WO2022089597A1

WO2022089597A1 - Filter comprising doped resonator, and multiplexer and communication device

Info

Publication number: WO2022089597A1
Application number: PCT/CN2021/127485
Authority: WO
Inventors: 徐利军; 庞慰
Original assignee: 诺思(天津)微系统有限责任公司
Priority date: 2020-10-30
Filing date: 2021-10-29
Publication date: 2022-05-05
Also published as: CN112332801A; CN112332801B

Abstract

Disclosed are a filter comprising a doped resonator, and a multiplexer and a communication device, wherein the doped resonator and a non-doped resonator are allocated to different positions in a filter topology, thereby saving the cost, reducing the package size and improving the filter performance.

Description

Filters and multiplexers containing doped resonators, communications equipment

technical field

The present invention relates to the technical field of filters, in particular to a filter, a multiplexer, and a communication device including a doped resonator.

Background technique

Wireless communication technology is developing rapidly in the direction of multi-band and multi-mode. As the key components of RF front-end, filters, duplexers and multiplexers have received extensive attention, especially in the fastest growing field of personal mobile communication. At present, the filters and duplexers that are widely used in the field of personal mobile communication are mostly made of surface acoustic wave resonators or bulk acoustic wave resonators. Compared with surface acoustic wave resonators, BAW resonators have better performance. BAW resonators have the characteristics of high Q value, wide frequency coverage, and good heat dissipation performance, which are more suitable for the development needs of future 5G communications. Since the resonance of the BAW resonator is generated by mechanical waves rather than electromagnetic waves as the source of resonance, the wavelength of mechanical waves is much shorter than that of electromagnetic waves. Therefore, the volume of the bulk acoustic wave resonator and the filter composed of it is greatly reduced compared to the size of the traditional electromagnetic filter.

In recent years, with the rapid development of the market, wireless communication terminals and equipment continue to develop in the direction of miniaturization, multi-mode-multi-band, and the duplexer for FDD (Frequency Division Duplexing) in wireless communication terminals The number also increased. Five-mode, 13-band, and even five-mode and 17-band have gradually become the standard requirements for mainstream mobile phones. Especially with the approach of 5G commercial use, more filters and duplexers will be integrated in mobile phone terminals. more stringent requirements. In fact, whether a filter or a duplexer, its total area is mainly determined by the area of the resonator. If the area of the resonator can be effectively reduced, then small-sized filters and duplexers will be easily realized. The area of the resonator is mainly determined by the thickness of the piezoelectric layer. The larger the thickness, the larger the area of the resonator, so the miniaturization of the filter can be achieved by reducing the thickness of the piezoelectric layer. The thickness is also related to the effective electromechanical coupling coefficient of the resonator. If the thickness of the piezoelectric layer is reduced, the effective electromechanical coupling coefficient will inevitably be reduced, which will lead to insufficient bandwidth of the filter and deteriorate its performance.

The commonly used piezoelectric materials for bulk acoustic wave resonators are aluminum nitride, zinc oxide, and lead zirconate titanate. Among them, aluminum nitride has the advantages of high acoustic wave velocity, high thermal conductivity, low dielectric constant, and compatibility with CMOS technology. It is an ideal material for the preparation of high-frequency, high-power and high-integration bulk acoustic wave resonators, but compared with zinc oxide and lead zirconate titanate, the piezoelectric coefficient (d33=5.5pC/N) and electromechanical coupling coefficient ( kt2=6.3%) is too small, which limits the wide application of aluminum nitride to a certain extent. Therefore, how to improve the electromechanical coupling coefficient of aluminum nitride has become a hot spot in the industry. A method of effectively enhancing the electromechanical coupling coefficient of aluminum nitride by doping rare earth elements such as scandium. The following description mainly takes the doping of scandium as an example.

