Bulk acoustic wave resonator, method of determining a doping concentration, filter, and electronic device

Abstract

The present application relates to a bulk acoustic wave resonator, comprising: a substrate; an acoustic mirror; a bottom electrode; a piezoelectric layer, the piezoelectric layer being a piezoelectric layer comprising a doping element, the doping element having a corresponding doping concentration; and a top electrode, wherein: the resonator has a resonance frequency higher than 2.5 GHz and has a layer thickness ratio E / P; the resonator has an electromechanical coupling coefficient Kt 2 , the doping concentration being less than a1, a1 being the electromechanical coupling coefficient Kt 2 corresponding to the layer thickness ratio E / P = 3. The present application also relates to a doping concentration determination method, the doping concentration being a doping concentration of a doping element of a piezoelectric layer of a bulk acoustic wave resonator, the resonator having an electromechanical coupling coefficient Kt 2 , the resonator having a resonance frequency higher than 2.5 GHz and having a layer thickness ratio E / P, the method comprising the step of: based on the layer thickness ratio E / P, selecting the doping concentration to be less than a1, a1 being the electromechanical coupling coefficient Kt 2 corresponding to the layer thickness ratio E / P = 3. The present application also relates to a filter and an electronic device.

Description

Technical Field

[0001] The embodiments of the present invention relate to the semiconductor field, and more particularly to a bulk acoustic wave resonator and a method for determining doping concentration, as well as a filter and an electronic device. Background Technology

[0002] With the development of 5G communication technology, increasingly higher demands are being placed on filters for large bandwidth. Under these circumstances, filter design requires filters with larger effective electromechanical coupling coefficients (kt). 2 The need for resonators has become urgent.

[0003] Thin-film bulk acoustic resonators (FBARs), as a new type of MEMS device, have advantages such as small size, light weight, low insertion loss, wide bandwidth and high quality factor, making them well-suited for the upgrading of wireless communication systems.

[0004] In existing technologies, there are still methods to maintain the kt of the resonator. 2 In cases where the value is relatively large, there is also a need to increase the Q value of the resonator.

[0005] Furthermore, as the frequency of the resonator increases, at Kt 2 Under fixed conditions, the area of ​​the resonator will decrease. While a smaller resonator area is beneficial for miniaturization of resonators and even filters, an excessively small area can lead to issues with power capacity per unit area when the resonator has high power requirements. When the power that a single resonator should withstand is constant, a smaller area results in a higher power density, making the resonator more prone to burnout.

[0006] Therefore, in existing technologies, there are also kt resonators that maintain a high frequency. 2 In cases where the area is relatively large, there is a need to ensure that the area is not too small. Summary of the Invention

[0007] The present invention is proposed to alleviate or solve at least one of the above-mentioned problems in the prior art.

[0008] According to one aspect of an embodiment of the present invention, a bulk acoustic resonator is provided, comprising:

[0009] Base;

[0010] Acoustic mirror;

[0011] Bottom electrode;

[0012] A piezoelectric layer, wherein the piezoelectric layer includes doped elements, and the doped elements have corresponding doping concentrations; and

[0013] Top electrode,

[0014] in:

[0015] The resonator has a resonant frequency higher than 2.5 GHz and a layer thickness ratio E / P.

[0016] The resonator has an electromechanical coupling coefficient Kt 2 The doping concentration is less than a1, where a1 is the electromechanical coupling coefficient Kt when the layer thickness ratio E / P = 3. 2 The corresponding doping concentration.

[0017] Embodiments of the present invention also relate to a method for determining the doping concentration, wherein the doping concentration is the doping concentration of the doping element in the piezoelectric layer of a bulk acoustic wave resonator, and the resonator has an electromechanical coupling coefficient Kt. 2 The resonator has a resonant frequency higher than 2.5 GHz and a layer thickness ratio E / P. The method includes the following steps:

[0018] Based on the layer thickness ratio E / P, the doping concentration is selected to be less than a1, where a1 is the electromechanical coupling coefficient Kt when the resonator layer thickness ratio E / P = 3. 2 The corresponding doping concentration.

[0019] Embodiments of the present invention also relate to a filter, including the resonator described above.

[0020] Embodiments of the present invention also relate to an electronic device, including the filter or the resonator described above. Attached Figure Description

[0021] The following description and accompanying drawings will better aid in understanding these and other features and advantages of the various embodiments disclosed herein, wherein the same reference numerals in the drawings always denote the same parts, wherein:

[0022] Figure 1 A schematic cross-sectional view of a bulk acoustic resonator;

[0023] Figure 2 A graph illustrating the relationship between the E / P value and the width of the protrusion structure and the Q value of the resonator is provided as an example.

[0024] Figure 3 An example diagram illustrates the relationship between the width of the protrusion structure and the Q value of the resonator;

[0025] Figure 4 An example is shown showing the E / P value and Kt. 2 Relationship diagram;

[0026] Figure 5 An example is shown where the doping concentration is related to Kt when E / P = 3. 2 Relationship diagram;

[0027] Figure 6An example is shown where the doping concentration is related to Kt when E / P = 2.8. 2 Relationship diagram;

[0028] Figure 7 An example is shown where the doping concentration is related to Kt when E / P = 2.6. 2 Relationship diagram;

[0029] Figure 8 An example is shown where the doping concentration is related to Kt when E / P = 2.4. 2 Relationship diagram;

[0030] Figure 9 An example is shown where, with E / P = 2.2, the doping concentration and Kt are... 2 Relationship diagram;

[0031] Figure 10 An example is shown where, with E / P = 2, the doping concentration and Kt are... 2 Relationship diagram;

[0032] Figure 11 An example is shown where the doping concentration is related to Kt when E / P = 1.8. 2 Relationship diagram;

[0033] Figure 12 An example is shown where the doping concentration is related to Kt when E / P = 1.0. 2 Relationship diagram;

[0034] Figure 13 An example is shown where the doping concentration is related to Kt when E / P = 0.85. 2 Relationship diagram;

[0035] Figure 14 An example is shown where the doping concentration is related to Kt when E / P = 0.75. 2 Relationship diagram;

[0036] Figure 15 An example is shown in Kt 2 A graph showing the relationship between the E / P value and the area of ​​the resonator when the E / P ratio is 5.9%.

