KR20230045799A - Filter with Bulk Acoustic Wave type resonator - Google Patents

Abstract

A filter including a bulk acoustic wave-type (BAW-type) resonator according to an embodiment of the present invention includes: a series resonator group in which at least two first BAW-type resonators are connected in series; and a parallel resonator group in which at least two second BAW-type resonators each branched from the series resonator group are connected in parallel. The first BAW-type resonators are disposed within the series resonator group, so that frequencies of each reflection notch generated by at least one of a wing structure and a raised frame formed on an upper electrode of each of the first BAW-type resonators are positioned in a dispersed manner. The present invention is to prevent an insertion loss from occurring in a pass band.

Description

Filter including a BAW-type resonator {Filter with Bulk Acoustic Wave type resonator}

The present invention relates to a filter usable for a radio frequency (RF) band communication, a duplexer, and the like, and more particularly, to a filter including BAW (Bulk Acoustic Wave) type resonators.

Wireless mobile communication technology requires various RF (Radio Frequency) parts that can efficiently transmit information in a limited frequency band. In particular, among RF components, a filter is one of the core components used in mobile communication technology, enabling high-quality communication by selecting a signal required by a user or filtering a signal to be transmitted among countless air waves.

Currently, the most widely used RF filters for wireless communication are dielectric filters and surface acoustic wave (hereinafter referred to as SAW) filters. Dielectric filters have the advantages of high permittivity, low insertion loss, stability at high temperatures, resistance to vibration, and resistance to shock. However, dielectric filters have limitations in miniaturization and MMIC (Monolithic Microwave IC), which are recent technological development trends. In addition, the SAW filter has the advantage of being smaller than the dielectric filter, easy to signal processing, simple circuit, and mass-produced by using a semiconductor process. In addition, the SAW filter has a higher side rejection in the pass band than the dielectric filter, and has the advantage of being able to exchange high-quality information. However, since the SAW filter process includes a process of exposure using ultraviolet (UV) light, there is a disadvantage in that the line width of an InterDigital Transducer (IDT) is limited to about 0.5 μm. Therefore, there is a problem that it is impossible to cover the ultra-high frequency (5 GHz or more) band using the SAW filter, and it is difficult to fundamentally configure the MMIC structure and single chip made on the semiconductor substrate.

In order to overcome the above limitations and problems, a BAW type filter including FBAR (Film Bulk Acoustic Resonator) that can completely MMIC the frequency control circuit by being integrated with other active elements on the existing semiconductor (Si, GaAs) substrate is proposed. It became.

FBAR is a thin film device that can be used in wireless communication devices and military radars in various frequency bands (900 MHz to 10 GHz) because it is low-cost, small, and has high Q coefficient characteristics. In addition, it can be miniaturized to one hundredth the size of a dielectric filter and a concentrated constant (LC) filter, and has a characteristic that insertion loss is much smaller than that of a SAW filter. Therefore, FBAR can be said to be the most suitable device for MMICs that require high stability and high quality coefficients.

FBAR deposits piezoelectric materials such as zinc oxide (ZnO) and aluminum nitride (AlN) on semiconductor substrates such as silicon (Si) or gallium arsenide (GaAs) by RF sputtering, and causes resonance due to piezoelectric properties. That is, in FBAR, a piezoelectric thin film is deposited between both electrodes and a bulk acoustic wave is induced to generate resonance.

Filters for RF band communication, especially in the case of application of mobile terminals (cell phones), require an increase in communication frequency and a wide bandwidth filter due to the increase in the amount of communication information. In the case of a BAW filter that meets the needs of the market, the reflection loss caused by the raised frame of the series resonator exists within the pass band due to the wide bandwidth, and a notch is formed within the pass band. As a result, a filter having a bandwidth desired by the consumer cannot be obtained. Accordingly, the raised frame of the series resonator is removed and only the frame structure of the shunt resonator is used.

However, when the raised frame of the series resonator is removed, a significant drop in Qp occurs, and the insertion loss in the high frequency band deteriorates or the edge cannot be set. Due to this, there is a problem in that the frequency margin for the temperature coefficient of frequency (TCF) of the BAW type filter is lost, resulting in TCF performance degradation, which may lead to high power degradation and durability degradation.

