Abstract
Piezoelectric nitride compound materials with improved properties is provided. The piezoelectric material comprises aluminium, nitrogen and ternary and quaternary dopants that can be selected from calcium, ruthenium, boron and/or yttrium.
Claims
1. A piezoelectric material, comprising: Al.sub.1-x[(Ca.sub.a, Ru.sub.b, Z1.sub.c1, Z2.sub.c2).sub.y].sub.xN as its main constituent, wherein: 0.055≤a≤1.33, 0.055≤b≤1.33, 0≤c1, 0≤c2, 0≤c=c1+c2≤1.33, y=1/(a+b+c), 0.03≤x≤0.75 and Z1 and Z2 are selected from B and Y.
2. The piezoelectric material of claim 1, wherein the main constituent is Al.sub.1-x[(Ca.sub.a, Ru.sub.b, Z1.sub.c1, Z2.sub.c2).sub.y].sub.xN and Z1 and Z2 is selected from B and Y or only B or only Y, and wherein: 0.165≤a≤0.66, 0.165≤b≤0.66, 0≤c1, 0≤c2, 0≤c=c1+c2≤0.66, y=1/(a+b+c), and 0.09≤x≤0.372.
3. The piezoelectric material of claim 1, wherein x is selected from 0.03, 0.06, 0.09, 0.12, 0.15, 0.18, 0.21, 0.24, 0.27, 0.30, 0.33, 0.36, 0.39, 0.42, 0.45, 0.48, 0.51, 0.54, 0.57, 0.60, 0.63, 0.66, 0.69, 0.72 and 0.75.
4. The piezoelectric material of claim 1, wherein the main constituent is Al.sub.0.814Ca.sub.0.062Ru.sub.0.062B.sub.0.062N.
5. The piezoelectric material of claim 1, wherein the main constituent is Al.sub.0.814Ca.sub.0.062Ru.sub.0.062B.sub.0.124N.
6. The piezoelectric material of claim 1, wherein the main constituent is Al.sub.0.876 Ca.sub.0.062Ru.sub.0.062B.sub.0.124N.
7. The piezoelectric material of claim 1, wherein the main constituent is Al.sub.0.69Ca.sub.0.124Ru.sub.0.124B.sub.0.062N.
8. The piezoelectric material of claim 1, wherein the main constituent is Al.sub.0.814Ca.sub.0.062Ru.sub.0.062Y.sub.0.062N.
9. The piezoelectric material of claim 1, wherein the main constituent is Al.sub.0.876Ca.sub.0.062Ru.sub.0.062N.
10. The piezoelectric material of claim 1, wherein 44.2 (atomic %), 53.5 (atomic %), 62.77 (atomic %), 72.1 (atomic %), 81.4 (atomic %), 90.7 (atomic %), 95.78 (atomic %), 98.25 (atomic %) or 99 (atomic %) are Al while the remaining balance is a combination of ternary or quaternary doped AlN piezoelectric material containing Ca (calcium), Ru (ruthenium), B (boron) and Y (yttrium).
11. The piezoelectric material of claim 1, wherein the piezoelectric material is part of a piezoelectric device.
12. The piezoelectric material of claim 11, the piezoelectric device being selected from: an electro acoustic resonator, a SAW resonator, a SAW filter, a solidly mounted resonator (SMR-type resonator), a (SMR-)BAW filter, a guided BAW (GBAW) resonator, a GBAW filter, a film bulk acoustic wave (FBAR) resonator, a FBAR filter, or a resonator working with Lamb waves, acoustic plate waves (APW), Rayleigh SAW (R-SAW), Sezawa mode waves, shear-horizontal SAWs (SH-SAWs), Love mode waves, pseudo-surface acoustic waves (PSAW) or Leaky SAWs (LSAW), or an acoustic device, a multiplexer, a duplexer, a quadplexer, a hexaplexer based on any of the above types of resonators, a piezoelectric generator, a piezoelectric sensor, a mass sensor, a microfluidic sensor, a piezoelectric transducer, an energy harvester, an ultrasound devices, a transducer, atransmitter, a piezo (MEMS) microphone, a device that utilizes direct or reverse piezolectric effect in a thin film or bulk ceramic form.