[0037] Figure 16 An example is shown of a resonator with a frequency of 3.5 GHz, in Kt 2 The relationship between doping concentration and resonator area at 5.9% doping concentration; and

[0038] Figure 17 An example is shown of a resonator with a frequency of 1.75 GHz, in Kt 2 The relationship between doping concentration and resonator area when the doping concentration is 5.9%. Detailed Implementation

[0039] The technical solution of the present invention will be further described in detail below through embodiments and in conjunction with the accompanying drawings. In this specification, the same or similar reference numerals indicate the same or similar components. The following description of the embodiments of the present invention with reference to the accompanying drawings is intended to explain the overall inventive concept of the present invention and should not be construed as a limitation thereof. These are only some embodiments of the invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0040] Figure 1 A cross-sectional view of a typical sandwich-structured bulk acoustic resonator is shown. Figure 1 The reference numerals in the attached figures are explained as follows:

[0041] 101: Substrate, with optional materials including single-crystal silicon, gallium nitride, gallium arsenide, sapphire, quartz, silicon carbide, diamond, etc.

[0042] 102: Acoustic mirror, which can be a cavity, or it can be a Bragg reflector layer or other equivalent forms. In the embodiments of the present invention, a cavity form is used.

[0043] 103: Bottom electrode (including bottom electrode pins), the material can be molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or a composite or alloy of the above metals, etc.

[0044] 104: The piezoelectric layer can be a single-crystal piezoelectric material, such as single-crystal aluminum nitride, single-crystal gallium nitride, single-crystal lithium niobate, single-crystal lead zirconate titanate (PZT), single-crystal potassium niobate, single-crystal quartz film, or single-crystal lithium tantalate, etc. It can also be a polycrystalline piezoelectric material (as opposed to single-crystal, a non-single-crystal material), such as polycrystalline aluminum nitride, zinc oxide, PZT, etc. It can also be a rare earth element doped with a certain atomic ratio of the above materials. Mixed materials, such as doped aluminum nitride, contain at least one rare earth element, such as scandium (Sc), yttrium (Y), magnesium (Mg), titanium (Ti), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), etc.

[0045] 105: Top electrode (including top electrode pin), the material can be molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or a composite or alloy of the above metals, etc.

[0046] 106: Passivation layer or process layer, which can be aluminum nitride, silicon nitride or silicon dioxide, etc.

[0047] 107: Protruding structure, materials can be selected from molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or the above metals or their alloys, etc.

[0048] For a bulk acoustic resonator, its electromechanical coupling coefficient Kt 2 The Q value of the bulk acoustic wave resonator is related to the layer thickness ratio E / P and the doping concentration of the dopant elements in the piezoelectric layer. Furthermore, the Q value of the bulk acoustic wave resonator is also related to the layer thickness ratio E / P.

[0049] Moreover, the area of ​​the resonator (referring to the area of ​​the effective region of the resonator, which is the region formed by the overlap of the top electrode, piezoelectric layer, bottom electrode and acoustic mirror in the thickness direction of the resonator) decreases as the resonant frequency increases when the electromechanical coupling coefficient of the resonator is fixed.

[0050] This invention proposes a method to maintain Kt by selecting a doping concentration lower than that based on a specific layer thickness ratio (i.e., setting an upper limit for the doping concentration). 2 Stability, and the ability to alleviate or eliminate power capacity issues caused by the small unit area of ​​the resonator when the resonator area is relatively small.

[0051] The present invention can also further limit the lower limit of the layer thickness ratio, and improve the performance of the resonator based on the layer thickness ratio that is higher than the lower limit of the layer thickness ratio.

[0052] The following is a brief explanation of the layer thickness ratio E / P.

[0053] like Figure 1 As shown, the thickness of the bottom electrode 103 is t1, the thickness of the piezoelectric layer 104 is t2, the thickness of the top electrode 105 is t3, and the thickness of the passivation layer 106 above the top electrode is t4. When the passivation layer 106 is not provided, the ratio of the electrode thickness to the piezoelectric layer thickness is defined as the layer thickness ratio E / P, which is (t1+t3) / t2. When the resonator has the passivation layer 106, the ratio of the electrode thickness to the piezoelectric layer thickness is defined as the layer thickness ratio E / P, which is (t1+t3+t4*a) / t2. Here, a is related to the ratio of the rate of influence of the passivation layer 106 on the resonant frequency Fs to the rate of influence of the top electrode 105 on the resonant frequency Fs. Specifically, assuming the rate of influence of the passivation layer 106 on the resonant frequency Fs is V1 nm / MHz and the rate of influence of the top electrode 105 on the resonant frequency Fs is V2 nm / MHz, then a = V2 / V1. If Mo is chosen as the material for the top and bottom electrodes, and AlN is chosen as the passivation layer, then the value of a is close to 1 / 3. If other functional layers are added to the stacked structure of the resonator based on the above, the layer thickness ratio E / P can also be calculated based on the above concept.

[0054] The following is a brief explanation of the doping concentration of elements in the piezoelectric layer.

[0055] Doping means that a portion of one or more elements in an originally undoped piezoelectric material is replaced by a dopant element. The doping concentration is defined as the ratio of the number of atoms of the dopant element per unit volume to the sum of the total number of atoms of the elements partially replaced by the dopant element and the total number of atoms of the dopant element. For example, in the case where the piezoelectric layer is aluminum nitride and the dopant element is scandium, some aluminum atoms are replaced by scandium atoms, and the doping concentration is the ratio of the number of scandium atoms per unit volume to the sum of the number of aluminum atoms and the number of scandium atoms (Sc / Al+Sc).

