KR102449366B1 - Bulk-acoustic wave resonator and method for fabricating the same - Google Patents

Abstract

The volume acoustic resonator according to an embodiment of the present invention includes a resonator in which a first electrode, a piezoelectric layer, and a second electrode are sequentially stacked on a substrate, and is disposed below the piezoelectric layer to form the piezoelectric layer and the second electrode. It includes an insertion layer partially raised, wherein the insertion layer may be formed of a material containing silicon (Si), oxygen (O), and nitrogen (N).

Description

Volumetric acoustic resonator and manufacturing method thereof

The present invention relates to a volumetric acoustic resonator and a method for manufacturing the same.

According to the trend of miniaturization of wireless communication devices, miniaturization of high-frequency component technology is actively required. For example, a bulk acoustic wave (BAW) type filter using semiconductor thin film wafer manufacturing technology is mentioned.

A volume acoustic resonator (BAW) is a thin film type device that induces resonance by depositing a piezoelectric dielectric material on a silicon wafer, which is a semiconductor substrate, and using the piezoelectric properties as a filter.

Recently, the interest in technology in 5G communication is increasing, and the development of a volumetric acoustic resonator technology that can be implemented in a candidate band is being actively carried out.

However, in the case of 5G communication using the Sub 6 GHz (4 to 6 GHz) frequency band, since the bandwidth increases and the communication distance decreases, the strength or power of a signal may be increased. In addition, as the frequency increases, losses occurring in the piezoelectric layer or the resonator may increase.

Accordingly, there is a demand for a volume acoustic resonator capable of minimizing leakage of energy from the resonator.

An object of the present invention is to provide a volumetric acoustic resonator capable of minimizing energy leakage and a method for manufacturing the same.

The volume acoustic resonator according to an embodiment of the present invention includes a resonator in which a first electrode, a piezoelectric layer, and a second electrode are sequentially stacked on a substrate, and is disposed below the piezoelectric layer to form the piezoelectric layer and the second electrode. It includes an insertion layer partially raised, wherein the insertion layer may be formed of a material containing silicon (Si), oxygen (O), and nitrogen (N).

In addition, the method for manufacturing a volume acoustic resonator according to an embodiment of the present invention includes the step of sequentially stacking a first electrode, a piezoelectric layer, and a second electrode on a substrate to form a resonance part, and the step of forming the resonance part includes: , forming an insertion layer disposed under the first electrode or between the first electrode and the piezoelectric layer to partially elevate the piezoelectric layer and the second electrode, wherein the insertion layer is formed of silicon (Si ), oxygen (O), and nitrogen (N) may be formed of a containing material.

Since the volume acoustic resonator according to the present invention forms the insertion layer of SiOxNy material, even if the photoresist formed on the insertion layer is repeatedly re-applied for patterning the insertion layer, the insertion layer can be formed precisely and stably. Therefore, it is easy to manufacture and the energy leakage of the volumetric acoustic resonator can be minimized.

1 is a plan view of an acoustic resonator according to an embodiment of the present invention;
FIG. 2 is a cross-sectional view taken along II′ of FIG. 1 .
3 is a cross-sectional view taken along II-II′ of FIG. 1 .
4 is a cross-sectional view taken along III-III′ of FIG. 1;
5 and 6 are views showing critical dimensions of a volume acoustic resonator in which an insertion layer is formed of a silicon dioxide material.
7 and 8 are views showing critical dimensions of a volume acoustic resonator in which an insertion layer is formed of a silicon dioxide material.
9 and 10 are views showing critical dimensions of a volume acoustic resonator in which an insertion layer is formed of a SiOxNy material.
11 and 12 are views showing critical dimensions of a volume acoustic resonator in which an insertion layer is formed of a SiOxNy material.
13 and 14 are views illustrating critical dimensions of a volume acoustic resonator in which an insertion layer is formed of SiOxNy material;
15 and 16 are views showing critical dimensions and content of each element of a volume acoustic resonator in which an insertion layer is formed of SiOxNy material;
17 is a schematic cross-sectional view of a volume acoustic resonator according to another embodiment of the present invention;
18 is a schematic cross-sectional view of a volume acoustic resonator according to another embodiment of the present invention;

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. However, the spirit of the present invention is not limited to the presented embodiment, and those skilled in the art who understand the spirit of the present invention may add, change, or delete other components within the scope of the same spirit, through addition, change, or deletion, etc. Other embodiments included within the scope of the inventive concept may be easily proposed, but this will also be included within the scope of the inventive concept.

In addition, throughout the specification, that a component is 'connected' to another component includes not only a case in which these components are 'directly connected', but also a case in which the component is 'indirectly connected' through another component. means that In addition, 'including' a certain component means that other components may be further included, rather than excluding other components, unless otherwise stated.

1 is a plan view of an acoustic resonator according to an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along II-I' of FIG. 1, FIG. 3 is a cross-sectional view taken along II-II' of FIG. 1, and FIG. It is a cross-sectional view along III-III'.