Scandium-doped concentration is closely related to its electromechanical coupling coefficient. Referring to FIG. 1, FIG. 1 is a schematic diagram of the relationship between scandium-doped concentration and scandium-doped aluminum nitride electromechanical coupling coefficient according to the prior art, wherein the abscissa is the scandium-doped concentration. (mass percent), and the ordinate is the electromechanical coupling coefficient of scandium-doped aluminum nitride. It can be seen from Figure 1 that the electromechanical coupling coefficient is proportional to the scandium-doped concentration. When the scandium-doped concentration increases from 0 to 0.16 (which is a mass percentage, i.e. 16%, the same below), the electromechanical coupling coefficient increases from 6.3%. to 12.2%, almost doubled. Correspondingly, for the same effective electromechanical coupling coefficient, the thickness of the piezoelectric layer of the scandium-doped resonator will become thinner, and the area of the resonator will become smaller. Table 1 shows the area and piezoelectricity of the resonator under various scandium-doped concentrations. Layer thickness comparison.

Table 1

It can be seen from Table 1 that while keeping the effective electromechanical coupling coefficient unchanged, the greater the scandium-doped concentration, the thinner the piezoelectric layer, and the smaller the corresponding resonator area. When the scandium-doped concentration changes from 0 to 0 When it reaches 0.2, the area of the 50 ohm resonator is reduced from 11200 square microns to 7500 square microns, that is, the area is reduced by 33%, so when using highly scandium-doped aluminum nitride as the piezoelectric material of the resonator, the filter can be greatly reduced. The package size of the device and the duplexer can also be reduced, and the cost can also be reduced.

However, studies have found that when the piezoelectric material in the resonator is doped with scandium, aluminum nitride or other impurities (the corresponding resonator is called a doped resonator, and the piezoelectric material without impurity resonator is called an undoped resonator). , the performance of the resonator has changed greatly. In addition to increasing the effective electromechanical coupling coefficient of the resonator, the loss of the resonator will increase, that is to say, the Q value of the resonator will deteriorate. Take scandium doping as an example to illustrate. Table 2 shows the comparison of Q values of resonators with different scandium doping concentrations. The molecular expression of scandium doping aluminum nitride is Al _1-x Sc _X N, and x is the scandium doping concentration.

Table 2

It can be seen from Table 2 that the higher the scandium-doped concentration, the more the Q value of the resonator decreases. For example, when the scandium-doped concentration increases from 0 to 0.15, its Q _p,m (the Q value at the parallel resonance frequency) From 739 to 348, a reduction of 52%. Therefore, although scandium doping in the aluminum nitride material can effectively improve the electromechanical coupling coefficient of the resonator, and can effectively reduce the package size and cost of the resonator and filter, a negative effect is that the Q value of the resonator will deteriorate, seriously affecting the The passband insertion loss of the filter.

Therefore, based on the scandium-doped aluminum nitride technology, how to use technical means to improve the filter insertion loss under the condition that the size of the filter and the duplexer can be reduced is still a technical problem to be solved.

SUMMARY OF THE INVENTION

In view of this, the present invention provides a filter and multiplexer including doped resonators, and communication equipment, wherein the doped resonators and the undoped resonators are allocated to different positions in the filter topology, either Cost savings, reduced package size, and improved filter performance.

The technical scheme of the present invention is as follows:

A filter comprising a doped resonator, the piezoelectric material in the doped resonator is doped with impurity elements, so that the electromechanical coupling coefficient of the piezoelectric material is improved, in the filter: the filter closest to the output end The resonator is an undoped resonator, and the other resonators are doped resonators; or, the one closest to the output end of all series resonators and the one closest to the output end of all parallel resonators are undoped resonators, Other resonators are doped resonators.

Optionally, the doping concentration of the doped resonator is such that the difference between the effective electromechanical coupling coefficients of the doped resonator and the undoped resonator is not more than 0.5%.

Optionally, the doping concentration of the doped resonator is between 0.2 and 0.4, or between 0.05 and 0.2.

Optionally, in the filter, the thickness of the piezoelectric layer of the doped resonator is smaller than the thickness of the piezoelectric layer of the undoped resonator.

Optionally, the piezoelectric material is aluminum nitride.

Optionally, the impurity element is a rare earth element.

Optionally, the rare earth element is scandium.