Republic of Korea Patent Publication No. 10-2014-0030177 (published on March 11, 2014)

The problem to be solved by the present invention is that insertion loss occurs in the pass band due to spurious mode (ie, reflection notch frequency) caused by a raised frame or wing (fixed beam) structure of a filter having a large bandwidth. It relates to a filter including a BAW-type resonator for preventing

A filter including a BAW-type resonator according to an embodiment of the present invention for solving the above problems includes a series resonator group in which at least two or more first BAW (Bulk Acoustic Wave) type resonators are connected in series; A raised frame including a parallel resonator group in which at least two or more second BAW-type resonators branched from the series resonator group are connected in parallel, and formed on upper electrodes of each of the first BAW-type resonators, and It is characterized in that the first BAW-type resonators are arranged in the series resonator group so that the frequencies of each reflection notch generated by at least one of the wing structures are dispersed from each other.

It is characterized in that those having the same reflection notch frequency among the first BAW-type resonators are arranged so as not to be adjacent to each other.

Among the first BAW-type resonators, those having the largest and smallest peak frequencies of reflection notches are disposed not adjacent to the input terminal or the output terminal of the filter.

Among the first BAW-type resonators, those having a relatively large width and depth of the reflection notch are disposed in a central region of the series resonator group.

Among the first BAW-type resonators, those having relatively small widths of reflection notches and depths of reflection notches are at least equal to or larger than those having relatively large widths of reflection notches and depths of reflection notches among the first BAW-type resonators. It is characterized in that the number is arranged in the series resonator group.

According to the present invention, by distributingly arranging BAW-type resonators in a series resonator group so that reflection notch frequencies generated by a raised frame and a wing structure are dispersed from each other, the broadband filter It has the effect of preventing insertion loss that may occur in the pass band and improving the skirt characteristic of the edge in the filter.

1 is a configuration diagram of an embodiment for explaining a filter including a BAW type resonator according to the present invention.
2 is a reference diagram illustrating resonator characteristics of first BAW-type resonators constituting a series resonator group.
3 is a reference diagram illustrating a raised frame and a wing structure formed in each of the first BAW-type resonators.
4 is a reference diagram illustrating a reflection notch frequency that may occur in each of the BAW-type resonators.
5 is a reference diagram illustrating various reflection notch frequencies that may occur in first BAW-type resonators.
FIG. 6 is a reference diagram illustrating Qp values according to types of the first BAW type resonators shown in FIG. 5 .
7 is a graph illustrating an example of a peak frequency of a reflection notch according to a thickness change of a raised frame.
8 is a reference diagram for explaining a performance improvement effect of a filter including a BAW type resonator according to the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art, and the following examples may be modified in many different forms, and the scope of the present invention It is not limited to the examples below. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the spirit of the invention to those skilled in the art.

Terms used in this specification are used to describe specific embodiments and are not intended to limit the present invention. As used herein, the singular form may include the plural form unless the context clearly indicates otherwise. Also, as used herein, the term "and/or" includes any one and all combinations of one or more of the listed items. Further, hereinafter, embodiments of the present invention will be described with reference to drawings schematically showing embodiments of the present invention.

In the filter including the BAW-type resonator according to the present invention, when an external signal is applied between the lower electrode and the upper electrode, a part of the electrical energy transmitted between the two electrodes is converted into mechanical energy according to the piezoelectric effect. And, in the process of converting this back into electrical energy, it resonates with respect to the frequency of the natural vibration according to the thickness of the piezoelectric layer. To this end, the BAW-type resonator includes a substrate, a lower electrode, a piezoelectric layer, and an upper electrode.

The substrate is a semiconductor substrate, and a normal silicon wafer may be used, and a high-resistance silicon substrate (HRS) may be preferably used. An insulating layer (not shown) may be formed on the upper surface of the substrate. The insulating layer may selectively employ a thermal oxide film that can be easily grown on a substrate, or an oxide film or a nitride film using a conventional deposition process such as chemical vapor deposition. The substrate may include a cavity on an upper surface. The cavity is formed by forming a space on the substrate, forming an insulating layer on the space, depositing a sacrificial layer on top of the insulating layer, flattening it by etching, and then removing the sacrificial layer. Here, the sacrificial layer uses a material such as polysilicon or SiO2, which has excellent surface roughness and is easy to form and remove. For example, SiO2, PSG, BPST, BSG or polysilicon may be employed as the sacrificial layer, and SiO2, PSG, BPST, BSG or polysilicon has excellent surface roughness and is easy to form and remove the sacrificial layer. , in particular, can be removed by applying dry etching in a subsequent process.

A lower electrode is formed on top of the substrate. The lower electrode is formed on the upper part of the cavity in the substrate and may surround the entire upper part or a part of the upper part of the cavity. The lower electrode is formed by depositing a predetermined material on top of the substrate and then patterning it. The material used as the lower electrode uses a common conductive material such as metal, preferably aluminum (Al), tungsten (W), gold (Au), platinum (Pt), nickel (Ni), titanium (Ti) , chromium (Cr), palladium (Pd), and molybdenum (Mo) may be used.