Description
[0042] In the figures:
[0043] FIG. 1 illustrates the arrangement of an interdigital structure of a SAW resonator;
[0044] FIG. 2 illustrates the arrangement of a SMR-type BAW resonator;
[0045] FIG. 3 illustrates the combination of electro acoustic resonators to establish a duplexer;
[0046] FIG. 4 shows comparisons between calculated values of electromechanical coupling coefficient, κ.sup.2 and measured values from actual SMR-BAW resonators with a piezoelectric layers made from different doping levels of Sc in AlN;
[0047] FIG. 5 shows comparison between extrapolated mechanical Quality Factor (Q.sub.m) for measured from SMR-BAW and obtained values from ab-initio calculations and it is showing how quickly Q.sub.m is changing with different doping levels of Sc in AlN;
[0048] FIG. 6 shows the dependence of C.sub.33 vs coupling coefficient κ.sup.2 behaviour for an alternative to Al.sub.1-xSc.sub.xN (0.0625≤x≤0.31) material with a higher C.sub.33 for a range of coupling coefficients κ.sup.2;
[0049] FIG. 7 shows the dependence of C.sub.33 vs coupling coefficient κ.sup.2 behaviour for an alternative to Al.sub.1-xSc.sub.xN (0.0625≤x≤0.31) material with a moderately higher C.sub.33 for a range of coupling coefficients κ.sup.2;
[0050] FIG. 8 shows a C.sub.33−κ.sup.2 dependence;
[0051] FIG. 9 shows the dependence of C.sub.33 vs coupling coefficient κ.sup.2 behaviour for an alternative to Al.sub.1-xSc.sub.xN (0.0625≤x≤0.31) material with a marginally equivalent C.sub.33 for a range of coupling coefficients κ.sup.2.
[0052] FIG. 1 illustrates a basic arrangement of electrode structures on a piezoelectric material PM that can be provided as a single crystal piezoelectric substrate or by piezoelectric material provided as a thin layer. The electrode structure has an interdigitated structure, IDS, comprising electrode fingers, EFI, arranged one next to another. Each of the electrode fingers, EFI, is electrically connected to one of two bus bars. In the arrangement shown in FIG. 3, the acoustic waves propagate at the surface of the piezoelectric material in a direction orthogonal to the electrode fingers.
[0053] FIG. 2 illustrates the basic construction of a BAW resonator BAWR. The BAW resonator BAWR has the piezoelectric material, PM, sandwiched between a bottom electrode, BE, and a top electrode, TE. FIG. 4 also illustrates an SMR-type resonator where the resonator structure comprising the two electrodes and the piezoelectric material is arranged on an acoustic mirror. The acoustic mirror has mirror layers, ML. Adjacent mirror layers, ML, have different acoustic impedance. At an interface between different mirror layers, ML, of different acoustic impedance, a part of the acoustic energy is reflected such that the combination of mirror layers, ML, establishes a Bragg mirror to confine the acoustic energy.
[0054] FIG. 3 illustrates the possibility of combining a transmission filter, TXF, and a reception filter, RXF, to establish a duplexer. The transmission filter, TXF, and the reception filter, RXF, comprise a signal path in which series resonators, SR, are electrically connected in series. Parallel resonators, PR, are electrically connected in shunt paths between the signal path and ground. An impedance matching circuit can be arranged between the transmission filter, TXF, and the reception filter, RXF, to provide matched frequency dependent impedances at the common port at which an antenna, AN, can be connected.
[0055] FIG. 4 shows a comparison between measured and calculated data. Curve (1) shows the (experimentally) measured dependence of the coupling factor, κ.sup.2, on the Sc doping level of Sc doped AlN (Al.sub.1-xSc.sub.xN) for different doping levels, x. Curve (2) shows the results of calculations made in a simulation for determining a theoretical model of Sc doped AlN. It can be seen that the experiments essentially verifies the ab-initio calculated results.
[0056] Similarly, FIG. 5 shows a comparison between measured and calculated data. Curve (3) shows the measured dependence of the mechanical quality factors, Qm, derived from the impedance response of physical (experimentally fabricated) resonators on the Sc doping level of Sc doped AlN (Al.sub.1-xSc.sub.xN). Curve (4) shows the results of calculations made in the simulation. Again, the experimentally derived values essentially verify the calculated results.
[0057] Thus, the calculations on which the present compositions base are reliable.