1 to 4 , the acoustic resonator 100 according to an embodiment of the present invention may be a bulk acoustic wave resonator (BAW), and includes a substrate 110 , a sacrificial layer 140 , and a resonator unit. 120 , and an insertion layer 170 .

The substrate 110 may be a silicon substrate. For example, a silicon wafer or a silicon on insulator (SOI) type substrate may be used as the substrate 110 .

An insulating layer 115 may be provided on the upper surface of the substrate 110 to electrically isolate the substrate 110 from the resonator 120 . In addition, the insulating layer 115 prevents the substrate 110 from being etched by the etching gas when the cavity C is formed during the manufacturing process of the acoustic resonator.

In this case, the insulating layer 115 may be formed of at least one of silicon dioxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), aluminum oxide (Al ₂ O ₃ ), and aluminum nitride (AlN), and chemical vapor deposition. (Chemical vapor deposition), RF magnetron sputtering (RF Magnetron Sputtering), and may be formed through any one of the evaporation (Evaporation) process.

The sacrificial layer 140 is formed on the insulating layer 115 , and a cavity C and an etch stopper 145 are disposed inside the sacrificial layer 140 .

The cavity C is formed as an empty space and may be formed by removing a portion of the sacrificial layer 140 .

As the cavity C is formed in the sacrificial layer 140 , the resonator 120 formed on the sacrificial layer 140 may be formed to be flat as a whole.

The etch stopper 145 is disposed along the boundary of the cavity C. The etch stop part 145 is provided to prevent etching from proceeding beyond the cavity region during the cavity C formation process.

The membrane layer 150 is formed on the sacrificial layer 140 and forms the upper surface of the cavity (C). Therefore, the membrane layer 150 is also formed of a material that is not easily removed in the process of forming the cavity (C).

For example, when a halide-based etching gas such as fluorine (F) or chlorine (Cl) is used to remove a portion (eg, a cavity region) of the sacrificial layer 140 , the membrane layer 150 is formed with the above-described etching gas. and may be made of a material with low reactivity. In this case, the membrane layer 150 may include at least one of silicon dioxide (SiO ₂ ) and silicon nitride (Si ₃ N ₄ ).

In addition, the membrane layer 150 is magnesium oxide (MgO), zirconium oxide (ZrO ₂ ), aluminum nitride (AlN), lead zirconate titanate (PZT), gallium arsenide (GaAs), hafnium oxide (HfO ₂ ), aluminum oxide ( Al ₂ O ₃ ), titanium oxide (TiO ₂ ), or a dielectric layer containing at least one of zinc oxide (ZnO), aluminum (Al), nickel (Ni), chromium (Cr), It may be formed of a metal layer containing at least one of platinum (Pt), gallium (Ga), and hafnium (Hf).

The resonator 120 includes a first electrode 121 , a piezoelectric layer 123 , and a second electrode 125 . In the resonance part 120 , a first electrode 121 , a piezoelectric layer 123 , and a second electrode 125 are sequentially stacked from the bottom. Accordingly, in the resonator 120 , the piezoelectric layer 123 is disposed between the first electrode 121 and the second electrode 125 .

Since the resonator 120 is formed on the membrane layer 150 , the membrane layer 150 , the first electrode 121 , the piezoelectric layer 123 , and the second electrode 125 are eventually formed on the substrate 110 . They are sequentially stacked to form the resonator 120 .

The resonator 120 may generate a resonant frequency and an anti-resonant frequency by resonating the piezoelectric layer 123 according to a signal applied to the first electrode 121 and the second electrode 125 .

The resonance part 120 includes a central part S in which the first electrode 121 , the piezoelectric layer 123 , and the second electrode 125 are stacked approximately flat, and the first electrode 121 and the piezoelectric layer 123 . The insertion layer 170 may be divided into an extended portion (E) interposed therebetween.

The central portion S is a region disposed at the center of the resonator 120 , and the extended portion E is a region disposed along the periphery of the central portion S. Therefore, the extension (E) is a region extending outward from the central part (S), and means a region formed in a continuous annular shape along the circumference of the central part (S). However, if necessary, some regions may be formed in a discontinuous ring shape.

Accordingly, as shown in FIG. 2 , in the cross-section of the resonance part 120 cut across the central part S, the extension parts E are disposed at both ends of the central part S, respectively. In addition, the insertion layer 170 is disposed on both sides of the extended portion E disposed at both ends of the central portion S.

The insertion layer 170 has an inclined surface L whose thickness increases as the distance from the central portion S increases.

In the extended portion E, the piezoelectric layer 123 and the second electrode 125 are disposed on the insertion layer 170 . Accordingly, the piezoelectric layer 123 and the second electrode 125 positioned in the extension portion E have inclined surfaces along the shape of the insertion layer 170 .

On the other hand, in the present embodiment, it is defined that the extension part (E) is included in the resonator part 120, and accordingly, resonance may be made in the extension part (E) as well. However, the present invention is not limited thereto, and, depending on the structure of the extension part E, resonance may not occur in the extension part E, but resonance may be made only in the central part S.