[0056] Figure 2 The diagram illustrates the relationship between the layer thickness ratio (E / P) and the width of the protrusion structure and the Q value of the resonator. Figure 2 In the diagram, the vertical axis represents the Q-value of the resonator, and the horizontal axis has two layers: the first layer represents the layer thickness ratio E / P of the resonator, and the second layer represents the width L (in μm) of the protrusion structure 107. Based on the first layer, Figure 2 An example is shown illustrating the relationship between the Q-factor of a resonator in the Band 1TX band (1920-1980MHz) and the layer thickness ratio E / P. Based on the second layer, Figure 2 An example is shown of the Q value of the resonator with different protrusion widths L for different layer thickness ratios E / P.

[0057] Figure 3 An exemplary diagram illustrates the relationship between the width L of the protrusion structure and the Q value of the resonator when the layer thickness ratio E / P = 1. Figure 3 It can be seen that the Q value of the resonator varies with the bump width L, and there are two peak values ​​when the bump width L = 1.25 μm and L = 5.25 μm. However, see... Figure 2 When the layer thickness ratio E / P is less than 1, Figure 3 The peak values ​​of both corresponding Q values ​​deteriorate as the layer thickness ratio E / P decreases. See also Figure 2 When E / P = 0.65, in Figure 3 Both maximum values ​​of Q in the data have deteriorated by more than 20%, and the maximum value at L = 1.25 no longer exists.

[0058] Therefore, the layer thickness ratio E / P directly affects the Q value of the resonator. To obtain a better Q value for the resonator, the layer thickness ratio E / P should not be lower than 0.75.

[0059] Figure 4 An example is shown showing the E / P value and Kt. 2 A graph showing the relationship between E and P, where the horizontal axis represents the E / P value and the vertical axis represents Kt. 2 More specifically, Figure 4An example is shown where, when the piezoelectric layer is an aluminum nitride-doped scandium layer, the doping concentration is 8.2%, kt 2 The change in kt with the layer thickness ratio E / P. It can be seen that as the layer thickness ratio E / P decreases, kt... 2 Increase. However, without severely degrading the resonator's performance, from Figure 2 The conclusion is that kt cannot be increased by infinitely decreasing the E / P value. 2 .

[0060] Figure 5-14 An example is shown showing the relationship between doping concentration and Kt. 2 The graph shows the relationship between doping concentration and Kt, where the horizontal axis represents the doping concentration and the vertical axis represents the doping concentration. 2 As can be seen, with increasing doping concentration, Kt 2 improve.

[0061] Therefore, a higher layer thickness ratio (E / P) can be selected, for example, the E / P value should not be lower than 0.75, to ensure a higher Q value for the resonator (but at this time, Kt...). 2 (If the performance requirements are not met or are not fully satisfied), Kt can be increased by selecting a doping concentration above a predetermined value. 2 To meet performance requirements or improve performance, kt can be increased by increasing the doping concentration while ensuring resonator performance (higher Q value). 2 .

[0062] Due to Kt 2 The E / P ratio is related to the layer thickness ratio and the doping concentration, and there is a lower limit to the E / P value (as previously stated, not less than 0.75). Therefore, even if Kt is desired... 2 The bigger the better, Kt 2 There is also an upper limit, which is determined by the lower limit of E / P, 0.75.

[0063] In other words, in this invention, for a bulk acoustic wave filter, the kt of the resonator can be increased by selecting the doping concentration. 2 However, for those who have selected kt 2 The resonator has a doping concentration within an optimal range determined by the E / P value to ensure high performance.

[0064] Furthermore, the area A of the resonator satisfies the following formula:

[0065] A∝t2 / (Fs*ε)–(1)

[0066] A: Area of ​​a 50Ω resonator

[0067] t2: Thickness of the piezoelectric layer

[0068] Fs: Resonant frequency of the resonator

[0069] ε: Dielectric constant of the piezoelectric layer

[0070] As the frequency increases, at a fixed kt 2 In this case, the thickness t2 of the piezoelectric layer will decrease. From the above formula (1), it can be seen that as the frequency Fs increases, the area of ​​the 50Ω resonator will decrease. For example, when the doping concentration is 0, when kt... 2 When it is 5.9%, see [reference needed]. Figure 17 The area of ​​the 50Ω resonator at 1.75GHz is approximately 21000μm. 2 And see Figure 16 The area of ​​the 50Ω resonator at 3.5GHz is approximately 5200μm. 2 As the frequency of a resonator increases and its area decreases, as mentioned in the background section, the power capacity per unit area becomes an issue when the resonator's power is high. When the power a single resonator should withstand is fixed, a smaller area results in a higher power density, making the resonator more prone to burnout. Therefore, for high-frequency filters or resonators, such as those above 2.5 GHz, it is necessary to consider increasing the resonator's area to reduce or eliminate the risk of burnout due to excessive power capacity per unit area.

[0071] Figure 15 An exemplary diagram illustrates the relationship between the layer thickness ratio E / P and the area of ​​the resonator, where Kt 2 It is 5.9%. Figure 15 In the diagram, the vertical axis represents the area of ​​the resonator, with units of μm. 2 The horizontal axis represents the E / P value. Therefore, for a fixed Kt... 2 ,based on Figure 15 As shown, the area of ​​the resonator can be increased by reducing the layer thickness ratio E / P. Also, as... Figure 4 As shown, with the E / P value decreasing, Kt remains constant. 2 It will rise. Also, see Figure 5-14 For a fixed E / P value, as the doping concentration decreases, Kt... 2 It will decrease. Based on the above, in order to increase the area of ​​the high-frequency resonator while maintaining Kt... 2 Stability can be achieved by reducing the layer thickness ratio E / P to increase the area, while simultaneously reducing the doping concentration to maintain the Kt of the resonator. 2 Stable (i.e., unchanged or fluctuating by 5% relative to the original value; in the embodiments of the present invention, it is described as remaining unchanged).

