 2 connected in parallel, the types of the first acoustic wave resonators are different from those of the second acoustic wave resonators, two ends of the series branch formed by the plurality of connected first acoustic wave resonators are respectively connected with a high mobility transistor switch 3, and a grid electrode of the high mobility transistor switch is connected with a power supply.
In this embodiment, in order to isolate the signal from the power supply, a high-resistance isolation resistor 4 formed by a heterojunction is further included, and is disposed between the power supply and the second acoustic wave resonator, i.e., the switchable bulk acoustic wave resonator.
In the present embodiment, any of bulk acoustic wave resonators, lamb wave resonators, surface acoustic wave resonators, and the like can be selected as the acoustic wave resonator.
In this embodiment 1, the first acoustic wave resonator is a non-switchable bulk acoustic wave resonator, the second acoustic wave resonator is a switchable bulk acoustic wave resonator, and the filter mentioned below is formed by this structure.
Further, the first and second acoustic resonators at least include a first metal layer and a piezoelectric layer, and in this embodiment 1, the first acoustic resonator and the second acoustic resonator are both sandwich-structured devices composed of the first metal layer, the piezoelectric layer, and the second metal layer.
The first metal layer is a high work function metal.
The second metal layer is a low acoustic loss metal.
The piezoelectric layer of the first acoustic wave resonator is a single layer and is made of the same piezoelectric semiconductor material, preferably AlN material. The piezoelectric layer of the second acoustic resonator comprises a first piezoelectric semiconductor material layer and a second piezoelectric semiconductor material layer, the first piezoelectric semiconductor material layer is preferably made of GaN, the second piezoelectric semiconductor material layer is preferably made of AlN, and the first piezoelectric semiconductor material layer and the second piezoelectric semiconductor material layer form a heterojunction to generate two-dimensional hole gas, and generation and depletion of the two-dimensional hole gas are regulated and controlled through a reverse biased Schottky junction.
Further, the second acoustic resonator for the parallel branch is specifically a switchable bulk acoustic resonator, as shown in fig. 3, and includes a first metal layer 5, a second metal layer 9, and a piezoelectric layer. The piezoelectric layers are composed of a first piezoelectric semiconductor material layer 6 and a second piezoelectric semiconductor material layer 8 which are different in forbidden band width. The first piezoelectric semiconductor material layer and the second piezoelectric semiconductor material layer having different forbidden band widths form a heterojunction 7 to generate two-dimensional hole gas.
In this embodiment, the thickness of the first piezoelectric semiconductor material layer is about 20nm, and the thickness of the second piezoelectric semiconductor material layer is about 1 um.
Further, the second acoustic wave resonator is controlled to be turned on and off by a low voltage, the low voltage is generally less than 12V, and the turning on and off of the embodiment takes the heterojunction to generate the two-dimensional hole gas as an example, specifically:
when a positive voltage is applied to the first metal layer, the two-dimensional hole gas is exhausted, the electric field can excite the second piezoelectric semiconductor material through the first piezoelectric semiconductor material layer, so that resonance can be generated for normal operation, and the second acoustic resonator is started.
When the first metal layer has no bias voltage, the piezoelectric layer of the second acoustic wave resonator is shielded by the two-dimensional cavity gas, so that the resonator cannot normally work to achieve the closing effect, at the moment, the resonator is converted into a large capacitor formed by insulating medium layers between the upper metal layer and the lower metal layer, and the second acoustic wave resonator is closed.
Further, the heterojunction refers to a junction composed of two materials with different forbidden band widths and lattice constants. Semiconductor materials with different forbidden band widths of the piezoelectric layers are contacted, and conduction band disconnection occurs at the conduction band edge at the heterojunction interface due to different energy levels of the two materials in contact, so that a narrow quantum well is formed. The narrow gap semiconductor material is positioned above the wide gap semiconductor material, and under the action of a polarization electric field, holes in the material on the narrow side of the band gap are transferred in the quantum well. Because the width of the quantum well is narrower than that of the channel, the movement of the hole in the direction vertical to the interface is limited, and the hole can only move in two dimensions along the heterojunction interface, so that two-dimensional hole gas is formed at the heterojunction interface.
The two high-mobility transistor switching tubes are respectively positioned at two ends in the filter and used as switching tubes of the filter, and the grid electrodes of the high-mobility transistor switching tubes are used for increasing positive voltage to control the on and off of the circuit. When the negative voltage is applied to the grid electrode, the switch tube is closed, and the switch tube is equivalent to a resistor with high resistance at the moment, so that signal isolation is realized. When the grid electrode is not biased by voltage, the switch tube presents a very low resistance value to form a signal path.