The first electrode 121 and the second electrode 125 may be formed of a conductor, for example, gold, molybdenum, ruthenium, iridium, aluminum, platinum, titanium, tungsten, palladium, tantalum, chromium, nickel, or any of these. It may be formed of a metal including at least one, but is not limited thereto.

In the resonator 120 , the first electrode 121 has a larger area than the second electrode 125 , and the first metal layer 180 is formed on the first electrode 121 along the periphery of the first electrode 121 . are placed Accordingly, the first metal layer 180 may be disposed to be spaced apart from the second electrode 125 by a predetermined distance, and may be disposed to surround the resonator 120 .

Since the first electrode 121 is disposed on the membrane layer 150 , the first electrode 121 is formed to be flat as a whole. On the other hand, since the second electrode 125 is disposed on the piezoelectric layer 123 , a curve may be formed corresponding to the shape of the piezoelectric layer 123 .

The first electrode 121 may be used as any one of an input electrode and an output electrode for inputting and outputting an electrical signal such as a radio frequency (RF) signal.

The second electrode 125 is entirely disposed in the central portion S, and is partially disposed in the extended portion E. Accordingly, the second electrode 125 may be divided into a portion disposed on the piezoelectric portion 123a of the piezoelectric layer 123 to be described later and a portion disposed on the bent portion 123b of the piezoelectric layer 123 .

More specifically, in the present embodiment, the second electrode 125 is disposed to cover the entire piezoelectric portion 123a and a portion of the inclined portion 1231 of the piezoelectric layer 123 . Accordingly, the second electrode (125a in FIG. 4 ) disposed in the extension part E has a smaller area than the inclined surface of the inclined part 1231 , and in the resonance part 120 , the second electrode 125 is a piezoelectric layer. (123) is formed with a smaller area.

Accordingly, as shown in FIG. 2 , in the cross-section in which the resonance part 120 is cut to cross the central part S, the end of the second electrode 125 is disposed in the extension part E. As shown in FIG. In addition, an end of the second electrode 125 disposed in the extension portion E is disposed such that at least a part thereof overlaps the insertion layer 170 . Here, overlap means that when the second electrode 125 is projected on the plane on which the insertion layer 170 is disposed, the shape of the second electrode 125 projected on the plane overlaps the insertion layer 170 . .

The second electrode 125 may be used as any one of an input electrode and an output electrode for inputting and outputting an electrical signal such as a radio frequency (RF) signal. That is, when the first electrode 121 is used as an input electrode, the second electrode 125 is used as an output electrode, and when the first electrode 121 is used as an output electrode, the second electrode 125 is an input electrode. can be used as

Meanwhile, as shown in FIG. 4 , when the end of the second electrode 125 is positioned on the inclined portion 1231 of the piezoelectric layer 123 to be described later, the acoustic impedance of the resonator 120 is Since the local structure is formed as a small/mil/small/mild structure from the central portion S, a reflection interface that reflects the horizontal wave toward the inside of the resonator 120 is increased. Accordingly, since most of the lateral waves cannot escape to the outside of the resonator 120 and are reflected into the resonator 120 , the performance of the acoustic resonator may be improved.

The piezoelectric layer 123 is a part that produces a piezoelectric effect that converts electrical energy into mechanical energy in the form of acoustic waves, and is formed on the first electrode 121 and the insertion layer 170 to be described later.

As a material of the piezoelectric layer 123, zinc oxide (ZnO), aluminum nitride (AlN), doped aluminum nitride, lead zirconate titanate, quartz, etc. may be selectively used. have. The doped aluminum nitride may further include a rare earth metal, a transition metal, or an alkaline earth metal. The rare earth metal may include at least one of scandium (Sc), erbium (Er), yttrium (Y), and lanthanum (La). The transition metal may include at least one of hafnium (Hf), titanium (Ti), zirconium (Zr), tantalum (Ta), and niobium (Nb). The alkaline earth metal may also include magnesium (Mg).

When the content of elements doped into aluminum nitride (AlN) to improve piezoelectric properties is less than 0.1 at%, higher piezoelectric properties than aluminum nitride (AlN) cannot be realized, and when the content of elements exceeds 30 at%, for deposition A non-uniform phase may be formed because it is difficult to fabricate and control the composition.

Accordingly, in the present embodiment, the content of elements doped into aluminum nitride (AlN) may be in the range of 0.1 to 30 at%.

In this embodiment, the piezoelectric layer is used by doping aluminum nitride (AlN) with scandium (Sc). In this case, the piezoelectric constant may be increased to increase the K _t ² of the acoustic resonator.

The piezoelectric layer 123 according to the present embodiment includes a piezoelectric part 123a disposed in the central portion S, and a bent portion 123b disposed in the expanded portion E. As shown in FIG.

The piezoelectric part 123a is a part directly stacked on the upper surface of the first electrode 121 . Accordingly, the piezoelectric part 123a is interposed between the first electrode 121 and the second electrode 125 to form a flat shape together with the first electrode 121 and the second electrode 125 .

