KR102029527B1

KR102029527B1 - Bulk acoustic resonator

Info

Publication number: KR102029527B1
Application number: KR1020160015872A
Authority: KR
Inventors: 이태경; 한원; 김성선; 김대호
Original assignee: 삼성전기주식회사
Priority date: 2016-02-11
Filing date: 2016-02-11
Publication date: 2019-10-07
Also published as: KR20170094728A

Abstract

According to an embodiment of the present invention, a volume acoustic resonator may include a substrate; And a resonator comprising a first electrode, a piezoelectric layer, and a second electrode, which are partitioned into an active region and an inactive region, and a frame formed inside the active region. Includes, the frame and the second electrode may have a different acoustic impedance.

Description

Volume acoustic resonator {BULK ACOUSTIC RESONATOR}

The present invention relates to a volume acoustic resonator.

With the recent rapid development of mobile communication devices, chemical and bio devices, the demand for small lightweight filters, oscillators, resonant elements, acoustic resonant mass sensors, etc. used in such devices Is also increasing.

A bulk acoustic resonator is known as a means for implementing such a compact lightweight filter, oscillator, resonator element, acoustic resonance mass sensor, and the like. The volume acoustic resonator can be mass-produced at a minimum cost and can be realized in a very small size. In addition, it is possible to implement high quality factor values, which are the main characteristics of the filter, and to use them in the micro frequency band, and to implement the personal communication system (PCS) and digital cordless system (DCS) bands. There is an advantage.

The volume acoustic resonator has a structure in which a resonator formed by sequentially stacking a lower electrode, a piezoelectric layer, and an upper electrode on a substrate is formed. When electrical energy is applied to the first electrode and the second electrode to induce an electric field in the piezoelectric layer, the electric field causes a piezoelectric phenomenon of the piezoelectric layer to cause the resonator to vibrate in a predetermined direction. As a result, acoustic waves are generated in the same direction as the vibration direction, causing resonance. However, when an acoustic wave is generated, a lateral wave may be generated at the upper electrode. The side wave lowers a quality factor of the resonator and a loss of an acoustic wave is generated. There is a problem that becomes large.

United States Patent Application Publication No. 2006-0103492

An object of the present invention is to provide a volume acoustic resonator capable of effectively trapping side waves.

The volume acoustic resonator according to an embodiment of the present invention may include a frame formed inside the active region, and the frame and the upper electrode may have different acoustic impedances.

The volume acoustic resonator according to an embodiment of the present invention can improve the quality factor and reduce the loss of acoustic waves.

1 is a cross-sectional view showing a volume acoustic resonator according to an embodiment of the present invention.
2 is a schematic cross-sectional view of a resonator unit that may be employed in the volume acoustic resonator of FIG. 1.
3 and 4 are simulation graphs of a volume acoustic resonator according to an embodiment of the present invention.

DETAILED DESCRIPTION The following detailed description of the invention refers to the accompanying drawings that show, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. It should be understood that the various embodiments of the present invention are different but need not be mutually exclusive. For example, certain shapes, structures, and characteristics described herein may be embodied in other embodiments without departing from the spirit and scope of the invention with respect to one embodiment. In addition, it is to be understood that the location or arrangement of individual components within each disclosed embodiment may be changed without departing from the spirit and scope of the invention. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention, if properly described, is defined only by the appended claims, along with the full range of equivalents to which such claims are entitled. Like reference numerals in the drawings refer to the same or similar functions throughout the several aspects.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention.

1 is a cross-sectional view showing a volume acoustic resonator according to an embodiment of the present invention.

The volume acoustic resonator 10 according to an embodiment of the present invention may be a thin film bulk acoustic resonator (FBAR).

Referring to FIG. 1, a substrate 110, an insulating layer 120, an air cavity 112, and a resonator 135 may be included.

The substrate 110 may be formed of a silicon substrate, and an insulating layer 120 may be provided on the upper surface of the substrate 110 to electrically isolate the resonator 135 from the substrate 110. The insulating layer 120 is formed by chemical vapor deposition, RF magnetron sputtering, or evaporation of silicon dioxide (SiO ₂ ) or aluminum oxide (Al ₂ O ₂ ). 110 may be formed on.

The air cavity 112 may be formed on the insulating layer 120. The air cavity 112 is positioned below the resonator 135 so that the resonator 135 may vibrate in a predetermined direction. The air cavity 112 forms an air cavity sacrificial layer pattern on the insulating layer 120 and then forms a membrane 130 on the air cavity sacrificial layer pattern and then etches and removes the air cavity sacrificial layer pattern. It can be formed by.