[0072] Therefore, if it is necessary to increase the resonator area by reducing the layer thickness ratio E / P (a smaller layer thickness ratio E / P will lead to a decrease in the resonator's Kt value), 2To increase Kt, it is necessary to simultaneously reduce the doping concentration. 2 To keep Kt 2 Stability. Since a larger resonator area necessitates a smaller E / P value, a lower E / P value and corresponding doping concentration can be chosen. This ensures that the resonator area isn't too small, preventing power capacity issues, while also maintaining the resonator's Kt value. 2 Stablize.

[0073] In this invention, the layer thickness ratio E / P is selected to be no greater than 3, and the upper limit of the doping concentration is determined based on this E / P value. Specifically, in this invention, for bulk acoustic wave filters, the area of ​​the resonator can be increased by selecting a lower E / P value; however, in order to maintain the kt of the resonator... 2 Stable, or for those who have chosen kt 2 For the resonator, the doping concentration also needs to be set within a preferred range. The upper limit of this preferred range is determined based on a smaller layer thickness ratio E / P (3 in this invention). This allows for both increasing the resonator area (by selecting a smaller E / P value) and maintaining Kt by selecting a smaller doping concentration value corresponding to that E / P value. 2 Stability. That is, in this invention, for high-frequency resonators, such as those with frequencies higher than 2.5 GHz, if both resonator performance and resonator area need to be increased, then not only does the doping concentration need to meet performance requirements, but there also needs to be an upper limit based on the resonator area requirements. For high-frequency products, in this invention, the E / P value is less than 3 and the doping concentration is less than the doping concentration corresponding to E / P = 3, which is beneficial for increasing the resonator area and meeting the relevant performance requirements of the resonator.

[0074] Based on the above, this invention proposes a bulk acoustic wave resonator, wherein the piezoelectric layer is a piezoelectric layer including doped elements with corresponding doping concentrations, the resonator has a resonant frequency higher than 2.5 GHz, and a layer thickness ratio E / P; the resonator has an electromechanical coupling coefficient Kt. 2 The doping concentration is less than a1, where a1 is the electromechanical coupling coefficient Kt when the layer thickness ratio E / P = 3. 2 The corresponding doping concentration.

[0075] Based on the above, this invention also proposes a method for determining the doping concentration of the piezoelectric layer of a bulk acoustic wave resonator. The piezoelectric layer of the resonator is a piezoelectric layer including doped elements, wherein the doped elements have corresponding doping concentrations, the resonant frequency of the resonator is higher than 2.5 GHz, and it has a layer thickness ratio E / P; the resonator has an electromechanical coupling coefficient Kt. 2The method includes the steps of: selecting, based on the layer thickness ratio E / P, the doping concentration being less than a1, where a1 is the electromechanical coupling coefficient Kt when the resonator layer thickness ratio E / P = 3. 2 The corresponding doping concentration.

[0076] In a more specific embodiment of the present invention, when the piezoelectric layer is an aluminum nitride-doped scandium layer, the upper limit of the doping concentration a1 is the electromechanical coupling coefficient Kt when the layer thickness ratio E / P = 3. 2 The corresponding doping concentration is determined by the following formula: Kt 2 =0.2977a1 2 +0.2085a1+0.033. In Figure 5 The figure shows the relationship between doping concentration a1 and Kt when E / P = 3. 2 Relationship diagram, in Figure 5 In this context, y corresponds to Kt. 2 , where x corresponds to the doping concentration a1.

[0077] In one embodiment of the present invention, the resonant frequency of the resonator is higher than 3.0 GHz, and the doping concentration is less than a2, where a2 is the electromechanical coupling coefficient Kt when the resonator layer thickness ratio E / P = 2.8. 2 The corresponding doping concentration. In a more specific embodiment of the present invention, when the piezoelectric layer is an aluminum nitride-doped scandium piezoelectric layer, the upper limit of the doping concentration a2 is the electromechanical coupling coefficient Kt when the layer thickness ratio E / P = 2.8. 2 The corresponding doping concentration is determined by the following formula: Kt 2 =0.3093a2 2 +0.2149a² + 0.0342. In Figure 6 The figure shows the relationship between doping concentration a2 and Kt when E / P = 2.8. 2 Relationship diagram, in Figure 6 In this context, y corresponds to Kt. 2 , where x corresponds to the doping concentration a2.

[0078] In one embodiment of the present invention, the resonant frequency of the resonator is higher than 3.5 GHz; the doping concentration is less than a3, where a3 is the electromechanical coupling coefficient Kt when the resonator layer thickness ratio E / P = 2.6. 2 The corresponding doping concentration. In a more specific embodiment of the present invention, when the piezoelectric layer is an aluminum nitride-doped scandium layer, the upper limit of the doping concentration a3 is the electromechanical coupling coefficient Kt when the layer thickness ratio E / P = 2.6. 2 The corresponding doping concentration is determined by the following formula: Kt 2 =0.3437a3 2 +0.2137a3+0.0364. In Figure 7 The figure shows the relationship between doping concentration a3 and Kt when E / P = 2.6. 2 Relationship diagram, in Figure 7 In this context, y corresponds to Kt. 2 , where x corresponds to the doping concentration a3.

[0079] In one embodiment of the present invention, the resonant frequency of the resonator is higher than 4 GHz; the doping concentration is less than a4, where a4 is the electromechanical coupling coefficient Kt when the resonator layer thickness ratio E / P = 2.4. 2 The corresponding doping concentration. In a more specific embodiment of the present invention, when the piezoelectric layer is an aluminum nitride-doped scandium layer, the upper limit of the doping concentration a4 is the electromechanical coupling coefficient Kt when the layer thickness ratio E / P = 2.4. 2 The corresponding doping concentration is determined by the following formula: Kt 2 =0.3508a4 2 +0.2213a4+0.0378. In Figure 8 The figure shows the relationship between doping concentration a4 and Kt when E / P = 2.4. 2 Relationship diagram, in Figure 8 In this context, y corresponds to Kt. 2 , where x corresponds to the doping concentration a4.