The bent portion 123b may be defined as a region extending outwardly from the piezoelectric portion 123a and positioned within the extended portion E.

The bent portion 123b is disposed on the insertion layer 170 to be described later, and is formed in a shape in which an upper surface of the insertion layer 170 is raised along the shape of the insertion layer 170 . Accordingly, the piezoelectric layer 123 is bent at the boundary between the piezoelectric part 123a and the bent part 123b , and the bent part 123b is raised to correspond to the thickness and shape of the insertion layer 170 .

The bent portion 123b may be divided into an inclined portion 1231 and an extended portion 1232 .

The inclined portion 1231 means a portion formed to be inclined along the inclined surface L of the insertion layer 170 to be described later. And the extension 1232 means a portion extending outwardly from the inclined portion 1231 .

The inclined portion 1231 may be formed parallel to the inclined surface L of the insertion layer 170 , and the inclined angle of the inclined portion 1231 may be formed to be the same as the inclined angle of the inclined surface L of the insertion layer 170 .

The insertion layer 170 is disposed along the surface formed by the membrane layer 150 , the first electrode 121 , and the etch stopper 145 . Accordingly, the insertion layer 170 is partially disposed in the resonance part 120 , and disposed between the first electrode 121 and the piezoelectric layer 123 .

The insertion layer 170 is disposed around the central portion S to support the bent portion 123b of the piezoelectric layer 123 . Accordingly, the bent portion 123b of the piezoelectric layer 123 may be divided into an inclined portion 1231 and an extended portion 1232 according to the shape of the insertion layer 170 .

In this embodiment, the insertion layer 170 is disposed in an area except for the central portion (S). For example, the insertion layer 170 may be disposed on the entire region except for the central portion S on the substrate 110 or may be disposed on a partial region.

The insertion layer 170 is formed in such a way that the thickness increases as the distance from the central portion S increases. For this reason, the insertion layer 170 is formed as an inclined surface L having a side surface disposed adjacent to the central portion S having a constant inclination angle θ.

When the inclination angle θ of the side surface of the insertion layer 170 is formed to be smaller than 5°, in order to manufacture it, the thickness of the insertion layer 170 must be formed very thin or the area of the slope L must be formed excessively large, so that substantially is difficult to implement.

In addition, when the inclination angle θ of the side surface of the insertion layer 170 is greater than 70°, the inclination angle of the piezoelectric layer 123 or the second electrode 125 stacked on the insertion layer 170 is formed to be greater than 70°. . In this case, since the piezoelectric layer 123 or the second electrode 125 stacked on the inclined surface L is excessively bent, cracks may occur in the bent portion.

Accordingly, in the present embodiment, the inclination angle θ of the inclined surface L is formed in a range of 5° or more and 70° or less.

Meanwhile, in the present embodiment, the inclined portion 1231 of the piezoelectric layer 123 is formed along the inclined surface L of the insertion layer 170 and is formed at the same inclination angle as the inclined surface L of the insertion layer 170 . Accordingly, the inclination angle of the inclined portion 1231 is formed in the range of 5° or more and 70° or less, similarly to the inclined surface L of the insertion layer 170 . Of course, this configuration is equally applied to the second electrode 125 stacked on the inclined surface L of the insertion layer 170 .

The insertion layer 170 may be formed of a material containing silicon (Si), oxygen (O), and nitrogen (N). For example, the insertion layer 170 may be formed of a SiOxNy thin film in which nitrogen (N) is injected into the SiO ₂ thin film.

The SiOxNy thin film may be formed by inserting a small amount of nitrogen into the SiO ₂ thin film using N ₂ gas or N ₂ O gas when the insertion layer 170 is formed of silicon dioxide (SiO ₂ ).

The resonator 120 is spaced apart from the substrate 110 through a cavity C formed as an empty space.

The cavity C may be formed by removing a portion of the sacrificial layer 140 by supplying an etching gas (or an etching solution) to the inlet hole (H of FIG. 1 ) during the manufacturing process of the acoustic resonator.

The protective layer 160 is disposed along the surface of the acoustic resonator 100 to protect the acoustic resonator 100 from the outside. The protective layer 160 may be disposed along a surface formed by the second electrode 125 and the bent portion 123b of the piezoelectric layer 123 .

Meanwhile, the first electrode 121 and the second electrode 125 may extend outside the resonator 120 . In addition, the first metal layer 180 and the second metal layer 190 may be disposed on the upper surface of the extended portion, respectively.

The first metal layer 180 and the second metal layer 190 may include gold (Au), a gold-tin (Au-Sn) alloy, copper (Cu), a copper-tin (Cu-Sn) alloy, and aluminum (Al); It may be made of any one material of aluminum alloy. Here, the aluminum alloy may be an aluminum-germanium (Al-Ge) alloy or an aluminum-scandium (Al-Sc) alloy.