An etch stop layer 125 may be additionally formed between the insulating layer 120 and the air cavity 112. The etch stop layer 125 serves to protect the substrate 110 and the insulating layer 120 from the etching process, and may serve as a base for the deposition of various other layers on the etch stop layer 125.

The resonator 135 is a first electrode 140, a piezoelectric layer 150 and the second electrode 160 and the second electrode 160 and / or a piezoelectric layer sequentially stacked so as to be located above the air cavity 112 It may include a frame 190 provided on the 150 to form a ring shape.

The first electrode 140 is formed on the upper surface of the membrane 130 to cover a portion of the membrane 130. The piezoelectric layer 150 is formed on the top surface of the membrane 130 and the first electrode 140 to cover a portion of the membrane 130 and a portion of the first electrode 140. For example, the first electrode 140 may include molybdenum (Mo).

The piezoelectric layer 150 generates a piezoelectric effect of converting electrical energy into mechanical energy in the form of an acoustic wave, and includes one of aluminum nitride (AlN), zinc oxide (ZnO), and lead zirconium titanium oxide (PZT; PbZrTiO). Can be.

The second electrode 160 may be formed on the piezoelectric layer 150. For example, the second electrode 160 may include ruthenium (Ru).

The resonator 135 may be divided into an active region and an inactive region. The active region of the resonator 135 vibrates in a predetermined direction due to a piezoelectric phenomenon generated in the piezoelectric layer 150 when electrical energy such as a radio frequency signal is applied to the first electrode 140 and the second electrode 160. The non-reactive region of the resonator 135 is a region that does not resonate by piezoelectric phenomenon even when electrical energy is applied to the first electrode 140 and the second electrode 160. Corresponding.

The resonator 135 outputs a radio frequency signal having a specific frequency by using a piezoelectric phenomenon. In detail, the resonator 135 may output a radio frequency signal having a resonant frequency corresponding to vibration caused by the piezoelectric phenomenon of the piezoelectric layer 150.

The protective layer 170 may be disposed on the second electrode 160 and the frame 190 of the resonator unit 135 to prevent the second electrode layer 160 and the frame 190 from being exposed to the outside. The protective layer 170 may be formed of an insulating material of silicon oxide-based, silicon nitride-based, and aluminum nitride-based. In addition, an electrode pad 180 for applying an electrical signal may be formed on the first electrode 140 and the second electrode 160 exposed to the outside.

When electrical energy such as a radio frequency signal is applied to the first electrode 140 and the second electrode 160, an acoustic wave is generated by the piezoelectric phenomenon generated in the piezoelectric layer 150. A lateral wave occurs in the second electrode 160. If the incident wave does not trap properly, the quality factor of the resonator is lowered and the loss of acoustic wave is increased.

According to an exemplary embodiment of the present invention, a frame 190 having a different acoustic impedance from the second electrode 160 may be disposed inside the active region of the resonator 135 to capture side waves into the resonator. As a result, the quality factor of the resonator may be improved, and the loss of the acoustic wave may be reduced.

2 is a schematic cross-sectional view of a resonator unit that may be employed in the volume acoustic resonator of FIG. 1.

2, in addition to the first electrode 140, the piezoelectric layer 150, and the second electrode 160, the resonator 135 may include a frame 190 formed inside the active region. In this case, the active region may correspond to a region in which at least one of the first electrode 140, the piezoelectric layer 150, and the second electrode 160 and the frame 190 overlap in the vertical direction above the air cavity 112. Can be.

Referring to FIG. 2A, the frame 190 may be formed on the first electrode 160, and specifically, the frame 190 may be formed on the edge of the second electrode 160.

Referring to FIG. 2B, the frame 190 may be formed outside the second electrode 160 to contact the second electrode 160. In this case, the frame 190 may be thicker than the second electrode 160.

Referring to FIG. 2 (c), the frame 190 is disposed outside the second electrode 160 to contact the first frame 191 and the second electrode 160 formed on the second electrode 160. It may include a second frame 192 is formed. In this case, the second frame 192 may be thicker than the second electrode 160, and the sum of the thicknesses of the first frame 191 and the second electrode 160 may be equal to the thickness of the second frame 192. Can be.

The frame 190 and the second electrode 160 may have different acoustic impedances. Acoustic impedance is determined according to density and speed of sound as shown in Equation 1 below.

Table 1 below shows the acoustic impedance and the electrical resistivity of the material determined according to Equation 1.