A piezoelectric layer is formed on top of the lower electrode. The piezoelectric layer may be formed by depositing a piezoelectric material on top of the lower electrode and then patterning it. As the piezoelectric material, aluminum nitride (AIN) or zinc oxide (ZnO) may be used. As the deposition method, an RF magnetron sputtering method, an evaporation method, and the like are used.

An upper electrode is formed on top of the piezoelectric layer. The upper electrode may be formed by depositing and patterning a metal film for the upper electrode on the piezoelectric layer. The upper electrode may use the same material and the same deposition method and patterning method as the lower electrode. The upper electrode may include a raised frame and/or a wing structure in order to increase Qp in the high frequency band or minimize insertion loss in the high frequency band.

1 is a configuration diagram of an embodiment for explaining a filter 10 including a BAW type resonator according to the present invention.

Referring to FIG. 1 , a filter 10 including a BAW type resonator includes a series resonator group 100 and a parallel resonator group 200 .

In the series resonator group 100 , at least two or more first BAW (Bulk Acoustic Wave) type resonators S1 , S2 , S3 , S4 , and S5 are connected in series.

In the parallel resonator group 200, at least two or more second BAW-type resonators P1, P2, P3, and P4 branched from the series resonator group 100 are connected in parallel.

2 is a reference diagram illustrating resonator characteristics of first BAW-type resonators S1, S2, S3, S4, and S5 constituting a series resonator group.

Referring to FIG. 2 , the series resonator group 100 includes five first BAW-type resonators S1, S2, S3, S4, and S5. Each of the first BAW-type resonators S1 , S2 , S3 , S4 , and S5 includes a raised frame formed on an upper electrode and a wing structure.

3 is a reference diagram illustrating a structure of a raised frame and a wing formed on each of the first BAW-type resonators S1 , S2 , S3 , S4 , and S5 .

Referring to FIG. 3, each of the first BAW-type resonators S1, S2, S3, S4, and S5 has an upper electrode formed on a piezoelectric layer, and at one side of the upper electrode, the thickness of the upper electrode is increased. A corresponding raised frame is formed, and a wing structure extending from the raised frame can be confirmed. Due to the raised frame and the wing structure, a reflection notch frequency is generated in the BAW type resonator.

4 is a reference diagram illustrating a reflection notch frequency that may occur in each of the BAW-type resonators. Referring to FIG. 4 , width and depth are defined for the reflection notch frequency. The greater the width of the notch frequency or the deeper the depth of the notch frequency, the higher the possibility of filter insertion loss.

5 is a reference diagram illustrating various reflection notch frequencies that may occur in the first BAW-type resonators, and FIG. 6 is a Qp value according to the types (A, B, and C) of the first BAW-type resonators shown in FIG. , and FIG. 7 is a graph showing a peak frequency of a reflection notch according to a thickness change of a raised frame.

Figure 5 (a) shows the reflection of any one BAW-type resonator (B) among the first BAW-type resonators, Figure 5 (b) is another BAW-type resonator among the first BAW-type resonators ( A) shows the reflection, and FIG. 5(c) shows the reflection of another BAW-type resonator (C) among the first BAW-type resonators.

It is confirmed that the peak frequency of the reflection notch of the BAW resonator B shown in FIG. 5 (a) belongs to a relatively low frequency band, and the width or depth of the notch frequency is large. In addition, the peak frequency in the reflection notch of the BAW resonator A shown in FIG. 5 (b) belongs to a relatively intermediate frequency band, and the width or depth of the notch frequency is confirmed to be medium. In addition, it is confirmed that the peak frequency in the reflection notch of the BAW resonator (C) shown in FIG. 5 (c) belongs to a relatively high frequency band, and the width or depth of the notch frequency is low.

The spurious modes, that is, types A, B, and C, generated by the combination of the raised frame and the wing structure, correspond to the peak value of Qp as shown in FIG. 6, and as shown in FIG. 7, the thickness of the raise frame It can be seen that the positions of the peak frequencies are different from each other. Since these types A, B, and C correspond to the peak values of Qp, the reflection notch frequency of the spurious mode generated by the combination of the raised frame and wing structure can be changed while maintaining the filter characteristics to the maximum.