The first metal layer 180 and the second metal layer 190 electrically connect the electrodes 121 and 125 of the acoustic resonator according to the present embodiment to the electrodes of another acoustic resonator disposed adjacent to each other on the substrate 110 . It can function as a wiring.

The first metal layer 180 passes through the passivation layer 160 and is bonded to the first electrode 121 .

In addition, in the resonator 120 , the first electrode 121 has a larger area than the second electrode 125 , and the first metal layer 180 is formed around the first electrode 121 .

Accordingly, the first metal layer 180 is disposed along the circumference of the resonator 120 , and is disposed to surround the second electrode 125 . However, the present invention is not limited thereto.

In addition, in the present embodiment, at least a portion of the protective layer 160 positioned on the resonator 120 is disposed to contact the first metal layer 180 and the second metal layer 190 . The first metal layer 180 and the second metal layer 190 are formed of a metal material having high thermal conductivity and have a large volume, so that the heat dissipation effect is large.

Therefore, so that the heat generated in the piezoelectric layer 123 can be quickly transferred to the first metal layer 180 and the second metal layer 190 via the protective layer 160, the protective layer 160 is 180 ) and the second metal layer 190 .

In this embodiment, at least a portion of the passivation layer 160 is disposed under the first metal layer 180 and the second metal layer 190 . Specifically, the protective layer 160 is disposed between the first metal layer 180 and the piezoelectric layer 123 and between the second metal layer 190 and the second electrode 125 and the piezoelectric layer 123 , respectively.

The volume acoustic resonator 100 according to the present exemplary embodiment configured as described above includes sequentially stacking a first electrode 121 , a piezoelectric layer 123 , and a second electrode 125 on a substrate 110 to form a resonator unit 120 . ) can be formed. Also, the forming of the resonator 120 may include disposing the insertion layer 170 under the first electrode 121 or between the first electrode 121 and the piezoelectric layer 123 .

Accordingly, the insertion layer 170 may be stacked on the first electrode 121 , or the first electrode 121 may be stacked on the insertion layer 170 .

At this time, the piezoelectric layer 123 and the second electrode 125 may be partially raised along the shape of the insertion layer 170 , and the insertion layer 180 may include silicon (Si), oxygen (O), and nitrogen ( It may be formed of a material containing N).

In the volume acoustic resonator 100 according to the present embodiment, the insertion layer 170 may be formed of a SiOxNy thin film. In this case, since a photomask pattern formed on the insertion layer 170 to pattern the insertion layer 170 may be more precisely formed during the manufacturing process, the precision of the insertion layer 170 may be improved. This will be described in more detail as follows.

The insertion layer 170 of the volume acoustic resonator 100 according to the present embodiment includes an insertion layer ( After forming 170 , it may be completed by removing unnecessary portions disposed in the region corresponding to the central portion S.

In this case, as a method of removing the unnecessary portion, a photolithography method using a photoresist may be used. In this case, the insertion layer 170 may also be precisely formed only when a photoresist serving as a mask is precisely formed.

When the insertion layer 170 is formed of silicon dioxide (SiO ₂ ), a hydroxyl group may be easily adsorbed on the surface or inside of the insertion layer 170 . Therefore, if a process such as removing the first applied photoresist and re-applying the photoresist (hereinafter, rework) is performed, the re-applied photoresist may not be formed precisely due to the hydroxyl group adsorbed on the SiO ₂ insertion layer. .

The applicant, through an experiment, forms the insertion layer 170 of silicon dioxide (SiO ₂ ) material, then applies a photoresist thereon and repeatedly forms a necessary pattern through an exposure/development process, It was confirmed that there was a variation between the critical dimension of the initially formed photoresist and the critical dimension of the reworked photoresist. In addition, it was confirmed that when an insertion layer was formed of a SiOxNy material and a photoresist was formed thereon, the variation between the critical dimension of the initially formed photoresist and the critical dimension of the reworked photoresist was minimized.

Meanwhile, in the present embodiment, the insertion layer was deposited through a plasma-enhanced CVD (PECVD) method, but the configuration of the present invention is not limited thereto. A chemical vapor deposition (CVD) method may be used.

5 and 6 are views showing critical dimensions of a volume acoustic resonator in which an insertion layer is formed of a silicon dioxide material. It is a table, and FIG. 6 is a diagram showing the critical dimension of FIG. 5 as a graph.

Here, points 1 to 9 mean nine points spaced apart in a grid form on the wafer.

Here, the measured value of FIG. 5 is a PECVD (Plasma Enhanced CVD) method by depositing silicon dioxide (SiO ₂ ) to a thickness of 3000 Å at a deposition temperature of 300° C. to form an insertion layer, and forming a photoresist thereon to Critical Dimension (CD) is a measured value. Here, the critical dimension of the photoresist was measured using a critical dimension measuring scanning microscope (CD-SEM) equipment.

In the present embodiment, the insertion layer made of silicon dioxide (SiO ₂ ) may be formed through Equation 1 below.