According to an embodiment, the frame 190 may be made of a material having a higher acoustic impedance than the second electrode 160. For example, the second electrode 160 may be made of ruthenium (Ru). At this time, referring to Table 1, the frame 190 has a higher acoustic impedance than ruthenium (Ru) and iridium (Ir) and tungsten ( W).

According to another embodiment, the frame 190 may be made of a material having a lower acoustic impedance than the second electrode 160. As an example, the second electrode 160 may be made of ruthenium (Ru). In this case, referring to Table 1, the frame 190 has a lower acoustic impedance than aluminum (Al) and gold (Ru). Au), nickel (Ni), copper (Cu), titanium (Ti), chromium (Cr), cobalt (Co), manganese (Zn), and magnesium (Mg) can be composed of one, considering the electrical resistivity Lower surfaces may include one of aluminum (Al), gold (Au), nickel (Ni), copper (Cu), cobalt (Co), manganese (Zn), and magnesium (Mg).

3 and 4 are simulation graphs of a volume acoustic resonator according to an embodiment of the present invention, and show gains according to frequencies of radio frequency signals.

3 and 4, the first electrode 140 is made of molybdenum (Mo), the piezoelectric layer 150 is made of aluminum nitride (AlN), and the second electrode 160 is made of ruthenium (Ru). 190) was set to have a thickness of 0.2 mu m and a width of 2 mu m.

3 and 4, Case 1 corresponds to the first embodiment of the present invention when the frame 190 is made of a material having a higher acoustic impedance than the second electrode 160, for example, tungsten (W). Case 2 corresponds to the second embodiment of the present invention when the frame 190 is made of a material having a lower acoustic impedance than the second electrode 160, for example, gold (Au), and Case 3 Corresponds to a comparative example when the frame 190 is made of a material having the same acoustic impedance as that of the second electrode 160.

Table 2 below shows data according to FIGS. 3 and 4.

Referring to Table 2, the resonant frequency (fs), the anti-resonant frequency (fp), the square of the effective electromechanical coupling coefficient (Kt ² ), and the series quality factor (Qs) are Case 1, Case 2 And there is no difference in Case 3, it can be seen that the parallel quality factor (Qp) is higher in Case 1 and Case 2 than Case 3.

That is, according to the exemplary embodiment of the present invention, the frame 190 having a different acoustic impedance from the second electrode 160 is disposed inside the active region of the resonator 135 to capture side waves into the resonator. As a result, the quality factor of the resonator can be improved, and the loss of acoustic waves can be reduced.

Although the present invention has been described by specific embodiments such as specific components and the like, but the embodiments and the drawings are provided to assist in a more general understanding of the present invention, the present invention is not limited to the above embodiments. For those skilled in the art, various modifications and variations can be made from these descriptions.

Accordingly, the spirit of the present invention should not be limited to the above-described embodiments, and all of the equivalents or equivalents of the claims, as well as the appended claims, fall within the scope of the spirit of the present invention. I will say.

110: substrate
112: air cavity
120: insulation layer
125: etch stop layer
130: membrane
135: resonator
140: first electrode
150: piezoelectric layer
160: second electrode
170: protective layer
180: electrode pad
190: frame
191: first frame
192: second frame

Claims

Board; And
A resonator including a first electrode, a piezoelectric layer, and a second electrode, which are partitioned into an active region and an inactive region, and a frame formed inside the active region; Including,
The frame and the second electrode have different acoustic impedances,
The active region corresponds to a region in which at least one of the frame and the second electrode, the first electrode, and the piezoelectric layer overlap, the inactive region corresponds to an outer region of the active region,
The frame includes a first frame formed on the second electrode and a second frame thicker than the second electrode and formed outside of the second electrode.

The method of claim 1, wherein the frame,
And a volume acoustic resonator made of a material having a higher acoustic impedance than the second electrode.

The method of claim 2,
The second electrode includes ruthenium (Ru),
The frame includes one of iridium (Ir) and tungsten (W).

The method of claim 1, wherein the frame,
A volume acoustic resonator made of a material having a lower acoustic impedance than the second electrode.

The method of claim 4, wherein the frame,
The second electrode includes ruthenium (Ru),
The frame is one of aluminum (Al), gold (Au), nickel (Ni), copper (Cu), titanium (Ti), chromium (Cr), cobalt (Co), manganese (Zn), and magnesium (Mg). Volume acoustic resonator comprising a.

delete

The method of claim 1,
The sum of the thickness of the first frame and the second electrode is equal to the thickness of the second frame.