A multiplexer including a doped resonator, including the filter of the present invention, and in the transmitting filter and the receiving filter of the multiplexer: the resonator closest to the antenna end is an undoped resonator, and the other The resonators are doped resonators; alternatively, the ones closest to the antenna end among all the series resonators and the ones closest to the antenna end among all the parallel resonators are undoped resonators, and the other resonators are doped resonators.

Optionally, in the transmitting filter and the receiving filter, the thickness of the piezoelectric layer of the doped resonator is smaller than the thickness of the piezoelectric layer of the undoped resonator.

Optionally, in the transmitting filter, the doped resonator is fabricated on one wafer, and the undoped resonator is fabricated on another wafer.

Optionally, in the receiving filter, the doped resonator is fabricated on one wafer, and the undoped resonator is fabricated on another wafer.

A communication device comprising the filter of the present invention.

A communication device includes the multiplexer of the present invention.

Description of drawings

For purposes of illustration and not limitation, the present invention will now be described in accordance with preferred embodiments thereof, particularly with reference to the accompanying drawings, wherein:

1 is a schematic diagram of the relationship between the concentration of scandium and the electromechanical coupling coefficient of scandium-doped aluminum nitride according to the prior art;

2A and 2B are schematic diagrams of the distribution of scandium-doped resonators and undoped resonators in filters according to embodiments of the present invention;

3A and 3B are schematic diagrams of the distribution of scandium-doped resonators and undoped resonators in a multiplexer according to an embodiment of the present invention;

4A and 4B are schematic diagrams illustrating the comparison of insertion loss between a duplexer according to an embodiment of the present invention and a duplexer in the prior art;

5 is a schematic diagram of the distribution of resonators of a duplexer on different wafers according to an embodiment of the present invention.

Detailed ways

In the embodiment of the present invention, a method of mixing doped and undoped resonators to form a filter is adopted. If the resonator doped with piezoelectric material increases the electromechanical coupling coefficient, it also increases the loss or loss of the resonator. If there are other performance degradations, the embodiments of the present invention have specific arrangements for the two, which helps to solve the above problems, not only can reduce the package size of the filter, reduce the cost, but also ensure that the deterioration of the filter passband insertion loss is suppressed. The principles and technical solutions disclosed in the present invention are described below with respect to filters and multiplexers (including duplexers). The structures of the filters and multiplexers in the figures are examples, and the filters and multiplexers in implementation may be series resonators and parallel resonators in other numbers and positions. The piezoelectric material here is, for example, aluminum nitride, and the dopant can be a rare earth element, such as scandium. The following is an example of the selection of scandium as an impurity.

For the filter, for the commonly used ladder topology, the resonator closest to the output uses the undoped resonator, while the other resonators use the scandium-doped resonator. The effective electromechanical coupling coefficients are equivalent, and the difference is not more than 0.5%, so that the series resonators and parallel resonators close to the output end can use undoped resonators, while other resonators use scandium-doped resonators. The effective electromechanical coupling coefficients of scandium and undoped resonators are comparable, and the difference is not more than 0.5%.

In the filter, the scandium-doped resonator has the same scandium-doped concentration, and its scandium-doped concentration is determined by the area of the filter. If you want the filter area to be as small as possible, a high-concentration scandium-doped resonator should be used. The scandium concentration is greater than 0.2 and less than 0.4. If both the filter area and the filter insertion loss are taken into account, that is, it is hoped that the filter insertion loss will deteriorate less while the filter area is reduced, then a low-concentration scandium-doped resonator should be used, such as The concentration of scandium is greater than 0.05 and less than 0.2.

2A and 2B are schematic diagrams of the distribution of scandium-doped and undoped resonators in a filter according to an embodiment of the present invention. As shown in Figures 2A and 2B, there are series resonators S11 to S15 and parallel resonators P11 to P14 between the input terminal 1 and the output terminal 2 of the filter, wherein the resonator S15 is the closest to the output terminal 2, so it can be The resonator S15 is an undoped resonator, as shown in block 102 in FIG. 2A , and the other resonators, ie, the resonators in block 101 , are scandium-doped resonators. In Figure 2A, the one closest to the output is a series resonator; for some filters, the one closest to the output is a parallel resonator, in this case, the parallel resonator is an undoped resonator, and the other resonators are Scandium-doped resonators.