(Formula 1) SiH ₄ + O ₂ → SiO ₂ + 2H ₂

Referring to FIGS. 5 and 6 , the average critical dimension of the photoresist initially applied was 3.29um and the dispersion range was good as 0.06um, but when rework was performed, the average critical dimension of the photoresist was 2.78um, the dispersion range was measured to be 0.43um.

Accordingly, it can be seen that when the insertion layer is formed of silicon dioxide (SiO ₂ ), the distribution of the critical dimension of the re-applied photoresist is significantly increased compared to the distribution of the critical dimension of the initially applied photoresist.

7 and 8 are examples in which only the deposition temperature was increased in the same environment as in FIGS. 5 and 6, and FIG. 7 is a table showing the values of critical dimensions measured at 9 points on the wafer, and FIG. It is a figure showing the critical dimension of 7 graphically.

Here, the measured value of FIG. 7 is a value obtained by depositing a silicon dioxide (SiO ₂ ) material by depositing at a thickness of 3000 Å at 400° C. in a PECVD method, and forming a photoresist thereon to measure the critical dimension. to be. The insertion layer of this embodiment may be formed through Equation 1 described above.

Referring to FIGS. 7 and 8 , the average critical dimension of the photoresist initially applied was 3.43um and the dispersion range was good as 0.08um, but when the first rework (Rework 1st) was performed, the average critical dimension of the photoresist was Silver increased to 3.28um and the dispersion range to 0.14um. And when the second rework (Rework 2nd) was performed, the average critical dimension of the photoresist was 2.76um, and the dispersion range was 0.32um, which was confirmed to increase further than the first rework.

Accordingly, when the deposition temperature is increased from 300° C. to 400° C. without changing the material of the insert layer, it can be seen that the dispersion does not increase significantly in the first rework, but increases significantly in the second rework.

9 and 10 are views showing critical dimensions of a volume acoustic resonator in which an insertion layer is formed of SiOxNy material. It is a figure showing the critical dimension of 9 graphically.

Here, the measured value of FIG. 9 is a PECVD method, but deposition of the insertion layer is performed at 300° C. to a thickness of 3000 Å, SiH ₄ and N ₂ O are mixed in an appropriate ratio to form an insertion layer made of SiOxNy material, and a photo A value obtained by measuring a critical dimension by forming a resist.

The SiOxNy insertion layer may be formed through Equation 2 below.

(Formula 2) SiH ₄ + N ₂ O → SiOxNy + H ₂

9 and 10 , the average critical dimension of the initially applied photoresist was 3.33um and the dispersion range was good as 0.04um, and when the first rework (Rework 1st) was performed, the critical dimension of the photoresist was The average dimension was 3.32um and the dispersion range was 0.03um, indicating no significant change compared to the initial period. In addition, when the second rework (Rework 2nd) was performed, the average critical dimension of the photoresist was 3.31 μm, and the dispersion range was 0.04 μm, confirming that there was still no significant change compared to the initial stage.

11 and 12 are views showing critical dimensions of a volume acoustic resonator in which an insertion layer is formed of SiOxNy material. It is a diagram showing the critical dimension of 11 as a graph.

Here, the measured value of FIG. 11 is a PECVD method, but deposition of the insertion layer at 400° C. to a thickness of 3000 Å, SiH ₄ and N ₂ O are mixed in an appropriate ratio to form an insertion layer made of SiOxNy material, and a photo A value obtained by measuring a critical dimension by forming a resist. Accordingly, the insertion layer may be formed through Equation 2 described above.

11 and 12 , the average critical dimension of the initially applied photoresist was 3.32um and the dispersion range was good as 0.03um, and when the first rework (Rework 1st) was performed, the critical dimension of the photoresist was The average dimension was 3.32um and the dispersion range was 0.03um, indicating no significant change compared to the initial period. In addition, in the case of the second rework (Rework 2nd), the average critical dimension of the photoresist was 3.31 μm, and the dispersion range was 0.02 μm, confirming that there was still no significant change compared to the initial stage.

13 and 14 are views showing critical dimensions of a volume acoustic resonator in which an insertion layer is formed of SiOxNy material. It is a figure showing the critical dimension of 13 graphically.

Here, the measured value of Figure 13 proceeds with the deposition of the insertion layer to a thickness of 3000 Å at 300 ° C in the PECVD method, SiH ₄ and O ₂ , N ₂ gas is mixed in an appropriate ratio to form an insertion layer made of SiOxNy material, A photoresist was formed thereon to measure a critical dimension.

The SiOxNy insertion layer may be formed through Equation 3 below.

(Formula 3) SiH ₄ + O ₂ + N ₂ → SiOxNy + H ₂

The average critical dimension of the initial photoresist was 3.29um and the dispersion range was 0.04um, which was good. It was measured that there was no significant change compared to the initial period. In addition, when the second rework (Rework 2nd) was performed, the average critical dimension of the photoresist was 3.34um and the dispersion range was 0.03um, confirming that there was still no significant change compared to the initial stage.

Meanwhile, the SiOxNy insertion layer 170 may have a different dispersion range depending on the nitrogen (N) content.