[0080] In one embodiment of the present invention, the resonant frequency of the resonator is higher than 4.5 GHz; the doping concentration is less than a5, where a5 is the electromechanical coupling coefficient Kt when the resonator layer thickness ratio E / P = 2.2. 2 The corresponding doping concentration. In a more specific embodiment of the present invention, when the piezoelectric layer is an aluminum nitride-doped scandium layer, the upper limit of the doping concentration a5 is the electromechanical coupling coefficient Kt when the layer thickness ratio E / P = 2.2. 2 The corresponding doping concentration is determined by the following formula: Kt 2 =0.3345a5 2 +0.2352a5+0.0399. In Figure 9 The figure shows the relationship between doping concentration a5 and Kt when E / P = 2.2. 2 Relationship diagram, in Figure 9 In this context, y corresponds to Kt. 2 , where x corresponds to the doping concentration a5.

[0081] In one embodiment of the present invention, the resonant frequency of the resonator is higher than 5 GHz; the doping concentration is less than a6, where a6 is the electromechanical coupling coefficient Kt when the resonator layer thickness ratio E / P = 2. 2The corresponding doping concentration. In a more specific embodiment of the present invention, when the piezoelectric layer is an aluminum nitride-doped scandium piezoelectric layer, the upper limit of the doping concentration a5 is the electromechanical coupling coefficient Kt when the layer thickness ratio E / P = 2. 2 The corresponding doping concentration is determined by the following formula: Kt 2 =0.407a6 2 +0.2315a6+0.0421. In Figure 10 The figure shows the relationship between doping concentration a6 and Kt when E / P = 2. 2 Relationship diagram, in Figure 10 In this context, y corresponds to Kt. 2 , where x corresponds to doping concentration a6.

[0082] In one embodiment of the present invention, the resonant frequency of the resonator is higher than 6 GHz; the doping concentration is less than a7, where a7 is the electromechanical coupling coefficient Kt when the resonator layer thickness ratio E / P = 1.8. 2 The corresponding doping concentration. In a more specific embodiment of the present invention, when the piezoelectric layer is an aluminum nitride-doped scandium layer, the upper limit of the doping concentration a7 is the electromechanical coupling coefficient Kt when the layer thickness ratio E / P = 1.8. 2 The corresponding doping concentration is determined by the following formula: Kt 2 =0.4801a7 2 +0.2157a7+0.0461. In Figure 11 The figure shows the relationship between doping concentration a6 and Kt when E / P = 1.8. 2 Relationship diagram, in Figure 11 In this context, y corresponds to Kt. 2 , where x corresponds to the doping concentration a7.

[0083] Furthermore, as mentioned above, for the E / P value, in order to make the Q value of the resonator relatively high, the E / P value should not be less than 0.75.

[0084] In one embodiment of the present invention, the doping concentration is not less than b1, where b1 is the electromechanical coupling coefficient Kt when the resonator layer thickness ratio E / P = 0.75. 2 The corresponding doping concentration. In a more specific embodiment of the present invention, when the piezoelectric layer is an aluminum nitride-doped scandium piezoelectric layer, the lower limit value of the doping concentration b1 is the electromechanical coupling coefficient Kt when the layer thickness ratio E / P = 0.75. 2 The corresponding doping concentration is determined by the following formula: Kt 2 =0.3909b1 2 +0.3056b1+0.062. In Figure 14 The figure shows the relationship between doping concentration b1 and Kt when E / P = 0.75.2 Relationship diagram, in Figure 14 In this context, y corresponds to Kt. 2 , where x corresponds to the doping concentration b1.

[0085] In one embodiment of the present invention, the doping concentration is not less than b2, where b2 is the electromechanical coupling coefficient Kt when the resonator layer thickness ratio E / P = 0.85. 2 The corresponding doping concentration. In a more specific embodiment of the present invention, when the piezoelectric layer is an aluminum nitride-doped scandium piezoelectric layer, the lower limit of the doping concentration b2 is the electromechanical coupling coefficient Kt when the layer thickness ratio E / P = 0.85. 2 The corresponding doping concentration is determined by the following formula: Kt 2 =0.4463b2 2 +0.2869b2+0.0603. In Figure 13 The figure shows the relationship between doping concentration b2 and Kt when E / P = 0.85. 2 Relationship diagram, in Figure 13 In this context, y corresponds to Kt. 2 , where x corresponds to the doping concentration b2.

[0086] In one embodiment of the present invention, the doping concentration is not less than b3, where b3 is the electromechanical coupling coefficient Kt when the resonator layer thickness ratio E / P = 1. 2 The corresponding doping concentration. In a more specific embodiment of the present invention, when the piezoelectric layer is an aluminum nitride-doped scandium piezoelectric layer, the lower limit of the doping concentration b3 is the electromechanical coupling coefficient Kt when the layer thickness ratio E / P = 1. 2 The corresponding doping concentration is determined by the following formula: Kt 2 =0.4147b3 2 +0.2774b3+0.057. In Figure 12 The figure shows the relationship between doping concentration b3 and Kt when E / P = 1. 2 Relationship diagram, in Figure 12 In this context, y corresponds to Kt. 2 , where x corresponds to the doping concentration b3.

[0087] The above resonators (based on the layer thickness ratio E / P, select an appropriate doping concentration to increase the resonator area while maintaining Kt) 2 Stable (or stable) filters can also be used.

[0088] In one embodiment of the present invention, the filter is a filter in the 2.515GHz-2.675GHz frequency band or the 3.3GHz-3.6GHz frequency band; and the doping concentration of the resonator in the filter ranges from 14.4% to 26.5%. Further, the doping concentration of the resonator in the filter ranges from 15.7% to 26.5%.

[0089] In one embodiment of the present invention, the filter is a filter operating in the 4.8 GHz-4.96 GHz frequency band; and the doping concentration of the resonator in the filter ranges from 1% to 12.4%. Further, the doping concentration of the resonator in the filter ranges from 2.6% to 12.4%.

[0090] In one embodiment of the present invention, the filter is a filter operating in the 5.15 GHz-5.85 GHz frequency band; and the doping concentration of the resonator in the filter ranges from 28.5% to 37%. Further, the doping concentration of the resonator in the filter ranges from 28.8% to 37%.