Furthermore, the source electrode and the drain electrode of the high-mobility transistor are made by forming ohmic contact between the deposited alloy and the semiconductor material, and the grid electrode of the high-mobility transistor is made by forming Schottky contact with the semiconductor material.
The control procedure of the switchable filter in this embodiment 1 is as follows:
the filter channel closing state comprises the following specific processes: the grid electrode of the high-mobility transistor is applied with positive voltage, and the transistor is in an off state and is represented as a large resistor; the first metal layer of the switchable bulk acoustic wave resonator in the parallel branch circuit has no voltage bias and is equivalent to a large capacitor, so that a signal is grounded, and the channel is in a closed state.
The filter channel opening state comprises the following specific processes: the grid electrode of the high-mobility transistor is free from voltage bias and presents a very low resistance value to form a signal path; the switchable bulk acoustic wave resonator in the parallel branch has no bias voltage on the first metal layer, and the resonator is in an open state and generates a filtering effect when working normally.
The positions of the series resonance point and the parallel resonance point of the resonator can be changed by finely adjusting the thickness of the first metal layer, when the series resonance point of the parallel resonator is superposed with the parallel resonance point of the series resonator, the filter has the best filtering performance, and the selectivity of the filter is improved along with the increase of the order.
The circuit simulation of the single-channel bulk acoustic wave filter is performed by adopting circuit simulation software, and the simulation result of comparing the S parameters of the starting state and the closing state of the bulk acoustic wave filter is shown in fig. 4. According to simulation results, the center frequency of the band-pass filter is 3.5GHz, and the loss of the filter caused by the switch structure in the starting state of the band-pass filter is less than 1 dB; under the closed state, the isolation effect is higher than 60dB, and the method has commercial development and use significance.
Example 2
As shown in fig. 5(a) -5 (h), a method for manufacturing a switchable acoustic wave filter mainly includes preparing a piezoelectric layer of a resonator, and preparing a source and a drain of a high mobility transistor; preparing a first metal layer of a resonator and a grid electrode of a switch tube; etching the piezoelectric layer; preparing a metal pad layer; and releasing the back.
The method comprises the following specific steps:
s1 silicon wafer cleaning
Selecting a high-resistance double-sided polishing crystal orientation (111) silicon wafer 10, and cleaning the silicon wafer by adopting a standard semiconductor cleaning process.
S2 preparation of piezoelectric layer
The second piezoelectric semiconductor material layer 12 and the thinner first piezoelectric semiconductor material layer 11 are grown by using a method of MOCVD (metal organic chemical vapor deposition) or MBE (molecular beam epitaxy), the first piezoelectric semiconductor material layer is located above the second piezoelectric semiconductor material layer, and the first piezoelectric semiconductor material layer is about 20 nm.
S3 etching piezoelectric layer
And patterning the piezoelectric layer, thinning the thickness of the piezoelectric layer of the series bulk acoustic wave resonator by ICP etching, and removing all the first piezoelectric semiconductor material layer and part of the second piezoelectric semiconductor material layer to form an etched second piezoelectric semiconductor material layer 13, so that the series resonator does not have the switching characteristic. Meanwhile, the thickness of the piezoelectric layer of the bulk acoustic wave resonator is reduced, so that the resonance point of the resonator moves to high frequency, and the series resonator and the parallel resonator can form a filter channel. For example, the piezoelectric layer is selected from GaN and AlGaN, and the plasma gas is selected from boron trichloride (B: the plasma is the plasma gas as the plasma is a plasma gas as the plasma is a plasma gas is a plasma gas is a plasma is provided as the plasma is provided as the plasma gas is provided as plasma gas is a plasma gas is provided, and is provided as plasma gas, and plasma is provided as plasma is provided, and is provided as plasma is provided, and plasma is provided asBCl 3 ) And so on.
S4 preparation of source and drain of switch tube
And depositing a plurality of metals 14 on the semiconductor material by using an electron beam evaporation method, stripping the metals to realize patterning, and placing the semiconductor material in a high-temperature furnace for rapid annealing to form an alloy to finish the manufacture of ohmic contact between the source electrode and the drain electrode of the switching tube. If the piezoelectric layer is selected from GaN and AlGaN, the source and drain metal can be selected from titanium/aluminum/nickel/gold (Ti/Al/Ni/Au).