As shown in FIG. 5, the series resonator group 100 includes first BAW-type resonators S1, S2, S3, S4, and S5 having various reflection notch frequencies, and these reflection notch frequencies are dispersed from each other. The first BAW type resonators S1 , S2 , S3 , S4 , and S5 are disposed in the series resonator group 100 so as to be located. At this time, in order to allow the reflection notch frequencies to be dispersed from each other, resonators having the same reflection notch frequency among the first BAW-type resonators S1, S2, S3, S4, and S5 are arranged not to be adjacent to each other. Meanwhile, a red line in FIG. 5 is a line set for simulation (mBVD).

In addition, in order to allow the reflection notch frequencies to be dispersed from each other, the largest and smallest peak frequencies of the reflection notch among the first BAW-type resonators (S1, S2, S3, S4, and S5) are input terminals or outputs of the filter. Place them so that they are not adjacent to the terminals. For example, as shown in FIG. 2, the types of BAW-type resonators adjacent to the input terminal and the output terminal are A-type resonators S1 and S5 whose peak frequency of the reflection notch relatively belongs to the middle frequency band. can be placed.

In addition, in order to allow the reflection notch frequencies to be dispersed from each other, those having a relatively large width and depth of the reflection notch among the first BAW-type resonators S1, S2, S3, S4, and S5 are series resonator groups. placed in the central area of For example, as shown in FIG. 2, among the first BAW-type resonators S1, S2, S3, S4, and S5, the B-type resonator S3 has a relatively large width and depth of the reflection notch. may be centered.

In addition, in order to allow the reflection notch frequencies to be dispersed from each other, those having a relatively small width and depth of the reflection notch among the first BAW resonators S1, S2, S3, S4, and S5 are the first BAW resonators. Among the BAW resonators, the series resonator group is disposed in at least equal to or greater numbers than those having a relatively large reflection notch width and a relatively large reflection notch depth.

For example, as shown in FIG. 2 , among the first BAW-type resonators S1 , S2 , S3 , S4 , and S5 , the B-type resonator S3 has the largest width and depth of the reflection notch. ) is disposed in the center, and among the first BAW-type resonators S1, S2, S3, S4, and S5, the width of the reflection notch and the depth of the reflection notch are intermediate A-type resonators (S1, S5) are disposed adjacent to the input terminal and the output terminal, and the C-type resonator has the lowest width of the reflection notch and depth of the reflection notch among the first BAW-type resonators (S1, S2, S3, S4, and S5) ( S2 and S4) are disposed between the A-type resonator and the B-type resonator, respectively.

8 is a reference diagram for explaining a performance improvement effect of a filter including a BAW type resonator according to the present invention.

8(a) shows a pass band due to a spurious mode generated by a raised frame and a wing structure when the bandwidth of the filter is large in the case of a conventional filter. band) illustrates the occurrence of insertion loss. In contrast, in (b) of FIG. 8, insertion that can occur in the pass band of a wideband filter is performed by arranging BAW-type resonators such that each reflection notch frequency generated by the raised frame and wing structure is dispersed from each other. Preventing insertion loss and improving skirt characteristics of edges in a filter are illustrated.

So far, the present invention has been looked at with respect to its preferred embodiments. Those skilled in the art to which the present invention pertains will understand that it may be implemented in a modified form without departing from the essential characteristics of the present invention. Therefore, the disclosed embodiments should be considered from an illustrative rather than a limiting point of view. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the equivalent scope will be construed as being included in the present invention.

Claims (5)

A series resonator group in which at least two or more first BAW (Bulk Acoustic Wave) type resonators are connected in series;
A parallel resonator group in which at least two or more second BAW-type resonators branched from the series resonator group are connected in parallel;
Each of the reflection notch frequencies generated by at least one of a raised frame and a wing structure formed on the upper electrode of each of the first BAW-type resonators is dispersed and located, A filter comprising a BAW-type resonator, characterized in that the first BAW-type resonators are arranged in the series resonator group. The method of claim 1,
A filter comprising a BAW-type resonator, characterized in that those having the same reflection notch frequency among the first BAW-type resonators are arranged so that they are not adjacent to each other. The method of claim 1,
A filter comprising a BAW-type resonator, characterized in that the largest and smallest peak frequencies of the reflection notch among the first BAW-type resonators are disposed so as not to be adjacent to the input terminal or the output terminal of the filter. The method of claim 1,
Among the first BAW-type resonators, those having a relatively large width and depth of the reflection notch are disposed in a central region of the series resonator group. The method of claim 1,
Among the first BAW-type resonators, those having a relatively small width of the reflection notch and a relatively small depth of the reflection notch are at least equal to or larger than those of the first BAW-type resonators having a relatively large width of the reflection notch and a relatively large depth of the reflection notch. A filter comprising a BAW-type resonator, characterized in that arranged in the series resonator group in number.

Images