15 and 16 are diagrams showing the critical dimension and content of each element of a volume acoustic resonator in which an insertion layer is formed of SiOxNy material. , FIG. 16 is a graph showing the critical dimension of FIG. 15 .

15 and 16 , it can be seen that the dispersion range of the SiOxNy thin film according to the content of nitrogen (N) in the present embodiment is changed.

In the present embodiment, the content ratio of nitrogen (N) to the SiOxNy thin film may be defined through the following Equation 4.

(Formula 4) Content ratio of nitrogen (N) = (at% of nitrogen (N)) / (at% of silicon (Si) + at% of oxygen (O) + at% of nitrogen (N))

As shown in FIG. 15 , as a result of measuring the dispersion range by changing the content ratio of nitrogen (N), when the content ratio of nitrogen (N) is 0.86% or more, the dispersion range is maintained at 0.03um even if the photoresist is repeatedly formed. It was confirmed that the resist pattern was stably implemented.

Accordingly, in the insertion layer of this embodiment, the at% content of nitrogen (N) in the SiOxNy thin film may be 0.86% or more of the at% content of the entire insertion layer 170 .

In addition, since the insertion layer 170 is used for the reflection structure of the horizontal wave of the volume acoustic resonator, it may be formed of a material having a small acoustic impedance. Therefore, it is advantageous to use a material having properties similar to that of SiO ₂ , which has been conventionally used as a material for the insertion layer 170 .

When the nitrogen content in the SiOxNy thin film is greater than that of oxygen, the characteristics of the insertion layer 170 are closer to those of Si ₃ N ₄ than those of SiO ₂ . In this case, the horizontal wave reflection characteristics of the volume acoustic resonator may be reduced have.

In more detail, this is as follows.

Referring to FIG. 4 , in the case of the volume acoustic resonator according to the present embodiment, the acoustic impedance of the resonator 120 is formed in a small/mil/small/mil structure from the central part S in the local structure. A plurality of reflection interfaces for reflecting the horizontal wave into the resonator 120 are provided.

Acoustic impedance is an intrinsic property of a material and is expressed as the product of the density (kg/m ³ ) of the material in the bulk state and the speed of sound waves in the material (m/s). In addition, in this embodiment, the high reflection characteristic of the acoustic resonator means that the loss generated as a lateral wave escapes to the outside of the resonator 120 is small. It means performance is improved.

In order to increase the horizontal wave reflection characteristics at each reflection interface, it is advantageous to configure the insertion layer 170 using a material having a large difference in acoustic impedance from the piezoelectric layer 123 and the electrodes 121 and 125 . The acoustic impedance of SiO ₂ is 12.96 kg/m ^2· s and that of Si ₃ N ₄ is 35.20 kg/m ^2· s. And AlN used as a material of the piezoelectric layer 123 has an acoustic impedance of 35.86 kg/m ^2· s, and in the case of molybdenum (Mo) used as a material of the first electrode, 55.51 kg/m ^2· s.

When the nitrogen content in the SiOxNy thin film is greater than that of oxygen, the Si ₃ N ₄ reaction occurs rapidly and the insertion layer 170 exhibits properties close to that of the Si ₃ N ₄ material. In this case, since the acoustic impedance of the insertion layer 170 becomes similar to the acoustic impedance of the piezoelectric layer 123 , the reflection characteristic is deteriorated. Conversely, when the oxygen content in the SiOxNy thin film is higher than that of nitrogen so that the characteristics of the insertion layer 170 are close to the characteristics of SiO ₂ , the acoustic impedance of the insertion layer 170 has a large difference from the acoustic impedance of the piezoelectric layer 123, Reflective properties are improved.

Therefore, in order to form the insertion layer 170 using a material having a large difference in acoustic impedance from the piezoelectric layer 123 or the first electrode, it is advantageous to form the insertion layer 170 using SiOxNy rather than Si ₃ N ₄ .

Accordingly, in the present embodiment, the insertion layer 170 is formed of a SiOxNy thin film, and nitrogen is contained in the SiOxNy thin film at at% less than oxygen. Through this configuration, horizontal wave reflection characteristics of the volume acoustic resonator can be secured, and the precision of the insertion layer 170 can be improved.

On the other hand, the content analysis of each element in the SiOxNy thin film can be confirmed by SEM (Scanning electron microscopy), TEM (Transmission Electron Microscope) EDS (Energy Dispersive X-ray Spectroscopy) analysis, but is not limited thereto, and XPS (X-ray It is also possible to use photoelectron spectroscopy) analysis or the like.

As such, in the volume acoustic resonator according to the present embodiment, the insertion layer 170 is formed of a SiOxNy material. Accordingly, even if the photoresist formed on the insertion layer 170 is repeatedly re-applied to pattern the insertion layer 170 , the dispersion of the critical dimension does not increase.

Therefore, even if the photoresist is repeatedly re-applied in the manufacturing process of the insertion layer 170, the photoresist and the insertion layer 170 can be formed precisely and stably. .