S5 preparation of first metal layer of resonator and grid of switch tube
Using electron beam evaporation, a high work function metal 15 such as nickel (Ni) is deposited on the semiconductor material and the metal is stripped to achieve patterning.
S6 preparation of metal bonding pad layer
And depositing metal 16 with good conductivity, such as gold (Au), on the device by using an electron beam evaporation method to serve as a device connecting lead and a metal bonding pad, and stripping the metal to realize patterning.
S7 Back Release
Reversing the wafer, patterning the back surface of the wafer, and using sulfur hexafluoride (F)SF 6 ) And octafluorocyclobutane (c)C 4 F 8 ) Carrying out ICP deep silicon etching by plasma gas to enable the section of the back opening to form an inverted trapezoid 17. The resonator is released from the substrate by removing the silicon substrate at the bottom of the acoustic wave resonator. Before the back is released, the whole wafer can be thinned, and the etching uniformity of different opening sizes is ensured.
S8 preparing the second metal layer, which is not required if the acoustic wave resonator does not have the second metal layer.
And depositing a second metal layer 18 in the silicon hole etched on the back of the wafer by adopting a magnetron sputtering method, and stripping the metal to realize patterning. The barrier layer for metal stripping can be selected from photoresist left after back etching or a surface adhesion metal mask.
The present embodiment utilizes the piezoelectric and semiconductor properties of gallium nitride (GaN) materials. The piezoelectric characteristics of the resonator are utilized to realize the mutual conversion of the acoustic-electric signals, and the resonator is excited to generate resonance, so that the acoustic wave resonator is manufactured; the semiconductor characteristic of the material is utilized to enable the material to form a heterojunction with a piezoelectric semiconductor material layer (commonly used as AlGaN) with different forbidden band widths so as to generate two-dimensional electron gas. The heterojunction structure not only enables the acoustic wave resonator to have the switching characteristic, but also is used as the grid electrode of the high-mobility transistor switching tube. Four metals of titanium/aluminum/nickel/gold (Ti/Al/Ni/Au) are deposited on a semiconductor material by a source electrode and a drain electrode of the high-mobility transistor, and an alloy is formed by annealing to realize ohmic contact manufacturing. And applying a direct current voltage to a first metal layer of the acoustic wave resonator to control the opening of the acoustic wave resonator, and applying a direct current voltage to a grid electrode of the high-mobility transistor to control the closing of the transistor.
Furthermore, the piezoelectric layer material provided by the invention can select a piezoelectric compound composed of other group III elements, group V elements and the like.
Example 3
As shown in fig. 1, a switchable bulk acoustic wave filter module is composed of a plurality of switchable acoustic wave filters (acoustic wave filter 1, acoustic wave filter 2 … … acoustic wave filter N) described in this embodiment 1, and an additional driving signal is applied to control the on and off of the filter channel, so that only the channel requiring a frequency signal is opened at a certain time, and other channels are closed.
The invention is further shown by a specific example two-channel filter bank. Each channel of the two-channel filter consists of high mobility transistor switching tubes at the front end and the rear end, a plurality of series-connected bulk acoustic wave resonators and a plurality of switchable bulk acoustic wave resonators connected in parallel. And (3) performing simulation by using circuit software, and selecting the piezoelectric layer as an AlN material to build two filter channels with the center frequencies of 2GHz (channel 1) and 2.4GHz (channel 2). The two filter channels are controlled to be opened and closed by externally added direct current signals, and S parameters of the two channels are shown in figure 6(a) when the two channels work independently and normally. When two filters are connected in parallel and only channel 1 is required to be on as shown in fig. 6(b), if the high mobility transistor switch in the channel 2 branch is not turned off (or there is no switch), a zero is generated at channel 2 and the passband insertion loss and flatness of channel 1 are deteriorated. When the high mobility transistor is turned off by applying a positive voltage, the isolation of the channel 2 is increased, and the response of the channel 1 returns to normal. But is often limited by the insertion loss of the transistor switch tube, and effective isolation between channels can not be ensured only by the switch tube. As shown in fig. 6(c), if the switch in the channel 2 branch is turned off but the switchable filter is not, the isolation is limited and spurs are generated at 2.4 GHz. Therefore, through preliminary analysis, the implantation of the high mobility transistor switch and the cooperation with the switchable filter are important guarantees for the normal operation of the reconfigurable switch filter bank. The S-parameters when both filter channels are on simultaneously are shown in fig. 6 (d). Through effective isolation design, the filter module can also simultaneously start a plurality of filters, so that a flexible multi-band filtering function is realized.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.