The distribution of scandium-doped resonators and undoped resonators can also be such that one of the series resonators closest to the output end and one of the parallel resonators closest to the output end are used as undoped resonators, and the other resonators are doped. A scandium resonator, as shown in FIG. 2B , the resonators S15 and P14 in the block 202 are the series resonator and the parallel resonator closest to the output end 2, respectively, and the two are undoped resonators, while in the block 201 The resonator is a scandium-doped resonator.

For the duplexer, the resonator near the antenna end has the greatest impact on the performance of the duplexer, so the resonator closest to the antenna end in the transmit and receive filters of the duplexer adopts the undoped resonator, and the rest of the resonators adopt the undoped resonator. Scandium-doped resonator, wherein the effective electromechanical coupling coefficients of the scandium-doped and undoped resonators of the transmitting filter are equivalent, and the difference is not greater than 0.5%, and the effective electromechanical coupling of the scandium-doped and undoped resonators of the receiving filter is also the same The coefficients are equivalent, the difference is not more than 0.5%, and it is also possible to use undoped resonators for the series resonators and parallel resonators near the antenna end in the transmit and receive filters of the duplexer, and scandium-doped resonators for the rest of the resonators. A resonator, wherein the effective electromechanical coupling coefficients of the scandium-doped and undoped resonators of the transmitting filter are equivalent, and the difference is not greater than 0.5%, and the effective electromechanical coupling coefficients of the scandium-doped and undoped resonators of the receiving filter are also equivalent , the difference is not more than 0.5%.

In the duplexer, the scandium-doped resonator has the same scandium-doped concentration, and its scandium-doped concentration is determined by the area of the filter. If you want the filter area to be as small as possible, a high-concentration scandium-doped resonator should be used, such as The scandium-doped concentration is greater than 0.2 and less than 0.4. If both the filter area and the filter insertion loss are taken into account, that is, it is hoped that the filter insertion loss deteriorates less while the filter area is reduced, then a low-concentration scandium-doped resonator should be used. Such as scandium doping concentration is greater than 0.05, less than 0.2.

3A and 3B are schematic diagrams of the distribution of scandium-doped and undoped resonators in a multiplexer according to an embodiment of the present invention. As shown in Figure 3A and Figure 3B, taking two channels as an example, the common port 1 is connected to an external antenna and a matching inductor L1, and there are series resonators S11 to S15 and parallel resonators P11 to P14 between the common port 1 and the transmitting port 2 , there are series resonators S21 to S25 and parallel resonators P21 to P25 between the common port 1 and the receiving port 3. When arranging the scandium-doped resonator, as shown in FIG. 3A, the resonator closest to the antenna end is used as the undoped resonator, and the other resonators are scandium-doped resonators, as shown in block 301 and block 302 in the figure respectively. Show. In the figure, the resonator closest to the antenna end is a series resonator as an example, and if the parallel resonator closest to the antenna end is a parallel resonator, the parallel resonator is an undoped resonator.

The distribution of scandium-doped resonators in the multiplexer can also be as shown in Fig. 3B, the series resonators and parallel resonators closest to the antenna end are selected as undoped resonators, as shown in block 401 in the figure, other resonators are selected. , that is, the resonator in block 402 is a scandium-doped resonator.

The effect of the technical solution in the embodiment of the present invention can be verified by simulation. Taking the solution shown in FIG. 3A as an example, for the case where the scandium-doped concentration is 0.2, according to the method shown in FIG. 3A and all the resonators are scandium-doped resonators The comparison of the insertion loss of the filter is shown in Fig. 4A and Fig. 4B. 4A and 4B are schematic diagrams illustrating comparison of insertion loss between a duplexer according to an embodiment of the present invention and a duplexer in the prior art. The solid line in the figure corresponds to the embodiment of the present invention, and the dotted line corresponds to the prior art. It can be seen from the figure that the filter insertion loss can be improved by 0.15dB by using the embodiment of the present invention.