17 is a cross-sectional view schematically illustrating a volume acoustic resonator according to another embodiment of the present invention.

In the volume acoustic resonator shown in this embodiment, the second electrode 125 is disposed on the entire upper surface of the piezoelectric layer 123 in the resonator 120 , and accordingly, the second electrode 125 is formed on the piezoelectric layer 123 . ) is formed on the inclined portion 1231 as well as the extended portion 1232 .

18 is a cross-sectional view schematically illustrating a volumetric acoustic resonator according to another embodiment of the present invention.

Referring to FIG. 18 , in the acoustic resonator according to the present embodiment, in a cross-section in which the resonator 120 is cut to cross the central portion S, the end portion of the second electrode 125 is the piezoelectric layer 123 . It is formed only on the upper surface of the front portion 123a, and is not formed on the bent portion 123b. Accordingly, the end of the second electrode 125 is disposed along the boundary between the piezoelectric part 123a and the inclined part 1231 .

As such, the volume acoustic resonator according to the present invention may be modified into various shapes as needed.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and variations are possible within the scope without departing from the technical spirit of the present invention described in the claims. It will be apparent to those of ordinary skill in the art. Also, each of the embodiments may be implemented in combination with each other.

100: acoustic resonator
110: substrate
120: resonance unit
121: first electrode
123: piezoelectric layer
125: second electrode
140: sacrificial layer
150: membrane layer
160: protective layer
170: insert layer

Claims (16)

a resonance unit in which a first electrode, a piezoelectric layer, and a second electrode are sequentially stacked on a substrate; and
and an insertion layer disposed under the piezoelectric layer to partially protrude the piezoelectric layer and the second electrode,
The insertion layer is formed of a material containing silicon (Si), oxygen (O), and nitrogen (N),
The at% content of nitrogen (N) contained in the insertion layer is 0.86% or more of the at% content of the entire insertion layer and is smaller than the at% content of oxygen (O).
delete According to claim 1, wherein the piezoelectric layer,
A volumetric acoustic resonator formed of aluminum nitride doped with aluminum nitride (AlN) or scandium (Sc).
According to claim 1,
The first electrode is a volume acoustic resonator formed of molybdenum (Mo).
According to claim 1, wherein the insertion layer,
A volume acoustic resonator formed of a material having a lower acoustic impedance than that of the first electrode and the piezoelectric layer.
According to claim 1,
The resonance part includes a central part disposed in the central region, and an extension part disposed along the periphery of the central part,
The insertion layer is disposed only in the extension part of the resonance part,
The insertion layer has an inclined surface that becomes thicker as it goes away from the central portion,
The piezoelectric layer includes an inclined portion disposed on the inclined surface.
7. The method of claim 6,
In a cross-section cut to cross the resonator, an end of the second electrode is disposed at a boundary between the central portion and the extended portion or is disposed on the inclined portion.
7. The method of claim 6,
The piezoelectric layer includes a piezoelectric part disposed in the central part and an extension part extending to the outside of the inclined part,
The second electrode is a volume acoustic resonator, at least a portion of which is disposed on the extension portion of the piezoelectric layer.
and sequentially stacking a first electrode, a piezoelectric layer, and a second electrode on a substrate to form a resonance part;
The step of forming the resonance part,
and forming an insertion layer disposed under the first electrode or between the first electrode and the piezoelectric layer to partially elevate the piezoelectric layer and the second electrode,
The insertion layer is formed of a material containing silicon (Si), oxygen (O), and nitrogen (N),
The at% content of nitrogen (N) contained in the insertion layer is 0.86% or more of the at% content of the entire insertion layer and is smaller than the at% content of oxygen (O).
delete The method of claim 9, wherein the insert layer,
A method of manufacturing a volumetric acoustic resonator formed by mixing SiH ₄ , N ₂ O gas in an appropriate ratio.
The method of claim 11, wherein the insert layer,
A CVD (Chemical Vapor Deposition) method and a method for manufacturing a volumetric acoustic resonator formed through Equation 1 below.
(Formula 1) SiH ₄ + N ₂ O → SiOxNy + H ₂

The method of claim 9, wherein the insert layer,
A method of manufacturing a volumetric acoustic resonator by mixing SiH ₄ , O ₂ , and N ₂ gases in an appropriate ratio. The method of claim 13, wherein the insert layer,
A CVD (Chemical Vapor Deposition) method and a volumetric acoustic resonator manufacturing method formed through Equation 2 below.
(Formula 2) SiH ₄ + O ₂ + N ₂ → SiOxNy + H ₂
10. The method of claim 9, wherein the piezoelectric layer,
A method of manufacturing a volumetric acoustic resonator formed of aluminum nitride (AlN) or scandium (Sc) doped aluminum nitride.
The method of claim 9, wherein the insert layer,
A method for manufacturing a volume acoustic resonator, wherein the first electrode and the piezoelectric layer are formed of a material having a lower acoustic impedance than that of the piezoelectric layer.

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