Claims (10)
1. A switchable acoustic wave filter is characterized by comprising a series branch, a parallel branch and two high mobility transistor switching tubes, wherein the two high mobility transistor switching tubes are arranged at two ends of the series branch, and the high mobility transistor switching tubes, the series branch and the parallel branch are integrated on the same chip;
the series branch comprises a plurality of first sound wave resonators connected in series, the parallel branch comprises a plurality of second sound wave resonators connected in parallel, the first sound wave resonators are non-switchable bulk acoustic wave resonators, and the second sound wave resonators are switchable bulk acoustic wave resonators.
2. The switchable acoustic wave filter of claim 1, wherein the first acoustic wave resonator and the second acoustic wave resonator at least include a first metal layer and a piezoelectric layer, the piezoelectric layer of the first acoustic wave resonator is a single layer, the piezoelectric layer of the second acoustic wave resonator includes a first piezoelectric semiconductor material layer and a second piezoelectric semiconductor material layer having different forbidden band widths, the second piezoelectric semiconductor material layer is thicker than the first piezoelectric semiconductor material layer and is located below the first piezoelectric semiconductor material layer to form a heterojunction with the first piezoelectric semiconductor material layer, and two-dimensional electron gas or two-dimensional hole gas is generated.
3. The switchable acoustic wave filter of claim 2, wherein the first layer of piezoelectric semiconductor material is comprised of AlGaN and the second layer of piezoelectric semiconductor material is comprised of GaN, the heterojunction formed at this time generating a two-dimensional electron gas; the first piezoelectric semiconductor material layer is composed of GaN, and the second piezoelectric semiconductor material layer is composed of AlN or AlGaN, and a heterojunction formed at this time generates two-dimensional hole gas.
4. The switchable acoustic wave filter according to claim 2, wherein the second acoustic resonator is turned on and off by a low voltage control, specifically:
when the heterojunction generates two-dimensional electron gas, the first metal layer of the second acoustic wave resonator applies negative voltage to control the opening of the resonator;
when the heterojunction generates two-dimensional hole gas, a first metal layer of the second acoustic wave resonator applies positive voltage to control the opening of the resonator;
when the first metal layer of the second acoustic resonator has no bias voltage, the second acoustic resonator is closed, and the second acoustic resonator is equivalent to a capacitor at the moment.
5. The switchable acoustic wave filter according to any of claims 1-4, wherein the on and off of the switchable acoustic wave filter is controlled by applying a voltage to the gate of the high mobility transistor switch, specifically:
when a positive voltage is applied to the grid electrode of the high-mobility transistor switch, the high-mobility transistor switch is turned off, and the high-mobility transistor switch is equivalent to a resistor, so that signal isolation is realized;
when the grid electrode of the high mobility transistor switching tube has no bias voltage, the high mobility transistor switching tube forms a signal path.
6. The switchable acoustic wave filter according to claim 4, wherein the position of the resonance point of the series arm is changed by etching the thickness of the piezoelectric layer.
7. A switchable acoustic wave filter module comprising a plurality of switchable acoustic wave filters according to any of claims 1-6 connected in parallel, each switchable acoustic wave filter forming an independent channel, with an applied drive signal controlling the channel switch.
8. A method of manufacturing a switchable acoustic wave filter according to any of claims 1-6, the method comprising:
preparing a piezoelectric layer on a silicon wafer, specifically growing a first semiconductor material layer and a second piezoelectric semiconductor material layer by adopting an MOCVD (metal organic chemical vapor deposition) or MBE (molecular beam epitaxy) method;
etching the piezoelectric layer, and removing the first piezoelectric semiconductor material layer and part of the second piezoelectric semiconductor material layer in a graphical mode to enable the first acoustic wave resonators connected in series to have no switching characteristics, and meanwhile reducing the thickness of the second piezoelectric semiconductor material layer to enable resonance points of the first acoustic wave resonators connected in series to move towards high frequency and form a filter channel with the second acoustic wave resonators connected in parallel;
preparing a source electrode and a drain electrode of the high-mobility transistor switching tube;
simultaneously preparing a first metal layer and a grid electrode of a high-mobility transistor;
and preparing a metal welding disc layer and releasing the back to obtain the switchable acoustic wave filter.
9. The method of claim 8, wherein the step of preparing the second metal layer is added after the back release of the partial acoustic wave resonator.
10. The method according to any one of claims 8 or 9, wherein the switchable acoustic wave filters of different frequency bands are simultaneously processed and manufactured on the same substrate.
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