[0091] In the above embodiments of the present invention, it is explained that the upper limit of the piezoelectric layer doping concentration of the resonator is selected based on the selected layer thickness ratio E / P, thereby ensuring that the Kt of the resonator can be controlled. 2 While maintaining stability, the resonator also boasts a large area. Furthermore, the lower limit of the piezoelectric layer doping concentration can be selected based on the chosen layer thickness ratio E / P, ensuring a high Q value for the resonator. This invention provides effective guidance on how to select the doping concentration of the piezoelectric layer to obtain a larger resonator area.

[0092] As those skilled in the art will understand, the material of the piezoelectric layer is not limited to aluminum nitride, but can also be other piezoelectric materials listed in this invention, and the doping element is not limited to scandium metal, but can also be other dopable metal elements listed in this invention. Although in a specific embodiment of the invention, aluminum nitride doped with scandium is used as an example to illustrate how to determine the upper or lower limit of the piezoelectric layer doping concentration of the resonator based on the selected layer thickness ratio E / P.

[0093] It should be noted that, in this invention, each numerical range, except where explicitly stated not to include endpoint values, can be either an endpoint value or the median of each numerical range, and all of these are within the protection scope of this invention.

[0094] As those skilled in the art will understand, bulk acoustic resonators can be used to form other semiconductor devices besides filters.

[0095] Based on the above, the present invention proposes the following technical solution:

[0096] 1. A bulk acoustic resonator, comprising:

[0097] Base;

[0098] Acoustic mirror;

[0099] Bottom electrode;

[0100] A piezoelectric layer, wherein the piezoelectric layer includes doped elements, and the doped elements have corresponding doping concentrations; and

[0101] Top electrode,

[0102] in:

[0103] The resonator has a resonant frequency higher than 2.5 GHz and a layer thickness ratio E / P.

[0104] The resonator has an electromechanical coupling coefficient Kt 2 The doping concentration is less than a1, where a1 is the electromechanical coupling coefficient Kt when the layer thickness ratio E / P = 3. 2 The corresponding doping concentration.

[0105] 2. The resonator according to 1, wherein:

[0106] The piezoelectric layer is an aluminum nitride layer doped with scandium, and a1 is determined by the following formula:

[0107] Kt 2 =0.2977a1 2 +0.2085a1+0.033.

[0108] 3. The resonator according to 1, wherein:

[0109] The resonant frequency of the resonator is higher than 3.0 GHz;

[0110] The doping concentration is less than a2, where a2 is the electromechanical coupling coefficient Kt when the resonator layer thickness ratio E / P = 2.8. 2 The corresponding doping concentration.

[0111] 4. The resonator according to 3, wherein:

[0112] The piezoelectric layer is an aluminum nitride layer doped with scandium, and a3 is determined by the following formula:

[0113] Kt 2 =0.3093a2 2 +0.2149a2+0.0342.

[0114] 5. The resonator according to 3, wherein:

[0115] The resonant frequency of the resonator is higher than 3.5 GHz;

[0116] The doping concentration is less than a3, where a3 is the electromechanical coupling coefficient Kt when the resonator layer thickness ratio E / P = 2.6. 2 The corresponding doping concentration.

[0117] 6. The resonator according to 5, wherein:

[0118] The piezoelectric layer is an aluminum nitride layer doped with scandium, and a3 is determined by the following formula:

[0119] Kt 2 =0.3437a3 2 +0.2137a3+0.0364.

[0120] 7. The resonator according to 5, wherein:

[0121] The resonator has a resonant frequency higher than 4 GHz;

[0122] The doping concentration is less than a4, where a4 is the electromechanical coupling coefficient Kt when the resonator layer thickness ratio E / P = 2.4. 2 The corresponding doping concentration.

[0123] 8. The resonator according to 7, wherein:

[0124] The piezoelectric layer is an aluminum nitride layer doped with scandium, and a4 is determined by the following formula:

[0125] Kt 2 =0.3508a4 2 +0.2213a4+0.0378.

[0126] 9. The resonator according to 7, wherein:

[0127] The resonator has a resonant frequency higher than 4.5 GHz;

[0128] The doping concentration is less than a5, where a5 is the electromechanical coupling coefficient Kt when the resonator layer thickness ratio E / P = 2.2. 2 The corresponding doping concentration.

[0129] 10. The resonator according to 9, wherein:

[0130] The piezoelectric layer is an aluminum nitride layer doped with scandium, and a5 is determined by the following formula:

[0131] Kt 2 =0.3345a5 2 +0.2352a5+0.0399.

[0132] 11. The resonator according to 9, wherein:

[0133] The resonator has a resonant frequency higher than 5 GHz;

[0134] The doping concentration is less than a6, where a6 is the electromechanical coupling coefficient Kt when the resonator layer thickness ratio E / P = 2. 2 The corresponding doping concentration.

[0135] 12. The resonator according to 11, wherein:

[0136] The piezoelectric layer is an aluminum nitride layer doped with scandium, and a6 is determined by the following formula:

[0137] Kt 2 =0.407a6 2 +0.2315a6+0.0421.

[0138] 13. The resonator according to 11, wherein:

[0139] The resonator has a resonant frequency higher than 6 GHz;

[0140] The doping concentration is less than a7, where a7 is the electromechanical coupling coefficient Kt when the resonator layer thickness ratio E / P = 1.8. 2 The corresponding doping concentration.

[0141] 14. The resonator according to 13, wherein:

[0142] The piezoelectric layer is an aluminum nitride layer doped with scandium, and a7 is determined by the following formula:

[0143] Kt 2 =0.4801a7 2 +0.2157a7+0.0461.

[0144] 15. The resonator according to any one of 1-14, wherein:

[0145] The doping concentration is not less than b1, where b1 is the electromechanical coupling coefficient Kt when the layer thickness ratio E / P = 0.75. 2 The corresponding doping concentration.