[0058] FIG. 6 shows a comparison between a plurality of parameters of Sc doped AlN and Al.sub.0.814Ca.sub.0.062Ru.sub.0.062B.sub.0.062N (corresponding to composition A) of the tables). The Sc doping level for the different Sc doped AlN composition essentially determines C.sub.33 as shown by curves (5). Curve (6) shows a polynomial interpolation of calculated data points indicating a C.sub.33 dependence on κ.sup.2 for different quasi-random structures of Al.sub.0.814Ca.sub.0.062Ru.sub.0.062B.sub.0.062N. The different quasi-random structures of Al.sub.0.814Ca.sub.0.062Ru.sub.0.062B.sub.0.062N differ in an exact position of each dopant that substitutes the Al atoms. The calculations show that in a real composition a mixture of these quasi-random structures is provided such that a κ.sup.2 of approximately 0.18 and a C.sub.33 of 270.4 GPa are obtained. Thus, Al.sub.0.814Ca.sub.0.062Ru.sub.0.062B.sub.0.062N has a C.sub.33 that is approximately 65.3 GPa larger than that of Sc doped AlN baseline system with very similar κ.sup.2 (close to 0.20), while the median value of Al.sub.0.814Ca.sub.0.062Ru.sub.0.062B.sub.0.062N has a C.sub.33 that is approximately 42.3 GPa larger than that of Sc doped AlN baseline system with the very similar κ.sup.2 (close to 0.15).
[0059] FIG. 7 shows a comparison between a plurality of parameters of Sc doped AlN and Al.sub.0.876Ca.sub.0.062Ru.sub.0.062B.sub.0.124N (corresponding to composition B) of the tables). The Sc doping level for the different Sc doped AlN composition essentially determines C.sub.33 as shown by curves (7). Curve (8) shows a polynomial interpolation of calculated data points indicating a C.sub.33 dependence on κ.sup.2 for different quasi-random structures of Al.sub.0.876Ca.sub.0.062Ru.sub.0.062B.sub.0.124N. The different quasi-random structures of Al.sub.0.876Ca.sub.0.062Ru.sub.0.062B.sub.0.124N differ in an exact position of each dopant that substitutes the Al atoms. The calculations show that in a real composition a mixture of these quasi-random structures is provided such that a κ.sup.2 of approximately 0.139 and a C.sub.33 of 274.2 GPa are obtained. Thus, Al.sub.0.876Ca.sub.0.062Ru.sub.0.062B.sub.0.124N has a C.sub.33 that is approximately 14 GPa with very similar κ.sup.2 (close to 0.13).
[0060] FIG. 8 shows calculated parameters for doped AlN.
[0061] FIG. 9 shows a comparison between a plurality of parameters of Sc doped AlN and Al.sub.0.814Ca.sub.0.062Ru.sub.0.062Y.sub.0.062N (corresponding to composition E) of the tables). The Sc doping level for the different Sc doped AlN composition essentially determines C.sub.33 as shown by curves (9). Curve (10) shows a polynomial interpolation of calculated data points indicating a C.sub.33 dependence on κ.sup.2 for different quasi-random structures of Al.sub.0.814Ca.sub.0.062Ru.sub.0.062Y.sub.0.062N. The different quasi-random structures of Al.sub.0.876Ca.sub.0.062Ru.sub.0.062B.sub.0.124N differ in an exact position of each dopant that substitutes the Al atoms. The calculations show that in a real composition a mixture of these quasi-random structures is provided such that a κ.sup.2 of approximately 0.179 and a C.sub.33 of 232 GPa are obtained. Thus, Al.sub.0.876Ca.sub.0.062Ru.sub.0.062B.sub.0.124N has a C.sub.33 that is approximately 18.8 GPa with very similar κ.sup.2 (0.18).
LIST OF REFERENCE SIGNS
[0062] AN: antenna [0063] BAWR: BAW resonator [0064] BE: bottom electrode [0065] DU: duplexer [0066] EFI: electrode finger [0067] IDS: interdigitated electrode structure [0068] ML: acoustic mirror layer [0069] PM: piezoelectric material [0070] PR: parallel resonator [0071] RXF: reception filter [0072] SAWR: SAW resonator [0073] SR: series resonator [0074] TE: top electrode [0075] TXF: transmission filter