In the manufacturing method of the multiplexer in the present invention, the scandium-doped resonator and the non-doped resonator are manufactured on different wafers, taking the duplexer as an example, as shown in FIG. Schematic diagram of the distribution of the resonators of the duplexer in different wafers according to the embodiment of the invention. In FIG. 5, 501 is a package substrate, which is an organic material, and a plurality of

wafers

502, 503, 504, 505 are soldered upside down on the substrate 501, wherein the wafer 502 is fabricated with a plurality of scandium-doped resonances in the emission filter. On the wafer 503 there are 1 or 2 undoped resonators in the transmit filter, and the wafer 502 and the wafer 503 together constitute the transmit filter; similarly, on the wafer 504 there is a receive filter. A plurality of scandium-doped resonators are fabricated on the wafer 505, while one or two undoped resonators in the receiving filter are fabricated on the wafer 505, and the wafer 504 and the wafer 505 together constitute the receiving filter.

After the resonator is doped with scandium, the effective electromechanical coupling coefficient will become larger, that is to say, if the effective electromechanical coupling coefficient is the same, the piezoelectric layer of the scandium-doped resonator will be thinner, so the area will be smaller, which can reduce the filter package size and cost savings.

Generally speaking, after the resonator is doped with scandium, its loss term will increase, that is, the Q value will decrease. If the filter uses scandium-doped resonators, the insertion loss will be worse, so we propose to use some undoped resonators. The rest use scandium-doped resonators, which can balance between saving cost, reducing size and improving filter insertion loss.

Since the Q value of the resonator at the output end has the greatest impact on the insertion loss, the undoped resonator with higher Q value is assigned to the output end, and the rest of the resonators are scandium-doped resonators.

For the duplexer, the resonators closest to the antenna end in the transmit and receive filters are undoped resonators, and the rest of the resonators are scandium-doped resonators.

The above-mentioned specific embodiments do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions may occur depending on design requirements and other factors. Any modifications, equivalent replacements and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

A filter comprising a doped resonator, the piezoelectric material in the doped resonator is doped with impurity elements, so as to improve the electromechanical coupling coefficient of the piezoelectric material, characterized in that, in the filter:

The resonator closest to the output is an undoped resonator and the other resonators are doped resonators; or,

The one closest to the output of all series resonators, and the one closest to the output of all parallel resonators, is an undoped resonator, and the other resonators are doped resonators.
The filter according to claim 1, wherein the doping concentration of the doped resonator is such that the difference between the effective electromechanical coupling coefficients of the doped resonator and the non-doped resonator is not more than 0.5%.
The filter according to claim 1, wherein the doping concentration of the doped resonator is between 0.2 and 0.4, or between 0.05 and 0.2.
The filter according to claim 1, wherein, in the filter, the thickness of the piezoelectric layer of the doped resonator is smaller than the thickness of the piezoelectric layer of the undoped resonator.
The filter according to claim 1, wherein the piezoelectric material is aluminum nitride.
The filter according to any one of claims 1 to 5, wherein the impurity element is a rare earth element.
The filter according to claim 6, wherein the rare earth element is scandium.
A multiplexer comprising a doped resonator, comprising the filter according to any one of claims 1 to 7, and in the transmit filter and the receive filter of the multiplexer:

The resonator closest to the antenna end is an undoped resonator, and the other resonators are doped resonators; or,

The one closest to the antenna end of all series resonators and the one closest to the antenna end of all parallel resonators are undoped resonators, and the other resonators are doped resonators.
The multiplexer according to claim 8, wherein in the transmitting filter and the receiving filter, the thickness of the piezoelectric layer of the doped resonator is smaller than the thickness of the piezoelectric layer of the undoped resonator.
The multiplexer according to claim 8 or 9, wherein, in the transmit filter, the doped resonator is fabricated on one wafer, and the undoped resonator is fabricated on another wafer.
The multiplexer according to claim 8 or 9, wherein in the receiving filter, the doped resonator is fabricated on one wafer, and the undoped resonator is fabricated on another wafer.
A communication device, characterized by comprising the filter according to any one of claims 1 to 7 .
A communication device, comprising the multiplexer according to any one of claims 8 to 11.