[0146] 16. The resonator according to 15, wherein:

[0147] The piezoelectric layer is an aluminum nitride layer doped with scandium, and b1 is determined by the following formula:

[0148] Kt 2 =0.3909b1 2 +0.3056b1+0.062.

[0149] 17. The resonator according to 16, wherein:

[0150] The doping concentration is not less than b2, where b2 is the electromechanical coupling coefficient Kt when the resonator layer thickness ratio E / P = 0.85. 2 The corresponding doping concentration.

[0151] 18. The resonator according to 17, wherein:

[0152] The piezoelectric layer is an aluminum nitride layer doped with scandium, and b2 is determined by the following formula:

[0153] Kt 2 =0.4463b2 2 +0.2869b2+0.0603.

[0154] 19. The resonator according to 17, wherein:

[0155] The doping concentration is not less than b3, where b3 is the electromechanical coupling coefficient Kt when the resonator layer thickness ratio E / P = 1.00. 2 The corresponding doping concentration.

[0156] 20. The resonator according to 19, wherein:

[0157] The piezoelectric layer is an aluminum nitride layer doped with scandium, and b3 is determined by the following formula:

[0158] Kt 2 =0.4147b3 2 +0.2774b3+0.057.

[0159] 21. A filter comprising a plurality of bulk acoustic resonators according to any one of 1-20.

[0160] 22. The filter according to 21, wherein:

[0161] The filter is a filter in the 2.515GHz-2.675GHz frequency band or the 3.3GHz-3.6GHz frequency band; and

[0162] The doping concentration of the resonator in the filter ranges from 14.4% to 26.5%.

[0163] 23. The filter according to 22, wherein:

[0164] The doping concentration of the resonator in the filter ranges from 15.7% to 26.5%.

[0165] 24. The filter according to 21, wherein:

[0166] The filter is a filter operating in the 4.8GHz-4.96GHz frequency band; and

[0167] The doping concentration of the resonator in the filter ranges from 1% to 12.4%.

[0168] 25. The filter according to 24, wherein:

[0169] The doping concentration of the resonator in the filter ranges from 2.6% to 12.4%.

[0170] 26. The filter according to 21, wherein:

[0171] The filter is a filter operating in the 5.15GHz-5.85GHz frequency band; and

[0172] The doping concentration of the resonator in the filter ranges from 28.5% to 37%.

[0173] 27. The filter according to 26, wherein:

[0174] The doping concentration of the resonator in the filter ranges from 28.8% to 37%.

[0175] 28. A method for determining doping concentration, wherein the doping concentration is the doping concentration of the doping element in the piezoelectric layer of a bulk acoustic wave resonator, and the resonator has an electromechanical coupling coefficient Kt. 2 The resonator has a resonant frequency higher than 2.5 GHz and a layer thickness ratio E / P. The method includes the following steps:

[0176] Based on the layer thickness ratio E / P, the doping concentration is selected to be not less than a1, where a1 is the electromechanical coupling coefficient Kt when the resonator layer thickness ratio E / P = 3. 2 The corresponding doping concentration.

[0177] 29. According to the method described in 28, wherein:

[0178] The piezoelectric layer is an aluminum nitride layer doped with scandium, and a1 is determined by the following formula:

[0179] Kt 2 =0.2977a1 2 +0.2085a1+0.033.

[0180] 30. According to the method described in 28, wherein:

[0181] The electromechanical coupling coefficient Kt is selected when the doping concentration is not less than b1, and b1 is the layer thickness ratio E / P = 0.75. 2 The corresponding doping concentration.

[0182] 31. According to the method described in 30, wherein:

[0183] The piezoelectric layer is an aluminum nitride layer doped with scandium, and b1 is determined by the following formula:

[0184] Kt 2 =0.3909b1 2 +0.3056b1+0.062.

[0185] 32. An electronic device comprising a filter according to any one of 21-27, or a bulk acoustic resonator according to any one of 1-20.

[0186] The electronic devices mentioned here include, but are not limited to, intermediate products such as radio frequency front-ends and filtering and amplification modules, as well as terminal products such as mobile phones, WIFI, and drones.

[0187] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that variations may be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A bulk acoustic resonator, comprising: Base; Acoustic mirror; Bottom electrode; A piezoelectric layer, wherein the piezoelectric layer includes doped elements, and the doped elements have a corresponding doping concentration; and Top electrode, in: The resonator has a resonant frequency higher than 2.5 GHz and a layer thickness ratio E / P. The resonator has an electromechanical coupling coefficient Kt 2 The doping concentration is less than a1, where a1 is the electromechanical coupling coefficient Kt corresponding to a layer thickness ratio E / P = 3. 2 The corresponding doping concentration, the electromechanical coupling coefficient Kt of the bulk acoustic resonator 2 The Q value of the bulk acoustic resonator is related to the layer thickness ratio E / P and the doping concentration of the doped elements in the piezoelectric layer.

2. The resonator according to claim 1, wherein: The piezoelectric layer is an aluminum nitride layer doped with scandium, and a1 is determined by the following formula: Kt 2 =0.2977a1 2 +0.2085a1+0.033。 3. The resonator according to claim 1, wherein: The resonant frequency of the resonator is higher than 3.0 GHz; The doping concentration is less than a2, where a2 is the electromechanical coupling coefficient Kt corresponding to a resonator layer thickness ratio E / P = 2.

8. 2 The corresponding doping concentration.

4. The resonator according to claim 3, wherein: The piezoelectric layer is an aluminum nitride layer doped with scandium, and a3 is determined by the following formula: Kt 2 =0.3093a2 2 +0.2149a2+0.0342。 5. The resonator according to claim 3, wherein: The resonant frequency of the resonator is higher than 3.5 GHz; The doping concentration is less than a3, where a3 is the electromechanical coupling coefficient Kt corresponding to a resonator layer thickness ratio E / P = 2.

6. 2 The corresponding doping concentration.

6. The resonator according to claim 5, wherein: The piezoelectric layer is an aluminum nitride layer doped with scandium, and a3 is determined by the following formula: Kt 2 =0.3437a3 2 +0.2137a3+0.0364。 7. The resonator according to claim 5, wherein: The resonator has a resonant frequency higher than 4 GHz; The doping concentration is less than a4, where a4 is the electromechanical coupling coefficient Kt corresponding to a resonator layer thickness ratio E / P = 2.

4. 2 The corresponding doping concentration.

8. The resonator according to claim 7, wherein: The piezoelectric layer is an aluminum nitride layer doped with scandium, and a4 is determined by the following formula: Kt 2 =0.3508a4 2 +0.2213a4+0.0378。 9. The resonator according to claim 7, wherein: The resonator has a resonant frequency higher than 4.5 GHz; The doping concentration is less than a5, where a5 is the electromechanical coupling coefficient Kt corresponding to a resonator layer thickness ratio E / P = 2.

2. 2 The corresponding doping concentration.

10. The resonator according to claim 9, wherein: The piezoelectric layer is an aluminum nitride layer doped with scandium, and a5 is determined by the following formula: Kt 2 =0.3345a5 2 +0.2352a5+0.0399。 11. The resonator according to claim 9, wherein: The resonator has a resonant frequency higher than 5 GHz; The doping concentration is less than a6, where a6 is the electromechanical coupling coefficient Kt corresponding to a resonator layer thickness ratio E / P = 2. 2 The corresponding doping concentration.

12. The resonator according to claim 11, wherein: The piezoelectric layer is an aluminum nitride layer doped with scandium, and a6 is determined by the following formula: Kt 2 =0.407a6 2 +0.2315a6+0.0421。 13. The resonator according to claim 11, wherein: The resonator has a resonant frequency higher than 6 GHz; The doping concentration is less than a7, where a7 is the electromechanical coupling coefficient Kt corresponding to a resonator layer thickness ratio E / P = 1.

8. 2 The corresponding doping concentration.

14. The resonator according to claim 13, wherein: The piezoelectric layer is an aluminum nitride layer doped with scandium, and a7 is determined by the following formula: Kt 2 =0.4801a7 2 +0.2157a7+0.0461。 15. The resonator according to any one of claims 1-14, wherein: The doping concentration is not less than b1, where b1 is the electromechanical coupling coefficient Kt corresponding to a layer thickness ratio E / P = 0.

75. 2 The corresponding doping concentration.

16. The resonator according to claim 15, wherein: The piezoelectric layer is an aluminum nitride layer doped with scandium, and b1 is determined by the following formula: Kt 2 =0.3909b1 2 +0.3056b1+0.062。 17. The resonator according to claim 16, wherein: The doping concentration is not less than b2, where b2 is the electromechanical coupling coefficient Kt corresponding to a resonator layer thickness ratio E / P = 0.

85. 2 The corresponding doping concentration.

18. The resonator according to claim 17, wherein: The piezoelectric layer is an aluminum nitride layer doped with scandium, and b2 is determined by the following formula: Kt 2 =0.4463b2 2 +0.2869b2+0.0603。 19. The resonator according to claim 17, wherein: The doping concentration is not less than b3, where b3 is the electromechanical coupling coefficient Kt corresponding to a resonator layer thickness ratio E / P = 1.

00. 2 The corresponding doping concentration.

20. The resonator according to claim 19, wherein: The piezoelectric layer is an aluminum nitride layer doped with scandium, and b3 is determined by the following formula: Kt 2 =0.4147b3 2 +0.2774b3+0.057。 21. A filter comprising a plurality of bulk acoustic resonators according to any one of claims 1-20.

22. The filter according to claim 21, wherein: The filter is a filter in the 2.515GHz-2.675GHz frequency band or the 3.3GHz-3.6GHz frequency band; and The doping concentration of the resonator in the filter ranges from 14.4% to 26.5%.

23. The filter according to claim 22, wherein: The doping concentration of the resonator in the filter ranges from 15.7% to 26.5%.

24. The filter according to claim 21, wherein: The filter is a filter operating in the 4.8GHz-4.96GHz frequency band; and The doping concentration of the resonator in the filter ranges from 1% to 12.4%.

25. The filter according to claim 24, wherein: The doping concentration of the resonator in the filter ranges from 2.6% to 12.4%.

26. The filter according to claim 21, wherein: The filter is a filter operating in the 5.15GHz-5.85GHz frequency band; and The doping concentration of the resonator in the filter ranges from 28.5% to 37%.

27. The filter according to claim 26, wherein: The doping concentration of the resonator in the filter ranges from 28.8% to 37%.

28. A method for determining doping concentration, wherein the doping concentration is the doping concentration of the doping element in the piezoelectric layer of a bulk acoustic wave resonator, the resonator having an electromechanical coupling coefficient Kt. 2 The resonator has a resonant frequency higher than 2.5 GHz and a layer thickness ratio E / P. The method includes the following steps: Based on the layer thickness ratio E / P, the doping concentration is selected to be less than a1, where a1 is the electromechanical coupling coefficient Kt corresponding to the resonator layer thickness ratio E / P = 3. 2 The corresponding doping concentration, the electromechanical coupling coefficient Kt of the bulk acoustic resonator 2 The Q value of the bulk acoustic resonator is related to the layer thickness ratio E / P and the doping concentration of the doped elements in the piezoelectric layer.

29. The method according to claim 28, wherein: The piezoelectric layer is an aluminum nitride layer doped with scandium, and a1 is determined by the following formula: Kt 2 =0.2977a1 2 +0.2085a1+0.033。 30. The method of claim 28, wherein: The doping concentration is selected to be not less than b1, where b1 is the electromechanical coupling coefficient Kt corresponding to a layer thickness ratio E / P = 0.

75. 2 The corresponding doping concentration.

31. The method according to claim 30, wherein: The piezoelectric layer is an aluminum nitride layer doped with scandium, and b1 is determined by the following formula: Kt 2 =0.3909b1 2 +0.3056b1+0.062。 32. An electronic device comprising a filter according to any one of claims 21-27, or a bulk acoustic resonator according to any one of claims 1-20.

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